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A brief review is given of recent progress in growing bulk crystals of mercuric iodide from the vapour phase. Two topics in particular are discussed in more detail: (a) kinetics of the growth; (b) perfection of the crystals.

Abstract: The influence of a transport current on the magnetic flux-line distribution in sintered YBCO was studied by means of μSR. Pronounced differences between zero-field-cooled (ZFC) and field-cooled (FC) signals and irreversible behavior were observed. In the ZFC case even a small transport current (10 A/cm2) tends to orderirreversibly the inhomogeneous flux-line distribution considerably, suggesting a broad distribution of pinning barriers. However, for a FC sample no noticeable change in the flux distribution in the presence of a transport current (up to 40 A/cm2) was detected, indicating that the FC state represents a stable flux-line configuration.

Abstract: A systematic μSR study of the local magnetic field distribution in a series of oxygen deficient YBa2Cu3O x samples with 6.5⩽x⩽7.0 is reported. Special attention was given to perform the experiments under the same conditions, so that the oxygen content of the measured samples was the only parameter varied. The behavior of the depolarization rate σ as a function of the oxygen contentx was found to have strong similarities with the behavior of the critical temperatureT c as a function ofx. In particular, two step-like increases of σ were observed abovex=6.7 and 6.9. The temperature dependence of the normalized depolarization rate σ(T)/σ(0) is well described by the two-fluid model forx⩾6.781(1) and clearly deviates from this behavior forx⩽6.704(1). Our results are compared to those obtained by other groups.

We report a far-infrared reflectivity study of DyBa2Cu4O8, HoBa2Cu4O8 and Y2Ba4Cu7O15-d superconductors in the temperature range 10–300 K. The assignment of thez-polarized infrared-acitve vibrations of the rare-earth-ion (R) was verified by the substitution ofR. Since the structure of the Y2Ba4Cu7O15-d compound inz-direction is an ordered sequence of YBa2Cu3O7-d and YBa2Cu4O8 blocks, the phonon spectrum of Y2Ba4Cu7O15-d is a superposition of their respective phonon modes. The temperature dependence of the infrared-active phonons in RBa2Cu4O8 and Y2Ba4Cu7O15-d was analyzed. A narrowing of the plane-oxygen phonon upon sample cooling was found to occur atTc, as it was reported for single-chain YBa2Cu3O7 materials; however a pronounced frequency softening of this mode for both RBa2Cu4O8 and Y2Ba4Cu7O15-d was found to start well aboveTc, suggesting the interaction of infrared-active phonons with an excitation gap similar to that observed in spin-dependent measurements.

By means of a quantitative analysis of extensive elastic neutron scattering experiments performed on theTc=78 K superconductor DyBa2Cu4O8 it is shown that two-dimensional (2D) antiferromagnetic Dy ordering in the (a,b)-plane remains stable in the whole temperature range fromTN=(1.10±0.02) K down to 7 mK. The magnetic difference pattern with good angular resolution fits well to the Warren equation for scattering on 2D systems with powder averaging. Consequently, the fitted sublattice magnetisation is found to have a 2D Ising character. Moreover, the Dy3+ crystal-field levels were determined by inelastic neutron scattering. From the resulting crystal-field parameters we calculate the sublattice magnetisation of Dy3+ at saturation to beµDy,CEF=6.0µB in good agreement withµDy,obs=(5.9±0.5)µB as measured by neutron diffraction.

The majority of sudden cardiac deaths in children occur in patients with prior arrhythmias and an abnormal heart. Amiodarone was given to 39 young patients (35 with an abnormal heart) with arrhythmias unresponsive to conventional treatment. Their age ranged from 6 weeks to 30 years with nine patients younger than 2 years of age. Atrial flutter was present in 16 patients, ventricular tachycardia in 14 patients and supraventricular tachycardia in 9 patients. The most common diagnosis (14 patients) was postoperative repair of congenital heart disease. The dose ranged from 2.5 to 21.6 mg/kg per day (mean 8.2).

We report on the electronic Raman scattering in YBa2Cu4O8 and find that, In contrast to the other superconducting cuprates, the continuum in the normal state is strongly temperature ?pendent in all polarizations. This temperature dependence is found to follow a Bose-Einstein-like form. We conclude that the absence of the Bose-Einstein factor in the electronic continuum is not essential to high-Tc superconductivity, as is sometimes implied. Additionally, we report on the rearrangement of the continuum which occurs belowTc.

Edward N. Luttwak, The Grand Strategy of the Soviet Union. With Appendices by Herbert Block and W. Seth Carus. New York: St. Martin's Press, 1983. 241 pp.Bogdan Mieczkowski and Oleg Zinam, Bureaucracy, Technology, Ideology: Quality of Life East and West. Charleston, Ill.: Association for the Study of the Nationalities in USSR and Eastern Europe, 1984. xiii, 463 pp. Paper.Theodore Freedman, ed., Anti-Semitism in the Soviet Union: Its Roots and Consequences. New York, N. Y.: Freedom Library Press of the Anti-Defamation League of the B'nai B'rith, 1984. 664 pp.Alexander Orbach, New Voices of Soviet Jewry : A Study of the Russian-Jewish Press of Odessa in the Era of the Great Reforms, 1860-1871. Leiden: Brill, 1980. xiv, 289 pp.Victor Zaslavsky and Robert J. Brym, Soviet-Jewish Emigration and Soviet Nationality Policy. New York: St. Martin's Press, 1983. vii, 185 pp.Jakub Blum and Vera Rich, The Image of the Jew in Soviet Literature: The Post-Stalin Period. New York: Ktav [for the Institute of Jewish Affairs, London], 1985. 276 pp.Jack Miller, ed., Jews in Soviet Culture. Transaction Books: New Brunswick and London, 1984. 325 pp.Rex Wade, Red Guards and Workers' Militias in the Russian Revolution, Stanford: Stanford University Press, 1984. 391 pp.Michael Bruchis, Nations - Nationalities - People: A Study of the Nationalities Policy of the Communist Party in Soviet Moldavia. Boulder, CO: East European Monographs, New York, 1984. 230 pp. Distributed by Columbia University Press.Ukrainskyi istoryk [The Ukrainian Historian]. U piatdysiatelittia smerty M. Hrushevskoho [On the Fiftieth Anniversary of the Death of M. Hrushevskyi]. New York, Toronto, and Munich: Ukrainian Historical Association. 1978. Vol. XXI, nos. 1-4 (81-84). 316 pp.Teresa Rakowska-Harmstone, ed., Communism in Eastern Europe, Second edition. Bloomington: Indiana University Press, 1984. viii, 391 pp. Paper.Michael J. Sodaro and Sharon L. Wolchik, eds., Foreign and Domestic Policy in Eastern Europe in the 1980s. New York: St. Martin's Press, 1983.265 pp.John F. N. Bradley, Czech Nationalism in the Nineteenth Century, Boulder, CO: East European Monographs, 1984. 200 pp. Distributed by Columbia University Press.Bogdan Szajkowski, Next to God ... Poland: Politics and Religion in Contemporary Poland. New York: St. Martin's Press, 1983. x, 264 pp.Alex N. Dragnich. The First Yugoslavia: Search for a Viable Political System. Stanford: California: Hoover Institution Press, 1983, 182 pp.Theodore George Tatsios, The Megali Idea and the Greek-Turkish War of 1897: The Impact of the Cretan Problem on Greek Irredentism, 1866-1897. Boulder, CO: East European Monographs, 1984. ix, 302 pp. Distributed by Columbia University Press.Justin McCarthy. Muslims and Minorities. The Population of Ottoman Anatolia at the End of the Empire. New York and London: New York University Press, 1983. $35.00.M. Mark Stolarik, Growing Up On The South Side: Three Generations of Slovaks in Bethlehem, Pennsylvania 1880-1976 Lewisburg: Bucknell University Press, 1985, 129 pp.

The interaction of oxygen with the high-temperature superconducting oxides is very important because several phenomena that influence the superconducting properties, such as the orthorhombic to tetragonal phase transformation, are dependent on the oxygen stoichiometry. In spite of this, many of the basic thermodynamic pressure data remain unpublished. The existing information indicates that the decomposition of YBa2Cu3O7–xstarts at T = 400 °C at Po2= 1 bar (ref. 1), and that the compound melts incongruently2. Pressure data and corresponding melting points are therefore needed, to ascertain if it is possible to change the phase diagram at higher oxygen pressures so that the compound melts congruently. If this were feasible, then the growth of large single crystals from a stoichiometric melt could be possible. Here we present the equilibrium oxygen pressure curve for the YBa2Cu3O7±xdecomposition (P–T phase diagram) up to 2,200 bar and 1,200 °C. To construct the three-dimensional P–T–x phase diagram of the pseudo-binary system O2–YBa2Cu3O7±x, we have also developed methods for measuring the T–x diagram at high pressure, and we present the first data at 10 bar oxygen pressure.

In the course of a systematic optimization of the materials properties of α-HgI2 crystals for room temperature γ- and X-ray detectors, we have investigated possible sources of defects and discuss briefly the possibility to supress them. Due to the particular structure of α-HgI2, large amount of impurities, particularly hydrocarbons, can be absorbed invan der Waals layers and lattice channels. Purification by sublimation does not work due to the affinity of hydrocarbons to iodine and their easy re-absorption in the sublimate. “Lattice filtering” of the large concentration of hydrocarbons contained even in “suprapure” iodine has been performed using the close spaced lattice of CuI. Oxidation of hydrocarbons by reaction of oxygen with HgI2 is another possibility for their removal.

The results of studies of the pressure dependence of the structures of YBa2Cu4O8 and La1·85Sr0·15CuO4 are presented. Comparison with the changes observed on oxidation of YBa2Cu3O7-δ show that the large dTc/dp in YBa2Cu4O8 can be attributed to charge transfer. By contrast the the behaviour of La1·85Sr0·15CuO4 shows no evidence of charge transfer.

Cell cycle progression is controlled by the sequential functions of cyclin-dependent kinases (cdks). Cdk activation requires phosphorylation of a key residue (on sites equivalent to Thr-160 in human cdk2) carried out by the cdk-activating kinase (CAK). Human CAK has been identified as a p40(MO15)/cyclin H/MAT1 complex that also functions as part of transcription factor IIH (TFIIH) where it phosphorylates multiple transcriptional components including the C-terminal domain (CTD) of the large subunit of RNA polymerase II. In contrast, CAK from budding yeast consists of a single polypeptide (Cak1p), is not a component of TFIIH, and lacks CTD kinase activity. Here we report that Cak1p and p40(MO15) have strikingly different substrate specificities. Cak1p preferentially phosphorylated monomeric cdks, whereas p40(MO15) preferentially phosphorylated cdk/cyclin complexes. Furthermore, p40(MO15) only phosphorylated cdk6 bound to cyclin D3, whereas Cak1p recognized monomeric cdk6 and cdk6 bound to cyclin D1, D2, or D3. We also found that cdk inhibitors, including p21(CIP1), p27(KIP1), p57(KIP2), p16(INK4a), and p18(INK4c), could block phosphorylation by p40(MO15) but not phosphorylation by Cak1p. Our results demonstrate that although both Cak1p and p40(MO15) activate cdks by phosphorylating the same residue, the structural mechanisms underlying the enzyme-substrate recognition differ greatly. Structural and physiological implications of these findings will be discussed.

A new high precision investigation of the unit cell geometry as a function of the oxygen content is presented for YBa2Cu3O6+x. The differences from earlier work by other groups are (a) the use of “near-equilibrium,” i.e., not quenched but very slowly cooled samples; (b) the use of high accuracy volumetric oxygen determination; and (c) the large number of compositions investigated (36 in the range of 0.5

Cell cycle progression is controlled by the sequential functions of cyclin-dependent kinases (cdks). Cdk activation requires phosphorylation of a key residue (on sites equivalent to Thr-160 in human cdk2) carried out by the cdk-activating kinase (CAK). Human CAK has been identified as a p40MO15/cyclin H/MAT1 complex that also functions as part of transcription factor IIH (TFIIH) where it phosphorylates multiple transcriptional components including the C-terminal domain (CTD) of the large subunit of RNA polymerase II. In contrast, CAK from budding yeast consists of a single polypeptide (Cak1p), is not a component of TFIIH, and lacks CTD kinase activity. Here we report that Cak1p and p40MO15have strikingly different substrate specificities. Cak1p preferentially phosphorylated monomeric cdks, whereas p40MO15preferentially phosphorylated cdk/cyclin complexes. Furthermore, p40MO15only phosphorylated cdk6 bound to cyclin D3, whereas Cak1p recognized monomeric cdk6 and cdk6 bound to cyclin D1, D2, or D3. We also found that cdk inhibitors, including p21CIP1, p27KIP1, p57KIP2, p16INK4a, and p18INK4c, could block phosphorylation by p40MO15but not phosphorylation by Cak1p. Our results demonstrate that although both Cak1p and p40MO15activate cdks by phosphorylating the same residue, the structural mechanisms underlying the enzyme-substrate recognition differ greatly. Structural and physiological implications of these findings will be discussed.

The transition temperature of YBa₂Cu₄O₈ (124) is increased by about 10 K by doping with calcium, whereas Ca substitution in Y₂Ba₄Cu₇O_14+x (247) has no effect on T_c. X-ray structure refinements of 13 YBa₂Cu₄O₈ and 12 Y₂Ba₄Cu₇O_14+x Ca-doped and undoped single crystals have been performed in order to determine structural changes due to Ca doping. In 124 a major fraction of Ca replaces Y; in 247 Ba1 (single-chain 123 unit) and Y are substituted by Ca in the ratio 3:2. The changes of the charge distribution caused by the substitution of trivalent Y³⁺ by divalent Ca²⁺ and ion size effects lead to structural changes in Ca-doped crystals. One structural consequence of the replacement of the small Y (r = 1.02 Å) by the larger Ca (r = 1.12 Å) is the increase of the distance between the adjacent oxygen planes in the c direction. In 247 the 123 unit is compressed due to the substitution of Ba1 by the smaller Ca. Ca doping diminishes the buckling of the CuO₂ superconducting layers. The Ba-O sublattices in the double-chain 124 units of 247 and 124 are identical and change in the same way upon Ca doping; differences are observed in the Ba-Y sublattice. Copyright 1994, 1999 Academic Press

It has long been believed that Cdk2 and its activator cyclin E play essential roles in the progression of the mitotic cell cycle. However, recent studies using knockout mouse models revealed that neither Cdk2 nor cyclin E are essential in vivo. The purpose of this mini-review is to compare both Cdk2 and cyclin E knockout mice models and to discuss potential mechanisms driving the cell cycle in the absence of Cdk2 or cyclin E. Particular emphasis is placed on possible non-catalytic roles of cyclin E, the expression and activity of the second cyclin binding partner of Cdk2, cyclin A, as well as on the expression and degradation of the Cdk2 inhibitor p27Kip1 in the absence of Cdk2.

Thermolysis of a mixture of [(η⁵-C5Me5)W(CO)3(CCPh)] and [Fe3(CO)9(μ3-Se)2] in toluene solvent at 90 °C in air yields the unusual diselenaoxoacetylide compound [(η⁵-C5Me5)W(O)(Se2)(CCPh)] (1). When the same reaction is carried out under nitrogen atmosphere, the pentaselenaacetylide compound [(η⁵-C5Me5)W(Se2)(Se3CCPh)] (2) and the previously reported cluster [(η⁵-C5Me5)2W2Fe3(CO)6(μ3-Se)2(μ4-CC(Ph)C(Ph)C] (3) are formed. Structures of 1 and 2 have been established crystallographically.

A new superconducting phase has been identified during measurements of the pressure–temperature–composition phase diagram of the pseudobinary system YBa2Cu3O6+x–O2(ref. 1). The new phase has formula unit Y2Ba4Cu7O14+x. Preliminary crystallographic results from electron diffraction showed a doubling of the c-axis1. Here we report the results of a single-crystal X-ray structural study and measurements of superconductivity in the new compound. The superconducting onset, from a.c. susceptibility measurements, is ˜40 K. The structure (space group Ammm) consists of single YBa2Cu3O6+x-type blocks containing single corner-sharing CuO4square-planar chains, alternating with single YBa2Cu4O8-type blocks containing double edge-sharing CuO4square-planar chains. This suggests the possibility of similar compounds with other ordered sequences of single and double chains.

A systematic study of the characteristic Raman active phonons due to the vibrations of the oxygen atoms (out-of-phase, in-phase of O2,3 and apex) has been carried out in the YBa2Cu3O6+xsuperconductor, with varying and very well defined amount of oxygen and with site selective substitution by 18O. The anharmonic behaviour of the three oxygen modes is examined as a function of the oxygen concentration and compared with previously published work. The association of the new modes which appear at low doping with the oxygen vibrations is delineated by the isotopic substitution. From the evolution of the spectral characteristics with oxygen content, the existence of other phases is investigated. Finally, a novel characteristic which appears in the spectra beyond optimum doping is discussed.

Measurements of the total oxygen isotope shift α0and the condensate density of nof YBa2Cu3Ox(6.53 < x < 6.99) are presented. The Tc(n) dependence exhibits a two-plateau behavior which is associated with the ortho-I and ortho-II phase, respectively. Around optimum doping (x≅6.9) and at the onset of the 60 K plateau where Tconly weakly depends on nthe small α0≅ 0.025 is associated to changes in the phonon spectrum. A further decrease of Tcleads to a rapid increase of α0∝ ∂Tc/∂nsuggesting that α0is related to a change of the condensate density nupon isotope exchange.

The superconducting phase YBa2Cu4O8('124') differs from YBa2Cu3O7('123') in having a double, instead of single, Cu–O chain running parallel to the b axis. It was first observed as a lattice defect in partly decomposed 123 powders1, and then as an ordered defect structure in inhomogeneous 123 thin films2,3, but has not up to now been synthesized in bulk. As part of a systematic study of the pressure–temperature–composition phase diagram of pseudo-binary Y–Ba–Cu–O systems at high oxygen pressure4,5, we have determined the approximate field of thermodynamic stability of the 124 phase. Here we report synthesis of the phase in bulk at 400 bar O2and 1,040 °C. In agreement with previous measurements in thin films, the transition temperature is 81 K. Unlike the 123 compound, the oxygen content in 124 is thermally stable up to 850 °C, which may prove important for applications.

We have measured resistivity and magnetic susceptibility of Y2Ba4Cu6+nO14+n (n=0,1,2) on bulk material and single crystals as well. We have found a pressure dependence of dTc/dp within the range of 0.05 to 0.55 K/kbar depending on the symmetry.

A micro-Raman systematic spectroscopic study at room temperature has been carried out on YBa2Cu3Ox polycrystalline compounds in the whole range from the antiferromagnetic insulating to the metallic state (6

A room temperature micro-Raman spectroscopic study at hydrostatic pressures up to 4GPa has been carried out on Y1−xCaxBa2Cu3O7−δ polycrystalline superconducting compounds with x = 0.00–0.20 and δ = 0.045-0.005. Apart from the five strong Raman active phonons (4Ag + 1B1g-like), additional structures have been observed in the y(cc)y (402 cm−1) and the y(xx)y (300 and 322 cm−1) scattering configurations with increasing intensities with the Ca content. The modes that appear in the out-of-phase B1g phonon of Opl are related to the disorder introduced by the Ca substitution for Y and to a local mode induced by the Ca atoms. The variation, with x, of the relative intensities of the constituent peaks of the Opl in-phase phonon indicates that this phonon behavior depends on the amount of oxygen and not the concentration of the Ca substitution introduced carriers. There seem to exist two oxygen content differentiated phases which are present also in the pure oxygen overdoped YBCO. The insensitivity of the Opl in-phase mode frequency combined with the behavior of the Oapex phonon, can be attributed to the excess charge distribution away from the CuO2 planes. A phase separation seems to be induced for hydrostatic pressures above 3GPa possibly related to the Ca atom cluster formation.

We have measured the optical reflectivity of La1.85Sr.15CuO4, La2CuO4and of related materials such as CuO and NaCuO2. Comparing the obtained spectra we point out the mixed valence nature of these new high Tcsuperconductors.

The valence of Tm in TmSe and its alloys has been controlled: by variation of non-stoichiometry between 3.0 + and 2.71 + ; by variation of composition in the new mixed crystal series TmSe1−xTexand Tm1−xEuxSe between 3.0 + and 2.0 + . In TmSe1−xTexpressure induced phase transitions are found during pulverization. The phase diagrams of these compounds show several phase transitions at high temperatures.

Microcrystallites of the series of YBa2Cu3Oxsuperconductors with oxygen doping in the range 6.44≤x6.98 have been studied by Raman spectroscopy at low temperatures. The abrupt softening of the O(2,3) in-phase phonon above optimum doping, previously reported at room temperature persists to the lowest temperatures studied (∼5K). The dependence of the linewidth of this mode on the oxygen concentration at low temperatures agrees, in general, with the already known room temperature dependence, except at the optimum doping where the phonon remains very wide, an indication of a phase transition. The temperature dependence of the phonon characteristics of the in-phase plane oxygen mode indicate an anharmonic behaviour which increases with decreasing x, in agreement with previously reported data at room temperature obtained with oxygen isotopic substitution. A similar anharmonicity but to a lesser degree is also observed for the apical phonon.