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Sample records for dot stimuli comparison

  1. Dot comparison stimuli are not all alike: the effect of different visual controls on ANS measurement.

    PubMed

    Clayton, Sarah; Gilmore, Camilla; Inglis, Matthew

    2015-10-01

    The most common method of indexing Approximate Number System (ANS) acuity is to use a nonsymbolic dot comparison task. Currently there is no standard protocol for creating the dot array stimuli and it is unclear whether tasks that control for different visual cues, such as cumulative surface area and convex hull size, measure the same cognitive constructs. Here we investigated how the accuracy and reliability of magnitude judgements is influenced by visual controls through a comparison of performance on dot comparison trials created with two standard methods: the Panamath program and Gebuis & Reynvoet's script. Fifty-one adult participants completed blocks of trials employing images constructed using the two protocols twice to obtain a measure of immediate test-retest reliability. We found no significant correlation between participants' accuracy scores on trials created with the two protocols, suggesting that tasks employing these protocols may measure different cognitive constructs. Additionally, there were significant differences in the test-retest reliabilities for trials created with each protocol. Finally, strong congruency effects for convex hull size were found for both sets of protocol trials, which provides some clarification for conflicting results in the literature.

  2. Sensitivity of the Goldfish Motion Detection System Revealed by Incoherent Random Dot Stimuli: Comparison of Behavioural and Neuronal Data

    PubMed Central

    Masseck, Olivia Andrea; Förster, Sascha; Hoffmann, Klaus-Peter

    2010-01-01

    Background Global motion detection is one of the most important abilities in the animal kingdom to navigate through a 3-dimensional environment. In the visual system of teleost fish direction-selective neurons in the pretectal area (APT) are most important for global motion detection. As in all other vertebrates these neurons are involved in the control of slow phase eye movements during gaze stabilization. In contrast to mammals cortical pathways that might influence motion detection abilities of the optokinetic system are missing in teleost fish. Results To test global motion detection in goldfish we first measured the coherence threshold of random dot patterns to elicit horizontal slow phase eye movements. In addition, the coherence threshold of the optomotor response was determined by the same random dot patterns. In a second approach the coherence threshold to elicit a direction selective response in neurons of the APT was assessed from a neurometric function. Behavioural thresholds and neuronal thresholds to elicit slow phase eye movements were very similar, and ranged between 10% and 20% coherence. In contrast to these low thresholds for the optokinetic reaction and APT neurons the optomotor response could only be elicited by random dot patterns with coherences above 40%. Conclusion Our findings suggest a high sensitivity for global motion in the goldfish optokinetic system. Comparison of neuronal and behavioural thresholds implies a nearly one-to-one transformation of visual neuron performance to the visuo-motor output. In addition, we assume that the optomotor response is not mediated by the optokinetic system, but instead by other motion detection systems with higher coherence thresholds. PMID:20209165

  3. Inhibition in Dot Comparison Tasks

    ERIC Educational Resources Information Center

    Clayton, Sarah; Gilmore, Camilla

    2015-01-01

    Dot comparison tasks are commonly used to index an individual's Approximate Number System (ANS) acuity, but the cognitive processes involved in completing these tasks are poorly understood. Here, we investigated how factors including numerosity ratio, set size and visual cues influence task performance. Forty-four children aged 7-9 years completed…

  4. Inhibition in Dot Comparison Tasks

    ERIC Educational Resources Information Center

    Clayton, Sarah; Gilmore, Camilla

    2015-01-01

    Dot comparison tasks are commonly used to index an individual's Approximate Number System (ANS) acuity, but the cognitive processes involved in completing these tasks are poorly understood. Here, we investigated how factors including numerosity ratio, set size and visual cues influence task performance. Forty-four children aged 7-9 years completed…

  5. Pictures of you: Dot stimuli cause motor contagion in presence of a still human form.

    PubMed

    Sparks, S; Sidari, M; Lyons, M; Kritikos, A

    2016-10-01

    In this study, we investigate which visual cues induce participants to encode a non-human motion stimulus in their motor system. Participants performed reach-to-grasp actions to a target after observing a dot moving in a direct or higher-arcing path across a screen. Dot motion occurred in the presence of a meaningless (scrambled human model) stimulus, a still human model, or a human model performing a direct or exaggeratedly curved reach to a target. Our results show that observing the dot displacement causes motor contagion (changes in the height of the observer's hand trajectory) when a human form was visually present in the background (either moving or still). No contagion was evident, however, when this human context was absent (i.e., human image scrambled and not identifiable). This indicates that visual cues suggestive of human agency can determine whether or not moving stimuli are encoded in the motor system.

  6. Congruency effects in dot comparison tasks: convex hull is more important than dot area.

    PubMed

    Gilmore, Camilla; Cragg, Lucy; Hogan, Grace; Inglis, Matthew

    2016-11-16

    The dot comparison task, in which participants select the more numerous of two dot arrays, has become the predominant method of assessing Approximate Number System (ANS) acuity. Creation of the dot arrays requires the manipulation of visual characteristics, such as dot size and convex hull. For the task to provide a valid measure of ANS acuity, participants must ignore these characteristics and respond on the basis of number. Here, we report two experiments that explore the influence of dot area and convex hull on participants' accuracy on dot comparison tasks. We found that individuals' ability to ignore dot area information increases with age and display time. However, the influence of convex hull information remains stable across development and with additional time. This suggests that convex hull information is more difficult to inhibit when making judgements about numerosity and therefore it is crucial to control this when creating dot comparison tasks.

  7. Congruency effects in dot comparison tasks: convex hull is more important than dot area

    PubMed Central

    Gilmore, Camilla; Cragg, Lucy; Hogan, Grace; Inglis, Matthew

    2016-01-01

    ABSTRACT The dot comparison task, in which participants select the more numerous of two dot arrays, has become the predominant method of assessing Approximate Number System (ANS) acuity. Creation of the dot arrays requires the manipulation of visual characteristics, such as dot size and convex hull. For the task to provide a valid measure of ANS acuity, participants must ignore these characteristics and respond on the basis of number. Here, we report two experiments that explore the influence of dot area and convex hull on participants’ accuracy on dot comparison tasks. We found that individuals’ ability to ignore dot area information increases with age and display time. However, the influence of convex hull information remains stable across development and with additional time. This suggests that convex hull information is more difficult to inhibit when making judgements about numerosity and therefore it is crucial to control this when creating dot comparison tasks. PMID:28163886

  8. Carbon-Dot-Coated Alginate Beads as a Smart Stimuli-Responsive Drug Delivery System.

    PubMed

    Majumdar, Sristi; Krishnatreya, Gargee; Gogoi, Neelam; Thakur, Debajit; Chowdhury, Devasish

    2016-12-21

    In this work, we report a smart stimuli-responsive drug delivery system (DDS) that can release drug depending upon the amount of pathogen (MRSA) present in the target. A greater amount of MRSA in the system will lead to more release of drug and vice versa. Carbon-dot-coated novel alginate beads (CA-CD) exhibiting superior stability was successfully used as smart drug delivery vehicle. Garlic extract (GE), which contains allicin, was taken as model drug system to demonstrate the phenomena. It was observed that GE loading was 19 and 78% with CA and CA-CD, respectively. CA-CD-GE shows pH-dependent controlled drug release, which results in increased therapeutic efficiency. CA-CD-GE is not only stimuli responsive but also a controlled drug release system as it releases drug according to the pathogen concentration (MRSA). All the three factors viz. drug release, MRSA concentration and pH of the medium are interdependent as when the cell divides, it produces secondary metabolites that lead to the decrease in pH of the medium. The drop in the pH value triggers drug release from the beads. And the effect of the drug is reflected by the MRSA cell death. Hence, we demonstrate a smart stimuli responsive DDS. However, such DDS will be useful in cases where increased amount of pathogen in the system will lead to reduction in pH.

  9. A comparison of vernier acuity for narrowband and broadband stimuli.

    PubMed

    Barrett, Brendan T; Whitaker, David

    2004-01-01

    This study investigates the influence of contrast and exposure duration on vernier acuity thresholds for abutting and separated narrowband stimuli, and asks whether these data can predict broadband vernier performance. Vernier thresholds were determined for sinusoidal grating stimuli at two spatial frequencies (1 and 8 c/deg) across a range of contrasts (0.05-0.8) and exposure durations (35-2100 ms). Performance was assessed for the abutting configuration, and when a gap equivalent to 0.5 to 1.5 times the spatial period of the grating was introduced between the upper and lower halves of the grating. Vernier thresholds were also determined for a square-wave stimulus as a function of contrast (0.06 to 0.78). Exposure duration was fixed at 2100 ms. In addition, thresholds were determined at the appropriate contrast levels for the fundamental frequency (1.8 c/deg) of the square-wave, and for a number of the harmonics (3F, 5F, 7F, 9F). Our results provide support for filter models of vernier acuity by showing that vernier performance for abutting and closely-separated broadband stimuli represents the envelope of vernier sensitivity of those spatial frequency mechanisms that are activated by the broadband stimulus. In the case of high frequency grating stimuli presented for long exposure durations, vernier performance can be invariant across much of the contrast range. Despite this, however, contrast independence is not exhibited for abutting broadband stimuli because, within the broadband stimuli, the contrast of the higher harmonic components never reaches a level to reveal this plateau.

  10. Symmetry in the pigeon with sample and comparison stimuli in different locations. II.

    PubMed

    Swisher, Melissa; Urcuioli, Peter J

    2015-09-01

    Pigeons were trained on arbitrary (hue-form) and identity (hue-hue and form-form) successive matching with center-key samples and left-key comparisons. Later, they were tested on form-hue (symmetry) probe trials that were structured either in the different-locations fashion as the baseline trials (viz., center-key samples and left-key comparisons) or with a constant location by using center-key samples and center-key comparisons. Three of four pigeons showed symmetry when the probe-trial samples and comparisons appeared in center- and left-key spatial locations, respectively, but none did when both appeared in one (center-key) location. Subsequently, pigeons previously tested with center-key samples and left-key comparisons were tested with those form-hue stimuli shown in the same (center-key) location, and vice versa for the other pigeons. None of the former pigeons showed symmetry on the second test even if they had on the first test. By contrast, two of three pigeons that had not shown symmetry with single-location samples and comparisons did so when those stimuli appeared in different (center- vs. left-key) locations. Taken together, these results show that symmetrical relations between the same, nominal matching stimuli depend on where those stimuli appear in testing vis-à-vis in training and, more generally, confirm that spatial location is part of the functional matching stimuli.

  11. SYMMETRY IN THE PIGEON WITH SAMPLE AND COMPARISON STIMULI IN DIFFERENT LOCATIONS

    PubMed Central

    Swisher, Melissa; Urcuioli, Peter J.

    2017-01-01

    Pigeons typically do not show evidence for symmetry in two-alternative matching-to-sample but do demonstrate this emergent relation in successive (go/no-go) matching-to-sample. Because the sample and comparison stimuli are presented in the same spatial location (viz., on one key) during successive matching training and testing, this may be one reason why pigeons pass tests for symmetry in this paradigm. To evaluate this, one group of pigeons received successive matching training with hue-sample stimuli on the center key and form-comparison stimuli on the left key of a three-key chamber. A control group was trained with all stimuli appearing on the same (left) key. Training also involved concurrent hue- and form-identity successive matching with the same spatial location arrangement as each group’s respective hue–form task. Later, nonreinforced form–hue (symmetry) probes structured in the same way as the baseline trials were given. Of the six birds in each group, five trained with different locations and two trained with constant location responded more to the reverse of baseline positive hue–form combinations than to negative ones in testing. Results confirm the prediction from Urcuioli’s (2008) theory that symmetry should emerge even with varying spatial locations, as long as functional stimuli are held constant. PMID:23703090

  12. Preparation and characterization of multi stimuli-responsive photoluminescent nanocomposites of graphene quantum dots with hyperbranched polyethylenimine derivatives

    NASA Astrophysics Data System (ADS)

    Liu, Xing; Liu, Hua-Ji; Cheng, Fa; Chen, Yu

    2014-06-01

    Oxidized graphene sheets (OGS) were treated with a hyperbranched polyethylenimine (PEI) under hydrothermal conditions to generate nanocomposites of graphene quantum dots (GQDs) functionalized with PEI (GQD-PEIs). The influence of the reaction temperature and the PEI/OGS feed ratio on the photoluminescence properties of the GQD-PEIs was studied. The obtained GQD-PEIs were characterized by TEM, dynamic light scattering, elemental analysis, FTIR, zeta potential measurements and 1H NMR spectroscopy, from which their structural information was inferred. Subsequently, isobutyric amide (IBAm) groups were attached to the GQD-PEIs through the amidation reaction of isobutyric anhydride with the PEI moieties, which resulted in GQD-PEI-IBAm nanocomposites. GQD-PEI-IBAm was not only thermoresponsive, but also responded to other stimuli, including inorganic salts, pH, and loaded organic guests. The cloud point temperature (Tcp) of aqueous solutions of GQD-PEI-IBAm could be modulated through changing the number of IBAm units in GQD-PEI-IBAm, by varying the type and concentration of the inorganic salts and loaded organic guests, or by varying the pH. All the obtained GQD-PEI-IBAm nanocomposites were photoluminescent, and their maximum emission wavelengths were not influenced by outside stimuli. Their emission intensities were influenced a little or negligibly by pH, traditional salting-out anions (Cl- and SO42-), and the relatively polar aspirin guest. However, the traditional salting-in I- anion and the more hydrophobic 1-pyrenebutyric acid (PBA) guest could effectively quench their fluorescence. 2D NOESY 1H NMR spectra verified that GQD-PEI-IBAm accommodated the relatively polar aspirin guest using the PEI-IBAm shell, but adsorbed the relatively hydrophobic PBA guest through the nanographene core. The release rate of the guest encapsulated by the thermoresponsive GQD is different below and above Tcp.Oxidized graphene sheets (OGS) were treated with a hyperbranched

  13. Automatic Direction of Spatial Attention to Male Versus Female Stimuli: A Comparison of Heterosexual Men and Women.

    PubMed

    Snowden, Robert J; Curl, Catriona; Jobbins, Katherine; Lavington, Chloe; Gray, Nicola S

    2016-05-01

    Abundant research has shown that men's sexual attractions are more category-specific in relation to gender than women's are. We tested whether the early automatic allocation of spatial attention reflects these sexual attractions. The dot-probe task was used to assess whether spatial attention was attracted to images of either male or female models that were naked or partially clothed. In Experiment 1, men were faster if the target appeared after the female stimulus, whereas women were equally quick to respond to targets after male or female stimuli. In Experiment 2, neutral cues were introduced. Men were again faster to female images in comparison to male or neutral images, but showed no bias on the male versus neutral test. Women were faster to both male and female pictures in comparison to neutral pictures. However, in this experiment they were also faster to female pictures than to male pictures. The results suggest that early attentional processes reveal category-specific interest to the preferred sexual category for heterosexual men, and suggest that heterosexual women do not have category-specific guidance of attentional mechanisms. The technique may have promise in measuring sexual interest in other situations where participants may not be able, or may not be willing, to report upon their sexual interests (e.g., assessment of paedophilic interest).

  14. The Scaling of Paired Comparison Data with One or More Extreme Stimuli: A Comparison of Three Models

    ERIC Educational Resources Information Center

    Wild, Bradford S.; Cabral, Robert M.

    1976-01-01

    Two models for scaling of paired comparison data are compared to the Thurstone case III model. Two goodness of fit indices are presented for each model for five data sets. The results illustrate the inability of the Thurstone model to adequately account for data when the scale includes extreme stimuli. (Author)

  15. Sexual preference for child and aggressive stimuli: comparison of rapists and child molesters using auditory and visual stimuli.

    PubMed

    Miner, M H; West, M A; Day, D M

    1995-06-01

    154 Ss were tested using penile plethysmography as part of intake into a voluntary inpatient sex offender treatment program. The testing protocol included slide stimuli of nude males and females in four age categories ranging from age 1 to adult; audiotaped descriptions of sexual activity with children of both genders which included fondling, sexual contact with no resistance, coercive sexual contact, sexual assault, nonsexual assault, and consensual sexual contact with an adult; videotaped depictions of rape of an adult woman, nonsexual assault of an adult woman and consensual sexual involvement with an adult woman, and audiotaped descriptions that paralleled the videotapes. The results indicated that child molesters (male victim) show a decidedly more offense related arousal profile than either child molesters (female victim) or rapists, and that the profiles of child molesters (female victim) and rapists are remarkably similar, although statistically significantly different from each other. Rapists respond significantly more to rape and nonsexual assault than either of the two child molester groups, with child molesters with female victims responding more than those with male victims. In all three groups, the highest level of noncoercive adult responding was to women, with differences among offense groups present for visual stimuli, but not in response to auditory stimuli. Overall, the patterns of results are similar whether they are based on composites across stimulus modality or on the individual stimuli.

  16. A comparison of sound quality judgments for monaural and binaural hearing aid processed stimuli.

    PubMed

    Balfour, P B; Hawkins, D B

    1992-10-01

    Fifteen adults with bilaterally symmetrical mild and/or moderate sensorineural hearing loss completed a paired-comparison task designed to elicit sound quality preference judgments for monaural/binaural hearing aid processed signals. Three stimuli (speech-in-quiet, speech-in-noise, and music) were recorded separately in three listening environments (audiometric test booth, living room, and a music/lecture hall) through hearing aids placed on a Knowles Electronics Manikin for Acoustics Research. Judgments were made on eight separate sound quality dimensions (brightness, clarity, fullness, loudness, nearness, overall impression, smoothness, and spaciousness) for each of the three stimuli in three listening environments. Results revealed a distinct binaural preference for all eight sound quality dimensions independent of listening environment. Binaural preferences were strongest for overall impression, fullness, and spaciousness. Stimulus type effect was significant only for fullness and spaciousness, where binaural preferences were strongest for speech-in-quiet. After binaural preference data were obtained, subjects ranked each sound quality dimension with respect to its importance for binaural listening relative to monaural. Clarity was ranked highest in importance and brightness was ranked least important. The key to demonstration of improved binaural hearing aid sound quality may be the use of a paired-comparison format.

  17. A direct comparison of the taste of electrical and chemical stimuli.

    PubMed

    Stevens, David A; Baker, Diane; Cutroni, Elizabeth; Frey, Alexander; Pugh, David; Lawless, Harry T

    2008-06-01

    Three multidimensional scaling studies were conducted to compare the taste qualities evoked from electrical and chemical stimulation, including ferrous sulfate as a typical "metallic" taste stimulus. Bipolar, anodal, and cathodal stimulation were delivered by 1.5- or 3-V batteries applied to the tongue. Solutions of chemical stimuli including prototypical tastes and binary mixtures were evaporated on small metal disks to provide tactile impressions similar to those of the battery stimuli and avoid any potential response biases induced by the subjects' knowledge of the form of the stimulus. Multidimensional unfolding was performed to place stimuli and verbal descriptors in common perceptual spaces. Bipolar, anodal, and cathodal stimuli were tested in separate experiments but generated very similar perceptual spaces and were differentiated from the chemical stimuli. Electrical stimuli were associated with descriptors, such as metallic, copper penny, and iron nail, regardless of the polarity of stimulation. Taste qualities evoked by electric stimuli may not be fully described by commonly used taste stimuli or their binary mixtures and appear most adequately described by a unique metallic taste.

  18. Comparison of Verbal Preference Assessments in the Presence and Absence of the Actual Stimuli

    ERIC Educational Resources Information Center

    Kuhn, David E.; DeLeon, Iser G.; Terlonge, Cindy; Goysovich, Richard

    2006-01-01

    Stimulus preference assessments for individuals with developmental disabilities typically involve offering choices among stimuli and providing immediate access to the chosen stimuli. Several researchers have explored the utility of presenting choices verbally, thereby obviating the need to present the choices in tangible form and deliver access to…

  19. Comparison of Verbal Preference Assessments in the Presence and Absence of the Actual Stimuli

    ERIC Educational Resources Information Center

    Kuhn, David E.; DeLeon, Iser G.; Terlonge, Cindy; Goysovich, Richard

    2006-01-01

    Stimulus preference assessments for individuals with developmental disabilities typically involve offering choices among stimuli and providing immediate access to the chosen stimuli. Several researchers have explored the utility of presenting choices verbally, thereby obviating the need to present the choices in tangible form and deliver access to…

  20. Comparison of EEG propagation speeds under emotional stimuli on smartphone between the different anxiety states

    PubMed Central

    Asakawa, Tetsuya; Muramatsu, Ayumi; Hayashi, Takuto; Urata, Tatsuya; Taya, Masato; Mizuno-Matsumoto, Yuko

    2014-01-01

    The current study evaluated the effect of different anxiety states on information processing as measured by an electroencephalography (EEG) using emotional stimuli on a smartphone. Twenty-three healthy subjects were assessed for their anxiety states using The State Trait Anxiety Inventory (STAI) and divided into two groups: low anxiety (I, II) or high anxiety (III and IV, V). An EEG was performed while the participant was presented with emotionally laden audiovisual stimuli (resting, pleasant, and unpleasant sessions) and emotionally laden sentence stimuli (pleasant sentence, unpleasant sentence sessions) and EEG data was analyzed using propagation speed analysis. The propagation speed of the low anxiety group at the medial coronal for resting stimuli for all time segments was higher than those of high anxiety group. The low anxiety group propagation speeds at the medial sagittal for unpleasant stimuli in the 0–30 and 60–150 s time frames were higher than those of high anxiety group. The propagation speeds at 150 s for all stimuli in the low anxiety group were significantly higher than the correspondent propagation speeds of the high anxiety group. These events suggest that neural information processes concerning emotional stimuli differ based on current anxiety state. PMID:25540618

  1. Comparison of EEG propagation speeds under emotional stimuli on smartphone between the different anxiety states.

    PubMed

    Asakawa, Tetsuya; Muramatsu, Ayumi; Hayashi, Takuto; Urata, Tatsuya; Taya, Masato; Mizuno-Matsumoto, Yuko

    2014-01-01

    The current study evaluated the effect of different anxiety states on information processing as measured by an electroencephalography (EEG) using emotional stimuli on a smartphone. Twenty-three healthy subjects were assessed for their anxiety states using The State Trait Anxiety Inventory (STAI) and divided into two groups: low anxiety (I, II) or high anxiety (III and IV, V). An EEG was performed while the participant was presented with emotionally laden audiovisual stimuli (resting, pleasant, and unpleasant sessions) and emotionally laden sentence stimuli (pleasant sentence, unpleasant sentence sessions) and EEG data was analyzed using propagation speed analysis. The propagation speed of the low anxiety group at the medial coronal for resting stimuli for all time segments was higher than those of high anxiety group. The low anxiety group propagation speeds at the medial sagittal for unpleasant stimuli in the 0-30 and 60-150 s time frames were higher than those of high anxiety group. The propagation speeds at 150 s for all stimuli in the low anxiety group were significantly higher than the correspondent propagation speeds of the high anxiety group. These events suggest that neural information processes concerning emotional stimuli differ based on current anxiety state.

  2. Auditory Evoked Potentials with Different Speech Stimuli: a Comparison and Standardization of Values

    PubMed Central

    Didoné, Dayane Domeneghini; Oppitz, Sheila Jacques; Folgearini, Jordana; Biaggio, Eliara Pinto Vieira; Garcia, Michele Vargas

    2016-01-01

    Introduction Long Latency Auditory Evoked Potentials (LLAEP) with speech sounds has been the subject of research, as these stimuli would be ideal to check individualś detection and discrimination. Objective The objective of this study is to compare and describe the values of latency and amplitude of cortical potentials for speech stimuli in adults with normal hearing. Methods The sample population included 30 normal hearing individuals aged between 18 and 32 years old with ontological disease and auditory processing. All participants underwent LLAEP search using pairs of speech stimuli (/ba/ x /ga/, /ba/ x /da/, and /ba/ x /di/. The authors studied the LLAEP using binaural stimuli at an intensity of 75dBNPS. In total, they used 300 stimuli were used (∼60 rare and 240 frequent) to obtain the LLAEP. Individuals received guidance to count the rare stimuli. The authors analyzed latencies of potential P1, N1, P2, N2, and P300, as well as the ampleness of P300. Results The mean age of the group was approximately 23 years. The averages of cortical potentials vary according to different speech stimuli. The N2 latency was greater for /ba/ x /di/ and P300 latency was greater for /ba/ x /ga/. Considering the overall average amplitude, it ranged from 5.35 and 7.35uV for different speech stimuli. Conclusion It was possible to obtain the values of latency and amplitude for different speech stimuli. Furthermore, the N2 component showed higher latency with the / ba / x / di / stimulus and P300 for /ba/ x / ga /. PMID:27096012

  3. Comparison of Pre-Attentive Auditory Discrimination at Gross and Fine Difference between Auditory Stimuli.

    PubMed

    Sanju, Himanshu Kumar; Kumar, Prawin

    2016-10-01

    Introduction Mismatch Negativity is a negative component of the event-related potential (ERP) elicited by any discriminable changes in auditory stimulation. Objective The present study aimed to assess pre-attentive auditory discrimination skill with fine and gross difference between auditory stimuli. Method Seventeen normal hearing individual participated in the study. To assess pre-attentive auditory discrimination skill with fine difference between auditory stimuli, we recorded mismatch negativity (MMN) with pair of stimuli (pure tones), using /1000 Hz/ and /1010 Hz/ with /1000 Hz/ as frequent stimulus and /1010 Hz/ as infrequent stimulus. Similarly, we used /1000 Hz/ and /1100 Hz/ with /1000 Hz/ as frequent stimulus and /1100 Hz/ as infrequent stimulus to assess pre-attentive auditory discrimination skill with gross difference between auditory stimuli. The study included 17 subjects with informed consent. We analyzed MMN for onset latency, offset latency, peak latency, peak amplitude, and area under the curve parameters. Result Results revealed that MMN was present only in 64% of the individuals in both conditions. Further Multivariate Analysis of Variance (MANOVA) showed no significant difference in all measures of MMN (onset latency, offset latency, peak latency, peak amplitude, and area under the curve) in both conditions. Conclusion The present study showed similar pre-attentive skills for both conditions: fine (1000 Hz and 1010 Hz) and gross (1000 Hz and 1100 Hz) difference in auditory stimuli at a higher level (endogenous) of the auditory system.

  4. Comparison of Methods for Collecting and Modeling Dissimilarity Data: Applications to Complex Sound Stimuli

    ERIC Educational Resources Information Center

    Giordano, Bruno L.; Guastavino, Catherine; Murphy, Emma; Ogg, Mattson; Smith, Bennett K.; McAdams, Stephen

    2011-01-01

    Sorting procedures are frequently adopted as an alternative to dissimilarity ratings to measure the dissimilarity of large sets of stimuli in a comparatively short time. However, systematic empirical research on the consequences of this experiment-design choice is lacking. We carried out a behavioral experiment to assess the extent to which…

  5. Comparisons of transient evoked otoacoustic emissions using chirp and click stimuli.

    PubMed

    Keefe, Douglas H; Feeney, M Patrick; Hunter, Lisa L; Fitzpatrick, Denis F

    2016-09-01

    Transient-evoked otoacoustic emission (TEOAE) responses (0.7-8 kHz) were measured in normal-hearing adult ears using click stimuli and chirps whose local frequency increased or decreased linearly with time over the stimulus duration. Chirp stimuli were created by allpass filtering a click with relatively constant incident pressure level over frequency. Chirp TEOAEs were analyzed as a nonlinear residual signal by inverse allpass filtering each chirp response into an equivalent click response. Multi-window spectral and temporal averaging reduced noise levels compared to a single-window average. Mean TEOAE levels using click and chirp stimuli were similar with respect to their standard errors in adult ears. TEOAE group delay, group spread, instantaneous frequency, and instantaneous bandwidth were similar overall for chirp and click conditions, except for small differences showing nonlinear interactions differing across stimulus conditions. These results support the theory of a similar generation mechanism on the basilar membrane for both click and chirp conditions based on coherent reflection within the tonotopic region. TEOAE temporal fine structure was invariant across changes in stimulus level, which is analogous to the intensity invariance of click-evoked basilar-membrane displacement data.

  6. A Comparison of Commercially Available Auditory Brainstem Response Stimuli at a Neurodiagnostic Intensity Level.

    PubMed

    Keesling, Devan A; Parker, Jordan Paige; Sanchez, Jason Tait

    2017-02-01

    iChirp-evoked auditory brainstem responses (ABRs) yield a larger wave V amplitude at low intensity levels than traditional broadband click stimuli, providing a reliable estimation of hearing sensitivity. However, advantages of iChirp stimulation at high intensity levels are unknown. We tested to see if high-intensity (i.e., 85 dBnHL) iChirp stimulation results in larger and more reliable ABR waveforms than click. Using the commercially available Intelligent Hearing System SmartEP platform, we recorded ABRs from 43 normal hearing young adults. We report that absolute peak latencies were more variable for iChirp and were ~3 ms longer: the latter of which is simply due to the temporal duration of the signal. Interpeak latencies were slightly shorter for iChirp and were most evident between waves I-V. Interestingly, click responses were easier to identify and peak-to-trough amplitudes for waves I, III and V were significantly larger than iChirp. These differences were not due to residual noise levels. We speculate that high intensity iChirp stimulation reduces neural synchrony and conclude that for retrocochlear evaluations, click stimuli should be used as the standard for ABR neurodiagnostic testing.

  7. A Comparison of Commercially Available Auditory Brainstem Response Stimuli at a Neurodiagnostic Intensity Level

    PubMed Central

    Keesling, Devan A.; Parker, Jordan Paige

    2017-01-01

    iChirp-evoked auditory brainstem responses (ABRs) yield a larger wave V amplitude at low intensity levels than traditional broadband click stimuli, providing a reliable estimation of hearing sensitivity. However, advantages of iChirp stimulation at high intensity levels are unknown. We tested to see if high-intensity (i.e., 85 dBnHL) iChirp stimulation results in larger and more reliable ABR waveforms than click. Using the commercially available Intelligent Hearing System SmartEP platform, we recorded ABRs from 43 normal hearing young adults. We report that absolute peak latencies were more variable for iChirp and were ~3 ms longer: the latter of which is simply due to the temporal duration of the signal. Interpeak latencies were slightly shorter for iChirp and were most evident between waves I-V. Interestingly, click responses were easier to identify and peak-to-trough amplitudes for waves I, III and V were significantly larger than iChirp. These differences were not due to residual noise levels. We speculate that high intensity iChirp stimulation reduces neural synchrony and conclude that for retrocochlear evaluations, click stimuli should be used as the standard for ABR neurodiagnostic testing. PMID:28286636

  8. Influence of correspondence noise and spatial scaling on the upper limit for spatial displacement in fully-coherent random-dot kinematogram stimuli.

    PubMed

    Tripathy, Srimant P; Shafiullah, Syed N; Cox, Michael J

    2012-01-01

    Correspondence noise is a major factor limiting direction discrimination performance in random-dot kinematograms. In the current study we investigated the influence of correspondence noise on Dmax, which is the upper limit for the spatial displacement of the dots for which coherent motion is still perceived. Human direction discrimination performance was measured, using 2-frame kinematograms having leftward/rightward motion, over a 200-fold range of dot-densities and a four-fold range of dot displacements. From this data Dmax was estimated for the different dot densities tested. A model was proposed to evaluate the correspondence noise in the stimulus. This model summed the outputs of a set of elementary Reichardt-type local detectors that had receptive fields tiling the stimulus and were tuned to the two directions of motion in the stimulus. A key assumption of the model was that the local detectors would have the radius of their catchment areas scaled with the displacement that they were tuned to detect; the scaling factor k linking the radius to the displacement was the only free parameter in the model and a single value of k was used to fit all of the psychophysical data collected. This minimal, correspondence-noise based model was able to account for 91% of the variability in the human performance across all of the conditions tested. The results highlight the importance of correspondence noise in constraining the largest displacement that can be detected.

  9. Influence of Correspondence Noise and Spatial Scaling on the Upper Limit for Spatial Displacement in Fully-Coherent Random-Dot Kinematogram Stimuli

    PubMed Central

    Tripathy, Srimant P.; Shafiullah, Syed N.; Cox, Michael J.

    2012-01-01

    Correspondence noise is a major factor limiting direction discrimination performance in random-dot kinematograms [1]. In the current study we investigated the influence of correspondence noise on Dmax, which is the upper limit for the spatial displacement of the dots for which coherent motion is still perceived. Human direction discrimination performance was measured, using 2-frame kinematograms having leftward/rightward motion, over a 200-fold range of dot-densities and a four-fold range of dot displacements. From this data Dmax was estimated for the different dot densities tested. A model was proposed to evaluate the correspondence noise in the stimulus. This model summed the outputs of a set of elementary Reichardt-type local detectors that had receptive fields tiling the stimulus and were tuned to the two directions of motion in the stimulus. A key assumption of the model was that the local detectors would have the radius of their catchment areas scaled with the displacement that they were tuned to detect; the scaling factor k linking the radius to the displacement was the only free parameter in the model and a single value of k was used to fit all of the psychophysical data collected. This minimal, correspondence-noise based model was able to account for 91% of the variability in the human performance across all of the conditions tested. The results highlight the importance of correspondence noise in constraining the largest displacement that can be detected. PMID:23056172

  10. Comprehension and Production of Non-Literal Comparisons (NLC) via Visual Stimuli in Children

    ERIC Educational Resources Information Center

    Douka, Glykeria; Motsiou, Eleni; Papadopoulou, Maria

    2014-01-01

    The present study focuses on the comprehension and production of non-literal comparisons (NLC) via visual means in three age groups: kindergarten, second grade and fifth grade students. Although non-literality is a cognitive process, the educational system does not take advantage of it in pedagogy, especially before the fourth grade. The research…

  11. [Auditory brainstem responses by click stimuli via an earphone--comparison with a headphone].

    PubMed

    Yoshiko, K; Fujita, Y

    1994-12-01

    To evaluate the variations of auditory brainstem responses (ABR) recorded using different receivers, the recordings of ABR were performed in 10 neurologically and audiometrically normal subjects who were all females (20-21 years of age) using a headphone (DR-513B-6) and an earphone (YE-102J). The peak latencies, the interpeak latencies, and the amplitudes of wave I, III, and V at each ABRs were compared. Unilateral auditory stimuli consisted of alternate click with 0.1 msec duration at intensity of 110 dB SPL and at rate of 13 Hz was given to the subjects who lay in the supine position at awake state. The active electrode was placed on the vertex (Cz) and the reference electrode on the left or right mastoid. The responses recorded from Cz to the ipsilateral mastoid were amplified by a factor of 10 microV/DIV with a bandpass filter of 10 Hz-3 KHz, a total of 1000 responses was averaged. It was recognized that the output intensity via the earphone was lower than the headphone, the difference was approximately 5 dB. Furthermore, the frequency response of the earphone was worse than the headphone at high frequency area (over 3.5 KHz). There were characteristic differences between ABRs recorded using the headphone and the earphone. The prolongation of the latency and the decrease of the amplitude were identified at only wave I of ABRs recorded using the earphone. However, no significant changes were founded at another components.(ABSTRACT TRUNCATED AT 250 WORDS)

  12. Analysing neuronal correlates of the comparison of two sequentially presented sensory stimuli.

    PubMed Central

    Brody, Carlos D; Hernández, Adrián; Zainos, Antonio; Lemus, Luis; Romo, Ranulfo

    2002-01-01

    In a typical sequential sensory discrimination task, subjects are required to make a decision based on comparing a sensory stimulus against the memory trace left by a previous stimulus. What is the neuronal substrate for such comparisons and the resulting decisions? This question was studied by recording neuronal responses in a variety of cortical areas of awake monkeys (Macaca mulatta), trained to carry out a vibrotactile sequential discrimination task. We describe methods to analyse responses obtained during the comparison and decision phases of the task, and describe the resulting findings from recordings in secondary somatosensory cortical area (S2). A subset of neurons in S2 become highly correlated with the monkey's decision in the task. PMID:12626017

  13. Comparison studies of infrared photodetectors with a quantum-dot and a quantum-wire base

    NASA Astrophysics Data System (ADS)

    El Tokhy, M. S.; Mahmoud, I. I.; Konber, H. A.

    2011-12-01

    This paper mainly presents a theoretical analysis for the characteristics of quantum dot infrared photodetectors (QDIPs) and quantum wire infrared photodetectors (QRIPs). The paper introduces a unique mathematical model of solving Poisson's equations with the usage of Lambert W functions for infrared detectors' structures based on quantum effects. Even though QRIPs and QDIPs have been the subject of extensive researches and development during the past decade, it is still essential to implement theoretical models allowing to estimate the ultimate performance of those detectors such as photocurrent and its figure-of-merit detectivity vs. various parameter conditions such as applied voltage, number of quantum wire layers, quantum dot layers, lateral characteristic size, doping density, operation temperature, and structural parameters of the quantum dots (QDs), and quantum wires (QRs). A comparison is made between the computed results of the implemented models and fine agreements are observed. It is concluded from the obtained results that the total detectivity of QDIPs can be significantly lower than that in the QRIPs and main features of the QRIPs such as large gap between the induced photocurrent and dark current of QRIP which allows for overcoming the problems in the QDIPs. This confirms what is evaluated before in the literature. It is evident that by increasing the QD/QR absorption volume in QDIPs/QRIPs as well as by separating the dark current and photocurrents, the specific detectivity can be improved and consequently the devices can operate at higher temperatures. It is an interesting result and it may be benefit to the development of QDIP and QRIP for infrared sensing applications.

  14. Comparison of performance of quantum dot and other types of infrared photodetectors

    NASA Astrophysics Data System (ADS)

    Martyniuk, P.; Rogalski, A.

    2008-04-01

    Investigations of the performance of quantum dot infrared photodetectors (QDIPs) as compared to other types of infrared photodetectors are presented. A model is based on fundamental performance limitations enabling a direct comparison between different infrared material technologies. It is assumed that the performance is due to thermal generation in the active detector's region. In comparative studies, the HgCdTe photodiodes, quantum well infrared photodetectors (QWIPs), type II superllatice photodiodes, Schottky barrier photoemissive detectors, doped silicon detectors, and high temperature superconductor detectors are considered. HgCdTe photodiodes indicate better performance in comparison with other types of infrared detectors. HgCdTe is characterized by high absorption coefficient and quantum efficiency and relatively low thermal generation rate compared to other types of devices. Theoretical predictions indicate that only type II superlattice photodiodes and QDIPs are expected to compete with HgCdTe photodiodes. QDIPs theoretically have several advantages compared with QWIPs including the normal incidence response, lower dark current, higher operating temperature, higher responsivity and detectivity. Comparison of theoretically predicted and experimental data indicates that, as so far, the QDIP devices have not demonstrated their potential advantages and are expected to posses the fundamental ability to achieve higher detector performance. Poor QDIP performance is generally linked to nonoptimal band structure and controlling the QDs size and density (nonuniformity in QD size).

  15. Neural correlates of apparent motion perception of impoverished facial stimuli: A comparison of ERP and ERSP activity

    PubMed Central

    Kolchinsky, Artemy; Puce, Aina

    2014-01-01

    Our brains readily decode human movements, as shown by neural responses to face and body motion. N170 event-related potentials (ERPs) are earlier and larger to mouth opening movements relative to closing in both line-drawn and natural faces, and gaze aversions relative to direct gaze in natural faces (Puce and Perrett, 2003; Puce et al., 2000). Here we extended this work by recording both ERP and oscillatory EEG activity (event-related spectral perturbations, ERSPs) to line-drawn faces depicting eye and mouth movements (Eyes: Direct vs Away; Mouth: Closed vs Open) and non-face motion controls. Neural activity was measured in 2 occipitotemporal clusters of 9 electrodes, one in each hemisphere. Mouth opening generated larger N170s than mouth closing, replicating earlier work. Eye motion elicited robust N170s that did not differ between gaze conditions. Control condition differences were seen, and generated the largest N170. ERSP difference plots across conditions in the occipitotemporal electrode clusters (Eyes: Direct vs Away; Mouth: Closed vs Open) showed statistically significant differences in beta and gamma bands for gaze direction changes and mouth opening at similar post-stimulus times and frequencies. In contrast, control stimuli showed activity in the gamma band with a completely different time profile and hemispheric distribution to facial stimuli. ERSP plots were generated in two 9 electrode clusters centered on central sites, C3 and C4. In the left cluster for all stimulus conditions, broadband beta suppression persisted from about 250 ms post-motion onset. In the right cluster, beta suppression was seen for control conditions only. Statistically significant differences between conditions were confined between 4 – 15 Hz, unlike occipitotemporal sites where differences occurred at much higher frequencies (high beta/gamma). Our data indicate that N170 amplitude is sensitive to the amount of movement in the visual field, independent of stimulus type. In

  16. A Comparison of Patients’ and Nurses’ Perceptions of Stimuli Experienced in an Intensive Care Unit

    DTIC Science & Technology

    1988-01-01

    adaptation to stimuli and the nurse’s role in promoting adaptation. Sister Callista Roy believes that all people are in constant interaction with their...Framework The theory used as a basis for this study was the Roy adaptation model ( Roy , 1984). The adaptation model centers on the patient’s...residual stimuli have been validated as influencing a possible response, they become contextual ( Roy , 1984). Roy (1984) identifies two subsystems, the

  17. Comparison of three cell fixation methods for high content analysis assays utilizing quantum dots.

    PubMed

    Williams, Y; Byrne, S; Bashir, M; Davies, A; Whelan, A; Gun'ko, Y; Kelleher, D; Volkov, Y

    2008-10-01

    Semiconductor nanoparticles or quantum dots are being increasingly utilized as fluorescent probes in cell biology both in live and fixed cell assays. Quantum dots possess an immense potential for use in multiplexing assays that can be run on high content screening analysers. Depending on the nature of the biological target under investigation, experiments are frequently required on cells retaining an intact cell membrane or also on those that have been fixed and permeabilized to expose intracellular antigens. Fixation of cell lines before or after the addition of quantum dots may affect their localization, emission properties and stability. Using a high content analysis platform we perform a quantitative comparative analysis of three common fixation techniques in two different cell lines exposed to carboxylic acid stabilized CdTe quantum dots. Our study demonstrates that in prefixed and permeabilized cells, quantum dots are readily internalized regardless of cell type, and their intracellular location is primarily determined by the properties of the quantum dots themselves. However, if the fixation procedures are preformed on live cells previously incubated with quantum dots, other important factors have to be considered. The choice of the fixative significantly influences the fluorescent characteristics of the quantum dots. Fixatives, regardless of their chemical nature, negatively affected quantum dots fluorescence intensity. Comparative analysis of gluteraldehyde, methanol and paraformaldehyde demonstrated that 2% paraformaldehyde was the fixative of choice. The presence of protein in the media did not significantly alter the quantum dot fluorescence. This study indicates that multiplexing assays utilizing quantum dots, despite being a cutting edge tool for high content cell imaging, still require careful consideration of the basic steps in biological sample processing.

  18. What a Difference a Parameter Makes: a Psychophysical Comparison of Random Dot Motion Algorithms

    PubMed Central

    Pilly, Praveen K.; Seitz, Aaron R.

    2009-01-01

    Random dot motion (RDM) displays have emerged as one of the standard stimulus types employed in psychophysical and physiological studies of motion processing. RDMs are convenient because it is straightforward to manipulate the relative motion energy for a given motion direction in addition to stimulus parameters such as the speed, contrast, duration, density, aperture, etc. However, as widely as RDMs are employed so do they vary in their details of implementation. As a result, it is often difficult to make direct comparisons across studies employing different RDM algorithms and parameters. Here, we systematically measure the ability of human subjects to estimate motion direction for four commonly used RDM algorithms under a range of parameters in order to understand how these different algorithms compare in their perceptibility. We find that parametric and algorithmic differences can produce dramatically different performances. These effects, while surprising, can be understood in relationship to pertinent neurophysiological data regarding spatiotemporal displacement tuning properties of cells in area MT and how the tuning function changes with stimulus contrast and retinal eccentricity. These data help give a baseline by which different RDM algorithms can be compared, demonstrate a need for clearly reporting RDM details in the methods of papers, and also pose new constraints and challenges to models of motion direction processing. PMID:19336240

  19. Hemispheric specialization for global and local processing: A direct comparison of linguistic and non-linguistic stimuli.

    PubMed

    Brederoo, Sanne G; Nieuwenstein, Mark R; Lorist, Monicque M; Cornelissen, Frans W

    2017-09-15

    It is often assumed that the human brain processes the global and local properties of visual stimuli in a lateralized fashion, with a left hemisphere (LH) specialization for local detail, and a right hemisphere (RH) specialization for global form. However, the evidence for such global-local lateralization stems predominantly from studies using linguistic stimuli, the processing of which has shown to be LH lateralized in itself. In addition, some studies have reported a reversal of global-local lateralization when using non-linguistic stimuli. Accordingly, it remains unclear whether global-local lateralization may in fact be stimulus-specific. To address this issue, we asked participants to respond to linguistic and non-linguistic stimuli that were presented in the right and left visual fields, allowing for first access by the LH and RH, respectively. The results showed global-RH and local-LH advantages for both stimulus types, but the global lateralization effect was larger for linguistic stimuli. Furthermore, this pattern of results was found to be robust, as it was observed regardless of two other task manipulations. We conclude that the instantiation and direction of global and local lateralization is not stimulus-specific. However, the magnitude of global,-but not local-, lateralization is dependent on stimulus type. Copyright © 2017 Elsevier Inc. All rights reserved.

  20. Comparison of the contractile responses to irregular and regular trains of stimuli during microstimulation of single human motor axons.

    PubMed

    Leitch, Michael; Macefield, Vaughan G

    2014-04-01

    During voluntary contractions, human motoneurons discharge with a physiological variability of ∼20%. However, studies that have measured the contractile responses to microstimulation of single motor axons have used regular trains of stimuli with no variability. We tested the hypothesis that irregular (physiological) trains of stimuli produce greater contractile responses than regular (nonphysiological) trains of identical mean frequency but zero variability. High-impedance tungsten microelectrodes were inserted into the common peroneal nerve and guided into fascicles supplying a toe extensor muscle. Selective microstimulation was achieved for 14 single motor axons. Contractile responses were measured via an angular displacement transducer over the relevant toe. After the responses to regular trains of 10 stimuli extending from 2 to 100 Hz were recorded, irregular trains of 10 stimuli, based on the interspike intervals recorded from single motor units during voluntary contractions, were delivered. Finally, the stimulation sequences were repeated following a 2-min period of continuous stimulation at 10 Hz to induce muscle fatigue. Regular trains of stimuli generated a sigmoidal increase in displacement with frequency, whereas irregular trains, emulating the firing of volitionally driven motoneurons, displayed significantly greater responses over the same frequency range (8-24 Hz). This was maintained even in the presence of fatigue. We conclude that physiological discharge variability, which incorporates short and long interspike intervals, offers an advantage to the neuromuscular system by allowing motor units to operate on a higher level of the contraction-frequency curve and taking advantage of catch-like properties in skeletal muscle.

  1. PSYCHOPHYSICAL METHODOLOGY I. COMPARISON OF THRESHOLDS OF THE METHOD OF LIMITS AND OF THE METHOD OF CONSTANT STIMULI.

    DTIC Science & Technology

    On the basis of this assumption (a) the relationships between the method of limits and the method of constant stimuli are derived, (b) a procedure for...comparing data obtained by the two methods is recommended, (c) a procedure for comparing ascending and descending series within the method of limits is given. (Author)

  2. ERP Responses of Elementary-Age Children to Video Game Simulations of Two Stimuli Types: Study 1 and 2 Comparisons

    ERIC Educational Resources Information Center

    Bergen, Doris; Schroer, Joseph E.; Thomas, Robin; Zhang, Xinge; Chou, Michael; Chou, Tricia

    2017-01-01

    The hypothesis that brain activity may differ during varied types of video game play was investigated in two studies of event-related potentials exhibited by children age 7 to 12 when processing game-based stimuli requiring correct/incorrect responses or choices between two imaginative alternative responses. The first study had 22 children of…

  3. ERP Responses of Elementary-Age Children to Video Game Simulations of Two Stimuli Types: Study 1 and 2 Comparisons

    ERIC Educational Resources Information Center

    Bergen, Doris; Schroer, Joseph E.; Thomas, Robin; Zhang, Xinge; Chou, Michael; Chou, Tricia

    2017-01-01

    The hypothesis that brain activity may differ during varied types of video game play was investigated in two studies of event-related potentials exhibited by children age 7 to 12 when processing game-based stimuli requiring correct/incorrect responses or choices between two imaginative alternative responses. The first study had 22 children of…

  4. Radiation Effects in Nanostructures: Comparison of Proton Irradiation Induced Changes on Quantum Dots and Quantum Wells

    NASA Technical Reports Server (NTRS)

    Leon, R.; Swift, G.; Magness, B.; Taylor, W.; Tang, Y.; Wang, K.; Dowd, P.; Zhang, Y.

    2000-01-01

    Successful implementation of technology using self-forming semiconductor Quantum Dots (QDs) has already demonstrated that temperature independent Dirac-delta density of states can be exploited in low current threshold QD lasers and QD infrared photodetectors.

  5. Comparison of two quantum dots for bioluminescence resonance energy transfer based on nucleic acid detection

    NASA Astrophysics Data System (ADS)

    Zhang, Daohong

    2017-05-01

    The performance of two commercially available quantum dots, quantum dot 605 (Qd605) and quantum dot 625 (Qd625), was tested and compared in the sensing system developed by our group previously. The sandwich format sensing system employed Renilla luciferase (Rluc) and quantum dots (Qds), could report the presence of targets with increasing bioluminescent resonance energy transfer (BRET) signal. The best spacing between the Rluc and Qds probes were 15 nucleotides. Both of Qd605 and Qd625 sensing system could quantify nucleic acid targets through 1-min hybridization from 0.2 picomoles. However, the Qd625 system showed higher BRET signal and better selectivity. Therefore, Qd625 is a better choice in this system compared to Qd605.

  6. Radiation Effects in Nanostructures: Comparison of Proton Irradiation Induced Changes on Quantum Dots and Quantum Wells

    NASA Technical Reports Server (NTRS)

    Leon, R.; Swift, G.; Magness, B.; Taylor, W.; Tang, Y.; Wang, K.; Dowd, P.; Zhang, Y.

    2000-01-01

    Successful implementation of technology using self-forming semiconductor Quantum Dots (QDs) has already demonstrated that temperature independent Dirac-delta density of states can be exploited in low current threshold QD lasers and QD infrared photodetectors.

  7. Quantum dots as active material for quantum cascade lasers: comparison to quantum wells

    NASA Astrophysics Data System (ADS)

    Michael, Stephan; Chow, Weng W.; Schneider, Hans Christian

    2016-03-01

    We review a microscopic laser theory for quantum dots as active material for quantum cascade lasers, in which carrier collisions are treated at the level of quantum kinetic equations. The computed characteristics of such a quantum-dot active material are compared to a state-of-the-art quantum-well quantum cascade laser. We find that the current requirement to achieve a comparable gain-length product is reduced compared to that of the quantum-well quantum cascade laser.

  8. A comparison between semi-spheroid- and dome-shaped quantum dots coupled to wetting layer

    SciTech Connect

    Shahzadeh, Mohammadreza; Sabaeian, Mohammad

    2014-06-15

    During the epitaxial growth method, self-assembled semi-spheroid-shaped quantum dots (QDs) are formed on the wetting layer (WL). However for sake of simplicity, researchers sometimes assume semi-spheroid-shaped QDs to be dome-shaped (hemisphere). In this work, a detailed and comprehensive study on the difference between electronic and transition properties of dome- and semi-spheroid-shaped quantum dots is presented. We will explain why the P-to-S intersubband transition behaves the way it does. The calculated results for intersubband P-to-S transition properties of quantum dots show two different trends for dome-shaped and semi-spheroid-shaped quantum dots. The results are interpreted using the probability of finding electron inside the dome/spheroid region, with emphasis on the effects of wetting layer. It is shown that dome-shaped and semi-spheroid-shaped quantum dots feature different electronic and transition properties, arising from the difference in lateral dimensions between dome- and semi-spheroid-shaped QDs. Moreover, an analogy is presented between the bound S-states in the quantum dots and a simple 3D quantum mechanical particle in a box, and effective sizes are calculated. The results of this work will benefit researchers to present more realistic models of coupled QD/WL systems and explain their properties more precisely.

  9. Statistical Comparison of Spike Responses to Natural Stimuli in Monkey Area V1 With Simulated Responses of a Detailed Laminar Network Model for a Patch of V1

    PubMed Central

    Schuch, Klaus; Logothetis, Nikos K.; Maass, Wolfgang

    2011-01-01

    A major goal of computational neuroscience is the creation of computer models for cortical areas whose response to sensory stimuli resembles that of cortical areas in vivo in important aspects. It is seldom considered whether the simulated spiking activity is realistic (in a statistical sense) in response to natural stimuli. Because certain statistical properties of spike responses were suggested to facilitate computations in the cortex, acquiring a realistic firing regimen in cortical network models might be a prerequisite for analyzing their computational functions. We present a characterization and comparison of the statistical response properties of the primary visual cortex (V1) in vivo and in silico in response to natural stimuli. We recorded from multiple electrodes in area V1 of 4 macaque monkeys and developed a large state-of-the-art network model for a 5 × 5-mm patch of V1 composed of 35,000 neurons and 3.9 million synapses that integrates previously published anatomical and physiological details. By quantitative comparison of the model response to the “statistical fingerprint” of responses in vivo, we find that our model for a patch of V1 responds to the same movie in a way which matches the statistical structure of the recorded data surprisingly well. The deviation between the firing regimen of the model and the in vivo data are on the same level as deviations among monkeys and sessions. This suggests that, despite strong simplifications and abstractions of cortical network models, they are nevertheless capable of generating realistic spiking activity. To reach a realistic firing state, it was not only necessary to include both N-methyl-d-aspartate and GABAB synaptic conductances in our model, but also to markedly increase the strength of excitatory synapses onto inhibitory neurons (>2-fold) in comparison to literature values, hinting at the importance to carefully adjust the effect of inhibition for achieving realistic dynamics in current network

  10. A pragmatic comparison of noise burst and electric shock unconditioned stimuli for fear conditioning research with many trials.

    PubMed

    Sperl, Matthias F J; Panitz, Christian; Hermann, Christiane; Mueller, Erik M

    2016-09-01

    Several methods that are promising for studying the neurophysiology of fear conditioning (e.g., EEG, MEG) require a high number of trials to achieve an adequate signal-to-noise ratio. While electric shock and white noise burst are among the most commonly used unconditioned stimuli (US) in conventional fear conditioning studies with few trials, it is unknown whether these stimuli are equally well suited for paradigms with many trials. Here, N = 32 participants underwent a 260-trial differential fear conditioning and extinction paradigm with a 240-trial recall test 24 h later and neutral faces as conditioned stimuli. In a between-subjects design, either white noise bursts (n = 16) or electric shocks (n = 16) served as US, and intensities were determined using the most common procedure for each US (i.e., a fixed 95 dB noise burst and a work-up procedure for electric shocks, respectively). In addition to differing US types, groups also differed in closely linked US-associated characteristics (e.g., calibration methods, stimulus intensities, timing). Subjective ratings (arousal/valence), skin conductance, and evoked heart period changes (i.e., fear bradycardia) indicated more reliable, extinction-resistant, and stable conditioning in the white noise burst versus electric shock group. In fear conditioning experiments where many trials are presented, white noise burst should serve as US. © 2016 Society for Psychophysiological Research.

  11. The Late Positive Potential (LPP) in Response to Varying Types of Emotional and Cigarette Stimuli in Smokers: A Content Comparison

    PubMed Central

    Minnix, Jennifer A.; Versace, Francesco; Robinson, Jason D.; Lam, Cho Y.; Engelmann, Jeffrey M.; Cui, Yong; Brown, Victoria L.; Cinciripini, Paul M.

    2013-01-01

    Identifying neural mechanisms associated with addiction has substantially improved the overall understanding of addictive processes. Indeed, research suggests that drug-associated cues may take advantage of neural mechanisms originally intended for emotional processing of stimuli relevant to survival. In this study, we investigated cortical responses to several categories of emotional cues (erotic, romance, pleasant objects, mutilation, sadness, unpleasant objects) as well as two types of smoking-related cues (people smoking and cigarette-related objects). We recorded ERPs from 180 smokers prior to their participation in a smoking cessation clinical trial and assessed emotional salience by measuring the amplitude of the late positive potential (LPP; 400 to 600 ms after picture onset). As expected, emotional and cigarette-related pictures prompted a significantly larger LPP than neutral pictures. The amplitude of the LPP increased as a function of picture arousal level, with high-arousing erotic and mutilation pictures showing the largest response in contrast to low-arousing pleasant and unpleasant objects, which showed the smallest response (other than neutral). Compared to females, male participants showed larger LPPs for high-arousing erotic and mutilation pictures. However, unlike emotional pictures, no difference was noted for the LPP between cigarette stimuli containing people versus those containing only objects, suggesting that in contrast to emotional objects, cigarette-related objects are highly relevant for smokers. We also compared the smokers to a small (N=40), convenience sample of never-smokers. We found that never-smokers had significantly smaller LPPs in response to erotic and cigarette stimuli containing only objects compared to smokers. PMID:23643564

  12. Comparison of blood volume pulse and skin conductance responses to mental and affective stimuli at different anatomical sites.

    PubMed

    Kushki, Azadeh; Fairley, Jillian; Merja, Satyam; King, Gillian; Chau, Tom

    2011-10-01

    Measurements of blood volume pulse (BVP) and skin conductance are commonly used as indications of psychological arousal in affective computing and human-machine interfaces. To date, palmar surfaces remain the primary site for these measurements. Placement of sensors on palmar surfaces, however, is undesirable when recordings are fraught with motion and pressure artifacts. These artifacts are frequent when the human participant has involuntary movements as in hyperkinetic cerebral palsy. This motivates the use of alternative measurement sites. The present study examined the correlation between measurements of blood volume pulse and skin conductance obtained from three different sites on the body (fingers, toes and ear for BVP; fingers, toes and arch of the foot for skin conductance) in response to cognitive and affective stimuli. The results of this pilot study indicated significant inter-site correlation among signal features derived from different sites, with the exception of BVP amplitude, the number of electrodermal reactions and the slope of the electrodermal activity response. We attribute these differences in part to inter-site discrepancies in local skin conditions, such as skin temperature. Despite these differences, significant changes from baseline were present in the responses to the cognitive and affective stimuli at non-palmar sites, suggesting that these sites may provide viable signal measurements for use in affective computing and human-machine interface applications.

  13. Comparison of V[Combining Dot Above]O2peak and Achievement of V[Combining Dot Above]O2peak Criteria in Three Modes of Exercise in Female Triathletes.

    PubMed

    Snoza, Colleen T; Berg, Kris E; Slivka, Dustin R

    2016-10-01

    Snoza, CT, Berg, KE, and Slivka, DR. Comparison of V[Combining Dot Above]O2peak and achievement of V[Combining Dot Above]O2peak criteria in three modes of exercise in female triathletes. J Strength Cond Res 30(10): 2816-2822, 2016-The purpose of this study was to compare peak aerobic capacity in female triathletes in 3 modes of exercise: treadmill, cycle, and arm ergometer. A second purpose was to determine the extent that physiologic criteria for achieving V[Combining Dot Above]O2peak were reached in each mode of exercise. Six criteria were examined: V[Combining Dot Above]O2 plateau, heart rate (HR), blood lactate concentration (BLC), respiratory exchange ratio, oxygen saturation, and rating of perceived exertion (RPE). Twelve recreational level female triathletes completed maximal tests on the treadmill, stationary bike, and arm ergometer. Results indicated V[Combining Dot Above]O2peak (ml·kg·min) is highest on a treadmill (46.8 ± 2.1), intermediate in cycling (40.7 ± 5.0), and lowest in arm ergometry (28.2 ± 3.3) with mean differences being significant (p ≤ 0.05). Blood lactate concentration and RPE criteria were met by the highest number of subjects across the 3 modes of testing while the HR criterion was not achieved in any participant in arm ergometry and only 2 in cycling. It was concluded that in moderately trained recreational level triathletes, V[Combining Dot Above]O2peak is highest in running and lowest in arm ergometry. Criteria for achieving V[Combining Dot Above]O2peak most frequently were blood lactate level and RPE. Coaches and researchers should appreciate that V[Combining Dot Above]O2peak values of moderately trained triathletes differ considerably in contrast to elite triathletes and tend to be highest on the treadmill and lowest in arm ergometry. Also, criteria used to determine achievement of V[Combining Dot Above]O2peak should be carefully selected and seem to be best achieved using BLC and RPE.

  14. Comparison of coherently coupled multi-cavity and quantum dot embedded single cavity systems.

    PubMed

    Kocaman, Serdar; Sayan, Gönül Turhan

    2016-12-12

    Temporal group delays originating from the optical analogue to electromagnetically induced transparency (EIT) are compared in two systems. Similar transmission characteristics are observed between a coherently coupled high-Q multi-cavity array and a single quantum dot (QD) embedded cavity in the weak coupling regime. However, theoretically generated group delay values for the multi-cavity case are around two times higher. Both configurations allow direct scalability for chip-scale optical pulse trapping and coupled-cavity quantum electrodynamics (QED).

  15. Comparison of the ballistic contractile responses generated during microstimulation of single human motor axons with brief irregular and regular stimuli.

    PubMed

    Leitch, Michael; Macefield, Vaughan G

    2017-08-01

    Ballistic contractions are induced by brief, high-frequency (60-100 Hz) trains of action potentials in motor axons. During ramp voluntary contractions, human motoneurons exhibit significant discharge variability of ∼20% and have been shown to be advantageous to the neuromuscular system. We hypothesized that ballistic contractions incorporating discharge variability would generate greater isometric forces than regular trains with zero variability. High-impedance tungsten microelectrodes were inserted into human fibular nerve, and single motor axons were stimulated with both irregular and constant-frequency stimuli at mean frequencies ranging from 57.8 to 68.9 Hz. Irregular trains generated significantly greater isometric peak forces than regular trains over identical mean frequencies. The high forces generated by ballistic contractions are not based solely on high frequencies, but rather a combination of high firing rates and discharge irregularity. It appears that irregular ballistic trains take advantage of the "catchlike property" of muscle, allowing augmentation of force. Muscle Nerve 56: 292-297, 2017. © 2016 Wiley Periodicals, Inc.

  16. Hi-C Observations of Penumbral Bright Dots: Comparison with the IRIS Results

    NASA Technical Reports Server (NTRS)

    Alpert, S. E.; Tiwari, S. K.; Moore, R. L.; Savage, S. L.; Winebarger, A. R.

    2014-01-01

    We observed bright dots (BDs) in a sunspot penumbra by using data acquired by the High Resolution Coronal Imager (Hi-C). The sizes of these BDs are on the order of 1 arcsecond (1') and are therefore hard to identify using the Atmospheric Imaging Assembly's (AIA) 0.6' pixel -1 resolution. These BDs become readily apparent with Hi-C's 0.1' pixel -1 resolution. Tian et al. (2014) found penumbral BDs in the transition region (TR) by using the Interface Region Imaging Spectrograph (IRIS). However, only a few of their dots could be associated with any enhanced brightness in AIA channels. In this work, we examine the characteristics of the penumbral BDs observed by Hi-C in a sunspot penumbra, including their sizes, lifetimes, speeds, and intensity. We also attempt to relate these BDs to the IRIS BDs. There are fewer Hi-C BDs in the penumbra than seen by IRIS, though different sunspots were studied and Hi-C had a short observation time. We use 193 A Hi-C data from July 11, 2012 which observed from 18:52:00 UT{18:56:00 UT and supplement it with data from AIA's 193 A passband to see the complete lifetime of the dots that were born before and/or lasted longer than Hi-C's 5-minute observation period. We use additional AIA passbands and compare the light curves of the BDs at different temperatures to test whether the Hi-C BDs are TR BDs. We find that most Hi-C BDs show clear movement, and of those that do, they move in a radial direction, toward or away from the sunspot umbra, sometimes doing both. BDs interact with other BDs, combining to fade away or brighten. The BDs that do not interact with other BDs tend to move less and last longer. We examine the properties of the Hi-C BDs and compare them with the IRIS BDs. Our BDs are similar to the exceptional values of the IRIS BDs: they move slower on average and their sizes and lifetimes are on the higher end of the distributions of IRIS BDs. We infer that our penumbral BDs are some of the larger BDs observed by IRIS.

  17. Attention training to pleasant stimuli in anxiety.

    PubMed

    Sass, Sarah M; Evans, Travis C; Xiong, Kue; Mirghassemi, Felicia; Tran, Huy

    2017-01-01

    Attentional bias for threatening stimuli in anxiety is a common finding in the literature. The present study addressed whether attention training toward pleasant stimuli can reduce anxiety symptoms and induce a processing bias in favor of pleasant information in nonpatients who were selected to score similarly to individuals with generalized anxiety or panic disorder on a measure of worry or physiological arousal, respectively. Participants were randomly assigned to attention training to pleasant (ATP) stimuli or to a placebo control (PC) condition. All participants completed baseline and post-test dot-probe measures of attentional bias while event-related brain potentials were recorded. As expected, worry symptoms decreased in the ATP and not PC condition. ATP was also associated with early evidence (P100 amplitude) of greater attentional prioritization of probes replacing neutral stimuli within threat-neutral word pairs from pre-to-post intervention and later RT evidence of facilitated processing of probes replacing pleasant stimuli within pleasant-threat word pairs at post compared to PC. PC was associated with later evidence (P300 latency) of less efficient evaluation of probes following pleasant stimuli within pleasant-threat word pairs from pre-to-post and later RT evidence of facilitated processing of probes following threat stimuli within pleasant-threat word pairs at post compared to ATP. Results highlight early and later mechanisms of attention processing changes and underscore the potential of pleasant stimuli in optimizing attention-training interventions for anxiety. Published by Elsevier B.V.

  18. Quantum dot-ring nanostructure — A comparison of different approaches

    NASA Astrophysics Data System (ADS)

    Janus-Zygmunt, Iwona; Kȩdzierska, Barbara; Gorczyca-Goraj, Anna; Zipper, Elżbieta; Maśka, Maciej M.

    2016-03-01

    It has been shown recently that a nanostructure composed of a quantum dot (QD) surrounded by a quantum ring (QR) possesses a set of very unique characteristics that make it a good candidate for future nanoelectronic devices. Its main advantage is the ability to easily tune transport properties on demand by so-called “wavefunction engineering”. In practice, the distribution of the electron wavefunction in the nanostructure can be controlled by, e.g., electrical gating. In order to predict some particular properties of the system, one has to know the exact wavefunctions for different shapes of the confining potential that defines the structure. In this paper, we compare three different methods that can be used to determine the energy spectrum, electron wavefunctions and transport properties of the system under investigation. In the first approach, we utilize the cylindrical symmetry of the confining potential and solve only the radial part of the Schrödinger equation; in the second approach, we discretize the Schrödinger equation in two dimensions and find the eigenstates with the help of the Lanczös method; in the third approach, we use package Kwant to solve a tight-binding approximation of the original system. To study the transport properties in all these approaches, we calculate microscopically the strength of the coupling between the nanosystem and leads. In the first two approaches, we use the Bardeen method, in the third one calculations are performed with the help of package Kwant.

  19. InAs/GaAs quantum-dot intermixing: comparison of various dielectric encapsulants

    NASA Astrophysics Data System (ADS)

    Alhashim, Hala H.; Khan, Mohammed Zahed Mustafa; Majid, Mohammed A.; Ng, Tien K.; Ooi, Boon S.

    2015-10-01

    We report on the impurity-free vacancy-disordering effect in InAs/GaAs quantum-dot (QD) laser structure based on seven dielectric capping layers. Compared to the typical SiO2 and Si3N4 films, HfO2 and SrTiO3 dielectric layers showed superior enhancement and suppression of intermixing up to 725°C, respectively. A QD peak ground-state differential blue shift of >175 nm (>148 meV) is obtained for HfO2 capped sample. Likewise, investigation of TiO2, Al2O3, and ZnO capping films showed unusual characteristics, such as intermixing-control caps at low annealing temperature (650°C) and interdiffusion-promoting caps at high temperatures (≥675°C). We qualitatively compared the degree of intermixing induced by these films by extracting the rate of intermixing and the temperature for ground-state and excited-state convergences. Based on our systematic characterization, we established reference intermixing processes based on seven different dielectric encapsulation materials. The tailored wavelength emission of ˜1060-1200 nm at room temperature and improved optical quality exhibited from intermixed QDs would serve as key materials for eventual realization of low-cost, compact, and agile lasers. Applications include solid-state laser pumping, optical communications, gas sensing, biomedical imaging, green-yellow-orange coherent light generation, as well as addressing photonic integration via area-selective, and postgrowth bandgap engineering.

  20. In vitro immunotoxicology of quantum dots and comparison with dissolved cadmium and tellurium.

    PubMed

    Bruneau, Audrey; Fortier, Marlene; Gagne, Francois; Gagnon, Christian; Turcotte, Patrice; Tayabali, Azam; Davis, Thomas A; Auffret, Michel; Fournier, Michel

    2015-01-01

    The increasing use of products derived from nanotechnology has raised concerns about their potential toxicity, especially at the immunocompetence level in organisms. This study compared the immunotoxicity of cadmium sulfate/cadmium telluride (CdS/Cd-Te) mixture quantum dots (QDs) and their dissolved components, cadmium chloride (CdCl2 )/sodium telluride (NaTeO3 ) salts, and a CdCl2 /NaTeO3 mixture on four animal models commonly used in risk assessment studies: one bivalve (Mytilus edulis), one fish (Oncorhynchus mykiss), and two mammals (mice and humans). Our results of viability and phagocytosis biomarkers revealed that QDs were more toxic than dissolved metals for blue mussels. For other species, dissolved metals (Cd, Te, and Cd-Te mixture) were more toxic than the nanoparticles (NPs). The most sensitive species toward QDs, according to innate immune cells, was humans (inhibitory concentration [IC50 ] = 217 μg/mL). However, for adaptative immunity, lymphoblastic transformation in mice was decreased for small QD concentrations (EC50 = 4 μg/mL), and was more sensitive than other model species tested. Discriminant function analysis revealed that blue mussel hemocytes were able to discriminate the toxicity of QDs, Cd, Te, and Cd-Te mixture (Partial Wilk's λ = 0.021 and p < 0.0001). For rainbow trout and human cells, the immunotoxic effects of QDs were similar to those obtained with the dissolved fraction of Cd and Te mixture. For mice, the toxicity of QDs markedly differed from those observed with Cd, Te, and dissolved Cd-Te mixture. The results also suggest that aquatic species responded more differently than vertebrates to these compounds. The results lead to the recommendation that mussels and mice were most able to discriminate the effects of Cd-based NPs from the effects of dissolved Cd and Te at the immunocompetence level.

  1. Do Rare Stimuli Evoke Large P3s by Being Unexpected? A Comparison of Oddball Effects Between Standard-Oddball and Prediction-Oddball Tasks

    PubMed Central

    Verleger, Rolf; Śmigasiewicz, Kamila

    2016-01-01

    The P3 component of event-related potentials increases when stimuli are rarely presented. It has been assumed that this oddball effect (rare-frequent difference) reflects the unexpectedness of rare stimuli. The assumption of unexpectedness and its link to P3 amplitude were tested here. A standard- oddball task requiring alternative key-press responses to frequent and rare stimuli was compared with an oddball-prediction task where stimuli had to be first predicted and then confirmed by key-pressing. Oddball effects in the prediction task depended on whether the frequent or the rare stimulus had been predicted. Oddball effects on P3 amplitudes and error rates in the standard oddball task closely resembled effects after frequent predictions. This corroborates the notion that these effects occur because frequent stimuli are expected and rare stimuli are unexpected. However, a closer look at the prediction task put this notion into doubt because the modifications of oddball effects on P3 by expectancies were entirely due to effects on frequent stimuli, whereas the large P3 amplitudes evoked by rare stimuli were insensitive to predictions (unlike response times and error rates). Therefore, rare stimuli cannot be said to evoke large P3 amplitudes because they are unexpected. We discuss these diverging effects of frequency and expectancy, as well as general differences between tasks, with respect to concepts and hypotheses about P3b’s function and conclude that each discussed concept or hypothesis encounters some problems, with a conception in terms of subjective relevance assigned to stimuli offering the most consistent account of these basic effects. PMID:27512527

  2. Semantic processing of crowded stimuli?

    PubMed

    Huckauf, Anke; Knops, Andre; Nuerk, Hans-Christoph; Willmes, Klaus

    2008-11-01

    Effects of semantic processing of crowded characters were investigated using numbers as stimuli. In an identification task, typical spacing effects in crowding were replicated. Using the same stimuli in a magnitude comparison task, a smaller effect of spacing was observed as well as an effect of response congruency. These effects were replicated in a second experiment with varying stimulus-onset asynchronies. In addition, decreasing performance with increasing onset-asynchrony (so-called type-B masking) for incongruent flankers indicates semantic processing of target and flankers. The data show that semantic processing takes place even in crowded stimuli. This argues strongly against common accounts of crowding in terms of early stimulus-driven impairments of processing.

  3. Comparison of quantum-dots- and fluorescein-isothiocyanate-based technology for detecting prostate-specific antigen expression in human prostate cancer.

    PubMed

    Ruan, Y; Yu, W; Cheng, F; Zhang, X; Rao, T; Xia, Y; Larré, S

    2011-06-01

    Quantum dots (QDs) are a new class of fluorescent labelling for biological and biomedical applications. In this study, the authors evaluated the sensitivity and stability of quantum-dots-based immunolabelling, in comparison with the conventional fluorescein-isothiocyanate-based immunolabelling (FITC), for detecting prostate-specific antigen (PSA) expression in human prostate cancer. The authors' data revealed that the two methods had similar sensitivity in differential display of the PSA expression correlated with tumour stage and grade (=0.88, p<0.001). Moreover, the intensity of QDs fluorescence remain stable for 10 days after conjugation to the PSA protein in 97% of the cases and more than 1 month in 92% of the cases, although the FITC fluorescence became undetectable after 6 min for all cases.

  4. Comparison of dynamic properties of InP/InAs quantum-dot and quantum-dash lasers

    NASA Astrophysics Data System (ADS)

    Sadeev, T.; Arsenijević, D.; Bimberg, D.

    2016-10-01

    The dynamic properties of MOVPE grown InP/InAs quantum-dot and quantum-dash lasers, showing identical structural design, emitting in the C-band are investigated and compared to each other. Based on the small-signal measurements, we show the impact of the density of states function on the cut-off frequency, being larger for quantum dots at low currents, and reaching similar values for quantum dashes only at higher currents. The large-signal measurements show error-free data transmission at 22.5 and 17.5 Gbit/s for the quantum-dot and quantum-dash lasers.

  5. Comparison of dot-ELISA and standard ELISA for detection of Neisseria meningitidis outer membrane complex-specific antibodies.

    PubMed

    Belo, Elza Ft; Farhat, Calil K; Gaspari, Elizabeth N De

    2010-01-01

    Dot-ELISA using the outer membrane complex antigens of Neisseria meningitidis as a target was standardized for rapid detection of meningococcal-specific antibodies in human serum. We investigated the level of meningococcal-specific IgG, IgA, and IgM in serum using dot-ELISA with outer membrane antigens prepared from Neisseria meningitidis serotype B:4.19:P1.15,3,7,9 (a strain isolated from a Brazilian epidemic). The dot-ELISA is based on the same principles as the standard ELISA and is useful for detection of anti-N. meningitidis B antibodies in serum of patients with meningococcal infections. For the assay, outer membrane complexes (OMCs) were absorbed by nitrocellulose membrane and blocked with a 5% skim milk solution. Serum samples were drawn upon hospital admission and during convalescence from patients with meningococcal septicemia, and single samples were drawn from uninfected controls. We retrospectively examined a total of 57 serum samples: 35 from patients infected with N. meningitidis B, 12 from patients infected with Haemophilus influenzae b, and 10 from health individuals. When performed at room temperature, dot-ELISA took approximately four hours to perform, and the optimum antigen concentration was 0.42 microg per dot. The specificity of IgG, IgM, and IgA demonstrates that dot-ELISA using OMCs from N. meningitidis B as a target is suitable for serologic verification of clinically suspected meningococcal disease in patients and for titer determination of antibodies produced during different phases of natural infection. Furthermore, the sensitivity of dot-ELISA was comparable to that of standard ELISA. Overall, dot-ELISA is simple to perform, rapid, and low cost. Further validation of the test as a screening tool is required.

  6. Dealing with large sample sizes: comparison of a new one spot dot blot method to western blot.

    PubMed

    Putra, Sulistyo Emantoko Dwi; Tsuprykov, Oleg; Von Websky, Karoline; Ritter, Teresa; Reichetzeder, Christoph; Hocher, Berthold

    2014-01-01

    Western blot is the gold standard method to determine individual protein expression levels. However, western blot is technically difficult to perform in large sample sizes because it is a time consuming and labor intensive process. Dot blot is often used instead when dealing with large sample sizes, but the main disadvantage of the existing dot blot techniques, is the absence of signal normalization to a housekeeping protein. In this study we established a one dot two development signals (ODTDS) dot blot method employing two different signal development systems. The first signal from the protein of interest was detected by horseradish peroxidase (HRP). The second signal, detecting the housekeeping protein, was obtained by using alkaline phosphatase (AP). Inter-assay results variations within ODTDS dot blot and western blot and intra-assay variations between both methods were low (1.04-5.71%) as assessed by coefficient of variation. ODTDS dot blot technique can be used instead of western blot when dealing with large sample sizes without a reduction in results accuracy.

  7. Comparison of electrically evoked compound action potential thresholds and loudness estimates for the stimuli used to program the Advanced Bionics cochlear implant.

    PubMed

    Jeon, Eun Kyung; Brown, Carolyn J; Etler, Christine P; O'Brien, Sara; Chiou, Li-Kuei; Abbas, Paul J

    2010-01-01

    In the mid-1990s, Cochlear Corporation introduced a cochlear implant (CI) to the market that was equipped with hardware that made it possible to record electrically evoked compound action potentials (ECAPs) from CI users of all ages. Over the course of the next decade, many studies were published that compared ECAP thresholds with levels used to program the speech processor of the Nucleus CI. In 2001 Advanced Bionics Corporation introduced the Clarion CII cochlear implant (the Clarion CII internal device is also known as the CII Bionic Ear). This cochlear implant was also equipped with a system that allowed measurement of the ECAP. While a great deal is known about how ECAP thresholds compare with the levels used to program the speech processor of the Nucleus CI, relatively few studies have reported comparisons between ECAP thresholds and the levels used to program the speech processor of the Advanced Bionics CI. To explore the relationship between ECAP thresholds and behavioral measures of perceptual dynamic range for the range of stimuli commonly used to program the speech processor of the Advanced Bionics CI. This prospective and experimental study uses correlational and descriptive statistics to define the relationship between ECAP thresholds and perceptual dynamic range measures. Twelve postlingually deafened adults participated in this study. All were experienced users of the Advanced Bionics CI system. ECAP thresholds were recorded using the commercially available SoundWave software. Perceptual measures of threshold (T-level), most comfortable level (M-level), and maximum comfortable level (C-level) were obtained using both "tone bursts" and "speech bursts." The relationship between these perceptual and electrophysiological variables was defined using paired t-tests as well as correlation and linear regression. ECAP thresholds were significantly correlated with the perceptual dynamic range measures studied; however, correlations were not strong. Analysis of

  8. Quantum Dots

    NASA Astrophysics Data System (ADS)

    Tartakovskii, Alexander

    2012-07-01

    Part I. Nanostructure Design and Structural Properties of Epitaxially Grown Quantum Dots and Nanowires: 1. Growth of III/V semiconductor quantum dots C. Schneider, S. Hofling and A. Forchel; 2. Single semiconductor quantum dots in nanowires: growth, optics, and devices M. E. Reimer, N. Akopian, M. Barkelid, G. Bulgarini, R. Heeres, M. Hocevar, B. J. Witek, E. Bakkers and V. Zwiller; 3. Atomic scale analysis of self-assembled quantum dots by cross-sectional scanning tunneling microscopy and atom probe tomography J. G. Keizer and P. M. Koenraad; Part II. Manipulation of Individual Quantum States in Quantum Dots Using Optical Techniques: 4. Studies of the hole spin in self-assembled quantum dots using optical techniques B. D. Gerardot and R. J. Warburton; 5. Resonance fluorescence from a single quantum dot A. N. Vamivakas, C. Matthiesen, Y. Zhao, C.-Y. Lu and M. Atature; 6. Coherent control of quantum dot excitons using ultra-fast optical techniques A. J. Ramsay and A. M. Fox; 7. Optical probing of holes in quantum dot molecules: structure, symmetry, and spin M. F. Doty and J. I. Climente; Part III. Optical Properties of Quantum Dots in Photonic Cavities and Plasmon-Coupled Dots: 8. Deterministic light-matter coupling using single quantum dots P. Senellart; 9. Quantum dots in photonic crystal cavities A. Faraon, D. Englund, I. Fushman, A. Majumdar and J. Vukovic; 10. Photon statistics in quantum dot micropillar emission M. Asmann and M. Bayer; 11. Nanoplasmonics with colloidal quantum dots V. Temnov and U. Woggon; Part IV. Quantum Dot Nano-Laboratory: Magnetic Ions and Nuclear Spins in a Dot: 12. Dynamics and optical control of an individual Mn spin in a quantum dot L. Besombes, C. Le Gall, H. Boukari and H. Mariette; 13. Optical spectroscopy of InAs/GaAs quantum dots doped with a single Mn atom O. Krebs and A. Lemaitre; 14. Nuclear spin effects in quantum dot optics B. Urbaszek, B. Eble, T. Amand and X. Marie; Part V. Electron Transport in Quantum Dots Fabricated by

  9. Comparison of the geometric and the contrast models of similarity by presentation of visual stimuli to the left and the right visual fields.

    PubMed

    Frost, R; Gati, I

    1989-01-01

    In this study we investigated by means of the "same-different" decision task the process of comparing visual stimuli (schematic faces, familiar objects, houseplants, and nonsense figures) when presented for 100-150 msec to the right or to the left visual hemifields. The analysis of incorrect "same" responses showed that the addition of a common component (e.g., glasses, buttons) to a pair of nonidentical stimuli increased the percentage of incorrect same responses whereas the addition of the same component to one stimulus only in the pair decreased the percentage of incorrect "same" responses. This pattern, which is in accordance with Tversky's contrast model of similarity, is incompatible with any geometric model. Second, for schematic faces the results revealed that the left hemisphere is more sensitive to common than to distinctive features, whereas the right hemisphere is more sensitive to distinctive than to common features. No such interaction was obtained for the other type of stimuli. The implications of these results for models of similarity and the difference between the present findings and the findings of Sergent (1984) are discussed.

  10. Colloidal Double Quantum Dots

    PubMed Central

    2016-01-01

    photon emission to classical emission. Dual emission also provides these NCs with more advanced functionalities than the isolated components. The ability to better tailor the emission spectrum can be advantageous for color designed LEDs in lighting and display applications. The different response of the two emission colors to external stimuli enables ratiometric sensing. Control over hot carrier dynamics within such structures allows for photoluminescence upconversion. This Account first provides a description of the main hurdles toward the synthesis of colloidal double QDs and an overview of the growing library of synthetic pathways toward constructing them. The main discoveries regarding their photophysical properties are then described in detail, followed by an overview of potential applications taking advantage of the double-dot structure. Finally, a perspective and outlook for their future development is provided. PMID:27108870

  11. Colloidal Double Quantum Dots.

    PubMed

    Teitelboim, Ayelet; Meir, Noga; Kazes, Miri; Oron, Dan

    2016-05-17

    emission to classical emission. Dual emission also provides these NCs with more advanced functionalities than the isolated components. The ability to better tailor the emission spectrum can be advantageous for color designed LEDs in lighting and display applications. The different response of the two emission colors to external stimuli enables ratiometric sensing. Control over hot carrier dynamics within such structures allows for photoluminescence upconversion. This Account first provides a description of the main hurdles toward the synthesis of colloidal double QDs and an overview of the growing library of synthetic pathways toward constructing them. The main discoveries regarding their photophysical properties are then described in detail, followed by an overview of potential applications taking advantage of the double-dot structure. Finally, a perspective and outlook for their future development is provided.

  12. Detection of Campylobacter antibodies in sheep sera by a Dot-ELISA using acid extracts from c. fetus ssp. fetus and c. jejuni strains and comparison with a complement fixation test.

    PubMed

    Gürtürk, K; Ekin, I H; Aksakal, A; Solmaz, H

    2002-04-01

    In this study, a dot-enzyme-linked immunosorbent assay (Dot-ELISA) was evaluated in comparison with a complement fixation test (CFT) for the detection of Campylobacter antibodies in sheep sera. Acid glycine extracts (AGE) of both Campylobacter fetus ssp. fetus and Campylobacter jejuni strains that had been isolated from the gall-bladder of slaughtered sheep was used as antigen in both tests. A total of 153 sheep sera from aborted (74) and slaughtered (79) sheep were examined by both Dot-ELISA and CFT. Twenty-two sera showed anti-complementary activity were not suitable for CFT. Of the 22 sera showing anti-complementary activity, two sera were found to be positive in Dot-ELISA. Eighty-eight (67.2%) of the remaining 131 sera were negative by both Dot-ELISA and CFT using AGE of both Campylobacter strains whereas 43 sera (32.8%) gave different reaction patterns in Dot-ELISA and CFT with the extracts of both Campylobacter strains. Twelve sera were positive by both tests using AGE of C. fetus ssp. fetus but CFT failed to detect antibodies in nine of these sera when AGE of C. jejuni was used. Twelve sera were positive by both tests only when AGE of C. fetus ssp. fetus was used. Eleven sera were positive only by CFT. Seven of these reacted only with the AGE of C. fetus ssp. fetus and four sera were positive by using AGE of both Campylobacter strains. The remaining eight sera were found to be positive only by dot-immunobinding assay either with the AGE of both Campylobacter strains or with the AGE of one of the Campylobacter strains. It is concluded that Dot-ELISA using AGE from C. fetus ssp. fetus could be employed for the detection of Campylobacter antibodies in sheep sera and the additional use of AGE from C. jejuni as antigen appeared not to be profitable for this purpose.

  13. Visual stimuli for the P300 brain-computer interface: a comparison of white/gray and green/blue flicker matrices.

    PubMed

    Takano, Kouji; Komatsu, Tomoaki; Hata, Naoki; Nakajima, Yasoichi; Kansaku, Kenji

    2009-08-01

    The white/gray flicker matrix has been used as a visual stimulus for the so-called P300 brain-computer interface (BCI), but the white/gray flash stimuli might induce discomfort. In this study, we investigated the effectiveness of green/blue flicker matrices as visual stimuli. Ten able-bodied, non-trained subjects performed Alphabet Spelling (Japanese Alphabet: Hiragana) using an 8 x 10 matrix with three types of intensification/rest flicker combinations (L, luminance; C, chromatic; LC, luminance and chromatic); both online and offline performances were evaluated. The accuracy rate under the online LC condition was 80.6%. Offline analysis showed that the LC condition was associated with significantly higher accuracy than was the L or C condition (Tukey-Kramer, p < 0.05). No significant difference was observed between L and C conditions. The LC condition, which used the green/blue flicker matrix was associated with better performances in the P300 BCI. The green/blue chromatic flicker matrix can be an efficient tool for practical BCI application.

  14. Charge photogeneration in hybrid solar cells: A comparison between quantum dots and in situ grown CdS

    NASA Astrophysics Data System (ADS)

    Reynolds, Luke X.; Lutz, Thierry; Dowland, Simon; MacLachlan, Andrew; King, Simon; Haque, Saif A.

    2012-02-01

    We demonstrate that blend films containing poly(3-hexylthiophene-2,5-diyl) and in situ grown CdS display a greater yield of photogenerated charges than a blend containing an equivalent amount of pre-synthesised CdS quantum dots. Moreover, we show that the greater charge yield in the in situ grown films leads to an improvement in device efficiency. The present findings also appear to suggest that charge photogeneration at the CdS/polymer heterojunction is facilitated by the formation of nanoparticle networks as a result of CdS aggregation.

  15. Spatial choices of macaque monkeys based on abstract visual stimuli.

    PubMed

    Nekovarova, Tereza; Nedvidek, Jan; Bures, Jan

    2006-11-01

    Our study investigates whether macaque monkeys (Macaca mulatta) are able to make spatial choices in a real space according to abstract visual stimuli presented on a computer screen. We tested whether there was a difference in the processing of stimuli reflecting the configuration of a response space ("spatial stimuli") and stimuli of simple geometrical patterns lacking implicit spatial information. We trained two monkeys to choose one of nine touch-holes on a transparent panel attached to a computer monitor according to one of four visual stimuli successively displayed on the screen. The first monkey followed the visual stimuli designed as a representation of the response space ("configurations"), the second monkey observed geometrical patterns or pictures without information about the response space. In the first phase the position or the size of the stimuli varied but the shapes remained the same. In the second phase we changed the stimuli - "configurations" represented the response space in a similar way as in the previous phase, but marked different touch-holes - the patterns were changed entirely. The comparison of these two monkeys using different stimuli was expected to reveal potential differences between pattern discrimination and using configuration information included in the stimuli. The results of this experiment showed that both monkeys were able to use visual stimuli in phase 1 effectively (independently on their position on the screen), but only the monkey that obtained configuration information learnt an effective strategy after the change of stimuli in phase 2.

  16. Cortical responses elicited by luminance and compound stimuli modulated by pseudo-random sequences: comparison between normal trichromats and congenital red-green color blinds.

    PubMed

    Risuenho, Bárbara B O; Miquilini, Letícia; Lacerda, Eliza Maria C B; Silveira, Luiz Carlos L; Souza, Givago S

    2015-01-01

    Conventional pattern-reversal visual evoked cortical potential (VECP) shows positivity for luminance and chromatic equiluminant stimuli while conventional pattern-onset VECP shows positivity for luminance pattern-onset and negativity for chromatic pattern-onset. We evaluated how the presentation mode affects VECPs elicited by luminance and compound (luminance plus chromatic) pseudo-random stimulation. Eleven normal trichromats and 17 red-green color-blinds were studied. Pattern-reversal and pattern-onset luminance and compound (luminance plus red-green) gratings were temporally modulated by m-sequence. We used a cross-correlation routine to extract the first order kernel (K1) and the first and second slices of the second order kernel (K2.1 and K2.2, respectively) from the VECP response. We integrated the amplitude of VECP components as a function of time in order to estimate its magnitude for each stimulus condition. We also used a normalized cross-correlation method in order to test the similarity of the VECP components. The VECP components varied with the presentation mode and the presence of red-green contrast in the stimuli. In trichromats, for compound conditions, pattern-onset K1, K2.1, and K2.2, and pattern-reversal K2.1 and K2.2 had negative-dominated waveforms at 100 ms. Small negativity or small positivity were observed in dichromats. Trichromats had larger VECP magnitude than color-blinds for compound pattern-onset K1 (with large variability across subjects), compound pattern-onset and pattern-reversal K2.1, and compound pattern-reversal K2.2. Trichromats and color-blinds had similar VECP amplitude for compound pattern-reversal K1 and compound pattern-onset K2.2, as well as for all luminance conditions. The cross-correlation analysis showed high similarity between waveforms of compound pattern-onset K2.1 and pattern-reversal K2.2 as well as pattern-reversal K2.1 and K2.2. We suggest that compound pattern-reversal K2.1 is an appropriate response to study

  17. Structural and spectroscopic comparison between polycrystalline, nanocrystalline and quantum dot visible light photo-catalyst Bi2WO6

    NASA Astrophysics Data System (ADS)

    Teck, Michael; Murshed, M. Mangir; Schowalter, Marco; Lefeld, Niels; Grossmann, Henrike K.; Grieb, Tim; Hartmann, Thomas; Robben, Lars; Rosenauer, Andreas; Mädler, Lutz; Gesing, Thorsten M.

    2017-10-01

    The structural and spectroscopic features of the visible light photocatalyst Bi2WO6 have been studied. Polycrystalline (PC), nanocrystalline (NC) and quantum dot (QD) sized samples were produced using solid state reaction, hydrothermal and flame spray pyrolysis methods, respectively. While the crystal structures of PC and NC Bi2WO6 are well characterized using X-ray powder diffraction data Rietveld refinements, the structural information of the QD are obtained from the complementary pair distribution function analysis and high-resolution transmission electron microscopy. The Raman spectra of the samples are compared with the phonon density of states calculated by DFT. A continuous phenomenological model describes selective optical phonon confinement into the QDs. The type of the electronic bandgaps obtained from the UV-VIS absorbance-spectra have been analyzed using two different methods, and compared with those calculated from the electronic band structures.

  18. Superposition of Quantum Confinement Energy (SQCE) model for estimating shell thickness in core-shell quantum dots: validation and comparison.

    PubMed

    Saran, Amit D; Mehra, Anurag; Bellare, Jayesh R

    2012-07-15

    A novel theoretical model based on superposition of core and shell band-gaps, termed as SQCE model, is developed and reported here, which enables one to estimate the shell thickness in a core-shell quantum dot (QD), which is critically important in deciding its optical and electronic properties. We apply the model to two experimental core-shell QD systems, CdSe-CdS and CdSe-ZnS, which we synthesize by microemulsion method. We synthesize and study two series of samples, R and S to study the optical properties. The core size is varied in the R-series (by varying water-to-surfactant ratio, R) whereas the shell thickness is varied in the S-series (by varying the shell-to-core precursor molar ratio, S). The core and core-shell QDs from R-series and S-series are characterized for particle size, shape and crystallographic information. The shell thickness for all core-shell QD samples is estimated by SQCE model, and experimentally measured with TEM and SAXS. A close match is observed between experimental values and model predictions, thus validating the model. Further, the optimum shell thickness (corresponding to maximum quantum yield) values for CdS and ZnS over a 4.26 nm CdSe core have been estimated as 0.585 nm and 0.689 nm, respectively, from the SQCE model. The SQCE model developed in this work is applicable to other core-shell quantum dots also, such as CdTe-CdS, CdTe-CdSe and CdS-ZnS, and will serve as a useful complement to experimental measurement.

  19. Transitive Responding in Hooded Crows Requires Linearly Ordered Stimuli

    ERIC Educational Resources Information Center

    Lazareva, Olga F.; Smirnova, Anna A.; Bagozkaja, Maria S.; Zorina, Zoya A.; Rayevsky, Vladimir V.; Wasserman, Edward A.

    2004-01-01

    Eight crows were taught to discriminate overlapping pairs of visual stimuli (A+ B-, B+ C-, C+ D-, and D+ E-). For 4 birds, the stimuli were colored cards with a circle of the same color on the reverse side whose diameter decreased from A to E (ordered feedback group). These circles were made available for comparison to potentially help the crows…

  20. Transitive Responding in Hooded Crows Requires Linearly Ordered Stimuli

    ERIC Educational Resources Information Center

    Lazareva, Olga F.; Smirnova, Anna A.; Bagozkaja, Maria S.; Zorina, Zoya A.; Rayevsky, Vladimir V.; Wasserman, Edward A.

    2004-01-01

    Eight crows were taught to discriminate overlapping pairs of visual stimuli (A+ B-, B+ C-, C+ D-, and D+ E-). For 4 birds, the stimuli were colored cards with a circle of the same color on the reverse side whose diameter decreased from A to E (ordered feedback group). These circles were made available for comparison to potentially help the crows…

  1. Blue light hazard performance comparison of phosphor-converted LED sources with red quantum dots and red phosphor

    NASA Astrophysics Data System (ADS)

    Zhang, Jingjing; Xie, Bin; Yu, Xingjian; Luo, Xiaobing; Zhang, Tao; Liu, Shishen; Yu, Zhihua; Liu, Li; Jin, Xing

    2017-07-01

    In this study, the blue light hazard performances of phosphor converted-light-emitting diodes (pc-LEDs) with red phosphor and red quantum dots (QDs) were compared and analyzed by spectral optimization, which boosts the minimum attainable blue light hazard efficiency of radiation (BLHER) at high values of color rendering index (CRI) and luminous efficacy of radiation (LER) when the correlated color temperature (CCT) value changes from 1800 to 7800 K. It is found that the minimal BLHER value increases with the increase in the CCT value, and the minimal BLHER values of the two spectral models are nearly the same. Note that the QDs' model has advantages at CCT coverage under the same constraints of CRI and LER. Then, the relationships between minimal BLHER, CRI, CCT, and LER of pc-LEDs with QDs' model were analyzed. It is found that the minimal BLHER values are nearly the same when the CRI value changes from 50 to 90. Therefore, the influence of CRI on minimal BLHER is insignificant. Minimal BLHER increases with the increase in the LER value from 240 to 360 lm/W.

  2. Diffuse optical tomography activation in the somatosensory cortex: specific activation by painful vs. non-painful thermal stimuli.

    PubMed

    Becerra, Lino; Harris, Will; Grant, Margaret; George, Edward; Boas, David; Borsook, David

    2009-11-24

    Pain is difficult to assess due to the subjective nature of self-reporting. The lack of objective measures of pain has hampered the development of new treatments as well as the evaluation of current ones. Functional MRI studies of pain have begun to delineate potential brain response signatures that could be used as objective read-outs of pain. Using Diffuse Optical Tomography (DOT), we have shown in the past a distinct DOT signal over the somatosensory cortex to a noxious heat stimulus that could be distinguished from the signal elicited by innocuous mechanical stimuli. Here we further our findings by studying the response to thermal innocuous and noxious stimuli. Innocuous and noxious thermal stimuli were applied to the skin of the face of the first division (ophthalmic) of the trigeminal nerve in healthy volunteers (N = 6). Stimuli temperatures were adjusted for each subject to evoke warm (equivalent to a 3/10) and painful hot (7/10) sensations in a verbal rating scale (0/10 = no/max pain). A set of 26 stimuli (5 sec each) was applied for each temperature with inter-stimulus intervals varied between 8 and 15 sec using a Peltier thermode. A DOT system was used to capture cortical responses on both sides of the head over the primary somatosensory cortical region (S1). For the innocuous stimuli, group results indicated mainly activation on the contralateral side with a weak ipsilateral response. For the noxious stimuli, bilateral activation was observed with comparable amplitudes on both sides. Furthermore, noxious stimuli produced a temporal biphasic response while innocuous stimuli produced a monophasic response. These results are in accordance with fMRI and our other DOT studies of innocuous mechanical and noxious heat stimuli. The data indicate the differentiation of DOT cortical responses for pain vs. innocuous stimuli that may be useful in assessing objectively acute pain.

  3. NESSTI: Norms for Environmental Sound Stimuli

    PubMed Central

    Hocking, Julia; Dzafic, Ilvana; Kazovsky, Maria; Copland, David A.

    2013-01-01

    In this paper we provide normative data along multiple cognitive and affective variable dimensions for a set of 110 sounds, including living and manmade stimuli. Environmental sounds are being increasingly utilized as stimuli in the cognitive, neuropsychological and neuroimaging fields, yet there is no comprehensive set of normative information for these type of stimuli available for use across these experimental domains. Experiment 1 collected data from 162 participants in an on-line questionnaire, which included measures of identification and categorization as well as cognitive and affective variables. A subsequent experiment collected response times to these sounds. Sounds were normalized to the same length (1 second) in order to maximize usage across multiple paradigms and experimental fields. These sounds can be freely downloaded for use, and all response data have also been made available in order that researchers can choose one or many of the cognitive and affective dimensions along which they would like to control their stimuli. Our hope is that the availability of such information will assist researchers in the fields of cognitive and clinical psychology and the neuroimaging community in choosing well-controlled environmental sound stimuli, and allow comparison across multiple studies. PMID:24023866

  4. Reduplication of visual stimuli.

    PubMed

    Young, A W; Hellawell, D J; Wright, S; Ellis, H D

    1994-01-01

    Investigation of P.T., a man who experienced reduplicative delusions, revealed significant impairments on tests of recognition memory for faces and understanding of emotional facial expressions. On formal tests of his recognition abilities, P.T. showed reduplication to familiar faces, buildings, and written names, but not to familiar voices. Reduplication may therefore have been a genuinely visual problem in P.T.'s case, since it was not found to auditory stimuli. This is consistent with hypotheses which propose that the basis of reduplication can lie in part in malfunction of the visual system.

  5. Localization of monocular stimuli in different depth planes.

    PubMed

    Shimono, Koichi; Tam, Wa James; Asakura, Nobuhiko; Ohmi, Masao

    2005-09-01

    We examined the phenomenon in which two physically aligned monocular stimuli appear to be non-collinear when each of them is located in binocular regions that are at different depth planes. Using monocular bars embedded in binocular random-dot areas that are at different depths, we manipulated properties of the binocular areas and examined their effect on the perceived direction and depth of the monocular stimuli. Results showed that (1) the relative visual direction and perceived depth of the monocular bars depended on the binocular disparity and the dot density of the binocular areas, and (2) the visual direction, but not the depth, depended on the width of the binocular regions. These results are consistent with the hypothesis that monocular stimuli are treated by the visual system as binocular stimuli that have acquired the properties of their binocular surrounds. Moreover, partial correlation analysis suggests that the visual system utilizes both the disparity information of the binocular areas and the perceived depth of the monocular bars in determining the relative visual direction of the bars.

  6. Quantum-dot-based suspension microarray for multiplex detection of lung cancer markers: preclinical validation and comparison with the Luminex xMAP® system

    NASA Astrophysics Data System (ADS)

    Bilan, Regina; Ametzazurra, Amagoia; Brazhnik, Kristina; Escorza, Sergio; Fernández, David; Uríbarri, María; Nabiev, Igor; Sukhanova, Alyona

    2017-03-01

    A novel suspension multiplex immunoassay for the simultaneous specific detection of lung cancer markers in bronchoalveolar lavage fluid (BALF) clinical samples based on fluorescent microspheres having different size and spectrally encoded with quantum dots (QDEM) was developed. The designed suspension immunoassay was validated for the quantitative detection of three lung cancer markers in BALF samples from 42 lung cancer patients and 10 control subjects. Tumor markers were detected through simultaneous formation of specific immune complexes consisting of a capture molecule, the target antigen, and biotinylated recognition molecule on the surface of the different QDEM in a mixture. The immune complexes were visualized by fluorescently labeled streptavidin and simultaneously analyzed using a flow cytometer. Preclinical validation of the immunoassay was performed and results were compared with those obtained using an alternative 3-plex immunoassay based on Luminex xMAP® technology, developed on classical organic fluorophores. The comparison showed that the QDEM and xMAP® assays yielded almost identical results, with clear discrimination between control and clinical samples. Thus, developed QDEM technology can become a good alternative to xMAP® assays permitting analysis of multiple protein biomarkers using conventional flow cytometers.

  7. Quantum-dot-based suspension microarray for multiplex detection of lung cancer markers: preclinical validation and comparison with the Luminex xMAP® system

    PubMed Central

    Bilan, Regina; Ametzazurra, Amagoia; Brazhnik, Kristina; Escorza, Sergio; Fernández, David; Uríbarri, María; Nabiev, Igor; Sukhanova, Alyona

    2017-01-01

    A novel suspension multiplex immunoassay for the simultaneous specific detection of lung cancer markers in bronchoalveolar lavage fluid (BALF) clinical samples based on fluorescent microspheres having different size and spectrally encoded with quantum dots (QDEM) was developed. The designed suspension immunoassay was validated for the quantitative detection of three lung cancer markers in BALF samples from 42 lung cancer patients and 10 control subjects. Tumor markers were detected through simultaneous formation of specific immune complexes consisting of a capture molecule, the target antigen, and biotinylated recognition molecule on the surface of the different QDEM in a mixture. The immune complexes were visualized by fluorescently labeled streptavidin and simultaneously analyzed using a flow cytometer. Preclinical validation of the immunoassay was performed and results were compared with those obtained using an alternative 3-plex immunoassay based on Luminex xMAP® technology, developed on classical organic fluorophores. The comparison showed that the QDEM and xMAP® assays yielded almost identical results, with clear discrimination between control and clinical samples. Thus, developed QDEM technology can become a good alternative to xMAP® assays permitting analysis of multiple protein biomarkers using conventional flow cytometers. PMID:28300171

  8. Single fibre motor evoked potentials to brain, spinal roots and nerve stimulation. Comparisons of the 'central' and 'peripheral' response jitter to magnetic and electric stimuli.

    PubMed

    Zarola, F; Caramia, M D; Paradiso, C; Mariorenzi, R; Martino, G; Traversa, R; Rossini, P M

    1989-08-28

    Single fibre motor evoked potentials to magnetic and electric non-invasive stimulation of brain, spinal cord and peripheral nerve were recorded in 8 healthy volunteers. The 'central motor jitter' and the 'peripheral motor jitter' were respectively calculated and a comparison between the magnetic and electric modalities was made. The highest degree of latency variability was observed for both magnetic and electric central motor jitter, whilst the peripheral motor jitter to nerve stimulation was as low as the neuromuscular one (range 16-60 microsecond). The magnetic 'central motor jitter' (range 94-1024 microsecond) was much larger than the electric one (range 55-280 microsecond), which was in the order of jitter calculated on H-reflex studies; moreover, the former was organized in a bi- or trimodal distribution. On the contrary, no significant differences were observed between the two modalities when the jitter to nerve stimulation was taken into account. Possible contributions of corticocortical circuitries containing several synaptic interruptions during magnetic as opposed to electric transcranial stimulation, is discussed.

  9. Processing of Sequential and Holistic Stimuli in Left and Right Visual Fields,

    DTIC Science & Technology

    1980-10-01

    Jobs continue to require more visual processing in in- creasingly restricted work space. This is particularly true in aircraft where the primary ...bila.terally symmetrical. When a stmuu--s viewed pa-Tove-al yi, there is an increasing decrement in visual acuity moving from the most central to the most...in a manner that permitted sequencing stimuli while maintaining constant illumination and a continuous central fixation reference dot. The stimuli were

  10. Comparison of dot chromosome sequences from D. melanogaster and D. virilis reveals an enrichment of DNA transposon sequences in heterochromatic domains

    PubMed Central

    Slawson, Elizabeth E; Shaffer, Christopher D; Malone, Colin D; Leung, Wilson; Kellmann, Elmer; Shevchek, Rachel B; Craig, Carolyn A; Bloom, Seth M; Bogenpohl, James; Dee, James; Morimoto, Emiko TA; Myoung, Jenny; Nett, Andrew S; Ozsolak, Fatih; Tittiger, Mindy E; Zeug, Andrea; Pardue, Mary-Lou; Buhler, Jeremy; Mardis, Elaine R; Elgin, Sarah CR

    2006-01-01

    Background Chromosome four of Drosophila melanogaster, known as the dot chromosome, is largely heterochromatic, as shown by immunofluorescent staining with antibodies to heterochromatin protein 1 (HP1) and histone H3K9me. In contrast, the absence of HP1 and H3K9me from the dot chromosome in D. virilis suggests that this region is euchromatic. D. virilis diverged from D. melanogaster 40 to 60 million years ago. Results Here we describe finished sequencing and analysis of 11 fosmids hybridizing to the dot chromosome of D. virilis (372,650 base-pairs) and seven fosmids from major euchromatic chromosome arms (273,110 base-pairs). Most genes from the dot chromosome of D. melanogaster remain on the dot chromosome in D. virilis, but many inversions have occurred. The dot chromosomes of both species are similar to the major chromosome arms in gene density and coding density, but the dot chromosome genes of both species have larger introns. The D. virilis dot chromosome fosmids have a high repeat density (22.8%), similar to homologous regions of D. melanogaster (26.5%). There are, however, major differences in the representation of repetitive elements. Remnants of DNA transposons make up only 6.3% of the D. virilis dot chromosome fosmids, but 18.4% of the homologous regions from D. melanogaster; DINE-1 and 1360 elements are particularly enriched in D. melanogaster. Euchromatic domains on the major chromosomes in both species have very few DNA transposons (less than 0.4 %). Conclusion Combining these results with recent findings about RNAi, we suggest that specific repetitive elements, as well as density, play a role in determining higher-order chromatin packaging. PMID:16507169

  11. Dot Matrix Impact Printers: An Overview and Guide.

    ERIC Educational Resources Information Center

    Warden, William H.; Warden, Bette M.

    1983-01-01

    Comparison of dot matrix impact printers details price, matrix density, speed, print sizes, feed width, interface connectors, and true descender characteristics. Dot matrix versus preformed characters, maintenance and repair, installing printers at microcomputer workstations, value comparisons, and descriptions of specific printers are…

  12. Temporally Extended Dopamine Responses to Perceptually Demanding Reward-Predictive Stimuli

    PubMed Central

    Nomoto, Kensaku; Schultz, Wolfram; Watanabe, Takeo; Sakagami, Masamichi

    2012-01-01

    Midbrain dopamine neurons respond to reward-predictive stimuli. In the natural environment reward-predictive stimuli are often perceptually complicated. Thus, to discriminate one stimulus from another, elaborate sensory processing is necessary. Given that previous studies have used simpler types of reward-predictive stimuli, it has yet to be clear whether and, if so, how dopamine neurons obtain reward information from perceptually complicated stimuli. To investigate this, we recorded the activities of monkey dopamine neurons while they were performing discrimination between two coherent motion directions in random-dot motion stimuli. These coherent directions were paired with different magnitudes of reward. We found that dopamine neurons showed reward-predictive responses to random-dot motion stimuli. Moreover, dopamine neurons showed temporally extended activity correlated with changes in reward prediction (i.e., reward prediction error) from coarse to fine scales between initial motion detection and subsequent motion discrimination phases. Noticeably, dopamine reward-predictive responses became differential in a later phase than previously reported. This response pattern was consistent with the time course of processing required for the estimation of expected reward value that parallels the motion direction discrimination processing. The results demonstrate that dopamine neurons are able to reflect the reward value of perceptually complicated stimuli, and suggest that dopamine neurons use the moment-to-moment reward prediction associated with environmental stimuli to compute a reward prediction error. PMID:20702700

  13. Attentional and affective processing of sexual stimuli in women with hypoactive sexual desire disorder.

    PubMed

    Brauer, Marieke; van Leeuwen, Matthijs; Janssen, Erick; Newhouse, Sarah K; Heiman, Julia R; Laan, Ellen

    2012-08-01

    Hypoactive sexual desire disorder (HSDD) is the most common sexual problem in women. From an incentive motivation perspective, HSDD may be the result of a weak association between sexual stimuli and rewarding experiences. As a consequence, these stimuli may either lose or fail to acquire a positive meaning, resulting in a limited number of incentives that have the capacity to elicit a sexual response. According to current information processing models of sexual arousal, sexual stimuli automatically activate meanings and if these are not predominantly positive, processes relevant to the activation of sexual arousal and desire may be interrupted. Premenopausal U.S. and Dutch women with acquired HSDD (n = 42) and a control group of sexually functional women (n = 42) completed a single target Implicit Association Task and a Picture Association Task assessing automatic affective associations with sexual stimuli and a dot detection task measuring attentional capture by sexual stimuli. Results showed that women with acquired HSDD displayed less positive (but not more negative) automatic associations with sexual stimuli than sexually functional women. The same pattern was found for self-reported affective sex-related associations. Participants were slower to detect targets in the dot detection task that replaced sexual images, irrespective of sexual function status. As such, the findings point to the relevance of affective processing of sexual stimuli in women with HSDD, and imply that the treatment of HSDD might benefit from a stronger emphasis on the strengthening of the association between sexual stimuli and positive meaning and sexual reward.

  14. Effects of vasoactive stimuli on blood flow to choroid plexus

    SciTech Connect

    Faraci, F.M.; Mayhan, W.G.; Williams, J.K.; Heistad, D.D. )

    1988-02-01

    The goal of this study was to examine effects of vasoactive stimuli on blood flow to choroid plexus. The authors used microspheres to measure blood flow to choroid plexus and cerebrum in anesthetized dogs and rabbits. A critical assumption of the microsphere method is that microspheres do not pass through arteriovenous shunts. Blood flow values obtained with simultaneous injection of 15- and 50-{mu}m microspheres were similar, which suggest that shunting of 15-{mu}m microspheres was minimal. Blood flow to choroid plexus under control conditions was 287 {plus minus} 26 (means {plus minus} SE) ml {center dot} min{sup {minus}1} {center dot} 100 g{sup {minus}1} in dogs and 385 {plus minus} 73 ml {center dot} min{sup {minus}1} 100 g{sup {minus}1} in rabbits. Consecutive measurements under control conditions indicated that values for blood flow are reproducible. Adenosine did not alter blood flow to cerebrum but increased blood flow to choroid plexus two- to threefold in dogs and rabbits. Norepinephrine and phenylephrine did not affect blood flow to choroid plexus and cerebrum but decreased blood flow to choroid plexus by {approx} 50%. The authors suggest that (1) the microsphere method provides reproducible valid measurements of blood flow to the choroid plexus in dogs and rabbits and (2) vasoactive stimuli may have profoundly different effects on blood flow to choroid plexus and cerebrum.

  15. Speech Cues and Sign Stimuli.

    ERIC Educational Resources Information Center

    Mattingly, Ignatius G.

    Parallels between sign stimuli and speech cues suggest some interesting speculations about the origins of language. Speech cues may belong to the class of human sign stimuli which, as in animal behavior, may be the product of an innate releasing mechanism. Prelinguistic speech for man may have functioned as a social-releaser system. Human language…

  16. Fluorescent Quantum Dots for Biological Labeling

    NASA Technical Reports Server (NTRS)

    McDonald, Gene; Nadeau, Jay; Nealson, Kenneth; Storrie-Lomardi, Michael; Bhartia, Rohit

    2003-01-01

    Fluorescent semiconductor quantum dots that can serve as "on/off" labels for bacteria and other living cells are undergoing development. The "on/off" characterization of these quantum dots refers to the fact that, when properly designed and manufactured, they do not fluoresce until and unless they come into contact with viable cells of biological species that one seeks to detect. In comparison with prior fluorescence-based means of detecting biological species, fluorescent quantum dots show promise for greater speed, less complexity, greater sensitivity, and greater selectivity for species of interest. There are numerous potential applications in medicine, environmental monitoring, and detection of bioterrorism.

  17. [Stimuli-sensitive polymer systems].

    PubMed

    Le Cerf, D

    2014-11-01

    The polymers can be found in different forms in solution (particles, capsules, pseudo-micelles, hydrogels…) or on surface with important prospects in many field applications. These polymer systems are particularly very good candidates to entrap, transport and deliver an active substance in biomedical applications however with many limitations on control of release of a given target. The stimuli-sensitive polymers, also called smart or environmentally sensitive polymers, present physical or chemical changes under the action of small variations of an external stimulus. This signal acts as a stimulus which causes the change of conformation and/or solvation of the macromolecular chains by modifying their various interactions. The stimuli are classified into two broad categories: physical or external stimuli: temperature, mechanical stress, light, magnetic and electric fields; chemical and biochemical or internal stimuli: pH, ionic strength, chemical molecule (glucose, redox) or biochemical (enzymes, antigens…). The use of stimuli-sensitive pathway is widely used in the literature to enhance or trigger the release of an active compound. In this paper, we present the different stimuli addressing the theoretical aspects, polymers corresponding to these stimuli. Some examples illustrate these systems for the controlled release of active compounds.

  18. Relevance drives attention: Attentional bias for gain- and loss-related stimuli is driven by delayed disengagement.

    PubMed

    Müller, Sascha; Rothermund, Klaus; Wentura, Dirk

    2016-01-01

    Attentional bias to gain- and loss-related stimuli was investigated in a dot-probe task. We used coloured stimuli that had acquired their valence during the experiment by signalling the chance to either win or lose points in a game task. Replicating previous findings with the additional singleton paradigm, we found attentional bias effects for both gain- and loss-related colours. The effects were due to delayed disengagement from valent stimuli, especially if they were positive, and could not be explained by nonattentional processes like behavioural freezing. Our findings suggest that stimuli signalling opportunities and dangers hold attention, supporting a general motivational relevance principle of the orienting of attention.

  19. Control by Contextual Stimuli in Novel Second-Order Conditional Discriminations

    ERIC Educational Resources Information Center

    Perez-Gonzalez, Luis Antonio; Martinez, Hector

    2007-01-01

    Eighteen undergraduates participated in studies designed to examine the factors that produce transfer of contextual functions to novel stimuli in second-order conditional discriminations. In Study 1, participants selected comparison B1 given sample A1 and comparison B2 given sample A2 in a matching-to-sample procedure. Contextual stimuli X1 or X2…

  20. Control by Contextual Stimuli in Novel Second-Order Conditional Discriminations

    ERIC Educational Resources Information Center

    Perez-Gonzalez, Luis Antonio; Martinez, Hector

    2007-01-01

    Eighteen undergraduates participated in studies designed to examine the factors that produce transfer of contextual functions to novel stimuli in second-order conditional discriminations. In Study 1, participants selected comparison B1 given sample A1 and comparison B2 given sample A2 in a matching-to-sample procedure. Contextual stimuli X1 or X2…

  1. Crowding of biological motion stimuli.

    PubMed

    Ikeda, Hanako; Watanabe, Katsumi; Cavanagh, Patrick

    2013-03-26

    It is difficult to identify a target in the peripheral visual field when it is flanked by distractors. In the present study, we investigated this "crowding" effect for biological motion stimuli. Three walking biological motion stimuli were presented horizontally in the periphery with various distances between them, and observers reported the walking direction of the central figure. When the inter-walker distance was small, discriminating the direction became difficult. Moreover, the reported direction for the central target was not simply noisier, but reflected a degree of pooling of the three directions from the target and two flankers. However, when the two flanking distractors were scrambled walking biological motion stimuli, crowding was not seen. This result suggests that the crowding of biological motion stimuli occurs at a high-level of motion perception.

  2. Rewarding properties of visual stimuli.

    PubMed

    Blatter, Katharina; Schultz, Wolfram

    2006-01-01

    The behavioral functions of rewards comprise the induction of learning and approach behavior. Rewards are not only related to vegetative states of hunger, thirst and reproduction but may also consist of visual stimuli. The present experiment tested the reward potential of different types of still and moving pictures in three operant tasks involving key press, touch of computer monitor and choice behavior in a laboratory environment. We found that all tested visual stimuli induced approach behavior in all three tasks, and that action movies sustained consistently higher rates of responding compared to changing still pictures, which were more effective than constant still pictures. These results demonstrate that visual stimuli can serve as positive reinforcers for operant reactions of animals in controlled laboratory settings. In particular, the coherently animated visual stimuli of movies have considerable reward potential. These observations would allow similar forms of visual rewards to be used for neurophysiological investigations of mechanisms related to non-vegetative rewards.

  3. Headphone localization of speech stimuli

    NASA Technical Reports Server (NTRS)

    Begault, Durand R.; Wenzel, Elizabeth M.

    1991-01-01

    Recently, three dimensional acoustic display systems have been developed that synthesize virtual sound sources over headphones based on filtering by Head-Related Transfer Functions (HRTFs), the direction-dependent spectral changes caused primarily by the outer ears. Here, 11 inexperienced subjects judged the apparent spatial location of headphone-presented speech stimuli filtered with non-individualized HRTFs. About half of the subjects 'pulled' their judgements toward either the median or the lateral-vertical planes, and estimates were almost always elevated. Individual differences were pronounced for the distance judgements; 15 to 46 percent of stimuli were heard inside the head with the shortest estimates near the median plane. The results infer that most listeners can obtain useful azimuth information from speech stimuli filtered by nonindividualized RTFs. Measurements of localization error and reversal rates are comparable with a previous study that used broadband noise stimuli.

  4. Headphone localization of speech stimuli

    NASA Technical Reports Server (NTRS)

    Begault, Durand R.; Wenzel, Elizabeth M.

    1991-01-01

    Recently, three dimensional acoustic display systems have been developed that synthesize virtual sound sources over headphones based on filtering by Head-Related Transfer Functions (HRTFs), the direction-dependent spectral changes caused primarily by the outer ears. Here, 11 inexperienced subjects judged the apparent spatial location of headphone-presented speech stimuli filtered with non-individualized HRTFs. About half of the subjects 'pulled' their judgements toward either the median or the lateral-vertical planes, and estimates were almost always elevated. Individual differences were pronounced for the distance judgements; 15 to 46 percent of stimuli were heard inside the head with the shortest estimates near the median plane. The results infer that most listeners can obtain useful azimuth information from speech stimuli filtered by nonindividualized RTFs. Measurements of localization error and reversal rates are comparable with a previous study that used broadband noise stimuli.

  5. Stimuli with identical contextual functions taught independently become functionally equivalent.

    PubMed

    Pérez-González, Luis Antonio; Díaz, Elvira; Fernández-García, Silvia; Baizán, Cristina

    2015-06-01

    A novel learning process that does not require stimulus associations was explored in humans. The hypothesis was that two contextual stimuli taught in separate settings, with different stimuli, become equivalent if they accomplish identical functions with regard to the relations between the stimuli presented with them. The procedure consisted of : (a) first teaching an AB conditional discrimination (e.g., match A1 to B1 and A2 to B2) and then teaching a second-order XAB conditional discrimination in which X1 indicated performing the same selections as in AB and X2 indicated selecting the alternative comparison (e.g., match A1 to B2 and A2 to B1); (b) repeating the procedure with completely new stimuli, YHJ, in which the functions of the Y stimuli were identical to those of X; and (c) conducting a final probe under extinction to verify the equivalence between the X and the Y stimuli. Three experiments were conducted to explore the process and to rule out the influence of alternative variables. Out of these, 13 of the 14 participants matched the stimuli to the same contextual functions. Thus, the hypothesis was verified. These results demonstrate that humans are able to match stimuli according to their functions in relation to other stimuli. This process may be very much involved in language; for example, understanding that words or clauses that have been learned in separate contexts and with separate stimuli share the same meaning. Understanding this process may help to identify learning or developmental problems, such as those shown by persons with autism, and help to treat them.

  6. Inter-dot strain field effect on the optoelectronic properties of realistic InP lateral quantum-dot molecules

    SciTech Connect

    Barettin, Daniele Auf der Maur, Matthias; De Angelis, Roberta; Prosposito, Paolo; Casalboni, Mauro; Pecchia, Alessandro

    2015-03-07

    We report on numerical simulations of InP surface lateral quantum-dot molecules on In{sub 0.48}Ga{sub 0.52 }P buffer, using a model strictly derived by experimental results by extrapolation of the molecules shape from atomic force microscopy images. Our study has been inspired by the comparison of a photoluminescence spectrum of a high-density InP surface quantum dot sample with a numerical ensemble average given by a weighted sum of simulated single quantum-dot spectra. A lack of experimental optical response from the smaller dots of the sample is found to be due to strong inter-dot strain fields, which influence the optoelectronic properties of lateral quantum-dot molecules. Continuum electromechanical, k{sup →}·p{sup →} bandstructure, and optical calculations are presented for two different molecules, the first composed of two dots of nearly identical dimensions (homonuclear), the second of two dots with rather different sizes (heteronuclear). We show that in the homonuclear molecule the hydrostatic strain raises a potential barrier for the electrons in the connection zone between the dots, while conversely the holes do not experience any barrier, which considerably increases the coupling. Results for the heteronuclear molecule show instead that its dots do not appear as two separate and distinguishable structures, but as a single large dot, and no optical emission is observed in the range of higher energies where the smaller dot is supposed to emit. We believe that in samples of such a high density the smaller dots result as practically incorporated into bigger molecular structures, an effect strongly enforced by the inter-dot strain fields, and consequently it is not possible to experimentally obtain a separate optical emission from the smaller dots.

  7. The neural circuitry supporting goal maintenance during cognitive control: a comparison of expectancy AX-CPT and dot probe expectancy paradigms

    PubMed Central

    Lesh, Tyler A.; Salo, Taylor; Barch, Deanna M.; MacDonald, Angus W.; Gold, James M.; Ragland, J. Daniel; Strauss, Milton; Silverstein, Steven M.; Carter, Cameron S.

    2016-01-01

    Goal maintenance is an aspect of cognitive control that has been identified as critical for understanding psychopathology according to criteria of the NIMH-sponsored CNTRICS (Cognitive Neuroscience Treatment Research to Improve Cognition in Schizophrenia) and Research Domain Criteria (RDoC) initiatives. CNTRICS proposed the expectancy AX-CPT, and its visual-spatial parallel the dot probe expectancy (DPX), as valid measures of the cognitive and neural processes thought to be relevant for goal maintenance. The goal of this study was to specifically examine the functional neural correlates and connectivity patterns of both goal maintenance tasks in the same subset of subjects to further validate their neural construct validity and clarify our understanding of the nature and function of the neural circuitry engaged by the tasks. Twenty-six healthy control subjects performed both the letter (AX) and dot pattern (DPX) variants of the CPT during fMRI. Behavioral performance was similar between tasks. The 2 tasks engaged the same brain networks including dorsolateral prefrontal cortex (DLPFC) and dorsal parietal regions, supporting their validity as complementary measures of the goal maintenance construct. Interestingly there was greater engagement of the frontal opercular insula region during the expectancy AX-CPT (letter) and greater functional connectivity between the PFC and medial temporal lobe in the DPX (dot pattern). These differences are consistent with differential recruitment of phonological and visual-spatial processes by the two tasks and suggest that additional long-term memory systems may be engaged by the dot probe version. PMID:26494483

  8. Selective attention to food-related stimuli in hunger: are attentional biases specific to emotional and psychopathological states, or are they also found in normal drive states?

    PubMed

    Mogg, K; Bradley, B P; Hyare, H; Lee, S

    1998-02-01

    Previous work has indicated that anxiety disorders and eating disorders are associated with selective processing of stimuli relevant to patients' concerns (e.g. Mathews and MacLeod, 1994; Annual Review of Psychology, 45, 25-50; Channon et al., 1988; British Journal of Clinical Psychology, 27, 259-260). A dot probe task was used to investigate whether attentional biases are also a feature of a normal drive state. Specifically, we examined whether hunger is associated with biases in selective attention and in pre-attentive processes for food-relevant stimuli. Subjects with high levels of hunger showed a greater attentional bias for food-related words presented in a suprathreshold exposure condition (words shown for 500 msec), in comparison with those with low hunger. There was no evidence in the present study of a hunger-related bias in pre-attentive processes (i.e. when words were shown for 14 msec and masked). Results suggest that a non-emotional motivational state, such as hunger, is associated with a bias in certain aspects of information processing, such as selective attention, for stimuli that are relevant to the motivational state. Findings are discussed in relation to recent research into emotion-related cognitive biases.

  9. How do people order stimuli?

    PubMed

    Kemp, Simon; Grace, Randolph C

    2014-08-01

    People may find it easier to construct an order after first representing stimuli on a scale or categorizing them, particularly when the number of stimuli to be ordered is large or when some of them must be remembered. Five experiments tested this hypothesis. In two of these experiments (1 and 3), we asked participants to rank line lengths or to rank photographs by artistic value. The participants provided evidence of how they performed these tasks, and this evidence indicated that they often made use of some preliminary representation--either a metric or a categorization. Two further experiments (2 and 4) indicated that people rarely produced rankings when given a choice of assessment measures for either the length of lines or the artistic value of photographs. In Experiment 5, when the number of lines was larger or lines were only visible one at a time, participants were faster at estimating line lengths as a percentage of the card covered than at rank ordering the lengths. Overall, the results indicate that ordering stimuli is not an easy or natural process when the number of stimuli is large or when the stimuli are not all perceptible at once. An implication is that the psychological measures available to individuals are not likely to be purely ordinal when many of the elements being measured must be recalled.

  10. Probing silicon quantum dots by single-dot techniques

    NASA Astrophysics Data System (ADS)

    Sychugov, Ilya; Valenta, Jan; Linnros, Jan

    2017-02-01

    Silicon nanocrystals represent an important class of non-toxic, heavy-metal free quantum dots, where the high natural abundance of silicon is an additional advantage. Successful development in mass-fabrication, starting from porous silicon to recent advances in chemical and plasma synthesis, opens up new possibilities for applications in optoelectronics, bio-imaging, photovoltaics, and sensitizing areas. In this review basic physical properties of silicon nanocrystals revealed by photoluminescence spectroscopy, lifetime, intensity trace and electrical measurements on individual nanoparticles are summarized. The fabrication methods developed for accessing single Si nanocrystals are also reviewed. It is concluded that silicon nanocrystals share many of the properties of direct bandgap nanocrystals exhibiting sharp emission lines at low temperatures, on/off blinking, spectral diffusion etc. An analysis of reported results is provided in comparison with theory and with direct bandgap material quantum dots. In addition, the role of passivation and inherent interface/matrix defects is discussed.

  11. Stimuli, Reinforcers, and Private Events

    PubMed Central

    Nevin, John A

    2008-01-01

    Radical behaviorism considers private events to be a part of ongoing observable behavior and to share the properties of public events. Although private events cannot be measured directly, their roles in overt action can be inferred from mathematical models that relate private responses to external stimuli and reinforcers according to the same quantitative relations that characterize public operant behavior. This approach is illustrated by a model of attending to stimuli and to anticipated reinforcers in delayed matching to sample, in which the probabilities of attending are related to reinforcer rates by an expression derived from research on behavioral momentum. PMID:22478505

  12. Stimuli, reinforcers, and private events.

    PubMed

    Nevin, John A

    2008-01-01

    Radical behaviorism considers private events to be a part of ongoing observable behavior and to share the properties of public events. Although private events cannot be measured directly, their roles in overt action can be inferred from mathematical models that relate private responses to external stimuli and reinforcers according to the same quantitative relations that characterize public operant behavior. This approach is illustrated by a model of attending to stimuli and to anticipated reinforcers in delayed matching to sample, in which the probabilities of attending are related to reinforcer rates by an expression derived from research on behavioral momentum.

  13. Comparison of low frequency charge noise in identically patterned Si/SiO{sub 2} and Si/SiGe quantum dots

    SciTech Connect

    Freeman, Blake M.; Schoenfield, Joshua S.; Jiang, HongWen

    2016-06-20

    We investigate and compare the charge noise in Si/SiO{sub 2} and Si/SiGe gate defined quantum dots with identically patterned gates by measuring the low frequency 1/f current noise through the biased quantum dots in the coulomb blockade regime. The current noise is normalized and used to extract a measurement of the potential energy noise in the system. Additionally, the temperature dependence of this noise is investigated. The measured charge noise in Si/SiO{sub 2} compares favorably with that of the SiGe device as well as previous measurements made on other substrates suggesting Si/SiO{sub 2} is a potential candidate for spin based quantum computing.

  14. Spatial frequency specific interaction of dot patterns and gratings.

    PubMed Central

    De Valois, K K; Switkes, E

    1980-01-01

    Adaptation to patterns of paired random dots produces loss of contrast sensitivity to sinusoidal luminance gratings oriented perpendicularly to the dot-pair direction. This adaptation loss is spatial frequency- and orientation-specific and varies with dot-pair separation in a manner predictable from the Fourier spectra of the stimuli and observed characteristics of the visual system. These results support the idea that the visual system acts as a periodicity analyzer with known restrictions and cannot be accounted for by a feature-detector model. When the bars of the test gratings are aligned in the dot-pair direction, there is no adaptational loss at any frequency despite the fact that the adaptation pattern contains significant spectral power at all frequencies in this orientation. This lack of adaptation may be due to inhibitory interactions among channels or to nonlinear effects within local receptive fields. Images PMID:6928651

  15. Consistency of Border-Ownership Cells across Artificial Stimuli, Natural Stimuli, and Stimuli with Ambiguous Contours.

    PubMed

    Hesse, Janis K; Tsao, Doris Y

    2016-11-02

    Segmentation and recognition of objects in a visual scene are two problems that are hard to solve separately from each other. When segmenting an ambiguous scene, it is helpful to already know the present objects and their shapes. However, for recognizing an object in clutter, one would like to consider its isolated segment alone to avoid confounds from features of other objects. Border-ownership cells (Zhou et al., 2000) appear to play an important role in segmentation, as they signal the side-of-figure of artificial stimuli. The present work explores the role of border-ownership cells in dorsal macaque visual areas V2 and V3 in the segmentation of natural object stimuli and locally ambiguous stimuli. We report two major results. First, compared with previous estimates, we found a smaller percentage of cells that were consistent across artificial stimuli used previously. Second, we found that the average response of those neurons that did respond consistently to the side-of-figure of artificial stimuli also consistently signaled, as a population, the side-of-figure for borders of single faces, occluding faces and, with higher latencies, even stimuli with illusory contours, such as Mooney faces and natural faces completely missing local edge information. In contrast, the local edge or the outlines of the face alone could not always evoke a significant border-ownership signal. Our results underscore that border ownership is coded by a population of cells, and indicate that these cells integrate a variety of cues, including low-level features and global object context, to compute the segmentation of the scene.

  16. Stress, Distress, and Psychosocial Stimuli

    ERIC Educational Resources Information Center

    Levi, Lennert

    1973-01-01

    This paper, presented at the Occupational Stress Conference of the Center for Occupational Mental Health, Sept. 22, 1972, discusses the possibility of a relationship between psychosocial stimuli and stress-related disease. Using Selye's understanding of stress, the author views it in relation to non-specific diseases and suggests hypotheses…

  17. Stimuli, Reinforcers, and Private Events

    ERIC Educational Resources Information Center

    Nevin, John A.

    2008-01-01

    Radical behaviorism considers private events to be a part of ongoing observable behavior and to share the properties of public events. Although private events cannot be measured directly, their roles in overt action can be inferred from mathematical models that relate private responses to external stimuli and reinforcers according to the same…

  18. Stimuli, Reinforcers, and Private Events

    ERIC Educational Resources Information Center

    Nevin, John A.

    2008-01-01

    Radical behaviorism considers private events to be a part of ongoing observable behavior and to share the properties of public events. Although private events cannot be measured directly, their roles in overt action can be inferred from mathematical models that relate private responses to external stimuli and reinforcers according to the same…

  19. Luminescent Quantum Dots as Ultrasensitive Biological Labels

    NASA Astrophysics Data System (ADS)

    Nie, Shuming

    2000-03-01

    Highly luminescent semiconductor quantum dots have been covalently coupled to biological molecules for use in ultrasensitive biological detection. This new class of luminescent labels is considerably brighter and more resistant againt photobleaching in comparison with organic dyes. Quantum dots labeled with the protein transferrin undergo receptor-mediated endocytosis (RME) in cultured HeLa cells, and those dots that were conjugated to immunomolecules recognize specific antibodies or antigens. In addition, we show that DNA functionalized quantum dots can be used to target specific genes by hybridization. We expect that quantum dot bioconjugates will have a broad range of biological applications, such as ligand-receptor interactions, real-time monitoring of molecular trafficking inside living cells, multicolor fluorescence in-situ hybridization (FISH), high-sensitivity detection in miniaturized devices (e.g., DNA chips), and fluorescent tagging of combinatorial chemical libraries. A potential clinical application is the use of quantum dots for ultrasensitive viral RNA detection, in which as low as 100 copies of hepatitis C and HIV viruses per ml blood should be detected.

  20. Bayesian-based integration of multisensory naturalistic perithreshold stimuli.

    PubMed

    Regenbogen, Christina; Johansson, Emilia; Andersson, Patrik; Olsson, Mats J; Lundström, Johan N

    2016-07-29

    Most studies exploring multisensory integration have used clearly perceivable stimuli. According to the principle of inverse effectiveness, the added neural and behavioral benefit of integrating clear stimuli is reduced in comparison to stimuli with degraded and less salient unisensory information. Traditionally, speed and accuracy measures have been analyzed separately with few studies merging these to gain an understanding of speed-accuracy trade-offs in multisensory integration. In two separate experiments, we assessed multisensory integration of naturalistic audio-visual objects consisting of individually-tailored perithreshold dynamic visual and auditory stimuli, presented within a multiple-choice task, using a Bayesian Hierarchical Drift Diffusion Model that combines response time and accuracy. For both experiments, unisensory stimuli were degraded to reach a 75% identification accuracy level for all individuals and stimuli to promote multisensory binding. In Experiment 1, we subsequently presented uni- and their respective bimodal stimuli followed by a 5-alternative-forced-choice task. In Experiment 2, we controlled for low-level integration and attentional differences. Both experiments demonstrated significant superadditive multisensory integration of bimodal perithreshold dynamic information. We present evidence that the use of degraded sensory stimuli may provide a link between previous findings of inverse effectiveness on a single neuron level and overt behavior. We further suggest that a combined measure of accuracy and reaction time may be a more valid and holistic approach of studying multisensory integration and propose the application of drift diffusion models for studying behavioral correlates as well as brain-behavior relationships of multisensory integration. Copyright © 2015 Elsevier Ltd. All rights reserved.

  1. Comparison of dot blot hybridization, polymerase chain reaction, and virus isolation for detection of bovine herpesvirus-1 (BHV-1) in artificially infected bovine semen.

    PubMed Central

    Xia, J Q; Yason, C V; Kibenge, F S

    1995-01-01

    Bovine semen samples spiked with bovine herpesvirus 1 (BHV-1) were used to compare dot blot hybridization, polymerase chain reaction (PCR), and virus isolation for detection of BHV-1 in bovine semen. The PCR amplification used primers targeting the BHV-1 thymidine kinase gene and a nucleic acid releasing cocktail (GeneReleaser); the PCR product was used as the DNA probe in dot blot hybridization; virus isolation was done in primary bovine fetal testis (BFT) cell cultures. Semen diluted 1:20 in tissue culture medium had the least cytotoxicity and inhibition of viral cytopathic effects in BFT cells, allowing detection of 1 TCID50/100 microL of BHV-1 suspension by virus isolation. The presence of foreign DNA such as bovine sperm DNA or salmon sperm DNA increased the sensitivity of dot blot hybridization in detecting BHV-1, allowing detection of 20,000 TCID50/100 microL of neat semen. The inhibition of PCR amplification of BHV-1 DNA in bovine semen was eliminated by diluting the samples 1:20 in tissue culture medium. The best PCR amplification was obtained when semen was diluted 1:20 and when a reaction buffer of pH 9.0, with 1.0 mM MgCl2 was used. Under these conditions, the PCR followed by ethidium bromide staining of agarose gels could detect 1 TCID20/100 microL of sample, whereas PCR followed by Southern blot hybridization could detect 0.01 TCID50/100 microL of sample.(ABSTRACT TRUNCATED AT 250 WORDS) Images Fig. 1. Fig. 2. Fig. 3. PMID:7648521

  2. Random-Dot Stereogram

    NASA Astrophysics Data System (ADS)

    Kuwayama, Tetsuro

    The technology and history of random-dot stereogram are described. The paper on two-picture type random-dot stereogram is delivered in 1960, and this technology came to be known widely in 1960s. On the other hand, the principle of the single image random-dot stereogram (Autostereogram) was invented in 1979, but came to be known since the announcement of SPIE conference in 1990. Wallpaper stereogram is also described.

  3. Cognitive robotic system for learning of complex visual stimuli

    NASA Astrophysics Data System (ADS)

    Potapov, A. S.; Rozhkov, A. S.

    2013-05-01

    The problem of learning of complex visual stimuli in cognitive robotics is considered. These stimuli should be selected on the base of rules supporting arbitrary comparisons of stimulus features with features of other salient objects (context). New perceptual knowledge representation based on the predicate logic is implemented to express such rules. Computable predicates are provided by low-level vision system. The rules are constructed using genetic algorithms on the base of a set of examples obtained by a robot during consequent trials. Dependence between the number of necessary trials and rule complexity is studied.

  4. Quantum dots in aperiodic order

    NASA Astrophysics Data System (ADS)

    Hörnquist, Michael; Ouchterlony, Thomas

    1998-12-01

    We study numerically with a Green-function technique one-dimensional arrays of quantum dots with two different models. The arrays are ordered according to the Fibonacci, the Thue-Morse, and the Rudin-Shapiro sequences. As a comparison, results from a periodically ordered chain and also from a random chain are included. The focus is on how the conductance (calculated within the Landauer-Büttiker formalism) depends on the Fermi level. In the first model, we find that in some cases rather small systems (≈60 dots) behave in the same manner as very large systems (>16,000 dots) and this makes it possible in these cases to interpret our results for the small systems in terms of the spectral properties of the infinite systems. In particular, we find that it is possible to see some consequences of the singular continuous spectra that some of the systems possess, at least for temperatures up to 100 mK. In the second model, we study the phenomenon ohmic addition, i.e. when the resistances of the constrictions add up to the total resistance. It results that of the systems studied, it is only the Rudin-Shapiro system that has this behaviour for large structures, while the resistances of the Fibonacci and the Thue-Morse systems might reach a limiting value (as a periodic system does).

  5. Visual stimuli in daily life.

    PubMed

    Kasteleijn-Nolst Trenité, Dorothée G A; van der Beld, Gerrit; Heynderickx, Ingrid; Groen, Paul

    2004-01-01

    People of all ages, but especially children and adolescents, are increasingly exposed to visual stimuli. Typical environmental stimuli that can trigger epileptic seizures in susceptible persons are televisions (TVs), computers, videogames (VGs), discothèque lights, venetian blinds, striped walls, rolling stairs (escalators), striped clothing, and sunlight reflected from snow or the sea or interrupted by trees during a ride in a car or train. Less common stimuli are rotating helicopter blades, disfunctioning fluorescent lighting, welding lights, etc. New potentially provocative devices turn up now and then unexpectedly. During the last decades especially, displays have become increasingly dominant in many of our daily-life activities. We therefore focus mainly on the characteristics of artificial light and on current and future developments in video displays and videogames. Because VG playing has been shown also to have positive effects, a rating system might be developed for provocativeness to inform consumers about the content. It is important that patients with epilepsy be informed adequately about their possible visual sensitivity.

  6. Bandgap Inhomogeneity of a PbSe Quantum Dot Ensemble from Two-Dimensional Spectroscopy and Comparison to Size Inhomogeneity from Electron Microscopy

    DOE PAGES

    Park, Samuel D.; Baranov, Dmitry; Ryu, Jisu; ...

    2017-01-03

    Femtosecond two-dimensional Fourier transform spectroscopy is used to determine the static bandgap inhomogeneity of a colloidal quantum dot ensemble. The excited states of quantum dots absorb light, so their absorptive two-dimensional (2D) spectra will typically have positive and negative peaks. We show that the absorption bandgap inhomogeneity is robustly determined by the slope of the nodal line separating positive and negative peaks in the 2D spectrum around the bandgap transition; this nodal line slope is independent of excited state parameters not known from the absorption and emission spectra. The absorption bandgap inhomogeneity is compared to a size and shape distributionmore » determined by electron microscopy. The electron microscopy images are analyzed using new 2D histograms that correlate major and minor image projections to reveal elongated nanocrystals, a conclusion supported by grazing incidence small-angle X-ray scattering and high-resolution transmission electron microscopy. Lastly, the absorption bandgap inhomogeneity quantitatively agrees with the bandgap variations calculated from the size and shape distribution, placing upper bounds on any surface contributions.« less

  7. A Comparison of Antibacterial Activity of Selected Thyme (Thymus) Species by Means of the Dot Blot Test with Direct Bioautographic Detection.

    PubMed

    Orłowska, Marta; Kowalska, Teresa; Sajewicz, Mieczysław; Jesionek, Wioleta; Choma, Irena M; Majer-Dziedzic, Barbara; Szymczak, Grażyna; Waksmundzka-Hajnos, Monika

    2015-01-01

    Bioautography carried out with the aid of thin-layer chromatographic adsorbents can be used to assess antibacterial activity in samples of different origin. It can either be used as a simple and cost-effective detection method applied to a developed chromatogram, or to the dot blot test performed on a chromatographic plate, where total antibacterial activity of a sample is scrutinized. It was an aim of this study to compare antibacterial activity of 18 thyme (Thymus) specimens and species (originating from the same gardening plot and harvested in the same period of time) by means of a dot blot test with direct bioautography. A two-step extraction of herbal material was applied, and at step two the polar fraction of secondary metabolites was obtained under the earlier optimized extraction conditions [methanol-water (27+73, v/v), 130°C]. This fraction was then tested for its antibacterial activity against Bacillus subtilis bacteria. It was established that all investigated extracts exhibited antibacterial activity, yet distinct differences were perceived in the size of the bacterial growth inhibition zones among the compared thyme species. Based on the results obtained, T. citriodorus "golden dwarf" (sample No. 5) and T. marschallianus (sample No. 6) were selected as promising targets for further investigations and possible inclusion in a herbal pharmacopeia, which is an essential scientific novelty of this study.

  8. Bandgap Inhomogeneity of a PbSe Quantum Dot Ensemble from Two-Dimensional Spectroscopy and Comparison to Size Inhomogeneity from Electron Microscopy.

    PubMed

    Park, Samuel D; Baranov, Dmitry; Ryu, Jisu; Cho, Byungmoon; Halder, Avik; Seifert, Sönke; Vajda, Stefan; Jonas, David M

    2017-02-08

    Femtosecond two-dimensional Fourier transform spectroscopy is used to determine the static bandgap inhomogeneity of a colloidal quantum dot ensemble. The excited states of quantum dots absorb light, so their absorptive two-dimensional (2D) spectra will typically have positive and negative peaks. It is shown that the absorption bandgap inhomogeneity is robustly determined by the slope of the nodal line separating positive and negative peaks in the 2D spectrum around the bandgap transition; this nodal line slope is independent of excited state parameters not known from the absorption and emission spectra. The absorption bandgap inhomogeneity is compared to a size and shape distribution determined by electron microscopy. The electron microscopy images are analyzed using new 2D histograms that correlate major and minor image projections to reveal elongated nanocrystals, a conclusion supported by grazing incidence small-angle X-ray scattering and high-resolution transmission electron microscopy. The absorption bandgap inhomogeneity quantitatively agrees with the bandgap variations calculated from the size and shape distribution, placing upper bounds on any surface contributions.

  9. Comparison of dynamic properties of ground- and excited-state emission in p-doped InAs/GaAs quantum-dot lasers

    SciTech Connect

    Arsenijević, D. Schliwa, A.; Schmeckebier, H.; Stubenrauch, M.; Spiegelberg, M.; Bimberg, D.; Mikhelashvili, V.; Eisenstein, G.

    2014-05-05

    The dynamic properties of ground- and excited-state emission in InAs/GaAs quantum-dot lasers operating close to 1.31 μm are studied systematically. Under low bias conditions, such devices emit on the ground state, and switch to emission from the excited state under large drive currents. Modification of one facet reflectivity by deposition of a dichroic mirror yields emission at one of the two quantum-dot states under all bias conditions and enables to properly compare the dynamic properties of lasing from the two different initial states. The larger differential gain of the excited state, which follows from its larger degeneracy, as well as its somewhat smaller nonlinear gain compression results in largely improved modulation capabilities. We demonstrate maximum small-signal bandwidths of 10.51 GHz and 16.25 GHz for the ground and excited state, respectively, and correspondingly, large-signal digital modulation capabilities of 15 Gb/s and 22.5 Gb/s. For the excited state, the maximum error-free bit rate is 25 Gb/s.

  10. Enhanced brain susceptibility to negative stimuli in adolescents: ERP evidences

    PubMed Central

    Yuan, Jiajin; Ju, Enxia; Meng, Xianxin; Chen, Xuhai; Zhu, Siyu; Yang, Jiemin; Li, Hong

    2015-01-01

    Background: Previous studies investigated neural substrates of emotional face processing in adolescents and its comparison with adults. As emotional faces elicit more of emotional expression recognition rather than direct emotional responding, it remains undetermined how adolescents are different from adults in brain susceptibility to emotionally stressful stimuli. Methods: Event-Related Potentials (ERPs) were recorded for highly negative (HN), moderately negative (MN), and neutral pictures in 20 adolescents and 20 adults while subjects performed a standard/deviant distinction task by pressing different keys, irrespective of the emotionality of deviant stimuli. Results: Adolescents exhibited more negative amplitudes for HN vs. neutral pictures in N1 (100–150 ms), P2 (130–190 ms), N2 (210–290 ms), and P3 (360–440 ms) components. In addition, adolescents showed more negative amplitudes for MN compared to neutral pictures in N1, P2, and N2 components. By contrast, adults exhibited significant emotion effects for HN stimuli in N2 and P3 amplitudes but not in N1 and P2 amplitudes, and they did not exhibit a significant emotion effect for MN stimuli at all these components. In the 210–290 ms time interval, the emotion effect for HN stimuli was significant across frontal and central regions in adolescents, while this emotion effect was noticeable only in the central region for adults. Conclusions: Adolescents are more emotionally sensitive to negative stimuli compared to adults, regardless of the emotional intensity of the stimuli, possibly due to the immature prefrontal control system over the limbic emotional inputs during adolescence. PMID:25972790

  11. Quantum Dots: Theory

    SciTech Connect

    Vukmirovic, Nenad; Wang, Lin-Wang

    2009-11-10

    This review covers the description of the methodologies typically used for the calculation of the electronic structure of self-assembled and colloidal quantum dots. These are illustrated by the results of their application to a selected set of physical effects in quantum dots.

  12. The Impact of Stimuli on Affect in Persons With Dementia

    PubMed Central

    Cohen-Mansfield, Jiska; Marx, Marcia S.; Thein, Khin; Dakheel-Ali, Maha

    2011-01-01

    Objective To examine how presentation of different stimuli impacts affect in nursing home residents with dementia. Method Participants were 193 residents aged 60 to 101 years from 7 Maryland nursing homes who had a diagnosis of dementia (derived from the medical chart or obtained from the attending physician). Cognitive functioning was assessed via the Mini-Mental State Examination (MMSE), and data pertaining to activities of daily living were obtained through the Minimum Data Set. Affect was assessed using observations of the 5 moods from Lawton’s Modified Behavior Stream. Baseline observations of affect were performed for comparisons. During the study, each participant was presented with 25 predetermined engagement stimuli in random order over a period of 3 weeks. Stimuli were categorized as live social, simulated social, manipulative, work/task-related, music, reading, or individualized to the participant’s self-identity. The dates of data collection were 2005–2007. Results Differences between stimulus categories were significant for pleasure (F6,144 = 25.137, P < .001) and interest (F6,144 = 18.792, P < .001) but not for negative affect. Pleasure and interest were highest for the live social category, followed by self-identity and simulated social stimuli for pleasure, and for manipulative stimuli in terms of the effect on interest. The lowest levels of pleasure and interest were observed for music. Participants with higher cognitive function had significantly higher pleasure (F1,97 = 6.27, P < .05). Although the general trend of the impact of the different categories was similar for different levels of cognitive function, there were significant differences in pleasure in response to specific stimuli (interaction effect: F6,92 = 2.31, P < .05). Overall, social stimuli have the highest impact on affect in persons with dementia. Conclusions The findings of the present study are important, as affect is a major indicator of quality of life and this study is

  13. Effects of complex aural stimuli on mental performance.

    PubMed

    Vij, Mohit; Aghazadeh, Fereydoun; Ray, Thomas G; Hatipkarasulu, Selen

    2003-06-01

    The objective of this study is to investigate the effect of complex aural stimuli on mental performance. A series of experiments were designed to obtain data for two different analyses. The first analysis is a "Stimulus" versus "No-stimulus" comparison for each of the four dependent variables, i.e. quantitative ability, reasoning ability, spatial ability and memory of an individual, by comparing the control treatment with the rest of the treatments. The second set of analysis is a multi-variant analysis of variance for component level main effects and interactions. The two component factors are tempo of the complex aural stimuli and sound volume level, each administered at three discrete levels for all four dependent variables. Ten experiments were conducted on eleven subjects. It was found that complex aural stimuli influence the quantitative and spatial aspect of the mind, while the reasoning ability was unaffected by the stimuli. Although memory showed a trend to be worse with the presence of complex aural stimuli, the effect was statistically insignificant. Variation in tempo and sound volume level of an aural stimulus did not significantly affect the mental performance of an individual. The results of these experiments can be effectively used in designing work environments.

  14. Quantum Dot Solar Cells

    NASA Technical Reports Server (NTRS)

    Raffaelle, Ryne P.; Castro, Stephanie L.; Hepp, Aloysius; Bailey, Sheila G.

    2002-01-01

    We have been investigating the synthesis of quantum dots of CdSe, CuInS2, and CuInSe2 for use in an intermediate bandgap solar cell. We have prepared a variety of quantum dots using the typical organometallic synthesis routes pioneered by Bawendi, et. al., in the early 1990's. However, unlike previous work in this area we have also utilized single-source precursor molecules in the synthesis process. We will present XRD, TEM, SEM and EDS characterization of our initial attempts at fabricating these quantum dots. Investigation of the size distributions of these nanoparticles via laser light scattering and scanning electron microscopy will be presented. Theoretical estimates on appropriate quantum dot composition, size, and inter-dot spacing along with potential scenarios for solar cell fabrication will be discussed.

  15. Quantum Dot Solar Cells

    NASA Technical Reports Server (NTRS)

    Raffaelle, Ryne P.; Castro, Stephanie L.; Hepp, Aloysius; Bailey, Sheila G.

    2002-01-01

    We have been investigating the synthesis of quantum dots of CdSe, CuInS2, and CuInSe2 for use in an intermediate bandgap solar cell. We have prepared a variety of quantum dots using the typical organometallic synthesis routes pioneered by Bawendi, et. al., in the early 1990's. However, unlike previous work in this area we have also utilized single-source precursor molecules in the synthesis process. We will present XRD, TEM, SEM and EDS characterization of our initial attempts at fabricating these quantum dots. Investigation of the size distributions of these nanoparticles via laser light scattering and scanning electron microscopy will be presented. Theoretical estimates on appropriate quantum dot composition, size, and inter-dot spacing along with potential scenarios for solar cell fabrication will be discussed.

  16. Emotional Stimuli and Motor Conversion Disorder

    ERIC Educational Resources Information Center

    Voon, Valerie; Brezing, Christina; Gallea, Cecile; Ameli, Rezvan; Roelofs, Karin; LaFrance, W. Curt, Jr.; Hallett, Mark

    2010-01-01

    Conversion disorder is characterized by neurological signs and symptoms related to an underlying psychological issue. Amygdala activity to affective stimuli is well characterized in healthy volunteers with greater amygdala activity to both negative and positive stimuli relative to neutral stimuli, and greater activity to negative relative to…

  17. Emotional Stimuli and Motor Conversion Disorder

    ERIC Educational Resources Information Center

    Voon, Valerie; Brezing, Christina; Gallea, Cecile; Ameli, Rezvan; Roelofs, Karin; LaFrance, W. Curt, Jr.; Hallett, Mark

    2010-01-01

    Conversion disorder is characterized by neurological signs and symptoms related to an underlying psychological issue. Amygdala activity to affective stimuli is well characterized in healthy volunteers with greater amygdala activity to both negative and positive stimuli relative to neutral stimuli, and greater activity to negative relative to…

  18. Attitude Formation, Novel Stimuli, and Exposure Effects.

    ERIC Educational Resources Information Center

    Grush, Joseph E.

    Ten Turkish words were used as stimuli in an exposure experiment. Twenty-five students from the University of Illinois subject pool were divided into five subgroups, differing only with respect to which stimuli occurred in which exposure conditions. After the stimuli were evaluated on 7-point "good-bad" scales, subjects completed a questionnaire…

  19. Blur-resistant Perimetric Stimuli

    PubMed Central

    Horner, Douglas G.; Dul, Mitchell W.; Swanson, William H.; Liu, Tiffany; Tran, Irene

    2013-01-01

    Purpose To develop perimetric stimuli which are resistant to the effects of peripheral defocus. Methods One eye each was tested on subjects free of eye disease. Experiment 1 assessed spatial frequency, testing 12 subjects at eccentricities from 2° to 7°, using blur levels from 0 D to 3 D for two (Gabor) stimuli (spatial standard deviation (SD) = 0.5°, spatial frequencies of 0.5 and 1.0 cpd). Experiment 2 assessed stimulus size, testing 12 subjects at eccentricities from 4° to 7°, using blur levels 0 D to 6 D, for two Gaussians with SDs of 0.5° and 0.25° and a 0.5 cpd Gabor with SD of 0.5°. Experiment 3 tested 13 subjects at eccentricities from fixation to 27°, using blur levels 0 D to 6 D, for Gabor stimuli at 56 locations; the spatial frequency ranged from 0.14 to 0.50 cpd with location, and SD was scaled accordingly. Results In experiment 1, blur by 3 D caused a small decline in log contrast sensitivity (CS) for the 0.5 cpd stimulus (mean ± SE = −0.09 ± 0.08 log unit) and a larger (t = 7.7, p <0.0001) decline for the 1.0 cpd stimulus (0.37 ± 0.13 log unit). In experiment 2, blur by 6 D caused minimal decline for the larger Gaussian, by −0.17 ± 0.16 log unit, and larger (t >4.5, p < 0.001) declines for the smaller Gaussian (−0.33 ± 0.16 log unit) and the Gabor (−0.36 ± 0.18 log unit). In experiment 3, blur by 6 D caused declines by 0.27 ± 0.05 log unit for eccentricities from 0° to 10°, by 0.20 ± 0.04 log unit for eccentricities from 10° to 20° and 0.13 ± 0.03 log unit for eccentricities from 20°–27°. Conclusions Experiments 1 & 2 allowed us to design stimuli for Experiment 3 that were resistant to effects of peripheral defocus. PMID:23584488

  20. Blur-resistant perimetric stimuli.

    PubMed

    Horner, Douglas G; Dul, Mitchell W; Swanson, William H; Liu, Tiffany; Tran, Irene

    2013-05-01

    To develop perimetric stimuli that are resistant to the effects of peripheral defocus. One eye each was tested on subjects free of eye disease. Experiment 1 assessed spatial frequency, testing 12 subjects at eccentricities from 2 to 7 degrees using blur levels from 0 to 3 diopters (D) for two (Gabor) stimuli (spatial SD, 0.5 degrees; spatial frequencies, 0.5 and 1.0 cycles per degree [cpd]). Experiment 2 assessed stimulus size, testing 12 subjects at eccentricities from 4 to 7 degrees using blur levels 0 to 6 D for two Gaussians with SD of 0.5 and 0.25 degrees and a 0.5-cpd Gabor with SD of 0.5 degrees. Experiment 3 tested 13 subjects at eccentricities from fixation to 27 degrees using blur levels 0 to 6 D for Gabor stimuli at 56 locations; the spatial frequency ranged from 0.14 to 0.50 cpd with location, and SD was scaled accordingly. In experiment 1, blur by 3 D caused a small decline in log contrast sensitivity for the 0.5-cpd stimulus (mean ± SE, 0.09 ± 0.08 log units) and a larger (t = 7.7, p < 0.0001) decline for the 1.0-cpd stimulus (0.37 ± 0.13 log units). In experiment 2, blur by 6 D caused minimal decline for the larger Gaussian, by 0.17 ± 0.16 log units, and larger (t > 4.5, p < 0.001) declines for the smaller Gaussian (0.33 ± 0.16 log units) and the Gabor (0.36 ± 0.18 log units). In experiment 3, blur by 6 D caused declines by 0.27 ± 0.05 log units for eccentricities from 0 to 10 degrees, by 0.20 ± 0.04 log units for eccentricities from 10 to 20 degrees, and 0.13 ± 0.03 log units for eccentricities from 20 to 27 degrees. Experiments 1 and 2 allowed us to design stimuli for experiment 3 that were resistant to effects of peripheral defocus.

  1. [Public health nurse support at initial community DOTS meetings with non-hospitalized tuberculosis patients--comparison of patients who did and did not complete treatment].

    PubMed

    Mori, Reiko; Gokan, Yoko; Ishihara, Takako

    2013-11-01

    This study focused on the initial meeting between public health nurses and TB patients to investigate the detection of patients' needs and the support provided by public health nurses during the meeting, with the aim of successfully implementing a directly observed treatment short course (DOTS) strategy for the community. A self-administered questionnaire was sent to nurses responsible for community DOTS strategy for TB in Aichi, Gifu, Mie, and Shizuoka prefectures in the Tokai region in order to collect the following information concerning the initial meeting between public health nurses and TB patients: nurses' characteristics, patient characteristics, information collected by the nurses, concerns expressed by patients, and specific support provided by the nurses. Data collected were compared between patients who completed TB treatment (complete treatment group) and those who did not (incomplete treatment group). Valid responses were obtained from 42 public health nurses regarding 158 TB patients. The incomplete treatment group had a high proportion of patients who received no support from their families, had irregular lifestyles, or had financial problems. There were discrepancies between the information collected by public health nurses and patients' concerns. It was also revealed that public health nurses provided more specific support and a wider range of support to the incomplete treatment group, suggesting that public health nurses give specific support in the initial meeting to patients who were likely to discontinue TB treatment, thereby motivating them to complete the treatment. It is essential to arrange initial public health nurse-patient meetings at an early stage to build patients awareness of the disease and the importance of treatment adherence. Continuous support is crucial until the patients complete treatment.

  2. Dissociating estimation from comparison and response eliminates parietal involvement in sequential numerosity perception.

    PubMed

    Cavdaroglu, Seda; Katz, Curren; Knops, André

    2015-08-01

    It has been widely debated whether the parietal cortex stores an abstract representation of numerosity that is activated for Arabic digits as well as for non-symbolic stimuli in a sensory modality independent fashion. Some studies suggest that numerical information in time-invariant (simultaneous) symbolic and non-symbolic visual stimuli is represented in the parietal cortex. In humans, whether the same representation is activated for time-variant (sequential) stimuli and for stimuli coming from different modalities has not been determined. To investigate this idea, we measured the brain activation of healthy adults performing estimation and/or comparison of sequential visual (series of dots) and auditory (series of beeps) numerosities. Our experimental design allowed us to separate numerosity estimation from comparison and response related factors. The BOLD response in the parietal cortex increased only when participants were engaged in the comparison of two consecutive numerosities that required a response. Using multivariate pattern analysis we trained a classifier to decode numerosity in various regions of interest (ROI). We failed to find any parietal ROI where the classifier could decode numerosities during the estimation phase. Rather, when participants were not engaged in comparison we were able to decode numerosity in an auditory cortex ROI for auditory stimuli and in a visual cortex ROI for visual stimuli. On the other hand, during the response period the classifier successfully decoded numerosity information in a parietal ROI for both visual and auditory numerosities. These results were further confirmed by support vector regression. In sum, our study does not support the involvement of the parietal cortex during estimation of sequential numerosity in the absence of an active task with a response requirement.

  3. Geometry of epitaxial GaAs/(Al,Ga)As quantum dots as seen by excitonic spectroscopy

    NASA Astrophysics Data System (ADS)

    Luo, Jun-Wei; Zunger, Alex

    2011-12-01

    It is shown that exciton and multiexciton emission lines (“spectral barcode”) of a quantum dot conceal nontrivial structural information on the shape and size of the dot, information which can be uncovered by comparison with atomistic many-body theory. Application to the newly established strain-free GaAs quantum dots grown via “droplet epitaxy” onto AlGaAs matrix reveal the shape and size as “seen” by spectroscopy. The results show that the previously determined dot height (˜14 nm) as “seen” by cross-sectional scanning tunneling microscopy (XSTM) could not possibly be consistent with the excitonic signature (1.7-1.9 eV), as the latter must reflect dot height of 1-4 nm. Multiexciton “barcode” and fine structure spitting suggest GaAs/AlGaAs dots are in Gaussian-shape in agreement with XSTM measurement. Both spectroscopy and XSTM measurements were done on GaAs dots capped by the Al0.3Ga0.7As barrier layer. The fact that XSTM sees tall dots and spectroscopy sees short dots is thus not because the dot change its height in one experiment relative to the other but because different dots must have been used. This was uncovered by theoretical simulation of the experiment showing that the two experiments could not possibly correspond to the same dot.

  4. Comparison of MOVPE grown GaAs, InGaAs and GaAsSb covering layers for different InAs/GaAs quantum dot applications

    NASA Astrophysics Data System (ADS)

    Zíková, Markéta; Hospodková, Alice; Pangrác, Jiří; Oswald, Jiří; Hulicius, Eduard

    2017-04-01

    InAs/GaAs quantum dot (QD) heterostructures with different covering layers (CLs) prepared by MOVPE are compared in this work. The recombination energy of a structure covered only by GaAs depends nonlinearly on CL thickness. Experimental data of photoluminescence (PL) were supported by theoretical simulations. These simulations prove that the strain plays a major role in the structures. InGaAs strain reducing layer (SRL) was studied as well. Due to the strain reduction, the recombination energy is decreased, so the structure has longer PL wavelength. By theoretical simulations it was shown that for high content of In in InGaAs covering layer (approximately 45% and more), the heterostructure is type II, which would normally be unreachable for flat layers. For the structure with GaAsSb SRL, the band alignment is highly dependent on the SRL composition. The type I/type II transition occurs for approximately 15% of Sb; this value also slightly depends on the QD size. All structures were also studied by HRTEM to show different behavior of the CLs on the interface with InAs which highly influences the structure quality.

  5. Comparison between the Skin Snip Test and Simple Dot Blot Assay as Potential Rapid Assessment Tools for Onchocerciasis in the Postcontrol Era in Ghana

    PubMed Central

    Guzmán, G. E.; Awadzi, K.; Opoku, N.; Narayanan, R. B.; Akuffo, H. O.

    2002-01-01

    Successful control of onchocerciasis through mass distribution of ivermectin needs to be coupled with reliable, sensitive, specific, yet affordable diagnostic methods to monitor and ensure the efficacy of such measures. The effort put into the development of diagnostic methods for onchocerciasis that can substitute for or work in combination with the present “gold standard,” the skin snip test, has resulted in the discovery of a number of immunogenic proteins with potential use as diagnostic tools in the postcontrol era. Most of these proteins have now been produced through recombinant DNA techniques. However, when costs are not a trivial issue, none of them have yet found their way into the areas where the disease still exists. In the present study, we have evaluated the performance of a simple dot blot assay which uses a mixture of native proteins designated PakF as a serious contender in the quest for a less invasive and more sensitive method to detect Onchocerca volvulus infection in areas with diverse endemicities. Our results indicate that the assay we propose is more sensitive than the skin snip test and shows high specificity, both characteristics required for a suitable tool for the monitoring of onchocerciasis in the postcontrol era. PMID:12204952

  6. Nanocomposite liposomes containing quantum dots and anticancer drugs for bioimaging and therapeutic delivery: a comparison of cationic, PEGylated and deformable liposomes

    NASA Astrophysics Data System (ADS)

    Wen, Chih-Jen; Sung, Calvin T.; Aljuffali, Ibrahim A.; Huang, Yu-Jie; Fang, Jia-You

    2013-08-01

    Multifunctional liposomes loaded with quantum dots (QDs) and anticancer drugs were prepared for simultaneous bioimaging and drug delivery. Different formulations, including cationic, PEGylated and deformable liposomes, were compared for their theranostic efficiency. We had evaluated the physicochemical characteristics of these liposomes. The developed liposomes were examined using experimental platforms of cytotoxicity, cell migration, cellular uptake, in vivo melanoma imaging and drug accumulation in tumors. The average size of various nanocomposite liposomes was found to be 92-134 nm. Transmission electron microscopy confirmed the presence of QDs within liposomal bilayers. The incorporation of polyethylene glycol (PEG) and Span 20 into the liposomes greatly increased the fluidity of the bilayers. The liposomes provided sustained release of camptothecin and irinotecan. The cytotoxicity and cell migration assay demonstrated superior activity of cationic liposomes compared with other carriers. Cationic liposomes also showed a significant fluorescence signal in melanoma cells after internalization. The liposomes were intratumorally administered to a melanoma-bearing mouse. Cationic liposomes showed the brightest fluorescence in tumors, followed by classical liposomes. This signal could last for up to 24 h for cationic nanosystems. Intratumoral accumulation of camptothecin from free control was 35 nmol g-1 it could be increased to 50 nmol g-1 after loading with cationic liposomes. However, encapsulation of irinotecan into liposomes did not further increase intratumoral drug accumulation. Cationic liposomes were preferable to other liposomes as nanocarriers in both bioimaging and therapeutic approaches.

  7. Plasma kinetics and biodistribution of water-soluble CdTe quantum dots in mice: a comparison between Cd and Te

    NASA Astrophysics Data System (ADS)

    Han, Ying; Xie, Guangyun; Sun, Zhiwei; Mu, Ying; Han, Sihai; Xiao, Yang; Liu, Na; Wang, Hui; Guo, Caixia; Shi, Zhixiong; Li, Yanbo; Huang, Peili

    2011-10-01

    Water-soluble quantum dots (QDs) have shown potential as tumor diagnostic agents. However, little is known about their biological behaviors in vivo. Male ICR mice were intravenously given a single dose (2.5 μmol kg-1 body weight) of water-soluble cadmium-telluride (CdTe) QDs (the QDs are approximately 4 nm in diameter and have maximal emission at 630 nm). Inductively coupled plasma mass spectrometry (ICP-MS) was used for measuring the kinetic action of 111Cd and 125Te for 7 days. The plasma kinetics of Cd and Te followed a two-compartment model, in which Cd exhibited greater apparent volume of distribution, greater clearance, faster distribution half-life, and significantly slower elimination half-life compared to Te. Contrary to its relatively transient fate in the plasma, high levels of Cd persisted in the liver and kidneys. Te accumulated primarily in the spleen. The different plasma kinetics and distribution patterns of Cd and Te imply that CdTe QDs have been part of the degradation or aggregation in vivo.

  8. Comparison of two methods for selegiline determination: A flow-injection chemiluminescence method using cadmium sulfide quantum dots and corona discharge ion mobility spectrometry

    NASA Astrophysics Data System (ADS)

    Khataee, Alireza; Lotfi, Roya; Hasanzadeh, Aliyeh; Iranifam, Mortaza; Zarei, Mahmoud; Joo, Sang Woo

    2016-01-01

    Two analytical approaches including chemiluminescence (CL) and corona discharge ionization ion mobility spectrometry (CD-IMS) were developed for sensitive determination of selegiline (SG). We found that the CL intensity of the KMnO4-Na2S2O3 CL system was significantly enhanced in the presence of L-cysteine capped CdS quantum dots (QDs). A possible CL mechanism for this CL reaction is proposed. In the presence of SG, the enhanced CL system was inhibited. Based on this inhibition, a simple and sensitive flow-injection CL method was proposed for the determination of SG. Under optimum experimental conditions, the decreased CL intensity was proportional to SG concentration in the range of 0.01 to 30.0 mg L- 1. The detection limit (3σ) was 0.004 mg L- 1. Also, SG was determined using CD-IMS, and under optimum conditions of CD-IMS, calibration curves were linear in the range of 0.15 to 42.0 mg L- 1, with a detection limit (3σ) of 0.03 mg L- 1. The precision of the two methods was calculated by analyzing samples containing 5.0 mg L- 1 of SG (n = 11). The relative standard deviations (RSDs%) of the flow-injection CL and CD-IMS methods are 2.17% and 3.83%, respectively. The proposed CL system exhibits a higher sensitivity and precision than the CD-IMS method for the determination of SG.

  9. Optimal excitation conditions for indistinguishable photons from quantum dots

    NASA Astrophysics Data System (ADS)

    Huber, Tobias; Predojević, Ana; Föger, Daniel; Solomon, Glenn; Weihs, Gregor

    2015-12-01

    In this paper, we present a detailed, all optical study of the influence of different excitation schemes on the indistinguishability of single photons from a single InAs quantum dot. For this study, we measure the Hong-Ou-Mandel interference of consecutive photons from the spontaneous emission of an InAs quantum dot state under various excitation schemes and different excitation conditions and give a comparison.

  10. Quantum dots for biophotonics.

    PubMed

    Yong, Ken-Tye

    2012-01-01

    This theme issue provides an excellent collection of reviews and original research articles on the study of various bioconjugated quantum dot formulations for diagnostics and therapy applications using biophotonic imaging and sensing approaches.

  11. Dots for Dummies

    NASA Astrophysics Data System (ADS)

    Shankar, R.

    2006-12-01

    Quantum dots pose an interesting problem in which three complications- disorder, interaction and finite size- come together. I describe progress that can be made by combining Random Matrix Theory (RMT) and the Renormalization Group (RG) to attack the problem.

  12. Regularity of approaching visual stimuli influences spatial expectations for subsequent somatosensory stimuli.

    PubMed

    Kimura, Tsukasa; Katayama, Jun'ichi

    2017-06-01

    This study examines how the regularity of visual stimuli approaching the body influences spatial expectations of subsequent somatosensory stimuli by recording event-related brain potentials (ERPs) during a simple reaction time (RT) task involving responses to somatosensory stimuli. Twenty-one participants were instructed to put their arms on a desk, and three LEDs were placed equidistantly between their arms. Electrical stimuli were presented with a high probability (80%) of being applied to one wrist and a low probability (20%) of being applied to the opposite wrist. One trial was composed of three visual stimuli followed by one electrical stimulus. In the regular approach condition, LEDs flashed sequentially toward the wrist with the high-probability somatosensory stimulus. In the irregular approach condition, the first and second visual stimuli were presented randomly, but the third visual stimulus was invariably presented near the wrist with the high-probability stimulus. In both conditions, RTs for low-probability stimuli were slower than those for high-probability stimuli, and the low-probability stimuli elicited larger P3 amplitudes than the high-probability stimuli. Furthermore, the largest P3 amplitude was elicited by low-probability stimuli under the regular approach condition, whereas the amplitudes of contingent negative variation (CNV) elicited before the presentation of the somatosensory stimuli did not differ between conditions. These results indicate that regularity of visual stimuli approaching the body facilitates an automatic spatial expectation for subsequent somatosensory stimuli.

  13. Comparison of cytotoxicity and expression of metal regulatory genes in zebrafish (Danio rerio) liver cells exposed to cadmium sulfate, zinc sulfate and quantum dots.

    PubMed

    Tang, Song; Allagadda, Vinay; Chibli, Hicham; Nadeau, Jay L; Mayer, Gregory D

    2013-10-01

    Recent advances in the ability to manufacture and manipulate materials at the nanometer scale have led to increased production and use of many types of nanoparticles. Quantum dots (QDs) are small, fluorescent nanoparticles composed of a core of semiconductor material (e.g. cadmium selenide, zinc sulfide) and shells or dopants of other elements. Particle core composition, size, shell, and surface chemistry have all been found to influence toxicity in cells. The aim of this study was to compare the toxicities of ionic cadmium (Cd) and zinc (Zn) and Cd- and Zn-containing QDs in zebrafish liver cells (ZFL). As expected, Cd(2+) was more toxic than Zn(2+), and the general trend of IC50-24 h values of QDs was determined to be CdTe < CdSe/ZnS or InP/ZnS, suggesting that ZnS-shelled CdSe/ZnS QDs were more cytocompatible than bare core CdTe crystals. Smaller QDs showed greater toxicity than larger QDs. Isolated mRNA from these exposures was used to measure the expression of metal response genes including metallothionein (MT), metal response element-binding transcription factor (MTF-1), divalent metal transporter (DMT-1), zrt and irt like protein (ZIP-1) and the zinc transporter, ZnT-1. CdTe exposure induced expression of these genes in a dose dependent manner similar to that of CdSO4 exposure. However, CdSe/ZnS and InP/ZnS altered gene expression of metal homeostasis genes in a manner different from that of the corresponding Cd or Zn salts. This implies that ZnS shells reduce QD toxicity attributed to the release of Cd(2+), but do not eliminate toxic effects caused by the nanoparticles themselves.

  14. Comparison of quantum dot technology with conventional immunohistochemistry in examining aldehyde dehydrogenase 1A1 as a potential biomarker for lymph node metastasis of head and neck cancer.

    PubMed

    Xu, Jing; Müller, Susan; Nannapaneni, Sreenivas; Pan, Lin; Wang, Yuxiang; Peng, Xianghong; Wang, Dongsheng; Tighiouart, Mourad; Chen, Zhengjia; Saba, Nabil F; Beitler, Jonathan J; Shin, Dong M; Chen, Zhuo Georgia

    2012-07-01

    This study explored whether the expression of aldehyde dehydrogenase 1 (ALDH1A1) in the primary tumour correlated with lymph node metastasis (LNM) of squamous cell carcinoma of the head and neck (HNSCC). We used both quantum dot (QD)-based immunohistofluorescence (IHF) and conventional immunohistochemistry (IHC) to quantify ALDH1A1 expression in primary tumour samples taken from 96 HNSCC patients, 50 with disease in the lymph nodes and 46 without. The correlation between the quantified level of ALDH1A1 expression and LNM in HNSCC patients was evaluated with univariate and multivariate analysis. The prognostic value of ALDH1A1 was examined by Kaplan-Meier analysis and Wald test. ALDH1A1 was highly correlated with LNM in HNSCC patients (p<0.0001 by QD-based IHF and 0.039 by IHC). The two methods (QD-based IHF and conventional IHC) for quantification of ALDH1A1 were found to be comparable (R=0.75, p<0.0001), but QD-IHF was more sensitive and objective than IHC. The HNSCC patients with low ALDH1A1 expression had a higher 5-year survival rate than those with high ALDH1A1 level (p=0.025). Our study suggests that ALDH1A1 is a potential biomarker for predicting LNM in HNSCC patients, though it is not an independent prognostic factor for survival of HNSCC patients. Furthermore, QD-IHF has advantages over IHC in quantification of ALDH1A1 expression in HNSCC tissues.

  15. Comparison of the performance in detection of HPV infections between the high-risk HPV genotyping real time PCR and the PCR-reverse dot blot assays.

    PubMed

    Zhang, Lahong; Dai, Yibei; Chen, Jiahuan; Hong, Liquan; Liu, Yuhua; Ke, Qiang; Chen, Yiwen; Cai, Chengsong; Liu, Xia; Chen, Zhaojun

    2017-08-29

    A new multiplex real-time PCR assay, the high-risk HPV genotyping real time PCR assay (HR HPV RT-PCR), has been developed to detect 15 high-risk HPV types with respective viral loads. In this report, a total of 684 cervical specimens from women diagnosed with vaginitis were assessed by the HR HPV RT-PCR and the PCR reaction and reverse dot blot (PCR-RDB) assays, using a PCR-sequencing method as a reference standard. A total coincidence of 97.7% between the HR HPV RT PCR and the PCR-RDB assays was determined with a Kappa value of 0.953. The HR HPV RT PCR assay had sensitivity, specificity, and concordance rates (accuracy) of 99.7%, 99.7%, and 99.7%, respectively, as confirmed by PCR-sequencing, while the PCR-RDB assay had respective rates of 98.8%, 97.1%, and 98.0%. The overall rate of HPV infection, determined by PCR-sequencing, in women diagnosed with vaginitis was 49.85%, including 36.26% of single infection and 13.6% of multiple infections. The most common infections among the 15 high-risk HPV types in women diagnosed with vaginitis were HPV-52, HPV-16, and HPV-58, with a total detection rate of 10.23%, 7.75%, and 5.85%, respectively. We conclude that the HR HPV RT PCR assay exhibits better clinical performance than the PCR-RDB assay, and is an ideal alternative method for HPV genotyping. In addition, the HR HPV RT PCR assay provides HPV DNA viral loads, and could serve as a quantitative marker in the diagnosis and treatment of single and multiple HPV infections. © 2017 Wiley Periodicals, Inc.

  16. Comparison of Toxicity of CdSe: ZnS Quantum Dots on Male Reproductive System in Different Stages of Development in Mice

    PubMed Central

    Amiri, Gholamreza; Valipoor, Akram; Parivar, Kazem; Modaresi, Mehrdad; Noori, Ali; Gharamaleki, Hamideh; Taheri, Jafar; Kazemi, Ali

    2016-01-01

    Background Quantum dots (QDs) are new types of fluorescent materials for biological labeling. QDs toxicity study is an essential requirement for future clinical applications. Therefore, this study aimed to evaluate cytotoxic effects of CdSe: ZnS QDs on male reproductive system. Materials and Methods In this experimental study, the different concentrations of CdSe: ZnS QDs (10, 20 and 40 mg/kg) were injected to 32 male mice (adult group) and 24 pregnant mice (embryo group) on day 8 of gestation. The histological changes of testis and epididymis were studied by a light microscopy, and the number of seminiferous tubules between two groups was compared. One-way analysis of variance (one-way Anova) using the Statistical Package for the Social Sciences (SPSS, SPSS Inc., USA) version 16 were performed for statistical analysis. Results In adult group, histological studies of testis tissues showed a high toxicity of CdSe: ZnS in 40 mg/kg dose followed by a decrease in lamina propria; destruction in interstitial tissue; deformation of seminiferous tubules; and a reduction in number of spermatogonia, spermatocytes, and spermatids. However, there was an interesting result in fetal testis development, meaning there was no significant effect on morphology and structure of the seminiferous tubules and number of sperm stem cells. Also histological study of epididymis tissues in both groups (adult and embryo groups) showed no significant effect on morphology and structure of tubule and epithelial cells, but there was a considerable reduction in number of spermatozoa in the lumen of the epididymal duct in 40 mg/kg dose of adult group. Conclusion The toxicity of QDs on testicular tissue of the mice embryo and adult are different before and after puberty. Due to lack of research in this field, this study can be an introduction to evaluate the toxicity of QDs on male reproduction system in different stages of development. PMID:26985339

  17. Cytotoxicity of quantum dots used for in vitro cellular labeling: role of QD surface ligand, delivery modality, cell type, and direct comparison to organic fluorophores.

    PubMed

    Bradburne, Christopher E; Delehanty, James B; Boeneman Gemmill, Kelly; Mei, Bing C; Mattoussi, Hedi; Susumu, Kimihiro; Blanco-Canosa, Juan B; Dawson, Philip E; Medintz, Igor L

    2013-09-18

    Interest in taking advantage of the unique spectral properties of semiconductor quantum dots (QDs) has driven their widespread use in biological applications such as in vitro cellular labeling/imaging and sensing. Despite their demonstrated utility, concerns over the potential toxic effects of QD core materials on cellular proliferation and homeostasis have persisted, leaving in question the suitability of QDs as alternatives for more traditional fluorescent materials (e.g., organic dyes, fluorescent proteins) for in vitro cellular applications. Surprisingly, direct comparative studies examining the cytotoxic potential of QDs versus these more traditional cellular labeling fluorophores remain limited. Here, using CdSe/ZnS (core/shell) QDs as a prototypical assay material, we present a comprehensive study in which we characterize the influence of QD dose (concentration and incubation time), QD surface capping ligand, and delivery modality (peptide or cationic amphiphile transfection reagent) on cellular viability in three human cell lines representing various morphological lineages (epithelial, endothelial, monocytic). We further compare the effects of QD cellular labeling on cellular proliferation relative to those associated with a panel of traditionally employed organic cell labeling fluorophores that span a broad spectral range. Our results demonstrate the important role played by QD dose, capping ligand structure, and delivery agent in modulating cellular toxicity. Further, the results show that at the concentrations and time regimes required for robust QD-based cellular labeling, the impact of our in-house synthesized QD materials on cellular proliferation is comparable to that of six commercial cell labeling fluorophores. Cumulatively, our results demonstrate that the proper tuning of QD dose, surface ligand, and delivery modality can provide robust in vitro cell labeling reagents that exhibit minimal impact on cellular viability.

  18. Comparison of two methods for selegiline determination: A flow-injection chemiluminescence method using cadmium sulfide quantum dots and corona discharge ion mobility spectrometry.

    PubMed

    Khataee, Alireza; Lotfi, Roya; Hasanzadeh, Aliyeh; Iranifam, Mortaza; Zarei, Mahmoud; Joo, Sang Woo

    2016-01-15

    Two analytical approaches including chemiluminescence (CL) and corona discharge ionization ion mobility spectrometry (CD-IMS) were developed for sensitive determination of selegiline (SG). We found that the CL intensity of the KMnO4-Na2S2O3 CL system was significantly enhanced in the presence of L-cysteine capped CdS quantum dots (QDs). A possible CL mechanism for this CL reaction is proposed. In the presence of SG, the enhanced CL system was inhibited. Based on this inhibition, a simple and sensitive flow-injection CL method was proposed for the determination of SG. Under optimum experimental conditions, the decreased CL intensity was proportional to SG concentration in the range of 0.01 to 30.0 mg L(-1). The detection limit (3σ) was 0.004 mg L(-1). Also, SG was determined using CD-IMS, and under optimum conditions of CD-IMS, calibration curves were linear in the range of 0.15 to 42.0 mg L(-1), with a detection limit (3σ) of 0.03 mg L(-1). The precision of the two methods was calculated by analyzing samples containing 5.0 mg L(-1) of SG (n=11). The relative standard deviations (RSDs%) of the flow-injection CL and CD-IMS methods are 2.17% and 3.83%, respectively. The proposed CL system exhibits a higher sensitivity and precision than the CD-IMS method for the determination of SG. Copyright © 2015. Published by Elsevier B.V.

  19. Conscious perception of emotional stimuli: brain mechanisms.

    PubMed

    Mitchell, Derek G V; Greening, Steven G

    2012-08-01

    Emotional stimuli are thought to gain rapid and privileged access to processing resources in the brain. The structures involved in this enhanced access are thought to support subconscious, reflexive processes. Whether these pathways contribute to the phenomenological experience of emotional visual awareness (i.e., conscious perception) is unclear. In this review, it is argued that subcortical networks associated with the rapid detection of emotionally salient stimuli also play a key role in shaping awareness. This proposal is based on the idea that awareness of visual stimuli should be considered along a continuum, having intermediate levels, rather than as an all-or-none construct. It is also argued that awareness of emotional stimuli requires less input from frontoparietal structures that are often considered crucial for visual awareness. Evidence is also presented that implicates a region of the medial prefrontal cortex, involved in emotion regulation, in modulating amygdala output to determine awareness of emotional visual stimuli; when emotional stimuli are present, the conscious perception of alternative stimuli requires greater regulatory influences from cortical structures. Thus, emotional stimuli are privileged not only for neuronal representation and impact on subconscious processes, but also for awareness, allowing humans to deal flexibly rather than merely reflexively to biologically significant stimuli.

  20. Visual stimuli: past and present

    NASA Astrophysics Data System (ADS)

    Westheimer, Gerald

    2013-03-01

    The fundamental properties of light and the principles of the structure and function of the visual system were discovered at a time when the only light sources were the sun and the flame of a candle. Contributions by Newton, Huygens, Thomas Young and Purkinje, Helmholtz's ophthalmoscope - all preceded the first incandescent filament. Light bulbs, Xenon arcs, lasers, light-emitting diodes (LEDs), computer monitors then sequentially enlarged the arsenal, and so did the steps from Nicol prism to Polaroid in polarizing light, and from glass and interference filters to laser light in generating monochromatic light. Technological advances have a deep impact on the research topics at any one time, expanding their scope. In particular, utilization of computers now allows the generation and manipulation of targets permitting questions to be approached that could not have been envisaged at the dawn of the technological era of vision research. Just beyond the immediate grasp of even the most thoughtful vision scientist, however, is the concern that stimulus sets originating in mathematicians' and physicists' toolboxes fail to capture some essential ingredients indigenous to human vision. The quest to study vision with stimuli in its own terms continues.

  1. Cardiorespiratory interactions to external stimuli.

    PubMed

    Bernardi, L; Porta, C; Spicuzza, L; Sleight, P

    2005-09-01

    Respiration is a powerful modulator of heart rate variability, and of baro- or chemo-reflex sensitivity. This occurs via a mechanical effect of breathing that synchronizes all cardiovascular variables at the respiratory rhythm, particularly when this occurs at a particular slow rate coincident with the Mayer waves in arterial pressure (approximately 6 cycles/min). Recitation of the rosary prayer (or of most mantras), induces a marked enhancement of these slow rhythms, whereas random verbalization or random breathing does not. This phenomenon in turn increases baroreflex sensitivity and reduces chemoreflex sensitivity, leading to increases in parasympathetic and reductions in sympathetic activity. The opposite can be seen during either verbalization or mental stress tests. Qualitatively similar effects can be obtained even by passive listening to more or less rhythmic auditory stimuli, such as music, and the speed of the rhythm (rather than the style) appears to be one of the main determinants of the cardiovascular and respiratory responses. These findings have clinical relevance. Appropriate modulation of breathing, can improve/restore autonomic control of cardiovascular and respiratory systems in relevant diseases such as hypertension and heart failure, and might therefore help improving exercise tolerance, quality of life, and ultimately, survival.

  2. Affective reactions to acoustic stimuli.

    PubMed

    Bradley, M M; Lang, P J

    2000-03-01

    Emotional reactions to naturally occurring sounds (e.g., screams, erotica, bombs, etc.) were investigated in two studies. In Experiment 1, subjects rated the pleasure and arousal elicited when listening to each of 60 sounds, followed by an incidental free recall task. The shape of the two-dimensional affective space defined by the mean ratings for each sound was similar to that previously obtained for pictures, and, like memory for pictures, free recall was highest for emotionally arousing stimuli. In Experiment 2, autonomic and facial electromyographic (EMG) activity were recorded while a new group of subjects listened to the same set of sounds; the startle reflex was measured using visual probes. Listening to unpleasant sounds resulted in larger startle reflexes, more corrugator EMG activity, and larger heart rate deceleration compared with listening to pleasant sounds. Electrodermal reactions were larger for emotionally arousing than for neutral materials. Taken together, the data suggest that acoustic cues activate the appetitive and defensive motivational circuits underlying emotional expression in ways similar to pictures.

  3. Social attention with real versus reel stimuli: toward an empirical approach to concerns about ecological validity

    PubMed Central

    Risko, Evan F.; Laidlaw, Kaitlin E. W.; Freeth, Megan; Foulsham, Tom; Kingstone, Alan

    2012-01-01

    Cognitive neuroscientists often study social cognition by using simple but socially relevant stimuli, such as schematic faces or images of other people. Whilst this research is valuable, important aspects of genuine social encounters are absent from these studies, a fact that has recently drawn criticism. In the present review we argue for an empirical approach to the determination of the equivalence of different social stimuli. This approach involves the systematic comparison of different types of social stimuli ranging in their approximation to a real social interaction. In garnering support for this cognitive ethological approach, we focus on recent research in social attention that has involved stimuli ranging from simple schematic faces to real social interactions. We highlight both meaningful similarities and differences in various social attentional phenomena across these different types of social stimuli thus validating the utility of the research initiative. Furthermore, we argue that exploring these similarities and differences will provide new insights into social cognition and social neuroscience. PMID:22654747

  4. Attentional Processing of Faces in ASD: A Dot-Probe Study

    ERIC Educational Resources Information Center

    Moore, David J.; Heavey, Lisa; Reidy, John

    2012-01-01

    The present study used the Dot-Probe paradigm to explore attentional allocation to faces compared with non-social images in high-functioning individuals with autism spectrum disorder (ASD) and typically developing controls. There was no evidence of attentional bias in either group when stimuli were presented at individually calculated…

  5. Narcissism dimensions differentially moderate selective attention to evaluative stimuli in incarcerated offenders

    PubMed Central

    Krusemark, Elizabeth A.; Lee, Christopher; Newman, Joseph P.

    2014-01-01

    Narcissistic personality disorder is associated with distinguishing traits including self-enhancement, arrogance and intense reactivity to ego threat. Theoretical accounts of narcissism suggest these heterogeneous behaviors reflect a defensive motivational style that functions to both uphold and protect the self-concept. However, the notion that narcissism can be characterized by grandiose and vulnerable dimensions raises the possibility that these diverse behaviors represent distinct expressions of narcissistic defensiveness. The present study examined whether both dimensions exhibit a general defensive style marked by selective attention to evaluative stimuli or are differentially associated with selective attention to positive and negative information, respectively. Using a dot probe task consisting of valenced and neutral trait adjectives, we evaluated these hypotheses in a group of male offenders. Results indicated that vulnerable narcissism was associated with attention biases for both positive and negative stimuli, though the dimension was further distinguished by disengagement difficulties and a greater recognition memory bias in response to negative words. Conversely, grandiose narcissism was associated with increased accuracy when attending to positive stimuli and directing attention away from negative stimuli. Overall, these findings suggest narcissistic individuals share motivated selective attention in response to evaluative stimuli, while simultaneously highlighting important phenotypic differences between grandiose and vulnerable dimensions. PMID:25330183

  6. Narcissism dimensions differentially moderate selective attention to evaluative stimuli in incarcerated offenders.

    PubMed

    Krusemark, Elizabeth A; Lee, Christopher; Newman, Joseph P

    2015-01-01

    Narcissistic personality disorder is associated with distinguishing traits including self-enhancement, arrogance, and intense reactivity to ego threat. Theoretical accounts of narcissism suggest these heterogeneous behaviors reflect a defensive motivational style that functions to both uphold and protect the self-concept. However, the notion that narcissism can be characterized by grandiose and vulnerable dimensions raises the possibility that these diverse behaviors represent distinct expressions of narcissistic defensiveness. The present study examined whether both dimensions exhibit a general defensive style marked by selective attention to evaluative stimuli or are differentially associated with selective attention to positive and negative information, respectively. Using a dot probe task consisting of valenced and neutral trait adjectives, we evaluated these hypotheses in a group of male offenders. Results indicated that vulnerable narcissism was associated with attention biases for both positive and negative stimuli, though the dimension was further distinguished by disengagement difficulties and a greater recognition memory bias in response to negative words. Conversely, grandiose narcissism was associated with increased accuracy when attending to positive stimuli and directing attention away from negative stimuli. Overall, these findings suggest narcissistic individuals share motivated selective attention in response to evaluative stimuli, while simultaneously highlighting important phenotypic differences between grandiose and vulnerable dimensions.

  7. The method of constant stimuli is inefficient

    NASA Technical Reports Server (NTRS)

    Watson, Andrew B.; Fitzhugh, Andrew

    1990-01-01

    Simpson (1988) has argued that the method of constant stimuli is as efficient as adaptive methods of threshold estimation and has supported this claim with simulations. It is shown that Simpson's simulations are not a reasonable model of the experimental process and that more plausible simulations confirm that adaptive methods are much more efficient that the method of constant stimuli.

  8. Sex Attracts: Investigating Individual Differences in Attentional Bias to Sexual Stimuli

    PubMed Central

    Kagerer, Sabine; Wehrum, Sina; Klucken, Tim; Walter, Bertram; Vaitl, Dieter; Stark, Rudolf

    2014-01-01

    We investigated the impact of sexual stimuli and the influence of sexual motivation on the performance in a dot-probe task and a line-orientation task in a large sample of males and females. All pictures (neutral, erotic) were rated on the dimensions of valence, arousal, disgust, and sexual arousal. Additionally, questionnaires measuring sexual interest/desire/motivation were employed. The ratings of the sexual stimuli point to a successful picture selection because sexual arousal did not differ between the sexes. The stimuli were equally arousing for men and women. Higher scores in the employed questionnaires measuring sexual interest/desire/motivation led to higher sexual arousal ratings of the sex pictures. Attentional bias towards sex pictures was observed in both experimental tasks. The attentional biases measured by the dot-probe and the line-orientation task were moderately intercorrelated suggesting attentional bias as a possible marker for a sex-attention trait. Finally, only the sexual sensation seeking score correlated with the attentional biases of the two tasks. Future research is needed to increase the predictive power of these indirect measures of sexual interest. PMID:25238545

  9. Quantum dot resonant tunneling spectroscopy

    NASA Astrophysics Data System (ADS)

    Reed, Mark A.; Randall, John N.; Luscombe, James H.; Frensley, William R.; Aggarwal, Raj J.; Matyi, Richard J.; Moore, Tom M.; Wetsel, Anna E.

    The electronic transport through 3-dimensionally confined semiconductor quantum wells (quantum dots) is investigated and analyzed. The spectra corresponds to resonant tunneling from laterally-confined emitter contact subbands through the discrete 3-dimensionally confined quantum dot states. Momentum nonconservation is observed in these structures. Results on coupled quantum dot states (molccules) will be presented.

  10. Dot-Projection Photogrammetry and Videogrammetry of Gossamer Space Structures

    NASA Technical Reports Server (NTRS)

    Pappa, Richard S.; Black, Jonathan T.; Blandino, Joseph R.; Jones, Thomas W.; Danehy, Paul M.; Dorrington, Adrian A.

    2003-01-01

    This paper documents the technique of using hundreds or thousands of projected dots of light as targets for photogrammetry and videogrammetry of gossamer space structures. Photogrammetry calculates the three-dimensional coordinates of each target on the structure, and videogrammetry tracks the coordinates versus time. Gossamer structures characteristically contain large areas of delicate, thin-film membranes. Examples include solar sails, large antennas, inflatable solar arrays, solar power concentrators and transmitters, sun shields, and planetary balloons and habitats. Using projected-dot targets avoids the unwanted mass, stiffness, and installation costs of traditional retroreflective adhesive targets. Four laboratory applications are covered that demonstrate the practical effectiveness of white-light dot projection for both static-shape and dynamic measurement of reflective and diffuse surfaces, respectively. Comparisons are made between dot-projection videogrammetry and traditional laser vibrometry for membrane vibration measurements. The paper closes by introducing a promising extension of existing techniques using a novel laser-induced fluorescence approach.

  11. Plasmonic fluorescent quantum dots.

    PubMed

    Jin, Yongdong; Gao, Xiaohu

    2009-09-01

    Combining multiple discrete components into a single multifunctional nanoparticle could be useful in a variety of applications. Retaining the unique optical and electrical properties of each component after nanoscale integration is, however, a long-standing problem. It is particularly difficult when trying to combine fluorophores such as semiconductor quantum dots with plasmonic materials such as gold, because gold and other metals can quench the fluorescence. So far, the combination of quantum dot fluorescence with plasmonically active gold has only been demonstrated on flat surfaces. Here, we combine fluorescent and plasmonic activities in a single nanoparticle by controlling the spacing between a quantum dot core and an ultrathin gold shell with nanometre precision through layer-by-layer assembly. Our wet-chemistry approach provides a general route for the deposition of ultrathin gold layers onto virtually any discrete nanostructure or continuous surface, and should prove useful for multimodal bioimaging, interfacing with biological systems, reducing nanotoxicity, modulating electromagnetic fields and contacting nanostructures.

  12. Dot junction solar cells

    NASA Technical Reports Server (NTRS)

    Daud, T.; Crotty, G. T.

    1986-01-01

    A design of solar cells with reduced junction area on the cell surface is investigated for reduction of saturation current and increase in open-circuit voltage. Equidiameter dot junctions distributed across the surface of the cell offer an efficient alternative, with variations in dot diameter and in the spacing between dots giving the required variations in the ratio of junction area to total surface area. A simplified analysis for short-circuit current and other cell parameters, which enables cell design optimization, is presented. Experimental solar-cell performance results, as functions of different area ratios, are presented and compared with the model. It is shown that saturation current reduction is possible for achieving efficiencies as high as 18 percent in flat-plate terrestrial applications.

  13. Nanoscale and Single-Dot Patterning of Colloidal Quantum Dots.

    PubMed

    Xie, Weiqiang; Gomes, Raquel; Aubert, Tangi; Bisschop, Suzanne; Zhu, Yunpeng; Hens, Zeger; Brainis, Edouard; Van Thourhout, Dries

    2015-11-11

    Using an optimized lift-off process we develop a technique for both nanoscale and single-dot patterning of colloidal quantum dot films, demonstrating feature sizes down to ~30 nm for uniform films and a yield of 40% for single-dot positioning, which is in good agreement with a newly developed theoretical model. While first of all presenting a unique tool for studying physics of single quantum dots, the process also provides a pathway toward practical quantum dot-based optoelectronic devices.

  14. The nature of the stimuli causing digestive juice secretion in Dionaea muscipula Ellis (venus's flytrap).

    PubMed

    Robins, R J

    1976-01-01

    An investigation into the stimuli of the secretory system in the carnivorous plant Dionaea muscipula is presented. Secretion of fluid and protein are both stimulated by various nitrogenous small molecules. These secretions are studied as a function of time. A new method is described for the collection of secreted juice. Significant differences are found between the quantities of fluid and protein produced in response to different stimuli. The results are discussed in comparison to the mammalian gastro-intestinal secretory systems.

  15. DOT Transmit Module

    NASA Technical Reports Server (NTRS)

    Quirk, Kevin J.; Gin, Jonathan W.; Sahasrabudhe, Adit; Patawaran, Ferze D.; Nguyen, Danh H.; Nguyen, Huy

    2013-01-01

    The Deep Space Optical Terminal (DOT) transmit module demonstrates the DOT downlink signaling in a flight electronics assembly that can be qualified for deep space. The assembly has the capability to generate an electronic pulse-position modulation (PPM) waveform suitable for driving a laser assembly to produce the optical downlink signal. The downlink data enters the assembly through a serializer/ deserializer (SERDES) interface, and is encoded using a serially concatenated PPM (SCPPM) forward error correction code. The encoded data is modulated using PPM with an inter-symbol guard time to aid in receiver synchronization. Monitor and control of the assembly is via a low-voltage differential signal (LVDS) interface

  16. Translocation of PEGylated quantum dots across rat alveolar epithelial cell monolayers

    PubMed Central

    Fazlollahi, Farnoosh; Sipos, Arnold; Kim, Yong Ho; Hamm-Alvarez, Sarah F; Borok, Zea; Kim, Kwang-Jin; Crandall, Edward D

    2011-01-01

    Background In this study, primary rat alveolar epithelial cell monolayers (RAECM) were used to investigate transalveolar epithelial quantum dot trafficking rates and underlying transport mechanisms. Methods Trafficking rates of quantum dots (PEGylated CdSe/ZnS, core size 5.3 nm, hydrodynamic size 25 nm) in the apical-to-basolateral direction across RAECM were determined. Changes in bioelectric properties (ie, transmonolayer resistance and equivalent active ion transport rate) of RAECM in the presence or absence of quantum dots were measured. Involvement of endocytic pathways in quantum dot trafficking across RAECM was assessed using specific inhibitors (eg, methyl-β-cyclodextrin, chlorpromazine, and dynasore for caveolin-, clathrin-, and dynamin-mediated endocytosis, respectively). The effects of lowering tight junctional resistance on quantum dot trafficking were determined by depleting Ca2+ in apical and basolateral bathing fluids of RAECM using 2 mM EGTA. Effects of temperature on quantum dot trafficking were studied by lowering temperature from 37°C to 4°C. Results Apical exposure of RAECM to quantum dots did not elicit changes in transmonolayer resistance or ion transport rate for up to 24 hours; quantum dot trafficking rates were not surface charge-dependent; methyl-β-cyclodextrin, chlorpromazine, and dynasore did not decrease quantum dot trafficking rates; lowering of temperature decreased transmonolayer resistance by approximately 90% with a concomitant increase in quantum dot trafficking by about 80%; and 24 hours of treatment of RAECM with EGTA decreased transmonolayer resistance by about 95%, with increased quantum dot trafficking of up to approximately 130%. Conclusion These data indicate that quantum dots do not injure RAECM and that quantum dot trafficking does not appear to take place via endocytic pathways involving caveolin, clathrin, or dynamin. We conclude that quantum dot translocation across RAECM takes place via both transcellular and

  17. Translocation of PEGylated quantum dots across rat alveolar epithelial cell monolayers.

    PubMed

    Fazlollahi, Farnoosh; Sipos, Arnold; Kim, Yong Ho; Hamm-Alvarez, Sarah F; Borok, Zea; Kim, Kwang-Jin; Crandall, Edward D

    2011-01-01

    In this study, primary rat alveolar epithelial cell monolayers (RAECM) were used to investigate transalveolar epithelial quantum dot trafficking rates and underlying transport mechanisms. Trafficking rates of quantum dots (PEGylated CdSe/ZnS, core size 5.3 nm, hydrodynamic size 25 nm) in the apical-to-basolateral direction across RAECM were determined. Changes in bioelectric properties (ie, transmonolayer resistance and equivalent active ion transport rate) of RAECM in the presence or absence of quantum dots were measured. Involvement of endocytic pathways in quantum dot trafficking across RAECM was assessed using specific inhibitors (eg, methyl-β-cyclodextrin, chlorpromazine, and dynasore for caveolin-, clathrin-, and dynamin-mediated endocytosis, respectively). The effects of lowering tight junctional resistance on quantum dot trafficking were determined by depleting Ca(2+) in apical and basolateral bathing fluids of RAECM using 2 mM EGTA. Effects of temperature on quantum dot trafficking were studied by lowering temperature from 37°C to 4°C. Apical exposure of RAECM to quantum dots did not elicit changes in transmonolayer resistance or ion transport rate for up to 24 hours; quantum dot trafficking rates were not surface charge-dependent; methyl-β-cyclodextrin, chlorpromazine, and dynasore did not decrease quantum dot trafficking rates; lowering of temperature decreased transmonolayer resistance by approximately 90% with a concomitant increase in quantum dot trafficking by about 80%; and 24 hours of treatment of RAECM with EGTA decreased transmonolayer resistance by about 95%, with increased quantum dot trafficking of up to approximately 130%. These data indicate that quantum dots do not injure RAECM and that quantum dot trafficking does not appear to take place via endocytic pathways involving caveolin, clathrin, or dynamin. We conclude that quantum dot translocation across RAECM takes place via both transcellular and paracellular pathways and, based on

  18. Preschoolers' dot enumeration abilities are markers of their arithmetic competence.

    PubMed

    Gray, Sarah A; Reeve, Robert A

    2014-01-01

    The abilities to enumerate small sets of items (e.g., dots) and to compare magnitudes are claimed to be indexes of core numerical competences that scaffold early math development. Insofar as this is correct, these abilities may be diagnostic markers of math competence in preschoolers. However, unlike magnitude comparison abilities, little research has examined preschoolers' ability to enumerate small sets, or its significance for emerging math abilities; which is surprising since dot enumeration is a marker of school-aged children's math competence. It is nevertheless possible that general cognitive functions (working memory, response inhibition in particular) are associated with preschoolers' math abilities and underlie nascent dot enumeration abilities. We investigated whether preschoolers' dot enumeration abilities predict their non-verbal arithmetic ability, over and above the influence of working memory and response inhibition. Two measures of dot enumeration ability were examined-inverse efficiency and paradigm specific (response time profiles) measures-to determine which has the better diagnostic utility as a marker of math competence. Seventy-eight 42-to-57 month-olds completed dot enumeration, working memory, response inhibition, and non-verbal addition and subtraction tasks. Dot enumeration efficiency predicted arithmetic ability over and above the influence of general cognitive functions. While dot enumeration efficiency was a better predictor of arithmetic ability than paradigm specific response time profiles; the response time profile displaying the smallest subitizing range and steepest subitizing slope, also displayed poor addition abilities, suggesting a weak subitizing profile may have diagnostic significance in preschoolers. Overall, the findings support the claim that dot enumeration abilities and general cognitive functions are markers of preschoolers' math ability.

  19. Preschoolers' Dot Enumeration Abilities Are Markers of Their Arithmetic Competence

    PubMed Central

    Gray, Sarah A.; Reeve, Robert A.

    2014-01-01

    The abilities to enumerate small sets of items (e.g., dots) and to compare magnitudes are claimed to be indexes of core numerical competences that scaffold early math development. Insofar as this is correct, these abilities may be diagnostic markers of math competence in preschoolers. However, unlike magnitude comparison abilities, little research has examined preschoolers' ability to enumerate small sets, or its significance for emerging math abilities; which is surprising since dot enumeration is a marker of school-aged children's math competence. It is nevertheless possible that general cognitive functions (working memory, response inhibition in particular) are associated with preschoolers' math abilities and underlie nascent dot enumeration abilities. We investigated whether preschoolers' dot enumeration abilities predict their non-verbal arithmetic ability, over and above the influence of working memory and response inhibition. Two measures of dot enumeration ability were examined—inverse efficiency and paradigm specific (response time profiles) measures—to determine which has the better diagnostic utility as a marker of math competence. Seventy-eight 42-to-57 month-olds completed dot enumeration, working memory, response inhibition, and non-verbal addition and subtraction tasks. Dot enumeration efficiency predicted arithmetic ability over and above the influence of general cognitive functions. While dot enumeration efficiency was a better predictor of arithmetic ability than paradigm specific response time profiles; the response time profile displaying the smallest subitizing range and steepest subitizing slope, also displayed poor addition abilities, suggesting a weak subitizing profile may have diagnostic significance in preschoolers. Overall, the findings support the claim that dot enumeration abilities and general cognitive functions are markers of preschoolers' math ability. PMID:24714052

  20. Isotopic and internal CX{sub 3} (X=D,H) rotational motion effects in the Ba{center_dot}{center_dot}{center_dot}FCX{sub 3}+h{nu}{yields}BaF+CX{sub 3} intracluster reactions

    SciTech Connect

    Rinaldi, C. A.; Gasmi, K.; Skowronek, S.; Gonzalez Urena, A.

    2006-06-28

    Photodepletion and action spectra of the laser-induced Ba{center_dot}{center_dot}{center_dot}FCD{sub 3} fragmentation have been measured over the 16 075-16 380 cm{sup -1} range. The observed band and peak structures allowed us to estimate the vibrational and rotational structures of the excited complex at the transition state configuration. The relative reaction probability P{sub R}(E) for the intracluster Ba{center_dot}{center_dot}{center_dot}FCD{sub 3}+h{nu}{yields}BaF+CD{sub 3} reaction has been determined over the cited energy range. P{sub R}(E) shows a peak structure with an energy spacing of 8.9 cm{sup -1} which was attributed to an internal rotation of the CD{sub 3} group in the intermediate state. A comparison with previous Ba{center_dot}{center_dot}{center_dot}FCH{sub 3} photofragmentation spectra reveals the dynamical role of the internal CX{sub 3} (X=H,D) motion which is manifested by the presence of rotational resonances in the laser-induced intracluster reaction.

  1. Effective Stimuli for Constructing Reliable Neuron Models

    PubMed Central

    Druckmann, Shaul; Berger, Thomas K.; Schürmann, Felix; Hill, Sean; Markram, Henry; Segev, Idan

    2011-01-01

    The rich dynamical nature of neurons poses major conceptual and technical challenges for unraveling their nonlinear membrane properties. Traditionally, various current waveforms have been injected at the soma to probe neuron dynamics, but the rationale for selecting specific stimuli has never been rigorously justified. The present experimental and theoretical study proposes a novel framework, inspired by learning theory, for objectively selecting the stimuli that best unravel the neuron's dynamics. The efficacy of stimuli is assessed in terms of their ability to constrain the parameter space of biophysically detailed conductance-based models that faithfully replicate the neuron's dynamics as attested by their ability to generalize well to the neuron's response to novel experimental stimuli. We used this framework to evaluate a variety of stimuli in different types of cortical neurons, ages and animals. Despite their simplicity, a set of stimuli consisting of step and ramp current pulses outperforms synaptic-like noisy stimuli in revealing the dynamics of these neurons. The general framework that we propose paves a new way for defining, evaluating and standardizing effective electrical probing of neurons and will thus lay the foundation for a much deeper understanding of the electrical nature of these highly sophisticated and non-linear devices and of the neuronal networks that they compose. PMID:21876663

  2. Functional specialization and generalization for grouping of stimuli based on colour and motion

    PubMed Central

    Zeki, Semir; Stutters, Jonathan

    2013-01-01

    This study was undertaken to learn whether the principle of functional specialization that is evident at the level of the prestriate visual cortex extends to areas that are involved in grouping visual stimuli according to attribute, and specifically according to colour and motion. Subjects viewed, in an fMRI scanner, visual stimuli composed of moving dots, which could be either coloured or achromatic; in some stimuli the moving coloured dots were randomly distributed or moved in random directions; in others, some of the moving dots were grouped together according to colour or to direction of motion, with the number of groupings varying from 1 to 3. Increased activation was observed in area V4 in response to colour grouping and in V5 in response to motion grouping while both groupings led to activity in separate though contiguous compartments within the intraparietal cortex. The activity in all the above areas was parametrically related to the number of groupings, as was the prominent activity in Crus I of the cerebellum where the activity resulting from the two types of grouping overlapped. This suggests (a) that, the specialized visual areas of the prestriate cortex have functions beyond the processing of visual signals according to attribute, namely that of grouping signals according to colour (V4) or motion (V5); (b) that the functional separation evident in visual cortical areas devoted to motion and colour, respectively, is maintained at the level of parietal cortex, at least as far as grouping according to attribute is concerned; and (c) that, by contrast, this grouping-related functional segregation is not maintained at the level of the cerebellum. PMID:23415950

  3. Functional specialization and generalization for grouping of stimuli based on colour and motion.

    PubMed

    Zeki, Semir; Stutters, Jonathan

    2013-06-01

    This study was undertaken to learn whether the principle of functional specialization that is evident at the level of the prestriate visual cortex extends to areas that are involved in grouping visual stimuli according to attribute, and specifically according to colour and motion. Subjects viewed, in an fMRI scanner, visual stimuli composed of moving dots, which could be either coloured or achromatic; in some stimuli the moving coloured dots were randomly distributed or moved in random directions; in others, some of the moving dots were grouped together according to colour or to direction of motion, with the number of groupings varying from 1 to 3. Increased activation was observed in area V4 in response to colour grouping and in V5 in response to motion grouping while both groupings led to activity in separate though contiguous compartments within the intraparietal cortex. The activity in all the above areas was parametrically related to the number of groupings, as was the prominent activity in Crus I of the cerebellum where the activity resulting from the two types of grouping overlapped. This suggests (a) that, the specialized visual areas of the prestriate cortex have functions beyond the processing of visual signals according to attribute, namely that of grouping signals according to colour (V4) or motion (V5); (b) that the functional separation evident in visual cortical areas devoted to motion and colour, respectively, is maintained at the level of parietal cortex, at least as far as grouping according to attribute is concerned; and (c) that, by contrast, this grouping-related functional segregation is not maintained at the level of the cerebellum. Copyright © 2013 Elsevier Inc. All rights reserved.

  4. Imaging characteristics of zinc sulfide shell, cadmium telluride core quantum dots.

    PubMed

    Daneshvar, Hamid; Nelms, Jennifer; Muhammad, Osman; Jackson, Heather; Tkach, Jean; Davros, William; Peterson, Todd; Vogelbaum, Michael A; Bruchez, Marcel P; Toms, Steven A

    2008-02-01

    Quantum dots are optical nanocrystals whose in vitro and in vivo use in molecular imaging is expanding rapidly. In comparison with organic fluorophores, quantum dots exhibit desirable properties, such as multiwavelength fluorescence emission, excellent brightness and resistance to photobleaching. Their electron-dense, metallic cores suggest utility in other clinical imaging modalities. Core-shell zinc sulfide-cadmium telluride quantum dots were studied by magnetic resonance and computed tomography phantoms. Quantum dots were also injected into rat brain, as well as intravenously, using convection-enhanced delivery, prior to animal imaging. Computed tomography studies suggest that current formulations of quantum dots might be imaged in vivo in animals. Used in conjunction with optical imaging techniques, quantum dots have the potential to function as multimodal imaging platforms in vivo. The ability to detect an optical nanoparticle preoperatively with clinical imaging modality offers a distinct advantage to clinicians engaged in image-guided surgical applications.

  5. Pointing Hand Stimuli Induce Spatial Compatibility Effects and Effector Priming

    PubMed Central

    Nishimura, Akio; Michimata, Chikashi

    2013-01-01

    The present study investigated the automatic influence of perceiving a picture that indicates other’s action on one’s own task performance in terms of spatial compatibility and effector priming. Participants pressed left and right buttons with their left and right hands respectively, depending on the color of a central dot target. Preceding the target, a left or right hand stimulus (pointing either to the left or right with the index or little finger) was presented. In Experiment 1, with brief presentation of the pointing hand, a spatial compatibility effect was observed: responses were faster when the direction of the pointed finger and the response position were spatially congruent than when incongruent. The spatial compatibility effect was larger for the pointing index finger stimulus compared to the pointing little finger stimulus. Experiment 2 employed longer duration of the pointing hand stimuli. In addition to the spatial compatibility effect for the pointing index finger, the effector priming effect was observed: responses were faster when the anatomical left/right identity of the pointing and response hands matched than when the pointing and response hands differed in left/right identity. The results indicate that with sufficient processing time, both spatial/symbolic and anatomical features of a static body part implying another’s action simultaneously influence different aspects of the perceiver’s own action. Hierarchical coding, according to which an anatomical code is used only when a spatial code is unavailable, may not be applicable if stimuli as well as responses contain anatomical features. PMID:23637688

  6. Synthesis and Characterization of Mercaptoacetic Acid Capped Cadmium Sulphide Quantum Dots.

    PubMed

    Wageh, S; Maize, Mai; Donia, A M; Al-Ghamdi, Ahmed A; Umar, Ahmad

    2015-12-01

    This paper reports the facile synthesis and detailed characterization of mercaptoacetic acid capped cadmium sulphide (CdS) quantum dots using various cadmium precursors. The mercaptoacetic acid capped CdS quantum dots were prepared by facile and simple wet chemical method and characterized by several techniques such as energy dispersive spectroscopy (EDS), X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, UV-vis. spectroscopy, photoluminescence spectroscopy, high-resolution transmission microscopy (HRTEM) and thremogravimetric analysis. The EDS studies revealed that the prepared quantum dots possess higher atomic percentage of sulfur compared to cadmium due to the coordination of thiolate to the quantum dots surfaces. The X-ray and absorption analyses exhibited that the size of quantum dots prepared by cadmium acetate is larger than the quantum dots prepared by cadmium chloride and cadmium nitrate. The increase in size can be attributed to the low stability constant of cadmium acetate in comparison with cadmium chloride and cadmium nitrate. The FTIR and thermogravimetric analysis showed that the nature of capping molecule on the surface of quantum dots are different depending on the cadmium precursors which affect the emission from CdS quantum dots. Photoemission spectroscopy revealed that the emission of quantum dots prepared by cadmium acetate has high intensity band edge emission along with low intensity trapping state emission. However the CdS quantum dots prepared by cadmium chloride and cadmium nitrate produced only trapping state emissions.

  7. Medial temporal lobe damage impairs representation of simple stimuli.

    PubMed

    Warren, David E; Duff, Melissa C; Tranel, Daniel; Cohen, Neal J

    2010-01-01

    Medial temporal lobe (MTL) damage in humans is typically thought to produce a circumscribed impairment in the acquisition of new enduring memories, but recent reports have documented deficits even in short-term maintenance. We examined possible maintenance deficits in a population of MTL amnesics, with the goal of characterizing their impairments as either representational drift or outright loss of representation over time. Patients and healthy comparisons performed a visual search task in which the similarity of various lures to a target was varied parametrically. Stimuli were simple shapes varying along one of several visual dimensions. The task was performed in two conditions, one presenting a sample target simultaneously with the search array and the other imposing a delay between sample and array. Eye-movement data collected during search revealed that the duration of fixations to items varied with lure-target similarity for all participants, i.e., fixations were longer for items more similar to the target. In the simultaneous condition, patients and comparisons exhibited an equivalent effect of similarity on fixation durations. However, imposing a delay modulated the effect differently for the two groups: in comparisons, fixation duration to similar items was exaggerated; in patients, the original effect was diminished. These findings indicate that MTL lesions subtly impair short-term maintenance of even simple stimuli, with performance reflecting not the complete loss of the maintained representation but rather a degradation or progressive drift of the representation over time.

  8. PREFACE: Quantum Dot 2010

    NASA Astrophysics Data System (ADS)

    Taylor, Robert A.

    2010-09-01

    These conference proceedings contain the written papers of the contributions presented at Quantum Dot 2010 (QD2010). The conference was held in Nottingham, UK, on 26-30 April 2010. The conference addressed topics in research on: 1. Epitaxial quantum dots (including self-assembled and interface structures, dots defined by electrostatic gates etc): optical properties and electron transport quantum coherence effects spin phenomena optics of dots in cavities interaction with surface plasmons in metal/semiconductor structures opto-electronics applications 2. Novel QD structures: fabrication and physics of graphene dots, dots in nano-wires etc 3. Colloidal quantum dots: growth (shape control and hybrid nanocrystals such as metal/semiconductor, magnetic/semiconductor) assembly and surface functionalisation optical properties and spin dynamics electrical and magnetic properties applications (light emitting devices and solar cells, biological and medical applications, data storage, assemblers) The Editors Acknowledgements Conference Organising Committee: Maurice Skolnick (Chair) Alexander Tartakovskii (Programme Chair) Pavlos Lagoudakis (Programme Chair) Max Migliorato (Conference Secretary) Paola Borri (Publicity) Robert Taylor (Proceedings) Manus Hayne (Treasurer) Ray Murray (Sponsorship) Mohamed Henini (Local Organiser) International Advisory Committee: Yasuhiko Arakawa (Tokyo University, Japan) Manfred Bayer (Dortmund University, Germany) Sergey Gaponenko (Stepanov Institute of Physics, Minsk, Belarus) Pawel Hawrylak (NRC, Ottawa, Canada) Fritz Henneberger (Institute for Physics, Berlin, Germany) Atac Imamoglu (ETH, Zurich, Switzerland) Paul Koenraad (TU Eindhoven, Nethehrlands) Guglielmo Lanzani (Politecnico di Milano, Italy) Jungil Lee (Korea Institute of Science and Technology, Korea) Henri Mariette (CNRS-CEA, Grenoble, France) Lu Jeu Sham (San Diego, USA) Andrew Shields (Toshiba Research Europe, Cambridge, UK) Yoshihisa Yamamoto (Stanford University, USA) Artur

  9. Newborns' Discrimination of Chromatic from Achromatic Stimuli.

    ERIC Educational Resources Information Center

    Adams, Russell J.; And Others

    1986-01-01

    Two experiments assessed the extent of newborns' ability to discriminate color. Results imply that newborns have some, albeit limited, capacity to discriminate chromatic from achromatic stimuli, and hence, are at least dichromats. (Author/DR)

  10. Modeling Stimuli-Responsive Nanoparticle Monolayer

    NASA Astrophysics Data System (ADS)

    Yong, Xin

    2015-03-01

    Using dissipative particle dynamics (DPD), we model a monolayer formed at the water-oil interface, which comprises stimuli-responsive nanoparticles. The solid core of the nanoparticle encompasses beads arranged in an fcc lattice structure and its surface is uniformly grafted with stimuli-responsive polymer chains. The surface-active nanoparticles adsorb to the interface from the suspension to minimize total energy of the system and create a monolayer covering the interface. We investigate the monolayer formation by characterizing the detailed adsorption kinetics. We explore the microstructure of the monolayer at different surface coverage, including the particle crowding and ordering, and elucidate the response of monolayer to external stimuli. The collective behavior of the particles within the monolayer is demonstrated quantitatively by vector-vector autocorrelation functions. This study provides a fundamental understanding of the interfacial behavior of stimuli-responsive nanoparticles.

  11. Stimuli, Reinforcers, and the Persistence of Behavior

    ERIC Educational Resources Information Center

    Nevin, John A.

    2009-01-01

    This article reviews evidence from basic and translational research with pigeons and humans suggesting that the persistence of operant behavior depends on the contingency between stimuli and reinforcers, and considers some implications for clinical interventions. (Contains 4 figures.)

  12. Stimuli, Reinforcers, and the Persistence of Behavior

    ERIC Educational Resources Information Center

    Nevin, John A.

    2009-01-01

    This article reviews evidence from basic and translational research with pigeons and humans suggesting that the persistence of operant behavior depends on the contingency between stimuli and reinforcers, and considers some implications for clinical interventions. (Contains 4 figures.)

  13. Stimuli-responsive photoluminescent liquid crystals.

    PubMed

    Yamane, Shogo; Tanabe, Kana; Sagara, Yoshimitsu; Kato, Takashi

    2012-01-01

    We describe mechanochromic and thermochromic photoluminescent liquid crystals. In particular, mechanochromic photoluminescent liquid crystals found recently, which are new stimuli-responsive materials are reported. For example, photoluminescent liquid crystals having bulky dendritic moieties with long alkyl chains change their photoluminescent colors by mechanical stimuli associated with isothermal phase transitions. The photoluminescent properties of molecular assemblies depend on their assembled structures. Therefore, controlling the structures of molecular assemblies with external stimuli leads to the development of stimuli-responsive luminescent materials. Mechanochromic photoluminescent properties are also observed for a photoluminescent metallomesogen and a liquid-crystalline polymer. We also show thermochromic photoluminescent liquid crystals based on origo-(p-phenylenevinylene) and anthracene moieties and a thermochromic photoluminescent metallocomplex.

  14. Depth Perception Not Found in Human Observers for Static or Dynamic Anti-Correlated Random Dot Stereograms

    PubMed Central

    Hibbard, Paul B.; Scott-Brown, Kenneth C.; Haigh, Emma C.; Adrain, Melanie

    2014-01-01

    One of the greatest challenges in visual neuroscience is that of linking neural activity with perceptual experience. In the case of binocular depth perception, important insights have been achieved through comparing neural responses and the perception of depth, for carefully selected stimuli. One of the most important types of stimulus that has been used here is the anti-correlated random dot stereogram (ACRDS). In these stimuli, the contrast polarity of one half of a stereoscopic image is reversed. While neurons in cortical area V1 respond reliably to the binocular disparities in ACRDS, they do not create a sensation of depth. This discrepancy has been used to argue that depth perception must rely on neural activity elsewhere in the brain. Currently, the psychophysical results on which this argument rests are not clear-cut. While it is generally assumed that ACRDS do not support the perception of depth, some studies have reported that some people, some of the time, perceive depth in some types of these stimuli. Given the importance of these results for understanding the neural correlates of stereopsis, we studied depth perception in ACRDS using a large number of observers, in order to provide an unambiguous conclusion about the extent to which these stimuli support the perception of depth. We presented observers with random dot stereograms in which correlated dots were presented in a surrounding annulus and correlated or anti-correlated dots were presented in a central circular region. While observers could reliably report the depth of the central region for correlated stimuli, we found no evidence for depth perception in static or dynamic anti-correlated stimuli. Confidence ratings for stereoscopic perception were uniformly low for anti-correlated stimuli, but showed normal variation with disparity for correlated stimuli. These results establish that the inability of observers to perceive depth in ACRDS is a robust phenomenon. PMID:24416195

  15. Depth perception not found in human observers for static or dynamic anti-correlated random dot stereograms.

    PubMed

    Hibbard, Paul B; Scott-Brown, Kenneth C; Haigh, Emma C; Adrain, Melanie

    2014-01-01

    One of the greatest challenges in visual neuroscience is that of linking neural activity with perceptual experience. In the case of binocular depth perception, important insights have been achieved through comparing neural responses and the perception of depth, for carefully selected stimuli. One of the most important types of stimulus that has been used here is the anti-correlated random dot stereogram (ACRDS). In these stimuli, the contrast polarity of one half of a stereoscopic image is reversed. While neurons in cortical area V1 respond reliably to the binocular disparities in ACRDS, they do not create a sensation of depth. This discrepancy has been used to argue that depth perception must rely on neural activity elsewhere in the brain. Currently, the psychophysical results on which this argument rests are not clear-cut. While it is generally assumed that ACRDS do not support the perception of depth, some studies have reported that some people, some of the time, perceive depth in some types of these stimuli. Given the importance of these results for understanding the neural correlates of stereopsis, we studied depth perception in ACRDS using a large number of observers, in order to provide an unambiguous conclusion about the extent to which these stimuli support the perception of depth. We presented observers with random dot stereograms in which correlated dots were presented in a surrounding annulus and correlated or anti-correlated dots were presented in a central circular region. While observers could reliably report the depth of the central region for correlated stimuli, we found no evidence for depth perception in static or dynamic anti-correlated stimuli. Confidence ratings for stereoscopic perception were uniformly low for anti-correlated stimuli, but showed normal variation with disparity for correlated stimuli. These results establish that the inability of observers to perceive depth in ACRDS is a robust phenomenon.

  16. Emotional stimuli and motor conversion disorder.

    PubMed

    Voon, Valerie; Brezing, Christina; Gallea, Cecile; Ameli, Rezvan; Roelofs, Karin; LaFrance, W Curt; Hallett, Mark

    2010-05-01

    Conversion disorder is characterized by neurological signs and symptoms related to an underlying psychological issue. Amygdala activity to affective stimuli is well characterized in healthy volunteers with greater amygdala activity to both negative and positive stimuli relative to neutral stimuli, and greater activity to negative relative to positive stimuli. We investigated the relationship between conversion disorder and affect by assessing amygdala activity to affective stimuli. We conducted a functional magnetic resonance imaging study using a block design incidental affective task with fearful, happy and neutral face stimuli and compared valence contrasts between 16 patients with conversion disorder and 16 age- and gender-matched healthy volunteers. The patients with conversion disorder had positive movements such as tremor, dystonia or gait abnormalities. We also assessed functional connectivity between the amygdala and regions associated with motor preparation. A group by affect valence interaction was observed. Post hoc analyses revealed that whereas healthy volunteers had greater right amygdala activity to fearful versus neutral compared with happy versus neutral as expected, there were no valence differences in patients with conversion disorder. There were no group differences observed. The time course analysis also revealed greater right amygdala activity in patients with conversion disorder for happy stimuli (t = 2.96, P = 0.006) (with a trend for fearful stimuli, t = 1.81, P = 0.08) compared with healthy volunteers, with a pattern suggestive of impaired amygdala habituation even when controlling for depressive and anxiety symptoms. Using psychophysiological interaction analysis, patients with conversion disorder had greater functional connectivity between the right amygdala and the right supplementary motor area during both fearful versus neutral, and happy versus neutral 'stimuli' compared with healthy volunteers. These results were confirmed with

  17. Approach of visual stimuli modulates spatial expectations for subsequent somatosensory stimuli.

    PubMed

    Kimura, Tsukasa; Katayama, Jun'ichi

    2015-06-01

    To examine how the approach of visual stimuli toward the body influences expectations regarding subsequent somatosensory stimuli, we recorded event-related brain potentials (ERPs; nose reference) during a simple reaction time to somatosensory stimuli task. Twelve participants were asked to place their arms on a desk, and three LEDs were placed between their arms at equal intervals. Electrical stimuli were presented to the left (or right) wrist at a high probability (80%) or to the opposite wrist at a low probability (20%). Each trial was composed of three visual stimuli followed by one electrical stimulus. In Experiment 1, the right, center, and left (or left, center, and right) LEDs were turned on sequentially toward the wrist to which the high probability somatosensory stimuli was presented (congruent condition), or the center LED were presented three times (neutral condition). Experiment 2 was composed of the congruent condition and the inverse of the congruent condition (incongruent condition). In both experiments, the reaction times to low probability stimuli were longer than those to high probability stimuli. Moreover, the low probability stimuli elicited a larger P3 amplitude than the high probability stimuli. In addition, the P3 amplitude was higher under the visual approach condition (i.e., the congruent condition in each experiment) than under the control condition (i.e., the neutral and incongruent conditions). Furthermore, no effect on the CNV amplitude before the somatosensory stimuli was found. These results suggest that visual stimuli directed toward the body induce an automatic spatial expectation for subsequent somatosensory stimuli. Copyright © 2015 Elsevier B.V. All rights reserved.

  18. Temporal binding of auditory and rotational stimuli.

    PubMed

    Sanders, Mark C; Chang, Nai-Yuan N; Hiss, Meghan M; Uchanski, Rosalie M; Hullar, Timothy E

    2011-05-01

    Integration of cues from multiple sensory channels improves our ability to sense and respond to stimuli. Cues arising from a single event may arrive at the brain asynchronously, requiring them to be "bound" in time. The perceptual asynchrony between vestibular and auditory stimuli has been reported to be several times greater than other stimulus pairs. However, these data were collected using electrically evoked vestibular stimuli, which may not provide similar results to those obtained using actual head rotations. Here, we tested whether auditory stimuli and vestibular stimuli consisting of physiologically relevant mechanical rotations are perceived with asynchronies consistent with other sensory systems. We rotated 14 normal subjects about the earth-vertical axis over a raised-cosine trajectory (0.5 Hz, peak velocity 10 deg/s) while isolated from external noise and light. This trajectory minimized any input from extravestibular sources such as proprioception. An 800-Hz, 10-ms auditory tone was presented at stimulus onset asynchronies ranging from 200 ms before to 700 ms after the onset of motion. After each trial, subjects reported whether the stimuli were "simultaneous" or "not simultaneous." The experiment was repeated, with subjects reporting whether the tone or rotation came first. After correction for the time the rotational stimulus took to reach vestibular perceptual threshold, asynchronies spanned from -41 ms (auditory stimulus leading vestibular) to 91 ms (vestibular stimulus leading auditory). These values are significantly lower than those previously reported for stimulus pairs involving electrically evoked vestibular stimuli and are more consistent with timing relationships between pairs of non-vestibular stimuli.

  19. Spatial localization of electrotactile stimuli on the fingertip in humans.

    PubMed

    Bobich, L R; Warren, J P; Sweeney, J D; Tillery, S I Helms; Santello, M

    2007-12-01

    This study was designed to determine the extent to which sensations elicited by discrete electrotactile stimulation can be spatially localized, with a qualitative comparison to mechanical stimulation, in a 2 x 2 electrode array on the fingertip. Electrotactile stimulation was delivered in two modes: (1) same current to all locations (constant) or (2) current adjusted to perceptual threshold of each location (varied). For each stimulus location, subjects were asked to identify the location of the stimulus. Mechanical stimulation of the same locations on the fingerpad was delivered through von Frey hairs (0.07, 0.2 and 0.4 g). The percentage of accurate responses was computed for all stimulation modes. We found that the accuracy of discrimination of stimulus location in both the constant (46%) and varied (40%) electrotactile stimulation modes was significantly higher than chance level (25%; p < 0.01). Furthermore, subjects were significantly more accurate in discriminating electrotactile stimuli in the constant than in the varied mode (p < 0.05). We also found that the accuracy of spatial discrimination was dependent on stimulation site for mechanical, but not electrotactile stimulation. Finally, we found a significant difference in accuracy over the duration of the experiment only for mechanical modes, which may indicate that electrotactile stimuli are less biased over time. These results suggest that, although low in accuracy, human subjects are able to extract spatial information from electrotactile stimuli. Further research is needed to optimize the amount of the information that can be delivered through electrotactile stimulation.

  20. Stimuli-responsive nanoparticles from ionic cellulose derivatives

    NASA Astrophysics Data System (ADS)

    Wang, Yonggui; Heinze, Thomas; Zhang, Kai

    2015-12-01

    Stimuli-responsive nanoparticles (NPs) based on sustainable polymeric feedstock still need more exploration in comparison with NPs based on synthetic polymers. In this report, stimuli-responsive NPs from novel ionic cellulose derivatives were prepared via a facile nanoprecipitation. Cellulose 10-undecenoyl ester (CUE) with a degree of substitution (DS) of 3 was synthesized by esterification of cellulose with 10-undecenoyl chloride. Then, CUE was modified by photo-induced thiol-ene reactions, in order to obtain organo-soluble ionic cellulose derivatives with DSs of ~3, namely cellulose 11-((3-carboxyl)ethylthio)undecanoate (CUE-MPA), cellulose 11-((2-aminoethyl)thio)undecanoate (CUE-CA), cellulose 11-(2-(2-(diethylamino)ethyl)thio)undecanoate (CUE-DEAET) and cellulose 11-(2-(2-(dimethylamino)ethyl)thio)undecanoate (CUE-DMAET). CUE-MPA could be transformed into NPs with average diameters in the range of 80-330 nm, but these NPs did not show particular stimuli-responsive properties. Moreover, the dropping technique resulted in smaller NPs than a dialysis technique. Stable NPs with average diameters in the range of 90-180 nm showing pH-responsive and switchable sizes were obtained from CUE-DEAET and CUE-DMAET possessing tertiary amines using nanoprecipitation. Thus, altering the terminal functional groups will be a new approach to prepare stimuli-responsive cellulose-derived polymeric NPs.Stimuli-responsive nanoparticles (NPs) based on sustainable polymeric feedstock still need more exploration in comparison with NPs based on synthetic polymers. In this report, stimuli-responsive NPs from novel ionic cellulose derivatives were prepared via a facile nanoprecipitation. Cellulose 10-undecenoyl ester (CUE) with a degree of substitution (DS) of 3 was synthesized by esterification of cellulose with 10-undecenoyl chloride. Then, CUE was modified by photo-induced thiol-ene reactions, in order to obtain organo-soluble ionic cellulose derivatives with DSs of ~3, namely cellulose

  1. Polydiacetylene-enclosed near-infrared fluorescent semiconducting polymer dots for bioimaging and sensing.

    PubMed

    Wu, Pei-Jing; Kuo, Shih-Yu; Huang, Ya-Chi; Chen, Chuan-Pin; Chan, Yang-Hsiang

    2014-05-20

    Semiconducting polymer dots (P-dots) recently have emerged as a new type of ultrabright fluorescent probe with promising applications in biological imaging and detection. With the increasing desire for near-infrared (NIR) fluorescing probes for in vivo biological measurements, the currently available NIR-emitting P-dots are very limited and the leaching of the encapsulated dyes/polymers has usually been a concern. To address this challenge, we first embedded the NIR dyes into the matrix of poly[(9,9-dioctylfluorene)-co-2,1,3-benzothiadiazole-co-4,7-di(thiophen-2-yl)-2,1,3-benzothiadiazole] (PF-BT-DBT) polymer and then enclosed the doped P-dots with polydiacetylenes (PDAs) to avoid potential leakage of the entrapped NIR dyes from the P-dot matrix. These PDA-enclosed NIR-emitting P-dots not only emitted much stronger NIR fluorescence than conventional organic molecules but also exhibited enhanced photostability over CdTe quantum dots, free NIR dyes, and gold nanoclusters. We next conjugated biomolecules onto the surface of the resulting P-dots and demonstrated their capability for specific cellular labeling without any noticeable nonspecific binding. To employ this new class of material as a facile sensing platform, an easy-to-prepare test paper, obtained by soaking the paper into the PDA-enclosed NIR-emitting P-dot solution, was used to sense external stimuli such as ions, temperature, or pH, depending on the surface functionalization of PDAs. We believe these PDA-coated NIR-fluorescing P-dots will be very useful in a variety of bioimaging and analytical applications.

  2. Cognitive biases to appearance-related stimuli in body dissatisfaction: A systematic review.

    PubMed

    Rodgers, Rachel F; DuBois, Russell H

    2016-06-01

    Emerging literature has documented the presence of cognitive biases toward body image related stimuli among individuals with high levels of body image concerns compared to those with low levels of body image concerns. However, the robustness and nature of these cognitive biases are unclear. The aims of this study were to conduct a systematic literature search and perform a critical synthesis of studies examining the relationship between cognitive biases toward body image-related stimuli and body image concerns. Our review identified 32 studies meeting inclusion criteria. Dot-probe, Stroop, free recall, and eye-tracking were among the most frequently used paradigms. The extant literature provides robust support for the presence of attention biases toward body image-related stimuli among individuals with high levels of body dissatisfaction compared to those with lower levels of concerns. Evidence was also found for the existence of judgment biases and memory biases. Furthermore, results suggest that body image-related cognitive biases, and levels of body dissatisfaction can be manipulated. Initial evidence was also found for differential patterns of biases toward "fat" and "thin" stimuli. These findings confirm the importance of considering cognitive biases within etiological models of body image concerns and suggest that these processes might provide novel treatment targets. Copyright © 2016 Elsevier Ltd. All rights reserved.

  3. Attentional Bias for Emotional Stimuli in Borderline Personality Disorder: A Meta-Analysis.

    PubMed

    Kaiser, Deborah; Jacob, Gitta A; Domes, Gregor; Arntz, Arnoud

    2016-01-01

    In borderline personality disorder (BPD), attentional bias (AB) to emotional stimuli may be a core component in disorder pathogenesis and maintenance. 11 emotional Stroop task (EST) studies with 244 BPD patients, 255 nonpatients (NPs) and 95 clinical controls and 4 visual dot-probe task (VDPT) studies with 151 BPD patients or subjects with BPD features and 62 NPs were included. We conducted two separate meta-analyses for AB in BPD. One meta-analysis focused on the EST for generally negative and BPD-specific/personally relevant negative words. The other meta-analysis concentrated on the VDPT for negative and positive facial stimuli. There is evidence for an AB towards generally negative emotional words compared to NPs (standardized mean difference, SMD = 0.311) and to other psychiatric disorders (SMD = 0.374) in the EST studies. Regarding BPD-specific/personally relevant negative words, BPD patients reveal an even stronger AB than NPs (SMD = 0.454). The VDPT studies indicate a tendency towards an AB to positive facial stimuli but not negative stimuli in BPD patients compared to NPs. The findings rather reflect an AB in BPD to generally negative and BPD-specific/personally relevant negative words rather than an AB in BPD towards facial stimuli, and/or a biased allocation of covert attentional resources to negative emotional stimuli in BPD and not a bias in focus of visual attention. Further research regarding the role of childhood traumatization and comorbid anxiety disorders may improve the understanding of these underlying processes. © 2016 The Author(s) Published by S. Karger AG, Basel.

  4. Attentional bias to alcohol stimuli predicts elevated cue-induced craving in young adult social drinkers.

    PubMed

    Manchery, Linda; Yarmush, Devorah E; Luehring-Jones, Peter; Erblich, Joel

    2017-07-01

    Considerable evidence has identified biased cognitive processing of alcohol-related stimuli as an important factor in the maintenance of alcohol-seeking and relapse among individuals suffering from alcohol use-disorders (AUDs). In addition, a large body of research has demonstrated that exposure to alcohol cues can elicit powerful alcohol cravings. Little is known, however, about the possible relationship between attentional bias and cue-induced cravings, and even less is known about these processes in social drinkers without a personal history of AUDs. The goal of this study was to examine the possibility that attentional biases toward alcohol-related stimuli would predict elevated cue-induced alcohol craving in this population. Young adult social drinkers (N=30, Mean age=22.8±1.9, 61% female) recruited from an urban university population completed a visual dot probe task in which they were presented with alcohol and neutral stimulus pictures that were immediately followed by a visual probe replacing one of the pictures. Attentional bias was measured by calculating reaction times to probes that replaced alcohol stimuli vs. neutral stimuli. Participants then completed a classic alcohol cue-exposure task and reported cravings immediately before and after alcohol and neutral cue-exposures. Not surprisingly, exposure to alcohol cues elicited significant cravings. Consistent with the study hypothesis, larger attentional biases toward alcohol stimuli predicted higher levels of alcohol craving. Findings demonstrate that heightened attention to alcohol stimuli can significantly impact motivation to consume in healthy young adults, and suggest a possible pathway linking cognitive processes early in the drinking trajectory to the later development of AUDs. Copyright © 2017 Elsevier Ltd. All rights reserved.

  5. Attentional Bias for Emotional Stimuli in Borderline Personality Disorder: A Meta-Analysis

    PubMed Central

    Kaiser, Deborah; Jacob, Gitta A.; Domes, Gregor; Arntz, Arnoud

    2017-01-01

    Background In borderline personality disorder (BPD), attentional bias (AB) to emotional stimuli may be a core component in disorder pathogenesis and maintenance. Sampling 11 emotional Stroop task (EST) studies with 244 BPD patients, 255 nonpatients (NPs) and 95 clinical controls and 4 visual dot-probe task (VDPT) studies with 151 BPD patients or subjects with BPD features and 62 NPs were included. Methods We conducted two separate meta-analyses for AB in BPD. One meta-analysis focused on the EST for generally negative and BPD-specific/personally relevant negative words. The other meta-analysis concentrated on the VDPT for negative and positive facial stimuli. Results There is evidence for an AB towards generally negative emotional words compared to NPs (standardized mean difference, SMD = 0.311) and to other psychiatric disorders (SMD = 0.374) in the EST studies. Regarding BPD-specific/personally relevant negative words, BPD patients reveal an even stronger AB than NPs (SMD = 0.454). The VDPT studies indicate a tendency towards an AB to positive facial stimuli but not negative stimuli in BPD patients compared to NPs. Conclusions The findings rather reflect an AB in BPD to generally negative and BPD-specific/personally relevant negative words rather than an AB in BPD towards facial stimuli, and/or a biased allocation of covert attentional resources to negative emotional stimuli in BPD and not a bias in focus of visual attention. Further research regarding the role of childhood traumatization and comorbid anxiety disorders may improve the understanding of these underlying processes. PMID:27642753

  6. Emotional stimuli and motor conversion disorder

    PubMed Central

    Brezing, Christina; Gallea, Cecile; Ameli, Rezvan; Roelofs, Karin; LaFrance, W. Curt; Hallett, Mark

    2010-01-01

    Conversion disorder is characterized by neurological signs and symptoms related to an underlying psychological issue. Amygdala activity to affective stimuli is well characterized in healthy volunteers with greater amygdala activity to both negative and positive stimuli relative to neutral stimuli, and greater activity to negative relative to positive stimuli. We investigated the relationship between conversion disorder and affect by assessing amygdala activity to affective stimuli. We conducted a functional magnetic resonance imaging study using a block design incidental affective task with fearful, happy and neutral face stimuli and compared valence contrasts between 16 patients with conversion disorder and 16 age- and gender-matched healthy volunteers. The patients with conversion disorder had positive movements such as tremor, dystonia or gait abnormalities. We also assessed functional connectivity between the amygdala and regions associated with motor preparation. A group by affect valence interaction was observed. Post hoc analyses revealed that whereas healthy volunteers had greater right amygdala activity to fearful versus neutral compared with happy versus neutral as expected, there were no valence differences in patients with conversion disorder. There were no group differences observed. The time course analysis also revealed greater right amygdala activity in patients with conversion disorder for happy stimuli (t = 2.96, P = 0.006) (with a trend for fearful stimuli, t = 1.81, P = 0.08) compared with healthy volunteers, with a pattern suggestive of impaired amygdala habituation even when controlling for depressive and anxiety symptoms. Using psychophysiological interaction analysis, patients with conversion disorder had greater functional connectivity between the right amygdala and the right supplementary motor area during both fearful versus neutral, and happy versus neutral ‘stimuli’ compared with healthy volunteers. These results were confirmed with

  7. Effects of visual stimuli on temporal order judgments of unimanual finger stimuli.

    PubMed

    Shibuya, Satoshi; Takahashi, Toshimitsu; Kitazawa, Shigeru

    2007-06-01

    Successive tactile stimuli, delivered one to each hand, are referred to spatial representation before they are ordered in time (Yamamoto and Kitazawa in Nat Neurosci 4:759-765 2001a). In the present study, we examined if this applies even when they are delivered unilaterally to fingers of a single hand. Tactile stimuli were delivered left-to-rightward relative to the body (2nd-3rd-4th) or in reverse with stimulus onset asynchrony of 100 ms. Simultaneously with the delivery of tactile stimuli, three of nine small squares arranged in a matrix of 3 x 3 were turned on as if they appeared near the tips of the fingers. Although subjects were instructed to ignore the visual stimuli and make a forced choice between the two orders of tactile stimuli, the correct-judgment probability depended on the direction of visual stimuli. It was greater than 95% when the direction of visual stimuli matched that of the tactile stimuli, but less than 50% when they were opposite to each other. When the right hand was rotated counterclockwise on the horizontal plane (90 degrees ) so that the fingers were pointing to the left, the preferred direction of visual stimuli that yielded the peak correct judgment was also rotated, although not to the full extent. These results show that subjects cannot be basing their tactile temporal order judgment solely on a somatotopic map, but rather on a spatial map on which both visual and tactile signals converge.

  8. Generalization of the disruptive effects of alternative stimuli when combined with target stimuli in extinction.

    PubMed

    Podlesnik, Christopher A; Miranda-Dukoski, Ludmila; Jonas Chan, C K; Bland, Vikki J; Bai, John Y H

    2017-09-01

    Differential-reinforcement treatments reduce target problem behavior in the short term but at the expense of making it more persistent long term. Basic and translational research based on behavioral momentum theory suggests that combining features of stimuli governing an alternative response with the stimuli governing target responding could make target responding less persistent. However, changes to the alternative stimulus context when combining alternative and target stimuli could diminish the effectiveness of the alternative stimulus in reducing target responding. In an animal model with pigeons, the present study reinforced responding in the presence of target and alternative stimuli. When combining the alternative and target stimuli during extinction, we altered the alternative stimulus through changes in line orientation. We found that (1) combining alternative and target stimuli in extinction more effectively decreased target responding than presenting the target stimulus on its own; (2) combining these stimuli was more effective in decreasing target responding trained with lower reinforcement rates; and (3) changing the alternative stimulus reduced its effectiveness when it was combined with the target stimulus. Therefore, changing alternative stimuli (e.g., therapist, clinical setting) during behavioral treatments that combine alternative and target stimuli could reduce the effectiveness of those treatments in disrupting problem behavior. © 2017 Society for the Experimental Analysis of Behavior.

  9. Comparative judgments of symbolic and non-symbolic stimuli yield different patterns of reaction times.

    PubMed

    Leibovich, Tali; Ashkenazi, Sarit; Rubinsten, Orly; Henik, Avishai

    2013-10-01

    Are different magnitudes, such as Arabic numerals, length and area, processed by the same system? Answering this question can shed light on the building blocks of our mathematical abilities. A shared representation theory suggested that discriminability of all magnitudes complies with Weber's law. The current work examined this suggestion. We employed comparative judgment tasks to investigate different types of comparisons - conceptual comparison of numbers, physical comparison of numbers and physical comparison of different shapes. We used 8 different size ratios and plotted reaction time as a function of these ratios. Our findings suggest that the relationship between discriminability and size ratio is not always linear, as previously suggested; rather, it is modulated by the type of comparison and the type of stimuli. Hence, we suggest that the representation of magnitude is not as rigid as previously suggested; it changes as a function of task demands and familiarity with the compared stimuli. © 2013.

  10. Stimuli-responsive smart gating membranes.

    PubMed

    Liu, Zhuang; Wang, Wei; Xie, Rui; Ju, Xiao-Jie; Chu, Liang-Yin

    2016-02-07

    Membranes are playing paramount roles in the sustainable development of myriad fields such as energy, environmental and resource management, and human health. However, the unalterable pore size and surface properties of traditional porous membranes restrict their efficient applications. The performances of traditional membranes will be weakened upon unavoidable membrane fouling, and they cannot be applied to cases where self-regulated permeability and selectivity are required. Inspired by natural cell membranes with stimuli-responsive channels, artificial stimuli-responsive smart gating membranes are developed by chemically/physically incorporating stimuli-responsive materials as functional gates into traditional porous membranes, to provide advanced functions and enhanced performances for breaking the bottlenecks of traditional membrane technologies. Smart gating membranes, integrating the advantages of traditional porous membrane substrates and smart functional gates, can self-regulate their permeability and selectivity via the flexible adjustment of pore sizes and surface properties based on the "open/close" switch of the smart gates in response to environmental stimuli. This tutorial review summarizes the recent developments in stimuli-responsive smart gating membranes, including the design strategies and the fabrication strategies that are based on the introduction of the stimuli-responsive gates after or during membrane formation, and the positively and negatively responsive gating models of versatile stimuli-responsive smart gating membranes, as well as the advanced applications of smart gating membranes for regulating substance concentration in reactors, controlling the release rate of drugs, separating active molecules based on size or affinity, and the self-cleaning of membrane surfaces. With self-regulated membrane performances, smart gating membranes show great power for use in global sustainable development.

  11. Quantum Dot Sensitized Photoelectrodes

    PubMed Central

    Macdonald, Thomas J.; Nann, Thomas

    2011-01-01

    Quantum Dots (QDs) are promising alternatives to organic dyes as sensitisers for photocatalytic electrodes. This review article provides an overview of the current state of the art in this area. More specifically, different types of QDs with a special focus on heavy-metal free QDs and the methods for preparation and adsorption onto metal oxide electrodes (especially titania and zinc oxide) are discussed. Eventually, the key areas of necessary improvements are identified and assessed.

  12. Quantum DOT IR Photodetectors

    DTIC Science & Technology

    2012-07-01

    4.1.3  ROIC Control and Readout Electronics ................................................................ 16  4.2  Device measurements...the voltage of the detector modifies its spectral response. In this effort a DWELL Quantum Dot device was fabricated and tested. The results...agility. Because of delays in the fabrication of the ROIC device by MOSIS, those results will not available for the final report until approximately

  13. Plasmonic fluorescent quantum dots

    PubMed Central

    Jin, Yongdong

    2009-01-01

    Combining multiple discrete components into a single multifunctional nanoparticle could be useful in a variety of applications. Retaining the unique optical and electrical properties of each component after nanoscale integration is, however, a long-standing problem1,2. It is particularly difficult when trying to combine fluorophores such as semiconductor quantum dots with plasmonic materials such as gold, because gold and other metals can quench the fluorescence3,4. So far, the combination of quantum dot fluorescence with plasmonically active gold has only been demonstrated on flat surfaces5. Here, we combine fluorescent and plasmonic activities in a single nanoparticle by controlling the spacing between a quantum dot core and an ultrathin gold shell with nanometre precision through layer-by-layer assembly. Our wet-chemistry approach provides a general route for the deposition of ultrathin gold layers onto virtually any discrete nanostructure or continuous surface, and should prove useful for multimodal bioimaging6, interfacing with biological systems7, reducing nanotoxicity8, modulating electromagnetic fields5 and contacting nanostructures9,10. PMID:19734929

  14. Recall and recognition hypermnesia for Socratic stimuli.

    PubMed

    Kazén, Miguel; Solís-Macías, Víctor M

    2016-01-01

    In two experiments, we investigate hypermnesia, net memory improvements with repeated testing of the same material after a single study trial. In the first experiment, we found hypermnesia across three trials for the recall of word solutions to Socratic stimuli (dictionary-like definitions of concepts) replicating Erdelyi, Buschke, and Finkelstein and, for the first time using these materials, for their recognition. In the second experiment, we had two "yes/no" recognition groups, a Socratic stimuli group presented with concrete and abstract verbal materials and a word-only control group. Using signal detection measures, we found hypermnesia for concrete Socratic stimuli-and stable performance for abstract stimuli across three recognition tests. The control group showed memory decrements across tests. We interpret these findings with the alternative retrieval pathways (ARP) hypothesis, contrasting it with alternative theories of hypermnesia, such as depth of processing, generation and retrieve-recognise. We conclude that recognition hypermnesia for concrete Socratic stimuli is a reliable phenomenon, which we found in two experiments involving both forced-choice and yes/no recognition procedures.

  15. Visual stimuli approaching toward the body influence temporal expectations about subsequent somatosensory stimuli.

    PubMed

    Kimura, Tsukasa; Katayama, Jun'ichi

    2017-06-01

    The present study investigated whether visual stimuli approaching the body influence temporal expectations about subsequent somatosensory stimuli. To examine this question, we recorded event-related brain potentials (ERPs) during a simple reaction time task using somatosensory stimuli. Fourteen participants were asked to place their arms on a desk, and three light-emitting diodes (LEDs) were placed at equal distances between their arms. Each trial was composed of three visual stimuli (i.e., LEDs), and one subsequent electrical stimulus (i.e., somatosensory stimulus) to one wrist. The stimulus onset asynchrony (SOA) between the visual stimuli was set to 1000ms. The SOA between the third visual stimulus and the somatosensory stimulus was set to 1000ms (standard; p=0.75), 500ms (early deviation; p=0.125), and 1500ms (late deviation; p=0.125). In the approach condition, the left, center, and right LEDs (or reverse) were turned sequentially toward the wrist to which the somatosensory stimulus was presented. In the neutral condition, the center LED was flashed three times. The N1 amplitudes for early deviations of stimuli were larger under the approach condition than under the neutral condition. These results show that prior visual stimuli facilitate temporal expectations about subsequent somatosensory stimuli, i.e., visual stimuli approaching toward the body facilitate the processing of early deviant stimuli. The present study indicates the existence of a function of supramodal temporal expectation and detection of deviation from this expectation using the approach of visual stimuli toward the body. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Intracellular distribution of nontargeted quantum dots after natural uptake and microinjection

    PubMed Central

    Damalakiene, Leona; Karabanovas, Vitalijus; Bagdonas, Saulius; Valius, Mindaugas; Rotomskis, Ricardas

    2013-01-01

    Background: The purpose of this study was to elucidate the mechanism of natural uptake of nonfunctionalized quantum dots in comparison with microinjected quantum dots by focusing on their time-dependent accumulation and intracellular localization in different cell lines. Methods: The accumulation dynamics of nontargeted CdSe/ZnS carboxyl-coated quantum dots (emission peak 625 nm) was analyzed in NIH3T3, MCF-7, and HepG2 cells by applying the methods of confocal and steady-state fluorescence spectroscopy. Intracellular colocalization of the quantum dots was investigated by staining with Lysotracker®. Results: The uptake of quantum dots into cells was dramatically reduced at a low temperature (4°C), indicating that the process is energy-dependent. The uptake kinetics and imaging of intracellular localization of quantum dots revealed three accumulation stages of carboxyl-coated quantum dots at 37°C, ie, a plateau stage, growth stage, and a saturation stage, which comprised four morphological phases: adherence to the cell membrane; formation of granulated clusters spread throughout the cytoplasm; localization of granulated clusters in the perinuclear region; and formation of multivesicular body-like structures and their redistribution in the cytoplasm. Diverse quantum dots containing intracellular vesicles in the range of approximately 0.5–8 μm in diameter were observed in the cytoplasm, but none were found in the nucleus. Vesicles containing quantum dots formed multivesicular body-like structures in NIH3T3 cells after 24 hours of incubation, which were Lysotracker-negative in serum-free medium and Lysotracker-positive in complete medium. The microinjected quantum dots remained uniformly distributed in the cytosol for at least 24 hours. Conclusion: Natural uptake of quantum dots in cells occurs through three accumulation stages via a mechanism requiring energy. The sharp contrast of the intracellular distribution after microinjection of quantum dots in comparison

  17. Dynamic bioactive stimuli-responsive polymeric surfaces

    NASA Astrophysics Data System (ADS)

    Pearson, Heather Marie

    This dissertation focuses on the design, synthesis, and development of antimicrobial and anticoagulant surfaces of polyethylene (PE), polypropylene (PP), and poly(tetrafluoroethylene) (PTFE) polymers. Aliphatic polymeric surfaces of PE and PP polymers functionalized using click chemistry reactions by the attachment of --COOH groups via microwave plasma reactions followed by functionalization with alkyne moieties. Azide containing ampicillin (AMP) was synthesized and subsequently clicked into the alkyne prepared PE and PP surfaces. Compared to non-functionalized PP and PE surfaces, the AMP clicked surfaces exhibited substantially enhanced antimicrobial activity against Staphylococcus aureus bacteria. To expand the biocompatibility of polymeric surface anticoagulant attributes, PE and PTFE surfaces were functionalized with pH-responsive poly(2-vinyl pyridine) (P2VP) and poly(acrylic acid) (PAA) polyelectrolyte tethers terminated with NH2 and COOH groups. The goal of these studies was to develop switchable stimuli-responsive polymeric surfaces that interact with biological environments and display simultaneous antimicrobial and anticoagulant properties. Antimicrobial AMP was covalently attached to --COOH terminal ends of protected PAA, while anticoagulant heparin (HEP) was attached to terminal --NH2 groups of P2VP. When pH < 2.3, the P2VP segments are protonated and extend, but for pH > 5.5, they collapse while the PAA segments extend. Such surfaces, when exposed to Staphylococcus aureus, inhibit bacterial growth due to the presence of AMP, as well as are effective anticoagulants due to the presence of covalently attached HEP. Comparison of these "dynamic" pH responsive surfaces with "static" surfaces terminated with AMP entities show significant enhancement of longevity and surface activity against microbial film formation. The last portion of this dissertation focuses on the covalent attachment of living T1 and Φ11 bacteriophages (phages) on PE and PTFE surface

  18. Neural responses to salient visual stimuli.

    PubMed Central

    Morris, J S; Friston, K J; Dolan, R J

    1997-01-01

    The neural mechanisms involved in the selective processing of salient or behaviourally important stimuli are uncertain. We used an aversive conditioning paradigm in human volunteer subjects to manipulate the salience of visual stimuli (emotionally expressive faces) presented during positron emission tomography (PET) neuroimaging. Increases in salience, and conflicts between the innate and acquired value of the stimuli, produced augmented activation of the pulvinar nucleus of the right thalamus. Furthermore, this pulvinar activity correlated positively with responses in structures hypothesized to mediate value in the brain right amygdala and basal forebrain (including the cholinergic nucleus basalis of Meynert). The results provide evidence that the pulvinar nucleus of the thalamus plays a crucial modulatory role in selective visual processing, and that changes in perceptual salience are mediated by value-dependent plasticity in pulvinar responses. PMID:9178546

  19. Neural responses to salient visual stimuli.

    PubMed

    Morris, J S; Friston, K J; Dolan, R J

    1997-05-22

    The neural mechanisms involved in the selective processing of salient or behaviourally important stimuli are uncertain. We used an aversive conditioning paradigm in human volunteer subjects to manipulate the salience of visual stimuli (emotionally expressive faces) presented during positron emission tomography (PET) neuroimaging. Increases in salience, and conflicts between the innate and acquired value of the stimuli, produced augmented activation of the pulvinar nucleus of the right thalamus. Furthermore, this pulvinar activity correlated positively with responses in structures hypothesized to mediate value in the brain right amygdala and basal forebrain (including the cholinergic nucleus basalis of Meynert). The results provide evidence that the pulvinar nucleus of the thalamus plays a crucial modulatory role in selective visual processing, and that changes in perceptual salience are mediated by value-dependent plasticity in pulvinar responses.

  20. VEP Responses to Op-Art Stimuli

    PubMed Central

    O’Hare, Louise; Clarke, Alasdair D. F.; Pollux, Petra M. J.

    2015-01-01

    Several types of striped patterns have been reported to cause adverse sensations described as visual discomfort. Previous research using op-art-based stimuli has demonstrated that spurious eye movement signals can cause the experience of illusory motion, or shimmering effects, which might be perceived as uncomfortable. Whilst the shimmering effects are one cause of discomfort, another possible contributor to discomfort is excessive neural responses: As striped patterns do not have the statistical redundancy typical of natural images, they are perhaps unable to be encoded efficiently. If this is the case, then this should be seen in the amplitude of the EEG response. This study found that stimuli that were judged to be most comfortable were also those with the lowest EEG amplitude. This provides some support for the idea that excessive neural responses might also contribute to discomfort judgements in normal populations, in stimuli controlled for perceived contrast. PMID:26422207

  1. Lingering representations of stimuli influence recall organization.

    PubMed

    Chan, Stephanie C Y; Applegate, Marissa C; Morton, Neal W; Polyn, Sean M; Norman, Kenneth A

    2017-03-01

    Several prominent theories posit that information about recent experiences lingers in the brain and organizes memories for current experiences, by forming a temporal context that is linked to those memories at encoding. According to these theories, if the thoughts preceding an experience X resemble the thoughts preceding an experience Y, then X and Y should show an elevated probability of being recalled together. We tested this prediction by using multi-voxel pattern analysis (MVPA) of fMRI data to measure neural evidence for lingering processing of preceding stimuli. As predicted, memories encoded with similar lingering thoughts about the category of preceding stimuli were more likely to be recalled together. Our results demonstrate that the "fading embers" of previous stimuli help to organize recall, confirming a key prediction of computational models of episodic memory.

  2. [Selection of visual hierarchical stimuli between global and local aspects in men and women].

    PubMed

    Razumnikova, O M; Vol'f, N V

    2011-01-01

    Sex differences in global-local hemispheric selective processing were examined by hierarchical letter presenting in conditions of their perception and comparison. Fifty-six right-handed males and 68 females (aged 17-22 years) participated in the experiment. During interference between global and local aspects of stimuli the mean reaction times for correct global responses was quicker than local responses, and the right hemisphere has been dominated during global selective processing independently from the sex. Sex differences in perception of visual hierarchical stimuli were more pronounced than in comparison condition: men prefer mostly the right-hemispheric global strategy of information processing, but women--the left-hemispheric local one. Dominance of global strategy in men and local strategy in women during visual hierarchical stimuli perception together with no sex differences in correct responses indicates possibility of similar results in cognitive activity by different ways.

  3. Stark effect and polarizability of graphene quantum dots

    NASA Astrophysics Data System (ADS)

    Pedersen, Thomas Garm

    2017-09-01

    The properties of graphene quantum dots can be manipulated via lateral electric fields. Treating electrons in such structures as confined massless Dirac fermions, we derive an analytical expression for the quadratic Stark shift valid for arbitrary angular momentum and quantum dot size. Moreover, we determine the perturbative regime, beyond which higher-order field effects are observed. The Dirac approach is validated by comparison with atomistic tight-binding simulations. Finally, we study the influence on the Stark effect of band gaps produced by, e.g., interaction with the substrate.

  4. A Single Mechanism Can Account for Human Perception of Depth in Mixed Correlation Random Dot Stereograms

    PubMed Central

    Cumming, Bruce G.

    2016-01-01

    In order to extract retinal disparity from a visual scene, the brain must match corresponding points in the left and right retinae. This computationally demanding task is known as the stereo correspondence problem. The initial stage of the solution to the correspondence problem is generally thought to consist of a correlation-based computation. However, recent work by Doi et al suggests that human observers can see depth in a class of stimuli where the mean binocular correlation is 0 (half-matched random dot stereograms). Half-matched random dot stereograms are made up of an equal number of correlated and anticorrelated dots, and the binocular energy model—a well-known model of V1 binocular complex cells—fails to signal disparity here. This has led to the proposition that a second, match-based computation must be extracting disparity in these stimuli. Here we show that a straightforward modification to the binocular energy model—adding a point output nonlinearity—is by itself sufficient to produce cells that are disparity-tuned to half-matched random dot stereograms. We then show that a simple decision model using this single mechanism can reproduce psychometric functions generated by human observers, including reduced performance to large disparities and rapidly updating dot patterns. The model makes predictions about how performance should change with dot size in half-matched stereograms and temporal alternation in correlation, which we test in human observers. We conclude that a single correlation-based computation, based directly on already-known properties of V1 neurons, can account for the literature on mixed correlation random dot stereograms. PMID:27196696

  5. A Single Mechanism Can Account for Human Perception of Depth in Mixed Correlation Random Dot Stereograms.

    PubMed

    Henriksen, Sid; Cumming, Bruce G; Read, Jenny C A

    2016-05-01

    In order to extract retinal disparity from a visual scene, the brain must match corresponding points in the left and right retinae. This computationally demanding task is known as the stereo correspondence problem. The initial stage of the solution to the correspondence problem is generally thought to consist of a correlation-based computation. However, recent work by Doi et al suggests that human observers can see depth in a class of stimuli where the mean binocular correlation is 0 (half-matched random dot stereograms). Half-matched random dot stereograms are made up of an equal number of correlated and anticorrelated dots, and the binocular energy model-a well-known model of V1 binocular complex cells-fails to signal disparity here. This has led to the proposition that a second, match-based computation must be extracting disparity in these stimuli. Here we show that a straightforward modification to the binocular energy model-adding a point output nonlinearity-is by itself sufficient to produce cells that are disparity-tuned to half-matched random dot stereograms. We then show that a simple decision model using this single mechanism can reproduce psychometric functions generated by human observers, including reduced performance to large disparities and rapidly updating dot patterns. The model makes predictions about how performance should change with dot size in half-matched stereograms and temporal alternation in correlation, which we test in human observers. We conclude that a single correlation-based computation, based directly on already-known properties of V1 neurons, can account for the literature on mixed correlation random dot stereograms.

  6. One tamed at a time: A new approach for controlling continuous magnitudes in numerical comparison tasks.

    PubMed

    Salti, Moti; Katzin, Naama; Katzin, David; Leibovich, Tali; Henik, Avishai

    2016-07-20

    Non-symbolic stimuli (i.e., dot arrays) are commonly used to study numerical cognition. However, in addition to numerosity, non-symbolic stimuli entail continuous magnitudes (e.g., total surface area, convex-hull, etc.) that correlate with numerosity. Several methods for controlling for continuous magnitudes have been suggested, all with the same underlying rationale: disassociating numerosity from continuous magnitudes. However, the different continuous magnitudes do not fully correlate; therefore, it is impossible to disassociate them completely from numerosity. Moreover, relying on a specific continuous magnitude in order to create this disassociation may end up in increasing or decreasing numerosity saliency, pushing subjects to rely on it more or less, respectively. Here, we put forward a taxonomy depicting the relations between the different continuous magnitudes. We use this taxonomy to introduce a new method with a complimentary Matlab toolbox that allows disassociating numerosity from continuous magnitudes and equating the ratio of the continuous magnitudes to the ratio of the numerosity in order to balance the saliency of numerosity and continuous magnitudes. A dot array comparison experiment in the subitizing range showed the utility of this method. Equating different continuous magnitudes yielded different results. Importantly, equating the convex hull ratio to the numerical ratio resulted in similar interference of numerical and continuous magnitudes.

  7. Context and Content Visuals and Performance on Listening Comprehension Stimuli.

    ERIC Educational Resources Information Center

    Ginther, April

    2002-01-01

    A nested cross-over design was used to examine the effects of visual condition, type of stimuli, and language proficiency on listening comprehension items of the Test of English as a Foreign Language. Three two-way interactions were significant: proficiency by type of stimuli, type of stimuli by visual condition, and type of stimuli by time.…

  8. Detecting spatial and temporal dot patterns in noise

    NASA Astrophysics Data System (ADS)

    Drum, Bruce

    1991-06-01

    The visual system can be thought of as an image processor that first reduces the dynamic retinal image to a temporal succession of noisy but redundant arrays of retinal ganglion cell signals and then reconstructs from these signals a stable representation of the external world. The process by which this reconstruction takes place is still poorly understood. An obvious requirement, however, is the capability to reject the noise in the individual neural signals. I am investigating the visual system's noise rejection capabilities by determining how much noise must be added to dot patterns to reduce them to detection threshold. The stimuli are patches of nonrandom dots surrounded by dynamic random dots of the same mean luminance and contrast. The non randomness, or coherence, of the stimulus patterns is controlled by randomizing a known percentage of stimulus dots in each frame of the dynamic display. The stimulus patterns can be limited to either spatial or temporal information. In addition to coherence, the size, duration and retinal location of the stimulus can be varied, as well as the temporal frequency, dot size, contrast and mean luminance of the entire display. Coherence thresholds are generally elevated by any operation that reduced the number of ganglion cells responding to the stimulus, either by reducing the stimulus area or duration or by limiting the response to a subset of ganglion cells (e.g., the receptive field overlap or response redundancy factor can be reduced by preferentially stimulating only one functional ganglion cell type, or by testing glaucoma patients with partially destroyed ganglion cell layers). The visual system thus appears to reduce noise effects by integrating neural responses that are correlated in either space or time.

  9. Transformation of the Discriminative and Eliciting Functions of Generalized Relational Stimuli

    ERIC Educational Resources Information Center

    Dougher, Michael J.; Hamilton, Derek; Fink, Brandi; Harrington, Jennifer

    2007-01-01

    In three experiments, match-to-sample procedures were used with undergraduates to establish arbitrary relational functions for three abstract visual stimuli. In the presence of samples A, B, and C, participants were trained to select the smallest, middle, and largest member, respectively, of a series of three-comparison arrays. In Experiment 1,…

  10. METHODOLOGICAL PROBLEMS OF THE PSYCHOPHYSICAL METHODS OF LIMITS AND CONSTANT STIMULI.

    DTIC Science & Technology

    The method of limits (ML) and the method of constant stimuli (MCS) can be related on the basis of simple probability considerations. From the...determinations, etc., (c) preferred methods for comparisons within the ML and between the ML and the MCS, (d) incompatibility of present-day assumptions concerning the ML and the MCS. (Author)

  11. Contingent Stimuli Signal Subsequent Reinforcer Ratios

    ERIC Educational Resources Information Center

    Boutros, Nathalie; Davison, Michael; Elliffe, Douglas

    2011-01-01

    Conditioned reinforcer effects may be due to the stimulus' discriminative rather than its strengthening properties. While this was demonstrated in a frequently-changing choice procedure, a single attempt to replicate in a relatively static choice environment failed. We contend that this was because the information provided by the stimuli was…

  12. Black Students' Responses to Afrocentric Communication Stimuli

    ERIC Educational Resources Information Center

    Armstrong, Ketra L.

    2005-01-01

    This study examined Black students' cognitive and affective responses to race of messenger and cultural content of message as Afrocentric communication stimuli. The sample consisted of 127 Black students (89 in the experimental group and 38 in the control group). Results of a 2 X 2 factorial MANOVA design indicated minimal yet significant main…

  13. Computer programming for generating visual stimuli.

    PubMed

    Bukhari, Farhan; Kurylo, Daniel D

    2008-02-01

    Critical to vision research is the generation of visual displays with precise control over stimulus metrics. Generating stimuli often requires adapting commercial software or developing specialized software for specific research applications. In order to facilitate this process, we give here an overview that allows nonexpert users to generate and customize stimuli for vision research. We first give a review of relevant hardware and software considerations, to allow the selection of display hardware, operating system, programming language, and graphics packages most appropriate for specific research applications. We then describe the framework of a generic computer program that can be adapted for use with a broad range of experimental applications. Stimuli are generated in the context of trial events, allowing the display of text messages, the monitoring of subject responses and reaction times, and the inclusion of contingency algorithms. This approach allows direct control and management of computer-generated visual stimuli while utilizing the full capabilities of modern hardware and software systems. The flowchart and source code for the stimulus-generating program may be downloaded from www.psychonomic.org/archive.

  14. Potential bronchoconstrictor stimuli in acid fog

    SciTech Connect

    Balmes, J.R.; Fine, J.M.; Gordon, T.; Sheppard, D.

    1989-02-01

    Acid fog is complex and contains multiple stimuli that may be capable of inducing bronchoconstriction. These stimuli include sulfuric and nitric acids, the principal inorganic acids present; sulfites, formed in the atmosphere as a reaction product of sulfur dioxide and water droplets; fog water itself, a hypoosmolar aerosol; the organic acid hydroxymethanesulfonate, the bisulfite adduct of formaldehyde; and gaseous pollutants, e.g., sulfur dioxide, oxides of nitrogen, ozone. Given this complexity, evaluation of the respiratory health effects of naturally occurring acid fog requires assessment of the bronchoconstrictor potency of each component stimulus and possible interactions among these stimuli. We summarize the results of three studies that involve characterization of the bronchoconstrictor potency of acid fog stimuli and/or their interaction in subjects with asthma. The results of the first study indicate that titratable acidity appears to be a more important stimulus to bronchoconstriction than is pH. The results of the second study demonstrate that sulfite species are capable of inducing bronchoconstriction, especially when inhaled at acid pH. The results of the third study suggest that acidity can potentiate hypoosmolar fog-induced bronchoconstriction.

  15. Potential bronchoconstrictor stimuli in acid fog.

    PubMed Central

    Balmes, J R; Fine, J M; Gordon, T; Sheppard, D

    1989-01-01

    Acid fog is complex and contains multiple stimuli that may be capable of inducing bronchoconstriction. These stimuli include sulfuric and niric acids, the principal inorganic acids present; sulfites, formed in the atmosphere as a reaction product of sulfur dioxide and water droplets; fog water itself, a hypoosmolar aerosol; the organic acid hydroxymethanesulfonate, the bisulfite adduct of formaldehyde; and gaseous pollutants, e.g., sulfur dioxide, oxides of nitrogen, ozone. Given this complexity, evaluation of the respiratory health effects of naturally occurring acid fog requires assessment of the bronchoconstrictor potency of each component stimulus and possible interactions among these stimuli. We summarize the results of three studies that involve characterization of the bronchoconstrictor potency of acid fog stimuli and/or their interaction in subjects with asthma. The results of the first study indicate that titratable acidity appears to be a more important stimulus to bronchoconstriction than is pH. The results of the second study demonstrate that sulfite species are capable of inducing bronchoconstriction, especially when inhaled at acid pH. The results of the third study suggest that acidity can potentiate hypoosmolar fog-induced bronchoconstriction. PMID:2539989

  16. Categorization of Multidimensional Stimuli by Pigeons

    ERIC Educational Resources Information Center

    Berg, Mark E.; Grace, Randolph C.

    2011-01-01

    Six pigeons responded in a visual category learning task in which the stimuli were dimensionally separable Gabor patches that varied in frequency and orientation. We compared performance in two conditions which varied in terms of whether accurate performance required that responding be controlled jointly by frequency and orientation, or…

  17. Scanning Quantum Dot Microscopy

    NASA Astrophysics Data System (ADS)

    Wagner, Christian; Green, Matthew F. B.; Leinen, Philipp; Deilmann, Thorsten; Krüger, Peter; Rohlfing, Michael; Temirov, Ruslan; Tautz, F. Stefan

    2015-07-01

    We introduce a scanning probe technique that enables three-dimensional imaging of local electrostatic potential fields with subnanometer resolution. Registering single electron charging events of a molecular quantum dot attached to the tip of an atomic force microscope operated at 5 K, equipped with a qPlus tuning fork, we image the quadrupole field of a single molecule. To demonstrate quantitative measurements, we investigate the dipole field of a single metal adatom adsorbed on a metal surface. We show that because of its high sensitivity the technique can probe electrostatic potentials at large distances from their sources, which should allow for the imaging of samples with increased surface roughness.

  18. Color appearance models and complex visual stimuli.

    PubMed

    Fairchild, Mark D

    2010-01-01

    Teeth in a patient's mouth in a dental office, or in the natural environment, represent very complex stimuli for the human color vision system. Predicting their perceived color is a daunting task at best. Colorimetry is designed mainly for the evaluation of uniform, flat, opaque, materials of fairly large size viewed on a medium-grey background under near-daylight sources of fairly high luminance. On the contrary, in situ teeth vary spatially, are curved and ridged, translucent, relatively small, and viewed against a variable background under nonuniform, and typically nonstandard, illumination. These differences in stimuli and viewing conditions summarize the difficulty in predicting the color appearance of teeth. The field of color science has extended basic colorimetry, as represented by CIE XYZ and CIELAB coordinates, to more complex visual stimuli and viewing environments. The CIECAM02 color appearance model accurately addresses issues of chromatic adaptation, luminance effects and adaptation, background and surround effects, and the higher dimensionality of color appearance. Such models represent a significant advance and are used successfully in a variety of applications. However, many stimuli vary in space and time at scales not addressed by typical color appearance models. For example, high-definition video images would fall into such a category and so would in situ human teeth. More recently, color appearance models and image quality metrics have been combined to create image appearance models for even more complex visual stimuli. This paper provides an overview of fundamental and advanced colorimetry leading up to color appearance and image appearance models and their potential application in dentistry. Copyright © 2010 Elsevier Ltd. All rights reserved.

  19. Skidmore Clips of Neutral and Expressive Scenarios (SCENES): Novel dynamic stimuli for social cognition research.

    PubMed

    Schofield, Casey A; Weeks, Justin W; Taylor, Lea; Karnedy, Colten

    2015-12-30

    Social cognition research has relied primarily on photographic emotional stimuli. Such stimuli likely have limited ecological validity in terms of representing real world social interactions. The current study presents evidence for the validity of a new stimuli set of dynamic social SCENES (Skidmore Clips of Emotional and Neutral Expressive Scenarios). To develop these stimuli, ten undergraduate theater students were recruited to portray members of an audience. This audience was configured to display (seven) varying configurations of social feedback, ranging from unequivocally approving to unequivocally disapproving (including three different versions of balanced/neutral scenes). Validity data were obtained from 383 adult participants recruited from Amazon's Mechanical Turk. Each participant viewed three randomly assigned scenes and provided a rating of the perceived criticalness of each scene. Results indicate that the SCENES reflect the intended range of emotionality, and pairwise comparisons suggest that the SCENES capture distinct levels of critical feedback. Overall, the SCENES stimuli set represents a publicly available (www.scenesstimuli.com) resource for researchers interested in measuring social cognition in the presence of dynamic and naturalistic social stimuli. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  20. Screened spin-1 and -1/2 Kondo effect in a triangular quantum dot system with interdot Coulomb repulsion

    NASA Astrophysics Data System (ADS)

    Xiong, Yong-Chen; Wang, Wei-Zhong; Luo, Shi-Jun; Yang, Jun-Tao; Huang, Hai-Ming

    2017-03-01

    By means of the numerical renormalization group (NRG) technique, we study the low temperature transport property and the phase transition for a triangular triple quantum dot system, including two centered dots (dot 1 and 2) and one side dot (dot 3). We focus on the effect of interdot repulsion V between two centered dots in a wide range of the interdot hopping tij (i,j = 1,2,3). When the hoppings between the centered dot and the side dot are symmetric, i.e., t13 = t23, and that between two centered dots t12 is small, two centered dots form a spin triplet when V is absent, and a totally screened spin-1 Kondo effect is observed. In this case, one has a spin 1 that is partially screened by the leads as in the usual spin-1 Kondo model, and the remaining spin 1/2 degree of freedom forms a singlet with the side dot. As V is large enough, one of the centered dots is singly occupied, while the other one is empty. The spin-1/2 Kondo effect is found when t13 is small. For large t12, two centered dots form a spin singlet when V = 0, leading to zero conductance. As V is large enough, the spin-1/2 Kondo effect is recovered in the case of small t13. For asymmetric t13≠t23 and small t12, a crossover is found as V increases in comparison with a first order quantum phase transition for the symmetric case. In the regime of large V, the spin-1/2 Kondo effect could also be found when both t13 and t23 are small. We demonstrate the present model is similar to the side-coupled double dot system in some appropriate regimes, and it appears as a possible realization of side-controllable molecular electronics and spintronics devices.

  1. Neurophysiological responses to music and vibroacoustic stimuli in Rett syndrome.

    PubMed

    Bergström-Isacsson, Märith; Lagerkvist, Bengt; Holck, Ulla; Gold, Christian

    2014-06-01

    People with Rett syndrome (RTT) have severe communicative difficulties. They have as well an immature brainstem that implies dysfunction of the autonomic nervous system. Music plays an important role in their life, is often used as a motivating tool in a variety of situations and activities, and caregivers are often clear about people with RTTs favourites. The aim of this study was to investigate physiological and emotional responses related to six different musical stimuli in people with RTT. The study included 29 participants with RTT who were referred to the Swedish Rett Center for medical brainstem assessment during the period 2006-2007. 11 children with a typical developmental pattern were used as comparison. A repeated measures design was used, and physiological data were collected from a neurophysiological brainstem assessment. The continuous dependent variables measured were Cardiac Vagal Tone (CVT), Cardiac Sensitivity to Baroreflex (CSB), Mean Arterial Blood Pressure (MAP) and the Coefficient of Variation of Mean Arterial Blood Pressure (MAP-CV). These parameters were used to categorise brainstem responses as parasympathetic (calming) response, sympathetic (activating) response, arousal (alerting) response and unclear response. The results showed that all participants responded to the musical stimuli, but not always in the expected way. It was noticeable that both people with and without RTT responded with an arousal to all musical stimuli to begin with. Even though the initial expressions sometimes changed after some time due to poor control functions of their brainstem, the present results are consistent with the possibility that the RTT participants' normal responses to music are intact. These findings may explain why music is so important for individuals with RTT throughout life. Copyright © 2014 Elsevier Ltd. All rights reserved.

  2. Regional brain responses in nulliparous women to emotional infant stimuli.

    PubMed

    Montoya, Jessica L; Landi, Nicole; Kober, Hedy; Worhunsky, Patrick D; Rutherford, Helena J V; Mencl, W Einar; Mayes, Linda C; Potenza, Marc N

    2012-01-01

    Infant cries and facial expressions influence social interactions and elicit caretaking behaviors from adults. Recent neuroimaging studies suggest that neural responses to infant stimuli involve brain regions that process rewards. However, these studies have yet to investigate individual differences in tendencies to engage or withdraw from motivationally relevant stimuli. To investigate this, we used event-related fMRI to scan 17 nulliparous women. Participants were presented with novel infant cries of two distress levels (low and high) and unknown infant faces of varying affect (happy, sad, and neutral) in a randomized, counter-balanced order. Brain activation was subsequently correlated with scores on the Behavioral Inhibition System/Behavioral Activation System scale. Infant cries activated bilateral superior and middle temporal gyri (STG and MTG) and precentral and postcentral gyri. Activation was greater in bilateral temporal cortices for low- relative to high-distress cries. Happy relative to neutral faces activated the ventral striatum, caudate, ventromedial prefrontal, and orbitofrontal cortices. Sad versus neutral faces activated the precuneus, cuneus, and posterior cingulate cortex, and behavioral activation drive correlated with occipital cortical activations in this contrast. Behavioral inhibition correlated with activation in the right STG for high- and low-distress cries relative to pink noise. Behavioral drive correlated inversely with putamen, caudate, and thalamic activations for the comparison of high-distress cries to pink noise. Reward-responsiveness correlated with activation in the left precentral gyrus during the perception of low-distress cries relative to pink noise. Our findings indicate that infant cry stimuli elicit activations in areas implicated in auditory processing and social cognition. Happy infant faces may be encoded as rewarding, whereas sad faces activate regions associated with empathic processing. Differences in motivational

  3. Efficient quantum dot-quantum dot and quantum dot-dye energy transfer in biotemplated assemblies.

    PubMed

    Achermann, Marc; Jeong, Sohee; Balet, Laurent; Montano, Gabriel A; Hollingsworth, Jennifer A

    2011-03-22

    CdSe semiconductor nanocrystal quantum dots are assembled into nanowire-like arrays employing microtubule fibers as nanoscale molecular "scaffolds." Spectrally and time-resolved energy-transfer analysis is used to assess the assembly of the nanoparticles into the hybrid inorganic biomolecular structure. Specifically, we demonstrate that a comprehensive study of energy transfer between quantum dot pairs on the biotemplate and, alternatively, between quantum dots and molecular dyes embedded in the microtubule scaffold comprises a powerful spectroscopic tool for evaluating the assembly process. In addition to revealing the extent to which assembly has occurred, the approach allows determination of particle-to-particle (and particle-to-dye) distances within the biomediated array. Significantly, the characterization is realized in situ, without need for further sample workup or risk of disturbing the solution-phase constructs. Furthermore, we find that the assemblies prepared in this way exhibit efficient quantum dot-quantum dot and quantum dot-dye energy transfer that affords faster energy-transfer rates compared to densely packed quantum dot arrays on planar substrates and to small-molecule-mediated quantum dot-dye couples, respectively.

  4. Size-Minimized Quantum Dots for Molecular and Cellular Imaging

    NASA Astrophysics Data System (ADS)

    Smith, Andrew M.; Wen, Mary M.; Wang, May D.; Nie, Shuming

    Semiconductor quantum dots, tiny light-emitting particles on thenanometer scale, are emerging as a new class of fluorescent labels for a broad range of molecular and cellular applications. In comparison with organic dyes and fluorescent proteins, they have unique optical and electronic properties such as size-tunable light emission, intense signal brightness, resistance to photobleaching, and broadband absorption for simultaneous excitation of multiple fluorescence colors. Here we report new advances in minimizing the hydrodynamic sizes of quantum dots using multidentate and multifunctional polymer coatings. A key finding is that a linear polymer containing grafted amine and thiol coordinating groups can coat nanocrystals and lead to a highly compact size, exceptional colloidal stability, strong resistance to photobleaching, and high fluorescence quantum yields. This has allowed a new generation of bright and stable quantum dots with small hydrodynamic diameters between 5.6 and 9.7 nm with tunable fluorescence emission from the visible (515 nm) to the near infrared (720 nm). These quantum dots are well suited for molecular and cellular imaging applications in which the nanoparticle hydrodynamic size needs to be minimized. Together with the novel properties of new strain-tunable quantum dots, these findings will be especially useful for multicolor and super-resolution imaging at the single-molecule level.

  5. Emotionally negative stimuli can overcome attentional deficits in patients with visuo-spatial hemineglect.

    PubMed

    Grabowska, A; Marchewka, A; Seniów, J; Polanowska, K; Jednoróg, K; Królicki, L; Kossut, M; Członkowska, A

    2011-10-01

    Left unilateral spatial neglect resulting from right brain damage is characterized by loss of awareness for stimuli in the contralesional side of space, despite intact visual pathways. We examined using fMRI whether patients with neglect are more likely to consciously detect in the neglected hemifield, emotionally negative complex scenes rather than visually similar neutral pictures and if so, what neural mechanisms mediate this effect. Photographs of emotional and neutral scenes taken from the IAPS were presented in a divided visual field paradigm. As expected, the detection rate for emotional stimuli presented in the neglected field was higher than for neutral ones. Successful detection of emotional scenes as opposed to neutral stimuli in the left visual field (LVF) produced activations in the parahippocampal and anterior cingulate areas in the right hemisphere. Detection of emotional stimuli presented in the intact right visual field (RVF) activated a distributed network of structures in the left hemisphere, including anterior and posterior cingulate cortex, insula, as well as visual striate and extrastriate areas. LVF-RVF contrasts for emotional stimuli revealed activations in right and left attention related prefrontal areas whereas RVF-LVF comparison showed activations in the posterior cingulate and extrastriate visual cortex in the left hemisphere. An additional analysis contrasting detected vs. undetected emotional LVF stimuli showed involvement of left anterior cingulate, right frontal and extrastriate areas. We hypothesize that beneficial role of emotion in overcoming neglect is achieved by activation of frontal and limbic lobe networks, which provide a privileged access of emotional stimuli to attention by top-down modulation of processing in the higher-order extrastriate visual areas. Our results point to the importance of top-down regulatory role of the frontal attentional systems, which might enhance visual activations and lead to greater salience of

  6. Quantum dot cascade laser

    PubMed Central

    2014-01-01

    We demonstrated an unambiguous quantum dot cascade laser based on InGaAs/GaAs/InAs/InAlAs heterostructure by making use of self-assembled quantum dots in the Stranski-Krastanow growth mode and two-step strain compensation active region design. The prototype generates stimulated emission at λ ~ 6.15 μm and a broad electroluminescence band with full width at half maximum over 3 μm. The characteristic temperature for the threshold current density within the temperature range of 82 to 162 K is up to 400 K. Moreover, our materials show the strong perpendicular mid-infrared response at about 1,900 cm-1. These results are very promising for extending the present laser concept to terahertz quantum cascade laser, which would lead to room temperature operation. PACS 42.55.Px; 78.55.Cr; 78.67.Hc PMID:24666965

  7. New quantum dot sensors

    NASA Astrophysics Data System (ADS)

    Gun'ko, Y. K.; Moloney, M. M.; Gallagher, S.; Govan, J.; Hanley, C.

    2010-04-01

    Quantum dots (QDs) are fluorescent semiconductor (e.g. II-VI) nanocrystals, which have a strong characteristic spectral emission. This emission is tunable to a desired energy by selecting variable particle size, size distribution and composition of the nanocrystals. QDs have recently attracted enormous interest due to their unique photophysical properties and range of potential applications in photonics and biochemistry. The main aim of our work is develop new chiral quantum dots (QDs) and establish fundamental principles influencing their structure, properties and biosensing behaviour. Here we present the synthesis and characterisation of chiral CdSe semiconductor nanoparticles and their utilisation as new chiral biosensors. Penicillamine stabilised CdSe nanoparticles have shown both very strong and very broad luminescence spectra. Circular dichroism (CD) spectroscopy studies have revealed that the D- and Lpenicillamine stabilised CdSe QDs demonstrate circular dichroism and possess almost identical mirror images of CD signals. Studies of photoluminescence and CD spectra have shown that there is a clear relationship between defect emission and CD activity. We have also demonstrated that these new QDs can serve as fluorescent nanosensors for various chiral biomolecules including nucleic acids. These novel nanosensors can be potentially utilized for detection of various chiral biological and chemical species with the broad range of potential applications.

  8. Inversion of contrast polarity abolishes spontaneous preferences for face-like stimuli in newborn chicks.

    PubMed

    Rosa Salva, Orsola; Regolin, Lucia; Vallortigara, Giorgio

    2012-03-01

    A spontaneous preference for face-like stimuli has been demonstrated in domestic chicks, similar to that shown by human newborns, suggesting evolutionary continuity across species. Inversion of contrast polarity of face-like stimuli abolishes face preferences in human newborns. Here we investigated the effects of contrast polarity inversion and brain lateralization in chicks' preferences for faces. In Experiment 1 face-naïve chicks were tested with a negative face obtained from a stimulus that elicited preferential approach in previous research. As in human newborns, reversal of contrast polarity abolished face-preferences. Experiments 2, 3 and 5 investigated the effect of adding a pupil-like dot within the inner features of the negative and of positive stimuli (a manipulation that re-established face-preference in human newborns). Chicks reacted to this by avoiding the face stimulus. In Experiments 4 and 6 we found that the preference expressed by chicks having only their left eye (right hemisphere) in use changed according to contrast polarity, whereas it remained unaffected in chicks having their right eye in use. Thus, in domestic chicks, as in human beings, a stimulus is perceived as face-like only if it presents the correct luminance pattern expected for a face under natural top-lit illumination and the right hemisphere seems to play a crucial role in this kind of social orienting responses. Copyright © 2011 Elsevier B.V. All rights reserved.

  9. The visual mismatch negativity elicited with visual speech stimuli

    PubMed Central

    Files, Benjamin T.; Auer, Edward T.; Bernstein, Lynne E.

    2013-01-01

    The visual mismatch negativity (vMMN), deriving from the brain's response to stimulus deviance, is thought to be generated by the cortex that represents the stimulus. The vMMN response to visual speech stimuli was used in a study of the lateralization of visual speech processing. Previous research suggested that the right posterior temporal cortex has specialization for processing simple non-speech face gestures, and the left posterior temporal cortex has specialization for processing visual speech gestures. Here, visual speech consonant-vowel (CV) stimuli with controlled perceptual dissimilarities were presented in an electroencephalography (EEG) vMMN paradigm. The vMMNs were obtained using the comparison of event-related potentials (ERPs) for separate CVs in their roles as deviant vs. their roles as standard. Four separate vMMN contrasts were tested, two with the perceptually far deviants (i.e., “zha” or “fa”) and two with the near deviants (i.e., “zha” or “ta”). Only far deviants evoked the vMMN response over the left posterior temporal cortex. All four deviants evoked vMMNs over the right posterior temporal cortex. The results are interpreted as evidence that the left posterior temporal cortex represents speech contrasts that are perceived as different consonants, and the right posterior temporal cortex represents face gestures that may not be perceived as different CVs. PMID:23882205

  10. Startle auditory stimuli enhance the performance of fast dynamic contractions.

    PubMed

    Fernandez-Del-Olmo, Miguel; Río-Rodríguez, Dan; Iglesias-Soler, Eliseo; Acero, Rafael M

    2014-01-01

    Fast reaction times and the ability to develop a high rate of force development (RFD) are crucial for sports performance. However, little is known regarding the relationship between these parameters. The aim of this study was to investigate the effects of auditory stimuli of different intensities on the performance of a concentric bench-press exercise. Concentric bench-presses were performed by thirteen trained subjects in response to three different conditions: a visual stimulus (VS); a visual stimulus accompanied by a non-startle auditory stimulus (AS); and a visual stimulus accompanied by a startle auditory stimulus (SS). Peak RFD, peak velocity, onset movement, movement duration and electromyography from pectoralis and tricep muscles were recorded. The SS condition induced an increase in the RFD and peak velocity and a reduction in the movement onset and duration, in comparison with the VS and AS condition. The onset activation of the pectoralis and tricep muscles was shorter for the SS than for the VS and AS conditions. These findings point out to specific enhancement effects of loud auditory stimulation on the rate of force development. This is of relevance since startle stimuli could be used to explore neural adaptations to resistance training.

  11. Startle Auditory Stimuli Enhance the Performance of Fast Dynamic Contractions

    PubMed Central

    Fernandez-Del-Olmo, Miguel; Río-Rodríguez, Dan; Iglesias-Soler, Eliseo; Acero, Rafael M.

    2014-01-01

    Fast reaction times and the ability to develop a high rate of force development (RFD) are crucial for sports performance. However, little is known regarding the relationship between these parameters. The aim of this study was to investigate the effects of auditory stimuli of different intensities on the performance of a concentric bench-press exercise. Concentric bench-presses were performed by thirteen trained subjects in response to three different conditions: a visual stimulus (VS); a visual stimulus accompanied by a non-startle auditory stimulus (AS); and a visual stimulus accompanied by a startle auditory stimulus (SS). Peak RFD, peak velocity, onset movement, movement duration and electromyography from pectoralis and tricep muscles were recorded. The SS condition induced an increase in the RFD and peak velocity and a reduction in the movement onset and duration, in comparison with the VS and AS condition. The onset activation of the pectoralis and tricep muscles was shorter for the SS than for the VS and AS conditions. These findings point out to specific enhancement effects of loud auditory stimulation on the rate of force development. This is of relevance since startle stimuli could be used to explore neural adaptations to resistance training. PMID:24489967

  12. The temporal primacy of self-related stimuli and negative stimuli: an ERP-based comparative study.

    PubMed

    Zhu, Min; Luo, Junlong; Zhao, Na; Hu, Yinying; Yan, Lingyue; Gao, Xiangping

    2016-10-01

    Numerous studies have shown there exist attention biases for self-related and negative stimuli. Few studies, however, have been carried out to compare the effects of such stimuli on the neural mechanisms of early attentional alertness and subsequent cognitive processing. The purpose of the present study was to examine the temporal primacy of both self-related stimuli and negative stimuli in the neurophysiologic level. In a modified oddball task, event-related potentials of the deviant stimuli (i.e., self-face, negative face and neutral face) were recorded. Results revealed that larger P2 amplitudes were elicited by self-related and negative stimuli than by neutral stimuli. Negative stimuli, however, elicited shorter P2 latencies than self-related and neutral stimuli. As for the N2 component, self-related and negative stimuli elicited smaller amplitudes and shorter latencies than neutral stimuli, but otherwise did not differ. Self-related stimuli also elicited larger P3 and late positive component (LPC) amplitudes than negative and neutral stimuli. The pattern of results suggests that the primacy of negative stimuli occurred at an early attention stage of processing, while the primacy of self-related stimuli occurred at the subsequent cognitive evaluation and memory stage.

  13. Judgment and memory performance for emotional stimuli in patients with alcoholic Korsakoff syndrome.

    PubMed

    Labudda, Kirsten; Todorovski, Saso; Markowitsch, Hans J; Brand, Matthias

    2008-02-01

    In this study we investigated whether alcoholic Korsakoff patients are impaired in categorizing neutral and emotional stimuli according to their valence and whether memory performance for this material is reduced. In a group of Korsakoff patients and a comparison group two experimental tasks--one containing emotional and neutral pictures and the other containing words-were administered. Results showed that patients had difficulties in affective judgments due to problems in classifying neutral stimuli. Memory for emotional and neutral material was impaired to a similar degree. Thus, the facilitating effect of emotional valence on memory performance is absent in Korsakoff patients.

  14. Engineering nanomedicines using stimuli-responsive biomaterials

    PubMed Central

    Wang, Yapei; Byrne, James D.; Napier, Mary E.; DeSimone, Joseph M.

    2012-01-01

    The ability to engineer particles has the potential to shift the paradigm in the creation of new medicines and diagnostics. Complete control over particle characteristics, such as size, shape, mechanical property, and surface chemistry, can enable rapid translation and facilitate the US Food and Drug Administration (FDA) approval of particle technologies for the treatment of cancer, infectious diseases, diabetes, and a host of other major illnesses. The incorporation of natural and artificial external stimuli to trigger the release of drugs enables exquisite control over the release profiles of drugs in a given environment. In this article, we examine several readily scalable top-down methods for the fabrication of shape-specific particles that utilize stimuli-responsive biomaterials for controlled drug delivery. Special attention is given to Particle Replication In Nonwetting Templates (PRINT®) technology and the application of novel triggered-release synthetic and natural polymers. PMID:22266128

  15. Photonic water dynamically responsive to external stimuli

    NASA Astrophysics Data System (ADS)

    Sano, Koki; Kim, Youn Soo; Ishida, Yasuhiro; Ebina, Yasuo; Sasaki, Takayoshi; Hikima, Takaaki; Aida, Takuzo

    2016-08-01

    Fluids that contain ordered nanostructures with periodic distances in the visible-wavelength range, anomalously exhibit structural colours that can be rapidly modulated by external stimuli. Indeed, some fish can dynamically change colour by modulating the periodic distance of crystalline guanine sheets cofacially oriented in their fluid cytoplasm. Here we report that a dilute aqueous colloidal dispersion of negatively charged titanate nanosheets exhibits structural colours. In this `photonic water', the nanosheets spontaneously adopt a cofacial geometry with an ultralong periodic distance of up to 675 nm due to a strong electrostatic repulsion. Consequently, the photonic water can even reflect near-infrared light up to 1,750 nm. The structural colour becomes more vivid in a magnetic flux that induces monodomain structural ordering of the colloidal dispersion. The reflective colour of the photonic water can be modulated over the entire visible region in response to appropriate physical or chemical stimuli.

  16. Contingent stimuli signal subsequent reinforcer ratios.

    PubMed

    Boutros, Nathalie; Davison, Michael; Elliffe, Douglas

    2011-07-01

    Conditioned reinforcer effects may be due to the stimulus' discriminative rather than its strengthening properties. While this was demonstrated in a frequently-changing choice procedure, a single attempt to replicate in a relatively static choice environment failed. We contend that this was because the information provided by the stimuli was nonredundant in the frequently-changing preparation, and redundant in the steady-state arrangement. In the present experiments, 6 pigeons worked in a steady-state concurrent schedule procedure with nonredundant informative stimuli (red keylight illuminations). When a response-contingent red keylight signaled that the next food delivery was more likely on one of the two alternatives, postkeylight choice responding was reliably for that alternative. This effect was enhanced after a history of extended informative red keylight presentation (Experiment 2). These results lend support to recent characterizations of conditioned reinforcer effects as reflective of a discriminative, rather than a reinforcing, property of the stimulus.

  17. Blind Braille readers mislocate tactile stimuli.

    PubMed

    Sterr, Annette; Green, Lisa; Elbert, Thomas

    2003-05-01

    In a previous experiment, we observed that blind Braille readers produce errors when asked to identify on which finger of one hand a light tactile stimulus had occurred. With the present study, we aimed to specify the characteristics of this perceptual error in blind and sighted participants. The experiment confirmed that blind Braille readers mislocalised tactile stimuli more often than sighted controls, and that the localisation errors occurred significantly more often at the right reading hand than at the non-reading hand. Most importantly, we discovered that the reading fingers showed the smallest error frequency, but the highest rate of stimulus attribution. The dissociation of perceiving and locating tactile stimuli in the blind suggests altered tactile information processing. Neuroplasticity, changes in tactile attention mechanisms as well as the idea that blind persons may employ different strategies for tactile exploration and object localisation are discussed as possible explanations for the results obtained.

  18. Unconscious processing of invisible visual stimuli

    PubMed Central

    Song, Chen; Yao, Haishan

    2016-01-01

    Unconscious processing of subliminal visual information, as illustrated by the above-chance accuracy in discriminating invisible visual stimuli, is evident in both blindsight patients and healthy human observers. However, the dependence of such unconscious processing on stimulus properties remains unclear. Here we studied the impact of stimulus luminance and stimulus complexity on the extent of unconscious processing. A testing stimulus presented to one eye was rendered invisible by a masking stimulus presented to the other eye, and healthy human participants made a forced-choice discrimination of the stimulus identity followed by a report of the perceptual awareness. Without awareness of the stimulus existence, participants could nevertheless reach above-chance accuracy in discriminating the stimulus identity. Importantly, the discrimination accuracy for invisible stimuli increased with the stimulus luminance and decreased with the stimulus complexity. These findings suggested that the input signal strength and the input signal complexity can affect the extent of unconscious processing without altering the subjective awareness. PMID:27941851

  19. Discrimination of auditory stimuli during isoflurane anesthesia.

    PubMed

    Rojas, Manuel J; Navas, Jinna A; Greene, Stephen A; Rector, David M

    2008-10-01

    Deep isoflurane anesthesia initiates a burst suppression pattern in which high-amplitude bursts are preceded by periods of nearly silent electroencephalogram. The burst suppression ratio (BSR) is the percentage of suppression (silent electroencephalogram) during the burst suppression pattern and is one parameter used to assess anesthesia depth. We investigated cortical burst activity in rats in response to different auditory stimuli presented during the burst suppression state. We noted a rapid appearance of bursts and a significant decrease in the BSR during stimulation. The BSR changes were distinctive for the different stimuli applied, and the BSR decreased significantly more when stimulated with a voice familiar to the rat as compared with an unfamiliar voice. These results show that the cortex can show differential sensory responses during deep isoflurane anesthesia.

  20. Preparation of stimuli for timbre perception studies.

    PubMed

    Labuschagne, Ilse B; Hanekom, Johan J

    2013-09-01

    Stimuli used in timbre perception studies must be controlled carefully in order to yield meaningful results. During psychoacoustic testing of individual timbre properties, (1) it must be ensured that timbre properties do not co-vary, as timbre properties are often not independent from one another, and (2) the potential influence of loudness, pitch, and perceived duration must be eliminated. A mathematical additive synthesis method is proposed which allows complete control over two spectral parameters, the spectral centroid (corresponding to brightness) and irregularity, and two temporal parameters, log rise-time (LRT) and a parameter characterizing the sustain/decay segment, while controlling for covariation in the spectral centroid and irregularity. Thirteen musical instrument sounds were synthesized. Perceptual data from six listeners indicate that variation in the four timbre properties mainly influences loudness and that perceived duration and pitch are not influenced significantly for the stimuli of longer duration (2 s) used here. Trends across instruments were found to be similar.

  1. Contingent Stimuli Signal Subsequent Reinforcer Ratios

    PubMed Central

    Boutros, Nathalie; Davison, Michael; Elliffe, Douglas

    2011-01-01

    Conditioned reinforcer effects may be due to the stimulus' discriminative rather than its strengthening properties. While this was demonstrated in a frequently-changing choice procedure, a single attempt to replicate in a relatively static choice environment failed. We contend that this was because the information provided by the stimuli was nonredundant in the frequently-changing preparation, and redundant in the steady-state arrangement. In the present experiments, 6 pigeons worked in a steady-state concurrent schedule procedure with nonredundant informative stimuli (red keylight illuminations). When a response-contingent red keylight signaled that the next food delivery was more likely on one of the two alternatives, postkeylight choice responding was reliably for that alternative. This effect was enhanced after a history of extended informative red keylight presentation (Experiment 2). These results lend support to recent characterizations of conditioned reinforcer effects as reflective of a discriminative, rather than a reinforcing, property of the stimulus. PMID:21765545

  2. Discrimination of Auditory Stimuli during Isoflurane Anesthesia

    PubMed Central

    Rojas, Manuel J; Navas, Jinna A; Greene, Stephen A; Rector, David M

    2008-01-01

    Deep isoflurane anesthesia initiates a burst suppression pattern in which high-amplitude bursts are preceded by periods of nearly silent electroencephalogram. The burst suppression ratio (BSR) is the percentage of suppression (silent electroencephalogram) during the burst suppression pattern and is one parameter used to assess anesthesia depth. We investigated cortical burst activity in rats in response to different auditory stimuli presented during the burst suppression state. We noted a rapid appearance of bursts and a significant decrease in the BSR during stimulation. The BSR changes were distinctive for the different stimuli applied, and the BSR decreased significantly more when stimulated with a voice familiar to the rat as compared with an unfamiliar voice. These results show that the cortex can show differential sensory responses during deep isoflurane anesthesia. PMID:19004371

  3. Photonic water dynamically responsive to external stimuli

    PubMed Central

    Sano, Koki; Kim, Youn Soo; Ishida, Yasuhiro; Ebina, Yasuo; Sasaki, Takayoshi; Hikima, Takaaki; Aida, Takuzo

    2016-01-01

    Fluids that contain ordered nanostructures with periodic distances in the visible-wavelength range, anomalously exhibit structural colours that can be rapidly modulated by external stimuli. Indeed, some fish can dynamically change colour by modulating the periodic distance of crystalline guanine sheets cofacially oriented in their fluid cytoplasm. Here we report that a dilute aqueous colloidal dispersion of negatively charged titanate nanosheets exhibits structural colours. In this ‘photonic water', the nanosheets spontaneously adopt a cofacial geometry with an ultralong periodic distance of up to 675 nm due to a strong electrostatic repulsion. Consequently, the photonic water can even reflect near-infrared light up to 1,750 nm. The structural colour becomes more vivid in a magnetic flux that induces monodomain structural ordering of the colloidal dispersion. The reflective colour of the photonic water can be modulated over the entire visible region in response to appropriate physical or chemical stimuli. PMID:27572806

  4. Physiological responses induced by pleasant stimuli.

    PubMed

    Watanuki, Shigeki; Kim, Yeon-Kyu

    2005-01-01

    The specific physiological responses induced by pleasant stimuli were investigated in this study. Various physiological responses of the brain (encephaloelectrogram; EEG), autonomic nervous system (ANS), immune system and endocrine system were monitored when pleasant stimuli such as odors, emotional pictures and rakugo, a typical Japanese comical story-telling, were presented to subjects. The results revealed that (i) EEG activities of the left frontal brain region were enhanced by a pleasant odor; (ii) emotional pictures related to primitive element such as nudes and erotic couples elevated vasomotor sympathetic nervous activity; and (iii) an increase in secretory immunoglobulin A (s-IgA) and a decrease in salivary cortisol (s-cortisol) were induced by rakugo-derived linguistic pleasant emotion. Pleasant emotion is complicated state. However, by considering the evolutionary history of human being, it is possible to assess and evaluate pleasant emotion from certain physiological responses by appropriately summating various physiological parameters.

  5. Blur tolerance for luminance and chromatic stimuli.

    PubMed

    Wuerger, S M; Owens, H; Westland, S

    2001-06-01

    We investigated the blur tolerance of human observers for stimuli modulated along the isoluminant red-green, the isoluminant yellow-blue, and the luminance (black-white) direction in color space. We report the following results: (i) Blur difference thresholds for red-green and luminance stimuli (of equal cone contrast) are very similar and as low as 0.5 min of visual angle; for yellow-blue the lowest blur thresholds are much higher (1.5 min of visual angle). (ii) The smallest blur thresholds are found for slightly blurred square waves (reference blur of 1 arc min) and not for sharp edges. (iii) Blur thresholds for red-green and black-white follow a Weber law for reference (pedestal) blurs greater than the optimum blur. (iv) Using the model proposed by Watt and Morgan [Vision Res. 24, 1387 (1984)] we estimated the internal blur of the visual system for the black-white and the red-green color directions and arrived at the following estimates: 1.2 arc min for black-white stimuli at 10% contrast and 0.9 arc min for red-green stimuli at 10% cone contrast. Blur tolerance for yellow-blue is independent of external blur and cannot be predicted by the model. (v) The contrast dependence of blur sensitivity is similar for red-green and luminance modulations (slopes of -0.15 and -0.16 in log-log coordinates, respectively) and slightly stronger for yellow-blue (slope = -0.75). Blur discrimination thresholds are not predicted by the contrast sensitivity function of the visual system. Our findings are useful for predicting blur tolerance for complex images and provide a spatial frequency cutoff point when Gaussian low-pass filters are used for noise removal in colored images. They are also useful as a baseline for the study of visual disorders such as amblyopia.

  6. Cortical Gating of Oropharyngeal Sensory Stimuli

    PubMed Central

    Wheeler-Hegland, Karen; Pitts, Teresa; Davenport, Paul W.

    2010-01-01

    Somatosensory evoked potentials provide a measure of cortical neuronal activation in response to various types of sensory stimuli. In order to prevent flooding of the cortex with redundant information various sensory stimuli are gated cortically such that response to stimulus 2 (S2) is significantly reduced in amplitude compared to stimulus 1 (S1). Upper airway protective mechanisms, such as swallowing and cough, are dependent on sensory input for triggering and modifying their motor output. Thus, it was hypothesized that central neural gating would be absent for paired-air puff stimuli applied to the oropharynx. Twenty-three healthy adults (18–35 years) served as research participants. Pharyngeal sensory evoked potentials (PSEPs) were measured via 32-electrode cap (10–20 system) connected to SynAmps2 Neuroscan EEG System. Paired-pulse air puffs were delivered with an inter-stimulus interval of 500 ms to the oropharynx using a thin polyethylene tube connected to a flexible laryngoscope. Data were analyzed using descriptive statistics and a repeated measures analysis of variance. There were no significant differences found for the amplitudes S1 and S2 for any of the four component PSEP peaks. Mean gating ratios were above 0.90 for each peak. Results supports our hypothesis that sensory central neural gating would be absent for component PSEP peaks with paired-pulse stimuli delivered to the oropharynx. This may be related to the need for constant sensory monitoring necessary for adequate airway protection associated with swallowing and coughing. PMID:21423402

  7. Psychophysics of Complex Auditory and Speech Stimuli

    DTIC Science & Technology

    1993-10-31

    harpsichord , violin, flute, and trumpet. These instruments were chosen on the basis of the characteristic physical properties of the stimuli they typically...from the piano, harpsichord , and brass instruments are all characterized as having a quick attack and rapid decay, whereas woodwinds and strings have...discriminable from one another. The harpsichord and piano served the role as possibly confusable instruments because of their similar timbres that may

  8. Illusory movement of dotted lines

    PubMed Central

    Ito, Hiroyuki; Anstis, Stuart; Cavanagh, Patrick

    2013-01-01

    When oblique rows of black and white dots drifted horizontally across a mid-grey surround, the perceived direction of motion was shifted to be almost parallel to the dotted lines and was often nearly orthogonal to the real motion. The reason is that the black/white contrast signals between adjacent dots along the length of the line are stronger than black/grey or white/grey contrast signals across the line, and the motion is computed as a vector sum of local contrast-weighted motion signals. PMID:19911636

  9. Low Threshold Quantum Dot Lasers.

    PubMed

    Iyer, Veena Hariharan; Mahadevu, Rekha; Pandey, Anshu

    2016-04-07

    Semiconductor quantum dots have replaced conventional inorganic phosphors in numerous applications. Despite their overall successes as emitters, their impact as laser materials has been severely limited. Eliciting stimulated emission from quantum dots requires excitation by intense short pulses of light typically generated using other lasers. In this Letter, we develop a new class of quantum dots that exhibit gain under conditions of extremely low levels of continuous wave illumination. We observe thresholds as low as 74 mW/cm(2) in lasers made from these materials. Due to their strong optical absorption as well as low lasing threshold, these materials could possibly convert light from diffuse, polychromatic sources into a laser beam.

  10. DOT`s perspective on in-line inspection

    SciTech Connect

    Ulrich, L.W.

    1996-12-01

    The US Department of Transportation (DOT) and its Office of Pipeline Safety (OPS) have been involved with in-line inspection (ILI) pigs since the construction of the Alaska crude oil pipeline. Congressionally mandated reports concerning ILI pigs, and a regulation requiring new and replaced pipe and components be designed and constructed to accommodate ILI pigs, were issued by DOT. DOT also may mandate ILI pigs to be run on some pipelines. There is no current federal requirement to run ILI pigs. They are required by OPS in selected compliance cases. DOT supports future ILI pig research. The use of ILI pig surveys, incorporated in pipeline operators` future risk management plans developed as safety alternatives to the established pipeline safety regulations, will be supported.

  11. Receptors and transduction of umami taste stimuli.

    PubMed

    Kinnamon, Sue C; Vandenbeuch, Aurelie

    2009-07-01

    L-glutamate and 5'-ribonucleotides, such as GMP and IMP, elicit the "umami" taste, also known as the fifth taste. This review will highlight recent advancements in our understanding of umami taste receptors and their downstream signaling effectors in taste receptor cells. Several G protein-coupled receptors that bind umami stimuli have been identified in taste buds, including the heterodimer T1R1/T1R3, truncated and brain forms of mGluR4 and mGluR1, brain mGluR2, and brain mGluR3. Further, ionotropic glutamate receptors are expressed in taste cells and may play a role in glutamate transduction or signaling between taste cells and/or nerve fibers. Knockout of T1R1 or T1R3 reduces, but does not eliminate, responses to umami stimuli, suggesting that multiple receptors contribute to umami taste. The signaling effectors downstream of umami G protein-coupled receptors involve Gbetagamma activation of PLCbeta2 to elicit Ca(2+) release from intracellular stores and activation of a cation channel, TRPM5. In fungiform and palatal taste buds, T1R1/T1R3 is co-expressed with Galpha gustducin and transducin, but the Galpha proteins involved in circumvallate taste buds have not been identified. In most taste fields, however, cAMP antagonizes responses to umami stimuli, suggesting that the Galpha subunit serves to modulate umami taste sensitivity.

  12. Spatial Brightness Perception of Trichromatic Stimuli

    SciTech Connect

    Royer, Michael P.; Houser, Kevin W.

    2012-11-16

    An experiment was conducted to examine the effect of tuning optical radiation on brightness perception for younger (18-25 years of age) and older (50 years of age or older) observers. Participants made forced-choice evaluations of the brightness of a full factorial of stimulus pairs selected from two groups of four metameric stimuli. The large-field stimuli were created by systematically varying either the red or the blue primary of an RGB LED mixture. The results indicate that light stimuli of equal illuminance and chromaticity do not appear equally bright to either younger or older subjects. The rank-order of brightness is not predicted by any current model of human vision or theory of brightness perception including Scotopic to Photopic or Cirtopic to Photopic ratio theory, prime color theory, correlated color temperature, V(λ)-based photometry, color quality metrics, linear brightness models, or color appearance models. Age may affect brightness perception when short-wavelength primaries are used, especially those with a peak wavelength shorter than 450 nm. The results suggest further development of metrics to predict brightness perception is warranted, and that including age as a variable in predictive models may be valuable.

  13. Spatiotemporal processing of somatosensory stimuli in schizotypy

    PubMed Central

    Ferri, Francesca; Ambrosini, Ettore; Costantini, Marcello

    2016-01-01

    Unusual interaction behaviors and perceptual aberrations, like those occurring in schizotypy and schizophrenia, may in part originate from impaired remapping of environmental stimuli in the body space. Such remapping is contributed by the integration of tactile and proprioceptive information about current body posture with other exteroceptive spatial information. Surprisingly, no study has investigated whether alterations in such remapping occur in psychosis-prone individuals. Four hundred eleven students were screened with respect to schizotypal traits using the Schizotypal Personality Questionnaire. A subgroup of them, classified as low, moderate, and high schizotypes were to perform a temporal order judgment task of tactile stimuli delivered on their hands, with both uncrossed and crossed arms. Results revealed marked differences in touch remapping in the high schizotypes as compared to low and moderate schizotypes. For the first time here we reveal that the remapping of environmental stimuli in the body space, an essential function to demarcate the boundaries between self and external world, is altered in schizotypy. Results are discussed in relation to recent models of ‘self-disorders’ as due to perceptual incoherence. PMID:27934937

  14. Visual stimuli recruit intrinsically generated cortical ensembles

    PubMed Central

    Miller, Jae-eun Kang; Ayzenshtat, Inbal; Carrillo-Reid, Luis; Yuste, Rafael

    2014-01-01

    The cortical microcircuit is built with recurrent excitatory connections, and it has long been suggested that the purpose of this design is to enable intrinsically driven reverberating activity. To understand the dynamics of neocortical intrinsic activity better, we performed two-photon calcium imaging of populations of neurons from the primary visual cortex of awake mice during visual stimulation and spontaneous activity. In both conditions, cortical activity is dominated by coactive groups of neurons, forming ensembles whose activation cannot be explained by the independent firing properties of their contributing neurons, considered in isolation. Moreover, individual neurons flexibly join multiple ensembles, vastly expanding the encoding potential of the circuit. Intriguingly, the same coactive ensembles can repeat spontaneously and in response to visual stimuli, indicating that stimulus-evoked responses arise from activating these intrinsic building blocks. Although the spatial properties of stimulus-driven and spontaneous ensembles are similar, spontaneous ensembles are active at random intervals, whereas visually evoked ensembles are time-locked to stimuli. We conclude that neuronal ensembles, built by the coactivation of flexible groups of neurons, are emergent functional units of cortical activity and propose that visual stimuli recruit intrinsically generated ensembles to represent visual attributes. PMID:25201983

  15. Multiaccommodative stimuli in VR systems: problems & solutions.

    PubMed

    Marran, L; Schor, C

    1997-09-01

    Virtual reality environments can introduce multiple and sometimes conflicting accommodative stimuli. For instance, with the high-powered lenses commonly used in head-mounted displays, small discrepancies in screen lens placement, caused by manufacturer error or user adjustment focus error, can change the focal depths of the image by a couple of diopters. This can introduce a binocular accommodative stimulus or, if the displacement between the two screens is unequal, an unequal (anisometropic) accommodative stimulus for the two eyes. Systems that allow simultaneous viewing of virtual and real images can also introduce a conflict in accommodative stimuli: When real and virtual images are at different focal planes, both cannot be in focus at the same time, though they may appear to be in similar locations in space. In this paper four unique designs are described that minimize the range of accommodative stimuli and maximize the visual system's ability to cope efficiently with the focus conflicts that remain: pinhole optics, monocular lens addition combined with aniso-accommodation, chromatic bifocal, and bifocal lens system. The advantages and disadvantages of each design are described and recommendation for design choice is given after consideration of the end use of the virtual reality system (e.g., low or high end, entertainment, technical, or medical use). The appropriate design modifications should allow greater user comfort and better performance.

  16. Visual stimuli recruit intrinsically generated cortical ensembles.

    PubMed

    Miller, Jae-eun Kang; Ayzenshtat, Inbal; Carrillo-Reid, Luis; Yuste, Rafael

    2014-09-23

    The cortical microcircuit is built with recurrent excitatory connections, and it has long been suggested that the purpose of this design is to enable intrinsically driven reverberating activity. To understand the dynamics of neocortical intrinsic activity better, we performed two-photon calcium imaging of populations of neurons from the primary visual cortex of awake mice during visual stimulation and spontaneous activity. In both conditions, cortical activity is dominated by coactive groups of neurons, forming ensembles whose activation cannot be explained by the independent firing properties of their contributing neurons, considered in isolation. Moreover, individual neurons flexibly join multiple ensembles, vastly expanding the encoding potential of the circuit. Intriguingly, the same coactive ensembles can repeat spontaneously and in response to visual stimuli, indicating that stimulus-evoked responses arise from activating these intrinsic building blocks. Although the spatial properties of stimulus-driven and spontaneous ensembles are similar, spontaneous ensembles are active at random intervals, whereas visually evoked ensembles are time-locked to stimuli. We conclude that neuronal ensembles, built by the coactivation of flexible groups of neurons, are emergent functional units of cortical activity and propose that visual stimuli recruit intrinsically generated ensembles to represent visual attributes.

  17. Observing of chain-schedule stimuli.

    PubMed

    Slezak, Jonathan M; Anderson, Karen G

    2014-06-01

    A classical-conditioning account of the processes maintaining behavior under chained schedules entails a backward transmission of conditioned-reinforcement effects. Assessing this process in traditional chain schedules is limited because the response maintained by stimulus onset accompanied by each link in a chain schedule may also be maintained by the primary reinforcer. In the present experiment, an observing response was used to measure the conditioned-reinforcing effects of stimuli associated with a three-link chain variable-time (VT) food schedule, and resistance-to-change tests (extinction and prefeeding) were implemented to examine if a backward transmission of reinforcement effects occur. Four pigeons served as subjects. Observing was maintained by the production of stimuli correlated with links of a three-link chain VT schedule with the middle-link stimulus maintaining the highest rate of observing, followed by the initial-link stimulus and the terminal-link stimulus maintaining the lowest observing rate. Results from resistance-to-change tests of extinction and prefeeding were not supportive of a backward transmission of reinforcement effects and in general, the pattern of resistance-to-change was forward. Based on past and current research, it appears that a backward pattern of relative rate decreases in responses maintained by stimuli correlated with a chain schedule due to disruption (i.e., extinction and prefeeding) is not a ubiquitous process that is evident within different chain-schedule arrangements.

  18. Anagrus breviphragma Soyka Short Distance Search Stimuli

    PubMed Central

    Chiappini, Elisabetta; Berzolla, Alessia; Oppo, Annalisa

    2015-01-01

    Anagrus breviphragma Soyka (Hymenoptera: Mymaridae) successfully parasitises eggs of Cicadella viridis (L.) (Homoptera: Cicadellidae), embedded in vegetal tissues, suggesting the idea of possible chemical and physical cues, revealing the eggs presence. In this research, three treatments were considered in order to establish which types of cue are involved: eggs extracted from leaf, used as a control, eggs extracted from leaf and cleaned in water and ethanol, used to evaluate the presence of chemicals soluble in polar solvents, and eggs extracted from leaf and covered with Parafilm (M), used to avoid physical stimuli due to the bump on the leaf surface. The results show that eggs covered with Parafilm present a higher number of parasitised eggs and a lower probing starting time with respect to eggs washed with polar solvents or eggs extracted and untreated, both when the treatments were singly tested or when offered in sequence, independently of the treatment position. These results suggest that the exploited stimuli are not physical due to the bump but chemicals that can spread in the Parafilm, circulating the signal on the whole surface, and that the stimuli that elicit probing and oviposition are not subjected to learning. PMID:26543865

  19. Reflection sensitivity of 1.3 μm quantum dot lasers epitaxially grown on silicon.

    PubMed

    Liu, Alan Y; Komljenovic, Tin; Davenport, Michael L; Gossard, Arthur C; Bowers, John E

    2017-05-01

    We present measurements of relative intensity noise versus various levels of optical feedback for 1.3 μm quantum dot lasers epitaxially grown on silicon for the first time. A systematic comparison is made with heterogeneously integrated 1.55 μm quantum well lasers on silicon. Our results indicate up to 20 dB reduced sensitivity of the quantum dot lasers on silicon compared to the quantum wells.

  20. Quantum dots: Rethinking the electronics

    SciTech Connect

    Bishnoi, Dimple

    2016-05-06

    In this paper, we demonstrate theoretically that the Quantum dots are quite interesting for the electronics industry. Semiconductor quantum dots (QDs) are nanometer-scale crystals, which have unique photo physical, quantum electrical properties, size-dependent optical properties, There small size means that electrons do not have to travel as far as with larger particles, thus electronic devices can operate faster. Cheaper than modern commercial solar cells while making use of a wider variety of photon energies, including “waste heat” from the sun’s energy. Quantum dots can be used in tandem cells, which are multi junction photovoltaic cells or in the intermediate band setup. PbSe (lead selenide) is commonly used in quantum dot solar cells.

  1. Quantum Dot Spins and Photons

    NASA Astrophysics Data System (ADS)

    Atature, Mete

    2012-02-01

    Self-assembled semiconductor quantum dots are interesting and rich physical systems. Their inherently mesoscopic nature leads to a multitude of interesting interaction mechanisms of confined spins with the solid state environment of spins, charges and phonons. In parallel, the relatively clean spin-dependent optical transitions make quantum dots strong candidates for stationary and flying qubits within the context of spin-based quantum information science. The recently observed quantum dot resonance fluorescence has become a key enabler for further progress in this context. I will first discuss the real-time optical detection (or single-shot readout) of quantum dot spins, and then I will discuss how resonance fluorescence allows coherent generation of single photons suitable (and tailored) for linear-optics quantum computation and for establishing a high-efficiency spin-photon quantum interface within a distributed quantum network.

  2. Quantum dots: Rethinking the electronics

    NASA Astrophysics Data System (ADS)

    Bishnoi, Dimple

    2016-05-01

    In this paper, we demonstrate theoretically that the Quantum dots are quite interesting for the electronics industry. Semiconductor quantum dots (QDs) are nanometer-scale crystals, which have unique photo physical, quantum electrical properties, size-dependent optical properties, There small size means that electrons do not have to travel as far as with larger particles, thus electronic devices can operate faster. Cheaper than modern commercial solar cells while making use of a wider variety of photon energies, including "waste heat" from the sun's energy. Quantum dots can be used in tandem cells, which are multi junction photovoltaic cells or in the intermediate band setup. PbSe (lead selenide) is commonly used in quantum dot solar cells.

  3. Quantum-Dot Cellular Automata

    NASA Astrophysics Data System (ADS)

    Snider, Gregory

    2000-03-01

    Quantum-dot Cellular Automata (QCA) [1] is a promising architecture which employs quantum dots for digital computation. It is a revolutionary approach that holds the promise of high device density and low power dissipation. A basic QCA cell consists of four quantum dots coupled capacitively and by tunnel barriers. The cell is biased to contain two excess electrons within the four dots, which are forced to opposite "corners" of the four-dot cell by mutual Coulomb repulsion. These two possible polarization states of the cell will represent logic "0" and "1". Properly arranged, arrays of these basic cells can implement Boolean logic functions. Experimental results from functional QCA devices built of nanoscale metal dots defined by tunnel barriers will be presented. The experimental devices to be presented consist of Al islands, which we will call quantum dots, interconnected by tunnel junctions and lithographically defined capacitors. Aluminum/ aluminum-oxide/aluminum tunnel junctions were fabricated using a standard e-beam lithography and shadow evaporation technique. The experiments were performed in a dilution refrigerator at a temperature of 70 mK. The operation of a cell is evaluated by direct measurements of the charge state of dots within a cell as the input voltage is changed. The experimental demonstration of a functioning cell will be presented. A line of three cells demonstrates that there are no metastable switching states in a line of cells. A QCA majority gate will also be presented, which is a programmable AND/OR gate and represents the basic building block of QCA systems. The results of recent experiments will be presented. 1. C.S. Lent, P.D. Tougaw, W. Porod, and G.H. Bernstein, Nanotechnology, 4, 49 (1993).

  4. Hydrophobin-Encapsulated Quantum Dots.

    PubMed

    Taniguchi, Shohei; Sandiford, Lydia; Cooper, Maggie; Rosca, Elena V; Ahmad Khanbeigi, Raha; Fairclough, Simon M; Thanou, Maya; Dailey, Lea Ann; Wohlleben, Wendel; von Vacano, Bernhard; de Rosales, Rafael T M; Dobson, Peter J; Owen, Dylan M; Green, Mark

    2016-02-01

    The phase transfer of quantum dots to water is an important aspect of preparing nanomaterials that are suitable for biological applications, and although numerous reports describe ligand exchange, very few describe efficient ligand encapsulation techniques. In this report, we not only report a new method of phase transferring quantum dots (QDs) using an amphiphilic protein (hydrophobin) but also describe the advantages of using a biological molecule with available functional groups and their use in imaging cancer cells in vivo and other imaging applications.

  5. Elevated Fear Conditioning to Socially Relevant Unconditioned Stimuli in Social Anxiety Disorder

    PubMed Central

    Lissek, Shmuel; Levenson, Jessica; Biggs, Arter L.; Johnson, Linda L.; Ameli, Rezvan; Pine, Daniel S.; Grillon, Christian

    2008-01-01

    Objective Though conditioned fear has long been acknowledged as an important etiologic mechanism in social anxiety disorder, past psychophysiological experiments have found no differences in general conditionability among social anxiety patients using generally aversive but socially nonspecific unconditioned stimuli (e.g., unpleasant odors and painful pressure). The authors applied a novel fear conditioning paradigm consisting of socially relevant unconditioned stimuli of critical facial expressions and verbal feedback. This study represents the first effort to assess the conditioning correlates of social anxiety disorder within an ecologically enhanced paradigm. Method Subjects with social anxiety disorder and age- and gender-matched healthy comparison subjects underwent differential classical conditioning. Conditioned stimuli included images of three neutral facial expressions, each of which was paired with one of three audiovisual unconditioned stimuli: negative insults with critical faces (USneg), positive compliments with happy faces (USpos), or neutral comments with neutral faces (USneu). The conditioned response was measured as the fear-potentiation of the startle-blink reflex elicited during presentation of the conditioned stimuli. Results Only social anxiety subjects demonstrated fear conditioning in response to facial expressions, as the startle-blink reflex was potentiated by the CSneg versus both CSneu and CSpos among those with the disorder, while healthy comparison subjects displayed no evidence of conditioned startle-potentiation. Such group differences in conditioning were independent of levels of anxiety to the unconditioned stimulus, implicating associative processes rather than increased unconditioned stimulus reactivity as the active mechanism underlying enhanced conditioned startle-potentiation among social anxiety subjects. Conclusions Results support a conditioning contribution to social anxiety disorder and underscore the importance of

  6. EEG Oscillation Evidences of Enhanced Susceptibility to Emotional Stimuli during Adolescence

    PubMed Central

    Meng, Xianxin; Liu, Wenwen; Zhang, Ling; Li, Xiang; Yao, Bo; Ding, Xinsheng; Yuan, JiaJin; Yang, Jiemin

    2016-01-01

    Background: Our recent event-related potential (ERP) study showed that adolescents are more emotionally sensitive to negative events compared to adults, regardless of the valence strength of the events. The current work aimed to confirm this age-related difference in response to emotional stimuli of diverse intensities by examining Electroencephalography (EEG) oscillatory power in time-frequency analysis. Methods: Time-frequency analyses were performed on the EEG data recorded for highly negative (HN), moderately negative (MN) and Neutral pictures in 20 adolescents and 20 adults during a covert emotional task. The results showed a significant age by emotion interaction effect in the theta and beta oscillatory power during the 500–600 ms post stimulus. Results: Adolescents showed significantly less pronounced theta synchronization (ERS, 5.5–7.5 Hz) for HN stimuli, and larger beta desynchronization (ERD; 18–20 Hz) for both HN and MN stimuli, in comparison with neutral stimuli. By contrast, adults exhibited no significant emotion effects in theta and beta frequency bands. In addition, the analysis of the alpha spectral power (10.5–12 Hz; 850–950 ms) showed a main effect of emotion, while the emotion by age interaction was not significant. Irrespective of adolescents or adults, HN and MN stimuli elicited enhanced alpha suppression compared to Neutral stimuli, while the alpha power was similar across HN and MN conditions. Conclusions: These results confirmed prior findings that adolescents are more sensitive to emotionally negative stimuli compared to adults, regardless of emotion intensity, possibly due to the developing prefrontal control system during adolescence. PMID:27242568

  7. Under Pressure: Adolescent Substance Users Show Exaggerated Neural Processing of Aversive Interoceptive Stimuli

    PubMed Central

    Berk, Lotte; Stewart, Jennifer L.; May, April C.; Wiers, Reinout W.; Davenport, Paul W.; Paulus, Martin P.; Tapert, Susan F.

    2015-01-01

    Background and Aims Adolescents with substance use disorders (SUD) exhibit hyposensitivity to pleasant internally generated (interoceptive) stimuli and hypersensitivity to external rewarding stimuli. It is unclear whether similar patterns exist for aversive interoceptive stimuli. We compared activation in the insular cortex and other brain regions during the anticipation and experience of aversive stimuli between adolescents with SUD and those without. Design and participants Cross-sectional experimental study with two groups: Adolescents (ages 15–17) with an alcohol or marijuana SUD (n=18) and healthy comparison subjects (CON, n=15). Participants were recruited by distributing flyers at local high schools. Setting Keck Imaging Center, University of California San Diego, USA. Measurements Behavioral and neural responses to a continuous performance task with inspiratory breathing load recorded during an fMRI session. Questionnaires assessed lifetime drug use, anxiety, sensation seeking, impulsivity, affect, and bodily awareness. Visual analogue scales assessed drug craving and breathing load responses. Findings Across subjects, experience of breathing load elicited greater bilateral anterior and posterior insula (AI and PI, respectively) activation than anticipation (F(1,31)=4.16, p<.05). SUD exhibited greater left AI and bilateral PI activation during breathing load than anticipation, compared with CON (F(1,31)=4.16, p<.05). In contrast, CON showed greater activation during anticipation than breathing load in left PI, compared with SUD (F(1,31)=4.16, p<.05). Conclusions Adolescents with alcohol and marijuana substance use disorders may be hypersensitive to aversive interoceptive stimuli. PMID:26234745

  8. Better than the real thing: eliciting fear with moving and static computer-generated stimuli.

    PubMed

    Courtney, Christopher G; Dawson, Michael E; Schell, Anne M; Iyer, Arvind; Parsons, Thomas D

    2010-11-01

    As the popularity of virtual reality as an exposure therapy increases, it is important to validate the use of computer-generated stimuli in comparison to standardized images of "real" phobic objects, such as those of the International Affective Picture System (IAPS). The present study examined physiological and subjective measures of negative affect when viewing static IAPS images, static computer-generated images and moving videos of computer-generated images of feared stimuli and other negative stimuli which were not specifically feared. For example, a picture of a spider would be a "feared" stimulus for a spider fearful participant, whereas a picture of a snake would be categorized as a "negative" stimulus for that participant. Eighteen participants scoring high (high fear (HF) cohort) on questionnaires assessing specific fears of spiders or snakes and 20 participants scoring low (low fear (LF) cohort) on the questionnaires viewed the stimuli. The computer-generated videos elicited greater physiological (skin conductance and startle eyeblink potentiation) and self-report arousal responses than the IAPS images and the computer-generated static images. Computer-generated stills and IAPS images did not differ in eliciting emotional responses. Additionally, HF participants showed greater heart rate acceleration and larger skin conductance responses to their feared stimulus than to the negative stimulus, especially when viewing computer-generated moving videos. The results demonstrate the importance of motion in eliciting fear and the usefulness of computer-generated stimuli in the study of emotion. Copyright © 2010 Elsevier B.V. All rights reserved.

  9. Differences in male and female subjective experience and physiological reactions to emotional stimuli.

    PubMed

    Poláčková Šolcová, Iva; Lačev, Alek

    2017-07-01

    Research based on self-reported data often indicates that women are the more emotional sex. The present study examined differences in emotion between the sexes across two components of the emotional process: subjective experience and physiological reactions to emotional stimuli. During the experimental study, participants (N=124; 22.5±2.88; 51 males) subjectively rated their emotional experience (valence and intensity) towards presented positive and negative affective stimuli, while physiological reactions (facial electromyography, heart rate, skin conductance, and finger skin temperature) were measured during expositions. Results from self-reports suggest that women declared more intensive emotional experiences for positive and negative stimuli and rated negative stimuli as more negative in comparison to men. Physiological measurements showed differences between the sexes in the physiological baseline measurements (facial electromyography, skin conductance and finger skin temperature). However, physiological responses towards positive or negative emotional stimuli did not prove to be different between men and women, except for finger skin temperature. Relations between self-reported subjective experiences and physiological changes were weak and insignificant. Collectively, our findings suggest certain emotional differences experienced between men and women. These differences can be found specifically in self-reported subjective experiences, while significant differences were not predominantly present in recorded physiological reactions. Copyright © 2017. Published by Elsevier B.V.

  10. Corneal and conjunctival sensitivity to air stimuli

    PubMed Central

    Stapleton, F; Tan, M E; Papas, E B; Ehrmann, K; Golebiowski, B; Vega, J; Holden, B A

    2004-01-01

    Aims: To determine the repeatability of ocular surface sensitivity to mechanical stimulation using air stimuli and the effect of contact lens (CL) wear on sensitivity. Methods: Repeatability: 14 subjects (24–39 years) participated. Mechanical sensitivity to warmed (34°C) and ambient (20°C) air was measured for the central cornea (CC), inferior cornea (IC), and inferior conjunctiva (ICON). Measurements were taken on 12 days; six morning and six afternoon measurements. Differences between sites, time of day, and stimulus temperature were evaluated. CL wear: 10 subjects (22–30 years) participated. Measurements were taken at the same time of day, either following no wear, wear of a CL of oxygen permeability [Dk] of 28×10−9 [cm/s][ml O2/ml mm Hg] or wear of a CL of Dk 140×10−9 [cm/s][ml O2/ml mm Hg]. Differences between sites and wear conditions were evaluated. Results: Repeatability: Sensitivity varied between sites (p<0.01), time of day (p<0.05), and stimulus temperatures (p<0.01). There were no significant differences between days. Mean thresholds for eye temperature stimuli were; CC 64.4 (SD 28.6) ml/min; IC 84.6 (40.0) ml/min; ICON 120.6 (40.4) ml/min and for ambient temperature stimuli were CC 53.9 (16.0) ml/min, IC 59.0 (20.0) ml/min; ICON 72.6 (43.7) ml/min. CL wear: Sensitivity varied between sites and wear conditions (p<0.05). Conjunctival sensitivity was increased after wear of highly oxygen permeable CLs but unaffected by wear of low oxygen permeable CLs. Conclusions: The prototype gas aesthesiometer is able to repeatably measure ocular surface sensitivity and measurements are consistent with previously reported techniques. PMID:15548810

  11. Olfactory Stimuli Increase Presence in Virtual Environments

    PubMed Central

    Munyan, Benson G.; Neer, Sandra M.; Beidel, Deborah C.; Jentsch, Florian

    2016-01-01

    Background Exposure therapy (EXP) is the most empirically supported treatment for anxiety and trauma-related disorders. EXP consists of repeated exposure to a feared object or situation in the absence of the feared outcome in order to extinguish associated anxiety. Key to the success of EXP is the need to present the feared object/event/situation in as much detail and utilizing as many sensory modalities as possible, in order to augment the sense of presence during exposure sessions. Various technologies used to augment the exposure therapy process by presenting multi-sensory cues (e.g., sights, smells, sounds). Studies have shown that scents can elicit emotionally charged memories, but no prior research has examined the effect of olfactory stimuli upon the patient’s sense of presence during simulated exposure tasks. Methods 60 adult participants navigated a mildly anxiety-producing virtual environment (VE) similar to those used in the treatment of anxiety disorders. Participants had no autobiographical memory associated with the VE. State anxiety, Presence ratings, and electrodermal (EDA) activity were collected throughout the experiment. Results Utilizing a Bonferroni corrected Linear Mixed Model, our results showed statistically significant relationships between olfactory stimuli and presence as assessed by both the Igroup Presence Questionnaire (IPQ: R2 = 0.85, (F(3,52) = 6.625, p = 0.0007) and a single item visual-analogue scale (R2 = 0.85, (F(3,52) = 5.382, p = 0.0027). State anxiety was unaffected by the presence or absence of olfactory cues. EDA was unaffected by experimental condition. Conclusion Olfactory stimuli increase presence in virtual environments that approximate those typical in exposure therapy, but did not increase EDA. Additionally, once administered, the removal of scents resulted in a disproportionate decrease in presence. Implications for incorporating the use of scents to increase the efficacy of exposure therapy is discussed. PMID

  12. Reflex seizures triggered by cutaneous stimuli.

    PubMed

    Sala-Padró, J; Toledo, M; Sarria, S; Santamarina, E; Gonzalez-Cuevas, M; Sueiras-Gil, M; Salas-Puig, J

    2015-12-01

    Among the different precipitating stimuli for reflex seizures, Touch-Induced Seizures (TIS) and Hot Water Seizures (HWS) are consistently described in different reports. The aim of this study was to analyze the clinical, EEG and image data of patients with TIS and HWS. We retrospectively analyzed patients who were followed up in our Epilepsy Unit and had seizures triggered by these stimuli. All patients were studied with electroencephalography (EEG) and magnetic resonance (MR). We recruited six patients, including five men, with an age range of 30-64 years-old. Four patients had TIS; all them had focal motor seizures after the stimuli, with epileptic foci in the fronto-central regions associated with peri-central gyri lesions on MR. One patient had HWS related to a septo-optic dysplasia with periopercular polymicrogyria, and one patient had focal seizures that evolved into bilateral convulsions triggered by washing the mouth with cold water. We considered this last patient to have water contact-induced seizures (WCIS). Seizures in TIS are most likely focal, without impairment of awareness, and refractory to medical treatment. Antiepileptic drugs can prevent the progression to bilateral convulsion. The origins of such seizures seem to be related to small lesions or epileptogenic zones in the perirolandic areas. Lesional HWS and WCIS are focal seizures that involve impairment of consciousness or focal seizures that evolve to bilateral convulsion, are not such location specific and involve larger ictogenic areas. In both epilepsies, stimulus avoidance is the most effective treatment. Copyright © 2015 British Epilepsy Association. Published by Elsevier Ltd. All rights reserved.

  13. Single to quadruple quantum dots with tunable tunnel couplings

    SciTech Connect

    Takakura, T.; Noiri, A.; Obata, T.; Yoneda, J.; Yoshida, K.; Otsuka, T.; Tarucha, S.

    2014-03-17

    We prepare a gate-defined quadruple quantum dot to study the gate-tunability of single to quadruple quantum dots with finite inter-dot tunnel couplings. The measured charging energies of various double dots suggest that the dot size is governed by the gate geometry. For the triple and quadruple dots, we study the gate-tunable inter-dot tunnel couplings. For the triple dot, we find that the effective tunnel coupling between side dots significantly depends on the alignment of the center dot potential. These results imply that the present quadruple dot has a gate performance relevant for implementing spin-based four-qubits with controllable exchange couplings.

  14. Imaging and Manipulating Energy Transfer Among Quantum Dots at Individual Dot Resolution.

    PubMed

    Nguyen, Duc; Nguyen, Huy A; Lyding, Joseph W; Gruebele, Martin

    2017-06-27

    Many processes of interest in quantum dots involve charge or energy transfer from one dot to another. Energy transfer in films of quantum dots as well as between linked quantum dots has been demonstrated by luminescence shift, and the ultrafast time-dependence of energy transfer processes has been resolved. Bandgap variation among dots (energy disorder) and dot separation are known to play an important role in how energy diffuses. Thus, it would be very useful if energy transfer could be visualized directly on a dot-by-dot basis among small clusters or within films of quantum dots. To that effect, we report single molecule optical absorption detected by scanning tunneling microscopy (SMA-STM) to image energy pooling from donor into acceptor dots on a dot-by-dot basis. We show that we can manipulate groups of quantum dots by pruning away the dominant acceptor dot, and switching the energy transfer path to a different acceptor dot. Our experimental data agrees well with a simple Monte Carlo lattice model of energy transfer, similar to models in the literature, in which excitation energy is transferred preferentially from dots with a larger bandgap to dots with a smaller bandgap.

  15. Competition Between Antecedent and Between Subsequent Stimuli in Causal Judgments

    ERIC Educational Resources Information Center

    Arcediano, Francisco; Matute, Helena; Escobar, Martha; Miller, Ralph R.

    2005-01-01

    In the analysis of stimulus competition in causal judgment, 4 variables have been frequently confounded with respect to the conditions necessary for stimuli to compete: causal status of the competing stimuli (causes vs. effects), temporal order of the competing stimuli (antecedent vs. subsequent) relative to the noncompeting stimulus,…

  16. Pupil Dilation to Explicit and Non-Explicit Sexual Stimuli.

    PubMed

    Watts, Tuesday M; Holmes, Luke; Savin-Williams, Ritch C; Rieger, Gerulf

    2017-01-01

    Pupil dilation to explicit sexual stimuli (footage of naked and aroused men or women) can elicit sex and sexual orientation differences in sexual response. If similar patterns were replicated with non-explicit sexual stimuli (footage of dressed men and women), then pupil dilation could be indicative of automatic sexual response in fully noninvasive designs. We examined this in 325 men and women with varied sexual orientations to determine whether dilation patterns to non-explicit sexual stimuli resembled those to explicit sexual stimuli depicting the same sex or other sex. Sexual orientation differences in pupil dilation to non-explicit sexual stimuli mirrored those to explicit sexual stimuli. However, the relationship of dilation to non-explicit sexual stimuli with dilation to corresponding explicit sexual stimuli was modest, and effect magnitudes were smaller with non-explicit sexual stimuli than explicit sexual stimuli. The prediction that sexual orientation differences in pupil dilation are larger in men than in women was confirmed with explicit sexual stimuli but not with non-explicit sexual stimuli.

  17. Developmental Changes in Infant Attention to Dynamic and Static Stimuli

    ERIC Educational Resources Information Center

    Shaddy, D. Jill; Colombo, John

    2004-01-01

    This study examined 4- and 6-month-olds' responses to static or dynamic stimuli using behavioral and heart-rate-defined measures of attention. Infants looked longest to dynamic stimuli with an audio track and least to a static stimulus that was mute. Overall, look duration declined with age to the different stimuli. The amount of time spent in…

  18. Performance analysis of quantum dots infrared photodetector

    NASA Astrophysics Data System (ADS)

    Liu, Hongmei; Zhang, Fangfang; Zhang, Jianqi; He, Guojing

    2011-08-01

    Performance analysis of the quantum dots infrared photodetector(QDIP), which can provide device designers with theoretical guidance and experimental verification, arouses a wide interest and becomes a hot research topic in the recent years. In the paper, in comparison with quantum well infrared photodetector(QWIP) characteristic, the performance of QDIP is mainly discussed and summarized by analyzing the special properties of quantum dots material. To be specific, the dark current density and the detectivity in the normalized incident phenomenon are obtained from Phillip performance model, the carrier lifetime and the dark current of QDIP are studied by combing with the "photon bottleneck" effect, and the detectivity of QDIP is theoretically derived from considering photoconduction gain under the influence of the capture probability. From the experimental results, a conclusion is made that QDIP can not only receive the normal incidence light, but also has the advantages of the long carrier life, the big photoconductive gain, the low dark current and so on, and it further illustrates a anticipated superiority of QDIP in performance and a wide use of QDIP in many engineering fields in the future.

  19. Modulation of human visual evoked potentials in 3-dimensional perception after stimuli produced with an integral imaging method.

    PubMed

    Omoto, Shu; Kuroiwa, Yoshiyuki; Otsuka, Saika; Wang, Chuanwei; Mizuki, Nobuhisa; Nagatani, Hiroyuki; Hirayama, Yuzo

    2012-10-01

    We investigated the neurophysiological correlates of stereoscopic 3-dimensional (3-D) depth perception by studying human visual evoked potentials (VEPs) with an integral imaging method characterized by horizontal but not vertical disparity. The VEPs were recorded in 10 healthy men under 4 conditions. In condition I, stimuli A (flat, 2-dimensional [2-D] image) and B (concave 3-D image) were presented at random. In condition II, stimuli A and C (convex 3-D image) were presented at random. In condition III, stimuli B and C were presented at random. In condition IV, stimuli A, B, and C were presented at random. The data for flat VEPs to stimulus A were combined in conditions I and II. The data for concave VEPs to stimulus B were combined in conditions I and III. The data for convex VEPs to stimulus C were combined in conditions II and III. When 2-way analysis of variance (ANOVA) for 2 factors, stimulus conditions (flat VEPs, concave VEPs, and convex VEPs) and electrode positions, was applied for VEP data, the N1 and N2 peak amplitudes differed significantly among the 3 stimulus conditions. In condition IV, the N1 peak amplitudes differed significantly among the 3 stimuli. Multiple comparisons followed by Bonferroni adjustment did not detect differences in the N1 peak amplitude between stimuli A and B, between stimuli A and C, or between stimuli B and C. We concluded that VEPs to concave or convex 3-D stimuli were significantly different from VEPs to flat 2-D stimuli. This is the first report showing modulation of human VEPs in 3-D perception with an integral imaging method.

  20. Transformation of the discriminative and eliciting functions of generalized relational stimuli.

    PubMed

    Dougher, Michael J; Hamilton, Derek A; Fink, Brandi C; Harrington, Jennifer

    2007-09-01

    In three experiments, match-to-sample procedures were used with undergraduates to establish arbitrary relational functions for three abstract visual stimuli. In the presence of samples A, B, and C, participants were trained to select the smallest, middle, and largest member, respectively, of a series of three-comparison arrays. In Experiment 1, the B (choose middle) stimulus was then used to train a steady rate of keyboard pressing before the A (choose smallest) and the C (choose largest) stimuli were presented. Participants pressed slower to A and faster to C than to B. Then B was paired with mild shock in a Pavlovian procedure with skin conductance change as the dependent variable. When presented with A and C, 6 of 8 experimental participants showed smaller skin conductance changes to A and larger skin conductance changes to C than to B. In Experiment 2, A was then used as a sample in a match-to-sample procedure to establish an arbitrary size ranking among four same-sized colored circle comparisons. One of the middle circles was then used to establish a steady rate of pressing before the other circles were presented. Five of 6 participants responded slower to the "smaller" circle and faster to the "larger" circle than they did to the "middle" circle. In Experiment 3, A, B, and C were then presented on a series of test trials requiring participants to pick the comparison that was less than, greater than, or equal to the sample. Novel stimuli were included on some trials. Results indicated that the relational training procedures produced derived relations among the stimuli used in training and that these allowed correct inferences of relative size ranking among novel stimuli.

  1. Quantum dot loaded immunomicelles for tumor imaging

    PubMed Central

    2010-01-01

    Background Optical imaging is a promising method for the detection of tumors in animals, with speed and minimal invasiveness. We have previously developed a lipid coated quantum dot system that doubles the fluorescence of PEG-grafted quantum dots at half the dose. Here, we describe a tumor-targeted near infrared imaging agent composed of cancer-specific monoclonal anti-nucleosome antibody 2C5, coupled to quantum dot (QD)-containing polymeric micelles, prepared from a polyethylene glycol/phosphatidylethanolamine (PEG-PE) conjugate. Its production is simple and involves no special equipment. Its imaging potential is great since the fluorescence intensity in the tumor is twofold that of non-targeted QD-loaded PEG-PE micelles at one hour after injection. Methods Para-nitrophenol-containing (5%) PEG-PE quantum dot micelles were produced by the thin layer method. Following hydration, 2C5 antibody was attached to the PEG-PE micelles and the QD-micelles were purified using dialysis. 4T1 breast tumors were inoculated subcutaneously in the flank of the animals. A lung pseudometastatic B16F10 melanoma model was developed using tail vein injection. The contrast agents were injected via the tail vein and mice were depilated, anesthetized and imaged on a Kodak Image Station. Images were taken at one, two, and four hours and analyzed using a methodology that produces normalized signal-to-noise data. This allowed for the comparison between different subjects and time points. For the pseudometastatic model, lungs were removed and imaged ex vivo at one and twenty four hours. Results The contrast agent signal intensity at the tumor was double that of the passively targeted QD-micelles with equally fast and sharply contrasted images. With the side views of the animals only tumor is visible, while in the dorsal view internal organs including liver and kidney are visible. Ex vivo results demonstrated that the agent detects melanoma nodes in a lung pseudometastatic model after a 24 hours

  2. Nitrogen and sulfur co-doped carbon dots for highly selective and sensitive detection of Hg (II) ions.

    PubMed

    Li, Libo; Yu, Bin; You, Tianyan

    2015-12-15

    Nitrogen and sulfur co-doped carbon dots (N,S/C-dots) with high fluorescence quantum yields (FLQY, 25%) was successfully synthesized by a one-step microwave-assisted method. In comparison with nitrogen doped C-dots (N/C-dots) prepared using the same method, the resulting N,S/C-dots featured small particle size, uniform surface state, insensitive FL properties to excitation wavelengths and environmental conditions, negligible cytotoxicity and excellent biocompatibility. Simultaneous doping of N and S effectively promoted electron-transfer and coordination interaction between N,S/C-dots and Hg(2+). Thus, when used as fluorescence probe for Hg(2+) label-free detection, the resulting N,S/C-dots showed good detection sensitivity and ion selectivity. The limit of detection was 2 μM; among 15 metal ions investigated, only Fe(3+) showed interference to the Hg(2+) detection. Fortunately, this interference could be effectively shielded using a chelating agent sodium hexametaphoshpate. The applicability of N,S/C-dots as fluorescence probe for Hg(2+) detection in lake water and tap water was demonstrated. Finally, based on its favorable features of negligible cytotoxicity and excellent biocompatibility, the N,S/C-dots were successfully applied to probe Hg(2+) in living cells, which broaden its application in biological system. Copyright © 2015 Elsevier B.V. All rights reserved.

  3. Stimuli-Responsive Nanomaterials for Biomedical Applications

    PubMed Central

    2015-01-01

    Nature employs a variety of tactics to precisely time and execute the processes and mechanics of life, relying on sequential sense and response cascades to transduce signaling events over multiple length and time scales. Many of these tactics, such as the activation of a zymogen, involve the direct manipulation of a material by a stimulus. Similarly, effective therapeutics and diagnostics require the selective and efficient homing of material to specific tissues and biomolecular targets with appropriate temporal resolution. These systems must also avoid undesirable or toxic side effects and evade unwanted removal by endogenous clearing mechanisms. Nanoscale delivery vehicles have been developed to package materials with the hope of delivering them to select locations with rates of accumulation and clearance governed by an interplay between the carrier and its cargo. Many modern approaches to drug delivery have taken inspiration from natural activatable materials like zymogens, membrane proteins, and metabolites, whereby stimuli initiate transformations that are required for cargo release, prodrug activation, or selective transport. This Perspective describes key advances in the field of stimuli-responsive nanomaterials while highlighting some of the many challenges faced and opportunities for development. Major hurdles include the increasing need for powerful new tools and strategies for characterizing the dynamics, morphology, and behavior of advanced delivery systems in situ and the perennial problem of identifying truly specific and useful physical or molecular biomarkers that allow a material to autonomously distinguish diseased from normal tissue. PMID:25474531

  4. Temporal masking of multidimensional tactual stimuli

    NASA Astrophysics Data System (ADS)

    Tan, Hong Z.; Reed, Charlotte M.; Delhorne, Lorraine A.; Durlach, Nathaniel I.; Wan, Natasha

    2003-12-01

    Experiments were performed to examine the temporal masking properties of multidimensional tactual stimulation patterns delivered to the left index finger. The stimuli consisted of fixed-frequency sinusoidal motions in the kinesthetic (2 or 4 Hz), midfrequency (30 Hz), and cutaneous (300 Hz) frequency ranges. Seven stimuli composed of one, two, or three spectral components were constructed at each of two signal durations (125 or 250 ms). Subjects identified target signals under three different masking paradigms: forward masking, backward masking, and sandwiched masking (in which the target is presented between two maskers). Target identification was studied as a function of interstimulus interval (ISI) in the range 0 to 640 ms. For both signal durations, percent-correct scores increased with ISI for each of the three masking paradigms. Scores with forward and backward masking were similar and significantly higher than scores obtained with sandwiched masking. Analyses of error trials revealed that subjects showed a tendency to respond, more often than chance, with the masker, the composite of the masker and target, or the combination of the target and a component of the masker. The current results are compared to those obtained in previous studies of tactual recognition masking with brief cutaneous spatial patterns. The results are also discussed in terms of estimates of information transfer (IT) and IT rate, are compared to previous studies with multidimensional tactual signals, and are related to research on the development of tactual aids for the deaf.

  5. Continuum Models of Stimuli-responsive Gels

    NASA Astrophysics Data System (ADS)

    Hong, Wei

    Immersed in a solution of small molecules and ions, a network of long-chain polymers may imbibe the solution and swell, resulting in a polymeric gel. Depending on the molecular structure of the polymers, the amount of swelling can be regulated by moisture, mechanical forces, ionic strength, electric field, pH value, and many other types of stimuli. Starting from the basic principles of non-equilibrium thermodynamics, this chapter formulates a field theory of the coupled large deformation and mass transportation in a neutral polymeric gel. The theory is then extended to study polyelectrolyte gels with charge-carrying networks by accounting for the electromechanical coupling and migration of solute ions. While the theoretical framework is adaptable to various types of material models, some representative ones are described through specific free-energy functions and kinetic laws. A specific material law for pH-sensitive gels—a special type of polyelectrolyte gels—is introduced as an example of incorporating chemical reactions in modeling stimuli-responsive gels. Finally, a simplified theory for the equilibrium but inhomogeneous swelling of a polymeric gel is deduced. The theory and the specific material models are illustrated through several examples.

  6. Distractor effects upon habituation of complex stimuli.

    PubMed

    Artigas, Antonio A; Sansa, Joan; Prados, Jose

    2012-06-01

    In two experiments, rats were given serial forward (the target followed by the distractor) or backward (the distractor followed by the target) exposure to two compound flavor stimuli that could be either similar (Salt-X/AX) or dissimilar (Salt-X/AY, Experiment 1; Salt/AX, Experiment 2). Following pre-exposure, the Salt element was presented in a compound with a novel flavor, N. The salience or effectiveness of the Salt element was then assessed by presenting the new flavor, N, under a state of salt appetite. Experiments 1 and 2 revealed that the order of presentation modulated the habituation of the Salt element only when the distractor was similar to the target: the Salt element was more salient after forward than backward pre-exposure. In the groups Dissimilar the order of pre-exposure was irrelevant; however, when the Salt element was presented in compound with a second element (Salt-X, Experiment 1), its salience was preserved, whereas when it was presented alone (Salt, Experiment 2) its salience was significantly reduced. These results, which are discussed in terms of Wagner (1981) theory of habituation, inform about the way in which stimuli presented closely in time are processed.

  7. Memory for sequences of stimuli and responses

    PubMed Central

    Wasserman, Edward A.; Nelson, Keith R.; Larew, Mark B.

    1980-01-01

    Two experiments sought to determine if pigeons could discriminate and remember recent sequences of stimuli and responses. A variant of Konorski's short-term memory procedure involving successive presentation of sample and test stimuli was used. The samples were stimulus-response pairs of the form, (S-R)1–(S-R)2. Differential test responding disclosed memory of the two-item samples, with birds showing earlier and greater control by the second item than the first (Experiment 1). When the retention interval separating the second item of the sample sequence from the test stimulus was lenghtened from .5 to 2.0 or 4.0 sec, a systematic loss of stimulus control resulted; however, when varied over the same temporal range, the interval between the two items of the sample sequence had a much smaller effect, or none at all (Experiment 2). These results support an account of response-sequence differentiation that stresses short-term memory of organized behavior patterns. PMID:16812179

  8. Remindings influence the interpretation of ambiguous stimuli.

    PubMed

    Tullis, Jonathan G; Braverman, Michael; Ross, Brian H; Benjamin, Aaron S

    2014-02-01

    Remindings-stimulus-guided retrievals of prior events-may help us interpret ambiguous events by linking the current situation to relevant prior experiences. Evidence suggests that remindings play an important role in interpreting complex ambiguous stimuli (Ross & Bradshaw Memory & Cognition, 22, 591-605, 1994); here, we evaluate whether remindings will influence word interpretation and memory in a new paradigm. Learners studied words on distinct visual backgrounds and generated a sentence for each word. Homographs were preceded by a biasing cue on the same background three items earlier, preceded by a biasing cue on a different background three items earlier, or followed by a biasing cue on the same background three items later. When biasing cues preceded the homographs on the same backgrounds as the homographs, the meanings of the homographs in learner-generated sentences were consistent with the biasing cues more often than in the other two conditions. These results show that remindings can influence word interpretation. In addition, later memory for the homographs and cues was greater when the meaning of the homograph in the sentence was consistent with the earlier biasing cue, suggesting that remindings enhanced mnemonic performance. Remindings play an important role in how we interpret ambiguous stimuli and enhance memory for the involved material.

  9. Testosterone and pupillary response to auditory sexual stimuli.

    PubMed

    Dabbs, J M

    1997-10-01

    Low-, medium-, and high-testosterone subjects listened to four 30-s recorded stimuli while a computer system continuously measured their pupil size. The stimuli dealt with sex, aggression, and two neutral topics. Subjects dilated more to sex than to the other topics. Male and female subjects responded similarly, although low-testosterone males did not dilate as long as other subjects to the sexual stimulus. Auditory stimuli avoid a brightness artifact associated with visual stimuli. Auditory stimuli can be used in a variety of pupillometry studies, including studies of ongoing conversation and social interaction.

  10. Optically active quantum dots

    NASA Astrophysics Data System (ADS)

    Gerard, Valerie; Govan, Joseph; Loudon, Alexander; Baranov, Alexander V.; Fedorov, Anatoly V.; Gun'ko, Yurii K.

    2015-10-01

    The main goal of our research is to develop new types of technologically important optically active quantum dot (QD) based materials, study their properties and explore their biological applications. For the first time chiral II-VI QDs have been prepared by us using microwave induced heating with the racemic (Rac), D- and L-enantiomeric forms of penicillamine as stabilisers. Circular dichroism (CD) studies of these QDs have shown that D- and L-penicillamine stabilised particles produced mirror image CD spectra, while the particles prepared with a Rac mixture showed only a weak signal. It was also demonstrated that these QDs show very broad emission bands between 400 and 700 nm due to defects or trap states on the surfaces of the nanocrystals. These QDs have demonstrated highly specific chiral recognition of various biological species including aminoacids. The utilisation of chiral stabilisers also allowed the preparation of new water soluble white emitting CdS nano-tetrapods, which demonstrated circular dichroism in the band-edge region of the spectrum. Biological testing of chiral CdS nanotetrapods displayed a chiral bias for an uptake of the D- penicillamine stabilised nano-tetrapods by cancer cells. It is expected that this research will open new horizons in the chemistry of chiral nanomaterials and their application in nanobiotechnology, medicine and optical chemo- and bio-sensing.

  11. Separating discriminative and function-altering effects of verbal stimuli.

    PubMed

    Schlinger, H D

    1993-01-01

    Ever since Skinner's first discussion of rule-governed behavior, behavior analysts have continued to define rules, either explicitly or implicitly, as verbal discriminative stimuli. Consequently, it is not difficult to find, in the literature on rule-governed behavior, references to stimulus control, antecedent control, or to rules occasioning behavior. However, some verbal stimuli have effects on behavior that are not easily described as discriminative. Such stimuli don't evoke behavior as discriminative stimuli, but rather alter the functions of other stimuli in a manner analogous to operant and respondent conditioning. Hence, this type of control has been called function altering. Any known stimulus function (e.g., evocative, or [conditioned] reinforcing or punishing functions) can apparently be altered by such function-altering stimuli. Describing these stimuli as discriminative stimuli obscures their possible function-altering effects and consequently may retard inquiry into them. This paper encourages behavior analysts to begin separating the discriminative and function-altering effects of verbal stimuli and suggests that by doing so, behavior analysts may better understand what may be most unique about these stimuli. Results from several experiments, especially those in which children served as subjects, are analyzed. Finally, some speculations are offered concerning the genesis of function-altering stimuli.

  12. Charge distribution in quantum dot with trapped exciton

    NASA Astrophysics Data System (ADS)

    Marín, J. H.; Mikhailov, I. D.; García, L. F.

    2007-08-01

    We calculate the ground state wave function of the exciton confined in the In 0.55Al 0.45As quantum disk, lens and pyramid deposited on a wetting layer (WL) and embedded in a matrix made of Al 0.35Ga 0.65As material. It is shown that tunneling of the electron into the barrier is significantly stronger than one of the holes due to the difference between their masses. In consequence, the central region of the dot with captured exciton is charged positively whereas the regions over, below and around quantum dot including the WL are charged negatively. The comparison of results obtained for quantum dots (QDs) with different geometry shows that the separation of the charges is stronger in spike-shaped quantum dots. We also find that the increase of the WL thickness leads to a lowering of the effective barrier height for both particles enhancing the separation between them in the lateral direction provided by reinforced the particles tunneling toward the WL.

  13. Electron states in semiconductor quantum dots

    SciTech Connect

    Dhayal, Suman S.; Ramaniah, Lavanya M.; Ruda, Harry E.; Nair, Selvakumar V.

    2014-11-28

    In this work, the electronic structures of quantum dots (QDs) of nine direct band gap semiconductor materials belonging to the group II-VI and III-V families are investigated, within the empirical tight-binding framework, in the effective bond orbital model. This methodology is shown to accurately describe these systems, yielding, at the same time, qualitative insights into their electronic properties. Various features of the bulk band structure such as band-gaps, band curvature, and band widths around symmetry points affect the quantum confinement of electrons and holes. These effects are identified and quantified. A comparison with experimental data yields good agreement with the calculations. These theoretical results would help quantify the optical response of QDs of these materials and provide useful input for applications.

  14. Dependencies between stimuli and spatially independent fMRI sources: towards brain correlates of natural stimuli.

    PubMed

    Ylipaavalniemi, Jarkko; Savia, Eerika; Malinen, Sanna; Hari, Riitta; Vigário, Ricardo; Kaski, Samuel

    2009-10-15

    Natural stimuli are increasingly used in functional magnetic resonance imaging (fMRI) studies to imitate real-life situations. Consequently, challenges are created for novel analysis methods, including new machine-learning tools. With natural stimuli it is no longer feasible to assume single features of the experimental design alone to account for the brain activity. Instead, relevant combinations of rich enough stimulus features could explain the more complex activation patterns. We propose a novel two-step approach, where independent component analysis is first used to identify spatially independent brain processes, which we refer to as functional patterns. As the second step, temporal dependencies between stimuli and functional patterns are detected using canonical correlation analysis. Our proposed method looks for combinations of stimulus features and the corresponding combinations of functional patterns. This two-step approach was used to analyze measurements from an fMRI study during multi-modal stimulation. The detected complex activation patterns were explained as resulting from interactions of multiple brain processes. Our approach seems promising for analysis of data from studies with natural stimuli.

  15. The histone methyltransferase Dot1/DOT1L as a critical regulator of the cell cycle

    PubMed Central

    Kim, Wootae; Choi, Minji; Kim, Ja-Eun

    2014-01-01

    Dot1/DOT1L catalyzes the methylation of histone H3 lysine 79 (H3K79), which regulates diverse cellular processes, such as development, reprogramming, differentiation, and proliferation. In regards to these processes, studies of Dot1/DOT1L-dependent H3K79 methylation have mainly focused on the transcriptional regulation of specific genes. Although the gene transcription mediated by Dot1/DOT1L during the cell cycle is not fully understood, H3K79 methylation plays a critical role in the progression of G1 phase, S phase, mitosis, and meiosis. This modification may contribute to the chromatin structure that controls gene expression, replication initiation, DNA damage response, microtubule reorganization, chromosome segregation, and heterochromatin formation. Overall, Dot1/DOT1L is required to maintain genomic and chromosomal stability. This review summarizes the several functions of Dot1/DOT1L and highlights its role in cell cycle regulation. PMID:24526115

  16. Mental transformations of spatial stimuli in humans and in monkeys: rotation vs. translocation.

    PubMed

    Nekovarova, Tereza; Nedvidek, Jan; Klement, Daniel; Rokyta, Richard; Bures, Jan

    2013-03-01

    according to the map presented in the other spatial frame depended on the type of stimulus manipulation. We demonstrated that for monkeys there was a difference between solving "mental rotation" and "mental translocation" in this experimental design. We showed that humans were able both to mentally rotate and translocate the displayed stimuli. However, the mental rotation was more difficult than mental translocation also for them. These experiments help us to understand how the monkeys perceive the abstract spatial information, create the representation of space and how they transform the information about the position obtained from one spatial frame into another. The comparison between humans and monkeys allows us to study this cognitive ability in phylogeny.

  17. Optical Fiber Sensing Using Quantum Dots

    PubMed Central

    Jorge, Pedro; Martins, Manuel António; Trindade, Tito; Santos, José Luís; Farahi, Faramarz

    2007-01-01

    Recent advances in the application of semiconductor nanocrystals, or quantum dots, as biochemical sensors are reviewed. Quantum dots have unique optical properties that make them promising alternatives to traditional dyes in many luminescence based bioanalytical techniques. An overview of the more relevant progresses in the application of quantum dots as biochemical probes is addressed. Special focus will be given to configurations where the sensing dots are incorporated in solid membranes and immobilized in optical fibers or planar waveguide platforms.

  18. Quantum dot behavior in graphene nanoconstrictions.

    PubMed

    Todd, Kathryn; Chou, Hung-Tao; Amasha, Sami; Goldhaber-Gordon, David

    2009-01-01

    Graphene nanoribbons display an imperfectly understood transport gap. We measure transport through nanoribbon devices of several lengths. In long (>/=250 nm) nanoribbons we observe transport through multiple quantum dots in series, while shorter (dots. New measurements indicate that dot size may scale with constriction width. We propose a model where transport occurs through quantum dots that are nucleated by background disorder potential in the presence of a confinement gap.

  19. Exposure to oscillating magnetic fields influences sensitivity to electrical stimuli. 1: Experiments on pigeons

    SciTech Connect

    Del Seppia, C.; Papi, F.; Ghione, S.; Luschi, P.

    1995-12-01

    The comparison of two measurements of the pigeon threshold for electrical stimuli, performed 2 h apart, reveals stress-induced analgesia as a result of stressful manipulations between the two tests. When pigeons are exposed to a weak, oscillating magnetic field between the two measurements, the analgesic response is inhibited and a hyperalgesic effect is recorded. The present findings are in agreement with previous studies showing that magnetic treatments may alter pigeons` emotional state and some of their behavior patterns.

  20. Control of molecular gelation by chemical stimuli.

    PubMed

    Segarra-Maset, Maria Dolores; Nebot, Vicent J; Miravet, Juan F; Escuder, Beatriu

    2013-09-07

    Molecular gels are formed by the self-assembly of low-molecular weight compounds by weak non-covalent interactions and thus, they may be easily disassembled in response to external stimuli. Chemically sensitive gels can be prepared by introducing in the molecular design functional groups that may interact either by covalent or non-covalent forces with other molecules present in the medium. Functional molecular gels have been reported that are sensitive to acids, bases, ions, redox-active compounds, neutral species, reactive compounds and enzymes. Here we present a broad revision of the different chemical inputs that can be used to tune gel properties through some appealing application-based selected examples.

  1. Stimuli-responsive polymers in gene delivery.

    PubMed

    Piskin, Erhan

    2005-07-01

    Recent interest in clinical therapy has been directed to deliver nucleic acids (DNA, RNA or short-chain oligonucleotides) that alter gene expression within a specific cell population, thereby manipulating cellular processes and responses, which in turn stimulate immune responses or tissue regeneration, or blocks expression at the level of transcription or translation for treatment of several diseases. Both ex vivo and in vivo gene delivery can be achieved mostly by using a delivery system (vector). Viral vectors exhibit high gene expression, but also have very significant side effects. Mainly cationic polymeric systems are used as nonviral vectors, although usually with low levels of transfection. Through the use of stimuli-responsive polymers as novel vectors for gene delivery, two benefits can be obtained: high gene expression efficiency and more selective gene expression.

  2. Violent Reactions from Non-Shock Stimuli

    NASA Astrophysics Data System (ADS)

    Sandusky, H. W.; Granholm, R. H.

    2007-12-01

    Most reactions are thermally initiated, whether from direct heating or dissipation of energy from mechanical, shock, or electrical stimuli. For other than prompt shock initiation, the reaction must spread through porosity or over large surface area to become more violent than just rupturing any confinement. While burning rates are important, high-strain mechanical properties are nearly so, either by reducing existing porosity or generating additional surface area through fracture. In studies of deflagration-to-detonation transition (DDT), it has been shown that reaction violence is reduced if the binder is softened, either by raising the initial temperature or adding a solvent. In studies of cavity collapse in explosives, those with soft rubber binders will deform and undergo mild reaction whereas those with stiff binders will fracture and generate additional surface area for a violent event.

  3. Stimuli dependent impedance of conductive magnetorheological elastomers

    NASA Astrophysics Data System (ADS)

    Wang, Yu; Xuan, Shouhu; Dong, Bo; Xu, Feng; Gong, Xinglong

    2016-02-01

    The structure dependent impedance of conductive magnetorheological elastomers (MREs) under different loads and magnetic fields has been studied in this work. By increasing the weight fraction of iron particles, the conductivity of the MREs increased. Dynamic mechanical measurements and synchrotron radiation x-ray computed tomography (SR-CT) were used and they provided reasons for the electrical properties changing significantly under pressure and magnetic field stimulation. The high sensitivity of MREs to external stimuli renders them suitable for application in force or magnetic field sensors. The equivalent circuit model was proposed to analyze the impedance response of MREs and it fits the experimental results very well. Each circuit component reflected the change of the inner interface under different conditions, thus relative changes in the microstructure could be distinguished. This method could be used not only to detect the structural changes in the MRE but also to provide a great deal of valuable information for the further understanding of the MR mechanism.

  4. Culture and sensory response to visual stimuli.

    PubMed

    Park, Inchan; Hong, Yeonkoo

    2016-04-28

    This study investigated the influence of culture on people's sensory responses, such as smell, taste, sound and touch to visual stimuli. The sensory feelings of university students from four countries (Japan, South Korea, Britain and France) to six images were evaluated. The images combined real and abstract objects and were presented on a notebook computer. Overall, 280 participants (144 men and 136 women; n = 70/country) were included in the statistical analysis. The chi-square independence analysis showed differences and similarities in the sensory responses across countries. Most differences were detected in smell and taste, whereas few variations were observed for sound responses. Large variations in the response were observed for the abstract coral and butterfly images, but few differences were detected in response to the real leaf image. These variations in response were mostly found in the British and Japanese participants. © 2016 International Union of Psychological Science.

  5. Stimuli-sensitive intrinsically disordered protein brushes

    NASA Astrophysics Data System (ADS)

    Srinivasan, Nithya; Bhagawati, Maniraj; Ananthanarayanan, Badriprasad; Kumar, Sanjay

    2014-10-01

    Grafting polymers onto surfaces at high density to yield polymer brush coatings is a widely employed strategy to reduce biofouling and interfacial friction. These brushes almost universally feature synthetic polymers, which are often heterogeneous and do not readily allow incorporation of chemical functionalities at precise sites along the constituent chains. To complement these synthetic systems, we introduce a biomimetic, recombinant intrinsically disordered protein that can assemble into an environment-sensitive brush. This macromolecule adopts an extended conformation and can be grafted to solid supports to form oriented protein brushes that swell and collapse dramatically with changes in solution pH and ionic strength. We illustrate the value of sequence specificity by using proteases with mutually orthogonal recognition sites to modulate brush height in situ to predictable values. This study demonstrates that stimuli-responsive brushes can be fabricated from proteins and introduces them as a new class of smart biomaterial building blocks.

  6. Excitonic optical properties of wurtzite ZnS quantum dots under pressure

    SciTech Connect

    Zeng, Zaiping; Garoufalis, Christos S.; Baskoutas, Sotirios; Bester, Gabriel

    2015-03-21

    By means of atomistic empirical pseudopotentials combined with a configuration interaction approach, we have studied the optical properties of wurtzite ZnS quantum dots in the presence of strong quantum confinement effects as a function of pressure. We find the pressure coefficients of quantum dots to be highly size-dependent and reduced by as much as 23% in comparison to the bulk value of 63 meV/GPa obtained from density functional theory calculations. The many-body excitonic effects on the quantum dot pressure coefficients are found to be marginal. The absolute gap deformation potential of quantum dots originates mainly from the energy change of the lowest unoccupied molecular orbital state. Finally, we find that the exciton spin-splitting increases nearly linearly as a function of applied pressure.

  7. Confinement and inhomogeneous broadening effects in the quantum oscillatory magnetization of quantum dot ensembles

    NASA Astrophysics Data System (ADS)

    Herzog, F.; Heedt, S.; Goerke, S.; Ibrahim, A.; Rupprecht, B.; Heyn, Ch; Hardtdegen, H.; Schäpers, Th; Wilde, M. A.; Grundler, D.

    2016-02-01

    We report on the magnetization of ensembles of etched quantum dots with a lateral diameter of 460 nm, which we prepared from InGaAs/InP heterostructures. The quantum dots exhibit 1/B-periodic de-Haas-van-Alphen-type oscillations in the magnetization M(B) for external magnetic fields B  >  2 T, measured by torque magnetometry at 0.3 K. We compare the experimental data to model calculations assuming different confinement potentials and including ensemble broadening effects. The comparison shows that a hard wall potential with an edge depletion width of 100 nm explains the magnetic behavior. Beating patterns induced by Rashba spin-orbit interaction (SOI) as measured in unpatterned and nanopatterned InGaAs/InP heterostructures are not observed for the quantum dots. From our model we predict that signatures of SOI in the magnetization could be observed in larger dots in tilted magnetic fields.

  8. Chiral Graphene Quantum Dots.

    PubMed

    Suzuki, Nozomu; Wang, Yichun; Elvati, Paolo; Qu, Zhi-Bei; Kim, Kyoungwon; Jiang, Shuang; Baumeister, Elizabeth; Lee, Jaewook; Yeom, Bongjun; Bahng, Joong Hwan; Lee, Jaebeom; Violi, Angela; Kotov, Nicholas A

    2016-02-23

    Chiral nanostructures from metals and semiconductors attract wide interest as components for polarization-enabled optoelectronic devices. Similarly to other fields of nanotechnology, graphene-based materials can greatly enrich physical and chemical phenomena associated with optical and electronic properties of chiral nanostructures and facilitate their applications in biology as well as other areas. Here, we report that covalent attachment of l/d-cysteine moieties to the edges of graphene quantum dots (GQDs) leads to their helical buckling due to chiral interactions at the "crowded" edges. Circular dichroism (CD) spectra of the GQDs revealed bands at ca. 210-220 and 250-265 nm that changed their signs for different chirality of the cysteine edge ligands. The high-energy chiroptical peaks at 210-220 nm correspond to the hybridized molecular orbitals involving the chiral center of amino acids and atoms of graphene edges. Diverse experimental and modeling data, including density functional theory calculations of CD spectra with probabilistic distribution of GQD isomers, indicate that the band at 250-265 nm originates from the three-dimensional twisting of the graphene sheet and can be attributed to the chiral excitonic transitions. The positive and negative low-energy CD bands correspond to the left and right helicity of GQDs, respectively. Exposure of liver HepG2 cells to L/D-GQDs reveals their general biocompatibility and a noticeable difference in the toxicity of the stereoisomers. Molecular dynamics simulations demonstrated that d-GQDs have a stronger tendency to accumulate within the cellular membrane than L-GQDs. Emergence of nanoscale chirality in GQDs decorated with biomolecules is expected to be a general stereochemical phenomenon for flexible sheets of nanomaterials.

  9. Dynamic observing tonometry (DOT)

    NASA Astrophysics Data System (ADS)

    Kanngiesser, Hartmut E.; Robert, Yves C.

    1999-06-01

    To help improve early detection of vascular eye diseases, a method, named Dynamic Observing Tonometry (DOT), for measuring the intra-ocular pressure (IOP) has been developed, which allows for simultaneous ophthalmoscopy and dynamic tonometry of the human eye. Material and Method. A system for the application of this method is presented, consisting of a transducer to be placed on the corneal surface and of a stand-alone base unit. The latter can be connected to a personal computer for further data processing and storage. The transducer consists of a Goldmann-type contact lens modified by implementing means for transparent pressure-measurement of IOP. A small flat membrane in the center of the lens applanates the cornea. A liquid transmits the applanation pressure from the opposite side of this membrane to a pressure sensor located outside the optical pathway. Time-dependent IOP's are transmitted telemetrically to the base unit for processing. Results. Current initial tests provide evidence for the viability of the concept and have demonstrated the performance of the system. Typical time dependent IOP measurements obtained with an experimental device are presented. Clinical trials with two prototypes are underway. Conclusion: The proposed device allows the ophthalmology to perform the ordinary slit-lamp fundus examinations combined with simultaneous dynamic tonometry. It offers for the first time easy and precise analysis of cardiac and respiratory- modulated intra-ocular pressure while directly observing the choroid and the papilla, as well as the analysis of heart rate variability and inspection of the iridocorneal angle at varying applied pressure. Moreover, dynamic observing tonometry gives easy access to examination procedures such as tonography and ophthalmodynamometry, which have been rarely performed despite their potential diagnostic value due to the complexity of experimental protocols hitherto used.

  10. Memory for verbal and nonverbal stimuli in learning disability subgroups: analysis by selective reminding.

    PubMed

    Fletcher, J M

    1985-10-01

    Memory for verbal and nonverbal stimuli was evaluated using selective reminding procedures in normal achieving children and four groups of disabled learners: (1) reading-spelling disabled (R-S); (2) reading-spelling-arithmetic disabled (R-S-A); (3) spelling-arithmetic disabled (S-A); and (4) arithmetic disabled (A). Each child received two analogous free-list memory tasks, one for verbal material (animal names) and the other for nonverbal material (random dot patterns). These tasks were administered using selective reminding procedures that permit separation of storage and retrieval aspects of memory by reminding children only of those words not recalled on previous trials. Results revealed that relative to controls, the A and S-A children had significantly lower storage and retrieval scores on the nonverbal task, but did not differ on the verbal task; the R-S children differed only on retrieval scores from the verbal task; and the R-S-A children on retrieval scores on the verbal task and storage and retrieval scores on the nonverbal task. Thus, results indicate that the memory performance of disabled learners varies according to (1) the type of learning problem (arithmetic vs reading), (2) the nature of the stimuli (verbal vs nonverbal), and (3) the aspect of memory being assessed (storage vs retrieval). This study provides external validation for the classification of disabled learners according to patterns of academic achievement, demonstrating a useful procedure for dealing with the intrasubject variability characteristic of disabled learners.

  11. Differences in the responses of heterozygous carriers of colorblindness and normal controls to briefly presented stimuli.

    PubMed

    Cohn, S A; Emmerich, D S; Carlson, E A

    1989-01-01

    Two experiments were conducted in order to investigate the possible effects of X-inactivation (Lyon, 1961) on female carriers of colorblindness. The results of the first experiment, like those of Grützner et al. (1976), were consistent with the prediction of the Lyon (1961) hypothesis that the retinas of female carriers are composed of mosaic patches of colorblind and normal areas. In this first experiment, rows and columns of colored spots were presented tachistoscopically, and subjects were asked to identify the colors of the spots. In the second experiment, plates from the Ishihara test of colorblindness were presented tachistoscopically and subjects were asked to identify the number which was embedded in the pattern of colored dots. Both experiments support the Lyon hypothesis in that female carriers were found to have more difficulty in perceiving patterns of colored stimuli than did control subjects, and they suggest that the amount of time that a carrier has to scan colored stimuli plays an important role in her ability to accurately perceive them.

  12. Caffeine deprivation state modulates coffee consumption but not attentional bias for caffeine-related stimuli.

    PubMed

    Stafford, L D; Yeomans, M R

    2005-11-01

    Previous research has shown that caffeine deprivation state can exert a strong influence on the ability of caffeine to reinforce behaviour. Recent work has also found evidence for an attentional bias in habitual caffeine users. It remains unclear whether deprivation state can influence attentional bias. Here we explored the relationship between caffeine deprivation, attentional bias to caffeine-related stimuli and subsequent caffeine reinforcement measured by consumption of coffee. In three experiments, participants (between-subjects: n=28; within-subjects: n=20, within-subjects: n=20) were preloaded with either caffeine (experiments 1 and 3 : 100 mg; experiment 2 : 150 mg) or placebo, and in experiments 1 and 2 they completed a novel attentional bias task involving pre-attentive word recognition, and in experiment 3 a dot-probe task. In experiments 2 and 3, this was followed by a test of coffee consumption. Greater recognition for caffeine-related words (experiments 1 and 2) and faster reaction times to probes replacing caffeine-related rather than control stimuli (experiment 3) confirmed caffeine-related attentional biases, but in no case was this affected by manipulation of caffeine-deprivation state. Participants in a deprived versus nondeprived state, however, experienced increases in drowsiness and headaches (experiment 2) and reduced alertness (experiment 3). Further, coffee consumption was greatest when participants were caffeine-deprived than when they were nondeprived. Findings are discussed in relation to prevailing theories of drug addiction.

  13. Is trait resilience characterized by specific patterns of attentional bias to emotional stimuli and attentional control?

    PubMed

    Schäfer, Judith; Wittchen, Hans-Ulrich; Höfler, Michael; Heinrich, Anke; Zimmermann, Peter; Siegel, Stefan; Schönfeld, Sabine

    2015-09-01

    Attentional processes have been suggested to play a crucial role in resilience defined as positive adaptation facing adversity. However, research is lacking on associations between attentional biases to positive and threat-related stimuli, attentional control and trait resilience. Data stem from the follow-up assessment of a longitudinal study investigating mental health and related factors among German soldiers. Trait resilience was assessed with the Connor-Davidson Resilience Scale and attentional control with the Attentional Control Scale. A subset of n = 198 soldiers also completed a dot probe task with happy, neutral and threatening faces. Attentional control was positively related to trait resilience. Results revealed no associations between both attentional biases and trait resilience. However, there was a negative association between attentional bias to threat and trait resilience when attentional control was low and a positive association between attentional bias to threat and trait resilience when attentional control was high. No such associations were found for attentional bias to positive stimuli. Generalizability to other populations may be limited since we exclusively focused on male soldiers. Also, the cross-sectional design does not allow for causal conclusions. Findings suggest that attentional processing may promote trait resilience. Future research on preventive interventions should consider these findings. Copyright © 2015 Elsevier Ltd. All rights reserved.

  14. Children's cortisol and salivary alpha-amylase interact to predict attention bias to threatening stimuli.

    PubMed

    Ursache, Alexandra; Blair, Clancy

    2015-01-01

    Physiological responses to threat occur through both the autonomic nervous system (ANS) and the hypothalamic pituitary adrenal (HPA) axis. Activity in these systems can be measured through salivary alpha-amylase (sAA) and salivary cortisol, respectively. Theoretical work and empirical studies have suggested the importance of examining the coordination of these systems in relation to cognitive functioning and behavior problems. Less is known, however, about whether these systems interactively predict more automatic aspects of attention processing such as attention toward emotionally salient threatening stimuli. We used a dot probe task to assess attention bias toward threatening stimuli in 347 kindergarten children. Cortisol and sAA were assayed from saliva samples collected prior to children's participation in assessments on a subsequent day. Using regression analyses, we examined relations of sAA and cortisol to attention bias. Results indicate that cortisol and sAA interact in predicting attention bias. Higher levels of cortisol predicted greater bias toward threat for children who had high levels of sAA, but predicted greater bias away from threat for children who had low levels of sAA. These results suggest that greater symmetry in HPA and ANS functioning is associated with greater reliance on automatic attention processes in the face of threat.

  15. A colloidal quantum dot spectrometer

    NASA Astrophysics Data System (ADS)

    Bao, Jie; Bawendi, Moungi G.

    2015-07-01

    Spectroscopy is carried out in almost every field of science, whenever light interacts with matter. Although sophisticated instruments with impressive performance characteristics are available, much effort continues to be invested in the development of miniaturized, cheap and easy-to-use systems. Current microspectrometer designs mostly use interference filters and interferometric optics that limit their photon efficiency, resolution and spectral range. Here we show that many of these limitations can be overcome by replacing interferometric optics with a two-dimensional absorptive filter array composed of colloidal quantum dots. Instead of measuring different bands of a spectrum individually after introducing temporal or spatial separations with gratings or interference-based narrowband filters, a colloidal quantum dot spectrometer measures a light spectrum based on the wavelength multiplexing principle: multiple spectral bands are encoded and detected simultaneously with one filter and one detector, respectively, with the array format allowing the process to be efficiently repeated many times using different filters with different encoding so that sufficient information is obtained to enable computational reconstruction of the target spectrum. We illustrate the performance of such a quantum dot microspectrometer, made from 195 different types of quantum dots with absorption features that cover a spectral range of 300 nanometres, by measuring shifts in spectral peak positions as small as one nanometre. Given this performance, demonstrable avenues for further improvement, the ease with which quantum dots can be processed and integrated, and their numerous finely tuneable bandgaps that cover a broad spectral range, we expect that quantum dot microspectrometers will be useful in applications where minimizing size, weight, cost and complexity of the spectrometer are critical.

  16. Use of a Remote Eye-Tracker for the Analysis of Gaze during Treadmill Walking and Visual Stimuli Exposition

    PubMed Central

    Serchi, V.; Peruzzi, A.; Cereatti, A.; Della Croce, U.

    2016-01-01

    The knowledge of the visual strategies adopted while walking in cognitively engaging environments is extremely valuable. Analyzing gaze when a treadmill and a virtual reality environment are used as motor rehabilitation tools is therefore critical. Being completely unobtrusive, remote eye-trackers are the most appropriate way to measure the point of gaze. Still, the point of gaze measurements are affected by experimental conditions such as head range of motion and visual stimuli. This study assesses the usability limits and measurement reliability of a remote eye-tracker during treadmill walking while visual stimuli are projected. During treadmill walking, the head remained within the remote eye-tracker workspace. Generally, the quality of the point of gaze measurements declined as the distance from the remote eye-tracker increased and data loss occurred for large gaze angles. The stimulus location (a dot-target) did not influence the point of gaze accuracy, precision, and trackability during both standing and walking. Similar results were obtained when the dot-target was replaced by a static or moving 2D target and “region of interest” analysis was applied. These findings foster the feasibility of the use of a remote eye-tracker for the analysis of gaze during treadmill walking in virtual reality environments. PMID:26904671

  17. Use of a Remote Eye-Tracker for the Analysis of Gaze during Treadmill Walking and Visual Stimuli Exposition.

    PubMed

    Serchi, V; Peruzzi, A; Cereatti, A; Della Croce, U

    2016-01-01

    The knowledge of the visual strategies adopted while walking in cognitively engaging environments is extremely valuable. Analyzing gaze when a treadmill and a virtual reality environment are used as motor rehabilitation tools is therefore critical. Being completely unobtrusive, remote eye-trackers are the most appropriate way to measure the point of gaze. Still, the point of gaze measurements are affected by experimental conditions such as head range of motion and visual stimuli. This study assesses the usability limits and measurement reliability of a remote eye-tracker during treadmill walking while visual stimuli are projected. During treadmill walking, the head remained within the remote eye-tracker workspace. Generally, the quality of the point of gaze measurements declined as the distance from the remote eye-tracker increased and data loss occurred for large gaze angles. The stimulus location (a dot-target) did not influence the point of gaze accuracy, precision, and trackability during both standing and walking. Similar results were obtained when the dot-target was replaced by a static or moving 2D target and "region of interest" analysis was applied. These findings foster the feasibility of the use of a remote eye-tracker for the analysis of gaze during treadmill walking in virtual reality environments.

  18. Collinear Suppression in Texture Segmentation for Temporally Modulated Stimuli

    NASA Astrophysics Data System (ADS)

    Zariņa, L.; Fomins, S.

    2010-03-01

    Collinear stimuli facilitate the neural signal in the case of Gabor's stimuli when a low-contrast stimulus inside the receptive field is flanked by higher contrast collinear elements located in surrounding regions of the visual space. Our previous studies pointed to the contextual modulation in the case of the textured stimuli. Collinear suppression was observed in 63% of the responses. In the current research we used Gabor's primitives for building the circular texture objects of vertical and diagonal orientation to be recognized on the horizontally-oriented background in the presence of collinear and orthogonal peripheral stimuli. The two-alternative forced choice (2AFC) psychophysical method with constant stimuli was used to gather the responses of the subjects which choose between left or right position of diagonally-oriented stimuli. The experimental stimuli consisted of two circularly shaped objects presented in visual angle of 2.76 degrees. The expositions of the stimuli varied from 13.3 to 93.3 ms arbitrarily. Visual stimuli were presented with a CRS Visage stimulus generator and shown on a CRT monitor of 75 Hz refresh rate. Our new findings support the concept of suppressing the target stimuli of the same orientation in the presence of a peripheral collinear stimulation.

  19. Nanoscale quantum-dot supercrystals

    NASA Astrophysics Data System (ADS)

    Baimuratov, Anvar S.; Turkov, Vadim K.; Rukhlenko, Ivan D.; Baranov, Alexander V.; Fedorov, Anatoly V.

    2013-09-01

    We develop a theory allowing one to calculate the energy spectra and wave functions of collective excitations in twoand three-dimensional quantum-dot supercrystals. We derive analytical expressions for the energy spectra of twodimensional supercrystals with different Bravias lattices, and use them to analyze the possibility of engineering the supercrystals' band structure. We demonstrate that the variation of the supercrystal's parameters (such as the symmetry of the periodic lattice and the properties of the quantum dots or their environment) enables an unprecedented control over its optical properties, thus paving a way towards the development of new nanophotonics materials.

  20. Reversible Photoswitching of Carbon Dots

    PubMed Central

    Khan, Syamantak; Verma, Navneet Chandra; Gupta, Abhishek; Nandi, Chayan Kanti

    2015-01-01

    We present a method of reversible photoswitching in carbon nanodots with red emission. A mechanism of electron transfer is proposed. The cationic dark state, formed by the exposure of red light, is revived back to the bright state with the very short exposure of blue light. Additionally, the natural on-off state of carbon dot fluorescence was tuned using an electron acceptor molecule. Our observation can make the carbon dots as an excellent candidate for the super-resolution imaging of nanoscale biomolecules within the cell. PMID:26078266

  1. Integration of motion energy from overlapping random background noise increases perceived speed of coherently moving stimuli.

    PubMed

    Chuang, Jason; Ausloos, Emily C; Schwebach, Courtney A; Huang, Xin

    2016-12-01

    The perception of visual motion can be profoundly influenced by visual context. To gain insight into how the visual system represents motion speed, we investigated how a background stimulus that did not move in a net direction influenced the perceived speed of a center stimulus. Visual stimuli were two overlapping random-dot patterns. The center stimulus moved coherently in a fixed direction, whereas the background stimulus moved randomly. We found that human subjects perceived the speed of the center stimulus to be significantly faster than its veridical speed when the background contained motion noise. Interestingly, the perceived speed was tuned to the noise level of the background. When the speed of the center stimulus was low, the highest perceived speed was reached when the background had a low level of motion noise. As the center speed increased, the peak perceived speed was reached at a progressively higher background noise level. The effect of speed overestimation required the center stimulus to overlap with the background. Increasing the background size within a certain range enhanced the effect, suggesting spatial integration. The speed overestimation was significantly reduced or abolished when the center stimulus and the background stimulus had different colors, or when they were placed at different depths. When the center- and background-stimuli were perceptually separable, speed overestimation was correlated with perceptual similarity between the center- and background-stimuli. These results suggest that integration of motion energy from random motion noise has a significant impact on speed perception. Our findings put new constraints on models regarding the neural basis of speed perception. Copyright © 2016 the American Physiological Society.

  2. Visual dot interaction with short-term memory.

    PubMed

    Etindele Sosso, Faustin Armel

    2017-06-01

    Many neurodegenerative diseases have a memory component. Brain structures related to memory are affected by environmental stimuli, and it is difficult to dissociate effects of all behavior of neurons. Here, visual cortex of mice was stimulated with gratings and dot, and an observation of neuronal activity before and after was made. Bandwidth, firing rate and orientation selectivity index were evaluated. A primary communication between primary visual cortex and short-term memory appeared to show an interesting path to train cognitive circuitry and investigate the basics mechanisms of the neuronal learning. The findings also suggested the interplay between primary visual cortex and short-term plasticity. The properties inside a visual target shape the perception and affect the basic encoding. Using visual cortex, it may be possible to train the memory and improve the recovery of people with cognitive disabilities or memory deficit.

  3. Protein microarrays and quantum dot probes for early cancer detection.

    PubMed

    Zajac, Aleksandra; Song, Dansheng; Qian, Wei; Zhukov, Tatyana

    2007-08-01

    We describe here a novel approach for detection of cancer markers using quantum dot protein microarrays. Both relatively new technologies; quantum dots and protein microarrays, offer very unique features that together allow detection of cancer markers in biological specimens (serum, plasma, body fluids) at pg/ml concentration. Quantum dots offer remarkable photostability and brightness. They do not exhibit photobleaching common to organic fluorophores. Moreover, the high emission amplitude for QDs results in a marked improvement in the signal to noise ratio of the final image. Protein microarrays allow highly parallel quantitation of specific proteins in a rapid, low-cost and low sample volume format. Furthermore the multiplexed assay enables detection of many proteins at once in one sample, making it a powerful tool for biomarker analysis and early cancer diagnostics. In a series of multiplexing experiments we investigated ability of the platform to detect six different cytokines in protein solution. We were able to detect TNF-alpha, IL-8, IL-6, MIP-1beta, IL-13 and IL-1beta down to picomolar concentration, demonstrating high sensitivity of the investigated detection system. We have also constructed and investigated two different models of quantum dot probes. One by conjugation of nanocrystals to antibody specific to the selected marker--IL-10, and the second by use of streptavidin coated quantum dots and biotinylated detector antibody. Comparison of those two models showed better performance of streptavidin QD-biotinylated detector antibody model. Data quantitated using custom designed computer program (CDAS) show that proposed methodology allows monitoring of changes in biomarker concentration in physiological range.

  4. Learned predictiveness influences rapid attentional capture: evidence from the dot probe task.

    PubMed

    Le Pelley, Mike E; Vadillo, Miguel; Luque, David

    2013-11-01

    Attentional theories of associative learning and categorization propose that learning about the predictiveness of a stimulus influences the amount of attention that is paid to that stimulus. Three experiments tested this idea by looking at the extent to which stimuli that had previously been experienced as predictive or nonpredictive in a categorization task were able to capture attention in a dot probe task. Consistent with certain attentional theories of learning, responses to the dot probe were faster when it appeared in a location cued by a predictive stimulus compared to a location cued by a nonpredictive stimulus. This result was obtained only with short (250-ms or 350-ms) but not long (1,000-ms) delays between onset of the stimuli and the dot probe, suggesting that the observed spatial cuing effect reflects the operation of a relatively rapid, automatic process. These findings are consistent with the approach to the relationship between attention and learning taken by the class of models exemplified by Mackintosh's (1975) theory. PsycINFO Database Record (c) 2013 APA, all rights reserved.

  5. The statistical theory of quantum dots

    NASA Astrophysics Data System (ADS)

    Alhassid, Y.

    2000-10-01

    A quantum dot is a sub-micron-scale conducting device containing up to several thousand electrons. Transport through a quantum dot at low temperatures is a quantum-coherent process. This review focuses on dots in which the electron's dynamics are chaotic or diffusive, giving rise to statistical properties that reflect the interplay between one-body chaos, quantum interference, and electron-electron interactions. The conductance through such dots displays mesoscopic fluctuations as a function of gate voltage, magnetic field, and shape deformation. The techniques used to describe these fluctuations include semiclassical methods, random-matrix theory, and the supersymmetric nonlinear σ model. In open dots, the approximation of noninteracting quasiparticles is justified, and electron-electron interactions contribute indirectly through their effect on the dephasing time at finite temperature. In almost-closed dots, where conductance occurs by tunneling, the charge on the dot is quantized, and electron-electron interactions play an important role. Transport is dominated by Coulomb blockade, leading to peaks in the conductance that at low temperatures provide information on the dot's ground-state properties. Several statistical signatures of electron-electron interactions have been identified, most notably in the dot's addition spectrum. The dot's spin, determined partly by exchange interactions, can also influence the fluctuation properties of the conductance. Other mesoscopic phenomena in quantum dots that are affected by the charging energy include the fluctuations of the cotunneling conductance and mesoscopic Coulomb blockade.

  6. Systematic safety evaluation on photoluminescent carbon dots

    NASA Astrophysics Data System (ADS)

    Wang, Kan; Gao, Zhongcai; Gao, Guo; Wo, Yan; Wang, Yuxia; Shen, Guangxia; Cui, Daxiang

    2013-03-01

    Photoluminescent carbon dots (C-dots) were prepared using the improved nitric acid oxidation method. The C-dots were characterized by tapping-mode atomic force microscopy, and UV-vis absorption spectroscopy. The C-dots were subjected to systematic safety evaluation via acute toxicity, subacute toxicity, and genotoxicity experiments (including mouse bone marrow micronuclear test and Salmonella typhimurium mutagenicity test). The results showed that the C-dots were successfully prepared with good stability, high dispersibility, and water solubility. At all studied C-dot dosages, no significant toxic effect, i.e., no abnormality or lesion, was observed in the organs of the animals. Therefore, the C-dots are non-toxic to mice under any dose and have potential use in fluorescence imaging in vivo, tumor cell tracking, and others.

  7. Modeling of the quantum dot filling and the dark current of quantum dot infrared photodetectors

    SciTech Connect

    Ameen, Tarek A.; El-Batawy, Yasser M.; Abouelsaood, A. A.

    2014-02-14

    A generalized drift-diffusion model for the calculation of both the quantum dot filling profile and the dark current of quantum dot infrared photodetectors is proposed. The confined electrons inside the quantum dots produce a space-charge potential barrier between the two contacts, which controls the quantum dot filling and limits the dark current in the device. The results of the model reasonably agree with a published experimental work. It is found that increasing either the doping level or the temperature results in an exponential increase of the dark current. The quantum dot filling turns out to be nonuniform, with a dot near the contacts containing more electrons than one in the middle of the device where the dot occupation approximately equals the number of doping atoms per dot, which means that quantum dots away from contacts will be nearly unoccupied if the active region is undoped.

  8. Colloidal quantum dot solar cells

    NASA Astrophysics Data System (ADS)

    Sargent, Edward H.

    2012-03-01

    Solar cells based on solution-processed semiconductor nanoparticles -- colloidal quantum dots -- have seen rapid advances in recent years. By offering full-spectrum solar harvesting, these cells are poised to address the urgent need for low-cost, high-efficiency photovoltaics.

  9. Reading Comprehension Strategy: Rainbow Dots

    ERIC Educational Resources Information Center

    Moore, Claire; Lo, Lusa

    2008-01-01

    An action research study was conducted using the Rainbow Dots strategy to evaluate its effectiveness on reading comprehension skills in a third-grade class with students both with and without a specific learning disability. Results of the study indicated that students' overall performances in reading comprehension have increased. Students also…

  10. Reading Comprehension Strategy: Rainbow Dots

    ERIC Educational Resources Information Center

    Moore, Claire; Lo, Lusa

    2008-01-01

    An action research study was conducted using the Rainbow Dots strategy to evaluate its effectiveness on reading comprehension skills in a third-grade class with students both with and without a specific learning disability. Results of the study indicated that students' overall performances in reading comprehension have increased. Students also…

  11. Designing quantum dots for solotronics

    PubMed Central

    Kobak, J.; Smoleński, T.; Goryca, M.; Papaj, M.; Gietka, K.; Bogucki, A.; Koperski, M.; Rousset, J.-G.; Suffczyński, J.; Janik, E.; Nawrocki, M.; Golnik, A.; Kossacki, P.; Pacuski, W.

    2014-01-01

    Solotronics, optoelectronics based on solitary dopants, is an emerging field of research and technology reaching the ultimate limit of miniaturization. It aims at exploiting quantum properties of individual ions or defects embedded in a semiconductor matrix. It has already been shown that optical control of a magnetic ion spin is feasible using the carriers confined in a quantum dot. However, a serious obstacle was the quenching of the exciton luminescence by magnetic impurities. Here we show, by photoluminescence studies on thus-far-unexplored individual CdTe dots with a single cobalt ion and CdSe dots with a single manganese ion, that even if energetically allowed, nonradiative exciton recombination through single-magnetic-ion intra-ionic transitions is negligible in such zero-dimensional structures. This opens solotronics for a wide range of as yet unconsidered systems. On the basis of results of our single-spin relaxation experiments and on the material trends, we identify optimal magnetic-ion quantum dot systems for implementation of a single-ion-based spin memory. PMID:24463946

  12. Valuation of Go Stimuli or Devaluation of No-Go Stimuli? Evidence of an Increased Preference for Attended Go Stimuli Following a Go/No-Go Task

    PubMed Central

    Inoue, Kazuya; Sato, Nobuya

    2017-01-01

    Attentional inhibition that occurs during discrimination tasks leads to the negative evaluation of distractor stimuli. This phenomenon, known as the distractor devaluation effect also occurs when go/no-go tasks require response inhibition. However, it remains unclear whether there are interactions between attention and response controls when the distractor devaluation effect occurs. The aims of this study were to investigate whether attention to stimuli in the go/no-go task plays a facilitative role in distractor devaluation through response inhibition, and to clarify whether this effect reflects a decreased preference for no-go stimuli. Participants evaluated the preference for pictures before and after a go/no-go task. In Experiments 1 and 2, they made a go or no-go response depending on the category of pictures displayed (gummy candies or rice crackers), whereas in Experiment 3 they did on the basis digit category, even or odd numbers, superimposed on such pictures. Experiments 1 and 2 demonstrated that the pictures presented as no-go stimuli in the preceding go/no-go task were evaluated as less positive than the pictures presented as go stimuli. This devaluation effect reflected an increased preference for the go stimuli but not a decreased preference for the no-go stimuli. Experiment 3 indicated that response inhibition did not affect the preference for the pictures that had not received attention in a preceding go/no-go task. These results suggest that although attention plays an important role in differential ratings for go and no-go stimuli, such differences, in fact, reflect the valuation of go stimuli. PMID:28439246

  13. Valuation of Go Stimuli or Devaluation of No-Go Stimuli? Evidence of an Increased Preference for Attended Go Stimuli Following a Go/No-Go Task.

    PubMed

    Inoue, Kazuya; Sato, Nobuya

    2017-01-01

    Attentional inhibition that occurs during discrimination tasks leads to the negative evaluation of distractor stimuli. This phenomenon, known as the distractor devaluation effect also occurs when go/no-go tasks require response inhibition. However, it remains unclear whether there are interactions between attention and response controls when the distractor devaluation effect occurs. The aims of this study were to investigate whether attention to stimuli in the go/no-go task plays a facilitative role in distractor devaluation through response inhibition, and to clarify whether this effect reflects a decreased preference for no-go stimuli. Participants evaluated the preference for pictures before and after a go/no-go task. In Experiments 1 and 2, they made a go or no-go response depending on the category of pictures displayed (gummy candies or rice crackers), whereas in Experiment 3 they did on the basis digit category, even or odd numbers, superimposed on such pictures. Experiments 1 and 2 demonstrated that the pictures presented as no-go stimuli in the preceding go/no-go task were evaluated as less positive than the pictures presented as go stimuli. This devaluation effect reflected an increased preference for the go stimuli but not a decreased preference for the no-go stimuli. Experiment 3 indicated that response inhibition did not affect the preference for the pictures that had not received attention in a preceding go/no-go task. These results suggest that although attention plays an important role in differential ratings for go and no-go stimuli, such differences, in fact, reflect the valuation of go stimuli.

  14. Lissajous Rocking Ratchet: Realization in a Semiconductor Quantum Dot

    NASA Astrophysics Data System (ADS)

    Platonov, Sergey; Kästner, Bernd; Schumacher, Hans W.; Kohler, Sigmund; Ludwig, Stefan

    2015-09-01

    Breaking time-reversal symmetry (TRS) in the absence of a net bias can give rise to directed steady-state nonequilibrium transport phenomena such as ratchet effects. Here we present, theoretically and experimentally, the concept of a Lissajous rocking ratchet based on breaking TRS. Our system is a semiconductor quantum dot with periodically modulated dot-lead tunnel barriers. Broken TRS gives rise to single electron tunneling current. Its direction is fully controlled by exploring frequency and phase relations between the two barrier modulations. The concept of Lissajous ratchets can be realized in a large variety of different systems, including nanoelectrical, nanoelectromechanical, or superconducting circuits. It promises applications based on a detailed on-chip comparison of radio-frequency signals.

  15. Lissajous Rocking Ratchet: Realization in a Semiconductor Quantum Dot.

    PubMed

    Platonov, Sergey; Kästner, Bernd; Schumacher, Hans W; Kohler, Sigmund; Ludwig, Stefan

    2015-09-04

    Breaking time-reversal symmetry (TRS) in the absence of a net bias can give rise to directed steady-state nonequilibrium transport phenomena such as ratchet effects. Here we present, theoretically and experimentally, the concept of a Lissajous rocking ratchet based on breaking TRS. Our system is a semiconductor quantum dot with periodically modulated dot-lead tunnel barriers. Broken TRS gives rise to single electron tunneling current. Its direction is fully controlled by exploring frequency and phase relations between the two barrier modulations. The concept of Lissajous ratchets can be realized in a large variety of different systems, including nanoelectrical, nanoelectromechanical, or superconducting circuits. It promises applications based on a detailed on-chip comparison of radio-frequency signals.

  16. Optical properties of geometrically optimized graphene quantum dots

    NASA Astrophysics Data System (ADS)

    Bugajny, Paweł; Szulakowska, Ludmiła; Jaworowski, Błazej; Potasz, Paweł

    2017-01-01

    We derive effective tight-binding model for geometrically optimized graphene quantum dots and based on it we investigate corresponding changes in their optical properties in comparison to ideal structures. We consider hexagonal and triangular dots with zigzag and armchair edges. Using density functional theory methods we show that displacement of lattice sites leads to changes in atomic distances and in consequence modifies their energy spectrum. We derive appropriate model within tight-binding method with edge-modified hopping integrals. Using group theoretical analysis, we determine allowed optical transitions and investigate oscillatory strength between bulk-bulk, bulk-edge and edge-edge transitions. We compare optical joint density of states for ideal and geometry optimized structures. We also investigate an enhanced effect of sites displacement which can be designed in artificial graphene-like nanostructures. A shift of absorption peaks is found for small structures, vanishing with increasing system size.

  17. Enhanced Attention Capture by Emotional Stimuli in Mild Traumatic Brain Injury

    PubMed Central

    Mäki-Marttunen, Verónica; Kuusinen, Venla; Brause, Maarja; Peräkylä, Jari; Polvivaara, Markus; dos Santos Ribeiro, Rodolfo; Öhman, Juha

    2015-01-01

    Abstract Mild traumatic brain injury (mTBI) may be associated with compromised executive functioning and altered emotional reactivity. Despite frequent affective and cognitive symptoms in mTBI, objective evidence for brain dysfunction is often lacking. Previously we have reported compromised performance in symptomatic mTBI patients in an executive reaction time (RT) test, a computer-based RT test engaging several executive functions simultaneously. Here, we investigated the cognitive control processes in mTBI in context of threat-related stimuli. We used behavioral measures and event-related potentials (ERP) to investigate attentional capture by task-relevant and task-irrelevant emotional stimuli during a Go-NoGo task requiring cognitive control. We also assessed subjective cognitive, somatic, and emotional symptoms with questionnaires. Twenty-seven subjects with previous mTBI and 17 controls with previous ankle injury participated in the study over 9 months post-injury. Electroencephalogram (EEG) was recorded while patients performed a modified executive RT-test. N2-P3 ERP component was used as a general measure of allocated attentional and executive processing resources. Although at the time of the testing, the mTBI and the control groups did not differ in symptom endorsement, mTBI patients reported having had more emotional symptoms overall since the injury than controls. The overall RT-test performance levels did not differ between groups. However, when threat-related emotional stimuli were used as Go-signals, the mTBI group was faster than the control group. In comparison to neutral stimuli, threat-related stimuli were associated with increased N2-P3 amplitude in all conditions. This threat-related enhancement of the N2-P3 complex was greater in mTBI patients than in controls in response to Go signals and NoGo signals, independent of relevance. We conclude that mTBI may be associated with enhanced attentional and executive resource allocation to threat

  18. Enhanced attention capture by emotional stimuli in mild traumatic brain injury.

    PubMed

    Mäki-Marttunen, Verónica; Kuusinen, Venla; Brause, Maarja; Peräkylä, Jari; Polvivaara, Markus; dos Santos Ribeiro, Rodolfo; Öhman, Juha; Hartikainen, Kaisa M

    2015-02-15

    Mild traumatic brain injury (mTBI) may be associated with compromised executive functioning and altered emotional reactivity. Despite frequent affective and cognitive symptoms in mTBI, objective evidence for brain dysfunction is often lacking. Previously we have reported compromised performance in symptomatic mTBI patients in an executive reaction time (RT) test, a computer-based RT test engaging several executive functions simultaneously. Here, we investigated the cognitive control processes in mTBI in context of threat-related stimuli. We used behavioral measures and event-related potentials (ERP) to investigate attentional capture by task-relevant and task-irrelevant emotional stimuli during a Go-NoGo task requiring cognitive control. We also assessed subjective cognitive, somatic, and emotional symptoms with questionnaires. Twenty-seven subjects with previous mTBI and 17 controls with previous ankle injury participated in the study over 9 months post-injury. Electroencephalogram (EEG) was recorded while patients performed a modified executive RT-test. N2-P3 ERP component was used as a general measure of allocated attentional and executive processing resources. Although at the time of the testing, the mTBI and the control groups did not differ in symptom endorsement, mTBI patients reported having had more emotional symptoms overall since the injury than controls. The overall RT-test performance levels did not differ between groups. However, when threat-related emotional stimuli were used as Go-signals, the mTBI group was faster than the control group. In comparison to neutral stimuli, threat-related stimuli were associated with increased N2-P3 amplitude in all conditions. This threat-related enhancement of the N2-P3 complex was greater in mTBI patients than in controls in response to Go signals and NoGo signals, independent of relevance. We conclude that mTBI may be associated with enhanced attentional and executive resource allocation to threat-related stimuli

  19. Combined atomic force microscopy and photoluminescence imaging to select single InAs/GaAs quantum dots for quantum photonic devices.

    PubMed

    Sapienza, Luca; Liu, Jin; Song, Jin Dong; Fält, Stefan; Wegscheider, Werner; Badolato, Antonio; Srinivasan, Kartik

    2017-07-24

    We report on a combined photoluminescence imaging and atomic force microscopy study of single, isolated self-assembled InAs quantum dots. The motivation of this work is to determine an approach that allows to assess single quantum dots as candidates for quantum nanophotonic devices. By combining optical and scanning probe characterization techniques, we find that single quantum dots often appear in the vicinity of comparatively large topographic features. Despite this, the quantum dots generally do not exhibit significant differences in their non-resonantly pumped emission spectra in comparison to quantum dots appearing in defect-free regions, and this behavior is observed across multiple wafers produced in different growth chambers. Such large surface features are nevertheless a detriment to applications in which single quantum dots are embedded within nanofabricated photonic devices: they are likely to cause large spectral shifts in the wavelength of cavity modes designed to resonantly enhance the quantum dot emission, thereby resulting in a nominally perfectly-fabricated single quantum dot device failing to behave in accordance with design. We anticipate that the approach of screening quantum dots not only based on their optical properties, but also their surrounding surface topographies, will be necessary to improve the yield of single quantum dot nanophotonic devices.

  20. Posturographic destabilization in eating disorders in female patients exposed to body image related phobic stimuli.

    PubMed

    Forghieri, M; Monzani, D; Mackinnon, A; Ferrari, S; Gherpelli, C; Galeazzi, G M

    2016-08-26

    Human postural control is dependent on the central integration of vestibular, visual and proprioceptive inputs. Psychological states can affect balance control: anxiety, in particular, has been shown to influence balance mediated by visual stimuli. We hypothesized that patients with eating disorders would show postural destabilization when exposed to their image in a mirror and to the image of a fashion model representing their body ideal in comparison to body neutral stimuli. Seventeen females patients attending a day centre for the treatment of eating disorders were administered psychometric measures of body dissatisfaction, anxiety, depression and underwent posturographic measures with their eyes closed, open, watching a neutral stimulus, while exposed to a full length mirror and to an image of a fashion model corresponding to their body image. Results were compared to those obtained by eighteen healthy subjects. Eating disordered patients showed higher levels of body dissatisfaction and higher postural destabilization than controls, but this was limited to the conditions in which they were exposed to their mirror image or a fashion model image. Postural destabilization under these conditions correlated with measures of body dissatisfaction. In eating disordered patients, body related stimuli seem to act as phobic stimuli in the posturographic paradigm used. If confirmed, this has the potential to be developed for diagnostic and therapeutic purposes.

  1. Invisible visual stimuli elicit increases in alpha-band power.

    PubMed

    Bareither, Isabelle; Chaumon, Maximilien; Bernasconi, Fosco; Villringer, Arno; Busch, Niko A

    2014-09-01

    The cerebral cortex responds to stimuli of a wide range of intensities. Previous studies have demonstrated that undetectably weak somatosensory stimuli cause a functional deactivation or inhibition in somatosensory cortex. In the present study, we tested whether invisible visual stimuli lead to similar responses, indicated by an increase in EEG alpha-band power-an index of cortical excitability. We presented subliminal and supraliminal visual stimuli after estimating each participant's detection threshold. Stimuli consisted of peripherally presented small circular patches that differed in their contrast to a background consisting of a random white noise pattern. We demonstrate that subliminal and supraliminal stimuli each elicit specific neuronal response patterns. Supraliminal stimuli evoked an early, strongly phase-locked lower-frequency response representing the evoked potential and induced a decrease in alpha-band power from 400 ms on. By contrast, subliminal visual stimuli induced an increase of non-phase-locked power around 300 ms that was maximal within the alpha-band. This response might be due to an inhibitory mechanism, which reduces spurious visual activation that is unlikely to result from external stimuli. Copyright © 2014 the American Physiological Society.

  2. Predator and heterospecific stimuli alter behaviour in cattle.

    PubMed

    Kluever, Bryan M; Howery, Larry D; Breck, Stewart W; Bergman, David L

    2009-05-01

    Wild and domestic ungulates modify their behaviour in the presence of olfactory and visual cues of predators but investigations have not exposed a domestic species to a series of cues representing various predators and other ungulate herbivores. We used wolf (Canis lupus), mountain lion (Puma concolor), and mule deer (Odocoileus hemionus) stimuli (olfactory and visual), and a control (no stimuli) to experimentally test for differences in behaviour of cattle (Bos taurus) raised in Arizona. We measured (1) vigilance, (2) foraging rates, (3) giving up density (GUD) of high quality foods and (4) time spent in high quality forage locations in response to location of stimuli treatments. In general, we found a consistent pattern in that wolf and deer treatments caused disparate results in all 4 response variables. Wolf stimuli significantly increased cattle vigilance and decreased cattle foraging rates; conversely, deer stimuli significantly increased cattle foraging rate and increased cattle use of high quality forage areas containing stimuli. Mountain lion stimuli did not significantly impact any of the 4 response variables. Our findings suggest that domestic herbivores react to predatory stimuli, can differentiate between stimuli representing two predatory species, and suggest that cattle may reduce antipredatory behaviour when near heterospecifics.

  3. Time- and Space-Order Effects in Timed Discrimination of Brightness and Size of Paired Visual Stimuli

    ERIC Educational Resources Information Center

    Patching, Geoffrey R.; Englund, Mats P.; Hellstrom, Ake

    2012-01-01

    Despite the importance of both response probability and response time for testing models of choice, there is a dearth of chronometric studies examining systematic asymmetries that occur over time- and space-orders in the method of paired comparisons. In this study, systematic asymmetries in discriminating the magnitude of paired visual stimuli are…

  4. Physical and optical dot gain: characterization and relation to dot shape and paper properties

    NASA Astrophysics Data System (ADS)

    Namedanian, Mahziar; Nyström, Daniel; Zitinski Elias, Paula; Gooran, Sasan

    2014-01-01

    The tone value increase in halftone printing commonly referred to as dot gain actually encompasses two fundamentally different phenomena. Physical dot gain refers to the fact that the size of the printed halftone dots differs from their nominal size, and is related to the printing process. Optical dot gain originates from light scattering inside the substrate, causing light exchanges between different chromatic areas. Due to their different intrinsic nature, physical and optical dot gains need to be treated separately. In this study, we characterize and compare the dot gain properties for offset prints on coated and uncoated paper, using AM and first and second generation FM halftoning. Spectral measurements are used to compute the total dot gain. Microscopic images are used to separate the physical and optical dot gain, to study ink spreading and ink penetration, and to compute the Modulation Transfer Function (MTF) for the different substrates. The experimental results show that the physical dot gain depends on ink penetration and ink spreading properties. Microscopic images of the prints reveal that the ink penetrates into the pores and cavities of the uncoated paper, resulting in inhomogeneous dot shapes. For the coated paper, the ink spread on top of the surface, giving a more homogenous dot shape, but also covering a larger area, and hence larger physical dot gain. The experimental results further show that the total dot gain is larger for the uncoated paper, because of larger optical dot gain. The effect of optical dot gain depends on the lateral light scattering within the substrate, the size of the halftone dots, and on the halftone dot shape, especially the dot perimeter.

  5. Neurons in Striate Cortex Signal Disparity in Half-Matched Random-Dot Stereograms.

    PubMed

    Henriksen, Sid; Read, Jenny C A; Cumming, Bruce G

    2016-08-24

    Human stereopsis can operate in dense "cyclopean" images containing no monocular objects. This is believed to depend on the computation of binocular correlation by neurons in primary visual cortex (V1). The observation that humans perceive depth in half-matched random-dot stereograms, although these stimuli have no net correlation, has led to the proposition that human depth perception in these stimuli depends on a distinct "matching" computation possibly performed in extrastriate cortex. However, recording from disparity-selective neurons in V1 of fixating monkeys, we found that they are in fact able to signal disparity in half-matched stimuli. We present a simple model that explains these results. This reinstates the view that disparity-selective neurons in V1 provide the initial substrate for perception in dense cyclopean stimuli, and strongly suggests that separate correlation and matching computations are not necessary to explain existing data on mixed correlation stereograms. The initial step in stereoscopic 3D vision is generally thought to be a correlation-based computation that takes place in striate cortex. Recent research has argued that there must be an additional matching computation involved in extracting stereoscopic depth in random-dot stereograms. This is based on the observation that humans can perceive depth in stimuli with a mean binocular correlation of zero (where a correlation-based mechanism should not signal depth). We show that correlation-based cells in striate cortex do in fact signal depth here because they convert fluctuations in the correlation level into a mean change in the firing rate. Our results reinstate the view that these cells provide a sufficient substrate for the perception of stereoscopic depth. Copyright © 2016 Henriksen et al.

  6. Neurons in Striate Cortex Signal Disparity in Half-Matched Random-Dot Stereograms

    PubMed Central

    Read, Jenny C. A.; Cumming, Bruce G.

    2016-01-01

    Human stereopsis can operate in dense “cyclopean” images containing no monocular objects. This is believed to depend on the computation of binocular correlation by neurons in primary visual cortex (V1). The observation that humans perceive depth in half-matched random-dot stereograms, although these stimuli have no net correlation, has led to the proposition that human depth perception in these stimuli depends on a distinct “matching” computation possibly performed in extrastriate cortex. However, recording from disparity-selective neurons in V1 of fixating monkeys, we found that they are in fact able to signal disparity in half-matched stimuli. We present a simple model that explains these results. This reinstates the view that disparity-selective neurons in V1 provide the initial substrate for perception in dense cyclopean stimuli, and strongly suggests that separate correlation and matching computations are not necessary to explain existing data on mixed correlation stereograms. SIGNIFICANCE STATEMENT The initial step in stereoscopic 3D vision is generally thought to be a correlation-based computation that takes place in striate cortex. Recent research has argued that there must be an additional matching computation involved in extracting stereoscopic depth in random-dot stereograms. This is based on the observation that humans can perceive depth in stimuli with a mean binocular correlation of zero (where a correlation-based mechanism should not signal depth). We show that correlation-based cells in striate cortex do in fact signal depth here because they convert fluctuations in the correlation level into a mean change in the firing rate. Our results reinstate the view that these cells provide a sufficient substrate for the perception of stereoscopic depth. PMID:27559177

  7. Accommodation and pupil responses to random-dot stereograms.

    PubMed

    Suryakumar, Rajaraman; Allison, Robert

    2016-01-01

    We investigated the dynamics of accommodative and pupillary responses to random-dot stereograms presented in crossed and uncrossed disparity in six visually normal young adult subjects (mean age=25.8±3.1 years). Accommodation and pupil measures were monitored monocularly with a custom built photorefraction system while subjects fixated at the center of a random-dot stereogram. On each trial, the stereogram initially depicted a flat plane and then changed to depict a sinusoidal corrugation in depth while fixation remained constant. Increase in disparity specified depth resulted in pupil constriction during both crossed and uncrossed disparity presentations. The change in pupil size between crossed and uncrossed disparity conditions was not significantly different (p>0.05). The change in pupil size was also accompanied by a small concomitant increase in accommodation. In addition, the dynamic properties of pupil responses varied as a function of their initial (starting) diameter. The finding that accommodation and pupil responses increased with disparity regardless of the sign of retinal disparity suggests that these responses were driven by apparent depth rather than shifts in mean simulated distance of the stimulus. Presumably the need for the increased depth of focus when viewing stimuli extended in depth results in pupil constriction which also results in a concomitant change in accommodation. Starting position effects in pupil response confirm the non-linearity in the operating range of the pupil.

  8. Accommodation and pupil responses to random-dot stereograms

    PubMed Central

    Suryakumar, Rajaraman; Allison, Robert

    2015-01-01

    We investigated the dynamics of accommodative and pupillary responses to random-dot stereograms presented in crossed and uncrossed disparity in six visually normal young adult subjects (mean age = 25.8 ± 3.1 years). Accommodation and pupil measures were monitored monocularly with a custom built photorefraction system while subjects fixated at the center of a random-dot stereogram. On each trial, the stereogram initially depicted a flat plane and then changed to depict a sinusoidal corrugation in depth while fixation remained constant. Increase in disparity specified depth resulted in pupil constriction during both crossed and uncrossed disparity presentations. The change in pupil size between crossed and uncrossed disparity conditions was not significantly different (p > 0.05). The change in pupil size was also accompanied by a small concomitant increase in accommodation. In addition, the dynamic properties of pupil responses varied as a function of their initial (starting) diameter. The finding that accommodation and pupil responses increased with disparity regardless of the sign of retinal disparity suggests that these responses were driven by apparent depth rather than shifts in mean simulated distance of the stimulus. Presumably the need for the increased depth of focus when viewing stimuli extended in depth results in pupil constriction which also results in a concomitant change in accommodation. Starting position effects in pupil response confirm the non-linearity in the operating range of the pupil. PMID:25891121

  9. Happiness increases distraction by auditory deviant stimuli.

    PubMed

    Pacheco-Unguetti, Antonia Pilar; Parmentier, Fabrice B R

    2016-08-01

    Rare and unexpected changes (deviants) in an otherwise repeated stream of task-irrelevant auditory distractors (standards) capture attention and impair behavioural performance in an ongoing visual task. Recent evidence indicates that this effect is increased by sadness in a task involving neutral stimuli. We tested the hypothesis that such effect may not be limited to negative emotions but reflect a general depletion of attentional resources by examining whether a positive emotion (happiness) would increase deviance distraction too. Prior to performing an auditory-visual oddball task, happiness or a neutral mood was induced in participants by means of the exposure to music and the recollection of an autobiographical event. Results from the oddball task showed significantly larger deviance distraction following the induction of happiness. Interestingly, the small amount of distraction typically observed on the standard trial following a deviant trial (post-deviance distraction) was not increased by happiness. We speculate that happiness might interfere with the disengagement of attention from the deviant sound back towards the target stimulus (through the depletion of cognitive resources and/or mind wandering) but help subsequent cognitive control to recover from distraction.

  10. Implicit training of nonnative speech stimuli.

    PubMed

    Vlahou, Eleni L; Protopapas, Athanassios; Seitz, Aaron R

    2012-05-01

    Learning nonnative speech contrasts in adulthood has proven difficult. Standard training methods have achieved moderate effects using explicit instructions and performance feedback. In this study, the authors question preexisting assumptions by demonstrating a superiority of implicit training procedures. They trained 3 groups of Greek adults on a difficult Hindi contrast (a) explicitly, with feedback (Experiment 1), or (b) implicitly, unaware of the phoneme distinctions, with (Experiment 2) or without (Experiment 3) feedback. Stimuli were natural recordings of consonant-vowel syllables with retroflex and dental unvoiced stops by a native Hindi speaker. On each trial, participants heard pairs of tokens from both categories and had to identify the retroflex sounds (explicit condition) or the sounds differing in intensity (implicit condition). Unbeknownst to participants, in the implicit conditions, target sounds were always retroflex, and distractor sounds were always dental. Post-training identification and discrimination tests showed improved performance of all groups, compared with a baseline of untrained Greek listeners. Learning was most robust for implicit training without feedback. It remains to be investigated whether implicitly trained skills can generalize to linguistically relevant phonetic categories when appropriate variability is introduced. These findings challenge traditional accounts on the role of feedback in phonetic training and highlight the importance of implicit, reward-based mechanisms.

  11. Human Infants’ Accommodation Responses to Dynamic Stimuli

    PubMed Central

    Tondel, Grazyna M.; Candy, T. Rowan

    2009-01-01

    Purpose A young infant’s environment routinely consists of moving objects. The dynamics of the infant accommodative system are almost unknown and yet have a large impact on habitual retinal image quality and visual experience. The goal of this study was to record infants’ dynamic accommodative responses to stimuli moving at a range of velocities. Methods Binocular accommodative responses were recorded at 25 Hz. Data from infants 8 to 20 weeks of age and pre-presbyopic adults were analyzed. A high-contrast image of a clown was moved between 20- and 50-cm viewing distances at four velocities (a step, 50 cm/s, 20 cm/s, and 5 cm/s). Results Most infants who had clear responses were able to initiate their response within a second of stimulus onset. The infants were able to discriminate the different stimulus velocities and to adjust their response velocities and durations in an appropriate fashion. Conclusions The data indicate that by the third postnatal month infants are able to respond with latencies within a factor of two of adults’ and that there is little immaturity in the motor capabilities of the accommodative system compared with the sensory visual system at the same age. PMID:17251499

  12. The Search for Optimal Visual Stimuli

    NASA Technical Reports Server (NTRS)

    Watson, Andrew B.; Ellis, Stephen R. (Technical Monitor)

    1997-01-01

    In 1983, Watson, Barlow and Robson published a brief report in which they explored the relative visibility of targets that varied in size, shape, spatial frequency, speed, and duration (referred to subsequently here as WBR). A novel aspect of that paper was that visibility was quantified in terms of threshold contrast energy, rather than contrast. As they noted, this provides a more direct measure of the efficiency with which various patterns are detected, and may be more edifying as to the underlying detection machinery. For example, under certain simple assumptions, the waveform of the most efficiently detected signal is an estimate of the receptive field of the visual system's most efficient detector. Thus one goal of their experiment Basuto search for the stimulus that the 'eye sees best'. Parenthetically, the search for optimal stimuli may be seen as the most general and sophisticated variant of the traditional 'subthreshold summation' experiment, in which one measures the effect upon visibility of small probes combined with a base stimulus.

  13. Anchoring in Numeric Judgments of Visual Stimuli

    PubMed Central

    Langeborg, Linda; Eriksson, Mårten

    2016-01-01

    This article investigates effects of anchoring in age estimation and estimation of quantities, two tasks which to different extents are based on visual stimuli. The results are compared to anchoring in answers to classic general knowledge questions that rely on semantic knowledge. Cognitive load was manipulated to explore possible differences between domains. Effects of source credibility, manipulated by differing instructions regarding the selection of anchor values (no information regarding anchor selection, information that the anchors are randomly generated or information that the anchors are answers from an expert) on anchoring were also investigated. Effects of anchoring were large for all types of judgments but were not affected by cognitive load or by source credibility in either one of the researched domains. A main effect of cognitive load on quantity estimations and main effects of source credibility in the two visually based domains indicate that the manipulations were efficient. Implications for theoretical explanations of anchoring are discussed. In particular, because anchoring did not interact with cognitive load, the results imply that the process behind anchoring in visual tasks is predominantly automatic and unconscious. PMID:26941684

  14. Anchoring in Numeric Judgments of Visual Stimuli.

    PubMed

    Langeborg, Linda; Eriksson, Mårten

    2016-01-01

    This article investigates effects of anchoring in age estimation and estimation of quantities, two tasks which to different extents are based on visual stimuli. The results are compared to anchoring in answers to classic general knowledge questions that rely on semantic knowledge. Cognitive load was manipulated to explore possible differences between domains. Effects of source credibility, manipulated by differing instructions regarding the selection of anchor values (no information regarding anchor selection, information that the anchors are randomly generated or information that the anchors are answers from an expert) on anchoring were also investigated. Effects of anchoring were large for all types of judgments but were not affected by cognitive load or by source credibility in either one of the researched domains. A main effect of cognitive load on quantity estimations and main effects of source credibility in the two visually based domains indicate that the manipulations were efficient. Implications for theoretical explanations of anchoring are discussed. In particular, because anchoring did not interact with cognitive load, the results imply that the process behind anchoring in visual tasks is predominantly automatic and unconscious.

  15. Psychophysiological Response Patterns to Affective Film Stimuli

    PubMed Central

    Bos, Marieke G. N.; Jentgens, Pia; Beckers, Tom; Kindt, Merel

    2013-01-01

    Psychophysiological research on emotion utilizes various physiological response measures to index activation of the defense system. Here we tested 1) whether acoustic startle reflex (ASR), skin conductance response (SCR) and heart rate (HR) elicited by highly arousing stimuli specifically reflect a defensive state and 2) the relation between resting heart rate variability (HRV) and affective responding. In a within-subject design, participants viewed film clips with a positive, negative and neutral content. In contrast to SCR and HR, we show that ASR differentiated between negative, neutral and positive states and can therefore be considered as a reliable index of activation of the defense system. Furthermore, resting HRV was associated with affect-modulated characteristics of ASR, but not with SCR or HR. Interestingly, individuals with low-HRV showed less differentiation in ASR between affective states. We discuss the important value of ASR in psychophysiological research on emotion and speculate on HRV as a potential biological marker for demarcating adaptive from maladaptive responding. PMID:23646134

  16. Haptic pop-out of movable stimuli.

    PubMed

    van Polanen, Vonne; Bergmann Tiest, Wouter M; Kappers, Astrid M L

    2012-01-01

    When, in visual and haptic search, a target is easily found among distractors, this is called a pop-out effect. The target feature is then believed to be salient, and the search is performed in a parallel way. We investigated this effect with movable stimuli in a haptic search task. The task was to find a movable ball among anchored distractors or the other way round. Results show that reaction times were independent of the number of distractors if the movable ball was the target but increased with the number of items if the anchored ball was the target. Analysis of hand movements revealed a parallel search strategy, shorter movement paths, a higher average movement speed, and a narrower direction distribution with the movable target, as compared with a more detailed search for an anchored target. Taken together, these results show that a movable object pops out between anchored objects and this indicates that movability is a salient object feature. Vibratory signals resulting from the movable ball were found to be a reasonable explanation regarding the sensation responsible for the pop-out of movability.

  17. QCAD simulation and optimization of semiconductor double quantum dots

    SciTech Connect

    Nielsen, Erik; Gao, Xujiao; Kalashnikova, Irina; Muller, Richard Partain; Salinger, Andrew Gerhard; Young, Ralph Watson

    2013-12-01

    We present the Quantum Computer Aided Design (QCAD) simulator that targets modeling quantum devices, particularly silicon double quantum dots (DQDs) developed for quantum qubits. The simulator has three di erentiating features: (i) its core contains nonlinear Poisson, e ective mass Schrodinger, and Con guration Interaction solvers that have massively parallel capability for high simulation throughput, and can be run individually or combined self-consistently for 1D/2D/3D quantum devices; (ii) the core solvers show superior convergence even at near-zero-Kelvin temperatures, which is critical for modeling quantum computing devices; (iii) it couples with an optimization engine Dakota that enables optimization of gate voltages in DQDs for multiple desired targets. The Poisson solver includes Maxwell- Boltzmann and Fermi-Dirac statistics, supports Dirichlet, Neumann, interface charge, and Robin boundary conditions, and includes the e ect of dopant incomplete ionization. The solver has shown robust nonlinear convergence even in the milli-Kelvin temperature range, and has been extensively used to quickly obtain the semiclassical electrostatic potential in DQD devices. The self-consistent Schrodinger-Poisson solver has achieved robust and monotonic convergence behavior for 1D/2D/3D quantum devices at very low temperatures by using a predictor-correct iteration scheme. The QCAD simulator enables the calculation of dot-to-gate capacitances, and comparison with experiment and between solvers. It is observed that computed capacitances are in the right ballpark when compared to experiment, and quantum con nement increases capacitance when the number of electrons is xed in a quantum dot. In addition, the coupling of QCAD with Dakota allows to rapidly identify which device layouts are more likely leading to few-electron quantum dots. Very efficient QCAD simulations on a large number of fabricated and proposed Si DQDs have made it possible to provide fast feedback for design

  18. Effect of metal oxide morphology on electron injection from CdSe quantum dots to ZnO

    NASA Astrophysics Data System (ADS)

    Zheng, Kaibo; Žídek, Karel; Abdellah, Mohamed; Chábera, Pavel; Abd El-sadek, Mahmoud S.; Pullerits, Tõnu

    2013-04-01

    Performance of quantum dot sensitized solar cells relies on a rapid electron injection from quantum dot to metal oxide. We studied the injection process in CdSe-ZnO system by ultrafast time-resolved absorption spectroscopy for two types of acceptor morphologies—nanowires and nanoparticles' films. Based on comparison between experimental data and Marcus theory, we demonstrate that the acceptor morphology has a significant impact on electron injection due to (i) change in material permittivity and (ii) different density of the band-edge states. The results open a reference to improve injection efficiency in quantum dot-metal oxide system by selection of the acceptor morphology.

  19. High Efficiency Quantum Dot Sensitized Solar Cells Based on Direct Adsorption of Quantum Dots on Photoanodes.

    PubMed

    Wang, Wenran; Jiang, Guocan; Yu, Juan; Wang, Wei; Pan, Zhenxiao; Nakazawa, Naoki; Shen, Qing; Zhong, Xinhua

    2017-07-12

    Unambiguously direct adsorption (DA) of initial oil-soluble quantum dots (QDs) on TiO2 film electrode is a convenient and simple approach in the construction of quantum dot sensitized solar cells (QDSCs). Regrettably, low QD loading amount and poor reproducibility shadow the advantages of DA route and constrain its practical application. Herein, the influence of experimental variables in DA process on QD loading amount as well as on the photovoltaic performance of the resultant QDSCs was investigated and optimized systematically, including the choice of solvent, purification of QDs, and sensitization time, as well as QD concentration. Experimental results demonstrated that it is essential to choose appropriate solvent as well as control purification cycles of original QD suspensions so as to realize satisfactory QD loading amount and ensure the high reproducibility. In addition, DA mode renders efficient electron injection from QD to TiO2, yet low QD loading amount and adverse QD agglomeration in comparison with the well-developed capping ligand induced self-assembly (CLIS) deposition approach. Mg(2+) treatment on TiO2 photoanodes can promote the QD loading amount in DA mode. The optimized QDSCs based on DA mode exhibited efficiencies of 6.90% and 9.02% for CdSe and Zn-Cu-In-Se QDSCs, respectively, which were comparable to the best results based on CLIS mode (6.88% and 9.56%, respectively).

  20. Neural responses to one- and two-tone stimuli in the hearing organ of the dengue vector mosquito

    PubMed Central

    Arthur, Ben J.; Wyttenbach, Robert A.; Harrington, Laura C.; Hoy, Ronald R.

    2010-01-01

    SUMMARY Recent studies demonstrate that mosquitoes listen to each other's wing beats just prior to mating in flight. Field potentials from sound-transducing neurons in the antennae contain both sustained and oscillatory components to pure and paired tone stimuli. Described here is a direct comparison of these two types of response in the dengue vector mosquito, Aedes aegypti. Across a wide range of frequencies and intensities, sustained responses to one- and two-tone stimuli are about equal in magnitude to oscillatory responses to the beats produced by two-tone stimuli. All of these responses are much larger than the oscillatory responses to one-tone stimuli. Similarly, the frequency range extends up to at least the fifth harmonic of the male flight tone for sustained responses to one- and two-tone stimuli and oscillatory responses at the beat frequency of two-tone stimuli, whereas the range of oscillatory response to a one-tone stimulus is limited to, at most, the third harmonic. Thresholds near the fundamental of the flight tone are lower for oscillatory responses than for sustained deflections, lower for males than for females, and within the behaviorally relevant range. A simple model of the transduction process can qualitatively account for both oscillatory and sustained responses to pure and paired tones. These data leave open the question as to which of several alternative strategies underlie flight tone matching behavior in mosquitoes. PMID:20348350

  1. Can Persons With Dementia Be Engaged With Stimuli?

    PubMed Central

    Cohen-Mansfield, Jiska; Marx, Marcia S; Dakheel-Ali, Maha; Regier, Natalie G.; Thein, Khin

    2011-01-01

    Objectives To determine which stimuli are 1) most engaging 2) most often refused by nursing home residents with dementia, and 3) most appropriate for persons who are more difficult to engage with stimuli. Methods Participants were 193 residents of seven Maryland nursing homes. All participants had a diagnosis of dementia. Stimulus engagement was assessed by the Observational Measure of Engagement. Results The most engaging stimuli were one-on-one socializing with a research assistant, a real baby, personalized stimuli based on the person’s self-identity, a lifelike doll, a respite video, and envelopes to stamp. Refusal of stimuli was higher among those with higher levels of cognitive function and related to the stimulus’ social appropriateness. Women showed more attention and had more positive attitudes for live social stimuli, simulated social stimuli, and artistic tasks than did men. Persons with comparatively higher levels of cognitive functioning were more likely to be engaged in manipulative and work tasks, whereas those with low levels of cognitive functioning spent relatively more time responding to social stimuli. The most effective stimuli did not differ for those most likely to be engaged and those least likely to be engaged. Conclusion Nursing homes should consider both having engagement stimuli readily available to residents with dementia, and implementing a socialization schedule so that residents receive one-on-one interaction. Understanding the relationship among type of stimulus, cognitive function, and acceptance, attention, and attitude toward the stimuli can enable caregivers to maximize the desired benefit for persons with dementia. PMID:20306565

  2. Processing of Voiced and Unvoiced Acoustic Stimuli in Musicians

    PubMed Central

    Ott, Cyrill Guy Martin; Langer, Nicolas; Oechslin, Mathias S.; Meyer, Martin; Jäncke, Lutz

    2011-01-01

    Past research has shown that musical training induces changes in the processing of supra-segmental aspects of speech, such as pitch and prosody. The aim of the present study was to determine whether musical expertise also leads to an altered neurophysiological processing of sub-segmental information available in the speech signal, in particular the voice-onset-time. Using high-density EEG-recordings we analyzed the neurophysiological responses to voiced and unvoiced consonant-vowel-syllables and noise-analogs in 26 German speaking adult musicians and non-musicians. From the EEG the N1 amplitude of the event-related potential and two microstates from the topographical EEG analysis (one around the N1 amplitude and one immediately preceding the N1 microstate) were calculated to the different stimuli. Similar to earlier studies the N1 amplitude was different to voiced and unvoiced stimuli in non-musicians with larger amplitudes to voiced stimuli. The more refined microstate analysis revealed that the microstate within the N1 time window was shorter to unvoiced stimuli in non-musicians. For musicians there was no difference for the N1 amplitudes and the corresponding microstates between voiced and unvoiced stimuli. In addition, there was a longer very early microstate preceding the microstate at the N1 time window to non-speech stimuli only in musicians. Taken together, our findings suggest that musicians process unvoiced stimuli (irrespective whether these stimuli are speech or non-speech stimuli) differently than controls. We propose that musicians utilize the same network to analyze unvoiced stimuli as for the analysis of voiced stimuli. As a further explanation it is also possible that musicians devote more neurophysiological resources into the analysis of unvoiced segments. PMID:21922011

  3. Attention and the speed of information processing: posterior entry for unattended stimuli instead of prior entry for attended stimuli.

    PubMed

    Weiß, Katharina; Hilkenmeier, Frederic; Scharlau, Ingrid

    2013-01-01

    Why are nearly simultaneous stimuli frequently perceived in reversed order? The origin of errors in temporal judgments is a question older than experimental psychology itself. One of the earliest suspects is attention. According to the concept of prior entry, attention accelerates attended stimuli; thus they have "prior entry" to perceptive processing stages, including consciousness. Although latency advantages for attended stimuli have been revealed in psychophysical studies many times, these measures (e.g. temporal order judgments, simultaneity judgments) cannot test the prior-entry hypothesis completely. Since they assess latency differences between an attended and an unattended stimulus, they cannot distinguish between faster processing of attended stimuli and slower processing of unattended stimuli. Therefore, we present a novel paradigm providing separate estimates for processing advantages respectively disadvantages of attended and unattended stimuli. We found that deceleration of unattended stimuli contributes more strongly to the prior-entry illusion than acceleration of attended stimuli. Thus, in the temporal domain, attention fulfills its selective function primarily by deceleration of unattended stimuli. That means it is actually posterior entry, not prior entry which accounts for the largest part of the effect.

  4. Attention and the Speed of Information Processing: Posterior Entry for Unattended Stimuli Instead of Prior Entry for Attended Stimuli

    PubMed Central

    Weiß, Katharina; Hilkenmeier, Frederic; Scharlau, Ingrid

    2013-01-01

    Why are nearly simultaneous stimuli frequently perceived in reversed order? The origin of errors in temporal judgments is a question older than experimental psychology itself. One of the earliest suspects is attention. According to the concept of prior entry, attention accelerates attended stimuli; thus they have “prior entry” to perceptive processing stages, including consciousness. Although latency advantages for attended stimuli have been revealed in psychophysical studies many times, these measures (e.g. temporal order judgments, simultaneity judgments) cannot test the prior-entry hypothesis completely. Since they assess latency differences between an attended and an unattended stimulus, they cannot distinguish between faster processing of attended stimuli and slower processing of unattended stimuli. Therefore, we present a novel paradigm providing separate estimates for processing advantages respectively disadvantages of attended and unattended stimuli. We found that deceleration of unattended stimuli contributes more strongly to the prior-entry illusion than acceleration of attended stimuli. Thus, in the temporal domain, attention fulfills its selective function primarily by deceleration of unattended stimuli. That means it is actually posterior entry, not prior entry which accounts for the largest part of the effect. PMID:23382884

  5. Effects of Emotional Stimuli on Cardiovascular Responses in Patients with Essential Hypertension Based on Brain/Behavioral Systems

    PubMed Central

    Taban Sadeghi, Mohammadreza; Namdar, Hossein; Vahedi, Shahram; Aslanabadi, Naser; Ezzati, Davoud; Sadeghi, Babak

    2013-01-01

    Introduction: Effects of emotional stimuli on hemodynamics in patients with essential hypertension based on brain/behavioral systems have not been studied broadly. Methods: Eighty five essential hypertensive male patients who had completed Carver-White BIS/BAS scale were enrolled to the study. Later, 25 BIS and 25 BAS patients were selected and their blood pressure and heart rate were recorded prior to stimuli induction. Participants were then exposed to stressor pictures. After that, 15 minutes of relaxation and cognitive tasks were performed. Finally, the participants were exposed to pleasant pictures. The blood pressure and heart rate were recorded after presenting of 2 stimuli. Results: Our study showed that BIS patients achieved higher scores in diastolic blood pressure and heart rate in comparison with BAS patients after presenting stressful stimuli. Also, BAS patients achieved lower scores in systolic blood pressure and heart rate in comparison with BIS patients after presenting pleasant stimuli. Conclusion: In summary, BIS patients experience negative emotions more than BAS patients. Therefore, the role of induced mood states is important in relation to physical health. PMID:24404349

  6. Green chitosan-carbon dots nanocomposite hydrogel film with superior properties.

    PubMed

    Konwar, Achyut; Gogoi, Neelam; Majumdar, Gitanjali; Chowdhury, Devasish

    2015-01-22

    In this work we report novel chitosan-carbon dots nanocomposite hydrogel films. A new green source "tea" was used as precursor for carbon dots (CDs). The electrostatic interaction of positive charge on chitosan and negative charge on CDs prepared from tea was used for the successful preparation of a stable and robust chitosan-carbon dots nanocomposite hydrogel film. The hydrogel films were characterized by UV-visible spectroscopy, X-ray diffraction (XRD), Fourier transformed infra-red spectroscopy (FTIR), scanning electron microscope (SEM), fluorescent microscopy, thermogravimetric analysis (TGA) and contact angle analysis. It was observed that chitosan-carbon dots hydrogel films are soft but tough with superior UV-visible blocking, swelling, thermal and mechanical properties in comparison to chitosan hydrogel film. Moreover chitosan-carbon dots films are more water repellent (hydrophobic) as indicated by their high contact angle values. Thus, fabrication of such green soft but tough biocompatible chitosan-carbon dots nanocomposite hydrogel films offers tremendous bio-medical and industrial applications.

  7. Resonant scattering in graphene with a gate-defined chaotic quantum dot

    NASA Astrophysics Data System (ADS)

    Schneider, Martin; Brouwer, Piet W.

    2011-09-01

    We investigate the conductance of an undoped graphene sheet with two metallic contacts and an electrostatically gated island (quantum dot) between the contacts. Our analysis is based on the matrix Green function formalism, which was recently adapted to graphene by Titov [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.104.076802 104, 076802 (2010)]. We find pronounced differences between the case of a stadium-shaped dot (which has chaotic classical dynamics) and a disk-shaped dot (which has integrable classical dynamics) in the limit that the dot size is small in comparison to the distance between the contacts. In particular, for the stadium-shaped dot the two-terminal conductance shows Fano resonances as a function of the gate voltage, which cross over to Breit-Wigner resonances only in the limit of completely separated resonances, whereas for a disk-shaped dot sharp Breit-Wigner resonances resulting from higher angular momentum remain present throughout.

  8. Comparison of the dot-immunobinding assay with the serum agglutination test, the rose bengal plate test and the milk ring test for the detection of Brucella antibodies in bovine sera and milk.

    PubMed

    Gürtürk, K; Boynukara, B; Ilhan, Z; Hakki Ekin, I; Gülhan, T

    1999-05-01

    In this study, Brucella antibodies in bovine sera and milk were detected using the dot-immunobinding assay (DIA), the serum agglutination test (SAT), the Rose Bengal plate test (RBPT) and the milk ring test (MRT). For this purpose, a total of 116 paired blood and milk samples collected at the same time from 56 aborted and from 60 healthy dairy cows was examined. In DIA, a nitrocellulose membrane (NCM) was used as the solid phase. Antigen adsorbed on the NCM was extracted from Brucella abortus S99 by heat treatment. The results obtained by DIA were compared with those of SAT, RBPT and MRT. Of the 116 paired blood and milk samples, 24 were positive and 72 were negative by all tests used. Serum samples of six aborted cows were positive by DIA, SAT and RBPT but the milk samples were negative by DIA and MRT. Serum and milk samples of four aborted cows gave positive reaction only by DIA tests. The remaining six aborted cows were negative only by MRT and two of them were negative by both RBPT and MRT. Four sera of healthy cows were found to be positive only by SAT.

  9. Violent Reactions from Non-Shock Stimuli

    NASA Astrophysics Data System (ADS)

    Sandusky, Harold

    2007-06-01

    Most reactions are thermally initiated, whether from direct heating or dissipation of energy from mechanical, shock, or electrical stimuli. For other than prompt shock initiation, the reaction must be able to spread through porosity or over large surface area to become more violent than just rupturing any confinement. While burning rates are important, high-strain mechanical properties are nearly so, either by reducing existing porosity or generating additional surface area through fracture. The first example is deflagration-to-detonation transition (DDT) in porous beds. During the early stages, weak compressive waves ahead of the convective ignition front will reduce porosity, thereby restricting the spread of combustion and the pressure buildup. If, however, pressure increases faster than can be relieved by loss of confinement, coalescing compressive waves can initiate reaction at hot spots from rapid pore collapse. This compressive reaction can drive a shockwave that transits to detonation, the most violent reaction in any scenario. It has been shown that reaction violence is reduced in DDT experiments if the binder is softened, either by raising the initial temperature or adding a solvent. An example of the role of mechanical properties in enhancing reaction violence through fracturing occurs when cavities in projectile fills collapse during acceleration in the gun barrel, which is referred to as setback. Explosives with soft rubber binders will deform and undergo mild reaction from shear heating within the explosive and adiabatic compression of any gas in the cavity. Stiff explosives are similarly ignited, but also fracture and generate additional surface area for a violent event. The last example to be considered is slow cook-off, where thermal damage can increase burning rate as well as provide porosity to enhance the pressure buildup. As reaction spreads from the zone of thermal run-away, an explosive binder that resists breakup will limit the violence.

  10. Imagery Arousal as a Function of Exposure to Artistic Stimuli.

    ERIC Educational Resources Information Center

    Bilotta, Joseph

    The purpose of this study was to determine to what extent music and art can arouse imagery experiences in an audience. Because of the relationship found between imagery and the arts in past research, it was hypothesized that artistic stimuli would have a greater influence on imagery than other kinds of stimuli (art-information or non-artistic).…

  11. Logical Rules and the Classification of Integral-Dimension Stimuli

    ERIC Educational Resources Information Center

    Little, Daniel R.; Nosofsky, Robert M.; Donkin, Christopher; Denton, Stephen E.

    2013-01-01

    A classic distinction in perceptual information processing is whether stimuli are composed of separable dimensions, which are highly analyzable, or integral dimensions, which are processed holistically. Previous tests of a set of logical-rule models of classification have shown that separable-dimension stimuli are processed serially if the…

  12. Exploring Visuomotor Priming Following Biological and Non-Biological Stimuli

    ERIC Educational Resources Information Center

    Gowen, E.; Bradshaw, C.; Galpin, A.; Lawrence, A.; Poliakoff, E.

    2010-01-01

    Observation of human actions influences the observer's own motor system, termed visuomotor priming, and is believed to be caused by automatic activation of mirror neurons. Evidence suggests that priming effects are larger for biological (human) as opposed to non-biological (object) stimuli and enhanced when viewing stimuli in mirror compared to…

  13. Product perception from sensory stimuli: the case of vacuum cleaner.

    PubMed

    Almeida e Silva, Caio Márcio; Okimoto, Maria Lúciar R L; Tanure, Raffaela Leane Zenni

    2012-01-01

    This paper discusses the importance of consideration of different sensory stimuli in the perception of the product. So we conducted an experiment that examined whether there is a difference between the perception of sensory stimuli from artificially isolated. The result is an analysis of the different sensory modalities, relating them to product an between them.

  14. Gender differences in identifying emotions from auditory and visual stimuli.

    PubMed

    Waaramaa, Teija

    2017-12-01

    The present study focused on gender differences in emotion identification from auditory and visual stimuli produced by two male and two female actors. Differences in emotion identification from nonsense samples, language samples and prolonged vowels were investigated. It was also studied whether auditory stimuli can convey the emotional content of speech without visual stimuli, and whether visual stimuli can convey the emotional content of speech without auditory stimuli. The aim was to get a better knowledge of vocal attributes and a more holistic understanding of the nonverbal communication of emotion. Females tended to be more accurate in emotion identification than males. Voice quality parameters played a role in emotion identification in both genders. The emotional content of the samples was best conveyed by nonsense sentences, better than by prolonged vowels or shared native language of the speakers and participants. Thus, vocal non-verbal communication tends to affect the interpretation of emotion even in the absence of language. The emotional stimuli were better recognized from visual stimuli than auditory stimuli by both genders. Visual information about speech may not be connected to the language; instead, it may be based on the human ability to understand the kinetic movements in speech production more readily than the characteristics of the acoustic cues.

  15. Retinal eccentricity effects on reaction time to imagined stimuli.

    PubMed

    Marzi, C A; Mancini, F; Metitieri, T; Savazzi, S

    2006-01-01

    To cast light on the possible neural substrate of visual imagery we tested normal participants and one hemianopic patient on simple reaction time (RT) to real and imagined visual stimuli. In one experiment participants were to detect as quickly as possible a luminous square presented at one out of two different retinal eccentricities. A well known effect with visual stimuli is that RT is slower for peripheral versus central stimuli. We found that imagined stimuli showed an eccentricity effect similar to that obtained with real stimuli. However, this was not the case in a patient with a hemianopic visual field loss (quadrantanopia) as a result of damage to the optic radiation. Even though the patient showed no difficulty in imaging stimuli in the affected hemifield she did not show an eccentricity effect as was the case in her intact side. In a second experiment, normal participants showed faster RT to stimuli of larger size with either real or imagined stimuli. Overall, these results show that visual perception and imagination share a similar visuotopic organisation that is disrupted following deafferentation of the visual cortex.

  16. Private Stimuli, Covert Responses, and Private Events: Conceptual Remarks

    ERIC Educational Resources Information Center

    Tourinho, E. Z.

    2006-01-01

    In this article, I discuss the concepts of "private stimuli," "covert responses," and "private events," emphasizing three aspects: the conditions under which private stimuli may acquire discriminative functions to verbal responses, the conditions of unobservability of covert responses, and the complexity of events or phenomena described as…

  17. Attentional Capture by Emotional Stimuli Is Modulated by Semantic Processing

    ERIC Educational Resources Information Center

    Huang, Yang-Ming; Baddeley, Alan; Young, Andrew W.

    2008-01-01

    The attentional blink paradigm was used to examine whether emotional stimuli always capture attention. The processing requirement for emotional stimuli in a rapid sequential visual presentation stream was manipulated to investigate the circumstances under which emotional distractors capture attention, as reflected in an enhanced attentional blink…

  18. THE RECOGNITION OF TRI-DIMENSIONAL VISUAL STIMULI,

    DTIC Science & Technology

    dimensions: form , color , and crosshatching. There were in all 10 different forms, 10 different colors, and 4 different crosshatchings. A tri...test stimuli. For each of the 80 test stimuli Ss had to judge whether its form , color , and crosshatching was or was not the same as the form , color , and

  19. Freeze or Flee? Negative Stimuli Elicit Selective Responding

    ERIC Educational Resources Information Center

    Estes, Zachary; Verges, Michelle

    2008-01-01

    Humans preferentially attend to negative stimuli. A consequence of this automatic vigilance for negative valence is that negative words elicit slower responses than neutral or positive words on a host of cognitive tasks. Some researchers have speculated that negative stimuli elicit a general suppression of motor activity, akin to the freezing…

  20. Inverse Target- and Cue-Priming Effects of Masked Stimuli

    ERIC Educational Resources Information Center

    Mattler, Uwe

    2007-01-01

    The processing of a visual target that follows a briefly presented prime stimulus can be facilitated if prime and target stimuli are similar. In contrast to these positive priming effects, inverse priming effects (or negative compatibility effects) have been found when a mask follows prime stimuli before the target stimulus is presented: Responses…

  1. Private Stimuli, Covert Responses, and Private Events: Conceptual Remarks

    ERIC Educational Resources Information Center

    Tourinho, E. Z.

    2006-01-01

    In this article, I discuss the concepts of "private stimuli," "covert responses," and "private events," emphasizing three aspects: the conditions under which private stimuli may acquire discriminative functions to verbal responses, the conditions of unobservability of covert responses, and the complexity of events or phenomena described as…

  2. Messages as Experimental Stimuli: Design, Analysis, and Inference.

    ERIC Educational Resources Information Center

    Slater, Michael D.

    The use of messages as experimental stimuli brings with it problems regarding the interpretability and generalizability of findings. Some psychologists and communication researchers have argued that message stimuli must be treated as random effects. A review of the literature examined data regarding experimental designs used in recent…

  3. Inverse Target- and Cue-Priming Effects of Masked Stimuli

    ERIC Educational Resources Information Center

    Mattler, Uwe

    2007-01-01

    The processing of a visual target that follows a briefly presented prime stimulus can be facilitated if prime and target stimuli are similar. In contrast to these positive priming effects, inverse priming effects (or negative compatibility effects) have been found when a mask follows prime stimuli before the target stimulus is presented: Responses…

  4. Freeze or Flee? Negative Stimuli Elicit Selective Responding

    ERIC Educational Resources Information Center

    Estes, Zachary; Verges, Michelle

    2008-01-01

    Humans preferentially attend to negative stimuli. A consequence of this automatic vigilance for negative valence is that negative words elicit slower responses than neutral or positive words on a host of cognitive tasks. Some researchers have speculated that negative stimuli elicit a general suppression of motor activity, akin to the freezing…

  5. Sex Differences in Response to Visual Sexual Stimuli: A Review

    PubMed Central

    Rupp, Heather A.; Wallen, Kim

    2009-01-01

    This article reviews what is currently known about how men and women respond to the presentation of visual sexual stimuli. While the assumption that men respond more to visual sexual stimuli is generally empirically supported, previous reports of sex differences are confounded by the variable content of the stimuli presented and measurement techniques. We propose that the cognitive processing stage of responding to sexual stimuli is the first stage in which sex differences occur. The divergence between men and women is proposed to occur at this time, reflected in differences in neural activation, and contribute to previously reported sex differences in downstream peripheral physiological responses and subjective reports of sexual arousal. Additionally, this review discusses factors that may contribute to the variability in sex differences observed in response to visual sexual stimuli. Factors include participant variables, such as hormonal state and socialized sexual attitudes, as well as variables specific to the content presented in the stimuli. Based on the literature reviewed, we conclude that content characteristics may differentially produce higher levels of sexual arousal in men and women. Specifically, men appear more influenced by the sex of the actors depicted in the stimuli while women’s response may differ with the context presented. Sexual motivation, perceived gender role expectations, and sexual attitudes are possible influences. These differences are of practical importance to future research on sexual arousal that aims to use experimental stimuli comparably appealing to men and women and also for general understanding of cognitive sex differences. PMID:17668311

  6. Exploring Visuomotor Priming Following Biological and Non-Biological Stimuli

    ERIC Educational Resources Information Center

    Gowen, E.; Bradshaw, C.; Galpin, A.; Lawrence, A.; Poliakoff, E.

    2010-01-01

    Observation of human actions influences the observer's own motor system, termed visuomotor priming, and is believed to be caused by automatic activation of mirror neurons. Evidence suggests that priming effects are larger for biological (human) as opposed to non-biological (object) stimuli and enhanced when viewing stimuli in mirror compared to…

  7. Identity Matching-to-Sample with Olfactory Stimuli in Rats

    ERIC Educational Resources Information Center

    Pena, Tracy; Pitts, Raymond C.; Galizio, Mark

    2006-01-01

    Identity matching-to-sample has been difficult to demonstrate in rats, but most studies have used visual stimuli. There is evidence that rats can acquire complex forms of olfactory stimulus control, and the present study explored the possibility that identity matching might be facilitated in rats if olfactory stimuli were used. Four rats were…

  8. Attentional capture by emotional stimuli is modulated by semantic processing.

    PubMed

    Huang, Yang-Ming; Baddeley, Alan; Young, Andrew W

    2008-04-01

    The attentional blink paradigm was used to examine whether emotional stimuli always capture attention. The processing requirement for emotional stimuli in a rapid sequential visual presentation stream was manipulated to investigate the circumstances under which emotional distractors capture attention, as reflected in an enhanced attentional blink effect. Emotional distractors did not cause more interference than neutral distractors on target identification when perceptual or phonological processing of stimuli was required, showing that emotional processing is not as automatic as previously hypothesized. Only when semantic processing of stimuli was required did emotional distractors capture more attention than neutral distractors and increase attentional blink magnitude. Combining the results from 5 experiments, the authors conclude that semantic processing can modulate the attentional capture effect of emotional stimuli.

  9. Emotional attention for erotic stimuli: Cognitive and brain mechanisms.

    PubMed

    Sennwald, Vanessa; Pool, Eva; Brosch, Tobias; Delplanque, Sylvain; Bianchi-Demicheli, Francesco; Sander, David

    2016-06-01

    It has long been posited that among emotional stimuli, only negative threatening information modulates early shifts of attention. However, in the last few decades there has been an increase in research showing that attention is also involuntarily oriented toward positive rewarding stimuli such as babies, food, and erotic information. Because reproduction-related stimuli have some of the largest effects among positive stimuli on emotional attention, the present work reviews recent literature and proposes that the cognitive and cerebral mechanisms underlying the involuntarily attentional orientation toward threat-related information are also sensitive to erotic information. More specifically, the recent research suggests that both types of information involuntarily orient attention due to their concern relevance and that the amygdala plays an important role in detecting concern-relevant stimuli, thereby enhancing perceptual processing and influencing emotional attentional processes.

  10. Rapid temporal recalibration is unique to audiovisual stimuli.

    PubMed

    Van der Burg, Erik; Orchard-Mills, Emily; Alais, David

    2015-01-01

    Following prolonged exposure to asynchronous multisensory signals, the brain adapts to reduce the perceived asynchrony. Here, in three separate experiments, participants performed a synchrony judgment task on audiovisual, audiotactile or visuotactile stimuli and we used inter-trial analyses to examine whether temporal recalibration occurs rapidly on the basis of a single asynchronous trial. Even though all combinations used the same subjects, task and design, temporal recalibration occurred for audiovisual stimuli (i.e., the point of subjective simultaneity depended on the preceding trial's modality order), but none occurred when the same auditory or visual event was combined with a tactile event. Contrary to findings from prolonged adaptation studies showing recalibration for all three combinations, we show that rapid, inter-trial recalibration is unique to audiovisual stimuli. We conclude that recalibration occurs at two different timescales for audiovisual stimuli (fast and slow), but only on a slow timescale for audiotactile and visuotactile stimuli.

  11. Optimal Decision Stimuli for Risky Choice Experiments: An Adaptive Approach

    PubMed Central

    Cavagnaro, Daniel R.; Gonzalez, Richard; Myung, Jay I.; Pitt, Mark A.

    2014-01-01

    Collecting data to discriminate between models of risky choice requires careful selection of decision stimuli. Models of decision making aim to predict decisions across a wide range of possible stimuli, but practical limitations force experimenters to select only a handful of them for actual testing. Some stimuli are more diagnostic between models than others, so the choice of stimuli is critical. This paper provides the theoretical background and a methodological framework for adaptive selection of optimal stimuli for discriminating among models of risky choice. The approach, called Adaptive Design Optimization (ADO), adapts the stimulus in each experimental trial based on the results of the preceding trials. We demonstrate the validity of the approach with simulation studies aiming to discriminate Expected Utility, Weighted Expected Utility, Original Prospect Theory, and Cumulative Prospect Theory models. PMID:24532856

  12. Exploring visuomotor priming following biological and non-biological stimuli.

    PubMed

    Gowen, E; Bradshaw, C; Galpin, A; Lawrence, A; Poliakoff, E

    2010-12-01

    Observation of human actions influences the observer's own motor system, termed visuomotor priming, and is believed to be caused by automatic activation of mirror neurons. Evidence suggests that priming effects are larger for biological (human) as opposed to non-biological (object) stimuli and enhanced when viewing stimuli in mirror compared to anatomical orientation. However, there is conflicting evidence concerning the extent of differences between biological and non-biological stimuli, which may be due to stimulus related confounds. Over three experiments, we compared how visuomotor priming for biological and non-biological stimuli was affected over views, over time and when attention to the moving stimulus was manipulated. The results indicated that the strength of priming for the two stimulus types was dependent on attentional location and load. This highlights that visuomotor priming is not an automatic process and provides a possible explanation for conflicting evidence regarding the differential effects of biological and non-biological stimuli.

  13. Hydrolytic enzymes conjugated to quantum dots mostly retain whole catalytic activity.

    PubMed

    Iyer, Aditya; Chandra, Anil; Swaminathan, Rajaram

    2014-09-01

    Tagging a luminescent quantum dot (QD) with a biological like enzyme (Enz) creates value-added entities like quantum dot-enzyme bioconjugates (QDEnzBio) that find utility as sensors to detect glucose or beacons to track enzymes in vivo. For such applications, it is imperative that the enzyme remains catalytically active while the quantum dot is luminescent in the bioconjugate. A critical feature that dictates this is the quantum dot-enzyme linkage chemistry. Previously such linkages have put constraints on polypeptide chain dynamics or hindered substrate diffusion to active site, seriously undermining enzyme catalytic activity. In this work we address this issue using avidin-biotin linkage chemistry together with a flexible spacer to conjugate enzyme to quantum dot. The catalytic activity of three biotinylated hydrolytic enzymes, namely, hen egg white lysozyme (HEWL), alkaline phosphatase (ALP) and acetylcholinesterase (AChE) was investigated post-conjugation to streptavidin linked quantum dot for multiple substrate concentrations and varying degrees of biotinylation. We demonstrate that all enzymes retain full catalytic activity in the quantum dot-enzyme bioconjugates in comparison to biotinylated enzyme alone. However, unlike alkaline phosphatase and acetylcholinesterase, the catalytic activity of hen egg white lysozyme was observed to be increasingly susceptible to ionic strength of medium with rising level of biotinylation. This susceptibility was attributed to arise from depletion of positive charge from lysine amino groups after biotinylation. We reasoned that avidin-biotin linkage in the presence of a flexible seven atom spacer between biotin and enzyme poses no constraints to enzyme structure/dynamics enabling retention of full enzyme activity. Overall our results demonstrate for the first time that streptavidin-biotin chemistry can yield quantum dot enzyme bioconjugates that retain full catalytic activity as native enzyme. Copyright © 2014 Elsevier B

  14. Distributed and Dynamic Neural Encoding of Multiple Motion Directions of Transparently Moving Stimuli in Cortical Area MT

    PubMed Central

    Xiao, Jianbo

    2015-01-01

    Segmenting visual scenes into distinct objects and surfaces is a fundamental visual function. To better understand the underlying neural mechanism, we investigated how neurons in the middle temporal cortex (MT) of macaque monkeys represent overlapping random-dot stimuli moving transparently in slightly different directions. It has been shown that the neuronal response elicited by two stimuli approximately follows the average of the responses elicited by the constituent stimulus components presented alone. In this scheme of response pooling, the ability to segment two simultaneously presented motion directions is limited by the width of the tuning curve to motion in a single direction. We found that, although the population-averaged neuronal tuning showed response averaging, subgroups of neurons showed distinct patterns of response tuning and were capable of representing component directions that were separated by a small angle—less than the tuning width to unidirectional stimuli. One group of neurons preferentially represented the component direction at a specific side of the bidirectional stimuli, weighting one stimulus component more strongly than the other. Another group of neurons pooled the component responses nonlinearly and showed two separate peaks in their tuning curves even when the average of the component responses was unimodal. We also show for the first time that the direction tuning of MT neurons evolved from initially representing the vector-averaged direction of slightly different stimuli to gradually representing the component directions. Our results reveal important neural processes underlying image segmentation and suggest that information about slightly different stimulus components is computed dynamically and distributed across neurons. SIGNIFICANCE STATEMENT Natural scenes often contain multiple entities. The ability to segment visual scenes into distinct objects and surfaces is fundamental to sensory processing and is crucial for

  15. Distributed and Dynamic Neural Encoding of Multiple Motion Directions of Transparently Moving Stimuli in Cortical Area MT.

    PubMed

    Xiao, Jianbo; Huang, Xin

    2015-12-09

    Segmenting visual scenes into distinct objects and surfaces is a fundamental visual function. To better understand the underlying neural mechanism, we investigated how neurons in the middle temporal cortex (MT) of macaque monkeys represent overlapping random-dot stimuli moving transparently in slightly different directions. It has been shown that the neuronal response elicited by two stimuli approximately follows the average of the responses elicited by the constituent stimulus components presented alone. In this scheme of response pooling, the ability to segment two simultaneously presented motion directions is limited by the width of the tuning curve to motion in a single direction. We found that, although the population-averaged neuronal tuning showed response averaging, subgroups of neurons showed distinct patterns of response tuning and were capable of representing component directions that were separated by a small angle--less than the tuning width to unidirectional stimuli. One group of neurons preferentially represented the component direction at a specific side of the bidirectional stimuli, weighting one stimulus component more strongly than the other. Another group of neurons pooled the component responses nonlinearly and showed two separate peaks in their tuning curves even when the average of the component responses was unimodal. We also show for the first time that the direction tuning of MT neurons evolved from initially representing the vector-averaged direction of slightly different stimuli to gradually representing the component directions. Our results reveal important neural processes underlying image segmentation and suggest that information about slightly different stimulus components is computed dynamically and distributed across neurons. Natural scenes often contain multiple entities. The ability to segment visual scenes into distinct objects and surfaces is fundamental to sensory processing and is crucial for generating the perception of our

  16. A quantum dot in topological insulator nanofilm.

    PubMed

    Herath, Thakshila M; Hewageegana, Prabath; Apalkov, Vadym

    2014-03-19

    We introduce a quantum dot in topological insulator nanofilm as a bump at the surface of the nanofilm. Such a quantum dot can localize an electron if the size of the dot is large enough, ≳5 nm. The quantum dot in topological insulator nanofilm has states of two types, which belong to two ('conduction' and 'valence') bands of the topological insulator nanofilm. We study the energy spectra of such defined quantum dots. We also consider intraband and interband optical transitions within the dot. The optical transitions of the two types have the same selection rules. While the interband absorption spectra have multi-peak structure, each of the intraband spectra has one strong peak and a few weak high frequency satellites.

  17. Quantum transport in ballistic quantum dots

    NASA Astrophysics Data System (ADS)

    Ferry, D. K.; Akis, R. A.; Pivin, D. P., Jr.; Bird, J. P.; Holmberg, N.; Badrieh, F.; Vasileska, D.

    1998-10-01

    Carriers in small 3D quantum boxes take us from unintentional qquantum dots in MOSFETs (arising from the doping fluctuations) tto single-electron quantum dots in semiconductor hheterostructures. In between these two extremes are the realm of oopen, ballistic quantum dots, in which the transport can be quite regular. Several issues must be considered in treating the transport in these dots, among which are: (1) phase coherence within the dot; (2) the transition between semi-classical and fully quantum transport, (3) the role of the contacts, vis-à-vis the fabricated boundaries, and (4) the actual versus internal boundaries. In this paper, we discuss these issues, including the primary observables in experiment, the intrinsic nature of oscillatory behavior in magnetic field and dot size, and the connection to semi-classical transport emphasizing the importance of the filtering by the input (and output) quantum point contacts.

  18. Dot-in-Well Quantum-Dot Infrared Photodetectors

    NASA Technical Reports Server (NTRS)

    Gunapala, Sarath; Bandara, Sumith; Ting, David; Hill, cory; Liu, John; Mumolo, Jason; Chang, Yia Chung

    2008-01-01

    Dot-in-well (DWELL) quantum-dot infrared photodetectors (QDIPs) [DWELL-QDIPs] are subjects of research as potentially superior alternatives to prior QDIPs. Heretofore, there has not existed a reliable method for fabricating quantum dots (QDs) having precise, repeatable dimensions. This lack has constituted an obstacle to the development of uniform, high-performance, wavelength-tailorable QDIPs and of focal-plane arrays (FPAs) of such QDIPs. However, techniques for fabricating quantum-well infrared photodetectors (QWIPs) having multiple-quantum- well (MQW) structures are now well established. In the present research on DWELL-QDIPs, the arts of fabrication of QDs and QWIPs are combined with a view toward overcoming the deficiencies of prior QDIPs. The longer-term goal is to develop focal-plane arrays of radiationhard, highly uniform arrays of QDIPs that would exhibit high performance at wavelengths from 8 to 15 m when operated at temperatures between 150 and 200 K. Increasing quantum efficiency is the key to the development of competitive QDIP-based FPAs. Quantum efficiency can be increased by increasing the density of QDs and by enhancing infrared absorption in QD-containing material. QDIPs demonstrated thus far have consisted, variously, of InAs islands on GaAs or InAs islands in InGaAs/GaAs wells. These QDIPs have exhibited low quantum efficiencies because the numbers of QD layers (and, hence, the areal densities of QDs) have been small typically five layers in each QDIP. The number of QD layers in such a device must be thus limited to prevent the aggregation of strain in the InAs/InGaAs/GaAs non-lattice- matched material system. The approach being followed in the DWELL-QDIP research is to embed In- GaAs QDs in GaAs/AlGaAs multi-quantum- well (MQW) structures (see figure). This material system can accommodate a large number of QD layers without excessive lattice-mismatch strain and the associated degradation of photodetection properties. Hence, this material

  19. Plasmonic quantum dot solar concentrator

    NASA Astrophysics Data System (ADS)

    Chandra, S.; Ahmed, H.; Doran, J.; McCormack, S. J.

    2017-02-01

    The quantum dot solar concentrator optical efficiency is undermined by the parameters of re-absorption, scattering, and escape cone losses. These losses can be address through enhancing quantum dot (QDs) absorption and emission. This have been achieved through plasmonic coupling between QDs and gold nanoparticles (Au NPs). The plasmonic composite of various concertation of QDs and Au NPs were studied. The spacing between QDs and Au NPs is controlled through concentration distribution of both QD and Au NPs in the plasmonic composite, and it showed a significant increase in absorption and which is more pronounced for higher spectral overlap of QDs and surface plasmon resonance (SPR) frequency. The optimum plasmonic coupling showed a 17 % increase in the fluorescence emission for QDs in plasmonic composite. The results have shown significant enhancement in absorption, fluorescence emission for the p-QDSC.

  20. Quantitative multiplexed quantum dot immunohistochemistry

    SciTech Connect

    Sweeney, E.; Ward, T.H.; Gray, N.; Womack, C.; Jayson, G.; Hughes, A.; Dive, C.; Byers, R.

    2008-09-19

    Quantum dots are photostable fluorescent semiconductor nanocrystals possessing wide excitation and bright narrow, symmetrical, emission spectra. These characteristics have engendered considerable interest in their application in multiplex immunohistochemistry for biomarker quantification and co-localisation in clinical samples. Robust quantitation allows biomarker validation, and there is growing need for multiplex staining due to limited quantity of clinical samples. Most reported multiplexed quantum dot staining used sequential methods that are laborious and impractical in a high-throughput setting. Problems associated with sequential multiplex staining have been investigated and a method developed using QDs conjugated to biotinylated primary antibodies, enabling simultaneous multiplex staining with three antibodies. CD34, Cytokeratin 18 and cleaved Caspase 3 were triplexed in tonsillar tissue using an 8 h protocol, each localised to separate cellular compartments. This demonstrates utility of the method for biomarker measurement enabling rapid measurement of multiple co-localised biomarkers on single paraffin tissue sections, of importance for clinical trial studies.

  1. Brightness-equalized quantum dots

    PubMed Central

    Lim, Sung Jun; Zahid, Mohammad U.; Le, Phuong; Ma, Liang; Entenberg, David; Harney, Allison S.; Condeelis, John; Smith, Andrew M.

    2015-01-01

    As molecular labels for cells and tissues, fluorescent probes have shaped our understanding of biological structures and processes. However, their capacity for quantitative analysis is limited because photon emission rates from multicolour fluorophores are dissimilar, unstable and often unpredictable, which obscures correlations between measured fluorescence and molecular concentration. Here we introduce a new class of light-emitting quantum dots with tunable and equalized fluorescence brightness across a broad range of colours. The key feature is independent tunability of emission wavelength, extinction coefficient and quantum yield through distinct structural domains in the nanocrystal. Precise tuning eliminates a 100-fold red-to-green brightness mismatch of size-tuned quantum dots at the ensemble and single-particle levels, which substantially improves quantitative imaging accuracy in biological tissue. We anticipate that these materials engineering principles will vastly expand the optical engineering landscape of fluorescent probes, facilitate quantitative multicolour imaging in living tissue and improve colour tuning in light-emitting devices. PMID:26437175

  2. Brightness-equalized quantum dots.

    PubMed

    Lim, Sung Jun; Zahid, Mohammad U; Le, Phuong; Ma, Liang; Entenberg, David; Harney, Allison S; Condeelis, John; Smith, Andrew M

    2015-10-05

    As molecular labels for cells and tissues, fluorescent probes have shaped our understanding of biological structures and processes. However, their capacity for quantitative analysis is limited because photon emission rates from multicolour fluorophores are dissimilar, unstable and often unpredictable, which obscures correlations between measured fluorescence and molecular concentration. Here we introduce a new class of light-emitting quantum dots with tunable and equalized fluorescence brightness across a broad range of colours. The key feature is independent tunability of emission wavelength, extinction coefficient and quantum yield through distinct structural domains in the nanocrystal. Precise tuning eliminates a 100-fold red-to-green brightness mismatch of size-tuned quantum dots at the ensemble and single-particle levels, which substantially improves quantitative imaging accuracy in biological tissue. We anticipate that these materials engineering principles will vastly expand the optical engineering landscape of fluorescent probes, facilitate quantitative multicolour imaging in living tissue and improve colour tuning in light-emitting devices.

  3. Photovoltaic Current in Quantum Dots

    NASA Astrophysics Data System (ADS)

    Switkes, M.; Marcus, C. M.; Campman, K.; Gossard, A. C.

    1998-03-01

    We investigate the DC photovoltaic current, I_pv, due to coherent ``pumping'' in open ( g >= e^2/h ) quantum dots with radio-frequency modulation of the confining potential(B. Spivak, F. Zhou, and M. T. Beal Monod, Phys. Rev. B 51), p. 13226 (1995). I_pv is on the order of 20 pA≈ 10ef for a modulation frequency f = 15 MHz. The photovoltaic current exhibits mesoscopic fluctuations with magnetic field and with the static shape of the confining potential which do not appear to be correlated with fluctuations in the conductance of the dot. The photovoltaic current induced by pumping with two independent shape distortion gates depends on their relative phase; the relationship of this phase to time reversal symmetry is investigated with a view toward defining a generalized Landauer-Büttiker relation.

  4. Exploring Combinations of Different Color and Facial Expression Stimuli for Gaze-Independent BCIs

    PubMed Central

    Chen, Long; Jin, Jing; Daly, Ian; Zhang, Yu; Wang, Xingyu; Cichocki, Andrzej

    2016-01-01

    Background: Some studies have proven that a conventional visual brain computer interface (BCI) based on overt attention cannot be used effectively when eye movement control is not possible. To solve this problem, a novel visual-based BCI system based on covert attention and feature attention has been proposed and was called the gaze-independent BCI. Color and shape difference between stimuli and backgrounds have generally been used in examples of gaze-independent BCIs. Recently, a new paradigm based on facial expression changes has been presented, and obtained high performance. However, some facial expressions were so similar that users couldn't tell them apart, especially when they were presented at the same position in a rapid serial visual presentation (RSVP) paradigm. Consequently, the performance of the BCI is reduced. New Method: In this paper, we combined facial expressions and colors to optimize the stimuli presentation in the gaze-independent BCI. This optimized paradigm was called the colored dummy face pattern. It is suggested that different colors and facial expressions could help users to locate the target and evoke larger event-related potentials (ERPs). In order to evaluate the performance of this new paradigm, two other paradigms were presented, called the gray dummy face pattern and the colored ball pattern. Comparison with Existing Method(s): The key point that determined the value of the colored dummy faces stimuli in BCI systems was whether the dummy face stimuli could obtain higher performance than gray faces or colored balls stimuli. Ten healthy participants (seven male, aged 21–26 years, mean 24.5 ± 1.25) participated in our experiment. Online and offline results of four different paradigms were obtained and comparatively analyzed. Results: The results showed that the colored dummy face pattern could evoke higher P300 and N400 ERP amplitudes, compared with the gray dummy face pattern and the colored ball pattern. Online results showed that

  5. Ultralow Noise Monolithic Quantum Dot Photonic Oscillators

    DTIC Science & Technology

    2013-10-28

    laser, the dual-mode quantum dot laser, and the optically- injected quantum dot distributed feedback laser. The key milestones achieved were: 1.) the...distributed feedback device using optical injection to generate microwave, mm- wave and THz signals, and 5.) the generation of relaxation oscillations over...a continuous 5 octaves (below 1 GHz to 40 GHz) in an optically- injected quantum dot laser. UU N/A N/A N/A 100-200 words 15 Shannon Denetchiley (505

  6. Improved Dot Diffusion For Image Halftoning

    DTIC Science & Technology

    1999-01-01

    The dot diffusion method for digital halftoning has the advantage of parallelism unlike the error diffusion method. The method was recently improved...by optimization of the so-called class matrix so that the resulting halftones are comparable to the error diffused halftones . In this paper we will...first review the dot diffusion method. Previously, 82 class matrices were used for dot diffusion method. A problem with this size of class matrix is

  7. Stimuli-Responsive Mechanically Adaptive Polymer Nanocomposites

    PubMed Central

    Shanmuganathan, Kadhiravan; Capadona, Jeffrey R.; Rowan, Stuart J.; Weder, Christoph

    2010-01-01

    A new series of biomimetic stimuli-responsive nanocomposites, which change their mechanical properties upon exposure to physiological conditions, was prepared and investigated. The materials were produced by introducing percolating networks of cellulose nanofibers or “whiskers” derived from tunicates into poly(vinyl acetate) (PVAc), poly(butyl methacrylate) (PBMA), and blends of these polymers, with the objective of determining how the hydrophobicity and glass-transition temperature (Tg) of the polymer matrix affect the water-induced mechanically dynamic behavior. Below the Tg (~60–70 °C), the incorporation of whiskers (15.1 – 16.5% v/v) modestly increased the tensile storage moduli (E′) of the neat polymers from 0.6 to 3.8 GPa (PBMA) and from 2 to 5.2 GPa (PVAc). The reinforcement was much more dramatic above Tg, where E′ increased from 1.2 to 690 MPa (PVAc) and ~1 to 1.1 GPa (PBMA). Upon exposure to physiological conditions (immersion in artificial cerebrospinal fluid, ACSF, at 37 °C) all materials displayed a decrease of E′. The most significant contrast was seen in PVAc; for example the E′ of a 16.5% v/v PVAc/whisker nanocomposite decreased from 5.2 GPa to 12.7 MPa. Only a modest modulus decrease was measured for PBMA/whisker nanocomposite; here the E′ of a 15.1% v/v PBMA/whisker nanocomposite decreased from 3.8 to 1.2 GPa. A systematic investigation revealed that the magnitude of the mechanical contrast was related to the degree of swelling with ACSF, which was shown to increase with whisker content, temperature, and polarity of the matrix (PVAc > PBMA). The mechanical morphing of the new materials can be described in the framework of both the percolation and Halpin-Kardos models for nanocomposite reinforcement, and is the result of changing interactions among the nanoparticles and plasticization of the matrix upon swelling. PMID:20305827

  8. How Attention Modulates Encoding of Dynamic Stimuli

    PubMed Central

    Oren, Noga; Shapira-Lichter, Irit; Lerner, Yulia; Tarrasch, Ricardo; Hendler, Talma; Giladi, Nir; Ash, Elissa L.

    2016-01-01

    When encoding a real-life, continuous stimulus, the same neural circuits support processing and integration of prior as well as new incoming information. This ongoing interplay is modulated by attention, and is evident in regions such as the prefrontal cortex section of the task positive network (TPN), and in the posterior cingulate cortex (PCC), a hub of the default mode network (DMN). Yet the exact nature of such modulation is still unclear. To investigate this issue, we utilized an fMRI task that employed movies as the encoded stimuli and manipulated attentional load via an easy or hard secondary task that was performed simultaneously with encoding. Results showed increased intersubject correlation (inter-SC) levels when encoding movies in a condition of high, as compared to low attentional load. This was evident in bilateral ventrolateral and dorsomedial prefrontal cortices and the dorsal PCC (dPCC). These regions became more attuned to the combination of the movie and the secondary task as the attentional demand of the latter increased. Activation analyses revealed that at higher load the prefrontal TPN regions were more activated, whereas the dPCC was more deactivated. Attentional load also influenced connectivity within and between the networks. At high load the dPCC was anti-correlated to the prefrontal regions, which were more functionally coherent amongst themselves. Finally and critically, greater inter-SC in the dPCC at high load during encoding predicted lower memory strength when that information was retrieved. This association between inter-SC levels and memory strength suggest that as attentional demands increased, the dPCC was more attuned to the secondary task at the expense of the encoded stimulus, thus weakening memory for the encoded stimulus. Together, our findings show that attentional load modulated the function of core TPN and DMN regions. Furthermore, the observed relationship between memory strength and the modulation of the dPCC points

  9. The Presentation of Olfactory-Trigeminal Mixed Stimuli Increases the Response to Subsequent Olfactory Stimuli.

    PubMed

    Walliczek-Dworschak, Ute; Poncelet, Johan; Baum, Daniel; Baki, Ramona; Sinding, Charlotte; Warr, Jonathan; Hummel, Thomas

    2017-01-09

    The aim of this study was to evaluate the effect of (1) the addition of trigeminal stimuli to an olfactory stimulus and (2) the congruence in the odorous mixture after repeated odor presentation. Twenty-five normosmic volunteers were enrolled and presented stimulation blocks, consisting of three habituation stimuli (H) (orange odor), one dishabituation (DH) (control condition, orange odor; congruent condition, orange odor + CO2; incongruent condition, orange odor + l-isopulegol), and one dishabituated stimulus (D) (orange odor). Olfactory event-related potentials were analyzed. Response amplitudes differed significantly in the incongruent condition (N1P2 between H3 and D; peak to peak N1P2 at electrode positions Cz, Fz, and Pz; response amplitudes between H3 and DH). The addition of CO2 modified the perception of orange odor, pronouncing a fruity note, whereas the addition of l-isopulegol as a DH pronounced the l-isopulegol note. This study provides evidence that incongruent trigeminal-olfactory stimulants increase the response to subsequent olfactory stimulus.

  10. Few-electron quantum dots

    NASA Astrophysics Data System (ADS)

    Kouwenhoven, L. P.; Austing, D. G.; Tarucha, S.

    2001-06-01

    We review some electron transport experiments on few-electron, vertical quantum dot devices. The measurement of current versus source-drain voltage and gate voltage is used as a spectroscopic tool to investigate the energy characteristics of interacting electrons confined to a small region in a semiconducting material. Three energy scales are distinguished: the single-particle states, which are discrete due to the confinement involved; the direct Coulomb interaction between electron charges on the dot; and the exchange interaction between electrons with parallel spins. To disentangle these energies, a magnetic field is used to reorganize the occupation of electrons over the single-particle states and to induce changes in the spin states. We discuss the interactions between small numbers of electrons (between 1 and 20) using the simplest possible models. Nevertheless, these models consistently describe a large set of experiments. Some of the observations resemble similar phenomena in atomic physics, such as shell structure and periodic table characteristics, Hund's rule, and spin singlet and triplet states. The experimental control, however, is much larger than for atoms: with one device all the artificial elements can be studied by adding electrons to the quantum dot when changing the gate voltage.

  11. Emotional enhancement of immediate memory: Positive pictorial stimuli are better recognized than neutral or negative pictorial stimuli

    PubMed Central

    Chainay, Hanna; Michael, George A.; Vert-pré, Mélissa; Landré, Lionel; Plasson, Amandine

    2012-01-01

    We examined emotional memory enhancement (EEM) for negative and positive pictures while manipulating encoding and retrieval conditions. Two groups of 40 participants took part in this study. Both groups performed immediate implicit (categorization task) and explicit (recognition task) retrieval, but for one group the tasks were preceded by incidental encoding and for the other group by intentional encoding. As indicated by the sensitivity index (dʹ), after incidental encoding positive stimuli were easier to recognize than negative and neutral stimuli. Participants’ response criterion was more liberal for negative stimuli than for both positive and neutral ones, independent of encoding condition. In the implicit retrieval task, participants were slower in categorizing positive than negative and neutral stimuli. However, the priming effect was larger for emotional than for neutral stimuli. These results are discussed in the context of the idea that the effect of emotion on immediate memory enhancement may depend on the intentionality to encode and retrieve information. PMID:22956991

  12. DOTS in China - removing barriers or moving barriers?

    PubMed

    Xu, B; Dong, H J; Zhao, Q; Bogg, L

    2006-09-01

    In 1992, China initiated its modern National TB Control Programme (NTP) with DOTS strategy through a project funded by a World Bank loan. Key motives for the revised NTP-DOTS were to reduce financial barriers to patients by removing fee charges for diagnosis and treatment, and to address regressive suppliers' incentives for appropriate referrals. This study aims to assess to what extent China's NTP subsidies are achieving the objective of removing financial barriers to care in terms of patients' expenditure. One county with NTP-DOTS - Jianhu - and one county without - Funing - were selected. A cohort of 493 tuberculosis patients newly diagnosed in 2002 was interviewed by questionnaire. The main outcome measure was tuberculosis patients' expenditure on medical care and transportation/accommodation from the onset of symptoms to treatment completion. During the follow-up period, Funing started implementing NTP-DOTS, which offered a possibility of longitudinal comparison both between counties and within county. Ninety-four per cent (465/493) of subjects were followed-up. The mean total patient's expenditure on TB medical care and transportation/accommodation before TB diagnosis was higher in Jianhu than in Funing (715 vs. 256CNY), whereas it was higher in Funing (835 vs. 157CNY) after diagnosis. After implementing NTP-DOTS in Funing, expenditure after diagnosis decreased slightly whereas expenditure before diagnosis increased remarkably. We found that the market incentive structures in the reformed health system appear to have a stronger regressive effect and may result in prolonged delays before effective treatment can be given. We believe that doctors adapt to new incentive structures, with bonus income being linked to the hospitals' fee-for-service revenue, and find new ways of keeping revenue at the old levels, which reduce or eliminate the intended effect of the subsidies. TB patients suffer a heavy economic burden even in counties where NTP-DOTS treatment is

  13. Optical Nonlinearities and Ultrafast Carrier Dynamics in Semiconductor Quantum Dots

    SciTech Connect

    Klimov, V.; McBranch, D.; Schwarz, C.

    1998-08-10

    Low-dimensional semiconductors have attracted great interest due to the potential for tailoring their linear and nonlinear optical properties over a wide-range. Semiconductor nanocrystals (NC's) represent a class of quasi-zero-dimensional objects or quantum dots. Due to quantum cordhement and a large surface-to-volume ratio, the linear and nonlinear optical properties, and the carrier dynamics in NC's are significantly different horn those in bulk materials. napping at surface states can lead to a fast depopulation of quantized states, accompanied by charge separation and generation of local fields which significantly modifies the nonlinear optical response in NC's. 3D carrier confinement also has a drastic effect on the energy relaxation dynamics. In strongly confined NC's, the energy-level spacing can greatly exceed typical phonon energies. This has been expected to significantly inhibit phonon-related mechanisms for energy losses, an effect referred to as a phonon bottleneck. It has been suggested recently that the phonon bottleneck in 3D-confined systems can be removed due to enhanced role of Auger-type interactions. In this paper we report femtosecond (fs) studies of ultrafast optical nonlinearities, and energy relaxation and trap ping dynamics in three types of quantum-dot systems: semiconductor NC/glass composites made by high temperature precipitation, ion-implanted NC's, and colloidal NC'S. Comparison of ultrafast data for different samples allows us to separate effects being intrinsic to quantum dots from those related to lattice imperfections and interface properties.

  14. Numerical renormalization group study of a dissipative quantum dot

    NASA Astrophysics Data System (ADS)

    Glossop, M. T.; Ingersent, K.

    2007-03-01

    We study the quantum phase transition (QPT) induced by dissipation in a quantum dot device at the degeneracy point. We employ a Bose-Fermi numerical renormalization group approach [1] to study the simplest case of a spinless resonant-level model that couples the charge density on the dot to a dissipative bosonic bath with density of states B(φ)ŝ. In anticipation of future experiments [2] and to assess further the validity of theoretical techniques in this rapidly developing area, we take the conduction-electron leads to have a pseudogap density of states: ρ(φ) |φ|^r, as considered in a very recent perturbative renormalization group study [3]. We establish the conditions on r and s such that a QPT arises with increasing dissipation strength --- from a delocalized phase, where resonant tunneling leads to large charge fluctuations on the dot, to a localized phase where such fluctuations are frozen. We present results for the single-particle spectrum and the response of the system to a local electric field, extracting critical exponents that depend in general on r and s and obey hyperscaling relations. We make full comparison with results of [3] where appropriate. Supported by NSF Grant DMR-0312939. [1] M. T. Glossop and K. Ingersent, PRL 95, 067202 (2005); PRB (2006). [2] L. G. G. V. Dias da Silva, N. P. Sandler, K. Ingersent, and S. E. Ulloa, PRL 97, 096603 (2006). [3] C.-H. Chung, M. Kir'can, L. Fritz, and M. Vojta (2006).

  15. Reconfigurable quantum dot monolithic multisection passive mode-locked lasers.

    PubMed

    Xin, Y C; Li, Y; Kovanis, Vassilios; Gray, A L; Zhang, L; Lester, L F

    2007-06-11

    We investigate the dynamical response of a quantum dot photonic integrated circuit formed with a combination of eleven passive and active gain cells operating when these cells are appropriately biased as a multi-section quantum dot passively mode-locked laser. When the absorber section is judiciously positioned in the laser cavity then fundamental frequency and harmonic mode-locking at repetition rates from 7.2GHz to 51GHz are recorded. These carefully engineered multi-section configurations that include a passive wave-guide section significantly lower the pulse width up to 34% from 9.7 to 6.4 picoseconds, as well increase by 49% the peak pulsed power from 150 to 224 mW, in comparison to conventional two-section configurations that are formed on the identical device under the same average power. In addition an ultra broad operation range with pulse width below ten picoseconds is obtained with the 3rd-harmonic mode-locking configuration. A record peak power of 234 mW for quantum dot mode-locked lasers operating over 40 GHz is reported for the first time.

  16. Charge state hysteresis in semiconductor quantum dots

    SciTech Connect

    Yang, C. H.; Rossi, A. Lai, N. S.; Leon, R.; Lim, W. H.; Dzurak, A. S.

    2014-11-03

    Semiconductor quantum dots provide a two-dimensional analogy for real atoms and show promise for the implementation of scalable quantum computers. Here, we investigate the charge configurations in a silicon metal-oxide-semiconductor double quantum dot tunnel coupled to a single reservoir of electrons. By operating the system in the few-electron regime, the stability diagram shows hysteretic tunnelling events that depend on the history of the dots charge occupancy. We present a model which accounts for the observed hysteretic behaviour by extending the established description for transport in double dots coupled to two reservoirs. We demonstrate that this type of device operates like a single-electron memory latch.

  17. Shortened night sleep impairs facial responsiveness to emotional stimuli.

    PubMed

    Schwarz, Johanna F A; Popp, Roland; Haas, Jessica; Zulley, Jürgen; Geisler, Peter; Alpers, Georg W; Osterheider, Michael; Eisenbarth, Hedwig

    2013-04-01

    Sleep deprivation deteriorates mood, impairs the recognition of facial expressions, and affects the ability to regulate emotions. The present study investigated the effect of partial sleep deprivation on facial responses to emotional stimuli. Thirty-three healthy undergraduates were tested twice: after a night with (i) 8h and (ii) 4h sleep. Self-reported sleepiness and sustained attention (Psychomotor Vigilance Task) were assessed. Emotional reactivity was measured with facial Electromyogram (EMG) while participants were asked to respond with either compatible or incompatible facial muscles to emotional stimuli in order to study whether partial sleep deprivation caused slower reactions mainly in response to incompatible stimuli (due to an additional effort to suppress the compatible reaction caused by decreased inhibitory control) or in response to both compatible and incompatible stimuli. Self-reported sleepiness and reaction times in a sustained attention task significantly increased after one night of partial sleep deprivation. Facial reactions to emotional stimuli were decelerated. No significant interaction between sleep restriction and compatibility of the muscle to the picture valence could be observed. Hence, volitional facial reactions in response to emotional stimuli were slower after one night of reduced sleep, but affective inhibitory control was not significantly impaired. However, slowed facial responding to emotional stimuli may affect social interaction after sleep restriction.

  18. Facilitation of responses by task-irrelevant complex deviant stimuli.

    PubMed

    Schomaker, J; Meeter, M

    2014-05-01

    Novel stimuli reliably attract attention, suggesting that novelty may disrupt performance when it is task-irrelevant. However, under certain circumstances novel stimuli can also elicit a general alerting response having beneficial effects on performance. In a series of experiments we investigated whether different aspects of novelty--stimulus novelty, contextual novelty, surprise, deviance, and relative complexity--lead to distraction or facilitation. We used a version of the visual oddball paradigm in which participants responded to an occasional auditory target. Participants responded faster to this auditory target when it occurred during the presentation of novel visual stimuli than of standard stimuli, especially at SOAs of 0 and 200 ms (Experiment 1). Facilitation was absent for both infrequent simple deviants and frequent complex images (Experiment 2). However, repeated complex deviant images did facilitate responses to the auditory target at the 200 ms SOA (Experiment 3). These findings suggest that task-irrelevant deviant visual stimuli can facilitate responses to an unrelated auditory target in a short 0-200 millisecond time-window after presentation. This only occurs when the deviant stimuli are complex relative to standard stimuli. We link our findings to the novelty P3, which is generated under the same circumstances, and to the adaptive gain theory of the locus coeruleus-norepinephrine system (Aston-Jones and Cohen, 2005), which may explain the timing of the effects. Copyright © 2014 Elsevier B.V. All rights reserved.

  19. Dynamic characteristics of photonic crystal quantum dot lasers.

    PubMed

    Banihashemi, Mehdi; Ahmadi, Vahid

    2014-04-20

    In this paper, we analyze the dynamic characteristics of quantum dot (QD) photonic crystal lasers by solving Maxwell equations coupled to rate equations through linear susceptibility of QDs. Here, we study the effects of the quality factor of the microcavity and temperature on the delay, relaxation oscillation frequency, and output intensity of the lasers. Moreover, we investigate the dependence of the Purcell factor on temperature. We show that when the quality factor of the microcavity is so high that we can consider its linewidth as a delta function in comparison with QDs, the Purcell factor significantly drops with increasing temperature.

  20. Neural Processing of Emotional Musical and Nonmusical Stimuli in Depression

    PubMed Central

    Atchley, Ruth Ann; Chrysikou, Evangelia; Martin, Laura E.; Clair, Alicia A.; Ingram, Rick E.; Simmons, W. Kyle; Savage, Cary R.

    2016-01-01

    Background Anterior cingulate cortex (ACC) and striatum are part of the emotional neural circuitry implicated in major depressive disorder (MDD). Music is often used for emotion regulation, and pleasurable music listening activates the dopaminergic system in the brain, including the ACC. The present study uses functional MRI (fMRI) and an emotional nonmusical and musical stimuli paradigm to examine how neural processing of emotionally provocative auditory stimuli is altered within the ACC and striatum in depression. Method Nineteen MDD and 20 never-depressed (ND) control participants listened to standardized positive and negative emotional musical and nonmusical stimuli during fMRI scanning and gave subjective ratings of valence and arousal following scanning. Results ND participants exhibited greater activation to positive versus negative stimuli in ventral ACC. When compared with ND participants, MDD participants showed a different pattern of activation in ACC. In the rostral part of the ACC, ND participants showed greater activation for positive information, while MDD participants showed greater activation to negative information. In dorsal ACC, the pattern of activation distinguished between the types of stimuli, with ND participants showing greater activation to music compared to nonmusical stimuli, while MDD participants showed greater activation to nonmusical stimuli, with the greatest response to negative nonmusical stimuli. No group differences were found in striatum. Conclusions These results suggest that people with depression may process emotional auditory stimuli differently based on both the type of stimulation and the emotional content of that stimulation. This raises the possibility that music may be useful in retraining ACC function, potentially leading to more effective and targeted treatments. PMID:27284693

  1. Misperceptions of speed for chromatic and luminance grating stimuli.

    PubMed

    Burton, M P; McKeefry, D J

    2007-05-01

    Errors in the perception of speed of moving visual stimuli can occur when presented stimuli are of unequal contrast and when they appear alongside additional modifier stimuli that move at different speeds. We have examined these misperceptions for chromatic and luminance grating stimuli in order to assess to what extent these different kinds of motion cue might be utilised in the analysis of speed of moving objects. We show that the dependence on contrast of speed matching for luminance and chromatic stimuli is similar over a range of stimulus speeds greater than 4 deg/s. Differences between the contrast dependencies of speed perception for chromatic and luminance stimuli are only evident at slow speeds (< 4 deg/s) and low contrasts. The presence of modifier stimuli can directly influence the perceived speed at both high and low velocities and contrasts. This influence was found to be independent of the modifiers' chromaticity and was greatest when the modifiers were adjacent to and presented simultaneously with the test and reference stimuli. However, the modifiers were still able to induce measurable changes in perceived speed for increased separations over space and time. Taken together these results indicate that whilst differences do exist in the contrast dependencies of speed perception for chromatic and luminance stimuli, they are evident only for a narrow range of stimulus parameters (i.e. low speed and low contrast). There appears to be ample scope for interactions between chromatic and luminance contrast in speed perception where there is the capacity to pool this information over a relatively broad spatio-temporal extent.

  2. Selective inattention to anxiety-linked stimuli.

    PubMed

    Blum, G S; Barbour, J S

    1979-06-01

    prior hypnotic programming of the same three subjects was similar to Experiment 1, used an anagram approach to comparable four-letter words, except that pleasure-loaded words were introduced as a control along with filler words. Four durations of tachistoscopic exposure of the anagrams were used with each individual, and the major dependent variable was response latency measured in milliseconds. An independent measure of perceptual discriminability of the scrambled stimulus letters was obtained to isolate perceptual from cognitive aspects of the task. The results indicated that both low perceivability and high solvability increase the likelihood of response delays specifically in the presence of anxiety-linked stimuli. Experiment 3 was a nonhypnotic replication of Experiment 2, using 12 male and 13 female subjects. The potential affective loading of key anxiety and pleasure words was accomplished by structured scenarios for the Blacky pictures in which subjects were asked to place themselves as vividly as possible...

  3. The stimuli drive the response: an fMRI study of youth processing adult or child emotional face stimuli.

    PubMed

    Marusak, Hilary A; Carré, Justin M; Thomason, Moriah E

    2013-12-01

    Effective navigation of the social world relies on the correct interpretation of facial emotions. This may be particularly important in formative years. Critically, literature examining the emergence of face processing in youth (children and adolescents) has focused on the neural and behavioral correlates of processing adult faces, which are relationally different from youth participants, and whose facial expressions may convey different meaning than faces of their peers. During a functional magnetic resonance imaging (fMRI) scan, we compared concurrent neural and behavioral responses as youth (N=25) viewed validated, emotionally varied (i.e., anger, fear, happy, and neutral) adult and child face stimuli. We observed that participants made fewer errors when matching adult, compared to child, face stimuli, and that while similar brain regions were involved in processing both adult and child faces, activation in the face processing neural network was greater for adult than child faces. This was true across emotions, and also when comparing neutral adult versus neutral child faces. Additionally, a valence by stimuli-type effect was observed within the amygdala. That is, within adult face stimuli, negative and neutral face stimuli elicited the largest effects, whereas within child face stimuli, happy face stimuli elicited the largest amygdala effects. Thus, heightened engagement of the amygdala was observed for happy child and angry adult faces, which may reflect age-specific salience of select emotions in early life. This study provides evidence that the relational age of the perceived face influences neural processing in youth.

  4. Single-dot optical emission from ultralow density well-isolated InP quantum dots

    SciTech Connect

    Ugur, A.; Hatami, F.; Masselink, W. T.; Vamivakas, A. N.; Lombez, L.; Atatuere, M.

    2008-10-06

    We demonstrate a straightforward way to obtain single well-isolated quantum dots emitting in the visible part of the spectrum and characterize the optical emission from single quantum dots using this method. Self-assembled InP quantum dots are grown using gas-source molecular-beam epitaxy over a wide range of InP deposition rates, using an ultralow growth rate of about 0.01 atomic monolayers/s, a quantum-dot density of 1 dot/{mu}m{sup 2} is realized. The resulting isolated InP quantum dots embedded in an InGaP matrix are individually characterized without the need for lithographical patterning and masks on the substrate. Such low-density quantum dots show excitonic emission at around 670 nm with a linewidth limited by instrument resolution. This system is applicable as a single-photon source for applications such as quantum cryptography.

  5. Do extraverts process social stimuli differently from introverts?

    PubMed

    Fishman, Inna; Ng, Rowena; Bellugi, Ursula

    2011-01-01

    The personality trait of extraversion has been linked to the network of brain systems controlling sensitivity to cues of reward and generating approach behavior in response, but little is known about whether extraverts' neural circuits are especially sensitive to social stimuli, given their preference for social engagement. Utilizing event-related potential (ERP) methodology, this study demonstrates that variation on the extraversion dimension is associated with the extent to which social stimuli evoke enhanced allocation of attention. Specifically, higher scores on extraversion were found to be associated with higher amplitudes of the P300 component of the ERPs elicited by human faces. This finding suggests that social stimuli carry enhanced motivational significance for individuals characterized by high extraversion, and that individual differences in personality are related to meaningful individual differences in neural responses to social stimuli.

  6. The effects of startle and non-startle auditory stimuli on wrist flexion movement in Parkinson's disease.

    PubMed

    Fernandez-Del-Olmo, Miguel; Bello, Olalla; Lopez-Alonso, Virginia; Marquez, G; Sanchez, Jose A; Morenilla, Luis; Valls-Solé, Josep

    2013-08-26

    Startle stimuli lead to shorter reaction times in control subjects and Parkinson's disease (PD) patients. However, non-startle stimuli also enhance movement initiation in PD. We wanted to examine whether a startle-triggered movement would retain similar kinematic and EMG-related characteristics compared to one induced by a non-startle external cue in PD patients. In this study we investigated the electromyography pattern and the reaction time during a wrist flexion movement in response to three different stimuli: a visual imperative stimulus; visual stimulus simultaneous with a non-startle auditory stimulus and with a startle auditory stimulus. Ten PD patients and ten aged matched controls participated in this study. The reaction times were faster for startle and non-startle stimuli in comparison with the visual imperative stimulus, in both patients and control subjects. The startle cue induced a faster reaction than the non-startle cue. The electromyography pattern remained unchanged across the conditions. The results suggest that the startle reaction effect for upper limb movements are unimpaired in PD patients and has different characteristics than the effect of non-startle stimuli. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

  7. Interhemispheric collaboration during digit and dot number-matching in younger and older adults.

    PubMed

    Patel, Urvi J; Barakat, Brandon K; Romero, Ruben; Apodaca, Daniel; Hellige, Joseph B; Cherry, Barbara J

    2014-11-01

    Digit and dot number-matching stimuli were used to replicate findings reported for younger adults by Patel and Hellige (2007) and to explore whether performance would differ for younger versus older participants. Participants were to make numerical matches of digits only, dots only, and digits and dots mixed conditions to determine whether reaction time (RT), percentage error, and efficiency scores that combine latency and accuracy for match trials were better on within- versus across-hemisphere trials. Sixty-six younger and 42 older participants were screened with the Mini-Mental State Examination (MMSE) and the Geriatric Depression Scale. They performed the three experimental conditions and were assessed with Digit Span Forward and Backward subscales from the Wechsler Adult Intelligence Scale-III. Results for younger adults demonstrated a within-hemisphere advantage for the Digits and Mixed conditions and an across-hemisphere advantage for the Dots condition, consistent with previous literature. Older participants showed a stronger within-hemisphere advantage for the Digits condition compared with younger participants and no advantage for within- or across-hemisphere processing for the Mixed condition when RT was considered, but they performed similarly to younger adults when efficiency scores were used and showed a relative across-hemisphere advantage for the Dots condition. Although RT suggests age-related differences in how information is distributed across the hemispheres of the brain, more comprehensive efficiency scores indicate that younger and older adults appear to use similar strategies in the coordination of interhemispheric transfer of information. MMSE scores regardless of age were related to type of task but not to across- versus within-hemisphere performance. PsycINFO Database Record (c) 2014 APA, all rights reserved.

  8. Bandgap engineering in semiconductor quantum dots

    NASA Astrophysics Data System (ADS)

    Chia, C. K.; Dong, J. R.; Chua, S. J.; Tripathy, S.

    2006-02-01

    Intermixing in InAs quantum dots (QDs) grown by molecular-beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD) techniques on GaAs and InP substrates have been investigated by rapid thermal annealing (RTA) and laser-irradiation techniques. In all cases, substantial energy shifts have been observed after RTA and laser annealing. A comparison between the intermixed QD and quantum well (QW) structures shows distinguished differences in photoluminescence (PL) intensity and full-width at half-maximum (FWHM). For QD structures, an increase in PL intensity and a reduction in FWHM were observed after intermixing, whereas for QW structures the FWHM increased and the PL intensity reduced after intermixing, suggesting degradation of the material quality in the QWs after intermixing. Examination of the role of the surrounding matrix in intermixing process shows that InAs QDs placed in a InGaAs QW can retain its good optical quality after high temperature annealing, as the InGaAs QW provides a foundation for the QDs to be fully desorbed in the well.

  9. Colloidal quantum dots as optoelectronic elements

    NASA Astrophysics Data System (ADS)

    Vasudev, Milana; Yamanaka, Takayuki; Sun, Ke; Li, Yang; Yang, Jianyong; Ramadurai, Dinakar; Stroscio, Michael A.; Dutta, Mitra

    2007-02-01

    Novel optoelectronic systems based on ensembles of semiconductor nanocrystals are addressed in this paper. Colloidal semiconductor quantum dots and related quantum-wire structures have been characterized optically; these optical measurements include those made on self-assembled monolayers of DNA molecules terminated on one end with a common substrate and on the other end with TiO II quantum dots. The electronic properties of these structures are modeled and compared with experiment. The characterization and application of ensembles of colloidal quantum dots with molecular interconnects are considered. The chemically-directed assembly of ensembles of colloidal quantum dots with biomolecular interconnects is demonstrated with quantum dot densities in excess of 10 +17 cm -3. A number of novel photodetectors have been designed based on the combined use of double-barrier quantum-well injectors, colloidal quantum dots, and conductive polymers. Optoelectronic devices including photodetectors and solar cells based on threedimensional ensembles of quantum dots are considered along with underlying phenomena such as miniband formation and the robustness of minibands to displacements of quantum dots in the ensemble.

  10. STED nanoscopy with fluorescent quantum dots

    NASA Astrophysics Data System (ADS)

    Hanne, Janina; Falk, Henning J.; Görlitz, Frederik; Hoyer, Patrick; Engelhardt, Johann; Sahl, Steffen J.; Hell, Stefan W.

    2015-05-01

    The widely popular class of quantum-dot molecular labels could so far not be utilized as standard fluorescent probes in STED (stimulated emission depletion) nanoscopy. This is because broad quantum-dot excitation spectra extend deeply into the spectral bands used for STED, thus compromising the transient fluorescence silencing required for attaining super-resolution. Here we report the discovery that STED nanoscopy of several red-emitting commercially available quantum dots is in fact successfully realized by the increasingly popular 775 nm STED laser light. A resolution of presently ~50 nm is demonstrated for single quantum dots, and sub-diffraction resolution is further shown for imaging of quantum-dot-labelled vimentin filaments in fibroblasts. The high quantum-dot photostability enables repeated STED recordings with >1,000 frames. In addition, we have evidence that the tendency of quantum-dot labels to blink is largely suppressed by combined action of excitation and STED beams. Quantum-dot STED significantly expands the realm of application of STED nanoscopy, and, given the high stability of these probes, holds promise for extended time-lapse imaging.

  11. Optically active quantum-dot molecules.

    PubMed

    Shlykov, Alexander I; Baimuratov, Anvar S; Baranov, Alexander V; Fedorov, Anatoly V; Rukhlenko, Ivan D

    2017-02-20

    Chiral molecules made of coupled achiral semiconductor nanocrystals, also known as quantum dots, show great promise for photonic applications owing to their prospective uses as configurable building blocks for optically active structures, materials, and devices. Here we present a simple model of optically active quantum-dot molecules, in which each of the quantum dots is assigned a dipole moment associated with the fundamental interband transition between the size-quantized states of its confined charge carriers. This model is used to analytically calculate the rotatory strengths of optical transitions occurring upon the excitation of chiral dimers, trimers, and tetramers of general configurations. The rotatory strengths of such quantum-dot molecules are found to exceed the typical rotatory strengths of chiral molecules by five to six orders of magnitude. We also study how the optical activity of quantum-dot molecules shows up in their circular dichroism spectra when the energy gap between the molecular states is much smaller than the states' lifetime, and maximize the strengths of the circular dichroism peaks by optimizing orientations of the quantum dots in the molecules. Our analytical results provide clear design guidelines for quantum-dot molecules and can prove useful in engineering optically active quantum-dot supercrystals and photonic devices.

  12. Thick-shell nanocrystal quantum dots

    SciTech Connect

    Hollingsworth, Jennifer A; Chen, Yongfen; Klimov, Victor I; Htoon, Han; Vela, Javier

    2011-05-03

    Colloidal nanocrystal quantum dots comprising an inner core having an average diameter of at least 1.5 nm and an outer shell, where said outer shell comprises multiple monolayers, wherein at least 30% of the quantum dots have an on-time fraction of 0.80 or greater under continuous excitation conditions for a period of time of at least 10 minutes.

  13. 14 CFR 302.18 - DOT decisionmaker.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 4 2014-01-01 2014-01-01 false DOT decisionmaker. 302.18 Section 302.18 Aeronautics and Space OFFICE OF THE SECRETARY, DEPARTMENT OF TRANSPORTATION (AVIATION PROCEEDINGS) PROCEDURAL... Proceedings § 302.18 DOT decisionmaker. (a) Assistant Secretary for Aviation and International Affairs....

  14. 14 CFR 302.18 - DOT decisionmaker.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 4 2010-01-01 2010-01-01 false DOT decisionmaker. 302.18 Section 302.18 Aeronautics and Space OFFICE OF THE SECRETARY, DEPARTMENT OF TRANSPORTATION (AVIATION PROCEEDINGS) PROCEDURAL... Proceedings § 302.18 DOT decisionmaker. (a) Assistant Secretary for Aviation and International Affairs....

  15. 14 CFR 302.18 - DOT decisionmaker.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 4 2012-01-01 2012-01-01 false DOT decisionmaker. 302.18 Section 302.18 Aeronautics and Space OFFICE OF THE SECRETARY, DEPARTMENT OF TRANSPORTATION (AVIATION PROCEEDINGS) PROCEDURAL... Proceedings § 302.18 DOT decisionmaker. (a) Assistant Secretary for Aviation and International Affairs....

  16. 14 CFR 302.18 - DOT decisionmaker.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 4 2013-01-01 2013-01-01 false DOT decisionmaker. 302.18 Section 302.18 Aeronautics and Space OFFICE OF THE SECRETARY, DEPARTMENT OF TRANSPORTATION (AVIATION PROCEEDINGS) PROCEDURAL... Proceedings § 302.18 DOT decisionmaker. (a) Assistant Secretary for Aviation and International Affairs....

  17. Research on Self-Assembling Quantum Dots.

    DTIC Science & Technology

    1995-10-30

    0K. in a second phase of this contract we turned our efforts to the fabrication and studies of self assembled quantum dots . We first demonstrated a...method for producing InAs-GasAs self assembled quantum dots (SAD) using MBE. (AN)

  18. STED nanoscopy with fluorescent quantum dots.

    PubMed

    Hanne, Janina; Falk, Henning J; Görlitz, Frederik; Hoyer, Patrick; Engelhardt, Johann; Sahl, Steffen J; Hell, Stefan W

    2015-05-18

    The widely popular class of quantum-dot molecular labels could so far not be utilized as standard fluorescent probes in STED (stimulated emission depletion) nanoscopy. This is because broad quantum-dot excitation spectra extend deeply into the spectral bands used for STED, thus compromising the transient fluorescence silencing required for attaining super-resolution. Here we report the discovery that STED nanoscopy of several red-emitting commercially available quantum dots is in fact successfully realized by the increasingly popular 775 nm STED laser light. A resolution of presently ∼ 50 nm is demonstrated for single quantum dots, and sub-diffraction resolution is further shown for imaging of quantum-dot-labelled vimentin filaments in fibroblasts. The high quantum-dot photostability enables repeated STED recordings with >1,000 frames. In addition, we have evidence that the tendency of quantum-dot labels to blink is largely suppressed by combined action of excitation and STED beams. Quantum-dot STED significantly expands the realm of application of STED nanoscopy, and, given the high stability of these probes, holds promise for extended time-lapse imaging.

  19. Olfactory speed - Temporal odor processing of paired stimuli.

    PubMed

    Schriever, V A; Frenzel, C; Wernecke, S; Croy, I; Valder, C; Hummel, T

    2015-06-04

    Compared to other senses, temporal perception of odors seems fairly slow. In addition it has been shown in previous studies that even not consciously perceived odors could influence our behavior. Aim of the current study therefore was to study the interstimulus interval (ISI) length, which is necessary between two repetitive stimuli to be able to perceive them separately. The additional aim focused on observing central odor processing of not perceived odorous stimuli. The study was divided into three parts. In each part healthy, normosmic volunteers were included. In part I and II stimulus pairs (CO2, H2S, orange and phenyl ethyl alcohol (PEA)) were presented to the subjects via a computer-controlled olfactometer with short ISI of 0.6-9s. The decision whether one or two stimuli were perceived was recorded. In addition the influence of odor valence, trigeminallity and concentrations was observed. In part III olfactory event-related potentials (OERPs) to perceived and not-perceived odors were recorded. The two stimuli of a stimulus pair were perceived separately more often with increasing ISI length. This increase was significant until an ISI between the stimuli of 4s. Odor intensity, pleasantness, trigeminallity and sex had no major influence on this. In addition we were able to observe that OERPs are less often detected in response to not perceived olfactory stimuli. However, the presence of OERP in response to not perceived stimuli in more than half of the cases indicated that even not perceived stimuli are centrally processed. Copyright © 2015 IBRO. Published by Elsevier Ltd. All rights reserved.

  20. Animation Stimuli System for Research on Instructor Gestures in Education.

    PubMed

    Cui, Jian; Popescu, Voicu; Adamo-Villani, Nicoletta; Wagner Cook, Susan; Duggan, Katherine A; Friedman, Howard S

    2017-01-01

    Education research has shown that instructor gestures can help capture, maintain, and direct the student's attention during a lecture as well as enhance learning and retention. Traditional education research on instructor gestures relies on video stimuli, which are time consuming to produce, especially when gesture precision and consistency across conditions are strictly enforced. The proposed system allows users to efficiently create accurate and effective stimuli for complex studies on gesture, without the need for computer animation expertise or artist talent.

  1. Visual, auditory and tactile stimuli compete for early sensory processing capacities within but not between senses.

    PubMed

    Porcu, Emanuele; Keitel, Christian; Müller, Matthias M

    2014-08-15

    We investigated whether unattended visual, auditory and tactile stimuli compete for capacity-limited early sensory processing across senses. In three experiments, we probed competitive audio-visual, visuo-tactile and audio-tactile stimulus interactions. To this end, continuous visual, auditory and tactile stimulus streams ('reference' stimuli) were frequency-tagged to elicit steady-state responses (SSRs). These electrophysiological oscillatory brain responses indexed ongoing stimulus processing in corresponding senses. To induce competition, we introduced transient frequency-tagged stimuli in same and/or different senses ('competitors') during reference presentation. Participants performed a separate visual discrimination task at central fixation to control for attentional biases of sensory processing. A comparison of reference-driven SSR amplitudes between competitor-present and competitor-absent periods revealed reduced amplitudes when a competitor was presented in the same sensory modality as the reference. Reduced amplitudes indicated the competitor's suppressive influence on reference stimulus processing. Crucially, no such suppression was found when a competitor was presented in a different than the reference modality. These results strongly suggest that early sensory competition is exclusively modality-specific and does not extend across senses. We discuss consequences of these findings for modeling the neural mechanisms underlying intermodal attention.

  2. Perception of social stimuli in mania: an fMRI study.

    PubMed

    Usnich, Tatiana; Spengler, Stephanie; Sajonz, Bastian; Herold, Dorrit; Bauer, Michael; Bermpohl, Felix

    2015-01-30

    Patients with mania show alterations of social behaviour. Neuropsychological studies in euthymic bipolar disorder (BD) have revealed deficits in cognitive, but not emotional aspects of social cognition (SC). Here, we studied the neural signature of social stimulus processing in mania. We expected alterations in regions associated with cognitive SC (dorsal-medial prefrontal cortex, dMPFC). Participants comprised 14 manic patients and 14 matched healthy controls who viewed standardized pictures with social and non-social content during functional magnetic resonance imaging (fMRI). Region-of-interest-analyses focused on areas related to SC (dorsal/ventral medial prefrontal cortex; temporo-parietal junction), determined by a quantitative meta-analysis. Between-group comparisons ('social>non-social') revealed reduced BOLD responses in the right dMPFC in manic patients, but no significant group difference in the ventral MPFC. In addition, manic patients showed elevated BOLD activation in the right temporo-parietal junction during perception of social stimuli, which was correlated with increased delusional ideation. Patients with mania show diminished BOLD responses to social stimuli in the right dMPFC, associated with cognitive SC and this may be related to reported deficits in understanding others' mental states. At the same time, manic patients show hyperactivation of the right temporo-parietal junction, likely related to exaggerated attribution of meaning to social stimuli. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  3. Electrodermal and behavioral responses of children with autism spectrum disorders to sensory and repetitive stimuli.

    PubMed

    McCormick, Carolyn; Hessl, David; Macari, Suzanne L; Ozonoff, Sally; Green, Cherie; Rogers, Sally J

    2014-08-01

    Parents frequently report that their children with autism spectrum disorders (ASD) respond atypically to sensory stimuli. Repetitive behaviors are also part of the ASD behavioral profile. Abnormal physiological arousal may underlie both of these symptoms. Electrodermal activity (EDA) is an index of sympathetic nervous system arousal. The goals of this study were twofold: (1) to pilot methods for collecting EDA data in young children and (2) to examine hypothesized relationships among EDA, and sensory symptoms and repetitive behaviors in children with ASD as compared with children with typical development. EDA was recorded on 54 young children with ASD and on 33 children with typical development (TD) during a protocol that included baseline, exposure to sensory and repetitive stimuli, and play. Parents completed standardized questionnaires regarding their child's sensory symptoms and repetitive behaviors. Frequency and type of repetitive behavior during play was coded offline. Comparisons between EDA data for ASD and TD groups indicated no significant between-group differences in any measures. Parents of children with ASD reported more abnormal responses to sensory stimuli and more repetitive behaviors, but scores on these measures were not significantly correlated with EDA or with frequency of observed repetitive behaviors. Parent report of frequency and severity of sensory symptoms was significantly correlated with reports of repetitive behaviors in both groups. Although parents of children with ASD report high levels of sensory symptoms and repetitive behaviors, these differences are not related to measured EDA arousal or reactivity.

  4. Spontaneous attention to faces in Asperger syndrome using ecologically valid static stimuli.

    PubMed

    Hanley, Mary; McPhillips, Martin; Mulhern, Gerry; Riby, Deborah M

    2013-11-01

    Previous eye tracking research on the allocation of attention to social information by individuals with autism spectrum disorders is equivocal and may be in part a consequence of variation in stimuli used between studies. The current study explored attention allocation to faces, and within faces, by individuals with Asperger syndrome using a range of static stimuli where faces were either viewed in isolation or viewed in the context of a social scene. Results showed that faces were viewed typically by the individuals with Asperger syndrome when presented in isolation, but attention to the eyes was significantly diminished in comparison to age and IQ-matched typical viewers when faces were viewed as part of social scenes. We show that when using static stimuli, there is evidence of atypicality for individuals with Asperger syndrome depending on the extent of social context. Our findings shed light on the previous explanations of gaze behaviour that have emphasised the role of movement in atypicalities of social attention in autism spectrum disorders and highlight the importance of consideration of the realistic portrayal of social information for future studies.

  5. Rapid DOTS expansion in India.

    PubMed Central

    Khatri, G. R.; Frieden, Thomas R.

    2002-01-01

    Since late 1998 the coverage of the DOTS strategy in India has been expanded rapidly. In both 2000 and 2001 the country probably accounted for more than half the global increase in the number of patients treated under DOTS and by early 2002 more than a million patients were being treated in this way in India. As a result, nearly 200 000 lives were saved. The lessons learnt relate to the importance of the following elements of the programme: (1) getting the science right and ensuring technical excellence; (2) building commitment and ensuring the provision of funds and flexibility in their utilization; (3) maintaining focus and priorities; (4) systematically appraising each area before starting service delivery; (5) ensuring an uninterrupted drug supply; (6) strengthening the established infrastructure and providing support for staff; (7) supporting the infrastructure required in urban areas; (8) ensuring full-time independent technical support and supervision, particularly during the initial phases of implementation; (9) monitoring intensively and giving timely feedback; and (10) continuous supervision. Tuberculosis (TB) control still faces major challenges in India. To reach its potential, the control programme needs to: continue to expand so as to cover the remaining half of the country, much of which has a weaker health infrastructure than the areas already covered; increase its reach in the areas already covered so that a greater proportion of patients is treated; ensure sustainability; improve the patient-friendliness of services; confront TB associated with human immunodeficiency virus (HIV) infection. It is expected that HIV will increase the number of TB cases by at least 10% and by a considerably higher percentage if HIV becomes much more widespread. India's experience shows that DOTS can achieve high case-detection and cure rates even with imperfect technology and often with an inadequate public health infrastructure. However, this can only happen if the

  6. Sensory dominance in combinations of audio, visual and haptic stimuli.

    PubMed

    Hecht, David; Reiner, Miriam

    2009-02-01

    Participants presented with auditory, visual, or bi-sensory audio-visual stimuli in a speeded discrimination task, fail to respond to the auditory component of the bi-sensory trials significantly more often than they fail to respond to the visual component--a 'visual dominance' effect. The current study investigated further the sensory dominance phenomenon in all combinations of auditory, visual and haptic stimuli. We found a similar visual dominance effect also in bi-sensory trials of combined haptic-visual stimuli, but no bias towards either sensory modality in bi-sensory trials of haptic-auditory stimuli. When presented with tri-sensory trials of combined auditory-visual-haptic stimuli, participants made more errors of responding only to two corresponding sensory signals than errors of responding only to a single sensory modality, however, there were no biases towards either sensory modality (or sensory pairs) in the distribution of both types of errors (i.e. responding only to a single stimulus or to pairs of stimuli). These results suggest that while vision can dominate both the auditory and the haptic sensory modalities, it is limited to bi-sensory combinations in which the visual signal is combined with another single stimulus. However, in a tri-sensory combination when a visual signal is presented simultaneously with both the auditory and the haptic signals, the probability of missing two signals is much smaller than of missing only one signal and therefore the visual dominance disappears.

  7. Sensorimotor synchronization with audio-visual stimuli: limited multisensory integration.

    PubMed

    Armstrong, Alan; Issartel, Johann

    2014-11-01

    Understanding how we synchronize our actions with stimuli from different sensory modalities plays a central role in helping to establish how we interact with our multisensory environment. Recent research has shown better performance with multisensory over unisensory stimuli; however, the type of stimuli used has mainly been auditory and tactile. The aim of this article was to expand our understanding of sensorimotor synchronization with multisensory audio-visual stimuli and compare these findings to their individual unisensory counterparts. This research also aims to assess the role of spatio-temporal structure for each sensory modality. The visual and/or auditory stimuli had either temporal or spatio-temporal information available and were presented to the participants in unimodal and bimodal conditions. Globally, the performance was significantly better for the bimodal compared to the unimodal conditions; however, this benefit was limited to only one of the bimodal conditions. In terms of the unimodal conditions, the level of synchronization with visual stimuli was better than auditory, and while there was an observed benefit with the spatio-temporal compared to temporal visual stimulus, this was not replicated with the auditory stimulus.

  8. Corticospinal Excitability Preceding the Grasping of Emotion-Laden Stimuli

    PubMed Central

    Nogueira-Campos, Anaelli Aparecida; de Oliveira, Laura Alice Santos; Della-Maggiore, Valeria; Esteves, Paula Oliveira; Rodrigues, Erika de Carvalho; D. Vargas, Claudia

    2014-01-01

    Evolutionary theories posit that emotions prime organisms for action. This study examined whether corticospinal excitability (CSE) is modulated by the emotional valence of a to-be-grasped stimulus. CSE was estimated based on the amplitude of motor evoked potentials (MEPs) elicited using transcranial magnetic stimulation (TMS) and recorded on the first dorsal interosseous (FDI) muscle. Participants were instructed to grasp (ACTION condition) or just look at (NO-ACTION condition) unpleasant, pleasant and neutral stimuli. TMS pulses were applied randomly at 500 or 250 ms before a go signal. MEP amplitudes were normalized within condition by computing a ratio for the emotion-laden stimuli by reference to the neutral stimuli. A divergent valence effect was observed in the ACTION condition, where the CSE ratio was higher during the preparation to grasp unpleasant compared to pleasant stimuli. In addition, the CSE ratio was lower for pleasant stimuli during the ACTION condition compared to the NO-ACTION condition. Altogether, these results indicate that motor preparation is selectively modulated by the valence of the stimulus to be grasped. The lower CSE for pleasant stimuli may result from the need to refrain from executing an imminent action. PMID:24732961

  9. Super-size me: self biases increase to larger stimuli.

    PubMed

    Sui, Jie; Humphreys, Glyn W

    2015-04-01

    Prior work has shown that simple perceptual match responses to pairings of shapes and labels are more efficient if the pairing is associated with the participant (e.g., circle-you) than if it is associated with another familiar person (e.g., square-friend). There is a similar advantage for matching associations with high-value rewards (circle-£9) versus low-value rewards (square-£1) (Sui, He, & Humphreys Journal of Experimental Psychology: Human Perception and Performance, 38, 1105-1117, 2012). Here we evaluated the relations between the self- and reward-bias effects by introducing occasional trials in which the size of a shape was varied unexpectedly (large or small vs. a standard medium). Participants favored stimuli that were larger than the standard when stimuli were associated with the self, and this enhancement of self bias was predicted by the degree of self bias that participants showed to standard (medium) sized stimuli. Although we observed a correlation between the magnitudes of the self and reward biases over participants, reward-bias effects were not increased to large stimuli. The data suggest both overlapping and independent components of the self and reward biases, and that self biases are uniquely enhanced when stimuli increase in size, consistent with previously reported motivational biases favoring large stimuli.

  10. The use of visual stimuli during auditory assessment.

    PubMed

    Pearlman, R C; Cunningham, D R; Williamson, D G; Amerman, J D

    1975-01-01

    Two groups of male subjects beyond 50 years of age were given audiometric tasks with and without visual stimulation to determine if visual stimuli changed auditory perception. The first group consisted of 10 subjects with normal auditory acuity; the second, 10 with sensorineural hearing losses greater than 30 decibels. The rate of presentation of the visual stimuli, consisting of photographic slides of various subjects, was determined in experiment I of the study. The subjects, while viewing the slides at their own rate, took an audiotry speech discrimination test. Advisedly they changed the slides at a speed which they felt facilitated attention while performing the auditory task. The mean rate of slide-changing behavior was used as the "optimum" visual stimulation rate in experiment II, which was designed to explore the interaction of the bisensory presentation of stimuli. Bekesy tracings and Rush Hughes recordings were administered without and with visual stimuli, the latter presented at the mean rate of slide changes found in experiment I. Analysis of data indicated that (1) no statistically significant difference exists between visual and nonvisual conditions during speech discrimination and Bekesy testing; and (2) subjects did not believe that visual stimuli as presented in this study helped them to listen more effectively. The experimenter concluded that the various auditory stimuli encountered in the auditory test situation may actually be a deterrent to boredom because of the variety of tasks required in a testing situation.

  11. Exteroceptive stimuli override interoceptive state in reaction time control.

    PubMed

    Yang, Xiao; Jennings, J Richard; Friedman, Bruce H

    2017-07-24

    The processing of reaction time (RT) stimulus is modulated by its timing relative to the cardiac cycle. RT stimulus processing is also influenced by task-irrelevant stimuli: a sensory stimulus speeds RT when it accompanies a cue to react in another sensory modality. Different theories have been proposed to explain this accessory stimulus effect (ASE). However, it is unclear whether the ASE interacts with the cardiac timing effect. In the present study, the relationship of the ASE, cardiac timing, and stimulus valence was examined. Fifty-two subjects performed 400 trials of a simple RT task. Images of neutral and fear faces served as visual accessory stimuli; the RT stimulus was a 75 dB tone. Electrocardiography was recorded. Visual and auditory stimuli were presented at either cardiac systole or diastole. The stimulus onset asynchrony between visual and auditory stimuli was either 0 or 75 ms. Repeated measures ANOVAs showed that cardiac timing modulated RT, but only when accessory stimuli were absent. RT was shorter when the accessory stimulus preceded the imperative stimulus with respect to simultaneous presentation. The ASE was not influenced by visual stimulus valence or cardiac timing. Results indicate that the ASE overrides cardiac timing effects, suggesting a dynamic balance between exteroceptive stimuli and interoceptive states, and highlight the importance of embodied information processing. © 2017 Society for Psychophysiological Research.

  12. Eyes versus hands: How perceived stimuli influence motor actions.

    PubMed

    Geiger, Alexander; Niessen, Eva; Bente, Gary; Vogeley, Kai

    2017-01-01

    Many studies showed that biological (e.g., gaze-shifts or hand movements) and non-biological stimuli (e.g., arrows or moving points) redirect attention. Biological stimuli seem to be more suitable than non-biological to perform this task. However, the question remains if biological stimuli do have different influences on redirecting attention and if this property is dependent on how we react to those stimuli. In two separate experiments, participants interact either with a biological or a non-biological stimulus (experiment 1), or with two biological stimuli (gaze-shifts, hand movements)(experiment 2) to which they responded with two different actions (saccade, button press), either in a congruent or incongruent manner. Results from experiment 1 suggest that interacting with the biological stimulus lead to faster responses, compared to the non-biological stimulus, independent of the response type. Results from experiment 2 show longer reaction times when the depicted stimulus was not matching the response type (e.g., reacting with hand movements to a moving object or gaze-shift) compared to a matching condition, while especially the gaze-following condition (reacting with a gaze shift to a perceived gaze shift) led to the fastest responses. These results suggest that redirecting attention is not only dependent on the perceived stimulus but also on the way how those stimuli are responded to.

  13. Gating of attention towards food stimuli in binge eating disorder.

    PubMed

    Schmitz, Florian; Naumann, Eva; Biehl, Stefanie; Svaldi, Jennifer

    2015-12-01

    Cognitive models of eating disorders propose that attentional biases for disorder-relevant stimuli contribute to eating disorder pathology. Empirical evidence of a contribution of attentional biases for binge eating disorder (BED) is still scarce. The aim of the present study was to assess attention engagement towards, and disengagement from, food stimuli in overweight females with BED (n = 25) and a group of overweight and obese women without BED (OW; n = 30). Participants completed a rapid serial visual presentation (RSVP) paradigm with food and neutral words as target stimuli. This task can be used to decompose an attentional bias for food stimuli into its stimulus engagement and stimulus disengagement components. Findings indicate that facilitated stimulus engagement for food stimuli over neutral stimuli was more pronounced in the BED group compared to the OW group. Conversely, there were no substantial disengagement effects in either group. Thereby, results support the idea that early attentional processes are biased in BED. Copyright © 2015 Elsevier Ltd. All rights reserved.

  14. What makes an event: temporal integration of stimuli or actions?

    PubMed

    Fournier, Lisa R; Gallimore, Jonathan M

    2013-08-01

    In this article, we ask what serves as the "glue" that temporarily links information to form an event in an active observer. We examined whether forming a single action event in an active observer is contingent on the temporal presentation of the stimuli (hence, on the temporal availability of the action information associated with these stimuli), or on the learned temporal execution of the actions associated with the stimuli, or on both. A partial-repetition paradigm was used to assess the boundaries of an event for which the temporal properties of the stimuli (i.e., presented either simultaneously or temporally separate) and the intended execution of the actions associated with these stimuli (i.e., executed as one, temporally integrated, response or as two temporally separate responses) were manipulated. The results showed that the temporal features of action execution determined whether one or more events were constructed; the temporal presentation of the stimuli (and hence the availability of their associated actions) did not. This suggests that the action representation, or "task goal," served as the "glue" in forming an event in an active observer. These findings emphasize the importance of action planning in event construction in an active observer.

  15. siRNA Delivery by Stimuli-Sensitive Nanocarriers

    PubMed Central

    Salzano, Giuseppina; Costa, Daniel F.; Torchilin, Vladimir P.

    2016-01-01

    Since its discovery in late 1990s, small interfering RNA (siRNA) has become a significant biopharmaceutical research tool and a powerful option for the treatment of different human diseases based on altered gene-expression. Despite promising data from many pre-clinical studies, concrete hurdles still need to be overcome to bring therapeutic siRNAs in clinic. The design of stimuli-sensitive nanopreparations for gene therapy is a lively area of the current research. Compared to conventional systems for siRNA delivery, this type of platform can respond to local stimuli that are characteristics of the pathological area of interest, allowing the release of nucleic acids at the desired site. Acidic pH, abnormal levels of enzymes, altered redox potential and magnetic field are examples of stimuli exploited in the design of stimuli-sensitive nanoparticles. In this review, we discuss on recent stimuli-sensitive strategies for siRNA delivery and we highlight on the potential of combining multiple stimuli-sensitive strategies in the same nano-platform for a better therapeutic outcome. PMID:26486143

  16. Quantum-dot supercrystals for future nanophotonics

    PubMed Central

    Baimuratov, Anvar S.; Rukhlenko, Ivan D.; Turkov, Vadim K.; Baranov, Alexander V.; Fedorov, Anatoly V.

    2013-01-01

    The study of supercrystals made of periodically arranged semiconductor quantum dots is essential for the advancement of emerging nanophotonics technologies. By combining the strong spatial confinement of elementary excitations inside quantum dots and exceptional design flexibility, quantum-dot supercrystals provide broad opportunities for engineering desired optical responses and developing superior light manipulation techniques on the nanoscale. Here we suggest tailoring the energy spectrum and wave functions of the supercrystals' collective excitations through the variation of different structural and material parameters. In particular, by calculating the excitonic spectra of quantum dots assembled in two-dimensional Bravais lattices we demonstrate a wide variety of spectrum transformation scenarios upon alterations in the quantum dot arrangement. This feature offers unprecedented control over the supercrystal's electromagnetic properties and enables the development of new nanophotonics materials and devices.

  17. Biocompatible Quantum Dots for Biological Applications

    PubMed Central

    Rosenthal, Sandra J.; Chang, Jerry C.; Kovtun, Oleg; McBride, James R.; Tomlinson, Ian D.

    2011-01-01

    Semiconductor quantum dots are quickly becoming a critical diagnostic tool for discerning cellular function at the molecular level. Their high brightness, long-lasting, sizetunable, and narrow luminescence set them apart from conventional fluorescence dyes. Quantum dots are being developed for a variety of biologically oriented applications, including fluorescent assays for drug discovery, disease detection, single protein tracking, and intracellular reporting. This review introduces the science behind quantum dots and describes how they are made biologically compatible. Several applications are also included, illustrating strategies toward target specificity, and are followed by a discussion on the limitations of quantum dot approaches. The article is concluded with a look at the future direction of quantum dots. PMID:21276935

  18. Biocompatible Quantum Dots for Biological Applications

    SciTech Connect

    Rosenthal, Sandra; Chang, Jerry; Kovtun, Oleg; McBride, James; Tomlinson, Ian

    2011-01-01

    Semiconductor quantum dots are quickly becoming a critical diagnostic tool for discerning cellular function at the molecular level. Their high brightness, long-lasting, size-tunable, and narrow luminescence set them apart from conventional fluorescence dyes. Quantum dots are being developed for a variety of biologically oriented applications, including fluorescent assays for drug discovery, disease detection, single protein tracking, and intracellular reporting. This review introduces the science behind quantum dots and describes how they are made biologically compatible. Several applications are also included, illustrating strategies toward target specificity, and are followed by a discussion on the limitations of quantum dot approaches. The article is concluded with a look at the future direction of quantum dots.

  19. Optophononics with Coupled Quantum Dots

    DTIC Science & Technology

    2014-02-18

    the molecular polaron can be used as an efficient and tunable coherent coupler for quantum states in spatially separated low-dimensional structures...cold finger of a closed cycle microscopy cryostat and kept at a temperature of 20K. A tunable diode laser with a tuning range from about 900 to 1,000...et al. Tunable exciton relaxation in vertically coupled semiconductor InAs quantum dots. Phys. Rev. B 84, 081404(R) (2011). 10 100 1,000 0 5 A m pl ifi

  20. Semiconductor double quantum dot micromaser.

    PubMed

    Liu, Y-Y; Stehlik, J; Eichler, C; Gullans, M J; Taylor, J M; Petta, J R

    2015-01-16

    The coherent generation of light, from masers to lasers, relies upon the specific structure of the individual emitters that lead to gain. Devices operating as lasers in the few-emitter limit provide opportunities for understanding quantum coherent phenomena, from terahertz sources to quantum communication. Here we demonstrate a maser that is driven by single-electron tunneling events. Semiconductor double quantum dots (DQDs) serve as a gain medium and are placed inside a high-quality factor microwave cavity. We verify maser action by comparing the statistics of the emitted microwave field above and below the maser threshold. Copyright © 2015, American Association for the Advancement of Science.

  1. Determination of carrier lifetime and mobility in colloidal quantum dot films via impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Rath, Arup K.; Lasanta, Tania; Bernechea, Maria; Diedenhofen, Silke L.; Konstantatos, Gerasimos

    2014-02-01

    Impedance Spectroscopy (IS) proves to be a powerful tool for the determination of carrier lifetime and majority carrier mobility in colloidal quantum dot films. We employ IS to determine the carrier lifetime in PbS quantum dot Schottky solar cells with Al and we verify the validity of the technique via transient photovoltage. We also present a simple approach based on an RC model that allows the determination of carrier mobility in PbS quantum dot films and we corroborate the results via comparison with space charge limited measurements. In summary, we demonstrate the potential of IS to characterize key-to-photovoltaics optoelectronic properties, carrier lifetime, and mobility, in a facile way.

  2. Flux extrapolation models used in the DOT IV discrete ordinates neutron transport code

    SciTech Connect

    Tomlinson, E.T.; Rhoades, W.A.; Engle, W.W. Jr.

    1980-05-01

    The DOT IV code solves the Boltzmann transport equation in two dimensions using the method of discrete ordinates. Special techniques have been incorporated in this code to mitigate the effects of flux extrapolation error in space meshes of practical size. This report presents the flux extrapolation models as they appear in DOT IV. A sample problem is also presented to illustrate the effects of the various models on the resultant flux. Convergence of the various models to a single result as the mesh is refined is also examined. A detailed comparison with the widely used TWOTRAN II code is reported. The features which cause DOT and TWOTRAN to differ in the converged results are completely observed and explained.

  3. Extraction of inhomogeneous broadening and nonradiative losses in InAs quantum-dot lasers

    SciTech Connect

    Chow, Weng W.; Liu, Alan Y.; Gossard, Arthur C.; Bowers, John E.

    2015-10-26

    We present a method to quantify inhomogeneous broadening and nonradiative losses in quantum dot lasers by comparing the gain and spontaneous emission results of a microscopic laser theory with measurements made on 1.3 μm InAs quantum-dot lasers. Calculated spontaneous-emission spectra are first matched to those measured experimentally to determine the inhomogeneous broadening in the experimental samples. This is possible because treatment of carrier scattering at the level of quantum kinetic equations provides the homogeneously broadened spectra without use of free parameters, such as the dephasing rate. We then extract the nonradiative recombination current associated with the quantum-dot active region from a comparison of measured and calculated gain versus current relations.

  4. Ultrafast Charge Dynamics in Trap‐Free and Surface‐Trapping Colloidal Quantum Dots

    PubMed Central

    Smith, Charles T.; Leontiadou, Marina A.; Page, Robert; O'Brien, Paul

    2015-01-01

    Ultrafast transient absorption spectroscopy is used to study subnanosecond charge dynamics in CdTe colloidal quantum dots. After treatment with chloride ions, these can become free of surface traps that produce nonradiative recombination. A comparison between these dots and the same dots before treatment enables new insights into the effect of surface trapping on ultrafast charge dynamics. The surface traps typically increase the rate of electron cooling by 70% and introduce a recombination pathway that depopulates the conduction band minimum of single excitons on a subnanosecond timescale, regardless of whether the sample is stirred or flowed. It is also shown that surface trapping significantly reduces the peak bleach obtained for a particular pump fluence, which has important implications for the interpretation of transient absorption data, including the estimation of absorption cross‐sections and multiple exciton generation yields. PMID:27980905

  5. Determination of carrier lifetime and mobility in colloidal quantum dot films via impedance spectroscopy

    SciTech Connect

    Rath, Arup K.; Lasanta, Tania; Bernechea, Maria; Diedenhofen, Silke L.; Konstantatos, Gerasimos

    2014-02-10

    Impedance Spectroscopy (IS) proves to be a powerful tool for the determination of carrier lifetime and majority carrier mobility in colloidal quantum dot films. We employ IS to determine the carrier lifetime in PbS quantum dot Schottky solar cells with Al and we verify the validity of the technique via transient photovoltage. We also present a simple approach based on an RC model that allows the determination of carrier mobility in PbS quantum dot films and we corroborate the results via comparison with space charge limited measurements. In summary, we demonstrate the potential of IS to characterize key-to-photovoltaics optoelectronic properties, carrier lifetime, and mobility, in a facile way.

  6. Selective recognition of Glutamate based on fluorescence enhancement of graphene quantum dot

    NASA Astrophysics Data System (ADS)

    Hosseini, Morteza; Khabbaz, Hossein; Dezfoli, Amin Shiralizadeh; Ganjali, Mohammad Reza; Dadmehr, Mehdi

    2015-02-01

    Graphene quantum dots (GQDs) have successfully been utilized as an efficient nano-sized fluorescence chemosensor to detect selectively Glutamate (Glu) in Tris-HCl buffer solution (pH = 9). The fluorescence emission spectrum of graphene quantum dots was at about 430 nm. The study showed that fluorescence intensity of the quantum dot gradually enhanced with increase in concentration of Glutamate and any change in fluorescence intensity was directly proportional to the concentration of Glutamate. Under optimum conditions, the linear range for the detection of Glutamate was 1.6 × 10-7 M to 1.0 × 10-5 M with a detection limit of 5.2 × 10-8 M. The sensor showed high selectivity toward Glutamate in comparison with other amino acids.

  7. Resonance in quantum dot fluorescence in a photonic bandgap liquid crystal host.

    PubMed

    Lukishova, Svetlana G; Bissell, Luke J; Winkler, Justin; Stroud, C R

    2012-04-01

    Microcavity resonance is demonstrated in nanocrystal quantum dot fluorescence in a one-dimensional (1D) chiral photonic bandgap cholesteric-liquid crystal host under cw excitation. The resonance demonstrates coupling between quantum dot fluorescence and the cholesteric microcavity. Observed at a band edge of a photonic stop band, this resonance has circular polarization due to microcavity chirality with 4.9 times intensity enhancement in comparison with polarization of the opposite handedness. The circular-polarization dissymmetry factor g(e) of this resonance is ~1.3. We also demonstrate photon antibunching of a single quantum dot in a similar glassy cholesteric microcavity. These results are important in cholesteric-laser research, in which so far only dyes were used, as well as for room-temperature single-photon source applications.

  8. Aqueous Exfoliation of Graphite into Graphene Assisted by Sulfonyl Graphene Quantum Dots for Photonic Crystal Applications.

    PubMed

    Zeng, Minxiang; Shah, Smit A; Huang, Dali; Parviz, Dorsa; Yu, Yi-Hsien; Wang, Xuezhen; Green, Micah J; Cheng, Zhengdong

    2017-09-13

    We investigate the π-π stacking of polyaromatic hydrocarbons (PAHs) with graphene surfaces, showing that such interactions are general across a wide range of PAH sizes and species, including graphene quantum dots. We synthesized a series of graphene quantum dots with sulfonyl, amino, and carboxylic functional groups and employed them to exfoliate and disperse pristine graphene in water. We observed that sulfonyl-functionalized graphene quantum dots were able to stabilize the highest concentration of graphene in comparison to other functional groups; this is consistent with prior findings by pyrene. The graphene nanosheets prepared showed excellent colloidal stability, indicating great potential for applications in electronics, solar cells, and photonic displays which was demonstrated in this work.

  9. Blood Compatibility Evaluations of Fluorescent Carbon Dots.

    PubMed

    Li, Sha; Guo, Zhong; Zhang, Yi; Xue, Wei; Liu, Zonghua

    2015-09-02

    Because of their unique advantages, fluorescent carbon dots are gaining popularity in various biomedical applications. For these applications, good biosafety is a prerequisite for their use in vivo. Studies have reported the preliminary biocompatibility evaluations of fluorescent carbon dots (mainly cytotoxicity); however, to date, little information is available about their hemocompatibility, which could impede their development from laboratory to bedside. In this work, we evaluated the hemocompatibility of fluorescent carbon dots, which we prepared by hydrothermal carbonization of α-cyclodextrin. The effects of the carbon dots on the structure and function of key blood components were investigated at cellular and molecular levels. In particular, we considered the morphology and lysis of human red blood cells, the structure and conformation of the plasma protein fibrinogen, the complement activation, platelet activation, and in vitro and in vivo blood coagulation. We found that the carbon dots have obvious concentration-dependent effects on the blood components. Overall, concentrations of the fluorescent carbon dots at ≤0.1 mg/mL had few adverse effects on the blood components, but at higher doses, the carbon dots impair the structure and function of the blood components, causing morphological disruptions and lysis of red blood cells, interference in the local microenvironments of fibrinogen, activation of the complement system, and disturbances in the plasma and whole blood coagulation function in vitro. However, the carbon dots tend to activate platelets only at low concentrations. Intravenous administration of the carbon dots at doses up to 50 mg/kg did not impair the blood coagulation function. These results provide valuable information for the clinical application of fluorescent carbon dots.

  10. Dynamic Adjustment of Stimuli in Real Time Functional Magnetic Resonance Imaging

    PubMed Central

    Feng, I. Jung; Jack, Anthony I.; Tatsuoka, Curtis

    2015-01-01

    The conventional fMRI image analysis approach to associating stimuli to brain activation is performed by carrying out a massive number of parallel univariate regression analyses. fMRI blood-oxygen-level dependent (BOLD) signal, the basis of these analyses, is known for its low signal-noise-ratio and high spatial and temporal signal correlation. In order to ensure accurate localization of brain activity, stimulus administration in an fMRI session is often lengthy and repetitive. Real-time fMRI BOLD signal analysis is carried out as the signal is observed. This method allows for dynamic, real-time adjustment of stimuli through sequential experimental designs. We have developed a voxel-wise sequential probability ratio test (SPRT) approach for dynamically determining localization, as well as decision rules for stopping stimulus administration. SPRT methods and general linear model (GLM) approaches are combined to identify brain regions that are activated by specific elements of stimuli. Stimulus administration is dynamically stopped when sufficient statistical evidence is collected to determine activation status across regions of interest, following predetermined statistical error thresholds. Simulation experiments and an example based on real fMRI data show that scan volumes can be substantially reduced when compared with pre-determined, fixed designs while achieving similar or better accuracy in detecting activated voxels. Moreover, the proposed approach is also able to accurately detect differentially activated areas, and other comparisons between task-related GLM parameters that can be formulated in a hypothesis-testing framework. Finally, we give a demonstration of SPRT being employed in conjunction with a halving algorithm to dynamically adjust stimuli. PMID:25785856

  11. Computational Simulation of Equivalence Class Formation Using the go/no-go Procedure with Compound Stimuli.

    PubMed

    Vernucio, Renato Roberto; Debert, Paula

    Research about equivalence has commonly utilized human participants as experimental subjects. More recently, computational models have been capable of reproducing performances observed in experiments with humans. The computational model often utilized is called RELNET, and it simulates training and testing trials of conditional relations using the matching-to-sample procedure (MTS). The differentiation between sample stimulus and comparison stimuli, indispensable in MTS, implies operational difficulties for simulations. For this reason, new studies seek to utilize alternative procedures to MTS, which do not differentiate the functions of the antecedent stimuli. This work evaluated the possibility of developing a new computational model to simulate equivalence class formation using the go/no-go procedure with compound stimuli. In Experiment 1, artificial neural networks were utilized to simulate training of the AB and BC relations as well as the testing of the AC relation. The results showed that four out of six runs demonstrated equivalence class formation. Experiment 2 evaluated whether the additional class training performed in Experiment 1, which was analogous to the simulation of pre-experimental experience of human participants, would be essential for simulating the establishment of equivalence classes. It was found that it was not possible to simulate equivalence class formation without the additional class training. Altogether, the experiments show that it is possible to simulate equivalence class formation using the go/no-go procedure with compound stimuli and that it is necessary to conduct additional class training. The model developed is, therefore, an alternative to RELNET for the study of equivalence relations using computational simulations.

  12. Compact Interconnection Networks Based on Quantum Dots

    NASA Technical Reports Server (NTRS)

    Fijany, Amir; Toomarian, Nikzad; Modarress, Katayoon; Spotnitz, Matthew

    2003-01-01

    Architectures that would exploit the distinct characteristics of quantum-dot cellular automata (QCA) have been proposed for digital communication networks that connect advanced digital computing circuits. In comparison with networks of wires in conventional very-large-scale integrated (VLSI) circuitry, the networks according to the proposed architectures would be more compact. The proposed architectures would make it possible to implement complex interconnection schemes that are required for some advanced parallel-computing algorithms and that are difficult (and in many cases impractical) to implement in VLSI circuitry. The difficulty of implementation in VLSI and the major potential advantage afforded by QCA were described previously in Implementing Permutation Matrices by Use of Quantum Dots (NPO-20801), NASA Tech Briefs, Vol. 25, No. 10 (October 2001), page 42. To recapitulate: Wherever two wires in a conventional VLSI circuit cross each other and are required not to be in electrical contact with each other, there must be a layer of electrical insulation between them. This, in turn, makes it necessary to resort to a noncoplanar and possibly a multilayer design, which can be complex, expensive, and even impractical. As a result, much of the cost of designing VLSI circuits is associated with minimization of data routing and assignment of layers to minimize crossing of wires. Heretofore, these considerations have impeded the development of VLSI circuitry to implement complex, advanced interconnection schemes. On the other hand, with suitable design and under suitable operating conditions, QCA-based signal paths can be allowed to cross each other in the same plane without adverse effect. In principle, this characteristic could be exploited to design compact, coplanar, simple (relative to VLSI) QCA-based networks to implement complex, advanced interconnection schemes. The proposed architectures require two advances in QCA-based circuitry beyond basic QCA-based binary

  13. Fearful thinking predicts hypervigilance towards pain-related stimuli in patients with chronic pain.

    PubMed

    He, Chun-Hong; Yu, Feng; Jiang, Zhao-Cai; Wang, Jin-Yan; Luo, Fei

    2014-09-01

    Cognitive impairment plays a role in the development and maintenance of chronic pain. Patients with painful disorders are reported to show attentional biases toward pain-related information. However, these findings are controversial, and rarely has any study examined whether chronic pain patients have attentional biases to pain-related conditioned stimuli (CS). In this study, twenty-one patients diagnosed with trigeminal neuralgia (TN) were recruited from the neurosurgical department of a large urban general hospital. Sixteen family members and twenty-one pain-free volunteers were included as two separate control groups. Pain ratings, pain-related anxiety, general anxiety, and depression were measured in all subjects using questionnaires. Two dot probe tests were performed, one that used pictures of painful versus neutral faces as cues, and another that presented three types of CS as cues that predicted certain, uncertain, or no pain. Our results demonstrate that the TN patients showed attentional biases towards painful faces and the CSs that signaled uncertain pain. Moreover, the ratings of negative emotion about their pain conditions correlated significantly with the presence of attentional biases. The patients' close family members, however, displayed biases towards uncertain-pain CS. This study demonstrates that patients with chronic pain have increased attention towards pain-related information, and the fearful thinking about pain was positively correlated with this phenomenon.

  14. Improved dot diffusion by diffused matrix and class matrix co-optimization.

    PubMed

    Guo, Jing-Ming; Liu, Yun-Fu

    2009-08-01

    Dot diffusion is an efficient approach which utilizes concepts of block-wise and parallel-oriented processing to generate halftones. However, the block-wise nature of processing reduces image quality much more significantly as compared to error diffusion. In this work, four types of filters with various sizes are employed in co-optimization procedures with class matrices of size 8 n 8 and 16 x 16 to improve the image quality. The optimal diffused weighting and area are determined through simulations. Many well-known halftoning methods, some of which includes direct binary search (DBS), error diffusion, ordered dithering, and prior dot diffusion methods, are also included for comparisons. Experimental results show that the proposed dot diffusion achieved quality close to some forms of error diffusion, and additionally, superior to the well-known Jarvis and Stucki error diffusion and Mese's dot diffusion. Moreover, the inherent parallel processing advantage of dot diffusion is preserved, allowing us to reap higher executing efficiency than both DBS and error diffusion.

  15. Biodetection using fluorescent quantum dots

    NASA Astrophysics Data System (ADS)

    Speckman, Donna M.; Jennings, Travis L.; LaLumondiere, Steven D.; Klimcak, Charles M.; Moss, Steven C.; Loper, Gary L.; Beck, Steven M.

    2002-07-01

    Multi-pathogen biosensors that take advantage of sandwich immunoassay detection schemes and utilize conventional fluorescent dye reporter molecules are difficult to make into extremely compact and autonomous packages. The development of a multi-pathogen, immunoassay-based, fiber optic detector that utilizes varying sized fluorescent semiconductor quantum dots (QDs) as the reporter labels has the potential to overcome these problems. In order to develop such a quantum dot-based biosensor, it is essential to demonstrate that QDs can be attached to antibody proteins, such that the specificity of the antibody is maintained. We have been involved in efforts to develop a reproducible method for attaching QDs to antibodies for use in biodetection applications. We have synthesized CdSe/ZnS core-shell QDs of differing size, functionalized their surfaces with several types of organic groups for water solubility, and covalently attached these functionalized QDs to rabbit anti-ovalbumin antibody protein. We also demonstrated that these labeled antibodies exhibit selective binding to ovalbumin antigen. We characterized the QDs at each step in the overall synthesis by UV-VIS absorption spectroscopy and by picosecond (psec) transient photoluminescence (TPL) spectroscopy. TPL spectroscopy measurements indicate that QD lifetime depends on the size of the QD, the intensity of the optical excitation source, and whether or not they are functionalized and conjugated to antibodies. We describe details of these experiments and discuss the impact of our results on our biosensor development program.

  16. Chiral quantum dot based materials

    NASA Astrophysics Data System (ADS)

    Govan, Joseph; Loudon, Alexander; Baranov, Alexander V.; Fedorov, Anatoly V.; Gun'ko, Yurii

    2014-05-01

    Recently, the use of stereospecific chiral stabilising molecules has also opened another avenue of interest in the area of quantum dot (QD) research. The main goal of our research is to develop new types of technologically important quantum dot materials containing chiral defects, study their properties and explore their applications. The utilisation of chiral penicillamine stabilisers allowed the preparation of new water soluble white emitting CdS quantum nanostructures which demonstrated circular dichroism in the band-edge region of the spectrum. It was also demonstrated that all three types of QDs (D-, L-, and Rac penicillamine stabilised) show very broad emission bands between 400 and 700 nm due to defects or trap states on the surfaces of the nanocrystals. In this work the chiral CdS based quantum nanostructures have also been doped by copper metal ions and new chiral penicilamine stabilized CuS nanoparticles have been prepared and investigated. It was found that copper doping had a strong effect at low levels in the synthesis of chiral CdS nanostructures. We expect that this research will open new horizons in the chemistry of chiral nanomaterials and their application in biotechnology, sensing and asymmetric synthesis.

  17. Sex-related memory recall and talkativeness for emotional stimuli.

    PubMed

    Arnone, Benedetto; Pompili, Assunta; Tavares, Maria Clotilde; Gasbarri, Antonella

    2011-01-01

    Recent studies have evidenced an increasing interest in sex-related brain mechanisms and cerebral lateralization subserving emotional memory, language processing, and conversational behavior. We used event-related-potentials (ERP) to examine the influence of sex and hemisphere on brain responses to emotional stimuli. Given that the P300 component of ERP is considered a cognitive neuroelectric phenomenon, we compared left and right hemisphere P300 responses to emotional stimuli in men and women. As indexed by both amplitude and latency measures, emotional stimuli elicited more robust P300 effects in the left hemisphere in women than in men, while a stronger P300 component was elicited in the right hemisphere in men compared to women. Our findings show that the variables of sex and hemisphere interacted significantly to influence the strength of the P300 component to the emotional stimuli. Emotional stimuli were also best recalled when given a long-term, incidental memory test, a fact potentially related to the differential P300 waves at encoding. Moreover, taking into account the sex-related differences in language processing and conversational behavior, in the present study we evaluated possible talkativeness differences between the two genders in the recollection of emotional stimuli. Our data showed that women used a higher number of words, compared to men, to describe both arousal and neutral stories. Moreover, the present results support the view that sex differences in lateralization may not be a general feature of language processing but may be related to the specific condition, such as the emotional content of stimuli.

  18. McGurk stimuli for the investigation of multisensory integration in cochlear implant users: The Oldenburg Audio Visual Speech Stimuli (OLAVS).

    PubMed

    Stropahl, Maren; Schellhardt, Sebastian; Debener, Stefan

    2017-06-01

    The concurrent presentation of different auditory and visual syllables may result in the perception of a third syllable, reflecting an illusory fusion of visual and auditory information. This well-known McGurk effect is frequently used for the study of audio-visual integration. Recently, it was shown that the McGurk effect is strongly stimulus-dependent, which complicates comparisons across perceivers and inferences across studies. To overcome this limitation, we developed the freely available Oldenburg audio-visual speech stimuli (OLAVS), consisting of 8 different talkers and 12 different syllable combinations. The quality of the OLAVS set was evaluated with 24 normal-hearing subjects. All 96 stimuli were characterized based on their stimulus disparity, which was obtained from a probabilistic model (cf. Magnotti & Beauchamp, 2015). Moreover, the McGurk effect was studied in eight adult cochlear implant (CI) users. By applying the individual, stimulus-independent parameters of the probabilistic model, the predicted effect of stronger audio-visual integration in CI users could be confirmed, demonstrating the validity of the new stimulus material.

  19. Quantum dots with single-atom precision.

    PubMed

    Fölsch, Stefan; Martínez-Blanco, Jesús; Yang, Jianshu; Kanisawa, Kiyoshi; Erwin, Steven C

    2014-07-01

    Quantum dots are often called artificial atoms because, like real atoms, they confine electrons to quantized states with discrete energies. However, although real atoms are identical, most quantum dots comprise hundreds or thousands of atoms, with inevitable variations in size and shape and, consequently, unavoidable variability in their wavefunctions and energies. Electrostatic gates can be used to mitigate these variations by adjusting the electron energy levels, but the more ambitious goal of creating quantum dots with intrinsically digital fidelity by eliminating statistical variations in their size, shape and arrangement remains elusive. We used a scanning tunnelling microscope to create quantum dots with identical, deterministic sizes. By using the lattice of a reconstructed semiconductor surface to fix the position of each atom, we controlled the shape and location of the dots with effectively zero error. This allowed us to construct quantum dot molecules whose coupling has no intrinsic variation but could nonetheless be tuned with arbitrary precision over a wide range. Digital fidelity opens the door to quantum dot architectures free of intrinsic broadening-an important goal for technologies from nanophotonics to quantum information processing as well as for fundamental studies of confined electrons.

  20. Metamorphic quantum dots: Quite different nanostructures

    SciTech Connect

    Seravalli, L.; Frigeri, P.; Nasi, L.; Trevisi, G.; Bocchi, C.

    2010-09-15

    In this work, we present a study of InAs quantum dots deposited on InGaAs metamorphic buffers by molecular beam epitaxy. By comparing morphological, structural, and optical properties of such nanostructures with those of InAs/GaAs quantum dot ones, we were able to evidence characteristics that are typical of metamorphic InAs/InGaAs structures. The more relevant are: the cross-hatched InGaAs surface overgrown by dots, the change in critical coverages for island nucleation and ripening, the nucleation of new defects in the capping layers, and the redshift in the emission energy. The discussion on experimental results allowed us to conclude that metamorphic InAs/InGaAs quantum dots are rather different nanostructures, where attention must be put to some issues not present in InAs/GaAs structures, namely, buffer-related defects, surface morphology, different dislocation mobility, and stacking fault energies. On the other hand, we show that metamorphic quantum dot nanostructures can provide new possibilities of tailoring various properties, such as dot positioning and emission energy, that could be very useful for innovative dot-based devices.