A comparative study on the jet loop reactor and continuos stirred tank reactor in the selective hydrogenation of palm olein (I.V.64)

Jet Loop Reactor (JLR) was developed to improve the overall performance of hydrogenation processes. Nevertheless, the application of JLR in the palm oil and oleochemical industries in Malaysia is still very much sparse. A substantial amount of investment and the lack of study conducted in Malaysia on the application of JLR have retarded the retrofitment and/or replacement of the conventional CSTR with this technology. In the wake of this, a comparative study was conducted to investigate the performance of JLR in the selective hydrogenation of palm olein with an IV of 64 in comparison to the hydrogenation in the conventional CSTR system. A pilot scale JLR with a capacity of 250 liter was used in the study. The circulation of the sample in the loop was achieved via a single speed pump. The experimental result was compared with result from the CSTR experiment. A down-scaled laboratory CSTR apparatus was used in the study for this purpose. A software package, developed via Microsoft Excel 2000 and Visual Basic Application (VBA) softwares, was used to simulate the behavior of the hydrogenation process in both, JLR and CSTR, under similar capacity. The outcome of the study showed that with the limitation of single speed pump, the JLR could not matched the superiority of CSTR in the selective hydrogenation process for it required slow reaction to produce high trans fatty acids hydrogenated product. On the positive note, the developed software package is a useful tool which allows an easy method to study the behavior of the hydrogenation process of JLR and CSTR. The prediction of the CSTR process was acceptable, but the prediction of JLR process was less accurate, revealing a maximum of 30% error. It can be concluded that the present analytical method used in the simulation of JLR required improvement on the modeling of the process, or to opt for the numerical solution, to produce a much better prediction. A retrofit method was also suggested in the study, for the possibility of fitting in the JLR facility in the existing CSTR system with minimal modification, for the system to have dual function of slow and fast reactions

The Importance of Physical Models for Deriving Dust Masses and Grain Size Distributions in Supernova Ejecta I: Radiatively Heated Dust in the Crab Nebula

Recent far-infrared (IR) observations of supernova remnants (SNRs) have revealed significantly large amounts of newly-condensed dust in their ejecta, comparable to the total mass of available refractory elements. The dust masses derived from these observations assume that all the grains of a given species radiate at the same temperature, regardless of the dust heating mechanism or grain radius. In this paper, we derive the dust mass in the ejecta of the Crab Nebula, using a physical model for the heating and radiation from the dust. We adopt a power-law distribution of grain sizes and two different dust compositions (silicates and amorphous carbon), and calculate the heating rate of each dust grain by the radiation from the pulsar wind nebula (PWN). We find that the grains attain a continuous range of temperatures, depending on their size and composition. The total mass derived from the best-fit models to the observed IR spectrum is 0.019-0.13 solar masses, depending on the assumed grain composition. We find that the power-law size distribution of dust grains is characterized by a power-law index of 3.5-4.0 and a maximum grain size larger than 0.1 microns. The grain sizes and composition are consistent with what is expected for dust grains formed in a Type IIP SN. Our derived dust mass is at least a factor of two less than the mass reported in previous studies of the Crab Nebula that assumed more simplified two-temperature models. The results of this study show that a physical model resulting in a realistic distribution of dust temperatures can constrain the dust properties and affect the derived dust masses. Our study may also have important implications for deriving grain properties and mass estimates in other SNRs and for the ultimate question of whether SNe are major sources of dust in the Galactic interstellar medium (ISM) and in external galaxies.Comment: 9 pages, 2 tables, 8 figures, Accepted to The Astrophysical Journa

Co-occurrence of risky lifestyle behavior with overweight, excess abdominal fat and high blood pressure - case oriented approach [Zajednička pojavnost rizičnog ponašanja i prekomjerne tjelesne težine, abdominalne debljine i visokog tlaka - studija slučajeva]

The objective was to estimate the proportion of cases developed interim risk factors (INTF: overweight, excess abdominal fat, high blood pressure) in relation with behavioral risk factors (BEHF: smoking, heavy alcohol intake, unhealthy diet, physical inactivity). NOBIR group was defined as cases with no BEHF and BIR as those with them. Both groups show higher proportions of INTF in older age. The increase by age varies of twofold (overweight: 13.2-29.2 for men, 18.1-42.6 for women) to six fold (high blood pressure: 4.6-26.5 for men, 6.6-40.8 for women) in proportions. Women show higher proportions of INTF than men in both groups, but BIR group shows higher proportions than NOBIR in all the age groups taking the both gender together. As a BEHF the physical inactivity has a markedly increase with age (from 4% to more than 25%). Smoking is the only BEHF decreasing in oldest for all the INTF

Expansion of the winter moth outbreak range : no restrictive effects of competition with the resident autumnal moth

1. Both direct and indirect competition can have profound effects on species abundance and expansion rates, especially for a species trying to strengthen a foothold in new areas, such as the winter moth (Operophtera brumata) currently in northernmost Finland. There, winter moths have overlapping outbreak ranges with autumnal moths (Epirrita autumnata), who also share the same host, the mountain birch (Betula pubescens ssp. czerepanovii). Competitive interactions are also possible, but so far unstudied, are explanations for the observed 1–3 years phase lag between the population cycles of the two moth species. 2. In two field experiments, we studied host plant-mediated indirect inter-specific competition and direct interference/exploitation competition between autumnal and winter moths. The experimental larvae were grown either with the competing species or with the same number of conspecifics until pupation. Inter-specific competition was judged from differences in pupal mass (reflecting lifespan fecundity), larval development time and larval survival. 3. Larval performance measurements suggested that neither direct nor indirect interspecific competition with the autumnal moth reduce the growth rate of winter moth populations. Winter moths even had a higher probability of survival when reared together with autumnal moths. 4. Thus, we conclude that neither direct nor indirect inter-specific competition is capable of suppressing the spread of the winter moth outbreak range and that both are also an unlikely cause for the phase lag between the phase-locked population cycles of the two moth species

Responses of generalist invertebrate predators to pupal densities of autumnal and winter moths under field conditions

1. Generalist natural enemies are usually not considered as being capable of causing population cycles in forest insects, but they may influence the population dynamics of their prey in the low density cycle phase when specialist enemies are largely absent. 2. In the present field study, the total response of the generalist invertebrate predator community to experimentally established pupal densities of the closely related autumnal (Epirrita autumnata) and winter moths (Operophtera brumata) was analysed. 3. Due to the high amount of variation in the dataset, the exact shape of the response curve could not be convincingly estimated. Nevertheless, two important conclusions can be drawn from the analyses. 4. Firstly, the natural invertebrate predator community seems to become saturated at rather low densities of both autumnal and winter moth pupae. Secondly, the predator community seems to become saturated at much lower densities of autumnal than of winter moth pupae. 5. Furthermore, pupal mass was significantly negatively correlated with invertebrate predation probability in autumnal moth pupae. 6. These results indicate that differences in the predator assemblage being able to consume pupae of the two moth species, as well as different handling times, could be responsible for the substantially higher predation rates in winter than in autumnal moth pupae. 7. As a consequence, the population dynamics of autumnal moths might be less affected by generalist invertebrate predators than those of winter moths, as autumnal moths seem able to escape from the regulating influence of generalist predators at much lower population densities than winter moths

The free energy of biomembrane and nerve excitation and the role of anesthetics

In the electromechanical theory of nerve stimulation, the nerve impulse consists of a traveling region of solid membrane in a liquid environment. Therefore, the free energy necessary to stimulate a pulse is directly related to the free energy difference necessary to induce a phase transition in the nerve membrane. It is a function of temperature and pressure, and it is sensitively dependent on the presence of anesthetics which lower melting transitions. We investigate the free energy difference of solid and liquid membrane phases under the influence of anesthetics. We calculate stimulus-response curves of electromechanical pulses and compare them to measured stimulus-response profiles in lobster and earthworm axons. We also compare them to stimulus-response experiments on human median nerve and frog sciatic nerve published in the literature.Comment: 10 pages, 6 figure

Reversed impacts by specialist parasitoids and generalist predators may explain a phase lag in moth cycles : a novel hypothesis and preliminary field tests

Among cyclic populations of herbivores, inter-specific temporal synchrony has been attributed to both climatic factors and trophic interactions. In northern Europe, winter and autumnal moths undergo regular 9–11 year population cycles. The winter moth cycle has typically been phase-locked with that of the autumnal moth, but with a 1–3- year phase lag. We examined potential effects of natural enemies on this phase lag using field experiments and observational data. We found that larval parasitism was significantly higher in autumnal than in winter moths. Conversely, pupal predation by generalist invertebrates was clearly greater in winter than in autumnal moths. The difference in parasitism rates may contribute to the earlier collapse of the autumnal moth cycle. In addition, the phase lag may be strengthened by higher pupal mortality in winter moths in the early increase phase of the cycles. As a consequence, we put forward a hypothesis on reversed effects of natural enemies, providing a potential explanation for phase-lagged population cycles of these moth species