On the evaluation of edgeless diode detectors for patient-specific QA in high-dose stereotactic radiosurgery

PurposeIn this work, the potential of an innovative “edgeless” silicon diode was evaluated as a response to the still unmet need of a reliable tool for plan dosimetry verification of very high dose, non-coplanar, patient-specific radiosurgery treatments. In order to prove the effectiveness of the proposed technology, we focused on radiosurgical treatments for functional disease like tremor or pain.MethodsThe edgeless diodes response has been validated with respect to clinical practice standard detectors by reproducing the reference dosimetry data adopted for the Treatment Planning System. In order to evaluate the potential for radiosurgery patient-specific treatment plan verification, the anthropomorphic phantom Alderson RANDO has been adopted along with three edgeless sensors, one placed in the centre of the Planning Target Volume, one superiorly and one inferiorly.ResultsThe reference dosimetry data obtained from the edgeless detectors are within 2.6% for output factor, off-axis ratio and well within 2% for tissue phantom ratio when compared to PTW 60,018 diode. The edgeless detectors measure a dose discrepancy of approximately 3.6% from the mean value calculated by the TPS. Larger discrepancies are obtained in very steep gradient dose regions when the sensors are placed outside the PTV.ConclusionsThe angular independent edgeless diode is proposed as an innovative dosimeter for patient quality assurance of brain functional disorders and other radiosurgery treatments. The comparison of the diode measurements with TPS calculations confirms that edgeless diodes are suitable candidates for patient-specific dosimetric verification in very high dose ranges delivered by non-isocentric stereotactic radiosurgery modalities.     

Comparison of two scanning electron microscope techniques for examining daily growth increments on fish otoliths

With a secondary detector and a backscatter detector, total primary increment counts on the same otoliths were similar, but more samples could be counted using the backscatter detector and the percentage of unreadable area was consistently lower with this technique.     

Imaging performance of phase-contrast breast computed tomography with synchrotron radiation and a CdTe photon-counting detector

PurposeWithin the SYRMA-CT collaboration based at the ELETTRA synchrotron radiation (SR) facility the authors investigated the imaging performance of the phase-contrast computed tomography (CT) system dedicated to monochromatic in vivo 3D imaging of the female breast, for breast cancer diagnosis.MethodsTest objects were imaged at 38 keV using monochromatic SR and a high-resolution CdTe photon-counting detector. Signal and noise performance were evaluated using modulation transfer function (MTF) and noise power spectrum. The analysis was performed on the images obtained with the application of a phase retrieval algorithm as well as on those obtained without phase retrieval. The contrast to noise ratio (CNR) and the capability of detecting test microcalcification clusters and soft masses were investigated.ResultsFor a voxel size of (60 μm)³, images without phase retrieval showed higher spatial resolution (6.7 mm⁻¹ at 10% MTF) than corresponding images with phase retrieval (2.5 mm⁻¹). Phase retrieval produced a reduction of the noise level and an increase of the CNR by more than one order of magnitude, compared to raw phase-contrast images. Microcalcifications with a diameter down to 130 μm could be detected in both types of images.ConclusionsThe investigation on test objects indicates that breast CT with a monochromatic SR source is technically feasible in terms of spatial resolution, image noise and contrast, for in vivo 3D imaging with a dose comparable to that of two-view mammography. Images obtained with the phase retrieval algorithm showed the best performance in the trade-off between spatial resolution and image noise.     

激光照射血液荧光光谱的初步研究

采用ＯＭＡ—ＩＩ微弱信号检测系统研究了人血液荧光光谱在激光照射下的变化情况。结果表明：在６３２．８ｎｍＨｅＮｅ激光诱导下,不同血液在６７０ｎｍ,７３０ｎｍ,９８１ｎｍ附近出现三个荧光峰;荧光强度在一定范围内与照射激光功率呈线性变化关系;随着激光照射时间的增加,三个峰位上的荧光强度下降,８分钟后趋于稳定值;在激光照射过程中,三个峰位出现不同数值的移动,同时在６７０ｎｍ和７３０ｎｍ两个荧光峰之间出现了竞争。     

Transepithelial transport of artepillin C in intestinal Caco-2 cell monolayers

The absorption characteristics of artepillin C (AC), an active ingredient of Brazilian propolis, were examined by measuring permeation across Caco-2 cell monolayers. The permeation rate in the basolateral-to-apical direction, J_bl → ap, in the presence of proton gradient was 0.14 nmol/min/mg protein, whereas J_bl → ap in the absence of proton gradient was 1.14 nmol/min/mg protein. The latter value is nearly the same as the permeation rate in the apical-to-basolateral direction, J_ap → bl, both in the presence and absence of proton gradient. In the presence of proton gradient, J_ap → bl was almost constant, irrespective of NaN₃ or benzoic acid. However, J_bl → ap dramatically increased upon the addition of NaN₃ or benzoic acid specifically to the apical side. In both the presence and absence of proton gradient, J_ap → bl also appeared to be constant irrespective of the paracellular permeability of Caco-2 cells. After AC was loaded apically in the presence of proton gradient, the intracellular AC increased with time. This accumulation was inhibited by apically loaded NaN₃. These indicate that AC transport occurs mainly via transcellular passive diffusion, although a considerable amount of AC was taken up intracellularly by monocarboxylic acid transporter (MCT) on the apical side and not transported out across the basolateral membrane, suggesting that different subtypes of MCT are involved.     

Speed encoding in correlation motion detectors as a consequence of spatial structure

For animals to carry out a wide range of detection, recognition and navigation tasks, visual motion signals are crucial. The encoding of motion information has therefore, attracted much attention in the experimental and computational study of brain function. Two main alternative mechanisms have been proposed on the basis of behavioural and physiological experiments. On one hand, correlation-type and motion energy detectors are simple and efficient in the design of their basic mechanism but are tuned to temporal frequency rather than to speed. On other hand, gradient-type motion detectors directly represent an estimate of speed, but may require more demanding processing mechanisms. We demonstrate here how the temporal frequency dependence observed for sine-wave gratings can disappear for less constrained stimuli, to be replaced by responses reflecting speed for stimuli like square waves when a phase-sensitive detection mechanism is employed. We conclude from these observations that temporal frequency tuning is not necessarily a limitation for motion vision based on correlation detectors, and more generally demonstrate in view of the typical Fourier composition of natural scenes, that correlation detectors operating in such environments can encode image speed. In the context of our results, we discuss the implications of the loss of phase sensitivity inherent in using a linear system approach to describe neural processing.     

Biogas generation apple pulp

In view of the pressing problem that appears in our region (Asturias, north of Spain) with the residues from the cider production, it was decided to test this kind of material as a co-substrate joint with slaughterhouse waste in a laboratory unit.     

Regulation of ROCKII membrane localization through its C-terminus

RhoA activated kinases (ROCKs) are potent effectors of RhoA signaling for regulation of the cytoskeleton. ROCKs have been shown to be localized to several different subcellular locations, suggesting that its localization is context specific and regulated. However, the signaling mechanisms that control ROCK localization have not been clearly described. In this study we measured ROCKII localization following stimulation with the chemokine CXCL12 or adhesion to collagen 1. Strikingly, each of these extracellular signals targeted ROCKII to membrane protrusions. We further determined that both RhoA and PI3-kinase signaling are required for these stimuli to induce efficient membrane localization. Furthermore, we used a mutational approach to show that two separate domains predicted to respond to these localization signals, the Rho Binding Domain (RBD) and the Pleckstrin Homology domain (PH). Unexpectedly, we found that these two domains work synergistically to lead to membrane localization. This suggests a novel mechanism for controlling ROCKII localization at the membrane, in which the ROCKII C-terminus acts as a coincidence detector for spatial regulatory signals. In other words, efficient membrane targeting requires the ROCKII RBD to receive the RhoA signal and the PH domain to receive the phospholipid signal.     

Development of anabolic-androgenic steroids purity certified reference materials for anti-doping

Background

The need for certified reference materials (CRM) of anabolic-androgenic steroids reference materials was emphasized by the Beijing 2008 Olympic game as a tool to improve comparability, ensuring accuracy and traceability of analytical results for competing athletes. The China National Institute of Metrology (NIM) responded to the state request by providing seven anabolic-androgenic steroids (AAS) reference materials for Beijing Olympic anti-doping, GBW (E) 100086-GBW (E) 100092.

Experimental

This work describes the production of the series of AAS CRMs, according to ISO Guides 34 and 35 [1] and [2], which comprises the material processing, homogeneity and stability assessment, CRMs’ characterization including moisture content, trace metal content. The AASs’ purity values were assigned with collaborative study involved eight laboratories applying high resolution liquid chromatography-diode array detector (HPLC-DAD). Homogeneity of the AAS CRMs were determined by an in-house validated liquid chromatographic methodology. Potential degradation during storage was also investigated and a shelf-life based on this value was established.

Results

The certified values of CRMs were 99.76 ± 0.079%, 99.76 ± 0.25%, 99.63 ± 0.09%, 99.67 ± 0.11%, 98.82 ± 0.56%, 96.30 ± 0.39% and 99.71 ± 0.49% (purity ± expanded uncertainty with confidence level of 95%) for methyltestosterone, testosterone propionate, nandrolone, nandrolone 17-propionate, boldenone, trenbolone acetate and testosterone respectively.

Conclusions

The certified values for all the studied AAS reference materials are traceable to the international system of units (SI). The CRMs developed were applied by 32 laboratory including sports organizations and analytical laboratories during the 2008 Olympic game for anti-doping control.     

陕北黄土高原气象要素对植被覆盖的空间分异影响及风险探测

陕北黄土高原地处我国西北生态环境脆弱区,近年来受退耕还林（草）影响,区域植被覆盖变化显著,与气象要素的响应关系也呈现出了复杂的空间分异性和不确定性,亟待厘清。以不同地貌分区为响应单元,探究了陕北黄土高原变绿前后（1982-1992年与2005-2015年）NDVI指数的时空演化特征,分析了植被覆盖变化与气象要素之间的分异性响应关系,并透过最优参数的地理探测器模型（OPGD）探测了气象要素变化对植被覆盖演变的交互影响及风险。研究结果表明：（1）陕北黄土高原及各地貌分区在研究期内NDVI指数均呈显著上升趋势,且阶段化分异明显;各地貌区气温和实际蒸散发量在高原变绿前后趋势变化差异明显,1982-1992年主要呈不显著增加趋势,而2005-2015年则表现为不显著减少趋势;两个时期降水量的空间异质性较为显著,其中北部地区为持续增加趋势,而南部地区则由减少逆转为增加趋势。（2）不同地貌区NDVI指数与气温和蒸散发均呈正相关,且蒸散发与NDVI的相关性强于气温;相对高原变绿前,2005-2015年NDVI指数对各气象要素的响应强度均有所增大。（3）OPGD因子检测结果显示5km空间网格是评价气候变化对陕北黄土高原植被覆盖变化影响的最佳空间尺度,各地貌分区对NDVI指数变化影响最大的气象因子依次为：气温（黄土塬）、降水（盖沙黄土丘陵）、蒸散发（黄土峁状丘陵）、降水（黄土梁状丘陵）、降水（黄土宽谷丘陵）、蒸散发（风沙丘陵）、降水（土石丘陵）;交互探测表明气象因子间的交互作用对NDVI指数的空间分异具有协同增强性,但不同时期各地貌区的主导交互因子略有差异。（4）风险探测发现不同实际蒸散发量对NDVI指数的影响有显著空间差异。（5）陕北黄土高原的植被覆盖变化并不能简单归因于退耕还林（草）等生态修复措施,而应是多要素耦合驱动的结果,气象要素在其中扮演了不可忽视的作用。