bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of spatial distribution of fibers on elastic properties of unidirectional carbon/carbon composites
Authors: Mohan M.V.N , Atul Ramesh Bhagat , Dwivedi Vijay Kumar
Published: October 2021

Carbon/Carbon composites finds its applications in several high temperature applications in the field of Space, Aviation etc. Designing of components or sub systems with carbon/carbon composites is a challenging task. It requires prediction of elastic properties with a very high accuracy. The prediction can be normally done by analytical, numerical or experimental methods. At the design stage the designers resort to numerical predictions as the experimental methods are not feasible during design stage. Analytical methods are complex and difficult to implement. The designers use numerical methods for prediction of elastic properties using Finite Element Modeling (FEM). The spatial distribution of fibers in matrix has an effect on results of prediction of elastic constants. The generation of random spatial distribution of fibers in representative volume element (RVE) challenging. The present work is aimed at study of effect of spatial distribution of fiber in numerical prediction of elastic properties of unidirectional carbon/carbon composites. MATLAB algorithm is used to generate the spatial distribution of fibers in unidirectional carbon/carbon composites. The RVE elements with various random fiber distributions are modeled using numerical Finite element Model using ABAQUS with EasyPBC plugin. The predicted elastic properties have shown significant variation to uniformly distributed fibers.
Investigation on Properties of Reactive Powder Concrete with Automobile Grinding Steel Waste as Fine Aggregate
Authors: Geetha S. , Selvakumar M. , Lakshmi S. Muthu
Published: October 2021

High strength concrete is seldom used in normal construction practice due to its high cost and difficulties in achieving the desired design strength. This paper gives an insight on using waste material which has been disposed in lands as a sustainable construction material to replace sand and to achieve desired strength. The compressive strength of Reactive powder concrete (RPC) produced in this work was 88 MPa and the flexural strength was 20 MPa. Also the influence of different curing methods on the properties of RPC has been investigated. Durability studies also show that the material satisfies the durable parameters to be used as a construction material.
Grey integrated Multiobjective-Particle Swarm Optimization (MOPSO) for Machining assessment and predictive modeling of Cutting Forces generated during Polymer nanocomposite Drilling
Authors: Kesarwani Shivi , Kumar Verma Rajesh
Published: October 2021

Carbon nanomaterials reinforced composite materials have been broadly utilized in manufacturing engineering due to improved thermal resistivity, reduced weight, and other improved mechanical properties. This article highlights the drilling experimentation of zero-dimensional (0-D) Carbon nano onion (CNO) reinforced polymer composite. For this, three drilling constraints was considered viz., spindle speed, feed rate, and weight % of nanomaterial reinforced. The objective is to achieve the desired value of generated drilling forces such as Torque (Nm) and Thrust Force (N) during the machining procedure of developed composite samples. The Multiobjective-Particle Swarm Optimization (MOPSO) is utilized to achieve optimal results from the multi-decision criterion for the Machining performance. Exploiting this optimization process, non-dominated solutions were obtained, and the Pareto front was identified. Practical applications for the discovered relationships include using Grey relation analysis (GRA) to extract the most relevant finding from the Pareto Front space of optimal solutions. Using the GRA, the optimum solution was found: Spindle Speed of 1000 RPM, Feed Rate of 100 mm/min, and CNO weight percentage of 0.5. After this, a confirmation test was performed, the expected effects have been confirmed. The findings reveal that the proposed optimization module can be recommended for online quality and productivity control.
Circular dichroism and its uses in biomolecular research - A Review
Authors: Sangeeta  , Pathania Anu Radha
Published: October 2021

The higher-order structure of proteins as well as their thermal stability can be determined using the circular dichroism (CD). CD is a common approach for swiftly assessing binding, secondary structure, and folding properties of proteins. In a nutshell, circular dichroism is an absorption spectroscopy technique that employs circularly polarized light to explore structural properties of optically active chiral compounds. Biological molecules, as well as their interactions with metals and other compounds, are studied extensively. Circular dichroism is becoming more widely acknowledged as a useful technique for studying the various conformations taken by proteins and nucleic acids in solution. Because CD is a quantitative approach, it can be used to track protein denaturation and protein-ligand interaction. These CD measures will have two key advantages: they can be performed on small amounts of material in a physiological buffer, and they will provide one of the greatest methods for monitoring any structural changes that occur as a result of changes in environmental conditions. It has proven possible to generate proteins on a big scale for therapeutic reasons utilizing recombinant DNA technology. Circular dichroism is also well-known as a useful method which is used for determining the folding characteristics of proteins. CD is used to see if a purified, produced peptide is either bended or if it has a mutation that impacts its strength and confirmation. The basic steps in getting this CD data, as well as the methodologies for interpreting the spectra in order to predict the protein structure, are summarized in this article. However, many researchers’ value is harmed when they use circular dichroism, either because of poor experimental design or because of insufficient data. The essential steps in getting this CD data, as well as the methodologies for interpreting the spectra in order to predict the protein structure, will be summarized in this article. However, the value of many investigations using circular dichroism is harmed due to insufficient attention to critical components of instrument calibration or sample characterization.
A variational sheath model for stationary gyrokinetic Vlasov–Poisson equations
Authors: Badsi Mehdi , Campos-Pinto Martin , Després Bruno , Godard-Cadillac Ludovic
Published: October 2021

We construct a stationary gyrokinetic variational model for sheaths close to the metallic wall of a magnetized plasma, following a physical extremalization principle for the natural energy. By considering a reduced set of parameters we show that our model has a unique minimal solution, and that the resulting electric potential has an infinite number of oscillations as it propagates towards the core of the plasma. We prove this result for the non linear problem and also provide a simpler analysis for a linearized problem, based on the construction of exact solutions. Some numerical illustrations show the well-posedness of the model after numerical discretization. They also exhibit the oscillating behavior.
Some Aspects of Photovoltaic/Thermal Systems Operation in Central European Climate
Authors: Chwieduk Dorota , Bigorajski Jaroslaw
Published: October 2021

The paper analyses the operation of a photovoltaic/thermal system in a single family house in a central European climate through simulation studies. The PV/T system is used for DHW heating and electricity generation. Glazed and unglazed modules are considered. Effective utilization of solar energy for heating purposes requires the use of heat storage, which is particularly visible not only in cold, but also in moderates climates. Consequently, the operation of solar systems is more complex, different modes of operation are possible to provide heat or electricity, or both. Possible modes of operation were appropriately modeled and the obtained energy gains were analyzed. When modeling the heat storage process, the heat stratification effect in the storage tank was taken into account. Monthly shares of solar energy in providing DHW heating energy and electricity for all months of the year are presented. The glazed modules can fully cover the DHW demand during 5 warm months, but they cannot cover the electricity demand. The share of electricity provided by PV can vary from 67% to 93%. On the contrary, in the case of unglazed PV/T modules during these 5 months the share of thermal demand can be covered only from 62% to 90%, but the electricity demand can by covered fully. In winter there is no significant solar thermal energy gained in both cases. Unglazed PV/T modules should be used in central European climate, if electricity generation is a priority. If DHW heating is equally important, then their operation should be coupled with glazed thermal collectors.
Diabetes und COVID-19
Authors: Friedrichsen Hans-Peter
Published: October 2021

Der westliche Lebensstil mit hyperkalorischer, nährstoffarmer Ernährung und körperlicher Inaktivität begünstigt weltweit Übergewicht, Diabetes und Hypertonie. Mit Diabetes und Adipositas verbundenen ist ein erhöhtes Risiko für schweren COVID-19-Krankheitsverlauf und höhere Mortalität als Folge von gestörter Immunantwort, erhöhter Thromboseneigung, vermehrter Bildung von AGEs und RAGE-Aktivierung, von Entzündung und oxidativem Stress. Dies begünstigt eine überschießende und unkontrollierte Zytokinantwort, die verantwortlich ist für das Acute Respiratory Distress Syndrome und Multiorganversagen. Eine Infektion löst Entzündung und Gewebeschädigung aus und führt zu erhöhter Stoffwechselaktivität, um geschädigtes Gewebe und Fremdmaterial zu entfernen. Bei Adipositas und Diabetes sind die Mechanismen zur Aufnahme von Fremdmaterial und Viren in die Zelle deutlich hochreguliert, sodass eine verstärkte Virusinfektion resultieren kann.
Rapid Multigram-Scale End-to-End Continuous-Flow Synthesis of Sulfonylurea Antidiabetes Drugs: Gliclazide, Chlorpropamide, and Tolbutamide
Authors: Watts Paul , Sagandira Cloudius R.
Published: October 2021

A multigram-scale robust, efficient, and safe end-to-end continuous-flow process for the diabetes sulfonylurea drugs gliclazide, chlorpropamide, and tolbutamide is reported. The drugs were prepared by the treatment of an amine with a haloformate affording carbamate, which was subsequently treated with a sulfonamide to afford sulfonylurea. Gliclazide was obtained in 87% yield within 2.5 minutes total residence time with 26 g/h throughput; 0.2 kg of the drug was produced in 8 hours of running the system continuously. Chlorpropamide and tolbutamide were both obtained in 94% yield within 1 minute residence time with 184–188 g/h throughput; 1.4–1.5 kg of the drugs was produced in 8 hours of running the system continuously. N-Substituted carbamates were used as safe alternatives to the hazardous isocyanates in constructing the sulfonyl urea moiety.
Evaluation and Management of Delirium
Authors: Ryan Sophia L. , Kimchi Eyal Y.
Published: October 2021

Delirium, sometimes referred to as encephalopathy, is an acute confusional state that is both common in hospitalized patients and associated with poor outcomes. For patients, families, and caregivers, delirium can be a traumatic experience. While delirium is one of the most common diagnoses encountered by the consulting neurologist, the majority of the time it will have been previously unrecognized as such by the care team. Neurologic syndromes such as dementia or aphasia can either be misdiagnosed as delirium or may coexist with it, necessitating careful neurologic assessment. Once the diagnosis of delirium has been established, a careful evaluation for predisposing and precipitating factors can help uncover modifiable contributors, which should be addressed as part of a multicomponent, primarily nonpharmacologic intervention. Importantly, delirium management, which begins with comprehensive prevention, should emphasize the humanity of the delirious patient and the challenges of caring for this vulnerable population. When considered, delirium represents an important opportunity for the neurologist to substantially enhance patient care.
Evaluation and Management of Acute Myelopathy
Authors: Sechi Elia , Flanagan Eoin P.
Published: October 2021

Acute myelopathies are spinal cord disorders characterized by a rapidly progressive course reaching nadir within hours to a few weeks that may result in severe disability. The multitude of underlying etiologies, complexities in confirming the diagnosis, and often unforgiving nature of spinal cord damage have always represented a challenge. Moreover, certain slowly progressive myelopathies may present acutely or show abrupt worsening in specific settings and thus further complicate the diagnostic workup. Awareness of the clinical and magnetic resonance imaging characteristics of different myelopathies and the specific settings where they occur is fundamental for a correct diagnosis. Neuroimaging helps distinguish compressive etiologies that may require urgent surgery from intrinsic etiologies that generally require medical treatment. Differentiation between various myelopathies is essential to establish timely and appropriate treatment and avoid harm from unnecessary procedures. This article reviews the contemporary spectrum of acute myelopathy etiologies and provides guidance for diagnosis and management.
Anticoagulation in Acute Neurological Disease
Authors: Sasannejad Cina , Sheth Kevin N.
Published: October 2021

While anticoagulation and its reversal have been of clinical relevance for decades, recent academic and technological advances have expanded the repertoire of its application in neurological disease. The advent of direct oral anticoagulants provides effective, mechanistically elegant, and relatively safer therapeutic options than warfarin for eligible patients at risk for neurological sequelae of prothrombotic states, particularly given the recent availability of corresponding reversal agents. In this review, we examine the provenance, indications, safety, and reversal tools for anticoagulant medications in the context of neurological disease, with specific attention to acute ischemic stroke, cerebral venous sinus thrombosis, and intracerebral hemorrhage. We will use specific clinical scenarios to illustrate the complex factors that must be considered in the use of anticoagulation, including intracranial pathology such as intracerebral hemorrhage, traumatic brain injury, or malignancy; metabolic complications such as chronic kidney disease; pregnancy; and advanced age.
Inpatient Diagnosis and Management of Neuromuscular Disorders
Authors: Doherty Leana , Chaudhry Vinay
Published: October 2021

Although many neuromuscular conditions are evaluated on an outpatient basis owing to their chronic or progressive nature, more urgent evaluation and management is often required for the inpatient presenting with acute to subacute focal or generalized numbness or weakness. This review focuses on clinical pattern recognition and basic anatomic localization principles to aid in the identification of common, as well as some less frequently encountered, neuromuscular disorders in hospitalized patients. The characteristic clinical and diagnostic features, associated complications, and recommended treatments of key neuromuscular conditions with acute and subacute manifestations are discussed. These conditions can be life-threatening in some cases, such as in Guillain–Barré syndrome, owing to associated oropharyngeal weakness, respiratory failure, or marked dysautonomia. Prompt recognition of the clinical and pathologic features is therefore necessary to reduce associated morbidity and mortality.
Approach to Neurologic Complications in the Immunocompromised Patient
Authors: Vishnevetsky Anastasia , Anand Pria
Published: October 2021

Neurologic complications are common in immunocompromised patients, including those with advanced human immunodeficiency virus, transplant recipients, and patients on immunomodulatory medications. In addition to the standard differential diagnosis, specific pathogens and other conditions unique to the immunocompromised state should be considered in the evaluation of neurologic complaints in this patient population. A thorough understanding of these considerations is critical to the inpatient neurologist in contemporary practice, as increasing numbers of patients are exposed to immunomodulatory therapies. In this review, we provide a chief complaint-based approach to the clinical presentations and diagnosis of both infectious and noninfectious complications particular to immunocompromised patients.
Lobar Radioembolization for Intermediate and Advanced Hepatocellular Carcinoma: Retrospective and Prospective Data
Authors: Lakhoo Janesh , Perez Thomas H. , Borgmann Anthony J. , Brown Daniel B.
Published: October 2021

Historically, outcomes reporting for radioembolization with yttrium-90 (90Y) of hepatocellular carcinoma has included patients across the range of Barcelona Clinic Liver Cancer (BCLC) stages. With the potential for curative radiation segmentectomy for BCLC 0/A patients and evolution of systemic therapy for BCLC C patients, focused review by group is of increasing interest. In this review, we report on efficacy of 90Y in patients with intermediate (BCLC B) and advanced (BCLC C) hepatocellular carcinoma as well as expected toxicities. Additionally, we review existing trials comparing 90Y to transarterial chemoembolization and systemic treatments in these patient groups and outline future studies.
Evaluation and Management of First-Time Seizure in Adults
Authors: Abdennadher Myriam , Saxena Aneeta , Pavlova Milena K.
Published: October 2021

First seizures are often perceived as devastating events by patients and their families due to the fear of having a life-long disease. One in 10 people experiences one or more seizures during their lifetime, while 1 in 26 people develops epilepsy. Acute symptomatic seizures are often related to a provoking factor or an acute brain insult and typically do not recur. Careful history and clinical examination should guide clinicians' management plans. Electroencephalography and brain imaging, preferably with epilepsy-specific magnetic resonance imaging, may help characterize both etiology and risk of seizure recurrence. Antiepileptic drugs should be initiated in patients with newly diagnosed epilepsy. In patients without an epilepsy diagnosis, the decision to prescribe drugs depends on individual risk factors for seizure recurrence and possible complications from seizures, which should be discussed with the patient. Counseling about driving and lifestyle modifications should be provided early, often at the first seizure encounter.
Quality of Life and Cost Considerations: Y-90 Radioembolization
Authors: Williams Stephen J. , Rilling William S. , White Sarah B.
Published: October 2021

Objective Transarterial radioembolization (TARE) offers a minimally invasive and safe treatment option for primary and metastatic hepatic malignancies. The benefits of TARE are manifold including prolonged overall survival, low associated morbidities, and improved time to progression allowing prolonged treatment-free intervals. The rapid development of new systemic therapies including immunotherapy has radically changed the treatment landscape for primary and metastatic liver cancer. Given the current climate, it is critical for interventional oncologists to understand the benefits of TARE relative to these other therapies. Therefore, this report aims to review quality-of-life outcomes and the cost comparisons of TARE as compared with systemic therapies.
Radioembolization in the Setting of Systemic Therapies
Authors: Mabud Tarub S. , Hickey Ryan
Published: October 2021

90Yttrium (Y90) radioembolization has been shown to improve outcomes for primary and metastatic liver cancers, but there is limited understanding of the optimal timing and safety of combining systemic therapies with Y90 treatment. Both therapeutic effects and toxicities could be synergistic depending on the timing and dosing of different coadministration paradigms. In particular, patients with liver-only or liver-dominant metastatic disease progression are often on systemic therapy when referred to interventional radiology for consideration of Y90 treatment. Interventional radiologists are frequently asked to offer insight into whether or not to hold systemic therapy, and for how long, prior to and following transarterial therapy. This study reviews the current evidence regarding the timing and safety of systemic therapy with Y90 treatment for hepatocellular carcinoma, metastatic colorectal carcinoma, intrahepatic cholangiocarcinoma, metastatic neuroendocrine tumors, and other hepatic metastases. A particular focus is placed on the timing, dosing, and toxicities of combined therapy.
Biliary-Caval Fistula following Y90 Radioembolization
Authors: Hall Alexander D. , White Sarah B. , Rilling William S.
Published: October 2021

The safety of radioembolization with yttrium-90 (90Y) is well documented and major complications are rare. Previous studies have demonstrated that biliary complications following 90Y, including bile duct injury and hepatic abscess formation, occur at an increased rate in patients who have had prior biliary surgery and interventions. This article reviews a case of a patient who developed recurrent cholangitis and sepsis as well as a biliary-caval fistula following radioembolization. Additionally, we review current data regarding biliary complications following radioembolization in patients with prior biliary intervention.
Case of the Very Rare Gallbladder Paraganglioma
Authors: Shreya Shukla , Kashikar Ritu , Shraddha Sinhasan R. , Shrinivas Desai
Published: October 2021

Gallbladder paraganglioma is a very rare condition, and only a few cases have been reported in the literature. Herein, we present and discuss the clinical and radiological findings of a 72-year-old woman who complained of heaviness, pain, and on and off watery discharge from the left ear for 1 year and reduced hearing in both ears. She was thoroughly investigated radiologically where multiple paragangliomas were found with the discovery of the very rare gallbladder paraganglioma. There is a need to realize the importance of thorough radiological evaluation in cases of head and neck paraganglioma to look for more such lesions in the body for early identification of patients with familial paraganglioma syndromes. With this practice, gene mutation carriers can be identified early in the course of their disease and brought to surgical attention before their disease becomes extensive and potentially life-threatening.
An Unusual Cause of Cholestasis in an Infant: Biliary Atresia Type IIB
Authors: Sherwani Poonam , Bolia Rishi , Kaushik Ashish , Kumar Sumit , Kishore Sanjeev , Chauhan Udit
Published: October 2021

Biliary atresia (BA) is a progressive destructive cholangiopathy of unknown etiology that presents in early infancy. It has a worldwide frequency of 1:8,000–1:15,000 and is common in Asia than in the west. Based on the level at which the lumen of the extrahepatic duct is obliterated, BA is classified into three types. Type III is the commonest (∼85%) type and has the most proximal level of obstruction in the porta hepatis, while type II in which the atresia is at the level of the common hepatic duct, is the least common (∼2.5%) and has been rarely reported. Here, we report the imaging features of an infant with type IIB biliary atresia.
Heart rate variability enhances the accuracy of non-invasive continuous blood pressure estimation under blood loss
Authors: Zhang Guang , Wang Zongge , Hou Feixiang , Wan Zongming , Chen Feng , Yu Ming , Wang Jinhai , Wang Huiquan
Published: October 2021

To propose a new method for real-time monitoring of blood pressure of blood loss (BPBL), this article combines pulse transit time (PTT) and heart rate variability (HRV) as input parameters to build a model for BPBL estimation. In this article, effective parameters such as PTT, R–R interval (RRI), and HRV were extracted and used to establish the blood pressure (BP) estimation. Three BP estimation models were created: the PTT model, the RRI model, and the HRV model, and they were divided into an experimental group and a control group. Finally, the effects of the different estimation models on the accuracy of BPBL were evaluated using the experimental results. The result showed that both the RRI model and the HRV model have a good improvement effect on the prediction accuracy of BPBL, and the HRV model has the highest prediction accuracy than the PTT model and the RRI model. The correlation coefficients between the actual systolic BP (SBP) and diastolic BP (DBP) and the estimated SBP and DBP of the HRV model were 0.9580 and 0.9749, respectively, and the root-mean-square error of the HRV model for both SBP and DBP were 7.59 and 6.56 mmHg, respectively. The results suggest that the accuracy of the BPBL estimated by the HRV models is better than that of the PTT model, which means that HRV seems to be more effective in improving the accuracy of BP estimation compared with RRI. These results in this article provide a new idea for other researchers in the field of BPBL estimation research.
Atypical secondary electron emission yield curves of very thin SiO2 layers: Experiments and modeling
Authors: Rigoudy C. , Makasheva K. , Belhaj M. , Dadouch S. , Teyssedre G. , Boudou L.
Published: October 2021

The secondary electron emission phenomenon often refers to the emission of electrons as a result of the interaction of impinging energetic electrons with the surface of a material. Although it is fairly well described for metals, with a typical shape of the total electron emission yield (TEEY) first increasing to reach a maximum and then decreasing along with the energy increase in the primary electrons, there is still a lack of data and detailed analysis for dielectrics, in particular thin layers. The present work proposes a new insight into the electron emission phenomenon from very thin dielectric layers. It reports on the TEEY from very thin SiO2 layers, less than 100 nm. It is found that a departure from the typical shape of the TEEY curve occurs for primary electrons with energy of around 1 keV. The TEEY curve presents a dip, a local minimum that might be as deep as below 1. This atypical shape depends substantially on the layer thickness. The measured TEEY is compared to an electron emission 1D-model in which we consider the combined effect of the space-charge electric field induced by trapped charges in the dielectric layer and of the processes of field-dependent conductivity and radiation-induced conductivity on the fate of secondary electrons. Those mechanisms govern the charge transport in the dielectric and, consequently, the electron emission. The effects of the SiO2 layer thickness, an incidence angle of the primary electrons, and an applied external electric field on the TEEY curves are reported.
Identification and techno-economic assessment of potential enhancement of existing biomass power generators with concentrated solar thermal input
Authors: Beath Andrew , Meybodi Mehdi Aghaei
Published: October 2021

Hybrid power generation systems that combine more than one renewable resource type are a potential option to improve the capability of renewable power generation systems to meet network demands reliably. This increases the system complexity and cost, so this must be compensated by achieving correspondingly higher capacity factors to achieve similar financial performance to simpler systems. In the analysis undertaken, the hybrid systems developed were limited to combinations of biomass combustion and concentrated solar thermal technology for production of steam to feed a Rankine cycle turbine system. To ensure that resource availability was realistic in the study, biomass availability was based on 5 years of historical data for an existing biomass power generation site in Australia that currently has limited seasonal operations and matching solar data for the same location. A technoeconomic assessment was undertaken in parallel with optimization of plant configurations by inclusion of additional plant components and varying sizing. This included plant designs with different storage capacities, both thermal storage for solar energy and torrefaction char from short-term surpluses of biomass. Several system options were identified where financial performance matched the simple biomass combustion system, but with significant increases in capacity factor through hybridization.
Approaching phase-imaging through defocusing shadowgraphy for acoustic resonator diagnosis and the capability of direct index-of-refraction measurements
Authors: You Yi , Riedel Jens
Published: October 2021

The visualization of index-of-refraction (IoR) distribution is one of the common methods to investigate fluid flow or pressure fields. While schlieren and shadowgraphy imaging techniques are widely accepted, their inherent limitations often lead to difficulties in elucidating the IoR distribution and extracting the true IoR information from the resulting images. While sophisticated solutions exist, the IoR-gradient-to-image was achieved by purposely introducing a commonly avoided “defect” into the optical path of a conventional coincident schlieren/shadowgraphy setup; the defect is a combination of slight defocusing and the use of non-conjugate optical components. As such, the method presented in this work is referred to as defocusing shadowgraphy, or DF-shadowgraphy. While retaining the ease of a conventional schlieren/shadowgraphy geometry, this DF approach allows direct visualization of complicated resonant acoustic fields even without any data processing. For instance, the transient acoustic fields of a common linear acoustic resonator and a two-dimensional one were directly visualized without inversion. Moreover, the optical process involved in DF-shadowgraphy was investigated from a theoretical perspective. A numerical solution of the sophisticated impulse response function was obtained, which converts the phase distortion into intensity distributions. Based on this solution, the IoRs of various gas streams (e.g., CO2 and isopropanol vapor) were determined from single images.
A four-state programmable mid-infrared band-stop filter exploiting a Ge2Sb2Te5 film and VO2 nanoparticles
Authors: Meng Yun , Li Dan , Zhang Chong , Wang Yang , Simpson Robert E. , Long Yi
Published: October 2021

We designed and demonstrated a four-state programmable mid-infrared band-stop absorber that exploits two different phase-change materials. This programmability is possible by exploiting Fabry–Pérot resonances in a Ge2Sb2Te5 film and vanadium dioxide nanoparticles' (VO2 NPs) dual layer. The reflectivity trough can be tuned to four different infrared (IR) wavelengths from 1906 to 2960 nm by heating the structure to different temperatures. The near-perfect absorber is reconfigurable, lithography-free, industrially scalable, polarization-insensitive, and omnidirectional. Our strategy opens a path for programmable infrared photonics.
Toward a flow-dependent phase-stability criterion: Osmotic pressure in sticky flowing suspensions
Authors: Huang Derek E. , Zia Roseanna N.
Published: October 2021

Equilibrium phase instability of colloids is robustly predicted by the Vliegenthart–Lekkerkerker (VL) critical value of the second virial efficient, but no such general criterion has been established for suspensions undergoing flow. A transition from positive to negative osmotic pressure is one mechanical hallmark of a change in phase stability in suspensions and provides a natural extension of the equilibrium osmotic pressure encoded in the second virial coefficient. Here, we propose to study the non-Newtonian rheology of an attractive colloidal suspension using the active microrheology framework as a model for focusing on the pair trajectories that underlie flow stability. We formulate and solve a Smoluchowski relation to understand the interplay between attractions, hydrodynamics, Brownian motion, and flow on particle microstructure in a semi-dilute suspension and utilize the results to study the viscosity and particle-phase osmotic pressure. We find that an interplay between attractions and hydrodynamics leads to dramatic changes in the nonequilibrium microstructure, which produces a two-stage flow-thinning of viscosity and leads to pronounced flow-induced negative osmotic pressure. We summarize these findings with an osmotic pressure heat map that predicts where hydrodynamic enhancement of attractive bonds encourages flow-induced aggregation or phase separation. We identify a critical isobar—a flow-induced critical pressure consistent with phase instability and a nonequilibrium extension of the VL criterion.
Design and implementation of DC-to-DC converter topology for current regulated lightning generator
Authors: Andraud V. , Sousa Martins R. , Zaepffel C. , Landfried R. , Testé P.
Published: October 2021

When aircraft are impacted by lightning strikes, structural fuselage and components are stressed by electric and thermo-mechanical constraints which impose a need for reliable experimental test benches to design accurate and enhanced lightning protections. The aim of this work is to investigate, design, and compare different topologies of DC high-current generators in order to experimentally reproduce the continuous lightning current waveform component applied to produce an electric arc up to 1 m long. An electrical model of a standard lightning C*-waveform for a 1 m long arc is set, leading to an equivalent resistor varying from 4 to 8 Ω. This model enables a theoretical comparison between the DC/DC converters’ Buck and Buck-boost topologies to generate such a current-regulated waveform through a load using a capacitor bank and applying a minimum initial stored energy criterion. The experimental implementations of Buck and Buck-boost configurations are designed and tested. Optimizations about the accuracy of the current regulation through the feedback loop and the respect of components’ operating electrical and power parameters are presented. In particular, the implementation of a snubber filter and a frequency control of the switching operations, which are mandatory elements in the operation of DC converters, are described to prevent the circuit from damaging initiated by transient overvoltage peaks. Both Buck and Buck-boost configurations are experimentally implemented to generate a standard C* waveform through a 4 Ω resistor and the Buck configuration proves the ability to generate electric arcs up to 1.5 m respecting the standard aeronautic waveform of lightning.
Hydrodynamics of a floating barge adjacent to fixed structure in transient wave fronts
Authors: Zhang Chongwei , Sun Xiaotong , Ding Zhenyu , Chen Lifen , Ning Dezhi
Published: October 2021

Physical experiments are carried out in the wave flume to investigate the effects of transient wave fronts acting on multiple floating bodies. Two identical barges are considered with one being allowed to sway freely and the other fixed. A time-frequency analysis method based on the improved empirical mode decomposition and the Hilbert–Huang transform is developed to help analyze the localized characteristics of non-stationary wave fronts and the corresponding barge responses. A series of problems of particular concern are investigated systematically, and rich results and discussions are provided. Transient wave fronts behaving in a chirp waveform are observed. Two types of wave peaks with respect to transversal waves are recognized in the gap between two barges, whose occurrence locations are derived mathematically. The barge motion is found to be composed of the mean trend and oscillatory components, where the trend component is largely determined by the mooring system, and the oscillatory component is more relevant to the wave property. In shorter incident waves, the motion of weather-side barge can evidently amplify the wave amplitude between two barges. Both amplitudes of the barge motion and maximum wave elevation in the gap generally increase with the reduction in the gap width. Physical understandings revealed in this study are significant to help guarantee the operation safety of offshore side-by-side floating structures in practice.
A 4He vector zero-field optically pumped magnetometer operated in the Earth-field
Authors: Bertrand F. , Jager T. , Boness A. , Fourcault W. , Le Gal G. , Palacios-Laloy A. , Paulet J. , Léger J. M.
Published: October 2021

Low intrinsic noise, high bandwidth, and high accuracy vector magnetometers are key components for many ground or space geophysical applications. Here, we report the design and the test of a 4He vector optically pumped magnetometer specifically dedicated to these needs. It is based on a parametric resonance magnetometer architecture operated in the Earth magnetic field with closed-loop compensation of the three components of the magnetic field. It provides offset-free vector measurements in a ±70 μT range with a DC to 1 kHz bandwidth. We demonstrate a vector sensitivity up to 130 fT/√Hz, which is about ten times better than the best available fluxgate magnetometers currently available for the same targeted applications.
Equivalent circuit and fundamental limit of multi-stage infrared photodetectors
Authors: Yang Rui Q.
Published: October 2021

Based on an equivalent circuit model, a signal current in a multi-stage infrared (IR) photodetector is derived and used to discover a meaningful relation among quantum efficiency, collection efficiency, and particle conversion efficiency. Based on such a relation, it is demonstrated theoretically that the ultimate detectivities in multi-stage interband cascade infrared photodetectors (ICIPs) with identical discrete absorbers are the same as that in a conventional single-absorber detector in the limit of perfect collection (i.e., independent of the number of cascade stages) but higher than that in the single-stage detector with a finite diffusion length. Detailed derivations and calculations, along with relevant discussion, are provided to show how ICIPs are optimized for maximizing the detectivity and to understand the underlying physics. Multi-stage ICIPs with identical discrete absorbers are robust and durable against structural variations without being restricted by current matching and, therefore, are of more significance for practical applications such as those that require high-speed response or circumventing the diffusion length limitation. The results obtained for ICIPs with identical discrete absorbers can also be applied for quantum cascade detectors and photovoltaic quantum well infrared photodetectors. The results and insights gained from this work will further improve the understanding of multi-stage IR photodetectors and generate increased interest in the development of ICIPs and related devices for useful applications.
Simulations of effects of fiber rigidity on wet press
Authors: Tang Yihsin , Li Kecheng , Qi Dewei
Published: October 2021

A previously developed lattice-Boltzmann lattice-spring method is applied to simulate a wet press process. In simulations, multi-individual flexible fibers are settled on a wire screen by the force of gravity, and a fiber network is formed on the top surface of the wire screen. Next, the coordinates and velocities of fluid and fiber solid particles are copied to a computer press simulator composed of two perforated plates. A pressure pulse is imposed at the fluid contact line of the two press plates. Water is squeezed out of the fiber network by the pressure. During simulations, fiber rigidity, fiber concentrations, and pressure pulses are varied and their effects on water removal and re-wet phenomena are systematically studied.
Nonreciprocal photonic composited Su–Schrieffer–Heeger chain
Authors: Li Jun , Gao Bo , Zhu Chengjie , Xu Jingping , Yang Yaping
Published: October 2021

We explore nonreciprocity based on the topological zero modes of a finite asymmetric composited Su–Schrieffer–Heeger (SSH) chain composed of spinning ring cavities theoretically. Here, the first cavity on the short side is designed as a rotating cavity, whose frequency is related to the transmission direction of the light due to the Fizeau light-dragging effect. There are two topological edge modes (TEMs) and one topological interface mode in the middle of the bandgap for the composited SSH chain. The structural asymmetry reduces the transmittance of the system significantly due to symmetry breaking of the field distribution induced for the three modes. However, a small amount of frequency shift of the rotating cavity by Fizeau drag can greatly increase the transmittance by compensating the asymmetry of the structure for one TEM. Therefore, by introducing the input and output waveguides to couple the two outermost ring cavities, we construct an efficient nonreciprocal chain (the maximum isolation ratio can exceed 50 dB) with significant characteristics of monochromaticity and robustness in a narrow frequency range. Moreover, we prove that choosing appropriate system parameters can reduce the requirements of frequency shift. Our work combines nonreciprocity and one-dimensional topological structure organically and provides a scheme to achieve long-range nonreciprocity with topological protection, which is a crucial element in the classical and quantum technologies of computing and information.
Chirality of exchange spin waves exposed: Scattering and emission from interfaces between antiferromagnetically coupled ferromagnets
Authors: Poimanov V. D. , Kruglyak V. V.
Published: October 2021

We have studied the effect of chirality of the magnetization precession on the emission and scattering of spin waves from interfaces between ferromagnets with antiparallel magnetization. The need to match the chirality of the magnetization precessions at such interfaces promotes coupling between propagating modes on one side of the interface and evanescent modes on the other. This leads to the following two major effects: (i) an asymmetrical (ultimately, unidirectional) emission of spin waves from such interfaces when they are driven by an elliptically polarized magnetic field, and (ii) a strong (ultimately, complete) suppression of the transmission of spin waves incident upon such interfaces. Our results are relevant to the construction of spin-wave devices and more generally to the interpretation of measurements and numerical simulations in the field of chiral magnonics.
Torque field and skyrmion motion by spin transfer torque in a quasi-2D interface in presence of strong spin–orbit interaction
Authors: Osca Javier , Sorée Bart
Published: October 2021

We investigate the torque field and skyrmion motion at an interface between a ferromagnet hosting a skyrmion and a material with a strong spin–orbit interaction. We analyze both semiconductor materials and topological insulators using a Hamiltonian model that includes a linear term. The spin torque-inducing current is considered to flow in the single band limit; therefore, a quantum model of current is used. Skyrmion motion due to spin transfer torque proves to be more difficult in the presence of a spin–orbit interaction in the case where only interface in-plane currents are present. However, edge effects in narrow nanowires can be used to drive the skyrmion motion and to exert a limited control on its motion direction. We also show the differences and similarities between torque fields due to electric current in the many and single band limits.
A quantitative model for the bipolar amplification effect: A new method to determine semiconductor/oxide interface state densities
Authors: Ashton James P. , Moxim Stephen J. , Purcell Ashton D. , Lenahan Patrick M. , Ryan Jason T.
Published: October 2021

We report on a model for the bipolar amplification effect (BAE), which enables defect density measurements utilizing BAE in metal–oxide–semiconductor field-effect transistors. BAE is an electrically detected magnetic resonance (EDMR) technique, which has recently been utilized for defect identification because of the improved EDMR sensitivity and selectivity to interface defects. In previous work, BAE was utilized exclusively in EDMR measurements. Although BAE EDMR improves the sensitivity of EDMR in studies of semiconductor/oxide interface defects, an understanding of BAE in both electrical measurements and EDMR has not yet been investigated. In this work, we develop a BAE theory based on a modified Fitzgerald–Grove surface recombination methodology, which, in theory, may be utilized to fine-tune conditions for EDMR measurements. BAE may also now be utilized as an analysis tool in purely “electronic” measurements. The model presented here may ultimately prove useful in the development of resonance-based theories of BAE EDMR.
Collisional drift wave instability in an ultracold neutral plasma
Authors: Chakrabarti Nikhil , Sen Abhijit
Published: October 2021

We study the linear stability of a collisional drift wave in an ultracold neutral plasma (UNP) with the aim of investigating the effect of strong coupling effects on its propagation characteristics. The dispersion relation obtained using the generalized hydrodynamic model for the ultracold ion dynamics is solved analytically in various limits for the real frequency and growth rate of the mode. It is found that strong coupling-induced viscous effects lead to a weakening of the growth rate and an enhancement in the real frequency of the mode. The impact is particularly pronounced in the “kinetic” regime, i.e., when the ion–ion correlation time is much larger than the wave period. In the regime where the density gradient is weak, we find that collisional effects can destabilize the transverse shear waves and longitudinal waves. We discuss the relevance and potential application of our results in future experimental and numerical simulation studies of UNPs.
Kinetics of carbon condensation in detonation of high explosives: First-order phase transition theory perspective
Authors: Purohit Apoorva , Velizhanin Kirill A.
Published: October 2021

The kinetics of carbon condensation, or carbon clustering, in detonation of carbon-rich high explosives is modeled by solving a system of rate equations for concentrations of carbon particles. Unlike previous efforts, the rate equations account not only for the aggregation of particles but also for their fragmentation in a thermodynamically consistent manner. Numerical simulations are performed, yielding the distribution of particle concentrations as a function of time. In addition to that, analytical expressions are obtained for all the distinct steps and regimes of the condensation kinetics, which facilitates the analysis of the numerical results and allows one to study the sensitivity of the kinetic behavior to the variation of system parameters. The latter is important because the numerical values of many parameters are not reliably known at present. The theory of the kinetics of first-order phase transitions is found adequate to describe the general kinetic trends of carbon condensation, as described by the rate equations. Such physical phenomena and processes as the coagulation, nucleation, growth, and Ostwald ripening are observed, and their dependence on various system parameters is studied and reported. It is believed that the present work will become useful when analyzing the present and future results for the kinetics of carbon condensation, obtained from experiments or atomistic simulations.
Integral equation theory based dielectric scheme for strongly coupled electron liquids
Authors: Tolias P. , Lucco Castello F. , Dornheim T.
Published: October 2021

In a recent paper, Lucco Castello et al. (arXiv:2107.03537) provided an accurate parameterization of classical one-component plasma bridge functions that was embedded in a novel dielectric scheme for strongly coupled electron liquids. Here, this approach is rigorously formulated, its set of equations is formally derived, and its numerical algorithm is scrutinized. A systematic comparison with available and new path integral Monte Carlo simulations reveals a rather unprecedented agreement especially in terms of the interaction energy and the long wavelength limit of the static local field correction.