bluuebunny/crossref_metadata_2025 huggingface dataset:
Physicochemical Profiling of Sartans: A Detailed Study of Ionization Constants and Distribution Coefficients
Authors: Tosco Paolo , Rolando Barbara , Fruttero Roberta , Henchoz Yveline , Martel Sophie , Carrupt Pierre‐Alain , Gasco Alberto
Published: March 2008

A detailed investigation of the ionization and lipophilicity profiles of selected sartans (valsartan, losartan, irbesartan, candesartan, candesartan cilexetil), a class of antihypertensives commonly used in therapy, is presented. The pKa macroconstants were determined by integrated potentiometry, capillary electrophoresis, and UV spectrophotometry. The measured pKa macroconstants were connected with the ionizable centers present in each molecule with the aid of model compounds. Potentiometric titrations with the GLpKa apparatus were performed to determine the distribution profile (log D vs. pH) of valsartan, while the shake‐flask procedure was used to characterize the distribution profile of the other compounds. Valsartan showed a lipophilicity profile consistent with the presence of two acidic centers. Losartan and irbesartan, which contain one acidic and one basic center, displayed the classical bell‐shaped profile of ordinary ampholytes. By contrast, a more complex situation emerged in the case of candesartan, due to the large number of ionization equilibria involved. The low solubility of candesartan cilexetil, together with the ease of hydrolysis of the ester moiety, prevented a successful investigation of its ionization and lipophilicity profiles.
New Oxygenated Lignans from Kadsura philippinensis
Authors: Shen Ya‐Ching , Lin Yu‐Chi , Cheng Yuan‐Bin , Chang Chia‐Ju , Lan Ting‐Wei , Liou Shorong‐Shii , Chien Ching‐Te , Liaw Chia‐Ching , Khalil Ashraf Taha
Published: March 2008

Seven new oxygenated lignans, kadsuphilins G–M (1–7, resp.), were isolated by chromatographic fractionation of an AcOEt extract of the aerial part of Kadsura philippinensis including four compounds with a dibenzocyclooctadiene skeleton, two with a bicyclooctane ring system, and one of 1,4‐biphenyldimethylbutane type. The structures of the isolated compounds were elucidated through extensive spectroscopic analyses, particularly 2D‐NMR experiments (HMQC, HMBC, and NOESY). The configuration of the chiral centers and the biphenyl moiety were determined by NOESY as well as CD spectroscopy, respectively.
Novel Bibenzyl Derivatives from the Tubers of Bletilla striata
Authors: Feng Jia‐Quan , Zhang Ru‐Jun , Zhao Wei‐Min
Published: March 2008

Three novel bibenzyl derivatives, blestritins A–C (1–3), along with 18 known constituents, were isolated from the tubers of Bletilla striata (Orchidaceae), a traditional Chinese medicine used for the treatment of tuberculosis and haemorrhage of the stomach and lungs. Their structures were identified on the basis of spectroscopic analyses.
An Oxidative Rearrangement of 6‐Phenylbicyclo[3.2.0]heptan‐6‐ol to 1,1′‐Biphenyl‐Carbaldehydes: A Mechanistic Study
Authors: Ceylan Mustafa , Fındık Esra , Seçen Hasan
Published: March 2008

Acid‐catalyzed rearrangement of 6‐phenylbicyclo[3.2.0]heptan‐6‐ol gave 1,1′‐biphenyl and 1,1′‐biphenyl‐carbaldehydes in small amounts as well as the expected rearrangement products. A detailed study of the reaction mechanism revealed that the conversion occurs via an oxidative process through the consecutive formation of cycloheptadienes, cycloheptatrienes, and 1,1′‐biphenyls. The acid‐catalyzed rearrangement of 6‐phenylbicyclo[3.2.0]hept‐2‐en‐6‐ols gave 1‐ and 2‐phenylcycloheptatrienes directly, from which 1,1′‐biphenyl and 1,1′‐biphenyl‐carbaldehydes were obtained by oxidation.
Macrorhynines A and B, Two Novel Norditerpenoid Alkaloids from Aconitum macrorhynchum
Authors: Yang Xiao‐Dong , Yang Shu , Yang Jin , Zhao Jing‐Feng , Zhang Hong‐Bin , Li Liang
Published: March 2008

Two novel norditerpenoid alkaloids, macrorhynines A and B (1 and 2), together with seven known compounds, were isolated from Aconitum macrorhynchum. The structures of the new compounds were elucidated as (1α,6α,14α)‐8‐acetoxy‐1,6,16‐trimethoxy‐4‐(methoxymethyl)aconitan‐14‐yl 4‐methoxybenzoate (1) and (1α,6α,14α)‐8‐acetoxy‐13‐hydroxy‐1,6,16‐trimethoxy‐4‐(methoxymethyl)aconitan‐14‐yl 4‐methoxybenzoate (2) on the basis of spectral analyses. The novel compounds were found to contain the rare C(19)N, azomethine, group.
Effect of water table drawdown on peatland dissolved organic carbon export and dynamics
Authors: Strack M. , Waddington J. M. , Bourbonniere R. A. , Buckton E. L. , Shaw K. , Whittington P. , Price J. S.
Published: March 2008

Peatlands play an important role in the global carbon cycle, and loss of dissolved organic carbon (DOC) has been shown to be important for peatland carbon budgets. The objective of this study was to determine how net production and export of DOC from a northern peatland may be affected by disturbance such as drainage and climate change.

The study was conducted at a poor fen containing several pool–ridge complexes: (1) control site–no water table manipulation; (2) experimental site–monitored for one season in a natural state and then subjected to a water table drawdown for 3 years; (3) drained site–subjected to a water table drawdown 9 years prior to monitoring. The DOC concentration was measured in pore water along a microtopographic gradient at each site (hummock, lawn and hollow), in standing water in pools, and in discharge from the experimental and drained sites. The initial water table drawdown released ∼3 g of carbon per square metre in the form of DOC, providing a large pulse of DOC to downstream ecosystems. This value, however, represents only 1–9% of ecosystem respiration at this site. Seasonal losses of DOC following drainage were 8–11 g of carbon per square metre, representing ∼17% of the total carbon exchange at the experimental study site. Immediately following water table drawdown, DOC concentrations were elevated in pore water and open water pools. In subsequent seasons, DOC concentration in the pool declined, but remained higher than the control site even 11 years after water‐table drawdown. This suggests continued elevated net DOC production under lower water table conditions likely related to an increase in vegetation biomass and larger water table fluctuations at the experimental and drained sites. However, the increase in concentration was limited to initially wet microforms (lawns and hollows) reflecting differences in vegetation community changes, water table and soil subsidence along the microtopographic gradient. Copyright © 2008 John Wiley & Sons, Ltd and Her Majesty the Queen in right of Canada.
Spatial and temporal perspectives on spring break‐up flooding in the Slave River Delta, NWT
Authors: Brock B. E. , Wolfe B. B. , Edwards T. W. D.
Published: March 2008

Spatial and temporal patterns of spring break‐up flooding in the Slave River Delta (SRD), Northwest Territories, are characterized during three years (2003–2005) using water isotope tracers and total inorganic suspended sediment (TSS) concentrations measured from lakewater samples collected shortly after the spring melt. Strongly contrasting spring melt periods led to a moderate flood in 2003, no flooding in 2004 and widespread flooding in 2005. Flooded lakes have isotopically‐depleted δ18O (δ2H) signatures, ranging between − 19·2‰ (−145‰) and − 17·1‰ (−146‰) and most have high TSS concentrations (>10 mg L−1), while non‐flooded lakes have more isotopically‐enriched δ18O (δ2H) signatures, ranging between − 18·2‰ (−149‰) and − 10·6‰ (−118‰) and low TSS concentrations (<10 mg L−1). These results, in conjunction with the isotopic signatures of Slave River water and snowmelt, are used to estimate the proportion of river‐ or snowmelt‐induced dilution in delta lakes during the spring of each study year. Calculations indicate river flooding caused dilution of ∼70–100% in delta lakes, while snowmelt dilution in the absence of river flooding ranged from ∼0–56%. A positive relationship exists between the spatial extent of spring flooding in the SRD and level and discharge on the Slave River and upstream tributaries, suggesting that upstream flow generation plays a key role in determining the magnitude of spring flooding in the SRD. Parallel variations in the 46‐year instrumental Slave River discharge record and flood stratigraphy in the active delta indicate that there is potential for extending the flood history of the SRD, a development that will contribute to a more robust understanding of the drivers of historic, contemporary and future flood frequency in the delta. Copyright © 2008 John Wiley & Sons, Ltd.
Predicting longitudinal dispersion coefficient in natural streams by artificial intelligence methods
Authors: Toprak Z. Fuat , Cigizoglu Hikmet Kerem
Published: March 2008

In this study, three artificial neural network methods, i.e. feed forward back propagation, the radial basis function neural network, and the generalized regression neural network are employed to compute the longitudinal dispersion coefficient in order to evaluate its behaviour in predicting dispersion characteristics in natural streams. These methods, which use hydraulic and geometrical data to predict dispersion coefficients, can easily be applied to natural streams and are proven to be superior in explaining their dispersion characteristics more precisely than existing equations. This method of predicting the longitudinal dispersion coefficient in river flows was tested on 65 data sets, obtained by researchers from 30 rivers in the USA. Results using the models are compared with results obtained in many other studies, and are shown to be more accurate than the other methods considered. Copyright © 2008 John Wiley & Sons, Ltd.
Delineating runoff processes and critical runoff source areas in a pasture hillslope of the Ozark Highlands
Authors: Leh M. D. , Chaubey I. , Murdoch J. , Brahana J. V. , Haggard B. E.
Published: March 2008

The identification of runoff contributing areas would provide the ideal focal points for water quality monitoring and Best Management Practice (BMP) implementation. The objective of this study was to use a field‐scale approach to delineate critical runoff source areas and to determine the runoff mechanisms in a pasture hillslope of the Ozark Highlands in the USA. Three adjacent hillslope plots located at the Savoy Experimental Watershed, north‐west Arkansas, were bermed to isolate runoff. Each plot was equipped with paired subsurface saturation and surface runoff sensors, shallow groundwater wells, H‐flumes and rain gauges to quantify runoff mechanisms and rainfall characteristics at continuous 5‐minute intervals. The spatial extent of runoff source areas was determined by incorporating sensor data into a geographic information‐based system and performing geostatistical computations (inverse distance weighting method). Results indicate that both infiltration excess runoff and saturation excess runoff mechanisms occur to varying extents (0–58% for infiltration excess and 0–26% for saturation excess) across the plots. Rainfall events that occurred 1–5 January 2005 are used to illustrate the spatial and temporal dynamics of the critical runoff source areas. The methodology presented can serve as a framework upon which critical runoff source areas can be identified and managed for water quality protection in other watersheds. Copyright © 2008 John Wiley & Sons, Ltd.
Hydrologic prediction for urban watersheds with the Distributed Hydrology–Soil–Vegetation Model
Authors: Cuo Lan , Lettenmaier Dennis P. , Mattheussen Bernt V. , Storck Pascal , Wiley Matthew
Published: March 2008

Some relatively straightforward modifications to the Distributed Hydrology–Soil–Vegetation Model (DHSVM) are described that allow it to represent urban hydrological processes. In the modified model, precipitation that falls on impervious surfaces becomes surface runoff, and a spatially varying (depending on land cover) fraction of surface runoff is connected directly to the stream channel, with the remainder stored and slowly released to represent the effects of stormwater detention. The model was evaluated through application to Springbrook Creek watershed in a partially urbanized area of King County, Washington. With calibration, the modified DHSVM simulates hourly streamflow from these urbanized catchments quite well. It is also shown how the revised model can be used to study the effects of continuing urbanization in the much larger Puget Sound basin. Model simulations confirm many previous studies in showing that urbanization increases peak flows and their frequency, and decreases peak flow lag times. The results show that the urbanization parameterizations for DHSVM facilitate use of the model for prediction and/or reconstruction of a range of historic and future changes in land cover that will accompany urbanization as well as other forms of vegetation change. Copyright © 2008 John Wiley & Sons, Ltd.
Growing season energy and water exchange from an oil sands overburden reclamation soil cover, Fort McMurray, Alberta, Canada
Authors: Carey Sean K.
Published: March 2008

The oil sands mining industry in Canada is required to return mining areas to a land capability equivalent to that which existed prior to mining. During the reclamation process, ecosystems are created that bear little similarity to boreal forests that existed prior to mining. Quantifying the water balance of reclaimed ecosystems is critical in establishing whether there is sufficient moisture for vegetation growth and in the fate of salts, which can be toxic when drawn to the surface or leached out of the covers. At Syncrude Canada Ltd's Mildred Lake mine north of Fort McMurray, Alberta, the surface energy balance was measured atop a reclaimed saline‐sodic overburden pile during three growing seasons using eddy covariance. At the onset of the study, the dominant vegetation was foxtail barley, which changed to sweet clover in 2004, and a low‐density species mix in 2005, including some aspen and white spruce seedlings. The 2005 growing season was cooler and wetter than 2003 and 2004, and there were seasonal differences in the delivery of precipitation among years. There were distinct differences in the surface energy balance among the study years related to weather, soil moisture, vegetation and stage of growth. Latent heat was the largest consumer of energy in 2003, and mid‐day fluxes of sensible and latent heat were approximately equal. In 2004, sensible heat became the dominant flux, primarily due to prolonged dry periods, whereas the wet 2005 season had the greatest latent heat flux density of any year. Ground heat flux declined throughout the growing season and ranged between 3 and 17% of net radiation. Total evapotranspiration was 246, 224 and 283 mm for 2003, 2004 and 2005, respectively. A total derivative analysis of the Penman‐Monteith equation reveals the influence of available energy, vapour pressure deficit and surface conductance in controlling evapotranspiration. Copyright © 2008 John Wiley & Sons, Ltd.
The research of degradability of a novel biodegradable coralline hydroxyapatite after implanted into rabbit
Authors: Ning Yuan , Wei Tian , Defu Chen , Yonggang Xing , Da He , Dafu Chen , Lei Sun , Zhizhong Gao
Published: March 2008

To examine the biodegradability and bone healing effect of a novel biodegradable coralline hydroxyapatite after implanting into the proximal tibia of rabbit. Seventy New Zealand white rabbits were enrolled, bone defects about 10 × 5 × 3 mm3 of bilateral proximal tibias were prepared by drilling, then coralline hydroxyapatite and iliac crest bone were grafted into bilateral bone defects, respectively. Each time five rabbits were sacrificed at 1, 2, 3, 4, 6, 8, 10, 12, 20, 24, 32, 36, 40, and 60 weeks after surgery. Then a series of examination were carried out, including eye view, roentgenographically, and nondecalcification histological examination. Eye view and roentgenographical examination indicate that all the defects grafted with coralline hydroxyapatite exhibited bone fusion, similar to the iliac crest autograft. The bone density of the graft site decreases with time on the X‐ray film. Nondecalcification histological examination results are as followed: In the early time on the sections, the coralline hydroxyapatite looks like interlinked trabecula. Few lymphocytes infiltrate around the trabecula. With time extending, coralline hydroxyapatite looks like thin line or thin circle remnant. The degradation sites are filled with renascence bone. Medulla cavity can be seen in the degradation sites. After grafted in body, coralline hydroxyapatite exhibits little local and general abnormal reaction. It conducts good bone fusion of fracture. Coralline hydroxyapatite can be degraded after grafted into body, which is good for remodeling of bone healing. Hence coralline hydroxyapatite is an ideal bone graft substitute of autograft. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009
Synthesis of amphiphilic poly(tetraethylene glycol succinate) and the thermosensitivity of its aggregation in water
Authors: Chen Shusen , Wang Yinong , Fan Yunge , Ma Jianbiao
Published: March 2008

Amphiphilic biodegradable polyester, poly(tetraethylene glycol succinate) (PTEGSuc), was synthesized via melt polycondensation of tetraethylene glycol and succinic acid on catalysis of p‐toluenesulfonic acid. It was observed that PTEGSuc could self‐assemble into micelles in water. In addition, thermosensitivity of PTEGSuc aggregation in water was first found in the experiment, and the critical aggregation temperatures could be controlled by solution concentration. Transmission electron microscopy was used to investigate the micellar morphologies of PTEGSuc in different solvents. It was found that particle shape is almost round although the micellar morphology is different depending on the solvent used. Based on the perfect properties, especially in micelle formation and thermosensitivity, PTEGSuc is promising in biomedical field as carrier of drug delivery system, scaffold of tissue engineering, and other medical devices. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009
Surface modification of collagen‐based artificial cornea for reduced endothelialization
Authors: Rafat Mehrdad , Matsuura Takeshi , Li Fengfu , Griffith May
Published: March 2008

Our objective was to develop collagen‐based hydrogels as tissue substitutes for corneal transplantation. The design of the full‐thickness corneal grafts includes prevention of cell migration onto the posterior surface of the implants, using a plasma‐assisted surface modification technique. Briefly, the hydrogel materials were subjected to ammonia plasma functionalization followed by grafting of alginate macromolecules to the target surface. The treated materials surfaces showed observable decreases in endothelial cell attachment. The decrease in cell attachment and adhesion was dependant upon the concentration of alginate and plasma radio frequency (RF) power. High concentrations of alginate 5% (w/v) and high RF power of 100 W produced surfaces with minimal cell attachment. The plasma‐alginate treatment did not adversely affect the optical or swelling properties of the constructs. Contact angle measurement analysis revealed that the posterior surface hydrophilicity significantly increased after the treatment. The grafting of alginate to the implants surfaces was confirmed by fourier transform infrared spectroscopy. Both of the untreated and alginate grafted corneal materials were found to be superior to human cornea in optical and swelling properties. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009
Mesenchymal stem cell‐seeded collagen matrices for bone repair: Effects of cyclic tensile strain, cell density, and media conditions on matrix contraction in vitro
Authors: Sumanasinghe Ruwan D. , Osborne Jason A. , Loboa Elizabeth G.
Published: March 2008

Type I collagen is the most abundant extracellular matrix protein in bone and contains arginine– glycine–aspartic acid sequences that promote cell adhesion and proliferation. We have previously shown that human mesenchymal stem cells (hMSCs) seeded in three‐dimensional (3D) collagen gels upregulate BMP‐2 mRNA expression in response to tensile strain, indicative of osteogenesis. Therefore, collagen could be a promising scaffold material for functional bone tissue engineering using hMSCs. However, high contraction of the collagen gels by hMSCs poses a challenge to creating large, tissue‐engineered bone constructs. The effects of cyclic tensile strain, medium (with and without dexamethasone), and hMSC seeding density on contraction of collagen matrices have not been investigated. hMSCs were seeded in 3D collagen gels and subjected to cyclic tensile strain of 10% or 12% for 4 h/day at a frequency of 1 Hz in osteogenic‐differentiating or complete MSC growth media for up to 14 days. Viability of hMSCs was not affected by strain or media conditions. While initial seeding density affected matrix contraction alone, there was a high interdependence of strain and medium on matrix contraction. These findings suggest a correlation between hMSC proliferation and osteogenic differentiation on collagen matrix contraction that is affected by media, cell‐seeding density, and cyclic tensile strain. It is vital to understand the effects of culture conditions on collagen matrix contraction by hMSCs in order to consider hMSC‐seeded collagen constructs for functional bone tissue engineering in vitro. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009
PMMA particle‐mediated DNA vaccine for cervical cancer
Authors: Lou Pei‐Jen , Cheng Wen‐Fang , Chung Yi‐Chen , Cheng Che‐Yuan , Chiu Lien‐Hua , Young Tai‐Horng
Published: March 2008

DNA vaccination is a novel immunization strategy that possesses many potential advantages over other vaccine strategies. One of the major difficulties hindering the clinical application of DNA vaccination is the relative poor immunogenicity of DNA vaccines. Poly(methyl methacrylate) (PMMA) is a synthetic polymer approved by the Food and Drug Administration for certain human clinical applications such as the bone cement. In vivo, PMMA particles are phagocytosable and have the potential to initiate strong immune responses by stimulating the production of inflammatory cytokines. In this study, we synthesized a series of PMMA particles (PMMA 1–5) with different particle sizes and surface charges to test the feasibility of implementing such polymer particles for DNA vaccination. To our knowledge, this is the first report to show that the gene gun can deliver DNA vaccine by propelling PMMA particles mixed with plasmid DNA for cervical cancer. It was found that PMMA 4 particles (particle size: 460 ± 160 nm, surface charge: +11.5 ± 1.8 mV) stimulated the highest level of TNF‐α production by macrophages in vitro and yielded the best result of antitumor protection in vivo. Therefore, our results possess the potential for translation and implementation of polymer particles in gene gun delivering DNA vaccination. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009
Suicidal risk in young adult offspring of mothers with bipolar or major depressive disorder: a longitudinal family risk study
Authors: Klimes‐Dougan Bonnie , Lee Chih‐Yuan S. , Ronsaville Donna , Martinez Pedro
Published: March 2008

Recent evidence has highlighted suicidal risk associated with bipolar disorder (BD). Using a family risk approach, the goal of this study was to evaluate suicidal thoughts and behaviors longitudinally from childhood to young adulthood in children of mothers with BD, Major depressive disorder (MDD), and well mothers. Few group differences were found for cross‐sectional assessments of suicidal thoughts and behavior in young adulthood; the offspring of MDD demonstrate an earlier onset and more persistent suicidality than other groups, but by young adulthood, BD offspring appear to be comparable to MDD offspring in their rates of suicidality. The longitudinal assessments reveal a pattern of higher suicidal risk in MDD offspring, more intermediate risk in BD offspring, and lower risk in well offspring. Precursors and correlates of suicidal thoughts and behaviors were also examined. These findings suggest diverse developmental trajectories based on family risk and have implications for planning preventive intervention. © 2008 Wiley Periodicals, Inc. J Clin Psychol 64: 531–540, 2008.
New bounds for the chromatic number of graphs
Authors: Zaker Manouchehr
Published: March 2008

In this article we first give an upper bound for the chromatic number of a graph in terms of its degrees. This bound generalizes and modifies the bound given in 11. Next, we obtain an upper bound of the order of magnitude ${\cal O}({n}^{{1}-\epsilon})$ for the coloring number of a graph with small K2,t (as subgraph), where n is the order of the graph. Finally, we give some bounds for chromatic number in terms of girth and book size. These bounds improve the best known bound, in terms of order and girth, for the chromatic number of a graph when its girth is an even integer. © 2008 Wiley Periodicals, Inc. J Graph Theory 58:110–122, 2008
Assessing the spatial and temporal variation in the skill of precipitation forecasts from an NWP model
Authors: Roberts Nigel
Published: March 2008

It is becoming increasingly important to be able to verify the spatial accuracy of precipitation forecasts, especially with the advent of high‐resolution numerical weather prediction (NWP) models. In this article, the fractions skill score (FSS) approach has been used to perform a scale‐selective evaluation of precipitation forecasts during 2003 from the Met Office mesoscale model (12 km grid length). The investigation shows how skill varies with spatial scale, the scales over which the data assimilation (DA) adds most skill, and how the loss of that skill is dependent on both the spatial scale and the rainfall coverage being examined. Although these results come from a specific model, they demonstrate how this verification approach can provide a quantitative assessment of the spatial behaviour of new finer‐resolution models and DA techniques. Copyright © 2008 Royal Meteorological Society
Simultaneous observation of glutamate, γ‐aminobutyric acid, and glutamine in human brain at 4.7 T using localized two‐dimensional constant‐time correlation spectroscopy
Authors: Watanabe H. , Takaya N. , Mitsumori F.
Published: March 2008

Localized two‐dimensional constant‐time correlation spectroscopy (CT‐COSY) was used to resolve glutamate (Glu), γ‐aminobutyric acid (GABA), and glutamine (Gln) in the human brain at 4.7 T. In this method, three‐dimensional localization was achieved using three radio frequency pulses of the CT‐COSY module for slice selection. As this sequence could decouple JHH along the F1 direction, peak resolution of metabolites was improved even on a magnitude‐mode display. In experiments on a phantom containing N‐acetylaspartate, creatine, Glu, Gln, and GABA with a constant time delay (Tct) of 110 ms, cross peaks of Glu, Gln, and GABA were obtained on a spectrum processed with standard sine‐bell windows, which emphasize sine‐dependent signals along the t2 direction. In contrast, diagonal peaks of Glu C4H at 2.35 ppm, GABA C2H at 2.28 ppm, and Gln C4H at 2.44 ppm were resolved on a spectrum processed with Gaussian windows, which emphasize cosine‐dependent signals along t2. Human brain spectra were obtained from a 27 mL voxel within the parieto‐occipital region using a volume transverse electromagnetic (TEM) coil for both transmission and reception. Tct was 110 ms; the total scan time was 30 min. Diagonal peaks of Glu C4H, GABA C2H, and Gln C4H were also resolved on the spectrum processed with Gaussian windows. These results show that the localized two‐dimensional CT‐COSY method featuring 1H decoupling along the F1 direction could resolve Glu, GABA, and Gln signals in the human brain. Copyright © 2008 John Wiley & Sons, Ltd.
Hyperbolicity, stability and monodromy of dynamical systems
Authors: Arai Zin
Published: March 2008

We propose a rigorous computational method for proving uniform hyperbolicity of dynamical systems. Besides finding structurally stable parameters, the algorithm can also be applied for the computation of the monodromy of dynamical systems. With this algorithm, we prove that the topology of the 2‐dimensional generalization of the Mandelbrot set is totally different from that of the original Mandelbrot set. Furthermore, we show that the monodromy of the complex Hénon map can be used to determine the dynamics of the real Hénon map. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Period‐doubling cascades and mode interactions in coupled systems
Authors: Aston P. J. , Mir H.
Published: March 2008

Suppose that an iterated map exhibits a period‐doubling cascade. If two such maps are coupled, then the synchronised state will exhibit the same period‐doubling cascade but there is also the additional possibility of symmetry‐breaking bifurcations to non‐synchronised states. By introducing a second parameter, a symmetry‐breaking bifurcation and a period‐doubling bifurcation can be made to occur at the same point, resulting in a mode interaction.

As the second parameter is varied from the value at the mode interaction, a second symmetry‐breaking bifurcation may occur from the period 2 solutions, which will then be involved in another mode interaction at the next period‐doubling bifurcation point. In this way, a complete cascade of mode interactions can occur.

A local analysis of such a mode interaction is considered. The global consequences together with a classification of different cases are then analysed. Renormalisation theory is used to determine the universal behaviour and parameter scalings of such a system. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the convergence of quasi‐random sampling importance resampling
Authors: Cools Ronald , Vandewoestyne Bart
Published: March 2008

The Sampling/Importance Resampling (SIR) algorithm can be used for generating representative point sets from a distribution known up to a multiplicative constant. Moreover, the Quasi‐random Sampling Importance Resampling (QSIR) scheme, based on quasi‐Monte Carlo methods, is a recent modification of the SIR algorithm and was empirically shown to have better convergence. We present error convergence results for QSIR that we obtained using quasi‐Monte Carlo theory. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical solution of a variational problem with L∞ functionals
Authors: Parente Lisandro A. , Aragone Laura S. , Lotito Pablo A. , Reyero Gabriela F.
Published: March 2008

We consider the problem which consists in finding an optimal Lipschitz extension to the domain Ω of functions that verify the restriction u = g on ∂Ω. This work deals with the numerical approximations of the problem in dimension two. Using a discretization procedure based on finite differences method we obtain a large scale non smooth convex minimization problem, which is solved via Variable Metric Hibrid Proximal Point Method. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Clustering of point vortices in a periodic box
Authors: Umeki Makoto
Published: March 2008

Motions of N point vortices with square periodic boundary conditions are studied numerically, where N is order of 100. The clustering property is examined by computing the L function familiar in the field of spatial ecology. The case of a positive value of L corresponds to the state of clustering and the Onsager's negative temperature. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Protein profile in neuroblastoma cells incubated with S‐ and R‐enantiomers of ibuprofen by iTRAQ‐coupled 2‐D LC‐MS/MS analysis: Possible action of induced proteins on Alzheimer's disease
Authors: Zhang Jianhua , Sui Jianjun , Ching Chi Bun , Chen Wei Ning
Published: March 2008

Ibuprofen is a member of the proprionic acid group of nonsteroidal anti‐inflammatory drugs (NSAID), with the S‐enantiomer being more active than the R‐enantiomer. It has been shown to display protective effects against neuroinflammation, which is linked to the pathogenesis of several neurodegenerative disorders, including Alzheimer's disease (AD). While its prophylactic effect on AD has been suggested, a comprehensive understanding of its mechanism of action remains unclear. Using iTRAQ‐coupled 2‐D LC‐MS/MS analysis, we report here the first study of protein profiles of neuroblastoma cells incubated separately with the two enantiomers of ibuprofen. Three types of cellular proteins, including metabolic enzymes, signaling molecules and cytoskeletal proteins, displayed changes. The changes in the level of a number of enzymes involved in fatty acid synthesis and antioxidant activity in cells incubated with the S‐enantiomer were further supported by the real‐time PCR analysis as well as the reduced level of reactive oxygen species in cells incubated with the S‐enantiomer of ibuprofen. Our findings, therefore, provide the possible mechanism of ibuprofen‐induced proteins on AD, and the beneficial effects of ibuprofen in reducing the development of AD.
The effect of low pH on protein expression by the probiotic bacterium Lactobacillus reuteri
Authors: Lee KiBeom , Lee Hong‐Gu , Pi KyungBae , Choi Yun‐Jaie
Published: March 2008

The ability of a lactic acid bacterium to survive passage through the gastrointestinal tract is a key point in its function as a probiotic. In this study, protein synthesis by the probiotic bacterium, Lactobacillus reuteri, was analyzed under transiently decreased pH conditions. L. reuteri cells grown to the midexponential growth phase at 37°C were exposed to transient (1 h) low‐pH stresses from pH 6.8 to pH 5.0, 4.5, or 4.0. 2‐DE allowed us to identify 40 common proteins that were consistently and significantly altered under all three low‐pH conditions. PMF was used to identify these 40 proteins, and functional annotation allowed them to be distributed to six major classes: (i) transport and binding proteins; (ii) transcription–translation; (iii) nucleotide metabolism and amino acid biosynthesis; (iv) carbon energy metabolism; (v) pH homeostasis and stress; and (vi) unassigned. These findings provide new insight into the inducible mechanisms underlying the capacity of gastrointestinal L. reuteri to tolerate acid stress.
Contact spotting of protein microarrays coupled with spike‐in of normalizer protein permits time‐resolved analysis of ERBB receptor signaling
Authors: Löbke Christian , Laible Mark , Rappl Claudia , Ruschhaupt Markus , Sahin Özgür , Arlt Dorit , Wiemann Stefan , Poustka Annemarie , Sültmann Holger , Korf Ulrike
Published: March 2008

Protein microarrays allow highly accurate comparison and quantification of numerous biological samples in parallel while requiring only little material. This qualifies protein arrays for systems biology and clinical research where only limited sample material is available, but a precise readout is required. With the introduction of signal normalization steps to monitor the drop size of manually contact‐spotted RP protein arrays, the usefulness of normalizer proteins to ensure a high‐throughput but inexpensive protein analysis was demonstrated. This approach was applied for the analysis of signaling through ERBB receptor activated kinases in the breast cancer cell line MCF‐7. Activation of ERK1/2 and AKT by ERBB1 (EGFR), ERRB2 (HER2/neu), and ERBB3‐4 was monitored in a time‐resolved manner. Analysis of pathway activation by stimulation with epidermal growth factor and heregulin, or inhibition by blocking with gefitinib or herceptin allowed a characterization of the distinct signaling properties of the different ERBB receptor subtypes.
Uniaxial anisotropy of organic thin films determined by ellipsometry
Authors: Heinemeyer U. , Hinderhofer A. , Alonso M. I. , Ossó J. O. , Garriga M. , Kytka M. , Gerlach A. , Schreiber F.
Published: March 2008

Organic thin films frequently exhibit strong anisotropic optical constants, which in many cases are uniaxial with the optic axis oriented along the surface normal. The data analysis presented here to obtain the anisotropic optical constants of thin films on silicon substrates is based on the model system diindenoperylene (DIP), but nevertheless applies to all uniaxial films on SiO2. In addition to variable angle spectroscopic ellipsometry, different substrates are used to perform a multiple sample analysis. This way of analysing data increases the sensitivity to uniaxial anisotropy. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
In‐situ spectroscopic ellipsometry: optimization of monitoring and closed‐loop‐control procedures
Authors: Humlíček J.
Published: March 2008

We discuss optimized extraction of information contained in a series of complex reflectance ratios in a series of consecutive, in‐situ SE measurements during the growth of thin films. We present a general computational scheme and discuss guidelines for the optimum data treatment. As an example, we analyze several hundreds of spectra recorded during the growth of diamond‐like carbon on TiCN/steel substrate. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Application of transmission ellipsometry to the determination of CD spectra of porphyrin J‐aggregates solid‐state samples
Authors: Arteaga O. , El‐Hachemi Z. , Canillas A.
Published: March 2008

Transmission‐mode perpendicular incidence phase modulated ellipsometry was applied to study anisotropic thin films of porphyrin J‐aggregates. A customized data acquisition system and measurement method was implemented to measure seven Mueller matrix elements, which allow us to determine the circular birefringence and dichroism as well as the linear birefringence and dichroism of solid‐state films. The examples shown illustrate the performance of the method for obtaining the true circular dichroism and consequently for detecting structural differences in chiral aggregates. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The anisotropic bond model of nonlinear optics
Authors: Adles E. J. , Aspnes D. E.
Published: March 2008

The anisotropic‐bond model (ABM) of nonlinear optics (NLO) provides a simple means of calculating NLO properties of materials by factoring the problem into four parts: first, determination of the local field at a bond‐charge site; second, solution of the anharmonic force equation of the bond charge; third, calculation of the radiation from the charge; and fourth, superposition of the radiation from all charges. Because this factorization is impossible in linear optics, this is one of the few cases where a nonlinear problem is simpler than its linear equivalent. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Real time spectroscopic ellipsometry of sputtered CdTe, CdS, and CdTe1−xSx thin films for photovoltaic applications
Authors: Li Jian , Podraza N. J. , Collins R. W.
Published: March 2008

Real time spectroscopic ellipsometry (RTSE) has been applied to study the deposition of polycrystalline CdTe, CdS, and CdTe1–x Sx thin films on crystalline silicon wafer substrates as well as the formation of CdS/CdTe and CdTe/CdS heterojunctions, all using a magnetron sputtering process. For CdTe and CdS, the key process variable is deposition temperature (T). The nucleation and growth behaviors of CdTe and CdS show strong variations with T and this influences the ultimate grain size of the polycrystalline films. For the co‐sputtered CdTe1–x Sx alloys, the key variables are the rf power levels applied to the CdTe and CdS targets and thus the resulting composition x. The dielectric functions of the alloys have been used as a database for real time investigation of inter‐diffusion at the CdS/CdTe and CdTe/CdS heterojunctions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mass spectrometry at a Ar/SF6/O2 chemically reactive plasma jet
Authors: Arnold Th. , Schindler A.
Published: March 2008

Chemically reactive plasma jets are tools for the treatment of surfaces with respect to material removal, deposition, and chemical modification. The plasma under investigation is created by introducing microwave power into a Ar/SF6/O2 subsonic gas flow to produce chemically reactive species for dry etching. In Ar/SF6/O2 plasma jets chemical reactions induced by electron impact form a large variety of SFx and SOx Fy radicals as well as free fluorine atoms. Low potential mass spectrometry was used to investigate the spatial structure of the plasma jet depending on gas composition. The mass spectra give information about different characteristic zones, which can be designated as the active and passive plasma zone, i.e. the dissociation and recombination zone, respectively. The knowledge of the kind of plasma‐chemical mechanisms and their spatial distributions is necessary to optimize gas composition and geometric parameters for effective silicon based material etching. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Anisotropic optical matrix elements in strained GaN‐quantum wells with various substrate orientations
Authors: Yamaguchi A. Atsushi
Published: March 2008

Polarization properties in compressively strained III‐nitride quantum wells (QWs) with various substrate orientations are numerically calculated using the 6×6 k·p Hamiltonian. It is shown that in‐plane optical anisotropies strongly depend on substrate orientation, QW width, and strain components. In particular, quantum confinement and compressive strain have the opposite effects on the anisotropies, and the in‐plane polarization degree is determined by the competition of these two effects. These characteristics are also verified by analytical calculations. On the basis of the calculation results, the structural design of laser diodes on semipolar and nonpolar substrates is also discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High drain current and low on resistance normally‐off‐mode AlGaN/GaN junction HFETs with a p‐type GaN gate contact
Authors: Fujii T. , Nakamura S. , Mizuno K. , Nega R. , Iwaya M. , Kamiyama S. , Amano H. , Akasaki I.
Published: March 2008

The normally‐off‐mode junction HFETs with a p‐type GaN gate contact showing high drain current and an extremely large on/off ratio were successfully fabricated by MOVPE. The drain currents were found to be very sensitive to the surface of the u‐AlGaN barrier exposed by RIE etching. A reproducible and stable high drain current was achieved using a very thin SiN passivation layer. The maximum drain current was 1.58×10–1 A/mm at VGS = 4 V, while the drain current at VGS = 0 V was as low as 1.45×10–8 A/mm. Therefore, an on/off ratio of 107 has been achieved. The sub‐threshold swing was as small as 90 mV/dec.. The on resistance was 3.4 mΩcm2, the threshold voltage was +0.45 V, and the breakdown voltage was over 325 V. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
AlGaN/GaN‐based MEMS with two‐dimensional electron gas for novel sensor applications
Authors: Niebelschütz F. , Cimalla V. , Tonisch K. , Haupt Ch. , Brückner K. , Stephan R. , Hein M. , Ambacher O.
Published: March 2008

Novel microelectromechanical resonators structures have been realized based on AlGaN/GaN heterostructures, which provide a basis for sophisticated sensor structures. There were grown on SiC substrates confining a two dimensional electron gas (2DEG). By means of the developed etching technology, freestanding resonators were patterned without degrading the sheet carrier concentration and electron mobility of the 2DEG inside the beams, which was confirmed by electrical measurements before and after the various process steps. As actuation and read out principle magnetomotive and piezoelectric effects were used, respectively. Due to the high sensitivity of the 2DEG and the chemical stability of the utilized materials these structures are suitable for chemical and biological sensor applications, where the sensitivity of the 2DEG on the surrounding environment acts as additional sensing signal, for example for simultaneous measurements of the viscosity and pH – value of a nanoliter droplet. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterization of a freestanding AlN substrate prepared by hydride vapor phase epitaxy
Authors: Kumagai Y. , Nagashima T. , Murakami H. , Takada K. , Koukitu A.
Published: March 2008

A thick AlN layer was grown on a (111)Si starting substrate at 1230 ºC by hydride vapor phase epitaxy (HVPE). A 112‐μm‐thick freestanding AlN substrate was successfully prepared by removing the Si substrate using a chemical etchant. The AlN substrate was transparent with a smooth (0001) surface. Immersion of the AlN substrate in an aqueous KOH solution revealed that the AlN layer grown on the (111)Si substrate predominately has Al‐polarity. Owing to improvement of crystalline quality by thick layer growth, a near‐band‐edge (NBE) emission could be obtained at 5.92 eV in the room‐temperature photoluminescence (PL) spectrum taken at the top surface of the AlN substrate. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Experimental and ab‐initio studies of temperature dependent InN decomposition in various ambient
Authors: Togashi R. , Kamoshita T. , Nishizawa Y. , Murakami H. , Kumagai Y. , Koukitu A.
Published: March 2008

N‐polarity InN layers grown on (0001) sapphire substrates by hydride vapor phase epitaxy (HVPE) were annealed in atmospheric N2, H2, H2 + NH3, or N2 + NH3 ambient at various temperatures. In the N2 ambient, InN decomposition became significant above 600 °C, whereas in the H2 ambient, InN layers reacted with H2 and decomposed at very low temperatures above 350 °C. The process of InN decomposition was also investigated using a first‐principles calculation. In a system free from H2, the rate‐limiting process was found to be desorption of N atoms from the surface as atomic N (N*), whereas in the H2 ambient, the desorption of In atoms as In, InH or InH3 is the rate‐limiting process. Thus, the decomposition reactions of InN layers in the ambient in the presence and absence of H2 are different. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Improved light extraction efficiency of GaN‐based light emitting diodes by using needle‐shape indium tin oxide p‐contact
Authors: Ishida Fumio , Yoshimura Kazumasa , Hoshino Katsuyuki , Tadatomo Kazuyuki
Published: March 2008

The high‐efficiency GaN‐based light emitting diodes (LEDs) with improved light extraction efficiency (LEE) using the needle‐shape indium tin oxide (ITO) p‐contact was successfully demonstrated. The needle‐shape ITO p‐contact was naturally grown by using electron‐beam evaporation method under the precisely controlled condition. The structure of ITO p‐contact varied sensitively from the planar‐shape to the needle‐shape with decreasing the deposition temperature and the partial oxygen pressure in the vacuum chamber. We fabricated the p‐side‐up GaN/sapphire LEDs with the needleshape ITO p‐contact and those with the planar‐shape ITO p‐contact using the same LED wafer (peak wavelength: 405 nm). The external quantum efficiency (EQE) of the needle‐shape ITO‐LEDs is 1.5 times larger than that of the planar‐shape ITO‐LEDs (at a forward current of 20 mA). This dramatic increase is attributed to the dramatic increasing of the LEE of the needle‐shape ITO‐LEDs. These results show that the optimizing shape of ITO p‐contact is the key technology to increase the EQE and the LEE of ITO‐LEDs. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effects of grown‐in defects on electron spin polarization in dilute nitride alloys
Authors: Wang X. J. , Buyanova I. A. , Chen W. M. , Hong Y. G. , Tu C. W.
Published: March 2008

Strong electron spin polarization in GaNAs epilayers and multiple quantum well structures is observed upon optical orientation at room temperature. The effect is explained in terms of spin dependent recombination (SDR) involving deep paramagnetic defects formed upon N incorporation in GaNAs. Concentration of the corresponding defects is shown to be enhanced during growth at low temperatures but is suppressed by post‐growth annealing. Optically detected magnetic resonance (ODMR) measurements performed in the studied structures reveal two paramagnetic defects participating in carrier recombination. One of them is identified as a complex involving AsGa antisite. Correlation between concentrations of the defects monitored via ODMR and in optical orientation measurements is observed which suggests that the same defects may be involved in both processes. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)