3D-2D crossover in the naturally layered superconductor (LaSe)1.14(NbSe2)

The temperature and angular dependencies of the resistive upper critical magnetic field $B_{c2}$ reveal a dimensional crossover of the superconducting state in the highly anisotropic misfit-layer single crystal of (LaSe)$_{1.14}$(NbSe$_2$) with the critical temperature $T_c$ of 1.23 K. The temperature dependence of the upper critical field $B_{c2\parallel ab}(T)$ for a field orientation along the conducting $(ab)$-planes displays a characteristic upturn at 1.1 K and below this temperature the angular dependence of $B_{c2}$ has a cusp around the parallel field orientation. Both these typical features are observed for the first time in a naturally crystalline layered system.Comment: 7 pages incl. 3 figure

Mechanism of KMT5B haploinsufficiency in neurodevelopment in humans and mice.

Pathogenic variants in KMT5B, a lysine methyltransferase, are associated with global developmental delay, macrocephaly, autism, and congenital anomalies (OMIM# 617788). Given the relatively recent discovery of this disorder, it has not been fully characterized. Deep phenotyping of the largest (n = 43) patient cohort to date identified that hypotonia and congenital heart defects are prominent features that were previously not associated with this syndrome. Both missense variants and putative loss-of-function variants resulted in slow growth in patient-derived cell lines. KMT5B homozygous knockout mice were smaller in size than their wild-type littermates but did not have significantly smaller brains, suggesting relative macrocephaly, also noted as a prominent clinical feature. RNA sequencing of patient lymphoblasts and Kmt5b haploinsufficient mouse brains identified differentially expressed pathways associated with nervous system development and function including axon guidance signaling. Overall, we identified additional pathogenic variants and clinical features in KMT5B-related neurodevelopmental disorder and provide insights into the molecular mechanisms of the disorder using multiple model systems

Mechanism of KMT5B haploinsufficiency in neurodevelopment in humans and mice.

Pathogenic variants in KMT5B, a lysine methyltransferase, are associated with global developmental delay, macrocephaly, autism, and congenital anomalies (OMIM# 617788). Given the relatively recent discovery of this disorder, it has not been fully characterized. Deep phenotyping of the largest (n = 43) patient cohort to date identified that hypotonia and congenital heart defects are prominent features that were previously not associated with this syndrome. Both missense variants and putative loss-of-function variants resulted in slow growth in patient-derived cell lines. KMT5B homozygous knockout mice were smaller in size than their wild-type littermates but did not have significantly smaller brains, suggesting relative macrocephaly, also noted as a prominent clinical feature. RNA sequencing of patient lymphoblasts and Kmt5b haploinsufficient mouse brains identified differentially expressed pathways associated with nervous system development and function including axon guidance signaling. Overall, we identified additional pathogenic variants and clinical features in KMT5B-related neurodevelopmental disorder and provide insights into the molecular mechanisms of the disorder using multiple model systems

LOW DIMENSIONAL CONDUCTORS : A NEW SERIES OF TRANSITION METAL TETRACHALCOGENIDES (MX_4)_nY (M = Nb, Ta ; X = S, Se ; Y = halogen) : STRUCTURAL DETERMINATIONS AND PHYSICAL PROPERTIES(EXPERIMENTS ON (MX_4)_nY COMPOUNDS, International Symposium on NONLINEAR TRANSPORT AND RELATED PHENOMENA IN INORGANIC QUASI ONE DIMENSIONAL CONDUCTORS)

この論文は国立情報学研究所の電子図書館事業により電子化されました。In studies concerning low-dimensional conductors, the chemist plays an important role. He has to prepare new materials taking in account some structural rules and ionicity structure relationship about the relative stability of atomic fibers or slabs in a given structure. Then he has to look for new polytypes associating in different ways the same slabs or fibers. He can also act upon the lateral bonds which link chains together, thus modifying the real dimensionality of the compounds. Finally, he also has to be concerned with the depinning of C.D.W. because the depinning field is impurity or defect dependent (defects being created by irradiation technique). In this paper, I would like to illustrate these points with some materials elaborated in our group at NANTES University. I will briefly remind you some aspects concerning trichalcogenides before presenting a new class of materials, the halogened tetrachalcogenides of transition metal (MX_4)_nY

Structures of misfit layer compounds (MS)nTS2 (M Sn, Pb, Bi, rare earth metals; TNb, Ta, Ti, V, Cr; 1.08<n<1.23)

Misfit layer compounds (MS)(n)TS2 (M = Sn, Pb, Bi, rare earth metals; T = Nb, Ta, Ti, V, Cr; 1.08 <n <1.23) are built of alternate double layers of MS, actually a distorted {001} slice of f.c.c. MS (for some compounds hypothetical), and sandwiches of TS2, with atoms T = Nb, Ta in slightly distorted trigonal prisms of sulphur atoms (as in the parent compounds 2H-NbS2 and 2H-NbS2 and 2H-TaS2) and atoms T = Ti, V, Cr in trigonal antiprisms of sulphur atoms (e.g. as in 1T-TiS2). The MS and TS2 subsystems have a different geometry in the a-b plane, the stacking direction being c. The MS lattice is approximately quadratic (a1 almost-equal-to b1 in the range 5.4-6.1 congruent-to angstrom, gamma-1 = 90-degrees) while the TS2 lattice is rectangular (b2/a2 almost-equal-to 3(1/2), a2 in the range 3.3-3.5 angstrom, gamma-2 = 90-degrees). The subsystems are always centred, either C centred (c almost-equal-to 11-12 angstrom) or F centred (c almost-equal-to 22-24 angstrom). Combinations CC, CF, FC and FF (first MS, second TS2) were found. Compounds with T = Nb, Ta have orthorhombic or monoclinic subsystems, the monoclinic angle being beta (beta-1 generally not equal to beta-2). Compounds with T = Ti, V, Cr have monoclinic subsystems, the monoclinic angle being alpha, or triclinic subsystems for which the c axes diverge. Stacking variants (CC, CF) exist also in this case. Compounds (PbS)1.14(NbS2)2 and (PbS)1.18(TiS2)2 with stacking sequence MS-TS2-TS2-MS etc. have been found recently. For all compounds investigated it was found that the subsystems have a common (b*, c*) reciprocal plane. This stems from the condition that layers cannot intersect and the interaction between M and sulphur of TS2, the M atoms being in between rows of sulphur of TS2 parallel to [100]. For the lanthanide (Ln) compounds the distances Ln-S of the LnS double layer and the distances of Ln to sulphur of TS2 are about the same and in agreement with Ln(III). The interaction between the subsystems is strong. For M = Sn, Pb the M-S distances of the MS double layer indicate M(II); the interaction between subsystems is weaker than for M = Ln

Structures and magnetic properties of Fe1+xNb3-xSe 10-ySy series

X-ray structural studies have been performed on both Fe1 +xNb3-xSe10 and Fe1+xNb 3 -xSe10-ySy single crystals. R factors converge to minimum values when x ≃ 0.25 and y ≃ 1.4 which confirms the non-stoichiometry previously mentioned. We also report magnetic and E.S.R. measurements together with a tentative explanation of those results.Une étude structurale aux rayons X a été entreprise sur des monocristaux de Fe1+xNb3-xSe10 et Fe1+xNb3-xSe10-ySy. Les facteurs de confiance tendent vers un minimum pour les valeurs x = 0,25 et y ≃ 1,4 en accord avec l'existence d'une non-stœchiométrie précédemment annoncée. Nous mentionnons également les résultats des mesures magnétiques et de R.P.E. ainsi qu'une tentative d'interprétation