Detection Thresholds of 10 Odor-active Compounds Naturally Occurring in Food Using a Replicated Forced-Choice Ascending Method of Limits

2014 ◽  
Vol 29 (1) ◽  
pp. 43-55 ◽  
Author(s):  
Sara R. Jaeger ◽  
H. Nihal de Silva ◽  
Harry T. Lawless
Keyword(s):  
Forced Choice ◽  
Detection Thresholds ◽  
Active Compounds ◽  
Naturally Occurring

Pitch versus Brightness of Timbre: Detecting Combined Shifts in Fundamental and Formant Frequency

1993 ◽  
Vol 11 (1) ◽  
pp. 1-13 ◽  
Author(s):  
Laurent Demany ◽  
Catherine Semal
Keyword(s):  
Power Spectrum ◽  
Fundamental Frequency ◽  
Forced Choice ◽  
Spectral Envelope ◽  
Adaptive Procedure ◽  
Formant Frequency ◽  
Detection Thresholds ◽  
Perceptual Integration ◽  
Standard Tone ◽  
Independence Model

The pitch of a periodic tone depends on its fundamental frequency (F0), and the brightness of its timbre depends on the centroid of its power spectrum (Fc). The goal of the present study was to determine whether small shifts in F0 and in Fc are detected independently of each other. The standard tone used had an F0 of 400 Hz, five harmonics (400-2000 Hz), and a triangular spectral envelope peaking at an Fc of 1000 Hz. With a forced-choice adaptive procedure, detection thresholds were measured for (1) shifts in F0 alone (Fc being fixed), (2) shifts in Fc alone (F0 being fixed), and (3) combined shifts in F0 and Fc. The two components of the combined shifts were chosen to have the same level of detectability when presented alone. Overall, as expected from the independence model, the combined shifts were not better detected when their two components had the same direction (F0 and Fc both increase, or both decrease) than when they had opposite directions. However, substantial differences between subjects were observed with respect to the perceptual integration of shifts in F0 and in Fc.

Central nervous system active compounds. XIII. The use of aminomethylene phthalides in the synthesis of phthalideisoquinoline alkaloids

1983 ◽  
Vol 36 (12) ◽  
pp. 2493 ◽  
Author(s):  
SI Clarke ◽  
B Kasum ◽  
RH Prager ◽  
AD Ward
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Acidic Solution ◽  
Reaction Sequence ◽  
Active Compounds ◽  
Naturally Occurring ◽  
Aqueous Acidic Solution

Dimethylaminomethyleneisobenzofuranones react with alkoxyphenylethylamines in aqueous acidic solution to give phthalide isoquinolines (tetrahydroisoquinolinylisobenzofuranones) in moderate yields. N-Methylation gives the naturally occurring phthalideisoquinoline alkaloids. A number of examples of this reaction sequence are reported, including the synthesis of (�)-cordrastine, (�)-corlumine and (�)-adlumine.

scholarly journals Chirospecific synthesis: Catalysis and chiral pool hand in hand

2011 ◽  
Vol 83 (3) ◽  
pp. 435-443 ◽  
Author(s):  
Ari M. P. Koskinen
Keyword(s):  
Amino Acids ◽  
Natural Products ◽  
Chemical Synthesis ◽  
New Technologies ◽  
Amino Alcohols ◽  
Biologically Active Compounds ◽  
Biologically Active ◽  
New Techniques ◽  
Active Compounds ◽  
Naturally Occurring

Nature provides us with a wonderful pool of enantiopure starting materials for synthesis: amino acids, sugars, and many (but not all!) terpenes can be isolated even in large quantities in an uncompromised 100 % ee. Vicinal amino alcohols constitute a versatile group of organic structures; they are, in principle, available in enantiopure form from the chiral pool compounds or through chiral catalysis; they are potent intermediates for the synthesis of natural products and medicinally/biologically active compounds, and they provide a highly desirable scaffold for the construction of ligands for metals as well as organocatalysts. These new techniques will open up valuable new possibilities for the invention of new technologies for chemical synthesis, the desired course of chemical discoveries for the future. A robust entry to enantiopure vicinal amino alcohols from inexpensive naturally occurring amino acids has therefore become a key challenge for our endeavors in the development of methodology.

Multiple routes of chemosensitivity to free fatty acids in humans

2007 ◽  
Vol 292 (5) ◽  
pp. G1206-G1212 ◽  
Author(s):  
Angela Chalé-Rush ◽  
John R. Burgess ◽  
Richard D. Mattes
Keyword(s):  
Fatty Acids ◽  
Linoleic Acid ◽  
Free Fatty Acids ◽  
Sensory Systems ◽  
Forced Choice ◽  
Lower Sensitivity ◽  
Detection Thresholds ◽  
Olfactory Stimuli ◽  
Multiple Routes ◽  
Presentation Procedure

Selected free fatty acids (FFAs) are documented effective somatosensory and olfactory stimuli whereas gustatory effects are less well established. This study examined orthonasal olfactory, retronasal olfactory, nasal irritancy, oral irritancy, gustatory, and multimodal threshold sensitivity to linoleic, oleic, and stearic acids. Sensitivity to oxidized linoleic acid was also determined. Detection thresholds were obtained using a three-alternative, forced-choice, ascending concentration presentation procedure. Participants included 22 healthy, physically fit adults sensitive to 6- n-propylthiouracil. Measurable thresholds were obtained for all FFAs tested and in 96% of the trials. Ceiling effects were observed in the remaining trials. Greater sensitivity was observed for multimodal stimulation and lower sensitivity for retronasal stimulation. There were no statistically significant correlations for linoleic acid thresholds between different modalities, suggesting that each route of stimulation contributes independently to fat perception. In summary, 18-carbon FFAs of varying saturation are detected by multiple sensory systems in humans.

scholarly journals Flavonoids from Ulex Species

2000 ◽  
Vol 55 (7-8) ◽  
pp. 506-510 ◽  
Author(s):  
Patrícia Máximo ◽  
Ana Lourenço ◽  
Sónia Savluchinske Feio ◽  
Jose Carlos Roseiro
Keyword(s):  
Antifungal Activity ◽  
Open Chain ◽  
Active Compounds ◽  
Cladosporium Cucumerinum ◽  
Naturally Occurring ◽  
Nmr Data ◽  
Bioautographic Method ◽  
C Nmr

Abstract Nine flavonoids have been isolated from Ulex jussiaei and U. minor (Leguminosae). From both species the isoflavonoids ulexin A and the new naturally occurring ulexin B have been identified, together with isoderrone, the pterocarpans (-)-maackiain and (-)-4-methoxymaackiain, and the chalcone isobavachromene. The pterocarpan (-)-2-methoxymaackiain was only present in the first species and the isoflavones isolupalbigenin and ulexone A have been identified in the second one. 13C NMR data of isobavachromene, isolupalbigenin and ulexone A are also included. The antifungal activity of the isolated compounds was tested by the bioautographic method against Cladosporium cucumerinum. The most active compounds were the pterocarpans, the chalcone and the isoflavones with non-hydroxylated open chain prenyl substituents.

scholarly journals Pitch discrimination performance of ferrets and humans on a go/no-go task

2017 ◽  
Author(s):  
Kerry MM Walker ◽  
Amelia Davies ◽  
Jennifer K Bizley ◽  
Jan WH Schnupp ◽  
Andrew J King
Keyword(s):  
Discrimination Performance ◽  
Forced Choice ◽  
Pitch Discrimination ◽  
List Type ◽  
Human Species ◽  
Detection Thresholds ◽  
Pitch Processing ◽  
Pitch Change ◽  
2Afc Task ◽  
Neurophysiological Basis

ABSTRACTAnimal models are widely used to examine the neurophysiological basis of human pitch perception, and it is therefore important to understand the similarities and differences in pitch processing across species. Pitch discrimination performance is usually measured using two-alternative forced choice (2AFC) procedures in humans and go/no-go tasks in animals, potentially confounding human-to-animal comparisons. We have previously shown that pitch discrimination thresholds of ferrets on a 2AFC task are markedly poorer than those reported for go/no-go tasks in other non-human species (Walker et al., 2009). To better compare the pitch discrimination performance of ferret with other species, here we measure pitch change detection thresholds of ferrets and humans on a common, appetitive go/no-go task design. We found that ferrets’ pitch thresholds were ~10 times larger than that of humans on the go/no-go task, and were within the range of thresholds reported in other non-human species. Interestingly, ferrets’ thresholds were 100 times larger than human thresholds on a 2AFC pitch discrimination task using the same stimuli. These results emphasize that sensory discrimination thresholds can differ across tasks, particularly for non-human animals. Performance on our go/no-go task is likely to reflect different neurobiological processes than that on our 2AFC task, as the former required the subjects only to detect a pitch change while the latter required them to label the direction of the pitch change.ABBREVIATIONS2AFC2-Alternative Forced ChoiceF0Fundamental FrequencyHIGHLIGHTSPitch discrimination thresholds of ferrets were 10 times larger than those of humans on a go/no-go taskFerrets’ pitch thresholds are similar to those reported for a range of other mammalsPitch thresholds of ferrets, but not humans, were drastically better on the go/no-go task than a 2AFC task using the same stimuli

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