Identification of genes potentially involved in solute stress response in Sphingomonas wittichii RW1 by transposon mutant recovery.

The term water stress refers to the effects of low water availability on microbial growth and physiology. Water availability has been proposed as a major constraint for the use of microorganisms in contaminated sites with the purpose of bioremediation. Sphingomonas wittichii RW1 is a bacterium capable of degrading the xenobiotic compounds dibenzofuran and dibenzo-p-dioxin, and has potential to be used for targeted bioremediation. The aim of the current work was to identify genes implicated in water stress in RW1 by means of transposon mutagenesis and mutant growth experiments. Conditions of low water potential were mimicked by adding NaCl to the growth media. Three different mutant selection or separation method were tested which, however recovered different mutants. Recovered transposon mutants with poorer growth under salt-induced water stress carried insertions in genes involved in proline and glutamate biosynthesis, and further in a gene putatively involved in aromatic compound catabolism. Transposon mutants growing poorer on medium with lowered water potential also included ones that had insertions in genes involved in more general functions such as transcriptional regulation, elongation factor, cell division protein, RNA polymerase β or an aconitase.

Patterns of neurovascular compression in patients with classic trigeminal neuralgia: A high-resolution MRI-based study.

PURPOSE: To describe the anatomical characteristics and patterns of neurovascular compression in patients suffering classic trigeminal neuralgia (CTN), using high-resolution magnetic resonance imaging (MRI). MATERIALS AND METHODS: The analysis of the anatomy of the trigeminal nerve, brain stem and the vascular structures related to this nerve was made in 100 consecutive patients treated with a Gamma Knife radiosurgery for CTN between December 1999 and September 2004. MRI studies (T1, T1 enhanced and T2-SPIR) with axial, coronal and sagital simultaneous visualization were dynamically assessed using the software GammaPlan?. Three-dimensional reconstructions were also developed in some representative cases. RESULTS: In 93 patients (93%), there were one or several vascular structures in contact, either, with the trigeminal nerve, or close to its origin in the pons. The superior cerebellar artery was involved in 71 cases (76%). Other vessels identified were the antero-inferior cerebellar artery, the basilar artery, the vertebral artery, and some venous structures. Vascular compression was found anywhere along the trigeminal nerve. The mean distance between the nerve compression and the origin of the nerve in the brainstem was 3.76±2.9mm (range 0-9.8mm). In 39 patients (42%), the vascular compression was located proximally and in 42 (45%) the compression was located distally. Nerve dislocation or distortion by the vessel was observed in 30 cases (32%). CONCLUSIONS: The findings of this study are similar to those reported in surgical and autopsy series. This non-invasive MRI-based approach could be useful for diagnostic and therapeutic decisions in CTN, and it could help to understand its pathogenesis.

Schizophrenia and oxidative stress: glutamate cysteine ligase modifier as a susceptibility gene.

Oxidative stress could be involved in the pathophysiology of schizophrenia, a major psychiatric disorder. Glutathione (GSH), a redox regulator, is decreased in patients' cerebrospinal fluid and prefrontal cortex. The gene of the key GSH-synthesizing enzyme, glutamate cysteine ligase modifier (GCLM) subunit, is strongly associated with schizophrenia in two case-control studies and in one family study. GCLM gene expression is decreased in patients' fibroblasts. Thus, GSH metabolism dysfunction is proposed as one of the vulnerability factors for schizophrenia.

Stress et satisfaction au travail des cadres intermédiaires dans les hôpitaux de Suisse romande dans un contexte de réformes

L'article vise à identifier les déterminants du stress et de la satisfaction au travail parmi une population de cadres intermédiaires exerçant dans des établissements hospitaliers de Suisse romande. Il vise également à combler un vide dans les études sur les administrations publiques suisses: mieux saisir, au moyen d'une enquête par questionnaires, quels sont les principales variables qui se trouvent à l'origine de la satisfaction au travail et qui peuvent être des ressources pour les acteurs afin de faire face au stress. L'étude confirme des résultats de recherches internationales, montrant que des facteurs relationnels et des caractéristiques du travail sont les principaux déterminants du stress et de la satisfaction. Elle souligne dès lors l'importance d'adopter une lecture « structurelle » et « organisationnelle » du stress et de la satisfaction, soulignant aussi que les caractéristiques individuelles de la population étudiée n'expliquent qu'une très infime variance de ces phénomènes.

Validation of the Postnatal Perceived Stress Inventory in a French-speaking population of primiparous women

Objective To develop a Postnatal Perceived Stress Inventory (PNPSI) and assess its psychometric properties. Design Cross-sectional quantitative study. Setting One nurse-managed labor and delivery unit in a university hospital in a major metropolitan area. Participants One hundred seventy-nine (179) primiparous French speaking women who gave birth at term. Methods The PNPSI was validated at 6 weeks postpartum. Its predictive validity for depression and anxiety was assessed at the same time. Results The exploratory analysis revealed a 19-item structure divided into six factors. This inventory has good internal consistency (Cronbach's alpha = .815). The predictive validity shows that the PNPSI significantly predicts depression and anxiety at 6 weeks postpartum, and that certain factors are particularly prominent. Conclusion The PNPSI's psychometric properties make it a useful tool for future research to evaluate interventions for perceived stress during the postnatal period. Its predictive power for depression indicates that it is also a promising tool for clinical settings.

Selecting Wavelet Filter for Compression of Spectra from Multispectral Images

The problem of selecting anappropriate wavelet filter is always present in signal compression based on thewavelet transform. In this report, we propose a method to select a wavelet filter from a predefined set of filters for the compression of spectra from a multispectral image. The wavelet filter selection is based on the Learning Vector Quantization (LVQ). In the training phase for the test images, the best wavelet filter for each spectrum has been found by a careful compression-decompression evaluation. Certain spectral features are used in characterizing the pixel spectra. The LVQ is used to form the best wavelet filter class for different types of spectra from multispectral images. When a new image is to be compressed, a set of spectra from that image is selected, the spectra are classified by the trained LVQand the filter associated to the largest class is selected for the compression of every spectrum from the multispectral image. The results show, that almost inevery case our method finds the most suitable wavelet filter from the pre-defined set for the compression.

Expanding view of phenotype and oxidative stress in Friedreich's ataxia patients with and without idebenone

Summary: Friedreich's ataxia (FRDA), the most common autosomal recessive ataxia, is characterised by progressive ataxia with dysarthria of speech, loss of deep-tendon reflexes, impaired vibratory and proprioceptive sensations and corticospinal weakness with a Babinski's sign. Patients eventually also develop kyphoscoliosis, cardiomyopathy and diabetes mellitus. The disease is a GAA repeat disorder resulting in severely reduced levels of frataxin, with secondary increased sensitivity to oxidative stress. The anti-oxidative drug, idebenone, is effective against FRDA-associated cardiomyopathy. We provide detailed clinical, electrophysiological and biochemical data from 20 genetically confirmed FRDA patients and have analysed the relation-ship between phenotype, genotype and malondialdehyde (MDA), which is a marker of superoxide formation. We assessed the effects of idebenone biochemically by measuring blood M DA and clinically by serial measurements of the International Cooperative Ataxia Rating Scale (ICARS). The GAA repeat length influenced the age at onset (p <0.001), the severity of ataxia (p= 0.02), the presence of cardiomyopathy (p =0.04) and of low-frequency hearing loss (p = 0.009). Multilinear regression analysis showed (p = 0.006) that ICARS was dependent on the two variables of disease duration (p = 0.01) and size of the GAA expansion (p = 0.02). We found no correlation to bilateral palpebral ptosis visual impairment, diabetes mellitus or skeletal deformities, all of which appear to be signs of disease progression rather than severity. We discuss more thoroughly two underrecognised clinical findings: palpebral ptosis and GAA length-dependent low-frequency hearing loss. The average ICARS remained unchanged in 10 patients for whom follow-up on treatment was available (mean 2.9 years), whereas most patients treated with idebenone reported an improvement in dysarthria (63%), hand dexterity (.58%) and fatigue (47%) after taking the drug for several weeks or months. Oxidative stress analysis showed an unexpected increase in blood MDA levels in patients on idebenone (p = 0.04), and we discuss the putative underlying mechanism for this result, which could then explain the unique efficacy of idebenone in treating the FRDA-associated cardiomyopathy, as opposed to other antioxidative drugs. Indeed, idebenone is not only a powerful stimulator of complexes II and III of the respiratory chain, but also an inhibitor of complex I activity, then promoting superoxide formation. Our preliminary clinical observations are the first to date supporting an effect of idebenone in delaying neurological worsening. Our MDA results point to the dual effect of idebenone on oxidative stress and to the need for controlled studies to assess its potential toxicity at high doses on the one hand, and to revisit the exact mechanisms underlying the .physiopathology of Friedreich's ataxia on the other hand, while recent reports suggest non-oxidative pathophysiology of the disease.

Multispectral image compression using the wavelet transform

Multispectral images contain information from several spectral wavelengths and currently multispectral images are widely used in remote sensing and they are becoming more common in the field of computer vision and in industrial applications. Typically, one multispectral image in remote sensing may occupy hundreds of megabytes of disk space and several this kind of images may be received from a single measurement. This study considers the compression of multispectral images. The lossy compression is based on the wavelet transform and we compare the suitability of different waveletfilters for the compression. A method for selecting a wavelet filter for the compression and reconstruction of multispectral images is developed. The performance of the multidimensional wavelet transform based compression is compared to other compression methods like PCA, ICA, SPIHT, and DCT/JPEG. The quality of the compression and reconstruction is measured by quantitative measures like signal-to-noise ratio. In addition, we have developed a qualitative measure, which combines the information from the spatial and spectral dimensions of a multispectral image and which also accounts for the visual quality of the bands from the multispectral images.

A modified structural stress method for fatigue assessment of welded structures

Fatigue life assessment of weldedstructures is commonly based on the nominal stress method, but more flexible and accurate methods have been introduced. In general, the assessment accuracy is improved as more localized information about the weld is incorporated. The structural hot spot stress method includes the influence of macro geometric effects and structural discontinuities on the design stress but excludes the local features of the weld. In this thesis, the limitations of the structural hot spot stress method are discussed and a modified structural stress method with improved accuracy is developed and verified for selected welded details. The fatigue life of structures in the as-welded state consists mainly of crack growth from pre-existing cracks or defects. Crack growth rate depends on crack geometry and the stress state on the crack face plane. This means that the stress level and shape of the stress distribution in the assumed crack path governs thetotal fatigue life. In many structural details the stress distribution is similar and adequate fatigue life estimates can be obtained just by adjusting the stress level based on a single stress value, i.e., the structural hot spot stress. There are, however, cases for which the structural stress approach is less appropriate because the stress distribution differs significantly from the more common cases. Plate edge attachments and plates on elastic foundations are some examples of structures with this type of stress distribution. The importance of fillet weld size and weld load variation on the stress distribution is another central topic in this thesis. Structural hot spot stress determination is generally based on a procedure that involves extrapolation of plate surface stresses. Other possibilities for determining the structural hot spot stress is to extrapolate stresses through the thickness at the weld toe or to use Dong's method which includes through-thickness extrapolation at some distance from the weld toe. Both of these latter methods are less sensitive to the FE mesh used. Structural stress based on surface extrapolation is sensitive to the extrapolation points selected and to the FE mesh used near these points. Rules for proper meshing, however, are well defined and not difficult to apply. To improve the accuracy of the traditional structural hot spot stress, a multi-linear stress distribution is introduced. The magnitude of the weld toe stress after linearization is dependent on the weld size, weld load and plate thickness. Simple equations have been derived by comparing assessment results based on the local linear stress distribution and LEFM based calculations. The proposed method is called the modified structural stress method (MSHS) since the structural hot spot stress (SHS) value is corrected using information on weld size andweld load. The correction procedure is verified using fatigue test results found in the literature. Also, a test case was conducted comparing the proposed method with other local fatigue assessment methods.

Lossless compression of hyperspectral images

Technological progress has made a huge amount of data available at increasing spatial and spectral resolutions. Therefore, the compression of hyperspectral data is an area of active research. In somefields, the original quality of a hyperspectral image cannot be compromised andin these cases, lossless compression is mandatory. The main goal of this thesisis to provide improved methods for the lossless compression of hyperspectral images. Both prediction- and transform-based methods are studied. Two kinds of prediction based methods are being studied. In the first method the spectra of a hyperspectral image are first clustered and and an optimized linear predictor is calculated for each cluster. In the second prediction method linear prediction coefficients are not fixed but are recalculated for each pixel. A parallel implementation of the above-mentioned linear prediction method is also presented. Also,two transform-based methods are being presented. Vector Quantization (VQ) was used together with a new coding of the residual image. In addition we have developed a new back end for a compression method utilizing Principal Component Analysis (PCA) and Integer Wavelet Transform (IWT). The performance of the compressionmethods are compared to that of other compression methods. The results show that the proposed linear prediction methods outperform the previous methods. In addition, a novel fast exact nearest-neighbor search method is developed. The search method is used to speed up the Linde-Buzo-Gray (LBG) clustering method.