167 research outputs found

    Structure Dependence of Kinetic and Thermodynamic Parameters in Singlet Fission Processes

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    Singlet fission—whereby one absorbed photon generates two coupled triplet excitons—is a key process for increasing the efficiency of optoelectronic devices by overcoming the Shockley–Queisser limit. A crucial parameter is the rate of dissociation of the coupled triplets, as this limits the number of free triplets subsequently available for harvesting and ultimately the overall efficiency of the device. Here we present an analysis of the thermodynamic and kinetic parameters for this process in parallel and herringbone dimers measured by electron paramagnetic resonance spectroscopy in coevaporated films of pentacene in p-terphenyl. The rate of dissociation is higher for parallel dimers than for their herringbone counterparts, as is the rate of recombination to the ground state. DFT calculations, which provide the magnitude of the electronic coupling as well as the distribution of molecular orbitals for each geometry, suggest that weaker triplet coupling in the parallel dimer is the driving force for faster dissociation. Conversely, localization of the molecular orbitals and a stronger triplet–triplet interaction result in slower dissociation and recombination. The identification and understanding of how the intermolecular geometry promotes efficient triplet dissociation provide the basis for control of triplet coupling and thereby the optimization of one important parameter of device performance

    Évaluation des compĂ©tences pratiques en fin de deuxiĂšme cycle des Ă©tudes mĂ©dicales : exemple du drainage du bas appareil urinaire

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    IntroductionLe drainage vĂ©sical peut, mal pratiquĂ©, ĂȘtre iatrogĂšne en se compliquant notamment d’infections et de traumatismes de l’appareil urinaire. Cette Ă©tude a pour objectif de dĂ©terminer la capacitĂ© des Ă©tudiants en mĂ©decine de fin de deuxiĂšme cycle Ă  pratiquer les diffĂ©rents moyens de drainage des urines. MatĂ©riel et mĂ©thodes Entre janvier et mars 2007, un questionnaire d’autoĂ©valuation des compĂ©tences de drainage urinaire a Ă©tĂ© envoyĂ© par mail Ă  un Ă©chantillon reprĂ©sentatif d’étudiants en mĂ©decine en derniĂšre annĂ©e d’externat, soit deux mois avant l’épreuve de l’examen national classant. RĂ©sultats Deux cent soixante-dix-sept rĂ©ponses ont Ă©tĂ© reçues et analysĂ©es. Soixante-douze Ă©tudiants (26 %) jugeaient qu’ils maĂźtrisaient le cathĂ©tĂ©risme urĂ©trovĂ©sical chez l’homme et 106 Ă©tudiants (38,3 %) chez la femme Ă  la fin de leur externat. Soixante et onze Ă©tudiants sur les 277 (25,5 %) avaient effectuĂ© un stage en urologie au cours de leur cursus. Parmi eux, 53,5 % estimaient acquis le sondage Ă  demeure (SAD) chez l’homme (p < 0,001) et 39 (54,9 %) chez la femme (p < 0,001). Soixante-treize Ă©tudiants (26,4 %) estimaient qu’ils maĂźtrisaient le sondage minute d’une femme ou d’un homme et un seul considĂ©rait la pose de cathĂ©ter sus-pubien comme acquis. Conclusion L’apprentissage des gestes de drainage urinaire est enseignĂ© de façon inappropriĂ©e au cours des Ă©tudes mĂ©dicales puisque de jeunes mĂ©decins se sentent incapables de les reproduire au terme de leur externat. Cela est critiquable, car le sondage doit pouvoir ĂȘtre rĂ©alisĂ© par tous mĂ©decins non urologues dans leur pratique quotidienne, notamment en terrain hospitalier. Cette Ă©tude doit mener Ă  une rĂ©flexion sur l’amĂ©lioration de l’enseignement des gestes pratiques mĂ©dicaux essentiels pendant l’externat

    Evidence-based medicine et étudiants en médecine français : état des lieux

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    IntroductionL’Evidence-Based Medicine (EBM) est indispensable Ă  l’exercice de la mĂ©decine. Notre objectif Ă©tait de connaĂźtre quel en Ă©tait son niveau de connaissance par les Ă©tudiants français. MatĂ©riel et MĂ©thodes Entre avril et mai 2008, un questionnaire a Ă©tĂ© envoyĂ© par courriel Ă  900 Ă©tudiants en derniĂšre annĂ©e du deuxiĂšme cycle des Ă©tudes mĂ©dicales participant Ă  des confĂ©rences publiques ou privĂ©es d’internat. RĂ©sultats Sur les 327 rĂ©ponses, 297 (91 %), 94 (29 %) et 85 (26 %) Ă©tudiants dĂ©claraient savoir lire, Ă©crire et parler l’anglais mĂ©dical. Quatre-vingt-dix Ă©tudiants (28 %) lisaient un article d’une revue mĂ©dicale française, une fois par mois et 43 (13 %) lisaient un article d’une revue mĂ©dicale internationale une fois par mois. Trois cent onze (95 %) connaissaient les bases de recherche mĂ©dicale sur Internet et 219 (67 %) les utilisaient. Vingt-quatre (7 %) avaient dĂ©jĂ  participĂ© Ă  la rĂ©daction d’un article mĂ©dical, sept (2 %) avait Ă©tĂ© co-auteurs. Deux cent soixante-douze (83 %) avait rĂ©alisĂ© une prĂ©sentation orale lors d’un staff mĂ©dical et trois (1 %) lors d’un congrĂšs. Enfin, 237 (73 %) comprenaient l’intĂ©rĂȘt de l’épreuve d’analyse critique d’article Ă  l’examen national classant (ECN) et 70 (21 %) pensaient y ĂȘtre prĂ©parĂ©s. Conclusion L’insuffisance de l’apprentissage de l’EBM est une des limites du systĂšme de formation français. L’introduction de la lecture critique d’article (LCA) Ă  l’ECN est un dĂ©but de rĂ©ponse concret Ă  ce problĂšme

    Double-J ureteral stent under local anesthesia for women

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    INTRODUCTION: Ureteral stent placement is a key urologic procedure used to manage ureteral obstructions. It is usually performed under general anesthesia (GA) with its inherent risks. The objective was to evaluate safety, feasibility and tolerance of ureteral stent placement under local anesthesia (LA) in women. MATERIALS AND METHODS: From January 2010 to January 2013, we prospectively and consecutively reviewed all female patients who had an urgent retrograde ureteral stent placement under LA. Only primary stent placements were included in the study. Pain was assessed after surgery by Visual Analog Scale (VAS) and pain and comfort assessment during stent placement were reported. We compared outcomes and tolerance with patients under general anesthesia (GA) matched by age and operatives indications during the same period. RESULTS: We included 36 patients (18 under LA and 18 under GA) with a mean age of 59.4 +/- 22.4 years. The mean operative time was 24.4 +/- 12.9 min and 18.8 +/- 6.5 min in LA group and GA group (p = 0.110), respectively. One patient needed GA due to a poor tolerance. The mean perioperative VAS scores under LA and GA were 5.89 +/-2.95 and 2.06 +/- 2.67 (p < 0.0001), respectively. There were no intraoperative complications in either group. The procedure was painful for 16 (88.8%) patients from the LA group and 9 (50%) patients would not accept to undergo this intervention under LA again. CONCLUSION: Ureteral stent placement under LA in women can be performed safely and effectively. However, this procedure is painful and should be proposed only to selected cases

    The Impact of the COVID-19 Pandemic on Healthy Lifestyle Behaviors and Perceived Mental and Physical Health of People Living with Non-Communicable Diseases: An International Cross-Sectional Survey

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    The huge burden and vulnerability imposed by non-communicable diseases (NCDs) during the COVID-19 pandemic highlighted how healthy lifestyle behaviors and the well-being of people living with NCDs need to be prioritized. The aim of our study is to better understand the impact of the COVID-19 pandemic on healthy lifestyle behaviors and perceived mental and physical health among adults living with NCDs, as compared to people without NCDs. We conducted a cross-sectional study using a global online survey through Qualtrics. Over four months, 3550 participants from 65 countries worldwide responded to the survey. The study included 3079 surveys with no missing data (complete survey responses) that were used for analysis. People with NCDs were more likely to report statistically significant worsening physical health (p = 0.001) and statistically insignificant worsening mental health (p = 0.354) when compared to pre-pandemic levels. They reported lower rates of smoking during the pandemic than those without NCDs, and a statistically significant (p < 0.001) relationship was found between weight gain and NCDs. Therefore, the perceived physical and mental health, including changes in body weight and tobacco consumption, of people with NCDs were significantly impacted during the pandemic. In conclusion, this study indicates that the pandemic had a significant impact on perceived physical and mental health, changes in body weight, and tobacco consumption among people with NCDs

    A high-resolution map of the Nile tilapia genome: a resource for studying cichlids and other percomorphs

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    Background: The Nile tilapia (Oreochromis niloticus) is the second most farmed fish species worldwide. It is also an important model for studies of fish physiology, particularly because of its broad tolerance to an array of environments. It is a good model to study evolutionary mechanisms in vertebrates, because of its close relationship to haplochromine cichlids, which have undergone rapid speciation in East Africa. The existing genomic resources for Nile tilapia include a genetic map, BAC end sequences and ESTs, but comparative genome analysis and maps of quantitative trait loci (QTL) are still limited. Results: We have constructed a high-resolution radiation hybrid (RH) panel for the Nile tilapia and genotyped 1358 markers consisting of 850 genes, 82 markers corresponding to BAC end sequences, 154 microsatellites and 272 single nucleotide polymorphisms (SNPs). From these, 1296 markers could be associated in 81 RH groups, while 62 were not linked. The total size of the RH map is 34,084 cR3500 and 937,310 kb. It covers 88% of the entire genome with an estimated inter-marker distance of 742 Kb. Mapping of microsatellites enabled integration to the genetic map. We have merged LG8 and LG24 into a single linkage group, and confirmed that LG16-LG21 are also merged. The orientation and association of RH groups to each chromosome and LG was confirmed by chromosomal in situ hybridizations (FISH) of 55 BACs. Fifty RH groups were localized on the 22 chromosomes while 31 remained small orphan groups. Synteny relationships were determined between Nile tilapia, stickleback, medaka and pufferfish. Conclusion:The RH map and associated FISH map provide a valuable gene-ordered resource for gene mapping and QTL studies. All genetic linkage groups with their corresponding RH groups now have a corresponding chromosome which can be identified in the karyotype. Placement of conserved segments indicated that multiple inter-chromosomal rearrangements have occurred between Nile tilapia and the other model fishes. These maps represent a valuable resource for organizing the forthcoming genome sequence of Nile tilapia, and provide a foundation for evolutionary studies of East African cichlid fishes.Additional co-authors: Thomas D Kocher, Catherine Ozouf-Costaz, Jean Francois Baroiller and Francis Galiber

    Identifying structure-absorption relationships and predicting absorption strength of non-fullerene acceptors for organic photovoltaics

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    Non-fullerene acceptors (NFAs) are excellent light harvesters, yet the origin of their high optical extinction is not well understood. In this work, we investigate the absorption strength of NFAs by building a database of time-dependent density functional theory (TDDFT) calculations of ∌500 π-conjugated molecules. The calculations are first validated by comparison with experimental measurements in solution and solid state using common fullerene and non-fullerene acceptors. We find that the molar extinction coefficient (Δd,max) shows reasonable agreement between calculation in vacuum and experiment for molecules in solution, highlighting the effectiveness of TDDFT for predicting optical properties of organic π-conjugated molecules. We then perform a statistical analysis based on molecular descriptors to identify which features are important in defining the absorption strength. This allows us to identify structural features that are correlated with high absorption strength in NFAs and could be used to guide molecular design: highly absorbing NFAs should possess a planar, linear, and fully conjugated molecular backbone with highly polarisable heteroatoms. We then exploit a random decision forest algorithm to draw predictions for Δd,max using a computational framework based on extended tight-binding Hamiltonians, which shows reasonable predicting accuracy with lower computational cost than TDDFT. This work provides a general understanding of the relationship between molecular structure and absorption strength in π-conjugated organic molecules, including NFAs, while introducing predictive machine-learning models of low computational cost

    Clinical relevance of genetic instability in prostatic cells obtained by prostatic massage in early prostate cancer

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    We investigated whether genetic lesions such as loss of heterozygosity (LOH) are detected in prostatic cells obtained by prostatic massage during early diagnosis of prostate cancer (CaP) and discussed their clinical relevance. Blood and first urine voided after prostatic massage were collected in 99 patients with total prostate-specific antigen (PSA) between 4 and 10 ng ml−1, prior to prostate biopsies. Presence of prostatic cells was confirmed by quantitative RT–PCR analysis of PSA mRNA. Genomic DNA was analysed for LOH on six chromosomal regions. One or more allelic deletions were found in prostatic fluid from 57 patients analysed, of whom 33 (58%) had CaP. Sensitivity and specificity of LOH detection and PSA free to total ratio <15% for positive biopsy were respectively 86.7 and 44% (P=0.002) for LOH, and 55 and 74% (P=0.006) for PSA ratio <15%. Analysis of LOH obtained from prostatic tumours revealed similar patterns compared to prostatic fluid cells in 86% of cases, confirming its accuracy. The presence of LOH of urinary prostatic cells obtained after prostatic massage is significantly associated with CaP on biopsy and may potentially help to identify a set of patients who are candidates for further prostate biopsies
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