bluuebunny/crossref_metadata_2025 huggingface dataset:
Reaction of Epichlorhydrin with Carbohydrate Polymers. Part I. Starch Reaction Kinetics
Authors: Kartha K. P. R. , Srivastava H. C.
Published: November 2006

The starch‐epichlorohydrin (ECH) reaction follows second order kinetics, first order with respect to ECH as well as starch. The activation energy for the reaction is of the order of 38 kJ/mole and the temperature coefficient K323/K303 is of the order of 2.
Stärken und ihre Hydrolysate als pharmazeutische Hilfsstoffe. Teil 1: Früherer Stand und Entwicklungstendenzen
Authors: Schierbaum Friedrich , Vorwerg Waltraud
Published: November 2006

Ausgehend von einer zusammenfassenden übersicht über den frühen Stand der Stärkeanwendung, datierend bis in die 70er Jahre, werden allgemeine Entwicklungstendenzen der stofflichen Basis und ausgewählte Anwendungen bis zur Gegenwart aufgezeigt. Einen Schwerpunkt bilden dabei die Struktur‐Eigenschaftsbeziehungen pharmazeutischer Hilfsstoffe. Sie leiten auf die Betrachtung ausgewählter alpha‐Glucane als aktuelle und potentielle Wirkstoffträger, Stabilisatoren und Plasmaexpander über.
Efficiency of Recrystallization Methods for the Purification of β‐Cyclodextrin
Authors: Li Wende , Corke Harold , Zhang Litian
Published: November 2006

Cyclodextrins are an important class of products made from starch, and have many applications in the food and other industries. Among the cyclodextrins, β‐cyclodextrin (β‐CD) is the most important and is produced in the largest amount. Some commercial preparations of β‐CD contain contaminants which must be eliminated to enhance the purity of the product. The purity of β‐CD was increased by four different methods, i.e. recrystallization in water, and purification with isopropanol, cyclohexane, or isopropanol and cyclohexane. Purity of β‐CD following the isopropanol method was over 99%, but the yield was only 40%. After cyclohexane treatment or the combined treatment with isopropanol and cyclohexane, purity was also over 99%, but yield was over 60%. Contaminants in commercial β‐CD may be soluble or insoluble. Some contaminants would be bound in the inclusion cavity, and elimination of such contaminants by recrystallization in water was not successful. The purity and endothermic energy changes of β‐CD were also determined by differential scanning calorimetry.
Explaining trust in political institutions: Some illustrations from the Baltic states
Authors: Lühiste Kadri
Published: November 2006

An important precondition of successful democratic consolidation is voters’ confidence that political institutions do not abuse their privileged position of power. Seeking to identify variables that explain trust in political institutions, the paper tests different theories of institutional trust with individual-level survey data from Estonia, Latvia and Lithuania. Building on prior research, two competitive theories—the cultural and performance explanation—are identified and tested, while also controlling for the effects of party preference, ethnicity, and socio-demographic factors. The results show that both cultural and performance variables influence citizens’ trust in political institutions. In other words, institutional trust depends on how much the individual trusts other people as well as on how well they believe the economic and the political system to function. Besides cultural and performance variables, most control variables also proved to be significantly associated with institutional trust, confirming the need to include correct control variables in models of institutional trust.
Outbreak of norovirus illness associated with a swimming pool
Authors: PODEWILS L. J. , ZANARDI BLEVINS L. , HAGENBUCH M. , ITANI D. , BURNS A. , OTTO C. , BLANTON L. , ADAMS S. , MONROE S. S. , BEACH M. J. , WIDDOWSON M.
Published: November 2006

On 3 February 2004, the Vermont Department of Health received reports of acute gastroenteritis in persons who had recently visited a swimming facility. A retrospective cohort study was conducted among persons attending the facility between 30 January and 2 February. Fifty-three of 189 (28%) persons interviewed developed vomiting or diarrhoea within 72 h after visiting the facility. Five specimens tested positive for norovirus and three specimen sequences were identical. Entering the smaller of the two pools at the facility was significantly associated with illness (RR 5·67, 95% CI 1·5–22·0,P=0·012). The investigation identified several maintenance system failures: chlorine equipment failure, poorly trained operators, inadequate maintenance checks, failure to alert management, and insufficient record keeping. This study demonstrates the vulnerability of recreational water to norovirus contamination, even in the absence of any obvious vomiting or faecal accident. Our findings also suggest that norovirus is not as resistant to chlorine as previously reported in experimental studies. Appropriate regulations and enforcement, with adequate staff training, are necessary to ensure recreational water safety.
Neue Möglichkeiten in der pränatalen Diagnostik
Authors: Lapaire  , Holzgreve  , Miny  , Hösli  , Hahn  , Tercanli
Published: November 2006

Mit den technischen Entwicklungen erweiterten sich in den letzten Jahren die Einsatzmöglichkeiten des pränatalen Ultraschalls. So konnten in den 80er und 90er-Jahren zunehmend fetale Fehlbildungen diagnostiziert und spezifiziert werden. Die Untersuchung mit der sonographischen Nackentransparenzmessung in der 11. bis 14. Schwangerschaftswoche findet nunmehr als wichtiges pränatales Screening zur individuellen Risikoabschätzung für Chromosomenstörungen Eingang in die pränatale Medizin. Neben der standardisierten Untersuchungstechnik sollte größter Wert auf die ausführliche Information und Beratung der Schwangeren sowie auf die Qualitätssicherung gelegt werden. Durch die Verbesserung der individuellen Risikospezifizierung mittels Sonographie, biochemischen Markern und dem mütterlichen Alter können unnötige invasive Untersuchungen vermieden und ihre Zahl insgesamt deutlich reduziert werden. Ein Trend, der sich auch anhand des nicht-invasiven Nachweises des fetalen Rhesus D Status und mit dem Einsatz der Dopplersonographie im Management fetaler Anämien verfolgen lässt.
Einstellungen zu Sterben und Tod im höheren und hohen Lebensalter
Authors: Wittkowski Joachim
Published: November 2006

Zusammenfassung: Der Artikel behandelt konzeptionelle Strukturierungen, Theoriebildung, Untersuchungsverfahren und Forschungsergebnisse zu Einstellungen gegenüber Sterben und Tod bei alten Menschen. Im Einzelnen werden die Dimensionen “Angst” und “Akzeptieren” der Einstellung gegenüber Sterben und Tod mit ihren jeweiligen Komponenten, ein umfassender und ein integrativer theoretischer Ansatz zur Erklärung der Angst vor dem Tod im höheren und hohen Lebensalter, deutschsprachige Verfahren zur Messung der Einstellungen gegenüber Sterben und Tod sowie Ergebnisse zu den Korrelaten “Alter”, “Geschlecht”, “Institutionalisierung”, “körperliche und psychische Beeinträchtigung”, “Ich-Integrität” und “Religiosität” vorgestellt. Der Beitrag schließt mit Schlussfolgerungen in sechs Punkten.
A model‐based interpretation of low‐frequency changes in the carbon cycle during the last 120,000 years and its implications for the reconstruction of atmospheric Δ14C
Authors: Köhler Peter , Muscheler Raimund , Fischer Hubertus
Published: November 2006

A main caveat in the interpretation of observed changes in atmospheric Δ14C during the last 50,000 years is the unknown variability of the carbon cycle, which together with changes in the 14C production rates determines the 14C dynamics. A plausible scenario explaining glacial/interglacial dynamics seen in atmospheric CO2 and δ13C was proposed recently (Köhler et al., 2005a). A similar approach that expands its interpretation to the 14C cycle is an important step toward a deeper understanding of Δ14C variability. This approach is based on an ocean/atmosphere/biosphere box model of the global carbon cycle (BICYCLE) to reproduce low‐frequency changes in atmospheric CO2 as seen in Antarctic ice cores. The model is forced forward in time by various paleoclimatic records derived from ice and sediment cores. The simulation results of our proposed scenario match a compiled CO2 record from various ice cores during the last 120,000 years with high accuracy (r2 = 0.89). We analyze scenarios with different 14C production rates, which are either constant or based on 10Be measured in Greenland ice cores or the recent high‐resolution geomagnetic field reconstruction GLOPIS‐75 and compare them with the available Δ14C data covering the last 50,000 years. Our results suggest that during the last glacial cycle in general less than 110‰ of the increased atmospheric Δ14C is based on variations in the carbon cycle, while the largest part (5/6) of the variations has to be explained by other factors. Glacial atmospheric Δ14C larger than 700‰ cannot not be explained within our framework, neither through carbon cycle‐based changes nor through variable 14C production. Superimposed on these general trends might lie positive anomalies in atmospheric Δ14C of ∼50‰ caused by millennial‐scale variability of the northern deep water production during Heinrich events and Dansgaard/Oeschger climate fluctuations. According to our model, the dominant processes that increase glacial Δ14C are a reduced glacial ocean circulation (+∼40‰), a restricted glacial gas exchange between the atmosphere and the surface ocean through sea ice coverage (+∼20‰), and the enrichment of dissolved inorganic carbon with 14C in the surface waters through isotopic fractionation during higher glacial marine export production caused by iron fertilization (+∼10‰).
Derivation of neutral oxygen density under charge exchange in the midlatitude topside ionosphere
Authors: Waldrop L. S. , Kudeki E. , González S. A. , Sulzer M. P. , Garcia R. , Butala M. , Kamalabadi F.
Published: November 2006

We describe a new technique to derive neutral atomic oxygen density, [O], in the upper thermosphere using coincident incoherent scatter radar (ISR) and airglow emission observations from Arecibo Observatory. The technique exploits the nearly resonant charge exchange coupling between neutral and ionized hydrogen and oxygen that serves as the dominant chemical source and sink of protons near and above the F region peak. Under charge exchange production and loss of H+, the proton continuity equation can be solved for [O] using twilight H density profiles derived from measured H emission brightness at 656.3 nm together with ion density, temperature, and flux obtained simultaneously by the Arecibo ISR. We present both equilibrium and nonequilibrium solutions for [O] between 500 and 1500 km during a single quiescent nighttime interval under moderate solar activity. Comparisons with theoretical expectations and with MSIS‐model calculations of O density are used to identify the altitude and local time extent over which the technique is justified. These comparisons generally support technique validity between ∼600 and 800 km, where sufficient reactant densities are present to validate the charge exchange formulation of the continuity equation. Equilibrium solutions for [O] near 650–700 km exhibit excellent agreement with MSIS estimates before midnight, but deviations arising from ion transport become increasingly significant both above this height and as dawn approaches. Incorporation of measured proton flux gradients into the nonequilibrium solutions improves agreement between the derived and modeled estimates significantly after midnight, while the minor nonequilibrium contributions during several hours before midnight lend additional support for the presence of charge exchange equilibrium.
Paleomagnetic study of the Great Foum Zguid dyke (southern Morocco): A positive contact test related to metasomatic processes
Authors: Silva P. F. , Henry B. , Marques F. O. , Madureira P. , Miranda J. M.
Published: November 2006

When a paleomagnetic pole is sought for in an igneous body, the host rocks should be subjected to a contact test to assure that the determined paleopole has the age of the intrusion. If the contact test is positive, it precludes the possibility that the measured magnetization is a later effect. Therefore, we investigated the variations of the remanent magnetization along cross‐sections of rocks hosting the Foum Zguid dyke (southern Morocco) and the dyke itself. A positive contact test was obtained, but it is mainly related with Chemical/Crystalline Remanent Magnetization due to metasomatic processes in the host‐rocks during magma intrusion and cooling, and not only with Thermo‐Remanent Magnetization as ordinarily assumed in standard studies. Paleomagnetic data obtained within the dyke then reflect the Earth magnetic field during emplacement of this well‐dated (196.9 ± 1.8 Ma) intrusion.
Quantifying recent pyroclastic and lava flows at Arenal Volcano, Costa Rica, using medium‐footprint lidar
Authors: Hofton M. A. , Malavassi E. , Blair J. B.
Published: November 2006

Arenal volcano is a small, active stratovolcano in Costa Rica. In 1998 and 2005, NASA's Laser Vegetation Imaging Sensor (LVIS) was used to collect wide‐swath 3‐dimensional topographic images of the volcano. The LVIS is a full‐waveform, scanning, medium‐sized footprint, airborne laser altimeter system. By digitally recording the shape of the returning laser pulse (waveform), the LVIS provides a precise and accurate view of both the sub‐canopy and canopy‐top topographies as well as the vertical and horizontal structure of vegetation at 15–25 m horizontal resolution. By comparing georeferenced waveform data collected in 1998 and 2005, we mapped lava and pyroclastic flows deposited during this period. The active crater grew by 3.82 m yr−1. A flow volume estimate of 2.19 × 107 m3 (Dense Rock Equivalent of 1.89 × 107 m3 or 0.085 m3s−1) was obtained for the period 1998 to 2005. Precise elevation and elevation change data such as those provided by the LVIS are essential to calculate eruption volume and to study magma‐supply dynamics, as well as assess the danger posed by the volcano to the local population from hazards such as pyroclastic flows.
A global study of nighttime midlatitude topside spread echoes
Authors: Earle G. D. , Musumba A. M. , McClure J. P.
Published: November 2006

Range spreading is frequently evident in midlatitude topside ionograms from the ISS‐B satellite. These ionograms provide a geographically unbiased perspective for the first global investigation of nighttime spread echo events that focuses solely on the midlatitude domain. The topside echo occurrence probability data show significant longitudinal variations, along with very large winter/equinox asymmetries in several geographic regions. The spread echoes are divided into two types and found to have different geophysical dependences. Small‐scale events that appear as spreading in one or two consecutive ionograms have a marked seasonal dependence on magnetic declination and no obvious correlation with auroral indices. Larger‐scale events in which the spreading is observed over spatial domains of 1000 km or more have less dependence on magnetic declination but are anticorrelated with the AE index in periods 6–8 hours prior to their appearance. The declination dependence for the small‐scale events suggests that the irregularities are most prevalent when the E region conductivity is low at both ends of the flux tube. This in turn suggests that electric fields mapping from the E region up to F region altitudes are likely involved in their generation. The correlation of the larger‐scale events with depressed AE signatures suggests that traveling ionospheric disturbances caused by auroral heating are not the most likely cause of these large features at midlatitudes.
East‐west and vertical spectral asymmetry associated with equatorial type I waves during strong electrojet conditions: 1. Pohnpei radar observations
Authors: Choudhary R. K. , St.‐Maurice J.‐P. , Ecklund Warner L. , Tsunoda Roland T.
Published: November 2006

We have studied a particularly strong vertical type I event with the equatorial Pohnpei radar. During that event, which lasted several hours, we routinely obtained type I waves in radar beams pointed vertically as well as at 14.3 degrees east and west of vertical. This data set has allowed us to revisit the question of the equatorial electrojet east‐west and up‐down asymmetries. These asymmetries are known to favor downshifted waves during the daytime electrojet. In our study we have contrasted type I spectra obtained simultaneously in the east and west beams, in addition to analyzing upshifted and downshifted waves in the vertical beam data. We have found that when the echoes become particularly strong, both the east‐west and up‐down power asymmetries may not only vanish but can even reverse their signs. Furthermore, these tendencies occur simultaneously in the east‐west and up‐down asymmetries. Finally, we have noted that the power asymmetry is accompanied by an asymmetry in type I Doppler shifts, which is only clearly visible, however, when the overall echo power is weaker.
Throwing light on DARC
Authors: Pruenster M. , Rot A.
Published: November 2006

Chemokines play a key role in directing and driving leucocyte trafficking. The efficient regulation of leucocyte recruitment by chemokines requires their appropriate localization in functional micro-anatomical domains, as well as setting limits to their effects in space and time. Both processes are influenced by silent chemokine receptors (interceptors), including DARC (Duffy antigen receptor for chemokines). Increasing experimental evidence suggests that DARC is involved in accumulation of extravascular chemokines in endothelial cells, chemokine transcytosis and presentation on their luminal surface, leading to leucocyte adhesion and emigration. Additionally, DARC is expressed on erythrocytes and can act as a sink for chemokines in blood. This limits the dissemination of chemokines through blood into distant organs and tissues as well as reducing their effects on the circulating leucocytes.
Recent structural studies of RNA polymerases II and III
Authors: Cramer P.
Published: November 2006

Here, I review three new structural studies from our laboratory. First, the crystal structure of RNA polymerase (Pol) II in complex with an RNA inhibitor revealed that this RNA blocks transcription initiation by preventing DNA loading into the active-centre cleft. Secondly, the structure of the SRI (Set2 Rpb1-interacting) domain of the histone methyltransferase Set2 revealed a novel fold for specific interaction with the doubly phosphorylated CTD (C-terminal repeat domain) of Pol II. Finally, we obtained the first structural information on Pol III, in the form of an 11-subunit model obtained by combining a homology model of the nine-subunit core enzyme with a new X-ray structure of the subcomplex C17/25.
A second paradigm for gene activation in bacteria
Authors: Buck M. , Bose D. , Burrows P. , Cannon W. , Joly N. , Pape T. , Rappas M. , Schumacher J. , Wigneshweraraj S. , Zhang X.
Published: November 2006

Control of gene expression is key to development and adaptation. Using purified transcription components from bacteria, we employ structural and functional studies in an integrative manner to elaborate a detailed description of an obligatory step, the accessing of the DNA template, in gene expression. Our work focuses on a specialized molecular machinery that utilizes ATP hydrolysis to initiate DNA opening and permits a description of how the events triggered by ATP hydrolysis within a transcriptional activator can lead to DNA opening and transcription. The bacterial EBPs (enhancer binding proteins) that belong to the AAA+ (ATPases associated with various cellular activities) protein family remodel the RNAP (RNA polymerase) holoenzyme containing the σ54 factor and convert the initial, transcriptionally silent promoter complex into a transcriptionally proficient open complex using transactions that reflect the use of ATP hydrolysis to establish different functional states of the EBP. A molecular switch within the model EBP we study [called PspF (phage shock protein F)] is evident, and functions to control the exposure of a solvent-accessible flexible loop that engages directly with the initial RNAP promoter complex. The σ54 factor then controls the conformational changes in the RNAP required to form the open promoter complex.
Regulation of splicing-associated SR proteins by HPV-16
Authors: Mole S. , Veerapraditsin T. , McPhillips M.G. , Graham S.V.
Published: November 2006

HPV-16 (human papillomavirus type 16) is a small dsDNA (double-stranded DNA) virus which infects mucosal epithelial tissue of the cervix. Epithelial tissue is composed of a basal layer of cells, capable of division, and a number of suprabasal layers, wherein the cells become more differentiated the closer to the surface of the epithelium they become. Expression of viral proteins is dependent upon epithelial differentiation status, and, within the HPV-16 genome, several elements have been found which control expression both transcriptionally and post-transcriptionally. Expression of the highly immunogenic capsid proteins, L1 and L2, is restricted to only the most differentiated cells, where immune surveillance is limited. However, L1 and L2 transcripts can be detected in less differentiated cells, suggesting post-transcriptional mechanisms exist to prevent their expression in these cells. Indeed, a number of cis-acting RNA elements have been observed within the HPV-16 late region which may be involved in control of capsid gene expression. Mechanisms controlling HPV-16 capsid gene expression and the cellular RNA-processing factors involved will be the focus of this article.
The transmissible spongiform encephalopathies: emerging and declining epidemics
Authors: Manson J.C. , Cancellotti E. , Hart P. , Bishop M.T. , Barron R.M.
Published: November 2006

TSEs (transmissible spongiform encephalopathies) are neurodegenerative diseases of various mammalian species, the best known of which include BSE (bovine spongiform encephalopathies) in cattle, CJD (Creutzfeldt–Jakob disease) in humans, scrapie in sheep and CWD (chronic wasting disease) in deer. This review examines the emergence of various TSE strains and their transmission, and discusses disease surveillance and control.
Cytochrome P450 subfamily CYP710A genes encode sterol C-22 desaturase in plants
Authors: Morikawa T. , Mizutani M. , Ohta D.
Published: November 2006

Sterols are isoprenoid-derived lipids that are produced via the mevalonate pathway and are involved in various cellular functions in eukaryotes such as maintenance of membrane integrity and biosynthetic precursors of steroid hormones. Among cellular sterols, Δ22-sterols containing a double bond at C-22 in the sterol side chain specifically occur in fungi (ergosterol) and plants (stigmasterol and brassicasterol), and several lines of experimental evidence have suggested specific physiological roles of Δ22-sterols in plants. Fungal cytochrome P450 (P450), CYP61, has been established as the sterol C-22 desaturase functioning at the penultimate step in the ergosterol biosynthetic pathway. On the other hand, no particular sequence has been assigned as to the enzyme responsible for the introduction of the double bond into the sterol side chain in plants. In this review, we summarize our recent findings demonstrating that CYP710A P450 family genes encode the plant sterol C-22 desaturases to produce stigmasterol and brassicasterol/crinosterol from β-sitosterol and 24-epi-campesterol respectively.
Control of neuronal excitability by phosphorylation and dephosphorylation of sodium channels
Authors: Scheuer T. , Catterall W.A.
Published: November 2006

Currents through voltage-gated sodium channels drive action potential depolarization in neurons and other excitable cells. Smaller currents through these channels are key components of currents that control neuronal firing and signal integration. Changes in sodium current have profound effects on neuronal firing. Sodium channels are controlled by neuromodulators acting through phosphorylation of the channel by serine/threonine and tyrosine protein kinases. That phosphorylation requires specific molecular interaction of kinases and phosphatases with the channel molecule to form localized signalling complexes. Such localization is required for effective neurotransmitter-mediated regulation of sodium channels by protein kinase A. Analogous molecular complexes between sodium channels, kinases and other signalling molecules are expected to be necessary for specific and localized transmitter-mediated modulation of sodium channels by other protein kinases.
A new approach for the investigation of reperfusion-related brain injury
Authors: Maier C.M. , Hsieh L. , Crandall T. , Narasimhan P. , Chan P.H.
Published: November 2006

Effective stroke therapies require recanalization of occluded cerebral blood vessels; however, early reperfusion can cause BBB (blood–brain barrier) injury, leading to cerebral oedema and/or devastating brain haemorrhage. These complications of early reperfusion, which result from excess production of ROS (reactive oxygen species), significantly limit the benefits of stroke therapies. Here, we summarize some of the findings that lead to the development of a novel animal model that facilitates identification of specific free radical-associated components of the reperfusion injury process and allows therapeutic interventions to be assessed. In this model, KO (knockout) mice containing 50% activity of the mitochondrial antioxidant manganese-SOD (superoxide dismutase) (SOD2-KO) undergo transient focal ischaemia followed by reperfusion. These animals have delayed (>24 h) BBB breakdown associated with activation of matrix metalloproteinase-9, inflammation and a high brain haemorrhage rate. These adverse consequences are absent from wild-type littermates, SOD2 overexpressors and minocycline-treated SOD2-KO animals. In addition, using microvessel isolations following in vivo ischaemia/reperfusion, we were able to show that the tight junction membrane protein, occludin, is an early and specific target in ROS-mediated microvascular injury. This new model is ideal for studying ischaemia/reperfusion-induced vascular injury and secondary brain damage and offers a unique opportunity to evaluate free radical-based neurovascular protective strategies.
Photoelectron imaging of large anionic methanol clusters: (MeOH)n− (n∼70–460)
Authors: Kammrath Aster , Verlet Jan R. R. , Griffin Graham B. , Neumark Daniel M.
Published: November 2006

Electron solvation in methanol anion clusters, (MeOH)n− (n∼70–460), is studied by photoelectron imaging. Two isomers are observed: methanol I, with vertical binding energies (VBE) ranging from 2–2.5eV, and methanol II, with much lower VBE’s between 0.2 and 0.5eV. The VBE’s of the two isomers depend linearly on n−1∕3 with nearly identical slopes. We propose that the excess electron is internally solvated in methanol I clusters, whereas in methanol II it resides in a dipole-bound surface-state. Evidence of an excited state accessible at 1.55eV is observed for methanol I.
Band lineup of pseudomorphic GaAs1−xSbx quantum-well structures with GaAs, GaAsP, and InGaP barriers grown by metal organic chemical vapor deposition
Authors: Noh M. S. , Ryou J. H. , Dupuis R. D. , Chang Y.-L. , Weissman R. H.
Published: November 2006

We report the growth of thin pseudomorphic GaAs1−xSbx (x∼0.3) quantum-well heterostructures by metal-organic chemical vapor deposition and the measurement of the band lineups for the heterointerface of GaAs1−xSbx (x∼0.3) quantum wells with GaAs, GaAs0.86P0.14, and In0.5Ga0.5P quantum-well barriers for 80Å double-quantum-well heterostructures using excitation-dependent cathodoluminescence measurements at 10K. GaAs1−xSbx (x∼0.3) quantum wells with GaAs and GaAs0.86P0.14 barriers show type-II band alignment, while GaAs1−xSbx (x∼0.3) quantum wells with In0.5Ga0.5P barriers exhibit a type-I band lineup. The type-I/type-II band alignment boundary condition as a function of the GaAs1−xSbx quantum-well composition and of the barrier materials and compositions is calculated. The pseudomorphic GaAs1−xSbx∕GaAs quantum-well heterointerface is estimated to have a type-II alignment. For GaAs1−xSbx∕GaAsP and GaAs1−xSbx∕InGaP heterostructures, both type-I and type-II alignments can occur depending on the quantum-well and barrier compositions. As the Sb composition of the quantum well increases, higher P alloy composition (in GaAsP barriers) and Ga (in InGaP barriers) composition are required in order to make the type-II to type-I transition.
Modeling the accelerated cyclic annealing kinetics
Authors: Krishnan Karthik , Sahay Satyam S. , Singh Sanjeev , Pal Deepankar
Published: November 2006

Cyclic thermal processing results in accelerated kinetics [Sahay et al. Acta Mater. 51, 339 (2003)], with significant impact on the productivity and energy consumption. Considering the commercial significance of thermal processing operations, it is imperative that the mechanism of such behavior be understood and quantitatively modeled. In the present work, the cyclic annealing kinetics has been quantitatively modeled by incorporating an additional nonisothermal rate constant to the Arrhenius equation. The model closely describes the experimental recrystallization and grain growth kinetics data carried out under cyclic conditions.
Second-harmonic spectroscopy of surface immobilized gold nanospheres above a gold surface supported by self-assembled monolayers
Authors: Tsuboi Kazuma , Abe Shinya , Fukuba Shinya , Shimojo Masayuki , Tanaka Miyoko , Furuya Kazuo , Fujita Katsuhiko , Kajikawa Kotaro
Published: November 2006

We have investigated linear and nonlinear optical properties of surface immobilized gold nanospheres (SIGNs) above a gold surface with a gap distance of a few nanometers. The nanogap was supported by amine or merocyanine terminated self-assembled monolayers (SAMs) of alkanethiolates. A large second-harmonic generation (SHG) was observed from the SIGN systems at localized surface plasmon resonance condition. The maximum enhancement factor of SHG intensity was found to be 3×105 for the SIGN system of nanospheres 100nm in diameter with a gap distance of 0.8nm. The corresponding susceptibility was estimated to be χ(2)=750pm∕V (1.8×10−6esu). In the SIGN system supported with the merocyanine terminated SAMs, the SHG response was also resonant to the merocyanine in the nanogap. It was found that the SHG response of the SIGN systems is strongly frequency dependent. This leads us to conclude that the large χ(2) is caused by enhanced electric fields at the localized surface plasmon resonance condition and is not due to an increase of the surface susceptibility following from the presence of the gold nanospheres. The observed SHG was consistent with the theoretical calculations involving Fresnel correction factors, based on the quasistatic approximation.
In situ x-ray diffraction study of the size dependent thermal expansion of silver nanowires
Authors: Xu Xi Jin , Fei Guang Tao , Yu Wen Hui , Zhang Li De , Ju Xin , Hao Xiao Peng , Wang Dan Ni , Wang Bao Yi
Published: November 2006

The thermal expansion of as-prepared and annealed silver nanowires embedded in anodic alumina membranes with different diameters was studied by in situ x-ray diffraction in the temperature range from 25to800°C. For both the as-prepared and annealed samples, the coefficients of thermal expansion have “V” shape change as the diameters increase; and the minimum values of the coefficients of thermal expansion do not correspond to the same diameters of nanowires. The collective effects of the surface tension, the limit effects of anodic alumina membrane, and the vacancies incorporated into the silver lattice were responsible for the thermal expansion.
Optical characterization of digital alloy In0.49Ga0.51P∕In0.49(Ga0.6Al0.4)0.51P multi-quantum-wells grown by molecular beam epitaxy
Authors: Kim J. M. , Park C. Y. , Lee Y. T. , Song J. D.
Published: November 2006

An In0.49Ga0.51P∕In0.49(Ga0.6Al0.4)0.51P multi-quantum-well (MQW) structure grown by molecular beam epitaxy using a digital alloy method was parametrically investigated by photoluminescence (PL) measurement performed in a temperature range of 10–290K. The PL peak energies did not change with increasing temperature up to 60K, while the PL peak energy monotonously decreased with increasing temperature beyond 60K. From the curve fit of the linewidth full width at half maximum of the PL peak, it was observed that the homogeneous broadening of In0.49Ga0.51P∕In0.49(Ga0.6Al0.4)0.51P MQW with digital alloy barriers due to scattering by longitudinal optical phonons was smaller than that of InGaAs∕InGaAlAs MQW with digital alloy barriers. This is in accordance with the existence of a relatively weak phonon-related PL peak in the PL spectrum of InGaAlP digital alloy, as compared with InGaAlAs digital alloy. The fit of the integrated PL intensity shows the occurrence of a nonradiative recombination process with an activation energy E1=24.4meV up to 60K. On the other hand, the process of nonradiative recombination with an activation energy E2=109meV occurred above 60K, which is in good agreement with one-half of the calculated total confinement energy ΔE of the electron-hole pair in the quantum well (∼108meV). The In0.49Ga0.51P∕In0.49(Ga0.6Al0.4)0.51P MQW structure with digital alloy barriers has larger activation energy (E2=109meV) than In0.49Ga0.51P∕In0.49(Ga0.6Al0.4)0.51P MQW (E2=90meV) with analog alloy barriers. Therefore, the thermal emission of carriers into the barrier can be reduced at temperatures above 60K due to the high effective barrier height.
Time-resolved postdischarge absolute silicon monoxide density measurement by resonant absorption spectroscopy in a nonthermal atmospheric plasma
Authors: Motret Olivier , Coursimault Fabien , Pouvesle Jean-Michel
Published: November 2006

In this study we present the technique of resonant absorption spectroscopy diagnostic developed to estimate the density of silicon monoxide (SiO) molecules during the postdischarge of an atmospheric dielectric barrier discharge plasma. The ultraviolet (0,0) rovibrational band of the SiO(AΠ1-XΣ+1) electronic transition was investigated. Effective values of absorption coefficient and absorption cross section for the rotational transitions under consideration were calculated. The SiO concentration was estimated by comparison between experimental and computed spectra. The self-absorption in the probe reactor was taken into account in the computed spectra.
Drawing suspended polymer micro-/nanofibers using glass micropipettes
Authors: Nain Amrinder S. , Wong Joanna C. , Amon Cristina , Sitti Metin
Published: November 2006

This letter proposes a method for fabricating suspended micro-/nanoscale polymer fibers continuously, in which polymeric micro-/nanofibers are formed by drawing and solidification of a viscous liquid polymer solution which is pumped through a glass micropipette. By controlling the drawing parameters, this method is demonstrated to form networks of suspended fibers having amorphous internal structure and uniform diameters from micrometers down to sub-50-nm for different molecular weights of polystyrene dissolved in xylene.
Relaxor behavior in CaCu3Ti4O12 ceramics
Authors: Ke Shanming , Huang Haitao , Fan Huiqing
Published: November 2006

The dielectric properties of CaCu3Ti4O12 (CCTO) ceramics have been investigated in a temperature range of 143–573K and a frequency range of 1Hz–10MHz. A dielectric anomaly has been observed between 350 and 600K. The broad dielectric peaks in ε′(T) can be well fitted by a modified Curie-Weiss law and a Vogel-Fulcher relationship, which is indicative of a relaxor ferroelectric behavior. A slim I-V loop as well as the P-E hysteresis loop and broad maxima in ε″(f) also suggest the existence of a relaxor ferroelectric behavior in CCTO ceramics.
Accurate modeling of copper precipitation kinetics including Fermi level dependence
Authors: Guo Hsiu-Wu , Dunham Scott T.
Published: November 2006

Copper is one of the most important contaminants for silicon electronics, and it has detrimental effects on device performance if present in active regions. In this work, the authors investigate copper precipitation models including Fermi level dependence that provide the foundation for simulating copper diffusion and precipitation processes in silicon. These models are verified by comparison to experimental measurements.
Investigation of carrier dynamics on InAs quantum dots embedded in InGaAs∕GaAs quantum wells based on time-resolved pump and probe differential photoluminescence
Authors: Mu Xiaodong , Ding Yujie J. , Ooi Boon S. , Hopkinson Mark
Published: November 2006

The authors have introduced a technique to investigate the carrier dynamics of semiconductor nanostructures. Such a technique is based on the measurement of time-resolved differential photoluminescence spectra induced by subpicosecond pump and probe laser pulses by adjusting the temporal delay between them. Their results obtained on the InAs quantum dots embedded in InGaAs∕GaAs quantum wells using such a technique indicate that the exciton decay time, integrated photoluminescence intensity, and photoluminescence linewidth exhibit unique dependences on temperature.
Equilibrium adsorption on single and aggregated nanospheres
Authors: Nie Chu , Marlow W. H.
Published: November 2006

The mean field density functional theory has been used to explore Ar adsorption onto single and double identical carbon dioxide nanospheres. We have studied adsorption from subsaturation up to saturation at several temperatures. For the single sphere case, the adsorption excesses and density profiles approach those of plane cases as the spherical substrate size increases; at each temperature, the transition from thin-film to thick-film adsorption is strongly dependent on the size of substrate and the adsorption behavior approaches to that of a plane when the substrate size goes to a large value. For the double sphere case, the cluster formed within the region analogous to the pendular region formed by two contacting identical nanospheres of radius of 1.7nm has also been studied. The two sphere structure favorites the cluster forming in the interstitial region but does not affect the adsorption transition.
Synergistic precipitation strengthening in TiAl alloys
Authors: Karadge M. , Kim Y.-W. , Gouma P. I.
Published: November 2006

Precipitation of creep-life enhancing H carbides and ζ silicides occurring during α2 dissolution in fully lamellar (α2+γ)-TiAl (alloyed with carbon and silicon) were studied by transmission electron microscopy. The α2→(γ+precipitate) transformation reaction consisted of the following sequence: α2 dissolution by ledge mechanism, silicide precipitation at the ledges/interfacial defects, followed by intralamellar H-carbide precipitation in the remainder thin α2 laths. Precipitation of H carbides inside the α2 laths is most likely caused by an uphill diffusion and segregation of carbon ahead of the propagating γ∕α2 interface.
Understanding and predicting the damage performance of KDxH2−xPO4 crystals under simultaneous exposure to 532- and 355-nm pulses
Authors: DeMange P. , Negres R. A. , Rubenchik A. M. , Radousky H. B. , Feit M. D. , Demos S. G.
Published: November 2006

Laser-induced initiation of bulk damage sites in KDxH2−xPO4 crystals is investigated under simultaneous exposure to 532 and 355nm nanosecond laser pulses in order to simulate the operational conditions during harmonic conversion as well as probe the damage mechanisms. The results demonstrate synergetic damage effects under the dual-wavelength excitation. Furthermore, the damage performance is directly related to and can be predicted from the damage performance at each wavelength separately. The measured relative effective absorption coefficients at the two wavelengths are found to depend on the laser fluence.
Buried p-type layers in Mg-doped InN
Authors: Anderson P. A. , Swartz C. H. , Carder D. , Reeves R. J. , Durbin S. M. , Chandril S. , Myers T. H.
Published: November 2006

Variable magnetic field Hall effect, photoluminescence, and capacitance-voltage (CV) analysis have been used to study InN layers grown by plasma assisted molecular beam epitaxy. All three techniques reveal evidence of a buried p-type layer beneath a surface electron accumulation layer in heavily Mg-doped samples. Early indications suggest the Mg acceptor level in InN may lie near 110meV above the valence band maximum. The development of p-type doping techniques offers great promise for future InN based devices.
Highly conductive Sb-doped layers in strained Si
Authors: Bennett N. S. , Cowern N. E. B. , Smith A. J. , Gwilliam R. M. , Sealy B. J. , O’Reilly L. , McNally P. J. , Cooke G. , Kheyrandish H.
Published: November 2006

The ability to create stable, highly conductive ultrashallow doped regions is a key requirement for future silicon-based devices. It is shown that biaxial tensile strain reduces the sheet resistance of highly doped n-type layers created by Sb or As implantation. The improvement is stronger with Sb, leading to a reversal in the relative doping efficiency of these n-type impurities. For Sb, the primary effect is a strong enhancement of activation as a function of tensile strain. At low processing temperatures, 0.7% strain more than doubles Sb activation, while enabling the formation of stable, ∼10-nm-deep junctions. This makes Sb an interesting alternative to As for ultrashallow junctions in strain-engineered complementary metal-oxide-semiconductor devices.
Growth of single-phase In2Se3 by using metal organic chemical vapor deposition with dual-source precursors
Authors: Chang K. J. , Lahn S. M. , Chang J. Y.
Published: November 2006

Single-phase γ-In2Se3 thin films have been prepared by the metal organic chemical vapor deposition technique using dual-source precursors, trimethylindium, and hydrogen selenide to obtain a different VI/III ratio by independent adjustment of the precursors’ flow rate. 2in Si(111) and Si(100) wafers are used as substrates. The films have been characterized by x-ray diffraction and scanning electron microscopy. The single-phase γ-In2Se3 films can be grown on both Si(111) and Si(100) substrates. The optical properties of the films have been studied by photoluminescence measurements. Strong exciton emissions were observed at around 2.14eV at 20K. The band gap of γ-In2Se3 at room temperature is estimated at approximately 1.93eV.
High temperature conductivity studies on nanoscale yttria-doped zirconia thin films and size effects
Authors: Karthikeyan Annamalai , Chang Chia-Lin , Ramanathan Shriram
Published: November 2006

Thin films of 9.5% yttria-doped zirconia in the range of 17–210nm thickness were deposited on MgO (100) substrates by electron beam evaporation. The conductivity of the films was found to increase as the film thickness decreased. The films were found to be a mixture of both cubic and tetragonal phases. The impedance and electrical modulus parameters indicate that the relaxation process is due to ionic conduction. Enhancements in conductivity are attributed to the space charge effects that occur at the interface and grain boundaries as evidenced by the high activation energy observed in the conductivity relaxation process.
Ecological correlates of extra-group paternity in mammals
Authors: Isvaran Kavita , Clutton-Brock Tim
Published: November 2006

Extra-group paternity (EGP) can form an important part of the mating system in birds and mammals. However, our present understanding of its extent and ecology comes primarily from birds. Here, we use data from 26 species and phylogenetic comparative methods to explore interspecific variation in EGP in mammals and test prominent ecological hypotheses for this variation. We found extensive EGP (46% of species showed more than 20% EGP), indicating that EGP is likely to play an important role in the mating system and the dynamics of sexual selection in mammals. Variation in EGP was most closely correlated with the length of the mating season. As the length of the mating season increased, EGP declined, suggesting that it is increasingly difficult for males to monopolize their social mates when mating seasons are short and overlap among females in oestrus is likely to be high. EGP was secondarily correlated with the number of females in a breeding group, consistent with the idea that as female clustering increases, males are less able to monopolize individual females. Finally, EGP was not related to social mating system, suggesting that the opportunities for the extra-group fertilizations and the payoffs involved do not consistently vary with social mating system.
Mycobacterium monacense sp. nov.
Authors: Reischl Udo , Melzl Holger , Kroppenstedt Reiner M. , Miethke Thomas , Naumann Ludmila , Mariottini Alessandro , Mazzarelli Gianna , Tortoli Enrico
Published: November 2006

Four bacterial strains were isolated from independent clinical specimens in different countries and their genotypic and phenotypic characters support their classification in a novel species within the genusMycobacterium. One strain was clearly responsible for a severe, post-traumatic wound infection in a healthy boy. The novel species, for which the nameMycobacterium monacensesp. nov. is proposed, is yellow-pigmented, non-photochromogenic and grows in less than a week on solid medium. Based on phenotypic investigations alone, distinction of these four strains from known scotochromogenic rapidly growing strains is problematic. However, the novel strains differ from any other mycobacterium in each of the molecular species markers investigated: the 16S rRNA gene, the 16S–23S rRNA gene internal transcribed spacer and thehsp65gene. Of the strains investigated, two different sequevars were detected for thehsp65region. Phylogenetic analysis revealed that these four strains were most closely related toMycobacterium doricum. The type strain ofMycobacterium monacensesp. nov. is B9-21-178T(=DSM 44395T=CIP 109237T).
Implications of mitochondrial DNA polyphyly in two ecologically undifferentiated but morphologically distinct migratory birds, the masked and white‐browed woodswallows Artamus spp. of inland Australia
Authors: Joseph Leo , Wilke Thomas , Ten Have José , Terry Chesser R.
Published: November 2006

The white‐browed woodswallow Artamus superciliosus and masked woodswallow A. personatus (Passeriformes: Artamidae) are members of Australia's diverse arid‐ and semi‐arid zone avifauna. Widely sympatric and among Australia's relatively few obligate long‐distance temperate‐tropical migrants, the two are well differentiated morphologically but not ecologically and vocally. They are pair breeders unlike other Artamus species, which are at least facultative cooperative breeders. For these reasons they are an excellent case in which to use molecular data in integrative study of their evolution from ecological and biogeographical perspectives. We used mitochondrial DNA (mtDNA) to test whether they are each other's closest relatives, whether they evolved migration independently, whether they have molecular signatures of population expansions like some other Australian arid zone birds, and to estimate the timing of any inferred population expansions. Their mtDNAs are monophyletic with respect to other species of Artamus but polyphyletic with respect to each other. The two species appear not to have evolved migration independently of each other but their morphological and mtDNA evolution have been strongly decoupled. Some level of hybridization and introgression cannot be dismissed outright as being involved in their mtDNA polyphyly but incomplete sorting of their most recent common ancestor's mtDNA is a simpler explanation consistent with their ecology. Bayesian phylogenetic inference and analyses of diversity within the two species (n=77) with conventional diversity statistics, statistical parsimony, and tests for population expansion vs stability (Tajima's D, Fu's Fs and Ramos‐Onsin and Rozas's R2) all favour recent population increases. However, a non‐starlike network suggests expansion(s) relatively early in the Pleistocene. Repeated population bottlenecks corresponding with multiple peaks of Pleistocene aridity could explain our findings, which add a new dimension to accruing data on the effects of Pleistocene aridity on the Australian biota.