bluuebunny/crossref_metadata_2025 huggingface dataset:
Theoretical study of olefin oxidation process on a dioxo‐μ‐oxo Mo catalyst
Authors: Griffe Beulah , Agrifoglio Giuseppe , Ruette Fernando , Brito Joaquín L.
Published: February 2008

The dimeric complex dioxo (μ‐oxo) thiocyanato of molybdenum(VI) bearing a 4,4′‐di‐ter‐butyl‐2,2′‐bipyridine ligand in trans conformation (complex 1) has been used in catalytic reactions of olefins (ethylene) oxidation, giving as intermediate a dimeric complex oxo bis (μ‐oxo) thiocyanato of molybdenum(V) in cis conformation (complex 2). Binding and electronic properties were calculated using the parametric quantum chemistry method for catalytic reactions, CATIVIC. The interaction of an ethylene molecule with complex 3 (cis version of complex 1) leads to the formation of the intermediate named complex 4. This complex is dissociated to form complex 5 plus ethylene oxide. Changes of electronic and bonding properties are analyzed in terms of atomic charge, orbital population, total binding energies, diatomic bond energies, diatomic energies, and Wiberg indexes, and equilibrium bond distances. The energy balance for the complete catalytic process is presented in a schematic way. Results confirm the extraordinary oxo‐transfer abilities of this complex, considering that the whole process is exothermic (−44 kcal/mol). Regeneration of the catalyst is also calculated by the interaction of H2O2 with complex 5. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Theoretical study of omeprazole behavior: Racemization barrier and decomposition reaction
Authors: Thais Bruni Aline , Castro Ferreira Márcia Miguel
Published: February 2008

Omeprazole is a substituted benzimidazole which suppresses gastric‐acid secretion by means of H+, K+‐ATPase inhibition. It is an optically active drug with the sulfur of the sulfoxide being the chiral center. This pro‐drug can be easily converted into its respective sulfenamide at low pH. In this work, omeprazole has been studied in relation to racemization barrier and decomposition reaction. Quantum chemistry coupled to PCA chemometric method were used to find all minimum energy structures. Conformational analysis and calculation of racemization barriers were carried out by PM3 semiempirical method (Gaussian 98). The average racemization energy barrier for all minimum energy structures (43.56 kcal mol−1) can be related to the velocity constant in Eyring's equation. The enormous half‐life time at 100°C (9.04 × 104years) indicates that the process cannot be observed in human time scale. On the other hand, the difference of free energy change (Δ(ΔG) = −266.78 kcal mol−1) for the decomposition reaction shows that the process is favorable to the sulfenamide formation. The highly negative Δ(ΔG) obtained for the decomposition reaction shows that this process is extremely exothermic. This result explains why omeprazole decomposes and does not racemize. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Inductive and resonance effects based on core‐electron binding energy shift
Authors: Takahata Yuji
Published: February 2008

It was shown that core‐electron binding energy shift (ΔCEBE) could be used as a criterion of inductive (and resonant) effect at each ring carbon atom of substituted cyclohexanes (and benzenes). CEBEs were calculated using density‐functional theory with the scheme ΔEKS (PW86‐PW91)/TZP//HF/6‐31G*. The inductive effect thus calculated correlate highly with the Taft inductive effect (σI). The inductive effect in a substituted benzene can be well approximated by that determined in a substituted cyclohexane. Resonant effect was defined as the difference between ΔCEBE of a substituted benzene and ΔCEBE of a substituted cyclohexane. The resonance effect thus defined at para atom in substituted benzenes correlates fairly well with Taft (experimental) resonance effect (σR), very highly with Taft (theoretical) resonance effect (σR, theory) of literature. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Theoretical study of mechanism of cycloaddition reaction between dimethylmethylenesilylene and formaldehyde
Authors: Lu Xiu Hui , Yu Hai Bin , Che Xin , Xiang Ping Ping
Published: February 2008

The mechanism of cycloaddition reaction between singlet dimethylmethylenesilylene and formaldehyde has been investigated with MP2/6‐31G* method, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. The energies of different conformations are calculated by CCSD(T)//MP2/6‐31G* method. From the potential energy surface, it can be considered in thermodynamics and dynamics that reaction (1) and reaction (4) are the two dominant competitive reaction channels of cycloaddition reaction between dimethylmethylenesilylene and formaldehyde. The reaction process of reaction (1) is that: the two reactants (R1, R2) first form intermediates INT1a and INT1b through two reaction paths, a and b, which are barrier‐free exothermic reactions of 31.8 and 43.9 kJ/mol; then, INT1a and INT1b isomerize to a four‐membered ring product P1 via transition states TS1a and TS1b, with energy barriers of 26.3 and 24.4 kJ/mol. Reaction (4) also has two reaction paths, a and b, each of which consists of three steps are as follows: (i) the two reactants (R1, R2) first form intermediates INT3a and INT3b, which are barrier‐free exothermic reactions of 64.5 and 44.2 kJ/mol. (ii) INT3a and INT3b further react with formaldehyde (R2) to form intermediates INT4a and INT4b, through barrier‐free exothermic reactions of 22.9 and 22.2 kJ/mol. (iii) INT4a and INT4b then isomerize to form silapolycyclic product P4 via transition states TS4a and TS4b, with energy barriers of 39.7 and 29.3 kJ/mol. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Mechanistic investigation of vibrational fine structure in e‐H2 scattering using local complex potential‐based time dependent wave packet approach
Authors: Sarma Manabendra , Adhikari S. , Mishra Manoj K.
Published: February 2008

The structural features of vibrational excitation cross‐sections in resonant e‐H2 scattering have been investigated using a time dependent wave packet approach and a local complex potential to describe the 2Σ H anion. An analysis of the partial contributions to the vibrational excitation cross‐sections reveals that all features of the excitation profile result from simple interference between bound vibrational levels of H2 and H. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Research on the axis shape of an active catheter
Authors: Fu Yili , Li Xianling , Wang Shuguo , Liu Hao , Liang Zhaoguang
Published: February 2008

Background

An active catheter is a minimally invasive surgery catheter that can perform deflectable motions. The active catheter can be controlled from outside the body and moves like a snake, utilizing a multi‐joint mechanism with distributed shape memory alloy (SMA) actuators.

Methods

It was considered that the deflection curve of the axis of the catheter is determined by the output force of the SMA actuators. Based on the large deflection theory, the deflection curve equation of the axis of the catheter was derived, using the precise form of the curvature.

Results

Through experimentation, the axial bending curve shape of the blended active catheter was measured precisely, and the experimental results were compared with the calculation results obtained from the large deflection theory and the circular arc hypothesis. The experimental results show that the curves calculated by large deflection theory are very close to the actual axis curves.

Conclusions

An active catheter prototype has been designed using the theory presented in this paper. Utilizing a vascular model, the active catheter‐based invasive surgery was simulated. The experiment confirmed that the large deflection theory calculation method can be used to guide the design of the active catheter. Copyright © 2008 John Wiley & Sons, Ltd.
Land vehicular propagation channel characterization of BGAN system
Authors: Gambaruto Elvio , Richharia M. , Trachtman Eyal
Published: February 2008

This paper summarizes the results of a measurement campaign, which set out to characterize Inmarsat's broadband global area network extension (BGAN‐X) L‐band land vehicular (LV) channels as a function of elevation angle and candidate antenna systems. Measurements were conducted with three types of directional antennas on motorway routes around London using Inmarsat's Indian Ocean Region (IOR), Atlantic Ocean Region‐East (AOR‐E) and Atlantic Ocean Region‐West (AOR‐W) satellite transmissions, corresponding to elevation angles of, respectively, ∼7.5°, ∼13° and ∼30°. Simultaneous recordings of data on two types of directive receivers enabled correlation of several channel parameters. Statistics were used to refine a baseline model that derived BGAN‐X LV channel parameters by scaling the statistics obtained from an omni‐directional antenna receiver. The measurements demonstrate that Ricean mean and Ricean factor vary significantly over the chosen routes at elevation angles below ∼13°. Further, the Doppler shift of the direct path can be predicted accurately. A qualitative analysis indicates that the multi‐path Doppler spread is generally (not always) caused by uniform scattering around the vehicle over short distances and undergoes spatial filtering due to the receiver antenna. A technique was established to derive statistics of a two‐state Markovian channel model at any specified fading threshold by gathering tracking system state, thereby allowing one to ascertain service expectations and operational parameters such as connection time‐out of a packet‐switched system or reliability threshold of a circuit‐switched system. The technique was used to identify and select appropriate routes, particularly for the IOR and the AOR‐W regions. Data analysis is in progress to establish the reason for the slow variations of signal mean at low‐elevation angles in Ricean conditions and to derive appropriate statistical models. Furthermore, image processing of the video recordings is expected to reveal the extent of optical and RF fades correlation. Copyright © 2008 John Wiley & Sons, Ltd.
Aspects of Latex Particle Size Control for Improved Water Blush Resistance
Authors: Starostin Natasha , Harvey Scott , Carlson Gary
Published: February 2008

Latex films have a tendency to “blush” when exposed to water. The swelling of trapped hydrophilic material, which results in pockets with different refractive indices, is proposed as a possible model for blushing. A pressure‐sensitive latex was developed on the basis of this model. The blush was improved by the choice of the surfactant and control of the particle diameter. The resulting latex has an unusual particle growth behavior during polymerization. The particle size distribution (PSD) was characterized by dynamic light scattering (DLS), electron microscopy (SEM/TEM) and atomic force microscopy (AFM). The data are in a good agreement with our proposed growth model. SCANNING 30: 000–000, 2008. © 2008 Wiley Periodicals, Inc.
A novel nano‐bubble inflation method for determining the viscoelastic properties of ultrathin polymer films
Authors: O'connell P. A. , McKenna G. B.
Published: February 2008

We describe a novel experimental technique for measuring the absolute creep compliance of ultrathin polymer films. The method is based on the classical bubble inflation technique for measuring the biaxial creep compliance of films, reduced in size to measure films with thicknesses down to at least 11.3 nm. The method uses the imaging capabilities of the atomic force microscope (AFM) to determine the time evolution of the geometry of nano‐bubbles and thus avoids the problems with data interpretation that can arise due to “contact mechanics” issues when the AFM is used as a direct mechanical testing device. SCANNING 30: 000–000, 2008. © 2008 Wiley Periodicals, Inc.
A simple method for the removal of thiols on gold surfaces using an NH4OH–H2O2–H2O solution
Authors: Kim Dae Jung , Pitchimani Rajasekar , Snow David E. , Hope‐Weeks Louisa J.
Published: February 2008

The removal behavior of self‐assembled monolayers (SAMs) of thiol molecules on a gold substrate by an NH4OH–H2O2–H2O solution was studied using attenuated total reflectance infrared spectroscopy (ATR‐IR) and atomic force microscopy (AFM). Furthermore, the impact of the concentration of NH4OH and H2O2 in the solution and reaction temperature on the SAM removal rate and efficiency was explored. The SAM removal rate and efficiency were significantly influenced by the concentration of NH4OH rather than H2O2. The solution containing the 2 : 1 molar ratio of NH4OH : H2O2 among three different solutions showed the highest removal rate and efficiency in the removal of 11‐mercapto‐1‐undecanol. The increase in the reaction temperature resulted in the enhancement on the SAM removal rate, but it led to the fast delamination of the gold layer. These results may be useful in the regeneration of sensor surfaces relying on gold/thiol chemistry. SCANNING 30: 000–000, 2008. © 2008 Wiley Periodicals, Inc.
Mitigating dead‐time effects during multivariate analysis of ToF‐SIMS spectral images
Authors: Keenan Michael R. , Smentkowski Vincent S. , Ohlhausen James A. (Tony) , Kotula Paul G.
Published: February 2008

ToF‐SIMS spectra are formed by bombarding a surface with a pulse of primary ions and detecting the resultant ionized surface species using a time‐of‐flight mass spectrometer. Typically, the detector is a time‐to‐digital converter. Once an ion is detected using such detectors, the detector becomes insensitive to the arrival of additional ions for a period termed as the (detector) dead‐time. Under commonly used ToF‐SIMS data acquisition conditions, the time interval over which ions arising from a single chemical species reach the detector is on the order of the detector dead‐time. Thus, only the first ion reaching the detector at any given mass is counted. The event registered by the data acquisition system, then, is the arrival of one or more ions at the detector. This behavior causes ToF‐SIMS data to violate, in the general case, the assumption of linear additivity that underlies many multivariate statistical analysis techniques. In this article, we show that high‐mass‐resolution ToF‐SIMS spectral‐image data follow a generalized linear model, and we propose a data transformation and scaling procedure that enables such data sets to be successfully analyzed using standard methods of multivariate image analysis. Copyright © 2008 John Wiley & Sons, Ltd.
Compatibilizing effect of functionalized polystyrene blends: a study of morphology, thermal, and mechanical properties
Authors: Shabbir Saima , Zulfiqar Sonia , Lieberwirth Ingo , Kausar Ayesha , Sarwar Muhammad Ilyas
Published: February 2008

Polystyrene (PS), being an amorphous polymer is immiscible with other polymers. To engender miscible blends, PS has been functionalized with an active amino‐functional group on the molecular chains of PS to yield amino‐substituted polystyrene (APS), which serves as a reactive compatibilizer. The compatibilization effect of amino functionalized polystyrene on the rubber toughening was explored and results were compared in terms of morphology, thermal, and mechanical properties of PS/SEBS‐g‐MA versus APS/SEBS‐g‐MA blends. In addition, the effect of rubber content on the blend morphology and mechanical properties were investigated. An appreciable change in the thermal stability of APS blends in comparison with PS blend has been probed. A marked correlation has been observed between phase morphology and thermal stability. Use of APS produced the compatibilized blends which render improved blend morphology, enhanced thermal and mechanical properties. Optimal thermal, morphological and mechanical profiles were depicted by 20‐wt% APS blend. Copyright © 2008 John Wiley & Sons, Ltd.
Innovative Starch Derivatives as Textile Auxiliaries for Application in Sizing, Finishing and Flocculation
Authors: Hebeish Aly , Aly Amal Ahmed , El‐Shafei Amira Mohamed , Zaghloul Saad
Published: February 2008

Innovative starch‐based polymeric products were synthesized for utilization as sizing agents, flocculants, and finishing agents. The synthesis involved reaction of starch and hydrolyzed starches with monochlorotriazinyl‐β‐cyclodextrin (MCT‐β‐CD) to yield starch grafted with cyclodextrin (St‐g‐CD). The latter was further reacted with 3‐chloro‐2‐hydroxypropyltrimethylammonium chloride (Quat‐188) to effect cationization of St‐g‐CD. Grafting of starch with cyclodextrin and cationization with Quat‐188 were concurrently expedited by reacting starch with both MCT‐β‐CD and Quat‐188 in a one‐step process using NaOH as catalyst. Maximization of the reaction of starch‐g‐CD with Quat‐188 (expressed as%N) and the concurrent reaction of starch with MCT‐β‐CD and Quat‐188 could be achieved at 40ºC for 90 and 120 min, respectively, by using NaOH as catalyst at concentrations of 8 and 15 mmol, respectively. These reaction conditions were employed to prepare six innovative polymeric starch derivatives. Derivatives I, II and III represent St‐g‐CD prepared from hydrolyzed starches having different molecular sizes after being cationized with Quat‐188. Derivatives IV, V and VI represent those prepared from reacting the hydrolyzed starch with both MCT‐β‐CD and Quat‐188 in a one‐step process. The six derivatives were characterized by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). Although all six derivatives bear cyclodextrin and Quat‐188 moieties, their characters and properties differ considerably, which was reflected on their efficiency as flocculants and sizing agents and as additive in durable press finishing (DP) of cotton fabric. The efficiency of the six derivatives when applied in these fields depends on the molecular size of the parent starch, the graft content of the in St‐g‐CD, the extent of cationization and the condition of application. At any event, however, the innovative derivatives in question exhibit salient features which advocate them for application in sizing, flocculation and DP finishing.
Pasting Behavior of Amylose, Amylopectin and Their Mixtures as Determined by RVA Curves and First Derivatives
Authors: Juhász Réka , Salgó András
Published: February 2008

The relationship between amylose to amylopectin ratio and functional properties of maize starch blends (system I) and “model mixtures” (system II) made of waxy and high amylose maize starch were investigated using the Rapid Visco Analyser (RVA). A 4‐5% difference in amylose content caused significant difference in RVA curves and their first derivatives. Based on the first derivative of the RVA curves four different parameters (Peak 2, Peak Time 2, Peak 3, Peak Time 3) were defined. Peak viscosity and parameters were negatively correlated with amylose content confirming that amylopectin is mainly responsible for water uptake. The final viscosity of starch was very high and decreased as amylopectin or amylose was added, indicating that this parameter is the most sensitive to interactions in starch. In system II amount and characteristics of amylopectin seemed to primarily determine the pasting properties. Traditional RVA curves and parameters proved to be feasible to detect the differences between gel properties of the two systems after cooling. First derivative viscograms and alternative parameters seemed to be suitable to demonstrate the importance of interactions between the starch components during gelatinization. Our results confirmed that the Rapid Visco Analyser is a sensitive rheological tool for evaluating effects of starch structure and chemical composition on functional properties providing valuable help for food technologists.
Morphological and Crystalline Properties of Starches from New Sources‐Traditional Chinese Medicines (TCMs)
Authors: Yu Jinglin , Wang Shujun
Published: February 2008

In China, there are many starch‐rich Traditional Chinese Medicines (TCMs) such as Fritillaria, Rhizoma Dioscorea Thunb., Pueraria Lobata Ohwi, Alisma Orientalis Juzep. and Polygonum Multiflorum Thunb. The low‐molecular weight bioactive ingredients present in these TCMs have been studied widely. However, starches are always ignored and discarded during the isolation of the small‐molecule active components, which results in large wastes of TCM resources. In order to understand and explore these new starches, the morphological and crystalline properties of starches from six TCMs have been evaluated. The starches differ in granular shape and size. The F. ussurensis Maxim. (FUM), F. cirrhosa D. Don. (FCD) and Rhizoma Dioscorea Thunb. (RDT) starches have larger granules than the other three TCM starches. Alisma Orientalis Juzep. (AOJ) starch possesses the smallest granules among the six starches. Polygonum Multiflorum Thunb. (PMT) starch has the lowest integrity of granule shape. RDT starch and Pueraria Lobata Ohwi (PLO) starches display the characteristics of typical C‐type diffraction pattern. FUM starch and FCD starch show typical B‐type diffraction pattern. AOJ and PMT starches have the strongest diffraction peaks at 17.8°, 20.1° and 27.4º which is indicative of an A‐type diffraction pattern.
Effect of Starch Modifications and Hydrocolloids on Freezable Water in Cassava Starch Systems
Authors: Tran Thierry , Thitipraphunkul Kittiwut , Piyachomkwan Kuakoon , Sriroth Klanarong
Published: February 2008

The effect of starch chemical modifications and hydrocolloids on the proportion of freezable water in starch gels at various moisture contents was studied. The proportion of freezable water increased with moisture content, from less than 6.1% to 84.9% (w/w) of the water fraction between 30% and 70% moisture content (wet weight basis, wwb). A transition between limited and excess water conditions was identified in the range 30‐40% moisture content (wwb), whereby the proportion of freezable water markedly increased from 6.1% to 40.4% (w/w) of the water fraction, in the case of the non‐modified starch control. At 30 and 40% moisture content (wwb), gels made of acetylated starch and hydroxypropylated starch had a significantly lower amount of freezable water than the control, in particular at 40% moisture content (wwb) the amount of freezable water was reduced from 40.4% to 15.3‐25.7% (w/w) of the water fraction. In systems with 50% moisture content (wwb) or higher, modified starches did not show a significant reduction in freezable water compared to the control. Two hydrocolloids, xanthan and carboxymethyl cellulose (CMC) used in a 40% moisture content (wwb) starch system significantly reduced freezable water from 40.4% to 23.9‐24.1% of the water fraction (w/w), at a hydrocolloid: starch ratio of 1:14 (w/w). The linear decrease in the freezable water proportion with xanthan and CMC concentration pointed to the absence of interactions between the starch and hydrocolloid fractions. Therefore, combinations of hydroxypropylated or acetylated starches and xanthan or CMC may be used to control freezable water, particularly in frozen food products with moisture contents around 40% (wwb).
Receptor‐activity modifying protein 1 expression is increased in the striatum following repeated L‐DOPA administration in a 6‐hydroxydopamine lesioned rat model of Parkinson's disease
Authors: Lee Joohyung , Gomez‐Ramirez Jordi , Johnston Tom H. , Visanji Naomi , Brotchie Jonathan M.
Published: February 2008

Abnormalities in signaling by G‐protein coupled receptors (GPCRs) within the striatum are involved in the pathophysiology of Parkinson's disease (PD) and L‐DOPA induced dyskinesia (LID). Receptor activity modifying proteins (RAMPs) are single transmembrane accessory proteins crucial for both trafficking and defining the phenotype of GPCRs. In the CNS, RAMP1 mRNA is predominantly expressed in striatum, cortex, and olfactory tubercles. In the present study, expression of RAMP1 mRNA is increased in the striatum (68–77%), following repeated L‐DOPA administration, in the 6‐hydroxydopamine‐lesioned rat. These data are the first to describe regulation of RAMP1 expression in the CNS and suggest that changes in RAMP1 activity are involved in the pathophysiology of LID. Synapse 62:310–313, 2008. © 2008 Wiley‐Liss, Inc.
Role for the skeletal muscle action potential in non‐Hebbian long‐term depression at the amphibian (Bufo marinus) neuromuscular junction
Authors: Etherington Sarah Jane , Everett Alan William
Published: February 2008

Retrograde signaling from skeletal muscle cells to motor nerve terminals is a recognized mechanism for modulating the strength of neuromuscular transmission. We recently described a form of long‐term depression of transmitter release at the mature neuromuscular junction that is dependent on the production of nitric oxide, most likely by the muscle cell (Etherington and Everett 2004 J Physiol (Lond) 559:507–517). We now show that the depression is blocked by treating neuromuscular preparations with μ‐conotoxin G111A, an antagonist of skeletal muscle voltage gated sodium channels, indicating that the depression requires postsynaptic action potential firing. Experiments on dually‐innervated sartorius muscles revealed that propagation of action potentials generated by low‐frequency stimulation of one nerve branch gives rise to nitric‐oxide mediated depression at unstimulated nerve terminals located many millimetres away on the same muscle fiber. The non‐Hebbian pattern of expression of the depression, as well as its reliance on postsynaptic action potential firing, distinguish it from forms of synaptic depression described at immature neuromuscular synapses and may provide a mechanism for coregulation of the strength of motoneurons innervating the same postsynaptic cell. Synapse 62:291–301, 2008. © 2008 Wiley‐Liss, Inc.
Application of DNA diffusion assay in earthworm coelomocytes
Authors: Apte A. A. , Manerikar R. S. , Ghole V. S.
Published: February 2008

We have applied the DNA diffusion assay proposed by Singh (2000) Exp Cell Res 256:328–337, for quantitative estimation of apoptosis in earthworm coelomocytes, exposed to Chromium (VI) and cypermethrin as model toxicants in vitro. The DNA diffusion assay was originally described for mammalian cells. H2O2, Sodium ascorbate, and hyperthermia were used as positive controls in present study. Apoptosis such as DNA diffusion occurred in dose‐dependent manner for Chromium (VI) and cypermethrin at very low concentration (1, 3, and 10 ppm for Chromium (VI) and 4, 8, and 16 ppm for cypermethrin). Three distinct patterns (apoptosis like DNA diffusion, necrosis, and normal) were observed in exposed and nonexposed cells. Present study is probably the first report of application of the DNA diffusion technique in earthworm coelomocytes. Findings of this study indicate that this assay has potential for use in invertebrate cells to differentiate between apoptosis and necrosis. © 2008 Wiley Periodicals, Inc. Environ Toxicol, 2008.
Toxicity of microcystin‐LR, a cyanobacterial toxin, to multiple life stages of the burrowing mayfly, Hexagenia, and possible implications for recruitment
Authors: Smith Juliette L. , Boyer Gregory L. , Mills Edward , Schulz Kimberly L.
Published: February 2008

Burrowing mayflies, genus Hexagenia, were extirpated from the major water bodies of North America in the early 1950s, paralleling an increase in eutrophication and organic pollution, and a decrease in dissolved oxygen concentrations. Burrowing mayflies recolonized the western basin of Lake Erie, but remain absent in other former habitats such as Oneida Lake, New York. Eutrophication is commonly associated with a shift in the phytoplankton community toward dominance by cyanobacteria, and therefore, one class of cyanobacterial toxins, microcystins, were investigated as a contributing factor to Hexagenia's eradication or as an impediment to recolonization. Laboratory experiments were conducted to determine if microcystin‐LR (MC‐LR) produced negative effects on Hexagenia at three points within its life cycle: egg, hatchling nymph (<24‐h old, <1 mm total length), and pre‐emergence nymph (>17 mm). Treatment concentrations ranged from the guideline set by the World Health Organization for drinking water (0.001 μg mL−1) to 0.1 μg mL−1 for the egg experiment and 10 μg mL−1 for the nymph trials. Eggs showed a delay in hatching and an altered distribution of hatching over the study period when submerged in 0.1 μg mL−1 MC‐LR (an elevated concentration representative of bloom scum). The 72‐h (1.1 μg mL−1) and 96‐h (0.049 μg mL−1) LC50 values for hatchling nymphs exceeded typical bloom concentrations of North American lakes, (0.01 μg mL−1). Large nymphs were more tolerant of the toxin, as indicated by 100% survival over seven days exposure to 10 μg mL−1, suggesting older larvae can withstand brief encounters with high microcystin levels for at least short periods of time. The sensitivity of young nymphs and eggs to MC‐LR may have implications for the recruitment of the genus in water bodies with persistent summer cyanobacterial blooms. © 2008 Wiley Periodicals, Inc. Environ Toxicol, 2008.
Atomlagenabscheidung als Werkzeug für die Nanotechnologie
Authors: Albert Matthias , Bartha Johann Wolfgang
Published: February 2008

Der charakteristische selbst begrenzende Wachstumsmechanismus der Atomlagenabscheidung (ALD) ermöglicht die Kontrolle der Schichtdicken im atomaren Bereich und erlaubt Beschichtungen komplexer Oberflächen. Diese Eigenschaft macht die ALD zu einer vielversprechenden Technik für die zukünftige Mikro ‐ und Nanotechnologie. Der Schlüssel für die ALD ist die Precursorchemie.
Kondensation: Ein unterschätzter Aspekt der Kurzwegdestillation
Authors: Schardt Stefan
Published: February 2008

Die Kurzwegdestillation hat sich seit Jahren sowohl im Labor als auch in der Technik einen festen Platz unter den etablierten thermischen Trennmethoden erobert. Wenn unter schonenden Bedingungen Substanzgemische mit bei Zimmertemperatur geringen Dampfdrücken destillativ aufgetrennt werden sollen, kann die Kurzwegdestillation häufig als wirtschaftliches und zuverlässiges Verfahren erfolgreich eingesetzt werden.

Der nachfolgende Artikel gibt einen Überblick über die Grundlagen der Kurzwegdestillation sowie die Beschreibung eines neuentwickelten Verfahrens zur Erzielung höherer Rückstands‐Reinheiten, das als Waschkondensation bezeichnet wird.
Vakuum‐Lineardurchführungen mit Magnetflüssigkeitsdichtungen
Authors: Ochoński Wlodzimierz
Published: February 2008

Die Arbeitsbedingungen der Magnetflüssigkeitsdichtungen sind bei der linearen Bewegung anders als bei der Drehbewegung. Daher ist der Anwendung der für die Drehbewegung typischen Dichtungen auch bei der hin‐ und hergehenden Bewegung nicht effektiv. Die Analyse des Dichtheitmechanismus der Magnetflüssigkeitsdichtungen bei der linearen Bewegung weist darauf hin, dass die Effektivität dieser Dichtungen bedeutend durch die Deformation und Übertragung der Magnetflüssigkeit im Dichtspalt beeinflusst wird, was von der Geschwindigkeit der Verschiebung der Stange abhängt. Wie die Untersuchungen bewiesen, ist die Deformation und Verminderung der Menge der Magnetflüssigkeit im Spalt infolge deren Anhaften an die Stangenfläche die Hauptursache des Dichtheitsverlustes dieser Dichtungen.

Zwecks Erhöhung der Wirkungseffektivität der oben beschriebenen Dichtungen werden Konstruktionslösungen angewendet, die die Übertragung der Magnetflüssigkeit im Dichtspalt bei der hin‐ und hergehenden Bewegung der Stange einschränken.

Lineardurchführungen mit Magnetflüssigkeitsdichtungen gewährleisten die höchste Reinheit im Vakuum bei geringen Geschwindigkeiten der Verschiebung (bis 1 m/s). Das Dichtelement ist eine magnetisierbare Flüssigkeit, die mit einem Magnetfeld an der Dichtstelle gehalten wird.

Diese Lineardurchführungen besitzen gegenüber konventionellen Dichtungsausführungen einzigartige Vorteile:

— hermetische Dichtheit,

— partikelfreier Betrieb, was in Vakuumprozessen höchste Reinheit sicherstellt,

— keinerlei Haftreibung,

— hohe Zuverlässigkeit und lange Lebensdauer.
Comparative analysis of knowledge gain between interpretive and fact‐only presentations at an animal training session: an exploratory study
Authors: Visscher Nick C. , Snider Richard , Vander Stoep Gail
Published: February 2008

Zoos and aquariums have recognized the importance of integrating living collections with personally delivered interpretation. One way for zoos to accomplish this is by conducting public animal training sessions accompanied by personal interpretation. Many institutions offer these types of interactions, but the term “interpretation” is used loosely and without clear definition. This exploratory study compared knowledge gain of individual students in three different fifth grade school groups visiting the Potter Park Zoo in Lansing, Michigan. Each group observed an animal training session, with two groups receiving two types of presentations and one group serving as a control group. Although hearing the same facts, the two treatment groups received different program types: an interpretive presentation and a fact‐only presentation. The third group viewed the training session but received no presentation. Results showed that individuals who received the interpretive presentation retained more information immediately after the training session than individuals in either of the other two groups. This exploratory study suggests that using an interpretive presentation style is more effective in producing knowledge gain than fact‐only presentations in informal learning environments such as zoos and aquariums. Zoo Biol 28:488–495, 2009. © 2008 Wiley‐Liss, Inc.
The Effect of Surgical Subspecialization on Outcomes in Peptic Ulcer Disease Complicated by Perforation and Bleeding
Authors: Robson Andrew J. , Richards Jennifer M. J. , Ohly Nicholas , Nixon Stephen J. , Paterson‐Brown Simon
Published: February 2008

Background

Emergency surgical services in Edinburgh were restructured in July 2002 to deliver subspecialist management of colorectal and upper‐gastrointestinal emergencies on separate sites. The effect of emergency subspecialization on outcome from perforated and bleeding peptic ulceration was assessed.

Methods

All patients admitted with complicated peptic ulceration (January 2000–February 2005) were identified from a prospectively compiled database.

Results

Perforation: 148 patients were admitted with perforation before the service reorganization (period A – 31 months) of whom 126 (85.1%) underwent surgery; 135 patients were admitted in period B (31 months) of whom 114 (84.4%) were managed operatively. The in‐hospital mortality was lower in period B (14/135, 10.4%) than period A (30/148, 20.3%; P = 0.023; relative risk (RR), 0.51; 95% confidence interval (CI), 0.28–0.91). There was a significantly higher rate of gastric resection in the second half of the study (period A 1/126 vs. period B 8/114; P = 0.015; RR, 8.84; 95% CI, 1.48–54.34). Length of hospital stay was similar for both groups. Bleeding: 51 patients underwent operative management of bleeding peptic ulceration in period A and 51 in period B. There were no differences in length of stay or mortality between these two groups.

Conclusion

Restructuring of surgical services with emergency subspecialization was associated with lower mortality for perforated peptic ulceration. Subspecialist experience, intraoperative decision‐making, and improved postoperative care have all contributed to this improvement.
Oughts and ends
Authors: Finlay Stephen
Published: February 2008

This paper advances a reductive semantics for ‘ought’ and a naturalistic theory of normativity. It gives a unified analysis of predictive, instrumental, and categorical uses of ‘ought’: the predictive ‘ought’ is basic, and is interpreted in terms of probability. Instrumental ‘oughts’ are analyzed as predictive ‘oughts’ occurring under an ‘in order that’ modifer (the end-relational theory). The theory is then extended to categorical uses of ‘ought’: it is argued that they are special rhetorical uses of the instrumental ‘ought’. Plausible conversational principles explain how this end-relational ‘ought’ can perform the expressive functions of the moral ‘ought’. The notion of an ‘ought-simpliciter’ is also discussed.
Proneural bHLH neurogenin 2 differentially regulates Nurr1‐induced dopamine neuron differentiation in rat and mouse neural precursor cells in vitro
Authors: Park Chang-Hwan , Kang Jin Sun , Yoon Eun-Hye , Shim Jae-Won , Suh-Kim Haeyoung , Lee Sang-Hun
Published: February 2008

Roles of Nurr1 and neurogenin 2 (Ngn2) have been shown in midbrain dopamine (DA) neuron development. We present here rat and mouse species‐dependent differences of Nurr1 and Ngn2 actions in DA neuron differentiation. Nurr1 exogene expression caused an efficient generation of tyrosine hydroxylase (TH)‐positive DA cells from rat neural precursor cells (NPCs). Nurr1‐induced TH+ cell yields were low and highly variable depending on the origins of NPCs in mouse cultures. Coexpression of Ngn2 repressed Nurr1‐induced generation of TH+ cells in rat cultures. In clear contrast, a robust enhancement in Nurr1‐induced DA cell yields was observed in mouse NPCs by Ngn2. These findings imply that DA neurons may develop differently in the midbrains of these two species.
Regulation of SIRT6 protein levels by nutrient availability
Authors: Kanfi Yariv , Shalman Ronnie , Peshti Victoria , Pilosof Shmuel N. , Gozlan Yosi M. , Pearson Kevin J. , Lerrer Batya , Moazed Danesh , Marine Jean-Christophe , de Cabo Rafael , Cohen Haim Y.
Published: February 2008

Sirtuins have been shown to regulate life‐span in response to nutritional availability. We show here that levels of the mammalian sirtuin, SIRT6, increased upon nutrient deprivation in cultured cells, in mice after fasting, and in rats fed a calorie‐restricted diet. The increase in SIRT6 levels is due to stabilization of SIRT6 protein, and not via an increase in SIRT6 transcription. In addition, p53 positively regulates SIRT6 protein levels under standard growth conditions but has no role in the nutrient‐dependent regulation of SIRT6. These observations imply that at least two sirtuins are involved in regulation of life‐span by nutrient availability.
Label‐free optical biosensor for ligand‐directed functional selectivity acting on β2 adrenoceptor in living cells
Authors: Fang Ye , Ferrie Ann M.
Published: February 2008

Recent realization of ligand‐directed functional selectivity demands high‐resolution tools for studying receptor biology and ligand pharmacology. Here we use label‐free optical biosensor to examine the dynamic mass redistribution of human epidermoid A431 cells in response to diverse β2‐adrenoceptor ligands. Multi‐parameter analysis reveals distinct patterns in activation and signaling of the receptor induced by different agonists. Sequential and co‐stimulation assays categorize various ligands for their ability to modulate signaling induced by catechol, a structural component of catecholamines. This study documents multiple ligand‐specific states of the β2‐adrenoceptor and highlights the power of the biosensor assays for screening pathway‐biased ligands.
Chemerin enhances insulin signaling and potentiates insulin‐stimulated glucose uptake in 3T3‐L1 adipocytes
Authors: Takahashi Michiko , Takahashi Yutaka , Takahashi Kenichi , Zolotaryov Fyodor N. , Hong Kyoung Su , Kitazawa Riko , Iida Keiji , Okimura Yasuhiko , Kaji Hidesuke , Kitazawa Sohei , Kasuga Masato , Chihara Kazuo
Published: February 2008

To explore a novel adipokine, we screened adipocyte differentiation‐related gene and found that TIG2/chemerin was strongly induced during the adipocyte differentiation. Chemerin was secreted by the mature 3T3‐L1 adipocytes and expressed abundantly in adipose tissue in vivo as recently described. Intriguingly, the expression of chemerin was differently regulated in the liver and adipose tissue in db/db mice. In addition, serum chemerin concentration was decreased in db/db mice. Chemerin and its receptor/ChemR23 were expressed in mature adipocytes, suggesting its function in autocrine/paracrine fashion. Finally, chemerin potentiated insulin‐stimulated glucose uptake concomitant with enhanced insulin signaling in the 3T3‐L1 adipocytes. These data establish that chemerin is a novel adipokine that regulates adipocyte function.
In vitro regulation of CaCO3 crystal polymorphism by the highly acidic molluscan shell protein Aspein
Authors: Takeuchi Takeshi , Sarashina Isao , Iijima Minoru , Endo Kazuyoshi
Published: February 2008

Biominerals, especially molluscan shells, generally contain unusually acidic proteins. These proteins are believed to function in crystal nucleation and inhibition. We previously identified an unusually acidic protein Aspein from the pearl oyster Pinctada fucata. Here we show that Aspein can control the CaCO3 polymorph (calcite/aragonite) in vitro. While aragonite is preferentially formed in Mg2+‐rich solutions imitating the extrapallial fluids of marine molluscs, Aspein exclusively induced calcite precipitation. Our results suggest that Aspein is involved in the specific calcite formation in the prismatic layer. Experiments using truncated Aspein demonstrated that the aspartic acid rich domain is crucial for the calcite precipitation.
The three‐dimensional structure of the analgesic α‐conotoxin, RgIA
Authors: Clark Richard J. , Daly Norelle L. , Halai Reena , Nevin Simon T. , Adams David J. , Craik David J.
Published: February 2008

The α‐conotoxin RgIA is a selective antagonist of the α9α10 nicotinic acetylcholine receptor and has been shown to be a potent analgesic and reduces nerve injury associated inflammation. RgIA was chemically synthesized and found to fold into two disulfide isomers, globular and ribbon. The native globular isomer inhibited ACh‐evoked currents reversibly in oocytes expressing rat α9α10 nAChRs but the ribbon isomer was inactive. We determined the three‐dimensional structure of RgIA using NMR methods to assist in elucidating the molecular role of RgIA in analgesia and inflammation.
D2/D3 receptor agonist ropinirole protects dopaminergic cell line against rotenone‐induced apoptosis through inhibition of caspase‐ and JNK‐dependent pathways
Authors: Chen Sheng , Zhang Xiaojie , Yang Dehua , Du Yunlan , Li Liang , Li Xuping , Ming Ming , Le Weidong
Published: February 2008

Ropinirole, a D2/D3 receptor agonist has been reported to have neuroprotective effects. We showed that ropinirole can prevent rotenone‐induced apoptosis in dopaminergic cell line SH‐SY5Y through D3 receptor. We found that ropinirole can block the rotenone‐induced phosphorylation of JNK, P38 and p‐c‐Jun, but promote the phosphorylation of ERK1/2. Furthermore, we demonstrated that ropinirole can reduce the rotenone‐induced cleavages of caspase 9, caspase 3 and PARP and elevate the expression of anti‐apoptotic proteins of p‐Akt and bcl‐2. These results provide a basis for neuroprotection by this drug for the treatment of Parkinson disease.
Structure of Escherichia coli tetrahydrodipicolinate N‐succinyltransferase reveals the role of a conserved C‐terminal helix in cooperative substrate binding
Authors: Nguyen Long , Kozlov Guennadi , Gehring Kalle
Published: February 2008

Tetrahydrodipicolinate N‐succinyltransferase is an enzyme present in many bacteria that catalyzes the first step of the succinylase pathway for the synthesis of meso‐diaminopimelate and the amino acid l‐lysine. Inhibition of the synthesis of meso‐diaminopimelate, a component of peptidoglycan present in the cell wall of bacteria, is a potential route for the development of novel anti‐bacterial agents. Here, we report the crystal structure of the DapD tetrahydrodipicolinate N‐succinyltransferase from Escherichia coli at 2.0 Å resolution. Comparison of the structure with the homologous enzyme from Mycobacterium bovis reveals the C‐terminal helix undergoes a large rearrangement upon substrate binding, which contributes to cooperativity in substrate binding.
Peroxisome proliferator‐activated receptor gamma coactivator‐1 alpha (PGC‐1α) upregulated E‐cadherin expression in HepG2 cells
Authors: Lee Hui-Ju , Su Yeu , Lui Wing-Yiu , Chau Gar-Yang , Yin Pen-Hui , Lee Hsin-Chen , Chi Chin-Wen
Published: February 2008

Peroxisome proliferator‐activated receptor gamma coactivator‐1 alpha (PGC‐1α), a highly inducible transcriptional coactivator regulating energy homeostasis, is down‐regulated in hepatoma tissues. To dissect its role in hepato‐tumorigenesis, Ingenuity® Pathway Analysis was applied to construct pathways affected by PGC‐1α upregulation in HepG2 hepatoma cells based on our microarray data. Interestingly, migration of these cells was markedly diminished by PGC‐1α overexpression in consistency with Ingenuity® results. Moreover, a deduced expression increase of E‐cadherin was also observed in PGC‐1α‐overexpressing HepG2 cells. Finally, transient transfection and chromatin‐immunoprecipitation assays suggested that increased histone acetylation might be responsible for PGC‐1α‐mediated transactivation of a minimal E‐cadherin promoter.
Redox state and gender differences in vascular smooth muscle cells
Authors: Malorni Walter , Straface Elisabetta , Matarrese Paola , Ascione Barbara , Coinu Rita , Canu Silvia , Galluzzo Paola , Marino Maria , Franconi Flavia
Published: February 2008

Vascular smooth muscle cells (VSMC) have been isolated from male and female rat aorta and studied to assess their susceptibility to ultraviolet radiation‐induced oxidative stress. Interestingly, a gender difference, in terms of reactive oxygen species production, was detected in both basal and irradiated VSMC. Namely, VSMC from male rats were more susceptible to radiation‐induced stress and easier underwent apoptosis in comparison to cells from female rats. Conversely, the latter, in the same experimental conditions, clearly displayed signs of premature senescence. These results indicate that a sort of “gender memory” can be conserved in VMSC in primary culture.
RNase domains determine the functional difference between IRE1α and IRE1β
Authors: Imagawa Yusuke , Hosoda Akira , Sasaka Shin-ichi , Tsuru Akio , Kohno Kenji
Published: February 2008

Endoplasmic reticulum (ER) stress is associated with the functional disorder of the ER. During conditions of ER stress, cells induce at least two responses to maintain ER function: transcriptional upregulation of ER quality control genes, and translational attenuation of protein synthesis. Induction of ER quality control proteins is mediated by IRE1α, which activates the transcription factor XBP1 via an unconventional splicing event, while a partial translational attenuation is mediated by IRE1β. Here, we show by both in vivo and in vitro analyses that the RNase domain of IRE1 determines the functional specificities of each of these isoforms.
Interaction between two quasi-geostrophic vortices of unequal potential vorticity
Authors: ÖZUĞURLU ERSIN , REINAUD JEAN N. , DRITSCHEL DAVID G.
Published: February 2008

In this paper we systematically investigate strong interactions between two like-signed quasi-geostrophic vortices containing different uniform potential vorticity. The interaction depends on six parameters: the potential vorticity ratio between the two vortices, their volume ratio, their individual height-to-width aspect ratio, their vertical offset, and their horizontal separation distance. We first determine the conditions under which a strong interaction may occur. To that end, we calculate equilibrium states using an asymptotic approach which models the vortices as ellipsoids and we additionally assess their linear stability. It is found that vortices having similar potential vorticity interact strongly (e.g. merge) at closer separation distances than do vortices with a dissimilar potential vorticity. This implies that interactions between vortices having significantly different potential vorticity may be more destructive, for a given separation distance. This is confirmed by investigating the nonlinear evolution of the vortices over a subset of the full parameter space, solving the full dynamical quasi-geostrophic equations. Many forms of interaction occur, but merger or partial merger (where the largest vortex grows in volume) is mostly observed for interactions between vortices of similar potential vorticity.