bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation of porous polyacrylamide hydrogels by frontal polymerization
Authors: Lu Guo Dong , Yan Qing Zhi , Ge Chang Chun
Published: April 2007

Polyacrylamide hydrogels with defined porous structure were synthesized through frontal polymerization (FP) in the presence of NaHCO3 as a foaming agent. Pore properties were analyzed using scanning electron microscopy and mercury intrusion porosimetry. The as‐prepared hydrogels displayed a small cell diameter of ca 2 µm. The dissolved foaming agent dispersing at the level of molecules and the polymerization front propagating step by step should be responsible for the small uniform cell structure. The pore volume varied from 0.63 to 3.65 cm3 g−1 and the bulk density changed from 0.48 to 0.28 g cm−3 for a foaming agent content from 0 to 18%. The hydrogels synthesized by FP exhibited higher swelling rate and swelling ratio with respect to conventional batch polymerization. The highest swelling ratio and rate were obtained at a foaming agent concentration of 12% based on monomer. Copyright © 2007 Society of Chemical Industry
Electrochemical polymerization and characterization of polyether‐substituted aniline derivatives
Authors: Tirkeş Seha , Cihaner Atilla , Önal Ahmet M
Published: April 2007

New compounds consisting of aniline units linked by polyether bridges have been synthesized and their electrochemical polymerization was performed via constant potential electrolysis and cyclic voltammetry in an aqueous solution containing 3.0 mol L−1 H2SO4. Chemical polymerization was carried out using (NH4)2S2O8 as oxidizing agent. It was found that both methods gave the same polymer product without any cleavage of the polyether bridge between aniline rings. The polymers were characterized using the Fourier transform infrared spectroscopic technique and the thermal behavior of electrochemically prepared polymers was investigated using thermogravimetric analysis. Spectroelectrochemical properties of the films were investigated using the in situ UV‐visible spectroscopic technique. Copyright © 2007 Society of Chemical Industry
Diabetes‐induced changes in the renal cortical proteome assessed with two‐dimensional gel electrophoresis and mass spectrometry
Authors: Tilton Ronald G. , Haidacher Sigmund J. , LeJeune Wanda S. , Zhang Xiaoquan , Zhao Yingxin , Kurosky Alexander , Brasier Allan R. , Denner Larry
Published: April 2007

To understand the spectrum of proteins affected by diabetes and to characterize molecular functions and biological processes they control, we analyzed the renal cortical proteome of db/db mice using 2‐DE combined with MALDI‐TOF, MALDI‐TOF/TOF, and LC‐MS/MS. This approach yielded 278 high confidence identifications whose expression levels were significantly increased or decreased >two‐fold by diabetes, of which 170 mapped to gene identifiers representing 147 nonredundant proteins. Gene Ontology classification demonstrated that 80% of these proteins modulated physiological functions, 55% involved metabolism, ˜25% involved carboxylic and organic acid metabolism, 14% involved biosynthesis or catabolism, and 12% involved fatty acid metabolism. Predominant molecular functions were catalytic (61%), oxidoreductase (20%), and transferase (17%) activities, and nucleotide and ATP binding (11–15%). Twenty eight percent of the proteins identified as significantly altered by diabetes were mitochondrial proteins. The top‐ranked network described by Ingenuity Pathway Analysis indicated PPARα was the most common node of interaction for the numerous enzymes whose expression levels were influenced by diabetes. These differentially regulated proteins create a foundation for a systems biology exploration of molecular mechanisms underlying the pathophysiology of diabetic nephropathy.
Preparation of poly(butylene‐co‐ε‐caprolactone carbonate) and their use as drug carriers for a controlled delivery system
Authors: Liu Yanfei , Huang Kelong , Peng Dongming , Liu Suqin , Wu Hong
Published: April 2007

Poly(butylene‐co‐ε‐caprolactone carbonate) (PBCCL) was successfully synthesized via terpolymerization of carbon dioxide, 1,2‐butylene oxide (BO), and ε‐caprolactone (ε‐CL). ε‐CL was inserted into the backbone of BO‐CO2. The glass transition temperature (Tg) and the decomposition temperature (Td) of PBCCL were much higher than those of poly(butylene carbonate) (PBC). The degradation rate of PBCCL was higher than that of PBC in a pH 7.4 phosphate‐buffered solution. ε‐CL offered an ester structural unit that gave the terpolymers remarkable degradability. PBC and PBCCL microcapsules containing a hydrophilic antibiotic drug pazufloxacin mesilate (PZFX) were elaborated by solvent evaporation method based on the formation of double W/O/W emulsion. Microcapsules were characterized in terms of the morphology, size, amount of encapsulated, and encapsulation efficiency. The results showed that the microcapsules had smooth and spherical surfaces, and the mean diameter of the microcapsules was in the range of 0.5–1 μm. Of all, 87.90% drug encapsulation efficiency has been achieved for microcapsules of 38.21% drug loading. In vitro drug release of these microcapsules was performed in a pH 7.4 phosphate‐buffered solution. The release profiles were investigated from the measurement of PZFX presented in the release medium at various intervals. The release profiles of PZFX from PBC and PBCL microcapsules were found to be biphasic with a burst release followed by a gradual release phase. The release rate of PZFX from the microcapsules increased with increasing the content of ε‐CL inserted into the copolymers. It showed that the release profiles of PZFX were highly polymer‐dependent. © 2007 Wiley Periodicals, Inc. JPolym Sci Part A: Polym Chem 45: 2152–2160, 2007
Synthesis and characterization of epoxy resin‐montmorillonite nanocomposites obtained by frontal polymerization
Authors: Mariani Alberto , Bidali Simone , Caria Giuseppe , Monticelli Orietta , Russo Saverio , Kenny José María
Published: April 2007

Frontal polymerization, a method that allows to convert a monomer into a polymer exploiting the exothermicity of the self‐same polymerization reaction, has been conveniently used for the easy and fast preparation of epoxy resin‐montmorillonite nanocomposites. The obtained materials have shown characteristics similar or even better than those prepared by the conventional polymerization routes. The synthetic methods and the thorough characterization of the obtained nanocomposites are described. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2204–2211, 2007
Site directed mutagenesis at position 193 of human trypsin 4 alters the rate of conformational change during activation: Role of local internal viscosity in protein dynamics
Authors: Tóth Júlia , Simon Zoltán , Medveczky Péter , Gombos Linda , Jelinek Balázs , Szilágyi László , Gráf László , Málnási‐Csizmadia András
Published: April 2007

Upon activation of trypsinogen four peptide segments flanked by hinge glycine residues undergo conformational changes. To test whether the degree of conformational freedom of hinge regions affects the rate of activation, we introduced amino acid side chains of different characters at one of the hinges (position 193) and studied their effects on the rate constant of the conformational change. This structural rearrangement leading to activation was triggered by a pH‐jump and monitored by intrinsic fluorescence change in the stopped‐flow apparatus. We found that an increase in the size of the side chain at position 193 is associated with the decrease of the reaction rate constant. To analyze the thermodynamics of the reaction, temperature dependence of the reaction rate constants was examined in a wide temperature range (5–60°C) using a novel temperature‐jump/stopped‐flow apparatus developed in our laboratory. Our data show that the mutations do not affect the activation energy (the exponential term) of the reaction, but they significantly alter the preexponential term of the Arrhenius equation. The effect of solvent viscosity on the rate constants of the conformational change during activation of the wild type enzyme and its R193G and R193A mutants was determined and evaluated on the basis of Kramers' theory. Based on this we propose that the reaction rate of this conformational transition is regulated by the internal molecular friction, which can be specifically modulated by mutagenesis in the hinge region. Proteins 2007. © 2007 Wiley‐Liss, Inc.
A simple way to compute protein dynamics without a mechanical model
Authors: Shih Chien‐Hua , Huang Shao‐Wei , Yen Shih‐Chung , Lai Yan‐Long , Yu Sung‐Huan , Hwang Jenn‐Kang
Published: April 2007

We found that in proteins the average atomic fluctuation is linearly related to the square of the atomic distance from the center of mass of the protein. Using this simple relation, we can accurately compute the temperature factors of proteins of a wide range of sizes and folds, and the correlation of the fluctuations in proteins. This simple relation provides a direct link between protein dynamics and the static protein's geometrical shape and offers a simple way to compute protein dynamics without either long time trajectory integration or any matrix operations. Proteins 2007. © 2007 Wiley‐Liss, Inc.
Deposition of polysiloxane‐like nanofilms onto an aluminium alloy by plasma polymerized hexamethyldisiloxane: characterization by XPS and contact angle measurements
Authors: Azioune A. , Marcozzi M. , Revello V. , Pireaux J.‐J.
Published: April 2007

In this work, aluminium (Alclad 2024‐T3) substrates were cleaned by an r.f. (13.56 MHz) plasma, using argon (Ar), oxygen (O2) and a mixture of O2/Ar (50:50) gases. The effectiveness of plasma cleaning was checked in situ using X‐ray photoelectron spectroscopy (XPS) and ex situ using water contact angle measurements. XPS O/Al surface atomic ratios are in excellent agreement with those of the crystalline boehmite and the pseudoboehmite. Oxygen O 1s peak‐fitting was used to quantify the proportion of hydroxyl ions and the functional composition on the aluminium surface: the surface cleaned with O2 plasma contains 50% of aluminium hydroxides, the ones cleaned with Ar plasma and with Ar/O2 plasma contain, respectively, 25 and 37% hydroxyl ions. The binding energy separation between Al 2p and O 1s is characteristic of AlO(OH). Thin SiOx films were subsequently deposited from a mixture of hexamethyldisiloxane (HMDSO) and oxygen. In the absence of oxygen, a hydrophobic (Θ≥ 100° ) film characteristic of polydimethylsiloxane (PDMS) is formed: polysiloxane‐like thinner films (SiOx) are obtained with the introduction of oxygen. XPS and contact angle measurements confirmed both the composition and the structure of these films. More importantly, contact angle measurements using different liquids and interpreted with the van Oss‐Good‐Chaudhury theory allowed determination of the surface free energy of the deposited films: the calculated values of surface tension of the film formed from HMDSO/O2: (50/50) are in excellent agreement with those of reference silica‐based materials such as a silicon wafer and cleaned glass. Copyright © 2007 John Wiley & Sons, Ltd.
Taking seriously the intellectual growth of students: Accommodations for self‐authorship
Authors: Wildman Terry M.
Published: April 2007

Student learning and student development are part of a unified framework rather than separate interests to be pursued independently.
Engaging differences: Self‐Authorship and the decision‐making process
Authors: Laughlin Anne , Creamer Elizabeth G.
Published: April 2007

Decisions that involve consideration of inconsistent or contradictory information provide a context for understanding and supporting intellectual development.
Tools and methods for genetic analysis of Saccharomyces castellii
Authors: Astromskas Eimantas , Cohn Marita
Published: April 2007

The budding yeast species Saccharomyces castellii has provided important new insights into molecular evolution when incorporated in comparative genomics studies and studies of mitochondrial inheritage. Although it shows some diversity in the specific molecular details, several analyses have shown that it contains many genetic pathways similar to those of S. cerevisiae. Here we have investigated the possibility of performing genetic analyses in S. castellii. We optimized the LiAc transformation protocol to achieve 200–300 transformants/µg plasmid DNA. We found that the commonly used plasmids for S. cerevisiae are stably maintained in S. castellii under selective conditions. Surprisingly, both 2µ and CEN/ARS plasmids are kept at a high copy number. Moreover, the kanMX cassette can be used as a resistance marker against the selective drug geneticin (G418). Finally, we determined that the S. cerevisiae GAL1 promoter can be used for the activation of transcription in S. castellii, thus enabling the controlled overexpression of genes when galactose is present in the medium. The availability of these tools provides the possibility of performing genetic analyses in S. castellii, and makes it a promising new model system in which hypotheses derived from bioinformatics studies can be experimentally tested. Copyright © 2007 John Wiley & Sons, Ltd.
Is distraction less effective when pain is threatening? An experimental investigation with the cold pressor task
Authors: Van Damme Stefaan , Crombez Geert , Van De Wever Kathleen Nieuwenborgh , Goubert Liesbet
Published: April 2007

Distraction is a commonly used strategy to control pain. However there is doubt about its effectiveness as a clinical tool, and results from both experimental and clinical studies remain inconclusive. Recent theoretical advancements suggest that distraction of attention may be less effective when pain is threatening. The aim of the present study was to experimentally investigate this hypothesis. Pain‐free volunteers (N=101) participated in a cold pressor test. Half of the participants simultaneously performed a cognitive distraction task, the other half did not. The threat value of the pain was manipulated by means of verbal information. The results showed that distraction resulted in less attention to the pain and lower pain ratings once the cold pressor procedure was halted. The hypothesis that the effectiveness of distraction is modulated by the threat value of pain could not be confirmed. However, threatening information increased catastrophic thoughts and anxiety, and interfered with performance on the distraction task. These findings suggest that caution is required in using distraction as a pain control strategy when the threat value is high, because fearful appraisal of pain is associated with less engagement in distraction tasks.
Transfection and expression of plasmid DNA in plant cells by an arginine‐rich intracellular delivery peptide without protoplast preparation
Authors: Chen Chung-Pin , Chou Jyh-Ching , Liu Betty Revon , Chang Microsugar , Lee Han-Jung
Published: April 2007

The delivery and expression of exogenous genes in plant cells have been of particular interest for plant research and biotechnology. Here, we present results demonstrating a simple DNA transfection system in plants. Short arginine‐rich intracellular delivery peptide, a protein transduction domain, was capable of delivering plasmid DNA into living plant cells non‐covalently. This peptide‐mediated DNA delivery conferred several advantages, such as nuclear targeting, non‐toxic effect, and ease of preparation without protoplast formulation. Thus, this novel technology shall provide a powerful tool to investigate gene function in vivo, and lay the foundation for the production of transgenic plants in future.
Pancreatic islet β‐cell and oxidative stress: The importance of glutathione peroxidase
Authors: Robertson R. Paul , Harmon Jamie S.
Published: April 2007

Pancreatic β‐cell function continuously deteriorates in type 2 diabetes despite optimal treatment regimens, which has been attributed to hyperglycemia itself via formation of excess levels of reactive oxygen species (ROS). Glutathione peroxidase GPx), by virtue of its ability to catabolize both H2O2 and lipid peroxides, is uniquely positioned to protect tissues from ROS. The level of this antioxidant in β cells is extremely low and overexpression of GPx in islets provides enhanced protection against oxidative stress. This suggests that GPx mimetics may represent a valuable ancillary treatment that could add a novel layer of protection for the β‐cell.
Analysis of βB1‐crystallin unfolding equilibrium by spin and fluorescence labeling: Evidence of a dimeric intermediate
Authors: Koteiche Hanane A. , Kumar M. Satish , Mchaourab Hassane S.
Published: April 2007

A central step in understanding lens aging is to characterize the thermodynamic stability of its proteins and determine the consequences of changes in the primary sequence on their folding equilibria. For this purpose, destabilized mutations were introduced in βB1‐crystallin targeting the domain interface within the fold of a subunit. Global unfolding was monitored by tryptophan fluorescence while concomitant structural changes at the dimer interface were monitored by fluorescence and spin labels. Both spectral probes report explicit evidence of multi‐state unfolding equilibrium. The biphasic nature of the unfolding curves was more pronounced at higher protein concentration. Distinct shifts in the midpoint of the second transition reflect the population of a dimeric intermediate. This intermediate may be a critical determinant for the life‐long stability of the β‐crystallins and has important consequences on interactions with α‐crystallin.
Amplification of magnetic fields by polaritonic flows in quantum pair plasmas
Authors: SHUKLA N. , SHUKLA P. K. , MORFILL G. E.
Published: April 2007

It is shown that equilibrium polaritonic flows can amplify magnetic fields in an ultra-cold quantum electron–positron/hole (polaritons) plasma. For this purpose, a linear dispersion relation has been derived by using the quantum generalized hydrodynamic equations for the polaritons, the Maxwell equation, and Faraday's law. The dispersion relation admits purely growing instabilities, the growth rates of which are proportional to the equilibrium streaming speeds of the polaritons. Possible applications of our work to the spontaneous excitation of magnetic fields and the associated cross-field transport of the polaritons in micromechanical systems, compact dense astrophysical objects (e.g. neutron stars), and intense laser–plasma interaction experiments are mentioned.
B-Vitamins and Homocysteine in Spanish Institutionalized Elderly
Authors: Gonzalez-Gross  , Sola  , Albers  , Barrios  , Alder  , Castillo  , Pietrzik
Published: April 2007

Background: Hyperhomocysteinemia is an accepted risk factor for cardiovascular disease, and possibly also for cognitive impairment and dementia. It has also been proposed as a marker for the status of the B vitamins, which participate in the metabolism of homocysteine. Therefore, especially in the elderly, it is important to know the prevalence of high homocysteine (tHcy) levels and the influence that B vitamins have on them. Material and Methods: 218 elderly of both sexes, aged 60–105, living in an elderly home in Granada (Spain), were screened for serum folate, red blood cell (RBC) folate, serum cobalamin (B12) (Abbott, IMx), holotranscobalamin II (Holo-TC II) (HoloTC RIA, Axis-Shield), methylmalonic acid (MMA) (MS-GC), total pyridoxine (B6) (HPLC), and total homocysteine (tHcy) (Abbott, IMx). Results: Hyperhomocysteinemia (tHcy > 12 μmol/L) was detected in 80.7%. Serum folate deficiency was severe (≤ 4 ng/mL) in 19.3% and moderate (4–7 ng/mL) in 43.1%. In 14.2% of the elderly RBC folate was ≤ 175 ng/mL, and in 61.0% it was between 175–400 ng/mL. Vitamin B12, measured in serum (≤ 200 pg/mL), was deficient in 15.8%, but if measured as Holo-TC II (≤ 45 pmol/L), deficiency ranged up to 39.1%. MMA was high (≥ 300 nmol/L) in 45.6%. Vitamin B6 (< 20 nmol/L) was low only in one person. In order to identify the factors that could predict tHcy levels, a multiple regression analysis was performed. Best results corresponded to the combination of log serum folate and log Holo-TC II, which gave values of R > 0.5. If analyzed independently, the highest correlation was with log serum folate (r = –0.290), followed by RBC folate (r = –0.263), Holo-TC II (r = –0.228), log B12 (r = –0.175), and log B6 (r = –0.078). Conclusion: There is a high prevalence of vitamin B deficiency and hyperhomocysteinemia in the studied population. Our data confirm the influence of these vitamins, especially folate, on tHcy levels, but hyperhomocysteinemia cannot be used as the only diagnostic criterion to detect subclinical vitamin deficiency in elderly people, especially to detect vitamin B12 deficiency.
Protective Role of Raphanus Sativus Root Extract on Paracetamol-Induced Hepatotoxicity in Albino Rats
Authors: Chaturvedi  , George  , Machacha
Published: April 2007

The methanol extract of Raphanus sativus root extract showed a protective effect on paracetamol-induced hepatotoxicity in a dose-dependent manner. Degree of lipid peroxidation caused by paracetamol was measured in terms of thiobarbituric acid reactive substances (TBARS) and protection was measured in reference to serum glutamate oxaloacetate transaminase (SGOT), serum glutamate aspartate transaminase (SGPT), and blood and hepatic levels of antioxidants like glutathione and catalase. Administration of extract along with paracetamol showed significant protection. Levels of TBARS were found to be low, activities of SGOT and SGPT were low, while hepatic glutathione levels were significantly higher in experimental rats that received the mixture of paracetamol and the extract as compared to rats that received paracetamol only. Activities of catalase were also high in all experimental groups. Thus this study indicates the involvement of Raphanus sativus root extract with antioxidants like glutathione and catalase in rendering protection against paracetamol-induced lipid peroxidation and hepatotoxicity.
Nutrient Intake in an Elderly Population in Southern France (POLANUT): Deficiency in some Vitamins, Minerals and ω-3 PUFA
Authors: Carrière  , Delcourt  , Lacroux  , Gerber  , POLANUT Study Group
Published: April 2007

Objective: Evaluation of the nutritional status of an elderly cohort from a French Mediterranean area. Design: Cross-sectional nutritional assessment in the framework of the population-based POLA cohort. Subjects and Methods: 832 subjects aged 70 years or older answered a 165-item, semi-quantitative food frequency questionnaire. Mean Nutritional Need (MNN) was defined as 77% of the French Recommended Daily Allowance (RDA). The risk for clinical deficiency (CD) was defined as intakes lower than the Limit Threshold Intake (70% of the MNN). Results: Consumption was characterized by an excess of saturated fatty acids (SFA) (95.4% of subjects above the RDA) and a deficit of ω-3 polyunsaturated fatty acids (PUFA) (60.1% and 46.9% of subjects at risk for CD for alpha-linolenic (ALA) and long-chain ω-3 PUFA, respectively). Median intakes of fiber, vitamins B6, B9, and D, calcium, and magnesium were below the RDA. Dairy products were the first providers of SFA, nuts of ALA, and fish of long-chain ω-3 PUFA and vitamin D. Conclusion: The study identified an unbalanced food intake, with an excess of mammal animal products, mainly of dairy products, and a deficit of fish and vegetal foods. This resulted in a deficiency in some vitamins, minerals, and ω-3 PUFA.
Selbstmanagementförderung bei chronischer Krankheit: Geschichte, Konzept und Herausforderungen
Authors: Haslbeck Jörg W. , Schaeffer Doris
Published: April 2007

Das Thema Selbstmanagement bei chronischer Krankheit wird international seit längerem diskutiert und vermehrt auch im deutschsprachigen Raum erörtert. Auch die Entwicklung von Programmen zur Selbstmanagementförderung ist in den letzten Jahren vorangeschritten. Zugleich hat Selbstmanagement im Zuge dessen mehr und mehr den Charakter eines Sammelbegriffs erhalten. Ziel des Beitrags ist es daher, zur Begriffsklärung beizutragen, konzeptionelle Aspekte zu diskutieren, die Aufgaben von Selbstmanagementförderung darzustellen und abschließend den bestehenden Diskussionsbedarf zu erörtern. Dabei wird der Schwerpunkt auf die Bedeutung von Selbstmanagementförderung für die Bewältigung chronischer Krankheit gelegt – einem der wichtigsten Anwendungsfelder des Konzepts.
Toward improved satellite estimates of short‐wave radiative fluxes—Focus on cloud detection over snow: 1. Methodology
Authors: Li Xu , Pinker Rachel T. , Wonsick M. M. , Ma Yingtao
Published: April 2007

A Coupled Cloud and Snow Detection Algorithm (CCSDA) for improving satellite capabilities to estimate downward surface short‐wave radiation under snow conditions has been developed and will be described here. Four channels of the GOES‐8 imager are used to detect clouds, snow, and to perform background analysis for each hour of the diurnal cycle. The Clear‐Sky Background Analysis (CSBA) is used as a reference state to generate dynamic and location‐dependent thresholds for cloud detection tests, and the CSBA of the visible channel is used as a required input for the solar radiation model. The implementation of any one component requires a priori information on the other two. Therefore the three components are coupled to iteratively update cloud detection variables, cloud amount, and snow cover. Snow detection aims to distinguish between snow‐covered and snow‐free pixels after a pixel is classified as clear. The CCSDA algorithm will be described, and preliminary evaluation of the impact of the improvements on surface radiative flux estimates will be presented in part 2 (Pinker et al., 2007).
Hubbard Glacier, Alaska: 2002 closure and outburst of Russell Fjord and postflood conditions at Gilbert Point
Authors: Motyka Roman J. , Truffer Martin
Published: April 2007

Hubbard Glacier, the largest temperate tidewater glacier in the world, has been advancing since 1895 AD and has now twice dammed 60‐km‐long Russell Fjord, once in 1986 and more recently in 2002. This paper focuses on the 2002 event, when a strong spring advance pushed shallow submarine proglacial sediments against Gilbert Point, closing off Russell Fjord by late June. As a consequence, upstream ice flow decelerated from 5 m d−1 to 1.5 m d−1, with flow diverging to either side of Gilbert Point. Lake height reached 15 m asl before intense rains caused lake water to overtop the moraine dam on 14 August 2002. Three cubic kilometers of water were released within 30 hours, with peak discharge reaching 55,000 m3 s−1 24 hours after the flood began. The discharge records for the 1986 and 2002 outbursts differ significantly and reflect differences in lake height (26 m versus 15 m) and dam types (ice versus moraine). The 2002 outburst proceeded in two stages: (1) relatively slow overtopping of the subaerial moraine with downward erosion rates of 1–2 m h−1 with little lateral expansion, (2) followed by faster downward erosion of the submarine moraine (up to 7 m h−1) with rapid lateral expansion of the channel by ice calving (∼7 m h−1). The annual average terminus position at Gilbert Point has remained constant since 2002, although there are seasonal variations of 100–200 m. The deep channel, strong tidal currents, and seasonally warm ocean water appear to have prevented the advance of this segment of the terminus despite the glacier's continued advance elsewhere along its terminus. Sediments are slowly filling in the channel at a rate of about 4 m yr−1, and their steady accumulation may eventually trigger the next closure.
Abrupt change in mantle fabric across northern Apennines detected using seismic anisotropy
Authors: Salimbeni S. , Pondrelli S. , Margheriti L. , Levin V. , Park J. , Plomerova J. , Babuska V.
Published: April 2007

We estimated SKS splitting parameters for 18 earthquakes observed over 2 years on a dense linear seismometer array crossing the Apennines orogen (Northern Italy). An abrupt (within 30 km) change in fast polarization occurs near the crest of the Apennines. Southwest of the crest, fast polarization parallels the Apennines strike (WNW–ESE), rotating to EW orientation near the Tyrrhenian Sea. Northeast of the crest, toward the Po Plain, fast polarization is NNE–SSW, roughly normal to the orogen's strike. Delay times (0.6–2.9s) do not show a remarkable pattern. Splitting parameters beneath the Apennines argue against anisotropy restricted to the crust, and suggest that the mantle region deformed by Apennines slab rollback is spatially limited. We hypothesize that the rollback process has been uneven, evolving to a contortion of the northern edge of the Apennines slab, and perhaps incipient detachment. Lithospheric anisotropy beneath the Po‐Plain may also be significant.
The Drosophila mitotic inhibitor Frühstart specifically binds to the hydrophobic patch of cyclins
Authors: Gawliński Pawel , Nikolay Rainer , Goursot Catherine , Lawo Steffen , Chaurasia Bhagirath , Herz Hans‐Martin , Kußler‐Schneider Yvonne , Ruppert Thomas , Mayer Matthias , Großhans Jörg
Published: April 2007

The hydrophobic patch of cyclins interacts with cyclin‐dependent kinase (Cdk) substrates and p27‐type Cdk inhibitors. Although this interaction is assumed to contribute to the specificity of different Cdk–Cyclin complexes, its role in specific steps of the cell cycle has not been demonstrated. Here, we show that in Drosophila the mitotic inhibitor Frühstart (Frs) binds specifically and with high affinity to the hydrophobic patch of cyclins. In contrast to p27‐type Cdk inhibitors, Frs does not form a stable interaction with the catalytic centre of Cdk and allows phosphorylation of generic model substrates, such as histone H1. Consistent with a 2.5 times stronger binding to CycA than to CycE in vitro, ectopic expression of frs induces endocycles, in a manner similar to that reported previously for downregulation of CycA or Cdk1. We propose that binding of Frs to cyclins blocks the hydrophobic patch to interfere with Cdk1 substrate recognition.
Pseudomonas aeruginosaand sPLA2 IB stimulate ABCA1-mediated phospholipid efflux via ERK-activation of PPARα–RXR
Authors: Agassandian Marianna , Miakotina Olga L. , Andrews Matthew , Mathur Satya N. , Mallampalli Rama K.
Published: April 2007

Bacterial infection triggers an acute inflammatory response that might alter phospholipid metabolism. We have investigated the acute-phase response of murine lung epithelia to Pseudomonas aeruginosa infection. Ps. aeruginosa triggered secretion of the pro-inflammatory lipase, sPLA2 IB (phospholipase A2 IB), from lung epithelium. Ps. aeruginosa and sPLA2 IB each stimulated basolateral PtdCho (phosphatidylcholine) efflux in lung epithelial cells. Pre-treatment of cells with glyburide, an inhibitor of the lipid-export pump, ABCA1 (ATP-binding cassette transporter A1), attenuated Ps. aeruginosa and sPLA2 IB stimulation of PtdCho efflux. Effects of Ps. aeruginosa and sPLA2 IB were completely abolished in human Tangier disease fibroblasts, cells that harbour an ABCA1 genetic defect. Ps. aeruginosa and sPLA2 IB induced the heterodimeric receptors, PPARα (peroxisome-proliferator-activated receptor-α) and RXR (retinoid X receptor), factors known to modulate ABCA1 gene expression. Ps. aeruginosa and sPLA2 IB stimulation of PtdCho efflux was blocked with PD98059, a p44/42 kinase inhibitor. Transfection with MEK1 (mitogen-activated protein kinase/extracellular-signal-regulated kinase kinase 1), a kinase upstream of p44/42, increased PPARα and RXR expression co-ordinately with increased ABCA1 protein. These results suggest that pro-inflammatory effects of Ps. aeruginosa involve release of an sPLA2 of epithelial origin that, in part, via distinct signalling molecules, transactivates the ABCA1 gene, leading to export of phospholipid.
Biochemical and structural exploration of the catalytic capacity of Sulfolobus KDG aldolases
Authors: Wolterink-van Loo Suzanne , van Eerde André , Siemerink Marco A. J. , Akerboom Jasper , Dijkstra Bauke W. , van der Oost John
Published: April 2007

Aldolases are enzymes with potential applications in biosynthesis, depending on their activity, specificity and stability. In the present study, the genomes of Sulfolobus species were screened for aldolases. Two new KDGA [2-keto-3-deoxygluconate (2-oxo-3-deoxygluconate) aldolases] from Sulfolobus acidocaldarius and Sulfolobus tokodaii were identified, overexpressed in Escherichia coli and characterized. Both enzymes were found to have biochemical properties similar to the previously characterized S. solfataricus KDGA, including the condensation of pyruvate and either D,L-glyceraldehyde or D,L-glyceraldehyde 3-phosphate. The crystal structure of S. acidocaldarius KDGA revealed the presence of a novel phosphate-binding motif that allows the formation of multiple hydrogen-bonding interactions with the acceptor substrate, and enables high activity with glyceraldehyde 3-phosphate. Activity analyses with unnatural substrates revealed that these three KDGAs readily accept aldehydes with two to four carbon atoms, and that even aldoses with five carbon atoms are accepted to some extent. Water-mediated interactions permit binding of substrates in multiple conformations in the spacious hydrophilic binding site, and correlate with the observed broad substrate specificity.
Functional diversification of a basic helix–loop–helix protein due to alternative transcription during generation of amphidiploidy in tobacco plants
Authors: Kodama Yutaka , Sano Hiroshi
Published: April 2007

A plastid-resident basic helix–loop–helix protein, previously identified in Nicotiana tabacum and designated as NtWIN4 (N. tabacum wound-induced clone 4), has been converted from a nuclear transcription repressor into a plastid-resident regulatory factor through replacement of the DNA-binding domain with a plastid transit sequence during evolution. N. tabacum is a natural amphidiploid plant derived from Nicotiana tomentosiformis and Nicotiana sylvestris and immunoblot staining using anti-NtWIN4 antibodies identified two protein species, a 26 kDa form and a 17 kDa form, in N. sylvestris, whereas only the 17 kDa form was found in N. tabacum. The 26 kDa protein is produced when translation starts from the first AUG codon of the mRNA and is predominantly localized in the cytoplasm and nucleus, whereas the 17 kDa protein is derived from a 24 kDa precursor protein, synthesized from the second AUG codon, and localizes only to plastids. Subsequent analyses revealed that the lengths of the mRNAs vary in the two plant species. One major form lacks the first AUG, while minor populations possess variable 5′-untranslated regions prior to the first AUG codon. Translation of the two types produces the 24 kDa and 26 kDa proteins respectively. In vitro translation assays indicated that initiation frequency from the first AUG codon is higher in mRNAs from N. sylvestris than from N. tabacum. In contrast, initiation from the second AUG codon was found to be equally efficient in mRNAs from both species. These results suggest that both mRNA populations and translation efficiency changed during the amphidiploidization responsible for generation of N. tabacum. This scheme could reflect a molecular mechanism of protein evolution in plants.
Acid–base catalysis in Leuconostoc mesenteroides sucrose phosphorylase probed by site-directed mutagenesis and detailed kinetic comparison of wild-type and Glu237→Gln mutant enzymes
Authors: Schwarz Alexandra , Brecker Lothar , Nidetzky Bernd
Published: April 2007

The role of acid–base catalysis in the two-step enzymatic mechanism of α-retaining glucosyl transfer by Leuconostoc mesenteroides sucrose phosphorylase has been examined through site-directed replacement of the putative catalytic Glu237 and detailed comparison of purified wild-type and Glu237→Gln mutant enzymes using steady-state kinetics. Reactions with substrates requiring Brønsted catalytic assistance for glucosylation or deglucosylation were selectively slowed at the respective step, about 105-fold, in E237Q. Azide, acetate and formate but not halides restored catalytic activity up to 300-fold in E237Q under conditions in which the deglucosylation step was rate-determining, and promoted production of the corresponding α-glucosides. In situ proton NMR studies of the chemical rescue of E237Q by acetate and formate revealed that enzymatically formed α-glucose 1-esters decomposed spontaneously via acyl group migration and hydrolysis. Using pH profiles of kcat/Km, the pH dependences of kinetically isolated glucosylation and deglucosylation steps were analysed for wild-type and E237Q. Glucosylation of the wild-type proceeded optimally above and below apparent pKa values of about 5.6 and 7.2 respectively whereas deglucosylation was dependent on the apparent single ionization of a group of pKa≈5.8 that must be deprotonated for reaction. Glucosylation of E237Q was slowed below apparent pKa≈6.0 but had lost the high pH dependence of the wild-type. Deglucosylation of E237Q was pH-independent. The results allow unequivocal assignment of Glu237 as the catalytic acid–base of sucrose phosphorylase. They support a mechanism in which the pKa of Glu237 cycles between ≈7.2 in free enzyme and ≈5.8 in glucosyl enzyme intermediate, ensuring optimal participation of the glutamate residue side chain at each step in catalysis. Enzyme deglucosylation to an anionic nucleophile took place with Glu237 protonated or unprotonated. The results delineate how conserved active-site groups of retaining glycoside hydrolases can accommodate enzymatic function of a phosphorylase.
Magnetic properties, phase evolution, and microstructure of melt spun SmCo7−xHfxCy (x=0–0.5; y=0–0.14) ribbons
Authors: Chang H. W. , Huang S. T. , Chang C. W. , Chiu C. H. , Chang W. C. , Sun A. C. , Yao Y. D.
Published: April 2007

Magnetic properties, phase evolution, and microstructure of melt spun SmCo7−xHfxCy (x=0–0.5; y=0–0.14) ribbons via direct quenching have been investigated. For SmCo7−xHfx series ribbons, proper volume fraction of Hf is effective to stabilize and increase the magnetocrystalline anisotropy field of the TbCu7-type structure. Accordingly, the optimal magnetic properties of Br=6.4kG, Hci=7.3kOe, and (BH)max=8.7MGOe could be obtained for x=0.1. Furthermore, a slight C addition to above alloys is helpful in refining the grain size of the ribbons from 100–400nm for C-free to 10–80nm for C-containing samples. As a result, the magnetic properties are further improved to Br=6.9kG, Hci=11.8kOe, and (BH)max=10.6MGOe for SmCo6.8Hf0.2C0.12 nanocomposite ribbons.
In-plane magnetic anisotropies of sputtered Co0.7Fe0.3 films on AlGaAs(001) spin light emitting diode heterostructures
Authors: Hindmarch A. T. , Kinane C. J. , Marrows C. H. , Hickey B. J. , Henini M. , Taylor D. , Arena D. A. , Dvorak J.
Published: April 2007

The in-plane magnetic properties of Co0.7Fe0.3 films sputtered onto Al0.1Ga0.9As and Al0.1Ga0.9As∕GaAs epilayers are consistent with a strongly oriented bcc crystal structure with clean metal-semiconductor interfaces. However, the interface induced uniaxial magnetic anisotropy is oriented along one of the in-plane ⟨100⟩, rather than ⟨110⟩, as is the case in molecular beam epitaxy—grown films. Resonant x-ray measurements show interfacial magnetic disorder in films on Al0.1Ga0.9As, which accounts for the difference in magnetic anisotropy behavior between samples on Al0.1Ga0.9As and Al0.1Ga0.9As∕GaAs epilayer substrates, and which may have significant consequences for the spin-injection efficiency across such interfaces.
Reduced particle and heat transport with quasisymmetry in the Helically Symmetric Experiment
Authors: Canik J. M. , Anderson D. T. , Anderson F. S. B. , Clark C. , Likin K. M. , Talmadge J. N. , Zhai K.
Published: April 2007

Measurements of particle and heat transport have been made in the Helically Symmetric Experiment [F. S. B. Anderson et al., Fusion Technology 27, 273 (1995)]. Experimental differences in the density and temperature profiles are reported between plasmas produced in a quasihelically symmetric (QHS) magnetic field and a configuration with the symmetry broken. The electron temperature is higher in the QHS configuration, due to a reduction in electron thermal diffusivity that is comparable to the neoclassical prediction. The density profile in plasmas with the symmetry broken is measured to be hollow, while in QHS plasmas the profile is centrally peaked. Calculations of the radial particle flux using the DEGAS code [D. Heifetz et al., J. Comput. Phys. 46, 309 (1982)] show that the hollow profile observed with the symmetry broken is due to neoclassical thermodiffusion. Thermodiffusion is reduced in the QHS configuration, resulting in a peaked density profile.
Phase velocity of the TEM (1,)+TEM (0,1) mode laser and electron accelerations in vacuum
Authors: Wu L. , Kong Q. , Ho Y. K. , Wang P. X. , Xu J. J. , Lin D. , Kawata S.
Published: April 2007

Unlike at any single TEM (n, m) mode laser, there is a subluminous phase velocity region located along the central region of a TEM (1,0)+TEM (0,1) mode laser. In conjunction with the high longitudinal electric field in this region, it forms another acceleration channel, which also locates inside the transverse ponderomotive potential trap. Through simulation, it is found that relativistic electrons injected into this acceleration channel can stand at the acceleration phase for a long time and be synchronously accelerated to high energies. Also, the accelerated electrons can be well confined inside the trap avoiding the transverse scattering problem.
Critical analysis and extension of the Hirshfeld atoms in molecules
Authors: Bultinck Patrick , Van Alsenoy Christian , Ayers Paul W. , Carbó-Dorca Ramon
Published: April 2007

The computational approach to the Hirshfeld [Theor. Chim. Acta 44, 129 (1977)] atom in a molecule is critically investigated, and several difficulties are highlighted. It is shown that these difficulties are mitigated by an alternative, iterative version, of the Hirshfeld partitioning procedure. The iterative scheme ensures that the Hirshfeld definition represents a mathematically proper information entropy, allows the Hirshfeld approach to be used for charged molecules, eliminates arbitrariness in the choice of the promolecule, and increases the magnitudes of the charges. The resulting “Hirshfeld-I charges” correlate well with electrostatic potential derived atomic charges.
Hafnium zirconate gate dielectric for advanced gate stack applications
Authors: Hegde R. I. , Triyoso D. H. , Samavedam S. B. , White B. E.
Published: April 2007

We report on the development of a hafnium zirconate (HfZrO4) alloy gate dielectric for advanced gate stack applications. The HfZrO4 and hafnium dioxide (HfO2) films were formed by atomic layer deposition using metal halides and heavy water as precursors. The HfZrO4 material properties were examined and compared with those of HfO2 by a wide variety of analytical methods. The dielectric properties, device performance, and reliability of HfZrO4 were investigated by fabricating HfZrO4/tantalum carbide (TaxCy) metal-oxide-semiconductor field effect transistor. The HfZrO4 dielectric film has smaller band gap, smaller and more uniform grains, less charge traps, and more uniform film quality than HfO2. The HfZrO4 dielectric films exhibited good thermal stability with silicon. Compared to HfO2, the HfZrO4 gate dielectric showed lower capacitance equivalent thickness value, higher transconductance, less charge trapping, higher drive current, lower threshold voltage (Vt), reduced capacitance-voltage (C-V) hysteresis, lower interface state density, superior wafer level thickness uniformity, and longer positive bias temperature instability lifetime. Incorporation of zirconium dioxide (ZrO2) into HfO2 enhances the dielectric constant (k) of the resulting HfZrO4 which is associated with structural phase transformation from mainly monoclinic to tetragonal. The tetragonal phase increases the k value of HfZrO4 dielectric to a large value as predicted. The improved device characteristics are attributed to less oxygen vacancy in the fine grained microstructure of HfZrO4 films.
Fast speed electro-optic polymer variable optical attenuator based on cascaded attenuated-total-reflection technique
Authors: Deng Xiaoxu , Zheng Xiang , Cao Zhuangqi , Shen Qishun , Li Honggen
Published: April 2007

A fast speed electro-optic polymer variable optical attenuator (VOA) is fabricated by utilizing cascaded attenuated-total-reflection technique. The proposed VOA demonstrates high dynamic range and low driving voltage. An ∼200ns response time of the device is obtained, and other measured parameters include a dynamic range up to 24.1dB, a driving voltage of 39.6V, and an insertion loss of 1.02dB.
Seasonal variation in the quality of a lucerne-based pasture and its relationship with morphological and maturity estimates
Authors: Machado C. F. , Morris S. T. , Hodgson J. , Matthew C. , Auza N.
Published: April 2007

To monitor seasonal changes in herbage quality, a lucerne-based pasture (Medicago sativa, Bromus willdenowii and Dactylis glomerata) was sampled in Argentina every 2 weeks for 28 months. The pasture was strip-grazed and samples were taken from the regrowth of a previously grazed strip, ready for regrazing, for which herbage mass was estimated with a calibrated rising plate meter. Each sample was sorted into dead and green components, and the latter subsequently separated into grass and lucerne, and then into lamina plus leaflet and stem plus pseudostem fractions. Similarly, at each sampling date, quantitative maturity indexes – mean stage by count and mean stage by weight – were applied to grasses and lucerne. Samples were also analysed for in vitro dry matter digestibility (DMD), crude protein (CP), fibre and non-structural carbohydrates. The dataset was divided into morphological, maturity and nutritional variables. Analyses of variance by season for both groups of variables were carried out using year as a block. Multiple regression analyses were performed for each season between maturity indices and predictors of herbage quality. DMD, and consequently metabolisable energy (ME), was significantly lower in the autumn and CP was lower in the summer compared with overall averages, which were consistently high throughout the year (overall average of 11.5 MJ ME/kg dry matter and 20.6% CP). The sward had a higher proportion of lucerne during summer and autumn, than winter and spring (averages 59.3 and 48.8%, respectively). The highest leaf : stem ratio (2.82) was during winter and the highest green content (97.5%) was during spring. Grasses had a higher mean stage by count and mean stage by weight during spring–summer, whereas lucerne had a higher mean stage by count and mean stage by weight during summer–autumn. Morphological and maturity estimates predicted satisfactorily the changes in the energy and fibre within season, but CP content was not well predicted in summer or winter. These results provide the basis for tactical grazing practices with further calibration.