bluuebunny/crossref_metadata_2025 huggingface dataset:
Aeroacoustic Analysis of Low-Speed Axial Fans With Different Rotational Speeds in the Design Point
Authors: Buchwald Patrick , Vogt Damian M. , Grilliat Julien , Laufer Wolfgang , Schmitz Michael B. , Lucius Andreas , Schneider Marc
Published: October 2017

One of the main design decisions in the development of low-speed axial fans is the right choice of the blade loading versus rotational speed, since a target pressure rise could either be achieved with a slow spinning fan and high blade loading or a fast spinning fan with less flow turning in the blade passages. Both the blade loading and the fan speed have an influence on the fan performance and the fan acoustics, and there is a need to find the optimum choice in order to maximize efficiency while minimizing noise emissions. This paper addresses this problem by investigating five different fans with the same pressure rise but different rotational speeds in the design point (DP). In the first part of the numerical study, the fan design is described and steady-state Reynolds-averaged Navier–Stokes (RANS) simulations are conducted in order to identify the performance of the fans in the DP and in off-design conditions. The investigations show the existence of an optimum in rotational speed regarding fan efficiency and identify a flow separation on the hub causing a deflection of the outflow in radial direction as the main loss source for slow spinning fans with high blade loadings. Subsequently, large eddy simulations (LES) along with the acoustic analogy of Ffowcs Williams and Hawkings (FW–H) are performed in the DP to identify the main noise sources and to determine the far-field acoustics. The identification of the noise sources within the fans in the near-field is performed with the help of the power spectral density (PSD) of the pressure. In the far-field, the sound power level (SWL) is computed using different parts of the fan surface as FW–H sources. Both methods show the same trends regarding noise emissions and allow for a localization of the noise sources. The flow separation on the hub is one of the main noise sources along with the tip vortex with an increase in its strength toward lower rotational speeds and higher loading. Furthermore, a horseshoe vortex detaching from the rotor leading edge and impinging on the pressure side as well as the turbulent boundary layer on the suction side represent significant noise sources. In the present investigation, the maximum in efficiency coincides with the minimum in noise emissions.
Measuring and Understanding Contact Area at the Nanoscale: A Review
Authors: Jacobs Tevis D. B. , Martini Ashlie
Published: October 2017

The size of the mechanical contact between nanoscale bodies that are pressed together under load has implications for adhesion, friction, and electrical and thermal transport at small scales. Yet, because the contact is buried between the two bodies, it is challenging to accurately measure the true contact area and to understand its dependence on load and material properties. Recent advancements in both experimental techniques and simulation methodologies have provided unprecedented insights into nanoscale contacts. This review provides a detailed look at the current understanding of nanocontacts. Experimental methods for determining contact area are discussed, including direct measurements using in situ electron microscopy, as well as indirect methods based on measurements of contact resistance, contact stiffness, lateral forces, and topography. Simulation techniques are also discussed, including the types of nanocontact modeling that have been performed and the various methods for extracting the magnitude of the contact area from a simulation. To describe and predict contact area, three different theories of nanoscale contact are reviewed: single-contact continuum mechanics, multiple-contact continuum mechanics, and atomistic accounting. Representative results from nanoscale experimental and simulation investigations are presented in the context of these theories. Finally, the critical challenges are described, as well as the opportunities, on the path to establishing a fundamental and actionable understanding of what it means to be “in contact” at the nanoscale.
Microscopic Interactions in Surface Generation Processes Using Abrasive Tools
Authors: (Subbu) Subramanian K. , Ramesh Babu N. , Jain Anant , Vairamuthu R.
Published: October 2017

Abrasive finishing is one among several surface generation processes, of which grinding process is a subset. In a typical grinding process, six different interactions can be identified at the grinding zone, resulting in surface generation. Among these six interactions, one is governed by the principles of machining, while the others are governed by the principles of tribology. A systematic analysis of these interactions helps to understand the role of both tribological mechanisms and machining interactions in a typical grinding process. Analysis and study of such microscopic interactions and their time-dependent variations also provide an ability to develop a common scientific framework that can be applied for a wide variety of grinding processes and applications. Such framework and associated system thinking enables engineers to be capable of addressing the needs to support a wide variety of industries and end user needs at a time of hyper specialization and narrow boundaries that constrain the professionals.
Numerical Simulation of Wave Interaction With a Hinged Multi-Module Floating Structure
Authors: Li Yabin , He Ming , Ren Bing , Wang Guoyu
Published: October 2017

This paper studies the interaction of water waves with a hinged multi-module floating structure, using a numerical model based on smoothed particle hydrodynamics (SPH) method. The simulation is performed in a 2D nonlinear numerical wave tank (NWT) equipped with an active absorbing wave maker and a sponge layer. The motion of the multi-module floating structure is calculated follow the Newton’s second law. The hydrodynamic forces on the floating modules are evaluated using the volume integration of the stress tensors obtained from the momentum equation in its compact support. A linear spring model is employed to calculate the mooring force. The collision forces acting on neighboring modules are acquired based on the strain-stress relationship of rubber bumper between the neighboring modules, and a continuity condition of linear acceleration at the hinge joint is built and implicit equations are solved utilizing Gauss-Jordan elimination method. To validate the numerical model, a laboratory experiment is conducted in a wave flume. Comparisons of the computed and measured data show reasonable agreements in terms of the wave surface profiles, mooring forces, connector forces and motion attitudes of the hinged multi-module floating structure in spite of slight discrepancies of the peak values of connector forces and the valley values of mooring forces.
Steep Wave Effects on Wave Induced Vertical Bending Moment Using a 3D Numerical Wave Tank
Authors: Ganesan Thirunaavukarasu Shivaji , Sen Debabrata , Parihar Yogendra
Published: October 2017

This paper presents a detail comparative study on wave induced vertical bending moment (VBM) between linear and approximate nonlinear calculations using a 3D numerical wave tank (NWT) method. The developed numerical approach is in time domain where the ambient incident waves can be defined by any suitable wave theory. Certain justifying approximations employed in the solution of the interaction hydrodynamics (diffraction and radiation) enabling the NWT to generate stable long duration time histories of all parameters of interest. This is an extension of our earlier works towards the development of a practical NWT based solution for wave-structure interactions [1]. After a brief outline of the implemented numerical details, a comprehensive validation and verification of vertical shear force (VSF) and bending moment RAOs computed using the linearized version of the NWT against the usual linear results of strip theory and 3D panel codes are presented. Next we undertake the comparative study between the fully linear and approximate nonlinear versions of the present code for different incident wave steepness. In the approximate nonlinear formulation, the ambient incident wave is defined by the full nonlinear numerical wave model based on Fourier approximation method which can generate very steep steady periodic nonlinear waves up to the near wave breaking limit. The nonlinearities associated with the incident Froude Krylov and hydrostatic restoring forces/moments are exact up to the instantaneous wetted surface at the displaced location, but the hydrodynamic diffraction and radiation effects are linearized around the mean wetted surface. The standard S175 container hull is considered for the comparative studies because of its geometric nonlinearities. Numerical simulations are performed for four different wave lengths with increasing wave steepness. It is observed that the computed wave induced VBM amidships from the approximate nonlinear results can be almost 30% higher compared to the results from a purely linear solution, which can be a critical issue from the safety point. Significant higher harmonics are also observed in the approximate nonlinear results which at some times may be responsible for exciting the undesirable whipping/springing responses.
Free-Surface Flow Simulations With Interactively Moving Bodies
Authors: Veldman Arthur E. P. , Seubers Henk , van der Plas Peter , Helder Joop
Published: October 2017

The simulation of free-surface flow around moored or floating objects faces a series of challenges, concerning the flow modelling and the numerical solution method. One of the challenges is the simulation of objects whose dynamics is determined by a two-way interaction with the incoming waves. The ‘traditional’ way of numerically coupling the flow dynamics with the dynamics of a floating object becomes unstable (or requires severe underrelaxation) when the added mass is larger than the mass of the object. To deal with this two-way interaction, a more simultaneous type of numerical coupling is being developed. The paper will focus on this issue. To demonstrate the quasi-simultaneous method, a number of simulation results for engineering applications from the offshore industry will be presented, such as the motion of a moored TLP platform in extreme waves, and a free-fall life boat dropping into wavy water.
Dynamic Simulation and Control of an Active Roll Reduction System Using Free-Flooding Tanks With Vacuum Pumps
Authors: Xu Jiafeng , Ren Zhengru , Li Yue , Skjetne Roger , Halse Karl Henning
Published: October 2017

Ship roll motion is often the critical factor for offshore operations due to its lack of damping mechanism. This paper demonstrates a dynamic simulation scheme of an active roll reduction system using free-flooding tanks controlled by vacuum pumps. The two tanks in the system are installed on each sides of a catamaran. The tank hatches are opened to the sea and the air chambers of both tanks are connected by an air duct. Vacuum pumps and air valve with active stabilization controller provides desired filling level for the tank. The ship is a dynamic model with single degree of freedom in roll. The hydrodynamic behavior of the ship is calculated using potential theory by SHIPX. The air chamber above is modelled as isothermal process of ideal gas. The behavior of the liquid flow in the tank is simulated by incompressible RANS solver using Volume of Fluid (VOF) model, then summarized as response function for the ship model. A simplified control plant model for the vacuum pumps is proposed where insignificant higher order behaviors are regarded as biases and noises. The stability is proved by Lapunov direct method. The performance of the entire system is evaluated in terms of roll reduction capability and power cost. The system is more suitable for roll reduction in low-speed or resting conditions.
Experimental Determination of the Effect of Bow Shape on the Wave Drift Load
Authors: Boorsma Anne , Aalbers Kees , van ‘t Veer Riaan , Huijsmans René
Published: October 2017

In the last forty years wave drift loads have been calculated with methods based on the near-field theory (hull pressure integration, Pinkster [4]) and/or the far field method (linear momentum theory). Both methods use linear theory and through its formulation ignore the ship’s hull form above the mean water line. It is evident that in survival sea-states the small motion assumptions are violated and the hull form above the mean water line can affect the motion characteristics of the ship and the drift loads. In order to get more insight in this effect, SBM has conducted a systematic model test campaign at the TU Delft using an Aframax size tanker.

The campaign included tests with two different bow shapes: the original bow with flare, and a wall-sided bow. Horizontal loads on the complete vessel and a section of the bow only were measured accompanied by measurements of the ship motions and relative wave heights. Measurements were performed for various wave heights and periods. Numerous repeat tests were conducted to establish the confidence level of the measurement data.

Measurements have shown motions and relative wave heights are dependent on wave height. It was suggested that viscous damping may play a part in this.

The relative wave height in high waves is affected by bow shape; namely the finite draft, the flare and the bulb. How this departure from linear theory affects the forces on the vessel should be investigated further.
Aspects in Model Testing of a Monopile in Steep Waves
Authors: Kristiansen Trygve , Bachynski Erin E. , Bickert Florent , Hniche Abdessamad , Kocher Vincent , Liandrat Antoine
Published: October 2017

Different aspects regarding model testing of a vertical, bottom-fixed monopile in steep waves are discussed. The different topics are related in the sense that they can improve the quality of experimental data. The discussion includes wave generation, wave absorption, tank wall effects, Reynolds number effects, the effect of sectioning of models and tank bottom topography. An automatic test procedure was developed with a significant gain in both quality and quantity of experimental data. The purpose of this paper is to increase the awareness of the many possible flaws that can be made in a closed wave tank, in order to contribute to increased quality of data. None of the topics are treated in much detail. However, they are exemplified by new experimental data as well as numerical simulations. The importance of the combined use of experiments, theory and numerical calculations is emphasized.
Optimal Process Design of Onboard Bog Partial Re-Liquefaction System for 170k LNG Carrier
Authors: Hwang Chulmin , Lim Youngsub
Published: October 2017

LNG carriers contain LNG at the cryogenic temperature of below −162°C and slightly above the atmospheric pressure. Although the LNG cargo tanks are well insulated, still the heat leak from the atmosphere and BOG (Boil-Off Gas) generation is inevitable. The re-liquefaction system was devised to prevent this loss of BOG by liquefaction of BOG to LNG. In recent years, with the appearance of the high pressure NG consuming engine (MEGI), the preference of partial re-liquefaction system in LNG carriers is increasing. However, there are insufficient studies about the optimal design of partial re-liquefaction process using the compression and expansion of BOG as a refrigerant for LNG carriers. This study studied the optimal process design of onboard BOG partial re-liquefaction system for LNG carriers based on cost estimation.
Development of Probabilistic Fracture Mechanics Method for Fatigue Life Prediction Based on EIFS Concept
Authors: Zou Guang , Banisoleiman Kian , González Arturo
Published: October 2017

A problem with fracture mechanics (FM) based fatigue analysis is that reliable information on initial crack/flaw size is often hard to obtain. Also, FM method can’t be applied directly to welded joints with relatively small initial flaws and long crack initiation life. This paper proposes a novel probabilistic FM method based on the equivalent initial flaw size (EIFS) concept. The initial crack size is substituted with EIFS to take both the crack initiation and propagation life into account. Three methods are tested to obtain mean value of EIFS: calibrating to S-N curves, Kitagawa-Takahashi (KT) diagram and fitting to test data. The obtained EIFSs are evaluated by comparing the predicted fatigue lives and crack evolutions with S-N curves and test crack evolution data. The suggested procedure is to derive the mean value of EIFS from S-N curves and the coefficient of variation from KT diagram.
Thruster-Wave Interaction During DP Stationkeeping: Model Tests in Open Water and Under a Ship Hull
Authors: Cozijn Hans , Choi Jin Woo , You Young-Jun
Published: October 2017

Wave orbital motions may cause variations in the inflow conditions of thrusters, resulting in variations in thrust and torque. Physical scale model tests were carried out to investigate these thruster-wave interaction effects, with an azimuthing thruster running at constant RPMs. The observed effects include a change in mean thrust and torque values, as well as wave frequency variations. The test conditions were systematically varied to investigate the effects of the incoming waves, the presence of the hull and the vessel motions.

First, measurements were carried out on an azimuthing thruster in open water conditions. The thrust and torque in regular waves were compared with bollard pull conditions.

Second, measurements were carried out on the azimuthing thruster under the hull of a vessel, which was rigidly connected to the basin carriage. Again, regular wave tests were performed, showing the effect of the presence of the hull.

Third, measurements were carried out on the same azimuthing thruster under the hull of the vessel in a soft-mooring system. This kept the vessel in position and at the required heading, while allowing unrestricted wave frequency motions. Again, regular wave tests were performed, now showing the combined effects of the passing waves, the presence of the vessel hull and the vessel motions.
Study of Offshore Jacket Platform Attached With Tuned Liquid Column Gas Damper
Authors: Sathish P. , Sajith A. S.
Published: October 2017

With increase in need of energy, scarcity of natural resources also increases. Need for energy has led the people to move into the ocean since they contain abundant natural resources. Offshore platforms play a major role in exploring and exploiting these resources. Jacket platform being a fixed offshore jacket platform is used in water depths 300 to 400 m. The study of behavior of these offshore structures is vital part in the design since they are subjected to dynamic loading of waves, wind, earthquake, ice etc. These structures in hostile environment are subjected to heavy loads. There is need for controlling the response of these structures. This can be achieved by providing external dampers.

There are various dampers available to control the response of structures. Tuned liquid dampers (TLD)s and Tuned Liquid Column Damper (TLCD)s use liquid inside to tune its frequency to natural frequency of structure. Tuned Liquid Column Gas Damper (TLCGD) is latest version of dampers. It has a unique flexibility of tuning frequency compared to all other dampers.

In the present study, jacket platform is modeled as Multi degree of freedom (MDOF) system. At later stage, for simplistic analysis, MDOF system is reduced to SDOF system using static condensation. Performance of TLCGD for both the systems is compared. Airy’s wave theory is used for wave force excitation. Equations of motions for Jacket platform models attached with TLCGD are developed and solved using Newmarks β method in MATLAB. TLCGD is found to be very flexible in tuning the frequency and maximum reductions in response, 21.3% and 23.14% are observed at 0.3 MPa for MDOF and SDOF systems respectively. Work done shows that the results for MDOF and SDOF are comparable and hence, jacket as SDOF can be used for analysis for reducing the complexities.
Modified Probability Density Evolution Method for the Solution of Multi-Degree-of-Freedom Nonlinear Stochastic Dynamical Systems
Authors: Zhou Xiaoyu , Li Hongxia , Huang Yi
Published: October 2017

A probability density evolution based exponential polynomial regression (PDEM-EPR) method to calculate the probability density function (PDF) of the high dimensional nonlinear stochastic dynamical systems is presented in this paper. Several typical examples, such as linear oscillator and Duffing oscillator are solved by PDEM-EPR method, and the results fit well with the analytical solutions. An engineering practice problem of ship nonlinear random roll in the beam waves is involved in this paper. The results obtained by PDEM-EPR is compared with those obtained by path integral method. The later results were given by Chai Wei [3]. It shows that PDEM-EPR method has the advantages as following: 1) The multi-degree-of-freedom (MDOF) nonlinear stochastic dynamical problems can be solved by PDEM-EPR method; 2) High efficiency can be obtained by PDEM-EPR method.
Nonlinear Dynamic Response of a Compliant Tower Under the Effect of Steady and Unsteady Sea States
Authors: Chatziioannou Konstantinos , Katsardi Vanessa , Koukouselis Apostolos , Mistakidis Euripidis
Published: October 2017

The purpose of this work is to highlight the importance of considering the actual nonlinear dynamic response for the analysis and design of fixed deep water platforms. The paper highlights the necessity of applying dynamic analysis through the comparison with the results obtained by the authors by applying static nonlinear analysis on the structure under examination. The example treated in the context of the present paper is a compliant tower, set-up in deep water. Nonlinearities are considered both for the calculation of the wave loadings and the structural analysis. The wave loading is based on linear random wave theory and comparisons are provided with the steady wave theories, Airy and Stokes 5th. The former solution is based on the most probable shape of a large linear wave on a given sea-state; the auto-correlation function of the underlying spectrum. On the other hand, in the field of structural analysis, two cases are considered for comparison, static analysis and time history dynamic analysis. For both types of analysis, two sub-cases are considered, a case in which geometric nonlinearity and nonlinearities related to the modelling of the soil are considered and a case in which the corresponding linear theories are employed (reference cases). The structural calculations were performed using the well-known structural analysis software SAP2000, which was enhanced by a special programming interface that was developed to calculate the wave loading and to directly apply the generated loads on the structural members. The results show that the consideration of the particle velocities associated with the linear random wave theory in the wave loading lead to significant differences with respect to the steady wave theories in terms of the displacements and stresses of the structure. Moreover, irrespectively of the adopted wave theory, the nonlinear analyses lead to significant discrepancies with respect to the linear ones. This is mainly associated with the nonlinear properties of the soil. Another source of discrepancies between the results of static and dynamic analyses stems from the change of the effective natural frequency of the structure when nonlinearities are considered.
The influence of mode coupling on waveguide invariant
Authors: Song Wenhua , Wang Ning , Gao Dazhi , Wang Haozhong , Hu Tao , Guo Shengming
Published: October 2017

The waveguide invariant β is typically discussed in terms of either a range-independent environment or a range-dependent environment under the adiabatic approximation, with few studies considering the effects of mode coupling. In this work, how internal solitary waves (ISWs) affect the waveguide invariant is investigated, and it is shown that mode-coupling effects introduce many additional components in the acoustic interference intensity. It is found that the striation slope and value of β for these additional components are determined not only by the acoustic modal dispersion, but are also dependent on the position where the mode coupling occurs. This can lead to a very complicated acoustic interference pattern and result in multiple peaks in the distribution of β. The sensitivity of β to the parameters of ISWs, such as amplitude, horizontal scale, and position, is analyzed. It is found that although all parameters can affect the energy of the peaks, only the position of the internal wave has an obvious impact on the peak values. This indicates that the peak values of β can be utilized for monitoring the position of the internal wave.
Infrasound propagation in tropospheric ducts and acoustic shadow zones
Authors: de Groot-Hedlin Catherine D.
Published: October 2017

Numerical computations of the Navier-Stokes equations governing acoustic propagation are performed to investigate infrasound propagation in the troposphere and into acoustic shadow zones. An existing nonlinear finite-difference, time-domain (FDTD) solver that constrains input sound speed models to be axisymmetric is expanded to allow for advection and rigid, stair-step topography. The FDTD solver permits realistic computations along a given azimuth. It is applied to several environmental models to examine the effects of nonlinearity, topography, advection, and two-dimensional (2D) variations in wind and sound speeds on the penetration of infrasound into shadow zones. Synthesized waveforms are compared to a recording of a rocket motor fuel elimination event at the Utah Test and Training Range. Results show good agreement in the amplitude, duration, and spectra of synthesized and recorded waveforms for propagation through 2D atmospheric models whether or not topography, advection, or nonlinearity is explicitly included. However, infrasound propagation through a one-dimensional, range-averaged, atmospheric model yields waveforms with lower amplitudes and frequencies, suggesting that small-scale atmospheric variability causes significant scatter within the troposphere, leading to enhanced infrasound penetration into shadow zones. Thus, unresolved fine-scale atmospheric dynamics are not required to explain infrasound propagation into shadow zones.
Conflict Management and Cultural Reparation: Consulting “Below Zero” With a College Basketball Team
Authors: Vealey Robin S.
Published: October 2017

Although sport psychology consultants typically engage in conflict resolution as part of team interventions, cases of extreme relationship conflict in teams resulting in distrust, tension, and hostility require special consideration for the consultant who is starting “below zero” when beginning a consultant relationship with a program. Such a case warrants not just culture building, but cultural reparation and the development of resolution efficacy among team members. The purpose of this case study is to describe an intervention program with a college basketball team that was experiencing multiple relationships conflicts and an extremely dysfunctional team culture. The intervention focused on (a) enabling players to take ownership of and be accountable for a “smart system” team culture, (b) initiating a process to build resolution efficacy that focused on accepting and managing task conflict (while reducing relationship conflict) and emphasized interpersonal risk-taking and vulnerability to build trust, and (c) enhancing coach-athlete relationships. Reflections on the case include the importance of vigilance about ethical boundary and confidentiality issues in “below zero” situations and the role of coaches who prefer transactional leadership styles in building team culture and resolution efficacy for conflict.
Structural plasticity of the social brain: Differential change after socio-affective and cognitive mental training
Authors: Valk Sofie L. , Bernhardt Boris C. , Trautwein Fynn-Mathis , Böckler Anne , Kanske Philipp , Guizard Nicolas , Collins D. Louis , Singer Tania
Published: October 2017

Training to understand the feelings and thoughts of others induces structural changes in two divergent social brain networks.
Risk preference shares the psychometric structure of major psychological traits
Authors: Frey Renato , Pedroni Andreas , Mata Rui , Rieskamp Jörg , Hertwig Ralph
Published: October 2017

On the basis of 39 risk-taking measures, this study finds evidence for a general and stable factor of risk preference.
Effective drug combination for
Caenorhabditis elegans
nematodes discovered by output-driven feedback system control technique
Authors: Ding Xianting , Njus Zach , Kong Taejoon , Su Wenqiong , Ho Chih-Ming , Pandey Santosh
Published: October 2017

An engineering approach yields a highly potent combination of four antinematode drugs at lower dosages than individual drugs.
The promise of spatial transcriptomics for neuroscience in the era of molecular cell typing
Authors: Lein Ed , Borm Lars E. , Linnarsson Sten
Published: October 2017

The stereotyped spatial architecture of the brain is both beautiful and fundamentally related to its function, extending from gross morphology to individual neuron types, where soma position, dendritic architecture, and axonal projections determine their roles in functional circuitry. Our understanding of the cell types that make up the brain is rapidly accelerating, driven in particular by recent advances in single-cell transcriptomics. However, understanding brain function, development, and disease will require linking molecular cell types to morphological, physiological, and behavioral correlates. Emerging spatially resolved transcriptomic methods promise to fill this gap by localizing molecularly defined cell types in tissues, with simultaneous detection of morphology, activity, or connectivity. Here, we review the requirements for spatial transcriptomic methods toward these goals, consider the challenges ahead, and describe promising applications.
RAB15 empowers dendritic cells to drive antiviral immunity
Authors: Wong Patrick , Iwasaki Akiko
Published: October 2017

CD1c
+
and CD141
+
dendritic cells cooperate to sustain antiviral T cell responses. See the related research article by Silvin
et al.
In silico modeling identifies CD45 as a regulator of IL-2 synergy in the NKG2D-mediated activation of immature human NK cells
Authors: Mukherjee Sayak , Jensen Helle , Stewart William , Stewart David , Ray William C. , Chen Shih-Yu , Nolan Garry P. , Lanier Lewis L. , Das Jayajit
Published: October 2017

The basis for how the cytokine IL-2 boosts the activation of natural killer cells in response to NKG2D stimulation is uncovered.
Voltage-dependent Ca
2+
entry into smooth muscle during contraction promotes endothelium-mediated feedback vasodilation in arterioles
Authors: Garland Christopher J. , Bagher Pooneh , Powell Chloe , Ye Xi , Lemmey Hamish A. L. , Borysova Lyudmyla , Dora Kim A.
Published: October 2017

Ca
2+
entry into vascular smooth muscle activates Ca
2+
signaling in the endothelium to protect tissue blood flow.
Processing of Potato Spindle Tuber Viroid RNAs in Yeast, a Nonconventional Host
Authors: Friday Dillon , Mukkara Priyadarshini , Owens Robert A. , Baumstark Tilman , Bruist Michael F.
Published: October 2017

Potato spindle tuber viroid (PSTVd) is a circular, single-stranded, noncoding RNA plant pathogen that is a useful model for studying the processing of noncoding RNA in eukaryotes. Infective PSTVd circles are replicated via an asymmetric rolling circle mechanism to form linear multimeric RNAs. An endonuclease cleaves these into monomers, and a ligase seals these into mature circles. All eukaryotes may have such enzymes for processing noncoding RNA. As a test, we investigated the processing of three PSTVd RNA constructs in the yeast
Saccharomyces cerevisiae
. Of these, only one form, a construct that adopts a previously described tetraloop-containing conformation (TL), produces circles. TL has 16 nucleotides of the 3′ end duplicated at the 5′ end and a 3′ end produced by self-cleavage of a delta ribozyme. The other two constructs, an exact monomer flanked by ribozymes and a trihelix-forming RNA with requisite 5′ and 3′ duplications, do not produce circles. The TL circles contain nonnative nucleotides resulting from the 3′ end created by the ribozyme and the 5′ end created from an endolytic cleavage by yeast at a site distinct from where potato enzymes cut these RNAs. RNAs from all three transcripts are cleaved in places not on path for circle formation, likely representing RNA decay. We propose that these constructs fold into distinct RNA structures that interact differently with host cell RNA metabolism enzymes, resulting in various susceptibilities to degradation versus processing. We conclude that PSTVd RNA is opportunistic and may use different processing pathways in different hosts.

IMPORTANCE
In higher eukaryotes, the majority of transcribed RNAs do not encode proteins. These noncoding RNAs are responsible for mRNA regulation, control of the expression of regulatory microRNAs, sensing of changes in the environment by use of riboswitches (RNAs that change shape in response to environmental signals), catalysis, and more roles that are still being uncovered. Some of these functions may be remnants from the RNA world and, as such, would be part of the evolutionary past of all forms of modern life. Viroids are noncoding RNAs that can cause disease in plants. Since they encode no proteins, they depend on their own RNA and on host proteins for replication and pathogenicity. It is likely that viroids hijack critical host RNA pathways for processing the host's own noncoding RNA. These pathways are still unknown. Elucidating these pathways should reveal new biological functions of noncoding RNA.
In Vitro
Approach To Identify Key Amino Acids in Low Susceptibility of Rabbit Prion Protein to Misfolding
Authors: Eraña Hasier , Fernández-Borges Natalia , Elezgarai Saioa R. , Harrathi Chafik , Charco Jorge M. , Chianini Francesca , Dagleish Mark P. , Ortega Gabriel , Millet Óscar , Castilla Joaquín
Published: October 2017

Prion diseases, or transmissible spongiform encephalopathies (TSEs), are a group of rare progressive neurodegenerative disorders caused by an abnormally folded prion protein (PrP
Sc
). This is capable of transforming the normal cellular prion protein (PrP
C
) into new infectious PrP
Sc
. Interspecies prion transmissibility studies performed by experimental challenge and the outbreak of bovine spongiform encephalopathy that occurred in the late 1980s and 1990s showed that while some species (sheep, mice, and cats) are readily susceptible to TSEs, others are apparently resistant (rabbits, dogs, and horses) to the same agent. To study the mechanisms of low susceptibility to TSEs of certain species, the mouse-rabbit transmission barrier was used as a model. To identify which specific amino acid residues determine high or low susceptibility to PrP
Sc
propagation, protein misfolding cyclic amplification (PMCA), which mimics PrP
C
-to-PrP
Sc
conversion with accelerated kinetics, was used. This allowed amino acid substitutions in rabbit PrP and accurate analysis of misfolding propensities. Wild-type rabbit recombinant PrP could not be misfolded into a protease-resistant self-propagating isoform
in vitro
despite seeding with at least 12 different infectious prions from diverse origins. Therefore, rabbit recombinant PrP mutants were designed to contain every single amino acid substitution that distinguishes rabbit recombinant PrP from mouse recombinant PrP. Key amino acid residue substitutions were identified that make rabbit recombinant PrP susceptible to misfolding, and using these, protease-resistant misfolded recombinant rabbit PrP was generated. Additional studies characterized the mechanisms by which these critical amino acid residue substitutions increased the misfolding susceptibility of rabbit PrP.

IMPORTANCE
Prion disorders are invariably fatal, untreatable diseases typically associated with long incubation periods and characteristic spongiform changes associated with neuronal loss in the brain. Development of any treatment or preventative measure is dependent upon a detailed understanding of the pathogenesis of these diseases, and understanding the mechanism by which certain species appear to be resistant to TSEs is critical. Rabbits are highly resistant to naturally acquired TSEs, and even under experimental conditions, induction of clinical disease is not easy. Using recombinant rabbit PrP as a model, this study describes critical molecular determinants that confer this high resistance to transmissible spongiform encephalopathies.
Beyond polycystic kidney disease
Authors: Santos Susana Franco , Francisco Telma , Cordeiro Ana Isabel , Lopes Maria João Paiva
Published: October 2017

Tuberous sclerosis(TS) is an autosomal dominant disease caused by mutations inTSC1andTSC2genes.TSC2gene is located in chromosome 16p13.3, adjacent toPKD1gene, responsible for the autosomal dominant polycystic kidney disease. In a rare subgroup of patients, the presence of a deletion which simultaneously affects theTSC2andPKD1genes has been confirmed. TSC2/PKD1-Contiguous Gene Syndrome is characterised by the early appearance of autosomal dominant polycystic kidney disease in combination with several phenotypic manifestations of TS. We present a 13-year-old girl with bilateral renal cysts detected at the age of 9 months. At the age of 13, she was referred to the Dermatology Outpatients Clinic due to a facial cutaneous eruption. She presented with facial erythema, fibroadenomas with malar distribution and disseminated hypomelanotic macules, meeting the criteria for TS. TSC2/PKD1 Contiguous Gene Syndrome deletion was suspected, being later confirmed by genetic testing.
Synthesis of polyhydroxyalkanoates (PHAs) from vegetable oils and free fatty acids by wild-type and mutant strains of Pseudomonas chlororaphis
Authors: Sharma Parveen K. , Munir Riffat I. , de Kievit Teresa , Levin David B.
Published: October 2017

Pseudomonas chlororaphis PA23 was isolated from soybean roots as a plant-growth-promoting rhizobacterium. This strain secretes a wide range of compounds, including the antibiotics phenazine-1-carboxylic acid (PCA), pyrrolnitrin, and 2-hydroxyphenazine. We have determined that P. chlororaphis PA23 can synthesize medium-chain-length polyhydroxyalkanoate (PHA) polymers utilizing free fatty acids, such as octanoic acid and nonanoic acid, as well as vegetable oils as sole carbon sources. Genome analysis identified a pha operon containing 7 genes in P. chlororaphis PA23 that were highly conserved. A nonpigmented strain that does not synthesize PCA, P. chlororaphis PA23-63, was also studied for PHA production. Pseudomonas chlororaphis PA23-63 produced 2.42–5.14 g/L cell biomass and accumulated PHAs from 11.7% to 32.5% cdm when cultured with octanoic acid, nonanoic acid, fresh canola oil, waste canola fryer oil, or biodiesel-derived waste free fatty acids under batch culture conditions. The subunit composition of the PHAs produced from fresh canola oil, waste canola fryer oil, or biodiesel-derived free fatty acids did not differ significantly. Addition of octanoic acid and nonanoic acid to canola oil cultures increased PHA production, but addition of glucose did not. PHA production in the phz mutant, P. chlororaphis PA23-63, was greater than that in the parent strain.
The switching behaviors induced by torsion angle in a diblock co-oligomer molecule with tailoring graphene nanoribbon electrodes
Authors: Yang Aiyun , Xia Caijuan , Zhang Boqun , Wang Jun , Su Yaoheng , Tu Zheyan
Published: October 2017

By applying first-principles method based on density functional theory combined with nonequilibrium Green’s function, we investigate the effect of torsion angle on the electronic transport properties in dipyrimidinyl–diphenyl co-oligomer molecular device with tailoring graphene nanoribbon electrodes. The results show that the torsion angle plays an important role on the electronic transport properties of the molecular device. When the torsion angle rotates from 0[Formula: see text] to 90[Formula: see text], the molecular devices exhibit very different current–voltage characteristics which can realize the on and off states of the molecular switch.
Wave bandgap formation and its evolution in two-dimensional phononic crystals composed of rubber matrix with periodic steel quarter-cylinders
Authors: Li Peng , Wang Guan , Luo Dong , Cao Xiaoshan
Published: October 2017

The band structure of a two-dimensional phononic crystal, which is composed of four homogenous steel quarter-cylinders immersed in rubber matrix, is investigated and compared with the traditional steel/rubber crystal by the finite element method (FEM). It is revealed that the frequency can then be tuned by changing the distance between adjacent quarter-cylinders. When the distance is relatively small, the integrality of scatterers makes the inner region inside them almost motionless, so that they can be viewed as a whole at high-frequencies. In the case of relatively larger distance, the interaction between each quarter-cylinder and rubber will introduce some new bandgaps at relatively low-frequencies. Lastly, the point defect states induced by the four quarter-cylinders are revealed. These results will be helpful in fabricating devices, such as vibration insulators and acoustic/elastic filters, whose band frequencies can be manipulated artificially.
All-dielectric metamaterial frequency selective surface
Authors: Wang Jun , Qu Shaobo , Li Liyang , Wang Jiafu , Feng Mingde , Ma Hua , Du Hongliang , Xu Zhuo
Published: October 2017

Frequency selective surface (FSS) has been extensively studied due to its potential applications in radomes, antenna reflectors, high-impedance surfaces and absorbers. Recently, a new principle of designing FSS has been proposed and mainly studied in two levels. In the level of materials, dielectric materials instead of metallic patterns are capable of achieving more functional performance in FSS design. Moreover, FSSs made of dielectric materials can be used in different extreme environments, depending on their electrical, thermal or mechanical properties. In the level of design principle, the theory of metamaterial can be used to design FSS in a convenient and concise way. In this review paper, we provide a brief summary about the recent progress in all-dielectric metamaterial frequency selective surface (ADM-FSS). The basic principle of designing ADM-FSS is summarized. As significant tools, Mie theory and dielectric resonator (DR) theory are given which illustrate clearly how they are used in the FSS design. Then, several design cases including dielectric particle-based ADM-FSS and dielectric network-based ADM-FSS are introduced and reviewed. After a discussion of these two types of ADM-FSSs, we reviewed the existing fabrication techniques that are used in building the experiment samples. Finally, issues and challenges regarding the rapid fabrication techniques and further development aspects are discussed.
Lung Cancer Heterogeneity and New Strategies for Drug Therapy
Authors: Wang, Diane C. , Wang, William , Zhu, Bijun , Wang Xiangdong
Published: October 2017

Lung cancer heterogeneity plays an important role in the development of drug resistance. Comprehensive molecular characterizations of lung cancer can describe hereditary and somatic gene changes, mutation, and heterogeneity. We discuss heterogeneity specificity, characterization, and roles of PIK3CD, TP53, and KRAS, as well as target-driven therapies and strategies applied in clinical trials based on a proposed precise self-validation system. The system is a specifically selected strategy of treatment for patients with cancer gene mutations and heterogeneity based on gene sequencing, following validation of the strategies in the patient's own cancer cells or in patient-derived xenografts using their own cancer cells isolated during surgery or biopsies. These results will be more precise if the drugs used in the strategies are selected through protein structure–guided compound screening or a DNA-encoded chemical library before validation in the patient's own cancer cells. Thus, a deeper understanding of heterogeneity mechanisms and improved validation of the therapeutic strategy will result in more precise treatments for patients.
ATP catabolism by tissue nonspecific alkaline phosphatase contributes to development of ARDS in influenza-infected mice
Authors: Woods Parker S. , Doolittle Lauren M. , Hickman-Davis Judy M. , Davis Ian C.
Published: October 2017

Influenza A viruses are highly contagious respiratory pathogens that are responsible for significant morbidity and mortality worldwide on an annual basis. We have shown previously that influenza infection of mice leads to increased ATP and adenosine accumulation in the airway lumen. Moreover, we demonstrated that A1-adenosine receptor activation contributes significantly to influenza-induced acute respiratory distress syndrome (ARDS). However, we found that development of ARDS in influenza-infected mice does not require catabolism of ATP to adenosine by ecto-5′-nucleotidase (CD73). Hence, we hypothesized that increased adenosine generation in response to infection is mediated by tissue nonspecific alkaline phosphatase (TNAP), which is a low-affinity, high-capacity enzyme that catabolizes nucleotides in a nonspecific manner. In the current study, we found that whole lung and BALF TNAP expression and alkaline phosphatase enzymatic activity increased as early as 2 days postinfection (dpi) of C57BL/6 mice with 10,000 pfu/mouse of influenza A/WSN/33 (H1N1). Treatment at 2 and 4 dpi with a highly specific quinolinyl-benzenesulfonamide TNAP inhibitor (TNAPi) significantly reduced whole lung alkaline phosphatase activity at 6 dpi but did not alter TNAP gene or protein expression. TNAPi treatment attenuated hypoxemia, lung dysfunction, histopathology, and pulmonary edema at 6 dpi without impacting viral replication or BALF adenosine. Treatment also improved epithelial barrier function and attenuated cellular and humoral immune responses to influenza infection. These data indicate that TNAP inhibition can attenuate influenza-induced ARDS by reducing inflammation and fluid accumulation within the lung. They also further emphasize the importance of adenosine generation for development of ARDS in influenza-infected mice.
Immune regulation of systemic hypertension, pulmonary arterial hypertension, and preeclampsia: shared disease mechanisms and translational opportunities
Authors: Jafri Salema , Ormiston Mark L.
Published: October 2017

Systemic hypertension, preeclampsia, and pulmonary arterial hypertension (PAH) are diseases of high blood pressure in the systemic or pulmonary circulation. Beyond the well-defined contribution of more traditional pathophysiological mechanisms, such as changes in the renin–angiotensin–aldosterone system, to the development of these hypertensive disorders, there is substantial clinical evidence supporting an important role for inflammation and immunity in the pathogenesis of each of these three conditions. Over the last decade, work in small animal models, bearing targeted deficiencies in specific cytokines or immune cell subsets, has begun to clarify the immune-mediated mechanisms that drive changes in vascular structure and tone in hypertensive disease. By summarizing the clinical and experimental evidence supporting a contribution of the immune system to systemic hypertension, preeclampsia, and PAH, the current review highlights the cellular and molecular pathways that are common to all three hypertensive disorders. These mechanisms are centered on an imbalance in CD4+helper T cell populations, defined by excessive Th17 responses and impaired Tregactivity, as well as the excessive activation or impairment of additional immune cell types, including macrophages, dendritic cells, CD8+T cells, B cells, and natural killer cells. The identification of common immune mechanisms in systemic hypertension, preeclampsia, and PAH raises the possibility of new therapeutic strategies that target the immune component of hypertension across multiple disorders.