bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transient helix formation in charged semiflexible polymers without confinement effects
Authors: Mitra Debarshi , Chatterji Apratim 
Published: September 2020

Abstract
Switching on generic interactions e.g. the Coulomb potential or other long ranged spherically symmetric repulsive interactions between monomers of bead-spring model of a semi-flexible polymer induce instabilities in a semiflexible polymer chain to form transient helical structures. Our proposed mechanism could explain the spontaneous emergence of helical order in stiff (bio-) polymers as a chain gets charged from a neutral state. But since the obtained helical structures dissolve away with time, hydrogen bonding (or other additional mechanisms), would be required to form stabilized helical structures as observed in nature (such as in biological macro-molecules). The emergence of the helix is independent of the molecular details of the monomer constituent. The key factors which control the emergence of the helical structure is the persistence length and the charge density. We have avoided using torsional potentials to obtain the transient helical structures. Moreover, we can drive the semiflexible polymer to form helices in a recurring manner by periodically increasing and decreasing the effective charge of the monomers. If the two polymer ends are tethered to two surfaces separated by a distance equal to the contour length of the polymeric chain, which could be in the range 10 nm–μ, the life time of the helical structures formed is increased.
Optical and hidden transport properties of BaFe1.91Ni0.09As2 film
Authors: Aleshchenko Yu A , Muratov A V , Ummarino G A , Richter S , Anna Thomas A , Hühne R 
Published: September 2020

Abstract
Optical spectroscopy was used to study the electrodynamics and hidden transport properties of a BaFe1.91Ni0.09As2 thin superconducting (SC) film. We analyzed the normal state data using a Drude–Lorentz model with two Drude components: one narrow (D1) and another broad one (D2). In the SC state, two gaps with

2

Δ

0

(

2

)

/

k

B

T

c

=
1.9

–2.0 and

2

Δ

0

(

1

)

/

k

B

T

c

=
4.0

–4.3 are formed from the narrow component D1 while the broad component D2 remains ungapped. The calculated total DC resistivity of the film and the low-temperature scattering rate for the narrow Drude component show a hidden Fermi-liquid behavior. The change of total electron–boson coupling (λ
tot) and representative energy (Ω0) in the normal state with respect to the SC state is typical of other iron-based materials as well as high-temperature superconducting (HTSC) cuprates.
Crystalline assembly of perylene in metal–organic framework thin film: J-aggregate or excimer? Insight into the electronic structure
Authors: Kozlowska Mariana , Pramudya Yohanes , Jakoby Marius , Heidrich Shahriar , Pan Liuyang , Richards Bryce S , A Howard Ian , Wöll Christof , Haldar Ritesh , Wenzel Wolfgang 
Published: September 2020

Abstract
The spatial orientation of chromophores defines the photophysical and optoelectronic properties of a material and serves as the main tunable parameter for tailoring functionality. Controlled assembly for achieving a predefined spatial orientation of chromophores is rather challenging. Metal–organic frameworks (MOFs) are an attractive platform for exploring the virtually unlimited chemical space of organic components and their self-assembly for device optimization. Here, we demonstrate the impact of interchromophore interactions on the photophysical properties of a surface-anchored MOF (SURMOF) based on 3,9-perylenedicarboxylicacid linkers. We predict the structural assembly of the perylene molecules in the MOF via robust periodic density functional theory calculations and discuss the impact of unit topology and π–π interaction patterns on spectroscopic and semiconducting properties of the MOF films. We explain the dual nature of excited states in the perylene MOF, where strong temperature-modulated excimer emission, enhanced by the formation of perylene J-aggregates, and low stable monomer emission are observed. We use band-like and hopping transport mechanisms to predict semiconducting properties of perylene SURMOF-2 films as a function of inter-linker interactions, demonstrating both p-type and n-type conduction mechanisms. Hole carrier mobility up to 7.34 cm2 Vs−1 is predicted for the perylene SURMOF-2. The results show a promising pathway towards controlling excimer photophysics in a MOF while controlling charge carrier mobility on the basis of a predictive model.
DNA-induced assembly of gold nanoprisms and polystyrene beads into 3D plasmonic SERS substrates
Authors: Chowdhury Emtias , Rahaman Mohammad Shahinur , Sathitsuksanoh Noppadon , Grapperhaus Craig A , O’Toole Martin G 
Published: September 2020

Abstract
The utilization of nanoparticle-polymer bead hybrid nanostructures as a SERS substrate depends on the control of the deposition, density, and distribution of nanoparticles on the bead surface. Here we demonstrate the fabrication of a large area SERS substate via a two- step DNA mediated assembly of gold nanoprisms and polystyrene (PS) beads into a large ensemble of beads that are densely coated with nanoprisms. First, nanoprisms are loaded on PS beads through DNA hybridization. The close packed arrangement of anisotropic nanoprisms in different orientations on a bead surface results in a plasmonic substrate with a variable nanogap size ranging 1–20 nm. Nanoprisms-coated beads are then assembled into a large stack or aggregate of beads using a DNA-induced crystallization approach. Each aggregate consists of 20–50 nanoprisms-coated beads, leading to the formation a large area of three-dimensional SERS substrate with a high-density of hot spots for SERS enhancement. An excellent enhancement factor (EF) of

1.09
×

10
5

and a very high detection sensitivity (up to 10–10 M) are observed for the analysis of a probe molecule (Methylene blue) using the SERS substrate.
Low frequency conductivity reconstruction based on a single current injection via MREIT
Authors: Song Yizhuang , Sajib Saurav Z K , Wang Haiyang , Kwon Hyeuknam , Chauhan Munish , Keun Seo Jin , Sadleir Rosalind 
Published: September 2020

Abstract
Conventional magnetic resonance electrical impedance tomography (MREIT) reconstruction methods require administration of two linearly independent currents via at least two electrode pairs. This requires long scanning times and inhibits coordination of MREIT measurements with electrical neuromodulation strategies. We sought to develop an isotropic conductivity reconstruction algorithm in MREIT based on a single current injection, both to decrease scanning time by a factor of two and enable MREIT measurements to be conveniently adapted to general transcranial- or implanted-electrode neurostimulation protocols. In this work, we propose and demonstrate an iterative algorithm that extends previously published MREIT work using two-current administration approaches. The proposed algorithm is a single-current adaptation of the harmonic B

z
algorithm. Forward modeling of electric potentials is used to capture changes of conductivity along current directions that would normally be invisible using data from a single-current administration. Computational and experimental results show that the reconstruction algorithm is capable of reconstructing isotropic conductivity images that agree well in terms of L
2 error and structural similarity with exact conductivity distributions or two-current-based MREIT reconstructions. We conclude that it is possible to reconstruct high quality electrical conductivity images using MREIT techniques and one current injection only.
Effect of the Si doping on the properties of AZO/SiC/Si heterojunctions grown by low temperature pulsed laser deposition
Authors: Boughelout Abderrahmane , Macaluso Roberto , Crupi Isodiana , Megna Bartolomeo , Brighet Amer , Trari Mohamed , Kechouane Mohamed 
Published: September 2020

Abstract
The structural and photoelectrical properties of Al-doped ZnO (AZO)/SiC/p-Si and AZO/SiC/n-Si heterojunctions, fabricated at low temperature by pulsed laser deposition, were investigated by means of a number of techniques. Raman analysis indicates that SiC layers have the cubic 3C-SiC phase, whilst X-ray diffraction measurements show that AZO films exhibit a hexagonal wurtzite structure, highly textured along the c-axis, with average crystallites size of 35.1 nm and lattice parameter c of 0.518 nm. The homogeneous and dense surface morphology observed by scanning electron microscopy was confirmed by atomic force microscopy images. Moreover, UV–Vis-NIR spectra indicated a high transmittance of SiC films in the region 550–2500 nm, about 80% transmittance of AZO films in the 450–1000 nm region, and optical band gaps in good agreement with literature. These results prove that pulsed laser deposition is a low-cost technique suitable to grow SiC and AZO films with excellent material properties. The effect of the Si doping on the current transport mechanisms in the heterojunctions was investigated by current-voltage measurements under dark and white light illumination. Both heterojunctions exhibit a diode behaviour and relatively low leakage current, with a noticeable superiority for the AZO/SiC/n-Si device also under illumination, with an illumination/dark ratio of about 400. Our results indicate that the AZO/SiC/p-Si heterojunctions, with higher values of ideality factor, series resistance and lower rectifying ratio, have a complex current transport compared to the diodes grown on n-type Si. Additionally, capacitance-voltage measurements and Mott-Schottky plot allowed to determine a built-in potential of 0.51 V for the Al/AZO/SiC/p-Si/Al device.
Adaptive damping tuning and circuit implementation for broad bandwidth energy harvesting
Authors: Sharma Yamini , Liu Mingyi , Jung Hyunjun , Zuo Lei 
Published: September 2020

Abstract
This paper presents a circuit to tune the electrical damping for optimal power harvesting at time varying excitation frequencies. Optimization of parameters, such as electrical damping to match the mechanical damping and the resonant frequency to match the excitation frequency have long been known. However, the electrical damping optimized at the resonant frequency is not necessarily the optimum point when the excitation frequency changes. This result is especially important in vibration energy harvesting systems since the vibration source is generally not at a single fixed frequency. The proposed circuit detects the excitation frequency and tunes the electrical damping based on a function, obtained from mechanical system modeling and simulation. A frequency detection circuit and a boost converter operating in critical conduction mode are used. Both modeling and experiment results show that the impedance tuning circuit provides the required optimal damping at different excitation frequencies and achieves a much broader bandwidth compared with the conventional system. When the excitation frequency increases to 1.1–1.4 times the natural frequency, the proposed adaptive damping tuning increases the power output by 30%–100% compared to the traditional one.
Electromagnetic and mechanical properties of conductive polyethylene composite antennas for utility location
Authors: Waldman Laura J , Brown Maximilian W , Mauzey Parker A , Singh Raman P , Roche Steven L , Hawrylak Peter J , Keller Michael W 
Published: September 2020

Abstract
Location of polyethylene utility pipes is improved by installing electromagnetic targets with the pipe. A new electromagnetic target could be created by impregnating polyethylene with conductive materials to impart it with electromagnetic properties necessary for use in utility location. Antennas created from this conductive polyethylene composite could be molded directly to the pipe during fabrication. The addition of high concentrations of conductive fillers into the material alters the mechanical performance of the material in addition to the electromagnetic properties, resulting in a material which displays brittle behavior, unlike neat polyethylene. Both electromagnetic and mechanical properties of the material are characterized to predict the behavior of the conductive polyethylene in service. In a layered composite with unmodified polyethylene and conductive polyethylene layers, the brittle behavior of the conductive polyethylene limits the strain to failure of the overall composite.
On space charge effects in laboratory-based photoemission electron microscopy using compact gas discharge extreme ultraviolet sources
Authors: Wilson Daniel , Schmitz Christoph , Rudolf Denis , Wiemann Carsten , Schneider Claus M , Juschkin Larissa 
Published: September 2020

Abstract
The analysis of electronic and structural properties of surfaces has been greatly advanced by photoemission electron microscopy and spectroscopy techniques. To further improve lateral and energy resolution of the instruments, it is necessary to optimize parameters of the radiation sources employed for photoemission studies (e.g. photon flux, pulse duration, spot size etc). We studied space charge effects observed in an energy-filtering photoemission electron microscope operated with a compact laboratory-scale gas-discharge extreme ultraviolet light source. In this system, we found limits of spatial- and energy-resolution controlled by the source radiation parameters. The pulse repetition rate can be varied in the kHz range and the duration of the EUV emission was measured to be several tens of nanoseconds long, and thereby very different from the standard synchrotron sources typically used for similar experiments. The spatial resolution could be improved by a factor of 5, but only on the expense of the photon density per pulse, which had to be decreased by a factor of 17 in order to reduce the image blur due to space charge effects. Furthermore, we found broadening of the x-ray photoelectron spectroscopy peaks for high photon fluxes. We have also performed a n-body Monte Carlo simulation to evaluate the difference between core-level photoelectrons and secondary electrons with respect to space charge.
Gratings with longitudinal variations in coupling coefficients: super-efficiency and unidirectionality in distributed feedback Raman fiber lasers
Authors: Tehranchi Amirhossein , Kashyap Raman 
Published: September 2020

Abstract
We propose a technique to design highly-efficient and -unidirectional DFB Raman fiber lasers based on the engineering of the grating’s coupling coefficient including a π-phase shift position in the fiber. For this purpose, first the ideal intra-cavity signal powers for different pump power levels are determined for given fiber lengths. Then, the sum and difference between the counter-propagating wave intensities at each small segment within fiber lengths are calculated resulting in determining the ideal grating’s coupling functions for co- and contra-directional-pumping. The steady-state behavior of the laser using realistic parameters is finally simulated for modified coupling functions considering the Kerr nonlinearity. For a 10 W co-directional-pumped, ∼1 m long single-mode super-efficient DFB, a ∼50% increase in the laser efficiency, more than 44 dB reduction in contra-directional lasing power, ∼15 times drop in the peak power of intra-cavity signal and ∼38% decrease in the unused-pump power are found, compared to those in a standard DFB with the same coupling-length product. Although an enhanced nonlinear refractive index due to thermal gradient reduces the output power of such lasers, it is shown that the super-efficient laser presents a better performance than the standard one, under such conditions.
Effects of inclined transversal magnetic fields on magnetohydrodynamic coupling duct flow states in liquid metal blankets: Under uniform magnetic fields
Authors: Zhang Xiujie , Wang Lei , Pan Chuanjie 
Published: September 2020

Abstract
Investigations of magnetohydrodynamic (MHD) coupling duct flows are important for liquid metal blankets of fusion reactors. In this study, numerical simulations are performed to systematically clarify the influence of the inclined transversal magnetic fields on the MHD flow states such as pressure gradients and velocity distributions through two coupling ducts with conducting walls. It is found that the MHD coupling effect in the co-flow case is much weaker than that in the counter-flow case. The inclined transversal magnetic fields have an obvious influence on the velocity distributions in the MHD coupling duct flows especially for the counter-flow case, which will induce large reversal flow regions. The inclined transversal magnetic fields will also have a significant impact on the pressure gradients in the two coupling ducts in the counter-flow case, for instance, the MHD coupling effect is so strong that the pressure gradients in the coupling ducts are several even dozens of times bigger than that in a single duct. The aspect ratio of the coupling ducts affects the MHD coupling effect significantly in the counter-flow case, and the coupling effect will be strengthen as the aspect ratio decreases. A special MHD coupling effect is firstly found, because of this effect the pressure gradients in the coupling ducts of the counter-flow case decrease with the increase of the coupling Hartmann wall thickness.
Machine-learning dessins d’enfants: explorations via modular and Seiberg–Witten curves
Authors: He Yang-Hui , Hirst Edward , Peterken Toby 
Published: September 2020

Abstract
We apply machine-learning to the study of dessins d’enfants. Specifically, we investigate a class of dessins which reside at the intersection of the investigations of modular subgroups, Seiberg–Witten (SW) curves and extremal elliptic K3 surfaces. A deep feed-forward neural network with simple structure and standard activation functions without prior knowledge of the underlying mathematics is established and imposed onto the classification of extension degree over the rationals, known to be a difficult problem. The classifications reached 0.92 accuracy with 0.03 standard error relatively quickly. The SW curves for those with rational coefficients are also tabulated.
High-resolution computer-generated hologram for creating 2D images with kinematic effects of motion
Authors: Goncharsky Anton , Durlevich Svyatoslav 
Published: September 2020

Abstract
A new method is proposed for computing the microrelief of phase diffractive optical elements (DOEs) forming 2D images with kinematic effects of motion. The DOE is subdivided into elementary areas with a size of approximately 50 microns. The synthesis of optical security elements includes the computation of the beam pattern in each elementary area. The beam pattern in each elementary area uniquely defines the phase function of the optical element. The computation of the phase function involves solving a nonlinear operator equation. Efficient methods are developed for computing the microrelief of DOEs forming 2D images with kinematic effects of motion. Sample optical elements are made using electron-beam technology. The microrelief is shaped with a precision of ∼10 nm, and the resolution is equal to ∼0.1 micron. The synthesis method developed is universal in nature. Given different sets of frames, one can achieve different behaviours of the motion of image fragments. The new optical elements can be used to protect banknotes, passports, IDs, and brands against counterfeiting.
Optical multimodal biometric encryption that uses digital holography
Authors: Rajput Sudheesh K , Matoba Osamu 
Published: September 2020

Abstract
In this paper, we propose an optical multimodal biometric encryption technique which uses digital holography (DH) for multiple biometric recording and successive optical encryption methods, by means of keys generated from biometric data. Physiological biometrics, such as fingerprints or iris scans, along with behavioral biometrics such as voice, are recorded simultaneously as multimodal biometrics, using multi-parameter off-axis DH. Moreover, multiple biometrics embedded in the same holograms are encrypted using the Fresnel domain double random phase encoding method, in which keys are generated from biometric data via a phase retrieval algorithm. By employing the decryption procedure for this encoding method, along with the correct keys and reconstruction parameters of DH, the original multimodal biometrics can be successfully retrieved . The proposed method provides multimodal biometrics with a higher level of security by availing itself of the advantages of optical techniques. Our proposed multimodal biometric security scheme is demonstrated and validated by the results of the optical recording and encryption of biometric data presented below.
Employing vanadium dioxide nanoparticles for flexible metasurfaces with switchable absorption properties at near-infrared frequencies
Authors: Ko Byoungsu , Badloe Trevon , Kim Soo-Jung , Hong Sung-Hoon , Rho Junsuk 
Published: September 2020

Abstract
Using the simple interference interactions in a three-layer thin film structure, absorbers in the near infrared with aesthetically pleasing reflective colouration were designed, fabricated, and characterised. By implementing the phase change material, vanadium dioxide (VO2), with its remarkable phase change properties, the absorbers are able to be switched between lower and higher absorption states depending on the external temperature. Conventional fabrication methods involving VO2 require an annealing process after deposition, but here, VO2 nanoparticles dispersed in a polymer mixture were employed to allow the simple and scalable spin coating process to be used, without the need for annealing. This simultaneously opens up the possibility of using flexible substrates for bendable devices. At a temperature of around 68 °C, a change in absorption of around 30% is observed between 800–1600 nm, while the vivid subtractive colours are maintained with almost no observable difference, on both silicon and flexible polymer-based substrates. The fabricated sample is robust to 2500 bending cycles, proving the possibility for scalable VO2 fabrication methods for practical applications.