Dynamical polarization, optical conductivity and plasmon mode of a linear triple component fermionic system.

We investigate the density and optical responses of a linear triple component fermionic system in both non-interacting and interacting regimes by computing its dynamical polarization function, random phase approximation dielectric function, plasmon mode and long wavelength optical conductivity and compare the results with those of Weyl fermions and three-dimensional free electron gas. Linear triple component fermions are pseudospin-1 generalization of Weyl fermions, consisting of two linearly dispersive bands and a flat band. The presence of flat band brings about notable modifications in the response properties with respect to Weyl fermions such as induction of a new region in the particle-hole continuum, increased static polarization, reduced plasmon gap, shift in absorption edge, enhanced rate of increase in energy absorption with frequency and highly suppressed intercone transitions in the long wavelength limit. The plasmon dispersion follows the usualω∼ω0+ω1q2nature as observed in other three-dimensional systems.

Berry curvature induced anisotropic magnetotransport in a quadratic triple-component fermionic system.

Triple-component fermions (TCFs) are pseudospin-1 quasiparticles hosted by certain three-band semimetals in the vicinity of their band-touching nodes (2019Phys. Rev.B100235201). The excitations comprise of a flat band and two dispersive bands. The energies of the dispersive bands areE±=±αn2k⊥2n+vz2kz2withk⊥=kx2+ky2andn= 1, 2, 3. In this work, we obtain the exact expression of Berry curvature, approximate form of density of states and Fermi energy as a function of carrier density for any value ofn. In particular, we study the Berry curvature induced electrical and thermal magnetotransport properties of quadratic (n= 2) TCFs using semiclassical Boltzmann transport formalism. Since the energy spectrum is anisotropic, we consider two orientations of magnetic field (B): (i)Bapplied in thex-yplane and (ii)Bapplied in thex-zplane. For both the orientations, the longitudinal and planar magnetoelectric/magnetothermal conductivities show the usual quadratic-Bdependence and oscillatory behavior with respect to the angle between the applied electric field/temperature gradient and magnetic field as observed in other topological semimetals. However, the out-of-plane magnetoconductivity has an oscillatory dependence on angle between the applied fields for the second orientation but is angle-independent for the first one. We observe large differences in the magnitudes of transport coefficients for the two orientations at a given Fermi energy. A noteworthy feature of quadratic TCFs which is typically absent in conventional systems is that certain transport coefficients and their ratios are independent of Fermi energy within the low-energy model.

Berry curvature induced magnetotransport in 3D noncentrosymmetric metals.

We study the magnetoelectric and magnetothermal transport properties of noncentrosymmetric metals using semiclassical Boltzmann transport formalism by incorporating the effects of Berry curvature (BC) and orbital magnetic moment (OMM). These effects impart quadratic-Bdependence to the magnetoelectric and magnetothermal conductivities, leading to intriguing phenomena such as planar Hall effect, negative magnetoresistance (MR), planar Nernst effect and negative Seebeck effect. The transport coefficients associated with these effects show the usual oscillatory behavior with respect to the angle between the applied electric field and magnetic field. The bands of noncentrosymmetric metals are split by Rashba spin-orbit coupling except at a band touching point (BTP). For Fermi energy below (above) the BTP, giant (diminished) negative MR is observed. This difference in the nature of MR is related to the magnitudes of the velocities, BC and OMM on the respective Fermi surfaces, where the OMM plays the dominant role. The absolute MR and planar Hall conductivity show a decreasing (increasing) trend with Rashba coupling parameter for Fermi energy below (above) the BTP.

Topological phase transition induced by band structure modulation in a Chern insulator.

We study a systematic evolution of the topological properties of a Chern insulator upon smooth variation of a hopping parameter (t1) of the electrons among a pair of nearest neighbour sites on a honeycomb lattice, while keeping the other two hopping terms (t) fixed. In the absence of a Haldane flux, the tuning oft1results in gradual shifting of the Dirac cones which eventually merge into one at theMpoint in the Brillouin zone (BZ) att1= 2twith a gapless semi-Dirac dispersion at low energies. In the presence of a Haldane flux, the system becomes a Chern insulator fort1< 2t, but turns gapless att1= 2twith the semi-Dirac dispersion being transformed to an anisotropic Dirac one. The spectrum eventually gaps out and transforms into a trivial insulator fort1> 2t. The Chern number phase diagram obtained via integrating the Berry curvature over the BZ shows a gradual shrinking of the 'topological' lobes, and vanishes just beyondt1= 2t, where a small but a finite Berry curvature still exists. Thus, there is a phase transition from a topological phase to a trivial phase across the semi-Dirac point (t1= 2t). The vanishing of the anomalous Hall conductivity plateau and the merger of the chiral edge states with the bulk bands near theMpoint provide robust support of the observed phase transition.

A Narrative Review on Clinical Applications of fNIRS.

Functional near-infrared spectroscopy (fNIRS) is a relatively new imaging modality in the functional neuroimaging research arena. The fNIRS modality non-invasively investigates the change of blood oxygenation level in the human brain utilizing the transillumination technique. In the last two decades, the interest in this modality is gradually evolving for its real-time monitoring, relatively low-cost, radiation-less environment, portability, patient-friendliness, etc. Including brain-computer interface and functional neuroimaging research, this technique has some important application of clinical perspectives such as Alzheimer's disease, schizophrenia, dyslexia, Parkinson's disease, childhood disorders, post-neurosurgery dysfunction, attention, functional connectivity, and many more can be diagnosed as well as in some form of assistive modality in clinical approaches. Regarding the issue, this review article presents the current scopes of fNIRS in medical assistance, clinical decision making, and future perspectives. This article also covers a short history of fNIRS, fundamental theories, and significant outcomes reported by a number of scholarly articles. Since this review article is hopefully the first one that comprehensively explores the potential scopes of the fNIRS in a clinical perspective, we hope it will be helpful for the researchers, physicians, practitioners, current students of the functional neuroimaging field, and the related personnel for their further studies and applications.

Abdominal Malignancy with Skin Manifestation and Thromboembolic Disease: An Unusual Presentation.

A 55-year-old male presented to our hospital with shortness of breath and leg swelling. Imaging studies revealed deep vein thrombosis and bilateral pulmonary embolism. The patient was placed on anticoagulation. A palpable umbilical nodule consistent with the appearance of Sister Mary Joseph's nodule (SMJN) raised the possibility of an underlying gastrointestinal malignancy. The patient also had significant ascites and underwent paracentesis with cytology, upper gastrointestinal and lower gastrointestinal endoscopy with the biopsy. Gastric lesion histology revealed gastric adenocarcinoma with peritoneal and colonic metastases. The patient was started on chemotherapy with 5-fluorouracil, leucovorin, oxaliplatin (FOLFOX) for disseminated gastric malignancy. SMJN is a rare cutaneous metastatic manifestation which needs to be considered as a differential diagnosis of an umbilical tumor for prompt diagnosis and initiation of treatment.

Feasibility and effectiveness of electronic vs. paper partograph on improving birth outcomes: A prospective crossover study design.

BACKGROUND: The partograph has been endorsed by World Health Organization (WHO) since 1994 which presents an algorithm for assessing maternal and foetal conditions and labor progression. Monitoring labour with a partograph can reduce adverse pregnancy outcomes such as prolonged labor, emergency C-sections, birth asphyxia and stillbirths. However, partograph use is still very low, particularly in low and middle income countries (LMICs). In Bangladesh the reported partograph user rate varies from 1.4% to 33.0%. Recently, an electronic version of the partograph, with the provision of online data entry and user aid for emergency clinical support, has been tested successfully in different settings. With this proven evidence, we conducted and operations research to test the feasibility and effectiveness of implementing an e-partograph, for the first time, in 2 public hospitals in Bangladesh. METHODS: We followed a prospective crossover design. Two secondary level referral hospitals, Jessore and Kushtia District Hospital (DH) were the study sites. All pregnant women who delivered in the study hospitals were the study participants. All nurse-midwives working in the labor ward of study hospitals were trained on appropriate use of both types of partograph along with standard labour management guidelines. Collected quantitative data was analyzed using SPSS 23 statistical software. Discrete variables were expressed as percentages and presented as frequency distribution and cross tabulations. Chi square tests were employed to test the association between exposure and outcome variables. Potential confounding factors were adjusted using multivariate binary logistic regression methods. Ethical approval was obtained from the institutional review board of the International Centre for Diarrheal Disease Research, Bangladesh (icddr,b). FINDINGS: In total 2918 deliveries were conducted at Jessore DH and 2312 at Kushtia DH during one-year study period. Of them, 1012 (506 in each facility) deliveries were monitored using partograph (paper or electronic). The trends of facility based C-section rates was downwards in both the hospitals; 43% to 37% in Jessore and from 36% to 25% in Kushtia Hospital. There was a significant reduction of prolonged labour with e-partograph use. In Kushtia DH, the prolonged labour rate was 42% during phase 1 with the paper version which came down to 29% during phase-2 with the e-partograph use. The similar result was observed in Jessore DH where the prolonged labour rate reduced to 7% with paper partograph from the reported 30% prolonged labour with e-partograph. The e-partograph user rate was higher than the paper partograph during both phases (phase 1: 3.31, CI: 2.04-5.38, p < .001 and in phase 2: 15.20 CI: 6.36-36.33, p < .001) after adjusting for maternal age, parity, gestational age, religion, mother's education, husband's education, and fetal sex. CONCLUSION: The partograph user rate has significantly improved with the e- partograph and was associated with an overall reduction in cesarean births. Use of the e-partograph was also associated with reduced rates of prolonged labour. This study has added to the growing body of evidence on the positive impact of e-partograph use. We recommend implementing e-partograph intervention at scale in both public and private hospitals in Bangladesh. TRIAL REGISTRATION: ClinicalTrials.gov NCT03509103.

Dynamics of a quasiparticle in the α-T3 model: role of pseudospin polarization and transverse magnetic field on zitterbewegung.

We consider the α-T 3 model which provides a smooth crossover between the honeycomb lattice with pseudospin 1/2 and the dice lattice with pseudospin 1 through the variation of a parameter α. We study the dynamics of a wave packet representing a quasiparticle in the α-T3 model with zero and finite transverse magnetic field. For zero field, it is shown that the wave packet undergoes a transient zitterbewegung (ZB). Various features of ZB depending on the initial pseudospin polarization of the wave packet have been revealed. For an intermediate value of the parameter α i.e. for [Formula: see text] the resulting ZB consists of two distinct frequencies when the wave packet was located initially in rim site. However, the wave packet exhibits single frequency ZB for [Formula: see text] and [Formula: see text]. It is also unveiled that the frequency of ZB corresponding to [Formula: see text] gets exactly half of that corresponding to the [Formula: see text] case. On the other hand, when the initial wave packet was in hub site, the ZB consists of only one frequency for all values of α. Using stationary phase approximation, we find analytical expression of velocity average which can be used to extract the associated timescale over which the transient nature of ZB persists. On the contrary, the wave packet undergoes permanent ZB in presence of a transverse magnetic field. Due to the presence of a large number of Landau energy levels, the oscillations in ZB appear to be much more complicated. The oscillation pattern depends significantly on the initial pseudospin polarization of the wave packet. Furthermore, it is revealed that the number of the frequency components involved in ZB depends on the parameter α.

Electrical and thermoelectric transport properties of two-dimensional fermionic systems with k-cubic spin-orbit coupling.

We investigate the effect of k-cubic spin-orbit interaction on the electrical and thermoelectric transport properties of two-dimensional fermionic systems. We obtain exact analytical expressions of the inverse relaxation time (IRT) and the Drude conductivity for long-range Coulomb and short-range delta scattering potentials. The IRT reveals that the scattering is completely suppressed along the three directions [Formula: see text] with [Formula: see text]. We also obtain analytical results of the thermopower and thermal conductivity at low temperature. The thermoelectric transport coefficients obey the Wiedemann-Franz law, even in the presence of k-cubic Rashba spin-orbit interaction (RSOI) at low temperature. In the presence of a quantizing magnetic field, the signature of the RSOI is revealed through the appearance of the beating pattern in the Shubnikov-de Haas (SdH) oscillations of thermopower and thermal conductivity in the low magnetic field regime. The empirical formulae for the SdH oscillation frequencies accurately describe the locations of the beating nodes. The beating pattern in magnetothermoelectric measurement can be used to extract the spin-orbit coupling constant.

Phonon-drag magnetoquantum oscillations in graphene.

A theory of low-temperature phonon-drag magnetothermopower [Formula: see text] is presented in graphene in a quantizing magnetic field. [Formula: see text] is found to exhibit quantum oscillations as a function of magnetic field B and electron concentration n e . The amplitude of the oscillations is found to increase (decrease) with increasing B (n e ). The behavior of [Formula: see text] is also investigated as a function of temperature. A large value of [Formula: see text] (∼few hundreds of µV K-1) is predicted. Numerical values of [Formula: see text] are compared with the measured magnetothermopower S xx and the diffusion component [Formula: see text] from the modified Girvin-Jonson theory.

Magnetotransport properties of the α-T 3 model.

Using the well-known Kubo formula, we evaluate magnetotransport quantities, such as the collisional and Hall conductivities of the α-T 3 model. The collisional conductivity exhibits a series of peaks at a strong magnetic field. Each of the conductivity peaks for [Formula: see text] (graphene) splits into two in the presence of a finite α. This splitting occurs due to a finite phase difference between the contributions coming from the two valleys. The density of states is also calculated to explore the origin of the splitting of conductivity peaks. As α approaches 1, the right split part of a conductivity peak comes closer to the left split part of the next conductivity peak. At [Formula: see text], they merge with each other to produce a new series of the conductivity peaks. On the other hand, the Hall conductivity undergoes a smooth transition from [Formula: see text] to [Formula: see text] with n = 0,1,2,... as we tune α from 0-1. For intermediate α, we obtain the Hall plateaus at values 0,2,4,6,8,... in units of e 2/h.

Optical conductivity of a 2DEG with anisotropic Rashba interaction at the interface of LaAlO3/SrTiO3.

We study optical conductivity of a two-dimensional electron gas with anisotropic k-cubic Rashba spin-orbit interaction formed at the LaAlO3/SrTiO3 interface. The anisotropic spin splitting energy gives rise to different features of the optical conductivity in comparison to the isotropic k-cubic Rashba spin-orbit interaction. For large carrier density and strong spin-orbit couplings, the density dependence of Drude weight deviates from the linear behavior. The charge and optical conductivities remain isotropic despite anisotropic nature of the Fermi contours. An infinitesimally small photon energy would suffice to initiate inter-band optical transitions due to degeneracy along certain directions in momentum space. The optical conductivity shows a single peak at a given photon energy depending on the system parameters and then falls off to zero at higher photon energy. These features are lacking for systems with isotropic k-cubic Rashba spin-orbit coupling. These striking features can be used to extract the information about nature of the spin-orbit interaction experimentally and illuminate some light on the orbital origin of the two-dimensional electron gas.

Evaluation of Preoperative Serum Levels of CA 125 and Expression of p53 in Ovarian Neoplasms: A Prospective Clinicopathological Study in a Tertiary Care Hospital.

OBJECTIVES: To assess the preoperative serum levels of CA 125 with its diagnostic role and to evaluate the p53 expression in patients of primary ovarian neoplasms. We also wished to judge their relationship with other parameters like clinical staging and histopathologic tumor type. MATERIALS AND METHODS: The present study was conducted on 86 patients during the study period of 2.5 years. Preoperative CA 125 levels were evaluated by an automated immunoassay analyzer. p53 expression was judged immunohistochemically with pre-diluted monoclonal antibody. An objective scoring was done depending on distinct nuclear immunopositivity. RESULTS: Median value of preoperative CA 125 levels was 32 U/mL in benign surface epithelial-stromal tumors (BSEST), 53 U/mL in borderline surface epithelial-stromal tumors (BOT), 346 U/mL in malignant surface epithelial-stromal tumors (MSEST) and 560 U/mL in serous adenocarcinomas (SAC). Most of ovarian tumors were in the FIGO stage I (64 cases, 74.4%), but higher stages (II, III, IV) were observed mostly in MSESTs. SACs displayed the maximum p53 expression. Considering the cut-off value of more than 35 U/mL in CA 125 levels, the sensitivity to diagnose MSESTs was 94.7%. Preoperative CA 125 levels strongly and positively correlated with FIGO staging and p53 expression. Similarly p53 expression strongly and positively correlated with FIGO staging and histopathological categories. CONCLUSION: Higher values of preoperative CA 125 levels and higher expression p53 are associated with MSESTs and BOTs especially of serous type. They strongly correlate with each other and with tumor stage. But there is no serum CA 125 concentration that can clearly differentiate benign and malignant ovarian masses.

Correlation of melanophore index with a battery of functional genomic stress indicators for measurement of environmental stress in aquatic ecosystem.

The correlation of primary stress indicator; melanophore index (MI) with set of genomic stress indicators is important for a better understanding of the cellular stress pathway induced by xenobiotics in aquatic species. This study presents a correlation between melanophore index (MI) and genomic stress indicators in Oreochromis mossambicus treated with lead nitrate, phenol and hexachlorocyclohexane (HCH). O. mossambicus was exposed to sub-lethal concentrations of the different LC50 values (96 h) of the tested chemicals at varying exposure periods and the response via genomic stress indicators and scale melanophores were assessed in accordance with standard protocols. Melanophore index decreased significantly (p<0.01) in a time dependent pattern to the tested chemicals. Gene expression showed significant time dependent increase in the expression of heat shock proteins (HSP70 and HSP60). Vitellogenin (Vtg) expression insignificantly altered. Significant increase in the expression of melanin concentrating hormone (MCH) was observed in response to hexachlorocyclohexane (HCH) in the treated fish. The findings demonstrated an inverse relationship between melanophore index and the set of genomic stress indicators.

Magnetotransport properties of 2D fermionic systems with k-cubic Rashba spin-orbit interaction.

The spin-orbit interaction in heavy hole gas formed at p-doped semiconductor heterojunctions and electron gas at SrTiO3 surfaces is cubic in momentum. Here we report magnetotransport properties of k-cubic Rashba spin-orbit coupled 2D fermionic systems. We study longitudinal and Hall components of the resistivity tensor analytically as well as numerically. The longitudinal resistivity shows a beating pattern due to different Shubnikov-de Haas (SdH) oscillation frequencies f ± for spin-up and spin-down fermions. We propose empirical forms of f ± as exact expressions are not available, which are being used to find locations of the beating nodes. The beating nodes and the number of oscillations between any two successive nodes obtained from exact numerical results are in excellent agreement with those calculated from the proposed empirical formula. In the Hall resistivity, an additional Hall plateau appears between the two conventional ones as the spin-orbit coupling constant increases. The width of this additional plateau increases with spin-orbit coupling constant.

Beating pattern in quantum magnetotransport coefficients of spin-orbit coupled Dirac fermions in gated silicene.

We report a theoretical study of magnetotransport coefficients of spin-orbit coupled gated silicene in the presence and absence of spatial periodic modulation. The combined effect of spin-orbit coupling and perpendicular electric field manifests through the formation of a regular beating pattern in Weiss and SdH oscillations. Analytical results, in addition to the numerical results, of the beating pattern formation are provided. The analytical results yield a beating condition which will be useful to determine the spin-orbit coupling constant by simply counting the number of oscillation between any two successive nodes. Moreover, the numerical results of modulation effect on collisional and Hall conductivities are presented.

Correlation of cytohistlogical expression and serum level of ca125 in ovarian neoplasm.

UNLABELLED: Context or Background: CA125 is a biomarker that has potential utility across the spectrum: risk assessment, early detection, diagnosis, prognosis, monitoring and therapy. AIMS AND OBJECTIVES: This study was conducted to establish the validity and reliability of correlation of CA125 serum level with immunochemistry expression in imprint cytology and tissues for diagnostic purpose. MATERIALS AND METHODS: A prospective study was done on 50 cases of clinically and radiologically diagnosed ovarian tumor. Imprint smears were made intraoperatively from fresh samples and stained with M.G.G. stain for air dried smears and Papanicoloau stain for alcohol fixed smears. Stained smear was assessed and compared with subsequent histopathology report. Preoperative blood samples were obtained from all patients and sent for the assay of serum CA125 levels. Analysis of CA125 immunochemistry expression in imprint cytology and tissue was done and correlated with preoperative serum blood CA125 levels. RESULTS: Significant positive correlation was found between elevated serum CA125 levels and cytohistological expression of CA125. Overall sensitivity was 100%, specificity was 86%, positive predictive value was 74% and negative predictive value 100%. Diagnostic accuracy was 90% with high statistical significance (p<0.001). CONCLUSION: We considered 35 U/mL as the cut-off value when evaluating serum CA125 ovarian cancer. Patients with high serum levels show good cytohistological expression.

Phonon-drag magnetothermopower in Rashba spin-split two-dimensional electron systems.

We study the phonon-drag contribution to the thermoelectric power in a quasi-two-dimensional electron system confined in GaAs/AlGaAs heterostructure in the presence of both Rashba spin-orbit interaction and perpendicular magnetic field at very low temperature. It is observed that the peaks in the phonon-drag thermopower split into two when the Rashba spin-orbit coupling constant is strong. This splitting is a direct consequence of the Rashba spin-orbit interaction. We show the dependence of phonon-drag thermopower on both magnetic field and temperature numerically. A power-law dependence of phonon-drag magnetothermopower on the temperature in the Bloch-Gruneisen regime is found. We also extract the exponent of the temperature dependence of phonon-drag thermopower for different parameters like electron density, magnetic field, and the spin-orbit coupling constant.

Phonon-drag thermopower and hot-electron energy-loss rate in a Rashba spin-orbit coupled two-dimensional electron system.

We theoretically study the phonon-drag contribution to the thermoelectric power and the hot-electron energy-loss rate in a Rashba spin-orbit coupled two-dimensional electron system in the Bloch-Gruneisen (BG) regime. We assume that electrons interact with longitudinal acoustic phonons through a deformation potential and with both longitudinal and transverse acoustic phonons through a piezoelectric potential. The effect of the Rashba spin-orbit interaction on the magnitude and temperature dependence of the phonon-drag thermoelectric power and hot-electron energy-loss rate is discussed. We numerically extract the exponent of temperature dependence of the phonon-drag thermopower and the energy-loss rate. We find that the exponents are suppressed due to the presence of the Rashba spin-orbit coupling.

Acoustic phonon-limited resistivity of spin-orbit coupled two-dimensional electron gas: the deformation potential and piezoelectric scattering.

We study the interaction between electron and acoustic phonons in a Rashba spin-orbit coupled two-dimensional electron gas using Boltzmann transport theory. Both the deformation potential and piezoelectric scattering mechanisms are considered in the Bloch-Grüneisen (BG) regime as well as in the equipartition (EP) regime. The effect of the Rashba spin-orbit interaction on the temperature dependence of the resistivity in the BG and EP regimes is discussed. We find that the effective exponent of the temperature dependence of the resistivity in the BG regime decreases due to spin-orbit coupling.