bluuebunny/crossref_metadata_2025 huggingface dataset:
Temporal Effect and Transient Simulation of Thin Liquid Film in Micro Channels
Authors: Jiang Yu-Yan , Tang Da-Wei
Published: July 2018

The evaporation and heat transfer of thin liquid film are crucial factors affecting on the heat transfer performance of boiling bubbles or slugs. For boiling in micro-channels, the flash evaporation of the liquid film may give rise to boiling instability, and the dry-out of the film leads to serious deterioration of the heat transport. The thin liquid film has multi-scale transitions, and hence the phase change and fluid dynamics need to be solved by special governing equations and numerical algorithm. The numerical studies to date have solved the steady state distribution of the film, but the difficulty consists in the transient simulation of time-variant liquid films. In the present study, unsteady form governing equations are developed. With inclusion of the temporal terms, we conducted transient simulations for flat liquid films formed during the flow boiling in micro-channels. The model predicts the developing of drying spot during growth of elongated bubbles. The results show that the film thickness and distribution change quickly in a growth period, which are functions of the heat flux, mass flow rate and the other parameters. The quantitative assessment of these effects helps to clarify the mechanism of boiling instability and the conditions for the occurrence of critical heat flux (CHF). The simulation needs special numerical scheme for time marching and stabilization treatment for the nonlinear terms, where the numerical accuracy and the significance of the temporal effects are also discussed.
A Dissipative Particle Dynamics Study of Liquid Crystals Under Electric Field
Authors: Gupta Man Prakash , Kumar Satish
Published: July 2018

We study the equilibrium and dynamic behavior of liquid crystals (LCs) under dc and ac electric field using a mesoscopic simulation technique, Dissipative Particle Dynamics (DPD). We quantify the reorientation of LC molecules and the change in their anisotropic character under external perturbation by an order parameter. We find that the electric field magnitude has to be above a critical value to initiate the reorientation of the director of the LC system along the applied electric field, which is consistent with the experimental observations. The response time of the reorientation process decreases as the magnitude of the electric increases for the dc fields. The effect of ac field frequency on the order parameter is correlated with the field amplitude. The cyclic variation in the order parameter follows the ac field when the oscillation period is greater than the response time of the system and the amplitude is greater than the critical value. Results suggest that the DPD technique can provide important insights in to the dynamic behavior of LC system under both dc and ac electric fields. This technique can further be applied to examine the properties of colloidal LCs which can be very useful for many practical applications.
Enhanced Damage Effects Induced by Cell-Level Hyperthermia With Higher Heating Rate or Allied Cooling Procedure
Authors: Jin Chao , Yi Li Ting , Liu Jing
Published: July 2018

As a core basis, the knowledge of cellular thermal responses is critical to understand the thermal damage mechanism of hyperthermia. In the aid of a cryo-stage system with controlled temperature ranging from −196°C to 125°C, the present work is dedicated to investigate the thermal behaviors of cancer cells (i.e. MCF-7 cells) subject to hyperthermia with a higher heating rate or allied with a rapid cooling procedure. The preliminary results show the following factors: (1) The MCF-7 cells show potential enhanced sensitivity to heat when the heating rate increases from 10 °C/min to 30°C/min; (2) The enhanced degree of thermal damages induced by the higher heating rate is time dependent; (3) The rapid cooling procedure following the hyperthermia would be another effective way to strengthen the killing effects of cancer cells. In addition, further microscopic experiments have also been implemented to observe the morphological changes of cells induced by the rapid heating treatment. The present study partly promotes the mechanistic understandings of cellular damage through an alternative heating approach, which would provide a valuable reference to improve the therapeutic efficiency in the coming time.
The (Atomistic-Continuum) Hybrid Taxonomy and the Hybrid-Hybrid Approach
Authors: Alexiadis Alessio , Lockerby Duncan A.
Published: July 2018

The Laplacian method, initially introduced in Alexiadis et al. 2013 (1), is here extended to 2D cases. The solution algorithm on which the method is based is modified in order to tackle the issue of numerical noise in 2D domains. We also introduce the idea of the hybrid taxonomy and of hybrid-hybrid methods. The connection of the hybrid taxonomy with the notion of scale inheritance is discussed and the role of the Laplacian method within the taxonomy highlighted.
Numerical Modeling of Droplet Splitting and Merging in a Parallel-Plate Electrowetting-on-Dielectric (EWOD) Device
Authors: Guan Yin , Tong Albert Y.
Published: July 2018

Micro water droplet splitting and merging in a parallel-plate electrowetting-on-dielectric (EWOD) device has been studied numerically. The transient governing equations for the microfluidic flow are solved by a finite volume scheme with a two-step projection method on a fixed computational domain. The interface between liquid and gas is tracked by a coupled Level Set and Volume-of-Fluid (CLSVOF) method. A Continuum Surface Force (CSF) model is employed to model the surface tension at the interface. The physics of the fluid dynamics within the EWOD device has been examined. Contact angle hysteresis, which is an essential component in EWOD, is implemented together with a simplified model for the viscous stresses exerted by the two plates at the solid-liquid interface. The results of the numerical model have been validated with published experimental data. A parametric study has been performed in which the effects of channel height and several other parameters on the fluid motion have been studied.
Mechanisms of Thin-Film Evaporation Considering Momentum and Energy Conservation
Authors: Yan Chunji , Pan Xinxiang , Lu Xiaowei
Published: July 2018

A mathematic model, which can be used to predict the evaporation and fluid flow in thin film region, is developed based on momentum and energy conservations and the augmented Young-Laplace equation in this paper. In the model the variations of the enthalpy and kinetics energy of the thin-film along the evaporating region are considered. By theoretical analysis, we have obtained the governing equation for thin film profile. The fluid flow and phase-change heat transfer in an evaporating extended meniscus are numerically studied. The differences between the model considering momentum conservation only and including both momentum and energy conservations are compared. It is found that the maximum heat flux of the thin-film evaporation by using two mathematical models obtained has no change, but when considering the momentum and energy conservations the total heat transfer rate unit width along the thin-film evaporation region is greater than that of only including momentum equation.
Study of Liquid Metal Based Thermal Micro-System for On-Chip Cell Culture Purpose
Authors: Gao Meng , Gui Lin
Published: July 2018

Room temperature liquid metal has been widely used in many MEMS applications, such as integrated heaters, sensors, electrodes and stretchable wires. Injecting the liquid metal into microchannels provides a simple, rapid and low-cost way to fabricate micro heaters and sensors. The liquid-metal-filled microstructures can be designed in any shape and easily integrated into micro devices. In this study, a liquid-metal based thermal micro-system was proposed for on-chip cell culture purpose. The thermal micro-system consisted of two same microchannels filled with the liquid metal as electrical heaters. At the same time, the heater also worked as a resistance temperature sensor to control the heating process. The temperature sensor was calibrated from 20 °C to 70 °C to give an accurate temperature control for the microsystem. To justify whether this micro-system is capable of providing a uniform temperature distribution, Rhodamine B was filled into the micro cell culture chamber of interest to monitor the temperature distribution. Thermal analysis was numerically carried out to reveal the temperature field of the chip. This thermal micro-system has great potential use in many microfluidic applications, such as on-chip PCR, temperature gradient focusing, protein crystallization or chemical synthesis.
Convective Heat Transfer Enhancement Using Carbon Nanofibers (CNFs): Influence of Amorphous Carbon Layer on Heat Transfer Performance
Authors: Taha T. J. , Lefferts L. , Van der Meer T. H.
Published: July 2018

In this work, an experimental heat transfer investigation was carried out to investigate the combined influence of both amorphous carbon (a-C) layer thickness and carbon nanofibers (CNFs) on the convective heat transfer behavior. Synthesis of these carbon nano structures was achieved using catalytic chemical vapor deposition process (CCVD) on a 50 μm nickel wire at 650°C. Due to their extremely high thermal conductivity, CNFs are used to augment/modify heat transfer surface. However, the inevitable layer of a-C that occurs during the synthesis of the CNFs layer exhibit low thermal conductivity which may result in insulating the surface. In contrast, the amorphous layer helps in supporting and mechanical stabilizing of the CNFs layer attachment to the polycrystalline nickel (Ni270) substrate material. To better understand the influences of these two layer on heat transfer, the growth mechanism of the CNFs layer and the layer of carbon is investigated and growth model is proposed. The combined impact of both a-C and CNFs layer on heat transfer performance is studied on three different samples which were synthesized by varying the deposition period (16 min, 23min and 30 min). The micro wire samples covered with CNF layers were subjected to a uniform flow from a nozzle. Heat transfer measurement was achieved by a controlled heat dissipation through the micro wire to attain a constant temperature during the flow. This measurement technique is adopted from hot wire anemometry calibration method. Maximum heat transfer enhancement of 18% was achieved. This enhancement is mainly attributed to the surface roughness and surface area increase of the samples with moderate CNFs surface area coverage on the sample.
Role of Nanoscale Roughness and Temperature on Poiseuille Flow at Liquid-Solid Interface
Authors: Wang Yan , Ling Xiang
Published: July 2018

Non-equilibrium molecular dynamics method is applied to determine the slip length of fluid in the vicinity of the boundaries in Poiseuille flow in a nano-channel with and without nanoscale roughness, in which pressure is imposed to the fluid. Our simulations reveal the boundary roughness effect on the interfacial interaction between the fluid and boundary, which will result in the change of fluid velocity, and this phenomenon is more distinct with boundary roughness height. Bonding energy between solid boundary and fluid atoms is also calculated to make a comparison with that of pure fluid. Roughness changes with highness and its shape, so the key factors controlling fluid flow are presented. The simulation results show that there’s a relationship between the bonding energy at fluid–solid boundary interface and the fluid kinetic properties. In the case of rough surfaces, the bonding strength between liquid and solid atoms has a strong signature in the fluid velocity close to the boundary. In addition, temperature effect is also considered in our simulations, and we find that temperature also affect the hydrodynamic properties of fluid flowing in nano-channel significantly.
Molecular Dynamics Simulation of Vapor Condensation on Nanotubes
Authors: Suh Donguk , Yasuoka Kenji , Zeng Xiao Cheng
Published: July 2018

Vapor condensation on silicon nanotubes has been simulated by classical molecular dynamics to understand how the nucleation and condensation process for pores is affected. Two different nanotube aspect ratios were examined to see if there are growth rate changes. The rate for the two different types of nanotubes did not show significant variation meaning that the aspect ratio is an insignificant factor to enhance condensation. This result is consistent with previous nanorod studies. The supersaturated vapor gathered both inside and outside of the tube. Unlike the growth rate, however, the occurrence of homogeneous nucleation was hindered contrary to other basic geometries in previous studies.
Thermal Interface Materials From Vertically Aligned Polymer Nanotube Arrays
Authors: Bougher Thomas L. , Singh Virendra , Cola Baratunde A.
Published: July 2018

A number of studies have reported enhancing the thermal conductivity of semi-crystalline polymers through mechanical stretching, but practical application of this process has proven difficult. Here we demonstrate the application of enhanced thermal conductivity in a purely amorphous polymer for a thermal interface material (TIM) without conductive fillers. Many polymer-based TIMs contain carbon fillers to enhance the thermal conductivity, however the TIMs reported herein are comprised solely of polymer nanotubes. The conjugated polymer polythiophene (Pth) is electropolymerized in nanotemplates to produce arrays of vertically aligned nanotubes, which adhere well to opposing substrates through van der Waals forces. We find that the total thermal resistances of the Pth-TIMs are a strong function of height with some dependence on bonding pressure, yet independent of applied pressure after bonding. Photoacoustic measurements show that the total thermal resistance of the TIMs ranges from 9.8 ± 3.8 to 155 ± 32 mm2-K/W depending on the array height and bonding pressure. Estimates of the component resistances indicate that the majority of the resistance is in the contact between the nanotube free tips and the opposing quartz substrate. These Pth-TIMs demonstrate that enhanced thermal conductivity polymers can be suitable for heat transfer materials without thermally conductive fillers.
Experimental Study on the Stability and Thermophysical Properties of Binary Propanol-Water Mixtures Based Phase Change Microencapsule Suspensions
Authors: Wang Liang , Liu Li , Wang Yifei , Chai Lei , Yang Zheng , Chen Haisheng , Tan Chunqing
Published: July 2018

Phase change microencapsules are the microsized particles made of phase change materials (paraffin wax ect.) sealed by the thin shell (polymer ect.) via the methods of microencapsulation. During last decade, due to the large amount of melting/solidifying heat, much attention have been paid on their application in environmental control, building, textiles and electronics ect. Also the novel thermal fluids by phase change microencapsules suspending in the traditional thermal fluids have shown their superior heat storage density and convective heat transfer performance, which can behave as heat storage media and heat transfer media simultaneously. However, the density difference between the phase change microencapsules and tranditional unitary fluid would lead to the unstable suspending states which seriously affect the heat storage and heat transfer performance.

Binary mixtures such as alcohol-water etc have already played the important roles in the heat transfer equipments. In this paper, binary propanol-water mixtures of various proportion were formulated as the base fluids, and their stabilities were studied. The result shows that binary propanol-water mixtures with the desity of 941kg/m3 showed the best stability and no stratification was found after standing for 48 hours.

The morphology and diameter distribution of the microencapsule particles were tested by the scanning electron microscope (SEM) and Malvern Nanosizer respectively, and the result show that the diameter of the particles is in the range of 10–80μm with the average value of 26.4μm. The phase change enthalpy and the effective heat capacity of phase change microencapsule suspensions with the concentration of 10–40wt% were measured by the differencial scanning calorimeter (DSC) and it was found the phase change enthalpy of the phase change microencapsule is 152.8J/g and the undercooling is only 7.3°C. The effect of concentration and temperature on the rheological behavior and viscosities of suspensions were experimentally studied by the TA DHR-G2 rheometer. The result shows that the suspensions behave as Newtonian fluids even when the concentration is as high as 40wt% and the viscosities fit well with Vand model. By the Hot Disk 2500S thermal constant analyzer (Sweden), the thermal conductivities of 0–40wt% suspensions were tested at 20–70°C and the variation was analyzed further. The concentration and expansion of MPCM particles during the phase change period were found to affect the thermal expansion coefficient of the MPCM suspensions obviously. The above experimental result and analyzation of stability and thermophysical properties will provide a complete and important data for the application in heat storage and heat transfer.
Numerical Model of Thermoelectric Topping Cycle of Coal Fired Power Plant
Authors: Silaen Armin , Wu Bin , Fu Dong , Zhou Chenn , Yazawa Kazuaki , Shakouri Ali
Published: July 2018

Traditional fossil fuel power generation process typically has low efficiency. Large amount of the energy loss in Rankine cycle steam turbines (ST) is due to the temperature difference between the combustion flame temperature ∼2250 K (adiabatic) and the high pressure steam temperature up to 900 K. However, some of this energy can be harvested using solid-state thermoelectric (TE) power generators which are placed into the gap between the flame temperature and the steam temperature that produce additional electrical power. This study investigates the potential placement of TE on water tube wall inside a boiler at a coal fired power plant. Three dimensional (3D) numerical model of a simplified TE module is developed and hot gas temperature and steam temperature from the boiler are used as boundary conditions at the hot side and cold side of the TE. The numerical results are compared with analytical calculations. The 3D effects of the thermal spreading in the TE module are investigated. Parameters such as TE leg cross-section area and TE fill factor are examined in order to maximize the electrical power production of the TE without sacrificing the boiler efficiency (i.e., reducing the steam temperature). The study also looks into the various locations inside the boiler that have good potential for TE installation.
Divergence of Radiative Heat Flux in Ultra-Short Time Scale in Axisymmetric Geometry With its Implications
Authors: Verma A. K. , Kar S. P. , Rath P. , Mahapatra S. K.
Published: July 2018

An axisymmetric transient radiative heat transfer model is developed taking into account the new formulation of divergence of radiative heat flux in ultrashort time scale. In order to predict the medium temperature, divergence of radiative heat flux is coupled with the energy equation. The conventional quasi steady divergence of radiative heat flux is modified taking into account the transient effect of photon transport. An axisymmetric domain is taken as a physical model in the present analysis. A critical examination revealed that even for pure scattering medium, the diveregence of flux is a non-zero quantity due to the inclusion of the new term called as propagation term in the formulation of the divergence of radiative heat flux in ultrashort time scale. A two-dimensional scheme is proposed to solve the radiative transfer equation (RTE) in an axisymmeric cylindrical domain. The step spatial scheme is used for discretizing the spatial term in the RTE. The medium is assumed to be absorbing, emitting and isotropically scattering. The walls are assumed as diffuse and gray. It is observed that the conventional quasi-steady divergence of radiative heat flux underpredicts the temperature of the medium in the time scale of the order of characteristic time scale of photon where transient radiation effect is predominant.
The Study of Argon’s Viscosity Near the Wall of Nanopore by Molecular Dynamics Simulations
Authors: Liu Qixin
Published: July 2018

Many uncommon gas flow phenomena in nanopores have been found by experiments. Besides that, another special characteristic of gas flow at nanopore is that gas’s number density shows uneven distribution. From the point of molecular motion, gas’s number density would affect its dynamic viscosity, so it’s very necessary to study whether the gas’s viscosity is uneven. Due to the gas density’s fluctuation usually takes place near the wall surface so the present paper focuses on the gas’s viscosity near the wall of nanopore. Our molecular dynamics simulation results indicate that the gas’s viscosity in the region near the wall surface isn’t a constant and fluctuates greatly. The profiles of gas’s viscosity and gas number density coincide very well.
A Method for Predicting Six Degrees-of-Freedom Ultimate Limit State of Subsea Mudmats
Authors: Feng Xiaowei , Gourvenec Susan
Published: July 2018

Rectangular mudmat foundations are extensively deployed in deep waters to support subsea infrastructure leading to renewed interest in optimizing the design of offshore shallow foundations. Offshore industry guidelines (e.g. API RP2GEO and ISO 19901-4) are based on classical bearing capacity theory of a plane strain strip foundation resting on the surface of a uniform Tresca material. More realistic conditions are accounted for through a range of superposed empirical modification factors and the effective width principle.

In practice, subsea foundations experience complex loading in six degrees-of-freedom (vertical load, biaxial horizontal load, biaxial moment and torsion), due to expansion and contraction of connected pipelines and jumpers; they may be able to mobilize transient tensile capacity; and they are typically three-dimensional in plan, shallowly embedded and founded on soft, normally consolidated, soils with linearly increasing strength with depth. Accurate determination of the ultimate limit state of subsea mudmats is best achieved by considering the relevant foundation, soil and loading boundary conditions explicitly.

In this paper, a simplified approach for predicting the ultimate limit state of mudmat foundations under six degrees-of-freedom, based on failure envelopes, obtained from extensive finite element analyses, is compared with the traditional bearing capacity methods as recommended in industry guidelines.
Sustained Uplift of Skirted Foundation in Clay
Authors: Li Xiaojun , Tian Yinghui , Cassidy Mark J. , Gaudin Christophe
Published: July 2018

A series of centrifuge tests have been performed to investigate the uplift behaviour of a shallow skirted foundation resting on clay subjected to various sustained loadings expressed as a fraction of the undrained bearing capacity in compression. Displacements, uplift loads, total and pore pressures underneath the foundation were monitored during testing to provide insight on the development of negative pore pressure (suction) at the foundation base and on the mechanism triggering breakout. The results indicate that the displacement rate and the time the uplift load can be sustained depend on the magnitude of the load, but also on the time the foundation experienced consolidation prior to uplift. Breakout was not observed at a relatively large time scale under low sustained loadings, while the foundation was pulled out directly under high loading levels. At intermediate loadings, breakout was inferred from the sudden increase in displacement rate. The breakout mechanism of the foundation is also discussed based on the observation of pore pressure variations underneath the foundation.

The outcomes of the present study have the potential to provide a better understanding of the suction mechanism for offshore foundations and to provide guidelines for offshore retrieval operations.
Effect of Preloading on the Response of a Shallow Skirted Foundation
Authors: Vulpe Cristina , Gourvenec Susan
Published: July 2018

The effect of preloading on the vertical settlement and bearing capacity of a circular skirted foundation was investigated as a function of relative preload and degree of consolidation by means of small strain finite element analyses. Significant gain in bearing capacity was observed for practical levels of preloads and duration of consolidation, offering an insight into potential efficiencies in foundation design.
Effect of Relative Density on P-Y Backbone Curves for Cyclic Lateral Load on Pile Foundations in Sandy Soil
Authors: Baek Sung-Ha , Kim Joon-Young , Lee Seung-Hwan , Chung Choong-Ki
Published: July 2018

Pile foundations installed to support offshore structures are primarily subjected to cyclic lateral loads due to wind, and waves. The p-y curve method, which represents a nonlinear relation between soil-pile reaction and lateral pile deflection, has been used to design cyclic laterally loaded piles. Recommended by the American Petroleum Institute (API) [10] and generally adopted to evaluate the behavior of static and cyclic laterally loaded piles installed in sandy soils, the API p-y curve contains a reduction factor for the initial horizontal subgrade modulus in order to take cyclic effects into consideration. When pile foundations are subjected to cyclic lateral loads, however, the initial horizontal subgrade modulus can both decrease and increase according to the relative density of the soil. In this paper, a series of cyclic lateral load model tests were performed on a preinstalled aluminum flexible pile to examine its cyclic lateral response under different relative density conditions. Model piles were embedded in sandy soils with relative densities of 40%, 70%, and 90% and were subjected to static as well as cyclic lateral loads. From the test results, cyclic p-y backbone curves were derived and compared with static p-y curves in identical soil conditions. Test results showed that the initial horizontal subgrade modulus increased for the model pile installed in sandy soil of 40% relative density, while decreased in relative densities of 70% and 90%. In addition, the infinite depth, above which cyclic lateral loads were supported, was evaluated and the test results were compared with the API p-y curve.
Numerical Study of the Combined Loading Envelope of a Skirted Spudcan Foundation
Authors: Cheng Ning , Cassidy Mark J. , Tian Yinghui
Published: July 2018

Foundations for offshore structures, such as mobile jack-up units, are subjected to large horizontal (H) and moment (M) loads in addition to changing vertical (V) loads. The use of a combined vertical, horizontal and moment (V-H-M) loading envelope to define foundation capacities has become increasingly applied in recent years. However, there is no study on the skirted spudcan, a new alternative foundation type to the conventional spudcan footing for jack-ups. In this study, the combined V-H-M yield envelope of a skirted spudcan foundation in clay soil is investigated with small strain finite element analyses using 3D modeling. The footing’s uniaxial bearing capacities and failure mechanisms are described. The failure envelope for the combined V-H-M loadings is presented. A comparison of the bearing capacities between the spudcan and skirted spudcan of various dimensions is also presented.
An Empirical Correlation for Compressibility of Shallow Depth Clays in Deepwater Gulf of Mexico
Authors: Won Jeong-Yun , Suroor Hadi
Published: July 2018

Settlement of subsea structures is an important design consideration, yet it is typically estimated using empirical correlations. A total of 74 consolidation test results from deepwater projects are collected and analyzed to develop an empirical correlation for shallow depth (less than 20 m) deepwater clays in the Gulf of Mexico. Compression indexes with and without clay structural effects are separately considered. Most of the published empirical correlations are irrelevant to offshore clays and the commonly used empirical correlation that uses liquid limit could significantly underestimate the peak compression index of deepwater offshore clays. Initial void ratio is selected as an independent variable for peak compression index estimation. A power function type correlation is proposed between the peak compression index and initial void ratio. With the lower and upper bounds (±30 %), the proposed empirical correlation encompasses the majority of the peak compression index data considering the structural effects. The proposed correlation is applicable for deepwater clays in the Gulf of Mexico having initial void ratios between 1 and 4.
Evaluation of Plate Anchors Capacity in Saturated Soils Using Different Constitutive Models
Authors: Aghazadeh Zahra , Rahman M. S. , Gabr M. A.
Published: July 2018

Evaluation of the uplift capacity of plate anchors in saturated clay is an important aspect in offshore anchoring of various structures. In most of the literature reviewed, a constitutive model such as Tresca or Mohr-Coulomb has been used in analyses. There exists a need to study the anchors’ pull out capacity using other advanced soil models and discern differences in results.

This study presents the results of finite element simulation of a rectangular or circular plate anchor in saturated clay. The capacity factors (Nc) of the plate are assessed through the application of displacement control approach and the results are compared to the lower bound solution as well as to data obtained from similar studies available in the literature.

In addition to Mohr-Coulomb model, two other constitutive models are used to represent the soil deformation. These are Modified Cam-Clay, and Soft Soil models. Undrained effective stress analyses are conducted using the computer program PLAXIS. A series of analyses using different embedment depths are performed for all three constitutive models. Results as Nq value from the three constitutive models are presented and discussed.
Numerical Modelling of Cyclic Pull-Out Behaviors of Embedded Plate Anchors in Saturated Soft Clay
Authors: Hu Cun , Gao Fu-ping
Published: July 2018

As a foundation for deep-water floating offshore structures, the embedded plate anchor should withstand the complicated marine conditions involving the cyclic loads. The pull-out behaviors of the embedded plate anchor under cyclic loading must be considered whilst designing. This paper presents a numerical approach for assessing the cyclic pull-out behaviors of the embedded plate anchor based on a recently proposed anisotropic bounding surface plasticity model, which can capture the non-failure stable and degradation characteristics of saturated soft clay under cyclic loading with different stress-levels. The pull-out behaviors of the embedded plate anchor under both monotonic and cyclic loading are simulated and investigated. Effects of the mean value, the amplitude of the cyclic loading on the cyclic pull-out behaviors are analyzed. The results demonstrate that under different cyclic loading levels three typical types of the cyclic pull-out behaviors are obtained, i.e., the cyclic stable, the cyclic hypo-stable and the cyclic degradation.
On the Set-Up of Piles
Authors: Grabe Jürgen , Busch Philipp , Hamann Thorben
Published: July 2018

It is well known that the bearing capacity and stiffness of displacement piles depends on short term effects during and shortly after pile installation as well as long term effects, a phenomenon usually referred to as set-up. During pile installation the surrounding soil is influenced by the installation process. The soil state e.g. the stress state, pore pressure or void ratio are changing due to complex mechanical processes in the soil. The change of the soil state has a great influence on the pile capacity and the behavior of the pile under vertical and horizontal loading. During the installation process phenomena like a temporary and locally limited liquefaction of the soil can occur. After the pile installation the bearing capacity may increase significantly with time due to set-up effects. In cohesive soils the set-up is commonly explained by consolidation processes in which the dissipation of the excess pore pressures around the pile leads to an increase in effective radial stresses. Case histories show that set-up may also occur in sand over a period which exceeds by far the consolidation process. Therefore, other effects apart from the dissipation of excess pore pressures must contribute to this long-term set-up effect. An understanding and a correct estimation of these effects is of great importance for a economical design of pile-founded structures e.g. offshore wind turbines. For the investigation of these phenomena different methods like numerical simulations, model scale or full scale tests are applicable. In this paper two methods are used: The installation process is investigated with numerical simulations and the set-up effects are investigated by long term in-situ measurements.
Experimental Study for Wave-Induced Oscillatory Pore Pressures in a Sandy Seabed
Authors: Liu Bo , Jeng Dong-Sheng , Ye Guanlin
Published: July 2018

In this paper, an experimental study for wave-induced pore pressures in marine sediments was reported. In the experiment, a one-dimensional facility was set up with a vertical cylinder and a 1.8 m thick sandy deposit and 0.2 m thick water above the deposit. Unlike the previous experiments [1], additional static water pressures were added on the harmonic dynamic wave pressure and more pore pressure gauges were buried in the deposit, which allowed us to simulate the case with larger water depth and better describe the distribution of pore pressure trend. A series of experiments with 3000 cycles in each test were conducted under numerous different wave and soil conditions, which allowed us to examine the influence of wave and soil parameters on the wave-induced pore pressures as well as liquefaction. The experimental results show the significant influence of liquefaction on sandy seabed in shallow water. Furthermore, some new experimental phenomenon was observed. The depth of sandy deposit was usually considered to be unchanged in theoretical calculation, while the depth of which was indeed changed periodic with wave loading, which was observed and recorded in the experiments.
Pipeline Upheaval Buckling in Clayey Backfill and Shore Approach
Authors: Koochekali Alahyar , Gatmiri Behrouz , Koochekali Amirabbas
Published: July 2018

True estimation of soil response during pipeline upheaval buckling is a key parameter in the safe design of subsea buried pipeline. In this paper the effects of sea mean water level over the buried pipeline and the effects of pipe burial depth on the soil response during vertical buckling are investigated. For that purpose a numerical modeling of pipeline upheaval buckling in clayey backfill has been conducted. Different sea mean water levels are considered to simulate the pipeline shore approach. In addition, various pipeline burial depths are considered to predict the soil uplift resistance and the soil failure mechanism. In order to model the large penetration of pipeline into the soft clay, Arbitrary Eulerian Lagrangian (ALE) method is employed. The results reveal that in the shallow water the sea mean water level may have considerable effects on the soil failure mechanism and soil uplift resistance. In addition, as the sea mean water level and pipe burial depth increases, a new transitional failure mechanism can be observed. The mechanism is a combination of vertical sliding block mechanism and the flow-around mechanism.
A Genome-Wide Screen of Deletion Mutants in the Filamentous Saccharomyces cerevisiae Background Identifies Ergosterol as a Direct Trigger of Macrophage Pyroptosis
Authors: Koselny Kristy , Mutlu Nebibe , Minard Annabel Y. , Kumar Anuj , Krysan Damian J. , Wellington Melanie
Published: July 2018

Phagocytic cells such as macrophages play an important role in the host defense mechanisms mounted in response to the common human fungal pathogen
Candida albicans
.
In vitro
,
C. albicans
triggers macrophage NLRP3-
Casp1/11
-mediated pyroptosis, an inflammatory programmed cell death pathway. Here, we provide evidence that
Casp1/11
-dependent pyroptosis occurs in the kidney of infected mice during the early stages of infection. We have also used a genome-wide screen of nonessential Σ1278b
Saccharomyces cerevisiae
genes to identify genes required for yeast-triggered macrophage pyroptosis. The set of genes identified by this screen was enriched for those with functions in lipid and sterol homeostasis and trafficking. These observations led us to discover that cell surface localization and/or total levels of ergosterol correlate with the ability of
S. cerevisiae
,
C. albicans
, and
Cryptococcus neoformans
to trigger pyroptosis. Since the mammalian sterol cholesterol triggers NLRP3-mediated pyroptosis, we hypothesized that ergosterol may also do so. Consistent with that hypothesis, ergosterol-containing liposomes but not ergosterol-free liposomes induce pyroptosis. Cell wall mannoproteins directly bind ergosterol, and we found that Dan1, an ergosterol receptor mannoprotein, as well as specific mannosyltransferases, is required for pyroptosis, suggesting that cell wall-associated ergosterol may mediate the process. Taken together, these data indicate that ergosterol, like mammalian cholesterol, plays a direct role in yeast-mediated pyroptosis.

IMPORTANCE
Innate immune cells such as macrophages are key components of the host response to the human fungal pathogen
Candida albicans
. Macrophages undergo pyroptosis, an inflammatory, programmed cell death, in response to some species of pathogenic yeast. Prior to the work described in this report, yeast-triggered pyroptosis has been observed only
in vitro
; here, we show that pyroptosis occurs in the initial stages of murine kidney infection, suggesting that it plays an important role in the initial response of the innate immune system to invasive yeast infection. We also show that a key component of the fungal plasma membrane, ergosterol, directly triggers pyroptosis. Ergosterol is also present in the fungal cell wall, most likely associated with mannoproteins, and is increased in hyphal cells compared to yeast cells. Our data indicate that specific mannoproteins are required for pyroptosis. This is consistent with a potential mechanism whereby ergosterol present in the outer mannoprotein layer of the cell wall is accessible to the macrophage-mediated process. Taken together, our data provide the first evidence that ergosterol plays a direct role in the host-pathogen interactions of fungi.
New Tools for Syphilis Research
Authors: Lukehart Sheila A.
Published: July 2018

Syphilis research has been severely limited by the necessity to propagate
Treponema pallidum
in vivo
in rabbits. After decades of erroneous or irreproducible reports of cultivation of
T. pallidum
, the recent very convincing report of its successful long-term
in vitro
propagation opens numerous opportunities for development of genetic tools for studying pathogenesis and protein function, antigenic variation, and surface exposure of antigens.
Similarities and differences in the associations between patient safety culture dimensions and self-reported outcomes in two different cultural settings: a national cross-sectional study in Palestinian and Belgian hospitals
Authors: Najjar Shahenaz , Baillien Elfi , Vanhaecht Kris , Hamdan Motasem , Euwema Martin , Vleugels Arthur , Sermeus Walter , Schrooten Ward , Hellings Johan , Vlayen Annemie
Published: July 2018

Objectives

To investigate the relationships between patient safety culture (PSC) dimensions and PSC self-reported outcomes across different cultures and to gain insights in cultural differences regarding PSC.

Design

Observational, cross-sectional study.

Setting

Ninety Belgian hospitals and 13 Palestinian hospitals.

Participants

A total of 2836 healthcare professionals matched for profession, tenure and working hours.

Primary and secondary outcome measures

The validated versions of the Belgian and Palestinian Hospital Survey on Patient Safety Culture were used. An exploratory factor analysis was conducted. Reliability was tested using Cronbach’s alpha (α). In this study, we examined the specific predictive value of the PSC dimensions and its self-reported outcome measures across different cultures and countries. Hierarchical regression and bivariate analyses were performed.

Results

Eight PSC dimensions and four PSC self-reported outcomes were distinguished in both countries. Cronbach’s α was α≥0.60. Significant correlations were found between PSC dimensions and its self-reported outcome (p value range <0.05 to <0.001). Hierarchical regression analyses showed overall perception of safety was highly predicted by hospital management support in Palestine (β=0.16, p<0.001) and staffing in Belgium (β=0.24, p<0.001). The frequency of events was largely predicted by feedback and communication in both countries (Palestine: β=0.24, p<0.001; Belgium: β=0.35, p<0.001). Overall grade for patient safety was predicted by organisational learning in Palestine (β=0.19, p<0.001) and staffing in Belgium (β=0.19, p<0.001). Number of events reported was predicted by staffing in Palestine (β=−0.20, p<0.001) and feedback and communication in Belgium (β=0.11, p<0.01).

Conclusion

To promote patient safety in Palestine and Belgium, staffing and communication regarding errors should be improved in both countries. Initiatives to improve hospital management support and establish constructive learning systems would be especially beneficial for patient safety in Palestine. Future research should address the association between safety culture and hard patient safety measures such as patient outcomes.
Prognostic value of chronic total occlusions detected on coronary computed tomographic angiography
Authors: Opolski Maksymilian P , Gransar Heidi , Lu Yao , Achenbach Stephan , Al-Mallah Mouaz H , Andreini Daniele , Bax Jeroen J , Berman Daniel S , Budoff Matthew J , Cademartiri Filippo , Callister Tracy Q , Chang Hyuk-Jae , Chinnaiyan Kavitha , Chow Benjamin JW , Cury Ricardo C , DeLago Augustin , Feuchtner Gudrun M , Hadamitzky Martin , Hausleiter Joerg , Kaufmann Philipp A , Kim Yong-Jin , Leipsic Jonathon A , Maffei Erica C , Marques Hugo , Pontone Gianluca , Raff Gilbert , Rubinshtein Ronen , Shaw Leslee J , Villines Todd C , Gomez Millie , Jones Erica C , Peña Jessica M , Min James K , Lin Fay Y
Published: July 2018

Objective

Data describing clinical relevance of chronic total occlusion (CTO) identified by coronary CT angiography (CCTA) have not been reported to date. We investigated the prognosis of CTO on CCTA.

Methods

We identified 22 828 patients without prior known coronary artery disease (CAD), who were followed for a median of 26 months. Based on CCTA, coronary lesions were graded as normal (no atherosclerosis), non-obstructive (1%–49%), moderate-to-severe (50%–99%) or totally occluded (100%). All-cause mortality, and major adverse cardiac events defined as mortality, non-fatal myocardial infarction and late coronary revascularisation (≥90 days after CCTA) were assessed.

Results

The distribution of patients with normal coronaries, non-obstructive CAD, moderate-to-severe CAD and CTO was 10 034 (44%), 7965 (34.9%), 4598 (20.1%) and 231 (1%), respectively. The mortality rate per 1000 person-years of CTO patients was non-significantly different from patients with moderate-to-severe CAD (22.95; 95% CI 12.71 to 41.45 vs 14.46; 95% CI 12.34 to 16.94; p=0.163), and significantly higher than of those with normal coronaries and non-obstructive CAD (p<0.001 for both). Among 14 382 individuals with follow-up for the composite end point, patients with CTO had a higher rate of events than those with moderate-to-severe CAD (106.56; 95% CI 76.51 to 148.42 vs 65.45; 95% CI 58.01 to 73.84, p=0.009). This difference was primarily driven by an increase in late revascularisations in CTO patients (27 of 35 events). After multivariable adjustment, compared with individuals with normal coronaries, the presence of CTO conferred the highest risk for adverse cardiac events (14.54; 95% CI 9.11 to 23.20, p<0.001).

Conclusions

The detection of CTO on non-invasive CCTA is associated with increased rate of late revascularisation but similar 2-year mortality as compared with moderate-to-severe CAD.

Trial registration number

NCT01443637.
Melatonin attenuates caspase-dependent apoptosis in the thoracic aorta by regulating element balance and oxidative stress in pinealectomised rats
Authors: Doğanlar Zeynep Banu , Uzun Metehan , Ovali Mehmet Akif , Dogan Ayten , Ongoren Gulin , Doğanlar Oğuzhan
Published: July 2018

The aim of this study was to explain the possible mechanisms by which melatonin deficiency results in cardiovascular injury and to investigate the effects of melatonin administration on important signalling pathways and element equilibrium in the thoracic aorta (TA). For this purpose, we analysed the cellular and molecular effects of melatonin deficiency or administration on oxidative stress, DNA damage, molecular chaperone response, and apoptosis induction in TA tissues of pinealectomised rats using ELISA, RAPD, qRT-PCR, and Western blot assays. The results showed that melatonin deficiency led to an imbalance in essential element levels, unfolded or misfolded proteins, increased lipid peroxidation, and selectively induced caspase-dependent apoptosis in TA tissues without significantly affecting the Bcl-2/BAX ratio (2.28 in pinealectomised rats, 2.73 in pinealectomised rats treated with melatonin). In pinealectomised rats, the genomic template stability (80.22%) was disrupted by the significantly increased oxidative stress, and heat shock protein 70 (20.96-fold), TNF-α (1.73-fold), caspase-8 (2.03-fold), and caspase-3 (2.87-fold) were markedly overexpressed compared with the sham group. Melatonin treatment was protective against apoptosis and inhibited oxidative damage. In addition, melatonin increased the survivin level and improved the regulation of element equilibrium in TA tissues. The results of the study indicate that melatonin deficiency induces TNF-α-related extrinsic apoptosis signals and that the administration of pharmacological doses of melatonin attenuates cardiovascular toxicity by regulating the increase in the rate of apoptosis caused by melatonin deficiency in TA tissue of Sprague–Dawley rats.
Analysis of surface erosion of cohesionless soils using a three-dimensional coupled computational fluid dynamics – discrete element method (CFD–DEM) model
Authors: Guo Yuan , Yu Xiong (Bill)
Published: July 2018

A fluid–solid interaction model has been implemented by coupling two numerical methods — computational fluid dynamics (CFD) and discrete element method (DEM) — that capture the mesoscale behaviors of the fluid–solid system. The model is first validated by comparing the results of simulations with two types of experiments: free settling of a single sphere in water and formation of angle of repose of particles under water, which show its capability in modeling the behaviors of both particle phase and fluid phase. The verified model is then used to study factors affecting the soil erodibility, where case studies are designed for soil particles deposited inside a pipe and subsequently subjected to water flow–induced surface erosion. Influencing factors for soil erodibility, including particle diameter and interparticle bond, are analyzed. For cohesionless soils without bond strength, the critical shear stress is found to be linearly related to particle size; while for soils with bond strength, simulation results show that interparticle bonding largely decelerates the erosion process and causes a much lower erosion rate. To further the understanding of soil surface erosion under turbulent flow, the “k–ε” turbulence model has been successfully implemented for the fluid phase. Comparison between the laminar model and the turbulence model shows turbulence significantly accelerates the erosion process.