Critical Point Approaches Research Articles

A simple and cost-effective method for reducing microbial load in Salacia chinensis and Picrorhiza kurroa using glutaraldehyde

Microorganisms like fungi, bacteria, and viruses are naturally present in different parts of a plant (root, bark, and leaf) and these become inhabitants of the plant. The establishment of modern Hazard Analysis and Critical Control Point (HACCP) approaches has therefore been made to evaluate the microbial load in medicinal plants. During the manufacturing of herbal extracts as drugs, the quality of the herbal extracts is dictated by the level of presence of microbes. In order to make the herbal extracts HACCP compliant as far as microbial load is concerned; we carried out studies with Glutaraldehyde (GA) as an antimicrobial agent in the manufacturing process in two randomly selected herbs of Salacia chinensis and Picrorhiza kurroa. The outcome of our analysis revealed that 0.5% of GA treatment to the pulverized raw material of Salacia chinensis and Picrorhiza kurroa is effective for reduction of > 99.99% microbial load with minimal effect on the percentage yield of extracts (10% - 20%) and their bioactive molecules Salacinol and Picroside I&II as seen by LC-MS and HPLC analysis, respectively. Furthermore, in this article, we demonstrate the use of sodium bisulfite for the removal of the residual GA in the extract to make the process eco-friendly and environment-safe.

Critical Point Approaches for a Class of Differential Equations with Sturm-Liouville Type Nonhomogeneous Boundary Conditions

A class of p-Laplacian equations with Sturm-Liouville type nonhomogeneous boundary value problem with nonlinear derivative depending on two control parameters is investigated. Existence and multiplicity of solutions are discussed by means of variational methods and critical point theory. Two examples supporting our theoretical results are also presented.

Good manufacturing practices for risk management in food safety sustainability: An empirical study

Food is an essential need for the sustainability of human life so that consumers have the right to get a product that is safe for consumption. However, food poisoning cases due to the risk of biological, chemical, physical, and other contamination still occur frequently. In this study, an empirical investigation was conducted on apple pie production in a food processing SME that is known to have a risk of physical, chemical, and biological. This study used the hazard analysis and critical control point (HACCP) and good manufacturing practice (GMP) approaches to analyze each production process’s hazards. This study also identified factors that harm using failure mode and effect analysis (FMEA) and provided recommendations for improving food safety and security for the SME business sustainability.

Spin-polarized Weyl cones and giant anomalous Nernst effect in ferromagnetic Heusler films

Weyl semimetals are characterized by the presence of massless band dispersion in momentum space. When a Weyl semimetal meets magnetism, large anomalous transport properties emerge as a consequence of its topological nature. Here, using in−situ spin- and angle-resolved photoelectron spectroscopy combined with ab initio calculations, we visualize the spin-polarized Weyl cone and flat-band surface states of ferromagnetic Co2MnGa films with full remanent magnetization. We demonstrate that the anomalous Hall and Nernst conductivities systematically grow when the magnetization-induced massive Weyl cone at a Lifshitz quantum critical point approaches the Fermi energy, until a high anomalous Nernst thermopower of ~6.2 μVK−1 is realized at room temperature. Given this topological quantum state and full remanent magnetization, Co2MnGa films are promising for realizing high efficiency heat flux and magnetic field sensing devices operable at room temperature and zero-field.

Critical Point Approaches to Generalized Yamabe Equations on Riemannian Manifolds and Applications to Emden–Fowler Problems

In this work, we continue the study of the multiplicity results for generalized Yamabe equations on Riemannian manifolds arising from conformal Riemannian geometry, astrophysics, and in the theories of thermionic emission, isothermal stationary gas sphere, and gas combustion. As applications, we consider the Emden–Fowler equations involving sublinear terms at infinity. In fact, employing two critical point theorems, we guarantee the existence of two and three solutions for our problem.

Heat Transfer in a Closed Domain of Inhomogeneous Supercritical Fluid under Weightlessness

The process of heat transfer in a closed domain of temperature-density inhomogeneous supercritical fluid (SCF) heated or cooled from the boundaries under weightlessness is studied numerically. The calculations near the thermodynamic critical point are carried out with the use of 1D equations of Navier-Stokes, mass conservation, energy balance, and van der Waals equation of state. It is obtained that when the critical point approaches the characteristic time of “piston effect”, τPE, in inhomogeneous SCF significantly increases in comparison with the homogeneous case. The larger temperature-density inhomogeneity and the closer the critical point, the longer time of “piston effect”. In addition the heating of the fluid causes the temperature-density inhomogeneity to be stronger, whereas cooling leads to the weakening of the inhomogeneity.

Magnetized effective QCD phase diagram

The QCD phase diagram in the temperature vs quark chemical potential plane is studied in the presence of a magnetic field, using the linear sigma model coupled to quarks. It is shown that the decrease of the couplings with increasing field strength obtained in this model leads to the critical temperature for the phase transition to decrease with increasing field intensity (inverse magnetic catalysis). This happens provided that plasma screening is properly accounted for. It is also found that with increasing field strength the location of the critical end point in the phase diagram moves toward lower values of the critical quark chemical potential and larger values of the critical temperature. In addition, the critical end point approaches the temperature axis for large values of the magnetic field. We argue that a similar behavior is to be expected in QCD, since the physical impact of the magnetic field, regardless of strength, is to produce a spatial dimension reduction, whereby virtual quark-antiquark pairs are closer on average and thus the strength of their interaction decreases due to asymptotic freedom.

Environmental (Saprozoic) Pathogens of Engineered Water Systems: Understanding Their Ecology for Risk Assessment and Management.

Major waterborne (enteric) pathogens are relatively well understood and treatment controls are effective when well managed. However, water-based, saprozoic pathogens that grow within engineered water systems (primarily within biofilms/sediments) cannot be controlled by water treatment alone prior to entry into water distribution and other engineered water systems. Growth within biofilms or as in the case of Legionella pneumophila, primarily within free-living protozoa feeding on biofilms, results from competitive advantage. Meaning, to understand how to manage water-based pathogen diseases (a sub-set of saprozoses) we need to understand the microbial ecology of biofilms; with key factors including biofilm bacterial diversity that influence amoebae hosts and members antagonistic to water-based pathogens, along with impacts from biofilm substratum, water temperature, flow conditions and disinfectant residual—all control variables. Major saprozoic pathogens covering viruses, bacteria, fungi and free-living protozoa are listed, yet today most of the recognized health burden from drinking waters is driven by legionellae, non-tuberculous mycobacteria (NTM) and, to a lesser extent, Pseudomonas aeruginosa. In developing best management practices for engineered water systems based on hazard analysis critical control point (HACCP) or water safety plan (WSP) approaches, multi-factor control strategies, based on quantitative microbial risk assessments need to be developed, to reduce disease from largely opportunistic, water-based pathogens.

Adiabatic Processes in the Liquid–Vapor Two-Phase Region. 1. Pure Fluids

Adiabatic processes in the liquid–vapor two-phase region were studied with several equations of state. The comparison of the resulting isentropes, particularly their patterns in quality (fraction of vapor phase) vs temperature diagrams, indicates that there are two different classes of fluids: One class shows a simple pattern where isentropes entering the two-phase region never leave it again; the other shows a more complicated pattern with reentrant isentropes, which may either cross the entire two-phase region or exhibit a retrograde behavior. The existence of these two classes can be related to the shapes of entropy–volume or temperature–entropy curves, and these in turn to the temperature dependence of ideal-gas heat capacities. The two-phase isentrope that runs to the critical point approaches it with an infinite slope in the quality–temperature diagram. The slope is positive for reference equations of state, but negative for all other equations of state used in this work.

A review of potential contaminants in Australian livestock feeds and proposed guidance levels for feed

Contaminants of man-made and natural origin need to be managed in livestock feeds to protect the health of livestock and that of human consumers of livestock products. This requires access to information on the transfer from feed to food to inform risk profiles and assessments, and to guide management interventions such as regulation or Hazard Analysis Critical Control Point approaches. This paper reviews contaminants of known and potential concern in the production of livestock feeds in Australia and compares existing but differing state and national regulatory standards with international standards. The contaminants considered include man-made organic chemical contaminants (e.g. legacy pesticides), elemental contaminants (e.g. arsenic, cadmium, lead), phytotoxins (e.g. gossypol) and mycotoxins (e.g. aflatoxins). Reference is made to scientific literature and evaluations by regulators to propose maximum levels that can be used for guidance by those involved in managing contamination incidents or developing feed safety programs.

Effect of pore morphology on vapor–liquid phase transition and crossover behavior of critical properties from 3D to 2D

Grand-canonical transition-matrix Monte Carlo (GC-TMMC) simulation, is used to investigate the effect of pore shape and surface-fluid strength on the vapor–liquid phase transition and crossover behavior of critical properties from 3D to 2D of a square well (SW) fluid. We present the vapor–liquid coexistence phase diagram in hard and attractive cylindrical pores of varying slit width from 4 to 50 molecular diameters. This investigation indicates that having same pore shape but different surface nature can significantly alter the coexistence envelopes and hence the critical point. Critical temperature is found to approach the 3D bulk value monotonically irrespective of the pore shape and surface nature. However, the rate of approach of critical point towards the 3D bulk value decreases as the effective confinement increases. On the other hand, approach of pore critical density towards the bulk 3D value follows a non-monotonic path, irrespective of pore shape and surface strength. Interestingly, with the same pore shape, attractive wall surface follows an opposite trend to approach the bulk critical density as compared to that of hard wall surface. Crossover from 3D to 2D behavior in the hard cylindrical pores is observed around 28 molecular diameters, which is significantly larger than that observed by earlier workers for hard and attractive slit pores.

Approach to a superconductor-to-Bose-insulator transition in disordered films

Through a detailed study of scaling near the magnetic field-tuned superconductor-to-insulator transition in strongly disordered films, we find that results for a variety of materials can be collapsed onto a single phase diagram. The data display two clear branches, one with weak disorder and an intervening metallic phase, the other with strong disorder. Along the strongly disordered branch, the resistance at the critical point approaches $R_Q = h/4e^2$ and the scaling of the resistance is consistent with quantum percolation, and therefore with the predictions of the dirty boson model.

Two-point Taylor expansions in the asymptotic approximation of double integrals. Application to the second and fourth Appell functions

The main difficulty in Laplace's method of asymptotic expansions of double integrals is originated by a change of variables. We consider a double integral representation of the second Appell function F 2 ( a , b , b ′ , c , c ′ ; x , y ) and illustrate, over this example, a variant of Laplace's method which avoids that change of variables and simplifies the computations. Essentially, the method only requires a Taylor expansion of the integrand at the critical point of the phase function. We obtain in this way an asymptotic expansion of F 2 ( a , b , b ′ , c , c ′ ; x , y ) for large b, b ′ , c and c ′ . We also consider a double integral representation of the fourth Appell function F 4 ( a , b , c , d ; x , y ) . We show, in this example, that this variant of Laplace's method is uniform when two or more critical points coalesce or a critical point approaches the boundary of the integration domain. We obtain in this way an asymptotic approximation of F 4 ( a , b , c , d ; x , y ) for large values of a , b , c and d. In this second example, the method requires a Taylor expansion of the integrand at two points simultaneously. For this purpose, we also investigate in this paper Taylor expansions of two-variable analytic functions with respect to two points, giving Cauchy-type formulas for the coefficients of the expansion and details about the regions of convergence.

Influence of the drops size on the coefficient of surface tension in a wide range of pressures and temperatures along the coexistence curve

The new method for estimation of Tolman δ-corrections for liquid droplets is proposed on the basis of equation of state. It is revealed that Tait equation of state for such evaluations can be used. The set of estimates was established for δ-correction in the case of H 2O and Ar in a wide temperature range. Both cases give δ < 0 that correlates with known estimates. It is proved that |δ| rises with temperature and diverges at critical point. Corresponding critical exponents estimate for Ar( δ ∼ | τ| − a) gives a = 0.5 (here τ= T c−T T c ). Studying of Tolman δ-corrections behavior within the framework of the mean-field theory is resulted in δ=− 1σ 0 16p c by using Van der Waals equations of state. Here σ 0 is an amplitude factor of the surface tension for the flat surface σ ∞ = σ 0 τ 3 2 . The analysis of experimental data for a set of fluids demonstrates the satisfactory fit of the obtained result with experiment. Using the scaling theory for description of an equation of state of the coexistence curve and surface tension give such δ ∼ τ β− ν , where β and ν are critical exponents. Thus, δ-correction has singular character as critical point approaches.

Phase Diagram of Ising Nano-Particles with Cubic Structures

The method of variational cumulant expansion (VCE) on the Ising model is applied to investigate phase transitions in magnetic alloy nano-particles, in which a random site distribution of component atoms is assumed. By introducing the effect exchange constant, it is shown numerically that nano-particles can be treated the same way as bulk materials. The Curie temperature and the Neel temperature of binary magnetic nano-particles with cubic lattices are calculated. It is found that both the Curie temperature and the Neel temperature decrease with decreasing size of the nano-particle. Phase diagrams of binary alloy nano-particles are investigated for variable doping concentration and the results are discussed. As the nano-particle size grows larger, the critical point approaches that of a bulk. On the other hand, the tri-critical point is independent of the nano-particle size and is always the same as that of the bulk.

Analytical Characters of 2-Dimensional Ising Model with Variational-Cumulant Expansion to the Seventh order11The project supported by Doctoral Foundation of Chinese Education Commission and National Natural Science Foundation of China.

In order to investigate the variational-cumulant expansion (VCE) method, the 2-dimensional Ising model is expanded to the seventh order by adopting the method of enumerating connected diagrams, in whose process, how to determine the variational parameter is analyzed. The internal energy , specific heat and spontaneous magnetization are calculated from the first order to the seventh order. The results show that the thermodynamic and magnetic quantities converge to the exact values very quickly and the critical point approaches the exact one order by order. The curve-pairing phenomenon is watched between neighboring order curves at high temperature region.

NEUTRON SCATTERING MESOSCOPIC AND MICROSCOPIC STRUCTURE DETERMINATION OF BINARY LIQUID MIXTURES UNDERGOING NON-METAL TO METAL TRANSITION (APPLICATION TO METAL-AMMONIA AND METAL MOLTEN SALTS)

NEUTRON SCATTERING MESOSCOPIC AND MICROSCOPIC STRUCTURE DETERMINATION OF BINARY LIQUID MIXTURES UNDERGOING NON-METAL TO METAL TRANSITION (APPLICATION TO METAL-AMMONIA AND METAL MOLTEN SALTS)

The cluster investigation of the q‐state potts model

AbstractThe thermodynamics of the q‐state Potts model is calculated by the cluster approximation. With two, three, and four particles as the basic cluster the free energy is obtained for any q. It is found that the transition is of the first order for all two‐dimensional and three‐dimensional Potts models. In the case of planar lattices for q = 3 and q = 4 it is found that the critical point approaches the Curie‐Weiss temperature but the discontinuity of the order parameter remains almost equal to that obtained by the mean‐field approximation.