bluuebunny/crossref_metadata_2025 huggingface dataset:
MNKs act as a regulatory switch for eIF4E1 and eIF4E3 driven mRNA translation in DLBCL
Authors: Landon Ari L. , Muniandy Parameswary A. , Shetty Amol C. , Lehrmann Elin , Volpon Laurent , Houng Simone , Zhang Yongqing , Dai Bojie , Peroutka Raymond , Mazan-Mamczarz Krystyna , Steinhardt James , Mahurkar Anup , Becker Kevin G. , Borden Katherine L. , Gartenhaus Ronald B.
Published: November 2014

The phosphorylation of eIF4E1 at serine 209 by MNK1 or MNK2 has been shown to initiate oncogenic mRNA translation, a process that favours cancer development and maintenance. Here, we interrogate the MNK-eIF4E axis in diffuse large B-cell lymphoma (DLBCL) and show a distinct distribution of MNK1 and MNK2 in germinal centre B-cell (GCB) and activated B-cell (ABC) DLBCL. Despite displaying a differential distribution in GCB and ABC, both MNKs functionally complement each other to sustain cell survival. MNK inhibition ablates eIF4E1 phosphorylation and concurrently enhances eIF4E3 expression. Loss of MNK protein itself downregulates total eIF4E1 protein level by reducing eIF4E1 mRNA polysomal loading without affecting total mRNA level or stability. Enhanced eIF4E3 expression marginally suppresses eIF4E1-driven translation but exhibits a unique translatome that unveils a novel role for eIF4E3 in translation initiation. We propose that MNKs can modulate oncogenic translation by regulating eIF4E1-eIF4E3 levels and activity in DLBCL.
Structure and function of a spectrin-like regulator of bacterial cytokinesis
Authors: Cleverley Robert M. , Barrett Jeffrey R. , Baslé Arnaud , Bui Nhat Khai , Hewitt Lorraine , Solovyova Alexandra , Xu Zhi-Qiang , Daniel Richard A. , Dixon Nicholas E. , Harry Elizabeth J. , Oakley Aaron J. , Vollmer Waldemar , Lewis Richard J.
Published: November 2014

Bacterial cell division is facilitated by a molecular machine—the divisome—that assembles at mid-cell in dividing cells. The formation of the cytokinetic Z-ring by the tubulin homologue FtsZ is regulated by several factors, including the divisome component EzrA. Here we describe the structure of the 60-kDa cytoplasmic domain of EzrA, which comprises five linear repeats of an unusual triple helical bundle. The EzrA structure is bent into a semicircle, providing the protein with the potential to interact at both N- and C-termini with adjacent membrane-bound divisome components. We also identify at least two binding sites for FtsZ on EzrA and map regions of EzrA that are responsible for regulating FtsZ assembly. The individual repeats, and their linear organization, are homologous to the spectrin proteins that connect actin filaments to the membrane in eukaryotes, and we thus propose that EzrA is the founding member of the bacterial spectrin family.
Period doubling induced by thermal noise amplification in genetic circuits
Authors: Ruocco G. , Fratalocchi A.
Published: November 2014

Rhythms of life are dictated by oscillations, which take place in a wide rage of biological scales. In bacteria, for example, oscillations have been proven to control many fundamental processes, ranging from gene expression to cell divisions. In genetic circuits, oscillations originate from elemental block such as autorepressors and toggle switches, which produce robust and noise-free cycles with well defined frequency. In some circumstances, the oscillation period of biological functions may double, thus generating bistable behaviors whose ultimate origin is at the basis of intense investigations. Motivated by brain studies, we here study an “elemental” genetic circuit, where a simple nonlinear process interacts with a noisy environment. In the proposed system, nonlinearity naturally arises from the mechanism of cooperative stability, which regulates the concentration of a protein produced during a transcription process. In this elemental model, bistability results from the coherent amplification of environmental fluctuations due to a stochastic resonance of nonlinear origin. This suggests that the period doubling observed in many biological functions might result from the intrinsic interplay between nonlinearity and thermal noise.
Nonstationary Precipitation Intensity-Duration-Frequency Curves for Infrastructure Design in a Changing Climate
Authors: Cheng Linyin , AghaKouchak Amir
Published: November 2014

Extreme climatic events are growing more severe and frequent, calling into question how prepared our infrastructure is to deal with these changes. Current infrastructure design is primarily based on precipitation Intensity-Duration-Frequency (IDF) curves with the so-called stationary assumption, meaning extremes will not vary significantly over time. However, climate change is expected to alter climatic extremes, a concept termed nonstationarity. Here we show that given nonstationarity, current IDF curves can substantially underestimate precipitation extremes and thus, they may not be suitable for infrastructure design in a changing climate. We show that a stationary climate assumption may lead to underestimation of extreme precipitation by as much as 60%, which increases the flood risk and failure risk in infrastructure systems. We then present a generalized framework for estimating nonstationary IDF curves and their uncertainties using Bayesian inference. The methodology can potentially be integrated in future design concepts.
Potential microRNA-mediated oncogenic intercellular communication revealed by pan-cancer analysis
Authors: Li Yue , Zhang Zhaolei
Published: November 2014

Carcinogenesis consists of oncogenesis and metastasis and intriguingly microRNAs (miRNAs) are involved in both processes. Although aberrant miRNA activities are prevalent in diverse tumor types, the exact mechanisms for how they regulate cancerous processes are not always clear. To this end, we performed a large-scale pan-cancer analysis via a novel probabilistic approach to infer recurrent miRNA-target interactions implicated in 12 cancer types using data from The Cancer Genome Atlas. We discovered ~20,000 recurrent miRNA regulations, which are enriched for cancer-related miRNAs/genes. Notably, miRNA 200 family (miR-200/141/429) is among the most prominent miRNA regulators, which is known to be involved in metastasis. Importantly, the recurrent miRNA regulatory network is not only enriched for cancer pathways but also for extracellular matrix (ECM) organization and ECM-receptor interactions. The results suggest an intriguing cancer mechanism involving miRNA-mediated cell-to-cell communication, which possibly involves delivery of tumorigenic miRNA messengers to adjacent cells via exosomes. Finally, survival analysis revealed 414 recurrent-prognostic associations, where both gene and miRNA involved in each interaction conferred significant prognostic power in one or more cancer types. Together, our comprehensive pan-cancer analysis provided not only biological insights into metastasis but also brought to bear the clinical relevance of the proposed recurrent miRNA-gene associations.
An Fe3O4@SiO2@polypyrrole magnetic nanocomposite for the extraction and preconcentration of Cd(ii) and Ni(ii)
Authors: Abolhasani Jafar , Khanmiri Rahim Hosseinzadeh , Ghorbani-Kalhor Ebrahim , Hassanpour Akbar , Asgharinezhad Ali Akbar , Shekari Nafiseh , Fathi Ahoura
Published: November 2014

A schematic diagram for the synthesis of Fe3O4@SiO2@polypyrrole nanocomposite.
Double-beam near-infrared spectroscopy to correct light source drift in aqueous glucose solution experiments
Authors: Min Xiaolin , Liu Rong , Hu Yongxiang , Fu Bo , Xu Kexin
Published: November 2014

Standard sample correction and reference design for exact extraction of the analyte of interest are investigated in this paper.
A novel leucine zipper motif-based hybrid peptide delivers a functional peptide cargo inside cells
Authors: Hakata Y. , Tsuchiya S. , Michiue H. , Ohtsuki T. , Matsui H. , Miyazawa M. , Kitamatsu M.
Published: November 2014

We delivered a hybrid of an autophagy-inducing peptide and a cell-penetrating peptide via heterodimeric leucine zippers into the cell. By this method, the peptide successfully induced autophagy without significant cell death.
The direct α-C(sp3)–H functionalisation of N-aryl tetrahydroisoquinolines via an iron-catalysed aerobic nitro-Mannich reaction and continuous flow processing
Authors: Brzozowski Martin , Forni Jose A. , Paul Savage G. , Polyzos Anastasios
Published: November 2014

An efficient nitro-Mannich type direct α-C(sp3)–H functionalisation of N-aryl-1,2,3,4-tetrahydroisoquinolines catalysed by simple iron salts in combination with O2 as the terminal oxidant is described.
Intermediates caught in the act: tracing insulin amyloid fibril formation in time by combined optical spectroscopy, light scattering, mass spectrometry and microscopy
Authors: Gladytz A. , Lugovoy E. , Charvat A. , Häupl T. , Siefermann K. R. , Abel B.
Published: November 2014

Insulin under acidic conditions. PDB-Databank structure visualized with VMD.
Fluorescent, MRI, and colorimetric chemical sensors for the first-row d-block metal ions
Authors: Zhu Hao , Fan Jiangli , Wang Benhua , Peng Xiaojun
Published: November 2014

This critical review focuses on the development of fluorescent sensors (fall into three classes: “turn-off”, “turn-on”, and ratiometric), colorimetric sensors, and responsive MRI contrast agents for the first-row d-block metals (except Cu and Zn): Cr, Mn, Fe, Co, and Ni (242 references).
Preparation and characterization of potassium nickel hexacyanoferrate-loaded hydrogel beads for the removal of cesium ions
Authors: Dwivedi Charu , Pathak Sanjay K. , Kumar Manmohan , Tripathi Subhash C. , Bajaj Parma N.
Published: November 2014

A novel synthetic approach has been used to prepare sorbent hydrogel composite beads of potassium nickel hexacyanoferrate (KNiHCF), using PVA and cross-linked alginate as the binding matrix.
Towards microfluidic-based depletion of stiff and fragile human red cells that accumulate during blood storage
Authors: Huang Sha , Hou Han Wei , Kanias Tamir , Sertorio Jonas Tadeu , Chen Huichao , Sinchar Derek , Gladwin Mark T. , Han Jongyoon
Published: November 2014

In this study, the effects of prolonged storage on several biophysical properties of red blood cells (RBCs) were investigated.
An integrated centrifugo-opto-microfluidic platform for arraying, analysis, identification and manipulation of individual cells
Authors: Burger R. , Kurzbuch D. , Gorkin R. , Kijanka G. , Glynn M. , McDonagh C. , Ducrée J.
Published: November 2014

In this work we present a centrifugal microfluidic system enabling highly efficient collective trapping and alignment of particles such as microbeads and cells, their multi-colour fluorescent detection and subsequent manipulation by optical tweezers.
From Ni-based nanoprecursors to NiO nanostructures: morphology-controlled synthesis and structure-dependent electrochemical behavior
Authors: Cheng Gang , Yan Yinan , Chen Rong
Published: November 2014

Phase transformation and morphology tailoring of NiO nanostructures employed for supercapacitor electrodes have been achieved using the Ni-based nanostructure precursors synthesized via a facile urea-controlled hydrothermal method.
A metal–organic framework as a highly efficient and reusable catalyst for the solvent-free 1,3-dipolar cycloaddition of organic azides to alkynes
Authors: Li Peng , Regati Sridhar , Huang Huicai , Arman Hadi D. , Zhao John C.-G. , Chen Banglin
Published: November 2014

A new highly efficient and reusable Cu-MOF has been developed for the regioselective synthesis of 1,2,3-triazoles via the 1,3-dipolar cycloaddition of organic azides to terminal alkynes under solvent-free conditions.
Polymeric ionic liquid modified reduced graphene oxide as adsorbent for highly selective isolation of acidic protein
Authors: Liu Jia-Wei , Wang Meng-Meng , Zhang Yue , Han Lu , Chen Xu-Wei , Wang Jian-Hua
Published: November 2014

A novel adsorbent is achieved by modifying reduced graphene oxide with polymeric ionic liquid and further assembly on SiO2nanoparticles. This nano-hybrid exhibits selective adsorption of ovalbumin with an ultra-high sorption capacity.
Ameliorating acidic soil using bioelectrochemistry systems
Authors: Zheng Yue , Wang Chao , Zheng Zhi-Yong , Che Jing , Xiao Yong , Yang Zhao-hui , Zhao Feng
Published: November 2014

Soil acidification has been a threat to sustainable agricultural development as a global environmental problem.
Triptycene based organosoluble polyamides: synthesis, characterization and study of the effect of chain flexibility on morphology
Authors: Mondal Snehasish , Das Neeladri
Published: November 2014

Triptycene based thermally stable, organosoluble and low viscous polyamides have been prepared. Polymers may be categorized as self-extinguishing materials. Relation between structural flexibility and surface morphology has been studied.
Fabrication of gold/polypyrrole core/shell nanowires on a flexible substrate for molecular imprinted electrochemical sensors
Authors: Huang Wei-Ren , Chen Yu-Liang , Lee Chi-Young , Chiu Hsin-Tien
Published: November 2014

Gold/polypyrrole core/shell nanowires electrochemically grown on flexible substrates are used as molecular imprinted polymer biosensors for dopamine detection.
Comprehensive study on a 2 × 2 full‐rate and linear decoding complexity space–time block code
Authors: Hosseini Seyyed Saleh , Talebi Siamak , Abouei Jamshid
Published: November 2014

This paper presents a comprehensive study on the Full‐Rate and Linear‐Receiver (FRLR) STBC proposed as a newly coding scheme with the low decoding complexity for a 2×2 MIMO system. It is shown that the FRLR code suffers from the lack of the non‐vanishing determinant (NVD) property that is a key parameter in designing a full‐rate STBC with a good performance in higher data rates, across QAM constellation. To overcome this drawback, we show that the existence of the NVD feature for the FRLR code depends on the type of the modulation. In particular, it is analytically proved that the FRLR code fulfills the NVD property across the PAM constellation but not for the QAM scheme. Simulation results show that, at a BER equal to 10−4, utilising the PAM modulation for the FRLR‐STBC, provides about 2 dB gain over a use of the QAM when the bandwidth efficiency is 6b/s/Hz. In addition, for the PAM constellation, the FRLR code significantly outperforms some existing full‐rate STBCs. Finally, we utilise the moment generating function approach to derive an exact closed‐form expression for the average error probability of the FRLR code with the BPSK modulation.
Experience with Mandibular Reconstruction Using Transport-Disc-Distraction Osteogenesis
Authors: Pingarrón-Martín Lorena , Otero T. González , Gallo L.J.Arias
Published: November 2014

The goal of transport-disc-distraction osteogenesis (TDDO) is to restore bone continuity by using in-situ bone. It may be useful following trauma, gunshot injuries, or tumor ablation, especially when there may be contraindications at the donor site or for prolonged surgery. To the best of the authors’ knowledge, this is the first time TDDO has been used for mandibular reconstruction reporting additional procedures, which include osseointegrated dental implants rehabilitation and orthognathic surgery. A retrospective study is performed analyzing all mandibular reconstruction cases that may be suitable for distraction from January 2006 to December 2011. A thorough description of the documented cases includes details about sex, gender, complications, duration of hospitalization, etiology, size, and location of the defect. Eight cases of mandibular reconstruction were included. Six cases correspond to mandibular ameloblastoma. The remaining two cases were mandibular gunshot comminuted fractures. Range of the defects was from 45 to 60 mm. Length of the transport disc was 15 to 20 mm. Protocolized technique consisted of 5 days of latency period, 19 to 45 days of activation term (average 30 days), and 8 to 12 weeks for consolidation. Mean distraction length achieved was 40.45 mm. We can conclude that TDDO is an alternative to conventional and more invasive procedures, when we face severe segmental mandibular defects reconstruction. It shows the potential to restore a better anatomical bone regeneration, also providing soft tissues and reducing donor-site morbidity. Patients’ education and awareness about the proper use of the transport-disc-distraction device is important to optimize functional outcomes.
Current sheath formation dynamics and structure for different insulator lengths of plasma focus device
Authors: Seng Y. S. , Lee P. , Rawat R. S.
Published: November 2014

The breakdown phase of the UNU-ICTP plasma focus (PF) device was successfully simulated using the electromagnetic particle in cell method. A clear uplift of the current sheath (CS) layer was observed near the insulator surface, accompanied with an exponential increase in the plasma density. Both phenomena were found to coincide with the surge in the electric current, which is indicative of voltage breakdown. Simulations performed on the device with different insulator lengths showed an increase in the fast ionization wave velocity with length. The voltage breakdown time was found to scale linearly with the insulator length. Different spatial profiles of the CS electron density, and the associated degree of uniformity, were found to vary with different insulator lengths. The ordering, according to the degree of uniformity, among insulator lengths of 19, 22, and 26 mm agreed with that in terms of soft X-ray radiation yield observed from experiments. This suggests a direct correlation between CS density homogeneity near breakdown and the radiation yield performance. These studies were performed with a linearly increasing voltage time profile as input to the PF device.
Surface Tension of Seawater
Authors: Nayar K. G. , Panchanathan D. , McKinley G. H. , Lienhard J. H.
Published: November 2014

New measurements and a reference correlation for the surface tension of seawater at atmospheric pressure are presented in this paper. Surface tension of seawater was measured across a salinity range of 20 ⩽ S ⩽ 131 g/kg and a temperature range of 1 ⩽ t ⩽ 92 °C at atmospheric pressure using the Wilhelmy plate method. The uncertainty within measurements varied from 0.18 to 0.37 mN/m with the average uncertainty being 0.22 mN/m. The experimental procedures were validated with tests conducted on ACS reagent grade water and aqueous sodium chloride solutions. Literature data and present measurements were evaluated and a reference correlation was developed expressing surface tension of seawater as a function of temperature and salinity. The average absolute percentage deviation between measurements and the correlation was 0.19% while the maximum deviation was 0.60%.
Excited states from quantum Monte Carlo in the basis of Slater determinants
Authors: Humeniuk Alexander , Mitrić Roland
Published: November 2014

Building on the full configuration interaction quantum Monte Carlo (FCIQMC) algorithm introduced recently by Booth et al. [J. Chem. Phys. 131, 054106 (2009)] to compute the ground state of correlated many-electron systems, an extension to the computation of excited states (exFCIQMC) is presented. The Hilbert space is divided into a large part consisting of pure Slater determinants and a much smaller orthogonal part (the size of which is controlled by a cut-off threshold), from which the lowest eigenstates can be removed efficiently. In this way, the quantum Monte Carlo algorithm is restricted to the orthogonal complement of the lower excited states and projects out the next highest excited state. Starting from the ground state, higher excited states can be found one after the other. The Schrödinger equation in imaginary time is solved by the same population dynamics as in the ground state algorithm with modified probabilities and matrix elements, for which working formulae are provided. As a proof of principle, the method is applied to lithium hydride in the 3-21G basis set and to the helium dimer in the aug-cc-pVDZ basis set. It is shown to give the correct electronic structure for all bond lengths. Much more testing will be required before the applicability of this method to electron correlation problems of interesting size can be assessed.
Growth and electrical characterization of two-dimensional layered MoS2/SiC heterojunctions
Authors: Lee Edwin W. , Ma Lu , Nath Digbijoy N. , Lee Choong Hee , Arehart Aaron , Wu Yiying , Rajan Siddharth
Published: November 2014

The growth and electrical characterization of the heterojunction formed between two-dimensional (2D) layered p-molybdenum disulfide (MoS2) and nitrogen-doped 4H silicon carbide (SiC) are reported. The integration of 2D semiconductors with the conventional three-dimensional (3D) substrates could enable semiconductor heterostructures with unprecedented properties. In this work, direct growth of p-type MoS2 films on SiC was demonstrated using chemical vapor deposition, and the MoS2 films were found to be high quality based on x-ray diffraction and Raman spectra. The resulting heterojunction was found to display rectification and current-voltage characteristics consistent with a diode for which forward conduction in the low-bias region is dominated by multi-step recombination tunneling. Capacitance-voltage measurements were used to determine the built-in voltage for the p-MoS2/n-SiC heterojunction diode, and we propose an energy band line up for the heterostructure based on these observations. The demonstration of heterogeneous material integration between MoS2 and SiC enables a promising new class of 2D/3D heterostructures.
Enhancing efficiency and power of quantum-dots resonant tunneling thermoelectrics in three-terminal geometry by cooperative effects
Authors: Jiang Jian-Hua
Published: November 2014

We propose a scheme of multilayer thermoelectric engine where one electric current is coupled to two temperature gradients in three-terminal geometry. This is realized by resonant tunneling through quantum dots embedded in two thermal and electrical resisting polymer matrix layers between highly conducting semiconductor layers. There are two thermoelectric effects, one of which is pertaining to inelastic transport processes (if energies of quantum dots in the two layers are different), while the other exists also for elastic transport processes. These two correspond to the transverse and longitudinal thermoelectric effects, respectively, and are associated with different temperature gradients. We show that cooperation between the two thermoelectric effects leads to markedly improved figure of merit and power factor, which is confirmed by numerical calculation using material parameters. Such enhancement is robust against phonon heat conduction and energy level broadening. Therefore, we demonstrated cooperative effect as an additional way to effectively improve performance of thermoelectrics in three-terminal geometry.
High-resolution, vacuum-ultraviolet absorption spectrum of boron trifluoride
Authors: Hughes Patrick P. , Beasten Amy , McComb Jacob C. , Coplan Michael A. , Al-Sheikhly Mohamad , Thompson Alan K. , Vest Robert E. , Sprague Matthew K. , Irikura Karl K. , Clark Charles W.
Published: November 2014

In the course of investigations of thermal neutron detection based on mixtures of 10BF3 with other gases, knowledge was required of the photoabsorption cross sections of 10BF3 for wavelengths between 135 and 205 nm. Large discrepancies in the values reported in existing literature led to the absolute measurements reported in this communication. The measurements were made at the SURF III Synchrotron Ultraviolet Radiation Facility at the National Institute of Standards and Technology. The measured absorption cross sections vary from 10−20 cm2 at 135 nm to less than 10−21 cm2 in the region from 165 to 205 nm. Three previously unreported absorption features with resolvable structure were found in the regions 135–145 nm, 150–165 nm, and 190–205 nm. Quantum mechanical calculations, using the TD-B3LYP/aug-cc-pVDZ variant of time-dependent density functional theory implemented in Gaussian 09, suggest that the observed absorption features arise from symmetry-changing adiabatic transitions.
The best orbital and pair function for describing ionic and excited states on top of the exact ground state
Authors: Klaiman Shachar , Cederbaum Lorenz S.
Published: November 2014

Many-body processes inevitably lead to the transition from one many-body wavefunction to another. Due to the complexity of the initial and final states many-body wavefunctions, one often wishes to try and describe such transitions using only a single-particle function. While there are numerous types of orbitals and densities which are commonly used, the question remains which one is optimal and in which sense. Here we present the optimal one and two body functions whose anti-symmetrized product with the initial state yields the maximal overlap with the final state. A definition of the above optimal condition and its rigorous proof are given. The resulting optimal functions shed additional light on the well-known Dyson orbital and reduced transition matrix, demonstrating further their physical meaning as independent functions.
Dynamical states in driven colloidal liquid crystals
Authors: Fischermeier Ellen , Marechal Matthieu , Mecke Klaus
Published: November 2014

We study a model colloidal liquid crystal consisting of hard spherocylinders under the influence of an external aligning potential by Langevin dynamics simulation. The external field that rotates in a plane acts on the orientation of the individual particles and induces a variety of collective nonequilibrium states. We characterize these states by the time-resolved orientational distribution of the particles and explain their origin using the single particle behavior. By varying the external driving frequency and the packing fraction of the spherocylinders we construct the dynamical state diagram.
Reptation and constraint release dynamics in bidisperse polymer melts
Authors: Langeloth Michael , Masubuchi Yuichi , Böhm Michael C. , Müller-Plathe Florian
Published: November 2014

Bidisperse melts of linear, entangled polymer chains were studied using dissipative particle dynamics. The entanglement constraints were mimicked with our newly developed slip-spring approach. The compositions cover blends with short matrix chains, slightly above the molecular entanglement weight as well as blends were both chain lengths exhibit distinct entangled dynamics at various weight fractions. The Struglinsky-Graessley parameter Gr, which is the ratio between the relaxation time of the long chains due to pure reptation and the relaxation time of the tube caused by constraint release, ranges between values high above and below unity. We compare our slip-spring model with simulations that use conventional generic polymer models where bond crossings are prevented by excluded-volume interactions and find fairly good agreement in terms of the mean squared displacement. However, the slip-spring approach requires only a fraction of the computational time, making large scale systems feasible. The dynamical interference of the two different chain lengths is discussed in terms of reptation and constraint release dynamics. For bidisperse melt compositions with Gr < 1.0 the relaxation time of the long chain component is not affected by constraint release. However, for compositions where constraint release is supposed to contribute significantly to the relaxation mechanism (Gr > 1.0), we find strong evidence that the long chains reptate inside a dilated tube whose diameter increases with an exponent of 1/2 towards lower weight fraction of the long chains. Furthermore we observe a linear relation between the relaxation time and weight fraction. Therefore, based on the relaxation times, our results support the validity of the tube dilation model as proposed by Doi et al. [Macromolecules 20, 1900–1906 (1987)].
New relationships of dark diffusion and recombination currents as a function of temperature for a crystalline cell photovoltaic
Authors: Hanen Salhi , Mohamed Ben Amar , Hekmet Samet
Published: November 2014

The effects of temperature and solar radiation on the characteristic p-n junction solar cells are investigated theoretically. The two-diode model is represented in this paper. This model requires only five parameters (the photocurrent, the shunt resistance, the series resistances, the diffusion, and the recombination dark current). The analytical resolution of continuity equations in each region of a crystalline solar cell, including the intrinsic carrier concentration, the energy band gap and the thickness of space charge layer as function of temperature, allowed us to determine the expressions of diffusion and recombination dark currents. We propose new relationships giving the expressions of these currents as a function of their reference values which are determined from both the data provided by the manufacturer and the different temperature values. To validate the accuracy of the proposed model, we compared predicted current–voltage curves with model double-diode model of Ishaque et al. and experimental data from various manufactures for two different cell technologies (single crystalline, poly crystalline). We determine the maximum power calculated by our proposed model to compare by double-diode model of Ishaque et al. for two cell type at the five conditions of generation rate. Generally, our model shows a better agreement with the experimental data than the Ishaque one. Our proposed work is useful because it provides to manufacturers an easy and comprehensive study to know the variation of the maximum power delivered by the photovoltaic module as a function of temperature and generation rate.
Lagrangian transport characteristics of a class of three-dimensional inline-mixing flows with fluid inertia
Authors: Speetjens M. F. M. , Demissie E. A. , Metcalfe G. , Clercx H. J. H.
Published: November 2014

Laminar mixing by the inline-mixing principle is a key to many industrial fluids-engineering systems of size extending from micrometers to meters. However, insight into fundamental transport phenomena particularly under the realistic conditions of three-dimensionality (3D) and fluid inertia remains limited. This study addresses these issues for inline mixers with cylindrical geometries and adopts the Rotated Arc Mixer (RAM) as a representative system. Transport is investigated from a Lagrangian perspective by identifying and examining coherent structures that form in the 3D streamline portrait. 3D effects and fluid inertia introduce three key features that are not found in simplified configurations: transition zones between consecutive mixing cells of the inline-mixing flow; local upstream flow (in certain parameter regimes); transition/inertia-induced breaking of symmetries in the Lagrangian equations of motion (causing topological changes in coherent structures). Topological considerations strongly suggest that there nonetheless always exists a net throughflow region between inlet and outlet of the inline-mixing flow that is strictly separated from possible internal regions. The Lagrangian dynamics in this region admits representation by a 2D time-periodic Hamiltonian system. This establishes one fundamental kinematic structure for the present class of inline-mixing flows and implies universal behavior in that all states follow from the Hamiltonian breakdown of one common integrable state. A so-called period-doubling bifurcation is the only way to eliminate transport barriers originating from this state and thus is a necessary (yet not sufficient) condition for global chaos. Important in a practical context is that a common simplification in literature, i.e., cell-wise fully-developed Stokes flow (“2.5D approach”), retains these fundamental kinematic properties and deviates from the generic 3D inertial case only in a quantitative sense. This substantiates its suitability for (at least first exploratory) studies on (qualitative) mixing properties.
Enhancing optical power of GaN-based light-emitting diodes by nanopatterning on indium tin oxide with tunable fill factor using multiple-exposure nanosphere-lens lithography
Authors: Zhang Yonghui , Wei Tongbo , Xiong Zhuo , Chen Yu , Zhen Aigong , Shan Liang , Zhao Yun , Hu Qiang , Li Jinmin , Wang Junxi
Published: November 2014

In this study, the multiple-exposure nanosphere-lens lithography method utilizing the polystyrene nanospheres with focusing behavior is investigated and introduced to fabricate diverse photonic crystals (PCs) on indium tin oxide to enhance the optical output power of GaN-based light-emitting diode (LED). Simulated results indicate that the focused light intensity decreases with increasing tilted angle due to the shadow effect introduced by adjacent nanospheres. The fill factor of nanopattern is tunable by controlling tilted angles and exposure times. To attain quadruple PC without overlapping patterns, mathematical calculation model is used to define the optimum range of tilted angles. Angular emission patterns and three-dimensional finite-difference time domain simulated results indicate that the enhanced light extraction of PC LEDs results mainly from diffused scattering effects, and the diffraction effects of PC on light extracted efficiency increase with the increase of fill factor. Furthermore, it is confirmed that the multiple PC can extract more light from GaN into air than common PC with same period and fill factor.
Compact deuterium-tritium neutron generator using a novel field ionization source
Authors: Ellsworth J. L. , Falabella S. , Sanchez J. , Tang V. , Wang H.
Published: November 2014

Active interrogation using neutrons is an effective method for detecting shielded nuclear material. A lightweight, lunch-box-sized, battery-operated neutron source would enable new concepts of operation in the field. We have developed at-scale components for a highly portable, completely self-contained, pulsed Deuterium-Tritium (DT) neutron source producing 14 MeV neutrons with average yields of 107 n/s. A gated, field ionization ion source using etched electrodes has been developed that produces pulsed ion currents up to 500 nA. A compact Cockcroft-Walton high voltage source is used to accelerate deuterons into a metal hydride target for neutron production. The results of full scale DT tests using the field ionization source are presented.
Study of possible chaotic, quasi-periodic and periodic structures in quantum dusty plasma
Authors: Ghosh Uday Narayan , Chatterjee Prasanta , Roychoudhury Rajkumar
Published: November 2014

Existence of chaotic, quasi-periodic, and periodic structures of dust-ion acoustic waves is studied in quantum dusty plasmas through dynamical system approach. A system of coupled differential equations is derived from the fluid model and subsequently, variational matrix is obtained. The characteristic equation is obtained at the equilibrium point, and the behavior of nonlinear waves is studied numerically using Runge-Kutta method. The behavior of the dynamical system changes significantly when any of plasma parameters, such as the dust concentration parameter, temperature ratio, or the quantum diffraction parameter, is varied. The change of the characteristic of solution of the system is extensively studied. It is found that the system changes its behavior from chaotic pattern to limit cycle behavior.
Self-focusing and frequency broadening of laser pulse in water
Authors: Sati Priti , Verma Updesh , Tripathi V. K.
Published: November 2014

An analytical model for the avalanche breakdown of water by an intense short laser pulse of finite spot size is developed. Initially, the laser undergoes self-focusing due to Kerr nonlinearity. As it acquires large intensity, it causes heating and avalanche breakdown of water. The plasma thus created on the laser axis causes nonlinear refraction induced defocusing of the laser. Thermal conduction tends to flatten the temperature profile and reduce the nonlinear refraction. The plasma density modification leads to frequency broadening of the laser.
High mobility field effect transistor based on BaSnO3 with Al2O3 gate oxide
Authors: Park Chulkwon , Kim Useong , Ju Chan Jong , Park Ji Sung , Kim Young Mo , Char Kookrin
Published: November 2014

We fabricated an n-type accumulation-mode field effect transistor based on BaSnO3 transparent perovskite semiconductor, taking advantage of its high mobility and oxygen stability. We used the conventional metal-insulator-semiconductor structures: (In,Sn)2O3 as the source, drain, and gate electrodes, Al2O3 as the gate insulator, and La-doped BaSnO3 as the semiconducting channel. The Al2O3 gate oxide was deposited by atomic layer deposition technique. At room temperature, we achieved the field effect mobility value of 17.8 cm2/Vs and the Ion/Ioff ratio value higher than 105 for VDS = 1 V. These values are higher than those previously reported on other perovskite oxides, in spite of the large density of threading dislocations in the BaSnO3 on SrTiO3 substrates. However, a relatively large subthreshold swing value was found, which we attribute to the large density of charge traps in the Al2O3 as well as the threading dislocations.
Dynamics of non-axisymmetric Beltrami flows
Authors: González Rafael
Published: November 2014

In previous works [R. González, G. Sarasua, and A. Costa, “Kelvin waves with helical Beltrami flow structure,” Phys. Fluids 20, 024106 (2008) and R. González, A. Costa, and E. S. Santini, “On a variational principle for Beltrami flows,” Phys. Fluids 22, 074102 (2010)], we analyzed the Beltrami flow structure of Kelvin waves in an ideal fluid. As a result, we were able to show an important feature of Beltrami flows: their stability for Beltrami perturbations with the same eigenvalue as the basic flow. Here, instead, we study the dynamics of Beltrami perturbations by performing a modal analysis. In the first place, we study the modes that are generated by perturbing a uniformly translating and solidly rotating basic flow. In order to simplify the analysis, we consider the non-inertial frame in which this basic flow is at rest. In the second place, we analyze a basic Beltrami flow that is stationary in the non-inertial frame considered and is perturbed with Beltrami modes. We find that the last case is only possible when the perturbation eigenvalue is the same as that of the basic Beltrami flow. This is what we have called dynamical property. In both cases, the dynamics are represented by progressive waves in the moving frame. We apply this analysis to a rotating flow in an infinite cylinder and to an axisymmetric rotating Beltrami flow in a semi-infinite cylinder. In both cases, the development of secondary Beltrami modes is possible due to the dynamical property.
Subwavelength acoustic focusing by surface-wave-resonance enhanced transmission in doubly negative acoustic metamaterials
Authors: Zhou Xiaoming , Badreddine Assouar M. , Oudich Mourad
Published: November 2014

We present analytical and numerical analyses of a yet unseen lensing paradigm that is based on a solid metamaterial slab in which the wave excitation source is attached. We propose and demonstrate sub-diffraction-limited acoustic focusing induced by surface resonant states in doubly negative metamaterials. The enhancement of evanescent waves across the metamaterial slab produced by their resonant coupling to surface waves is evidenced and quantitatively determined. The effect of metamaterial parameters on surface states, transmission, and wavenumber bandwidth is clearly identified. Based on this concept consisting of a wave source attached on the metamaterial, a high resolution of λ/28.4 is obtained with the optimum effective physical parameters, opening then an exciting way to design acoustic metamaterials for ultrasonic focused imaging.
Continuous tuning of W-doped VO2 optical properties for terahertz analog applications
Authors: Karaoglan-Bebek G. , Hoque M. N. F. , Holtz M. , Fan Z. , Bernussi A. A.
Published: November 2014

Vanadium dioxide (VO2), with its characteristic metal-insulator phase transition, is a prospective active candidate to realize tunable optical devices operating at terahertz (THz) frequencies. However, the abrupt phase transition restricts its practical use in analog-like continuous applications. Incorporation of tungsten is a feasible approach to alter the phase transition properties of thin VO2 films. We show that amplitude THz modulation depth of ∼65%, characteristic phase transition temperature of ∼40 °C, and tuning range larger than 35 °C can be achieved with W-doped VO2 films grown on sapphire substrates. W-doped VO2 films can also be used to suppress Fabry-Perot resonances at THz frequencies but at temperatures much lower than that observed for undoped VO2 films. The gradual phase transition temperature window allows for precise control of the W-doped VO2 optical properties for future analog based THz devices.
On violation of local closure of transport relation in high-temperature magnetized plasmas
Authors: Kasuya N. , Sugita S. , Inagaki S. , Itoh K. , Yagi M. , Itoh S.-I.
Published: November 2014

Rapid propagation of heat modulation and a hysteresis in the gradient-flux relation are found in a global nonlinear simulation of drift-interchange mode turbulence in toroidal helical plasmas. A global mode is excited nonlinearly and induces the turbulence flux in a limited radial region. The nonlinear couplings take a finite temporal duration for redistributing the energy. The mode also has a seesaw effect: increase of the amplitude of the global mode, at the other radii, works to absorb the energy form microscopic modes to suppress the turbulence. Successive excitations of microscopic modes cause the accelerated propagation of change of the heat flux like turbulence spreading after the onset of modulation. Owing to these processes, the hysteresis appears in the gradient-flux relation, which is compared with experiments.
Simultaneous generation of quasi-monoenergetic electron and betatron X-rays from nitrogen gas via ionization injection
Authors: Huang K. , Li D. Z. , Yan W. C. , Li M. H. , Tao M. Z. , Chen Z. Y. , Ge X. L. , Liu F. , Ma Y. , Zhao J. R. , Hafz N. M. , Zhang J. , Chen L. M.
Published: November 2014

Upon the interaction of 60 TW Ti: sapphire laser pulses with 4 mm long supersonic nitrogen gas jet, a directional x-ray emission was generated along with the generation of stable quasi-monoenergetic electron beams having a peak energy of 130 MeV and a relative energy spread of ∼ 20%. The betatron x-ray emission had a small divergence of 7.5 mrad and a critical energy of 4 keV. The laser wakefield acceleration process was stimulated in a background plasma density of merely 5.4 × 1017 cm−3 utilizing ionization injection. The non-self-focusing and stable propagation of the laser pulse in the pure nitrogen gaseous plasma should be responsible for the simultaneous generation of the high-quality X-ray and electron beams. Those ultra-short and naturally-synchronized beams could be applicable to ultrafast pump-probe experiments.
A (Nd, Zr)(Fe, Co)11.5Ti0.5Nx compound as a permanent magnet material
Authors: Suzuki S. , Kuno T. , Urushibata K. , Kobayashi K. , Sakuma N. , Washio K. , Kishimoto H. , Kato A. , Manabe A.
Published: November 2014

We studied NdFe11TiNx compounds as permanent magnet materials. The (Nd0.7,Zr0.3)(Fe0.75Co0.25)11.5Ti0.5N0.52 powder that contained a limited amount of the α-(Fe, Co) phase shows fairly good magnetic properties, such as a saturation polarization (Js) of 1.68 T and an anisotropic field (Ha) of 2.88 (Law of approach to saturation) – 4.0 MA/m (Intersection of magnetization curves). Both properties are comparable to those of the Nd2Fe14B phase.
Widely tunable room temperature semiconductor terahertz source
Authors: Lu Q. Y. , Slivken S. , Bandyopadhyay N. , Bai Y. , Razeghi M.
Published: November 2014

We present a widely tunable, monolithic terahertz source based on intracavity difference frequency generation within a mid-infrared quantum cascade laser at room temperature. A three-section ridge waveguide laser design with two sampled grating sections and a distributed-Bragg section is used to achieve the terahertz (THz) frequency tuning. Room temperature single mode THz emission with a wide tunable frequency range of 2.6–4.2 THz (∼47% of the central frequency) and THz power up to 0.1 mW is demonstrated, making such device an ideal candidate for THz spectroscopy and sensing.
Analysis of deep sub-micron resolution in microsphere based imaging
Authors: Sundaram Vijay M. , Wen Sy-Bor
Published: November 2014

Based on full wave simulations, ∼0.3 λ and ∼0.24 λ imaging resolutions can be achieved for incoherent transverse and longitudinal point dipoles, respectively, when the dipoles are on an aluminum oxide base with a fused silica microsphere as the imaging lens. These high spatial resolutions (better than 0.5 λ) can be attributed to almost 90° light acceptance angle of the microsphere and the solid immersion effects from the microsphere/base material. These simulation results can explain the ≳0.3 λ and ≳0.24 λ minimum resolvable center to center separation distance for thin metallic nanostructures and elongated metallic nanostructures, respectively, which is equal to ≳0.1–0.14 λ edge to edge distance observed in previous microsphere imaging experiments.
EPS Prize Lecture: Cognitive underpinnings of social interaction
Authors: Hamilton Antonia F. de C.
Published: November 2014

Human social interaction is part of what defines us. Here I present an overview of recent studies of imitation, a subdomain of social interaction that can be dissected and examined in a scientific fashion. I use these studies to test two core claims: (a) that there is more than one copying mechanism in the human brain and (b) that mimicry (a form of copying) is particularly relevant for understanding social behaviour. Evidence in favour of the first claim comes from neuroimaging studies that show distinct brain systems for understanding action kinematics, action goals, and irrational actions. Further studies of participants with autism show abnormal copying of irrational actions. Evidence in favour of the second claim comes from behavioural studies of the social cues that prime mimicry and from neuroimaging studies of the pathways involved in this priming. These studies suggest that medial prefrontal cortex has a core role in controlling mimicry responses and support the STORM (social top-down response modulation) model. Future work should determine what organizing principles govern the control of social responses and how these critical mechanisms for interpersonal connection differ in autism.
Adapting to catastrophic water scarcity in agriculture through social networking and inter-generational occupational transitioning
Authors: Ranjan Ram
Published: November 2014

Increasing frequency of drought threatens the long-term viability of agriculture in many regions of the world. Some farmers will exit the agricultural industry abruptly, but for many, the path out of agriculture is prolonged and involves several generations within a household. This paper presents a model of dynamic inter-generational preferences and occupational choices to explore possible transition paths out of agriculture. Differing preferences across generations within a farming household are incorporated through a dynamically-evolving utility function, which influences the time paths of optimal investments in human, social and natural capital. A dwindling natural resource base, such as groundwater, requires increasing reliance on urban livelihoods. However, inter-generational differences in preferences for rural versus urban lifestyles, modelled as different weights in the household's utility function, may determine whether this occupational transition can be attained.