Mono- and bifunctionaltert-alcohols, i.e., cumyl alcohol (CumOH), 2,4,4-trimethyl-2-pentanol (TMPOH), 2,6-dihydroxy-2,4, 4, 6-tetramethylheptane (TMHDiOH), in conjunction with BCl3 have been shown to be efficient initiating systems for the living polymerization of isobutylene (IB) in CH3Cl or CH2Cl2 solvents in the –10° to –80°C range. The living nature of the polymerizations was demonstrated by linear Mn versus amount of polyisobutylene (PIB) formed (WPIB) plots starting at the origin and corresponding horizontal number of PIB moles formed (N) versus WPIB plots. Quenching with methanol producestert-chlorine terminated PIBs. Quantitative dehydrochlorination of the latter products yields exo-olefin (isopropylidene) end groups. These experiments demonstrate that living carbocationic polymerizations have in fact been conducted in these laboratories long ago (1) without having been recognized as such. 相似文献
Kinetic measurements at low temperatures (310–360 K) using gas chromatography (GC) for benzene hydrogenation on Pt(100) and
Pt(111) single crystal surfaces have been carried out at Torr pressures. These kinetic measurements demonstrated a linear
compensation effect for the production of cyclohexane. A detailed application of the model of selective energy transfer to
the experimentally obtained results yields the vibrational frequency of the adsorbate leading to reaction. This frequency
is attributed to ring distortion modes. The vibrational frequency of the heat bath, or catalyst, is ascribed to a Pt-H mode.
An approximate heat of adsorption of the reacting molecule is also calculated from the model. 相似文献
Mass transport, accompanied by chemical reaction through membrane reactor has been investigated in the case of varying diffusion coefficient and solubility coefficient. In reality, both parameters might depend on the concentration and/or on the inhomogeneity of the membrane layer. General mathematical models were developed to describe the mass transport, taking into account the external mass transfer resistances as well, when the solubility coefficient can vary, e.g. according to the Langmuir–Hinschelwood adsorption theory or when the value of diffusion coefficient depends on the concentration/anisotropy in the membrane. A general solution has been given that can be applied to most of the mathematical functions of the parameters mentioned. The concentration distribution and the mass transfer rate will be given in closed mathematical forms. The value of the mass transfer rates could be strongly altered by the varying diffusion- and/or solubility coefficient. The mathematical model and the effect of the varying parameters have been discussed in this paper. 相似文献
H-AITS-1 zeolite with Si/Ti = 50 and Si/Al = 50 was employed in preparing catalyst samples by ion-exchange and impregnation with a copper nitrate solution to obtain 0.24–1.15 wt.% and 1.5, 2 and 2.5 wt.% Cu loading, respectively. The catalytic properties for the NO decomposition were compared with that of Cu-ZSM-5 (Si/Al = 25 with 2 wt.% Cu loading) and similarity was found between the AITS-1 based samples and Cu-ZSM-5. Due to the higher acidity, the activity at 500°C per total copper atoms (an apparent turnover frequency, TOF) was significantly higher over Cu based AITS-1 samples being 2–3 × 10−3 s−1 as compared to 1 × 10−3 s−1 measured on Cu-ZSM-5. For the ion-exchanged Cu-AITS-1 there was an increase in TOF with increasing copper content, whereas on the impregnated samples a decrease in TOF was found. On all catalysts there was a maximum in the NO conversion at 500–550°C. The amount of NO per copper atom measured by temperature programmed desorption (TPD) was about the same as that on Cu-ZSM-5 and the features of the TPD were also similar. At the first contact of the catalyst at 500°C with the 2 vol% NO/Ar gas a transient N2O formation and a considerable delay in the O2 formation was observed. This could, however, be reproduced only on fresh catalyst, while all further transients showed different but reproducible features using the same sample. 相似文献
The phosphorylation of serine 10 in histone 3 (p-S10H3) has recently been demonstrated to participate in spinal nociceptive processing. However, superficial dorsal horn (SDH) neurons involved in p-S10H3-mediated nociception have not been fully characterized. In the present work, we combined immunohistochemistry, in situ hybridization with the retrograde labeling of projection neurons to reveal the subset of dorsal horn neurons presenting an elevated level of p-S10H3 in response to noxious heat (60 °C), causing burn injury. Projection neurons only represented a small percentage (5%) of p-S10H3-positive cells, while the greater part of them belonged to excitatory SDH interneurons. The combined immunolabeling of p-S10H3 with markers of already established interneuronal classes of the SDH revealed that the largest subset of neurons with burn injury-induced p-S10H3 expression was dynorphin immunopositive in mice. Furthermore, the majority of p-S10H3-expressing dynorphinergic neurons proved to be excitatory, as they lacked Pax-2 and showed Lmx1b-immunopositivity. Thus, we showed that neurochemically heterogeneous SDH neurons exhibit the upregulation of p-S10H3 shortly after noxious heat-induced burn injury and consequential tissue damage, and that a dedicated subset of excitatory dynorphinergic neurons is likely a key player in the development of central sensitization via the p-S10H3 mediated pathway. 相似文献
The dried bean beetle, Acanthoscelides obtectus, is an economically important, worldwide pest of legume crops including dry beans, Phaseolus vulgaris. Assessment of A. obtectus infestation levels in pre-harvest field crops and post-harvest granaries is difficult to achieve because there is no effective monitoring tool for early detection so that interventions can be deployed as needed. Because A. obtectus is a generic pollen and nectar feeder, we adopted an electrophysiological (EAG) screening approach, using the antennae of female A. obtectus to identify physiologically active, volatile phytochemicals, which could then be investigated for their attractiveness to A. obtectus in laboratory behavioral assays and preliminary field tests. Of the 27 compounds tested in EAG screening, 5 compounds, i.e., methyl anthranilate, methyl eugenol, benzyl alcohol, (RS)-lavandulol, and 2-phenylethanol, elicited stronger EAG responses than the standard (1-phenylethanol). In 4-arm olfactometer bioassays, female A. obtectus preferred the olfactometer arm containing the odor of either methyl anthranilate or benzyl alcohol compared to the solvent control. In preliminary field tests using these 2 compounds as a binary mixture, at least 5 times as many beetles were caught on baited traps compared to non-baited traps. The field data also suggested that benzyl alcohol was primarily responsible for the field activity of the blend. We hypothesize that the attraction of A. obtectus to the combined benzyl alcohol/methyl anthranilate and the single benzyl alcohol baits is connected to the species` nectar- and pollen-feeding behaviour and not to its intraspecific communication. To our knowledge, this is the first evidence that A. obtectus behavior in the field can be modified by the deployment of plant-derived semiochemicals.
Catalysis Letters - Heterogeneous catalysis is a chemical process achieved at solid–gas or solid–liquid interfaces. Many factors including the particle size, shape and metal-support... 相似文献
This paper investigates the development of loosening at flange joints owing to creep and relaxation of gaskets at medium high temperature. The model presented here is able to describe the interaction of gasket and flange in addition to the viscoelastic behaviour of a non-metallic gasket. The time-dependent material characteristics of the investigated gaskets were determined by standard tests whilst the reliability and preciseness of the derived equations are proved by test results. The paper deals with the dimensioning of flange joints on leak tightness operating at medium high temperatures. 相似文献