Transversal dose distribution optimization for laser-accelerated proton beam medical applications by means of Geant4

The main purpose of this paper is to quantitatively study the possibility of delivering dose distributions of clinical relevance with laser-driven proton beams. A Monte Carlo application has been developed with the Geant4 toolkit, simulating the ELIMED (MEDical and multidisciplinary application at ELI-Beamlines) transport and dosimetry beam line which is being currently installed at the ELI-Beamlines in Prague (CZ). The beam line will be used to perform irradiations for multidisciplinary studies, with the purpose of demonstrating the possible use of optically accelerated ion beams for therapeutic purposes. The ELIMED Geant4-based application, already validated against reference transport codes, accurately simulates each single element of the beam line, necessary to collect the accelerated beams and to select them in energy. Transversal dose distributions at the irradiation point have been studied and optimized to try to quantitatively answer the question if such kind of beam lines, and specifically the systems developed for ELIMED in Prague, will be actually able to transport ion beams not only for multidisciplinary applications, such as pitcher-catcher nuclear reactions (e.g. neutrons), PIXE analysis for cultural heritage and space radiation, but also for delivering dose patterns of clinical relevance in a future perspective of possible medical applications.     

福建沙溪口水电站库区混合输移参数研究

本文以沙溪口水电站水库为例,对河道式水库混合输移参数的识别作了若干研究。阐述示踪实验确定这些参数的原理、方法,提供沙溪口电站库区河段枯水期的参数值。在示踪实验基础上,提出适用于水电站不同运行状态混合输移参数的估算公式。可为有关部门研究水环境容量,制订水质规划等提供参考。     

Effects of taxol treatment on the microtubular system and mitochondria of Tetrahymena

Complex investigation was done using immunocytochemical confocal microscopy, electron microscopy and flow cytometry on the effect of taxol to the microtubular arrangement and dynamics. The most interesting phenomenon was the rapid disappearance of transversal microtubule bands, while longitudinal microtubule bands remained and were submitted to the known effects of taxol. There was a broad variation in mitochondrial effect, some of them remained normal, while others swollen, desintegrated and their tubules disoriented. Treatment with 50 nM taxol significantly reduced the binding of anti alpha-tubulin antibody and a lesser degree anti-acetylated tubulin antibody. The difference between the transversal and longitudinal microtubules is emphasized by the results and the paper discusses the possibilities of indirect effects of taxol to the transversal microtubules (tubulin-GTP interaction, faster turnover, mitochondrial interaction). Polyglutamylation of tubulin has not a role in this difference.     

Impact of transversal calf muscle loading on plantarflexion

Muscle compression commonly occurs in daily life (for instance wearing backpacks or compression garments, and during sitting). However, the effects of the compression on contraction dynamics in humans are not well examined. The aim of the study was to quantify the alterations of contraction dynamics and muscle architecture in human muscle with external transverse loads.The posterior tibialis nerve of 29 subjects was stimulated to obtain the maximal double-twitch force of the gastrocnemius muscle with and without transverse compression that was generated using an indentor. The muscle architecture was determined by a sonographic probe that was embedded within the indentor. Five stimulations each were conducted at 5 conditions: (1) pretest (unloaded), (2) indentor loading with 2 kg, (3) 4.5 kg, (4) 10 kg, and (5) posttest (unloaded).Compared to the pretest maximal force decreased by 9%, 13% and 16% for 2 kg, 4.5 kg and 10 kg, respectively. The half-relaxation time increased with increased transverse load whereas the rate of force development decreased from pretest to 2 kg and from 4.5 kg to 10 kg. The lifting height of the indentor increased with transverse load from 2 kg to 4.5 kg but decreased from 4.5 kg to 10 kg. Increases in pennation during the twitches were reduced at the highest transverse load.The results demonstrate changes of the contraction dynamics due to transversal muscle loading. Those alterations are associated with the applied pressure, changes in muscle architecture and partitioning of muscle force in transversal and longitudinal direction.     

Morphological changes and transversal growth kinetics along the apical meristem in the pericycle cell types of the onion adventitious root

Summary In the apical meristem of the adventitious root ofAllium cepa, all pericycle cells show a marked increase in cross-sectional area between 400 and 800 m behind the tip, this transversal growth ceasing in the 1,200–1,400 m interval. However, different pericycle cell types (opposite xylem, intervening and opposite phloem) show different transversal growth kinetics. Along the meristem, the opposite xylem cells are narrower than both the intervening and opposite phloem cells, and these latter are similar in cross-sectional area. Another relevant difference is in the polarity of the transversal expansion, which in turn gives rise to changes in cell shape. In fact, in apical most portions of the meristem, the opposite phloem cells mainly expand tangentially, while the intervening cells do so radially, and the opposite xylem cells undergo a similar tangential and radial expansion. By contrast, in basal most portions of the meristem, radial expansion continues in the opposite phloem cells when it has ceased in the intervening cells. These latter expand tangentially once again when tangential expansion has ceased in the opposite phloem cells. As a consequence of this transversal growth, the opposite xylem cells, which can initiate lateral root primordia, retain their isodiametric transversal shape along the meristem, whereas the transversal shape of the opposite phloem and intervening cells initially changes from isodiametric to markedly enlarged tangentially (opposite phloem) or radially (intervening), after which both cell types tend to become more rounded in shape.     

Remineralisation study of artificial root caries lesions after fluoride treatment. An in vitro study using electric caries monitor and transversal micro-radiography

Aims: To evaluate and compare remineralisation of root caries lesions after in vitro treatment with various fluoride (F) agents using an Electric Caries Monitor (ECM) and Transversal Micro‐Radiography (TMR). Materials: Permanent human teeth were extracted and root surface specimens were sectioned, prepared (n = 35), and randomly allocated into seven different experimental groups (groups 1–7). Methods: Root surfaces were demineralised in an acidified gel (pH = 5.0) for 3 weeks followed by various F treatments and stored in a standardised remineralising solution at 37°C for 6 weeks. The root surfaces were treated twice daily with different dentifrice slurries for 2 min, either with a neutral placebo dentifrice without F (group 5); or a neutral sodium fluoride (NaF) 1400 p.p.m. F dentifrice (group 1); or a neutral 1250 p.p.m. F dentifrice (group 6); or an acid dentifrice (pH 4.7) with 1400 p.p.m. F containing amine fluoride (AmF) (groups 3 and 4) or a 1250 p.p.m. (pH 4.7) AmF dentifrice (group 6). In groups 1, 2, 5, 6, and 7, the root surfaces were additionally rinsed for 2 min with a neutral non‐F placebo solution. In groups 3 and 4, rinsing were performed for 2 min with an acid (pH 4.7) 250 p.p.m. F solution, containing 125 p.p.m. F as AmF and 125 p.p.m. F as potassium fluoride (KF), once or twice per day respectively. ECM was used to measure electrical resistance on root surfaces at baseline and after 3 and 6 weeks respectively. TMR technique was used to measure and compare root surface lesion depths and mineral loss. Results: Six weeks daily treatment with a dentifrice slurry containing AmF followed by rinsing with a combination of equal amounts of AmF and KF solution twice a day showed a statistical significant higher ECM values compared with the other groups. TMR data measuring lesion depths and mineral loss reduction supported the results of the ECM findings. Conclusions: Daily application of a dentifrice slurry containing 1400 p.p.m. F as AmF combined with twice daily rinsing with a 250 p.p.m. F solution containing equal amount of AmF and KF significantly remineralise primary root caries lesions in vitro. ECM and TMR are valuable complementary methods in order to analyse the remineralisation processes.     

Local distribution of macrophytes and consequences for sampling methods in large rivers

During the years 2003 and 2004, the distribution of macrophytes was studied at eight sites in two large rivers in the southwest of France (the Dordogne and Garonne). Using a pinpoint method, we obtained 7,083 observations and recorded physical parameters such as depth, distance from bank, water velocity, and substrate type. By using logistic regressions, we showed that a combination of these factors significantly influences the distribution of macrophytes. This enabled us to highlight transversal distribution patterns. Helophyte spermatophytes, free-floating taxa, and most of the nonanchored algae were characteristic of the shallow areas located near the banks. The deepest areas were characterized by a reduced number of species with a majority of submerged spermatophytes which are resistant to high velocity, anchored algae, and bryophytes. These results can be used to implement the Macrophyte Biological Index for Rivers (IBMR) for large rivers. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Handling editor: S. M. Thomaz