The growth of antibiotic resistant microorganisms and the increasing demand for nonthermal antimicrobial treatment in the food and beverage industry motivates research into alternative inactivation ...methods. Pulsed electric fields (PEFs) provide an athermal method for inactivating microorganisms by creating nanometer-sized membrane pores in microorganisms, inducing cell death when the PEF duration and intensity are sufficient such that the pores cannot reseal after the PEFs through a process referred to as irreversible electroporation. While PEF inactivation has been studied for several decades, recent studies have focused on extending the technique to various liquids in the food industry and optimizing microorganism inactivation while minimizing adverse effects to the treated sample. This minireview will assess the biophysical mechanisms and theory of PEF-induced cellular interactions and summarize recent advances in applying this technology for microorganism inactivation alone and synergistically in combination with other technologies, including temperature, pressure, natural ingredients, and pharmaceuticals.
Full text
Available for:
CEKLJ, DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Although atmospheric cold plasma is well known for nonthermal inactivation of microorganisms on surfaces, few studies examine its application to liquid food within a package. This study explores the ...decontamination efficiency of high voltage atmospheric cold plasma (HVACP) on
Salmonella enterica
serovar Typhimurium (
S
.
enterica
) in orange juice (OJ). Both direct and indirect HVACP treatments of 25-mL OJ induce greater than a 5-log reduction in
S
.
enterica
following 30 s of treatment with air and MA65 gas with no storage. For 50-mL OJ, 120 s of direct HVACP treatment followed by 24-h storage induced a 2.9-log reduction of
S
.
enterica
in air and a 4.7-log reduction in MA65 gas; 120 s of indirect HVACP treatment followed by 24-h storage resulted in a 2.2-log reduction in air and a 3.8-log reduction in MA65. No significant (
P
< 0.05) Brix or pH change occurred following 120-s HVACP treatment. Applying 120-s HVACP direct treatment reduced vitamin C by 22% in air (compared to 50% for heat pasteurization) and pectin methylesterase activity by 74% in air and 82% in MA65. These results demonstrate that HVACP can effectively inactivate
Salmonella
in OJ with minimal quality degradation.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The electron spokes for stable operation in the L-4953 crossed-field amplifier (CFA) from Stellant Systems are characterized via particle-in-cell (PIC) code simulations in VSim (TechX). The CFA is a ...pulsed, re-entrant, backward wave device with a peak output power <inline-formula> <tex-math notation="LaTeX">{P}_{\text {out}}^{\text {peak}}\approx {5}~\text {MW} </tex-math></inline-formula>, gain <inline-formula> <tex-math notation="LaTeX">{G}\approx {11.2}~\text {dB} </tex-math></inline-formula>, and a bandwidth from <inline-formula> <tex-math notation="LaTeX">{f}={1.28}~\text {to}~{1.35}~\text {GHz} </tex-math></inline-formula>. Spatial, spatial-temporal, spatial-spectral, and spatial-tonal visualizations of the electron density in both the lab and rotating frames of reference were developed to characterize the spokes. The spatial visualizations for simulations at the operation frequency <inline-formula> <tex-math notation="LaTeX">{f}_{\text {op}}={1.3}~\text {GHz} </tex-math></inline-formula> identify the Brillouin and cycloidal electron flow within the spoke for space-charge limited emission (SCLE) and non-SCLE, respectively. The spatial-temporal/spectral visualizations identify an oscillation (transit wobble) within the spoke at a third of the operation frequency <inline-formula> <tex-math notation="LaTeX">\text {(}{f}_{\text {transit}}={f}_{\text {op}}/{3}={0.43}~\text {GHz}\text {)} </tex-math></inline-formula> caused by the spoke transiting 360° in the re-entrant design. This fundamental spoke oscillation, though, does not directly appear on the output. However, a much lower amplitude oscillation at <inline-formula> <tex-math notation="LaTeX">{f}_{\text {sideband}}={0.18}~\text {GHz} </tex-math></inline-formula> identified on the front of the spoke directly appears as sidebands on the output. While the mechanisms that initiate sideband oscillations within the spoke and generate noise on the output are relatively unknown, spatial-tonal visualizations show that the phase difference of the oscillations between spokes is critical to this process. The ability of the visualizations to directly connect oscillations within the spoke to the output is demonstrated, but strategies are still needed to interpret the visualizations to identify and characterize noise generation mechanisms.
Nonlinear transmission lines (NLTLs) have been increasingly studied to produce high power microwaves (HPM) at higher repetition rates than conventional HPM devices without requiring the same ...auxiliary systems. The ability to array NLTLs to produce higher power and achieve beam steering provides an additional capability. This review summarizes the various NLTL topologies designed to achieve these design objectives. Specifically, we summarize modeling and experimental studies for three primary topologies: the lumped element NLTL, the split ring resonator, and the traditional transmission line geometry using nonlinear materials. The lumped element NLTL and the traditional transmission line constructed with nonlinear materials lend themselves to higher power applications, while the split ring resonator is better suited for applications involving antennas. We provide a detailed summary of past studies for these topologies and conclude by exploring ongoing work and future opportunities for technological development.
Self-consistent evaluations of membrane electroporation along with local heating in single spherical cells arising from external AC radiofrequency electrical stimulation have been carried out. The ...present numerical study seeks to determine whether healthy and malignant cells exhibit separate electroporative responses with regards to operating frequency. It is shown that cells of Burkitt's lymphoma would respond to frequencies >4.5 MHz, while normal B-cells would have negligible porative effects in that higher frequency range. Similarly, a frequency separation between the response of healthy T-cells and malignant species is predicted with a threshold of about 4 MHz for cancer cells. The present simulation technique is general and so would be able to ascertain the beneficial frequency range for different cell types. The demonstration of higher frequencies to induce poration in malignant cells, while having minimal affecting healthy ones, suggests the possibility of selective electrical targeting for tumor treatments and protocols. It also opens the doorway for tabulating selectivity enhancement regimes as a guide for parameter selection towards more effective treatments while minimizing deleterious effects on healthy cells and tissues.
While exact analytic solutions for space-charge-limited currents (SCLCs) are well-established for parallel plate geometries, they have only recently been derived for concentric cylindrical and ...spherical geometries using variational calculus (VC). However, actual diode systems and slow-wave structures are usually more complicated, making SCLC calculations more difficult. In this article, we apply conformal mapping to derive the analytical solutions for SCLC for various complicated geometries exhibiting curvilinear flow. We first replicate the exact solution of SCLC for concentric cylindrical electrodes from VC using conformal mapping to transform from the Child-Langmuir (CL) law for a planar geometry. We then derive SCLC in other geometries using conformal transformations to either the planar or the concentric cylinder solution. Because the SCLC calculated using such conformal mappings depends only on the CL law, this may permit future incorporation of relativistic or quantum corrections to determine the appropriate relationships for more complicated geometries.
Abstract
Multiple electron emission mechanisms often contribute in electron devices, motivating theoretical studies characterizing the transitions between them. Previous studies unified thermionic ...and field emission, defined by the Richardson-Laue-Dushman (RLD) and Fowler–Nordheim (FN) equations, respectively, with the Child-Langmuir (CL) law for vacuum space-charge limited current (SCLC); another study unified FN and CL with the Mott-Gurney (MG) law for collisional SCLC. However, thermionic emission, which introduces a nonzero injection velocity, may also occur in gas, motivating this analysis to unify RLD, FN, CL, and MG. We exactly calculate the current density as a function of applied voltage over a range of injection velocity (i.e., temperature), mobility, and gap distance. This exact solution approaches RLD, FN, and generalized CL (GCL) and MG (GMG) for nonzero injection velocity under appropriate limits. For nonzero initial velocity, GMG approaches zero for sufficiently small applied voltage and mobility, making these gaps always space-charge limited by either GMG at low voltage or GCL at high voltage. The third-order nexus between FN, GMG, and GCL changes negligibly from the zero initial velocity calculation over ten orders of magnitude of applied voltage. These results provide a closed form solution for GMG and guidance on thermionic emission in a collisional gap.
Full text
Available for:
IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
While analytic equations for space-charge limited current density (SCLCD) have been derived for planar and nonplanar geometries, the SCLCD for emission from a sharp tip has not been derived. In this ...article, we use variational calculus (VC) to derive an exact analytic equation for SCLCD for a 1-D tip-to-tip geometry, represented by hyperboloids in the prolate spheroidal coordinates, and recover the SCLCD for a tip-to-plate geometry as a special case. We then consider circles in the extended Poincaré disk, which is the stereographic projection of hyperboloids onto a plane, as conformal transformations to derive the SCLCD for a misaligned tip-to-tip geometry, where the axes of rotation of the hyperboloids are displaced by a small distance. This mapping technique is also applied to study the effect of a small angle tilt in a tilted tip-to-tip geometry, where the axes of rotation of the hyperboloids meet at an angle.
PDF
