bluuebunny/crossref_metadata_2025_split huggingface dataset:
Scherk‐Schwarz reductions and their quantum moduli space
Authors: Angelantonj C. 
Published: May 2007

AbstractThe one‐loop vacuum energy is computed for a class of perturbative string vacua where supersymmetry is spontaneously broken by a stringy Scherk‐Schwarz deformation. The spectrum of light excitations is tachyon‐free and the generated quantum potential exhibits an anti de Sitter minimum where the geometric moduli are naturally stabilised.
M‐theory compactifications on hyperbolic spaces
Authors: Orlando D. 
Published: May 2007

AbstractNegatively‐curved, maximally symmetric hyperbolic spaces enjoy a number of remarkable properties that can be traced back to Riemannian geometry, group theory and algebraic geometry. In this note we recall some such properties and find Hn as M‐theory solutions. Based on a talk given at the RTN Workshop 2006, Napoli.
Matrix factorizations and D‐branes on K3
Authors: Brunner I. 
Published: May 2007

AbstractWe review the description of D‐branes in Landau Ginzburg models using Matrix Factorizations. A number of simple examples are discussed, the main example being Matrix factorizations for the K3 given by the quartic hypersurface in P3. We discuss deformations of matrix factorizations and their obstructions in simple cases. Based on Brunner et al., J. High Energy Phys. 0606, 015 (2006) [arXiv:hep‐th/0603196].
GaN alternating current light‐emitting device
Authors: Yen Hsi‐Hsuan , Yeh Wen‐Yung , Kuo Hao‐Chung 
Published: May 2007

AbstractWe report a new design of the light‐emitting device which can be operated under alternating current source directly. The new type alternating current driven light‐emitting device (AC LED) can increase the radition area in each bias direction to improve the device efficiency by the Wheatstone Bridge (WB) circuit design. WB‐AC LEDs with different designs were fabricated and the electrical and optical characteristics were measured. It is found that the efficiency of the WB‐AC LED is influenced by the varied area ratio of the rectified microchip to the central one because of the different current density and forward bias of each microchip. Additionally, the relationship between the area ratio of microchips and the wall plug efficiency of the WB‐AC LED has also been discussed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
N‐face high electron mobility transistors with a GaN‐spacer
Authors: Wong M. H. , Rajan S. , Chu R. M. , Palacios T. , Suh C. S. , McCarthy L. S. , Keller S. , Speck J. S. , Mishra U. K. 
Published: May 2007

AbstractN‐face AlGaN (cap)/GaN (channel)/AlGaN (barrier)/GaN (buffer) high electron mobility transistors (HEMTs) provide a simple solution for strong confinement of the two‐dimensional electron gas (2DEG) from the back since carriers are induced on top of the AlGaN barrier. To reduce the adverse effects of random alloy scattering from the AlGaN barrier, an N‐face GaN‐spacer HEMT was designed with an epi‐structure consisting of an AlGaN (cap)/GaN (channel)/AlN/GaN (spacer)/AlGaN (barrier)/GaN (buffer). The 2DEG is confined at the GaN (channel)/AlN interface, while the GaN‐spacer layer separates the 2DEG from the AlGaN barrier. The large polarization‐induced electric field of the AlN and its large conduction band discontinuity with GaN provide strong confinement for good pinch‐off and low output conductance under high electric fields. Up to 20% improvement in electron mobility was measured in these devices. The devices showed a current gain cut‐off frequency (ft) of 24 GHz and power gain cut‐off frequency (fmax) of 44 GHz for a nominal gate length of 0.7 μm. An output power density of 4.5 W/mm was measured at 4 GHz, with 34% power added efficiency and a gain of 10.3 dB at a drain bias of 40 V. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Chemical susceptibility of fullerenes in view of Hartree–Fock approach
Authors: Sheka Elena F. 
Published: May 2007

AbstractConstituting a part of fullerenes odd electrons which are removed from the covalent bonding (Int J Quantum Chem, 2004, 100, 375), effectively unpaired electrons are posed by the singlet instability of the unrestricted Hartree–Fock SCF solution. The feature occurs to be of a particular importance leading to a quantitative description of atomically matched chemical susceptibility of the odd‐electron molecular species via the relevant electron density on atoms. A correct determination of the total number of effectively unpaired electrons ND and its partial density NDA is well provided by the UHF solution. The calculation procedure and the obtained results reliability are justified for a set of diatomic molecules and ethylene. Practically full identity of the distribution of both NDA values and independently calculated free valence over atoms of X60 (X = C, Si) and C70 molecules makes it possible to consider the NDA maps as chemical portraits of the fullerenes. The NDA value is offered to be a quantitative pointer of the atom chemical activity thus highlighting targets, which are the most favorable for addition reactions of any type. Basic grounds for a NDA‐based computational synthesis of the fullerene derivatives are illustrated for initial steps of C60 fluorination. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007
High‐performance liquid chromatography‐diode array detection/electrospray ionization mass spectrometry for the simultaneous analysis of cis‐, trans‐ and dihydro‐2‐glucosyloxycinnamic acid derivatives from Dendrobium medicinal plants
Authors: Yang Li , Nakamura Norio , Hattori Masao , Wang Zhengtao , Bligh S. W. Annie , Xu Luoshan 
Published: May 2007

AbstractSensitive, selective and reliable high‐performance liquid chromatography (HPLC)‐diode array detection (DAD)/electrospray ionization multi‐stage mass spectrometry (ESI‐MSn) methods have been developed for the characterization of nine 2‐glucosyloxycinnamic acid derivatives and quantitative analysis of three of the major 2‐glucosyloxycinnamic acids, cis‐melilotoside, trans‐melilotoside and dihydromelilotoside, present in Dendrobium medicinal plants. The identities of the latter three major 2‐glucosyloxycinnamic acids were confirmed by comparing their retention times, UV and mass spectra with those of the reference standards. The characteristic ESI‐MSn fragmentation patterns of the remaining six 2‐glucosyloxycinnamic acid derivatives, which are similar to the three major compounds, have allowed the putative elucidation of their structures. The concentrations of the cis‐, trans‐ and dihydromelilotosides were simultaneously determined by HPLC/ESI‐MS2 using the multiple reaction monitoring (MRM) mode in extracts of Dendrobium species. The method was validated with respect to the overall intra‐ and inter‐day variation (RSD less than 8%) and the limits of quantification for the cis‐, trans‐ and dihydromelilotosides were 0.09, 0.09 and 0.01 µg/mL, respectively. Copyright © 2007 John Wiley & Sons, Ltd.
Lethal and sublethal responses of an aquatic insect Culex quinquefasciatus (Diptera: Culicidae) challenged with individual and joint exposure to dissolved sodium selenate and methylmercury chloride
Authors: Jensen Peter D. , Sorensen Mary A. , Walton William E. , Trumble John T. 
Published: May 2007

AbstractPollutants rarely occur alone in the natural environment, and few studies have focused on the potential interactions between metals or metalloids. In this study an aquatic insect, the southern house mosquito (Culex quinquefasciatus: Diptera), was used to test the individual and joint effects of dissolved sodium selenate (Se) and methyl mercury chloride (MeHg). We conducted ovipositional preference tests and 14‐day chronic toxicity studies to determine lethal and sublethal responses of C. quinquefasciatus to a range of Se and MeHg concentrations and mixtures. No evidence was found for female ovipositional preference in field trials using artificial ponds. Larvae were more sensitive to MeHg than Se, with LC50 values of 30 μg/L (CI = 28–31 μg/L) and 11 mg/L (CI = 10–12 mg/L) respectively. In addition, larval survival was significantly reduced at concentrations as low as 25 μg/L of MeHg and 8 mg/L of Se. A synergistic interaction was observed in the toxicity of the Se‐MeHg mixtures to C. quinquefasciatus larvae. Larval mosquito survival was significantly reduced at 7.5 μg/L MeHg + 2.75 mg/L Se and an LC50 value of 9 μg/L MeHg + 3.4 mg/L Se was determined for a fixed ratio mixture. The rate of growth of the larvae was analyzed using a Growth Index that provided a sensitive measure of the developmental effects of toxicant exposure. Sodium selenate at concentrations as low as 2 mg/L caused a significant decrease in growth between larvae in treatment versus control solutions after only 4 days. Similarly, MeHg at concentrations as low as 25 μg/L and a Se‐MeHg mixture of 3 μg/L MeHg plus 1.1 mg/L Se caused significant growth reductions after only 2 and 3 days, respectively. These are the first reported survival and developmental data for an aquatic insect exposed to MeHg and Se‐MeHg mixtures. © 2007 Wiley Periodicals, Inc. Environ Toxicol 22: 287–294, 2007.
Effect of di(n‐butyl) phthalate on testicular oxidative damage and antioxidant enzymes in hyperthyroid rats
Authors: Lee Ena , Ahn Mee Young , Kim Hee Jin , Kim In Young , Han Soon Young , Kang Tae Seok , Hong Jin Hwan , Park Kui Lea , Lee Byung Mu , Kim Hyung Sik 
Published: May 2007

AbstractThis study compared the effects of di(n‐butyl) phthalate (DBP) on the oxidative damage and antioxidant enzymes activity in testes of hyperthyroid rats. Hyperthyroidism was induced in pubertal male rats by intraperitoneal injection of triiodothyronine (T3, 10 μg/kg body weight) for 30 days. An oral dose of DBP (750 mg/kg) was administered simultaneously to normal or hyperthyroid (T3) rats over a 30‐day period. No changes in body weight were observed in the hyperthyroid groups (T3, T3 + DBP) compared with controls. There were significantly higher serum T3 levels observed in the hyperthyroid rats than in the control, but the serum thyroid stimulating hormone levels were markedly lower in the hyperthyroid rats. DBP significantly decreased the weight of the testes in the normal (DBP) and hyperthyroid (T3 + DBP) groups. The serum testosterone concentrations were significantly lower in only DBP group. DBP significantly increased the 8‐hydroxy‐2‐deoxyguanosine (8‐OHdG) level in the testes, whereas the DBP‐induced 8‐OHdG levels were slightly higher in T3 + DBP group. Superoxide dismutase and glutathione peroxidase activities were significantly higher in the testes of the DBP or T3 + DBP groups. Catalase (CAT) activity was significantly higher in the DBP treatment group, but the T3 + DBP group showed slightly lower DBP‐induced CAT activity. The testicular expression of thyroid hormone receptor α‐1 (TRα‐1) was significantly higher in the DBP groups, and androgen receptor (AR) expression was not detected in the DBP treatment group. In addition, DBP significantly increased the peroxisome proliferator‐activated receptor‐r (PPAR‐r) levels in the testis. These results suggest that hyperthyroidism can cause a change in the expression level of PPAR‐r in testes, and may increase the levels of oxidative damage induced by the metabolic activation of DBP. © 2007 Wiley Periodicals, Inc. Environ Toxicol 22: 245–255, 2007.
Bioaccumulation and ROS generation in liver of freshwater fish, goldfish Carassius auratus under HC Orange No. 1 exposure
Authors: Sun Yuanyuan , Yin Ying , Zhang Jingfei , Yu Hongxia , Wang Xiaorong 
Published: May 2007

AbstractHC Orange No. 1 (CAS No. 54381‐08‐7, 2‐nitro‐4′‐hydroxydiphenylamine) is used as a color additive in hair dyes. In this study, laboratory experiment was carried out to determine HC Orange No. 1 bioaccumulation and oxidative stress in the liver of freshwater fish, goldfish Carassius auratus. Fish were exposed to different concentrations (0.05, 0.1, 0.2, 0.5, and 1.0 mg/L) of HC Orange No. 1 for 10 days, with one group assigned as control. The accumulation of HC Orange No. 1 in liver increased with the exposure concentration (R2 = 0.94). A secondary spin trapping technique was used followed by electron paramagnetic resonance (EPR) analysis to study the reactive oxygen species (ROS) production. On the basis of the hyperfine splitting constants and shape of the EPR spectrum, the ROS generated in fish liver after exposure was identified as hydroxyl radical (•OH). There is a good correlation between the exposure concentrations and •OH generation (R2 = 0.92). The •OH signal intensity of the EPR spectrum showed a significant increase (P < 0.05) when the HC Orange No. 1 concentration was 1.0 mg/L, compared with that of the control. A good positive relationship (R2 = 0.95) was found between the •OH formation and accumulation level of HC Orange No. 1 in liver. The changes of the activities of catalase (CAT), superoxide dismutase (SOD), glutathione S‐transferase (GST), and contents of reduced glutathione (GSH) were also detected. These observations indicated a possible mechanism of oxidative stress induced by HC Orange No. 1 on fish. © 2007 Wiley Periodicals, Inc. Environ Toxicol 22: 256–263, 2007.
Engineering volatile thiol release in Saccharomyces cerevisiae for improved wine aroma
Authors: Swiegers Jan H. , Capone Dimitra L. , Pardon Kevin H. , Elsey Gordon M. , Sefton Mark A. , Francis I. Leigh , Pretorius Isak S. 
Published: May 2007

AbstractVolatile thiols, such as 4‐mercapto‐4‐methylpentan‐2‐one (4MMP), 3‐mercaptohexan‐1‐ol (3MH) and 3‐mercaptohexyl acetate (3MHA), are among the most potent aroma compounds found in wine and can have a significant effect on wine quality and consumer preferences. At optimal concentrations in wine, these compounds impart flavours of passionfruit, grapefruit, gooseberry, blackcurrant, lychee, guava and box hedge. The enzymatic release of aromatic thiols from grape‐derived, non‐volatile cysteinylated precursors (Cys‐4MMP and Cys‐3MH) and the further modification thereof (conversion of 3MH into 3MHA) during fermentation, enhance the varietal characters of wines such as Sauvignon Blanc. Wine yeast strains have limited and varying capacities to produce aroma‐enhancing thiols from their non‐volatile counterparts in grape juice. Even under optimal fermentation conditions, the most efficient thiol‐releasing Saccharomyces cerevisiae wine strain known realizes less than 5% of the thiol‐related flavour potential of grape juice. The objective of this study was to develop a wine yeast able to unleash the untapped thiol aromas in grape juice during winemaking. To achieve this goal, the Escherichia coli tnaA gene, encoding a tryptophanase with strong cysteine‐β‐lyase activity, was cloned and overexpressed in a commercial wine yeast strain under the control of the regulatory sequences of the yeast phosphoglycerate kinase I gene (PGK1). This modified strain expressing carbon–sulphur lyase activity released up to 25 times more 4MMP and 3MH in model ferments than the control host strain. Wines produced with the engineered strain displayed an intense passionfruit aroma. This yeast offers the potential to enhance the varietal aromas of wines to predetermined market specifications. Copyright © 2007 John Wiley & Sons, Ltd.
A methodology to model spatially distributed uncertainties in thin‐walled structures
Authors: Machina G. , Zehn M.W. 
Published: May 2007

AbstractIn modern engineering structures, light weight and thin walled composite parts play an important role. The thin walled composite and other structural elements show uncertainties in material properties and in geometry (e.g., wall thickness) among other due to the manufacturing process. These uncertainties are generally spatially distributed in nature, which cannot be reduced by any refined discretization. To obtain information about the distribution of system responses, the uncertainties have to be included in the modelling and calculation. The implementation of these parameters into finite element (FE) models requires a statistical approach. From our research and experience, the variogram method is the tool to model different types of spatially distributed uncertainties. However, the application of the variogram approach is quite common procedure in various fields but it is still widely unknown in mechanical engineering. This paper presents some theoretical background for the application of variogram method to thin walled composite and other structures, as basis for the implementation of the simulated parameters into FE models.
Late Holocene environmental reconstruction using cave sediments from Belize
Authors: Polk Jason S. , van Beynen Philip E. , Reeder Philip P. 
Published: May 2007

AbstractCave sediments collected from Reflection Cave on the Vaca Plateau, Belize show variations in the δ13C values of their fulvic acids (FAs), which indicate periods of vegetation change caused by climatic and Maya influences during the late Holocene. The δ13C values range from − 27.11‰ to − 21.52‰, a shift of ∼ 5.59‰, which suggests fluctuating contributions of C3 and C4 plants throughout the last 2.5 ka, with C4 plant input reflecting periods of Maya agriculture. Maya activity in the study area occurred at different intensities from ∼ 2600 cal yr BP until ∼ 1500 cal yr BP, after which agricultural practices waned as the Maya depopulated the area. These changes in plant assemblages were in response to changes in available water resources, with increased aridity leading to the eventual abandonment of agricultural areas. The Ix Chel archaeological site, located in the study area, is a highland site that would have been among the first agricultural settlements to be affected during periods of aridity. During these periods, minimal water resources would have been available in this highly karstified, well-drained area, and supplemental groundwater extraction would have been difficult due to the extreme depth of the water table.
Urine flavonoids and plasma carotenoids in the validation of fruit, vegetable and tea intake during pregnancy in the Norwegian Mother and Child Cohort Study (MoBa)
Authors: Brantsæter Anne Lise , Haugen Margaretha , Rasmussen Salka E , Alexander Jan , Samuelsen Sven Ove , Meltzer Helle Margrete 
Published: May 2007

AbstractObjectiveTo validate a new food-frequency questionnaire (FFQ) for measuring the intake of fruit, vegetables and tea reported by women participating in the Norwegian Mother and Child Cohort Study (MoBa).DesignIntake of fruits, vegetables and tea estimated by the FFQ was compared with urinary flavonoid excretion, plasma carotenoid concentration and intake measured by a 4-day weighed food diary (FD). The triangular method was applied to calculate FFQ validity coefficients using two independent biomarkers.Setting and subjectsOne hundred and nineteen women participating in MoBa.ResultsThe FFQ estimate of fruit intake was significantly correlated with urine phloretin (r = 0.33), citrus fruit/juice with urine hesperetin (r = 0.44), cooked vegetables with plasma α-carotene (r = 0.37), and tea with urine kaempferol (r = 0.41) (P < 0.01 for all). On average, 60% of the participants fell into the same or adjacent quintiles when classified by FFQ and biomarkers. Significant correlations between the FFQ and FD were found for fruit (r = 0.39), vegetables (r = 0.34), juices (r = 0.50) and tea (r = 0.53). The FFQ validity coefficient was 0.65 for citrus fruit/juice and 0.59 for cooked vegetables as calculated by the triangular method.ConclusionsThe validation study shows that the MoBa FFQ can be used to estimate fruit, juice, vegetable and tea intake in pregnant Norwegian women, and to rank individuals within the distribution.
First Report of Citrus Blight in Costa Rica
Authors: Villalobos W. , Moreira L. , Derrick K. S. , Beretta M. J. G. , Rivera C. 
Published: May 2007

Citrus blight (CB), causing a chronic decline of citrus, has been an important disease in Florida for over 100 years. CB was first reported in Brazil in the 1980s and is now responsible for the removal of nearly 10% of the trees from production annually. No causal agent has been identified, but CB has been root-graft transmitted to healthy trees, suggesting that the causal agent is infectious (3). Since 1997, CB symptoms were observed in several groves in northern Costa Rica, the most important citrus area of approximately 25,000 ha. Symptoms observed include a general decline and wilt of the tree canopy, off-color leaves, leaf drop, twig dieback, small fruit, delayed blossom, poor growth, and death. A survey near Guanacaste revealed CB symptoms in 7-yr-old Valencia and Pineapple orange trees (Citrus sinensis (L.) Osbeck) grafted on Carrizo citrange (C. sinensis (L.) Osbeck × Poncirus trifoliata (L.) Raf.) rootstock. Since 1997, 6% of the trees in this area have been replanted annually because of CB symptoms. Similar situations were observed in other groves in the northern citrus area. Dot immunobinding assays (DIBA) (1) were used to detect the P12 protein associated with CB with 20 of 22 trees showing CB-like symptoms giving a positive test. Zinc (Zn) accumulation in trunk wood and water uptake tests were done according to Roistacher (2) in 8 healthy and 20 symptomatic trees which were positive for CB using DIBA. The average Zn concentration of 16 declining trees was 4.6 ± 1.9, whereas the average concentration for 8 healthy trees was 2.0 ± 0.9. The average water uptake in 1 min was 14 ml for healthy trees, and virtually zero for the 20 symptomatic trees. These diagnostic tests confirm the presence of CB in the northern citrus area of Costa Rica, and the surveys indicate the disease is beginning to spread and become economically important. To our knowledge, this is the first report of CB in commercial citrus in Costa Rica. References: (1) K. S. Derrick et al. Plant Dis. 74:168, 1990. (2) C. N. Roistacher. Pages 57–66 in: Graft-Transmissible Diseases of Citrus. Handbook for Detection and Diagnosis. C.N. Roistacher, ed. Food and Agriculture Organization, Rome, 1991. (3) D. P. H. Tucker et al. Plant Dis. 68:979, 1984.