bluuebunny/crossref_metadata_2025 huggingface dataset:
Drying method and origin of standard affect condensed tannin (CT) concentrations in perennial herbaceous legumes using simplified butanol‐HCl CT analysis
Authors: Wolfe Richard M , Terrill Thomas H , Muir James P
Published: February 2008

BACKGROUND: Several factors affect condensed tannin (CT) levels in plants and accuracy of the butanol‐HCl assay for total CT. Six native, perennial, herbaceous legumes from Texas were harvested at three stages of growth over a growing season; young vegetation, initial flowering, and late season. The samples were subjected to oven‐drying and freeze‐drying and analyzed for extractable (ECT), protein‐bound (PBCT), and fiber‐bound (FBCT) CT using a butanol‐HCl procedure, comparing several types of purified CT as standards.

RESULTS: There was a wide range of CT concentration in the legumes, but little change in ECT and total (TCT) tannin concentrations over the growing season. Oven‐drying decreased (P < 0.05) ECT and increased (P < 0.05) PBCT and FBCT concentrations compared with freeze‐drying, but both methods ranked the forages similarly throughout the growing season relative to TCT. Quebracho tannin as a standard increased CT values for the forages compared with purified legume CT standards, but all standards ranked the forages similarly relative to tannin concentration. Modifications to the procedure increased speed and ease of using the CT analysis method.

CONCLUSION: Quantitative CT values have limited value except to allow a relative ranking of forages. Selection of appropriate standards is important in providing realistic CT values. Improvements in the total (extractable + bound) CT analysis method will allow wider use of this procedure. Although ECT and TCT values changed little in native legumes over a growing season, biological activity and potential nutritional/medicinal benefits of CT in these plants needs further evaluation. Copyright © 2008 Society of Chemical Industry
Simultaneous determination of non‐volatile, semi‐volatile, and volatile organic acids in tobacco by SIM–Scan mode GC–MS
Authors: Wang Baoxing , Yang Shihua , Chen Guohui , Wu Yi , Hou Ying , Xu Guowang
Published: February 2008

A method for simultaneous determination of seven nonvolatile organic acids (NVOAs), five semivolatile organic acids (SVOAs), and twelve volatile organic acids (VOAs) in tobacco by synchronous SIM (Selected Ion Monitoring)‐scan mode GC–MS was developed. The collection of NVOAs and SVOAs data was performed in full‐scan mode, and that of VOAs data was carried out with SIM. Recoveries of NVOAs and SVOAs varied from 90.0 to 103.0%, and RSDs were less than 4.0%; recoveries of VOAs ranged from 89.5 to 99.3%, and their RSDs were less than 3.0%. Twelve tobacco samples were analyzed by the described method, and the results show that the method is applicable for the simultaneous determination of VOAs, NVOAs, and SVOAs in tobacco.
The orthogonal character of stationary phases for gas chromatography
Authors: Poole Salwa K. , Poole Colin F.
Published: February 2008

A database of system constants for 32 open‐tubular columns at 100°C is used to identify stationary phases for obtaining a wide selectivity space in comprehensive GC. Three parameters based on the Euclidean distance (D‐parameter) or vectors (d‐parameter and cosθ) in hyperspace are used to establish the chemical similarity and retention correlation as an inverse scale of selectivity differences. It is shown that the poly(methyloctylsiloxane) stationary phase is the best candidate for a low‐selectivity stationary phase and affords a wider selectivity space when combined with a selective polar stationary phase than poly(dimethylsiloxanes). The most suitable polar stationary phases are poly(ethylene glycols) or bis(cyanopropylsiloxane‐co‐silarylenes and to a lesser extent poly(methyltrifluoropropylsiloxanes). No systems are truly orthogonal but angles between individual stationary phase vectors of about 75° are possible by choosing the correct combination of stationary phases.
A process‐based classification of knowledge maps and application examples
Authors: Eppler Martin J.
Published: February 2008

This paper discusses pragmatic ways of classifying knowledge maps to give an overview of their application contexts and formats. In the paper, we show where and how the term knowledge map has been previously used and what criteria must be met in a sound and useful knowledge map classification that can support knowledge management processes. Various classification principles are presented and discussed. A table then matches map formats to knowledge management purposes and knowledge‐related contents in order to serve as a selection and organizing framework. Examples of some of the main types of knowledge maps are presented to illustrate the varieties of knowledge mapping present in the classification. The paper concludes by discussing its limitations and future research questions in the area of knowledge mapping. Copyright © 2008 John Wiley & Sons, Ltd.
Laser Direct Machining – Diversity is Key
Authors: Schulze Matthias , Venkat Sri
Published: February 2008

Lasers are now used to directly machine microstructures and surface patterns in a wide range of materials including plastics, metals and semiconductors. The laser is chosen because it often reduces the number of production steps, delivers superior results, or enables greener processes – making it an ideal tool for volume manufacturing in an increasingly environmentally sensitive world. This article examines just a few representative laser‐based processes and outlines the key laser characteristics for each.
The G389R mutation in the MAPT gene presenting as sporadic corticobasal syndrome
Authors: Rossi Giacomina , Marelli Cecilia , Farina Laura , Laurà Matilde , Maria Basile Anna , Ciano Claudia , Tagliavini Fabrizio , Pareyson Davide
Published: February 2008

A few patients with mutations in the microtubule‐associated protein tau gene (MAPT), affected by frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP‐17T), may clinically present with a corticobasal syndrome (CBS). We report a case of apparently sporadic CBS bearing a mutation in the MAPT gene so far associated with frontotemporal dementia (FTD) phenotype. The patient is a 41‐year‐old man with progressive asymmetric signs of cortical and basal ganglia involvement consistent with CBS. Magnetic resonance imaging showed asymmetric cortical atrophy and unusual corticospinal tract hyperintensity in T2‐weighted images. Genetic testing revealed a heterozygous G to C mutation at the first base of codon 389 of the MAPT gene, changing glycine to arginine (G389R), in the patient and his unaffected elderly father. In conclusion, the MAPT G389R mutation shows phenotypic variability resulting in both FTD and CBS. The mutation also demonstrates incomplete penetrance. Corticospinal tract degeneration is an exceptional finding. © 2008 Movement Disorder Society
The mammalian target of rapamycin pathway and its role in molecular nutrition regulation
Authors: Lian Jun , Yan Xiang‐Hua , Peng Jian , Jiang Si‐Wen
Published: February 2008

Mammalian target of rapamycin (mTOR) is a protein serine‐threonine kinase that functions as a central element in signaling pathway involved in control of cell growth and proliferation. mTOR exists in at least two distinct multi‐protein complexes, mTORC1 and mTORC2. mTOR kinase controls the translation machinery, in response to nutrients and growth factors, via activation of p70 ribosomal S6 kinase and inhibition of eukaryotic initiation factor‐4E‐binding protein. In this report, we review the mTOR signaling pathway and its interaction with food intake, insulin resistance, lifespan and adipogenic regulation during the molecular nutrition regulation.
Magnetic microparticle aggregation for viscosity determination by MR
Authors: Hong Rui , Cima Michael J. , Weissleder Ralph , Josephson Lee
Published: February 2008

Micron‐sized magnetic particles were induced to aggregate when placed in homogeneous magnetic fields, like those of MR imagers and relaxometers, and then spontaneously returned to their dispersed state when removed from the field. Associated with the aggregation and dispersion of the magnetic particles were time‐dependent increases and decreases in the spin–spin relaxation time (T2) of the water. Magnetic nanoparticles, with far smaller magnetic moments per particle, did not undergo magnetically induced aggregation and exhibited time‐independent values of T2. The rate of T2 change associated with magnetic microparticle aggregation was used to determine the viscosity of liquid samples, providing a method that can be of particular advantage for determining the viscosity of small volumes of potentially biohazardous samples of blood or blood plasma. Magn Reson Med 59:515–520, 2008. © 2008 Wiley‐Liss, Inc.
MR imaging of adventitial vasa vasorum in carotid atherosclerosis
Authors: Kerwin W.S. , Oikawa M. , Yuan C. , Jarvik G.P. , Hatsukami T.S.
Published: February 2008

Vasa vasorum in the adventitia of atherosclerotic arteries may play a role in plaque progression. In this investigation, a method for characterizing vasa vasorum in the carotid artery is proposed, in which the perfusion properties of the adventitia are probed via dynamic contrast‐enhanced (DCE) MRI. A parametric “vasa vasorum image” is automatically generated that depicts the plasma volume (vp) and transfer constant (Ktrans). The average Ktrans within the adventitia is proposed as a quantitative measurement related to the extent of the vasa vasorum. In 25 subjects with lesions meeting the requirements for carotid endarterectomy (CEA) significantly higher adventitial Ktrans of 0.155 ± 0.045 min–1 was observed, compared to 0.122 ± 0.029 min–1 in the remaining 20 subjects with moderate disease (P < 0.01). In the 25 subjects with endarterectomy specimens, histological evaluation showed that adventitial Ktrans was significantly correlated with the amount of neovasculature (R = 0.41; P = 0.04) and macrophages (R = 0.49; P = 0.01) in the excised plaque. In the remaining 20 subjects without histology, elevated adventitial Ktrans was significantly correlated with the log of C‐reactive protein (CRP) levels (R = 0.57; P = 0.01) and was elevated in active smokers compared to nonsmokers (0.141 ± 0.036 vs. 0.111 ± 0.017 min–1; P = 0.02). Because these factors are all associated with higher risk of atherosclerotic complications, these results suggest that adventitial Ktrans may be a marker of risk as well. Magn Reson Med 59:507–514, 2008. © 2008 Wiley‐Liss, Inc.
School refusal behavior associated with separation anxiety disorder: A cognitive‐behavioral approach to treatment
Authors: Doobay Alissa F.
Published: February 2008

School refusal behavior can lead to disruptions in both educational attainment and social development. One of the common causes of school refusal behavior is separation anxiety disorder (SAD). Research suggests that children with SAD and school refusal behavior show an increased rate of psychiatric consultation and a decreased likelihood of becoming parents in adulthood, likely indicating limited social skills (Flakierska‐Praquin, Lindström, & Gillberg, 1997). This article provides a brief overview of the current literature on the association between SAD and school refusal behavior, as well as a proposed treatment for school refusal behavior associated with SAD based on cognitive‐behavioral theory. © 2008 Wiley Periodicals, Inc.
Spectrum and outcome of prenatally diagnosed fetal tumors
Authors: Kamil D. , Tepelmann J. , Berg C. , Heep A. , Axt‐Fliedner R. , Gembruch U. , Geipel A.
Published: February 2008

Objective

To describe the spectrum of prenatally diagnosed fetal tumors, and the course and fetal outcome in affected pregnancies.

Methods

This was a retrospective study in two German tertiary referral centers of 84 fetuses with tumors diagnosed in the prenatal period. The tumors were classified according to their location and histology.

Results

The most common site of origin was the heart (20/84, 23.8%), followed by the face and neck region (19/84, 22.6%) and the abdomen (16/84, 19%). Lymphangiomas (21/84, 25%) and rhabdomyomas (19/84, 22.6%) comprised half of the tumor histology. Less frequently, teratomas (14/84, 16.6%) and hemangiomas (12/84, 14.2%) were seen. Complications included arrhythmia in cases with rhabdomyoma (8/19, 42%) and signs of heart failure in cases with hemangioma (4/12, 33%) and teratoma (4/14, 28.6%). The overall survival rate was 75%. Cases with either a histological diagnosis of teratoma or tumor located in the brain had the worst prognosis.

Conclusion

The combination of sonographic features and their location allows reliable prediction of the histological type in the vast majority of fetal tumors. Malignancy, associated malformations and aneuploidy are observed infrequently. Knowledge of the presence of a fetal tumor facilitates close surveillance by a specialized team, which might lead to early recognition of problems and improve perinatal outcome. Copyright © 2008 ISUOG. Published by John Wiley & Sons, Ltd.
Error‐resistant RFID‐assisted wireless sensor networks for cardiac telehealthcare
Authors: Hu Fei , Celentano Laura , Xiao Yang
Published: February 2008

Wireless transmission of a patient's electrocardiogram (ECG) signals can be used to reduce cardiac healthcare cost. However, wireless transmissions have high error rates due to radio interference. The ECG signal, where every second of data could mean abnormal patterns, cannot tolerate such losses. Due to this healthcare crisis, the ability for a device to remotely monitor a patient's medication intake and transmit accurate ECG readings, while being cost efficient, is a major innovation. In this research, we integrate a multi‐hop wireless sensor network (WSN) with radio frequency identification (RFID) readers. Our system has two distinct features: (1) remotely supervise patient medication intakeviaRFID technology, and (2) accurately and remotely transmitting a patient's ECG by adopting extended Kalman filter (EKF) for wireless error recovery. Copyright © 2008 John Wiley & Sons, Ltd.
Ultrastructural features of hepatocytes in cultured Eurasian perch (Perca fluviatilisL.) as affected by nutritional and husbandry conditions
Authors: Blanchard Gersande , Gardeur Jean N. , Mathis Nicolas , Brun-Bellut Jean , Kestemont Patrick
Published: February 2008

A wide range of factors can be attributed to the syndrome of fatty liver observed in some cultured fish species. The objective of the study was therefore to quantify different hepatocyte ultrastructural features as potentially influenced by twelve nutritional and husbandry factors, in order to discriminate the most influent factors in Eurasian perch (Perca fluviatilis), a typical carnivorous temperate fish species. Twenty-four groups of juveniles (initial weight 57·6 (sd14·4) g) were intensively reared for 116 d and fed sixteen different isoproteic diets. The distribution of the experimental treatments was based on a multivariate fractional factorial design (L24212) with either high (+1) or low ( − 1) level of each of the following factors: diet (lipid and protein sources, lipid content, astaxanthin enrichment), feeding level, daily and weekly distribution frequency, fish density, initial weight heterogeneity, temperature, photoperiod, and light spectrum. Liver lipid droplets, glycogen, mitochondria and rough endoplasmic reticulum (RER) were semi-quantified and analysed by a soft imaging system using transmission electronic microscopy photographs. Important variability of hepatocyte ultrastructural features was observed. The present study confirms that the rearing temperature, through its influences in the general metabolic activity, seems to be the main factor modifying mainly lipid droplet accumulation and RER development. However, factors that could be pooled under the designation of factors leading to food accessibility and lipid and protein quality intensify or compensate the effect of temperature.
The Contribution of Economists to Military Intelligence During World War II
Authors: GUGLIELMO MARK
Published: February 2008

Economists played a crucial role in military intelligence during World War II. Economists working at the Office of Strategic Services estimated enemy battle casualties, analyzed the intentions and capabilities of both enemies and allies, and helped to prepare for negotiations regarding the postwar settlement. Economists working at the Enemy Objectives Unit helped to select enemy targets for bombing. Finally, economists working at the Statistical Research Group worked on a variety of problems brought to them by the U.S. military services. As a consequence of their usefulness during the war, the military continued to employ economists after the war.
Small-amplitude analysis of a non-thermal variable charge dust soliton
Authors: TRIBECHE MOULOUD
Published: February 2008

Small-amplitude electrostatic solitary waves are investigated in an unmagnetized dusty plasma with hot variable charge non-thermal dust grains. These nonlinear localized structures are small-amplitude self-consistent solutions of the Vlasov equation in which the dust response is non-Maxwellian. Localized solitary structures that may possibly occur are discussed and the dependence of their characteristics on physical parameters is traced. Our investigation may be taken as a prerequisite for the understanding of the electrostatic solitary waves that may occur in space dusty plasmas.
Psychologische Alternsforschung: Beiträge und Perspektiven
Authors: Wahl Hans-Werner , Diehl Manfred , Kruse Andreas , Lang Frieder R. , Martin Mike
Published: February 2008

Zusammenfassung. In den demografischen Wandlungsprozessen unserer Gesellschaft liegen zahlreiche neue Herausforderungen und Chancen für die Psychologie. Die hierbei besonders angesprochene psychologische Alternsforschung sollte im Sinne einer bedeutsamen Querschnittsaufgabe der Psychologie begriffen werden. Einerseits nutzt die psychologische Alternsforschung neue theoretische und methodische Zugänge zur Untersuchung psychologischer Kernfragen und eröffnet neue Berufsfelder. Andererseits unterstützt sie die Vernetzung von Theorien, Methoden und Befunden aus verschiedenen psychologischen Disziplinen. Zuerst zeigen wir, wie meta-theoretische und methodische Innovationen innerhalb der psychologischen Alternsforschung in fruchtbarer Weise zur Psychologie beigetragen haben. Danach wird diese produktive Rolle der psychologischen Alternsforschung anhand des gegenwärtigen Forschungsstands in vier zentralen Themenbereichen ausdifferenziert: (1) Kognitive Leistungsfähigkeit, (2) Altern der Persönlichkeit als System von motivationalen und emotionalen Prozessen, (3) Altern in sozial-räumlichen Kontexten und (4) “Alte“ und “neue“ Entwicklungsaufgaben des Alterns. Schließlich gehen wir noch auf Anwendungsaspekte ein.
Modeling weathering pathways and processes of the fragmentation of salt weathered quartz‐chlorite schist
Authors: Wells T. , Willgoose G. R. , Hancock G. R.
Published: February 2008

The relationship between the rate of rock breakdown and environmental and geological factors must be understood in order to establish the conditions under which weathering limits erosion. In this study qualitative and quantitative models of the rock fragmentation process are fitted to previously published data obtained from laboratory salt weathering trials of quartz‐chlorite schist. Weathering was modeled as a combination of (1) a fragmentation event that fragments the parent particle into a number of daughter particles while preserving mass, and (2) a fracture probability, that determines the probability that a fragmentation event will occur in a given time period. We show that observations of the complex breakdown of salt weathered schist are consistent with model assumptions of a simple fracture geometry model and an increase in fracture probability with time. For the fragmentation geometry the best fit to the experimental data was achieved by assuming that each fragmentation event involves splitting of the parent particle into two daughter fragments of equal volume. For the fragmentation rate the data could best be described with a fracture probability, and hence the weathering rate, that increased linearly with time. This paper shows that it is possible to use a physically based fragmentation model to infer the process of fragmentation for individual particles using a time evolving particle size distribution for the weathering rock fragments.
Diurnal cycles of precipitation, clouds, and lightning in the tropics from 9 years of TRMM observations
Authors: Liu Chuntao , Zipser Edward J.
Published: February 2008

The diurnal cycles of surface rainfall, population of precipitation systems, deep intense convection reaching near the tropopause, lightning flash counts, cold clouds, and vertical structure of precipitation are analyzed over the tropics, using 9 years of TRMM Precipitation Radar, Visible and Infrared Scanner, and Lightning Imaging Sensor measurements. The diurnal cycles over land include a late afternoon maximum of precipitation systems, with phase differences among cloud, precipitation, flash counts, and radar echo at different altitudes. Over ocean, the diurnal cycles are interpreted as having contributions from nocturnal precipitation systems and early afternoon showers. There are double peaks of radar reflectivity above 12 km near 0230 and 0530 local time over oceans. The oceanic clouds with infrared brightness temperature < 235 K have two peaks, one during the night and the other in early afternoon.
Intensified turbulent mixing in the boundary current system of southern Greenland
Authors: Lauderdale Jonathan M. , Bacon Sheldon , Naveira Garabato Alberto C. , Holliday N. Penny
Published: February 2008

The southern Greenland Deep Western Boundary Current (DWBC) advects major components of North Atlantic Deep Water. Turbulent diapycnal mixing rates of ∼10−4 m2 s−1 commonly occur in the DWBC. These diffusivities, estimated with an internal wave strain‐based parameterisation, are independently confirmed by budgets of density and dissolved O2. “Moderate” mixing rates (∼10−4 m2 s−1) over the DWBC path between Denmark Strait and Cape Farewell (∼1000 km) drive a similar net increase in volume transport by diapycnal entrainment to the more intense (∼10−3 m2 s−1), localised mixing rates found near the Denmark Strait overflow sill. Therefore turbulent mixing associated with the DWBC south of Denmark Strait is instrumental in establishing the magnitude of the North Atlantic Meridional Overturning Circulation. Elevated mixing rates are also seen in the East and West Greenland Currents; this may be significant in preconditioning seasonal restratification of the intermediate layers of the Irminger and Labrador basins.
Atmospheric comparison of electrochemical cell ozonesondes from different manufacturers, and with different cathode solution strengths: The Balloon Experiment on Standards for Ozonesondes
Authors: Deshler Terry , Mercer Jennifer L. , Smit Herman G. J. , Stubi Rene , Levrat Gilbert , Johnson Bryan J. , Oltmans Samuel J. , Kivi Rigel , Thompson Anne M. , Witte Jacquelyn , Davies Jonathan , Schmidlin F. J. , Brothers G. , Sasaki Toru
Published: February 2008

A balloon flight to compare 18 ozonesondes with an ozone photometer and with ozone column measurements from Dobson and Brewer spectrophotometers was completed in April 2004. The core experiment consisted of 12 electrochemical concentration cell ozonesondes, 6 from Science Pump Corporation (SP) and 6 from ENSCI Corporation (ES), prepared with cathode solution concentrations of 0.5% KI (half buffer) and 1.0% KI (full buffer). Auxiliary ozonesondes consisted of two electrochemical concentration cell sondes with 2.0% KI (no buffer), two reconditioned sondes, and two Japanese‐KC96 sondes. Precision of each group of similarly prepared ozonesondes was <2–3%. The six ozonesondes prepared according to the manufacturer's recommendations (SP, 1.0% KI, ES 0.5% KI) overestimated the photometer measurements by 5–10% in the stratosphere, but provided ozone columns in good agreement with the ground‐based spectrophotometer measurements. This is consistent with the difference (∼5%) in ozone photometer and column measurements observed during the experiment. Using cathode cell concentrations of 1.0% KI for ES sondes caused overestimates of the photometer by 10–15% and of ozone column by 5–10%. In contrast, 0.5% KI in SP sondes led to good agreement with the photometer, but underestimates of ozone column. The KC96 sondes underestimated the photometer measurements by about 5–15% at air pressures above 30 hPa. Agreement was within 5% at lower pressures. Diluting the solution concentration and the buffers from 1.0% to 0.5% KI causes an approximately linear pressure‐dependent decrease in ozone for both SP and ES sondes, ratio (0.5 KI/1.0 KI) = 0.9 + 0.024 * log10(Pressure).
Remagnetizations as a tool to analyze the tectonic history of inverted sedimentary basins: A case study from the Basque‐Cantabrian basin (north Spain)
Authors: Soto Ruth , Villalaín Juan J. , Casas‐Sainz Antonio M.
Published: February 2008

In this work we use syntectonic remagnetization data to determine the synrift geometry of inverted basins. This methodology analyzes remagnetization directions in order to obtain the tilting of beds at the moment of the acquisition of the overprint, filtering the subsequent compressional deformation. We collected samples from Jurassic and Lower Cretaceous limestones and red beds (Cabuérniga and Pas Groups) in the Cabuérniga basin, one of the most important Mesozoic basins developed near the Iberia‐Europe Mesozoic plate boundary in northern Spain, that later inverted during the uplift of the Pyrenees. These deposits represent the synrift sequence linked to a widespread extensional stage in the Iberian basins during the Mesozoic. All sampled rocks show a normal polarity remagnetization. Fold and conglomerate tests indicate that remagnetization postdates the main extensional stage of basin formation (Late Jurassic−Barremian) and was acquired before the subsequent compressional deformation. The analysis of these overprinted directions allows the basin geometry of the studied area to be restored at the moment of acquisition of the remagnetization. This approach represents a powerful tool to study basinal evolution and uplift of sedimentary basins, to be tested in other inverted basins with syn‐extensional related secondary overprints.
The ecohydrologic significance of hydraulic redistribution in a semiarid savanna
Authors: Scott Russell L. , Cable William L. , Hultine Kevin R.
Published: February 2008

Recent studies have illuminated the process of hydraulic redistribution, defined as the translocation of soil moisture via plant root systems, but the long‐term ecohydrologic significance of this process is poorly understood. We investigated hydraulic redistribution (HR) by Prosopis velutina Woot. (velvet mesquite) in an upland savanna ecosystem over a two‐year period. Our goal was to quantify patterns of HR by mesquite roots and assess how this affects tree water use and productivity. We used the heat ratio method to monitor bi‐directional sap flow, an analog of HR, in both lateral and tap roots. Additionally, we monitored soil water content and used the eddy covariance technique to quantify ecosystem carbon dioxide and water exchange. Mesquite roots redistributed large amounts of water throughout the year, even during periods of canopy dormancy. Dormant season precipitation (November–March) was often taken up by shallow lateral roots and transferred downward in the soil profile by deeper lateral and tap roots. Such a transfer was also apparent when the trees were active and moisture from summer rainfall was plant available in the upper soil layers. As the upper soil layers dried, sap flow moving toward the canopy in the lateral roots diminished and water use from deeper soils increased via the taproots. The relationship between root sap flow and above‐canopy fluxes suggested that deeper “stored” water from HR allowed the trees to transpire more in the spring that followed a winter with significant downward redistribution. Patterns of lateral and tap root sap flow also implied that redistribution may extend the growing season of the trees after summer rains have ended and surface soils are dry, thus allowing the trees to photosynthesize through periods of seasonal drought. The large hydrologic magnitude and the ecological effects of HR we studied, along with mounting evidence of this process occurring in many other ecosystems, indicates that HR should be accounted for in many ecohydrologic modeling efforts.
Estimation of bulk liquid properties from Monte Carlo simulations of Lennard-Jones clusters
Authors: Barrett Jonathan C. , Knight Andrew P.
Published: February 2008

Monte Carlo simulations are performed to determine the free energies of clusters containing between i=20 and i=100 atoms interacting via the Lennard-Jones potential at dimensionless temperatures T* between 0.25 and 0.875. A cluster is defined by the condition that all atoms are within a specified distance of their mutual center of mass. A function of the form [b−α(i−1)−θ(i2∕3−1)] is found to provide a good fit to the Monte Carlo data and the fitted values of the temperature-dependent parameters α and θ agree reasonably well with the predictions of bulk simulations (extrapolated as necessary) for the vapor pressure and surface energy per atom in the range T*=0.375–0.7.
A new dipole-free sum-over-states expression for the second hyperpolarizability
Authors: Pérez-Moreno Javier , Clays Koen , Kuzyk Mark G.
Published: February 2008

The generalized Thomas-Kuhn sum rules are used to eliminate the explicit dependence on dipolar terms in the traditional sum-over-states (SOS) expression for the second hyperpolarizability to derive a new, yet equivalent, SOS expression. This new dipole-free expression may be better suited to study the second hyperpolarizability of nondipolar systems such as quadrupolar, octupolar, and dodecapolar structures. The two expressions lead to the same fundamental limits of the off-resonance second hyperpolarizability; and when applied to a particle in a box and a clipped harmonic oscillator, have the same frequency dependence. We propose that the new dipole-free equation, when used in conjunction with the standard SOS expression, can be used to develop a three-state model of the dispersion of the third-order susceptibility that can be applied to molecules in cases where normally many more states would have been required. Furthermore, a comparison between the two expressions can be used as a convergence test of molecular orbital calculations when applied to the second hyperpolarizability.
Structure and magnetic properties of CoFeZrMBCu soft nanocrystalline alloys
Authors: Daniil M. , Willard M. A.
Published: February 2008

In this article, we report on the effect of substituting Nb, Hf, and Ta for Zr on the crystallization behavior, crystal structure, and magnetic properties of (Co0.95Fe0.05)88Zr7−xMxB4Cu1 (x=0, 1, and 3.5). Samples annealed at temperatures up to 550°C lead to the partial crystallization of very fine bcc-(Co,Fe) and fcc-(Co,Fe) grains, while annealing at 750°C lead to coarser fcc-(Co,Fe) grains and Co–M intermetallic phases. All of the compositions except those with 3.5at.% Nb or Ta show similar low coercive behavior in the as-spun and annealed states. The coercivity of annealed ribbons below 550°C is varied from 0.15to0.46Oe and the magnetization from 128to133emu∕g. High temperature hysteresis loop measurements revealed a nearly constant coercivity for up to 400°C and 20% reduction in magnetic induction, exceeding the performance of Finemet alloys at this temperature.
Temperature- and field-induced entropy changes in nanomagnets
Authors: Skomski Ralph , Binek Christian , Mukherjee T. , Sahoo S. , Sellmyer D. J.
Published: February 2008

Room-temperature magnetic-entropy changes in nanostructures for magnetic refrigeration are investigated by model calculations. Using a mean-field approach, the magnetic entropy is calculated as a function of temperature, magnetic field, particle size, anisotropy, and interaction strength. Both isotropic (Heisenberg) and uniaxial (Ising and XY) anisotropies are considered. The nanoparticle entropy strongly depends on the character of the anisotropy, in contrast to atomic ferromagnetism, where the anisotropy energy is much smaller than the interaction energy. Most promising are isotropic particles and particles with weak easy axis anisotropy, as well as easy-plane particle with the field in the plane. The optimum nanoparticle size is not much larger than 1nm, because the relative magnetization direction in a nanoparticle is usually frozen and do not contribute to the entropy change.
Local and global properties of mixtures in one-dimensional systems. Part I. Mixtures of two simple components
Authors: Ben-Naim Arieh
Published: February 2008

Two sets of quantities are calculated for two-component mixtures in one dimension. One consists of the traditional excess thermodynamic quantities which provide global information on the mixtures. The second, referred to as local properties, consists of the Kirkwood–Buff integrals, local composition, solvation, and preferential solvation quantities. In this part, we discuss simple particles interacting via either square-well potential or hard rod potential. It is shown that a host of new information can be obtained from the local properties of the mixtures which supplements the information conveyed by the global properties.
Atomistic and electronic structure of bimetallic cobalt/rhenium clusters from density functional theory calculations
Authors: Bakken Vebjørn , Swang Ole
Published: February 2008

We have carried out computational density functional investigations of CoIReJ (J=0,1,2; I+J=14) metal atom clusters. Through thorough optimization of geometry, spin polarization, and electronic configuration, the most stable structures for each cluster have been identified. While the global minima are found to be well defined and energetically well separated from other local minima, the study reveals a plethora of different structures and symmetries only moderately higher in energy. A key point of interest is the effect of doping the cobalt clusters with rhenium. Aside from significant structural reorganizations, rhenium is found to stabilize the clusters and couple down the spin. Furthermore, the most stable clusters comprise highly coordinated rhenium and, in the case of Co12Re2, Re–Re bonding. Our results are compared to earlier experimental and computational data.
Comment on “Instability of isolated planar shock waves” [Phys. Fluids 19, 094102 (2007)]
Authors: Tumin Anatoli
Published: February 2008

It is shown that Erpenbeck’s solution of the initial-value problem for small perturbations in the presence of shocks [J. J. Erpenbeck, Phys. Fluids 5, 604 (1962); 5, 1181 (1962)] leads to a straightforward and simple method for analysis of rippled shocks as well. Particularly, the result for the ripple amplitude of a shock is the same as the result of Bates derived from an integral equation for the shock displacement function [J. W. Bates, Phys. Rev. E 69, 056313 (2004); Phys Fluids 19, 094102 (2007)].
Deformation behavior and magnetostriction of polycrystalline Fe–Ga–X (X=B,C,Mn,Mo,Nb,NbC) alloys
Authors: Na Suok-Min , Flatau Alison B.
Published: February 2008

Single crystal samples of quenched Fe81.3Ga18.7 and of slow cooled Fe81.3Ga18.6C0.08 exhibit magnetostriction of ∼400ppm. However, they also exhibit a sufficiently high permeability that eddy currents, which form in proportion to sample thickness, limit their operation at high frequencies. During attempts to roll thin sheets of Fe81.3Ga18.7 and carbon-added Fe81Ga19 alloys, cracks formed along grain boundaries and subsequently samples fractured during hot rolling such that the alloy was too brittle to make thin sheets. In this paper, the influence of alloying additions of B, Mn, Mo, Nb, and NbC on the deformation behavior and magnetostriction of Fe–Ga alloy was investigated. These alloying additions except Mn improved the roll ability and provided a high quality finished rolled sheets with thickness ranging from 0.18to0.35mm. Results are shown to demonstrate that the fracture mode of 1.0% Mo- or 0.5% B-added Fe81Ga19 alloy was changed from an intergranular to a transgranular fracture mode with cleavage. Annealed sheets with additions of 0.5% B, 1.0% B, 0.5% Mo, 2.0% Mo, 0.5% Nb, and 1.0% NbC exhibited the maximum magnetostrictions of 103, 160, 127, 88, 121, and 183ppm, respectively. Electron backscattering diffraction (EBSD) analysis showed texture in the 1.0% B-added sheet changed from γ-fiber texture (as rolled) to the Goss texture {110}⟨001⟩ (annealed).
Stochastic approach to the receptivity problem applied to bypass transition in boundary layers
Authors: Hœpffner Jérôme , Brandt Luca
Published: February 2008

To study the flow behavior in the presence of external disturbances of chaotic nature, a stochastic approach is pursued. In particular, transition to turbulence in boundary layers exposed to high levels of free-stream turbulence is considered. The late stages of this transition scenario, characterized by the growth and breakdown of streamwise-elongated streaks, are examined by considering the linear evolution of perturbations to a base flow consisting of the Blasius profile and the streaks. A stochastic initial condition is considered where the free-stream perturbations are described by the correlations of isotropic homogeneous turbulence. The spatial correlation of the excited flow at later times can be computed by the numerical solution of a Lyapunov equation. It is shown that free-stream turbulence has the necessary features to excite secondary energy growth, thus playing a central role in the transition to turbulence. The method proposed here can be used to examine the receptivity of other flows to external noise whose statistical properties are known or can be modeled.
Response to “Comment on ‘Instability of isolated planar shock waves’” [Phys. Fluids 20, 029101 (2008)]
Authors: Bates J. W.
Published: February 2008

In a recent article [J. W. Bates, “Instability of isolated planar shock waves,” Phys. Fluids 19, 094102 (2007)], we derived linear instability criteria for an isolated, planar, two-dimensional shock wave propagating through an inviscid fluid with an arbitrary equation of state. The basis for this analysis was a novel solution for the time-dependent Fourier amplitude of a single-mode perturbation on the front, which was expressed in the form of a Volterra equation. In the comment by Tumin [“Comment on ‘Instability of isolated planar shock waves’,” Phys. Fluids 20, 029101 (2008)], the author demonstrated the consistency of our results with those of Erpenbeck, whose mathematical approach avoided the derivation of an integral equation in the time domain, but required a complicated, inverse Laplace-transform operation to ascertain the temporal evolution of disturbances at the shock’s surface. Here, we emphasize that such information is obtained more readily from a direct solution of the aforementioned Volterra equation using modern numerical techniques.
Distinct evolution of magnetism and anisotropy of ultrathin CoFe and Co films on Cu(110) upon gas adsorption
Authors: Küpper D. , Ionescu A. , Easton S. , Kurebayashi H. , Bland J. A. C.
Published: February 2008

We report on the effects of O2 and H2 dosing on the magnetism of Co75Fe25 films, highlighting the extreme sensitivity of the magnetic behavior of ultrathin films to specific chemical interactions at the surface. We have performed a systematic in situ study of the magnetic behavior as a function of O2 and H2 dosage on ultrathin CoFe and Co films grown on Cu(110) by means of the magneto-optical Kerr effect and low energy electron diffraction. Oxygen and hydrogen dosing are found to have distinctly different influences on the evolution of the coercive field Hc of the CoFe and Co films. Significant differences become also apparent for the evolution of the M-H loop squareness upon gas adsorption. Oxygen dosing leads to a rapid decrease in squareness above 10L (1L≡10−6Torrs) for CoFe films. For Co films, however, the squareness increases initially and then stabilizes at a higher dosage level. Furthermore, a striking sensitivity of the easy axis magnetization in the CoFe films was observed; 50L of O2 caused a rotation of the easy axis by 60° within the plane. The observed differences between the different gases and between the different ferromagnetic films are briefly discussed in terms of d band occupation and details of chemical bonding.
Optical tweezers with 2.5kHz bandwidth video detection for single-colloid electrophoresis
Authors: Otto Oliver , Gutsche Christof , Kremer Friedrich , Keyser Ulrich F.
Published: February 2008

We developed an optical tweezers setup to study the electrophoretic motion of colloids in an external electric field. The setup is based on standard components for illumination and video detection. Our video based optical tracking of the colloid motion has a time resolution of 0.2ms, resulting in a bandwidth of 2.5kHz. This enables calibration of the optical tweezers by Brownian motion without applying a quadrant photodetector. We demonstrate that our system has a spatial resolution of 0.5nm and a force sensitivity of 20fN using a Fourier algorithm to detect periodic oscillations of the trapped colloid caused by an external ac field. The electrophoretic mobility and zeta potential of a single colloid can be extracted in aqueous solution avoiding screening effects common for usual bulk measurements.
Dispersive gain and loss in midinfrared quantum cascade laser
Authors: Revin D. G. , Soulby M. R. , Cockburn J. W. , Yang Q. , Manz C. , Wagner J.
Published: February 2008

We report the measurements of dispersive gain (simultaneous coexistence of gain and losses on a single intersubband transition) in a quantum cascade laser. Broadband transmission spectra through the waveguide of a λ∼4.7μm In0.53Ga0.47As∕AlAs0.56Sb0.44∕InP quantum cascade laser have been studied at a bias below laser threshold and at different temperatures. For a certain range of current, and at temperatures higher than about 150K, the transmission spectra show clear dispersive gain/loss behavior with the possibility for intersubband gain to be observed even without global population inversion between laser levels.
Surface proximity and boron concentration effects on end-of-range defect formation during nonmelt laser annealing
Authors: Sharp J. A. , Smith A. J. , Webb R. P. , Kirkby K. J. , Cowern N. E. B. , Giubertoni D. , Gennaro S. , Bersani M. , Foad M. A. , Fazzini P. F. , Cristiano F.
Published: February 2008

The effects of surface proximity and B concentration on end-of-range defect formation during nonmelt laser annealing in preamorphized silicon have been studied. These effects were analyzed by observing the activation and diffusion of an ultrashallow B implant, using Hall effect and secondary ion mass spectrometry measurements. By adjusting the preamorphizing implant and laser annealing conditions, B deactivation and diffusion were minimized, resulting in a sheet resistance of ∼600Ω∕sq with a 16nm junction depth. This is attributed to a combination of enhanced dissolution of end-of-range defects and preferential formation of B-interstitial clusters due to the surface proximity and high B concentration, respectively.
High temperature resistance of small diameter, metallic single-walled carbon nanotube devices
Authors: Kane Alexander A. , Loutherback Kevin , Goldsmith Brett R. , Collins Philip G.
Published: February 2008

The effects of high temperature cycling on the resistance of metallic single-walled carbon nanotube (SWCNT) devices is measured in situ. Individual, small-diameter SWCNTs contacted by palladium or titanium electrodes were measured from room temperature up to 1000K in ultrahigh vacuum. Upon the first thermal cycling, the device resistances fluctuate and generally decrease. Pd-contacted devices typically become stable by 450K, whereas Ti-contacted devices require higher treatments above 600K. Once these temperatures have been exceeded, subsequent thermal cycling has minimal effects. Heat-treated devices exhibit linear temperature dependences, with Pd and Ti contacts producing average temperature coefficients of −3×10−4∕K and 1.1×10−3∕K, respectively.
Simple tandem organic photovoltaic cells for improved energy conversion efficiency
Authors: Zhang Chunfu , Tong Shi Wun , Jiang Changyun , Kang E. T. , Chan D. S. H. , Zhu Chunxiang
Published: February 2008

We proposed and demonstrated a simple tandem structure of organic photovoltaic (PV) cell for efficient light harvesting. In this device structure, a soluble fullerene derivative of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) is employed simultaneously to form a bilayer heterojunction PV subcell with the underlying copper phthalocyanine (CuPc) and a bulk heterojunction PV subcell with blended poly(3-hexylthiophene-2,5-diyl) (P3HT). In comparison with the conventional tandem structure, the omission of the semitransparent intercellular connection layer reduces the complexity of the device and the light loss. The enhanced short circuit current density (JSC=8.63mA∕cm2) and power conversion efficiency (PCE) (2.79%) of the tandem structure are nearly the sum of those of the stand-alone cells of CuPc/PCBM (JSC=2.09mA∕cm2, PCE=0.43%) and P3HT:PCBM (JSC=6.87mA∕cm2, PCE=2.50%).
Spectroscopic analysis of the epitaxial CaO (111)–GaN (0002) interface
Authors: Craft H. S. , Collazo R. , Losego M. D. , Mita S. , Sitar Z. , Maria J.-P.
Published: February 2008

We report an x-ray photoelectron spectroscopy (XPS) study of the CaO∕GaN interface. Epitaxial films of CaO (111) were grown on GaN (0002) and analyzed in situ using XPS. We observe Stranski–Krastanov growth, in which CaO coalesces rapidly, then converts to a three-dimensional mode. Data suggest coalescence within the first nanometer of film growth, indicating growth behavior different from published reports of the analogous MgO–GaN system. We find 1.0±0.2eV for the valence band offset and a 2.5±0.2eV conduction band offset. The results are discussed in terms of their utility in oxide-nitride electronic devices.
The effect of long-duration high-temperature annealing in an air ambient on the properties of AlGaN∕GaN heterostructures
Authors: Chen D. J. , Liu B. , Chen G. Q. , Xu F. , Xie Z. L. , Han P. , Zhang R. , Zheng Y. D. , Narayanamurti V.
Published: February 2008

The effects of a long-duration high-temperature annealing in an air ambient on the strain of the AlGaN barrier layer and high-temperature transport properties of the two-dimensional electron gas (2DEG) in AlGaN∕GaN heterostructures were investigated. The results show that the annealing induces a nonreversible lattice relaxation in the AlGaN layer and increases remarkably the 2DEG density due to the incorporation of oxygen atoms into the AlGaN surface and decreases the 2DEG mobility in the AlGaN∕GaN heterostructure. However, the conductivity of the 2DEG has no obvious change in our samples within the measured temperature range before and after the annealing, indicating that AlGaN∕GaN heterostructures are possibly promising for electron devices operated at high temperatures based on atmospheric exposure.
Arsenic δ-doped HgTe∕HgCdTe superlattices grown by molecular beam epitaxy
Authors: Tsen G. K. O. , Musca C. A. , Dell J. M. , Antoszewski J. , Faraone L. , Becker C. R.
Published: February 2008

Arsenic incorporation in HgTe∕Hg0.05Cd0.95Te superlattices grown by molecular beam epitaxy (MBE) is reported. The incorporation was carried out by a δ-doping approach where arsenic was incorporated during MBE growth as acceptors. The superlattices were characterized via high resolution x-ray diffraction, Fourier transform infrared spectroscopy, secondary ion mass spectrometry, and magnetotransport Hall measurements coupled with the quantitative mobility spectrum analysis algorithm.