bluuebunny/crossref_metadata_2025 huggingface dataset:
Demonstration of GaN-channel high electron mobility transistors with regrown InAs/GaAs source and drain
Authors: Hoshi Takuya , Yoshiya Yuki , Sugiyama Hiroki , Nakajima Fumito
Published: April 2024

We demonstrated the crystal growth of group-III arsenides (III-As) on GaN via an arsenidation layer and GaN-channel electron mobility transistors (HEMTs) with a regrowth InAs/GaAs source and drain (S/D) region. By annealing under an AsH3 atmosphere, the surface of a GaN (0001) template is arsenided. We grew ⟨111⟩ oriented InAs and GaAs on arsenided GaN. Silicon-doped n-type InAs with a carrier mobility of over 1500 cm2/V s and a carrier concentration of over 1 × 1019 cm−3 was successfully obtained. The fabrication process and direct-current characteristics of GaN-channel HEMTs with the regrown Si-doped InAs/GaAs S/D region were demonstrated for the first time. A maximum transconductance estimated from transfer characteristics was as high as ∼195 mS/mm for the HEMT with a gate length of 2 μm without passivation, which is comparable to those for the HEMT without any S/D regrowth. The impact of the InAs/GaAs S/D region on the on-resistance of the fabricated HEMTs was estimated to be ∼0.9 Ω mm, which can be reduced by optimizing the device structures and process conditions. These results indicate that the process of GaN arsenidation and III-As regrowth can be used without any device performance degradation. Therefore, further lowering the ohmic contact resistivity and on-resistance of GaN-channel HEMTs is possible by maturing the manufacturing-process technology of III-As-contained GaN-channel HEMTs.
Retrieving positions of closely packed subwavelength nanoparticles from their diffraction patterns
Authors: Wang Benquan , An Ruyi , Chan Eng Aik , Adamo Giorgio , So Jin-Kyu , Li Yewen , Shen Zexiang , An Bo , Zheludev Nikolay I.
Published: April 2024

Distinguishing two objects or point sources located closer than the Rayleigh distance is impossible in conventional microscopy. Understandably, the task becomes increasingly harder with a growing number of particles placed in close proximity. It has been recently demonstrated that subwavelength nanoparticles in closely packed clusters can be counted by AI-enabled analysis of the diffraction patterns of coherent light scattered by the cluster. Here, we show that deep learning analysis can return the actual positions of nanoparticles in the cluster. The Pearson correlation coefficient between the ground truth and reconstructed positions of nanoparticles exceeds 0.7 for clusters of ten nanoparticles and 0.8 for clusters of two nanoparticles of 0.16λ in diameter, even if they are separated by distances below the Rayleigh resolution limit of 0.68λ, corresponding to a lens with numerical aperture NA = 0.9.
Responses of assembled structures of block polyelectrolytes to electrostatic interaction strength
Authors: Wang Fujia , Liu Xinyi , Yang Wei , Chen Yao , Liu Liyan
Published: April 2024

In this paper, the responses of assembled behaviors of block polyelectrolytes (PEs) to the strength of electrostatic interactions are studied through molecular dynamic simulations. The results show that the assembled structures closely depend on the electrostatic strength. It should be noted that PE coacervation can outweigh the nucleation of hydrophobic blocks and invert the micelle structures at strong electrostatic strengths, leading to the formation of inverted micelles of PE cores and hydrophobic coronas. In the poor solvent condition for neutral block, diverse anisotropic micelles are presented; candy-like conventional micelles of hydrophobic cores and PE patches coexist with inverted candy-like micelles of PE cores and hydrophobic patches and with Janus micelles of semi-neutral aggregate and semi-PE cluster in the presence of divalent and trivalent counterions. The formation of conventional or inverted micelle is largely determined by the type of micellar fusion, which results from the nucleation competition between electrostatic correlation and hydrophobic interaction. The merge of micelles mediated by hydrophobic attraction leads to conventional hydrophobic cores, and the fusion induced by electrostatic correlations results in PE cores micelles. At strong electrostatic strengths, the PE chains exhibit rich conformations at trivalent counterions, ranging from a fully collapsed state to a rod-like state, and parallel alignment of PE chains is found.
An analog to digital converter in a SiC CMOS technology for high-temperature applications
Authors: Mo Jiarui , Niu Yunfan , May Alexander , Rommel Mathias , Rossi Chiara , Romijn Joost , Zhang Guoqi , Vollebregt Sten
Published: April 2024

Integrated circuits based on wide bandgap semiconductors are considered an attractive option for meeting the demand for high-temperature electronics. Here, we report an analog-to-digital converter fabricated in a silicon carbide complementary metal–oxide–semiconductor technology now available through Europractice. The MOSFET component in this technology was measured up to 500 °C, and the key parameters, such as threshold voltage, field-effect mobility, and channel-length modulation parameters, were extracted. A 4-bit flash data converter, consisting of 266 transistors, is implemented with this technology and demonstrates correct operation up to 400 °C. Finally, the gate oxide quality is investigated by time-dependent dielectric breakdown measurements at 500 °C. A field-acceleration factor of 4.4 dec/(MV/cm) is obtained by applying the E model.
Plasmonic couplings in Ag–Au heterodimers
Authors: Gomrok Saghar , Eldridge Brinton King , Chaffin Elise A. , Barr James W. , Huang Xiaohua , Hoang Thang B. , Wang Yongmei
Published: April 2024

The plasmonic coupling between silver (Ag) and gold (Au) nanoparticles (NPs) under four polarization modes was examined: a longitudinal mode (L-mode), where the electric field of a linearly polarized incident light parallels the dimer axis, and three transverse modes (T-modes), where the electric field of the light is perpendicular to the dimer axis. The coupling was studied using the discrete dipole approximation followed by an in-house postprocessing code that determines the extinction (Qext), absorption (Qabs), and near-field (Qnf) spectra from the individual NPs as well as the whole system. In agreement with the literature results, the extinction/absorption spectra of the whole dimer have two peaks, one near the Ag localized surface plasmon resonance (LSPR) region and the other at the Au LSPR region, with the peak at Ag LSPR being reduced in all modes and the peak at Au LSPR being red-shifted and increased in the L-mode but not in the T-modes. It is further shown that the scattering at the Ag LSPR region is reduced and becomes less than the isolated Ag NPs, but the absorption at the Ag LSPR is increased and becomes greater than the isolated Ag NPs for the 50 nm Ag–Au heterodimer. This suggests that the scattering from Ag NPs is being reabsorbed by the neighboring Au NPs due to the interband electronic transition in Au at that wavelength range. The Qext from the individual NP in the heterodimer shows the presence of the Fano profile on the Au NP but not on the Ag NP. This phenomenon was further investigated by using a dielectric particle (DP) placed near the Ag or Au NPs. The Fano profile appears in the absorbing DP spectra placed near either Ag or Au NPs. However, the Fano profile is masked upon further increases in the refractive index value of the DP particle. This explains the absence of a Fano profile on the Ag NPs in the Ag–Au heterodimer. The large near-field enhancement on both Ag and Au NPs at the Au plasmonic wavelength in the L-mode for large NPs was investigated through a DP-Au system. The large enhancement was shown to arise from a large imaginary component of the DP refractive index and a small real component. Through examination of both the near- and far-field properties of the individual NPs as well as the whole system and examinations of DP-Ag and DP-Au systems, our study provides a new understanding of the couplings between Ag and Au NPs.
Significant conductivity enhancement in Al-rich n-AlGaN by modulation doping
Authors: Fang Xuzhou , Wang Jiaming , Xu Fujun , Zhang Lisheng , Lang Jing , Guo Xueqi , Ji Chen , Ji Chengzhi , Wu Yong , Yang Xuelin , Kang Xiangning , Qin Zhixin , Tang Ning , Wang Xinqiang , Ge Weikun , Shen Bo
Published: April 2024

Enhancing the conductivity in Al-rich n-AlGaN is a key issue for realizing AlGaN-based ultraviolet light-emitting diodes (UV-LEDs) with low operating voltage and high wall-plug efficiency, especially in a planar geometry of flip–chip configuration. An approach of modulation doping is herein proposed, where an alternating-layer structure consisting of Si-doped and unintentionally doped AlGaN is assembled to achieve the spatial separation of electron activation and transport. As massive electrons diffuse from the AlGaN:Si layer into the neighboring i-AlGaN ones and then drift, the ionized-donor scattering is effectively weakened, leading to a significant enhancement of mobility as well as conductivity. An impressive electrical property of n-Al0.6Ga0.4N with a lateral conductivity of 201.7 S/cm is realized as a consequence, being 2.1 times of that in the continuously doped one. Furthermore, the operating voltage of 280 nm UV-LEDs is correspondingly reduced by 0.1–0.2 V at 100 mA by adopting modulation-doped n-AlGaN in the n-cladding layer.
Extracting fundamental parameters of 2D natural thermal convection using convolutional neural networks
Authors: Ali Boroumand Mohammad , Morra Gabriele , Mora Peter
Published: April 2024

The Lattice Boltzmann Method (LBM) is an approach for modeling mesoscopic fluid flow and heat transfer, based on modeling distributions of particles moving and colliding on a lattice. Using a perturbative formulation of the Boltzmann equation, it scales to the macroscopic Navier–Stokes equation. We simulate natural thermal convection via LBM in a 2D rectangular box being heated from below and cooled from above, and use the results as training, testing, and generalization datasets to build a deep learning model. GoogLeNet, a convolutional neural network, is used to classify the simulation results based on two parameters: Rayleigh (Ra) and Prandtl (Pr) numbers, from a single snapshot of either the entire modeling field of resolution 1024×1024, or a 224×224 crop. For each fixed Pr in a range from 1 to 128, increasing by a factor of 2, we estimate Ra with an accuracy varying from 40% to 90%, depending on the chosen augmentation strategy. For each fixed Ra in the range from 105 to 109, increasing of a factor 10, the method predicts Pr with a systematically lower accuracy ranging from 30% to 80%. This approach has great potential for industrial applications like being able to control the industrial flow or scientific research on geophysical ones including the transport of heat in the earth’s interiors, ocean, and atmosphere.
An experimental and computational view of the photoionization of diol–water clusters
Authors: Wannenmacher Anna , Lu Wenchao , Amarasinghe Chandika , Cerasoli Frank , Donadio Davide , Ahmed Musahid
Published: April 2024

In the interstellar medium, diols and other prebiotic molecules adsorb onto icy mantles surrounding dust grains. Water in the ice may affect the reactivity and photoionization of these diols. Ethylene glycol (EG), 1,2-propylene glycol, and 1,3-propylene glycol clusters with water clusters were used as a proxy to study these interactions. The diol–water clusters were generated in a continuous supersonic molecular beam, photoionized by synchrotron-based vacuum ultraviolet light from the Advanced Light Source, and subsequently detected by reflectron time-of-flight mass spectrometry. The appearance energies for the detected clusters were determined from the mass spectra, collected at increasing photon energy. Clusters of both diol fragments and unfragmented diols with water were detected. The lowest energy geometry optimized conformers for the observed EG–water clusters and EG fragment–water clusters have been visualized using density functional theory (DFT), providing insight into hydrogen bonding networks and how these affect fragmentation and appearance energy. As the number of water molecules clustered around EG fragments (m/z 31 and 32) increased, the appearance energy for the cluster decreased, indicating a stabilization by water. This trend was supported by DFT calculations. Fragment clusters from 1,2-propylene glycol exhibited a similar trend, but with a smaller energy decrease, and no trend was observed from 1,3-propylene glycol. We discuss and suggest that the reactivity and photoionization of diols in the presence of water depend on the size of the diol, the location of the hydroxyl group, and the number of waters clustered around the diol.
Structural heterogeneity in tetra-armed gels revealed by computer simulation: Evidence from a graph theory assisted characterization
Authors: Li Yingxiang , Zhao Wenbo , Cheng Zhiyuan , Sun Zhao-Yan , Liu Hong
Published: April 2024

Designing homogeneous networks is considered one typical strategy for solving the problem of strength and toughness conflict of polymer network materials. Experimentalists have proposed the hypothesis of obtaining a structurally homogeneous hydrogel by crosslinking tetra-armed polymers, whose homogeneity was claimed to be verified by scattering characterization and other methods. Nevertheless, it is highly desirable to further evaluate this issue from other perspectives. In this study, a coarse-grained molecular dynamics simulation coupled with a stochastic reaction model is applied to reveal the topological structure of a polymer network synthesized by tetra-armed monomers as precursors. Two different scenarios, distinguished by whether internal cross-linking is allowed, are considered. We introduce the Dijkstra algorithm from graph theory to precisely characterize the network structure. The microscopic features of the network structure, e.g., loop size, dispersity, and size distribution, are obtained via the Dijkstra algorithm. By comparing the two reaction scenarios, Scenario II exhibits an overall more idealized structure. Our results demonstrate the feasibility of the Dijkstra algorithm for precisely characterizing the polymer network structure. We expect this work will provide a new insight for the evaluation and description of gel networks and further help to reveal the dynamic process of network formation.
NMP limits silver particle size to solve deposited film breakup problems
Authors: Yuan Meng , Jiang Xin , Liu Yitong , Xu Anqing , Tang Xin , Wang Xiaohua , Yuan Long , Duan Yu
Published: April 2024

Metal based electroreflective devices (MERDs) have gained wide attention in recent years in the fields of smart windows and automotive glass due to their excellent photo-thermal modulation capability in the visible and near-infrared wavelength bands due to their high reflectivity. However, the high porosity due to the island-like growth of silver particles makes the devices susceptible to electrodeposited film breakage during prolonged energization or bleaching. This will seriously affect the effectiveness and stability of the device. In this paper, it is shown that the problem of Ag electrodeposition film fragmentation can be effectively overcome by replacing dimethyl sulfoxide solvent by N-methylpyrrolidone (NMP). The optical constants during film deposition were tested by the spectroscopic ellipsometry technique, and the porosity was calculated (reduced by 21.6%). The results show that MERDs with NMP as the solvent have more and more dispersed silver deposition sites, which leads to lower porosity of the silver deposited film during the deposition process. In addition, the lower turn-on voltage, greater contrast, longer memory effect, and greater coloring efficiency reveal that they are more promising for energy-saving applications.
High entropy metallic glasses, what does it mean?
Authors: Afonin G. V. , Qiao J. C. , Makarov A. S. , Konchakov R. A. , Goncharova E. V. , Kobelev N. P. , Khonik V. A.
Published: April 2024

We performed calorimetric measurements on 30 bulk metallic glasses, each differing in their mixing entropies ΔSmix. On this basis, the excess entropies ΔS and excess enthalpies ΔH of glasses with respect to their maternal crystalline states are calculated. It is found that the excess entropy ΔS on the average decreases with increasing mixing entropy ΔSmix. This means that the so-called “high-entropy metallic glasses” (i.e., the glasses having highΔSmix) actually constitute glasses with low excess entropy ΔS. We predict that such glasses should have reduced relaxation ability. We also found that the excess enthalpy ΔH of glass linearly increases with its excess entropy ΔS, in line with a general thermodynamic estimate.
Deposition of high entropy alloy sub-surface films on metal substrates via DC magnetron sputtering with a CoCrFeMnNi target
Authors: Tanada Daisuke , Lyth Stephen M. , Ishikawa Kazuhiro , Miyajima Yoji
Published: April 2024

High entropy alloys and high entropy alloy films (HEFs) are gaining increasing attention in the research community due to their superior mechanical properties. CoCrFeMnNi is one of the most investigated of these alloys in the literature; however, CoCrFeMnNi HEFs have not yet been extensively reported. To improve our understanding of the processes occurring during fabrication of CoCrFeMnNi HEFs, here, DC magnetron sputtering using a CoCrFeMnNi equimolar target is used to deposit HEFs on glass substrates, A5052 aluminum sheets, and S45C steel sheets. The resulting HEFs are observed to be embedded as sub-surface bands, less than a micrometer under the substrate surface. This is attributed to implantation of the HEF elements into the base material due to the high deposition energy of sputtering. Another possibility is that substrate elements migrate to the surface in an Ar plasma-assisted process. The HEF crystallite size on glass substrates was determined by x-ray diffraction to be several nanometers, meaning that high hardness is expected in HEFs produced by DC magnetron sputtering.
Fluidic undulation effects on carangiform swimmers propelled by internal active bending moments
Authors: Xu MengFan , Zhou TianYi , Yu YongLiang
Published: April 2024

With different shapes and material properties, fish all achieve undulatory swimming gait under the action of internal active muscle stimulation and external fluid forces. Such locomotion can be decomposed into deformation affected by internal and external forces in the body frame and overall translation and rotation solely determined by fluid forces. In order to revisit the undulatory swimming gait, we investigate the hydrodynamic performance of two-dimensional flexible carangiform swimmers with varying stiffnesses and thicknesses, which are driven by the active internal bending moments, and employ the complex orthogonal decomposition and Fourier decomposition methods to quantitatively measure and analyze the proportion of undulation. It is found that standing wave deformation characteristics are prominently observed along fish-like bodies with high stiffness, whereas traveling wave characteristics are more evident in bodies with lower stiffness. The self-propelled fish body demonstrates lateral oscillation and rotation around its center of mass, namely, the heaving and pitching movement, particularly in specimens with high stiffness. The present analysis shows that the heaving and pitching locomotion induced by the fluid significantly increase the traveling wave proportion by modulating the amplitude and phase of the left and right traveling waves viewed in forward frame. We called it fluidic undulation effects (FUE), which is different from the undulation of body deformation. This effect is more pronounced for large stiffnesses and thin airfoils. The standing wave deformation observed with a large stiffness transforms into a traveling wave propulsion pattern, with its traveling wave index even slightly surpassing that of a small-stiffness pattern. Although the efficiency of the standing wave deformation is low, it facilitates a faster forward speed (body lengths per stroke). The positive impact of the FUE on the swimming performance is also confirmed by restricting the recoil motions of the lateral translation and rotation of the body. Furthermore, we observe that there is no undulatory swimming gait that has both the highest energy efficiency and the highest speed.
Upper and lower bounds on phase-space rearrangements
Authors: Kolmes E. J. , Fisch N. J.
Published: April 2024

Broad classes of plasma phenomena can be understood in terms of phase-space rearrangements. For example, the net effect of a wave–particle interaction may consist of moving populations of particles from one region of phase space to another. Different phenomena drive rearrangements that obey different rules. When those rules can be specified, it is possible to calculate bounds that limit the possible effects the rearrangement could have (such as limits on how much energy can be extracted from the particles). This leads to two problems. The first is to understand the mapping between the allowed class of rearrangements and the possible outcomes that these rearrangements can have on the overall distribution. The second is to understand which rules are appropriate for which physical systems. There has been recent progress on both fronts, but a variety of interesting questions remain unanswered.
Modeling oceanic sedimentary methane hydrate growth through molecular dynamics simulation
Authors: Fernández-Fernández Ángel M. , Bárcena Álvaro , Conde María M. , Pérez-Sánchez Germán , Pérez-Rodríguez Martín , Piñeiro Manuel M.
Published: April 2024

The crystallization process of methane hydrates in a confined geometry resembling seabed porous silica sedimentary conditions has been studied using molecular dynamics simulations. With this objective in mind, a fully atomistic quartz silica slit pore has been designed, and the temperature stability of a methane hydrate crystalline seed in the presence of water and guest molecule methane has been analyzed. NaCl ion pairs have been added in different concentrations, simulating salinity conditions up to values higher than average oceanic conditions. The structure obtained when the hydrate crystallizes inside the pore is discussed, paying special attention to the presence of ionic doping inside the hydrate and the subsequent induced structural distortion. The shift in the hydrate stability conditions due to the increasing water salinity is discussed and compared with the case of unconfined hydrate, concluding that the influence of the confinement geometry and pore hydrophilicity produces a larger deviation in the confined hydrate phase equilibria.
Effects of cornering conditions on the aerodynamic characteristics of a high-performance vehicle and its rear wing
Authors: Rijns Steven , Teschner Tom-Robin , Blackburn Kim , Brighton James
Published: April 2024

This study investigates the aerodynamic behavior of a high-performance vehicle and the interaction with its rear wing in straight-line and steady-state cornering conditions. Analyses are performed with Reynolds-averaged Navier–Stokes based computational fluid dynamics simulations using a moving reference frame and overset mesh technique, validated against moving ground wind tunnel experiments. The results indicate a significant 20% decrease in downforce and 35% increase in drag compared to straight-line conditions at the smallest considered corner radius of 2.9 car-lengths. Downforce losses primarily stem from performance deficits on the underbody and rear wing, alongside elevated upper body lift. Drag penalties mainly result from additional pressure drag induced by a recirculation wake vortex generated behind the vehicle's inboard side. The vehicle's lateral pressure distribution is also affected, introducing a centripetal force that increases with smaller corner radii. Additionally, analyses of the rear wing reveal alternations of its aerodynamic characteristics in cornering, particularly impacting vortical flow and suction on the lower surface. Throughout the operating conditions, the rear wing's individual downforce contribution falls off beyond its stall angle. At higher angles of attack, the rear wing primarily generates downforce by pressurizing the vehicle's upper surfaces, but its interaction with the near-wake leads to a substantially increased pressure drag. Overall, these findings provide crucial insights into the intricate aerodynamic interactions of high-performance vehicles in diverse operating conditions as well as form an essential foundation for future research on static and active aerodynamic designs in the pursuit to optimize vehicle performance in dynamic driving conditions.
Experimental and numerical investigation on effects of gas adsorption pressures on damage behaviors, failure characteristics, and energy evolution of coals
Authors: Zheng Wenqi , Gao Feng , Xing Yan , Zhou Chunbo , Ming Li
Published: April 2024

Coal and gas outbursts are anthropogenic hazards that can be divided into four stages: preparation, occurrence, development, and termination. Studying the influence of gas on coal damage and energy changes during the formation of outbursts is highly important for investigating the entire hazard. In this paper, laboratory experiments were performed on samples. The energy changes and failure mechanism of coal under different gas pressures were revealed, and a seepage model was established based on compressibility and adsorption to investigate gas-induced coal damage. The results demonstrated that gas pressure caused initial damage within the coal, resulting in nonlinear deformation and strength deterioration of the coal. Gas-induced damage affected the energy evolution mechanism of coal under loading, as pressure caused the premature release of energy at the tips of internal microcracks and reduced the ability to accumulate energy. These changes increased the proportion of dissipative energy under unstable conditions. The combined acoustic emission (AE) parameters—rising angle (RA) and average frequency (AF)—were used to study the fracture mode of gas-containing coal. As the gas pressure increased from 0 to 4 MPa, the RA–AF distribution pattern changed from tensile failure to tensile–shear composite failure, with the proportion of shear cracks increasing from 0.30% to 25.44%. As the complexity of the crack network increased, the randomness of crack propagation increased, and the fracture surface roughness parameters, arithmetic mean height Sa, root mean square height Sq, and maximum height Sz increased by 90.33%, 94.02%, and 81.70%, respectively. These findings could contribute to a comprehensive understanding of the underlying mechanism of coal and gas outbursts and guide for predicting and preventing these hazards.
Perspectives on nitride ferroelectric semiconductors: Challenges and opportunities
Authors: Wang Danhao , Yang Samuel , Liu Jiangnan , Wang Ding , Mi Zetian
Published: April 2024

The recent demonstration of ferroelectricity in nitride materials has enabled a broad spectrum of applications across electronics, optoelectronics, photovoltaics, photonics, ferroelectrics, acoustoelectronics, and quantum devices and systems. Ensuring that nitride ferroelectrics meet the rigorous demands of modern microelectronics and photonics necessitates addressing significant challenges, such as large coercive fields, low endurance, poor stability, high leakage current, and high optical loss. In this perspective, we review the latest advancements, highlight the distinctive properties and notable achievements of nitride ferroelectrics, and delve into their origins, material synthesis, operational mechanisms and devices. Moreover, we highlight the principal obstacles faced by nitride ferroelectrics in practical applications. Finally, we discuss potential solutions, future research directions, and the prospects for further advancements in this rapidly evolving domain.
A conserved strategy to attack collagen: The activator domain in bacterial collagenases unwinds triple-helical collagen
Authors: Serwanja Jamil , Wieland Alexander C. , Haubenhofer Astrid , Brandstetter Hans , Schönauer Esther
Published: April 2024

Bacterial collagenases are important virulence factors, secreted by several pathogenic
Clostridium
,
Bacillus
,
Spirochaetes
, and
Vibrio
species. Yet, the mechanism by which these enzymes cleave collagen is not well understood. Based on biochemical and mutational studies we reveal that collagenase G (ColG) from
Hathewaya histolytica
recognizes and processes collagen substrates differently depending on their nature (fibrillar vs. soluble collagen); distinct dynamic interactions between the activator and peptidase domain are required based on the substrate type. Using biochemical and circular dichroism studies, we identify the presumed noncatalytic activator domain as the single-domain triple helicase that unwinds collagen locally, transiently, and reversibly.
“Prison Life Can Make You Go Crazy”: Insights Into the Situation for People With a Mental Illness in the Malawi Prison System
Authors: Van Hout Marie Claire , Kaima Ruth , Magwejani Chisomo , Kasunda Vivian , Nyson Kesten , Khoviwa Peace , Phiri Malumbo , Mhango Victor , Kewley Stephanie
Published: April 2024

Little is known with regard to due process and forensic assessment capacities in Africa, where over one million are deprived of their liberty on any given day. A rapid situation assessment explored multi-stakeholder perspectives regarding the situation of people with a mental illness in the Malawi prison system. In-depth interviews were conducted with 10 regional professional stakeholders, 18 former prisoners, and five prison staff from two maximum-security prisons. Reflexive thematic analysis yielded five themes; occurrence of mental illness among people living in prison; prison environment exacerbating harm and levels of mental illness; security responses to the presence of psychiatric disorders; availability and coverage of specialist psychiatric and psychological care; and diversion, other non-custodial measures and continuity of care on release. Narratives highlight the substantial causal impact of the prison environment in amplifying existing and new mental illness, vulnerability and exploitation of people with a mental disorder. Malawi prisons are hampered by lack of specialist forensic capacity nationally; centralized mental health surveillance system; and insufficient skilled staff to conduct evidence-based screening and care. Security operations implement the use of pharmacological and physical restraint measures at times. Faith-based organizations play an important role in providing psychological and spiritual support. Release and reintegration require family involvement. A cross departmental intersectoral partnership response spanning government ministries, key civil society organizations, the Malawi Prison Inspectorate and Malawi Human Rights Commission is warranted. Recommendations include alleviation of prison congestion, prison staff capacity building and investment in forensic mental health services with adequate geographic coverage.
Reduction of mechanical losses in ion-beam sputtered tantalum oxide thin films via partial crystallization
Authors: Favaro Giulio , Milotti Valeria , Alonso Diaz Riega Diego , Busdon Nicole , Bazzan Marco , Granata Massimo , Hofman David , Michel Christophe , Pinard Laurent , Conti Livia , Capaccioli Simone , Shcheblanov Nikita S , Lemaître Anaël , Martinez Valérie , Cagnoli Gianpietro , Piergiovanni Francesco , Fabrizi Federica , Pelizzo Maria G , Corso Alain J
Published: April 2024

This study explores the impact of crystalline fraction on the mechanical losses of amorphous tantalum oxide (tantala, Ta2O5) thin films intended for gravitational wave detectors. We use ion beam sputtering technique to prepare a series of samples, which are then subjected to controlled thermal annealing to achieve varying degrees of crystallized fraction. The microscopic structure of the annealed samples is characterized by combining different analytical techniques. Our investigation reveals that the amorphous films comprise randomly distributed crystalline grains, whose density and average size depends on the duration of thermal treatment. To assess mechanical losses of the coatings, a gentle nodal suspension system is applied. Remarkably, a substantial reduction of approximately 20% in the coating’s mechanical loss angle with respect to annealed amorphous coatings is observed for samples exhibiting a crystalline fraction of around 5%. This improvement may lead to the definition of alternative thermal treatments to improve the mechanical performances of coatings for gravitational wave detectors or other highly sensitive optical experiments. However the reduction in mechanical losses comes at the expense of an increase in optical scattering. The possibility of reducing the optical losses to the level required by gravitational interferometers by modifying the grain size distribution via appropriate annealing treatments is discussed.
Optical properties of germania and titania at 1064 nm and at 1550 nm
Authors: Diksha D , Amato A , Spagnuolo V , McGhee G I , Chicoine M , Clark C , Hill S , Hough J , Johnston R , Keil R , Mavridi N , Reid S , Rowan S , Schapals T , Schiettekatte F , Tait S C , Martin I W , Steinlechner J
Published: April 2024

One of the main noise sources in current gravitational-wave detectors is the thermal noise of the high-reflectivity coatings on the main interferometer optics. Coating thermal noise is dominated by the mechanical loss of the high-refractive index material within the coating stacks,

Ta
2

O
5

mixed with

TiO
2

. For upgrades to room-temperature detectors, a mixture of

GeO
2

and

TiO
2

is an interesting alternative candidate coating material. While the rather low refractive index of GeO2 increases with increasing

TiO
2

content, a higher

TiO
2

content results in a lower threshold temperature before heat treatment leads to crystallisation, and potentially to a degradation of optical properties. For future cryogenic detectors, on the other hand, a higher

TiO
2

content is beneficial as the TiO2 suppresses the low-temperature mechanical loss peak of GeO2. In this paper, we present the optical properties of coatings—produced by plasma-assisted ion-beam evaporation—with high TiO2 content at 1550 nm, a laser wavelength considered for cryogenic gravitational-wave detectors, as a function of heat-treatment temperature. For comparison, the absorption of pure GeO2 was also measured. Furthermore, results at the currently-used wavelength of 1064 nm are presented.
Crossed Andreev reflection in normal-superconductor-normal junction based on Kekulé-Y patterned graphene
Authors: Li Xue-Si , Liu Dong-Yan , Jin Zhao , He Chun-Lin
Published: April 2024

We theoretically study the crossed Andreev reflection (CAR) of the normal metal-superconductor-normal metal (NSN) heterojunction based on Kekulé-Y patterned graphene with two doping types, i.e. nSn and nSp configurations. It is found that the enhanced CAR is more likely to occur in the nSp junction rather than the nSn junction. To be concrete, the almost perfect CAR occurs in a large range of incident angle in the single Dirac cone phase when the incident energy is inside the gap of the nonlinear band. Furthermore, the roles of the length of superconductor and pseudospin-valley coupling on conductance are also evaluated.
A CGLS-based method for solving magnetic moments of hybrid-model magnetic targets
Authors: Lu Binjie , Zhang Xiaobing , Dai Zhonghua
Published: April 2024

In order to solve the problem of magnetic moment estimation of magnetic targets, the inverse problem of magnetic moment estimation was constructed based on the hybrid model of ellipsoid and magnetic dipole array. In order to solve the ill-posed problem of the magnetic moment estimation equations, the method was designed to estimate the magnetic moment parameters of the ellipsoid and magnetic dipole array, and the improved discrepancy principle and the maximum chi-square distribution stop criterion were introduced to improve the semi-convergence behavior of the conjugate gradient least squares (CGLS) method. Through simulation examples of magnetic target magnetic moment estimation and ship model measurement data, the performance of two CGLS methods, Tikhonov algorithm and stepwise regression method, were compared and analyzed from four aspects: relative error of magnetic moment estimation, relative error of magnetic field fitting, relative error of magnetic field extrapolation, and computational time complexity. The CGLS method has the advantages of high accuracy of magnetic moment estimation, high immunity of magnetic moment estimation to interference, high accuracy of magnetic field fitting and extrapolation, and low computational time complexity.
Measuring the profile of aircraft engine blades using spectral confocal sensors
Authors: Chen Ze , Xue Kaiyan , Sun Chuanzhi , Liu Yongmeng , Tan Jiubin
Published: April 2024

The geometric parameters of aircraft engine blades need to be precisely measured to ensure the quality of the blades for the normal operation of aircraft engines. This study aims to address the challenges of existing measurement systems in balancing efficiency, accuracy, and completeness. Additionally, it aims to enhance the accuracy and robustness of the algorithm for extracting blade profile characteristic parameters. In this paper, a spectral confocal sensor is employed to establish a blade profile measurement system. The design includes a probe sampling strategy, and a standard ball is used to calibrate the sensor probe’s light emission direction and the precise rotation center of the turntable. The paper proposes the use of methods such as partition search algorithm, binary search, and curvature segmentation to process point cloud data of blade body and tenon. We have conducted experimental measurements on the blades of an aircraft engine. The acquired three-dimensional point cloud data of multiple sets of blade cross-sections and dovetail sections were processed. After calculation, the maximum measurement errors for chord length, maximum blade thickness, tenon width, bottom height, top angle, and bottom angle are −0.0036 mm, −0.00721 mm, −0.0102 mm, −0.00928 mm, 0.0086°, and −0.0058°, respectively. This process validates the effectiveness of the proposed method and has high measurement accuracy. Compared with the CMM method, this method is more accurate in measuring small pits and large curvature micro surfaces, with higher measurement integrity and higher measurement efficiency.
Structure-led manifestation of photocatalytic activity in magnetically recoverable spinel CuFe2O4 nanoparticles and its application in degradation of industrial effluent dyes under solar light
Authors: Zala Devanshi , Mishra Atul K , Mukhopadhyay Indrajit , Ray Abhijit
Published: April 2024

An efficient removal of the photocatalysts used in the decontamination of water is crucial after its application beside its expected visible light sensitive activities. This study presents the synthesis of magnetically separable CuFe2O4 nanoparticles (CFNPs) with enhanced photoactivity under AM 1.5 G sunlight. A simple two-step process involving co-precipitation and hydrothermal treatment is employed, with subsequent annealing at temperatures from 200 °C to 1000 °C to synthesize the CFNPs. The characteristic features of the highest photoactive tetragonal phase of CFNP are confirmed by powder XRD studies with Rietveld refinement. This scheme strategically controls the growth of a highly photoactive tetragonal phase with predominant (224) facets over other less active facets in cubic CuFe2O4. Mott–Schottky analysis confirms the p-type semiconducting nature of CFNPs. A favourable direct optical band gap of 1.73 eV, as well as photoluminescence emission quenching for visible photons, show that the (224) oriented CFNPs are good photocatalysts in the visible spectrum with demonstrated organic dye degradations, including methylene blue and others. A density functional theory-based approach validates that the adsorption of such dye is thermodynamically more favourable on (224) facets of CuFe2O4 to facilitate the redox action by the excitons.
Robust ZTO-reinforced Ag nanowire hybrid transparent conductive thin films with absorption-enhanced electromagnetic interference shielding property
Authors: Jenifer K , Parthiban S
Published: April 2024

Technological advances have accelerated the pursuit of transparent conducting thin films (TCFs) with superior mechanical properties, durability, efficient optoelectrical performance and substrate compatibility as a pivotal focus in the realm of flexible transparent electronics. Against this background, this work investigates the fabrication of multilayer silver nanowire (AgNW) thin films reinforced by zinc tin oxide (ZTO) thin film encapsulation on polycarbonate substrates by a combination of sputtering and spin-coating techniques. An investigation of the influence of AgNW percolation networks on the optoelectrical properties of ZTO/AgNW/ZTO hybrid thin films was carried out. The impact of ZTO protective layers on the enhancement of electrical properties, adhesivity, flexibility and environmental stability of the multilayer TCF was elucidated. Additionally, to explore the compatibility of the fabricated TCF in integrated device and stealth applications, its electromagnetic interference shielding properties were investigated. The hybrid TCF showed 99.47% EMI shielding efficiency with an absorption-dominant EMI shielding effectiveness of 22.7 dB in the x-band region.
Melanin-Ce6-loaded polydopamine nanoparticles-based enhanced phototherapy for B16 melanoma cancer cells
Authors: Shinde Vinod Ravasaheb , Thanekar Ajinkya Madhukar , Khatun Sajmina , Buddhiraju Hima Sree , Bhattacharjee Basu , Rengan Aravind Kumar
Published: April 2024

Melanoma is one of the most aggressive and lethal types of cancer owing to its metastatic propensity and chemoresistance property. An alternative therapeutic option is photodynamic and photothermal therapies (PDT/PTT), which employ near-infrared (NIR) light to generate heat and reactive oxygen species (ROS). As per previous reports, Melanin (Mel), and its synthetic analogs (i.e. polydopamine nanoparticles) can induce NIR light-mediated heat energy, thereby selectively targeting and ameliorating cancer cells. Similarly, chlorin e6 (Ce6) also has high ROS generation ability and antitumor activity against various types of cancer. Based on this tenet, In the current study, we have encapsulated Mel-Ce6 in a polydopamine (PDA) nanocarrier (MCP NPs) synthesized by the oxidation polymerization method. The hydrodynamic diameter of the synthesized spherical MCP NPs was 139 ± 10 nm. The MCP NPs, upon irradiation with NIR 690 nm laser for 6 min, showed photothermal efficacy of more than 50 °C. Moreover, the red fluorescence in the MCP NPs due to Ce6 can be leveraged for diagnostic purposes. Further, the MCP NPs exhibited considerable biocompatibility with the L929 cell line and exerted nearly 70% ROS-mediated cytotoxicity on the B16 melanoma cell line after the laser irradiation. Thus, the prepared MCP NPs could be a promising theranostic agent for treating the B16 melanoma cancer.
Multi-scale feature aggregation and fusion network with self-supervised multi-level perceptual loss for textures preserving low-dose CT denoising
Authors: Zhang Yuanke , Wan Zhaocui , Wang Dong , Meng Jing , Ma Fei , Guo Yanfei , Liu Jianlei , Li Guangshun , Liu Yang
Published: April 2024

Objective. The textures and detailed structures in computed tomography (CT) images are highly desirable for clinical diagnosis. This study aims to expand the current body of work on textures and details preserving convolutional neural networks for low-dose CT (LDCT) image denoising task. Approach. This study proposed a novel multi-scale feature aggregation and fusion network (MFAF-net) for LDCT image denoising. Specifically, we proposed a multi-scale residual feature aggregation module to characterize multi-scale structural information in CT images, which captures regional-specific inter-scale variations using learned weights. We further proposed a cross-level feature fusion module to integrate cross-level features, which adaptively weights the contributions of features from encoder to decoder by using a spatial pyramid attention mechanism. Moreover, we proposed a self-supervised multi-level perceptual loss module to generate multi-level auxiliary perceptual supervision for recovery of salient textures and structures of tissues and lesions in CT images, which takes advantage of abundant semantic information at various levels. We introduced parameters for the perceptual loss to adaptively weight the contributions of auxiliary features of different levels and we also introduced an automatic parameter tuning strategy for these parameters. Main results. Extensive experimental studies were performed to validate the effectiveness of the proposed method. Experimental results demonstrate that the proposed method can achieve better performance on both fine textures preservation and noise suppression for CT image denoising task compared with other competitive convolutional neural network (CNN) based methods. Significance. The proposed MFAF-net takes advantage of multi-scale receptive fields, cross-level features integration and self-supervised multi-level perceptual loss, enabling more effective recovering of fine textures and detailed structures of tissues and lesions in CT images.
Compressive properties of a modified re-entrant chiral auxetic structure (MRCA) under uniaxial quasi-static loading
Authors: Alomarah Amer , Hamdoon Farouk Omar , Al-Ibraheemi Zahraa A , Ruan Dong
Published: April 2024

Auxetics are a unique class of innovative materials/structures. Auxetic material/structures possess a negative value of Poisson’s ratio owing to the distinguished deformation behavior represented by the transvers expansion or contraction when they experience uniaxial stretching or compression, respectively. The aim of this manuscript is to show contributions of the structural modification on an auxetic hybrid structure. The in-plane properties of an auxetic structure, called the modified re-entrant chiral auxetic (MRCA) structure under quasi-static compression were experimentally and numerically explored. The experimental specimens were 3D printed using fused deposition modeling technique. The commercial ABAQUS/Explicit solver was used to develop the simulated models. Results showed that the structural modification have led to effectively improve deformation coordination (i.e. uniform deformation patterns) and the compressive properties of the modified structure. Young’s moduli were 1.75 and 12.7 higher than those of the original geometry, while values of plateau stress were 3.1 and 1.23 higher than those of the original geometry when they were compressed along the X and Y axes, respectively. The specific energy absorptions per unit mass were 4.7 J g−1 and 3.9 J g−1 when the MRCA specimens were compressed along the X and Y axes, respectively. However, the added cylinders limited the auxeticity (i.e. the transvers contraction) of the specimens during the compression tests.