bluuebunny/crossref_metadata_2025 huggingface dataset:
High-Speed Shadowgraphy Measurements of an Erosive Particle-Laden Jet Under High-Pressure Compressor Conditions
Authors: Hufnagel Max , Werner-Spatz Christian , Koch Christian , Staudacher Stephan
Published: August 2017

Erosive damage done to jet engine compressor blading by solid particles has a negative influence on the compressor aerodynamic properties and hence decreases performance. The erosive change of shape has been investigated in a multitude of experiments ranging from eroding flat plates to eroding full engines. The basic challenge to transfer the results from very simple tests to real life erosion remains. Up to date measurement techniques today allow closing this gap. The necessary experimental and analytical steps are shown. The erosion resistance of Ti–6Al–4V at realistic flow conditions with fluid velocities ranging from 200 to 400 m/s is used. The erodent used was quartz sand with a size distribution corresponding to standardized Arizona Test Dust A3 (1–120 μm). Flat plates out of Ti–6Al–4V were eroded at different impingement angles. The particle velocities and sizes were investigated using a high-speed laser shadowgraphy technique. A dimensional analysis was carried out to obtain nondimensional parameters suitable for describing erosion. Different averaging methods of the particle velocity were examined in order to identify a representative particle velocity. Compared to the fluid velocity and the mean particle velocity, the energy averaged particle velocity is found to be the best representation of the erosiveness of a particle stream. The correlations derived from the dimensional analysis are capable of precisely predicting erosion rates for different rig operating points (OPs). The results can be applied to the methodology published by Schrade et al. (2015, “Experimental and Numerical Investigation of Erosive Change of Shape for High-Pressure Compressors,” ASME Paper No. GT2015-42061).
An Improved Assembling Algorithm in Boundary Elements With Galerkin Weighting Applied to Three-Dimensional Stokes Flows
Authors: Sarraf Sofia , López Ezequiel , Battaglia Laura , Ríos Rodríguez Gustavo , D'Elía Jorge
Published: August 2017

In the boundary element method (BEM), the Galerkin weighting technique allows to obtain numerical solutions of a boundary integral equation (BIE), giving the Galerkin boundary element method (GBEM). In three-dimensional (3D) spatial domains, the nested double surface integration of GBEM leads to a significantly larger computational time for assembling the linear system than with the standard collocation method. In practice, the computational time is roughly an order of magnitude larger, thus limiting the use of GBEM in 3D engineering problems. The standard approach for reducing the computational time of the linear system assembling is to skip integrations whenever possible. In this work, a modified assembling algorithm for the element matrices in GBEM is proposed for solving integral kernels that depend on the exterior unit normal. This algorithm is based on kernels symmetries at the element level and not on the flow nor in the mesh. It is applied to a BIE that models external creeping flows around 3D closed bodies using second-order kernels, and it is implemented using OpenMP. For these BIEs, the modified algorithm is on average 32% faster than the original one.
Influence of the Nozzle Shape on the Breakup Behavior of Continuous Ink Jets
Authors: Rosello Maxime , Maîtrejean Guillaume , Roux Denis C. D. , Jay Pascal , Barbet Bruno , Xing Jean
Published: August 2017

In this work, the influence of nozzle shape on microfluidic ink jet breakup is investigated. First, an industrial ink used in continuous inkjet (CIJ) printing devices is selected. Ink rheological properties are measured to ensure an apparent Newtonian behavior and a constant surface tension. Then, breakup lengths and shapes are observed on a wide range of disturbance amplitude for four different nozzles. Later on, ink breakup behaviors are compared to the linear theory. Finally, these results are discussed using numerical simulations to highlight the influence of the velocity profiles at the nozzle outlet. Using such computations, a simple approach is derived to accurately predict the breakup length for industrial CIJ nozzles.
Experimental Studies on the Effect of Suction Chamber Angle on the Entrainment of Passive Fluid in a Steam Ejector
Authors: Ramesh A. S. , Joseph Sekhar S.
Published: August 2017

In this experimental study, the impact of suction chamber angle (SCA) on the entrainment ratio of a steam ejector refrigeration system (ERS) of 700 W was investigated. The basic dimensions of the ejector were derived from the compressible fluid flow equations using matlab. The system was tested with six different SCAs with various operating conditions, and its performance was analyzed. It is inferred that the entrainment of passive fluid from the evaporator is the strong function of the SCA. For all the active steam pressures, the entrainment of the passive fluid increases up to 12 deg of SCA, and above that the performance decreases significantly. Optimum angle of suction chamber increases the entrainment ratio for at least 49.96%. It is also found that the SCA has a minor influence on the back pressure.
Computational Fluid Dynamics Study of the Dead Water Problem
Authors: Esmaeilpour Mehdi , Ezequiel Martin J. , Carrica Pablo M.
Published: August 2017

The dead water problem, in which under certain conditions a vessel advancing in a stratified fluid experiences a considerable increase in resistance respect to the equivalent case without stratification, was studied using computational fluid dynamics (CFD). The advance of a vessel in presence of a density interface (pycnocline) results in the generation of an internal wave that in the most adverse conditions can increase the total resistance coefficient by almost an order of magnitude. This paper analyses the effects of stratification on total and friction resistance, the near field wake, internal and free surface waves, and resistance dynamics. Some of these effects are reported for the first time, as limitations of previous efforts using potential flow are overcome by the use of a viscous, free surface CFD solver. A range of densimetric Froude numbers from subcritical to supercritical are evaluated changing both the ship speed and pycnocline depth, using as platform the research vessel athena. It was found that the presence of the internal wave causes a favorable pressure gradient, acceleration of the flow in the downstream of the hull, resulting in thinning of the boundary layer and increases of the friction resistance coefficient of up to 30%. The total resistance presents an unstable region that results in a hysteretic behavior, though the characteristic time to establish the speed–resistance curve, dominated by the formation of the internal waves, is very long and unlikely to cause problems in modern ship speed controllers.
A Computer-Aided Design and Manufacturing Implementation of the Atomic Force Microscope Tip-Based Nanomachining Process for Two-Dimensional Patterning
Authors: Brousseau E. B. , Thiery S. , Arnal B. , Nyiri E. , Gibaru O. , Mayor J. R.
Published: August 2017

This paper reports a feasibility study that demonstrates the implementation of a computer-aided design and manufacturing (CAD/CAM) approach for producing two-dimensional (2D) patterns on the nanoscale using the atomic force microscope (AFM) tip-based nanomachining process. To achieve this, simple software tools and neutral file formats were used. A G-code postprocessor was also developed to ensure that the controller of the AFM equipment utilized could interpret the G-code representation of tip path trajectories generated using the computer-aided manufacturing (CAM) software. In addition, the error between a machined pattern and its theoretical geometry was also evaluated. The analyzed pattern covered an area of 20 μm × 20 μm. The average machined error in this case was estimated to be 66 nm. This value corresponds to 15% of the average width of machined grooves. Such machining errors are most likely due to the flexible nature of AFM probe cantilevers. Overall, it is anticipated that such a CAD/CAM approach could contribute to the development of a more flexible and portable solution for a range of tip-based nanofabrication tasks, which would not be restricted to particular customised software or AFM instruments. In the case of nanomachining operations, however, further work is required first to generate trajectories, which can compensate for the observed machining errors.
Structure of Electrospray Printed Deposits for Short Spray Times
Authors: Brown Nicholas A. , Zhu Yaqun , Li Ao , Zhao Mingfei , Yong Xin , Chiarot Paul R.
Published: August 2017

In electrospray printing, a plume of highly charged droplets is created from a conductive ink. Printing occurs by positioning a target substrate (TS) in the path of the emitted material. Here, the ink used is a colloidal dispersion consisting of nanoparticles suspended in a volatile solvent. The selection of a volatile solvent allows for rapid evaporation of the droplets in-flight to produce dry nanoparticles. A net electric charge is imparted on the emitted particles during electrospray. The interaction of this charge with the global electric field and with other charged particles/droplets governs the particles' trajectory and determines the microstructure of the printed deposit. In this study, we characterized the structure of nanoparticle deposits printed using electrospray for deposits with low particle count. During printing, the TS was: (i) held stationary and (ii) translated with various short spray times and substrate velocities, respectively. Examination of both a static and translating TS provided fundamental insights into the printing process. Electrospray printing is capable of exerting much finer control over microstructure compared to other printing techniques. This has significant implications for the manufacturing of thin-films.
Unsteady RANS Simulations of Wells Turbine Under Transient Flow Conditions
Authors: Hu Qiuhao , Li Ye
Published: August 2017

This paper presents our recent numerical simulations of a high-solidity Wells turbine under both steady and unsteady conditions by solving Reynolds-averaged Navier–Stokes (RANS) equations. For steady conditions, the equations are solved in a reference frame with the same angular velocity of the turbine. Good agreement between numerical simulation result and experimental data has been obtained in the operational region and incipient stall conditions. The exact value of stall point has been accurately predicted. Through analyzing the detailed fluid fields, we find that the stall occurs near the tip of the blade while the boundary layer keeps attached near the hub, due to the effect of radial flow. For unsteady conditions, two types of control methods are studied: constant angular velocity and constant damping moment. For the constant angular velocity, the behaviors of the turbine under both high and low sea wave frequency are calculated to compare with those obtained by quasi-steady method. The hysteresis characteristic can be observed and deeply affects the behaviors of the Wells turbine with high wave frequency. For the constant damping moment, the turbine angular velocity is time dependent. Under sinusoidal flow, the incident flow velocity in the operational region can be improved to avoid the stall.
Dry Sliding Wear Behavior of 2218 Al-Alloy-Al2O3(TiO2) Hybrid Composites
Authors: Tirth Vineet
Published: August 2017

AA2218–Al2O3(TiO2) composites are synthesized by stirring 2, 5, and 7 wt % of 1:2 mixture of Al2O3:TiO2 powders in molten AA2218 alloy. T61 heat-treated composites characterized for microstructure and hardness. Dry sliding wear tests conducted on pin-on-disk setup at available loads 4.91–13.24 N, sliding speed of 1.26 m/s up to sliding distance of 3770 m. Stir cast AA2218 alloy (unreinforced, 0 wt % composite) wears quickly by adhesion, following Archard's law. Aged alloy exhibits lesser wear rate than unaged (solutionized). Mathematical relationship between wear rate and load proposed for solutionized and peak aged alloy. Volume loss in wear increases linearly with sliding distance but drops with the increase in particle wt % at a given load, attributed to the increase in hardness due to matrix reinforcement. Minimum wear rate is recorded in 5 wt % composite due to increased particles retention, lesser porosity, and uniform particle distribution. In composites, wear phenomenon is complex, combination of adhesive and abrasive wear which includes the effect of shear rate, due to sliding action in composite, and abrasive effect (three body wear) of particles. General mathematical relationship for wear rate of T61 aged composite as a function of particle wt % load is suggested. Fe content on worn surface increases with the increase in particle content and counterface temperature increases with the increase in load. Coefficient of friction decreases with particle addition but increases in 7 wt % composite due to change in microstructure.
Friction and Wear Performance of Epoxy Resin Reinforced With Boron Nitride Nanoplatelets
Authors: Ekrem Mürsel , Düzcükoğlu Hayrettin , Ali Şenyurt Muhammet , Sinan Şahin Ömer , Avcı Ahmet
Published: August 2017

In this study, the effects of addition of boron nitride nanoplatelets (BNNPs) upon friction and wear behavior of epoxy resin have been investigated by using pin-on-disk test. It has been reported in the literature that certain amounts of BNNP addition can be useful for enhancement of mechanical properties. Therefore, it is very important to obtain the effect of such addition upon friction and wear performance of epoxy resin. BNNPs have been incorporated at 0.3–0.5–0.7–1 wt %. It is shown that BNNP addition results in decrease in friction coefficient and wear. It is also shown that the best results are obtained with 0.5% nanoplatelet addition. It is also observed that heat conduction of epoxy resin is enhanced by the nanoplatelet addition.
Bifurcation Analysis of a Rotor Supported by Five-Pad Tilting Pad Journal Bearings Using Numerical Continuation
Authors: Kim Sitae , Palazzolo Alan B.
Published: August 2017

This paper presents analytical bifurcations analysis of a “Jeffcott” type rigid rotor supported by five-pad tilting pad journal bearings (TPJBs). Numerical techniques such as nonautonomous shooting/arc-length continuation, Floquet theory, and Lyapunov exponents are employed along with direct numerical integration (NI) to analyze nonlinear characteristics of the TPJB-rotor system. A rocker pivot type five-pad TPJB is modeled with finite elements to evaluate the fluid pressure distribution on the pads, and the integrated fluid reaction force and moment are utilized to determine coexistent periodic solutions and bifurcations scenarios. The numerical shooting/continuation algorithms demand significant computational workload when applied to a rotor supported by a finite element bearing model. This bearing model may be significantly more accurate than the simplified infinitely short-/long-bearing approximations. Consequently, the use of efficient computation techniques such as deflation and parallel computing methods is applied to reduce the execution time. Loci of bifurcations of the TPJB-rigid rotor are determined with extensive numerical simulations with respect to both rotor spin speed and unbalance force magnitude. The results show that heavily loaded bearings and/or high unbalance force may induce consecutive transference of response in forms of synchronous to subsynchronous, quasi-periodic responses, and chaotic motions. It is revealed that the coexistent responses and their solution manifolds are obtainable and stretch out with selections of pad preload, pivot offset, and lubricant viscosity so that the periodic doubling bifurcations, saddle node bifurcations, and corresponding local stability are reliably determined by searching parameter sets. In case the system undergoes an aperiodic state, the rate of divergence/convergence of the attractor is examined quantitatively by using the maximum Lyapunov exponent (MLE).
Multiple-wavelength neutron holography with pulsed neutrons
Authors: Hayashi Kouichi , Ohoyama Kenji , Happo Naohisa , Matsushita Tomohiro , Hosokawa Shinya , Harada Masahide , Inamura Yasuhiro , Nitani Hiroaki , Shishido Toetsu , Yubuta Kunio
Published: August 2017

Multiple-wavelength neutron holography demonstrated a reconstruction of highly precise 3D atomic images around dopants.
Identifying time scales for violation/preservation of Stokes-Einstein relation in supercooled water
Authors: Kawasaki Takeshi , Kim Kang
Published: August 2017

Various time scales characterizing transport coefficients reveal the origin of Stokes-Einstein violation in supercooled water.
Mach-Zehnder interferometry using spin- and valley-polarized quantum Hall edge states in graphene
Authors: Wei Di S. , van der Sar Toeno , Sanchez-Yamagishi Javier D. , Watanabe Kenji , Taniguchi Takashi , Jarillo-Herrero Pablo , Halperin Bertrand I. , Yacoby Amir
Published: August 2017

We realize an electronic Mach-Zehnder interferometer with quantum Hall edge channels along a pn junction in graphene.
Correlation-induced superconductivity dynamically stabilized and enhanced by laser irradiation
Authors: Ido Kota , Ohgoe Takahiro , Imada Masatoshi
Published: August 2017

Laser irradiation stabilizes strong-coupling superconductivity without charge inhomogeneities that is inaccessible in equilibrium.
High-density array of ferroelectric nanodots with robust and reversibly switchable topological domain states
Authors: Li Zhongwen , Wang Yujia , Tian Guo , Li Peilian , Zhao Lina , Zhang Fengyuan , Yao Junxiang , Fan Hua , Song Xiao , Chen Deyang , Fan Zhen , Qin Minghui , Zeng Min , Zhang Zhang , Lu Xubing , Hu Shejun , Lei Chihou , Zhu Qingfeng , Li Jiangyu , Gao Xingsen , Liu Jun-Ming
Published: August 2017

Robust and reversible polar topological center domains were found in BiFeO
3
nanodots, which are individually controllable.
Crystallization-induced emission enhancement: A novel fluorescent Au-Ag bimetallic nanocluster with precise atomic structure
Authors: Chen Tao , Yang Sha , Chai Jinsong , Song Yongbo , Fan Jiqiang , Rao Bo , Sheng Hongting , Yu Haizhu , Zhu Manzhou
Published: August 2017

Crystallization-induced emission enhancement was achieved in metal nanoclusters for the first time.
Liquid crystalline cellulose-based nematogels
Authors: Liu Qingkun , Smalyukh Ivan I.
Published: August 2017

An ordered network of cellulose nanofibers infiltrated with a liquid crystal forms an electrically tunable nematogel.
Tunable chiral metal organic frameworks toward visible light–driven asymmetric catalysis
Authors: Zhang Yin , Guo Jun , Shi Lin , Zhu Yanfei , Hou Ke , Zheng Yonglong , Tang Zhiyong
Published: August 2017

A general way to prepare chiral MOFs as adjustable catalysts for efficient asymmetric catalysis under visible light.
Probing topology by “heating”: Quantized circular dichroism in ultracold atoms
Authors: Tran Duc Thanh , Dauphin Alexandre , Grushin Adolfo G. , Zoller Peter , Goldman Nathan
Published: August 2017

Physicists demonstrate how heating a quantum system can be used as a universal probe for exotic states of matter.
Zika virus activates de novo and cross-reactive memory B cell responses in dengue-experienced donors
Authors: Rogers Thomas F. , Goodwin Eileen C. , Briney Bryan , Sok Devin , Beutler Nathan , Strubel Alexander , Nedellec Rebecca , Le Khoa , Brown Michael E. , Burton Dennis R. , Walker Laura M.
Published: August 2017

Preexisting dengue virus immunity could negatively affect protective antibody responses to Zika virus.
Differences in Temperature and Water Chemistry Shape Distinct Diversity Patterns in Thermophilic Microbial Communities
Authors: Chiriac Cecilia M. , Szekeres Edina , Rudi Knut , Baricz Andreea , Hegedus Adriana , Dragoş Nicolae , Coman Cristian
Published: August 2017

This report describes the biodiversity and ecology of microbial mats developed in thermal gradients (20 to 65°C) in the surroundings of three drillings (Chiraleu [CH], Ciocaia [CI], and Mihai Bravu [MB]) tapping a hyperthermal aquifer in Romania. Using a metabarcoding approach, 16S rRNA genes were sequenced from both DNA and RNA transcripts (cDNA) and compared. The relationships between the microbial diversity and the physicochemical factors were explored. Additionally, the cDNA data were used for
in silico
functionality predictions, bringing new insights into the functional potential and dynamics of these communities. The results showed that each hot spring determined the formation of distinct microbial communities. In the CH mats (40 to 53°C), the abundance of
Cyanobacteria
decreased with temperature, opposite to those of
Chloroflexi
and
Proteobacteria
.
Ectothiorhodospira
,
Oscillatoria
, and methanogenic archaea dominated the CI communities (20 to 65°C), while the MB microbial mats (53 to 65°C) were mainly composed of
Chloroflexi
,
Hydrogenophilus
,
Thermi
, and
Aquificae
. Alpha-diversity was negatively correlated with the increase in water temperature, while beta-diversity was shaped in each hot spring by the unique combination of physicochemical parameters, regardless of the type of nucleic acid analyzed (DNA versus cDNA). The rank correlation analysis revealed a unique model that associated environmental data with community composition, consisting in the combined effect of Na
+
, K
+
, HCO
3
−
, and PO
4
3−
concentrations, together with temperature and electrical conductivity. These factors seem to determine the grouping of samples according to location, rather than with the similarities in thermal regimes, showing that other parameters beside temperature are significant drivers of biodiversity.

IMPORTANCE
Hot spring microbial mats represent a remarkable manifestation of life on Earth and have been intensively studied for decades. Moreover, as hot spring areas are isolated and have a limited exchange of organisms, nutrients, and energy with the surrounding environments, hot spring microbial communities can be used in model studies to elucidate the colonizing potential within extreme settings. Thus, they are of great importance in evolutionary biology, microbial ecology, and exobiology. In spite of all the efforts that have been made, the current understanding of the influence of temperature and water chemistry on the microbial community composition, diversity, and abundance in microbial mats is limited. In this study, the composition and diversity of microbial communities developed in thermal gradients in the vicinity of three hot springs from Romania were investigated, each having particular physicochemical characteristics. Our results expose new factors that could determine the formation of these ecosystems, expanding the current knowledge in this regard.
Coordinated Regulation of the EII
Man
and
fruRKI
Operons of Streptococcus mutans by Global and Fructose-Specific Pathways
Authors: Zeng Lin , Chakraborty Brinta , Farivar Tanaz , Burne Robert A.
Published: August 2017

The glucose/mannose-phosphotransferase system (PTS) permease EII
Man
encoded by
manLMN
in the dental caries pathogen
Streptococcus mutans
has a dominant influence on sugar-specific, CcpA-independent catabolite repression (CR). Mutations in
manL
affect energy metabolism and virulence-associated traits, including biofilm formation, acid tolerance, and competence. Using promoter::reporter fusions, expression of the
manLMN
and the
fruRKI
operons, encoding a transcriptional regulator, a fructose-1-phosphate kinase and a fructose-PTS permease EII
Fru
, respectively, was monitored in response to carbohydrate source and in mutants lacking CcpA, FruR, and components of EII
Man
. Expression of genes for EII
Man
and EII
Fru
was directly regulated by CcpA and CR, as evinced by
in vivo
and
in vitro
methods. Unexpectedly, not only was the
fruRKI
operon negatively regulated by FruR, but also so was
manLMN
. Carbohydrate transport by EII
Man
had a negative influence on expression of
manLMN
but not
fruRKI
. In agreement with the proposed role of FruR in regulating these PTS operons, loss of
fruR
or
fruK
substantially altered growth on a number of carbohydrates, including fructose. RNA deep sequencing revealed profound changes in gene regulation caused by deletion of
fruK
or
fruR
. Collectively, these findings demonstrate intimate interconnection of the regulation of two major PTS permeases in
S. mutans
and reveal novel and important contributions of fructose metabolism to global regulation of gene expression.

IMPORTANCE
The ability of
Streptococcus mutans
and other streptococcal pathogens to survive and cause human diseases is directly dependent upon their capacity to metabolize a variety of carbohydrates, including glucose and fructose. Our research reveals that metabolism of fructose has broad influences on the regulation of utilization of glucose and other sugars, and mutants with changes in certain genes involved in fructose metabolism display profoundly different abilities to grow and express virulence-related traits. Mutants lacking the FruR regulator or a particular phosphofructokinase, FruK, display changes in expression of a large number of genes encoding transcriptional regulators, enzymes required for energy metabolism, biofilm development, biosynthetic and degradative processes, and tolerance of a spectrum of environmental stressors. Since fructose is a major component of the modern human diet, the results have substantial significance in the context of oral health and the development of dental caries.
Transcriptional Regulator PhlH Modulates 2,4-Diacetylphloroglucinol Biosynthesis in Response to the Biosynthetic Intermediate and End Product
Authors: Yan Xu , Yang Rui , Zhao Rui-Xue , Han Jian-Ting , Jia Wen-Juan , Li Di-Yin , Wang Yong , Zhang Nannan , Wu Yi , Zhang Li-Qun , He Yong-Xing
Published: August 2017

Certain strains of biocontrol bacterium
Pseudomonas fluorescens
produce the secondary metabolite 2,4-diacetylphloroglucinol (2,4-DAPG) to antagonize soilborne phytopathogens in the rhizosphere. The gene cluster responsible for the biosynthesis of 2,4-DAPG is named
phlACBDEFGH
and it is still unclear how the pathway-specific regulator
phlH
within this gene cluster regulates the metabolism of 2,4-DAPG. Here, we found that PhlH in
Pseudomonas fluorescens
strain 2P24 represses the expression of the
phlG
gene encoding the 2,4-DAPG hydrolase by binding to a sequence motif overlapping with the −35 site recognized by σ
70
factors. Through biochemical screening of PhlH ligands we identified the end product 2,4-DAPG and its biosynthetic intermediate monoacetylphloroglucinol (MAPG), which can act as signaling molecules to modulate the binding of PhlH to the target sequence and activate the expression of
phlG
. Comparison of 2,4-DAPG production between the Δ
phlH
, Δ
phlG
, and Δ
phlHG
mutants confirmed that
phlH
and
phlG
impose negative feedback regulation over 2,4-DAPG biosynthesis. It was further demonstrated that the 2,4-DAPG degradation catalyzed by PhlG plays an insignificant role in 2,4-DAPG tolerance but contributes to bacterial growth advantages under carbon/nitrogen starvation conditions. Taken together, our data suggest that by monitoring and down-tuning
in situ
levels of 2,4-DAPG, the
phlHG
genes could dynamically modulate the metabolic loads attributed to 2,4-DAPG production and potentially contribute to rhizosphere adaptation.

IMPORTANCE
2,4-DAPG, which is synthesized by biocontrol pseudomonad bacteria, is a broad-spectrum antibiotic against bacteria, fungi, oomycetes, and nematodes and plays an important role in suppressing soilborne plant pathogens. Although most of the genes in the 2,4-DAPG biosynthetic gene cluster (
phl
) have been characterized, it is still not clear how the pathway-specific regulator
phlH
is involved in 2,4-DAPG metabolism. This work revealed the role of PhlH in modulating 2,4-DAPG levels by controlling the expression of 2,4-DAPG hydrolase PhlG in response to 2,4-DAPG and MAPG. Since 2,4-DAPG biosynthesis imposes a metabolic burden on biocontrol pseudomonads, it is expected that the fine regulation of
phlG
by PhlH offers a way to dynamically modulate the metabolic loads attributed to 2,4-DAPG production.
Crystal Structure of TetR Family Repressor AlkX from Dietzia sp. Strain DQ12-45-1b Implicated in Biodegradation of
n
-Alkanes
Authors: Liang Jie-Liang , Gao Yuan , He Zheng , Nie Yong , Wang Meng , JiangYang Jing-Hong , Zhang Xuejun C. , Shu Wen-Sheng , Wu Xiao-Lei
Published: August 2017

n
-Alkanes are ubiquitous in nature and are widely used by microorganisms as carbon sources. Alkane hydroxylation by alkane monooxygenases is a critical step in the aerobic biodegradation of
n
-alkanes, which plays important roles in natural alkane attenuation and is used in industrial and environmental applications. The alkane oxidation operon,
alkW1-alkX
, in the alkane-degrading strain
Dietzia
sp. strain DQ12-45-1b is negatively autoregulated by the TetR family repressor AlkX via a product positive feedback mechanism. To predict the gene regulation mechanism, we determined the 3.1-Å crystal structure of an AlkX homodimer in a non-DNA-bound state. The structure showed traceable long electron density deep inside a hydrophobic cavity of each monomer along the long axis of the helix bundle, and further gas chromatography-mass spectrometry analysis of AlkX revealed that it contained the
Escherichia coli
-derived long-chain fatty acid molecules as a ligand. Moreover, an unusual structural feature of AlkX is an extra helix, α6′, forming a lid-like structure with α6 covering the inducer-binding pocket and occupying the space between the two symmetrical DNA-binding motifs in one dimer, indicating a distinct conformational transition mode in modulating DNA binding. Sequence alignment of AlkX homologs from
Dietzia
strains showed that the residues involved in DNA and inducer binding are highly conserved, suggesting that the regulation mechanisms of
n
-alkane hydroxylation are possibly a common characteristic of
Dietzia
strains.

IMPORTANCE
With
n
-alkanes being ubiquitous in nature, many bacteria from terrestrial and aquatic environments have evolved
n
-alkane oxidation functions. Alkane hydroxylation by alkane monooxygenases is a critical step in the aerobic biodegradation of
n
-alkanes, which plays important roles in natural alkane attenuation and petroleum-contaminating environment bioremediation. The gene regulation of the most common alkane hydroxylase, AlkB, has been studied widely in Gram-negative bacteria but has been less explored in Gram-positive bacteria. Our previous study showed that the TetR family regulator (TFR) AlkX negatively autoregulated the alkane oxidation operon,
alkW1-alkX
, in the Gram-positive strain
Dietzia
sp. strain DQ12-45-1b. Although TFRs are one of the most common transcriptional regulator families in bacteria, the TFR involved in
n
-alkane metabolism has been reported only recently. In this study, we determined the crystal structure of AlkX, which implies a distinct DNA/ligand binding mode. Our results shed light upon the regulation mechanism of the common alkane degradation process in nature.
Heterologous Production of the Photosynthetic Reaction Center and Light Harvesting 1 Complexes of the Thermophile Thermochromatium tepidum in the Mesophile Rhodobacter sphaeroides and Thermal Stability of a Hybrid Core Complex
Authors: Jun D. , Huang V. , Beatty J. T.
Published: August 2017

The photosynthetic complexes of the thermophile
Thermochromatium tepidum
are of considerable interest in biohybrid solar cell applications because of the ability of thermophilic proteins to tolerate elevated temperatures. Synthetic operons encoding reaction center (RC) and light harvesting 1 (LH1) pigment-protein complexes of
T. tepidum
were expressed in the mesophile
Rhodobacter sphaeroides
. The
T. tepidum
RC (TRC) was assembled and was found to be functional with the addition of menadione to populate the Q
A
pocket. The production of
T. tepidum
LH1 (TLH1) was increased by selection of a phototrophy-capable mutant after UV irradiation mutagenesis, which yielded a hybrid RC-TLH1 core complex consisting of the
R. sphaeroides
RC and
T. tepidum
TLH1, confirmed by the absorbance peak of TLH1 at 915 nm. Affinity chromatography partial purification and subsequent sucrose gradient analysis of the hybrid RC-TLH1 core complex indicated that this core complex assembled as a monomer. Furthermore, the RC-TLH1 hybrid core complex was more tolerant of a temperature of 70°C than the
R. sphaeroides
RC-LH1 core complexes in both the dimeric and monomeric forms; after 1 h, the hybrid complex retained 58% of the initial starting value, compared to values of 11% and 53% for the
R. sphaeroides
RC-LH1 dimer and monomer forms, respectively.

IMPORTANCE
This work is important because it is a new approach to bioengineering of photosynthesis proteins for potential use in biophotovoltaic solar energy capture. The work establishes a proof of principle for future biohybrid solar cell applications.
The K186E Amino Acid Substitution in the Canine Influenza Virus H3N8 NS1 Protein Restores Its Ability To Inhibit Host Gene Expression
Authors: Nogales Aitor , Chauché Caroline , DeDiego Marta L. , Topham David J. , Parrish Colin R. , Murcia Pablo R. , Martínez-Sobrido Luis
Published: August 2017

Canine influenza viruses (CIVs) are the causative agents of canine influenza, a contagious respiratory disease in dogs, and include the equine-origin H3N8 and the avian-origin H3N2 viruses. Influenza A virus (IAV) nonstructural protein 1 (NS1) is a virulence factor essential for counteracting the innate immune response. Here, we evaluated the ability of H3N8 CIV NS1 to inhibit host innate immune responses. We found that H3N8 CIV NS1 was able to efficiently counteract interferon (IFN) responses but was unable to block general gene expression in human or canine cells. Such ability was restored by a single amino acid substitution in position 186 (K186E) that resulted in NS1 binding to the 30-kDa subunit of the cleavage and polyadenylation specificity factor (CPSF30), a cellular protein involved in pre-mRNA processing. We also examined the frequency distribution of K186 and E186 among H3N8 CIVs and equine influenza viruses (EIVs), the ancestors of H3N8 CIV, and experimentally determined the impact of amino acid 186 in the ability of different CIV and EIV NS1s to inhibit general gene expression. In all cases, the presence of E186 was responsible for the control of host gene expression. In contrast, the NS1 protein of H3N2 CIV harbors E186 and blocks general gene expression in canine cells. Altogether, our results confirm previous studies on the strain-dependent ability of NS1 to block general gene expression. Moreover, the observed polymorphism on amino acid 186 between H3N8 and H3N2 CIVs might be the result of adaptive changes acquired during long-term circulation of avian-origin IAVs in mammals.

IMPORTANCE
Canine influenza is a respiratory disease of dogs caused by two CIV subtypes, the H3N8 and H3N2 viruses, of equine and avian origins, respectively. Influenza NS1 is the main viral factor responsible for the control of host innate immune responses, and changes in NS1 can play an important role in host adaptation. Here we assessed the ability of H3N8 CIV NS1 to inhibit host innate immune responses and gene expression. The H3N8 CIV NS1 did not block host gene expression, but this activity was restored by a single amino acid substitution (K186E), which was responsible for NS1 binding to the host factor CPSF30. In contrast, the H3N2 CIV NS1, which contains E186, blocks general gene expression. Our results suggest that the ability to block host gene expression is not required for influenza virus replication in mammals but might be important in the long-term adaptation of avian-origin influenza viruses to mammals.
PrP P102L and Nearby Lysine Mutations Promote Spontaneous
In Vitro
Formation of Transmissible Prions
Authors: Kraus Allison , Raymond Gregory J. , Race Brent , Campbell Katrina J. , Hughson Andrew G. , Anson Kelsie J. , Raymond Lynne D. , Caughey Byron
Published: August 2017

Accumulation of fibrillar protein aggregates is a hallmark of many diseases. While numerous proteins form fibrils by prion-like seeded polymerization
in vitro
, only some are transmissible and pathogenic
in vivo
. To probe the structural features that confer transmissibility to prion protein (PrP) fibrils, we have analyzed synthetic PrP amyloids with or without the human prion disease-associated P102L mutation. The formation of infectious prions from PrP molecules
in vitro
has required cofactors and/or unphysiological denaturing conditions. Here, we demonstrate that, under physiologically compatible conditions without cofactors, the P102L mutation in recombinant hamster PrP promoted prion formation when seeded by minute amounts of scrapie prions
in vitro
. Surprisingly, combination of the P102L mutation with charge-neutralizing substitutions of four nearby lysines promoted spontaneous prion formation. When inoculated into hamsters, both of these types of synthetic prions initiated substantial accumulation of prion seeding activity and protease-resistant PrP without transmissible spongiform encephalopathy (TSE) clinical signs or notable glial activation. Our evidence suggests that PrP's centrally located proline and lysine residues act as conformational switches in the
in vitro
formation of transmissible PrP amyloids.

IMPORTANCE
Many diseases involve the damaging accumulation of specific misfolded proteins in thread-like aggregates. These threads (fibrils) are capable of growing on the ends by seeding the refolding and incorporation of the normal form of the given protein. In many cases such aggregates can be infectious and propagate like prions when transmitted from one individual host to another. Some transmitted aggregates can cause fatal disease, as with human iatrogenic prion diseases, while other aggregates appear to be relatively innocuous. The factors that distinguish infectious and pathogenic protein aggregates from more innocuous ones are poorly understood. Here we have compared the combined effects of prion seeding and mutations of prion protein (PrP) on the structure and transmission properties of synthetic PrP aggregates. Our results highlight the influence of specific sequence features in the normally unstructured region of PrP that influence the infectious and neuropathogenic properties of PrP-derived aggregates.
Overweight and obese children do not consult their general practitioner more often than normal weight children for musculoskeletal complaints during a 2-year follow-up
Authors: van Leeuwen Janneke , van Middelkoop Marienke , Paulis Winifred D , Bueving Herman J , Bindels Patrick J E , Koes Bart W
Published: August 2017

Background

Childhood obesity is associated with self-reported musculoskeletal complaints, injuries and fractures. In the current study, we investigated the association between weight status of children and the frequency and type of musculoskeletal consultations at the general practitioner (GP) during a 2-year follow-up.

Methods

Data from a prospective longitudinal cohort study including children aged 2–18 years presenting in general practices in the Netherlands were used. Height and weight were measured at baseline, at 6-month, 1-year and 2-year follow-ups. Electronic medical files were used to collect information on the frequency and type of consultations at the GP during the 2-year follow-up period. Associations between weight status and frequency and type of GP consultations were calculated.

Results

Of the 617 included children, 111 (18%) were overweight or obese and 506 (82%) were non-overweight. Overweight children were significantly older (mean age in years (SD): 9.8 (3.6)vs7.8 (4.0), p=0.004). Overweight children consulted the GP in general significantly more frequent during the 2-year follow-up than non-overweight children (mean (SD): 7.3 (5.7)vs6.7 (5.4), OR 1.09, 95% CI 1.01 to 1.18). No significant difference was seen in the number of overweight and non-overweight children consulting their GP for musculoskeletal complaints (OR 1.20 (0.86 to 1.68)). Additionally, no significant difference between overweight and non-overweight children was seen for the number of consultations for further specified musculoskeletal disorders.

Conclusion

No association was seen between childhood weight status and the frequency and type of musculoskeletal consultations at the GP during a 2-year follow-up.
Impact of child death on paediatric trainees
Authors: Hollingsworth Clare E , Wesley Carla , Huckridge Jaymie , Finn Gabrielle M , Griksaitis Michael J
Published: August 2017

Objective

To assess the prevalence of symptoms of acute stress reactions (ASR) and post-traumatic stress disorder (PTSD) in paediatric trainees following their involvement in child death.

Design

A survey designed to identify trainees’ previous experiences of child death combined with questions to identify features of PTSD. Quantitative interpretation was used alongside a χ2 test. A p value of <0.05 was considered significant.

Setting

604 surveys were distributed across 13 UK health education deaneries.

Participants

303/604 (50%) of trainees completed the surveys.

Results

251/280 (90%) of trainees had been involved with the death of a child, although 190/284 (67%) had no training in child death. 118/248 (48%) of trainees were given a formal debrief session following their most recent experience. 203/251 (81%) of trainees reported one or more symptoms or behaviours that could contribute to a diagnosis of ASR/PTSD. 23/251 (9%) of trainees met the complete criteria for ASR and 13/251 (5%) for PTSD. Attending a formal debrief and reporting feelings of guilt were associated with an increase in diagnostic criteria for ASR/PTSD (p=0.036 and p<0.001, respectively).

Conclusions

Paediatric trainees are at risk of developing ASR and PTSD following the death of a child. The feeling of guilt should be identified and acknowledged to allow prompt signposting to further support, including psychological assessment or intervention if required. Clear recommendations need to be made about the safety of debriefing sessions as, in keeping with existing evidence, our data suggest that debrief after the death of a child may be associated with the development of symptoms suggestive of ASR/PTSD.
Successful treatment of direct carotid–cavernous fistula in a patient with Ehlers–Danlos syndrome type IV without arterial puncture: the transvenous triple-overlay embolization (TAILOREd) technique
Authors: Huynh Thien J , Morton Ryan P , Levitt Michael R. , Ghodke Basavaraj V. , Wink Onno , Hallam Danial K.
Published: August 2017

We report successful transvenous treatment of direct carotid–cavernous fistula in a patient with Ehlers–Danlos syndrome type IV using a novel triple-overlay embolization (TAILOREd) technique without the need for arterial puncture, which is known to be highly risky in this patient group. The TAILOREd technique allowed for successful treatment using preoperative MR angiography as a three-dimensional overlay roadmap combined with cone beam CT and live fluoroscopy, precluding the need for an arterial puncture.
Idiopathic spontaneous lesser sac haematoma: a perplexing case of abdominal apoplexy
Authors: Da Cunha Nikita , Narayanan Aravindan , Marimuthu Kalimuthu , Piramanayagam Bala
Published: August 2017

A 37-year-old woman presented with a 3-hour history of back pain, nausea and vomiting and an episode of syncope. A fluid collection in the lesser sac was detected on ultrasound and CT scan. Emergency laparoscopy and subsequent laparotomy were performed and a large blood clot was evacuated from the lesser sac. No identifiable source or predisposition to bleeding was found. She made a full recovery postoperatively. There are few reported cases of spontaneous intraperitoneal haemorrhage. In a third of cases, there is no identifiable source of bleeding. Unfortunately, patients present late with non-specific symptoms and a prompt diagnosis is difficult to make. The case reiterates the importance of awareness of lesser sac haematoma formation; an unusual clinical entity with a high morbidity and mortality rate. A high index of suspicion, radiological adjuncts and appropriate surgical intervention, especially in unstable patients, is essential for a good outcome.
Renal cell carcinoma presenting as a cutaneous horn and nodules on the gingiva and scalp
Authors: Georgy Josh Thomas , Mathuram Alice Joan , George Anu Anna , Chandramohan Jagan
Published: August 2017

A 63-year-old man presented with a pulsatile cutaneous horn on the nose and multiple angiomatous nodules on the gingiva and scalp, which appeared over 2 months. He had severe hypercalcaemia, lytic lesions in multiple bones and acute kidney injury. Excision biopsy from the gingival nodule showed a clear cell neoplasm. The bone marrow showed atypical cells with similar morphology. Imaging showed a 7 cmx7.5 cm mass at the upper pole of the left kidney with metastases to the bones, liver and lung. Immunohistochemistry was consistent with metastatic renal cell carcinoma. Renal cell carcinoma presenting as a cutaneous horn is extremely rare and to the best of our knowledge only one other case was found in the literature. There was visible regression in the size of the cutaneous horn and nodules following initiation of pazopanib therapy. However, he succumbed to his illness a month later.
Priapism due to essential thrombocythaemia: a rare causation
Authors: Goel Sunny , Sokhal Ashok Kumar , Singh Bhupendra Pal , Aggarwal Ajay
Published: August 2017

Priapism is rarely caused by essential thrombocytosis, a disorder characterised by increased number of megakaryocytes. We report a case of a 21-year-old man who presented with priapism and on investigation was found to have essential thrombocytosis as the cause.
Developing standards for the development of glaucoma virtual clinics using a modified Delphi approach
Authors: Kotecha Aachal , Longstaff Simon , Azuara-Blanco Augusto , Kirwan James F , Morgan James Edwards , Spencer Anne Fiona , Foster Paul J
Published: August 2017

Purpose

To obtain consensus opinion for the development of a standards framework for the development and implementation of virtual clinics for glaucoma monitoring in the UK using a modified Delphi methodology.

Methods

A modified Delphi technique was used that involved sampling members of the UK Glaucoma and Eire Society (UKEGS). The first round scored the strength of agreement to a series of standards statements using a 9-point Likert scale. The revised standards were subjected to a second round of scoring and free-text comment. The final standards were discussed and agreed by an expert panel consisting of seven glaucoma subspecialists from across the UK. A version of the standards was submitted to external stakeholders for a 3-month consultation.

Results

There was a 44% response rate of UKEGS members to rounds 1 and 2, consisting largely of consultant ophthalmologists with a specialist interest in glaucoma. The final version of the standards document was validated by stakeholder consultation and contains four sections pertaining to the patient groups, testing methods, staffing requirements and governance structure of NHS secondary care glaucoma virtual clinic models.

Conclusions

Use of a modified Delphi approach has provided consensus agreement for the standards required for the development of virtual clinics to monitor glaucoma in the UK. It is anticipated that this document will be useful as a guide for those implementing this model of service delivery.