Search results for "ACTIVATION"
showing 10 items of 2079 documents
Annealing of color centers in LiBaF 3
2002
Results of the glow rate technique to analyze the activation energy of thermostimulated annealing of X-ray created F -type color centers in LiBaF 3 crystals are presented, showing pure and containing oxygen centers. It is shown that depending on the impurity composition two alternative mechanisms are involved in the annealing of color centers. It is proposed that either the anion vacancy governed migration of F -centers resulting in recombination with complementary defects, or the thermal delocalization of radiation created fluorine ( F i ) interstitials captured by anti-structure defects followed by recombination with all kinds of complementary F -type centers are responsible for the recom…
Study of the recombination around the excitonic region of MBE ZnSe:Cl thin films
2008
The recombination processes around the excitonic region of undoped ZnSe and chlorine doped ZnSe thin films were studied by continuous-wave photoluminescence (cw-PL) and time-resolved photoluminescence (TRPL) spectroscopies. Samples with different chlorine concentration were obtained by varying the temperature of the Cl source. The evolution of the PL signal and its decay time were analyzed as a function of temperature. Activation energy (Ea) values associated to the quenching of the D0X and band-to-band emission were obtained from the temperature dependent cw-PL experiments. The activation energy was lower for the film with higher Cl content. The characteristic exponential decay time (TPL) …
The discovery of nuclear fission 50 years ago a few remarks
1990
Abstract A historical account on the details of the discovery of nuclear fission in 1939 is given.
Toward large-area targets for “TRAKULA”
2011
Abstract TRAKULA ( Tra nsmutationsrelevante k ernphysikalische U ntersuchungen l anglebiger A ktinide, i.e., nuclear physical investigations of long-lived actinides with relevance to transmutation) is a joint research project of the German Federal Ministry of Science and Education (BMBF) on nuclear physics investigations with modern scientific, technological and numerical methods. Experiments concerning the transmutation of radioactive waste are a central topic of the project. For this, large-area samples (≥40 cm 2 ) of 235,238 U and 239,242 Pu compounds are required for the calibration of fission chambers and for fission yield measurements. Another topic within the project requires large-a…
Activation cross-sections for some 14·8 MeV neutron-induced nuclear reactions on caesium: Isomer ratios of 134Cs, 133Xe and 130I
1970
Abstract Absolute cross-sections for 14·8 MeV neutron-induced reactions on 133Cs were determined using the activation technique. The results, with maximum errors of 15 per cent, are: ρ(n,γ)=7·1 mb (ρ(n,γ) 134m Cs =1·82 mb , ρ(n,γ) 134g Cs =5·3 mb ; ρ(n,2n) 132 Cs =1620 mb ; ρ(n,p)=10·5 mb (ρ(n,p) 133m Xe =4·8 mb , ρ(n,p) 133g Xe =5·7 mb ; ρ(n,α)=1·14 mb (ρ(n,α) 130m I =0·54 mb , ρ(n,α) 130g I =0·6 mb ; ρ(n, 3 He ) 131 I =3·2 μ barn ; ρ(n,2p) 132 I ⩽12 μ barn . At this particle energy direct interaction processes also contribute. The isomer cross-section ratios σ m σ g for 134Cs, 133Xe and 130I are 0·34±0·08, 0·85±0·15 and 0·91±0·2 respectively. A reinvestigation of the alleged 127I (n, 3n)1…
Understanding the polar mechanism of the ene reaction. A dft study
2014
The molecular mechanism of ene reactions has been characterised by DFT methods at the MPWB1K/6-311G(d,p) level of theory. Most reactions take place along a two-stage one-step mechanism in which the C-C bond formation takes place before the hydrogen transfer process. A very good correlation between the polar character of the reaction measured by the global electron density transfer at the transition state and the activation energy has been found. This behaviour allows establishing a useful classification of ene reactions in N-ene having a very high activation energy, P-ene reactions having activation energies between 35 and 20 kcal mol(-1), and H-ene reactions having activation energies belo…
Priming effects of an olfactory food cue on subsequent food-related behaviour
2013
International audience; Studies in cognitive psychology have highlighted a link between perception and action, by revealing the non-conscious influence that a cue can have on thinking and doing. The present study aimed at exploring whether an olfactory food cue could have an impact on food choices. We chose fruity odours as olfactory food cues, in order to examine if this kind of olfactory cue could lead individuals to choose fruit and vegetables. In the first experiment, 58 participants were assigned randomly to either a control or a melon-scent condition. In the melon-scent condition, they were unobtrusively exposed to a melon odorant in a waiting room, while in the control condition the …
Recent advances in the application of pulsed light processing for improving food safety and increasing shelf life
2019
Abstract Background New technologies of non-thermal disinfection such as pulsed light (PL) have emerged lately as an alternative to traditional (thermal and chemical) disinfection and preservation methods. PL can be used to decontaminate a great variety of foods as well as to decontaminate contact surfaces, thus improving safety in foods and extending their shelf life. Moreover, this technology can prevent or reduce some of the detrimental effects of traditional methods on nutrients and bioactive compounds of food products. Scope and approach The combination of PL with other techniques such as ultraviolet light (UV), thermosonication (TS), pulsed electric fields (PEF), manothermosonication …
Homogeneous Metal-Based Catalysis in Supercritical Carbon Dioxide as Reaction Medium
2016
Above 31.1 degrees C and 73.8 bar, carbon dioxide reaches the supercritical state, being transformed into a fluid (scCO(2)) that has attracted interest in the last few decades as reaction medium for several transition-metal-catalyzed organic transformations. The main feature of this fluid rests on its capability to dissolve large amounts of other gases such as hydrogen, carbon monoxide, ethylene, or even methane and light alkanes. In this manner, very high concentrations of these reactants are available for catalysis. In this contribution a review of the main achievements of the use of transition-metal complexes as catalysts in scCO(2) is presented.
Rat olfactory bulb and epithelium UDP-glucuronosyltransferase 2A1 (UGT2A1) expression: in situ mRNA localization and quantitative analysis.
2001
UDP-glucuronosyltransferases (UGTs) form a multigenic family of enzymes involved in the biotransformation and elimination of numerous endo- and xenobiotic compounds. Beside the diverse UGT isoforms present in the liver as well as in other tissues, the UGT2A1 isoform, also called olfactory UGT, was initially thought to be expressed in the nasal epithelium only. In this work, we demonstrate the UGT2A1 mRNA expression in the olfactory bulb, using in situ hybridization and quantitative reverse transcription-polymerase chain reaction (RT-PCR) techniques. Within the epithelium, UGT2A1 mRNA is mainly found in the sustentacular cells and to a lesser extent in Bowman's gland cells. Moreover, in situ…