bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermoplast/phenolic resin aqueous dispersions
Authors: Demmer Christopher G. , Garnish Edward W. , Massy D. James R.
Published: April 2007

Combinations of phenolic resols with high molecular weight thermoplasts in the form of aqueous dispersions can be prepared by dissolving the thermoplast in the phenol and reacting with aqueous formaldehyde solution in the presence of emulsifiers. The scope of this procedure has been explored and the wide variety of thermoplasts that can be utilised is demonstrated. Several of the products from this process show promising results in metal‐bonding applications. Some of the physical and chemical changes taking place during the reaction and dispersion are described.
Determination of number‐average molecular weight of atactic polystyrene and cellulose diacetate by vapour pressure osmometry
Authors: Kamide Kenji , Terakawa Toshikazu , Matsuda Shigenobu
Published: April 2007

The usefulness of vapour pressure osmometry (v.p.o.) as a method for determining the number average molecular weight Mn was examined in comparison with other methods such as gel‐permeation chromatography (g.p.c.) and membrane osmoetry (m.o.). For this purpose, the weight‐ and number‐average molecular weights Mw and Mn were determined on well‐defined atactic polystyrene and cellulose acetate (degree of substitution DS = 2.46) samples. The experimental difference between Mn (v.p.o.) and Mn (g.p.c.) for any given sample are note significant at a 95 per cent level. The v.p.o. method were reproducible to ± 7–9 per cent or better, being useful in Mn range 2–12×104.
Conformational transition in PMMA. Methyl isobutyl ketone
Authors: Katime I. , Pereg M. Garay
Published: April 2007

In this work we have studied the viscometric behaviour of several fractions of PMMA in methyl isobutyl ketone as a function of temperature. A conformational transition has been found in the temperature range 25–35°C.

Likewise, the influence of solvent nature on the magnitude of the conformational transition has been studied.
Lignins as formulating agents for controlled release in agriculture
Authors: Wilkins Richard M.
Published: April 2007

The use of naturally‐occurring polymers, and in particular, kraft lignin, for controlled release pesticide formulations is reviewed. A matrix of kraft lignin containing polar pesticides can be prepared in granular form and the release rates of the active ingredient from this formulation are described. Successful applications of this type of formulation include herbicides for weed control in conifer plantation and insecticides in tropical flooded rice.
Studies in heterocyclic polymers, Pt VIII the preparation of o‐cyanobenzoic acid and some derivatives
Authors: Hodd Kenneth A. , Shadbolt Phillip
Published: April 2007

In a study of the synthesis of polyiminoimides the preparation of 2‐cyano‐benzoic acid (VI) and some derivatives has been examined. Both the symmetrical (XII) and the asymmetrical (XIII) phthaloyl dichlorides were found to give good yields of (VI) upon ammonolysis with (XII) the more efficient precursor. Conversion of the acid (VI) to its acid chloride (IX) was readily effected with PCl5. A number of substituted 2‐cyanobenzanilides were prepared from (IX) and their cyclisation to the related 2‐substituted‐3‐iminoisoindolinones studied using DSC. The nature of the substituent appeared to have little influence upon the rate of cyclisation which occurred spontaneously upon melting the parent anilide.

The synthesis of mixed dicyanodicarboxylic acids from pyromellitic dianhydride and from benzophenone — 3,3′,4,4‐tetracarboxylic acid dianhydride was also studied but difficulties were encountered in resolving the products.
Characterisation of a bisphenol a epoxy resin. A collaborative study carried out by technical panel PTP3 of the technical cooperation programme
Authors: Wright W. William
Published: April 2007

A collaborative study has been made by a number of laboratories of samples of nominally the same bisphenol A epoxy resin prepared in different countries and its cure with diaminodiphenylsulphone. A variety of techniques have been used to characterise the resin samples and their relative value for structural analysis and specification purposes assessed. Physical and mechanical properties of cured cast resin samples have also been measured and related to the resin structures observed. The study shows that some of the techniques do indicate differences in resin composition, but that these were not reflected in differences in mechanical properties.
13C N.m.r. Spectra of ring‐opened polymers of 1‐methylbicyclo[2.2.1]hept‐2‐ene and their hydrogenated products
Authors: Hamilton James G. , Ivin Kenneth J. , Rooney John J.
Published: April 2007

The 13C n.m.r. spectra of the title polymers have been completely assigned for a comprehensive range of cis contents (σc = 0–1) and head‐tail bias (HT/(HH + TT) = 1 −∞). In the unsaturated polymers (II), cis HH dyads are never found, so that all‐cis polymers are also all‐Ht, but cis TT dyads are formed in cis‐trans polymers, equal to the difference between trans HH and trans TT. The olefinic region consists of seven triplets; two each from cis HT and trans HT, and one each from cis TT, trans TT and trans HH. In the case of trans each triplet consists of a main centre peak due to ttt and ctc sequences and two wing peaks due to ttc and ctt sequences, as defined in the text. The upfield peaks also show cc/ct or tt/tc splittings as well as HH/HT or TT/TH splittings in most cases. In the saturated polymers C6 is sensitive to m/r ring dyad sequences. A corrected assignment is given for the hydrogenated polymer of norbornene.
Effects of fillers on and the role of hydrogen chloride in the behaviour of PVC in fires
Authors: Matthews George , Plemper George S.
Published: April 2007

Calcium carbonate fillers react with hydrogen chloride liberated during pyrolysis of PVC to an extent depending on their particle sizes and concentrations. The effects of these and other fillers on the critical oxygen index is more complex and depends on a number of factors additional to the extent of hydrogen chloride retention, of which char formation in particular is not readily assessed numerically. Differential thermal analyses suggest that the reaction of hydrogen chloride with calcium carbonate or calcium oxide fillers proceeds rapidly upon liberation. Hydrogen chloride added to the gas stream raises the critical oxygen index to a considerably greater extent than do carbon dioxide or nitrogen. It is concluded that the exotherm due to reaction between calcium carbonate fillers and pyrolysis hydrogen chloride contributes only slightly to flammability, and that the involvement of hydrogen chloride in reducing flammability is chemical rather than physical.
Synthesis and micellar behaviour of some novel amphiphilic acrylate and methacrylate monomers
Authors: Hamid Shakeeb M. , Sherrington David C.
Published: April 2007

The syntheses of a number of acrylate and methacrylate based amphiphiles are described. One group consists essentially of quaternary ammonium salts and the other of potassium carboxylates. Two non‐ionic species based on oligoethylene oxides are also described. The critical micelle concentration of each has been determined from conductance and dye absorption data, and the values compare satisfactorily with literature data on similar non‐polymerisable molecules. The compounds readily oligomerised in bulk, and in the micellar state the dye absorption data also indicated oligomerisation initiated by a free radical source.
The tacticity of poly(tri‐n‐butyl tin methacrylate) determined by 13C n.m.r.
Authors: Dambatta Bello B. , Ebdon John R.
Published: April 2007

The tacticities of poly(tri‐n‐butyl tin methacrylate)s prepared with radical initiators at various temperatures have been measured by 13C n.m.r. As expected, the polymers are predominantly syndiotactic and this syndiotacticity decreases with an increase in temperature. The activation parameters governing the tacticity are similar to those published for poly(methyl methacrylate) but differ somewhat from values published for poly(trimethyl tin methacrylate).
Studies of polycarbonate — poly (butylene terephthalate) blends
Authors: Birley Arthur W. , Chen Xin Yue
Published: April 2007

The composition and microstructure of a blend of bisphenol‐A polycarbonate (PC) and poly (butylene terephthalate) (PBT) have been established by a variety of physical methods. The composition was established by solvent extraction and infra‐red spectrophotometry, while the microstructure was determined by these and the additional methods of differential scanning calorimetry and dynamic mechanical thermal analysis. The PBT retained its crystallinity in the commercial blend, (Xenoy CL‐100), but blending reduced the main glass‐rubber transition of the PC from 147°C to approximately 100°C. Conditioning of the blend at high temperatures resulted in progressive transesterification: 3 minutes at 240°C gave a small but significant effect, while 30 minutes at 270°C yielded large changes in the structure. These findings are important in respect of processing the material, and the limitations which might be incurred in plant recycling of scrap.
Studies on the photopolymerisation of vinyl monomers using amine‐organic halide systems as initiators
Authors: Pramanick Dinabandhu , Bhattacharyya Ramanath
Published: April 2007

Amine‐organic halide systems have been found to be good photo‐initiators for the polymerisation of vinyl monomers in a benzene medium. The n‐tertiary butylamine‐carbonte‐trachloride (TBA‐CC14) system is most suitable for the polymerisation of methyl meth‐acrylate (MMA) in the presence of light. The rate of polymerisation (Rp) and degree of polymerisation (P̄n) are found to be independent of incident light intensity (Io). Rp and 1/P̄n are linearly related to [TBA]0.5 up to [TBA] = 0.108M, but above this concentration, TBA acts predominantly as a retarder. Rp and 1/P̄n are proportional to [CC14]0.5 at low [CC14]. At [CC14] > 0.099M it acts predominantly as a transfer agent. Furthermore, Rp is always proportional to [MMA]1.0 Endgroup analysis by dye‐partition test shows that both amine bearing radicals and CC13 radicals are the initiating species and an average of about one total endgroup per polymer molecule up to [CC14] = 0.099M indicates bimolecular termination of the poly (MMA) radicals through disproportionation. Higher chlorine endgroup and total endgroup incorporation at [CC14] > 0.099M gives additional evidence of the preponderance of chain transfer under this condition. A suitable mechanism of polymerisation is suggested, based on kinetics and endgroup evidence.
A chemical demonstration of the randomness of epoxidation of natural rubber
Authors: Davey John E. , Loadman M. John R.
Published: April 2007

During the development of chemical methods for determining the epoxide content of epoxidised natural rubber (ENR) two methods were found to give results which were identical but which showed a progressive divergence from values obtained by absolute instrumental methods as the level of epoxidation increased.

Statistical analysis of the sequence distribution of the epoxide groups, based on a random epoxidation, showed a good correlation between the value obtained by chemical analysis and the number of epoxide blocks rather than the number of epoxide groups.

Two further instrumental methods for measuring the total epoxide content, using infra red spectroscopy and differential scanning calorimetry, were developed. Analytical procedures and calibration data are supplied.

A combination of one chemical and one instrumental method can thus provide the absolute level of epoxidation and indicate whether the reaction has proceeded randomly or not, a point of crucial importance in the large scale manufacture of this material.
Matrix polymerisation of vinyl acetate in the presence of molecular sieves
Authors: Bezdade Mariana , Cascaval C. N.
Published: April 2007

Polymerisation of vinyl acetate in the presence of some molecular sieves, Sephadex and CaX type Zeolite, led, in well defined experimental conditions, to polymers with a regular structure. Evidence of the role of molecular sieves as a matrix for stereoregular polymerisation was provided by n.m.r. spectra and scanning electron microscopy, while the pyrolysis‐ gas chromatography and elemental analysis have pointed out the separation of polymer from matrix. The experimental data obtained on polymerisation of vinyl acetate in the presence of molecular sieves allowed us to postulate the presence of a donor‐acceptor type reaction mechanism.
Lack of statistical significance
Authors: Kehle Thomas J. , Bray Melissa A. , Chafouleas Sandra M. , Kawano Takuji
Published: April 2007

Criticism has been leveled against the use of statistical significance testing (SST) in many disciplines. However, the field of school psychology has been largely devoid of critiques of SST. Inspection of the primary journals in school psychology indicated numerous examples of SST with nonrandom samples and/or samples of convenience. In this article we present an argument against SST and its consequent p values in favor of the use of confidence intervals and effect sizes. Further, we present instances of common errors that impede cumulative knowledge in the literature related to school psychology. © 2007 Wiley Periodicals, Inc. Psychol Schs 44: 417–422, 2007.
Effect sizes, confidence intervals, and confidence intervals for effect sizes
Authors: Thompson Bruce
Published: April 2007

The present article provides a primer on (a) effect sizes, (b) confidence intervals, and (c) confidence intervals for effect sizes. Additionally, various admonitions for reformed statistical practice are presented. For example, a very important implication of the realization that there are dozens of effect size statistics is that authors must explicitly tell readers what effect sizes they are reporting. With respect to confidence intervals, when interpreting a 95% interval, we should never say that we are 95% confident that our interval captures the estimated population parameter. It is explained that effect sizes should be reported even for statistically nonsignificant effects. And, most importantly of all, it is emphasized that effect sizes should not be interpreted using Cohen's benchmarks. Instead, we ought to interpret our effects in direct and explicit comparison against the effects in the related prior literature. © 2007 Wiley Periodicals, Inc. Psychol Schs 44: 423–432, 2007.
RNASEL Arg462Gln polymorphism and prostate cancer in PLCO
Authors: Daugherty Sarah E. , Hayes Richard B. , Yeager Meredith , Andriole Gerald L. , Chatterjee Nilanjan , Huang Wen‐Yi , Isaacs William B. , Platz Elizabeth A.
Published: April 2007

BACKGROUND

The Gln allele of the Arg462Gln polymorphism in RNASEL results in a threefold decrease in enzymatic activity, a reported deficiency in apoptotic response, and has been associated with prostate cancer in some high‐risk family studies. The relationship of this variant to sporadic prostate cancer remains uncertain.

METHODS

We conducted a nested case‐control study of 1,317 prostate cancer cases and 1,842 controls from the screening arm of the prostate, lung, colorectal, and ovarian (PLCO) cancer screening trial. Conditional logistic regression was used to evaluate the association between the RNASEL Arg462Gln polymorphism and prostate cancer.

RESULTS

No statistically significant association was observed between the Arg462Gln polymorphism and prostate cancer (compared to Arg/Arg, Gln/Arg: OR= 0.99 95% CI 0.84–1.16; Gln/Gln: OR= 0.95 95% CI 0.74–1.21), although slight non‐significant differences in risk were observed among men with the Gln/Gln genotype by stage and grade.

CONCLUSIONS

These results suggest that the RNASEL Gln/Gln genotype does not play an important role in the etiology of prostate cancer in the general population. Prostate 67: 849–854, 2007. Published 2007 Wiley‐Liss, Inc.
Dynamic α‐helices: Conformations that do not conform
Authors: Sandhu Kuljeet Singh , Dash Debasis
Published: April 2007

Structural transitions are important for the stability and function of proteins, but these phenomena are poorly understood. An extensive analysis of Protein Data Bank entries reveals 103 regions in proteins with a tendency to transform from helical to nonhelical conformation and vice versa. We find that these dynamic helices, unlike other helices, are depleted in hydrophobic residues. Furthermore, the dynamic helices have higher surface accessibility and conformational mobility (P‐value = 3.35e‐07) than the rigid helices. Contact analyses show that these transitions result from protein‐ligand, protein‐nucleic acid, and crystal‐contacts. The immediate structural environment differs quantitatively (P‐value = 0.003) as well as qualitatively in the two alternate conformations. Often, dynamic helix experiences more contacts in its helical conformation than in the nonhelical counterpart (P‐value = 0.001). There is differential preference for the type of short contacts observed in two conformational states. We also demonstrate that the regions in protein that can undergo such large conformational transitions can be predicted with a reasonable accuracy using logistic regression model of supervised learning. Our findings have implications in understanding the molecular basis of structural transitions that are coupled with binding and are important for the function and stability of the protein. Based on our observations, we propose that several functionally relevant regions on the protein surface can switch over their conformation from coil to helix and vice‐versa, to regulate the recognition and binding of their partner and hence these may work as “molecular switches” in the proteins to regulate certain biological process. Our results supports the idea that protein structure–function paradigm should transform from static to a highly dynamic one. Proteins 2007. © 2007 Wiley‐Liss, Inc.
Agreeing on treatment through shared decision‐making
Authors: Oakley Sue
Published: April 2007

Sue Oakley explains how the process of shared decision‐making brings together patient preferences and the doctor's evidence‐based practice to reach a shared decision on a proposed treatment. Copyright © 2007 Wiley Interface Ltd
Building an eco‐industrial park as a public project in South Korea. The stakeholders' understanding of and involvement in the project
Authors: Kim Heungsoon
Published: April 2007

This study aims to investigate the actual development of an eco‐industrial park (EIP) in South Korea by employing a case study approach and deals with a pilot eco‐industrial park project in the Macheon Industrial Park of Jinhae, Gyeongnam, in the south of Korea. This paper reviews the stakeholders' understanding of EIPs. Furthermore, research was conducted on the barriers to the actual promotion of the project in South Korea. First, stakeholders' understanding of EIPs is identified as being self‐interested. The need for EIPs is mostly found in responding to civil complaints and pollutants resulting from the industrial park. However, the need is quite different from the original intention of EIPs. As a result, the project unsuccessfully deals with the needs of the stakeholders because of technical, economic, and social obstacles. Second, support from the public sector for the project seems quite inadequate. The public sector appears to lack the proper policy means and will to actualize the project. In conclusion, the Korean government needs to participate more actively in the project than it currently is doing. Copyright © 2007 John Wiley & Sons, Ltd and ERP Environment.
Using system dynamics modeling to understand the impact of social change initiatives
Authors: Hirsch Gary B. , Levine Ralph , Miller Robin Lin
Published: April 2007

Community psychologists have a long history of interest in understanding social systems and how to bring about enduring positive change in these systems. However, the methods that community psychologists use to anticipate and evaluate the changes that result from system change efforts are less well developed. In the current paper, we introduce readers to system dynamics modeling, an action research approach to studying complex systems and the consequences of system change. We illustrate this approach by describing a system dynamics model of educational reform. We provide readers with an introduction to system dynamics modeling, as well as describe the strengths and limitations of the approach for application to community psychology.
The Hansenula polymorpha peroxisomal targeting signal 1 receptor, Pex5p, functions as a tetramer
Authors: Moscicka Katarzyna B. , Klompmaker Sandra H. , Wang Dongyuan , van der Klei Ida J. , Boekema Egbert J.
Published: April 2007

We have studied Hansenula polymorpha Pex5p and Pex20p, peroxins involved in peroxisomal matrix protein import. In vitro binding experiments suggested that H. polymorpha Pex5p and Pex20p physically interact. We used single particle electron microscopy (EM) to analyze the structure of purified Pex5p and its possible association with Pex20p. Upon addition of Pex20p, a multimeric Pex20p complex was observed to be associated to the periphery of the Pex5p tetramer. In this Pex5p–Pex20p complex, the conformation of tetrameric Pex5p had changed from a closed conformation with a diameter of 115 Å into an open conformation of 134 Å. EM also indicated that the Pex5p–Pex20p complex was capable to bind native, folded catalase, a peroxisomal PTS1 protein. This suggests that the Pex5p–Pex20p complex may be functional as receptor complex.
Stress to endoplasmic reticulum of mouse osteoblasts induces apoptosis and transcriptional activation for bone remodeling
Authors: Hamamura Kazunori , Yokota Hiroki
Published: April 2007

ATF4 is an essential regulator in osteogenesis as well as in stress responses to the endoplasmic reticulum (ER). We addressed a question: Does ER stress to osteoblasts upregulate ATF4 expression? If so, do they exhibit ATF4‐mediated bone remodeling or apoptosis? ER stress, induced by Thapsigargin and tunicamycin, elevated a phosphorylated form of eIF2α and ATF4, but the cellular fate depended on treatment duration. The treatment for 1 h, for instance, activated Runx2, and type I collagen, while the treatment for 24 h induced apoptosis. Our observations suggest that there is a threshold for ER stress and osteoblasts present a bi‐phasic pattern of their fate.
Pre-operative nutritional status does not alter the metabolic response to major gastrointestinal surgery in patients with oesophageal cancer
Authors: Bisschop Peter H. , Klein Samuel , Ackermans Mariëtte T. , Patterson Bruce W. , Endert Erik , van Lanschot Jan J. B. , Romijn Johannes A. , Sauerwein Hans P.
Published: April 2007

Malnutrition is associated with an increased incidence of perioperative morbidity and mortality. To evaluate the effect of malnutrition on the metabolic and inflammatory response to surgery in patients with oesophageal cancer, we studied the effects of oesophagectomy in six patients with major (13·9 (se 1·3) %) weight loss and five patients with minor (0·7 (se 0·6) %) weight loss in the 6 months before to surgery. Rates of appearance (Ra) of glucose, glycerol, leucine and urea were determined by stable isotopically labelled tracer infusion before and after surgery. C-reactive protein was measured as an inflammation marker. BMI was lower in the patients with major weight loss than those with minor weight loss (20·3 (se 0·7) and 24·9 (se 1·5) kg/m2, P = 0·02). With the exception of greater glucose Ra in the major weight loss than minor weight loss subjects (11·1 (se 0·3) v. 9·5 (se 0·3) μmol/kg per min, P = 0·01), there were no differences in substrate kinetics before surgery between groups. Surgery increased glucose Ra, leucine Ra and urea Ra by 41, 24 and 58 %, respectively, in the total group. Changes in substrate kinetics in response to surgery were not different between patients with major and minor weight loss. Surgery increased C-reactive protein concentrations to a comparable extent in both groups. In conclusion, major upper gastrointestinal tract surgery in patients with oesophageal cancer elicits a catabolic response, characterized by increased inflammation, glucose production and protein breakdown. However, this catabolic response does not seem to be influenced by pre-operative nutritional status.
A dietary pattern rich in olive oil and raw vegetables is associated with lower mortality in Italian elderly subjects
Authors: Masala Giovanna , Ceroti Marco , Pala Valeria , Krogh Vittorio , Vineis Paolo , Sacerdote Carlotta , Saieva Calogero , Salvini Simonetta , Sieri Sabina , Berrino Franco , Panico Salvatore , Mattiello Amalia , Tumino Rosario , Giurdanella Maria C. , Bamia Christina , Trichopoulou Antonia , Riboli Elio , Palli Domenico
Published: April 2007

Dietary habits play an important role in healthy ageing. We have investigated the role of dietary patterns on overall mortality in a large series of Italian elderly, recruited in five EPIC cohorts in Northern (Varese and Turin), Central (Florence) and Southern Italy (Naples and Ragusa).A total of 5611 subjects (72·6 % women) aged 60 years or older, enrolled in 1993–1998, were prospectively followed (median 6·2 years), with 152 deaths (98 women). Four major dietary patterns were identified by using an exploratory factor analysis based on dietary information collected at enrolment. The associations between these dietary patterns and overall mortality were evaluated by Cox models adjusted for potential confounders. The ‘Olive Oil & Salad’ pattern, characterised by a high consumption of olive oil, raw vegetables, soups and poultry, emerged as being inversely associated with overall mortality in both crude and adjusted models. After adjustment for gender, age and caloric intake, overall mortality was reduced by approximately 50 % in the highest quartile and a significant trend emerged (P = 0·008). This association persisted after adjusting for several additional confounders (hazard ratio (HR) 0·50; 95 % CI 0·29, 0·86; P for trend =  0·02). An association of the ‘Pasta & Meat’ pattern (characterised by pasta, tomato sauce, red meat, processed meat, added animal fat, white bread and wine) with increased overall mortality was also suggested, but only for the highest quartile in a multivariate model. Dietary recommendations aimed at the Italian elderly population should support a dietary pattern characterised by a high consumption of olive oil, raw vegetables and poultry.
Exogenous nucleic acids and nucleotides are efficiently hydrolysed and taken up as nucleosides by intestinal explants from suckling piglets
Authors: Gil Angel , Gómez-León Carmen , Rueda Ricardo
Published: April 2007

Human milk is a rich source of RNA, free nucleotides (NT) and nucleosides (NS). To determine the uptake of different NS sources by the intestinal epithelium, jejunal explants from suckling piglets were cultured in a medium supplemented with a mixture of NS (adenosine, cytidine, guanosine, inosine, uridine; 10 mg/l each), a mixture of five NT (AMP, CMP, GMP, IMP, UMP; 7 mg/l each) or RNA (60 mg/l), respectively. Aliquots from the media were taken at different times (0·5, 2, 5, 15, 30, 60, 180 min). NS and NT concentrations were analysed in the different supernatants at those periods using solid-phase extraction followed by HPLC. When explants were cultured in the presence of NS the concentration of these compounds, excepting cytidine, rapidly decreased, suggesting that they are efficiently taken up. When explants were incubated in the presence of NT, the total concentration of these compounds decreased while the total concentration of NS increased, suggesting that enterocytes efficiently hydrolyse NT into NS. Likewise, when explants were incubated in the presence of RNA, the total concentration of both NT and NS increased, indicating that intestinal explants are able to hydrolyse RNA to NT and then to NS in the absence of luminal enzymes. In conclusion, the jejunum of piglets at weaning is able to hydrolyse RNA and free NT to NS, and NS, excepting cytidine, are efficiently taken up by the small intestine. These results suggest that the current concentration of NT used to supplement infant formulas should be reconsidered.
Orbital microwave measurement of river discharge and ice status
Authors: Brakenridge G. Robert , Nghiem Son V. , Anderson Elaine , Mic Rodica
Published: April 2007

Satellite passive microwave sensors provide global coverage of the Earth's land surface on a near‐daily basis without severe interference from cloud cover. Using a strategy first developed for wide‐area optical sensors, and in conjunction with even limited ground‐based discharge information, such microwave data can be used to estimate river discharge changes, river ice status, and watershed runoff. Water surface area in a river reach increases as flow widens, and any temporally calibrated observation sensitive to changing water area monitors discharge. The sensor spatial resolution is less important than the scene‐to‐scene calibration and the contrast in upwelling radiance between water and land. We use the Advanced Microwave Scanning Radiometer (AMSR‐E) band at 36.5 GHz, descending orbit, horizontal polarization, and the resampled Level‐3 daily global data product. The discharge estimator HR is a ratio of calibration‐target radiance (expressed as brightness temperature), for a local land parcel unaffected by the river, to measurement‐target brightness temperature, for a pixel centered over the river. At midlatitudes, pixel dimensions are approximately 25 km. Because of low emission from water surfaces, HR increases with discharge as in‐pixel water area expands. It increases sharply once overbank flow conditions occur. River ice‐cover is also detectable. The sensitivity and accuracy of the orbital measurements is tested along U.S. rivers monitored by in situ gaging stations, with favorable results. Other tests demonstrate that for seasonally variable rivers, AMSR‐E can provide useful international measurements of daily river discharge even if only fragmentary monthly mean discharge data are available for calibration.
Thickness dependence of intrinsic dielectric response and apparent interfacial capacitance in ferroelectric thin films
Authors: Pertsev N. A. , Dittmann R. , Plonka R. , Waser R.
Published: April 2007

We studied theoretically the influence of the progressive strain relaxation and the depolarizing-field effect on the thickness dependence of the out-of-plane dielectric response of epitaxial ferroelectric thin films sandwiched between extended metal electrodes. The calculations show that the inverse of the measured capacitance varies with the film thickness almost linearly in the most part of the thickness range at the majority of temperatures. Extrapolation of this linear dependence to zero thickness usually gives considerable nonzero intercept even in the absence of nonferroelectric interfacial layers. Remarkably, such apparent “interfacial capacitance” in a certain temperature range becomes negative. The physical meaning of the effective dielectric constant, which can be extracted from the slope of the reciprocal capacitance thickness dependence, is also analyzed. The theoretical predictions are compared with the experimental data obtained for single-crystalline SrRuO3∕Ba0.7Sr0.3TiO3∕SrRuO3 and Pt∕Ba0.7Sr0.3TiO3∕SrRuO3 thin-film capacitors.
Density matrix based time-dependent density functional theory and the solution of its linear response in real time domain
Authors: Wang Fan , Yam Chi Yung , Chen GuanHua , Fan Kangnian
Published: April 2007

A density matrix based time-dependent density functional theory is extended in the present work. Chebyshev expansion is introduced to propagate the linear response of the reduced single-electron density matrix upon the application of a time-domain δ-type external potential. The Chebyshev expansion method is more efficient and accurate than the previous fourth-order Runge-Kutta method and removes a numerical divergence problem. The discrete Fourier transformation and filter diagonalization of the first-order dipole moment are implemented to determine the excited state energies. It is found that the filter diagonalization leads to highly accurate values for the excited state energies. Finally, the density matrix based time-dependent density functional is generalized to calculate the energies of singlet-triplet excitations.
Dynamic analysis of axially prestressed micro/nanobeam structures based on nonlocal beam theory
Authors: Lu Pin
Published: April 2007

In this article, a nonlocal Euler beam model with axial prestress is established based on the theory of nonlocal elasticity. Frequency equations and modal shape functions of beam structures with axial compressive or tensile prestresses under some typical boundary conditions are derived based on the model. The corresponding dynamic properties are presented and discussed in detail, which are shown to be very different from those predicted by classic elasticity theory. The theoretical model and results presented in this article can be considered as modifications of their counterparts based on classical continuum theory and can be applied to modeling and characterization of size-dependent mechanical properties of micro- or nanobeam-based devices.
Magnetoresistance after initial demagnetization in La0.67Sr0.33MnO3∕SrTiO3∕La0.67Sr0.33MnO3 magnetic tunnel junctions
Authors: Wertz E. T. , Li Q.
Published: April 2007

Magnetic tunnel junctions were fabricated from La0.67Sr0.33MnO3 (LSMO)∕SrTiO3∕La0.67Sr0.33MnO3 heterostructures. Junctions initially demagnetized at 5K with an in-plane magnetic field showed larger tunneling magnetoresistance (TMR) and sharper switching than standard TMR scans. Magnetoresistive switching from the demagnetized state was stable in fields <80G yielding a TMR of 475% and a ΔMR∕ΔH≈200%∕G. Changes in resistance achievable at <500G yielded a TMR of ≈850%. A similar TMR was seen when rotating the magnetic field from an in-plane to out-of-plane orientation. The demagnetized high resistance state may indicate that the LSMO layers preferentially choose a more efficient opposite magnetic domain alignment.
Characterization of the Schottky barrier in SrRuO3∕Nb:SrTiO3 junctions
Authors: Hikita Y. , Kozuka Y. , Susaki T. , Takagi H. , Hwang H. Y.
Published: April 2007

Internal photoemission spectroscopy was used to determine the Schottky barrier height in rectifying SrRuO3∕Nb-doped SrTiO3 junctions for 0.01 and 0.5wt% Nb concentrations. Good agreement was obtained with the barrier height deduced from capacitance-voltage measurements, provided that a model of the nonlinear permittivity of SrTiO3 was incorporated in extrapolating the built-in potential, particularly for high Nb concentrations. Given the generic polarizability of perovskites under internal/external electric fields, internal photoemission provides a valuable independent probe of the interface electronic structure.
Air stable high resolution organic transistors by selective laser sintering of ink-jet printed metal nanoparticles
Authors: Ko Seung H. , Pan Heng , Grigoropoulos Costas P. , Luscombe Christine K. , Fréchet Jean M. J. , Poulikakos Dimos
Published: April 2007

A high resolution organic field effect transistor (OFET) fabrication process has been developed based on the selective laser sintering of ink-jet printed nanoparticle inks and the recent development of an air stable carboxylate-functionalized polythiophene semiconducting polymer. The entire fabrication and device characterization are performed at room temperature, ambient pressure, and air environment without using complex lithographic methods. This low temperature OFET fabrication process based on nanoparticle laser sintering has great potential for realizing inexpensive, large area flexible electronics on heat sensitive polymer substrates.
Coupling between long range surface plasmon polariton mode and dielectric waveguide mode
Authors: Liu Fang , Rao Yi , Huang Yidong , Zhang Wei , Peng Jiangde
Published: April 2007

Coupling of TM mode between long range surface plasmon polariton (LRSPP) mode and conventional dielectric waveguide mode is demonstrated numerically with finite element method. The characteristics of a hybrid coupler, which consists of the LRSPP waveguide and conventional single mode dielectric waveguide, are analyzed. The high efficient coupling shows a possible route for integrating the SPP device and conventional dielectric optical devices together and a method to excite LRSPP mode with dielectric waveguide. Because the coupling just occurs on TM mode, this kind of the hybrid coupler can be used as polarization mode splitter and combiner.
Broadband dielectric microwave microscopy on micron length scales
Authors: Tselev Alexander , Anlage Steven M. , Ma Zhengkun , Melngailis John
Published: April 2007

We demonstrate that a near-field microwave microscope based on a transmission line resonator allows imaging in a substantially wide range of frequencies, so that the microscope properties approach those of a spatially resolved impedance analyzer. In the case of an electric probe, the broadband imaging can be used in a direct fashion to separate contributions from capacitive and resistive properties of a sample at length scales on the order of one micron. Using a microwave near-field microscope based on a transmission line resonator we imaged the local dielectric properties of a focused ion beam milled structure on a high-dielectric-constant Ba0.6Sr0.4TiO3 thin film in the frequency range from 1.3 to 17.4 GHz. The electrostatic approximation breaks down already at frequencies above ∼10 GHz for the probe geometry used, and a full-wave analysis is necessary to obtain qualitative information from the images.
Experimental setup for lensless imaging via soft x-ray resonant scattering
Authors: Sacchi Maurizio , Spezzani Carlo , Carpentiero Alessandro , Prasciolu Mauro , Delaunay Renaud , Lüning Jan , Polack François
Published: April 2007

We have developed a setup for measuring holographically formed interference patterns using an integrated sample-mask design. The direct space image of the sample is obtained via a two-dimensional Fourier transform of the x-ray diffraction pattern. We present the details of our setup, commenting on the influence of geometrical parameters on the imaging capabilities. As an example, we present and discuss the results of test experiments on a patterned Co film.
Hydrophobic association of α-helices, steric dewetting, and enthalpic barriers to protein folding
Authors: MacCallum Justin L. , Moghaddam Maria Sabaye , Chan Hue Sun , Tieleman D. Peter
Published: April 2007

Efficient protein folding implies a microscopic funnel-like multidimensional free-energy landscape. Macroscopically, conformational entropy reduction can manifest itself as part of an empirical barrier in the traditional view of folding, but experiments show that such barriers can also entail significant unfavorable enthalpy changes. This observation raises the puzzling possibility, irrespective of conformational entropy, that individual microscopic folding trajectories may encounter large uphill moves and thus the multidimensional free-energy landscape may not be funnel-like. Here, we investigate how nanoscale hydrophobic interactions might underpin this salient enthalpic effect in biomolecular assembly by computer simulations of the association of two preformed polyalanine or polyleucine helices in water. We observe a high, positive enthalpic signature at room temperature when the helix separation is less than a single layer of water molecules. Remarkably, this unfavorable enthalpy change, with a parallel increase in void volume, is largely compensated for by a concomitant increase in solvent entropy, netting only a small or nonexistent microscopic free-energy barrier. Thus, our findings suggest that high enthalpic folding barriers can be consistent with a funnel picture of folding and are mainly a desolvation phenomenon indicative of a cooperative mechanism of simultaneous formation of multiple side-chain contacts at the rate-limiting step.
Subversion of B lymphocyte tolerance by hydralazine, a potential mechanism for drug-induced lupus
Authors: Mazari Lynda , Ouarzane Meryem , Zouali Moncef
Published: April 2007

Accumulating evidence indicates that epigenetic alterations contribute to exacerbated activation or deregulation of the mechanisms that maintain tolerance to self-antigens in patients with lupus, a systemic autoimmune disease that can be triggered by medications taken to treat a variety of conditions. Here, we tested the effect of hydralazine, an antihypertensive drug that triggers lupus, on receptor editing, a chief mechanism of B lymphocyte tolerance to self-antigens. Using mice expressing transgenic human Igs, we found that hydralazine impairs up-regulation ofRAG-2gene expression and reduces secondary Ig gene rearrangements. Receptor editing was also partially abolished in a dose-dependent manner by a specific inhibitor of MEK1/2. Adoptive transfer of bone marrow B cells pretreated with hydralazine or with a MEK inhibitor to naïve syngeneic mice resulted in autoantibody production. We conclude that, by disrupting receptor editing, hydralazine subverts B lymphocyte tolerance to self and contributes to generation of pathogenic autoreactivity. We also postulate that inhibition of the Erk signaling pathway contributes to the pathogenesis of hydralazine-induced lupus and idiopathic human lupus.
Reduced expression of mitochondrial frataxin in mice exacerbates diet-induced obesity
Authors: Pomplun Doreen , Voigt Anja , Schulz Tim J. , Thierbach René , Pfeiffer Andreas F. , Ristow Michael
Published: April 2007

Published evidence suggests that adiposity in humans may be linked to impaired energy expenditure for reasons widely unresolved. We have generated mice with a systemic impairment of oxidative phosphorylation (OXPHOS) due to
aP2 cre
-mediated targeted disruption, and unexpectedly ubiquitous reduction of mitochondrial frataxin protein expression. Only when maintained on a high-calorie diet resembling Westernized eating habits, these animals accumulate additional body fat, leading to increased body mass, and develop diabetes mellitus, despite the fact that both calorie uptake and physical activity were identical to that in control animals. This phenotype is caused by a mild but significant reduction in total energy expenditure paralleled by increased expression of ATP citrate lyase, a rate-limiting step in
de novo
synthesis of fatty acids and triglycerides. Taken together, these findings indicate that a limited impairment in oxidative metabolism within the mitochondria directly predisposes mammals to excessive body weight gain.
In vivoCD8+T cell control of immunodeficiency virus infection in humans and macaques
Authors: Asquith Becca , McLean Angela R.
Published: April 2007

Forty million people are estimated to be infected with HIV-1, and only a small fraction of those have access to life-prolonging antiretroviral treatment. As the epidemic grows there is an urgent need for effective therapeutic and prophylactic vaccines. Nonhuman primate models of immunodeficiency virus infection are essential for the preclinical evaluation of candidate vaccines. To interpret the results of these trials, comparative studies of the human and macaque immune responses are needed. Despite the widespread use of macaques to evaluate vaccines designed to elicit a CD8+cytotoxic T lymphocyte (CTL) response, the efficiency with which CTL control immunodeficiency virus infections has not been compared between humans and macaques, largely because of difficulties in assaying the functional CTL response. We recently developed a method for estimating the rate at which CTLs kill cells productively infected with HIV-1 in humansin vivo. Here, using the same technique, we quantify the rate at which CTLs kill infected cells in macaque models of HIV infection. We show that CTLs kill productively infected cells significantly faster (P= 0.004) and that escape variants have significantly higher fitness costs (P= 0.003) in macaques compared with humans. These results suggest that it may be easier to elicit a protective CTL response in macaques than in humans and that vaccine studies conducted in macaques need to be interpreted accordingly.
Protein identification by spectral networks analysis
Authors: Bandeira Nuno , Tsur Dekel , Frank Ari , Pevzner Pavel A.
Published: April 2007

Advances in tandem mass spectrometry (MS/MS) steadily increase the rate of generation of MS/MS spectra. As a result, the existing approaches that compare spectra against databases are already facing a bottleneck, particularly when interpreting spectra of modified peptides. Here we explore a concept that allows one to perform an MS/MS database search without ever comparing a spectrum against a database. We propose to take advantage of spectral pairs, which are pairs of spectra obtained from overlapping (often nontryptic) peptides or from unmodified and modified versions of the same peptide. Having a spectrum of a modified peptide paired with a spectrum of an unmodified peptide allows one to separate the prefix and suffix ladders, to greatly reduce the number of noise peaks, and to generate a small number of peptide reconstructions that are likely to contain the correct one. The MS/MS database search is thus reduced to extremely fast pattern-matching (rather than time-consuming matching of spectra against databases). In addition to speed, our approach provides a unique paradigm for identifying posttranslational modifications by means of spectral networks analysis.
Competing ferromagnetism in high-temperature copper oxide superconductors
Authors: Kopp Angela , Ghosal Amit , Chakravarty Sudip
Published: April 2007

The extreme variability of observables across the phase diagram of the cuprate high-temperature superconductors has remained a profound mystery, with no convincing explanation for the superconducting dome. Although much attention has been paid to the underdoped regime of the hole-doped cuprates because of its proximity to a complex Mott insulating phase, little attention has been paid to the overdoped regime. Experiments are beginning to reveal that the phenomenology of the overdoped regime is just as puzzling. For example, the electrons appear to form a Landau Fermi liquid, but this interpretation is problematic; any trace of Mott phenomena, as signified by incommensurate antiferromagnetic fluctuations, is absent, and the uniform spin susceptibility shows a ferromagnetic upturn. Here, we show and justify that many of these puzzles can be resolved if we assume that competing ferromagnetic fluctuations are simultaneously present with superconductivity, and the termination of the superconducting dome in the overdoped regime marks a quantum critical point beyond which there should be a genuine ferromagnetic phase at zero temperature. We propose experiments and make predictions to test our theory and suggest that an effort must be mounted to elucidate the nature of the overdoped regime, if the problem of high-temperature superconductivity is to be solved. Our approach places competing order as the root of the complexity of the cuprate phase diagram.