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排序方式: 共有18条查询结果,搜索用时 15 毫秒
1.
A 92–95% conversion of high fructose corn syrup (HFCS) or crystalline D -fructose to 5-chloromethylfurfuraldehyde (CMF) was achieved using 300 mol% of concentrated hydrochloric acid in chlorobenzene, under a nitrogen atmosphere, a reaction temperature of 75°C and a reaction time of 1–2 h. Constant high-speed stirring was essential for high yields and purity of CMF. Inferior yields of CMF were obtained from glucose and starch. Saccharine, phenyl sulphone and thiuronium derivatives were prepared and characterised. The use of surfactants did not improve the yields of CMF.  相似文献   
2.
Carbon nanofibers (CNFs), cylindrical nanostructures containing graphene, were synthesized directly from South African fly ash (a waste product formed during the combustion of coal). The CNFs (as well as other carbonaceous materials like carbon nanotubes (CNTs)) were produced by the catalytic chemical vapour deposition method (CCVD) in the presence of acetylene gas at temperatures ranging from 400°C to 700°C. The fly ash and its carbonaceous products were characterized by transmission electron microscopy (TEM), thermogravimetric analysis (TGA), laser Raman spectroscopy and Brunauer-Emmett-Teller (BET) surface area measurements. It was observed that as-received fly ash was capable of producing CNFs in high yield by CCVD, starting at a relatively low temperature of 400°C. Laser Raman spectra and TGA thermograms showed that the carbonaceous products which formed were mostly disordered. Small bundles of CNTs and CNFs observed by TEM and energy-dispersive spectroscopy (EDS) showed that the catalyst most likely responsible for CNF formation was iron in the form of cementite; X-ray diffraction (XRD) and Mössbauer spectroscopy confirmed these findings.  相似文献   
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In recent years, concern has been raised about girls’ involvement in sexual activity at progressively younger ages. Little is known about the prevalence of emerging intimate behaviors, the psychosocial factors associated with these behaviors, or the moderating effects of ethnicity on these associations in early adolescence. In the current prospective study, we examined the prevalence and predictors of sexually intimate behaviors at age 12 years in an urban community sample of 1,116 ethnically diverse girls. Cluster analysis revealed 3 groups at age 12: no sexual behavior, mild behavior (e.g., holding hands), and moderate behavior (e.g., laying together). Minority status girls reported higher rates of both mild and moderate sexually intimate behaviors compared with European American girls. After controlling for the significant effects of age 11 intimate behaviors, lifetime alcohol use, poor parent–child communication, deviant peer behavior, onset of menarche, and interactions between ethnicity and impulsivity, social self-worth and depression uniquely increased the odds of engaging in moderately intimate behaviors at age 12 years. Parenting characteristics increased the likelihood of moderate, relative to mild, behaviors. For European American girls only, high levels of impulsivity and low social self-worth were associated with a higher likelihood of engaging in moderate intimate behaviors, whereas high levels of depressive symptoms reduced the odds. The results suggest that early prevention efforts need to incorporate awareness of different social norms relating to sexual behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
5.
This paper describes a system for performing alignment of subtitles to audio on multigenre broadcasts using a lightly supervised approach. Accurate alignment of subtitles plays a substantial role in the daily work of media companies and currently still requires large human effort. Here, a comprehensive approach to performing this task in an automated way using lightly supervised alignment is proposed. The paper explores the different alternatives to speech segmentation, lightly supervised speech recognition and alignment of text streams. The proposed system uses lightly supervised decoding to improve the alignment accuracy by performing language model adaptation using the target subtitles. The system thus built achieves the third best reported result in the alignment of broadcast subtitles in the Multi–Genre Broadcast (MGB) challenge, with an F1 score of 88.8%. This system is available for research and other non–commercial purposes through webASR, the University of Sheffield’s cloud–based speech technology web service. Taking as inputs an audio file and untimed subtitles, webASR can produce timed subtitles in multiple formats, including TTML, WebVTT and SRT.  相似文献   
6.
Food Science and Biotechnology - In the present work, we addressed the impact of a human–food web–animal interface on the prevalence of food-borne pathogens in mixed farms of Tamil...  相似文献   
7.
The pulp extracts of twenty-one varieties of citrus fruits (oranges, satsumah, clementine, mandarins, tangor, bergamot, lemon, tangelos, kumquat, calamondin and pamplemousses), commonly grown in Mauritius, were characterised in terms of their total soluble solids (TSS), titratable acidity (TA), polyphenol composition and vitamin C contents. Total phenolics ranged from 406.3 ± 14 to 1694 ± 19 ??g g− 1 fresh weight (FW). Total flavonoids varied between 133 ± 6 and 965 ± 7 ??g g− 1 FW and vitamin C contents were from 166 ± 19 ??g/mL to 677 ± 22 ??g/mL. The pulp of a pamplemousse variety had the highest TSS/TA ratio whereas lemon pulps had lowest TSS/TA ratios. The antioxidant activities of the pulp extracts were assessed and total phenolics correlated strongly with the trolox equivalent antioxidant capacity (TEAC), ferric reducing antioxidant capacity (FRAP) and hypochlorous acid (HOCl) scavenging activity assays. Based on their antioxidant activities, nine citrus fruits namely, one orange, tangor, kumquat, calamondin and pamplemousse variety and two mandarin and tangelo varieties were further characterised for their flavanone, flavonol and flavone levels by HPLC. Hesperidin (6.89 ± 0.06 to 26.98 ± 0.07 mg/g FW) and narirutin (0.27 ± 0.01 and 20.91 ± 0.10 mg/g FW) were present at high concentrations compared to the other flavonoid glycosides in the pulp extracts. Naringin was detected only in pulp extracts of pamplemousses. In the light of the data obtained, citrus fruit pulps represent an important source of phytochemicals with potent antioxidant capacity.  相似文献   
8.
A novel method to quantify 1,4-dioxane in finished cleaning products using headspace gas chromatograph with mass spectrometry (HS GC/MS), single ion monitoring, and a fully deuterated internal standard has been developed. The method generates very linear calibration curves with a R2 of at least 0.99, excellent accuracy with spike/recovery of 97%–102%, and effective precision of 1%–7%RSD for different cleaning products. The method also produces an instrument limit of quantitation (LOQ) of <20 ppb, and sample LOQ of <100 ppb. The method robustness was demonstrated with a ten-lab round-robin exercise that showed that even with some unexpected deviations from the method, excellent analytical results were obtained from the different labs. This new method will be valuable to evaluate consumer products impacted by government regulation to limit 1,4-dioxane concentrations in complex matrices.  相似文献   
9.
The high visibility trim requirements for NFPA 1971 (2007 ed.) turnout gear are intended to provide the user conspicuity enhancements in both daytime and nighttime environments. This study evaluated the reflectance, color and fluorescence properties of high visibility trim on firefighters used turnout gear. Forty-four used garments, grouped in age categories from 2 to 10 years (retired), were visually evaluated according to the Section 4 of the NFPA 1851—Advanced Inspection Checklist. Advanced inspection identified damaged trim on 21 of the 46 garments. The damaged areas, located primarily at the cuffs and lower front hem, were not as reflective but passed the subjective flashlight test. A data sampling plan for retroreflective values was constructed for the coats and pants and the coefficients of retroreflection were collected to provide a measure of the nighttime conspicuity. To characterize the fluorescent (daytime) properties of the trim on the used garments the values for fluorescence and color box coordinates were measured. The measured coefficient of retroreflection (RA, cd/lux/m2) for all garments (average of all values in the sampling plan) was greater than 3× the minimum NFPA 1851 requirement. Therefore, all used gear provided substantial nighttime conspicuity enhancement including the retired gear.  相似文献   
10.
This study sought to identify some of the factors that lead to assertive responding to sexual harassment. Responses of 120 female undergraduates (aged 19–50 yrs) to hypothetical scenarios of sexual harassment by male professors or teaching assistants were investigated. Two situational variables (ambiguity of the behavior and harasser status) and 1 individual difference variable (coping style) were examined. Participants completed a coping inventory and a questionnaire containing 1 of 4 harassment scenarios, with measures of affect, perceptions of the instructor, acknowledgment of the behavior as sexual harassment, and behavioral responses at 2 stages. Less ambiguous harassment situations were associated with greater negative affect, acknowledgment of sexual harassment, and more assertive responding. Coping style, but not harasser status, was also related to response strategies. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
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