Cellular automaton model of precipitation/dissolution coupled with solute transport

Precipitation/dissolution reactions coupled with solute transport are modelled as a cellular automaton in which solute molecules perform a random walk on a regular lattice and react according to a local probabilistic rule. Stationary solid particles dissolve with a certain probability and, provided solid is already present or the solution is saturated, solute particles have a probability to precipitate. In our simulation of the dissolution of a solid block inside uniformly flowing water we obtain solid precipitation downstream from the original solid edge, in contrast to the standard reaction-transport equations. The observed effect is the result of fluctuations in solute density and diminishes when we average over a larger ensemble. The additional precipitation of solid is accompanied by a substantial reduction in the relatively small solute concentration. The model is appropriate for the study of the r\^ole of intrinsic fluctuations in the presence of reaction thresholds and can be employed to investigate porosity changes associated with the carbonation of cement.Comment: LaTeX file, 13 pages. To appear in Journal of Statistical Physics (Proceedings of Lattice Gas'94, June 1994, Princeton). Figures available from author. Requests may be submitted by E-mail ([email protected]) or ordinary mail (Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland

Quasi-classical Lie algebras and their contractions

After classifying indecomposable quasi-classical Lie algebras in low dimension, and showing the existence of non-reductive stable quasi-classical Lie algebras, we focus on the problem of obtaining sufficient conditions for a quasi-classical Lie algebras to be the contraction of another quasi-classical algebra. It is illustrated how this allows to recover the Yang-Mills equations of a contraction by a limiting process, and how the contractions of an algebra may generate a parameterized families of Lagrangians for pairwise non-isomorphic Lie algebras.Comment: 17 pages, 2 Table

Expanding Lie (super)algebras through abelian semigroups

We propose an outgrowth of the expansion method introduced by de Azcarraga et al. [Nucl. Phys. B 662 (2003) 185]. The basic idea consists in considering the direct product between an abelian semigroup S and a Lie algebra g. General conditions under which relevant subalgebras can systematically be extracted from S \times g are given. We show how, for a particular choice of semigroup S, the known cases of expanded algebras can be reobtained, while new ones arise from different choices. Concrete examples, including the M algebra and a D'Auria-Fre-like Superalgebra, are considered. Finally, we find explicit, non-trace invariant tensors for these S-expanded algebras, which are essential ingredients in, e.g., the formulation of Supergravity theories in arbitrary space-time dimensions.Comment: 42 pages, 8 figures. v2: Improved figures, updated notation and terminolog

Non-solvable contractions of semisimple Lie algebras in low dimension

The problem of non-solvable contractions of Lie algebras is analyzed. By means of a stability theorem, the problem is shown to be deeply related to the embeddings among semisimple Lie algebras and the resulting branching rules for representations. With this procedure, we determine all deformations of indecomposable Lie algebras having a nontrivial Levi decomposition onto semisimple Lie algebras of dimension $n\leq 8$, and obtain the non-solvable contractions of the latter class of algebras.Comment: 21 pages. 2 Tables, 2 figure

Extent of hypoattenuation on CT angiography source images in Basilar Artery occlusion: prognostic value in the Basilar Artery International Cooperation Study

<p><b>Background and Purpose:</b> The posterior circulation Acute Stroke Prognosis Early CT Score (pc-ASPECTS) quantifies the extent of early ischemic changes in the posterior circulation with a 10-point grading system. We hypothesized that pc-ASPECTS applied to CT angiography source images predicts functional outcome of patients in the Basilar Artery International Cooperation Study (BASICS).</p> <p><b>Methods:</b> BASICS was a prospective, observational registry of consecutive patients with acute symptomatic basilar artery occlusion. Functional outcome was assessed at 1 month. We applied pc-ASPECTS to CT angiography source images of patients with CT angiography for confirmation of basilar artery occlusion. We calculated unadjusted and adjusted risk ratios (RRs) of pc-ASPECTS dichotomized at ≥8 versus <8. Primary outcome measure was favorable outcome (modified Rankin Scale scores 0–3). Secondary outcome measures were mortality and functional independence (modified Rankin Scale scores 0–2).</p> <p><b>Results:</b> Of 158 patients included, 78 patients had a CT angiography source images pc-ASPECTS ≥8. Patients with a pc-ASPECTS ≥8 more often had a favorable outcome than patients with a pc-ASPECTS <8 (crude RR, 1.7; 95% CI, 0.98–3.0). After adjustment for age, baseline National Institutes of Health Stroke Scale score, and thrombolysis, pc-ASPECTS ≥8 was not related to favorable outcome (RR, 1.3; 95% CI, 0.8–2.2), but it was related to reduced mortality (RR, 0.7; 95% CI, 0.5–0.98) and functional independence (RR, 2.0; 95% CI, 1.1–3.8). In post hoc analysis, pc-ASPECTS dichotomized at ≥6 versus <6 predicted a favorable outcome (adjusted RR, 3.1; 95% CI, 1.2–7.5).</p> <p><b>Conclusions:</b> pc-ASPECTS on CT angiography source images independently predicted death and functional independence at 1 month in the CT angiography subgroup of patients in the BASICS registry.</p&gt

Trivalent influenza vaccine in patients on haemodialysis: impaired seroresponse with differences for A-H3N2 and A-H1N1 vaccine components

One hundred and one patients on haemodialysis, 21 patients on peritoneal dialysis and 30 healthy controls received a trivalent split vaccine containing 15 micrograms haemagglutinin of a recent influenza A-H3N2, influenza A-H1N1 and influenza B strain, respectively. Antibody production after four weeks was determined by the haemagglutination-inhibition test and expressed as response rate, protection rate and overall mean fold increase. The patients on haemodialysis revealed a diminished seroresponse, as compared to patients on peritoneal dialysis and controls. For influenza A-H3N2, this was less distinct than for the other two antigens. In patients on haemodialysis the protection rate was 66% against the A-H3N2 vaccine component (versus 85% in controls, not significant), but only 25% against A-H1N1 and 27% against B (versus 84 and 77% in controls, p less than 0.001). Duration of haemodialysis up to eight years did not affect seroresponse. Patients on haemodialysis who were primed for influenza A-H1N1 in the period 1947-1957, reacted markedly better to the A-H1N1 vaccine component than subjects of other priming periods. A booster injection of the same vaccine dosage four weeks after the first immunization, performed in 98 patients on haemodialysis, was of little value: it had virtually no effect with regard to influenza A-H1N1 and influenza B, and showed, though significantly better, still poor results for A-H3N2. The differences in seroresponse between the A-H3N2 and A-H1N1 vaccine component suggest a major defect of primary, and a minor defect of secondary humoral response in patients on haemodialysis. The consequences for vaccine policy in these patients are discussed

Galilei invariant theories. I. Constructions of indecomposable finite-dimensional representations of the homogeneous Galilei group: directly and via contractions

All indecomposable finite-dimensional representations of the homogeneous Galilei group which when restricted to the rotation subgroup are decomposed to spin 0, 1/2 and 1 representations are constructed and classified. These representations are also obtained via contractions of the corresponding representations of the Lorentz group. Finally the obtained representations are used to derive a general Pauli anomalous interaction term and Darwin and spin-orbit couplings of a Galilean particle interacting with an external electric field.Comment: 23 pages, 2 table

De Behoefte aan Psychosociale Steun bij Deelnemers aan het Nederlandse Cross-over Transplantatie Programma

Final technical report of the project.The Dutch kidney exchange donation program started in January 2004. A literature review has shown that several factors of the exchange program could influence the psychological well being of participants, such as the loss of the possibility of a “medical excuse” for unwilling donors and the issue of anonymity. However, these factors have not been the subject of empirical study yet. We therefore studied these factors to determine whether additional psychosocial support is necessary for donors and recipients in the Dutch kidney exchange program. We used structured interviews for all 48 donors and recipients that had undergone exchange donation/ transplantation in 2004. A psychologist interviewed the participants before and 3 months after transplantation. We included a comparison group of 48 donors and recipients participating in the regular living kidney donation program. Donors did not experience additional pressure to donate due to the exchange donation. Most participants preferred anonymity between the couples. We found few needs for additional emotional support. In this respect the exchange group did not differ from the comparison group. We conclude that the psychosocial support offered to exchange couples can be comparable to the support normally offered to participants in the regular living kidney donation program

Living Kidney Donation: Psychological and Ethical Aspects

DOELSTELLING Nierdonatie bij leven levert medisch en maatschappelijk gezien veel voordelen op, maar toch willen of kunnen niet alle nierpatiënten op de wachtlijst en/of hun naasten zich opgeven voor het nierdonatie bij leven programma. De doelstelling van het project ‘Nierdonatie bij leven: psychologische en ethische aspecten’ is het verkrijgen van meer inzicht in de kennis en acceptatie van nierdonatie bij leven. Het gaat hierbij om kennis en acceptatie onder proefpersonen die daadwerkelijk in aanmerking komen voor nierdonatie/ transplantatie bij leven, dat wil zeggen (1) patiënten met eindfase nierfalen op de wachtlijst voor een niertransplantatie en (2) de mensen uit hun omgeving; de potentiële donoren. Het benaderen van deze groepen is de strategie om uit te vinden of, en onder welke voorwaarden, uitbreiding van het nierdonatie bij leven programma praktisch haalbaar en ethisch verdedigbaar is. VRAAGSTELLINGEN Het project omvat twee vraagstellingen. De eerste vraagstelling is: wat zijn de psychologische barrières voor nierdonatie bij leven voor patiënten op de wachtlijst, en de mensen uit hun omgeving? De tweede vraagstelling luidt: wat zijn de morele argumenten om de patiënt en de mensen uit de omgeving van de patiënt (de potentiële donoren) al dan niet actief te benaderen over nierdonatie bij leven? In andere woorden; in hoeverre zijn interventies ethisch verdedigbaar? OPZET PATIËNTEN EN (POTENTIËLE) DONOREN Wij hebben allereerst de groep patiënten die op de wachtlijst voor niertransplantatie staat benaderd (regio Erasmus MC). Aan de patiënt vragen wij toestemming om ook de potentiële donoren uit zijn of haar omgeving te benaderen. Indien beiden hiermee instemmen, vindt het interview met deze potentiële donor plaats. Voor deze studie hebben we tevens een controlegroep benaderd. In de controlegroep zitten patiënten en donoren die nog geen familietransplantatie hebben ondergaan, maar die wel al hebben besloten door te gaan met de donatie bij leven procedure en dit met hun artsen hebben overlegd. INTERVIEW Alle deelnemers aan ons onderzoek zijn geïnterviewd middels een semi-gestructureerd interview. Voorafgaand onderzoek heeft aangetoond dat een aantal factoren een rol kan spelen bij het niet kunnen of willen ondergaan van nierdonatie bij leven. Deze factoren komen terug in de interviews: · Demografische en medische variabelen · Kennis en informatie · Standpunten en argumenten ten aanzien van nierdonatie bij leven, · Communicatie met de arts en de omgeving · Risicoperceptie · Verwachtingen ten aanzien van de gevolgen voor de persoonlijke relatie tussen donor en ontvanger. ETHISCHE ANALYSE De resultaten van de empirische gedeelte van deze studie dienen als basis voor de ethische analyse. Argumenten zoals gevonden in het empirische gedeelte van de studie worden getoetst op houdbaarheid met behulp van ethische theorieën over de structuur van argumenten.,Wij hebben met name gebruik gemaakt van de theorien zoals die geformuleerd zijn door Toulmin, Rawls en Nagel. BEREIKTE RESULTATEN/NIEUWE INZICHTEN De bereidheid om een nier van iemand in de naaste omgeving te accepteren is zeer hoog voor de patiënten in de onderzoeksgroep: slecht 19% is negatief over donatie bij leven. Het is dus niet zo dat de patiënt in het algemeen niet zou willen. Voor een aantal variabelen vonden we verschillen tussen de onderzoeksgroep en de controlegroep. Een opvallende uitkomst is dat in vrijwel àlle gevallen in de controle groep de communicatie over de donatie gestart wordt vanuit de donor: het al dan niet aangeboden krijgen van een nier lijkt bepalend voor het doorgaan van de (levende donor) transplantatie. Patiënten vinden het erg moeilijk om uit zichzelf over het onderwerp te beginnen. Ethische analyse laat zien dat de argumenten en bezwaren tegen nierdonatie bij leven zoals gevonden in de onderzoeksgroep weerlegbaar zijn. Dit gegeven draagt bij aan de rechtvaardiging van interventies in de situatie van paPURPOSE Living kidney donation offers many advantages, both from a medical and societal point of view. However, there is a group of patients that cannot or will not make use of the living kidney donation program. The purpose of the study ‘Living Kidney donation: psychological and ethical aspects’ is to gain insight into the knowledge and acceptance of this form of kidney transplantation. The group we investigate is the group that actually is eligible for living kidney donation / transplantation, namely (1) patients with end stage renal disease on the transplantation waiting list and (2) the persons in their close environment, the potential donors. Investigating these groups is the strategy to find out if, and under what circumstances, expansion of the living kidney donation program is feasible and ethically acceptable. RESEARCH QUESTIONS The project comprises two research questions. The first research question is: what are the psychological barriers for living kidney donation for the patients and the people in their close environment? The second research question is: what are the moral arguments to deal or actively or passively with the persons in the close environment of the patients who are the potential donors? In other words, to what extent are interventions morally acceptable? DESIGN PATIENTS We have approached the group of patients on the waiting list for a kidney transplant (region of the Erasmus University Medical Center). We asked the patients for permission to approach individuals in their personal environment, the potential donors. If both (patient and relative of patient) agreed on this, we interviewed these potential donors as well. We also included a control group in our study. This group consists of patients and their actual donors who have planned to undergo living kidney donation/transplantation in the near future and had already made arrangements together with their clinicians. INTERVIEW All participants in our study were interviewed by means of a semi-structured interview. Former research has shown various variables that influence willingness to undergo living kidney donation / transplantation. These variables are included in the interview: · Sociodemographic and medical variables · Knowledge and information · Acceptance of, and argument about of living kidney donation · Communication with the specialist and the personal environment · Risk perception · Expectations regarding the personal relationship between patient and donor. ETHICAL ANALYSIS Ethical analysis is based on the results of the empirical part of the study. Reasoning as found in the empirical part of the study is tested for ethical justification, using ethical theory on the structure of argumentation especially the theories as formulated by Toulmin, Rawls and Nagel. BEREIKTE RESULTATEN/NIEUWE INZICHTEN The willingness to accept the offer of a living kidney donor is very high for patients in the group of interest: only 19% has a negative attitude towards ling donation. Thus, it is not a matter of unwillingness of the patients to accept a living kidney donor. We found a number of differences between the group of interest and the control group. A notable finding is that the communication about kidney donation in the control group is almost always initiated by the donor : being offered a kidney (or not) seems to be decisive for either or not pursuing living kidney donation. Patients find it very difficult to bring up the topic them selves. Ethical analysis shows that the arguments or objections against living kidney donation as raised by the group of interest can be refuted. This adds to the moral acceptability of interventions in the situation of patients on the waiting list for transplantation who do not enter the living kidney donation program initially

Control of human endometrial stromal cell motility by PDGF-BB, HB-EGF and trophoblast-secreted factors

Human implantation involves extensive tissue remodeling at the fetal-maternal interface. It is becoming increasingly evident that not only trophoblast, but also decidualizing endometrial stromal cells are inherently motile and invasive, and likely contribute to the highly dynamic processes at the implantation site. The present study was undertaken to further characterize the mechanisms involved in the regulation of endometrial stromal cell motility and to identify trophoblast-derived factors that modulate migration. Among local growth factors known to be present at the time of implantation, heparin-binding epidermal growth factor-like growth factor (HB-EGF) triggered chemotaxis (directed locomotion), whereas platelet-derived growth factor (PDGF)-BB elicited both chemotaxis and chemokinesis (non-directed locomotion) of endometrial stromal cells. Supernatants of the trophoblast cell line AC-1M88 and of first trimester villous explant cultures stimulated chemotaxis but not chemokinesis. Proteome profiling for cytokines and angiogenesis factors revealed neither PDGF-BB nor HB-EGF in conditioned media from trophoblast cells or villous explants, while placental growth factor, vascular endothelial growth factor and PDGF-AA were identified as prominent secretory products. Among these, only PDGF-AA triggered endometrial stromal cell chemotaxis. Neutralization of PDGF-AA in trophoblast conditioned media, however, did not diminish chemoattractant activity, suggesting the presence of additional trophoblast-derived chemotactic factors. Pathway inhibitor studies revealed ERK1/2, PI3 kinase/Akt and p38 signaling as relevant for chemotactic motility, whereas chemokinesis depended primarily on PI3 kinase/Akt activation. Both chemotaxis and chemokinesis were stimulated upon inhibition of Rho-associated, coiled-coil containing protein kinase. The chemotactic response to trophoblast secretions was not blunted by inhibition of isolated signaling cascades, indicating activation of overlapping pathways in trophoblast-endometrial communication. In conclusion, trophoblast signals attract endometrial stromal cells, while PDGF-BB and HB-EGF, although not identified as trophoblast-derived, are local growth factors that may serve to fine-tune directed and non-directed migration at the implantation site