| 1131. |
- Soderkvist, I., et al.
(författare)
-
ON CONDITION NUMBERS AND ALGORITHMS FOR DETERMINING A RIGID-BODY MOVEMENT
- 1994
-
Ingår i: Bit. ; 34:3, s. 424-436
-
Tidskriftsartikel (refereegranskat)abstract
- Using a set of landmarks to represent a rigid body, a rotation of the body can be determined in least-squares sense as the solution of an orthogonal Procrustes problem. We discuss some geometrical properties of the condition number for the problem of determining the orthogonal matrix representing the rotation. It is shown that the condition number critically depends on the configuration of the landmarks. The problem is also reformulated as an unconstrained nonlinear least-squares problem and the condition number is related to the geometry of such problems. In the common 3-D case, the movement can be represented by using a screw axis. Also the condition numbers for the problem of determining the screw axis representation are shown to closely depend on the configuration of the landmarks. The condition numbers are finally used to show that the used algorithms are stable.
|
|
| 1132. |
- SOITAMO, AJ, et al.
(författare)
-
OVER-PRODUCTION OF THE D1 PROTEIN OF PHOTOSYSTEM-II REACTION-CENTER IN THE CYANOBACTERIUM SYNECHOCOCCUS SP PCC-7942
- 1994
-
Ingår i: Plant Molecular Biology. - 0167-4412 .- 1573-5028. ; 26:2, s. 709-721
-
Tidskriftsartikel (refereegranskat)abstract
- The unicellular cyanobacterium Synechococcus sp. PCC 7942 has three psbA genes encoding two different forms of the photosystem II reaction centre protein D1 (D1:1 and D1:2). The level of expression of these psbA genes and the synthesis of D1:1 and D1:2 are strongly regulated under varying light conditions. In order to better understand the regulatory mechanisms underlying these processes, we have constructed a strain of Synechococcus sp. PCC 7942 capable of over-producing psbA mRNA and D1 protein. In this study, we describe the over-expression of D1:1 using a tac-hybrid promoter in front of the psbAI gene in combination with lacI(Q) repressor system. Over-production of D1:1 was induced by growing cells for 12 h at 50 mu mol photons m(-2) s(-1) in the presence of 40 or 80 mu g/ml IPTG. The amount of psbAI mRNA and that of D1:1 protein in cells grown with IPTG was three times and two times higher, respectively. A higher concentration of IPTG (i.e., 150 mu g/ml) did not further increase the production of the psbAI message or D1:1. The over-production of D1:1 caused a decrease in the level of D1:2 synthesised, resulting in most PSII reaction centres containing D1:1. However, the over-production of D1:1 had no effect on the pigment composition (chlorophyll a or phycocyanin/number of cells) or the light-saturated rate of photosynthesis. This and the fact that the total amounts of D1 and D2 proteins were not affected by IPTG suggest that the number of PSII centres within the membranes remained unchanged. From these results, we conclude that expression of psbAI can be regulated by using the tac promoter and lacI(Q) system. However, the accumulation of D1:1 protein into the membrane is regulated by the number of PSII centres.
|
|
| 1133. |
- Staberg, Else-Marie, 1933-
(författare)
-
Olika världar, skilda värderingar : Hur flickor och pojkar möter högstadiets fysik, kemi och teknik
- 1992
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This study investigates how Swedish pupils meet science (chemistry and physics) and technology in compulsory school. It explores girls' and boys' actions in and thoughts about these subjects. The study has a feminist perspective focusing on girls. Two teaching groups were followed from the start in grade 7 in compulsory school, when the pupils were 13 years old, until they made their choice of study programmes in upper secondary school in grade 9. The main methods were classroom observations and taped interviews.The results have been divided into the following four parts: the pupils' family background and recreation interests, classroom interactions, girls' and boys' approaches to science, and their choices of study programmes in upper secondary school. Girls and boys have different experiences and interests when they first meet science in grade 7 and boys have, thanks to their recreation interests, greater opportunities to participate in or take an interest in science/technology. The pupils come from different worlds determined by gender and social background. In the classroom girls get and take upon themselves the role of keeping the lessons together, thus fostering a responsible rationality, while boys strive to dominate the public arena. The process of shaping diligent, working, responsible girls as opposed to more childish, playful and competing boys continues in grades 7-9. Girls and boys prefer different subject areas. Boys have a practical while girls have a more theoretical approach to science. Even if there are important differences between girls, primarily owing to family background, there are significant differences between girls and boys. Girls seek "connected knowledge" and even the successful girls question their own understanding, which can be interpreted as a result of their learning style but also of their knowledge of the historical construction of women as unfit for science.The majority of the girls have, over the years, come to construct femininity - and maturity - as being opposed to enjoying experiments which are regarded as boys' play and as part of the masculine world. Boys also criticize girls for both failure and success and they try to get power over the subject content and the apparatus. This is interpreted as a reconstruction of the masculinity of the subjects. Girls who, nevertheless, take an interest in physics and chemistry often have supporting scientist fathers or at least parents with a higher education. Technology is rejected by all girls. The mutual construction and reconstruction of gender and of science/technology contribute to gendered choices of study programmes in upper secondary school.
|
|
| 1134. |
|
|
| 1135. |
- Staun Olsen, J., et al.
(författare)
-
High pressure studies up to 50 GPa of Bi-based high-Tc superconductors
- 1991
-
Ingår i: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 44:2, s. 211-213
-
Tidskriftsartikel (refereegranskat)abstract
- The high-Tc superconductor with nominal composition BiSrCaCu2Ox has been studied at high pressure, i.e. up to 50 GPa. A tetragonal structure was compatible with the measurements at all pressures, and no phase change was observed. The bulk modulus, B0 = 62.5 GPa, obtained has a somewhat smaller value than the one estimated earlier.
|
|
| 1136. |
- Stegmayr, B., et al.
(författare)
-
Septic shock induced by group A streptococcal infection : clinical and therapeutic aspects
- 1992
-
Ingår i: Scand J Infect Dis. ; 24:5, s. 589-97
-
Tidskriftsartikel (refereegranskat)abstract
- During 1988 and 1989 > 500 cases of serious group A streptococcal infections were reported in Sweden, many with a fatal outcome. We report here on 11 consecutive patients with septic preshock/shock and multiorgan failure, including acute renal failure. 10 had verified group A streptococci (GAS) serotype T1M1 infections while 1 patient was culture negative but with clinical signs of severe infection and serological evidence of GAS infection. Presenting symptoms were high fever, relative bradycardia, edema and renal failure. In all patients the condition deteriorated despite conventional treatment including volume substitution and antibiotics. Systolic blood pressure was transiently < 80 mmHg in 10 patients and 9 of them needed infusion of inotropic agents to avoid fatal circulatory shock. In 9 patients respiratory aid was instituted and 7 were dialysed. Plasma exchange was performed in 7, while the remaining 4 received transfusions with blood and plasma without plasma exchange. 10 patients improved and were discharged within 8 weeks. One woman died within 2 days after admission to the hospital. Renal function recovered in all survivors, with a follow-up serum creatinine < 80 mumol/l. The complicated clinical picture in these patients with many simultaneous therapeutic events confounds the interpretation of the effect of single actions. The favourable outcome in these severely ill patients suggests that potent inotropic agents, immunoglobulin therapy and plasma exchange might be beneficial in severe streptococcal disease when conventional treatment fails.
|
|
| 1137. |
- Stenberg, Berndt, 1948-
(författare)
-
Office illness : the worker, the work and the workplace
- 1994
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The work started with the clinical observations in patients working in buildings with indoor air problems. Signs of seborrhoeic dermatitis, erythematous facial skin conditions and itching conditions on the trunk were noted. Another point of departure was the attribution of facial skin symptoms to VDT work by patients. A questionnaire-based prevalence study of symptoms compatible with the Sick Building Syndrome (SBS) and facial skin symptoms in 4,943 office workers formed the basis for two case referent studies, one focusing on SBS, the other on facial skin symptoms in VDT workers.The prevalence of SBS was three times higher in women than men. The prevalence was higher in young persons and in atopies. Facial skin symptoms showed the same pattern. Psychosocial work load, paper and VDT work were also risk indicators for SBS and for skin symptoms. The symptom excess in women was analyzed with reference to differences in biological or acquired risks and different illness and reporting behaviour. In spite of inequalities in social conditions at home and at work and differences in physical working conditions, these differences could only explain a small part of the gender difference. The odds ratio for SBS in women was lowered from 3.4 in the crude analysis to 3.0 in the multivariate analysis. Effect modification was in most cases stronger in men and the clinical validation of the questionnaire refuted the hypothesis that women over-report symptoms. The results indicate that the gender difference in symptom prevalence is part of a general pattem common to psychosomatic illnesses.In the case referent study of SBS, atopy, psychosocial work load, buildings built or renovated after 1977, the presence of photocopiers and a low outdoor air flow rate were risk indicators. The association between air quality and the occurrence of SBS symptoms was demonstrated by a flow-response relation between the outdoor air flow rate and SBS symptoms. In the case referent study of skin symptoms in VDT work, psychosocial work load, electric background fields, the presence of fluorescent lights with plastic shields and low cleaning frequency were risk indicators. The clinical findings in the two case groups and their referents supported the applied relevance of the studies. Compared with the referents, the SBS cases had more work- related facial erythema, seborriioeic dermatitis and general pruritus, while skin symptom cases, had more work-related facial erythema than their referents.The results show that SBS symptoms and facial skin symptoms have a multifactorial background with constitutional, psychosocial and physical risk indicators. As the indoor air quality is a determinant of SBS symptoms, and the building itself is but one source of indoor air pollution, it is suggested that the name Sick Building Syndrome (SBS) be replaced by Indoor Air Syndrome (IAS).
|
|
| 1138. |
|
|
| 1139. |
|
|
| 1140. |
- Stevens, James R., et al.
(författare)
-
A comparison of acetone and poly(propylene glycol) as solvents for lithium triflate and lithium perchlorate
- 1991
-
Ingår i: Canadian journal of chemistry (Print). - : Canadian Science Publishing. - 0008-4042 .- 1480-3291. ; 69:12, s. 1980-1984
-
Tidskriftsartikel (refereegranskat)abstract
- Solutions of LiCF3SO3 and LiClO4 in acetone and in poly(propylene glycol) (PPG 400 and PPG 4000) have been compared by studying the nondegenerate, symmetric stretch (A1,SO3) and (A1,ClO4) Raman modes. The Raman spectra contain bands due to the symmetric stretching motion of the "free" anion and due to the symmetric stretching motion of anions in ion aggregates. It is concluded that "free" ions, ion pairs, triplets, and aggregates are present. Although PPG has a much lower dielectric constant, it is a better solvent for these salts than the dipolar aprotic acetone. These findings have ramifications on the current controversy of whether "free" ions are present at all in polyether–salt complexes such as PPG 4000/LiCF3SO3.
|
|
