bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quantum dot photoluminescence as charge probe for plasma exposed surfaces
Authors: Hasani M , Klaassen G , Marvi Z , Pustylnik M , Beckers J 
Published: November 2022

Abstract
Quantum dots (QDs) are used as nanometer-sized in situ charge probes for surfaces exposed to plasma. Excess charges residing on an electrically floating surface immersed in a low-pressure argon plasma are detected and investigated by analysis of variations in the photoluminescence spectrum of laser-excited QDs that were deposited on that surface. The experimentally demonstrated redshift of the PL spectrum peak is linked to electric fields associated with charges near the QDs’ surfaces, a phenomenon entitled the quantum-confined Stark effect. Variations in the surface charge as a function of plasma input power result in different values of the redshift of the peak position of the PL spectrum. The values of redshift are detected as 0.022 nm and 0.073 for 10 and 90 W plasma input powers, respectively; therefore indicating an increasing trend. From that, a higher microscopic electric field,

9.29
×

10
6

V m−1 for 90 W compared to

3.29
×

10
6

V m−1 for 10 W input power, which is coupled to an increased electric field in the plasma sheath, is sensed by the QDs when plasma input power is increased.
Strain-induced ultrahigh power conversion efficiency in BP-MoSe2 vdW heterostructure
Authors: Tu Jiarui , Lei Xueling , Li Pengfei 
Published: November 2022

Abstract
Photocatalytic water splitting is a promising method for hydrogen production, and the search for efficient photocatalysts has received extensive attention. Two-dimensional van der Waals (vdW) heterostructures have recently been considered excellent candidates for photocatalytic water splitting. In this work, a BP-MoSe2 vdW heterostructure composed of a blue phosphorus (BP) and MoSe2 monolayer was studied as a potential photocatalyst for water splitting using first-principles calculations. The results show that the heterostructure has a type-II band structure, and the band edges straddle water redox potentials under biaxial strains from −3% to 2%, satisfying the requirements for photocatalytic water splitting. In addition, the heterostructure has excellent power conversion efficiency (PCE) and strong optical absorption in both visible light and near-ultraviolet region, indicating that it is a very promising candidate for photocatalytic water splitting. Specifically, the PCE was enhanced to ∼20.2% under a tensile strain of 2%. The Gibbs free energy profiles indicate that BP-MoSe2 vdW heterostructure exhibits good catalytic performance in hydrogen and oxygen evolution reactions. In particular, high carrier mobility implies that the transfer of carriers to reactive sites is easy, and the recombination probability of photogenerated electron–hole pairs is reduced.
Embedded ultra-high stability flexible transparent conductive films based on exfoliated graphene-silver nanowires-colorless polyimide
Authors: Qian Peng-Fei , Wang Jing-Qi , Wang Tao , Huai Xuguo , Geng Wen-Hao , Zhu Qiangxia , Tian Ying , Jing Li-Chao , Bao Ze-Long , Geng Hong-Zhang 
Published: November 2022

Abstract
Transparent conductive films with high stability were prepared by embedding silver nanowires in colorless polyimide and adding a protective layer of exfoliated graphene. The films exhibit great light transmission and conductivity with a sheet resistance of 22 Ω sq−1 at transmittance of 83%. Due to its special embedded structure, the conductive layer can withstand several peeling experiments without falling off. In addition, the most outstanding advantage is the ultra-high stability of the films, including high mechanical robustness, strong chemical corrosion resistance and high operating voltage capacity. The organic light-emitting diode devices prepared based on this transparent conductive electrode exhibit comparable efficiency to indium tin oxide (ITO) based devices, with C.E.
max = 2.78 cd A−1, P

−1

.E.
max = 1.89 lm W−1, EQE
max = 0.89%. Moreover, the efficiencies were even higher than that of ITO devices when the operating voltage of the device exceeds 5 V. The above performances show that the transparent conductive electrode based on this structure has high potential for application in organic electronic devices.
Stochastic and parameter analysis for an integrative cancer model
Authors: Reale Marcela V , Margarit David H , Scagliotti Ariel F , Romanelli Lilia M 
Published: November 2022

Abstract
In previous work, we presented a model that integrates cancer cell differentiation and immunotherapy, analysing a particular therapy against cancer stem cells by cytotoxic cell vaccines. As every biological system is exposed to random fluctuations, is important to incorporate stochasticity in the models to adequate their behaviour to experimental observations. Thus, we propose a necessary upgrade to the former model incorporating fluctuations in it. On the one hand, we added multiplicative noise throughout the proposed system, and on the other, we specifically analysed the influence of demographic and multiplicative noise on the parameters of reproduction and death in cancer cells. In both cases, we studied the dynamics for different values of the parameters involved. It was observed that the final number of cancer cells decreases for different combinations of these parameters and noise intensity.
Tailoring ZnO/CoFe2O4 nanocomposites: structure, optical, dielectric and magnetic study
Authors: Mahdy Manal A , Azab A A , El Zawawi I K , Turky G 
Published: November 2022

Abstract
The structural, morphology, optical, magnetic and dielectric properties of the (ZnO)1–x(CoFe2O4)x, (x = 1, 3 and 5 wt%) nanocomposites synthetized by sonomechanical method were investigated using XRD, FE-SEM, HR-TEM, UV-visible, VSM and BDS. XRD analysis shows that, ZnO and CoFe2O4 acquired hexagonal and cubic phases, respectively. The optical band gap was reduced from 3.22 eV for pure ZnO to 3.15 eV after adding 5wt % of CoFe2O4. Addition of 1wt% CoFe2O4 to ZnO matrix showed a noticeable ferromagnetic behavior that was predominant in the prepared nanocomposites and confirmed by the convex Arrott–Belov–Kouvel curves. The dielectric constant, ε′, at higher frequencies of the investigated nanocomposites is relatively high (8–10) accompanied by low values of dielectric loss, ε″ ranging between 0.001 and 0.003 and hence very low values of the dissipation factor D (= ε″/ε′) making them applicable in the field of microwave shielding. On the other hand, the dc-conductivity, σ
dc at 25 C shows a remarkable increase by Addition of 1wt% CoFe2O4 to ZnO matrix and decreases gradually with further increase of the ferrite. This indicates the effect of mobility and/or the number density of charge carriers on the conductivity. The investigation at higher temperature, 150 C, shows a gradual decrease in the conductivity with increasing CoFe2O4 content.
Theoretical design of multilayered VO2-based switchable terahertz metasurfaces as broadband functional devices
Authors: Liu DaoHong , Zhang ChuanYu , Duan Zhenkun 
Published: November 2022

Abstract
In this paper, a switchable terahertz metasurface based on VO2 multilayer structure is raised, which utilizes the temperature phase-transition properties of VO2 to achieve the functions of switchable polarization conversion and reflection phase modulation for arbitrarily polarized waves at different temperatures. The simulation results show that at high-temperature and low-temperature, the metasurface develop a resonant system to achieve polarization conversion for circularly polarized (CP) and linearly polarized (LP) waves, respectively. For the conversion of the CP wave at high-temperature, the polarization conversion rate exceeds 90% in the terahertz frequency range of 1.01 ∼ 2.00 THz, and at low-temperature, the polarization conversion of the LP wave reaches a near-perfect polarization conversion rate at frequencies ν = 0.65, 1.07, and 1.50 THz. Arbitrary phase regulation can be achieved by rotating the VO2 strips and altering the geometry of the C-shaped split resonator ring (CSRR) to form a periodic array with a constant gradient phase. In order to verify that the device has the function of wavefront phase modulation, we use the device to simulate the abnormal reflection based on the generalized Snell’s law.Additionally, we generated a bifocal focused beam within a cross-channel in LP incidence mode using the propagation phase principle.
Quantum effects on the propagation of surface magnetoplasmon polaritons in a graphene-plasmonic structure
Authors: Eid I S , Mohamed B F , Guo Bin 
Published: November 2022

Abstract
We investigate the properties of surface magnetoplasmon polaritons (SMPPs) in a graphene-plasmonic structure which is constructed as a graphene film sandwiched with two semi-infinite dielectrics under a perpendicular configuration. By solving Maxwell equations and quantum magneto-hydrodynamic equations with considering the quantum statistical and quantum diffraction effects, we deduce the dispersion relation of graphene SMPPs (GSMPPs) in detail. We show how the graphene electron density, the external magnetic field, and the dielectric constant, affect the features of the dispersion of GSMPPs in both classical and quantum cases. We find that the quantum effects (QEs) significantly alter the properties of GSMPPs, which are entirely different from those in a classical model. We find that the propagation speed of classical GSMPPs has small increases while the propagation speed of quantum GSMPPs has fast and sharp increases along with the increases in graphene electron density. We further find that the propagation speed decreases gradually by increasing the applied magnetic field in both classical and quantum GSMPPs. Moreover, we also find that the propagation speed of classical GSMPPs has fast decreases tending to zero at large wavenumber while the propagation speed of quantum GSMPPs has slow decreases tending to infinity with increasing the dielectric constant. Our findings elucidate that QEs play a crucial role in the properties of GSMPPs and their response to different parameters.
Focal electrical stimulation of human retinal ganglion cells for vision restoration
Authors: Madugula Sasidhar S , Gogliettino Alex R , Zaidi Moosa , Aggarwal Gorish , Kling Alexandra , Shah Nishal P , Brown Jeff B , Vilkhu Ramandeep , Hays Madeline R , Nguyen Huy , Fan Victoria , Wu Eric G , Hottowy Pawel , Sher Alexander , Litke Alan M , Silva Ruwan A , Chichilnisky E J 
Published: November 2022

Abstract

Objective. Vision restoration with retinal implants is limited by indiscriminate simultaneous activation of many cells and cell types, which is incompatible with reproducing the neural code of the retina. Recent work has shown that primate retinal ganglion cells (RGCs), which transmit visual information to the brain, can be directly electrically activated with single-cell, single-spike, cell-type precision – however, this possibility has never been tested in the human retina. In this study we aim to characterize, for the first time, direct in situ extracellular electrical stimulation of individual human RGCs. Approach. Extracellular electrical stimulation of individual human RGCs was conducted in three human retinas ex vivo using a custom large-scale, multi-electrode array capable of simultaneous recording and stimulation. Measured activation properties were compared directly to extensive results from macaque. Main results. Precise activation was in many cases possible without activating overlying axon bundles, at low stimulation current levels similar to those used in macaque. The major RGC types could be identified and targeted based on their distinctive electrical signatures. The measured electrical activation properties of RGCs, combined with a dynamic stimulation algorithm, was sufficient to produce an evoked visual signal that was nearly optimal given the constraints of the interface. Significance. These results suggest the possibility of high-fidelity vision restoration in humans using bi-directional epiretinal implants.
Align, then memorise: the dynamics of learning with feedback alignment*
Authors: Refinetti Maria , d’Ascoli Stéphane , Ohana Ruben , Goldt Sebastian 
Published: November 2022

Abstract
Direct feedback alignment (DFA) is emerging as an efficient and biologically plausible alternative to backpropagation for training deep neural networks. Despite relying on random feedback weights for the backward pass, DFA successfully trains state-of-the-art models such as transformers. On the other hand, it notoriously fails to train convolutional networks. An understanding of the inner workings of DFA to explain these diverging results remains elusive. Here, we propose a theory of feedback alignment algorithms. We first show that learning in shallow networks proceeds in two steps: an alignment phase, where the model adapts its weights to align the approximate gradient with the true gradient of the loss function, is followed by a memorisation phase, where the model focuses on fitting the data. This two-step process has a degeneracy breaking effect: out of all the low-loss solutions in the landscape, a network trained with DFA naturally converges to the solution which maximises gradient alignment. We also identify a key quantity underlying alignment in deep linear networks: the conditioning of the alignment matrices. The latter enables a detailed understanding of the impact of data structure on alignment, and suggests a simple explanation for the well-known failure of DFA to train convolutional neural networks. Numerical experiments on MNIST and CIFAR10 clearly demonstrate degeneracy breaking in deep non-linear networks and show that the align-then-memorize process occurs sequentially from the bottom layers of the network to the top.
Approximate message passing with spectral initialization for generalized linear models*
Authors: Mondelli Marco , Venkataramanan Ramji 
Published: November 2022

Abstract
We consider the problem of estimating a signal from measurements obtained via a generalized linear model. We focus on estimators based on approximate message passing (AMP), a family of iterative algorithms with many appealing features: the performance of AMP in the high-dimensional limit can be succinctly characterized under suitable model assumptions; AMP can also be tailored to the empirical distribution of the signal entries, and for a wide class of estimation problems, AMP is conjectured to be optimal among all polynomial-time algorithms. However, a major issue of AMP is that in many models (such as phase retrieval), it requires an initialization correlated with the ground-truth signal and independent from the measurement matrix. Assuming that such an initialization is available is typically not realistic. In this paper, we solve this problem by proposing an AMP algorithm initialized with a spectral estimator. With such an initialization, the standard AMP analysis fails since the spectral estimator depends in a complicated way on the design matrix. Our main contribution is a rigorous characterization of the performance of AMP with spectral initialization in the high-dimensional limit. The key technical idea is to define and analyze a two-phase artificial AMP algorithm that first produces the spectral estimator, and then closely approximates the iterates of the true AMP. We also provide numerical results that demonstrate the validity of the proposed approach.
Equilibrium and non-equilibrium regimes in the learning of restricted Boltzmann machines*
Authors: Decelle Aurélien , Furtlehner Cyril , Seoane Beatriz 
Published: November 2022

Abstract
Training restricted Boltzmann machines (RBMs) have been challenging for a long time due to the difficulty of precisely computing the log-likelihood gradient. Over the past few decades, many works have proposed more or less successful training recipes but without studying the crucial quantity of the problem: the mixing time, i.e. the number of Monte Carlo iterations needed to sample new configurations from a model. In this work, we show that this mixing time plays a crucial role in the dynamics and stability of the trained model, and that RBMs operate in two well-defined regimes, namely equilibrium and out-of-equilibrium, depending on the interplay between this mixing time of the model and the number of steps, k, used to approximate the gradient. We further show empirically that this mixing time increases with the learning, which often implies a transition from one regime to another as soon as k becomes smaller than this time. In particular, we show that using the popular k (persistent) contrastive divergence approaches, with k small, the dynamics of the learned model are extremely slow and often dominated by strong out-of-equilibrium effects. On the contrary, RBMs trained in equilibrium display faster dynamics, and a smooth convergence to dataset-like configurations during the sampling. Finally, we discuss how to exploit in practice both regimes depending on the task one aims to fulfill: (i) short k can be used to generate convincing samples in short learning times, (ii) large k (or increasingly large) is needed to learn the correct equilibrium distribution of the RBM. Finally, the existence of these two operational regimes seems to be a general property of energy based models trained via likelihood maximization.
Encounter-based model of a run-and-tumble particle
Authors: Bressloff Paul C 
Published: November 2022

Abstract
In this paper we extend the encounter-based model of diffusion-mediated surface absorption to the case of an unbiased run-and-tumble particle (RTP) confined to a finite interval [0, L] and switching between two constant velocity states ±v at a rate α. The encounter-based formalism is motivated by the observation that various surface-based reactions are better modeled in terms of a reactivity that is a function of the amount of time that a particle spends in a neighborhood of an absorbing surface, which is specified by a functional known as the boundary local time. The effects of surface reactions are taken into account by identifying the first passage time (FPT) for absorption with the event that the local time crosses some random threshold

ℓ

^

. In the case of a Brownian particle, the local time ℓ(t) is a continuous non-decreasing function of the time t. Taking

Ψ

(

ℓ

)

≡
P

[

ℓ

^

>
ℓ

]

to be an exponential distribution,

Ψ

[

ℓ

]

=

e

−

κ

0

ℓ

, is equivalent to imposing a Robin boundary condition with a constant rate of absorption κ
0. One major difference in the encounter-based model of an RTP is that the boundary local time ℓ(t) is a now a discrete random variable that counts the number of collisions of the RTP with the boundary. Given this modification, we show that in the case of a geometric distribution Ψ(ℓ) = z

ℓ
, z = 1/(1 + κ
0/v), we recover the RTP analog of the Robin boundary condition. This allows us to solve the boundary value problem (BVP) for the joint probability density for particle position and the local time, and thus incorporate more general models of absorption based on non-geometric distributions Ψ(ℓ). We illustrate the theory by calculating the mean FPT (MFPT) for absorption at x = L given a totally reflecting boundary at x = 0. We also determine the splitting probability for absorption at x = L when the boundary at x = 0 is totally absorbing.
Development of optical sensor system and hardware base frame for checking the light and radiation fields of a linear accelerator
Authors: Lee B. , Kang S.W. , Kim J.Y. , Lee J. , Kim H.J. , Kim W.C. , Song C. , Eom K.Y. , Kim I.A. , Kim J.S. , Chung J.B. 
Published: November 2022

Abstract
This study aims to quantitatively evaluate the light and radiation fields of a linear accelerator by developing an optical sensor quality assurance (QA) system using a cadmium sulfide (CdS) photodetector cell and a hardware base frame manufactured in-house. The CdS photodetector cell used as the optical sensor has a size of 3.4 × 4.1 mm2, can measure up to 100 lux of light, and has a response time of approximately 20 to 30 ms. To check the alignment of the light field, it was manufactured with a CdS cell optical fiber holder, and the microcontroller board and control module were configured to scan the light field profile. Additionally, for accurate operation of the sensor, it was programmed using the integrated development environment (IDE) sketch. The alignment check of the radiation field was analyzed using the image data measured with electronic portal imaging device (EPID) using the manufactured hardware base frame. An analysis program written in MATLAB was used to evaluate the alignment of the radiation field. For symmetric fields measured using the optical sensor QA system, the full width at half maximum (FWHM) values of crossline (X) and inline (Y) profiles were 100.391 mm and 98.725 mm, respectively, for a field size of 100 × 100 mm2, and 199.093 mm and 198.886 mm, respectively, for a field size of 200 × 200 mm2. The X and Y FWHM values measured by the sensor system for the light fields were within 1 mm of the field size of the visual inspection. In addition, the FWHM value of the asymmetric radiation field measured using the fabricated frame and EPID was measured from the center bearing ball of the field to the bearing ball in each field of the four directions in the EPID image, and when the X1, X2, Y1, and Y2 jaws were opened by 50 mm, FWHM values were 50.120 mm, 50.240 mm, 48.860 mm, and 49.870 mm, respectively. The corresponding values were 99.520 mm, 99.570 mm, 99.010 mm, and 99.880 mm when the jaw fields were opened by 100 mm. The optical sensor system and hardware base frame developed in this study demonstrated the ability to evaluate both light and radiation fields more simply and quantitatively when compared to the conventional QA process. This QA system will provide medical physicists with more reliable QA results than the conventional QA method that uses graph paper and film.
Annelid-inspired high-elongation origami robot using partial material removal
Authors: Wei Xianhe , Zhao Yanzhi , Fan Zhengwei , Guo Zhifeng , Han Zhen , Shan Yu , Liu Zhixin 
Published: November 2022

Abstract
Existing soft robots face challenges given the need for an improved flexible robot elongation rate, bending angle and movement flexibility in space target acquisition, disaster search and rescue, unknown environment detection and other fields. Yoshimura tubular origami shows good applied performance with regard to the axial elongation ratio. However, due to the characteristics of nonrigid folding and a negative Poisson’s ratio, the axial elongation length and bending angle of the Yoshimura tubular origami mechanism are limited. Annelids show highly flexible body movement. By analyzing the main factors limiting the axial elongation rate of the Yoshimura tubular origami mechanism and imitating the morphological characteristics and motion mechanism of annelid somite joints, we proposed a method to achieve high flexibility and large angle bending of a tubular origami mechanism based on local material removal and macroscopic elimination of the negative Poisson’s ratio. Combined with a Ni–Ti memory alloy wire segmented driving scheme based on force constraints and geometric constraints a continuous origami robot is designed. The optimal cutting amount of the origami mechanism is determined by experiments, and the maximum elongation ratio and bending angle of the origami mechanism reach 2.5 and 3 times those before material removal, respectively. The paper folding module unit was solved in a kinematic analysis workspace. Finally, a prototype was used to verify the performance and demonstrate the application potential of the robot in an unstructured rescue scene.