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排序方式: 共有1271条查询结果,搜索用时 15 毫秒
991.
Marie Yang Kevin Flavin Ilona Kopf Gabor Radics Claire H. A. Hearnden Gavin J. McManus Barry Moran Adrian Villalta‐Cerdas Luis A. Echegoyen Silvia Giordani Ed C. Lavelle 《Small (Weinheim an der Bergstrasse, Germany)》2013,9(24):4194-4206
The inflammatory effects of carbon nanoparticles (NPs) are highly disputed. Here it is demonstrated that endotoxin‐free preparations of raw carbon nanotubes (CNTs) are very limited in their capacity to promote inflammatory responses in vitro, as well as in vivo. Upon purification and selective oxidation of raw CNTs, a higher dispersibility is achieved in physiological solutions, but this process also enhances their inflammatory activity. In synergy with toll‐like receptor (TLR) ligands, CNTs promote NLRP3 inflammasome activation and it is shown for the first time that this property extends to spherical carbon nano‐onions (CNOs) of 6 nm in size. In contrast, the benzoic acid functionalization of purified CNTs and CNOs leads to significantly attenuated inflammatory properties. This is evidenced by a reduced secretion of the inflammatory cytokine IL‐1β, and a pronounced decrease in the recruitment of neutrophils and monocytes following injection into mice. Collectively, these results reveal that the inflammatory properties of carbon NPs are highly dependent on their physicochemical characteristics and crucially, that chemical surface functionalization allows significant moderation of these properties. 相似文献
992.
Inorganic arsenic in rice bran and its products are an order of magnitude higher than in bulk grain 总被引:1,自引:0,他引:1
Sun GX Williams PN Carey AM Zhu YG Deacon C Raab A Feldmann J Islam RM Meharg AA 《Environmental science & technology》2008,42(19):7542-7546
Rice is more elevated in arsenic than all other grain crops tested to date, with whole grain (brown) rice having higher arsenic levels than polished (white). It is reported here that rice bran, both commercially purchased and specifically milled for this study, have levels of inorganic arsenic, a nonthreshold, class 1 carcinogen, reaching concentrations of approximately 1 mg/kg dry weight, around 10-20 fold higher than concentrations found in bulk grain. Although pure rice bran is used as a health food supplement, perhaps of more concern is rice bran solubles, which are marketed as a superfood and as a supplement to malnourished children in international aid programs. Five rice bran solubles products were tested, sourced from the United States and Japan, and were found to have 0.61-1.9 mg/kg inorganic arsenic. Manufactures recommend approximately 20 g servings of the rice bran solubles per day, which equates to a 0.012-0.038 mg intake of inorganic arsenic. There are no maximum concentration levels (MCLs) set for arsenic or its species in food stuffs. EU and U.S. water regulations, set at 0.01 mg/L total or inorganic arsenic, respectively, are based on the assumption that 1 L of water per day is consumed, i.e., 0.01 mg of arsenic/ day. At the manufacturers recommended rice bran solubles consumption rate, inorganic arsenic intake exceeds 0.01 mg/ day, remembering that rice bran solubles are targeted at malnourished children and that actual risk is based on mg kg(-1) day(-1) intake. 相似文献
993.
Angelo Pedro Jacomino Ricardo Alfredo Kluge Claire Isabel Grígoli de Luca Sarantpoulos Jos Maria Monteiro Sigrist 《Packaging Technology and Science》2001,14(1):11-19
Guavas cv. ‘Kumagai’ were packed in several plastic materials and stored at 10°C and 85–90% relative humidity (RH) for 7, 14, 21 and 28 days (+3 days at 25°C). The plastic materials studied were: multilayer co‐extruded polyolephine film with selective permeability (PSP), low‐density polyethylene film (LDPE), LDPE film with mineral incorporation (LDPEm) and heat‐shrinkable polyolephine film (SHR). Guavas not packed were taken as control samples. The physicochemical characteristics of the fruits, O2 and CO2 transmission rates of the packaging materials and gas composition at the package headspace were evaluated. The LDPE film, 69 µm in thickness, with the lowest permeability to both O2 and CO2, led to anaerobiosis and high CO2 concentration inside the packages and promoted physiological disturbances and changes in fruit flavour. The SHR film, 15 µm in thickness, was the most permeable to CO2 and had quite high O2 transmission, which modified the inner atmosphere of the packages slightly. The fruits packed in this film showed a poorer quality than the controls, possibly due to the heat produced during the shrinking of the film. The LDPEm film, 24 µm in thickness, was almost as permeable to CO2 but had reduced O2 transmission, promoting an atmosphere of equilibrium of 3% O2 and 4.5% CO2. Fruits packed in this film kept their skin colour and pulp firmness, suitable for consumption up to 14 days. The PSP film, 35 µm in thickness, had the greatest O2 transmission but just over half of the CO2 transmission of LDPEm, promoting an atmosphere of equilibrium of 0.5% O2 and 4.5% CO2 inside the packages. Fruits packed in such packages kept their physicochemical characteristics up to 21 days. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
994.
Criticality of the geological copper family 总被引:1,自引:0,他引:1
Nassar NT Barr R Browning M Diao Z Friedlander E Harper EM Henly C Kavlak G Kwatra S Jun C Warren S Yang MY Graedel TE 《Environmental science & technology》2012,46(2):1071-1078
Because modern technology depends on reliable supplies of a wide variety of materials, and because of increasing concern about those supplies, a comprehensive methodology has been created to quantify the degree of criticality of the metals of the periodic table. In this paper, we apply this methodology to the elements of the geological copper family: Cu, As, Se, Ag, Te, and Au. These elements are technologically important, but show a substantial variation in different factors relating to their supply risk, vulnerability to supply restriction, and environmental implications. Assessments are made on corporate, national, and global levels for year 2008. Evaluations of each of the multiple indicators are presented and the results plotted in "criticality space", together with Monte Carlo simulation-derived "uncertainty cloud" estimates for each of the aggregated evaluations. For supply risk over both the medium term and long term, As is the highest risk of the six metals, with Se and Ag nearly as high. Gold has the most severe environmental implications ranking. Vulnerability to supply restriction (VSR) at the corporate level for an invented solar cell manufacturing firm shows Se, Te, and Cu as approximately equal, Cu has the highest VSR at the national level, and Cu and Au have the highest VSRs at the global level. Criticality vector magnitudes are greatest at the global level for As (and then Au and Ag) and at the national level for As and Au; at the corporate level, Se is highest with Te and Cu lower. An extension of this work, now in progress, will provide criticality estimates for several different development scenarios for the period 2010-2050. 相似文献
995.
996.
Influence of energy balance on the somatotrophic axis and matrix metalloproteinase expression in the endometrium of the postpartum dairy cow 总被引:1,自引:0,他引:1
Wathes DC Cheng Z Fenwick MA Fitzpatrick R Patton J 《Reproduction (Cambridge, England)》2011,141(2):269-281
Postpartum dairy cows enter a period of negative energy balance (NEB) associated with low circulating IGF1, during which the uterus must undergo extensive repair following calving. This study investigated the effects of NEB on expression of IGF family members and related genes in the involuting uterus. Cows were allocated to two treatments using differential feeding and milking regimes to produce mild NEB or severe NEB (SNEB). Uterine endometrial samples collected 2 weeks post partum were analysed by quantitative PCR. The expression of IGF-binding protein 4 (IGFBP4) mRNA increased in the endometrium of SNEB cows, with trends towards increased IGFBP1 and reduced IGFBP6 expression. There were no significant differences between treatments in mRNA expression of IGF1, IGF2 or of any hormone receptor studied, but significant correlations across all cows in the expression levels of groups of receptors suggested common regulatory mechanisms: type 1 IGF receptor (IGF1R), IGF2R and insulin receptor (INSR); GHR with ESR1; and ESR2 with NR3C1. The expression of IGF1R and INSR also positively correlated with the circulating urea concentration. Matrix metalloproteinases (MMPs) are important in tissue remodelling and can affect IGF signalling via interaction with IGFBPs. The expression levels of MMP1, MMP3, MMP9 and MMP13 mRNAs all showed major upregulation in the endometrium of cows in SNEB and all except MMP9 were highly correlated with expression of IGFBP4. Alpha(2)-HS-glycoprotein (AHSG) and PDK4, two genes implicated in insulin resistance, were also highly expressed in SNEB. These results suggest that cows in SNEB experience alterations to the IGF and insulin signalling pathways in the postpartum endometrium. This may affect the rate of tissue repair with a possible negative impact on subsequent fertility. 相似文献
997.
Application of factorial kriging analysis to the FOREGS European topsoil geochemistry database 总被引:1,自引:0,他引:1
Imrie CE Korre A Munoz-Melendez G Thornton I Durucan S 《The Science of the total environment》2008,393(1):96-110
Concern about increasing levels of trace elements in the environment has led to the development and implementation of a global programme to determine the current baseline levels of these chemicals in the Earth's surface. The FORum of European Geological Surveys (FOREGS) has recently published a geochemical database for Europe, while progress on similar databases is continuing in other major regions of the world. The FOREGS database comprises multimedia samples collected at a resolution of approximately 72x72 km from 26 European countries. This enables the investigation of the factors governing geochemical variation on a continental scale, potentially allowing contributions of natural processes to be appreciated prior to setting environmental quality standards. This paper investigates the variation in European topsoil geochemistry using factorial kriging analysis, which performs principal components analysis at different spatial scales. The results are interpreted with the aid of a GIS database. Four spatial scales were identified: a nugget component representing variation over a range less than the sampling density; a 'short' scale component with a range of 296 km; an 'intermediate' scale component (875 km); and a 'long' scale component (1750 km). The first three principal components (PCs) of the nugget covariance matrix explained 22.2% of the overall variance, representing local variation in geology, land use, weathering and organic matter content. The first two PCs of the short range structure explained 12.6% of the variance, representing variation according to the major structural divisions of Europe, and to carbonate content. The first PC of the intermediate structure explained 7.2% of the variance and was found to relate to glacial history and Quaternary deposition. Finally, the first three PCs of the long range structure explained 29.6% of the variance and represented variation due to mineralisation, soil texture, climate and possibly anthropogenic contamination. 相似文献
998.
Positive and negative emotionality: Trajectories across six years and relations with social competence. 总被引:1,自引:0,他引:1
Sallquist Julie Vaughan; Eisenberg Nancy; Spinrad Tracy L.; Reiser Mark; Hofer Claire; Zhou Qing; Liew Jeffrey; Eggum Natalie 《Canadian Metallurgical Quarterly》2009,9(1):15
The goals of the present study were to examine (1) the mean-level stability and differential stability of children's positive emotional intensity, negative emotional intensity, expressivity, and social competence from early elementary school-aged to early adolescence, and (2) the associations between the trajectories of children's emotionality and social functioning. Using four waves of longitudinal data (with assessments 2 years apart), parents and teachers of children (199 kindergarten through third grade children at the first assessment) rated children's emotion-related responding and social competence. For all constructs, there was evidence of mean-level decline with age and stability in individual differences in rank ordering. Based on age-centered growth-to-growth curve analyses, the results indicated that children who had a higher initial status on positive emotional intensity, negative emotional intensity, and expressivity had a steeper decline in their social skills across time. These findings provide insight into the stability and association of emotion-related constructs to social competence across the elementary and middle school years. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
999.
Matthews J. S.; Ponitz Claire Cameron; Morrison Frederick J. 《Canadian Metallurgical Quarterly》2009,101(3):689
This study examined gender differences in self-regulation in the fall and spring of kindergarten and their connection to gender differences in 5 areas of early achievement: applied problems (math), general knowledge, letter–word identification, expressive vocabulary, and sound awareness. Behavioral self-regulation was measured using both an objective direct measure (N = 268; Head-Toes-Knees-Shoulders task) and, for a subsample of children, a teacher report of classroom self-regulatory behavior (n = 156; Child Behavior Rating Scale). Results showed that girls outperformed boys in both assessments. Although gender differences in self-regulation were clear, no significant gender differences were found on the 5 academic achievement outcomes, as measured by the Woodcock–Johnson III Tests of Achievement. Self-regulation consistently predicted math and sound awareness, although links were stronger with the direct measure as compared with teacher reports. Implications for understanding the role of gender and self-regulation in early and later academic achievement and the role of self-regulation in particular areas of achievement are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
1000.
Claire Ducrot-Boisgontier Julien Parmentier Luc Delmotte Joël Patarin 《Journal of Materials Science》2009,44(24):6571-6575
Ordered microporous carbons were synthesized by the nanocasting process using EMC-2 zeolite (EMT structure type) and acetylene
as a mould and a carbon precursor, respectively. In this study, the conditions of the synthesis methods for preparing the
ordered microporous carbons were examined. Temperature and duration parameters for the chemical vapour infiltration were optimized
to yield an ordered carbon replica that displays up the three XRD diffraction peaks. This faithful replica exhibits also a
high micropore volume (1.3–1.4 cm3/g) with mainly supermicroporosity, a high specific surface area (>2900 m2/g) and nearly no mesoporosity. The pore size distribution calculated with NLDFT method from nitrogen physisorption data shows
three maxima at 0.6, 1.0 and 1.8 nm diameters. The second is due to the zeolite wall dissolution. The first and the third
are attributed to different types of default. Compared to the classical two-step procedure, the direct infiltration with acetylene
appears an interesting route for the preparation of ordered microporous carbon replicas with high micropore volume. 相似文献