bluuebunny/crossref_metadata_2025 huggingface dataset:
Lagrangian approach to time-dependent laminar dispersion in rectangular conduits. Part 1. Two-dimensional flows
Authors: Haber Shimon , Mauri Roberto
Published: April 2006

Time-dependent mean velocities and dispersion coefficients are evaluated for a general two-dimensional laminar flow. A Lagrangian method is adopted by which a Brownian particle is traced in an artificially restructured velocity field. Asymptotic expressions for short, medium and long periods of time are obtained for Couette flow, plane Poiseuille flow and open-channel flow over an inclined flat surface. A new formula is suggested by which the Taylor dispersion coefficient can be evaluated from purely kinematical considerations. Within an error of less than one percent, over the entire time domain and for various flow fields, a very simple analytical expression is derived for the time-dependent dispersion coefficient
\[
\tilde{D}(\tau) = D + D^T\left(1-\frac{1-{\rm e}^{-\alpha\tau}}{a\tau}\right),
\]
where D is the molecular diffusion coefficient, DT denotes the Taylor dispersion coefficient, τ stands for the non-dimensional time π2Dt/Y/, Y is the distance between walls and a = (N + 1)2 is an integer which is determined by the number of symmetry planes N that the flow field possesses. For Couette and open-channel flow there are no planes of symmetry and a = 1; for Poiseuille flow there is one plane of symmetry and a = 4.
Influence of wall suction on the organized motion in a turbulent boundary layer
Authors: Antonia R. A. , Fulachier L. , Krishnamoorthy L. V. , Benabid T. , Anselmet F.
Published: April 2006

The effect of wall suction on the organized motion of a tubulent boundary layer is examined experimentally both in a wind tunnel and in a water tunnel. In the windtunnel boundary layer, which developed over a slighly heated surface, temperature fluctuations were simultaneously obtained at several points, aligned in either the x (streamwise) or y (normal to the wall) direction. The temperature traces reveal the existence of two spatially coherent events, characterized either by a sudden decrease (cooling) or by a sudden increase (heating) of temperature. Estimates are presented for the average convection velocity, and average frequency of these events. The average convection velocity of ‘coolings’ is about 15% larger than that of ‘heatings’, the velocity of both events exhibiting an important local maximum in the buffer region. Near the wall, the convection velocity of both events is increased slightly by suction while their average frequency is reduced by suction. Away from the wall, the average inclination of ‘coolings’ and ‘heatings’ is about 40° without suction; suction does not alter the inclination of ‘coolings’ but increases that of ‘heatings’ to about 50°. Visualizations in the water tunnel indicate that suction increases the stability and the longitudinal coherence of low-speed streaks. They also show that suction reduces the average frequency of dye ejections into the outer layer.
Turbulent structure in low-concentration drag-reducing channel flows
Authors: Luchik T. S. , Tiederman W. G.
Published: April 2006

A two-component laser-Doppler velocimeter was used to measure simultaneously velocity components parallel and normal to the wall in two fully developed, wellmixed, low-concentration (1-2 p.p.m.) drag-reducing channel flows and one turbulent channel flow of water. The mean velocity profiles, root-mean-square velocity profiles and the distributions of the ūv turbulent correlation confirm that the additives modify the buffer region of the flow. The principal influence of the additives is to damp velocity fluctuations normal to the wall in the buffer region.

The structural results show that the average time between bursts increased for the drag-reducing flows. When compared to a water flow at the same wall shear stress, this increase in the timescale was equal to the increase in the average streak spacing. Conditionally averaged velocity signals of y+ = 30 centred on the leading edge of a burst, as well as those centred on the trailing edge, have the same general characteristics in all three flows indicating that the basic structure of the fundamental momentum transport event is the same in these drag-reducing flows. However, it was clearly shown that the lower-threshold Reynolds-stress-producing motions were damped while the higher-threshold motions were not damped. In the buffer region of the drag-reducing flows this yields a larger mean velocity gradient with damped fluctuations normal to the wall and increased fluctuations in the streamwise direction. It is hypothesized that some strong turbulent motions are required to maintain extended polymer molecules, which produce a solution with properties that can damp lower threshold turbulence and thereby reduce viscous drag.
Experimental characterization of steady two-dimensional vortex couples
Authors: Duc Jean-Michel Nguyen , Sommeria Joël
Published: April 2006

We study the evolution of unsteady two-dimensional vorticity structures surrounded by fluid at rest. The flow is initiated by a short fluid impulse in a horizontal layer of mercury and is constrained to be two-dimensional by a vertical uniform magnetic field. The impulse is generated by an electric pulse between two electrodes, and a flow circulation can be produced by diverting part of the current through the external frame. The velocity field is measured from the streaks of small particles floating on the free upper surface, and the vorticity is then obtained by means of an analytical interpolation and differentiation. The flow always evolves toward a set of independent steady structures with symmetry which are either circular vortices (monopoles) or couples (dipoles). The latter have a linear or circular steady motion depending on the flow circulation around them. The region of non-zero vorticity is always close to a circle. The steadiness is confirmed by plotting the vorticity versus the stream function in the frame of reference moving with the couple. We obtain a curve, as appropriate for a steady solution of the Euler equation. The slope of this curve is either constant or has no maximum. We suggest that this result could correspond to a general stability condition. The interaction between two symmetric couples at various angles of incidence yields two new couples by exchange of their vortices. Oscillations of the resulting couples are often damped by releasing a circular vortex.
Three-dimensional thermal cellular convection in rectangular boxes
Authors: Kirchartz K. R. , Jr H. Oertel
Published: April 2006

The extension of the classic Rayleigh–Bénard problem of a horizontal layer heated from below to the three-dimensional convection in rectangular boxes is dealt with in this paper both numerically and experimentally. Also discussed is the influence of shear flows in tilted boxes and the transition to time-dependent oscillatory convection. Three-dimensional numerical simulations allow the calculation of stationary solutions and the direct simulation of oscillatory instabilities. We limited ourselves to laminar and transcritical flows. For studying the particular characteristics of three-dimensional convection in horizontal containers, we carefully selected two container geometries with aspect ratios of 10:4:1 and 4:2:1. The onset of steady cellular convection in tilted boxes is calculated by an iterative application of a combined finite-difference method and a Galerkin method. The appearance of longitudinal and transverse convection rolls is determined by means of inter-ferometrical measuring techniques and is compared with the results of the linear stability theory. The spatial flow structure and the transition to oscillatory convection is calculated for selected examples in the range of supercritical Rayleigh numbers. Experimental investigations concerning the stability behaviour of the steady solutions with regard to time-dependent disturbances show a distinct influence of the Prandtl number and confirm the importance of nonlinear effects.
A numerical study of three-dimensional stratified flow past a sphere
Authors: Hanazaki Hideshi
Published: April 2006

A numerical study is described of the Boussinesq flow past a sphere of a viscous, incompressible and non-diffusive stratified fluid. The approaching flow has uniform velocity and linear stratification. The Reynolds number Re (= 2ρ0Ua/μ) based on the sphere diameter is 200 and the internal Froude number F(= U/Na) is varied from 0.25 to 200. Here U is the velocity, N the Brunt-Väisälä frequency, a the radius of the sphere, μ the viscosity and ρ0 the mean density. The numerical results show changes in the flow pattern with Froude number that are in good agreement with earlier theoretical and experimental results. For F < 1, the calculations show the flow passing round rather than going over the obstacle, and confirm Sheppard's simple formula for the dividing-streamline height. When the Froude number is further reduced (F < 0.4), the flow becomes approximately two-dimensional and qualitative agreement with Drazin's three-dimensional low-Froude-number theory is obtained. The relation between the wavelength of the internal gravity wave and the position of laminar separation on the sphere is also investigated to obtain the suppression and induction of separation by the wave. It is also found that the lee waves are confined in the spanwise direction to a rather narrow strip just behind the obstacle as linear theory predicts. The calculated drag coefficient CD of the sphere shows an interesting Froude-number dependence, which is quite similar to the results given by experiments. In this study not only CD but also the pressure distribution which contributes to the change of CD are obtained and the mechanism of the change is closely examined.
Breaking of relativistic simple waves
Authors: Muscato O.
Published: April 2006

The breaking of relativistic simple waves, for one-dimensional flow in the space-time of special relativity, is investigated. The cases of relativistic acoustic and magnetoacoustic waves are treated in detail and the critical time for breaking is evaluated.
On the stability of laminar boundary-layer flow over a flat plate with a compliant surface
Authors: Sen P. K. , Arora D. S.
Published: April 2006

The problem has been examined using a kinematic model for wall pliability, wherein a kinematic postulation of the wall boundary conditions is made. A form of the normalized wall-displacement and its phase are used as additional parameters in an extended eigenvalue problem. Using this technique the entire gamut of possibilities regarding stability of flow past (normally) pliable walls can be examined, yet without recourse to any specific material properties for the wall. Rather, the results based on the kinematic model can be used to back-calculate the material properties corresponding to any chosen model for the dynamics of the wall. A sample back calculation is discussed herein for the Benjamin–Landahl wall model, and based on this some predictions are made regarding both stabilization of the flow and physical realizability of modes. It is believed that the kinematic model will prove useful in further understanding of the problem, and in the design of stabilizing coatings.

The results show that there are three important ‘mode classes’ (distinct from ‘modes’), namely the Tollmien–Schlichting (TS), resonant (R) and Kelvin–Helmholtz (KH). Whereas the TS and R mode classes broadly agree with modes bearing similar names as found by earlier workers, the present KH mode class is difficult to classify based on earlier work. Moreover, there are also important transitional mode classes in the regions of bifurcations of the regular mode classes.

Two important concepts evolve in connection with the TS and R mode classes, namely the existence of ‘stable pockets’ for the former and ‘unstable pockets’ for the latter. It is also confirmed herein that there are conflicting requirements on the damping d to stabilize TS and R modes. Considering these points it has been suggested that TS and R modes be avoided by keeping soft surfaces as compliant coatings. However, this in turn leads to instabilities from one of the transitional mode classes. It is also seen that a soft surface that is also marginally active (i.e. having a small negative value of d) could render even better stabilization.
The effect of small surface perturbations on the pulsatile boundary layer on a semi-infinite flat plate
Authors: Duck P. W.
Published: April 2006

The laminar pulsatile flow over a semi-infinite flat plate, on which is located a small (steady) surface distortion is investigated; triple-deck theory provides the basis for the study. The problem is of direct relevance to the externally imposed acoustic excitation of boundary layers. The investigation is primarily numerical and involves the solution of the nonlinear, unsteady boundary-layer equations which arise from the lower deck. The numerical method involves the use of finite differencing in the transverse direction, Crank-Nicolson marching in time, and Fourier transforms in the streamwise direction, and as such is an extension of the spectral method of Burggraf & Duck (1982). Supersonic and incompressible flows are studied. A number of the computations presented suggest that the small surface distortion can excite a large-wavenumber, rapidly growing instability, leading to a breakdown of the solution, with the wall shear at a point seeming to increase without bound as a finite time is approached. Rayleigh modes for the basic (undisturbed) velocity profile are computed and there is some correlation between the existence and magnitude of the growth rate of these unstable modes, and the occurrence of the apparent singularity. Streamline plots indicate that this phenomenon is linked to the formation of closed (or ‘cats-eye’) eddies in the main body of the boundary layer, away from the wall. Tollmien-Schlichting instabilities are clearly seen in the case of incompressible flows.
Orientalist fantasy in the poetic dialogues of Solomon and Saturn
Authors: Powell Kathryn
Published: April 2006

A tenth-century ‘orientalist’ fantasy informs the poetic dialogues of Solomon and Saturn and serves to screen certain anxieties about the cultural identity of the English people. By placing these poems in the context of other vernacular works circulating in the tenth century, I would suggest that anxieties about the acquisition and dissemination of knowledge, the stability of kingdoms and the efficacy of religious faith were likely to have been prevalent at the time when the poems were preserved in Cambridge, Corpus Christi College 422. The Solomon and Saturn poems address these anxieties by displacing any lack of knowledge, political stability or faith onto the Eastern and pagan figure of Saturn and the Chaldean people he represents, while English readers are encouraged to identify with the ideals and behaviours of the Christian figure of Solomon. In this way, the poems construct a degraded East as a support for English, Christian culture.
Nanoscaled interfacial oxide layers of bonded n- and p-type GaAs wafers
Authors: Ouyang Hao , Sermon Wu YewChung , Cheng Ji-Hao , Lu Cheng-Lun , Chiou Shan-Haw , Ouyang Wen
Published: April 2006

This work examined in detail the electrical characteristics and microstructures of in- and antiphase bonded interfaces for both n- and p-type GaAs wafers treated at 500 and 600°C, respectively. The n-GaAs wafers did not bond directly to itself but instead via an amorphous oxide layer at 500°C. These temperatures are lower than most other works. The nonlinear behavior of the current versus the voltage is related to the potential barrier formed at the continuous oxide interface. Both experimental observation and first-principles calculations confirm the existence of this barrier. The higher interface energy for the antiphase bonding tends to stabilize the interfacial oxide layer. The evolution of interfacial layers occurred much faster for the p-type wafers than for n-type wafers. Electrical performance was found to be closely related to the variation of nanosized interface morphology.
Value Structure Among Students and Steelworkers1
Authors: Koivula Nina , Verkasalo Markku
Published: April 2006

The two‐dimensional value structure postulated in Schwartz's (1992) theory has previously found support in samples of teachers and university students, but groups with other professions or low educational level have been understudied. The current study employed the 40‐item Portrait Value Questionnaire (PVQ; Schwartz et al., 2001), multidimensional scaling, and transformation analysis to test the universality of the value structures among manual workers (n=815) and white‐collar workers (n=459) in a Finnish steel company. Also, the validity of the instrument was confirmed by comparing the current PVQ sample of Finnish university students (n=309) and a previous sample of Finnish university students (n=615) studied with the original Schwartz Value Survey. The value structures of the steel workers followed Schwartz's theoretical model, regardless of the educational level, except for the security value.
A population pharmacokinetic model for cefuroxime using cystatin C as a marker of renal function
Authors: Viberg Anders , Lannergård Anders , Larsson Anders , Cars Otto , Karlsson Mats O. , Sandström Marie
Published: April 2006

Aims

Since cefuroxime mainly is excreted by renal filtration, dosing is currently based on serum creatinine (Scr) or creatinine clearance (CLcr). However, it has been suggested that cystatin C (CysC) is superior to Scr as a marker of renal function. The aim of this prospective study was to develop a population model that describes the pharmacokinetics of cefuroxime and to investigate the usefulness of CysC as a covariate of the model parameters.

Methods

Ninety‐seven patients were studied (CLcr range 6.5–115 ml min−1). Blood samples (n = 407) for the determination of cefuroxime were withdrawn according to a sparse data sampling schedule and analysed by liquid chromatography mass spectrometry. The population analysis was performed in NONMEM.

Results

A two‐compartment model described the data well. The biomarkers Scr, CLcr and CysC were evaluated as covariates on clearance (CL). The model that included CysC generated the best fit. In the final population model CL was a function of CysC and body weight, whereas V1 was only a function of body weight. Final parameter estimates (relative standard errors) were 6.00 (3.2%) l h−1, 11.4 (5.3%) l and 5.11 (11%) l for CL, V1 and V2, respectively.

Conclusions

Based on the results of the present study, and because CysC is practical to use in the clinic, it is suggested that individual dosing of cefuroxime may be based on CysC rather than on Scr or CLcr. Furthermore, our final population model may be useful as a tool when designing new dosing schedules for cefuroxime.
Dose‐dependent effect of dobutamine on chemoreflex activity in healthy volunteers
Authors: Pathak Atul , Velez‐Roa Sonia , Xhaët Olivier , Najem Boutaina , Van De Borne Philippe
Published: April 2006

Aims  β‐adrenergic agonists increase peripheral chemoreceptor sensitivity in humans. We tested the hypothesis that β1‐agonist‐related increase in peripheral chemoreflex sensitivity is selective and dose‐dependent.

Methods  Using a double‐blind, placebo‐controlled, randomized, crossover study, we examined the effects of dobutamine (n = 17 healthy subjects) at perfusion rates of 2.5 µg kg−1 min−1 (D2.5) and 7.5 µg kg−1 min−1 (D7.5) on ventilation, haemodynamics and sympathetic nerve activity during normoxia, isocapnic hypoxia, posthypoxic maximal voluntary end‐expiratory apnoea, hyperoxic hypercapnia and cold pressor test (CPT). We analysed the effect of pretreatment with atenolol on dobutamine‐evoked chemosensitivity.

Results  Dobutamine dose‐dependently increased ventilation (placebo 6.7 ± 0.5 vs. D2.5 7.8 ± 0.4 vs. D7.5 8.7 ± 0.4 l min−1, P < 0.005) during normoxia, enhanced the ventilatory (placebo 14.4 ± 0.6 vs. D2.5 17.3 ± 0.8 vs. D7.5 22.5 ± 1.9 l min−1, P < 0.0001) and sympathetic (placebo + 215 ± 31 vs. D2.5 + 285 ± 19 vs. D7.5 + 395 ± 50% of baseline, P < 0.03) responses at the fifth minute of isocapnic hypoxia and enhanced the sympathetic response to apnoea performed after hypoxia (increase after 5 min of hypoxia: + 290 ± 43% for placebo vs.+ 360 ± 21% for D2.5 vs. 537 ± 69% for D7.5, P < 0.05). No differences were observed between dobutamine and placebo in the responses to hyperoxic hypercapnia and CPT. Atenolol inhibited the dobutamine‐related hyperventilation and apnoea shortening during normoxia and hypoxia.

Conclusion  Dobutamine enhances peripheral chemosensitivity at low infusion rates selectively and in a dose‐dependent manner. There is a β1 adrenoceptor component in dobutamine‐evoked increase in peripheral chemosensititivity; however, a contribution of additional adrenoceptor subtypes cannot be excluded.
Design of a complement mannose-binding lectin pathway-specific activation system applicable at low serum dilutions
Authors: Harboe M , Garred P , Borgen M S , Stahl G L , Roos A , Mollnes T E
Published: April 2006

Recently we showed that alternative pathway (AP) amplification was responsible for more than 80% of specific classical pathway-induced terminal pathway activation under physiological conditions. The present study aimed to design a system for specific lectin pathway (LP) activation applicable at low serum dilutions with a fully functional AP. Comparison between activation of normal human serum (NHS), a mannose-binding lectin (MBL) homozygous D/D-deficient serum, and sera deficient in C1q and C2, all diluted 1 : 2, was essential to document optimal conditions for LP specificity. Mannan on the solid phase of enzyme-linked immunosorbent assay (ELISA) plates was used for activation, showing 0·5 µg mannan/well to give optimal conditions because at this concentration a good signal was preserved for C4 and TCC deposition in NHS, whereas the C3 deposition observed in C2-deficient serum at higher mannan concentrations reached nadir at 0·5 µg/well, indicating a lack of direct AP activation under these conditions. Pooled NHS and C1q-deficient serum gave the same degree of C4 and terminal complement complex (TCC) deposition, whereas deposition of these products was not obtained with MBL-deficient serum. Reconstitution with purified MBL, however, restored the depositions. A blocking anti-MBL monoclonal antibody (mAb) completely abolished the complement deposition, in contrast to a non-inhibiting anti-MBL mAb. Activation of C2-deficient serum induced C4 deposition similar to NHS, but negligible deposition of C3 and TCC, confirming the lack of direct activation of AP. Thus, this assay is unique in being LP-specific at low serum dilution and thus particularly suitable to study LP activation mechanisms and the role of AP amplification under physiological conditions.
GH replacement does not increase the risk of recurrence in patients with craniopharyngioma
Authors: Karavitaki Niki , Warner Justin T. , Marland Anne , Shine Brian , Ryan Fiona , Arnold Jayanth , Turner Helen E. , Wass John A. H.
Published: April 2006

Background  A significant number of patients with craniopharyngioma are GH deficient. The safety of GH replacement in these subjects has not been established.

Objective  To assess the effect of GH replacement upon recurrence in patients with craniopharyngioma.

Patients and methods  All the patients with craniopharyngioma followed‐up at the Departments of Endocrinology or Paediatrics in Oxford and treated or not with GH were studied retrospectively. These were recruited from the databases of the departments consisting of subjects diagnosed between January 1964 and July 2005. The impact of GH replacement upon recurrence was evaluated after adjusting for possible confounding factors.

Results  Forty‐one subjects received GH replacement. Nine of them did not have follow‐up imaging during GH therapy and were not included in the statistical analyses. The remaining 32 (22 males/10 females) received GH for a mean period of 6·3 ± 4·6 years (median 5·1, range 0·8–22); 21 started during childhood (13 of them continued after the achievement of final height with an adult dose) and 11 during adult life. The mean duration of their follow‐up (from surgery until last assessment) was 10·8 ± 9·2 years (range 1·9–40). Fifty‐three subjects had not received GH therapy (30 men/23 women). The mean duration of their follow‐up (from surgery until last assessment) was 8·3 ± 8·8 years (range 0·5–36). During the observation period, 4 patients treated with GH and 22 non‐GH treated ones developed tumour recurrence. After adjusting for sex, age at tumour diagnosis and type of tumour therapy (gross total removal, partial removal, surgery + irradiation), GH treatment was not a significant independent predictor of recurrence (P = 0·06; hazard ratio = 0·309). Similar results were obtained when the impact of GH replacement was assessed according to its duration (P = 0·18; hazard ratio = 0·991/month of treatment). None of the nine patients with insufficient imaging data for inclusion in the statistical analyses [5 men/4 women, 3 treated with GH during childhood/6 during adult life, mean duration of GH therapy 2·9 ± 2·4 years (median 1·8, range 0·4–7)] showed clinical features suggestive of recurrence during the period of GH replacement.

Conclusion  Based on the data of the craniopharyngiomas database in Oxford, there is no evidence that GH replacement is associated with an increased risk of tumour recurrence.
Helical distribution of the bacterial chemoreceptor via colocalization with the Sec protein translocation machinery
Authors: Shiomi Daisuke , Yoshimoto Masayuki , Homma Michio , Kawagishi Ikuro
Published: April 2006

In Escherichia coli, chemoreceptor clustering at a cell pole seems critical for signal amplification and adaptation. However, little is known about the mechanism of localization itself. Here we examined whether the aspartate chemoreceptor (Tar) is inserted directly into the polar membrane by using its fusion to green fluorescent protein (GFP). After induction of Tar–GFP, fluorescent spots first appeared in lateral membrane regions, and later cell poles became predominantly fluorescent. Unexpectedly, Tar–GFP showed a helical arrangement in lateral regions, which was more apparent when a Tar–GFP derivative with two cysteine residues in the periplasmic domain was cross‐linked to form higher oligomers. Moreover, similar distribution was observed even when the cytoplasmic domain of the double cysteine Tar–GFP mutant was replaced by that of the kinase EnvZ, which does not localize to a pole. Observation of GFP–SecE and a translocation‐defective MalE–GFP mutant, as well as indirect immunofluorescence microscopy on SecG, suggested that the general protein translocation machinery (Sec) itself is arranged into a helical array, with which Tar is transiently associated. The Sec coil appeared distinct from the MreB coil, an actin‐like cytoskeleton. These findings will shed new light on the mechanisms underlying spatial organization of membrane proteins in E. coli.
The effect of promoter strength, supercoiling and secondary structure on mutation rates in Escherichia coli
Authors: Schmidt Karen H. , Reimers Jacqueline M. , Wright Barbara E.
Published: April 2006

Four mutations resulting in opal stop codons were individually engineered into a plasmid‐borne chloramphenicol‐resistance (cat) gene driven by the lac promoter. These four mutations were located at different sites in secondary structures. The mutations were analysed with the computer program mfg, which predicted their relative reversion frequencies. Reversion frequencies determined experimentally correlated with the mutability of the bases as predicted by mfg. To examine the effect of increased transcription on reversion frequencies, the lac promoter was replaced with the stronger tac promoter, which resulted in 12‐ to 30‐fold increases in reversion rates. The effect of increased and decreased supercoiling was also investigated. The cat mutants had higher reversion rates in a topA mutant strain with increased negative supercoiling compared with wild‐type levels, and the cat reversion rates were lower in a topA gyrB mutant strain with decreased negative supercoiling, as predicted.
Using a standard framework for the phenotypic analysis of Medicago truncatula: an effective method for characterizing the plant material used for functional genomics approaches
Authors: MOREAU DELPHINE , SALON CHRISTOPHE , MUNIER‐JOLAIN NATHALIE
Published: April 2006

A crucial step for identifying genes of interest in legume crops is to determine gene function in Medicago truncatula. To facilitate functional genomics in this species, an ecophysiological framework of analysis was developed. Our primary aim was to establish a standard terminology for identifying each organ on the plant. A standard system for the characterization of the vegetative and the reproductive developmental stages was then proposed. Using these tools, the time course of vegetative development of nitrogen‐fixing A17 plants was analysed in experiments conducted under different environmental conditions. To take into account the influence of temperature on plant development timing, an original approach was used by modelling vegetative development as a function of thermal time. Interestingly, the use of thermal time highlighted genotypic constants in plant development. Thereafter, to illustrate how this methodology can be used in explaining phenotypic alterations, the phenotype of two allelic mutants was analysed. Because the tools proposed in this paper allow the following: (1) standardization of how the plant material should be characterized to be used for functional genomics; (2) prediction of plant vegetative development; and (3) a more accurate phenotyping, the use of these tools by the M. truncatula community should provide a relevant framework for facilitating the production of reproducible functional genomics data.
Transitions in the functioning of the shoot apical meristem in birch (Betula pendula) involve ethylene
Authors: Ruonala Raili , Rinne Päivi L.H. , Baghour Mourad , Moritz Thomas , Tuominen Hannele , Kangasjärvi Jaakko
Published: April 2006

In many trees, a short photoperiod (SD) triggers substantial physiological adjustments necessary for over‐wintering. We have used transgenic ethylene‐insensitive birches (Betula pendula), which express the Arabidopsis ethylene receptor gene ETR1 carrying the dominant mutation etr1‐1, to investigate the role of ethylene in SD‐induced responses in the shoot apical meristem (SAM). Under SD, the ethylene‐insensitive trees ceased elongation growth comparably to the wild‐type. In contrast, the formation of terminal buds, which in trees is typically induced by SD, was abolished. However, although delayed, endo‐dormancy did eventually develop in the ethylene‐insensitive trees. This, together with the rapid resumption of growth in the ethylene‐insensitive trees after transfer from non‐permissive to permissive conditions suggests that ethylene facilitates the SD‐induced terminal bud formation, as well as growth arrest. In addition, apical buds of the ethylene‐insensitive birch did not accumulate abscisic acid (ABA) under SD, suggesting interaction between ethylene and ABA signalling in the bud. Alterations in SAM functioning were further exemplified by reduced apical dominance and early flowering in ethylene‐insensitive birches. Gene expression analysis of shoot apices revealed that the ethylene‐insensitive birch lacked the marked increase in expression of a beta‐xylosidase gene typical to the SD‐exposed wild‐type. The ethylene‐dependent beta‐xylosidase gene expression is hypothesized to relate to modification of cell walls in terminal buds during SD‐induced growth cessation. Our results suggest that ethylene is involved in terminal bud formation and in the timely suppression of SAM activity, not only in the shoot apex, but also in axillary and reproductive meristems.
AhSSK1, a novel SKP1‐like protein that interacts with the S‐locus F‐box protein SLF
Authors: Huang Jian , Zhao Lan , Yang Qiuying , Xue Yongbiao
Published: April 2006

The S‐locus F‐box (SLF/SFB) protein, recently identified as the pollen determinant of S‐RNase‐based self‐incompatibility (SI) in Solanaceae, Scrophulariaceae and Rosaceae, has been proposed to serve as the subunit of an SCF (SKP1–CUL1–F‐box) ubiquitin ligase and to target its pistil counterpart S‐RNase during the SI response. However, the underlying mechanism is still in dispute, and the putative SLF‐binding SKP1‐equivalent protein remains unknown. Here, we report the identification of AhSSK1, Antirrhinum hispanicumSLF‐interacting SKP1‐like1, using a yeast two‐hybrid screen against a pollen cDNA library. GST pull‐down assays confirmed the SSK1–SLF interaction, and showed that AhSSK1 could connect AhSLF to a CUL1‐like protein. AhSSK1, despite having a similar secondary structure to other SKP1‐like proteins, appeared quite distinctive in sequence and unique in a phylogenetic analysis, in which no SSK1 ortholog could be predicted in the sequenced genomes of Arabidopsis and rice. Thus, our results suggest that the pollen‐specific SSK1 could be recruited exclusively as the adaptor of putative SCFSLF in those plants with S‐RNase‐based SI, providing an important clue to dissecting the function of the pollen determinant.
Contribution of polymeric immunoglobulin receptor to regulation of intestinal inflammation in dextran sulfate sodium‐induced colitis
Authors: Murthy Ashlesh K , Dubose Candice N , Banas Jeffrey A , Coalson Jacqueline J , Arulanandam Bernard P
Published: April 2006

Background:  Inflammatory bowel disease (IBD) affects approximately 4 million people worldwide and can be caused by dysregulated mucosal immune responses to the intestinal commensal microflora. Immunoglobulin A (IgA) is considered to be the principal antibody in intestinal secretions and functions to prevent commensals and pathogenic organisms from gaining access to epithelial cell surfaces. Immunoglobulin A deficiency in humans has been associated with celiac disease and ulcerative colitis. However, the precise role of IgA in the pathogenesis of these disorders is yet to be fully understood.

Methods:  Mice with a targeted disruption in IgA production (IgA–/– mice) and polymeric immunoglobulin receptor (pIgR–/– mice) were analyzed for the contribution of secretory immunity in the pathogenesis of dextran sulfate sodium (2.5%)‐induced colitis.

Results:  It was found that dextran sulfate sodium‐treated pIgR–/– mice displayed greater loss of bodyweight and had severe clinical illness compared to similarly treated IgA–/– mice and wild‐type animals. Additionally, colonic tissues from the pIgR–/– mice exhibited progressively and significantly greater degrees of mucosal edema, ulceration, crypt abscesses and macrophage infiltration when compared to similarly treated IgA–/– mice and wild‐type animals.

Conclusions:  The results indicate that secretory immunoglobulins contribute to protection of the colonic mucosa against dextran sulfate sodium‐induced epithelial injury, although the isotype of the secretory immunoglobulin (IgA or IgM) may not be a decisive factor in such protection. Collectively, the pIgR and/or the secretory component are important for the maintenance of epithelial integrity and mucosal homeostasis in the colonic epithelium.
Transabdominal gastroesophageal devascularization without transection for bleeding varices: Results and indicators of prognosis
Authors: Goyal Neerav , Singhal Dinesh , Gupta Subash , Soin Arvinder S , Nundy Samiran
Published: April 2006

Background:  Esophagogastric devascularization is an operation that can be performed for endoscopically uncontrolled variceal bleeding in hospitals having only basic surgical instruments and is therefore an appropriate procedure for small hospitals in developing countries. The aim of this study was to analyze one hospital’s experience of this operation in consecutive patients with variceal bleeding.

Methods:  Between 1996 and 2003, 45 patients (30 male, 15 female) who had a mean age of 40 years (range 7–78 years) underwent devascularization procedures. Of the 45, 23 had cirrhosis and 22 had non‐cirrhotic portal hypertension (11 extrahepatic portal venous obstruction, 11 non‐cirrhotic portal fibrosis), and 18 patients had emergency procedures and 27 were elective. Mortality, morbidity, rebleeding rates and the prognostic factors for death were assessed.

Results:  Elective and emergency mortality was one (3.7%) and 11 (61%) patients, respectively. There was no rebleeding in hospital. At follow up (mean 48 months, range 3–92 months) overall survival in patients with cirrhosis was 7 out of 20 and in patients with non‐cirrhotic portal hypertension was 19 of 21. Five (17%) had recurrent variceal hemorrhage, of whom three, all cirrhotic patients, died. Preoperative prognostic indicators for death were emergency surgery, a Child–Pugh score ≥10, preoperative blood transfusion ≥20 units and renal failure.

Conclusions:  Gastroesophageal devascularization effectively controls variceal bleeding especially in non‐cirrhotic patients with portal hypertension. In the elective situation it carries a low mortality and rebleed rate. In emergencies the prognosis is poor with advanced cirrhosis, following large quantities of blood transfusion and deranged renal function. It is suggested that this operation be offered especially to non‐cirrhotic patients in hospitals in developing countries where facilities for more sophisticated procedures are not available.
Specific COX‐2 inhibitor, meloxicam, suppresses proliferation and induces apoptosis in human HepG2 hepatocellular carcinoma cells
Authors: Li Jie , Chen Xiaoping , Dong Xuesong , Xu Zongzhen , Jiang Hongchi , Sun Xueying
Published: April 2006

Background and Aims:  Cyclooxygenase‐2 (COX‐2) is associated with carcinogenesis. The aim of this study was to investigate the expression of COX‐2 in four hepatocellular carcinoma (HCC) cell lines, and evaluate the effect of a selective COX‐2 inhibitor, meloxicam, in HepG2, a high COX‐2 expressing cell line.

Methods:  Expression of COX‐2 was detected using RT‐PCR, Western blotting and immunohistochemical analysis. Cell proliferation was measured using MTT assay. Cell cycle distribution was determined by flow cytometry. Apoptosis was detected with TUNEL method. Expression of proliferating cell nuclear antigen (PCNA), cell cycle regulatory proteins including cyclins A, B1, D1 and E, and apoptosis‐related proteins including Fas, Fas ligand and Bcl‐2 were examined using Western blotting.

Results:  Cyclooxygenase‐2 was intensely expressed in HepG2, HLE and BEL7402 cells, but weakly expressed in SMMC‐7402 cells. Meloxicam suppressed proliferation of HepG2 cells in a dose‐ and time‐dependent manner, resulting in cell cycle arrest in S phase and cell accumulation in G0/G1 phase. Expression of PCNA, cyclin A but not cyclin B1, cyclin D1 or cyclin E was down‐regulated by meloxicam. Meloxicam also induced apoptosis of HepG2 cells, with increased expression of Fas ligand, but the expression of Fas and Bcl‐2 was not affected by meloxicam treatment.

Conclusions:  The present study demonstrates that the specific COX‐2 inhibitor meloxicam suppresses proliferation and induces apoptosis in HCC cells that express COX‐2, suggesting that COX‐2 inhibition may offer a novel chemopreventive and therapeutic approach for HCC.
Evaluation of epitope tags for protein detection after in vivo CNS gene transfer
Authors: Shevtsova Z. , Malik J. M. I. , Michel U. , Schöll U. , Bähr M. , Kügler S.
Published: April 2006

Functional characterization of disease‐related proteins, their splice variants and dominant negative mutants in the context of complex CNS tissues such as brain and retina is frequently assessed by in vivo gene transfer. For correct interpretation of results it is imperative that the protein under investigation is unambiguously detected in the transduced cell types and can be distinguished from any endogenously expressed physiological variants. Therefore the first systematic evaluation of epitope tags used to trace ectopically expressed proteins in the central nervous system is presented here. Substantial differences in the performances of various epitope tag–antibody combinations with respect to sensitivity, specificity and influence of the epitope tag on the fusion protein are elucidated. Epitope tags already established for protein detection in vitro and to some extent in vivo (c‐Myc, HA and FLAG tags) were immunohistochemically detected with high sensitivity. However, detection of these tags revealed problems with background staining and we also document structural and functional influence of the tags on the fusion protein. In order to prevent such unwanted side‐effects, epitope tags which have not yet been used for in vivo applications (IRS, EE and AU1 tags) were characterized in brain, retina and cultured neurons. While use of the IRS and EE tags was hindered by low sensitivity or specificity, optimal results were obtained with the AU1 epitope, which may develop into a standard tool for detection of ectopic protein expression in the central nervous system.
Persistent changes in action potential broadening and the slow afterhyperpolarization in rat CA1 pyramidal cells after febrile seizures
Authors: Kamal Amer , Notenboom Robbert G. E. , De Graan Pierre N. E. , Ramakers Geert M. J.
Published: April 2006

Febrile (fever‐induced) seizures (FS) are the most common form of seizures during childhood and have been associated with an increased risk of epilepsy later in life. The relationship of FS to subsequent epilepsy is, however, still controversial. Insights from animal models do indicate that especially complex FS are harmful to the developing brain and contribute to a hyperexcitable state that may persist for life. Here, we determined long‐lasting changes in neuronal excitability of rat hippocampal CA1 pyramidal cells after prolonged (complex) FS induced by hyperthermia on postnatal day 10. We show that hyperthermia‐induced seizures at postnatal day 10 induce a long‐lasting increase in the hyperpolarization‐activated current Ih. Furthermore, we show that a reduction in the amount of spike broadening and in the amplitude of the slow afterhyperpolarization following FS are also likely to contribute to the hyperexcitability of the hippocampus long term.
Lesion patterns and etiology of ischemia in the anterior inferior cerebellar artery territory involvement: a clinical – diffusion weighted – MRI study
Authors: Kumral E. , Kısabay A. , Ataç C.
Published: April 2006

The topography and mechanism of stroke in the anterior inferior cerebellar artery (AICA) territory are delineated before, but the detailed clinical spectrum of lesions involving AICA territory was not studied by diffusion weighted imaging (DWI). We reviewed 1350 patients with posterior circulation ischemic stroke in our registry. We included patients if the diagnosis of AICA territory involvement was confirmed, and DWI, and magnetic resonance angiography were obtained in the 3 days of symptoms onset. The potential feeding arteries of the AICA territory were evaluated on magnetic resonance imaging (MRI) using a three‐dimensional rotating cineoangiographic method. There were 23 consecutive patients with lesion involving AICA territory, six with isolated lesion in the AICA territory, six with posterior inferior cerebellar artery, 11 with multiple posterior circulation infarcts (MPCIs). The clinical feature of isolated AICA infarct was vertigo, tinnitus, dysmetria, ataxia, facial weakness, facial sensory deficits, lateral gaze palsy, and sensory‐motor deficits in patients with pontine involvement. Patients with largest lesion extending to the anterior and inferolateral cerebellum showed mixed symptomatology of the lateral medullary (Wallenberg's syndrome) and AICA territory involvement. Patients with MPCIs presented various clinical pictures with consciousness disturbances and diverse clinical signs because of involvement of different anatomical structures. Large‐artery atherosclerotic disease in the vertebrobasilar system was the main cause of stroke in 12 (52%) patients, cardioembolism (CE) in one (4%), and coexisting large‐artery disease and a source of CE in four (17%). The main cause of stroke was atheromatous vertebrobasilar artery disease either in the distal vertebral or proximal basilar artery. The outcome was usually good except those with multiple lesions. The new MRI techniques and clinical correlations allow better definition of the diverse topographical and etiological spectrum of AICA territory involvement and associated infarcts which was previously based on pathological and conventional MRI studies.
The uncelebrated parent: stories of mothers with learning difficulties caught in the child protection net
Authors: Booth Tim , Booth Wendy
Published: April 2006

This paper presents the stories of three mothers with learning difficulties whose children have been involved in care proceedings. Drawing on the example of the legendary interviewer, Studs Terkel, the authors let the mothers describe their experiences of the child protection system in their own words. From out of their intensely personal accounts comes a political narrative about the role of the state in the policing of marginalized and vulnerable families.
Toward a More Reliable Federal Survey for Tracking Health Insurance Coverage and Access
Authors: Kenney Genevieve , Holahan John , Nichols Len
Published: April 2006

Objective. Examination of the extent to which federal surveys provide the data needed to estimate the coverage/cost impacts of policy alternatives to address the problem of uninsurance.

Data Sources/Study Setting. Assessment of the major federal household surveys that regularly provide information on health insurance and access to care based on an examination of each survey instrument and related survey documentation and the methodological literature.

Study Design. Identification of the data needed to address key policy questions on insurance coverage, assessment of how well existing surveys meet this need, definition of the critical elements of an ideal survey, and examination of the potential for building on existing surveys.

Data Collection/Extraction Methods. Collection and critical assessment of pertinent survey documentation and methodological studies.

Principal Findings. While all the federal surveys examined provide valuable information, the information available to guide key policy decisions still has major gaps. Issues include measurement of insurance coverage and critical content gaps, inadequate sample sizes to support precise state and substate estimates, considerable delays between data collection and availability, and concerns about response rates and item nonresponse. Our assessment is that the Current Population Survey (CPS) and the National Health Interview Survey could be most readily modified to address these issues.

Conclusions. The vast resources devoted to health care and the magnitude of the uninsurance problem make it critical that we have a reliable source for tracking health care and coverage at the national and state levels and for major local areas. It is plausible that this could be more cost effectively done by building on existing surveys than by designing and fielding a new one, but further research is needed to make a definitive judgment. At a minimum, the health insurance information collected on the CPS should be revised to address existing measurement problems.