Weak Disorder Research Articles

Role of Disorder in the Intrinsic Orbital Hall Effect.

The orbital Hall effect (OHE) has garnered much attention as a promising approach to realize highly efficient "orbitronic" devices with a wide range of materials. However, the existing theories that attempt to explain the experimental evidence focus on the intrinsic effect, neglecting the omnipresent disorder. Here, we formulate the impact of random defect scattering on the orbital Hall effect by a quantum Boltzmann equation and solve it for a generic two-band model including the in-scattering collision integral (vertex correction). In contrast to the common belief that the intrinsic OHE is robust against the disorder, we find that diffuse scattering by an arbitrarily weak disorder affects and can even fully suppress the intrinsic orbital Hall current, depending on the character of orbital states and the disorder.

Secondary Sarcopenia in Patients with Locomotor Disorders: Prevalence, Diagnosis and Medical Rehabilitation. A Review

INTRODUCTION. The development of rehabilitation methods for patients with sarcopenia, a generalized age-associated loss of skeletal muscle mass and strength, is important, since sarcopenia leads to pronounced weakness, functional and motor disorders and an increased risk of death in the elderly. AIM. To analyze the prevalence, features of pathogenesis, diagnosis of secondary sarcopenia, including against the background of motor disorders due to stroke, as well as methods of treatment and medical rehabilitation of such patients. MAIN CONTENT. Among the secondary forms, sarcopenia is of the greatest clinical importance against the background of the consequences of acute cerebrovascular accident (ACA), due to muscular atrophy associated with paralysis and immobility, spasticity, inflammation and denervation of muscles, malnutrition and intestinal absorption of protein and vitamin D. Recent studies show that the prevalence of sarcopenia in stroke patients in emergency hospitals is 8.5–33.8 %, according to other data — more than 42 %. Muscle weakness after a stroke contributes to a decrease in physical functions and the development of disability, and sarcopenia leads to adverse outcomes 90 days after a stroke. According to the meta-analysis, which included 7 cohort studies with a total sample of 1,774 patients who underwent ACA, 27.1 % of them had sarcopenia. Moreover, the presence of sarcopenia negatively affected the clinical and functional outcomes of ACA, as well as the results of medical rehabilitation (odds ratio: 2.42, 95 % confidence interval: 1.76–3.33, p 0.001). CONCLUSION. Despite the prevalence and relevance of this pathology, rehabilitation programs for patients with sarcopenia against the background of the consequences of ACA have not been developed. Isolated foreign publications demonstrate the effectiveness of certain methods of physical therapy and electrical stimulation, but the evidence base for their effectiveness is low.

Universality in the 2d Quasi-periodic Ising Model and Harris–Luck Irrelevance

We prove that in the 2D Ising model with a weak bidimensional quasi-periodic disorder in the interaction, the critical behavior is the same as in the non-disordered case; that is, the critical exponents for the specific heat and energy-energy correlations are identical, and no logarithmic corrections are present. The disorder produces a quasi-periodic modulation of the amplitude of the correlations and a renormalization of the velocities, that is, the coefficients of the rescaling of positions, and of the critical temperature. The result establishes the validity of the prediction based on the Harris–Luck criterion, and it provides the first rigorous proof of universality in the Ising model in the presence of quasi-periodic disorder in both directions and for any angle. Small divisors are controlled assuming a Diophantine condition on the frequencies, and the convergence of the series is proved by Renormalization Group analysis.

Investigation of Physical Fitness in Children and Adolescents with Juvenile Idiopathic Arthritis: A Case-Control Study.

Swelling, effusion, tenderness, and pain seen in the joints of juvenile idiopathic arthritis (JIA). This disease may cause limitation in joint movements, muscle weakness, atrophy, balance, and gait disorders. Physical fitness is accepted as an important determinant of health in both childhood and adolescence. The aim was to evaluate the physical fitness of children/adolescents with JIA and compare it with healthy peers. Seventy children/adolescents were included (35 JIA and 35 healthy). The Childhood Health Assessment Questionnaire (CHAQ) and the Brockport physical fitness test battery were used for evaluation. The Brockport physical fitness test battery consists of dominant handgrip strength, curl-up, push-up, trunk lift, shoulder stretch, sit and reach tests, skinfold thickness (calf/triceps/subscapular) measurements, and PACER 20 m test. A significant difference was found in all sub-parameters of CHAQ (P < .05) and dominant hand grip strength (P = .037), curl-up test (P < .001), trunk lift test (P = .018), shoulder stretch (P < .001) and PACER 20 m test (P < .001) tests in favor of the healthy group. Children/adolescents with JIA demonstrated lower performance compared to their healthy peers in muscular and cardiovascular capacity tests (curl-up test, PACER 20 m test, trunk lift test, dominant hand grip strength test, and shoulder stretch test). Their functional abilities are more impaired, and they experience higher levels of pain and lower levels of general well-being compared to healthy peers.

Unified theory for the scaling of the crossover between strong and weak disorder behaviors of optimal paths and directed or undirected polymers in disordered media.

In this paper, we are concerned with the crossover between strong disorder (SD) and weak disorder (WD) behaviors in three well-known problems that involve minimal paths: directed polymers (directed paths with fixed starting point and length), optimal paths (undirected paths with a fixed end-to-end or spanning distance), and undirected polymers (undirected paths with a fixed starting point and length). We present a unified theoretical framework from which we can easily deduce the scaling of the crossover point of each problem in an arbitrary dimension. Our theory is based on the fact that the SD limit behavior of these systems is closely related to the corresponding percolation problem. As a result, the properties of those minimal paths are completely controlled by the so-called red bonds of percolation theory. Our model is first addressed numerically and then approximated by a two-term approach. This approach provides us with an analytical expression that seems to be reasonably accurate. The results are in perfect agreement with our simulations and with most of the results reported in related works. Our research also leads us to propose this crossover point as a universal measure of the disorder strength in each case. Interestingly, that measure depends on both the statistical properties of the disorder and the topological properties of the network.

Exploring the Association between Diabetes Mellitus, Obesity, and Recurrent Stroke Events: a Cross-sectional Study

Stroke is the most significant cause of death and cause of disability in the world because it causes neurological deficits in sufferers, such as muscle paralysis, swallowing weakness, communication damage, and vision disorders to cause death. Stroke can be recurrent and have a severe impact compared to the initial attack. The purpose of this study was to explore the association between diabetes mellitus, obesity, and the incidence of recurrent strokes in post-stroke patients at a regional general hospital in Aceh province. It is a cross-sectional study carried out from 3–12 August 2022. The sampling technique used in this study was a purposive sampling of 154 patients. The instruments used were questionnaires of patient demographic characteristics, data analysis using chi-square assays, and logistic regression. The results showed that there was no association between diabetes mellitus (p&gt;0.05) and obesity (p&gt;0.05) with the incidence of recurrent strokes. One of the preventive measures for the occurrence of recurrent strokes is to provide education about the prevention of recurrent strokes related to diabetes mellitus and obesity, one of which is a healthy lifestyle. In conclusion, there is no relationship between diabetes mellitus, obesity, and the incidence of recurrent strokes in post-stroke patients at a regional general hospital in Aceh province.

Topological Anderson phases in heat transport

Topological Anderson phases (TAPs) offer intriguing transitions from ordered to disordered systems in photonics and acoustics. However, achieving these transitions often involves cumbersome structural modifications to introduce disorders in parameters, leading to limitations in flexible tuning of topological properties and real-space control of TAPs. Here, we exploit disordered convective perturbations in a fixed heat transport system. Continuously tunable disorder-topology interactions are enabled in thermal dissipation through irregular convective lattices. In the presence of a weak convective disorder, the trivial diffusive system undergos TAP transition, characterized by the emergence of topologically protected corner modes. Further increasing the strength of convective perturbations, a second phase transition occurs converting from TAP to Anderson phase. Our work elucidates the pivotal role of disorders in topological heat transport and provides a novel recipe for manipulating thermal behaviors in diverse topological platforms.

Approach to gait disorders and orthotic management in adult onset neuromuscular diseases.

In order to understand abnormal gait, this article will first review normal gait, discuss how neuromuscular diseases disturb gait patterns and review orthotic interventions. In normal gait, concentric contractions accelerate and eccentric contractions decelerate the limb. Neuromuscular gait disorders can be grouped into (1) proximal weakness, (2) distal weakness, (3) nonlength-dependent or generalized weakness, (4) asymmetric weakness, and (5) sensory disorders. Identification of gait disturbance type in neuromuscular diseases leads to the appropriate orthotic prescription since orthotic strategies are grouped into (1) proximal weakness, (2) distal weakness, and (3) sensory disturbances. Orthotics is not indicated in all types of gait disturbance. Weakness in proximal hip musculature can be managed with gait aids such as walkers. In contrast, distal muscle weakness can be managed with orthotics. Preservation of gait assists in maintenance of daily function and integration in society.

Post-COVID asthenia, sarcopenia and muscle weakness among geriatric patients

Sarcopenia, asthenia, and motor activity restriction are common among geriatric patients in the post-COVID period. The SARS-CoV-2 virus triggers a cytokine storm in the human body and induces a direct viral effect on skeletal muscles. Manifestations of post-acute sequelae of COVID-19 (PASC) can include organ and system dysfunction, asthenia, muscle weakness, dyspnea, chest pain, cognitive impairment, depression, anxiety, and sleep disorders. Hypoxemia, comorbidity, and prolonged inactivity contribute to changes in the structure and functionality of the muscular fibers. One of the recent studies is ALMI-index, which indicates that a decrease in muscle mass of the upper and lower extremities may cause functional limitations in patients with long-COVID conditions. Rehabilitation of patients with post-COVID syndrome involves daily exercise with weights, considering load tolerance; mandatory medication; and nutritional and psychological support.

Palliative care considerations in frail older adults.

Frailty is a common geriatric syndrome characterized by a decline in physical and cognitive abilities and an increased vulnerability to stressors such as illnesses and injuries. As the global population is aging, the prevalence of frailty is growing. Frail older adults are at substantial risk of developing mobility and self-care difficulties, hospitalization, and death. Frailty is also associated with a high symptom burden and psychosocial stress, including malnutrition, pain, fatigue, weakness, cognitive loss, depression, falls, and sleep disorders, among others. The role of palliative care is gaining attention in medical literature because frailty is associated with increased morbidity and mortality. While there are no specific guidelines yet for when palliative care should be consulted in older patients with frailty, it has been proposed that palliative care should be considered in frail patients with continued functional decline, increased healthcare utilization, and uncontrolled symptoms. Palliative care can aid in communication with patients and families, establishing goals of care and treatment preferences, improving pain and symptom control, addressing psychosocial and spiritual needs, advance care planning, caregiver needs, and end-of-life care. Once frailty is identified, a comprehensive evaluation of the patient's physical, psychosocial, and spiritual aspects of care is essential for establishing a patient-centered treatment plan. This paper aims to guide clinicians in providing patient-centered care for older adults with frailty in the outpatient setting. Through a comprehensive literature review, we describe the leading models of frailty, frailty screening tools used in the clinical setting, and the assessment and management of palliative care needs in frail patients. We also describe emerging models of care focusing on palliative care for older adults with frailty and discuss issues related to access to palliative care for this population.

Electric-field-controlled electronic structures and quantum transport in monolayer InSe nanoribbons

Electronic structures and quantum transport properties of the monolayer InSe nanoribbons are studied by adopting the tight-binding model in combination with the lattice Green function method. Besides the normal bulk and edge electronic states, a unique electronic state dubbed as edge-surface is found in the InSe nanoribbon with zigzag edge type. In contrast to the zigzag InSe nanoribbon, a singular electronic state termed as bulk-surface is observed along with the normal bulk and edge electronic states in the armchair InSe nanoribbons. Moreover, the band gap, the transversal electron probability distributions in the two sublayers, and the electronic state of the topmost valence subband can be manipulated by adding a perpendicular electric field to the InSe nanoribbon. Further study shows that the charge conductance of the two-terminal monolayer InSe nanoribbons can be switched on or off by varying the electric field strength. In addition, the transport of the bulk electronic state is delicate to even a weak disorder strength, however, that of the edge and edge-surface electronic states shows a strong robustness against to the disorders. These findings may be helpful to understand the electronic characteristics of the InSe nanostructures and broaden their potential applications in two-dimensional nanoelectronic devices as well.

Excitation spectrum and spin Hamiltonian of the frustrated quantum Ising magnet Pr3BWO9

We present a thorough experimental investigation on of the rare-earth based frustrated quantum antiferromagnet Pr3BWO9, a purported spin-liquid candidate on the breathing kagome lattice. This material possesses a disordered ground state with an unusual excitation spectrum involving a coexistence of sharp spin waves and broad continuum excitations. Nevertheless, we show through a combination of thermodynamic, magnetometric, and spectroscopic probes with detailed theoretical modeling that it should be understood in a completely different framework. The crystal field splits the lowest quasidoublet states into two singlets moderately coupled through frustrated superexchange, resulting in a simple effective Hamiltonian of an Ising model in a transverse magnetic field. While our neutron spectroscopy data do point to significant correlations within the kagome planes, the dominant interactions are out-of-plane, forming frustrated triangular spin-tubes through two competing ferro-antiferromagnetic bonds. The resulting ground state is a simple quantum paramagnet, where the presence of strongly hyperfine-coupled nuclear moments and weak structural disorder causes significant modifications to both thermodynamic and dynamic properties. Published by the American Physical Society 2024

Interaction-enhanced many-body localization in a generalized Aubry-André model

We study the many-body localization (MBL) transition in a generalized Aubry-André model (also known as the GPD model) introduced by Ganeshan, Pixley, and Das Sarma []. In contrast to MBL in other disordered or quasiperiodic models, the interaction seems to unexpectedly enhance MBL in the GPD model in some parameter range. To understand this counterintuitive result, we demonstrate that the highest-energy single-particle band in the GPD model is unstable against weak disorder, which leads to this surprising MBL phenomenon in the interacting model. We develop a mean-field theory description to understand the coupling between extended and localized states, which we validate using extensive exact diagonalization and modified density matrix renormalization group (DMRG-X) numerical results. Published by the American Physical Society 2024

Topological superfluid responses of superconducting Dirac semimetals

We demonstrate that topological constraints do not only dictate the geometric part of the superfluid stiffness, but can also govern the superfluid stiffness. By introducing a general adiabatic approach for superfluid responses, we showcase such a possibility by proving that the stiffness of a superconducting Dirac cone in two dimensions (2D) is proportional to its topological charge. By relying on the emergent Lorentz invariance of Dirac electrons, we unify the superfluid stiffness and quantum capacitance in these systems. Based on this connection, we further predict a topological origin for the quantum capacitance of a Josephson junction where 2D massless Dirac electrons are sandwiched between two conventional superconductors. We show that the topological responses persist upon effecting strain, are resilient against weak disorder, and can be experimentally controlled via a Zeeman field. Remarkably, the nonuniversal topological quantization of the two superfluid responses, yet implies the universal topological quantization of the admittance modulus of the superconducting Dirac system in units of conductance. The quantum admittance effect arises when embedding the superconducting Dirac system in an ac electrical circuit with a frequency tuned at the absorption edge. These findings are in principle experimentally observable in graphene-superconductor hybrids. Published by the American Physical Society 2024

A programmable topological photonic chip

Controlling topological phases of light allows the observation of abundant topological phenomena and the development of robust photonic devices. The prospect of more sophisticated control with topological photonic devices for practical implementations requires high-level programmability. Here we demonstrate a fully programmable topological photonic chip with large-scale integration of silicon photonic nanocircuits and microresonators. Photonic artificial atoms and their interactions in our compound system can be individually addressed and controlled, allowing the arbitrary adjustment of structural parameters and geometrical configurations for the observation of dynamic topological phase transitions and diverse photonic topological insulators. Individual programming of artificial atoms on the generic chip enables the comprehensive statistical characterization of topological robustness against relatively weak disorders, and counterintuitive topological Anderson phase transitions induced by strong disorders. This generic topological photonic chip can be rapidly reprogrammed to implement multifunctionalities, providing a flexible and versatile platform for applications across fundamental science and topological technologies.

Fragile dislocation modes in obstructed atomic topological phases

We here introduce the concept of fragile dislocation modes, which are localized only in a fraction of a topological phase while otherwise leaking into the bulk continuum. As we demonstrate here, such dislocation modes are hosted in an obstructed atomic topological phase in the two-dimensional Su-Schrieffer-Heeger model but only in a finite region with an indirect gap at high energy. They are realized as chiral pairs at finite energies with protection stemming from a combination of the chiral (unitary particle-hole) and the point group (C4v) symmetries, but only when the indirect gap is open. In this regime, we corroborate the stability of the defect modes by following their localization and also by explicitly adding a weak chemical potential disorder. Our findings should, therefore, be consequential for the experimental observation of such modes in designer topological crystals and classical metamaterials. Published by the American Physical Society 2024

Cryptotanshinone-Induced Permeabilization of Model Phospholipid Membranes: A Biophysical Study.

The Danshen terpenoid cryptotanshinone (CPT) is gaining enormous interest in light of its various outstanding biological activities. Among those, CPT has been shown to interact with cell membranes and, for instance, to have antibacterial activity. Several works have shown that CPT alone, or in combination with other drugs, can effectively act as an antibiotic against various infectious bacteria. Some authors have related the mechanism underlying this action to CPT-membrane interaction. This work shows that CPT readily partitions into phosphatidylcholine membranes, but there is a limiting capacity of accommodation of ca. 1 mol CPT to 3 mol phospholipid. The addition of CPT to unilamellar liposomes composed of 1-palmitoyl-2-oleoylphosphatidylcholine (POPC) causes membrane permeabilization, as shown by fluorescent probe leakage. This process has been kinetically studied, as well as its modulation by incorporation of phosphatidylethanolamine or phosphatidylglycerol, as a model for pathogenic cell membranes. The thermotropic behavior of 1,2-dimyristoylphosphatidylcholine (DMPC) model membranes is weakly affected by CPT, but the terpenoid causes significant dehydration of the polar region of the bilayer and weak disordering of the acyl chain palisade, as observed in Fourier-transform infrared spectroscopy (FTIR) results. Small-angle X-ray scattering (SAXS) shows that CPT increases DMPC bilayer thickness, which could be due to localization near the phospholipid/water interface. Molecular dynamics (MD) simulations show that the lateral diffusion coefficient of the phospholipid increases with the presence of CPT. CPT extends from the polar head region to the center of the bilayer, being centered between the carbonyl groups and the unsaturated region of the POPC, where there is greater overlap. Interestingly, the free energy profiles of a water molecule crossing the lipid membrane show that the POPC membrane becomes more permeable in the presence of CPT. In summary, our results show that CPT perturbs the physicochemical properties of the phospholipid membrane and compromises its barrier function, which could be of relevance to explain part of its antimicrobial or anticancer activities.

The influence of Gaussian pinning on the melting scenario of a two-dimensional soft-disk system: First-order versus continuous transition

Two-dimensional systems are realized experimentally as thin layers on a substrate. The substrate can have some imperfections (defects of the crystalline structure, chemical impurities, etc.) with strong interactions with particles within and near the defects. Such randomly distributed centers of strong interactions are called ”pinning centers”. The presence of random pinning can substantially change the behavior of the system. It not only shifts the melting point of the system, but can also change the melting scenario itself. In the present paper the influence of Gaussian pinning on the melting scenario of a two-dimensional system of soft disks is studied by means of molecular dynamics simulation. We randomly introduce into the system of soft disks a set of “pinning centers” which attract the particles via the Gauss potential. We observe that increasing the depth of a Gaussian well leads to a change in the melting scenario of the system: from melting occurring via a first-order liquid-hexatic transition followed by a continuous hexatic-crystal transition to two continuous transitions through an intermediate hexatic phase. We show that there are still two transition stages for strong disorder, but the melting scenario is qualitatively different from that for weak disorder. The results demonstrate that the simple kind of quenched disorder can significantly affect the melting scenario of two-dimensional systems and offer the possibility of their application for the interpretation of complex experiments.

Extreme magnetoresistance at high-mobility oxide heterointerfaces with dynamic defect tunability

Magnetic field-induced changes in the electrical resistance of materials reveal insights into the fundamental properties governing their electronic and magnetic behavior. Various classes of magnetoresistance have been realized, including giant, colossal, and extraordinary magnetoresistance, each with distinct physical origins. In recent years, extreme magnetoresistance (XMR) has been observed in topological and non-topological materials displaying a non-saturating magnetoresistance reaching 103−108% in magnetic fields up to 60 T. XMR is often intimately linked to a gapless band structure with steep bands and charge compensation. Here, we show that a linear XMR of 80,000% at 15 T and 2 K emerges at the high-mobility interface between the large band-gap oxides γ-Al2O3 and SrTiO3. Despite the chemically and electronically very dissimilar environment, the temperature/field phase diagrams of γ-Al2O3/SrTiO3 bear a striking resemblance to XMR semimetals. By comparing magnetotransport, microscopic current imaging, and momentum-resolved band structures, we conclude that the XMR in γ-Al2O3/SrTiO3 is not strongly linked to the band structure, but arises from weak disorder enforcing a squeezed guiding center motion of electrons. We also present a dynamic XMR self-enhancement through an autonomous redistribution of quasi-mobile oxygen vacancies. Our findings shed new light on XMR and introduce tunability using dynamic defect engineering.

Oral Health-Related Quality of Life in Rare Disorders of Congenital Facial Weakness.

Congenital facial weakness (CFW) encompasses a heterogenous set of rare disorders presenting with decreased facial movement from birth, secondary to impaired function of the facial musculature. The aim of the present study is to provide an analysis of subject-reported oral health-related quality of life (OHRQoL) in congenital facial weakness (CFW) disorders. Forty-four subjects with CFW and age- and sex- matched controls were enrolled in an Institutional Review Board (IRB)-approved study. Demographic data, medical and surgical history, comprehensive oral examination, and the Oral Health Impact Profile (OHIP-14) were obtained. Compared to unaffected controls, subjects with CFW had higher OHIP-14 scores overall (mean ± SD: 13.11 ± 8.11 vs. 4.46 ± 4.98, p < 0.0001) and within five of seven oral health domains, indicating decreased OHRQoL. Although subjects with Moebius syndrome (MBS) were noted to have higher OHIP-14 scores than those with Hereditary Congenital Facial Paresis (HCFP), there was no significant correlation in OHIP-14 score to age, sex, or specific diagnosis. An increase in OHIP-14 scores in subjects was detected in those who had undergone reanimation surgery. In conclusion, subjects with CFW had poorer OHRQoL compared to controls, and subjects with MBS had poorer OHRQoL than subjects with HCFP. This study provides better understanding of oral health care needs and quality of life in a CFW cohort and suggests that guidelines for dental treatment are required.