3,721 research outputs found
Phase Behavior of Short Range Square Well Model
Various Monte Carlo techniques are used to determine the complete phase
diagrams of the square well model for the attractive ranges
and . The results for the latter case are in agreement with
earlier Monte Carlo simulations for the fluid-fluid coexistence curve and yield
new results for the liquidus-solidus lines. Our results for
are new. We find that the fluid-fluid critical point is metastable for both
cases, with the case being just below the threshold value for
metastability. We compare our results with prior studies and with experimental
results for the gamma-II crystallin.Comment: 8 figures, 1 tabl
A Finite-Size Scaling Study of a Model of Globular Proteins
Grand canonical Monte Carlo simulations are used to explore the metastable
fluid-fluid coexistence curve of the modified Lennard-Jones model of globular
proteins of ten Wolde and Frenkel (Science, v277, 1975 (1997)). Using both
mixed-field finite-size scaling and histogram reweighting methods, the joint
distribution of density and energy fluctuations is analyzed at coexistence to
accurately determine the critical-point parameters. The subcritical coexistence
region is explored using the recently developed hyper-parallel tempering Monte
Carlo simulation method along with histogram reweighting to obtain the density
distributions. The phase diagram for the metastable fluid-fluid coexistence
curve is calculated in close proximity to the critical point, a region
previously unattained by simulation.Comment: 17 pages, 10 figures, 2 Table
Understanding Variation in the Practice of Employee Discipline: The Perspective of the First-Line Supervisor
First-line supervisors' responses to employee-related problems can vary widely from one supervisor to another. Assuming fair and consistent disciplinary activity is valued by organizations, then discovery of the factors causing supervisors to respond differently to similar situations is a valuable activity. Using a case study approach for four organizations in Puerto Rico, this article explores how factors such as sector, union presence, and managerial and human resource department support influence the choice of a discipline strategy. When present, some of these factors were found to encourage supervisors to comply with formal disciplinary policy. Organizations can use these findings to assess the degree to which there is consistency in these factors and take strategic action to assure that first-line supervisors receive clear and consistent signals regarding appropriate disciplinary strategies.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline
Role of solvent for globular proteins in solution
The properties of the solvent affect the behavior of the solution. We propose
a model that accounts for the contribution of the solvent free energy to the
free energy of globular proteins in solution. For the case of an attractive
square well potential, we obtain an exact mapping of the phase diagram of this
model without solvent to the model that includes the solute-solvent
contribution. In particular we find for appropriate choices of parameters upper
critical points, lower critical points and even closed loops with both upper
and lower critical points, similar to one found before [Macromolecules, 36,
5845 (2003)]. In the general case of systems whose interactions are not
attractive square wells, this mapping procedure can be a first approximation to
understand the phase diagram in the presence of solvent. We also present
simulation results for both the square well model and a modified Lennard-Jones
model.Comment: 18 pages, 9 figure
An In Situ Study of the Role of Pressure on Fe Recrystallization and Grain Growth during Thermomechanical Processing
Elevated pressures are encountered in many metal forming processes that can
alter microstructural evolution rates. Here we measure rate changes with
pressure in recrystallization and grain growth in Fe through adaptation of
synchrotron-compatible multi-anvil presses, originally designed for study of
the mantle. Recrystallization and grain growth are monitored in situ using
high-energy X-ray diffraction. Principal component analysis applied to the
diffraction images is used to quantify evolution rates, with increasing
pressure significantly slowing the process
Analytical strategies for the determination of biogenic amines in dairy products
Biogenic amines (BA) are mainly produced by the decarboxylation of amino acids by enzymes from microorganisms that emerge during food fermentation or due to incorrectly applied preservation processes. The presence of these compounds in food can lead to a series of negative effects on human health. To prevent the ingestion of high amounts of BA, their concentration in certain foods needs to be controlled. Although maximum legal levels have not yet been established for dairy products, potential adverse effects have given rise to a substantial number of analytical and microbiological studies: they report concentrations ranging from a few mg/kg to several g/kg. This article provides an overview of the analytical methods for the determination of biogenic amines in dairy products, with particular focus on the most recent and/or most promising advances in this field. We not only provide a summary of analytical techniques but also list the required sample pretreatments. Since high performance liquid chromatography with derivatization is the most widely used method, we describe it in greater detail, including a comparison of derivatizing agents. Further alternative techniques for the determination of BA are likewise described. The use of biosensors for BA in dairy products is emerging, and current results are promising; this paper thus also features a section on the subject. This review can serve as a helpful guideline for choosing the best option to determine BA in dairy products, especially for beginners in the field
Mechanism of Bacterial Inactivation by (+)-Limonene and Its Potential Use in Food Preservation Combined Processes
This work explores the bactericidal effect of (+)-limonene, the major constituent of citrus fruits' essential oils, against E. coli. The degree of E. coli BJ4 inactivation achieved by (+)-limonene was influenced by the pH of the treatment medium, being more bactericidal at pH 4.0 than at pH 7.0. Deletion of rpoS and exposure to a sub-lethal heat or an acid shock did not modify E. coli BJ4 resistance to (+)-limonene. However, exposure to a sub-lethal cold shock decreased its resistance to (+)-limonene. Although no sub-lethal injury was detected in the cell envelopes after exposure to (+)-limonene by the selective-plating technique, the uptake of propidium iodide by inactivated E. coli BJ4 cells pointed out these structures as important targets in the mechanism of action. Attenuated Total Reflectance Infrared Microspectroscopy (ATR-IRMS) allowed identification of altered E. coli BJ4 structures after (+)-limonene treatments as a function of the treatment pH: ß-sheet proteins at pH 4.0 and phosphodiester bonds at pH 7.0. The increased sensitivity to (+)-limonene observed at pH 4.0 in an E. coli MC4100 lptD4213 mutant with an increased outer membrane permeability along with the identification of altered ß-sheet proteins by ATR-IRMS indicated the importance of this structure in the mechanism of action of (+)-limonene. The study of mechanism of inactivation by (+)-limonene led to the design of a synergistic combined process with heat for the inactivation of the pathogen E. coli O157:H7 in fruit juices. These results show the potential of (+)-limonene in food preservation, either acting alone or in combination with lethal heat treatments
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