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Redox-sensitivity is a common property of several transient receptor potential (TRP) ion channels. Oxidants and UVA-light activate TRPV2 by oxidizing methionine pore residues which are conserved in the capsaicin-receptor TRPV1. However, the redox-sensitivity of TRPV1 is regarded to depend on intracellular cysteine residues. In this study we examined if TRPV1 is gated by UVA-light, and if the conserved methionine residues are relevant for redox-sensitivity of TRPV1. Patch clamp recordings were performed to explore wildtype (WT) and mutants of human TRPV1 (hTRPV1). UVA-light induced hTRPV1-mediated membrane currents and potentiated both proton- and heat-evoked currents. The reducing agent dithiothreitol (DTT) prevented and partially reversed UVA-light induced sensitization of hTRPV1. UVA-light induced sensitization was reduced in the mutant hTRPV1-C158A/C387S/C767S (hTRPV1-3C). The remaining sensitivity to UVA-light of hTRRPV1-3C was not further reduced upon exchange of the methionine residues M568 and M645. While UVA-induced sensitization was reduced in the protein kinase C-insensitive mutant hTRPV1-S502A/S801A, the PKC-inhibitors chelerythrine chloride, staurosporine and Go6976 did not reduce UVA-induced effects on hTRPV1-WT. While hTRPV1-3C was insensitive to the cysteine-selective oxidant diamide, it displayed a residual sensitivity to H2O2 and chloramine-T. However, the exchange of M568 and M645 in hTRPV1-3C did not further reduce these effects. Our data demonstrate that oxidants and UVA-light gate hTRPV1 by cysteine-dependent as well as cysteine-independent mechanisms. In contrast to TRPV2, the methionine residues 568 and 645 seem to be of limited relevance for redox-sensitivity of hTRPV1. Finally, UVA-light induced gating of hTRPV1 does not seem to require activation of protein kinase C.

The mobility of toxic metals and the transformation of organic pollutants in the environment are influenced and in many cases even controlled by iron minerals. Therefore knowing the factors influencing iron mineral formation and transformation by Fe(II)-oxidizing and Fe(III)-reducing bacteria is crucial for understanding the fate of contaminants and for the development of remediation technologies. In this study we followed mineral formation by the nitrate-reducing Fe(II)-oxidizing strain Acidovorax sp. BoFeN1 in the presence of the crystalline Fe(III) (oxyhydr)oxides goethite, magnetite and hematite added as potential nucleation sites. Mössbauer spectroscopy analysis of minerals precipitated by BoFeN1 in (57)Fe(II)-spiked microbial growth medium showed that goethite was formed in the absence of mineral additions as well as in the presence of goethite or hematite. The presence of magnetite minerals during Fe(II) oxidation induced the formation of magnetite in addition to goethite, while the addition of humic substances along with magnetite also led to goethite but no magnetite. This study showed that mineral formation not only depends on the aqueous geochemical conditions but can also be affected by the presence of mineral nucleation sites that initiate precipitation of the same underlying mineral phases.

International audience; Green rust (GR) as highly reactive iron mineral potentially plays a key role for the fate of (in)organic contaminants, such as chromium or arsenic, and nitroaromatic compounds functioning both as sorbent and reductant. GR forms as corrosion product of steel but is also naturally present in hydromorphic soils and sediments forming as metastable intermediate during microbial Fe(III) reduction. Although already suggested to form during microbial Fe(II) oxidation, clear evidence for GR formation during microbial Fe(II) oxidation was lacking. In the present study, powder XRD, synchrotronbased XAS, Mössbauer spectroscopy, and TEM demonstrated unambiguously the formation of GR as an intermediate product during Fe(II) oxidation by the nitratereducing Fe(II)-oxidizer Acidovorax sp. strain BoFeN1. The spatial distribution and Fe redox-state of the precipitates associated with the cells were visualized by STXM. It showed the presence of extracellular Fe(III), which can be explained by Fe(III) export from the cells or extracellular Fe(II) oxidation by an oxidant diffusing from the cells. Moreover, GR can be oxidized by nitrate/nitrite and is known as a catalyst for oxidation of dissolved Fe(II) by nitrite/nitrate and may thus contribute to the production of extracellular Fe(III). As a result, strain BoFeN1 may contribute to Fe(II) oxidation and nitrate reduction both by an direct enzymatic pathway and an indirect GR-mediated process.

Analyses of energy consumption in manufacturing processes have shown that most of the energy is needed for the production of material such as aluminum or steel and not for further manufacturing steps like forming or cutting. To reduce energy consumption and also a reduction of CO 2 emissions in manufacturing processes, a reduction of the amount of primary material, made from first melting after mining, as well as secondary material, made from melting of recycled scrap material, is needed. In this work, the re-use of aluminum AA-6060 scrap based on milling and turning chips, by direct hot extrusion is presented. To prevent further use of primary aluminum or melting of the chips the process aims at using compacted chips as billet material. The production of the chips as well as the compaction of billets, the extrusion process and the properties of the final profile is presented. In addition to the use of chips based on one alloy the mixture and extrusion of aluminum and SiC particles is presented. The investigations have shown that using billets made of AA-6060 chips can lead to similar mechanical and microstructural properties as using of conventional cast aluminum billets. Investigations on an additional cutting or drilling of the extruded profiles have shown even improved properties due to a reduced chip length.

Construction parts consisting of modern polymer materials still need to be machined. Thereby special attention has to be paid to the machining quality. The machining quality implies dimensional accuracy as well as a defect-free peripheral zone. Machining defects often occur as a consequence of excessive mechanical loads, which are often caused by unfavorable process conditions. Besides mechanical loads, the thermal influence on the composite material, which is induced by the cutting process itself, has to be considered as crucial. According to the thermo physical material properties of polymer materials the boundary conditions differ from the machining of metals. Especially the drilling of polymer composites is introduced in this article and moreover the influences of the material properties and the process conditions on the process temperatures are presented.

The objective of the study was to assess individual distribution of antineoplastic drugs into the tumor. Twelve advanced-stage primary breast cancer patients with neoadjuvant epirubicin+paclitaxel chemotherapy were studied. Plasma concentrations of epirubicin and paclitaxel were monitored for 24 h. Epirubicin concentrations in subcutaneous and tumor tissues were measured using microdialysis up to 12 h postdose. Epirubicin concentrations were described by a compartmental population pharmacokinetic model (NONMEM). Noncompartmental analysis was used for paclitaxel. Plasma pharmacokinetics corresponded to published data. Mean epirubicin exposure in the tumor and in subcutaneous tissue was very similar, but tissue Cmax and area under the curve values reached only (means) 1% and 11%, respectively, of plasma values. Epirubicin doses were significantly correlated to tumor exposure irrespective of body surface area. There is no specific barrier for epirubicin to reach primary breast cancer tumors.

This is a retrospective cohort study on the safety and efficacy profiles of weekly docetaxel at varying doses in patients with pretreated metastatic breast cancer. Patients and Methods: Twenty-five anthracycline-pretreated patients received docetaxel administered on a weekly basis, as a one-hour infusion, at various dosage levels (25, 30, 35, 40 mg/m2) depending on their baseline Karnofsky index. Each 8-week cycle consisted of 6 weeks of drug infusion, followed by a 2-week rest period. Results: Of the 25 patients investigated, none achieved complete response (CR), while 9 patients showed partial response (PR), which corresponds to an overall response rate of 36%. Five patients (20%) maintained stable disease (SD), whereas 11 patients (44%) suffered tumor progression (PD) during treatment. Clinical response (defined as PR+SD) was achieved in 14 patients (56%). Median time to progression was 231 days (95% CI, 187-275). The baseline Karnofsky index was 87% ± 9% (range: 70-100). Patients pretreated with anthracyclines only tended to have a better response than anthracycline/paclitaxel-pretreated patients (n = 6, p = 0.054). Higher dosages were associated with neurotoxicity, skin/nail toxicity, leukopenia, nausea/vomiting, fatigue/asthenia, peripheral edema, but not with diarrhea and alopecia. The cumulative dose per patient was largest for a weekly docetaxel dosage of 35 mg/m2 and almost as large for 30 mg/m2. Conclusion: Balancing toxicity vs. efficacy/cumulative dosage delivered, our results support weekly administration of docetaxel at dosages of 30-35 mg/m2 in metastatic breast cancer. Response in patients pretreated with anthracyclines and taxanes may be poorer than in those pretreated with anthracyclines only.

Background: During conventional cardiac surgery ischemia and reperfusion may cause excessive production of reactive oxygen species leading to tissue damage including early arrhythmias. We therefore assessed the kinetics of markers of radical stress including oxidized and reduced glutathione (GSSG/GSH), oxidized proteins (PCG) and malondialdehyde (MDA), and tested the hypothesis that different steroid treatments inhibit these markers and early reperfusion-associated supraventricular and ventricular extrasystolic beats. Methods: In a randomized, controlled, blinded, prospective trial 36 patients received a preoperative infusion of methylprednisolone (MP, 15 mg kg−1, n = 12), tirilazad mesylate (TM, 10 mg kg−1, n = 12) or placebo (PL, NaCl, n = 12). Coronary sinus and arterial blood was drawn at baseline and 2, 5, 15, 30, 60 and 240 min after aortic declamping. Holter-ECG analysis was used to identify arrhythmias. Results: Cardiac GSSG release occurred very early ( 4 h and was significantly reduced only by TM. Cardiac MDA release was short (

Poly(L-lactide) (PLLA), prepared by a tin(II)-octoate initiated ring-opening melt-polymerization was separately modified with tert-butylperoxy benzoate (0.1, 0.25 and 0.5 wt%) in an extruder. The peroxide modification retarded the melt degradation and caused changes in the morphology of the polymer. Injection molded specimens of unmodified and peroxide modified PLLA were prepared. Changes in weight, mechanical strength, molar mass and in the morphology were studied during degradation in soil. The peroxide modified samples underwent a more rapid degradation than the unmodified ones, which can be related to the morphological changes caused by the peroxide modification. The degradation behavior could mainly be related to accessibility to water.

The absolute configuration of the gamete-releasing and gamete-attracting pheromone desmarestene 2 from the North Atlantic brown alga Desmarestia aculeata is determined as (6 R ) by synthesis and biological activity tests. Utilising the cis-endo transition state geometry of the Cope rearrangement of 1,2- cis -vinylalkenylcyclopropanes, a non-stereoselective Wittig approach with a single chiral precursor providing ( E )- and ( Z )- 12 , gives access to both cnantiomers of 2 . According to GLC on a chiral stationary phase calling females of Desmarestia aculeata and Cladostephus spongiosus release (6 R )- 2 with high enantiomeric purity (87% e.e. and 96% e.e. respectively) while female gametes of the South American D. firma secrete (6 R )- 2 with only 28% e.e.

The polarization and population dynamics of resonantly generated excitons in GaAs/AlGaAs quantum well structures are investigated using transient three-pulse four-wave mixing. The decay dynamics show strongly nonexponential behavior for both variation of the delay between the first two pulses reflecting the polarization dynamics and variation of the delay between the second two pulses, which reflects the population dynamics. A comparison with a theoretical model shows that the dynamics of both polarization and population are mainly determined by frequency fluctuations and not by scattering processes or by recombination. The characteristic time of the fluctuations T C has to be energy-dependent to fully describe the results

The influence of inhomogeneous broadening on results obtained from spectrally resolved transient four-wave mixing in semiconductors is studied and the homogeneous and inhomogeneous linewidths are simultaneously deduced. Experimental results obtained from the impurity-bound exciton I 1 in CdSe and the heavy-hole and light-hole excitons in GaAs multiple quantum well structures are presented. Furthermore, the case is investigated when more resonances are coherently excited leading to quantum beats

Biexcitons localized at neutral acceptor sites in the direct-gap II–VI semiconductors CdS and CdSe are identified with different spectroscopic techniques such as photoluminescence, two-photon absorption and nonlinear quantum beat spectroscopy (NQBS). The NQBS offers the possibility to distinguish between quantum beats from a three-level system and polarization interference from independent two-level systems. The localized biexciton states are discussed in analogy with excited states of holes in neutral donor complexes.

Aluminum is one of the promising lightweight materials of the twenty-first century. Due to its good machinability, surface properties and a low density, it is often used in production of aircrafts, automobiles, transport systems and consumer products. But one of the greatest disadvantages of this material is the high energy requirement for the primary raw material production, from bauxite to Aluminum ingots. This melting process requires almost 25 times more energy than that needed for the primary steel production. Furthermore the aluminum recycling process needs as much energy as required for the primary steel production. In order to develop an energy-efficient process chain for aluminum recycling, this paper presents a method to recycle aluminum scrap of AA-7175 and AA-7475 alloys directly by a hot extrusion process without an energy intensive re-melting process. The aluminum scrap is in a first step characterized, compacted to billets and finally extruded to new profiles without melting. In this investigation, the scrap material as well as the extruded profiles is characterized by their microhardness. The final profiles from scrap are compared with regard to their strength with conventional profiles by carrying out tensile tests.

With the technique of nonlinear quantum beat spectroscopy (NQBS), based on time-integrated, spectrally resolved four-wave mixing, the nonlinearities of biexcitons localized at neutral acceptor sites in CdSe are investigated. The NQBS offers the possibility to distinguish between quantum beats from a three-level system and polarization interference from independent two-level systems. The localized biexciton states are discussed in analogy with excited states of holes in neutral donor complexes.

By observing quantum beats in the self-diffracted signal from a nonlinear mixing process in a crystal, and by spectrally resolving this signal, information is obtained about solid state parameters, such as energy splittings and energy shifts. This technique is used to study bound excitons in CdSe with a strong, resonant third-order susceptibility. Furthermore, in the region of free exciton propagation, effects on the third-order nonlinear polarization are observed and explained by quantum beats between propagating polaritons

Picosecond lasers allow to detect the dynamics of excitons directly in the time domain. Mere examples of such experiments are presented for high quality AlGaAs MQW samples at low temperatures and in the low and medium density regime. The phase relaxation time T 2 is measured in FWM experiments and quantum beats are observed between the hh and lh exciton and between exciton and biexciton states. A value of the biexciton binding energy of 1.75 meV is deduced in agreement with our luminescence data. The T 2 times are compared with scattering times τ obtained from diffusion measurements using ps and ns laser-induced gratings. Interface-roughness scattering occurs only for thermalized excitons

Dynamics of free and bound excitons in CdSe and localized excitons in CdSe x S 1-x are studied by degenerate four-wave mixing and light-induced grating experiments. In the coherent range, the dephasing of excitons is determined as a function of temperature, density and energy. For incoherent excitons, recombination lifetimes and diffusion coefficients are determined. In particular, the mobility of excitons in CdSe x S 1-x near the mobility edge is studied

The time evolution of the adsorption due to exciton-biexciton transitions and the subsequent relaxation, diffusion and recombination of excitons and exciton complexes are investigated in CdSe by differential transmission experiments and by laser-induced grating experiments. Transitions from free excitons and impurity bound excitons as well as direct two-photon absorption (TPA) to the biexciton state are identified. For a quasi-equilibrium situation, a few hundred picoseconds after the excitation, a diffusion coefficient D x = 3.6 cm 2 /s and a recombination lifetime T x = 1500 ps is determined for free excitons at a lattice temperature of 30 K.

We have observed the direct two-photon absorption (TPA) to the excitonic molecule state in CdSe for the first time by a differential transmission technique and estimated the binding energy E b xm = 4.1 meV of the molecule. Excitons bound to impurities strongly enhance the TPA and as well induce two-step transitions to the biexciton state. Out of the time resolved measurements of the induced absorption a lifetime T 1 = 600 ps of the bound exciton is determined.

Experiments are discussed wherein scattering of excitonic polaritons with acoustic phonons between different polariton modes can be observed. Information about this dissipation process is given by the luminescence of deep impurities acting as microscopic detectors within the crystal which are sensitive to the distribution of energy to the different polariton branches. The calculated intensity for an ensemble of ideal micro-detectors containing constant quantum yield and absorption probability agrees excellently with measurements. Es werden Experimente vorgestellt, in denen die fur die Dissipation verantwortliche Streuung von exzitonischen Polaritonen an akustischen Phononen beobachtet wird. Die Detektion des gestreuten Lichtes erfolgt anhand der Lumineszenz tiefer Storstellen. Dabei stellen die betracteten Zentren mikrosk opische Detektoren der, die empfindlich die Verteilung der Energie auf die Verschiedenen Polaritonenmoden registrieren. Die fur ein Ensemble von idealen Mikro-Detektoren, unter Berucksichtigung einer konstanten Quantenausbeute und einer konstanten Absorptionswahrscheinlichkeit, berechnete Intensitatsverteilung stimmt hervorragend mit Messungen uberein.

We investigate theoretically the coupling between the ordinary and extraordinary beam in CdS which can be caused by external perturbations of the crystal symmetry and manifests themselves by non-diagonal elements of the susceptibility tensor. The theory based on Stahl's coherent band-gap dynamics yields the dispersion relation for the two waves propagating in the crystal. The dispersion establishes a relation between microscopic band structure parameters and macroscopic wave vectors and determines the diagonal elements of the susceptibility. The transmission problem is solved exactly by means of the classical electrodynamics. The obtained formulas contain a fit parameter related to a non-diagonal element of the susceptibility tensor which can be determined by fitting measured spectra around the isotropic point.

The An=1-exciton in CdS can hardly be excited by light of polarisation E ∥ c. By simple rotating the sample connected with an increasing of the transition probability the energy transfer between excitons and impurities can widely be changed. The measured excitation spectra of the integrated luminescence (720 nm < λ < 900 nm) are compared with the absorption, thereby unintentionally doped and thin crystals are used. Das An=1-Exziton in CdS ist fur Licht der Polarisation E ∥ c nur schwach anregbar. Durch einfaches Drehen der Probe, verbunden mit einer Vergroserung der Ubergangswahrscheinlichkeit, kann der Energieubertrag des Exzitons an die Storstellen in weiten Grenzen variiert werden. Die gemessenen Anregungsspektren der integralen Lumineszenz zwischen 720 und 900 nm an nicht vorsatzlich dotierten, dunnen Kristallen werden quantitativ mit der Absorption verglichen.

(Zn) [7440-66-6] Zn (MW 65.39) InChI = 1S/Zn InChIKey = HCHKCACWOHOZIP-UHFFFAOYSA-N (AgNO3) [7761-88-8] AgNO3 (MW 169.88) InChI = 1S/Ag.NO3/c;2-1(3)4/q+1;-1 InChIKey = SQGYOTSLMSWVJD-UHFFFAOYSA-N (Cu(OAc)2·H2O) [6046-93-1] C4H8CuO5 (MW 199.67) InChI = 1S/2C2H4O2.Cu.H2O/c2*1-2(3)4;;/h2*1H3,(H,3,4);;1H2/q;;+2;/p-2 InChIKey = NWFNSTOSIVLCJA-UHFFFAOYSA-L (reagent for selective reduction of activated or conjugated triple bonds to (Z)-alkenes;1, 2 compatible with many functional groups) Physical Data: see Zinc, Copper(II) Acetate, and Silver(I) Nitrate. Solubility: insol organic solvents and water; reacts with dilute acids and bases. Preparative Method: argon is passed for ca. 15 min through a well stirred suspension of commercial zinc dust (5.0 g, ca. 230 mesh ASTM) in water (30 mL). Cu(OAc)2·H2O (0.5 g) is added and after 15 min AgNO3 (0.5 g) is introduced (exothermic reaction). The mixture is stirred for 30 min, and the activated metal is collected by suction filtration under argon. The dark solid is washed with water (2 × 30 mL), MeOH (2 × 30 mL), acetone (2 × 30 mL), and Et2O (2 × 30 mL). The Et2O-moist Zn dust is transferred into 20 mL MeOH/H2O (1∶1, v/v) and is ready for use. Handling, Storage, and Precautions: the reagent has to be freshly prepared prior to use. The activated metal may be briefly stored covered with solvent (e.g. MeOH/H2O; 1/1, v/v) in the absence of oxygen. The dry reagent is pyrophoric!

Results of an international ring-test of two laboratory methods are presented for investigating the biodegradability of organic polymeric test materials in aquatic test systems based on respirometry and the evolution of carbon dioxide. These methods are developed further from the well-known standardized biodegradation tests ISO 9408 (1999) and ISO 9439 (1999), which have been successfully used for many years. The most important improvements are the extension of the test period up to six months, the increase of the buffer capacity and nutrient supply of the inorganic medium, an optimization of the inoculation, and optionally, the possibility of a carbon balance. A ring test, organized by the International Biodeterioration Research Group (IBRG), was run using a poly(,-caprolactone)-starch blend and an aliphatic-aromatic co-polyester as test materials and a microcrystalline cellulose powder as a reference material. The test results and the experience gained by the participants showed that the methods are suitable and practicable. The test methods have been meanwhile established as standards ISO 14851 (1999) and ISO 14852 (1999).

1. Male Sprague-Dawley rats were pretreated via bilateral infusion of the VTA with the selective neuronal nitric oxide synthase inhibitor, 7-nitroindazole (0, 8, or 40 ng/hemisphere), prior to each of 7 daily systemic cocaine (30 mg/kg, i.p.) or saline (1 ml/kg) treatments. 2. After a 7-day treatment withdrawal period, rats received a final systemic challenge with either cocaine (30 mg/kg, i.p.) or saline (1 ml/kg). 3. Locomotor and stereotypic activity were measured following the first and last treatments. 4. Daily cocaine treatment led to the development of sensitization to its stereotypic effects as revealed upon drug challenge. 5. The development of sensitization of cocaine-induced stereotypy was completely blocked by daily intra-VTA pretreatment with 7-nitroindazole. 6. In addition, attenuation of the locomotor effects of cocaine challenge was also observed in animals that received daily intra-VTA 7-nitroindazole (40 ng/hemisphere) infusions. 7. The results indicate that VTA nitric oxide is necessary for the development of sensitization of cocaine-induced stereotypic behavior, and that its repeated inhibition may produce lasting effects on the locomotor response to the drug.

The measurement of the degree of oxidative stress in patients often causes problems because of the lack of useful parameters. Therefore, we used an ELISA technique to evaluate serum protein carbonyls as a parameter of oxidative stress in patients during coronary heart surgery. Protein carbonyls were detected in serum samples of 14 patients undergoing coronary surgery and cardiopulmonary artery bypass grafting. A clear 2- to 3-fold increase in protein carbonyls in serum samples taken from human venous coronary sinus could be detected in the reperfusion period of the heart. We compared these data with markers of oxidative stress previously used, such as the glutathione status and the lipid peroxidation product malondialdehyde (MDA). Strong correlations of the protein carbonyl formation with MDA (r2 = 0.86) and oxidized glutathione (r2 = 0.81) were found in the early reperfusion stage. Increased levels of oxidized glutathione and MDA were detected only in the early reperfusion period. In contrast, the serum protein carbonyl content remained elevated for several hours, indicating a considerably slower serum clearance of oxidized proteins compared with that of lipid peroxidation products and the normalization of the glutathione status. We therefore concluded that the measurement of serum carbonyls by this ELISA technique is suitable to detect oxidative stress in serum samples of patients. The relative stability of the parameter makes the protein carbonyl detection even more valuable for clinical purposes.

Non-Fermi-liquid (nFl) behavior caused by a single site effect could be confirmed by measurements of the electric resistivity of Y 0.8 U 0.2 Pd 3 , doped with zirconium on the uranium sites. For high temperatures T > T K the resistivity shows Kondo-like behavior, while for low temperatures T ⪡ T K there is nFl behavior with Δρ ( T )/ Δρ (0)=1− a ( T / T K ) n ( n =1.07±0.10, independent of the uranium concentration).

In transient laser-induced grating experiments, the diffusion coefficients and lifetimes of free excitons are determined in CdSe at temperatures between 2 and 40 K and for different densities. We find that the diffusion coefficient D decreases and that the recombination lifetime ${\mathit{T}}_{1}$ increases with increasing temperature. The increase of ${\mathit{T}}_{1}$ with temperature is due to the release of excitons bound to impurities and to an increase of the radiative lifetime. From the measured D values for motion parallel and perpendicular to the crystal c axis, we extract momentum relaxation rates which are discussed in terms of exciton-acoustic-phonon scattering. In pure samples, and for lattice temperatures T10 K, the interaction via the deformation potential is dominating, while for higher temperatures, the interaction via the piezoelectric potential becomes significant.

By analyzing simultaneously measured transmission and reflection spectra of thin CdS crystals in the spectral region of excitonic polaritons, we succeded in determining the energy dependence of γ to be proportional to the group velocity dω/dk of the polaritons. Such a dependence can be explained by polariton scattering at charged impurities. With the help of this known energy dependence of the abc's it could be unambiguously shown that Pekar's assumption is the only one to explain all the experimental results.

Mesure simultanee des spectres d'absorption et de reflexion entre 2,548 et 2,558 eV; determination du spectre d'amortissement par iteration et mise en evidence de son accord satisfaisant avec la vitesse de groupe des polaritons

Aus N-Chlorcarbonyl-ketiminen 3 oder α-Chlor-alkylisocyanaten 4 werden mit tert.-Butylhydroperoxid und Pyridin N-tert.-Butylperoxycarbonyl-ketimine 7 dargestellt. Kinetische Messungen und Produktanalysen zeigen, das die Peroxide 7 bei 110–130° Spontanzerfall unter homolytischer Spaltung der Peroxidbindung erleiden. Organic Peroxides, XV1). – Synthesis and Thermal Decomposition of N-t.-Butylperoxycarbonylketimines The title compounds 7 are prepared by the reaction of N-chlorocarbonylketimines 3 or α-chloroalkyl isocyanates 4 with t-butyl hydroperoxide and pyridine. It is shown by kinetic experiments and product analysis that the peroxides 7 are decomposing at 110–130° by homolytic cleavage of the peroxide bond.

α-Cyanperoxycarbonsaure-tert-butylester wurden dargestellt, ihre Thermolyse wurde kinetisch und praparativ untersucht. In allen Beispielen wurde Homolyse nachgewiesen, die α-Cyangruppe ubt dabei einen zerfallshemmenden Einflus, im Vergleich mit den unsubstituierten Peroxycarbonsaureestern aus. Dies wird durch einen polaren Substituenteneffekt und eine nur geringe Dehnung der C-α–CO-Bindung im Ubergangszustand des Peroxysaureester-Zerfalls gedeutet. Eine allgemeine Beziehung zwischen dem Einflus von α-Methyl-gruppen auf die Peroxysaureester-Fragmentierung und den Taftschen σI-Konstanten wird aufgezeigt. Organic Peroxides, XVII. Preparation and Thermolysis of tert-Butyl α-Cyanoperoxycarboxylates A series of tert-butyl α-cyanoperoxycarboxylates was prepared. The kinetics and products of their homolysis were investigated. α-Cyano groups exert a rate retarding effect in comparison to the unsubstituted peroxycarboxylates. This is interpretated by only little stretching of the C-α–CO-bond in the transition state and by the influence of a polar substituent effect. A general relationship between the rate enhancing effect of α-methyl groups on peroxyester decompositions and Taft′s σI constants was observed.

Investigations concerning the temperature dependence of the degree of fluorescence polarization of fluorene, fluoranthene, perylene and 9,10-dimethylanthracene in ethanol show that the excess energy fed into the system by excitation at short wavelength is dissipated in such a short time that neither enhanced rotational diffusion nor a change in local temperature are observable.

Drei O-tert.-Butylperoxycarbonyl-ketoxime (3a–c) wurden dargestellt. Ihr thermischer Zerfall in Athylbenzol wurde praparativ und kinetisch untersucht. Die Erwartung, das wegen der Stabilitat der Iminoxy-Radikale bei der Thermolyse dieser Perester homolytische Fragmentierung erfolgt, bestatigte sich nicht. Die grose thermische Stabilitat dieser neuen Peroxide schliest einen homolytischen Fragmentierungsmechanismus aus. Homolytische Perester-Fragmentierungen werden demnach nicht durch die Stabilitat der dabei entstehenden Radikale ausgelost, vielmehr steht die Bedeutung polarer Effekte im Vordergrund. Organic Peroxides, XII. Preparation and Thermolysis of O-(tert-Butylperoxycarbonyl)ketoximes Three O-(tert-butylperoxycarbonyl)ketoximes (3a–c) were prepared. The kinetics and the products of their thermolysis in ethylbenzene were investigated. Despite the known stability of iminoxy radicals, these peresters did not decompose readily. Consequently a homolytic fragmentation mechanism may be excluded. Homolytic perester fragmentations are therefore not induced by the stability of the radicals being generated but depend mainly on favorable polar effects.

It is shown that the fluorescence quantum yield depends on temperature rather than on the viscosity of the solvent. The intersystem crossing rate can be described as a sum of a temperature independent and a temperature dependent term. For most of the molecules investigated in this paper the latter can be assumed to have the Arrhenius form. With anthracene, however, significant deviations from the Arrhenius behaviour are observed. With a more general expression involving the density of states the temperature dependence of the fluorescence quantum yield can be satisfactorily described.

Die im Titel genannte Verbindung 5 wurde aus N.N-Phthaloyl-O-chlorformyl-hydroxylamin (4) und tert.-Butylhydroperoxid dargestellt und in Athylbenzol bei 110–130° thermolysiert. Die Kinetik der Thermolyse und die dabei entstehenden Produkte zeigen einen homolytischen Zerfall an, der durch Spaltung der Peroxidbindung und anschliesende Decarboxylierung eingeleitet wird. Ein Fragmentierungsmechanismus konnte ausgeschlossen werden. Organic Peroxides, XIV1). – Synthesis and Thermal Decomposition of tert.-Butylperoxycarbonyl-N,N-phthaloylhydroxylamines The title compound 5 was prepared from N,N-phthaloyl-O-chloroformylhydroxylamine (4) and t.-butyl hydroperoxide and decomposed in ethylbenzene at 110–130°. The kinetics and the products of the decomposition indicate an homolytic decomposition mechanism. It is initiated by homolysis of the peroxide bond which is followed by decarboxylation. A homolytic fragmentation process was excluded.

It is shown that the observation of the degree of polarization of the fluorescence of 9,9′-spirobifluorene VI and of 2,2′-diamino-7,7′-dinitro-9,9′-spirobifluorene VII allows a determination of the rate constant for energy transfer from the initially excited to the unexcited part. The rate constants are of the order of 108 s−1 for VI and 3 · 109 s−1 for VII. The corresponding electronic matrix elements of interaction are evaluated. They are rather due to the Coulomb-interaction of the transition densities than to spiroconjugation. In VI the coupling vanishes in the equilibrium conformation, vibronic effects must be evoked for explaining its existence.

Die Korrosion von Stahl in den beiden Wassern unterliegt jahreszeitlichen Schwankungen; die Korrosionsmaxima liegen im Frubjabr und Herbst. Die Schwankungen konnen nicht allein einer Anderung der Wassertemperatur, der Salzkonzentration oder des Sauerstoffgehalts zugeschrieben werden, sondern beruhen auf einem Zusammenwirken von biotischen und abiotischen Fartoren, die erstgenannten sind verantwortlich fur Schwankungen der Korrosion in Ab-hangigkeit von der Temperatur. Die Aktivitat der Bakterien tritt erst bei Temperaturen ab 10 °C auf, da dort der Stoffwechsel aktiviert wird und die Stoffwechselprodukte das Eisen angrei- Influences of bacteria on iron corrosion in brackish and sea waters The corrosion of steel in seawaters is subject to seasonal variations; the corrosion maxma being in spring and autumn. The variations are not attribuable to changes in water temperature, salt concentration or oxygen content but are due to the co-action of biotic and abiotic factors, the former givin rise to temperature dependent variations of corrosion. The activity of bacteria becomes bovious only at temperatures above 10 °C; at these temperatures metablolism is activated and the products of matabolism may attack iron (or bac

The T-T spectra, the triplet quantum yield φ T and the fluorescence quantum yield φ F of 2-tert. butyl-4-methylindazole and 1,3-dimethylindazole have been measured in the temperature range of +25° to −196°C in solvents of different viscosities. It could be shown that in all cases where photochemical reactions from the first excited singlet state are absent, the sum φ F + φ T equals unity within the limits of error.