bluuebunny/crossref_metadata_2025 huggingface dataset:
Light self-focusing in the atmosphere: thin window model
Authors: Vaseva Irina A. , Fedoruk Mikhail P. , Rubenchik Alexander M. , Turitsyn Sergei K.
Published: August 2016

Ultra-high power (exceeding the self-focusing threshold by more than three orders of magnitude) light beams from ground-based laser systems may find applications in space-debris cleaning. The propagation of such powerful laser beams through the atmosphere reveals many novel interesting features compared to traditional light self-focusing. It is demonstrated here that for the relevant laser parameters, when the thickness of the atmosphere is much shorter than the focusing length (that is, of the orbit scale), the beam transit through the atmosphere in lowest order produces phase distortion only. This means that by using adaptive optics it may be possible to eliminate the impact of self-focusing in the atmosphere on the laser beam. The area of applicability of the proposed “thin window” model is broader than the specific physical problem considered here. For instance, it might find applications in femtosecond laser material processing.
Lysophosphatidylcholine acts in the constitutive immune defence against American foulbrood in adult honeybees
Authors: Riessberger-Gallé Ulrike , Hernández-López Javier , Rechberger Gerald , Crailsheim Karl , Schuehly Wolfgang
Published: August 2016

Honeybee (Apis mellifera) imagines are resistant to the Gram-positive bacteriumPaenibacillus larvae(P. larvae), causative agent of American foulbrood (AFB), whereas honeybee larvae show susceptibility against this pathogen only during the first 48 h of their life. It is known that midgut homogenate of adult honeybees as well as a homogenate of aged larvae exhibit strong anti-P. larvaeactivity. A bioactivity-guided LC-HRMS analysis of midgut homogenate resulted in the identification of 1-oleoyl-sn-glycero-3-phosphocholine (LPC) pointing to a yet unknown immune defence in adult honeybees againstP. larvae. Antimicrobial activity of LPC was also demonstrated againstMelissococcus plutonius, causative agent of European Foulbrood. To demonstrate an AFB-preventive effect of LPC in larvae, artificially reared larvae were supplemented with LPC to evaluate its toxicity and to assess whether, after infection withP. larvaespores, LPC supplementation prevents AFB infection. 10 μg LPC per larva applied for 3 d significantly lowered mortality due to AFB in comparison to controls. A potential delivery route of LPC to the larvae in a colony via nurse bees was assessed through a tracking experiment using fluorescent-labelled LPC. This yet undescribed and non-proteinous defense of honeybees againstP. larvaemay offer new perspectives for a treatment of AFB without the utilization of classic antibiotics.
Fibroblast Growth Factor-2 facilitates the growth and chemo-resistance of leukemia cells in the bone marrow by modulating osteoblast functions
Authors: Sugimoto Keiki , Miyata Yasuhiko , Nakayama Takayuki , Saito Shigeki , Suzuki Ritsuro , Hayakawa Fumihiko , Nishiwaki Satoshi , Mizuno Hiroki , Takeshita Kyosuke , Kato Hidefumi , Ueda Ryuzo , Takami Akiyoshi , Naoe Tomoki
Published: August 2016

Stromal cells and osteoblasts play major roles in forming and modulating the bone marrow (BM) hematopoietic microenvironment. We have reported that FGF2 compromises stromal cell support of normal hematopoiesis. Here, we examined the effects of FGF2 on the leukemia microenvironment. In vitro, FGF2 significantly decreased the number of stromal-dependent and stromal-independent G0-leukemia cells in the stromal layers. Accordingly, CML cells placed on FGF2-treated stromal layers were more sensitive to imatinib. Conversely, FGF2 increased the proliferation of osteoblasts via FGFR1 IIIc, but its effects on osteoblast support of leukemia cell growth were limited. We next treated a human leukemia mouse model with Ara-C with/without systemic FGF2 administration. BM sections from FGF2-treated mice had thickened bone trabeculae and increased numbers of leukemia cells compared to controls. Leukemia cell density was increased, especially in the endosteal region in FGF2/Ara-C -treated mice compared to mice treated with Ara-C only. Interestingly, FGF2 did not promote leukemia cell survival in Ara-C treated spleen. Microarray analysis showed that FGF2 did not alter expression of many genes linked to hematopoiesis in osteoblasts, but modulated regulatory networks involved in angiogenesis and osteoblastic differentiation. These observations suggest that FGF2 promotes leukemia cell growth in the BM by modulating osteoblast functions.
Graphene–Selenium Hybrid Microballs as Cathode Materials for High-performance Lithium–Selenium Secondary Battery Applications
Authors: Youn Hee-Chang , Jeong Jun Hui , Roh Kwang Chul , Kim Kwang-Bum
Published: August 2016

In this study, graphene–selenium hybrid microballs (G–SeHMs) are prepared in one step by aerosol microdroplet drying using a commercial spray dryer, which represents a simple, scalable continuous process, and the potential of the G–SeHMs thus prepared is investigated for use as cathode material in applications of lithium–selenium secondary batteries. These morphologically unique graphene microballs filled with Se particles exhibited good electrochemical properties, such as high initial specific capacity (642 mA h g−1 at 0.1 C, corresponding to Se electrochemical utilisation as high as 95.1%), good cycling stability (544 mA h g−1 after 100 cycles at 0.1 C; 84.5% retention) and high rate capability (specific capacity of 301 mA h g−1 at 5 C). These electrochemical properties are attributed to the fact that the G–SeHM structure acts as a confinement matrix for suppressing the dissolution of polyselenides in the organic electrolyte, as well as an electron conduction path for increasing the transport rate of electrons for electrochemical reactions. Notably, based on the weight of hybrid materials, electrochemical performance is considerably better than that of previously reported Se-based cathode materials, attributed to the high Se loading content (80 wt%) in hybrid materials.
Mesenchymal stem cells protect against the tissue fibrosis of ketamine-induced cystitis in rat bladder
Authors: Kim Aram , Yu Hwan Yeul , Heo Jinbeom , Song Miho , Shin Jung-Hyun , Lim Jisun , Yoon Soo-Jung , Kim YongHwan , Lee Seungun , Kim Seong Who , Oh Wonil , Choi Soo Jin , Shin Dong-Myung , Choo Myung-Soo
Published: August 2016

Abuse of the hallucinogenic drug ketamine promotes the development of lower urinary tract symptoms that resemble interstitial cystitis. The pathophysiology of ketamine-induced cystitis (KC) is largely unknown and effective therapies are lacking. Here, using a KC rat model, we show the therapeutic effects of human umbilical cord-blood (UCB)-derived mesenchymal stem cells (MSCs). Daily injection of ketamine to Sprague-Dawley rats for 2-weeks resulted in defective bladder function, indicated by irregular voiding frequency, increased maximum contraction pressure, and decreased intercontraction intervals and bladder capacity. KC bladders were characterized by severe mast-cell infiltration, tissue fibrosis, apoptosis, upregulation of transforming growth factor-β signaling related genes, and phosphorylation of Smad2 and Smad3 proteins. A single administration of MSCs (1 × 106) into bladder tissue not only significantly ameliorated the aforementioned bladder voiding parameters, but also reversed the characteristic histological and gene-expression alterations of KC bladder. Treatment with the antifibrotic compound N-acetylcysteine also alleviated the symptoms and pathological characteristics of KC bladder, indicating that the antifibrotic capacity of MSC therapy underlies its benefits. Thus, this study for the first-time shows that MSC therapy might help to cure KC by protecting against tissue fibrosis in a KC animal model and provides a foundation for clinical trials of MSC therapy.
Spatiotemporal dynamics of urban green spaces and human–wildlife conflicts in Tokyo
Authors: Hosaka Tetsuro , Numata Shinya
Published: August 2016

Although urban green spaces are increasingly important both for humans and wildlife, an increase in urban green spaces may also increase human–wildlife conflicts in urban areas. However, few studies have examined the relationship between the size of green spaces and the level of conflicts with wildlife in multiple taxa, including invertebrates and vertebrates. To better understand current pest statistics and predict changes that will occur as the area of green spaces increases, we analysed a dataset compiling the number of pest consultations in 53 metropolitan districts in Tokyo over a 20-year period and its relationships with the area of green space. Stinging insects (e.g., wasps) made up over 50% of pest consultations, followed (in order) by rats and other nuisance animals (e.g., snakes). The number of consultations per unit population did not correlate, or was even negatively correlated, with the proportions of green spaces (mainly forest) for many indoor pests, but did positively correlate for some outdoor pests, such as wasps and snakes. Therefore, wasps and snakes can increase when urban green spaces increase. Because even minor nuisances are relevant for urban lifestyles, considerations of ways to minimise conflicts with wildlife are critical for urban green space management.
The effect of temperature and humidity on adhesion of a gecko-inspired adhesive: implications for the natural system
Authors: Stark Alyssa Y. , Klittich Mena R. , Sitti Metin , Niewiarowski Peter H. , Dhinojwala Ali
Published: August 2016

The adhesive system of geckos has inspired hundreds of synthetic adhesives. While this system has been used relentlessly as a source of inspiration, less work has been done in reverse, where synthetics are used to test questions and hypotheses about the natural system. Here we take such an approach. We tested shear adhesion of a mushroom-tipped synthetic gecko adhesive under conditions that produced perplexing results in the natural adhesive system. Synthetic samples were tested at two temperatures (12 °C and 32 °C) and four different humidity levels (30%, 55%, 70% and 80% RH). Surprisingly, adhesive performance of the synthetic samples matched that of living geckos, suggesting that uncontrolled parameters in the natural system, such as surface chemistry and material changes, may not be as influential in whole-animal performance as previously thought. There was one difference, however, when comparing natural and synthetic adhesive performance. At 12 °C and 80% RH, adhesion of the synthetic structures was lower than expected based on the natural system’s performance. Our approach highlights a unique opportunity for both biologists and material scientists, where new questions and hypotheses can be fueled by joint comparisons of the natural and synthetic systems, ultimately improving knowledge of both.
MicroRNAs as biomarkers for major depression: a role for let-7b and let-7c
Authors: Gururajan A , Naughton M E , Scott K A , O'Connor R M , Moloney G , Clarke G , Dowling J , Walsh A , Ismail F , Shorten G , Scott L , McLoughlin D M , Cryan J F , Dinan T G
Published: August 2016

There is a growing emphasis in the field of psychiatry on the need to identify candidate biomarkers to aid in diagnosis and clinical management of depression, particularly with respect to predicting response to specific therapeutic strategies. MicroRNAs are small nucleotide sequences with the ability to regulate gene expression at the transcriptomic level and emerging evidence from a range of studies has highlighted their biomarker potential. Here we compared healthy controls (n=20) with patients diagnosed with major depression (n=40) and who were treatment-resistant to identify peripheral microRNA biomarkers, which could be used for diagnosis and to predict response to electroconvulsive therapy (ECT) and ketamine (KET) infusions, treatments that have previously shown to be effective in treatment-resistant depression (TRD). At baseline and after treatment, blood samples were taken and symptom severity scores rated using the Hamilton Depression Rating Scale (HDRS). Samples were analyzed for microRNA expression using microarray and validated using quantitative PCR. As expected, both treatments reduced HDRS scores. Compared with controls, the baseline expression of the microRNA let-7b was less by ~40% in TRD patients compared with controls. The baseline expression of let-7c was also lower by ~50% in TRD patients who received ECT. Bioinformatic analysis revealed that let-7b and let-7c regulates the expression of 27 genes in the PI3k-Akt-mTOR signaling pathway, which has previously been reported to be dysfunctional in depression. The expression of miR-16, miR-182, miR-451 and miR-223 were similar to that in controls. Baseline microRNA expression could not predict treatment response and microRNAs were unaffected by treatment. Taken together, we have identified let-7b and let-7c as candidate biomarkers of major depression.
[1,2,5]Chalcogenodiazolo[3,4-c]pyridine and selenophene based donor–acceptor–donor electrochromic polymers electrosynthesized from high fluorescent precursors
Authors: Lu Baoyang , Ming Shouli , Lin Kaiwen , Zhen Shijie , Liu Hongtao , Gu Hua , Chen Shuai , Li Yuzhen , Zhu Zhengyou , Xu Jingkun
Published: August 2016

Two selenophene precursors, exhibiting yellow and red emission characteristics, were electropolymerized at low potentials to form the near-infrared electrochromic films.
Nanofibrous polymeric beads from aramid fibers for efficient bilirubin removal
Authors: Peng Zihang , Yang Ye , Luo Jiyue , Nie Chuanxiong , Ma Lang , Cheng Chong , Zhao Changsheng
Published: August 2016

Polymer based hemoperfusion has been developed as an effective therapy to remove the extra bilirubin from patients.
Recent progress in nanomaterials for gene delivery applications
Authors: Keles Erhan , Song Yang , Du Dan , Dong Wen-Ji , Lin Yuehe
Published: August 2016

Thanks to the availability of a wide range of surface modifications, graphene has emerged as one of the most promising nanomaterials for gene delivery applications in nanomedicine.
Exceptional gravimetric and volumetric CO2 uptake in a palladated NbO-type MOF utilizing cooperative acidic and basic, metal–CO2 interactions
Authors: Spanopoulos I. , Bratsos I. , Tampaxis C. , Vourloumis D. , Klontzas E. , Froudakis G. E. , Charalambopoulou G. , Steriotis T. A. , Trikalitis P. N.
Published: August 2016

A novel NbO-type MOF based on a palladated organic linker shows exceptional gravimetric and volumetric CO2 uptake.
The diastereoselective synthesis of octahedral cationic iridium hydride complexes with a stereogenic metal centre
Authors: Humbert Nicolas , Mazet Clément
Published: August 2016

We report herein the highly diastereoselective synthesis of octahedral cationic Ir(iii) hydride complexes with a stereogenic metal centre following various strategies.
Quasi-chemical approximation for polyatomic mixtures
Authors: Dávila M. V. , Pasinetti P. M. , Matoz-Fernandez D. A. , Ramirez-Pastor A. J.
Published: August 2016

The statistical thermodynamics of interacting binary mixtures of polyatomic species was developed.
The role of a small-scale cutoff in determining molecular layers at fluid interfaces
Authors: Sega Marcello
Published: August 2016

Molecular correlations at the liquid/vapour interface can be quantitatively associated to successive layers by using a natural choice for the small scale cutoff in surface identification algorithms.
Colloidal stability of reduced graphene oxide materials prepared using different reducing agents
Authors: Qi Yu , Xia Tianjiao , Li Yao , Duan Lin , Chen Wei
Published: August 2016

The aggregation tendency of GO/RGO correlates poorly with the degree of reduction but strongly with the types and concentrations of surface O functionalities.
Determination of relative sensitivity factors of elements in high purity copper by doping-melting and doping-pressed methods using glow discharge mass spectrometry
Authors: Zhang Jianying , Zhou Tao , Tang Yichuan , Cui Yanjie , Li Jinying
Published: August 2016

The calibration samples were prepared from high pure copper powder doped with standard solutions of graduated and defined concentration. And then a part of them was melted into bulks and another was pressed to tablets.
Hydrodynamic trapping for rapid assembly and in situ electrical characterization of droplet interface bilayer arrays
Authors: Nguyen Mary-Anne , Srijanto Bernadeta , Collier C. Patrick , Retterer Scott T. , Sarles Stephen A.
Published: August 2016

This work demonstrates a low-volume microfluidic system that enables rapid assembly of droplet interface bilayers with in situ electrical characterization.
Microfluidic platforms for DNA methylation analysis
Authors: Kurita Ryoji , Niwa Osamu
Published: August 2016

This review discusses epigenetics and the microfluidic platforms developed for DNA methylation analysis.
Abnormally high oscillator strengths of the graphene nanoribbons electronic spectrum: quantum chemistry calculations
Authors: Maslov V. G. , Svitenkov Andrey I. , Krzhizhanovskaya V. V.
Published: August 2016

Armchair-edged narrow graphene nanoribbons (GNRs) are modelled by semi-empirical Hartree–Fock based quantum chemistry method ZINDO/S-CI. ​Abnormally high oscillator strengths of over 200 are found in long GNRs (length > 150 hexagonal carbon rings).
Ab initio investigation on the stability of H-6 Carbon
Authors: Fthenakis Zacharias G.
Published: August 2016

H-6 Carbon is unstable due to the synergetic action of its interchain interactions (Uinter) with its zig-zag chain rotations (Urot), which eliminate the energy barrier provided by its intrachain interactions (Uintra), transforming it to diamond.
Hyaluronic acid anchored paclitaxel nanocrystals improves chemotherapeutic efficacy and inhibits lung metastasis in tumor-bearing rat model
Authors: Sharma Shweta , Singh Jyotsana , Verma Ashwni , Teja Banala Venkatesh , Shukla Ravi P. , Singh Sandeep K. , Sharma Veena , Konwar Rituraj , Mishra P. R.
Published: August 2016

Paclitaxel (PTX) is a first line anti-tumor agent and is widely used in the treatment of breast cancer.
Acidithiobacillus ferrooxidans improved H2S gas sensing properties of tubular hydroxyapatite at room temperature
Authors: Tan Yanni , Li Huixia , Liu Yong , Xie Jianping , He Jia , Pan Jun
Published: August 2016

H2S gas sensing properties of HAp was significantly improved by mixing withAcidithiobacillus ferrooxidans.
Insights into the electrooptical anion sensing properties of a new organic receptor: solvent dependent chromogenic response and DFT studies
Authors: P. Srikala , Tarafder Kartick , Shetty A. Nityananda , Trivedi Darshak R.
Published: August 2016

AcO− ion mediated color transition properties of an organic receptor in solvents of varying polarity highlighting the influence of dipole moment in stabilizing the excited state.
Selectfluor-mediated highly selective radical dioxygenation of alkenes
Authors: Lv Yunhe , Wang Xin , Cui Hao , Sun Kai , Pu Weiya , Li Gang , Wu Yingtao , He Jialin , Ren Xiaoran
Published: August 2016

Selectfluor mediated highly selective radical dioxygenation of alkenes using hydroxylamines and O2 was achieved under mild conditions.
SNR aware SBIA in multiple‐input–single‐output broadcast channel
Authors: Yang Qing , Jiang Ting , Zhou Zheng
Published: August 2016

Blind interference alignment (BIA) can eliminate users’ interference without channel state information and greatly improve the channel capacity, which has been regarded as a promising technique in next generation wireless systems. However, current BIA mechanisms neglect noise accumulations, resulting in final signal‐to‐noise ratio (fSNR) deterioration and reduced transmission rates. Motivated by ameliorating such negative impact induced by noise accumulations, this study establishes an SNR aware semi‐BIA (SNR SBIA) framework in the multi‐input–single‐output broadcast channel, where the users form different groups performing BIA for different SNR reductions. An SNR SBIA algorithm is further proposed based on tabu search for maximising the overall performance ensuring all users’ fSNRs higher than an SNR threshold. Extensive evaluations demonstrate that SNR SBIA can adapt to the users’ diverse received SNRs and the corresponding achievable sum rate is about 1.38 times and 1.92 times that in standard BIA and grouped hierarchical BIA, respectively.
New dynamic spectrum access algorithm for TV white space cognitive radio networks
Authors: Martin John Hugh , Dooley Laurence Sean , Wong Kam Cheung Patrick
Published: August 2016

As more user applications emerge for wireless devices, the corresponding amount of traffic is rapidly expanding, with the corollary that ever‐greater spectrum capacity is required. Service providers are experiencing deployment blockages due to insufficient bandwidth being available to accommodate such devices. TV White Space (TVWS) represents an opportunity to supplement existing licensed spectrum by exploiting unlicensed resources. TVWS spectrum has materialised from the unused TV channels in the switchover from analogue to digital platforms. The main obstacles to TVWS adoption are reliable detection of primary users (PUs) i.e. TV operators and consumers, allied with specifically, the hidden node problem. This study presents a new Generalised Enhanced Detection Algorithm (GEDA) that exploits the unique way Digital Terrestrial TV (DTT) channels are deployed in different geographical areas. GEDA effectively transforms an energy detector into a feature sensor to achieve significant improvements in detection probability of a DTT PU. Furthermore, by framing a novel margin strategy utilising a keep‐out contour, the hidden node issue is resolved and a viable secondary user sensing solution formulated. Experimental results for a cognitive radio TVWS model have formalised both the bandwidth and throughput gains secured by TVWS users with this new paradigm.
Broad‐band embroidered spiral antenna for off‐body communications
Authors: Zhang Shiyu , Paraskevopoulos Anastasios , Luxey Cyril , Pinto Jon , Whittow William
Published: August 2016

An embroidered wearable spiral antenna is presented in this study. The spiral antenna is compact and flexible, yet has broad‐band performance. The novelty of this study includes considering the antenna–body interaction rather than just considering the antenna alone. The antenna has been simulated and measured on a specific anthropomorphic mannequin torso phantom and a real person. The far‐field on‐body performance of the embroidered antenna on the phantom has been measured using a novel cylindrical near‐field to far‐field transformation technique. This technique allows the fast extraction of the full spherical radiation pattern and the corresponding far‐field antenna characteristics on the human body without the need of rotating the phantom with expensive positioning systems. The on‐body antenna performance including realised gain, directivity, radiation efficiency, radiation pattern and axial ratio have been presented.
Decoupling using diamond‐shaped patterned ground resonator for small MIMO antennas
Authors: Wu Di , Cheung Sing Wai , Li Qin Long , Yuk Tung Ip
Published: August 2016

A decoupling technique using a patterned ground structure for small multiple‐input multiple‐output (MIMO) antennas is proposed in this study. The MIMO antenna consists of two symmetrical L‐shaped inverted‐F antenna (IFA) elements designed to operate in the wireless‐local‐area‐network band and installed on a compact printed‐circuit board (PCB) with a size of 72.4 × 20 mm2 serving as ground. The two IFA elements have a very short separating distance of only 16.2 mm (0.13λ). To reduce strong mutual coupling, a diamond‐shaped patterned ground resonator (DSPGR) with a compact size of 16.2 × 10.13 mm2 is printed on the PCB between the two IFA elements. The effect of the DSPGR on reducing mutual coupling is studied using computer simulation. The impedance bandwidth, mutual coupling, peak gain, radiation pattern and efficiency, envelope‐correlation coefficient and multiplexing efficiency of the MIMO antenna are studied using simulation and measurement. Results show that the DSPGR can dramatically reduce mutual coupling between the two IFA elements to below −20 dB within the operating frequency range of 2.18–2.65 GHz (19.5%).
Combining droop and direct current vector control for control of parallel inverters in microgrid
Authors: Ramezani Malek , Li Shuhui , Sun Yang
Published: August 2016

Traditionally, active and reactive power sharing between parallel inverters based on droop control method is considered as a high priority for operating an islanded microgrid. An issue in droop control of parallel inverters in the islanding mode is the voltage drop associated with reactive power sharing within a microgrid. However, maintaining microgrid voltage stability while sharing active power between parallel inverters should be the primary objective for a microgrid. This study proposes to integrate droop and direct‐current vector control (DCVC) techniques for active power sharing and bus voltage control within a microgrid. The proposed approach consists of a droop‐only controlled unit whose function is similar to a traditional slack bus generator and the rest inverters controlled by using a combined droop‐DCVC technique. The droop‐DCVC controlled units provide active power sharing among parallel inverters and at the same time maintain microgrid voltage level by injecting the needed reactive power that is determined automatically from the droop‐DCVC controllers. Parallel inverter units with loads for a microgrid in the islanding mode are simulated using Matlab/Simulink and Opal‐RT real‐time simulation system. The hardware experiment is also conducted for two parallel inverters. Results show the effectiveness and excellent performance of parallel inverters in the microgrid by combining DCVC and droop methods.
Reflections on science advisory systems in Canada
Authors: Quirion Remi , Carty Arthur , Dufour Paul , Jabr Ramia
Published: August 2016

As the evolution of our world has triggered complexity and technological sophistication, it is now essential to consider sound scientific evidence as an integral element of decision-making. Science advisers or chief scientists have to take into account many factors in giving advice. Depending on the nature and level of advice, factors such as the ideology of the governing body, the state of the social, economic and scientific development in the country or region, potential impacts on the health, environment and security of the community, the balance of risk and reward in various options, must all be considered. Canada has lived through a few of these issues in its recent experience with science advice and advisory systems. This article will elaborate on the impact and influence of changes in science advisory bodies at the federal and Quebec government levels and will provide a perspective on their impact. It examines the historical evolution of the advisory apparatus for science throughout Canada’s history and underscores some of their successes and failures under different regimes. The conclusion drawn in this article is that science and science advisory systems in Canada have lacked continuity and a solid foundation thus weakening efforts to enable sound science-based policy into decision-making. The article argues for a more institutionalized and pluralistic approach to ensuring that evidence and science advice can endure—both at the federal and provincial levels. In many ways, the experience with these advisory mechanisms suggests a growing need to ensure sound advice within increasingly complex decision-making as well as a demand by citizens to have scientific evidence considered more carefully in public policy and for the public interest. This article is published as part of a collection on scientific advice to governments.
Molecular dynamics investigation of hexagonal boron nitride sputtering and sputtered particle characteristics
Authors: Smith Brandon D. , Boyd Iain D.
Published: August 2016

The sputtering of hexagonal boron nitride (h-BN) by impacts of energetic xenon ions is investigated using a molecular dynamics (MD) model. The model is implemented within an open-source MD framework that utilizes graphics processing units to accelerate its calculations, allowing the sputtering process to be studied in much greater detail than has been feasible in the past. Integrated sputter yields are computed over a range of ion energies from 20 eV to 300 eV, and incidence angles from 0° to 75°. Sputtering of boron is shown to occur at energies as low as 40 eV at normal incidence, and sputtering of nitrogen at as low as 30 eV at normal incidence, suggesting a threshold energy between 20 eV and 40 eV. The sputter yields at 0° incidence are compared to existing experimental data and are shown to agree well over the range of ion energies investigated. The semi-empirical Bohdansky curve and an empirical exponential function are fit to the data at normal incidence, and the threshold energy for sputtering is calculated from the Bohdansky curve fit as 35 ± 2 eV. These results are shown to compare well with experimental observations that the threshold energy lies between 20 eV and 40 eV. It is demonstrated that h-BN sputters predominantly as atomic boron and diatomic nitrogen, and the velocity distribution function (VDF) of sputtered boron atoms is investigated. The calculated VDFs are found to reproduce the Sigmund-Thompson distribution predicted by Sigmund's linear cascade theory of sputtering. The average surface binding energy computed from Sigmund-Thompson curve fits is found to be 4.5 eV for ion energies of 100 eV and greater. This compares well to the value of 4.8 eV determined from independent experiments.
Improved edge charge exchange recombination spectroscopy in DIII-D
Authors: Chrystal C. , Burrell K. H. , Grierson B. A. , Haskey S. R. , Groebner R. J. , Kaplan D. H. , Briesemeister A.
Published: August 2016

The charge exchange recombination spectroscopy diagnostic on the DIII-D tokamak has been upgraded with the addition of more high radial resolution view chords near the edge of the plasma (r/a > 0.8). The additional views are diagnosed with the same number of spectrometers by placing fiber optics side-by-side at the spectrometer entrance with a precise separation that avoids wavelength shifted crosstalk without the use of bandpass filters. The new views improve measurement of edge impurity parameters in steep gradient, H-mode plasmas with many different shapes. The number of edge view chords with 8 mm radial separation has increased from 16 to 38. New fused silica fibers have improved light throughput and clarify the observation of non-Gaussian spectra that suggest the ion distribution function can be non-Maxwellian in low collisionality plasmas.
Nanoflow over a fractal surface
Authors: Papanikolaou Michail , Frank Michael , Drikakis Dimitris
Published: August 2016

This paper investigates the effects of surface roughness on nanoflows using molecular dynamics simulations. A fractal model is employed to model wall roughness, and simulations are performed for liquid argon confined by two solid walls. It is shown that the surface roughness reduces the velocity in the proximity of the walls with the reduction being accentuated when increasing the roughness depth and wettability of the solid wall. It also makes the flow three-dimensional and anisotropic. In flows over idealized smooth surfaces, the liquid forms parallel, well-spaced layers, with a significant gap between the first layer and the solid wall. Rough walls distort the orderly distribution of fluid layers resulting in an incoherent formation of irregularly shaped fluid structures around and within the wall cavities.
Permeability and effective slip in confined flows transverse to wall slippage patterns
Authors: Kumar Avinash , Datta Subhra , Kalyanasundaram Dinesh
Published: August 2016

The pressure-driven Stokes flow through a plane channel with arbitrary wall separation having a continuous pattern of sinusoidally varying slippage of arbitrary wavelength and amplitude on one/both walls is modelled semi-analytically. The patterning direction is transverse to the flow. In the special situations of thin and thick channels, respectively, the predictions of the model are found to be consistent with lubrication theory and results from the literature pertaining to free shear flow. For the same pattern-averaged slip length, the hydraulic permeability relative to a channel with no-slip walls increases as the pattern wave-number, amplitude, and channel size are decreased. Unlike discontinuous wall patterns of stick-slip zones studied elsewhere in the literature, the effective slip length of a sinusoidally patterned wall in a confined flow continues to scale with both channel size and the pattern-averaged slip length even in the limit of thin channel size to pattern wavelength ratio. As a consequence, for sufficiently small channel sizes, the permeability of a channel with sinusoidal wall slip patterns will always exceed that of an otherwise similar channel with discontinuous patterns on corresponding walls. For a channel with one no-slip wall and one patterned wall, the permeability relative to that of an unpatterned reference channel of same pattern-averaged slip length exhibits non-monotonic behaviour with channel size, with a minimum appearing at intermediate channel sizes. Approximate closed-form estimates for finding the location and size of this minimum are provided in the limit of large and small pattern wavelengths. For example, if the pattern wavelength is much larger than the channel thickness, exact results from lubrication theory indicate that a worst case permeability penalty relative to the reference channel of ∼23% arises when the average slip of the patterned wall is ∼2.7 times the channel size. The results from the current study should be applicable to microfluidic flows through channels with hydrophobized/super-hydrophobic surfaces.
A stretch/compress scheme for a high temporal resolution detector for the magnetic recoil spectrometer time (MRSt)
Authors: Hilsabeck T. J. , Frenje J. A. , Hares J. D. , Wink C. W.
Published: August 2016

A time-resolved detector concept for the magnetic recoil spectrometer for time-resolved measurements of the NIF neutron spectrum is presented. The measurement is challenging due to the time spreading of the recoil protons (or deuterons) as they transit an energy dispersing magnet system. Ions arrive at the focal plane of the magnetic spectrometer over an interval of tens of nanoseconds. We seek to measure the time-resolved neutron spectrum with 20 ps precision by manipulating an electron signal derived from the ions. A stretch-compress scheme is employed to remove transit time skewing while simultaneously reducing the bandwidth requirements for signal recording. Simulation results are presented along with design concepts for structures capable of establishing the required electromagnetic fields.
Bubbling behaviors induced by gas-liquid mixture permeating through a porous medium
Authors: Hu Liang , Li Mingbo , Chen Wenyu , Xie Haibo , Fu Xin
Published: August 2016

This paper investigates the bubbling behaviors induced by gas-liquid mixture permeating through porous medium (PM), which was observed in developing immersion lithography system and was found having great differences with traditional bubbling behaviors injected with only gas phase through the PM. An experimental setup was built up to investigate the bubbling characteristics affected by the mixed liquid phase. Both the flow regimes of gas-liquid mixture in micro-channel (upstream of the PM) and the bubbling flow regimes in water tank (downstream of the PM) were recorded synchronously by high-speed camera. The transitions between the flow regimes are governed by gas and liquid Weber numbers. Based on the image analysis, the characteristic parameters of bubbling region, including the diameter of bubbling area on PM surface, gas-phase volume flux, and dispersion angle of bubbles in suspending liquid, were studied under different proportions of gas and liquid flow rate. Corresponding empirical correlations were developed to describe and predict these parameters. Then, the pertinent bubble characteristics in different bubbling flow regimes were systematically investigated. Specifically, the bubble size distribution and the Sauter mean diameter affected by increasing liquid flow rate were studied, and the corresponding analysis was given based on the hydrodynamics of bubble-bubble and bubble-liquid interactions. According to dimensionless analysis, the general prediction equation of Sauter mean diameter under different operating conditions was proposed and confirmed by experimental data. The study of this paper is helpful to improve the collection performance of immersion lithography and aims to reveal the differences between the bubbling behaviors on PM caused by only gas flow and gas-liquid mixture flow, respectively, for the researches of fluid flow.
Extraordinary acoustic transmission through annuluses in air and its applications in acoustic beam splitter and concentrator
Authors: Ge Yong , Sun Hong-xiang , Liu Shu-sen , Yuan Shou-qi , Xia Jian-ping , Guan Yi-jun , Zhang Shu-yi
Published: August 2016

We report an extraordinary acoustic transmission through two layer annuluses made of metal cylinders in air both numerically and experimentally. The effect arises from the enhancement and reconstruction of the incident source induced by different Mie-resonance modes of the annuluses. The proposed system takes advantages of the consistency in the waveform between the input and output waves, the high amplitude amplification of output waves, and the easy adjustment of structure. More interestingly, we investigate the applications of the extraordinary acoustic transmission in the acoustic beam splitter and acoustic concentrator. Our finding should have an impact on ultrasonic applications.
A robust and accurate formulation of molecular and colloidal electrostatics
Authors: Sun Qiang , Klaseboer Evert , Chan Derek Y. C.
Published: August 2016

This paper presents a re-formulation of the boundary integral method for the Debye-Hückel model of molecular and colloidal electrostatics that removes the mathematical singularities that have to date been accepted as an intrinsic part of the conventional boundary integral equation method. The essence of the present boundary regularized integral equation formulation consists of subtracting a known solution from the conventional boundary integral method in such a way as to cancel out the singularities associated with the Green’s function. This approach better reflects the non-singular physical behavior of the systems on boundaries with the benefits of the following: (i) the surface integrals can be evaluated accurately using quadrature without any need to devise special numerical integration procedures, (ii) being able to use quadratic or spline function surface elements to represent the surface more accurately and the variation of the functions within each element is represented to a consistent level of precision by appropriate interpolation functions, (iii) being able to calculate electric fields, even at boundaries, accurately and directly from the potential without having to solve hypersingular integral equations and this imparts high precision in calculating the Maxwell stress tensor and consequently, intermolecular or colloidal forces, (iv) a reliable way to handle geometric configurations in which different parts of the boundary can be very close together without being affected by numerical instabilities, therefore potentials, fields, and forces between surfaces can be found accurately at surface separations down to near contact, and (v) having the simplicity of a formulation that does not require complex algorithms to handle singularities will result in significant savings in coding effort and in the reduction of opportunities for coding errors. These advantages are illustrated using examples drawn from molecular and colloidal electrostatics.
Thickness effect on the structure, grain size, and local piezoresponse of self-polarized lead lanthanum zirconate titanate thin films
Authors: Melo M. , Araújo E. B. , Shvartsman V. V. , Shur V. Ya. , Kholkin A. L.
Published: August 2016

Polycrystalline lanthanum lead zirconate titanate (PLZT) thin films were deposited on Pt/TiO2/SiO2/Si substrates to study the effects of the thickness and grain size on their structural and piezoresponse properties at nanoscale. Thinner PLZT films show a slight (100)-orientation tendency that tends to random orientation for the thicker film, while microstrain and crystallite size increases almost linearly with increasing thickness. Piezoresponse force microscopy and autocorrelation function technique were used to demonstrate the existence of local self-polarization effect and to study the thickness dependence of correlation length. The obtained results ruled out the bulk mechanisms and suggest that Schottky barriers near the film-substrate are likely responsible for a build-in electric field in the films. Larger correlation length evidence that this build-in field increases the number of coexisting polarization directions in larger grains leading to an alignment of macrodomains in thinner films.
Band alignments in Fe/graphene/Si(001) junctions studied by x-ray photoemission spectroscopy
Authors: Le Breton J.-C. , Tricot S. , Delhaye G. , Lépine B. , Turban P. , Schieffer P.
Published: August 2016

The control of tunnel contact resistance is of primary importance for semiconductor-based spintronic devices. This control is hardly achieved with conventional oxide-based tunnel barriers due to deposition-induced interface states. Manipulation of single 2D atomic crystals (such as graphene sheets) weakly interacting with their substrate might represent an alternative and efficient way to design new heterostructures for a variety of different purposes including spin injection into semiconductors. In the present paper, we study by x-ray photoemission spectroscopy the band alignments and interface chemistry of iron–graphene-hydrogenated passivated silicon (001) surfaces for a low and a high n-doping concentration. We find that the hydrogen passivation of the Si(001) surface remains efficient even with a graphene sheet on the Si(001) surface. For both doping concentrations, the semiconductor is close to flat-band conditions which indicates that the Fermi level is unpinned on the semiconductor side of the Graphene/Si(001):H interface. When iron is deposited on the graphene/Si(001):H structures, the Schottky barrier height remains mainly unaffected by the metallic overlayer with a very low barrier height for electrons, a sought-after property in semiconductor based spintronic devices. Finally, we demonstrate that the graphene layer intercalated between the metal and semiconductor also serves as a protection against iron-silicide formation even at elevated temperatures preventing from the formation of a Si-based magnetic dead layer.
Ultra-thin, single-layer polarization rotator
Authors: Son T. V. , Truong V. V. , Do P. A. , Haché A.
Published: August 2016

We demonstrate light polarization control over a broad spectral range by a uniform layer of vanadium dioxide as it undergoes a phase transition from insulator to metal. Changes in refractive indices create unequal phase shifts on s- and p-polarization components of incident light, and rotation of linear polarization shows intensity modulation by a factor of 103 when transmitted through polarizers. This makes possible polarization rotation devices as thin as 50 nm that would be activated thermally, optically or electrically.
Record-breaking protein images have applications for drug discovery
Authors: Miller Johanna L.
Published: August 2016

Thanks to new electron detectors, cryoelectron microscopy is experiencing a revolution. It can now solve the structures of small biomolecules at high resolution.
The colors of radiative beta decay
Authors: Miller Johanna L.
Published: August 2016

The energy distribution of photons produced in a rare neutron-decay mode has now been measured.
Dynamic periplasmic chaperone reservoir facilitates biogenesis of outer membrane proteins
Authors: Costello Shawn M. , Plummer Ashlee M. , Fleming Patrick J. , Fleming Karen G.
Published: August 2016

Significance

The study of bacterial outer membrane proteins (OMPs) is critical to understanding cellular communication, metabolic transport across membranes, and pathogenesis. We used a holistic computational approach to examine how the OMP biogenesis machinery maintains cellular proteostasis under biologically relevant conditions. This treatment overcomes common limitations of both in vitro and in vivo experiments because we can simultaneously investigate unfolded OMP (uOMP) transport and folding trajectories at a microscopic level and phenotypes at a macroscopic level. This analysis provides global insight into the dynamic process of periplasmic uOMP transport and highlights the unique contributions of individual chaperones in the maintenance of outer membrane and periplasmic proteostasis.
Constraint, natural selection, and the evolution of human body form
Authors: Savell Kristen R. R. , Auerbach Benjamin M. , Roseman Charles C.
Published: August 2016

Significance

Human morphological variation is thought to have been partially shaped by natural selection associated with environmental factors like climate. Patterns of variation in body form correspond with latitude, but evolutionary processes that yielded this variation are not yet established. Examining the traits used in these studies (e.g., limb lengths) independently ignores their genetic covariation, which affects their responses to evolutionary forces. To address this relationship, we estimated the directional selection necessary to evolve correlated traits reflecting body shape across latitudes and examined trait-specific responses. Although most traits appear to be under directional selection, their response is constrained by between-trait covariance. This finding suggests that trait differences among human groups may not directly reflect the forces of selection that shaped them.
Partial squeeze film levitation modulates fingertip friction
Authors: Wiertlewski Michaël , Fenton Friesen Rebecca , Colgate J. Edward
Published: August 2016

Significance

Touchscreens have redefined human–computer interfaces. Although flexibility in the design of interfaces has dramatically increased, users are still confronted with a flat, featureless glass plate that cannot provide any tactile cues. Exciting this plate with ultrasonic waves reduces the friction experienced by a user’s finger, enabling tactile feedback directly on the surface. For vibration amplitudes of ±3 μm, we measured a reduction of up to 95% in the friction force experienced by a sliding finger. Using special illumination techniques and microsecond imaging, we show that this reduction of friction is because of the skin bouncing on a layer of air trapped between the plate and the surface of the finger.
Reducing C-terminal truncation mitigates synucleinopathy and neurodegeneration in a transgenic model of multiple system atrophy
Authors: Bassil Fares , Fernagut Pierre-Olivier , Bezard Erwan , Pruvost Alain , Leste-Lasserre Thierry , Hoang Quyen Q. , Ringe Dagmar , Petsko Gregory A. , Meissner Wassilios G.
Published: August 2016

Significance

Multiple system atrophy (MSA) is a fatal neurodegenerative disorder associated with the accumulation of alpha-synuclein (α-syn) aggregates in oligodendrocytes. There is currently no treatment to slow down the aggressive neurodegenerative process. C-terminal truncation of α-syn promotes the formation of oligomers and aggregates that, in turn, mediate neurotoxicity in synucleinopathies including MSA. We present here an in vivo proof of concept of the ability of the caspase-1 inhibitor VX-765 to mitigate α-syn pathology and provide neuroprotection in a transgenic mouse model of MSA through reduction of α-syn C-terminal truncation. These findings suggest that VX-765, a well-tolerated drug in a 6 wk-long phase II trial in patients with epilepsy, is a promising candidate to achieve disease modification in MSA by limiting α-syn accumulation.