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71.
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74.
A simple and rapid method for the determination of naturally occurring, potentially hazardous glycoalkaloids (GAs) in potatoes
and their products has been developed. The procedure is based on the on-line solid-phase extraction of the acetic acid extracts
from potato products and combined with liquid chromatography (LC)-mass spectrometry (MS) in a fully automated system (Symbiosis™,
Spark Holland Instruments, Emmen, The Netherlands). As sorbent material HySphere™ 18HD was used for alkaloid enrichment. GAs
were eluted with the LC gradient and directly analysed by MS. Detection of the analytes was achieved in the sensitive multiple
reaction monitoring mode using two characteristic ions (m/z 98 as a qualifier for GAs and m/z 868.3 as a quantifier for α-solanine or m/z 852.4 for α-chaconine). Typical validation data for method precision (v
k α-solanine = 5.3–6.5, v
k α-chaconine = 3.4–15.4), accuracy (average recovery of α-solanine = 84%, average recovery of α-chaconine = 87%) and linearity
over the range from 1 to 1,000 ng ml−1 (R
2 = 0.9915 for α-solanine, R
2 = 0.9939 for α-chaconine) with detection limits of 0.3 ng ml−1 for α-chaconine and 0.5 ng ml−1 for α-solanine were obtained. GA contents of commercial potato products were determined by the new on-line method and afterwards
compared with those obtained with an established high-performance LC routine procedure. Better performance of the on-line
procedure was obvious from the standard deviations of both methods. Other advantages included a strong reduction of overall
analysis time, human intervention and solvent consumption as well as waste production. The time required for the on-line analysis
was 5 min, which would allow processing of almost 100 samples in 8 h. 相似文献
75.
E. Melanie DuPuis 《Agriculture and Human Values》2000,17(3):285-295
The advent of rBGH (recombinant bovinegrowth hormone) has spurred the establishment of anorganic milk industry. The food systems/commoditychain
analytical framework cannot fully explain therise of this new food. An adequate understanding ofthe consumer's role in the
food system/commodity chainrequires more attention to consumption as a form ofpolitics. One way to do this is to look at thepolitics
of other new social movements, especiallythose contesting mainstream notions of risk. From thisapproach, organic milk consumption
challenges rBGHfrom a ``Not-in-my-Body' or ``NIMB' politics of refusal,similar to the political refusal of neighborhoodresidents
in ``Not-in-My-Backyard' or ``NIMBY'environmental movements. The NIMB form of politics isnot a social movement of politically
consciousconsumers, yet it is still a political activity inwhich consumers participate in the formation of theindustry through
a process of ``reflexive consumption.'An analysis of producer-consumer discourse on milkcartons reveals the nature of this
political formation. 相似文献
76.
The impacts of crop rotations and N fertilization on microbial biomass C (Cmic) and N (Nmic) were studied in soils of two long-term field experiments initiated in 1978 at the Northeast Research Center (NERC) and in
1954 at the Clarion-Webster Research Center (CWRC), both in Iowa. Surface soil samples were taken in 1996 and 1997 from plots
of corn (Zea mays L.), soybeans (Glycine max (L.) Merr.), oats (Avena sativa L.), or meadow (alfalfa) (Medicago sativa L.) that had received 0 or 180 kg N ha–1 before corn and an annual application of 20 kg P and 56 kg K ha–1. The Cmic and Nmic values were determined by the chloroform-fumigation-extraction method and the chloroform-fumigation-incubation method, respectively.
The Cmic and Nmic values were significantly affected (P<0.05) by crop rotation and plant cover at time of sampling, but not by N fertilization. In general, the highest Cmic and Nmic contents were found in the multicropping systems (4-year rotations) taken in oats or meadow plots, and the lowest values
were found in continuous corn and soybean systems. On average, Cmic made up about 1.0% of the organic C (Corg), and Nmic contributed about 2.4% of the total N (Ntot) in soils at both sites and years of sampling. The Cmic values were significantly correlated with Corg contents (r≥0.41**), whereas the relationship between Cmic and Ntot was significant (r≤0.53***) only for the samples taken in 1996 at the NERC site. The Cmic : Nmic ratios were, on average, 4.3 and 6.4 in 1996, and 7.6 and 11.4 in 1997 at the NERC and CWRC sites, respectively. Crop rotation
significantly (P<0.05) affected this ratio only at the NERC site, and N fertilization showed no effect at either site. In general, multicropping
systems resulted in greater Cmic : Corg (1.1%) and Nmic : Ntot (2.6%) ratios than monocropping systems (0.8% and 2.1%, respectively).
Received: 9 February 1999 相似文献
77.
Karol A. Mathews DVM DVSc Melanie J. Brooks RVT Anne E. Valliant BSC 《Journal of Veterinary Emergency and Critical Care》1996,6(1):33-43
A one year prospective study was conducted to determine the association between intravenous catheter contamination and increased dwell time, and to identify any related risk factors. Intravenous catheters obtained from 23 cats and 98 dogs in the Intensive Care Unit at the Ontario Veterinary College with dwell times > 72 hours for the test group (n=58) and < 72 hours for a corresponding control group (n=63) were cultured between April 1991 and March 1992. One hundred and twenty one catheters were cultured, 16 jugular, 99 cephalic, and 6 saphenous. The overall contamination rate was 13 out of 121 catheters cultured (10.7%); 9/63 (14.3%) control and 4/58 (6.9%) test catheters. The bacteria isolated were E.aerogenes, S.aureus (3), P.aeruginosa, P.multocida, and Bacillus sp (7). The Bacillus sp positive catheters (5 control and 2 test) were placed during a five day period, and contaminated gauze squares were identified as the source of infection in these catheters. After these were removed from the study, the group infection rate was 6.9% control and 3.6% test. There was no significant difference between groups and no associated risk factors were identified. We conclude that intravenous dwell time need not be restricted to <72 hours. 相似文献
78.
Fijen Thijs P. M. Read Samantha F. J. Walker Melanie K. Gee Megan Nelson Warrick R. Howlett Brad G. 《Landscape Ecology》2022,37(7):1787-1799
Landscape Ecology - Landscape simplification is a main driver of insect decline, threatening crop pollination services. Changes in functional features in simplified agroecosystems may impact the... 相似文献
79.
Melanie C. Wergin Med. Vet. Kurt Ballmer-Hofer PhD Malgorzata Roos PhD Roger E. Achermann Med. Vet. Natalie Inteeworn Med. Vet. Margarete K. Akens Med. Vet. Hans Blattmann PhD Barbara Kaser-Hotz Dr. Med. Vet. 《Veterinary radiology & ultrasound》2004,45(3):247-254
High plasma vascular endothelial growth factor (VEGF) concentrations are associated with radiation resistance and poor prognosis. After an exposure to ionizing radiation in cell culture an early phase and a late phase of increased VEGF have been documented. The activation was dependent on the radiation dose. Therefore, the purpose of this study was to measure baseline plasma VEGF and changes in VEGF over the course of fractionated radiation therapy in dogs with spontaneous tumors. Dogs with tumors had a significantly higher pretreatment plasma VEGF than did dogs without tumors. Immediately after irradiation no increased plasma VEGF was observed. Over the course of radiation therapy there was an increased plasma VEGF in dogs treated with low doses per fraction/high total dose, whereas plasma VEGF remained stable in dogs irradiated with high doses per fraction/low total dose. The regulatory mechanisms are very complex, and therefore the value of plasma VEGF measurements as an indirect marker of angiogenesis induced by radiotherapy is limited. 相似文献
80.
Boly M Garrido MI Gosseries O Bruno MA Boveroux P Schnakers C Massimini M Litvak V Laureys S Friston K 《Science (New York, N.Y.)》2011,332(6031):858-862
Frontoparietal cortex is involved in the explicit processing (awareness) of stimuli. Frontoparietal activation has also been found in studies of subliminal stimulus processing. We hypothesized that an impairment of top-down processes, involved in recurrent neuronal message-passing and the generation of long-latency electrophysiological responses, might provide a more reliable correlate of consciousness in severely brain-damaged patients, than frontoparietal responses. We measured effective connectivity during a mismatch negativity paradigm and found that the only significant difference between patients in a vegetative state and controls was an impairment of backward connectivity from frontal to temporal cortices. This result emphasizes the importance of top-down projections in recurrent processing that involve high-order associative cortices for conscious perception. 相似文献