| 261. |
- Sun, J. G.
(författare)
-
Perturbation analysis of generalized singular subspaces
- 1998
-
Ingår i: Numerische Mathematik. ; 79:4, s. 615-641
-
Tidskriftsartikel (refereegranskat)abstract
- This paper, as a continuation of the paper [20] in Numerische Mathematik, studies the subspaces associated with the, generalized singular value decomposition. Second order perturbation expansions, Frechet derivatives and condition numbers, and perturbation bounds for the subspaces are derived.
|
|
| 262. |
- Sun, J. G.
(författare)
-
Perturbation theory for algebraic Riccati equations
- 1998
-
Ingår i: Siam Journal on Matrix Analysis and Applications. ; 19:1, s. 39-65
-
Tidskriftsartikel (refereegranskat)abstract
- New perturbation results for the two different algebraic Riccati equations (continuous time and discrete time) are derived in a uniform manner. The new results are illustrated by numerical examples.
|
|
| 263. |
- Sun, J. G.
(författare)
-
Residual bounds of approximate solutions of the discrete-time algebraic Riccati equation
- 1998
-
Ingår i: Numerische Mathematik. ; 78:3, s. 463-478
-
Tidskriftsartikel (refereegranskat)abstract
- Let (X) over tilde be a Hermitian matrix which approximates the unique Hermitian positive semi-definite solution X to the discrete-time algebraic Riccati equation (DARE) X - (FXF)-X-H + F(H)XG(1)(G(2) + G(1)(H)XG(1))(-1)G(1)(H)XF + (CC)-C-H = 0; where F is an element of C-nxn, C-2 is an element of C-mxm is Hermitian positive definite, G(1) is an element of C-nxm,C is an element of C-rxn, the pair (F, G(1)) is stabilizable, and the pair (C, F) is detectable. Assume that I + G (X) over tilde is nonsingular, and (I + G (X) over tilde)F-1 is stable. Let G = G(1)G(2)(-1)G(1)(H), H = 2 (CC)-C-H, and let (R) over cap = (X) over tilde - F-H (X) over tilde(I + G (X) over tilde)F-1 - H be the residual of the DARE with respect to (X) over tilde. Define the linear operator L by LW = W - F-H(I + (X) over tilde G)W-1(I + G (X) over tilde)F-1, W = W-H is an element of C-nxn. The main result of this paper is: If epsilon = parallel to L-1(R) over cap parallel to less than or equal to l/gamma(2 phi(2) + 2 phi root phi(2) + l + l)' where parallel to parallel to denotes any unitarily invariant norm, and l = parallel to L(-1)parallel to(-1), phi = parallel to(I + G (X) over tilde)F-1 parallel to(2), gamma = parallel to(I + G (X) over tilde)(-1)G parallel to(2), then \\(X) over tilde - X\\ less than or equal to 2l epsilon/(1 + gamma epsilon)l + root(1 + gamma epsilon)(2)l(2) - 4(phi(2) + l)gamma l epsilon(-) less than or equal to 2\\L-1(R) over cap\\/1 + gamma\\L-1(R) over cap R\\(.)
|
|
| 264. |
- Sundbom, Elisabet, et al.
(författare)
-
Personality and defenses : a cross-cultural study of psychiatric patients and healthy individuals in Nicaragua and Sweden.
- 1998
-
Ingår i: Psychological Reports. - 0033-2941 .- 1558-691X. ; 83:3 Pt 2, s. 1331-47
-
Tidskriftsartikel (refereegranskat)abstract
- This study examined cross-cultural variability in personality and defenses among Nicaraguan and Swedish healthy individuals, patients with borderline personality disorder and schizophrenic disorders by means of the projective perceptual Defense Mechanism Test. The over-all aim was to test the hypothesis proposed by Anthony Marsella of 'severity related cross-cultural variability' suggesting that differences in symptom profile or personality patterns between cultures are most pronounced among healthy individuals and less so among individuals with severe mental disorders as they are perceived as more universal and less culturally determined. The over-all results showed that cross-cultural differences were in accordance with the proposed hypothesis. In addition, there were significant intracultural differences between the different diagnostic groups in both countries. The conclusion is that the Defense Mechanism Test and Partial Least Squares analysis seem to be powerful methods for personality assessment and potentially for cross-cultural research, and culture-specific norms in the Defense Mechanism Test must be employed.
|
|
| 265. |
- Sundqvist, Bertil
(författare)
-
Comment on "Pressure and temperature diagram of polymerized fullerite"
- 1998
-
Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 57:5, s. 3164-3165
-
Tidskriftsartikel (refereegranskat)abstract
- Fullerenes such as C60 can be polymerized by treatment under high-pressure, high-temperature conditions. I point out that there is a strong correlation between the rotational state of the C60 molecules in the initial (pristine) material and the structure of the resulting polymer.
|
|
| 266. |
- Sundqvist, Bertil
(författare)
-
Improving thermal insulation in high pressure experiments
- 1998
-
Ingår i: Review of Scientific Instruments. - : American Institute of Physics. - 0034-6748 .- 1089-7623. ; 69:9, s. 3433-3434
-
Tidskriftsartikel (refereegranskat)abstract
- The use of internal ovens is common in high-temperature–high-pressure experiments. Improving the thermal insulation means better efficiency and lower thermal strain on pressure vessels and feedthroughs, but is difficult when using solid media. The addition of a layer of amorphous solid (glass) in the form of a mixed powder is reported to give a significant reduction (20%–50%) in the power dissipated in a high pressure oven.
|
|
| 267. |
- Tao, D L, et al.
(författare)
-
Active oxygen scavengers during cold acclimation of Scots pine seedlings in relation to freezing tolerance
- 1998
-
Ingår i: Cryobiology. - 0011-2240 .- 1090-2392. ; 37:1, s. 38-45
-
Tidskriftsartikel (refereegranskat)abstract
- Freezing injury of plants may be caused by the deleterious reactions of active oxygen species, and free-radical scavenging systems may be important in the alleviation of freezing stress. To test the feasibility of this hypothesis, enzymes and metabolites that cooperatively scavenge O-2(-) and H2O2 were analyzed in Scots pine (Pinus sylvestris L.) seedlings during a stepwise cold acclimation procedure. Elevated levels of enzymatic scavengers such as ascorbate peroxidase, glutathione reductase, monodehydroascorbate reductase, and dehy droascorbate reductase were found, along with increased freezing tolerance during cold acclimation, supporting the hypothesis. Induction of the scavenging systems during acclimation is discussed in relation to freezing tolerance. (C) 1998 Academic Press.
|
|
| 268. |
- Thøgersen, AM, et al.
(författare)
-
High plasminogen activator inhibitor and tissue plasminogen activator levels in plasma precede a first acute myocardial infarction in both men and women. : Evidence for the fibrinolytic system as an independent primary risk factor
- 1998
-
Ingår i: Circulation. - 0009-7322 .- 1524-4539. ; 98:21, s. 2241-2247
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: In patients with established ischemic heart disease, prospective cohort studies have indicated that plasminogen activator inhibitor (PAI-1), the inhibitor of the fibrinolytic system, may predict cardiovascular events. So far, there have been no primary prospective studies of PAI-1. METHODS AND RESULTS: The aim of the present study was to test whether plasma levels of PAI-1, tissue-type plasminogen activator (tPA), von Willebrand factor (vWF), and thrombomodulin (TM) could predict the occurrence of a first acute myocardial infarction (AMI) in a population with high prevalence of coronary heart disease by use of a prospective nested case-control design. Mass concentrations of PAI-1 and tPA were significantly higher for the 78 subjects who developed a first AMI compared with the 156 references matched for age, sex, and sampling time; for tPA, this increase was independent of smoking habits, body mass index, hypertension, diabetes, cholesterol, and apolipoprotein A-I. The ratio of quartile 4 to 1 for tPA was 5.9 for a patient to develop a first AMI. The association between tPA and AMI was seen in both men and women. Increased levels of vWF were associated with AMI in a univariate analysis. High levels of TM were associated with AMI in women but not in men. CONCLUSIONS: The plasma levels of PAI-1, tPA, and vWF are associated with subsequent development of a first AMI; for PAI-1 and tPA, this relation was found in both men and women. For tPA but not for PAI-1 and vWF, this association is independent of established risk factors.
|
|
| 269. |
- Trogen, G B, et al.
(författare)
-
The solution NMR structure of a blue-green algae hepatotoxin, microcystin-RR--a comparison with the structure of microcystin-LR.
- 1998
-
Ingår i: European Journal of Biochemistry. - 0014-2956 .- 1432-1033. ; 258:2, s. 301-12
-
Tidskriftsartikel (refereegranskat)abstract
- The microcystin-RR structures are compared with the structures of microcystin-LR in solution as well as in the crystal structure of the complex with protein phosphatase. The gross structures of the two peptides are similar, but with a more accentuated and compact saddle structure for microcystin-RR. The structural differences affect the hydrogen-bond pattern in the peptides and the location of the side chain of N-methyldehydroalanine, both of which are important for the ability of the peptide to form a tight complex with protein phosphatase. These structural differences may contribute to the observed differences in toxicity of microcystin-RR and microcystin-LR.
|
|
| 270. |
- Van Landeghem, G F, et al.
(författare)
-
Transferrin C2, metal binding and Alzheimer's disease.
- 1998
-
Ingår i: NeuroReport. - 0959-4965 .- 1473-558X. ; 9:2, s. 177-9
-
Tidskriftsartikel (refereegranskat)abstract
- Significant associations between the transferrin (TF) variant C2 and a number of disorders suspected to be caused by oxygen free radicals have been reported. Thus an increased frequency of the TFC2 variant has been found in patients with Alzheimer's disease (AD), and it has been hypothesized that AD is caused by free radical damage due to defective binding of iron and aluminium by TFC2. In a study of 64 patients with AD from northern Sweden we were able to confirm the association between TFC2 and AD, but there were no significant differences between TFC2 and other TF variants with respect to the binding of iron and aluminium.
|
|
