bluuebunny/crossref_metadata_2025 huggingface dataset:
A Novel Numerical Scheme for Outlet Boundary Conditions in Large Density Ratio Lattice Boltzmann Model
Authors: Li Long , Liu Yongwen
Published: March 2016

In the past decades, the Lattice Boltzmann method has gained much success in variety fields especially in multiphase flow, porous media flow, and other complex flow, and become a promising method for computational fluid dynamic (CFD). The outlet boundary condition (OBC) and its numerical scheme are critical issues in CFD, which may influence the accuracy and stability of the calculation. The common OBCs i.e. Neumann boundary condition (NBC), extrapolation boundary condition (EBC), and convection boundary condition (CBC), which have been widely investigated in single-phase LB model, have rarely been investigated in multiphase LB model. The previous research on the OBCs for two-phase LB model only aims at small density ratio. While in most industrial applications, the density ratio often ranges from a hundred to a thousand, and a large density ratio would bring some problems such as parasitic current and bad stability in LB method. Lee and Fischer have proposed an improved LB model which is suitable for large density ratio two-phase flow. In order to assess the OBCs for large density ratio LB model, the OBCs are investigated. And it is found that the existing OBC numerical scheme cannot be directly applied to the large density ratio LB model. In present study, a novel numerical scheme for the OBCs is proposed assuming that the outlet velocity is gained by the outlet boundary condition instead of the momentum equation which is an improvement of previous scheme, and it can be used in large density ratio LB model. The performance of the proposed OBC scheme is examined for different density ratios. The results show that the proposed OBC scheme could converge in a stable manner. Comparing with the reference flow condition, the CBC scheme shows a better performance than the NBC scheme and the EBC scheme. The NBC scheme would lead a large droplet deformation, large velocity peaks at the outlet, and large errors for both small and large density ratio. And the EBC scheme keeps a good droplet shape, but it would lead large velocity peaks at the outlet and large error when large density ratio is considered. The CBC scheme always shows superior performance including a good droplet shape, smooth outlet velocity profile, and small errors no matter whether the density ratio is small or large. Hence the CBC scheme could be applied in large density ratio LB model for the outlet boundary condition, which has a good accuracy and stability in the calculation.
Heat Exchanger Improvement via Curved Microfluidic Channels: Part 2 — Investigation Into Heat Transfer Enhancement due to the Dynamics of Dean Vortices
Authors: Marshall Samuel D. , Arayanarakool Rerngchai , Balasubramaniam Lakshmi , Li Bing , Lee Poh Seng , Chen Peter C. Y.
Published: March 2016

The efficiency of conventional heat exchangers is restricted by many factors, such as effectiveness of convective heat transfer and the cost of their operation. The current research deals with these issues by developing a novel method for building a lower-cost yet more efficient heat sink. This method involves using a specially designed curved microchannel to utilise the enhanced fluid mixing characteristics of Dean vortices, and thus transferring heat efficiently.

Numerical models have been employed to investigate the heat transfer enhancement of curved channels over straight equivalents, with the aim of optimising the heat exchanger design based on the parameters of maximising heat transfer whilst minimising pressure drop and unit cost. These studies examined the variation of Nusselt Number over the length of the channel, for a range of different curvatures (and hence Dean numbers). The results showed significantly higher heat transfer occurring in curved channels, especially in areas where the generated Dean vortices are strongest, with the variation in Nusselt Number forming the shape of an ‘arc’. In this way, a relationship between the Dean Number and the Nusselt Number is characterised and discussed, leading to suggestions regarding optimal microfluidic heat transfer design.
Uncertainty Analysis of Melting and Resolidification of Gold Film Irradiated by Nano- to Femtosecond Lasers Using Stochastic Method
Authors: Afrin Nazia , Zhang Yuwen , Chen J. K.
Published: March 2016

A sample-based stochastic model is presented to investigate the effects of uncertainties of various input parameters, including laser fluence, laser pulse duration, thermal conductivity constants for electron, and electron-lattice coupling factor, on solid-liquid phase change of gold film under nano- to femtosecond laser irradiation. Rapid melting and resolidification of a free standing gold film subject to nano- to femtosecond laser are simulated using a two-temperature model incorporated with the interfacial tracking method. The interfacial velocity and temperature are obtained by solving the energy equation in terms of volumetric enthalpy for control volume. The convergence of variance (COV) is used to characterize the variability of the input parameters, and the interquartile range (IQR) is used to calculate the uncertainty of the output parameters. The IQR analysis shows that the laser fluence and the electron-lattice coupling factor have the strongest influences on the interfacial location, velocity, and temperatures.
Numerical and Experimental Investigation of Bubble Dynamics via Electrowetting-on-Dielectric (EWOD)
Authors: Wang Sheng , Shi Junxiang , Chen Hsiu-Hung , Xu Tiancheng , Chen Chung-Lung (C. L.)
Published: March 2016

With the inspiration from electrowetting-controlled droplets, the potential advantages of electrowetting for bubble dynamics are investigated experimentally and numerically. In our experimental system, a 100 nanometer thin film gold metal was used as an electrode, and a 6.5 micrometer polydimethylsiloxane (PDMS) was spin-coated on the electrode acting both as an dielectric layer and hydrophobic surface. A two-phase model coupled with a electrostatics was used in our simulation work, where the body force due to the electric field acts as an external force. Our numerical results demonstrated that electrowetting can help the detachment of a small bubble by changing the apparent contact angle. Similar results were observed in our experiments that with electrowetting on dielectric, the contact angle of bubble on a hydrophobic surface will obviously decrease when a certain electrical field is applied either with a small size bubble (diameter around 1mm) or a relatively larger size bubble (diameter around 3 mm). When the applied voltage becomes high enough, both the experimental and numerical results demonstrate the characteristics of bubble detachment within a thin film liquid layer.
Tungsten Nanowire Metamaterials as Selective Solar Thermal Absorbers by Excitation of Magnetic Polaritons
Authors: Chang J.-Y. , Wang H. , Wang L. P.
Published: March 2016

The present study focuses on nanowire based metamaterials with excitation of magnetic polariton (MP) as selective solar absorbers. Finite-difference time-domain simulation is employed for numerically designing a broadband solar absorber made of lossy tungsten nanowires which exhibit spectral selectivity due to the excitation of MP. An inductor-capacitor circuit model of the nanowire array is developed in order to predict the resonance wavelengths of the MP harmonic modes. The effects of geometric parameters such as nanowire diameter, height, and array period are investigated and understood on tuning the magnetic polariton resonance and the resulting optical and radiative properties. In addition, the independence of incidence angles is demonstrated, which illustrates the potential applicability of the nanowire-based metamaterial as a high-efficiency wide-angle selective solar absorber. The results will facilitate the design of novel low-cost and high-efficiency materials for enhancing solar thermal energy harvesting and conversion.
An Experimental Study on the Thermal Performance of the Flat Heat Pipe
Authors: Xiaohong Hao , Guan Jiqing , Zhao Jingbo
Published: March 2016

As the rapid growing of the semiconductor logic gate number and operation speed, the heat dissipated from electronic devices increases drastically. Moreover, most of the heat flux can reach about 100 W/cm2, therefore efficient removal of the heat from the electronic devices is essential to ensure the reliable operation of the electronic devices. The traditional direct cooling system, such as air cooling, liquid cooling, would not be able to transfer the high heat flux owing to their heat transfer limits, so advanced cooling solutions are necessary.

The flat heat pipes have some advantages, such as small scale, strong heat transfer capacity, low weight penalty and low environmental requirements, therefore, in recent years, researchers have shown great interest for the flat heat pipe. But most of them played the important on the structure design of the flat heat pipes, and few of them focused on the study of the effect of the working fluid on the heat transfer performance.

In this paper, a flat heat pipe with rectangular channel is designed and manufactured, and an experimental set up was built to study working fluid on the effects of the flat heat Pipe thermal performance.

The flat heat pipe is heated via a 35mmx20mm rectangular electrical resistance (the evaporator side), and the other side (the condenser side) is cooled by convection of a heat sink. In the experimental work, three types of working fluid are used in the heat pipe: (A) deionized water, (B) deionized water-based Fe3O4 nano fluid (1, 1.5wt%). A comparison is performed for the thermal performance of different size flat heat pipe.

Finally, the experimental results showed that nano fluid could improve the thermal performance of the FHP. With the same charge volume, the heat transfer coefficient of the FHPs filled with nano fluid were higher than that of DI water. There was an optimal mass concentration which was estimated to be 1.5 wt% to achieve the maximum heat transfer enhancement.
Thermal Viscous Dissipative Couette Flow in a Porous Medium Filled Microchannel
Authors: Baig Farrukh Mirza , Chen G. M. , Lim B. K.
Published: March 2016

The increasing demand for high-performance electronic devices and surge in power density accentuates the need for heat transfer enhancement. In this study, a thermal viscous dissipative Coeutte flow in a micochannel filled with fluid saturated porous medium is looked into. The study explores the fluid flow and heat transfer phenomenon for a Coeutte flow in a microchannel as well as to establish the relationship between the heat convection coefficient and viscous dissipation. The moving boundary in this problem is subjected to uniform heat flux while the fixed plate is assumed adiabatic. In order to simplify the problem, we consider a fully developed flow and assume local thermal equilibrium in the analysis. An analytical Nusselt number expression is developed in terms of Brinkman number as a result of this study, thus providing essential information to predict accurately the thermal performance of a microchannel. The results obtained without viscous dissipation are in close agreement with published results whereas viscous dissipation has a more significant effect on Nusselt number for a porous medium with higher porous medium shape factor. The Nusselt number versus Brinkman number plot shows an asymptotic Brinkman number, indicating a change in sign of the temperature difference between the bulk mean temperature and the wall temperature. The effects of Reynolds number on the two dimensional temperature profile for a Couette flow in a microchannel are investigated. The temperature distribution of a microscale duct particularly along the axial direction is a strong function of viscous dissipation. The significance of viscous dissipation to a microscale duct as compared to a conventional scale duct is also discussed and compared in this study.
Prediction of Refrigerant Flow Boiling Hysteresis With an Augmented Separated-Flow Model
Authors: Gao Jianwei , Li Hongxia , Almheiri Saif , Zhang TieJun
Published: March 2016

Thermal management is essential to compact devices particularly for high heat flux removal applications. As a popular thermal technology, refrigeration cooling is able to provide relatively high heat flux removal capability and uniform device surface temperature. In a refrigeration cycle, the performance of evaporator is extremely important to the overall cooling efficiency. In a well-designed evaporator, effective flow boiling heat transfer can be achieved whereas the critical heat flux (CHF) or dryout condition must be avoided. Otherwise the device surface temperature would rise significantly and cause device burnout due to the poor heat transfer performance of film boiling. In order to evaluate the influence of varying imposed heat fluxes, saturated flow boiling in the evaporator is systematically studied. The complete refrigerant flow boiling hysteresis between the imposed heat flux and the exit wall superheat is characterized. Upon the occurrence of CHF at the evaporator wall exit, the wall heat flux redistributes due to the axial wall heat conduction, which drives the dryout point to propagate upstream in the evaporator. As a result, a significant amount of thermal energy is stored in the evaporator wall. While the heat flux starts decreasing, the dryout point moves downstream and closer to the exit. The stored heat in the wall dissipates slowly and leads to the delay in rewetting or quenching, which is the key to understand and predict the flow boiling hysteresis. In order to reveal the transient heat releasing mechanism, an augmented separated-flow model is developed to predict the moving rewetting point and minimum heat flux at the evaporator exit, and the model predictions are further validated by experimental data from a refrigeration cooling testbed.
Numerical Simulation of Gravity-Driven Droplet Displacement on an Inclined Micro-Grooved Surface
Authors: Wang Qilin , Li Yan , Yu Zhicheng , Guo Bin
Published: March 2016

Gravity-driven displacement of droplet on an inclined micro-grooved surface is studied using Pseudo-potential model of lattice Boltzmann method. To validate the numerical method, we find good agreement of the LB simulations with the pressure difference by Laplace’s law. The equilibrium contact angle of a droplet wetting on a smooth horizontal surface is studied as a function of the wettability, finding good agreement with an empirical scheme obtained with Young’s equation. The dynamic behavior of a droplet wetting on micro-grooved horizontal surface is found to be complex and greatly affected by the fraction of the grooved area and the groove width, the results indicate that the effect of grooves on contact angle is dependent on the fraction of the grooved area and the groove width has not a consistent effect on contact angles. For an inclined nonwetting micro-grooved surface, in given range, higher fraction of the grooved area and smaller groove width lead to greater benefit for droplet sliding down. What’s more, the results indicate that higher gravity value leads to a higher decrease of movement resistance of the droplet by decreasing the contact area between the droplet and solid surface.
Enhanced Pool Boiling Heat Transfer on Mono and Multi-Layer Micro-Nano Bi-Porous Copper Surfaces
Authors: Wang Ya-Qiao , Mo Dong-Chuan , Lyu Shu-shen
Published: March 2016

Boiling heat transfer is widely used in industry and aerospace, and it can be enhanced by surface structure treatment. Here, two types of Micro-Nano bi-porous copper surfaces (MNBPCS) were prepared by hydrogen bubble template method and then sintered in reducing atmosphere. The effect of surface morphology on the saturated pool boiling of ultrapure water was investigated. Results show that, both NMBPCS have superior heat transfer performance to the plain copper surface. When the heat flux is 100W/cm2, the wall superheat of the two MNBPCS are about 7 and 9 °C lower than the plain copper surface respective. When the heat flux is lower than 130W/cm2, the wall superheat of the mono-layer MNBPCS is lower than that of the multi-layer one, because the bubbles formed on the mono-layer MNBPCS can departure more easily than those on the multi-layer one. When the heat flux is higher than 130W/cm2, the multi-layer MNBPCS has lower wall superheat than that of the mono-layer one, own to its better liquid accommodation from the morphology structure. Significant hysteresis phenomenon was only found on the Multi-layer MNBPCS. Its wall superheat keeps almost the same at about 13°C for its bottom layer structure with smaller cave diameter, when the heat flux is higher than 75W/cm2. The CHF of each MNBPCS is higher than 200W/cm2, and the multi-layer one is higher than the mono-layer one own to its better liquid accommodation from the morphology structure.
Particulate Fouling and Mitigation Approach in Microchannel Heat Exchanger
Authors: Yan Zhibin , Huang Xiaoyang , Yang Chun
Published: March 2016

Particulate fouling at elevated temperature is a crucial issue for microchannel heat exchangers. In this work, a microfluidic system is designed to experimentally study on the deposition of micro-particles suspended in microchannels, which simulates the working fluid in microscale heat exchangers. We have directly measured the deposition rate of microparticles and found that the number density of deposited particles was monotonically increased with solution temperature when constant flow rate of samples was maintained. Moreover, our results show that pulsatile flow, which was generated by a piezoelectric unit, could mitigate the particulate fouling in microchannels, and the deposition rate was decreased with increasing the frequency of pulsation within a low frequency region. Our findings are expected to gain better understanding of thermally driven particulate fouling as well as provide useful information for design and fabrication of microchannel heat exchangers.
Experimental Study on Enhanced Falling Film Absorption Process Using H2O/LiBr Nanofluids
Authors: Zhang L. Y. , Liu Y. Y. , Wang Y. , Li H. Q. , Yang X. H. , Jin L. W.
Published: March 2016

Absorption air conditioning system could be driven by low grade energy, such as solar energy and industrial exhaust heat, for the purposes of energy conservation and emission reduction. Its development is limited by its huge volume and high initial investment. The nanofluids, which possess the superior thermophysical properties, exhibit a great potential in enhancing heat and mass transfer performance. In this paper, nanofluids of H2O/LiBr with Fe3O4 nanoparticles were introduced into absorption air conditioning system. The effects of some parameters, such as the flow rate of H2O/LiBr nanofluids, nanoparticle size and mass fraction, on the falling film absorption were investigated. The H2O/LiBr nanofluids with Fe3O4 nanoparticle mass fractions of 0.01 wt%, 0.05 wt% and 0.1 wt%, and nanoparticle size of 20 nm, 50 nm and 100 nm were tested by experiment. The results imply that the water vapour absorption rate could be improved by adding nanoparticles to H2O/LiBr solution. The smaller the nanoparticle size, the greater enhancement of the heat and mass transfer performance. The absorption enhancement ratio increases sharply at first by increasing the nanoparticle mass fraction within a range of relatively low mass fraction, and then exhibits a slow growing even reducing trends with increasing the mass fraction further. For Fe3O4 nanoparticle mass fraction of 0.05wt% and nanoparticle size of 20nm, the maximum mass transfer enhancement ratio is achieved about 2.28 at the flow rate of 100 L·h−1.
The Control Method of Surface Morphology and Etch Rates for Silicon Etch Process With Extremely Deep and High Aspect Ratio
Authors: Xu Tiantong , Tao Zhi , Tan Xiao , Li Haiwang
Published: March 2016

The manufacture method based on the silicon etching process is one of the most important methods to fabricate micro mechanical structure, e.g. micro-engine. In the processing, the high aspect ratio silicon etch process (HARSE process) is very important to improve the efficiency of structure. At the same time, the surface morphology should be controlled exactly to keep the performance of structure.

In this paper, the feasibilities of controlling the surface morphology and Si etch rates were experimentally investigated. In the experiments, the width of structure changes from 15um to 1500um and the depth changes from 50um to 500um. The parameters of surface morphology including sidewall angle, surface roughness, and so on were measured and compared. The influence mechanisms of etching parameters were analyzed.

The etching process were completed in a surface technology system (STS) multiplex advanced silicon etcher inductively coupled plasma (ICP) system with SF6/O2 plasma as etching plasma and C4F8 as passivation plasma. In the experiments, the etching experiments were conducted in a low pressure (5–50mTorr), high density, inductively coupled plasma etching reactor (ICP) with a planar coil. The Si etches rates and sidewall angle were investigated as a function of chamber pressure, cathode RF-power, and gas flow.

The results indicated that the increasing of total etching time results in an acceleration in etch rate as well as the decrease in sidewall angle (the top width of trench is narrow than the bottom width). Meanwhile, the total passivation time has an opposite effect in the influence of etch rate and sidewall angle. All the experiments indicate that the quick shift between etch and passivation period leads to a smoother surface. An interesting phenomenon were discovered that the etch rate will not change with the changing of width parameter in most of the high aspect ratio silicon etch recipes when the width-depth ratio is upper than 0.34. An experiential function formula were fitted based on four parameters, including width and depth of the structure, and total etching and passivation time.
Low-Directivity Quasi-Monochromatic Thermal Radiation From Microcavities Covered by Thin Metal Film
Authors: Kohiyama Asaka , Shimizu Makoto , Iguchi Fumitada , Yugami Hiroo
Published: March 2016

Here, closed-end microcavity is proposed in which a semi-transparent metal film was formed atop microcavity. The structure shows weak angular dependence as well as quasi-monochromatic absorptance. Au is employed as material of the cavity walls and the covering thin film. Quasi-monochromatic absorption from the structure is observed in numerical simulation. High quality factor (Q factor) is obtained by strong confinement in the closed-end microcavity. Asymmetric and quasi-monochromatic absorption band with a Q factor of ∼28 at 1.85 μm was observed. This value was about 4-fold larger than that of the open-end microcavity. Additionally, the closed-end microcavity structure filled with SiO2 in cavity exhibits isotropic and quasi-monochromatic thermal radiation over a wide solid angle. This result suggests that both quasi-monochromatic and low-directivity absorptance can be realized by using this configuration.
High Throughput Cell-Free Extraction of Plasma by an Integrated Microfluidic Device Combining Inertial Microfluidics and Membrane
Authors: Zhang Jun , Yan Sheng , Yuan Dan , Alici Gursel , Nguyen Nam-trung , Li Weihua
Published: March 2016

Plasma is a host of various analytes such as proteins, metabolites, circulating nucleic acids (CNAs), pathogens. The key process of plasma extraction is to eliminate the contamination from blood cells. Conventional methods, such as centrifugation and membrane filtration, are generally lab-intensive, time consuming and even dangerous. In this study, we report an integrated microfluidic device that combines inertial microfluidics and membrane filter. The integrated microfluidic device was evaluated by the diluted (x1/10, x1/20) whole blood, and the quality of the extracted blood plasma was tested. It was found that quality of extracted blood plasma from integrated device was equivalent to that obtained by the centrifugation. This study demonstrates a significant progress towards the practical application of inertial microfluidics with membrane filter for high-throughput and high efficient blood plasma extraction.
Effect of Porous Wettability on the Bubble Penetrability and Gas-Liquid Separation Character
Authors: Chen Hongxia , Yan Yuying
Published: March 2016

To micro-structures of porous materials, the capillary force which is deeply affected by wettability plays an important role. In this paper, directly oxidation method and functionalization by trichloro (1H, 1H, 2H, 2H-perfluorooctyl) - silane are used to modify metal mesh wettability and superhydrophilic and superhydrophobic copper meshes are fabricated. Super-hydrophilic mesh can block bubbles from flowing through, while the superhydrophobic mesh can hold a column of liquid by counteracting gravity which is defined as a self-compatibility of meshes in this paper. As reported in the previous studies, the mesh with micro-pores can modulate two phase flow pattern to enhance heat transfer. In the present study, the dynamic principle of bubbles as they flow through meshes with different wettabilities is studied. A mathematical model between the critical diameter and flow conditions is developed. A fundamental conclusion for the modulation theory of two phase flow in porous structures can be reached.
Experimental Research of Shell and Tube Condenser With the Middle Liquid Separation Structure
Authors: Zhu Kai
Published: March 2016

For the state of condensation in tube, liquid condensate separation in middle process can prolong the state of steam entrance region of higher heat transfer coefficient. It is called short-tube effect theory. Combined with the traditional condenser, a shell and tube condenser was designed for experiment research in this paper, and compared with the traditional condenser by opening liquid distribution pipes arranged in both sides of condenser. The results showed that liquid distribution pipes with different diameter have different condensation effect. Under the same steam flow rate of inlet, liquid distribution pipes with different combination of diameter and number indicated that its coefficient of heat transfer are higher than the traditional heat transfer by 14.2%, 15.5% and 25.1%. This result illustrated that heat exchange efficiency of a shell and tube condenser with liquid distribution pipes is better than a traditional condenser.
Characterisation of cellulose and hardwood organosolv lignin reference materials by XPS
Authors: Bañuls-Ciscar Jorge , Abel Marie-Laure , Watts John F.
Published: March 2016

Cellulose and lignin reference samples have been investigated to enable the easier identification of the composition of pine wood strands in XPS. Presented here are the survey and high resolution x-ray photoelectron spectra of cellulose and lignin. Cellulose is characterised by a lack of intensity of the aliphatic carbon peak in addition to an intense carbon-oxygen peak corresponding to alcohols groups. Lignin is characterised by the presence of an intense aliphatic peak and a π-π* shake-up.
Get Real! — Physically Reasonable Values for Teaching Electrostatics
Authors: Morse Robert A.
Published: March 2016

Students get a sense of realistic values for physical situations from texts, but more importantly from solving problems. Therefore, problems should use realistic values for quantities to provide needed practice. Unfortunately, some problems on tests and in textbooks do not use realistic values. Physical situations in electrostatics seem to be particularly problematic.
The Nature of the Electron
Authors: Lincoln Don
Published: March 2016

Winston Churchill once said of Russia that it was a riddle wrapped in mystery inside an enigma. Were the British Bulldog a physicist, he might have been talking of something other than our Slavic comrades. He might have been talking about an electron.
Some Surprising Introductory Physics Facts and Numbers
Authors: Mallmann A. James
Published: March 2016

In the entertainment world, people usually like, and find memorable, novels, short stories, and movies with surprise endings. This suggests that classroom teachers might want to present to their students examples of surprising facts associated with principles of physics. Possible benefits of finding surprising facts about principles of physics are opportunities to expand beyond traditional presentations—and, in some cases, to achieve a deeper and broader understanding of those principles. I believe, moreover, that some of the facts presented here may inspire physics teachers to produce some challenge problems for students.
Melting metal on a playing card
Authors: Greenslade Thomas B.
Published: March 2016

Many of us are familiar with the demonstration of boiling water in a paper cup held over a candle or a Bunsen burner; the ignition temperature of paper is above the temperature of 100 °C at which water boils under standard conditions. A more dramatic demonstration is melting tin held in a playing card. This illustration is from Tissandier's book on scientific recreations.
How the Television Show “MythBusters” Communicates the Scientific Method
Authors: Zavrel Erik , Sharpsteen Eric
Published: March 2016

The importance of understanding and internalizing the scientific method can hardly be exaggerated. Unfortunately, it is all too common for high school—and even university—students to graduate with only a partial or oversimplified understanding of what the scientific method is and how to actually employ it. Help in remedying this situation may come from an unlikely source: television. One television show that is conspicuously good at communicating the scientific method in an easy-to-understand, pedantic-free, entertaining manner is the Discovery Channel's “MythBusters,” which began airing in 2003 and continues to produce new episodes. In this content analysis, episodes of the popular program were analyzed for aspects of the scientific method. In addition, segments from the show were used in a classroom activity to introduce the scientific method and the concept of experimental controls to high school physics students.
Effects of L1 prosody on segmental contrast in L2: The case of English stop voicing contrast produced by Korean speakers
Authors: Choi Jiyoun , Kim Sahyang , Cho Taehong
Published: March 2016

This study investigated how the L1 phonetics-prosody interface transfers to L2 by examining prosodic strengthening effects (due to prosodic position and focus) on English voicing contrast (bad-pad) as produced by Korean vs English speakers. Under prosodic strengthening, Korean speakers showed a greater F0 difference due to voicing than English speakers, suggesting that their experience with the macroprosodic use of F0 in Korean transfers into L2. Furthermore, Korean speakers produced voiced stops with low F0 and short voice onset time as English speakers did, although such a cue pairing is absent in Korean, showing dissociation of cues from L1 segments for L2 production.
Road traffic noise impact assessment in a breeding colony of cinereous vultures (Aegypius monachus) in Spain
Authors: Iglesias-Merchán Carlos , Diaz-Balteiro Luis , de la Puente Javier
Published: March 2016

There is a global and growing concern with regard to anthropogenic noise impact on wildlife and natural habitats, but it is difficult to find consensus regarding scoping and assessment tools. This study adapts noise mapping procedures, common to most European countries, to a low traffic road (below 1000 vehicles per day) noise impact assessment in a breeding colony of the largest bird of prey in Europe. Results show that nest sites are located avoiding road traffic Leq levels higher than 40 dB. This means a road-effect zone of up to 500 m width from road margins, which previous scientific literature only refers in cases of traffic volumes higher than 10 000 vehicles per day. This finding is a noticeable impact by road traffic noise that reduces the breeding potential habitat more than 11% within the study area. This work shows the feasibility of expanding common methods and mapping tools for assessing and managing environmental noise in protected areas, which has worthwhile implications for both acoustics and conservation.
Paper of note in
Science Translational Medicine
Authors: Ferrarelli Leslie K.
Published: March 2016

This week’s article describes a new way to kill metastatic ovarian cancer cells by inducing the production of a protein in immune cells recruited to the metastatic lesion.
From maternal infection to aberrant fetal brain development
Authors: Gough Nancy R.
Published: March 2016

Bacterial cell wall stimulates fetal neuroproliferation that results in cognitive and behavioral defects.
Acquisition of Extended-Spectrum β-Lactamases by Escherichia coli and Klebsiella pneumoniae in Gut Microbiota of Pilgrims during the Hajj Pilgrimage of 2013
Authors: Leangapichart Thongpan , Dia Ndèye Méry , Olaitan Abiola Olumuyiwa , Gautret Philippe , Brouqui Philippe , Rolain Jean-Marc
Published: March 2016

We reported the acquisition of extended-spectrum-β-lactamase (ESBL)-producing bacteria in rectal samples of 129 pilgrims during the 2013 Hajj (pilgrimage to Makkah). When returning from the Hajj, there was a significant increase in the number of pilgrims carrying
E. coli
resistant to ceftriaxone (
P
= 0.008). The CTX-M gene was detected in rectal samples, with the detection rate increasing from 10.08% to 32.56% of samples after the Hajj (
P
< 0.001).
Evaluation of the
In Vitro
Activity of Ceftazidime-Avibactam and Ceftolozane-Tazobactam against Meropenem-Resistant Pseudomonas aeruginosa Isolates
Authors: Buehrle Deanna J. , Shields Ryan K. , Chen Liang , Hao Binghua , Press Ellen G. , Alkrouk Ammar , Potoski Brian A. , Kreiswirth Barry N. , Clancy Cornelius J. , Nguyen M. Hong
Published: March 2016

We compared ceftazidime-avibactam, ceftolozane-tazobactam, ceftazidime, cefepime, and piperacillin-tazobactam MICs for 38 meropenem-resistant
Pseudomonas aeruginosa
isolates. No isolates harbored carbapenemases; 74% were
oprD
mutants. Ceftazidime-avibactam and ceftolozane-tazobactam were active against 92% of the isolates, including 80% that were resistant to all three β-lactams. Forty-three percent of ceftazidime-avibactam-susceptible isolates and 6% of ceftolozane-tazobactam-susceptible isolates exhibited MICs at the respective breakpoints. Ceftolozane-tazobactam and ceftazidime-avibactam are therapeutic options for meropenem-resistant
P. aeruginosa
infections that should be used judiciously to preserve activity.
Inactivation of Lytic Transglycosylases Increases Susceptibility to Aminoglycosides and Macrolides by Altering the Outer Membrane Permeability of Stenotrophomonas maltophilia
Authors: Wu Chao-Jung , Huang Yi-Wei , Lin Yi-Tsung , Yang Tsuey-Ching
Published: March 2016

Stenotrophomonas maltophilia
harbors six lytic transglycosylases (LTs):
mltA
,
mltB1
,
mltB2
,
mltD1
,
mltD2
, and
slt
. LT deletion increased susceptibility of
S. maltophilia
to aminoglycosides (AGs) and macrolides, and the underlying mechanisms were investigated. The expression of AG-modifying enzymes and efflux pumps was evaluated by quantitative reverse transcription-PCR (qRT-PCR). Susceptibility to 1-
N
-phenylnaphthylamine, vancomycin, SDS, and bile salts was measured to assess outer membrane permeability. In conclusion, increased outer membrane permeability contributes to LT deletion-mediated increase in aminoglycoside and macrolide susceptibility.
Bacterial Dose-Dependent Role of G Protein-Coupled Receptor Kinase 5 in Escherichia coli-Induced Pneumonia
Authors: Packiriswamy Nandakumar , Steury Michael , McCabe Ian C. , Fitzgerald Scott D. , Parameswaran Narayanan
Published: March 2016

G protein-coupled receptor kinase 5 (GRK5) is a serine/threonine kinase previously shown to mediate polymicrobial sepsis-induced inflammation. The goal of the present study was to examine the role of GRK5 in monomicrobial pulmonary infection by using an intratrachealEscherichia coliinfection model of pneumonia. We used sublethal and lethal doses ofE. colito examine the mechanistic differences between low-grade and high-grade inflammation induced byE. coliinfection. With a sublethal dose ofE. coli, GRK5 knockout (KO) mice exhibited higher plasma CXCL1/KC levels and enhanced lung neutrophil recruitment early after infection, and lower bacterial loads, than wild-type (WT) mice. The inflammatory response was also diminished, and resolution of inflammation advanced, in the lungs of GRK5 KO mice. In contrast to the reduced bacterial loads in GRK5 KO mice following a sublethal dose, at a lethal dose ofE. coli, the bacterial burdens remained high in GRK5 KO mice relative to those in WT mice. This occurred in spite of enhanced plasma CXCL1 levels as well as neutrophil recruitment in the KO mice. But the recruited neutrophils (following high-dose infection) exhibited decreased CD11b expression and reduced reactive oxygen species production, suggesting decreased neutrophil activation or increased neutrophil exhaustion in the GRK5 KO mice. In agreement with the increased bacterial burden, KO mice showed poorer survival than WT mice followingE. coliinfection at a lethal dose. Overall, our data suggest that GRK5 negatively regulates CXCL1/KC levels during bacterial pneumonia but that the role of GRK5 in the clinical outcome in this model is dependent on the bacterial dose.
Multiscale Model of Mycobacterium tuberculosis Infection Maps Metabolite and Gene Perturbations to Granuloma Sterilization Predictions
Authors: Pienaar Elsje , Matern William M. , Linderman Jennifer J. , Bader Joel S. , Kirschner Denise E.
Published: March 2016

Granulomas are a hallmark of tuberculosis. Inside granulomas, the pathogenMycobacterium tuberculosismay enter a metabolically inactive state that is less susceptible to antibiotics. UnderstandingM. tuberculosismetabolism within granulomas could contribute to reducing the lengthy treatment required for tuberculosis and provide additional targets for new drugs. Two key adaptations ofM. tuberculosisare a nonreplicating phenotype and accumulation of lipid inclusions in response to hypoxic conditions. To explore how these adaptations influence granuloma-scale outcomesin vivo, we present a multiscalein silicomodel of granuloma formation in tuberculosis. The model comprises host immunity,M. tuberculosismetabolism,M. tuberculosisgrowth adaptation to hypoxia, and nutrient diffusion. We calibrated our model toin vivodata from nonhuman primates and rabbits and apply the model to predictM. tuberculosispopulation dynamics and heterogeneity within granulomas. We found that bacterial populations are highly dynamic throughout infection in response to changing oxygen levels and host immunity pressures. Our results indicate that a nonreplicating phenotype, but not lipid inclusion formation, is important for long-termM. tuberculosissurvival in granulomas. We used virtualM. tuberculosisknockouts to predict the impact of both metabolic enzyme inhibitors and metabolic pathways exploited to overcome inhibition. Results indicate that knockouts whose growth rates are below ∼66% of the wild-type growth rate in a culture medium featuring lipid as the only carbon source are unable to sustain infections in granulomas. By mapping metabolite- and gene-scale perturbations to granuloma-scale outcomes and predicting mechanisms of sterilization, our method provides a powerful tool for hypothesis testing and guiding experimental searches for novel antituberculosis interventions.
Trypanosoma cruzi Differentiates and Multiplies within Chimeric Parasitophorous Vacuoles in Macrophages Coinfected with Leishmania amazonensis
Authors: Pessoa Carina Carraro , Ferreira Éden Ramalho , Bayer-Santos Ethel , Rabinovitch Michel , Mortara Renato Arruda , Real Fernando
Published: March 2016

The trypanosomatids
Leishmania amazonensis
and
Trypanosoma cruzi
are excellent models for the study of the cell biology of intracellular protozoan infections. After their uptake by mammalian cells, the parasitic protozoan flagellates
L. amazonensis
and
T. cruzi
lodge within acidified parasitophorous vacuoles (PVs). However, whereas
L. amazonensis
develops in spacious, phagolysosome-like PVs that may enclose numerous parasites,
T. cruzi
is transiently hosted within smaller vacuoles from which it soon escapes to the host cell cytosol. To investigate if parasite-specific vacuoles are required for the survival and differentiation of
T. cruzi
, we constructed chimeric vacuoles by infection of
L. amazonensis
amastigote-infected macrophages with
T. cruzi
epimastigotes (EPIs) or metacyclic trypomastigotes (MTs). These chimeric vacuoles, easily observed by microscopy, allowed the entry and fate of
T. cruzi
in
L. amazonensis
PVs to be dynamically recorded by multidimensional imaging of coinfected cells. We found that although
T. cruzi
EPIs remained motile and conserved their morphology in chimeric vacuoles,
T. cruzi
MTs differentiated into amastigote-like forms capable of multiplying. These results demonstrate that the large adaptive vacuoles of
L. amazonensis
are permissive to
T. cruzi
survival and differentiation and that noninfective EPIs are spared from destruction within the chimeric PVs. We conclude that
T. cruzi
differentiation can take place in
Leishmania
-containing vacuoles, suggesting this occurs prior to their escape into the host cell cytosol.
The RipA and RipB Peptidoglycan Endopeptidases Are Individually Nonessential to Mycobacterium smegmatis
Authors: Martinelli Daniel J. , Pavelka Martin S.
Published: March 2016

Mycobacteria possess a series of Rip peptidoglycan endopeptidases that have been characterized in various levels of detail. The RipA and RipB proteins have been extensively studied and are
dl
-endopeptidases, and RipA has been considered essential to
Mycobacterium smegmatis
and
Mycobacterium tuberculosis
. We show here that the
ripA
and
ripB
genes are individually dispensable in
M. smegmatis
and that at least one of the genes must be expressed for viability. We characterized strains carrying in-frame deletion mutations of
ripA
and
ripB
and found that both mutant strains exhibited increased susceptibility to a limited number of antibiotics and to detergent but that only the Δ
ripA
mutant displayed hypersusceptibility to lysozyme. We also constructed and characterized Δ
ripD
and Δ
ripA
Δ
ripD
mutants and found that the single mutant had only an intermediate lysozyme hypersusceptibility phenotype compared to that of wild-type cells while loss of
ripD
in the Δ
ripA
background partially rescued the antibiotic and lysozyme phenotypes of the Δ
ripA
mutant.

IMPORTANCE
We show that the RipA endopeptidase, which has been considered essential for cell division in certain mycobacteria, is not essential but that at least it or a similar protein, RipB, must be expressed by the bacteria for viability. This work is the first description of strains carrying single deletion mutations of RipA, RipB, and a novel endopeptidase-like protein, RipD.
Effects of different metabolic states and surgical models on glucose metabolism and secretion of ileal L-cell peptides: protocol for a cross-sectional study
Authors: Celik Alper , Dixon John B , Pouwels Sjaak , Celik Bahri Onur , Karaca Fatih Can , Gupta Adarsh , Santoro Sergio , Ugale Surendra
Published: March 2016

Introduction

Obesity and type 2 diabetes mellitus are increasing worldwide, reaching pandemic proportions. The understanding of the role of functional restriction and gut hormones can be a beneficial tool in treating obesity and diabetes. However, the exact hormonal profiles in different metabolic states and surgical models are not known.

Methods and analysis

The HIPER-1 Study is a single-centre cross-sectional study in which 240 patients (in different metabolic states and surgical models) will receive an oral mixed-meal tolerance test (OMTT). At baseline and after 30, 60 and 120 min, peptide YY and glucagon-like peptide 1 levels and glucose and insulin sensitivity will be measured. The primary end point of the study will be the area under the glucagon-like peptide 1 and peptide YY curves after the OMTT. Secondary study end points will include examination of the difference in plasma levels of the distal ileal hormones in subjects with various health statuses and in patients who have been treated with different surgical techniques.

Ethics and dissemination

An independent ethics committee, the Institutional Review Board of Istanbul Sisli Kolan International Hospital, Turkey, has approved the study protocol. Dissemination will occur via publication, national and international conference presentations, and exchanges with regional, provincial and national stakeholders.

Trial registration number

NCT02532829; Pre-results.
Active push deployment technique improves stent/vessel-wall interaction in endovascular treatment of acute stroke with stent retrievers
Authors: Wiesmann Martin , Brockmann Marc-Alexander , Heringer Sarah , Müller Marguerite , Reich Arno , Nikoubashman Omid
Published: March 2016

Background

The optimal interaction between stent struts and thrombus is crucial for successful revascularization in endovascular stroke therapy with stent retrievers. Deploying the stent retriever by actively pushing it into the thrombus increases the radial force with which the stent struts expand into the thrombus.

Objective

To examine theactive push deployment(APD) technique in an in vitro model and present our clinical experience with this technique.

Methods

In an in vitro experiment we investigated the configuration of a Solitaire and a Trevo ProVue device (both 4×20 mm), depending on whether the devices were deployed using the APD technique or simple unsheathing. We retrospectively assessed the effectiveness and safety of this technique by analyzing 130 patients with large vessel occlusions (carotid T or M1 segment of the middle cerebral artery), who received endovascular treatment with a Trevo device (4×20 mm) that was deployed using the APD technique.

Results

In vitro experiment:the APD technique improved apposition of the devices to the vessel wall. There was widening of 30% (Trevo) and 19% (Solitaire) at the cost of a shortening of 5% and 4%, respectively, when the devices were deployed in a carotid T model.Clinical study: the revascularization rate (Thrombolysis in Cerebral Infarction ≥2b) with the Trevo device was 90%. There were no retriever-associated dissections or perforations in 278 retrieval maneuvers.

Conclusions

The APD technique improves apposition of the tested devices to the vessel wall. The widening effect comes at the cost of minimal shortening of the devices. Our clinical experience shows that using the APD technique to deploy the Trevo device is effective and safe.