Prediction and observation of an antiferromagnetic topological insulator.

Magnetic topological insulators are narrow-gap semiconductor materials that combine non-trivial band topology and magnetic order1. Unlike their nonmagnetic counterparts, magnetic topological insulators may have some of the surfaces gapped, which enables a number of exotic phenomena that have potential applications in spintronics1, such as the quantum anomalous Hall effect2 and chiral Majorana fermions3. So far, magnetic topological insulators have only been created by means of doping nonmagnetic topological insulators with 3d transition-metal elements; however, such an approach leads to strongly inhomogeneous magnetic4 and electronic5 properties of these materials, restricting the observation of important effects to very low temperatures2,3. An intrinsic magnetic topological insulator-a stoichiometric well ordered magnetic compound-could be an ideal solution to these problems, but no such material has been observed so far. Here we predict by ab initio calculations and further confirm using various experimental techniques the realization of an antiferromagnetic topological insulator in the layered van der Waals compound MnBi2Te4. The antiferromagnetic ordering  that MnBi2Te4  shows makes it invariant with respect to the combination of the time-reversal and primitive-lattice translation symmetries, giving rise to a ℤ2 topological classification; ℤ2 = 1 for MnBi2Te4, confirming its topologically nontrivial nature. Our experiments indicate that the symmetry-breaking (0001) surface of MnBi2Te4 exhibits a large bandgap in the topological surface state. We expect this property to eventually enable the observation of a number of fundamental phenomena, among them quantized magnetoelectric coupling6-8 and axion electrodynamics9,10. Other exotic phenomena could become accessible at much higher temperatures than those reached so far, such as the quantum anomalous Hall effect2 and chiral Majorana fermions3.

On the nature of sub-THz continuum absorption in CO2 gas, its mixture with Ar, and in pure water vapor.

Detailed analysis of the unique broadband millimeter-wave (70-360 GHz) collision-induced absorption spectra in pure CO2 and in its mixture with Ar is presented. The nature of the observed continuum absorption is examined using classical trajectory simulation along with statistical physics consideration. Bimolecular continuum is decomposed in the phase space into separate contributions from the so-called free, quasibound, and true bound molecular pairs, the proportions of which greatly vary with temperature. This partitioning is supported by consideration of the second virial coefficient and excluded volume in pure CO2, Ar, and CO2-Ar. Close similarity between collision-induced absorption in the CO2 containing gases and the water vapor continuum in the subterahertz spectral range is demonstrated. This similarity suggests that the physical principles underlying both continuum absorption phenomena have much in common and, therefore, can be used for continuum modeling.

The high-accuracy spectroscopy of H2 rovibrational transitions in the (2-0) band near 1.2 µm.

Accurate transition frequencies of six lines of the (2-0) vibrational band of H2 are reported near 1.2 µm, namely Q1-Q4, S0, and S1. These weak electric-quadrupole transitions were measured at room temperature by comb-referenced cavity ring-down spectroscopy. Accurate transition frequencies were determined by applying a multi-spectrum fit procedure with various profile models including speed-dependent collisional broadening and shifting phenomena. Although none of the considered profiles allows reproducing the shape of the strongest lines at the noise level, the zero-pressure line centers are found mostly independent of the used profile. The obtained values are the first H2 (2-0) transition frequencies referenced to an absolute frequency standard. As a result, a 1σ-accuracy better than 100 kHz was achieved for the Q1, S0, and S1 transition frequencies, improving by three orders of magnitude the accuracy of previous measurements. For the six measured transitions, the most recent calculated frequencies were found to be systematically underestimated by about 2.51 MHz, about twice their claimed uncertainties. The energy separation between J = 2 and J = 0 rotational levels of the vibrational ground state was derived from Q2 and S0 transition frequencies and found within the 110 kHz uncertainty of its theoretical value. The same level of agreement was achieved for the energy separation between the J = 3 and J = 1 rotational levels obtained by the difference of Q3 and S1 transition frequencies. The ab initio values of the intensity of the six transitions were validated within a few thousandths.

Expanding indications for laparoscopic parenchyma-sparing resection of posterosuperior liver segments in patients with colorectal metastases: comparison with open hepatectomy for immediate and long-term outcomes.

BACKGROUND: Laparoscopic liver resection (LLR) of posterosuperior segments (PSS) is still technically demanding procedure for highly selective patients. There is no long-term survival comparative estimation after LLR and open liver resection (OLR) for colorectal liver metastases (CRLM) located in PSS. We aimed to compare long-term overall (OS) and disease-free survival (DFS) after parenchyma-sparing LLR with expanding indications and open liver resection (OLR) of liver PSS in patients with CRLM. METHODS: Two Russian centers took part in the study. Patients with missing data, hemihepatectomy and extrahepatic tumors were excluded. One of contraindications for LLR was suspicion for tumor invasion in large hepatic vessels. Logistic regression was used for 1:1 propensity score matching (PSM). RESULTS: PSS were resected in 77 patients, which accounted for 42% of the total number of liver resections for CRLM. LLR were performed in 51 (66%) patients. Before and after matching, no differences were found between groups in the following factors: median size of the largest metastatic tumor; proximity to the large liver vessels; the rate of anatomical parenchyma sparing resection of PSS; a positive response to chemotherapy before and after surgery. Regardless of matching, the size of the largest metastases was above 50 mm in more than one-third of patients who received LLR. Before matching, intraoperative blood loss, ICU stay and hospital stay were significantly greater in the group of OLR. No 90-day mortality was observed within both groups. There were no differences in long-term oncological outcomes: 5-year OS after PSM was 78% and 63% after LLR and OLR, respectively; 4-year DFS after PSM was 27% in both groups. CONCLUSION: Laparoscopic parenchyma-sparing resection of PSS for CRLM are justified in majority of patients who have an indication for OLR if performed in high volume specialized centers expertized in laparoscopic liver surgery.

Complexes Formed via Bioconjugation of Genetically Modified TMV Particles with Conserved Influenza Antigen: Synthesis and Characterization.

Recently we obtained complexes between genetically modified Tobacco Mosaic Virus (TMV) particles and proteins carrying conserved influenza antigen such as M2e epitope. Viral vector TMV-N-lys based on TMV-U1 genome was constructed by insertion of chemically active lysine into the exposed N-terminal part of the coat protein. Nicotiana benthamiana plants were agroinjected and TMV-N-lys virions were purified from non-inoculated leaves. Preparation was analyzed by SDS-PAGE/Coomassie staining; main protein with electrophoretic mobility of 21 kDa was detected. Electron microscopy confirmed the stability of modified particles. Chemical conjugation of TMV-N-lys virions and target influenza antigen M2e expressed in E. coli was performed using 5 mM 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide and 1 mM N-hydroxysuccinimide. The efficiency of chemical conjugation was confirmed by Western blotting. For additional characterization we used conventional electron microscopy. The diameter of the complexes did not differ significantly from the initial TMV-N-lys virions, but complexes formed highly organized and extensive network with dense "grains" on the surface. Dynamic light scattering demonstrated that the single peaks, reflecting the complexes TMV-N-lys/DHFR-M2e were significantly shifted relative to the control TMV-N-lys virions. The indirect enzyme-linked immunosorbent assay with TMV- and DHFR-M2e-specific antibodies showed that the complexes retain stability during overnight adsorption. Thus, the results allow using these complexes for immunization of animals with the subsequent preparation of a candidate universal vaccine against the influenza virus.

[Age Dynamics of Telomere Length in Endemic Baikal Planarians].

Age-related changes in telomere length (TL) in somatic tissues are not limited only to shortening. It is known that many organisms show different TL dynamics. Such species specificity indicates the complexity of the mechanisms involved in the regulation of TL. Owing to their morphological, physiological, and ecological features, Baikal planarians are an interesting model for studying the TL dynamics and the factors influencing it in comparison with species living outside Baikal. In this work, we investigated telomerase activity and age-related changes in TL in three endemic species of planarians from the Dendrocoelidae family. Two species are giant deep-water species (7-12 cm long, Sorocelis hepatizon and Rimacephalus arecepta), and one is a coastal shallow species (1 cm long, Baikalobia guttata). In addition, we investigated the telomere biology in another small Siberian species from the Planariidae family (2 cm in length, Phagocata sibirica), which is not found in Baikal. TL and telomerase activity were determined using real-time PCR and the TRAP method. Three types of age-related TL dynamics were detected with active telomerase: (1) TL shortening at the juvenile stage of development and subsequent maintenance (R. arecepta, Ph. sibirica), (2) gradual TL shortening during ontogeny (S. hepatizon) and (3) cyclic dynamics of TL (B. guttata). Thus, the changes of TL in the studied planarians does not have an obvious connection with body size, habitat depth, phylogenetic relationship and is probably a consequence of species features in the regulation of telomerase activity.

Cowpox in a human, Russia, 2015.

We investigated the first laboratory-confirmed human case of cowpox virus infection in Russia since 1991. Phylogenetic studies of haemagglutinin, TNF-α receptor-like protein and thymidine kinase regions showed significant differences with known orthopoxviruses, including unique amino-acid substitutions and deletions. The described cowpox virus strain, taking into account differences, is genetically closely related to strains isolated years ago in the same geographical region (European part of Russia and Finland), which suggests circulation of viral strains with common origin in wild rodents without spread over long distances and appearance in other parts of the world.

EVALUATION OF VASCULOGENIC POTENTIAL OF MODIFIED FIBRIN HYDROGEL.

In recent years, engineering of blood vessels, which can provide the effective transport of nutrients and various metabolites, is one of the major challenges in tissue reconstruction. Many researches are carried out to develop cell-seeded bioconstructs based on natural polymers, particularly on PEGylated fibrin. Therefore, the aim of this study was to reveal the optimal component ratio for modified fibrin hydrogels in order to provide favorable conditions for vascular development of endothelial and mesenchymal stem cell co-culture. It has been found out that the PEGylated fibrin hydrogels can support 3D cell growth in HUVECs and hASCs co-culture. The microporous filamentous hydrogel prepared from PEGylated 5 : 1 fibrinogen and using the 1 : 0.2 protein to thrombin ratio had the most favorable microenvironment for cell distribution, growth and development in the studied co-culture that resulted in high levels of expression of proteins required for angiogenesis.

Formation of Neural Networks in 3D Scaffolds Fabricated by Means of Laser Microstereolithography.

We developed and tested new 3D scaffolds for neurotransplantation. Scaffolds of predetermined architectonic were prepared using microstereolithography technique. Scaffolds were highly biocompatible with the nervous tissue cells. In vitro studies showed that the material of fabricated scaffolds is not toxic for dissociated brain cells and promotes the formation of functional neural networks in the matrix. These results demonstrate the possibility of fabrication of tissue-engineering constructs for neurotransplantation based on created scaffolds.

[Compatibility of cells of the nervous system with structured biodegradable chitosan-based hydrogel matrices].

Hydrogel matrices for cell cultivation have been generated by two-photon laser polymerization of unsaturated chitosan derivatives and methacrylated hyaluronic acid. The adhesive and toxic properties of the matrices have been assessed, and the matrices have been shown to have a good compatibility with primary hippocampal cell cultures. The formation of morphologically normal neural networks by cells of the nervous system cultured on the surface of hydrogel matrices has been observed. The metabolic status of dissociated hippocampal cells cultured on the matrices was similar to that of the control cultures, as shown by the results of MTT reductase activity assay. Thus, matrices based on unsaturated polysaccharide derivatives crosslinked by laser irradiation showed good compatibility with differentiated cells of the nervous system and considerable potential for use in neurotransplantation.

[Length and structure of telomeric DNA in three species of Baikal gastropods (Caenogastropoda: Hydrobioidea: Benedictiidae)].

The structure of telomeric repeat (TTAGGG)n was determined and the length of telomeric DNA (tDNA) was measured in three species of gastropods from the family Benedictiidae that are endemic to Lake Baikal. Fluorescence in situ hybridization (FISH) confirmed the localization of a telomeric repeat at the chromosome ends. The sizes of tDNA in "giant" eurybathic, psammo-pelobiontic species Benedictia fragilis and shallow water litho-psammobiontic species B. baicalensis with medium shell sizes were similar (16 ± 2.9 and 15 ± 2.1 kb, respectively), but they had a greater length than that of the shallow water spongio-litobiontic species Kobeltocochlea martensiana with small shells (10.5 ± 1.5 kb). We discuss tendencies in age-related changes in tDNA length in snails and a possible mechanism for maintaining tDNA size in ontogeny.

[Some aspects of prevention activity of the teacher, directed to the improvement of the health of schoolchildren].

The problem of bottom quality of prevention work directed to the saving and strengthening the health of schoolchildren, today is a very urgent and requires a joint activity of the pedagogical and medical community. In the article there are presented data proving the feasibility of an active teacher's work on the formation of health saving space in a present school. Conspicuous is the interest of schoolchildren to the problems of a healthy lifestyle during performance of interesting preventive measures with them and as a result risk mitigation subsequently. At the same time, there was noted a low level of training teachers in various fields (including biologists) on specialized problems of the prevention of healthy lifestyles, which points to the need for introduction into the curricula of higher educational institutions additional modules on health saving, as well as conducting training courses involving health care workers as for teachers as parents.

[Telomere length and phylogenetic relationship of Baikal and Siberian planarians (Turbellaria, Tricladida)].

Dynamics of the telomeric DNA (tDNA) and the phylogeny of the Baikal and Siberian planarians have been studied based on the analysis of the 18S rDNA and beta-actin gene fragments. A relationship between tDNA and the planarians size has been demonstrated. Giant planarians with a minor exception have longer tDNA than little planarians. Phylogenetic affinity between the species that have the stretched tracks of tDNA, big size and similar habitats may indicate possible role of tDNA in the development of the indefinite regenerative capacity of planarians.

[Consensus ensemble neural network multitarget model of RAGE inhibitory activity of chemical compounds]. / Konsensusnaia ansamblevaia neirosetevaia mul'titargetnaia model' RAGE-ingibiruiushchei aktivnosti khimicheskikh soedinenii.

RAGE signal transduction via the RAGE-NF-κB signaling pathway is one of the mechanisms of inflammatory reactions that cause severe complications in diabetes mellitus. RAGE inhibitors are promising pharmacological compounds that require the development of new predictive models. Based on the methodology of artificial neural networks, consensus ensemble neural network multitarget model has been constructed. This model describes the dependence of the level of the RAGE inhibitory activity on the affinity of compounds for 34 target proteins of the RAGE-NF-κB signal pathway. For this purpose an expanded database of valid three-dimensional models of target proteins of the RAGE-NF-κB signal chain was created on the basis of a previously created database of three-dimensional models of relevant biotargets. Ensemble molecular docking of known RAGE inhibitors from a verified database into the sites of added models of target proteins was performed, and the minimum docking energies for each compound in relation to each target were determined. An extended training set for neural network modeling was formed. Using seven variants of sampling by the method of artificial multilayer perceptron neural networks, three ensembles of classification decision rules were constructed to predict three level of the RAGE-inhibitory activity based on the calculated affinity of compounds for significant target proteins of the RAGE-NF-κB signaling pathway. Using a simple consensus of the second level, the predictive ability of the created model was assessed and its high accuracy and statistical significance were shown. The resultant consensus ensemble neural network multitarget model has been used for virtual screening of new derivatives of different chemical classes. The most promising substances have been synthesized and sent for experimental studies.

Non-monotonic variation of the Kramers point band gap with increasing magnetic doping in BiTeI.

Polar Rashba-type semiconductor BiTeI doped with magnetic elements constitutes one of the most promising platforms for the future development of spintronics and quantum computing thanks to the combination of strong spin-orbit coupling and internal ferromagnetic ordering. The latter originates from magnetic impurities and is able to open an energy gap at the Kramers point (KP gap) of the Rashba bands. In the current work using angle-resolved photoemission spectroscopy (ARPES) we show that the KP gap depends non-monotonically on the doping level in case of V-doped BiTeI. We observe that the gap increases with V concentration until it reaches 3% and then starts to mitigate. Moreover, we find that the saturation magnetisation of samples under applied magnetic field studied by superconducting quantum interference device (SQUID) magnetometer has a similar behaviour with the doping level. Theoretical analysis shows that the non-monotonic behavior can be explained by the increase of antiferromagnetic coupled atoms of magnetic impurity above a certain doping level. This leads to the reduction of the total magnetic moment in the domains and thus to the mitigation of the KP gap as observed in the experiment. These findings provide further insight in the creation of internal magnetic ordering and consequent KP gap opening in magnetically-doped Rashba-type semiconductors.

[Interspecific variability of telomeric DNA length in some Siberian and endemic Baikal planarians (Plathelminthes, Tricladida)].

The length of the telomeric DNA in nine species of planarians inhabiting Lake Baikal and one Siberian species from Baikal rivers was determined using Southern hybridization. According to preliminary estimations, it varied in the range of 25-30 kb (Rimacephalus arecepta, Rimacephalus pulvinar, Sorocelis hepatizon, Sorocelis nigrofasciata, Protocotylus sp., Baikalobia guttata, Bdellocephala baikalensis, Phagocata sibirica) and 50 kb (Baikaloplana valida, Baikalobia copulatrix). It is the first estimation of the values of telomeric region lengths for Baikal free-living flat worms.

Percutaneous radiofrequency-assisted liver partition versus portal vein embolization before hepatectomy for perihilar cholangiocarcinoma.

BACKGROUND: Percutaneous radiofrequency-assisted liver partition with portal vein embolization in staged liver resection (PRALPPS) represents an alternative to portal vein embolization (PVE) followed by major liver resection in patients with perihilar cholangiocarcinoma. METHODS: This was an observational case-control study. Both procedures were applied in patients with a future liver remnant (FLR) volume of less than 40 per cent. The main end points of the study were short-term morbidity and mortality for the two procedures. The study also compared the efficacy of the preresection phases estimated by kinetic growth rate (KGR), time interval and degree of hypertrophy of the FLR. RESULTS: The first phase (preresection) was completed in 11 and 18 patients, and the second phase (resection) in nine and 14 patients, in the PRALPPS and PVE groups respectively. Major morbidity after the first stage did not differ between the groups. There were no differences in blood loss, severe morbidity or liver failure rate after the second stage, with no deaths. The mean KGR of the FLR after the preresection phase for PRALPPS was 3·8 (0·6-9·8) per cent/day, and that after PVE was 1·8 (0-6·7) per cent/day (P = 0·037). The mean time interval for FLR hypertrophy in the PRALPPS and PVE groups was 15 (6-29) and 20 (8-35) days respectively (P = 0·039). CONCLUSION: Short-term outcomes were similar for PRALPPS and PVE in terms of safety. Remnant hypertrophy was achieved more rapidly by PRALPPS.

ANTECEDENTES: La partición hepática asistida por radiofrecuencia percutánea con embolización de la vena porta en la resección hepática en varios tiempos quirúrgicos (percutaneous radio-frequency assisted liver partition with portal vein embolization in staged liver resection, PRALPPS) representa una alternativa a la embolización de la vena porta seguida de resección hepática mayor (portal vein embolization, PVE) en pacientes con colangiocarcinoma perihiliar (perihiliar cholangiocarcioma, PHCC). MÉTODOS: Se trata de un estudio observacional de casos y controles. Se efectuaron ambos procedimientos en pacientes con un volumen hepático remanente futuro (future liver remnant, FLR) < 40%. Los resultados principales del estudio fueron la morbilidad a corto plazo y la mortalidad de ambos procedimientos. En el estudio también se comparó la eficacia de las fases de pre-resección mediante la tasa cinética de crecimiento (kinetic growth rate, KGR), el intervalo de tiempo y el grado de hipertrofia del FLR. RESULTADOS: Se completaron la primera (pre-resección) y la segunda (resección) fase en 11/9 y 18/14 pacientes en los grupos PRALPPS y PVE, respectivamente. La morbilidad mayor tras el primer tiempo no difirió entre los grupos. No se observaron diferencias en la pérdida de sangre, morbilidad grave y tasa de insuficiencia hepática tras el segundo tiempo, sin que ocurriera ningún fallecimiento. La media de KGR del FLR tras la fase de pre-resección fue de 3,8 (0,6-9,8) %/día en el grupo PRALPPS y de 1,8 (0-6,7) %/día tras PVE (P = 0,037). La media de intervalo de tiempo de la hipertrofia del FLR en los grupos PRALPPS y PVE fue de 15 (6-29) días y 20 (8-35) días, respectivamente (P = 0,039). CONCLUSIÓN: Los resultados a corto plazo fueron similares en términos de seguridad. La hipertrofia del hígado remanente se alcanzó más rápidamente con la PRALPPS.

Development of two-photon polymerised scaffolds for optical interrogation and neurite guidance of human iPSC-derived cortical neuronal networks.

Recent progress in the field of human induced pluripotent stem cells (iPSCs) has led to the efficient production of human neuronal cell models for in vitro study. This has the potential to enable the understanding of live human cellular and network function which is otherwise not possible. However, a major challenge is the generation of reproducible neural networks together with the ability to interrogate and record at the single cell level. A promising aid is the use of biomaterial scaffolds that would enable the development and guidance of neuronal networks in physiologically relevant architectures and dimensionality. The optimal scaffold material would need to be precisely fabricated with submicron resolution, be optically transparent, and biocompatible. Two-photon polymerisation (2PP) enables precise microfabrication of three-dimensional structures. In this study, we report the identification of two biomaterials that support the growth and differentiation of human iPSC-derived neural progenitors into functional neuronal networks. Furthermore, these materials can be patterned to induce alignment of neuronal processes and enable the optical interrogation of individual cells. 2PP scaffolds with tailored topographies therefore provide an effective method of producing defined in vitro human neural networks for application in influencing neurite guidance and complex network activity.

Digging deeper: structural background of PEGylated fibrin gels in cell migration and lumenogenesis.

Fibrin is a well-known tool in tissue engineering, but the structure of its modifications created to improve its properties remains undiscussed despite its importance, e.g. in designing biomaterials that ensure cell migration and lumenogenesis. We sought to uncover the structural aspects of PEGylated fibrin hydrogels shown to contribute to angiogenesis. The analysis of the small-angle X-ray scattering (SAXS) data and ab initio modeling revealed that the PEGylation of fibrinogen led to the formation of oligomeric species, which are larger at a higher PEG : fibrinogen molar ratio. The improvement of optical properties was provided by the decrease in aggregates' sizes and also by retaining the bound water. Compared to the native fibrin, the structure of the 5 : 1 PEGylated fibrin gel consisted of homogenously distributed flexible fibrils with a smaller space between them. Moreover, as arginylglycylaspartic acid (RGD) sites may be partly bound to PEG-NHS or masked because of the oligomerization, the number of adhesion sites may be slightly reduced that may provide the better cell migration and formation of continuous capillary-like structures.

[Psychopathological features of victimity in hemophiliacs]. / Psikhopatologicheskie osobennosti viktimnosti u bol'nykh, stradaiushchikh gemofiliei.

AIM: To study psychopathological features of victimity in hemophiliacs. MATERIAL AND METHODS: Thirty-one men with hemophilia, aged 17-63 years, mean age 33.43±9.09, illness duration 16-62 years, were included in the study. All patients were admitted to the hospital due to the main disease and its complications. One of the inclusion criteria was a mental disorder with the symptoms of victimity. A clinical/psychopathological method was used in the study. RESULTS AND CONCLUSION: Mental state of the patients depended on the type of personality disorder. Four types of victimity (paranoiac, dissociative, dissocial, dependent) were singled out. Psychopathological features of each type and correlation with the psychiatric diagnosis were described.