The effects of die shapes and additives on the physical and biodegradable properties of biodegradable cushioning extruded foams

In this study, efforts were focused on the effects of the operating parameters, i.e. die shapes (DS), PVA ratio (PR), additives (AT) on the physical and biodegradable properties of the corn/PVA extrudates. We also evaluated the extrudates as cushioning materials. The process variables were the operating, conditions, die shapes (○, ∞, ? and O ), PVA ratio (40%, 50%, 60%) and additives [sodium bicarbonate (NaHCO₃), calcium carbonate (CaCO₃) and calcium hydroxide (Ca(OH)₂)]. The experiment is a 4 × 3 × 3 factorial design. Samples of each treatment were collected and the physical, mechanical and chemical properties were measured and analysed using the PROC ANOVA and PROC CORR of the SAS 6.0 software package. 35 The experimental results indicated that: (a) The change of die shapes (DS) had a significant effect on the longitudinal expansion, bulk density, compressibility and biodegradability properties of the extrudates; (b) the change of PVA ratio (PR) had a significant effect on the longitudinal expansion, bulk density and compressibility, but no effect on the biodegradability properties of the extrudates; and (c) the change of additives (AT) had a significant effect on the longitudinal expansion, bulk density and compressibility, but no effect on the spring index of the extrudates. Copyright © 2003 John Wiley & Sons, Ltd.     

Untersuchungen über das Strangpressen kubisch-flächenzentrierter Metalle. Teil II: Kraftbedarf und Kraftverteilung

Investigation of the extrudability of face-centred cubic metals Part II: During continuous extrusion at certain intervals dry oxides are discharged. This is explained with the aid of rheological investigations. If a shearing device according to DIN standard is used the results may show errors in a range of 70% and more. A new device is described which avoids this source of error. The shear strength of high purity aluminium was determined at various temperatures and rates of deformation. Investigations were conducted under similar conditions on the extrusion of aluminium and a relationship between shear strength and power requirement was established. On this basis the power requirement to extrude new alloys may be predicted by comparing the shear strength of this alloy with the shear strength of an alloy whose extrudability is known. Direct extrusion experiments under isothermal conditions were conducted in the reduction range R = 1.2–300. The linear relationship in double logarithmic scale exists only in the range of R = 4–40. Indirect extrusion experiments also showed a linear relationship below the reduction rate R = 4 in a logarithmic scale. It was found that during indirect extrusion a dead metal zone is also formed and this explains the divergence of the found pressure distribution from the theoretical values. The normal pressure of the container was measured at a number of points at various temperatures and reduction rates. In the range of 150°–170°C peculiar unsteadiness occured. Normal pressure on the change of the velocity of extrusion was investigated with the aid of a stepped-down die and a strong dependence was found. A device was developed to compare the plasticity of cubic face centered metals, and it was found that the maximum plasticity is reached at 90% of the melting point in degrees absolute. Efficiency investigations during extrusion showed that the power consumption required to overcome the radial shear in continuous extrusion is 60% to 77%, whereas the power required to overcome the total shear in extrusion in a piston driven press is 94% to 87%. Extrusions inside a calorimeter showed, on the basis of mechanothermodynamic conversion, that 85% to 94% of the power was used for the deformation of the metal.     

99mTc-MIBI used for diagnosis of portal hypertension: an experimental study

The authors investigated the relationship between portal-systemic shunting and portal pressure in 16 CCl4-induced cirrhotic wistar rats by 99mTc-MIBI photography of heart and liver. Based on radio-counts taken at 30 minutes after 99mTc-MIBI was given per rectum 8 rats or medial clonic vein 8 rats, heart radio-counts/liver radio-counts (H/L) and portal-systemic shunting index (SI) were recorded. It was shown that 1. H/L and SI of the two cirrhotic groups were greater than those of normals (P < 0.001); 2. H/L in cirrhotic rats by rectum 99mTc-MIBI administration was more closely related to free portal pressure (FPP, r = 0.83, P < 0.01) than in those by venous route (r = 0.74, P < 0.05) and its regressive formation FPP (kPa) = 0. 24 + 4.06 (H/L) was deduced and used to calculate portal pressure of cirrhotic rats. The very good relationship between the calculated and measured portal venous pressure was shown in a group of 12 cirrhotic rats (r = 0.85, P < 0.01). These findings suggested that the rectum administration of 99mTc-MIBI may be a useful method in calculating portal pressure and portal-systemic shunting in portal hypertensive patients.     

Studies on the solvent exchange technique for making dry cellulose acetate membranes for the separation of gaseous mixtures

The effect of the pore size on the surface of the water-wet reverse osmosis membrane and the solvents used in the solvent exchange process on the pore size of the resulting dry cellulose acetate membrane was studied with respect to the separation of a CO₂/CH₄ mixture. It has been found that there is a critical pore size on the surface of wet membrane that results in the smallest pore size on the dry membrane and, consequently, in the highest separation factor. Such critical pore sizes become greater when the boiling point of the second solvent is increased.     

Measurement of intermodulation products generated by structuralcomponents

A computer-controlled measurement system is described, developed to investigate intermodulation products generated by nonlinear junctions in antenna towers, mast support and mounting components. Results are presented which suggest that certain mechanical features, commonly encountered in some components, should be regarded as more likely to be associated with this cause of interference     

Wireless sensor networks scheduling for full angle coverage

Many current studies in tracking and surveillance assume that a target can be monitored by a single sensor. However, there are situations where a sensor can only monitor a certain portion of the object. Examples include image capturing and coastline monitoring. In our previous work, we develop the Minimum Cost Cover algorithm to identify a set of sensors which preserve 360° coverage of a target with minimum cost, such that when different cost functions for the sensors are used, covers with different optimization objectives can be identified. In this work, we study the scheduling problem to monitor a target continuously with full angle coverage. To increase network lifetime, we develop several algorithms by adopting different cost functions in selecting the sensors. We evaluate the performance of our schemes through extensive simulations. The simulation results show that our proposed Conditional Scheduling metric can help to improve the network lifetime as well as the time to the first node failure.

Use of low dose e-beam irradiation to reduce E. coli O157:H7, non-O157 (VTEC) E. coli and Salmonella viability on meat surfaces

This study determined the extent that irradiation of fresh beef surfaces with an absorbed dose of 1 kGy electron (e-) beam irradiation might reduce the viability of mixtures of O157 and non-O157 verotoxigenic Escherichia coli (VTEC) and Salmonella. These were grouped together based on similar resistances to irradiation and inoculated on beef surfaces (outside flat and inside round, top and bottom muscle cuts), and then e-beam irradiated. Salmonella serovars were most resistant to 1 kGy treatment, showing a reduction of ≤ 1.9 log CFU/g. This treatment reduced the viability of two groups of non-O157 E. coli mixtures by ≤ 4.5 and ≤ 3.9 log CFU/g. Log reductions of ≤ 4.0 log CFU/g were observed for E. coli O157:H7 cocktails. Since under normal processing conditions the levels of these pathogens on beef carcasses would be lower than the lethality caused by the treatment used, irradiation at 1 kGy would be expected to eliminate the hazard represented by VTEC E. coli.     

百合多糖脱蛋白方法的研究

研究中对几种百合多糖脱蛋白方法进行了对比实验，结果显示采用酶法与Seveage法联用法效果最好，是一种有效的植物多糖中的脱蛋白方法。     

大蒜精油对食用油脂的抗氧化特性

以过氧化值（POV）为指标研究了大蒜精油对花生油的抗氧化性能。结果表明：大蒜精油对花生油具有较强的抗氧化作用，且具有剂量效应关系；添加了大蒜精油的花生油应尽量贮存于低温条件下；VC、柠檬酸、酒石酸对大蒜精油的抗氧化作用均有协同增效作用；大蒜精油与合成抗氧化剂混合使用时，其抗氧化能力均好于只添加单一抗氧化剂的效果；使用0．2％大蒜精油和0．04％大蒜精油＋0．005％PG为花生油的抗氧化剂时，可使花生油在20℃下的贷架寿命由4．2个月延长至24．3个月和14．1个月。