bluuebunny/crossref_metadata_2025 huggingface dataset:
A common mechanism of proteasome impairment by neurodegenerative disease-associated oligomers
Authors: Thibaudeau Tiffany A. , Anderson Raymond T. , Smith David M.
Published: March 2018

Protein accumulation and aggregation with a concomitant loss of proteostasis often contribute to neurodegenerative diseases, and the ubiquitin–proteasome system plays a major role in protein degradation and proteostasis. Here, we show that three different proteins from Alzheimer’s, Parkinson’s, and Huntington’s disease that misfold and oligomerize into a shared three-dimensional structure potently impair the proteasome. This study indicates that the shared conformation allows these oligomers to bind and inhibit the proteasome with low nanomolar affinity, impairing ubiquitin-dependent and ubiquitin-independent proteasome function in brain lysates. Detailed mechanistic analysis demonstrates that these oligomers inhibit the 20S proteasome through allosteric impairment of the substrate gate in the 20S core particle, preventing the 19S regulatory particle from injecting substrates into the degradation chamber. These results provide a novel molecular model for oligomer-driven impairment of proteasome function that is relevant to a variety of neurodegenerative diseases, irrespective of the specific misfolded protein that is involved.
Efficacy and safety of apatinib in patients with previously treated metastatic colorectal cancer: a real-world retrospective study
Authors: Gou Miaomiao , Si Haiyan , Zhang Yong , Qian Niansong , Wang Zhikuan , Shi Weiwei , Dai Guanghai
Published: March 2018

No definitive treatment strategy has been established for patients with metastatic colorectal cancer (mCRC) who experienced progression after three or more lines of chemotherapy. A total of 36 mCRC patients were enrolled in this retrospective study who received apatinib therapy under non-clinical trial setting after progression in People’s liberation army general Hospital from March 2015 and August 2017. Progression free survival (PFS), overall survival (OS), disease control rate (DCR), objective response rate (ORR) and treatment-related adverse events (AEs) were reviewed and evaluated. Five patients achieved partial response (PR), and 25 achieved stable disease (SD), and 6 achieved progression disease (PD), illustrating a DCR of 83.3% and an ORR of 13.9%. Median PFS was 3.82 m and median OS was not reached. The toxicities associated with apatinib were generally acceptable with a total grade 3/4 adverse event incidence of 27.8%. The most common grade 3/4 adverse events were hypertension (n = 4, 11.1%), liver function damage (n = 3, 8.3%) and hand–foot syndrome (n = 2, 5.6%). No drug-related death occurred. Apatinib therapy provides a reasonable option with an acceptable safety profile for Chinese mCRC patients failed to prior chemotherapy.
Sperm activation through orbital and self-axis revolutions using an artificial cilia embedded serpentine microfluidic platform
Authors: Panigrahi Bivas , Lu Chang-Hung , Ghayal Neha , Chen Chia-Yuan
Published: March 2018

The zebrafish sperm activation profoundly depends upon the homogeneous mixing of the sperm cells with its diluent in a quick succession as it alters the cell’s extracellular medium and initiates their motility. Manual stirring, the traditional method for zebrafish sperm activation is tedious, time-consuming, and has a poor outcome. In this aspect, an artificial cilia embedded serpentine microfluidic is designed through which hydrodynamic factors of the microfluidic environment can be precisely regulated to harness uniform mixing, hence ensuring a superior sperm activation. To quantify the sperm motility, computer assisted sperm analysis software (CASA) was used whereas to quantify the generated flow field, micro particle image velocimetry (μPIV) was used. With this proposed microfluidic, 74.4% of the zebrafish sperm were activated which is 20% higher than its currently existing manual measurements. The μPIV analysis demonstrates that the curvature of the microchannel induces an orbital rotation to the flow field along the length of the microchannel together with the artificial cilia actuation which instigates a local rotation to the flow field of the artificial cilia location. The collective rotation in the whole flow field induce vorticity that promotes the change in temporal dynamics of the sperm cells towards their activation.
Antiviral Effect of Ribavirin against HCV Associated with Increased Frequency of G-to-A and C-to-U Transitions in Infectious Cell Culture Model
Authors: Galli Andrea , Mens Helene , Gottwein Judith M. , Gerstoft Jan , Bukh Jens
Published: March 2018

Ribavirin (RBV) is a broad-spectrum antiviral active against a wide range of RNA viruses. Despite having been used for decades in the treatment of chronic hepatitis C virus (HCV) infection, the precise mechanism of action of RBV is unknown. In other viruses, it inhibits propagation by increasing the rate of G-to-A and C-to-U transitions. Here, we utilized the J6/JFH1 HCV cell-culture system to investigate whether RBV inhibits HCV through the same mechanism. Infected Huh7.5 cells were treated with increasing concentrations of RBV or its phosphorylated forms. A fragment of the HCV NS5B-polymerase gene was amplified, cloned, and sequenced to estimate genetic distances. We confirm that the antiviral effect of all three RBV-drug forms on HCV relies on induction of specific transitions (G-to-A and C-to-U). These mutations lead to generation of non-infectious virions, reflected by decreased spread of HCV in cell culture despite relatively limited effect on virus genome titers. Moreover, treatment experiments conducted on a novel Huh7.5 cell line stably overexpressing adenosine kinase, a key enzyme for RBV activation, yielded comparable results. This study indicates that RBV action on HCV in hepatoma cell-culture is exerted through increase in mutagenesis, mediated by RBV triphosphate, and leading to production of non-infectious viruses.
Long-term effects of mild traumatic brain injuries to oculomotor tracking performances and reaction times to simple environmental stimuli
Authors: Danna-Dos-Santos Alessander , Mohapatra Sambit , Santos Maria , Degani Adriana M.
Published: March 2018

Understanding the long-term effects of concussive events remains a challenge for the development of modern medical practices and the prevention of recurrent traumas. In this study, we utilized indices of oculomotor performance and the ability to react to simple environmental stimuli to assess the long-term motor effects of traumatic brain injury in its mildest form (mTBI). We performed analysis of eye movement accuracy, investigated the presence of abnormal eye movements, and quantified time to react to simple environmental stimuli on long-term mTBI survivors. Results indicated the presence of impairments to basic neural functions used to explore and respond to environmental demands long after the occurrence of mTBIs. Specifically, the result revealed the presence of abnormal saccadic eye movements while performing horizontal smooth pursuit, diminished accuracy of primary saccadic horizontal eye movement, and a widespread slower reaction to both visual and auditory stimuli. The methodology used in this study indicated to be potentially useful in aiding future investigations of neural circuitry impaired by mTBI and provide indices of recovery in future clinical trials testing mTBI-related clinical interventions.
Nd3+-doped transparent tellurite ceramics bulk lasers
Authors: Dolhen Morgane , Tanaka Masayuki , Couderc Vincent , Chenu Sébastien , Delaizir Gaëlle , Hayakawa Tomokatsu , Cornette Julie , Brisset François , Colas Maggy , Thomas Philippe , Duclère Jean-René
Published: March 2018

We report on the laser emission of the polycrystalline ceramic obtained from the full and congruent crystallization of the parent glass 1Nd3+:75TeO2-12.5Bi2O3-12.5Nb2O5 composition. In particular, the current work underlines the importance of carefully controlling the heat treatment in order to solely crystallize the Bi0.8Nb0.8Te2.4O8 cubic phase and consequently avoid the formation of the BiNbTe2O8 orthorhombic phase that would be detrimental for optical purpose. The structure, microstructure and photoluminescence properties of the resulting transparent tellurite ceramics are characterized. The continuous-wave and gain-switching laser performances reveal that the emission remains perfectly single transversal mode in the range of pump powers explored. The maximum output power achieved was ~28.5 mW, for a pump power threshold of ~67 mW, and with associated efficiency and slope efficiency of ~22.5% and ~50%, respectively. These data definitely stand among the best results obtained so far for bulk laser tellurite materials and thus demonstrate the potential of such polycrystalline transparent ceramics as optically active materials. Finally, the laser emission characteristics in pulsed regime, at low and high repetition rates, are also provided: more than 6.5 W of peak power at a repetition rate of 728 kHz can be obtained.
Author Correction: DNA metabarcoding and morphological macroinvertebrate metrics reveal the same changes in boreal watersheds across an environmental gradient
Authors: Emilson Caroline E. , Thompson Dean G. , Venier Lisa A. , Porter Teresita M. , Swystun Tom , Chartrand Derek , Capell Scott , Hajibabaei Mehrdad
Published: March 2018

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.
Author Correction: Periodontal pathogenic bacteria, Aggregatibacter actinomycetemcomitans affect non-alcoholic fatty liver disease by altering gut microbiota and glucose metabolism
Authors: Komazaki Rina , Katagiri Sayaka , Takahashi Hirokazu , Maekawa Shogo , Shiba Takahiko , Takeuchi Yasuo , Kitajima Yoichiro , Ohtsu Anri , Udagawa Sayuri , Sasaki Naoki , Watanabe Kazuki , Sato Noriko , Miyasaka Naoyuki , Eguchi Yuichiro , Anzai Keizo , Izumi Yuichi
Published: March 2018

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.
Engineering antimicrobial coating of archaeal poly-γ-glutamate-based materials using non-covalent crosslinkages
Authors: Ashiuchi Makoto , Hakumai Yuichi , Nakayama Sawami , Higashiuchi Haruna , Shimada Kosuke
Published: March 2018

We are now entering a new age of intelligent material development using fine, sustainable polymers from extremophiles. Herein we present an innovative (but simple) means of transforming archaeal poly-γ-glutamate (PGA) into extremely durable polyionic complexes with potent antimicrobial performance. This new supra-polymer material (called PGA/DEQ) was subjected to nuclear magnetic resonance and X-ray diffraction spectroscopies to characterize in structural chemistry. Calorimetric measurements revealed its peculiar thermal properties; to the best of our knowledge, it is one of the most heat-resistant biopolymer-based polyionic complexes developed to date. PGA/DEQ is particularly useful in applications where surface functionalization is important, e.g., antimicrobial coatings. The spontaneously assembled PGA/DEQ coatings (without any additional treatments) were remarkably resistant to certain organic solvents (including chloroform), even at high salt concentrations (theoretically greater than those found in sea water), and various pH values. However, the pH-response tests also implied that the PGA/DEQ coatings could be removed only when concentrated citrate di-salts were used, whereas most crosslinked polymer composites (e.g., thermoset matrices) are difficult to recycle and treat downstream. We also discuss PGA/DEQ-immobilized surfaces that exhibit enigmatic microbicidal mechanisms.
Cell pairing and polyethylene glycol (PEG)-mediated cell fusion using two-step centrifugation-assisted single-cell trapping (CAScT)
Authors: Huang Lu , Chen Yin , Huang Wei , Wu Hongkai
Published: March 2018

We present a strategy of two-step centrifugation-assisted single-cell trapping (CAScT) for heterotypic cell pairing and demonstrate its compatibility with polyethylene glycol (PEG)-mediated cell fusion.
Polymeric nanorods with aggregation-induced emission characteristics for enhanced cancer targeting and imaging
Authors: Feng Guangxue , Mao Duo , Liu Jie , Goh Chi Ching , Ng Lai Guan , Kong Deling , Tang Ben Zhong , Liu Bin
Published: March 2018

Bright polymeric AIE nanorods with higher tumor accumulation and more efficient tumor cell uptake are reported for enhanced cancer imaging.
Labeling of native proteins with fluorescent RAFT polymer probes: application to the detection of a cell surface protein using flow cytometry
Authors: Duret D. , Haftek-Terreau Z. , Carretier M. , Berki T. , Ladavière C. , Monier K. , Bouvet P. , Marvel J. , Leverrier Y. , Charreyre M.-T. , Favier A.
Published: March 2018

Fluorescent RAFT polymer probes with an activated ester reactive end-group can be advantageously used to label native proteins.
Iodoargentate/iodobismuthate-based materials hybridized with lanthanide-containing metalloviologens: thermochromic behaviors and photocurrent responses
Authors: Wang Dao-Hua , Zhao Li-Ming , Lin Xiao-Yan , Wang Yu-Kang , Zhang Wen-Ting , Song Kai-Yue , Li Hao-Hong , Chen Zhi-Rong
Published: March 2018

New hybrids combined metalloviologens with Ag/Cu iodides exhibit reversible thermochromisms, photocurrent responses, whose mechanisms are disclosed.
Heterotrimetallic complexes in molecular magnetism
Authors: Andruh Marius
Published: March 2018

The most representative examples of coordination compounds containing three different paramagnetic metal ions are reviewed, with a special emphasis on their magnetic properties.
Lewis acid catalyzed asymmetric [4+2] cycloaddition of cyclobutenones to synthesize α,β-unsaturated δ-lactones
Authors: Yao Qian , Yu Han , Zhang Hang , Dong Shunxi , Chang Fenzhen , Lin Lili , Liu Xiaohua , Feng Xiaoming
Published: March 2018

Here we report an efficient asymmetric cycloaddition of CO double bonds with cyclobutenones catalyzed by a chiral N,N′-dioxide/Yb(iii) complex.
Four 3d–4f heterometallic Ln45M7 clusters protected by mixed ligands
Authors: Fan Shen , Xu Su-Hui , Zheng Xiu-Ying , Yan Zhi-Hao , Kong Xiang-Jian , Long La-Sheng , Zheng Lan-Sun
Published: March 2018

A series of high-nuclearity 3d–4f clusters Ln45M7 were obtained based on acetate and propionate as mixed protecting ligands and ClO4− and CO32− as mixed anion templates.
NaCl as a solid solvent to assist the mechanochemical synthesis and post-synthesis of hierarchical porous MOFs with high I2vapour uptake
Authors: Yang Junyi , Feng Xiao , Lu Guangnong , Li Yulin , Mao Chaochao , Wen Zhongliang , Yuan Wenbing
Published: March 2018

The pore- and function-adjustable MOFs with high I2uptake are efficiently synthesized by salt-assisted mechanochemical reactions.
3D-printed Quake-style microvalves and micropumps
Authors: Lee Yuan-Sheng , Bhattacharjee Nirveek , Folch Albert
Published: March 2018

Here we demonstrate a 3D-printable microvalve that is transparent, built with a biocompatible resin, and has a simple architecture that can be easily scaled up into large arrays.
Intraword Variability in Children With Cochlear Implants: The Long-Term Development up to 5 Years of Age and a Comparison With Children With Normal Hearing
Authors: Faes Jolien , Gillis Steven
Published: March 2018

Purpose

This study evaluates intraword or token-to-token variability in the spontaneous speech of Dutch-speaking children with cochlear implants (CIs) longitudinally up to 5 years of age in comparison with intraword variability in age-matched peers with normal hearing (NH).

Method

Spontaneous speech samples of 9 children with CI were collected longitudinally up to age 5. The data of the NH control group consisted of cross-sectional recordings. Children's word productions were categorized into 4 response types of the variability score (consistent correct, consistent incorrect, variable with hits, variable with no hits), and the proportion of whole-word variation (PWV) was calculated.

Results

PWV was high in both groups of children but decreased with age. All response types of the variability score appeared in both groups. Children with CI were significantly more variable than their peers with NH up to age 4, but this difference has disappeared by age 5. Longer words had a higher PWV and were more often consistent incorrect and variable.

Conclusions

Intraword variability was characteristic of children with CI's spontaneous speech productions as it was in children with NH, and a similar factor (word length) affected variability in production. Group comparisons showed higher rates of intraword variability in children with CI, but they seemed to catch up with their peers with NH by age 5.
Playback continuity and video quality driven optimisation for dynamic adaptive streaming over HTTP clients over wireless networks
Authors: He Lijun , Liu Guizhong , Huang Xinyu
Published: March 2018

In this study, the authors focus on segment characteristic analysis and joint optimisation of modulation and coding scheme (MCS) selection, resource block (RB) assignment and the block error ratio (BLER) determination and segment adaptation scheme to satisfy dynamic adaptive streaming over HTTP (DASH) clients over wireless networks. First, the authors define a utility function as the continuous playback time that the packets scheduled with the allocated resource can support. Then, the authors formulate the MCS selection, RB assignment and BLER determination into a mathematical model. The relationship among the above three factors can be explored instead of performing MCS selection and RB assignment with the fixed BLER. By decomposing the original problem into some sub‐problems, the authors can get a solution to the original problem with low complexity. At the client level, the authors develop an adaptive segment request strategy based on the playback information, the segments' characteristics and the estimated transmission rate. To decrease the influence of the inaccurate estimations, an adaptive guard time interval based on the real playback information and transmission information of the previous segments is introduced. Simulation results show that the proposed algorithm can efficiently improve playback continuity and video quality over the existing algorithms.
Security analysis of M‐DES and key‐based coded permutation ciphers in wireless channels
Authors: Yap Wun‐She , Heng Swee‐Huay , Goi Bok‐Min
Published: March 2018

Encryption is primarily used to ensure the confidentiality of information transmitted over an insecure wireless channel. However, an encrypted signal may be received with some errors due to noise and interference in the wireless channel. To alleviate these errors in the received encrypted signal, Zibideh and Matalgah proposed two different versions of key‐based coded permutation cipher (KBCPC) aimed to improve the error performance and security of the transmission in the wireless channel. These two versions were designed based on the modified data encryption standard (M‐DES) and provide different levels of security. This study presents a divide‐and‐conquer attack on both M‐DES and KBCPC by exploiting the function that extends the length of output. Their analysis shows that these two ciphers can only provide 56‐bit level of security instead of the claimed 136‐bit and 173.67‐bit level of security for different versions. The authors' analysis is further verified through experiments. More importantly, their attack can be easily adapted to other schemes with a different encryption design but the same coding technique used in M‐DES or KBCPC.
Design and performance analysis of generalised carrier index M‐ary differential chaos shift keying modulation
Authors: Cheng Guixian , Wang Lin , Chen Qiwang , Chen Guanrong
Published: March 2018

In this study, two generalised carrier index M‐ary differential chaos shift keying (CI‐MDCSK) schemes are proposed, which combine index modulation with multicarrier M‐ary DCSK (MC‐MDCSK). At the transmitter, two different index selectors based on two different mapping rulers are employed to select active carriers, where the modulated bits are transmitted by the active carriers through M‐ary DCSK modulation, which is based on the Hilbert transform and constellation theory. At receiver, maximum or minimum energy detection is employed to determine the active carriers, where the bits carried on these active carriers are demodulated. The analytical bit error rate (BER) expressions over additive white Gaussian noise as well as multipath Rayleigh fading channels are derived. Simulations are performed with different numbers of carriers and different constellation sizes. Both analytical and simulation results show the superiority of the new schemes in BER performance or spectral efficiency (SE) compared with the MC‐MDCSK scheme. Moreover, compared with conventional DCSK, CI‐MDCSK schemes owns both better BER performance and SE in some cases, where the constellation is not greater than 8.
Imperfect CSI‐based large MIMO systems
Authors: M.K. Arti , Seema Shimpee
Published: March 2018

The authors address the problem of channel estimation and data detection in a large multiple‐input multiple‐output (MIMO) systems in Rayleigh fading environment. A method of channel estimation and data detection is proposed in large MIMO systems. The channel matrix is decomposed in channel matrices; where and are the number of antennas at the destination and source, respectively. The pilot signals are clubbed with data symbols encoded in orthogonal space‐time block codes (OSTBC), and then by using the properties of null matrix, channel estimation is performed. A decoder of OSTBC data is derived by assuming the perfect channel state information (CSI) at the destination; then perfect CSI is replaced by estimated CSI in the decision metric. The expression for the moment generating function (MGF) of the received signal‐to‐noise ratio at the destination node is derived for the proposed scheme. Using the MGF expressions, they obtain the analytical symbol error rate for the proposed channel estimation‐based decoders for general OSTBCs with M‐ary phase‐shift keying modulation symbols.
Global sizing optimisation using dual‐level response surface method based on mixed‐resolution central composite design for permanent magnet synchronous generators
Authors: Asef Pedram , Perpina Ramon Bargallo , Barzegaran Mohammadreza
Published: March 2018

This study presents a global sizing design optimisation of a permanent magnet synchronous generator (PMSG) using the three‐dimensional finite‐element analysis (3D FEA). To build an optimal parametric model structure, the efficiency improvement of the PMSG is taken as the main objective, where iron and copper losses were minimised. A dual‐level response surface methodology (D‐RSM) with a window‐zoom‐in approach for a variable‐speed‐range analysis as a global optimisation technique is employed to find out the optimal design variables of the objective function. The D‐RSM using mixed‐resolution central composite design (MR‐CCD), full factorial design, central composite design (CCD), and box‐Behnken design are applied to optimise the geometry with very small error. Analysis of variance and multi‐level RSM plots are used to check the adequacy of fit. However, the MR‐CCD exceeds the range of the boundary in the design region. Hence, a modified MR‐CCD is used that improves the efficiency and proposes the parameter settings to manufacture the high‐class quality wind generator. The validation of the analytical and numerical fashions is successfully achieved through rigorous FEA, and the experimental verifications perfectly marked the theoretical and significance optimisation design.
Study of rain attenuation effects for 5G Mm‐wave cellular communication in tropical location
Authors: Nandi Dalia , Maitra Animesh
Published: March 2018

Millimetre (mm)‐wave communication is a viable solution to the future 5G cellular services. For different temperate locations, rain attenuation does not contribute significantly to the overall path loss at the mm‐wave band for a small cell size of 200 m. However, in various tropical locations, the rain attenuation effect cannot be ignored even for this small cell size of the system. If the authors increase either frequency or path length, the attenuation increases significantly under tropical raining conditions. In this study, time series of predicted rain rate values are used for real‐time prediction of rain attenuation over terrestrial paths.
Low‐cost and reliable geometry scaling of compact microstrip couplers with respect to operating frequency, power split ratio, and dielectric substrate parameters
Authors: Koziel Slawomir , Bekasiewicz Adrian
Published: March 2018

A technique for rapid re‐design of miniaturised microstrip couplers with respect to operating conditions as well as material parameters of the dielectric substrate is proposed. The dimension scaling process is based on a set of pre‐optimised reference designs, obtained for an equivalent circuit model of the coupler at hand. The reference designs are utilised to construct an inverse surrogate model which – upon suitable correction – yields the optimum geometry parameter values of the structure re‐designed for required values of operating conditions and substrate parameters. An iterative fine‐tuning process necessary to account for the surrogate model inaccuracies is also developed. The proposed methodology is validated using a compact rat‐race coupler example. The obtained results demonstrate that accurate scaling is possible at a low cost of up to three EM simulations of the structure. For a considered example, the scaling is realised within a wide range of operating conditions (1–2 GHz for the operating frequency, −3 to 0 dB for power split) and substrate parameters (0.7–1.5 mm for the thickness, and 2.5–3.5 for dielectric permittivity). Numerical results are validated experimentally.
Laboratory verification of Fast & Furious phase diversity: Towards controlling the low wind effect in the SPHERE instrument
Authors: Wilby M. J. , Keller C. U. , Sauvage J.-F. , Dohlen K. , Fusco T. , Mouillet D. , Beuzit J.-L.
Published: March 2018

Context. The low wind effect (LWE) refers to a characteristic set of quasi-static wavefront aberrations seen consistently by the SPHERE instrument when dome-level wind speeds drop below 3 ms−1. The LWE produces bright low-order speckles in the stellar point-spread function (PSF), which severely limit the contrast performance of SPHERE under otherwise optimal observing conditions.

Aims. In this paper we propose the Fast & Furious (F&F) phase diversity algorithm as a viable software-only solution for real-time LWE compensation, which would utilise image sequences from the SPHERE differential tip-tilt sensor (DTTS) and apply corrections via reference slope offsets on the AO system’s Shack-Hartmann wavefront sensor.

Methods. We evaluated the closed-loop performance of F&F on the MITHIC high-contrast test-bench, under conditions emulating LWE-affected DTTS images. These results were contrasted with predictive simulations for a variety of convergence tests, in order to assess the expected performance of an on-sky implementation of F&F in SPHERE.

Results. The algorithm was found to be capable of returning LWE-affected images to Strehl ratios of greater than 90% within five iterations, for all appropriate laboratory test cases. These results are highly representative of predictive simulations, and demonstrate stability of the algorithm against a wide range of factors including low image signal-to-noise ratio (S/N), small image field of view, and amplitude errors. It was also found in simulation that closed-loop stability can be preserved down to image S/N as low as five while still improving overall wavefront quality, allowing for reliable operation even on faint targets.

Conclusions. The Fast & Furious algorithm is an extremely promising solution for real-time compensation of the LWE, which can operate simultaneously with science observations and may be implemented in SPHERE without requiring additional hardware. The robustness and relatively large effective dynamic range of F&F also make it suitable for general wavefront optimisation applications, including the co-phasing of segmented ELT-class telescopes.
A statistical analysis of two-dimensional patterns and its application to astrometry
Authors: Zavada Petr , Píška Karel
Published: March 2018

Here we develop a general statistical procedure for the analysis of finite two-dimensional (2D) patterns inspired by the analysis of heavy-ion data. The method is used in the study of publicly available data obtained by the Gaia-ESA mission. We prove that the procedure can be sensitive to the limits of accuracy of measurement, and can also clearly identify the real physical effects on the large background of random distributions. As an example, the method confirms the presence of binary and ternary star systems in the studied data. At the same time, the possibility of the statistical detection of the gravitational microlensing effect is discussed.
The minimal resistance problem in a class of non convex bodies
Authors: Mainini Edoardo , Monteverde Manuel , Oudet Edouard , Percivale Danilo
Published: March 2018

We characterize the solution to the Newton minimal resistance problem in a class of radial q-concave profiles. We also give the corresponding result for one-dimensional profiles. Moreover, we provide a numerical optimization algorithm for the general nonradial case.
Rapidly Expanding Lateral Ventricular Meningioma Presenting with Intraventricular Hemorrhage following Remote Whole Brain Radiation and Stereotactic Radiosurgery
Authors: Prickett Joshua , Klein Brendan , Busch Christopher , Cuoco Joshua , Apfel Lisa , Marvin Eric
Published: March 2018

Intraventricular meningiomas are uncommon intracranial tumors and infrequently present with hemorrhage. With only 10 reported cases in the literature, it is exceedingly rare for meningiomas of the ventricular system to present with hemorrhage. To our knowledge, this is the first report of a patient presenting with an acute intraventricular hemorrhage in relation to a ventricular meningioma suspected to be radiation induced. In addition, we review the current literature on hemorrhagic intraventricular meningiomas and review the natural history of radiation-induced meningiomas.
Exact analytical solutions of the Schrödinger equation for a two dimensional purely sextic double-well potential
Authors: Le Dai-Nam , Hoang Ngoc-Tram D. , Le Van-Hoang
Published: March 2018

Exact analytical solutions of the Schrödinger equation for a two-dimensional purely sextic double-well potential are proved to exist for a denumerably infinite set of the geometry parameter of the well. First, the geometry values which allow exact solutions are determined. Then, explicit wave functions and corresponding energies are calculated for the allowed geometry values. Concrete exact solutions are given for the principal quantum number n up to 10. Moreover, some interesting rules for the obtained exact analytical solutions are also given; particularly, the number of negative energy levels for a given geometry parameter is obtained. For analyzing the obtained exact solutions and for their classification by quantum number, we also use numerical calculations by the Feranchuk-Komarov operator method.
A fully automated temperature-dependent resistance measurement setup using van der Pauw method
Authors: Pandey Shivendra Kumar , Manivannan Anbarasu
Published: March 2018

The van der Pauw (VDP) method is widely used to identify the resistance of planar homogeneous samples with four contacts placed on its periphery. We have developed a fully automated thin film resistance measurement setup using the VDP method with the capability of precisely measuring a wide range of thin film resistances from few mΩ up to 10 GΩ under controlled temperatures from room-temperature up to 600 °C. The setup utilizes a robust, custom-designed switching network board (SNB) for measuring current-voltage characteristics automatically at four different source-measure configurations based on the VDP method. Moreover, SNB is connected with low noise shielded coaxial cables that reduce the effect of leakage current as well as the capacitance in the circuit thereby enhancing the accuracy of measurement. In order to enable precise and accurate resistance measurement of the sample, wide range of sourcing currents/voltages are pre-determined with the capability of auto-tuning for ∼12 orders of variation in the resistances. Furthermore, the setup has been calibrated with standard samples and also employed to investigate temperature dependent resistance (few Ω–10 GΩ) measurements for various chalcogenide based phase change thin films (Ge2Sb2Te5, Ag5In5Sb60Te30, and In3SbTe2). This setup would be highly helpful for measurement of temperature-dependent resistance of wide range of materials, i.e., metals, semiconductors, and insulators illuminating information about structural change upon temperature as reflected by change in resistances, which are useful for numerous applications.
Passive inference of collision frequency in magnetized capacitive argon discharge
Authors: Binwal S. , Joshi J. K. , Karkari S. K. , Kaw P. K. , Nair L.
Published: March 2018

A non-invasive method of determining the collision frequency νm by measuring the net plasma impendence in a magnetized, capacitive-coupled, radio-frequency (rf) discharge circuit is developed. The collision frequency has been analytically expressed in terms of bulk plasma reactance, wherein standard sheath models have been used to estimate the reactance offered due to the capacitive rf sheaths at the discharge plates. The experimental observations suggest that in the un-magnetized case, νm remains constant over a range of rf current but steadily increases as the background pressure reduces. In the magnetized case, the collision frequency has been observed to decay with the increase in rf current while it remains unaffected by the background pressure. A qualitative discussion has been presented to explain these characteristics.
B1-B2 phase transition mechanism and pathway of PbS under pressure
Authors: Adeleke Adebayo A. , Yao Yansun
Published: March 2018

Experimental studies at finite Pressure-Temperature (P-T) conditions and a theoretical study at 0 K of the phase transition in lead sulphide (PbS) have been inconclusive. Many studies that have been done to understand structural transformation in PbS can broadly be classified into two main ideological streams—one with Pnma and another with Cmcm orthorhombic intermediate phase. To foster better understanding of this phenomenon, we present the result of the first-principles study of phase transition in PbS at finite temperature. We employed the particle swarm-intelligence optimization algorithm for the 0 K structure search and first-principles metadynamics simulations to study the phase transition pathway of PbS from the ambient pressure, 0 K Fm-3m structure to the high-pressure Pm-3m phase under experimentally achievable P-T conditions. Significantly, our calculation shows that both streams are achievable under specific P-T conditions. We further uncover new tetragonal and monoclinic structures of PbS with space group P21/c and I41/amd, respectively. We propose the P21/c and I41/amd as a precursor phase to the Pnma and Cmcm phases, respectively. We investigated the stability of the new structures and found them to be dynamically stable at their stability pressure range. Electronic structure calculations reveal that both P21/c and I41/amd phases are semiconducting with direct and indirect bandgap energies of 0.69(5) eV and 0.97(3) eV, respectively. In general, both P21/c and I41/amd phases were found to be energetically competitive with their respective orthorhombic successors.
Tuning of polarization, internal electric field, and hysteresis loop behaviours in BaTiO3/BaxSr1-xTiO3 superlattices
Authors: Lim Kok-Geng , Chew Khian-Hooi
Published: March 2018

A thermodynamic model based on the Landau-Ginzburg theory is developed to study the polarization and hysteresis loop behaviors in ferroelectric superlattices with technologically important BaxSr1-xTiO3 (BST) solid solutions. Our study shows that the polarization, coercive field, and hysteresis loop behaviors can be tailored by changing the thickness ratio and the Ba/Sr content of BST. The study also found that the sign of the internal fields depends sensitively on both thickness ratio and Ba/Sr content of BST. Both results imply that the internal electric field of superlattice can be tuned to yield zero polarizing or depolarizing field via manipulation of thickness ratio and composition. These findings could pave the way to enhance the efficiency of ferroelectric photovoltaic devices by manipulating the internal electric field through thickness and composition.
An experimental platform for pulsed-power driven magnetic reconnection
Authors: Hare J. D. , Suttle L. G. , Lebedev S. V. , Loureiro N. F. , Ciardi A. , Chittenden J. P. , Clayson T. , Eardley S. J. , Garcia C. , Halliday J. W. D. , Robinson T. , Smith R. A. , Stuart N. , Suzuki-Vidal F. , Tubman E. R.
Published: March 2018

We describe a versatile pulsed-power driven platform for magnetic reconnection experiments, based on the exploding wire arrays driven in parallel [Suttle et al., Phys. Rev. Lett. 116, 225001 (2016)]. This platform produces inherently magnetised plasma flows for the duration of the generator current pulse (250 ns), resulting in a long-lasting reconnection layer. The layer exists for long enough to allow the evolution of complex processes such as plasmoid formation and movement to be diagnosed by a suite of high spatial and temporal resolution laser-based diagnostics. We can access a wide range of magnetic reconnection regimes by changing the wire material or moving the electrodes inside the wire arrays. We present results with aluminium and carbon wires, in which the parameters of the inflows and the layer that forms are significantly different. By moving the electrodes inside the wire arrays, we change how strongly the inflows are driven. This enables us to study both symmetric reconnection in a range of different regimes and asymmetric reconnection.
Efficient frequency conversion by combined photonic–plasmonic mode coupling
Authors: Weber N. , Hoffmann S. P. , Albert M. , Zentgraf T. , Meier C.
Published: March 2018

Due to its strong nonlinear susceptibility tensor components, zinc oxide (ZnO) provides highly efficient frequency conversion when excited with near-infrared pulses. Three-photon absorption offers an alternative to conventional ultraviolet sources for sub-bandgap excitation of ZnO. In this work, plasmonic nanoantennas are used to enhance coupling of infrared light into photonic ZnO resonators. The nanoantennas provide a strong field localization, which allows for a more efficient second- and third-harmonic generation within the ZnO film, as well as an immensely increased spontaneous photoluminescence emission due to interband absorption. The results demonstrate that the combination of plasmonic nanoantennas with photonic microresonators leads to a strongly enhanced nonlinear light-matter-interaction in thin ZnO films.
A non-JKL density matrix functional for intergeminal correlation between closed-shell geminals from analysis of natural orbital configuration interaction expansions
Authors: van Meer R. , Gritsenko O. V. , Baerends E. J.
Published: March 2018

Almost all functionals that are currently used in density matrix functional theory have been created by some a priori ansatz that generates approximations to the second-order reduced density matrix (2RDM). In this paper, a more consistent approach is used: we analyze the 2RDMs (in the natural orbital basis) of rather accurate multi-reference configuration interaction expansions for several small molecules (CH4, NH3, H2O, FH, and N2) and use the knowledge gained to generate new functionals. The analysis shows that a geminal-like structure is present in the 2RDMs, even though no geminal theory has been applied from the onset. It is also shown that the leading non-geminal dynamical correlation contributions are generated by a specific set of double excitations. The corresponding determinants give rise to non-JKL (non Coulomb/Exchange like) multipole-multipole dispersive attractive terms between geminals. Due to the proximity of the geminals, these dispersion terms are large and cannot be omitted, proving pure JKL functionals to be essentially deficient. A second correction emerges from the observation that the “normal” geminal-like exchange between geminals breaks down when one breaks multiple bonds. This problem can be fixed by doubling the exchange between bond broken geminals, effectively restoring the often physically correct high-spin configurations on the bond broken fragments. Both of these corrections have been added to the commonly used antisymmetrized product of strongly orthogonal geminals functional. The resulting non-JKL functional Extended Löwdin-Shull Dynamical-Multibond is capable of reproducing complete active space self-consistent field curves, in which one active orbital is used for each valence electron.
Characterization of iron in silicon by low-temperature photoluminescence and deep-level transient spectroscopy
Authors: Nakamura Minoru , Murakami Susumu , Udono Haruhiko
Published: March 2018

We investigate the relationship between the intensity of band-edge (BDE) photoluminescence (PL) from 10 to 70 K and the concentration of iron diffused in boron-doped p-type silicon. Because of the nonradiative recombination activity of the interstitial iron-boron complex (FeiB center), the BDE-PL intensity at each temperature varies distinctively and systematically with the iron concentration, which means that this method has the potential to make the accurate measurements of a wide range of interstitial iron concentrations in silicon. The iron precipitates formed in the bulk and/or at the surface are found to exert much weaker recombination activity for excess carriers than FeiB center by exploiting both PL and deep-level transient spectroscopy (DLTS) measurements. The unexpected enhancement in BDE-PL intensity from iron-diffused silicon between 20 and 50 K is attributed to the passivation of the Si-oxide/Si interface by iron. For the samples diffused with trace amounts of iron, the iron concentration within 20 μm of the surface is significantly greater than that in the bulk, as measured by DLTS. This result is tentatively attributed to the affinity of iron with the Si-oxide.
Shock interactions with heterogeneous energetic materials
Authors: Yarrington Cole D. , Wixom Ryan R. , Damm David L.
Published: March 2018

The complex physical phenomenon of shock wave interaction with material heterogeneities has significant importance and nevertheless remains little understood. In many materials, the observed macroscale response to shock loading is governed by characteristics of the microstructure. Yet, the majority of computational studies aimed at predicting phenomena affected by these processes, such as the initiation and propagation of detonation waves in explosives or shock propagation in geological materials, employ continuum material and reactive burn model treatment. In an effort to highlight the grain-scale processes that underlie the observable effects in an energetic system, a grain-scale model for hexanitrostilbene (HNS) has been developed. The measured microstructures were used to produce synthetic computational representations of the pore structure, and a density functional theory molecular dynamics derived equation of state (EOS) was used for the fully dense HNS matrix. The explicit inclusion of the microstructure along with a fully dense EOS resulted in close agreement with historical shock compression experiments. More recent experiments on the dynamic reaction threshold were also reproduced by inclusion of a global kinetics model. The complete model was shown to reproduce accurately the expected response of this heterogeneous material to shock loading. Mesoscale simulations were shown to provide a clear insight into the nature of threshold behavior and are a way to understand complex physical phenomena.
Defect stabilization and reverse annealing in ZnO implanted with nitrogen at room and cryogenic temperature
Authors: Azarov Alexander , Wendler Elke , Monakhov Edouard , Svensson Bengt G.
Published: March 2018

Despite the fact that nitrogen is a potential acceptor dopant and one of the most studied elements in ZnO, lacking understanding of associated defects and their thermal evolution limits realization of reliable p-type doping of ZnO. Here, we use ion implantation to introduce N at room temperature (RT) and 15 K in ZnO samples with/without a pre-existing buried disorder layer formed by Ag ion bombardment aligned along the [0001] direction. The buried layer contains a high concentration of extended defects, which act as traps for migrating point defects. Channeling analysis shows that reverse annealing occurs in all the N implanted samples during post-implant heat treatment above 600 °C with strong non-linear additive damage accumulation in the co-implanted samples. The reverse annealing effect is less stable in the RT co-implanted sample and the data suggest that a high local concentration of intrinsic point defects, like Zn interstitials, promotes the stability of the N-defect clusters responsible for the reverse annealing. This suggestion is also corroborated by enhanced and defect-mediated Ag outdiffusion at 1100 °C in the RT co-implanted samples.
Structure and magnetic properties of an epitaxial Fe(110)/MgO(111)/GaN(0001) heterostructure
Authors: Khalid N. , Kim J.-Y. , Ionescu A. , Hussain T. , Oehler F. , Zhu T. , Oliver R. A. , Farrer I. , Ahmad R. , Barnes C. H. W.
Published: March 2018

We present the structural and magnetic properties of fully epitaxial Fe(110)/MgO(111)/GaN(0001) tunnel barrier structures grown by molecular beam epitaxy. In-situ reflection high-energy electron diffraction and ex-situ X-ray diffraction measurements indicate epitaxial Fe(110) films on top of an epitaxial 2 nm MgO(111) tunnel barrier on GaN(0001). X-ray reflectivity measurements confirm a roughness of approximately 0.3 nm and 0.7 nm for the MgO/GaN and the Fe/MgO interfaces, respectively. Results of in-situ magneto-optical Kerr effect measurements indicate that 1 nm thick Fe film shows signs of in-plane ferromagnetism at room temperature. Vibrating sample magnetometer measurements determine the saturation magnetisation of the 5 nm thick film to be 1660 ± 100 emu/cm3 and show that this system has a predominant uniaxial anisotropy contribution despite the presence of cyclic twinned crystals. We estimate the values of effective uniaxial (KUeff) and cubic (K1eff) anisotropy constants to be 11700 ± 170 erg cm−3 and −3300 ± 700 erg cm−3 by fitting the angular dependence of the magnetising energy.
High-efficiency ventilated metamaterial absorber at low frequency
Authors: Wu Xiaoxiao , Au-Yeung Ka Yan , Li Xin , Roberts Robert Christopher , Tian Jingxuan , Hu Chuandeng , Huang Yingzhou , Wang Shuxia , Yang Zhiyu , Wen Weijia
Published: March 2018

We demonstrate a ventilated metamaterial absorber operating at low frequency (<500 Hz). With only two layers of absorption units, high-efficiency absorption (>90%) has been achieved in both simulations and experiments. This high-efficiency absorption under the ventilation condition originates from the weak coupling of two identical split tube resonators constituting the absorber, which leads to the hybridization of the degenerate eigenmodes and breaks the absorption upper limit of 50% for conventional transmissive symmetric acoustic absorbers. The absorber can also be extended to an array and work in free space. The absorber should have potential applications in acoustic engineering where both noise reduction and ventilation are required.