bluuebunny/crossref_metadata_2025 huggingface dataset:
Use of the Connectivity of Runoff Model (CRUM) to investigate the influence of storm characteristics on runoff generation and connectivity in semi‐arid areas
Authors: Reaney S. M. , Bracken L. J. , Kirkby M. J.
Published: August 2006

Much attention has been given to the surface controls on the generation and transmission of runoff in semi‐arid areas. However, the surface controls form only one part of the system; hence, it is important to consider the effect that the characteristics of the storm event have on the generation of runoff and the transmission of flow across the slope. The impact of storm characteristics has been investigated using the Connectivity of Runoff Model (CRUM). This is a distributed, dynamic hydrology model that considers the hydrological processes relevant to semi‐arid environments at the temporal scale of a single storm event. The key storm characteristics that have been investigated are the storm duration, rainfall intensity, rainfall variability and temporal structure. This has been achieved through the use of a series of defined storm hydrographs and stochastic rainfall. Results show that the temporal fragmentation of high‐intensity rainfall is important for determining the travel distances of overland flow and, hence, the amount of runoff that leaves the slope as discharge. If the high‐intensity rainfall is fragmented, then the runoff infiltrates a short distance downslope. Longer periods of high‐intensity rainfall allow the runoff to travel further and, hence, become discharge. Therefore, storms with similar amounts of high‐intensity rainfall can produce very different amounts of discharge depending on the storm characteristics. The response of the hydrological system to changes in the rainfall characteristics can be explained using a four‐stage model of the runoff generation process. These stages are: (1) all water infiltrating, (2) the surface depression store filling or emptying without runoff occurring, (3) the generation and transmission of runoff and (4) the transmission of runoff without new runoff being generated. The storm event will move the system between the four stages and the nature of the rainfall required to move between the stages is determined by the surface characteristics. This research shows the importance of the variable‐intensity rainfall when modelling semi‐arid runoff generation. The amount of discharge may be greater or less than the amount that would have been produced if constant rainfall intensity is used in the model. Copyright © 2006 John Wiley & Sons, Ltd.
A review of the National Groundwater Monitoring Network in Korea
Authors: Lee Jin‐Yong , Yi Myeong‐Jae , Yoo Young‐Kwon , Ahn Kyung‐Hwan , Kim Gyoo‐Bum , Won Jong‐Ho
Published: August 2006

The drastic expansion of cities and the rapid economic growth in Korea have caused dramatic increases to demand from groundwater supplies for drinking, domestic, agricultural and industrial water usage. The Ministry of Construction and Transportation and the Korea Water Resources Corporation have constructed and operated the National Groundwater Monitoring Network (NGMN) throughout the country since 1995. The NGMN, an official project establishing a total of 320 groundwater monitoring stations, was completed in 2005. Each national groundwater monitoring station serves as a baseline and primary station to monitor long‐term general trends in water‐level fluctuations and in groundwater quality. The present NGMN and its monitoring capabilities were evaluated to enhance the efficiency of groundwater monitoring and to meet the new societal conditions. Based on reviews and evaluations, some suggestions and recommendations are made with regard to improvements of the national network, including the installation of rainfall gauges in groundwater monitoring stations, gathering groundwater data every hour instead of every 6 h as at present, involving major cations and anions in the regular and periodic chemical analyses, regular periodic analyses of collected groundwater data, and construction of 199 additional groundwater monitoring stations to supplement the existing groundwater monitoring network. Copyright © 2006 John Wiley & Sons, Ltd.
Cytoskeletal response of microvessel endothelial cells to an applied stress force at the submicrometer scale studied by atomic force microscopy
Authors: Ma Wanyun , Sun Yunxu , Han Dong , Chu Weiguo , Lin Danying , Chen Dieyan
Published: August 2006

Cytoskeleton fibers form an intricate three‐dimensional network to provide structure and function to microvessel endothelial cells. During accommodation to blood flowing, stress fiber bundles become more prominent and align with the direction of blood flow. This network either mechanically resists the applied shear stress (lateral force) or, if deformed, is dynamically remodeled back to a preferred architecture. However, the detailed response of these stress fiber bundles to applied lateral force at submicrometer scales are as yet poorly understood. In our in vitro study, the tip, topography probe in lateral force microscopy of atomic force microscopy, acted as a tool for exerting quantitative vertical and lateral force on the filaments of the cytoskeleton. Moreover, the authors developed a formula to calculate the value of lateral force exerted on every point of the filaments. The results show that cytoskeleton fibers of healthy tight junctions in rat cerebral microvessel endothelial cells formed a cross‐type network, and were reinforced and elongated in the direction of scanning under lateral force of 15–42 nN. Under peroxidation (H2O2 of 300 μmol/L), the cytoskeleton remodeled at intercellular junctions, and changed over the meshwork structures into a dense bundle, that redistributed the stress. Once mechanical forces were exerted on an area, the cells shrank and lost morphologic tight junctions. It would be useful in our understanding of certain pathological processes, such as cerebral ischemia/reperfusion injury, which maybe caused by biomechanical forces and which are overlooked in current disease models. Microsc. Res. Tech., 2006. © 2006 Wiley‐Liss, Inc.
Real‐time automated tracking and trapping system for sperm
Authors: Z. Shi Linda , Nascimento Jaclyn , Chandsawangbhuwana Charlie , Berns Michael W. , Botvinick Elliot L.
Published: August 2006

We have developed a microscope system for real‐time single sperm tracking with an automated laser tweezers escape power assay. Phase contrast images of swimming sperm are digitized to the computer at video rate. The custom algorithm creates a region of interest centered about a sperm in response to a mouse click and performs all subsequent tasks autonomously. Microscope stage movement responds to feedback from video analysis of swimming sperm to center the sperm with respect to the field of view. For escape power assays, sperm are automatically relocated to the laser trap focus where they are held for a user‐defined duration at fixed power, or held as laser power is gradually reduced. The sperm's position is automatically monitored to measure the laser power at which the sperm escapes the trap. Sperm are tracked for extended durations before and after laser trap experiments. Motility measurements including the curvilinear velocity and the absolute position of the sperm relative to the cell chamber are calculated and written to the hard drive at video rate. Experimental throughput is increased over 30 times compared to off‐line data analysis. The efficacy of the “track and trap” algorithm is validated through examples and comparisons with the manually collected data. Microsc. Res. Tech., 2006. © 2006 Wiley‐Liss, Inc.
Blood attenuation with SSFP‐compatible saturation (BASS)
Authors: Lin Hung‐Yu , Dale Brian M. , Flask Chris A. , Duerk Jeffrey L.
Published: August 2006

Purpose

To investigate a rapid flow‐suppression method for improving the contrast‐to‐noise ratio (CNR) between the vessel wall and the lumen for cardiovascular imaging applications.

Materials and Methods

In this study a new dark‐blood steady‐state free precession (SSFP) sequence utilizing two excitation pulses per TR was developed. The first pulse is applied immediately adjacent to the slice of interest, while the second is a conventional slice‐selective pulse designed to excite an SSFP signal for the static spins in the slice of interest. The slice‐selective pulse is followed by fully refocused gradients along all three imaging axes over each TR. The signal amplitude (SA) from the moving spins excited by the “saturation” pulse is attenuated since they are not fully refocused at the TE.

Results

This work provides confirmation, by both simulation and experiments, that modest adaptations of the basic True‐FISP structure can limit unwanted “bright blood” signal within the vessels while simultaneously preserving the contrast and speed advantages of this well‐established rapid imaging method.

Conclusion

Animal imaging trials confirm that dark‐blood contrast is achieved with the BASS sequence, which substantially reverses the lumen‐to‐muscle CNR of a conventional True‐FISP “bright blood” acquisition from 14.77 (bright blood) to −13.96 (dark blood) with a modest increase (24.2% of regular TR of SSFP for this implementation) in acquisition time to accommodate the additional slab‐selective excitation pulse and gradient pulses. J. Magn. Reson. Imaging 2006. © 2006 Wiley‐Liss, Inc.
In vivo R1‐enhancement mapping of canine myocardium using ceMRI with Gd(ABE‐DTTA) in an acute ischemia‐reperfusion model
Authors: Kiss P. , Suranyi P. , Simor T. , Saab‐Ismail N.H. , Elgavish A. , Hejjel L. , Elgavish G.A.
Published: August 2006

Purpose

To demonstrate the usefulness of normalized ΔR1 (ΔR1n) mapping in myocardial tissue following the administration of the contrast agent (CA) Gd(ABE‐DTTA).

Materials and Methods

Ischemia‐reperfusion experiments were carried out in 11 dogs. The method exploited the relatively long tissue lifetime of Gd(ABE‐DTTA), and thus no fast R1 measurement technique was needed. Myocardial perfusion was determined with colored microspheres (MP).

Results

With varying extent of ischemia, impaired wall motion (WM) and lower ΔR1n values were detected in the ischemic sectors, as opposed to the nonischemic sectors where normal WM and higher ΔR1n were observed. Based on the ΔR1n, data from the myocardial perfusion assay and the ΔR1n maps were compared in the ischemic sectors. A correlation analysis of these two parameters demonstrated a significant correlation (R = 0.694, P < 0.005), validating the ΔR1n‐mapping method for the quantitation of ischemia. Similarly, pairwise correlations were found for the MP, ΔR1n, and wall thickening (WT) values in the same areas. Based on the correlation between ΔR1n and MP, ΔR1n maps calculated with a pixel‐by‐pixel resolution can be converted to similarly high‐resolution myocardial perfusion maps.

Conclusion

These results suggest that the extent of the severity of ischemia can be quantitatively represented by ΔR1n maps obtained in the presence of our CA. J. Magn. Reson. Imaging 2006. © 2006 Wiley‐Liss, Inc.
Model‐free parameters from dynamic contrast‐enhanced‐MRI: Sensitivity to EES volume fraction and bolus timing
Authors: Jesberger John A. , Rafie Niusha , Duerk Jeffrey L. , Sunshine Jeffrey L. , Mendez Matthew , Remick Scot C. , Lewin Jonathan S.
Published: August 2006

Purpose

To quantify the unknown relative sensitivities of semiquantitative measures from dynamic contrast‐enhanced (DCE) MRI to variations in the volume fraction Ve of the extravascular extracellular space (EES), and the duration of the contrast injection.

Materials and Methods

Tissue‐uptake curves were simulated across various values of F, PS, Ve, and bolus timings, with and without additive noise and at different image reacquisition rates. From each, the peak of the first derivative (Gpeak), the total uptake after the rapid first phase (CE), and the IAUC were calculated and plotted against F for each experimental condition. Relationships between each measure and the corresponding quantitative measure Ktrans were also examined, particularly for linearity.

Results

The highest sensitivity to flow was achieved for shorter bolus timings for Gpeak, CE, and IAUC. Gpeak and IAUC were most linearly related to Ktrans. The sensitivity to Ve was lowest for Gpeak, followed by IAUC and CE. Long sampling intervals resulted in severe underestimation of Gpeak, while IAUC was unaffected provided that the limits of integration were properly applied. Gpeak could not be properly calculated in the presence of noise without a prior smoothing of the acquired curves, while IAUC was again unaffected by noise.

Conclusion

Gpeak and IAUC are both useful model‐free analogs of blood flow (i.e., Ktrans) for pre‐ and posttreatment comparisons. Gpeak may be the better choice in cases where larger changes in Ve are likely, but only if sufficient noise reduction and fast image sampling are applied. If Ve is expected to remain stable, IAUC is superior to Gpeak by virtue of its stability in the face of noise and more reliable estimation over a wider range of sampling rates. J. Magn. Reson. Imaging 2006. © 2006 Wiley‐Liss, Inc.
Longitudinal assessment of Alzheimer's β‐amyloid plaque development in transgenic mice monitored by in vivo magnetic resonance microimaging
Authors: Braakman Niels , Matysik Jörg , van Duinen Sjoerd G. , Verbeek Fons , Schliebs Reinhard , de Groot Huub J.M. , Alia A.
Published: August 2006

Purpose

To assess the development of β‐amyloid (Aβ) plaques in the brain with age in the transgenic mouse model of Alzheimer's disease (AD) pathology by in vivo magnetic resonance microimaging (μMRI).

Materials and Methods

Live transgenic mice (Tg2576) and nontransgenic littermates (control) were studied at regular intervals between the ages of 12 and 18 months. Plaques were visualized using a T2‐weighted rapid acquisition with relaxation enhancement (RARE) sequence. Changes in T2 relaxation times were followed using a multislice multiecho (MSME) sequence. Plaque load and numerical density in MR images were calculated using SCIL image software.

Results

Aβ plaques were clearly detected with the T2‐weighted RARE sequence in the hippocampal and cortical regions of the brain of Tg2576 mice but not in control mice. Following the plaque development in the same animals with age showed that plaque area, number, and size increased markedly, while T2 relaxation time showed a decreasing trend with age.

Conclusion

These results demonstrate that μMRI is a viable method for following the development of Aβ plaques in vivo, and suggest that this method may be feasible for assessing the effect of therapeutic interventions over time in the same animals. J. Magn. Reson. Imaging 2006. © 2006 Wiley‐Liss, Inc.
Dobutamine cardiovascular magnetic resonance: A review
Authors: Mandapaka Sangeeta , Hundley William Gregory
Published: August 2006

Dobutamine cardiovascular magnetic resonance (DCMR) is useful for identifying myocardial ischemia and viability in patients with known or suspected coronary artery disease (CAD). This article reviews the performance and utility of DCMR, its association with dobutamine stress echocardiography (DSE), and areas of active investigative research. J. Magn. Reson. Imaging 2006. © 2006 Wiley‐Liss, Inc.
Development of a novel optimized breathhold technique for myocardial T2 measurement in thalassemia
Authors: He Taigang , Gatehouse Peter D. , Anderson Lisa J. , Tanner Mark , Keegan Jennifer , Pennell Dudley J. , Firmin David N.
Published: August 2006

Purpose

To develop a reproducible fast spin‐echo (FSE) technique for accurate myocardial T2 measurement with application to iron overload assessment in thalassemia.

Materials and Methods

An FSE sequence was developed to permit acquisition of multiple TE images in one breathhold (BH‐FSE). A dynamic black‐blood scheme was introduced to better cancel blood signal. A nonselective refocusing train was also adopted to suppress stimulated echoes. The optimized technique was tested on phantoms and then applied to 10 normal volunteers and 10 thalassemia patients. Interstudy reproducibility was measured on all the 20 subjects.

Results

The mean difference in T2 values was 1.7% from phantom experiments between BH‐FSE and the conventional spin‐echo (SE) technique. High contrast BH‐FSE images were acquired from human subjects, with minimal stimulated echoes and effective blood suppression (P = 0.0005). The coefficient of variation for interstudy reproducibility was 4.3%. T2 values from thalassemia patients were substantially lower than those from the normal subjects (45.2 ± 26.1 msec vs. 56.9 ± 8.4ms, P = 0.02).

Conclusion

The dynamic black‐blood T2 sequence is a fast reproducible acquisition that compares favorably with conventional techniques, is robust to motion artifacts, and yields high blood‐myocardium contrast. This technique may provide a useful tool in thalassemia and other scenarios requiring myocardial T2 quantification. J. Magn. Reson. Imaging 2006. © 2006 Wiley‐Liss, Inc.
Adaptive bilateral breast MRI using projection reconstruction time‐resolved imaging of contrast kinetics
Authors: Ramsay E. , Causer P. , Hill K. , Plewes D.
Published: August 2006

Purpose

To introduce a bilateral implementation of an adaptive imaging technique in which both dynamic and high resolution breast MR images are acquired simultaneously.

Materials and Methods

Adaptive three‐dimensional bilateral breast imaging in the sagittal plane was achieved by combining two elements: a projection reconstruction time‐resolved imaging of contrast kinetics (PR‐TRICKS) k‐space trajectory and a slab interleaved sequence that imaged alternate breasts every TR. A pilot study was performed to evaluate image quality and contrast uptake behavior, using eight patients with previously identified benign lesions.

Results

Adaptive reconstruction demonstrated breast lesions in all eight women with similar image quality and signal‐to‐noise ratio (SNR) to Cartesian images with comparable imaging parameters. Contrast enhancement curves covering the entire postinjection time period were obtained from the dynamic images and in one case compared to previous enhancement profiles from a conventional Cartesian trajectory.

Conclusion

Bilateral dynamic and high spatial resolution images with high SNR can be achieved in a clinically feasible manner, providing both kinetic and morphologic analysis with a single data set. This may obviate the need for multiple MRI examinations for a thorough breast MRI workup. J. Magn. Reson. Imaging 2006. © 2006 Wiley‐Liss, Inc.
Competitive AMPA receptor antagonists
Authors: Catarzi Daniela , Colotta Vittoria , Varano Flavia
Published: August 2006

Glutamic acid (Glu) is the major excitatory neurotransmitter in the mammalian central nervous system (CNS) where it is involved in the physiological regulation of different processes. It has been well established that excessive endogenous Glu is associated with many acute and chronic neurodegenerative disorders such as cerebral ischaemia, epilepsy, amiotrophic lateral sclerosis, Parkinson's, and Alzheimer's disease. These data have consequently added great impetus to the research in this field. In fact, many Glu receptor antagonists acting at theN‐methyl‐D‐aspartic acid (NMDA), 2‐amino‐3‐(3‐hydroxy‐5‐methylisoxazol‐4‐yl)propionic acid (AMPA), and/or kainic acid (KA) receptors have been developed as research tools and potential therapeutic agents. Ligands showing competitive antagonistic action at the AMPA type of Glu receptors were first reported in 1988, and the systemically active 2,3‐dihydroxy‐6‐nitro‐7‐sulphamoyl‐benzo[f]quinoxaline (NBQX) was first shown to have useful therapeutic effects in animal models of neurological disease in 1990. Since then, the quinoxaline template has represented the backbone of various competitive AMPA receptor antagonists belonging to different classes which had been developed in order to increase potency, selectivity and water solubility, but also to prolong the “in vivo” action. Compounds that present better pharmacokinetic properties and less serious adverse effects with respect to the others previously developed are undergoing clinical evaluation. In the near future, the most important clinical application for the AMPA receptor antagonists will probably be as neuroprotectant in neurodegenerative diseases, such as epilepsy, for the treatment of patients not responding to current therapies. The present review reports the history of competitive AMPA receptor antagonists from 1988 up to today, providing a systematic coverage of both the open and patent literature. © 2006 Wiley Periodicals, Inc.
Percent infarct mapping: An R1‐map‐based CE‐MRI method for determining myocardial viability distribution
Authors: Surányi Pál , Kiss Pál , Brott Brigitta C. , Simor Tamás , Elgavish Ada , Ruzsics Balázs , Saab‐Ismail Nada H. , Elgavish Gabriel A.
Published: August 2006

Viability detection is crucial for the management of myocardial infarction (MI). Signal intensity (SI)‐based MRI methods may overestimate infarct size in vivo. In contrast to SI, the longitudinal relaxation‐rate enhancement (ΔR1) is an intrinsic parameter that is linearly proportional to the concentration of contrast agent (CA). Determining ΔR1 in the presence of an infarct‐avid persistent CA (PCA) allows determination of the per‐voxel percentage of infarcted tissue. Introduced here is a ΔR1‐based CE‐MRI method, termed percent infarct mapping (PIM), for quantifying myocardial viability following delayed PCA accumulation. In a canine MI model (N = 6), PIMs were generated using a persistent CA (PCA) and validated using triphenyltetrazolium‐chloride (TTC) histochemistry. Voxel‐by‐voxel R1 maps of the entire left ventricle (LV) were generated 24 and 48 hr after PCA administration using inversion recovery (IR) with multiple inversion times (TIs). PI values were calculated voxel by voxel. Significant correlations (P < 0.01, R = 0.97) were obtained for PI per slice (PIS) determined using PIM vs. corresponding TTC‐based values. Median deviations of PIS with PIM from that with TTC were only 1.01% and –0.53%, at 24 hr and 48 hr. Median deviations from the true infarction fraction (IF) were 1.23% and 0.49% of LV at 24 hr and 48 hr, respectively. No significant difference was found between PIM24 hr and PIM48 hr. ΔR1‐based PIM is an accurate and reproducible method for quantifying myocardial viability distribution, and thus enhances the clinical utility of CE‐MRI. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.
Proton spectral editing for discrimination of lactate and threonine 1.31 ppm resonances in human brain in vivo
Authors: Choi Changho , Coupland Nicholas J. , Kalra Sanjay , Bhardwaj Paramjit P. , Malykhin Nikolai , Allen Peter S.
Published: August 2006

A single‐voxel proton NMR J‐difference editing method for discriminating between the 1.31 ppm resonances of lactate (Lac) and threonine (Thr) in human brain in vivo at 3 T is reported. One double‐band and two triple‐band Gaussian 180° RF pulses, all with a bandwidth of 15 Hz, were employed within an adiabatic‐refocused double‐echo localization sequence to induce the target signals of Lac and Thr and simultaneously acquire a creatine singlet in each subscan. The optimum echo time and the editing efficiency were obtained by numerical analysis of the filtering performance. The Lac and Thr signals were extracted, without lipid contamination, from three subspectra. Using the calculated yields, the concentrations of Lac and Thr in the human occipital cortex were estimated to be 0.47 ± 0.07 and 0.56 ± 0.06 mM (mean ± SD, N = 7), respectively, with reference to Cr at 8 mM. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.
Amide proton transfer imaging of human brain tumors at 3T
Authors: Jones Craig K. , Schlosser Michael J. , van Zijl Peter C.M. , Pomper Martin G. , Golay Xavier , Zhou Jinyuan
Published: August 2006

Amide proton transfer (APT) imaging is a technique in which the nuclear magnetization of water‐exchangeable amide protons of endogenous mobile proteins and peptides in tissue is saturated, resulting in a signal intensity decrease of the free water. In this work, the first human APT data were acquired from 10 patients with brain tumors on a 3T whole‐body clinical scanner and compared with T1‐ (T1w) and T2‐weighted (T2w), fluid‐attenuated inversion recovery (FLAIR), and diffusion images (fractional anisotropy (FA) and apparent diffusion coefficient (ADC)). The APT‐weighted images provided good contrast between tumor and edema. The effect of APT was enhanced by an approximate 4% change in the water signal intensity in tumor regions compared to edema and normal‐appearing white matter (NAWM). These preliminary data from patients with brain tumors show that the APT is a unique contrast that can provide complementary information to standard clinical MRI measures. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.
Reduction of reconstruction time for time‐resolved spiral 3D contrast‐enhanced magnetic resonance angiography using parallel computing
Authors: Kressler Bryan , Spincemaille Pascal , Prince Martin R. , Wang Yi
Published: August 2006

Time‐resolved 3D MRI with high spatial and temporal resolution can be achieved using spiral sampling and sliding‐window reconstruction. Image reconstruction is computationally intensive because of the need for data regridding, a large number of temporal phases, and multiple RF receiver coils. Inhomogeneity blurring correction for spiral sampling further increases the computational work load by an order of magnitude, hindering the clinical utility of spiral trajectories. In this work the reconstruction time is reduced by a factor of >40 compared to reconstruction using a single processor. This is achieved by using a cluster of 32 commercial off‐the‐shelf computers, commodity networking hardware, and readily available software. The reconstruction system is demonstrated for time‐resolved spiral contrast‐enhanced (CE) peripheral MR angiography (MRA), and a reduction of reconstruction time from 80 min to 1.8 min is achieved. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.
Steady state of echo–shifted sequences with radiofrequency phase cycling
Authors: Ganter Carl
Published: August 2006

Due to a delayed echo–formation, echo–shifted gradient echo sequences (ES–GRE) allow for an enhanced T2*–weighting at short repetition times. While they are in use with and without RF spoiling, analytical solutions are only known for the latter. The signal formation in the former could only be assessed in approximative form, so far. In this article an exact analytical solution is presented for TR–periodic ES–GRE sequences with RF phase cycling. Besides providing a better numerical performance, it should be useful for systematic sequence development. The relation to recent approximative solutions is discussed. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.
Motor unit number estimation predicts disease onset and survival in a transgenic mouse model of amyotrophic lateral sclerosis
Authors: Shefner Jeremy M. , Cudkowicz Merit , Brown Robert H.
Published: August 2006

Motor unit number estimation (MUNE) has proved useful in predicting rate of progression and survival in patients with amyotrophic lateral sclerosis (ALS). In animal models, it has demonstrated physiological effects of experimental medications that were not evident behaviorally. We sought to determine more specifically what aspects of function and survival that MUNE could predict in the G93A transgenic mouse model of ALS. Transgenic mice were examined in two distinct treatment studies, neither of which showed an effect of drug on survival, behavioral measures, or MUNE. MUNE was performed using a modification of the incremental stimulation method by stimulating the sciatic nerve at the sciatic notch, and recording with a circumferential surface electrode around the ipsilateral distal hindlimb. Both limbs were studied and the results averaged. MUNE was performed longitudinally on all animals from near onset to premorbid state. Each study was evaluated separately. For both studies, MUNE at initial study correlated significantly with behavioral determination of disease onset, and MUNE slope from initial to final study correlated significantly with disease duration, as measured from onset to time of death. However, the final MUNE value did not correlate with survival. Thus, in two studies involving animals with quite different disease courses, initial MUNE effectively predicted symptom onset and MUNE slope predicted survival. This suggests that MUNE has potential efficacy as a useful functional outcome measure in both animal and human studies of ALS. Muscle Nerve, 2006
High‐repetition cyclic loading is a risk factor for a lumbar disorder
Authors: Navar Daniel , Zhou Bing‐He , Lu Yun , Solomonow Moshe
Published: August 2006

Epidemiological data suggest that prolonged exposure to cyclic lumbar flexion elicits a chronic neuromuscular disorder and disability in workers. This study provides a physiological and biomechanical assessment of various repetitions of cyclic lumbar flexion sessions as a risk factor for development of an acute neuromuscular disorder. An in vivo feline model was subjected to 10 minutes of cyclic (0.25‐HZ) loading, followed by a 10‐minute rest period, repeated three times in one experimental group, six times in a second group, and nine times in the third group, followed by rest for 7 hours. Displacement of the lumbar viscoelastic tissue and reflex electromyographic (EMG) activity from the lumbar multifidus muscle were monitored. Creep developed and accumulated during each load/rest period and partially recovered during the subsequent rest. Loading periods were characterized by a decrease in reflex EMG activity with superimposed spasms. In the 7‐hour recovery period, initial hyperexcitability was present in all groups, whereas only the six‐ and nine‐repetition groups displayed significant delayed hyperexcitability, indicating the presence of acute inflammation. The mathematical model developed fit the data reasonably well, as the R2 values were generally near 0.90. It was concluded that the resulting delayed muscular hyperexcitability constitutes an acute neuromuscular disorder associated with exposure to many repetitions of cyclic lumbar flexion. The acute disorder can become chronic if not allowed sufficient rest to resolve itself. Workers engaged in cyclic lumbar flexion (e.g., loading/unloading, assembly workers) should avoid long‐term exposure in order to prevent the development of a chronic neuromuscular condition known as cumulative trauma disorder. Muscle Nerve, 2006
Formation of Si and Ge quantum structures by laser‐induced etching
Authors: Mavi H. S. , Prusty Sudakshina , Kumar Manoj , Kumar Rajesh , Shukla A. K. , Rath S.
Published: August 2006

Quantum structures were fabricated by immersing a crystalline silicon (Si) or germanium (Ge) wafer in hydrofluoric acid followed by laser‐induced etching with a laser photon energy of 2.41 eV. Atomic force microscopy (AFM) investigations of Si(100) etched samples reveal a complex surface morphology with pits from the top view and pillar‐like structures from the three‐dimensional view of the pit wall. For Ge(111) laser‐etched samples, AFM shows parallel wall‐type structures and Ge quantum structures on the surface of the walls. Laser‐induced etching of Ge is reported for the first time. Observation of photoluminescence spectra from both samples confirms the presence of quantum confined structures. Line‐shape analysis of Raman spectra is used to estimate the size of the quantum structures. The sizes of nanoparticles can be controlled by the laser power density and irradiation time for etching. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Color centers in Yb:YAG crystals grown by temperature‐gradient techniques
Authors: Dong Yongjun , Xu Jun , Zhou Guoqing , Zhao Guangjun , Su Liangbi , Xu Xiaodong , Li Hongjun , Si JiLiang , Qian Xiaobo , Li Xiaoqing , Shen Jun
Published: August 2006

Yb:YAG (Yb:Y3Al5O12) crystals have been grown by temperature‐gradient techniques (TGT) and their color centers and impurity defects were investigated by means of gamma irradiations and thermal treatment. Two color centers located at 255 and 290 nm were observed in the as‐grown TGT‐Yb:YAG. Analysis shows that the 255 nm band may be associated with Fe3+ ions. Absorption intensity changes of the 290 nm band after gamma irradiation and thermal treatment indicate that this band may be associated with oxygen‐vacancy defects. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Perovskite phase formation, microstructure and improvement of dielectric properties in iron‐containing ferroelectrics
Authors: Fang Bijun , Geng Baoyou , Wei Xianwen , Shan Yuejin , Tezuka Keitaro , Imoto Hideo
Published: August 2006

Pure perovskite‐phase lead iron scandium niobate, Pb(Fe1/4Sc1/4Nb1/2)O3 (PFScN), ceramics have been prepared by a conventional solid‐state reaction method via a B‐site oxide mixing route. Although synthesis conditions have been tailored to optimization, strong frequency dispersion of the dielectric properties cannot be improved by modifying ceramic processing, which is considered as correlating to the nature of iron‐containing ferroelectrics. Sintering in an O2 atmosphere and MnO2 and Li2CO3 dopings tend to decrease the dielectric loss of the iron‐containing dielectrics. The strong frequency dispersion of the dielectric response and the abnormally recurrent increase of the dielectric constant and loss in the paraelectric region are correspondingly suppressed. This improvement of dielectric properties in the iron‐containing ferroelectrics is interpreted by an electron compensation mechanism, in which the generation of donor electrons is based on different ionization paths. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of annealing atmosphere on oxygen precipitation and formation of denuded zone in Czochralski silicon wafer
Authors: Cui Can , Yang Deren , Ma Xiangyang , Fan Ruixin , Que Duanlin
Published: August 2006

In this paper, the effect of annealing atmosphere on oxygen precipitation and formation of denuded zone (DZ) in Czochralski (CZ) silicon has been investigated. It was revealed that the high‐temperature annealings in various atmospheres resulted in almost identical oxygen outdiffusion length but different widths of DZ in the silicon wafers. It was confirmed that the high‐temperature annealing in nitrogen atmosphere induced a high concentration of vacancies in silicon to enhance oxygen precipitation, while the annealing in oxidizing atmosphere or steam‐mixed atmosphere induced a high concentration of silicon self‐interstitials to retard oxygen precipitation. Moreover, it was confirmed that the steam mixed into the nitrogen atmosphere could suppress the indiffusion of nitrogen atoms. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermoelectric properties of higher manganese silicide films with addition of carbon
Authors: Hou Q. R. , Zhao W. , Zhang H. Y. , Chen Y. B. , He Y. J.
Published: August 2006

Polycrystalline higher manganese silicide (MnSi1.73, HMS) films with addition of carbon were prepared on thermally oxidized silicon substrates by magnetron sputtering. A carbon cap layer was used as the doping source. Both the Seebeck coefficient and the resistivity were strongly dependent on the amount of carbon added to the films. When the thickness ratio of carbon to manganese was about 17%, the Seebeck coefficient and resistivity at room temperature were about 35 μV/K and 4.45 × 10–3 Ω cm, respectively. By reducing the thickness ratio to about 3%, the Seebeck coefficient and resistivity at room temperature increased to 107 μV/K and 18 × 10–3 Ω cm, respectively. With addition of carbon, both the maximum value of the Seebeck coefficient and the temperature at which the maximum occurred increased. Several shallow (0.028–0.085 eV) and deep (0.106–0.299 eV) energy levels were observed from the curves of the resistivity versus temperature. The activation energies of 0.845 and 1.11 eV were consistent with the reported energy band gaps for higher manganese silicide. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
“As‐cast” microstructure investigation of two iron aluminides
Authors: Schön Cláudio Geraldo , Scuracchio Bruno Geoffroy
Published: August 2006

The “as‐cast” microstructure of Fe–30Al–6Cr and Fe–30Al–10Ti high purity alloys was investigated using Electron Backscatter Diffraction. The first alloy is characterized by a highly textured columnar grain microstructure with large grains, while the second is characterized by an equiaxed grain microstructure with small grains and a random texture. These differences are discussed with regard to the higher reactivity of Ti compared with Cr, leading to nanometric nitride or oxide, which may act as sites for heterogeneous nucleation, and the ordered state of the BCC phase in equilibrium with the liquid during solidification and its effect upon dendrite growth kinetics. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structural and acoustic investigations of calcium borate glasses
Authors: Manupriya  , Thind K. S. , Sharma G. , Rajendran V. , Singh K. , Gayathri Devi A. V. , Aravindan S.
Published: August 2006

Acoustic and structural properties of x CaO · (1–x ) B2O3 (0.2 ≤ x ≥ 0.7) glass system have been studied at ambient temperature. The ultrasonic velocity and attenuation for different compositions of calcium borate glasses were measured at 5 MHz at room temperature (303 K) using a pulse echo overlap method. The elastic moduli, Debye temperature, Poisson's ratio and other acoustic parameters have been obtained from experimental data. Fourier transform infrared spectroscopic analysis has been used to further support the results of acoustic studies. The results obtained indicate that the calcium oxide enters the glass network as a modifier by occupying the interstitial spaces in the network and by increasing the nonbridging oxygen atoms (NBOs). (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structure and electrical transport of some Cd‐doped La0.67Sr0.33MnO3manganites
Authors: Venkataiah G. , Prasad V. , Venugopal Reddy P.
Published: August 2006

A systematic investigation of cadmium‐doped manganites with compositional formula La0.67(Sr0.33–yCdy) MnO3(y= 0–0.33) has been undertaken mainly to understand their structural as well as their electrical transport behavior. The materials were prepared by the citrate‐gel route and were characterized by X‐ray diffraction (XRD). By analyzing the XRD data using the Rietveld refinement technique, it has been concluded that these materials have rhombohedral structure with R$ \bar 3 $c space group. It has been found that the ferro–paramagnetic transition temperature (TC) values decrease continuously with increasing Cd concentration, while the metal–insulator transition temperatures (TP1), except in the cases of two samples (withy= 0.066 and 0.132), are found to decrease. A qualitative explanation for the observed behavior is offered. With a view to understanding the conduction mechanism, electrical resistivity and thermopower measurements were carried out and the data were analyzed using various theoretical models. It has been concluded that the resistivity (ρ) data in the ferromagnetic metallic part (T<TP1) is in agreement withρ(T) =ρ0+ρ2T2+ρ4.5T4.5, indicating the importance of grain/domain boundary effects, electron–electron and two‐magnon scattering processes in the conduction mechanism, while, at high temperature (T>TP1), the paramagnetic insulating regime, the adiabatic small polaron model fits well, thereby indicating that polaron hopping might be responsible for the conduction mechanism. Finally, the low‐temperature thermopower (TTP1) data were analyzed by Mott's equation. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Feature Article: Hot phonons in GaN channels for HEMTs
Authors: Matulionis A.
Published: August 2006

In the Feature Article [1] a fluctuation technique is used to obtain the hot electron energy relaxation time (blue symbols in the cover picture) and the hot phonon lifetime (red) for a biased two‐dimensional channel in an AlGaN/AlN/GaN heterostructure as a function of the supplied electric power. The close proximity of red and blue symbols illustrates that the relaxation is mainly determined by the phonon conversion into other vibrational modes being able to drain the Joule heat out of the channel. The red inset shows the momenta of hot phonons launched by hot electrons. The green line presents the electron energy relaxation time obtained by Monte Carlo simulation for lightly doped GaN under the assumption that hot phonons are absent. A strong effect of hot phonons on the electron energy relaxation is evident.

The author Arvydas Matulionis is Professor of Physics and head of the Fluctuation Research Laboratory of the Vilnius Semiconductor Physics Institute. He investigates hot electron fluctuations and other high electric field effects in semiconductor heterostructures for microwave electronics.

The Editor's Choice “Anomalous charge relaxation in channels of pentacene‐based organic field‐effect transistors: a charge transient spectroscopy study” by I. Thurzo et al. [2] is also part of the present issue.
6th International Symposium on Blue Laser and Light Emitting Diodes (ISBLLED 2006), Montpellier, France, 15–19 May 2006
Authors: Duboz Jean‐Yves
Published: August 2006

Conference Reports are meant to offer an authoritative view on a recently held scientific meeting rather than a comprehensive list of the conference presentations. Authors are invited to describe what they feel were the most interesting contributions.

The full Proceedings of ISBLLED 2006 will be published in phys. stat. sol. (a) and phys. stat. sol. (c) at the end of 2006.
Protonation of phenylboronic acid: Comparison of G3B3 and G2MP2 methods
Authors: De Senjuti , Drew Michael G. B. , Price David W. , Nag Samik , Datta Dipankar
Published: August 2006

G3B3 and G2MP2 calculations using Gaussian 03 have been carried out to investigate the protonation preferences for phenylboronic acid. All nine heavy atoms have been protonated in turn. With both methodologies, the two lowest protonation energies are obtained with the proton located either at the ipso carbon atom or at a hydroxyl oxygen atom. Within the G3B3 formalism, the lowest‐energy configuration by 4.3 kcal · mol−1 is found when the proton is located at the ipso carbon, rather than at the electronegative oxygen atom. In the resulting structure, the phenyl ring has lost a significant amount of aromaticity. By contrast, calculations with G2MP2 show that protonation at the hydroxyl oxygen atom is favored by 7.7 kcal · mol−1. Calculations using the polarizable continuum model (PCM) solvent method also give preference to protonation at the oxygen atom when water is used as the solvent. The preference for protonation at the ipso carbon found by the more accurate G3B3 method is unexpected and its implications in Suzuki coupling are discussed. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007
Common generating function for two‐dimensional hydrogen atom complete wave functions
Authors: Chaos‐Cador L. , Ley‐Koo E.
Published: August 2006

The Schrödinger equation for the two‐dimensional hydrogen atom is known to be separable and integrable in circular, parabolic, and elliptical coordinates. This makes it possible to construct a common generating function for the complete wave functions of the atom in the respective coordinates. The connections with the corresponding generating function and wave functions for the harmonic oscillator are recognized and applied in this work. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007
Structure and stability of Be6, Be, and Be clusters
Authors: Zhao Yi , Li Nan , Xu Wen Guo , Li Qian Shu
Published: August 2006

The structure and stability of Be6, Be, and Be clusters have been investigated at the B3LYP, B3PW91, and second‐order Møller–Plesset (MP2) levels of theory, along with the 6‐311G* basis set for neutral and cationic clusters and the 6‐311+G* basis set for anion clusters. CCSD(T)/6‐311+G* has also been used to calculate some neutral structure to find the most stable structure. Twelve Be6, six Be, and eight Be isomers are identified. The distortion octahedron structure, pentagonal pyramids structure, and trapezoidal bipyramid structure are found to be the most stable structure on the neutral, cationic, and anionic surface, respectively. They are in agreement with the results reported previously. Natural bond orbital (NBO) analysis, molecular orbital (MO) pictures, and the nucleus independent chemical shift (NICS) values suggest aromatic of the neutral and cationic clusters and antiaromatic of the anionic cluster. The multi‐center σ bonds and delocalized π bonds play important role in the bonding of the beryllium clusters. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007
Optimization of nonlinear wave function parameters
Authors: Shepard Ron , Minkoff Michael
Published: August 2006

An energy‐based optimization method is presented for our recently developed nonlinear wave function expansion form for electronic wave functions. This expansion form is based on spin eigenfunctions, using the graphical unitary group approach (GUGA). The wave function is expanded in a basis of product functions, allowing application to closed‐shell and open‐shell systems and to ground and excited electronic states. Each product basis function is itself a multiconfigurational function that depends on a relatively small number of nonlinear parameters called arc factors. The energy‐based optimization is formulated in terms of analytic arc factor gradients and orbital‐level Hamiltonian matrices that correspond to a specific kind of uncontraction of each of the product basis functions. These orbital‐level Hamiltonian matrices give an intuitive representation of the energy in terms of disjoint subsets of the arc factors, they provide for an efficient computation of gradients of the energy with respect to the arc factors, and they allow optimal arc factors to be determined in closed form for subspaces of the full variation problem. Timings for energy and arc factor gradient computations involving expansion spaces of >1024 configuration state functions are reported. Preliminary convergence studies and molecular dissociation curves are presented for some small molecules. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006
Quantal density functional theory: Wave function arbitrariness of the noninteracting fermion model
Authors: Sahni Viraht , Slamet Marlina
Published: August 2006

In quantal density functional theory (Q‐DFT), the mapping from either a ground or excited state of the interacting system to one of noninteracting fermions with equivalent density is such that the state of the latter model S system is arbitrary. Thus, in principle, there are an infinite number of local (multiplicative) effective potential energy functions that can reproduce the density of the interacting system. In the present work, we note that there is also an arbitrariness in the wave function of the model fermions when the S system is constructed in an excited state. Different wave functions lead to the same density. As the principal requirement of the model system is met, viz. to reproduce the interacting system density, these wave functions are all equally valid representations, irrespective of whether they are eigenfunctions of various symmetry operators. However, the corresponding nonlocal properties such as the Fermi and Coulomb hole charge distributions, and the resulting Pauli and Coulomb energies, will differ. This wave function arbitrariness within Q‐DFT is demonstrated via the exactly solvable Hooke's atom. Finally, Q‐DFT and Kohn–Sham DFT are contrasted with regard to the state and wave function arbitrariness of the model S system. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006