Modeling of Surface Runoff in Xitiaoxi Catchment,China

Xitiaoxi catchment is one of the most important catchments in the Taihu basin in China. Due to its significant contribution of surface runoff and associated nutrients input to Lake Taihu, understanding of the processes of surface runoff in this catchment is, therefore, of primary importance in quantifying water and nutrient balances for Lake Taihu. The generation of surface runoff in the catchment is mainly controlled by rainfall and land cover, so the variety of surface runoff in Xitiaoxi catchment is seasonal. Moreover, the annual change of surface runoff is distinct. Because of the diversity of land use and variety of hydrological characteristics, numerical simulation of the generation of surface runoff over this catchment is not straightforward. In this paper, attempts were made in applying the Large Scale Catchment Model (LASCAM) to Xitiaoxi catchment. The Xitiaoxi catchment is divided into 47 subcatchments connected via a river network based on topology. The model was first run in an optimization mode to calibrate the parameters against the observed runoff for the period of 1968–1977, and then was run in a prediction mode to try to reproduce the runoff for the next 10 years from 1978 to 1987. The model indicates that saturation excess runoff is probably the dominant process for the catchment. The modeling results indicate that water storage in shallow soils near the stream has a high correlation with daily rainfall, while the water storage changes in deep aquifers demonstrate an annual change trend, showing a rising level for wet seasons and a declining level for dry seasons. The success in modeling surface runoff leads to confidence in modeling nutrients transport as the next step of modeling work.     

Characterization of SNARE protein expression in beta cell lines and pancreatic islets

Pancreatic beta cells and cell lines were used in the present study to test the hypothesis that the molecular mechanisms controlling exocytosis from neuronal cells may be used by the beta cell to regulate insulin secretion. Using specific antisera raised against an array of synaptic proteins (SNAREs) implicated in the control of synaptic vesicle fusion and exocytosis, we have identified the expression of several SNAREs in the islet beta cell lines, beta TC6-f7 and HIT-T15, as well as in pancreatic islets. The v-SNARE vesicle-associated membrane protein (VAMP)-2 but not VAMP-1 immunoreactive proteins were detected in beta TC6-f7 and HIT-T15 cells and pancreatic islets. In these islet-derived cell lines, this 18-kDa protein comigrated with rat brain synaptic vesicle VAMP-2, which was cleaved by Tetanus toxin (TeTx). Immunofluorescence confocal microscopy and electron microscopy localized the VAMP-2 to the cytoplasmic side of insulin containing secretory granule membrane. In streptolysin O permeabilized HIT-T15 cells, TeTx inhibited Ca2+-evoked insulin release by 83 +/- 4.3%, which correlated well to the cleavage of VAMP-2. The beta cell lines were also shown to express a second vesicle (v)-SNARE, cellubrevin. The proposed neuronal target (t)-membrane SNAREs, SNAP-25, and syntaxin isoforms 1-4 were also detected by Western blotting. The beta cell 25-kDa SNAP-25 protein and syntaxin isoforms 1-3 were specifically cleaved by botulinum A and C toxins, respectively, as observed with the brain isoforms. These potential t-SNARES were localized by immunofluorescence microscopy primarily to the plasma membrane in beta cell lines as well as in islet beta cells. To determine the specific identity of the immunoreactive syntaxin-2 and -3 isoforms and to explore the possibility that these beta cells express the putative Ca2+-sensing molecule synaptotagmin III, RT-PCR was performed on the beta cell lines. These studies confirmed that betaTC6-F7 cells express syntaxin-2 isoforms, 2 and 2', but not 2' and express syntaxin-3. They further demonstrate the expression of synaptotagmin III. DNA sequence analysis revealed that rat and mouse beta cell syntaxins 2, 2' and synaptotagmin III are highly conserved at the nucleotide and predicted amino acid levels (95-98%). The presence of VAMP-2, nSec/Munc-18, SNAP-25 and syntaxin family of proteins, along with synaptotagmin III in the islet cells and in beta cell lines provide evidence that neurons and beta cells share similar molecular mechanisms for Ca2+-regulated exocytosis. The inhibition of Ca2+-evoked insulin secretion by the proteolytic cleavage of HIT-T15 cell VAMP-2 supports the hypothesis that these proteins play an integral role in the control of insulin exocytosis.     

Carbon Nanotubes Grown by RF Heating and Their Morphological and Structural Properties

Multiwall and single-wall carbon nanotubes were synthesized on Fe-Co/CaCO₃ and a Fe-Co/MgO catalyst system, respectively, by using two different catalytic chemical vapor deposition methods, external furnace (EF) heating and radio frequency (RF) excitation. The carbon nanotubes synthesized with radio frequency excitation have a smaller outer diameter, fewer layers (smaller outer/inner diameter ratio), and better crystalline properties than the nanotubes grown with external furnace heating. The radio frequency process was found to be responsible for a faster growth rate of the carbon nanotubes over longer periods of time due to a higher localized heating. These findings can be explained by the skin currents induced in the metallic catalytic clusters, which keep the catalysts active for longer periods of time and diminish the amount of noncrystalline carbon formed in the synthesis process.     

Stability and consumer acceptance of long-chain omega-3 fatty acids (eicosapentaenoic acid, 20:5, n-3 and docosahexaenoic acid, 22:6, n-3) in cream-filled sandwich cookies

ABSTRACT:  We formulated a filling for sandwich cookies containing 400 mg of eicosapentaenoic acid, 20:5, n-3 (EPA) + docosahexaenoic acid, 22:6, n-3 (DHA) encapsulated in a matrix of starch and gelatin. Cookies were stored at 2 different temperatures (18 °C and 35 °C) and under 2 different packaging conditions (atmospheric and vacuum packed) for 28 d. At regular intervals, cookies were analyzed for moisture, water activity, and concentrations of EPA, DHA, and dienes. Results showed that there were no significant losses of EPA and DHA during storage under the conditions of study. A maximum loss of 5% was observed after 28 d of storage. The concentration of dienes obtained under different conditions were low (< 25 mmol/kg) as compared to a salmon oil sample with appreciable signs of oxidation (600 mmol/kg). Sensory evaluation of cookies by an untrained panel of healthy consumers and ulcerative colitis patients revealed no aftertaste and high acceptability of the cookies. Our results demonstrated that it is possible to make shelf-stable fortified foods with high levels of long-chain ω3FA.     

Adaptive helical mirror for generation of optical phase singularity

We report a specially designed adaptive mirror that can be bent into a helical shape for generation of an optical phase singularity. The adaptive helical mirror (AHM) reported here is a reflective device that can provide a continuous phase variation of the optical field in the azimuthal direction. The construction details and evaluation of the AHM are presented. A Michelson interferometer is used for the detection of the phase singularity. The AHM can be used for generation of a singular beam having multiple topological charges, positive or negative, just by controlling the excitation voltage of the AHM.     

Catalytic effect of carbon nanostructures on the hydrogen storage properties of MgH2–NaAlH4 composite

The present investigation describes the hydrogen storage properties of 2:1 molar ratio of MgH₂–NaAlH₄ composite. De/rehydrogenation study reveals that MgH₂–NaAlH₄ composite offers beneficial hydrogen storage characteristics as compared to pristine NaAlH₄ and MgH₂. To investigate the effect of carbon nanostructures (CNS) on the de/rehydrogenation behavior of MgH₂–NaAlH₄ composite, we have employed 2 wt.% CNS namely, single wall carbon nanotubes (SWCNT) and graphene nano sheets (GNS). It is found that the hydrogen storage behavior of composite gets improved by the addition of 2 wt.% CNS. In particular, catalytic effect of GNS + SWCNT improves the hydrogen storage behavior and cyclability of the composite. De/rehydrogenation experiments performed up to six cycles show loss of 1.50 wt.% and 0.84 wt.% hydrogen capacity in MgH₂–NaAlH₄ catalyzed with 2 wt.% SWCNT and 2 wt.% GNS respectively. On the other hand, the loss of hydrogen capacity after six rehydrogenation cycles in GNS + SWCNT (1.5 + 0.5) wt.% catalyzed MgH₂–NaAlH₄ is diminished to 0.45 wt.%.     

Measuring and predicting head space pressure during retorting of thermally processed foods

Traditional metal cans and glass jars have been the mainstay in thermally processed canned foods for more than a century, but are now sharing shelf space with increasingly popular flexible pouches and semi-rigid trays. These flexible packages lack the strength of metal cans and glass jars, and need greater control of external retort pressure during processing. Increasing internal package pressure without counter pressure causes volumetric expansion, putting excessive strain on package seals that may lead to serious container deformation and compromised seal integrity. The primary objective of this study was to measure internal pressure build-up within a rigid air-tight container (module) filled with various model food systems undergoing a retort process in which internal product temperature and pressure, along with external retort temperature and pressure, were measured and recorded at the same time. The pressure build-up in the module was compared with the external retort pressure to determine the pressure differential that would cause package distortion in the case of a flexible package system. The secondary objective was to develop mathematical models to predict these pressure profiles in response to known internal temperature and initial and boundary conditions for the case of the very simplest of model food systems (pure water and aqueous saline and sucrose solutions), followed by food systems of increasing compositional complexity (green beans in water and sweet peas in water). Results showed that error between measured and predicted pressures ranged from 2% to 4% for water, saline, and green beans, and 7% to 13% for sucrose solution and sweet peas. PRACTICAL APPLICATION: Flexible packages have limited strength, and need more accurate and closer control of retort pressure during processing. The package becomes more flexible as it heats and might expand with increasing internal pressure that may cause serious deformation or rupture if not properly controlled and/or counterbalanced with external retort pressure. This article describes methods for determining exactly what the retort pressure profile will need to be to avoid this problem during retorting, and mathematical models to predict these pressures in response to known internal temperature and initial/boundary conditions.