No abstract available

No abstract available

No abstract available

[en] Purpose: To retrospectively compare the clinical outcome for cervical cancer patients treated with high-dose-rate (HDR) vs. low-dose-rate (LDR) brachytherapy. Methods and Materials: One hundred ninety-one LDR patients were treated from 1977 to 1988 and compared to 173 HDR patients treated from 1989 to 1996. Patients of similar stage and tumor volumes were treated with identical external beam fractionation schedules. Brachytherapy was given in either 1 or 2 LDR implants for the earlier patient cohort, and 5 HDR implants for the latter cohort. For both patient groups, Point A received a minimum total dose of 80 Gy. The linear-quadratic formula was used to calculate the LDR dose-equivalent contribution to Point A for the HDR treatments. The primary endpoints assessed were survival, pelvic control, relapse-free survival, and distant metastases. Endpoints were estimated using the Kaplan-Meier method. Comparisons between treatment groups were performed using the log-rank test and Cox proportional hazards models. Results: The median follow-up was 65 months (2 to 208 months) in the LDR group and 22 months (1 to 85 months) in the HDR group. For all stages combined there was no difference in survival, pelvic control, relapse-free survival, or distant metastases between LDR and HDR patients. For Stage IB and II HDR patients, the pelvic control rates were 85% and 80% with survival rates of 86% and 65% at 3 years, respectively. In the LDR group, Stage IB and II patients had 91% and 78% pelvic control rates, with 82% and 58% survival rates at 3 years, respectively. No difference was seen in survival or pelvic control for bulky Stage I and II patients combined (> 5 cm). Pelvic control at 3 years was 44% (HDR) versus 75% (LDR) for Stage IIIB patients (p = 0.002). This difference in pelvic control was associated with a lower survival rate in the Stage IIIB HDR versus LDR population (33% versus 58%, p = 0.004). The only major difference, with regard to patient characteristics, between the Stage IIIB patients was the incidence of hydronephrosis in the HDR vs. LDR group--28% vs. 12%, respectively (p = 0.05). For Stage IIIB patients treated with HDR, our analysis suggested that pelvic control rates improved when the first brachytherapy insertion was performed after the majority of external beam radiotherapy had been delivered. Conclusion: Similar outcome was observed for Stage IB and II patients treated with either HDR or LDR brachytherapy--regardless of tumor volume. However, poorer survival and pelvic control rates were observed for Stage IIIB patients treated with HDR brachytherapy. If HDR is used for Stage IIIB patients, our results suggest the majority of external beam radiotherapy should be delivered prior to initiating the brachytherapy to allow for adequate tumor regression. HDR brachytherapy is more convenient for patients, decreases the radiation exposure for health care workers, and should be considered a standard therapy for women with Stage I or II cervical cancer

[en] 172 cases of invasive carcinoma of the cervix treated at the Johns Hopkins Hospital are reviewed. Failure rates are examined by stage, demonstrating a high percentage of local recurrences in patients with late stage disease treated by a traditional regime of radiotherapy. Reasons for these failures are explored and a proposal for a more individualized approach to therapy is made

[en] Biological membranes are examples of 'smart' materials whose properties and behaviour emerge from the propagation across many scales of the molecular characteristics of their constituents. Artificial smart materials, such as drug delivery vehicles and biosensors, often rely on modifying naturally occurring soft matter, such as polymers and lipid vesicles, so that they possess useful behaviour. However, the complexity of natural membranes, both in their static properties, exemplified in their phase behaviour, and in their dynamic properties, as in the kinetics of their formation and interactions, hinders their rational modification. Mesoscopic simulations, such as dissipative particle dynamics (DPD), allow in silico experiments to be easily and cheaply performed on complex, soft materials requiring as input only the molecular structure of the constituents at a coarse-grained level. They can therefore act as a guide to experimenters prior to performing costly assays. Additionally, mesoscopic simulations provide the only currently feasible window on the length- and timescales relevant to important biophysical processes such as vesicle fusion. We review here the development of computational models of bilayer membranes, and in particular the use of mesoscopic simulations to follow the molecular rearrangements that occur during membrane fusion

[en] The authors have evaluated, at different temperatures, the second and fourth order anisotropy constants of Nd₂Fe₁₄B-based melt spun samples in which Nd was partly replaced by Dy. This was done through an analysis of the first quadrant demagnetization branches of the hysteresis loops in terms of a one sublattice coherent rotation model of non interacting isotropically distributed grains. The results evidence how the increase in Dy content corresponds both to the increase of the second order anisotropy constant and to a decrease of the fourth order one

[en] The peripheral benzodiazepine receptor ligand PK11195 has been used as an in vivo marker of neuroinflammation in positron emission tomography studies in man. One of the methodological issues surrounding the use of the ligand in these studies is the highly variable kinetic behavior of [¹¹C]PK11195 in plasma. We therefore undertook a study to measure the binding of [³H]PK11195 to whole human blood and found a low level of binding to blood cells but extensive binding to plasma proteins. Binding assays using [³H]PK11195 and purified human plasma proteins demonstrated a strong binding to α1-acid glycoprotein (AGP) and a much weaker interaction with albumin. Immunodepletion of AGP from plasma resulted in the loss of plasma [³H]PK11195 binding demonstrating: (i) the specificity of the interaction and (ii) that AGP is the major plasma protein to which PK11195 binds with high affinity. PK11195 was able to displace fluorescein-dexamethasone from AGP with IC₅₀ of <1.2 μM, consistent with a high affinity interaction. These findings are important for understanding the behavior of the ligand in positron emission tomography studies for three reasons. Firstly, AGP is an acute phase protein and its levels will vary during infection and pathological inflammatory diseases such as multiple sclerosis. This could significantly alter the free plasma concentrations of the ligand and contribute to its variable kinetic behavior. Secondly, AGP and AGP-bound ligand may contribute to the access of [¹¹C]PK11195 to the brain parenchyma in diseases with blood brain barrier breakdown. Finally, local synthesis of AGP at the site of brain injury may contribute the pattern of [¹¹C]PK11195 binding observed in neuroinflammatory diseases

[en] In this work we have studied the temperature dependence of several hysteresis parameters measured in PrNdFeB samples that were obtained from melt spun amorphous precursors crystallized by employing different heating rates. Analysis of the spin reorientation temperature by means of thermal evolution of the remanence and of the demagnetization differential susceptibility revealed the presence in all samples of at least two hard 2:14:1 phases (Nd rich and Pr rich, respectively). The demagnetization curves of most samples exhibited a single magnetization reversal process thus indicating that the hard phases were coupled. Despite the multiphase character of the samples, it was possible to carry out the analysis of the temperature dependence reversal process through micromagnetic and global models, and by accepting a linear variation of the intrinsic properties with the degree of substitution of Nd by Pr. Best fits for both models were obtained when using parameters corresponding to Nd-rich 2:14:1 phases, which indicates that the collective single reversal process is driven by the Nd-rich 2:14:1 grains. copyright 1997 American Institute of Physics

[en] Sequential ion implantation has been used to synthesize Pd-based alloy nanoclusters in SiO₂. Three systems have been investigated (PdCu, PdAg and PdFe) in terms of nanocluster formation and stability under thermal annealing. In particular, we focused on the role played by the annealing atmosphere. A comparison is made with similar alloy-based systems obtained by sequential ion implantation in silica of Au-Ag or Au-Cu followed by annealing under similar conditions. Strong similarities have been found in the compositional evolution of Pd-based and Au-based nanoclusters