Toxic potential of materials at the nanolevel   总被引：12，自引：0，他引：12  

Nel A  Xia T  Mädler L  Li N 《Science (New York, N.Y.)》2006,311(5761):622-627

Nanomaterials are engineered structures with at least one dimension of 100 nanometers or less. These materials are increasingly being used for commercial purposes such as fillers, opacifiers, catalysts, semiconductors, cosmetics, microelectronics, and drug carriers. Materials in this size range may approach the length scale at which some specific physical or chemical interactions with their environment can occur. As a result, their properties differ substantially from those bulk materials of the same composition, allowing them to perform exceptional feats of conductivity, reactivity, and optical sensitivity. Possible undesirable results of these capabilities are harmful interactions with biological systems and the environment, with the potential to generate toxicity. The establishment of principles and test procedures to ensure safe manufacture and use of nanomaterials in the marketplace is urgently required and achievable.  相似文献   

An adaptive composite density estimator for <Emphasis Type="Italic">k</Emphasis>-tree sampling     

Steen Magnussen  Lutz Fehrman  William J. Platt 《European Journal of Forest Research》2012,131(2):307-320

Density estimators for k-tree distance sampling are sensitive to the amount of extra Poisson variance in distances to the kth tree. To lessen this sensitivity, we propose an adaptive composite estimator (COM). In simulated sampling from 16 test populations, a three-component composite density estimator (COM)–with weights determined by a multinomial logistic function of four readily available ancillary variables–was identified as superior in terms of average relative absolute bias. Results from a different set of nine validation populations–with widely different stem densities and spatial patterns of tree locations—confirmed that relative root mean squared errors (RRMSE) of COM were, on average, considerably lower than those obtained with the three-component k-tree density estimators. The RRMSE performance of COM improved with increasing values of k. With k = 6 and sample sizes of 10, 20, and 30, the average relative bias of COM was between −5 and 5% in seven validation populations but in an open low-density savanna-like population bias reached −12% (1979 data) and 7% (1996 data). For k = 6 and n = 10, the RRMSE of COM was, in six of the nine validation populations, within 3.3 percentage points of the RRMSE for sampling with fixed-area plots. Jackknife estimates of the precision of COM estimates of density were negatively biased, leading to under-coverage (7%) of computed 95% confidence intervals.  相似文献   

Erratum to: An adaptive composite density estimator for k-tree sampling     

Steen Magnussen  Lutz Fehrman  William J. Platt 《European Journal of Forest Research》2012,131(2):321-321

  相似文献   

Ocean science. A dive to Challenger Deep     

Lutz RA  Falkowski PG 《Science (New York, N.Y.)》2012,336(6079):301-302

  相似文献   

Bordetella bronchiseptica infection in cats. ABCD guidelines on prevention and management     

Herman Egberink  Diane Addie  Sándor Belák  Corine Boucraut-Baralon  Tadeusz Frymus  Tim Gruffydd-Jones  Katrin Hartmann  Margaret J. Hosie  Albert Lloret  Hans Lutz  Fulvio Marsilio  Maria Grazia Pennisi  Alan D. Radford  Etienne Thiry  Uwe Truyen  Marian C. Horzinek 《Journal of Feline Medicine and Surgery》2009,11(7):610-614

  相似文献   

Restorative removal of plant litter and vegetation 40 years after abandonment enhances re-emergence of steppe grassland vegetation   总被引：1，自引：0，他引：1  

Eszter Ruprecht  Márton Z. Enyedi  R. Lutz Eckstein 《Biological conservation》2010,143(2):449-456

  相似文献   

Serum cobalamin, urine methylmalonic acid, and plasma total homocysteine concentrations in Border Collies and dogs of other breeds     

S Lutz  AC Sewell  B Bigler  B Riond  CE Reusch  PH Kook 《American journal of veterinary research》2012,73(8):1194-1199

Objective-To determine reference ranges for serum cobalamin (Cbl), urine methylmalonic acid (uMMA), and plasma total homocysteine (tHcys) concentrations and to compare values for healthy control dogs with values for Border Collies (BCs), a breed in which hereditary cobalamin deficiency has been identified. Animals-113 BCs, 35 healthy control dogs fed a typical diet, and 12 healthy dogs fed a bone and raw food diet exclusively. Procedures-Urine and blood samples were obtained from each dog and Cbl, uMMA, and tHcys concentrations were determined. Results-Reference ranges for Cbl (261 to 1,001 ng/L), uMMA (0 to 4.2 mmol/mol of creatinine), and tHcys (4.3 to 18.4 μmol/L) concentrations were determined. Four BCs had a Cbl concentration lower than the assay detection limit (150 ng/L); median uMMA and tHcys concentrations in these dogs were 4,064 mmol/mol of creatinine and 51.5 μmol/L, respectively. Clinical abnormalities included stunted growth, lethargy, anemia, and proteinuria. Abnormalities improved after administration of cobalamin. Of the 109 healthy BCs with Cbl and tHcys concentrations within reference ranges, 41 (37.6%) had a high uMMA concentration (range, 5 to 360 mmol/mol). Results for dogs fed raw food were similar to those for control dogs. Conclusions and Clinical Relevance-Hereditary cobalamin deficiency is a rare disease with various clinical signs. The finding of methylmalonic aciduria in healthy eucobalaminemic BCs and BCs with clinical signs of Cbl deficiency was surprising and indicated these dogs may have defects in intracellular processing of Cbl or intestinal Cbl malabsorption, respectively. Studies investigating Cbl absorption and metabolic pathways are warranted.  相似文献   

THE REACTION OF DROSOPHILA TO ULTRAVIOLET     

Lutz FE  Richtmyer FK 《Science (New York, N.Y.)》1922,55(1428):519-520

  相似文献   

SPECIAL ARTICLES     

Lutz FE 《Science (New York, N.Y.)》1905,22(556):249-250

  相似文献   

Anaplasma phagocytophilum infection in a dog: identifying the causative agent using PCR     

Kirtz G  Meli M  Leidinger E  Ludwig P  Thum D  Czettel B  Kölbl S  Lutz H 《The Journal of small animal practice》2005,46(6):300-303

A diagnosis of Anaplasma phagocytophilum infection was confirmed in a two-year-old male golden retriever displaying few clinical and haematological abnormalities. This was achieved by demonstrating ehrlichial organisms in circulating neutrophils, by indirect immunofluorescence assay using A phagocytophilum as an antigen, and by detecting DNA specific for the 16S rRNA gene of granulocytic Anaplasma by PCR. After treatment with doxycycline for 10 days the dog showed improvement and the laboratory values returned to normal.  相似文献