Degenerate Materials Research Articles

Single crystal synthesis and characterization of proposed eight-fold degenerate topological material Bi2PdO4

Materials with nonsymmorphic symmetries have numerous applications and have recently come to the forefront as potentially containing novel topological states of matter, such as eight-fold fermions. In this paper, we report the single crystal growth of eight-fold degenerate topological material, Bi2PdO4 via melt-growth technique. The structural properties and chemical composition are confirmed by X-ray diffraction (XRD) and energy-dispersive x-ray analysis studies, respectively. Powder XRD shows that Bi2PdO4 crystallizes in the tetragonal P4/ncc (#130) type structure which is made up of PdO4 square planar units along the c direction. Because of the decreasing trend of magnetization with field, this sample exhibits room temperature diamagnetism. Our temperature dependent resistivity measurement suggests the semiconducting nature of the compound with an estimated band gap of ∼153 meV from Arrhenius fitting. Our Raman spectroscopy data shows peak shifting with decreasing temperature from 300 K to 100 K. Our density functional theory calculation suggests eightfold band crossing at the A point. From our DFT calculations, we determined a band gap of 176 meV in the absence of Spin-Orbit Coupling (SOC) and 180 meV with SOC. This aligns with our experimental observations. Finally, our present study provides a new direction for further transport and spectroscopic investigation in this compound.

A Single-Institution Case Series of Total Endovascular Relining for Type 3 Endoleaks in Traditional Endovascular Aneurysm Repair (EVAR) Grafts with Raised Bifurcations

The endovascular repair of infrarenal abdominal aortic aneurysms can be performed with a wide variety of devices. Many of these grafts elevate the aortic bifurcation which can limit future repairs if the graft material fails thereby creating a type III endoleak to aorto-uniliac grafts. Many manufacturers have grafts susceptible to this, but we have seen this in the Medtronic AneuRx graft. Our goal is to provide technical details and outcomes regarding a novel technique to reline these grafts while maintaining inline flow to the iliac arteries. This was a single-institution review of patients who had endoleaks requiring intervention after a previously placed graft with an elevated aortic bifurcation. Primary outcomes included technical success defined as placement of all planned devices, resolution of type III endoleak, aneurysm size at follow-up, and requirement of reintervention. Secondary outcomes included 30-day complications, aneurysm-related mortality, and all-cause mortality. Technical details of the operation include back-table deployment of an Ovation device, modification of the deployment system tether and pre-emptive placement of an up and over 0.014″ wire. The wire is placed up and over and hung outside the contralateral gate. Once the main body is introduced above the old graft, the 0.014" is snared from the contralateral side and externalized. The main body is then able to be seated at the bifurcation as the limb is not fully deployed and then device deployment is completed per instructions for use. Our study consists of 4 individuals, 3 of which had an abdominal aortic aneurysm initially managed with an AneuRx endovascular aneurysm repair and 1 with a combination of Gore and Cook grafts. All 4 patients were male with an average age of 84.5years at time of reline. All patients had at least 10years between initial surgery and reline at our institution. Primary outcomes revealed no type 1 or 3 endoleaks at follow-up, technical success was 100% and 1 patient required reintervention for aneurysm growth and type 2 endoleak. In terms of our secondary outcomes, there was 1 postoperative complication which was cardiac dysfunction secondary to demand ischemia, aneurysm-related mortality was 0% and all-cause mortality was 25% at average follow-up of 2.44years. As individuals continue to age, there are more patients who would benefit from less invasive reinterventions following endovascular aneurysm repair. Whether this is due to aortic degeneration, stent migration, or stent material damage is not always known. In this study, we present an endovascular approach to treating type III endoleak patients with a previous graft and elevated aortic bifurcation using Ovation stent grafts and found no evidence of type 1 or 3 endoleaks on follow-up imaging. This approach may allow patients with type III endoleak the option of a minimally invasive, percutaneous approach where they previously would not have had one.

Study of La Doping on the Electronic Structure and Magneto-Optical Properties of ZnO by GGA+U Method

Based on the density functional theory, the effect of rare-earth La doping at different concentrations on the electronic structure, optical properties, and magnetic properties of ZnO was calculated by using the GGA+U method under the condition of spin polarization. The calculation results show that the cell of a La-doped ZnO system is distorted, resulting in a formation energy less than zero, in which case it is easy to dope. After La doping, the band gap narrows, the Fermi level enters the conduction band, and the excess carriers induced by La atoms degenerate to form n-type degenerate semiconductor materials. In the visible light region, a blue shift in the optical absorption edge of the La-doped ZnO system causes an increased average static dielectric constant, stronger polarization ability, stronger binding ability on charges, and the photoconductivity of the doped ZnO system is improved. The magnetic moment of the La-doped ZnO system is zero, so it is not magnetic.

Highly degenerate 2D ferroelectricity in pore decorated covalent/metal organic frameworks.

Two-dimensional (2D) ferroelectricity, a fundamental concept in low-dimensional physics, serves as the basis of non-volatile information storage and various electronic devices. Conventional 2D ferroelectric (FE) materials are usually two-fold degenerate, meaning that they can only store two logical states. In order to break such limitation, a new concept of highly degenerate ferroelectricity with multiple FE states (more than 2) coexisting in a single 2D material is proposed. This is obtained through the asymmetrical decoration of porous covalent/metal organic frameworks (COFs/MOFs). Using first-principles calculations and Monte Carlo (MC) simulations, Li-decorated 2D Cr(pyz)2 is systematically explored as a prototype of highly degenerate 2D FE materials. We show that 2D FE Li0.5Cr(pyz)2 and LiCr(pyz)2 are four-fold and eight-fold degenerate, respectively, with sizable spontaneous electric polarization that can be switched across low transition barriers. In particular, the coupling between neighbouring electric dipoles in LiCr(pyz)2 induces novel ferroelectricity-controlled ferroelastic transition and direction-controllable hole transport channels. Moreover, three-fold and six-fold degenerate ferroelectricity is also demonstrated in P-decorated g-C3N4 and Ru-decorated C2N, respectively. Our work presents a general route to obtain highly degenerate 2D ferroelectricity, which goes beyond the two-state paradigm of traditional 2D FE materials and substantially broadens the applications of 2D FE compounds.

The electronic structure of a strongly bound sandwich MoS2-WS2 heterobilayer.

First of all, we show that two kinds of sandwich bilayers (BLs) are dynamically, thermally, and mechanically stable, which are degenerate p-type materials with intercalated Ca atoms, i.e., Nb-doped MoS2 homobilayers (HoBLs) and Nb-doped WS2-MoS2 heterobilayers (HtBLs) with 25% Nb content. Specifically, their interlayer bindings are five times stronger than van der Waals interactions in their pristine counterparts. Both of them are semiconductors with indirect band gaps in the visible region within the HSE06 exchange-correlation functional. Depending upon the presence and absence of centrosymmetry, they display interesting spin-valley coupling effects in such a way that opposite hidden spin polarization or opposite spin splitting is observed at opposite k-points. They can be easily engineered into direct gap materials under compressive (>2%) strain along the zigzag direction even with an explicit consideration of giant spin splitting. Under strain, they satisfy thermodynamic conditions for bifunctional catalysis in photocatalytic water splitting. In addition, the photoholes of the BLs can be subjected to lower overpotentials than those of pristine BLs for the oxygen evolution reaction. Electrons and holes in the sandwich HtBL can be separated into different layers under photon irradiation, allowing it to be more efficient than the corresponding HoBL in solar energy harvesting.

Uniform in‐plane elastic field inside a monoclinic elliptical inhomogeneity with non‐confocal elliptical interphase layer

We employ the Stroh quartic formalism to study the in-plane deformations of a three-phase composite consisting of an elliptical inhomogeneity embedded in an infinite matrix via an intermediate interphase layer itself bounded by two elliptical boundaries. The matrix is subjected to uniform remote in-plane loading. The two corresponding elliptical interfaces (one between the inhomogeneity and the interphase layer and the other between the interphase layer and the surrounding matrix) are non-confocal. The inhomogeneity and the matrix are assumed to be monoclinic materials with the symmetry plane at x3 = 0 whilst the intermediate interphase layer is composed of a mathematically degenerate orthotropic material. The non-confocal character of the two elliptical interfaces is carefully designed according to the orthotropic property of the interphase layer. Two simple conditions are found that ensure that the internal elastic field of stresses and strains inside the elliptical inhomogeneity is uniform. For given material and geometric parameters of the composite, these two conditions give two simple relationships among the three remote in-plane stresses. In addition, the internal uniform elastic field inside the elliptical inhomogeneity and the non-uniform elastic field in the interphase layer are determined in real-form in terms of the two 4 × 4 fundamental elasticity matrices for the inhomogeneity and the matrix and the three 2 × 2 Barnett-Lothe tensors for (only) the matrix.

The effect of vitamin E on the histological structure of kidney in rats treated with cyclophosphamide

Cyclophosphamide (CP) is a cytotoxic alkylating drug that is commonly used to treat autoimmune disorders and cancer. CP causes nephrotoxicity by producing highly reactive radicals devoid of oxygen. A fat-soluble vitamin E that interacts as a free radical scavenger, inhibiting nitrosamine production and blocking lipid peroxidation from polyunsaturated fatty acids. The aim of this research was to see if vitamin E may help combating CP induced nephrotoxicity. Thirty-two adult albino female Westar rats were randomly divided into four groups (n=8) and received daily treatment for thirty days. Group A considered as control group, receiving normal saline IP at dose of 0.3 ml, group B given 15 mg/kg b.w. of cyclophosphamide IP, while group C received cyclophosphamide with vitamin E at dose 200 mg/kg, oral administration of vitamin E one hour before injection of cyclophosphamide, in group D they received vitamin E orally at dose of 200 mg kg body weight mixed with olive oil daily by oral gavage. In group B the cyclophosphamide causes highly significant reduction in body weight and histologically showed atrophy of most glomeruli, distention in bowman’s space, tubular degeneration and luminal hyaline cast material, while in group C showed most of the glomeruli normal except atrophy of few number of glomeruli and focal epithelial degeneration of renal tubules. Our study found that one of the primary mechanisms induced by cyclophosphamide may be nephrotoxicity due to oxidative stress, and pretreatment with vitamin E reduces cyclophosphamide-induced nephrotoxicity.

Stroh formalism for various types of materials and deformations

Abstract The Stroh formalism is a complex variable formulation developed originally for solving the problems of two-dimensional linear anisotropic elasticity. By separation of the third variable for the linear variation of displacements along the thickness direction, it was proved to be applicable for the problems with coupled stretching-bending deformation. By the Radon transform which maps a three-dimensional solid to a two-dimensional plane, it can be applied to the three-dimensional deformation. By the elastic-viscoelastic correspondence principle, it is also valid for the viscoelastic materials in the Laplace domain. By expansion of the matrix dimension, it can be generalized to the coupled-field materials such as piezoelectric, piezomagnetic and magneto-electro-elastic materials. By introducing a small perturbation on the material constants, it can also be applied to the degenerate materials such as isotropic materials. Thus, in this paper, the Stroh formalism for several different types of materials (anisotropic elastic, piezoelectric, piezomagnetic, magneto-electro-elastic, viscoelastic) and deformations (two-dimensional, coupled stretching-bending, three-dimensional) are organized together and presented in the same mathematical form.

A powerful matrix formalism for stress singularities in anisotropic multi-material corners. Homogeneous (orthogonal) boundary and interface conditions

A computational code based on a semianalytic procedure for the determination of the characteristic exponents and the singular stress and displacement fields in multi-material corners is developed. Linear elastic anisotropic materials under generalized plane strain state are considered. This code is a universal computational tool able to analyze both open and closed (periodic) corners, composed of one or multiple materials with isotropic, transversely isotropic or orthotropic constitutive laws, covering both mathematically non-degenerate and degenerate materials in the framework of Stroh formalism. In multi-material corners, material junctions with perfectly bonded or frictionless sliding interfaces can be studied. The considered homogeneous boundary conditions cover stress free and fixed faces, or faces with some restricted or allowed direction of displacements, defined either in the reference frame aligned with the cylindrical coordinate system or in an inclined reference frame. The code is developed in MATLAB and it is based on the Stroh matrix formalism for anisotropic elasticity, the concept of transfer matrix for single material wedges, and on the matrix formalism for homogeneous (orthogonal) boundary conditions. The comparison of the characteristic exponents obtained by the present code and by the solution of closed-form eigenequations available in the literature, has a two-fold objective, first to exhaustively check the general computational implementation of the matrix formalism presented, and second to check the closed-form expressions of eigenequations for relevant specific cases published in the literature.

Emergency laparoscopic cholecystectomy for hemorrhagic cholecystitis: A case report.

IntroductionHemorrhagic cholecystitis (HC) is a rare but specific complication of acute cholecystitis. HC progression often leads to fatal and severe outcomes.Presentation of caseWe describe the case of a 64-year-old man who was diagnosed with HC. Intraoperatively, the gallbladder surface was congested. The resected specimen had no gallstones and showed basophilic degenerate material toward the mucosal surface. In addition, vascular congestion and red cell extravasation were noted at the bottom of the layer. The patient's postoperative course was good, and he was discharged with remission 4 days following the operation.DiscussionDiagnosis and treatment during early stages are the most critical aspects of HC management and may lead to improved outcomes.We successfully performed timely laparoscopic cholecystectomy for the treatment of HC.ConclusionIn cases where HC occurs, appropriate treatment should be chosen by experiential judgment and consideration of the current literature.

Local-Disorder-Induced Low Thermal Conductivity in Degenerate Semiconductor Cu22Sn10S32.

S-based semiconductors are attracting attention as environmentally friendly materials for energy-conversion applications because of their structural complexity and chemical flexibility. Here, we show that the delicate interplay between the chemical composition and cationic order/disorder allows one to stabilize a new sphalerite derivative phase of cubic symmetry in the Cu-Sn-S diagram: Cu22Sn10S32. Interestingly, its crystal structure is characterized by a semiordered cationic distribution, with the Cu-Sn disorder being localized on one crystallographic site in a long-range-ordered matrix. The origin of the partial disorder and its influence on the electronic and thermal transport properties are addressed in detail using a combination of synchrotron X-ray diffraction, Mössbauer spectroscopy, transmission electron microscopy, theoretical modeling, and transport property measurements. These measurements evidence that this compound behaves as a pseudogap, degenerate p-type material with very low lattice thermal conductivity (0.5 W m-1 K-1 at 700 K). We show that localized disorder is very effective in lowering κL without compromising the integrity of the conductive framework. Substituting pentavalent Sb for tetravalent Sn is exploited to lower the hole concentration and doubles the thermoelectric figure of merit ZT to 0.55 at 700 K with respect to the pristine compound. The discovery of this semiordered cubic sphalerite derivative Cu22Sn10S32 furthers the understanding of the structure-property relationships in the Cu-Sn-S system and more generally in ternary and quaternary Cu-based systems.

Degenerate orthotropic materials in the Stroh formalism for steady state problems

Degenerate orthotropic materials in the Stroh formalism for steady state problems

Continuum time-delayed electron hopping in the extended dynamical molecules and entropy-ruled Einstein relation for organic semiconductors

Charge transport (CT) in dynamically disordered molecular systems is still unclear; though it is fundamentally important to understand the semiconducting properties of molecular devices. In this regard, we explore vibronically coupled polaron hopping transport in the extended hopping systems (N + 1 sites) of thiazolothiazole (TZTZ) based molecules. The molecular vibrations correlated charge transfer integral and site energy fluctuation effects on polaron transport are analyzed by kinetic Monte-Carlo simulations. In order to quantify the CT properties more precisely, we have proposed the continuum time delayed CT mechanism, which takes account of typical disordered (static or dynamic) effect via dispersion on each CT quantity (like charge transfer rate, diffusion coefficient, mobility, current density and etc) at each hopping. The charge compressibility analysis further addresses the electronic level understanding of all CT quantities, which originally relates the thermodynamic density of states with CT. Using differential entropy-dependent charge density and diffusion expressions, the drift-diffusion transport has been elucidated for different extended systems of TZTZ derivatives. Besides, we have mainly developed entropy-ruled diffusion-mobility relation for both degenerate and nondegenerate materials to study the validity and limitations of original Einstein relation, which directly pertain to the device performance. Here, the traversing chemical potential along the hopping sites is the deterministic parameter of diffusion-mobility ratio. Using our continuum time delayed model, we can categorize the typical disordered transport in the molecular semiconductors; whether is dynamic or static or intermediate disordered transport.

Эффективность сочетанной терапии неоваскулярной возрастной макулярной дегенерации с применением анти-VEGF-препарата афлиберцепт и нутрицевтика «Ресвега форте»

Purpose. To evaluate the clinical efficacy of using the angiogenesis inhibitor aflibercept in combination with the nutraceutical «Resvega Forte» in the treatment of neovascular age-related macular degeneration (nAMD) Material and methods. The clinical study involved 25 patients (25 eyes) with nAMD, who received 3 «loading» intravitreal injections of aflibercept (IIA) 2.0 mg (0.05 ml) at intervals of 1 time per month. Further, during the year, all patients received therapy according to the «heal and extend the interval» protocol. The patients of the main group (14 people) were supplemented with triple IIA with the administration of the «Resvega Forte» complex, 1 capsule 2 times a day for three months and then, after 6 months, continued with a second course. Patients of the comparison group (11 persons) did not receive the «Resvega Forte» complex. The central retinal thickness (CRT), the presence of detachment of the retinal pigment epithelium and neuroepithelium, subretinal, intraretinal or fluid under the pigment epithelium were assessed. Results. By the 12th month of observation, none of the patients of the main group against the background of two complexes «Resvega Forte» was found to have a resumption of disease activity. The maximum corrected visual acuity increased 3 times and amounted to 0.75±0.03 compared to the initial 0.25±0.06. The circulatory system in these patients on average corresponded to the norm – 254.6±11.3 µm. In the comparison group, the resumption of disease activity was noted twice, which was accompanied by a decrease in the functional and morphological parameters of the retina. Conclusion. The inclusion of the nutraceutical «Resvega Forte» in the treatment regimen allows not only to reduce the risk of progression of nAMD, but also to increase the functional and morphological parameters of the retina. An integrated approach makes it possible to increase the interval between injections and reduce the required number of them without additional monitoring, which reduces the burden on both the patient and the doctor. Key words: neovascular age-related macular degeneration, aflibercept, nutraceutical «Resvega forte».

Revisiting Einstein's diffusion-mobility relation for universal quantum materials: A generalized paradigm

We have revisited the Einstein diffusion-mobility ratio, on the basis of the generalized Einstein relation, which quantifies both the quantum and classical levels of understanding on electron-hole dynamics in ordered and disordered materials. While the Einstein relation (diffusion-mobility ratio, D/) works only for classical systems under equilibrium cases, our generalized paradigm is quite general and works for systems ranging from classical to quantum systems in any dimensions. The proposed D/ formalism relies on the chemical potential which provides the cooperative nature between electronic and temperature counterparts on fundamental transport. Our generalized paradigm is applicable to both degenerate and non-degenerate cases, and explains the transition from linear to nonlinear relationship between the charge density and chemical potential. The symmetrical nature of electron-hole transport in highly degenerate two-dimensional quantum materials gives linear dispersion, preserving the time-reversal invariance property, while the symmetry is found to be broken in the nonlinear regime. Our generalized diffusion-mobility relation explains both the relativistic (Dirac particles) and non-relativistic regimes (Schrödinger particles) from low temperature to high temperature, and reproduces the classical Einstein relation in an appropriate limit.

High occurrence rate of xanthomatosis and nephrocalcinosis in aquarium-housed Atlantic wolffish Anarhichas lupus and spotted wolffish A. minor.

The Atlantic wolffish (AW) and the spotted wolffish (SW) are long-lived fish found in the North Atlantic and Arctic oceans and are respectively classified as special concern and threatened species, mainly due to fisheries bycatch. To better understand health issues associated with the care of these species in public aquaria, reports from all necropsies performed in 2 zoological institutions between 2009 and 2019 were reviewed (31 AW and 8 SW). These wolffish were fed with a similar fish-based diet and kept in multi-species exhibits with comparable environmental parameters. The most frequent necropsy findings were the presence of xanthomas (AW: 41.9%; SW: 75.0%), nephrocalcinosis (AW: 42.9%; SW: 75.0%) and urocystoliths (AW: 6.5%; SW: 62.5%). Xanthomas were mostly located at the base of pectoral fins and were characterized by extensive granulomatous inflammation centered on accumulations of partly mineralized degenerate fatty material, mainly composed of cholesterol crystals. Nephrocalcinosis was characterized by the deposition of calcium salts within the renal tubules and was commonly associated with tubular necrosis. The aquarium-housed wolffish were fed a coldwater fish-based diet. However, the natural diet of wolffish is composed mostly of invertebrates such as urchins and crustaceans. Differences in nutrient composition between these diets, such as lipid and mineral content, may have contributed to the development of xanthomatosis, nephrocalcinosis and urocystolithiasis in wolffish housed in these institutions.

Co-emergence of magnetic order and structural fluctuations in magnetite

The nature of the Verwey transition occurring at TV ≈ 125 K in magnetite (Fe3O4) has been an outstanding problem over many decades. A complex low temperature electronic order was recently discovered and associated structural fluctuations persisting above TV are widely reported, but the origin of the underlying correlations and hence of the Verwey transition remains unclear. Here we show that local structural fluctuations in magnetite emerge below the Curie transition at TC ≈ 850 K, through X-ray pair distribution function analysis. Around 80% of the low temperature correlations emerge in proportion to magnetization below TC. This confirms that fluctuations in Fe-Fe bonding arising from magnetic order are the primary electronic instability and hence the origin of the Verwey transition. Such hidden instabilities may be important to other spin-polarised conductors and orbitally degenerate materials.

Centrosymmetric Li2NaN: a superior topological electronic material with critical-type triply degenerate nodal points

Li2NaN is a realistic triply degenerate nodal point material with several superior characteristics.

Novel approach for calculating the charge carrier mobility and Hall factor for semiconductor materials

The additive Matthiessen's rule is the simplest and most widely used rule for the rapid experimental characterization and modeling of the charge carrier mobility. However, the error when using this rule can be higher than 40% and the contribution of the assumed additional scattering channels due to the difference between the experimental data and results calculated based on this rule can be misestimated by several times. In this study, a universal semi-additive equation is proposed for the total mobility and Hall factor, which is applicable to any quantity of scattering mechanisms, where it considers the energy dependence of the relaxation time and the error is 10–20 times lower compared with Matthiessen's rule. Calculations with accuracy of 99% are demonstrated for materials with polar-optical phonon, acoustic phonon via the piezoelectric potential, ionized, and neutral impurity scattering. The proposed method is extended to the deformation potential, dislocation, localized defect, alloy potential, and dipole scattering, for nondegenerate and partially degenerate materials.

A Materials Roadmap to Functional Neural Interface Design.

Advancement in neurotechnologies for electrophysiology, neurochemical sensing, neuromodulation, and optogenetics are revolutionizing scientific understanding of the brain while enabling treatments, cures, and preventative measures for a variety of neurological disorders. The grand challenge in neural interface engineering is to seamlessly integrate the interface between neurobiology and engineered technology, to record from and modulate neurons over chronic timescales. However, the biological inflammatory response to implants, neural degeneration, and long-term material stability diminish the quality of interface overtime. Recent advances in functional materials have been aimed at engineering solutions for chronic neural interfaces. Yet, the development and deployment of neural interfaces designed from novel materials have introduced new challenges that have largely avoided being addressed. Many engineering efforts that solely focus on optimizing individual probe design parameters, such as softness or flexibility, downplay critical multi-dimensional interactions between different physical properties of the device that contribute to overall performance and biocompatibility. Moreover, the use of these new materials present substantial new difficulties that must be addressed before regulatory approval for use in human patients will be achievable. In this review, the interdependence of different electrode components are highlighted to demonstrate the current materials-based challenges facing the field of neural interface engineering.