bluuebunny/crossref_metadata_2025 huggingface dataset:
Photocatalytic reduction of CO2 using molybdenum-doped titanate nanotubes in a MEA solution
Authors: Wu Hung-Yu , Nguyen Nhat Huy , Bai Hsunling , Chang Sue-min , Wu Jeffrey C. S.
Published: July 2015

In this study, the photocatalytic reduction of CO2 in a monoethanolamine solution to form valuable energy sources was investigated using Mo-doped TNTs photocatalysts for the first time.
Energetic interpenetrating polymer network based on orthogonal azido–alkyne click and polyurethane for potential solid propellant
Authors: Tanver Abbas , Huang Mu-Hua , Luo Yunjun , Khalid Syed , Hussain Tariq
Published: July 2015

High energetic propellants with synergistic mechanical strength are the prerequisites for aerospace industry and missile technology; though glycidyl azide polymer (GAP) is a renowned and a promising energetic polymer which shows poor mechanical and low-temperature properties.
Direct spray deposition of silver nanoparticle films for biosensing applications
Authors: Byrne Daragh , Zhao Yan , O'Brien Peter , McDonagh Colette
Published: July 2015

Direct spray deposition of silver nanoparticle films as a rapid approach for a metal enhanced fluorescence biosensing platform.
Intrinsic therapeutic and biocatalytic roles of ionic liquid mediated self-assembled platinum–phytase nanospheres
Authors: Soni Sarvesh K. , Sarkar Sampa , Selvakannan P. R. , Sarkar Dhiman , Bhargava Suresh K.
Published: July 2015

Intrinsic therapeutic and biocatalytic roles of ionic liquid mediated self-assembled phytase, platinum–phytase and platinum–phytase–curcumin nanospheres.
Efficient dye-sensitized solar cells using mesoporous submicrometer TiO2 beads
Authors: Cao Kun , Lu Jianfeng , Li Hao , Shen Yan , Wang Mingkui
Published: July 2015

Co-sensitized photoelectrodes using mesoporous submicrometer TiO2 beads as “building blocks” can improve light absorption over a broad wavelength region.
An overview on visible light responsive metal oxide based photocatalysts for hydrogen energy production
Authors: Martha Satyabadi , Chandra Sahoo Prakash , Parida K. M.
Published: July 2015

The present review summarizes the recent development and challenges in visible light responsive metal oxide based photocatalysts for water splitting.
Promoting effects of MgO and Pd modification on the catalytic performance of hierarchical porous ZSM-5 for catalyzing benzene alkylation with methanol
Authors: Hu Hualei , Lyu Jinghui , Cen Jie , Zhang Qunfeng , Wang Qingtao , Han Wenwen , Rui Jiayao , Li Xiaonian
Published: July 2015

The dual modification catalyst (MgO and Pd) could effectively combine the effect of MgO for suppressing the side reaction of methanol to olefins and the effect of Pd for inhibiting the formation of ethylbenzene and coke.
Experimental and theoretical studies of DMH as a complexing agent for a cyanide-free gold electroplating electrolyte
Authors: Ren Xuefeng , Song Ying , Liu Anmin , Zhang Jie , Yang Peixia , Zhang Jinqiu , An Maozhong
Published: July 2015

Golden bright gold electrodeposit with a smooth and compact surface can be obtained from the introduced cyanide-free gold electroplating electrolyte.
Watching paint dry; more exciting than it seems
Authors: van der Kooij Hanne M. , Sprakel Joris
Published: July 2015

We highlight the challenges that lie ahead in understanding film formation of coatings and show some of the exciting soft matter phenomena which can be observed beneath surface of drying paints.
Cysteine-containing oligopeptide β-sheets as redispersants for agglomerated metal nanoparticles
Authors: Mizutaru Tsukasa , Sakuraba Taro , Nakayama Toru , Marzun Galina , Wagener Philipp , Rehbock Christoph , Barcikowski Stephan , Murakami Katsuhisa , Fujita Junichi , Ishii Noriyuki , Yamamoto Yohei
Published: July 2015

Fmoc-pentapeptide β-sheets with amino acid residues of cysteine, lysine and valine work as redispersants for agglomerated ligand-free metal nanoparticles.
Fabrication of highly elastic resilin/silk fibroin based hydrogel by rapid photo-crosslinking reaction
Authors: Whittaker J. L. , Dutta N. K. , Elvin C. M. , Choudhury N. R.
Published: July 2015

A new type of hydrogel combining the highly elastic soft phase of Rec1-resilin and the mechanically strong hard phase ofBombyx morisilk fibroin has been reported using a rapid photo-crosslinking method.
Controllable synthesis of polydopamine nanoparticles in microemulsions with pH-activatable properties for cancer detection and treatment
Authors: Liu Fuyao , He Xiuxia , Zhang Junping , Chen Hongda , Zhang Huimao , Wang Zhenxin
Published: July 2015

A simple reverse microemulsion-based method was used to elaborate pH-activatable PEG–Fe–PDA nanoparticles for cancer diagnosis and therapy.
A facile approach to synthesize an oxo-functionalized graphene/polymer composite for low-voltage operating memory devices
Authors: Wang Zhenxing , Eigler Siegfried , Ishii Yoshitaka , Hu Yichen , Papp Christian , Lytken Ole , Steinrück Hans-Peter , Halik Marcus
Published: July 2015

Polystyrene-derivative wrapped oxo-functionalized graphene, prepared by controlled chemistry, can be used as a floating gate in memory devices operating at 3 V.
Correction: Di-amidosils with tunable structure, morphology and emission quantum yield: the role of hydrogen bonding
Authors: Nunes S. C. , Hümmer J. , Freitas V. T. , Ferreira R. A. S. , Carlos L. D. , Almeida P. , de Zea Bermudez V.
Published: July 2015

Correction for ‘Di-amidosils with tunable structure, morphology and emission quantum yield: the role of hydrogen bonding’ by S. C. Nunes et al., J. Mater. Chem. C, 2015, 3, 6844–6861.
Down-regulation of EPHX2 gene transcription by Sp1 under high-glucose conditions
Authors: Oguro Ami , Oida Shoko , Imaoka Susumu
Published: July 2015

sEH (soluble epoxide hydrolase), which is encoded by the EPHX2 gene, regulates the actions of bioactive lipids, EETs (epoxyeicosatrienoic acids). Previously, we found that high-glucose-induced oxidative stress suppressed sEH levels in a hepatocarcinoma cell line (Hep3B) and sEH was decreased in streptozotocin-induced diabetic mice in vivo. In the present study, we investigated the regulatory mechanisms underlying EPHX2 transcriptional suppression under high-glucose conditions. The decrease in sEH was prevented by an Sp1 (specificity protein 1) inhibitor, mithramycin A, and overexpression or knockdown of Sp1 revealed that Sp1 suppressively regulated sEH expression, in contrast with the general role of Sp1 on transcriptional activation. In addition, we found that AP2α (activating protein 2α) promoted EPHX2 transcription. The nuclear transport of Sp1, but not that of AP2α, was increased under high glucose concomitantly with the decrease in sEH. Within the EPHX2 promoter −56/+32, five Sp1-binding sites were identified, and the mutation of each of these sites showed that the first one (SP1_1) was important in both suppression by Sp1 and activation by AP2α. Furthermore, overexpression of Sp1 diminished the binding of AP2α by DNA-affinity precipitation assay and ChIP, suggesting competition between Sp1 and AP2α on the EPHX2 promoter. These findings provide novel insights into the role of Sp1 in transcriptional suppression, which may be applicable to the transcriptional regulation of other genes.
The Nature of Nasal Fricatives: Articulatory-Perceptual Characteristics and Etiologic Considerations
Authors: Zajac David J.
Published: July 2015

Nasal fricatives (NFs) are unusual, maladaptive articulations used by children both with and without palatal anomalies to replace oral fricatives. Nasal fricatives vary in articulatory, aerodynamic, and acoustic-perceptual characteristics with two generally distinct types recognized. One type is produced with velopharyngeal (VP) constriction that results in turbulent nasal airflow and, frequently, tissue vibration (flutter) at the VP port. Trost (1981) described these as posterior NFs that have a distinctive snorting quality. A second type of NF is produced without significant VP constriction resulting in turbulent airflow generated at the anterior liminal valve of the nose. Of importance, both types are “active” alternative articulations in that the speaker occludes the oral cavity to direct all airflow through the nose (Harding & Grunwell, 1998). It is this oral gesture that differentiates NFs from obligatory (or passive) nasal air escape that may sound similar due to incomplete VP closure. The purpose of this article is to (1) describe the articulatory, aerodynamic, and acoustic-perceptual nature of NFs, and (2) propose a theoretical framework for the acquisition of NFs by children both with and without cleft palate.
Radiographic Analysis of the Sacropelvic Parameters of the Spine and Their Correlation in Normal Asymptomatic Subjects
Authors: Sudhir G. , Acharya Shankar , Kalra K.L. , Chahal Rupinder
Published: July 2015

Study Design

Cross-sectional study.

Objective

Sacropelvic parameters in various spine and hip disorders have been published in various studies. We aimed to study the normal sacropelvic parameters and curvatures of the spine and their correlation in asymptomatic Indian adults in relation to variations in sex and age.

Methods

The study included 101 asymptomatic adults (50 men and 51 women with an average age of 47.16 and 48.59 years, respectively). For each subject, the thoracic kyphosis (TK), lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT), and sacral slope (SS) were measured from standing lateral radiographs. After stratification of the group by sex and age with a cutoff of 50 years, descriptive, correlation, and regression analysis were performed using SPSS software.

Results

The average PI, SS, PT, LL, and TK values were 55.48 (±5.31), 35.99 (±7.53), 17.97 (±7.16), 48.84 (±9.82), and 32.55 (±10.92), respectively. No statistically significant difference was observed in these values with regards to sex and age < 50 years and > 50 years but the pelvic incidence was found to be higher in women. A positive correlation between the PI and SS and a negative correlation between the SS and PT was observed. A positive correlation between the TK and LL was found in subjects > 50 years. Simple and multiple regression analyses were also performed for different groups.

Conclusion

The current study is the first of asymptomatic Indian adults and provides invaluable information to the clinicians about the normal range of sacropelvic and spinopelvic parameters, which is useful to plan spinal deformity corrections and to evaluate pathologic conditions associated with abnormal angular values.
En Bloc Resection of Solitary Functional Secreting Spinal Metastasis
Authors: Goodwin C. Rory , Clarke Michelle J. , Gokaslan Ziya L. , Fisher Charles , Laufer Ilya , Weber Michael H. , Sciubba Daniel M.
Published: July 2015

Study Design

Literature review.

Objective

Functional secretory tumors metastatic to the spine can secrete hormones, growth factors, peptides, and/or molecules into the systemic circulation that cause distinct syndromes, clinically symptomatic effects, and/or additional morbidity and mortality. En bloc resection has a limited role in metastatic spine disease due to the current paradigm that systemic burden usually determines morbidity and mortality. Our objective is to review the literature for studies focused on en bloc resection of functionally active spinal metastasis as the primary indication.

Methods

A review of the PubMed literature was performed to identify studies focused on functional secreting metastatic tumors to the spinal column. We identified five cases of patients undergoing en bloc resection of spinal metastases from functional secreting tumors.

Results

The primary histologies of these spinal metastases were pheochromocytoma, carcinoid tumor, choriocarcinoma, and a fibroblast growth factor 23–secreting phosphaturic mesenchymal tumor. Although studies of en bloc resection for these rare tumor subtypes are confined to case reports, this surgical treatment option resulted in metabolic cures and decreased clinical symptoms postoperatively for patients diagnosed with solitary functional secretory spinal metastasis.

Conclusion

Although the ability to formulate comprehensive conclusions is limited, case reports demonstrate that en bloc resection may be considered as a potential surgical option for the treatment of patients diagnosed with solitary functional secretory spinal metastatic tumors. Future prospective investigations into clinical outcomes should be conducted comparing intralesional resection and en bloc resection for patients diagnosed with solitary functional secretory spinal metastasis.
Intrawound Vancomycin Powder for Spine Tumor Surgery
Authors: Okafor Richard , Molinari William , Molinari Robert , Mesfin Addisu
Published: July 2015

Study Design

Retrospective evaluation of prospectively collected data.

Objective

To evaluate infection rates following intrawound vancomycin powder application during spine tumor surgery.

Methods

Patients ≥18 years old undergoing spine tumor surgery and receiving intrawound vancomycin powder at a single center between January 2008 and January 2015 were enrolled. Patient demographics (age, sex, body mass index [BMI]), tumor type (metastatic, primary) and location, surgical data (estimated blood loss [EBL], levels fused, type of decompression, length of surgery and hospitalization, discharge status from hospital), radiation therapy use, and infection rates (surgery to a minimum of 30 days postoperative) were evaluated.

Results

Forty patients (46 procedures) undergoing spine tumor surgery and intrawound vancomycin powder application were identified. Five were excluded because of death less than 30 days postoperatively, and 35 patients (41 procedures) were enrolled: 11 women and 24 men with an average age of 61.4 years (range 19 to 92) and average BMI of 27.3 (range 17.4 to 36.8). Three cases were primary spine tumors. Five were hematologic malignancies, and 27 were metastatic cancers. Twenty-one tumors were in the thoracic spine, 12 in the lumbar spine, and 8 in the cervical spine. Average EBL was 899 mL (range 25 to 3,500), average length of surgery was 241 minutes (range 78 to 495), and average hospital stay was 15.1 days (range 3 to 49). Two culture-proven infections ( Staphylococcus aureus, Enterobacter cloacae) were noted in 41 procedures (4.9%). Ten patients (28.6%) had preoperative radiation only; 14 (40%) had postoperative radiation only, 5 (14.3%) had both preoperative and postoperative radiation, and 6 (17.1%) had no radiation. There were no associations between radiation treatment and postsurgical infections ( p = 0.19).

Conclusion

In this first study evaluating intrawound vancomycin powder for spine tumor surgery, we report an infection rate of 4.9%. We found no correlations between radiation treatment and postsurgical infections.
Non-adiabatic current densities, transitions, and power absorbed by a molecule in a time-dependent electromagnetic field
Authors: Mandal Anirban , Hunt Katharine L. C.
Published: July 2015

The energy of a molecule subject to a time-dependent perturbation separates completely into adiabatic and non-adiabatic terms, where the adiabatic term reflects the adjustment of the ground state to the perturbation, while the non-adiabatic term accounts for the transition energy [A. Mandal and K. L. C. Hunt, J. Chem. Phys. 137, 164109 (2012)]. For a molecule perturbed by a time-dependent electromagnetic field, in this work, we show that the expectation value of the power absorbed by the molecule is equal to the time rate of change of the non-adiabatic term in the energy. The non-adiabatic term is given by the transition probability to an excited state k, multiplied by the transition energy from the ground state to k, and then summed over the excited states. The expectation value of the power absorbed by the molecule is derived from the integral over space of the scalar product of the applied electric field and the non-adiabatic current density induced in the molecule by the field. No net power is absorbed due to the action of the applied electric field on the adiabatic current density. The work done on the molecule by the applied field is the time integral of the power absorbed. The result established here shows that work done on the molecule by the applied field changes the populations of the molecular states.
On the evolution of the invariants of the velocity gradient tensor in single-square-grid-generated turbulence
Authors: Zhou Yi , Nagata Koji , Sakai Yasuhiko , Ito Yasumasa , Hayase Toshiyuki
Published: July 2015

Direct numerical simulations were performed to investigate the topological evolution of turbulence generated by a single square grid. Immediately behind the single square grid (i.e., in the irrotational dissipation region), the conditional mean trajectories (CMTs) of R and Q are distinctly different from those in homogeneous isotropic turbulence (HIT), where R and Q are the third and second invariants, respectively, of the velocity gradient tensor. In this region, the non-local influence of the pressure Hessian is dominant, which causes irrotational viscous dissipation. The anisotropic part of the pressure Hessian may be responsible for the irrotational viscous dissipation found at the turbulent/nonturbulent interface in turbulent jets [C. B. da Silva and J. C. F. Pereira, “Invariants of the velocity-gradient, rate-of-strain, and rate-of-rotation tensors across the turbulent/nonturbulent interface in jets,” Phys. Fluids 20, 055101 (2008) and Watanabe et al., “Vortex stretching and compression near the turbulent/non-turbulent interface in a planar jet,” J. Fluid Mech. 758, 754 (2014)]. In the transition region, the CMTs of R and Q gradually acquire an evolution pattern similar to that in HIT. The expansion of the (R, Q) map at Q > 0 is associated with the effects of the restricted Euler term. Finally, in the fully turbulent region, the CMTs of R and Q demonstrate a clockwise evolution toward a point close to the origin. However, the cyclic spiraling seen in HIT is not found. The lack of the cyclic evolution may be attributed to the considerably large effect of the viscous term owing to the relatively small local Reynolds number. On average, the combined influences of the restricted Euler term and anisotropic part of the pressure Hessian contribute to the generation of small-scale motions, and the viscous term tends to remove small-scale motions.
In-operando synchronous time-multiplexed O K-edge x-ray absorption spectromicroscopy of functioning tantalum oxide memristors
Authors: Kumar Suhas , Graves Catherine E. , Strachan John Paul , Kilcoyne A. L. David , Tyliszczak Tolek , Nishi Yoshio , Williams R. Stanley
Published: July 2015

Memristors are receiving keen interest because of their potential varied applications and promising large-scale information storage capabilities. Tantalum oxide is a memristive material that has shown promise for high-performance nonvolatile computer memory. The microphysics has been elusive because of the small scale and subtle physical changes that accompany conductance switching. In this study, we probed the atomic composition, local chemistry, and electronic structure of functioning tantalum oxide memristors through spatially mapped O K-edge x-ray absorption. We developed a time-multiplexed spectromicroscopy technique to enhance the weak and possibly localized oxide modifications with spatial and spectral resolutions of <30 nm and 70 meV, respectively. During the initial stages of conductance switching of a micrometer sized crosspoint device, the spectral changes were uniform within the spatial resolution of our technique. When the device was further driven with millions of high voltage-pulse cycles, we observed lateral motion and separation of ∼100 nm-scale agglomerates of both oxygen interstitials and vacancies. We also demonstrate a unique capability of this technique by identifying the relaxation behavior in the material during electrical stimuli by identifying electric field driven changes with varying pulse widths. In addition, we show that changes to the material can be localized to a spatial region by modifying its topography or uniformity, as against spatially uniform changes observed here during memristive switching. The goal of this report is to introduce the capability of time-multiplexed x-ray spectromicroscopy in studying weak-signal transitions in inhomogeneous media through the example of the operation and temporal evolution of a memristor.
Influence of wall plasma on microwave frequency and power in relativistic backward wave oscillator
Authors: Sun Jun , Wu Ping , Cao Yibing , Teng Yan , Zhang Yuchuan , Chen Changhua
Published: July 2015

The RF breakdown of the slow wave structure (SWS), which will lead to the generation of the wall plasma, is an important cause for pulse shortening in relativistic backward wave oscillators. Although many researchers have performed profitable studies about this issue, the influence mechanism of this factor on the microwave generation still remains not-so-clear. This paper simplifies the wall plasma with an “effective” permittivity and researches its influence on the microwave frequency and power. The dispersion relation of the SWS demonstrates that the introduction of the wall plasma will move the dispersion curves upward to some extent, which is confirmed by particle-in-cell (PIC) simulations and experiments. The plasma density and volume mainly affect the dispersion relation at the upper and lower frequency limits of each mode, respectively. Meanwhile, PIC simulations show that even though no direct power absorption exists since the wall plasma is assumed to be static, the introduction of the wall plasma may also lead to the decrease in microwave power by changing the electrodynamic property of the SWS.
Theory of hysteresis during electron heating of electromagnetic wave scattering by self-organized dust structures in complex plasmas
Authors: Tsytovich Vadim , Gusein-zade Namik , Ignatov Alexander
Published: July 2015

Dust structuring is a natural and universal process in complex plasmas. The scattering of electromagnetic waves by dust structures is governed by the factor of coherency, i.e., the total number of coherent electrons in a single structure. In the present paper, we consider how the factor of coherency changes due to additional pulse electron heating and show that it obeys a hysteresis. After the end of the pulse heating, the scattering intensity differs substantially from that before heating. There are three necessary conditions for scattering hysteresis: first, the radiation wavelength should be larger than the pattern (structure) size; second, the total number of coherent electrons confined by the structure should be large; and third, the heating pulse duration should be shorter than the characteristic time of dust structure formation. We present the results of numerical calculations using existing models of self-consistent dust structures with either positively or negatively charged dust grains. It is shown that, depending on the grain charge and the ionization rate, two types of hysteresis are possible: one with a final increase of the scattering and the other with a final decrease of the scattering. It is suggested that the hysteresis of coherent scattering can be used as a tool in laboratory experiments and that it can be a basic mechanism explaining the observed hysteresis in radar scattering by noctilucent clouds during active experiments on electron heating in mesosphere.
Vortex flow structures and interactions for the optimum thrust efficiency of a heaving airfoil at different mean angles of attack
Authors: Martín-Alcántara A. , Fernandez-Feria R. , Sanmiguel-Rojas E.
Published: July 2015

The thrust efficiency of a two-dimensional heaving airfoil is studied computationally for a low Reynolds number using a vortex force decomposition. The auxiliary potentials that separate the total vortex force into lift and drag (or thrust) are obtained analytically by using an elliptic airfoil. With these auxiliary potentials, the added-mass components of the lift and drag (or thrust) coefficients are also obtained analytically for any heaving motion of the airfoil and for any value of the mean angle of attack α. The contributions of the leading- and trailing-edge vortices to the thrust during their down- and up-stroke evolutions are computed quantitatively with this formulation for different dimensionless frequencies and heave amplitudes (Stc and Sta) and for several values of α. Very different types of flows, periodic, quasi-periodic, and chaotic described as Stc, Sta, and α, are varied. The optimum values of these parameters for maximum thrust efficiency are obtained and explained in terms of the interactions between the vortices and the forces exerted by them on the airfoil. As in previous numerical and experimental studies on flapping flight at low Reynolds numbers, the optimum thrust efficiency is reached for intermediate frequencies (Stc slightly smaller than one) and a heave amplitude corresponding to an advance ratio close to unity. The optimal mean angle of attack found is zero. The corresponding flow is periodic, but it becomes chaotic and with smaller average thrust efficiency as |α| becomes slightly different from zero.
Polyamorphism in tetrahedral substances: Similarities between silicon and ice
Authors: Garcez K. M. S. , Antonelli A.
Published: July 2015

Tetrahedral substances, such as silicon, water, germanium, and silica, share various unusual phase behaviors. Among them, the so-called polyamorphism, i.e., the existence of more than one amorphous form, has been intensively investigated in the last three decades. In this work, we study the metastable relations between amorphous states of silicon in a wide range of pressures, using Monte Carlo simulations. Our results indicate that the two amorphous forms of silicon at high pressures, the high density amorphous (HDA) and the very high density amorphous (VHDA), can be decompressed from high pressure (∼20 GPa) down to the tensile regime, where both convert into the same low density amorphous. Such behavior is also observed in ice. While at high pressure (∼20 GPa), HDA is less stable than VHDA, at the pressure of 10 GPa both forms exhibit similar stability. On the other hand, at much lower pressure (∼5 GPa), HDA and VHDA are no longer the most stable forms, and, upon isobaric annealing, an even less dense form of amorphous silicon emerges, the expanded high density amorphous, again in close similarity to what occurs in ice.
The relationship between node degree and dissipation rate in networks of diffusively coupled oscillators and its significance for pancreatic beta cells
Authors: Gosak Marko , Stožer Andraž , Markovič Rene , Dolenšek Jurij , Marhl Marko , Slak Rupnik Marjan , Perc Matjaž
Published: July 2015

Self-sustained oscillatory dynamics is a motion along a stable limit cycle in the phase space, and it arises in a wide variety of mechanical, electrical, and biological systems. Typically, oscillations are due to a balance between energy dissipation and generation. Their stability depends on the properties of the attractor, in particular, its dissipative characteristics, which in turn determine the flexibility of a given dynamical system. In a network of oscillators, the coupling additionally contributes to the dissipation, and hence affects the robustness of the oscillatory solution. Here, we therefore investigate how a heterogeneous network structure affects the dissipation rate of individual oscillators. First, we show that in a network of diffusively coupled oscillators, the dissipation is a linearly decreasing function of the node degree, and we demonstrate this numerically by calculating the average divergence of coupled Hopf oscillators. Subsequently, we use recordings of intracellular calcium dynamics in pancreatic beta cells in mouse acute tissue slices and the corresponding functional connectivity networks for an experimental verification of the presented theory. We use methods of nonlinear time series analysis to reconstruct the phase space and calculate the sum of Lyapunov exponents. Our analysis reveals a clear tendency of cells with a higher degree, that is, more interconnected cells, having more negative values of divergence, thus confirming our theoretical predictions. We discuss these findings in the context of energetic aspects of signaling in beta cells and potential risks for pathological changes in the tissue.
The dynamics of a capsule in a wall-bounded oscillating shear flow
Authors: Zhu LaiLai , Rabault Jean , Brandt Luca
Published: July 2015

The motion of an initially spherical capsule in a wall-bounded oscillating shear flow is investigated via an accelerated boundary integral implementation. The neo-Hookean model is used as the constitutive law of the capsule membrane. The maximum wall-normal migration is observed when the oscillation period of the imposed shear is of the order of the relaxation time of the elastic membrane; hence, the optimal capillary number scales with the inverse of the oscillation frequency and the ratio agrees well with the theoretical prediction in the limit of high-frequency oscillation. The migration velocity decreases monotonically with the frequency of the applied shear and the capsule-wall distance. We report a significant correlation between the capsule lateral migration and the normal stress difference induced in the flow. The periodic variation of the capsule deformation is roughly in phase with that of the migration velocity and normal stress difference, with twice the frequency of the imposed shear. The maximum deformation increases linearly with the membrane elasticity before reaching a plateau at higher capillary numbers when the deformation is limited by the time over which shear is applied in the same direction and not by the membrane deformability. The maximum membrane deformation scales as the distance to the wall to the power 1/3 as observed for capsules and droplets in near-wall steady shear flows.
Versatile alignment layer method for new types of liquid crystal photonic devices
Authors: Finnemeyer V. , Bryant D. , Reich R. , Clark H. , Berry S. , Bozler C. , Yaroshchuk O. , Lu L. , Bos P.
Published: July 2015

Liquid crystal photonic devices are becoming increasingly popular. These devices often present a challenge when it comes to creating a robust alignment layer in pre-assembled cells. In this paper, we describe a method of infusing a dye into a microcavity to produce an effective photo-definable alignment layer. However, previous research on such alignment layers has shown that they have limited stability, particularly against subsequent light exposure. As such, we further describe a method of utilizing a pre-polymer, infused into the microcavity along with the liquid crystal, to provide photostability. We demonstrate that the polymer layer, formed under ultraviolet irradiation of liquid crystal cells, has been effectively localized to a thin region near the substrate surface and provides a significant improvement in the photostability of the liquid crystal alignment. This versatile alignment layer method, capable of being utilized in devices from the described microcavities to displays, offers significant promise for new photonics applications.
Weakly nonlinear theory of secondary rippling instability in surfaces of stressed solids
Authors: Du Lin , Dasgupta Dwaipayan , Maroudas Dimitrios
Published: July 2015

Numerical simulations of the surface morphological evolution of uniaxially stressed elastic crystalline solids have demonstrated that in addition to Asaro-Tiller/Grinfeld (surface cracking) instabilities, long-wavelength perturbations from the planar surface morphology can trigger a tip-splitting instability that causes formation of a pattern of secondary ripples, which cannot be explained by linear stability theory. In this study, we develop a weakly nonlinear stability theory, which can explain the occurrence of such secondary rippling instabilities and predict the number of secondary ripples that form on the surface as a function of perturbation wavelength. The theory shows that this type of surface pattern formation arises entirely due to the competition between surface energy and elastic strain energy, regardless of surface diffusional anisotropy or the action of externally applied fields. The origin of secondary rippling is explained through nonlinear terms included in the analysis which generate sub-harmonic ripples in the surface morphology with wave numbers that are multiples of the original surface perturbation wave number. Based on the weakly nonlinear theory, we have developed simple analytical expressions that predict the critical wavelength for the onset of secondary rippling, the increase in the number of secondary ripples with increasing perturbation wavelength, and how the onset of the secondary rippling instability and the rippled surface pattern are affected by surface diffusional anisotropy and the action of an applied electric field. The conclusions of the theory are validated by systematic comparisons with results of self-consistent dynamical simulations of surface morphological evolution.
Electromigration induced stress evolution under alternate current and pulse current loads
Authors: Sukharev V. , Huang X. , Tan S. X.-D.
Published: July 2015

Stress evolution in a metal line embedded in a rigid confinement caused by the arbitrary wave-form time-dependent current loads is resolved by a direct analytic solution of the one-dimensional (1-D) Korhonen's equation. Electromigration induced stress buildup and relaxation kinetics resulted by time-dependent current density are obtained as functions of the relevant physical parameters. A novel methodology for physics based conversion between the time-dependent and effective DC current densities is developed based on a condition of equal void nucleation times resulted by these currents. It is shown that in the case of high frequency currents, with periods much smaller than the characteristic time of stress evolution, the stress buildup is proportional to the pulse duty factor. It is demonstrated that very short metal lines with preexisted thermal voids loaded with symmetrical bi-directional currents can demonstrate a notable resistance increase when a specific temperature oscillation is generated in the line by active devices of the integrated circuit.
The effect of three-dimensional fields on bounce averaged particle drifts in a tokamak
Authors: Hegna C. C.
Published: July 2015

The impact of applied 3D magnetic fields on the bounce-averaged precessional drifts in a tokamak plasma are calculated. Local 3D MHD equilibrium theory is used to construct solutions to the equilibrium equations in the vicinity of a magnetic surface for a large aspect ratio circular tokamak perturbed by applied 3D fields. Due to modulations of the local shear caused by near-resonant Pfirsch-Schlüter currents, relatively weak applied 3D fields can have a large effect on trapped particle precessional drifts.
Dynamics of solvation and desolvation of rubidium attached to He nanodroplets
Authors: von Vangerow J. , John O. , Stienkemeier F. , Mudrich M.
Published: July 2015

The real-time dynamics of photoexcited and photoionized rubidium (Rb) atoms attached to helium (He) nanodroplets is studied by femtosecond pump-probe mass spectrometry. While excited Rb atoms in the perturbed 6p-state (Rb*) desorb off the He droplets, Rb+ photoions tend to sink into the droplet interior when created near the droplet surface. The transition from Rb+ solvation to full Rb* desorption is found to occur at a delay time τ ∼ 600 fs for Rb* in the 6pΣ-state and τ ∼ 1200 fs for the 6pΠ-state. Rb+He ions are found to be created by directly exciting bound Rb*He exciplex states as well as by populating bound Rb+He-states in a photoassociative ionization process.
Selective excitation enables assignment of proton resonances and 1H-1H distance measurement in ultrafast magic angle spinning solid state NMR spectroscopy
Authors: Zhang Rongchun , Ramamoorthy Ayyalusamy
Published: July 2015

Remarkable developments in ultrafast magic angle spinning (MAS) solid-state NMR spectroscopy enabled proton-based high-resolution multidimensional experiments on solids. To fully utilize the benefits rendered by proton-based ultrafast MAS experiments, assignment of 1H resonances becomes absolutely necessary. Herein, we propose an approach to identify different proton peaks by using dipolar-coupled heteronuclei such as 13C or 15N. In this method, after the initial preparation of proton magnetization and cross-polarization to 13C nuclei, transverse magnetization of desired 13C nuclei is selectively prepared by using DANTE (Delays Alternating with Nutations for Tailored Excitation) sequence and then, it is transferred to bonded protons with a short-contact-time cross polarization. Our experimental results demonstrate that protons bonded to specific 13C atoms can be identified and overlapping proton peaks can also be assigned. In contrast to the regular 2D HETCOR experiment, only a few 1D experiments are required for the complete assignment of peaks in the proton spectrum. Furthermore, the finite-pulse radio frequency driven recoupling sequence could be incorporated right after the selection of specific proton signals to monitor the intensity buildup for other proton signals. This enables the extraction of 1H-1H distances between different pairs of protons. Therefore, we believe that the proposed method will greatly aid in fast assignment of peaks in proton spectra and will be useful in the development of proton-based multi-dimensional solid-state NMR experiments to study atomic-level resolution structure and dynamics of solids.
Towards quantifying the role of exact exchange in predictions of transition metal complex properties
Authors: Ioannidis Efthymios I. , Kulik Heather J.
Published: July 2015

We estimate the prediction sensitivity with respect to Hartree-Fock exchange in approximate density functionals for representative Fe(II) and Fe(III) octahedral complexes. Based on the observation that the range of parameters spanned by the most widely employed functionals is relatively narrow, we compute electronic structure property and spin-state orderings across a relatively broad range of Hartree-Fock exchange (0%-50%) ratios. For the entire range considered, we consistently observe linear relationships between spin-state ordering that differ only based on the element of the direct ligand and thus may be broadly employed as measures of functional sensitivity in predictions of organometallic compounds. The role Hartree-Fock exchange in hybrid functionals is often assumed to play is to correct self-interaction error-driven electron delocalization (e.g., from transition metal centers to neighboring ligands). Surprisingly, we instead observe that increasing Hartree-Fock exchange reduces charge on iron centers, corresponding to effective delocalization of charge to ligands, thus challenging notions of the role of Hartree-Fock exchange in shifting predictions of spin-state ordering.
In search of optimal mode localization in two coupled mechanical resonators
Authors: Li Lijie
Published: July 2015

Since thirty years ago in 1982 when the concept of mode localization of the two coupled mechanical structures was introduced, there have been many investigations on this phenomenon, leading to applications in various areas, one of which is focused on transducers. This phenomenon is linked closely to Anderson localization theory in condensed matter physics; in fact, it is regarded as one-dimensional representation of the Anderson localization. Later, the configuration of two coupled mechanical structures has been extended to multiple coupled structures having one or more localized modes. All these investigations have pointed out that a weaker coupling factor will result in stronger mode localization; sometimes, it was noted that the weakest coupling has the greatest localization effect. However, it is not sufficiently precise, as the “weakest” coupling is for the structures that are nearly separate. Here, in this article, we conduct a theoretical and experimental study to unveil that there exists an optimal coupling for coupled mechanical structures at which the energy localization effect reaches to the maximum.
Injection current dependences of electroluminescence transition energy in InGaN/GaN multiple quantum wells light emitting diodes under pulsed current conditions
Authors: Zhang Feng , Ikeda Masao , Zhou Kun , Liu Zongshun , Liu Jianping , Zhang Shuming , Yang Hui
Published: July 2015

Injection current dependences of electroluminescence transition energy in blue InGaN/GaN multiple quantum wells light emitting diodes (LEDs) with different quantum barrier thicknesses under pulsed current conditions have been analyzed taking into account the related effects including deformation caused by lattice strain, quantum confined Stark effects due to polarization field partly screened by carriers, band gap renormalization, Stokes-like shift due to compositional fluctuations which are supposed to be random alloy fluctuations in the sub-nanometer scale, band filling effect (Burstein-Moss shift), and quantum levels in finite triangular wells. The bandgap renormalization and band filling effect occurring at high concentrations oppose one another, however, the renormalization effect dominates in the concentration range studied, since the band filling effect arising from the filling in the tail states in the valence band of quantum wells is much smaller than the case in the bulk materials. In order to correlate the carrier densities with current densities, the nonradiative recombination rates were deduced experimentally by curve-fitting to the external quantum efficiencies. The transition energies in LEDs both with 15 nm quantum barriers and 5 nm quantum barriers, calculated using full strengths of theoretical macroscopic polarization given by Barnardini and Fiorentini [Phys. Status Solidi B 216, 391 (1999)] are in excellent accordance with experimental results. The LED with 5 nm barriers has been shown to exhibit a higher transition energy and a smaller blue shift than those of LED with 15 nm barriers, which is mainly caused by the smaller internal polarization field in the quantum wells.
Optimal orientations of LiTaO3 for application in plate mode resonators
Authors: Naumenko Natalya F.
Published: July 2015

Optimal cuts of LiTaO3 for application in plate mode resonators were found via rigorous numerical investigations of zero- and higher-order plate modes propagating parallel or normal to the X-axis in rotated Y-cuts of LiTaO3; the plates were tested with a periodic metal grating on top of the plate and metal electrode present or absent on the plate bottom. In some cuts, high electromechanical coupling coefficients up to 20% could be combined with low or even zero temperature coefficients of frequency (TCF). Other cuts ensured moderate coupling of 12%–14% and low TCF in addition to high velocity of a higher-order plate mode up to 20 000 m/s. Metallization of a plate bottom helped to enhance coupling of certain modes. Interaction of a plate mode with electrodes of an interdigital transducer or with periodic metal gratings used for its excitation and reflection in resonators is illustrated by examples of dispersion plots. The nature of the analyzed modes was studied via visualization of the mechanical displacements accompanying wave propagation.
Evaluation of fatty acid composition of the microalgae Choricystis minor var. minor according to two different nutrient feeding strategies
Authors: Menezes R. S. , Soares A. T. , Lopes R. G. , Magnotti C. , Derner R. B. , Mori C. C. , Vieira A. A. H. , Antoniosi Filho N. R.
Published: July 2015

The microalgae biomass, mainly rich in lipids, carbohydrates, and other groups of compounds, has been considered as a promising raw material for renewable fuels production, particularly biodiesel. However, further knowledge on this subject is still needed. The objective of this study was to evaluate the effect of culture growth conditions (nutrient fractionation) on the cell biomass levels, fatty acid profile, as well as the content of fatty acids methyl esters (FAME) of freshwater microalgae Choricystis minor var. minor. The experiment consisted in determining the culture growth (biomass levels) employing WC medium in two treatments: full initial addition (100%) and fractional addition of nutrients on three specific days. The biomass produced was harvested in the exponential and stationary phases of the growth curve. No significant differences were found in the biomass levels (approximately 0.5 g l−1 at 8 days of culture) using different treatments. The FAME yields varied between 213.7 and 276.8 mg g−1 of dry biomass. Regarding the qualitative composition, fatty acid profiles were similar under tested culture growth conditions, whereas the quantitative content changed between them. The results from this investigation suggested that cultivation with full initial nutrient addition and biomass harvested at the stationary phase provided higher FAME yield and lower tri-unsaturated fatty acids (9.6%) and polyunsaturated fatty acids (4.0%) levels. Because of these characteristics, this culture growth conditions represent, among the studied strategies, the most interesting for Choricystis minor var. minor cultivation in order to produce biodiesel.
Recovering the vorticity of a light beam after scattering
Authors: Salla Gangi Reddy , Perumangattu Chithrabhanu , Prabhakar Shashi , Anwar Ali , Singh Ravindra P.
Published: July 2015

We generate optical vortices and scatter them through a rough surface. However, the scattered light passing through a lens shows the same vorticity when probed at the Fourier plane. The vorticity is measured using a nonseparable state of polarization and orbital angular momentum of light as it cannot be confirmed by the standard interferometric technique. The observed vorticity is found to be independent of the amount of scattered light collected. Therefore, vortices can be used as information carriers even in the presence of scattering media. The experimental results are well supported by the theoretical results.
Epitaxial growth and properties of La0.7Sr0.3MnO3 thin films with micrometer wide atomic terraces
Authors: Yuan Wei , Zhao Yuelei , Tang Chi , Su Tang , Song Qi , Shi Jing , Han Wei
Published: July 2015

La0.7Sr0.3MnO3 (LSMO) films with extraordinarily wide atomic terraces are epitaxially grown on SrTiO3 (100) substrates by pulsed laser deposition. Atomic force microscopy measurements on the LSMO films show that the atomic step is ∼4 Å and the atomic terrace width is more than 2 μm. For a 20 monolayers (MLs) LSMO film, the magnetization is determined to be 255 ± 15 emu/cm3 at room temperature, corresponding to 1.70 ± 0.11 μB per Mn atom. As the thickness of LSMO increases from 8 MLs to 20 MLs, the critical thickness for the temperature dependent insulator-to-metal behavior transition is shown to be 9 MLs. Furthermore, post-annealing in oxygen environment improves the electron transport and magnetic properties of the LSMO films.
Effect of segregated elements on the interactions between twin boundaries and screw dislocations in Mg
Authors: Yoshida Takashi , Yuasa Motohiro , Mabuchi Mamoru , Chino Yasumasa
Published: July 2015

Interactions of {101¯2} and {101¯1} twin boundaries (TBs), segregated by X (X = Sc, Y, or Nd), with screw partial dislocations were simulated using molecular dynamics (MD). In addition, mechanical tests were carried out on pure Mg and Mg–Y alloy. The MD simulation results suggested that the dislocations passed through the {101¯2} TB in all the models and that the shear strains for transmission in the Mg–X models were larger than that in the pure Mg model; in particular, the shear strain in the Mg–Y model was the largest. This corresponded to the experimental result that strain hardening was enhanced by Y addition. For interactions of a {101¯1} TB, some segregated atoms induced the emission of dislocations from the TB, whereas other segregated atoms locked the dislocation absorbed in the TB. As a result, the interaction behaviors of the {101¯1} TB were divided into five patterns. The interactions of this TB could be explained by the criterion of energy variations, as well as the interactions, of the {101¯2} TB, although segregation complicated the interactions of the {101¯1} TB.