bluuebunny/crossref_metadata_2025 huggingface dataset:
Microwave-induced solid dispersion technology to improve bioavailability of glipizide
Authors: Isaac Jinu , Kaity Santanu , Ganguly Swastika , Ghosh Animesh
Published: October 2012

Objectives

The effect of microwave (MW) irradiation and conventional heating (CH) on solid dispersion (SD) of poorly water-soluble glipizide (GPZ) and polyethylene glycol 4000 (PEG 4000) were studied in detail.

Methods

The chemical stability of GPZ on exposure to MW irradiation and CH was confirmed by high-performance liquid chromatography, Fourier transform infra red spectroscopy, proton nuclear magnetic resonance and mass spectroscopy studies. Comparative bioavailability studies were performed in rabbits using glipizide sustained-release tablets prepared using MW irradiation (MW-SD) or CH (CH-SD), with Glytop 2.5 mg SR as a reference.

Key findings

The MW-assisted melt mixing showed higher efficiency than CH in obtaining a homogeneous mixture having glass transparency. The polymorphic transformation of GPZ in each case was further confirmed by powder X-ray diffraction study. The solubility of GPZ in phosphate buffer pH 6.8 was greater for MW-SD (72.250 ± 0.154 μg/ml) than CH-SD (46 ± 0.201 μg/ml). The MW-SD matrix tablet (2.5 mg) displayed retarded drug release (releasing 99.320 ± 4.992% drug in 12 h). In-vivo pharmacokinetic study in rabbits revealed that the relative bioavailability of GPZ from MW-SD tablets improved greatly (153.73 ± 9.713%).

Conclusions

MW-induced SD technology could be a better alternative to CH-SD for the enhanced solubility and bioavailability of GPZ.
Anti-inflammatory, antioxidative and matrix metalloproteinase inhibitory properties of 20(R)-ginsenoside Rh2 in cultured macrophages and keratinocytes
Authors: Choi Woo-Yong , Lim Hye-Won , Lim Chang-Jin
Published: October 2012

Objectives

This work aimed to assess the matrix metalloproteinase inhibitory and related pharmacological actions of 20(R)-ginsenoside Rh2 (20(R)-Rh2) in cultured macrophages and keratinocytes.

Methods

In-vitro anti-inflammatory activity of 20(R)-Rh2 was evaluated by analysing nitric oxide (NO) and prostaglandin E2 (PGE2) contents in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophage cells. Its antioxidant activity was determined by measuring the level of reactive oxygen species (ROS) in the macrophage and keratinocyte cells. Matrix metalloproteinase-9 (MMP-9) and -2 (MMP-2) activity in the culture medium was detected using zymography.

Key findings

20(R)-Rh2 was able to suppress NO, PGE2, ROS and pro-matrix metalloproteinase-9 (pro-MMP-9) levels that were enhanced in the LPS-stimulated murine RAW264.7 macrophage cells. 20(R)-Rh2 also exhibited inhibitory effects on the level of ROS and the activity of MMP-9 and -2 in human HaCat keratinocyte cells without stimulant exposure. 20(R)-Rh2 could suppress the gelatinolytic activity of MMP-9 enhanced by tumour necrosis factor-α in the keratinocytes.

Conclusions

20(R)-Rh2, a minor stereoisomer of ginsenoside Rh2, possesses matrix metalloproteinase inhibitory, anti-inflammatory and antioxidative activity.
Measuring change for a multidimensional test using a generalized explanatory longitudinal item response model
Authors: Cho Sun‐Joo , Athay Michele , Preacher Kristopher J.
Published: October 2012

Even though many educational and psychological tests are known to be multidimensional, little research has been done to address how to measure individual differences in change within an item response theory framework. In this paper, we suggest a generalized explanatory longitudinal item response model to measure individual differences in change. New longitudinal models for multidimensional tests and existing models for unidimensional tests are presented within this framework and implemented with software developed for generalized linear models. In addition to the measurement of change, the longitudinal models we present can also be used to explain individual differences in change scores for person groups (e.g., learning disabled students versus non‐learning disabled students) and to model differences in item difficulties across item groups (e.g., number operation, measurement, and representation item groups in a mathematics test). An empirical example illustrates the use of the various models for measuring individual differences in change when there are person groups and multiple skill domains which lead to multidimensionality at a time point.
QT Interval Variability in Type 2 Diabetic Patients with Cardiac Sympathetic Dysinnervation Assessed by 123I‐Metaiodobenzylguanidine Scintigraphy
Authors: SACRE JULIAN W. , FRANJIC BENNETT , COOMBES JEFF S. , MARWICK THOMAS H. , BAUMERT MATHIAS
Published: October 2012

QT Variability and Sympathetic Dysinnervation. Introduction: The mechanism of adverse prognosis attributable to proarrhythmic cardiac sympathetic dysinnervation in patients with type 2 diabetes is incompletely understood. This study sought the association of cardiac sympathetic dysinnervation with temporal instability of ventricular repolarization assessed by beat‐to‐beat QT interval variability.

Methods and Results: 123I‐metaiodobenzylguanidine (123I‐MIBG) scintigraphy was analyzed in 31 type 2 diabetic patients for cardiac sympathetic dysinnervation (4‐hour heart‐to‐mediastinum ratio <1.8) and regional sympathetic integrity and washout rate (from 15‐minute 123I‐MIBG uptake). Relative QT variability was defined from a continuous 5‐minute ECG in the supine position (n = 31) and standing position (subgroup; n = 15) by the log ratio of absolute QT variability (QT variance divided by the mean QT interval squared) to heart rate (HR) variability (HR variance divided by the mean HR squared). Patients with (n = 16; 52%) versus without cardiac sympathetic dysinnervation demonstrated higher relative QT variability in the supine position (P < 0.001), owing to lower HR variability. However, on standing, absolute QT variability was significantly raised in these patients (P = 0.009) despite similar HR variability in the 2 groups. Correlations of heart‐to‐mediastinum ratio with standing QT variability (relative [r =−0.63, P = 0.013] and absolute [r =−0.79, P = 0.001]) were superior to corresponding supine measures (relative [r =−0.47, P = 0.008] and absolute [P = NS]). No associations of QT variability with washout rate or regional 123I‐MIBG uptake were identified.

Conclusion: Elevated QT variability is associated with cardiac sympathetic dysinnervation in type 2 diabetes and may contribute to adverse prognosis. Moreover, QT variability may be more specific for cardiac sympathetic innervation when measured in the context of sympathetic activation. (J Cardiovasc Electrophysiol, Vol. 24, pp. 305‐313, March 2013)
New Cardiomechanic Pacing Lead Sensor Based on High Frequency Parameters: Experimental Studies in Sheep
Authors: BRUSICH SANDRO , TOMASIC DANKO , SOVILJ SINIŠA , MAGJAREVIC RATKO , FEREK‐PETRIC BOZIDAR
Published: October 2012

Pacing Lead as a High Frequency Cardiomechanic Sensor. Introduction: The purpose of this study was to investigate the possibility of detecting and quantifying ventricular contraction in sheep utilizing the cardiomechanic sensor based upon the high frequency (HF) parameters measurements on bipolar cardiac pacing leads. Measurement of the HF reflection coefficient yields the lead‐bending signal (LBS) caused by myocardial contraction. The correlation between the lead‐bending acceleration (LBA) expressed as the rate of rise of LBS and LV dP/dt should reveal that LBS may be utilized as a cardiomechanic sensor in implantable cardiac electrotherapy devices.

Methods and Results: We implanted 3 different pacing leads and tested the measurement system in 9 sheep (42 ± 6 kg) at baseline and during acute hemodynamic intervention with dobutamine infusion and tachycardia induced by VVI pacing at 200 bpm. A stable, consistent, and reproducible LBS was obtained in all sheep during the implantation procedure and 4 months after the implantation during different experimental conditions that included hemodynamic interventions. The dependence between LBAmax and LV dP/dtmax was found to be statistically significant and with high Pearson's correlation coefficient (r = 0.855, P <0.001). We could also observe the hemodynamic deterioration caused by fast ventricular pacing with the decrease of LV dp/dt and LBA compared with sinus rhythm.

Conclusion: This study confirms the feasibility and efficacy of the hemodynamic sensor based upon HF lead parameters. Moreover, it was demonstrated that LBAmax is highly correlated to the ventricular contractility and, therefore, can be efficiently used as a hemodynamic and cardiomechanic sensor. (J Cardiovasc Electrophysiol, Vol. 24, pp. 338‐346, March 2013)
Comparison of Fixed Tilt and Tuned Defibrillation Waveforms: The PROMISE Study
Authors: GOLD MICHAEL R. , VAL‐MEJIAS JESUS , CUOCO FRANK , SIDDIQUI MUKKARAM
Published: October 2012

Comparison of Defibrillation Waveforms. Background: All modern defibrillation systems use biphasic shock waveforms. Typically a fixed tilt waveform is used for implantable defibrillators (ICDs), but a tuned waveform with duration based on shock impedance may be superior based on theoretical calculations.

Objective:
The objective of this study was to compare defibrillation efficacy of fixed tilt and tuned waveforms.

Methods:
PROMISE was designed as a prospective, within‐patient, randomized study of defibrillation thresholds (DFTs) comparing a tuned (assuming a 3.5 milliseconds membrane time constant) versus a 50/50% tilt waveform. All patients had a left pectoral implant (active can) and testing was performed with a single coil shocking configuration (“SVC coil OFF”). DFTs were measured in random order with a binary search method in 52 patients, using the high‐voltage lead impedance to select the pulse widths for both waveforms.

Results:
At the DFT, the tuned waveform had similar delivered energy (10.5 ± 6.3 vs 9.5 ± 5.5 J, P = 0.47), stored energy (13.6 ± 7.9 vs 11.3 ± 6.3 J, P = 0.06), peak current (7.5 ± 3.0 vs 6.8 ± 2.2 A, P = 0.09), and delivered voltage (451.0 ± 134.5 vs 411.5 ± 120.7 V, P = 0.05) compared with the 50/50% tilt waveform.

Conclusion:
The DFTs for 3.5‐millisecond time constant based tuned and 50/50% tilt waveforms are similar using a single coil, left pectoral active can. (J Cardiovasc Electrophysiol, Vol. 24, pp. 323‐327, March 2013)
Presence of anti‐müllerian hormone in the squirrel monkey (Saimiri boliviensis): gender and seasonal differences
Authors: Roudebush William E. , Nethery R. Andrew , Heldreth Todd
Published: October 2012

Background

Anti‐mullerian hormone (AMH) is a glycoprotein of the transforming growth factor‐β superfamily secreted by male Sertoli cells and female ovarian granulosa cells. This study determined squirrel monkey AMH levels as influenced by gender and seasonality.

Methods

Squirrel monkey sera AMH were measured by an enzymatically amplified two‐site immunoassay.

Results

A significant difference (P < 0.001) was found in AMH levels between male (mean = 3.46 ng/ml) and female squirrel monkeys (mean = 22.12 ng/ml). A significant difference (P < 0.05) was found in male AMH levels between breeding (mean = 4.21 ng/ml) and non‐breeding seasons (mean = 2.78 ng/ml). No significant differences were found between female groups.

Conclusions

Anti‐mullerian hormone levels in female squirrel monkeys are the highest in any primate species reported, whereas in the male, levels are within reported ranges. The AMH assay may allow us soon to assess the squirrel monkey fertility potential as a function of various factors.
Growth‐related structural, biochemical, and mechanical properties of the functional bone–cartilage unit
Authors: Hamann Nina , Zaucke Frank , Dayakli Münire , Brüggemann Gert‐Peter , Niehoff Anja
Published: October 2012

Articular cartilage and subchondral bone act together, forming a unit as a weight‐bearing loading‐transmitting surface. A close interaction between both structures has been implicated during joint cartilage degeneration, but their coupling during normal growth and development is insufficiently understood. The purpose of the present study was to examine growth‐related changes of cartilage mechanical properties and to relate these changes to alterations in cartilage biochemical composition and subchondral bone structure. Tibiae and femora of both hindlimbs from 7‐ and 13‐week‐old (each n = 12) female Sprague‐Dawley rats were harvested. Samples were processed for structural, biochemical and mechanical analyses. Immunohistochemical staining and protein expression analyses of collagen II, collagen IX, COMP and matrilin‐3, histomorphometry of cartilage thickness and COMP staining height were performed. Furthermore, mechanical testing of articular cartilage and micro‐CT analysis of subchondral bone was conducted. Growth decreased cartilage thickness, paralleled by a functional condensation of the underlying subchondral bone due to enchondral ossification. Cartilage mechanical properties seem to be rather influenced by growth‐related changes in the assembly of major ECM proteins such as collagen II, collagen IX and matrilin‐3 than by growth‐related alterations in its underlying subchondral bone structure. Importantly, the present study provides a first insight into the growth‐related structural, biochemical and mechanical interaction of articular cartilage and subchondral bone. Finally, these data contribute to the general knowledge about the cooperation between the articular cartilage and subchondral bone.
Distress experienced by nurses in response to the challenging behaviour of residents – evidence fromGerman nursing homes
Authors: Schmidt Sascha G , Dichter Martin N , Palm Rebecca , Hasselhorn Hans Martin
Published: October 2012

Aims and objectives

The aim of this research is to investigate the degree of distress experienced by nurses in response to the challenging behaviour of nursing home residents (residents' challenging behaviour) and their impact on nurses individual resources (general health, burnout and work ability).

Background

Because of the increasing and ageing population of nursing home residents, professional nursing care faces several challenges. One highly prevalent issue among nursing home residents is the so‐called ‘challenging behaviour’. However, to date, ‘challenging behaviour’ has not yet been recognised as an occupational stressor, and the extent of the impact of ‘challenging behaviour’ on nurses' well‐being and functioning is not well understood.

Design

Cross‐sectional study.

Method

Self‐report questionnaire data collected from 731 registered nurses and nursing aides in 56 German nursing homes were used in a secondary data analysis. The level of residents' challenging behaviour‐related distress that nurses experienced was assessed using a scale consisting of nine questions. Validated instruments were used for the assessment of individual resources.

Results

The mean score for residents' challenging behaviour‐related distress was 41·3 (SD21·2). Twenty‐seven per cent of all nurses reported over 50 residents' challenging behaviour. Residents' challenging behaviour had a significant impact on all three measures of individual resources. Specifically, nurses exposed to frequent residents' challenging behaviour reported a significantly lower quality of general health, reduced workability and high burnout levels.

Conclusion

Our findings indicate that residents' challenging behaviour‐related distress is a significant work place stressor for nurses in nursing homes with a clear impact on general health, the risk of burnout and work ability.

Relevance to clinical practice

Our findings suggest that residents' challenging behaviour is a stressor for nurses in nursing homes. Further scientific and practical attention is necessary from the point of view of working conditions for nurses. The development of preventive concepts for nursing staff and residents is recommended.
SHIPPING COSTS, INFORMATION COSTS, AND THE SOURCES OF INDUSTRIAL COAGGLOMERATION*
Authors: Gallagher Ryan M.
Published: October 2012

ABSTRACT Direct trade between establishments, coupled with costs of trading goods and information across space, has long been considered a primary determinant of industrial colocation. However, researchers have had difficulty decomposing the effects of interindustry trade into these two cost components. Using new techniques for separately estimating shipping and information costs, this paper provides an empirical framework for identifying the various sources of industrial coagglomeration among U.S. manufacturing industries. My findings suggest that both interindustry shipping costs and information costs influence metropolitan‐level coagglomeration. Additional evidence points to the significant role of direct information costs in determining intraindustry agglomerations.
Association between periodontal status and pre‐term and/or low‐birth weight in Spain: clinical and microbiological parameters
Authors: Santa Cruz I. , Herrera D. , Martin C. , Herrero A. , Sanz M.
Published: October 2012

Background and Objective

Studies performed over the last 15 years have suggested that periodontal diseases may be associated with adverse pregnancy outcomes. However, this association has not been found in all populations. The aim of this study was to evaluate whether periodontal status and the presence of specific periodontal pathogens may influence the incidence of adverse pregnancy outcomes.

Material and Methods

Pregnant women were clinically examined before 26th week of gestation, and divided in two groups: non‐periodontitis and periodontitis. Microbial samples were obtained in the periodontitis group and processed by anaerobic culturing. After delivery, data on the pregnancy outcome were taken; mother's socio‐demographic and risk factors were obtained at inclusion. Simple and multiple regression analysis were performed.

Results

One hundred and seventy women were included in the study (116 non‐periodontitis and 54 with periodontitis). The incidence of preterm (PTB) and low‐birth weight (LBW) was 2.94% and 3.53%, respectively. Periodontal status did not show any association with adverse pregnancy outcomes. The presence of Eikenella corrodens was significantly related to PTB (p = 0.022) and the presence Capnocytophaga spp. was related to LBW (p = 0.008). The multivariate analyses showed a significant association between PTB and newborn weight and counts of E. corrodens. Maternal health and counts of E. corrodens were significantly associated with PTB or LBW.

Conclusion

The clinical periodontal condition was not associated with adverse pregnancy outcomes in a Spanish Caucasian population with medium‐high educational level. The presence and counts of E. corrodens and the presence of Capnocytophaga spp. showed a significant association with PTB and LBW, respectively, in the bivariate and/or multivariate model.
Low glomerular filtration rate is a risk factor for ribavirin‐associated anaemia in old patients with chronic hepatitis C
Authors: Borroni G. , Cazzaniga M. , Andreoletti M. , Ceriani R. , Guerzoni P. , Omazzi B. , Pich M. G. L. , Prada A. , Spinzi G. , Terreni N. , Salerno F.
Published: October 2012

Elderly patients with chronic hepatitis C have a reduced responsiveness to antiviral therapy with Peg‐interferon and ribavirin. The dose reduction or the discontinuation of ribavirin due to the occurrence of anaemia is one of the most important causes for the low sustained viral response observed in older patients. We aimed to evaluate the relationship between baseline renal function and the early onset of ribavirin‐associated anaemia in older (≥60 years) patients. Using data from 348 patients with chronic hepatitis C consecutively treated with peg‐interferon plus ribavirin, we investigated which factors were associated with the occurrence of anaemia in elderly patients (≥60 years). Ribavirin‐induced anaemia occurred in 40.5% of patients. Older patients showed a rate of anaemia significantly higher than younger patients (51.5% vs 36.3%; P = 0.009). Consequently, the rate of ribavirin dose reduction or discontinuation due to anaemia was 35.1% in older patients and 23.5% in younger patients (P = 0.029). A significantly higher proportion of older patients had a low baseline glomerular filtration rate (GFR) compared with younger patients (56.7% vs 27.1%; P < 0.001). At the multivariate regression analysis, low baseline GFR (<70 mL/min) was associated with an increased risk of ribavirin‐associated anaemia only in the older patients (OR: 3.526; 95% CI: 1.385–8.979; P = 0.008). In this subset, baseline GFR was significantly correlated with both absolute (r = −0.320; P < 0.001) and relative (r = −0.324; P < 0.001) haemoglobin decrease within the first 8 weeks of treatment. In patients aged >60 years, a low pre‐treatment GFR was strongly associated with the risk to develop ribavirin‐related anaemia with consequent reduction in ribavirin doses.
Pharmacokinetics of macrolides in foals
Authors: Villarino N. , Martín‐Jiménez T.
Published: October 2012

Macrolides are used for treatment of pneumonia and extrapulmonary conditions caused byRhodococcus equi. In foals, macrolides have an extraordinary capacity to accumulate in different lung tissue compartments. These drugs show unique pharmacokinetic features such as rapid and extensive distribution and long persistence in pulmonary epithelial lining fluid (PELF) and bronchoalveolar lavage (BAL) cells from foals. This article reviews the pharmacokinetic characteristics of erythromycin, azithromycin, clarithromycin, tulathromycin, telithromycin, gamithromycin, and tilmicosin in foals, with emphasis onPELFandBALcell concentrations.
Assessment of Sperm Function Parameters and DNA Fragmentation in Ejaculated Alpaca Sperm (Lama Pacos) by Flow Cytometry
Authors: Cheuquemán C , Merino O , Giojalas L , Von Baer A , Sánchez R , Risopatrón J
Published: October 2012

Contents

Flow cytometry has been shown to be an accurate and highly reproducible tool for the analysis of sperm function. The main objective of this study was to assess sperm function parameters in ejaculated alpaca sperm by flow cytometry. Semen samples were collected from six alpaca males and processed for flow cytometric analysis of sperm viability and plasma membrane integrity using SYBR‐14⁄PI staining; acrosomal membrane integrity using FITC‐conjugated Pisum Sativum Agglutinin⁄PI labelling; mitochondrial membrane potential (Δψm) by staining with JC‐1 and DNA Fragmentation Index (DFI) by TUNEL. The results indicate that the mean value for sperm viability was 57 ± 8 %. Spermatozoa with intact acrosome membrane was 87.9 ± 5%, and viable sperm with intact acrosomal membrane was 46.8 ± 9%, high mitochondrial membrane potential (Δψm) was detected in 66.32 ± 9.51% of spermatozoa and mean DFI value was 0.91 ± 0.9%. The DFI was inversely correlated with high Δψm (p = 0.04; r = −0.41) and with plasma membrane integrity (p = 0.01; r = −0.47). To our knowledge, this is the first report of the assessment on the same sample of several parameters of sperm function in ejaculated alpaca sperm by flow cytometry.
The combined use of photoaffinity labeling and surface plasmon resonance‐based technology identifies multiple salicylic acid‐binding proteins
Authors: Tian Miaoying , von Dahl Caroline C. , Liu Po‐Pu , Friso Giulia , van Wijk Klaas J. , Klessig Daniel F.
Published: October 2012

Salicylic acid (SA) is a small phenolic molecule that not only is the active ingredient in the multi‐functional drug aspirin, but also serves as a plant hormone that affects diverse processes during growth, development, responses to abiotic stresses and disease resistance. Although a number of SA‐binding proteins (SABPs) have been identified, the underlying mechanisms of action of SA remain largely unknown. Efforts to identify additional SA targets, and thereby elucidate the complex SA signaling network in plants, have been hindered by the lack of effective approaches. Here, we report two sensitive approaches that utilize SA analogs in conjunction with either a photoaffinity labeling technique or surface plasmon resonance‐based technology to identify and evaluate candidate SABPs from Arabidopsis. Using these approaches, multiple proteins, including the E2 subunit of α‐ketoglutarate dehydrogenase and the glutathione S‐transferases GSTF2, GSTF8, GSTF10 and GSTF11, were identified as SABPs. Their association with SA was further substantiated by the ability of SA to inhibit their enzymatic activity. The photoaffinity labeling and surface plasmon resonance‐based approaches appear to be more sensitive than the traditional approach for identifying plant SABPs using size‐exclusion chromatography with radiolabeled SA, as these proteins exhibited little to no SA‐binding activity in such an assay. The development of these approaches therefore complements conventional techniques and helps dissect the SA signaling network in plants, and may also help elucidate the mechanisms through which SA acts as a multi‐functional drug in mammalian systems.
A Numerical Investigation of Rotating Instability in Steam Turbine Last Stage
Authors: Zhang L. Y. , He L. , Stüer H.
Published: October 2012

The unsteady flow phenomenon (identified as rotating instability) in the last stage of a low-pressure model steam turbine operated at very low mass flow conditions is numerically studied. This kind of instability has been observed previously in compressors and can be linked to the high structural stress levels associated with flow-induced blade vibrations. The overall objective of the study is to enhance the understanding of the rotating instability in steam turbines at off design conditions. A numerical analysis using a validated unsteady nonlinear time-domain CFD solver is performed. The 3D solution captures the massively separated flow structure in the rotor-exhaust region and the pressure ratio characteristics around the rotor tip of the test model turbine stage in good comparison with the experiment. A computational study with a multi-passage whole annulus domain on two different 2D blade sections is subsequently carried out. The computational results clearly show that a rotating instability in a turbine blading configuration can be captured by the 2D model. The frequency and spatial modal characteristics are analyzed. The simulations seem to be able to predict a rotating fluid dynamic instability with the similar characteristic features to those of the experiment. In contrast to many previous observations, the results for the present configurations suggest that the onset and development of rotating instabilities can occur without 3D and tip-leakage flows, although a quantitative comparison with the experimental data can only be expected to be possible with fully 3D unsteady solutions.
Effect of Wake Flow Nonuniformity on Wind Turbine Performance and Aerodynamics
Authors: Barber S. , Chokani N. , Abhari R.S.
Published: October 2012

Dynamically scaled experiments and numerical analyses are performed to study the effects of the wake from an upstream wind turbine on the aerodynamics and performance of a downstream wind turbine. The experiments are carried out in the dynamically scaled wind turbine test facility at ETH Zurich. A five-hole steady-state probe is used to characterize the cross-sectional distribution of velocity at different locations downstream of the wake-generating turbine. The performance of the downstream wind turbine is measured with an in-line torquemeter. The velocity field in the wind turbine wake is found to differ significantly from the velocity field assumed in numerical wake models. The velocity at hub height does not increase monotonically up to the freestream velocity with downstream distance in the wake. Furthermore, the flowfield is found to vary significantly radially and azimuthally. The application of wake models that assume a constant axial velocity profile in the wake based on the measured hub-height velocity can lead to errors in annual energy production predictions of the order of 5% for typical wind farms. The application of wake models that assume an axisymmetric Gaussian velocity profile could lead to prediction errors of the order of 20%. Thus modeling wind turbine wakes more accurately, in particular by accounting for radial variations correctly, could increase the accuracy of annual energy production predictions by 5%–20%.
Optimization Strategy for a Coupled Design of the Last Stage and the Successive Diffuser in a Low Pressure Steam Turbine
Authors: Musch Christian , Stüer Heinrich , Hermle Georg
Published: October 2012

In this study, an effective yet numerically simple approach for a coupled design of the last stage running blade and diffuser is presented. The method applied uses a two-dimensional streamline curvature code combined with a boundary layer solver for the prediction of flow separation within the diffuser. An accurate representation of the diffuser flow is vital for the assessment of the overall performance. Thus, the major influences from the turbine stage on the diffuser flow, i.e., the tip leakage jet and the swirl of the flow, are taken into account. Secondary effects like blade wakes are neglected. The basic capability of the method to correctly represent the flow is demonstrated by a comparison with three-dimensional CFD simulations of a sample configuration. Solid correlation can be found between both cases. For the optimization process, a genetic algorithm is used. Optimization parameters include the blade exit angle and the diffuser contour. The results of the optimization are again scrutinized with the assistance of three-dimensional CFD simulations.
Determination of Thermal Barrier Coatings Average Surface Temperature After Engine Operation for Lifetime Validation
Authors: Witz Grégoire , Bossmann Hans-Peter
Published: October 2012

Assessment of ex-service parts is important for the power generation industry. It gives us the opportunity to correlate part conditions to specific operating conditions like fuel used, local atmospheric conditions, operating regime, and temperature load. For assessment of thermal barrier coatings, one of the most valuable pieces of information is the local thermal condition. A method has been developed in Alstom, allowing determination of a thermal barrier coating average surface temperature after engine operation. It is based on the analysis of the phase composition of the thermal barrier coating by the acquisition of an X-ray diffraction spectrum of the coating surface, and its analysis using Rietveld refinement. The method has been validated by comparing its outcome to thermal models and base metal temperature mapping data. It is used for assessment of combustor and turbine coatings with various purposes: Determination of remnant coating life, building of lifing models, or determination of the coating degradation mechanisms under some specific operating conditions. Examples will be presented showing applications of this method.
Kinematic Acquisition of Geometric Constraints for Task-Oriented Design of Planar Mechanisms
Authors: Wu Jun , Ge Q. J. , Su Hai-Jun , Gao Feng
Published: October 2012

A motion task can be given in various ways. It may be defined parametrically or discretely in terms of an ordered sequence of displacements or in geometric means. This paper studies a new type of motion analysis problem in planar kinematics that seeks to acquire geometric constraints associated with a planar motion task which is given either parametrically or discretely. The resulting geometric constraints can be used directly for type as well as dimensional synthesis of a physical device such as mechanical linkage that generates the constrained motion task. Examples are provided toward the end of the paper to illustrate how geometric constraints acquired can be used for task-oriented mechanism design.
An Algorithm to Study the Elastodynamics of Parallel Kinematic Machines With Lower Kinematic Pairs
Authors: Cammarata Alessandro , Condorelli Davide , Sinatra Rosario
Published: October 2012

In this paper, an algorithm to help designers to integrate the elastodynamics analysis along with the inverse positioning and orienting problems of a parallel kinematic machine (PKM) into a single package is conceived. The proposed algorithm applies concepts from the matrix structural analysis (MSA) and finite element analysis (FEA) to determine the generalized stiffness matrix and the linearized elastodynamics equations of a PKM with only lower kinematic pairs. A PKM is modeled as a system of flexible links and rigid bodies connected by means of joints. Three cases are analyzed to consider the combinations between flexible and rigid bodies in order to find the local stiffness matrices. The latter are combined to obtain the limb matrices and, then, the global stiffness matrix of the whole robotic system. The same nodes coming from the links discretization are considered to include joint masses/inertias into the model. Finally, a case study is proposed to show some feasible applications and to compare results to commercial software for validation.
Underactuated Part Alignment System for Industrial Assembly Applications
Authors: Slaboch Brian J. , Voglewede Philip A.
Published: October 2012

This paper introduces the underactuated part alignment system (UPAS) as a cost-effective and flexible approach to aligning parts in the vertical plane prior to an industrial robotic assembly task. The advantage of the UPAS is that it utilizes the degrees of freedom (DOFs) of a SCARA (selective compliant assembly robot arm) type robot in conjunction with an external fixed post to achieve the desired part alignment. Additionally, the UPAS is not constrained to work with rigid, polygonal parts. Three path planning techniques are presented that can be used with the UPAS to achieve the proper part rotation. The results from laboratory testing show that the UPAS can be used to consistently achieve the desired part rotation to within 0.5% of the desired value.
Component-Wise Method Applied to Vibration of Wing Structures
Authors: Carrera E. , Pagani A. , Petrolo M.
Published: October 2012

This paper proposes advanced approaches to the free vibration analysis of reinforced-shell wing structures. These approaches exploit a hierarchical, one-dimensional (1D) formulation, which leads to accurate and computationally efficient finite element (FE) models. This formulation is based on the unified formulation (UF), which has been recently proposed by the first author and his coworkers. In the study presented in this paper, UF was used to model the displacement field above the cross-section of reinforced-shell wing structures. Taylor-like (TE) and Lagrange-like (LE) polynomial expansions were adopted above the cross-section. A classical 1D FE formulation along the wing's span was used to develop numerical applications. Particular attention was given to the component-wise (CW) models obtained by means of the LE formulation. According to the CW approach, each wing's component (i.e. spar caps, panels, webs, etc.) can be modeled by means of the same 1D formulation. It was shown that Msc/Patran® can be used as pre- and postprocessor for the CW models, whereas Msc/Nastran® DMAP alters can be used to solve the eigenvalue problems. A number of typical aeronautical structures were analyzed and CW results were compared to classical beam theories (Euler-Bernoulli and Timoshenko), refined models (TE) and classical solid/shell FE solutions from the commercial code Msc/Nastran®. The results highlight the enhanced capabilities of the proposed formulation. In fact, the CW approach is clearly the natural tool to analyze wing structures, since it leads to results that can only be obtained through 3D elasticity (solid) elements whose computational costs are at least one-order of magnitude higher than CW models.
Stress Distribution in a Bilayer Elastic Model of a Coronary Artery
Authors: Takamizawa Keiichi , Nakayama Yasuhide
Published: October 2012

In earlier studies on stress distribution in arteries, a monolayer wall model was often used. An arterial wall consists of three layers, the intima, the media, and the adventitia. The intima is mechanically negligible as a stress supporting layer against the blood pressure in young healthy vessels, although it is important as an interface between blood and arterial wall. The media and adventitia layers are considered to support blood pressure. Recently, residual strain and a constitutive law for porcine coronary arteries have been investigated in separated media and adventitia. Using the data obtained through these investigations, a stress analysis considering residual stress (strain) in each layer was performed in this study, and residual strain and stress were computed for a bilayer model. The circumferential residual stress was compressive in the inner region, tensile in the outer region, and had discontinuity at the boundary between the media and adventitia. A peak circumferential stress occurred in the media at the boundary between the media and adventitia under a physiological condition, and an almost flat distribution was obtained in the adventitia. This pattern does not change under a hypertensive condition. These results suggest that a remodeling with hypertension occurs in the media.
Flaw Tolerance in a Viscoelastic Strip
Authors: Chen Lei , Chen Shaohua , Gao Huajian
Published: October 2012

Load-bearing biological materials such as bone, teeth, and nacre have acquired some interesting mechanical properties through evolution, one of which is the tolerance of cracklike flaws incurred during tissue function, growth, repair, and remodeling. While numerous studies in the literature have addressed flaw tolerance in elastic structures, so far there has been little investigation of this issue in time-dependent, viscoelastic systems, in spite of its importance to biological materials. In this paper, we investigate flaw tolerance in a viscoelastic strip under tension and derive the conditions under which a pre-existing center crack, irrespective of its size, will not grow before the material fails under uniform rupture. The analysis is based on the Griffith and cohesive zone models of crack growth in a viscoelastic material, taking into account the effects of the loading rate along with the fracture energy, Young’s modulus, and theoretical strength of material.
How wood evolves: a new synthesis
Authors: Carlquist Sherwin
Published: October 2012

Recent advances in wood physiology, molecular phylogeny, and ultrastructure (chiefly scanning electron microscopy, SEM), as well as important new knowledge in traditional fields, provide the basis for a new vision of how wood evolves. Woody angiosperms have, in the main, shifted from conductive safety to conductive efficiency (with many variations and modifications) and from ability to resist cavitation (low vulnerability) to ability to refill vessels. The invention of the vessel was a kind of dimorphism (vessel elements plus tracheids) that permitted division of labor and many kinds of wood repatterning that suit conductive safety–efficiency trade-offs. Angiosperms were primarily adapted to mesic habitats but were not failures or “unstable.” They have survived to the present in such habitats well, along with older structural adaptations (e.g., the scalariform perforation plate) that are still suited to such habitats. These “primitive” features are evident in earlier branchings of phylogenetic trees based on multiple genes. Older features may still be functional and thus persist, although newer formulations are overriding in effect. There are, however, numerous instances of “breakouts” in a number of clades (ecological iterations and bursts of speciation and diversification related to new ways of dealing with water economy), whereas in other branchings, other clades show ecological stasis over long periods of time. Newer physiological and anatomical mechanisms have permitted entry into habitats with marked fluctuation in moisture availability. Wood evolves progressively, and literal character state reversal may be unusual: genomic and developmental information holds answers to these changes. Wood is a complex tissue, and each of the histological components shows polymorphism as an evolutionary mechanism. Cell types within wood evolve collaboratively. Shifts in wood features (e.g., simplification of the scalariform perforation plate) are commonly homoplastic. Manifold changes in habit and in leaf physiology, morphology, and anatomy accompany wood evolution, and wood should be studied with relationship to real-world ecology, information that cannot be gleaned from literature or other secondary sources. Heterochrony (protracted juvenilism, accelerated adulthood) characterizes angiosperm xylem extensively, far more so than in other vascular plants, and these mechanisms have resulted in many remarkable changes (e.g., monocots have permanently juvenile xylem, woody trees represent accelerated adulthood). Understanding the many successful features of angiosperm wood evolution must ultimately rest on syntheses.
Tree size affects accumulation of carbon and nitrogen metabolites in white spruce seedlings during short day-induced bud formation
Authors: Dhont Catherine , Bertrand Annick , Castonguay Yves , Cooke Janice E.K. , Isabel Nathalie
Published: October 2012

The present study documents the changes in carbon and nitrogen metabolites occurring in apical buds and previous year stems of white spruce seedlings ( Picea glauca [Moench] Voss) with contrasting growth phenotypes (tall vs. small) after transfer to short day (SD; 8 h) photoperiod to induce bud formation. Concentrations of total nonstructural carbohydrates markedly increased in the developing buds within the days after transfer to SD, mainly as a result of increased concentrations of monosaccharides such as glucose, fructose, and pinitol. At the same time, starch levels declined, with the resulting carbohydrates presumably used to meet early carbon requirements of the SD-induced apical bud. Concentrations of glutamine, glutamic acid and proline also decreased immediately after transfer to SD in both organs. Later stages of SD-induced bud formation were characterized by an increase in starch, sucrose, and glutamine concentrations in previous year stems, concomitant with an increase in the steady-state levels of UDP-glucose pyrophosphorylase and glutamine synthetase protein. In contrast, arginine levels increased after 2 weeks of SD exposure, indicating a transition in arginine metabolism at the time of initiation of shoot stem primordia and bud elongation. Higher accumulation of total nonstructural carbohydrates and total amino acids in previous year stems of small trees could indicate lower sink strength of apical bud during its development, which could in turn impact subsequent tree growth.
Does long-distance GABA signaling via the phloem really occur?
Authors: Shelp Barry J.
Published: October 2012

The ubiquitous nonprotein amino acid known as γ-aminobutyrate (GABA) has been proposed as a mechanism whereby environmental and developmental cues are translocated in phloem. Information about the composition of translocation fluids from various species that bleed spontaneously reveals that GABA is always present in xylem at minor levels, but sometimes absent in phloem. In species that do not bleed spontaneously, GABA is also absent or present at minor levels in aphid stylet exudate. By contrast, GABA in ethylenediaminetetraacetate-facilitated phloem exudates is relatively abundant compared to other amino acids or the concentration of total amino acids present in xylem. Evidence indicates that xylem-borne GABA is primarily retrieved and metabolized by mature leaves, and tissue pools of GABA reflect in situ biosynthesis. Recovery of significant GABA from phloem might be an artifact of wounding and the use of ethylenediaminetetraacetate. Scarce data from aphid stylectomy experiments indicates that GABA is a wound signal. However, the composition of phloem sap collected by this method is not uniform, shedding doubt on some results in the scientific literature. Elevated GABA levels in the host plant are known to influence the success of biotic interactions; however, these outcomes could be attributed to the impact of wounding at local sites, rather than delivery of GABA via phloem. Further research is required to provide unambiguous support for long-distance γ-aminobutyrate signaling in phloem.
Differences in tissue concentrations of hydrogen peroxide in the roots and cotyledons of annual and perennial species of flax (Linum)
Authors: Brown Jason C.L. , Marshall Katie E. , Staples James F.
Published: October 2012

Short-lived annuals should allocate more resources towards reproduction, whereas long-lived perennials should allocate more resources towards tissue maintenance. Although ecological data support this hypothesis, no studies have examined the physiological basis for lifespan differences between annuals and perennials. Based on the oxidative theory of aging, hydrogen peroxide (H2O2) levels should be lower in perennating tissues (e.g., basal roots) — but not nonperennating tissues (e.g., cotyledons) — from perennials compared with annuals. We tested this prediction using two annual and two perennial species of flax ( Linum ). As predicted, H2O2concentrations were lower in roots from perennials than from annuals, reflecting higher catalase activity in roots from perennials. In cotyledons, contrary to our predictions, H2O2concentrations were actually higher in perennials than in annuals, despite higher catalase activity in perennials as well, likely reflecting higher H2O2production via peroxisomes and chloroplasts. Therefore, we propose that, consistent with the oxidative theory of aging, perennial flax species have a lower oxidative burden in their roots, but this comes at the cost of a greater oxidative burden in their shoots. As we demonstrate, perenniality is ancestral in Linum, and so derivation of the annual condition likely involved a physiological shift towards a more equitable oxidative burden between roots and shoots.
The Drift des Demoiselles on the Magdalen Islands (Québec, Canada): sedimentological and micromorphological evidence of a Late Wisconsinan glacial diamict
Authors: Rémillard Audrey M. , Hétu Bernard , Bernatchez Pascal , Bertran Pascal
Published: October 2012

The deposits identified as being the Drift des Demoiselles, which is the upper unit of the southern Magdalen Islands (Québec, Canada), belong to two units of different origin, glacial and glaciomarine. At Anse à la Cabane, the glacial deposit comprises two subunits: a glacitectonite at the base and a subglacial traction till at the top. Numerous glaciotectonic deformation structures suggest ice flow towards the southeast. The till is above an organic horizon dated to ∼47–50 ka BP. New data presented here show that the southern part of the Magdalen archipelago was glaciated during the Late Wisconsinan. We relate this ice flow to the Escuminac ice cap, whose centre of dispersion was located in the Gulf of St. Lawrence, northwest of the islands. At Anse au Plâtre, the top of the Drift des Demoiselles is a glaciomarine deposit. At Anse à la Cabane, the till is covered by a stratified subtidal unit located at ∼20 m above sea level. Both were deposited during the marine transgression that followed deglaciation. At Anse à la Cabane, three ice-wedge casts truncate the till and the subtidal unit, providing evidence that periglacial conditions occurred on the archipelago after deglaciation.