试论在中国生活垃圾治理中实行循环经济的若干问题

论述了在中国生活垃圾治理中实行循环经济的重要性和紧迫性。阐述了循环经济的内涵。研讨了在中国生活垃圾治理中实行循环经济的方式、方法、措施、效益及对策。     

垃圾分拣与循环经济——由上海市浦东新区垃圾分拣压缩转运站的建设与运营谈起

针对目前国内大中型垃圾转运站建设热潮，提出在垃圾压缩中转之前，配套建设大件垃圾破碎、生活垃圾分拣、废旧物资回收、废旧物资分类打包等辅助措施，将垃圾分拣与压缩装运这二个互为独立的系统构成一个有机的整体，使传统意义上的垃圾转运站成为实现循环经济理念的垃圾分类工厂。通过提高废旧资源的回收利用率，来提高垃圾转运站的经济效益、环境效益和社会效益，从而充分实现循环经济与可持续科学发展理念。     

会展旅游垃圾的资源化处理技术及可行性分析

根据会展旅游垃圾的特性,论述了国内外资源化利用的新技术及其可行性,并结合我国城市垃圾处理的实际情况,提出了会展旅游垃圾资源化的循环经济发展模式.     

创建北京市海淀区循环经济产业园区的思考

调查了北京市海淀区生活垃圾及其他固体废物的处理处置现状，分析了建立循环经济产业园的有利条件和不利因素，以及建设循环经济产业园区对海淀区的重要意义。     

城市应急避难场所的垃圾管理生态化研究初探

依据传统工业生态思想,提出垃圾管理的生命周期,即垃圾存储、收运、处理处置等。在对环境资源化及循环经济认识基础上,提出城市应急避难场所垃圾管理可以借鉴传统工业循环经济模式,并指明应急避难场所规划建设可以参照工业生态园模式进行尝试性建设。     

石家庄市餐厨垃圾现状及资源化利用

本文阐述了餐厨垃圾对人体和环境的危害，介绍了国内外的一些处理方法，提出了餐厨垃圾的处置需要全社会的支持，发展循环经济。     

城市生活垃圾处理产业化模式设计

从循环经济理论、3R理论、生命周期理论等角度出发,通过对现阶段我国生活垃圾管理中存在的实际问题的研究,提出企业化、市场化、产业化3步走的生活垃圾产业化模式及对策.     

城市垃圾处理综合园区异味防控的探讨与实践

以北京市朝阳循环经济产业园为例,分析了垃圾处理中的可能异味源,总结了异味排查工作主要做法和经验,提出进一步加强异味防控工作的建议。     

北京市装饰装修垃圾处置现状及对策

分析了北京市装饰装修垃圾的污染特点及存在问题,结合北京市的实际情况提出了收集、运输、处置方案;同时对装饰装修垃圾处置设施的建设、运营方案、配套政策法规等方面都提出了合理化的建议;并从循环经济的角度,提出装饰装修垃圾处置设施的合理规划与布局.     

循环经济与垃圾管理的需求探究

循环经济下垃圾管理需要政策支持、技术支持；需要时间使人们行为习惯逐渐养成及进行市场的培育；并且需要有经济投入才能使垃圾作为资源得到再利用。     

Development and calculation of an energy dependent normal brain tissue neutron RBE for evaluating neutron fields for BNCT

In Boron Neutron Capture Therapy (BNCT) of malignant brain tumors, the energy dependence of a clinically relevant Relative Biological Effectiveness (RBE) for epithermal neutrons, RBE(En), is important in neutron field design. In the first half of this paper, we present the development of an expression for the energy dependent normal-tissue RBE, RBE(En). We then calculate a reasonable estimate for RBE(En) for adult brain tissue. In the second half of the paper, two separate RBE expressions are developed, one for the RBE of the neutrons that interact in tissue via the 14N(n,p)14C reaction, denoted RBE(N), and one for the RBE of the neutrons which interact in tissue via the 1H(n,n')1H reaction, denoted RBE(H). The absorbed-dose-averaged values of these expressions are calculated for the neutron flux spectrum in phantom for the Brookhaven Medical Research Reactor (BMRR) epithermal neutron beam. The calculated values, [RBE(norm)N] = 3.4 and [RBE(norm)H] = 3.2, are within 6% of being equal, and support the use of equal values for RBEN and RBE(H) by researchers at Brookhaven National Laboratory (BNL). Finally, values of [RBE(norm)N] and [RBE(norm)H], along with the absorbed-dose-averaged RBE for brain, [RBE(norm)b], were calculated as a function of depth along the centerline of an ellipsoidal head phantom using flux spectra calculated for our Accelerator-Based Neutron Source (ABNS). These values remained essentially constant with depth, supporting the use of constant values for RBE, as is done at BNL.     

Radiobiological characterization of proton beam at the National Cancer Center in Korea

Estimation of the relative biological effectiveness (RBE) of the proton beam at the National Cancer Center Proton Therapy Center in Korea (NCCPTC) is required clinically for the treatment of cancer. The proton beam was fixed at 190 MeV with 6 cm a spread out Bragg peaks (SOBP) for which corresponds to most frequent clinical condition. The RBE was estimated from the survival of human salivary gland (HSG) cells using the traditional colonogenic and MTT assays. The HSG cells were also irradiated in a cell-stack chamber and monitored for survival to identify whether the characteristic depth-dependent survival pattern was observed. The RBE of the NCCPTC was estimated to be 1.024 +/- 0.007 and 1.049 +/- 0.028 at the middle of SOBP using colonogenic and MTT assays, respectively. Further analysis of the biological response of proton exposure revealed no difference compared to conventional X-ray treatment in western blot, and FACS analysis. The proton beam of the NCCPTC also exhibited the characteristic depth-dependent survival pattern. The estimated RBE value of NCCPTC was slightly smaller than generic RBE value of 1.1 for protons of the majority of centers. Due to the recommendation of a generic RBE of 1.1 for protons, a representative RBE value of 1.1 was assigned for clinical application for proton beams at the NCCPTC.     

Relative biological effectiveness of simulated solar particle event proton radiation to induce acute hematological change in the porcine model

The present study was undertaken to determine relative biological effectiveness (RBE) values for simulated solar particle event (SPE) radiation on peripheral blood cells using Yucatan minipigs and electron-simulated SPE as the reference radiation. The results demonstrated a generally downward trend in the RBE values with increasing doses of simulated SPE radiation for leukocytes in the irradiated animals. The fitted RBE values for white blood cells (WBCs), lymphocytes, neutrophils, monocytes and eosinophils were above 1.0 in all three radiation dose groups at all time-points evaluated, and the lower limits of the 95% confidence intervals were > 1.0 in the majority of the dose groups at different time-points, which together suggest that proton-simulated SPE radiation is more effective than electron-simulated SPE radiation in reducing the number of peripheral WBCs, lymphocytes, neutrophils, monocytes and eosinophils, especially at the low end of the 5–10 Gy dose range evaluated. Other than the RBE values, the responses of leukocytes to electron-simulated SPE radiation and proton-simulated SPE radiation exposure are highly similar with respect to the time-course, the most radiosensitive cell type (the lymphocytes), and the shape of the dose–response curves, which is generally log-linear. These findings provide additional evidence that electron-simulated SPE radiation is an appropriate reference radiation for determination of RBE values for the simulated SPE radiations, and the RBE estimations using electron-simulated SPE radiation as the reference radiation are not complicated by other characteristics of the leukocyte response to radiation exposure.     

RBE and w(R) values of Auger emitters and low-range beta emitters with particular reference to tritium.

An apparent disparity exists between RBE (relative biological effectiveness) values for low-range beta and Auger emitters, and the current value for their radiation weighting factor (w(R)). This paper presents evidence that the current w(R) value of unity for these nuclides is inconsistent with most RBE evidence and should be increased by a factor of two to three. It recommends that the ICRP should clearly state that the most appropriate RBE value for these nuclides, and not the w(R) value, should be used in specific dose calculations, retrospective dose estimations and epidemiological studies. The ICRP should also publish guidance as to the methods and data sources that could be used for these RBE values.     

Why does a rural background make medical students more likely to intend to work in rural areas and how consistent is the effect? A study of the rural background effect

Objective: Evidence indicates that medical graduates with a rural background are more likely to become rural doctors than those with an urban background (the rural background effect (RBE)). Exactly why this is so has rarely been studied. This study sought to identify the role of social, environmental and economic factors in addition to isolation characterising rural environments that either explain or modify the association between rural background and becoming a rural doctorrural practice intention. Design and setting: Secondary analysis of linked databases from the Medical Schools Outcomes Database (MSOD), Australian Bureau of Statistics and other government sources. Participants: Seven thousand four hundred twenty‐two commencing medical students who took part in the MSOD survey and for whom external data could be linked. Results: No social, environmental or economic factor studied or isolation significantly contributed to explaining the RBE, although there is some evidence that areas of more attractive climate strengthen the RBE. However, even when the RBE is at its weakest, it remains a strong, positive predictor of attraction to rural practice. Conclusion: Why the RBE occurs remains unexplained. Evidence was found of a reduced RBE under certain climatic conditions and personal circumstances, but further work is required to better understand why rural background is so strongly related with rural medical intention and practice.     

Relation between lineal energy distribution and relative biological effectiveness for photon beams according to the microdosimetric kinetic model

Our cell survival data showed the obvious dependence of RBE on photon energy: The RBE value for 200 kV X-rays was approximately 10% greater than those for mega-voltage photon beams. In radiation therapy using mega-voltage photon beams, the photon energy distribution outside the field is different with that in the radiation field because of a large number of low energy scattering photons. Hence, the RBE values outside the field become greater. To evaluate the increase in RBE, the method of deriving the RBE using the Microdosimetric Kinetic model (MK model) was proposed in this study. The MK model has two kinds of the parameters, tissue-specific parameters and the dose-mean lineal energy derived from the lineal energy distributions measured with a Tissue-Equivalent Proportional Counter (TEPC). The lineal energy distributions with the same geometries of the cell irradiations for 200 kV X-rays, (60)Co γ-rays, and 6 MV X-rays were obtained with the TEPC and Monte Carlo code GEANT4. The measured lineal energy distribution for 200 kV X-rays was quite different from those for mega-voltage photon beams. The dose-mean lineal energy of 200 kV X-rays showed the greatest value, 4.51 keV/μm, comparing with 2.34 and 2.36 keV/μm for (60)Co γ-rays and 6 MV X-rays, respectively. By using the results of the TEPC and cell irradiations, the tissue-specific parameters in the MK model were determined. As a result, the RBE of the photon beams (y(D): 2~5 keV/μm) in arbitrary conditions can be derived by the measurements only or the calculations only of the dose-mean lineal energy.     

Relative biological effectiveness of 280 keV neutrons for apoptosis in human lymphocytes

The relative biological effectiveness (RBE) of neutrons varies from unity to greater than ten depending upon neutron energy and the biological endpoint measured. In our study, we examined apoptosis in human lymphocytes to assess the RBE of low energy 280 keV neutrons compared to Cs gamma radiation and found the RBE to be approximately one. Similar results have been observed for high energy neutrons using the same endpoint. As apoptosis is a major process that influences the consequences of radiation exposure, our results indicate that biological effect and the corresponding weighting factors for 280 keV neutrons may be lower in some cell types and tissues.     

Relative biological effectiveness of 290 MeV/u carbon ions for the growth delay of a radioresistant murine fibrosarcoma

The relative biological effectiveness (RBE) for animal tumors treated with fractionated doses of 290 MeV/u carbon ions was studied. The growth delay of NFSa fibrosarcoma in mice was investigated following various daily doses given with carbon ions or those given with cesium gamma-rays, and the RBE was determined. Animal tumors were irradiated with carbon ions of various LET (linear energy transfer) in a 6-cm SOBP (spread-out Bragg peak), and the isoeffect doses; i.e. the dose necessary to induce a tumor growth delay of 15 days were studied. The iso-effect dose for carbon ions of 14 and 20 keV/microm increased with an increase in the number of fractions up to 4 fractions. The increase in the isoeffect dose with the fraction number was small for carbon ions of 44 keV/microm, and was not observed for 74 keV/microm. The alpha and beta values of the linear-quadratic model for the radiation dose-cell survival relationship were calculated by the Fe-plot analysis method. The alpha values increased linearly with an increase in the LET, while the beta values were independent of the LET. The alpha/beta ratio was 129 +/- 10 Gy for gamma-rays, and increased with an increase in the LET, reaching 475 +/- 168 Gy for 74 keV/microm carbon ions. The RBE for carbon ions relative to Cs-137 gamma-rays increased with the LET. The RBE values for 14 and 20 keV/microm carbon ions were 1.4 and independent of the number of fractions, while those for 44 and 74 keV/microm increased from 1.8 to 2.3 and from 2.4 to 3.0, respectively, when the number of fractions increased from 1 to 4. Increasing the number of fractions further from 4 to 6 was not associated with an increase in the RBE. These results together with our earlier study on the skin reaction support the use of an RBE of 3.0 in clinical trials of 80 keV/microm carbon beams. The RBE values for low doses of carbon beams were also considered.     

Monte Carlo simulation of the RBE of I-131 radiation using DNA damage as biomarker

In general, a weighting factor of one is applied for low linear energy transfer radiations. However, several studies indicate that relative biological effectiveness (RBE) of low energy photons and electrons is greater than one. The aim of this current study was calculating the RBE of I-131 radiation relative to Co-60 gamma photons in 100 μm spheroid cells using Monte Carlo (MC) simulations. These calculations were compared to experimentally measured results. MCNPX2.6 was used to simulate the I-131 and Co-60 irradiation setups and calculate the secondary electron spectra at energies higher than 1 keV with varying oxygen concentrations. The electron spectra at energies lower than 1 keV were obtained by extrapolation (down to 10 eV). The calculated electron spectra were input into the MCDS micro-dosimetric Monte Carlo code to calculate the DSB induction and related RBE. The calculated RBE of I-131 radiation relative to Co-60 photons, as the reference radiation recommended by the International Commission on Radiation Protection (ICRP), was 1.06, 1.03 and 1.02 for oxygen concentrations of 0, 5 and 100%, respectively. Results of MC simulations indicate the RBE of I-131 is greater than one. This finding, despite a 10% discrepancy with the findings of the previous in vitro study of one of the authors of this paper, reemphasizes that I-131 radiation induces more severe biological damage than current ICRP recommendations.     

Exploration of "over kill effect" of high-LET Ar- and Fe-ions by evaluating the fraction of non-hit cell and interphase death

The reason why RBE for cell killing fell to less than unity (1.0) with very high-LET heavy-ions ((40)Ar: 1,640 keV/microm; (56)Fe: 780, 1,200, 2,000 keV/microm) was explored by evaluating the fraction of non-hit cell (time-lapse observation) and cells undergoing interphase death (calculation based on our previous data). CHO cells were exposed to 4 Gy (30% survival dose) of Ar (1,640 keV/microm) or Fe-ions (2,000 keV/microm). About 20% of all cells were judged to be non-hit, and about 10% cells survived radiation damage. About 70% cells died after dividing at least once (reproductive death) or without dividing (interphase death). RBE for reproductive (RBE[R]) and interphase (RBE[I]) death showed a similar LET dependence with maximum around 200 keV/microm. In this LET region, at 30% survival level, about 10% non-survivors underwent interphase death. The corresponding value for very high-LET Fe-ions (2,000 keV/microm) was not particularly high (approximately 15%), whereas that for X-rays was less than 3%. However, reproductive death (67%) predominated over interphase death (33%) even in regard to rather severely damaged cells (1% survival level) after exposure to Fe-ions (2,000 keV/microm). These indicate that interphase death is a type of cell death characteristic for the cells exposed to high-LET radiation and is not caused by "cellular over kill effect". Both NHF37 (non-hit fraction at 37% survival) and inactivation cross-section for reproductive death (sigma[R]) began to increase when LET exceeded 100 keV/microm. The exclusion of non-hit fraction in the calculation of surviving fraction partially prevented the fall of RBE[R] when LET exceeded 200 keV/microm. On the other hand, the mean number of lethal damage per unit dose (NLD/Gy) showed the same LET-dependent pattern as RBE[R]. These suggest that the increase in non-hit fraction and sigma[R] with an increasing LET is caused by enhanced clustering of ionization and DNA damage which lowers the energy efficiency for producing damage and RBE.