bluuebunny/crossref_metadata_2025 huggingface dataset:
The addition of calcium ion chelator, EGTA to thawing solution improves fertilizing ability in frozen–thawed boar sperm
Authors: OKAZAKI Tetsuji , YOSHIDA Shuji , TESHIMA Hisanori , SHIMADA Masayuki
Published: March 2011

In our previous study, seminal plasma effectively suppressed the induction of sperm to capacitation‐like status and acrosome loss during the thawing process. However, because boar seminal plasma is contaminated with various kinds of bacteria and/or viruses, it is necessary to develop a thawing solution without animal‐derived materials. In this study, we focused on the increase of intracellular Ca2+ ([Ca2+]i) in sperm after thawing and the negative effects of sperm qualities. After thawing, the fluorescent intensity of [Ca2+]i indicator, Fluo‐3/AM, and the level of phosphorylated tyrosine residue of protein were increased in the sperm. Next, we investigated whether the addition of Ca2+ chelators (ethylenediaminetetraacetic acid (EDTA) and ethyleneglycoltetraacetic acid (EGTA)) improved post‐thawed sperm motility. When the frozen–thawed sperm were treated with 6 mmol/L EDTA + 6 mmol/L EGTA, sperm motility was significantly increased as compared with control (6 mmol/L EDTA alone) at all incubation periods (P < 0.05). The combinational treatment significantly suppressed the elevation of [Ca2+]i and the tyrosine phosphorylation, which improved the acrosomal status and fertilizing ability in vitro. Furthermore, when the thawing method was applied for artificial insemination, the fertilization rate was significantly higher than control (P < 0.05, 33% vs. 82%). Thus, we conclude that the addition of EDTA + EGTA to thawing solution is a beneficial tool for artificial insemination using frozen–thawed boar sperm.
Seed Dispersal Spectrum of Woody Species in South Ecuadorian Dry Forests: Environmental Correlates and the Effect of Considering Species Abundance
Authors: Jara‐Guerrero Andrea , De la Cruz Marcelino , Méndez Marcos
Published: March 2011

This study examines the seed dispersal spectrum of the tropical dry forests of Southern Ecuador, in an effort to contribute to the knowledge of the complex dynamics of tropical dry forests. Seed dispersal spectrum was described for a total number of 160 species. Relationships of dispersal syndromes with plant growth form and climatic seasonality were explored. For a subset of 97 species, we determined whether dispersal spectrum changes when species abundance, in addition to species number, is taken into account. The same subset was used to relate dispersal syndromes with the environmental conditions. Zoochorous species dominated in the studied community. When considering the individual abundance of each species, however, anemochory was the prevalent dispersal syndrome. We found a significant difference in the frequency of dispersal syndromes among plant growth forms, with epizoochory only occurring in shrub species. The dispersal spectrum was dependent on climatic seasonality. The largest proportion of anemochorous species fructified during the dry season, while zoochorous diaspores dominated during the rainy season. A fourth‐corner analysis indicated that the seed dispersal spectrum of Southern Ecuador dry forests is controlled by environmental conditions such as annual precipitation, annual temperature range or topography. Our results suggest that spatio‐temporal changes in the environmental conditions may affect important ecological processes for dispersal. Thus, the predominance of one syndrome or another may depend on the spatial variation of environmental conditions.

Abstract in Spanish is available at http://www.blackwell‐synergy.com/loi/btp.
Effect of Host Tree Traits on Epiphyte Diversity in Natural and Anthropogenic Habitats in Ecuador
Authors: Köster Nils , Nieder Jürgen , Barthlott Wilhelm
Published: March 2011

Vascular epiphytes represent a highly diverse element of tropical rain forests, but they depend strongly on the structure and taxonomic composition of their tree communities. For conservation planning, it is therefore critical to understand the effect of host tree characteristics on epiphyte species richness in natural and anthropogenically transformed vegetation. Our study compares the effect of human land‐use on epiphyte diversity based on 220 study plots in a lowland rain forest and an Andean cloud forest in western Ecuador. We evaluate the relevance of host tree size and taxonomic identity for epiphyte species richness in contiguous primary forests, forest fragments, isolated remnant trees (IRTs), and secondary forests. At both study sites, epiphyte diversity was highest in primary forests, and it was lowest on IRTs and in secondary forests. Epiphyte species numbers of forest fragments were significantly reduced compared with the contiguous primary forest at the lowland study site, but not in the cloud forest area. Host tree size was a core predictor among secondary forests, but it had less significance within other habitat types. Taxonomic identity of the host trees also explained up to 61 percent of the variation in epiphyte diversity, especially for IRTs. The structural and taxonomic composition of the tree community in anthropogenically transformed habitat types proved to be fundamental to epiphyte diversity. This highlights the importance of deliberate selection of tree species for reforestation in conservation programs and the possible negative effects of selective logging in primary forests.

Abstract in Spanish is available at http://www.blackwell‐synergy.com/loi/btp.
Which Extent is Plasticity to Light Involved in the Ecotypic Differentiation of a Tree Species from Savanna and Forest?
Authors: Goulart Maíra F. , Lovato Maria B. , de Vasconcellos Barros Fernanda , Valladares Fernando , Lemos‐Filho José P.
Published: March 2011

Light intensity and heterogeneity are some of the main environmental factors that differ between forest and savanna habitats, and plant species from these habitats form distinct functional types. In this study, we tested the hypothesis that not only differences in morphological and physiological traits but also phenotypic plasticity in response to light are involved in adaptation to forest and savanna habitats by investigating ecotypic differentiation between populations of Plathymenia reticulata (Leguminosae: Mimosoideae), a tree from the Brazilian Atlantic Forest and the Brazilian Cerrado (savanna). Seeds from four natural populations (one from each biome core area and two from ecotonal regions) were grown in a common garden with four light treatments. Fifteen morphological and physiological characteristics were evaluated until individuals reached 6 mo old. Comparisons among populations showed differences for seven traits in at least one light treatment. These differences pointed to local adaptation to different biomes. Populations showed different levels of phenotypic plasticity in response to light in seven traits. Higher plasticity was found either in the forest core population or ecotonal populations; lower values were found in the cerrado core population. Lower plasticity in the cerrado population emphasizes the stress resistant syndrome, as lower plasticity is probably advantageous in a habitat where a conservative resource use is crucial. Higher plasticity in forest individuals suggests higher ability in exploiting the light heterogeneity in this habitat. Also, higher plasticity in ecotonal populations can be important to ensure the maintenance of P. reticulata in these temporally and spatially dynamic areas.

Abstract in Portugese is available at http://www.blackwell‐synergy.com/loi/btp.
Tropical UnderstoryPiperShrubs Maintain High Levels of Genotypic Diversity Despite Frequent Asexual Recruitment
Authors: Lasso Eloisa , Dalling James W. , Bermingham Eldredge
Published: March 2011

Many plant species have the capacity to regenerate asexually by resprouting from stem and leaf fragments. In the pan‐tropical shrub genusPiper, this tendency is thought to be higher in shade‐tolerant than light‐demanding species, and to represent a trade‐off with annual seed production. Here we use molecular markers to identify clones in fivePiperspecies varying in light requirements. We test predictions that (i) asexual recruitment success is highest in shade‐tolerant species, and (ii) that consequently, shade‐tolerant species are characterized by lower genotypic diversity than light‐demandingPiper. We found that two shade‐tolerantPiperspecies recruited asexually more frequently (36–42% of sampled shoots were of asexual origin) than, two light‐demanding and one shade‐tolerant species (0–26%). Furthermore, as predicted, genotypic diversity was negatively correlated with the frequency of asexual recruitment in the population. Nonetheless, genotypic diversity ofPiperwas high compared with other clonal plants. The proportion of unique genotypes found per population ranged from 0.58 to 1.0 and the genotypic Simpson's diversity ranged from 0.93 to 1.0 for all five species. Our results suggest that even though asexual reproduction plays an important role in maintaining local populations ofPiperin the understory, it does not seem to reduce genotypic diversity to levels that will threaten these species ability to respond to environmental change.

Abstract in Spanish is available in the online version of this article.
Exposure to International Migration and Its Effect on Childbearing in Turkey
Authors: White Kari , Buckley Cynthia J.
Published: March 2011

International migration alters social norms, family structures, and population development in sending regions. Each of these factors affects fertility, making the impact of international migration on childbearing an increasingly important area of study. In many sending regions, the Demographic and Health Surveys (DHS) provide a promising, but underutilized, source of data for understanding the relationship between international migration and childbearing. Using the household and individual questionnaires in the 2003 Turkish DHS, we develop a multi-layered approach for measuring international migration. We then use these measures to examine differences in childbearing among women in migrant and non-migrant households, assessing the effects of migrant selection and migration-related roles and attitudes on the number of children born. After adjusting for selection characteristics, we find return female migrants and migrant wives are not significantly different from women in non-migrant households; role and attitude differences have only modest impacts on the association between women's exposure to migration and childbearing.
Labor Shortages and U.S. Immigration Reform: Promises and Perils of an Independent Commission
Authors: Martin Philip , Ruhs Martin
Published: March 2011

Comprehensive U.S. immigration reform proposals have three major elements: improved border and workplace controls, dealing with the 11 million unauthorized foreigners in the U.S., and managing “future flows” of foreign workers requested by U.S. employers. Improved controls and dealing with unauthorized foreigners were discussed extensively in the U.S. Senate in 2006 and 2007. Future flows were not. This article reviews the decisions governments face when employers request migrant workers, Britain's independent Migration Advisory Committee, and the promises and perils of a similar U.S. commission to manage labor migration. We conclude that a U.S. commission could help to clarify the trade-offs involved in migrant labor policy, but cannot replace the need for inherently political choices between competing policy objectives.
Cyclic AMP is both a pro‐apoptotic and anti‐apoptotic second messenger
Authors: Insel P. A. , Zhang L. , Murray F. , Yokouchi H. , Zambon A. C.
Published: March 2011

The second messenger cyclic AMP (cAMP) can either stimulate or inhibit programmed cell death (apoptosis). Here, we review examples of cell types that show pro‐apoptotic or anti‐apoptotic responses to increases in cAMP. We also show that cells can have both such responses, although predominantly having one or the other. Protein kinase A (PKA)‐promoted changes in phosphorylation and gene expression can mediate pro‐apoptotic responses, such as in murine S49 lymphoma cells, based on evidence that mutants lacking PKA fail to undergo cAMP‐promoted, mitochondria‐dependent apoptosis. Mechanisms for the anti‐apoptotic response to cAMP likely involve Epac (Exchange protein activated by cAMP), a cAMP‐regulated effector that is a guanine nucleotide exchange factor (GEF) for the low molecular weight G‐protein, Rap1. Therapeutic approaches that activate PKA‐mediated pro‐apoptosis or block Epac‐mediated anti‐apoptotisis may provide a means to enhance cell killing, such as in certain cancers. In contrast, efforts to block PKA or stimulate Epac have the potential to be useful in diseases settings (such as heart failure) associated with cAMP‐promoted apoptosis.
Determinants of spider species richness in coastal dunes along a gradient of mediterraneity
Authors: CARVALHO JOSÉ C. , CARDOSO PEDRO , CRESPO LUÍS C. , HENRIQUES SÉRGIO , CARVALHO RUI , GOMES PEDRO
Published: March 2011

Abstract.  1. The Iberian Peninsula is one of the most relevant areas in terms of species richness, rarity and endemism in the Mediterranean Basin. Using spiders as a model, we studied the relative importance of environmental and non‐environmental spatial variation along a gradient of mediterraneity on the western coast of the Iberian Peninsula.

2. We performed a spatially explicit analysis to evaluate the contribution of pure environmental and pure spatial effects and their shared influence on spider species richness by variation partitioning and principal coordinates of neighbour matrices (PCNM). We dissect the spatial variation of species richness into additive scale‐specific models through PCNM analysis and estimate the relative importance of environmental variables for each model.

3. Variation partitioning revealed that 72.8% of species richness variation could be explained by the environmental (climate and dune stability) and spatial variables. Most of this variation (51.3%) corresponds to the environmental spatially structured component.

4. The influence of environmental variables was scale‐dependent. At the broadest scales, the latitudinal‐climatic gradient was the dominant factor that influenced spider species richness variation. At the finest scale, stability of the dune system was the most important component.

5. In conclusion, spider species richness patterns were determined mostly by spatially structured environmental variation. More importantly, this study shows that different environmental factors act at multiple scales. Hence, our results reinforce the importance of the incorporation of both local and broad‐scale factors when examining species richness patterns.
Habitats Directive species lists: urgent need of revision
Authors: CARDOSO PEDRO
Published: March 2011

Abstract.  1. The European Habitats Directive is the main legislative work regarding Europe’s nature conservation policy. It lists the protected habitats and species in the European Union. The species lists include 122 arthropods.

2. The current lists of arthropods (Annexes II and IV) present, possibly among other, five obvious biases: taxonomic, geographic, range, size and aesthetic biases. Species of selected taxa (Lepidoptera, Coleoptera, Odonata and Orthoptera), from Northern or Central Europe, relatively widespread, of a large body size and attractive are favoured over species of other taxa, from southern and Mediterranean Europe, endemic or relatively small or inconspicuous. Such biases are obstacles to the effective protection of the European fauna.

3. Two main strategies should be followed to avoid these problems and therefore increase the effectiveness of conservation policies: (i) the adoption of objective and transparent criteria for the listing of protected species, and (ii) implement regular updates and amendments to the lists based on such criteria.
Value of embolisation of collateral veins from gastric varices before balloon‐occluded retrograde transvenous obliteration
Authors: Yamagami Takuji , Tanaka Osamu , Yoshimatsu Rika , Miura Hiroshi , Nishimura Tsunehiko
Published: March 2011

Objective: The purpose of our investigation was to determine the safety and usefulness of embolisation procedures in balloon occluded retrograde transvenous obliteration (BRTO) as treatment of gastric varices after portal hypertension.

Materials and Methods: Between June 2004 and August 2009, 40 patients underwent BRTO for gastric varices that occurred after portal hypertension in our institution. When large collateral vessels of gastric varices had developed as drainage veins other than the gastro‐renal shunt, these collateral vessels were embolised prior to BRTO.

Results: Embolisation was performed for 18 collateral vessels in 16 cases before BRTO. Embolised collateral vessels were the left inferior phrenic vein (n = 14), intercostal vein (n = 3), and ascending lumbar vein communicating with the gastro‐renal shunt (n = 1). Mean number of micro‐coils used was 5.7 in left inferior phrenic veins, 4.7 in intercostal veins and 4 in the ascending lumbar vein. In 36 (90%) patients, contrast‐enhanced abdominal CT after BRTO showed that the gastric varices were well obliterated. The rate of occurrence of cases in which the remnant of the enhanced area in the gastric varices was seen even after BRTO was statistically higher in cases requiring embolisation of collateral vessels than in those who did not (4/16 versus 0/24, P = 0.0199 according to Fisher's exact probability test). Recurrence of gastric varices was determined by endoscopy in 1 (2.5%) case necessitating embolisation of collateral vessels. There were no serious complications.

Conclusion: Embolisation of collateral vessels before BRTO is a safe and useful procedure. However, especially in cases having collaterals sufficiently large to require embolisation, careful follow‐up for recurrence of gastric varices is necessary.
Reducing delay in the diagnosis of pregnancy‐associated breast cancer: How imaging can help us
Authors: Taylor Donna , Lazberger Joanne , Ives Angela , Wylie Elizabeth , Saunders Christobel
Published: March 2011

Introduction: The evaluation of breast symptoms during pregnancy or lactation can be challenging but prompt, appropriate assessment of symptoms may lead to earlier cancer detection.

Methods: A review of breast imaging from 22 women with breast cancer during or within 1 year of pregnancy was undertaken as part of a large population‐based study of gestational breast cancer. Consensus findings of three reads using the Breast Imaging Reporting and Data System lexicon were recorded.

Results: The commonest presenting symptom was a lump. Diagnosis by percutaneous biopsy was made correctly in 21 of 23 lesions. Lesions were predominantly invasive ductal carcinoma (91%). One third had extensive associated ductal carcinoma in situ (DCIS). Ultrasound (US) was abnormal in all symptomatic patients. The most common sonographic finding was a solitary hypoechoic mass with irregular margins. ‘Expanded stroma’ with prominent ducts and architectural distortion was noted in three cases; all had extensive high‐grade DCIS. In three women, bilateral breast US detected cancer in the asymptomatic breast. Mammography (performed in 86% of women) was abnormal in 74%, despite the presence of dense breast tissue in 47%. Widespread calcifications were visible in 26%, with detection of asymptomatic contra‐lateral disease in one patient. MRI was performed in six patients. Background parenchymal enhancement did not impair lesion detection; however, overestimation of lesion size can occur.

Conclusions: Ultrasonography is recommended for the initial diagnosis of breast symptoms during pregnancy and lactation. A negative study should not delay direct fine needle aspiration of a palpable lesion. Mammography is indicated where initial assessment suggests malignancy. MRI may have a role in selected cases.
Patterns of care for cervical cancer in Auckland, New Zealand, 2003–2007
Authors: Capelle Lisa , Stevens Wendy , Brooks Susan
Published: March 2011

Introduction: The purpose of this review is to document current patterns of care for the International Federation of Gynecology and Obstetrics (FIGO) stage IB1 to IVA cervical cancer in a New Zealand cancer centre.

Methods: This is a retrospective review of women with newly diagnosed FIGO Stage IB1–IVA cervical cancer in the Auckland/Northland regions between 2003 and 2007.

Results: Two hundred seven patients were identified. Fifty‐three percent were stage IB, 24% stage II, 19% stage III and 3% stage IVA. Factors associated with stage ≥IIB were age >50, lack of participation in cervical screening and public first specialist assessment. Ninety percent (90/100) of stage IB1 patients and 73% (8/11) of stage IB2 patients were treated with primary surgery. Thirty‐eight percent of surgically treated stage IB1 and 100% of surgically treated stage IB2 tumours had indications for adjuvant radiotherapy. Radiotherapy utilisation rates were: stage IB 49% (IB1 44%, IB2 91%); stage II 93%; stage III 90%; and stage IVA 71%. Brachytherapy utilisation rate (BTU) for stages IIB to IVA was 64% overall and 75% in definitively treated patients. Seventy‐five percent of patients treated with definitive radiotherapy received concurrent cisplatin chemotherapy.

Conclusion: Both radiotherapy and brachytherapy utilization rates were below optimal and are being addressed. No formal surgical or chemotherapy utilisation estimates exist for comparison; however, the use of concurrent cisplatin chemotherapy was similar to other groups. A high rate of adjuvant (chemo)radiotherapy was noted in surgically treated Stage IB patients, suggesting a need for an increased consideration of primary chemoradiotherapy in these patients to avoid the unnecessary toxicity of trimodality therapy. Future outcome analysis is planned.
Dosimetric analysis of imaging changes following pulmonary stereotactic body radiation therapy
Authors: Prendergast Brendan M , Bonner James A , Popple Richard A , Spencer Sharon A , Fiveash John B , Keene Kimberly S , Cerfolio Robert J , Minnich Douglas J , Dobelbower Michael C
Published: March 2011

Introduction: The aim of this study was to determine whether late patterns of pulmonary fibrosis are related to specific radiation doses administered during thoracic stereotactic body radiation therapy (SBRT).

Methods: The records of all patients treated with SBRT for either pulmonary metastases or inoperable primary lung tumours at the University of Alabama at Birmingham from November 2005 to July 2008 were reviewed. Patients selected for analysis had diagnostic chest computed tomography (CT) scans acquired at least 180 days after completion of therapy. CT scans acquired at follow‐up were co‐registered with the original treatment planning CT scans for 12 eligible patients (17 lesions), and late‐occurring pulmonary imaging abnormalities (IAs) were contoured. Dosimetric parameters analysed include D80, D90, V18 and Vprescription dose of the IA and V14 and V18 of the lung.

Results: Late pulmonary IAs were identified in 11 treated areas from nine patients. Late IAs could not be identified in six treated areas from three patients secondary to emphysema, tumour progression and severe atelectasis, respectively. The mean doses to 80% (D80) and 90% (D90) of the IAs were 18.4 and 14.5 Gy, respectively (ranges: 5.6–27.8 and 3.3–22.4 Gy). On average, 79.4% (range: 45.6–97.5%) of the IA received at least 18 Gy, while an average of 19.3% (range: 0.2–42.2%) received the prescription dose. On average, only 4.2% (range: 1.1–7.8%) of the lungs received 18 Gy.

Conclusion: Imaging abnormalities consistent with pulmonary fibrosis are common after SBRT and are well approximated by the 18 Gy isodose distribution. The clinical ramification of these findings should be evaluated in future studies.
THE EFFECTS OF REDUCING MATING LIKELIHOOD ON POPULATION VIABILITY
Authors: GORDILLO LUIS F.
Published: March 2011

Abstract The success a species may have invading a patch previously unoccupied is of considerable interest for pest managers and conservation ecologists. The purpose here is to present a mechanistic approach to analyze reproductive Allee effects appearing through the failure in the process of fertilization in a two‐sex population and observe how the survival in an invaded patch is affected. This is in contrast to the usually employed stochastic models with a deterministic skeleton that describe the presence of Allee effects. A Poisson–Ricker model, which includes stochastic demography and sex determination with females classified as successfully fertilized or not fertilized, is used. Numerical approximations to the probabilities of extinction and the mean time to extinction are presented, for fixed parameter values, suggesting how stochasticity in the mating process combined with random fluctuations in the male and female densities, at each generation, contribute to the risk of extinction of a population which started an invasion at a low density.
Potential danger of toothbrushes for children
Authors: Lalitha R.M. , Ranganath K. , Prasad Kavitha , Agrawal Khemraj , Perumal Mahendra
Published: March 2011

Toothbrush, the innocent cleaning aid, has been reported to cause life threatening oropharyngeal injuries in pediatric literature. A case of a 4‐year‐old child reporting to an emergency department with a toothbrush impaled in her mouth while her father was forcefully brushing her teeth is reported here. Hemostasis was achieved by digital pressure and the impaled toothbrush was removed surgically. Uneventful recovery was noted. Parental anxiety and a lack of patient cooperation was noted. Such impaled objects fractured and left behind have been reported to cause serious space infections and mediastinitus. Advising parents to be careful with their children's toothbrush is important as prevention of injuries from such commonly used object could be easily achieved.
Primitivity testing of finite nilpotent linear groups
Authors: Rossmann Tobias
Published: March 2011

We describe a practical algorithm for primitivity testing of finite nilpotent linear groups over various fields of characteristic zero, including number fields and rational function fields over number fields. For an imprimitive group, a system of imprimitivity can be constructed. An implementation of the algorithm inMagmais publicly available.
An Investigation of Magnetic-Field-Assisted Material Removal in Micro-EDM for Nonmagnetic Materials
Authors: Heinz Ken , Kapoor Shiv G. , DeVor Richard E. , Surla Vijay
Published: March 2011

Previous magnetic-field-assisted microelectrical discharge machining (μ-EDM) techniques have been limited to use with magnetic materials. Therefore, a novel process has been developed and tested to improve material removal rate in magnetic-field-assisted μ-EDM for nonmagnetic materials. The workpiece electrodes were oriented to promote directionality in the current flowing through the workpiece, while an external magnetic field was applied in such a way as to produce a Lorentz force in the melt pool. Single-discharge events were carried out on nonmagnetic Grade 5 titanium workpieces to investigate the mechanical effects of the Lorentz force on material removal. Erosion efficiency, melt pool volume analysis, plasma temperature, electron density, and debris field characterization were used as the response metrics to quantify and explain the change in material removal with the applied Lorentz force. By orienting the Lorentz force to act in a direction pointing into the workpiece surface, volume of material removed was shown to increase by up to nearly 50%. Furthermore, erosion efficiency is observed to increase by over 54%. Plasma temperature is unaffected and electron density shows a slight decrease with the addition of the Lorentz force. The distribution of debris around the crater is shifted to greater distances from the discharge center with the Lorentz force. Taken together, these facts strongly suggest that the Lorentz force process developed produces a mechanical effect on the melt pool to aid in increasing material removal. The application of the Lorentz force is not found to negatively impact tool wear.
Natural Convection in a Saturated Variable-Porosity Medium Due to Microwave Heating
Authors: Pakdee Watit , Rattanadecho Phadungsak
Published: March 2011

Microwave heating of a porous medium with a nonuniform porosity is numerically investigated based on a proposed numerical model. A two-dimensional variation of porosity of the medium is considered. The generalized non-Darcian model developed takes into account the presence of a solid drag and the inertial effect. The transient Maxwell’s equations are solved by using the finite difference time domain method to describe the electromagnetic field in the waveguide and medium. The temperature profile and velocity field within a medium are determined by solution of the momentum, energy, and Maxwell’s equations. The coupled nonlinear set of these equations is solved using the SIMPLE algorithm. In this work, a detailed parametric study is conducted on heat transport inside a rectangular enclosure filled with a saturated porous medium of constant or variable porosity. The numerical results agree well with the experimental data. Variations in porosity significantly affect the microwave heating process as well as the convective flow pattern driven by microwave energy.
Computation of Fluid Forces Acting on an Infinite Cylinder Submitted to a Single Phase Cross Flow
Authors: Adobes Andre´ , Jusserand Franc¸ois , Benhamadouche Sofiane , Kahil Yacine , Belouah Salma
Published: March 2011

In Pressurized Water Reactors (PWR), Steam Generator (SG) tubes constitute one of the three barriers which preserve the environment from radioactivity. Excessive tube vibrations under fluid forces, due to the steam-water mixture flow across the tube bundle, can lead to the failure of some tube. Several methods have been proposed to estimate some upper bounds for these forces. These bounds are applicable at the design stage and are helpful to avoid tube failures. Most of the available methods are based on experimental results that have been obtained on tube bundles installed in scaled test-facilities. Unlike this popular test-based approach, one combines here Computational Fluid Dynamics (CFD) to High Performance Computing (HPC), in order to estimate fluid forces in a simple case by applying the Direct Numerical Simulation (DNS) method to solve the Navier-Stokes equations. In the first paragraph, one summarizes the general standard method which allows one to derive the auto-power spectral density of the displacement response at any point of an SG tube, departing from the cross-power spectral densities of fluid forces between any two points along the tube. In the second paragraph, one recalls the equivalent dimensionless spectrum, which was proposed by Axisa et al. in the early nineties, and which still remains a useful reference in the domain. One then applies DNS to the test case of a single infinite cylinder, which is submitted to a single phase cross-flow in a rectangular channel. The Reynolds number is equal to 3900. One presents the time dependent tensors of fluid pressure and viscous stresses, and uses this tensor to estimate the field of non stationary forces that are applied by the fluid, per unit length, at a set of equidistant locations along the tube. Even if they do still require experimental validations, our computation results are more abundant and detailed than standard experimental results, as well as more flexible to use. They therefore provide an interesting additional source of information. They already allow us to try to get new insights into quantities that would be, in any case, very difficult to obtain experimentally. Lift, drag, and even the forces acting in the direction of the tube axis, are computed, and can be distinguished one from the other. Fluid forces due to viscous stresses can also be compared to the ones caused by pressure. The degree of correlation of the forces along the tube can also be examined.
Fluid-Structure Coupling in Gas Damping Response of Nanowire Resonators
Authors: Bhiladvala Rustom B.
Published: March 2011

Nanowires vibrating at resonance in a gas can serve as sensitive detectors of mass (< 10−18 grams), of use to molecular diagnosis of disease. They can also serve as sensitive detectors of damping force in an ambient gas environment. The Q-factor of resonance spectra, quantifies the sharpness of the peak and is a measure of the ratio of inertial to dissipative (damping) forces. Q-factor data enable quantification of the gas damping force in different regimes of rarefied gas dynamics. Measurements were made with silicon and rhodium nanowires of comparable size, in pure dry nitrogen, with pressure increasing from high vacuum (10−10 atm) to one atmospheric pressure. The data show that, for the silicon nanowires, the Q-factor begins to decrease from its high-vacuum value at a lower pressure and reaches a lower minimum value at one atmosphere, compared to the rhodium nanowires. We show that nanowire structural properties, namely the elastic modulus and intrinsic damping, are responsible for these differing sensitivities to a similar gas damping force range. The results show an important coupling of fluid and structural interaction for rarefied gas dynamics at nanoscale. For practical sensing applications in an ambient gas, this coupling indicates that silicon nanowires are better suited for gas damping force sensing, while rhodium nanowires would fare better as mass sensors for molecular diagnosis.
Uncertainty Quantification and Bifurcation Behavior of an Aeroelastic System
Authors: Desai Ajit , Sarkar Sunetra
Published: March 2011

Aeroelastic stability remains an important concern for the design of modern structures such as wind turbine rotors, more so with the use of increasingly flexible blades and military aircrafts with increasing maneuvering capabilities etc. A nonlinear aeroelastic system has been considered in the present study with parametric uncertainties. The analysis has been put in a stochastic framework and the propagation of system uncertainties have been quantified in the aeroelastic response. A spectral uncertainty quantification tool called Polynomial Chaos Expansion has been used. A projection based non-intrusive Polynomial Chaos approach is compared to its classical Galerkin based counterpart, and proven to be more efficient as order of chaos expansion increases. Effect of system randomness on the bifurcation behavior and the flutter boundary has been significant. Stochastic bifurcation results and bifurcation of probability density functions are presented here.
Dynamics of a Fluid-Conveying Cantilevered Pipe With Intermediate Spring Support
Authors: Ghayesh Mergen H. , Pai¨doussis Michael P.
Published: March 2011

The aim of this study is to investigate the three-dimensional (3-D) nonlinear dynamics of a fluid-conveying cantilevered pipe, additionally supported by an array of four springs attached at a point along its length. In the theoretical analysis, the 3-D equations are discretized via Galerkin’s technique, yielding a set of coupled nonlinear differential equations. These equations are solved numerically using a finite difference technique along with the Newton-Raphson method. The dynamic behaviour of the system is presented in the form of bifurcation diagrams, along with phase-plane plots, time-histories, PSD plots, and Poincare´ maps for two different spring locations and inter-spring configurations. Interesting dynamical phenomena, such as planar or circular flutter, divergence, quasiperiodic and chaotic motions, have been observed with increasing flow velocity. Experiments were conducted for the cases studied theoretically, and good qualitative and quantitative agreement was observed.
Acoustically-Coupled Flows in Coaxial Side Branch Resonators With Bluff Rectangular Splitter Plates
Authors: Velikorodny Alexey , Oshkai Peter
Published: March 2011

Fully turbulent inflow past symmetrically located side branches mounted in a duct can give rise to pronounced flow oscillations due to coupling between separated shear layers and standing acoustic waves. The acoustically-coupled flows were investigated using digital particle image velocimetry (PIV) in conjunction with unsteady pressure measurements. Global instantaneous, phase- and time-averaged flow images were evaluated to provide insight into the flow physics during flow tone generation. Onset of the locked-on resonant states was characterized in terms of the acoustic pressure amplitude and frequency of the resonant pressure peak. Structure of the acoustic noise source was characterized in terms of patterns of generated acoustic power, which was evaluated by applying the vortex sound theory in conjunction with global quantitative flow imaging and numerical simulation of the acoustic field. In addition to the basic side branch configuration, the effect of bluff rectangular splitter plates located along the centerline of the main duct was investigated. The first mode of the shear layer oscillation was inhibited by the presence of the plates, which resulted in substantial reduction of the amplitude of acoustic pulsations and the strength of the acoustic source.
Hydroelastic Responses of a Flexible Hydrofoil in Turbulent, Cavitating Flow
Authors: Ducoin Antoine , Young Yin Lu , Sigrist Jean-Franc¸ois
Published: March 2011

The objective of this work is to develop and validate a robust method to simulate the hydroelastic responses of flexible hydrofoil in turbulent, cavitating flow. A two degrees-of-freedom (2-DOF) model is used to simulate the plunging and pitching motion at the foil tip due to bending and twisting deformation of a 3-D cantilevered hydrofoil. The 2-DOF model is loosely coupled with the commercial computational fluid dynamics (CFD) solver STAR-CCM+ to efficiently simulate the fluid-structure interaction (FSI) responses of a cantilevered, rectangular hydrofoil. The numerical predictions are compared with experimental measurements for cases with and without cavitation. The experimental studies were conducted in the cavitation tunnel at the French Naval Academy (IRENav), France. Only quasi-steady cases with Reynolds number (Re) of 750,000 are shown in this paper. In general, the numerical results agree well with the experimental measurements and observations. The results show that elastic deformation of the POM polyacetate (flexible) hydrofoil lead to increases in the angle of attack, which resulted in higher lift and drag coefficients, lower lift to drag ratio, and longer cavities compared to the stainless steel (rigid) hydrofoil. Whereas only stable cavitation cases are considered in this paper, significant interaction effects were observed during experiments for cases with unstable cavitation due to interations between the foil natural frequencies and the cavity shedding frequencies. Transient analysis of the FSI responses of 3-D elastic hydrofoils in turbulent, cavitating flow is currently under work.
Coupled-Mode Dynamic Instability of Tainter Gates With Parallel Bending Vibration of the Skinplate
Authors: Anami Keiko , Ishii Noriaki , Tsuji Takuma , Oku Tatsuya , Goto Masaru , Yagi Kazuaki , Knisely Charles W.
Published: March 2011

As part of the investigation of the dynamic instability of the gate closely related to the Folsom Dam Tainter-gate failure, and in order to assure the dynamic stability of the gate, the field vibration tests on three full-scale operational Tainter-gates were conducted. From these tests, the possible existence of another coupled-mode self excited vibration mechanism, which involves the dangerous dynamic coupling of the whole gate rigid-body rotational vibration with a “parallel” bending vibration of the skinplate was suggested. This paper presents the mechanism of the suggested coupled-mode self-excited vibration, theoretical analysis for the suggested dynamic instability, and 2-dimensional laboratory model tests results. Further, the need for retrofit countermeasures for Tainter gates which are currently installed in both Japan and the USA and susceptible to this dangerous coupled-mode dynamic instability is emphasized.
Screech Tone Suppression in Non Circular Twin Jet
Authors: Boopathi sabareesh V. , Srinivasan K. , Sundararajan T.
Published: March 2011

The acoustic characteristics of twin jet screech tone is studied for various jet configurations such as both square and diamond. The measurement is carried out along the jet direction for various angles at two different planes using a microphone and the jet flow visualization is done by the shadowgraph technique. It is observed that the screech tone suppression is taken place for diamond jet configuration for the small jet spacing S = 0.5. By comparing the directivity pattern of twin jets with single jet, it is found that the twin jet behave as a single jet at higher nozzle pressure ratio.
Spanwise Correlation of Surface Pressure Fluctuations in Heat Exchanger Tube Arrays
Authors: Mahon John , Cheeran Paul , Meskell Craig
Published: March 2011

An experimental study of the surface spanwise pressure on a cylinder in the third row of two normal triangular tube arrays (P/d = 1.32 and 1.58) with air cross flow has been conducted. A range of flow velocities were examined. The correlation of surface pressure fluctuations due to various vibration excitation mechanisms along the span of heat exchanger tubes has been assessed. The turbulent buffeting is found to be uncorrelated along the span which is consistent with generally accepted assumptions in previous studies. Vortex shedding and acoustic resonances were well correlated along the span of the cylinder, with correlations lengths approaching the entire length of the cylinder. Jet switching was observed in the pitch ratio of 1.58 and was found to be correlated along the cylinder, although the spatial behaviour is complex. This result suggests that the excitation force used in fretting wear models may need to be updated to include jet switching in the calculation.
Vibration Excitation Forces in a Rotated Triangular Tube Bundle Subjected to Two-Phase Cross Flow
Authors: Senez H. , Mureithi N. W. , Pettigrew M. J.
Published: March 2011

Two-phase cross flow exists in many shell-and-tube heat exchangers. Flow-induced vibration excitation forces can cause tube motion that will result in long-term fretting wear or fatigue. Detailed flow and vibration excitation force measurements in tube bundles subjected to two-phase cross flow are required to understand the underlying vibration excitation mechanisms. Studies on this subject have already been done, providing results on flow regimes, fluidelastic instabilities, and turbulence-induced vibration. The spectrum of turbulence-induced forces has usually been expected to be similar to that in single-phase flow. However, a recent study, using tubes with a diameter larger than that in a real steam generator, showed the existence of significant quasi-periodic forces in two-phase flow. An experimental program was undertaken with a rotated-triangular array of cylinders subjected to air-water cross-flow, to simulate two-phase mixtures. The tube bundle here has the same geometry as that of a real steam generator. The quasi-periodic forces have now also been observed in this tube bundle. The present work aims to understand turbulence-induced forces acting on the tube bundle, providing results on drag and lift force spectra and their behaviour according to flow parameters, and describing their correlations. Detailed experimental test results are presented in this paper. Comparison is also made with previous measurements with larger diameter tubes. The present results suggest that quasi-periodic fluid forces are not uncommon in tube arrays subjected to two-phase cross-flow.
Vibration Response Behaviour of a High Solidity, Low Rotational Velocity, Vertical Axis Wind Turbine
Authors: McLaren Kevin W. , Tullis Stephen W. , Ziada Samir
Published: March 2011

A series of full scale experimental wind tunnel tests were performed to determine the aerodynamic loading behaviour on the airfoils of a high solidity, low rotational velocity, 3 bladed H-type vertical axis wind turbine. The primary vibration response was resonance excitation of the dominant whirling mode of the turbine. However, for a significant number of test cases, resonance behaviour was also observed in the bending strains of the airfoil support struts, primarily corresponding to higher natural frequencies. Furthermore, under various test conditions, vibration amplitude within the support struts was observed to change dramatically during a single test run, suggesting that the vibration was jumping between sets of airfoil support struts in a complex beating mode. In order to isolate the numerous vibration excitation and response behaviours, tests were performed over a range of flow velocities from 8 m/s to 11 m/s with two different support shaft end conditions.
Experimental Investigation of the Source Locations for Whistling Short Corrugated Pipes
Authors: Golliard Joachim , Tonon Devis , Belfroid Stefan
Published: March 2011

The goal of this study is to investigate the issue of the aeroacoustic source location within corrugated pipes. A configuration with a short pipe and well defined boundary conditions has been chosen, in order to have a precise knowledge of the distribution of the acoustic velocity and pressure within the pipe. The source locations have been investigated methodologically by using straight pipe segments to replace the corrugated section near the acoustic velocity nodes or near the acoustic velocity antinodes. The main locations of the sound sources have been identified to be the sections of the corrugated pipe near the acoustic velocity antinodes.
Turbulent Wake of Surface-Mounted Finite Aspect Ratio Bluff Bodies: Effect of Aspect Ratio and Cross Section Shape
Authors: Sattari Pooria , Bourgeois Jason A. , Martinuzzi Robert J.
Published: March 2011

Dynamic shedding characteristics in the wake of vertical, surface mounted square and circular cylinders of aspect ratio (H/D) 0.5, 2, 4 and 8 are investigated using high frame-rate particle image velocimetry and thermal anemometry for Reynolds numbers, based on the obstacle width/diameter ranging between 6 × 103 and 105. The wavelet transform was used to determine the instantaneous phase relationship for either pressure or velocity fluctuations on opposite sides of the obstacles. Except for the smallest aspect ratio, two shedding modes with different vortex configurations are observed in the formation region: i) Alternate formation of vortices accompanied by high-amplitude fluctuation; ii) Events of simultaneous formation of two vortices resulting in low-amplitude activity and varying phase relationship between opposing sides. These counter-rotating coexisting vortices are generally shed alternately. In the case of aspect ratio 0.5 prism, periodic activity is irregular and the shedding behavior is different from higher aspect ratio bodies.