bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation for methods of anesthesia and euthanasia for rat fetuses in developmental toxicity studies
Authors: Kato Hirohito , Dokai Momoko , Katagiri Ryuichi , Arima Akihiro , Ooshima Yojiro
Published: October 2012

Abstract 

Japan Association for Laboratory Animal Medicine (JALAM) recommends humane handling of rat fetuses. However, it is a challenge to accept proposed euthanizing methods such as cervical dislocation, decapitation and/or intracardiac injection of potassium chloride, because these methods would damage fetal specimens for skeletal and visceral examinations in developmental toxicity studies. The present study aimed at seeking better methodologies for fetal euthanasia and anesthesia. We were unable to accomplish fetal euthanasia directly, but instead, we could euthanize fetuses under pain‐controlled anesthesia. It is recommended that hypothermia by immersion in cold physiological saline is an appropriate method for anesthesia. Moreover, we recommend that the anesthetized fetuses should be euthanized immediately by removal of the vital organs or immersion in appropriate fixatives.
Caring for older people with dementia: An exploratory study of staff knowledge and perception of training in three Australian dementia care facilities
Authors: Jones Cindy , Moyle Wendy , Stockwell‐Smith Gillian
Published: October 2012

Aim

To ascertain care staff's knowledge of dementia relating to aetiology and/or pathology, symptoms and care/treatment; and explore their perceptions of the importance and adequacy of dementia education and training opportunities.

Methods

Thirty‐five care staff working in three secure dementia care facilities were recruited. Dementia knowledge was surveyed using the Staff Knowledge of Dementia Test (SKDT). Perceptions of dementia education and training were examined via semi‐structured individual interviews.

Results

An average of 21 out of 33 SKDT questions (SD = 4.0) was correctly answered. Knowledge discrepancy was attributed to participants’ cultural and ethnic origin and the length of residency in Australia of migrant care staff. Participants acknowledged the importance of dementia education and training but were critical of the content relevancy to direct care practices.

Conclusion

There is a need to improve care staff knowledge of dementia, and dementia education and training should include direct practical competencies required for effective care delivery.
Photosynthetic response of Tempranillo grapevine to climate change scenarios
Authors: Salazar‐Parra C. , Aguirreolea J. , Sánchez‐Díaz M. , Irigoyen J.J. , Morales F.
Published: October 2012

Photosynthesis in C3 plants is CO2 limited and therefore any increase in Rubisco carboxylation substrate may increase net CO2 fixation, unless plants experience acclimation or other limitations. These aspects are largely unexplored in grapevine. Photosynthesis analysis was used to assess the stomatal, mesophyll, photochemical and biochemical contributions to the decreasing photosynthesis observed in Tempranillo grapevines (Vitis vinifera) from veraison to ripeness, modulated by CO2, temperature and water availability. Photosynthesis and photosystem II photochemistry decreased from veraison to ripeness. The elevated CO2 and temperature increased photosynthesis, but transiently, in both well irrigated (WI) and water‐stressed plants. Photosynthetic rates were maxima 1 week after the start of elevated CO2 and temperature treatments, but differences with treatments of ambient conditions disappeared with time. There were not marked changes in leaf water status, leaf chlorophyll or leaf protein that could limit photosynthesis at ripeness. Leaf total soluble sugars remained at ripeness as high as 2 weeks after the start of treatments. On the other hand, and as expected, CO2 diffusional limitations impaired photosynthesis in grapevine plants grown under water scarcity, stomatal and mesophyll conductances to CO2 decreased and in turn low chloroplastic CO2 concentrations limited photosynthetic CO2 fixation. In summary, photochemistry and photosynthesis from veraison to ripeness in Tempranillo grapevine were dominated by a developmental‐related decreasing trend that was only transiently influenced by elevated CO2 concentrations.
Dual source CT angiography in popliteal artery entrapment syndrome
Authors: Sun Xiaoli , Liu Cheng , Wang Rengui , Hou Dailun , Chen JiuHong
Published: October 2012

Aim

To evaluate the clinical value of dual source computed tomography (DSCT) angiography in the diagnosis and treatment for popliteal artery entrapment syndrome (PAES).

Materials and Methods

8 patients with PAES were retrospectively reviewed. 64‐slice dual source CT angiography was performed based on the following protocol: 100 mL of Iopamidol (370 mgI/mL) was injected at a rate of 3.5 mL/s and arterial phase images were obtained by using bolus tracking. Axial DSCT images and reconstructed images including multi‐planar reconstruction (MPR), maximum intensity projection (MIP), volume rendering (VR) were collected and analysed. All patients underwent Doppler colour ultrasound examinations and surgeries.

Results

The popliteal artery and the neighbouring muscular structures were clearly shown on the axial images revealing the cause of the arterial entrapment. Furthermore, the site and length of the segmental occlusion and collateral developments were well demonstrated on reconstructed images. Characterisation and classification based on DSCT angiography were confirmed by surgeries. PAES was accurately diagnosed by DSCT angiography in all enrolled patients. In contrary, only 5 PAES cases were accurately diagnosed by ultrasound examination.

Conclusion

DSCT angiography is a noninvasive and valuable tool in the diagnosis of PAES and plays an important role in the determination of treatment plans.
Significance of hepatic resection for hepatocellular carcinoma with sustained virological response to interferon therapy for chronic hepatitis C
Authors: Sugimachi Keishi , Kinjo Nao , Ikebe Masahiko , Yamashita Naoki , Kajiwara Eiji , Mimori Koshi , Higashi Hidefumi
Published: October 2012

Aim

A sustained virological response (SVR) to interferon (IFN) therapy for chronic hepatitis C decreases but does not eliminate the risk of hepatocellular carcinoma (HCC). The significance of hepatectomy for HCC in patients with SVR has not been clarified. The short‐ and long‐term outcomes of hepatectomy for HCC in patients with SVR were studied.

Methods

From 2006–2011, 69 patients with chronic hepatitis C underwent hepatic resection for primary HCC in our hospital. Of these, 12 patients (17.4%) had SVR to IFN therapy at the time of hepatectomy. The clinicopathological factors and long‐term outcomes of these patients were retrospectively reviewed and were compared with those of patients without SVR.

Results

The mean time from achievement of SVR to diagnosis of HCC was 62 months (range, 7–174). The histological inflammation of liver parenchyma had improved after IFN therapy in SVR cases. The preoperative serum alanine transaminase, albumin and prothrombin time were significantly preserved in patients with SVR. Intraoperative blood loss and blood transfusion rate were lower, and recurrence‐free survival rate was significantly higher, in patients with SVR.

Conclusion

In patients undergoing hepatectomy for HCC, those with SVR had better perioperative safety and a more favorable long‐term prognosis than those without SVR.
The Speed of Stock Price Adjustments to Market Wide Information in India*
Authors: Prasanna Krishna , Menon Anish
Published: October 2012

The speed of price adjustment hypothesis suggests that some stocks tend to adjust faster to market wide information than others. This paper uses the speed of price adjustment hypothesis to identify firm level characteristics that determine the information assimilation pace of individual stocks in the Indian markets. The research sample consists of 64 stocks with yearly data for 10 years, a total of 640 firm‐year observations. Panel data analysis was used to study the effects of firm specific characteristics upon the speed of adjustment proxy DELAY. It was found that parameters such as firm size, trading volume and turnover had a significant influence on information assimilation. Large firms, as well as those firms with high turnover and trading volume, assimilated the market wide news faster, when compared with others. Stocks with high firm value and share price volatility were also found to adjust to market information faster. Firms with higher financial leverage take a longer time for price adjustments. The stock price adjustments were found to be much slower during the world financial crisis period of 2008–2010. While firm size remains a significant feature even during the crisis period, the volume and value traded were not found to be influencing factors for stock price movements during this time.
Job satisfaction in mainland China: comparing critical care nurses and general ward nurses
Authors: Zhang Aihua , Tao Hong , Ellenbecker Carol Hall , Liu Xiaohong
Published: October 2012

Aim

To explore the level of nurses' job satisfaction and compare the differences between critical care nurses and general ward nurses in Mainland China.

Background

Hospitals continue to experience high nurse turnover. Job satisfaction is a key factor to retain skilled nurses. The differences in job satisfaction among critical care nurses and general ward nurses are unknown.

Design

A cross‐sectional design was selected for this descriptive correlation study.

Methods

Cross‐sectional study of critical care nurses (n = 446) and general ward nurses (n = 1118) in 9 general hospitals by means of questionnaires that included the Chinese Nurses Job Satisfaction Scale and demographic scale. The data were collected from June 2010–November 2010.

Results

Chinese nurses had moderate levels of job satisfaction, were satisfied with co‐workers and family/work balance; and dissatisfied with pay and professional promotion. Critical care nurses were younger; less educated and had less job tenure when compared with nurses working on general wards. Critical care nurses were significantly less satisfied than general ward nurses with many aspects of their job.

Conclusion

Levels of nurses' job satisfaction can be improved. The lower job satisfaction of critical care nurses compared with general ward nurses should warn the healthcare administrators and managers of potentially increasing the critical care nurses turn over. Innovative and adaptable managerial interventions need to be taken to improve critical care nurse' job satisfaction and retain skilled nurse.
Cryoballoon Versus Radiofrequency for Pulmonary Vein Re‐Isolation After a Failed Initial Ablation Procedure in Patients with Paroxysmal Atrial Fibrillation
Authors: POKUSHALOV EVGENY , ROMANOV ALEXANDER , ARTYOMENKO SERGEY , BARANOVA VERA , LOSIK DENIS , BAIRAMOVA SEVDA , KARASKOV ALEXANDER , MITTAL SUNEET , STEINBERG JONATHAN S.
Published: October 2012

Cryoballoon versus Radiofrequency Ablation. Aim: Catheter ablation of paroxysmal atrial fibrillation (PAF) is associated with an important risk of early and late recurrence, necessitating repeat ablation procedures. The aim of this prospective randomized patient‐blind study was to compare the efficacy and safety of cryoballoon (Cryo) versus radiofrequency (RF) ablation of PAF after failed initial RF ablation procedure.

Methods: Patients with a history of symptomatic PAF after a previous failed first RF ablation procedure were eligible for this study. Patients were randomized to Cryo or RF redo ablation. The primary endpoint of the study was recurrence of atrial tachyarrhythmia, including AF and left atrial flutter/tachycardia, after a second ablation procedure at 1 year of follow‐up. All patients were implanted with a cardiac monitor (Reveal XT, Medtronic) to continuously track the cardiac rhythm. Patients with an AF burden (AF%) ≤ 0.5% were considered AF‐free (Responders), while those with an AF% > 0.5% were classified as patients with AF recurrences (non‐Responders).

Results: Eighty patients with AF recurrences after a first RF pulmonary vein isolation (PVI) were randomized to Cryo (N = 40) or to RF (N = 40). Electrical potentials were recorded in 77 mapped PVs (1.9 ± 0.8 per patient) in Cryo Group and 72 PVs (1.7 ± 0.8 per patient) in RF Group (P = 0.62), all of which were targeted. In Cryo group, 68 (88%) of the 77 PVs were re‐isolated using only Cryo technique; the remaining 9 PVs were re‐isolated using RF. In RF group, all 72 PVs were successfully re‐isolated (P = 0.003 vs Cryo). By intention‐to‐treat, 23 (58%) RF patients were AF‐free vs 17 (43%) Cryo patients on no antiarrhythmic drugs at 1 year (P = 0.06). Three patients had temporary phrenic nerve paralysis in the Cryo group; the RF group had no complications. Of the 29 patients who had only Cryo PVI without any RF ablation, 11 (38%) were AF‐free vs 20 (59%) of the 34 patients who had RF only (P = 0.021).

Conclusion: When patients require a redo pulmonary vein isolation ablation procedure for recurrent PAF, RF appears to be the preferred energy source relative to Cryo. (J Cardiovasc Electrophysiol, Vol. 24, pp. 274‐279, March 2013)
Preventive effects of trehalose on osteoclast differentiation in rat periodontitis model
Authors: Endo Yasumasa , Tomofuji Takaaki , Ekuni Daisuke , Azuma Tetsuji , Irie Koichiro , Kasuyama Kenta , Morita Manabu
Published: October 2012

Aim

Trehalose, which is a disaccharide formed by a 1,1 linkage of two glucose molecules, was suggested to have a suppressive effect on bone resorption. In this study, we examined the effects of topical application of trehalose on osteoclast differentiation in a rat periodontitis model.

Material and Methods

Rats were divided into four groups. One group received no treatment. In the other groups, experimental periodontitis was induced by ligature placement. These rats with experimental periodontitis received topical application of pure water (vehicle group), 30 mg/ml trehalose solution (30 mg/ml trehalose group) or 60 mg/ml trehalose solution (60 mg/ml trehalose group) to the gingival sulcus respectively.

Results

The vehicle group showed higher numbers of polymorphonuclear leucocytes, receptor activator of nuclear factor kappa B ligand (RANKL)‐positive cells and osteoclasts compared with the no treatment group respectively. Trehalose‐applied groups exhibited lower numbers of these cells compared with the vehicle group. Gene expressions of tumour necrosis factor‐α, RANKL and toll‐like receptor 4 were suppressed by trehalose. In addition, protein expressions of RANKL inducing pathway were less activated by trehalose.

Conclusion

Topical application of trehalose could suppress osteoclast differentiation by inactivation of RANKL inducing pathway in the rat periodontitis model.
Enhancing genotyping of MAOA‐LPR and 5‐HTT‐LPR in rhesus macaques (Macaca mulatta)
Authors: Karere Genesio M. , Sullivan Erin , Kinnally Erin L. , Capitanio John P. , Lyons Leslie A.
Published: October 2012

Background

Genetic variation in monoamine oxidase A (MAOA) and serotonin transporter (5‐HTT)‐linked polymorphic regions (LPR) is associated with neuropsychiatric behavior.

Methods

We genotyped 37 macaques using conventional PCR product gel fractionation and by capillary electrophoresis of multiplexed amplicons and compared the data.

Results

Genotype concordance was 97% and 95% for MAOA‐LPR and 5‐HTT‐LPR, respectively. Capillary electrophoresis was more sensitive and cost‐effective.

Conclusions

Multiplexing MAOA‐LPR and 5‐HTT‐LPR will enhance the genotyping of large sample sets.
Expression profiling of microRNAs in RAW264.7 cells treated with a combination of tumor necrosis factor alpha and RANKL during osteoclast differentiation
Authors: Kagiya T. , Nakamura S.
Published: October 2012

Background and Objective

Tumor necrosis factor alpha (TNF‐α), a cytokine involved in the pathogenesis of periodontal disease, induces osteoclast differentiation and indirectly promotes alveolar bone resorption. We investigated TNF‐α‐regulated osteoclast differentiation, focusing on microRNAs. MicroRNAs are small, noncoding RNAs that are involved in various biological processes, including cellular differentiation, proliferation and apoptosis. Aside from miR‐21, miR‐155 and miR‐223, the identities of the microRNAs that play roles in osteoclast differentiation are unknown. Notably, no previous studies have reported the expression profiling of microRNAs during TNF‐α‐regulated osteoclast differentiation.

Material and Methods

We used microarrays to screen the levels of expression of mature microRNAs in RAW264.7 cells treated with a combination of TNF‐α and RANKL, or RANKL alone for 0, 24 or 82 h during osteoclast formation. We validated the results of the microarray analyses through quantitative RT‐PCR analyses of representative microRNAs in RAW264.7 cells and murine bone marrow macrophages.

Results

During osteoclast formation, the expression of 44 mature microRNAs differed by more than twofold between untreated cells and cells treated with a combination of TNF‐α and RANKL, and the expression of 52 mature microRNAs differed upon RANKL treatment. According to quantitative RT‐PCR analyses, miR‐378 was upregulated and miR‐223 was downregulated during osteoclast formation. Furthermore, miR‐21, miR‐29b, miR‐146a, miR‐155 and miR‐210 were highly expressed during osteoclast differentiation in TNF‐α/RANKL‐treated cells compared with RANKL‐treated cells.

Conclusions

These results suggest that miR‐223 and miR‐378 may play important roles in osteoclastogenesis, and that miR‐21, miR‐29b, miR‐146a, miR‐155 and miR‐210 are involved in TNF‐α‐regulated osteoclast differentiation.
Waterscape genetics of the yellow perch (Perca flavescens): patterns across large connected ecosystems and isolated relict populations
Authors: Sepulveda‐Villet Osvaldo J. , Stepien Carol A.
Published: October 2012

Comparisons of a species' genetic diversity and divergence patterns across large connected populations vs. isolated relict areas provide important data for understanding potential response to global warming, habitat alterations and other perturbations. Aquatic taxa offer ideal case studies for interpreting these patterns, because their dispersal and gene flow often are constrained through narrow connectivity channels that have changed over geological time and/or from contemporary anthropogenic perturbations. Our research objective is to better understand the interplay between historic influences and modern‐day factors (fishery exploitation, stocking supplementation and habitat loss) in shaping population genetic patterns of the yellow perch
Perca flavescens (Percidae: Teleostei) across its native North American range. We employ a modified landscape genetics approach, analysing sequences from the entire mitochondrial DNA control region and 15 nuclear DNA microsatellite loci of 664 spawning adults from 24 populations. Results support that perch from primary glacial refugium areas (Missourian, Mississippian and Atlantic) founded contemporary northern populations. Genetic diversity today is highest in southern (never glaciated) populations and also is appreciable in northern areas that were founded from multiple refugia. Divergence is greater among isolated populations, both north and south; the southern Gulf Coast relict populations are the most divergent, reflecting their long history of isolation. Understanding the influence of past and current waterway connections on the genetic structure of yellow perch populations may help us to assess the roles of ongoing climate change and habitat disruptions towards conserving aquatic biodiversity.
Variation of the folding and dynamics of the Escherichia coli chromosome with growth conditions
Authors: Hadizadeh Yazdi Nastaran , Guet Calin C. , Johnson Reid C. , Marko John F.
Published: October 2012

We examine whether the Escherichia coli chromosome is folded into a self‐adherent nucleoprotein complex, or alternately is a confined but otherwise unconstrained self‐avoiding polymer. We address this through in vivo visualization, using an inducible GFP fusion to the nucleoid‐associated protein Fis to non‐specifically decorate the entire chromosome. For a range of different growth conditions, the chromosome is a compact structure that does not fill the volume of the cell, and which moves from the new pole to the cell centre. During rapid growth, chromosome segregation occurs well before cell division, with daughter chromosomes coupled by a thin inter‐daughter filament before complete segregation, whereas during slow growth chromosomes stay adjacent until cell division occurs. Image correlation analysis indicates that sub‐nucleoid structure is stable on a 1 min timescale, comparable to the timescale for redistribution time measured for GFP–Fis after photobleaching. Optical deconvolution and writhe calculation analysis indicate that the nucleoid has a large‐scale coiled organization rather than being an amorphous mass. Our observations are consistent with the chromosome having a self‐adherent filament organization.
Association of CD28 and CTLA‐4 gene polymorphisms with aggressive periodontitis in Brazilians
Authors: e Silva MRMA , Moreira PR , da Costa GC , Saraiva AM , Souza PEA de , Amormino SAF , Costa JE da , Gollob KJ , Dutra WO
Published: October 2012

Objective

Susceptibility to and severity of periodontal disease is influenced by gene polymorphisms related to the immune response. Co‐stimulatory molecules, such as CD28 and CTLA‐4, are critical in the development of such responses. Our hypothesis is that polymorphisms in genes that code for these molecules may be associated with periodontitis. The aim of the study was to investigate the association between +17 (T/C) CD28 and +49 (A/G) CTLA‐4 gene polymorphisms and periodontitis in Brazilians.

Materials and methods

Genomic DNA was obtained from oral swabs of 424 individuals categorized into three groups (control group, aggressive, and chronic periodontitis) considering clinical parameters such as probing depth and clinical attachment loss. The genotyping was performed by polymerase chain reaction–restriction fragment length polymorphism.

Results

There was an association between the T− genotype of the CD28 polymorphism and aggressive periodontitis (P = 0.04). Moreover, the A+ genotype for CTLA‐4 was associated with greater clinical attachment loss in non‐smokers with aggressive periodontitis (P = 0.006, OR = 16.25, CI = 2.25–117.11).

Conclusions

These findings show that T− in CD28 + 17 (T/C) and the A+ in CTLA‐4 +49 (A/G) genotypes are associated with susceptibility to aggressive periodontal disease. Thus, our study highlights these polymorphisms as potential genetic susceptibility markers of periodontitis in Brazilians.
Is Informal Sector Work an Alternative to Workfare Benefits? The Case of Pre‐program Expansion and Economic Crisis
Authors: Khamis Melanie
Published: October 2012

Limited availability of workfare programs, limited unemployment insurance and a large informal sector are features of the Argentine labor market at the outset of the 2001/02 economic crisis. This paper tests the hypothesis whether informal work is an alternative to workfare participation before a large‐scale program expansion took place. Results from the propensity score matching indicate that observable characteristics of informal low‐income workers and current workfare participants are significantly different. However, within these groups, it is possible to identify subgroups with similar observable characteristics. This indicates that only a subset of the individuals sees workfare and informal work as substitutable alternatives.
NephroTalk: Communication Tools to Enhance Patient‐Centered Care
Authors: Schell Jane O. , Arnold Robert M.
Published: October 2012

Nephrologists frequently must discuss serious news with patients, especially those with advanced comorbidities. These discussions include giving bad news, addressing prognosis, and assisting with treatment decision making. Few data exist about how nephrologists approach these difficult conversations. This article presents a framework for engaging in these discussions using a case example, and provides tools for assisting with treatment decision making for initiating or forgoing dialysis. Communication skills presented include Ask‐Tell‐Ask for discussing serious news, the N‐U‐R‐S‐E acronym for recognizing and responding to emotion; tools for naming uncertainty when addressing prognosis; and using big picture questions to elicit patient care preferences for treatment decision making. This article provides nephrologists with the framework and skills to better engage in patient‐centered decision making.
Lake sediments as natural seismographs: A compiled record of Late Quaternary earthquakes in Central Switzerland and its implication for Alpine deformation
Authors: Strasser Michael , Monecke Katrin , Schnellmann Michael , Anselmetti Flavio S.
Published: October 2012

Central Switzerland lies tectonically in an intraplate area and recurrence rates of strong earthquakes exceed the time span covered by historic chronicles. However, many lakes are present in the area that act as natural seismographs: their continuous, datable and high‐resolution sediment succession allows extension of the earthquake catalogue to pre‐historic times. This study reviews and compiles available data sets and results from more than 10 years of lacustrine palaeoseismological research in lakes of northern and Central Switzerland. The concept of using lacustrine mass‐movement event stratigraphy to identify palaeo‐earthquakes is showcased by presenting new data and results from Lake Zurich. The Late Glacial to Holocene mass‐movement units in this lake document a complex history of varying tectonic and environmental impacts. Results include sedimentary evidence of three major and three minor, simultaneously triggered basin‐wide lateral slope failure events interpreted as the fingerprints of palaeoseismic activity. A refined earthquake catalogue, which includes results from previous lake studies, reveals a non‐uniform temporal distribution of earthquakes in northern and Central Switzerland. A higher frequency of earthquakes in the Late Glacial and Late Holocene period documents two different phases of neotectonic activity; they are interpreted to be related to isostatic post‐glacial rebound and relatively recent (re‐)activation of seismogenic zones, respectively. Magnitudes and epicentre reconstructions for the largest identified earthquakes provide evidence for two possible earthquake sources: (i) a source area in the region of the Alpine or Sub‐Alpine Front due to release of accumulated north‐west/south‐east compressional stress related to an active basal thrust beneath the Aar massif; and (ii) a source area beneath the Alpine foreland due to reactivation of deep‐seated strike‐slip faults. Such activity has been repeatedly observed instrumentally, for example, during the most recent magnitude 4·2 and 3·5 earthquakes of February 2012, near Zug. The combined lacustrine record from northern and Central Switzerland indicates that at least one of these potential sources has been capable of producing magnitude 6·2 to 6·7 events in the past.
Simultaneous cutaneous infection due to Paecilomyces lilacinus and Alternaria in a heart transplant patient
Authors: Lavergne R.A. , Cassaing S. , Nocera T. , Pauwels C. , Cointault O. , Basse G. , Lavayssière L. , Berry A. , Kamar N. , Lamant L. , Iriart X. , Linas M.D. , Valentin A. , Fillaux J. , Paul C. , Magnaval J.F.
Published: October 2012

Paecilomyces lilacinus is an emerging pathogen in immunocompromised patients. We report here a case of cutaneous hyphomycosis in a 63‐year‐old heart transplant recipient caused by the simultaneous presence of 2 molds: Paecilomyces lilacinus and Alternaria alternata. The infection was successfully treated with local voriconazole followed by oral terbinafine.
Weld Residual Stress Analysis and the Effects of Structural Overlay on Various Nuclear Power Plant Nozzles
Authors: Zhang Tao , Brust Frederick W. , Wilkowski Gery , Huang Chin-Cheng , Liu Ru-Feng , Ranganath Sam , Wang Lihua , Tsai Yao Long
Published: October 2012

Welding is a commonly used and one of the most important material-joining processes in industry. The incidences of defects had been located by ultrasonic testing in various pressurizer nozzle dissimilar metal welds (DMW) at nuclear power plants. In order to evaluate the crack propagation, it is required to calculate the stress distribution including weld residual stress and operational stress through the wall thickness in the weld region. The analysis procedure in this paper included not only the pass-by-pass welding steps but also other essential fabrication steps of surge, safety/relief, and spray nozzles. In this paper, detailed welding simulation analyses have been conducted to predict the magnitude of these stresses in the weld material. To prevent primary water stress corrosion cracking (PWSCC) in pressurized water reactors (PWR) on susceptible welded pipes with dissimilar metal welds, the weld overlay process has been applied to repair nuclear reactor pipe joints in plants. The objectives of such repairs are to induce compressive axial residual stresses on the pipe inside surface, as well as increase the pipe thickness with a weld material that is not susceptible to stress corrosion cracking. Hence, understanding the residual stress distribution is important to evaluate the reliability of pipe joints with weld overlay repairs. The finite element results in this paper showed that, after deposition of the DMW nozzle and stainless steel welds, tensile weld residual stresses still exist at regions of the DMW through the thickness. This tensile weld residual stress region was significantly reduced after welding the overlay. The overlay weld also provides a more uniform and large compressive region through the thickness, which has a beneficial effect on the structural integrity of the DMW in the plant.
Experimental Characterization of Heat Transfer and Pressure Drop Inside a Tubular Evaporator Utilizing Advanced Microgrooved Surfaces
Authors: Jha Vibhash , Dessiatoun Serguei , Ohadi Michael , Al Hajri Ebrahim
Published: October 2012

Performance enhancement of heat exchangers with a focus in optimum weight/volume and the amount of working fluid in circulation is of significance to a diverse range of industries. This paper presents heat transfer and pressure drop characteristics of a compact tubular evaporator which utilizes a manifold force-fed microchannel design. A microgrooved structure with an aspect ratio of 3:1 (channel width of 100 μm and channel height of 300 μm) forms the channels used on the refrigerant side and minichannels of 1 mm depth were used on the water side. The system was tested using R134a as the refrigerant with a refrigerant flow rate of 6 to 22 g/s and water flow rate of 150 to 640 ml/s. Overall heat transfer coefficients of more than 10,000 W/m2 K were obtained with modest values of pressure drop. The present results indicate a significant enhancement in thermal performance when compared to the state-of-the-art technologies in the same application area.
An Empirical Stationary Fuel Cell Model Using Limited Experimental Data for Identification
Authors: Meiler M. , Hofer E. P. , Nuhic A. , Schmid O.
Published: October 2012

New technologies for efficient operation of fuel cells require modern techniques in system modeling. Such fuel cell models do not require giving any information about physical mechanisms or internal states of the system. They must be rather precise and should consume less computing time. From the point of view of system theory, polymer electrolyte membrane fuel cells (PEMFC) are multiple input and single output (MISO) systems. The inputs of a fuel cell are the drawn current, the gas pressures at anode and cathode side, and the humidity of these gases which influence the system output, namely the cell voltage, in a nonlinear way. The state of the art in the industry is to describe such nonlinear systems by the usage of lookup tables with a large amount of data. An alternative way to model the input-output behavior of nonlinear systems is the usage of so called black-box and gray-box model approaches. In the last decade, artificial neuronal networks (ANN) became more popular in black-box modeling of nonlinear systems with multiple inputs. Further, if some of the internal processes of a nonlinear system can be mathematically described, a gray-box model is more preferred. In the first part of this paper, the suitability of ANN's in the form of a multilayer perceptron (MLP) network with different numbers of hidden neurons is investigated. A way to confirm the validity for the identified network was worked out. In the second part of this contribution, a gray-box model, valid for a large operating area, based on published semi-empirical models is introduced. Six experimental campaigns for parameter identification and model validation were carried out. The five inputs previously described were varied in a wide range to cover a large operating range. In the last part of this paper, both modeling approaches are investigated with respect to their ability to identify model parameters using a limited number of experimental data.
A Thermoeconomic Study of Low-Temperature Intercooled-Recuperated Cycles for Pure-Solar Gas-Turbine Applications
Authors: Spelling James , Laumert Björn , Fransson Torsten
Published: October 2012

A dynamic model of a megawatt-scale low-temperature intercooled-recuperated solar gas-turbine power plant has been developed in order to allow determination of the thermodynamic and economic performance. The model was then used for multi-objective thermoeconomic optimization of both the power plant performance and cost, using a population-based algorithm. In order to examine the trade-offs that must be made and identify ‘optimal’ plant sizes and operating conditions, two conflicting objectives were considered, namely minimum investment costs and maximum annual electricity production. Levelized electricity costs from a 65 MWe power plant operating at 950 °C are predicted to be below 130 USD/MWhe, competitive with other solar thermal power technologies. Optimal plant sizes and configurations have been identified.
PennSyn 2.0: Enhancements to a Synthesis Software for Compliant Mechanisms
Authors: Saxena Anupam , Yin Luzhong , Ananthasuresh G. K.
Published: October 2012

PennSyn 2.0 is intended as a user-friendly synthesis tool for planar, single-piece compliant mechanisms. This is one of the two synthesis software programs currently available for compliant mechanisms. As an enhancement to its previous version PennSyn, which was developed using Matlab™ with a graphical user interface, the new version includes more design formulations and solution procedures with additional design parameterizations: (i) The multi-criteria formulation in the previous version is generalized, and failure-criteria are included as a new design strategy. (ii) Three more solution procedures, namely, the method of moving asymptotes, genetic algorithms, and simulated annealing are added to complement the existing optimality criteria and sequential quadratic programming schemes. (iii) The existing super ground structure domain approximation with frame elements is now supplemented with plane stress/strain element-based discretization to generate continuum topologies. These capabilities provide enough flexibility to a designer in choosing the design parameterization, solution formulation and a strategy to obtain the best possible, practical design of a compliant mechanism for a task at hand specified in terms of forces and desired displacements. Many illustrative examples and educational use of the software are also described in the paper.
Topology Design of Multifunctional Compliant Mechanisms With Smart Material Actuation
Authors: Dziedzic Ryan P. , Frecker Mary I. , Haluck Randy S.
Published: October 2012

A method for designing multifunctional compliant mechanisms with smart material actuation is presented. A topology optimization approach is proposed where both passive and active elements can act as design variables. The target application is multifunctional instruments for minimally invasive surgery, which stands to benefit significantly from the advances provided by compliant mechanisms and smart material actuators. Design examples are presented to illustrate the method and the effect of including actuator elements as design variables on the topology and performance of the optimal solution.
Effect of Bending Stiffness on the Dynamic and Steady-State Responses of Belt-Drives
Authors: Wasfy Tamer M. , Leamy Michael
Published: October 2012

In this study, an explicit time integration finite element model is used to study the effect of belt bending on the dynamic and steady-state responses of belt-drives. Three-node beam elements based on the torsional-spring formulation are used to model the belt. The pulleys are modeled as rigid circular bodies. The driver pulley’s angular velocity is prescribed. Frictional contact between the pulleys and the belt is modeled using a penalty formulation with the frictional contact governed by a Coulomb-like tri-linear friction law. Several response quantities are generated including the normal contact force and tangential friction force distributions between the pulleys and the belt, the driven pulley angular velocity, and the belt-spans mid-span tensions and transverse vibrations.
On Dynamic Modeling of Robot Manipulators: The Method of Virtual Links
Authors: Abo-Shanab R. F. , Sepehri N. , Wu Q.
Published: October 2012

A new method for dynamic modelling of a class of manipulators is introduced. This class includes manipulators with non-fixed bases or those with joints having more than one degree of freedom. By introducing virtual links appropriately, the method allows transformation of these types of manipulators into the ones having fixed bases and one degree of freedom joints. Conventional methods for dynamic modelling of fixed base serial link manipulators with one degree of freedom joints can then be easily employed. Examples of modelling a link with a spherical joint and a non-fixed base planar manipulator are presented.
Singularity Principle and Distribution of 6-3 Stewart Parallel Manipulator
Authors: Huang Z. , Chen L. H.
Published: October 2012

Based on the kinematics relationship of rigid body, this paper presents a new principle and method of kinematics to analyze the singularity of Stewart parallel manipulator. We study the necessary and sufficient condition that three velocities of three non-collinear points in a body can determine a screw motion. With the condition above, the singularity loci and distribution characteristics of a 6-3 Stewart parallel manipulator for some orientations of the moving platform are studied in three-dimensional space. The singularity loci for the orientations will be a plane and hyperholic paraboloid, or three planes.
Advances in Polynomial Continuation for Solving Problems in Kinematics
Authors: Sommese Andrew J. , Verschelde Jan , Wampler Charles W.
Published: October 2012

For many mechanical systems, including nearly all robotic manipulators, the set of possible configurations that the links may assume can be described by a system of polynomial equations. Thus, solving such systems is central to many problems in analyzing the motion of a mechanism or in designing a mechanism to achieve a desired motion. This paper describes techniques, based on polynomial continuation, for numerically solving such systems. Whereas in the past, these techniques were focused on finding isolated roots, we now address the treatment of systems having higher-dimensional solution sets. Special attention is given to cases of exceptional mechanisms, which have an higher degree of freedom of motion than predicted by their mobility. In fact, such mechanisms often have several disjoint assembly modes, and the degree of freedom of motion is not necessarily the same in each mode. Our algorithms identify all such assembly modes, determine their dimension and degree, and give sample points on each.
The Finite Screw System Associated With the Displacement of a Line
Authors: Huang Chintien , Wang Jin-Cheng
Published: October 2012

In determining the screw systems associated with incompletely specified displacements, the displacement of a line was known to be an exceptional case. Recent research has concluded that all possible screws for the finite displacement of a line do not form a screw system. This paper utilizes Dimentberg’s definition of pitch to demonstrate that all possible screws for displacing a line from one position to another can indeed form a screw system of the third order. Two different approaches are taken: one uses the concept of a screw triangle, and the other is based on analytical geometry. A set of three linearly independent screws of the screw system is shown to be perpendicularly intersecting the external bisector of the initial and final positions of the line.
Computer Aided Detection of Graph Equivalence Among Multiple Jointed Kinematic Chains and Their Links
Authors: Rao A. C. , Prasad Raju Pathapati V. V. N. R.
Published: October 2012

Graph isomorphism problem essentially involves the comparison of the structures of a given pair of graphs for similarity. It is a research topic that originated from “graph theory”. This problem has been receiving wide attention mainly because of its practical importance. As kinematic chains can be drawn in different ways, it is difficult to detect similarity in kinematic structures by visual inspection. In the structural synthesis and analysis of kinematic chains the isomorphism problem in chains merits special attention since all the existing methods generate a number of isomorphic chains, and the structural analysis of kinematic chains can be expressed as one of an isomorphism problem. Many methods are available for a kinematician in case of simple jointed kinematic chains but there are very few methods in case of multiple jointed kinematic chains. In fact, the most tedious task in structural synthesis of multiple jointed kinematic chains is that of comparison for isomorphism since it does not render itself easily for adoption of adjacency (0, 1) matrices. Using the loop technique a method is proposed in this paper which is based on the disposition of ‘edge’ (here in after called ‘links’) and ‘vertices’ (here in after called ‘joints’) in various loop formations. A new structural invariant called “Multiple Jointed Chain loop string” is developed for a kinematic chain with multiple joints, which takes into account the value of the joints. Another invariant called the “Coincident Link String” is developed which is a by-product of the same method to identify distinct mechanisms for a given kinematic chain.
Projective Convexity in Computational Kinematic Geometry
Authors: Ge Q. J.
Published: October 2012

In recent years, there is an increasing interest in developing geometric algorithms for kinematic computations. The aim of this paper is to present the notion of projective convexity as a key element for a new framework for kinematic geometry, that allows for the development of more elegant and efficient algorithms for geometric computations with kinematic applications. The resulting framework, called computational kinematic geometry, is developed by combining the oriented projective geometry with the kinematic geometry of rigid body motions.
A 2T-2R, 4-DOF Parallel Manipulator
Authors: Chen Wen-jia , Zhao Ming-yang , Zhou Ji-ping , Qin Yong-fa
Published: October 2012

From the first ideas of parallel manipulator proposed by Gough and Stewart, parallel manipulators have been found in many industrial applications. In the past two decades, a number of interesting mechanical devices and design methods have been extensively studied. However, most efforts are dedicated to six degrees of freedom (6-DOF) or 3-DOF manipulators. There is a need for equipment providing more than 3 DOFs arranged in parallel and based on simpler arrangements than 6-DOF arrangements in application. This paper presents a novel 4-DOF parallel platform manipulator with base mounted prismatic actuators. The movable platform of the manipulator can translate along two directions and rotate around two axes respectively (2T-2R). The kinematics model is formulated, which describes the inverse and forward kinematics transformation. The singularity analysis of this new 2T-2R, 4-DOF parallel manipulator is introduced.
The Synthesis of Parallel Manipulators for Optimal Desired Workspaces With Respect to the Condition Number
Authors: Hay A. M. , Snyman J. A.
Published: October 2012

The main objective of this paper is to find a fundamentally sound and robust numerical methodology for synthesizing parallel manipulators for desired workspaces. The constrained optimization formulation presented here is aimed at determining a manipulator design so that a prescribed workspace is fully enclosed, but that the workspace is also well-conditioned with respect to some performance index. The particular manipulators used to illustrate and evaluate the formulation are planar 2- and 3-dof parallel manipulators. Solutions to the manipulator design problems are found in an efficient and convincing manner.
On the Development of a Planar 3-DOF Reactionless Parallel Mechanism
Authors: Foucault Simon , Gosselin Cle´ment M.
Published: October 2012

This paper addresses the dynamic balancing of a planar three-degree-of-freedom (DOF) parallel mechanism. A mechanism is said to be dynamically balanced if, for any motion of the mechanism, the reaction forces and torques at the base are identically equal to zero, at all times. The proposed mechanism is based on legs consisting of five-bar parallelogram linkages. The balancing equations are first obtained. Then, optimization is used in order to minimize the mass and inertia of the moving links. Finally, a numerical verification of the dynamic balancing is provided and the prototype is presented.
A New Technique for Clearance Influence Analysis in Planar Mechanisms
Authors: Parenti-Castelli Vincenzo , Venanzi Stefano
Published: October 2012

In this paper a new deterministic method for evaluating the influence of kinematic pair clearance on planar mechanism configuration is presented. The method works in two steps: first, the position error of the link of interest in a given mechanism configuration is defined as a three component function, then the maximum value of each component is determined. The innovative aspect is that no external load is needed, whereas its knowledge is usually required by other methods in this kind of analysis. Consequently, a more general approach to the problem is allowed. The numerical efficiency of the method is finally shown by the application to an ordinary quick-return mechanism.
Two Position, Two Velocity Synthesis of a Spherical Mechanism With Translating Center
Authors: Perry Lauren S. , Turner Michael L. , Murray Andrew P.
Published: October 2012

In this paper we present a methodology for determining the link dimensions of a two-actuator device capable of guiding a part through two specified spatial positions. In addition, the device must be capable of producing two specified linear velocities, one at each spatial position. This represents a spatial pick-and-place operation with a fixture holding the part at both ends. The device we seek to dimension is a spherical four-bar mechanism mounted on a prismatic joint. In order to achieve the specified positions and velocities, we assume the following actuation scheme. The spherical four-bar is actuated to start the motion from the first position, then moves in tandem with the prismatic joint. The prismatic joint completes its slide, and then the spherical four-bar aligns the body with the second position. An example of the methodology is shown.