Your browser doesn't support javascript.
loading
Montrer: 20 | 50 | 100
Résultats 1 - 17 de 17
Filtrer
1.
Urolithiasis ; 51(1): 120, 2023 Oct 06.
Article de Anglais | MEDLINE | ID: mdl-37801124

RÉSUMÉ

This study is aimed to determine whether postoperative low dose computed tomography (LDCT) imaging is necessary after percutaneous nephrolithotomy (PCNL), or the surgeon's intraoperative assessment of residual fragments (RF) is sufficient and avoidance of postoperative imaging with reduction of radiation exposure can be achieved. Data of all 610 patients who underwent PCNL in prone position in our institution from February 2009 to September 2020 was collected. Parameters such as age, gender, BMI, ASA-Classification, stone related parameters and the surgeon's assessment of stone-free status were analyzed. The LDCT performed postoperatively was compared to the intraoperative assessment of the surgeon regarding RF. The mean age of patients was 52.82 years; the mean BMI was 28.18 kg/m2. In 418 cases, the surgeon made a clear statement about the presence of RF and postoperative LDCT was carried out. The discrepancy between the two methods (surgeon´s assessment vs. LDCT) was significant at p < 0.0001. The sensitivity, specificity, positive and negative predictive value of the surgeon when assessing RF were 24.05%, 99.45%, 98.28% and 50%. Stone free rate (SFR) after primary PCNL was 45.57%. The overall SFR at discharge was 96.23%. Although the surgeon´s assessment of RF was reliable, postoperative LDCT imaging should still be performed if endoscopic stone clearance is suspected due to the high false negative rate and the low negative predictive value. The optimal timing of postoperative imaging following PCNL remains unclear.


Sujet(s)
Calculs rénaux , Néphrolithotomie percutanée , Néphrostomie percutanée , Humains , Adulte d'âge moyen , Néphrolithotomie percutanée/effets indésirables , Néphrolithotomie percutanée/méthodes , Études rétrospectives , Calculs rénaux/imagerie diagnostique , Calculs rénaux/chirurgie , Calculs rénaux/étiologie , Tomodensitométrie , Valeur prédictive des tests , Résultat thérapeutique , Néphrostomie percutanée/effets indésirables , Néphrostomie percutanée/méthodes
2.
Urologe A ; 60(3): 331-336, 2021 Mar.
Article de Allemand | MEDLINE | ID: mdl-33559693

RÉSUMÉ

BACKGROUND: Surgery is challenging during the coronavirus disease 2019 (COVID-19) pandemic. This study aimed to investigate the preoperative severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) testing in elective and emergency surgery and to calculate the patient contacts during hospital stay. MATERIALS AND METHODS: All surgeries defined by the German procedural classification (starting with a 5) from 1 June until 29 November 2020 were retrospectively evaluated regarding the preoperative SARS-CoV­2 nasopharyngeal swab test. The results were then divided in emergency and elective surgeries. To show the personal contacts of the patients in a university hospital, we calculated the patient pathway within the department of urology and urosurgery for April 2020. Therefor we used the electronic patient records. RESULTS: Altogether 7745 surgical procedures in 5985 patients were performed, whereby 39 (0.5%) SARS-CoV­2 tests were positive. 2833 (37%) surgical procedures were emergency cases and 4912 (63%) were elective procedures. 25 (0.9%) of the emergency group and 14 (0.3%) of the elective surgeries had a positive SARS-CoV­2 test. The average number of contacts in the patient room was 12.83 (0-50) and 84.22 (0-249) at the ward level, not counting contacts with the clinic staff. CONCLUSIONS: Nearly 1% of the preoperative SARS-CoV­2 tests of either emergency or elective surgeries tested positive in the 6 months prior to November 2020. Although the risk of undetected SARS-CoV­2 infection appears to be low in terms of costs and personnel, preoperative screening is useful in high-risk areas to ensure further necessary surgeries, especially concerning cancer patients and to prevent virus spread in a hospital.


Sujet(s)
COVID-19 , Coronavirus , Dépistage de la COVID-19 , Humains , Pandémies , Études rétrospectives , SARS-CoV-2
3.
mSystems ; 6(1)2021 Feb 09.
Article de Anglais | MEDLINE | ID: mdl-33563780

RÉSUMÉ

Compound biodegradability tests with natural microbial communities form an important keystone in the ecological assessment of chemicals. However, biodegradability tests are frequently limited by a singular focus either on the chemical and potential transformation products or on the individual microbial species degrading the compound. Here, we investigated a methodology to simultaneously analyze community compositional changes and biomass growth on dosed test compound from flow cytometry (FCM) data coupled to machine-learned cell type recognition. We quantified the growth of freshwater microbial communities on a range of carbon dosages of three readily biodegradable reference compounds, phenol, 1-octanol, and benzoate, in comparison to three fragrances, methyl jasmonate, myrcene, and musk xylene (as a nonbiodegradable control). Compound mass balances with between 0.1 to 10 mg C · liter-1 phenol or 1-octanol, inferred from cell numbers, parent compound analysis, and CO2 evolution, as well as use of 14C-labeled compounds, showed between 6 and 25% mg C · mg C-1 substrate incorporation into biomass within 2 to 4 days and 25 to 45% released as CO2 In contrast, similar dosage of methyl jasmonate and myrcene supported slower (4 to 10 days) and less (2.6 to 6.6% mg C · mg C-1 with 4.9 to 22% CO2) community growth. Community compositions inferred from machine-learned cell type recognition and 16S rRNA amplicon sequencing showed substrate- and concentration-dependent changes, with visible enrichment of microbial subgroups already at 0.1 mg C · liter-1 phenol and 1-octanol. In general, community compositions were similar at the start and after the stationary phase of the microbial growth, except at the highest used substrate concentrations of 100 to 1,000 mg C · liter-1 Flow cytometry cell counting coupled to deconvolution of communities into subgroups is thus suitable to infer biodegradability of organic chemicals, permitting biomass balances and near-real-time assessment of relevant subgroup changes.IMPORTANCE The manifold effects of potentially toxic compounds on microbial communities are often difficult to discern. Some compounds may be transformed or completely degraded by few or multiple strains in the community, whereas others may present inhibitory effects. In this study, we benchmark a new method based on machine-learned microbial cell recognition to rapidly follow dynamic changes in aquatic communities. We further determine productive biodegradation upon dosing of a number of well-known readily biodegradable tester compounds at a variety of concentrations. Microbial community growth was quantified using flow cytometry, and the multiple cell parameters measured were used in parallel to deconvolute the community on the basis of similarity to previously standardized cell types. Biodegradation was further confirmed by chemical analysis, showing how distinct changes in specific populations correlate to degradation. The method holds great promise for near-real-time community composition changes and deduction of compound biodegradation in natural microbial communities.

4.
Urologe A ; 60(3): 306-317, 2021 Mar.
Article de Allemand | MEDLINE | ID: mdl-33559012

RÉSUMÉ

The coronavirus has challenged all medical systems worldwide. Herein both waves of COVID-19 (coronavirus disease 2019) in spring and autumn 2020 differ principally. Whereas Europe was hit by the first wave more or less unprepared, which was aggravated by the high virulence of COVID-19, the second wave is characterized by a much higher contagiosity of the virus with very high incidences. On the other hand the virus has attenuated, which is reflected by the significantly lower incidence-related mortality rate. However, the overall increasing number of infected patients represents again a great challenge for the medical management of the disease. France and Spain are doing better in comparison to Germany and Italy this time. The absolute number of deaths per week is higher than during the peak of the first wave. However, urologists in these countries have also experienced greater restrictions in their activities in the second shutdown than in Germany, where there is only a reduction of beds to between 75 and 90%. Mostly all levels are operated. Of importance for Germany, however, is the plateau on a high level for several weeks probably due to the reduced efficacy of a light lock-down. This finally resulted in a total lock-down in mid-December 2020. Subsequently in Germany some hospitals are also reaching their limits with similar consequences for the departments of urology facing a 50% reduction of beds and operating only level III and IV indications. Nevertheless, the management of urologic patients during the COVID-19 pandemic is carried out in Europa on a high standard. Therefor the risk of secondary harm to our patients is expected to be rather minimal in the long run.


Sujet(s)
COVID-19 , Urologie , Contrôle des maladies transmissibles , Europe , France , Allemagne/épidémiologie , Humains , Italie , Pandémies , SARS-CoV-2
5.
Urologe A ; 59(9): 1017-1025, 2020 Sep.
Article de Allemand | MEDLINE | ID: mdl-32533201

RÉSUMÉ

BACKGROUND: Percutaneous access to the renal pelvis still remains the most difficult step before nephrolitholapaxy (PCNL). New imaging techniques, such as 3D imaging and various navigation instruments such as electromagnetic, sonographic, CT-controlled and marker-based/iPAD try to simplify this step and reduce complications. OBJECTIVES: In this review, various new techniques for puncturing the renal collecting system are presented and their advantages and disadvantages are evaluated. MATERIALS AND METHODS: A systematic literature search was carried out in MEDLINE, whereby only puncture techniques that have already been evaluated in clinical studies were included. RESULTS: Five different navigation methods for puncturing the renal pelvis before PCNL were found. CONCLUSION: Intraoperative navigation can be useful when puncturing the collecting system. The combination of ultrasound and fluoroscopy currently remains the gold standard. However, there is still a need for further, primarily clinical, prospective studies to determine which new imaging technology and navigation systems will prevail and thus facilitate the access route to the kidney, especially in the case of special anatomical conditions.


Sujet(s)
Calculs rénaux/chirurgie , Rein/imagerie diagnostique , Rein/chirurgie , Interventions chirurgicales mini-invasives/méthodes , Néphrostomie percutanée/méthodes , Ponctions/méthodes , Humains , Calculs rénaux/imagerie diagnostique
6.
Eur J Surg Oncol ; 45(7): 1260-1265, 2019 Jul.
Article de Anglais | MEDLINE | ID: mdl-30827801

RÉSUMÉ

INTRODUCTION: Aim of this study was to analyse the perioperative outcome of patients undergoing radical cystectomy under continuous antiplatelet therapy with acetylsalicylic acid. MATERIALS AND METHODS: Using prospectively maintained databases of two departments of urology, we identified 461 consecutive patients who underwent radical cystectomy for bladder cancer (2011-2017). Patients were divided into three groups: 1) on-going antiplatelet therapy with acetylsalicylic acid (n = 50), 2) discontinuing antiplatelet therapy (n = 65) and 3) no antiplatelet therapy (n = 346). Perioperative outcome was compared between the three groups using ANOVA, likelihood ratio or Kruskal Wallis test with post-hoc testing. Uni- and multivariate analyses were performed to identify predictor for perioperative complications and transfusion. RESULTS: Group 1 showed an average estimated blood loss of 732 ±â€¯424, group 2 752 ±â€¯488 and group 3 810 ±â€¯544 ml (p = 0.51). There was no significant difference in transfusion rate (44% in group 1, 45% and 39% in groups 2 and 3, p = 0.63). Severe complications occurred in 26%, 15% and 15% in groups 1-3 (p = 0.19). Ischemic complications were more often observed in group 1 (n = 4, 8%) and 2 (n = 5, 8%) than group 3 (n = 7, 2%), p = 0.02. 90-day readmission (n = 99, 22%) and mortality rate (n = 10, 2.2%) were low and did not show any significant differences between the groups. In uni- and multivariate analysis ongoing therapy with acetylsalicylic acid was no independent risk factor for transfusion or severe complications. CONCLUSION: Perioperative continuation of therapy with acetylsalicylic acid in radical cystectomy is safe with no difference in intraoperative blood loss, transfusion rate, complications or mortality.


Sujet(s)
Acide acétylsalicylique/usage thérapeutique , Cystectomie , Déprescriptions , Antiagrégants plaquettaires/usage thérapeutique , Complications postopératoires/épidémiologie , Tumeurs de la vessie urinaire/chirurgie , Dérivation urinaire , Sujet âgé , Perte sanguine peropératoire/statistiques et données numériques , Transfusion sanguine/statistiques et données numériques , Maladies cardiovasculaires/traitement médicamenteux , Maladies cardiovasculaires/prévention et contrôle , Études cas-témoins , Maladie coronarienne/complications , Maladie coronarienne/traitement médicamenteux , Bases de données factuelles , Femelle , Humains , Lymphadénectomie , Mâle , Adulte d'âge moyen , Mortalité , Analyse multifactorielle , Infarctus du myocarde/épidémiologie , Infarctus du myocarde/thérapie , Réadmission du patient/statistiques et données numériques , Pelvis , Période périopératoire , Hémorragie postopératoire/épidémiologie , Hémorragie postopératoire/thérapie , Prévention primaire , Réintervention , Études rétrospectives , Prévention secondaire , Tumeurs de la vessie urinaire/complications
7.
Urologe A ; 57(9): 1075-1090, 2018 Sep.
Article de Allemand | MEDLINE | ID: mdl-30030596

RÉSUMÉ

The monopoly of robotic surgical devices of the last 15 years will end in 2019 when key patents of Intuitive Surgical expire. Thus, we can expect an interesting competitive situation in the coming years. Based on personal experience with robot-assisted surgery since 2001, we conducted a search of the current literature together with a search of relevant patents in this field. Finally, we visited the websites of manufacturers of existing and future robotic surgical devices with possible applications in urology. Such devices have to prove that they meet the high-quality standard of the current Da Vinci series (SI, X, XI). For this purpose, we propose to classify the main features of the different devices, such as type of console (closed/open), arrangement of robotic arms (single/multiple carts/attached to operating room table), type of three-dimensional videosystem (by mirror/ocular/using polarizing glasses) or degrees of freedom (DOF) of end effectors (5 vs. 7 DOF). In the meantime, there are also robotic systems used in endourology: Avicenna Roboflex® and the AquaBeam® system for robot-assisted aquablation therapy of the prostate. While Roboflex® improves the ergonomics of flexible ureteroscopy-similar to the Da Vinci robot, AquaBeam® may for the first time eliminate the surgeon, who might only be needed to manage severe postoperative bleeding.


Sujet(s)
Laparoscopie , Interventions chirurgicales robotisées/méthodes , Interventions chirurgicales robotisées/tendances , Urétéroscopie/méthodes , Procédures de chirurgie urologique/tendances , Urologie/tendances , Endoscopie , Ingénierie humaine , Humains , Laparoscopie/tendances , Mâle , Chirurgie vidéoassistée/tendances
8.
Rev. bras. plantas med ; 18(1): 201-214, jan.-mar. 2016. tab, graf
Article de Portugais | LILACS | ID: lil-780035

RÉSUMÉ

RESUMO As plantas medicinais apresentam várias propriedades terapêuticas, as quais estão relacionadas com a presença de compostos bioativos. Dentre os compostos, destacam-se as pectinas, que compreendem um grupo de polissacarídeos ácidos de relevante importância medicinal e nutracêutica. As pectinas são formadas por unidades de ácido galacturônico, unidas por ligação do tipo α-(1→4), sendo classificadas em homogalacturonanas e ramnogalacturonanas tipo I (RG-I) e tipo II (RG-II). Outros polissacarídeos constituídos por arabinose e/ou galactose têm sido isolados em associação com polissacarídeos pécticos, como as arabinogalactanas (AG) (tipo I e tipo II). As AG-II podem estar associadas a proteínas, denominadas de arabinogalactana-proteínas (AGPs). Inúmeros relatos demonstram que as pectinas, bem como as AG e AGPs, podem atuar como moduladores do sistema imunológico, sendo, por isso, consideradas modificadores da resposta biológica. A imunomodulação pode estar relacionada tanto com a atividade de macrófagos quanto com as vias do sistema complemento. Em geral, os polissacarídeos provocam um estímulo da atividade fagocitária; no aumento da produção de espécies reativas de oxigênio e da secreção de citocinas pró-inflamatórias. Em relação ao sistema complemento, os polissacarídeos podem modular tanto a via clássica como a via alternativa. A presente revisão tem como objetivo principal descrever os aspectos estruturais de pectinas e suas atividades biológicas relacionadas à modulação do sistema imune. Utilizando literatura específica, estão descritas informações de 29 espécies de plantas medicinais, que apresentam como constituintes pectinas, arabinogalactanas e/ou AGPs, correlacionando suas propriedades terapêuticas com as atividades biológicas associadas ao sistema imune. Na maioria dos casos descritos na literatura, é difícil determinar como as características estruturais específicas podem estar envolvidas na modulação da atividade de macrófagos. Porém, em relação à modulação da atividade do sistema complemento fica sugerido que a presença de estruturas tipo AG-II contribuiria mais significativamente para esta atividade. Entretanto, os possíveis mecanismos de modulação de pectinas, AGs e AGPs sobre a atividade de macrófagos e/ou sobre o sistema complemento ainda não estão totalmente esclarecidos, mesmo assim, estes polímeros podem ser considerados potenciais candidatos para estudos que visam ao desenvolvimento de novos agentes terapêuticos com propriedades moduladoras benéficas para o sistema imunológico.


ABSTRACT Medicinal plants have many therapeutic properties that are related to the presence of biologically active compounds. Pectins, a group of acid polysaccharides that have relevant medicinal and nutraceutical properties, are an example of such biological compounds. Pectins contain a main chain with galacturonic acid units that are α-(1→4) linked; they can be classified into homogalacturonans and type I and type II rhamnogalacturonans (RG-I and RG-II). Other polysaccharides containing arabinose, galactose, or both have been isolated in association with pectin-type polysaccharides are known as arabinogalactans (AGs, type I and type II). Arabinogalactan-proteins (AGPs) comprise AG-II associated with proteins. Several studies have reported that pectins, as well as AG and AGPs, can act as modulators of the immune system and can therefore be considered biological response modifiers. The immunomodulation is related to the activity of macrophages as on the complement system pathways. In general, polysaccharides cause stimulation of phagocytic activity, increase production of reactive oxygen species and secretion of pro-inflammatory cytokines. Polysaccharides can modulate the classical and alternative complement pathways. The aim of this review has to describe the structural aspects of pectins and their biological activities related to the modulation of the immune system. Using literature, we reported data of 29 medicinal plant species, which present as constituents pectins, arabinogalactan and/or AGPs, correlating their therapeutic properties with biological activities associated to the immune system. In most cases described in the literature, it is difficult to determine how the specific structural characteristics can be involved in modulation of macrophage activity. However, with respect to the modulation of the activity of the complement system is proposed that the presence of AG-II-type structures would contribute most significantly to this activity. The possible mechanisms of modulation of pectins, AGs and AGPs on macrophage activity and/or the complement system are not yet fully clear, even if, these polymers can be considered potential candidates for studies aimed at the development of new therapeutic agents with modulatory properties beneficial to the immune system.


Sujet(s)
Plantes médicinales/classification , Pectine/analyse , Immunomodulation , Macrophages
9.
Carbohydr Polym ; 125: 241-8, 2015 Jul 10.
Article de Anglais | MEDLINE | ID: mdl-25857980

RÉSUMÉ

The native polysaccharide of cashew-nut tree gum exudate (CNTG) and its arabinogalactan-protein component (CNTG-AGP) were tested by using immuno-stimulant and anti-inflammatory in vitro assays of murine peritoneal macrophage activities. In the assay for immuno-stimulant activity (without previous treatment with lipopolysaccharide; LPS), CNTG increased the production of interleukin (IL)-10 and both CNTG and CNTG-AGP decreased the concentrations of IL6. When the macrophages were incubated in the presence of LPS and CNTG a decrease in the levels of nitric oxide (NO(·)) and IFN-γ was observed. The results could explain the popular use of CNTG as an anti-inflammatory. In addition, CNTG is the main component of the cashew-nut tree gum exudate, which has been considered a versatile polymer with potential pharmaceutical and food industry applications. These data may contribute to the study of the immunomodulation activity of plant polysaccharides, as well as encourage future experiments in the field of cashew-nut tree gum exudate applications.


Sujet(s)
Anacardium/composition chimique , Macrophages péritonéaux/effets des médicaments et des substances chimiques , Gommes végétales/pharmacologie , Animaux , Cellules cultivées , Interféron gamma/génétique , Interféron gamma/métabolisme , Interleukine-10/génétique , Interleukine-10/métabolisme , Macrophages péritonéaux/métabolisme , Souris , Mucoprotéines/composition chimique , Mucoprotéines/pharmacologie , Monoxyde d'azote/métabolisme , Gommes végétales/composition chimique , Protéines végétales/composition chimique , Protéines végétales/pharmacologie
10.
Chemosphere ; 131: 63-70, 2015 Jul.
Article de Anglais | MEDLINE | ID: mdl-25769113

RÉSUMÉ

The persistence of synthetic cyclohexyl- and norbornyl-derived ketones was assessed by using OECD 301F and 301D biodegradation tests. While cyclohexyl-derived ketones either reached or came close to the pass level (60%) after 60 d, the corresponding norbornyl derivatives yielded significantly less biodegradation (<40%). By analyzing extracts at 60 d, the key degradation products of four norbornyl derivatives were identified. Consistently, 2-bicyclo[2.2.1]heptane carboxylic acid was found as a principal degradation product with minor quantities of bicyclo[2.2.1]heptan-2-one and 2-bicyclo[2.2.1]heptane acetic acid. When the three degradation products were re-synthesized and tested individually for biodegradability, the former two were found to be ultimately biodegradable after 60 d in OECD 301D tests, thus proving non-persistence. Similarly, 2-bicyclo[2.2.1]heptane acetic acid was found to be degraded significantly, albeit with long lag phases exceeding 60 d in the case of freshwater inoculum, then ultimately reaching the pass level. On the other hand, norbornyl ketones were still only partially biodegradable in the same test. We conclude that despite the potential for ultimate biodegradation of norbornyl-derived ketones, current screening tests yield an incomplete picture of their biodegradability, particularly when applying strict OECD criteria. The appearance of long lag phases when re-testing norbornyl ketone degradation products underlines the importance of extending tests to well beyond 28 and even 60 d in the case of freshwater inocula.


Sujet(s)
Composés bicycliques pontés/analyse , Cyclohexanones/analyse , Monoterpènes de type norbornane/analyse , Polluants chimiques de l'eau/analyse , Dépollution biologique de l'environnement , Composés bicycliques pontés/composition chimique , Cyclohexanones/composition chimique , Eau douce/composition chimique , Cétones/analyse , Cétones/composition chimique , Modèles théoriques , Structure moléculaire , Monoterpènes de type norbornane/composition chimique , Organisation de coopération et de développement économiques , Eaux d'égout/composition chimique , Eaux usées/composition chimique , Polluants chimiques de l'eau/composition chimique
11.
Environ Sci Pollut Res Int ; 21(16): 9487-94, 2014.
Article de Anglais | MEDLINE | ID: mdl-24277432

RÉSUMÉ

The degradation of Romandolide ([1-(3',3'-dimethyl-1'-cyclohexyl)ethoxycarbonyl] methyl propanoate), a synthetic alicyclic musk, by activated sludge inocula was investigated using both the manometric respirometry test OECD 301F and the CO2 evolution test. In addition to measuring its biodegradability, key steps of the upper part of the metabolic pathway responsible for Romandolide degradation were identified using extracts at different time points of incubation. Early metabolism of Romandolide yielded ester hydrolysis products, including Cyclademol (1-(3,3-dimethylcyclohexyl)ethanol). The principal metabolites after 31 days were identified as 3,3-dimethyl cyclohexanone and 3,3-dimethyl cyclohexyl acetate. Formation of 3,3-dimethyl cyclohexanone from Cyclademol by sludge was confirmed in subsequent experiments using Cyclademol as a substrate, indicating the involvement of an oxygen insertion reminiscent of a Baeyer-Villiger oxidation. Further mineralization of 3,3-dimethyl cyclohexanone was also confirmed in subsequent studies. Three steps were thus required for complete biodegradation of the alicyclic musk: (1) successive ester hydrolyses leading to the formation of Cyclademol with concomitant degradation of the resulting acids, (2) conversion of Cyclademol into 3,3-dimethyl cyclohexanone, and (3) further mineralization via ring cleavage.


Sujet(s)
Dépollution biologique de l'environnement , Parfum/composition chimique , Eaux d'égout/composition chimique , Polluants chimiques de l'eau/composition chimique , Acétates , Structure moléculaire , Oxydoréduction , Facteurs temps
12.
Opt Express ; 19(20): 19422-9, 2011 Sep 26.
Article de Anglais | MEDLINE | ID: mdl-21996883

RÉSUMÉ

The influence of the geometric shape of optically confining structures on the emission properties of ZnSe-based microcavities is studied. Elliptical as well as coupled circular structures were fabricated with quantum wells or quantum dots as optical active material. For the elliptical pillars a lifting of the polarization degeneracy of the resonator modes is observed as it is favorable to control the polarization state of the emitted photons. The influence of the ellipticity on the polarization splitting of the fundamental mode as well as on the quality factor of the sample is discussed. For the coupled pillar microcavities the effect of their distance on the energy splitting of the fundamental resonator mode is analyzed. Furthermore, detailed measurements of the spatial mode distribution in elliptically shaped pillars and photonic molecules are performed. By comparing these results to the calculated mode distribution their analogy to a diatomic molecule is illustrated. It turns out that the observed mode splitting into localized bonding and delocalized antibonding states in ZnSe-based microcavities is more pronounced for elliptical geometries. The realization of delocalized mode profiles is favorable for the coupling of spatially separated quantum dots.


Sujet(s)
Nanotechnologie/instrumentation , Photons , Boîtes quantiques , Réfractométrie/instrumentation , Conception d'appareillage , Test de matériaux , Taille de particule
13.
FEMS Microbiol Lett ; 154(2): 337-45, 1997 Sep 15.
Article de Anglais | MEDLINE | ID: mdl-9311132

RÉSUMÉ

When grown on glycerol as sole carbon and energy source, cell extracts of Clostridium pasteurianum exhibited activities of glycerol dehydrogenase, dihydroxyacetone kinase, glycerol dehydratase and 1,3-propanediol dehydrogenase. The genes encoding the latter two enzymes were cloned by colony hybridization using the dhaT gene of Citrobacter freundii as a heterologous DNA probe and expressed in Escherichia coli. The native molecular mass of 1,3-propanediol dehydrogenase (DhaT) is 440,000 Da. The dhaT gene of C. pasteurianum was subcloned and its nucleotide sequence (1158 bp) was determined. The deduced gene product (41,776 Da) revealed high similarity to DhaT of C. freundii (80.5% identity; 89.8% similarity).


Sujet(s)
Alcohol oxidoreductases/génétique , Clostridium/métabolisme , Gènes bactériens , Glycérol/métabolisme , Propylène glycols/métabolisme , Alcohol dehydrogenase , Séquence d'acides aminés , Séquence nucléotidique , Clonage moléculaire , Clostridium/génétique , Données de séquences moléculaires
14.
J Bacteriol ; 178(19): 5793-6, 1996 Oct.
Article de Anglais | MEDLINE | ID: mdl-8824629

RÉSUMÉ

The genes encoding coenzyme B12-dependent glycerol dehydratase of Citrobacter freundii were cloned and overexpressed in Escherichia coli. The B12-free enzyme was purified to homogeneity. It consists of three types of subunits whose N-terminal sequences are in accordance with those deduced from the open reading frames dhaB, dhaC, and dhaE, coding for subunits of 60,433 (alpha), 21,487 (beta), and 16,121 (gamma) Da, respectively. The enzyme complex has the composition alpha2beta2gamma2. Amino acid alignments with the subunits of the recently sequenced diol dehydratase of Klebsiella oxytoca (T. Tobimatsu, T. Hara, M. Sakaguchi, Y. Kishimoto, Y. Wada, M. Isoda, T. Sakai, and T. Toraya, J. Biol. Chem. 270:7142-7148, 1995) revealed identities between 51.8 and 70.9%.


Sujet(s)
Protéines bactériennes/génétique , Citrobacter freundii/génétique , Cobamides/métabolisme , Gènes bactériens , Hydro-lyases/génétique , Protéines bactériennes/biosynthèse , Protéines bactériennes/isolement et purification , Chromatographie d'affinité , Citrobacter freundii/enzymologie , Clonage moléculaire , Escherichia coli/génétique , Hydro-lyases/biosynthèse , Hydro-lyases/isolement et purification , Données de séquences moléculaires , Conformation des protéines , Protéines recombinantes/biosynthèse , Protéines recombinantes/isolement et purification , Analyse de séquence d'ADN , Similitude de séquences d'acides aminés , Spécificité d'espèce
15.
Appl Opt ; 22(9): 1402, 1983 May 01.
Article de Anglais | MEDLINE | ID: mdl-18195976
16.
Appl Opt ; 22(3): 492-6, 1983 Feb 01.
Article de Anglais | MEDLINE | ID: mdl-18195815

RÉSUMÉ

A method for measuring transmittance and reflectance of plant material in glass cuvettes using a single-beam spectrophotometer with an integrating sphere attachment is described. This method requires extensive processing of the originally measured values as these are distorted by multiple reflections of the diffusely transmitted or reflected light. Most of the theories on light interaction with scattering materials require data processing to meet the theory's prerequisites. Therefore, the complicated evaluation does not restrict the applicability of the method. Special attention is given to the 60 degree/diffuse incidence requirement of the Kubelka-Munk theory. It is argued that the 60 degree/diffuse requirement is not essential for thick scattering layers. It is further stressed that a better knowledge of the optical properties should be of great help in many fields of biology.

17.
RN ; 37(7): 48-9, 1974 Jul.
Article de Anglais | MEDLINE | ID: mdl-4494979
SÉLECTION CITATIONS
DÉTAIL DE RECHERCHE
...