The boundary element approach to Van der Waals interactions

We develop a boundary element method to calculate Van der Waals interactions for systems composed of domains of spatially constant dielectric response. We achieve this by rewriting the interaction energy expression exclusively in terms of surface integrals of surface operators. We validate this approach in the Lifshitz case and give numerical results for the interaction of two spheres as well as the van der Waals self-interaction of a uniaxial ellipsoid. Our method is simple to implement and is particularly suitable for a full, non-perturbative numerical evaluation of non-retarded van der Waals interactions between objects of a completely general shape.Comment: 4 pages, 4 figures, RevTe

Agentschappen: kruiwagen voor modernisering?

Het agentschapsmodel werd begin jaren negentig geïntroduceerd in Nederland. De populariteit lijkt groot; het aantal agentschappen neemt hand over hand toe. Veron-dersteld wordt dat agentschappen doelmatiger zijn in het uitvoeren van publieke ta-ken dan de overheidsbureaucratie, en dat ze bijdragen aan de modernisering van de overheid. Evaluaties bevestigen dit deels maar er is ook kritiek, zowel op agent-schappen als op de ministeries die hen moeten aansturen. Dat heeft geleid tot aan-passing van de instellingsprocedure

Closed-form analytical expressions for the potential fields generated by triangular monolayers with linearly distributed source strength

The solution of the mixed boundary value problem of potential theory involves the computation of the potential field generated by monolayer and double layer source distributions on surfaces at which boundary conditions are known. Closed-form analytical expressions have been described in the literature for the potential field generated by double layers having a linearly distributed strength over triangular source elements. This contribution presents the corresponding expression for the linearly distributed monolayer strength. The solution is shown to be valid for all observation points in space, including those on the interior, edges and vertices of the source triangle

EORTC (30885) randomised phase III study with recombinant interferon alpha and recombinant interferon alpha and gamma in patients with advanced renal cell carcinoma. The EORTC Genitourinary Group.

In the treatment of renal cell carcinoma both complete (CRs) and partial remissions (PRs) have been obtained using recombinant (r) interferon alpha (IFN-alpha), with response rates ranging from 0 to 31% (mean 16%). rIFN-gamma is a potent immunostimulating agent, but the clinical experience of its use is limited and results are conflicting. In a phase II study with the combination of rIFN-alpha 2c (Boehringer Ingelheim) and rIFN-gamma (Genentech, supplied by Boehringer Ingelheim) in 31 eligible patients, a response rate of 25% was recorded. Based on this observation a randomised phase III study was initiated to investigate the possible advantage of the addition rIFN-gamma to rIFN-alpha 2c treatment. Treatment consisted of rIFN-alpha 2c 30 micrograms m-2 = 10 x 10(6) IU m-2 s.c. twice weekly in arm A and the same dose of rIFN-alpha combined with rIFN-gamma 100 micrograms m-2 = 2 x 10(6) IU m-2 in arm B. Eligibility criteria included documented progression of disease; patients with bone lesions only and overt central nervous system metastases were excluded. Between November 1988 and September 1990, 102 patients were entered into the study. An interim analysis showed a response in 7/53 (13%) patients (two CRs and five PRs) in the rIFN-alpha 2c monotherapy arm and in 2/45 (4%) (one CR and one PR) patients in the combination arm. This difference was not statistically significant (P = 0.17). The probability of missing an eventual 10% advantage for the combination is 0.001. The numbers are insufficient to rule out a negative effect of the addition of rIFN-gamma. The dose intensity of IFN-alpha 2c for the two treatment arms was the same. The addition of rIFN-gamma does not improve the response rate of rIFN-alpha 2c monotherapy. A possible detrimental effect cannot be excluded

Atrial repolarization as observable in the PQ interval

Objective: To study the involvement of atrial repolarization in body surface potentials. Methods: Electrocardiograms of healthy subjects were recorded using a 64-lead system. The data analysis focused on the PQ intervals, while devoting special attention to the low-amplitude signals during the PQ segment: the segment from the end of the P wave till onset QRS. The data were analyzed by inspecting body surface potential maps and the XYZ signals of the vector cardiogram. Results: Standard P wave features exhibited normal values. The local potential extremes were found at positions not sampled by the standard leads. The PQ segment was found to be not iso-electric, the potential distribution being very similar to that at the timing of apex P but for a reversed polarity and a 3-fold lower magnitude. Conclusion: The results demonstrate a significant involvement of atrial repolarization during the PQ interval, with essentially non-concomitant atrial T waves

Diallel Analysis of the Stay-Green Trait and Its Components in Sorghum

Stay-green in sorghum [Sorghum bicolor (L.) Moench] is an important component of post-flowering drought tolerance. This research was conducted to describe (i) stay-green as post-flowering green leaf area duration (GLAD) and its components [green leaf area (GLA) flowering, timing for onset of senescence, and senescence rate] and (ii) the expression of heterosis for stay-green in terms of heterosis for its components. The study was conducted during the 1992 to 1993 and 1993 to 1994 post-rainy season at ICRISAT headquarters near Hyderabad, India. It involved a nine-parent complete diallel, in two experiments differing in soil-water availability after flowering. Weekly estimations of % GLA were made on 36 leaves per plot. Relative (%days) and absolute (m2 days) GLAD and their components were derived from a fitted logistic function. The variances in both relative and absolute GLAD were each fully (R2 > 0.96) accounted for by their components. In spite of significant genotype × environment interactions for the component traits, the expression of heterosis for non-senescence as related to the stay-green trait was stable across experiments. The inheritance of the onset of senescence was additive, but a slow senescence rate was dominant over a fast rate. Consequently, a large relative GLAD (slow senescence) was partially dominant over a small relative GLAD. Because of the dominance of a large leaf area at flowering, the partial dominance in relative GLAD translated into overdominance for a large absolute GLAD. These results offer an opportunity for improving drought tolerance of sorghum in environments with post-flowering drought stress