bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical investigation of the effectiveness of a bored pile wall for the minimisation of settlement resulting from tunnel driving
Authors: Kirsch Ansgar , Piazzi Lukas
Published: November 2009

Bored pile walls can be constructed between buildings and tunnel alignments to protect sensitive buildings from settlement resulting from tunnelling. The aim of the research work presented here was to evaluate the effectiveness of such a bored pile wall with FE calculations and identify influential parameters. Two methods of predicting settlement were investigated with the programme ABAQUS: The GAP method, where the deformations of the tunnel contour are prescribed, and the stress reduction method, with which the support pressure at the tunnel contour is reduced. The ground is modelled as linear‐elastic, ideal‐plastic with a Mohr‐Coulomb failure criterion as well as with a hypoplastic constitutive law. The contact surface between wall and ground was modelled with complete bonding as well as with a contact law with friction.

The simulation results with the stress reduction method and the hypoplastic material model show the best results qualitatively. The predict settlements agree well with empirical methods and centrifuge tests from the literature. The simulations show that the effectiveness of the wall is significantly influenced by the contact properties in the boundary surface. It achieves the best protection effect when frictionless.

Zur Abschirmung sensibler Gebäude vor Setzungen infolge Tunnelvortrieb können Bohrpfahlwände zwischen Gebäude und Tunneltrasse eingesetzt werden. Ziel der hier präsentierten Forschungsarbeit war es, die Wirksamkeit einer solchen Bohrpfahlwand mit FE‐Berechnungen nachzuvollziehen und Einflussparameter zu identifizieren. Mit dem Programm ABAQUS wurden zwei Möglichkeiten zur Setzungsprognose untersucht: Die GAPMethode, bei der die Verschiebungen der Tunnelkontur vorgegeben werden, und die Spannungsreduktions‐Methode, bei welcher der Stützdruck an der Tunnelkontur reduziert wird. Der Boden wurde als linear‐elastisch, ideal‐plastisch mit Grenzbedingung nach Mohr‐Coulomb sowie mit einem hypoplastischen Stoffgesetz modelliert. Die Kontaktfläche zwischen Wand und Boden wurde sowohl mit vollständigem Verbund als auch mit einem Kontaktgesetz mit Reibung modelliert.

Die Simulationsergebnisse mit der Spannungsreduktions‐Methode und dem hypoplastischen Materialmodell zeigen die qualitativ besten Ergebnisse. Die Setzungsprognosen stimmen gut mit empirischen Ansätzen und Zentrifugenversuchen aus der Literatur überein. Die Simulationen veranschaulichen, dass die Wirksamkeit der Wand maßgeblich von den Kontakteigenschaften in der Grenzfläche beeinflusst wird. Die größte Abschirmwirkung erzielt sie bei Reibungsfreiheit.
Fitting ACE structural equation models to case‐control family data
Authors: Javaras K. N. , Hudson J. I. , Laird N. M.
Published: November 2009

Investigators interested in whether a disease aggregates in families often collect case‐control family data, which consist of disease status and covariate information for members of families selected via case or control probands. Here, we focus on the use of case‐control family data to investigate the relative contributions to the disease of additive genetic effects (A), shared family environment (C), and unique environment (E). We describe an ACE model for binary family data; this structural equation model, which has been described previously, combines a general‐family extension of the classic ACE twin model with a (possibly covariate‐specific) liability‐threshold model for binary outcomes. We then introduce our contribution, a likelihood‐based approach to fitting the model to singly ascertained case‐control family data. The approach, which involves conditioning on the proband's disease status and also setting prevalence equal to a prespecified value that can be estimated from the data, makes it possible to obtain valid estimates of the A, C, and E variance components from case‐control (rather than only from population‐based) family data. In fact, simulation experiments suggest that our approach to fitting yields approximately unbiased estimates of the A, C, and E variance components, provided that certain commonly made assumptions hold. Further, when our approach is used to fit the ACE model to Austrian case‐control family data on depression, the resulting estimate of heritability is very similar to those from previous analyses of twin data. Genet. Epidemiol. 34: 238–245, 2010.   © 2009 Wiley‐Liss, Inc.
Comparing apples and oranges: equating the power of case‐control and quantitative trait association studies
Authors: Yang Jian , Wray Naomi R. , Visscher Peter M.
Published: November 2009

Genome‐wide association studies have achieved unprecedented success in the identification of novel genes and pathways implicated in complex traits. Typically, studies for disease use a case‐control (CC) design and studies for quantitative traits (QT) are population based. The question that we address is what is the equivalence between CC and QT association studies in terms of detection power and sample size? We compare the binary and continuous traits by assuming a threshold model for disease and assuming that the effect size on disease liability has similar feature as on QT. We derive the approximate ratio of the non‐centrality parameter (NCP) between CC and QT association studies, which is determined by sample size, disease prevalence (K) and the proportion of cases (v) in the CC study. For disease with prevalence <0.1, CC association study with equal numbers of cases and controls (v=0.5) needs smaller sample size than QT association study to achieve equivalent power, e.g. a CC association study of schizophrenia (K=0.01) needs only ∼55% sample size required for association study of height. So a planned meta‐analysis for height on ∼120,000 individuals has power equivalent to a CC study on 33,100 schizophrenia cases and 33,100 controls, a size not yet achievable for this disease. With equal sample size, when v=K, the power of CC association study is much less than that of QT association study because of the information lost by transforming a quantitative continuous trait to a binary trait. Genet. Epidemiol. 34: 254–257, 2010.   © 2009 Wiley‐Liss, Inc.
Comparison of different irrigation methods based on the parametric evaluation approach in the plain West of Shush, Iran
Authors: Albaji Mohammad , Nasab Saeed Boroomand , Kashkoli Hydar Ali , Naseri Abdali
Published: November 2009

The main objective of this research was to compare the suitability of land for surface and drip irrigation methods according to a parametric evaluation system in the plains west of the city of Shush, in south‐west Iran. After analysing and evaluating soil properties, suitability maps were generated for both methods by means of remote sensing (RS) and a geographic information system (GIS). The results showed that 9031 ha (21.5%) of the studied area was highly suitable for surface irrigation methods, whereas 32 500 ha (77.5%) of the study area was highly suitable for drip irrigation methods. Also some land units covering an area of 2111 ha (5.0%) were not suitable to be used for surface irrigation systems. One land unit with an area of 724 ha (1.7%) was classified as not suitable for drip irrigation systems. Moreover, the results indicated that a larger amount of the land (30 100 ha – 71.8%) can be classified as more suitable for drip than surface irrigation. Ultimately, the application of a drip irrigation system was suggested as the best method to be applied to the study area. The main limiting factors in using surface irrigation methods in this area were sandy soil texture and slope; moreover, for drip irrigation methods, the main limiting factor was soil calcium carbonate. Copyright © 2009 John Wiley & Sons, Ltd.
Predicting water allocations and trading prices to assist water markets
Authors: Khan Shahbaz , Dassanayake Dharma , Mushtaq Shahbaz , Hanjra Munir A
Published: November 2009

Uncertain water allocations and water trading prices are a key constraint to efficient irrigated cropping and water trading decisions. This study shows that neural network models can reasonably forecast seasonal allocations and trading prices in water markets. These models can complement other forecasting techniques such as regression analysis and time series models as the former can better capture the non‐linearities in the water trading system. Using a 50% probability risk factor for water variability, the water allocation model showed minor estimation error; however, in one instance the model underestimated the water allocation by 21%. This may be due to exceptionally low initial water allocations and borrowing of water from future years which was outside the training data sets. Similarly, the water trading price forecast model showed modest estimation error of about 11% during 2004/05 probably due to drought. Overall the models have good water allocation and price forecasting accuracy, and the determinants of water trading prices identified by the neural network models are those expected of the econometric models/economic theory. Copyright © 2009 John Wiley & Sons, Ltd.
Dual role of parathyroid hormone in endothelial progenitor cells and marrow stromal mesenchymal stem cells
Authors: Di Bernardo Giovanni , Galderisi Umberto , Fiorito Carmela , Squillaro Tiziana , Cito Letizia , Cipollaro Marilena , Giordano Antonio , Napoli Claudio
Published: November 2009

Hematopoietic stem cells derive regulatory information also from parathyroid hormone (PTH). To explore the possibility that PTH may have a role in regulation of other stem cells residing in bone marrow, such as mesenchymal stem cells (MSCs) and endothelial progenitor cells (EPCs) we assessed the effect of this hormone on the in vitro behavior of MSCs and EPCs. We evidenced that MSCs were much more responsive to PTH than EPCs. PTH increased the proliferation rate of MSCs with a diminution of senescence and apoptosis. Taken together, our results may suggest a protective effect of PTH on MSCs that reduces stress phenomena and preserve genome integrity. At the opposite, PTH did not modify the fate of EPCs in culture. J. Cell. Physiol. 222: 474–480, 2010. © 2009 Wiley‐Liss, Inc.
Paclitaxel and beta‐lapachone synergistically induce apoptosis in human retinoblastoma Y79 cells by downregulating the levels of phospho‐Akt
Authors: D'Anneo Antonella , Augello Giuseppa , Santulli Andrea , Giuliano Michela , di Fiore Riccardo , Messina Concetta , Tesoriere Giovanni , Vento Renza
Published: November 2009

Paclitaxel (PTX) and beta‐lapachone (LPC) are naturally occurring compounds that have shown a large spectrum of anticancer activity. In this article we show for the first time that PTX/LPC combination induces potent synergistic apoptotic effects in human retinoblastoma Y79 cells. Combination of suboptimal doses of PTX (0.3 nM) and LPC (1.5 µM) caused biochemical and morphological signs of apoptosis at 48 h of treatment. These effects were accompanied by potent lowering in inhibitor of apoptosis proteins and by activation of Bid and caspases 3 and 6 with lamin B and PARP breakdown. PTX/LPC combination acted by favoring p53 stabilization through a lowering in p‐Akt levels and in ps166‐MDM2, the phosphorylated‐MDM2 form that enters the nucleus and induces p53 export and degradation. Treatment with wortmannin or transfection with a dominant negative form of Akt anticipated at 24 h the effects induced by PTX/LPC, suggesting a protective role against apoptosis played by Akt in Y79 cells. In line with these results, we demonstrated that Y79 cells contain constitutively active Akt, which forms a cytosolic complex with p53 and MDM2 driving p53 degradation. PTX/LPC treatment induced a weakness of Akt–MDM2–p53 complex and increased nuclear p53 levels. Our results suggest that phospho‐Akt lowering is at the root of the apoptotic action exerted by PTX/LPC combination and provide strong validation for a treatment approach that targets survival signals represented by phospho‐Akt and inhibitor of apoptosis proteins. J. Cell. Physiol. 222: 433–443, 2010. © 2009 Wiley‐Liss, Inc.
Altered lumbar spine structure, biochemistry, and biomechanical properties in a canine model of mucopolysaccharidosis type VII
Authors: Smith Lachlan J. , Martin John T. , Szczesny Spencer E. , Ponder Katherine P. , Haskins Mark E. , Elliott Dawn M.
Published: November 2009

Mucopolysaccharidosis VII (MPS VII) is a lysosomal storage disorder characterized by a deficiency in β‐glucuronidase activity, leading to systemic accumulation of poorly degraded glycosaminoglycans (GAG). Along with other morbidities, MPS VII is associated with pediatric spinal deformity. The objective of this study was to examine potential associations between abnormal lumbar spine matrix structure and composition in MPS VII, and spine segment and tissue‐level mechanical properties, using a naturally occurring canine model with a similar clinical phenotype to the human form of the disorder. Segments from juvenile MPS VII and unaffected dogs were allocated to: radiography, gross morphology, histology, biochemistry, and mechanical testing. MPS VII spines had radiolucent lesions in the vertebral body epiphyses. Histologically, this corresponded to a GAG‐rich cartilaginous region in place of bone and elevated GAG staining was seen in the annulus fibrosus. Biochemically, MPS VII samples had elevated GAG in the outer annulus fibrosus and epiphyses, low calcium in the epiphyses, and high water content in all regions except the nucleus pulposus. MPS VII spine segments had higher range of motion and lower stiffness than controls. Endplate indentation stiffness and failure loads were significantly lower in MPS VII samples, while annulus fibrosus tensile mechanical properties were normal. Vertebral body lesions in MPS VII spines suggest a failure to convert cartilage to bone during development. Low stiffness in these regions likely contributes to mechanical weakness in motion segments and is a potential factor in the progression of spinal deformity. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:616–622, 2010
Comparative study of carpal tunnel compliance in the human, dog, rabbit, and rat
Authors: Tung Wen‐Lin , Zhao Chunfeng , Yoshii Yuichi , Su Fong‐Chin , An Kin‐Nan , Amadio Peter C.
Published: November 2009

The purpose of this study was to measure the compliance of the carpal tunnel in candidate animal models of carpal tunnel syndrome (CTS), by measuring the resistance when passing a tapered metal rod through the carpal tunnel. Forepaws from 10 dogs, 10 rabbits, and 10 rats with intact carpal tunnels, and 10 fresh frozen human wrist cadavers were used. The slopes of the linear part of the force‐displacement curve (a measure of stiffness), normal force, and increasing area ratio (InAR) were significantly different among the four species (p < 0.05). Post hoc analysis indicated that the mean slopes for the human carpal tunnel were the largest, indicating the least compliance, whereas those of the rat were the least (p < 0.05). The features of the compliance for the dog carpal tunnel were closest to the human. The development of animal models of CTS should consider the compliance of the carpal tunnel, as it will be more difficult to increase pressure in a more compliant tunnel. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:652–656, 2010
Vibrational spectroscopic study of Sr2ZnTeO6 double perovskites
Authors: Dias Anderson , Subodh Ganesanpotti , Sebastian Mailadil T. , Moreira Roberto L.
Published: November 2009

Sr2ZnTeO6 ceramics were prepared by the solid‐state route and their vibrational phonon modes were investigated using optical spectroscopic techniques, for the first time. X‐ray diffraction (XRD) and Raman and infrared spectroscopies were employed to investigate the structures of these perovskite materials and the results analysed together with group‐theoretical predictions. The number and behaviour of the first‐order modes observed in both spectroscopic techniques are in agreement with the calculations for a tetragonal I4/m space group. The complete set of the optical phonon modes was determined, and the intrinsic dielectric properties of the materials were evaluated, allowing us to discuss their potential application in microwave (MW) circuitry. Copyright © 2009 John Wiley & Sons, Ltd.
FT‐IR and FT‐Raman investigations of the chemosensing material para‐hexafluoroisopropanol aniline
Authors: Kong Lingtao , Wang Jin , Jia Yong , Guo Zheng , Liu Jinhuai
Published: November 2009

As an important chemosensing material involving hexafluoroisopropanol (HFIP) for detecting nerve agents, para‐HFIP aniline (p‐HFIPA) has been firstly synthesized through a new reaction approach and then characterized by nuclear magnetic resonance and mass spectrometry experiments. Fourier transform infrared absorption spectroscopy (FT‐IR) and FT‐Raman spectra of p‐HFIPA have been obtained in the regions of 4000–500 and 4000–200 cm−1, respectively. Detailed identifications of its fundamental vibrational bands have been given for the first time. Moreover, p‐HFIPA has been optimized and vibrational wavenumber analysis can be subsequently performed via density functional theory (DFT) approach in order to assist these identifications in the experimental FT‐IR and FT‐Raman spectra. The present experimental FT‐IR and FT‐Raman spectra of p‐HFIPA are in good agreement with theoretical FT‐IR and FT‐Raman spectra. Copyright © 2009 John Wiley & Sons, Ltd.
Angel finance: the other venture capital
Authors: Wong Andrew , Bhatia Mihir , Freeman Zachary
Published: November 2009

The procurement of capital is an important consideration for an entity transforming from an entrepreneurial idea to a revenue generating company.

Angel financing is one of the most common, but least studied methods, to finance new ventures.

The term “Angel Investor” generally refers to a high net‐worth individual who typically invests in small, private firms on his or her own account.

Using a unique dataset of firms financed by angels between 1994 and 2001, our research provides some insight into the role of angels in funding, monitoring and guiding their investments.

Although exposed to greater uncertainty by investing earlier in the life of a firm compared to venture capital investors, angel investors do not rely on traditional control mechanisms such as board control, staging, or contractual provisions to protect against expropriation.

Angels may use more informal methods of control such as investing in close geographic proximity and syndicating investments with other angels to mitigate risks.

The results of the study indicate that angels have a complementary role to venture capital in the financing of new ventures.

Copyright © 2009 John Wiley & Sons, Ltd.
Price setting and market structure: an empirical analysis of micro data in Slovakia
Authors: Coricelli Fabrizio , Horváth Roman
Published: November 2009

Most empirical studies on price setting that use micro data focus on advanced industrial countries. In this paper we analyze the experience of an emerging economy, Slovakia, using a large micro‐level dataset that accounts for a substantial part of the consumer price index (about 5 million observations). We find that market structure is an important determinant of pricing behavior. The effect of market structure on persistence of inflation results from two conflicting forces. Increased competition may reduce persistence by increasing the frequency of price changes. On the contrary, higher competition may increase persistence through inertial behaviour induced by the strategic complementarity among price setters. In our case study, we find that the latter effects dominate. Indeed, the dispersion of prices is higher while persistence is lower in the non‐tradable sectors, suggesting that higher competition is not conducive to lower persistence. Furthermore, we find that the frequency of price changes depends negatively on the price dispersion and positively on the product‐specific inflation. These results seem consistent with predictions of Calvo's staggered price model. Copyright © 2009 John Wiley & Sons, Ltd.
Structural determination of prunusins A and B, new C‐alkylated flavonoids from Prunus domestica, by 1D and 2D NMR spectroscopy
Authors: Mahmood Azhar , Fatima Itrat , Kosar Shaheen , Ahmed Rehana , Malik Abdul
Published: November 2009

Prunusins A (1) and B (2), the new C‐alkylated flavonoids, have been isolated from the seed kernels of Prunus domestica. Their structures were assigned from 1H and 13C nuclear magnetic resonating spectra, DEPT and by correlation spectroscopy, HMQC and HMBC experiments. 3, 5, 7, 4′‐Tetrahydroxyflavone (3) and 3, 5, 7‐trihydroxy‐8, 4′‐dimethoxyflavone (4) have also been reported from this species. Both compounds (1) and (2) showed significant antifungal activity against pathogenic fungus Trichophyton simmi. Copyright © 2009 John Wiley & Sons, Ltd.
T2 relaxation time abnormalities in bipolar disorder and schizophrenia
Authors: Öngür Dost , Prescot Andrew P. , Jensen J. Eric , Rouse Elizabeth D. , Cohen Bruce M. , Renshaw Perry F. , Olson David P.
Published: November 2009

There are substantial abnormalities in the number, density, and size of cortical neurons and glial cells in bipolar disorder and schizophrenia. Because molecule‐microenvironment interactions modulate metabolite signals characteristics, these cellular abnormalities may impact transverse (T2) relaxation times. We measured T2 relaxation times for three intracellular metabolites (N‐acetylaspartate + N‐acetylaspartylglutamate, creatine + phosphocreatine, and choline‐containing compounds) in the anterior cingulate cortex and parieto‐occipital cortex from 20 healthy subjects, 15 patients with bipolar disorder, and 15 patients with schizophrenia at 4 T. Spectra used in T2 quantification were collected from 8‐cc voxels with varying echo times (30 to 500 ms, in 10‐ms steps). Both bipolar disorder and schizophrenia groups had numerically shorter T2 relaxation times than the healthy subjects group in both regions; these differences reached statistical significance for creatine + phosphocreatine and choline‐containing compounds in bipolar disorder and for choline‐containing compounds in schizophrenia. Metabolite T2 relaxation time shortening is consistent with reduced cell volumes and altered macromolecule structures, and with prolonged water T2 relaxation times reported in bipolar disorder and schizophrenia. These findings suggest that metabolite concentrations reported in magnetic resonance spectroscopy studies of psychiatric conditions may be confounded by T2 relaxation and highlight the importance of measuring and correcting for this variable. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
A short‐breath‐hold technique for lung pO2 mapping with 3He MRI
Authors: Miller G. Wilson , Mugler John P. , Altes Talissa A. , Cai Jing , Mata Jaime F. , de Lange Eduard E. , Tobias William A. , Cates Gordon D. , Brookeman James R.
Published: November 2009

A pulse‐sequence strategy was developed for generating regional maps of alveolar oxygen partial pressure (pO2) in a single 6‐sec breath hold, for use in human subjects with impaired lung function. Like previously described methods, pO2 values are obtained by measuring the oxygen‐induced T1 relaxation of inhaled hyperpolarized 3He. Unlike other methods, only two 3He images are acquired: one with reverse‐centric and the other with centric phase‐encoding order. This phase‐encoding arrangement minimizes the effects of regional flip‐angle variations, so that an accurate map of instantaneous pO2 can be calculated from two images acquired a few seconds apart. By combining this phase‐encoding strategy with variable flip angles, the vast majority of the hyperpolarized magnetization goes directly into the T1 measurement, minimizing noise in the resulting pO2 map. The short‐breath‐hold pulse sequence was tested in phantoms containing known O2 concentrations. The mean difference between measured and prepared pO2 values was 1 mm Hg. The method was also tested in four healthy volunteers and three lung‐transplant patients. Maps of healthy subjects were largely uniform, whereas focal regions of abnormal pO2 were observed in diseased subjects. Mean pO2 values varied with inhaled O2 concentration. Mean pO2 was consistent with normal steady‐state values in subjects who inhaled 3He diluted only with room air. Magn Reson Med 63:127–136, 2010. © 2009 Wiley‐Liss, Inc.
RF shimming for spectroscopic localization in the human brain at 7 T
Authors: Hetherington Hoby P. , Avdievich Nikolai I. , Kuznetsov Andrey M. , Pan Jullie W.
Published: November 2009

Spectroscopic imaging of the human head at short echo times (≤15 ms) typically requires suppression of signals from extracerebral tissues. However, at 7 T, decreasing efficiency in B generation (hertz/watt) and increasing spectral bandwidth result in dramatic increases in power deposition and increased chemical shift registration artifacts for conventional gradient‐based in‐plane localization. In this work, we describe a novel method using radiofrequency shimming and an eight‐element transceiver array to generate a B field distribution that excites a ring about the periphery of the head and leaves central brain regions largely unaffected. We have used this novel B distribution to provide in‐plane outer volume suppression (>98% suppression of extracerebral lipids) without the use of gradients. This novel B distribution is used in conjunction with a double inversion recovery method to provide suppression of extracerebral resonances with T1s greater than 400 ms, while having negligible effect on metabolite ratios of cerebral resonances with T1s > 1000 ms. Despite the use of two adiabatic pulses, the high efficiency of the ring distribution allows radiofrequency power deposition to be limited to 3‐4 W for a pulse repetition time of 1.5 sec. The short echo time enabled the acquisition of images of the human brain, displaying glutamate, glutamine, macromolecules, and other major cerebral metabolites. Magn Reson Med, 2010. © 2009 Wiley‐Liss, Inc.
MRI using radiofrequency magnetic field phase gradients
Authors: Sharp Jonathan C. , King Scott B.
Published: November 2009

Conventionally, MR images are formed by applying gradients to the main static magnetic field (B0). However, the B0 gradient equipment is expensive, power‐hungry, complex, and noisy and can induce eddy currents in nearby conducting structures, including the patient. Here, we describe a new silent, B0 gradient‐free MRI principle, Transmit Array Spatial Encoding (TRASE), based on phase gradients of the radio‐frequency (RF) field. RF phase gradients offer a new method of k‐space traversal. Echo trains using at least two different RF phase gradients allow spin phase to accumulate, causing k‐space traversal. Two such RF fields provide one‐dimensional imaging and three are sufficient for two‐dimensional imaging. Since TRASE is a k‐space method, analogues of many conventional pulse sequences are possible. Experimental results demonstrate one‐dimensional and two‐dimensional RF MRI and slice selection using a single‐channel, transmit/receive, 0.2 T, permanent magnet, human MR system. The experimentally demonstrated spatial resolution is much higher than that provided by RF receive coil array sensitivity encoding alone but lower than generally achievable with B0 gradients. Potential applications are those in which one or more of the features of simplified equipment, lower costs, silent MRI, or the different physics of the image formation process are particularly advantageous. Magn Reson Med, 2010. © 2009 Wiley‐Liss, Inc.
A multislice gradient echo pulse sequence for CEST imaging
Authors: Dixon W. Thomas , Hancu Ileana , Ratnakar S. James , Sherry A. Dean , Lenkinski Robert E. , Alsop David C.
Published: November 2009

Chemical exchange–dependent saturation transfer and paramagnetic chemical exchange–dependent saturation transfer are agent‐mediated contrast mechanisms that depend on saturating spins at the resonant frequency of the exchangeable protons on the agent, thereby indirectly saturating the bulk water. In general, longer saturating pulses produce stronger chemical and paramagnetic exchange–dependent saturation transfer effects, with returns diminishing for pulses longer than T1. This could make imaging slow, so one approach to chemical exchange–dependent saturation transfer imaging has been to follow a long, frequency‐selective saturation period by a fast imaging method. A new approach is to insert a short frequency‐selective saturation pulse before each spatially selective observation pulse in a standard, two‐dimensional, gradient‐echo pulse sequence. Being much less than T1 apart, the saturation pulses have a cumulative effect. Interleaved, multislice imaging is straightforward. Observation pulses directed at one slice did not produce observable, unintended chemical exchange–dependent saturation transfer effects in another slice. Pulse repetition time and signal‐to noise ratio increase in the normal way as more slices are imaged simultaneously. Magn Reson Med, 2010. © 2009 Wiley‐Liss, Inc.
Motion correction using an enhanced floating navigator and GRAPPA operations
Authors: Lin Wei , Huang Feng , Börnert Peter , Li Yu , Reykowski Arne
Published: November 2009

A method for motion correction in multicoil imaging applications, involving both data collection and reconstruction, is presented. The floating navigator method, which acquires a readout line off center in the phase‐encoding direction, is expanded to detect translation/rotation and inconsistent motion. This is done by comparing floating navigator data with a reference k‐space region surrounding the floating navigator line, using a correlation measure. The technique of generalized autocalibrating partially parallel acquisition is further developed to correct for a fully sampled, motion‐corrupted dataset. The flexibility of generalized autocalibrating partially parallel acquisition kernels is exploited by extrapolating readout lines to fill in missing “pie slices” of k‐space caused by rotational motion and regenerating full k‐space data from multiple interleaved datasets, facilitating subsequent rigid‐body motion correction or proper weighting of inconsistent data (e.g., with through‐plane and nonrigid motion). Phantom and in vivo imaging experiments with turbo spin‐echo sequence demonstrate the correction of severe motion artifacts. Magn Reson Med, 2010. © 2009 Wiley‐Liss, Inc.
Quantification of T2 in the abdomen at 3.0 T using a T2‐prepared balanced turbo field echo sequence
Authors: Hoad Caroline L. , Cox Eleanor F. , Gowland Penny A.
Published: November 2009

The T2‐prepared balanced turbo field echo sequence has been used to measure T2 in phantoms and in vivo in the abdomen with low sensitivity to radiofrequency pulse errors. The effects of noise, errors in the pulse flip angles, and off resonance effects on the results have been simulated. It was found from simulations that for normal conditions, including the flip angle in the fit improved the systematic errors due to radiofrequency pulse errors and noise in the results to less than 1% without significantly increasing the random errors. For a 0.3% noise level, the standard deviation in the measured T2 was approximately 0.003 ms. Off‐resonance effects had a minimal effect on the measured T2 value. The T2 at 3.0 T of various abdominal organs was measured, in particular the liver (31 ± 6 ms), spleen (54 ± 15 ms), kidney cortex (76 ± 6 ms), kidney medulla (61 ± 8 ms), and pancreas (42 ± 20 ms). Magn Reson Med, 2010. © 2009 Wiley‐Liss, Inc.
Change in the proton T1 of fat and water in mixture
Authors: Hu Houchun H. , Nayak Krishna S.
Published: November 2009

This work describes observed changes in the proton T1 relaxation time of both water and lipid when they are in relatively homogeneous mixtures. Results obtained from vegetable oil–water emulsions, pork kidney and lard mixtures, and excised samples of white and brown adipose tissues are presented to demonstrate this change in T1 as a function of mixture fat fraction. As an initial proof of concept, a simpler acetone‐water experiment was performed to take advantage of complete miscibility between acetone and water and both components' single chemical shift peaks. Single‐voxel MR spectroscopy was used to measure the T1 of predominant methylene spins in fat and the T1 of water spins in each setup. In the vegetable oil–water emulsions, the T1 of fat varied by as much as 3‐fold when water was the dominant mixture component. The T1 of pure lard increased by 170 msec (+37%) when it was blended with lean kidney tissue in a 16% fatty mixture. The fat T1 of lipid‐rich white adipose tissue was 312 msec. In contrast, the fat T1 of leaner brown adipose tissue (fat fraction 53%) was 460 msec. A change in the water T1 from that of pure water was also observed in the experiments. Magn Reson Med, 2010. © 2009 Wiley‐Liss, Inc.
Evidence of gender‐specific motor templates to resist valgus loading at the knee
Authors: Cammarata Martha L. , Dhaher Yasin Y.
Published: November 2009

Gender differences in neuromuscular control of the lower extremity may contribute to increased injury risk in females, but the neurophysiological mechanisms underlying these differences remain unclear. In this study, we sought to explore the effect of gender on volitional and reflex neuromuscular responses to a rapid valgus perturbation at the knee applied under “intervene” and “do not intervene” conditions. Multiple 7° ramp‐and‐hold valgus perturbations were applied at the neutrally extended knee of 12 male and 12 female healthy subjects, while surface electromyography over the quadriceps and hamstrings recorded the neuromuscular response. Volitional responses did not vary between groups, perhaps reflecting the relative novelty of the loading direction. However, reflex responses observed under the “do not intervene” paradigm did vary by gender. Males demonstrated much more frequent and consistent reflex muscle activation than females. Moreover, muscle activation patterns were gender‐specific. Diminished responses in female subjects may indicate that the position‐based valgus perturbation did not produce the necessary mechanical stimulus to elicit reflexes. These gender differences in reflex control of the knee provide new insight into the control of frontal‐plane knee joint movement and loading and may elucidate the neuromechanical underpinnings associated with neuromuscular control. Muscle Nerve, 2010
Redetermination of the optimal stimulation intensity modifies resting H‐reflex recovery after a sustained moderate‐intensity muscle contraction
Authors: Rupp Thomas , Girard Olivier , Perrey Stéphane
Published: November 2009

This study aimed to determine whether the time‐course of maximal resting H‐reflex amplitude (Hmax) recovery after a prolonged moderate‐intensity muscle contraction differs according to the optimal stimulation intensity used (predetermined vs. readjusted). Thirteen males performed a sustained isometric plantar flexion at 40% of their maximal voluntary contraction torque output until exhaustion. Hmax of the soleus muscle was recorded before and 2, 6, 10, and 14 min after the end of the contraction, then normalized by the respective maximal M‐wave to form the Hmax/Mmax ratio. During recovery, pre‐ and redetermined optimal stimulation intensities (mini‐recruitment curve drawn before each recovery measurement) were applied randomly to measure Hmax. When using redetermined stimulation intensities, normalized H‐reflex values were systematically greater (+11, +16, +15, and +15% after 2‐, 6‐, 10‐, and 14‐min recovery periods, respectively) than those obtained with the predetermined intensity. Keeping the stimulation intensity constant to evoke Hmax after a sustained muscle contraction can underestimate the H‐reflex facilitation occurring after exhaustive exercise. It is therefore more appropriate to redefine the optimal stimulation intensity to evoke Hmax (using mini‐recruitment curves) when the purpose is to analyze spinal modulation during the recovery phase. Muscle Nerve, 2010
Schwann cells as a source of insulin‐like growth factor‐1 for extraocular muscles
Authors: Feng Chengyuan , Von Bartheld Christopher S.
Published: November 2009

Precise force regulation is fundamentally important for extraocular muscle (EOM) function. Insulin‐like growth factor‐1 (IGF‐1) plays a major role in EOM force regulation, but the source of endogenous IGF‐1 is unclear. Multiple IGF‐1 sources may supply EOMs, including: the EOM itself; the systemic circulation; innervating motoneurons; and Schwann cells within nerves. IGF‐1 expression was measured in chicken during oculomotor system maturation by using real‐time polymerase chain reaction (PCR). Accumulation of radiolabeled IGF‐1 in EOMs was compared after either injection into the vascular circulation or into the trochlear nerve. Schwann cells were the most prominent IGF‐1 source. A microtubule‐dependent mechanism exists to anterogradely transport IGF‐1 to EOMs. EOMs were significantly more efficient in extracting IGF‐1 from the nerve than from the systemic circulation. Therefore, Schwann cells are the most prominent and potentially the most important source of IGF‐1 for EOMs. These findings may contribute to a better understanding of EOM force regulation and its failure in strabismus. Muscle Nerve, 2010
Diffuse large B‐cell lymphoma presenting as piriformis syndrome
Authors: Ye Byoung Seok , Sunwoo Il Nam , Suh Bum Chun , Park Jong‐Pil , Shim Dong‐Suk , Kim Seung Min
Published: November 2009

Piriformis syndrome (PS) is a rare condition characterized by pain and paresthesia of the buttock, often radiating to the posterior thigh. A patient with sciatica that was clinically suspicious for PS, underwent diagnostic work‐up. A diagnosis of diffuse large B‐cell lymphoma with neurolymphomatosis (NL) was made. To our knowledge, this is the first report of NL presenting as PS. NL is a possible cause of secondary PS. Muscle Nerve, 2010
Acute‐onset chronic inflammatory demyelinating polyneuropathy with cranial nerve involvement, dysautonomia, respiratory failure, and autoantibodies
Authors: Hantson Philippe , Kevers Luc , Fabien Nicole , Van Den Bergh Peter
Published: November 2009

We examined a 27‐year‐old woman who developed rapidly progressive quadriplegia and acute respiratory failure that required mechanical ventilation in the intensive care unit. It was unclear whether this was a presentation of Guillain–Barré syndrome (GBS) or acute‐onset chronic inflammatory demyelinating polyradiculoneuropathy (A‐CIDP). Remarkable features included multiple cranial nerve involvement, respiratory failure, dysautonomia, and skin manifestations. Several autoantibodies were elevated, including antinuclear (ANA), anticardiolipin (aCL), thyroid, and calcium‐sensing receptor (CaSR) autoantibodies. The patient was initially diagnosed with GBS and treated with intravenous immunoglobulin (IVIg). After almost complete recovery, relapse with quadriplegia and respiratory failure was observed 12 weeks after motor symptom onset. She then received IVIg and steroid pulse therapy followed by maintenance oral methylprednisolone and plasma exchange. She recovered completely 4 months after the relapse. The further clinical and serological course was consistent with systemic lupus erythematosus (SLE)‐associated CIDP. Herein we evaluate the association between A‐CIDP and some biological markers of autoimmunity. Muscle Nerve, 2010
A Patient with neurofibromatosis type 1 and Charcot–Marie–Tooth disease type 1B
Authors: Lancaster Eric , Elman Lauren B. , Scherer Steven S.
Published: November 2009

We describe a patient with both neurofibromatosis type 1 and Charcot–Marie–Tooth disease type 1B. Although one might expect an overwhelming tumor burden due to the combination of these two disorders, the two mutations did not appear to interact. Muscle Nerve 41: 555–558, 2010
Ocular myasthenia gravis in a senior population: Diagnosis, therapy, and prognosis
Authors: Allen Jeffrey A. , Scala Stephanie , Jones H. Royden
Published: November 2009

The objectives of this study were (I) to explore the prognosis of ocular myasthenia gravis (OMG) in patients with onset at age 70 years and above (i.e. senior persons); (2) to identify predictors of secondary generalization in this age group; and 3) to address the effects of immunotherapy on this population of patients. We performed a retrospective analysis of 39 patients with myasthenia gravis who presented with only ocular signs and symptoms after age 70 years. Generalized myasthenia gravis (GMG) developed in 12 OMG patients (31%). None of the GMG patients required ventilator assistance or a feeding tube. Of the 12 ocular patients progressing to GMG, only one (8%) received immunotherapy prior to generalization. Of those OMG patients who did not progress to GMG, 52% received immunomodulatory therapy. Our senior OMG patients had a prognosis comparable with those of the published data for younger individuals. Although the presence of increased acetylceholine receptor antibody titers and occasionally abnormal repetitive nerve stimulation were useful tools to diagnose OMG, no test was predictive of later generalization. Senior onset OMG patients who received immunotherapy less frequently developed GMG than those not so treated. Muscle Nerve, 2010
Monotonic and cyclic modeling of interface between geotextile and gravelly soil
Authors: Zhang Ga , Wang Liping , Zhang Jian‐Min
Published: November 2009

This paper describes a modified elasto‐plasticity damage model to capture monotonic and cyclic behavior of the interface between a geotextile and gravelly soil. New damage variable and shear strength criterion are introduced on the basis of test observations. The formulations of the modified model are obtained by extending those of the original interface model. The model parameters with physical meaning are easily determined from a group of cyclic shear tests and a confining compression test. The model predictions are compared with the results of a series of direct shear tests and large‐scale pullout tests. The comparison results demonstrate that the model accurately describes the monotonic and cyclic stress–strain relationship of the interface between a geotextile and gravelly soil while capturing new characteristics: (1) the strength that is nonlinearly dependent on the normal stress; (2) significant shear strain‐softening; (3) the comprehensive volumetric strain response with dependency on the shear direction; and (4) the evolution of behavior associated with the changes in the physical state that includes the geotextile damage. This model is used in a finite element analysis of pullout tests, indicating that the tensile modulus of a geotextile has a significant effect on the response of the geotextile–gravel system. Copyright © 2009 John Wiley & Sons, Ltd.
Characterizing user‐level network virtualization: performance, overheads and limits
Authors: Tsugawa Mauricio , Fortes José A. B.
Published: November 2009

Connectivity limitations in the current Internet have motivated the development of many overlay networking technologies that enable applications to transparently overcome such limitations. For easy development and deployment, overlay networks are typically implemented via a user‐level network virtualization software layer, often using high‐level languages. Existing solutions report performance that can keep up with slow wide‐area links—however, the question remains as to how overlay networks perform on new high‐speed Internet connections. This paper characterizes the performance of user‐level packet processing, which is at the core of most overlay networks implementations. To this end, building blocks of packet‐processing software are identified and characterized, and performance of IP forwarders developed in C and Java are compared through extensive measurements. Factors that affect the performance of overlay networks and limitations of existing solutions are characterized, providing insights on possible improvements. Experimental results show the following: to achieve maximum throughput, only a few microseconds (2–5) can be spent in virtual network processing; processing of small packets can limit TCP throughput; and overlays need to be carefully architected as encapsulation overheads can be substantial. Copyright © 2009 John Wiley & Sons, Ltd.
Using virtual topologies to manage inter‐domain QoS in next‐generation networks
Authors: Freitas Ricardo B. , de Paula Luciano B. , Madeira Edmundo , Verdi Fabio L.
Published: November 2009

Recently, several computer fields have turned to virtualization as a way to simplify complex problems. In this context, the Virtual Topology Service (VTS) was created to manage the advertisement and acquisition of virtual topologies (abstractions of the network status of a domain) and their use in inter‐domain resource reservation to provide end‐to‐end quality of service (QoS). As an effort to create new network architectures which could attend current requirements like mobility and context‐aware applications and support autonomous, heterogeneous and mobile domains next‐generation networks (NGNs) emerged, with Ambient Networks (AN) as one of its instances. With an ever increasing multitude of online applications, end‐to‐end QoS has become increasingly important, especially for media and real‐time uses. In this context, in order to better manage inter‐domain QoS in these new networks, better coping with mobile nodes and domains, this work presents a new design and implementation of the VTS, adapted to the AN environment. The new VTS stores resource reservation information to enable the reuse of these reservations when re‐establishing QoS after a node/domain movement. This implementation was tested on a real NGN prototype and showed considerable time saving when compared to QoS re‐establishment without reusing the reservations. Copyright © 2009 John Wiley & Sons, Ltd.
Depression in family caregivers of elders: A theoretical model of caregiver burden, sociotropy, and autonomy
Authors: Clark Michele C. , Diamond Pamela M.
Published: November 2009

To test the diathesis‐stress model for family caregivers, two structural equation models were developed to explain depression measured by the Center for Epidemiologic Studies Depression Scale. A cross‐sectional convenience sample of 112 caregivers completed questionnaires to measure burden, personality traits, dysfunctional attitudes, and depression. The final model included direct paths from caregiver burden to autonomy and sociotropy, and indirect paths from burden to depression through sociotropy and autonomy. The final model fit adequately (χ2 [224, N = 112] = 308.60, p < .00; CFI = .951; RMSEA = .058). Levels of burden influenced caregiver depression scores. One pathway to depression was though the personality traits of sociotropy and autonomy; both had a larger influence on depression scores than burden alone. © 2009 Wiley Periodicals, Inc. Res Nurs Health 33:20–34, 2010
Binary and ternary blends of high‐density polyethylene with poly(ethylene terephthalate) and polystyrene based on recycled materials
Authors: Razavi S. , Shojaei A. , Bagheri R.
Published: November 2009

Binary blends of recycled high‐density polyethylene (R‐HDPE) with poly(ethylene terephthalate) (R‐PET) and recycled polystyrene (R‐PS), as well as the ternary blends, i.e. R‐HDPE/R‐PET/R‐PS, with varying amounts of the constituents were prepared by twin screw extruder. The mechanical, rheological, thermal, and scanning electron microscopy (SEM) analyses were utilized to characterize the samples. The results revealed that both R‐HDPE/R‐PET and R‐HDPE/R‐PS blends show phase inversion but at different compositions. The R‐PET was found to have much higher influence on the properties enhancement of the R‐HDPE compared to R‐PS, but at the phase inverted situation, a significant loss in the tensile strength of R‐HDPE/R‐PET blend was observed due to the weak interaction at this morphological state. However, the ternary blends with higher loading of second phase, namely greater than 50 wt% of R‐PET+R‐PS, demonstrated better mechanical properties than the binary blends with the same content of either R‐PET or R‐PS. Copyright © 2009 John Wiley & Sons, Ltd.