bluuebunny/crossref_metadata_2025 huggingface dataset:
Mitochondrial introgressive hybridization following a demographic expansion in the tomato frogs of Madagascar, genus Dyscophus
Authors: Orozco‐terWengel Pablo , Andreone Franco , Louis Edward , Vences Miguel
Published: November 2013

Madagascar is a biodiversity hotspot with a unique fauna and flora largely endemic at the species level and highly threatened by habitat destruction. The processes underlying population‐level differentiation in Madagascar's biota are poorly understood and have been proposed to be related to Pleistocene climatic cycles, yet the levels of genetic divergence observed are often suggestive of ancient events. We combined molecular markers of different variability to assess the phylogeography of Madagascar's emblematic tomato frogs (Dyscophus guineti and D. antongilii) and interpret the observed pattern as resulting from ancient and recent processes. Our results suggest that the initial divergence between these taxa is probably old as reflected by protein‐coding nuclear genes and by a strong mitochondrial differentiation of the southernmost population. Dramatic changes in their demography appear to have been triggered by the end of the last glacial period and possibly by the short return of glacial conditions known as the 8K event. This dramatic change resulted in an approximately 50‐fold reduction of the effective population size in various populations of both species. We hypothesize these species' current mitochondrial DNA diversity distribution reflects a swamping of the mitochondrial genetic diversity of D. guineti by that of D. antongilii previous to the populations' bottlenecks during the Holocene, and probably as a consequence of D. antongilii demographic expansion approximately 1 million years ago. Our data support the continued recognition of D. antongilii and D. guineti as separate species and flag D. guineti as the more vulnerable species to past and probably also future environmental changes.
Infection withHaemoproteus iwaaffects vector movement in a hippoboscid fly—frigatebird system
Authors: Levin Iris I. , Parker Patricia G.
Published: November 2013

Haemosporidian parasites, which require both a vertebrate and invertebrate host, are most commonly studied in the life stages occurring in the vertebrate. However, aspects of the vector's behaviour and biology can have profound effects on parasite dynamics. We explored the effects of a haemosporidian parasite,Haemoproteus iwa, on a hippoboscid fly vector,Olfersia spinifera.Olfersia spiniferais an obligate ectoparasite of the great frigatebird,Fregata minor, living among bird feathers for all of its adult life. This study examined the movements ofO. spiniferabetween great frigatebird hosts. Movement, or host switching, was inferred by identifying host (frigatebird) microsatellite genotypes from fly bloodmeals that did not match the host from which the fly was collected. Such host switches were analysed using a logistic regression model, and the best‐fit model included theH. iwainfection status of the fly and the bird host sex. Uninfected flies were more likely to have a bird genotype in their bloodmeal that was different from their current host's genotype (i.e. to have switched hosts) than infected flies. Flies collected from female birds were more likely to have switched hosts than those collected on males. Reduced movement of infected flies suggests that there may be a cost of parasitism for the fly. The effect of host sex is probably driven by differences in the sex ratio of bird hosts available to moving flies.
Should I stay or should I go: biogeographic and evolutionary history of a polyploid complex (Chrysanthemum indicum complex) in response to Pleistocene climate change in China
Authors: Li Jing , Wan Qian , Guo Yan‐Ping , Abbott Richard J. , Rao Guang‐Yuan
Published: November 2013

Quaternary climatic oscillations greatly influenced the distribution and pattern of biodiversity in the Northern Hemisphere. Here we examine how such oscillations in South East Asia may have affected the demographic and evolutionary history of a polyploid plant complex associated with semi‐dry habitats.

We analyzed plastid and nuclear ribosomal DNA (rDNA) internal transcribed spacer (ITS) sequence variation within the Chrysanthemum indicum complex (Asteraceae), which comprises diploid and polyploid plants distributed throughout China. In total, 368 individuals from 47 populations across the geographical range of the complex were analyzed.

We show that the relatively widespread tetraploid form of C. indicum expanded its range southward in the Pleistocene, possibly during the most recent or previous glacial period when conditions became drier and forests retreated in southern China. In marked contrast, diploid and other polyploid members of the complex failed to expand their ranges at these times or have since undergone range contractions in contrast to tetraploid C. indicum.

We conclude that hybridization and gene flow between taxa occurred frequently during the evolutionary history of the complex, causing considerable sharing of chlorotypes and ITS types. Nevertheless, taxa within ploidy levels could be largely distinguished according to chlorotype and/or ITS type.
The physiological importance of developmental mechanisms that enforce proper stomatal spacing in Arabidopsis thaliana
Authors: Dow Graham J. , Berry Joseph A. , Bergmann Dominique C.
Published: November 2013

Genetic and cell biological mechanisms that regulate stomatal development are necessary to generate an appropriate number of stomata and enforce a minimum spacing of one epidermal cell between stomata. The ability to manipulate these processes in a model plant system allows us to investigate the physiological importance of stomatal patterning and changes in density, therein testing underlying theories about stomatal biology.

Twelve Arabidopsis thaliana genotypes that have varied stomatal characteristics as a result of mutations or transgenes were analyzed in this study. Stomatal traits were used to categorize the genotypes and predict maximum stomatal conductance to water vapor (Anatomical gsmax) for individuals. Leaf‐level gas‐exchange measurements determined Diffusive gsmax, net carbon assimilation (A), water‐use efficiency (WUE), and stomatal responses to increasing CO2 concentration.

Genotypes with proper spacing (< 5% of stomata in clusters) achieved Diffusive gsmax values comparable to Anatomical gsmax across a 10‐fold increase in stomatal density, while lines with patterning defects (> 19% clustering) did not. Genotypes with clustering also had reduced A and impaired stomatal responses, while WUE was generally unaffected by patterning.

Consequently, optimal function per stoma was dependent on maintaining one epidermal cell spacing and the physiological parameters controlled by stomata were strongly correlated with Anatomical gsmax.
A MYB coiled‐coil transcription factor interacts with NSP2 and is involved in nodulation in Lotus japonicus
Authors: Kang Heng , Chu Xiaojie , Wang Chao , Xiao Aifang , Zhu Hui , Yuan Songli , Yang Zhenzhen , Ke Danxia , Xiao Shaobo , Hong Zonglie , Zhang Zhongming
Published: November 2013

Transcription factor complex formation is a central step in regulating gene expression. In this report, a novel MYB coiled‐coil transcription factor referred to as IPN2, for Interacting Protein of NSP2, is described.

The interaction between IPN2 and NSP2 was examined by protein pull‐down assays and bimolecular fluorescence complementation (BiFC). Subcellular localization of proteins, gene expression and gene function were assessed in transgenic hairy roots expressing tagged recombinant proteins, promoter‐reporter and RNA interference (RNAi) constructs, respectively.

The GRAS domain of NSP2 and the coiled‐coil domain of IPN2 were found to be responsible for the interaction between the two proteins. IPN2 had strong transcription activation activity, bound directly to the NIN gene promoter, and was localized to the nuclei of Lotus japonicus root cells. The expression of IPN2 was elevated during nodule development, coinciding with increased NSP2 gene expression during nodule organogenesis. RNAi‐mediated knockdown expression of IPN2 did not affect arbuscular mycorrhizal development, but had deleterious effects on rhizobial infection and nodule formation in L. japonicus.

These results demonstrate an important role of IPN2 in nodule organogenesis and place a new MYB transcription factor in the Nod signaling pathway.
OsPT2, a phosphate transporter, is involved in the active uptake of selenite in rice
Authors: Zhang Lianhe , Hu Bin , Li Wei , Che Ronghui , Deng Kun , Li Hua , Yu Feiyan , Ling Hongqing , Li Youjun , Chu Chengcai
Published: November 2013

Selenite is a predominant form of selenium (Se) available to plants, especially in anaerobic soils, but the molecular mechanism of selenite uptake by plants is not well understood.

ltn1, a rice mutant previously shown to have increased phosphate (Pi) uptake, was found to exhibit higher selenite uptake than the wild‐type in both concentration‐ and time‐dependent selenite uptake assays. Respiratory inhibitors significantly inhibited selenite uptake in the wildtype and the ltn1 mutant, indicating that selenite uptake was coupled with H+ and energy‐dependent. Selenite uptake was greatly enhanced under Pi‐starvation conditions, suggesting that Pi transporters are involved in selenite uptake.

OsPT2, the most abundantly expressed Pi transporter in the roots, is also significantly up‐regulated in ltn1 and dramatically induced by Pi starvation. OsPT2‐overexpressing and knockdown plants displayed significantly increased and decreased rates of selenite uptake, respectively, suggesting that OsPT2 plays a crucial role in selenite uptake. Se content in rice grains also increased significantly in OsPT2‐overexpressing plants.

These data strongly demonstrate that selenite and Pi share similar uptake mechanisms and that OsPT2 is involved in selenite uptake, which provides a potential strategy for breeding Se‐enriched rice varieties.
The Prevalence and Contents of Advance Directives in Patients with Pacemakers
Authors: PASALIC DARIO , TAJOURI TANYA H. , OTTENBERG ABIGALE L. , MUELLER PAUL S.
Published: November 2013

Background

Little is known about the use of advance directives (ADs) in patients who have implantable cardiac pacemakers (PMs).

Methods

We conducted a retrospective review of the medical records of residents of Olmsted County, Minnesota, who underwent implantation of a cardiac PM at Mayo Clinic (Rochester, Minnesota) during 2006 and 2007, and determined the prevalence and contents of ADs in these patients.

Results

During the study period, 205 residents of Olmsted County (men, 53%) underwent PM implantation (mean age [standard deviation] at implantation, 77 [15] years). Overall, 120 patients (59%) had ADs. Of these, 63 ADs (53%) were executed more than 12 months before and 33 (28%) were executed after PM implantation. Many patients specifically mentioned life‐prolonging treatments in their ADs: cardiopulmonary resuscitation, 76 (63%); mechanical ventilation, 56 (47%); and hemodialysis, 31 (26%). Pain control was mentioned in 79 ADs (66%) and comfort measures were mentioned in 42 ADs (35%). Furthermore, the AD of many patients contained a general statement about end‐of‐life care (e.g., no “heroic measures”). However, only one AD (1%) specifically addressed the end‐of‐life management of the PM.

Conclusions

More than half of the patients with PMs in our study had executed an AD, but only one patient specifically mentioned her PM in her AD. These results suggest that patients with PMs should be encouraged to execute ADs and specifically address end‐of‐life device management in their ADs. Doing so may prevent end‐of‐life ethical dilemmas related to PM management.
The Effect of Anxiety and Depression on Symptoms Attributed to Atrial Fibrillation
Authors: THOMPSON TIFFANY S. , BARKSDALE DEBRA J. , SEARS SAMUEL F. , MOUNSEY JOHN PAUL , PURSELL IRION , GEHI ANIL K.
Published: November 2013

Background

Symptoms attributed to atrial fibrillation (AF) are nonspecific, and it remains unclear what influences perception of symptoms. Anxiety or depression may be important in modulating perception of AF symptoms. However, few longitudinal studies have addressed this effect.

Methods

A total of 378 patients with AF completed anxiety and depression severity questionnaires as well as AF symptom and frequency severity questionnaires. Patients were offered treatment strategies including catheter ablation or antiarrhythmic or rate‐controlling medications. Patients were followed at 3‐month intervals and completed follow‐up questionnaires including repeat assessment of anxiety, depression, and AF symptoms. A method of generalized estimating equations was used for longitudinal analyses.

Results

Analysis revealed that increased anxiety or depression was associated with increased AF symptom severity (AFSS), after adjusting for potential confounders. In both unadjusted and adjusted follow‐up analyses, antiarrhythmic drug therapy or catheter ablation reduced AFSS (P < 0.001). However, none of anxiety severity, depression severity, or the perception of AF frequency severity improved significantly with AF treatment.

Conclusions

Our results extend previous studies demonstrating that anxiety and depression are associated with worsened AFSS. Antiarrhythmic drug therapy or catheter ablation reduces AFSS but does not affect depression and anxiety symptoms. To achieve more comprehensive AF symptom relief, treatment of both AF and psychological comorbidities may be beneficial.
Comparison of ICD Implantation in Obese and Nonobese Patients
Authors: VENKATARAMAN GANESH , MATHUR DEEPTI , JOSHI SIDDHI , STRICKBERGER ADAM
Published: November 2013

Background

Implantable defibrillator (ICD) therapy improves mortality in patients at risk for sudden cardiac death. Obese patients pose challenges during ICD implantation and may have an increased risk of procedure‐related complications. The comparison of acute procedural success and safety of ICD implantation in obese and nonobese patients has not been previously reported.

Methods

A total of 181 patients underwent ICD implantation at a single institution. Obesity was defined as a body mass index (BMI) greater than or equal to 30 kg/m2. Acute safety and efficacy data were collected and analyzed from a prospectively maintained database, with retrospective chart review, as required.

Results

Among the 181 patients, 58 (32.0%) were obese. Mean BMI was 36.7 ± 6.3 kg/m2 among obese patients and was 24.6 ± 3.1 kg/m2 among nonobese patients (P < 0.001). Successful ICD implantation occurred in 58 of 58 (100%) obese patients and 122 of 123 (99.2%) nonobese patients (P = 1.0). A complication was observed in three of 58 (5.2%) obese patients and in seven of 123 (5.7%) nonobese patients (P = 1.0). Similarly, there was no difference in acute procedural success and safety in patients receiving a cardiac resynchronization therapy (CRT)‐ICD.

Conclusions

Acute success and safety of ICD implantation is similar in both obese and nonobese patients. This finding extended to patients treated with a CRT‐ICD and among patients with extreme obesity. Obesity should probably not be a factor in determining whether a patient is a candidate for ICD implantation.
Atrial Electromechanical Conduction Delay in Patients with Neurocardiogenic Syncope
Authors: SUCU MURAT , ERCAN SULEYMAN , UKU OKKES , DAVUTOGLU VEDAT , ALTUNBAS GOKHAN
Published: November 2013

Aim

We aimed to investigate the presence of atrial electromechanical conduction delay in patients with neurocardiogenic syncope, which was diagnosed with head‐up tilt table test (HUTT).

Materials and Methods

A total of 29 patients (mean age: 30.6 ± 15.9 years) with vasovagal syncope, as diagnosed by HUTT, and 23 healthy control subjects (mean age: 34.7 ± 16.3 years) with a negative HUTT were enrolled to the study. Atrial electromechanical conduction delay was defined as the time elapsed from the beginning of the P wave in the electrogardiogram to the beginning of the Am wave in tissue Doppler.

Results

There was no statistically significant difference between the groups in terms of interatrial conduction delay, whereas the difference was significant with regard to the right intraatrial electromechanical conduction delay (P < 0.01) and the left intraatrial electromechanical conduction delay (P < 0.0001). There was a negative correlation between the left intraatrial electromechanical conduction delay and the right intraatrial electromechanical conduction delay (r = –0.486, P = 0.001), whereas a positive correlation was present with the interatrial electromechanical conduction delay (r = 0.507, P = 0.001).

Conclusion

In this study, the tissue Doppler method revealed that there is left and right intraatrial electromechanical conduction delay in patients with vasovagal syncope. The impact and role of atrial conduction delay as a pathophysiological determinant should be confirmed in further studies.
Validation of Conventional Fluoroscopic and ECG Criteria for Right Ventricular Pacemaker Lead Position Using Cardiac Computed Tomography
Authors: PANG BENJAMIN J. , JOSHI SUBODH B. , LUI ELAINE H. , TACEY MARK A. , LING LIANG‐HAN , ALISON JEFF , SENEVIRATNE SUJITH K. , CAMERON JAMES D. , MOND HARRY G.
Published: November 2013

Introduction

It is hypothesized that pacing the right ventricular (RV) septum is associated with less deleterious outcomes than RV apical pacing. Our aim was to validate fluoroscopic and electrocardiography (ECG) criteria for describing pacemaker and implantable cardioverter defibrillator RV “septal” lead position against the proposed gold standard: cardiac computed tomography (CT).

Methods

Using the conventional fluoroscopic criteria, we intended to place RV nonapical leads on the interventricular septum. Lead positions were later retrospectively analyzed with CT and correlated with ECGs and fluoroscopic projections: posterior‐anterior, 40° left anterior oblique (LAO), 40° right anterior oblique (RAO), and left lateral.

Results

Only 21% (nine of 35) of presumed “septal” RV nonapical leads using the conventional fluoroscopic criteria were on the true septum. A schema developed to define septal position in the RAO fluoroscopic view had high agreement with CT images. ECG criteria had only fair to moderate agreement with CT. The paced QRS duration was significantly longer (P < 0.001) with RV apical pacing (176 ± 10.7 ms), compared to RV nonapical pacing (144.5 ± 14.3 ms).

Conclusion

Using the conventional fluoroscopic criteria, only a minority of RV leads were implanted on the true RV septum. Instead, aiming for the middle of the cardiac silhouette in the RAO fluoroscopic view, confirming rightward orientation in the LAO view, and having a paced QRS duration <140 ms may allow the implanting cardiologist a simple, more accurate method to achieve true RV septal lead positioning.
Hydrogel‐Forming and Dissolving Microneedles for Enhanced Delivery of Photosensitizers and Precursors
Authors: Donnelly Ryan F. , Morrow Desmond I. J. , McCrudden Maelíosa T. C. , Alkilani Ahlam Zaid , Vicente‐Pérez Eva M. , O'Mahony Conor , González‐Vázquez Patricia , McCarron Paul A. , Woolfson A. David
Published: November 2013

We present “one‐step application” dissolving and hydrogel‐forming microneedle arrays (MN) for enhanced delivery of photosensitizers/precursors. MN (280 μm) prepared from 20% w/w poly(methylvinylether/maelic acid) and cross‐linked with glycerol by esterification to form hydrogels upon skin insertion, or allowed to dissolve rapidly in skin, were combined with patches containing 19 mg cm−2 of 5‐aminolevulinic acid (ALA) or meso‐tetra (N‐methyl‐4‐pyridyl) porphine tetra tosylate (TMP) for drug delivery. Both MN types were mechanically robust, with compression forces of 20.0 N only causing height reductions of 14%. Application forces as low as 8.0 N per array allowed >95% of the MN in each array type to penetrate excised porcine skin, with the MN penetrating to approximately 220 μm. MN significantly enhanced transdermal delivery of ALA and TMP in vitro, with the hydrogel‐forming system comparable with the dissolving system for ALA delivery (approximately 3000 nmol cm−2 over 6 h), but superior for delivery of the much larger TMP molecule (approximately 14 nmol cm−2 over 24 h, compared to 0.15 nmol cm−2). As this technology clearly has potential in enhanced photodynamic therapy of neoplastic skin lesions, we are currently planning animal studies, to be followed by preliminary human evaluations. GMP manufacturing scale‐up is ongoing.
Panel design effects on response rates and response quality
Authors: Segers Rene , Franses Philip Hans
Published: November 2013

To understand changes in individuals' opinions and attitudes, it would be best to collect data through panels. Such panels, however, often cause irritation among respondents, resulting in low response rates and low response quality. We address whether this problem can be alleviated by designing a panel survey in an alternative way. For this purpose, we perform two field studies where we measure the effects of several panel design characteristics on response rates and response quality. These characteristics include the number of waves and the time between subsequent waves, which may be either fixed or random. Our findings suggest that response rates and response quality can be improved significantly by surveying at random time intervals. It is then crucial that panel members are not informed about the dates they will be surveyed, because in this case, respondents are less likely to develop expectations as to when they will be surveyed again. The methodology we put forward can be used to improve the efficiency of a panel study by carefully calibrating the studies' panel design parameters.
Collaborative Ontology Development for the Geosciences
Authors: Kalbasi Reza , Janowicz Krzysztof , Reitsma Femke , Boerboom Luc , Alesheikh Ali
Published: November 2013

Ontology‐based information publishing, retrieval, reuse, and integration have become popular research topics to address the challenges involved in exchanging data between heterogeneous sources. However, in most cases ontologies are still developed in a centralized top‐down manner by a few knowledge engineers. Consequently, the role that developers play in conceptualizing a domain such as the geosciences is disproportional compared with the role of domain experts and especially potential end‐users. These and other drawbacks have stimulated the creation of new methodologies focusing around collaboration. Based on a review of existing approaches, this article presents a two‐step methodology and implementation to foster collaborative ontology engineering in the geosciences. Our approach consists of the development of a minimalistic core ontology acting as a catalyst and the creation of a virtual collaborative development cycle. Both methodology and prototypical implementation have been tested in the context of the EU‐funded ForeStClim project which addresses environmental protection with respect to forests and climate change.
Low Copy Numbers of DC‐SIGN in Cell Membrane Microdomains: Implications for Structure and Function
Authors: Liu Ping , Wang Xiang , Itano Michelle S. , Neumann Aaron K. , de Silva Aravinda M. , Jacobson Ken , Thompson Nancy L.
Published: November 2013

Presently, there are few estimates of the number of molecules occupying membrane domains. Using a total internal reflection fluorescence microscopy (TIRFM) imaging approach, based on comparing the intensities of fluorescently labeled microdomains with those of single fluorophores, we measured the occupancy of DC‐SIGN, a C‐type lectin, in membrane microdomains. DC‐SIGN or its mutants were labeled with primary monoclonal antibodies (mAbs) in either dendritic cells (DCs) or NIH3T3 cells, or expressed as GFP fusions in NIH3T3 cells. The number of DC‐SIGN molecules per microdomain ranges from only a few to over 20, while microdomain dimensions range from the diffraction limit to > 1 µm. The largest fraction of microdomains, appearing at the diffraction limit, in either immature DCs or 3 T3 cells contains only 4–8 molecules of DC‐SIGN, consistent with our preliminary super‐resolution Blink microscopy estimates. We further show that these small assemblies are sufficient to bind and efficiently internalize a small (∼50 nm) pathogen, dengue virus, leading to infection of host cells.
Velocity and Momentum Decay Characteristics of a Submerged Viscoplastic Jet
Authors: Hammad Khaled J.
Published: November 2013

Velocity and momentum decay characteristics of a submerged viscoplastic non-Newtonian jet are studied within the steady laminar flow regime. The governing mass and momentum conservation equations along with the Bingham rheological model are solved numerically using a finite-difference scheme. A parametric study is performed to reveal the influence of the initial velocity profile, flow inertia, and yield stress presence on the flow field characteristics. Two initial velocity profiles are considered, a top-hat and fully developed pipe jets. The centerline velocity decay is found to be more rapid for the pipe jet than the top-hat one when the fluid is Newtonian while the opposite trend is observed for yield stress Bingham fluids. The decay in the momentum flux of the pipe jet is always less than that of the top-hat jet. Momentum and velocity based jet depths of penetration are introduced and used to analyze the obtained flow field information for a wide range of Reynolds and yield numbers. Depths of penetration are found to linearly increase with the Reynolds number and substantially decrease with the yield number. The presence of yield stress significantly reduces the momentum and velocity penetration depths of submerged top-hat and pipe jets. Penetration depths of yield stress fluids are shown to be more than an order of magnitude smaller than the ones corresponding to Newtonian fluids.
Draft: Stick-Slip Motions of a Rotor-Stator System
Authors: Vlajic Nicholas , Liao Chien-Min , Karki Hamad , Balachandran Balakumar
Published: November 2013

In the current study, the authors examine the torsional vibrations of a rotor enclosed within a stator subjected to dry friction. Through the experiments, it is demonstrated that forward whirling of the rotor occurs while in contact with the stator, backward whirling occurs with contact, as well as impacting motions, which are characterized by nonsynchronous whirling with rotor-stator collisions. While undergoing these motions, the torsional oscillations are excited by stick-slip interactions. Experimental data are presented to show the presence of a stable torsional mode dominated motion while subjected to stick-slip forces during dry-friction whirling. In this motion state, the torsional oscillation response occurs at a combination of frequencies including drive and whirl frequencies. A finite dimensional model is constructed and simulations carried out by using this model are able to capture the system dynamics, including the torsional responses observed during dry-friction whirling. Numerical results obtained by using this model are consistent with experimental observations. The findings of this study are relevant to whirling motions experienced by rotating, long flexible structures, such as drill strings used in oil-well explorations.
The Power and Efficiency Limits of Piezoelectric Energy Harvesting
Authors: Shafer Michael W. , Garcia Ephrahim
Published: November 2013

The fundamental limits of cantilevered piezoelectric energy harvesters have not been well established. As with any other power generation technology, it is critical to establish the limits of power output and efficiency. Mathematical models for piezoelectric energy harvester power output have seen continued refinement, but these models have mainly been used and compared to individual harvester designs. Moreover, existing models all assume power scales with acceleration input, and take no account for the upper limit of the acceleration due to the ultimate strength of the piezoelectric material. Additionally, models for efficiency have been developed, but the limits have not been thoroughly explored. In this paper, we present the upper limits of input acceleration and output power for a piezoelectric harvester device. We then use these expressions, along with a previously developed ideal design method, to explore the upper limits of power production across a range of system masses and excitation frequencies. We also investigate general efficiency limits of these devices. We show the upper limit using an existing model and develop an alternate model that is applicable to excitation sources that are not capable of energy recovery.
Numerical Investigation of the Flutter of a Spherical Shell
Authors: Menaa Mohamed , Lakis Aouni A.
Published: November 2013

In this study, aeroelastic analysis of a spherical shell subjected to external supersonic airflow is carried out. The structural model is based on a combination of the linear spherical shell theory and the classic finite element method (FEM). In this hybrid method, the nodal displacements are found from the exact solution of shell governing equations rather than approximated by polynomial functions. Therefore, the number of elements chosen is a function of the complexity of the structure. Convergence is rapid. It is not necessary to choose a large number of elements to obtain good results. Linearized first-order potential (piston) theory with the curvature correction term is coupled with the structural model to account for pressure loading. The linear mass, stiffness, and damping matrices are found using the hybrid finite element formulation. Aeroelastic equations are numerically derived and solved. The results are validated using the numerical and theoretical data available in literature. The analysis is accomplished for spherical shells with different boundary conditions, geometries, flow parameters, and radius to thickness ratios. the results show that the spherical shell loses its stability through coupled-mode flutter. This proposed hybrid FEM can be used efficiently for the design and analysis of spherical shells employed in high speed aircraft structures.
Electrostatically Driven Creep in Viscoelastic Dielectric Elastomers
Authors: Wang Jin , Nguyen Thao D. , Park Harold S.
Published: November 2013

We utilize a nonlinear, dynamic finite element model coupled with a finite deformation viscoelastic constitutive law to study the inhomogeneous deformation and instabilities resulting from the application of a constant voltage to dielectric elastomers. The constant voltage loading is used to study electrostatically driven creep and the resulting electromechanical instabilities for two different cases that have all been experimentally observed, i.e., electromechanical snap-through instability and bursting drops in a dielectric elastomer. We find that in general, increasing the viscoelastic relaxation time leads to an increase in time needed to nucleate the electromechanical instability. However, we find for these two cases that the time needed to nucleate the instability scales with the relaxation time.
Residence Time Distribution in a Swirling Flow at Nonreacting, Reacting, and Steam-Diluted Conditions
Authors: Göckeler Katharina , Terhaar Steffen , Oliver Paschereit Christian
Published: November 2013

Residence time distributions in a swirling, premixed combustor flow are determined by means of tracer experiments and a reactor network model. The measurements were conducted at nonreacting, reacting, and steam-diluted reacting conditions for steam contents of up to 30% of the air mass flow. The tracer distribution was obtained from the light scattering of seeding particles employing the quantitative light sheet technique (QLS). At steady operating conditions, a positive step of particle feed was applied, yielding cumulative distribution functions (CDF) for the tracer response. The shape of the curve is characteristic for the local degree of mixedness. Fresh and recirculating gases were found to mix rapidly at nonreacting and highly steam-diluted conditions, whereas mixing was more gradual at dry reacting conditions. The instantaneous mixing near the burner outlet is related to the presence of a large-scale helical structure, which was suppressed at dry reacting conditions. Zones of similar mixing time scales, such as the recirculation zones, are identified. The CDF curves in these zones are reproduced by a network model of plug flow and perfectly mixed flow reactors. Reactor residence times and inlet volume flow fractions obtained in this way provide data for kinetic network models.
Impact of Wall Temperature on Turbine Blade Tip Aerothermal Performance
Authors: Zhang Q. , He L.
Published: November 2013

Currently the aerodynamics and heat transfer over a turbine blade tip tend to be analyzed separately with the assumption that the wall thermal boundary conditions do not affect the over-tip-leakage (OTL) flow field. There are some existing correlations for correcting the wall temperature effect on heat transfer when scaled to engine realistic conditions. But they were either developed to account for the temperature dependence of fluid properties largely empirically, or based on a boundary-layer model. It would be difficult (if not impossible) to define a boundary layer in many parts of a realistic blade passage with marked three-dimensional (3D) end wall and secondary flows (including those within a blade tip and around it). The questions to be asked here are: is the OTL aerodynamics significantly affected by the wall thermal condition? And if it is, how can we count this effect consistently in turbine blade tip design and analysis using modern CFD methods? In the present study the problem has been examined for typical high-pressure turbine blade tip configurations. An extensively developed RANS code (HYDRA) is employed and validated against the experimental data from a high speed linear cascade testing rig. The numerical analysis reveals that the wall–gas temperature ratio could greatly affect the transonic OTL flow field and there is a strong two-way coupling between aerodynamics and heat transfer. The feedbacks of the thermal boundary condition to aerodynamics behave differently at different flow regimes over the tip, clearly indicating a highly localized dependence of the convective heat transfer coefficient (HTC) upon wall temperatures. This implies that to use HTC for blade metal temperature predictions without resorting a fully conjugate solution, the temperature dependence needs to be corrected locally. A nonlinear correction approach has been adopted in the present work, and the results demonstrate its effectiveness for the transonic turbine tip configurations studied.
A quantification strategy for missing bone mass in case of osteolytic bone lesions
Authors: Fränzle Andrea , Bretschi Maren , Bäuerle Tobias , Giske Kristina , Hillengass Jens , Bendl Rolf
Published: November 2013

Purpose:

Most of the patients who died of breast cancer have developed bone metastases. To understand the pathogenesis of bone metastases and to analyze treatment response of different bone remodeling therapies, preclinical animal models are examined. In breast cancer, bone metastases are often bone destructive. To assess treatment response of bone remodeling therapies, the volumes of these lesions have to be determined during the therapy process. The manual delineation of missing structures, especially if large parts are missing, is very time‐consuming and not reproducible. Reproducibility is highly important to have comparable results during the therapy process. Therefore, a computerized approach is needed. Also for the preclinical research, a reproducible measurement of the lesions is essential. Here, the authors present an automated segmentation method for the measurement of missing bone mass in a preclinical rat model with bone metastases in the hind leg bones based on 3D CT scans.

Methods:

The affected bone structure is compared to a healthy model. Since in this preclinical rat trial the metastasis only occurs on the right hind legs, which is assured by using vessel clips, the authors use the left body side as a healthy model. The left femur is segmented with a statistical shape model which is initialised using the automatically segmented medullary cavity. The left tibia and fibula are segmented using volume growing starting at the tibia medullary cavity and stopping at the femur boundary. Masked images of both segmentations are mirrored along the median plane and transferred manually to the position of the affected bone by rigid registration. Affected bone and healthy model are compared based on their gray values. If the gray value of a voxel indicates bone mass in the healthy model and no bone in the affected bone, this voxel is considered to be osteolytic.

Results:

The lesion segmentations complete the missing bone structures in a reasonable way. The mean ratiovr/vm of the reconstructed bone volume vr and the healthy model bone volume vm is 1.07, which indicates a good reconstruction of the modified bone.

Conclusions:

The qualitative and quantitative comparison of manual and semi‐automated segmentation results have shown that comparing a modified bone structure with a healthy model can be used to identify and measure missing bone mass in a reproducible way.
Cancer cachexia and diabetes: similarities in metabolic alterations and possible treatment,
Authors: Chevalier Stéphanie , Farsijani Samaneh
Published: November 2013

Cancer cachexia is a metabolic syndrome featuring many alterations typical of type 2 diabetes (T2D). While muscle wasting is a hallmark of cachexia, epidemiological evidence also supports an accelerated age-related muscle loss in T2D. Insulin resistance manifests in both conditions and impairs glucose disposal and protein anabolism by tissues. A greater contribution of gluconeogenesis to glucose production may limit amino acid availability for muscle protein synthesis, further aggravating muscle loss. In the context of inter-dependence between glucose and protein metabolism, the present review summarizes the current state of knowledge on alterations that may lead to muscle wasting in human cancer. By highlighting the similarities with T2D, a disease that has been more extensively studied, the objective of this review is to provide a better understanding of the pathophysiology of cancer cachexia and to consider potential treatments usually targeted for T2D. Nutritional approaches aimed at stimulating protein anabolism might include specially formulated food with optimal protein and amino acid composition. Because the gradual muscle loss in T2D may be attenuated by diabetes treatment, anti-diabetic drugs might be considered in cachexia treatment. Metformin emerges as a choice candidate as it acts both on reducing gluconeogenesis and improving insulin sensitivity, and has demonstrated tumour suppressor properties in multiple cancer types. Such a multimodal approach to slow or reverse muscle wasting in cachexia warrants further investigation.
Investigating interconnected fisheries: a coupled model of the lobster and herring fisheries in New England
Authors: Lehuta Sigrid , Holland Daniel S. , Pershing Andrew J.
Published: November 2013

Ostensibly separate fisheries are often linked through ecological, environmental, and human mediated processes that can impact their productivity, profitability, and resilience; however, managers rarely explicitly account for these linkages. We present a coupled bioeconomic model of the American lobster (Homarus americanus) and Atlantic herring (Clupea harengus) fisheries in the northeast United States. The model builds upon existing stock assessment models and includes key characteristics of both fisheries including size- or age-structured populations, seasonal patterns of lobster exploitation, and seasonal-spatial patterns of herring exploitation. The lobster and herring models are linked through a bait market module that drives behavior of the herring fleet and affects catches, costs, and revenues in both fisheries. The model illustrates how changes in management or ecosystem conditions in one fishery can propagate to another. The model suggests that the lobster fishery is robust to declines in herring recruitment and limited changes in the spatial allocation of the herring total allowable catch. However, herring catches and stocks are affected by changes in lobster management that impact effort levels.
Reorganizations of complex networks: Compounding and reducing
Authors: Shao Fengjing , Sui Yi
Published: November 2013

Real networks interact with each other by different kinds of topological connections, which are usually demonstrated by linking nodes of different networks. Simple connection, such as one-to-one corresponding, random connection and similar connection are adopted for studying the interacted networks. Practical interrelations established between the two networks are ignored. In this study, a generalized framework of multi-subnet composited complex network that allowed us to investigate interrelations among several subnets is developed. Based on that, reorganizations of networks: compounding (compound subnets into a "bigger" one) and reducing (obtain a "smaller" network from a "bigger" one) are proposed. As an empirical evidence, influence of compounding on traffic dynamics is discussed. And the properties of nodes linking two networks are also considered. Onset of compounding between two networks is revealed. Numerical simulations on artificial networks as well as real bus and tube networks of Qingdao in China agree well with our analysis, which show validity of our model.
Cascading failures in complex networks with community structure
Authors: Lin Guoqiang , Di Zengru , Fan Ying
Published: November 2013

Much empirical evidence shows that when attacked with cascading failures, scale-free or even random networks tend to collapse more extensively when the initially deleted node has higher betweenness. Meanwhile, in networks with strong community structure, high-betweenness nodes tend to be bridge nodes that link different communities, and the removal of such nodes will reduce only the connections among communities, leaving the networks fairly stable. Understanding what will affect cascading failures and how to protect or attack networks with strong community structure is therefore of interest. In this paper, we have constructed scale-free Community Networks (SFCN) and Random Community Networks (RCN). We applied these networks, along with the Lancichinett–Fortunato–Radicchi (LFR) benchmark, to the cascading-failure scenario to explore their vulnerability to attack and the relationship between cascading failures and the degree distribution and community structure of a network. The numerical results show that when the networks are of a power-law distribution, a stronger community structure will result in the failure of fewer nodes. In addition, the initial removal of the node with the highest betweenness will not lead to the worst cascading, i.e. the largest avalanche size. The Betweenness Overflow (BOF), an index that we developed, is an effective indicator of this tendency. The RCN, however, display a different result. In addition, the avalanche size of each node can be adopted as an index to evaluate the importance of the node.
Non-Gaussian behavior of the internet topological fluctuations
Authors: Chen Qu , Qian Jiang-Hai , Han Ding-Ding
Published: November 2013

The traditional Gibrat's hypotheses were once used to model the topological fluctuations of Internet. Although it seems to reproduce the scaling relation of Internet's degree distribution, the detailed micro-dynamics have never been empirically validated. Here, we analyze the distribution of degree growth rates of the Internet for various time scales. We find that in contrast to the traditional Gibrat's assumptions, none of the degree growth rates are normally distributed, but behaves as an exponential decrease on its body and a power-law decay on its tail. Moreover, the observed growth rate distribution turns out independent of the initial degree when the time interval enlarges to a year. Our observations do not consist with the traditional Gibrat law model and suggest a more complex fluctuation mechanism underlying the evolution of Internet.
Effects of multiple spreaders in community networks
Authors: Hu Zhao-Long , Ren Zhuo-Ming , Yang Guang-Yong , Liu Jian-Guo
Published: November 2013

Human contact networks exhibit the community structure. Understanding how such community structure affects the epidemic spreading could provide insights for preventing the spreading of epidemics between communities. In this paper, we explore the spreading of multiple spreaders in community networks. A network based on the clustering preferential mechanism is evolved, whose communities are detected by the Girvan–Newman (GN) algorithm. We investigate the spreading effectiveness by selecting the nodes as spreaders in the following ways: nodes with the largest degree in each community (community hubs), the same number of nodes with the largest degree from the global network (global large-degree) and randomly selected one node within each community (community random). The experimental results on the SIR model show that the spreading effectiveness based on the global large-degree and community hubs methods is the same in the early stage of the infection and the method of community random is the worst. However, when the infection rate exceeds the critical value, the global large-degree method embodies the worst spreading effectiveness. Furthermore, the discrepancy of effectiveness for the three methods will decrease as the infection rate increases. Therefore, we should immunize the hubs in each community rather than those hubs in the global network to prevent the outbreak of epidemics.
DARK ENERGY AND DARK MATTER IN A SUPERFLUID UNIVERSE
Authors: HUANG KERSON
Published: November 2013

The vacuum is filled with complex scalar fields, such as the Higgs field. These fields serve as order parameters for superfluidity (quantum phase coherence over macroscopic distances), making the entire universe a superfluid. We review a mathematical model consisting of two aspects: (a) emergence of the superfluid during the big bang; (b) observable manifestations of superfluidity in the present universe. The creation aspect requires a self-interacting scalar field that is asymptotically free, i.e. the interaction must grow from zero during the big bang, and this singles out the Halpern–Huang potential, which has exponential behavior for large fields. It leads to an equivalent cosmological constant that decays like a power law, and this gives dark energy without "fine-tuning." Quantum turbulence (chaotic vorticity) in the early universe was able to create all the matter in the universe, fulfilling the inflation scenario. In the present universe, the superfluid can be phenomenologically described by a nonlinear Klein–Gordon equation. It predicts halos around galaxies with higher superfluid density, which is perceived as dark matter through gravitational lensing. In short, dark energy is the energy density of the cosmic superfluid, and dark matter arises from local fluctuations of the superfluid density.
IS BIMETRIC GRAVITY REALLY GHOST FREE?
Authors: KLUSOŇ J.
Published: November 2013

We perform the Hamiltonian analysis of the bimetric theory of gravity introduced in S. F. Hassan and R. A. Rosen, J. High Energy Phys.1202, 126 (2012), arXiv:1109.3515 [hep-th]. We carefully analyze the requirement of the preservation of all constraints and we find that there is no additional constraint that could eliminate the ghost mode.