bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Gas Flow on the Temperature Rise of a Micro-Beam-Type Thermal Conductivity Detector
Authors: Takamatsu Hiroshi , Hisada Kosuke , Fukunaga Takanobu , Kurata Kosaku
Published: July 2018

We have proposed a “micro-beam” MEMS sensor for measuring the thermal conductivity of gases and liquids. It is a beam-shaped metallic foil sensor, approximately 10 μm in length, that is built over a trench on a silicon substrate. The principle of the measurement is to determine the thermal conductivity of a sample from the temperature rise of the sensor at a steady state, which is achieved within a millisecond. Potential application of the sensor would be gas sensors and gas chromatography, where the sensor is exposed to a gas flow. Hence the objective of the present study is to examine the effect of flow on the temperature of the sensor.

A chip with a platinum sensor fabricated on its surface was embedded in a flat PVC plate and placed in the potential core of an air flow from a nozzle. The electrical resistance of the sensor was measured by a four-wire technique with heating the sensor with DC current. The results showed that the temperature rise at a given heating rate, which indicates the heat dissipating potential to the air, did not change with increasing the air velocity. It also agreed well each other irrespective of the angle of attack or the length from the leading edge. The results demonstrated that the temperature rise of the sensor was independent of the air flow, suggesting that the heat dissipation was governed only by the heat conduction to the air.
Experimental Study on Thermal Contact Resistance of Multi-Walled Carbon Nanotubes
Authors: Tsuru Kazunari , Yamada Yutaka , Ikuta Tatsuya , Nishiyama Takashi , Takahashi Koji
Published: July 2018

Heat transfer at solid-solid interface is very fascinating where no one knows the full mechanism which has a huge impact in many applications in engineering and science. In many kinds of interfaces, we treat a van der Waals contact of perfectly-smooth surfaces by using multi-walled carbon nanotubes (CNTs). Their thermal contact resistance (TCR) is estimated by comparing measured thermal conductivity of CNT specimen and numerical simulation result. The TCR per unit area is estimated as 1.58∼3.33×10−8 m2K/W at room temperature in vacuum, which is much higher than our previous result in air. It was also found that TCR is inversely proportional with the temperature to the 1.92th power different from the simple phonon model represented by the diffuse mismatch model.
Interfacial Thermal Conductance Between Carbon Nanotubes From Nonequilibrium Green’s Function Method
Authors: Liu Chenhan , Wang Jian , Chen Weiyu , Wei Zhiyong , Yang Juekuan , Chen Yunfei
Published: July 2018

In this paper, the interfacial thermal conductance between two single-wall carbon nanotubes (SWCNTs) is evaluated using the nonequilibrium Green’s function (NEGF) method. The calculation results show that, for offset parallel contact type, interfacial thermal conductance increases almost linearly with the overlap length. This is because the coupling atom number in overlap region is the main contributor to heat flow through interface. With the same overlap length, interfacial thermal conductance of the nested contact type is much higher than that of the offset parallel contact type. By comparing the phonon transmission function between the two contact types, it is found that the nested contact type has much larger transmission function than the offset parallel contact type due to more atoms involving in the interfacial coupling in the overlap region. By adjusting the chirality of SWCNTs in the offset parallel contact type, it is found that the difference of phonon spectrum can reduce interfacial thermal transfer. We also find the transmission function profiles with only different overlap length are quite similar, that is, changing in the overlap length will not change the phonon transmission probability at the interface. Moreover, acoustic phonon is the main contributor to the interfacial thermal conductance and the radical breathing mode is the vital mode of coupling modes for CNT-CNT system. The calculated results in this paper indicate that increasing the coupling atom number between CNTs would increase the heat energy transfer in CNT-based composites.
Thermal Radiative Properties of a 2-D Silicon Carbide Grating Mediated With a Photonic Crystal
Authors: Wang Weijie , Fu Ceji , Tan Wenchang
Published: July 2018

We present in this paper numerical results of the thermal radiative properties of a two-dimensional rectangular SiC grating atop a photonic crystal, which is capable of exciting different resonant modes within a specified spectral band. We demonstrate that diffraction of waves in both extended directions of the two-dimensional grating, even for s-polarized waves, could efficiently give rise to excitation of surface phonon polaritons, which is responsible for large enhancement of thermal emission from the structure. However, the emission curves reveal different angle and geometry dependence for s- and p-polarized waves. Furthermore, due to the interaction of different modes, quasi-diffuse characteristics of thermal radiation from the proposed structure can be found for both polarizations.
Quantifying the Growth Rate and Morphology of Ice Crystals Growing in Cryoprotectants via High-Speed Camera and Cryo-Microscope
Authors: Xue Xu , He Zhi Zhu , Liu Jing
Published: July 2018

Recently, several significant progresses have been made on the studies of extracellular and intracellular ice formation based on high-speed camera and cryomicroscope. This experimental methodology could accurately capture rapid formation process of ice crystals at micro-scale. In this paper, we are dedicated to quantify and comparatively investigate the growth rate and morphology of ice crystals growing in DMSO, sucrose and trehalose, respectively via high-speed camera and cryo-microscope. Several impact factors such as the concentration of cryoprotectants and the cooling rate have been investigated. The results indicate that the species and concentration of cryoprotectants and the cooling rate could significantly affect the growth rate and morphology of ice crystals. DMSO is better than trehalose and sucrose as cryoprotectant because of its molecular structure. This work may enhance current understanding of the factors for ice crystals formation and help optimize the cryopreservation process in the near future.
Investigation of Two Phase Heat Transfer Coefficients of Cryogenic Mixed Refrigerants
Authors: Baek Seungwhan , Jeong Sangkwon
Published: July 2018

Mixed Refrigerant Joule Thomson (MR-JT) refrigerators are widely used in various kinds of cryogenic systems these days. Although heat transfer coefficient estimation for a multiphase and multi-component fluid in cryogenic temperature range is necessarily required in the heat exchanger design of MR-JT refrigerator, it has been rarely discussed so far. In this paper, condensation and evaporation heat transfer coefficients of mixed refrigerant are measured in a microchannel heat exchanger. Printed Circuit Heat Exchanger (PCHE) has been developed as a compact microchannel heat exchanger and used in the experiment. Several two-phase heat transfer coefficient correlations are examined to discuss the experimental measurement results. The result of this paper shows that cryogenic mixed refrigerant heat transfer coefficients can be estimated by conventional two-phase heat transfer coefficient correlations.
An Ab Initio Molecular Dynamics Simulation of Femtosecond Laser Processing of Germanium
Authors: Ji Pengfei , Zhang Yuwen
Published: July 2018

An ab initio molecular dynamics study of femtosecond laser processing of germanium is presented in this paper. The method based on the finite temperature density functional theory is adopted to probe the nanostructure change, thermal motion of the atoms, dynamic property of the velocity autocorrelation, and the vibrational density of states. Starting from a cubic system at room temperature (300 K) containing 64 germanium atoms with an ordered arrangement of 1.132 nm in each dimension, the femtosecond laser processing is simulated by imposing the Nose Hoover thermostat to the electron subsystem lasting for ∼100 fs and continuing with microcanonical ensemble simulation of ∼200 fs. The simulation results show solid, liquid and gas phases of germanium under adjusted intensities of the femtosecond laser irradiation. We find the irradiated germanium distinguishes from the usual germanium crystal by analyzing their melting and dynamic properties.
Phonon Conduction Normal to Polysilicon Films on Diamond
Authors: Cho Jungwan , Chao Pane C. , Asheghi Mehdi , Goodson Kenneth E.
Published: July 2018

Silicon films of thickness near and below one micrometer play a central role in many advanced technologies for computation and energy conversion. Numerous data on the thermal conductivity of silicon thin films are available in the literature, but mainly for the in-plane thermal conductivity of polycrystalline and single-crystal films. Here we use picosecond time-domain thermoreflectance (TDTR), transmission electron microscopy, and phonon transport theory to investigate heat conduction normal to polycrystalline silicon films on diamond substrates. The data agree with predictions that account for the coupled effects of phonon scattering on film boundaries and defects concentrated near grain boundaries. Using the data and the model, we estimate the polysilicon-diamond interface resistance to be 6.5–8 m2 K GW−1.
Enhanced Flow Boiling of HFE 7000 by Chaotic Mixers in Microchannels
Authors: Yang Fanghao , Alwazzan Mohammad , Li Chen
Published: July 2018

Improving mixing is an effective method to enhance flow boiling in microchannels. However, it is challenging to induce since the flow in microchannels is laminar under typical operating conditions. We report that flow boiling of 1-methoxyheptafluoropropane (HFE 7000) in a parallel microchannel array was significantly enhanced by chaotic mixers patterned on the bottom walls. The microchannel array consists of five parallel channels (height, width, length: 250 μm × 220 μm × 10 mm). The chaotic mixers consist of seven cycles with 12 staggered herringbone grooves (50 μm depth and width with 90° between two asymmetric arms) in each cycle. Its asymmetry is defined by the off center position of the apex of the herringbone groove. Compared with a smooth-wall microchannel array with identical channel dimensions, heat transfer coefficient and critical heat flux of flow boiling on HFE 7000 were enhanced up to 45 % and 61 % using chaotic mixer pairs in microchannels. Mass fluxes range from 1000 to 2200 kg/m2-s and wall heat fluxes from 10 to 198 W/cm2.
Effect of Material of Nanoparticle on Mass Transfer Enhancement and a Convective Diffusion Model to Predict the Enhancement
Authors: Khanolkar Ratnesh U. , Suresh A. K.
Published: July 2018

While particles smaller than the thickness of the diffusion film have been known to enhance rates of interfacial mass transfer [1], a relatively new result is the discovery that nanoparticles in suspension show enhancements that far exceed the earlier reported enhancements, and without any apparent adsorptive or reactive effects[2]. Different mechanisms for the enhancements have been speculated upon, but there is a paucity of data on different nanoparticulate materials, collected in a systematic way on model contactors so that rational comparisons may be made. In this work, enhancement in Carbon dioxide absorption in water has been studied using SiO2 and TiO2 nanoparticles using the same capillary tube apparatus for which previous results of Fe3O4 were reported. For 0.4% silica particles and 0.0118% TiO2 nanoparticles, 165% and 155% enhancement was observed respectively. A phenomenological convective diffusion model has been proposed to explain the observed effects of particle size, holdup and material density. The model accounts for the overall effect of the Brownian (and any diffusiophoretic) motion of the nanoparticles on the surrounding fluid in terms of an ‘effective’ convective velocity, which is determined from the experimental data and correlated to the modified Sherwood Number proposed earlier [2], volume fraction of Nanoparticles and a solid Reynolds number Rp. This model provides a good fit to the data from wetted wall column and capillary tube experiment for iron oxide from the previous literature, as well as for the data on silica and Titanium dioxide nanoparticles from this work, the average error being 8.3%.
Simulation of an Integrated Microfluidic Device for Bioparticle Wash, Separation and Concentration
Authors: Çetin Barbaros , Büyükkoçak Süleyman , Zeinali Soheila , Özer Bülent
Published: July 2018

Washing, separation and concentration of bioparticles are key operations for many biological and chemical analyses. In this study, the simulation of an integrated microfluidic device is studied. The proposed device has the capability to wash the bioparticles (transferring the bioparticles from one buffer solution to another), to separate the particles based on their dielectric properties and to concentrate the bioparticles. Washing and concentration of bioparticles are performed by acoustophoresis and the separation is performed by dielectrophoresis. For simulating the flow within the microchannel, a computational fluid dynamics model using COMSOL Multiphysics software is implemented. In order to simulate the particle trajectories under ultrasonic and electric field, point-particle assumption is chosen using MATLAB software. To account for the size variation of the bioparticles, particles with normal size distributions are used inside the microchannel. The effect of the key design parameters such as flow rate, applied voltage etc. on the performance of the device is discussed.
Switching On and Off the Coffee-Ring Effect in Drying Sessile Nanofluid Droplets
Authors: Crivoi Alexandru , Duan Fei
Published: July 2018

The diffusion-limited cluster aggregation (DLCA) model has been implemented in a three-dimensional (3D) domain with a shape of an approximately spherical cap for simulating the drying process of a sessile nanofluid droplet. The droplet evaporation is investigated with the pinned three-phase line, resulting in shrinking contact angle and outward capillary flow. The cluster-cluster aggregation between the particles is taken into account in the model, and the transition from the uniform deposition to the coffee-ring pattern is established by altering the sticking probability parameter. The results of the simulation turn to be consistent with the experimental observation. The influence of the parameters, such as particle volumetric concentration and relative domain size, are studied.
Experimental Investigation of Ultrasonic Effect on an Acetone Oscillating Heat Pipe
Authors: Zhao Nannan , Fu Benwei , Zhao Dianli , Ma Hongbin
Published: July 2018

The ultrasonic effect on the oscillating motion and heat transfer in an oscillating heat pipe (OHP) containing acetone was investigated experimentally. The ultrasonic sound was applied to the evaporating section of the OHP by using electrically-controlled piezoelectric ceramics. The ultrasonic sound is used to generate and maintain the oscillating motion, and, thereby, heat transfer is enhanced. The heat pipe was tested with or without the ultrasonic sound. In addition, the effects of heat load, filling ratio, orientation, operating temperature, and input power from 15 W to 200 W were investigated. The experimental results demonstrate that ultrasonic sound can affect the oscillating motions and enhance the heat transfer performance of the acetone OHP. In particular, the application of the ultrasonic sound on an acetone OHP can significantly reduce the thermal resistance of the acetone OHP and enhance the heat transfer performance in a low power input region. The investigation will provide an insight into the oscillating mechanism of the acetone OHP influenced by ultrasonic sound and provide a new way to enhance the heat transfer performance of the OHP.
Investigation of Two-Phase Frictional Pressure Drop and Thermal Entrance Length in a Minichannel Helical Heat Exchanger
Authors: Okaeme Charles , Li Guanqiu , Alzoubi Mahmoud , Zhang TieJun
Published: July 2018

Experimental investigations are conducted to determine the two-phase frictional pressure drop of refrigerant R134a and the thermal entrance length for flow in a helically coiled mini-tube of 2mm inner diameter. The objective of this work is to study the effect of the tube curvature on the frictional pressure drop in two-phase flow as well as the thermal entrance length in laminar single phase flow. The two-phase frictional pressure drop is investigated through flow boiling of the refrigerant under uniform wall temperature boundary conditions. A generalized correlation is proposed to predict the single phase and two-phase frictional pressure drop through the coiled tube. A large set of experimental data is collected to evaluate the prediction performance of the proposed two-phase correlation. The results of the prediction are fairly good when compared with the measured pressure drop from experiments. A Computational Fluid Dynamics (CFD) analysis is also performed to compare with the thermal entrance length study from experiments. The results from the experimental analyses and CFD are seen to be in good agreement. It is found that the thermal entrance length for the coiled tube is 27–103.3% larger than a straight tube of equal length and cross-section.
Simulation of Band Gap Characteristics for High Temperature PCs as a Thermal Control Structure
Authors: Zhang H.-C. , Qiu C.-H. , Li Y. , Zhao Y. , Yu H.-Y.
Published: July 2018

Photonic crystals is a kind of material with band gap, the photons in which frequencies are in the band gap cannot propagate in a structure. Band gap characteristics for an innovative high temperature thermal control structure, integrated with PCs are presented by numerical simulation based on electromagnetic theory. Focused on 3D PCs structure, the plane wave expansion method is applied, and effects of ball radius and dielectric constant on the band gap characteristics are simulated. In addition, the influencing trend of the bandwidth is also discussed.
Pore-Scale Investigation of Two-Phase Drainage Process in a Microchannel
Authors: Yap Y. F. , Goharzadeh A. , Vargas F. M. , Chai J. C.
Published: July 2018

This article presents a level-set method to investigate two-phase drainage of oil by water in microchannel with numerous blockages in the middle section, mimicking a porous medium of different permeability at the pore-scale level. The presented framework is intended for gaining an understanding of the nature of flow and transport at the pore-scale level. In particular, the sweeping efficiency for the drainage process is parametrically studied for system with different viscosities and surface tension.
Characterisation of Residual Shear Strength at the Sheringham Shoal Offshore Wind Farm
Authors: Le Thi Minh Hue , Eiksund Gudmund Reidar , Strøm Pål Johannes
Published: July 2018

For offshore foundations, the residual shear strength is an important soil parameter for the evaluation of installation resistance and axial pile capacity (for jacket foundation). Estimation of residual shear strength can be conducted in a shear box test in the conventional way, or with the introduction of an interface to evaluate the change in residual shear strength under influence of friction between soil and the interface. In addition, the residual effective friction angle can be measured in the ring shear test using the Bromhead apparatus. In this study, the three above-mentioned methods are employed to estimate the values of residual shear strength of two soil units: the Swarte Bank Formation and the Chalk Unit sampled from the Sheringham Shoal offshore wind farms. The Swarte Bank Formation is dominated by heavily over-consolidated stiff clay, while the Chalk Unit is characterized by putty white chalk which behaves in a similar manner to stiff clay if weathered, or to soft rock if unweathered. These soil units are located at the bottom of the soil profile at the Sheringham Shoal wind farm and hence are important in providing axial capacity to the foundation.

Samples from the two soil units are tested and compared at different rates of shearing to evaluate the change in axial capacity and installation resistance of the offshore wind turbine foundations under various possible loading and drainage conditions. Comparison is also made between residual shear strength with and without a reconsolidation period to assess the potential for soil set-up and its influence on the soil capacity. The results show that, for both the clay and the chalk, the estimated residual shear strengths are quite similar between the conventional and interface shear tests and tend to increase with increasing shearing rate. This can be attributed to the increasing dominance of the turbulent shearing mode. Relative to the peak shear strength, the values of residual shear strength are approximately 5 to 35% lower in most cases. Reconsolidation for a period of 24 hours appears to have, if any, marginal positive effect on residual shear strength of the two soils in both shear box and interface shear box tests. The residual friction angles derived from the shear box and ring shear tests are comparable and fall in the immediate range of shear strength. The various test results imply that the pile foundations at the Sheringham Shoal would have considerably large axial capacity, assuming that the horizontal stress is similar to the normal stress used in testing. The test data however should be used with caution and combined with piling experience in comparable soils where possible. The study aims to provide a source of reference for design of pile foundations for sites with similar soil conditions.
Group Effects of TLP Tendon Driven Piles in Normally Consolidated (NC) Clay
Authors: Cao Jianchun
Published: July 2018

Long large-diameter driven piles (i.e., 2.0∼3.0m-diameter piles with a 100m penetration or deeper) have been usually used as Tension Leg Platforms’ (TLP) foundations in normally consolidated clay. In order to optimize a design, TLP designers would like to reduce the pile spacing, resulting in a pile group effect issue for pile geotechnical designers. This paper presents the development of a three-Dimensional Finite Element Analysis (3D FEA) model using Finite Element Code PLAXIS 3D to investigate the pile group effect of the TLP driven piles in normally consolidated clay. Using this model, a series of FEA runs were carried out. Firstly, the FEA model was used to examine the mobilization of axial capacity and the related group effect of a pile group, with various numbers of piles per group and different pile spacing. Secondly, the FEA model was used to investigate the group effects on the lateral capacity of a pile group, with respects of mobilization of lateral capacity, influence of loading direction, influence of pile spacing, and influence of number of piles in one group. These FEA results were also compared with the literature studies. Finally, recommendations on pile group effects for both axial capacity and lateral capacity were provided for TLP driven pile geotechnical designs in normally consolidated clay.
Experimental Study on the Strain Softening Behavior of Plate Anchors in Clay Under Cyclic Loading
Authors: Yu Long , Zhou Qi , Liu Jun
Published: July 2018

Many geotechnical designs require knowledge of soil uplift resistance where the foundation must withstand tensile forces, such as wind loading on transmission towers, wave action on offshore structures, and buoyancy forces on buried pipelines. Most existing researches on the bearing capacity of plate anchors are limited to static analyses. The effects of offshore cyclic loading on the bearing capacity of plate anchors are not very clear. The ultimate pullout capacity of plate anchors in clay may decrease as the accumulated plastic shear strain grows due to the strain-softening of clay under cyclic loading. In this study, 1 g model tests were carried out to estimate the softening behavior of plate anchors including one low stress level case and two high stress level cases. PIV (Particle Image Velocimetry) technique was used to investigate the soil flow mechanism of the anchor at low stress level. Numerical analyses are carried out to simulate the large deformation behavior of the anchor at high stress level under cyclic loading.
Poro-Elasto-Plastic Model for Wave-Induced Liquefaction
Authors: Liao Chengcong , Zhao Hongyi , Jeng Dong-Sheng
Published: July 2018

In this study, a two-dimensional poro-elasto-plastic model for the wave-induced liquefaction in a porous seabed was presented. Two mechanisms of the wave-induced pore pressures were considered. Both elastic components (for oscillatory) and the plastic components (for residual) were integrated to predict the wave-induced excess pore pressures in marine sediments. The proposed 2D poro-elasto-plastic model allows for the pore pressure build-up process in a sandy seabed. The proposed model overall agreed well with the previous wave experiments and centrifuge tests. Numerical example shows that the pattern of progressive waves -induced liquefaction gradually changed from 2D to 1D.
Dynamic Model Test of Monopile for Offshore Wind Turbines
Authors: Hanssen Stian Baardsgaard , Eiksund Gudmund
Published: July 2018

In current practice, the most common foundation type for Offshore Wind Turbine generators (OWT’s) at moderate water depths is the monopile. A model pile in scale 1:20 of a typical monopile foundation for offshore wind turbine has undergone lateral vibration testing in dry laboratory sand. Eigen-frequencies are determined based on acceleration measurements. The aim of the tests is to provide benchmark results for validation of different calculation methods for offshore wind monopile foundations. The stiffness contribution from the sand is evaluated on behalf of measuring the first natural frequency of the pile-soil interaction system. Preliminary results from back-calculations of the model tests using both 3D -FEM and a simple beam on elastic foundation model indicate that strain-dependent soil stiffness plays an important role for determining the system stiffness. In this paper, the model tests and their results are presented, along with the preliminary results from the back-calculation.
Upper Bound Solutions of Vertical Bearing Capacity of a New Type Bucket Foundation in Sand
Authors: Liu Run , Chen Guangsi , Ding Hongyan , Lian Jijian
Published: July 2018

Offshore wind turbine is a new solution of the energy crisis, and stable foundation is an important guarantee for its safety. An important characteristic of wind turbine foundation is to bear the vertical load, horizontal load and moment at runtime. A large diameter wide-shallow bucket foundation, as a new foundation type, is proposed by Tianjin University for applying to the specific load conditions. The diameter of the foundation is generally more than 30 m, and its embedment ratio is between 0.2 and 0.5. Compared with other traditional forms of ocean engineering foundation, there have been no standards and theories for bucket foundation designing currently. The vertical bearing capacity is an important basic indicator in the process of offshore wind turbine foundation designing, which determines the size of wind turbines and the cost of engineering. This paper proposes two failure mechanisms about vertical bearing capacity of bucket foundation through the experiment. The upper value of vertical bearing capacity of bucket foundation has been derived through the upper bound theorem of classical plasticity theory. Soil damaging rate is specified as a new empirical parameter in the formula. It is defined as the rate between the thickness of the soil which is broken inside the foundation and the radius of foundation, which indicates the range of soil failure. And the number range of soil damaging rate is obtained through the vertical bearing capacity experiments. Relationship between bearing capacity factor Nγ and friction angle also discussed under the specific soil damaging rates. These results are helpful in reducing the uncertainties related to the method of analysis in bearing capacity calculations, paving the way for more cost-effective foundation design.
Two new species of Scapheremaeus from Southern Japan (Acari: Oribatida: Cymbaeremaeidae), with genetic information
Authors: Bayartogtokh Badamdorj , Hiruta Shimpei F. , Shimano Satoshi
Published: July 2018

The present paper deals with two new species of oribatid mites of the genus Scapheremaeus Berlese, 1910 from the subtropical islands in Southern Japan. Scapheremaeus nakanoshimensis sp. nov. and Scapheremaeus boninensis sp. nov. are proposed on the basis of adults. Furthermore, we present data on distribution, diversity and habitat ecology of all known species of Scapheremaeus in Japan, and a key is provided for identification of hitherto recorded species in this country. Majority of Scapheremaeus species found in Japan are known to be restricted to areas of Southern Japan and Eastern China. Only one of the species has a relatively broad distribution in South America and East Asia. Most species of Scapheremaeus in Japan are inhabitants of soil and litter of various forests, and mosses growing on rocks, but few of them are arboreal. The D3 fragments of the 28S rRNA (28S D3) and 18S rRNA genes of Scapheremaeus nakanoshimensis sp. nov. are sequenced and data are available in the sequence database. Comparison of the 28S D3 gene sequence of Scapheremaeus nakanoshimensis sp. nov. with other oribatid mites gene sequences identifies that the representatives of Scutoverticidae (Scutovertex, Provertex, Exochocepheus) and Eremaeozetidae (Eremaeozetes), Ameronothridae (Ameronothrus) and Phenopelopidae (Eupelops) are the closest relatives to Scapheremaeus with regard to the species included in this analysis.
A simplified model for thin acoustic screens
Authors: Gaborit Mathieu , Dazel Olivier , Göransson Peter
Published: July 2018

A generalization of the commonly used pressure jump modeling of thin porous layers is proposed. The starting point is a transfer matrix model of the layer derived using matrix exponentials. First order expansions of the propagating terms lead to a linear approximation of the associated phenomena and the resulting matrix is further simplified based on physical assumptions. As a consequence, the equivalent fluid parameters used in the model may be reduced to simpler expressions and the transfer matrix rendered sparser. The proposed model is validated for different backing conditions, from normal to grazing incidence and for a wide range of thin films. In the paper, the physical hypotheses are discussed, together with the origin of the field jumps.
Do Fungi Undergo Apoptosis-Like Programmed Cell Death?
Authors: Hardwick J. Marie
Published: July 2018

This question of whether fungi undergo apoptosis-like programmed cell death can be separated into two questions. One question is about applying the term “apoptosis” to fungi, and the other is a more challenging question of whether fungi have evolved mechanisms that inflict self-injury.
Migration of Type III Secretion System Transcriptional Regulators Links Gene Expression to Secretion
Authors: Charova Spyridoula N. , Gazi Anastasia D. , Mylonas Efstratios , Pozidis Charalambos , Sabarit Blanca , Anagnostou Dimitrios , Psatha Konstantina , Aivaliotis Michalis , Beuzon Carmen R. , Panopoulos Nickolas J. , Kokkinidis Michael
Published: July 2018

Many plant-pathogenic bacteria of considerable economic importance rely on type III secretion systems (T3SSs) of the Hrc-Hrp 1 family to subvert their plant hosts. T3SS gene expression is regulated through the HrpG and HrpV proteins, while secretion is controlled by the gatekeeper HrpJ. A link between the two mechanisms was so far unknown. Here, we show that a mechanistic coupling exists between the expression and secretion cascades through the direct binding of the HrpG/HrpV heterodimer, acting as a T3SS chaperone, to HrpJ. The ternary complex is docked to the cytoplasmic side of the inner bacterial membrane and orchestrates intermediate substrate secretion, without affecting early substrate secretion. The anchoring of the ternary complex to the membranes potentially keeps HrpG/HrpV away from DNA. In their multiple roles as transcriptional regulators and gatekeeper chaperones, HrpV/HrpG provide along with HrpJ potentially attractive targets for antibacterial strategies.

IMPORTANCE
On the basis of scientific/economic importance,
Pseudomonas syringae
and
Erwinia amylovora
are considered among the top 10 plant-pathogenic bacteria in molecular plant pathology. Both employ type III secretion systems (T3SSs) of the Hrc-Hrp 1 family to subvert their plant hosts. For Hrc-Hrp 1, no functional link was known between the key processes of T3SS gene expression and secretion. Here, we show that a mechanistic coupling exists between expression and secretion cascades, through formation of a ternary complex involving the T3SS proteins HrpG, HrpV, and HrpJ. Our results highlight the functional and structural properties of a hitherto-unknown complex which orchestrates intermediate T3SS substrate secretion and may lead to better pathogen control through novel targets for antibacterial strategies.
Monoassociation with Lactobacillus plantarum Disrupts Intestinal Homeostasis in Adult Drosophila melanogaster
Authors: Fast David , Duggal Aashna , Foley Edan
Published: July 2018

Adult
Drosophila melanogaster
raised in the absence of symbiotic bacteria have fewer intestinal stem cell divisions and a longer life span than their conventionally reared counterparts. However, we do not know if increased stem cell divisions are essential for symbiont-dependent regulation of longevity. To determine if individual symbionts cause aging-dependent death in
Drosophila
, we examined the impacts of common symbionts on host longevity. We found that monoassociation of adult
Drosophila
with
Lactobacillus plantarum
, a widely reported fly symbiont and member of the probiotic
Lactobacillus
genus, curtails adult longevity relative to germfree counterparts. The effects of
Lactobacillus plantarum
on life span were independent of intestinal aging. Instead, we found that association with
Lactobacillus plantarum
causes an extensive intestinal pathology within the host, characterized by loss of stem cells, impaired epithelial renewal, and a gradual erosion of epithelial ultrastructure. Our study uncovers an unknown aspect of
Lactobacillus plantarum
-
Drosophila
interactions and establishes a simple model to characterize symbiont-dependent disruption of intestinal homeostasis.

IMPORTANCE
Under homeostatic conditions, gut bacteria provide molecular signals that support the organization and function of the host intestine. Sudden shifts in the composition or distribution of gut bacterial communities impact host receipt of bacterial cues and disrupt tightly regulated homeostatic networks. We used the
Drosophila melanogaster
model to determine the effects of prominent fly symbionts on host longevity and intestinal homeostasis. We found that monoassociation with
Lactobacillus plantarum
leads to a loss of intestinal progenitor cells, impaired epithelial renewal, and disruption of gut architecture as flies age. These observations uncover a novel phenotype caused by monoassociation of a germfree host with a common symbiont and establish a simple model to characterize symbiont-dependent loss of intestinal homeostasis.
Reverse Genetics for Type I Feline Coronavirus Field Isolate To Study the Molecular Pathogenesis of Feline Infectious Peritonitis
Authors: Ehmann Rosina , Kristen-Burmann Claudia , Bank-Wolf Barbara , König Matthias , Herden Christiane , Hain Torsten , Thiel Heinz-Jürgen , Ziebuhr John , Tekes Gergely
Published: July 2018

Feline infectious peritonitis (FIP), one of the most important lethal infections of cats, is caused by feline infectious peritonitis virus (FIPV), the high-virulence biotype of feline coronaviruses (FCoVs). FIPVs are suggested to emerge from feline enteric coronaviruses (FECVs) by acquiring mutations in specific genes in the course of persistent infections. Although numerous studies identified mutations predicted to be responsible for the FECV-FIPV biotype switch, the presumed roles of specific genetic changes in FIP pathogenesis have not been confirmed experimentally. Reverse genetics systems established previously for serotype I and the less common serotype II FCoVs were based on cell culture-adapted FIPV strains which, however, were shown to be unsuitable for FIP pathogenesis studiesin vivo. To date, systems to produce and manipulate recombinant serotype I field viruses have not been developed, mainly because these viruses cannot be grownin vitro. Here, we report the first reverse genetics system based on a serotype I FECV field isolate that is suitable to produce high-titer stocks of recombinant FECVs. We demonstrate that these recombinant viruses cause productive persistent infections in cats that are similar to what is observed in natural infections. The system provides an excellent tool for studying FCoVs that do not grow in standard cell culture systems and will greatly facilitate studies into the molecular pathogenesis of FIP. Importantly, the system could also be adapted for studies of other RNA viruses with large genomes whose production and characterizationin vivoare currently hampered by the lack ofin vitropropagation systems.

IMPORTANCEThe availability of recombinant serotype I FCoV field isolates that are amenable to genetic manipulation is key to studying the molecular pathogenesis of FIP, especially since previous studies using cell culture-adapted FIPVs had proven unsuccessful. To our knowledge, we report the first serotype I FECV field isolate-based reverse genetics system that allows the production of high-titer recombinant virus stocks that can be used for subsequentin vivostudies in cats. The system represents a milestone in FCoV research. It provides an essential tool for studying the molecular pathogenesis of FIP and, more specifically, the functions of specific gene products in causing a fundamentally different progression of disease following acquisition of specific mutations. The system developed in this study will also be useful for studying other coronaviruses or more distantly related RNA viruses with large genomes for which suitablein vitroculture systems are not available.
On-the-farm cardiovascular risk screening among migrant agricultural workers in Southeast Minnesota: a pilot prospective study
Authors: Rajjo Tamim , Mohammed Khaled , Rho Jennifer , Murad M. Hassan
Published: July 2018

Introduction

Accessibility to healthcare services is a major concern facing migrant agricultural workers (MAWs) in the USA. We aimed to test the feasibility of implementing cardiovascular risk screening at farm sites.

Methods

This was a pilot prospective cohort study providing on-site monthly screenings of cardiovascular risk factors. We estimated the prevalence of cardiovascular risk factors and evaluated the success of this approach via modified validated satisfaction surveys.

Results

We enrolled 38 MAWs and diagnosed 18 cases of pre-diabetes, diabetes, hypertension and hyperlipidaemia in 15 subjects (39.4%). Mean scores of workers’ satisfaction were high (≥4) on a 5-point scale except ‘Time spent with provider’. Over 80% of workers were likely to use this model if it was permanently available on the farm. Only 8.7% of workers were able to follow up after referral to a clinic.

Conclusions

Cardiovascular risk factors are highly prevalent in MAWs. On-the-farm screening is a feasible and satisfactory model of healthcare delivery; however, other barriers continue to hinder MAWs from receiving follow-up care.

Trial registration number

NCT02418637. Results.
Retrospective review of the management of acute infections and the indications for antibiotic prescription in primary care in northern Thailand
Authors: Greer Rachel C , Intralawan Daranee , Mukaka Mavuto , Wannapinij Prapass , Day Nicholas P J , Nedsuwan Supalert , Lubell Yoel
Published: July 2018

Introduction

Antibiotic use in low-income and middle-income countries continues to rise despite the knowledge that antibiotic overuse can lead to antimicrobial resistance. There is a paucity of detailed data on the use of antibiotics in primary care in low-resource settings.

Objective

To describe the presentation of acute infections and the indications for antibiotic prescription.

Design

A 2-year retrospective review of routinely collected data.

Setting

All 32 primary care units in one district in northern Thailand.

Participants

Patients attending primary care with a history of fever, documented temperature, International Statistical Classification of Diseases 10 code for infection or prescribed a systemic antibiotic. Patients attending after the initiation of a study on C-reactive protein testing in four centres were excluded.

Outcome measures

The proportion of patients prescribed an antibiotic and the frequency of clinical presentations.

Results

762 868 patients attended the health centres, of whom 103 196 met the inclusion criteria, 5966 were excluded resulting in 97 230 attendances consisting of 83 661 illness episodes.

46.9% (39 242) of the patients were prescribed an antibiotic during their illness. Indications for antibiotic prescription in the multivariable logistic regression analysis included male sex (adjusted OR (aOR) 1.21 (95% CI 1.16 to 1.28), p<0.001), adults (aOR 1.77 (95% CI 1.57 to 2), p<0.001) and a temperature >37.5°C (aOR 1.24 (95% CI 1.03 to 1.48), p=0.020). 77.9% of the presentations were for respiratory-related problems, of which 98.6% were upper respiratory tract infections. The leading infection diagnoses were common cold (50%), acute pharyngitis (18.9%) and acute tonsillitis (5%) which were prescribed antibiotics in 10.5%, 88.7% and 87.1% of cases, respectively. Amoxicillin was the most commonly prescribed antibiotic.

Conclusions

Nearly half of the patients received an antibiotic, the majority of whom had a respiratory infection. The results can be used to plan interventions to improve the rational use of antibiotics. Further studies in private facilities, pharmacies and dental clinics are required.
Prospective investigation of folic acid supplements before and during early pregnancy and paediatric and adult cancers in the Chinese children and families cohort: a pilot study in a sample of rural and urban families
Authors: Linet Martha S , Wang Linhong , Wang Ning , Berry Robert J , Chao Ann , Hao Ling , Li Zhu , Fang Liwen , Yin Peng , Potischman Nancy , Sun Xin , Meng Fanweng , Yang Ruilan , Cong Shu , Fan Jing , Kitahara Cari M , Liang Xiaofeng , Liu Fang , Lu Xiaojun , Lv Fan , Mu Chunhua , Sampson Joshua , Tang Yongmin , Wan Weiqing , Wang Baohua , Wang Hongsheng , Zhang Leping , Wang Yu
Published: July 2018

Objective

To determine the feasibility of long-term prospective follow-up and ascertainment of cancer in offspring and mothers from the 1993–1995 Chinese Community Intervention Program that provided folic acid supplements before and during early pregnancy to reduce neural tube defects.

Design

Feasibility pilot study for a prospective cohort study.

Setting

Families residing during 2012–2013 in one rural and one urban county from 21 counties in 3 provinces in China included in the Community Intervention Program campaign.

Participants

The feasibility study targeted 560 families, including 280 from the rural and 280 from the urban county included in the large original study; about half of mothers in each group had taken and half had not taken folic acid supplements.

Intervention

The planned new study is observational.

Primary and secondary outcome measures

Primary: incidence of paediatric cancers in offspring; secondary: other chronic diseases in offspring and chronic diseases in mothers

Results

Only 3.4% of pilot study families could not be found, 3.9% had moved out of the study area and 8.8% refused to participate. Interviews were completed by 82% of mothers, 79% of fathers and 83% of offspring in the 560 families. Almost all mothers and offspring who were interviewed also participated in anthropometric measurements. We found notable urban–rural differences in sociodemographic and lifestyle characteristics of the parents, but fewer differences among the offspring. In eight catchment area hospitals, we identified a broad range of paediatric cancers diagnosed during 1994–2013, although paediatric brain tumours, lymphomas and rarer cancers were likely under-represented.

Conclusions

Overall, 20 years after the original Community Intervention Program, the pilot study achieved high levels of follow-up and family member interview participation, and identified substantial numbers of paediatric malignancies during 1994–2013 in catchment area hospitals. Next steps and strategies for overcoming limitations are described.
The problem with pay-for-performance schemes
Authors: Gondi Suhas , Soled Derek , Jha Ashish
Published: July 2018

‘The Problem with…’ series covers controversial topics related to efforts to improve healthcare quality, including widely recommended but deceptively difficult strategies for improvement and pervasive problems that seem to resist solution.
Sleeping habits of adolescents in relation to their physical activity and exercise output: results from the ELSPAC study
Authors: Máchal Jan , Zlámal Filip , Kukla Lubomír , Švancara Jan , Pikhart Hynek , Bienertová-Vašků Julie
Published: July 2018

Background

Little is known about the effects of physical activity and fitness on sleep timing parameters in adolescence.

Methods

We investigated the development of sleep timing between age 8 and 15 and its association with physical fitness at age 15 in 787 adolescents (408 males, 379 females). Physical fitness was measured using the physical work capacity (PWC) protocol. Information on sport activity was collected at ages 11 and 15. Finally, the contribution of other covariates (sex, body mass index (BMI), parental education and occupational skill level) to the association between sleep parameters and physical fitness was evaluated. The correlation of BMI and physical fitness was assessed separately.

Results

Mild correlation of sleep duration at ages 8 and 15 was observed (r=0.08–0.16). Higher sport activity participation and physical fitness were found to be mildly associated with delayed bedtime and reduced sleep duration; the association with bedtime was significant after adjustment for all covariates. Sport activity at age 11 was not associated with sleep timing at age 15. Interestingly, higher BMI was linked to delayed bedtime and higher physical fitness.

Conclusion

Our findings do not support existing hypotheses suggesting the association of low physical activity and fitness with shorter sleep duration and high BMI in a generally non-obese adolescent population without severe sleep restriction.