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Detection Thresholds (detection + threshold)

Distribution by Scientific Domains

Medical Sciences	51%
Life Sciences	16%
Chemistry	16%
Physics and Astronomy	6%
Earth and Environmental Science	6%

Distribution within Medical Sciences

Neurology	27%
Dermatology	23%
Pathology	7%
8 Other Subdomains	43%

Selected Abstracts

Best Estimated Aroma and Taste Detection Threshold for Guaiacol in Water and Apple Juice

JOURNAL OF FOOD SCIENCE, Issue 4 2005
Thomas A. Eisele
ABSTRACT: Alicyclobacillus acidoterrestris can produce sufficient guaiacol (methoxyphenol), a metabolic by-product of the bacterium, in apple juice to cause a detectable taint characterized by an antiseptic off-odor or distinct medicinal flavor and lingering aftertaste. Bacterial spoilage may not be visibly detectable. The objective of this study was to determine the best estimate threshold (BET) for detection of guaiacol in water and commercial pasteurized apple juice from concentrate using the forced-choice ascending concentration method of limits with an experienced 17-member sensory panel. The mean BET for aroma detection of guaiacol in water and apple juice was 0.48 ppb and 0.91 ppb, respectively. The mean BET for taste detection of guaiacol in water and apple juice was 0.17 ppb and 0.24 ppb, respectively. Individual aroma BET values ranged from 0.06 ppb to 4.71 ppb guaiacol in water and 0.17 ppb to 4.71 ppb for guaiacol in apple juice. Individual taste BET values ranged from 0.01 ppb to 4.71 ppb for guaiacol in water and apple juice. The taste BET was equal to or lower than the aroma BET for guaiacol in both water and apple juice for all panelists. There was about a 500-fold range in guaiacol taste detection between panelists, with some individuals exhibiting a BET value as low as 10 ppt (trillion). The information should be useful for developing quality assurance sensory methodology to evaluate potential apple juice flavor spoilage by Alicyclobacillus spp. [source]

Determination of Ortho- and Retronasal Detection Thresholds for 2-Isopropyl-3-Methoxypyrazine in Wine

JOURNAL OF FOOD SCIENCE, Issue 7 2007
G.J. Pickering
ABSTRACT:, 2-isopropyl-3-methoxypyrazine (IPMP) is a grape-derived component of wine flavor in some wine varieties as well as the causal compound of the off-flavor known as ladybug taint (LBT), which occurs when Harmonia axyridis beetles are incorporated with the grapes during juice and wine processing. The main objective of this study was to obtain robust estimates of the orthonasal (ON) and retronasal (RN) detection thresholds (DTs) for IPMP in wines of differing styles. The ASTM E679 ascending forced choice method of limits was used to determine DTs for 47 individuals in 3 different wines,Chardonnay, Gewürztraminer, and a red wine blend of Baco Noir and Marechel Foch. The group best estimate thresholds (BETs) obtained for IPMP (ng/L) were Chardonnay, ON: 0.32; Gewürztraminer, ON: 1.56, RN: 1.15, and red wine blend, ON: 1.03, RN: 2.29. A large variation in individual DTs was observed. Familiarity with LBT was inversely correlated with DTs for Gewürztraminer, and no difference in thresholds was observed between winemakers and nonwinemakers. We conclude that the human DT for IPMP is extremely low and influenced significantly by wine style and evaluation mode. We recommend against the reporting of single-threshold values for wine flavor compounds, and encourage the determination of consumer rejection thresholds for IPMP in wine. [source]

Neural correlates of binaural masking level difference in the inferior colliculus of the barn owl (Tyto alba)

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 4 2010
Ali Asadollahi
Abstract Humans and animals are able to detect signals in noisy environments. Detection improves when the noise and the signal have different interaural phase relationships. The resulting improvement in detection threshold is called the binaural masking level difference. We investigated neural mechanisms underlying the release from masking in the inferior colliculus of barn owls in low-frequency and high-frequency neurons. A tone (signal) was presented either with the same interaural time difference as the noise (masker) or at a 180° phase shift as compared with the interaural time difference of the noise. The changes in firing rates induced by the addition of a signal of increasing level while masker level was kept constant was well predicted by the relative responses to the masker and signal alone. In many cases, the response at the highest signal levels was dominated by the response to the signal alone, in spite of a significant response to the masker at low signal levels, suggesting the presence of occlusion. Detection thresholds and binaural masking level differences were widely distributed. The amount of release from masking increased with increasing masker level. Narrowly tuned neurons in the central nucleus of the inferior colliculus had detection thresholds that were lower than or similar to those of broadly tuned neurons in the external nucleus of the inferior colliculus. Broadly tuned neurons exhibited higher masking level differences than narrowband neurons. These data suggest that detection has different spectral requirements from localization. [source]

Detection thresholds of capsaicin: a new test to assess facial skin neurosensitivity

INTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 6 2005
R. Jourdain
The goal of this study was to assess the accuracy/reliability of a new test designed to measure cutaneous neurosensitivity. The test was carried out on a random population of 150 healthy adult women and was based on the determination of individual detection thresholds of topically applied capsaicin. Five capsaicin concentrations were used in 10% ethanol aqueous solution (3.16 × 10,5%; 1 × 10,4%; 3.16 × 10,4%; 1 × 10,3%; 3.16 × 10,3%). The methodology used to attain the detection threshold was capsaicin application in increasing concentration on the nasolabial folds. The vehicle was simultaneously applied following a split-face, single-blind plan. The test was stopped as soon as the subject reported a specific sensation lasting more than 30 s on the capsaicin side. The safety of the test was judged as excellent by the panellists since all the reported sensations were considered as slightly or moderately perceptible. The test allowed the classification of the test population according to six threshold levels corresponding to the sensitive reaction to one of the five capsaicin concentrations and to the absence of sensitivity to the highest concentration. Surprisingly, the distribution of the population was not unimodal and seemed to reveal the existence of two different sub-groups: individuals with a low capsaicin detection threshold and those with a high threshold. These two sub-populations strongly differed in their respective self-perception of sensitive skin. The higher the self-declared sensitive skin incidence was, the lower the detection threshold was. This new test of skin neurosensitivity is easy, quick, and truly painless. It appears to be a promising tool for the cosmetic diagnosis of sensitive skin. [source]

Bifunctional Eu3+ -doped Gd2O3 nanoparticles as a luminescent and T1 contrast agent for stem cell labeling

CONTRAST MEDIA & MOLECULAR IMAGING, Issue 2 2010
Zhilong Shi
Abstract Magnetic resonance tracking of stem cells has recently become an emerging application for investigating cell,tissue interactions and guiding the development of effective stem cell therapies for regeneration of damaged tissues and organs. In this work, anionic Eu3+ -doped Gd2O3 hybrid nanoparticles were applied as a contrast agent both for fluorescence microscopy and T1 -weighted MRI. The nanoparticles were synthesized through the polyol method and further modified with citric acid to obtain anionic nanoparticles. These nanoparticles were internalized into human mesenchymal stem cells (hMSCs) as confirmed by confocal laser scanning microscopy and quantified by inductively coupled plasma,mass spectrometry. MTT assay of the labeled cells showed that the nanoparticles did not possess significant cytotoxicity. In addition, the osteogenic, adipogenic and chondrogenic differentiation of the hMSCs was not influenced by the labeling process. With MRI, the in vitro detection threshold of cells after incubation with nanoparticles at a Gd concentration of 0.5,mMfor 2,h was estimated to be about 10 000 cells. The results from this study indicate that the biocompatible anionic Gd2O3 nanoparticles doped with Eu3+ show promise both as a luminescent and T1 contrast agent for use in visualizing hMSCs. Copyright © 2010 John Wiley & Sons, Ltd. [source]

Thermal pain thresholds are decreased in the migraine preattack phase

EUROPEAN JOURNAL OF NEUROLOGY, Issue 11 2008
T. Sand
Background and purpose:, Migraine patients may have cutaneous allodynia during attacks. In order to investigate if pain physiology changes in the preattack phase we estimated heat pain and cold pain detection threshold (HPT and CPT) on three different days in 41 migraine patients and 28 controls. Methods:, A thermode was applied at four sites bilaterally: forehead, face, neck, and hand. A subgroup of 11 migraine patients had been tested within 24 h before their next attack and in the interictal phase. Results:, In the preattack phase, HPT was lower compared with the paired interictal recording for the hand (44.8°C vs. 45.9°C, P = 0.009), neck (46.8°C vs. 48.2°C, P = 0.02), and forehead (45.1°C vs. 46.3°C, P = 0.02). Neck and hand CPT were higher in the preattack phase than interictally (10°C vs. 7.3°C, P = 0.01 and 11.6°C vs. 9.4°C, P = 0.06, respectively). Preattack forehead changes were most apparent on the headache side of the subsequent attack. Discussion:, Subclinical preattack thermal pain hypersensitivity seems to be a feature of the process that leads to a migraine attack. [source]

Neural correlates of binaural masking level difference in the inferior colliculus of the barn owl (Tyto alba)

Spatiotemporal characterization of interswarm period seismicity in the focal area Nový Kostel (West Bohemia/Vogtland) by a short-term microseismic study

GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2009
Martin Häge
SUMMARY The West Bohemia/Vogtland region is one of the seismically most interesting areas in Europe because of its swarm-like occurrence of seismicity. The installation of the local West Bohemian seismological network (WEBNET) has made the recording of small magnitude seismicity (detection threshold ML,,0.5) possible. We investigated if microseismicity exists below the detection threshold of WEBNET. A microseismic field campaign was carried out in the focal area Nový Kostel. The measurement was performed with three small arrays lasting for 6 d in a seismically quiet, interswarm period. We were able to detect and locate 13 microearthquakes in the magnitude range ,1.5 ,ML,,0.1 and achieved a detection threshold about one magnitude lower than the local network. A relative location suggests that the recorded seismicity is rather related to a specific fault segment than randomly distributed. The determined fault zone is aligned NW,SW and confirms the viability of mapping active faults with short-term measurements. The results demonstrate that a linear extrapolation of the b -value, determined by the network bulletin, down to ML=,0.5 fits well with the amount of our recorded events. [source]

Detection thresholds of capsaicin: a new test to assess facial skin neurosensitivity

Eye movements during fixation as velocity noise in minimum motion detection

JAPANESE PSYCHOLOGICAL RESEARCH, Issue 2 2010
IKUYA MURAKAMI
Abstract The functional roles and perceptual consequences of fixational eye movements are argued. The retinal image motions due to these eye movements are viewed as normally unnoticed velocity noise that limits performance of minimum motion detection without reference. When the motion detection threshold and the variability of eye velocity during fixation were measured for a group of normal adult observers, an interobserver correlation was established between psychophysical and oculomotor data. In particular, when both eyes were open, the threshold of unreferenced motion was positively correlated with the fixation instability of the eye, making larger drifts. Preliminary data also suggested the possibility that the fixation instability of this eye still dominates the detection threshold if this eye was occluded during the task. Possible schemes of living with such velocity noise as originating from fixation instability are discussed. [source]

Sensory function and pain in a population of patients treated for breast cancer

ACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 6 2009
O. J. VILHOLM
Background: Chronic pain is often reported after surgery for breast cancer. This study examined pain and sensory abnormalities in women following breast cancer surgery. Methods: Sensory tests were carried out on the operated and contra-lateral side in 55 women with chronic pain after breast cancer treatment and in a reference group of 27 pain-free women, who had also undergone treatment for breast cancer. Testing included a numeric rating score of spontaneous pain, detection and pain threshold to thermal and dynamic mechanical stimuli and temporal summation to repetitive pinprick stimulation. The neuropathic pain symptom inventory was applied for participants with chronic pain. Results: The mean age was 58.6 years for the pain patients and 60.6 years for the pain-free patients. Thermal thresholds were significantly higher on the operated side than on the contra-lateral side in both groups and side difference in warmth detection threshold was significantly higher in the pain group than in the pain-free group (mean 3.8 °C vs. 1.1 °C, P=0.01). The frequency of cold allodynia was higher in participants with pain than in pain-free participants (15/53 vs. 1/25, P=0.01), and the frequency of temporal summation evoked by repetitive pinprick was higher in participants with pain than in pain-free participants (23/53 vs. 2/25, P=0.0009). The frequency of dynamic mechanical allodynia did not differ significantly between the two groups. Conclusion: These findings suggest that chronic pain after surgery for breast cancer is associated with sensory hyperexcitability and is a neuropathic pain condition. [source]

Impact of Harvesting and Processing Conditions on Green Leaf Volatile Development and Phenolics in Concord Grape Juice

JOURNAL OF FOOD SCIENCE, Issue 3 2010
M.M. Iyer
ABSTRACT:, The disruption of plant cell walls during fruit juice processing results in the enzymatic formation of herbaceous-smelling green leaf volatiles (GLVs). Our objective was to assess the impact of thermal processing conditions on resulting levels of GLVs (hexanal, trans -2-hexenal, hexanol, cis -3-hexenol, and trans -2-hexenol), total phenols, monomeric anthocyanins, and percent polymeric color in Concord grape juice. The effects of fruit maturity and stage of juice processing on juice GLV content was also assessed. Of the GLVs studied, only trans -2-hexenal routinely exceeded its published sensory threshold in finished juice. We observed an inverse linear correlation between berry maturity (total soluble solids) and trans -2-hexenal levels in finished juice (P,< 0.05, R 2= 0.91). Trans -2-hexenal was at a maximum immediately following crushing (569 ,g/kg, >30-fold over detection threshold [DT]), decreased to 100 ,g/kg following depectinization, pressing, and pasteurization, and to 32 ,g/kg following cold-stabilization. The loss of trans -2-hexenal could be explained primarily by its reduction to trans -2-hexenol, which increased from 53 ,g/kg after crushing to 500 ,g/kg after cold-stabilization. High temperature pretreatment of must immediately following crushing ("hot break") resulted in 5- to 6-fold higher concentrations of trans -2-hexenal in the final bottled juice as compared to conventional hot press. Contrary to expectations, no significant increase in phenolics and anthocyanins were observed in hot break conditions. These results indicate that hot break procedures may thermally inactivate enzymes responsible for transforming trans -2-hexenal under normal processing conditions and potentially alter the flavor qualities of the finished Concord juice. Different equivalent pasteurization regimes (82 to 93 °C) prior to bottling had no significant effect on GLV content of the finished Concord juices (P,> 0.05). Practical Application: Introducing new processing techniques to fruit juice production can potentially result in undesirable changes to organoleptic properties. We have observed significantly higher levels of trans- 2-hexenal, a potent herbaceous off-flavor, in Concord grape juice prepared with an initial high temperature heat treatment ("hot break"). Concord juice producers should be cautious in using hot break processing, especially with immature fruit, as it may result in persistence of green aromas in juice. [source]

The effect of tooth clenching on the sensory and pain perception in the oro-facial region of symptom-free men and women

JOURNAL OF ORAL REHABILITATION, Issue 7 2009
I. OKAYASU
Summary, The aim of this study was (i) to examine the effect of light tooth contact as in diurnal tooth clenching on the tactile detection threshold (TDT), the filament-prick pain detection threshold (FPT) and the pressure pain threshold (PPT) in the oro-facial region and (ii) to examine the possible gender difference in this effect on the tactile and pain perception. Twenty healthy volunteers participated. The TDT and the FPT were measured by means of Semmes-Weinstein monofilaments, on the cheek skin (CS) overlying the masseter muscles (MM) and on the skin overlying the palm side of the thenar skin (TS). The PPT was measured at the central part of the MM using a pressure algometer. Each parameter was measured before and after keeping light tooth contact for 5 min (session 1) and after keeping the jaw relaxed for 5 min (session 2) as a control. Although there were no significant session effects on any of the parameters, there were significant effects of experimental condition on the TDT in both men and women (P < 0·001). Men had a significant higher FPT of the left CS (P < 0·05) and TS (P < 0·01) and a significant higher PPT of the MM than women (P < 0·001). These results illustrate that sensitivity to pain (FPT, PPT) was higher in women than in men. Although there were no significant gender differences in habituation of sensory perception, the increase of TDT after clenching/no clenching was larger in women, which warrants further study. [source]

Craniomandibular pain, oral parafunctions, and psychological stress in a longitudinal case study

JOURNAL OF ORAL REHABILITATION, Issue 8 2004
M. K. A. van Selms
summary, In a single case study, the most frequently suggested contributing factors to craniomandibular pain, viz., oral parafunctions and psychological stress, were studied in more detail. During a 13-week study period, questionnaires were completed, in which, among others, jaw muscle pain, bruxism behaviour, and experienced/anticipated stress were noted. During about 40% of the nights, nocturnal masticatory muscle activity (NMMA) was recorded, using single-channel electromyography (EMG). The number of NMMA events per recorded hour was scored, using a detection threshold of 10% of the maximum voluntary contraction level. This threshold was established in a separate study, in which EMG was compared with polysomnography. Stepwise regression analyses indicated, that morning jaw muscle pain could be explained by evening jaw muscle pain for 64% and by alcohol intake for another 2%. In turn, evening jaw muscle pain was explained by daytime clenching for 56% and by vacuum sucking of the tongue for an additional 6%. Finally, daytime clenching was significantly explained by experienced stress for 30%. Data of the recorded nights showed, that variations in NMMA did not contribute to variations in morning jaw muscle pain. This case study corroborates the paradigm that experienced stress may be related to daytime clenching and, in turn, to evening and morning jaw muscle pain. [source]

Formation of hard very high energy gamma-ray spectra of blazars due to internal photon,photon absorption

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2008
Felix A. Aharonian
ABSTRACT The energy spectra of TeV gamma-rays from blazars, after being corrected for intergalatic absorption in the extragalactic background light (EBL), appear unusually hard, a fact that poses challenges to the conventional models of particle acceleration in TeV blazars and/or to the EBL models. In this paper, we show that the internal absorption of gamma-rays caused by interactions with dense narrow-band radiation fields in the vicinity of compact gamma-ray production regions can lead to the formation of gamma-ray spectra of an almost arbitrary hardness. This allows significant relaxation of the current tight constraints on particle acceleration and radiation models, although at the expense of enhanced requirements to the available non-thermal energy budget. The latter, however, is not a critical issue, as long as it can be largely compensated by the Doppler boosting, assuming large (>10) Doppler factors of the relativistically moving gamma-ray production regions. The suggested scenario of formation of hard gamma-ray spectra predicts detectable synchrotron radiation of secondary electron,positron pairs which might require a revision of the current ,standard paradigm' of spectral energy distributions of gamma-ray blazars. If the primary gamma-rays are of hadronic origin related to pp or p, interactions, the ,internal gamma-ray absorption' model predicts neutrino fluxes close to the detection threshold of the next generation high-energy neutrino detectors. [source]

The Role of Central Hypersensitivity in the Determination of Intradiscal Mechanical Hyperalgesia in Discogenic Pain

PAIN MEDICINE, Issue 5 2010
Juerg Schliessbach PhD
Abstract Objective., The primary aim of the present study was to investigate whether there is a relationship between central hypersensitivity (assessed by pressure pain thresholds of uninjured tissues) and intradiscal pain threshold during discography. The secondary aim was to test the hypothesis that peripheral noxious stimulation dynamically modulates central hypersensitivity. Patients., Twenty-four patients with positive provocation discography were tested for central hypersensitivity by pressure algometry before and after the intervention with assessments of pressure pain detection and tolerance thresholds. Intradiscal pain threshold was assessed by measuring intradiscal pressure at the moment of pain provocation during discography. Correlation analyses between intradiscal pain threshold and pressure algometry were made. For the secondary aim, pressure algometry data before and after discography were compared. Results., Significant correlation with intradiscal pain threshold was found for pressure pain detection threshold at the toe (regression coefficient: 0.03, P = 0.05) and pressure pain tolerance thresholds at the nonpainful point at the back (0.02, P = 0.024). Tolerance threshold at the toe was a significant predictor for intradiscal pain threshold only in multiple linear regression (0.036, P = 0.027). Detection as well as tolerance thresholds significantly decreased after discography at the painful and the nonpainful point at the back, but not at the toe. Conclusions., Central hypersensitivity may influence intradiscal pain threshold, but with a modest quantitative impact. The diagnostic value of provocation discography is therefore not substantially impaired. Regional, but not generalized central hypersensitivity is dynamically modulated by ongoing peripheral nociceptive input. [source]

Wilms' tumor 1 message and protein expression in bone marrow failure syndrome and acute leukemia

PATHOLOGY INTERNATIONAL, Issue 10 2007
Takashi Iwasaki
Wilms' tumor 1 (WT1) is a useful marker for the diagnosis of acute leukemia and myelodysplastic syndromes (MDS). In the current study quantitative reverse transcription,polymerase chain reaction and immunostaining were used simultaneously to examine the relationship between WT1 RNA and protein level and also to evaluate WT1 as a tool to differentiate aplastic anemia (AA) and MDS refractory anemia (RA). Three types of WT1 messages (total, exon 5(+) and KTS(+)) and WT1 immunostaining of these diseases were analyzed. An increase of all three WT1 messages in high-grade MDS and acute leukemia was observed as compared with the normal control, whereas there was no significant difference in WT1 message between AA and RA, suggesting that WT1 message is not a good tool to discriminate AA and RA. No significant difference was observed between normal and RA, except for exon 5 message. Three WT1 message levels had a significant correlation, suggesting that the total WT1 message is sufficient for clinical practice. Positive immunostaining of WT1 was observed only in the portion of acute leukemia and overt leukemia (OL) transformed from MDS with a high WT1 message level, suggesting the relatively high detection threshold of WT1 protein with the immunostaining method. [source]

Development of nitrergic neurons in the nervous system of the locust embryo

THE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 8 2010
Michael Stern
We followed the development of the nitric oxide-cyclic guanosine monophosphate (NO-cGMP) system during locust embryogenesis in whole mount nervous systems and brain sections by using various cytochemical techniques. We visualized NO-sensitive neurons by cGMP immunofluorescence after incubation with an NO donor in the presence of the soluble guanylyl cyclase (sGC) activator YC-1 and the phosphodiesterase-inhibitor isobutyl-methyl-xanthine (IBMX). Central nervous system (CNS) cells respond to NO as early as 38% embryogenesis. By using the NADPH-diaphorase technique, we identified somata and neurites of possible NO-synthesizing cells in the CNS. The first NADPH-diaphorase-positive cell bodies appear around 40% embryogenesis in the brain and at 47% in the ventral nerve cord. The number of positive cells reaches the full complement of adult cells at 80%. In the brain, some structures, e.g., the mushroom bodies acquire NADPH-diaphorase staining only postembryonically. Immunolocalization of L-citrulline confirmed the presence of NOS in NADPH-diaphorase-stained neurons and, in addition, indicated enzymatic activity in vivo. In whole mount ventral nerve cords, citrulline immunolabeling was present in varying subsets of NADPH-diaphorase-positive cells, but staining was very variable and often weak. However, in a regeneration paradigm in which one of the two connectives between ganglia had been crushed, strong, reliable staining was observed as early as 60% embryogenesis. Thus, citrulline immunolabeling appears to reflect specific activity of NOS. However, in younger embryos, NOS may not always be constitutively active or may be so at a very low level, below the citrulline antibody detection threshold. For the CNS, histochemical markers for NOS do not provide conclusive evidence for a developmental role of this enzyme. J. Comp. Neurol. 518:1157,1175, 2010. © 2010 Wiley-Liss, Inc. [source]

Development of nitrergic neurons in the nervous system of the locust embryo

THE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 8 2010
Michael Stern
Abstract We followed the development of the nitric oxide-cyclic guanosine monophosphate (NO-cGMP) system during locust embryogenesis in whole mount nervous systems and brain sections by using various cytochemical techniques. We visualized NO-sensitive neurons by cGMP immunofluorescence after incubation with an NO donor in the presence of the soluble guanylyl cyclase (sGC) activator YC-1 and the phosphodiesterase-inhibitor isobutyl-methyl-xanthine (IBMX). Central nervous system (CNS) cells respond to NO as early as 38% embryogenesis. By using the NADPH-diaphorase technique, we identified somata and neurites of possible NO-synthesizing cells in the CNS. The first NADPH-diaphorase-positive cell bodies appear around 40% embryogenesis in the brain and at 47% in the ventral nerve cord. The number of positive cells reaches the full complement of adult cells at 80%. In the brain, some structures, e.g., the mushroom bodies acquire NADPH-diaphorase staining only postembryonically. Immunolocalization of L-citrulline confirmed the presence of NOS in NADPH-diaphorase-stained neurons and, in addition, indicated enzymatic activity in vivo. In whole mount ventral nerve cords, citrulline immunolabeling was present in varying subsets of NADPH-diaphorase-positive cells, but staining was very variable and often weak. However, in a regeneration paradigm in which one of the two connectives between ganglia had been crushed, strong, reliable staining was observed as early as 60% embryogenesis. Thus, citrulline immunolabeling appears to reflect specific activity of NOS. However, in younger embryos, NOS may not always be constitutively active or may be so at a very low level, below the citrulline antibody detection threshold. For the CNS, histochemical markers for NOS do not provide conclusive evidence for a developmental role of this enzyme. J. Comp. Neurol. 518:1157,1175, 2010. © 2009 Wiley-Liss, Inc. [source]

A concept for a satellite mission to measure cloud ice water path, ice particle size, and cloud altitude,

THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue S2 2007
S. A. Buehler
Abstract A passive satellite radiometer operating at submillimetre wavelengths can measure cloud ice water path (IWP), ice particle size, and cloud altitude. The paper first discusses the scientific background for such measurements. Formal scientific mission requirements are derived, based on this background and earlier assessments. The paper then presents a comprehensive prototype instrument and mission concept, and demonstrates that it meets the requirements. The instrument is a conically scanning 12-channel radiometer with channels between 183 and 664 GHz, proposed to fly in tandem with one of the Metop satellites. It can measure IWP with a relative accuracy of approximately 20% and a detection threshold of approximately 2 g m,2. The median mass equivalent sphere diameter of the ice particles can be measured with an accuracy of approximately 30 µm, and the median IWP cloud altitude can be measured with an accuracy of approximately 300 m. All the above accuracies are median absolute error values; root mean square error values are approximately twice as high, due to rare outliers. Copyright © 2007 Royal Meteorological Society [source]

Supersoft sources in M31: Comparing the XMM-Newton deep survey, ROSAT and Chandra catalogues,

ASTRONOMISCHE NACHRICHTEN, Issue 2 2010
H. Stiele
Abstract To investigate the transient nature of supersoft sources (SSSs) in M 31, we compared SSS candidates ofthe XMM-Newton Deep Survey, ROSAT PSPC surveys and the Chandra catalogues in the same field. We found 40 SSSs in the XMM-Newton observations. While 12 of the XMM-Newton sources were brighter than the limiting flux of the ROSAT PSPC survey, only two were detected with ROSAT ,10 yr earlier. Five correlate with recent optical novae which explains why they were not detected by ROSAT. The remaining 28 XMM-Newton SSSs have fluxes below the ROSAT detection threshold. Nevertheless we found one correlation with a ROSAT source, which had significantly larger fluxes than during the XMM-Newton observations. Ten of the XMM-Newton SSSs were detected by Chandra with <1, ,6yr between the observations. Five were also classified as SSSs by Chandra. Of the 30 ROSAT SSSs three were confirmed with XMM-Newton, while for 11 sources other classifications are suggested. Of the remaining 16 sources one correlates with an optical nova. Of the 42 Chandra very-soft sources five are classified as XMM-Newton SSSs, while for 22 we suggest other classifications. Of the remaining 15 sources, nine are classified as transient by Chandra, one of them correlates with an optical nova. These findings underlined the high variability of the sources of this class and the connection between SSSs and optical novae. Only three sources, were detected by all three missions as SSSs. Thus they are visible for more than a decade, despite their variability (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

On the electrodetection threshold of aquatic vertebrates with ampullary or mucous gland electroreceptor organs

BIOLOGICAL REVIEWS, Issue 3 2007
Rob C. Peters
Abstract Reinterpretation of research on the electric sense in aquatic organisms with ampullary organs results in the following conclusions. The detection limit of limnic vertebrates with ampullary organs is 1 ,Vcm,1, and of marine fish is 20 nVcm,1. Angular movements are essential for stimulation of the ampullary system in uniform d.c. fields. Angular movements in the geomagnetic field also generate induction voltages, which exceed the 20 nVcm,1 limit in marine fish. As a result, marine electrosensitive fish are sensitive to motion in the geomagnetic field, whereas limnic fish are not. Angular swimming movements generate a.c. stimuli, which act like the noise in a stochastic resonance system, and result in a detection threshold in marine organisms as low as 1 nVcm,1. Fish in the benthic space are exposed to stronger electric stimuli than fish in the pelagic space. Benthic fish scan the orientation plane for the maximum potential difference with their raster of electroreceptor organs, in order to locate bioelectric prey. This behaviour explains why the detection threshold does not depend on fish size. Pelagic marine fish are mainly exposed to electric fields caused by movements in the geomagnetic field. The straight orientation courses found in certain shark species might indicate that the electric sense functions as a simple bisensor system. Symmetrical stimulation of the sensory raster would provide an easy way to keep a straight course with respect to a far-field stimulus. The same neural mechanism would be effective in the location of a bioelectric prey generating a near-field stimulus. The response criteria in conditioning experiments and in experiments with spontaneous reactions are discussed. [source]

Ethnic variations in facial skin neurosensitivity assessed by capsaicin detection thresholds

CONTACT DERMATITIS, Issue 6 2009
Roland Jourdain
Background: Ethnic variations in sensitive skin have not been thoroughly explored and remain controversial. Objective: To objectively assess ethnic variations in facial skin neurosensitivity through individual detection thresholds of topically applied capsaicin. Patients/Methods: The single-blind, controlled study was performed in 144 women from three ethnicities: Asian, African, and Caucasian. Five solutions with increasing capsaicin concentration were successively applied to one side of nasolabial folds, while the other side simultaneously received the vehicle as control. The test was discontinued when the volunteer reported on the capsaicin side a sensation whatever its nature. Otherwise the experimenter continued the test, using the next solution with higher capsaicin content and so on, until the subject experienced a sensation on the capsaicin side. Results: Each ethnic group was divided into six sub-groups according to the level of sensitivity to capsaicin, i.e. from detection of the lowest concentration up to no detection of the highest concentration, 100-fold higher. Asian women tended to have higher capsaicin detection thresholds than Caucasians, but lower thresholds than Africans. Nevertheless, the distribution did not greatly differ between the three ethnicities. Conclusions: The capsaicin skin neurosensitivity test is painless and the changes across individuals of different ethnic backgrounds appear minimal. [source]

Measuring kinaesthetic sensitivity in typically developing children

DEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 9 2009
KRISTEN PICKETT MS
This study presents a method to quantify a child's sensitivity to passive limb motion, which is an important aspect of kinaesthesia not easily examined clinically. Psychophysical detection thresholds to passive forearm motion were determined in a group of 20 typically developing pre-adolescent children (mean age 12y 6mo, SD 10mo, range 11,13y) and a group of 10 healthy adults (mean age 29y 10mo, SD 10y 7mo, range 18,50y). A newly designed passive motion apparatus was used to measure the time to detection of forearm motion and the errors in determining movement direction. Results showed that limb motion sensitivity became increasingly variable below 0.3°/s in children and adults. In comparison with adults, movement detection times in the pediatric group were increased by between 4% and 108% for the range of tested velocities (0.075,1.35°/s). At 0.075°/s, 5% of the children, but 50% of the adults, made no directional error, indicating that motion perception became unreliable at such low velocity in both groups. The findings demonstrate that sensitivity to passive forearm motion in children should be tested at a range between 0.075 and 0.3°/s. They further suggest that passive motion sensitivity may not be fully developed in pre-adolescent children. [source]

Prolonged maturation of auditory perception and learning in gerbils

DEVELOPMENTAL NEUROBIOLOGY, Issue 9 2010
Emma C. Sarro
Abstract In humans, auditory perception reaches maturity over a broad age range, extending through adolescence. Despite this slow maturation, children are considered to be outstanding learners, suggesting that immature perceptual skills might actually be advantageous to improvement on an acoustic task as a result of training (perceptual learning). Previous non-human studies have not employed an identical task when comparing perceptual performance of young and mature subjects, making it difficult to assess learning. Here, we used an identical procedure on juvenile and adult gerbils to examine the perception of amplitude modulation (AM), a stimulus feature that is an important component of most natural sounds. On average, Adult animals could detect smaller fluctuations in amplitude (i.e., smaller modulation depths) than Juveniles, indicating immature perceptual skills in Juveniles. However, the population variance was much greater for Juveniles, a few animals displaying adult-like AM detection. To determine whether immature perceptual skills facilitated learning, we compared naïve performance on the AM detection task with the amount of improvement following additional training. The amount of improvement in Adults correlated with naïve performance: those with the poorest naïve performance improved the most. In contrast, the naïve performance of Juveniles did not predict the amount of learning. Those Juveniles with immature AM detection thresholds did not display greater learning than Adults. Furthermore, for several of the Juveniles with adult-like thresholds, AM detection deteriorated with repeated testing. Thus, immature perceptual skills in young animals were not associated with greater learning. © 2010 Wiley Periodicals, Inc. Develop Neurobiol 70: 636,648, 2010 [source]

Neural correlates of binaural masking level difference in the inferior colliculus of the barn owl (Tyto alba)

Learning to filter out visual distractors

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 8 2009
Viktor Gál
Abstract When learning to master a visual task in a cluttered natural environment, it is important to optimize the processing of task-relevant information and to efficiently filter out distractors. However, the mechanisms that suppress task-irrelevant information are not well understood. Here we show that training leads to a selective increase in motion coherence detection thresholds for task-irrelevant motion directions that interfered with the processing of task-relevant directions during training. Furthermore, using functional magnetic resonance imaging we found that training attenuated neural responses associated with the task-irrelevant direction compared with the task-relevant direction in the visual cortical areas involved in processing of visual motion. The strongest suppression of functional magnetic resonance imaging responses to task-irrelevant motion information was observed in human area MT+. These findings reveal that perceptual learning leads to the suppression and efficient filtering of task-irrelevant visual information. [source]

Regional monitoring of infrasound events using multiple arrays: application to Utah and Washington State

GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2008
Stephen J. Arrowsmith
SUMMARY In this paper, we present an integrated set of algorithms for the automatic detection, association, and location of low-frequency acoustic events using regional networks of infrasound arrays. Here, low-frequency acoustic events are characterized by transient signals, which may arise from a range of natural and anthropogenic sources, examples of which include (but are not limited to) earthquakes, volcanic eruptions, explosions, rockets and bolides. First, we outline a new technique for detecting infrasound signals that works successfully in the presence of correlated noise. We use an F -statistic, sequentially adapted to ambient noise conditions, in order to obtain detections at a given statistical significance while accounting for real background noise. At each array, individual arrivals are then grouped together based on measured delay-times and backazimuths. Each signal is identified as either a first or later arrival. First arrivals at spatially separated arrays are then associated using a grid-search method to form events. Preliminary event locations are calculated from the geographic means and spreads of grid nodes associated with each event. We apply the technique to regional infrasound networks in Utah and Washington State. In Utah, over a period of approximately 1 month, we obtain a total of 276 events recorded at three arrays in a geographic region of 6 × 4°. For four ground-truth explosions in Utah, the automatic algorithm detects, associates, and locates the events within an average offset of 5.4 km to the actual explosion locations. In Washington State, the algorithm locates numerous events that are associated with a large coalmine in Centralia, Washington. An example mining-explosion from Centralia is located within 8.2 km of the mine. The methodology and results presented here provide an initial framework for assessing the capability of infrasound networks for regional infrasound monitoring, in particular by quantifying detection thresholds and localization errors. [source]

Dynamic Assessment of Abnormalities in Central Pain Transmission and Modulation in Tension-type Headache Sufferers

HEADACHE, Issue 2 2000
Jonathan D. Neufeld PhD
Objective.,To examine and compare central pain processing and modulation in young tension-type headache sufferers with that of matched healthy controls using an induced headache "challenge" paradigm. Background.,Recent research has suggested that abnormalities in central pain processing and descending pain modulation may contribute to chronic tension-type headache. These abnormalities, if they contribute to headache pathogenesis, should be present in young adult tension-type headache sufferers. Recent research using static measures of physiological variables, such as muscle tenderness and exteroceptive suppression, has identified chronic muscle tenderness as a characteristic of young tension-type headache sufferers, but other central nervous system functional abnormalities may require a dynamic "challenge" to be observed. Methods.,Twenty-four young women meeting the International Headache Society diagnostic criteria for tension-type headache (headache-prone) and a matched group of 24 healthy women who reported fewer than 10 problem headaches per year (control) participated in a double-blind, placebo-controlled, crossover study. Subjects completed jaw clenching and a placebo condition on different days in counterbalanced order. Pericranial muscle tenderness, pressure-pain thresholds on the temporalis, and exteroceptive suppression periods were assessed before and after each procedure. Head pain was recorded for 12 to16 hours following each condition. Results.,Headache-prone subjects were more likely than controls to experience headaches after both the jaw clenching and placebo procedures, but neither group was significantly more likely to experience headaches following jaw clenching than placebo. In pretreatment measurements, headache-prone subjects exhibited greater muscle tenderness than controls, but pressure-pain detection thresholds and exteroceptive suppression periods did not differ in the two groups. Control subjects showed increases in muscle tenderness and exteroceptive suppression periods following both the clenching and placebo procedures, whereas headache-prone subjects exhibited no significant changes in any of the physiological measures following either experimental manipulation. Conclusions.,These results confirm previous findings indicating abnormally high pericranial muscle tenderness in young tension headache sufferers even in the headache-free state. In addition, the results suggest that the development of headaches following noxious stimulation is more strongly related to headache proneness and associated abnormalities in central pain transmission or modulation (indexed by pericranial muscle tenderness and exteroceptive suppression responses) than muscle strain induced by jaw clenching. [source]