The traditional Mediterranean diet is characterized by a high intake of olive oil, fruit, nuts, vegetables, and cereals; a moderate intake of fish and poultry; a low intake of dairy products, red meat, processed meats, and sweets; and wine in moderation, consumed with meals. 1 In observational cohort studies 2,3 and a secondary prevention trial (the Lyon Diet Heart Study), 4 increasing adherence to the Mediterranean diet has been consistently beneficial with respect to cardiovascular risk. 2-4 A systematic review ranked the Mediterranean diet as the most likely dietary model to provide protection against coronary heart disease. 5 Small clinical trials have uncovered plausible biologic mechanisms to explain the salutary effects of this food pattern. 6-9 We designed a randomized trial to test the efficacy of two Mediterranean diets (one supplemented with extra-virgin olive oil and another with nuts), as compared with a control diet (advice on a low-fat diet), on primary cardiovascular prevention. Methods Study Design The PREDIMED trial (Prevención con Dieta Mediterránea) was a parallel-group, multicenter, randomized trial. Details of the trial design are provided elsewhere. 10-12 The trial was designed and conducted by the authors, and the protocol was approved by the institutional review boards at all study locations. The authors vouch for the accuracy and completeness of the data and all analyses and for the fidelity of this report to the protocol , which is available with the full text of this article at NEJM.org. Supplemental foods were donated, including extra-virgin olive oil (by Hojiblanca and Patrimonio Comunal Olivarero, both in Spain), walnuts (by the California Walnut Commission), almonds (by Borges, in Spain), and hazelnuts (by La Morella Nuts, in Spain). None of the sponsors had any role in the trial design, data analysis, or reporting of the results. Participant Selection and Randomization Eligible participants were men (55 to 80 years of age) and women (60 to 80 years of age) with no cardiovascular disease at enrollment, who had either type 2 diabetes mellitus or at least three of the following major risk factors: smoking, hypertension, elevated low-density lipoprotein cholesterol levels, low high-density lipoprotein cholesterol levels, overweight or obesity, or a family history of premature coronary heart disease. Detailed enrollment criteria are provided in the Supplementary Appendix , available at NEJM.org. All participants provided written informed consent. Beginning on October 1, 2003, participants were randomly assigned, in a 1:1:1 ratio, to one of three dietary intervention groups: a Mediterranean diet supplemented with extra-virgin olive oil, a Mediterranean diet supplemented with nuts, or a control diet. Randomization was performed centrally by means of a computer-generated random-number sequence. Interventions and Measurements The dietary intervention 8,10-13 is detailed in the Supplementary Appendix . The specific recommended diets are summarized in Table 1 Table 1 Summary of Dietary Recommendations to Participants in the Mediterranean-Diet Groups and the Control-Diet Group. . Participants in the two Mediterranean-diet groups received either extra-virgin olive oil (approximately 1 liter per week) or 30 g of mixed nuts per day (15 g of walnuts, 7.5 g of hazelnuts, and 7.5 g of almonds) at no cost, and those in the control group received small nonfood gifts. No total calorie restriction was advised, nor was physical activity promoted. For participants in the two Mediterranean-diet groups, dietitians ran individual and group dietary-training sessions at the baseline visit and quarterly thereafter. In each session, a 14-item dietary screener was used to assess adherence to the Mediterranean diet 8,14 (Table S1 in the Supplementary Appendix ) so that personalized advice could be provided to the study participants in these groups. Participants in the control group also received dietary training at the baseline visit and completed the 14-item dietary screener used to assess baseline adherence to the Mediterranean diet. Thereafter, during the first 3 years of the trial, they received a leaflet explaining the low-fat diet (Table S2 in the Supplementary Appendix ) on a yearly basis. However, the realization that the more infrequent visit schedule and less intense support for the control group might be limitations of the trial prompted us to amend the protocol in October 2006. Thereafter, participants assigned to the control diet received personalized advice and were invited to group sessions with the same frequency and intensity as those in the Mediterranean-diet groups, with the use of a separate 9-item dietary screener (Table S3 in the Supplementary Appendix ). A general medical questionnaire, a 137-item validated food-frequency questionnaire, 15 and the Minnesota Leisure-Time Physical Activity Questionnaire were administered on a yearly basis. 10 Information from the food-frequency questionnaire was used to calculate intake of energy and nutrients. Weight, height, and waist circumference were directly measured. 16 Biomarkers of compliance, including urinary hydroxytyrosol levels (to confirm compliance in the group receiving extra-virgin olive oil) and plasma alpha-linolenic acid levels (to confirm compliance in the group receiving mixed nuts), were measured in random subsamples of participants at 1, 3, and 5 years (see the Supplementary Appendix ). End Points The primary end point was a composite of myocardial infarction, stroke, and death from cardiovascular causes. Secondary end points were stroke, myocardial infarction, death from cardiovascular causes, and death from any cause. We used four sources of information to identify end points: repeated contacts with participants, contacts with family physicians, a yearly review of medical records, and consultation of the National Death Index. All medical records related to end points were examined by the end-point adjudication committee, whose members were unaware of the study-group assignments. Only end points that were confirmed by the adjudication committee and that occurred between October 1, 2003, and December 1, 2010, were included in the analyses. The criteria for adjudicating primary and secondary end points are detailed in the Supplementary Appendix . Statistical Analysis We initially estimated that a sample of 9000 participants would be required to provide statistical power of 80% to detect a relative risk reduction of 20% in each Mediterranean-diet group versus the control-diet group during a 4-year follow-up period, assuming an event rate of 12% in the control group. 10,17 In April 2008, on the advice of the data and safety monitoring board and on the basis of lower-than-expected rates of end-point events, the sample size was recalculated as 7400 participants, with the assumption of a 6-year follow-up period and underlying event rates of 8.8% and 6.6% in the control and intervention groups, respectively. Power curves under several assumptions can be found in Figure S1 in the Supplementary Appendix . Yearly interim analyses began after a median of 2 years of follow-up. With the use of O'Brien–Fleming stopping boundaries, the P values for stopping the trial at each yearly interim analysis were 5×10 −6 , 0.001, 0.009, and 0.02 for benefit and 9×10 −5 , 0.005, 0.02, and 0.05 for adverse effects. 18 The stopping boundary for the benefit of the Mediterranean diets with respect to the primary end point was crossed at the fourth interim evaluation; on July 22, 2011, the data and safety monitoring board recommended stopping the trial on the basis of end points documented through December 1, 2010. All primary analyses were performed on an intention-to-treat basis by two independent analysts. Time-to-event data were analyzed with the use of Cox models with two dummy variables (one for the Mediterranean diet with extra-virgin olive oil and another for the Mediterranean diet with nuts) to obtain two hazard ratios for the comparison with the control group. To account for small imbalances in risk factors at baseline among the groups, Cox regression models were used to adjust for sex, age, and baseline risk factors. We tested the proportionality of hazards with the use of time-varying covariates. All analyses were stratified according to center. Prespecified subgroup analyses were conducted according to sex, age, body-mass index (BMI), cardiovascular-risk-factor status, and baseline adherence to the Mediterranean diet. Sensitivity analyses were conducted under several assumptions, including imputation of data for missing values and participants who dropped out (see the Supplementary Appendix ). Results Baseline Characteristics of the Study Participants From October 2003 through June 2009, a total of 8713 candidates were screened for eligibility, and 7447 were randomly assigned to one of the three study groups (Figure S2 in the Supplementary Appendix ). Their baseline characteristics according to study group are shown in Table 2 Table 2 Baseline Characteristics of the Participants According to Study Group. . Drug-treatment regimens were similar for participants in the three groups, and they continued to be balanced during the follow-up period (Table S4 in the Supplementary Appendix ). Participants were followed for a median of 4.8 years (interquartile range, 2.8 to 5.8). After the initial assessment, 209 participants (2.8%) chose not to attend subsequent visits, and their follow-up was based on reviews of medical records. By December 2010, a total of 523 participants (7.0%) had been lost to follow-up for 2 or more years. Dropout rates were higher in the control group (11.3%) than in the Mediterranean-diet groups (4.9%) (Figure S2 in the Supplementary Appendix ). As compared with participants who remained in the trial, those who dropped out were younger (by 1.4 years), had a higher BMI (the weight in kilograms divided by the square of the height in meters; by 0.4), a higher waist-to-height ratio (by 0.01), and a lower score for adherence to the Mediterranean diet (by 1.0 points on the 14-item dietary screener) (P0.05 for all comparisons). Compliance with the Dietary Intervention Participants in the three groups reported similar adherence to the Mediterranean diet at baseline ( Table 2 , and Figure S3 in the Supplementary Appendix ) and similar food and nutrient intakes. During follow-up, scores on the 14-item Mediterranean-diet screener increased for the participants in the two Mediterranean-diet groups (Figure S3 in the Supplementary Appendix ). There were significant differences between these groups and the control group in 12 of the 14 items at 3 years (Table S5 in the Supplementary Appendix ). Changes in objective biomarkers also indicated good compliance with the dietary assignments (Figure S4 and S5 in the Supplementary Appendix ). Participants in the two Mediterranean-diet groups significantly increased weekly servings of fish (by 0.3 servings) and legumes (by 0.4 servings) in comparison with those in the control group (Table S6 in the Supplementary Appendix ). In addition, participants assigned to a Mediterranean diet with extra-virgin olive oil and those assigned to a Mediterranean diet with nuts significantly increased their consumption of extra-virgin olive oil (to 50 and 32 g per day, respectively) and nuts (to 0.9 and 6 servings per week, respectively). The main nutrient changes in the Mediterranean-diet groups reflected the fat content and composition of the supplemental foods (Tables S7 and S8 in the Supplementary Appendix ). No relevant diet-related adverse effects were reported (see the Supplementary Appendix ). We did not find any significant difference in changes in physical activity among the three groups. End Points The median follow-up period was 4.8 years. A total of 288 primary-outcome events occurred: 96 in the group assigned to a Mediterranean diet with extra-virgin olive oil (3.8%), 83 in the group assigned to a Mediterranean diet with nuts (3.4%), and 109 in the control group (4.4%). Taking into account the small differences in the accrual of person-years among the three groups, the respective rates of the primary end point were 8.1, 8.0, and 11.2 per 1000 person-years ( Table 3 Table 3 Outcomes According to Study Group. ). The unadjusted hazard ratios were 0.70 (95% confidence interval , 0.53 to 0.91) for a Mediterranean diet with extra-virgin olive oil and 0.70 (95% CI, 0.53 to 0.94) for a Mediterranean diet with nuts ( Figure 1 Figure 1 Kaplan–Meier Estimates of the Incidence of Outcome Events in the Total Study Population. ) as compared with the control diet (P=0.015, by the likelihood ratio test, for the overall effect of the intervention). The results of multivariate analyses showed a similar protective effect of the two Mediterranean diets versus the control diet with respect to the primary end point ( Table 3 ). Regarding components of the primary end point, only the comparisons of stroke risk reached statistical significance ( Table 3 , and Figure S6 in the Supplementary Appendix ). The Kaplan–Meier curves for the primary end point diverged soon after the trial started, but no effect on all-cause mortality was apparent ( Figure 1 ). The results of several sensitivity analyses were also consistent with the findings of the primary analysis (Table S9 in the Supplementary Appendix ). Subgroup Analyses Reductions in disease risk in the two Mediterranean-diet groups as compared with the control group were similar across the prespecified subgroups ( Figure 2 Figure 2 Results of Subgroup Analyses. , and Table S10 in the Supplementary Appendix ). In addition, to account for the protocol change in October 2006 whereby the intensity of dietary intervention in the control group was increased, we compared hazard ratios for the Mediterranean-diet groups (both groups merged vs. the control group) before and after this date. Adjusted hazard ratios were 0.77 (95% CI, 0.59 to 1.00) for participants recruited before October 2006 and 0.49 (95% CI, 0.26 to 0.92) for those recruited thereafter (P=0.21 for interaction). Discussion In this trial, an energy-unrestricted Mediterranean diet supplemented with either extra-virgin olive oil or nuts resulted in an absolute risk reduction of approximately 3 major cardiovascular events per 1000 person-years, for a relative risk reduction of approximately 30%, among high-risk persons who were initially free of cardiovascular disease. These results support the benefits of the Mediterranean diet for cardiovascular risk reduction. They are particularly relevant given the challenges of achieving and maintaining weight loss. The secondary prevention Lyon Diet Heart Study also showed a large reduction in rates of coronary heart disease events with a modified Mediterranean diet enriched with alpha-linolenic acid (a key constituent of walnuts). That result, however, was based on only a few major events. 4,19,20 There were small between-group differences in some baseline characteristics in our trial, which were not clinically meaningful but were statistically significant, and we therefore adjusted for these variables. In fully adjusted analyses, we found significant results for the combined cardiovascular end point and for stroke, but not for myocardial infarction alone. This could be due to stronger effects on specific risk factors for stroke but also to a lower statistical power to identify effects on myocardial infarction. Our findings are consistent with those of prior observational studies of the cardiovascular protective effects of the Mediterranean diet, 2,5 olive oil, 21-23 and nuts 24,25 ; smaller trials assessing effects on traditional cardiovascular risk factors 6-9 and novel risk factors, such as markers of oxidation, inflammation, and endothelial dysfunction 6,8,26-28 ; and studies of conditions associated with high cardiovascular risk — namely, the metabolic syndrome 6,16,29 and diabetes. 30-32 Thus, a causal role of the Mediterranean diet in cardiovascular prevention has high biologic plausibility. The results of our trial might explain, in part, the lower cardiovascular mortality in Mediterranean countries than in northern European countries or the United States. 33 The risk of stroke was reduced significantly in the two Mediterranean-diet groups. This is consistent with epidemiologic studies that showed an inverse association between the Mediterranean diet 2,34 or olive-oil consumption 22 and incident stroke. Our results compare favorably with those of the Women's Health Initiative Dietary Modification Trial, wherein a low-fat dietary approach resulted in no cardiovascular benefit. 35 Salient components of the Mediterranean diet reportedly associated with better survival include moderate consumption of ethanol (mostly from wine), low consumption of meat and meat products, and high consumption of vegetables, fruits, nuts, legumes, fish, and olive oil. 36,37 Perhaps there is a synergy among the nutrient-rich foods included in the Mediterranean diet that fosters favorable changes in intermediate pathways of cardiometabolic risk, such as blood lipids, insulin sensitivity, resistance to oxidation, inflammation, and vasoreactivity. 38 Our study has several limitations. First, the protocol for the control group was changed halfway through the trial. The lower intensity of dietary intervention for the control group during the first few years might have caused a bias toward a benefit in the two Mediterranean-diet groups, since the participants in these two groups received a more intensive intervention during that time. However, we found no significant interaction between the period of trial enrollment (before vs. after the protocol change) and the benefit in the Mediterranean-diet groups. Second, we had losses to follow-up, predominantly in the control group, but the participants who dropped out had a worse cardiovascular risk profile at baseline than those who remained in the study, suggesting a bias toward a benefit in the control group. Third, the generalizability of our findings is limited because all the study participants lived in a Mediterranean country and were at high cardiovascular risk; whether the results can be generalized to persons at lower risk or to other settings requires further research. As with many clinical trials, the observed rates of cardiovascular events were lower than anticipated, with reduced statistical power to separately assess components of the primary end point. However, favorable trends were seen for both stroke and myocardial infarction. We acknowledge that, even though participants in the control group received advice to reduce fat intake, changes in total fat were small and the largest differences at the end of the trial were in the distribution of fat subtypes. The interventions were intended to improve the overall dietary pattern, but the major between-group differences involved the supplemental items. Thus, extra-virgin olive oil and nuts were probably responsible for most of the observed benefits of the Mediterranean diets. Differences were also observed for fish and legumes but not for other food groups. The small between-group differences in the diets during the trial are probably due to the facts that for most trial participants the baseline diet was similar to the trial Mediterranean diet and that the control group was given recommendations for a healthy diet, suggesting a potentially greater benefit of the Mediterranean diet as compared with Western diets. In conclusion, in this primary prevention trial, we observed that an energy-unrestricted Mediterranean diet, supplemented with extra-virgin olive oil or nuts, resulted in a substantial reduction in the risk of major cardiovascular events among high-risk persons. The results support the benefits of the Mediterranean diet for the primary prevention of cardiovascular disease.
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Functional similarity of gene products can be estimated by controlled biological vocabularies, such as Gene Ontology (GO). Four methods have been presented to determine the semantic similarity of two GO terms based on the annotation statistics of their common ancestor terms (Resnik (Philip, 1999), Jiang (Jiang and Conrath, 1997), Lin (Lin, 1998) and Schlicker (Schlicker et al., 2006)). Wang (Wang et al., 2007) proposed a new method to measure the similarity based on the graph structure of GO. Each of these methods has its own advantages and weaknesses. Recently, Yu andcolleagues developed a R package namedGOSemSim, which can be used to compute semantic similarity among GO terms, sets of GO terms, gene products, and gene clusters, Inaddition, GOSemSim provides all five methods mentioned above. More information about GOSemSim was presented at: http://www.bioconductor.org/packages/release/bioc/html/GOSemSim.html References Guangchuang Yu, Fei Li, Yide Qin, Xiaochen Bo, Yibo Wu, and Shengqi Wang. Gosemsim: an r package for measuring semantic similarity among go terms and gene products. Bioinformatics, 26:976–978, 2010. Guangchuang Yu, Chuan-Le Xiao, Xiaochen Bo, Chun-Hua Lu, Yide Qin, Sheng Zhan, and Qing-Yu He. A new method for measuring functional similarity of micrornas. Journal of Integrated OMICS, 1(1):49–54, 2011. Guangchuang Yu, Le-Gen Wang, Yanyan Han, and Qing-Yu He. clusterprofiler: an r package for comparing biological themes among gene clusters. OMICS: A Journal of Integrative Biology, 16, 2012.
2012年5月23日， Nature 在线发表了意大利分子肿瘤研究所首席研究员 Fabrizio d'Adda di Fagagna 课题组的一篇题为Site-specific DICER and DROSHA RNA products control the DNA-damage response的科研论文，报道了一种新的非编码小RNA 用于在DNA损伤部位控制DNA 损伤反应的激活。 DNA损伤反应机制包括细胞的染色体DNA损伤监控和修复机制，是维护基因组稳定性的重要机制之一。DNA损伤反应( DNA damage response ，DDR)系统对肿瘤的发生、发展及治疗具有重要的作用。 MicroRNA（miRNA）是近几年在真核生物中发现的一类具有调控功能的非编码RNA，它们主要参与基因转录后水平的调控。miRNA基因的转录初产物 (pri-miRMA)很快被一种核糖核酸酶ⅢDrosha加工成为miRNA前体 (pre—miRNA)，然后由细胞核转运至细胞质中，经另一种核糖核酸酶ⅢDicer识别剪切为成熟miRNA。至今，关于Dicer和 Drosha 加工而成的非编码RNA 激活DNA损伤反应，还未见报道。 本研究发现，DDR聚焦点（foci）对核糖核酸酶A的处理非常敏感。在核糖核酸酶A处理的细胞中，需要Dicer和 Drosha依赖的RNA产物修复DDR聚焦点。还发现，Dicer和 Drosha对于激活DNA损伤反应是必须的，而不是RNA干扰信号通路中的下游元件。 通过对DNA双链断链切口的RNA深度测序（deep sequencing）和DNA损伤反应激活的研究，证明了DDR聚焦点的形成需要位点专一的依赖Dicer和 Drosha的 小 RNA。此小RNA被称为DDRNAs。 DDRNAs，无论由化学合成还是由Dicer加工而来，对于修复RNase-A处理的细胞来说，都是足够的。在不存在其他细胞内RNA时也是如此。 本研究不仅发现了一种新的非编码RNA，而且拓宽了对非编码RNA功能的理解和认识。 doi：10.1038/nature11179 PMC: PMID: Site-specific DICER and DROSHA RNA products control the DNA-damage response Sofia Francia，Flavia Michelini，Alka Saxena，Dave Tang，Michiel de Hoon，Viviana Anelli，Marina Mione，Piero CarninciFabrizio d’Adda di Fagagna Non-coding RNAs (ncRNAs) are involved in an increasingly recognized number of cellular events1. Some ncRNAs are processed by DICER and DROSHA RNases to give rise to small double-stranded RNAs involved in RNA interference (RNAi)2. The DNA-damage response (DDR) is a signalling pathway that originates from a DNA lesion and arrests cell proliferation3. So far， DICER and DROSHA RNA products have not been reported to control DDR activation. Here we show， in human， mouse and zebrafish， that DICER and DROSHA， but not downstream elements of the RNAi pathway， are necessary to activate the DDR upon exogenous DNA damage and oncogene-induced genotoxic stress， as studied by DDR foci formation and by checkpoint assays. DDR foci are sensitive to RNase A treatment， and DICER- and DROSHA-dependent RNA products are required to restore DDR foci in RNase-A-treated cells. Through RNA deep sequencing and the study of DDR activation at a single inducible DNA double-strand break， we demonstrate that DDR foci formation requires site-specific DICER- and DROSHA-dependent small RNAs， named DDRNAs， which act in a MRE11–RAD50–NBS1-complex-dependent manner (MRE11 also known as MRE11A； NBS1 also known as NBN). DDRNAs， either chemically synthesized or in vitro generated by DICER cleavage， are sufficient to restore the DDR in RNase-A-treated cells， also in the absence of other cellular RNAs. Our results describe an unanticipated direct role of a novel class of ncRNAs in the control of DDR activation at sites of DNA damage.
一个关于PubMed数据库各种API的webinar： Software developers are invited to join NLM data experts as they showcase NLM APIs and provide valuable information on how to find, use, and incorporate medical literature, drug, clinical trial, consumer health information, molecular biology, and other data into novel products. The free webinar, NLM API Showcase: Using NLM APIs for Product Development , will be held April 10, 2012 from 2:00 p.m. - 3:30 p.m. (ET) . 具体内容见如下网址： http://www.nlm.nih.gov/pubs/techbull/ma12/ma12_api_webinar.html
Abstract New molecular entities (NMEs), as defined by the FDA, are new drug products containing as their active ingredient a chemical substance marketed for the first time in the United States. The following descriptions of NMEs approved in 2010–2011 ( Table 1 ) detail the basic clinical and pharmacologic profile of each new drug, as well as key precautions and warnings. Also included for each drug is a brief summary of selected pharmacokinetic, adverse-reaction, drug-interaction, and dosing data submitted to the FDA in support of the manufacturer's New Drug Application. This review is intended to be objective rather than evaluative in content. The information for each NME was obtained primarily from sources published prior to FDA approval. Experience clearly shows that many aspects of a new drug's therapeutic profile are not detected in premarketing studies and emerge after the drug is used in large numbers of patients. Studies have clearly demonstrated the appearance of "new" adverse reactions for many NMEs within 2 to 3 years of first becoming available. Some of these drugs may eventually acquire at least one black box warning for serious adverse reactions or are withdrawn from the market for safety reasons not recognized at the time of approval. Hence, while this review offers a starting point for learning about new drugs, it is essential that practitioners be aware of changes in a drug's therapeutic profile as reported by their own patients and in the pharmaceutical literature. 来源： http://www.medscape.com/viewarticle/752616
欧盟出了纳米材料的定义,The European Commission said its newly unveiled common nanomaterial definition will provide a basis for clear regulation that will boost industry’s ability to develop products while safeguarding consumers. 50%的颗粒，任何一维的尺寸介于1-100nm。国内也出过纳米材料定义，美日也出台过类似文献。对于纳米材料尺度上限限定为100nm是相同的。 把纳米材料定义为至少一维的尺寸为1-100nm的材料,没有把纳米材料的单分散性的要求相结合,这不符合科学规律。 没有和单分散结合起来的纳米尺寸定义并无实质物理化学意义.应当说这是对于纳米材料其量子力学本质,没有研究清楚,而给出的笼统错误概念。 通过对我们自己十几年来的亚微米和纳米粉体长期实验结果总结,我们对此专门作过研究,实际每一种单分散纳米材料都有可表征其特性的特定的纳米尺寸,而这一尺寸是与其本身化学键性质直接相关的,单分散本身还与分散的介质相关（但是在此处单分散可以参照的标准是以常温常压下空气中标准状态为准，理想标准状态是以绝对真空为准，当然液体中单分散也会有其极限特征尺寸），这也是物质的基本性质。可以这么说单分散纳米材料是物质的新态(注意因为有人说中国人没有基础原创,我想这应当算一个(单分散状态纳米材料是物质的新态，其微观结构、热力学和动力学状态包括物化性质都有其特点，其特征尺寸也是物质的基本性质之一，理论上每一种纳米材料都会有不同的单分散特征尺寸,我们把它定义为dc, 这是由理论和实验支持的结果.因此其纳米材料的性质每种材料存在的尺寸并不一样),科学网网友可以共同作证。这些内容在我们公开发表的论文中，已经有了明确理论机理论述，所以再次在科学网上予以交流。 先从纳米材料的单一分散性为何会困难谈起,很多人都被这一难题困住了,包括美国科学院院士和国内多位院士也在谈话和报告中谈到对此类问题自己的困惑.我们自己在实验中已经解决了很多种纳米粉体在空气中的单分散问题,并且对于部分同一种材料微米\亚微米\纳米粉体系列化尺度和形貌效应也作了研究比较,所以对此有了部分规律性的认识。最重要的一点是,总结的分散理论规律也帮助自己解决了多种新系列的纳米粉体材料分散难题，成功指导我自己的试验研究，而且我们关于纳米尺度的理论已可以解决和解释自己所制和文献报道的纳米材料特性的理论成因，指导我们的试验,这几年来试验出很多新的单分散纳米材料。这才让我下决心把已发表的论文个别理论要点，整理后与大家分享，来阐明我们为何认为纳米材料定义尺寸1-100nm的不妥之处。 1。纳米材料的单分散对于每一种材料在不同尺寸都有不同的工艺方法，这应当是做过此项研究者的共识。这说明把纳米材料尺寸划为任一维度小于100nm以下，这一标准太简单化了，没有结合纳米材料分散的问题，这也应不是我一人的体会。 2。我们的研究结果是，每一种材料都有其特定的纳米材料特征尺寸，举例来说，单分散碳巴基球在50nm以下可以视作纳米颗粒，在50-200nm视为处于纳米和微米材料过渡区，200纳米以上与宏观材料性质一致。金纳米颗粒在100nm以下是纳米颗粒，但是在100-500nm之间为过渡区，500纳米以上与宏观材料一致。对于单分散碳纳米管，管径小于80nm以下，可以视为是纳米材料，80-200nm为过渡区，再大性质会不稳定，这是径向的；在轴向上，理论上可以达到几十毫米或者更长，超过后也会不稳定。石墨烯可以理解为轴向在约五十层的范围内属于纳米材料，再增加层数至几百层属于过渡区，再多与石墨无异；径向单层悬浮石墨烯其纳米尺寸稳定上限为几十微米,实际我对于诺奖石墨烯的很多结论，提出了批评,直接的原因源于此,当然还有我们十几年试验的经验。（以上这些我们有理论计算结果，具体与实验会有误差,但是我们已经有部分试验工作也在开展中,实际称为过渡区这是我们自己的暂定定义,具体也是有明确数值的,因为纳米材料的特征尺寸与外界温度和压力也相关,所以我们定义为过渡区,还有可以补充的是因为理论计算很多参数目前无准确的测定值,参数人为设定导致一个区间值,而不是边界定值），但此处举例是为了说明每一种纳米材料，都有不同的纳米尺寸特征上限，统一限定为100nm是不妥的。钛酸钡颗粒，在500nm以下都可以视为纳米颗粒，再大一些，可以视为与宏观尺寸性质相同（关于钛酸钡的结论，不但有理论，我们还有十几年积累的丰富实验数据支持，包括粒径从几微米到几十纳米范围），其他还有多种自制纳米粉体的实验数据也支持我的结果.纳米粉体单分散状态下，这一特征尺寸具体与颗粒原子或者分子大小和本身自身的化学键性质直接相关。反过来说，纳米材料在特定外界环境条件下(可以限定为是理想真空或者标准的空气状态等)，单分散时其上限特征尺寸也是物质的特性之一。（如同熔点等性质一样）。 3.当然这个观点,还有其他几方面的我们研究的理论结果，也支持我们的结论,会根据论文公开的速度，在后续博文发表.
2011年8月25日更新的MODIS Conversion Toolkit ，支持143种现有的modis数据产品直接处理，同时提供批量数据处理的IDL开发函数接口。 简介： The MODIS Conversion Toolkit (MCTK) is a plugin for ENVI that can ingest, process, and georeference every known MODIS product (currently 143) through your choice of an easy-to-use interactive widget interface or a fully-accessible programmatic interface. Supported products include: - Level 1A Uncalibrated Radiance - Level 1B Calibrated Radiance - Level 2 Swath - Level 2G, Level 3, and Level 4 Grid The interface allows you to take a "cafeteria" approach to MODIS data by providing a list of all available datasets within a file, from which you can choose the ones to process. The ENVI equivalents of MRT and MRTSwath are built in as well, which means that you can input a file, have its contents converted to scientifically meaningful values, and then project those contents into the coordinate system of your choice--all within one interface. Bow tie correction is also available for all swath products. The user guide (included with the plugin) contains: Descriptions of how the plugin interacts with each major MODIS product categoryScreen captures to aid in using the interactive versionA complete explanation of the programming interface with fully functional sample programs for each major MODIS product category.A list of all supported MODIS product。
3 June 2011 | By Stephen Harris Carbon dioxide is bad. That’s the common thread in public discourse. We’re constantly told of the need to reduce the amount of CO2 in the atmosphere and that it’s destroying the planet. Of course the reality is that carbon dioxide is a key part of the natural cycle of energy and vital to the survival of all life on this planet. It also has a wide range of commercial uses. So should we see CO2 as more of a resource than a problem? Our supplies of the gas are set to increase massively as carbon-capture power plants become a reality, and scientists and industry are increasingly looking for new ways to use and hopefully monetise it. Carbon dioxide is already used in food preparation and preservation, in drug and chemical processing, in water treatment, welding and pneumatics. None of these applications will soak up all the CO2 we’re going to produce in the next fifty years, though at least CCS power stations could become more cost-effective if they sell the gas on. But what if we could develop a use for carbon dioxides that actually helped the climate change cause and made a big impact on greenhouse gas emissions? Injecting CO2 into oil wells as they dry up keeps it out of the atmosphere but also helps get more oil out, meaning we have more fossil fuels to burn and even more CO2 to deal with. A different idea, as highlighted in our recent feature , is to mineralise CO2 to create products for use in the construction and food industries. If we can make it economical and energy efficient, we could even take the waste materials of existing cement-making processes – ash and carbon dioxide – and combine them to make a stronger form of cement. Nature, as so often is the case, could also provide a solution – photosynthesis. It gives plants their own wonderful use for CO2, but unless we literally go back to living in forests by covering the whole world in trees, there’s really only so much they can do for us. Instead, some scientists are hoping to deliver an artificial version of photosynthesis that effectively turns carbon dioxide into an energy storage medium. If we can efficiently use sunlight to power the reaction, we can transform the pesky gas (and water) into usable fuels. Of course, we are already turning plants into fuel with serious consequences for food prices. Around 40 per cent of corn grown in the US is now used to make ethanol instead of feeding humans and animals, according to the Department of Agriculture. Photosynthesising algae could provide one alternative to this. Another idea is to do the energy conversion ourselves. Scientists at MIT have already developed a ‘practical artificial leaf’ that uses solar energy and inexpensive catalysts to produce hydrogen from water with efficiencies much greater than those of real leaves. Find a way of efficiently adding carbon dioxide to this artificial process and we could create biofuels to use in our existing fuel infrastructure without the need to rely on growing plants (and impacting food production). Though all these ideas are still at the laboratory stage, the business world is taking notice. Spanish research institute MATGAS, which is majority-owned by industrial gas company Air Products, is coming to the end of a Though all these ideas are still at the laboratory stage, the business world is taking notice. Spanish research institute MATGAS, which is majority-owned by industrial gas company Air Products, is coming to the end of a
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