bluuebunny/crossref_metadata_2025 huggingface dataset:
Technical note: The numerical solution of the system of 3‐D nonlinear elliptic equations with mixed derivatives and variable coefficients using fourth‐order difference methods
Authors: Mohanty R. K. , Jain M. K.
Published: August 2005

In this article, we report two fourth‐order difference methods for the numerical integration of the system of general 3‐D nonlinear elliptic equations subject to Dirichlet boundary conditions on a uniform cubic grid. When the coefficients of uxy, uyz, and uzx are not equal to zero and the coefficients of uxx, uyy, and uzz are equal, we require 27 grid points; when the coefficients of uxy, uyz, and uzx are equal to zero, we require only 19 grid points. The utility of the new methods is shown by testing the methods on various examples, including 3‐D steady state viscous incompressible Navier–Stokes' model equations and Poisson's equation in polar coordinates, which confirm the accurate and oscillation‐free solutions for large Reynolds numbers even in the vicinity of singularity. © 1995 John Wiley & Sons, Inc.
Long‐time behavior of some Galerkin and Petrov–Galerkin methods for thermoelastic consolidation
Authors: Murad Márcio A. , Loula Abimael F. D.
Published: August 2005

Numerical analysis of some finite element methods for the quasi‐static thermoelastic consolidation problem of fluid‐filled porous materials is presented for the case of smooth exact solutions. Taking advantage of the exponential decay of the error in the initial data with time, error estimates describing the long‐time behavior of the semidiscrete approximation are presented and postprocessing techniques are proposed to improve the accuracy of the pore pressure, heat flux, and effective stress approximations. © 1995 John Wiley & Sons, Inc.
Concentrated protein solutions in the analytical ultracentrifuge
Authors: Lundh Søren
Published: August 2005

Concentrated solutions of transferrin, albumin, immunoglobulin, chymotrypsinogen, transfer‐RNA, dextran, and polystyrene were pelleted in the analytical ultracentrifuge. The proteins developed a solvent/pellet boundary which was chracterized at equilibrium by an asymmetric schlieren peak with a “shoulder”. The schlieren curve was at the same level inside the protein pellet as in the solvent above the pellet, indicating that the protein molecules had been packed homogeneously. The protein concentration in the pellet ranged from 0.6 to 0.7 g/ml. Immediately after deceleration was begun, the “shoulder” of the pellet boundary changed into a very sharp peak, leading to a boundary composed of two schlieren peaks. Sedimentation rates were measured for transferrin solutions at concentrations up to 0.3 g/ml.
The dependence of craze velocity on the pressure and temperature of the environmental gas
Authors: Brown Norman , Metzger Bruce D.
Published: August 2005

The craze velocity was determined for poly(chlorotrifluoroethylene) (PCTFE) in CH4 and for PCTFE, polystyrene, and poly(methyl methacrylate) in N2. It was found that for temperatures near the boiling point the velocity and number of crazes depended on the relative pressure given by P exp[‐(Qv/R) (TB−1 ‐ T−1)], where P is the pressure, Qv is the heat of vaporization, and TB is the boiling point. The craze velocity was related to the coverage of the adsorbed gas. For coverages corresponding to a few monolayers the logarithm of the velocity was proportional to the relative pressure. As the temperature increases from TB, the creep rate decreases because gas desorbs with increasing temperature; the creep rate attains a minimum value at a temperature where the general process of thermally activated deformation becomes dominant.
Effect of diphenylbutadiyne on the free radical polymerization of vinyl monomers in solution
Authors: Navarro Rosa Elena , Ogawa Takeshi
Published: August 2005

The free radical polymerization of vinyl monomers such as styrene, methylmethacrylate, methyacrylate, acrylonitrile, vinylacetate, etc. in the presence of diphenylbutadiyne, was investigated. Both rates of polymerization and molecular weights of polymer decreased by the addition of diphenylbutadiyne. The degree of retardation depended on the stability of propagating radicals. The butadiyne does not react with the propagating radicals having high Q values, but it seems to trap the radicals temporarily thus retarding the polymerization
Kinetics of photopolymerization of acrylamide in AOT reverse micelles
Authors: Carver M. T. , Dreyer U. , Knoesel R. , Candau F. , Fitch R. M.
Published: August 2005

The kinetics of the photoinitiated polymerization of acrylamide in toluene/AOT/water inverse microemulsions have been examined for systems initiated by AIBN or a dye: triethanolamine redox reaction. The rates of polymerization were determined by dilatometry, the data being corrected for the effect of reaction exotermicity. For both the oil‐soluble and the water‐soluble initiating systems, the rate of polymerization was found to be proportional to the first power of the incident light intensity. For AIBN‐initiated systems, the rate of polymerization was also found to be proportional to the first power of the initiator concentration. The molecular weights of the polymers produced were independent of the rates of polymerization and initiation. These results suggest that exclusively monoradical termination, involving a degradative chain transfer, is occurring in these systems
Effect of solution components on the termination mechanism in acrylamide microemulsion polymerizations
Authors: Carver Michael T. , Candau Françoise , Fitch Robert M.
Published: August 2005

A study of the effect of the various solution components on the kinetics of the polymerization of acrylamide in water/oil (w/o) microemulsions has been performed. For the polymerizations with toluene as the continuous phase, both the rate of polymerization, Rp, and the molecular weight of the polyacrylamide were found to be first order in monomer concentration. Furthermore, for the low temperatures (10°C) involved in these experiments, nondegradative chain transfer to monomer appears to be insignificant. When the continuous‐phase solvent was changed, an exponential dependence, X, of Rp on the incident light intensity in the order of toluene (X = 1.06) > heptane (X = 0.73) > benzene (X = 0.55) was found. Thus, the monoradical termination found in the toluene microemulsions is likely due to degradative transfer to toluene, forming a stable benzyl radical, while polymerization in benzene (no labile hydrogen atoms) leads to biradical termination
Polypropylene ionomers
Authors: Landoll L. M. , Breslow D. S.
Published: August 2005

The preparation and properties of highly crystalline ionomers formed by the copolymerization of propylene and low levels of ethylcholoroaluminium 10‐undecenoate have been investigated. Few of the variables studied had dramatic effects on the copolymerization. Thus, a five‐fold increase in undecenoate concentration gave only about a 20% increase in acid incorporation into the copolymer. Increasing temperature resulted in increased acid content, but handling problems in a I gal stirred reactor limited polymerization of 80°C. Rates were lowered in the presence of complex, but the effect was minimized by hydrogen. Rheological measurements showed an increase in low shear melt viscosity of the pottasium salts by up two orders of magnitude relative to the acid from. Ionomers containing two or more carboxyl groups as their potassium salts, and having a broad molecular weight distribution, had an extended rubbery plateau range, covering most of the shear ranges of normal processing. The zero‐shear activation energy for viscous flow was 42 kcal, comparable to ABS and polystyrene. These ionomers are promising candidates for thermoforming applications
Copolymerization of toluene with tetrafluoromethane or octafluorocyclobutane by plasma technique
Authors: Ye Mu , Chen Jie , Yang Zhenhua , Lu Lizhen , Li Shaoyu , Sun Ying
Published: August 2005

Plasma copolymerization of toluene with tetrafluoromethane or octafluorocyclobutane was carried out in a capacitively coupled tubular reactor with external electrodes. The polymer structure was characterized by means of XPS, IR, and pyrolysis/GC/MS and the condensates of the gases in the plasma reaction chamber were measured by GC–MS. It is observed that the monomers undergo a plasma states polymerization in a glow discharge and only those monomer fragments with sufficient reactivity join the copolymerization. The types of fluorine‐containing groups in the polymer structure are related to the chemical structure of the flurocarbons. The fluorine content depends upon the discharge power, the system pressure, and the fraction of fluorocarbons in the monomers
Thermal degradation processes in aliphatic polydithiocarbonates
Authors: Montaudo Giorgio , Puglisi Concetto , Berti Corrado , Marianucci Elisabetta , Pilati Francesco
Published: August 2005

The thermal degradation of three aliphatic polythiocarbonates was investigated by direct pyrolysis in the ion source of a mass spectrometer operating both in electron and chemical ionization modes. The overall evidence indicates that these polymers start decomposing at about 250–280°C by an end‐biting process initiating from the SH end‐groups, which produces a mixture of cyclic sulfides, disulfides, and dithiocarbonates. Another decomposition step is observed at higher temperature (ca. 350–370°C), producing essentially the same compounds evolved in the first stage, but with significant differences in their relative abundances. An intramolecular exchange (back‐biting) process is believed to be responsible for the second thermal decomposition stage
Side‐chain liquid crystalline polymers containing 4‐[2‐(S)‐methyl‐1‐butoxy]‐4′‐(11‐undecanyl‐1‐oxy)‐α‐methylstilbene side groups
Authors: Percec Virgil , Hahn Bruce
Published: August 2005

The synthesis and characterization of polymethacrylate, polyacrylate, poly(methylsiloxane), and 1,3,5,7‐tetramethylcyclotetrasiloxane containing chiral 4‐[2‐(S)‐methyl‐1‐ butoxy]‐4′‐(11‐undecanyl‐1‐oxy)‐α‐methylstilbene side groups are described. All polymers exhibit an enantiotropic SA mesophase and side‐chain crystallization. The 1,3,5,7‐tetramethylcyclotetrasiloxane containing mesogenic side groups represents a mixture of four stereoisomers and displays a monotropic SA mesophase
The ozonolysis of butyl and halobutyl elastomers
Authors: Ho K. W. , Guthmann J. E.
Published: August 2005

The ozonolysis of butyl elastomer and its halogenated derivatives, as well as their model compounds in hexane, was studied. It was found that while the ozonolysis of butyl and chlorobutyl elastomers involves the normal cleavage of olefinic double bonds, the mechanism of ozonolysis of bromobutyl elastomer is more complicated. In the presence of ozone, bromobutyl elastomer was found to rearrange from the exomethylene structure to the bromomethyl structure, thereby generating more in‐chain double bonds. This reaction provides an explanation as to why bromobutyl elastomer degrades faster and to a greater extent than chlorobutyl elastomer containing the same number of olefinic double bonds. Different additives were found to have different effects on the chain scission and rearrangement of bromobutyl elastomer. Diphenylamine and triisopropyl phosphite are much more effective than hexylamine and 2,6‐di‐tert‐butyl cresol in inhibiting the chain scission of the bromobutyl elastomer and diphenylamine is more effective than triisopropyl phosphite in suppressing the rearrangement of this elastomer
Crystallization behavior and morphology of poly(butylene succinate) modified with rosin maleopimaric acid anhydride
Authors: Liu Xiaoqing , Li Chuncheng , Guan Guohu , Yuan Xuepei , Xiao Yaonan , Zhang Dong
Published: August 2005

The melting behavior, crystallization behavior, and morphology of PBSR, which is Poly(butylene succinate) modified with rosin maleopimaric acid anhydride (RMA), were investigated with differential scanning calorimetry (DSC) and polarized optical microscope (POM). The multiple endotherms were ascribed to the recrystallization during DSC measurement and the equilibrium melting temperature determined by the Peak L, which was associated with the fusion of the crystals grown by normal primary crystallization, was 125.9 °C. After the kinetic parameters for isothermal crystallization of PBSR were determined by Avrami equation, to make a detailed regime transition analysis, the well‐established Lauritzen–Hoffman equation was employed. The results indicated that there were two regimes, regime II and regime III, in the range of higher and lower crystallization temperature, respectively. The regime transition temperature is about 81 °C. At last, the spherulitic morphologies of PBSR after being crystallized isothermally at different temperature were observed with the help of POM. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2694–2704, 2005
Surface Analysis of Plasma Deposited Polymer Films, 5
Authors: Oran Umut , Swaraj Sufal , Friedrich Jörg F. , Unger Wolfgang E. S.
Published: August 2005

Summary: The effect of the composite plasma parameter P/F, where P is the plasma power and F is the monomer flow rate, on the chemical character of pulsed plasma deposited allyl alcohol films was investigated by ToF‐SSIMS. Information on the unsaturated character, the cross‐linked and/or branched character of the plasma polymer films was derived in detail. The problem of the retention of OH groups in plasma deposited allyl alcohol films was elucidated in detail using SSIMS data. The lowest conversion rate from the monomer's hydroxyl groups to other oxygen functionalities in the plasma was concluded for the plasma polymer film produced at a P/F ratio of 0.05 W · sccm−1. It was found that the overall oxygen content of the films decreased vs. increasing P/F ratio. Because the freshly prepared films were investigated without air exposure, ageing on ambient air could be studied in detail. It was found that in the case of plasma deposited allyl alcohol films the ageing on air is probably based on two competing processes which are discussed in detail. Additionally, a review of literature data on the characterization of plasma deposited allyl alcohol films is given.

Reduced SSIMS data of plasma deposited allyl alcohol films prepared at different P/F ratios. Retention of the OH groups were derived from the (m − H)+/(m + H)+ intensity ratios. Note that the arrow indicates the increase for the retention of OH groups.

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Reduced SSIMS data of plasma deposited allyl alcohol films prepared at different P/F ratios. Retention of the OH groups were derived from the (m − H)+/(m + H)+ intensity ratios. Note that the arrow indicates the increase for the retention of OH groups.
Surface Analysis of Plasma‐Deposited Polymer Films, 6
Authors: Swaraj Sufal , Oran Umut , Lippitz Andreas , Friedrich Jörg F. , Unger Wolfgang E. S.
Published: August 2005

Summary:XPS and NEXAFS spectroscopy results were used for chemical characterization of pulsed plasma deposited allyl alcohol films before and after exposure to ambient air. The influence of the composite plasma parameter, effective plasma power (P) to monomer flow rate (F) ratio on the spectroscopic results was investigated. From this data, information about the chemical character of the plasma polymerized films, such as retention of the hydroxyl groups in the deposited sample, the amount of long living radicals and branching and/or crosslinking was derived. A high degree of hydroxyl retention was observed, which, however, decreased along with the oxygen content of the film, as the P/F ratio increased. A trend in the extent of the oxygen loss according to the variation of the P/F ratio was deduced, which agrees with earlier ToF‐SSIMS findings (Plasma Process. Polym.2005,2, 563).

XPS spectra of plasma deposited allyl alcohol in situ and after exposure to ambient air (reference sample: poly(vinyl alcohol)).

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XPS spectra of plasma deposited allyl alcohol in situ and after exposure to ambient air (reference sample: poly(vinyl alcohol)).
Interaction of Photons with Polymers: From Surface Modification to Ablation
Authors: Lippert Thomas
Published: August 2005

Summary: This work reviews the interaction of photons with polymers with an emphasis on UV laser ablation and surface modification using VUV lamps. Laser ablation of polymers is an established process in industrial applications, but the mechanisms of ablation are still controversial. Different polymers, such as poly(methyl methacrylate), polyimides and specially designed polymers are used as examples to show that the mechanism is a mixture of photochemical and photothermal features which are closely related to the polymer structure and properties. Different approaches to probe the ablation mechanisms and to improve ablation are discussed. Photoactive groups have been introduced into the polymer structure to improve the quality of ablation and to elucidate the ablation mechanisms. The experimental techniques to probe the ablation mechanism range from time‐resolved measurements, such as shadowgraphy, ToF‐MS, and ns‐surface interferometry to variations of the irradiation wavelengths and pulse lengths. The necessity for a critical evaluation of the experimental procedures and analysis is discussed exemplary for polyimides. The data for different types of polyimides are mixed up and some experimental procedures are possibly causing problems for the data evaluation. Various recent trends for laser ablation, such as ultrafast ablation or VUV ablation are also discussed. Surface modifications of polymers using VUV photons from lamps are discussed for oxidation and nitriding of poly dimethylsiloxane (PDMS) and polyolefines. The mechanism of the PDMS surface oxidation is presented in detail.

Ablation pattern in TP1 created by 308 nm irradiation using a gray tone phase mask.

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Ablation pattern in TP1 created by 308 nm irradiation using a gray tone phase mask.
Genome instability as a cause of ageing and cancer: Implications of RecQ helicases
Authors: Skouboe Camilla , Bjergbaek Lotte , Andersen Anni H.
Published: August 2005

Members of the RecQ helicase family are mutated in several human genomic instability syndromes, such as Werner and Bloom syndromes. The syndromes are characterized by premature ageing and cancer predisposition, respectively, and are therefore extensively used as model systems for studies of ageing and cancer. RecQ homologues are widely expressed enzymes, and genetic and biochemical investigations have pointed to their involvement in homologous recombinational DNA repair pathways. In the review we will focus on the implications of RecQ helicases for genome maintenance with specific emphasis on the homologues found in yeast.
Impaired left ventricular relaxation in type 2 diabetic rats is related to myocardial accumulation of Nɛ‐(carboxymethyl) lysine
Authors: Schäfer Stefan , Huber Jochen , Wihler Cornelia , Rütten Hartmut , Busch Andreas E. , Linz Wolfgang
Published: August 2005

Myocardial dysfunction in the absence of myocardial ischemia is frequent in patients with diabetes mellitus but the underlying pathomechanism is unclear. We investigated whether accumulation of advanced glycation end products (AGEs) in the diabetic myocardium is related to its functional abnormalities.

In 11 male homozygous Zucker diabetic fatty rats (ZDF/Gmi‐fa/fa) aged 37 weeks (OBESE) and 11 non‐obese, non‐diabetic littermates (LEAN), we measured left ventricular function (pressure–volume catheter) and levels of Nɛ‐(carboxymethyl) lysine (CML), a prototypical AGE, in serum and the left ventricle (competitive enzyme linked immuno‐assay).

Overt diabetes mellitus (HbA1c >9%) was present in all OBESE animals but not in LEAN. Systolic left ventricular function was not different between the groups, but the markers of left ventricular relaxation, dP/dtmin and the relaxation constant τ, were impaired in OBESE. In parallel, CML levels were increased in serum (273±15 vs. 197±10 ng/ml, p<0.05) and in the left ventricle (18.4±1.1 vs. 12.5±2.0 ng/mg protein, p<0.05) in OBESE compared to LEAN. There was a linear correlation between τ and the left ventricular CML levels (r=0.65; p<0.05).

We conclude that type 2 diabetes is associated with predominant left ventricular diastolic dysfunction. Myocardial accumulation of advanced glycation end products may contribute to relaxation abnormalities in type 2 diabetes.
Chronic pancreatitis patients show hyperalgesia of central origin: A pilot study
Authors: Buscher Hessel C.J.L. , Wilder‐Smith Oliver H.G. , van Goor Harry
Published: August 2005

Background The pain of chronic pancreatitis remains challenging to manage, with treatment all too often being unsuccessful. A main reason for this is lacking understanding of underlying mechanisms of chronic pain in these patients.

Aim To document, using somatic quantitative sensory testing, changes in central nervous system processing (neuroplasticity) associated with chronic pancreatitis pain and thus gain insight into underlying pain mechanisms.

Patients and methods We studied 10 chronic pancreatitis patients on stable opioid analgesic medication. Ten matched surgical patients without pain served as controls. Pain verbal numeric rating scores (NRS) and thresholds to electric skin stimulation and pressure pain were measured in dermatomes T10 (pancreatic area), C5, T4, L1 and L4.

Results The pancreatitis patients had a median NRS pain score of 5 (range 3–8). Electric sensation and pain thresholds were significantly increased in the pancreatic region, tending to be more so in female pancreatitis patients. Pressure pain thresholds were significantly lower in pancreatitis patients than in controls, with men tending towards greater generalised relative hyperalgesia than women.

Conclusions Chronic pancreatitis patients show pronounced generalised deep hyperalgesia that is present despite opioid therapy. These signs, consistent with central sensitisation, appear relatively more prominent in men than women. There is also evidence suggesting that women may have a better segmental inhibitory response than men, possibly explaining their relatively less prominent generalised deep tissue hyperalgesia compared to men.
Excitation energy trapping in photosystem I complexes depleted in Lhca1 and Lhca4
Authors: Ihalainen Janne A. , Klimmek Frank , Ganeteg Ulrika , van Stokkum Ivo H.M. , van Grondelle Rienk , Jansson Stefan , Dekker Jan P.
Published: August 2005

We report a time‐resolved fluorescence spectroscopy characterization of photosystem I (PSI) particles prepared from Arabidopsis lines with knock‐out mutations against the peripheral antenna proteins of Lhca1 or Lhca4. The first mutant retains Lhca2 and Lhca3 while the second retains one other light‐harvesting protein of photosystem I (Lhca) protein, probably Lhca5. The results indicate that Lhca2/3 and Lhca1/4 each provides about equally effective energy transfer routes to the PSI core complex, and that Lhca5 provides a less effective energy transfer route. We suggest that the specific location of each Lhca protein within the PSI–LHCI supercomplex is more important than the presence of so‐called red chlorophylls in the Lhca proteins.
Deletion of flavoredoxin gene in Desulfovibrio gigas reveals its participation in thiosulfate reduction
Authors: Broco Manuela , Rousset Marc , Oliveira Solange , Rodrigues-Pousada Claudina
Published: August 2005

The gene encoding Desulfovibrio gigas flavoredoxin was deleted to elucidate its physiological role in the sulfate metabolism. Disruption of flr gene strongly inhibited the reduction of thiosulfate and exhibited a reduced growth in the presence of sulfite with lactate as electron donor. The growth with sulfate was not however affected by the lack of this protein. Additionally, flr mutant cells revealed a decrease of about 50% in the H2 consumption rate using thiosulfate as electron acceptor. Altogether, our results show in vivo that during sulfite respiration, trithionate and thiosulfate are produced and that flavoredoxin is specific for thiosulfate reduction.
Inhibitory role of peroxiredoxin II (Prx II) on cellular senescence
Authors: Han Ying-Hao , Kim Hyun-Sun , Kim Jin-Man , Kim Sang-Keun , Yu Dae-Yeul , Moon Eun-Yi
Published: August 2005

Reactive oxygen species (ROS) were generated in all oxygen‐utilizing organisms. Peroxiredoxin II (Prx II) as one of antioxidant enzymes may play a protective role against the oxidative damage caused by ROS. In order to define the role of Prx II in organismal aging, we evaluated cellular senescence in Prx II−/− mouse embryonic fibroblast (MEF). As compared to wild type MEF, cellular senescence was accelerated in Prx II−/− MEF. Senescence‐associated (SA)‐β‐galactosidase (Gal)‐positive cell formation was about 30% higher in Prx II−/− MEF. N‐Acetyl‐l‐cysteine (NAC) treatment attenuated SA‐β‐Gal‐positive cell formation. Prx II−/− MEF exhibited the higher G2/M (41%) and lower S (1.6%) phase cells as compared to 24% and 7.4% in wild type MEF, respectively. A high increase in the p16 and a slight increase in the p21 and p53 levels were detected in PrxII−/− MEF cells. The cellular senescence of Prx II−/− MEF was correlated with the organismal aging of Prx II−/− mouse skin. While extracellular signal‐regulated kinase (ERK) and p38 activation was detected in Prx II−/− MEF, ERK and c‐Jun N‐terminal kinase (JNK) activation was detected in Prx II−/− skin. These results suggest that Prx II may function as an enzymatic antioxidant to prevent cellular senescence and skin aging.
Analysis of mTOR signaling by the small G‐proteins, Rheb and RhebL1
Authors: Tee Andrew R. , Blenis John , Proud Christopher G.
Published: August 2005

The small G protein Rheb (Ras homologue enriched in brain) is known to promote mammalian target of rapamycin (mTOR) signaling. In this study, we show that Rheb like‐1 protein (RhebL1) rescues mTOR signaling during nutrient withdrawal and that tuberous sclerosis complex‐1 (TSC) and TSC2 impairs RhebL1‐mediated signaling through mTOR. We identify critical residues within the switch I region (N41) and ‘constitutive’ effector (Ec) region (Y/F54 and L56) of Rheb and RhebL1, which are required for their efficient activation of mTOR signaling. Mutation of Rheb and RhebL1 at N41 impaired their interaction with mTOR, which identifies mTOR as a common downstream target of both Rheb and RhebL1.
Transthyretin‐related proteins function to facilitate the hydrolysis of 5‐hydroxyisourate, the end product of the uricase reaction
Authors: Lee Youra , Lee Do Hee , Kho Chang Won , Lee Ah Young , Jang Mi , Cho Sayeon , Lee Choong Hwan , Lee Jong Suk , Myung Pyung Keun , Park Byoung Chul , Park Sung Goo
Published: August 2005

Purine catabolic pathway in Bacillus subtilis is consisted of more than 14 genes. Among these genes, pucL and pucM are required for uricase activity. While PucL is known to encode the uricase itself, the function of PucM is still unclear although this protein is also indispensable for uric acid decomposition. Here, we provide evidence that PucM, a transthyretin‐related protein, functions to facilitate the hydrolysis of 5‐hydroxyisourate, the end product of the uricase reaction. Based on these results, we propose that transthyretin‐related proteins present in diverse organisms are not functionally related to transthyretin but actually function as a hydroxyisourate hydrolase.
Ectoine and hydroxyectoine inhibit aggregation and neurotoxicity of Alzheimer's β‐amyloid
Authors: Kanapathipillai Mathumai , Lentzen Georg , Sierks Michael , Park Chan Beum
Published: August 2005

β‐Amyloid peptide (Aβ) is the major constituent of senile plaques, the key pathological feature of Alzheimer's disease. Aβ is physiologically produced as a soluble form, but aggregation of Aβ monomers into oligomers/fibrils causes neurotoxic change of the peptide. In nature, many microorganisms accumulate small molecule chaperones (SMCs) under stressful conditions to prevent the misfolding/denaturation of proteins and to maintain their stability. Hence, it is conceivable that SMCs such as ectoine and hydroxyectoine could be potential inhibitors against the aggregate formation of Alzheimer's Aβ, which has not been studied to date. The current work shows the effectiveness of ectoine and hydroxyectoine on the inhibition of Aβ42 aggregation and toxicity to human neuroblastoma cells. The characterization tools used for this study include thioflavin‐T induced fluorescence, atomic force microscopy and cell viability assay. Considering that ectoine and hydroxyectoine are not toxic to cellular environment even at concentrations as high as 100 mM, the results may suggest a basis for the development of ectoines as potential inhibitors associated with neurodegenerative diseases.
The parkinsonism producing neurotoxin MPP+ affects microtubule dynamics by acting as a destabilising factor
Authors: Cappelletti Graziella , Surrey Thomas , Maci Rosalba
Published: August 2005

Dysfunction of the microtubule system is emerging as a contributing factor in a number of neurodegenerative diseases. Looking for the potential role played by the microtubule cytoskeleton in neuron degeneration underlying Parkinson's disease (PD), we investigate the influence of the parkinsonism producing neurotoxin 1‐methyl‐4‐phenylpyridinium (MPP+) on microtubule dynamics. We find that it acts as a strong catastrophe promoter causing a decrease of the average length of microtubules assembled from purified tubulin. We also find that it reduces the number of microtubules nucleated from purified centrosomes. Finally, binding assays demonstrate that the neurotoxin binds specifically to tubulin in the microtubule lattice in a close to stoichiometric manner. This paper provides the first evidence that dynamic instability of microtubules is specifically affected by MPP+ and suggests that it could play a role in neuronal cell death underlying PD.
Disruption of perlecan binding and matrix assembly by post‐translational or genetic disruption of dystroglycan function
Authors: Kanagawa Motoi , Michele Daniel E. , Satz Jakob S. , Barresi Rita , Kusano Hajime , Sasaki Takako , Timpl Rupert , Henry Michael D. , Campbell Kevin P.
Published: August 2005

Dystroglycan is a cell‐surface matrix receptor that requires LARGE‐dependent glycosylation for laminin binding. Although the interaction of dystroglycan with laminin has been well characterized, less is known about the role of dystroglycan glycosylation in the binding and assembly of perlecan. We report reduced perlecan‐binding activity and mislocalization of perlecan in the LARGE‐deficient Largemyd mouse. Cell‐surface ligand clustering assays show that laminin polymerization promotes perlecan assembly. Solid‐phase binding assays provide evidence for the first time of a trimolecular complex formation of dystroglycan, laminin and perlecan. These data suggest functional disruption of the trimolecular complex in glycosylation‐deficient muscular dystrophy.
Mechanism of direct degradation of IκBα by 20S proteasome
Authors: Alvarez-Castelao Beatriz , Castaño José G.
Published: August 2005

IκBα regulates activation of the transcription factor NF‐κB. NF‐κB is activated in response to several stimuli, i.e. proinflamatory cytokines, infections, and physical stress. This signal dependent pathway involves IκBα phosphorylation, ubiquitylation, and degradation by 26S proteasome. A signal independent (basal) turnover of IκBα has also been described. Here, we show that IκBα can be directly degraded by 20S proteasomes. Deletion constructs of IκBα allow us to the determine that N‐terminal (ΔN 1–70) and C‐terminal regions (ΔC 280–327, removing the PEST region) of IκBα are not required for IκBα degradation, while a further C‐terminal deletion including part of the arm repeats (ΔC2 245–327) almost completely suppress the degradation by 20S proteasome. Binding and competition experiments demonstrate that the degradation of IκBα involves specific interactions with α2(C3) subunit of the proteasome. Finally, p65/relA (not itself a substrate for 20S proteasome) inhibits the degradation of IκBα by the proteasome. These results recapitulate in vitro the main characteristics of signal independent (basal) turnover of IκBα demonstrated in intact cells.
Rapid disruption of intestinal barrier function by gliadin involves altered expression of apical junctional proteins
Authors: Sander Guy R. , Cummins Adrian G. , Powell Barry C.
Published: August 2005

Coeliac disease is a chronic enteropathy caused by the ingestion of wheat gliadin and other cereal prolamines derived from rye and barley. In the present work, we investigated the mechanisms underlying altered barrier function properties exerted by gliadin‐derived peptides in human Caco‐2 intestinal epithelial cells. We demonstrate that gliadin alters barrier function almost immediately by decreasing transepithelial resistance and increasing permeability to small molecules (4 kDa). Gliadin caused a reorganisation of actin filaments and altered expression of the tight junction proteins occludin, claudin‐3 and claudin‐4, the TJ‐associated protein ZO‐1 and the adherens junction protein E‐cadherin.
Alternative splicing of Slo channel gene programmed by estrogen, progesterone and pregnancy
Authors: Zhu Ning , Eghbali Mansoureh , Helguera Gustavo , Song Min , Stefani Enrico , Toro Ligia
Published: August 2005

STREX alternative‐exon adds to Slo channel a phosphorylation sequence that can invert protein kinase A (PKA) regulation from excitatory to inhibitory. Because pregnancy switches Slo responsiveness to PKA from inhibitory to excitatory, we hypothesized that STREX expression diminishes with pregnancy and is regulated by sex hormones. Different from total‐rSlo, which is elevated around mid‐pregnancy and decreases at term, STREX transcripts progressively decreased with pregnancy near 80% at term. STREX downregulation was mimicked by estrogen, and opposed by estrogen‐receptor antagonist ICI 182,780 or progesterone (Pg). The regulation of STREX splicing directed by estrogen and Pg provides a mechanism for Slo's PKA‐related phenotypic alteration with pregnancy.
Thyroid cancer in pregnancy
Authors: Yasmeen S. , Cress R. , Romano P.S. , Xing G. , Berger‐Chen S. , Danielsen B. , Smith L.H.
Published: August 2005

Objective: To compare stage at diagnosis, treatment and survival among pregnant women with thyroid cancer to non‐pregnant women with thyroid cancer, and to assess the impact of treatment on maternal and perinatal outcomes. Methods: A database containing maternal and newborn discharge records linked to the California Cancer Registry was queried to obtain information on all thyroid cancers from 1991–1999. Women with thyroid cancer occurring during pregnancy were compared to age‐matched non‐pregnant women with thyroid cancer. Results: 595 cases of thyroid cancers were identified (129 antepartum and 466 postpartum). About 64% of thyroid cancers were diagnosed at stage 2 among pregnant women versus 58% among non‐pregnant controls. The odds of thyroid cancer were 1.5 times higher among Asian/Pacific Islanders than among Non‐Hispanic White women. Pregnancy had no significant effect on mortality after diagnosis of thyroid cancer. Thyroidectomy during pregnancy was not associated with adverse maternal or neonatal outcomes. Conclusions: Thyroid cancer discovered during or after pregnancy does not appear to have a significant impact on the prognosis of the disease.
Magnetic Resonance Imaging in the Diagnosis of Glomus Tumours of the Hand
Authors: AL-QATTAN M. M. , AL-NAMLA A. , AL-THUNAYAN A. , AL-SUBHI F. , EL-SHAYEB A. F.
Published: August 2005

This paper studies the sensitivity, specificity and predictive values of MRI in the diagnosis of glomus tumours of the hand and investigates the final diagnosis and outcome in cases with false positive or negative imaging tests. A total of 42 cases with the clinical diagnosis of a glomus tumour were included in the study. All patients underwent MRI and the results of MRI were correlated with the final histological diagnosis of the excised lesion. MRI had a sensitivity of 90%, a specificity of 50%, a positive predictive value of 97% and a negative predictive value of 20%. The four cases in which the MRI was negative all proved histologically to be glomus tumours. All four tumours were small (2–3 mm in diameter) and the lack of delineation of the lesions by MRI was attributed to their small size. Despite negative MRIs, surgical exploration identified the glomus tumours. Based on the results of the current study and the cost of MRI, the senior author has stopped ordering pre-operative MRIs in patients clinically diagnosed with a glomus tumour.
Southern Hemisphere ionosphere and plasmasphere response to the interplanetary shock event of 29–31 October 2003
Authors: Yizengaw E. , Moldwin M. B. , Dyson P. L. , Immel T. J.
Published: August 2005

We analyze the effects on the Southern Hemisphere ionosphere and plasmasphere due to the 29–31 October 2003 geomagnetic storms (the so‐called series of Halloween storms). Solar wind data from ACE and ionospheric data from the GPS (Global Position System) ground and LEO (Low Earth Orbit) receivers, the TOPEX/Poseidon altimeter, the IMAGE FUV camera, and the DMSP drift meter are used to understand the ionospheric dynamics as a function of the storm phase. The detailed structure of the ionosphere has been obtained using tomographic reconstruction applied to data from both ground‐ and space‐based GPS receivers. The tomographic approach using LEO observations of signals received from GPS satellites above the LEO's horizon allows us to investigate the topside ionospheric and plasmaspheric density distribution in more detail than can be obtained using ground‐based GPS receivers. This is because with ground‐based receivers, the higher topside ionosphere and plasmasphere contribute only a small fraction to the total electron content (TEC) and so the measurements are dominated by the ionospheric structure at the F2 peak. In contrast, the Australian LEO satellite, FedSat, which has been used for this study, orbits at 800 km altitude, well above the F2 peak and hence the TEC measured is primarily due to the upper topside ionosphere and plasmasphere. This paper presents the tomographically reconstructed topside ionosphere and plasmasphere electron density distributions using LEO observations. The temporal and regional maps of TEC and the IMAGE FUV data show that the storm that commenced on 29 October dramatically decreased the plasma density in the Southern Hemisphere middle and high latitudes. The region remained depleted of plasma for more than 24 hours until 31 October, when the second severe storm began. TOPEX/Poseidon data shows a daytime localized density enhancement occurred above the middle of the Pacific Ocean. These results show large interhemispheric and longitudinally narrow storm‐time structure in the ionosphere and topside ionosphere/plasmasphere.
Spatial filtering of interfering signals at the initial Low Frequency Array (LOFAR) phased array test station
Authors: Boonstra A. J. , van der Tol S.
Published: August 2005

The Low Frequency Array (LOFAR) is a radio telescope currently being designed. Its targeted observational frequency window lies in the range of 10–250 MHz. In frequency bands in which there is interference, the sensitivity of LOFAR can be enhanced by interference mitigation techniques. In this paper we demonstrate spatial filtering capabilities at the LOFAR initial test station (ITS) and relate it to the LOFAR radio frequency interference mitigation strategy. We show that in frequency ranges which are occupied with moderate‐intensity man‐made radio signals, the strongest observed astronomical sky sources can be recovered by spatial filtering. We also show that under certain conditions, intermodulation products of point‐like interfering sources remain point sources. This means that intermodulation product filtering can be done in the same way as for “direct” interference. We further discuss some of the ITS system properties such as cross‐talk and sky noise limited observations. Finally, we demonstrate the use of several beam former types for ITS.
A method for detecting season‐dependent modes of climate variability: S‐EOF analysis
Authors: Wang Bin , An Soon‐Il
Published: August 2005

Anomalous climate is often regulated by the annual cycle. Based on this physical consideration, we propose a new method termed as Season‐reliant Empirical Orthogonal Function (S‐EOF) analysis to detect major modes of climate variability. The S‐EOF analysis of Indo‐Pacific SST during the past 54 years reveals two statistically significant leading modes, which are not obtainable by using conventional EOF analysis. These modes represent the Indo‐Pacific Low‐Frequency (LF) and Quasi‐Biennial (QB) modes associated ENSO, and reveal the fundamental differences between the LF and QB modes in their seasonal evolution, fractional variance structure, and interdecadal variation and trend. The interdecadal variability is coupled with the LF mode, suggesting that decadal‐interdecadal SST variation is primarily represented by the ENSO‐like interdecadal regime shift in the late 1970s. A warming trend is mingled with the QB mode, accounting for a large portion of the local SST variability in the Maritime Continent‐western Pacific horseshoe region.
Changes in the strength of the Brewer‐Dobson circulation in a simple AGCM
Authors: Eichelberger Scott J. , Hartmann Dennis L.
Published: August 2005

A simple general circulation model is used to explore the response of the Brewer‐Dobson circulation to warming of the tropical troposphere typically associated with greenhouse gas warming in climate models. The strength of the modeled Brewer‐Dobson circulation increases in response to tropospheric tropical warming. The tropical warming causes the midlatitude baroclinicity to increase, which leads to an increase in the wave activity at synoptic and planetary scales. Increased wave propagation from the troposphere causes stronger EP flux convergence in the stratosphere. The EP flux convergence drives a stronger Brewer‐Dobson circulation via downward control arguments. These results are compared to other recent GCM studies.
Physical and electrical properties of lanthanide-incorporated tantalum nitride for n-channel metal-oxide-semiconductor field-effect transistors
Authors: Ren C. , Chan D. S. H. , Wang X. P. , Faizhal B. B. , Li M.-F. , Yeo Y.-C. , Trigg A. D. , Agarwal A. , Balasubramanian N. , Pan J. S. , Lim P. C. , Huan A. C. H. , Kwong D.-L.
Published: August 2005

Lanthanide-incorporated tantalum nitride (TaN) is studied as a potential metal gate candidate for n-channel metal-oxide-semiconductor field-effect transistors (n-MOSFETs). Lanthanides such as terbium (Tb), erbium (Er), and ytterbium (Yb) are introduced into TaN to form Ta1−xTbxNy, Ta1−xErxNy, and Ta1−xYbxNy metal gates, respectively, on SiO2 dielectric. The resistivity, crystallinity, film composition, and work function of Ta1−xTbxNy, Ta1−xErxNy, and Ta1−xYbxNy films were investigated at different post-metal-anneal temperatures and for different lanthanide concentrations. It was found that the work function of lanthanide-incorporated TaN can be effectively tuned by increasing the concentration of lanthanide. Work functions of about 4.2–4.3eV can be achieved even after a 1000°C rapid thermal anneal, making lanthanide-incorporated TaN a promising metal gate candidate for n-MOSFETs. The enhanced nitrogen concentration and the possible presence of lanthanide-N or Ta-N-lanthanide compounds in lanthanide-incorporated TaN film could be responsible for its chemical-thermal stability on SiO2.
Structure and property investigation of a Bi-based perovskite solid solution: (1−x)Bi(Ni1∕2Ti1∕2)O3–xPbTiO3
Authors: Choi Soon Mok , Stringer Craig J. , Shrout Thomas R. , Randall Clive A.
Published: August 2005

Extending the investigations on Bi-based perovskite solid solutions for high-temperature piezoelectric ceramics, this paper considers the binary solid-solution system (1−x)Bi(Ni1∕2Ti1∕2)O3–xPbTiO3 [(1−x)BNT–xPT] for 0.39⩽x⩽1.00. High-density polycrystalline ceramics were fabricated using conventional solid-state processing methods. These ceramics are then taken for structural and electrical properties and differential scanning calorimetry measurements. A morphotropic phase boundary (MPB) was found at the composition 0.51BNT–0.49PT, with a corresponding paraelectric-ferroelectric phase transition TC≈400°C. The electrical poled ceramics demonstrated piezoelectric d33 coefficients≈260pC∕N at room temperature for the MPB BNT–PT compositions. Experimental data are also given for the influence of MnO2 doping to the BNT–PT system close to the MPB compositions, noting an improvement in dielectric losses but a reduction in d33≈180pC∕N. Tricritical behavior is also identified in the tetragonal phase field, with a TC enhancement above TC∼495°C found similar to other Bi(Me′Me″)O3–PbTiO3 systems with high MPB transitions.
Quantum hydrodynamics: Capturing a reactive scattering resonance
Authors: Derrickson Sean W. , Bittner Eric R. , Kendrick Brian K.
Published: August 2005

The hydrodynamic equations of motion associated with the de Broglie-Bohm formulation of quantum mechanics are solved using a meshless method based upon a moving least-squares approach. An arbitrary Lagrangian-Eulerian frame of reference and a regridding algorithm which adds and deletes computational points are used to maintain a uniform and nearly constant interparticle spacing. The methodology also uses averaged fields to maintain unitary time evolution. The numerical instabilities associated with the formation of nodes in the reflected portion of the wave packet are avoided by adding artificial viscosity to the equations of motion. A new and more robust artificial viscosity algorithm is presented which gives accurate scattering results and is capable of capturing quantum resonances. The methodology is applied to a one-dimensional model chemical reaction that is known to exhibit a quantum resonance. The correlation function approach is used to compute the reactive scattering matrix, reaction probability, and time delay as a function of energy. Excellent agreement is obtained between the scattering results based upon the quantum hydrodynamic approach and those based upon standard quantum mechanics. This is the first clear demonstration of the ability of moving grid approaches to accurately and robustly reproduce resonance structures in a scattering system.
Dynamic molecular interferometer: Probe of inversion symmetry in I2− photodissociation
Authors: Mabbs Richard , Pichugin Kostyantyn , Sanov Andrei
Published: August 2005

Time-resolved photoelectron imaging of negative ions is employed to examine 780-nm dissociation dynamics of I2−, emphasizing the effects of interference in time-resolved photoelectron angular distributions obtained with 390-nm probe. No energetic changes are observed after about 700fs, but the evolution of the photoelectron anisotropy persists for up to 2.5ps, indicating that the electronic wave function of the dissociating anion continues to evolve long after the asymptotic energetic limit of the reaction has been effectively reached. The time scale of the anisotropy variation corresponds to a fragment separation of the same order of magnitude as the de Broglie wavelength of the emitted electrons (λ=35Å). These findings are interpreted by considering the effect of I2− inversion symmetry and viewing the dissociating anion as a dynamic molecular-scale “interferometer,” with the electron waves emitted from two separating centers. The predictions of the model are in agreement with the present experiment and shed new light on previously published results [A. V. Davis, R. Wester, A. E. Bragg, and D. M. Neumark, J. Chem. Phys. 118, 999 (2003)].