bluuebunny/crossref_metadata_2025 huggingface dataset:
Prevalence and risk factors for development of hemorrhagic gastro‐intestinal disease in veterinary intensive care units in the United Kingdom
Authors: Swann James W. , Maunder Christina L. , Roberts Emma , McLauchlan Gerard , Adamantos Sophie
Published: December 2015

Objective

To determine the prevalence of hemorrhagic gastro‐intestinal (GI) disease developing in dogs and cats admitted for management of non‐GI disease in veterinary intensive care units (ICUs).

Design

Retrospective study of animals presented between October 2012 and July 2013.

Setting

Three ICUs located in veterinary teaching hospitals in the United Kingdom.

Animals

Dogs (n = 272) and cats (n = 94) were consecutively enrolled from 3 ICUs if they were hospitalized in the unit for at least 24 hours. Cases were excluded if they had hemorrhagic GI disease in the 48‐hour period before presentation or in the 24‐hour period after admission. Cases were also excluded if they suffered skull fracture, epistaxis, or hemoptysis, if they underwent surgical procedures of the GI or upper respiratory tracts, or if they were presented for management of GI disease.

Measurements and Main Results

Hemorrhagic GI disease was observed in dogs at all 3 units, but at different rates (Center 1: 10.3%, Center 2: 4.8%, Center 3: 2.2%). Hemorrhagic GI disease was not observed in cats at any of the participating centers. Construction of a multivariable logistic regression model revealed that serum albumin concentration, administration of prophylactic gastro‐protectant drugs, and institution were significantly associated with the development of hemorrhagic GI disease in dogs. Development of hemorrhagic GI disease and placement of a feeding tube were significantly associated with mortality during the period of hospitalization in dogs. Thirty‐seven (13.6%) dogs and 12 (12.8%) cats died or were euthanized while hospitalized, with a higher mortality rate (42.1%) in dogs with hemorrhagic GI disease.

Conclusions

Hemorrhagic GI disease does develop in dogs hospitalized for management of non‐GI disease, but this phenomenon was not observed in cats. Development of hemorrhagic GI disease appeared to have a significant impact on survival in veterinary ICUs.
New considerations on the phylogeny of cyrtophorian ciliates (Protozoa, Ciliophora): expanded sampling to understand their evolutionary relationships
Authors: Chen Xiao , Pan Hongbo , Huang Jie , Warren Alan , Al‐Farraj Saleh A. , Gao Shan
Published: December 2015

To rationalize the confusing relationships among the cyrtophorian ciliates, we expanded the taxon sampling by sequencing the small subunit ribosomal RNA (SSU rRNA) gene of representatives of 12 genera (20 species, 23 new sequences). The SSU rRNA sequences of Spirodysteria, Agnathodysteria, Brooklynella and Odontochlamys are reported for the first time. Phylogenetic trees were constructed, and secondary structures of variable region 4 (V4) of all genera for which SSU rRNA gene sequence data are available were predicted. The results indicate that (i) Brooklynella is likely an intermediate taxon between Dysteriidae and Hartmannulidae; (ii) the genus Dysteria is paraphyletic with Spirodysteria and Mirodysteria nested within it; (iii) the genus Agnathodysteria is well separated from Dysteria based on both molecular and morphological data; and (iv) Trithigmostoma is a basal genus of Chilodonellidae, based on both the morphological and molecular data.
Do antioxidant supplements interfere with skeletal muscle adaptation to exercise training?
Authors: Merry Troy L. , Ristow Michael
Published: December 2015

A popular belief is that reactive oxygen species (ROS) and reactive nitrogen species (RNS) produced during exercise by the mitochondria and other subcellular compartments ubiquitously cause skeletal muscle damage, fatigue and impair recovery. However, the importance of ROS and RNS as signals in the cellular adaptation process to stress is now evident. In an effort to combat the perceived deleterious effects of ROS and RNS it has become common practice for active individuals to ingest supplements with antioxidant properties, but interfering with ROS/RNS signalling in skeletal muscle during acute exercise may blunt favourable adaptation. There is building evidence that antioxidant supplementation can attenuate endurance training‐induced and ROS/RNS‐mediated enhancements in antioxidant capacity, mitochondrial biogenesis, cellular defence mechanisms and insulin sensitivity. However, this is not a universal finding, potentially indicating that there is redundancy in the mechanisms controlling skeletal muscle adaptation to exercise, meaning that in some circumstances the negative impact of antioxidants on acute exercise response can be overcome by training. Antioxidant supplementation has been more consistently reported to have deleterious effects on the response to overload stress and high‐intensity training, suggesting that remodelling of skeletal muscle following resistance and high‐intensity exercise is more dependent on ROS/RNS signalling. Importantly there is no convincing evidence to suggest that antioxidant supplementation enhances exercise‐training adaptions. Overall, ROS/RNS are likely to exhibit a non‐linear (hormetic) pattern on exercise adaptations, where physiological doses are beneficial and high exposure (which would seldom be achieved during normal exercise training) may be detrimental.

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Research agenda for the built environment in Latin America
Authors: Murray Claudia Beatriz , Abiko Alex , Monetti Eliane , Peinado Ponton Javier
Published: December 2015

Este artículo divulga los resultados de una serie de seminarios interdisciplinares y multisectoriales de investigación que se enfocaron en los problemas actuales de una región en rápido crecimiento urbano. Se recogió información cualitativa sobre varias de las mayores economías de América Latina, se hicieron mesas redondas y talleres que incluían profesionales en ejercicio y funcionarios estatales. Los autores agruparon estas discusiones por temas y los enmarcaron en debates académicos contemporáneos. Tras estimar la aptitud de la teoría para responder en la práctica, el artículo concluye planteando cuatro áreas clave para seguir investigando, con el propósito final de incrementar el análisis académico capaz de informar mejor sobre las políticas de desarrollo de las economías emergentes.
Prospectiva estratégica para fortalecer un convenio docenciaservicio de enfermería
Authors: Montoya Restrepo Ivan , Montoya Luz Alexandra , Sánchez Herrera Beatriz
Published: December 2015

Objetivo: Implementar y evaluar la utilidad de la metodología prospectiva estratégica para respaldar el desarrollo de un convenio docencia-servicio entre el Instituto Nacional de Cancerología (INC) ESE y la Facultad de Enfermería de la Universidad Nacional de Colombia. Método: Ejercicio prospectivo estratégico con seguimiento de un año desarrollado como parte de un programa más amplio y que se desarrolló en tres fases: 1) análisis sobre la situación de enfermería en el INC; 2) desarrollo de un
taller para determinar el papel del Departamento de Enfermería dentro del INC, y 3) seguimiento de los resultados del taller por un año (24 de septiembre de 2012 a 24 de septiembre de 2013) para evaluar la utilidad de la metodología prospectiva estratégica como elemento de trabajo conjunto en el marco del convenio docencia-servicio. Resultados: Enfermería quiere un cambio que fortalezca su capacidad de cuidado
dentro del INC. La prospectiva facilitó la identificación de siete elementos estratégicos que incluyen el cuidado, la educación, la investigación, la sistematización, el modelo de gestión, el desarrollo del talento humano y la proyección social que, en conjunto, permitieron determinar el papel del Departamento de Enfermería dentro del INC, como se puede evidenciar en el seguimiento del convenio docente asistencial durante un año. Conclusiones: La metodología de prospectiva estratégica demostró ser un mecanismo útil, novedoso e importante para respaldar el convenio docencia-servicio. La revisión de logros y limitaciones permite avanzar en un trabajo conjunto con una visión compartida que fortalece a las partes interactuantes.
Utilización de Métodos Anticonceptivos en estudiantes de Enfermería
Authors: Covarrubias Esmeralda , Ramírez Villegas Raquel , Ramírez Villegas Raquel , Verde Flota Elsy Elizabeth de Jesús , Verde Flota Elsy Elizabeth de Jesús , Rivas Espinosa Juan Gabriel , Rivas Espinosa Juan Gabriel , Rivero Rodríguez Luis Fernando , Rivero Rodríguez Luis Fernando
Published: December 2015

Objetivo: Identificar el uso de métodos anticonceptivos como medida de prevención de infecciones de transmisión sexual (ITS) y embarazos no planeados, en estudiantes de la Licenciatura en Enfermería de una universidad pública de la Ciudad de México. Método: Estudio cuantitativo, descriptivo y transversal. Se realizó en una población total de 364 estudiantes, con una muestra de 71 universitarios, mayores de 18 años, de ambos sexos e inscritos en alguno de los últimos nueve módulos de la Licenciatura en Enfermería. Se utilizó un diseño de muestreo aleatorio por conglomerados y un instrumento cerrado para la obtención de datos. Se realizaron medidas de tendencia central para el análisis de datos. Resultados: Participó una mayor proporción de mujeres en comparación con los hombres (62 % y 38 %, respectivamente). La edad promedio fue de 22 años. El 80 % de los estudiantes declaró haber iniciado vida sexual, de los cuales el 82 % mencionó haber utilizado algún método anticonceptivo. El 56 % de los estudiantes que mencionó tener una vida sexual activa utilizó la anticoncepción de emergencia en el último año. Conclusiones: A pesar de estar involucrados en una carrera de la salud, los estudiantes no toman las medidas efectivas para evitar un embarazo no planeado y tampoco para prevenir una ITS. La adquisición de medidas de autocuidado requiere la elaboración de programas y estrategias que apoyen y combinen la sensibilidad, la educación y la consejería oportuna que permitan el conocimiento y la apropiación del cuerpo como espacio de cuidado.
Validez de dos instrumentos para medir la relación interpersonal de la enfermera con el paciente y su familia en la unidad de cuidado intensivo
Authors: Parrado lozano Yaneth Mercedes , Sáenz Montoya Ximena , Soto Lesmes Virginia Inés , Guáqueta Parada Sandra Rocío , Amaya Rey Pilar , Caro Castillo Clara Virginia , Parra Vargas Myriam , Triana Restrepo Martha Cecilia
Published: December 2015

Objetivo: Construir, refinar, validar facialmente y de contenido dos instrumentos para medir la relación interpersonal enfermera-familia y enfermera-paciente adulto en la unidad de cuidado intensivo (UCI). Método: Estudio metodológico de abordaje cuantitativo, realizado por fases, para el diseño, validación facial, de contenido y refinamiento
de dos instrumentos. Se consideraron los criterios de redacción, gramática, cohesión y coherencia en la validez facial, y la pertinencia y concordancia de cada ítem en la validez de contenido. Resultados: Dos instrumentos; valoración de la relación interpersonal enfermera-paciente en la UCI (VRIEP-UCI) y valoración de la relación interpersonal enfermera-familia o acompañante del paciente en la UCI (VRIEF-UCI),
instrumentos a los cuales se les realizó validación facial mediante el juicio de 7 expertas, y de contenido mediante el coeficiente de concordancia de Kappa, superior a 0,50 con una fuerza de concordancia moderada según Landis y koch. Esto permitió ajuste en su diseño y refinamiento con mejor seguridad y exactitud. Conclusión: Esta investigación aporta dos instrumentos diseñados, validados y estructurados para la práctica del cuidado de enfermería en la UCI con población colombiana adulta, que
permiten crear evidencia al valorar en el cuidado la relación interpersonal entre la enfermera y el paciente, y entre la enfermera y la familia del paciente.
Estimation of Collapse Load for Thin-Walled Rectangular Tubes Under Bending
Authors: Chen D. H. , Masuda K.
Published: December 2015

In two recent papers, the authors investigated the bending collapse load of rectangular tubes consisting of a perfectly elastoplastic material. From these investigations, it is found that the collapse may also occur due to the buckling of web in a rectangular tube under bending, when the tube has a cross section with a large aspect ratio of web to flange b/a. In order to evaluate the collapse load of such tubes under bending, the effective width concept given by Rusch and Lindner for a plate compressed with stress gradient was used to calculate the postbuckling strength of the tube web. However, in the solution of Rusch and Lindner, the plate is supported at only one longitudinal edge with the other longitudinal edge being free. This boundary condition is obviously different from that of the tube web. This paper complements the previous work by addressing the postbuckling strength of the web under stress gradients. The postbuckling strength of the web under stress gradients is also calculated using the effective width concept given in AS/NZS 4600 standard and North American specification (NAS) for a plate compressed with stress gradient and supported at both two longitudinal edges. Moreover, the web slenderness also affects the condition for reaching cross-sectional fully plastic yielding when the web is wider. A new method is proposed to predict the maximum moment considering the effect of web slenderness on the cross-sectional fully plastic yielding. The validity of the collapse load estimation is checked by the results of FEM (finite element method) numerical analysis.
Generalized Component Mode Synthesis for the Spatial Motion of Flexible Bodies With Large Rotations About One Axis1
Authors: Ziegler Pascal , Humer Alexander , Pechstein Astrid , Gerstmayr Johannes
Published: December 2015

In industrial practice, the floating frame of reference formulation (FFRF)—often combined with the component mode synthesis (CMS) in order to reduce the number of flexible degrees-of-freedom—is the common approach to describe arbitrarily shaped bodies in flexible multibody systems. Owed to the relative formulation of the flexible deformation with respect to the reference frame, the equations of motion show state-dependent nonconstant inertia terms. Such relative description, however, comes along with considerable numerical costs, since both the mass matrix and gyroscopic forces, i.e., the quadratic velocity vector, need to be evaluated in every integration step. The state dependency of the inertia terms can be avoided by employing an alternative formulation based on the mode shapes as in the classical CMS approach. In this approach, which is referred to as generalized component mode synthesis (GCMS), the total (absolute) displacements are approximated directly. Consequently, the mass matrix is constant, no quadratic velocity vector appears, and the stiffness matrix is a corotated but otherwise constant matrix. In order to represent the same flexible deformation as in the classical FFRF-based CMS, however, a comparatively large number of degrees-of-freedom is required. The approach described in the present paper makes use of the fact that a majority of components in technical systems are constrained to motions showing large rotations only about a single spatially fixed axis. For this reason, the GCMS is adapted for multibody systems that are subjected to small flexible deformations and undergo a rigid body motion showing large translations, large rotations about one axis, but small rotations otherwise. Thereby, the number of shape functions representing the flexible deformation is reduced, which further increases numerical efficiency compared to the original GCMS formulation for arbitrary rotations.
Comparison of the Three-Dimensional Boundary Layer on Flat Versus Contoured Turbine Endwalls
Authors: Lynch Stephen P. , Thole Karen A.
Published: December 2015

The boundary layer on the endwall of an axial turbomachine passage is influenced by streamwise and cross-stream pressure gradients, as well as a large streamwise vortex, that develop in the passage. These influences distort the structure of the boundary layer and result in heat transfer and friction coefficients that differ significantly from simple two-dimensional boundary layers. Three-dimensional contouring of the endwall has been shown to reduce the strength of the large passage vortex and reduce endwall heat transfer, but the mechanisms of the reductions on the structure of the endwall boundary layer are not well understood. This study describes three-component measurements of mean and fluctuating velocities in the passage of a turbine blade obtained with a laser Doppler velocimeter (LDV). Friction coefficients obtained with the oil film interferometry (OFI) method were compared to measured heat transfer coefficients. In the passage, the strength of the large passage vortex was reduced with contouring. Regions where heat transfer was increased by endwall contouring corresponded to elevated turbulence levels compared to the flat endwall, but the variation in boundary layer skew across the passage was reduced with contouring.
Build Direction Effects on Additively Manufactured Channels
Authors: Snyder Jacob C. , Stimpson Curtis K. , Thole Karen A. , Mongillo Dominic
Published: December 2015

With the advance of direct metal laser sintering (DMLS), also generically referred to as additive manufacturing (AM), novel geometric features of internal channels for gas turbine cooling can be achieved beyond those features using traditional manufacturing techniques. There are many variables, however, in the DMLS process that affect the final quality of the part. Of most interest to gas turbine heat transfer designers are the roughness levels and tolerance levels that can be held for the internal channels. This study investigates the effect of DMLS build direction and channel shape on the pressure loss and heat transfer measurements of small-scale channels. Results indicate that differences in pressure loss occur between the test cases with differing channel shapes and build directions, while little change is measured in heat transfer performance.
Identification of Nonlinear Viscoelastic Models of Flexible Polyurethane Foam From Uniaxial Compression Data
Authors: Azizi Yousof , Davies Patricia , Bajaj Anil K.
Published: December 2015

Flexible polyethylene foam is used in many engineering applications. It exhibits nonlinear and viscoelastic behavior which makes it difficult to model. To date, several models have been developed to characterize the complex behavior of foams. These attempts include the computationally intensive microstructural models to continuum models that capture the macroscale behavior of the foam materials. In this research, a nonlinear viscoelastic model, which is an extension to previously developed models, is proposed and its ability to capture foam response in uniaxial compression is investigated. It is hypothesized that total stress can be decomposed into the sum of a nonlinear elastic component, modeled by a higher-order polynomial, and a nonlinear hereditary type viscoelastic component. System identification procedures were developed to estimate the model parameters using uniaxial cyclic compression data from experiments conducted at six different rates. The estimated model parameters for individual tests were used to develop a model with parameters that are a function of strain rates. The parameter estimation technique was modified to also develop a comprehensive model which captures the uniaxial behavior of all six tests. The performance of this model was compared to that of other nonlinear viscoelastic models.
Measurement of High-Performance Thermal Interfaces Using a Reduced Scale Steady-State Tester and Infrared Microscopy
Authors: Smith Andrew N. , Jankowski Nicholas R. , Boteler Lauren M.
Published: December 2015

Thermal interface materials (TIMs) have reached values approaching the measurement uncertainty of standard ASTM D5470 based testers of approximately ±1 × 10−6 m2 K/W. This paper presents a miniature ASTM-type steady-state tester that was developed to address the resolution limits of standard testers by reducing the heat meter bar thickness and using infrared (IR) thermography to measure the temperature gradient along the heat meter bar. Thermal interfacial resistance measurements on the order of 1 × 10−6 m2 K/W with an order of magnitude improvement in the uncertainty of ±1 × 10−7 m2 K/W are demonstrated. These measurements were made on several TIMs with a thermal resistance as low as 1.14 × 10−6 m2 K/W.
Convective Heat Transfer in Elliptical Microchannels Under Slip Flow Regime and H1 Boundary Conditions
Authors: Vocale Pamela , Morini Gian Luca , Spiga Marco
Published: December 2015

In this work, hydrodynamically and thermally fully developed gas flow through elliptical microchannels is numerically investigated. The Navier–Stokes and energy equations are solved by considering the first-order slip flow boundary conditions and by assuming that the wall heat flux is uniform in the axial direction, and the wall temperature is uniform in the peripheral direction (i.e., H1 boundary conditions). To take into account the microfabrication of the elliptical microchannels, different heated perimeter lengths are analyzed along the microchannel wetted perimeter. The influence of the cross section geometry on the convective heat transfer coefficient is also investigated by considering the most common values of the elliptic aspect ratio, from a practical point of view. The numerical results put in evidence that the Nusselt number is a decreasing function of the Knudsen number for all the considered configurations. On the contrary, the role of the cross section geometry in the convective heat transfer depends on the thermal boundary condition and on the rarefaction degree. With the aim to provide a useful tool for the designer, a correlation that allows evaluating the Nusselt number for any value of aspect ratio and for different working gases is proposed.
A Subscale Experimental Test Method to Characterize Extrusion-Based Elastomer Seals
Authors: Jayanath Shiyan , Achuthan Ajit , Mashue Aaron , Huang Ming
Published: December 2015

Extrusion-based elastomer seals are used in many applications, such as the seal in a variable bore ram valve used in offshore oil and gas drilling. Performing full-scale closing pressure experiments of such valves to characterize the seal performance and material failure of elastomer, especially under various temperature conditions, are quite expensive and time consuming. Conversely, simple coupon tests to characterize the elastomer mechanical properties and failure do not capture the complex deformation associated with the extrusion and subsequent sealing type that these materials undergo in the valves. In view of this, a simple subscale experimental test method capable of simulating the extrusion and sealing type deformation is developed. The extrusion and sealing deformation are realized by bonding the rectangular elastomer sample to metal pieces on top and bottom surfaces, and then compressing the sample in the vertical direction, while the deformation of the three lateral surfaces is kept constrained. As a result, sample deforms and extrudes out of the front surface, eventually forming the seal against a flat rigid metal plate placed at an appropriate distance. Simple scaling rules to determine the appropriate sample size and initial sealing gap, equivalent to the full-scale valve in terms of similar strain conditions, are derived and then verified using finite element analysis (FEA). Finally, the experimental test method is demonstrated by characterizing the contact pressure of nitrile (NBR) samples under different operating temperatures, ranging from 21 °C to 160 °C using pressure-sensitive film sensor.
Absorption Spectra and Electron-Vibration Coupling of Ti:Sapphire From First Principles
Authors: Bao Hua , Ruan Xiulin
Published: December 2015

First-principles calculations are performed to study the absorption spectra and electron-vibration coupling of titanium-doped sapphire (Ti:Al2O3). Geometry optimization shows a local structure relaxation after the doping of Ti. Electronic band structure calculation shows that five additional dopant energy bands are observed around the band gap of Al2O3, and are attributed to the five localized d orbitals of the Ti dopant. The optical absorption spectra are then predicted by averaging the oscillator strength during a 4 ps first-principles molecular dynamics (MD) trajectory, and the spectra agree well with the experimental results. Electron-vibration coupling is further investigated by studying the response of the ground and excited states to the Eg vibrational mode, for which a configuration coordinate diagram is obtained. Stokes shift effect is observed, which confirms the red shift of emission spectra of Ti:sapphire. This work offers a quantitative understanding of the optical properties and crystal-field theory of Ti-doped sapphire. The first-principles calculation framework developed here can also be followed to predict the optical properties and study the electron-vibration coupling in other doped materials.
Experimental Approach of Measuring Thermal Properties for Ecological Materials Based on Additives Cork or Wool and Illite
Authors: Mounir Soumia , Khabbazi Abdelhamid , Maaloufa Youssef , Khaldoun Asmae , El Hamdouni Yassine
Published: December 2015

This work is a contribution to understand the thermal properties of Illite with ecological additives granular presented by cork or fiber by wool in order to use those composites in building construction, the composites are air dried. Knowing that the clay composites were studied before, a series of experimental studies confirmed by complete theoretical models were conducted using different methods such as the asymmetrical hot plate in transient, steady-state regime, and flash methods in order to determine the thermal properties of the composite clay with ecological additives. Also, an analysis of sensibility of thermal properties was studied. For this purpose, a thermal characterization using hot plate and flash methods confirmed by complete theoretical models was studied. Then an analysis of the physicochemical characterization of clay was done to determine its characteristics. Finally, a study of depth heat flow diffusion was conducted to see the effect of additives on penetrating exterior heat flow inside house.
A Dynamic Model for Double-Planet Planetary Gearsets
Authors: Fyler Dylan C. , Inalpolat Murat
Published: December 2015

In this study, a two-dimensional (2D), steady-state, discrete dynamic model of a double-planet planetary gearset is proposed. The dynamic model is generalized such that it can consist of N number of planet branches and can operate under any operating conditions (load and speed). The contact between each external to external and external to internal gear pair is modeled to obtain stiffnesses and mesh displacement excitations using a generalized load distribution model. The natural modes are computed by solving the corresponding eigenvalue problem. The forced vibration response to gear mesh excitations is obtained by applying the modal summation technique. The model is capable of predicting gear mesh dynamic load and dynamic transmission error spectra for each gear mesh, dynamic bearing load spectra for each bearing as well as gear body dynamic displacements. Forced vibration response of an example system that consists of three double-planet branches is studied to demonstrate the influence of some of the key design parameters.
Predicting Subjective Responses From Human Motion: Application to Vehicle Ingress Assessment
Authors: Masoud Hadi I. , Reed Matthew P. , Paynabar Kamran , Wang Nanxin , (Judy) Jin Jionghua , Wan Jian , Kozak Ksenia K. , Gomez-Levi Gianna
Published: December 2015

The ease of entering a car is one of the important ergonomic factors that car manufacturers consider during the process of car design. This has motivated many researchers to investigate factors that affect discomfort during ingress. The patterns of motion during ingress may be related to discomfort, but the analysis of motion is challenging. In this paper, a modeling framework is proposed to use the motions of body landmarks to predict subjectively reported discomfort during ingress. Foot trajectories are used to identify a set of trials with a consistent right-leg-first strategy. The trajectories from 20 landmarks on the limbs and torso are parameterized using B-spline basis functions. Two group selection methods, group non-negative garrote (GNNG) and stepwise group selection (SGS), are used to filter and identify the trajectories that are important for prediction. Finally, a classification and prediction model is built using support vector machine (SVM). The performance of the proposed framework is then evaluated against simpler, more common prediction models.
Selective Laser Melting Additive Manufacturing of Hard-to-Process Tungsten-Based Alloy Parts With Novel Crystalline Growth Morphology and Enhanced Performance
Authors: Gu Dongdong , Dai Donghua , Chen Wenhua , Chen Hongyu
Published: December 2015

Selective laser melting (SLM) additive manufacturing (AM) of hard-to-process W-based parts with the addition of 2.5 wt.% TiC was performed using a new metallurgical processing mechanism with the complete melting of the high-melting-point powder. The influence of SLM processing parameters, especially laser scan speed and attendant laser fluence (LF), on densification behavior, microstructural development, and hardness/wear performance of SLM-processed W-based alloy parts was disclosed. The densification response of SLM-processed W-based parts decreased both at a low LF of 10.7 J/mm2, caused by the limited SLM working temperature and wetting characteristics of the melt, and at an excessively high LF of 64 J/mm2, caused by the significant melt instability and resultant balling effect and microcracks formation. The laser-induced complete melting/solidification mechanism contributed to the solid solution alloying of Ti and C in W matrix and the development of unique microstructures of SLM-processed W-based alloy parts. As the applied LF increased by lowering laser scan speed, the morphologies of W-based crystals in SLM-processed alloy parts experienced a successive change from the cellular crystal to the cellular dendritic crystal and, finally, to the equiaxed dendritic crystal, due to an elevated constitutional undercooling and a decreased thermal undercooling. The optimally prepared W-based alloy parts by SLM had a nearly full densification rate of 97.8% theoretical density (TD), a considerably high microhardness of 809.9 HV0.3, and a superior wear/tribological performance with a decreased coefficient of friction (COF) of 0.41 and a low wear rate of 5.73 × 10−7 m3/(N m), due to the combined effects of the sufficiently high densification and novel crystal microstructures of SLM-processed W-based alloy parts.
A Study of Build Edge Profile for Prediction of Surface Roughness in Fused Deposition Modeling
Authors: Taufik Mohammad , Jain Prashant K.
Published: December 2015

Surface roughness prediction studies in fused deposition modeling (FDM) process are usually based on a perimeter profile of each deposited layer. This study categorizes three types of build edge profile composed of perimeter, raster, and combination of both layer deposition patterns, which have been considered to reduce the predictive error of roughness models. Furthermore, an innovative approach based on combination of theoretical and empirical methods is used to analyze and predict the randomness in the geometry of build edge profiles. The same methodology is used to model the roughness profile and surface roughness behaviors. The proposed models have been tested for robustness against varying build orientations and with data available in the existing literature. The robustness of the proposed models is compared with the existing models. The results clearly demonstrate that the proposed models are very useful in reducing prediction errors.
The Foldability of Cylindrical Foldable Structures Based on Rigid Origami
Authors: Cai Jianguo , Zhang Yuting , Xu Yixiang , Zhou Ya , Feng Jian
Published: December 2015

Foldable structures, a new kind of space structures developed in recent decades, can be deployed gradually to a working configuration and also can be folded for transportation, thus have potentially broad application prospects in the fields of human life, military, aerospace, building structures, and so on. Combined with the technology of origami folding, foldable structures derive more diversified models, and the foldable structures in cylindrical shape are mainly studied in this paper. Some researchers use the theory of quaternion representing spatial fixed-point rotation and construct the rotating vector model to obtain the quaternion rotation sequence method (QRS method) analyzing origami, but the method is very limited and not suitable for the cylindrical foldable structures. In order to solve the problem, a new method is developed, which combines the QRS method and the dual quaternion method. After analyzing the folding angle via the QRS method for multivertex crease system and calculating the coordinates of all vertices via the dual quaternion, the rigid foldability can be checked. Finally, two examples are carried out to confirm validity and versatility of the method.
An Experimental Model Study of Steam Generator Tube Loading During a Sudden Depressurization
Authors: Hamouda Ouajih , Weaver David S. , Riznic Jovica
Published: December 2015

This paper presents the results of an experimental model study of the transient loading of steam generator tubes during a postulated main steam line break (MSLB) accident in a nuclear power plant. The problem involves complex transient two-phase flow dynamics and fluid-structural loading processes. A better understanding of this phenomenon will permit the development of improved design tools to ensure steam generator tube integrity. The pressure and temperature were measured upstream and downstream of a sectional model of a tube bundle in cross-flow, and the transient tube loads were directly measured using dynamic piezoelectric load cells. High-speed videos were taken to observe and better understand the flow phenomena causing the tube loading. The working fluid was R-134a and the tube bundle was a normal triangular array with a pitch ratio of 1.36. The flow through the bundle was choked for the majority of the transient. The transient tube loading is explained in terms of the associated fluid mechanics. An empirical model is developed that enables the prediction of the maximum tube loads once the pressure drop is known.
Experimental and Numerical Investigation of the Flow in a Low-Pressure Industrial Steam Turbine With Part-Span Connectors
Authors: Häfele Markus , Traxinger Christoph , Grübel Marius , Schatz Markus , Vogt Damian M. , Drozdowski Roman
Published: December 2015

An experimental and numerical study on the flow in a three-stage low-pressure (LP) industrial steam turbine is presented and analyzed. The investigated LP section features conical friction bolts in the last and a lacing wire in the penultimate rotor blade row. These part-span connectors (PSC) allow safe turbine operation over an extremely wide range and even in blade resonance condition. However, additional losses are generated which affect the performance of the turbine. In order to capture the impact of PSCs on the flow field, extensive measurements with pneumatic multihole probes in an industrial steam turbine test rig have been carried out. State-of-the-art three-dimensional computational fluid dynamics (CFD) applying a nonequilibrium steam (NES) model is used to examine the aerothermodynamic effects of PSCs on the wet steam flow. The vortex system in coupled LP steam turbine rotor blading is discussed in this paper. In order to validate the CFD model, a detailed comparison between measurement data and steady-state CFD results is performed for several operating conditions. The investigation shows that the applied one-passage CFD model is able to capture the three-dimensional flow field in LP steam turbine blading with PSC and the total pressure reduction due to the PSC with a generally good agreement to measured values and is therefore sufficient for engineering practice.
Microstructural, nanomechanical, and microtribological properties of Pb thin films prepared by pulsed laser deposition and thermal evaporation techniques
Authors: Broitman Esteban , Flores-Ruiz Francisco J. , Di Giulio Massimo , Gontad Francisco , Lorusso Antonella , Perrone Alessio
Published: December 2015

In this work, the authors compare the morphological, structural, nanomechanical, and microtribological properties of Pb films deposited by thermal evaporation (TE) and pulsed laser deposition (PLD) techniques onto Si (111) substrates. Films were investigated by scanning electron microscopy, surface probe microscopy, and x-ray diffraction in θ-2θ geometry to determine their morphology, root-mean-square (RMS) roughness, and microstructure, respectively. TE films showed a percolated morphology with densely packed fibrous grains while PLD films had a granular morphology with a columnar and tightly packed structure in accordance with the zone growth model of Thornton. Moreover, PLD films presented a more polycrystalline structure with respect to TE films, with RMS roughness of 14 and 10 nm, respectively. Hardness and elastic modulus vary from 2.1 to 0.8 GPa and from 14 to 10 GPa for PLD and TE films, respectively. A reciprocal friction test has shown that PLD films have lower friction coefficient and wear rate than TE films. Our study has demonstrated for first time that, at the microscale, Pb films do not show the same simple lubricious properties measured at the macroscale.
Observation of negative differential resistance in GaN-based multiple-quantum-well light-emitting diodes
Authors: Yang J. , Zhao D. G. , Jiang D. S. , Chen P. , Zhu J. J. , Liu Z. S. , Le L. C. , Li X. J. , He X. G. , Liu J. P. , Zhang L. Q. , Yang H.
Published: December 2015

Anomalous current–voltage behaviors, such as negative differential resistance (NDR) and current hysteresis, are observed in the room-temperature current–voltage (I-V) curves of InGaN/GaN multiple-quantum-well light-emitting diodes. It is found that the NDR can be observed in the positive voltage range of the I-V curve only when the samples are pretreated with a negative voltage before sweeping, and the NDR disappears permanently after an over-current treatment. The dependence of the NDR upon the negative voltage and sweeping conditions leads to the conclusion that a variation of the charging state of the defect-induced hole traps is responsible for the anomalous I-V behaviors. Therefore, NDR is excluded as a feature of the tunneling transport mechanism, especially in GaN-based devices with a high defect density.
High Prevalence of SXT/R391-Related Integrative and Conjugative Elements Carrying
bla
CMY-2
in Proteus mirabilis Isolates from Gulls in the South of France
Authors: Aberkane Salim , Compain Fabrice , Decré Dominique , Dupont Chloé , Laurens Chrislène , Vittecoq Marion , Pantel Alix , Solassol Jérôme , Carrière Christian , Renaud François , Brieu Nathalie , Lavigne Jean-Philippe , Bouzinbi Nicolas , Ouédraogo Abdoul-Salam , Jean-Pierre Hélène , Godreuil Sylvain
Published: December 2015

The genetic structures involved in the dissemination of
bla
CMY-2
carried by
Proteus mirabilis
isolates recovered from different gull species in the South of France were characterized and compared to clinical isolates.
bla
CMY-2
was identified in
P. mirabilis
isolates from 27/93 yellow-legged gulls and from 37/65 slender-billed gulls. It was carried by a conjugative SXT/R391-like integrative and conjugative element (ICE) in all avian strains and in 3/7 human strains. Two clinical isolates had the same genetic background as six avian isolates.
Bacteriophage Combinations Significantly Reduce Clostridium difficile Growth
In Vitro
and Proliferation
In Vivo
Authors: Nale Janet Y. , Spencer Janice , Hargreaves Katherine R. , Buckley Anthony M. , Trzepiński Przemysław , Douce Gillian R. , Clokie Martha R. J.
Published: December 2015

The microbiome dysbiosis caused by antibiotic treatment has been associated with both susceptibility to and relapse of
Clostridium difficile
infection (CDI). Bacteriophage (phage) therapy offers target specificity and dose amplification
in situ
, but few studies have focused on its use in CDI treatment. This mainly reflects the lack of strictly virulent phages that target this pathogen. While it is widely accepted that temperate phages are unsuitable for therapeutic purposes due to their transduction potential, analysis of seven
C. difficile
phages confirmed that this impact could be curtailed by the application of multiple phage types. Here, host range analysis of six myoviruses and one siphovirus was conducted on 80 strains representing 21 major epidemic and clinically severe ribotypes. The phages had complementary coverage, lysing 18 and 62 of the ribotypes and strains tested, respectively. Single-phage treatments of ribotype 076, 014/020, and 027 strains showed an initial reduction in the bacterial load followed by the emergence of phage-resistant colonies. However, these colonies remained susceptible to infection with an unrelated phage. In contrast, specific phage combinations caused the complete lysis of
C. difficile
in vitro
and prevented the appearance of resistant/lysogenic clones. Using a hamster model, the oral delivery of optimized phage combinations resulted in reduced
C. difficile
colonization at 36 h postinfection. Interestingly, free phages were recovered from the bowel at this time. In a challenge model of the disease, phage treatment delayed the onset of symptoms by 33 h compared to the time of onset of symptoms in untreated animals. These data demonstrate the therapeutic potential of phage combinations to treat CDI.
Towards Rational Dosing Algorithms for Vancomycin in Neonates and Infants Based on Population Pharmacokinetic Modeling
Authors: Janssen Esther J. H. , Välitalo Pyry A. J. , Allegaert Karel , de Cock Roosmarijn F. W. , Simons Sinno H. P. , Sherwin Catherine M. T. , Mouton Johan W. , van den Anker Johannes N. , Knibbe Catherijne A. J.
Published: December 2015

Because of the recent awareness that vancomycin doses should aim to meet a target area under the concentration-time curve (AUC) instead of trough concentrations, more aggressive dosing regimens are warranted also in the pediatric population. In this study, both neonatal and pediatric pharmacokinetic models for vancomycin were externally evaluated and subsequently used to derive model-based dosing algorithms for neonates, infants, and children. For the external validation, predictions from previously published pharmacokinetic models were compared to new data. Simulations were performed in order to evaluate current dosing regimens and to propose a model-based dosing algorithm. The AUC/MIC over 24 h (AUC
24
/MIC) was evaluated for all investigated dosing schedules (target of >400), without any concentration exceeding 40 mg/liter. Both the neonatal and pediatric models of vancomycin performed well in the external data sets, resulting in concentrations that were predicted correctly and without bias. For neonates, a dosing algorithm based on body weight at birth and postnatal age is proposed, with daily doses divided over three to four doses. For infants aged <1 year, doses between 32 and 60 mg/kg/day over four doses are proposed, while above 1 year of age, 60 mg/kg/day seems appropriate. As the time to reach steady-state concentrations varies from 155 h in preterm infants to 36 h in children aged >1 year, an initial loading dose is proposed. Based on the externally validated neonatal and pediatric vancomycin models, novel dosing algorithms are proposed for neonates and children aged <1 year. For children aged 1 year and older, the currently advised maintenance dose of 60 mg/kg/day seems appropriate.
The Cholestanol-Conjugated Sulfated Oligosaccharide PG545 Disrupts the Lipid Envelope of Herpes Simplex Virus Particles
Authors: Said Joanna S. , Trybala Edward , Görander Staffan , Ekblad Maria , Liljeqvist Jan-Åke , Jennische Eva , Lange Stefan , Bergström Tomas
Published: December 2015

Herpes simplex virus (HSV) and many other viruses, including HIV, initiate infection of host cells by binding to glycosaminoglycan (GAG) chains of cell surface proteoglycans. Although GAG mimetics, such as sulfated oligo- and polysaccharides, exhibit potent antiviral activities in cultured cells, the prophylactic application of these inhibitors as vaginal microbicides failed to protect women upon their exposure to HIV. A possible explanation for this failure is that sulfated oligo- and polysaccharides exhibit no typical virucidal activity, as their interaction with viral particles is largely electrostatic and reversible and thereby vulnerable to competition with GAG-binding proteins of the genital tract. Here we report that the cholestanol-conjugated sulfated oligosaccharide PG545, but not several other sulfated oligosaccharides lacking this modification, exhibited virucidal activity manifested as disruption of the lipid envelope of HSV-2 particles. The significance of the virus particle-disrupting activity of PG545 was also demonstrated in experimental animals, as this compound, in contrast to unmodified sulfated oligosaccharide, protected mice against genital infection with HSV-2. Thus, PG545 offers a novel prophylaxis option against infections caused by GAG-binding viruses.
Amikacin Pharmacokinetics/Pharmacodynamics in a Novel Hollow-Fiber Mycobacterium abscessus Disease Model
Authors: Ferro Beatriz E. , Srivastava Shashikant , Deshpande Devyani , Sherman Carleton M. , Pasipanodya Jotam G. , van Soolingen Dick , Mouton Johan W. , van Ingen Jakko , Gumbo Tawanda
Published: December 2015

The treatment of pulmonary
Mycobacterium abscessus
disease is associated with very high failure rates and easily acquired drug resistance. Amikacin is the key drug in treatment regimens, but the optimal doses are unknown. No good preclinical model exists to perform formal pharmacokinetics/pharmacodynamics experiments to determine these optimal doses. We developed a hollow-fiber system model of
M. abscessus
disease and studied amikacin exposure effects and dose scheduling. We mimicked amikacin human pulmonary pharmacokinetics. Both amikacin microbial kill and acquired drug resistance were linked to the peak concentration-to-MIC ratios; the peak/MIC ratio associated with 80% of maximal kill (EC
80
) was 3.20. However, on the day of the most extensive microbial kill, the bacillary burden did not fall below the starting inoculum. We performed Monte Carlo simulations of 10,000 patients with pulmonary
M. abscessus
infection and examined the probability that patients treated with one of 6 doses from 750 mg to 4,000 mg would achieve or exceed the EC
80
. We also examined these doses for the ability to achieve a cumulative area under the concentration-time curve of 82,232 mg · h/liter × days, which is associated with ototoxicity. The standard amikacin doses of 750 to 1,500 mg a day achieved the EC
80
in ≤21% of the patients, while a dose of 4 g/day achieved this in 70% of the patients but at the cost of high rates of ototoxicity within a month or two. The susceptibility breakpoint was an MIC of 8 to 16 mg/liter. Thus, amikacin, as currently dosed, has limited efficacy against
M. abscessus
. It is urgent that different antibiotics be tested using our preclinical model and new regimens developed.