bluuebunny/crossref_metadata_2025 huggingface dataset:
Particulate reinforced PC/PBT composites. I. Effect of particle size (nanotalc versus fine talc particles) on dimensional stability and properties
Authors: DePolo W.S. , Baird D.G.
Published: April 2008

The effect of particle size (nanotalc versus fine talc) on the dimensional stability, mechanical properties, and morphology of composites consisting of polycarbonate (PC), poly(butylene terephthalate) (PBT), and talc was investigated at various talc loadings. It was found that, by using nanotalc as opposed to fine talc particles, the level of talc reinforcement could be reduced from 6 to 1 wt% without sacrificing the dimensional stability, i.e. coefficient of linear thermal expansion and shrinkage of injection‐molded plaques, or flexural modulus of the PC/PBT/talc composites at a PC‐to‐PBT blend ratio of 60/40 by weight or greater. Further benefits included a 14% increase in flexural strength, 120% increase in the tensile toughness and 3% reduction in the density of the PC/PBT/talc composites. The improved stiffness is attributed to the higher aspect ratio (diameter/thickness of the platelets) of nanotalc (20–25) relative to that of the fine talc (5–10). An increase in the flexural modulus of the PC/PBT/talc composites with an increase in nanotalc loading was observed even though there was evidence of significant degradation in the molecular weight of the PC/PBT matrix. Possible degradation in the molecular weight of the PC/PBT matrix was supported by a significant reduction in the storage modulus and complex viscosity, at high frequencies of the composites generated with the nanotalc relative to that of the unfilled matrix. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers.
The six‐minute walk test in outpatients with obesity: reproducibility and known group validity
Authors: Larsson Ulla Evers , Reynisdottir Signy
Published: April 2008

Background and Purpose. To assess the reproducibility and validity of the six‐minute walk test (6MWT) in men and women with obesity in order to facilitate evaluation of treatment outcome. Method. A test—retest design was used to test reproducibility and a comparative design to test known group validity. Forty‐three obese outpatients (16 male), mean age 47 (21–62) years, mean body mass index (BMI) 40 (3–62)kg‐m–2 performed the 6MWT twice within one week. Intraclass correlation (ICC1.1) and measurement error (Sw) were calculated from the mean square values derived from a one‐way repeated‐measures ANOVA (fixed effect model). The reproducibility was also analysed by means of coefficient of variation (CV) and the Bland Altman method including 95% limits of agreement. The variance of the distance walked was analysed by means of regressions. The known group validity of the 6MWT (distance walked and the work of walking) in obese participants was shown by comparisons with 41 lean participants (18 male), mean age 47 (24–65) years, mean BMI 22.7kg‐m–2 (19–25). Results. The obese group walked 534 m (confidence interval [CI] 508–560 the first and 552 m (CI 523–580) the second walk (p < 0.001). Sw was 25 m, CV 4.7%, ICC1.1 was 0.96. The limits of agreement were –46 m+80 m. The validity tests showed that they walked 162 m shorter (p < 0.001) and performed much heavier work (p < 0.001) than the lean group. In the obese group, BMI alone explained 38% of the variance of the distance walked. Conclusions. The 6MWT showed good reproducibility and known group validity and can be recommended for evaluating walking ability in subjects with obesity. For individual evaluation, however, an improved walking distance of at least 80 m was required to make the difference clinically significant. Despite shorter walking distance the obese participants performed heavier work than the lean. Copyright © 2008 John Wiley & Sons, Ltd.
Effects of metabolic inhibitors on activity of Cry1Ab toxin to inhibit growth of Ephestia kuehniella larvae
Authors: Hubert Jan , Nesvorná Marta , Zemek Rostislav , Stará Jitka , Stejskal Václav
Published: April 2008

BACKGROUND: Although the toxins of Bacillus thuringiensis Berliner (Bt) are frequently used to control lepidopteran pests, the tolerance or resistance of some lepidopteran moth strains may limit Bt applications. In this study, insecticidal cocktails consisting of sublethal doses of Cry1Ab toxin and additive compounds were tested for their suppressive effect on larval relative growth rate (RGR) in Ephestia kuehniella Zeller under laboratory conditions.

RESULTS: In the first step, the suppressive effect of diflubenzuron, soybean trypsin inhibitor (STI) and chitinase on RGR was confirmed. In the second step, these compounds were incorporated into a mixture of crushed kernels of Bt maize hybrid MON 810‐YieldGard® and its isoline with concentrations of Cry1Ab toxin ranging from 0.011 to 0.091 µg g−1 diet. An additive effect on the suppression of larval RGR in E. kuehniella was found in a combination of diflubenzuron, STI and STI + chitinase as secondary compounds in insecticidal cocktails. Chitinase showed no additive effect on RGR.

CONCLUSION: The highest suppression level was found in cocktails with STI + chitinase as a secondary compound. It is hypothesized that the protease inhibitor (STI) protects both chitinase and Cry1Ab proteins from endogenous proteases in the larval midgut and prolongs their insecticidal activities. The possible application of insecticidal cocktails in the control of E. kuehniella is discussed. Copyright © 2008 Society of Chemical Industry
Using reflectance anisotropy spectroscopy to characterize capped silver nanostructures grown on silicon
Authors: Fleischer K. , Jacob J. , Chandola S. , Esser N. , McGilp J. F.
Published: April 2008

Using the single domain Si(111)‐3×1‐Ag surface as a template, room temperature deposition of two or more monolayers of Ag leads to the formation of metallic nanostructures. Reflectance anisotropy spectroscopy (RAS) in the infrared (IR) spectral region is used to analyse the anisotropic conductivity of the structures. The anisotropy is found to be influenced by the offcut angle of the substrate, and hence the terrace width. The Ag nanostructures were capped with Si to form a near‐IR transparent protecting layer. The samples are stable to exposure to ambient conditions for significant periods. The RAS spectra are compared to model calculations, which support the conclusion that the buried metallic Ag nanostructures survive the capping process. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Determining magnetization curves using optical second‐harmonic generation
Authors: McGilp J. F. , Carroll L. , Fleischer K.
Published: April 2008

Magnetic second‐harmonic generation (MSHG) allows the interfacial magnetism of centrosymmetric materials to be explored through thin capping layers. However, the variation of the MSHG intensity with magnetic field does not measure hysteresis loops directly, because the loops are displaced by an amount dependent on the crystallographic response and its phase difference with respect to the magnetic response, and also because there is a quadratic magnetization contribution to the SH intensity. Two new procedures are reported for extracting hysteresis loops directly from the MSHG intensity. The first is applicable to all magnetic interfaces, including exchange‐biased structures, where the saturation magnetization for positive and negative magnetic fields is equal and opposite, while the second applies to all centrosymmetric hysteresis loops. These procedures correct for the quadratic response, allowing experimental geometries to be chosen that maximize the magnetic contribution, thus improving the signal‐to‐noise ratio. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
DNA nanobioelectronics
Authors: Lakhno V. D.
Published: April 2008

The main lines of the development of DNA nanobioelectronics are reviewed. Results of recent experiments on charge transfer in DNA and conducting properties of DNA fragments are presented. Basic theoretical approaches to the description of charge transfer in DNA and conducting properties of DNA are given. Various DNA‐based electronic devices, such as electronic nanobiochip, electronic memory, and logical elements are considered. Perspectives of DNA‐based nanoelectronics are discussed. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Interaction of FeO+ cation with benzene, aniline, and 3‐methylaniline: DFT study of oxygen insertion mechanism
Authors: Kwapien Karolina , Broclawik Ewa
Published: April 2008

The reaction pathways and energetics for oxygen insertion into CH bond in benzene, aniline, and 3‐methylaniline by FeO+ in the gas phase were investigated by means of the DFT methodology with the B3LYP exchange‐correlation functional and 6‐311G** basis set. The main aim of this work was to elucidate the influence of substituents in phenyl ring on stationary points along the energy profile on sextet and quartet surfaces for the reaction of FeO+ with substituted benzenes. The studies show that the amino and methyl groups change the energetics of oxygen insertion by lowering the energy profile along the reaction pathway. The substituents studied in this work facilitate the insertion of oxygen into the aromatic CH bond by stabilizing the intermediate sigma complex (σ‐complex), the amino group being by far more effective. On the other hand, both functional groups increase the activation energy of the rate‐determining step in the gas phase, so that they have unfavorable influence on the kinetics. The comparison of the energy diagrams for the sextet and quartet spin states indicates the dominance of the low‐spin reactivity in oxygen insertion into aromatic CH bond. Aniline and 3‐methylaniline oxidation occurs via electrophilic addition while the conversion of benzene to phenol by FeO+ is mediated by a σ‐complex with mixed radical and cationic character. Present results are also discussed in the context of oxyferryl group reactivity. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Faunal migration in late‐glacial central Italy: implications for human resource exploitation
Authors: Pellegrini Maura , Donahue Randolph E. , Chenery Carolyn , Evans Jane , Lee‐Thorp Julia , Montgomery Janet , Mussi Margherita
Published: April 2008

The hunter‐gatherer transhumance model presents foragers as specialised hunters of migratory ungulates, which moved seasonally between coastal lowlands and interior uplands. We studied six animal teeth of horse (Equus hydruntinus) and red deer (Cervus elaphus) from four different archaeological sites: the Grotta di Vado all'Arancio, Grotta di Settecannelle, Grotta Polesini and Grotta di Pozzo, in central Italy to test whether the migratory patterns and seasonal variations recorded in their teeth were consistent with expectations of the transhumance model for this region during the late Upper Palaeolithic. Sequential sub‐samples of enamel were analysed from each tooth for oxygen, carbon and strontium isotope ratios to reconstruct mobility and yearly seasonal variations. The results show little evidence that these animals were moving over different geological terrains throughout the year, although small variations in Sr isotope ratios and concentrations were detected that corresponded to probable seasonal variations as shown by variability in oxygen isotope sequences. The results do, however, demonstrate that Cervus elaphus and Equus hydruntinus had different ranging behaviours, with the former moving over wider areas than the latter. This methodology produces results appropriate to assess animal migratory behaviour and, in turn, to test the consistency of proposed models of hunter‐gatherer subsistence and mobility strategies. Copyright © 2008 John Wiley & Sons, Ltd.
River bed evolution due to channel expansion: general behaviour and application to a case study (Kugart River, Kyrgyz Republic)
Authors: Siviglia A. , Repetto R. , Zolezzi G. , Tubino M.
Published: April 2008

We study the effect of spatial variations of river width on bed aggradation and degradation processes, making use of a one‐dimensional numerical model of channel morphodynamics. We refer to a peculiar case, the downstream reach of the Kugart River (Kyrgyzstan). The river has been partly channelized in the recent past with the aim of reducing the flooding risk for the surrounding villages; the consequent reduction of channel width in some reaches was also expected to improve channel conveyance with respect to the high sediment load produced in the upper river basin. The resulting longitudinal sequence of relatively sharp channel expansions and contractions has, however, triggered rapid siltation rates, especially in the narrowest reaches. This motivated the application of a 1‐D numerical model of river morphodynamics.

Abrupt channel expansions are found to be the main driving forces for aggrading processes, which may extend for long distances from where they are generated. In order to obtain a thorough understanding of the morphodynamics of channel expansions, we first apply the model to simple test cases. This allows us to characterize the basic features of the problem and the dependence of bed evolution on the upstream Froude number Fr and on the expansion ratio rb, which are the most relevant controlling parameters. We invariably find that deposition occurs in expansion regions with bed aggradation observed both upstream and downstream. The deposition prism progressively increases its height and lengthens both in the upstream and downstream directions. The deposition process is particularly intense, in terms of deposition prism height, in super‐critical conditions. Moreover, it is found that higher values of Fr strongly reduce the time scale of morphological processes and faster deposition rates are further facilitated by abrupt expansions.

The present outcomes are relevant for assessing the expected altimetric response of river bed to the implementation of localized channelization works and to local river widening, a practise which is increasingly being employed within river restoration projects, with the aim of enhancing habitat diversity. Copyright © 2008 John Wiley & Sons, Ltd.
Refined Betz limit for rotors with a finite number of blades
Authors: Okulov Valery L. , Sørensen Jens N.
Published: April 2008

The criterion of Betz for optimum rotors with a finite number of blades is revisited and used to determine the performance of wind turbines. The Betz criterion states that ideal efficiency is obtained when the distribution of circulation along the blade produces a rigidly helicoid wake that moves in the direction of its axis with a constant velocity. Theories based on this criterion were more than 60 years ago developed by Goldstein and Theodorsen. Although these theories made it possible to determine optimum circulation distributions on rotors, they fail to determine correctly the associated optimum power coefficient. Especially, they fail to reproduce the results of the general momentum theory when the number of blades goes to infinity. The present theory is a modification to the original model of Goldstein using a new analytical solution to the wake vortex problem. In contrast to earlier models, the new model is consistent with the general momentum theory and enables for the first time to determine the theoretical maximum efficiency of rotors with an arbitrary number of blades. Copyright © 2008 John Wiley & Sons, Ltd.
Is Total Thyroidectomy the Surgical Procedure of Choice for Benign Multinodular Goiter? An Evidence‐Based Review
Authors: Agarwal Gaurav , Aggarwal Vivek
Published: April 2008

Background

Benign multinodular goiter is one of the most common endocrine surgical problems. The appropriate surgical procedure for its effective and safe management is a matter of debate. Though seen by some as an overly hazardous procedure because of the risk of recurrent laryngeal nerve injury and damage to parathyroid function, total thyroidectomy has replaced subtotal thyroidectomy as the procedure of choice, as the latter is associated with significant recurrences.

Methods

A systemic literature review was undertaken of all available medical literature to evaluate whether total thyroidectomy is the appropriate, safe and effective surgical procedure for benign multinodular goiter.

Results

There is consistent level II–IV evidence that subtotal thyroidectomy results in recurrence in up to 50% patients. Incidental thyroid cancers are detected in 3%–16.6% of apparently benign goiters in numerous studies, mostly providing level IV evidence, one third of which would need further surgical treatment after subtotal thyroidectomy. Studies comparing subtotal thyroidectomy and total thyroidectomy, including two each of prospective randomized and prospective nonrandomized ones, provide level II–IV evidence that permanent complication rates associated with subtotal thyroidectomy and total thyroidectomy are not different, although the rate of transient hypocalcemia is higher with total thyroidectomy. On basis of these findings, a grade B recommendation can be made that subtotal thyroidectomy is associated with significant recurrence of goiter, leaves a small number of incidentally detected thyroid cancers inadequately treated, and provides little significant safety advantage over total thyroidectomy. Grade C recommendations can also be made about total thyroidectomy being a safe and effective procedure for benign multinodular goiters in the hands of expert surgeons, based on the extensive level IV evidence, and limited level II and level III evidence, which show that the risk of permanent vocal cord palsy and hypoparathyroidism associated with total thyroidectomy is below the acceptable 2% rate, but not without exceptions.

Conclusion

Total thyroidectomy is the procedure of choice for the surgical management of benign multinodular goiter.
Local and global instabilities in the wake of a sphere
Authors: PIER BENOÎT
Published: April 2008

The global dynamics of open shear flows is closely related to the nature of their local instability characteristics, either convective or absolute. The present investigation revisits the wake of a sphere, obtains its global behaviour by direct numerical simulations and derives its local stability features, computed for the underlying basic flow under a quasi-parallel flow assumption. It is shown that both the axisymmetric and the planar symmetric basic flows exhibit domains of local absolute instability in the near-wake region. The largest absolute growth rates occur for instabilities developing on the non-axisymmetric basic wake and conserving its planar symmetry.
Evolution of clusters of sedimenting low-Reynolds-number particles with Oseen interactions
Authors: SUBRAMANIAN G. , KOCH DONALD L.
Published: April 2008

A theoretical framework is developed to describe, in the limit of small but finite Re, the evolution of dilute clusters of sedimenting particles. Here, Re =aU/ν is the particle Reynolds number, where a is the radius of the spherical particle, U its settling velocity, and ν the kinematic viscosity of the suspending fluid. The theory assumes the disturbance velocity field at sufficiently large distances from a sedimenting particle, even at small Re, to possess the familiar source--sink character; that is, the momentum defect brought in via a narrow wake behind the particle is convected radially outwards in the remaining directions. It is then argued that for spherical clusters with sufficiently many particles, specifically with N much greater than O(R0U/ν), the initial evolution is strongly influenced by wake-mediated interactions; here, N is the total number of particles, and R0 is the initial cluster radius. As a result, the cluster first evolves into a nearly planar configuration with an asymptotically small aspect ratio of O(R0U/N ν), the plane of the cluster being perpendicular to the direction of gravity; subsequent expansion occurs with an unchanged aspect ratio. For relatively sparse clusters with N smaller than O(R0U/ν), the probability of wake interactions remains negligible, and the cluster expands while retaining its spherical shape. The long-time expansion in the former case, and that for all times in the latter case, is driven by disturbance velocity fields produced by the particles outside their wakes. The resulting interactions between particles are therefore mutually repulsive with forces that obey an inverse-square law. The analysis presented describes cluster evolution in this regime. A continuum representation is adopted with the clusters being characterized by a number density field (n(r, t)), and a corresponding induced velocity field (u (r, t)) arising on account of interactions. For both planar axisymmetric clusters and spherical clusters with radial symmetry, the evolution equation admits a similarity solution; either cluster expands self-similarly for long times. The number density profiles at different times are functions of a similarity variable η = (r/t1/3), r being the radial distance away from the cluster centre, and t the time. The radius of the expanding cluster is found to be of the form Rcl (t) = A (ν a)1/3N1/3t1/3, where the constant of proportionality, A, is determined from an analytical solution of the evolution equation; one finds A = 1.743 and 1.651 for planar and spherical clusters, respectively. The number density profile in a planar axisymmetric cluster is also obtained numerically as a solution of the initial value problem for a canonical (Gaussian) initial condition. The numerical results compare well with theoretical predictions, and demonstrate the asymptotic stability of the similarity solution in two dimensions for long times, at least for axisymmetric initial conditions.
The wake structure and thrust performance of a rigid low-aspect-ratio pitching panel
Authors: BUCHHOLZ JAMES H. J. , SMITS ALEXANDER J.
Published: April 2008

Thrust performance and wake structure were investigated for a rigid rectangular panel pitching about its leading edge in a free stream. ForReC=O(104), thrust coefficient was found to depend primarily on Strouhal numberStand the aspect ratio of the panelAR. Propulsive efficiency was sensitive to aspect ratio only forARless than 0.83; however, the magnitude of the peak efficiency of a given panel with variation in Strouhal number varied inversely with the amplitude to span ratioA/S, while the Strouhal number of optimum efficiency increased with increasingA/S. Peak efficiencies between 9% and 21% were measured. Wake structures corresponding to a subset of the thrust measurements were investigated using dye visualization and digital particle image velocimetry. In general, the wakes divided into two oblique jets; however, when operating at or near peak efficiency, the near wake in many cases represented a Kármán vortex street with the signs of the vortices reversed. The three-dimensional structure of the wakes was investigated in detail forAR= 0.54,A/S= 0.31 andReC= 640. Three distinct wake structures were observed with variation in Strouhal number. For approximately 0.20 <St< 0.25, the main constituent of the wake was a horseshoe vortex shed by the tips and trailing edge of the panel. Streamwise variation in the circulation of the streamwise horseshoe legs was consistent with a spanwise shear layer bridging them. ForSt> 0.25, a reorganization of some of the spanwise vorticity yielded a bifurcating wake formed by trains of vortex rings connected to the tips of the horseshoes. ForSt> 0.5, an additional structure formed from a perturbation of the streamwise leg which caused a spanwise expansion. The wake model paradigm established here is robust with variation in Reynolds number and is consistent with structures observed for a wide variety of unsteady flows. Movies are available with the online version of the paper.
Instabilities of plane Poiseuille flow with a streamwise system rotation
Authors: MASUDA S. , FUKUDA S. , NAGATA M.
Published: April 2008

We analyse the stability of plane Poiseuille flow with a streamwise system rotation. It is found that the instability due to two-dimensional perturbations, which sets in at the well-known critical Reynolds number, Rc = 5772.2, for the non-rotating case, is delayed as the rotation is increased from zero, showing a stabilizing effect of rotation. As the rotation is increased further, however, the laminar flow becomes most unstable to perturbations which are three-dimensional. The critical Reynolds number due to three-dimensional perturbations at this higher rotation case is many orders of magnitude less than the corresponding value due to two-dimensional perturbations. We also perform a nonlinear analysis on a bifurcating three-dimensional secondary flow. The secondary flow exhibits a spiral vortex structure propagating in the streamwise direction. It is confirmed that an antisymmetric mean flow in the spanwise direction is generated in the secondary flow.
Spatial optimal disturbances in swept attachment-line boundary layers
Authors: GUÉGAN ALAN , SCHMID PETER J. , HUERRE PATRICK
Published: April 2008

A formulation based on direct and adjoint parabolized equations is developed to account for the spatial evolution of perturbations in swept attachment-line boundary layers. For sweep Reynolds numbers larger than Re = 100 the dynamics is dominated by a lift-up mechanism which is responsible for large energy amplification by transforming spanwise vortices into spanwise streaks. This mechanism favours steady perturbations with a chordwise scale that quantitatively matches its counterpart for classical Blasius boundary layers.
Communities of interpretation in the study of religion in Burma
Authors: Schober Juliane
Published: April 2008

The paper delineates stages in the interpretation of religion in Burma. Beginning with colonial constructions, the discussion moves to subsequent studies in anthropology and history from which emerged an emphasis on localised articulations of Theravada Buddhist traditions. Others examined religion as a site for colonial resistance and as a means for engaging issues of modernity. More recent interpreters focused on Buddhist voices in the public domain of contemporary Burma and some recent studies moved beyond received boundaries of inquiry to consider religions among ethnic minorities and diaspora communities. The final section charts future development in the study of religion in Burma.
Communities of the past: A new view of the old walls and hydraulic system at Sriksetra, Myanmar (Burma)
Authors: Hudson Bob , Lustig Terry
Published: April 2008

New data from an archaeological survey of Sriksetra suggests that this important site is set for a major reinterpretation. The city functioned over a much longer period than was previously believed. There are many more buildings than had been previously recorded. Some of the city walls and moats, once considered to have been military fortifications, prove to be part of a multifunctional and evolving system of hydraulic management.
The neural correlates of fatigue: an exploratory imaginal fatigue provocation study in chronic fatigue syndrome
Authors: Caseras X. , Mataix-Cols D. , Rimes K. A. , Giampietro V. , Brammer M. , Zelaya F. , Chalder T. , Godfrey E.
Published: April 2008

Background

Fatigue is the central symptom in chronic fatigue syndrome (CFS) and yet very little is known about its neural correlates. The aim of this study was to explore the functional brain response, using functional magnetic resonance imaging (fMRI), to the imaginal experience of fatigue in CFS patients and controls.

Method

We compared the blood oxygen level dependent (BOLD) responses of 12 CFS patients and 11 healthy controls to a novel fatigue provocation procedure designed to mimic real-life situations. A non-fatiguing anxiety-provoking condition was also included to control for the non-specific effects of negative affect.

Results

During the provocation of fatigue, CFS patients reported feelings of both fatigue and anxiety and, compared to controls, they showed increased activation in the occipito-parietal cortex, posterior cingulate gyrus and parahippocampal gyrus, and decreased activation in dorsolateral and dorsomedial prefrontal cortices. The reverse pattern of findings was observed during the anxiety-provoking scenarios.

Conclusions

The results may suggest that, in CFS patients, the provocation of fatigue is associated with exaggerated emotional responses that patients may have difficulty suppressing. These findings are discussed in relation to the cognitive-behavioural model of CFS.
Asymptotic behavior of distribution of frequencies of digits
Authors: BARREIRA LUIS , VALLS CLAUDIA
Published: April 2008

We present an approach to compute the Hausdorff dimension of a class of sets of real numbers that are defined in terms of nonlinear relations between frequencies of digits in some integer base m. We consider the model case of quadratic perturbations, for which the computations are already rather involved. We show that the Hausdorff dimension is analytic in the parameter determining the perturbation. Our approach also allows to estimate the asymptotic behavior of the Taylor coefficients of the dimension in terms of m.
Estimations of the remainder of spherical harmonic series
Authors: CHANG XIRONG , DAI FENG , WANG KUNYANG
Published: April 2008

An asymptotic estimate is obtained for the error in approximation of functions by partial sums of spherical harmonic expansions. The precise constant in the main term is found and the order of growth of the remainder term is given.
Polyarteritis Nodosa – eine verschwindende Erkrankung dank Identifikation der Hauptursache
Authors: Frey Felix J.
Published: April 2008

Die Polyarteritis Nodosa ist eine Vaskulitis, bei der die Hauptursache, die Hepatitis B, die zur überschießenden Immunantwort führt, identifiziert werden konnte. Diese Entdeckung führte von einer symptomatischen immunsuppressiven Therapie weg zu einem kausalen Vorgehen. Dank Impfung gegen Hepatitis B wurde die Häufigkeit dieser Erkrankung reduziert. Tritt die Polyarteritis Nodosa unabhängig von einer Hepatitis B auf, was selten ist, so bleibt lediglich der Versuch einer symptomatischen immunsuppressiven Therapie. Die Geschichte der Polyarteritis Nodosa illustriert, dass bei sogenannten Autoimmunerkrankungen in Zukunft der Fokus auf die Ursachen und nicht auf die immunologischen Effektormechanismen oder die symptomatische Therapie gelegt werden sollte.
Das Sjögren-Syndrom – mehr als nur trockene Schleimhäute
Authors: Seitz Michael
Published: April 2008

Leitsymptome dieser exemplarischen Autoimmunerkrankung sind eine Xerostomie und Xerophthalmie, welche durch eine lymphoplasmazelluläre destruktive Entzündung exokriner Drüsen, insbesondere der Speichel- und Tränendrüsen und durch den Nachweis von Autoantikörpern gegen Ro/SS-A und La/SS-B Kernantigene charakterisiert sind. Im Krankheitsverlauf entwickelt sich meist eine polyklonale Hypergammaglobulinämie als Ausdruck der chronischen B-Zell-Stimulation, welche nicht selten zu einem malignen B-Zell-Lymphom führen kann und daher einer periodischen klinischen und labormäßigen Überwachung bedarf. Als extraglanduläre entzündliche Manifestationen können eine nicht-erosive Polyarthritis, Serositis, leukozytoklastische Hautvaskulitis und eine periphere Polyneuropathie auftreten, welche gelegentlich die Abgrenzung gegenüber anderen autoimmunen Konnektiviten erschweren, welche ebenfalls häufig mit einem Sicca-Syndrom einhergehen können. Man spricht dann auch von einem sekundären Sjögren-Syndrom. Die Behandlung ist meist rein symptomatisch und immunsuppressive Medikamente kommen nur bei vital gefährdender Organbeteiligung zum Einsatz.
Systemsklerose
Authors: Villiger Peter M.
Published: April 2008

Die Systemsklerose ist charakterisiert durch autoimmune Phänomene und eine progressive Fibrose. Klinische Charakteristika sind neben der Sklerodermie ein ausgeprägtes Raynaud-Phänomen und Abnormitäten der Nagelfalzkapillaren, ferner pulmonale, renale, kardiale und intestinale Veränderungen. In der Regel wird eine diffuse von einer limitierten Form unterschieden. Die diffuse Form führt zu einer Sklerose des gesamten Integumentes, ist assoziiert mit dem Auto-antikörper Scl-70 und zeichnet sich durch eine rasche Krankheitsprogression aus. Die limitierte Form betrifft die distalen Extremitäten und das Gesicht, ist assoziiert mit dem centromer Autoantikörper und führt schleichend, über mehrere Jahre zu viszeralen Problemen. Neue therapeutische Möglichkeiten können zu einer besseren Lebensqualität verhelfen und verpflichten zu einem systematischen Krankheitsmonitoring.
Vaskulitiden der Lungen
Authors: Speich Rudolf
Published: April 2008

Traditionell teilt man die Vaskulitiden in solche mit Befall der großen, der mittelgroßen und der kleinen Gefäße ein. Je nach Typ ist ein Lungenbefall mehr oder weniger häufig. Besonders sind bei der Wegener’s Granulomatose, beim Churg-Strauss-Syndrom, und etwas seltener bei der mikroskopischen Polyangitis die Lungen betroffen. Praktisch pathognomonisch ist dabei eine alveoläre Hämorrhagie. Dabei handelt es sich um eine Trias mit 1) bilateralen azinären Lungeninfiltraten vergleichbar mit einem Lungenödem, 2) einer Anämie und 3) einer Hämoptoe, die aber fehlen kann. Die Diagnose wird mittels bronchoalveolärer Lavage gemacht, bei der alle drei hintereinander gewonnenen Proben gleich oder zunehmend blutig sind. Im Verlauf der letzten Dekaden hat die Diagnostik mittels Autoantikörpern das Management der Vaskulitiden revolutioniert. Im Folgenden werden ausgesuchte Krankheitsbilder hinsichtlich klinischer Erscheinung, diagnostischer Vorgehensweise und Therapiemodalitäten besprochen.
Das Burnout-Syndrom: eine medizinische Perspektive
Authors: von Känel R.
Published: April 2008

Das Burnout-Syndrom ist unklar definiert. Relativ übereinstimmend lässt es sich auf einen Symptomkomplex mit dem Kardinalsymptom Erschöpfung als Reaktion auf eine lange andauernde emotionale und interpersonelle Belastung am Arbeitsplatz beziehen. Die Prävalenz für Burnout ist bei schweizerischen Grundversorgern bemerkenswert hoch. Trotz der begrifflichen Unschärfe ist Burnout eine ernstzunehmende Stresskrankheit mit weitreichenden medizinischen und ökonomischen Konsequenzen. Der therapeutische Zugang ist multimodal und orientiert sich an den Empfehlungen zum psychosomatischen Management von funktionellen somatischen Syndromen ergänzt durch Interventionen bezogen auf die Arbeitssituation. Die Rezidivprophylaxe mit frühzeitiger Erkennung von Warnzeichen ist ein ständiger Prozess.
Notfall - News 2007
Authors: Heer K.
Published: April 2008

Im Jahr 2007 gab es eine Fülle von interessanten Publikationen zu Themen der Notfallmedizin. Für einen Workshop an der 6. Zentralschweizer Internistenwoche habe ich eine persönliche Auswahl aus der aktuellen Literatur getroffen. Anhand der hier präsentierten Arbeiten wurden entweder Neuerungen in Diagnostik und Therapie oder Qualitätsfragen diskutiert, aber auch bewährte Vorgehensweisen bestätigt.
Is the critical Shields stress for incipient sediment motion dependent on channel‐bed slope?
Authors: Lamb Michael P. , Dietrich William E. , Venditti Jeremy G.
Published: April 2008

Data from laboratory flumes and natural streams show that the critical Shields stress for initial sediment motion increases with channel slope, which indicates that particles of the same size are more stable on steeper slopes. This observation is contrary to standard models that predict reduced stability with increasing slope due to the added downstream gravitational force. Processes that might explain this discrepancy are explored using a simple force‐balance model, including increased drag from channel walls and bed morphology, variable friction angles, grain emergence, flow aeration, and changes to the local flow velocity and turbulent fluctuations. Surprisingly, increased drag due to changes in bed morphology does not appear to be the cause of the slope dependency because both the magnitude and trend of the critical Shields stress are similar for flume experiments and natural streams, and significant variations in bed morphology in flumes is unlikely. Instead, grain emergence and changes in local flow velocity and turbulent fluctuations seem to be responsible for the slope dependency due to the coincident increase in the ratio of bed‐roughness scale to flow depth (i.e., relative roughness). A model for the local velocity within the grain‐roughness layer is proposed based on a 1‐D eddy viscosity with wake mixing. In addition, the magnitude of near‐bed turbulent fluctuations is shown to depend on the depth‐averaged flow velocity and the relative roughness. Extension of the model to mixed grain sizes indicates that the coarser fraction becomes increasingly difficult to transport on steeper slopes.
Interpretation of pumping tests in a mixed flow karst system
Authors: Maréchal Jean‐Christophe , Ladouche Bernard , Dörfliger Nathalie , Lachassagne Patrick
Published: April 2008

A long‐duration pumping test performed in the conduit of a mixed flow karst system (MFKS) is analyzed and interpreted. It constitutes a unique experiment of catchment wide response of a karst system, with drawdowns measured both in the pumped conduit and in the matrix. A modeling approach is proposed for this interpretation. The developed double continuum model consists of two reservoirs ‐ karst conduits and the surrounding carbonate rocks ‐ between which flow exchange is modeled using the superposition principle and the hypothesis of Darcian flow in the matrix considered as an equivalent porous media. The karst conduits are assumed to have an infinite hydraulic conductivity. Model calibration results in a very good match (relative root mean square [rRMS] = 2.3 %) with drawdown measured at the pumping well (karst conduit). It shows that the matrix hydrodynamic parameters (hydraulic conductivity and storativity) have a greater influence on the drawdown than the storage capacity of the conduit network. The accuracy of the model relies mostly on a very good knowledge of both pumping rate and natural discharge at the spring (with and without pumping). This type of approach represents an advance in double continuum modeling of karst systems. It also provides a methodology for the management of water resources from karst aquifers.
In Situ Mouse Carotid Perfusion Model: Glucose and Cholesterol Transport in the Eye and Brain
Authors: Cattelotte Julie , André Pascal , Ouellet Mélissa , Bourasset Fanchon , Scherrmann Jean-Michel , Cisternino Salvatore
Published: April 2008

The in situ mouse brain perfusion method for measuring blood—brain barrier permeability was adapted to assess transport of solutes at the blood—brain and blood—eye barriers. The procedure was checked with radiolabeled markers in oxygenated bicarbonate-buffered fluid infused for 30 to 120 secs via a carotid artery. Vascular flow estimated with diazepam was 2.2-fold lower in the eye than in the brain. The vascular volume and the integrity markers sucrose and inulin indicated that a perfusion flow rate of 2.5 mL/min preserved the physical integrity of these organs. However, the brain vasculature integrity was more sensitive to acute perfusion pressure than the eye vasculature. The functional capacities of blood barriers were assessed with d-glucose; its transport followed Michaelis—Menten kinetics with an apparent Km of 7.6 mmol/L and a Vmax of 23 μmol/sec per g in the brain, and a Km of 22.9 mmol/L and a Vmax of 40 μmol/sec per g in the eye. The transport of cholesterol to the brain and eye was significantly enhanced by adding the Abca1 inhibitor probucol, suggesting an Abca1-mediated efflux at the mouse brain and eye blood barriers. Thus in situ carotid perfusion is suitable for elucidating transport processes at the blood—brain and blood-eye barriers.
Hypoxia and Hypotension Transform the Blood Flow Response to Cortical Spreading Depression from Hyperemia into Hypoperfusion in the Rat
Authors: Sukhotinsky Inna , Dilekoz Ergin , Moskowitz Michael A , Ayata Cenk
Published: April 2008

Cortical spreading depression (CSD) evokes a large cerebral blood flow (CBF) increase in normal rat brain. In contrast, in focal ischemic penumbra, CSD-like periinfarct depolarizations (PID) are mainly associated with hypoperfusion. Because PIDs electrophysiologically closely resemble CSD, we tested whether conditions present in ischemic penumbra, such as tissue hypoxia or reduced perfusion pressure, transform the CSD-induced CBF response in nonischemic rat cortex. Cerebral blood flow changes were recorded using laser Doppler flowmetry in rats subjected to hypoxia, hypotension, or both. Under normoxic normotensive conditions, CSD caused a characteristic transient CBF increase (74 ± 7%) occasionally preceded by a small hypoperfusion (−4 ± 2%). Both hypoxia ( pO2 45 ± 3 mm Hg) and hypotension (blood pressure 42 ± 2 mm Hg) independently augmented this initial hypoperfusion (−14 ± 2% normoxic hypotension; −16 ± 6% hypoxic normotension; −21 ± 5% hypoxic hypotension) and diminished the magnitude of hyperemia (44 ± 10% normoxic hypotension; 43 ± 9% hypoxic normotension; 27 ± 6% hypoxic hypotension). Hypotension and, to a much lesser extent, hypoxia increased the duration of hypoperfusion and the DC shift, whereas CSD amplitude remained unchanged. These results suggest that hypoxia and/or hypotension unmask a vasoconstrictive response during CSD in the rat such that, under nonphysiologic conditions (i.e., mimicking ischemic penumbra), the hyperemic response to CSD becomes attenuated resembling the blood flow response during PIDs.
Assessing the Microstructure of Written Language Using a Retelling Paradigm
Authors: Puranik Cynthia S. , Lombardino Linda J. , Altmann Lori J. P.
Published: April 2008

Purpose

The primary goal of this study was to document the progression of the microstructural elements of written language in children at 4 grade levels. The secondary purpose was to ascertain whether the variables selected for examination could be classified into valid categories that reflect the multidimensional nature of writing.

Method

Written language samples were collected and transcribed from 120 children in Grades 3 through 6 using an expository text-retelling paradigm. Nine variables at various levels of language were analyzed.

Results

Using a text-retelling paradigm, measures of productivity (e.g., total number of words and ideas) improved steadily with age, whereas measures of complexity (e.g., mean length of T-unit) did not. Results for measures of accuracy (e.g., spelling and writing conventions) were mixed, with some showing improvement across grades. Grade 3 students showed consistently poorer performance than students in Grades 4, 5, and 6. Grade 4 students showed poorer performance than students in Grades 5 and 6. Exploratory factor analysis suggests that writing can be represented by 3 factors: Productivity, Complexity, and Accuracy.

Conclusions

Clinicians can use this multidimensional scheme for examining writing skills using text-retelling formats with children from Grades 3 through 6. This empirically based framework for measuring microstructural variables of writing provides clinicians with a 3-prong conceptual framework for determining children’s strengths and weaknesses within the translational stage of writing.
Shear small-angle light scattering studies of shear-induced concentration fluctuations and steady state viscoelastic properties
Authors: Endoh Maya K. , Takenaka Mikihito , Inoue Tadashi , Watanabe Hiroshi , Hashimoto Takeji
Published: April 2008

We aimed at elucidating the influence of shear-induced structures (shear-enhanced concentration fluctuations and/or shear-induced phase separation), as observed by rheo-optical methods with small-angle light scattering under shear flow (shear-SALS) and shear-microscopy, on viscoelastic properties in semidilute polystyrene (PS) solutions of 6.0wt% concentration using dioctyl phthalate (DOP) as a Θ solvent and tricresyl phosphate (TCP) as a good solvent. In order to quantify the effects of the shear-induced structures, we conducted a numerical analysis of rheological properties in a homogeneous solution based on the constitutive equation developed by Kaye-Bernstein, Kearsley, and Zapas (K-BKZ). In the low-to-intermediate shear rate γ̇ region between τw−1 and τe−1, where τw and τe are, respectively, terminal relaxation time and the relaxation time for chain stretching, the steady state rheological properties, such as shear stress σ and the first normal stress difference N1, for the PS/DOP and PS/TCP solutions are found to be almost same and also well predicted by the K-BKZ equation, in spite of the fact that there is a significant difference in the shear-induced structures as observed by shear-SALS and shear-microscopy. This implies that the contribution of the concentration fluctuations built up by shear flow to the rheological properties seems very small in this γ̇ region. On the other hand, once γ̇ exceeds τe−1, σ and N1 for both PS/DOP and PS/TCP start to deviate from the predicted values. Moreover, when γ̇ further increases and becomes higher than γ̇a,DOP (sufficiently higher than τe−1), above which rheological and scattering anomalies are observed for PS/DOP, σ and N1 for PS/DOP and PS/TCP are significantly larger than those predicted by K-BKZ. Particularly, a steep increase of σ and N1 for PS/DOP above γ̇a,DOP is attributed to an excess free energy stored in the system via the deformation of interface of well-defined domains, which are aligned into the stringlike structure developed parallel to the flow axis, and stretching of the chains connecting the domains in the stringlike structures. Thus, we advocate that the effect of shear-induced structures should be well considered on the behavior of σ and N1 at the high γ̇ region above τe−1 in semidilute polymer solutions.
Observations of vertically propagating driven dust acoustic waves: Finite temperature effects
Authors: Williams Jeremiah D. , Thomas Edward , Marcus Lydia
Published: April 2008

In this study, the first measurement of the dispersion relationship for a vertically propagating (i.e., parallel to gravity), driven dust acoustic wave is reported. Finite dust temperature effects were observed in the dispersion relation of the dust acoustic wave.
Bichromatically driven double well: Parametric perspective of the strong field control landscape reveals the influence of chaotic states
Authors: Sethi Astha , Keshavamurthy Srihari
Published: April 2008

The aim of this work is to understand the influence of chaotic states in control problems involving strong fields. Towards this end, we numerically construct and study the strong field control landscape of a bichromatically driven double well. A novel measure based on correlating the overlap intensities between Floquet states and an initial phase space coherent state with the parametric motion of the quasienergies is used to construct and interpret the landscape features. “Walls” of no control, which are robust under variations of the relative phase between the fields, are seen on the control landscape and associated with multilevel interactions involving chaotic Floquet states.
Observation of asymmetric ferroelectric switching in fatigued ferroelectric vinylidene fluoride and trifluoroethylene copolymer films
Authors: Zhu GuoDong , Zeng ZhiGang , Zhang Qun , Yan XueJian , Liu Ran
Published: April 2008

In this paper, we illuminated the observation of asymmetric ferroelectric switching phenomena in fatigued P(VDF-TrFE) copolymer films. Two types of asymmetric switching were observed: one was the occurrence of switching dual peaks obtained from films with asymmetric electrode structure and the other was the jump of remanent polarization during fatigue process, as was obtained mostly from films with asymmetric electrodes and occasionally from films with symmetric electrodes. No evidence indicated the dependence between the switching dual peaks and the jump of remanent polarization. The possible mechanism of such asymmetric phenomena was also discussed.