Showing papers by "Swedish Institute published in 1991"

Thermal Degradation of Carotenes and Influence on their Physiological Functions

Abstract: Raw carrot juice contains a considerable amount of α -and β-carotene, which makes carrot an excellent source of vitamin A. Heat treatment of the juice at temperatures comparable to those at pasteurization and boiling does not change the carotenes, while heating at temperatures used during sterilization results in rearrangement of the carotene molecules and a decrease in total carotenes. The all-trans α-and β-carotenes appear partly as cis-isomers, especially the 13-cis-isomer. Isomerization of the carotenes leads to a decrease in their vitamin A activity. Carotenes also seem to be anticarcinogens but the extent to which this property is influenced by isomerization is still unknown.

Formation, crystallisation and oxidation of selected glasses in the YSiAlON system

Abstract: Oxynitride glasses were prepared which correspond to the compositions of the intergranular phase in Si3N4 ceramics fabricated with additions of Y2O3 and Al2O3 as sintering aids. Transparent glasses were obtained after melting for 10 h at a firing temperature of 1450°C. Two distinct melting temperatures of 1310°C and 1375°C were obtained for all compositions within the oxynitride glass-forming region. For all N-containing compositions the glass softening point (Mg) was 975°C which is an increase of ≈ 110°C over that of the corresponding oxide glass. Devitrification of the glasses in N2 required 12 h at 1200°C and the phases present after crystallisation included Y2Si2O7, Si2N2O and 3Y2O3.5Al2O3 (YAG). The oxynitride glasses oxidised rapidly in air at temperatures in excess of the softening point. Porous oxide ‘scales’ developed from the evolution of nitrogen was during oxidation and the main crystalline phases that formed in the scale were Y2Si2O7 and 3Al2O3.2SiO2 (mullite).

Lipids in light and dark muscle of farmed rainbow trout (Oncorhynchus mykiss)

Abstract: Dark muscle tissue of farmed rainbow trout (Oncorhynchus mykiss Walbaum) was found to have a higher total lipid content than light muscle—73 vs 30 g kg−1—which was mainly due to a higher content of neutral lipids. In accordance with this the phospholipid content in the dark muscle tissue was 322 g kg−1 of total lipids compared with 569 g kg−1 in light muscle tissue. Lipids from light muscle tissue contained higher percentages of polyunsaturated fatty acids than the dark muscle lipids, and docosahexaenoic acid was the major fatty acid present.

Oxidation of pressureless sintered Si2N2O materials

Abstract: The oxidation behaviour of pressureless sintered Si2N2O materials prepared from both amorphous and crystalline starting powders has been examined The materials exhibited excellent oxidation resistance at temperatures of up to 1350°C Thin protective oxide scales formed which had a duplex morphology after long exposures to air at high temperatures Substantial crystallisation of the intergranular glass phase with formation of Y2Si2O7 occurred during oxidation at 1200°C and 1350°C Catastrophic oxidation occurred at temperatures ≥ 1400°C This behaviour is enhanced by an oxidation-induced shift in the composition of the material to a liquid-forming region in the Y-Si-Al-O-N system

Cost effectiveness of blood substitution in elective orthopedic operations

Abstract: Cost effectiveness was compared between substitu- Our study showed that predonated blood alone, tion with autologous blood, implying no risk of with a donation of up to four units, was the most suittransmission of diseases, and homologous blood, able and cost-effective method for substitution of with a definite risk of transmission. Primary and blood losses up to about 2.5-3 liters A combination revision hip arthroplasties were included in this of predonated blood and intraoperative autotransfustudy, as well as scoliosis operations. The risk of sion was more suitable and less expensive for substicontracting chronic non-A, non-B hepatitis (NANBH) tuting blood losses of 2.5 liters or more. Homologous was included in the calculations of the long-term blood was the least cost-effective alternative consideconomic consequences of a transmittable disease. ering the influence of non-A, non-B hepatitis.

Changes in microhardness and creep modulus during the ageing of polypropylene

Abstract: This letter reports results of ageing studies on polypropylene (PP) in which both time-dependent microhardness (MH) tests and low stress-strain creep experiments were performed. The purpose of the research was to ascertain whether the relationships that applied to creep and MH of HDPE could also be applied to PP, and whether the MH and variation of MH with indentation time were affected by ageing

Microstructural characterization of cemented carbides using SEM based automatic image analysis

Abstract: Methods for SEM based automatic image analysis of cemented carbide microstructure were developed. Two different categories of hard metal were investigated: WC-Co grades and WC-γ-Co grades, i.e. cemented carbides containing cubic carbides (γ-phase) as well as tungsten carbide WC. The materials represented a wide range in grain size, chemical composition and structure complexity. Automatic object detection and evaluation of carbide grain size, carbide contiguity and volume fractions were possible through the combination of optimized specimen preparation, high resolution microscopy and image processing in a software oriented image analyzer. The importance of careful specimen preparation in order to obtain maximum contrast and structure definition was emphasized. High spatial resolution in SEM was achieved by working at low accelerating voltages. Two different back scattered electron contrast modes were utilized: atomic number (Z) contrast and channelling contrast. Mean values of WC and cubic carbide (γ-phase) grain size in the range 0·–2 μm were measured; values which were considerably lower than values obtained according to conventional methods. The difference was explained by the low detection limit in the SEM based analysis, enabling detection of fine carbide grain populations. Binder mean free path increased and carbide contiguity decreased with increasing binder volume and with increasing carbide grain size in the WC-Co alloys. The results of the automatic measurements were of fully sufficient accuracy for a wide range of hard metals. In cases of very weak contrast, limited manual editing was sufficient to obtain results close to actual values. It was concluded that automatic methods can be successfully applied to the characterization of complex cemented carbide microstructures.

Evidence of a response-bias explanation of noneuclidean cognitive maps*

Abstract: Two groups of subjects with varying amounts of experience with the city in which they lived judged from memory distances between familiar locations. The distance judgments were processed by a multidimensional scaling algorithm (MULTISCALE) that estimates the parameters of a power function transformation of the response scale and the coordinates of the locations in k-dimensional euclidean space. The results for both subject groups suggested that inaccuracies of distance cognition do not reflect the noneuclidean nature of urban cognitive maps but are caused by response bias.

Characterization and properties of new shape memory alloys in the NiFeAl system

Abstract: Rapidly solidified ribbons (∼ 40 μ thich) have been produced by melt spinning. The alloys studied have the composition (Ni x Fe y Al z ) 0.9983 B 0.0017 , where x = 58−60, y = 13−15, and z = 26−28 (at.%). The ribbons have been characterized by thermal analysis (DSC), X-ray diffraction analysis and microstructural analysis. Heat treatment and recoverable strain measurements have also been made. Five different alloy compositions produced at three different wheel velocities all show the shape memory effect, and by DSC and recoverable strain measurements the martensite transformation is clearly seen for all but one alloy. Transformation temperatures vary widely between the alloys in the ranges: M s = 244 − 465 K, M f = 200 − 395 K, A s = 236 − 427 K, and A f = 262 − 526 K, measured by DSC. The change in enthalpy during the transformation varies from 0.22 cal g −1 to 1.33 cal g −1 . Measured values of the recoverable strain vary between 0.5% and 1.3%. Phase identification by X-ray diffraction is not complete, but indicates the presence of at least three different phases: AlNi, AlNi 3 and γ(Fe, Ni).

Contracts in Database Federations

Abstract: A model for information sharing in a loose association of information/database systems is proposed Such a system is referred to as a federation, where the fundamental characteristic is the autonomy of the member systems (the nodes) The model for sharing is based on the establishment of bilateral agreements between nodes These agreements are represented by contracts, the terms of which define the rules for information exchange The model provides flexibility for resource sharing and for cooperation in a decentralized setting

On the formation of impurity-containing phases in cemented carbides

Abstract: This work is a part of a COST programme undertaken to study the influence of some impurities on the properties of cemented carbides. The precipitation of inclusions containing Ca, Al, Si, P, S and O was studied by combining calculated phase equilibria with sintering experiments based on two cemented carbide grades. Minor amounts of Ca, Al, P and Si were added to the raw materials used and by sintering in furnace atmospheres, having increased sulphur or oxygen potentials, the formation of oxides and sulphides was facilitated. A comprehensive investigation of as-sintered surfaces, polished cross sections and fracture surfaces was made, and the type and amount of impurity-containing phases were compared to the calculated diagrams. It was found that CaS is always formed whenever Ca and S are present. Excess amounts of either Ca or S were evaporated, and also Si to some extent. Aluminum is often found in oxides together with Ca and Si. Both Al and P are present in the sintered material to the same extent as had been added to the raw materials. No phosphorus or very small amounts of the phosphorus added were found in the inclusions investigated. It is believed that P is evenly distributed throughout the material to a high degree.

Lipid oxidation in potato slices under conditions simulating the production of potato granules

Abstract: The formation of volatile compounds in potato slices was analyzed by means of gas Chromatographie headspace analysis. The experimental variables selected for the treatment of the potato slices were chosen to simulate the conditions during the first stages of an “add-back type” of process for production of potato granules. The potato slices (2 cm thick) were exposed to air of low temperature (4°C) and water at blanching temperature (76°C). Both the surface and the middle of each slice were analyzed for volatile compounds. Hexanal was the most abundant aldehyde formed. At the elevated temperature, in particular, there was an obvious formation of hexanal. After 15 min of blanching, the amount of hexanal was higher in the middle of the slices than at the surface. This difference in hexanal concentration was probably due both to the leakage of hexanal into the blanching water from the surfaces of the potato slices, and to the inac-tivation of lipoxygenase at the surfaces which prevented further oxidation during the subsequent chilling period. The hexanal formation indicates that lipid oxidation occurs during the process. The formation of other volatile compounds also is discussed.

Semi-insulating InP:Fe regrowth by the hydride VPE technique around p -InP substrate laser mesas fabricated by reactive ion etching

Abstract: Successful regrowth of semi-insulating (SI) InP: Fe by the hydride vapour phase epitaxy technique around reactive ion etched vertical mesas of laser grown on Zn dopedp-InP substrate is demonstrated. The device performance of the buried heterostructure laser is presented. The current confining property of the regrown SI-InP: Fe are good although it lies adjacent to InP: Zn.

Microstructure of a rapidly solidified 65Al-20Cu-15Fe (at. %) alloy

Abstract: The microstructure of rapidly solidified 65Al-20Cu-15Fe (at. %) powders was investigated by analytical transmission electron microscopy. It was found that segregation in the powder particle occurred during solidification. The major phase present in the powder particles was the icosahedral quasicrystalline l-phase, which was determined to have space group\(\bar 3\bar 5\). Two other crystalline phases, β-AlCu3 and θ-Al13Fe4, coexisted with the l-phase. The l-phase was revealed by convergent beam electron diffraction to have three-dimensional quasiperiodicity (τ = 1.618) which is different from quasicrystals in the other systems. The compositions of the three phases have been analysed by energy dispersive X-ray analysis. The l-phase in this system could be approximately described as Al5CuFe. The composition of the θ-Al13Fe4 was very close to the equilibrium condition while β-AlCu3 was far from stoichiometry. An orientation relationship between β-AlCu3 and θ-Al13Fe4 was found as follows: [110]β∥[010]θ [111]β∥[001]θ

CuInSe2/CdS Interface Formation Studied by XPS

Abstract: The formation of the CdS/CuInSe2 thin film interface is studied by sequential growth of thin CdS layer and surface analysis by XPS. The CuInSe2 layer is prepared by the two-step (Boeing) coevaporation method. The growth of CdS is studied on a CuInSe2 bottom layer (slightly Cu-rich) as well as on composite layers. It is shown that CuInSe2 double layers yield an abrubt interface whereas CdS growth on a slightly Cu-rich CuInSe2 layer results in the formation of copper-sulphide nodules.

The Impact of Crevices beneath Surface Mounted Devices on the Cleaning Efficiency

Abstract: The transition to surface mounted device (SMD) technology in electronics manufacturing has placed new demands on the post‐solder cleaning process. For spacecraft electronic systems it is of the utmost importance that all flux residues be removed. This paper reports the results of an investigation of the impact of component stand‐off heights and the distance between solder joints on the cleaning process efficiency. The capability to clean beneath large chip carriers was evaluated for four different cleaning methods using isopropanol or CFC‐113 (Freon TMS) as cleaning liquid. The results show that the cleaning efficiency decreases considerably if the stand‐off height is less than 240 µm for 100 mil pitch chip carriers. For 50 mil pitch chip carriers the stand‐off height needs to be greater than 240 µm to achieve high cleaning efficiency. The cleaning efficiency beneath chip carriers with small stand‐off heights can be increased by using ultrasonic cleaning. However, a very thin layer of white residues is left where the flux has been removed if isopropanol is used as the cleaning liquid.

Production of superconducting Cu-Nb-Sn alloy by hot extrusion of rapidly solidified powder

Abstract: A Cu92.5Nb5Sn2.5 alloy has been rapidly quenched into a powder by ultrasonic gas atomization. The structure of the powder consists of finely dispersed Nb particles in a Cu-Sn matrix. The powder has been consolidated by hot extrusion at 650°C. The extrusion does not change the phases present in the material appreciably but annealing for 100 h at 650°C causes a transformation of the Nb particles to Nb3Sn.

Hrem Studies of Rapidly Solidified Ni-Fe-Al-B Shape Memory Alloys.

Abstract: A series of $${({\text{N}}{{\text{i}}_{\text{x}}}{\text{F}}{{\text{e}}_{\text{y}}}{\text{A}}{{\text{l}}_{\text{z}}})_{{{0.9983}^{\text{B}}}0.0017}}$$ (where x=58–60, y=13–15 and z=26–28, in at%) alloys have been rapidly solidified by - melt spinning. The ribbons have been characterized by HREM, DSC, X-ray diffraction and recoverable strain measurements. The as-cast alloys exhibit excellent bend ductility (in contrast to B2 type alloys conventionally cast) and a wide range of transformation temperatures: Ms=244–466 K, Mf=200–395K, As=236–427K and Af=262–526K. X-ray diffraction shows the presence of β (NiAl), β′ (NiAl), γ (Ni3Al), γ′ (Ni3Al), Ni and other phases such as Fe3Al, FeAl, FeNi and Al5Fe2. It is the β- β′ diffusionless transformation which is responsible for the shape memory effect. The results obtained by transmission electron microscopy (TEM) show two different types of crystalline grains. In one case, the grains have a high density of twins which are the fingerprints of the martensite transformation. However, other areas in the specimen show crystalline grains with very poor image contrast due to the transformation from β′ - β. There are also sections in the specimens with domains of both crystalline grains in coexistance. Both crystalline grains have large amounts of precipitates. In the β′ (NiAl) phase the size of the precipitates range fron 1nm to 10nm. In the γ (Ni3Al) phase large precipitates (20nm) can be found. Some of them display pentagonal shapes which resemble the image contrast obtained in the TEM for small icosahedral metallic particles. Experimental evidence is also obtained on different habit or twin planes. HREM images from the twinned areas suggest diferent kinds of atomic structures for the parent and martensite crystalline sections. These results give some insights into the nature of the martensite transformation.