Emergence of Fermi arcs due to magnetic splitting in an antiferromagnet.

The Fermi surface plays an important role in controlling the electronic, transport and thermodynamic properties of materials. As the Fermi surface consists of closed contours in the momentum space for well-defined energy bands, disconnected sections known as Fermi arcs can be signatures of unusual electronic states, such as a pseudogap1. Another way to obtain Fermi arcs is to break either the time-reversal symmetry2 or the inversion symmetry3 of a three-dimensional Dirac semimetal, which results in formation of pairs of Weyl nodes that have opposite chirality4, and their projections are connected by Fermi arcs at the bulk boundary3,5-12. Here, we present experimental evidence that pairs of hole- and electron-like Fermi arcs emerge below the Neel temperature (TN) in the antiferromagnetic state of cubic NdBi due to a new magnetic splitting effect. The observed magnetic splitting is unusual, as it creates bands of opposing curvature, which change with temperature and follow the antiferromagnetic order parameter. This is different from previous theoretically considered13,14 and experimentally reported cases15,16 of magnetic splitting, such as traditional Zeeman and Rashba, in which the curvature of the bands is preserved. Therefore, our findings demonstrate a type of magnetic band splitting in the presence of a long-range antiferromagnetic order that is not readily explained by existing theoretical ideas.

Analysis of the Polymorphisms and Expression Levels of the BCL2, BAX and c-MYC Genes in Patients with Ovarian Cancer.

Ovarian cancer (OC) is one of the biggest problems in gynecological oncology and is one of the most lethal cancers in women worldwide. Most patients with OC are diagnosed at an advanced stage; therefore, there is an urgent need to find new biomarkers for this disease. Gene expression profiling is proving to be a very effective tool for exploring new molecular markers for OC patients, although the relationship between such markers and patient survival and clinical outcomes is still elusive. Moreover, polymorphisms in genes encoding both apoptosis-associated proteins and oncoproteins may serve as key markers of cancer susceptibility. The aim of our study was to analyze the polymorphisms and expressions of the BCL2, BAX and c-MYC genes in a group of 198 women, including 98 with OC. The polymorphisms and mRNA expressions of the BCL2, BAX and c-MYC genes were analyzed using real-time PCR. The analysis of the BAX (rs4645878; G>A) and c-MYC (rs4645943; C>T) polymorphisms showed no association with ovarian cancer risk. The BCL2 polymorphism (rs2279115; C>A) showed a significant difference in the frequency of genotypes between the studied groups (CC: 23.47% vs. 16.00%, AA: 25.51% vs. 37.00%; p = 0.046; OR = 1.61). Furthermore, the expression levels of the BCL2 and c-MYC genes showed a decrease at the transcript level for OC patients compared to the control group (BCL2: 17.46% ± 3.26 vs. 100% ± 8.32; p < 0.05; c-MYC: 37.56% ± 8.16 vs. 100% ± 9.12; p < 0.05). No significant changes in the mRNA level were observed for the BAX gene (104.36% ± 9.26 vs. 100% ± 9.44; p > 0.05). A similar relationship was demonstrated in the case of the protein expressions of the studied genes. These findings suggest that the CC genotype and C allele of the BCL2 polymorphism could be genetic risk factors for OC development. A gene expression analysis indicated that BCL2 and c-MYC are associated with OC risk.

Relaxation Dynamics of Zero-Field Skyrmions over a Wide Temperature Range.

The promise of magnetic skyrmions in future spintronic devices hinges on their topologically enhanced stability and the ability to be manipulated by external fields. The technological advantages of nonvolatile zero-field skyrmion lattice (SkL) are significant if their stability and reliability can be demonstrated over a broad temperature range. Here, we study the relaxation dynamics including the evolution and lifetime of zero-field skyrmions generated from field cooling (FC) in an FeGe single-crystal plate via in situ Lorentz transmission electron microscopy (L-TEM). Three types of dynamic switching between zero-field skyrmions and stripes are identified and distinguished. Moreover, the generation and annihilation of these metastable skyrmions can be tailored during and after FC by varying the magnetic fields and the temperature. This dynamic relaxation behavior under the external fields provides a new understanding of zero-field skyrmions for their stability and reliability in spintronic applications and also raises new questions for theoretical models of skyrmion systems.

The rs1256044 polymorphism in the ESR2 gene and the risk for osteoporosis in Polish postmenopausal women.

Population association studies have demonstrated a strong association between ESR2 SNPs and BMD, indicating that ESR2 may influence attainment of bone mass. The aim of the study was to investigate the ESR2 gene, located on chromosome 14q linked with BMD, which demonstrates a correlation with changes in bone mass in healthy Caucasian women. The study included 675 unrelated Polish postmenopausal women, including 109 with osteopenia, 333 with osteoporosis and 233 healthy women. The women were classified into the following groups: osteopenia, osteoporosis and normal T-score. Analysis of genotype frequency for the ESR2 rs1256044 polymorphism revealed no statistically significant differences. No statistically significant differences were noted for the allele frequency. However, it is noticeable that the CT genotype occurred more often in women with osteopenia (50.4%, OR = 1.14) and osteoporosis (54.7%, OR = 1.33) than controls (47.7%). There were statistically significant differences between the clinical parameters and distribution of genotypes in patients with osteopenia but not osteoporosis. ESR2 polymorphisms demonstrate minimal influence on BMD changes in women. Identification of various genes with little impact on BMD, such as ESR2, might help design a screening panel for osteoporosis risk assessment in healthy subjects.

Expression profiling of genes modulated by rosmarinic acid (RA) in MCF-7 breast cancer cells.

OBJECTIVES: Cancer is the second most common cause of death, with breast cancer (BC) as the most frequently diagnosed neoplasm among females. The origin of BC is multifactorial and depends on environmental and genetic factors. The disease presents a significant challenge due to its drug resistance and frequent metastasis. Thus, new effective therapies and metastasis prevention are much needed. Rosmarinic acid (RA) is a natural polyphenol which possesses the ability to inhibit BC cell proliferation and demonstrates cytotoxic properties against those cells. In our study, we examined the effect of RA on the expression of ZEB1, MDM2, ABCB1, PTEN and TWIST1 genes in MCF-7 breast cancer cells. MATERIAL AND METHODS: MCF-7 cell cultures were treated with 0.2 µM doxorubicin (DOX) and 1.5, 15 or 50 µM of RA. Real-time PCR reaction was performed to analyze gene expression levels. RESULTS: PCR analysis showed a significant increase of the ZEB1 gene expression, which was about 3-fold for DOX 0.2 µM, 9-fold for 0.2 µM DOX + 1.5 µM RA and 0.2 µM DOX + 15 µM RA (p < 0.05), and about 6.5-fold for 0.2 µM DOX + 50 µM RA (p < 0.05). Furthermore, a decrease of the MDM2 gene expression was observed in all of the examined variants and was about 40-75% (p < 0.05). No influence of DOX and RA combined with DOX on the ABCB1, TWIST1 and PTEN genes was found. CONCLUSIONS: The results of our study suggest that RA might be used as an adjuvant therapeutic factor in BC treatment.

Spectroscopic evidence for a type II Weyl semimetallic state in MoTe2.

In a type I Dirac or Weyl semimetal, the low-energy states are squeezed to a single point in momentum space when the chemical potential µ is tuned precisely to the Dirac/Weyl point. Recently, a type II Weyl semimetal was predicted to exist, where the Weyl states connect hole and electron bands, separated by an indirect gap. This leads to unusual energy states, where hole and electron pockets touch at the Weyl point. Here we present the discovery of a type II topological Weyl semimetal state in pure MoTe2, where two sets of Weyl points (, ) exist at the touching points of electron and hole pockets and are located at different binding energies above EF. Using angle-resolved photoemission spectroscopy, modelling, density functional theory and calculations of Berry curvature, we identify the Weyl points and demonstrate that they are connected by different sets of Fermi arcs for each of the two surface terminations. We also find new surface 'track states' that form closed loops and are unique to type II Weyl semimetals. This material provides an exciting, new platform to study the properties of Weyl fermions.

Polymorphic variants of genes involved in choline pathway and the risk of intrauterine fetal death.

OBJECTIVES: Choline and folate metabolism disturbances may be involved in the occurrence of intrauterine fetal death (IUFD). The proper activity of this metabolism could be determined by genetic variants involved in choline pathway e.g. CHKA (gene encoding choline kinase α), PCYT1A (gene encoding CCTα) and CHDH (gene encoding choline dehydrogenase). Our study aimed at determining the genotype and allele frequencies of CHKA rs7928739, PCYT1A rs712012, PCYT1A rs7639752, CHDH rs893363 and CHDH rs2289205 polymorphisms in mothers with IUFD occurrence. MATERIAL AND METHODS: The study involved 76 mothers with IUFD occurrence and 215 mothers of healthy children. Genetic analysis was performed with the use of PCR/RFLP method. RESULTS: The frequency of genotypes and alleles of studied polymorphisms was similar in both groups. The study revealed no association of PCYT1A, CHKA and CHDH polymorphisms in analysed groups of women. While evaluating the co-existence of analysed polymorphisms statistically significant correlation was revealed. Co-existence of CHKA rs7928739 AC/CHDH rs2289205 AA genotypes was observed statistically more frequently in the study group than in the control group (p = 0,031). CONCLUSIONS: There is no correlation between single CHKA rs7928739, PCYT1A rs712012, PCYT1A rs7639752, CHDH rs893363 and CHDH rs2289205 polymorphisms and the incidence of intrauterine fetal death. However, revealed statistically significant difference between co-existence of CHKA rs7928739 AC/CHDH rs2289205 AA genotypes between study groups suggest the need of further analysis.

The importance of polymorphic variants of collagen 1A2 gene (COL1A2) in the development of osteopenia and osteoporosis in postmenopausal women.

OBJECTIVES: Collagen type I plays an important role in the bone matrix and is encoded by COL1A2 (collagen type I alpha 2) gene that may be a potential candidate for osteoporotic fracture. The aim of this study is to determine whether EcoRI, Del38 and PvuII polymorphisms of COL1A2 are associated with the development of osteoporosis and osteopenia in post-menopausal Polish women. Moreover, analysis of relationship between frequency of COL1A2 gene polymorphic variants and clinical parameters of bone turnover and degree of osteoporosis was performed. MATERIAL AND METHODS: The study group comprised of women with osteoporosis (n = 90), osteopenia (n = 56) and healthy individuals (n = 56). The EcoRI, Del38 and PvuII polymorphisms in COL1A2 gene were detected by PCR-RFLP method. RESULTS: In women with osteoporosis the TT genotype of EcoRI polymorphism had the lowest Z-score value compared to other genotypes (p = 0.034). In case of Del28 polymorphism, there was a statistically significant correlation between lower BMI values and the DD genotype in women with osteopenia (p = 0.041). There was no statistically significant correlation between polymorphic variants of Del28 polymorphism and clinical parameters of women with osteoporosis. The analysis of PvuII polymorphism showed that in women with osteopenia the CC genotype had the lowest body weight compared to other genotypes (p = 0.039). PvuII polymorphism and clinical parameters in the group of women with osteoporosis had no statistically significant correlations. CONCLUSIONS: The analyzed COL1A2 polymorphisms seem to be related to osteoporosis development and their particular clinical parameters. Hence, the COL1A2 polymorphism may be a genetic risk factor related to the development of osteoporosis.

Discovery of an Unconventional Charge Density Wave at the Surface of K_{0.9}Mo_{6}O_{17}.

We use angle resolved photoemission spectroscopy, Raman spectroscopy, low energy electron diffraction, and x-ray scattering to reveal an unusual electronically mediated charge density wave (CDW) in K_{0.9}Mo_{6}O_{17}. Not only does K_{0.9}Mo_{6}O_{17} lack signatures of electron-phonon coupling, but it also hosts an extraordinary surface CDW, with T_{S_CDW}=220 K nearly twice that of the bulk CDW, T_{B_CDW}=115 K. While the bulk CDW has a BCS-like gap of 12 meV, the surface gap is 10 times larger and well in the strong coupling regime. Strong coupling behavior combined with the absence of signatures of strong electron-phonon coupling indicates that the CDW is likely mediated by electronic interactions enhanced by low dimensionality.

Enhancement of the Superconducting Gap by Nesting in CaKFe_{4}As_{4}: A New High Temperature Superconductor.

We use high resolution angle resolved photoemission spectroscopy and density functional theory with measured crystal structure parameters to study the electronic properties of CaKFe_{4}As_{4}. In contrast to the related CaFe_{2}As_{2} compounds, CaKFe_{4}As_{4} has a high T_{c} of 35 K at stochiometric composition. This presents a unique opportunity to study the properties of high temperature superconductivity in the iron arsenides in the absence of doping or substitution. The Fermi surface consists of several hole and electron pockets that have a range of diameters. We find that the values of the superconducting gap are nearly isotropic (within the explored portions of the Brillouin zone), but are significantly different for each of the Fermi surface (FS) sheets. Most importantly, we find that the momentum dependence of the gap magnitude plotted across the entire Brillouin zone displays a strong deviation from the simple cos(k_{x})cos(k_{y}) functional form of the gap function, proposed by the scenario of Cooper pairing driven by a short range antiferromagnetic exchange interaction. Instead, the maximum value of the gap is observed on FS sheets that are closest to the ideal nesting condition, in contrast to previous observations in other ferropnictides. These results provide strong support for the multiband character of superconductivity in CaKFe_{4}As_{4}, in which Cooper pairing forms on the electron and the hole bands interacting via a dominant interband repulsive interaction, enhanced by band nesting.

The RANKL/RANK/OPG signal trail: significance of genetic polymorphisms in the etiology of postmenopausal osteoporosis.

OBJECTIVES: Recent studies have demonstrated that disorders of bone metabolism, which is regulated by RANK/RANKL/OPG signaling pathway, are the cause of osteoporosis. The aim of the study was to investigate the distribution of genotypes of the RANK 575C>T and RANKL -643C>T polymorphisms and to analyze their relationship with bone parameters in postmenopausal women. MATERIAL AND METHODS: A total of 310 postmenopausal Caucasian women (139 with osteoporosis, 107 with osteopenia, and 64 healthy postmenopausal controls) were included. Bone mineral density (BMD) at the lumbar region of the spine (L2-L4) was measured by dual energy X-ray absorptiometry (DXA). Genetic analysis was performed using the PCR-RFLP method. RESULTS: Analysis of the frequency of genotypes and alleles of the RANK 575C>T and RANKL -643C>T polymorphisms did not show any statistically significant differences between the study groups (osteoporosis and osteopenia) and postmenopausal women with normal t-score value (ns). Notably, a significant association between the RANKL -643C>T polymorphism and body mass, such as BMI values in osteoporotic women (p<0.05), was observed. CONCLUSIONS: Our results suggest lack of association between the 575C>T RANK polymorphism and the development of osteoporosis. The -643C>T RANKL polymorphism, through its significant influence on body weight and BMI value, may contribute to the development of osteoporosis in postmenopausal women.

Temperature-Induced Lifshitz Transition in WTe2.

We use ultrahigh resolution, tunable, vacuum ultraviolet laser-based, angle-resolved photoemission spectroscopy (ARPES), temperature- and field-dependent resistivity, and thermoelectric power (TEP) measurements to study the electronic properties of WTe2, a compound that manifests exceptionally large, temperature-dependent magnetoresistance. The Fermi surface consists of two pairs of electron and two pairs of hole pockets along the X-Γ-X direction. Using detailed ARPES temperature scans, we find a rare example of a temperature-induced Lifshitz transition at T≃160 K, associated with the complete disappearance of the hole pockets. Our electronic structure calculations show a clear and substantial shift of the chemical potential µ(T) due to the semimetal nature of this material driven by modest changes in temperature. This change of Fermi surface topology is also corroborated by the temperature dependence of the TEP that shows a change of slope at T≈175 K and a breakdown of Kohler's rule in the 70-140 K range. Our results and the mechanisms driving the Lifshitz transition and transport anomalies are relevant to other systems, such as pnictides, 3D Dirac semimetals, and Weyl semimetals.

Competition between the pseudogap and superconductivity in the high-T(c) copper oxides.

In a classical Bardeen-Cooper-Schrieffer superconductor, pairing and coherence of electrons are established simultaneously below the critical transition temperature (T(c)), giving rise to a gap in the electronic energy spectrum. In the high-T(c) copper oxide superconductors, however, a pseudogap extends above T(c). The relationship between the pseudogap and superconductivity is one of the central issues in this field. Spectral gaps arising from pairing precursors are qualitatively similar to those caused by competing electronic states, rendering a standard approach to their analysis inconclusive. The issue can be settled, however, by studying the correlation between the weights associated with the pseudogap and superconductivity spectral features. Here we report a study of two spectral weights using angle-resolved photoemission spectroscopy. The weight of the superconducting coherent peak increases away from the node following the trend of the superconducting gap, but starts to decrease in the antinodal region. This striking non-monotonicity reveals the presence of a competing state. We demonstrate a direct correlation, for different values of momenta and doping, between the loss in the low-energy spectral weight arising from the opening of the pseudogap and a decrease in the spectral weight associated with superconductivity. We therefore conclude that the pseudogap competes with the superconductivity by depleting the spectral weight available for pairing.

Electronic phase diagram of high-temperature copper oxide superconductors.

In order to understand the origin of high-temperature superconductivity in copper oxides, we must understand the normal state from which it emerges. Here, we examine the evolution of the normal state electronic excitations with temperature and carrier concentration in Bi(2)Sr(2)CaCu(2)O(8+δ) using angle-resolved photoemission. In contrast to conventional superconductors, where there is a single temperature scale T(c) separating the normal from the superconducting state, the high-temperature superconductors exhibit two additional temperature scales. One is the pseudogap scale T(∗), below which electronic excitations exhibit an energy gap. The second is the coherence scale T(coh), below which sharp spectral features appear due to increased lifetime of the excitations. We find that T(∗) and T(coh) are strongly doping dependent and cross each other near optimal doping. Thus the highest superconducting T(c) emerges from an unusual normal state that is characterized by coherent excitations with an energy gap.

The importance of 8993C>T (Thr399Ile) TLR4 polymorphism in etiology of osteoporosis in postmenopausal women.

INTRODUCTION: Toll-like receptors (TLR) may play a key role in initiating cellular signaling pathways by increasing the levels of inflammatory cytokines which, cooperating with osteoclasts, influence bone turnover Numerous research articles focused on the genetic background of this condition, among others on polymorphic variants in TLR genes. The aim of the study was to examine the role of 20877G>A (Arg753GIn) in TLR2 gene and 8993C>T (Thr399lle) in TLR4 gene in the etiopathogenesis of postmenopausal osteoporosis in Polish women. MATERIAL AND METHODS: This study included 180 postmenopausal women (t-score < or = -2.5), 153 postmenopausal women with osteopenia (t-score between -2.5 and -1), and 91 postmenopausal healthy women with correct t-score (t-score >-1). The 20877G>A TLR2 and 8993C>T TLR4 polymorphisms were determined by PCR/RFLP analysis. RESULTS: The analysis did not reveal statistically significant differences in the distribution of genetic variants of 20877G>A TLR2 polymorphism between the investigated groups of women. The most interesting results were connected with 8993C>T TLR4 polymorphism. Comparison of the group with osteoporosis and controls revealed overrepresentation of heterozygous 8993CT genotype (13.3 vs. 5.5%, OR=2.65, p=0.03). Also, mutated 8993T allele was overrepresented in the group with osteoporosis (6.7 vs. 2.7%, OR=2.52, p=0.04). Higher frequency of heterozygous 8993CT genotype (13.3 vs. 4.6%, OR=3.21, p=0.004) and mutated 8993T allele (6.7 vs. 2.3%, OR=3.05, p=0. 005) was noted in osteoporotic women as compared to the group with osteopenia. Higher frequency of heterozygous 8993CT genotype (13.3% vs. 5.3%, OR=2.73, p=0.003) and mutated 8993T allele (6.7 vs. 2.7%, OR=2.67, p=0.004) was observed in the group with osteoporosis as compared to women with osteopenia and with correct t-score. CONCLUSIONS: Results of our study suggest an important role of mutated 8993T allele of 8993C>T TLR4 polymorphisms in the etiology of postmenopausal osteoporosis. Nevertheless, this observation requires further investigation with larger sample size comprised of Polish women.

Change in Striatal Functional Connectivity Networks Across Two Years Due to Stimulant Exposure in Childhood ADHD: Results from the ABCD Sample.

Widely prescribed for Attention-Deficit/Hyperactivity Disorder (ADHD), stimulants (e.g., methylphenidate) have been studied for their chronic effects on the brain in prospective designs controlling dosage and adherence. While controlled approaches are essential, they do not approximate real-world stimulant exposure contexts where medication interruptions, dosage non-compliance, and polypharmacy are common. Brain changes in real-world conditions are largely unexplored. To fill this gap, we capitalized on the observational design of the Adolescent Brain Cognitive Development (ABCD) study to examine effects of stimulants on large-scale bilateral cortical networks' resting-state functional connectivity (rs-FC) with 6 striatal regions (left and right caudate, putamen, and nucleus accumbens) across two years in children with ADHD. Bayesian hierarchical regressions revealed associations between stimulant exposure and change in rs-FC of multiple striatal-cortical networks, affiliated with executive and visuo-motor control, which were not driven by general psychotropic medication. Of these connections, three were selective to stimulants versus stimulant naive: reduced rs-FC between caudate and frontoparietal network, and between putamen and frontoparietal and visual networks. Comparison with typically developing children in the ABCD sample revealed stronger rs-FC reduction in stimulant-exposed children for putamen and frontoparietal and visual networks, suggesting a normalizing effect of stimulants. 14% of stimulant-exposed children demonstrated reliable reduction in ADHD symptoms, and were distinguished by stronger rs-FC reduction between right putamen and visual network. Thus, stimulant exposure for a two-year period under real-world conditions modulated striatal-cortical functional networks broadly, had a normalizing effect on a subset of networks, and was associated with potential therapeutic effects involving visual attentional control.

Formation of gapless Fermi arcs and fingerprints of order in the pseudogap state of cuprate superconductors.

We use angle-resolved photoemission spectroscopy and a new quantitative approach based on the partial density of states to study properties of seemingly disconnected portions of the Fermi surface (FS) that are present in the pseudogap state of cuprates called Fermi arcs. We find that the normal state FS collapses very abruptly into Fermi arcs at the pseudogap temperature (T*). Surprisingly, the length of the Fermi arcs remains constant over an extended temperature range between T* and T(pair), consistent with the presence of an ordered state below T*. These arcs collapse again at the temperature below which pair formation occurs (T(pair)) either to a point or a very short arc, whose length is limited by our experimental resolution. The tips of the arcs span between points defining a set of wave vectors in momentum space, which are the fingerprints of the ordered state that causes the pseudogap.

Unusual temperature dependence of band dispersion in Ba(Fe(1-x)Ru(x))2As2 and its consequences for antiferromagnetic ordering.

We have performed detailed studies of the temperature evolution of the electronic structure in Ba(Fe(1-x)Ru(x))(2)As(2) using angle resolved photoemission spectroscopy. Surprisingly, we find that the binding energy of both hole and electron bands changes significantly with temperature in both pure and Ru substituted samples. The hole and electron pockets are well nested at low temperature in unsubstituted (BaFe(2)As(2)) samples, which likely drives the spin density wave and resulting antiferromagnetic order. Upon warming, this nesting is degraded as the hole pocket shrinks and the electron pocket expands. Our results demonstrate that the temperature dependent nesting may play an important role in driving the antiferromagnetic-paramagnetic phase transition.

Rational design of network properties in guest-host assembled and shear-thinning hyaluronic acid hydrogels.

Shear-thinning hydrogels afford direct injection or catheter delivery to tissues without potential premature gel formation and delivery failure or the use of triggers such as chemical initiators or heat. However, many shear-thinning hydrogels require long reassembly times or exhibit rapid erosion. We developed a shear-thinning hyaluronic acid (HA) hydrogel based on the guest-host interactions of adamantane modified HA (guest macromer, Ad-HA) and ß-cyclodextrin modified HA (host macromer, CD-HA). The ability of the guest and host molecules to interact with their counterpart following conjugation to HA was confirmed by (1)H NMR spectroscopy and was similar to that of the native complex. Mixing of Ad-HA and CD-HA resulted in rapid formation of a hydrogel composed of guest-host bonds. The hydrogel physical properties, including mechanics and flow characteristics, were dependent on cross-link density and network structure, which were controlled through macromer concentration, the extent of guest macromer modification, and the molar ratio of guest and host functional groups. The guest-host assembly mechanism permitted both shear-thinning behavior for ease of injection and near-instantaneous reassembly for material retention at the target sight. The hydrogel erosion and release of a model biomolecule were also dependent on design parameters and were sustained for over 60 days. These hydrogels show potential as a minimally invasive injectable hydrogel for biomedical applications.