Process Intensification of the Propane Dehydrogenation Considering Coke Formation, Catalyst Deactivation and Regeneration—Transient Modelling and Analysis of a Heat-Integrated Membrane Reactor

A heat-integrated packed-bed membrane reactor is studied based on detailed, transient 2D models for coupling oxidative and thermal propane dehydrogenation in one apparatus. The reactor is structured in two telescoped reaction zones to figure out the potential of mass and heat integration between the exothermic oxidative propane dehydrogenation (ODH) in the shell side, including membrane-assisted oxygen dosing and the endothermic, high selective thermal propane dehydrogenation (TDH) in the inner core. The developing complex concentration, temperature and velocity fields are studied, taking into account simultaneous coke growth corresponding with a loss of catalyst activity. Furthermore, the catalyst regeneration was included in the simulation in order to perform an analysis of a periodic operating system of deactivation and regeneration periods. The coupling of the two reaction chambers in a new type of membrane reactor offers potential at oxygen shortage and significantly improves the achievable propene yield in comparison with fixed bed and well-established membrane reactors in the distributor configuration without inner mass and heat integration. The methods developed allow an overall process optimization with respect to maximum spacetime yield as a function of production and regeneration times

Microscopic theory of the coupling of intrinsic Josephson oscillations and phonons

A microscopic theory for the coupling of intrinsic Josephson oscillations and dispersive phonon branches in layered superconductors is developed. Thereby the effect of phonons on the electronic c-axis transport enters through an effective longitudinal dielectric function. This coupling provides an explanation of recently observed subgap resonances in the $I_{dc}$-$V_{dc}$- curve of anisotropic cuprate superconductors forming a stack of short Josephson junctions. Due to the finite dispersion these resonances can appear at van-Hove-singularities of both optical and acoustical phonon branches, explaining low-voltage structures in the I-V-characteristic, which are not understood in phonon models without dispersion. In long junctions the dispersion of collective electron-phonon modes parallel to the layers is investigated.Comment: 4 pages, 3 figures, 1 table, espcrc2.sty, invited contribution to "Materials and Mechanisms of Superconductivity and High Temperature Superconductors VI - M2S-HTSC-VI", Houston, Texas, 20-25 Feb 2000, to appear in Physica

How to catch more prey with less effective traps: explaining the evolution of temporarily inactive traps in carnivorous pitcher plants.

Carnivorous Nepenthes pitcher plants capture arthropods with specialized slippery surfaces. The key trapping surface, the pitcher rim (peristome), is highly slippery when wetted by rain, nectar or condensation, but not when dry. As natural selection should favour adaptations that maximize prey intake, the evolution of temporarily inactive traps seems paradoxical. Here, we show that intermittent trap deactivation promotes 'batch captures' of ants. Prey surveys revealed that N. rafflesiana pitchers sporadically capture large numbers of ants from the same species. Continuous experimental wetting of the peristome increased the number of non-recruiting prey, but decreased the number of captured ants and shifted their trapping mode from batch to individual capture events. Ant recruitment was also lower to continuously wetted pitchers. Our experimental data fit a simple model that predicts that intermittent, wetness-based trap activation should allow safe access for 'scout' ants under dry conditions, thereby promoting recruitment and ultimately higher prey numbers. The peristome trapping mechanism may therefore represent an adaptation for capturing ants. The relatively rare batch capture events may particularly benefit larger plants with many pitchers. This explains why young plants of many Nepenthes species additionally employ wetness-independent, waxy trapping surfaces

How to catch more prey with less effective traps: explaining the evolution of temporarily inactive traps in carnivorous pitcher plants.

Carnivorous Nepenthes pitcher plants capture arthropods with specialized slippery surfaces. The key trapping surface, the pitcher rim (peristome), is highly slippery when wetted by rain, nectar or condensation, but not when dry. As natural selection should favour adaptations that maximize prey intake, the evolution of temporarily inactive traps seems paradoxical. Here, we show that intermittent trap deactivation promotes 'batch captures' of ants. Prey surveys revealed that N. rafflesiana pitchers sporadically capture large numbers of ants from the same species. Continuous experimental wetting of the peristome increased the number of non-recruiting prey, but decreased the number of captured ants and shifted their trapping mode from batch to individual capture events. Ant recruitment was also lower to continuously wetted pitchers. Our experimental data fit a simple model that predicts that intermittent, wetness-based trap activation should allow safe access for 'scout' ants under dry conditions, thereby promoting recruitment and ultimately higher prey numbers. The peristome trapping mechanism may therefore represent an adaptation for capturing ants. The relatively rare batch capture events may particularly benefit larger plants with many pitchers. This explains why young plants of many Nepenthes species additionally employ wetness-independent, waxy trapping surfaces

ADUBAÇÃO FOLIAR A BASE DE CÁLCIO E BORO NO CULTIVO DA SOJA (Glycine max)

The objective of this study was evaluated the effects of calcium (Ca) and boron (B), applied to leaf spraying at different stages of soybean, on yield components and productivity of soybean (Glycine Max).The experimental design was randomized blocks with four blocks. The treatments consisted of spraying the commercial solution with calcium and boron (10.0% Ca, 0.5% B), at dose of 3.0 L ha-1 in four different phases: 10 days before flowering (flower buds closed) R1 stage, in full bloom (with more than 80% anthesis) R2 stage, 15 days after full bloom (pods with 3 to 5mm) R3 stage and 30 days after full bloom (pods with 15mm) R4 stage, and a control without application of foliar fertilizer. The yield components evaluated were legumen number/plant, grain number/legumem, grain weight and productivity. Application of Ca and B did not influence soybean yield in any application stage. The yield components; legumen number/plant, grain number/legumem, grain weight did not differ significantly with application to leaf spraying of Ca and B, probably due to their adequate content in soil and water availability during the growing season.  O objetivo do trabalho foi avaliar os efeitos de cálcio e boro, aplicados em pulverização foliar, em diferentes estádios da cultura de soja, nos componentes de produção e produtividade da soja (Glycine Max). O delineamento experimental utilizado foi em blocos casualizados com quatro blocos. Os tratamentos consistiram na aplicação do fertilizante foliar comercial a base de cálcio e boro (10,0% Ca, 0,5% B) na cultura da soja na dose de 3,0 L ha-1 em quatro épocas: 10 dias antes do florescimento (botões florais fechados) estádio R1, no florescimento pleno (mais de 80% com antese floral) estádio R2, 15 dias após o florescimento pleno (vagens com 3 a 5mm) estádio R3 e 30 dias após o florescimento pleno (vagens com 15mm) estádio R4, e uma testemunha sem aplicação de fertilizante foliar. A aplicação foliar de Ca e B não influenciaram a produtividade da soja em nenhum estádio de aplicação. O número de vagens por planta, número médio de grãos por vagem e massa de mil grãos não diferiram estatisticamente com a aplicação foliar de Ca e B, provavelmente devido ao teor adequado dos mesmos no solo e boa disponibilidade hídrica durante o desenvolvimento da cultura. &nbsp

Formation of DNA Adducts by 1-Methoxy-3-indolylmethylalcohol, a Breakdown Product of a Glucosinolate, in the Mouse: Impact of the SULT1A1 Status - Wild-Type, Knockout or Humanised

We previously found that feeding rats with broccoli or cauliflower leads to the formation of characteristic DNA adducts in the liver, intestine and various other tissues. We identified the critical substances in the plants as 1-methoxy-3-indolylmethyl (1-MIM) glucosinolate and its degradation product 1-MIM-OH. DNA adduct formation and the mutagenicity of 1-MIM-OH in cell models were drastically enhanced when human sulfotransferase (SULT) 1A1 was expressed. The aim of this study was to clarify the role of SULT1A1 in DNA adduct formation by 1-MIM-OH in mouse tissues in vivo. Furthermore, we compared the endogenous mouse Sult1a1 and transgenic human SULT1A1 in the activation of 1-MIM-OH using genetically modified mouse strains. We orally treated male wild-type (wt) and Sult1a1-knockout (ko) mice, as well as corresponding lines carrying the human SULT1A1-SULT1A2 gene cluster (tg and ko-tg), with 1-MIM-OH. N2-(1-MIM)-dG and N6-(1-MIM)-dA adducts in DNA were analysed using isotope-dilution UPLC-MS/MS. In the liver, caecum and colon adducts were abundant in mice expressing mouse and/or human SULT1A1, but were drastically reduced in ko mice (1.2–10.6% of wt). In the kidney and small intestine, adduct levels were high in mice carrying human SULT1A1-SULT1A2 genes, but low in wt and ko mice (1.8–6.3% of tg-ko). In bone marrow, adduct levels were very low, independently of the SULT1A1 status. In the stomach, they were high in all four lines. Thus, adduct formation was primarily controlled by SULT1A1 in five out of seven tissues studied, with a strong impact of differences in the tissue distribution of mouse and human SULT1A1. The behaviour of 1-MIM-OH in these models (levels and tissue distribution of DNA adducts; impact of SULTs) was similar to that of methyleugenol, classified as “probably carcinogenic to humans”. Thus, there is a need to test 1-MIM-OH for carcinogenicity in animal models and to study its adduct formation in humans consuming brassicaceous foodstuff