Development of a portable spectrofluorimeter for measuring the microbial spoilage of minced beef

The evaluation of meat spoilage is based on sensory and microbiological analyses. The disadvantages of sensory analyses are its reliance on highly trained panelists, a procedure which makes it costly and unattractive for routine analyses. Moreover, the classical microbiological analyses are lengthy, costly and destructive. In this study a portable fluorescence spectrometer was tested to quantify minced beef spoilage. This study was investigated on samples stored aerobically and under vacuum at 5 and 15 °C. Total viable counts (TVC), Pseudomonas, lactic acid bacteria, and yeast/molds counts were investigated with classical culture methods. Fluorescence spectra were recorded on the same samples using different excitation LEDs (280, 320, and 380 nm). PLS-R with leave-one-out cross validation was used to perform calibration and validation models. The PLS-R models presented good R2(CV) (0.50-0.99) and ratio of standard deviation (RPD(CV): 1.40-8.95) values after cross-validation. It could be concluded that portable spectrofluorimeters are promising devices to evaluate spoilage in minced beef.     

Structural changes of milk components during acid-induced coagulation kinetics as studied by synchronous fluorescence and mid-infrared spectroscopy

Dynamic oscillatory experiments and front-face synchronous fluorescence spectroscopy and mid-infrared (mid-IR) spectroscopy have been used to investigate structure evolution, at the macroscopic and molecular levels, during milk acidification kinetics. The studies were performed using skim milk, at two different temperatures (30 °C and 40 °C), to which was added glucono-δ-lactone (GDL) to generate different structural changes in casein micelles and gels. Synchronous fluorescence spectra were recorded in the 250-500 nm excitation wavelength range using an offset of 80 nm between the excitation and emission monochromators for each system during the 300 min acidification kinetics. The change in the fluorescence intensity at 281 nm reflects the pH-induced physicochemical changes of casein micelles and, in particular, structural changes in the micelles in the pH range 5.5-5.0. Regarding mid-infrared spectroscopy, the region located between 1700 and 1500 cm(-1), corresponding to the amide I and II bands, and the 1500-900 cm(-1) region, called the fingerprint region, were considered for the characterization of milk coagulation kinetics. Changes in the absorbance at 1063 cm(-1) as a function of pH for kinetics recorded at 30 °C and 40 °C reflected pH-induced phosphate dissolution in the pH range 5.5-5.0. Compared to rheometry, which reveals microstructure changes only in the gel state, spectroscopic methods make it possible to monitor molecular structure changes in micelles throughout the acidification processes.     

Evaluation of the effects of acetyl tributyl citrate as bio‐based plasticizer on the physical,thermal, and dynamical mechanical properties of poly(vinyl chloride)/polymethyl methacrylate blends

This article details our work in studying the plasticization of Poly(vinyl chloride) (PVC)/Polymethyl methacrylate (PMMA) blends with bio‐based acetyl tributyl citrate (ATBC) in place of conventional plasticizers such as di(2‐ethylhexyl) phthalate. PMMA was blended with PVC in various ratios from 0 to 100 wt% by melt compounding with or without the plasticizer ATBC. Both the glass transition temperatures of the blends (differential scanning calorimetry) and Tα (dynamic mechanical thermal analysis) are consistent with a miscibility of the components, and Fourier transforms infrared spectroscopy studies show that there are specific interactions in the PVC/PMMA blends favoring the miscibility. The thermal degradation of the blends was studied by thermogravimetric analysis that shows the thermal degradation of rigid and plasticized PVC/PMMA is a process composed of two‐steps and that PMMA exercises a stabilizing effect on the thermal degradation of PVC during the first step by decreasing the rate of dehydrochlorination. J. VINYL ADDIT. TECHNOL., 25:E73–E82, 2019. © 2018 Society of Plastics Engineers     

Correction of pressure drop in a heavily loaded hybrid bearing when starting by using a constant flow lubrication system- Application to a rotary cement mill

We analyzed a lubricated journal plain bearing supporting heavy loaded rotary mill. During start-up operating, after the shaft is lifted by high external pressure lubricant, the speed of the shaft grows from 0 to the operating hydrodynamic speed when, suddenly after the first thirty seconds of shaft rotation, the pressure drops in one recess causing excessive damage to the pad bearing interface. The aim was to understand and provide some answers to the pressure drop in order to give an appropriate correction. Misalignment between the shaft and bearing surfaces was considered and analyzed in first part of the study. According to the obtained results the proposed correction is to use a suitable constant flow lubrication system which avoids the pressure to drop in recesses. A real application was made on a partial pad bearing supporting a heavy rotary cement mill localized at the cement plant of Chlef in Algeria.

     

Rapid manufacturing of metal components by laser forming

This overview will focus on the direct fabrication of metal components by using laser-forming techniques in a layer-by-layer fashion. The main driving force of rapid prototyping (RP) or layer manufacturing techniques changed from fabrication of prototypes to rapid tooling (RT) and rapid manufacturing (RM). Nowadays, the direct fabrication of functional or structural end-use products made by layer manufacturing methods, i.e. RM, is the main trend. The present paper reports on the various research efforts deployed in the past decade or so towards the manufacture of metal components by different laser processing methods (e.g. selective laser sintering, selective laser melting and 3-D laser cladding) and different commercial machines (e.g. Sinterstation, EOSINT, TrumaForm, MCP, LUMEX 25, Lasform). The materials and applications suitable to RM of metal parts by these techniques are also discussed.     

Influence of manufacturing errors on the dynamic behavior of planetary gears

Planetary gears are widely used in the transmissions of helicopters, automobiles, aircraft engines, etc. They have substantial advantages such as compactness and a large torque-to-weight ratio. In this work, a plane model of a planetary gear was investigated. The energetic Lagrange formulation was used to recover the equations of motion of the system. A modal analysis was performed, and the influence of gyroscopic effect in particular was scrutinized. The dynamic response was computed by an iterative spectral method. The excitation is induced by time-varying the gearmesh stiffness. The cases of a healthy planetary gear and one with the presence of eccentricity and profile error were compared. The influence on the transmission ratio was also studied.     

Structural robustness and service reachability in urban settings

The concept of city or urban resilience has emerged as one of the key challenges for the next decades. As a consequence, institutions like the United Nations or Rockefeller Foundation have embraced initiatives that increase or improve it. These efforts translate into funded programs both for action “on the ground” and to develop quantification of resilience, under the for of an index. Ironically, on the academic side there is no clear consensus regarding how resilience should be quantified, or what it exactly refers to in the urban context. Here we attempt to link both extremes providing an example of how to exploit large, publicly available, worldwide urban datasets, to produce objective insight into one of the possible dimensions of urban resilience. We do so via well-established methods in complexity science, such as percolation theory—which has a long tradition at providing valuable information on the vulnerability in complex systems. Our findings uncover large differences among studied cities, both regarding their infrastructural fragility and the imbalances in the distribution of critical services.     

Adaptive multistage parallel interference cancellation for CDMA

Although the multistage interference cancellation detector is simple in structure, its performance degrades when the number of active users becomes large. In some cases, the performance is even worse than that without cancellation, due to the lack of the exact knowledge of the interfering signal in cancellation. Partial interference cancellation suggested by Divsalar and Simon (see IEEE Trans. Commun., vol.46, p.258-68, 1998) tries to remedy this weakness by reducing the cost of a wrong interference estimation through a weight in each stage. This paper presents an adaptive multistage structure based on the partial interference cancellation approach. In this structure, the weights are obtained by minimizing the mean-square error between the received signal and its estimate through a least mean square (LMS) algorithm. The resulting weights contain reliability information for the hard decisions made in the previous stage. Neither a training sequence nor a pilot signal is needed in the proposed scheme, and its complexity is much lower than that of linear multiuser detectors. Simulation results show that the proposed scheme can outperform some of the existing interference cancellation methods in both the additive white Gaussian noise (AWGN) and the multipath fading channels