Excitonic Bound State in the Extended Anderson Model with c-f Coulomb Interaction

The Anderson model with the Coulomb interaction between the local and conduction electrons is studied in the semiconducting phase. Based on a perturbation theory from the atomic limit, leading contributions for the c-f Coulomb interaction are incorporated as a vertex correction to hybridization. An analytical solution shows that the effective attraction in the intermediate states leads to a bound state localized at the local electron site. Self-consistent equations are constructed as an extension of the non-crossing approximation (NCA) to include the vertex part yielding the bound state. A numerical calculation demonstrates the excitonic bound state inside the semiconducting gap for single-particle excitations, and a discontinuity at the gap edge for magnetic excitations.Comment: 15 pages, 20 figures, submitted to J. Phys. Soc. Jp

Resistivity, Hall effect and Shubnikov-de Haas oscillations in CeNiSn

The resistivity and Hall effect in CeNiSn are measured at temperatures down to 35 mK and in magnetic fields up to 20 T with the current applied along the {\it b} axis. The resistivity at zero field exhibits quadratic temperature dependence below $\sim$0.16 K with a huge coefficient of the $T^2$ term (54 $\mu$$\Omega$cm/K$^2$). The resistivity as a function of field shows an anomalous maximum and dip, the positions of which vary with field directions. Shubnikov-de Haas (SdH) oscillations with a frequency {\it F} of $\sim$100 T are observed for a wide range of field directions in the {\it ac} and {\it bc} planes, and the quasiparticle mass is determined to be $\sim$10-20 {\it m}$_e$. The carrier density is estimated to be $\sim10^{-3}$ electron/Ce. In a narrow range of field directions in the {\it ac} plane, where the magnetoresistance-dip anomaly manifests itself clearer than in other field directions, a higher-frequency ($F=300\sim400\text{T}$) SdH oscillation is found at high fields above the anomaly. This observation is discussed in terms of possible field-induced changes in the electronic structure.Comment: 15 pages, 5 figures, to appear in Phys. Rev. B (15 Sept. 2002 issue

Clustered mutations in the GRIK2 kainate receptor subunit gene underlie diverse neurodevelopmental disorders

Kainate receptors (KARs) are glutamate-gated cation channels with diverse roles in the central nervous system. Bi-allelic loss of function of the KAR-encoding gene GRIK2 causes a nonsyndromic neurodevelopmental disorder (NDD) with intellectual disability and developmental delay as core features. The extent to which mono-allelic variants in GRIK2 also underlie NDDs is less understood because only a single individual has been reported previously. Here, we describe an additional eleven individuals with heterozygous de novo variants in GRIK2 causative for neurodevelopmental deficits that include intellectual disability. Five children harbored recurrent de novo variants (three encoding p.Thr660Lys and two p.Thr660Arg), and four children and one adult were homozygous for a previously reported variant (c.1969G>A [p.Ala657Thr]). Individuals with shared variants had some overlapping behavioral and neurological dysfunction, suggesting that the GRIK2 variants are likely pathogenic. Analogous mutations introduced into recombinant GluK2 KAR subunits at sites within the M3 transmembrane domain (encoding p.Ala657Thr, p.Thr660Lys, and p.Thr660Arg) and the M3-S2 linker domain (encoding p.Ile668Thr) had complex effects on functional properties and membrane localization of homomeric and heteromeric KARs. Both p.Thr660Lys and p.Thr660Arg mutant KARs exhibited markedly slowed gating kinetics, similar to p.Ala657Thr-containing receptors. Moreover, we observed emerging genotype-phenotype correlations, including the presence of severe epilepsy in individuals with the p.Thr660Lys variant and hypomyelination in individuals with either the p.Thr660Lys or p.Thr660Arg variant. Collectively, these results demonstrate that human GRIK2 variants predicted to alter channel function are causative for early childhood development disorders and further emphasize the importance of clarifying the role of KARs in early nervous system development.Genetics of disease, diagnosis and treatmen

Clustered mutations in the GRIK2 kainate receptor subunit gene underlie diverse neurodevelopmental disorders (vol 108, pg 1692, 2021)

Neurolog

More than smell - COVID-19 is associated with severe impairment of smell, taste, and chemesthesis

Recent anecdotal and scientific reports have provided evidence of a link between COVID-19 and chemosensory impairments, such as anosmia. However, these reports have downplayed or failed to distinguish potential effects on taste, ignored chemesthesis, and generally lacked quantitative measurements. Here, we report the development, implementation, and initial results of a multilingual, international questionnaire to assess self-reported quantity and quality of perception in 3 distinct chemosensory modalities (smell, taste, and chemesthesis) before and during COVID-19. In the first 11 days after questionnaire launch, 4039 participants (2913 women, 1118 men, and 8 others, aged 19-79) reported a COVID-19 diagnosis either via laboratory tests or clinical assessment. Importantly, smell, taste, and chemesthetic function were each significantly reduced compared to their status before the disease. Difference scores (maximum possible change ±100) revealed a mean reduction of smell (-79.7 ± 28.7, mean ± standard deviation), taste (-69.0 ± 32.6), and chemesthetic (-37.3 ± 36.2) function during COVID-19. Qualitative changes in olfactory ability (parosmia and phantosmia) were relatively rare and correlated with smell loss. Importantly, perceived nasal obstruction did not account for smell loss. Furthermore, chemosensory impairments were similar between participants in the laboratory test and clinical assessment groups. These results show that COVID-19-associated chemosensory impairment is not limited to smell but also affects taste and chemesthesis. The multimodal impact of COVID-19 and the lack of perceived nasal obstruction suggest that severe acute respiratory syndrome coronavirus strain 2 (SARS-CoV-2) infection may disrupt sensory-neural mechanisms. © 2020 The Author(s) 2020. Published by Oxford University Press. All rights reserved

Multiancestry analysis of the HLA locus in Alzheimer’s and Parkinson’s diseases uncovers a shared adaptive immune response mediated by HLA-DRB1*04 subtypes

Across multiancestry groups, we analyzed Human Leukocyte Antigen (HLA) associations in over 176,000 individuals with Parkinson’s disease (PD) and Alzheimer’s disease (AD) versus controls. We demonstrate that the two diseases share the same protective association at the HLA locus. HLA-specific fine-mapping showed that hierarchical protective effects of HLA-DRB1*04 subtypes best accounted for the association, strongest with HLA-DRB1*04:04 and HLA-DRB1*04:07, and intermediary with HLA-DRB1*04:01 and HLA-DRB1*04:03. The same signal was associated with decreased neurofibrillary tangles in postmortem brains and was associated with reduced tau levels in cerebrospinal fluid and to a lower extent with increased Aβ42. Protective HLA-DRB1*04 subtypes strongly bound the aggregation-prone tau PHF6 sequence, however only when acetylated at a lysine (K311), a common posttranslational modification central to tau aggregation. An HLA-DRB1*04-mediated adaptive immune response decreases PD and AD risks, potentially by acting against tau, offering the possibility of therapeutic avenues

Narcolepsie : une maladie auto-immune affectant un peptide de l’éveil liée à un mimétisme moléculaire avec des épitopes du virus de la grippe

La narcolepsie et la cataplexie sont décrites pour la première fois à la fin du XIXe siècle en Allemagne et en France. La prévalence de la maladie est établie à 0,05 % et un modèle canin est découvert dans les années 1970. En 1983, une étude japonaise révèle que les patients narcoleptiques sont porteurs d’un marqueur génétique unique, l’antigène leucocytaire HLA-DR2, suggérant l’auto-immunité comme cause de la maladie. Il faudra attendre 1992 pour qu’il soit montré, grâce à une étude chez des patients afro-américains, que DQ0602, un autre gène HLA, est la véritable cause de cette association. Des études pharmacologiques conduites sur le modèle canin établissent que la stimulation dopaminergique est le mode d’action des stimulants sur l’éveil, tandis que les antidépresseurs suppriment la cataplexie en inhibant la recapture adrénergique. Aucune association HLA n’est cependant mise en évidence chez les chiens, suggérant une cause distincte de la maladie humaine. Une étude de liaison génétique chez les chiens, initiée en 1988, révèle en 1999 que la narcolepsie canine est causée par des mutations du récepteur 2 de l’hypocrétine (orexine). En 2000, l’hypocrétine-1/orexine A est mesurée dans le liquide céphalo-rachidien (LCR) et on découvre qu’elle est indétectable chez la plupart des patients narcoleptiques, établissant qu’un déficit hypocrétinergique est la cause de la narcolepsie humaine. La diminution de l’hypocrétine-1 dans le LCR, secondaire à la perte des 70 000 neurones hypothalamiques produisant l’hypocrétine, est démontrée, ce qui, avec l’association au locus HLA, suggère qu’une destruction immunitaire de ces cellules est la cause de la maladie. D’autres études génétiques, notamment d’association à l’échelle du génome (GWAS), révèlent l’existence de nombreux facteurs génétiques prédisposant à la narcolepsie, la plupart étant également impliqués dans d’autres maladies auto-immunes. Une association forte et unique avec les loci des récepteurs lymphocytaires T (TCR) alpha et bêta est aussi observée, suggérant un rôle prépondérant des lymphocytes T. En dépit de nombreux efforts, toutes les tentatives visant à démontrer la présence d’auto-anticorps contre les cellules à hypocrétine dans la narcolepsie échouent, et la cause auto-immune présumée de cette maladie reste à l’état d’hypothèse. À la suite de la grippe pandémique influenza A pH1N1 en 2009, de nombreux cas de narcolepsie apparaissent, suggérant un mimétisme moléculaire avec le virus de la grippe qui pourrait déclencher la maladie auto-immune. Cette hypothèse est confirmée par un criblage peptidique montrant une plus grande réactivité des lymphocytes T CD4+ à un segment spécifique de l’hypocrétine (HCRTNH2) et une réactivité croisée des TCR correspondants à un segment d’hémagglutinine de pH1N1 qui partage une homologie avec HCRTNH2. De façon remarquable, le TCR le plus fréquent dans la population et qui reconnaît ces antigènes contient des séquences TRAJ24 ou TRVB4-2, segments modulés par des polymorphismes génétiques associés à la narcolepsie dans les études GWAS. Il est probable que les lymphocytes T CD4+ autoréactifs avec HCRTNH2 recrutent par la suite des lymphocytes T CD8+ qui détruisent les cellules à hypocrétine. On peut s’attendre à ce que d’autres séquences mimiques grippales inconnues soient découvertes prochainement puisque la narcolepsie existait avant 2009. Ces découvertes démontrent enfin la cause auto-immune de la narcolepsie. Les travaux menés au cours des années sur la narcolepsie offrent une perspective unique sur la conduite de la recherche sur l’étiopathogénie d’une maladie bien identifiée

Nuclear-induced resistivity drop in the Kondo alloy Au-171 Yb

The electrical resistivities of monoisotopic dilute alloys of Au- 171Yb and Au-174Yb have been measured down to 18 mK. A resistivity drop is observed in Au-171Yb, below 90 mK. This effect is shown to result from the magnetic hyperfine coupling in 171Yb which splits the electro-nuclear levels into a singlet ground state and a triplet excited state. A simple model is proposed which accounts for the experimental results.La résistivité électrique d'alliages dilués monoisotopiques d'Au- 171Yb et de Au-174Yb a été mesurée jusqu'à 18 mK. Dans l'Au-171Yb, on observe une chute de résistivité en dessous de 90 mK. On montre que cet effet résulte du couplage hyperfin magnétique dans l'171Yb qui lève la dégénérescence des niveaux électronucléaires en produisant un état fondamental singulet et un état excité triplet. On propose un modèle simple qui rend compte des résultats expérimentaux

Observation of an electronic singlet ground state in Au171 Yb

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