Two thousand‐sixteen basal cell carcinomas (BCCs) were documented in terms of age, anatomic location, tumor diameter, initial excision depth, safety margin, histologic type, and the position of tumor outgrowths as determined by three‐dimensional histologic study of the tumor margins in paraffin sections (micrographic surgery). The extent of each subsequent excision was recorded until tumor‐free tissue was reached. The results showed that BCCs have a highly irregular infiltration pattern and a predilection for small, fingerlike outgrowths whose bases occupy 1–30 degrees of the tumor circumference. When superficial extension was expressed mathematically, the resulting exponential functions varied highly significantly (P = .001) according to histologic tumor type and diameter. The resulting curves permitted very precise prediction of the probability of tumor‐positive margins (ie, subtotal excision), depending on the safety margin, histologic tumor type, and tumor diameter. For example, the probability of tumor‐positive margins after excision of a BCC up to 10 mm in diameter is 30% with a safety margin of 2 mm, 16% with a safety margin of 3 mm, and 5% with a safety margin of 5 mm. The probability of tumor‐positive margins for fibrosing primary BCCs 10–20 mm in diameter is 48, 34, and 18% with safety margins of 2, 3, and 5 mm, respectively. Recurrent tumors have a significantly higher probability of positive margins (P = .001) than primary ones. Anatomic location and tumor age affect subclinical extension only indirectly.
As ivermectin is supposed to have a paralyzing effect, the emergence of Onchocerca volvulus microfilariae from skin snips before and after treatment was examined. Before treatment 79.8% of the microfilariae emerged from the skin snips. Three days after treatment the microfilarial skin density had dropped to 83% (placebo), 28% (100 microgram/kg ivermectin), 19% (150 micrograms/kg) and 14% (200 micrograms/kg) of the pretreatment values but the microfilarial emergence was not altered distinctly. The majority of the remaining microfilariae were mobile and able to leave the biopsy. Only a slight, but significant, dose-dependent trend of reduced emergence could be shown. From our results no direct support is derived for the hypothesis that O. volvulus microfilariae are paralyzed or immobilized by ivermectin.
Diekmann et al. (1991) developed a model for calculating Ro for a multi-state disease including pair formation and dissolution.This model is analogous to a model of Blythe and Anderson (1988) and Jacquez et al. (1988) which did not include pair formation.The model in Diekmann et al. (1991) is a generalization of the model of Diekmann et al. (1990).In the sequel to Diekmann et al. (1991), Dietz et al. (1993) investigated the effects of variable HIV-infectivity.This paper will summarize the model and results of Dietz et al. (1993) and will present further results obtained with the same model.We assume four stages of HIV-infection, three pre-AIDS, and the final stage, AIDS.The parameters incorporated in the model are: 0,
The quantum theory of a finite quantum system with L degrees of freedom is usually set up by associating it with a Hilbert space of dimension d(L) and identifying observables and states in the matrix algebra . For the case d = 2m, m integer, this algebra can be identified with the Clifford algebra . The case of d = 2m dimensions is simply realized by a system with m dichotomic degrees of freedom, an m-qubit system for instance. The physically relevant new point is the appearance of a new (symmetry-?)group SO(2m). A possible interpretation of the space in which this group operates is proposed. It is shown that the eigenvalues of m-qubit-type states only depend on SO(2m)-invariants. We use this fact to determine state parameter domains (generalized Bloch spheres) for states classified as SO(2m)-tensors. The classification of states and interactions of components of a physical m-qubit system as k-tensors and pseudotensors (0 ⩽ k ⩽ m) leads to rules similar to those found in elementary quantum mechanics. The question of electromagnetic interactions is shortly broached. We sketch, pars pro toto, a graphical interpretation of tensor contractions appearing in perturbative expansions.
Nowadays, chloroquine-resistant malaria appears in almost all endemic regions. Ferroquine is a derivative of chloroquine and shows good activity in vitro and in animal models, but the development of cross-resistance is of concern. We tested in vitro susceptibilities of Plasmodium falciparum field isolates from Gabon to ferroquine, chloroquine, and artesunate. As expected, chloroquine resistance was present in all parasite isolates (median 50% inhibitory concentration = 113 nmol/L). Ferroquine (1.94 nmol/L) and artesunate (0.96 nmol/L) were highly active, and no significant correlation between any of the three drugs was observed. In contrast to our findings, previous studies showed an association between chloroquine and ferroquine activities. We could reproduce this association by using different initial parasitemias, but analysis of covariance revealed that initial parasitemia and not parasite strain was the critical determinant for the correlation between chloroquine and ferroquine activities. We conclude that ferroquine is highly active in chloroquine-resistant parasites, and we anticipate no enhanced selection for resistance against ferroquine in chloroquine-resistant parasites.
We propose a stochastic model for the relationship between the entomologic inoculation rate (EIR) for Plasmodium falciparum malaria and the force of infection in endemic areas. The model incorporates effects of increased exposure to mosquito bites as a result of the growth in body surface area with the age of the host, naturally acquired pre-erythrocytic immunity, and the reduction in the proportion of entomologically assessed inoculations leading to infection, as the EIR increases. It is fitted to multiple datasets from field studies of the relationship between malaria infection and the EIR. We propose that this model can account for non-monotonic relationships between the age of the host and the parasite prevalence and incidence of disease. It provides a parsimonious explanation for the faster acquisition of natural immunity in adults than in children exposed to high EIRs. This forms one component of a new stochastic model for the entire transmission cycle of P. falciparum that we have derived to estimate the potential epidemiologic impact of malaria vaccines and other malaria control interventions.
The aim of the study was to assess the influence of carbogen (95% O(2), 5% CO(2)) or pure oxygen breathing on renal oxygenation measured by blood oxygenation level dependent (BOLD) magnetic resonance imaging at 3.0 T. Seven healthy young volunteers (median age 25, range 23-35 years) participated in the study. A T2*-weighted fat-saturated spoiled gradient-echo sequence was implemented on a 3.0 T whole-body imager (TE/TR = 27.9 ms/49 ms, excitation angle 20 degrees ) with an acquisition time of approximately 5.3 s. A total of 100 images were acquired during 22 min. A block design was applied for gas administration: 4 min room air, 4 min carbogen/oxygen, 4 min room air, 4 min carbogen/oxygen and 6 min room air. A compartment model was fitted to the data sets accounting for time-dependent increase/decrease of renal oxygenation as well as baseline changes of the scanner. T2*-weighted images showed good image quality without notable artefacts or distortions. Mean relative signal increase due to carbogen breathing was 2.73% (95% confidence interval: 1.34-5.54) in the right kidney and 3.76% (1.53-9.20) in the left kidney, while oxygen breathing led to a signal enhancement of 3.20% (2.57-3.98) in the right kidney and 3.16% (1.83-5.45) in the left kidney. No statistical difference was found between carbogen and oxygen breathing or between the oxygenation of the right and the left kidney. A significant difference was found in the characteristic time constant for the signal increase with a faster saturation taking place for oxygen breathing. Renal tissue oxygenation is clearly influenced by carbogen or oxygen breathing. The changes can be assessed by T2*-weighted MRI at high field strengths. The effects are in the expected range for the BOLD effect of 3-4% at 3.0 T. The proposed technique might be interesting for the assessment of renal tissue oxygenation and its regulation in patients with kidney diseases.
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