bluuebunny/crossref_metadata_2025 huggingface dataset:
Recent developments in the field of monolithic stationary phases for capillary electrochromatography
Authors: Svec Frantisek
Published: April 2005

This review summarizes the contributions to the rapidly growing area of monolithic columns based on both silica and synthetic polymers for capillary electrochromatography and chip electrochromatography, with a focus on those published during the year 2004. A wide variety of both modified approaches to the “old” monoliths and new monoliths have been reported despite the very short period of time covered. This demonstrates that monolithic stationary phases have become a well‐established format in the field of electrochromatography. The simplicity of their preparation as well as the good control over their porous properties and surface chemistries make the monolithic separation media an attractive alternative to capillary columns packed with particulate materials.
Influence of steric hindrance on enantioseparation of Dns‐amino acids and pesticides on terguride based chiral selectors in capillary electrophoresis
Authors: Honzátko Aleš , Cvak Jan , Vaingátová Silvie , Flieger Miroslav
Published: April 2005

Three urea derivatives of ergoline‐based chiral selectors (CSs), differing in the size of the urea side chain, i. e. dimethyl‐ (CSI), diethyl‐ (CSII), and diisopropylurea (CSIII), were used to study the effect of steric hindrance on the enantioseparation of dansyl amino acids (Dns‐AAs), pesticides, and mandelic acid under condition of capillary electrophoresis (CE) in linear polyacrylamide coated capillaries. A mixture of organic modifiers (MeOH/THF, 4 : 1 v/v) in a BGE consisting of 100 mM β‐alanine‐acetate was used to increase the solubility of CSs up to 25 mM. The capillary was filled with CS (high UV absorption), and the inlet and outlet vials contained buffer solutions only. The best enantioseparation of Dns‐AAs was achieved on CSI. Increased steric hindrance of the chiral binding site led to reduction of both enantioselectivity and resolution. The opposite pattern was observed for the separation of mandelic acid enantiomers, where the best enantioseparation and resolution was obtained with CSIII. Most of the pesticides studied reached maximum selectivity on the diethylurea ergoline derivative (CSII). Enantioseparation of fenoxaprop was found to be independent of steric hindrance.
The topology of the spaces of regular and absolutely regular Hankel‐transformable distributions
Authors: Jerez C. , Marrero I.
Published: April 2005

New topologies on the spaces of regular and absolutely regular Hankel‐transformable distributions are proposed and compared. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Huntington's disease and minocycline
Authors: Hödl Anna K. , Bonelli Raphael M.
Published: April 2005

A reply to this letter has been published in Movement DisordersMov Disord (2005) 20 (4) 511.
Wilson's disease presenting with an unusual cough
Authors: Crone Nathan E. , Jinnah H. A. , Reich Stephen G.
Published: April 2005

A 26‐year‐old man developed an unusual repetitive, nonproductive cough. Extensive pulmonary and otolaryngology investigations failed to disclose a cause. It was only after he developed additional neurological manifestations ultimately leading to the diagnosis of Wilson's disease (WD) that a neurological basis for the cough was suspected. Features of the cough suggest it was a form of respiratory dyskinesia, a previously unreported presentation of WD. © 2005 Movement Disorder Society
Interaction of the conserved meiotic regulators, BOULE (BOL) and PUMILIO‐2 (PUM2)
Authors: Urano Jun , Fox Mark S. , Reijo Pera Renee A.
Published: April 2005

Germ cell development is complex; it encompasses specification of germ cell fate, mitotic replication of early germ cell populations, and meiotic and postmeiotic development. Meiosis alone may require several hundred genes, including homologs of the BOULE (BOL) and PUMILIO (PUM) gene families. Both BOL and PUM homologs encode germ cell specific RNA binding proteins in diverse organisms where they are required for germ cell development. Here, we demonstrate that human BOL forms homodimers and is able to interact with a PUMILIO homolog, PUM2. We mapped the domain of BOL that is required for dimerization and for interaction with PUM2. We also show that BOL and PUM2 can form a complex on a subset of PUM2 RNA targets that is distinct from targets bound by PUM2 and another deleted in azoospermia (DAZ) family member, DAZ‐like (DAZL). This suggests that RNA sequences bound by PUM2 may be determined by protein interactions. This data also suggests that although the BOL, DAZ, and DAZL proteins are all members of the same gene family, they may function in distinct molecular complexes during human germ cell development. Mol. Reprod. Dev. © 2005 Wiley‐Liss, Inc.
The analysis of telomere length and telomerase activity in cloned pigs and cows
Authors: Jeon H.Y. , Hyun S.H. , Lee G.S. , Kim H.S. , Kim S. , Jeong Y.W. , Kang S.K. , Lee B.C. , Han J.Y. , Ahn C. , Hwang W.S.
Published: April 2005

Inefficiency in the production of cloned animals is most likely due to epigenetic reprogramming errors after somatic cell nuclear transfer (SCNT). In order to investigate whether nuclear reprogramming restores cellular age of donor cells after SCNT, we measured telomere length and telomerase activity in cloned pigs and cattle. In normal pigs and cattle, the mean telomere length was decreased with biological aging. In cloned or transgenic cloned piglets, the mean telomere length was elongated compared to nuclear donor fetal fibroblasts and age‐matched normal piglets. In cloned cattle, no increases in mean telomere length were observed compared to nuclear donor adult fibroblasts. In terms of telomerase activity, significant activity was observed in nuclear donor cells and normal tissues from adult or new‐born pigs and cattle, with relatively higher activity in the porcine tissues compared to the bovine tissues. Cloned calves and piglets showed the same level of telomerase activity as their respective donor cells. In addition, no difference in telomerase activity was observed between normal and transgenic cloned piglets. However, increased telomerase activity was observed in porcine SCNT blastocysts compared to nuclear donor cells and in vitro fertilization (IVF)‐derived blastocysts, suggesting that the elongation of telomere lengths observed in cloned piglets could be due to the presence of higher telomerase activity in SCNT blastocysts. In conclusion, gathering from the comparative studies with cattle, we were able to demonstrate that telomere length in cloned piglets was rebuilt or elongated with the use of cultured donor fetal fibroblasts. Mol. Reprod. Dev. © 2005 Wiley‐Liss, Inc.
Intraoviductal introduction of plasmid DNA and subsequent electroporation for efficient in vivo gene transfer to murine oviductal epithelium
Authors: Sato Masahiro
Published: April 2005

Various growth factors and proteins produced by oviductal cells have been demonstrated to interact with developing embryos. However, little is known concerning the function of mammalian oviducts at the molecular biological level. This may be partly due to lack of efficient gene transfer to oviductal cells. In this study, we developed an efficient method for transfection of oviductal epithelium using in vivo electroporation (EP) in mice. One microliter of solution containing enhanced green fluorescent protein (EGFP) expression plasmid (0.5 μg) and 0.05% trypan blue (TB) were directly introduced into the ampulla of the eCG‐hCG‐treated B6C3F1 females at embryonic day (E) 0.6 of pregnancy (corresponding to 14:00–15:00 of the day the plug was recognized). The entire oviduct was then electroporated using tweezer‐type electrodes attached to a T820 electroporator (BTX Genetronics, Inc., San Diego, CA) with eight square‐wave pulses, 50 V in strength and 50 msec in duration. On E 3.4, embryos at morula/early blastocyst stages were collected and their number, morphology, and EGFP‐derived fluorescence recorded. Fluorescence in oviducts was also examined. In some cases, these fluorescent oviducts were subjected to cryostat sectioning. Strong fluorescence was observed in some of the oviductal epithelia, with a maximum level of 36%. Neither the number nor morphology of the collected embryos was affected by EP. Some embryos possessed fluorescence in the blastocoel, but not cytoplasm, suggesting incorporation of EGFP present in the oviductal luminal fluid. This system may enable development of new factors regulating development of preimplantation embryos and offers the prospect of a new approach to understanding oviductal function. Mol. Reprod. Dev. © 2005 Wiley‐Liss, Inc.
Comparing the function of the corticospinal system in different species: Organizational differences for motor specialization?
Authors: Lemon Roger N. , Griffiths James
Published: April 2005

An appreciation of the comparative functions of the corticospinal tract is of direct relevance to the understanding of how results from animal models can advance knowledge of the human motor system and its disorders. Two critical functions of the corticospinal tract are discussed: first, the role of descending projections to the dorsal horn in the control of sensory afferent input, and second, the capacity of direct cortico‐motoneuronal projections to support voluntary execution of skilled hand and finger movements. We stress that there are some important differences in corticospinal projections from different cortical regions within a particular species and that these projections support different functions. Therefore, any differences in the organization of corticospinal projections across species may well reflect differences in their functional roles. Such differences most likely reflect features of the sensorimotor behavior that are characteristic of that species. Insights into corticospinal function in different animal models are of direct relevance to understanding the human motor system, providing they are interpreted in relation to the functions they underpin in a given model. Studies in non‐human primates will continue to be needed for understanding special features of the human motor system, including feed‐forward control of skilled hand movements. These movements are often particularly vulnerable to neurological disease, including stroke, cerebral palsy, movement disorders, spinal injury, and motor neuron disease. Muscle Nerve, 2005
Phase diagram and enhanced piezoelectricity in the strontium titanate doped potassium–sodium niobate solid solution
Authors: Wang Ruiping , Xie Rong‐Jun , Hanada Kotaro , Matsusaki Kunio , Bando Hiroshi , Itoh Mitsuru
Published: April 2005

The dielectric and the piezoelectric properties of the (1–x)(Na0.5K0.5)NbO3–xSrTiO3 ceramics, densified by the Spark‐Plasma‐Sintering method, have been studied. A phase diagram was established from the temperature dependence of the dielectric constant. A tetragonal–orthorhombic morpho‐tropic phase boundary (MPB) was found at x ∼ 0.05. Around the MPB, piezoelectric properties were greatly improved. The origin for the enhanced piezoelectricity has been proposed. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Quantum chemical studies on molecular structural conformations and hydrated forms of salicylamide and O‐hydroxybenzoyl cyanide
Authors: Anandan K. , Kolandaivel P. , Kumaresan R.
Published: April 2005

Ab initio and density functional theory (DFT) methods have been employed to study the molecular structural conformations and hydrated forms of both salicylamide (SAM) and O‐hydroxybenzoyl cyanide (OHBC). Molecular geometries and energetics have been obtained in the gaseous phase by employing the Møller–Plesset type 2 MP2/6‐311G(2d,2p)and B3LYP/6‐311G(2d,2p)levels of theory. The presence of an electron‐releasing group (SAM) leads to an increase in the energy of the molecular system, while the presence of an electron‐withdrawing group (OHBC) drastically decreases the energy. Chemical reactivity parameters (η and μ) have been calculated using the energy values of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) obtained at the Hartree–Fock (HF)/6‐311G(2d,2p)level of theory for all the conformers and the principle of maximum hardness (MHP) has been tested. The condensed Fukui functions have been calculated using the atomic charges obtained through the natural bond orbital (NBO) analysis scheme for all the optimized structures at the B3LYP/6‐311G(2d,2p)level of theory, and the most reactive sites of the molecules have been identified. Nuclear magnetic resonance (NMR) studies have been carried out at the B3LYP/6‐311G(2d,2p)level of theory for all the conformers in the gaseous phase on the basis of the method of Cheeseman and coworkers. The calculated chemical shift values have been used to discuss the delocalization activity of the electron clouds. The dimeric structures of the most stable conformers of both SAM and OHBC in the gaseous phase have been optimized at the B3LYP/6‐311G(2d,2p)level of theory, and the interaction energies have been calculated. The most stable conformers of both compounds bear an intramolecular hydrogen bond, which gives rise to the formation of a pseudo‐aromatic ring. These conformers have been allowed to interact with the water molecule. Special emphasis has been given to analysis of the intermolecular hydrogen bonds of the hydrated conformers. Self‐consistent reaction field (SCRF) theory has been employed to optimize all the conformers in the aqueous phase (ε = 78.39) at the B3LYP/6‐311G(2d,2p)level of theory, and the solvent effect has been studied. Vibrational frequency analysis has been performed for all the optimized structures at MP2/6‐311G(2d,2p)level of theory, and the stationary points corresponding to local minima without imaginary frequencies have been obtained for all the molecular structures. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Structural phases of coupled polyacetylene chains with impurities
Authors: Guimarães Paulo Henrique Alves , Silva Geraldo Magela E
Published: April 2005

The study of quasi‐particles in conducting polymers is concentrated in single‐chain works. It is shown in the present study that interchain interactions can be determinant in the relative presence of solitons, polarons, or bipolarons in conjugated polymers. We consider a modified version of the SSH model for polyacetylene. The results show that the presence of different impurities, bonded to different chains sites, led to quite different relative chains configurations and phases related to bond alignment order, presence of quasi‐particles, and their respective charges. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Quantitative analysis of wine yeast gene expression profiles under winemaking conditions
Authors: Varela Cristian , Cárdenas Javier , Melo Francisco , Agosin Eduardo
Published: April 2005

Wine fermentation is a dynamic and complex process in which the yeast cell is subjected to multiple stress conditions. A successful adaptation involves changes in gene expression profiles where a large number of genes are up‐ or downregulated. Functional genomic approaches are commonly used to obtain global gene expression profiles, thereby providing a comprehensive view of yeast physiology. We used SAGE to quantify gene expression profiles in an industrial strain of Saccharomyces cerevisiae under winemaking conditions. The transcriptome of wine yeast was analysed at three stages during the fermentation process, mid‐exponential phase, and early‐ and late‐stationary phases. Upon correlation with the yeast genome, we found three classes of transcripts: (a) sequences that corresponded to ORFs; (b) expressed sequences from intergenic regions; and (c) messengers that did not match the published reference yeast genome. In all fermentation phases studied, the most highly expressed genes related to energy production and stress response. For many pathways, including glycolysis, different transcript levels were observed during each phase. Different isoenzymes, including hexose transporters (HXT), were differentially induced, depending on the growth phase. About 10% of transcripts matched non‐annotated ORF regions within the yeast genome and could correspond to small novel genes originally omitted in the first gene annotation effort. Up to 22% of transcripts, particularly at late‐stationary phase, did not match any known location within the genome. As the available reference yeast genome was obtained from a laboratory strain, these expressed sequences could represent genes only expressed by an industrial yeast strain. Further studies are necessary to identify the role of these potential genes during wine fermentation. Copyright © 2005 John Wiley & Sons, Ltd.
Rapid enrichment and analysis of yeast phosphoproteins using affinity chromatography, 2D‐PAGE and peptide mass fingerprinting
Authors: Makrantoni Vasso , Antrobus Robin , Botting Catherine H. , Coote Peter J.
Published: April 2005

A combination of affinity purification, 2D‐PAGE and peptide mass fingerprinting was employed to study the phosphoprotein complement of Saccharomyces cerevisiae. Protein extracts were first passed through a phosphoprotein affinity column, and the phosphoprotein‐enriched eluate fractions were then separated on 2D gels and visualized by staining with SYPRO Ruby. Proteins were excised from the gels and identified by peptide mass fingerprinting; 11/13 protein spots identified from a gel of the phosphoprotein‐enriched fraction had prior published evidence indicating that they were phosphoproteins. Additional experiments using a specific stain for phosphoproteins, prior incubation of the protein extract with alkaline phosphatase and blotting with monoclonal antibodies to phosphothreonine, phosphoserine and phosphotyrosine demonstrated that the phosphoprotein affinity column was an effective method for enriching phosphoproteins. Further validating the method, growth of yeast in the presence of sorbic acid resulted in altered phosphorylation of 17 proteins, 13 of which had prior published evidence that they were phosphoproteins or had ATP binding activity. Copyright © 2005 John Wiley & Sons, Ltd.
Deep‐sea sediment records of the Laschamp geomagnetic field excursion (∼41,000 calendar years before present)
Authors: Lund Steve P. , Schwartz Martha , Keigwin Lloyd , Johnson Thomas
Published: April 2005

We have recovered two new high‐resolution paleomagnetic records of the Laschamp Excursion (∼41,000 calendar years B.P.) from deep‐sea sediments of the western North Atlantic Ocean. The records document that the Laschamp Excursion was characterized locally by (1) declination changes of ±120°, (2) inclination changes of more than 140°, (3) ∼1200‐year oscillations in both inclination and declination, (4) near 90° out‐of‐phase relationships between inclinations and declinations that produced two clockwise loops in directions and virtual geomagnetic poles (VGPs) followed by a counterclockwise loop, (5) excursional VGPs during both intervals of clockwise looping, (6) magnetic field intensities less than 10% of normal that persisted for almost 2000 years, (7) marked similarity in excursional directions over ∼5000 km spatial scale length, and (8) secular variation rates comparable to historic field behavior but persisting in sign for hundreds of years. All of these features, with the exception of anomalously large directional amplitude, are consistent with normal magnetic field secular variation. Comparison of our Laschamp Excursion paleomagnetic records with other late Quaternary excursion records suggests that there is a group of excursions, which we term class I, which have strikingly similar patterns of field behavior and likely share a common cause as part of the overall core dynamo process. Three general models of secular variation are described that can qualitatively produce class I excursions. On the basis of these observations we conclude that class I excursions, epitomized by the Laschamp Excursion, are more closely related to normal secular variation and are not necessarily a prelude to magnetic field reversal.
Sea ice concentrations in the Weddell Sea: A comparison of SSM/I, ULS, and GCM data
Authors: Connolley W. M.
Published: April 2005

The sea ice fraction in the interior of the pack, especially in winter, is important for climate studies and for validation of sea ice models. When ice concentration is high, a difference of only a few percent in ice fraction can have a major effect on the ocean‐air fluxes. Satellite estimates of the ice fraction in the Antarctic winter based on microwave emissions are typically 90–95%, with values from the “Bootstrap” algorithm higher than the “NASA team”. However coupled ocean‐atmosphere models usually show higher concentrations. A recent evaluation for the Arctic has shown that the true winter ice fractions can be very high, above 99%. Upward looking sonar data from the Weddell Sea is used to show that Antarctic concentrations are higher than previously estimated, and to reevaluate climate model results in this light. The bootstrap algorithm is found to provide a better fit to the sonar data.
Intraseasonal variation of raindrop size distribution at Koto Tabang, West Sumatra, Indonesia
Authors: Kozu Toshiaki , Shimomai Toyoshi , Akramin Zainul , Marzuki  , Shibagaki Yoshiaki , Hashiguchi Hiroyuki
Published: April 2005

Intraseasonal variation of raindrop size distribution (DSD) in response to Madden Julian Oscillation (MJO) is studied using a 2D video disdrometer (2DVD), a boundary layer radar (BLR) and the Equatorial Atmosphere Radar, operated at Koto Tabang, west Sumatra, as well as GOES‐9 infra‐red brightness temperature. As a parameter of DSD, ΔZMP, which is defined as the difference between a measured radar reflectivity in dB and that from the Marshall‐Palmer (MP) radar reflectivity (Z) ‐ rain rate (R) relationship, Z = 200 R1.6, is used. It is found that in non‐active phase of MJO, 2DVD‐derived ΔZMPs are generally positive, indicating that DSDs are broad, while they decrease toward negative values as the phase of MJO shifts to active ones. Rain‐top height derived from the BLR indicates that the convective processes are more intense in the non‐active MJO phase than in the active phase, which would cause the difference in DSDs.
Constraining the source separation with coda wave interferometry: Theory and application to earthquake doublets in the Hayward fault, California
Authors: Snieder Roel , Vrijlandt Mark
Published: April 2005

The relative location of seismic sources is of importance for the location of aftershocks on a fault, for the positioning of sources in repeat seismic surveys, and for monitoring induced seismicity. In this paper we show how the seismic coda can be used to infer a measure of the source separation of two identical seismic sources from the correlation of the waveforms recorded at a single receiver. The theory is applicable to an explosive source in an acoustic or elastic medium and for a point force or double couple in an elastic medium. For an explosive source the source separation is constrained to be located on a sphere, while for a point force and a double couple the source separation can be constrained to be located on an ellipsoid whose symmetry axis is determined by the point force or double couple. We validate the theory with synthetic seismograms and apply the theory to earthquake doublets on the Hayward fault, California. The distance between events obtained from the coda waves agrees with the distance obtained from the double‐difference method.
Aerosol characteristics of air masses in northern Europe: Influences of location, transport, sinks, and sources
Authors: Tunved P. , Nilsson E. D. , Hansson H.‐C. , Ström J. , Kulmala M. , Aalto P. , Viisanen Y.
Published: April 2005

Synoptic‐scale air masses at different stations were classified following a definition based on Berliner Wetterkarte. This air mass classification has been related to 1 year of aerosol number size distributions measurements performed at four different stations extending from Aspvreten in Sweden (58.8°N) to Pallas in northern Finland (68°N). The air mass classification describes both class of air mass, based on the origin of the air mass, and character of air in terms of marine, mixed, and continental air masses. The aerosol size distribution properties were evaluated in relation to the air masses. Emphasis was put on the differences between marine, mixed, and continental character air masses. It is shown that continental air masses exceed marine and mixed character air masses both in number and mass concentration. Different classes of air masses were further associated with different aerosol size distribution properties. It is also shown that although serving as a somewhat good qualifier for the aerosol at individual stations, the air mass classification cannot be used to estimate the aerosol burden over large geographical areas. Instead, a sharp gradient was shown to exist between different stations, although aerosol properties were observed in equal air masses according to the definition by Berliner Wetterkarte. This gradient manifests as a south‐northerly decrease in aerosol total number and volume, indicating that the aerosol properties including the aerosol size distribution are less conservative than the thermodynamic properties (e.g., pseudo‐potential temperature and humidity profiles) that characterize the different air masses. Further, using a pseudo‐Lagrangian approach, the aerosol turnover time was estimated for different sized aerosols in air moving from south to north (i.e., depletion of aerosols in air arriving from the continent). Turnover time of Aitken particles was found to be in the range of 1–2 days, while accumulation mode turnover time was estimated to be in the order of 2–3 days.
Top‐of‐atmosphere shortwave broadband observed radiance and estimated irradiance over polar regions from Clouds and the Earth's Radiant Energy System (CERES) instruments on Terra
Authors: Kato Seiji , Loeb Norman G.
Published: April 2005

Empirical angular distribution models for estimating top‐of‐atmosphere shortwave irradiances from radiance measurements over permanent snow, fresh snow, and sea ice are developed using CERES measurements on Terra. Permanent snow angular distribution models depend on cloud fraction, cloud optical thickness, and snow brightness. Fresh snow and sea ice angular distribution models depend on snow and sea ice fraction, cloud fraction, cloud optical thickness, and snow and ice brightness. These classifications lead to 10 scene types for permanent snow and 25 scene types for fresh snow and sea ice. The average radiance over clear‐sky permanent snow is more isotropic with satellite viewing geometry than that over overcast permanent snow. On average, the albedo of clear‐sky permanent snow varies from 0.65 to 0.68 for solar zenith angles between 60° and 80°, while the corresponding albedo of overcast scenes varies from 0.70 to 0.73. Clear‐sky permanent snow albedos over Antarctica estimated from two independent angular distribution models are consistent to within 0.6%, on average. Despite significant variability in sea ice optical properties with season, the estimated mean relative albedo error is −1.0% for very dark sea ice and 0.1% for very bright sea ice when albedos derived from different viewing angles are averaged. The estimated regional root‐mean‐square (RMS) relative albedo error is 5.6% and 2.6% when the sea ice angular distribution models are applied to a region that contains very dark and very bright sea ice, respectively. Similarly, the estimated relative albedo bias error for fresh snow is −0.1% for very dark snow scenes and 0.1% for very bright snow scenes. The estimated regional RMS relative albedo error is 3.5% and 5.0% when angular distribution models are applied to a region that contains very dark and very bright fresh snow, respectively. These error estimates are only due to angular distribution model error and do not include the error caused by scene identification.
Long‐term isoprene flux measurements above a northern hardwood forest
Authors: Pressley Shelley , Lamb Brian , Westberg Hal , Flaherty Julia , Chen Jack , Vogel Christoph
Published: April 2005

We report continuous whole canopy isoprene emission fluxes from a northern hardwood forest in Michigan for the 1999–2002 growing seasons. The eddy covariance fluxes of isoprene, CO2, latent heat, and sensible heat are presented along with an analysis of the seasonal and year‐to‐year variations. Measurements were made in collaboration with the AmeriFlux site located at the University of Michigan Biological Station (UMBS) and the Program for Research on Oxidants: PHotochemistry, Emissions, and Transport (PROPHET). In general, isoprene emissions increased throughout the day with increasing temperature and light levels, peaked at midafternoon, and declined to zero by night. There were significant variations from one 30‐min period to the next, and from one day to the next. Average midday isoprene fluxes were 2.8, 3.2, and 2.9 mg C m−2 h−1 for 2000 through 2002, respectively. Insufficient data were available to include 1999. Last frost and full leaf out were significantly later in 2002 compared to the other years; however, total accumulated isoprene emissions for each year varied by less than 10%. Fully developed isoprene emissions occurred between 400 and 500 heating degree days, roughly half those required at other sites. Using long‐term net ecosystem exchange measurements from the UMBS∼Flux group, isoprene emissions represent between 1.7 to 3.1% of the net carbon uptake at this site. Observations for 2000–2002 were compared with the BEIS3 emission model. Estimates agree well with observations during the midsummer period, but BEIS3 overestimates observations during the spring onset of emissions and the fall decline in emissions. This work provides a unique long‐term data set useful for verifying canopy scale models and to help us better understand the dynamics of biosphere‐atmosphere exchange of isoprene.
The twentieth‐century pluvial in the western United States
Authors: Woodhouse Connie A. , Kunkel Kenneth E. , Easterling David R. , Cook Edward R.
Published: April 2005

Persistent, widespread wet conditions in the western United States in the early twentieth century have been noted in a number of studies. Here, we investigate the character of this pluvial, which covered a roughly 9‐state region and lasted about 13 years. Paleoclimatic data used to evaluate the period in a long‐term context indicate that the twentieth‐century pluvial is an extremely rare event, as previous studies have suggested, even when assessed in the context of a 1186‐year reconstruction of regional drought. An analysis of twentieth‐century climate data, characterizing precipitation seasonality, intensity, and frequency, shows that the pluvial was primarily a result of winter season, heavy to moderately heavy precipitation events, during a handful of extremely wet winters. Temperatures were also anomalously cool. The combination of duration, intensity, and spatial extent make this an unusual event, not only in twentieth century, but in the past 12 centuries.
Comparison of low-order multireference many-body perturbation theories
Authors: Chaudhuri Rajat K. , Freed Karl F. , Hose Gabriel , Piecuch Piotr , Kowalski Karol , Włoch Marta , Chattopadhyay Sudip , Mukherjee Debashis , Rolik Zoltán , Szabados Ágnes , Tóth Gábor , Surján Péter R.
Published: April 2005

Tests have been made to benchmark and assess the relative accuracies of low-order multireference perturbation theories as compared to coupled cluster (CC) and full configuration interaction (FCI) methods. Test calculations include the ground and some excited states of the Be, H2,BeH2,CH2, and SiH2 systems. Comparisons with FCI and CC calculations show that in most cases the effective valence shell Hamiltonian (Hv) method is more accurate than other low-order multireference perturbation theories, although none of the perturbative methods is as accurate as the CC approximations. We also briefly discuss some of the basic differences among the multireference perturbation theories considered in this work.
High-temperature annealing of optical centers in type-I diamond
Authors: Collins Alan T. , Connor Alex , Ly Cheng-Han , Shareef Abdulla , Spear Paul M.
Published: April 2005

Diamonds previously subjected to radiation damage have been annealed at temperatures up to 1750°C at ambient pressure, and at 2300°C using a stabilizing pressure of 5GPa. The results have been compared with those from similar measurements using natural brown diamonds. The investigation has led to an improved understanding of the commercial process for enhancing the color of brown diamonds by high-pressure, high-temperature (HPHT) annealing. The study has confirmed that the H4 center is less stable than the H3 center, and shown that the destruction of the H4 center in irradiated type-IaB diamonds coincides with the formation of a number of optical centers found to occur naturally in brown diamonds. In type-IaA diamonds the annealing out of the H1b absorption coincides with the production of H2 centers. Annealing measurements on brown diamonds indicate that the plastic deformation, associated with the brown color, occurred at a late stage in the diamonds’ history. Optical centers, such as H3 and (NV)−, that are produced in brown diamonds by HPHT annealing, are destroyed by this process in irradiated dislocation-free diamonds. Formation of these centers during the HPHT annealing of brown diamonds occurs as a result of the release of vacancies from the dislocations, and the present results therefore indicate that the production of these centers is a dynamic process with the generation and annealing in competition.
Shock-compression response of an alumina-filled epoxy
Authors: Setchell R. E. , Anderson M. U.
Published: April 2005

Alumina-filled epoxies are composites having constituents with highly dissimilar mechanical properties. Complex behavior during shock compression and release can result, particularly at higher alumina loadings. In the current study, a particular material containing 43% alumina by volume was examined in planar-impact experiments. Laser interferometry was used to measure particle velocity histories in both reverse-impact and transmitted-wave configurations. Hugoniot states and release-wave velocities were obtained at shock stresses up to 10GPa, and represented smooth extensions of previous data at lower stresses. Surprisingly high release-wave velocities continued to be the most notable feature. Measured profiles of transmitted waves show a gradual transition from viscoelastic behavior at high shock stresses to a more complex behavior at lower stresses in which viscous mechanisms produce a broadened wave structure. This wave structure was examined in some detail for peak stress dependence, evolution towards steady-wave conditions, and initial temperature effects.
Precessional switching on exchange biased patterned magnetic media with perpendicular anisotropy
Authors: Belmeguenai M. , Devolder T. , Chappert C.
Published: April 2005

We propose to use an in-plane exchange bias field to assist the applied field to obtain precessional switching of the magnetization in a high perpendicular anisotropy media. Our calculation is made in the limit of a nondamped macrospin particle. From the energy conservation, we derive the magnetic trajectories for any applied field magnitude and orientation. Precessional switching is shown to occur only for sufficiently large but not too high applied fields. The writing window associated with this switching field interval enlarges when the exchange bias field increases, as calculated quantitatively in the case of perpendicular recording. The potential application of this concept to magnetic recording is discussed. Compared to conventional media, the switching field distribution will be narrowed because the exchange bias provides a better immunity to texture dispersion. Since exchange bias reduces significantly the reversal field, we can use higher anisotropy materials and enhance the areal density while preserving the thermal stability.
Coherent third-order spectroscopic probes of molecular chirality
Authors: Abramavicius Darius , Mukamel Shaul
Published: April 2005

The third-order optical response of a system of coupled localized anharmonic vibrations is studied using a Green’s function solution of the nonlinear exciton equations for bosonized excitons, which are treated as interacting quasiparticles. The explicit calculation of two-exciton states is avoided and the scattering of quasiparticles provides the mechanism of optical nonlinearities. To first-order in the optical wave vector we find several rotationally invariant tensor components for isotropic ensembles which are induced by chirality. The nonlocal nonlinear susceptibility tensor is calculated for infinitely large periodic structures in momentum space, where the problem size reduces to the exciton interaction radius. Applications are made to α and 310 helical infinite peptides.
Heat transfer and fluid flow in laser microwelding
Authors: He X. , Elmer J. W. , DebRoy T.
Published: April 2005

The evolution of temperature and velocity fields during linear and spot Nd-yttrium aluminum garnet laser microwelding of 304 stainless steel was simulated using a well-tested, three-dimensional, numerical heat transfer and fluid flow model. Dimensional analysis was used to understand both the importance of heat transfer by conduction and convection as well as the roles of various driving forces for convection in the weld pool. Compared with large welds, smaller weld pool size for laser microwelding restricts the liquid velocities, but convection still remains an important mechanism of heat transfer. On the other hand, the allowable range of laser power for laser microwelding is much narrower than that for macrowelding in order to avoid formation of a keyhole and significant contamination of the workpiece by metal vapors and particles. The computed weld dimensions agreed well with the corresponding independent experimental data. It was found that a particular weld attribute, such as the peak temperature or weld penetration, could be obtained via multiple paths involving different sets of welding variables. Linear and spot laser microwelds were compared, showing differences in the temperature and velocity fields, thermal cycles, temperature gradients, solidification rates, and cooling rates. It is shown that the temperature gradient in the liquid adjacent to the mushy zone and average cooling rate between 800 and 500 °C for laser spot microwelding are much higher than those in linear laser microwelding. The results demonstrate that the application of numerical transport phenomena can significantly improve current understanding of both spot and linear laser microwelding.
Mechanisms leading to erratic snapback behavior in bipolar junction transistors with base emitter shorted
Authors: Chatterjee Amitabh , Schrimpf Ronald D. , Pendharkar Sameer , Banerjee Kaustav
Published: April 2005

This paper discusses two different modes of breakdown in the reverse-biased I–V characteristics observed generically in bipolar junction transistors (BJTs) with the base emitter shorted, showing an erratic behavior, in the presence of large displacement currents. Experimental observations related to reverse-biased collector junctions of BJTs, that exhibit two different states of breakdown when a fast voltage ramp is applied are presented. Numerical simulations of the transient behavior of avalanche injection in p∕n−∕n+ structures show that two very close breakdown states coexist. The mechanisms leading to the erratic behavior of the second breakdown are discussed. The jittery nature of the breakdown is attributed to the delay associated with the buildup of the electric field across the n−∕n+ junction.
Chaotic advection in a cavity flow with rigid particles
Authors: Hwang Wook Ryol , Anderson Patrick D. , Hulsen Martien A.
Published: April 2005

The effect of freely suspended rigid particles on chaotic material transport in a two-dimensional cavity flow is studied. We concentrate on the understanding of the mechanism how the presence of a particle affects the dynamical system of the flow. In contrast to the case studied by Vikhansky [“Chaotic advection of finite-single bodies in a cavity flow,” Phys. Fluids 15, 1830 (2003)], we show that even a regular periodic motion of a single particle can induce chaotic advection around the particle, as a result of the perturbation of the flow introduced by the freely rotating solid particle. This perturbation is of a hyperbolic nature. In fact, stretching and folding of the fluid elements are guaranteed by the occurrence of the hyperbolic flow perturbation centered at the particle and by the rotation of the freely suspended particle, respectively. The fluid-solid flow problem has been solved by a fictitious-domain/finite-element method based on a rigid-ring description of the solid particle. A single-particle system is studied in detail in view of the dynamical systems theory and then extended to two- and three-particle systems.
High-field conduction in barium titanate
Authors: Morrison F. D. , Zubko P. , Jung D. J. , Scott J. F. , Baxter P. , Saad M. M. , Bowman R. M. , Gregg J. M.
Published: April 2005

We present current–voltage studies of very thin (∼77nm) barium titanate single crystals up to 1.3GV∕m applied field. These show that the mechanism of leakage current at high fields is that of space charge limited conduction (SCLC) in a regime with a continuous distribution of traps, according to the original model of Rose [Phys. Rev. 97, 1538 (1955)]. This study represents a factor of ×5 in field compared with the early studies of BaTiO3 conduction [A. Branwood et al., Proc. Phys. Soc. London 79, 1161 (1962)]. Comparison is also given with ceramic multilayer barium titanate capacitors, and with variable range hopping [B. I. Shklovskii, Sov. Phys. Semicond. 6, 1964 (1973)], reported in SrTiO3 films [D. Fuchs, M. Adam, and R. Schneider, J. Phys. IV France 11, 71 (2001)].
Enhanced superconducting properties of Cu1-xTlxBa2Ca2-yMgyCu3O10-δ (y=, 0.5, 1.0, and 1.5)
Authors: Khan Nawazish A. , Khurram A. A.
Published: April 2005

In the present studies, the interplane couplings in Cu0.5Tl0.5Ba2Ca2Cu3O10-δ superconductor have been enhanced by Mg doping. With the improved interplane coupling a- and c-axis lengths are decreased while critical current density [Jc(H=0)] is enhanced by two orders of magnitude and the zero resistivity critical temperature [Tc(R=0)] is increased by 10 K. Predominant single phase of Cu1-xTlxBa2Ca2-yMgyCu3O10-δ (y=0, 0.5, 1.0, and 1.5) was prepared by the solid state reaction of Ba(NO3)2, Ca(NO3)2, MgO, and Cu(CN). The material was checked by x-ray diffraction for crystallinity and was found to be the predominant single phase of Cu1-xTlxBa2Ca2-yMgyCu3O10-δ (y=0, 0.5, 1.0, and 1.5) with a- and c-axes lengths 3.840 and 14.20 Å, respectively. The c-axis length decreases with the increased concentration of Mg in the compound. Fourier transform infrared absorption measurements have shown softening of apical oxygen modes with increased Mg doping and improved interplane coupling.
Enhanced boron diffusion in excimer laser preannealed Si
Authors: Monakhov E. V. , Svensson B. G. , Linnarsson M. K. , La Magna A. , Spinella C. , Bongiorno C. , Privitera V. , Fortunato G. , Mariucci L.
Published: April 2005

We have investigated boron diffusion during rapid thermal annealing in Si implanted with boron using an energy of 1keV and a dose of 1×1016cm−2. Two types of samples have been studied: As-implanted and pretreated with excimer laser annealing. For both types an enhanced diffusion of boron has been observed with an enhancement by a factor of 3–5 over the “standard” diffusion. It is suggested that the high concentration of implanted boron is a dominant factor for the diffusion enhancement as compared to the effect of implantation-induced damage. The data indicate that the proximity of the surface can also affect the boron diffusion enhancement.
The majority of human genes have regions repeated in other human genes
Authors: Britten Roy J.
Published: April 2005

Amino acid sequence comparisons have been made between all of 25,193 human proteins with each of the others by using
blast
software (National Center for Biotechnology Information) and recording the results for regions that are significantly related in sequence, that is, have an expectation of <1 × 10
–3
. The results are presented for each amino acid as the number of identical or similar amino acids matched in these aligned regions. This approach avoids summing or dealing directly with the different regions of any one protein that are often related to different numbers and types of other proteins. The results are presented graphically for a sample of 140 proteins. Relationships are not observed for 26.5% of the 12,728,866 amino acids. The average number of related amino acids is 36.5 for the majority (73.5%) that show relationships. The median number of recognized relationships is ≈3 for all of the amino acids, and the maximum number is 718. The results demonstrate the overwhelming importance of gene regional duplication forming families of proteins with related domains and show the variety of the resulting patterns of relationship. The magnitude of the set of relationships leads to the conclusion that the principal process by which new gene functions arise has been by making use of preexisting genes.
An exact solution of a diffusive predator–prey system
Authors: Petrovskii Sergei , Malchow Horst , Li Bai-Lian
Published: April 2005

We consider a system of two nonlinear partial differential equations describing the spatio-temporal dynamics of a predator–prey community where the preyper capitagrowth rate is damped by the Allee effect. Using an appropriate change of variables, we obtain an exact solution of the system, which appears to be related to the issue of biological invasion. In the large-time limit, or for appropriate parameter values, this solution describes the propagation of a travelling population front. We show that the properties of the solution exhibit biologically reasonable dependence on the parameter values; in particular, it predicts that the travelling front of invasive species can be stopped or reversed owing to the impact of predation.
On impacting liquid jets and drops onto polymethylmethacrylate targets
Authors: Bourne N.K
Published: April 2005

The impact of liquid drops upon polymers is important for several reasons. In particular, in cases of rain erosion after drop impact and of jets formed with cavities collapsing onto surfaces. An experimental study has detailed the evolution of damage within a material during loading. In particular, the temporal development of the pressure fields owing to the passage of stress waves leads to a series of failures in compression and tension from which erosion of the material and reduction in strength results. This work follows from a previous paper in which a methodology was demonstrated by which liquid impact upon liquid masses was modelled. In this paper, the impact response of polymethylmethacrylate is reviewed and its response to impact evaluated. The comparison between jet and drop impact is examined in experiment and simulation. The numerical simulation is validated for jet impact and target response, and future uses of the technique in more complex interactions are suggested.
Activation of diatomic molecules at solid surfaces
Authors: Ertl Gerhard
Published: April 2005

The interaction of a diatomic molecule with a well-defined single crystal surface represents the prototype of the elementary processes involved in heterogeneous catalysis, and it can be studied down to atomic length and extremely short (fs) time-scales. Our present understanding is illustrated by examples concerning the activation of hydrogen (including also the breakdown of thermal equilibrium during rapid laser-induced associative desorption), the role of steps as ‘active sites’ in the dissociative adsorption of NO or N
2
, and the mechanism and kinetics of the catalytic oxidation of CO.