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排序方式: 共有492条查询结果,搜索用时 46 毫秒
31.
PURPOSE: To study the effects of two lipid excipients, Peceol and Gelucire 44/14 on the in vitro pancreatic lipase activity. METHODS: A 50 microL reaction mixture, consisting of 45 microL (3H) triolein as the radiolabeled substrate, 2.5 microL Peceol or Gelucire 44/14 (0.05-0.5%), either alone or in combination, 2.5 microL colipase (100 microg/mL), and 2.5 microL pancreatic lipase (1 mg/mL), was incubated for 10 min at room temperature. At the end of incubation, the reaction was stopped by the addition of an extraction solvent containing chloroform, methanol, and n-heptane (12.5:14:10), and the mixture vortexed briefly. Subsequently, 250 microL of 50 mM sodium carbonate was added and the aqueous and organic phase separated by centrifugation for 5 min at 1000 g. One hundred microliters of the supernatant was transferred to a scintillation counter and then radioactivity measured after the addition of 3.6 mL of scintillation fluid. Pancreatic lipase activity was determined by measuring the amount of free fatty acid released into the incubation medium and expressed as micromol free fatty acid released/min. RESULTS: When used alone, Peceol inhibited the pancreatic lipase activity significantly in a concentration-dependent manner, with a maximum inhibition of 57% at 0.4% of the excipient [p < 0.05, one-way analysis of variance (ANOVA)]. Similarly, Gelucire 44/14 alone caused inhibition of lipase activity in a concentration-dependent manner. However, the maximum inhibition (30%) was smaller in magnitude compared with the former agent. When the two excipients were used in combination, the inhibitory effects on the enzyme activity were similar to those observed with the individual agents (p < 0.05, one-way ANOVA). However, the maximum inhibition of 30% was lower than that observed with Peceol alone. CONCLUSIONS: The results from this study suggest that these lipid excipients inhibit in vitro pancreatic lipase activity and should be taken into consideration when developing oral formulations using these agents. 相似文献
32.
Zibar D. Johansson L. A. Chou H.-F. Ramaswamy A. Rodwell M. Bowers J. E. 《Photonics Technology Letters, IEEE》2007,19(9):686-688
A novel phase-locked coherent demodulator, based on a sampling phase-locked loop, is presented and investigated theoretically. The demodulator is capable of operating at high frequencies, by using optical sampling to downconvert the high-frequency input radio-frequency signal to the frequency range of the baseband loop. We develop a detailed theoretical model of the (sampling) phase-locked coherent demodulator and perform detailed numerical simulations. The simulation results show that the operation of the sampling demodulator resembles the operation of the baseband demodulator for very short optical pulses (<2 ps). Furthermore, we investigate how the signal-to-noise ratio of the demodulator is affected by timing and amplitude jitter of the pulsed optical source 相似文献
33.
Klamkin J. Ramaswamy A. Johansson L. A. Chou H.-F. Sysak M. N. Raring J. W. Parthasarathy N. DenBaars S. P. Bowers J. E. Coldren L. A. 《Photonics Technology Letters, IEEE》2007,19(3):149-151
Waveguide uni-traveling-carrier photodiodes (UTC-PDs) have been fabricated and tested. Output saturation currents greater than 40 mA at 1 GHz are demonstrated for a 10 mumtimes150mum photodiode (PD). The third-order intermodulation distortion is also measured and exhibits a third-order output intercept point of 43 dBm at 20 mA and 34 dBm at 40 mA for this same PD. UTC-PDs with geometries of 5 mumtimes100 mum and 10 mumtimes100 mum are also compared and it is shown that a wider waveguide PD has improved saturation characteristics due to the lower optical power density which reduces the saturation at the front end of the device 相似文献
34.
The combined effects of different heating methods (conventional (CH) vs. Ohmic (OH)), types of acidifying agent (citric vs malic acid) and pH levels (pH 4.5, 5.5 and 6.2) were investigated to study their influence on destruction kinetics of spores of Bacillus licheniformis. The ultimate aim to generate relevant kinetic data on an indicator microbial spore is useful for assessing the efficacy of thermal processes for acid or acidified low acid foods. Kinetic parameters were evaluated according to the first-order kinetic model. Temperature and pH showed a highly significant (p < 0.01) effect on the spore destruction kinetics. Ohmic heating showed marginally better rate of bacterial destruction than conventional heating. The overall range of D and z values were 1.1–11.2 min and 12.6–17 °C, respectively, depending up on the pH and temperature levels, method of heating as well as the type of acidulate used. The shortest D97°C = 1.1 min was obtained at pH of 4.5 when citric acid was used as an acidifying agent in OH. No significant difference (p > 0.05) was observed with respect to D and z values between the two types of acidifying agents. 相似文献
35.
Barber K.S. Liu T.H. Ramaswamy S. 《IEEE transactions on systems, man, and cybernetics. Part B, Cybernetics》2001,31(4):616-628
This paper describes techniques developed for conflict detection during plan integration. Agents' intensions are represented with intended goal structure (IGS) and the E-PERT diagrams. Conflicts are classified as goal, plan, and belief conflicts. Before integrating individual plans and detecting plan conflicts, agents first detect and eliminate their goal conflicts by exchanging their IGS. Plan integration is done through merging individual E-PERT diagrams. Project estimation and review technique (PERT) diagrams have been used extensively in the systems analysis area since the 1980s to provide a global consistent view of parallel activities within a project. We extended the PERT diagrams for use in the plan integration activity within multi-agent systems (MAS). The E-PERT diagram contributes to maintain traceable temporal relations among agents' local scheduled actions. Combined with pattern matching, plan conflicts due to resource sharing, or conflicting conditions (i.e., postconditions of one action disabling preconditions of another action) can be detected. The conflict detection techniques are implemented in a sensible agent testbed to promote deployment and performance analysis. 相似文献
36.
A variational, finite-difference method for computing the normalized propagation constants and the normalized field profiles of channel waveguides with arbitrary index profiles as well as aspect ratios is presented. Mode dispersion curves and the field profiles of the fundamental mode of channel waveguides having profiles of practical interest are included. 相似文献
37.
ABSTRACT The effect of temperature gradient on moisture migration during microwave heating of food materials was analyzed in this study. The analysis was performed using the finite element model developed and validated previously (Zhou et al., 1994b). Potato and bread were used as test materials. For high density food material (potato), temperature gradient effect on moisture migration was found to be negligible (less than 5%). For low density and porous food material (bread), percentage contribution of moisture movement due to temperature gradient was high (114%). However, the absolute difference of moisture content with and without considering temperature gradient effect was small for the microwave process studied, i.e., one-minute of microwave heating followed by three-minute of holding time period. 相似文献
38.
An Object-Oriented Modeling and Simulation Environment for Reactive Systems Development 总被引:1,自引:1,他引:0
Bernard T. Barcio S. Ramaswamy K. Suzanne Barber 《International Journal of Flexible Manufacturing Systems》1997,9(1):51-80
An environment to support the modeling, analysis, simulation, and development of state transition models, SMOOCHES (State Machines for Object-Oriented Concurrent Hierarchical Engineering Specifications), is presented. SMOOCHES allows the hierarchical construction, analysis, and simulation of state transition models in an object-oriented distributed environment. Statecharts (see Harel 1987b), a powerful mechanism for state transition specification, are fundamental to the development of SMOOCHES. To assist in the specification of hierarchical state transition models for distributed and reactive systems, statecharts are extended by introducing the concept of exit-safe states. SMOOCHES allows the specification of objects in the system with hierarchical state transition models and the derivation of new classes of objects through inheritance. A graphical monitoring system has been developed to represent and simulate the object state life cycles and monitor event generations. The example presented illustrates the modeling and simulation of different state life cycles of an assembly robot. 相似文献
39.
Jasim Ahmed Hosahalli S. Ramaswamy Vijaya G.S. Raghavan 《Journal of food engineering》2007,80(4):1125-1133
Dielectric properties of Indian Basmati rice samples (dry ground flour and wet aqueous slurry) were measured over the frequency range 500–2500 MHz. Temperature dependence of dielectric properties of rice flour slurries (20, 30 and 50 g flour per 100 g water yielding approximately 1:5, 1:3 and 1:2 flour to water ratio) were studied between 30 and 80 °C. Results indicated that dielectric constants (ε′) generally did not vary with frequency while the loss factor (ε″) showed an increasing trend. A sharp change in dielectric parameters were noted above 70 °C attributable to rice starch gelatinization, an observation confirmed later by differential scanning calorimetry. An increase in flour slurry concentration systematically reduced ε′ during the entire frequency range while variations in ε″ values were mixed. Addition of 1% salt markedly increased ε″ of slurries whereas butter resulted in significant reduction in ε′ values. Rice flour slurry containing both salt and butter exhibited intermediate values of dielectric properties. Both ε′ and ε″ data of rice slurries generally fitted a 2nd order polynomial relationship with temperature. These results suggest that dielectric measurements could be used to study frequency, concentration, ingredient and temperature dependent changes in starch–water systems during heating. 相似文献
40.
Michèle Marcotte Cuiren R. Chen Stefan Grabowski Hosahalli S. Ramaswamy & Jean-Paul Gabriel Piette 《International Journal of Food Science & Technology》2008,43(4):673-684
Traditional cooking‐cooling of processed meat and poultry products is industrially carried out in smokehouses or autoclaves. A mathematical model was developed to simulate these operations. Equations, describing heat transfer and thermal destruction of micro‐organisms and quality characteristics, were solved numerically. The model was validated experimentally for heat transfer and energy consumption and was used to perform a sensitivity analysis. Input variables were: process time (PT), smokehouse temperature (TSH), bologna size (diameter, D and height, H), surface heat transfer coefficients (hheat and hcool), product thermal diffusivity (αheat and αcool). Output variables were: product core temperature (Tc), core and volume‐average lethality (Pcm and Pvm) and cook (Cc and Cv) values as well as surface (Qs) and volume‐average (Qv) quality retention, total specific energy consumption (En) and energy efficiency (Ce). Multiple linear regression models were developed to predict Cc and Cv from five inputs and used to obtain acceptable deviation ranges. 相似文献