bluuebunny/crossref_metadata_2025 huggingface dataset:
Symptomatische Behandlungsoptionen chronischer, neurologischer Gangstörungen
Authors: Schniepp Roman , Möhwald Ken , Wuehr Max
Published: April 2021

Störungen des Gehens, der Mobilität und Stürze sind häufige Gesundheitsprobleme von Patienten mit chronischen, neurologischen Erkrankungen. Daher ist es wichtig, neben der Behandlung der neurologischen Grunderkrankung auch symptomatische Therapieoptionen mit dem Ziel der Verbesserung des Gehens einzusetzen.

Mittels einer selektiven Literaturrecherche von Studien mit expliziter Untersuchung der Gehfähigkeit wurden symptomatische Therapiemöglichkeiten in den folgenden klinischen Entscheidungsfeldern identifiziert und diskutiert: (1) hypokinetische Gangstörung (z.B. bei M. Parkinson, Normaldruckhydrocephalus und vaskulärer Enzephalopathie), (2) Gangunsicherheit mit Ataxie (sensorisch und zerebellär) und (3) spastisch-paretische Gangstörung (bei Multipler Sklerose). Es werden medikamentöse und nicht-medikamentöse Therapieoptionen analysiert, speziell zu den Funktionsbereichen „Lokomotion“, „posturale Kontrolle“, „Modulation“ und „Adaptionsfähigkeit“. Die medikamentösen Behandlungskonzepte orientieren sich vorwiegend an den pathophysiologischen Veränderungen der Grunderkrankungen. Physikalisch-medizinische Basistherapien sowie Gang- und Bewegungstherapien erweitern das therapeutische Spektrum. Zudem können geh-relevante Einzelsymptome effizient mittels physikalisch-medizinischer oder pharmakologischer Therapien verbessert werden.

Die Behandlungsoptionen neurologischer Gangstörungen sind gut und systematisch untersucht und ermöglichen eine individuelle Anpassung an die zugrundeliegende neurologische Erkrankung, an die Funktionsdefizite der individuellen Gangstörung sowie an relevante Einzelsymptome, welche das Gehen nochmals verschlechtern.
Cross-Dehydrogenative Coupling Reaction and Arylation of Quinoxalin-2(1H)-ones under Iodide/Peroxide Conditions
Authors: Ma Chen , Wu Yujuan , Chu Xianglong , Yang Di , Xie Caixia
Published: April 2021

A simple method has been developed for the synthesis of ­3-(2-oxo-2-phenylethylidene)-3,4-dihydroquinoxalin-2(1H)-one and ­3-aryl-quinoxalin-2(1H)-one derivatives through C–H activation of quinoxalin-2(1H)-ones by peroxides and iodide. In this protocol, the per­oxide (TBPB) serves as both the radical initiator and aryl source, realizing arylation of quinoxalin-2(1H)-one in a one-step reaction. The methodology has the advantages of being a metal-free strategy and having broad functional group tolerance.
Proton-Mediated Practical Synthesis of McGeachin-Type Bisaminals
Authors: Du Hongguang , Xu Jiaxi , Yang Zhanhui , Chen Yang , Wang Tingting
Published: April 2021

A proton-mediated practical synthesis of McGeachin-type bisaminals from 2-(alkylamino)arenecarbaldehydes and primary amines is achieved, with trifluoroacetic acid as the proton donor. The use of a proton, a smallest electrophilic activator, allows previously inviable ortho­-substituted anilines and linear and branched aliphatic amines to be viable substrates for McGeachin bisaminal synthesis. Overcoming the steric and electronic limitations provides a practical synthetic method. The applications in product derivation and pharmaceutical molecule modification are also demonstrated.
Capacity Building in Mental Health for Bihar: Overview of the 1-Year Blended Training Program for Nonspecialist Medical Officers
Authors: Bairy Bhavya K , Ganesh Aurobind , Kaur Sandeepa , Chand Prabhat Kumar , Kumar Channaveerachari Naveen , Manjunatha Narayana , Math Suresh Bada , Sinha Narendra Kumar , Arora Sanjeev
Published: April 2021

Objective The aim of this study is to give an experiential overview of a 1-year blended training program for nonspecialist medical officers (primary care doctors; PCDs) of Bihar State of India. The training program was aimed to enable PCDs identify, diagnose, and treat commonly presenting psychiatric disorders in primary care

Methods PCDs had a brief onsite orientation program to psychiatric practice at National Institute of Mental Health and Neuro-Sciences (NIMHANS), followed by 10 months of online blended training. The online program followed the NIMHANS Virtual Knowledge- Extension for Community Healthcare Outcomes (ECHO) model, that is, a hub and spokes model of training

Results Twenty-two PCDs participated in this program. Eleven of them got accredited at the end. The onsite orientation consisted of exposure to various psychiatry facilities at NIMHANS, in addition to learning psychiatric history taking and mental status examination. The ECHO model of online learning consisted of fortnightly sessions, lasting 2 hours each. There were 20 such sessions. Each session consisted of a didactic lecture by the psychiatrist followed by a case discussion. The cases were presented by PCDs, moderated by the hub specialists (NIMHANS). At the end of the training, participants rated an average of 4.5/5 on the mode, content and relevance of training and increase in knowledge due to the training. Around 23,000 patients were cared for during the said 1 year by the trained PCDs.

Conclusion Training PCDs in a manner that enables retaining the learnt skills is feasible. However, rigorous evaluation protocols are needed in order to test this in a systematic fashion.
Reviewing the Ethical Concerns of the Convalescent Plasma Therapy in COVID-19
Authors: Raturi Manish , Kala Mansi , Das Kunal , Kusum Anuradha
Published: April 2021

The understanding of coronavirus disease 2019 (COVID-19) is evolving periodically. There is also a marked increase in COVID-19 patients’ demand for the provision of COVID-19 convalescent plasma (CCP) therapy. With the review of the literature, the stage of speculation is quickly moving towards conformity, with the interim guidelines given by the Food and Drug Administration (FDA) in the United States, United Kingdom’s blood transfusion services, Saudi’s FDA, and the Indian Council for Medical Research, in addition to the European health authorities. It is prudent to address the ethical concerns that merit consideration while harvesting and utilizing CCP as a therapeutic tool in local hospital setting.
Tourism in Afghanistan.
Authors: Najimi Abdul Wassay
Published: April 2021

This chapter accounts for the status of tourism development in Afghanistan before the civil war and the situation today, exploring the policies and promotional tools the government has enacted and the options available ahead.
Drymaria cordata (tropical chickweed).
Authors: Rojas-Sandoval Julissa , Acevedo-Rodríguez Pedro
Published: April 2021

D. cordata is a vigorous fast-growing herb included in the Global Compendium of Weeds (Randall, 2012) and listed as one of the most aggressive weeds invading moist habitats in tropical and subtropical regions of the world (Holm et al., 1997; USDA-ARS, 2014). It is listed as a weed in 31 crops in more than 45 countries within and outside its native distribution range. D. cordata produces large amount of seeds (> 600 seeds/plants) and also spreads vegetatively rooting from the nodes, which is a trait that enable plants to multiply rapidly and colonize large areas very quickly. It has the potential to harm other plants by smothering them under a solid blanket of leaves and by climbing into the bushes (Holm et al., 1997).
Eleusine indica (goose grass).
Authors: Rojas-Sandoval Julissa , Acevedo-Rodríguez Pedro
Published: April 2021

E. indica is primarily listed as an agricultural and environmental weed (Randall, 2012) and is considered a "serious weed" in at least 42 countries (Holm et al., 1979). This species is described as a "dominant weed" especially in farming systems and annual row-crops where it grows vigorously and produces abundant seedlings (Holm et al., 1979). A single plant may produce more than 50,000 small seeds, which can be easily dispersed by wind and water, attached to animal fur and machinery and as a contaminant in soil (Waterhouse, 1993). E. indica invades disturbed habitats in natural areas and the margins of natural forests and grasslands, marshes, stream banks and coastal areas. It is also a common weed along roads, pavements, and powerline corridors (Queensland Department of Primary Industries and Fisheries, 2011). Currently it is listed as invasive in several countries in Europe, Asia, Central and South America, the Caribbean and on many islands in the Pacific Ocean (see Distribution Table for details).
Monochamus leuconotus (white coffee stem borer).
Authors: Schoeman Schalk
Published: April 2021

M. leuconotus is indigenous to Africa south of the Sahara. Although another species with the same common name occurs in the Indian subcontinent, it is an entirely different species. This insect is not particularly invasive but because it severely affects coffee wherever it is grown in Africa it may create an impression of invasiveness. M. leuconotus is not on an alert list and due to its wide distribution, it cannot be considered as threatened.
EURAMET key comparison between INRiM and UME in Vickers hardness scales (HV1 - HV30) - EURAMET.M.H-K1.b and c
Authors: Germak A , Kuzu C , Origlia C , Pelİt E
Published: April 2021

Main text

This report describes the method and results of a bilateral EURAMET Key Comparison in Vickers hardness scales of two National Metrology Institutes (NMIs) of Italy and Turkey, INRiM and UME, respectively. The Pilot Laboratory (PL) is INRiM in the comparison in which one set of hardness reference blocks with three hardness levels for the Vickers Hardness scales of both HV1 and HV30 was used. The comparison was realized as planned in the Technical Protocol with some delay. The aim of this comparison is to link the UME measurement results to the CCM.H-K1.b.c through the PL (INRiM) as a participant of the CCM key comparison. The measurement results and uncertainty assessments declared by INRiM and UME are in consistency with each other and UME results are also in consistency with the CCM.H-K1.b.c Key Comparison Reference Values (KCRVs). The CCM.H-K1.b.c was realized during 2001 to 2003 to investigate the metrological equivalence of national standards among national metrology institutes (NMIs) within the CCM.

To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.

The final report has been peer-reviewed and approved for publication by the CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).
Gravitational analog of the canonical acoustic black hole in Einstein–scalar–Gauss–Bonnet theory
Authors: Cañate Pedro , Sultana Joseph , Kazanas Demosthenes
Published: April 2021

In this work, in the context of modified gravity, a curved spacetime analogous to the ‘canonical acoustic black hole (CABH)’ is constructed. The source is a self-interacting scalar field which is non-minimally coupled to gravity through the Gauss–Bonnet invariant. The scalar-Gauss–Bonnet coupling function is characterized by three positive parameters: σ with units of (length), μ with units of (length)4, and a dimensionless parameter s, thus defining a three-parameter model for which the line element of CABH is a solution. The spacetime is equipped with spherical and static symmetry and has a single horizon determined in Schwarzschild coordinates by the region r = μ
1/4. The solution admits a photon sphere at r = (3μ)1/4, and it is shown that in the region (3μ)1/4 ⩽ r < ∞ the scalar field satisfies the null, weak, and strong energy conditions. Nonetheless, the model with s = 1 has major physical relevance since for this case the scalar field is well defined in the entire region r ⩾ μ
1/4, while for s ≠ 1 the scalar field blows up on the horizon.
An historical account of the two-fluid theory for superfluidity
Authors: Hernández-Gómez J J , Gómez-González R W
Published: April 2021

In 1924, Einstein showed the theoretical possibility of the three-dimensional Bose–Einstein condensate, for mass particles. When published, his work did not attract the scientific community, until approximately ten years later, when Fritz London retook it along with Laszlo Tisza, to generate a theory able to explain the superfluidity in terms of two fluids: one formed by atoms within the condensate state, and the second formed with atoms in the normal state. Later, under the commitment of Kapitsa, Landau began the research about the superfluidity problem, with conceptually different assumptions than those of London and Tisza. Landau thought that atoms are the medium in which excitations are propagated, through a two-fluid model. The development of such theories took place in the 1930s and 1940s, when Europe was convulsed by political and social problems. In this work, we clarify the differences between both models, usually confused, and we analyse the influence of the historical reality in which the main scientific actors that gave birth to such theories were involved, elucidating why the path initiated by Einstein, ended in two different intents to describe the superfluidity phenomenon: two two-fluid theories.

April is the cruellest month...

Thomas S. Eliot
Ultra-broadband solar light wave trapping by gradient cavity-thin-film metasurface
Authors: Liao Zhefu , Liu Zhengqi , Wu Qizhao , Zhan Xuefeng , Liu Mulin , Liu Guiqiang
Published: April 2021

Despite the fact that solar energy has been widely used as a renewable and clean energy source for decades, when designing solar irradiation absorbers one is generally confronted with the dilemma of choosing between higher absorption but narrowband or broadband but lower absorption, which has greatly limited the development of the solar energy industry. In this work, a gradient cavity-thin-film metasurface (GCM) made up of alternating multiple layers of titanium (Ti) and silicon dioxide (SiO2) exhibits ultra-broadband strong absorption in 354–2980 nm. The operating bandwidth covers the dominating portion of the solar irradiation spectrum. The absorption spectrum can be manipulated by adjusting the structural parameters of the unit cell. It is worth noting that the spectrally weighted solar absorption efficiency reaches 98.28% under the AM 1.5G illumination. This impressive near-unity absorption could be attributed to multiple light–matter interactions including surface plasmon resonances, cavity resonance, and the intrinsic spectral responses of multi-layer refractory material. In addition, the absorption response is insensitive to the incident angle and polarization states. These high performances provide the GCM with great potential for practical applications in solar thermal energy harvesting and photothermal conversion, etc.
Enhancing infrared emission behavior of polymer coatings for radiative cooling applications
Authors: Chen Meijie , Pang Dan , Chen Xingyu , Yan Hongjie
Published: April 2021

Radiative cooling can cool objects on Earth without an energy input, which has drawn significant attention recently. While polymers have been widely studied for radiative cooling applications due to their promising infrared emission behaviors, ease of fabrication and low cost, the cooling performance of polymer coatings still needs to be enhanced through structure design. In this work, the effects of polymer materials, coating thicknesses and surface microstructures on the cooling performance of coatings were studied. Results showed that the PDMS coating can achieve a great radiative cooling ability with less materials consumption and the polymer coating can reach a relative high saturation value of thermal emittance (

ε
ˉ

LWIR

) in the atmosphere’s long-wave infrared transmission window (8–13

μ

m

) with a large thickness, but interface reflectance in the wavelength range from 8 to 13

μ

m

limits the further enhancement of

ε
ˉ

LWIR

. By introducing a grating-pattern microstructure, the minimal reflectance at

λ

=

8–13

μ

m

was nearly zero and the low emittance region at

λ

=

9–11

μ

m

of the bare PDMS coating was greatly enhanced. At the coating thickness of t

=

200

m

,

ε
ˉ

LWIR

and the net nighttime cooling power of the PDMS coating can reach 0.996 and 110.5 W m−2, respectively, when the ambient temperature is 298.15 K. In addition, the solar reflectance of the PDMS coating can reach 0.946 using the Ag substrate, making it attractive for radiative cooling applications.
Internal photoemission of electrons from 2D semiconductor/3D metal barrier structures
Authors: Shlyakhov I , Achra S , Bosman N , Asselberghs I , Huyghebaert C , Radu I , Chai J , Yang M , Wang S J , Bol A , Iakoubovskii K , Houssa M , Stesmans A , Afanas’ev V V
Published: April 2021

Understanding the energy alignment of electronic bands, which originate from ultrathin MoS2 layers and metal electrodes attached to them, is crucial for the design of MoS2-based electronic devices. We have applied internal photoemission spectroscopy (IPE) to analyze this alignment. We demonstrate that IPE can yield the barrier heights in the metal/ two-dimensional semiconductor/insulator stacks when the top metal electrode is sufficiently thin for allowing both the photoexcitation of electrons and their transport towards the insulator. The electron barrier at the interface between Al and monolayer (1ML) of MoS2 is estimated at 0.7 eV, and this value explains the experimentally observed attenuated quantum yield contribution from the aluminum. Based on the relative energies of the low-energy threshold position and the Fermi level of aluminum at the interface with the SiO2 insulator, we provide a simple explanation for the observed current photoinjection at the interface between aluminum and 1ML MoS2.
Thermal Hall and Nernst responses in ultrathin magnetic films of pyrochlore lattice
Authors: Sheikhi Bahman , Kargarian Mehdi , Langari Abdollah
Published: April 2021

The ultrathin films of pyrochlore lattice along [111] direction provide a fertile ground for exploring topological states in oxide materials, where the electron correlations are strong and magnetically ordered states are favored. As a result of strong interactions, most of states are magnetic insulators with strong Dzyaloshinskii–Moriya and anisotropic spin interactions. We considered three types of heterostructures, a bilayer of triangular-kagome (TK), and two trilayers of triangular-kagome-triangular (TKT) and kagome-triangular-kagome (KTK) thin films. The ground states are magnetically ordered with the low-energy excitations, the magnons, characterized by nontrivial topology. While for TK model the lowest magnon band is trivial, the lowest bands in TKT and KTK model are topological. These features have direct consequences on the thermal Hall conductivity, where we observed that the latter quantity onsets at lower temperature in multilayer models, suggesting that the thermal Hall response can be controlled by engineering lattice-driven magnetic band structure. We also introduce the thermal sublattice Nernst effect in these layers and found the corresponding response is as large as the thermal Hall response.
Decomposition mechanism on different surfaces of copper azide
Authors: Han Xiuzhen , Du Huifang , Guo Wei
Published: April 2021

Copper azide, a potential primary explosives that may replace traditional primers such as lead azide, mercury fulminate and silver azide, has received widespread attention, but its decomposition mechanism remains unclear. Here, based on first-principles calculations, (010)N3, (100)N3 and (001) facets with a copper/nitrogen atom ratio of 1/6 are found to be the most stable surfaces of copper azide crystal. Through transition state (TS) calculations, we find that during the decomposition process on the surface, there is a synergy effect between two Cu–N1–N2–N3 chains, where the terminal N2–N3 bonds on two chains break simultaneously, and the dissociated N3 atom bonds with another N3′ atom of adjacent chain to form a N2 molecule. Next, the Cu–N bond will rupture, and two more N2 molecules (N1–N2, N1′–N2′) desorb from the surface. The overall reaction releases above 4 eV energy at a barrier of 1.23 eV on (001) surface. Electronic structure calculations reveal that the TS of N2–N3 rupture is more stabilized than that of N1–N2. According to the above results, we propose a new decomposition mechanism based on simulations of N–N bond breaking on different surfaces of copper azide. The results underscore the surface effect in decomposition of energetic materials.
Enhancement of the accuracy of ultrasonic flowmeters by applying the PCA algorithm in predicting flow patterns
Authors: Tran Ngoctan , Wang Chi-Chuan
Published: April 2021

In the current study, a novel arrangement of acoustic paths with an on-off technique upon ultrasonic waves is proposed to enhance the accuracy and reduce the frequency of calibration of the ultrasonic flowmeter (USFM). In addition, a web of chord probes on the velocity profile with a novel rotating method is also proposed. Twenty velocity profiles, including 19 selected Salami asymmetric velocity profiles and a centrosymmetric developed velocity profile, are combined with the proposed chord-probe mesh to build a novel velocity database. The built database includes 2241 900 sets of 12 mean velocities, ranging from 0.1 m s−1 to 25 m s−1. Furthermore, the principal component analysis algorithm is employed and trained by the developed database to predict the flow patterns in a practically flowing measurement. The predictive ability of the developed algorithm is examined in 10 different scenarios. In all cases in this study, it is found that the proposed USFM can not only measure the volumetric flow rate of the asymmetric flows with extremely high accuracy, but can also eliminate the influences of flow regimes and the effects of the installed location.
A broadcast ephemeris design of LEO navigation augmentation satellites based on the integration-type ephemeris model
Authors: Meng Lingdong , Chen Junping , Wang Jiexian , Zhang Yize
Published: April 2021

Low Earth orbit (LEO) satellites are a promising type of navigation augmentation satellite for current global navigation satellite systems. Aiming at the navigation function, an effective broadcast ephemeris model needs to be designed for LEO satellites. An enhanced integration-type broadcast ephemeris model is proposed in this study. First, the short-term periodical variation characteristics of LEOs’ accelerations in the Earth-centered Earth-fixed coordinate system are analyzed. The Chebyshev polynomials and harmonic functions are then applied to represent the variation perturbation of accelerations. Tests using simulated and real data from LEO satellites at altitudes from 600 to 1400 km are conducted to evaluate the fit accuracy of the proposed models in terms of arc length, integration method, integration step length, orbital altitude, inclination, eccentricity, etc. The fit accuracy is dramatically improved compared to that of the current GLONASS integration-type broadcast model, where fit errors less than 10 cm are achieved with an arc length of 20 min.
Characterisation and effective monitoring of 4D printed structures through microgeometry analysis
Authors: Trych-Wildner Anna , Wildner Krzysztof
Published: April 2021

This paper presents a basic study of the possible application of roughness parameters for monitoring of the life cycle of 4D printed structures. Experiments were performed with the purpose of gaining some insight into a novel manufacturing technique that may be of future interest and to investigate measurement procedures which may be helpful in the effectively monitoring, maintenance and design of 4D structures. This article describes changes in certain roughness parameters, i.e., Ra, Rsk, RSm, and Sa during the repeated bending of 4D printed beams. The quantitative values of these parameters are also provided and discussed.
Sources of error for single-shot PMT-based phosphor thermometry in harsh conditions
Authors: Feuk Henrik , Sanned David , Richter Mattias , Aldén Marcus
Published: April 2021

This study investigates photomultiplier tube (PMT) nonlinearities, relevant for lifetime phosphor thermometry, at various decay times to assess and minimize the impact on temperature measurement accuracy. The focus is single-shot measurements performed in harsh environments where phosphor signal attenuation often is a concern. The sensitivity of decay time measurements to changing phosphorescence intensity is therefore investigated. The experimental results show that for the studied phosphors and detectors, shorter decay times between 20 ns and 6 µs, saturation effects in the PMTs decreased the measured decay time with increasing signal attenuation. For longer phosphorescence decay times, in the millisecond regime, nonlinearity effects led to an increase in the measured decay time with increasing signal attenuation. The specific detector nonlinearity response will vary among detectors, but the introduced methodology for detector analysis is a useful resource for assessing and improving accuracy in lifetime phosphor thermometry measurements.
Activation of buried p-GaN through nanopipes in large-size GaN-based tunnel junction LEDs
Authors: Yan Shumeng , Feng Meixin , Fan Shizhao , Zhou Rui , Tang Yongjun , Jiang Tianhao , Liu Jianxun , Zhou Yu , Sun Qian , Yang Hui
Published: April 2021

In GaN-based light-emitting diodes (LEDs), tunnel junctions offer a way of replacing the highly resistive p-type GaN (p-GaN) ohmic contact with a low-resistance n-GaN ohmic contact. However, the p-GaN would be re-passivated by hydrogen atoms during the subsequent growth of n-GaN in a metal-organic chemical vapor deposition (MOCVD) chamber. The n-GaN layer, acting as a hydrogen diffusion barrier, hinders the thermal activation of the underlying p-GaN. Here, we report a method to thermally activate the buried p-GaN in tunnel junction LED (TJ-LED) through vertically aligned nanopipe arrays across the top n-GaN layer, which provides a hydrogen outgassing passage. The fabrication of nanopipes is realized via inductive coupled plasma etching using a mask prepared by self-assembled nanosphere arrays. As a result, we attain large-size TJ-LED chips, exhibiting nearly equivalent p-GaN activation and superior light extraction compared to conventional LEDs. Specifically, the light extraction efficiency is boosted by 44% relative to conventional LEDs at an injection current density of 100 A cm−2.
Metasurface circular polarizer based on rotational symmetric nanoholes
Authors: Lv Haoran , Mou Zhen , Zhou Changda , Wang Shuyun , He Xiaobo , Han Zhanghua , Teng Shuyun
Published: April 2021

A circular polarizer is proposed based on a single layered metasurface. This metasurface circular polarizer is composed of L-shaped nanoholes etched on the silver film. The L-shaped nanoholes are rotational symmetric, and the special symmetric structure determines the polarization selection transmission of the metasurface. The theoretical analysis elaborates the design process of the metasurface circular polarizer. The proposed metasurface circular polarizers have good polarization selective transmittance, and more interestingly, they take on the opposite circular dichroism at different wavebands. The numerical simulations and experiment measurement confirm the circular dichroism of the proposed circular polarizers. The compact design, ultrathin thickness and available performance can expand the applications of the metasurface circular polarizers in the integrated optics.
Unconventional plasmonic sensitization of graphene in mid-infrared
Authors: Paria Debadrita , Vadakkumbatt Vaisakh , Ravindra Pramod , Avasthi Sushobhan , Ghosh Ambarish
Published: April 2021

Light–matter interaction in graphene can be engineered and substantially enhanced through plasmonic sensitization, which has led to numerous applications in photodetection, sensing, photocatalysis and spectroscopy. The majority of these designs have relied on conventional plasmonic materials such as gold, silver and aluminum. This limits the implementation of such devices to the ultraviolet and visible regimes of the electromagnetic spectrum. However, for many practical applications, including those relevant to security and defense, the development of new strategies and materials for sensing and detection of infra red (IR) light is crucial. Here we use surface enhanced Raman spectroscopy (SERS), for direct visualization and estimation of enhanced light–matter interaction in graphene in the mid-IR regime, through sensitization by an unconventional plasmonic material. Specifically, we fabricate a hybrid device consisting of a single layer graphene and a two-dimensional array of nanodiscs of aluminum doped zinc oxide (AZO), which is a highly doped semiconductor, exhibiting plasmonic resonance in the mid-IR. We find that the enhancement in the SERS signal of graphene is of similar magnitude to what has been achieved previously in the visible using conventional plasmonic materials. Our results establish the potential of such hybrid systems for graphene-based optical and optoelectronic applications in the mid-IR.
Near-field probing of dielectric screening by hexagonal boron nitride in graphene integrated on silicon photonics
Authors: Wang Binbin , Kim Sera , Zhai Tingting , Seok Jinbong , Yang Heejun , Salas-Montiel Rafael
Published: April 2021

Hexagonal boron nitride (hBN) is one of the most suitable 2D materials for supporting graphene in electronic devices, and it plays a fundamental role in screening out the effect of charge impurities in graphene in contrast to inhomogeneous supports such as silicon dioxide (SiO2). Although many interesting surface science techniques such as scanning tunneling microscopy (STM) revealed dielectric screening by hBN and emergent physical phenomena were observed, STM is only appropriate for graphene electronics. In this paper, we demonstrate the dielectric screening by hBN in graphene integrated on a silicon photonic waveguide from the perspective of a near-field scanning optical microscopy (NSOM) and Raman spectroscopy. We found shifts in the Raman spectra and about three times lower slope decrease in the measured electric near-field amplitude for graphene on hBN relative to that for graphene on SiO2. Based on finite-difference time-domain simulations, we confirm lower electric field slope and scattering rate in graphene on hBN, which implies dielectric screening, in agreement with the NSOM signal. Graphene on hBN integrated on silicon photonics can pave the way for high-performance hybrid graphene photonics.
Microwave thermoacoustic tomographic (MTT) imaging
Authors: Lin James C
Published: April 2021

Microwave thermoacoustic tomography (MTT) uses microwave pulse-induced thermoelastic pressure waves to form planar or tomographic images. Since the generation and detection of thermoelastic pressure waves depends on dielectric permittivity, specific heat, thermal expansion, and acoustic properties of tissue, microwave thermoacoustic imaging possesses the characteristic features of a dual-modality imaging system. The unique attributes of the high contrast offered by microwave absorption and the fine spatial resolution furnished by ultrasound are being explored to provide a nonionizing and noninvasive imaging modality for characterization of tissues, especially for early detection of breast cancer. This paper reviews the research being conducted in developing MTT imaging for medical diagnosis. It discusses the science of thermoelastic wave generation and propagation in biological tissues, the design of prototype MTT systems, the reconstruction of tomographic images, and the application and accomplishment of prototype MTT systems in phantom models and experimental subjects.
Performance comparison of a dedicated total breast PET system with a clinical whole-body PET system: a simulation study
Authors: Samanta Suranjana , Jiang Jianyong , Hamdi Mahdjoub , Register Alan Z , Majewski Stanislaw , Williams Mark B , Turkington Timothy G , Tornai Martin P , Laforest Richard , O’Sullivan Joseph A , Tai Yuan-Chuan
Published: April 2021

This paper presents a novel PET geometry for breast cancer imaging. The scanner consists of a ‘stadium’ (a rectangle with two semi-circles on opposite sides) shaped ring, along with anterior and posterior panels to provide high sensitivity and high spatial resolution for an imaging field-of-view (FOV) that include both breasts, mediastinum and axilla. We simulated this total-breast PET system using GATE and reconstructed the coincidence events using a GPU-based list-mode image reconstruction implementing maximum likelihood expectation-maximization (ML-EM) algorithm. The rear-panel is made up of a single layer of LSO crystals (3.2 × 3.2 × 20 mm3 each), while the ‘stadium’-shaped elongated ring and the anterior panel are made with dual-layered LSO crystals (1.6 × 1.6 × 6 mm3 each). The energy resolution and coincidence resolving time of all detectors are assumed to be 12% and 250 ps full-width-at-half-maximum, respectively. Various sized simulated lesions (4, 5, 6 mm) having 4:1, 5:1, and 6:1 lesion-to-background radioactivity concentration ratios, mimicking different biological uptakes, were strategically located throughout a volumetric torso phantom. We compared system sensitivity and lesion detectability of the dedicated total-breast PET system to a state-of-the-art clinical whole-body PET scanner. The mean sensitivity of the total-breast PET system is 3.21 times greater than that of a whole-body PET scanner in the breast regions. The total-breast PET system also provides better contrast-recovery coefficients for lesions of all sizes and lesion-to-background ratios in the breast when compared to a reference clinical whole-body PET scanner. Receiver operating characteristics (ROC) study shows the area under the ROC curve is 0.948 and 0.924 for the total-breast system and the whole-body PET scanner, respectively, in the detection of 4 mm diameter lesions with 4:1 lesion-to-background ratio. This study demonstrates our novel geometry can provide an imaging FOV larger than conventional PEM systems to simultaneously image both breasts, chest wall and axillae with significantly improved lesion detectability in the breasts when compared to a whole-body PET scanner.
PET image reconstruction with deep progressive learning
Authors: Lv Yang , Xi Chen
Published: April 2021

Convolutional neural networks (CNNs) have recently achieved state-of-the-art results for positron emission tomography (PET) imaging problems. However direct learning from input image to target image is challenging if the gap is large between two images. Previous studies have shown that CNN can reduce image noise, but it can also degrade contrast recovery for small lesions. In this work, a deep progressive learning (DPL) method for PET image reconstruction is proposed to reduce background noise and improve image contrast. DPL bridges the gap between low quality image and high quality image through two learning steps. In the iterative reconstruction process, two pre-trained neural networks are introduced to control the image noise and contrast in turn. The feedback structure is adopted in the network design, which greatly reduces the parameters. The training data come from uEXPLORER, the world’s first total-body PET scanner, in which the PET images show high contrast and very low image noise. We conducted extensive phantom and patient studies to test the algorithm for PET image quality improvement. The experimental results show that DPL is promising for reducing noise and improving contrast of PET images. Moreover, the proposed method has sufficient versatility to solve various imaging and image processing problems.
Investigating the role of pericytes in cerebral autoregulation: a modeling study
Authors: Milanovic Selena , Shaw Kira , Hall Catherine , Payne Stephen
Published: April 2021

The brain’s inability to store nutrients for more than a few seconds makes it one of the most tightly regulated systems in the body. Driven by metabolic demand, cerebral autoregulation (CA) ensures a constant cerebral blood flow (CBF) over a ±50% change in arterial blood pressure (ABP) from baseline. Recent evidence suggests that pericytes, contractile cells in the capillary bed, play a previously-ignored regulatory role. To elucidate the CA phenomenon, the role of oxygen metabolism, pericyte activity and neural signaling in CBF modulation were quantified. Driven by nutrient metabolism in the tissue and pressure sensitivity in the vasculature, the model introduced here successfully replicates CA. To highlight the role of different vessel sizes, vessels with a diameter above 1 mm were represented using a lumped parameter model while the microvasculature was illustrated as a branching tree network model. This novel approach elucidated the relationship between the microvasculature’s nutrient supply and arterial regulation. Capillary responses to local increases in neuronal activity were experimentally determined, showing that pericytes can increase the diameter of the adjacent vessel by 2.5% in approximately 1 s. Their response was quantified and included in the computational model as an active component of the capillary bed. To compare the efficacy model presented here to existing ones, four feedback mechanisms were tested. To simulate dynamic CBF regulation a 10% increase in ABP was imposed. This resulted in a 23.79%–34.33% peak increase in CBF, depending on the nature of the feedback mechanism of the model. The four feedback mechanisms that were studied significantly differ in the response time, ultimately highlighting that capillaries play a fundamental role in the rapid regulation of CBF. Conclusively, this study indicates that while pericytes do not greatly alter the peak CBF change, they play a fundamental role in the speed of regulation.
Radiation hardness studies of thin and low bulk resistivity LGADs
Authors: Jain Geetika , Jain Chakresh , Saumya Saumya , Agrawal Namrata , Bhardwaj Ashutosh , Ranjan Kirti
Published: April 2021

The low gain avalanche detector (LGAD), having a unique feature of built-in charge multiplication, is more efficient in terms of charge collection (CC) than the traditional silicon detector even after irradiation. However, a dramatic decrease in the charge multiplication beyond a fluence of 3 × 1014

n

eq

⋅

cm−2 is observed in the measurements. In the reported work, TCAD CC simulations are carried out on various physical and geometrical LGAD design parameters with the aim to understand and extend the radiation hardness capabilities. It is observed that a thin LGAD with low bulk resistivity may survive up to a fluence of 3 × 1015

n

eq

⋅

cm−2 for an optimal choice of p-well design. A detailed investigation including CC and leakage current validation with experimental data and 1D electric field profile, in support of optimizations performed, is also provided.
A cantilevered piezoelectric energy harvester excited by an axially pushed wedge cam using repulsive magnets for rotary motion
Authors: Kan Junwu , Zhang Min , Wang Shuyun , Zhang Zhonghua , Zhu Yana , Wang Jin
Published: April 2021

Harvesting energy from the rotary environment to replace the conventional electrochemical batteries has gained considerable interest. Different from the existing rotation-induced energy harvesters based on the bidirectional deformation of piezoelectric vibrators, a novel cantilevered piezoelectric energy harvester excited by an axially pushed wedge cam using repulsive magnets for rotary motion was presented and fabricated in this paper. The new piezoelectric rotary energy harvester (PREH) was characterized by the simultaneous realization of unidirectional deformation and limited amplitude for piezoelectric vibrators. To verify the feasibility of the proposed principle and design, a theoretical model was established based on Fourier series as well as superposition principle. Meanwhile, the influence of the system parameters on the response characteristic of the presented PREH were obtained by simulation. And then, the experiments of rotating speed response were performed to evaluate the energy harvesting performance in terms of the deformation and open-circuit voltage. Both simulation and experimental results showed that the amplitude of the piezo-cantilever could be limited by using the cam mechanism and there were obvious resonance peaks on the amplitude-rotary speeds curves. Thus, the relatively stable output voltage could be maintained over a broad rotating speed range. Also, the stable voltage increased with the increasing of cam lift, but the effective rotating speed range became narrow. With the increasing of the cam angle, the effective rotating speed bandwidth could be increased, whereas the self-locking phenomenon of the piezo-cantilever would occur when the angle was increased to some extent. Besides, the bandwidth could be adjusted by changing the number of exciting magnets and stiffness of cam system. Under the optimum matching parameters, the maximum power 10.88 mW was reached for the presented PREH.
A novel chiral metamaterial with multistability and programmable stiffness
Authors: Wang Jia-Xin , Yang Qing-Sheng , Wei Yu-Ling , Tao Ran
Published: April 2021

Chiral metamaterials are widely studied for their unique mechanical properties, but still have problems such as low stiffness and few available scenarios. Based on the tetra-chiral metamaterial, a type of metamaterial with programmable stiffness and multistability is designed in this paper. The stiffness of two-dimensional (2D) metamaterial can be adjusted programmatically by changing its geometric parameters. The equivalent elastic modulus and Poisson’s ratio were obtained by using an analytical solution and finite element method. Then the 2D metamaterials were extended to cylindrical tubes with multistability. The deformation patterns of the 2D metamaterials and cylindrical tubes with different geometric parameters were investigated. It is found that the cylindrical tubes can exhibit compression–torsion coupling and multistability deformation characteristics. This work can provide a valuable reference for designs of novel metamaterials with coupled deformation, as well as further expanding the field of application.
An approach for the design and validation of high frequency vibration energy harvesting devices
Authors: Munk David J , Ellul Ethan J G , Moss Scott D
Published: April 2021

The aim of this work is to explore a topology optimisation approach for the design of high frequency vibration energy harvesting devices capable of operating in the range of 1800–2600 Hz. The main objective of the approach is to develop an optimisation algorithm for tailoring the resonant behaviour of the cantilever energy harvesters to the dominant frequencies of the available vibrations present in a Bell 206B-1 Kiowa helicopter main rotor gearbox. Hence, the devices designed are to be operated in the high frequency, highly loaded, extreme environments commonly found on aircraft structures. A multi-physics model capable of predicting the performance of the developed cantilever energy harvesters is presented and the design optimisation problem is formulated and then solved with the bi-directional evolutionary structural optimisation method. Two designs were experimentally validated; one that is sensitive to a single mode in the range 1800–2600 Hz equipped with a single transducer having a 6.35 mm diameter and 0.5 mm thickness and the other sensitive to three modes in the same range equipped with two transducers. Output powers of 0.3–3.1 mW were measured, demonstrating the approach’s potential to design harvesters capable of powering many useful sensor types.
Microwave single-tone optomechanics in the classical regime
Authors: Golokolenov Ilya , Cattiaux Dylan , Kumar Sumit , Sillanpää Mika , Mercier de Lépinay Laure , Fefferman Andrew , Collin Eddy
Published: April 2021

We report on the quantitative experimental illustration of elementary optomechanics within the classical regime. All measurements are performed in a commercial dilution refrigerator on a mesoscopic drumhead aluminium resonator strongly coupled to a microwave cavity, using only strict single-tone schemes. Sideband asymmetry is reported using in-cavity microwave pumping, along with noise squashing and back-action effects. Results presented in this paper are analysed within the simple classical electric circuit theory, emphasizing the analogous nature of classical features with respect to their usual quantum description. The agreement with theory is obtained with no fitting parameters. Besides, based on those results a simple method is proposed for the accurate measurement of the ratio between microwave internal losses and external coupling.
Uniaxial strain induced symmetry lowering and valleys drift in MoS2
Authors: Jiang Cunyuan , Xiong Wen , Li Chong , Niu Chunyao , Wang Fei
Published: April 2021

The uniaxial strain is an effective way to change the symmetry of a crystal and thus tuning their electronic properties. In the present work, we elucidate the physical mechanism of the symmetry-broken-induced energy valleys drift in monolayer molybdenum disulfide. When the uniaxial strain reduces the rotational symmetry of valleys from C

3
to C

1
and an in-plane electric field breaks the balance of electron distribution of valleys, the valley dipole can survive readily and quantum nonlinear Hall effect might be realized. Our work offers key insights for understanding the uniaxial strain induced valleys drift in monolayer MoS2, which is critical to precisely control the valleytronics properties of two-dimensional materials.
Uncovering double-stripe and plaquette antiferromagnetic states in the one-band Hubbard model on a frustrated square lattice
Authors: Ruan Ze , Jiang Xiu-Cai , Song Ze-Yi , Zhang Yu-Zhong
Published: April 2021

Groundstate magnetism of the one-band Hubbard model on the frustrated square lattice where both nearest-neighbour t
1 and next-nearest-neighbour t
2 hoppings are considered at half-filling are revisited within mean field approximation. Two new magnetic phases are detected at intermediate strength of Hubbard U and relative strong frustration of t
2/t
1, named double-stripe and plaquette antiferromagnetic states, both of which are metallic and stable even at finite temperature and electron doping. The nature of the phase transitions between different phases and the properties of the two new states are analyzed in detail. Our results of various magnetic states emerging from geometric frustration in the minimal model suggests that distinct antiferromagnetism observed experimentally in the parent states of two high-T
c superconducting families, i.e. cuprates and iron-based superconductors, may be understood from a unified microscopic origin, irrespective of orbital degrees of freedom, or hoppings further than next-nearest neighbor, etc.
Improved ammonia vapor sensing properties of Al-doped ZnO nanoparticles prepared by sol-gel process
Authors: Poul Raj I Loyola , Gobalakrishnan S , Praseetha P K , Chidhambaram N , Saravanakumar S , Ganesh V , AlFaify S , Algarni H , Yahia I S
Published: April 2021

Aluminium-doped ZnO nanoparticles were synthesized using the simple and cost-effective sol-gel route. Their structural, morphological, optical, and ammonia vapor sensing properties were compared with the pristine ZnO sample. The x-ray diffraction results showed that the pristine and Al-doped ZnO samples exhibit a hexagonal structure with the P63mc space group. A detailed structural investigation was carried through the Rietveld refinement technique. The decrease in crystallite size and the increasing nature of the sample’s microstrain were observed through the Williamson-Hall (W-H) analysis. 1-D, 2-D, and 3-D electron density distribution in a single unit cell of ZnO nanoparticles were studied with the maximum entropy method and it is confirmed that the ionic nature of the Zn-O bond increases by Al doping. The surface morphology of the samples was altered significantly after the addition of aluminum with ZnO. Aluminium doping causes a notable bandgap broadening in the ZnO nanostructures. A momentous enhancement of ammonia detection sensitivity of 129% at 25 ppm was observed for the ZnO:Al(3%) sample and its response time is greater than the other tested samples. Further, ZnO:Al(3%) sample exhibits the best response and recovery time of 28 and 8 s, respectively. It has also shown a stable ammonia vapor sensing ability for five consecutive cycles.