Mathematical modeling the cross-contamination of Escherichia coli O157:H7 on the surface of ready-to-eat meat product while slicing

Microbial cross-contamination either at home or production site is one of the major factors of causing contamination of foods and leading to the foodborne illness. The knowledge regarding Escherichia coli O157:H7 surface transfer on ready-to-eat (RTE) deli meat and the slicer used for slicing different RTE products are needed to ensure RTE food safety. The objectives of this study were to investigate and to model the surface cross-contamination of E. coli O157:H7 during slicing operation. A five-strain cocktail of E. coli O157:H7 was inoculated directly onto a slicer's round blade rim area at an initial level of ca. 4, 5, 6, 7 or 8 log CFU/blade (ca. 3, 4, 5, 6 or 7 log CFU/cm² of the blade edge area), and then the RTE deli meat (ham) was sliced to a thickness of 1–2 mm. For another cross-contamination scenario, a clean blade was initially used to slice ham which was pre-surface-inoculated with E. coli O157:H7 (ca. 4, 5, 6, 7 or 8 log CFU/100 cm² area), then, followed by slicing un-inoculated ham. Results showed that the developed empirical models were reasonably accurate in describing the transfer trend/pattern of E. coli O157:H7 between the blade and ham slices when the total inoculum level was ≥5 log CFU on the ham or blade. With an initial inoculum level at ≤4 log CFU, the experimental data showed a rather random microbial surface transfer pattern. The models, i.e., a power equation for direct-blade-surface-inoculation, and an exponential equation for ham-surface-inoculation are microbial load and sequential slice index dependent. The surface cross-contamination prediction of E. coli O157:H7 for sliced deli meat (ham) using the developed models were demonstrated. The empirical models may provide a useful tool in developing the RTE meat risk assessment.     

An envelope analysis based on the resonance modes of the mechanical system for the bearing defect diagnosis

In this paper, an envelope estimation algorithm based on the resonance modes of the mechanical system is proposed and the exponential decay frequency of the envelope signal could be further estimated to be a quantified index for the bearing defect diagnosis. According to the vibration spectrum of the bearing system, the resonance frequencies in the range of its corresponding resonance modes could be initially designated and further revised. Under the assumption of stepwise functions for the envelope signals, the vibration signal could be decomposed into the sinusoidal function bases with fundamental frequencies at the corresponding resonance frequencies. Thus, the envelope signals could be retrieved by estimating the stepwise functions. In addition, the reconstructed signal with noise rejection could be derived from the envelope signals. According to the envelope signals, the exponential decay frequency is estimated to be the diagnosis index of the bearing running condition. In the simulated and experimental studies, it is found that the envelope estimation algorithm could be effectively applied in the signal processing for the bearing vibrations. In addition, the envelope spectra also show good consistency between the proposed method and the high-frequency resonance technique. Finally, it is shown that the exponential decay frequency could successfully be the quantified index for the bearing defect diagnosis.     

Foliage transmission measurements using a ground-based ultrawideband (300-1300 MHz) SAR system

The attenuation of a forest clearly impacts the ability of airborne SAR systems to image objects within the forest. The level of this attenuation is a function of tree characteristics over the frequency band used in the radar. To experimentally measure the transmission properties of foliage, a bistatic (line-of-site) wide-band system has been built by the Environmental Research Institute of Michigan (ERIM), sponsored by the Air Force's Wright Laboratory, Avionics directorate. This system is polarimetric and can operate coherently over the band from 300 to 1300 MHz. The variation in foliage transmission over the frequency band is important because an imaging radar typically operates coherently over a bandwidth. The system can scan foliage in angle to determine spatial variations in the foliage attenuation. This angular variation in foliage attenuation is quite important because imaging radars typically synthesize an aperture by scanning over a range of angles. The ERIM Wide-Band System is ground-based, with one antenna attached to a carriage which can move 10 m horizontally along an elevated rigid track and the other antenna attached to a fixed tripod. Measurements with the system were conducted during July 1991 at the University of Michigan Biological Field Station in Pellston, MI. The measurements of the mean attenuation as a function of depression angle (15-45°) and frequency (300-1300 MHz) of four different forest types are presented. In addition to mean attenuation, the variance in attenuation and the autocorrelation of the attenuation (in angle) are presented. These results imply that the variation of the foliage properties over the bandwidth and scan geometry (or angular variation) will degrade the ability of a radar to focus a foliage obscured object     

Effect of Various Factors on the Corrosion and Rusting of Tooling Material Used for Tablet Manufacturing

Various factors that cause the rusting of tablet punches and dies by a hydrochloride salt were evaluated. Tooling material rich in nickel content was found to have the best resistance to rusting by the hydrochloride salt. Other factors such as humidity, temperature and contact time with this hydrochloride salt were also found to be responsible for rusting of tooling material.

The hydrogen chloride liberated from the salt was found to be the cause of rusting of tooling. A correlation between the stability of hydrochloride salt as determined by thermogravimetric analysis and its effect on rusting of tooling material was demonstrated. Optimization of tooling composition during preformulation is recommended.     

Melatonin Alleviates Liver Apoptosis in Bile Duct Ligation Young Rats

Bile duct ligation (BDL)-treated rats display cholestasis and liver damages. The potential protective activity of melatonin in young BDL rats in terms of apoptosis, mitochondrial function, and endoplasmic reticulum (ER) homeostasis has not yet been evaluated. Three groups of young male Sprague-Dawley rats were used: one group received laparotomy (Sham), a second group received BDL for two weeks (BDL), and a third group received BDL and intraperitoneal melatonin (100 mg/day) for two weeks (BDL + M). BDL group rats showed liver apoptosis, increased pro-inflamamtory mediators, caspases alterations, anti-apoptotic factors changes, and dysfunction of ER homeostasis. Melatonin effectively reversed apoptosis, mainly through intrinsic pathway and reversed ER stress. In addition, in vitro study showed melatonin exerted its effect mainly through the melatonin 2 receptor (MT2) in HepG2 cells. In conclusion, BDL in young rats caused liver apoptosis. Melatonin rescued the apoptotic changes via the intrinsic pathway, and possibly through the MT2 receptor. Melatonin also reversed ER stress induced by BDL.     

A quantified index for bearing vibration analysis based on the resonance modes of mechanical system

In this paper, an envelope estimation algorithm based on the resonance modes of the mechanical system is proposed to apply in the signal processing for the bearing vibrations and the exponential decay frequency of the envelope signal could be further estimated to be a quantified index for the bearing vibration analysis. According to the vibration spectrum of the bearing system, the resonance frequencies in the range of the corresponding resonance modes could be initially designated and further estimated. Under the assumption of stepwise functions for the envelope signals in the corresponding resonance modes, the vibration signal could be decomposed into the sinusoidal function bases with fundamental frequencies at the resonance frequencies. The envelope signals could be derived from their corresponding resonance modes. In addition, the vibration signal could be directly reconstructed from the envelope signals to reject the low-frequency mechanical noise. According to the envelope signals, the exponential decay frequency is also estimated to be a quantified index for diagnosing the running condition of roller bearing. In the simulation study, the envelope spectra show good consistency between the proposed method and the high frequency resonance technique. Finally, the experimental study shows that the envelope estimation algorithm could be effectively applied in the signal processing for the bearing vibrations and the exponential decay frequency could successfully be a quantified index for the bearing defect diagnosis.     

Microstructure and electrochemical properties of LBO-coated Li-excess Li1+xMn2O4 cathode material at elevated temperature for Li-ion battery

An amorphous glass film, Li₂O-2B₂O₃ (LBO) glass, was coated on the surface of the cathode material by solution method. The Li-excess cathode powder Li_1+xMn₂O₄ derived from co-precipitation method was calcined with various weight percentage of the surface modified lithium boron glass. Fine powders with distinct particle size, size distribution and morphology were fabricated. The electron probe microanalyzer (EPMA) was employed to evaluate the composition of LBO-coated Li_1+xMn₂O₄. The morphology was observed with a field emission scanning electron microscope (FE-SEM), and the particle size in the range of several microns measured by laser scattering. The electrochemical behavior of the cathode powder was examined by using two-electrode test cells consisted of a cathode, metallic lithium as anode, and an electrolyte of 1 M lithium hexafluorophosphate (LiPF₆). Cyclic charge/discharge testing of the coin cells, fabricated by both LBO-coated and base Li_1+xMn₂O₄ material were conducted. The LBO-coated cathode powder with the fading rate of only 7% after 25 cycles showed better cycleability than the base one with the fading rate of 17% after 25 cycles, particularly at higher temperature. It is demonstrated that the employment of LBO glass coated Li_1+xMn₂O₄ cathode material exhibited higher discharge capacity and significantly reduced the fading rate after cyclic test.