Magnetic field and pressure effects on charge density wave, superconducting, and magnetic states in Lu5_5Ir4_4Si10_{10} and Er5_5Ir4_4Si10_{10}

We have studied the charge-density-wave (CDW) state for the superconducting Lu$_5$Ir$_4$Si$_{10}$ and the antiferromagnetic Er$_5$Ir$_4$Si$_{10}$ as variables of temperature, magnetic field, and hydrostatic pressure. For Lu$_5$Ir$_4$Si$_{10}$, the application of pressure strongly suppresses the CDW phase but weakly enhances the superconducting phase. For Er$_5$Ir$_4$Si$_{10}$, the incommensurate CDW state is pressure independent and the commensurate CDW state strongly depends on the pressure, whereas the antiferromagnetic ordering is slightly depressed by applying pressure. In addition, Er$_5$Ir$_4$Si$_{10}$ shows negative magnetoresistance at low temperatures, compared with the positive magnetoresistance of Lu$_5$Ir$_4$Si$_{10}$.Comment: 12 pages, including 6 figure

Superconductivity in the two dimensional Hubbard Model.

Quasiparticle bands of the two-dimensional Hubbard model are calculated using the Roth two-pole approximation to the one particle Green's function. Excellent agreement is obtained with recent Monte Carlo calculations, including an anomalous volume of the Fermi surface near half-filling, which can possibly be explained in terms of a breakdown of Fermi liquid theory. The calculated bands are very flat around the (pi,0) points of the Brillouin zone in agreement with photoemission measurements of cuprate superconductors. With doping there is a shift in spectral weight from the upper band to the lower band. The Roth method is extended to deal with superconductivity within a four-pole approximation allowing electron-hole mixing. It is shown that triplet p-wave pairing never occurs. Singlet d_{x^2-y^2}-wave pairing is strongly favoured and optimal doping occurs when the van Hove singularity, corresponding to the flat band part, lies at the Fermi level. Nearest neighbour antiferromagnetic correlations play an important role in flattening the bands near the Fermi level and in favouring superconductivity. However the mechanism for superconductivity is a local one, in contrast to spin fluctuation exchange models. For reasonable values of the hopping parameter the transition temperature T_c is in the range 10-100K. The optimum doping delta_c lies between 0.14 and 0.25, depending on the ratio U/t. The gap equation has a BCS-like form and (2*Delta_{max})/(kT_c) ~ 4.Comment: REVTeX, 35 pages, including 19 PostScript figures numbered 1a to 11. Uses epsf.sty (included). Everything in uuencoded gz-compressed .tar file, (self-unpacking, see header). Submitted to Phys. Rev. B (24-2-95

Pan-cancer Alterations of the MYC Oncogene and Its Proximal Network across the Cancer Genome Atlas

Although the MYC oncogene has been implicated in cancer, a systematic assessment of alterations of MYC, related transcription factors, and co-regulatory proteins, forming the proximal MYC network (PMN), across human cancers is lacking. Using computational approaches, we define genomic and proteomic features associated with MYC and the PMN across the 33 cancers of The Cancer Genome Atlas. Pan-cancer, 28% of all samples had at least one of the MYC paralogs amplified. In contrast, the MYC antagonists MGA and MNT were the most frequently mutated or deleted members, proposing a role as tumor suppressors. MYC alterations were mutually exclusive with PIK3CA, PTEN, APC, or BRAF alterations, suggesting that MYC is a distinct oncogenic driver. Expression analysis revealed MYC-associated pathways in tumor subtypes, such as immune response and growth factor signaling; chromatin, translation, and DNA replication/repair were conserved pan-cancer. This analysis reveals insights into MYC biology and is a reference for biomarkers and therapeutics for cancers with alterations of MYC or the PMN. We present a computational study determining the frequency and extent of alterations of the MYC network across the 33 human cancers of TCGA. These data, together with MYC, positively correlated pathways as well as mutually exclusive cancer genes, will be a resource for understanding MYC-driven cancers and designing of therapeutics

LOW TEMPERATURE HEAT CAPACITY OF NONMAGNETIC RARE EARTH MOLYBDENUM CHALCOGENIDES

Nous rapportons les mesures de la chaleur spécifique des composés ternaires supraconducteurs Mo6X8 (M=La, Lu,Y, Sc ; X=S, Se). La théorie de Debye décrit bien la chaleur spécifique de la plupart de ces ternaires . Pour YMo6S7 et Lu1.2Mo6S8 la présence d'un pic d'Einstein dans le spectre des phonons est indiquée par une déviation par rapport à la théorie de Debye.We report specific heat measurements between 1K and 14K for the superconducting ternary compounds MMo6X8 where M=La, Lu, Y, Sc and X=S, Se. The lattice contribution to the heat capacity of most of these ternaries is described well by a modified Debye model ; however, for YMo6S7, and Lu1.2Mo6S8, the presence of an Einstein peak in the phonon spectrum is indicated by a marked departure from Debye-type behavior

LOW TEMPERATURE SPECIFIC HEAT OF THE MAGNETIC SUPERCONDUCTOR Gd1.0Mo6Se8

Des mesures de chaleur spécifique du composé supraconducteur (Tc= 5,8K)Gd1,0Mo6Se8 sont présentées pour un domaine de température 0,l K ≤ T ≤ 4,0 K et des champs appliqués 0 ≤ H ≤ 18 kOe. L'entropie associée à un important pic à 0,75 K et H = 0 indique que les spins Gd3+ s'ordonnent bien que le composé reste supraconducteur. La chaleur spécifique dépend fortement du champ appliqué.Measurements of the specific heat of the superconductor (Tc=5.8 K)Gdl,0Mo6Se8 are reported for the temperature range 0.1 K ≤ T ≤ 4.0 K with applied magnetic fields of O ≤ H ≤ 18 kOe. The entropy associated with a large peak at 0.75 K for H = 0 indicates that the Gd3+ spins become ordered even though the material remains superconducting. The specific heat is strongly affected by an applied field