A comparison of wet-dry swabbing and excision sampling methods for microbiological testing of bovine, porcine, and ovine carcasses at red meat slaughterhouses

A comparison of wet-dry swabbing and surface tissue excision of carcasses by coring was undertaken. Samples from 1,352 bovine, 188 ovine, and 176 porcine carcasses were collected from 70 separate visits to commercial slaughterhouses operating under normal conditions. The mean total aerobic viable bacterial counts (TVCs) for all species sampled by excision was 5.36 log units, which was significantly greater than the 4.35 log units measured for swabbing. Poorly correlated linear relationships between swab- and excision-derived bacterial numbers from near-adjacent carcasses were observed for all three animal species. R2 values for least squares regressions for bovine, ovine, and porcine carcasses were 0.09, 0.27, and 0.21, respectively. The reasons why it was not possible to calculate a factor that allowed the interconversion of bacterial numbers between samples collected by each sampling method were investigated. Uncertainty associated with laboratory analyses was a contributing factor because the geometric relative standard deviations measured for TVCs were 0.174 and 0.414 for excision and swabbing, respectively. Uneven distribution of bacteria at identical sampling sites on near-adjacent carcasses on processing lines was also a contributory factor. The implications of these findings for process control verification were investigated by intensive sampling for 13 weeks in three commercial slaughterhouses. As many as 4 log units of difference in TVCs were observed in duplicate samples collected within a narrow timeframe from near-adjacent carcasses on the processing line. We conclude that it might not be appropriate to institute corrective actions in slaughterhouses on the basis of a single week's test results.     

A control synthesis approach for time discrete event systems

In this paper, we introduce a control synthesis method for discrete event systems whose behavior is dependent on explicit values of time. Our goal is to control the occurrence dates of the controllable events so that the functioning of the system respects given specifications. The system to be controlled is modeled by a time Petri net. In a previous work we proposed a systematic method to build the timed automaton which models the exact behavior of a time Petri net. Furthermore, the forbidden behaviors of the system are modeled by forbidden timed automaton locations. This paper focuses on the control synthesis method, which consists in computing new firing conditions for the timed automaton transitions so that the forbidden locations are no longer reachable.     

Electronic structure of antiferromagnetic PbCrO3 (0 0 1) surfaces

Surfaces of cubic perovksite PbCrO₃ in (0 0 1) plane are investigated through density functional theory. The plane wave pseudopotential method is applied with generalized gradient approximation scheme. Hubbard U correction (GGA + U) is included in all calculations in order to simulate on-site Coulomb interactions between Cr-d states. Two types of terminations, namely, PbO- and CrO₂-terminations are considered in construction of the surfaces. Surfaces of both terminations show convergence at 9-layer slab geometry. The density of states calculations on the converged slab geometry yield a metallic behavior for both PbO- and CrO₂-terminations. Both metal atoms, Pb and Cr, in the uppermost layer of the respective terminations, have inward atomic relaxations much larger in magnitude than the oxygen atoms of the respective layer. However, Cr atoms which are labeled as up and down according to their spin orientation show different relaxations. The interlayer distance between the uppermost layer and the first one next to it decreases in both PbO- and CrO₂-terminated surface geometries. The calculations of the relative movement of the oxygen atom with respect to the Pb or Cr atom in each terminations give a positive rumpling in the uppermost layer.     

A2-MAKE: An efficient anonymous and accountable mutual authentication and key agreement protocol for WMNs

Multi-hop hybrid wireless mesh networks (WMNs) have recently attracted increasing attention and deployment. For easy acceptance and wide deployment of WMNs, security, privacy, and accountability issues have to be addressed by providing efficient, reliable, and scalable protocols. The fact that regular users, which may be resource-constrained wireless devices, are involved in routing activities highlights the need for efficiency and compactness. However, the said objectives, i.e., security, privacy, accountability, efficiency etc., are, most of the time, not compatible. So far no previous work has adequately reconciled these conflicting objectives in a practical framework. In this paper, we design and implement such a framework named as A²-MAKE, which is a collection of protocols. The framework provides an anonymous mutual authentication protocol whereby legitimate users can connect to network from anywhere without being identified or tracked unwillingly. No single party (or authority, network operator, etc.) can violate the privacy of a user, which is provided in our framework in the strongest sense. Our framework utilizes group signatures, where the private keys and corresponding credentials of the users are generated in a secure three-party protocol. User accountability is implemented via user identification and revocation protocols that can be executed by two semi-trusted authorities, one of which is the network operator. The assumptions about the trust level of the network operator are relaxed with respect to similar protocols. Our framework makes use of more efficient signature generation and verification algorithms in terms of computational complexity than their counterparts in literature, where signature size is almost the same as the shortest signatures proposed for similar purposes so far.     

Effects of storage on quality of carrot juices produced with lactofermentation and acidification

In this study, effects on the yield and the quality of product properties of carrot juice produced with lactofermentation and added citric acid, and with and without total enzymatic liquefaction (Pectinex Ultra SP-L) were investigated. Samples were stored at room temperature for 6 months and analytical changes which might occur were determined at day 0 and after 2, 4 and 6 months by quality control tests. In enzyme-treated samples, the yield and the quality of mineral incrementation were determined. Accordingly, ash and water-soluble dry matter contents were increased in the samples. Galacturonic acid formed after enzymatic breakdown of pectin in the raw material increased the total acidity of the samples. Sensorial tests of the product were also carried out. According to the test results, the products produced with enzyme treatment at day 0, after 2 and 4 months storages were found to be the ones mostly preferred. However the samples without enzyme treatment were preferred by the panelists after long-term (6 months) storage.     

The kinetics of heat-induced structural changes of beta-lactoglobulin

Heat-induced structural changes of beta-lactoglobulin were studied at temperatures ranging from 67.5 to 82.5 degrees C, and at pH 7.5. These changes were monitored by measurement of surface hydrophobicity, thiol availability, and protein solubility. Kinetic studies were conducted to quantitatively describe the contribution of hydrophobic and SH/SS interchange reactions to the thermal structural changes of beta-lactoglobulin. Results indicate that beta-lactoglobulin is sensitive to heat-induced interchange reactions with consequences for protein solubility. The extent of changes measured by the increase in surface hydrophobicity and the decrease in slow-reacting SH groups content could be described by a first-order fractional conversion model and were characterized by activation energy values of 233.9 +/- 8.6 and 148.2 +/- 6.7 kJ/mol, respectively. The break in the Arrhenius plot suggested in literature for beta-lactoglobulin denaturation was confirmed in this study only for the kinetics of exposed SH groups.     

Effects of Silicon Content on the Mechanical Properties and Lubricated Wear Behaviour of Al–40Zn–3Cu–(0–5)Si Alloys

In this work, one ternary Al–40Zn–3Cu and seven quaternary Al–40Zn–3Cu–(0.25–5)Si alloys were synthesized by permanent mould casting. Their microstructure, mechanical and lubricated wear properties were investigated using appropriate test apparatus and techniques. As the silicon content increased the hardness of the alloys increased, but their elongation to fracture decreased. Tensile strength of the alloys decreased with increasing silicon content following a sharp decrease and a slight increase. Among the silicon-containing quaternary alloys the highest and the lowest tensile strength values (348 and 305 MPa) were obtained with the Al–40Zn–3Cu–2Si and Al–40Zn–3Cu–5Si alloys, respectively, while the base alloy (Al–40Zn–3Cu) exhibited a tensile strength of 390 MPa. However, the volume loss due to wear of the alloys increased with increasing silicon content after showing an initial increase and a sharp decrease. The lowest wear loss was obtained with the alloy containing approximately 2% Si which has the highest tensile strength among the quaternary alloys containing more than 0.25% Si. Wear surfaces of the alloys were characterized mainly by smearing indicating that adhesion is the dominant wear mechanism for the experimental alloys.