Reduced trials and reliability of visual-acuity thresholds obtained by the method of constant stimuli.

To determine the effect of a reduction in trials per stimulus upon reliability of visual-acuity thresholds computed by the method of constant stimuli, visual-acuity thresholds were determined for 15 Ss, using a Landolt ring. Thresholds were computed using 5 stimulus values and 5, 10, 20, 30, 40, and 50 presentations per stimulus. Retest reliabilities of .92 and higher were obtained for as few as 10 trials per stimulus. It is concluded that "1… . classical… investigators probably tended to utilize more judgments than are necessary… 2… . for purposes of estimating absolute thresholds, the Müller-Urban constant method with five stimulus sizes appears to yield satisfactorily reliable thresholds… when as few as 10 trials per stimulus and 4-choice response categories are used." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Isolation of a bacterial enzyme releasing axillary malodor and its use as a screening target for novel deodorant formulations

Axillary odor is known since 50 years to be formed upon the action of Corynebacteria on odorless axilla secretions, but the nature of the bacterial enzymes involved in this process remained a mystery. We identified the known axilla odor determinant 3-methyl-2-hexenoic acid in hydrolyzed axilla secretions along with a new, chemically related compound, 3-hydroxy-3-methyl-hexanoic acid. The natural, odorless precursors of both these acids were purified from non-hydrolyzed fresh axilla secretions. The malodorous acids were shown to be covalently linked to a glutamine residue in fresh axilla secretions. Corynebacteria, but not Staphylococci, isolated from the axilla were found to release the acids from these precursors in vitro. A Zn(2+) -dependent aminoacylase mediating this cleavage was then purified from Corynebacterium striatum Ax20 and the corresponding gene agaA was cloned and heterologously expressed in Escherichia coli. Based on these biochemical findings, novel approaches in research on axilla malodor control are presented: (a) With a new test method using the isolated Corynebacteria and their enzymatic activity, the direct malodor-controlling activity of existing cosmetic ingredients was evaluated. (b) The structure of the natural malodor precursor was modified by replacing the malodor acid with fragrance molecules. These new fragrance precursors were shown to be cleaved by the same aminoacylase.     

Scotopic sensitivity in coyotes (Canis latrans).

The absolute scotopic limen for light intensity was measured for three 10-mo-old female coyotes. The methodology was similar to that used by Blough in determining psychophysical thresholds in pigeons. Three coyotes were operantly conditioned to depress one of two foot treadles, left or right, depending on the condition of the stimulus light. Scotopic adaptation curves for each coyote were generated. Nonlinear regression curves were then fitted to the raw data. The mean scotopic thresholds did not differ significantly. However, time to the curves' asymptotes did differ significantly for one of the coyotes. The adaptation curves showed a distinct rod-cone "break," and retinal histology confirmed that the coyote has a duplex retina with a preponderance of rods. In addition, electroretinographic analysis showed the relative contributions of rods and cones at various light intensities and indicated a rod-cone break at approximately 15 min. Scotopic spectral sensitivity curves were also generated. The coyotes' scotopic visual threshold is exceeded by the natural illumination available under many nocturnal conditions. The results are discussed in relation to the ecology of the species. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Complex dynamics in a threshold advertising model

During the last decade economic models of varying complexity have been studied by using the qualitative theory of nonlinear dynamical systems theory. The purpose of the present paper is to analyze an economic model which is as simple as possible but exhibits sufficient nonlinearity to admit chaotic orbits. A firm's market share is assumed to be influenced only by a simple threshold advertising rule. It turns out that such a simple rule may create complex behavioural patterns, i.e., periodic orbits of any length and even chaotic, seemingly unpredictable time paths. By using the package LOCBIF we are able to investigate for which model parameters chaos arises and how the transition from stable equilibrium to chaos occurs.This work has been financially supported by the Austrian Science Foundation, project No. 7783-PHY.     

HS-SPME-GC-MS/MS结合ROAV值鉴定新疆库车小白杏的关键香气物质

该研究优化了顶空固相微萃取-气相色谱双质谱（Headspace Solid Phase Microextraction with Gas Chromatography Coupled to Tandem Mass Spectrometry,HS-SPME-GC-MS/MS）联用技术检测新疆库车小白杏挥发性化合物组成的方法,并基于相对香气活性值（Relative Odor Activity Value,ROAV）鉴定其关键性香气物质,对小白杏呈香属性指纹进行分析。结果表明：使用50/30 μm聚二乙烯基苯/碳吸附剂/聚二甲基硅氧烷（Divinylbenzene/Carboxen/Polydimethylsiloxane,DVB/CAR/PDMS）的萃取纤维,萃取温度为65 ℃,萃取时间为50 min时,萃取效率最高。在该条件下,共鉴定出小白杏中含有的46种挥发性物质,其中醇类物质含量最高（34.57%）,其次是酯类（33.77%）和醛类物质（24.77%）。ROAV分析表明,β-紫罗兰酮、γ-癸内酯、二氢-β-紫罗兰酮、芳樟醇、月桂烯以及α-紫罗兰酮为关键香气物质（ROAV>1）,赋予了小白杏浓郁的果香、花香以及木香。呈香属性指纹分析表明,与吊干杏相比,小白杏的青草香、果香、椰子香、柑橘香以及花香更为强烈,只有木香较弱。该研究确定了新疆库车小白杏中含有的关键香气成分,可为探索具有小白杏风味的产品研发提供参考依据。     

GC-MS/O结合香气活性值表征烧麦中关键香气成分及其贮存过程中的变化情况

为确定烧麦中的关键香气成分及其贮存过程中的变化情况,采用溶剂萃取结合溶剂辅助风味成分蒸发提取烧麦中的挥发性成分,所得提取物经气相色谱-嗅闻联用仪与气相色谱-质谱联用仪分析,共鉴定出50个香气活性成分。通过香气提取物稀释分析,测定香气活性成分的香气稀释因子,其中1-辛烯-3-醇、茴香脑、愈创木酚、2-戊基呋喃等具有最高的香气稀释因子（6 561）。采用内标标准曲线法对37个香气稀释因子不低于81的成分进行定量分析;根据定量结果和阈值,计算物质的香气活性值,其中21个香气活性成分的香气活性值不低于1,被确定为烧麦的关键香气成分。通过分析室温贮存0～13个月后烧麦中37个成分含量并计算其香气活性值,发现烧麦贮存过程中关键香气成分的数量不变,除酱油酮、己醛和4-乙烯基愈创木酚的含量下降外,烧麦中多数重要香气活性成分含量变化较小。     

基于ROAV和嗅闻技术分析乳脂的关键风味化合物

利用固相微萃取-气相色谱-质谱（solid phase microextraction-gas chromatography-mass,SPME-GC-MS）分析国内市场常见的8种乳脂产品（4种黄油、2种稀奶油及2种发酵黄油）的挥发性化合物,并采用相对气味活度值（relative odor activity value,ROAV）和气相色谱-嗅闻（gas chromatography-olfactometry,GC-O）鉴定关键风味化合物。结果发现：8种乳脂产品中共检出40种挥发性化合物,主要包括7种醛类、6种甲基酮类、7种脂肪酸类和7种内酯类。ROAV法确定的关键风味化合物共17种,GC-O可识别7种关键风味化合物。其中,乙酸、丁酸、己酸、δ-辛内酯、δ-癸内酯、γ-十二内酯的ROAV大于1,且可被GC-O识别,是最为重要的6种关键风味化合物。     

基于电子鼻技术分析开花对前胡气味的影响

为研究开花前后两种前胡样品的气味指纹变化,探讨电子鼻应用于中药质量评价的可能性。采用电子鼻检测开花前后两种前胡样品气味在传感器上的响应值,采用主成分分析法(PCA)、判别因子分析法(DFA)进行分析,建立气味指纹图,并进行统计质量控制分析(SQC)。结果表明,电子鼻对开花前后两种前胡样品气味变化反应灵敏,可以完全区分,可以应用于中药气味鉴别研究。     

Steering nitrogen fertilisation by means of portable chlorophyll meter reduces nitrogen input and improves quality of fertigated cantaloupe (Cucumis melo L. var. cantalupensis Naud.)

BACKGROUND: Farming is considered one of the main causes of land degradation and underground water pollution. The increased availability of agricultural inputs has led to a dramatic rise in yields, which has resulted in soil fertility spoilage and overuse of fertilisers. Therefore horticultural practice improvement must consider appropriate nitrogen (N) management. This paper reports results on the application of an optical diagnostic system (N‐tester) to guide N fertilisation in muskmelon (Cucumis melo L.) over a 3 year trial. Results on fresh and postharvest quality are also presented. RESULTS: Fertilisation events mirrored increases in N‐tester values during the season, and a significant linear relationship (R² = 0.628) was observed between N‐tester readings and leaf chlorophyll content. The N‐tester‐guided fertilisation treatments were characterised by yields comparable to the control, but with significantly lower applications of N (down to 17–66% of the N distributed in the control). Moreover, the N‐tester treatments yielded fruits with higher sugar content. This was also true after storage, when N‐tester fruits also showed reduced weight loss associated with lower transpiration and ethylene emission rates. CONCLUSION: Through the use of ‘spy plots’ kept at optimal nutritional status and the adoption of a threshold for N application throughout the growing cycle of muskmelon, the N supply was significantly reduced. Therefore a correct application of N‐tester allowed the plant N requirement to be reduced and the fruit sugar content and storability to be increased without adversely affecting the yield. Copyright © 2009 Society of Chemical Industry     

非均匀光照条件下PCB图像的一种阈值分割方法

针对不均匀光照条件下的PCB图像及其特点,提出了用于消除伪边缘的判别因子,并结合边缘检测与局部阈值分割方法,对图像进行二值化处理.结果显示,与其他已有的几种分割方法相比,该方法有助于得到良好的分割结果,操作算法简单.