bluuebunny/crossref_metadata_2025 huggingface dataset:
Accumulation pattern of toxin β-ODAP during lifespan and effect of nutrient elements on β-ODAP content in Lathyrus sativus seedlings
Authors: JIAO CHENG-JIN , XU QUAN-LE , WANG CHONG-YING , LI FENG-MIN , LI ZHI-XIAO , WANG YA-FU
Published: July 2006

In order to assess the influence of nutrient elements on the accumulation of β-N-oxalyl-L-α, β-diaminopropionic acid (β-ODAP; the probable cause of lathyrism) in Lathyrus sativus L. (grass pea), it was first examined under field conditions during the lifespan of a grass pea plant using high-performance liquid chromatography (HPLC). β-ODAP mainly accumulated in young seedlings, in developing and mature seeds and in young leaves, especially in young seedlings. In contrast, all mature leaves, roots, and stems showed a low level of β-ODAP. The β-ODAP accumulation pattern in seedlings grown in a nutrient-deficient solution was highest (3·57 mg/g) in shoots at 7 d growing in the nitrogen-deficient solution and higher compared to the control (2·31 mg/g) in zinc-, calcium-, phosphorus- and molybdenum-deficient shoots (P<0·05). The contents of β-ODAP in seedlings growing in other element-deficient solutions were similar to controls. When the content of β-ODAP in grass pea seedlings fertilized with different forms of organic nitrogen was assayed the results indicated that amino acids such as glutamine and serine, as well as nucleotide nitrogen, all significantly enhanced the accumulation of β-ODAP in young seedlings relative to controls (P<0·05). Taken together, these data suggest that β-ODAP accumulation in grass pea might be related to the level of total free nitrogenous compounds and that nitrogen and phosphate may be the crucial nutrient factors influencing β-ODAP content under field conditions. Thus, the application of appropriate nitrogen and phosphorus fertilizers to the soil could decrease the content of β-ODAP in the seeds and leaves of grass pea.
Effects of intercropping tomato (Lycopersicon esculentum) at different times with cowpea (Vigna unguiculata) or okra (Abelmoschus esculentus) on crop damage by major insect pests
Authors: PITAN OLUFEMI O. R. , OLATUNDE G. O.
Published: July 2006

Two 2-year field trials were conducted in Nigeria to investigate the effectiveness of tomato intercropped at different times with cowpea or okra in controlling the field densities of cowpea pod-sucking bugs and okra flea beetles. The two experiments were arranged as split-plots within a randomized complete block design. The main plots were 4-week-old tomato seedlings transplanted into a field, with cowpea or okra intercropped at 0, 2 or 4 weeks after transplanting tomatoes, while the two sub-plots were cowpea or okra sole crop and tomato/cowpea or tomato/okra intercrop. The densities of the pod-sucking bugs Clavigralla tomentosicollis, Riptortus dentipes, Anoplocnemis curvipes and Nezara viridula were significantly lower (P<0·05) on cowpea intercropped at 2 weeks after transplanting tomatoes than those obtained in the sole crop. Similarly, cowpea seed damage was significantly lower (P<0·05) on cowpea planted at 2 and 4 weeks after transplanting tomatoes than in the monocrop and when cowpea and tomato were planted simultaneously. Cowpea yields were influenced by both time of intercropping and cropping system; in the intercrop, the highest yield was obtained at 2 weeks after transplanting tomatoes. In the tomato/okra intercrop, the numbers of flea beetles (Podagrica spp.) were significantly influenced (P<0·05) by cropping system alone; their density was significantly lower (P<0·05) in the intercrop than in the sole crop irrespective of time of intercropping. Similarly, damage was significantly higher (P<0·05) in the sole crop than in the intercrop while yield comparable to that of the monocrop was obtained at 2 WAT. The highest land equivalent ratio (LER) for cowpea (1·8 and 1·6) or okra (0·7 and 0·8) was obtained at 2 weeks after transplanting tomatoes in both years. Two weeks after tomato establishment appeared to be the best time to introduce either cowpea or okra into the cropping system.
The Clarifying Reagent, or how to make the analysis of milk and dairy products easier
Authors: Humbert Gérard , Guingamp Marie-France , Linden Guy , Gaillard Jean-Luc
Published: July 2006

Difficulties with the analysis of opaque milk and dairy products can be resolved by rendering the sample transparent. This allows direct photometric measurements of the reaction mixtures, and all sample pre-treatment steps become unnecessary. For this, several reagents have been reported in literature. Among them, the ‘Clarifying Reagent’ is mainly described here: its composition is given because it is now released from patenting restrictions. Its main property is a low absorbance between 340 and 800 nm. So it can be used in many chemical and enzymatic colorimetric measurements for estimating the quality of milk and dairy products.
A novel technique for differentiation of proteins in the development of acid gel structure from control and heat treated milk using confocal scanning laser microscopy
Authors: Dubert-Ferrandon Alix , Niranjan Keshaven , Grandison Alistair S
Published: July 2006

The incorporation of caseins and whey proteins into acid gels produced from unheated and heat treated skimmed milk was studied by confocal scanning laser microscopy (CSLM) using fluorescent labelled proteins. Bovine casein micelles were labelled using Alexa Fluor 594, while whey proteins were labelled using Alexa Fluor 488. Samples of the labelled protein solutions were introduced into aliquots of pasteurised skim milk, and skim milk heated to 90 °C for 2 min and 95 °C for 8 min. The milk was acidified at 40 °C to a final pH of 4·4 using 20 g glucono-delta-lactone/l (GDL). The formation of gels was observed with CSLM at two wavelengths (488 nm and 594 nm), and also by visual and rheological methods. In the control milk, as pH decreased distinct casein aggregates appeared, and as further pH reduction occurred, the whey proteins could be seen to coat the casein aggregates. With the heated milks, the gel structure was formed of continuous strands consisting of both casein and whey protein. The formation of the gel network was correlated with an increase in the elastic modulus for all three treatments, in relation to the severity of heat treatment. This model system allows the separate observation of the caseins and whey proteins, and the study of the interactions between the two protein fractions during the formation of the acid gel structure, on a real-time basis. The system could therefore be a valuable tool in the study of structure formation in yoghurt and other dairy protein systems.
Interactions between EPS-producing Streptococcus thermophilus strains in mixed yoghurt cultures
Authors: Folkenberg Ditte M , Dejmek Petr , Skriver Anne , Ipsen Richard
Published: July 2006

Mixed cultures of different EPS-producing Streptococcus thermophilus strains in combination with a Lactobacillus delbrueckii subsp. bulgaricus strain with negligible EPS-production were used for yoghurt production. The yoghurt texture was characterised with respect to sensory, rheological and microstructural properties and the EPS-concentrations were determined. The cultures resulted in yoghurts with highly different texture properties, and positive interactions between certain Streptococcus thermophilus strains were observed. The underlying properties of yoghurt texture are multidimensional, but a number of microstructural characteristics were apparent in the yoghurts with the highest mouth thickness, creaminess and viscosity. A strong protein network, not too dense and with medium size pores containing EPS, seems associated with these properties. The presence of capsular polysaccharides (CPS) also appeared to be beneficial as did a combination of EPS types, which were distributed differently in the protein network (in serum pores, respectively in association with protein). Obviously, a certain concentration of EPS must be present to provide for these effects on yoghurt texture, but other factors than concentration per se seem more important.
Disrupting life events and the sleep-wake cycle in depression
Authors: HAYNES PATRICIA L. , McQUAID JOHN R. , ANCOLI-ISRAEL SONIA , MARTIN JENNIFER L.
Published: July 2006

Background. Social rhythm disruption life events are significant predictors of mood relapse in bipolar patients. However, no research has examined the relationship between these events and their hypothesized mechanism of action: disrupted sleep-wake patterns. The goal of this study was to test whether participants with major depressive disorder have a greater disruption of daily sleep and motor activity following disrupting life events when compared to normal controls.

Method. Over the course of 2 weeks, 39 normal controls and 39 individuals with major depressive disorder completed life events interviews and wore actigraphs to obtain estimates of sleep/wake activity.

Results. Statistically significant interactions indicated that the presence of at least one disrupting life event in the previous 4 months correlated with elevations in the amount of time spent awake after sleep onset [β=0·45, ΔF(1,73)=4·80, p<0·05], and decreases in the percentage of time spent asleep [β=−0·53, ΔF(1,73)=6·57, p<0·05], in depressed individuals but not in normal controls.

Conclusions. The results indicated that depressed individuals may be more susceptible to the effects of life events on sleep than normal controls. This is the first study to date to correlate life events with objective measures of sleep. However, prospective longitudinal research is necessary to clarify the temporal relationship among these variables.
English in a multilingual Spain
Authors: Reichelt Melinda
Published: July 2006

IN RECENT years an increasing amount of literature has become available regarding the learning and use of English in a wide range of contexts, notably including continental Europe: cf. Berns 1995; Cenoz & Jessner 2000; Dushku 1998; Fonzari 1999; McCallen 1991; O'Reilly 1998; Petzold & Berns 2000; Phillipson & Skutnab-Kangas 1997; Schleppegrell 1991; and Van Essen 1997. However, little recent published work has explored the role of the language in Spain. The information provided here is based on on-site investigation, interviews with English teachers and other language specialists in Spain, and an examination of relevant curricular documents and other published sources. The aim of the article is to cover three areas in particular: the history of English in Spain; its current status in the nation's multilingual context; and the learning and teaching of the language nationwide of proficiency.
‘I'm not west. I'm not east. So how leh?’
Authors: Ho Debbie G. E.
Published: July 2006

WHILE recent articles and research studies on Singapore Colloquial English (SCE, or simply ‘Singlish’) have so far tended to focus on the structure, grammar and the functional roles of Singlish in Singapore, this paper presents an insider's viewpoint of this local variety from a perspective that incorporates both linguistic ideology and cultural politics. Focusing on the spoken version at the basilectal end of the English speech continuum, the article attempts to explore Singlish from a cultural-political viewpoint and challenges popular belief that Singlish encapsulates an established Singapore identity. In the process, it throws up some insights about language, identity and culture. Based on two significant contributing factors to the unmarked use of Singlish in Singapore, the paper argues that – more than just a language used for wider intra-communication in this tiny republic and city state – this variety, with its odd mix of English and local ethnic languages, mirrors a people who find themselves struggling with a myriad conflicting and contrasting cultures, a people in cultural and linguistic flux, who are still searching – desperately – for an identity, and a language they can call their own.
Making fine-grained and coarse-grained sense distinctions, both manually and automatically
Authors: PALMER MARTHA , DANG HOA TRANG , FELLBAUM CHRISTIANE
Published: July 2006

In this paper we discuss a persistent problem arising from polysemy: namely the difficulty of finding consistent criteria for making fine-grained sense distinctions, either manually or automatically. We investigate sources of human annotator disagreements stemming from the tagging for the English Verb Lexical Sample Task in the SENSEVAL-2 exercise in automatic Word Sense Disambiguation. We also examine errors made by a high-performing maximum entropy Word Sense Disambiguation system we developed. Both sets of errors are at least partially reconciled by a more coarse-grained view of the senses, and we present the groupings we use for quantitative coarse-grained evaluation as well as the process by which they were created. We compare the system's performance with our human annotator performance in light of both fine-grained and coarse-grained sense distinctions and show that well-defined sense groups can be of value in improving word sense disambiguation by both humans and machines.
Modeling future glacier mass balance and volume changes using ERA‐40 reanalysis and climate models: A sensitivity study at Storglaciären, Sweden
Authors: Radić Valentina , Hock Regine
Published: July 2006

Modeling the response of glaciers to future climate change is important for predicting changes in global sea level rise and local water resources. We compute until the year 2100 the mass balance and volume evolution of Storglaciären, a small valley glacier in Sweden, using a temperature index mass balance model. We focus on the sensitivity of results to the choice of climate model and variants of adjusting ERA‐40 temperatures to local conditions. ERA‐40 temperature and precipitation series from 1961 to 2001 are validated and used both as input to the mass balance model and for statistical downscaling of one regional and six global climate models (GCMs). Future volume projections are computed using area‐volume scaling and constant glacier area. ERA‐40 data correlate well with observations and capture observed interannual variability of temperature and precipitation. The mass balance model driven by several variants of ERA‐40 input performs similarly well regardless of temporal resolution of the input series (daily or monthly). The model explains ∼70% of variance of measured mass balance when the input temperatures are reduced by the lapse rate that maximizes model performance. Fitting ERA‐40 temperatures to observations close to the glacier does not improve the performance of the model, leading us to conclude that ERA‐40 can be used for mass balance modeling independent of meteorological observations. Projected future volume series show a loss of 50–90% of the initial volume by 2100. The differences in volume projections vary by 40% of the initial volume for six different GCMs input to mass balance model, while each volume projection varies by 20% depending on whether volume‐area scaling or constant area is used and by 10% depending on details in the mass balance model used. The correction of biases in the seasonal temperature cycle of the GCMs with respect to the ERA‐40 data is crucial for deriving realistic volume evolution. Static mass balance sensitivities to temperature and precipitation change in the 21st century are −0.48 m yr−1 K−1 and 0.025 m yr−1 per % increase, respectively.
Aerosol chemistry and climate: Laboratory studies of the carbonate component of mineral dust and its reaction products
Authors: Gibson Elizabeth R. , Hudson Paula K. , Grassian Vicki H.
Published: July 2006

The hygroscopicity, cloud condensation nucleation (CCN) activity and infrared optical extinction of CaCO3, a reactive component of mineral dust aerosol, and Ca(NO3)2, a product of atmospherically‐aged CaCO3 through reaction with nitrogen oxides, have been measured. The hygroscopic growth and CCN activity of Ca(NO3)2 are orders of magnitude greater than CaCO3 and more similar to ammonium sulfate. Ca(NO3)2 particles also reflect a greater amount of near infrared radiation at higher relative humidity. These measurements provide the first quantitative assessment of the important changes in climate forcing that can occur as mineral dust aerosol is transported, reacted and aged in the atmosphere.
Strong spatial variability of snow accumulation observed with helicopter‐borne GPR on two adjacent Alpine glaciers
Authors: Machguth H. , Eisen O. , Paul F. , Hoelzle M.
Published: July 2006

This study compares high‐resolution helicopter‐borne radar measurements to extensive ground‐based profiling of the snow cover on Findel‐ and Adler Glacier, Switzerland. The results demonstrate that derived accumulation values of either method are well in accordance. The spatial distribution of radar based snow depth allows a clear distinction of three zones of different accumulation characteristics: (1) The lower part of Findel Glacier shows a clear altitudinal trend while (2) the upper part has no trend in altitude but high spatial fluctuations in snow depth. (3) Adler Glacier's accumulation characteristics are similar to zone (2). However, despite their close vicinity, accumulation on (3) is reduced by 40% compared to (2). The observed strong spatial variability emphasises the need for spatially continuous measurements for studies involving accumulation on glaciers. Finally, reasons for observed variations (e.g., preferential snow deposition and snow redistribution) are discussed.
Solar control of radar wave absorption by the Martian ionosphere
Authors: Morgan D. D. , Gurnett D. A. , Kirchner D. L. , Huff R. L. , Brain D. A. , Boynton W. V. , Acuña M. H. , Plaut J. J. , Picardi G.
Published: July 2006

The MARSIS active sounder aboard the Mars Express spacecraft, under certain conditions in the Martian ionosphere, fails to detect the planetary surface. We have generated a statistical measure of the surface reflection visibility, which we plot as a time series and compare with both in situ particle data taken at Mars and solar x‐ray data taken at Earth. We show that loss of the surface signal is closely related to the influx of solar protons at tens of MeV energies. We infer that the influx of high energy solar protons causes impact ionization, increasing the electron density in the Martian ionosphere. At altitudes close to or below 100 km, where the electron‐neutral collision frequency is high and the electron density typically has a local maximum, the increased electron density raises the damping coefficient to levels sufficient for complete absorption of the sounding wave over an altitude range of a few tens of kilometers.
Energy Metabolism in Astrocytes: High Rate of Oxidative Metabolism and Spatiotemporal Dependence on Glycolysis/Glycogenolysis
Authors: Hertz Leif , Peng Liang , Dienel Gerald A
Published: July 2006

Astrocytic energy demand is stimulated by K+ and glutamate uptake, signaling processes, responses to neurotransmitters, Ca2+ fluxes, and filopodial motility. Astrocytes derive energy from glycolytic and oxidative pathways, but respiration, with its high-energy yield, provides most adenosine 5' triphosphate (ATP). The proportion of cortical oxidative metabolism attributed to astrocytes (~30%) in in vivo nuclear magnetic resonance (NMR) spectroscopic and autoradiographic studies corresponds to their volume fraction, indicating similar oxidation rates in astrocytes and neurons. Astrocyte-selective expression of pyruvate carboxylase (PC) enables synthesis of glutamate from glucose, accounting for two-thirds of astrocytic glucose degradation via combined pyruvate carboxylation and dehydrogenation. Together, glutamate synthesis and oxidation, including neurotransmitter turnover, generate almost as much energy as direct glucose oxidation. Glycolysis and glycogenolysis are essential for astrocytic responses to increasing energy demand because astrocytic filopodial and lamellipodial extensions, which account for 80% of their surface area, are too narrow to accommodate mitochondria; these processes depend on glycolysis, glycogenolysis, and probably diffusion of ATP and phosphocreatine formed via mitochondrial metabolism to satisfy their energy demands. High glycogen turnover in astrocytic processes may stimulate glucose demand and lactate production because less ATP is generated when glucose is metabolized via glycogen, thereby contributing to the decreased oxygen to glucose utilization ratio during brain activation. Generated lactate can spread from activated astrocytes via low-affinity monocarboxylate transporters and gap junctions, but its subsequent fate is unknown. Astrocytic metabolic compartmentation arises from their complex ultrastructure; astrocytes have high oxidative rates plus dependence on glycolysis and glycogenolysis, and their energetics is underestimated if based solely on glutamate cycling.
TWEAK—Fn14 Pathway Inhibition Protects the Integrity of the Neurovascular Unit during Cerebral Ischemia
Authors: Zhang Xiaohui , Winkles Jeffrey A , Gongora Maria C , Polavarapu Rohini , Michaelson Jennifer S , Hahm Kyungmin , Burkly Linda , Friedman Meyer , Li Xiao-Jiang , Yepes Manuel
Published: July 2006

Tumor necrosis factor-like weak inducer of apoptosis (TWEAK) is a member of the tumor necrosis factor superfamily. TWEAK acts via binding to a cell surface receptor named Fn14. To study the role of this cytokine in the regulation of the permeability of the neurovascular unit (NVU) during cerebral ischemia, TWEAK activity was inhibited in wild-type mice with a soluble Fn14-Fc decoy receptor administered either immediately or 1 h after middle cerebral artery occlusion (MCAO). Administration of Fn14-Fc decoy resulted in faster recovery of motor function and a 66.4%±10% decrease in Evans blue dye extravasation when treatment was administered immediately after MCAO and a 46.1%±13.1% decrease when animals were treated 1 h later ( n=4, P<0.05). Genetic deficiency of Fn14 resulted in a 60%±12.8% decrease in the volume of the ischemic lesion ( n=6, P<0.05), and a 87%±22% inhibition in Evans blue dye extravasation 48 h after the onset of the ischemic insult ( n=6, P<0.005). Compared with control animals, treatment with Fn14-Fc decoy or genetic deficiency of Fn14 also resulted in a significant inhibition of nuclear factor-κB pathway activation, matrix metalloproteinase-9 activation and basement membrane laminin degradation after MCAO. These findings show that the cytokine TWEAK plays a role in the disruption of the structure of the NVU during cerebral ischemia and that TWEAK antagonism is a potential therapeutic strategy for acute cerebral ischemia.
Stroke Induces Gene Profile Changes Associated with Neurogenesis and Angiogenesis in Adult Subventricular Zone Progenitor Cells
Authors: Liu Xian Shuang , Zhang Zheng Gang , Zhang Rui Lan , Gregg Sara , Morris Daniel C , Wang Ying , Chopp Michael
Published: July 2006

Neural progenitor cells in the subventricular zone (SVZ) of the lateral ventricular wall give rise to new neurons throughout rodent life. Ischemic stroke induces angiogenesis and neurogenesis. Using laser capture microdissection (LCM) in combination with microarrays containing approximately 400 known genes associated with stem cells and angiogenesis, we investigated gene profiles of SVZ cells in the adult mouse subjected to middle cerebral artery occlusion. Our data revealed that nonstroke SVZ cells expressed sets of genes that are important for neural progenitor cell proliferation, differentiation, and migration. In addition, stroke SVZ cells expressed many genes involved in neurogenesis during embryonic development but were not detected in nonstroke SVZ cells. Stroke upregulated genes were verified by real-time reverse transcriptase-polymerase chain reaction and immunostaining. These data indicate that adult SVZ cells recapture embryonic molecular signals after stroke and provide insight into the molecular mechanisms, which regulate the biological function of neural progenitor cells in the SVZ of adult rodent brain under physiological and stroke conditions.
Free fall plasma-arc reactor for synthesis of carbon nanotubes in microgravity
Authors: Alford J. M. , Mason G. R. , Feikema D. A.
Published: July 2006

High temperatures inside the plasma of a carbon arc generate strong buoyancy driven convection which has an effect on the growth and morphology of the single-walled carbon nanotubes (SWNTs). To study the effect of buoyancy on the arc process, a miniature carbon arc apparatus was designed and developed to synthesize SWNTs in a microgravity environment substantially free from buoyant convective flows. An arc reactor was operated in the 2.2 and 5.18s drop towers at the NASA Glenn Research Center. The apparatus employed a 4mm diameter anode and was powered by a portable battery pack capable of providing in excess of 300A at 30V to the arc for the duration of a 5s drop. However, the principal result is that no dramatic difference in sample yield or composition was noted between normal gravity and 2.2 and 5s long microgravity runs. Much longer duration microgravity time is required for SWNT’s growth such as the zero-G aircraft, but more likely will need to be performed on the international space station or an orbiting spacecraft.
La
0.7
Sr
0.3
Mn
O
3
nanoparticles coated with fatty amine
Authors: Rajagopal Rajashree , Mona J. , Kale S. N. , Bala Tanushree , Pasricha Renu , Poddar P. , Sastry M. , Prasad B. L. V. , Kundaliya Darshan C. , Ogale S. B.
Published: July 2006

We report on the synthesis of La0.7Sr0.3MnO3 (LSMO) nanoparticles having perovskite structure and particle size of the order of 30nm. The process involves citrate-gel synthesis, size filtering, and surface coating with a shell of octadecyl amine (ODA) using electrostatic interaction-assisted novel chemical route. Magnetic measurements show the Curie temperature of ∼360K establishing the desired stoichiometry and phase. Fourier transform infrared studies bring out that the amine group of ODA interacts with the LSMO surface. Refluidization yields uniform redispersion of the coated and dried powder.
Phase space quantization and the operator moment problem
Authors: Kiukas J. , Lahti P. , Ylinen K.
Published: July 2006

We consider questions related to a quantization scheme in which a classical variable f:Ω→R on a phase space Ω is associated with a (preferably unique) semispectral measure Ef, such that the moment operators of Ef are required to be of the form Γ(fk), with Γ a suitable mapping from the set of classical variables to the set of (not necessarily bounded) operators in the Hilbert space of the quantum system. In particular, we investigate the situation where the map Γ is implemented by the operator integral with respect to some fixed positive operator measure. The phase space Ω is first taken to be an abstract measurable space, then a locally compact unimodular group, and finally R2, where we determine explicitly the relevant operators Γ(fk) for certain variables f, in the case where the quantization map Γ is implemented by a translation covariant positive operator measure. In addition, we consider the question under what conditions a positive operator measure is projection valued.
Investigation of field emission properties of carbon nanotube arrays defined using nanoimprint lithography
Authors: Vieira Sara M. C. , Teo Kenneth B. K. , Milne William I. , Gröning Oliver , Gangloff Laurent , Minoux Eric , Legagneux Pierre
Published: July 2006

We demonstrate the use of nanoimprint lithography as an alternative low-cost fabrication route for the production of ordered arrays of individual carbon nanotube field emitters. A high emission site density of 4×105cm−2 was observed and is well within the specification of the cathode for a field emission display. The measured field enhancement values from the geometry of the nanotubes were in reasonable agreement with the values obtained through electrical measurements. We also show that the distribution of the field enhancement factor is Gaussian, indicative of the presence of well ordered arrays of carbon nanotube field emitters.
Spin-orbit mechanism of predissociation in the Wulf band of ozone
Authors: Grebenshchikov S. Yu. , Qu Z.-W. , Zhu H. , Schinke R.
Published: July 2006

Previously calculated resonance widths of the ground vibrational levels in the electronic states 1A″3 (A23) and 1A′3 (B23), which belong to the Wulf band system of ozone, are significantly smaller than observed experimentally. We demonstrate that predissociation is drastically enhanced by spin-orbit coupling between 1A″3∕XA′1 and 1A′3∕1A″3. Multistate quantum mechanical calculations using ab initio spin-orbit coupling matrix elements give linewidths of optically bright components of the right order of magnitude.
Technique for measuring D2 pellet mass loss through a curved guide tube using two microwave cavity detectors
Authors: Combs S. K. , Caughman J. B. O. , Wilgen J. B.
Published: July 2006

Two microwave cavity mass detectors have been used to measure the mass loss of deuterium (D2) pellets transported through a curved guide tube. The test tube was a mock-up of the pellet injection guide tube for the proposed ITER experiment, which will be used to transport pellets, including deuterium-tritium (D-T), from the pellet acceleration device to the inner wall (or magnetic high-field side) of the large tokamak for pellet injection and core fueling of plasmas. An accurate estimate of the mass loss is particularly important for D-T injection, because the inventory of the radioactive isotope (T) for ITER is limited and accountability and recycling will be crucial issues. In the laboratory, frozen cylindrical D2 pellets of nominal 5.3-mm diameter were shot through the stainless steel test tube (≈10m in length and 10-mm inside diameter), with each end equipped with a microwave cavity. As the pellet passes through each tuned microwave cavity, the peak output signal from the electronics is directly proportional to the pellet mass. An absolute calibration of the cavities, which can be problematic, is not needed for the nondestructive technique described here. Instead, a cross calibration of the two cavities with pellets of varying masses provides the relationship to determine mass loss more precisely than any other technique previously reported. In addition, the individual output signals from the cavities can be used to identify intact pellets (a single signal peak) or broken pellets (multiple signal peaks). For the pellet speed range tested in this study (100–500m∕s), the mass loss for intact pellets was directly dependent on the pellet speed, with ≈10% mass loss at 300m∕s. The microwave cavities and the associated electronics, as well as some basic theory, are described; calibration and experimental data are presented and discussed.
Controlled blueshift of the resonant wavelength in porous silicon microcavities using ion irradiation
Authors: Mangaiyarkarasi D. , Breese M. B. H. , Ow Y. S. , Vijila C.
Published: July 2006

High-energy focused proton beam irradiation has been used to controllably blueshift the resonant wavelength of porous silicon microcavities in heavily doped p-type wafers. Irradiation results in an increased resistivity, hence a locally reduced rate of anodization. Irradiated regions are consequently thinner and of a higher refractive index than unirradiated regions, and the microcavity blueshift arises from a net reduction in the optical thickness of each porous layer. Using this process wafers are patterned on a micrometer lateral scale with microcavities tuned to different resonant wavelengths, giving rise to high-resolution full-color reflection images over the full visible spectrum.
Impact of gate materials on positive charge formation in HfO2∕SiO2 stacks
Authors: Zhao C. Z. , Zhang J. F. , Zahid M. B. , Groeseneken G. , Degraeve R. , De Gendt S.
Published: July 2006

The use of metal gates removes gate depletion and allows aggressive downscaling of equivalent oxide thickness. The impact of changing gate from poly-Si to metal on device reliability has not been fully addressed. This work focuses on how TaN gate affects the positive charge formation in HfO2∕SiO2 stacks. Under positive gate bias stresses, the results show that positive charge formation in metal-gated samples is significantly higher than in poly-Si gated samples. However, positive charge formation is similar in these two types of samples, when stressed under negative gate bias. The results are explained by assuming that there are more hydrogenous species at the metal/dielectric interface and the hydrogen release from the anode dominates the positive charge formation. The behavior of positive charges in the stack is also compared with that in a single SiO2 layer.
Relevance of the parallel nonlinearity in gyrokinetic simulations of tokamak plasmas
Authors: Candy J. , Waltz R. E. , Parker S. E. , Chen Y.
Published: July 2006

The influence of the parallel nonlinearity on transport in gyrokinetic simulations is assessed for values of ρ* which are typical of current experiments. Here, ρ*=ρs∕a is the ratio of gyroradius, ρs, to plasma minor radius, a. The conclusion, derived from simulations with both GYRO [J. Candy and R. E. Waltz, J. Comput. Phys., 186, 585 (2003)] and GEM [Y. Chen and S. E. Parker J. Comput. Phys., 189, 463 (2003)] is that no measurable effect of the parallel nonlinearity is apparent for ρ*<0.012. This result is consistent with scaling arguments, which suggest that the parallel nonlinearity should be O(ρ*) smaller than the E×B nonlinearity. Indeed, for the plasma parameters under consideration, the magnitude of the parallel nonlinearity is a factor of 8ρ* smaller (for 0.000 75<ρ*<0.012) than the other retained terms in the nonlinear gyrokinetic equation.
Enhanced voltage-current characteristics of GaN nanowires treated by a selective reactive ion etching
Authors: Jeon D. Y. , Kim K. H. , Park S. J. , Huh J. H. , Kim H. Y. , Yim C. Y. , Kim G. T.
Published: July 2006

In characterizing the electrical properties of individual NWs (nanowires), the amorphous oxide layer on the surface of NWs is known to limit the electrical conductivity owing to the contact barriers between metal electrodes and NWs. To remove the native oxide layer, a systematic reactive ion etching (RIE) was performed, resulting in a gradual decrease of the diameters of NWs. Voltage-current characteristics of the GaN NW devices treated by tuning the RIE process were improved as reflected by a 1000 times increase in conductance, which was in turn attributed to the removal of the thick (d∼3.5nm) contact barrier formed by the native oxide layer.
Investigation of multilayer electronic vertically coupled InAs∕GaAs quantum dot structures using surface photovoltage spectroscopy
Authors: Chan C. H. , Chen H. S. , Kao C. W. , Hsu H. P. , Huang Y. S. , Wang J. S.
Published: July 2006

Using room-temperature surface photovoltage spectroscopy, we have characterized several 30-layer stacked self-assembled InAs∕GaAs quantum dot (QD) structures with different spacer layer (SL) thicknesses. Signals from every relevant portion of the samples, including QDs, wetting layer, and GaAs barrier have been observed. The strain-induced field for thinner SL is responsible for a significant modification of the band structure, possibly resulting in the appearance of an additional excited state lying higher than the second excited QD state. A peculiar feature below the fundamental transition is tentatively attributed to the optical absorption from uncoupled dots of which the density is significantly lower than that of vertically coupled ones. The spectra show blueshifted features with a decrease of the SL thickness, indicating that the materials intermixing between InAs QDs and GaAs SL are strongly driven by strain.
Mapping substrate/film adhesion with contact-resonance-frequency atomic force microscopy
Authors: Hurley D. C. , Kopycinska-Müller M. , Langlois E. D. , Kos A. B. , Barbosa N.
Published: July 2006

We have used contact-resonance-frequency atomic force microscopy techniques to nondestructively image variations in adhesion at a buried interface. Images were acquired on a sample containing a 20nm gold (Au) blanket film on silicon (Si) with a 1nm patterned interlayer of titanium (Ti). This design produced regions of very weak adhesion (Si∕Au) and regions of strong adhesion (Si∕Ti∕Au). Values of the contact stiffness were 5% lower in the regions of weak adhesion. The observed behavior is consistent with theoretical predictions for layered systems with disbonds. Our results represent progress towards quantitative measurement of adhesion parameters on the nanoscale.
Simultaneous formation of visible and ultraviolet random lasings in ZnO films
Authors: Li H. D. , Yu S. F. , Lau S. P. , Leong Eunice S. P.
Published: July 2006

We have demonstrated visible and ultraviolet random laser actions simultaneously from highly disordered ZnO polycrystalline thin films under optical excitation. It is found that the realization of ZnO grain boundaries by thermal annealing can provide sufficient optical gain (i.e., related to deep-defect-level radiative recombination) and coherent feedback to achieve random laser action at visible wavelength. Furthermore, the coexistence of visible and ultraviolet random lasings inside the highly disordered ZnO films is due to the size difference of the random cavities at different wavelengths.
Magnetoresistance in silicon-based semiconductor-metal hybrid structures
Authors: Troup A. S. , Hasko D. G. , Wunderlich J. , Williams D. A.
Published: July 2006

Recent experimental and theoretical studies have shown that nonmagnetic semiconductor-metal hybrid (SMH) structures can exhibit a very large geometrical magnetoresistance response. We report the realization of silicon-based SMH structures where the metal is replaced by metallic silicide, and we identify key process and material requirements. The devices exhibit larger magnetoresistance responses than homogeneous silicon systems, and a finite element model correctly predicts these responses. In particular, it is experimentally verified that the response is further increased by alternating the current leads/voltage probes. Such scalable systems may be used to study the geometrical magnetoresistance in generic SMH structures as carrier transport moves from the diffusive to the ballistic regime.
Anomalous temperature dependence of absorption edge in narrow-gap HgCdTe semiconductors
Authors: Yue Fangyu , Shao Jun , Lü Xiang , Huang Wei , Chu Junhao , Wu Jun , Lin Xingchao , He Li
Published: July 2006

Abnormal temperature dependence of absorption edge is reported for narrow-gap Hg1−xCdxTe semiconductors at low temperature. Infrared absorption spectra are taken for bulk and molecular-beam epitaxial Hg1−xCdxTe, respectively, in the temperature range of 11–300K. The results indicate an abnormal shift of the absorption edge around the temperature range of 30–70K. Analysis suggests that (i) the phenomenon is introduced by Hg vacancies in the samples, of which the energy level locates about 9–12meV above the Hg1−xCdxTe valence band, and (ii) the conventional criterion for the determination of band gap energy, Eg, from absorption spectra is not accurate enough as soon as Hg vacancies exist, especially at a temperature above 77K. It hence provides an explanation why there should exist difference between the cutoff wavelength of the detector and the absorption-edge (Eg) wavelength of the material the detector was made of.
Stabilized switchable “black state” in Mg2NiH4∕Ti∕Pd thin films for optical hydrogen sensing
Authors: Pasturel M. , Slaman M. , Borsa D. M. , Schreuders H. , Dam B. , Griessen R. , Lohstroh W. , Borgschulte A.
Published: July 2006

A triple layer thin film (30nm Mg2Ni∕100nm Ti∕10nm Pd sputtered on glass) switches reversibly from a shiny metallic to a “black” state upon exposure to moderate hydrogen pressure (≈5.103Pa). This black state resembles that obtained in thick Mg2NiHx layers and has the great advantage of being stable and easily controlled. Both the reversible high optical contrast (Rreflective∕Rblack≈10 in the red wavelength range) and the fast kinetics of hydrogen absorption and desorption make this material interesting for applications as optical hydrogen sensors.
When Frames Conflict: Policy Dialogue on Waste
Authors: Saarikoski Heli
Published: July 2006

The author discusses the notion of environmental controversies as frame conflicts through a case study of the waste-policy dialogue in Finland. The argument that intractable policy controversies result from internally consistent but incompatible normative – prescriptive scripts which name and frame problems differently is explored. Different waste-policy frames are identified and it is suggested that these frames do indeed contribute to the stubbornness of on-going debate on incineration versus waste reduction. However, the importance of interest, identities, and ineffectual communication in these controversies is also highlighted, and it is suggested that consensus building can result in practical agreements even in the face of seemingly incompatible frames.
Cell cycle regulator E2F1 modulates angiogenesis via p53-dependent transcriptional control of VEGF
Authors: Qin Gangjian , Kishore Raj , Dolan Christine M. , Silver Marcy , Wecker Andrea , Luedemann Corinne N. , Thorne Tina , Hanley Allison , Curry Cynthia , Heyd Lindsay , Dinesh Deepika , Kearney Marianne , Martelli Fabio , Murayama Toshinori , Goukassian David A. , Zhu Yan , Losordo Douglas W.
Published: July 2006

The transcription factor E2F1 is known to regulate cell proliferation and has been thought to modulate tumorigenesis via this mechanism alone. Here we show that mice deficient in E2F1 exhibit enhanced angiogenesis. The proangiogenic phenotype in E2F1 deficiency is the result of overproduction of vascular endothelial growth factor (VEGF) and is prevented by VEGF blockade. Under hypoxic conditions, E2F1 down-regulates the expression of VEGF promoter activity by associating with p53 and specifically down-regulating expression of VEGF but not other hypoxia-inducible genes, suggesting a promoter structure context-dependent regulation mechanism. We found that the minimum VEGF promoter mediating transcriptional repression by E2F1 features an E2F1- binding site with four Sp-1 sites in close proximity. These data disclose an unexpected function of endogenous E2F1: regulation of angiogenic activity via p53-dependent transcriptional control of VEGF expression.
Cross-species analysis of biological networks by Bayesian alignment
Authors: Berg Johannes , Lässig Michael
Published: July 2006

Complex interactions between genes or proteins contribute a substantial part to phenotypic evolution. Here we develop an evolutionarily grounded method for the cross-species analysis of interaction networks by
alignment
, which maps bona fide functional relationships between genes in different organisms. Network alignment is based on a scoring function measuring mutual similarities between networks, taking into account their interaction patterns as well as sequence similarities between their nodes. High-scoring alignments and optimal alignment parameters are inferred by a systematic Bayesian analysis. We apply this method to analyze the evolution of coexpression networks between humans and mice. We find evidence for significant conservation of gene expression clusters and give network-based predictions of gene function. We discuss examples where cross-species functional relationships between genes do not concur with sequence similarity.
Talking about Work: School Students’ Views on their Paid Employment
Authors: Hobbs Sandy , Stack Niamh , McKechnie Jim , Smillie Lynn
Published: July 2006

Seventy 15‐year‐old students in rural and urban Scottish schools, who had previously answered questionnaires about the extent of their part‐time employment, were interviewed. Work appears to be the norm in their communities, 79 per cent having worked and most of the others anticipating working before leaving school. Although the interviewees’ accounts of their jobs give some support to those who argue that most of the paid employment school students undertake is routine and boring, it was also found that most of the young workers found their work satisfying and believed that their experience of working helped to prepare them for adult life. It is proposed that research on the meaning of employment for school students should be extended and that the self‐report techniques currently employed might be supplemented by observational studies. © 2006 The Author(s). Copyright © 2005 National Children's Bureau.
Joined‐Up Services for Young Children and Their Families: Papering Over the Cracks or Re‐Constructing the Foundations?
Authors: Warin Jo
Published: July 2006

The idea that services can be provided for young children within their families in a seamless way that serves the interests of children and families simultaneously is problematic. A theoretical flaw underpinning the ideal of integrated services is that families are assumed to be homogenous units. This article explores competing goals for children and families by examining data from the evaluation of three Early Excellence Centres in the north of England piloted by the Department for Education and Employment from 1999 to 2002. The article recommends that extended childcare services should be clearly targeted to the needs of the child‐within‐the‐family, thereby providing a clear theoretical foundation for re‐conceptualising joined‐up services. © 2006 The Author(s). Journal compilation © 2006 National Children's Bureau.
Young Carers: Conventional or Exaggerated Levels of Involvement in Domestic and Caring Tasks?
Authors: Warren Janet
Published: July 2006

Historically, research about young carers has focused on defining the tasks and responsibilities undertaken by children caring for ill or disabled family members and the impacts of such care, without reference to the domestic and caring work undertaken by children and young people in families where there are only non‐disabled or well members. This study presents new evidence of what children and young people generally do to assist in the home and examines how the lives of young carers differ from children and young people who are not carers. It concludes by examining the implications of these research findings for evidence‐informed policy and practice. Copyright © 2006 The Author(s). Journal compilation © 2006 National Children's Bureau.
Marker or mediator? The effects of adolescent substance use on young adult educational attainment
Authors: King Kevin M. , Meehan Barbara T. , Trim Ryan S. , Chassin Laurie
Published: July 2006

Aims  We tested the effects of adolescent substance use on college attendance and completion by young adulthood in the context of the behavioral and familial risk factors that influence substance use.

Design, setting and participants  Longitudinal data were collected from a community sample of children of alcoholics (248) and matched controls (206) at three adolescent assessments (µage = 13–15) and a long‐term follow‐up in young adulthood (µage = 25).

Measurements  College attendance and degree completion by age 25 were self‐reported in young adulthood. During adolescence, self‐reports of alcohol and drug use were assessed with log‐transformed quantity/frequency measures; substance use risk factors [e.g. parental monitoring, externalizing and internalizing symptoms and Diagnostic and Statistical Manual version III (DSM‐III) diagnosis of parental alcoholism] were assessed by both self‐ and parent‐report, and adolescent reading achievement was assessed using a standardized assessment of reading achievement (Wide Range Achievement Test).

Findings  Using growth curve modeling, we found that mean levels and growth in adolescent substance use mark, or identify, those adolescents who are at risk for reduced odds of attending and completing college. Moreover, adolescent substance use was not merely a marker of risk, in that growth in drug use (but not alcohol use) significantly mediated the effects of parental alcoholism and early externalizing behavior on later college completion, partially explaining the effects of these risk factors on college completion.

Conclusions  The current study provides evidence for both the marker and the mediator hypotheses, and identifies multiple pathways to higher educational attainment. The findings point to the importance of studying the effects of adolescent substance use in a broader developmental context of its correlated risk factors to specify more effectively the key pathways to later developmental outcomes.