Miscible blends of styrene–cinnamic acid copolymers with poly(ethyl methacrylate)

Differential scanning calorimetry and inverse gas chromatography have been used to investigate the miscibility behaviour of blends of poly(ethyl methacrylate) (PEMA) with styrene–cinnamic acid statistical copolymers PSCA5, PSCA8, PSCA23 having compositions of, respectively, 5, 8 and 23 mol% of cinnamic acid. Several probes with different chemical nature and polarity have been used to determine the polymer–solute and polymer–polymer interaction parameters. DSC and CPGI measurements indicate that poly(ethyl methacrylate) is miscible with each poly[(styrene)‐co‐(cinnamic acid)] copolymer as established from the observation of a single composition‐dependent glass transition temperature. This deduction is corroborated by the IGC data; comparison of the experimental retention volume of the blend with the algebraic average retention volumes of the pure components, together with negative values of the apparent polymer–polymer interaction parameter, establish the miscibility of the studied systems. Furthermore, the polymer–polymer interaction parameters are found to show marked probe dependence; this is discussed in terms of the Δχ effect. As indicated by the variation of the glass transition temperature with blend composition, the application of the Kwei and the Schneider approaches to the calorimetric results suggests the occurrence of strong specific interactions within the blends; the strength of these intermolecular interactions increases with the cinnamic acid content in the PSCA copolymer. © 2001 Society of Chemical Industry     

An experimental study of mixed convection around a rotating isothermal cylinder

The mixed convective flows generated by a heated rotating horizontal cylinder have been investigated experimentally. The presence of rotation represents an important complication and extension of previous studies on convective flow and heat transfer around heated stationary horizontal cylinders in an otherwise quiescent medium. Significant qualitative, as well as quantitative, differences in the heat transfer characteristics and flow patterns generated by the rotating cylinders are observed as compared to those for stationary cylinders. When the Reynolds number reaches a value corresponding to the rotational parameter σ ≡ Gr/Re² being just below unity, the thermal plume becomes unstable and eventually breaks down. This event corresponds to the onset of a secondary mean flow which appears to be periodic in the axial direction. Mean Nusselt number measurements are presented, which show a dramatic increase in heat transfer at the onset of the secondary flow. Also, the structure of the secondary flow and the behavior of the plume are elucidated through Schlieren photography.     

The initial freezing point temperature of beef rises with the rise in pH: A short communication

This study tested the hypothesis that the initial freezing point temperature of meat is affected by pH. Sixty four bovine M. longissimus thoracis et lumborum were classified into two ultimate pH groups: low (< 5.8) and high pH (> 6.2) and their cooling and freezing point temperatures were determined. The initial freezing temperatures for beef ranged from − 0.9 to − 1.5 °C (? = 0.6 °C) with the higher and lower temperatures associated with high and low ultimate pH respectively. There was a significant correlation (r = + 0.73, P < 0.01) between beef pH and freezing point temperature in the present study. The outcome of this study has implications for the meat industry where evidence of freezing (ice formation) in a shipment as a result of high pH meat could result in a container load of valuable chilled product being downgraded to a lower value frozen product.     

A comparison of a fluoroscopy-free mechanical targeting system and a free-hand technic for the placement of distal interlocking screws of tibial nails

Recently, radiation-independent aiming devices for the tibia which compensate for insertion-related implant deformation have been developed, but the benefits of such systems have not been determined. This study prospectively evaluated the duration of the nailing procedure, the length of radiation time, and the accuracy of interlocking screw placement with a radiation-independent distal aiming system and the free-hand technique. In an oblique cadaveric tibial fracture, a surgeon inexperienced with either technique performed a statically locked intramedullary nailing. For the aiming system and free-hand technique respectively, the total operation time was 25.4 +/- 11.3 vs 30.9 +/- 14.3 min (P = 0.029), the distal locking time was 16.7 +/- 8.6 vs 21.9 +/- 10.5 min (P = 0.004), the total fluoroscopy time was 9 +/- 5 vs 93 +/- 34 s (P < 0.0001), the distal locking fluoroscopy time was 0 versus 88 +/- 33 s (P < 0.0001), and the screw destruction was -0.7 +/- 5.2 vs 26.8 +/- 31.6 microns (P = 0.001). The failure rate was 1.6% (1 of 60 screws) in both groups. These results suggest that aiming devices can eliminate the need for radiation during distal interlocking screw placement.     

An efficient heuristic approach for parallel machine scheduling with job splitting and sequence-dependent setup times

In this paper, we consider a simplified real-life identical parallel machine scheduling problem with sequence-dependent setup times and job splitting to minimize makespan. We propose a heuristic to solve this problem. Our method is composed of two parts. The problem is first reduced into a single machine scheduling problem with sequence-dependent setup times. This reduced problem can be transformed into a Traveling Salesman Problem (TSP), which can be efficiently solved using Little's method. In the second part, a feasible initial solution to the original problem is obtained by exploiting the results of the first part. This initial solution is then improved in a step by step manner, taking into account the setup times and job splitting. We develop a lower bound and evaluate the performances of our heuristic on a large number of randomly generated instances. The solution given by our heuristic is less than 4.88% from the lower bound.     

Preliminary studies to determine the chaperoning properties of bovine casein and crystallin proteins at reducing beef muscle protein aggregation during heating

The ability of small heat shock proteins (sHSP) at preventing the aggregation and precipitation of unfolded and misfolded proteins because of changes in pH and temperature is widely recognised. The performance of sHSP from bovine lens extract at protecting sarcoplasmic proteins from heat induced denaturation and aggregation was compared with other chaperones including bovine serum albumin, α_s‐casein, β‐casein and a synthetic peptide based upon αA‐crystallin (AAC). Beef sarcoplasmic proteins were heated in the presence or absence of exogenous chaperone and the solubility, surface hydrophobicity and enzymatic activities of the sarcoplasmic proteins was determined. Lens extract prevented the aggregation of sarcoplasmic proteins, maintaining solubility and clarity up to 65 °C relative to 60 °C for β‐casein. By contrast, α_s‐ and β‐casein proteins protected the activity of endogenous enzymes at temperatures between 37 °C and 52 °C, unlike lens sHSP. Our findings support the addition of casein proteins as potential thermal stabilisers of meat proteins in food systems.     

Heat transfer in a rectangular chamber with differentially heated horizontal walls: Effects of a vibrating sidewall

Heat transfer in a gas-filled closed enclosure with differentially heated horizontal walls is investigated numerically. One of the sidewalls vibrates with specified frequency and amplitude to induce forced convective flows in the enclosure. The vibrating and the stationary sidewalls are considered to be thermally insulated while the two horizontal walls are differentially heated. To simulate the flow field, the full compressible form of the Navier–Stokes equations is considered and solved by a highly accurate flux-corrected transport algorithm. In the numerical model, temperature dependant heat conductivity and viscosity are taken into account. The presence of acoustic streaming is found to have significant effect on the heat transfer. Also the presence of temperature gradients in the enclosure is found to affect the formation of acoustically induced streaming flows.     

Preoperative staging of rectal carcinoma by magnetic resonance imaging with a pelvic phased-array coil

BACKGROUND: The use of surface coils for magnetic resonance imaging (MRI) allows enhanced image definition and so potentially more accurate staging of colorectal cancer. Endorectal coil imaging is invasive, operator dependent and impossible in a high proportion of patients due to rectal stricture. The phased-array pelvic coil, however, is non-invasive and applicable to all rectal tumours. METHODS: A pelvic phased-array coil was used for preoperative MRI staging of 38 primary rectal carcinomas. Results were expressed according to the Dukes and tumour nodes metastasis (TNM) classifications. After resection of the tumour, the stage predicted on MRI was compared with the pathological classification. RESULTS: The overall accuracy of preoperative staging with the pelvic phased-array coil was 55 per cent for both Dukes class and T stage. Assessment of nodal involvement gave an overall accuracy for MRI of 76 per cent with a sensitivity of 57 per cent and specificity of 88 per cent. CONCLUSION: Use of a pelvic phased-array coil did not improve the staging accuracy of MRI to a clinically useful level.     

Modeling of fluid flow and heat transfer in the plasma region of the dc electric arc furnace

A mathematical model describing the transport processes in the plasma arc in dc electric arc furnaces has been developed. The equations of conservation of mass, momentum, and energy are solved numerically in conjunction with Maxwell's equations of the electromagnetic field to calculate the velocity and temperature distributions in the plasma region. The heat transfer from the arc to a rigid anode surface is calculated. The model is applied to obtain quantitative results on the relative importance of the various modes of heat transfer from the electric arc to the anode surface. Computational results were obtained for varying arc current magnitudes and anode-cathode distances. The model predicts higher arc jet velocity and a broader arc core at higher arc current. The shorter arc length is more efficient for transferring heat to the anode.