bluuebunny/crossref_metadata_2025 huggingface dataset:
Increasing atmospheric CO2 overrides the historical legacy of multiple stable biome states in Africa
Authors: Moncrieff Glenn R. , Scheiter Simon , Bond William J. , Higgins Steven I.
Published: October 2013

The dominant vegetation over much of the global land surface is not predetermined by contemporary climate, but also influenced by past environmental conditions. This confounds attempts to predict current and future biome distributions, because even a perfect model would project multiple possible biomes without knowledge of the historical vegetation state.

Here we compare the distribution of tree‐ and grass‐dominated biomes across Africa simulated using a dynamic global vegetation model (DGVM). We explicitly evaluate where and under what conditions multiple stable biome states are possible for current and projected future climates.

Our simulation results show that multiple stable biomes states are possible for vast areas of tropical and subtropical Africa under current conditions. Widespread loss of the potential for multiple stable biomes states is projected in the 21st Century, driven by increasing atmospheric CO2. Many sites where currently both tree‐dominated and grass‐dominated biomes are possible become deterministically tree‐dominated.

Regions with multiple stable biome states are widespread and require consideration when attempting to predict future vegetation changes. Testing for behaviour characteristic of systems with multiple stable equilibria, such as hysteresis and dependence on historical conditions, and the resulting uncertainty in simulated vegetation, will lead to improved projections of global change impacts.
Solid tumors following kidney transplantation in children
Authors: Smith Jodi M. , Martz Karen , McDonald Ruth A. , Harmon William E.
Published: October 2013

Kidney transplant recipients have an increased risk of cancer. Data on non‐LPD malignancies (solid tumors) in pediatric renal transplant recipients are limited. We performed a cohort study using the NAPRTCS transplant registry to describe the incidence of non‐LPD malignancy compared with the general pediatric population. The observed incidence rate of non‐LPD malignancy in the NAPRTCS transplant registry was 72.1 per 100 000 person‐years (SIR 6.7; 95% CI, 5.3, 8.5); a 6.7‐fold increased risk compared with the general pediatric population (10.7 cases per 100 000 person‐years). Non‐LPD malignancy was diagnosed in 35 subjects at a median of 726 days post‐transplant. The most common type of malignancy was renal cell carcinoma. The increased risk of non‐LPD malignancy was seen in all patients regardless of age, gender, race, etiology of end‐stage kidney disease, and transplant era. The specific type of immunosuppression was not identified as a risk factor. In this first large‐scale study of North American pediatric renal transplant recipients, we observed a 6.7‐fold increased risk of non‐LPD malignancy compared with the general pediatric population. Further examination of this unique patient population may provide greater insight into the impact of transplant and immunosuppression on malignancy risk.
Flt3 ligand treatment modulates parasitemia during infection with rodent malaria parasites via MyD88‐ and IFN‐γ‐dependent mechanisms
Authors: Tamura T. , Akbari M. , Kimura K. , Kimura D. , Yui K.
Published: October 2013

We previously showed that treatment of mice with the Flt3 ligand (Flt3L) prevents development of lethal experimental cerebral malaria and inhibits parasitemia during Plasmodium berghei ANKA (PbA) infection. In this study, we investigated the mechanisms underlying the reduction of parasitemia in Flt3L‐treated mice. Studies using gene knockout mice and antibody treatment indicated that the anti‐parasitemia effect of Flt3L was mediated by innate immune system and was dependent on MyD88, IFN‐γ, IL‐12 and natural killer (NK) cells. The number of NK cells and their ability to produce IFN‐γ was enhanced in Flt3L‐treated mice. Phagocytic activity of splenocytes was increased in Flt3L‐treated mice after PbA infection when compared with that in untreated mice, and this activity was mainly mediated by the accumulation of F4/80midCD11b+ cells in the spleen. In both MyD88−/− and IFN‐γ−/− mice, the proportion of F4/80midCD11b+ cells was not increased in the spleen of Flt3L‐treated mice after infection. These correlations suggest that NK cells produce IFN‐γ in Flt3L‐treated mice, and accumulation of F4/80midCD11b+ cells in the spleen is promoted by an IFN‐γ ‐dependent manner, culminating in the inhibition of parasitemia. These findings imply that Flt3L promotes effective innate immunity against malaria infection mediated by interplay among varieties of innate immune cells.
Brain‐derived neurotrophic factor Val66Met polymorphism and cognitive function in persons with cardiovascular disease
Authors: Szabo Ashley J. , Alosco Michael L. , Miller Lindsay A. , McGeary John E. , Poppas Athena , Cohen Ronald A. , Gunstad John
Published: October 2013

Aim

Cognitive impairment is common among persons with cardiovascular disease (CVD), and several potential aetiological mechanisms have been described, including contributions of genetic markers such as variations in the brain‐derived neurotrophic (BDNF) gene. This current study examined the associations of BDNF genotype with cognitive function among individuals with CVD.

Methods

This study included 110 participants with CVD who completed a comprehensive neuropsychological battery that assessed global cognitive function, attention/executive function, memory, language, and visuospatial abilities. All participants also underwent blood draw to provide a DNA sample that was used to determine BDNF genotype. Carriers of either one or two copies of the methionine allele of BDNF were categorized into one group (n = 33); non‐carriers were categorized into a second group (n = 77).

Results

After adjustment for demographic and medical characteristics, hierarchical regression analyses revealed persons with one or more methionine alleles displayed better performance than valine/valine individuals for attention/executive function (β = 0.22, P = 0.047) and memory (β = 0.25, P = 0.03), as well as a trend for language (β = 0.19, P = 0.08) and visuospatial abilities (β = 0.21, P = 0.06).

Conclusions

BDNF Val66Met had little impact on cognitive functioning in a sample of older adults with CVD, and significant findings contradicted that predicted by past work. Future work is much needed to clarify the mechanisms of these findings, particularly studies examining both circulating BDNF levels and genetic variation in the BDNF gene and cognitive function over time.
Leadership and Meaningful Work in the Public Sector
Authors: Tummers Lars G. , Knies Eva
Published: October 2013

There have been many important studies on leadership in the public administration discipline; however, scholarly inquiry still lags behind related disciplines such as psychology and business administration. This article helps fill that gap by analyzing the role that public leaders play in making work more meaningful for their employees, which, in turn, has a positive influence on employee job outcomes. Specifically, the authors analyze the mediating role of work meaningfulness in the relationships between leader‐member exchange and organizational commitment, work effort, and work‐to‐family enrichment. Samples from education, health care, and local government are used. Results show that leadership strongly influences work meaningfulness, which, in turn, influences job outcomes. In addition, the impact and extent of leadership and work meaningfulness are higher in health care and education than in local government. The results emphasize the importance of leadership and meaningful work in the public sector.
Population genomic analyses from low‐coverage RAD‐Seq data: a case study on the non‐model cucurbit bottle gourd
Authors: Xu Pei , Xu Shizhong , Wu Xiaohua , Tao Ye , Wang Baogen , Wang Sha , Qin Dehui , Lu Zhongfu , Li Guojing
Published: October 2013

Restriction site‐associated DNA sequencing (RAD‐Seq), a next‐generation sequencing‐based genome ‘complexity reduction’ protocol, has been useful in population genomics in species with a reference genome. However, the application of this protocol to natural populations of genomically underinvestigated species, particularly under low‐to‐medium sequencing depth, has not been well justified. In this study, a Bayesian method was developed for calling genotypes from an F2 population of bottle gourd [Lagenaria siceraria (Mol.) Standl.] to construct a high‐density genetic map. Low‐depth genome shotgun sequencing allowed the assembly of scaffolds/contigs comprising approximately 50% of the estimated genome, of which 922 were anchored for identifying syntenic regions between species. RAD‐Seq genotyping of a natural population comprising 80 accessions identified 3226 single nuclear polymorphisms (SNPs), based on which two sub‐gene pools were suggested for association with fruit shape. The two sub‐gene pools were moderately differentiated, as reflected by the Hudson's FST value of 0.14, and they represent regions on LG7 with strikingly elevated FST values. Seven‐fold reduction in heterozygosity and two times increase in LD (r2) were observed in the same region for the round‐fruited sub‐gene pool. Outlier test suggested the locus LX3405 on LG7 to be a candidate site under selection. Comparative genomic analysis revealed that the cucumber genome region syntenic to the high FST island on LG7 harbors an ortholog of the tomato fruit shape gene OVATE. Our results point to a bright future of applying RAD‐Seq to population genomic studies for non‐model species even under low‐to‐medium sequencing efforts. The genomic resources provide valuable information for cucurbit genome research.
Circulating elephants: unpacking the geographies of a cosmopolitan animal
Authors: Barua Maan
Published: October 2013

Cosmopolitanism has emerged as an important concept in geography and the social sciences. The rise of mobility, circulation and transnational networks has been paralleled by academic scholarship on un‐parochial others: diasporas, travellers and itinerant social groups. However, the role of nonhumans as participants in and subjects of cosmopolitanism has received scant attention. This paper seeks to develop a ‘more‐than‐human’ cosmopolitanism that accounts for the presence of nonhuman animals and entities in stories of circulation and contact. Through a multi‐sited ethnography of elephant conservation in India and the UK, the paper illustrates how animals become participants in forging connections across difference. Through their circulation, elephants become cosmopolitan, present in diverse cultures and serving banal global consumption. The paper then illustrates how cosmopolitan elephants may be coercive, giving rise to political frictions and new inequalities when mobilised by powerful, transnational environmental actors. It concludes by discussing the methodological and conceptual implications of a more‐than‐human cosmopolitanism.
Allogeneic peripheral blood stem cell transplantation using reduced‐intensity conditioning in an outpatient setting in ABO‐incompatible patients: are survival and graft‐versus‐host disease different?
Authors: Gutiérrez‐Aguirre Cesar Homero , Gómez‐De‐León Andrés , Alatorre‐Ricardo Julio , Cantú‐Rodríguez Olga Graciela , González‐Llano Oscar , Jaime‐Pérez José Carlos , Mancías‐Guerra Consuelo , Flores‐Jiménez Juan Antonio , Gómez‐Almaguer David
Published: October 2013

Background

Graft‐versus‐host disease (GVHD) is a major cause of morbimortality after allogeneic hematopoietic stem cell transplantation (allo‐HSCT). Minor ABO incompatibility has been associated with an increased risk of GVHD. We analyzed the impact of ABO matching on patient outcome after peripheral blood, reduced‐intensity allo‐HSCT in an outpatient setting, and its relationship with GVHD.

Study Design and Methods

Data of 121 patients were included. All patients received allo‐HSCT from HLA‐identical siblings as outpatients using a reduced‐intensity conditioning regimen. Influence of ABO matching as a risk factor for the development of GVHD and survival was analyzed using logistic regression and Cox proportional hazards regression, respectively.

Results

Median age was 36 years (range, 1‐71 years); 88 patients were ABO identical: 13 presented major mismatch and 20 minor mismatch, with an ABO incompatibility rate of 27.3%. The median follow‐up period was 54 months (range, 0.3‐120 months). Minor ABO incompatibility patients presented the highest rate of acute GVHD (aGVHD; 25%), in comparison with ABO‐identical (20.5%) and major ABO incompatibility patients (15.4%; p = 0.79). The highest incidence of chronic GVHD (cGVHD) occurred in the context of minor ABO incompatibility (35%), in contrast to ABO‐identical (30.8%) and major ABO incompatibility (15.4%). Survival was higher for patients in the minor ABO mismatch group; however, there was no significant correlation between ABO matching status and survival (p = 0.45).

Conclusion

Using this type of peripheral blood stem cell transplantation, minor ABO‐mismatched allo‐HSCT was associated with a higher incidence of aGVHD and cGVHD and with increased survival, albeit with no significance.
Development of common metrics for donation attitude, subjective norm, perceived behavioral control, and intention for the blood donation context
Authors: France Janis L. , Kowalsky Jennifer M. , France Christopher R. , McGlone Sarah T. , Himawan Lina K. , Kessler Debra A. , Shaz Beth H.
Published: October 2013

Background

The Theory of Planned Behavior has been widely used in blood donation research, but the lack of uniform, psychometrically sound measures makes it difficult to draw firm conclusions or compare results across studies. Accordingly, the goal of this study was to develop such measures of donation attitude, subjective norm, perceived behavioral control, and intention.

Study Design and Methods

Exploratory and confirmatory factor analyses (CFAs) were conducted on survey responses collected from college students (n = 1080). The resulting scales were then administered to an independent sample of experienced donors (n = 433) for additional CFAs and to test whether the Theory of Planned Behavior model provided a good fit to the data.

Results

CFAs conducted on both samples support the use of six‐item scales, with two factors each, to measure donation attitude, subjective norm, and perceived behavioral control and a single‐factor three‐item scale to measure donation intention. Further, structural equation modeling of these measures revealed that the Theory of Planned Behavior provided a strong fit to the data (comparative fit index, 0.976; root mean square error of approximation, 0.041; standardized root mean square residual, 0.055) and accounted for 73.7% of the variance in donation intention.

Conclusion

The present findings confirm the applicability of the Theory of Planned Behavior to the blood donation context and more importantly provide psychometric support for the future use of four brief measures of donation attitude, subjective norm, perceived behavioral control, and intention.
Adverse effects of rifampicin in dogs and serum alanine aminotransferase monitoring recommendations based on a retrospective study of 344 dogs
Authors: Bajwa Jangbir , Charach Michael , Duclos David
Published: October 2013

Background

Rifampicin has been reported to have potent activity againstStaphylococci, including meticillin‐resistantStaphylococcus pseudintermedius. There is limited documented information regarding adverse effects and recommendations for serum biochemistry monitoring.

Hypothesis/Objectives

The aims of this retrospective study were as follows: (i) to document the occurrence of adverse events in dogs receiving oral rifampicin; (ii) to determine the relationship between adverse events and the dosage/duration of therapy and concurrent medications; and (iii) to report findings associated with changes on serum alanine aminotransferase (ALT).

Animals

Client‐owned dogs.

Methods

A retrospective review of 344 medical records was carried out. SerumALTconcentrations and adverse effects were recorded and analysed. Correlations between different time intervals (days 0–9, 10–18, 19–27, 28–36 and >36) and serumALTelevation were compared.

Results

Dogs received 2.9–16 mg/kg/day of rifampicin. Adverse events occurred in 16.27% of dogs (56 of 344) and included vomiting (6.97%), anorexia (6.10%) and lethargy (3.77%). Adverse events were significantly more common in dogs concurrently treated with trimethoprim–sulfamethoxazole (P = 0.018), doxycycline (P = 0.044), levothyroxine sodium (P = 0.044), cephalosporins (P = 0.002) and nonsteroidal anti‐inflammatories (P < 0.001). Twenty‐five of 94 dogs (26.59%) had serum elevations ofALT. These increases were significantly associated with the duration of therapy during two time periods, 19–27 days (P = 0.04) and >36 days (P = 0.01).

Conclusions and clinical importance

Significant adverse events were noted in association with concurrent drug administration and with serumALTelevations. Pretreatment and weekly serum biochemistry monitoring is recommended to identify dogs at risk for hepatotoxicosis.
An Innovative Method for Optimization Based, High Order Controller Autotuning
Authors: Zimmerman Yaron , Gutman P.-O.
Published: October 2013

A new automatic method to tune the parameters of high order linear controllers is presented. The autotuning is achieved by minimizing, without constraints, a cost function that is related to the open loop shaping problem. The effort demanded from the designer is similar to that required to tune a low order controller, such as proportional integral (PI) or proportional integral differential (PID). The capabilities of the new method are demonstrated on two examples.
Stability Analysis of Nonlinear Dynamic Systems by Nonlinear Takagi–Sugeno–Kang Fuzzy Systems
Authors: Namadchian Zahra , Zare Assef , Namadchian Ali
Published: October 2013

This paper proposes a systematic procedure to address the limit cycle prediction of a Nonlinear Takagi–Sugeno–Kang (NTSK) fuzzy control system with adjustable parameters. NTSK fuzzy can be linearized by describing function method. The stability of the equivalent linearized system is then analyzed using the stability equations and the parameter plane method. After that the gain–phase margin (PM) tester has been added, then gain margin (GM) and phase margin for limit cycle are analyzed. Using NTSK fuzzy control system can help to have fewer rules. In order to analyze the stability with the same technique of stability analysis, the results of NTSK fuzzy control system will be compared with Dynamic fuzzy control system [1]. Computer simulations show differences between both systems.
A Hybrid Molecular Dynamics/Atomic-Scale Finite Element Method for Quasi-Static Atomistic Simulations at Finite Temperature
Authors: Xu Ran , Liu Bin
Published: October 2013

In this paper, a hybrid quasi-static atomistic simulation method at finite temperature is developed, which combines the advantages of MD for thermal equilibrium and atomic-scale finite element method (AFEM) for efficient equilibration. Some temperature effects are embedded in static AFEM simulation by applying the virtual and equivalent thermal disturbance forces extracted from MD. Alternatively performing MD and AFEM can quickly obtain a series of thermodynamic equilibrium configurations such that a quasi-static process is modeled. Moreover, a stirring-accelerated MD/AFEM fast relaxation approach is proposed in which the atomic forces and velocities are randomly exchanged to artificially accelerate the “slow processes” such as mechanical wave propagation and thermal diffusion. The efficiency of the proposed methods is demonstrated by numerical examples on single wall carbon nanotubes.
Assembly Time Estimation: Assembly Mate Based Structural Complexity Metric Predictive Modeling
Authors: Owensby Joseph E. , Summers Joshua D.
Published: October 2013

This paper presents an automated tool for estimating assembly times of products based on a three step process: connectivity graph generation from assembly mate information, structural complexity metric analysis of the graph, and application of the complexity metric vector to predictive artificial neural network models. The tool has been evaluated against different training set cases, suggesting that partially defined assembly models and training product variety are critical characteristics. Moreover, the tool is shown to be robust and insensitive to different modeling engineers. The tool has been implemented in a commercial CAD system and shown to yield results of within ±25% of predicted values. Additional extensions and experiments are recommended to improve the tool.
Determination of the Active Medium Temperature in Media Based Press Hardening Processes
Authors: Drossel Welf-Guntram , Pierschel Norbert , Paul Alexander , Katzfuß Klaus , Demuth Rico
Published: October 2013

Safety, lightweight design, and reduction of emissions are terms which are key issues in modern vehicle construction. These challenges can be met by new lightweight design strategies, e.g., by using lightweight materials and high-strength steels as well as innovative forming technologies such as media based press hardening (MBPH). MBPH as a sub-production technique of hydroforming is a tempered internal high-pressure forming process of closed profiles, which this article is about, or sheet metals by gaseous media. Due to the high process requirements (internal pressure up to 70 MPa and temperatures up to 1000 °C), it has not been possible to measure the temperature curve of the active medium in a reliable way until now. The aim of the research project described in this article was to develop an innovative measuring instrument to determine the gas temperature curve with a measuring frequency of at least 1 Hz. Analytical and numerical calculations have indicated that the active medium has a significant influence on the thermodynamic of the forming process. The finite element analysis (FEA) of the heat flow during the forming process has indicated that the influence of the gas on the cooling process of the work piece is about 15% of the total influence of the tool. Consequently, the active medium in media based press hardening processes is an important thermal influencing factor. Experiments have confirmed that it is possible to determine the calculated curve of the gas temperature and maximum temperatures of the active media up to 500 °C. The findings of these studies make a significant contribution to identifying and analyzing the complete temperature balance in tempered active media based forming processes.
Research on Air Content Estimation of Tributyl Phosphate Hydraulic Fluids: A Novel Approach Based on the Vacuum Method
Authors: Ouyang Xiaoping , Fan Boqian , Yang Huayong , Qing Rong
Published: October 2013

The air content in hydraulic transmission fluids significantly reduces bulk modulus of the fluid and causes a drop in the stiffness and response of the hydraulic system. It is consequently very important to monitor the air content in hydraulic fluid for ensuring the hydraulic works in good condition. In this paper, a novel method is presented in which the sampled fluid flows slowly into a vacuum chamber and the pressure of separated air is measured. A model of pressure-time characteristics is established, with moisture content taken into account as well, since moisture is volatile in vacuum and its content in tributyl phosphate (TBP) based fluid is usually too high to be neglected. The model can be simplified, which turned out to be a nonlinear least square problem. Comparison between the measured and calculated value shows that the model matches well with the experimental data.
Weight Function Method With Segment-Wise Polynomial Interpolation to Calculate Stress Intensity Factors for Complicated Stress Distributions
Authors: Li Yinsheng , Hasegawa Kunio , Xu Steven X. , Scarth Douglas A.
Published: October 2013

Many solutions of the stress intensity factor have been proposed in recent years. However, most of them take only third or fourth-order polynomial stress distributions into account. For complicated stress distributions which are difficult to be represented as third or fourth-order polynomial equations over the stress distribution area such as residual stress distributions or thermal stress distributions in dissimilar materials, it is important to further improve the accuracy of the stress intensity factor. In this study, a weight function method with segment-wise polynomial interpolation is proposed to calculate solutions of the stress intensity factor for complicated stress distributions. By using this method, solutions of the stress intensity factor can be obtained without employing finite element analysis or difficult calculations. It is therefore easy to use in engineering applications. In this method, the stress distribution area is firstly divided into several segments and the stress distribution in each segment is curve fitted to segment-wise polynomial equation. The stress intensity factor is then calculated based on the weight function method and the fitted stress distribution in each segment. Some example solutions for both infinite length cracks and semi-elliptical cracks are compared with the results from finite element analysis. In conclusion, it is confirmed that this method is applicable with high accuracy to the calculation of the stress intensity factor taking actual complicated stress distributions into consideration.
Sensitivity of Combustion Driven Structural Dynamics and Damage to Thermo-Acoustic Instability: Combustion-Acoustics-Vibration
Authors: Can Altunlu A. , van der Hoogt Peter J. M. , de Boer André
Published: October 2013

The dynamic combustion process generates high amplitude pressure oscillations due to thermo-acoustic instabilities, which are excited within the gas turbine. The combustion instabilities have a significant destructive impact on the life of the liner material due to the high cyclic vibration amplitudes at elevated temperatures. This paper presents a methodology developed for mechanical integrity analysis relevant to gas turbine combustors and the results of an investigation of the combustion-acoustics-vibration interaction by means of structural dynamics. In this investigation, the combustion dynamics was found to be very sensitive to the thermal power of the system and the air-fuel ratio of the mixture fed into the combustor. The unstable combustion caused a dominant pressure peak at a characteristic frequency, which is the first acoustic eigenfrequency of the system. Besides, the higher-harmonics of this peak were generated over a wide frequency-band. The frequencies of the higher-harmonics were observed to be close to the structural eigenfrequencies of the system. The structural integrity of both the intact and damaged test specimens mounted on the combustor was monitored by vibration-based and thermal-based techniques during the combustion operation. The flexibility method was found to be accurate to detect, localize, and identify the damage. Furthermore, a temperature increase was observed around the damage due to hot gas leakage from the combustor that can induce detrimental thermal stresses enhancing the lifetime consumption.
Melt Pool Flow and Surface Evolution During Pulsed Laser Micro Polishing of Ti6Al4V
Authors: Ma Chao , Vadali Madhu , Duffie Neil A. , Pfefferkorn Frank E. , Li Xiaochun
Published: October 2013

Extensive experimental work has shown that pulsed laser micro polishing (PLμP) is effective for polishing micro metallic parts. However, the process physics have not been fully understood yet, especially with respect to the melt pool flow. A reliable physical model can be of significant assistance in understanding the fluid flow in the melt pool and its effect on PLμP. In this paper, a two-dimensional axisymmetric transient model that couples heat transfer and fluid flow is described that was constructed using the finite element method. The model not only provided the solutions to the temperature and velocity fields but also predicted the surface profile evolution on a free deformable surface. The simulated melt depth and resolidified surface profiles matched those obtained from optical images of PLμPed Ti6Al4V sample cross-sections. The model was also used to study the effect of laser pulse duration on the melt pool flow. The study suggests that longer pulses produce more significant fluid flows. The cut-off pulse duration between capillary and thermocapillary regimes, below which minimal Maragoni flow should be expected, was estimated to be 0.66 μs for Ti6Al4V, which also matched well with the experimental results. It is evident that the coupled model offers reliable predictions and thus can be extended for a more complex parametric study to provide further insights for PLμP.
Origami-Inspired Integrated Planar-Spherical Overconstrained Mechanisms
Authors: Wei Guowu , Dai Jian S.
Published: October 2013

This paper presents two integrated planar-spherical overconstrained mechanisms that are inspired and evolved from origami cartons with a crash-lock base. Investigating the crash-lock base of the origami cartons, the first overconstrained mechanism is evolved by integrating a planar four-bar linkage with two spherical linkages in the diagonal corners. The mechanism has mobility one and the overconstraint was exerted by the two spherical linkages. This mechanism is then evolved into another integrated planar-spherical overconstrained mechanism with two double-spherical linkages at the diagonal corners. The evolved mechanism has mobility one. It is interesting to find that the double-spherical linkage at the corner of this new mechanism is an overconstrained 6R linkage. The geometry evolution is presented and the constraint matrices of the mechanisms are formulated using screw-loop equations verifying mobility of the mechanisms. The paper further reveals the assembly conditions and geometric constraint of the two overconstrained mechanisms. Further, with mechanism decomposition, geometry and kinematics of the mechanisms are investigated with closed-form equations, leading to comparison of these two mechanisms with numerical simulation. The paper further proposes that the evolved overconstrained mechanism can in reverse lead to new origami folds and crease patterns. The paper hence not only lays the groundwork for kinematic investigation of origami-inspired mechanisms but also sheds light on the investigation of integrated overconstrained mechanisms.
Fluid Flow and Heat Transfer in a Novel Microchannel Heat Sink Partially Filled With Metal Foam Medium
Authors: Farsad E. , Abbasi S. P. , Zabihi M. S.
Published: October 2013

Performance of microchannel heatsink (MCHS) partially filled with foam is investigated numerically. The open cell copper foams have the porosity and pore density in the ranges of 60–90% and 60–100 PPI (pore per inch), respectively. The three-dimensional steady, laminar flow, and heat transfer governing equations are solved using finite volume method. The performance of microchannel heatsink is evaluated in terms of overall thermal resistance, pressure drop, and heat transfer coefficient and temperature distribution. It is found that the results of the surface temperature profile are in good agreement with numerical data. The results show the microchannel heatsink with insert foam appears to be good candidates as the next generation of cooling devices for high power electronic devices. The thermal resistance for all cases decreases with the decrease in porosity. The uniformity of temperature in this heatsink is enhanced compared the heatsink with no foam. The thermal resistance versus the pumping power is depicted, it is found that 80% is the optimal porosity for the foam at 60 PPI with a minimum thermal resistance 0.346 K/W. The results demonstrate the microchannel heatsink partially filled with foam is capable for removing heat generation 100 watt over an area of 9 × 10−6 m2 with the temperature of heat flux surface up to 59 °C.
Simulation of Solarized Combined Cycles: Comparison Between Hybrid Gas Turbine and ISCC Plants
Authors: Barigozzi Giovanna , Franchini Giuseppe , Perdichizzi Antonio , Ravelli Silvia
Published: October 2013

The present paper investigates two different solarized combined cycle layout configurations. In the first scheme, a solarized gas turbine is coupled to a solar tower. Pressurized air at the compressor exit is sent to the solar tower receiver before entering the gas turbine (GT) combustor. Here, temperature is increased up to the nominal turbine inlet value through natural gas combustion. In the second combined cycle (CC) layout, solar energy is collected by line focusing parabolic trough collectors and used to produce superheated steam in addition to the one generated in the heat recovery boiler. The goal of the paper is to compare the thermodynamic performance of these concentrating solar power (CSP) technologies when working under realistic operating conditions. Commercial software and in-house computer codes were combined together to predict CSP plant performance both on design and off-design conditions. Plant simulations have shown the beneficial effect of introducing solar energy at high temperature in the Joule–Brayton cycle and the drawback in terms of GT performance penalization due to solarization. Results of yearly simulations on a 1 h basis for the two considered plant configurations are presented and discussed. The main thermodynamic parameters such as temperatures, pressure levels, and air and steam flow rates are reported for two representative days.
A Shear Strength Degradation Model for Anisotropic Conductive Adhesive Joints Under Hygrothermal Conditions
Authors: Tao Bo , Wu Guanghua , Yin Zhouping , Xiong Youlun
Published: October 2013

Hygrothermal environments can degrade anisotropic conductive adhesive (ACA) joints by weakening the shear strength of adhesive interface. In this paper, the shear strength degradation model of ACA joints under hygrothermal conditions was formulated through experimental testing and theoretical modeling. The shear strength degradation data were obtained from different hygrothermal aging tests and the ACA moisture properties were characterized for the corresponding hygrothermal conditions. Theoretical models considering the hygrothermal factors of T (temperature), RH (relative humidity), and t (time), were used to fit the shear strength degradation data. It was found that the inverse exponential law was the best candidate model to predict the degradation data. The shear strength degradation model of ACA joints under hygrothermal conditions was proposed, where the relationship of the S (shear strength) and the hygrothermal factors (T, RH, and t) was expressed in an analytical model. The degradation model was validated by experiments, and the model predictions agreed well with the test results.
Three-Dimensional Finite Element Elastic–Plastic Model for Subsurface Initiated Spalling in Rolling Contacts
Authors: Bomidi John A. R. , Sadeghi Farshid
Published: October 2013

In this investigation, a three-dimensional (3D) finite element (FE) model was developed to study subsurface initiated spalling observed in rolling line contact of tribo components such as bearings. An elastic–kinematic hardening–plastic material model is employed to capture the material behavior of bearing steel and is coupled with the continuum damage mechanics (CDM) approach to capture the material degradation due to fatigue. The fatigue damage model employs both stress and accumulated plastic strain based damage evolution laws for fatigue failure initiation and propagation. Failure is modeled by mesh partitioning along unstructured, nonplanar, intergranular paths of the microstructure topology represented by randomly generated Voronoi tessellations. The elastic–plastic model coupled with CDM was used to predict both ratcheting behavior and fatigue damage in heavily loaded contacts. Fatigue damage induced due to the accumulated plastic strains around broken intergranular joints drive the majority of the crack propagation stage, resulting in a lower percentage of life spent in propagation. The 3D FE model was used to determine fatigue life at different contact pressures ranging from 2 to 4.5 GPa for 33 different randomly generated microstructure topology models. The effect of change in contact pressure due to subsurface damage and plastic strain accumulation was also captured by explicitly modeling the rolling contact geometry and the results were compared to those generated assuming a Hertzian pressure profile. The spall shape, fatigue lives, and their dispersion characterized by Weibull slopes obtained from the model correlate well with the previously published experimental results.
Simulation of Micromechanical Measurement of Mass Accretion: Quantifying the Importance of Material Selection and Geometry on Performance
Authors: Martin Michael James
Published: October 2013

Micro- and nanomechanical resonators operating in liquid have been used to measure the change in the mass of either cells or functionalized surfaces attached to the resonator. As the system accretes mass, the natural frequency of the system changes, which can be measured experimentally. The current work extends methods previously developed for simulation of an atomic force microscope operating in liquid to study this phenomenon. A silicon cantilever with a 10 micron width, an 800 nm thickness, and a length of 30 microns was selected as a baseline configuration. The change in resonant frequency as the system accretes mass was determined through simulation. The results show that the change in natural frequency as mass accretes on the resonator is predictable through simulation. The geometry and material of the cantilever were varied to optimize the system. The results show that shorter cantilevers yield large gains in system performance. The width does not have a large impact on the system performance. Selecting the optimal thickness requires balancing the increase in overall system mass with the improvement in frequency response as the structure becomes thicker. Because there is no limit to the maximum system stiffness, the optimal materials will be those with higher elastic moduli. Based on these criteria, the optimum resonator for mass accretion measurements will be significantly different than an optimized atomic-force microscopy (AFM) cantilever.
Accurate timbre and localization of binaural recordings through headphones using sound pressure measurement at the eardrum.
Authors: Griesinger David
Published: October 2013

Individual HRTFs are almost universally measured with blocked or partially blocked ear canals, and individual headphone equalization is obtained in the same way. Using this method binaural reproduction without head tracking usually results in a significant alteration of timbre as well as inaccurate and/or in the head localization. The error is important—auralizations using incorrect timbre can lead to misleading conclusions. This problem was studied with the help of a dummy head that precisely models the author’s pinna, ear canals, and eardrum resonance. A new type of probe microphone was also developed that allows comfortable recordings and measurements at the eardrum. Data from this equipment show that while the spatial variation in HRTFs can be captured with a blocked ear canal up to a frequency of 7 kHz, errors in headphone equalization made with a blocked canal are typically in error by more than 10 dB at midfrequencies. Eardrum measurements of HRTFs and headphones result in superior performance for an individual, and a pair of headphones correctly equalized for an average individual produces out-of-head localization for at least 50% of other individuals in our tests. Data and theory and a noninvasive method for equalization will be presented.
Response of fish sound production to short-term ocean upwelling events at the LEO-15 (Long-term Ecosystem Observatory at 15 m depth) ocean observatory.
Authors: Mann David A. , Grothues Thomas M.
Published: October 2013

Understanding factors controlling the distribution and reproduction of fishes is crucial for developing ecosystem models of fish populations. Yet these observations are difficult to make on physically relevant time and space scales. A hydrophone was used to record fish sound production associated with reproduction at the LEO-15 ocean observatory to determine the relationship between variation in fish calling behavior and oceanographic variation. Sound production was dominated by Atlantic croaker (Micropogonias undulatus), weakfish (Cynoscion regalis), and striped cusk-eel (Ophidion marginatum). Striped cusk-eels called with a crepuscular pattern, with a strong peak at dusk, less sound production during the night, and a lesser peak in sound production at dawn. Sciaenids called mostly at dusk and night. Nine advection events bringing colder waters to the LEO-15 site were correlated with greatly reduced levels of sound production in Atlantic croaker and weakfish on daily time scales. Our results show how ocean observatories with passive acoustics can study tightly coupled physical oceanographic influences on fish behavior on daily time scales.
Recordings of sonic muscle activity of the Lusitanian toadfish Halobatrachus didactylus during sound production.
Authors: Jordão Joana M. , Amorim Maria Clara , Fonseca Paulo
Published: October 2013

Male Lusitanian toadfish, Halobatrachus didactylus, are territorial and have a wide acoustic repertoire. The sound production apparatus consists of a pair of intrinsic large sonic muscles on the two lobes of the swimbladder. Sonic muscle activity and the variability of the vocalizations were related using electromyograms (EMGs). EMG electrodes were cirurgically implanted on the sonic muscles of several territorial males. After recovery, the subjects were released into an experimental tank with an available nest. Sonic muscle activity was registered and the vocalizations were simultaneously recorded using a hydrophone. Social context was manipulated by releasing different kinds of intruders, male(s) or female(s). This action elicited the production of boatwhistles, while grunts were generated during fish disturbance. Preliminary analysis shows that, unlike previously reported, the bilateral sonic muscles contract simultaneously during the generation of both signal types. The muscle contraction period is halved during the production of the grunt relative to the boatwhistle. The EMG period matches the sound pulse period and determines the fundamental sound frequency. [JMJ was supported by a Post-doc grant (SFRH/BPD/36510/2007).]
Head and body kinematics of pulse sound generation and feeding in longnose butterflyfishes (Genus Forcipiger).
Authors: Boyle Kelly S. , Tricas Timothy C.
Published: October 2013

Both species of butterflyfish (Chaetododntidae) in the genus Forcipiger produce pulsatile sounds during territorial interactions. Sounds of one species, the forcepsfish (F. flavissimus), are approximately 20 ms and occur with rapid dorsoventral head motion (headbob). We performed laboratory sound production and feeding experiments with high-speed video (600 fps) to test predictions of the hypothesis that sound production in this genus results from evolutionary modification of stereotyped feeding behavior. Cranial elevation is an important component of prey capture for a variety of teleost fishes and facilitates opening of the buccal cavity and oral jaws. Studies on kinematics of feeding in Forcipiger by other authors revealed a minor contribution of cranial elevation compared to other fishes. Preliminary results indicate cranial elevation during headbobs involves a comparable range of motion relative to prey capture (approximately 3°–7°), but maximal elevation occurs within 12 ms during the headbob compared to 25 ms in feeding. Additionally, sound emission during feeding is weak to nonexistent. Electroymyography has revealed involvement of anterior epaxialis muscles with cranial elevation during feeding and headbob sound production. These experiments will allow further kinematic comparisons of head movements and associated muscle firing patterns during feeding and acoustic behaviors.
Sound source localization by the plainfin midshipman fish, Porichthys notatus.
Authors: Zeddies David , Fay Richard R. , Alderks Peter W. , Shaub Kiel , Sisneros Joseph A.
Published: October 2013

Sound source localization of the plainfin midshipman fish (Porichthys notatus) was studied using the phonotactic response of gravid females to synthetic male advertisement calls. Playback experiments were conducted in a 3.65-m-diameter outdoor concrete tank at the UC Bodega Marine Laboratory in Bodega Bay, CA using a J-9 transducer placed near the center of the tank. The sound field in the tank was measured at 5-cm intervals using an eight-hydrophone array to measure the pressure gradients from which particle motion vectors were calculated. The acoustic measurements confirmed that the J-9 projector was operating as a monopole source. One hundred twenty-two gravid females were released 100 cm away from the center of the sound source while their behavioral responses were video taped during experiments with playback sound “On” (90 Hz tone) and sound “Off” (Controls). A total of 45 positive phonotactic responses from naïve gravid females were recorded from the 62 trials with sound “On.” The phonotactic responses consisted primarily of straight to slightly curved tracks to the sound source while abrupt changes in trajectory to the sound source were rarely observed. The results confirm that fish can locate sound sources in the near field. [Work supported by NSF.]
Comparative studies of the cocktail party problem using birdsong.
Authors: Dent Micheal L. , Shinn-Cunningham Barbara G. , Sen Kamal
Published: October 2013

Many animals are adept at identifying communication calls in the presence of different masking sounds, much like humans navigating a cocktail party. In order to compare human and avian abilities in analyzing signals in complex acoustic mixtures, we measured identification of birdsong by humans and birds in the presence of different maskers and compared results to physiological recordings in zebra finches. In humans, spectrotemporal similarity of targets and maskers causes difficulties in segregating and selecting the target out of the sound mixture; however, for similar targets and maskers, spatial separation alleviates this interference. Field L recordings in finches reveal differences in the forms of neural interference caused by the various masker types, consistent with human behavior. However, avian identification performance is similar for the different maskers. Moreover, spatial separation of target and masker causes little improvement in avian target identification unless target and masker have distinct temporal envelopes. When target and masker envelopes differ, avian identification performance improves significantly, regardless of masker type. These experiments demonstrate that both birds and humans can segregate communication signals from a sound mixture, but suggest that the acoustic attributes that the two species use to solve the cocktail party problem differ.