The use of the eigenvectors of the spectral matrix. Seismic application

The spectral matrix filtering is a technique Chat enables separation of data obtained front an antenna into a signal part and a noise part . In certain circumstances it has been use for wave separation . The aim of the process is to build models of propagation at the antenna level . Using these models each wave is then estimated by a least-squares method . When this process is applied to seismic data, the spectral matrix has to he estimated in a special way . The estimation of models is particularly efficient using a time-domain representation of the eigenvectors of the spectral matrix . Two new separation processes are proposed, the matched model and the tapered model . The scalar product of the two différent waves is a parameter to be used when estimating the performance of the process . Application to four différent types of seismic data illustrates the efficiency of this type of filtering .La matrice spectrale est un outil utilisé pour séparer les signaux reçus sur une antenne en une partie signal et une partie bruit. Dans certains cas elle est utilisée pour séparer les ondes constituant la partie signal. La méthode consiste à estimer des modèles de propagation de ces ondes au niveau de l'antenne; les signaux sont alors obtenus par estimation aux moindres carrés. Appliquée à la sismique, cette méthode nécessite des opérations particulières d'estimation de la matrice spectrale. La détermination des modèles s'avère particulièrement efficace lorsque l'on utilise la représentation des vecteurs propres (de la matrice spectrale) dans le domaine temporel

Health services research into postnatal depression : results from a preliminary cross-cultural study

Background: Little is known about the availability and uptake of health and welfare services by women with postnatal depression in different countries. Aims: Within the context of a cross- cultural research study, to develop and test methods for undertaking quantitative health services research in postnatal depression. Method: Interviews with service planners and the collation of key health indicators were used to obtain a profile of service availability and provision. A service use questionnaire was developed and administered to a pilot sample in a number of European study centres. Results: Marked differences in service access and use were observed between the centres, including postnatal nursing care and contacts with primary care services.Rates of use of specialist services were generally low.Common barriers to access to care included perceived service quality and responsiveness. On the basis of the pilot work, a postnatal depression version of the Service Receipt Inventory was revised and finalised. Conclusions: This preliminary study demonstrated the methodological feasibility of describing and quantifying service use, highlighted the varied and often limited use of care in this population, and indicated the need for an improved understanding of the resource needs and implications of postnatal depression

Dose-Dependent Effect of Rosuvastatin on VLDL–Apolipoprotein C-III Kinetics in the Metabolic Syndrome

OBJECTIVE—Dysregulated apolipoprotein (apo)C-III metabolism may account for hypertriglyceridemia and increased cardiovascular risk in the metabolic syndrome. This study investigated the dose-dependent effect of rosuvastatin on VLDL apoC-III transport in men with the metabolic syndrome

Postnatal depression across countries and cultures : a qualitative study

Background: Postnatal depression seems to be a universal condition with similar rates in different countries. However, anthropologists question the cross-cultural equivalence of depression, particularly at a life stage so influenced by cultural factors. Aims: To develop a qualitative method to explore whether postnatal depression is universally recognised, attributed and described and to enquire into people’s perceptions of remedies and services for morbid states of unhappiness within the context of local services. Method: The study took place in 15 centres in 11 countries and drew on three groups of informants: focus groups with new mothers, interviews with fathers and grandmothers, and interviews with health professionals.Textual analysis of these three groups was conducted separately in each centre and emergent themes compared across centres. Results: All centres described morbid unhappiness after childbirth comparable to postnatal depression but not all saw this as an illness remediable by health interventions. Conclusions: Although the findings of this study support the universality of a morbid state of unhappiness following childbirth, they also support concerns about the cross-cultural equivalence of postnatal depression as an illness requiring the intervention of health professionals; this has implications for future research

Brazilian network for the surveillance of maternal potentially life threatening morbidity and maternal near-miss and a multidimensional evaluation of their long term consequences

<p>Abstract</p> <p>Background</p> <p>It has been suggested that the study of women who survive life-threatening complications related to pregnancy (maternal near-miss cases) may represent a practical alternative to surveillance of maternal morbidity/mortality since the number of cases is higher and the woman herself is able to provide information on the difficulties she faced and the long-term repercussions of the event. These repercussions, which may include sexual dysfunction, postpartum depression and posttraumatic stress disorder, may persist for prolonged periods of time, affecting women's quality of life and resulting in adverse effects to them and their babies.</p> <p>Objective</p> <p>The aims of the present study are to create a nationwide network of scientific cooperation to carry out surveillance and estimate the frequency of maternal near-miss cases, to perform a multicenter investigation into the quality of care for women with severe complications of pregnancy, and to carry out a multidimensional evaluation of these women up to six months.</p> <p>Methods/Design</p> <p>This project has two components: a multicenter, cross-sectional study to be implemented in 27 referral obstetric units in different geographical regions of Brazil, and a concurrent cohort study of multidimensional analysis. Over 12 months, investigators will perform prospective surveillance to identify all maternal complications. The population of the cross-sectional component will consist of all women surviving potentially life-threatening conditions (severe maternal complications) or life-threatening conditions (the maternal near miss criteria) and maternal deaths according to the new WHO definition and criteria. Data analysis will be performed in case subgroups according to the moment of occurrence and determining cause. Frequencies of near-miss and other severe maternal morbidity and the association between organ dysfunction and maternal death will be estimated. A proportion of cases identified in the cross-sectional study will comprise the cohort of women for the multidimensional analysis. Various aspects of the lives of women surviving severe maternal complications will be evaluated 3 and 6 months after the event and compared to a group of women who suffered no severe complications in pregnancy. Previously validated questionnaires will be used in the interviews to assess reproductive function, posttraumatic stress, functional capacity, quality of life, sexual function, postpartum depression and infant development.</p

Perceptions of postnatal depression across countries and cultures: from a TransCultural Study of PostNatal Depression (TCS-PND)

Objectives The qualitative study was conducted within the international “Transcultural study of postnatal depression (PND)” in 17 centres located in 13 different countries. The aim was to explore perceptions of PND by lay and professional key informants, specifically regarding description of symptoms, awareness of this pathology and of possible care. Methods Broad areas of inquiry and open-ended probes were developed by the TCS-PND research group during international workshops to obtain data comparable between countries on perceptions of PND. A non-random convenience sampling method was used to recruit postpartum mothers for focus groups, and fathers and grandmothers for interviews. Influential healthcare planners and clinicians were interviewed as professional key informants in each centre. Within sites, transcripts of focus groups and interviews underwent a process of text analysis in the original language until exhaustive theme extraction was achieved. Themes (in English) from all the centres were combined into broader categories and after consensus discussions these categories were revalidated. Results and discussion Qualitative data were supplemented in each centre with sociodemographic data to address the issues of: (i) whether perceptions of PND are related to some specific cultural perception of mental heath and/or of status of parenthood and (ii) how high or low levels of general care and specificity of health policy relate to differences in perception of needs for care. Data collected using the same probes and methodology in different countries and cultures has enabled a comparative analysis of perceptions of PND. In addition it has shown that, although not described with the same words, PND is a well-recognised condition by recent mothers in all countries in this study. Data on focus groups and interviews from selected countries are given in the following abstracts to illustrate some similarities and differences in perceptions between countries

Postpartum psychiatric disorders

Pregnancy is a complex and vulnerable period that presents a number of challenges to women, including the development of postpartum psychiatric disorders (PPDs). These disorders can include postpartum depression and anxiety, which are relatively common, and the rare but more severe postpartum psychosis. In addition, other PPDs can include obsessive–compulsive disorder, post-traumatic stress disorder and eating disorders. The aetiology of PPDs is a complex interaction of psychological, social and biological factors, in addition to genetic and environmental factors. The goals of treating postpartum mental illness are reducing maternal symptoms and supporting maternal–child and family functioning. Women and their families should receive psychoeducation about the illness, including evidence-based discussions about the risks and benefits of each treatment option. Developing effective strategies in global settings that allow the delivery of targeted therapies to women with different clinical phenotypes and severities of PPDs is essential

Trace Pair Filtering for Separation of Upgoing and Downgoing Waves in Vsp (Vertical Seismic Profile) Filtrage à deux canaux pour la séparation des ondes montantes et descendantes en PSV (Profil Sismique Vertical)

Most multichannel algorithms used for separation of upgoing and downgoing waves in VSPs assume depth-stationarity of the signal on all the traces used in the separation filter. However, if the depth-window of the filters becomes too large (100-200 m) signal stationarity cannot be assumed. On the other hand, stationarity is a physically reasonable assumption for two neighbouring probe locations (5-20 m). A comparison is made of three algorithms used for the separation of upgoing and downgoing waves, that require only two adjacent traces and their first arrival times. They are independent of in-depth trace-spacing, provided there are no geological discontinuities between adjacent traces. The first approach (near-theoretical solution) operates in the frequency domain. A system of two equations and two unknowns is solved for every frequency within the best coherencebandwidth. The second approach (simple solution) is a delay-and-sum, and subtraction filter based on the semblance of the signals. The third approach (Wiener solution) uses a Wiener filter to predict the strongest wave, which is generally the downgoing wave. The upgoing wave is then obtained by subtracting the estimated downgoing wave from the full wave record. A second application of the Wiener filter on the upgoing waves can enhance them. The near-theoretical solution and the simple solution are narrow-pass velocity filters and are applicable to zero-offset VSPs. The simple solution is suitable for noisy data. When the signal-to-noise ratio is high, the best results are obtained using the near-theoretical solution. The velocity-filter bandwidth can be increased in the Wiener solution, so that it can also be used in case of dipping reflectors or offset VSPs. The Wiener solution is suitable for noisy data, and its effectiveness can be increased by using a reference trace. The performance of these algorithms on synthetic and field data is evaluated in terms of signal-to-noise ratio, detection of upgoing waves and sensitivity to first arrival time estimates. La plupart des algorithmes utilisés pour la séparation des ondes montantes et descendantes en PSV font l'hypothèse que le signal est stationnaire en fonction de la profondeur sur toutes les traces utilisées dans le filtre de séparation. Cependant, le signal ne peut plus être supposé stationnaire lorsque les filtres sont appliqués sur une fenêtre en profondeur trop grande (100-200 m). Par contre, la stationnarité du signal peut être considérée comme une hypothèse physiquement raisonnable pour deux positions voisines de la sonde (5-20 m). Cet article présente trois algorithmes pour la séparation des ondes montantes et descendantes, qui ne nécessitent que deux traces adjacentes et les temps de première arrivée sur chacune des traces. Dans la mesure où il n'existe pas de discontinuités géologiques entre ces traces, les algorithmes sont indépendants de la distance en profondeur entre traces. Le premier algorithme (solution pseudo-théorique) travaille dans le domaine fréquentiel. La séparation des ondes est obtenue par résolution d'un système de deux équations à deux inconnues pour chaque fréquence. Cette opération est effectuée dans la bande passante correspondant à la meilleure cohérence. Le second algorithme (solution simple) réalise une addition et soustraction, basées sur la semblance des signaux, des traces décalées en temps. Le troisième algorithme (solution de Wiener) utilise un filtre de Wiener pour prédire le champ d'ondes le plus énergique, qui correspond généralement aux ondes descendantes. Les ondes montantes sont ensuite obtenues par soustraction des ondes montantes estimées, au champ d'ondes total. Le filtre de Wiener peut être ensuite de nouveau appliqué aux ondes montantes de façon à les renforcer. La solution pseudo-théorique et la solution simple réalisent des filtres en vitesse apparente de bande passante étroite, et sont applicables aux PSV sans déport. La solution simple est bien adaptée aux données bruitées. Lorsque le rapport signal sur bruit est bon, les meilleurs résultats sont obtenus avec la solution pseudo-théorique. La bande passante du filtre en vitesse apparente peut être élargie dans la solution de Wiener. En conséquence, cet algorithme peut être également utilisé en cas de réflecteurs pentés ou de PSV avec déport. La solution de Wiener est bien adaptée aux données bruitées, et son efficacité peut être augmentée par l'utilisation d'une trace de référence. La performance de ces algorithmes sur données synthétiques et réelles est évaluée en termes de rapport signal sur bruit, de détection des ondes montantes et de sensibilité à la précision de temps de première arrivée