992 resultados para hyperpolarized, xenon, Polarizer, GE180, T1 xenon
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Abstract Background: Extrapulmonary tuberculosis (EPTB) constitutes about 10% to 20% of all cases of tuberculosis in immunocompetent patients and more than 50% of the cases in HIV-positive individuals worldwide. Little information is available on the clonal diversity of Mycobacterium species in Ethiopia from EPTB. Methods: This study was carried out on smear-negative EPTB patients to molecularly characterize Mycobacterium tuberculosis complex strains. A questionnaire, smear staining, culture, deletion typing, and spoligotyping were employed. Results: The proportional distribution of EPTB and isolates did not vary substantially (p > 0.05) amongst the socio-demographic parameters considered in the current investigation. Out of 98 fine needle aspirates processed for culture, 36.7% (36/98) were positive for mycobacterial growth. Further speciation of those culture-positive isolates showed that 88.9% were M. tuberculosis and the remaining could be non-tuberculous mycobacterial species. Spoligotyping revealed 16 clusters out of which 2 were new to the SITVIT database. The most dominant spoligotypes were SIT54, SIT53, and SIT149 in decreasing order. SIT54, SIT134, SIT173, SIT345, SIT357, SIT926, SIT91088, and SIT1580 were reported for the first time in Ethiopia. The family with the highest frequency identified was M. tuberculosis family T1, followed by family 33. Most of the strains belonged to Euro-American (61.4%) and Indo-Oceanic (36.3%) lineages. Conclusions: The present study shows the importance of M. tuberculosis as a major cause of EPTB in the study area. Moreover, the majority of isolates of M. tuberculosis were found in clusters, suggesting the possibility of the existence of recent transmission. This warrants strengthening of the control programs for EPTB in the study area.
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BACKGROUND Little is known about the healthcare process for patients with prostate cancer, mainly because hospital-based data are not routinely published. The main objective of this study was to determine the clinical characteristics of prostate cancer patients, the, diagnostic process and the factors that might influence intervals from consultation to diagnosis and from diagnosis to treatment. METHODS We conducted a multicentre, cohort study in seven hospitals in Spain. Patients' characteristics and diagnostic and therapeutic variables were obtained from hospital records and patients' structured interviews from October 2010 to September 2011. We used a multilevel logistic regression model to examine the association between patient care intervals and various variables influencing these intervals (age, BMI, educational level, ECOG, first specialist consultation, tumour stage, PSA, Gleason score, and presence of symptoms) and calculated the odds ratio (OR) and the interquartile range (IQR). To estimate the random inter-hospital variability, we used the median odds ratio (MOR). RESULTS 470 patients with prostate cancer were included. Mean age was 67.8 (SD: 7.6) years and 75.4 % were physically active. Tumour size was classified as T1 in 41.0 % and as T2 in 40 % of patients, their median Gleason score was 6.0 (IQR:1.0), and 36.1 % had low risk cancer according to the D'Amico classification. The median interval between first consultation and diagnosis was 89 days (IQR:123.5) with no statistically significant variability between centres. Presence of symptoms was associated with a significantly longer interval between first consultation and diagnosis than no symptoms (OR:1.93, 95%CI 1.29-2.89). The median time between diagnosis and first treatment (therapeutic interval) was 75.0 days (IQR:78.0) and significant variability between centres was found (MOR:2.16, 95%CI 1.45-4.87). This interval was shorter in patients with a high PSA value (p = 0.012) and a high Gleason score (p = 0.026). CONCLUSIONS Most incident prostate cancer patients in Spain are diagnosed at an early stage of an adenocarcinoma. The period to complete the diagnostic process is approximately three months whereas the therapeutic intervals vary among centres and are shorter for patients with a worse prognosis. The presence of prostatic symptoms, PSA level, and Gleason score influence all the clinical intervals differently.
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BACKGROUND Fragile X syndrome (FXS) is an inherited neurodevelopmental condition characterised by behavioural, learning disabilities, physical and neurological symptoms. In addition, an important degree of comorbidity with autism is also present. Considered a rare disorder affecting both genders, it first becomes apparent during childhood with displays of language delay and behavioural symptoms.Main aim: To show whether the combination of 10 mg/kg/day of ascorbic acid (vitamin C) and 10 mg/kg/day of α-tocopherol (vitamin E) reduces FXS symptoms among male patients ages 6 to 18 years compared to placebo treatment, as measured on the standardized rating scales at baseline, and after 12 and 24 weeks of treatment.Secondary aims: To assess the safety of the treatment. To describe behavioural and cognitive changes revealed by the Developmental Behaviour Checklist Short Form (DBC-P24) and the Wechsler Intelligence Scale for Children-Revised. To describe metabolic changes revealed by blood analysis. To measure treatment impact at home and in an academic environment. METHODS/DESIGN A phase II randomized, double-blind pilot clinical trial. SCOPE male children and adolescents diagnosed with FXS, in accordance with a standardized molecular biology test, who met all the inclusion criteria and none of the exclusion criteria. INSTRUMENTATION clinical data, blood analysis, Wechsler Intelligence Scale for Children-Revised, Conners parent and teacher rating scale scores and the DBC-P24 results will be obtained at the baseline (t0). Follow up examinations will take place at 12 weeks (t1) and 24 weeks (t2) of treatment. DISCUSSION A limited number of clinical trials have been carried out on children with FXS, but more are necessary as current treatment possibilities are insufficient and often provoke side effects. In the present study, we sought to overcome possible methodological problems by conducting a phase II pilot study in order to calculate the relevant statistical parameters and determine the safety of the proposed treatment. The results will provide evidence to improve hyperactivity control and reduce behavioural and learning problems using ascorbic acid (vitamin C) and α-tocopherol (vitamin E). The study protocol was approved by the Regional Government Committee for Clinical Trials in Andalusia and the Spanish agency for drugs and health products. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT01329770 (29 March 2011).
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OBJECTIVE: The objective of our study was to report the MRI findings in dorsal fractures of the triquetrum, with an emphasis on dorsal carpal ligament injuries. MATERIALS AND METHODS: A total of 21 patients (16 men, five women; mean age, 41.9 years) with acute or subacute (≤ 6 weeks) dorsal triquetral fractures on radiography and MRI were included in this two-center retrospective study. MRI of the wrist was performed on 3-T units with transverse T1-weighted, coronal or transverse (or both) fat-suppressed T2weighted, transverse gadolinium-enhanced fat-suppressed T1-weighted turbo spin-echo, and 3D gadolinium-enhanced fat-suppressed T1-weighted gradient-recalled echo sequences. Three musculoskeletal radiologists evaluated the ulnar styloid process index (USPI) on radiographs and the following MRI features: fracture pattern (types 1-6), bone fragment size and displacement, bone marrow edema distribution, and dorsal carpal ligament tears. RESULTS: Eight type 1, one type 2, six type 3, five type 4, and one type 5 fractures were identified. These fractures were associated with 14 (66.7%), 17 (81.0%), and 16 (76.2%) tears of the dorsal radiocarpal, ulnotriquetral, and intercarpal ligaments, respectively. There was no correlation between bone marrow edema distribution and dorsal carpal ligament injuries (all p > 0.05). The mean (± SD) bone fragment volume and displacement were 205 ± 157 mm(3) and 1.0 ± 1.1 mm, respectively. The mean USPI was 0.21 ± 0.10. CONCLUSION: Dorsal fractures of the triquetrum are frequently associated with dorsal carpal ligament injuries. Bone marrow edema distribution is not correlated with these ligament tears.
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Age and sex have been identified as predictors of outcome in malignant melanoma (MM). This aim of this multicentre, cross-sectional study was to analyse the role of age and sex as explanatory variables for the diagnosis of thin MM. A total of 2430 patients with MM were recruited. Cases of in situ-T1 MM were more frequent than T2-T4 MM (56.26% vs. 43.74%). Breslow thickness increased throughout decades of life (analysis of variance (ANOVA) p < 0.001), with a weak correlation between Breslow thickness and patient's age (r   = 0.202, p < 0.001). Breslow thickness was significantly less in women (1.79 vs. 2.38 mm, p = 0.0001). Binary logistic regression showed a significant (p < 0.001) odds ratio for age 0-29 years (1.18), and 30-59 years (1.16), and for women (1.09). Age and sex explained 3.64% of the variation observed in Tis-T1 frequency (R2 = 0.0364). Age and sex appear to explain a low percentage of the variation in the early detection of MM.
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On the basis of MRI examinations in 88 neonates and infants with perinatal asphyxia, we defined 6 different patterns on T2-weighted images: pattern A--scattered hyperintensity of both hemispheres of the telencephalon with blurred border zones between cortex and white matter, indicating diffuse brain injury; pattern B--parasagittal hyperintensity extending into the corona radiata, corresponding to the watershed zones; pattern C--hyper- and hypointense lesions in thalamus and basal ganglia, which relate to haemorrhagic necrosis or iron deposition in these areas; pattern D--periventricular hyperintensity, mainly along the lateral ventricles, i.e. periventricular leukomalacia (PVL), originating from the matrix zone; pattern E--small multifocal lesions varying from hyper--to hypointense, interpreted as necrosis and haemorrhage; pattern F--periventricular centrifugal hypointense stripes in the centrum semiovale and deep white matter of the frontal and occipital lobes. Contrast was effectively inverted on T1-weighted images. Patterns A, B and C were found in 17%, 25% and 37% of patients, and patterns D, E and F in 19%, 17% and 35%, respectively. In 49 patients a combination of patterns was observed, but 30% of the initial images were normal. At follow-up, persistent abnormalities were seen in all children with patterns A and D, but in only 52% of those with pattern C. Myelination was retarded most often in patients with diffuse brain injury and PVL (patterns A and D).
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The renin-angiotensin system is a major contributor to the pathophysiology of cardiovascular diseases such as congestive heart failure and hypertension. Antagonizing angiotensin (Ang) II at the receptor site may produce fewer side effects than inhibition of the promiscuous converting enzyme. The present study was designed to assess in healthy human subjects the effect of LRB081, a new orally active AT1-receptor antagonist, on the pressor action of exogenous Ang II. At the same time, plasma hormones and drug levels were monitored. At 1-week intervals and in a double-blind randomized fashion, 8 male volunteers received three doses of LRB081 (10, 40, and 80 mg) and placebo. Blood pressure (BP) was measured at a finger by photoplethysmograph. The peak BP response to intravenous injection of a standard dose of Ang II was determined before and for < or = 24 h after administration of an oral dose of LRB081 or placebo. After drug administration, the blood BP response to Ang II was expressed in percent of the response before drug administration. At the same time, plasma renin activity (PRA), Ang II, aldosterone, catecholamine (radioassays), and drug levels (by high-performance liquid chromatography) were monitored. After LRB081 administration, a dose dependent inhibition of the BP response to Ang II was observed. Maximal inhibition of the systolic BP response was 54 +/- 3 (mean +/- SEM), 63 +/- 2, and 93 +/- 1% with 10, 40, and 80 mg LRB081, respectively. The time to peak was 3 h for 6 subjects and 4 and 6 h for 2 others. Preliminary plasma half-life (t1/2) was calculated at 2 h. With the highest dose, the inhibition remained significant for 24 h (31 +/- 5%, p < 0.05). Maximal BP-blocking effect and maximal plasma drug level coincided, suggesting that the unmetabolized LRB081 is responsible for the antagonistic effect. PRA and Ang II increased dose dependently after LRB081 intake. Aldosterone, epinephrine, and norepinephrine concentrations remained unchanged. No clinically significant adverse reaction was observed during the study. LRB081 is a well-tolerated, orally active, potent, and long-acting Ang II receptor antagonist. Unlike in the case of losartan, no active metabolite of LRB081 has been shown to be responsible for the main effects.
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Résumé : Objectif: Analyse d'un traitement de chimiothérapie à base de cisplatine de type néoadjuvant en comparaison à un traitement de radio-chimiothérapie suivi de la résection chirurgicale chez des patients présentant un carcinome pulmonaire non à petites cellules de stade Ill (N2) prouvé histologiquement par médiastinoscopie. Evaluation de la morbidité postopératoire, du down-staging ganglionnaire, des taux de survie globale et sans récidive ainsi que du site de récidive. Matériel et méthodes : 82 patients ont été inclus dans l'étude entre Janvier 1994 et Juin 2003, parmi eux 36 ont été traités avec une chimiothérapie néoadjuvante à base de cisplatine et doxétacel (groupe l). Les autres 46 patients ont été soumis à une radio-chimiothérapie néoadjuvante avec administration de 44 Gy (groupe II), soit de façon séquentielle (25 cas) soit concomitante (21 cas). Dans tous les cas des métastases à distance ont été exclues par une évaluation préopératoire comprenant une scintigraphie osseuse, un Ct scan thoraco-abdominal, ou un examen PET scan ainsi qu'une IRM cérébrale. La médiastinoscopie effectuée avant le traitement d'induction chez la totalité des patients, de même que la résection chirurgicale de la tumeur pulmonaire et la lymphadenectomie médiastinale ont été effectuées par le même chirurgien. Résultats : La tumeur pulmonaire était de stade Ti à T2 dans respectivement 47% et 28% des patients des groupes (e II, T3 dans 45% et 41% et T4 dans 8% et 31% des cas. Le type de résection effectué (lobectomie, lobectomie en manchon, pneumonectomie) était comparable dans les deux collectifs (p=0.03) Le taux de mortalité postopératoire à 90 jours était de respectivement 3% et 4 "Vo (p=0.6). Une résection complète (RO) a pu être obtenue dans 92% et 94% des cas (p=0.6) avec un downstaging ganglionnaire médiastinal dans 61% et 78% des patients respectivement (p<0.001). Les taux de survie globale à 5 ans et de survie sans récidive à 5 ans s'élevaient à 40% et à 36% respectivement, sans différence significative entre des tumeurs de stade Ti à T3 et T4. Le taux de survie globale n'était pas significativement différent entre les deux modalités de traitement d'induction, toutefois après radio-chimiothérapie on observait une plus longue survie sans récidive (p.0.04). Il n'y avait par ailleurs pas de différence significative, en termes de morbidité post-opératoire, résecabilité, downstaging ganglionnaire, survie globale et sans récidive, entre les patients traités par radio-chimiothérapie séquentielle ou concomitante. Conclusions : En cas de carcinome pulmonaire non à petites cellules de stade III (N2) un traitement d'induction par radio chimiothérapie suivi de la résection chirurgicale est associé avec un meilleur downstaqing médiastinal ainsi qu'une plus longue survie sans récidive en comparaison au traitement d'induction par chimiothérapie seule. Abstract : Objective: Comparison of prospectively treated patients with neoadjuvant cisplatin-based chemotherapy vs radiochemotherapy followed by resection for mediastinoscopically proven stage III NZ non-small cell lung cancer with respect to postoperative morbidity, pathological nodal downstaging, overall and disease-free survival, and site of recurrence. Methods: Eighty-two patients were enrolled between January 1994 to June 2003, 36 had cisplatin and doxetacel-based chemotherapy (group I) and 46 cisplatin-based radiochemotherapy up to 44 Gy (group II), either as sequential (25 patients) or concomitant (21 patients) treatment. All patients had evaluation of absence of distant metastases by bone scintigraphy, thoracoabdominal CT scan or PET scan, and brain MRI, and all underwent pre-induction mediastinoscopy, resection and mediastinal lymph node dissection by the same surgeon. Results: Group I and II comprised T1/2 tumors in 47 and 28%, 13 tumors in 45 and 41%, and 14 tumors in 8 and 31% of the patients, respectively (P=0.03). There was a similar distribution of the extent of resection (lobectomy, sleeve lobectomy, left and right pneumonectomy) in both groups (P=0.9). Group I and II revealed a postoperative 90-d mortality of 3 and 4% (P=0.6), a RO-resection rate of 92 and 94% (P=0.9), and a pathological mediastinal downstaging in 61 and 78% of the patients (P<0.01), respectively. 5y-overall survival and disease-free survival of all patients were 40 and 36%, respectively, without significant difference between T1-3 and T4 tumors. There was no significant difference in overall survival rate in either induction regimens, however, radiochemotherapy was associated with a longer disease-free survival than chemotherapy (P=0.04). There was no significant difference between concurrent vs sequential radiochemotherapy with respect to postoperative morbidity, resectability, pathological nodal downstaging, survival and disease-free survival. Conclusions: Neoadjuvant cisplatin-based radiochemotherapy was associated with a similar postoperative mortality, an increased pathological nodal downstaging and a better disease-free survival as compared to cisplatin doxetacel-based chemotherapy in patients with stage III (N2) NSCLC although a higher number of 14 tumors were admitted to radiochemotherapy.
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PURPOSE: To compare the apparent diffusion coefficient (ADC) values of malignant liver lesions on diffusion-weighted MRI (DWI) before and after successful radiofrequency ablation (RF ablation). MATERIALS AND METHODS: Thirty-two patients with 43 malignant liver lesions (23/20: metastases/hepatocellular carcinomas (HCC)) underwent liver MRI (3.0T) before (<1month) and after RF ablation (at 1, 3 and 6months) using T2-, gadolinium-enhanced T1- and DWI-weighted MR sequences. Jointly, two radiologists prospectively measured ADCs for each lesion by means of two different regions of interest (ROIs), first including the whole lesion and secondly the area with the visibly most restricted diffusion (MRDA) on ADC map. Changes of ADCs were evaluated with ANOVA and Dunnett tests. RESULTS: Thirty-one patients were successfully treated, while one patient was excluded due to focal recurrence. In metastases (n=22), the ADC in the whole lesion and in MRDA showed an up-and-down evolution. In HCC (n=20), the evolution of ADC was more complex, but with significantly higher values (p=0.013) at 1 and 6months after RF ablation. CONCLUSION: The ADC values of malignant liver lesions successfully treated by RF ablation show a predictable evolution and may help radiologists to monitor tumor response after treatment.
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Background: New ways of representing diffusion data emerged recently and achieved to create structural connectivitymaps in healthy brains (Hagmann P et al. (2008)). These maps have the capacity to study alterations over the entire brain at the connection and network level. This is of high interest in complex disconnection diseases like schizophrenia. In this Pathology where multiple lines of evidence suggest the association of the pathology with abnormalities in neural circuitry and impaired structural connectivity, the diffusion imaging has been widely applied. Despite the large findings, most of the research using the diffusion just uses some scalar map derived from diffusion to show that some markers of white matter integrity are diminished in several areas of the brain (Kyriakopoulos M et al (2008)). Thanks to the structural connectionmatrix constructed by the whole brain tractography, we report in this work the network connectivity alterations in the schizophrenic patients. Methods: We investigated 13 schizophrenic patients as assessed by the DIGS (Diagnostic Interview for genetic studies, DSM IV criteria) and 13 healthy controls. We have got from each volunteer a DT-MRI as well as Qball imaging dataset and a high resolution anatomic T1 performed during the same session; with a 3 T clinical MRI scanner. The controls were matched on age, gender, handedness, and parental social economic-status. For all the subjects, a low resolution connection matrix is obtained by dividing the cortex into 66 gyral based ROIs. A higher resolution matrix is constructed using 250 ROIs as described in Hagmann P et al. (2008). These ROIs are respectively used jointly with the diffusion tractography to construct the high and low resolution densities connection matrices for each subject. In a first step the matrices of the groups are compared in term of connectivity, and not in term of density to check if the pathological group shows a loss of global connectivity. In this context the density connection matrices were binarized. As some local connectivity changes were also suspected, especially in frontal and temporal areas, we have also looked for the areas where the connectivity showed significant changes. Results: The statistical analysis revealed a significant loss of global connectivity in the schizophrenic's brains at level 5%. Furthermore, by constructing specific statistics which represent local connectivity within the anatomical regions (66 ROIs) using the data obtained by the finest resolution (250 ROIs) to improve the robustness, we found the regions that cause this significant loss of connectivity. The significance is observed after multiple testing corrections by the False Discovery Rate. Discussion: The detected regions are almost the same as those reported in the literature as the involved regions in schizophrenia. Most of the connectivity decreases are noted in both hemispheres in the fronto-frontal and temporo-temporal regions as well as some temporal ROIs with their adjacent ROIs in parietal and occipital lobes.
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From November 1992 to December 1997, 25 patients (inoperable or refusing cystectomy) were included in a prospective study to assess the feasibility, tolerance, and curative potential of accelerated radiotherapy (RT) and concomitant cisplatin. Median age was 74 years (range 49-86). Stage distribution was as follows: 1 T1, 10 T2, 8 T3, and 6 T4. Two patients had clinically positive pelvic nodes. The goal was to deliver a total dose of 40 Gy to the whole pelvis and bladder in 4 weeks using a concomitant boost of 20 Gy to the tumor or to the whole bladder during the third and fourth weeks (total dose 60 Gy), with daily cisplatin (6 mg/m(2)) before RT for patients with creatinine clearance > 50 ml/min. All but one patient completed the RT protocol. Daily cisplatin was successfully delivered in 18 patients. One patient presented with grade III ototoxicity. Diarrhea was scored grade III in two and grade IV in two patients. Acute urinary toxicity was scored grade III in one patient. Posttreatment late effects included bladder grade II and grade III in two patients and one patient, respectively; large bowel grade III in one; urethral grade III in one; and femoral head radionecrosis in one. Four-year overall and disease-specific survival rates were 23% and 35%, respectively. The latter was 60% for patients with T2 tumors. The 4-year actuarial locoregional control rate for all patients was 61%. In summary, accelerated RT and concomitant cisplatin is feasible with acceptable tolerance even in relatively old patients. Although outcome was better for patients with low-stage tumors, local control and survival rates appeared similar to those of standard RT schedules for a similar patient population.
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BACKGROUND: This study assesses the benefits of an individualized therapy (RECOS program) compared with the more general cognitive remediation therapy (CRT). METHODS: 138 participants took part with 65 randomized to CRT and 73 to RECOS. In the RECOS group, participants were directed towards one of five training modules (verbal memory, visuo-spatial memory and attention, working memory, selective attention or reasoning) corresponding to their key cognitive concern whereas the CRT group received a standard program. The main outcome was the total score on BADS (Behavioural Assessment of Dysexecutive Syndrome) and the secondary outcomes were: cognition (executive functions; selective attention; visuospatial memory and attention; verbal memory; working memory) and clinical measures (symptoms; insight; neurocognitive complaints; self-esteem). All outcomes were assessed at baseline (T1), week 12 (posttherapy, T2), and follow-up (week 36, i.e., 6months posttherapy, T3). RESULTS: No difference was shown for the main outcome. A significant improvement was found for BADS' profile score for RECOS at T2 and T3, and for CRT at T3. Change in BADS in the RECOS and CRT arms were not significantly different between T1 and T2 (+0.86, p=0.108), or between T1 and T3 (+0.36, p=0.540). Significant improvements were found in several secondary outcomes including cognition (executive functions, selective attention, verbal memory, and visuospatial abilities) and clinician measures (symptoms and awareness to be hampered by cognitive deficits in everyday) in both treatment arms following treatment. Self-esteem improved only in RECOS arm at T3, and working memory improved only in CRT arm at T2 and T3, but there were no differences in changes between arms. CONCLUSIONS: RECOS (specific remediation) and CRT (general remediation) globally showed similar efficacy in the present trial.
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This article presents the Antenatal Perceived Stress Inventory. The originality of this scale is to assess the impact of events experienced during pregnancy on the stress perceived by mothers. Scale validation was performed using data from 150 French-speaking nulliparous mothers and collected between 36 and 39 weeks of gestation (T1), and between 2 days (T2) and 6 weeks postpartum (T3). Factor analysis revealed a hierarchical three-factor structure that closely fit the data, including medical and obstetric risks/fetal health (F1), psychosocial changes (F2), and the prospect of childbirth (F3). The Antenatal Perceived Stress Inventory is a valid French prenatal stress scale with good psychometric properties.
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[1] We present new analytical data of major and trace elements for the geological MPI-DING glasses KL2-G, ML3B-G, StHs6/80-G, GOR128-G, GOR132-G, BM90/21-G, T1-G, and ATHO-G. Different analytical methods were used to obtain a large spectrum of major and trace element data, in particular, EPMA, SIMS, LA-ICPMS, and isotope dilution by TIMS and ICPMS. Altogether, more than 60 qualified geochemical laboratories worldwide contributed to the analyses, allowing us to present new reference and information values and their uncertainties ( at 95% confidence level) for up to 74 elements. We complied with the recommendations for the certification of geological reference materials by the International Association of Geoanalysts (IAG). The reference values were derived from the results of 16 independent techniques, including definitive ( isotope dilution) and comparative bulk ( e. g., INAA, ICPMS, SSMS) and microanalytical ( e. g., LA-ICPMS, SIMS, EPMA) methods. Agreement between two or more independent methods and the use of definitive methods provided traceability to the fullest extent possible. We also present new and recently published data for the isotopic compositions of H, B, Li, O, Ca, Sr, Nd, Hf, and Pb. The results were mainly obtained by high-precision bulk techniques, such as TIMS and MC-ICPMS. In addition, LA-ICPMS and SIMS isotope data of B, Li, and Pb are presented.
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A select-divide-and-conquer variational method to approximate configuration interaction (CI) is presented. Given an orthonormal set made up of occupied orbitals (Hartree-Fock or similar) and suitable correlation orbitals (natural or localized orbitals), a large N-electron target space S is split into subspaces S0,S1,S2,...,SR. S0, of dimension d0, contains all configurations K with attributes (energy contributions, etc.) above thresholds T0={T0egy, T0etc.}; the CI coefficients in S0 remain always free to vary. S1 accommodates KS with attributes above T1≤T0. An eigenproblem of dimension d0+d1 for S0+S 1 is solved first, after which the last d1 rows and columns are contracted into a single row and column, thus freezing the last d1 CI coefficients hereinafter. The process is repeated with successive Sj(j≥2) chosen so that corresponding CI matrices fit random access memory (RAM). Davidson's eigensolver is used R times. The final energy eigenvalue (lowest or excited one) is always above the corresponding exact eigenvalue in S. Threshold values {Tj;j=0, 1, 2,...,R} regulate accuracy; for large-dimensional S, high accuracy requires S 0+S1 to be solved outside RAM. From there on, however, usually a few Davidson iterations in RAM are needed for each step, so that Hamiltonian matrix-element evaluation becomes rate determining. One μhartree accuracy is achieved for an eigenproblem of order 24 × 106, involving 1.2 × 1012 nonzero matrix elements, and 8.4×109 Slater determinants