Elekta Infinity直线加速器治疗床对放疗剂量的影响

目的:研究Elekta Infinity直线加速器治疗床在常用X射线能量下对放疗剂量的影响。方法:将圆柱体模体分别置于碳纤维主治疗床、延长板以及治疗床与延长板衔接处正中,旋转机架,分别让6和10 MV高能X射线穿过治疗床,利用指形电离室测量固体水中间的绝对剂量,得出不同角度下的剂量分布,并计算治疗床对X射线的衰减因子。结果:治疗床与延长板衔接处在120°和240°两个机架角处的剂量衰减因子在6和10 MV两种治疗模式下分别达到了36.02%和36.01%以及30.46%和30.63%,而当机架角为140°~220°时,衔接处与主治疗床的剂量衰减因子相近,在6与10 MV能量下的剂量衰减因子平均值及标准差分别为2.56%±0.49%和2.14%±0.39%以及2.55%±0.48%和1.95%±0.41%,机架角由180°增大或减小时两处的剂量衰减均呈上升趋势,二者均在120°和240°附近达到最大;6和10 MV两种能量下延长板在该角度区间的剂量衰减因子平均值及标准差分别为1.55%±0.24%和1.07%±0.25%,并在115°和245°附近达到最大值,剂量衰减因子分别为4.08%和3.97%以及3.20%和3.34%。结论:后斜野主体部分在主治疗床与衔接处对剂量的衰减低于3%,在延长板处对剂量的衰减小于2%,但在120°和240°附近以及115°和245°附近3处位置的剂量衰减会达到最大,需在计划系统中考虑床的影响;此外,主治疗床与延长板衔接处在120°和240°附近对剂量的衰减急剧增大,不适合作为治疗区域,在治疗病人时需注意避免将靶区移到该区域。     

Applying synthetic radiography to intraoral tomosynthesis: a step towards achieving 3D imaging in the dental clinic

Objectives:A practical approach to three-dimensional (3D) intraoral imaging would have many potential applications in clinical dentistry. Stationary intraoral tomosynthesis (sIOT) is an experimental 3D imaging technology that holds promise. The purpose of this study was to explore synthetic radiography as a tool to improve the clinical utility of the images generated by an sIOT scan.Methods:Extracted tooth specimens containing either caries adjacent to restorations (CAR) or vertical root fractures (VRF) were imaged by sIOT and standard dental radiography devices. Qualitative assessments were used to compare the conspicuity of these pathologies in the standard radiographs and in a set of multi-view synthetic radiographs generated from the information collected by sIOT.Results:The sIOT-based synthetic 2D radiographs contained less artefact than the image slices in the reconstructed 3D stack, which is the conventional approach to displaying information from a tomosynthesis scan. As a single sIOT scan can be used to generate synthetic radiographs from multiple viewing angles, the interproximal space was less likely to be obscured in the synthetic images compared to the standard radiograph. Additionally, the multi-view synthetic radiographs can potentially improve the display of CAR and VRFs as compared to a single standard radiograph.Conclusions:This preliminary experience combining synthetic radiography and sIOT in extracted tooth models is encouraging and supports the ongoing study of this promising approach to 3D intraoral imaging with many potential applications.     

Reverse Iodine Transfer Polymerization (RITP) of 1,1,2,2‐Tetrahydroperfluorodecyl Acrylate in Supercritical Carbon Dioxide

Reverse iodine transfer polymerization (RITP) of 1,1,2,2‐tetrahydroperfluorodecyl acrylate (FDA) is successfully performed in supercritical carbon dioxide (scCO₂) at 70 °C under a CO₂ pressure of 300 bar. PolyFDA (PFDA) of increasing molecular weights (from 10 000 to 100 000 g mol^?1) is synthesized with good agreement between theoretical, ¹H NMR spectroscopy and and size exclusion chromatography/refractive index/right‐angle laser‐light scattering/differential viscometer (SEC/RI/RALLS/DV)‐estimated molecular weights (). Furthermore, the increase of goes with a decrease of the dispersity of the polymers (? from 2.06 to 1.33), which is consistent with a controlled radical polymerization (CRP). Lastly, the structure of final PFDA and therefore the RITP process are confirmed by matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) analyses.

     

Concentration Fluctuations and Segmental Dynamics in Weakly Dynamic Asymmetric Blends in the Presence of Surface‐Functionalized Multiwall Carbon Nanotubes

Surface‐functionalized multiwall carbon nanotubes (MWCNTs) are incorporated in poly(methyl methacrylate)/styrene acrylonitrile (PMMA/SAN) blends and the pretransitional regime is monitored in situ by melt rheology and dielectric spectroscopy. As the blends exhibit weak dynamic asymmetry, the obvious transitions in the melt rheology due to thermal concentration fluctuations are weak. This is further supported by the weak temperature dependence of the correlation length (ξ ≈ 10–12 Å) in the vicinity of demixing. Hence, various rheological techniques in both the temperature and frequency domains are adopted to evaluate the demixing temperature. The spinodal decomposition temperature is manifested in an increase in the miscibility gap in the presence of MWCNTs. Furthermore, MWCNTs lead to a significant slowdown of the segmental dynamics in the blends. Thermally induced phase separation in the PMMA/SAN blends lead to selective localization of MWCNTs in the PMMA phase. This further manifests itself in a significant increase in the melt conductivity.

     

Grafting of Chitosan with Styrene and Maleic Anhydride via Nitroxide‐Mediated Radical Polymerization in Supercritical Carbon Dioxide

A novel synthesis route is used to produce chitosan‐graft‐poly(styrene‐maleic anhydride)‐OH‐TEMPO (CTS‐g‐PSMA‐T). A three‐step reaction scheme is proposed: 1) bromine 4‐OH‐TEMPO oxoammonium salt is synthesized. 2) Hydroxyl‐targeted groups in the CTS molecule are reacted with the synthesized salt in aqueous acid solution. A functionalization of 18.9% is achieved. 3) Graft copolymerization of styrene and maleic anhydride is done via NMRP by a unimolecular initiation system. The reaction is run in a dispersion in supercritical carbon dioxide (scCO₂) in the presence of camphorsulfonic acid (CSA) to avoid autopolymerization. A modified CTS with a graft content of 68% in weight is obtained.

     

柿叶总黄酮对急性肝损伤小鼠肝组织的保护作用

目的探讨柿叶总黄酮(PLF)对四氯化碳(CCl 4)诱导的小鼠急性肝损伤的保护作用。方法采用CCl 4肝损伤模型,测定小鼠血清中谷丙转氨酶(ALT)和谷草转氨酶(AST)的含量及肝组织中超氧化物歧化酶(SOD)、脂质过氧化物丙二醛(MDA)、还原型谷胱甘肽(GSH)和肿瘤坏死因子-α(TNF-α)的含量,HE染色观察肝脏组织病理形态学的改变。结果PLF高、中、低剂量组均能降低肝损伤小鼠ALT和AST的含量,提高肝组织SOD和GSH含量,降低MDA和TNF-α含量,并能改善肝组织的病理损伤程度。结论PLF对CCl 4所致的小鼠肝损伤有较好的保护作用,其作用机制可能与提高小鼠的抗脂质氧化能力有关。     

Particle radiotherapy for prostate cancer

Recent advances in external beam radiotherapy have allowed us to deliver higher doses to the tumors while decreasing doses to the surrounding tissues. Dose escalation using high‐precision radiotherapy has improved the treatment outcomes of prostate cancer. Intensity‐modulated radiation therapy has been widely used throughout the world as the most advanced form of photon radiotherapy. In contrast, particle radiotherapy has also been under development, and has been used as an effective and non‐invasive radiation modality for prostate and other cancers. Among the particles used in such treatments, protons and carbon ions have the physical advantage that the dose can be focused on the tumor with only minimal exposure of the surrounding normal tissues. Furthermore, carbon ions also have radiobiological advantages that include higher killing effects on intrinsic radio‐resistant tumors, hypoxic tumor cells and tumor cells in the G0 or S phase. However, the degree of clinical benefit derived from these theoretical advantages in the treatment of prostate cancer has not been adequately determined. The present article reviews the available literature on the use of particle radiotherapy for prostate cancer as well as the literature on the physical and radiobiological properties of this treatment, and discusses the role and the relative merits of particle radiotherapy compared with current photon‐based radiotherapy, with a focus on proton beam therapy and carbon ion radiotherapy.     

Bone mineral density improvement after lung volume reduction surgery for severe emphysema

BACKGROUND: In patients with severe emphysema, bone mineral density (BMD) is reduced and the risk of osteoporosis is increased. STUDY OBJECTIVES: To identify the impact of lung volume reduction surgery on BMD. DESIGN: Prospective cohort study. SETTING: University hospital. PATIENTS AND INTERVENTIONS: Forty emphysematous patients, all receiving oral steroid therapy, underwent bilateral lung volume reduction surgery. Thirty similar patients, who refused the operation, followed a standard respiratory rehabilitation program. MEASUREMENTS: All subjects were evaluated pretreatment and 12 months posttreatment for respiratory function, nutritional status, and bone-related biochemical parameters. BMD was assessed by dual-energy radiograph absorptiometry. RESULTS: After surgery, we observed significant improvements in respiratory function (FEV1, + 18.8% [p < 0.01]; residual volume [RV], -29.6% [p < 0.001]; diffusing capacity of the lung for carbon monoxide [Dlco], + 21.6% [p < 0.01]) nutritional parameters (fat-free mass, + 6.0% [p < 0.01]), levels of bone-related hormones (free-testosterone, + 20.5% [p < 0.01]; parathormone, -11.2% [p < 0.01]), bone turnover markers (osteocalcin, -12.7% [p < 0.05]; bone-alkaline-phosphatase, -14.0% [p < 0.05]; beta-crosslaps, -33.6% [p < 0.001]), BMD (lumbar, + 8.8% [p < 0.01]; femoral, + 5.5% [p < 0.01]), and T-score (lumbar, + 21.0% [p < 0.01]; femoral, + 12.4% [p < 0.01]) with reduction in osteoporosis rate (50 to 25%). Nineteen patients who had undergone surgery were able to discontinue treatment with oral steroids. These subjects showed a more significant improvement in BMD (lumbar, + 9.6%; femoral, + 6.8%; p < 0.001) and T-score (lumbar, + 27.3%; femoral, + 14.3%; p < 0.001). The remaining 21 patients who had undergone surgery experienced significant improvement compared to respiratory rehabilitation subjects despite continued therapy with oral steroids (BMD: lumbar, + 4.5% vs -0.7%, respectively [p < 0.01]; femoral, + 2.7% vs -1.1%, respectively [p < 0.05]; T-score: lumbar, + 14 vs -2.1, respectively [p < 0.01]; femoral, + 7.4 vs -2.7, respectively [p < 0.01]). The increase in lumbar BMD was correlated with the surgical reduction of RV (p = 0.02) and with the increase in Dlco (p = 0.01) and fat-free mass (p = 0.01). CONCLUSIONS: Lung volume reduction surgery significantly improves BMD compared to respiratory rehabilitation therapy, even in patients requiring oral steroids. The increase in BMD correlates with RV, Dlco, and fat-free mass, suggesting that the restoration of respiratory dynamics, gas exchange, and nutritional status induces improvement in bone metabolism and mineral content.     

Coal fly ash is a major carbon flux in the Chang Jiang (Yangtze River) basin

Fly ash—the residuum of coal burning—contains a considerable amount of fossilized particulate organic carbon (FOC_ash) that remains after high-temperature combustion. Fly ash leaks into natural environments and participates in the contemporary carbon cycle, but its reactivity and flux remained poorly understood. We characterized FOC_ash in the Chang Jiang (Yangtze River) basin, China, and quantified the riverine FOC_ash fluxes. Using Raman spectral analysis, ramped pyrolysis oxidation, and chemical oxidation, we found that FOC_ash is highly recalcitrant and unreactive, whereas shale-derived FOC (FOC_rock) was much more labile and easily oxidized. By combining mass balance calculations and other estimates of fly ash input to rivers, we estimated that the flux of FOC_ash carried by the Chang Jiang was 0.21 to 0.42 Mt C⋅y⁻¹ in 2007 to 2008—an amount equivalent to 37 to 72% of the total riverine FOC export. We attributed such high flux to the combination of increasing coal combustion that enhances FOC_ash production and the massive construction of dams in the basin that reduces the flux of FOC_rock eroded from upstream mountainous areas. Using global ash data, a first-order estimate suggests that FOC_ash makes up to 16% of the present-day global riverine FOC flux to the oceans. This reflects a substantial impact of anthropogenic activities on the fluxes and burial of fossil organic carbon that has been made less reactive than the rocks from which it was derived.

Fossil particulate organic carbon (FOC) is a geologically stable form of carbon that was produced by the ancient biosphere and then buried and stored in the lithosphere; it is a key player in the geological carbon cycle (1–7). Uplift and erosion liberate FOC from bedrock, delivering it to the surficial carbon cycle. Some is oxidized in sediment routing systems, but a portion escapes and can be transported by rivers to the oceans (5, 8–10). Oxidation of FOC represents a long-term atmospheric carbon source and O₂ sink, whereas the reburial of FOC in sedimentary basins has no long-term net effect on atmospheric CO₂ and O₂ (1, 9, 11). Exhumation and erosion of bedrock provide a natural source of FOC (2, 8), which we refer to as FOC_rock. Human activities have introduced another form of FOC from the mining and combustion of coal. Burning coal emits CO₂ to the atmosphere but also leaves behind solid waste that contains substantial amounts of organic carbon (OC) that survives high-temperature combustion (12–14). This fossil-fuel-sourced carbon represents a poorly understood anthropogenic flux in the global carbon cycle; it also provides a major source of black carbon, which is a severe pollutant and climate-forcing agent (12–15).Previous studies sought to quantify black carbon in different terrestrial and marine environments and to distinguish fossil fuel versus forest fire sources (14–18). In this study, we focused on fly ash—the material left from incomplete coal combustion. As a major fossil fuel, coal supplies around 30% of global primary energy consumption (19, 20). Despite efforts to capture and utilize fly ash, a fraction enters soils and rivers; the resulting fossil OC from fly ash (FOC_ash) has become a measurable part of the contemporary carbon cycle (14). FOC_ash is also referred to as “unburned carbon” in fly ash (21–25); it provides a useful measure of combustion efficiency and the quality of fly ash as a building material (e.g., in concrete) (23–26). Industrial standards of FOC_ash content in fly ash have been established for material quality assurance (23, 24, 26, 27). However, the characteristics and fluxes of FOC_ash released to the environment, and how these compare to FOC_rock from bedrock erosion, remain less well understood.To fill this knowledge gap, we examined the Chang Jiang (Yangtze River) basin in China—a system that allowed us to evaluate the influence of FOC_ash on the carbon cycle at continental scales. In the 2000s, China became the largest coal-consuming country in the world, with an annual coal consumption of over 2,500 Mt, equating to ∼50% of worldwide consumption (19, 20, 28). Coal contributed over 60% of China’s national primary energy consumption through the 2000s. A significant portion of this coal (approximately one-third) was consumed in the Chang Jiang (CJ) basin, where China’s most populated and economically developed areas are located (29). Significant amounts of fly ash and FOC_ash continue to be produced and consumed in the CJ basin. To determine the human-induced FOC_ash flux, we investigated the FOC_ash cycle in the CJ basin. We characterized OC in a series of samples including fly ash, bedrock sedimentary shale, and river sediment through multiple geochemical analyses. We then estimated the CJ-exported FOC_ash flux and evaluated how human activities modulated FOC transfer at basin scales. We found that in the CJ basin, coal combustion and dam construction have conspired to boost the FOC_ash flux and reduce the FOC_rock flux carried by the CJ; as a result, these two fluxes converged over an interval of 60 y.     

A case-control study of obstructive sleep apnea-hypopnea syndrome in obese and nonobese chinese children

BACKGROUND: Obesity is a risk factor for obstructive sleep apnea-hypopnea syndrome (OSAHS) in adults. However, the prevalence of OSAHS in children is not clear, and the relationship between obesity and OSAHS remains controversial. METHODS: Obese children were recruited from the endocrinology, respiratory, and ear, nose, and throat clinics. Weight-matched, age-matched, and sex-matched children were recruited as control subjects. Standard questionnaires were administered, and a standardized physical examination was carried out. Lateral neck roentgenography, sleep polysomnography, full blood count, and arterial blood gas analysis were also performed. Children with body mass index z-scores of > 1.96 were considered to be obese. An adenoidal/nasopharygeal ratio of > 0.67 was considered to constitute adenotonsillar hypertrophy (ATH). OSAHS was defined as an apnea-hypopnea index (AHI) score of > 5 or obstructive apnea index (OAI) score of > 1. RESULTS: Ninety-nine obese children and 99 control subjects were recruited into the study. Obese patients had significantly higher AHI and OAI scores, and lower sleep efficiency and minimum arterial oxygen saturation (MinSao(2)) than control subjects. The prevalence of OSAHS was significantly higher in obese children with or without the ATH groups than their nonobese counterparts (odds ratio, 1.9 vs 108, respectively; 95% confidence interval, 1.21 to 4.7 vs 6.2 to 191, respectively). Obesity, tonsillar hypertrophy, and adenoid hypertrophy were independent risk factors for OSAHS (p < 0.001, p = 0.042, and p = 0.004, respectively). There was a positive correlation between the degree of obesity and AHI (r = 0.535; p < 0.001), and an inverse correlation between obesity and MinSao(2) (r = -0.507; p < 0.001). End-tidal CO(2), Paco(2), and bicarbonate levels were within the normal range. CONCLUSIONS: Obesity is a risk factor for OSAHS, and the degree of obesity is positively correlated with the severity of OSAHS.