bluuebunny/crossref_metadata_2025 huggingface dataset:
Culture studies on early development of Lessonia trabeculata (Phaeophyceae, Laminariales): Seasonality and acclimation to light and temperature
Authors: Murúa Pedro , Westermeier Renato , Patiño David J. , Müller Dieter G.
Published: April 2013

Lessonia trabeculata is an important economic and ecological algal resource of Chile. Due to intense use in abalone and alginate industries, severe problems of over‐harvesting are emerging. We compared sporophyte‐initiation and ‐growth in two populations from northern and southern Chile (Bahía Inglesa and Maicolpué) under laboratory conditions. Irradiance and temperature were the most important factors affecting gametophyte development. Meiospores harvested in spring exhibited maximum reproductive and growth potential, while spores released during autumn were moribund, and died within a few days. In both study sites, we found evidence for acclimation: Meiospores collected in summer required higher levels of irradiance and temperature for maximum development than winter spores. Juvenile sporophytes from both localities responded similarly to temperature and/or irradiance. The best conditions for recruitment of sporophytes from both localities were 15°C and white fluorescent light of 40–70 μmol m−2 s−1. Although due to its low growth potential L. trabeculata is not a good candidate for mariculture, our results provide the necessary knowledge for laboratory‐based seedling production, which is needed for restoration and repopulation projects in damaged areas.
An Expected Consequence Approach to Route Choice in the Maritime Transportation of Crude Oil
Authors: Siddiqui Atiq , Verma Manish
Published: April 2013

Maritime transportation is the major conduit of international trade, and the primary link for global crude oil movement. Given the volume of oil transported on international maritime links, it is not surprising that oil spills of both minor and major types result, although most of the risk‐related work has been confined to the local settings. We propose an expected consequence approach for assessing oil‐spill risk from intercontinental transportation of crude oil that not only adheres to the safety guidelines specified by the International Maritime Organization but also outlines a novel technique that makes use of coarse global data to estimate accident probabilities. The proposed estimation technique, together with four of the most popular cost‐of‐spill models from the literature, were applied to study and analyze a realistic size problem instance. Numerical analyses showed that: a shorter route may not necessarily be less risky; an understanding of the inherent oil‐spill risk of different routes could potentially facilitate tanker routing decisions; and the associated negotiations over insurance premium between the transport company and the not‐for‐profit prevention and indemnity clubs. Finally, we note that only the linear model should be used with one of the three nonlinear cost‐of‐spill models for evaluating tanker routes.
Body Regard as a Moderator of the Relation between Emotion Dysregulation and Nonsuicidal Self‐Injury
Authors: Muehlenkamp Jennifer J. , Bagge Courtney L. , Tull Matthew T. , Gratz Kim L.
Published: April 2013

Despite research documenting a strong association between emotion dysregulation and nonsuicidal self‐injury (NSSI), the moderators of this association have received little attention. Thus, it remains unclear why some individuals with heightened emotion dysregulation engage in NSSI and others do not. Body regard (i.e., how one perceives, experiences, and cares for the body) may be one such moderator, explaining the risk for NSSI among some individuals with emotion dysregulation. The current study used structural equation modeling within a sample of 398 undergraduates (26% reporting NSSI, mean frequency = 25.16, SD = 40.5) to test the interactive effect of emotion dysregulation and body regard on NSSI frequency when controlling for negative affect and borderline personality disorder symptoms. The interaction model provided a strong fit to the data and showed that emotion regulation was associated with NSSI only when low levels of body regard were present. Results suggest that body regard may be important to understanding who engages in NSSI within the context of emotion dysregulation. Possible mechanisms underlying the interaction between body regard and emotion dysregulation are discussed along with treatment and prevention implications.
Identification of the novel HLA‐B*15:257 allele by polymerase chain reaction sequence‐based typing in a Chinese individual
Authors: Han Z.‐D. , Zhang W. , Zhu F.‐M. , He J. , Lv H.‐J.
Published: April 2013

HLA‐B*15:257 has one nucleotide change in exon 2 at position 232C>G from B*15:01:01:01.
Multiple joint metastasis of a transitional cell carcinoma in a dog
Authors: Colledge Sarah L. , Raskin Rose E. , Messick Joanne B. , Tiffany Reed L. , Wigle William L. , Balog Kelley A.
Published: April 2013

An 8‐year‐old castrated male hound mix was referred to the Purdue University Veterinary Teaching Hospital for severe lameness, pollakiuria, and dyschezia. On presentation, the dog was nonweight bearing on the right rear limb and the right carpus was diffusely swollen. Synovial fluid analysis from the right carpus revealed a population of epithelial cells displaying marked anisocytosis, anisokaryosis, multinucleation, and prominent, variably sized nucleoli. A metastatic carcinoma with presumed prostatic or urothelial origin was diagnosed based on cytomorphology. Subsequent cytologic evaluation of peripheral lymph nodes revealed the presence of a similar neoplastic population. The dog was euthanized and synovial fluid from both stifle joints, as well as impression smears of the prostate gland, were collected. Carcinoma cells were identified in each stifle joint and in the prostate gland. Immunocytochemistry was performed on synovial fluid smears from 2 of the joints (right stifle and right carpus) and on impression smears of the prostate gland. The neoplastic population in the joints and prostate gland showed strong immunoreactivity to uroplakin III, a urothelial marker, indicating metastasis of a transitional cell carcinoma to multiple joints. In addition, evidence for epithelial to mesenchymal transition was identified using cytokeratin, an epithelial marker, and vimentin, a mesenchymal marker. A necropsy was performed and histopathology confirmed the presence of metastatic transitional cell carcinoma in various tissues. This case illustrates the importance of considering metastatic disease when a patient is presented with severe lameness and joint pain, and the clinical utility of synovial fluid cytology for diagnosis of metastasis in these cases.
Adenosine A1 receptor activation mediates the developmental shift at layer 5 pyramidal cell synapses and is a determinant of mature synaptic strength
Authors: Kerr Michael I. , Wall Mark J. , Richardson Magnus J. E.
Published: April 2013

Key points

Neocortical layer 5 pyramidal cell synapses exhibit a developmental reduction in neurotransmitter release probability. Mature synapses are weaker, less reliable and show greater facilitation than immature connections.

Using paired intracellular recordings our study identifies the mechanism that mediates this developmental change as being due to an increased activation of presynaptic adenosine A1 receptors.

Unlike immature connections, which showed little A1 receptor activation, mature connections demonstrated a broad range of activation that was inversely correlated to mature synaptic strength.

We show that the functional efficacy of A1 receptors does not change over development and so our evidence points to concentrations of extracellular adenosine at synapses increasing locally over development.

The increased adenosine levels significantly affect synaptic efficacy suggesting that the emplacement of adenosine sources and sinks might be a novel mechanism for long‐term plasticity at layer 5 pyramidal cell synapses.

Abstract  During the first postnatal month glutamatergic synapses between layer 5 pyramidal cells in the rodent neocortex switch from an immature state exhibiting a high probability of neurotransmitter release, large unitary amplitude and synaptic depression to a mature state with decreased probability of release, smaller unitary amplitude and synaptic facilitation. Using paired recordings, we demonstrate that the developmental shift in release probability at synapses between rat somatosensory layer 5 thick‐tufted pyramidal cells is mediated by a higher and more heterogeneous activation of presynaptic adenosine A1 receptors. Immature synapses under control conditions exhibited distributions of coefficient of variation, failure rate and release probability that were almost coincident with the A1 receptor blocked condition; however, mature synapses under control conditions exhibited much broader distributions that spanned those of both the A1 receptor agonized and antagonized conditions. Immature and mature synapses expressed A1 receptors with no observable difference in functional efficacy and therefore the heterogeneous A1 receptor activation seen in the mature neocortex appears due to increased adenosine concentrations that vary between synapses. Given the central role demonstrated for A1 receptor activation in determining synaptic amplitude and the statistics of transmission between mature layer 5 pyramidal cells, the emplacement of adenosine sources and sinks near the synaptic terminal could constitute a novel form of long‐term synaptic plasticity.
Excitability and the safety margin in human axons during hyperthermia
Authors: Howells James , Czesnik Dirk , Trevillion Louise , Burke David
Published: April 2013

Key points

In six healthy subjects, the excitability of both motor and sensory axons was altered during hyperthermia, lowering their safety margin.

The results suggest that slow K+ channels play a significant role in these changes in axonal excitability during hyperthermia.

Inward rectification was reduced during hyperthermia, and the modelling suggests that the hyperpolarization‐activated cation current, Ih, was reduced, thus hampering its ability to counter activity‐dependent hyperpolarization.

Hyperthermia lowers the safety margin for action potential generation and propagation. Differences in their responses to hyperthermia suggest that motor axons undergo conduction block more readily than sensory axons during fever, particularly when the safety margin is already impaired.

Abstract  Hyperthermia challenges the nervous system's ability to transmit action potentials faithfully. Neuromuscular diseases, particularly those involving demyelination have an impaired safety margin for action potential generation and propagation, and symptoms are commonly accentuated by increases in temperature. The aim of this study was to examine the mechanisms responsible for reduced excitability during hyperthermia. Additionally, we sought to determine if motor and sensory axons differ in their propensity for conduction block during hyperthermia. Recordings of axonal excitability were performed at normal temperatures and during focal hyperthermia for motor and sensory axons in six healthy subjects. There were clear changes in excitability during hyperthermia, with reduced superexcitability following an action potential, faster accommodation to long‐lasting depolarization and reduced accommodation to hyperpolarization. A verified model of human motor and sensory axons was used to clarify the effects of hyperthermia. The hyperthermia‐induced changes in excitability could be accounted for by increasing the modelled temperature by 6°C (and adjusting the maximum conductances and activation kinetics according to their Q10 values; producing a 2 mV hyperpolarization of resting membrane potential), further hyperpolarizing the voltage dependence of Ih (motor, 11 mV; sensory, 7 mV) and adding a small depolarizing current at the internode (motor, 20 pA; sensory, 30 pA). The modelling suggested that slow K+ channels play a significant role in reducing axonal excitability during hyperthermia. The further hyperpolarization of the activation of Ih would limit its ability to counter the hyperpolarization produced by activity, thereby allowing conduction block to occur during hyperthermia.
Evaluation of Weld Root Failure Using Battelle Structural Stress Method
Authors: Hong Jeong K.
Published: April 2013

Weld related fatigue failure is one of the most common concerns in welded structures. From the fatigue design point of view, weld toe failure is preferable to weld root failure. Base plate thickness is a controlling parameter for weld toe failure, while weld metal size is a controlling parameter for weld root failure. However, controlling the weld metal size is not easy because the actual weld penetration and weld leg size vary along a weld and from weld to weld. Therefore, analyzing fatigue test data for weld root failure tends to enlarge scatter band due to variability in weld penetration and weld leg size when the nominal weld size is considered. The structural stress based weld fatigue master S-N curve adopted by 2007 ASME section VIII Div. 2 and new API 579/ASME FFS-1 was constructed by incorporating only clearly defined weld toe fatigue data. In this article, a simplified structural stress procedure was developed and a design master S-N curve for weld root failure was established based on the published fatigue test data. Consequently, the mean design master S-N curve for weld root failure is downshifted relative to the mean master S-N curve for weld toe failure, and has a wider scatter band. To be conservative, a crack path along weld throat is recommended for structural stress calculation. Also, the transverse shear stress effects on structural stress calculation can be ignored.
Hydroelasticity of Four Flexible Cylinders in Square Arrangement Subjected to Uniform Cross-Flow
Authors: Sanaati Bijan , Kato Naomi
Published: April 2013

Groups of cylinders can be found in many engineering fields such as marine and civil applications. The behavior of the group cylinders can be very complex because it undergoes the mutual effects of adjacent cylinders arranged in different positions. In this paper, the results of a study on the dynamics of a group of flexible cylinders in square arrangements along with a single (isolated) cylinder subjected to uniform cross-flow (CF) are presented. Four flexible cylinders of the same size, properties, and pretensions were tested in two configurations with different center-to-center separations. Reynolds number ranged from 1400 to 20,000 (subcritical regime).The parameter of reduced velocity reached up to 19. The aspect ratio of all the cylinders was 162 (length/diameter). Mass ratio (cylinders mass/displaced water) was 1.17. The amplitude ratio of the CF vibration of the downstream cylinders, hydrodynamic force coefficients including mean and fluctuating components of the drag and lift forces, tension variation of the downstream cylinder, and frequency responses in both CF and inline (IL) directions were analyzed. All the cylinders excited up to the second and fourth mode of vibrations for CF and IL directions, respectively. Mean drag coefficient of the upstream cylinders are almost twice those of the downstream cylinders. The mean lift coefficient is much higher for the upstream cylinders than the downstream cylinders with different positive and negative signs. The IL and CF frequencies of the downstream cylinders are lower than those of the upstream ones and the single cylinder.
Evaluation of Computational Fluid Dynamics and Coupled Fluid-Solid Modeling for a Direct Transfer Preswirl System
Authors: Javiya Umesh , Chew John , Hills Nick , Dullenkopf Klaus , Scanlon Timothy
Published: April 2013

The prediction of the preswirl cooling air delivery and disk metal temperature are important for the cooling system performance and the rotor disk thermal stresses and life assessment. In this paper, standalone 3D steady and unsteady computation fluid dynamics (CFD), and coupled FE-CFD calculations are presented for prediction of these temperatures. CFD results are compared with previous measurements from a direct transfer preswirl test rig. The predicted cooling air temperatures agree well with the measurement, but the nozzle discharge coefficients are under predicted. Results from the coupled FE-CFD analyses are compared directly with thermocouple temperature measurements and with heat transfer coefficients on the rotor disk previously obtained from a rotor disk heat conduction solution. Considering the modeling limitations, the coupled approach predicted the solid metal temperatures well. Heat transfer coefficients on the rotor disk from CFD show some effect of the temperature variations on the heat transfer coefficients. Reasonable agreement is obtained with values deduced from the previous heat conduction solution.
Reconditioning Technologies for Film Cooled Single Crystal Turbine Blading
Authors: Kissel Harald Peter , Shahin Hosam , Stankowski Alexander , Ambrosy Guenter , Bissig Hans
Published: April 2013

Increased availability, reliability, and performance combined with reduced maintenance costs are key factors for the success of gas turbine users. This paper focuses on the reconditioning of film cooled single crystal (SX) components used in the GT24 and GT26 fleet and the latest enabling technologies. The general reconditioning strategy is based on a thorough analysis of the accumulated field experience with SX parts and a controlled, stepwise introduction of new techniques. Reconditioning processes have been developed for different damage scenarios for components. This would include the most technically challenging SX “heavy” scope reconditioning. This paper gives an overview about the reconditioning sequence for SX components and some of its key process steps. As an example, the crack braze repair process is described in detail and several novel SX welding techniques for crack repairs and blade tip and temperature controlled leading edge wall thickness restoration are shown. This covers different processes such as tungsten inert gas (TIG) welding or laser metal forming (LMF) of SX components. During the last few years, highly automated production solutions and innovative production tools have been implemented, which enable high capacity and consistently high quality of reconditioning. After their successful validation and a limited phase of monitored production, these techniques are applied on rotating and stationary SX turbine parts. Validation criteria and the experience gained during the first years of commercial production and operation in the field will be presented.
Durability of Oxide/Oxide Ceramic Matrix Composites in Gas Turbine Combustors
Authors: van Roode Mark , Bhattacharya Arun K.
Published: April 2013

An integrated creep rupture strength degradation and water vapor degradation model for gas turbine oxide-based ceramic matrix composite (CMC) combustor liners was expanded with heat transfer computations to establish the maximum turbine rotor inlet temperature (TRIT) for gas turbines with 10:1 pressure ratio. Recession rates and average CMC operating temperatures were calculated for an existing baseline N720/A (N720/Al2O3) CMC combustor liner system with and without protective Al2O3 friable graded insulation (FGI) for 30,000-h liner service life. The potential for increasing TRIT by Y3Al5O12 (YAG) substitution for the fiber, matrix, and FGI constituents of the CMC system was explored, because of the known superior creep and water vapor degradation resistance of YAG compared to Al2O3. It was predicted that uncoated N720/A can be used as a combustor liner material up to a TRIT of ∼1200  °C, offering no TRIT advantage over a conventional metal + thermal barrier coating (TBC) combustor liner. A similar conclusion was previously reached for a SiC/SiC CMC liner with barium strontium aluminum silicate (BSAS)-type environmental barrier coating (EBC). The existing N720/A + Al2O3 FGI combustor liner system can be used at a maximum TRIT of ∼1350  °C, a TRIT increase over metal + TBC, and uncoated N720/A of ∼150  °C. Replacing the Al2O3 with YAG is predicted to increase the maximum allowable TRIT. Substitution of the fiber or matrix in N720/A increases TRIT by ∼100  °C. A YAG FGI improves the TRIT of the N720/A + Al2O3 FGI by ∼50  °C, enabling a TRIT of ∼1400 °C, similar to that predicted for SiC/SiC CMCs with protective rare earth monosilicate EBCs.
Multiple Frequencies Elliptical Whirling Orbit Model and Transient RANS Solution Approach to Rotordynamic Coefficients of Annual Gas Seals Prediction
Authors: Li Zhigang , Li Jun , Yan Xin
Published: April 2013

A numerical method using the multiple frequencies elliptical whirling orbit model and transient Reynolds-averaged Navier–Stokes (RANS) solution was proposed for prediction of the frequency dependent rotordynamic coefficients of annular gas seals. The excitation signal was the multiple frequencies waveform that acts as the whirling motion of the rotor center. The transient RANS solution combined with mesh deformation method was utilized to solve the leakage flow field in the annular gas seal and obtain the transient response forces on the rotor surface. Frequency dependent rotordynamic coefficients were determined by transforming the dynamic monitoring data of response forces and rotor motions to the frequency domain using the fast fourier transform. The frequency dependent rotordynamic coefficients of three types of annular gas seals, including a labyrinth seal, a fully partitioned pocket damper seal and a hole-pattern seal, were computed using the presented numerical method at thirteen or fourteen frequencies of 20–300 Hz. The obtained rotordynamic coefficients of three types of annular gas seals were all well agreement with the experimental data. The accuracy and availability of the proposed numerical method was demonstrated. The static pressure distributions and leakage flow rate of three types of annular gas seals were also illustrated.
Model Test of Influence of Propeller Arrangements Aboard a Four Propeller Boat
Authors: Bi J. Y. , Zong Z.
Published: April 2013

Although it is not uncommon to employ four propellers on a high speed displacement vessel, there is a lack of literature on this subject. This paper presents the propulsive performance of a four-propeller craft and gives the influence of propeller arrangements on the propulsive performance. According to the rotation direction, the transverse and longitudinal positions of four propellers, five factors are designed as the possible influential factors and 18 propeller arrangements are selected depending on the Taguchi orthogonal array. In fact, there are only 15 self-propulsion tests because the outer and inner propellers are overlapped in the same longitudinal position. The results of the model tests indicate that the influence of the hull form is negligible for high-speed craft because the frictional wake is small. In order to solve the problem of three missing self-propulsion tests, an unbalanced analysis of variance (ANOVA) is adopted. The propulsive efficiency, propeller thrust, and torque are considered as response variables in order to explore the importance of each factor. The order of importance is also obtained to provide designers with valuable guidance information.
A Model of Transient Heat and Mass Transfer in a Heterogeneous Medium of Ceria Undergoing Nonstoichiometric Reduction
Authors: Keene Daniel J. , Davidson Jane H. , Lipiński Wojciech
Published: April 2013

The redox chemistry of nonstoichiometric metal oxides can be used to produce chemical fuels by harnessing concentrated solar energy to split water and/or carbon dioxide. In such a process, it is desirable to use a porous reactive substrate for increased surface area and improved gas transport. The present study develops a macroscopic-scale model of porous ceria undergoing thermal reduction. The model captures the coupled interactions between the heat and mass transfer and the heterogeneous chemistry using a local thermal nonequilibrium (LTNE) formulation of the volume-averaged conservation of mass and energy equations in an axisymmetric cylindrical domain. The results of a representative test case simulation demonstrate strong coupling between gas phase mass transfer and the chemical kinetics as well as the pronounced impact of optical thickness on the temperature distribution and thus global solar-to-chemical energy conversion.
An Ontology for the Autonomous Reconfiguration of a Flexible Fixture Device
Authors: Gmeiner Thomas , Shea Kristina
Published: April 2013

The need for reconfigurable manufacturing systems has long been recognized as a key factor to gain the necessary flexibility for economical production of small batch sizes. Automation of the reconfiguration processes is a challenge both on the hardware and the software level. Addressing this issue in the field of fixture design, a new reconfigurable fixture device for a CNC milling machine has been developed. The developed vise contains interchangeable and customizable jaws enabling the secure fixture of a variety of workpiece geometries. To enable automated reconfiguration, a reasoning system is needed that can determine feasible fixture configurations based on the given workpiece and part as well as the available fixture components. In this paper, an ontology for representing fixture design and reconfiguration knowledge for vise-type flexible fixtures is presented. The ontology builds on and extends an existing ontology for modular fixture design. The creation of the ontology is based on a systematic building methodology, going from informal to formal concept definitions in a middle-out approach. The core concepts and relations of the ontology are presented and the ontology is validated both on the informal and on the formal level by its ability to find feasible fixture configurations, i.e., appropriate vise jaw pairs to fix example workpieces. The ontology can represent type-specific fixture designs in an unambiguous way and can hence serve as a basis for the development of applications needed to create an autonomous fixture design system.
An Investigation of the Lattice Boltzmann Method for Large Eddy Simulation of Complex Turbulent Separated Flow
Authors: Premnath Kannan N. , Pattison Martin J. , Banerjee Sanjoy
Published: April 2013

Lattice Boltzmann method (LBM) is a relatively recent computational technique for fluid dynamics that derives its basis from a mesoscopic physics involving particle motion. While the approach has been studied for different types of fluid flow problems, its application to eddy-capturing simulations of building block complex turbulent flows of engineering interest has not yet received sufficient attention. In particular, there is a need to investigate its ability to compute turbulent flow involving separation and reattachment. Thus, in this work, large eddy simulation (LES) of turbulent flow over a backward facing step, a canonical benchmark problem which is characterized by complex flow features, is performed using the LBM. Multiple relaxation time formulation of the LBM is considered to maintain enhanced numerical stability in a locally refined, conservative multiblock gridding strategy, which allows efficient implementation. Dynamic procedure is used to adapt the proportionality constant in the Smagorinsky eddy viscosity subgrid scale model with the local features of the flow. With a suitable reconstruction procedure to represent inflow turbulence, computation is carried out for a Reynolds number of 5100 based on the maximum inlet velocity and step height and an expansion ratio of 1.2. It is found that various turbulence statistics, among other flow features, in both the recirculation and reattachment regions are in good agreement with direct numerical simulation and experimental data.
Confocal Image-Based Computational Modeling of Nitric Oxide Transport in a Rat Mesenteric Lymphatic Vessel
Authors: Wilson John T. , Wang Wei , Hellerstedt Augustus H. , Zawieja David C. , Moore, James E.
Published: April 2013

The lymphatic system plays important roles in protein and solute transport as well as in the immune system. Its functionality is vital to proper homeostasis and fluid balance. Lymph may be propelled by intrinsic (active) vessel pumping or passive compression from external tissue movement. With regard to the former, nitric oxide (NO) is known to play an important role modulating lymphatic vessel contraction and vasodilation. Lymphatic endothelial cells (LECs) are sensitive to shear, and increases in flow have been shown to cause enhanced production of NO by LECs. Additionally, high concentrations of NO have been experimentally observed in the sinus region of mesenteric lymphatic vessels. A computational flow and mass transfer model using physiologic geometries obtained from confocal images of a rat mesenteric lymphatic vessel was developed to determine the characteristics of NO transport in the lymphatic flow regime. Both steady and unsteady analyses were performed. Production of NO was shear-dependent; basal cases using constant production were also generated. Simulations revealed areas of flow stagnation adjacent to the valve leaflets, suggesting the high concentrations observed here experimentally are due to minimal convection in this region. LEC sensitivity to shear was found to alter the concentration of NO in the vessel, and the convective forces were found to profoundly affect the concentration of NO at a Péclet value greater than approximately 61. The quasisteady analysis was able to resolve wall shear stress within 0.15% of the unsteady case. However, the percent difference between unsteady and quasisteady conditions was higher for NO concentration (6.7%). We have shown high NO concentrations adjacent to the valve leaflets are most likely due to flow-mediated processes rather than differential production by shear-sensitive LECs. Additionally, this model supports experimental findings of shear-dependent production, since removing shear dependence resulted in concentrations that are physiologically counterintuitive. Understanding the transport mechanisms and flow regimes in the lymphatic vasculature could help in the development of therapeutics to treat lymphatic disorders.
Simulations and Measurements of the Vibroacoustic Effects of Replacing Rolling Element Bearings With Journal Bearings in a Simple Gearbox
Authors: Hambric Stephen A. , Shepherd Micah R. , Campbell Robert L. , Hanford Amanda D.
Published: April 2013

The effects of replacing rolling element bearings with journal bearings on the noise and vibration of a simple gearbox are computationally and experimentally evaluated. A modified component mode synthesis (CMS) approach is used, where the component modes of the shafting and gearbox housing are modeled using finite element analysis (FEA). Instead of using component modes with free boundary conditions, which is typical of CMS, the shafting and gearbox are coupled using nominal impedances computed for the different bearing types, improving convergence of the solution. Methods for computing the actual bearing impedances, including the high damping coefficients in journal bearings, are summarized. The sound radiated by the gearbox is computed using a boundary element (BE) model. The modeling results are validated against measurements made at the NASA Glenn Research Center. Both simulations and measurements reveal that the journal bearings, although highly damped, do not necessarily lead to strong reductions in gearbox vibration and noise.
On the Modeling of an Intervertebral Disc Using a Novel Large Deformation Multi-Shell Approach
Authors: Demers Sébastien , Bouzid Abdel-Hakim , Nadeau Sylvie
Published: April 2013

The objective of this study is to develop an analytical model to predict the stresses and displacements in the lamellae of the intervertebral disc subjected to a compressive force. This is achieved by developing a model based on membrane theory combined to large deformation multishell structural behavior. Equations for longitudinal and circumferential stresses are formulated for each lamella of the anulus fibrosus. Multilamellae interaction is a statically indeterminate problem, which requires equations of compatibility of the displacements of adjacent lamellae to be resolved. The large deformation inherent to soft tissue is considered and the solution is obtained using an iterative process. Elastic interactions with a large deformation is a novelty in analytical modeling of soft tissues. This provides model realism and offers the possibility for new and in-depth investigations. Results are given for longitudinal and circumferential stresses and displacements as well as contact pressures for every lamella of the anulus fibrosus. The analytical results are compared to those of two finite element models. The results suggest that the most highly stressed zone is located on the innermost lamella. Stresses decrease through disc thickness and are at a maximum at the innermost lamella. Circumferential stress is predominant and the difference is less than 5% at any point of the anulus fibrosus when the analytical model is compared to the finite element model using coupled degrees of freedom at the lamellae interface. When compared to the finite element model using contact elements, the difference is below 11%. Contact pressures from the inside to the outside of the anulus fibrosus are shown to decrease nonlinearly. The model presented in this study has demonstrated that it is possible to analytically simulate the complex mechanical behavior of a multishell intervertebral disc subjected to compression, provided some simplifications. Further improvements are suggested to increase model realism and recommendations are given for future experimentation necessary to support both the analytical and numerical models.
Mechanical Loading Causes Detectable Changes in Morphometric Measures of Trabecular Structure in Human Cancellous Bone
Authors: Yeni Yener N. , Wu Brenda , Huang Lily , Oravec Daniel
Published: April 2013

The relationships between mechanical loads and bone microstructure are of interest to those who seek to predict bone mechanical properties from microstructure or to predict how organization of bone microstructure is driven by mechanical loads. While strains and displacements in the material are inherently responsible for mechanically caused changes in the appearance of the microstructure, it is the morphometric measures of microstructural organization that are often available for assessment of bone quality. Therefore, an understanding of how strain history is reflected in morphometric measures of bone microstructure has practical implications in that it may provide clinically measurable indices of mechanical history in bone and improve interpretation of bone mechanical properties from microstructural information. The objective of the current study was to examine changes in morphometric measures of cancellous bone microstructure in response to varying levels of continuum level strains. The experimental approach included stereologic analysis of microcomputed tomography (μCT) images of human cancellous bone samples obtained at sequentially increasing levels of strain in a custom-made loading apparatus mounted in a μCT scanner. We found that the degree of anisotropy (DA) decreased from baseline to failure and from failure to postfailure. DA partially recovered from postfailure levels upon unloading; however, the final DA was less than at failure and less than at baseline. We also found that average trabecular thickness (Tb.Th.Av) increased with displacements at postfailure and did not recover when unloaded. Average trabecular number decreased when the specimens were unloaded. In addition, the heterogeneity of Tb.Th as measured by intra-specimen standard deviation (Tb.Th.SD) increased and that of trabecular number (Tb.N.SD) decreased with displacements at postfailure. Furthermore, the intraspecimen coefficient of variation of trabecular number decreased at postfailure displacements but did not recover upon unloading. Finally, the coefficient of variation of trabecular separation at unload was less than that at baseline. These measures can be developed into image-based indices to estimate strain history, damage, and residual mechanical properties where direct analysis of stresses and strains, such as through finite element modeling, may not be feasible. It remains to be determined how wide a time interval can be used to estimate strain history before remodeling becomes an overriding effect on the trabecular architecture.
Neutral Beam Heating in the Princeton Large Torus
Authors: Grisham L. R.
Published: April 2013

Beams of energetic atoms were injected to heat the plasma contained in the Princeton Large Torus tokamak. The plasma reached ion temperatures of about 6.5 kiloelectron volts (≈ 75 million K) and electron temperatures of about 4.0 kiloelectron volts or greater (≈ 46 million K)—both the highest yet achieved in a tokamak device. Although a new type of density fluctuation in the plasma was observed at the highest injection powers and lowest plasma densities, the energy confinement properties of the discharge did not appear to deteriorate even at the low collisionalities relevant to a thermonuclear reactor plasma. The electron energy confinement in the central plasma appeared to be enhanced during beam injection.
Yakataga Gap, Alaska: Seismic History and Earthquake Potential
Authors: McCann William R. , Pérez Omar J. , Sykes Lynn R.
Published: April 2013

A 250-kilometer-long seismic gap in southern Alaska, which is situated along the boundary between the North American and Pacific plates, ruptured in two great earthquakes in 1899. Within the gap, earthquakes of moderate size form a ring of activity around a region of very low seismicity. The number of shocks of magnitude 6 or larger in this ring appears to have increased significantly since the 1958 earthquake, which occurred on the adjacent part of the plate boundary. This space-time pattern is similar to long-term patterns that preceded several large earthquakes in Japan. A shock of magnitude 7.7 on 28 February 1979 ruptured only a small part of the seismic gap. The remaining part, which already may have stored sufficient strain to generate a great shock, warrants intensive study to evaluate its potential for such an event.
Deep-Sea Primary Production at the Galápagos Hydrothermal Vents
Authors: Karl D. M. , Wirsen C. O. , Jannasch H. W.
Published: April 2013

Dense animal populations surrounding recently discovered hydrothermal vents at the Galápagos Rift sea-floor spreading center, 2550 meters deep, are probably sustained by microbial primary production. Energy in the form of geothermically reduced sulfur compounds emitted from the vents is liberated during oxidation and used for the reduction of carbon dioxide to organic matter by chemosynthetic bacteria.
Mass Measurement at the National Bureau of Standards: A Revision
Authors: Schoonover R. M. , Davis R. S. , Bower V. E.
Published: April 2013

In 1975, the results of a series of mass measurements undertaken by the National Bureau of Standards were published in
Science
. The inconsistencies reported seemed to depend on barometric pressure. An inference to be drawn from the report is that buoyant forces on objects weighed in air are somehow incorrectly accounted for by the usual appeal to Archimedes' principle in which the density of air, ρ, is computed from an equation of state. The magnitude of the unexpected effect was estimated as approaching 1 milligram in 1 kilogram over a pressure range from 0.5 to 2.0 atmospheres for objects having a volume difference of 200 cubic centimeters. In a new experiment at the National Bureau of Standards, in which more elaborate and precise equipment was used, the calculation of air density from the atmospheric variables is confirmed to within 0.05 percent, hence within the uncertainty usually claimed for the air density and buoyancy calculations.
Alaskan Seismic Gap Only Partially Filled by 28 February 1979 Earthquake
Authors: Lahr J. C. , Stephens C. D. , Hasegawa H. S. , Boatwright John
Published: April 2013

The Saint Elias, Alaska, earthquake (magnitude 7.7) of 28 February 1979 is the first major earthquake since 1900 to occur along the complex Pacific-North American plate boundary between Yakutat Bay and Prince William Sound. This event involved complex rupture on a shallow, low-angle, north-dipping fault beneath the Chugach and Saint Elias Mountains. The plate boundary between Yakutat Bay and Prince William Sound had been identified as a seismic gap, an area devoid of major earthquakes during the last few decades, and was thought to be a likely site for a future major earthquake. Since the Saint Elias earthquake fills only the eastern quarter of the gap, the remainder of the gap to the west is a prime area for the study of precursory and coseismic phenomena associated with large earthquakes.
Control of the Rhesus Monkey Menstrual Cycle: Permissive Role of Hypothalamic Gonadotropin-Releasing Hormone
Authors: Knobil E. , Plant T. M. , Wildt L. , Belchetz P. E. , Marshall G.
Published: April 2013

In rhesus monkeys with hypothalamic lesions (which appear to abolish the endogenous production of gonadotropin-releasing hormone), normal ovulatory menstrual cycles were reestablished by an unvarying, long-term replacement regimen consisting of one intravenous pulse of synthetic gonadotropic-releasing hormone per hour. This finding is in accord with the hypothesis that the pattern of pituitary gonadotropin secretion throughout the menstrual cycle (basal secretion interrupted, once every 28 days on the average, by a preovulatory surge) is not directed by alterations in hypothalamic gonadotropic-releasing hormone secretion but by the ebb and flow of ovarian estrogens acting directly on the pituitary gland.
Microwaves Induce Peripheral Vasodilation Squirrel Monkeys
Authors: Adair Eleanor R. , Adams Barbara W.
Published: April 2013

Vasomotor activity in cutaneous tail veins was indexed by changes in local skin temperature during exposure of the whole body to 12.3-centimeter continuous microwaves. At an ambient temperature (26°C) just below that at which tail vessels normally vasodilate, criterion dilation was initiated by 5-minute exposures to a microwave power density of 8 milliwatts per square centimeter. This intensity deposits energy equivalent to approximately 20 percent of the monkey's resting metabolic rate but produces no observable change in deep body temperature. Intensity increments of 3 to 4 milliwatts per square centimeter for 1°C reductions in ambient temperature below 26°C produced identical responses. That no vasodilation occurred during infrared exposures of equivalent power density suggests that noncutaneous thermosensitive structures may mediate microwave activation of thermoregulatory responses in the peripheral vasomotor system.
Intensity Fluctuation Spectroscopy Monitors Contractile Activation in "Resting" Cardiac Muscle
Authors: Lappé Donald L. , Lakatta Edward G.
Published: April 2013

Intensity fluctuations in a laser beam scattered by nonbeating isolated rat cardiac muscle varied directly with the calcium concentrations in the bathing fluid. The steady-state level of these fluctuations varied directly with calcium-dependent force suggesting that the intensity fluctuations reflect an interaction of calcium ions with the myofilaments. The demonstration that both a portion of resting force and the frequency of intensity fluctuations vary directly with calcium even in quiescent conditions indicates that some contractile activation is present in the resting muscle.
Brainstem Catecholamine Neurons Are Target Sites for Sex Steroid Hormones
Authors: Heritage Aileen S. , Stumpf Walter E. , Sar Madhabananda , Grant Lester D.
Published: April 2013

Sex steroid hormones and catecholamines have physiological interactions in the brain. By the combined use of autoradiography and fluorescence histochemistry, steroid hormone target sites and catecholamine neurons were visualized simultaneously in the same tissue preparation. By this dual localization method, [3H]estradiol and [3H]dihydrotestosterone target sites were identified in nuclei of many catecholamine cell bodies in the brainstem, and catecholamine nerve terminals were observed near certain steroid hormone target neurons. These results suggest close anatomical interrelations between steroid hormone sites of action and catecholamine sites of production and action in the brain.
Uncovering a Hidden Talent
Authors: Callahan Margaret K.
Published: April 2013

Anthracycline chemotherapy activates an anticancer immune response.
A Cool Intervention for Posttraumatic Epilepsy
Authors: Eid Tore
Published: April 2013

Mild passive focal cooling prevents epileptic seizures after head injury in rats.
Corpus cavernosum abscess from a blind-ending urethra after urinary diversion surgery
Authors: Kumabe Ayako , Kenzaka Tsuneaki , Yamamoto Yu , Kajii Eiji
Published: April 2013

Corpus cavernosum abscesses are rarely seen in the clinical setting. We report the case of an early diagnosis of corpus cavernosum abscess due to a blind-ending urethra in a 60-year-old man without known risk factors and who was successfully treated by antibiotic therapy alone. In this case, the blind-ending urethra after urinary diversion surgery was considered a risk factor of the abscess formation. If the physician notes that the patient has fever of uncertain cause after urinary diversion surgery, he/she should examine the penis and perineum in consideration of the possibility of corpus cavernosum abscess.
Tumour lysis syndrome in a patient with intravascular spread from a recurrent epithelial ovarian cancer
Authors: Camarata Michelle , Davies Roger , Copley Sue , Blagden Sarah
Published: April 2013

Tumour lysis syndrome is a potentially life-threatening oncological emergency most commonly encountered in patients with rapidly proliferating, treatment-responsive haematological malignancies. It is rarely observed in solid tumours and, to our knowledge, this is the first time that it has been reported in a cancer with an intravascular tumour extension. In this report, we describe a case of a woman who presented with recurrent ovarian cancer and was found to have tumour invading into her vasculature. The patient subsequently developed tumour lysis syndrome after receiving chemotherapy. The case highlights the importance of considering tumour lysis syndrome prophylaxis when treating patients with intravascular involvement from a solid malignancy even if, as in this case, it is a recurrent tumour. Included is a brief review of the literature. We propose that ‘intravascular tumour invasion is recognised as an important risk factor for the development of tumour lysis syndrome.