Unconventional Hysteretic Transition in a Charge Density Wave.

Hysteresis underlies a large number of phase transitions in solids, giving rise to exotic metastable states that are otherwise inaccessible. Here, we report an unconventional hysteretic transition in a quasi-2D material, EuTe_{4}. By combining transport, photoemission, diffraction, and x-ray absorption measurements, we observe that the hysteresis loop has a temperature width of more than 400 K, setting a record among crystalline solids. The transition has an origin distinct from known mechanisms, lying entirely within the incommensurate charge density wave (CDW) phase of EuTe_{4} with no change in the CDW modulation periodicity. We interpret the hysteresis as an unusual switching of the relative CDW phases in different layers, a phenomenon unique to quasi-2D compounds that is not present in either purely 2D or strongly coupled 3D systems. Our findings challenge the established theories on metastable states in density wave systems, pushing the boundary of understanding hysteretic transitions in a broken-symmetry state.

Externally Controlled Magnetism and Band Gap in Twisted Bilayer Graphene.

We theoretically study the effects of electron-electron interaction in twisted bilayer graphene in a transverse dc electric field. When the twist angle is not very small, the electronic spectrum of the bilayer consists of four Dirac cones inherited from each graphene layer. An applied bias voltage leads to the appearance of two holelike and two electronlike Fermi surface sheets with perfect nesting among electron and hole components. Such a band structure is unstable with respect to the exciton band-gap opening due to the screened Coulomb interaction. The exciton order parameter is accompanied by spin-density-wave order. The gap depends on the twist angle and can be varied by a bias voltage. This result correlates well with recent transport measurements [J.-B. Liu et al., Sci. Rep. 5, 15285 (2015)SRCEC32045-232210.1038/srep15285]. Our proposal allows the coexistence of (i) an externally controlled semiconducting gap and (ii) a nontrivial multicomponent magnetic order. This is interesting for both fundamental research and applications.

Spin-Valley Half-Metal as a Prospective Material for Spin Valleytronics.

Half-metallicity (full spin polarization of the Fermi surface) usually occurs in strongly correlated electron systems. We demonstrate that doping a spin-density wave insulator in the weak-coupling regime may also stabilize half-metallic states. In the absence of doping, the spin-density wave is formed by four nested bands [i.e., each band is characterized by charge (electron or hole) and spin (up or down) labels]. Of these four bands, only two accumulate the charge carriers introduced by doping, forming a half-metallic two-valley Fermi surface. Depending on the parameters, the spin polarizations of the electronlike and holelike valleys may be either (i) parallel or (ii) antiparallel. The Fermi surface of (i) is fully spin polarized (similar to usual half-metals). Case (ii), referred to as "a spin-valley half-metal," corresponds to complete polarization with respect to the spin-valley operator. The properties of these states are discussed.

Heat Transport in Spin Chains with Weak Spin-Phonon Coupling.

The heat transport in a system of S=1/2 large-J Heisenberg spin chains, describing closely Sr(2)CuO(3) and SrCuO(2) cuprates, is studied theoretically at T≪J by considering interactions of the bosonized spin excitations with optical phonons and defects. Treating rigorously the multiboson processes, we derive a microscopic spin-phonon scattering rate that adheres to an intuitive picture of phonons acting as thermally populated defects for the fast spin excitations. The mean-free path of the latter exhibits a distinctive T dependence reflecting a critical nature of spin chains and gives a close description of experiments. By the naturalness criterion of realistically small spin-phonon interaction, our approach stands out from previous considerations that require large coupling constants to explain the data and thus imply a spin-Peierls transition, absent in real materials.

EFFECT OF CYP2C19 GENETIC POLYMORPHISMS ON THE EFFICACY OF PROTON PUMP INHIBITOR-BASED TRIPLE ERADICATION THERAPY IN SLAVIC PATIENTS WITH PEPTIC ULCERS: A META-ANALYSIS.

INTRODUCTION: Several meta-analyzes reported the effect of CYP2C19 genetic polymorphisms on the efficacy of proton pump inhibitor-based triple therapy for Helicobacter pylori eradication. Most of the studies which were included in these meta-analyzes were held on Asian population. Thus, there is lack of information about the effect of CYP2C19 genetic polymorphisms on the efficacy of proton pump inhibitor-based triple eradication therapy in Slavic patients with peptic ulcers. The aim of the study - to determine whether CYP2C19 affect the efficacy of proton pump inhibitor-based triple eradica- tion therapy in Slavic patients with peptic ulcers. METHODS: Data search was performed using Russian index of scientific citation database, Google Scholar and MEDLINE PubMed. Statistics was held in Review Manager v 5.3. The odds ratio (OR) and 95% confidence interval (95% Cl) for eradication of H.pylori was estimated in a fixed-effect model when no heterogeneity across the studies was indicated. RESULTS: Four articles published between 2008 and 2015 were included in meta-analysis (three Russian studies, one Polish study). Eradication rates were significantly lower in CYP2C19 extensive metabolizers of proton pump inhibitors than in a combined group of intermediate and poor metabolizers (OR = 1,90, CI-95% 1,08-3,34, p = 0,03; heterogeneity: 12= 0%, p = 0,74). We also found that proton pump inhibitor-based triple eradication therapy achieved higher rates in poor metabolizers than in a combined group of intermediate and extensive metabolizers of CYP2C19 (OR= 5,48 CI-95% 1,51-19,93, p = 0,01; heterogeneity: F= 0%, p = 0,66). CONCLUSION: The impact of CYP2C19 genetic polymorphisms on the efficacy of proton pump inhibitor-based triple eradication therapy in Slavic patients appears significant.

One-dimensional fermions with neither Luttinger-liquid nor Fermi-liquid behavior.

It is well known that, generically, one-dimensional interacting fermions cannot be described in terms of a Fermi liquid. Instead, they present a different phenomenology, that of a Tomonaga-Luttinger liquid: the Landau quasiparticles are ill defined, and the fermion occupation number is continuous at the Fermi energy. We demonstrate that suitable fine tuning of the interaction between fermions can stabilize a peculiar state of one-dimensional matter, which is dissimilar to both Tomonaga-Luttinger and Fermi liquids. We propose to call this state a quasi-Fermi liquid. Technically speaking, such a liquid exists only when the fermion interaction is irrelevant (in the renormalization group sense). The quasi-Fermi liquid exhibits the properties of both a Tomonaga-Luttinger liquid and a Fermi liquid. Similar to a Tomonaga-Luttinger liquid, no finite-momentum quasiparticles are supported by the quasi-Fermi liquid; on the other hand, its fermion occupation number demonstrates a finite discontinuity at the Fermi energy, which is a hallmark feature of a Fermi liquid. A possible realization of the quasi-Fermi liquid with the help of cold atoms in an optical trap is discussed.

Instabilities of the AA-stacked graphene bilayer.

Tight-binding calculations predict that the AA-stacked bilayer graphene has one electron and one hole conducting band, and that the Fermi surfaces of these bands coincide. We demonstrate that as a result of this degeneracy, the bilayer becomes unstable with respect to a set of spontaneous symmetry violations. Which of the symmetries is broken depends on the microscopic details of the system. For strong on-site Coulomb interaction we find that antiferromagnetism is the most stable order parameter. For an on-site repulsion energy typical for graphene systems, the antiferromagnetic gap can exist up to room temperature.

Evaluation of the two-particle propagator for the Hubbard model with the help of the Hubbard-I approximation.

The Hubbard-I approximation is generalized to allow for direct evaluation of the equal-time anomalous two-electron propagator for the Hubbard model on a two-dimensional square lattice. This propagator is compared against the quantum Monte Carlo data obtained by Aimi and Imada (2007 J. Phys. Soc. Japan 76 113708) in the limit of strong electron-electron interaction. The Hubbard-I predictions are in good qualitative agreement with the Monte Carlo results. In particular, d-wave correlations decay as cr( - 3) ('free-electron' behaviour) if the separation r exceeds 2-3 lattice constants. However, the Hubbard-I approximation underestimates the coefficient c by a factor of about 3. We conclude that the Hubbard-I approximation, despite its simplicity and artefacts, captures the qualitative behaviour of the two-particle propagator for the Hubbard model, at least for moderate values of r.

Effect of artrofoon and SCENAR therapy on parameters of LPO and antioxidant system of the blood in patients with peritonitis in postoperative period.

Administration of artrofoon in combination with SCENAR therapy to patients with localized suppurative peritonitis in the postoperative period considerably reduced plasma MDA level, stabilized ceruloplasmin activity, and increased catalase activity in erythrocytes compared to the corresponding parameters in patients receiving standard treatment in combination with SCENAR therapy.

Thermal conductivity of quasi-one-dimensional antiferromagnetic spin-chain materials.

We study heat transport in quasi-one-dimensional spin-chain systems by considering the model of one-dimensional bosonic spin excitations interacting with three-dimensional phonons and impurities in the limit of weak spin-lattice coupling and fast spin excitations. A combined effect of the phonon and impurity scatterings yields the following spin-boson thermal conductivity behavior: kappa(s) proportional to T2 at low, kappa(s) proportional to T-1 at intermediate, and kappa(s)= const at higher temperatures. Our results agree well with the existing experimental data for Sr2CuO3. We predict an unusual dependence on the impurity concentration for a number of observables and propose further experiments.

[Functional characteristics of the upper leg stumps after knee joint disarticulation and prosthesis]. / Funktsional'nye osobennosti kul'tei bedra posle vychleneniia v kolennom sustave i protezirovanie.

In this article is presented the 20-years experience of surgical preparation and prosthetics of 62 invalids with the femur stumps after knee joint exarticulation at the age of 5-65 years in the clinic of LNIIP. New methods of distal epiphysis transposition with muscle connection preservation instead of diaphysial femur amputations were applied to the patients with the integument defects. There have been broadened and made more accurate indications for knee joint exarticulation as a consequence of a trauma as well as in case of vascular diseases. Prosthetic appliances are made with utilization of modified monocentric knee units, polycentric modules and frame-type full-contact sockets of new design.

[Thermovision in the evaluation of the quality of fitting of acceptable intake sockets of shin prostheses]. / Otsenka kachestva podgonki priemnykh gil'z protezov goleni teplovizionnym sposobom.

The authors investigated the internal surface of the intake socket and thermal reaction of skin surfaces when walking on the crus prostheses by means of thermovision. There has been revealed an obvious improvement of capable-of support stump tissue trophism when walking on the crus prosthesis with full-contact socket. The prospects of thermovision application for evaluation of prosthetics quality and in the process of fitting of intake sockets have been determined.

[Insertable orthopedic devices in the treatment of flatness of the anterior section of the foot and valgus deviation of the great toe]. / Vkladnye ortopedicheskie prisposobleniia pri lechenii rasplastannosti perednego otdela stopy i val'gusnogo otkloneniia I pal'tsa.

The article draws attention to the urgency of the problem of orthopaedic provision of patients with flatness of anterior section of foot and valgus deviation of the first toe for conservative treatment as well as after surgical intervention. Based on clinical and biomechanical peculiarities of foot, in the institute have been developed insertable orthopaedic devices for mass-produced footwear for mentioned pathology: corrective device with unloading element and curative insole. Orthopaedic articles ensure complex influence upon the foot deforming components, improve redressing effect on the first toe. Mass production is planned for 1991.