bluuebunny/crossref_metadata_2025 huggingface dataset:
Are Adequate Vitamin D Levels Helpful in Fighting COVID-19? A Look at the Evidence
Authors: Huilin Koh , Aravamudan Veeraraghavan Meyyur , Lin Jaime Hui Xian , Hoong Caroline Wei Shan , Cho Sanda
Published: September 2020

COVID-19 is a global pandemic with high mortality in vulnerable groups. Given the current lack of definitive treatment or vaccine that significantly reduces mortality rate, governments, researchers and healthcare providers are racing to find possible solutions to the crisis. Vitamin D and its analogues have been previously studied for their non-skeletal benefits. In particular, questions regarding their role in the modulation of immunity have re-surfaced, in view of possible epidemiological links observed between COVID-19 and vitamin D levels in selected populations. In this review, we highlight potential mechanisms and summarise the evidence for and against the potential role of vitamin D supplementation in our fight against COVID-19.
Gastric adenomas and their management in familial adenomatous polyposis
Authors: Martin Isabel , Roos Victorine H. , Anele Chukwuemeka , Walton Sarah-Jane , Cuthill Victoria , Suzuki Noriko , Bastiaansen Barbara A. , Clark Susan K. , von Roon Alexander , Dekker Evelien , Latchford Andrew
Published: September 2020

Background Patients with familial adenomatous polyposis (FAP) are at increased risk of developing gastric adenomas. There is limited understanding of their clinical course and no consensus on management. We reviewed the management of gastric adenomas in patients with FAP from two centers.

Methods Patients with FAP and histologically confirmed gastric adenomas were identified between 1997 and 2018. Patient demographics, adenoma characteristics, and management/surveillance outcomes were collected.

Results Of 726 patients with FAP, 104 (14 %; 49 female) were diagnosed with gastric adenomas at a median age of 47 years (range 19 – 80). The median size of gastric adenomas was 6 mm (range 1.5 – 50); 64 (62 %) patients had adenomas located distally to the incisura. Five patients (5 %) had gastric adenomas demonstrating high-grade dysplasia (HGD) on initial diagnosis, distributed equally within the stomach. The risk of HGD was associated with adenoma size (P = 0.04). Of adenomas > 20 mm, 33 % contained HGD. Two patients had gastric cancer at initial gastric adenoma diagnosis. A total of 63 patients (61 %) underwent endoscopic therapy for gastric adenomas. Complications occurred in three patients (5 %) and two (3 %) had recurrence, all following piecemeal resection of large (30 – 50 mm) lesions. Three patients were diagnosed with gastric cancer at median follow-up of 66 months (range 66 – 115) after initial diagnosis.

Conclusions We observed gastric adenomas in 14 % of patients with FAP. Of these, 5 % contained HGD; risk of HGD correlated with adenoma size. Endoscopic resection was feasible, with few complications and low recurrence rates, but did not completely eliminate the cancer risk.
Lateral Suboccipital Approach in Semisitting Position for Resection of Vagal Schwannoma: 2-Dimensional Operative Video
Authors: Lieber Stefan , Nunez Maximiliano , Tatagiba Marcos
Published: September 2020

We present a case of a sizeable vagal schwannoma that was resected through a lateral suboccipital approach in semisitting position. An extra-axial lesion, occupying the left cerebellomedullary cistern and extending from the pontomedullary junction to the jugular foramen was incidentally discovered in a 40-year-old woman afflicted with secondary progressive multiple sclerosis during repeated magnetic resonance imaging (Fig. 1). On physical examination, a mild deviation of the uvula to the right and a diminished gag reflex were observed. The patient was referred to our department after considerable growth of the lesion was noted and a broad interdisciplinary consensus was reached to treat the lesion surgically.

A gross total resection was achieved, histopathology confirmed a WHO I schwannoma with a low proliferation index. Postoperative dysphonia resolved completely within a few weeks, there was no collateral neurological deficit and especially no functional dysphagia. At 3-year follow-up, there was no indication of residual or recurrence.

This 2-dimensional video demonstrates pre- and postoperative imaging, positioning and set-up of operating room, anatomical and surgical nuances of the skull base approach, and the operative technique for microdissection of the schwannoma from the critical neurovascular structures (Fig. 2).

In summary, the lateral suboccipital approach in semisitting position is a powerful tool in the armamentarium for the microsurgical management of various pathologies residing in the posterior cranial fossa, especially large and vascularized schwannomas. Provided the necessary anesthesiological precautions and intraoperative procedures the semisitting position is safe and effective.

The link to the video can be found at: https://youtu.be/-9o_qJGkQhg.
Endoscopic Transnasal Odontoidectomy
Authors: Falco Jeffrey J. , Solares C. Arturo , Reyes Camilo
Published: September 2020

Objectives The video demonstrates the steps for an endoscopic transnasal approach for resection of the odontoid causing platybasia with basilar invasion.

Design The video reviews the clinical presentation, preoperative workup and imaging, patient positioning, technical nuances of the procedure, reconstruction, and clinical outcomes including postoperative imaging.

Setting The surgery was performed by a skull base team including otolaryngologists and neurological surgeons at a large regional tertiary care facility.

Participants A 59-year-old female with the Chiari I malformation with history of multiple revision cervical spinal surgeries presents with neck pain. Preoperative imaging showed a hypoplastic clivus and platybasia with basilar invasion.

Main Outcome Measures The main outcome measures consist of safely removing the odontoid with appropriate closure, reversal of the patient symptoms, and prevention of both operative complications and ventral compression of the brainstem.

Results The patient's neck pain improved. There were no intraoperative or postoperative complications besides anterior rightward nasal septal deviation causing unilateral nasal obstruction. A septoplasty was performed to correct the septal deviation 6 months after the initial procedure.

Conclusions The endoscopic transnasal approach to the resection of odontoid is a safe and effective treatment to address basilar invasion and ventral compression of the brainstem.

The link to the video can be found at: https://youtu.be/m_c3-Vn-l80.
Distinguishing Periprosthetic Crystalline Arthropathy from Infection in Total Knee Arthroplasty: A Systematic Review
Authors: Bradley Alexander T. , King Connor A. , Lin Ye , Sculco Peter , Balach Tessa , Landy David C.
Published: September 2020

Distinguishing periprosthetic crystalline arthropathy from periprosthetic joint infection (PJI) remains a diagnostic challenge as both symptom presentation and diagnostic tests overlap. Accurate differentiation is important as treatment plans vary significantly. We sought to systematically review all cases of total knee arthroplasty (TKA) periprosthetic crystalline arthropathy reported in the literature and summarize clinical, diagnostic, and operative findings in the context of guidelines for diagnosing PJI. The goal of this systematic review is to determine the amount of diagnostic overlap and to identify best practices for differentiating between these two diagnoses. MEDLINE and Google Scholar were searched to identify cases of crystalline arthropathy following TKA. Case reports were reviewed for patient characteristics, clinical symptoms, physical exam, laboratory results, and treatment outcomes. These findings were summarized across patients and dichotomized based on current thresholds for diagnosing PJI according to Musculoskeletal Infection Society criteria. Twenty-six articles were identified which included 42 cases of periprosthetic crystalline arthropathy (17 gout, 16 pseudogout, one both, and eight not specified). Of these cases, 25 presented over 1 year after their index arthroplasty and 15 had no prior history of crystalline arthropathy. Only six cases had a superimposed infection based on aspiration or intraoperative cultures. For cases without a culture-positive infection, several diagnostic tests overlap with PJI thresholds: 95% of patients had C-reactive protein greater than 1 mg/dL, 76% had an erythrocyte sedimentation rate greater than 30 mm/hour, 91% had a synovial white blood cell greater than 3,000 cells, and 76% had a synovial polymorphonuclear cells percent greater than 80%. Patients without co-infection were managed with non-steroidal anti-inflammatory drugs, colchicine, allopurinol, steroids, or a combination of these treatments and most had complete resolution of symptoms within 1 week. Commonly used markers of PJI fail to reliably distinguish periprosthetic crystalline arthropathy from infection. Though clinical judgement and consideration of the implications of delayed treatment for acute PJI remain paramount, in the setting of synovial crystals, surgeons may wish to consider this alternate etiology as the source of the patient's clinical symptoms.
Different Types of Statins and All-Cause Mortality during Anticoagulation for Venous Thromboembolism: Validation Study from RIETE Registry
Authors: Siniscalchi Carmine , Suriñach José M. , Visonà Adriana , Fernández-Reyes José L. , Gómez-Cuervo Covadonga , Verhamme Peter , Marchena Pablo J. , Farge-Bancel Dominique , Moisés Jorge , Monreal Manuel ,   and the RIETE Investigators
Published: September 2020

Introduction We previously reported that during the course of anticoagulation for venous thromboembolism (VTE) patients using statins were at a lower risk to die than nonusers.

Methods We used the Registro Informatizado Enfermedad TromboEmbólica (RIETE) registry to validate our previous findings in a subsequent cohort of patients and to compare the risk of death according to the use of different types of statins.

Results From January 2018 to December 2019, 19,557 patients with VTE were recruited in RIETE. Of them, 4,065 (21%) were using statins (simvastatin, 1,406; atorvastatin, 1,328; rosuvastatin, 246; and others, 1,085). During anticoagulation (192 vs.182 days, for statin and no statin users respectively), 500 patients developed a VTE recurrence, 519 suffered major bleeding, and 1,632 died (fatal pulmonary embolism [PE], 88 and fatal bleeding, 78). On multivariable analysis, statin users were at a lower risk to die (hazard ratio [HR] = 0.68; 95% confidence interval [CI]: 0.59–0.79) than nonusers. When separately analyzing the drugs, on multivariable analysis, patients using simvastatin (HR = 0.64; 95% CI: 0.52–0.80), atorvastatin (HR 0.72; 95% CI: 0.58–0.89), or other statins (HR = 0.67; 95% CI: 0.52–0.87) were at a lower risk to die than nonusers. For those using rosuvastatin, difference was not statistically significant (HR = 0.77; 95% CI: 0.50–1.19), maybe due to the sample size.

Conclusion Our data validate previous findings and confirm that VTE patients using statins at baseline are at a lower risk to die than nonusers. No statistically differences were found according to type of statins.
Starting the Stereotactic Radiosurgery Facility in Bangladesh: An Initial Experience
Authors: Kumar Narendra , Appasamy Murugan , Ahsan Sania , Das Sandip Kumar , Yasmin Taohida , Rana K.M. Masud , Kumar R. Arun , Joardar Aliuzzaman , Rahman Zillur , Chanda Amitabha , Chapal Saiful Islam
Published: September 2020

Radiotherapy is an integral part of a well-defined cancer management program. Bangladesh is a fast-growing East Asian country with 161 million population, and approximately 2 lakh cancer patients are diagnosed newly ever year. Though there are several modern treatment facilities to deliver radiotherapy, only limited facilities were available to deliver stereotactic radiotherapy (SRS) programs for needy patients. Evercare Hospitals Dhaka has recently started SRS and stereotactic therapy (SRT) with a dedicated team of trained people. The hospital is equipped with modern linear accelerator capable of delivering high dose rate mode and micro multileaf collimators with 2.45-mm thickness at isocenter to deliver larger doses of radiation precisely. This paper summarizes patient selection criteria and workflow for the SRS/SRT treatment established, including patient preparation, image data acquisition, target and organ at risk delineation on CT (computed tomography) and MRI (magnetic resonance imaging) images, treatment planning process, and quality assurance. Each stage of the process is explained in detail, with specific emphasis on certain areas to achieve a higher degree of accuracy. This article also highlights the need for dedicated timeout procedures to be followed to avoid drastic errors in treatment delivery. We also summarized demographics data of patients treated in the first 6 months, including diagnosis, sizes of lesions, and dose fraction. The dosimetric and setup uncertainties encountered during SRS/SRT treatment delivery are also described. Though, initially, we faced challenges, SRS/SRT treatment was successfully implemented and more than 35 patients were treated, with appreciable clinical outcomes.
On determining the power-law fluid friction factor in a partially porous channel using the lattice Boltzmann method
Authors: Meira Rodrigo E. C. P. , De Lai Fernando C. , Negrão Cezar O. R. , Junqueira Silvio L. M.
Published: September 2020

In the present work, the power-law fluid flow in a channel partially filled with a porous medium is numerically investigated using the lattice Boltzmann method (LBM). The porous domain, placed in the lower half of the channel, is represented according to a heterogeneous approach by a matrix of solid square disconnected blocks. The apparent viscosity of the power-law fluid is computed by locally varying the LBM relaxation factor. The results show the influence of geometry (porosity, number of obstacles, and hydraulic diameter), inertia (Reynolds number), and fluid properties (power-law index) over the partially porous-to-impermeable channel friction factor ratio. In general, the higher the porosity and the lower the number of obstacles, Reynolds number, and power-law index, the lower the friction factor. Finally, a correlation for the friction factor ratio as a function of the free region hydraulic diameter, permeability, and power-law index is presented for a specific channel configuration.
From deformation localization to melting and chemical segregation in metallic glass nanoparticles under high strain rate
Authors: Zhang Qi , Li Qi-Kai , Li Mo
Published: September 2020

Nanoparticles possess many distinguished properties due to their small size and unique internal and surface structures. For metallic glass nanoparticles, the small size combined with disordered atomic structure results in many unexpected results, some of which are superior to crystalline particles. This field, however, remains largely unexplored. Here, we report the mechanical and thermomechanical responses caused by the increasing strain rate in metallic glass nanoparticles under compression. The mechanical properties of nanoparticles resemble those of the bulk when the strain rate is below 1010 s−1; above this threshold, the nanoparticle exhibits localized deformation and then melting and even chemical segregation at the contact surface area. We reveal that these unique behaviors are the direct results of the lack of effective energy dissipation mechanisms in the disordered materials that are different from crystalline nanoparticles.
Strong interface-induced spin-charge conversion in YIG/Cr heterostructures
Authors: Ni Lijun , Chen Zhendong , Lu Xianyang , Yan Yu , Jin Lichuan , Zhou Jian , Yue Wencheng , Zhang Zhe , Zhang Longlong , Wang Wenqiang , Wang Yong-Lei , Ruan Xuezhong , Liu Wenqing , He Liang , Zhang Rong , Zhang Huaiwu , Liu Bo , Liu Ronghua , Meng Hao , Xu Yongbing
Published: September 2020

Here, we have investigated the spin pumping effect of Y3Fe5O12 (YIG)/Cu (tCu nm)/Cr heterostructures at room temperature with the thickness of the Cu interlayer varying from 0.4 nm to 5.0 nm. A huge charge signal Ic = 0.239 μA is observed in a YIG/Cr bilayer with direct contact, whereas Ic drops dramatically by two orders of magnitude when thin Cu interlayers down to 0.4 nm are inserted between YIG and Cr. Meanwhile, the injected spin current Js stays almost invariant for all the heterostructures. The effective spin Hall angle “θSH” of the YIG/Cr interface is found to be three orders of magnitude larger than the spin Hall angle θSH of the bulk Cr layer in YIG/Cu/Cr. The huge spin-charge conversion efficiency at the YIG/Cr interface is attributed to the inverse Rashba–Edelstein effect. Our experimental results demonstrate the dominant role of the interfacial effect in the spin-charge conversion process of the YIG/Cr heterostructures.
Efficient green InP quantum dot light-emitting diodes using suitable organic electron-transporting materials
Authors: Iwasaki Yukiko , Motomura Genichi , Ogura Kei , Tsuzuki Toshimitsu
Published: September 2020

Quantum dot light-emitting diodes (QD-LEDs) are expected to be used in wide-color-gamut displays because the emission colors from QDs are highly saturated. InP-based QDs are one of the most promising candidates for low-toxicity QDs. Here, we report an efficient green QD-LED whose emitting layer was composed of InP-based QDs and an organic electron-transporting material (ETM). To investigate ETMs suitable for combining with the QDs, the device characteristics of QD-LEDs with various ETMs were compared. The external quantum efficiency (EQE) and the driving voltage were found to be markedly improved by the incorporation of suitable ETMs. We demonstrated green QD-LEDs with a high maximum EQE of 10.0% and a low turn-on voltage of 2.4 V by using 2,4,6-tris(3′-(pyridin-3-yl)biphenyl-3-yl)-1,3,5-triazine (TmPPPyTz) as an ETM. Furthermore, to clarify the origin of the difference in device characteristics, we investigated their hole- and electron-transporting properties. The results suggested that the hole-current leakage from the QD layer was substantially suppressed in the QD-LEDs with TmPPPyTz. Using an ETM with such hole-suppressing ability is demonstrated to be an effective approach to improving the EQEs of QD-LEDs.
Controllable laser output of high-quality cylindrical vector beam through intra-cavity mode conversion
Authors: Zhang Yipeng , Wang Tianxin , Cheng Yue , Wei Dunzhao , Yao Wenzhe , Chen Pengcheng , Zhang Yong , Xiao Min
Published: September 2020

We experimentally demonstrate the controllable laser output of cylindrical vector (CV) beams, which feature flexibility, high efficiency, and good beam quality. Particularly, the CV laser beams have negligible radial components, distinguishing themselves from the extra-cavity-generated CV beams. The output state is controlled by an intra-cavity vortex half-wave plate (VWP). By changing the topological charge (l) of VWP, we produce l = 1 and l = 2 CV beams for example. Through rotating the half-wave plate inside the cavity, the laser outputs arbitrary CV beams around the equator of the corresponding high-order Poincaré spheres. For l = 1 and l = 2 CV beams, the polarization purities are as high as 97.8% and 96.7%, the sloping efficiencies are 15.5% and 5.4%, and the beam quality factors are 2.10 and 3.31, respectively. Our result provides a reliable CV laser source for advanced applications in optical imaging and optical manipulation.
Toward an ultra-high resolution phased-array system for 3D ultrasonic imaging of solids
Authors: Ohara Yoshikazu , Remillieux Marcel C. , Onuma Tomomi , Tsunoda Kosuke , Tsuji Toshihiro , Mihara Tsuyoshi
Published: September 2020

Ultrasonic phased-array (PA) systems have been widely adopted in the field of nondestructive evaluation for material characterization and imaging of internal defects. Whereas many defects exhibit complex three-dimensional structures, most PA systems provide only two-dimensional images. In this Letter, we demonstrate the ability to create high-resolution 3D images of internal defects using a PA system based on a piezoelectric and laser ultrasonic system (PLUS). The PLUS combines a piezoelectric transmitter to insonify the structure to be inspected with a laser Doppler vibrometer to create a matrix array of receiver points without contact. The small size of the laser beam results in an ultra-multiple number of elements on the order of thousands, which is impossible to achieve with a conventional piezoelectric matrix array transducer. An emission from a piezoelectric transmitter compensates for the intrinsically low sensitivity of a laser Doppler vibrometer. After formulating the 3D imaging algorithm of the PLUS, we demonstrate that the PLUS with 4096 receiving points (i.e., 64 × 64 points) achieves high-resolution 3D imaging in a specimen with a flat bottom hole. We also visualize the complex structure of stress corrosion cracking. We believe that the 3D imaging capability of the PLUS may open up new avenues to the accurate evaluation of material strength, the identification of the types of defects, and the elucidation of the mechanisms of defect initiation.
Black phosphorus field effect transistors stable in harsh conditions via surface engineering
Authors: Jiang Bei , Huang Hao , Chen Rui , Li Guoli , Flandre Denis , Wan Da , Chen Xue , Liu Xingqiang , Ye Cong , Liao Lei
Published: September 2020

Black phosphorus (BP) has potential for fabricating p-type transistors in ultra-thin 2D-material complementary circuits. However, as the synergetic effect of water and oxygen leads to performance degradation under an ambient atmosphere, it is urgent to develop a passivation strategy for robust stability. Herein, a scalable superhydrophobic passivation layer is designed to improve the stability of BP transistors, which consists of fluoroalkylsilane-coated titanium dioxide (TiO2) nanoparticles. Due to the superhydrophobic property of the passivation layer, the BP transistors preserve intrinsic performance in extremely wet conditions, including humid air, water, HCl, and KOH. After 28 days in atmospheric conditions, the performance presents only 20% channel current degradation and the device can work even after 60 days. This work not only experimentally demonstrates robust stable BP transistors in harsh conditions but also provides a highly efficient and damage-free strategy to suppress the influence of water adsorption in atmospheric conditions for highly stable 2D materials devices.
Sound velocity and refractive index of pure N2 fluid and of equimolar N2–CO2 fluid mixture up to 15 GPa
Authors: Ninet S. , Weck G. , Dewaele A. , Datchi F. , Giordano V. M. , Loubeyre P.
Published: September 2020

The sound velocity and refractive index of pure N2 and of the equimolar N2–CO2 mixture are measured up to 15 GPa and 700 K in a resistive heating diamond anvil cell. The refractive index vs pressure is obtained by an interferometric method. The adiabatic sound velocity is then determined from the measurement of the Brillouin frequency shift in the backscattering geometry and the refractive index data. No phase separation of the N2–CO2 fluid mixture is observed. The fluid mixture properties are discussed in terms of ideal mixing.
Correlation between linear and nonlinear material functions under large amplitude oscillatory shear
Authors: Liu Zhiwei , Xiong Zhongqiang , Nie Zhijun , Yu Wei
Published: September 2020

Fourier transform rheology is the most frequently used method to interpret the nonlinear rheological behavior of complex fluids under large amplitude oscillatory shear (LAOS). However, the unclear relationship between the higher harmonics and the fundamental harmonic obscures the physical meaning of the nonlinear functions. Here, we hypothesize that all the nonlinear oscillatory shear functions and normal stress functions can be expressed as linear combinations of linear viscoelastic functions or their derivatives at different frequencies under both strain-controlled LAOS (LAOStrain) and stress-controlled LAOS (LAOStress). We check this hypothesis using the time-strain separable Wagner model, Giesekus model, and modified Leonov model. We find such correlations between the nonlinear material functions and the linear material functions are intrinsic for viscoelastic liquids under LAOStrain, and for viscoelastic solids under LAOStress. Finally, these correlations are justified by a viscoelastic standard polydimethylsiloxane, an ethylene–octene multiblock copolymer melt, and a typical simple yield stress material (0.25 wt. % Carbopol).
Anomalous features in internal cylinder flow instabilities subject to uncertain rotational effects
Authors: Akhavan-Safaei Ali , Seyedi S. Hadi , Zayernouri Mohsen
Published: September 2020

We study the flow dynamics inside a high-speed rotating cylinder after introducing strong symmetry-breaking disturbance factors at cylinder wall motion. We propose and formulate a mathematically robust stochastic model for the rotational motion of the cylinder wall alongside the stochastic representation of incompressible Navier–Stokes equations. We employ a comprehensive stochastic computational fluid dynamics framework combining the spectral/hp element method and the probabilistic collocation method to obtain high-fidelity realizations of our mathematical model in order to quantify the propagation of parametric uncertainty for dynamics-representative quantities of interests. We observe that the modeled symmetry-breaking disturbances cause a flow instability arising from the wall. Utilizing global sensitivity analysis approaches, we identify the dominant source of uncertainty in our proposed model. We next perform a qualitative and quantitative statistical analysis on the fluctuating fields characterizing the fingerprints and measures of intense and rapidly evolving non-Gaussian behavior through space and time. We claim that such non-Gaussian statistics essentially emerge and evolve due to an intensified presence of coherent vortical motions initially triggered by the flow instability due to the symmetry-breaking rotation of the cylinder. We show that this mechanism causes memory effects in the flow dynamics in a way that noticeable anomaly in the time-scaling of enstrophy record is observed in the long run apart from the onset of instability. Our findings suggest an effective strategy to exploit controlled flow instabilities in order to enhance the turbulent mixing in engineering applications.
Nanoassembly technique of carbon nanotubes for hybrid circuit-QED
Authors: Cubaynes T. , Contamin L. C. , Dartiailh M. C. , Desjardins M. M. , Cottet A. , Delbecq M. R. , Kontos T.
Published: September 2020

A complex quantum dot circuit based on a clean and suspended carbon nanotube embedded in a circuit quantum electrodynamic (cQED) architecture is a very attractive platform to investigate a large spectrum of physics phenomena ranging from qubit physics to nanomechanics. We demonstrate a carbon nanotube transfer process allowing us to integrate clean carbon nanotubes into complex quantum dot circuits inside a cQED platform. This technique is compatible with various contacting materials such as superconductors or ferromagnets. This makes it suitable for hybrid quantum devices. Our results are based on eight different devices demonstrating the robustness of this technique.
Development of fluorescence-yield wavelength-dispersive x-ray absorption spectroscopy in the soft x-ray region for time-resolved experiments
Authors: Amemiya K. , Sakata K. , Suzuki-Sakamaki M.
Published: September 2020

A fluorescence-yield wavelength-dispersive x-ray absorption spectroscopy technique in the soft x-ray region, by which the x-ray absorption spectra are recorded without scanning the monochromator, has been developed. The wavelength-dispersed soft x rays, in which the wavelength (photon energy) continuously changes as a function of the position, illuminate the sample, and the emitted fluorescence soft x rays at each position are separately focused by an imaging optics onto each position at a soft x-ray detector. Ni L-edge x-ray absorption spectra for Ni and NiO thin films taken in the wavelength-dispersive mode are shown in order to demonstrate the validity of the technique. The development of the technique paves the way for a real-time observation of time-dependent processes, such as surface chemical reactions, with much higher gas pressure compared to the electron-yield mode, as well as under magnetic and electric fields.
Lightweight protective configurations against blast and fragments impact: Experimental and numerical studies
Authors: Ahmed Khurshid , Malik Abdul Qadeer , Hussain Arshad , Ahmad Iram Raza , Ahmad Iftikhar
Published: September 2020

Lightweight protective configurations against blast and fragment impacts were studied experimentally and numerically. The configurations comprised different combinations of Kevlar fabrics, laminated GFRP (Glass Fiber Reinforced Polyester), polyurethane (PU) foam, and alumina (Al2O3). The polyurethane (PU)–sand multi-layer composition and a mixture of polyurethane–sand and polyurethane–alumina powder were also studied. The protective configurations were tested under static detonation of a scaled down artillery shell. Protective capabilities were tested against a peak incident overpressure of 57 psi and fragments weighing up to 4.3 g carrying velocities in the range of 961 m/s–1555 m/s. Numerical simulations were performed using ANSYS AUTODYN. The coupled SPH (Smoothed Particle Hydrodynamics)–ALE (Arbitrary Lagrangian–Eulerian) approach was used to simulate the interaction of fragments with protective configurations. A coupled Euler–ALE approach was employed for blast wave loading on protective configurations. The Kevlar fabrics, laminated GFRP, and PU foam compositions provided significant absorption and attenuation to impacting fragments. Configurations employing alumina tile were able to withstand both blast and fragment impacts without significant backface signatures (blunt force trauma). The configurations can be employed as body armor, vehicle armor, and for the safety and security of other critical infrastructures against blast wave and high velocity fragment impact. Numerical simulation results are in fair agreement with experimental results.
Two-phase flow boiling in a microfluidic channel at high mass flux
Authors: Keepaiboon Chanyoot , Dalkilic Ahmet Selim , Mahian Omid , Ahn Ho Seon , Wongwises Somchai , Mondal Pranab Kumar , Shadloo Mostafa Safdari
Published: September 2020

We report the experimental investigations of two-phase flow boiling heat transfer characteristics of a refrigerant in a microfluidic channel at a high mass flux (more than 1000 kg/m2 s). We investigate the heat transfer coefficients at a heat flux range of 7.63 kW/m2–49.46 kW/m2, mass flux range of 600 kg/m2 s–1400 kg/m2 s (high mass flux), and saturation temperature range of 23 °C–31 °C. We propose the new two-phase flow boiling heat transfer correlation of a refrigerant, which is used as the working fluid for the present experiments, at the microfluidic scale. We experimentally establish the functional relationship of two-phase flow boiling heat transfer correlation of the refrigerant during flow boiling in a rectangular microchannel with the Reynolds number, the boiling number, and the Weber number. We believe that the inferences of this study may provide a design basis for the micro-heat exchanger, typically used for thermal management in electronic devices, micro-electro-mechanical systems, and electric vehicle battery cooling system.
Identity and heritage: changing politics and appropriation of heritage in Zimbabwe
Authors: Chiwaura Henry , Naidoo Salachi
Published: September 2020

This article is an explanation of the use of heritage representations and narratives within the ever-changing political matrix in Zimbabwe. The analysis is done within the context of heritage being regarded as a cultural process rather than as a product. Focus is on how heritage has been appropriated by both the colonial and post-colonial state in building national identities. From 1890 the settlers appropriated some of the existing heritage that belonged to indigenous groups on the land between Limpopo and Zambezi Rivers. The article fully acknowledges that identity is a fluid and controversial concept that is influenced by cultural frameworks, historical period and those in power at any particular time. Therefore, heritage herein is viewed as an identity influencer and, in the case of emerging nations; heritage is responsible for the construction of national identity.
Multi-omic comparison of Alzheimer’s variants in human ESC–derived microglia reveals convergence at APOE
Authors: Liu Tongfei , Zhu Bing , Liu Yan , Zhang Xiaoming , Yin Jun , Li Xiaoguang , Jiang LuLin , Hodges Andrew P. , Rosenthal Sara Brin , Zhou Lisa , Yancey Joel , McQuade Amanda , Blurton-Jones Mathew , Tanzi Rudolph E. , Huang Timothy Y. , Xu Huaxi
Published: September 2020

Variations in many genes linked to sporadic Alzheimer’s disease (AD) show abundant expression in microglia, but relationships among these genes remain largely elusive. Here, we establish isogenic human ESC–derived microglia-like cell lines (hMGLs) harboring AD variants in CD33, INPP5D, SORL1, and TREM2 loci and curate a comprehensive atlas comprising ATAC-seq, ChIP-seq, RNA-seq, and proteomics datasets. AD-like expression signatures are observed in AD mutant SORL1 and TREM2 hMGLs, while integrative multi-omic analysis of combined epigenetic and expression datasets indicates up-regulation of APOE as a convergent pathogenic node. We also observe cross-regulatory relationships between SORL1 and TREM2, in which SORL1R744X hMGLs induce TREM2 expression to enhance APOE expression. AD-associated SORL1 and TREM2 mutations also impaired hMGL Aβ uptake in an APOE-dependent manner in vitro and attenuated Aβ uptake/clearance in mouse AD brain xenotransplants. Using this modeling and analysis platform for human microglia, we provide new insight into epistatic interactions in AD genes and demonstrate convergence of microglial AD genes at the APOE locus.
On congruences of Laguerre cycles and their envelopes
Authors: Pacheco R , Santos S D
Published: September 2020

In the cyclographic model of Laguerre geometry, the isotropy projection establishes a correspondence between submanifolds in the Lorentz (n + 1)-space and oriented hypersphere congruences in the Euclidean n-space. In this paper, we investigate the relation between the Lorentzian geometry of the sphere congruences and the Euclidean geometry of the corresponding oriented envelopes. We introduce the notion and discuss the existence of marginally outer trapped submanifolds associated to an (n − 1)-dimensional Legendre submanifold of the unit tangent bundle over the Euclidean n-space. This extends the notion of Laguerre–Gauss map of an oriented surface. Two special classes of marginally outer trapped surfaces are characterized in terms of their oriented envelopes. The Lorentzian geometry of several families of spheres whose envelopes are well-known surfaces in the Euclidean three-space is investigated.
An efficient macro model for CMOS-MEMS thermal wind speed sensor
Authors: Zhang Jia-Zhen , Zhou Zai-Fa , Qin Ming , Huang Qing-An
Published: September 2020

In this paper, we propose a thermal wind speed sensor Verilog-A model with thermal-fluid-electric hybrid characteristics. Because the structure of the thermal wind sensor and the interface circuit chip are designed separately, which cannot effectively carry out MEMS-IC (integrated circuit) co-simulation, the overall performance of the sensor and interface circuit chip is prone to large deviation. At the same time, the separation of MEMS structure and IC design process leads to long product development cycle and high cost. This paper proposes an improved simulation model by analyzing the behavior characteristics of the thermal wind speed sensor. The simulation model consists of 11 thermistors, 3 capacitors, a voltage-controlled voltage source, and a voltage-controlled current source. The Taylor series expansion of the differential equation of heat conduction is carried out, and then the thermistor and capacitor networks are established according to the corresponding relationship between the thermal parameters and the electrical parameters, including the thermal conduction unit, the convection unit and the heat capacity in the chip. The model fully considers the effects of various physical effects and parasitic effects, and is implemented using the hardware description language Verilog-A. The sensor and interface circuit can be simulated simultaneously to optimize the circuit design. It is beneficial to the integration of sensors and interface circuit, reducing the number of tape-outs, increasing the success rate, and reducing costs. The consistency between the simulation results and the experimental curves verified the correctness of the macro model. The behavior characteristics of constant power (CP) and constant temperature heating were described. In CP mode, the output voltage error is less than ± 6.5%, the chip temperature error is less than 4.0%. The presented modeling approach can be the basis for the development of complete MEMS-IC design technology library of thermal wind speed sensor, aiming at optimum designs of integrated thermal wind speed sensor.
Optical evidence of many-body effects in the zincblende Al

x

Ga

1−x

N alloy system
Authors: Baron Elias , Feneberg Martin , Goldhahn Rüdiger , Deppe Michael , Tacken Fabian , As Donat J
Published: September 2020

We present a quantitative description of the change in optical properties of zincblende aluminium-gallium-nitride thin films dependent on the free-carrier concentration due to band filling and renormalization effects. Free-electron concentrations above 1020 cm−3 in GaN are achieved by introducing germanium as a donor. Spectroscopic ellipsometry in the infrared and ultraviolet spectral range yields the dielectric function (DF). The plasmon contribution for the infrared part of the DF allows to determine the free-electron concentration all-optically. Furthermore, by utilizing the Kane model for the band structure of semiconductors near the Γ-point of the Brillouin zone as well as taking into account Burstein-Moss-shift and band-gap renormalization, measured transition energies are efficiently described.
Determining accurate hand positions in three-dimensional space using twin-axis electrogoniometer sensors
Authors: Zargaripour Elham , Fallah Ali , Maleki Ali , Naghibi Seyedeh Somayeh
Published: September 2020

Electrogoniometers are low price sensors which are easily attached to the body in any environment. Although electrogoniometer sensors are typically used for angular measurements, they can also be used to determine position. This study aimed to accurately determine hand position during the performance of five daily life activities using two electrogoniometer sensors to measure shoulder and elbow angles simultaneously. The measurement of joint angles involves some errors which are divided into intrinsic and extrinsic errors. These errors cause considerable inaccuracies in the estimated hand positions. To overcome this issue, the errors identified are compensated for in two phases, the angular phase and the positional phase, in which a polynomial function and an Elman neural network are used for error compensation, respectively. The derived hand trajectories and the decrease of the
root mean square error at every stage of the error compensation, along with the variance accounted for of the Elman networks for each task, show the effectiveness of the proposed method.
Numerical investigation of tensile response of notched bulk metallic glass composite specimens
Authors: Dutta Tanmay , Chauniyal Ashish , Singh I , Narasimhan R
Published: September 2020

In this work, plane strain finite element and atomistic simulations of tensile response of double edge notched bulk metallic glass composite (BMGC) samples are conducted. A special constitutive model is used to represent the response of the bulk metallic glass matrix along with J
2 flow theory of plasticity to characterize the crystalline dendrites in the former, while a CuZr based glass matrix containing single crystal Cu dendrites is modeled in the latter. It is found that the ratio of notch root radius to the distance between the notch tip and the nearest dendrite, R/l
1, is an important parameter that governs the plastic deformation behavior and possible failure mechanisms. Both finite element and atomistic analyses show that as R/l
1 increases from a small to moderate value, a transition occurs in plastic flow through multiple shear banding with deflection by dendrites to ligament necking. On further increase in the above notch acuity parameter, the deformation behavior again changes to multiple shear banding without much hindrance from dendrites. Specimens with moderately blunt notches (as characterized by the value of R/l
1) having high hardening elongated dendrites exhibit pronounced plastic deformation along the ligament resulting in necking. The influence of BMGC microstructure and hardening of dendrites is also investigated from the finite element analyses.
Lateral monolayer MoS2 homojunction devices prepared by nitrogen plasma doping
Authors: Lu Jingjing , Guo Zhenyu , Wang Wenzhao , Lu Jichang , Hu Yishuo , Wang Junhao , Xiao Yonghong , Wang Xiya , Wang Shibo , Zhou Yufei , Zeng Xiangbin
Published: September 2020

Monolayer MoS2 possesses good electron mobility, structural flexibility and a direct band gap, enabling it to be a promising candidate for flexible and wearable optoelectronic devices. In this article, the lateral monolayer MoS2 homojunctions were prepared by a nitrogen plasma selective doping technique. The monolayer MoS2 thin films were synthesized by chemical vapor deposition and characterized by photoluminescence, atom force microscope and Raman spectroscopy. The electronic and photoelectric properties of the lateral pn and npn homojunctions were discussed. The results showed that the rectifying ratio of the pn homojunction diode is ∼103. As a photodetector of pn homojunction, the optical responsivity is up to 48.5 A W−1, the external quantum efficiency is 11 301%, the detectivity is ∼109 Jones and the response time is 20 ms with the laser of 532 nm and the reverse bias voltage of 10 V. As a bipolar junction transistor of npn homojunction, the amplification coefficient reached ∼102. A controllable plasma doping technique, compatible with traditional CMOS process, is utilized to realize the monolayer MoS2 based pn and npn homojunctions, and it propels the potential applications of 2D materials in the electronic, optoelectronic devices and circuits.
Unlocking the potential of metal organic frameworks for synergized specific and areal capacitances via orientation regulation
Authors: Deng Ting , Shi Xiaoyuan , Zhang Wei , Wang Zizhun , Zheng Weitao
Published: September 2020

Metal organic frameworks (MOFs) with numerous potential pseudocapacitive sites are quite appealing to supercapacitors with high specific and areal capacitances. However, MOFs suffer from a low conductivity nature, resulting in a mediocre electrochemical performance. Herein, we propose a template-growth strategy of MOF to enhance both specific and areal capacitances of MOF as the electrode material for supercapacitor. As the loading mass of MOF increases from 2 to 5 mg, the specific capacitance also increases from 937 to 2387 Fg−1 (431 to 1098 Cg−1) and areal capacitance 1.87 to 11.94 Fcm−2 (0.86 to 5.49 Ccm−1). Accordingly, a hybrid MOF//AC supercapacitor can deliver a maximum energy density of 67 Wh kg−1 and a maximum power density of 6000 W kg−1. These results point to a way to fabricate MOF electrode of supercapacitor with high specific and areal capacitance, which leads them to a more practical future.
Ionization waves in the PK-4 direct current neon discharge
Authors: Hartmann Peter , Rosenberg Marlene , Juhasz Zoltan , Matthews Lorin S , Sanford Dustin L , Vermillion Katrina , Carmona-Reyes Jorge , Hyde Truell W
Published: September 2020

The PK-4 system is a micro-gravity dusty plasma experiment currently in operation on-board the International Space Station. The experiment utilizes a long DC discharge in neon or argon gases. We apply our 2D particle-in-cell with Monte Carlo collisions discharge simulation to compute local plasma parameters that serve as input data for future dust dynamics models. The simulation includes electrons, Ne+ ions, and Ne
m
metastable atoms in neon gas and their collisions at solid surfaces including secondary electron emission and glass wall charging. On the time scale of the on-board optical imaging, the positive column appears stable and homogeneous. On the other hand, our simulations show that on microsecond time scales the positive column is highly inhomogeneous: ionization waves with phase velocities in the range between 500 m s−1 and 1200 m s−1 dominate the structure. In these waves, the electric field and charged particle densities can reach amplitudes up to 10 times of their average value. Our experiments on ground-based PK-4 replica systems fully support the numerical findings. In the experiment, the direction of the DC current can be alternated, which has been found to favor dust particle chain formation. We discuss possible mechanisms for how the highly oscillatory plasma environment contributes to the dust particle chain formation.
Design, prototyping, and evaluation of a concept for a shape-changing smart material building surface tile
Authors: Zupan Robert J , Clifford Dale T , Beblo Richard V , Brigham John C
Published: September 2020

A design concept for shape-changing smart material tiles for applications in environmentally responsive building facades is presented. In particular, the application considered is a tile that would change the shape of the building surface to favorably affect the interaction with solar irradiance. A lab-scale prototype system for smart material tiles composed of 3D printed thermally responsive shape memory polymer (SMP) and utilizing localized thermal material activation and uniform pressure actuation is examined. Tests utilizing the prototype tile are used to create and validate a computational (finite element) representation of the adaptive surface tile system. Toward developing this computational representation, a strategy is presented to determine and validate the material parameters for the 3D printed SMP by matching the tile shape predicted by the numerical model to the tile shape measured experimentally. This numerical representation was then implemented into a computational approach to explore the design space for this adaptive tile to have an effect on the solar irradiance on a building surface. More specifically, a series of numerical examples are considered that determine the location and size of material activation that minimize the area of the tile exposed to solar irradiance. Results indicate that the adaptive tile can change the surface of a structure to considerably improve the structure’s interaction with solar irradiance. Additionally, the importance of the control strategy for a multi-tile system was displayed, particularly with respect to the capability to significantly reduce the energy cost and affect the solar irradiance to a higher degree by accounting for neighboring tile interaction.