Theoretical and Experimental Aspects of Electrode Reactions with Coupled Homogeneous Redox Reactions: D. C. and A. C. Polarography

We present here a survey of theoretical and experimental studies performed in our: laboratories, which deal with influences of homogeneous redox reactions in d. c. and a. c. polarography, with primary emphasis on the latter. These jnvestigations date back to the early 1960\u27s when effects of the catalytic mechanism on a. c. polarography were examined. However, the main thrust in this direction occurred in the past four years when theoretical strategies for handling second order homogeneous reactions coupled to heterogeneous electron transfer were perfected. This development permHted a focused theo,retical effort on this topic which encompassed a variety of mechani:srtic schemes, such as those involving disproportLonatiOl! l, and »nuances« of the consecutive and parallel ECE mechanisms. Experimental results obtained to date satisfactorily support predictiOIIls of the theoretical rate Jaws. One concludes from our studies and parallel efforts in other laboratories that kinetic characteristics of homogeneous redox reactions can substantially influence rthe polarographic observables under many circumstances. The COl!lclusicm follows that kinetic characteristics of homogeneous redox reactions are more broadly access1ble via polarographic, and other electrochemical relaxation techniques than previously thought. Also, proper care must be taken to account for, or show negligibility of, homogeneous redox reaction effects in studies whose attention is centered on the heterogeneous processes or on multi-component analysis

Theoretical and Experimental Aspects of Electrode Reactions with Coupled Homogeneous Redox Reactions: D. C. and A. C. Polarography

We present here a survey of theoretical and experimental studies performed in our: laboratories, which deal with influences of homogeneous redox reactions in d. c. and a. c. polarography, with primary emphasis on the latter. These jnvestigations date back to the early 1960\u27s when effects of the catalytic mechanism on a. c. polarography were examined. However, the main thrust in this direction occurred in the past four years when theoretical strategies for handling second order homogeneous reactions coupled to heterogeneous electron transfer were perfected. This development permHted a focused theo,retical effort on this topic which encompassed a variety of mechani:srtic schemes, such as those involving disproportLonatiOl! l, and »nuances« of the consecutive and parallel ECE mechanisms. Experimental results obtained to date satisfactorily support predictiOIIls of the theoretical rate Jaws. One concludes from our studies and parallel efforts in other laboratories that kinetic characteristics of homogeneous redox reactions can substantially influence rthe polarographic observables under many circumstances. The COl!lclusicm follows that kinetic characteristics of homogeneous redox reactions are more broadly access1ble via polarographic, and other electrochemical relaxation techniques than previously thought. Also, proper care must be taken to account for, or show negligibility of, homogeneous redox reaction effects in studies whose attention is centered on the heterogeneous processes or on multi-component analysis

Separate effects tests on hydrogen combustion during direct containment heating events

Experimente zur Wasserstoffverbrennung bei DCH-Prozessen Im Rahmen der Forschung zu schweren Unfällen in Leichtwasserreaktoren werden im Institut für Energie- und Kerntechnik des Forschungszentrums Karlsruhe seit 1998 die Versuchanlagen DISCOC und DISCO-H betrieben, konzipiert zur Untersuchung der Druckbelastung des Sicherheitsbehälters durch Schmelzedispersion (Direct Containment Heating, DCH) bei Versagen des Reaktordruckbehälters (RDB). Vorangegangene Experimente haben die Schmelzeverteilung und Druckerhöhung im Sicherheitsbehälter bei verschiedenen europäischen Reaktorgeometrien untersucht, unter Anwendung von Eisen-Aluminium-Schmelzen und Dampf als Modellfluide. Die Analyse dieser Experimente hat gezeigt, dass der Druckanstieg sowohl durch den Wärmeübergang von der Schmelze an das Gas, aber auch zum nicht unerheblichen Teil durch Wasserstoffverbrennung verursacht wurde. So hat sich die Notwendigkeit ergeben, die charakteristischen Eigenschaften der Wasserstoffverbrennung während des DCH-Prozesses besser beschreiben zu können. Um diese Fragen zu klären, wurden Einzeleffektexperimente in der DISCO-H Versuchsanlage durchgeführt. Mit Ausnahme der Schmelzedispersion laufen in diesen Experimenten die gleichen Prozesse ab, wie sie während des DCH-Vorganges auftreten, das sind das Abblasen einer heißen Wasserstoff-Dampf Mischung in den Sicherheitsbehälter und die Zündung dieses Gasgemisches in einer LuftDampf-Wasserstoff Atmosphäre. Der Effekt der Schmelzepartikel als Zünder wurde mit Thermitkerzen simuliert. Die experimentellen Daten werden benutzt, um Modelle in Verbrennungscodes zu kalibrieren und um auf Reaktormaßstab zu extrapolieren. Die Experimente wurden in zwei Schritten durchgeführt. Für eine Serie von 6 Tests wurde eine vereinfachte Geometrie benutzt, um die Hauptparameter der Verbrennung zu studieren. Dann wurden zwei Tests in einer prototypischeren Geometrie durchgeführt, bei der das Gas aus der Grube zuerst in einen separaten Reaktorraum und von dort in den Sicherheitsbehälter strömt. Die Versuchsbedingungen waren wie folgt: • Als Anfangsbedingung im Sicherheitsbehälter wurde eine Luft- bzw. ein Luft-Dampf-Atmosphäre bei 100°C und 2 bar eingestellt, mit Wasserstoffkonzentrationen zwischen 0 und 7 mol%, repräsentativ für die Atmosphäre im Containment bei Versagen des RDB. • Einblasen eines heißen Dampf-Wasserstoffgemisches in die Reaktorgrube bei 20 bar, repräsentativ für ein Kühlmittelabblasen durch ein Leck im RDB und der Wasserstofferzeugung während dieser Phase. Die wichtigsten gemessenen Größen waren (1) der Druckanstieg im Sicherheitsbehälter, (2) die Gastemperaturen und (3) die Anzahl der verbrannten Wasserstoffmole. Diese Experimente kennzeichnen die Rate der Wasserstoffverbrennung, die Vollständigkeit und die Art der Verbrennung bei verschiedenen Anfangsbedingungen. Der Anteil des verbrannten Wasserstoffs betrug zwischen 55% und 100% der Gesamtmenge in der einfachen Geometrie und 46% bzw. 67% in der mehr prototypischen Geometrie. Der Wirkungsgrad hinsichtlich Druckerhöhung im Sicherheitsbehälter lag zwischen 46% und 67%. Spezielle Verbrennungscodes müssen angewendet werden um zu prüfen, ob diese Ergebnisse auch für den Reaktormaßstab gelten

Single photon source characterization with a superconducting single photon detector

Superconducting single photon detectors (SSPD) based on nanopatterned niobium nitride wires offer single photon counting at fast rates, low jitter, and low dark counts, from visible wavelengths well into the infrared. We demonstrate the first use of an SSPD, packaged in a commercial cryocooler, for single photon source characterization. The source is an optically pumped, microcavity-coupled InGaAs quantum dot, emitting single photons on demand at 902 nm. The SSPD replaces the second silicon Avalanche Photodiode (APD) in a Hanbury-Brown Twiss interferometer measurement of the source second-order correlation function, g (2) (tau). The detection efficiency of the superconducting detector system is >2 % (coupling losses included). The SSPD system electronics jitter is 170 ps, versus 550 ps for the APD unit, allowing the source spontaneous emission lifetime to be measured with improved resolution.Comment: 8 page

Tunable phenotypic variability through an autoregulatory alternative sigma factor circuit.

Genetically identical individuals in bacterial populations can display significant phenotypic variability. This variability can be functional, for example by allowing a fraction of stress prepared cells to survive an otherwise lethal stress. The optimal fraction of stress prepared cells depends on environmental conditions. However, how bacterial populations modulate their level of phenotypic variability remains unclear. Here we show that the alternative sigma factor σV circuit in Bacillus subtilis generates functional phenotypic variability that can be tuned by stress level, environmental history and genetic perturbations. Using single-cell time-lapse microscopy and microfluidics, we find the fraction of cells that immediately activate σV under lysozyme stress depends on stress level and on a transcriptional memory of previous stress. Iteration between model and experiment reveals that this tunability can be explained by the autoregulatory feedback structure of the sigV operon. As predicted by the model, genetic perturbations to the operon also modulate the response variability. The conserved sigma-anti-sigma autoregulation motif is thus a simple mechanism for bacterial populations to modulate their heterogeneity based on their environment

High-energy neutron irradiation of superconducting compounds

The effect of high-energy neutron irradiation (E greater than 1 MeV) at ambient reactor temperatures on the superconducting properties of a variety of superconducting compounds is reported. The materials studied include the A-15 compounds Nb$sub 3$Sn, Nb$sub 3$Al, Nb$sub 3$Ga, Nb$sub 3$Ge and V$sub 3$Si, the C-15 Laves phase HfV$sub 2$, the ternary molybdenum sulfide Mo$sub 3$Pb$sub 0$.$sub 5$S$sub 4$ and the layered dichalcogenide NbSe$sub 2$. The superconducting transition temperature has been measured for all of the above materials for neutron fluences up to 5 x 10$sup 19$ n/cm$sup 2$. The critical current for multifilamentary Nb$sub 3$Sn has also been determined for fields up to 16 T and fluences between 3 x 10$sup 17$ n/cm$sup 2$ and 1.1 x 10$sup 19$ n/ cm$sup 2$. (auth

Treatment of displaced intra-articular calcaneal fractures by ligamentotaxis: current concepts’ review

Introduction: A large variety of therapeutic modalities for calcaneal fractures have been described in the literature. No single treatment modality for displaced intra-articular calcaneal fractures has proven superior over the other. This review describes and compares the different percutaneous distractional approaches for intra-articular calcaneal fractures. The history, technique, anatomical and fracture considerations, limitations and the results of different distractional approaches reported in the literature are reviewed. Method: Literature review on different percutaneous distractional approaches for displaced intra-articular calcaneal fractures. Results: Eight studies in which application of a distraction technique was used for the treatment of calcaneal fractures were identified. Because of the use of different classification, techniques, and outcome scoring systems, a meta-analysis was not possible. A literature review reveals overall fair to poor result in 10-29% of patients. Ten up to 26% of patients are unable to return to work after percutaneous treatment of their fracture. A secondary arthrodesis has to be performed in 2-15% of the cases. Infectious complications occur in 2-15%. Some loss of reduction is reported in 4-67%. Conclusion: Percutaneous distractional reduction and fixation appears to be a safe technique with overall good results and an acceptable complication rate, compared with other treatment modalities for displaced intra-articular calcaneal fractures. A meta-analysis, based on Cochrane Library criteria is not possible, because of a lack of level 1 and 2 trials on this subject

c-Met overexpression in inflammatory breast carcinomas: automated quantification on tissue microarrays

Inflammatory breast carcinoma (IBC) is a rare but aggressive tumour associated with poor outcome owing to early metastases. Increased expression of c-Met protein correlates with reduced survival and high metastatic risk in human cancers including breast carcinomas and is targetable by specific drugs, that could potentially improve the prognosis. In the present study, we compared c-Met expression in IBC (n=41) and non-IBC (n=480) immunohistochemically (Ventana Benchmark autostainer) in two tissue microarrays (TMA) along with PI3K and E-cadherin. The results were quantified through an automated image analysis device (SAMBA Technologies). We observed that (i) c-Met was significantly overexpressed in IBC as compared with non-IBC (P<0.001), (ii) PI3K was overexpressed (P<0.001) in IBC, suggesting that the overexpressed c-Met is functionally active at least through the PI3K signal transduction pathway; and (iii) E-cadherin was paradoxically also overexpressed in IBC. We concluded that overexpressed c-Met in IBC constitutes a potential target for specific therapy for the management of patients with poor-outcome tumours such as IBC. Automated image analysis of TMA proved to be a valuable tool for high-throughput immunohistochemical quantification of the expression of intratumorous protein markers

The Boston criteria version 2.0 for cerebral amyloid angiopathy:a multicentre, retrospective, MRI–neuropathology diagnostic accuracy study

BACKGROUND: Cerebral amyloid angiopathy (CAA) is an age-related small vessel disease, characterised pathologically by progressive deposition of amyloid β in the cerebrovascular wall. The Boston criteria are used worldwide for the in-vivo diagnosis of CAA but have not been updated since 2010, before the emergence of additional MRI markers. We report an international collaborative study aiming to update and externally validate the Boston diagnostic criteria across the full spectrum of clinical CAA presentations. METHODS: In this multicentre, hospital-based, retrospective, MRI and neuropathology diagnostic accuracy study, we did a retrospective analysis of clinical, radiological, and histopathological data available to sites participating in the International CAA Association to formulate updated Boston criteria and establish their diagnostic accuracy across different populations and clinical presentations. Ten North American and European academic medical centres identified patients aged 50 years and older with potential CAA-related clinical presentations (ie, spontaneous intracerebral haemorrhage, cognitive impairment, or transient focal neurological episodes), available brain MRI, and histopathological assessment for CAA diagnosis. MRI scans were centrally rated at Massachusetts General Hospital (Boston, MA, USA) for haemorrhagic and non-haemorrhagic CAA markers, and brain tissue samples were rated by neuropathologists at the contributing sites. We derived the Boston criteria version 2.0 (v2.0) by selecting MRI features to optimise diagnostic specificity and sensitivity in a prespecified derivation cohort (Boston cases 1994-2012, n=159), then externally validated the criteria in a prespecified temporal validation cohort (Boston cases 2012-18, n=59) and a geographical validation cohort (non-Boston cases 2004-18; n=123), comparing accuracy of the new criteria to the currently used modified Boston criteria with histopathological assessment of CAA as the diagnostic standard. We also assessed performance of the v2.0 criteria in patients across all cohorts who had the diagnostic gold standard of brain autopsy. FINDINGS: The study protocol was finalised on Jan 15, 2017, patient identification was completed on Dec 31, 2018, and imaging analyses were completed on Sept 30, 2019. Of 401 potentially eligible patients presenting to Massachusetts General Hospital, 218 were eligible to be included in the analysis; of 160 patient datasets from other centres, 123 were included. Using the derivation cohort, we derived provisional criteria for probable CAA requiring the presence of at least two strictly lobar haemorrhagic lesions (ie, intracerebral haemorrhages, cerebral microbleeds, or foci of cortical superficial siderosis) or at least one strictly lobar haemorrhagic lesion and at least one white matter characteristic (ie, severe visible perivascular spaces in centrum semiovale or white matter hyperintensities in a multispot pattern). The sensitivity and specificity of these criteria were 74·8% (95% CI 65·4-82·7) and 84·6% (71·9-93·1) in the derivation cohort, 92·5% (79·6-98·4) and 89·5% (66·9-98·7) in the temporal validation cohort, 80·2% (70·8-87·6) and 81·5% (61·9-93·7) in the geographical validation cohort, and 74·5% (65·4-82·4) and 95·0% (83·1-99·4) in all patients who had autopsy as the diagnostic standard. The area under the receiver operating characteristic curve (AUC) was 0·797 (0·732-0·861) in the derivation cohort, 0·910 (0·828-0·992) in the temporal validation cohort, 0·808 (0·724-0·893) in the geographical validation cohort, and 0·848 (0·794-0·901) in patients who had autopsy as the diagnostic standard. The v2.0 Boston criteria for probable CAA had superior accuracy to the current Boston criteria (sensitivity 64·5% [54·9-73·4]; specificity 95·0% [83·1-99·4]; AUC 0·798 [0·741-0854]; p=0·0005 for comparison of AUC) across all individuals who had autopsy as the diagnostic standard. INTERPRETATION: The Boston criteria v2.0 incorporate emerging MRI markers of CAA to enhance sensitivity without compromising their specificity in our cohorts of patients aged 50 years and older presenting with spontaneous intracerebral haemorrhage, cognitive impairment, or transient focal neurological episodes. Future studies will be needed to determine generalisability of the v.2.0 criteria across the full range of patients and clinical presentations. FUNDING: US National Institutes of Health (R01 AG26484)