HIGH-Tc UPDATE E-MAIL VERSION, VOL. 7, NO. 12, June 15, 1993.Published
for the Division of Materials Sciences, Office of Basic Energy
Sciences, USDOE, under Contract W-7405-eng-82 with the Ames
Laboratory, Iowa State University.  Funded by DMS/BES/USDOE,
DARPA/DOD, ONR/DOD, EPRI, NASA, and other agencies, organizations, and
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a Macintosh Microsoft Word file and turned into a text file that can
be transferred electronically.  Formatting commands, Greek symbols,
diacritical marks, etc. are lost in this transformation.  In order to
improve the readability of the e-mail version, the newsletter staff
add explanatory marks as needed to the text file.  For example, a
carat (10^5) indicates a superscript (ten to the fifth).  A carat
followed by a bracket (cm^[-2]) indicates everything within the
brackets is superscripted (centimeter to the minus 2).  A bracket
followed by a carat ([18]^O) indicates everything before the carat is
superscripted.  An underline (M_i) indicates a subscript (M subscript
i).  Most Greek letters are spelled out (Delta, mu, tau, pi, Omega),
although delta is left as "d." In most instances, easily
recognizable formulas or units are left as they appear: Tc, Jc,
YBa2Cu3O7, O2.  Mu-m is changed to micrometers.  Diacritical marks
(accents, tildes, carats, etc.) are removed, but the German umlaut
(e.g., a, o, or u with two dots over it) is changed into a, o, or u
followed by e.  If needed for clarity, hyphens are occasionally
inserted between spelled-out Greek letters or symbols (Omega-cm,
sin-theta).---------------------------------------------------------------------NOTA
BENE: Hg-Ba-Ca-Cu-O We have received several inquiries from
researchers attempting to replicate the results of A. Schilling et
al., Nature 363, 56 (1993), who found superconductivity at 133 K in
the Hg-Ba-Ca-Cu-O system [see the May 15 High-Tc Update].  In response
to our request for more details on the processing of this system,
Schilling provided us with the following information:"Our recent
synthesis experiments were quite successful in the sense that the
volume fraction of the Hg-1223 phase significantly increased [>20%
from field-cooled chi(T) and 30-40% from electron microscopic
investigations].  The phase also can be unambiguously identified in
corresponding x-ray diffraction patterns.  Moreover, the fraction of
the (unwanted) Hg-1212 phase decreased to nearly zero, but a lot of
Hg-1212/Hg-1223 intergrowths could be identified from HRTEM images.
However, the main phase in our latest experiments is Hg-1223; a
corresponding chi(T) curve shows that there is essentially one Tc at
~133 K.  In some older samples, we occasionally observed n = 4 and n =
5 intergrowths.  The highest onset-of-diamagnetism temperature
measured to date is Tc ~ 134.2 K."The preparation technique was
not changed to reproduce the formation of the Hg-1223 phase.  We found
it preferable to heat the containers slowly, and in this way all our
quartz tubes remained intact after sintering at 800^oC for 5 hours.
To cheer up unsuccessful experimentalists, it can be said that only
about 20% of our synthesis experiments result in the formation of
Hg-1212 or Hg-1223 in our samples."HgBa2CuO4+d A preprint by
I. Bryntse (Stockholm) and S. N. Putilin (Moscow State) reports
studies of HgBa2CuO4+d (Hg-1201) by scanning electron microscopy,
high-resolution electron microscopy, and energy dispersive
spectrometry.  From x-ray powder diffraction patterns, the authors
determined that the space group is P4/mmm, that the primitive
unit-cell lattice parameters are a = 3.8797(5) Angstroms and c =
9.509(2) Angstroms, and that the structure is well
ordered.Local-density-approximation calculations of the electronic
structure of HgBa2CuO4 are reported by D. J. Singh (NRL).  He finds
that for the stoichiometric material the only band crossing the Fermi
energy is the CuO2-derived antibonding state characteristic of high-Tc
cuprates, and this band is half-filled.  The stoichiometric material
is thus expected to be a Mott insulator, as are the other undoped
cuprates.  The excess oxygen reported in the synthesized material is
no doubt essential for superconductivity.  The author also calculates
electric-field gradients and compares these with those for other
cuprates.  The positron wave- function is found to have maximum weight
in the rather large holes in the Hg layer.  Unlike the majority of
high-Tc materials, however, there is substantial weight throughout the
unit cell, including the CuO2-layer region.More on Hg-Ba-Ca-Cu-OA
preprint by S. N. Putilin (Moscow State) et al. reports the synthesis
of HgBa2CaCu2O6+d (Hg-1212) by solid state reaction, carried out at
800^oC under 50 kbar.  The x-ray diffraction powder pattern, refined
by Rietveld analysis, yielded the lattice parameters a = 3.8556(8)
Angstroms and c = 12.652(4) Angstroms, with no major impurities.  The
structure of Hg-1212 is built of alternating rock-salt and perovskite
layers, [(BaO)(HgOd)(BaO)][(CuO2)(Ca)(CuO2)], while the corresponding
sequence in HgBa2CuO4+d is [(BaO)(HgOd)(BaO)][CuO2].  The oxygen sites
in the Hg layer are only partially filled.  From ac magnetic
susceptibility measurements, the authors found a
paramagnetic-to-diamagnetic transition well above 120 K.  The authors
suggest that the multi-transition nature of the susceptibility curves
indicates that the samples contained some intergrowths.  In a few of
the samples, a transition as high as 132 K was observed, which the
authors suggest might correspond to the Hg-1223 member of the series.A
new mercury-based superconductor, Hg1-xMxBa2Y0.6Ca0.4Cu2O6+y with M =
Cu + Ca, has been isolated by A. Maignan et al. (Caen), who report
that it crystallizes in the space group P4/mmm with a = 3.870(1)
Angstroms and c = 12.537(1) Angstroms.  Investigations by
energy-dispersive x-ray (EDX) analysis, x-ray diffraction (XRD), and
high-resolution electron microscopy (HREM) revealed that this
cuprate's structure is very similar to that of Tl-1212.  The structure
can be described as built up from double pyramidal copper layers,
which are intergrown with oxygen-deficient rock-salt-type layers
containing not only Hg but also other cations (Cu and Ca) in small
amounts.  A schematic of the structure shows the layer-stacking
sequence [(BaO)(Hg1-xMxOy)(BaO)][(CuO2)(Y0.6Ca0.4)(CuO2)].  The onset
Tc determined from dc susceptibility was 90 K, with a diamagnetic
volume fraction of 27% at 4.2 K.  The authors suggest that the
Hg1-xMxOy layers should be able to accommodate a large number of
different elements M (Cd, Ca, Sr, Ga, etc.), and that the Tc's of this
material should be improved by changing the Ca/Y ratio.The electronic
structure of HgBa2Ca2Cu3O8 has been calculated by D. J. Singh (NRL)
using the local-density approximation.  The author finds, in contrast
to the case of the single-CuO2-layer material, that in the
stoichiometric material a Hg-derived band dips below the Fermi energy,
and this band hole-dopes the cuprate planes.  The author explains this
effect in terms of the electronegativity of stacks of CuO2 layers;
two- and three-layer stacks are less electronegative than a single
layer.A preprint by I. Z. Kostadinov (Sofia) et al. reports evidence
for superconductivity in samples of HgBa3CuO5+d (Hg-1301).  The
authors used a 1201 mixture of the oxides but applied rapid annealing
for several minutes up to 800^oC in O2.  They say that in this way
"levitating samples" were easily obtained.  The authors
report that the zero-resistance state was observed only at about 30 K
but that a sharp drop in resistivity was found above 110 K using a
current of about 1 muA.  Since the transition was suppressed to about
100 K at 50 muA, the authors attribute the behavior to
polycrystallinity.  Scanning-electron-microscope (SEM) micrographs
revealed the presence of small grains, in which the composition was
found to be Hg (9.91), Ba (28.73), and Cu (11.36), and hence the
authors concluded that the structure is Hg-1301.  They report that the
structure, determined by x-ray powder diffraction, had space group
P4/mmm and cell dimensions a = 3.8837(16) Angstroms and c =
19.0329(22) Angstroms.  The authors note that, although they did not
determine the atomic arrangement within the unit cell, what is of
interest is the doubling of the c lattice parameter from that found in
Hg-1201.  The critical temperature determined from the ac
susceptibility was about 90 K.Other New
SuperconductorsSuperconductivity in the system
(Pb1-xVx)Sr2(Ca1-zYz)Cu2O7-d (0.1 <= x <= 0.7, 0 <= z <=
1), which has the Tl-1212 structure, has been investigated by
W. Widder et al. (Bayreuth).  None of the as-prepared samples,
synthesized at 950^oC in air, nor any of the samples post-treated in
oxygen was superconducting.  On the other hand, some of the samples
post-treated in argon at 500^oC exhibited superconductivity.  The new
superconducting cuprate (Pb0.7V0.3)Sr2(Ca0.4Y0.6)Cu2O7-d was found to
have a tetragonal unit cell with a = 3.822 Angstroms and c = 11.818
Angstroms, and its resistive transition showed an onset Tc of 40 K.
The authors suggest that oxygen vacancies probably appear in the SrO
layers.  The smallness of the diamagnetic signal measured using SQUID
magnetometry could be explained by the material's small grain size,
which is of the order of the expected penetration depth.A preprint by
D. Pelloquin et al. (Caen) reports the isolation of a new
superconductor, Bi2Sr6-xCu3(CO3)2O10.  Using an ac susceptometer, the
authors found this oxycarbonate to have an onset Tc of 40 K and a
Meissner volume fraction of 20%.  The material is orthorhombic with a
= 5.469(2) Angstroms, b = 5.483(2) Angstroms, and c = 54.26(1)
Angstroms.  Extra reflections, in incommensurate positions along b*,
are observed corresponding to b' ~ 9 x 5.5 Angstroms.  High-resolution
electron microscopy (HREM) shows that this structure corresponds to
the intergrowth of double Sr2CuO2CO3 layers with single Bi2Sr2CuO6
layers.Electron-doped infinite-layer superconductors, based on the
SrCuO2 parent compound, have been investigated by J. L. Cobb et
al. (Texas-Austin).  The authors report SQUID magnetization, x-ray
diffraction, and transport studies of polycrystalline Sr1-xLnxCuO2 (Ln
= lanthanide element, x = 0 - 0.16).  The samples were synthesized at
high pressure (25 kbar), typically at temperatures in the range 950^oC
- 1085^oC.  The x-ray results indicated that the solid-solution phase
boundary occurs at x ~~ 0.10, somewhat lower than previously supposed.
The magnetic and superconducting properties were found to be a
sensitive function of synthesis conditions, with optimal
superconducting behavior (-4pi_chi ~~ 0.6 - 0.9) observed for a very
narrow (~10^oC) synthesis window.  Only a small variation of Tc (~~43
K) with dopant-ion size was observed; a smaller Tc for Ln = Gd (which
has a large magnetic moment) may imply an appreciable exchange
coupling (J ~~11 meV) between rare-earth ions and the superconducting
electrons.A preprint by K. Imaeda et al. (IMS-Okazaki) reports
superconductivity with Tc around 12 K in a new Na-N-C60 compound.  The
authors prepared sodium-doped C60 using the thermal decomposition of
sodium azide (NaN3).  Superconductivity was detected via the
low-magnetic-field signal (LFS) in microwave absorption and by dc
SQUID magnetometry.  The authors propose that the new superconducting
phase is NaxNyC60, where x is between 3 and 4, and y is still
unknown.Bi Copper OxidesHighly regular dislocation networks in
superconducting Bi2Sr2CaCu2Ox single crystals have been observed by
P. Shang et al. (Birmingham) using transmission electron microscopy
(TEM).  The authors present a model describing the network
configuration, Burgers vector, and formation mechanism, and they
estimate the ratio of the stacking fault energy to the shear modulus.
The model describes a periodic array of stacking-fault regions
generated by the dissociation of <110> dislocations.  These
stacking-fault regions form a triangular lattice with spacing
typically 140 to 200 nm.The correlation between these defect
structures and the magnetic hysteresis measured with a
vibrating-sample magnetometer (VSM) has been studied by G. Yang et
al. (Birmingham) in a number of Bi2Sr2CaCu2Ox single crystals in the
as-grown state and after annealing in oxygen or vacuum above 400^oC.
The authors conclude that in these crystals there are two principal
flux-pinning mechanisms: At low temperatures the dominant pinning
depends on the degree of sample oxygenation and is almost certainly
due to point defects (oxygen vacancies) pinning the 3D vortex lattice.
When the temperature rises above 25 K, however, thermal fluctuations
result in a vortex structure transition from 3D to 2D pancake vortices
in superconducting layers with little correlation between layers.
Decoupled 2D vortices interact strongly with the extended dislocation
networks observed by TEM.  This pinning is expected to be particularly
strong when the pancake vortex spacing matches that of the network
structure, thereby explaining the pronounced peak observed in the
magnetic hysteresis at 60-100 mT.  The temperature and field
dependence of the magnetic hysteresis thus can be understood in terms
of a competition in pinning between point defects and the dislocation
networks, which reverse their relative importance above and below the
3D to 2D transition at around 25 K.The magnetic properties of
Bi2Sr2CaCu2Ox single crystals have been examined by A. Arribere
(Bariloche) et al. using dc magnetization and ac susceptibility (chi'
and chi").  In dc magnetic fields perpendicular to the CuO2
layers, the ac susceptibility was measured in two orientations, one
(h_[ac] || c) in which the ac magnetic field is perpendicular to the
layers and induced ac currents flow parallel to the layers, and the
other (h_[ac] perpendicular c) in which the ac field is parallel to
the layers and induced currents flow partly parallel and partly
perpendicular to the layers.  The loss peaks chi" for the two
orientations of h_[ac] occur at different temperatures (lower
temperatures for h_[ac] perpendicular c), indicating that the
dissipative processes associated with intraplanar and interplanar
currents are distinctly different.  The authors conclude that at the
dc irreversibility line the vortex system has no long-range order in
the c direction; in other words, the irreversibility line marks the
temperature where the 2D pancake vortices are depinned.Measurements of
the critical-current density in the c direction J_c^c in Bi2Sr2CaCu2Ox
single crystals have been made by E. Rodriguez (Bariloche) et
al. using parallel dc field and current orientations: H_[dc] || J ||
c.  In zero-field-cooled (ZFC) samples to which fields of 0.5 T, 1 T,
and 3 T were then applied, the authors found that J_c^c initially
increased with temperature, reached a broad maximum at about 12 - 15
K, and then decreased with temperature.  A consequence of this is that
a current density could be found for which the c-direction electrical
resistance of ZFC samples was nonzero a low temperatures, went to zero
at higher temperatures, and then became nonzero again at still higher
temperatures.  Surprisingly, these effects did not occur for
field-cooled (FC) samples.  The authors explain their results in terms
of 2D pancake vortices in the superconducting layers, with Josephson
vortices between them.  Since the pancake-vortex array is rather
disordered in the ZFC state and much better ordered in the FC state,
the experiments indicate the importance of interplanar, c-direction
order in determining transport properties in the c-direction.Detailed
measurements of the critical-current anisotropy Jc(B,theta) of
Ag-sheathed Bi-2223 tapes at 77 K have been made by Q. Y. Hu
(Atominstitut der Oesterreichischen Universitaeten, Vienna) et al.  In
agreement with previous reports, the authors find that Jc(B,theta) =
Jc(Bcos_theta,0^o) for a wide range of angles theta, the angle between
B and the c axis.  When the field direction is within about 10^o of
being parallel to the ab planes, however, the data do not follow this
simple relationship.  The authors attribute this to local
misalignments of individual grains with an angular spread of 2phi_0,
where phi_0 ~~ 10^o.A preprint by H. Kumakura et al. (NRIM-Tsukuba)
reports that silver and iodine can be intercalated simultaneously into
the Bi2Sr2CaCu2Ox superconductor.  After intercalation, the lattice
parameter along the c axis is expanded from 30.9 Angstroms to 45.6
Angstroms (22.8 Angstroms x 2).  From x-ray diffraction analysis the
authors infer that Ag and I atoms are inserted between double BiO
layers in the stacking sequence Bi-I-Ag-I-Bi and that the
stoichiometric composition is AgI2Bi2Sr2CaCu2Ox.  As measured by ac
susceptibility, the onset Tc of the new material is 60.7 K, which is
comparable with that of the stage-1 IBi2Sr2CaCu2Ox obtained by the
same heat treatment.The synthesis of Bi2-xPbxSr2Ca2Cu3O10-y (x = 0,
0.3) via the glass route has been studied by R. Cloots (Liege) et
al. by annealing at 820^oC, 850^oC, and 870^oC for different times.
The authors conclude that the 2223 phase does not crystallize directly
from the amorphous phase.  As suggested by previous authors, the
authors find that during the annealing treatment the 2212 phase
crystallizes first.  A rise in temperature brings about melting of the
2212 phase, and the 2201 phase then precipitates and reacts rapidly
with the melt to form the 2223 phase.  Above 856^oC, however, the 2223
phase is thermodynamically unstable and decomposes into 2212 and
secondary phases.YBCOA preprint by L. Gao et al. (TCSUH) reports the
trapping of a 4 T magnetic field at the surface of unirradiated,
high-quality, monolithic, single-grain YBa2Cu3O7-d disks at 11 K.
Below 11 K, however, large flux jumps (flux avalanches caused by
thermal stability) severely limit the remanent trapped field.  Thus
flux jumps, rather than J_cd, dictate the maximum trapped field at low
temperatures.  The authors propose that much higher trapped fields
should be achievable by properly arranging high-temperature
superconducting tiles of dimensions smaller than the critical
dimension.TEM and critical-current-density studies of melt-textured
YBa2Cu3O7-d/15 wt% silver (123/Ag) samples with Y2BaCuO5 (211)
additions are reported by M. Mironova et al. (TCSUH).  In an effort to
ascertain the likely flux-pinning centers responsible for the observed
Jc increase when 211 is added to melt-textured 123, the authors
observed microstructural defects and transport critical-current
densities in the same domains.  The authors found that, while large
211 inclusions possess defect-free interfaces, the interfaces of
micron-sized 211 particles with high surface curvature are associated
with numerous dislocations, where the local dislocation density is on
the order of 10^[10]/cm^2.  These interface-associated defects are
believed to be responsible for the enhancement in Jc by 211
additions.Vortex DynamicsThe contribution of vortex oscillations to
the specific heat of the vortex lattice C_v in highly anisotropic
layered superconductors has been calculated by L. N. Bulaevskii and
M. P. Maley (Los Alamos) for B perpendicular to the layers in the
field range H_[c1] << B << H_[c2].  The model of the
overdamped quantum oscillator is used to describe the vortex dynamics
at low temperatures.  The authors find that C_v(T,B) is linear in
temperature at low T and increases with field as C_v proportional to
ln B for weak pinning and C_v proportional to B for strong pinning.
The authors stress that measurements of the temperature dependence of
C_v would provide direct information about the vortex viscosity at low
temperatures, where this parameter currently is unknown for the
high-Tc superconductors.A preprint by C. J. van der Beek (Argonne) et
al. presents a theoretical analysis of the ac response of a vortex
system.  Linear response and nonlinear response are derived as two
opposite limits of the same diffusion-like equation for magnetic flux.
In the linear regime the response is similar to the skin effect,
whereas in the nonlinear limit the current density is spatially almost
constant over the region of penetration.  The authors discuss the
magnitude and frequency dependence of the nonlinearity threshold
(amplitude of the ac field where one crosses from essentially linear
to strongly nonlinear response) for both the vortex-liquid and
vortex-glass states.A simple one-dimensional model has been introduced
by W. Barford et al. (Sheffield) to simulate the establishment of the
Bean critical state.  The authors assume a pseudo-random
pinning-center distribution and an intervortex interaction force that
has range xi_v and decreases linearly with separation.  The authors
find that the dynamics of the flux lines entering the superconductor
are dominated by avalanches and that the distribution of distances
moved by vortices in avalanches obeys a power law with an exponent -1.
The authors thus suggest that the Bean state is a self-organized
critical state.  The density of fluxons is found to vary as the square
root of the distance from the depth of maximum penetration.A preprint
by P. Martinoli et al. (Neuchatel) describes experiments probing
vortex dynamics in square and triangular
superconducting-normal-superconducting Josephson-junction arrays.  The
authors have used a low-frequency two-coil mutual-inductance technique
to investigate phase coherence in these samples.  In a perpendicular
magnetic field the interaction of the field-induced vortices with the
periodic pinning structure provided by the array leads to frustration
effects, which differ in the two types of arrays.  The difference in
behavior arises from the smaller pinning energy in the triangular
array.The ab-plane resistivity in La1.86Sr0.14CuO4 has been studied by
S. L. Yuan et al. (NRIM-Tsukuba) as a function of field, temperature,
and angle theta between H and the c axis.  The authors have developed
a phenomenological model, based on the Josephson coupling model, by
which all features of the resistivity experiments can be fit over six
orders of magnitude.Thin FilmsAs reported by S. Koike et
al. (SRL-ISTEC), thin films of single-TlO-layer TlBa2Ca2Cu3Ox
(Tl-1223) have been prepared on SrTiO3 (100) substrates by depositing
Ba-Ca-Cu-O precursor via the metalorganic deposition (MOD) method and
then reacting with Tl2O3 vapor.  The films (thickness 1 micrometer)
were highly c-axis-oriented and composed entirely of the 1223 phase.
The films had a zero-resistance Tc of 106 K, and at 77 K and zero
applied magnetic field they had a transport critical current I_c of
6.3 A with a 1-mm-wide bridge, corresponding to a transport
critical-current density Jc = 6.3 x 10^5 A/cm^2.  When a 1 T magnetic
field was applied perpendicular to the CuO2 layers, Jc was 2.0 x 10^4
A/cm^2 at 77 K and 6.0 x 10^5 A/cm^2 at 40 K.  In a parallel 7 T
magnetic field, Jc was 1.0 x 10^5 A/cm^2 at 77 K.  While no history
effect was found in Jc in magnetic fields below 0.1 T at 77 K, a small
hysteresis effect was found at 40 K and 60 K.  The authors conclude
that Tl-1223 films formed by the MOD method have strong magnetic
flux-pinning characteristics and good intergranular
connectivity.High-Tc Josephson junctions have been fabricated by
S. K. Tolpygo (SUNY-Stony Brook) et al. using direct electron-beam
writing across YBa2Cu3O7-d thin-film microbridges with a scanning
transmission electron microscope (STEM) of 80-120 kV accelerating
voltage.  Annealing at 330-380 K increased Tc and Ic of the junctions
and made them more stable.  In the operating range of a few degrees
below Tc the junctions showed 100% magnetic-field modulation of the
critical current, microwave-induced Shapiro steps to high order, and
RSJ I-V curves with I_cR_n products up to 0.5 - 0.6 mV at 75 K and 0.3
mV at 77 K.Spin-Fluctuation-Induced SuperconductivityDetailed
theoretical work to determine the role of spin fluctuations in
producing superconductivity in YBa2Cu3O7 is described in a preprint by
P. Monthoux (UC-Santa Barbara) and D. Pines (Illinois-Urbana).  They
carry out strong-coupling calculations of superconductivity in
YBa2Cu3O7 using the Eliashberg formalism with parameters chosen from
band theory and fits to ARPES and NMR experiments.  The coupling
constant describing the spin-fluctuation-induced interaction between
quasiparticles is chosen so that Tc is the experimentally measured
critical temperature.  Solutions are found only for d-wave
(d_[x^2-y^2]) superconductivity.  The authors find that the influence
of potential impurity scattering upon Tc is relatively weak.  On the
other hand, because it disrupts local magnetic correlations, the
substitution of Zn on the Cu sites in the CuO2-plane sites is found to
have a strong effect in suppressing Tc.The authors consider the
competition between antiferromagnetic and superconducting
instabilities, and as the temperature is lowered they find that the
instability of the normal state to a superconducting state always
comes first.  The authors also find that, with parameters of the
spin-fluctuation spectrum chosen to be consistent with NMR
measurements, a superconducting transition temperature of 90 K is
obtained with a dimensionless coupling constant lamba < 1/2.  Their
calculations yield a normal-state in-plane resistivity rho_[ab](T)
that varies linearly with temperature T, with a magnitude at 100 K of
20 mu_Omega_cm.  In addition, they obtain a frequency dependence of
the optical conductivity sigma(omega) that is in quantitative
agreement with experiment for energies less than 50 meV.  They also
find that the c-axis resistivity rho_c(T) is linear in temperature,
with a magnitude at 150 K of 2.5 m_Omega_cm.More TheoryAs described in
a preprint by V. V. Dorin (Argonne) et al., the contributions to the
c-axis conductivity from fluctuations of the normal quasiparticle
density of states are opposite in sign to the Aslamazov-Larkin and
Maki-Thompson contributions, leading to a peak in the overall c-axis
resistivity rho_c(T) above Tc.  The authors show that in a magnetic
field H || c this peak increases in magnitude and shifts to lower T by
an amount proportional to H^2 for weak fields and to H for strong
fields.  The authors apply their results in discussing recent
experiments on YBa2Cu3O7-d and Bi2Sr2CaCu2O8+d.The hopping amplitudes
for an electron and a hole added to the molecule H_2 have been
calculated by J. E. Hirsch (UC-San Diego) using a linear combination
of atomic orbitals (LCAO) approach and the Hartree approximation.  The
hopping amplitudes for electrons and holes are found to be different,
reflecting the fundamental electron-hole asymmetry of condensed
matter.  The author stresses that in solids, everything else being
equal, superconductivity is favored by having hole states, rather than
electron states, at the Fermi energy.According to a preprint by
D. Ariosa et al. (Neuchatel), the superconducting transition
temperatures of (Y1-xPrx)Ba2Cu3O7 alloys and YBa2Cu3O7/PrBa2Cu3O7
multilayers can be explained by a common dominant mechanism, the 2D
quantum fluctuations of the phase of the superconducting order
parameter.  In this work the authors use a model of electrostatically
coupled superconducting layers.Ginzburg-Landau calculations have been
done by S. J. Chapman (Oxford) et al. to treat superconducting-normal
junctions and superconductors containing normal impurities.  The
authors also present calculations showing the interaction of vortices
with these structures.The semiclassical approach of Onsager and
Pippard has been applied by B. S. Chandrasekhar and D. Einzel (Walther
Meissner Institute) to obtain the tensor that relates the supercurrent
density to the vector potential.  This tensor involves band and
Fermi-surface parameters, as well as the energy gap, which may be
anisotropic.  The authors stress that, while this tensor is commonly
expressed in terms of an effective mass tensor in anisotropic
Ginzburg-Landau theory, such effective masses in general are not the
same as the band masses obtained in electronic-structure
calculations.Other ActivitiesThe specific heat C_p of Nd2-xCexCuO4 (0
<= x <= 0.2) has been measured by T. Brugger et
al. (KfK-Karlsruhe) in the temperature range 35 mK - 10 K.  A Schottky
anomaly in undoped Nd2CuO4, resulting from exchange interactions
between Nd and ordered Cu moments, shifts with increasing Ce content
to lower temperatures and changes its character.  In the metallic
state (x >= 0.15), a large linear term with coefficient gamma ~~ 4
J/K^2 per mole Nd is found below about 300 mK.  For x = 0.2, a
constant value of the magnetic susceptibility in the same temperature
range and changes of C_p induced by a magnetic field suggest an
interpretation of these data in analogy to a heavy-fermion system
resulting from an effective coupling between Nd moments and conduction
electrons at the Cu sites.A preprint by Z. J. Yang et al. (Dalhousie)
solves for the force on a magnetic point dipole in a long hole of
square cross section in a superconductor.  Because of forces from
image dipoles, the equilibrium position of the magnetic dipole is at
the center of the hole.  The results indicate the possible potential
for a superconducting tube to be used as a means for guiding a beam of
neutrons.OverviewThe evidence for antiferromagnetic spin fluctuations
as the mechanism for superconductivity in the cuprates is reviewed by
D. Pines (Illinois-Urbana).  He gives a brief review of the
weak-coupling calculations of Monthoux, Balatsky, and Pines and the
strong-coupling calculations of Monthoux and Pines, which demonstrate
that the spin-fluctuation-induced interaction between planar
quasiparticles in a nearly antiferromagnetic Fermi liquid produces a
transition to a superconducting d_[x^2-y^2] pairing state at high
temperatures.  He then reviews recent theoretical calculations and
experiments that build a strong case that YBa2Cu3O7 in its normal
state is a nearly antiferromagnetic Fermi liquid, with commensurate
nearly antiferromagnetic spin fluctuations providing the mechanism for
high Tc.  The author observes that what is needed is an experiment
that provides a direct "smoking gun" for the role played by
spin fluctuations in determining high-temperature superconductivity.
He notes that a promising candidate is the experimental evidence from
the Osaka group on the influence of Zn impurities on both the planar
[63]^Cu spin-lattice relaxation rate and Tc.  Contributed by John
R. ClemContents: Preprints begin on page 6; Coming Events begin on
page 12; and Resouces begin on page 13. High-Tc Update is available
without charge to interested persons.  Recipients are expected to
participate in this information exchange by sending us preprints,
reprints, meeting news, research news, etc.  Contributions to defray
the cost of newsletter printing and mailing are welcome.PREPRINTS To
obtain a particular preprint, contact the first author at the address
given at the end of the citation.  Help us expand this list by sending
us your complete preprint.  Please specify where and when your paper
was submitted.  An * next to an entry indicates it is a correction or
revision of a previous entry.  PACS codes and/or key words are given
at the end of the citation.D. Ariosa, T. Luthy, V. Tsaneva,
B. Jeanneret, H. Beck, and P. Martinoli, "Superconductivity and
Quantum Fluctuations in High Tc Alloys and Multilayers."
Submitted to the Int. Conf. on Low-Temp. Phys. (LT20), Eugene, OR,
Aug. 4-11, 1993; Proc. to be published in Physica B.  Institut de
Physique, Universite de Neuchatel, CH-2000 Neuchatel,
SWITZERLAND.A. Arribere, H. Pastoriza, M. F. Goffman, F. de la Cruz,
D. B. Mitzi, and A. Kapitulnik, "Loss of Interplane Correlation
in Bi2Sr2CaCu2O8 Single Crystals." Preprint #CNEA-CAB 93/011;
submitted to Phys. Rev. B, March 22, 1993.  Centro Atomico Bariloche,
Comision Nacional de Energia Atomica, 8400 San Carlos de Bariloche,
Rio Negro, ARGENTINA; telefax +54-944-61006; telex 80723 CAB AR.
74.70.Vy; 74.60.Ge; 74.60.Jg; 74.40.+k.W. Barford, W. H. Beere, and
M. Steer, "The Dynamics of the Bean Critical State." To be
published in J. Phys. (Cond. Matt.).  Department of Physics, The
University of Sheffield, Sheffield S3 7RH, UNITED KINGDOM; telephone
+44 742 768555; telefax +44 742 728079; telex 547216 UGSHEF G.
74.60.Ge.J. Borck, S. Linzen, K. Zach, and P. Seidel, "A
Morphological Growth Model for Laser Ablated Y1Ba2Cu3O7-x Thin
Films." To be published in Physica C.  Institute of Solid State
Physics, Friedrich Schiller University Jena, Helmholtzweg 5, O-6900
Jena, GERMANY; P. Seidel's telephone and telefax +49 3641-8225230;
e-mail pih@rz.uni-jena.de.  Key words: thin films, film morphology,
scanning electron microscopy, grain alignment (texturing).  68.55.Jk;
74.75.+t.M. Breuer, B. Buechner, H. Micklitz, E. Baggio-Saitovitch,
I. Souza Azevedo, R. Scorzelli, and M. M. Abd-Elmeguid, "[57]^Fe
and [119]^Sn Mossbauer Studies on La1.25Nd0.6Sr0.15CuO4: Evidence for
Local Magnetic Ordering Below ~~ 32 K." Submitted to Z. Phys. B.
II. Physikalisches Institut, Universitaet zu Koeln, Zuelpicher Strasse
77, W-5000 Cologne 41, GERMANY.T. Brugger, T. Schreiner, G. Roth,
P. Adelmann, and G. Czjzek, "Heavy-Fermion-Like Excitations in
Metallic Nd2-yCeyCuO4." Submitted to Phys. Rev. Lett.
Kernforschungs- zentrum Karlsruhe, Institut fuer Nukleare
Festkoerperphysik, Postfach 3640, W-7500 Karlsruhe 1, GERMANY.
74.72.Jt; 71.27.+a; 71.70.Gm; 74.25.Bt.I. Bryntse and S. N. Putilin,
"Electron Microscopy Studies of the Mercury-Based Superconductor
HgBa2CuO4+d." To be published in Physica C, Vol. 212 (in press).
Arrhenius Laboratory, Department of Inorganic Chemistry, Stockholm
University, S-10691 Stockholm, SWEDEN.S. L. Bud'ko, H. H. Feng,
M. F. Davis, J. C. Wolfe, and P. H. Hor, "Persistent
Photoconductivity in Insulating and Superconducting YBa2Cu3Ox Thin
Films: Temperature and Spectral Dependence." Preprint #93:032;
submitted to Phys. Rev. B, May 24, 1993.  Texas Center for
Superconductivity, University of Houston, Houston, TX 77204-5932;
telephone (713) 743-8200; telefax (713) 743-8201.  73.50.Pz;
74.75.+t.L. N. Bulaevskii and M. P. Maley, "Low Temperature
Specific Heat of the Vortex Lattice in Layered Superconductors."
Preprint #LA-UR-93-1888.  Theoretical Division, Los Alamos National
Laboratory, Los Alamos, NM 87545.  74.60.Ge.H. Chamati and
N. S. Tonchev, "Long-Range Order in a Quantum Model of Structural
Phase Transition." Preprint #E17-92-565.  Georgy Nadjakov
Institute of Solid State Physics, Bulgarian Academy of Sciences,
Tzarigradsko Chaussee 72, 1784 Sofia, BULGARIA.B. S. Chandrasekhar and
D. Einzel, "The Superconducting Penetration Depth from the
Semiclassical Model." To be published in Ann. Phys.  Walther
Meissner Institute, 85748 Garching, GERMANY.  Key words: real metals
and superconductors, Fermi surface, generalized London equation,
penetration depth, anisotropy.S. Jonathan Chapman, Qiang Du, and Max
D. Gunzburger, "A Ginzburg-Landau Type Model of
Superconducting/Normal Junctions Including Josephson Junctions."
Mathematical Institute, University of Oxford, 24-29 Saint Giles',
Oxford OX1 3LB, UNITED KINGDOM.C. C. Chin, T. Morishita, and
T. Sugimoto, "The Influence of the Surface Roughness of the
Substrates on the Surface Morphology of YBa2Cu3O7-x Thin Films."
To be published in J. Cryst. Growth.  Superconductivity Research
Laboratory, International Superconductivity Technology Center, 10-13
Shinonome 1-chome, Koto-ku, Tokyo 135, JAPAN; telephone +81 3
3536-5703 through -5705; telefax +81 3 3536-5714 or
-5717.T. W. Clinton, J. W. Lynn, J. Z. Liu, Y. X. Jia, and
R. N. Shelton, "Two- and Three-Dimensional Magnetic Order of Er
in Superconducting ErBa2Cu3O7." Submitted to Phys. Rev. B, May
1993.  Center for Superconductivity Research, Department of Physics,
University of Maryland, College Park, MD 20742.  74.70.Hk; 75.30.-m;
75.25.+z.R. Cloots, A. C. Romaine, A. Rulmont, P. Diko,
P. H. Duvigneaud, C. Hannay, F. Gillet, P. A. Godelaine, and
M. Ausloos, "Study of the Crystallization Process in
Bi2-xPbxSr2Ca2Cu3O10-y Glass System: Optical Polarized Light
Microscopy and X-ray Diffraction Analysis." Submitted to
J. Cryst. Growth.  S.U.P.R.A.S., Institute of Chemistry, B6,
University of Liege, Sart Tilman, B-4000 Liege, BELGIUM.R. Cloots,
A. Rulmont, F. Gillet, and M. Ausloos, "Investigations of
Chemical Interaction Between Bi-Based 2212 and (RE)Ba2Cu3O7 High-Tc
Superconducting Materials." Submitted to Cryogenics.
S.U.P.R.A.S., Institute of Chemistry, B6, University of Liege, Sart
Tilman, B-4000 Liege, BELGIUM.R. Cloots, S. Stassen, A. Rulmont,
P. A. Godelaine, H. W. Vanderschueren, and M. Ausloos,
"Microstructural and Electrical Investigations Before and After
Crystallization in Bi2-xPbxSr2Ca2Cu3O10-y Glass System."
Submitted to the GEMS Conf., Madrid, Spain, Sept. 1993.  S.U.P.R.A.S.,
Institute of Chemistry, B6, University of Liege, Sart Tilman, B-4000
Liege, BELGIUM.J. L. Cobb, A. Morosoff, L. Stuk, and J. T. Markert,
"Electron-Doped Infinite-Layer Sr1-xLnxCuO2 Superconductors:
Synthesis, Magnetism, and Transport." To be presented at the
Int. Conf. on Low-Temp. Phys. (LT20), Eugene, OR, Aug. 4-11, 1993; to
be published in the Proc. in Physica B.  Department of Physics,
University of Texas, Austin, TX 78712.  74.72.Jt; 75.40.Cx;
81.20.ev.M. Darula, P. Seidel, F. Busse, and S. Benacka, "Dynamic
Properties of a SQUID Containing Arrays of Josephson Junctions."
To be published in J. Appl. Phys.  Institut fuer Festkoerperphysik,
Friedrich Schiller University Jena, Helmholtzweg 5, O-6900 Jena,
GERMANY; P. Seidel's telephone and telefax +49 3641-8225230; e-mail
pih@rz.uni-jena.de.  74.50.+r.S. N. Das and P. N. Dheer, "Normal
and Superconducting State Properties of Y1BaxCu3Oy Compounds." To
be published in Indian J. Pure Appl. Phys.  Department of Physics and
Astrophysics, University of Delhi, Delhi 110 007, INDIA; telephone +91
11 291 8993.V. V. Dorin, R. A. Klemm, A. A. Varlamov, A. I. Buzdin,
and D. V. Livanov, "Magnetic Field Enhancement of the c-Axis
Resistivity Peak Near Tc in Layered Superconductors." Submitted
to Phys. Rev. B.  Materials Science Division, Argonne National
Laboratory, 9700 South Cass Avenue, Argonne, IL 60439.  74.20;
74.40.+k.Qiang Du, "Finite Element Methods for the Time-Dependent
Ginzburg-Landau Model of Superconductivity." To be published in
Comp. Math. Appl.  Department of Mathematics, Michigan State
University, East Lansing, MI 48824.  Key words: superconductivity,
time-dependent Ginzburg-Landau equations, finite-element
methods.*Qiang Du, "Global Existence and Uniqueness of Solutions
of the Time-Dependent Ginzburg-Landau Model for
Superconductivity." To be published in Applic. Anal.  Department
of Mathematics, Michigan State University, East Lansing, MI 48824.
Key words: superconductivity, time-dependent Ginzburg-Landau
equations, choice of gauge, initial-boundary value problems, global
existence and uniqueness, finite dimensional approximations.
*Citation information.Qiang Du and Max D. Gunzburger, "A Model
for Superconducting Thin Films Having Variable Thickness."
Department of Mathematics, Michigan State University, East Lansing, MI
48824.Qiang Du, Max D. Gunzburger, and Janet S. Peterson,
"Modeling and Analysis of a Periodic Ginzburg-Landau Model for
Type-II Superconductors." To be published in SIAM
J. Appl. Math. (in press).  Department of Mathematics, Michigan State
University, East Lansing, MI 48824.  Key words: superconductivity,
Ginzburg-Landau equations, periodic solutions, type-II
superconductors.Barry Friedman, "Electronic Absorption Spectra in
C_[60]^- and C_[60]^+." Preprint #93:023; to be published in
Phys. Rev. B.  Texas Center for Superconductivity, University of
Houston, Houston, TX 77204-5932; telephone (713) 743-8200; telefax
(713) 743-8201.  78.65.Hc; 74.70.Kn; 36.40.+d.L. Gao, Y. Y. Xue,
D. Ramirez, Z. J. Huang, R. L. Meng, and C. W. Chu, "High
Magnetic Field Trapping in Monolithic Single-Grain YBa2Cu3O7-d Bulk
Materials." Preprint #93:026; submitted to Appl. Phys. Lett.,
Jan. 13, 1993.  Texas Center for Superconductivity, University of
Houston, Houston, TX 77204-5932; telephone (713) 743-8200; telefax
(713) 743-8201.  Key words: high-temperature superconductors,
superconducting magnetics, trap field, thermal instability.  74.60.-w;
85.25.Ly.I. I. Gurevich, V. N. Duginov, V. G. Firsov, V. G. Grebinnik,
E. P. Krasnoperov, T. N. Mamedov, B. A. Nikolsky, V. G. Olshevsky,
V. Yu. Pomjakushin, A. N. Ponomarev, V. A. Suetin, and V. A. Zhukov,
"On the muSr Activity at LNP JINR Phasotron." Preprint
#E14-92-574.  RSC, Kurchatov Institute of Atomic Energy, 123182,
Moscow, RUSSIA.HAO Xue-jun, ZHOU Yun-song, ZHANG Li-yuan, and WANG
Huai-yu, "Effect of Doping Zn on the Electronic Structure of
La1.85Sr0.15CuO4." Submitted to Int. J. Mod. Phys. B, April 1993.
Department of Physics, Peking University, Beijing 100871, PEOPLE'S
REPUBLIC OF CHINA.  71.20; 74.70.Vy.H. Harashina, T. Nishikawa,
T. Kiyokura, S. Shamoto, M. Sato, and K. Kakurai, "Cu-Site Doping
Effects, Transport and Magnetic Properties of High-Tc Oxides and Their
Hole Concentration Dependence." To be published in Physica C,
Vol. 212 (in press).  Department of Physics, Faculty of Science,
Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-01, JAPAN.  Key
words: La2-ySryCu1-xMxO4, YBa2(Cu1-xZnx)3O6+y, electron localization,
magnetic excitation spectra, hole concentration dependence.J. Hauck,
B. Bishchof, K. Mika, E. Janning, H. Libutzki, and J. Plewa,
"Reaction of H_2 Gas with Perovskite Related Cuprates." To
be published in Physica C (in press).  Institut fuer
Festkoerperforschung, KFA Forschungszentrum Juelich, W-5170 Juelich,
GERMANY.  Key words: oxygen stoichiometry, phase diagram,
thermogravimetry, hydrogen reaction.J. Hauck and K. Mika,
"Structural Relation Between Aurivillius Phases,
Ruddlesden-Popper Phases and Superconducting Oxides." To be
published in Int. J. Mod. Phys. B, Vol. 7 (19), Aug. 1993 (in press).
Institut fuer Festkoerperforschung, KFA Forschungszentrum Juelich,
W-51709 Juelich, GERMANY.  Key words: Aurivillius phases,
Ruddlesden-Popper phases, superconducting oxides, structural
relation.J. E. Hirsch, "Electron and Hole Hopping Amplitudes in a
Diatomic Molecule." Department of Physics, University of
California at San Diego, La Jolla, CA 92093-0319.J. E. Hirsch,
"Electron and Hole Hopping Amplitudes in a Diatomic Molecule: II.
Effect of Radial Correlations." Department of Physics, University
of California at San Diego, La Jolla, CA 92093-0319.K. Imaeda,
I. I. Khairullin, K. Yakushi, M. Nagata, N. Mizutani, H. Kitagawa, and
H. Inokuchi, "New Superconducting Sodium-Nitrogen-C60 Ternary
Compound." To be published in Solid State Commun.  Institute for
Molecular Science, Myodaiji, Okazaki 444, JAPAN.Heesang Kim and Paul
Muzikar, "1/N Expansion for the Superconducting Order Parameter
Near an Anderson Impurity." Submitted to the Int. Conf. on
Low-Temp. Phys. (LT20), Eugene, OR, Aug. 4-11, 1993; to be published
in Physica B.  Department of Physics, Purdue University, West
Lafayette, IN 47907.Shuichi Koike, Toshihide Nabatame, and Izumi
Hirabayashi, "Preparation and Transport Properties of
TlBa2Ca2Cu3Oy Thin Films by Metalorganic Deposition." Preprint
#N92332; to be published in Jpn. J. Appl. Phys.  Superconductivity
Research Laboratory, International Superconductivity Research Center,
2-4-1 Mutuno Atsuta-ku, Nagoya 456, JAPAN.  Key words: TlBa2Ca2Cu3Oy
thin film, metalorganic deposition method, transport Jc-B properties,
history effect of J_c-B.I. Z. Kostadinov, B. Alexandrov, O. Petrov,
E. Dinolova, and M. Michov, "Superconductivity in
HgBa3CuO5." Department of Physics, University of Sofia, 5
J. Baucher Blvd., 1126 Sofia, BULGARIA; e-mail
physfac2@bgearn.bitnet.Z. Koziol and P. F. de Chatel, "Non-Linear
Diffusion Equation and Relaxation Processes in Solids."
Universiteit van Amsterdam, Van der Waals-Zeeman Laboratorium,
Valckenierstraat 65, 1018 XE Amsterdam, THE NETHERLANDS; e-mail
koziol@phys.uva.nl.Z. Koziol, A. A. Menovsky, K. Bakker, and
J.J.M. Franse, "Anisotropic Low-Field Magnetization of
Heavy-Fermion Superconductor URu2Si2." Universiteit van
Amsterdam, Van der Waals-Zeeman Laboratorium, Valckenierstraat 65,
1018 XE Amsterdam, THE NETHERLANDS; e-mail koziol@phys.uva.nl.Hiroaki
Kumakura, Jinhua Ye, Jun-ichi Shimoyama, Hitoshi Kitaguchi, and
Kazumasa Togano, "Preparation of Ag-I Intercalated Bi2Sr2CaCu2Oy
Superconductor." To be published in Jpn. J. Appl. Phys.  National
Research Institute for Metals, 1-2-1 Sengen, Tsukuba, Ibaraki 305,
JAPAN.  Key words: intercalation, iodine, silver, Bi2Sr2CaCu2Oy,
transition temperature.H. Kuepfer, R. Kresse, R. Meier-Hirmer,
K. Salama, D. Lee, and V. Selvamanickam, "Investigation of
Collective Creep in YBaCuO." Preprint #93:025; submitted to the
Proc. of the Second Int. Conf. on High-Tc Supercond., Eilat, Israel,
Jan. 4-7, 1993.  Contact Texas Center for Superconductivity,
University of Houston, Houston, TX 77204-5932; telephone (713)
743-8200; telefax (713) 743-8201.A. L. Kuzemsky, H. Beck, and
J. C. Parlebas, "Non-Local Correlations and Quasiparticle
Interactions in the Anderson Model." Preprint #E17-92-564.  Joint
Institute for Nuclear Research, Dubna H.P.O. Box 79, 101000 Moscow,
RUSSIA.W. Lang, C. Fussenegger, P. Schwab, X. Z. Wang, and
D. Baeuerle, "Current-Density Dependence of the Vortex Pinning
Energy in YBaCuO." Submitted to the Int. Conf. on
Low-Temp. Phys. (LT20), Eugene, OR, Aug. 4-11, 1993; Proc. to be
published in Physica B.  Ludwig Boltzmann Institut fuer
Festkoerperphysik, Kopernikusgasse 15, A-1060 Vienna, AUSTRIA;
telephone +43 1 563409-21; telefax +43 1 563409-13; e-mail
a8231dag@awiuni11.univie.ac.at or a8231dag@- awiuni11.bitnet.W. Lang,
W. Kula, and R. Sobolewski, "Superconducting Fluctuations:
Paraconductivity, Excess Hall Effect and Magnetoconductivity in
2223-BiSrCaCuO Thin Films." Submitted to the Int. Conf. on
Low-Temp. Phys. (LT20), Eugene, OR, Aug. 4-11, 1993; Proc. to be
published in Physica B.  Ludwig Boltzmann Institut fuer
Festkoerperphysik, Kopernikusgasse 15, A-1060 Vienna, AUSTRIA; phone
+43 1 563409-21; telefax +43 1 563409-13; e-mail a8231dag@
awiuni11.univie.ac.at or a8231dag@awiuni11.bitnet.Alexandros Lappas
and Kosmas Prassides, "Oxygen-Defect Geometry in Oxygen-Rich
La2CoxCu1-xO4+d Layered Oxides." To be published in J. Solid
State Chem. (in press).  School of Chemistry and Molecular Sciences,
University of Sussex, Brighton BN1 9QJ, UNITED KINGDOM.A. Maignan,
G. Van Tendeloo, M. Hervieu, C. Michel, and B. Raveau, "A New
'1212' Mercury Based 90 K Superconductor:
Y0.6Ca0.4Ba2Cu2[Hg1-xMx]O6+y." To be published in Physica C (in
press).  Laboratoire CRISMAT, ISMRA/Universite de Caen, Boulevard du
Marechal Juin, F-14050 Caen Cedex, FRANCE.P. Martinoli, R. Theron,
J.-B. Simond, R. Meyer, Y. Jaccard, and Ch. Leemann,
"Superconducting Vortices in Triangular and Square Josephson
Junction Arrays." To be published in Physica Scripta.  Institut
de Physique, Universite de Neuchatel, CH-2000 Neuchatel, SWITZERLAND.
74.40.+k; 74.50.+r.Chang Jiang Mei and Vedene H. Smith, Jr., "The
ab initio Electronic Structure and Stability of the Bucky Tube."
To be published in Physica C (in press).  Department of Chemistry,
Queen's University, Kingston, Ontario K7L 3N6, CANADA.  71.25.Pi;
71.30.+h; 74.70.Vy; 75.10.Lp.R. Meyer, B. Jeanneret, S. E. Korshunov,
and P. Martinoli, "Observation of Dilational Symmetry Breaking in
a Superconducting Array of Sierpinski Gaskets." Submitted to the
Int. Conf. on Low-Temp. Phys. (LT20), Eugene, OR, Aug. 4-11, 1993;
Proc. to be published in Physica B.  Institut de Physique, Universite
de Neuchatel, CH-2000 Neuchatel, SWITZERLAND.M. Mironova, D. F. Lee,
and K. Salama, "TEM and Critical Current Density Studies of
Melt-Textured YBa2Cu3Ox with Silver and Y2BaCuO5 Additions."
Preprint #93:029; submitted to Physica C, Feb. 1, 1993.  Texas Center
for Superconductivity, University of Houston, Houston, TX 77204-5932;
telephone (713) 743-8200; telefax (713) 743-8201.P. Monthoux and
D. Pines, "Spin-Fluctuation-Induced Superconductivity and Normal
State Properties of YBa2Cu3O7." Institute for Theoretical
Physics, University of California, Santa Barbara, CA 93106.  74.20.-z;
74.20.Fg; 74.20.Mn.Beom-hoan O, C. T. Winkelmann, A. L. Barr, and
J. T. Markert, "Rare-Earth and Copper Magnetism in
RSr2Cu2GaO7." To be presented at the Int. Conf. on
Low-Temp. Phys. (LT20), Eugene, OR, Aug. 4-11, 1993; to be published
in the Proc. in Physica B.  Department of Physics, University of
Texas, Austin, TX 78712.  75.40.Cx; 75.20.Ck; 74.72.Jt.D. Pelloquin,
A. Maignan, M. Caldes, M. Hervieu, C. Michel, and B. Raveau, "The
Bismuth Oxycarbonate Bi2Sr6-xCu3O10(CO3)2, a New 40 K Superconductor,
Second Member of the Series (Bi2Sr2CuO6)n(Sr2CuO2CO3)n'." To be
published in Physica C (in press).  Laboratoire CRISMAT,
ISMRA/Universite de Caen, Boulevard du Marechal Juin, F-14050 Caen
Cedex, FRANCE.David Pines, "Nearly Antiferromagnetic Fermi
Liquids are High Temperature Superconductors: Are the Superconducting
Cuprates Nearly Antiferromagnetic Liquids?" Presented at the
Conf. on Spectroscopies of Novel Supercond., Sante Fe, NM, March 1993;
to be published in J. Chem. Phys. Solids.  Department of Physics,
University of Illinois at Urbana-Champaign, 1110 West Green Street,
Urbana, IL 61801-3080.  Key words: nearly antiferromagnetic Fermi
liquid, antiferromagnetic spin fluctuations, d_[x^2-y^2] pairing,
cuprate superconductors.P. Sumana Prabhu, M. S. Ramachandra Rao, and
G. V. Subba Rao, "Structure and Superconductivity Studies on Fe
and Co Doped Bi-2212." To be published in Physica C, Vol. 211 (in
press).  Materials Science Research Centre, Indian Institute of
Technology, Madras 600 036, INDIA.E. Rodriguez, M. F. Goffman,
A. Arribere, F. de la Cruz, and L. F. Schneemeyer, "Low
Temperature Superconducting Critical State of Bi2Sr2CaCu2O8:
Experimental Evidence for an Uncorrelated Quasi-Two-Dimensional Vortex
System." Preprint #CNEA-CAB 3012; submitted to Phys. Rev. Lett.,
March 29, 1993.  Centro Atomico Bariloche, Comision Nacional de
Energia Atomica, 8400 San Carlos de Bariloche, Rio Negro, ARGENTINA;
telefax +54-944-61006; telex 80723 CAB AR.  74.70.Vy; 74.60.Ge;
74.60.Jg; 74.40.+k.F. Romero-Borja, D. L. Schmidt, and L. T. Wood,
"A Modular Infrared Microspectrometer with Cryosampling
Capabilities." Preprint #93:031; submitted to Appl. Optics, May
17, 1993.  Texas Center for Superconductivity, University of Houston,
Houston, TX 77204-5932; telephone (713) 743-8200; telefax (713)
743-8201.  Key words: infrared microspectroscopy, cryosampling,
high-Tc superconductors.K. Salama, V. Selvamanickam, and D. F. Lee,
"Process-Induced Flux Pinning in Melt-Textured YBCO
Superconductor." Preprint #93:024; submitted to the Proc. of the
Second Int. Conf. on High-Tc Supercond., Eilat, Israel, Jan. 4-7,
1993.  Texas Center for Superconductivity, U. of Houston, Houston, TX
77204-5932; phone (713) 743-8200; fax (713) 743-8201.A. Sequeira,
H. Rajagopal, I. K. Gopalakrishnan, J. V. Yakhmi, and R. M. Iyer,
"The Influence of Ba Content and Ce Doping on the Structural
Features of YBa2Cu4O8 Superconductor: A Neutron Study." To be
published in J. Supercond.  Solid State Physics Division, Bhabha
Atomic Research Centre, Trombay, Bombay 400 085, INDIA; J. V. Yakhmi's
telephone +91 22-556 3060 or -551 9339; telefax +91 22-556 0750; telex
011-71017 BARC IN; e-mail yakhmi@magnum. barct1.ernet.in.  Key words:
YBa2Cu4O8 superconductor, Ba addition, Ce doping, Cu(2)-O(4), chemical
pressure, neutron diffraction.P. Shang, G. Yang, I. P. Jones,
C. E. Gough, and J. S. Abell, "Dislocation Networks in
Bi2Sr2CaCu2Oy Single Crystals." To be published in
Appl. Phys. Lett.  Superconductivity Research Group, School of
Metallurgy and Materials, The U. of Birmingham, Edgbaston, Birmingham
B15 2TT, UNITED KINGDOM; C. E. Gough's phone +44 21 414 4669; telefax
+44 21 414 6709; telex 333762 UOBHAM G.Z. B. Shao, K. R. Liu,
L. Q. Liu, H. K. Liu, and S. X. Dou, "Equilibrium Phase Diagrams
in the Systems PbO-Ag and CuO-Ag." Department of Chemistry,
Northeast University, Shenyang, PEOPLE'S REPUBLIC OF CHINA.  Key
words: phase equilibrium, copper oxide, lead oxide, deferential
thermal analysis, x-ray diffraction.David J. Singh, "Electronic
Structure of HgBa2CuO4." To be published in Physica C, Vol. 212
(in press).  Complex Systems Theory Branch, Naval Research Laboratory,
Washington, DC 20375-5345.David J. Singh, "Electronic Structure
of HgBa2Ca2Cu3O8: The Role of Mercury." Submitted to
Phys. Rev. B, May 1993.  Complex Systems Theory Branch, Naval Research
Laboratory, Washington, DC 20375-5345.Yang Kook Sun and Wha Young Lee,
"Preparation of High Purity 110 K Phase in the Bi(Pb)-Sr-Ca-Cu-O
Superconductor Using the Modified Citrate Process." To be
published in Physica C, Vol. 212 (in press).  Department of Chemical
Engineering, Seoul National University, Shinlim-dong San 56-1,
Kwanak-Ku, Seoul 151-742, KOREA.  Key words: Bi(Pb)-Sr-Ca-Cu-O
superconductor, high-Tc phase, sol gel, tartaric acid, modified
citrate process.R. Suryanarayanan, V. Psycharis, S. Leelaprute, Hari
Kishen, O. Gorochov, and D. Niarchos, "Structural and
Superconducting Properties of Sm1-xCaxSrBaCu3O6+z (x = 0, 0.05 and
0.1)." To be published in Physica C.  Laboratoire de Physique des
Solides de Bellevue, CNRS, F-92195 Meudon, FRANCE; e-mail
suryanar@cnrs-bellevue.fr.  Key words: ac susceptibility, Hall effect,
magnetization, effect of Ca, Rietveld fitting, Cu1-oxygen apical
distance, intergranular critical current, Sm(Ca)SrBaCuO.Yuan Kai Tao
and P. H. Hor, "Synthesis of Pb2Sr3Pr5Cu5Ox and Pb2Sr3PrCuOd by
the Citrate Gel Method." Preprint #93:028; submitted to
Mater. Chem. Phys. (Mater. Sci. Commun.), Dec. 2, 1992.  Texas Center
for Superconductivity, University of Houston, Houston, TX 77204-5932;
telephone (713) 743-8200; telefax (713) 743-8201.S. K. Tolpygo,
S. Shokhor, B. Nadgorny, A. Bourdillon, J.-Y. Lin, S. Y. Hou, Julia
M. Phillips, and M. Gurvitch, "High Quality YBa2Cu3O7 Josephson
Junctions Made by Direct Electron Beam Writing." Submitted to
Appl. Phys. Lett.  Department of Physics, State University of New York
at Stony Brook, Stony Brook, NY 11794-3800; telephone (516) 632-7298;
telefax (516) 632-8176.S. I. Tyutyunnikov, V. N. Shalyapin,
N. I. Balalykin, and Sh. Khromik, "The Interaction Effects of
Quasi-Impulse Radiation with YBa2Cu3O7-d Films in the Visible and Near
Infrared Spectrum Range." Preprint #P14-92-575; abstract in
English, paper in Russian.  Joint Institute for Nuclear Research,
Dubna H.P.O. Box 79, 101000 Moscow, RUSSIA.C. J. van der Beek,
V. B. Geshkenbein, and V. M. Vinokur, "Linear and Nonlinear ac
Response in the Superconducting Mixed State." Submitted to
Phys. Rev. B1.  Materials Science Division, Argonne National
Laboratory, 9700 South Cass Avenue, Argonne, IL 60439.  74.30.Ci;
74.60.Ge.A. T. Werner, J. Anders, H. J. Byrne, W. K. Maser, M. Kaiser,
A. Mittelbach, and S. Roth, "Broadband Electroluminescent
Emission from Fullerene Crystals." To be published in
Appl. Phys. A, Vol. 56, 1993.  Max-Planck-Institut fuer
Festkoerperforschung, Heisenbergstrasse 1, W-7000 Stuttgart 80,
GERMANY; telefax +49 711 689 1010.  36.20.Kd; 85.60.Jb;
72.20.-i.W. Widder, M. Franz, L. Bauernfeind, and H. F. Braun,
"Superconductivity at 40 K in the 1212 System
(Pb1-xVx)Sr2(Ca1-zYz)Cu2O7-d." Submitted to Physica C, May 11,
1993.  Physikalisches Institut, Universitaet Bayreuth, W-95440
Bayreuth, GERMANY.D. S. Wu, Y. F. Yang, H.-C.I. Kao, and C. M. Wang,
"The Effect of Ca/Ba Ratio on the Superconductivity of the
La3CaxBa4-xCu7Oy." To be published in Physica C (in press).
Department of Chemstry, Tamkang University, Tamsui, Taiwan 25137,
REPUBLIC OF CHINA.  Key words: La3CaxBa4-xCu7Oy, substitution effect,
high-Tc oxide superconductor, peritectic point, magnetic
susceptibility.Yunhui Xu and Weiyan Guan, "Ion Size Effect on Tc
in RBa2Cu3-xGaxO7-y Systems (R = Er,Y,Dy,Eu, and Nd)." To be
published in Physica C (in press).  Institut fuer Schicht und
Ionentechnik der Forschungszentrum Juelich GmbH, Postfach 1913, W-5170
Juelich, GERMANY.  Key words: substitution, O-T transition, Mott
transition, localization, density of states.G. Yang, P. Shang,
S. D. Sutton, I. P. Jones, J. S. Abell, and C. E. Gough,
"Competing Pinning Mechanisms in Bi2Sr2CaCu2Oy Single Crystals by
Magnetic and Defect Structural Studies." To be published in
Phys. Rev. B.  Superconductivity Research Group, The University of
Birmingham, Edgbaston, Birmingham B15 2TT, UNITED KINGDOM;
C. E. Gough's telephone +44 21 414 4669; telefax +44 21 414 6709;
telex 333762 UOBHAM G.  74.60.Ge; 74.42.Hs.Z. J. Yang, R. A. Dunlap,
and D.J.W. Geldart, "Motion of a Point Dipole in an Infinite Hole
Through a Superconductor." To be published in Phys. Rev. B1.
Department of Physics, Dalhousie University, Halifax B3H 3J5, NS,
CANADA.  Key words: superconductor, Meissner effect, neutron beam.
61.12.Ex; 41.20.Gz; 74.25.Ha; 84.90.+a.Z. J. Yang, D.J.W. Geldart, and
R. A. Dunlap, "Harmonic Oscillation of a Dipole in a Hole Through
a Superconductor." Submitted to the Int. Conf. on
Low-Temp. Phys. (LT20), Eugene, OR, Aug. 4-11, 1993; to be published
in Physica B.  Department of Physics, Dalhousie University, Halifax
B3H 3J5, NS, CANADA.N. Yu, D. Marton, F. Romero-Borja, Z. H. Zhang,
X. T. Cui, J. R. Liu, K. M. Forster, J. W. Rabalais, L. T. Wood,
W. K. Chu, and R. R. Reeber, "Formation of Boron Nitride and
Boron Carbide Composite by Nitrogen Implantation at Elevated
Temperature." Preprint #93:030; submitted to Appl. Phys. Lett.,
May 10, 1993.  Texas Center for Superconductivity, University of
Houston, Houston, TX 77204-5932; telephone (713) 743-8200; telefax
(713) 743-8201.  61.70.Vn.S. L. Yuan, K. Kadowaki, T. Mochiku,
K. Kishio, T. Kimuna, and K. Kitazawa, "Vortex Dynamics Above the
Irreversibility Line in LSCO." Submitted to the Int. Conf. on
Low-Temp. Phys. (LT20), Eugene, OR, Aug. 4-11, 1993.  National
Research Institute for Metals, Tsukuba Laboratories, 1-2-1 Sengen,
Tsukuba 305, JAPAN.  74.70.Vy; 74.60.Ge.ZHOU Guien, SHI Lei, HUANG
Yunlan, YAO Lianzeng, JIA Yunbo, and ZHANG Yuheng, "The
Comparison of Structural Characteristics Between 2212 and 2201 Phases
in the Bi-Sr-Ca-Cu-O System." To be published in Physica C,
Vol. 212 (in press).  Structure Research Laboratory, University of
Science and Technology of China, Academia Sinica, Hefei, Anhui 230026,
PEOPLE'S REPUBLIC OF CHINA.  Key words: Laue photography, 2212-phase
single crystal, 2201-phase single crystal, the difference of the
structural characteristics.COMING EVENTS(An * indicates new
information on a previously listed event.)Sept. 21 - 25, 1993: 5th
International Conference on Nuclear Spectroscopic Studies of Hyperfine
Interactions, Dubna, Russia.  Organized by Joint Institute for Nuclear
Research (JINR), Russian Academy of Sciences, and Moscow State
University.  Topics: hyperfine interactions in atomic and nuclear
physics; hyperfine magnetic fields, electric field gradients, and
electron densities at nuclei in condensed matter; neutronographic
methods, muSR spectroscopy, positron annihilation, etc.; and new
methods and applications.  Call for review and original talks as well
as posters.  Registration deadline, July 1, 1993.  Registration fee,
$200.  Contact Prof. V. S. Shpinel, Institute of Nuclear Physics,
Moscow State U., 119899 Moscow, Russia; telephone +7-95-939-24-97;
telefax +7-95-939-08-96; telex 411483 MGU SU; V. Duginov's e-mail
duginov@main1.jinr.dubna.su.Feb. 27 - March 3, 1994: High-Tc Symposium
at 1994 TMS Annual Meeting, San Francisco, CA.  Symposium to examine
progress and issues in high-temperature superconductor research.
Topics include but are not limited to flux-pinning mechanisms,
processing for high critical-current densities, relationships between
microstructure and properties, phase diagrams, substitution effects,
preparation of new materials, single-crystal growth, and improved
processing of wires, tapes, and bulk.  It is anticipated that
proceedings will be published in special issue of
J. Electron. Materials.  Abstract deadline, Aug. 1, 1993.  Submit
abstracts to Paul J. McGinn, Center for Materials Science and Engr.,
Dept. of Electrical Engr., U. of Notre Dame, Notre Dame, IN 46556;
phone (219) 631-6151; fax (219) 631-4393.Feb. 27 - March 4, 1994: The
Pittsburgh Conf. & Exposition on Analytical Chemistry and Applied
Spectroscopy (Pittcon '94), McCormick Place, Chicago, IL.  Over 200
scientists will present latest technological developments in 33
organized symposia.  Abstract deadline, Aug. 3, 1993.  Contact Alma
Johnson, Program Secretary, The Pittsburgh Conference, 300 Penn Center
Blvd., Suite 332, Pittsburgh, PA 15235-5503; telephone (412) 825-3220;
telefax (412) 825-3224.March 17 - 19, 1994: JFCC International
Workshop on Fine Ceramics '94: Materials Processing and Design: Grain
Boundary Controlled Properties of Fine Ceramics (II), Mikawa Heights,
Koda-Cho, Nukata-Gun, Aichi Pref., Japan.  Aim: to bring together
ceramists, metallurgists, and solid-state physicists involved in
research related to the processing of these materials.  Objective: to
provide a forum for discussion of the potential for improving
processing and design of fine ceramics.  Call for papers on
qualitative and quantitative evaluation of grain boundaries,
mechanical properties limited by grain boundaries, electrical
properties based on grain boundaries, and thermodynamics of grain
boundary phases and intra-grain phases.  Abstract deadline, Aug. 31,
1993.  Proceedings will be published.  Contact Koichi Nihara, ISIR
(Sanken), Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567, Japan;
telephone +81 6-877-5111; telefax +81 6-875-4957.  To register,
contact Secretariat: Noriyuki Kosuge, Japan Fine Ceramics Center,
2-4-1 Mutsuno, Atsuta, Nagoya, 456 Japan; telephone +81 52-871-3500;
telefax +81 52-871-3599.March 29 -31, 1994: Third International
Conference on Multichip Modules, Denver, CO.  Sponsored by
International Electronics Packaging Soc. and International Soc. of
Hybrid Microelectronics.  Program co-chairs, John Nelson (Unisys) and
Phil Garrou (Dow Chemical).  Topics include applications, design and
test, assembly and interconnections, materials, electrical and thermal
performance, structure-type, etc.  Abstract deadline, Nov. 1, 1993.
Send abstracts to ISHM, 1861 Wiehle Ave., Suite 260, Reston, VA 22090.
Or contact William D. Ashman, IEPS, telephone (708) 260-1044.May 22 -
27, 1994: Fullerenes: Chemistry, Physics, and New Directions VI,
Hilton Square Hotel, San Francisco, CA.  Keynote speaker, Robert
Haddon (AT&T Bell Labs), "Without Boundary Conditions:
Chemistry and Physics of Fullerenes." Sponsored by the New
Technology Subcommittee of The Electrochemical Society.  Fullerene
symposium organized with the intention of "providing a forum for
presentation of latest developments on these fascinating new
allotropes of carbon, including nanotubes and nanopoly- hedra."
Organizers welcome papers on new research by scientists who might not
have attended previous symposia.  Organizers welcome attendance by
scientists in former Soviet Union and Baltic States and are asking the
International Science Foundation for support.  Send title and rough
draft of abstract to Rod Ruoff ASAP.  "Please contact and tell
[former Soviet Union/Baltic States] colleagues about our offer to try
to help get them to this meeting."Topics include fundamental
understanding of physical properties and structures, synthesis and
separation, chemical reactions and new derivatives, charge transfer
reactions and electrochemistry, conductivity and superconductivity,
possible applications, and new directions.  Abstract deadline,
Jan. 15, 1994.  Abstracts, suggestions, and inquiries should be sent
to BOTH symposium organizers: (1) Karl M. Kadish, Dept. of Chemistry,
U. of Houston, Houston, TX 77204-5641; telephone (713) 743-2740;
telefax (713) 743-2745; and (2) Rodney S. Ruoff, Molecular Physics
Laboratory, SRI International, 333 Ravenswood Ave., Menlo Park, CA
94025; telephone (415) 859-2667; telefax (415) 859-6196.Dec. 19 - 22,
1994: 1994 International Conference on Electronic Materials (ICEM
1994), Convention Center of Industrial Technology Research Institute
(ITRI), Hsinchu, Taiwan, ROC.  To be held jointly with the
IUMRS-International Conf. in Asia (IUMRS-ICA).  Combined conference
organized by Materials Research Society-Taiwan under auspices of
International Union of Materials Research Societies (IUMRS), sponsored
by various ROC ministries and laboratories of the ITRI.  Program
includes plenary lectures, 10 symposia with invited contributors,
joint session, exhibition, and poster sessions.  Call for papers in
numerous areas, including high-temperature superconductors and
thin-film materials.  Abstract deadline, April 15, 1994.  Contact
conference secretary, Jongq-Min Liu, Materials Research Laboratories,
ITRI, Conference Dept., ICEM '94, Bldg. 77, 195 Chung-hsing Rd.,
Sec. 4, Chutung, Hsinchu 310, Taiwan, ROC; telephone +886 35-820064;
telefax +886 35-820247 or -8320262.RESOURCESInformationNew high-Tc
books: Processing and Properties of High-Tc Superconductors, Vol. 1:
Bulk Materials, edited by Sungho Jin (AT&T Bell Labs).  "The
aim of this book is to offer a comprehensive, state-of-the-art review
of various aspects of processing, properties, and applications of
high-Tc superconductors.  This volume deals mainly with bulk materials
(mostly cuprate superconductors, with a chapter devoted to the new
K3C60-type superconductors); thin-film materials, device fabrications,
and other aspects will be included in later volumes." 11
chapters: by R. J. Cava, L. F. Schneemeyer, D. T. Shaw and S. Jin,
K. Sato, K. Salama et al., M. Murakami, R. D. Blaugher, L. Civale,
J. W. Ekin, D. W. Murphy et al., and S. Jin and C. W. Chu.  Topics
include synthesis and crystal chemistry, ceramic processing and wire
fabrication, melt processing, thallium-oxide superconductors,
preparing low-resistivity contacts, status and prospects in bulk
processing, etc.  Publ., 1993; ISBN 981-02-1165-1; 482 pp.; cost,
$98.00.  Electrodynamics of High-Temperature Superconductors, Vol. 48:
Lecture Notes in Physics, by Alan M. Portis (Dept. of Physics, U. of
California at Berkeley).  "These lecture notes are concerned with
the application of high-temperature superconductors to passive and
active high-frequency devices.  The central issue addressed is the
electrodynamics of granular superconductors, particularly where grain
boundaries (either natural or synthetic) act as Josephson weak links.
Grain boundaries are responsible for residual dissipation and for a
dependence of the electromagnetic properties on ambient magnetic field
and on elevated power level.  Properly controlled, synthetic grain
boundaries may be the key to high sensitivity dc and rf SQUIDs at
accessible temperatures, and to modulators, mixers, and detectors.
Such structures may lead to superconductive electronic devices as well
as to coherent sources of radiation in the very far infrared." 15
chapters.  Publ. 1993; ISBN 981-02-12151-1, hard cover cost, $68.00;
ISBN 981-02-1248-8 paperback cost, $28.00; 247 pp.  For both books,
contact World Scientific Publishing Co., Inc., Suite IB, 1060 Main
St., River Edge, NJ 07661; telephone (800) 227-7562 or (201) 487-9655;
telefax (201) 487-9656.  In Europe, World Scientific Publishing
Co. Pte. Ltd., 73 Lynton Mead, Totteridge, London N20 8DH, England;
telephone +44 (81) 4462461; telefax +44 (81) 4463356.  In Asia, World
Scientific Publishing Co. Pte. Ltd., Farrer Road, P.O. Box 128,
Singapore 9128; telephone +65 3825663; telefax +65 3825919; telex RS
28561 WSPC; cable COSPUB.You're invited: Nova Science Publishers
welcomes ideas for new articles, books, book series, and journals.  If
you have an interest in learning more about their publishing program
or would like to propose a new publication, contact Frank Columbus,
Editor-in-Chief, Nova Science Publishers, Inc., 6080 Jericho Turnpike
- Suite 207, Commack, NY 11725; telephone (516) 499-3103; telefax
(516) 499-3146; e-mail Novasci1@aol.com.Products and Services9 tesla
system: Lake Shore introduces a new 9-tesla ac susceptometer/dc
magnetometer system, "the most comprehensive magnetic property
characterization system available today." Model 7229 provides for
measurement of ac susceptibility as a function of temperature, ac
field amplitude, and frequency.  Provides superior low-field ac
measurement capability and sensitivity (better than 2 x 10^[-8] emu).
Also has capability of performing ac measurements in conjunction with
dc bias fields (up to += 9 tesla) for study of field-induced
transitions, etc.  In dc moment measurement mode, provides for
sensitivity levels to 5 x 10^[-5] emu, with effective dynamic range
beyond 10^3 emu.  Contact Lake Shore Cryotronics, 64 East Walnut St.,
Westerville, OH 43081-2399; telephone (614) 891-2243; telefax (614)
891-1392.HYPRES chips: HYPRES has program offering 4 free chip sites
of 5 mm x 5 mm in a 10-level niobium technology.  Program is offered
on a mask-sharing basis; hence, the current density requirement for
all designs must be the same.  Standard Jc is 1000 A/cm^2, although
other Jc's are run on occasion.  Mask set is released on average every
6 weeks.  Chips are routinely delivered to customers 2.5 weeks after a
mask release.  Minimum junction size is 3 microns; minimum line width
is 2 micrometer.  Resister level is 1 ohm/sq.  HYPRES offers
individual sites at a very low cost as well.  Contact Edwin J. Hill,
V.-P. of Operations, HYPRES, Inc., 175 Clearbrook Road, Elmsford, NY
10523; telephone (914) 592-1190, ext. 7822; telefax (914)
347-2239.Helium meter: American Magnetics, Inc., announces Model 150A
portable/battery operated liquid helium level meter.  Light-weight,
hand-held meter for use with helium storage dewars on loading docks
and storage rooms or in remote helium level operations where line
power is unavailable.  Ability to measure helium level sensors with
active lengths of up to 60"; also, battery life for over 1,000
level readings.  Include 3.5 digit LCD display with readout accuracy
of 0.1%.  Rechargable batteries.  Contact American Magnetics, Inc.,
P.O. Box 2509, Oak Ridge, TN 37831-2509; phone (615) 482-1056; telefax
(615) 482-5472; telex
557-592.---------------------------------------------------------------------High-Tc
Update is the high-Tc superconductivity information exchange
newsletter.  Please send 1) preprints, reprints, and other research
reports; 2) descriptions of on-going work; 3) meeting announcements
and summaries.  Your preprint abstracts will be forwarded to OSTI for
inclusion in the SIS data base, unless you request otherwise.The
information contained herein is intended for limited distribution.
Readers are expected to respect the rights of the authors.Please
address all contributions and inquiries to:Dr. Ellen O. Feinberg, A219
Physics, Ames Laboratory/Iowa State University, Ames, Iowa 50011-3020.
Telephone: (515) 294-3877.  Telefax: (515) 294-1134.  Telex: 269266.
E-mail: FEINBERGE@VAXLD.AMESLAB.GOV or
FEINBERG@ALISUVAX.BITNET. Project Director/Editor: Ellen O. Feinberg.
Science Editor: John R. Clem High-Tc Update, Vol. 7, #12, June 15,
1993.---------------------------------------------------------------------