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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. 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.

  5. 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.

  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. 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.

  9. 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.

  10. 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

  11. 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).

  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. 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.

  14. 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.

  15. 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…

  16. 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.

  17. 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.

  18. 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

  19. 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…

  20. 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.

  1. 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

  2. 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

  3. 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.

  4. 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.

  5. Time-resolved X-, K-, and W-band EPR of the radical pair state P{sub 700}{sup {center_dot}-}A{sub 1}{sup {center_dot}-} of photosystem I in comparison with P{sub 865}{sup {center_dot}+}Q{sub A}{sup {center_dot}-} in bacterial reaction centers

    SciTech Connect

    Est, A. van der; Prisner, T.; Moebius, K.; Stehlik, D.; Bittl, R.; Fromme, P.; Lubitz, W.

    1997-02-20

    The spin-polarized EPR spectra at 95 GHz (W-band), 24 GHz (K-band), and 9 GHz (X-band) of the radical pair P{sub 700}{sup {center_dot}+}A{sub 1}{sup {center_dot}-} in highly purified photosystem I particles are presented. The spectra are analyzed to obtain both the magnetic parameters of the radical pair as well as the relative orientation of the two species. From the analysis, the g-tensor of A{sub 1}{sup {center_dot}-} is found to be g{sub xx} = 2.0062, g{sub yy} = 2.0051, and g{sub zz} = 2.0022, and it is shown that A{sub 1} is oriented such that the carbonyl bonds are parallel to the vector joining the centers of P{sub 700}{sup {center_dot}+} and A{sub 1}{sup {center_dot}-}. The anisotropy of the g-tensor is considerably larger than that obtained for chemically reduced phylloquinone in frozen 2-propanol solution. Possible reasons for this difference and their implications for the A{sub 1} binding site are discussed. The relative orientation of P{sub 700}{sup {center_dot}+} and A{sub 1}{sup {center_dot}-} is compared with earlier estimates obtained using less accurate g-values for A{sub 1}{sup {center_dot}-}. A comparison with the spectra of P{sub 865}{sup {center_dot}+}Q{sub A}{sup {center_dot}-} in bacterial reaction centers (bRCs) of Rhodobacter sphaeroides R-26 in which the nonheme iron has been replaced by zinc (Zn-bRCs) allows the structural and magnetic properties of the charge-separated state in the two systems to be compared. 52 refs., 5 figs., 7 tabs.

  6. 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

  7. 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.

  8. 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)

  9. 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…

  10. 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.

  11. 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.

  12. 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.

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

    NASA Astrophysics Data System (ADS)

    Shahzadeh, Mohammadreza; Sabaeian, Mohammad

    2014-06-01

    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.

  14. 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.

  15. 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).

  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. 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

  18. 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.

  19. 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.

  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. 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.

  2. 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.

  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. 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

  5. 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.

  6. 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

  7. 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

  8. 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.

  9. 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.

  10. 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…

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. 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.

  16. 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…

  17. 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.

  18. 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

  19. 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.

  20. [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.

  1. 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…

  2. 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…

  3. 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.

  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. 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.

  6. 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.

  7. 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.

  8. 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

  9. 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

  10. 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.

  11. 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…

  12. 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.

  13. 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.

  14. A Stimuli-Responsive Smart Lanthanide Nanocomposite for Multidimensional Optical Recording and Encryption.

    PubMed

    Li, Xiang; Xie, Yujie; Song, Bo; Zhang, Hao-Li; Chen, Hao; Cai, Huijuan; Liu, Weisheng; Tang, Yu

    2017-03-01

    A stimuli-responsive lanthanide-based smart nanocomposite has been fabricated by supramolecular assembly and applied as an active material in multidimensional memory materials. Conjugation of the lanthanide complexes with carbon dots provides a stimuli response that is based on the modulation of the energy level of the ligand and affords microsecond-to-nanosecond fluorescence lifetimes, giving rise to intriguing memory performance in the spatial and temporal dimension. The present study points to a new direction for the future development of multidimensional memory materials based on inorganic-organic hybrid nanosystems.

  15. 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.

  16. 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

  17. 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

  18. 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

  19. 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…

  20. 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…

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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).

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

    PubMed

    Kimura, Tsukasa; Katayama, Jun'ichi

    2017-03-07

    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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. 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.

  20. 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

  1. 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.

  2. 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.

  3. 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

  4. 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.

  5. 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.

  6. 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.

  7. 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…

  8. 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

  9. 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.

  10. 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.

  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. 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

  13. 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

  14. 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.

  15. 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

  16. Quantum dots as FRET acceptors for highly sensitive multiplexing immunoassays

    NASA Astrophysics Data System (ADS)

    Geissler, Daniel; Hildebrandt, Niko; Charbonnière, Loïc J.; Ziessel, Raymond F.; Löhmannsröben, Hans-Gerd

    2009-02-01

    Homogeneous immunoassays have the benefit that they do not require any time-consuming separation steps. FRET is one of the most sensitive homogeneous methods used for immunoassays. Due to their extremely strong absorption over a broad wavelength range the use of quantum dots as FRET acceptors allows for large Foerster radii, an important advantage for assays in the 5 to 10 nm distance range. Moreover, because of their size-tunable emission, quantum dots of different sizes can be used with a single donor for the detection of different analytes (multiplexing). As the use of organic dyes with short fluorescence decay times as donors is known to be inefficient with quantum dot acceptors, lanthanide complexes with long luminescence decays are very efficient alternatives. In this contribution we present the application of commercially available biocompatible CdSe/ZnS core/shell quantum dots as multiplexing FRET acceptors together with a single terbium complex as donor in a homogeneous immunoassay system. Foerster radii of 10 nm and FRET efficiencies of 75 % are demonstrated. The high sensitivity of the terbium-toquantum dot FRET assay is shown by sub-100-femtomolar detection limits for two different quantum dots (emitting at 605 and 655 nm) within the same biotin-streptavidin assay. Direct comparison to the FRET immunoassay "gold standard" (FRET from Eu-TBP to APC) yields a three orders of magnitude sensitivity improvement, demonstrating the big advantages of quantum dots not only for multiplexing but also for highly sensitive nanoscale analysis.

  17. 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.

  18. 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

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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

  6. 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.

  7. 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.

  8. 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

  9. 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

  10. 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.

  11. 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

  12. 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.…

  13. 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)

  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. Preterm Infants' Responses to Aversive Stimuli.

    ERIC Educational Resources Information Center

    Riese, Marilyn L.

    Irritability levels and activity reactivity to aversive tactile stimuli were compared for 144 full-term neonates and 191 preterm infants. Irritability ratings increased across the five trials both during and post stimulation for full-term females and males and for preterm females, but not for preterm males. Activity ratings decreased across trials…

  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. 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…

  18. 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.

  19. 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…

  20. 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.

  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.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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

  14. 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.

  15. Psychophysics of Complex Auditory and Speech Stimuli.

    DTIC Science & Technology

    1996-10-01

    it more distinctive (i.e. in a different instrument timbre than the other musical voices) and less distinctive (i.e. presenting the musical pieces in...complex acoustic signals, including speech and music . Traditional, solid psycho- ,physical procedures were employed to systematically investigate...result in the perception of classes of complex auditory i stimuli, including speech and music . In health, industry, and human factors, the M.. SUBJECT

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. 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.

  2. 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

  3. 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.

  4. 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.

  5. 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

  6. 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

  7. 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

  8. 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

  9. 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.

  10. 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,…

  11. 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.

  12. 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…

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. 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

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. 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.

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. Multi-Stimuli Responsive Macromolecules and Their Assemblies

    PubMed Central

    Zhuang, Jiaming; Gordon, Mallory; Ventura, Judy; Li, Longyu; Thayumanavan, S.

    2013-01-01

    In this review, we outline examples that illustrate the design criteria for achieving macromolecular assemblies that incorporate a combination of two or more chemical, physical or biological stimuli-responsive components. Progress in both fundamental investigation into the phase transformations of these polymers in response to multiple stimuli and their utilization in a variety of pratical applications have been highlighted. Using these examples, we aim to explain the origin of employed mechanisms of stimuli responsiveness which may serve as a guideline to inspire future design of multi-stimuli responsive materials. PMID:23765263

  5. 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…

  6. 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.

  7. 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

  8. 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.

  9. 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

  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. 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

  12. 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

  13. 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

  14. 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

  15. 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.

  16. 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.

  17. 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.

  18. 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…

  19. 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…

  20. 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…

  1. 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

  2. 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…

  3. 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).…

  4. 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…

  5. 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…

  6. 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

  7. 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.

  8. 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.

  9. Effects of mechanical stimuli on adaptive remodeling of condylar cartilage.

    PubMed

    Sriram, D; Jones, A; Alatli-Burt, I; Darendeliler, M A

    2009-05-01

    Trabecular bone has been shown to be responsive to low-magnitude, high-frequency mechanical stimuli. This study aimed to assess the effects of these stimuli on condylar cartilage and its endochondral bone. Forty female 12-week-old C3H mice were divided into 3 groups: baseline control (killed at day 0), sham (killed at day 28 without exposure to mechanical stimuli), and experimental (killed following 28 days of exposure to mechanical stimuli). The experimental group was subjected to mechanical vibration of 30 Hz, for 20 minutes per day, 5 days per week, for 28 days. The specimens were analyzed by micro-computed tomography. The experimental group demonstrated a significant decrease in the volume of condylar cartilage and also a significant increase in bone histomorphometric parameters. The results suggest that the low-magnitude, high-frequency mechanical stimuli enhance adaptive remodeling of condylar cartilage, evidenced by the advent of endochondral bone replacing the hypertrophic cartilage.

  10. 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.

  11. 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.

  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. 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.

  14. 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.

  15. 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

  16. 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

  17. 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.

  18. 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

  19. 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

  20. 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

  1. 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.

  2. 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

  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. 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.

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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...

  12. 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…

  13. 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

  14. 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

  15. 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.

  16. 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.

  17. Color-switchable, emission-enhanced fluorescence realized by engineering C-dot@C-dot nanoparticles.

    PubMed

    Guo, Zhen; Zhang, Zhiqiang; Zhang, Wei; Zhou, Lianqun; Li, Haiwen; Wang, Hongmei; Andreazza-Vignolle, Caroline; Andreazza, Pascal; Zhao, Dongxu; Wu, Yihui; Wang, Quanlong; Zhang, Tao; Jiang, Keming

    2014-12-10

    This paper reports the preparation and properties of color-switchable fluorescent carbon nanodots (C-dots). C-dots that emit dark turquoise and green-yellow fluorescence under 365 nm UV illumination were obtained from the hydrothermal decomposition of citric acid. Dark green fluorescent C-dots were obtained by conjugating prepared C-dots to form C-dot@C-dot nanoparticles. After successful conjugation of the C-dots, the fluorescence emission undergoes a blue-shift of nearly 20 nm (∼0.15 eV) under UV excitation at 370 nm. The C-dots emit goldenrod, green-yellow, and gold light under excitation at 455 nm, which shows that the prepared C-dots are color-switchable. Furthermore, conjugation of the C-dots results in enhanced, red-shifted absorption of the π-π* transition of the aromatic sp(2) domains due to the conjugated π-electron system. N incorporation in the carbon structure leads to a degree of dipoles for all the aromatic sp(2) bonds. The enhanced absorption in a wide range from 226 to 601 nm indicates extended conjugation in the C-dot@C-dot structure. The time-resolved average lifetimes for the three different types of C-dots prepared in this study are 7.10, 7.65, and 4.07 ns. The radiative rate (reduced decay lifetime) increases when the C-dots are conjugated in the C-dot@C-dot nanoparticles, leading to the enhanced fluorescence emission. The fluorescence emission of the C-dot@C-dot nanoparticles can be used in applications such as flow cytometry and cell imaging.

  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. 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.

  20. 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.

  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. 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.

  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. 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.

  5. 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

  6. 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.

  7. 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

  8. 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.

  9. 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

  10. 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.

  11. 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

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  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

    2016-08-25

    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. 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).

  20. 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.

  1. 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.

  2. Quantum Dot Detectors with Plasmonic Structures

    DTIC Science & Technology

    2015-05-15

    AFRL-RV-PS- AFRL-RV-PS- TR-2015-0102 TR-2015-0102 QUANTUM DOT DETECTORS WITH PLASMONIC STRUCTURES Sanjay Krishna University of...SUBTITLE Quantum Dot Detectors with Plasmonic Structures 5a. CONTRACT NUMBER FA9453-12-1-0131 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 63401F 6...characterization, of multi-spectral quantum dots-in-a-double well (DDWELL) infrared detectors, by the integration of a surface Plasmon (SP) assisted resonant

  3. Double Quantum Dots in Carbon Nanotubes

    DTIC Science & Technology

    2010-06-02

    occupation of one dot is favored by increasing the detuning between the dots, the Coulomb interaction causes strong correlation effects realized by...of an additional val- ley degree of freedom, the two-electron eigenstates can be separated in an orbital part and a spin-valley part that are, to a...detuning, each dot is populated by a single electron and tunneling is sup- pressed because of Coulomb interactions. Thus, interdot coupling only occurs

  4. Barrier Engineered Quantum Dot Infrared Photodetectors

    DTIC Science & Technology

    2015-06-01

    AFRL-RV-PS- AFRL-RV-PS- TR-2015-0111 TR-2015-0111 BARRIER ENGINEERED QUANTUM DOT INFRARED PHOTODETECTORS Sanjay Krishna Center for High Technology...2011 – 22 May 2012 4. TITLE AND SUBTITLE Barrier Engineered Quantum Dot Infrared Photodetectors 5a. CONTRACT NUMBER FA9453-12-1-0336 5b. GRANT...is Unlimited. 13. SUPPLEMENTARY NOTES 14. ABSTRACT To investigate barrier engineered designs to reduce the dark current in quantum dot infrared

  5. 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

  6. 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.

  7. Synthetic Developments of Nontoxic Quantum Dots.

    PubMed

    Das, Adita; Snee, Preston T

    2016-03-03

    Semiconductor nanocrystals, or quantum dots (QDs), are candidates for biological sensing, photovoltaics, and catalysis due to their unique photophysical properties. The most studied QDs are composed of heavy metals like cadmium and lead. However, this engenders concerns over heavy metal toxicity. To address this issue, numerous studies have explored the development of nontoxic (or more accurately less toxic) quantum dots. In this Review, we select three major classes of nontoxic quantum dots composed of carbon, silicon and Group I-III-VI elements and discuss the myriad of synthetic strategies and surface modification methods to synthesize quantum dots composed of these material systems.

  8. 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.

  9. 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.

  10. Logical rules and the classification of integral-dimension stimuli.

    PubMed

    Little, Daniel R; Nosofsky, Robert M; Donkin, Christopher; Denton, Stephen E

    2013-05-01

    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 dimensions are spatially separated and as a mixture of serial and parallel processes if the dimensions are spatially overlapping (Fifić, Little, & Nosofsky, 2010; Little, Nosofsky, & Denton, 2011). In the current research, the logical-rule models are applied to predict response-time (RT) data from participants trained to classify integral-dimension color stimuli into rule-based categories. In dramatic contrast to the previous results for separable-dimension stimuli, analysis of the current data indicated that processing was best captured by a single-channel coactive model. The results converge with previous operations that suggest holistic processing of integral-dimension stimuli and demonstrate considerable generality for the application of the logical-rule models to predicting RT data from rule-based classification experiments.

  11. Protein-surface interactions on stimuli-responsive polymeric biomaterials.

    PubMed

    Cross, Michael C; Toomey, Ryan G; Gallant, Nathan D

    2016-03-04

    Responsive surfaces: a review of the dependence of protein adsorption on the reversible volume phase transition in stimuli-responsive polymers. Specifically addressed are a widely studied subset: thermoresponsive polymers. Findings are also generalizable to other materials which undergo a similarly reversible volume phase transition. As of 2015, over 100,000 articles have been published on stimuli-responsive polymers and many more on protein-biomaterial interactions. Significantly, fewer than 100 of these have focused specifically on protein interactions with stimuli-responsive polymers. These report a clear trend of increased protein adsorption in the collapsed state compared to the swollen state. This control over protein interactions makes stimuli-responsive polymers highly useful in biomedical applications such as wound repair scaffolds, on-demand drug delivery, and antifouling surfaces. Outstanding questions are whether the protein adsorption is reversible with the volume phase transition and whether there is a time-dependence. A clear understanding of protein interactions with stimuli-responsive polymers will advance theoretical models, experimental results, and biomedical applications.

  12. Private Stimuli, Covert Responses, and Private Events: Conceptual Remarks

    PubMed Central

    Tourinho, Emmanuel Zagury

    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 private. I argue that the role of private stimuli in the control of self-descriptive verbal responses is dependent on a relation (correlation or equivalence relation) with public stimuli, and that responses vary along a continuum of observability. These remarks on private stimuli and covert responses are introductory to an examination of the varying complexity of phenomena described as private. I argue that private events is a verbal response emitted under the control of phenomena of different degrees of complexity, and I interpret these phenomena, based on the principle of selection by consequences. I introduce the notion of inclusiveness to suggest that some phenomena related to privacy are less or more complex as they include relations of a phylogenetic, ontogenetic, and cultural origin. PMID:22478451

  13. 49 CFR 40.227 - May employers use the ATF for non-DOT tests, or non-DOT forms for DOT tests?

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... Transportation PROCEDURES FOR TRANSPORTATION WORKPLACE DRUG AND ALCOHOL TESTING PROGRAMS Testing Sites, Forms, Equipment and Supplies Used in Alcohol Testing § 40.227 May employers use the ATF for non-DOT tests, or non... for non-DOT alcohol tests. You are also prohibited from using non-DOT forms for DOT alcohol...

  14. The variability of multisensory processes of natural stimuli in human and non-human primates in a detection task

    PubMed Central

    Juan, Cécile; Cappe, Céline; Alric, Baptiste; Roby, Benoit; Gilardeau, Sophie; Barone, Pascal; Girard, Pascal

    2017-01-01

    Background Behavioral studies in both human and animals generally converge to the dogma that multisensory integration improves reaction times (RTs) in comparison to unimodal stimulation. These multisensory effects depend on diverse conditions among which the most studied were the spatial and temporal congruences. Further, most of the studies are using relatively simple stimuli while in everyday life, we are confronted to a large variety of complex stimulations constantly changing our attentional focus over time, a modality switch that can impact on stimuli detection. In the present study, we examined the potential sources of the variability in reaction times and multisensory gains with respect to the intrinsic features of a large set of natural stimuli. Methodology/Principle findings Rhesus macaque monkeys and human subjects performed a simple audio-visual stimulus detection task in which a large collection of unimodal and bimodal natural stimuli with semantic specificities was presented at different saliencies. Although we were able to reproduce the well-established redundant signal effect, we failed to reveal a systematic violation of the race model which is considered to demonstrate multisensory integration. In both monkeys and human species, our study revealed a large range of multisensory gains, with negative and positive values. While modality switch has clear effects on reaction times, one of the main causes of the variability of multisensory gains appeared to be linked to the intrinsic physical parameters of the stimuli. Conclusion/Significance Based on the variability of multisensory benefits, our results suggest that the neuronal mechanisms responsible of the redundant effect (interactions vs. integration) are highly dependent on the stimulus complexity suggesting different implications of uni- and multisensory brain regions. Further, in a simple detection task, the semantic values of individual stimuli tend to have no significant impact on task

  15. Persistent perceptual delay for head movement onset relative to auditory stimuli of different durations and rise times.

    PubMed

    Barnett-Cowan, Michael; Raeder, Sophie M; Bülthoff, Heinrich H

    2012-07-01

    The perception of simultaneity between auditory and vestibular information is crucially important for maintaining a coherent representation of the acoustic environment whenever the head moves. It has been recently reported, however, that despite having similar transduction latencies, vestibular stimuli are perceived significantly later than auditory stimuli when simultaneously generated. This suggests that perceptual latency of a head movement is longer than a co-occurring sound. However, these studies paired a vestibular stimulation of long duration (~1 s) and of a continuously changing temporal envelope with a brief (10-50 ms) sound pulse. In the present study, the stimuli were matched for temporal envelope duration and shape. Participants judged the temporal order of the two stimuli, the onset of an active head movement and the onset of brief (50 ms) or long (1,400 ms) sounds with a square- or raised-cosine-shaped envelope. Consistent with previous reports, head movement onset had to precede the onset of a brief sound by about 73 ms in order for the stimuli to be perceived as simultaneous. Head movements paired with long square sounds (~100 ms) were not significantly different than brief sounds. Surprisingly, head movements paired with long raised-cosine sound (~115 ms) had to be presented even earlier than brief stimuli. This additional lead time could not be accounted for by differences in the comparison stimulus characteristics (temporal envelope duration and shape). Rather, differences between sound conditions were found to be attributable to variability in the time for head movement to reach peak velocity: the head moved faster when paired with a brief sound. The persistent lead time required for vestibular stimulation provides further evidence that the perceptual latency of vestibular stimulation is greater than the other senses.

  16. Migraine is associated with altered processing of sensory stimuli.

    PubMed

    Harriott, Andrea M; Schwedt, Todd J

    2014-11-01

    Migraine is associated with derangements in perception of multiple sensory modalities including vision, hearing, smell, and somatosensation. Compared to people without migraine, migraineurs have lower discomfort thresholds in response to special sensory stimuli as well as to mechanical and thermal noxious stimuli. Likewise, the environmental triggers of migraine attacks, such as odors and flashing lights, highlight basal abnormalities in sensory processing and integration. These alterations in sensory processing and perception in migraineurs have been investigated via physiological studies and functional brain imaging studies. Investigations have demonstrated that migraineurs during and between migraine attacks have atypical stimulus-induced activations of brainstem, subcortical, and cortical regions that participate in sensory processing. A lack of normal habituation to repetitive stimuli during the interictal state and a tendency towards development of sensitization likely contribute to migraine-related alterations in sensory processing.

  17. Generating Stimuli for Neuroscience Using PsychoPy.

    PubMed

    Peirce, Jonathan W

    2008-01-01

    PsychoPy is a software library written in Python, using OpenGL to generate very precise visual stimuli on standard personal computers. It is designed to allow the construction of as wide a variety of neuroscience experiments as possible, with the least effort. By writing scripts in standard Python syntax users can generate an enormous variety of visual and auditory stimuli and can interact with a wide range of external hardware (enabling its use in fMRI, EEG, MEG etc.). The structure of scripts is simple and intuitive. As a result, new experiments can be written very quickly, and trying to understand a previously written script is easy, even with minimal code comments. PsychoPy can also generate movies and image sequences to be used in demos or simulated neuroscience experiments. This paper describes the range of tools and stimuli that it provides and the environment in which experiments are conducted.

  18. Pedophilic brain potential responses to adult erotic stimuli.

    PubMed

    Knott, Verner; Impey, Danielle; Fisher, Derek; Delpero, Emily; Fedoroff, Paul

    2016-02-01

    Cognitive mechanisms associated with the relative lack of sexual interest in adults by pedophiles are poorly understood and may benefit from investigations examining how the brain processes adult erotic stimuli. The current study used event-related brain potentials (ERP) to investigate the time course of the explicit processing of erotic, emotional, and neutral pictures in 22 pedophilic patients and 22 healthy controls. Consistent with previous studies, early latency anterior ERP components were highly selective for erotic pictures. Although the ERPs elicited by emotional stimuli were similar in patients and controls, an early frontal positive (P2) component starting as early as 185 ms was significantly attenuated and slow to onset in pedophilia, and correlated with a clinical measure of cognitive distortions. Failure of rapid attentional capture by erotic stimuli suggests a relative reduction in early processing in pedophilic patients which may be associated with relatively diminished sexual interest in adults.

  19. Behavioral detection of passive whisker stimuli requires somatosensory cortex.

    PubMed

    Miyashita, Toshio; Feldman, Daniel E

    2013-07-01

    Rodent whisker sensation occurs both actively, as whiskers move rhythmically across objects, and in a passive mode in which externally applied deflections are sensed by static, non-moving whiskers. Passive whisker stimuli are robustly encoded in the somatosensory (S1) cortex, and provide a potentially powerful means of studying cortical processing. However, whether S1 contributes to passive sensation is debated. We developed 2 new behavioral tasks to assay passive whisker sensation in freely moving rats: Detection of unilateral whisker deflections and discrimination of right versus left whisker deflections. Stimuli were simple, simultaneous multi-whisker deflections. Local muscimol inactivation of S1 reversibly and robustly abolished sensory performance on these tasks. Thus, S1 is required for the detection and discrimination of simple stimuli by passive whiskers, in addition to its known role in active whisker sensation.

  20. Stimuli-Responsive Nanomaterials for Therapeutic Protein Delivery

    PubMed Central

    Lu, Yue; Sun, Wujin; Gu, Zhen

    2014-01-01

    Protein therapeutics have emerged as a significant role in treatment of a broad spectrum of diseases, including cancer, metabolic disorders and autoimmune diseases. The efficacy of protein therapeutics, however, is limited by their instability, immunogenicity and short half-life. In order to overcome these barriers, tremendous efforts have recently been made in developing controlled protein delivery systems. Stimuli-triggered release is an appealing and promising approach for protein delivery and has made protein delivery with both spatiotemporal- and dosage-controlled manners possible. This review surveys recent advances in controlled protein delivery of proteins or peptides using stimuli-responsive nanomaterials. Strategies utilizing both physiological and external stimuli are introduced and discussed. PMID:25151983

  1. Electrotactile stimuli delivered across fingertips inducing the Cutaneous Rabbit Effect.

    PubMed

    Warren, Jay P; Santello, Marco; Helms Tillery, Stephen I

    2010-10-01

    Previous studies have been unable to induce the Cutaneous Rabbit Effect (CRE) when the most likely perceived location of the illusory stimulus is on a non-continuous skin area. To determine whether the CRE could be elicited when each of the delivered stimuli were on non-continuous skin areas, we developed a new electrotactile stimulation paradigm attempting to induce the CRE across the fingertips. Though our stimulation paradigm differed from classic reduced CRE paradigms through the use of electrotactile stimuli, focusing the subject attention to a 'likely' illusory site, and the inclusion of a fourth stimulation site (two stimuli after the illusory stimulus), these factors were not the cause of the illusory effect we observed. Experiments conducted on the forearm validated that our paradigm elicited similar results to those reported in previous CRE studies that used either 3-stimulation-point mechanical or electrotactile stimuli with subject attention focused on the 'likely' illusory site. Across the fingertips, we observed an increase in stimulus mislocalization onto the middle fingertip, the 'likely' perceived location of the illusory stimuli, under Illusory Rabbit Trains compared to the Motion Bias Trains. Because the Motion Bias Trains should not induce a perceived location shift of the illusory stimulus but stimulates the adjacent digits in a similar way to the Illusory Rabbit Trains, differences observed between their mislocalization rates between these trains indicate that the CRE can be induced across the fingertips. These results provide the first evidence that the CRE can 'jump' when the stimuli occur across non-continuous skin areas.

  2. Exposure to virtual social stimuli modulates subjective pain reports

    PubMed Central

    Vigil, Jacob M; Torres, Daniel; Wolff, Alexander; Hughes, Katy

    2014-01-01

    BACKGROUND: Contextual factors, including the gender of researchers, influence experimental and patient pain reports. It is currently not known how social stimuli influence pain percepts, nor which types of sensory modalities of communication, such as auditory, visual or olfactory cues associated with person perception and gender processing, produce these effects. OBJECTIVES: To determine whether exposure to two forms of social stimuli (audio and visual) from a virtual male or female stranger modulates cold pressor task (CPT) pain reports. METHODS: Participants with similar demographic characteristics conducted a CPT in solitude, without the physical presence of an experimenter or another person. During the CPT, participants were exposed to the voice and image of a virtual male or female stranger. The voices had analogous vocal prosody, provided no semantic information (spoken in a foreign language) and differed only in pitch; the images depicted a middle-age male or female health care practitioner. RESULTS: Male participants, but not females, showed higher CPT pain intensity when they were exposed to the female stimuli compared with the male stimuli. Follow-up analyses showed that the association between the social stimuli and variability in pain sensitivity was not moderated by individual differences in subjective (eg, self-image) or objective measurements of one’s physical stature. DISCUSSION: The findings show that exposure to virtual, gender-based auditory and visual social stimuli influences exogenous pain sensitivity. CONCLUSION: Further research on how contextual factors, such as the vocal properties of health care examiners and exposure to background voices, may influence momentary pain perception is necessary for creating more standardized methods for measuring patient pain reports in clinical settings. PMID:24911175

  3. EEG-power and -coherence changes in a unimodal and a crossmodal working memory task with visual and kinesthetic stimuli.

    PubMed

    Seemüller, A; Müller, E M; Rösler, F

    2012-01-01

    We investigated EEG-power and EEG-coherence changes in a unimodal and a crossmodal matching-to-sample working memory task with either visual or kinesthetic stimuli. Angle-shaped trajectories were used as stimuli presented either as a moving dot on a screen or as a passive movement of a haptic device. Effects were evaluated during the different phases of encoding, maintenance, and recognition. Alpha power was modulated during encoding by the stimulus modality, and in crossmodal conditions during encoding and maintenance by the expected modality of the upcoming test stimulus. These power modulations were observed over modality-specific cortex regions. Systematic changes of coherence for crossmodal compared to unimodal tasks were not observed during encoding and maintenance but only during recognition. There, coherence in the theta-band increased between electrode sites over left central and occipital cortex areas in the crossmodal compared to the unimodal conditions. The results underline the importance of modality-specific representations and processes in unimodal and crossmodal working memory tasks. Crossmodal recognition of visually and kinesthetically presented object features seems to be related to a direct interaction of somatosensory/motor and visual cortex regions by means of long-range synchronization in the theta-band and such interactions seem to take place at the beginning of the recognition phase, i.e. when crossmodal transfer is actually necessary.

  4. Emerging applications of stimuli-responsive polymer materials

    NASA Astrophysics Data System (ADS)

    Stuart, Martien A. Cohen; Huck, Wilhelm T. S.; Genzer, Jan; Müller, Marcus; Ober, Christopher; Stamm, Manfred; Sukhorukov, Gleb B.; Szleifer, Igal; Tsukruk, Vladimir V.; Urban, Marek; Winnik, Françoise; Zauscher, Stefan; Luzinov, Igor; Minko, Sergiy

    2010-02-01

    Responsive polymer materials can adapt to surrounding environments, regulate transport of ions and molecules, change wettability and adhesion of different species on external stimuli, or convert chemical and biochemical signals into optical, electrical, thermal and mechanical signals, and vice versa. These materials are playing an increasingly important part in a diverse range of applications, such as drug delivery, diagnostics, tissue engineering and 'smart' optical systems, as well as biosensors, microelectromechanical systems, coatings and textiles. We review recent advances and challenges in the developments towards applications of stimuli-responsive polymeric materials that are self-assembled from nanostructured building blocks. We also provide a critical outline of emerging developments.

  5. Stimuli responsive release of metalic nanoparticles on semiconductor substrates.

    PubMed

    Santiago-Cordoba, Miguel; Topal, Özge; Allara, David L; Kalkan, A Kaan; Demirel, Melik C

    2012-04-10

    Optically active metal nanoparticles have been of recent and broad interest for applications to biomarker detection because of their ability to enable high sensitivity enhancements in various optical detection techniques. Here, we report stimuli responsive release of metallic nanoparticles on a semiconductor thin film array structure based on pH change. The metallic nanoparticles are obtained by a simple redox procedure on the semiconductor surface. This approach allows controlling nanoparticle surface coatings in situ for biomolecule conjugation, such as DNA probes on nanoparticles, and rapid stimuli responsive release of these nanoparticles upon pH change.

  6. 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....

  7. 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....

  8. 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....

  9. 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....

  10. 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)

  11. 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.

  12. 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.

  13. Thick-shell nanocrystal quantum dots

    DOEpatents

    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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. 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

  1. 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.

  2. 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.

  3. Impaired Prioritization of Novel Onset Stimuli in Autism Spectrum Disorder

    ERIC Educational Resources Information Center

    Keehn, Brandon; Joseph, Robert M.

    2008-01-01

    Background: Deficiency in the adaptive allocation of attention to relevant environmental stimuli is an associated feature of autism spectrum disorder (ASD). Recent evidence suggests that individuals with ASD may be specifically impaired in attentional prioritization of novel onsets. Method: We investigated modulation of attention by novel onset…

  4. A Study of the Affective Responses Elicited by Occupational Stimuli

    ERIC Educational Resources Information Center

    Schoon, Craig G.

    1976-01-01

    The semantic differential was used to assess the properties of affect elicited by occupational stimuli. Vocationally committed men studying medicine, business, and engineering responded to a semantic differential containing occupational concepts. Results show a semantic space for all three groups composed of three orthogonal dimensions of affect…

  5. Stimuli-responsive magnetic nanoparticles for monoclonal antibody purification.

    PubMed

    Borlido, Luís; Moura, Leila; Azevedo, Ana M; Roque, Ana C A; Aires-Barros, Maria R; Farinha, José Paulo S

    2013-06-01

    Monoclonal antibodies (mAbs) are important therapeutic proteins. One of the challenges facing large-scale production of monoclonal antibodies is the capacity bottleneck in downstream processing, which can be circumvented by using magnetic stimuli-responsive polymer nanoparticles. In this work, stimuli-responsive magnetic particles composed of a magnetic poly(methyl methacrylate) core with a poly(N-isopropylacrylamide-co-acrylic acid) (P(NIPAM-co-AA)) shell cross-linked with N, N'-methylenebisacrylamide were prepared by miniemulsion polymerization. The particles were shown to have an average hydrodynamic diameter of 317 nm at 18°C, which decreased to 277 nm at 41°C due to the collapse of the thermo-responsive shell. The particles were superparamagnetic in behavior and exhibited a saturation magnetization of 12.6 emu/g. Subsequently, we evaluated the potential of these negatively charged stimuli-responsive magnetic particles in the purification of a monoclonal antibody from a diafiltered CHO cell culture supernatant by cation exchange. The adsorption of antibodies onto P(NIPAM-co-AA)-coated nanoparticles was highly selective and allowed for the recovery of approximately 94% of the mAb. Different elution strategies were employed providing highly pure mAb fractions with host cell protein (HCP) removal greater than 98%. By exploring the stimuli-responsive properties of the particles, shorter magnetic separation times were possible without significant differences in product yield and purity.

  6. The Effect of Being Able to Control Aversive Stimuli.

    ERIC Educational Resources Information Center

    Geer, James H.

    Research was conducted to investigate the phenomena associated with an individual's having perceived control or actual control over aversive stimuli. In all, 10 studies were conducted, 7 of which were directly relevant to investigating variables affecting perceived or actual control, and 3 being "spin-off" experiments. The seven studies…

  7. Auditory Long Latency Responses to Tonal and Speech Stimuli

    ERIC Educational Resources Information Center

    Swink, Shannon; Stuart, Andrew

    2012-01-01

    Purpose: The effects of type of stimuli (i.e., nonspeech vs. speech), speech (i.e., natural vs. synthetic), gender of speaker and listener, speaker (i.e., self vs. other), and frequency alteration in self-produced speech on the late auditory cortical evoked potential were examined. Method: Young adult men (n = 15) and women (n = 15), all with…

  8. Habituation of Infants' Cardiac Response to Speech Stimuli.

    ERIC Educational Resources Information Center

    Trehub, Sandra E.; Curran, Susanne

    1979-01-01

    Four groups of infants, 4 1/2 to 5 1/2 months of age, were presented with repeated speech stimuli which were synthesized exemplars of the sound, "baba," natural exemplars of "baba" or "kaba," or novel syllables on each trial. (RH)

  9. Emergence of Intraverbal Responding Following Tact Instruction with Compound Stimuli

    ERIC Educational Resources Information Center

    Devine, Bailey; Carp, Charlotte L.; Hiett, Kiley A.; Petursdottir, Anna Ingeborg

    2016-01-01

    Effective intraverbal responding often requires control by multiple elements of a verbal stimulus. The purpose of this study was to examine the emergence of such intraverbal relations following tact instruction with compound stimuli and to analyze any resulting error patterns. Participants were seven typically developing children between 3 and…

  10. Cognitive control modulates preferential sensory processing of affective stimuli.

    PubMed

    Steinhauser, Marco; Flaisch, Tobias; Meinzer, Marcus; Schupp, Harald T

    2016-10-01

    Adaptive human behavior crucially relies on the ability of the brain to allocate resources automatically to emotionally significant stimuli. This ability has consistently been demonstrated by studies showing preferential processing of affective stimuli in sensory cortical areas. It is still unclear, however, whether this putatively automatic mechanism can be modulated by cognitive control processes. Here, we use functional magnetic resonance imaging (fMRI) to investigate whether preferential processing of an affective face distractor is suppressed when an affective distractor has previously elicited a response conflict in a word-face Stroop task. We analyzed this for three consecutive stages in the ventral stream of visual processing for which preferential processing of affective stimuli has previously been demonstrated: the striate area (BA 17), category-unspecific extrastriate areas (BA 18/19), and the fusiform face area (FFA). We found that response conflict led to a selective suppression of affective face processing in category-unspecific extrastriate areas and the FFA, and this effect was accompanied by changes in functional connectivity between these areas and the rostral anterior cingulate cortex. In contrast, preferential processing of affective face distractors was unaffected in the striate area. Our results indicate that cognitive control processes adaptively suppress preferential processing of affective stimuli under conditions where affective processing is detrimental because it elicits response conflict.

  11. Reliable activation to novel stimuli predicts higher fluid intelligence.

    PubMed

    Euler, Matthew J; Weisend, Michael P; Jung, Rex E; Thoma, Robert J; Yeo, Ronald A

    2015-07-01

    The ability to reliably respond to stimuli could be an important biological determinant of differences in fluid intelligence (Gf). However, most electrophysiological studies of Gf employ event-related potential (ERP) measures that average brain activity over trials, and hence have limited power to quantify neural variability. Time-frequency analyses can capture cross-trial variation in the phase of neural activity, and thus can help address the importance of neural reliability to differences in Gf. This study recruited a community sample of healthy adults and measured inter-trial phase clustering (ITPC), total spectral power, and ERP amplitudes elicited by Repeated and Novel non-target stimuli during two visual oddball tasks. Condition effects, relations among the EEG measures, and relations with Gf were assessed. Early visual responses to Repeated stimuli elicited higher ITPC, yet only ITPC elicited by Novel stimuli was associated with Gf. Analyses of spectral power further highlighted the contribution of phase consistency to the findings. The link between Gf and reliable responding to changing inputs suggests an important role for flexible resource allocation in fluid intellectual skills.

  12. Alliesthesia to food cues: heterogeneity across stimuli and sensory modalities.

    PubMed

    Jiang, Tao; Soussignan, Robert; Rigaud, Daniel; Martin, Sylviane; Royet, Jean-Pierre; Brondel, Laurent; Schaal, Benoist

    2008-10-20

    Negative alliesthesia to olfactory and visual stimuli was assessed in 29 normal-weight women who, on alternate days, were either fasting or in a postprandial state after an ad libitum lunch. The participants were alternatively exposed to food and non-food pictures and odorants, and then rated for their hedonic appreciation (liking) and their desire to ingest (wanting) the evoked foods. While negative alliesthesia was observed only for food stimuli, it did not equally affect all food categories in either sensory modality. The stimuli representing foods eaten in typical local main dishes or having high energy density (e.g., pizza, bacon, beef, cheese) evoked clear negative alliesthesia, whereas this was not the case for those less consumed within a customary meal or associated with desserts (i.e., fruits). Furthermore, the visual food stimuli triggered a more negative shift in liking than did the food odours. Finally, the shift in wanting between pre- and post-meal state was more important than the shift in liking. These results suggest that alliesthesia may be influenced by both metabolic and non-metabolic factors.

  13. Experimenter Effects on Responses to Explicity Sexual Stimuli

    ERIC Educational Resources Information Center

    Abramson, Paul R.; And Others

    1975-01-01

    In an attempt to assess the effect of the general experimental situation on subjects in research on human sexuality, the present study addresses itself to systematically investigating the effect of the experimenter in experimentally induced reactions to sexually explicit stimuli. (Author/RK)

  14. Tagging Multiple Emotional Stimuli: Negative Valence Has Little Benefit

    ERIC Educational Resources Information Center

    Watson, Derrick G.; Blagrove, Elisabeth

    2012-01-01

    Six experiments examined the influence of emotional valence on the tagging and enumeration of multiple targets. Experiments 1, 5 and 6 found that there was no difference in the efficiency of tagging/enumerating multiple negative or positive stimuli. Experiment 2 showed that, when neutral-expression face distractors were present, enumerating…

  15. Reward Contexts Extend Dopamine Signals to Unrewarded Stimuli

    PubMed Central

    Kobayashi, Shunsuke; Schultz, Wolfram

    2014-01-01

    Summary Basic tenets of sensory processing emphasize the importance of accurate identification and discrimination of environmental objects [1]. Although this principle holds also for reward, the crucial acquisition of reward for survival would be aided by the capacity to detect objects whose rewarding properties may not be immediately apparent. Animal learning theory conceptualizes how unrewarded stimuli induce behavioral reactions in rewarded contexts due to pseudoconditioning and higher-order context conditioning [2–6]. We hypothesized that the underlying mechanisms may involve context-sensitive reward neurons. We studied short-latency activations of dopamine neurons to unrewarded, physically salient stimuli while systematically changing reward context. Dopamine neurons showed substantial activations to unrewarded stimuli and their conditioned stimuli in highly rewarded contexts. The activations decreased and often disappeared entirely with stepwise separation from rewarded contexts. The influence of reward context suggests that dopamine neurons respond to real and potential reward. The influence of reward context is compatible with the reward nature of phasic dopamine responses. The responses may facilitate rapid, default initiation of behavioral reactions in environments usually containing reward. Agents would encounter more and miss less reward, resulting in survival advantage and enhanced evolutionary fitness. PMID:24332545

  16. Using propensity score matching to construct experimental stimuli.

    PubMed

    Huber, Stefan; Dietrich, Julia F; Nagengast, Benjamin; Moeller, Korbinian

    2016-07-15

    Propensity score matching is widely used in various fields of research, including psychology, medicine, education, and sociology. It is usually applied to find a matched control group for a treatment group. In the present article, we suggest that propensity score matching might also be used to construct item sets matched for different parameters. We constructed stimuli to illustrate the use of propensity score matching in item construction for the exemplary cases of numerical cognition research and reading research. In particular, we provide a step-by-step approach, using the statistics software R, for how to apply propensity score matching for constructing matched stimuli. This approach involves deciding on a population of stimuli, determining and calculating the covariates, and finally applying the propensity-matching method to find a set of items matched to another predefined set. Thereby, we were able to construct well-matched item sets for both examples. Hence, we conclude that the propensity-score-matching method is useful for constructing matched stimuli. Further cases of application are discussed.

  17. Stress improves selective attention towards emotionally neutral left ear stimuli.

    PubMed

    Hoskin, Robert; Hunter, M D; Woodruff, P W R

    2014-09-01

    Research concerning the impact of psychological stress on visual selective attention has produced mixed results. The current paper describes two experiments which utilise a novel auditory oddball paradigm to test the impact of psychological stress on auditory selective attention. Participants had to report the location of emotionally-neutral auditory stimuli, while ignoring task-irrelevant changes in their content. The results of the first experiment, in which speech stimuli were presented, suggested that stress improves the ability to selectively attend to left, but not right ear stimuli. When this experiment was repeated using tonal stimuli the same result was evident, but only for female participants. Females were also found to experience greater levels of distraction in general across the two experiments. These findings support the goal-shielding theory which suggests that stress improves selective attention by reducing the attentional resources available to process task-irrelevant information. The study also demonstrates, for the first time, that this goal-shielding effect extends to auditory perception.

  18. Submillisecond unmasked subliminal visual stimuli evoke electrical brain responses.

    PubMed

    Sperdin, Holger F; Spierer, Lucas; Becker, Robert; Michel, Christoph M; Landis, Theodor

    2015-04-01

    Subliminal perception is strongly associated to the processing of meaningful or emotional information and has mostly been studied using visual masking. In this study, we used high density 256-channel EEG coupled with an liquid crystal display (LCD) tachistoscope to characterize the spatio-temporal dynamics of the brain response to visual checkerboard stimuli (Experiment 1) or blank stimuli (Experiment 2) presented without a mask for 1 ms (visible), 500 µs (partially visible), and 250 µs (subliminal) by applying time-wise, assumption-free nonparametric randomization statistics on the strength and on the topography of high-density scalp-recorded electric field. Stimulus visibility was assessed in a third separate behavioral experiment. Results revealed that unmasked checkerboards presented subliminally for 250 µs evoked weak but detectable visual evoked potential (VEP) responses. When the checkerboards were replaced by blank stimuli, there was no evidence for the presence of an evoked response anymore. Furthermore, the checkerboard VEPs were modulated topographically between 243 and 296 ms post-stimulus onset as a function of stimulus duration, indicative of the engagement of distinct configuration of active brain networks. A distributed electrical source analysis localized this modulation within the right superior parietal lobule near the precuneus. These results show the presence of a brain response to submillisecond unmasked subliminal visual stimuli independently of their emotional saliency or meaningfulness and opens an avenue for new investigations of subliminal stimulation without using visual masking.

  19. Superior Detection of Threat-Relevant Stimuli in Infancy

    ERIC Educational Resources Information Center

    LoBue, Vanessa; DeLoache, Judy S.

    2010-01-01

    The ability to quickly detect potential threat is an important survival mechanism for humans and other animals. Past research has established that adults have an attentional bias for the detection of threat-relevant stimuli, including snakes and spiders as well as angry human faces. Recent studies have documented that preschool children also…

  20. Delivery of continuously-varying stimuli using channelrhodopsin-2

    PubMed Central

    Tchumatchenko, Tatjana; Newman, Jonathan P.; Fong, Ming-fai; Potter, Steve M.

    2013-01-01

    To study sensory processing, stimuli are delivered to the sensory organs of animals and evoked neural activity is recorded downstream. However, noise and uncontrolled modulatory input can interfere with repeatable delivery of sensory stimuli to higher brain regions. Here we show how channelrhodopsin-2 (ChR2) can be used to deliver continuous, subthreshold, time-varying currents to neurons at any point along the sensory-motor pathway. To do this, we first deduce the frequency response function of ChR2 using a Markov model of channel kinetics. We then confirm ChR2's frequency response characteristics using continuously-varying optical stimulation of neurons that express one of three ChR2 variants. We find that wild-type ChR2 and the E123T/H134R mutant (“ChETA”) can pass continuously-varying subthreshold stimuli with frequencies up to ~70 Hz. Additionally, we find that wild-type ChR2 exhibits a strong resonance at ~6–10 Hz. Together, these results indicate that ChR2-derived optogenetic tools are useful for delivering highly repeatable artificial stimuli that mimic in vivo synaptic bombardment. PMID:24367294

  1. Differences in Sensorimotor Processing of Visual and Proprioceptive Stimuli

    ERIC Educational Resources Information Center

    Kamen, Gary and Morris, Harold H.

    1988-01-01

    A paradox in studying sensory perception is that people often attend to a stimulus which provides the least optimal information. Usually, this is a visual stimulus. The study sought to lessen this reliance on vision by training subjects to respond to proprioceptive stimuli. Results are discussed. (Author/JL)

  2. Infants' Preferential Attention to Sung and Spoken Stimuli

    ERIC Educational Resources Information Center

    Costa-Giomi, Eugenia; Ilari, Beatriz

    2014-01-01

    Caregivers and early childhood teachers all over the world use singing and speech to elicit and maintain infants' attention. Research comparing infants' preferential attention to music and speech is inconclusive regarding their responses to these two types of auditory stimuli, with one study showing a music bias and another one…

  3. Slowed response to peripheral visual stimuli during strenuous exercise.

    PubMed

    Ando, Soichi; Komiyama, Takaaki; Kokubu, Masahiro; Sudo, Mizuki; Kiyonaga, Akira; Tanaka, Hiroaki; Higaki, Yasuki

    2016-07-01

    Recently, we proposed that strenuous exercise impairs peripheral visual perception because visual responses to peripheral visual stimuli were slowed during strenuous exercise. However, this proposal was challenged because strenuous exercise is also likely to affect the brain network underlying motor responses. The purpose of the current study was to resolve this issue. Fourteen participants performed a visual reaction-time (RT) task at rest and while exercising at 50% (moderate) and 75% (strenuous) peak oxygen uptake. Visual stimuli were randomly presented at different distances from fixation in two task conditions: the Central condition (2° or 5° from fixation) and the Peripheral condition (30° or 50° from fixation). We defined premotor time as the time between stimulus onset and the motor response, as determined using electromyographic recordings. In the Central condition, premotor time did not change during moderate (167±19ms) and strenuous (168±24ms) exercise from that at rest (164±17ms). In the Peripheral condition, premotor time significantly increased during moderate (181±18ms, P<0.05) and strenuous exercise (189±23ms, P<0.001) from that at rest (173±17ms). These results suggest that increases in Premotor Time to the peripheral visual stimuli did not result from an impaired motor-response network, but rather from impaired peripheral visual perception. We conclude that slowed response to peripheral visual stimuli during strenuous exercise primarily results from impaired visual perception of the periphery.

  4. Developmental Complexity of the Stimuli Included in Mispronunciation Detection Tasks

    ERIC Educational Resources Information Center

    McNeill, Brigid C.; Hesketh, Anne

    2010-01-01

    Background: Phonological representations are important for speech and literacy development. Mispronunciation detection tasks have been proposed as an appropriate measure of phonological representations for children with speech disorder. There has been limited analysis, however, of the developmental complexity of task stimuli. Further, the tasks…

  5. Impact prediction by looming visual stimuli enhances tactile detection.

    PubMed

    Cléry, Justine; Guipponi, Olivier; Odouard, Soline; Wardak, Claire; Ben Hamed, Suliann

    2015-03-11

    From an ecological point of view, approaching objects are potentially more harmful than receding objects. A predator, a dominant conspecific, or a mere branch coming up at high speed can all be dangerous if one does not detect them and produce the appropriate escape behavior fast enough. And indeed, looming stimuli trigger stereotyped defensive responses in both monkeys and human infants. However, while the heteromodal somatosensory consequences of visual looming stimuli can be fully predicted by their spatiotemporal dynamics, few studies if any have explored whether visual stimuli looming toward the face predictively enhance heteromodal tactile sensitivity around the expected time of impact and at its expected location on the body. In the present study, we report that, in addition to triggering a defensive motor repertoire, looming stimuli toward the face provide the nervous system with predictive cues that enhance tactile sensitivity on the face. Specifically, we describe an enhancement of tactile processes at the expected time and location of impact of the stimulus on the face. We additionally show that a looming stimulus that brushes past the face also enhances tactile sensitivity on the nearby cheek, suggesting that the space close to the face is incorporated into the subjects' body schema. We propose that this cross-modal predictive facilitation involves multisensory convergence areas subserving the representation of a peripersonal space and a safety boundary of self.

  6. 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

  7. 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.

  8. Sex differences in emotional and psychophysiological responses to musical stimuli.

    PubMed

    Nater, Urs M; Abbruzzese, Elvira; Krebs, Monika; Ehlert, Ulrike

    2006-11-01

    Although it is known that men and women differ in their music preferences and emotional reactions to music, little is known about sex differences in physiological reactions to music. In our study, we therefore set out to examine the differential reactivity to two musical stimuli that elicit distinct psychological and physiological reaction patterns. Fifty-three healthy subjects (mean age: 26.13, SD: 3.97; 26 males, 27 females) were examined. Heart rate, electrodermal activity, skin temperature, salivary cortisol, salivary alpha-amylase, and psychological variables were assessed during the course of the whole study. Following baseline assessment, two musical stimuli, which were carefully selected and rated in a pre-study as relaxing and pleasant (renaissance music) and arousing and unpleasant (heavy metal), respectively, were introduced. They were presented on two different days in a randomized order. Whereas psychological variables did not differ between men and women, results of electrophysiological measures indicate significantly different reactivity patterns between men and women. Women displayed elevated response curves to the arousing and unpleasant stimulus, whereas men did not. However, no differences were found with regards to endocrine measures in saliva. Our results demonstrate sex differences in reactivity patterns to musical stimuli in psychophysiological measures. In our study, we were able to show that women tend to show hypersensitivity to aversive musical stimuli. This finding is in accordance with previous literature on sex differences in emotion research. Furthermore, our study indicates that the confounding effects of sex differences have to be considered when using musical stimuli for emotion induction.

  9. Extrastriate body area underlies aesthetic evaluation of body stimuli.

    PubMed

    Calvo-Merino, B; Urgesi, C; Orgs, G; Aglioti, S M; Haggard, P

    2010-07-01

    Humans appear to be the only animals to have developed the practice and culture of art. This practice presumably relies on special processing circuits within the human brain associated with a distinct subjective experience, termed aesthetic experience, and preferentially evoked by artistic stimuli. We assume that positive or negative aesthetic judgments are an important function of neuroaesthetic circuits. The localisation of these circuits in the brain remains unclear, though neuroimaging studies have suggested several possible neural correlates of aesthetic preference. We applied repetitive transcranial magnetic stimulation (rTMS) over candidate brain areas to disrupt aesthetic processing while healthy volunteers made aesthetic preference judgments between pairs of dance postures, or control non-body stimuli. Based on evidence from visual body perception studies, we targeted the ventral premotor cortex (vPMC) and extrastriate body area (EBA), in the left and right hemispheres. rTMS over EBA reduced aesthetic sensitivity for body stimuli relative to rTMS over vPMC, while no such difference was found for non-body stimuli. We interpret our results within the framework of dual routes for visual body processing. rTMS over either EBA or vPMC reduced the contributions of the stimulated area to body processing, leaving processing more reliant on the unaffected route. Disruption of EBA reduces the local processing of the stimuli and reduced observers' aesthetic sensitivity. Conversely, disruption of the global route via vPMC increased the relative contribution of the local route via EBA and thus increased aesthetic sensitivity. In this way, we suggest a complementary contribution of both local and global routes to aesthetic processing.

  10. Cortical responses from adults and infants to complex visual stimuli.

    PubMed

    Schulman-Galambos, C; Galambos, R

    1978-10-01

    Event-related potentials (ERPs) time-locked to the onset of visual stimuli were extracted from the EEG of normal adult (N = 16) and infant (N = 23) subjects. Subjects were not required to make any response. Stimuli delivered to the adults were 150 msec exposures of 2 sets of colored slides projected in 4 blocks, 2 in focus and 2 out of focus. Infants received 2-sec exposures of slides showing people, colored drawings or scenes from Disneyland, as well as 2-sec illuminations of the experimenter as she played a game or of a TV screen the baby was watching. The adult ERPs showed 6 waves (N1 through P4) in the 140--600-msec range; this included a positive wave at around 350 msec that was large when the stimuli were focused and smaller when they were not. The waves in the 150--200-msec range, by contrast, steadily dropped in amplitude as the experiment progressed. The infant ERPs differed greatly from the adult ones in morphology, usually showing a positive (latency about 200 msec)--negative(5--600msec)--positive(1000msec) sequence. This ERP appeared in all the stimulus conditions; its presence or absence, furthermore, was correlated with whether or not the baby seemed interested in the stimuli. Four infants failed to produce these ERPs; an independent measure of attention to the stimuli, heart rate deceleration, was demonstrated in two of them. An electrode placed beneath the eye to monitor eye movements yielded ERPs closely resembling those derived from the scalp in most subjects; reasons are given for assigning this response to activity in the brain, probably at the frontal pole. This study appears to be one of the first to search for cognitive 'late waves' in a no-task situation. The results suggest that further work with such task-free paradigms may yield additional useful techniques for studying the ERP.

  11. The effect of repeated laser stimuli to ink-marked skin on skin temperature—recommendations for a safe experimental protocol in humans

    PubMed Central

    Madden, Victoria J.; Catley, Mark J.; Grabherr, Luzia; Mazzola, Francesca; Shohag, Mohammad

    2016-01-01

    Background. Nd:YAP laser is widely used to investigate the nociceptive and pain systems, generating perpetual and laser-evoked neurophysiological responses. A major procedural concern for the use of Nd:YAP laser stimuli in experimental research is the risk of skin damage. The absorption of Nd:YAP laser stimuli is greater in darker skin, or in pale skin that has been darkened with ink, prompting some ethics boards to refuse approval to experimenters wishing to track stimulus location by marking the skin with ink. Some research questions, however, require laser stimuli to be delivered at particular locations or within particular zones, a requirement that is very difficult to achieve if marking the skin is not possible. We thoroughly searched the literature for experimental evidence and protocol recommendations for safe delivery of Nd:YAP laser stimuli over marked skin, but found nothing. Methods. We designed an experimental protocol to define safe parameters for the use of Nd:YAP laser stimuli over skin that has been marked with black dots, and used thermal imaging to assess the safety of the procedure at the forearm and the back. Results. Using thermal imaging and repeated laser stimulation to ink-marked skin, we demonstrated that skin temperature did not increase progressively across the course of the experiment, and that the small change in temperature seen at the forearm was reversed during the rest periods between blocks. Furthermore, no participant experienced skin damage due to the procedure. Conclusion. This protocol offers parameters for safe, confident and effective experimentation using repeated Nd:YAP laser on skin marked with ink, thus paving the way for investigations that depend on it. PMID:26793428

  12. 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.

  13. 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.

  14. Hyperactivation to Pleasant Interoceptive Stimuli Characterizes the Transition to Stimulant Addiction*

    PubMed Central

    Stewart, Jennifer L.; May, April C.; Tapert, Susan F.; Paulus, Martin P.

    2015-01-01

    Aims Altered interoception, how the brain processes afferents from the body, may contribute to the urge to take drugs, and subsequently, the development of addiction. Although chronic stimulant dependent individuals exhibit attenuated brain responses to pleasant interoceptive stimuli, it is unclear whether this deficit exists early-on in the process of transition to stimulant addiction. Methods To this end, we compared problem stimulant users (PSU; n=18), desisted stimulant users (DSU; n=15), and stimulant naïve comparison subjects (CTL; n=15) during functional magnetic resonance imaging (fMRI) while they anticipated and experienced pleasant soft touch (slow brushstroke to the palm and forearm). Results Groups did not differ in behavioral performance or visual analog scale ratings of soft touch stimuli. fMRI results indicated that PSU exhibited greater right anterior insula, left inferior frontal gyrus, and right superior frontal gyrus activation than DSU and CTL during the anticipation and experience of soft touch. Moreover, during the experience of soft touch, PSU demonstrated higher bilateral precentral gyrus/middle insula and right posterior temporal gyrus activation than DSU and CTL. Conclusions In contrast to chronic stimulant dependence, individuals who have recently developed stimulant use disorders show exaggerated neural processing of pleasant interoceptive stimuli. Thus, increased processing of body-relevant information signaling pleasant touch in those individuals who develop problem use may be a predictive interoceptive biomarker. However, future investigations will need to determine whether the combination of probing pleasant interoception using neuroimaging is sufficiently sensitive and specific to help identify individuals at high risk for future problem use. PMID:26228575

  15. Electrical vestibular stimuli to enhance vestibulo-motor output and improve subject comfort.

    PubMed

    Forbes, Patrick A; Dakin, Christopher J; Geers, Anoek M; Vlaar, Martijn P; Happee, Riender; Siegmund, Gunter P; Schouten, Alfred C; Blouin, Jean-Sébastien

    2014-01-01

    Electrical vestibular stimulation is often used to assess vestibulo-motor and postural responses in both clinical and research settings. Stochastic vestibular stimulation (SVS) is a recently established technique with many advantages over its square-wave counterpart; however, the evoked muscle responses remain relatively small. Although the vestibular-evoked responses can be enhanced by increasing the stimulus amplitude, subjects often perceive these higher intensity electrical stimuli as noxious or painful. Here, we developed multisine vestibular stimulation (MVS) signals that include precise frequency contributions to increase signal-to-noise ratios (SNR) of stimulus-evoked muscle and motor responses. Subjects were exposed to three different MVS stimuli to establish that: 1) MVS signals evoke equivalent vestibulo-motor responses compared to SVS while improving subject comfort and reducing experimentation time, 2) stimulus-evoked vestibulo-motor responses are reliably estimated as a linear system and 3) specific components of the cumulant density time domain vestibulo-motor responses can be targeted by controlling the frequency content of the input stimulus. Our results revealed that in comparison to SVS, MVS signals increased the SNR 3-6 times, reduced the minimum experimentation time by 85% and improved subjective measures of comfort by 20-80%. Vestibulo-motor responses measured using both EMG and force were not substantially affected by nonlinear distortions. In addition, by limiting the contribution of high frequencies within the MVS input stimulus, the magnitude of the medium latency time domain motor output response was increased by 58%. These results demonstrate that MVS stimuli can be designed to target and enhance vestibulo-motor output responses while simultaneously improving subject comfort, which should prove beneficial for both research and clinical applications.

  16. Optical Spectroscopy of Hybrid Semiconductor Quantum Dots and Metal Nanoparticles

    DTIC Science & Technology

    2014-11-07

    SECURITY CLASSIFICATION OF: Optical studies of semiconductor quantum dots (SQDs), metal nanoparticles (MNPs), and their hybrid nanomaterials are...Distribution Unlimited Final Report: Optical Spectroscopy of Hybrid Semiconductor Quantum Dots and Metal Nanoparticles The views, opinions and/or findings...Semiconductor Quantum Dots and Metal Nanoparticles Report Title Optical studies of semiconductor quantum dots (SQDs), metal nanoparticles (MNPs), and their

  17. The effects of listener training on discriminative control by elements of compound stimuli in children with disabilities.

    PubMed

    Ribeiro, Daniela M; Miguel, Caio F; Goyos, Celso

    2015-07-01

    The purpose of the current study was to assess whether the establishment of listener relations with compound stimuli as samples and comparisons would lead to the emergence of: (1) speaker behavior in the form of tacts of the compound stimuli; (2) listener and tact responses for untaught compounds; and (3) listener and tact responses for the isolated properties of compounds. Participants were four boys diagnosed with autism and one diagnosed with intellectual disability. We taught participants to select among three compound comparisons consisting of combinations of shapes and patterns in the presence of the corresponding dictated word. Subsequently, we tested for the emergence of tacts for the trained compounds, as well as tact and listener relations for six untaught compounds and their properties. In general, results showed that the acquisition of listener relations led to the emergence of the corresponding tacts, as well as the emergence of listener and tact responses for untaught combinations for three out of five participants. By contrast, the other two participants showed responding characteristic of restricted stimulus control. These results suggest that the establishment of bidirectional relations between listener and speaker behaviors may facilitate the emergence of control by properties of compound stimuli.

  18. The Bank of Standardized Stimuli (BOSS), a New Set of 480 Normative Photos of Objects to Be Used as Visual Stimuli in Cognitive Research

    PubMed Central

    Brodeur, Mathieu B.; Dionne-Dostie, Emmanuelle; Montreuil, Tina; Lepage, Martin

    2010-01-01

    There are currently stimuli with published norms available to study several psychological aspects of language and visual cognitions. Norms represent valuable information that can be used as experimental variables or systematically controlled to limit their potential influence on another experimental manipulation. The present work proposes 480 photo stimuli that have been normalized for name, category, familiarity, visual complexity, object agreement, viewpoint agreement, and manipulability. Stimuli are also available in grayscale, blurred, scrambled, and line-drawn version. This set of objects, the Bank Of Standardized Stimuli (BOSS), was created specifically to meet the needs of scientists in cognition, vision and psycholinguistics who work with photo stimuli. PMID:20532245

  19. The Bank of Standardized Stimuli (BOSS), a new set of 480 normative photos of objects to be used as visual stimuli in cognitive research.

    PubMed

    Brodeur, Mathieu B; Dionne-Dostie, Emmanuelle; Montreuil, Tina; Lepage, Martin

    2010-05-24

    There are currently stimuli with published norms available to study several psychological aspects of language and visual cognitions. Norms represent valuable information that can be used as experimental variables or systematically controlled to limit their potential influence on another experimental manipulation. The present work proposes 480 photo stimuli that have been normalized for name, category, familiarity, visual complexity, object agreement, viewpoint agreement, and manipulability. Stimuli are also available in grayscale, blurred, scrambled, and line-drawn version. This set of objects, the Bank Of Standardized Stimuli (BOSS), was created specifically to meet the needs of scientists in cognition, vision and psycholinguistics who work with photo stimuli.

  20. Personalized medicine and follow-up of therapeutic delivery through exploitation of quantum dot toxicity.

    PubMed

    Manshian, Bella B; Jiménez, Julio; Himmelreich, Uwe; Soenen, Stefaan J

    2017-03-05

    Tumor therapy using nanoparticles (NPs) is mainly aimed at using the NPs as carriers for therapeutic drugs or as mediators for external stimuli to generate heat. Recent studies have shown that the toxicity of NPs can also be specifically exploited to kill cancer cells. In the present work, we employ core-only CdTe quantum dots and study their cytotoxicity using a validated high-content screening approach. The data revealed a clear correlation between toxicity and quantum dot degradation, which could be monitored through loss of fluorescence intensity. Based on the in vitro data obtained, the in vivo dose was calculated relative to the estimated number of tumor cells based on luminescence measurements. The obtained results show a clear increase in reproducibility of the therapeutic effect compared to normal conditions, where a set dose of quantum dots was administered regardless of the tumor size. The therapeutic delivery could also be monitored in vivo, where the loss of fluorescence intensity correlated with the anticancer efficacy. The present work highlights the benefits of noninvasive imaging to monitor therapeutic delivery and to optimize treatment via personalized medicine.

  1. 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.

  2. 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.

  3. Are Dementia Patient's Engagement Using Tailored Stimuli the Same? The Apathy Dilemma in Nursing Home Residents.

    PubMed

    Leone, Elsa; Deudon, Audrey; Piano, Julie; Robert, Philippe; Dechamps, Arnaud

    2012-01-01

    Background. Apathy is the most frequent behavioural disturbance understanding how apathy drives engagement in resident's activities of interests is a milestone to better understanding and tailored challenging interventions targeting engagement enhancement. Method. Residents aged 60 and older with dementia according to the ICD 10 from four nursing homes in the south east of France. A set of 25 stimuli were used and categorized by participant into Work, Leisure, Family, or Personal categories, an additional "not interested" category was used for comparison of engagement. The participants stimuli allocation was randomized in guided and unguided situations over a two-week period with 15minute interaction for each stimulus (n = 2) of each category (5×(15 min×2)). Clinical trial identifier: NCT01314131. Results. The mean age, 95% confidence interval (CI) of the 40 participants was 85.4 (83.8-87) with a mean MMSE score, CI95% of 17.7 (16.5-19). Analyses revealed a significant superiority effect of guidance over unguided interaction in duration of engagement in all categories of interest except for the stimulus category "family" and all P < .05. Apathetic participants when guided had longer engagement duration in stimulus Leisure and Personal (all P < .01). Conclusion. Guidance and better activities of interest can lead to enhanced engagement time in participants with dementia.

  4. Bayesian Mapping Reveals That Attention Boosts Neural Responses to Predicted and Unpredicted Stimuli.

    PubMed

    Garrido, Marta I; Rowe, Elise G; Halász, Veronika; Mattingley, Jason B

    2017-04-10

    Predictive coding posits that the human brain continually monitors the environment for regularities and detects inconsistencies. It is unclear, however, what effect attention has on expectation processes, as there have been relatively few studies and the results of these have yielded contradictory findings. Here, we employed Bayesian model comparison to adjudicate between 2 alternative computational models. The "Opposition" model states that attention boosts neural responses equally to predicted and unpredicted stimuli, whereas the "Interaction" model assumes that attentional boosting of neural signals depends on the level of predictability. We designed a novel, audiospatial attention task that orthogonally manipulated attention and prediction by playing oddball sequences in either the attended or unattended ear. We observed sensory prediction error responses, with electroencephalography, across all attentional manipulations. Crucially, posterior probability maps revealed that, overall, the Opposition model better explained scalp and source data, suggesting that attention boosts responses to predicted and unpredicted stimuli equally. Furthermore, Dynamic Causal Modeling showed that these Opposition effects were expressed in plastic changes within the mismatch negativity network. Our findings provide empirical evidence for a computational model of the opposing interplay of attention and expectation in the brain.

  5. "McGurk illusion" to bilateral administration of sensory stimuli in patients with hemispatial neglect.

    PubMed

    Soroker, N; Calamaro, N; Myslobodsky, M

    1995-04-01

    The illusion of McGurk (Nature 264, 746-748, 1976) refers to the blending of conflicting audio-visual messages. By taking advantage of this phenomenon the study explored whether visual cues (i.e. manner of articulation) in ipsilesional (right) space would help a patient with auditory neglect to mentally reconstruct syllabic sounds voiced in contralesional (left) space. We examined seven patients with clinically detectable visual neglect following right hemisphere damage. All had signs of auditory neglect as documented by the inferior identification of syllables delivered through a loudspeaker on the left side. In contrast, syllabic sounds delivered contralesionally together with visual stimuli in the ipsilesional space significantly increased identification of "neglected" syllabic sounds. Of the increased responses, 23% were classified as illusory blends, thereby suggesting that manner of articulation provides a valuable clue as to the possible "best fit" for a consonant. The susceptibility to the blend illusion was identical in patients and controls. Results indicate that neglected auditory stimuli are retrieved in patients with right hemisphere lesion by the mechanism of the ventriloquist illusion in the presence of a carefully timed sequence of comparisons of auditory signals in the neglected space with visual signals in the attended space. The possibility that neuronal mechanisms that serve audio-visual merger in spatial localization are also utilized for processing speech distinctions is discussed.

  6. Fibrous networks with incorporated macrocycles: a chiral stimuli-responsive supramolecular supergelator and its application to biocatalysis in organic media.

    PubMed

    Qi, Zhenhui; Wu, Changzhu; Malo de Molina, Paula; Sun, Han; Schulz, Andrea; Griesinger, Christian; Gradzielski, Michael; Haag, Rainer; Ansorge-Schumacher, Marion B; Schalley, Christoph A

    2013-07-29

    A new and versatile, crown ether appended, chiral supergelator has been designed and synthesized based on the bis-urea motif. The introduction of a stereogenic center improved its gelation ability significantly relative to its achiral analogue. This low-molecular-weight gelator forms supramolecular gels in a variety of organic solvents. It is sensitive to multiple chemical stimuli and the sol-gel phase transitions can be reversibly triggered by host-guest interactions. The gel can be used to trap enzymes and release them on demand by chemical stimuli. It stabilizes the microparticles in Pickering emulsions so that enzyme-catalyzed organic reactions can take place in the polar phase inside the microparticles, the organic reactants diffusing through the biphasic interface from the surrounding organic phase. Because of the higher interface area between the organic and polar phases, enzyme activity is enhanced in comparison with simple biphasic systems.

  7. Room-temperature blue-green emission from InGaN/GaN quantum dots made by strain-induced islanding growth

    NASA Astrophysics Data System (ADS)

    Damilano, B.; Grandjean, N.; Dalmasso, S.; Massies, J.

    1999-12-01

    InGaN/GaN self-assembled quantum dots (QDs) were obtained by molecular beam epitaxy making use of the Stranski-Krastanov growth mode. Room-temperature photoluminescence (PL) energy of QDs was observed from 2.6 to 3.1 eV depending on the dot size. PL linewidths as low as 40-70 meV at 10 K and 90-110 meV at 300 K indicate low dot size dispersion. The comparison of PL intensity versus temperature of an InGaN epilayer and InGaN/GaN QDs demonstrates the higher radiative efficiency of the latter.

  8. Quantum Dots Investigated for Solar Cells

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

    The NASA Glenn Research Center has been investigating the synthesis of quantum dots of CdSe and CuInS2 for use in intermediate-bandgap solar cells. Using quantum dots in a solar cell to create an intermediate band will allow the harvesting of a much larger portion of the available solar spectrum. Theoretical studies predict a potential efficiency of 63.2 percent, which is approximately a factor of 2 better than any state-of-the-art devices available today. This technology is also applicable to thin-film devices--where it offers a potential four-fold increase in power-to-weight ratio over the state of the art. Intermediate-bandgap solar cells require that quantum dots be sandwiched in an intrinsic region between the photovoltaic solar cell's ordinary p- and n-type regions (see the preceding figure). The quantum dots form the intermediate band of discrete states that allow sub-bandgap energies to be absorbed. However, when the current is extracted, it is limited by the bandgap, not the individual photon energies. The energy states of the quantum dot can be controlled by controlling the size of the dot. Ironically, the ground-state energy levels are inversely proportional to the size of the quantum dots. We have prepared a variety of quantum dots using the typical organometallic synthesis routes pioneered by Ba Wendi et al., in the early 1990's. The most studied quantum dots prepared by this method have been of CdSe. To produce these dots, researchers inject a syringe of the desired organometallic precursors into heated triocytlphosphine oxide (TOPO) that has been vigorously stirred under an inert atmosphere (see the following figure). The solution immediately begins to change from colorless to yellow, then orange and red/brown, as the quantum dots increase in size. When the desired size is reached, the heat is removed from the flask. Quantum dots of different sizes can be identified by placing them under a "black light" and observing the various color differences in

  9. Electronic properties of aperiodic quantum dot chains

    NASA Astrophysics Data System (ADS)

    Korotaev, P. Yu.; Vekilov, Yu. Kh.; Kaputkina, N. E.

    2012-04-01

    The electronic spectral and transport properties of aperiodic quantum dot chains are investigated. The systems with singular continuous energy spectrum are considered: Thue-Morse chain, double-periodic chain, Rudin-Shapiro chain. The influence of electronic energy in quantum dot on the spectral properties, band structure, density of states and spectral resistivity, is discussed. Low resistivity regions correspond to delocalized states and these states could be current states. Also we discuss the magnetic field application as the way to tune electronic energy in quantum dot and to obtain metallic or insulating conducting states of the systems.

  10. Zeeman transitions in spherical quantum dot

    NASA Astrophysics Data System (ADS)

    Yakar, Y.; ćakır, B.; Yılmazer, F.; Özmen, A.

    2017-02-01

    In this study, the effects of external magnetic field on the energy states of a spherical quantum dot with infinite potential barrier have been investigated by using Quantum Genetic Algorithm (QGA) and Hartree-Fock Roothaan (HFR) method. Linear Zeeman states and Zeeman transition energies are calculated as a function of dot radius and magnetic field strength. We also carry out the effect of external magnetic field on the ground state binding energy. The results show that the impurity energy states, binding energy and Zeeman transition energies are strongly affected by magnetic field strength and dot radius.

  11. Stimuli-responsive hydrogels in drug delivery and tissue engineering.

    PubMed

    Sood, Nikhil; Bhardwaj, Ankur; Mehta, Shuchi; Mehta, Abhinav

    2016-01-01

    Hydrogels are the three-dimensional network structures obtained from a class of synthetic or natural polymers which can absorb and retain a significant amount of water. Hydrogels are one of the most studied classes of polymer-based controlled drug release. These have attracted considerable attention in biochemical and biomedical fields because of their characteristics, such as swelling in aqueous medium, biocompatibility, pH and temperature sensitivity or sensitivity towards other stimuli, which can be utilized for their controlled zero-order release. The hydrogels are expected to explore new generation of self-regulated delivery system having a wide array of desirable properties. This review highlights the exciting opportunities and challenges in the area of hydrogels. Here, we review different literatures on stimuli-sensitive hydrogels, such as role of temperature, electric potential, pH and ionic strength to control the release of drug from hydrogels.

  12. Gender differences in detecting unanticipated stimuli: an ERP study.

    PubMed

    Jin, Yan; Yan, Ke; Zhang, Yuhe; Jiang, Yijie; Tao, Ran; Zheng, Xifu

    2013-03-22

    The aim of the present study was to investigate the gender differences during an emotional anticipation task. Sixteen females and sixteen males participated in the experiment. Event-related potentials (ERPs) were measured in a modified cue-target paradigm and were recorded following stimuli that differed in two dimensions: (1) predictable vs. unpredictable pictures and (2) negative vs. neutral pictures. Cue-induced ERP results demonstrated that females had enhanced positive component (P2) compared to males. Moreover, results showed that during the unpredictable condition, females displayed larger P2 amplitudes in negative and neutral anticipation than males. This study demonstrates that females have greater sensitivity to the unanticipated stimuli, which may contribute to evolution.

  13. Chords and harmonies in mixed optical and acoustical stimuli

    NASA Astrophysics Data System (ADS)

    Hahlweg, Cornelius; Dannenberg, Florian; Dörfler, Joachim; Weber, Bernhard; Weyer, Cornelia; Gercke-Hahn, Harald; Freimuth, Steffen; Heucke, Sören; Gutzmann, Holger Ludwig

    2014-09-01

    The paper is a follow up of the work presented in last year's Optics and Music session on the perception of coherence between low frequency power modulated light and periodical acoustic stimuli. The composition of chords and harmonies from power modulated light sources and their effect as stand-alone stimulus and in conjunction with the equivalent acoustic signal is discussed. Of special interest here is the modulation near perceptible flicker frequency. The substitution of acoustical chord components by their optical counterpart and vice versa is investigated. Further, concepts of a training application for trombone players and other instrumentalists are presented: since the mean slide of the trombone does not have fixed positions, the note must be found and two players might influence each other. The possibility of helping them to synchronize by optical stimuli derived from their playing is investigated. Beside possible applications in emotional reinforcing multimedia oriented entertainment and training support for musicians, again implications for occupational medicine are discussed.

  14. Pure agnosia for mirror stimuli after right inferior parietal lesion.

    PubMed

    Priftis, Konstantinos; Rusconi, Elena; Umiltà, Carlo; Zorzi, Marco

    2003-04-01

    This study reports the experimental investigation of G.R., a patient suffering from a highly specific disorder in discriminating mirror stimuli following a right temporoparietal cerebrovascular accident. G.R. showed intact perceptual, attentional, mnestic, linguistic and executive abilities. Object recognition was accurate even under unusual viewing conditions. He was highly accurate in defining the canonical orientation of common objects and in discriminating misoriented objects among identical distracters. However, he was severely impaired in tasks requiring mirror-stimulus discrimination, a deficit that persisted even when the object's coordinates were systematically misaligned with respect to his body. The disorder was also dependent upon the frame of reference (allocentric versus egocentric) activated on the basis of task demands. These results demonstrate the existence of a highly specific disorder in discriminating mirror stimuli defined in object-based coordinates, suggesting a failure in processing the directionality of an object's intrinsic x-axis.

  15. Effects of rectilinear acceleration, optokinetic and caloric stimuli in space

    NASA Technical Reports Server (NTRS)

    Vonbaumgarten, R.

    1981-01-01

    The set of experiments comprising the Spacelab 1ES201 package designed to investigate the human vestibular system and equilibratory function in weightlessness are described. The specific objectives of the experiments include: (1) the determination of the threshold of perception of linear oscillatory motion; (2) measurement of physiological and subjective responses to supra threshold, linear and angular motion stimuli; (3) study of the postural adjustments, eye movements, and illusions of attitude and motion evoked by optokinetic stimuli, (i.e., moving visual patterns) in order to assess visual/vestibular interactions; (4) examination of the effect of thermal stimulations of the vestibular apparatus to determine if the eye movements elicited by the 'caloric test' are used by a density gradient in the semicircular canal; and (5) investigation of the pathogenesis of space motion sickness by recording signs and symptoms during the course of vestibular stimulation and, specifically, when the test subject is exposed to sustained, linear oscillatory motion.

  16. Behavioral responses to noxious stimuli shape the perception of pain

    PubMed Central

    May, Elisabeth S.; Tiemann, Laura; Schmidt, Paul; Nickel, Moritz M.; Wiedemann, Nina; Dresel, Christian; Sorg, Christian; Ploner, Markus

    2017-01-01

    Pain serves vital protective functions. To fulfill these functions, a noxious stimulus might induce a percept which, in turn, induces a behavioral response. Here, we investigated an alternative view in which behavioral responses do not exclusively depend on but themselves shape perception. We tested this hypothesis in an experiment in which healthy human subjects performed a reaction time task and provided perceptual ratings of noxious and tactile stimuli. A multi-level moderated mediation analysis revealed that behavioral responses are significantly involved in the translation of a stimulus into perception. This involvement was significantly stronger for noxious than for tactile stimuli. These findings show that the influence of behavioral responses on perception is particularly strong for pain which likely reflects the utmost relevance of behavioral responses to protect the body. These observations parallel recent concepts of emotions and entail implications for the understanding and treatment of pain. PMID:28276487

  17. Affective Priming by Eye Gaze Stimuli: Behavioral and Electrophysiological Evidence

    PubMed Central

    Chen, Tingji; Peltola, Mikko J.; Ranta, Lotta J.; Hietanen, Jari K.

    2016-01-01

    The present study employed the affective priming paradigm and measurements of event-related potentials (ERPs) to investigate implicit affective reactions elicited by gaze stimuli. Participants categorized positive and negative words primed by direct gaze, averted gaze and closed eyes. The behavioral response time (RT) results indicated that direct gaze implicitly elicited more positive affective reactions than did closed eyes. Analyses of the ERP responses to the target words revealed a priming effect on the N170 and an interaction on late positive potential (LPP) responses, and congruently with the behavioral results, suggested that, compared to closed eyes, direct gaze was affectively more congruent with positive words and more incongruent with negative words. The priming effect on the N170 response indicated that gaze stimuli influenced the subsequent affective word processing at an early stage of information processing. In conclusion, the present behavioral and electrophysiological evidence suggests that direct gaze automatically activates more positive affective reactions than closed eyes. PMID:28003803

  18. Stimuli-responsive Pickering emulsions: recent advances and potential applications.

    PubMed

    Tang, Juntao; Quinlan, Patrick James; Tam, Kam Chiu

    2015-05-14

    Pickering emulsions possess many advantages over traditional surfactant stabilized emulsions. For example, Pickering emulsions impart better stability against coalescence and, in many cases, are biologically compatible and environmentally friendly. These characteristics open the door for their use in a variety of industries spanning petroleum, food, biomedicine, pharmaceuticals, and cosmetics. Depending on the application, rapid, but controlled stabilization and destabilization of an emulsion may be necessary. As a result, Pickering emulsions with stimuli-responsive properties have, in recent years, received a considerable amounts of attention. This paper provides a concise and comprehensive review of Pickering emulsion systems that possess the ability to respond to an array of external triggers, including pH, temperature, CO2 concentration, light intensity, ionic strength, and magnetic field. Potential applications for which stimuli-responsive Pickering emulsion systems would be of particular value, such as emulsion polymerization, enhanced oil recovery, catalyst recovery, and cosmetics, are discussed.

  19. Multifunctional, stimuli-sensitive nanoparticulate systems for drug delivery

    PubMed Central

    Torchilin, Vladimir P.

    2015-01-01

    The use of nanoparticulate pharmaceutical drug delivery systems (NDDSs) to enhance the in vivo effectiveness of drugs is now well established. The development of multifunctional and stimulus-sensitive NDDSs is an active area of current research. Such NDDSs can have long circulation times, target the site of the disease and enhance the intracellular delivery of a drug. This type of NDDS can also respond to local stimuli that are characteristic of the pathological site by, for example, releasing an entrapped drug or shedding a protective coating, thus facilitating the interaction between drug-loaded nanocarriers and target cells or tissues. In addition, imaging contrast moieties can be attached to these carriers to track their real-time biodistribution and accumulation in target cells or tissues. Here, I highlight recent developments with multifunctional and stimuli-sensitive NDDSs and their therapeutic potential for diseases including cancer, cardiovascular diseases and infectious diseases. PMID:25287120

  20. Behavioral responses to noxious stimuli shape the perception of pain.

    PubMed

    May, Elisabeth S; Tiemann, Laura; Schmidt, Paul; Nickel, Moritz M; Wiedemann, Nina; Dresel, Christian; Sorg, Christian; Ploner, Markus

    2017-03-09

    Pain serves vital protective functions. To fulfill these functions, a noxious stimulus might induce a percept which, in turn, induces a behavioral response. Here, we investigated an alternative view in which behavioral responses do not exclusively depend on but themselves shape perception. We tested this hypothesis in an experiment in which healthy human subjects performed a reaction time task and provided perceptual ratings of noxious and tactile stimuli. A multi-level moderated mediation analysis revealed that behavioral responses are significantly involved in the translation of a stimulus into perception. This involvement was significantly stronger for noxious than for tactile stimuli. These findings show that the influence of behavioral responses on perception is particularly strong for pain which likely reflects the utmost relevance of behavioral responses to protect the body. These observations parallel recent concepts of emotions and entail implications for the understanding and treatment of pain.

  1. Joint attention for stimuli on the hands: ownership matters

    PubMed Central

    Taylor, J. E. T.; Pratt, Jay; Witt, Jessica K.

    2015-01-01

    The visual system treats the space near the hands with unique, action-related priorities. For example, attention orients slowly to stimuli on the hands (Taylor and Witt, 2014). In this article, we asked whether jointly attended hands are attended in the same way. Specifically, we examined whether ownership over the hand mattered: do we attend to our hands and the hands of others in the same way? Pairs of participants performed a spatial cueing task with stimuli that could be projected onto one partner’s hands or on a control surface. Results show delayed orienting of attention to targets appearing on the hands, but only for the owner of the hands. For an observer, others’ hands are like any other surface. This result emphasizes the importance of ownership for hand-based effects on vision, and in doing so, is inconsistent with some expectations of the joint action literature. PMID:25983713

  2. Dopamine encoding of Pavlovian incentive stimuli diminishes with extended training.

    PubMed

    Clark, Jeremy J; Collins, Anne L; Sanford, Christina Akers; Phillips, Paul E M

    2013-02-20

    Dopamine is highly implicated both as a teaching signal in reinforcement learning and in motivating actions to obtain rewards. However, theoretical disconnects remain between the temporal encoding properties of dopamine neurons and the behavioral consequences of its release. Here, we demonstrate in rats that dopamine evoked by Pavlovian cues increases during acquisition, but dissociates from stable conditioned appetitive behavior as this signal returns to preconditioning levels with extended training. Experimental manipulation of the statistical parameters of the behavioral paradigm revealed that this attenuation of cue-evoked dopamine release during the postasymptotic period was attributable to acquired knowledge of the temporal structure of the task. In parallel, conditioned behavior became less dopamine dependent after extended training. Thus, the current work demonstrates that as the presentation of reward-predictive stimuli becomes anticipated through the acquisition of task information, there is a shift in the neurobiological substrates that mediate the motivational properties of these incentive stimuli.

  3. Bears "Count" Too: Quantity Estimation and Comparison in Black Bears (Ursus Americanus).

    PubMed

    Vonk, Jennifer; Beran, Michael J

    2012-07-01

    Studies of bear cognition are notably missing from the comparative record despite bears' large relative brain size and interesting status as generalist carnivores facing complex foraging challenges, but lacking complex social structures. We investigated the numerical abilities of three American black bears (Ursus Americanus) by presenting discrimination tasks on a touch-screen computer. One bear chose the larger of two arrays of dot stimuli, while two bears chose the smaller array of dots. On some trials the relative number of dots was congruent with the relative total area of the two arrays. On other trials number of dots was incongruent with area. All of the bears were above chance on trials of both types with static dots. Despite encountering greater difficulty with dots that moved within the arrays, one bear was able to discriminate numerically larger arrays of moving dots, and a subset of moving dots from within the larger array, even when area and number were incongruent. Thus, although the bears used area as a cue to guide responding, they were also able to use number as a cue. The pattern of performance was similar to that found previously with monkeys, and suggests that bears may also show other forms of sophisticated quantitative abilities.

  4. Lack of sleep affects the evaluation of emotional stimuli.

    PubMed

    Tempesta, Daniela; Couyoumdjian, Alessandro; Curcio, Giuseppe; Moroni, Fabio; Marzano, Cristina; De Gennaro, Luigi; Ferrara, Michele

    2010-04-29

    Sleep deprivation (SD) negatively affects various cognitive performances, but surprisingly evidence about a specific impact of sleep loss on subjective evaluation of emotional stimuli remains sparse. In the present study, we assessed the effect of SD on the emotional rating of standardized visual stimuli selected from the International Affective Picture System. Forty university students were assigned to the sleep group (n=20), tested before and after one night of undisturbed sleep at home, or to the deprivation group, tested before and after one night of total SD. One-hundred and eighty pictures (90 test, 90 retest) were selected and categorized as pleasant, neutral and unpleasant. Participants were asked to judge their emotional reactions while viewing pictures by means of the Self-Assessment Manikin. Subjective mood ratings were also obtained by means of Visual Analog Scales. No significant effect of SD was observed on the evaluation of pleasant and unpleasant stimuli. On the contrary, SD subjects perceived the neutral pictures more negatively and showed an increase of negative mood and a decrease of subjective alertness compared to non-deprived subjects. Finally, an analysis of covariance on mean valence ratings of neutral pictures using negative mood as covariate confirmed the effect of SD. Our results indicate that sleep is involved in regulating emotional evaluation. The emotional labeling of neutral stimuli biased toward negative responses was not mediated by the increase of negative mood. This effect can be interpreted as an adaptive reaction supporting the "better safe than sorry" principle. It may also have applied implications for healthcare workers, military and law-enforcement personnel.

  5. Interpersonal touch suppresses visual processing of aversive stimuli

    PubMed Central

    Kawamichi, Hiroaki; Kitada, Ryo; Yoshihara, Kazufumi; Takahashi, Haruka K.; Sadato, Norihiro

    2015-01-01

    Social contact is essential for survival in human society. A previous study demonstrated that interpersonal contact alleviates pain-related distress by suppressing the activity of its underlying neural network. One explanation for this is that attention is shifted from the cause of distress to interpersonal contact. To test this hypothesis, we conducted a functional MRI (fMRI) study wherein eight pairs of close female friends rated the aversiveness of aversive and non-aversive visual stimuli under two conditions: joining hands either with a rubber model (rubber-hand condition) or with a close friend (human-hand condition). Subsequently, participants rated the overall comfortableness of each condition. The rating result after fMRI indicated that participants experienced greater comfortableness during the human-hand compared to the rubber-hand condition, whereas aversiveness ratings during fMRI were comparable across conditions. The fMRI results showed that the two conditions commonly produced aversive-related activation in both sides of the visual cortex (including V1, V2, and V5). An interaction between aversiveness and hand type showed rubber-hand-specific activation for (aversive > non-aversive) in other visual areas (including V1, V2, V3, and V4v). The effect of interpersonal contact on the processing of aversive stimuli was negatively correlated with the increment of attentional focus to aversiveness measured by a pain-catastrophizing scale. These results suggest that interpersonal touch suppresses the processing of aversive visual stimuli in the occipital cortex. This effect covaried with aversiveness-insensitivity, such that aversive-insensitive individuals might require a lesser degree of attentional capture to aversive-stimulus processing. As joining hands did not influence the subjective ratings of aversiveness, interpersonal touch may operate by redirecting excessive attention away from aversive characteristics of the stimuli. PMID:25904856

  6. Equivalence-Equivalence: Matching Stimuli with Same Discriminative Functions

    ERIC Educational Resources Information Center

    Carpentier, Franck; Smeets, Paul M.; Barnes-Holmes, Dermot

    2004-01-01

    Previous studies have shown that after being trained on A-B and A-C match-to-sample tasks, adults match not only same-class B and C stimuli (equivalence) but also BC compounds with same-class elements and with different-class elements (BC-BC). The assumption was that the BC-BC performances are based on matching equivalence and nonequivalence…

  7. Mechanism of unpinning spirals by a series of stimuli

    NASA Astrophysics Data System (ADS)

    Gao, Xiang; Zhang, Hong

    2014-06-01

    Antitachycardia pacing (ATP) is widely used to terminate tachycardia before it proceeds to lethal fibrillation. The important prerequisite for successful ATP is unpinning of the spirals anchored to the obstacle by a series of stimuli. Here, to understand the mechanism of unpinning spirals by ATP, we propose a theoretical explanation based on a nonlinear eikonal relation and a kinematical model. The theoretical results are quantitatively consistent with the numerical simulations in both weak and high excitabilities.

  8. Discrimination learning with light stimuli in restrained American lobster.

    PubMed

    Tomina, Yusuke; Takahata, Masakazu

    2012-04-01

    Operant discrimination learning has been extensively utilized in the study on the perceptual ability of animals and their higher order brain functions. We tested in this study whether American lobster Homarus americanus, which was previously found to possess ability of operant learning with claw gripping, could be trained to discriminate light stimuli of different intensities. For the current purpose, we newly developed a PC-controlled operant chamber that allowed the animal under a body-fixed condition to perform operant reward learning with claw gripping. Lobsters were first reinforced when they gripped the sensor bar upon presentation of a light cue. Then they were trained to grip the bar only when the light stimulus of a specific intensity was presented to obtain food reward while the stimuli of three different intensities including the reinforced one were presented in a random order. Finally, they were re-trained to grip the bar only when the light stimulus of another intensity that was not rewarded in the preceding training to obtain food while other intensities including the one that was rewarded previously were not rewarded any more. In these training procedures, the operant behavior occurred more frequently in response to the rewarded cue than to the non-rewarded one. The action latency for the reinforced stimuli showed a significant decrease in the course of training. These data demonstrate that lobsters can be trained with the light cues of different intensity as discriminative stimuli under a restrained condition that would allow application of electrophysiological techniques to the behaving subjects.

  9. Memory bias for schema-related stimuli in individuals with bulimia nervosa.

    PubMed

    Legenbauer, Tanja; Maul, Bärbel; Rühl, Ilka; Kleinstäuber, Maria; Hiller, Wolfgang

    2010-03-01

    This study investigates whether individuals with bulimia nervosa (BN) have a memory bias in relation to explicit memory (cued and free recall vs. verbal and pictorial recognition tasks). Twenty-five participants diagnosed with BN and 27 normal controls (NC) were exposed to body-related, food-related, and neutral TV commercials, and then recall and recognition rates were assessed. Poorer recognition and recall of body-related stimuli was found for BN in comparison to NC, suggesting a memory bias. Results are discussed in relation to previous studies, along with suggestions as to how future studies can gain more insight into dysfunctions in information processing that can lead to the maintenance of eating disorders.

  10. Quantity estimation and comparison in western lowland gorillas (Gorilla gorilla gorilla).

    PubMed

    Vonk, Jennifer; Torgerson-White, Lauri; McGuire, Molly; Thueme, Melissa; Thomas, Jennifer; Beran, Michael J

    2014-05-01

    We investigated the quantity judgment abilities of two adult male western lowland gorillas (Gorilla gorilla gorilla) by presenting discrimination tasks on a touch-screen computer. Both gorillas chose the larger quantity of two arrays of dot stimuli. On some trials, the relative number of dots was congruent with the relative total area of the two arrays. On other trials, number of dots was incongruent with area. The gorillas were first tested with static dots, then with dots that moved within the arrays, and finally on a task where they were required to discriminate numerically larger subsets within arrays of moving dots. Both gorillas achieved above-chance performance on both congruent and incongruent trials with all tasks, indicating that they were able to use number as a cue even though ratio of number and area significantly controlled responding, suggesting that number was not the only relevant dimension that the gorillas used. The pattern of performance was similar to that found previously with monkeys and chimpanzees but had not previously been demonstrated in gorillas within a computerized test format, and with these kinds of visual stimuli.

  11. Tailoring Magnetism in Quantum Dots

    NASA Astrophysics Data System (ADS)

    Zutic, Igor; Abolfath, Ramin; Hawrylak, Pawel

    2007-03-01

    We study magnetism in magnetically doped quantum dots as a function of particle numbers, temperature, confining potential, and the strength of Coulomb interaction screening. We show that magnetism can be tailored by controlling the electron-electron Coulomb interaction, even without changing the number of particles. The interplay of strong Coulomb interactions and quantum confinement leads to enhanced inhomogeneous magnetization which persists at substantially higher temperatures than in the non-interacting case or in the bulk-like dilute magnetic semiconductors. We predict a series of electronic spin transitions which arise from the competition between the many-body gap and magnetic thermal fluctuations. Cond-mat/0612489. [1] R. Abolfath, P. Hawrylak, I. Zuti'c, preprint.

  12. Optophononics with coupled quantum dots.

    PubMed

    Kerfoot, Mark L; Govorov, Alexander O; Czarnocki, Cyprian; Lu, Davis; Gad, Youstina N; Bracker, Allan S; Gammon, Daniel; Scheibner, Michael

    2014-01-01

    Modern technology is founded on the intimate understanding of how to utilize and control electrons. Next to electrons, nature uses phonons, quantized vibrations of an elastic structure, to carry energy, momentum and even information through solids. Phonons permeate the crystalline components of modern technology, yet in terms of technological utilization phonons are far from being on par with electrons. Here we demonstrate how phonons can be employed to render a single quantum dot pair optically transparent. This phonon-induced transparency is realized via the formation of a molecular polaron, the result of a Fano-type quantum interference, which proves that we have accomplished making typically incoherent and dissipative phonons behave in a coherent and non-dissipative manner. We find the transparency to be widely tunable by electronic and optical means. Thereby we show amplification of weakest coupling channels. We further outline the molecular polaron's potential as a control element in phononic circuitry architecture.

  13. Quantum dot-based theranostics

    NASA Astrophysics Data System (ADS)

    Ho, Yi-Ping; Leong, Kam W.

    2010-01-01

    Luminescent semiconductor nanocrystals, also known as quantum dots (QDs), have advanced the fields of molecular diagnostics and nanotherapeutics. Much of the initial progress for QDs in biology and medicine has focused on developing new biosensing formats to push the limit of detection sensitivity. Nevertheless, QDs can be more than passive bio-probes or labels for biological imaging and cellular studies. The high surface-to-volume ratio of QDs enables the construction of a ``smart'' multifunctional nanoplatform, where the QDs serve not only as an imaging agent but also a nanoscaffold catering for therapeutic and diagnostic (theranostic) modalities. This mini review highlights the emerging applications of functionalized QDs as fluorescence contrast agents for imaging or as nanoscale vehicles for delivery of therapeutics, with special attention paid to the promise and challenges towards QD-based theranostics.

  14. Neural conflict-control mechanisms improve memory for target stimuli.

    PubMed

    Krebs, Ruth M; Boehler, Carsten N; De Belder, Maya; Egner, Tobias

    2015-03-01

    According to conflict-monitoring models, conflict serves as an internal signal for reinforcing top-down attention to task-relevant information. While evidence based on measures of ongoing task performance supports this idea, implications for long-term consequences, that is, memory, have not been tested yet. Here, we evaluated the prediction that conflict-triggered attentional enhancement of target-stimulus processing should be associated with superior subsequent memory for those stimuli. By combining functional magnetic resonance imaging (fMRI) with a novel variant of a face-word Stroop task that employed trial-unique face stimuli as targets, we were able to assess subsequent (incidental) memory for target faces as a function of whether a given face had previously been accompanied by congruent, neutral, or incongruent (conflicting) distracters. In line with our predictions, incongruent distracters not only induced behavioral conflict, but also gave rise to enhanced memory for target faces. Moreover, conflict-triggered neural activity in prefrontal and parietal regions was predictive of subsequent retrieval success, and displayed conflict-enhanced functional coupling with medial-temporal lobe regions. These data provide support for the proposal that conflict evokes enhanced top-down attention to task-relevant stimuli, thereby promoting their encoding into long-term memory. Our findings thus delineate the neural mechanisms of a novel link between cognitive control and memory.

  15. Non-nutritive sweeteners are not super-normal stimuli

    PubMed Central

    Antenucci, Rachel G.; Hayes, John E.

    2014-01-01

    Background It is often claimed that non-nutritive sweeteners (NNS) are ‘sweeter than sugar’, with the implicit implication high potency sweeteners are super-normal stimuli that encourage exaggerated responses. This study aimed to investigate the perceived sweetness intensity of a variety of nutritive (Sucrose, Maple Syrup, and Agave Nectar) and NNS (Acesulfame-K (AceK), Rebaudioside A (RebA), Aspartame, and Sucralose) in a large cohort of untrained participants using contemporary psychophysical methods. Methods Participants (n=401 total) rated the intensity of sweet, bitter, and metallic sensations for nutritive and NNS in water using the general labeled magnitude scale (gLMS). Results Sigmoidal Dose-Response functions were observed for all stimuli except AceK. That is, sucrose follows a sigmoidal function if the data are not artifactually linearized via prior training. More critically, there is no evidence that NNS have a maximal sweetness (intensity) greater than sucrose; indeed, the maximal sweetness for AceK, RebA and Sucralose were significantly lower than for concentrated sucrose. For these sweeteners, mixture suppression due to endogenous dose-dependent bitter or metallic sensations appears to limit maximal perceived sweetness. Conclusions In terms of perceived sweetness, non-nutritive sweeteners cannot be considered super-normal stimuli. These data do not support the view that non-nutritive sweeteners hijack or over-stimulate sweet receptors to product elevated sweet sensations. PMID:24942868

  16. Purpose in life predicts better emotional recovery from negative stimuli.

    PubMed

    Schaefer, Stacey M; Morozink Boylan, Jennifer; van Reekum, Carien M; Lapate, Regina C; Norris, Catherine J; Ryff, Carol D; Davidson, Richard J

    2013-01-01

    Purpose in life predicts both health and longevity suggesting that the ability to find meaning from life's experiences, especially when confronting life's challenges, may be a mechanism underlying resilience. Having purpose in life may motivate reframing stressful situations to deal with them more productively, thereby facilitating recovery from stress and trauma. In turn, enhanced ability to recover from negative events may allow a person to achieve or maintain a feeling of greater purpose in life over time. In a large sample of adults (aged 36-84 years) from the MIDUS study (Midlife in the U.S., http://www.midus.wisc.edu/), we tested whether purpose in life was associated with better emotional recovery following exposure to negative picture stimuli indexed by the magnitude of the eyeblink startle reflex (EBR), a measure sensitive to emotional state. We differentiated between initial emotional reactivity (during stimulus presentation) and emotional recovery (occurring after stimulus offset). Greater purpose in life, assessed over two years prior, predicted better recovery from negative stimuli indexed by a smaller eyeblink after negative pictures offset, even after controlling for initial reactivity to the stimuli during the picture presentation, gender, age, trait affect, and other well-being dimensions. These data suggest a proximal mechanism by which purpose in life may afford protection from negative events and confer resilience is through enhanced automatic emotion regulation after negative emotional provocation.

  17. Hemispheric specialization in dogs for processing different acoustic stimuli.

    PubMed

    Siniscalchi, Marcello; Quaranta, Angelo; Rogers, Lesley J

    2008-01-01

    Considerable experimental evidence shows that functional cerebral asymmetries are widespread in animals. Activity of the right cerebral hemisphere has been associated with responses to novel stimuli and the expression of intense emotions, such as aggression, escape behaviour and fear. The left hemisphere uses learned patterns and responds to familiar stimuli. Although such lateralization has been studied mainly for visual responses, there is evidence in primates that auditory perception is lateralized and that vocal communication depends on differential processing by the hemispheres. The aim of the present work was to investigate whether dogs use different hemispheres to process different acoustic stimuli by presenting them with playbacks of a thunderstorm and their species-typical vocalizations. The results revealed that dogs usually process their species-typical vocalizations using the left hemisphere and the thunderstorm sounds using the right hemisphere. Nevertheless, conspecific vocalizations are not always processed by the left hemisphere, since the right hemisphere is used for processing vocalizations when they elicit intense emotion, including fear. These findings suggest that the specialisation of the left hemisphere for intraspecific communication is more ancient that previously thought, and so is specialisation of the right hemisphere for intense emotions.

  18. Purpose in Life Predicts Better Emotional Recovery from Negative Stimuli

    PubMed Central

    Schaefer, Stacey M.; Morozink Boylan, Jennifer; van Reekum, Carien M.; Lapate, Regina C.; Norris, Catherine J.; Ryff, Carol D.; Davidson, Richard J.

    2013-01-01

    Purpose in life predicts both health and longevity suggesting that the ability to find meaning from life’s experiences, especially when confronting life’s challenges, may be a mechanism underlying resilience. Having purpose in life may motivate reframing stressful situations to deal with them more productively, thereby facilitating recovery from stress and trauma. In turn, enhanced ability to recover from negative events may allow a person to achieve or maintain a feeling of greater purpose in life over time. In a large sample of adults (aged 36-84 years) from the MIDUS study (Midlife in the U.S., http://www.midus.wisc.edu/), we tested whether purpose in life was associated with better emotional recovery following exposure to negative picture stimuli indexed by the magnitude of the eyeblink startle reflex (EBR), a measure sensitive to emotional state. We differentiated between initial emotional reactivity (during stimulus presentation) and emotional recovery (occurring after stimulus offset). Greater purpose in life, assessed over two years prior, predicted better recovery from negative stimuli indexed by a smaller eyeblink after negative pictures offset, even after controlling for initial reactivity to the stimuli during the picture presentation, gender, age, trait affect, and other well-being dimensions. These data suggest a proximal mechanism by which purpose in life may afford protection from negative events and confer resilience is through enhanced automatic emotion regulation after negative emotional provocation. PMID:24236176

  19. Select noxious stimuli induce changes on corneal nerve morphology.

    PubMed

    Hegarty, Deborah M; Hermes, Sam M; Yang, Katherine; Aicher, Sue A

    2017-06-01

    The surface of the cornea contains the highest density of nociceptive nerves of any tissue in the body. These nerves are responsive to a variety of modalities of noxious stimuli and can signal pain even when activated by low threshold stimulation. Injury of corneal nerves can lead to altered nerve morphology, including neuropathic changes which can be associated with chronic pain. Emerging technologies that allow imaging of corneal nerves in vivo are spawning questions regarding the relationship between corneal nerve density, morphology, and function. We tested whether noxious stimulation of the corneal surface can alter nerve morphology and neurochemistry. We used concentrations of menthol, capsaicin, and hypertonic saline that evoked comparable levels of nocifensive eye wipe behaviors when applied to the ocular surface of an awake rat. Animals were sacrificed and corneal nerves were examined using immunocytochemistry and three-dimensional volumetric analyses. We found that menthol and capsaicin both caused a significant reduction in corneal nerve density as detected with β-tubulin immunoreactivity 2 hr after stimulation. Hypertonic saline did not reduce nerve density, but did cause qualitative changes in nerves including enlarged varicosities that were also seen following capsaicin and menthol stimulation. All three types of noxious stimuli caused a depletion of CGRP from corneal nerves, indicating that all modalities of noxious stimuli evoked peptide release. Our findings suggest that studies aimed at understanding the relationship between corneal nerve morphology and chronic disease may also need to consider the effects of acute stimulation on corneal nerve morphology.

  20. Expression of human hyaluronan synthases in response to external stimuli.

    PubMed Central

    Jacobson, A; Brinck, J; Briskin, M J; Spicer, A P; Heldin, P

    2000-01-01

    In the present study we have investigated the expression of mRNAs for hyaluronan synthase isoforms (HAS1, HAS2 and HAS3) in different cells in response to various stimuli. Human mesothelial cells, which synthesize large amounts of hyaluronan, express mRNAs encoding all three HAS isoforms, whereas their transformed counterparts, mesothelioma cells, which produce only minute amounts of hyaluronan, express only HAS3 mRNA. Human lung fibroblasts and the glioma cell line U-118 MG express only the HAS2 and HAS3 genes. The expression of the transcripts was higher in subconfluent than in confluent cultures and was well correlated with the production of hyaluronan by the cells. Stimulation of mesothelial cells with platelet-derived growth factor-BB induced an up-regulation of mRNA for HAS2 to a maximum after 6 h of stimulation; HAS1 and HAS3 genes were only induced slightly. Transforming growth factor-beta1 reduced HAS2 mRNA slightly, and hydrocortisone reduced it strongly, within 6 h of stimulation in mesothelial cell cultures but did not significantly affect the expression of mRNAs for HAS1 and HAS3. Induction of HAS1 and HAS2 protein levels in response to the stimuli above correlated with HAS transcript levels. Thus the expression of the three HAS isoforms is more prominent in growing cells than in resting cells and is differentially regulated by various stimuli suggesting distinct functional roles of the three proteins. PMID:10794710

  1. Attention modulates the dorsal striatum response to love stimuli.

    PubMed

    Langeslag, Sandra J E; van der Veen, Frederik M; Röder, Christian H

    2014-02-01

    In previous functional magnetic resonance imaging (fMRI) studies concerning romantic love, several brain regions including the caudate and putamen have consistently been found to be more responsive to beloved-related than control stimuli. In those studies, infatuated individuals were typically instructed to passively view the stimuli or to think of the viewed person. In the current study, we examined how the instruction to attend to, or ignore the beloved modulates the response of these brain areas. Infatuated individuals performed an oddball task in which pictures of their beloved and friend served as targets and distractors. The dorsal striatum showed greater activation for the beloved than friend, but only when they were targets. The dorsal striatum actually tended to show less activation for the beloved than the friend when they were distractors. The longer the love and relationship duration, the smaller the response of the dorsal striatum to beloved-distractor stimuli was. We interpret our findings in terms of reinforcement learning. By virtue of using a cognitive task with a full factorial design, we show that the dorsal striatum is not activated by beloved-related information per se, but only by beloved-related information that is attended.

  2. Facilitated processing of visual stimuli associated with the body.

    PubMed

    Whiteley, Louise; Kennett, Steffan; Taylor-Clarke, Marisa; Haggard, Patrick

    2004-01-01

    Recent work on tactile perception has revealed enhanced tactile acuity and speeded spatial-choice reaction times (RTs) when viewing the stimulated body site as opposed to viewing a neutral object. Here we examine whether this body-view enhancement effect extends to visual targets. Participants performed a speeded spatial discrimination between two lights attached either to their own left index finger or to a wooden finger-shaped object, making a simple distal--proximal decision. We filmed either the finger-mounted or the object-mounted lights in separate experimental blocks and the live scene was projected onto a screen in front of the participants. Thus, participants responded to identical visual targets varying only in their context: on the body or not. Results revealed a large performance advantage for the finger-mounted stimuli: reaction times were substantially reduced, while discrimination accuracy was unaffected. With this finding we address concerns associated with previous work on the processing of stimuli attributed to the self and extend the finding of a performance advantage for such stimuli to vision.

  3. Electroencephalographic spectral correlates of caress-like affective haptic stimuli.

    PubMed

    Valenza, Gaetano; Greco, Alberto; Nardelli, Mimma; Bianchi, Matteo; Lanata, Antonio; Rossi, Simone; Scilingo, Enzo Pasquale

    2015-01-01

    This paper describes how brain dynamics, as estimated through spectral analysis of electroencephalographic (EEG) oscillatory rhythms, is modified by quantifiable, affective haptic stimuli. Specifically, 32 healthy subjects (16 females) interacted with a haptic device able to convey caress-like stimuli while varying force and velocity of the device itself. More specifically, 2 values of force (i.e., "strength of the caress") and 3 velocity levels (i.e. "velocity of the caress") were combined to control the device during the experiment. Subjects were also asked to self-assess the haptic stimuli in terms of arousal (activation/ deactivation) and valence (pleasure/displeasure) scores. Results, shown in terms of p-values topographic maps, revealed a suppression of the oscillations over the controlateral somatosensory cortex, during caresses performed with the lowest force (2N) and the highest velocity (65 mm/s). This occurred in all of the frequency bands considered, α, β, and γ. Lower velocities (9.4 mm/s and 37 mm/s) did not significantly modify EEG reactivity in such bands. Concerning caresses administered at high force (6N), there was a significant decrease of EEG oscillatory activity focused on mid-frontal electrodes, in all of the considered frequency bands, when the velocity of the caresses was the lowest one. Significant sparse decrease of EEG power spectra, in all of the considered frequency bands, occurred at higher strength and velocity of the caress.

  4. Goldfish and oscars have comparable responsiveness to dipole stimuli

    NASA Astrophysics Data System (ADS)

    Nauroth, Ines Eva; Mogdans, Joachim

    2009-12-01

    The relative roles of the fish lateral line and inner ear for the perception of hydrodynamic stimuli are poorly investigated. Here, we studied responsiveness to a 100 Hz vibrating sphere (dipole stimulus) of goldfish and oscars, two species that differ in peripheral lateral line morphology, inner ear morphology, mechanical linkage between inner ear and swim bladder, and inner ear sensitivity. We measured unconditioned dipole-evoked changes in breathing activity in still water and in the presence of a 5-cm s-1 background flow. In still water, individuals from both species responded to sound pressure levels (SPLs) between 92 and 109 dB SPL re 1 μPaRMS. Responsiveness was not affected by background flow or by temporary inactivation of the lateral line. The data suggest that fish with different lateral line and inner ear morphologies have similar sensitivities to vibrating sphere stimuli and can detect and respond to dipole sources equally well in still water and in moderate background flows. Moreover, behavioral responses were not dependent on a functional lateral line, suggesting that in this type of experiment, the inner ear is the dominant sense organ for the perception of hydrodynamic stimuli.

  5. Dynamism of Stimuli-Responsive Nanohybrids: Environmental Implications

    PubMed Central

    Plazas-Tuttle, Jaime; Rowles, Lewis S.; Chen, Hao; Bisesi, Joseph H.; Sabo-Attwood, Tara; Saleh, Navid B.

    2015-01-01

    Nanomaterial science and design have shifted from generating single passive nanoparticles to more complex and adaptive multi-component nanohybrids. These adaptive nanohybrids (ANHs) are designed to simultaneously perform multiple functions, while actively responding to the surrounding environment. ANHs are engineered for use as drug delivery carriers, in tissue-engineered templates and scaffolds, adaptive clothing, smart surface coatings, electrical switches and in platforms for diversified functional applications. Such ANHs are composed of carbonaceous, metallic or polymeric materials with stimuli-responsive soft-layer coatings that enable them to perform such switchable functions. Since ANHs are engineered to dynamically transform under different exposure environments, evaluating their environmental behavior will likely require new approaches. Literature on polymer science has established a knowledge core on stimuli-responsive materials. However, translation of such knowledge to environmental health and safety (EHS) of these ANHs has not yet been realized. It is critical to investigate and categorize the potential hazards of ANHs, because exposure in an unintended or shifting environment could present uncertainty in EHS. This article presents a perspective on EHS evaluation of ANHs, proposes a principle to facilitate their identification for environmental evaluation, outlines a stimuli-based classification for ANHs and discusses emerging properties and dynamic aspects for systematic EHS evaluation. PMID:28347054

  6. Detection of IgM and IgG antibodies against Brucella by dot-ELISA in humans.

    PubMed

    Barbuddhe, S B; Yadava, V K; Singh, D K

    1994-03-01

    Dot-enzyme linked immunosorbent assay (dot-ELISA) with autoclaved extract of B. abortus S99 was used for the detection of Brucella antibodies in human sera. Results were compared with those of STAT, RBPT and CFT. Out of 80 sera 8(10 per cent), 15(18.7 per cent), 20(25 per cent) and 13(16.25 per cent) were found positive by RBPT, STAT, IgM dot-ELISA and IgG dot-ELISA respectively. Out of 74 sera samples tested with CFT 9(12.16 per cent) proved positive. The relative sensitivity and relative specificity in comparison with CFT was found to be 33.33 per cent, 96.92 percent for RBPT, 33.33 per cent and 84.61 per cent for STAT and 88.88 per cent and 76.92 per cent for dot-ELISA, respectively. The dot-ELISA was found to be a more sensitive, economical and a rapid test for screening of human brucellosis under field conditions.

  7. Contradictory behavioral biases result from the influence of past stimuli on perception.

    PubMed

    Raviv, Ofri; Lieder, Itay; Loewenstein, Yonatan; Ahissar, Merav

    2014-12-01

    Biases such as the preference of a particular response for no obvious reason, are an integral part of psychophysics. Such biases have been reported in the common two-alternative forced choice (2AFC) experiments, where participants are instructed to compare two consecutively presented stimuli. However, the principles underlying these biases are largely unknown and previous studies have typically used ad-hoc explanations to account for them. Here we consider human performance in the 2AFC tone frequency discrimination task, utilizing two standard protocols. In both protocols, each trial contains a reference stimulus. In one (Reference-Lower protocol), the frequency of the reference stimulus is always lower than that of the comparison stimulus, whereas in the other (Reference protocol), the frequency of the reference stimulus is either lower or higher than that of the comparison stimulus. We find substantial interval biases. Namely, participants perform better when the reference is in a specific interval. Surprisingly, the biases in the two experiments are opposite: performance is better when the reference is in the first interval in the Reference protocol, but is better when the reference is second in the Reference-Lower protocol. This inconsistency refutes previous accounts of the interval bias, and is resolved when experiments statistics is considered. Viewing perception as incorporation of sensory input with prior knowledge accumulated during the experiment accounts for the seemingly contradictory biases both qualitatively and quantitatively. The success of this account implies that even simple discriminations reflect a combination of sensory limitations, memory limitations, and the ability to utilize stimuli statistics.

  8. EPA-DOT Memorandum of Understanding (MOU)

    EPA Pesticide Factsheets

    National Memorandum of Understanding Between the U.S. Department of Transportation and the U.S. Environmental Protection Agency (EPA Publication #EPA-420-F-00-020 and EPA-DOT Memorandum of Understanding (MOU) on Transportation Conformity.

  9. Spin Dynamics of Charged Colloidal Quantum Dots

    NASA Astrophysics Data System (ADS)

    Stern, N. P.

    2005-03-01

    Colloidal semiconductor quantum dots are promising structures for controlling spin phenomena because of their highly size- tunable physical properties, ease of manufacture, and nanosecond-scale spin lifetimes at room temperature. Recent experiments have succeeded in controlling the charging of the lowest electronic state of colloidal quantum dots ootnotetextC. Wang, B. L. Wehrenberg, C. Y. Woo, and P. Guyot-Sionnest, J. Phys. Chem B 108, 9027 (2004).. Here we use time-resolved Faraday rotation measurements in the Voigt geometry to investigate the spin dynamics of colloidal CdSe quantum dot films in both a charged and uncharged state at room temperature. The charging of the film is controlled by applying a voltage in an electrochemical cell and is confirmed by absorbance measurements. Significant changes in the spin precession are observed upon charging, reflecting the voltage- controlled electron occupation of the quantum dot states and filling of surface states.

  10. Teleportation on a quantum dot array.

    PubMed

    de Pasquale, F; Giorgi, G; Paganelli, S

    2004-09-17

    We present a model of quantum teleportation protocol based on a double quantum dot array. The unknown qubit is encoded using a pair of quantum dots, with one excess electron, coupled by tunneling. It is shown how to create a maximally entangled state using an adiabatically increasing Coulomb repulsion between different dot pairs. This entangled state is exploited to perform teleportation again using an adiabatic coupling between itself and the incoming unknown state. Finally, a sudden separation of Bob's qubit allows a time evolution of Alice's, which amounts to a modified version of standard Bell measurement. A transmission over a long distance could be obtained by considering the entangled state of a chain of N coupled double quantum dots. The system is shown to be increasingly robust with N against decoherence due to phonons.

  11. Concentration-mediated multicolor fluorescence polymer carbon dots.

    PubMed

    Jeong, Chan Jin; Lee, Gibaek; In, Insik; Park, Sung Young

    2016-05-01

    Polymer dots (PDs) showing concentration-mediated multicolor fluorescence were first prepared from sulfuric acid-treated dehydration of Pluronic® F-127 in a single step. Pluronic-based PDs (P-PDs) showed high dispersion stability in solvent media and exhibited a fluorescence emission that was widely tunable from red to blue by adjusting both the excitation wavelengths and the P-PD concentration in an aqueous solution. This unique fluorescence behavior of P-PDs might be a result of cross-talk in the fluorophores of the poly(propylene glycol)-rich core inside the P-PD through either energy transfer or charge transfer. Reconstruction of the surface energy traps of the P-PDs mediated through aggregation may lead to a new generation of carbon-based nanomaterials possessing a fluorescence emission and tunable by adjusting the concentration. These structures may be useful in the design of multifunctional carbon nanomaterials with tunable emission properties according to a variety of internal or external stimuli.

  12. Single Molecule Analysis of Serotonin Transporter Regulation Using Quantum Dots

    NASA Astrophysics Data System (ADS)

    Chang, Jerry; Tomlinson, Ian; Warnement, Michael; Ustione, Alessandro; Carneiro, Ana; Piston, David; Blakely, Randy; Rosenthal, Sandra

    2011-03-01

    For the first time, we implement a novel, single molecule approach to define the localization and mobility of the brain's major target of widely prescribed antidepressant medications, the serotonin transporter (SERT). SERT labeled with single quantum dot (Qdot) revealed unsuspected features of transporter mobility with cholesterol-enriched membrane microdomains (often referred to as ``lipid rafts'') and cytoskeleton network linked to transporter activation. We document two pools of surface SERT proteins defined by their lateral mobility, one that exhibits relatively free diffusion in the plasma membrane and a second that displays significantly restricted mobility and localizes to cholesterol-enriched microdomains. Diffusion model prediction and instantaneous velocity analysis indicated that stimuli that act through p38 MAPK-dependent signaling pathways to activate SERT trigger rapid SERT movements within membrane microdomains. Cytoskeleton disruption showed that SERT lateral mobility behaves a membrane raft-constrained, cytoskeleton-associated manner. Our results identify an unsuspected aspect of neurotransmitter transporter regulation that we propose reflects the dissociation of inhibitory, SERT-associated cytoskeletal anchors.

  13. Selectivity of lingual nerve fibers to chemical stimuli

    PubMed Central

    1993-01-01

    The cell bodies of the lingual branch of the trigeminal nerve were localized in the trigeminal ganglion using extracellular recordings together with horseradish peroxidase labeling from the tongue. Individual lingual nerve fibers were characterized with regard to their conduction velocities, receptive fields, and response to thermal, mechanical, and chemical stimuli. Fibers were classified as C, A delta, A beta, cold, and warm. The chemical stimuli included NaCl, KCl, NH4Cl, CaCl2, menthol, nicotine, hexanol, and capsaicin. With increasing salt concentration the latency of the response decreased and the activity increased. The responses elicited by salts (to 2.5 M), but not nonpolar stimuli such as menthol, were reversibly inhibited by 3.5 mM of the tight junction blocker, LaCl3. These data suggest that salts diffuse into stratified squamous epithelia through tight junctions in the stratum corneum and stratum granulosum, whereupon they enter the extracellular space. 11 C fibers were identified and 5 were characterized as polymodal nociceptors. All of the C fibers were activated by one or more of the salts NaCl, KCl, or NH4Cl. Three C fibers were activated by nicotine (1 mM), but none were affected by CaCl2 (1 M), menthol (1 mM), or hexanol (50 mM). However, not all C fibers or even the subpopulation of polymodals were activated by the same salts or by nicotine. Thus, it appears that C fibers display differential responsiveness to chemical stimuli. A delta fibers also showed differential sensitivity to chemicals. Of the 35 characterized A delta mechanoreceptors, 8 responded to NaCl, 9 to KCl, 9 to NH4Cl, 0 to CaCl2, menthol, or hexanol, and 2 to nicotine. 8 of 9 of the cold fibers (characterized as A delta's) responded to menthol, none responded to nicotine, 8 of 16 were inhibited by hexanol, 9 of 19 responded to 2.5 M NH4Cl, 5 of 19 responded to 2.5 M KCl, and 1 of 19 responded to 2.5 M NaCl. In summary, lingual nerve fibers exhibit responsiveness to chemicals

  14. Development of degradable renewable polymers and stimuli-responsive nanocomposites

    NASA Astrophysics Data System (ADS)

    Eyiler, Ersan

    The overall goal of this research was to explore new living radical polymerization methods and the blending of renewable polymers. Towards this latter goal, polylactic acid (PLA) was blended with a new renewable polymer, poly(trimethylene-malonate) (PTM), with the aim of improving mechanical properties, imparting faster degradation, and examining the relationship between degradation and mechanical properties. Blend films of PLA and PTM with various ratios (5, 10, and 20 wt %) were cast from chloroform. Partially miscible blends exhibited Young's modulus and elongation-to-break values that significantly extend PLA's usefulness. Atomic force microscopy (AFM) data showed that incorporation of 10 wt% PTM into PLA matrix exhibited a Young's modulus of 4.61 GPa, which is significantly higher than that of neat PLA (1.69 GPa). The second part of the bioplastics study involved a one-week hydrolytic degradation study of PTM and another new bioplastic, poly(trimethylene itaconate) (PTI) using DI water (pH 5.4) at room temperature, and the effects of degradation on crystallinity and mechanical properties of these films were examined by differential scanning calorimetry (DSC) and AFM. PTI showed an increase in crystallinity with degradation, which was attributed to predominately degradation of free amorphous regions. Depending on the crystallinity, the elastic modulus increased at first, and decreased slightly. Both bulk and surface-tethered stimuli-responsive polymers were studied on amine functionalized magnetite (Fe3O4) nanoparticles. Stimuli-responsive polymers studied, including poly(N-isopropylacrylamide) (PNIPAM), poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA), and poly(itaconic acid) (PIA), were grafted via surface-initiated aqueous atom transfer radical polymerization (SI-ATRP). Both Fourier transform infrared spectroscopy (FTIR) and x-ray photoelectron spectroscopy (XPS) spectroscopies showed the progression of the grafting. The change in particle size as a

  15. Exploring Extragalactic Emission: The Hα Dot Survey

    NASA Astrophysics Data System (ADS)

    Rampalli, Rayna; Salzer, John Joseph

    2016-01-01

    The Hα Dot Survey was established as a result of finding point sources of strong line emission in the data obtained for the ALFALFA Hα Survey (Van Sistine et al. 2015). In the latter survey, broad-band R and narrow-band Hα filters were used to examine target galaxies from the ALFALFA blind HI survey (Giovanelli et al. 2005, Haynes et al. 2011). In the process of reducing the ALFALFA Hα Survey data the "Hα Dots" were discovered (Kellar et al. 2008, 2012). Using specialized image analysis tools, a large population of dots has already been detected in the more than 1500 ALFALFA Hα narrow-band images taken with the 0.9m WIYN and 2.1m KPNO telescopes. Follow-up spectra of over 200 Hα Dots discovered from the 0.9m images reveal that these objects are a mix of nearby low-luminosity star-forming galaxies, compact starbursts and Seyfert 2 galaxies at intermediate redshifts, and high-redshift QSOs. Here we present the first list of Hα Dots detected using 2.1m telescope data. The 2.1m images yield a sample of Dots that average almost two magnitudes fainter than those detected with the 0.9m. The current REU project is designed to characterize the set of Hα Dots detected in the deeper 2.1m telescope images, while the broad goals of the Hα Dot Survey include the desire to understand better the chemical evolution of galaxies over cosmic time. This project was supported in part by the NSF REU grant 1358980, by the Maria Mitchell Association (Nantucket, MA), and by the Massachusetts Space Grant Consortium.

  16. First principle thousand atom quantum dot calculations

    SciTech Connect

    Wang, Lin-Wang; Li, Jingbo

    2004-03-30

    A charge patching method and an idealized surface passivation are used to calculate the single electronic states of IV-IV, III-V, II-VI semiconductor quantum dots up to a thousand atoms. This approach scales linearly and has a 1000 fold speed-up compared to direct first principle methods with a cost of eigen energy error of about 20 meV. The calculated quantum dot band gaps are parametrized for future references.

  17. Distinctive signature of indium gallium nitride quantum dot lasing in microdisk cavities.

    PubMed

    Woolf, Alexander; Puchtler, Tim; Aharonovich, Igor; Zhu, Tongtong; Niu, Nan; Wang, Danqing; Oliver, Rachel; Hu, Evelyn L

    2014-09-30

    Low-threshold lasers realized within compact, high-quality optical cavities enable a variety of nanophotonics applications. Gallium nitride materials containing indium gallium nitride (InGaN) quantum dots and quantum wells offer an outstanding platform to study light-matter interactions and realize practical devices such as efficient light-emitting diodes and nanolasers. Despite progress in the growth and characterization of InGaN quantum dots, their advantages as the gain medium in low-threshold lasers have not been clearly demonstrated. This work seeks to better understand the reasons for these limitations by focusing on the simpler, limited-mode microdisk cavities, and by carrying out comparisons of lasing dynamics in those cavities using varying gain media including InGaN quantum wells, fragmented quantum wells, and a combination of fragmented quantum wells with quantum dots. For each gain medium, we use the distinctive, high-quality (Q ∼ 5,500) modes of the cavities, and the change in the highest-intensity mode as a function of pump power to better understand the dominant radiative processes. The variations of threshold power and lasing wavelength as a function of gain medium help us identify the possible limitations to lower-threshold lasing with quantum dot active medium. In addition, we have identified a distinctive lasing signature for quantum dot materials, which consistently lase at wavelengths shorter than the peak of the room temperature gain emission. These findings not only provide better understanding of lasing in nitride-based quantum dot cavity systems but also shed insight into the more fundamental issues of light-matter coupling in such systems.

  18. Do emotional stimuli enhance or impede recall relative to neutral stimuli? An investigation of two "false memory" tasks.

    PubMed

    Monds, Lauren A; Paterson, Helen M; Kemp, Richard I

    2016-10-06

    Many eyewitness memory situations involve negative and distressing events; however, many studies investigating "false memory" phenomena use neutral stimuli only. The aim of the present study was to determine how both the Deese-Roediger-McDermott (DRM) procedure and the Misinformation Effect Paradigm tasks were related to each other using distressing and neutral stimuli. Participants completed the DRM (with negative and neutral word lists) and viewed a distressing or neutral film. Misinformation for the film was introduced and memory was assessed. Film accuracy and misinformation susceptibility were found to be greater for those who viewed the distressing film relative to the neutral film. Accuracy responses on both tasks were related, however, susceptibility to the DRM illusion and Misinformation Effect were not. The misinformation findings support the Paradoxical Negative Emotion (PNE) hypothesis that negative stimuli will lead to remembering more accurate details but also greater likelihood of memory distortion. However, the PNE hypothesis was not supported for the DRM results. The findings also suggest that the DRM and Misinformation tasks are not equivalent and may have differences in underlying mechanisms. Future research should focus on more ecologically valid methods of assessing false memory.

  19. Semiconductor Quantum Dots with Photoresponsive Ligands.

    PubMed

    Sansalone, Lorenzo; Tang, Sicheng; Zhang, Yang; Thapaliya, Ek Raj; Raymo, Françisco M; Garcia-Amorós, Jaume

    2016-10-01

    Photochromic or photocaged ligands can be anchored to the outer shell of semiconductor quantum dots in order to control the photophysical properties of these inorganic nanocrystals with optical stimulations. One of the two interconvertible states of the photoresponsive ligands can be designed to accept either an electron or energy from the excited quantum dots and quench their luminescence. Under these conditions, the reversible transformations of photochromic ligands or the irreversible cleavage of photocaged counterparts translates into the possibility to switch luminescence with external control. As an alternative to regulating the photophysics of a quantum dot via the photochemistry of its ligands, the photochemistry of the latter can be controlled by relying on the photophysics of the former. The transfer of excitation energy from a quantum dot to a photocaged ligand populates the excited state of the species adsorbed on the nanocrystal to induce a photochemical reaction. This mechanism, in conjunction with the large two-photon absorption cross section of quantum dots, can be exploited to release nitric oxide or to generate singlet oxygen under near-infrared irradiation. Thus, the combination of semiconductor quantum dots and photoresponsive ligands offers the opportunity to assemble nanostructured constructs with specific functions on the basis of electron or energy transfer processes. The photoswitchable luminescence and ability to photoinduce the release of reactive chemicals, associated with the resulting systems, can be particularly valuable in biomedical research and can, ultimately, lead to the realization of imaging probes for diagnostic applications as well as to therapeutic agents for the treatment of cancer.

  20. Positioning of quantum dots on metallic nanostructures.

    PubMed

    Kramer, R K; Pholchai, N; Sorger, V J; Yim, T J; Oulton, R; Zhang, X

    2010-04-09

    The capability to position individual emitters, such as quantum dots, near metallic nanostructures is highly desirable for constructing active optical devices that can manipulate light at the single photon level. The emergence of the field of plasmonics as a means to confine light now introduces a need for high precision and reliability in positioning any source of emission, which has thus far been elusive. Placing an emission source within the influence of plasmonic structures now requires accuracy approaching molecular length scales. In this paper we report the ability to reliably position nanoscale functional objects, specifically quantum dots, with sub-100-nm accuracy, which is several times smaller than the diffraction limit of a quantum dot's emission light. Electron beam lithography-defined masks on metallic surfaces and a series of surface chemical functionalization processes allow the programmed assembly of DNA-linked colloidal quantum dots. The quantum dots are successfully functionalized to areas as small as (100 nm)(2) using the specific binding of thiolated DNA to Au/Ag, and exploiting the streptavidin-biotin interaction. An analysis of the reproducibility of the process for various pattern sizes shows that this technique is potentially scalable to the single quantum dot level with 50 nm accuracy accompanied by a moderate reduction in yield.

  1. Quantum-dot-in-perovskite solids.

    PubMed

    Ning, Zhijun; Gong, Xiwen; Comin, Riccardo; Walters, Grant; Fan, Fengjia; Voznyy, Oleksandr; Yassitepe, Emre; Buin, Andrei; Hoogland, Sjoerd; Sargent, Edward H

    2015-07-16

    Heteroepitaxy-atomically aligned growth of a crystalline film atop a different crystalline substrate-is the basis of electrically driven lasers, multijunction solar cells, and blue-light-emitting diodes. Crystalline coherence is preserved even when atomic identity is modulated, a fact that is the critical enabler of quantum wells, wires, and dots. The interfacial quality achieved as a result of heteroepitaxial growth allows new combinations of materials with complementary properties, which enables the design and realization of functionalities that are not available in the single-phase constituents. Here we show that organohalide perovskites and preformed colloidal quantum dots, combined in the solution phase, produce epitaxially aligned 'dots-in-a-matrix' crystals. Using transmission electron microscopy and electron diffraction, we reveal heterocrystals as large as about 60 nanometres and containing at least 20 mutually aligned dots that inherit the crystalline orientation of the perovskite matrix. The heterocrystals exhibit remarkable optoelectronic properties that are traceable to their atom-scale crystalline coherence: photoelectrons and holes generated in the larger-bandgap perovskites are transferred with 80% efficiency to become excitons in the quantum dot nanocrystals, which exploit the excellent photocarrier diffusion of perovskites to produce bright-light emission from infrared-bandgap quantum-tuned materials. By combining the electrical transport properties of the perovskite matrix with the high radiative efficiency of the quantum dots, we engineer a new platform to advance solution-processed infrared optoelectronics.

  2. Hemodynamic and Light-Scattering Changes of Rat Spinal Cord and Primary Somatosensory Cortex in Response to Innocuous and Noxious Stimuli

    PubMed Central

    He, Ji-Wei; Liu, Hanli; Peng, Yuan Bo

    2015-01-01

    Neuroimaging technologies with an exceptional spatial resolution and noninvasiveness have become a powerful tool for assessing neural activity in both animals and humans. However, the effectiveness of neuroimaging for pain remains unclear partly because the neurovascular coupling during pain processing is not completely characterized. Our current work aims to unravel patterns of neurovascular parameters in pain processing. A novel fiber-optic method was used to acquire absolute values of regional oxy- (HbO) and deoxy-hemoglobin concentrations, oxygen saturation rates (SO2), and the light-scattering coefficients from the spinal cord and primary somatosensory cortex (SI) in 10 rats. Brief mechanical and electrical stimuli (ranging from innocuous to noxious intensities) as well as a long-lasting noxious stimulus (formalin injection) were applied to the hindlimb under pentobarbital anesthesia. Interhemispheric comparisons in the spinal cord and SI were used to confirm functional activation during sensory processing. We found that all neurovascular parameters showed stimulation-induced changes; however, patterns of changes varied with regions and stimuli. Particularly, transient increases in HbO and SO2 were more reliably attributed to brief stimuli, whereas a sustained decrease in SO2 was more reliably attributed to formalin. Only the ipsilateral SI showed delayed responses to brief stimuli. In conclusion, innocuous and noxious stimuli induced significant neurovascular responses at critical centers (e.g., the spinal cord and SI) along the somatosensory pathway; however, there was no single response pattern (as measured by amplitude, duration, lateralization, decrease or increase) that was able to consistently differentiate noxious stimuli. Our results strongly suggested that the neurovascular response patterns differ between brief and long-lasting noxious stimuli, and can also differ between the spinal cord and SI. Therefore, a use of multiple-parameter strategy

  3. Delivering quantum dots to cells: bioconjugated quantum dots for targeted and nonspecific extracellular and intracellular imaging.

    PubMed

    Biju, Vasudevanpillai; Itoh, Tamitake; Ishikawa, Mitsuru

    2010-08-01

    Bioconjugated nanomaterials offer endless opportunities to advance both nanobiotechnology and biomedical technology. In this regard, semiconductor nanoparticles, also called quantum dots, are of particular interest for multimodal, multifunctional and multiplexed imaging of biomolecules, cells, tissues and animals. The unique optical properties, such as size-dependent tunable absorption and emission in the visible and NIR regions, narrow emission and broad absorption bands, high photoluminescence quantum yields, large one- and multi-photon absorption cross-sections, and exceptional photostability are the advantages of quantum dots. Multimodal imaging probes are developed by interfacing the unique optical properties of quantum dots with magnetic or radioactive materials. Besides, crystalline structure of quantum dots adds scope for high-contrast X-ray and TEM imaging. Yet another unique feature of a quantum dot is its spacious and flexible surface which is promising to integrate multiple ligands and antibodies and construct multi-functional probes for bioimaging. In this critical review, we will summarize recent advancements in the preparation of biocompatible quantum dots, bioconjugation of quantum dots, and applications of quantum dots and their bioconjugates for targeted and nonspecific imaging of extracellular and intracellular proteins, organelles and functions (181 references).

  4. (In,Mn)As multilayer quantum dot structures

    SciTech Connect

    Bouravleuv, Alexei; Sapega, Victor; Nevedomskii, Vladimir; Khrebtov, Artem; Samsonenko, Yuriy; Cirlin, George

    2014-12-08

    (In,Mn)As multilayer quantum dots structures were grown by molecular beam epitaxy using a Mn selective doping of the central parts of quantum dots. The study of the structural and magneto-optical properties of the samples with three and five layers of (In,Mn)As quantum dots has shown that during the quantum dots assembly, the out-diffusion of Mn from the layers with (In,Mn)As quantum dots can occur resulting in the formation of the extended defects. To produce a high quality structures using the elaborated technique of selective doping, the number of (In,Mn)As quantum dot layers should not exceed three.

  5. Noninvasive detection of charge rearrangement in a quantum dot

    NASA Astrophysics Data System (ADS)

    Fricke, C.; Rogge, M. C.; Harke, B.; Reinwald, M.; Wegscheider, W.; Hohls, F.; Haug, R. J.

    2007-04-01

    We demonstrate new results on electron redistribution on a single quantum dot caused by magnetic field. A quantum point contact is used to detect changes in the quantum dot charge. We are able to measure both the change of the quantum dot charge and also changes of the electron configuration at constant number of electrons on the quantum dot. These features are used to exploit the quantum dot in a high magnetic field where transport through the quantum dot displays the effects of Landau shells and spin blockade.

  6. How does not responding to appetitive stimuli cause devaluation: Evaluative conditioning or response inhibition?

    PubMed

    Chen, Zhang; Veling, Harm; Dijksterhuis, Ap; Holland, Rob W

    2016-12-01

    In a series of 6 experiments (5 preregistered), we examined how not responding to appetitive stimuli causes devaluation. To examine this question, a go/no-go task was employed in which appetitive stimuli were consistently associated with cues to respond (go stimuli), or with cues to not respond (either no-go cues or the absence of cues; no-go stimuli). Change in evaluations of no-go stimuli was compared to change in evaluations of both go stimuli and of stimuli not presented in the task (untrained stimuli). Experiments 1 to 3 show that not responding to appetitive stimuli in a go/no-go task causes devaluation of these stimuli regardless of the presence of an explicit no-go cue. Experiments 4a and 4b show that the devaluation effect of appetitive stimuli is contingent on the percentage of no-go trials; devaluation appears when no-go trials are rare, but disappears when no-go trials are frequent. Experiment 5 shows that simply observing the go/no-go task does not lead to devaluation. Experiment 6 shows that not responding to neutral stimuli does not cause devaluation. Together, these results suggest that devaluation of appetitive stimuli by not responding to them is the result of response inhibition. By employing both go stimuli and untrained stimuli as baselines, alternative explanations are ruled out, and apparent inconsistencies in the literature are resolved. These experiments provide new theoretical insight into the relation between not responding and evaluation, and can be applied to design motor response training procedures aimed at changing people's behavior toward appetitive stimuli. (PsycINFO Database Record

  7. A dual-stimuli-responsive fluorescent switch ultrathin film

    NASA Astrophysics Data System (ADS)

    Li, Zhixiong; Liang, Ruizheng; Liu, Wendi; Yan, Dongpeng; Wei, Min

    2015-10-01

    Stimuli-responsive fluorescent switches have shown broad applications in optical devices, biological materials and intelligent responses. Herein, we describe the design and fabrication of a dual-stimuli-responsive fluorescent switch ultrathin film (UTF) via a three-step layer-by-layer (LBL) technique: (i) encapsulation of spiropyran (SP) within an amphiphilic block copolymer (PTBEM) to give the (SP@PTBEM) micelle; (ii) the mixture of riboflavin (Rf) and poly(styrene 4-sulfonate) (PSS) to enhance the adhesion ability of small molecules; (iii) assembly of negatively charged SP@PTBEM and Rf-PSS with cationic layered double hydroxide (LDH) nanoplatelets to obtain the (Rf-PSS/LDH/SP@PTBEM)n UTFs (n: bilayer number). The assembly process of the UTFs and their luminescence properties, as monitored by fluorescence spectroscopy and scanning electron microscopy (SEM), present a uniform and ordered layered structure with stepwise growth. The resulting Rf-PSS/LDH/SP@PTBEM UTF serves as a three-state switchable multicolor (green, yellow, and red) luminescent system based on stimulation from UV/Vis light and pH, with an acceptable reversibility. Therefore, this work provides a facile way to fabricate stimuli-responsive solid-state film switches with tunable-color luminescence, which have potential applications in the areas of displays, sensors, and rewritable optical memory and fluorescent logic devices.Stimuli-responsive fluorescent switches have shown broad applications in optical devices, biological materials and intelligent responses. Herein, we describe the design and fabrication of a dual-stimuli-responsive fluorescent switch ultrathin film (UTF) via a three-step layer-by-layer (LBL) technique: (i) encapsulation of spiropyran (SP) within an amphiphilic block copolymer (PTBEM) to give the (SP@PTBEM) micelle; (ii) the mixture of riboflavin (Rf) and poly(styrene 4-sulfonate) (PSS) to enhance the adhesion ability of small molecules; (iii) assembly of negatively charged SP

  8. Lack of correlation between the amplitudes of TRP channel-mediated responses to weak and strong stimuli in intracellular Ca(2+) imaging experiments.

    PubMed

    Alpizar, Yeranddy A; Sanchez, Alicia; Radwan, Ahmed; Radwan, Islam; Voets, Thomas; Talavera, Karel

    2013-11-01

    It is often observed in intracellular Ca(2+) imaging experiments that the amplitudes of the Ca(2+) signals elicited by newly characterized TRP agonists do not correlate with the amplitudes of the responses evoked subsequently by a specific potent agonist. We investigated this rather controversial phenomenon by first testing whether it is inherent to the comparison of the effects of weak and strong stimuli. Using five well-characterized TRP channel agonists in commonly used heterologous expression systems we found that the correlation between the amplitudes of the Ca(2+) signals triggered by two sequentially applied stimuli is only high when both stimuli are strong. Using mathematical simulations of intracellular Ca(2+) dynamics we illustrate that the innate heterogeneity in expression and functional properties of Ca(2+) extrusion (e.g. plasma membrane Ca(2+) ATPase) and influx (TRP channels) pathways across a cellular population is a sufficient condition for low correlation between the amplitude of Ca(2+) signals elicited by weak and strong stimuli. Taken together, our data demonstrate that this phenomenon is an expected outcome of intracellular Ca(2+) imaging experiments that cannot be taken as evidence for lack of specificity of low-efficacy stimuli, or as an indicator of the need of other cellular components for channel stimulation.

  9. Stimuli sensitive hydrogels for ophthalmic drug delivery: A review.

    PubMed

    Kushwaha, Swatantra Ks; Saxena, Prachi; Rai, Ak

    2012-04-01

    Amongst the various routes of drug delivery, the field of ocular drug delivery is one of the most interesting and challenging endeavors facing the pharmaceutical scientist for past 10-20 years. As an isolated organ, eye is very difficult to study from a drug delivery point of view. Despite this limitation, improvements have been made with the objective of maintaining the drug in the biophase for an extended period. A major problem in ocular therapeutics is the attainment of an optimal drug concentration at the site of action. To achieve effective ophthalmic therapy, an adequate amount of active ingredient must be delivered and maintained within the eye. The most frequently used dosage forms, i.e., eye solution, eye ointments, eye gels, and eye suspensions are compromised in their effectiveness by several limitations leading to poor ocular bioavailability. Ophthalmic use of viscosity-enhancing agents, penetration enhancers, cyclodextrins, prodrug approaches, and ocular inserts, and the ready existing drug carrier systems along with their application to ophthalmic drug delivery are common to improve ocular bioavailability. Amongst these hydrogel (stimuli sensitive) systems are important, which undergo reversible volume and/or sol-gel phase transitions in response to physiological (temperature, pH and present of ions in organism fluids, enzyme substrate) or other external (electric current, light) stimuli. They help to increase in precorneal residence time of drug to a sufficient extent that an ocularly delivered drug can exhibit its maximum biological action. The concept of this innovative ophthalmic delivery approach is to decrease the systemic side effects and to create a more pronounced effect with lower doses of the drug. The present article describes the advantages and use stimuli sensitive of hydrogel systems in ophthalmic drug delivery.

  10. Stimuli sensitive hydrogels for ophthalmic drug delivery: A review

    PubMed Central

    Kushwaha, Swatantra KS; Saxena, Prachi; Rai, AK

    2012-01-01

    Amongst the various routes of drug delivery, the field of ocular drug delivery is one of the most interesting and challenging endeavors facing the pharmaceutical scientist for past 10-20 years. As an isolated organ, eye is very difficult to study from a drug delivery point of view. Despite this limitation, improvements have been made with the objective of maintaining the drug in the biophase for an extended period. A major problem in ocular therapeutics is the attainment of an optimal drug concentration at the site of action. To achieve effective ophthalmic therapy, an adequate amount of active ingredient must be delivered and maintained within the eye. The most frequently used dosage forms, i.e., eye solution, eye ointments, eye gels, and eye suspensions are compromised in their effectiveness by several limitations leading to poor ocular bioavailability. Ophthalmic use of viscosity-enhancing agents, penetration enhancers, cyclodextrins, prodrug approaches, and ocular inserts, and the ready existing drug carrier systems along with their application to ophthalmic drug delivery are common to improve ocular bioavailability. Amongst these hydrogel (stimuli sensitive) systems are important, which undergo reversible volume and/or sol-gel phase transitions in response to physiological (temperature, pH and present of ions in organism fluids, enzyme substrate) or other external (electric current, light) stimuli. They help to increase in precorneal residence time of drug to a sufficient extent that an ocularly delivered drug can exhibit its maximum biological action. The concept of this innovative ophthalmic delivery approach is to decrease the systemic side effects and to create a more pronounced effect with lower doses of the drug. The present article describes the advantages and use stimuli sensitive of hydrogel systems in ophthalmic drug delivery. PMID:23119233

  11. Behavioral response of Caenorhabditis elegans to localized thermal stimuli

    PubMed Central

    2013-01-01

    Background Nociception evokes a rapid withdrawal behavior designed to protect the animal from potential danger. C. elegans performs a reflexive reversal or forward locomotory response when presented with noxious stimuli at the head or tail, respectively. Here, we have developed an assay with precise spatial and temporal control of an infrared laser stimulus that targets one-fifth of the worm’s body and quantifies multiple aspects of the worm’s escape response. Results When stimulated at the head, we found that the escape response can be elicited by changes in temperature as small as a fraction of a degree Celsius, and that aspects of the escape behavior such as the response latency and the escape direction change advantageously as the amplitude of the noxious stimulus increases. We have mapped the behavioral receptive field of thermal nociception along the entire body of the worm, and show a midbody avoidance behavior distinct from the head and tail responses. At the midbody, the worm is sensitive to a change in the stimulus location as small as 80 μm. This midbody response is probabilistic, producing either a backward, forward or pause state after the stimulus. The distribution of these states shifts from reverse-biased to forward-biased as the location of the stimulus moves from the middle towards the anterior or posterior of the worm, respectively. We identified PVD as the thermal nociceptor for the midbody response using calcium imaging, genetic ablation and laser ablation. Analyses of mutants suggest the possibility that TRPV channels and glutamate are involved in facilitating the midbody noxious response. Conclusion Through high resolution quantitative behavioral analysis, we have comprehensively characterized the C. elegans escape response to noxious thermal stimuli applied along its body, and found a novel midbody response. We further identified the nociceptor PVD as required to sense noxious heat at the midbody and can spatially differentiate

  12. Napping Promotes Inter-Session Habituation to Emotional Stimuli

    PubMed Central

    Pace-Schott, Edward F.; Shepherd, Elizabeth; Spencer, Rebecca M.C.; Marcello, Matthew; Tucker, Matthew; Propper, Ruth E.; Stickgold, Robert

    2010-01-01

    The effects of a daytime nap on inter-session habituation to aversive visual stimuli were investigated. Healthy young adult volunteers viewed repeated presentations of highly negative and emotionally neutral (but equally arousing) International Affective Picture System (IAPS) photographs during two afternoon sessions separated by 2.5 hrs. Half of the photographs were shown at both sessions (Repeated Sets) and half differed between sessions (Novel Sets). For each stimulus presentation, evoked skin conductance response (SCR), heart rate deceleration (HRD) and corrugator supercilii EMG response (EMG), were computed and range corrected using respective maximum session-1 responses. Following each presentation, subjects rated each photograph on dimensions of pleasantness and arousability. During the inter-session interval, Nap subjects had a 120-min polysomnographically monitored sleep opportunity, whereas Wake subjects watched a non-stimulating video. Nap and Wake subjects did not differ in their subjective ratings of photographs. However, for Repeated-Set photographs, Nap subjects demonstrated greater inter-session habituation in SCR and EMG but a trend toward lesser inter-session habituation in HRD. These group differences were absent for Novel-Set photographs. Group differences across all measures were greater for negative stimuli. Occurrence of SWS during the nap was associated with greater inter-session habituation of EMG whereas occurrence of REM was associated with lesser inter-session habituation of SCR to negative stimuli. Sleep may therefore promote emotional adjustment at the level of somatic responses. Physiological but not subjective inter-session habituation to aversive images was enhanced by a daytime nap. PMID:20969968

  13. PC-compatible computer-generated stimuli for video-task testing

    NASA Technical Reports Server (NTRS)

    Washburn, David A.

    1990-01-01

    A program for automatic computer generation of novel nonverbal stimuli is described. The program, STIMGEN, allows menu-driven control over the type and appearance of stimuli. Data are presented in which two monkeys matched to sample with high accuracy using stimuli generated with STIMGEN. These data are interpreted to support the usefulness and value of automatic stimulus generation in a variety of applications.

  14. Understanding the Effects of Moving Visual Stimuli on Unilateral Neglect Following Stroke

    ERIC Educational Resources Information Center

    Plummer, Prudence; Dunai, Judith; Morris, Meg E.

    2006-01-01

    Moving visual stimuli have been shown to reduce unilateral neglect (ULN), however, the mechanisms underlying these effects remain poorly understood. This study compared lateralised and non-lateralised moving visual stimuli to investigate whether the spatial characteristics or general alerting properties of moving visual stimuli are responsible for…

  15. Post-conflict slowing after incongruent stimuli: from general to conflict-specific.

    PubMed

    Rey-Mermet, Alodie; Meier, Beat

    2016-03-28

    Encountering a cognitive conflict not only slows current performance, but it can also affect subsequent performance, in particular when the conflict is induced with bivalent stimuli (i.e., stimuli with relevant features for two different tasks) or with incongruent trials (i.e., stimuli with relevant features for two response alternatives). The post-conflict slowing following bivalent stimuli, called "bivalency effect", affects all subsequent stimuli, irrespective of whether the subsequent stimuli share relevant features with the conflict stimuli. To date, it is unknown whether the conflict induced by incongruent stimuli results in a similar post-conflict slowing. To investigate this, we performed six experiments in which participants switched between two tasks. In one task, incongruent stimuli appeared occasionally; in the other task, stimuli shared no feature with the incongruent trials. The results showed an initial performance slowing that affected all tasks after incongruent trials. On further trials, however, the slowing only affected the task sharing features with the conflict stimuli. Therefore, the post-conflict slowing following incongruent stimuli is first general and then becomes conflict-specific across trials. These findings are discussed within current task switching and cognitive control accounts.

  16. [The Contribution of the Orbitofrontal Cortex to the Preference for Visual Stimuli].

    PubMed

    Funahashi, Shintaro

    2015-06-01

    Both humans and animals like to watch neutral and biologically insignificant visual stimuli. Behavioral studies have revealed that animals more frequently select stimuli with symmetrical and regular patterns and short movies compared to stimuli with unsymmetrical and irregular patterns and photographs. Preferred visual stimuli can serve as rewards for animals performing behavioral tasks. Preferences for visual stimuli are determined by the magnitude of the pleasant feelings that are experienced when the stimuli are seen. The orbitofrontal cortex is known to participate in the detection and prediction of reward, the estimation of the value of the stimuli as a reward, and positive emotion. Human neuroimaging studies and animal neurophysiological studies have shown that the magnitude of orbitofrontal responses to the presentation of neutral visual stimuli correlates with the strength of the preference for the stimuli in the behavioral studies. These results suggest that the magnitude of orbitofrontal responses to the visual stimuli correlates with the strength of the pleasant feelings that are produced by the stimuli and that the orbitofrontal cortex plays an important role in the judgment of the preference for visual stimuli.

  17. Do Live versus Audio-Recorded Narrative Stimuli Influence Young Children's Narrative Comprehension and Retell Quality?

    ERIC Educational Resources Information Center

    Kim, Young-Suk Grace

    2016-01-01

    Purpose: The primary aim of the present study was to examine whether different ways of presenting narrative stimuli (i.e., live narrative stimuli versus audio-recorded narrative stimuli) influence children's performances on narrative comprehension and oral-retell quality. Method: Children in kindergarten (n = 54), second grade (n = 74), and fourth…

  18. Sharp peaks in the conductance of a double quantum dot and a quantum-dot spin valve at high temperatures: A hierarchical quantum master equation approach

    NASA Astrophysics Data System (ADS)

    Wenderoth, S.; Bätge, J.; Härtle, R.

    2016-09-01

    We study sharp peaks in the conductance-voltage characteristics of a double quantum dot and a quantum dot spin valve that are located around zero bias. The peaks share similarities with a Kondo peak but can be clearly distinguished, in particular as they occur at high temperatures. The underlying physical mechanism is a strong current suppression that is quenched in bias-voltage dependent ways by exchange interactions. Our theoretical results are based on the quantum master equation methodology, including the Born-Markov approximation and a numerically exact, hierarchical scheme, which we extend here to the spin-valve case. The comparison of exact and approximate results allows us to reveal the underlying physical mechanisms, the role of first-, second- and beyond-second-order processes and the robustness of the effect.

  19. Alloying Strategy in Cu-In-Ga-Se Quantum Dots for High Efficiency Quantum Dot Sensitized Solar Cells.

    PubMed

    Peng, Wenxiang; Du, Jun; Pan, Zhenxiao; Nakazawa, Naoki; Sun, Jiankun; Du, Zhonglin; Shen, Gencai; Yu, Juan; Hu, Jin-Song; Shen, Qing; Zhong, Xinhua

    2017-02-15

    I-III-VI2 group "green" quantum dots (QDs) are attracting increasing attention in photoelectronic conversion applications. Herein, on the basis of the "simultaneous nucleation and growth" approach, Cu-In-Ga-Se (CIGSe) QDs with light harvesting range of about 1000 nm were synthesized and used as sensitizer to construct quantum dot sensitized solar cells (QDSCs). Inductively coupled plasma atomic emission spectrometry (ICP-AES), wild-angle X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analyses demonstrate that the Ga element was alloyed in the Cu-In-Se (CISe) host. Ultraviolet photoelectron spectroscopy (UPS) and femtosecond (fs) resolution transient absorption (TA) measurement results indicate that the alloying strategy could optimize the electronic structure in the obtained CIGSe QD material, thus matching well with TiO2 substrate and favoring the photogenerated electron extraction. Open circuit voltage decay (OCVD) and impedance spectroscopy (IS) tests indicate that the intrinsic recombination in CIGSe QDSCs was well suppressed relative to that in CISe QDSCs. As a result, CIGSe based QDSCs with use of titanium mesh supported mesoporous carbon counter electrode exhibited a champion efficiency of 11.49% (Jsc = 25.01 mA/cm(2), Voc = 0.740 V, FF = 0.621) under the irradiation of full one sun in comparison with 9.46% for CISe QDSCs.

  20. [Responses of squirrel visual cortex neurons to patterned visual stimuli].

    PubMed

    Supin, A Ia

    1975-01-01

    The responses of visual cortical neurons to patterned visual stimuli were studied in squirrel Sciurus vulgaris. The direction selective, orientation-selective and non-selective neurons were observed. Most direction-selective and non-selective neurons were sensitive to high speeds of stimulus movement--hundreds deg/s. The direction-selective neurons exhibited their selectivity at such high speeds in spite of the short time of the stimulus movement through the receptive field. Orientation-selective neurons (with simple or complex receptive fields) were sensitive to lower speeds of the stimulus movement (tens deg/s). Some mechanisms of the properties described are discussed.

  1. On hemispheric differences in evoked potentials to speech stimuli

    NASA Technical Reports Server (NTRS)

    Galambos, R.; Benson, P.; Smith, T. S.; Schulman-Galambos, C.; Osier, H.

    1975-01-01

    Confirmation is provided for the belief that evoked potentials may reflect differences in hemispheric functioning that are marginal at best. Subjects were right-handed and audiologically normal men and women, and responses were recorded using standard EEG techniques. Subjects were instructed to listen for the targets while laying in a darkened sound booth. Different stimuli, speech and tone signals, were used. Speech sounds were shown to evoke a response pattern that resembles that to tone or clicks. Analysis of variances on peak amplitude and latency measures showed no significant differences between hemispheres, however, a Wilcoxon test showed significant differences in hemispheres for certain target tasks.

  2. Conditioning arbitrary stimuli to cigarette smoke intake: a preliminary study.

    PubMed

    Payne, T J; Etscheidt, M; Corrigan, S A

    1990-01-01

    This study represents an attempt to classically condition arbitrary stimuli to cigarette smoke intake. A smoker either smoked or mock-smoked a cigarette in two discriminative contexts for 20 sessions. The contingencies were reversed during an additional last two sessions. Measures of heart rate, skin temperature, and puff duration were monitored during all sessions. Results suggested that both manipulations of smoke delivery and context cues were related to puff duration. The pattern of psychophysiological reactivity was mixed and not easily interpreted. This experimental paradigm may be useful in the investigation of conditioning factors underlying addictive behaviors.

  3. Hydrophilic-oleophobic stimuli-responsive materials and surfaces

    NASA Astrophysics Data System (ADS)

    Howarter, John A.

    Due to their high surface energy, hydrophilic surfaces are susceptible to contamination which is difficult to remove and often ruins the surface. Hydrophilic-oleophobic coatings have a diverse engineering potential including applications as self-cleaning surfaces, extended life anti-fog coatings, and environmental remediation in the selective filtration of oil-in-water mixtures. A successful design model for hydrophilic-oleophobic behavior has been developed using perfluorinated surfactants covalently bound to a surface. Within this design model, a variety of materials have been explored which the surfactants are covalently bound to a substrate; similarly, the surfactants may also be incorporated as a monomer into bulk copolymers. Surfactant based surfaces exhibited simultaneous hydrophilicity, necessary for anti-fogging, and oleophobicity, necessary for contamination resistance. The combination of these features rendered the surface as self-cleaning. Surfactant based brushes, composed of polyethylene glycol and perfluorinated constituents were grafted on to silica surfaces. The relationship between brush density and stimuli-responsiveness was determined by varying grafting conditions. The resultant surfaces were characterized with respect to chemical composition, brush thickness, and wetting behavior of water and hexadecane. Optimized surfaces exhibited stimuli-responsive behavior such that the surfaces will be wetted by water but not by oil. Surfactants were incorporated into random copolymers to create self-cleaning polymers which could be easily coated on to surfaces post-synthesis. Acrylic acid, methyl methacrylate, and hydroxyethyl methacrylate were used as comonomers; feed ratio was varied to establish compositional limits of stimuli-responsive behavior. Polymer composition dictated coating durability and self-cleaning performance as determined by water and hexadecane contact angle. The ability of select coatings to mitigate fogging was assessed in two

  4. Construction of Hindi Speech Stimuli for Eliciting Auditory Brainstem Responses.

    PubMed

    Ansari, Mohammad Shamim; Rangasayee, R

    2016-12-01

    Speech-evoked auditory brainstem responses (spABRs) provide considerable information of clinical relevance to describe auditory processing of complex stimuli at the sub cortical level. The substantial research data have suggested faithful representation of temporal and spectral characteristics of speech sounds. However, the spABR are known to be affected by acoustic properties of speech, language experiences and training. Hence, there exists indecisive literature with regards to brainstem speech processing. This warrants establishment of language specific speech stimulus to describe the brainstem processing in specific oral language user. The objective of current study is to develop Hindi speech stimuli for recording auditory brainstem responses. The Hindi stop speech of 40 ms containing five formants was constructed. Brainstem evoked responses to speech sound |da| were gained from 25 normal hearing (NH) adults having mean age of 20.9 years (SD = 2.7) in the age range of 18-25 years and ten subjects (HI) with mild SNHL of mean 21.3 years (SD = 3.2) in the age range of 18-25 years. The statistically significant differences in the mean identification scores of synthesized for speech stimuli |da| and |ga| between NH and HI were obtained. The mean, median, standard deviation, minimum, maximum and 95 % confidence interval for the discrete peaks and V-A complex values of electrophysiological responses to speech stimulus were measured and compared between NH and HI population. This paper delineates a comprehensive methodological approach for development of Hindi speech stimuli and recording of ABR to speech. The acoustic characteristic of stimulus |da| was faithfully represented at brainstem level in normal hearing adults. There was statistically significance difference between NH and HI individuals. This suggests that spABR offers an opportunity to segregate normal speech encoding from abnormal speech processing at sub cortical level, which implies that

  5. Notes from "Pavlov's Wednesdays": Gestalt relationships as conditioned stimuli.

    PubMed

    Kimmel, H D

    1976-12-01

    When A.O. Dolin's dog Ger was trained to differentiate between metronomic frequencies of 60 (positive) and 120 (negative) per minute, its conditioned salivary reaction to the positive stimulus was attenuated immediately after a test on a more positive stimulus (30 per minute) and that to the negative stimulus was augmented immediately after a test on a more negative stimulus (200 per minute). Pavlov and his colleagues considered explanations based on the relationship between the test and trained stimuli, on reciprocal induction, and on gradients of generalized excitation and inhibition à la Spence. This was just before Pavlov's death, but his last words on the topic leaned in the Gestalt relational direction.

  6. Thermoregulatory responses during exercise and a hot water immersion and the affective responses to peripheral thermal stimuli

    NASA Astrophysics Data System (ADS)

    Fujishima, K.

    1986-03-01

    Tympanic (Tty), mean skin (¯Tsk) and mean body (¯Tb) temperatures and heart rate (HR) increased more in low Vo2 max group (LG) than in high Vo2 max group (HG) during exercise. The regression coefficient of body temperatures (Tty and ¯Tb) on HR and the increased rate of heat storage were larger in LG than in HG during exercise. The local sweat rate (per min/cm2) during a hot water bath exhibited a considerable large quantity in comparison with the amount during exercise. Internal and skin temperatures during a hot water bath increased more immediately than those during exercise. The levels of comfort sensation during the preovulatory phase in women and pre-exercise period in men were higher at 40‡C than at 20‡C as peripheral thermal stimulus. The levels during the postovulatory and post-exercise phases in the same subjects were higher with the cool stimuli than with the warm stimuli. Above results suggest that thermoregulatory responses during submaximal exercise are different according to physical fitness and that these responses are different from those during hot water immersion. In addition, these suggest that the scores of thermal sensation with warm and cool stimuli are different during the pre- and post-ovulatory phases and the pre- and post-exercise periods.

  7. Beyond DOtS: avenues ahead in the management of tuberculosis.

    PubMed

    Chaudhury, Ranjit Roy; Thatte, Urmila

    2003-01-01

    India has almost 30% of the global burden of tuberculosis (TB)--one person dies of the disease every minute in our country. India has mounted the second-largest DOTS programme in the world to control this disease. However, DOTS has its limitations and newer approaches have been developed over the years to overcome the global burden of tuberculosis. Problems with health facilities, patients, drugs and the disease itself constitute some of the hurdles in the implementation of the DOTS programme. In an attempt to go beyond DOTS, the WHO launched the 'Stop TB Initiative' in 1988. Against the background of irrational antituberculosis drug use, which contributes to increasing drug resistance, the effective involvement of private healthcare providers is imperative to achieve better geographical and patient coverage for the implementation of DOTS. The WHO is currently addressing the issue of involving private practitioners in tuberculosis control in a programme called Public-Private Mix DOTS (PPM DOTS). The Stop TB Initiative is also active in the area of dual infection with HIV and tuberculosis, and the initiatives that have been taken in this area include 'ProTEST', community contribution to tuberculosis care, and development and dissemination of training materials and guidelines. The DOTS-Plus strategy for the management of multidrug resistant (MDR)-TB and the establishment of the Green Light Committee to review project applications in this area are initiatives taken to curb the problem of drug resistance in tuberculosis. Even decades after the introduction of the DOTS strategy, much needs to be done to expand the services to the entire population; it is now essential to develop strategies that go beyond DOTS.

  8. Advancements in the Field of Quantum Dots

    NASA Astrophysics Data System (ADS)

    Mishra, Sambeet; Tripathy, Pratyasha; Sinha, Swami Prasad.

    2012-08-01

    Quantum dots are defined as very small semiconductor crystals of size varying from nanometer scale to a few micron i.e. so small that they are considered dimensionless and are capable of showing many chemical properties by virtue of which they tend to be lead at one minute and gold at the second minute.Quantum dots house the electrons just the way the electrons would have been present in an atom, by applying a voltage. And therefore they are very judiciously given the name of being called as the artificial atoms. This application of voltage may also lead to the modification of the chemical nature of the material anytime it is desired, resulting in lead at one minute to gold at the other minute. But this method is quite beyond our reach. A quantum dot is basically a semiconductor of very tiny size and this special phenomenon of quantum dot, causes the band of energies to change into discrete energy levels. Band gaps and the related energy depend on the relationship between the size of the crystal and the exciton radius. The height and energy between different energy levels varies inversely with the size of the quantum dot. The smaller the quantum dot, the higher is the energy possessed by it.There are many applications of the quantum dots e.g. they are very wisely applied to:Light emitting diodes: LEDs eg. White LEDs, Photovoltaic devices: solar cells, Memory elements, Biology : =biosensors, imaging, Lasers, Quantum computation, Flat-panel displays, Photodetectors, Life sciences and so on and so forth.The nanometer sized particles are able to display any chosen colour in the entire ultraviolet visible spectrum through a small change in their size or composition.

  9. Electromechanical transition in quantum dots

    NASA Astrophysics Data System (ADS)

    Micchi, G.; Avriller, R.; Pistolesi, F.

    2016-09-01

    The strong coupling between electronic transport in a single-level quantum dot and a capacitively coupled nanomechanical oscillator may lead to a transition towards a mechanically bistable and blocked-current state. Its observation is at reach in carbon-nanotube state-of-art experiments. In a recent publication [Phys. Rev. Lett. 115, 206802 (2015), 10.1103/PhysRevLett.115.206802] we have shown that this transition is characterized by pronounced signatures on the oscillator mechanical properties: the susceptibility, the displacement fluctuation spectrum, and the ring-down time. These properties are extracted from transport measurements, however the relation between the mechanical quantities and the electronic signal is not always straightforward. Moreover the dependence of the same quantities on temperature, bias or gate voltage, and external dissipation has not been studied. The purpose of this paper is to fill this gap and provide a detailed description of the transition. Specifically we find (i) the relation between the current-noise and the displacement spectrum; (ii) the peculiar behavior of the gate-voltage dependence of these spectra at the transition; (iii) the robustness of the transition towards the effect of external fluctuations and dissipation.

  10. Submonolayer Quantum Dot Infrared Photodetector

    NASA Technical Reports Server (NTRS)

    Ting, David Z.; Bandara, Sumith V.; Gunapala, Sarath D.; Chang, Yia-Chang

    2010-01-01

    A method has been developed for inserting submonolayer (SML) quantum dots (QDs) or SML QD stacks, instead of conventional Stranski-Krastanov (S-K) QDs, into the active region of intersubband photodetectors. A typical configuration would be InAs SML QDs embedded in thin layers of GaAs, surrounded by AlGaAs barriers. Here, the GaAs and the AlGaAs have nearly the same lattice constant, while InAs has a larger lattice constant. In QD infrared photodetector, the important quantization directions are in the plane perpendicular to the normal incidence radiation. In-plane quantization is what enables the absorption of normal incidence radiation. The height of the S-K QD controls the positions of the quantized energy levels, but is not critically important to the desired normal incidence absorption properties. The SML QD or SML QD stack configurations give more control of the structure grown, retains normal incidence absorption properties, and decreases the strain build-up to allow thicker active layers for higher quantum efficiency.

  11. Profiling the local carrier concentration across a semiconductor quantum dot

    SciTech Connect

    Walrath, J. C.; Lin, Yen-Hsiang; Huang, S.; Goldman, R. S.

    2015-05-11

    We profile the local carrier concentration, n, across epitaxial InAs/GaAs quantum dots (QDs) consisting of 3D islands on top of a 2D alloy layer. We use scanning thermoelectric microscopy to measure a profile of the temperature gradient-induced voltage, which is converted to a profile of the local Seebeck coefficient, S. The S profile is then converted to a conduction band-edge profile and compared with Poisson-Schrodinger band-edge simulations. Our combined computational-experimental approach suggests a reduced carrier concentration in the QD center in comparison to that of the 2D alloy layer. The relative roles of free carrier trapping and/or dopant expulsion are discussed.

  12. Bioconjugated Quantum Dots for In Vivo Molecular and Cellular Imaging

    PubMed Central

    Smith, Andrew M.; Duan, Hongwei; Mohs, Aaron M.; Nie, Shuming

    2008-01-01

    Semiconductor quantum dots (QDs) are tiny light-emitting particles on the nanometer scale, and are emerging as a new class of fluorescent labels for biology and medicine. In comparison with organic dyes and fluorescent proteins, they have unique optical and electronic properties, with size-tunable light emission, superior signal brightness, resistance to photobleaching, and broad absorption spectra for simultaneous excitation of multiple fluorescence colors. QDs also provide a versatile nanoscale scaffold for designing multifunctional nanoparticles with both imaging and therapeutic functions. When linked with targeting ligands such as antibodies, peptides or small molecules, QDs can be used to target tumor biomarkers as well as tumor vasculatures with high affinity and specificity. Here we discuss the synthesis and development of state-of-the-art QD probes and their use for molecular and cellular imaging. We also examine key issues for in vivo imaging and therapy, such as nanoparticle biodistribution, pharmacokinetics, and toxicology. PMID:18495291

  13. Coulomb-blockade peak spacing statistics of graphene quantum dots on SiO2

    NASA Astrophysics Data System (ADS)

    Herrmann, O.; Gould, C.; Molenkamp, L. W.

    2016-10-01

    Extrinsic disorder strongly affects the performance of graphene-based quantum dots. The standard SiO2 substrate is generally considered to be one major factor besides edge-induced disorder. In this report we present the fabrication of lithographically defined quantum dots on SiO2 with short and narrow constrictions and different central island sizes. Low temperature transport measurements display distinct Coulomb-blockade peaks with amplitudes exceeding what is commonly observed experimentally. The analysis of the normalized Coulomb-blockade peak spacing shows a size dependence, which has not previously been observed for devices on SiO2. Furthermore, a quantitative comparison of the peak spacing distribution to the literature shows that one of the two devices compares favorably to a similar sized dot placed on hexagonal boron nitride, which is known to reduce the substrate disorder. Our findings suggest that the other sources of extrinsic disorder, such as lithography residues, may play an important role for the performance of large graphene quantum dots.

  14. Mass-profile quantum dots in graphene and artificial periodic structures

    NASA Astrophysics Data System (ADS)

    Gutiérrez-Rubio, A.; Stauber, T.

    2015-04-01

    We analyze the bound-state spectra of mass-profile quantum dots in graphene, a system at current experimental reach. Homogeneous perpendicular magnetic fields are also considered which result in breaking the valley degeneracy. The spectra show rich features, arising from the chiral band structure of graphene and its Landau levels and we identify three different regimes depending on the ratio between the radius of the dot and the magnetic length. We further carry out a comparison with potential-well quantum dots discussed in Recher et al. [Phys. Rev. B 79, 085407 (2009), 10.1103/PhysRevB.79.085407] and conclude that mass confinement may offer significant advantages for optical applications in the THz and infrared regime. Also due to experimental advances, we additionally analyze the band structure of a linear chain of mass-profile quantum dots, where overlap-assisted hopping processes play a major role for closely packed arrays. The inclusion of Coulomb interactions between electron-hole pairs of adjacent sites leads to a new regime where Förster transfer processes become dominant.

  15. Klinefelter syndrome has increased brain responses to auditory stimuli and motor output, but not to visual stimuli or Stroop adaptation.

    PubMed

    Wallentin, Mikkel; Skakkebæk, Anne; Bojesen, Anders; Fedder, Jens; Laurberg, Peter; Østergaard, John R; Hertz, Jens Michael; Pedersen, Anders Degn; Gravholt, Claus Højbjerg

    2016-01-01

    Klinefelter syndrome (47, XXY) (KS) is a genetic syndrome characterized by the presence of an extra X chromosome and low level of testosterone, resulting in a number of neurocognitive abnormalities, yet little is known about brain function. This study investigated the fMRI-BOLD response from KS relative to a group of Controls to basic motor, perceptual, executive and adaptation tasks. Participants (N: KS = 49; Controls = 49) responded to whether the words "GREEN" or "RED" were displayed in green or red (incongruent versus congruent colors). One of the colors was presented three times as often as the other, making it possible to study both congruency and adaptation effects independently. Auditory stimuli saying "GREEN" or "RED" had the same distribution, making it possible to study effects of perceptual modality as well as Frequency effects across modalities. We found that KS had an increased response to motor output in primary motor cortex and an increased response to auditory stimuli in auditory cortices, but no difference in primary visual cortices. KS displayed a diminished response to written visual stimuli in secondary visual regions near the Visual Word Form Area, consistent with the widespread dyslexia in the group. No neural differences were found in inhibitory control (Stroop) or in adaptation to differences in stimulus frequencies. Across groups we found a strong positive correlation between age and BOLD response in the brain's motor network with no difference between groups. No effects of testosterone level or brain volume were found. In sum, the present findings suggest that auditory and motor systems in KS are selectively affected, perhaps as a compensatory strategy, and that this is not a systemic effect as it is not seen in the visual system.

  16. Klinefelter syndrome has increased brain responses to auditory stimuli and motor output, but not to visual stimuli or Stroop adaptation

    PubMed Central

    Wallentin, Mikkel; Skakkebæk, Anne; Bojesen, Anders; Fedder, Jens; Laurberg, Peter; Østergaard, John R.; Hertz, Jens Michael; Pedersen, Anders Degn; Gravholt, Claus Højbjerg

    2016-01-01

    Klinefelter syndrome (47, XXY) (KS) is a genetic syndrome characterized by the presence of an extra X chromosome and low level of testosterone, resulting in a number of neurocognitive abnormalities, yet little is known about brain function. This study investigated the fMRI-BOLD response from KS relative to a group of Controls to basic motor, perceptual, executive and adaptation tasks. Participants (N: KS = 49; Controls = 49) responded to whether the words “GREEN” or “RED” were displayed in green or red (incongruent versus congruent colors). One of the colors was presented three times as often as the other, making it possible to study both congruency and adaptation effects independently. Auditory stimuli saying “GREEN” or “RED” had the same distribution, making it possible to study effects of perceptual modality as well as Frequency effects across modalities. We found that KS had an increased response to motor output in primary motor cortex and an increased response to auditory stimuli in auditory cortices, but no difference in primary visual cortices. KS displayed a diminished response to written visual stimuli in secondary visual regions near the Visual Word Form Area, consistent with the widespread dyslexia in the group. No neural differences were found in inhibitory control (Stroop) or in adaptation to differences in stimulus frequencies. Across groups we found a strong positive correlation between age and BOLD response in the brain's motor network with no difference between groups. No effects of testosterone level or brain volume were found. In sum, the present findings suggest that auditory and motor systems in KS are selectively affected, perhaps as a compensatory strategy, and that this is not a systemic effect as it is not seen in the visual system. PMID:26958463

  17. Moving Stimuli Facilitate Synchronization But Not Temporal Perception

    PubMed Central

    Silva, Susana; Castro, São Luís

    2016-01-01

    Recent studies have shown that a moving visual stimulus (e.g., a bouncing ball) facilitates synchronization compared to a static stimulus (e.g., a flashing light), and that it can even be as effective as an auditory beep. We asked a group of participants to perform different tasks with four stimulus types: beeps, siren-like sounds, visual flashes (static) and bouncing balls. First, participants performed synchronization with isochronous sequences (stimulus-guided synchronization), followed by a continuation phase in which the stimulus was internally generated (imagery-guided synchronization). Then they performed a perception task, in which they judged whether the final part of a temporal sequence was compatible with the previous beat structure (stimulus-guided perception). Similar to synchronization, an imagery-guided variant was added, in which sequences contained a gap in between (imagery-guided perception). Balls outperformed flashes and matched beeps (powerful ball effect) in stimulus-guided synchronization but not in perception (stimulus- or imagery-guided). In imagery-guided synchronization, performance accuracy decreased for beeps and balls, but not for flashes and sirens. Our findings suggest that the advantages of moving visual stimuli over static ones are grounded in action rather than perception, and they support the hypothesis that the sensorimotor coupling mechanisms for auditory (beeps) and moving visual stimuli (bouncing balls) overlap. PMID:27909419

  18. EEG Responses to Auditory Stimuli for Automatic Affect Recognition.

    PubMed

    Hettich, Dirk T; Bolinger, Elaina; Matuz, Tamara; Birbaumer, Niels; Rosenstiel, Wolfgang; Spüler, Martin

    2016-01-01

    Brain state classification for communication and control has been well established in the area of brain-computer interfaces over the last decades. Recently, the passive and automatic extraction of additional information regarding the psychological state of users from neurophysiological signals has gained increased attention in the interdisciplinary field of affective computing. We investigated how well specific emotional reactions, induced by auditory stimuli, can be detected in EEG recordings. We introduce an auditory emotion induction paradigm based on the International Affective Digitized Sounds 2nd Edition (IADS-2) database also suitable for disabled individuals. Stimuli are grouped in three valence categories: unpleasant, neutral, and pleasant. Significant differences in time domain domain event-related potentials are found in the electroencephalogram (EEG) between unpleasant and neutral, as well as pleasant and neutral conditions over midline electrodes. Time domain data were classified in three binary classification problems using a linear support vector machine (SVM) classifier. We discuss three classification performance measures in the context of affective computing and outline some strategies for conducting and reporting affect classification studies.

  19. Crosslinked ionic polysaccharides for stimuli-sensitive drug delivery.

    PubMed

    Alvarez-Lorenzo, Carmen; Blanco-Fernandez, Barbara; Puga, Ana M; Concheiro, Angel

    2013-08-01

    Polysaccharides are gaining increasing attention as components of stimuli-responsive drug delivery systems, particularly since they can be obtained in a well characterized and reproducible way from the natural sources. Ionic polysaccharides can be readily crosslinked to render hydrogel networks sensitive to a variety of internal and external variables, and thus suitable for switching drug release on-off through diverse mechanisms. Hybrids, composites and grafted polymers can reinforce the responsiveness and widen the range of stimuli to which polysaccharide-based systems can respond. This review analyzes the state of the art of crosslinked ionic polysaccharides as components of delivery systems that can regulate drug release as a function of changes in pH, ion nature and concentration, electric and magnetic field intensity, light wavelength, temperature, redox potential, and certain molecules (enzymes, illness markers, and so on). Examples of specific applications are provided. The information compiled demonstrates that crosslinked networks of ionic polysaccharides are suitable building blocks for developing advanced externally activated and feed-back modulated drug delivery systems.

  20. Healable thermoset polymer composite embedded with stimuli-responsive fibres.

    PubMed

    Li, Guoqiang; Meng, Harper; Hu, Jinlian

    2012-12-07

    Severe wounds in biological systems such as human skin cannot heal themselves, unless they are first stitched together. Healing of macroscopic damage in thermoset polymer composites faces a similar challenge. Stimuli-responsive shape-changing polymeric fibres with outstanding mechanical properties embedded in polymers may be able to close macro-cracks automatically upon stimulation such as heating. Here, a stimuli-responsive fibre (SRF) with outstanding mechanical properties and supercontraction capability was fabricated for the purpose of healing macroscopic damage. The SRFs and thermoplastic particles (TPs) were incorporated into regular thermosetting epoxy for repeatedly healing macroscopic damages. The system works by mimicking self-healing of biological systems such as human skin, close (stitch) then heal, i.e. close the macroscopic crack through the thermal-induced supercontraction of the SRFs, and bond the closed crack through melting and diffusing of TPs at the crack interface. The healing efficiency determined using tapered double-cantilever beam specimens was 94 per cent. The self-healing process was reasonably repeatable.

  1. Response time to colored stimuli in the full visual field

    NASA Technical Reports Server (NTRS)

    Haines, R. F.; Dawson, L. M.; Galvan, T.; Reid, L. M.

    1975-01-01

    Peripheral visual response time was measured in seven dark adapted subjects to the onset of small (45' arc diam), brief (50 msec), colored (blue, yellow, green, red) and white stimuli imaged at 72 locations within their binocular field of view. The blue, yellow, and green stimuli were matched for brightness at about 2.6 sub log 10 units above their absolute light threshold, and they appeared at an unexpected time and location. These data were obtained to provide response time and no-response data for use in various design disciplines involving instrument panel layout. The results indicated that the retina possesses relatively concentric regions within each of which mean response time can be expected to be of approximately the same duration. These regions are centered near the fovea and extend farther horizontally than vertically. Mean foveal response time was fastest for yellow and slowest for blue. Three and one-half percent of the total 56,410 trials presented resulted in no-responses. Regardless of stimulus color, the lowest percentage of no-responses occurred within 30 deg arc from the fovea and the highest within 40 deg to 80 deg arc below the fovea.

  2. Dynamic Stimuli And Active Processing In Human Visual Perception

    NASA Astrophysics Data System (ADS)

    Haber, Ralph N.

    1990-03-01

    Theories of visual perception traditionally have considered a static retinal image to be the starting point for processing; and has considered processing both to be passive and a literal translation of that frozen, two dimensional, pictorial image. This paper considers five problem areas in the analysis of human visually guided locomotion, in which the traditional approach is contrasted to newer ones that utilize dynamic definitions of stimulation, and an active perceiver: (1) differentiation between object motion and self motion, and among the various kinds of self motion (e.g., eyes only, head only, whole body, and their combinations); (2) the sources and contents of visual information that guide movement; (3) the acquisition and performance of perceptual motor skills; (4) the nature of spatial representations, percepts, and the perceived layout of space; and (5) and why the retinal image is a poor starting point for perceptual processing. These newer approaches argue that stimuli must be considered as dynamic: humans process the systematic changes in patterned light when objects move and when they themselves move. Furthermore, the processing of visual stimuli must be active and interactive, so that perceivers can construct panoramic and stable percepts from an interaction of stimulus information and expectancies of what is contained in the visual environment. These developments all suggest a very different approach to the computational analyses of object location and identification, and of the visual guidance of locomotion.

  3. Organic Nanofibers Embedding Stimuli-Responsive Threaded Molecular Components

    PubMed Central

    2014-01-01

    While most of the studies on molecular machines have been performed in solution, interfacing these supramolecular systems with solid-state nanostructures and materials is very important in view of their utilization in sensing components working by chemical and photonic actuation. Host polymeric materials, and particularly polymer nanofibers, enable the manipulation of the functional molecules constituting molecular machines and provide a way to induce and control the supramolecular organization. Here, we present electrospun nanocomposites embedding a self-assembling rotaxane-type system that is responsive to both optical (UV–vis light) and chemical (acid/base) stimuli. The system includes a molecular axle comprised of a dibenzylammonium recognition site and two azobenzene end groups and a dibenzo[24]crown-8 molecular ring. The dethreading and rethreading of the molecular components in nanofibers induced by exposure to base and acid vapors, as well as the photoisomerization of the azobenzene end groups, occur in a similar manner to what observed in solution. Importantly, however, the nanoscale mechanical function following external chemical stimuli induces a measurable variation of the macroscopic mechanical properties of nanofibers aligned in arrays, whose Young’s modulus is significantly enhanced upon dethreading of the axles from the rings. These composite nanosystems show therefore great potential for application in chemical sensors, photonic actuators, and environmentally responsive materials. PMID:25264943

  4. Task-irrelevant blindsight and the impact of invisible stimuli.

    PubMed

    Stoerig, Petra

    2011-01-01

    Despite their subjective invisibility, stimuli presented within regions of absolute cortical blindness can both guide forced-choice behavior when they are task-relevant and modulate responses to visible targets when they are task-irrelevant. We here tested three hemianopic patients to learn whether their performance in an attention-demanding rapid serial visual presentation task would be affected by task-irrelevant stimuli. Per trial, nine black letters and one white target letter appeared briefly at fixation; the white letter was to be named at the end of each trial. On 50% of trials, a task-irrelevant disk (-0.6 log contrast) was presented to the blind field; in separate blocks, the same or a very low negative contrast distractor was presented to the sighted field. Mean error rates were high and independent of distractor condition, although the high-contrast sighted-field disk impaired performance significantly in one participant. However, when trials with and without distractors were considered separately, performance was most impaired by the high-contrast disk in the blind field, whereas the same disk in the sighted field had no effect. As this disk was least visible in the blind and most visible in the sighted field, attentional suppression was inversely related to visibility. We suggest that visual awareness, or the processes that generate it and are compromised in the blind hemisphere, enhances or enables effective attentional suppression.

  5. Polymer-based stimuli-responsive nanosystems for biomedical applications.

    PubMed

    Joglekar, Madhura; Trewyn, Brian G

    2013-08-01

    The application of organic polymers and inorganic/organic hybrid systems in numerous fields of biotechnology has seen a considerable growth in recent years. Typically, organic polymers with diverse structures, compositional variations and differing molecular weights have been utilized to assemble polymeric nanosystems such as polymeric micelles, polymersomes, and nanohydrogels with unique features and structural properties. The architecture of these polymeric nanosystems involves the use of both hydrophobic and hydrophilic polymeric blocks, making them suitable as vehicles for diagnostic and therapeutic applications. Recently, "smart" or "intelligent" polymers have attracted significant attention in the biomedical field wherein careful introduction of specific polymeric modalities changes a banal polymeric nanosystem to an advanced stimuli-responsive nanosystem capable of performing extraordinary functions in response to an internal or external trigger such as pH, temperature, redox, enzymes, light, magnetic, or ultrasound. Further, incorporation of inorganic nanoparticles such as gold, silica, or iron oxide with surface-bound stimuli-responsive polymers offers additional advantages and multifunctionality in the field of nanomedicine. This review covers the physical properties and applications of both organic and organic/inorganic hybrid nanosystems with specific recent breakthroughs in drug delivery, imaging, tissue engineering, and separations and provides a brief discussion on the future direction.

  6. Task Attention Facilitates Learning of Task-Irrelevant Stimuli

    PubMed Central

    Huang, Tsung-Ren; Watanabe, Takeo

    2012-01-01

    Attention plays a fundamental role in visual learning and memory. One highly established principle of visual attention is that the harder a central task is, the more attentional resources are used to perform the task and the smaller amount of attention is allocated to peripheral processing because of limited attention capacity. Here we show that this principle holds true in a dual-task setting but not in a paradigm of task-irrelevant perceptual learning. In Experiment 1, eight participants were asked to identify either bright or dim number targets at the screen center and to remember concurrently presented scene backgrounds. Their recognition performances for scenes paired with dim/hard targets were worse than those for scenes paired with bright/easy targets. In Experiment 2, eight participants were asked to identify either bright or dim letter targets at the screen center while a task-irrelevant coherent motion was concurrently presented in the background. After five days of training on letter identification, participants improved their motion sensitivity to the direction paired with hard/dim targets improved but not to the direction paired with easy/bright targets. Taken together, these results suggest that task-irrelevant stimuli are not subject to the attentional control mechanisms that task-relevant stimuli abide. PMID:22563424

  7. Determining hierarchical functional networks from auditory stimuli fMRI.

    PubMed

    Patel, Rajan S; Bowman, F Dubois; Rilling, James K

    2006-05-01

    We determined connectivity of the human brain using functional magnetic resonance imaging (fMRI) while subjects experienced auditory stimuli in a 2-by-2 factorial design. The two factors in this study were "speaker" (same or different speaker) and "sentence" (same or different sentences). Connectivity studies allow us to ask how spatially remote brain regions are neurophysiologically related given these stimuli. In the context of this study, we examined how the "speaker" effect and "sentence" effect influenced these relationships. We applied a Bayesian connectivity method that determines hierarchical functional networks of functionally connected brain regions. Hierarchy in these functional networks is determined by conditional probabilities of elevated activity. For example, a brain region that becomes active a superset of the time of another region is considered ascendant to that brain region in the hierarchical network. For each factor level, we found a baseline functional network connecting the primary auditory cortex (Brodmann's Area [BA] 41) with the BA 42 and BA 22 of the superior temporal gyrus (STG). We also found a baseline functional network that includes Wernicke's Area (BA 22 posterior), STG, and BA 44 for each factor level. However, we additionally observed a strong ascendant connection from BA 41 to the posterior cingulate (BA 30) and Broca's Area and a stronger connection from Wernicke's Area to STG and the posterior cingulate while passively listening to different sentences rather than the same sentence repeatedly. Finally, our results revealed no significant "speaker" effect or interaction between "speaker" and "sentence."

  8. Healable thermoset polymer composite embedded with stimuli-responsive fibres

    PubMed Central

    Li, Guoqiang; Meng, Harper; Hu, Jinlian

    2012-01-01

    Severe wounds in biological systems such as human skin cannot heal themselves, unless they are first stitched together. Healing of macroscopic damage in thermoset polymer composites faces a similar challenge. Stimuli-responsive shape-changing polymeric fibres with outstanding mechanical properties embedded in polymers may be able to close macro-cracks automatically upon stimulation such as heating. Here, a stimuli-responsive fibre (SRF) with outstanding mechanical properties and supercontraction capability was fabricated for the purpose of healing macroscopic damage. The SRFs and thermoplastic particles (TPs) were incorporated into regular thermosetting epoxy for repeatedly healing macroscopic damages. The system works by mimicking self-healing of biological systems such as human skin, close (stitch) then heal, i.e. close the macroscopic crack through the thermal-induced supercontraction of the SRFs, and bond the closed crack through melting and diffusing of TPs at the crack interface. The healing efficiency determined using tapered double-cantilever beam specimens was 94 per cent. The self-healing process was reasonably repeatable. PMID:22896563

  9. Disruption of postural readaptation by inertial stimuli following space flight

    NASA Technical Reports Server (NTRS)

    Black, F. O.; Paloski, W. H.; Reschke, M. F.; Igarashi, M.; Guedry, F.; Anderson, D. J.

    1999-01-01

    Postural instability (relative to pre-flight) has been observed in all shuttle astronauts studied upon return from orbital missions. Postural stability was more closely examined in four shuttle astronaut subjects before and after an 8 day orbital mission. Results of the pre- and post-flight postural stability studies were compared with a larger (n = 34) study of astronauts returning from shuttle missions of similar duration. Results from both studies indicated that inadequate vestibular feedback was the most significant sensory deficit contributing to the postural instability observed post flight. For two of the four IML-1 astronauts, post-flight postural instability and rate of recovery toward their earth-normal performance matched the performance of the larger sample. However, post-flight postural control in one returning astronaut was substantially below mean performance. This individual, who was within normal limits with respect to postural control before the mission, indicated that recovery to pre-flight postural stability was also interrupted by a post-flight pitch plane rotation test. A similar, though less extreme departure from the mean recovery trajectory was present in another astronaut following the same post-flight rotation test. The pitch plane rotation stimuli included otolith stimuli in the form of both transient tangential and constant centripetal linear acceleration components. We inferred from these findings that adaptation on orbit and re-adaptation on earth involved a change in sensorimotor integration of vestibular signals most likely from the otolith organs.

  10. Moving Stimuli Facilitate Synchronization But Not Temporal Perception.

    PubMed

    Silva, Susana; Castro, São Luís

    2016-01-01

    Recent studies have shown that a moving visual stimulus (e.g., a bouncing ball) facilitates synchronization compared to a static stimulus (e.g., a flashing light), and that it can even be as effective as an auditory beep. We asked a group of participants to perform different tasks with four stimulus types: beeps, siren-like sounds, visual flashes (static) and bouncing balls. First, participants performed synchronization with isochronous sequences (stimulus-guided synchronization), followed by a continuation phase in which the stimulus was internally generated (imagery-guided synchronization). Then they performed a perception task, in which they judged whether the final part of a temporal sequence was compatible with the previous beat structure (stimulus-guided perception). Similar to synchronization, an imagery-guided variant was added, in which sequences contained a gap in between (imagery-guided perception). Balls outperformed flashes and matched beeps (powerful ball effect) in stimulus-guided synchronization but not in perception (stimulus- or imagery-guided). In imagery-guided synchronization, performance accuracy decreased for beeps and balls, but not for flashes and sirens. Our findings suggest that the advantages of moving visual stimuli over static ones are grounded in action rather than perception, and they support the hypothesis that the sensorimotor coupling mechanisms for auditory (beeps) and moving visual stimuli (bouncing balls) overlap.

  11. Disruption of postural readaptation by inertial stimuli following space flight.

    PubMed

    Black, F O; Paloski, W H; Reschke, M F; Igarashi, M; Guedry, F; Anderson, D J

    1999-01-01

    Postural instability (relative to pre-flight) has been observed in all shuttle astronauts studied upon return from orbital missions. Postural stability was more closely examined in four shuttle astronaut subjects before and after an 8 day orbital mission. Results of the pre- and post-flight postural stability studies were compared with a larger (n = 34) study of astronauts returning from shuttle missions of similar duration. Results from both studies indicated that inadequate vestibular feedback was the most significant sensory deficit contributing to the postural instability observed post flight. For two of the four IML-1 astronauts, post-flight postural instability and rate of recovery toward their earth-normal performance matched the performance of the larger sample. However, post-flight postural control in one returning astronaut was substantially below mean performance. This individual, who was within normal limits with respect to postural control before the mission, indicated that recovery to pre-flight postural stability was also interrupted by a post-flight pitch plane rotation test. A similar, though less extreme departure from the mean recovery trajectory was present in another astronaut following the same post-flight rotation test. The pitch plane rotation stimuli included otolith stimuli in the form of both transient tangential and constant centripetal linear acceleration components. We inferred from these findings that adaptation on orbit and re-adaptation on earth involved a change in sensorimotor integration of vestibular signals most likely from the otolith organs.

  12. Emotional stimuli exert parallel effects on attention and memory.

    PubMed

    Talmi, Deborah; Ziegler, Marilyne; Hawksworth, Jade; Lalani, Safina; Herman, C Peter; Moscovitch, Morris

    2013-01-01

    Because emotional and neutral stimuli typically differ on non-emotional dimensions, it has been difficult to determine conclusively which factors underlie the ability of emotional stimuli to enhance immediate long-term memory. Here we induced arousal by varying participants' goals, a method that removes many potential confounds between emotional and non-emotional items. Hungry and sated participants encoded food and clothing images under divided attention conditions. Sated participants attended to and recalled food and clothing images equivalently. Hungry participants performed worse on the concurrent tone-discrimination task when they viewed food relative to clothing images, suggesting enhanced attention to food images, and they recalled more food than clothing images. A follow-up regression analysis of the factors predicting memory for individual pictures revealed that food images had parallel effects on attention and memory in hungry participants, so that enhanced attention to food images did not predict their enhanced memory. We suggest that immediate long-term memory for food is enhanced in the hungry state because hunger leads to more distinctive processing of food images rendering them more accessible during retrieval.

  13. Depth attraction and repulsion of disparate foveal stimuli.

    PubMed

    Westheimer, G; Levi, D M

    1987-01-01

    Interaction in the domain of disparity can be either of the kind where the depth difference between adjacent targets is enhanced, as if the two targets repelled each other in depth, or it may be in the opposite direction, i.e. having the character of attraction. In the fovea, interaction between stimuli is of the latter kind if targets are separated by less than 2-8 min of arc, dependent on their positions and the observer; for further separations, repulsion is exhibited. When disparate neighbors induce a change in depth of a visual feature, only a portion of the effect can be ascribed to monocular localization shifts in the two monocular retinal images. Both attraction and repulsion can occur between targets of opposite contrast. Depth interaction measured by a psychophysical nulling method increases monotonically with disparity in the regions clearly governed by the repulsion and the attraction regimen; in the transition region, repulsion overtakes attraction when the disparity becomes larger. If the concept of "pooling" of disparity is invoked to account for the affinity of seen depth of closely-adjacent stimuli, the signals involved cannot be simply those of light weighted by disparity, but must be associated with individual features.

  14. EEG Responses to Auditory Stimuli for Automatic Affect Recognition

    PubMed Central

    Hettich, Dirk T.; Bolinger, Elaina; Matuz, Tamara; Birbaumer, Niels; Rosenstiel, Wolfgang; Spüler, Martin

    2016-01-01

    Brain state classification for communication and control has been well established in the area of brain-computer interfaces over the last decades. Recently, the passive and automatic extraction of additional information regarding the psychological state of users from neurophysiological signals has gained increased attention in the interdisciplinary field of affective computing. We investigated how well specific emotional reactions, induced by auditory stimuli, can be detected in EEG recordings. We introduce an auditory emotion induction paradigm based on the International Affective Digitized Sounds 2nd Edition (IADS-2) database also suitable for disabled individuals. Stimuli are grouped in three valence categories: unpleasant, neutral, and pleasant. Significant differences in time domain domain event-related potentials are found in the electroencephalogram (EEG) between unpleasant and neutral, as well as pleasant and neutral conditions over midline electrodes. Time domain data were classified in three binary classification problems using a linear support vector machine (SVM) classifier. We discuss three classification performance measures in the context of affective computing and outline some strategies for conducting and reporting affect classification studies. PMID:27375410

  15. Neural response to emotional stimuli during experimental human endotoxemia.

    PubMed

    Kullmann, Jennifer S; Grigoleit, Jan-Sebastian; Lichte, Philipp; Kobbe, Philipp; Rosenberger, Christina; Banner, Christina; Wolf, Oliver T; Engler, Harald; Oberbeck, Reiner; Elsenbruch, Sigrid; Bingel, Ulrike; Forsting, Michael; Gizewski, Elke R; Schedlowski, Manfred

    2013-09-01

    Increases in peripheral cytokines during acute inflammation may affect various neuropsychological functions. The aim of this functional magnetic resonance imaging (fMRI) study was to investigate the effects of acute endotoxemia on mood and the neural response to emotionally aversive visual stimuli in healthy human subjects. In a double-blind, randomized crossover study, 18 healthy males received a bolus injection of bacterial lipopolysaccharide (LPS; 0.4 ng/kg) or saline. Plasma levels of pro- and anti-inflammatory cytokines and cortisol as well as mood ratings were analyzed together with the blood-oxygen-level dependent (BOLD) response during the presentation of aversive versus neutral pictures. Endotoxin administration induced pronounced transient increases in plasma levels of TNF-α, IL-1ra, IL-6, IL-10, and cortisol. Positive mood was decreased and state anxiety increased. In addition, activation of right inferior orbitofrontal cortex (OFC) in response to emotional visual stimuli was significantly increased in the LPS condition. Increased prefrontal activation during the presentation of emotional material may reflect enhanced cognitive regulation of emotions as an adaptive response during an acute inflammation. These findings may have implications for the putative role of inflammatory processes in the pathophysiology of depression.

  16. Analyzing the User Behavior toward Electronic Commerce Stimuli.

    PubMed

    Lorenzo-Romero, Carlota; Alarcón-Del-Amo, María-Del-Carmen; Gómez-Borja, Miguel-Ángel

    2016-01-01

    Based on the Stimulus-Organism-Response paradigm this research analyzes the main differences between the effects of two types of web technologies: Verbal web technology (i.e., navigational structure as utilitarian stimulus) versus non-verbal web technology (music and presentation of products as hedonic stimuli). Specific webmosphere stimuli have not been examined yet as separate variables and their impact on internal and behavioral responses seems unknown. Therefore, the objective of this research consists in analyzing the impact of these web technologies -which constitute the web atmosphere or webmosphere of a website- on shopping human behavior (i.e., users' internal states -affective, cognitive, and satisfaction- and behavioral responses - approach responses, and real shopping outcomes-) within the retail online store created by computer, taking into account some mediator variables (i.e., involvement, atmospheric responsiveness, and perceived risk). A 2 ("free" versus "hierarchical" navigational structure) × 2 ("on" versus "off" music) × 2 ("moving" versus "static" images) between-subjects computer experimental design is used to test empirically this research. In addition, an integrated methodology was developed allowing the simulation, tracking and recording of virtual user behavior within an online shopping environment. As main conclusion, this study suggests that the positive responses of online consumers might increase when they are allowed to freely navigate the online stores and their experience is enriched by animate gifts and music background. The effect caused by mediator variables modifies relatively the final shopping human behavior.

  17. Origins and optimization of entanglement in plasmonically coupled quantum dots

    NASA Astrophysics Data System (ADS)

    Otten, Matthew; Larson, Jeffrey; Min, Misun; Wild, Stefan M.; Pelton, Matthew; Gray, Stephen K.

    2016-08-01

    A system of two or more quantum dots interacting with a dissipative plasmonic nanostructure is investigated in detail by using a cavity quantum electrodynamics approach with a model Hamiltonian. We focus on determining and understanding system configurations that generate multiple bipartite quantum entanglements between the occupation states of the quantum dots. These configurations include allowing for the quantum dots to be asymmetrically coupled to the plasmonic system. Analytical solution of a simplified limit for an arbitrary number of quantum dots and numerical simulations and optimization for the two- and three-dot cases are used to develop guidelines for maximizing the bipartite entanglements. For any number of quantum dots, we show that through simple starting states and parameter guidelines, one quantum dot can be made to share a strong amount of bipartite entanglement with all other quantum dots in the system, while entangling all other pairs to a lesser degree.

  18. Surface treatment of nanocrystal quantum dots after film deposition

    DOEpatents

    Sykora, Milan; Koposov, Alexey; Fuke, Nobuhiro

    2015-02-03

    Provided are methods of surface treatment of nanocrystal quantum dots after film deposition so as to exchange the native ligands of the quantum dots for exchange ligands that result in improvement in charge extraction from the nanocrystals.

  19. Effect of stimuli presentation method on perception of room size using only acoustic cues

    NASA Astrophysics Data System (ADS)

    Hunt, Jeffrey Barnabas

    People listen to music and speech in a large variety of rooms and many room parameters, including the size of the room, can drastically affect how well the speech is understood or the music enjoyed. While multi-modal (typically hearing and sight) tests may be more realistic, in order to isolate what acoustic cues listeners use to determine the size of a room, a listening-only tests is conducted here. Nearly all of the studies to-date on the perception of room volume using acoustic cues have presented the stimuli only over headphones and these studies have reported that, in most cases, the perceived room volume is more highly correlated with the perceived reverberation (reverberance) than with actual room volume. While reverberance may be a salient acoustic cue used for the determination or room size, the actual sound field in a room is not accurately reproduced when presented over headphones and it is thought that some of the complexities of the sound field that relate to perception of geometric volume, specifically directional information of reflections, may be lost. It is possible that the importance of reverberance may be overemphasized when using only headphones to present stimuli so a comparison of room-size perception is proposed where the sound field (from modeled and recorded impulse responses) is presented both over headphones and also over a surround system using higher order ambisonics to more accurately produce directional sound information. Major results are that, in this study, no difference could be seen between the two presentation methods and that reverberation time is highly correlated to room-size perception while real room size is not.

  20. Across- and within-session variability of ratings of painful contact heat stimuli

    PubMed Central

    Quiton, Raimi L.; Greenspan, Joel D.

    2016-01-01

    This study examined within- and across-session consistency of visual analog scale (VAS) pain intensity and unpleasantness ratings of contact heat stimuli in 64 subjects (32 male). Subjects participated in four sessions over 14 days, with three stimulus series per session. Two levels of painful heat (pain-lo: rated 40, and pain-hi: rated 70 on a 0–100 VAS) were delivered in randomized order during each series, with temperatures selected on an individual subject basis to equalize pain perception across subjects. Across-session ratings declined by the fourth session for both pain levels (p=0.01). Within-session ratings declined by the third series for both pain levels (p<0.001). While significant, changes in across- and within-session ratings were of small magnitude. Comparison of coefficients of variation (CV) for across- and within-session ratings revealed that pain-lo ratings were more variable than pain-hi ratings (p<0.001). Across- and within-session CVs were highly correlated for each pain level (pain-lo p<0.001; pain-hi p=0.001), suggesting that variability of VAS ratings is a characteristic of individual subjects over both short and long time scales. Across- and within-session CVs were significantly negatively correlated with individual ratings of the stimuli, but were not correlated with demographic or psychosocial factors. Furthermore, sex did not impact consistency of ratings, demonstrating that neither sex is more variable in ratings than the other over time. Taken together, these findings suggest that VAS ratings of painful contact heat are relatively stable over time but the variability of these ratings is significantly impacted by the perceived intensity of the stimulus. PMID:17942227

  1. Subliminal presentation of emotionally negative vs positive primes increases the perceived beauty of target stimuli.

    PubMed

    Era, Vanessa; Candidi, Matteo; Aglioti, Salvatore Maria

    2015-11-01

    Emotions have a profound influence on aesthetic experiences. Studies using affective priming procedures demonstrate, for example, that inducing a conscious negative emotional state biases the perception of abstract stimuli towards the sublime (Eskine et al. Emotion 12:1071-1074, 2012. doi: 10.1037/a0027200). Moreover, subliminal happy facial expressions have a positive impact on the aesthetic evaluation of abstract art (Flexas et al. PLoS ONE 8:e80154, 2013). Little is known about how emotion influences aesthetic perception of non-abstract, representational stimuli, especially those that are particularly relevant for social behaviour, like human bodies. Here, we explore whether the subliminal presentation of emotionally charged visual primes modulates the explicit subjective aesthetic judgment of body images. Using a forward/backward masking procedure, we presented subliminally positive and negative, arousal-matched, emotional or neutral primes and measured their effect on the explicit evaluation of perceived beauty (high vs low) and emotion (positive vs negative) evoked by abstract and body images. We found that negative primes increased subjective aesthetic evaluations of target bodies or abstract images in comparison with positive primes. No influence of primes on the emotional dimension of the targets was found, thus ruling out an unspecific arousal effect and strengthening the link between emotional valence and aesthetic appreciation. More specifically, that subliminal negative primes increase beauty ratings compared to subliminal positive primes indicates a clear link between negative emotions and positive aesthetic evaluations and vice versa, suggesting a possible link between negative emotion and the experience of sublime in art. The study expands previous research by showing the effect of subliminal negative emotions on the subjective aesthetic evaluation not only of abstract but also of body images.

  2. Quantum Dot Detector Enhancement for Narrow Band Multispectral Applications

    DTIC Science & Technology

    2013-12-01

    AFRL-RY-WP-TR-2013-0168 QUANTUM DOT DETECTOR ENHANCEMENT FOR NARROW BAND MULTISPECTRAL APPLICATIONS John Derov and Neda Mojaverian... QUANTUM DOT DETECTOR ENHANCEMENT FOR NARROW BAND MULTISPECTRAL APPLICATIONS 5a. CONTRACT NUMBER In-house 5b. GRANT NUMBER 5c. PROGRAM ELEMENT...enhancement of quantum dot photodetectors was also investigated. 15. SUBJECT TERMS quantum dot, quantum well, photodetectors, plasmonics 16

  3. The value of social attributes of stimuli for promoting engagement in persons with dementia.

    PubMed

    Cohen-Mansfield, Jiska; Thein, Khin; Dakheel-Ali, Maha; Regier, Natalie G; Marx, Marcia S

    2010-08-01

    The present study examined the impact of different attributes of social stimuli using the stimulus attributes aspect of the Comprehensive Process Model of Engagement ( Am J Geriatr Psychiatry. 17:299-307). Participants were 193 residents of 7 Maryland nursing homes with a diagnosis of dementia. Stimuli were chosen to represent different levels of the following social attributes: social versus not social, realistic versus not realistic, animated versus nonanimated, human versus nonhuman, and alive versus not alive. Participants had significantly longer engagement, were significantly more attentive, and displayed a significantly more positive attitude with social stimuli than with nonsocial stimuli. Longer durations and higher ratings of attention and attitude were seen with realistic and animated stimuli as compared to their counterparts. Human and live stimuli resulted in significantly more engagement than their counterparts. Giving any social stimulus to the residents is preferable to providing none, and the social attributes of stimuli should be maximized.

  4. An evaluation of the effects of matched stimuli on behaviors maintained by automatic reinforcement.

    PubMed Central

    Piazza, C C; Adelinis, J D; Hanley, G P; Goh, H L; Delia, M D

    2000-01-01

    The purpose of the current investigation was to extend the literature on matched stimuli to three dissimilar forms of aberrant behavior (dangerous climbing and jumping, saliva manipulation, and hand mouthing). The results of functional analyses suggested that each behavior was automatically reinforced. Preference assessments were used to identify two classes of stimuli: items that matched the hypothesized sensory consequences of aberrant behavior (matched stimuli) and items that produced sensory consequences that were not similar to those produced by the aberrant behavior (unmatched stimuli). The effects of providing continuous and noncontingent access to either the most highly preferred matched or the most highly preferred unmatched stimuli were assessed relative to a condition in which no stimuli were available. Overall results suggested that providing access to items that matched the hypothesized sensory consequences of aberrant behavior may be more effective than simply selecting stimuli either arbitrarily or based on the results of preference assessments alone. PMID:10738949

  5. The Motivating Effect of Antecedent Stimuli on the Web Shop: A Conjoint Analysis of the Impact of Antecedent Stimuli at the Point of Online Purchase

    ERIC Educational Resources Information Center

    Fagerstrom, Asle

    2010-01-01

    This article introduces the concept of motivating operation (MO) to the field of online consumer research. A conjoint analysis was conducted to assess the motivating impact of antecedent stimuli on online purchasing. Stimuli tested were in-stock status, price, other customers' reviews, order confirmation procedures, and donation to charity. The…

  6. Effect of size on electronic states in a strained pyramidal InAs-GaAs quantum dot system

    SciTech Connect

    Ripan, G. H.; Woon, C. Y.; Gopir, G.

    2015-09-25

    The effect of size on electronic states in a strained pyramidal InAs-GaAs quantum dot system was studied. A comparison was made between two InAs quantum pyramids of different sizes embedded inside a cubic GaAs susbtrate material. Strain relaxation was carried out via the Metropolis Monte Carlo method and the calculated local strain tensors were then included to solve the energy values and the wave functions of the electronic states inside the two simulation cube. The 3D finite difference scheme was employed to solve the time independent Schrödinger equation based on the decoupled electron-hole model. Calculated energy values of the four lowest electronic states showed that the transitions between the electron and hole states widen as the size of the dot becomes smaller especially between the ground states. The confinement of electrons and holes become weaker as the size of the dot reduces.

  7. Trapping of an electron in coupled quantum dots in graphene

    NASA Astrophysics Data System (ADS)

    Hewageegana, Prabath; Apalkov, Vadym

    2009-03-01

    Due to Klein’s tunneling the electronic states of a quantum dot in graphene have finite widths and an electron in quantum dot has a finite trapping time. This property introduces a special type of interdot coupling in a system of many quantum dots in graphene. The interdot coupling is realized not as a direct tunneling between quantum dots but as coupling through the continuum states of graphene. As a result the interdot coupling modifies both the positions and the widths of the energy levels of the quantum dot system. We study the system of quantum dots in graphene theoretically by analyzing the complex energy spectra of the quantum dot system. We show that in a double-dot system some energy levels become strongly localized with an infinite trapping time. Such strongly localized states are achieved only at one value of the interdot separation. We also study a periodic array of quantum dots in graphene within a tight-binding mode for a quantum dot system. The values of the hopping integrals in the tight-binding model are found from the expression for the energy spectra of the double quantum dot system. In the array of quantum dots the states with infinitely large trapping time are realized at all values of interdot separation smaller than some critical value. Such states have nonzero wave vectors.

  8. Random Access: The DotsPlus Tactile Font Set.

    ERIC Educational Resources Information Center

    Gardner, John

    1998-01-01

    Describes "DotsPlus," a tactile font set that allows computers to print documents in any language which uses the Roman alphabet in tactile form. DotsPlus overcomes such Braille problems as code translation, Braille numbers, exotic symbols, and symbols out of context. A new printing technology (TIGER--Tactile Graphics Embosser) produces DotsPlus…

  9. Fluorescence correlation spectroscopy using quantum dots: advances, challenges and opportunities.

    PubMed

    Heuff, Romey F; Swift, Jody L; Cramb, David T

    2007-04-28

    Semiconductor nanocrystals (quantum dots) have been increasingly employed in measuring the dynamic behavior of biomacromolecules using fluorescence correlation spectroscopy. This poses a challenge, because quantum dots display their own dynamic behavior in the form of intermittent photoluminescence, also known as blinking. In this review, the manifestation of blinking in correlation spectroscopy will be explored, preceded by an examination of quantum dot blinking in general.

  10. Quantum-dot-based cell motility assay.

    PubMed

    Gu, Weiwei; Pellegrino, Teresa; Parak, Wolfgang J; Boudreau, Rosanne; Le Gros, Mark A; Gerion, Daniele; Alivisatos, A Paul; Larabell, Carolyn A

    2005-06-28

    Because of their favorable physical and photochemical properties, colloidal CdSe/ZnS-semiconductor nanocrystals (commonly known as quantum dots) have enormous potential for use in biological imaging. In this report, we present an assay that uses quantum dots as markers to quantify cell motility. Cells that are seeded onto a homogeneous layer of quantum dots engulf and absorb the nanocrystals and, as a consequence, leave behind a fluorescence-free trail. By subsequently determining the ratio of cell area to fluorescence-free track area, we show that it is possible to differentiate between invasive and noninvasive cancer cells. Because this assay uses simple fluorescence detection, requires no significant data processing, and can be used in live-cell studies, it has the potential to be a powerful new tool for discriminating between invasive and noninvasive cancer cell lines or for studying cell signaling events involved in migration.

  11. Angiogenic Profiling of Synthesized Carbon Quantum Dots.

    PubMed

    Shereema, R M; Sruthi, T V; Kumar, V B Sameer; Rao, T P; Shankar, S Sharath

    2015-10-20

    A simple method was employed for the synthesis of green luminescent carbon quantum dots (CQDs) from styrene soot. The CQDs were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared, and Raman spectroscopy. The prepared carbon quantum dots did not show cellular toxicity and could successfully be used for labeling cells. We also evaluated the effects of carbon quantum dots on the process of angiogenesis. Results of a chorioallantoic membrane (CAM) assay revealed the significant decrease in the density of branched vessels after their treatment with CQDs. Further application of CQDs significantly downregulated the expression levels of pro-angiogenic growth factors like VEGF and FGF. Expression of VEGFR2 and levels of hemoglobin were also significantly lower in CAMs treated with CQDs, indicating that the CQDs inhibit angiogenesis. Data presented here also show that CQDs can selectively target cancer cells and therefore hold potential in the field of cancer therapy.

  12. Fluorescent carbon nanomaterials: "quantum dots" or nanoclusters?

    PubMed

    Dekaliuk, Mariia O; Viagin, Oleg; Malyukin, Yuriy V; Demchenko, Alexander P

    2014-08-14

    Despite many efforts, the mechanisms of light absorption and emission of small fluorescent carbon nanoparticles (C-dots) are still unresolved and are a subject of active discussion. In this work we address the question as to whether the fluorescence is a collective property of these nanoparticles or they are composed of assembled individual emitters. Selecting three types of C-dots with "violet", "blue" and "green" emissions and performing a detailed study of fluorescence intensity, lifetime and time-resolved anisotropy as a function of excitation and emission wavelengths together with the effect of viscogen and dynamic fluorescence quencher, we demonstrate that the C-dots represent assemblies of surface-exposed fluorophores. They behave as individual emitters, display electronic anisotropy, do not exchange their excited-state energies via homo-FRET and possibly display sub-nanosecond intra-particle mobility.

  13. Slow Electron Cooling in Colloidal Quantum Dots

    NASA Astrophysics Data System (ADS)

    Pandey, Anshu; Guyot-Sionnest, Philippe

    2008-11-01

    Hot electrons in semiconductors lose their energy very quickly (within picoseconds) to lattice vibrations. Slowing this energy loss could prove useful for more efficient photovoltaic or infrared devices. With their well-separated electronic states, quantum dots should display slow relaxation, but other mechanisms have made it difficult to observe. We report slow intraband relaxation (>1 nanosecond) in colloidal quantum dots. The small cadmium selenide (CdSe) dots, with an intraband energy separation of ~0.25 electron volts, are capped by an epitaxial zinc selenide (ZnSe) shell. The shell is terminated by a CdSe passivating layer to remove electron traps and is covered by ligands of low infrared absorbance (alkane thiols) at the intraband energy. We found that relaxation is markedly slowed with increasing ZnSe shell thickness.

  14. Invisible Security Ink Based on Water-Soluble Graphitic Carbon Nitride Quantum Dots.

    PubMed

    Song, Zhiping; Lin, Tianran; Lin, Lihua; Lin, Sen; Fu, Fengfu; Wang, Xinchen; Guo, Liangqia

    2016-02-18

    Stimuli-responsive photoluminescent (PL) materials have been widely used as fluorescent ink for data security applications. However, traditional fluorescent inks are limited in maintaining the secrecy of information because the inks are usually visible by naked eyes either under ambient light or UV-light illumination. Here, we introduced metal-free water-soluble graphitic carbon nitride quantum dots (g-CNQDs) as invisible security ink for information coding, encryption, and decryption. The information written by the g-CNQDs is invisible in ambient light and UV light, but it can be readable by a fluorescence microplate reader. Moreover, the information can be encrypted and decrypted by using oxalic acid and sodium bicarbonate as encryption reagent and decryption reagent, respectively. Our findings provide new opportunities for high-level information coding and protection by using water-soluble g-CNQDs as invisible security ink.

  15. Auditory Brainstem Responses for Click and CE-chirp Stimuli in Individuals with and without Occupational Noise Exposure

    PubMed Central

    Pushpalatha, Zeena Venkatacheluvaiah; Konadath, Sreeraj

    2016-01-01

    Introduction: Encoding of CE-chirp and click stimuli in auditory system was studied using auditory brainstem responses (ABRs) among individuals with and without noise exposure. Materials and Methods: The study consisted of two groups. Group 1 (experimental group) consisted of 20 (40 ears) individuals exposed to occupational noise with hearing thresholds within 25 dB HL. They were further divided into three subgroups based on duration of noise exposure (0–5 years of exposure-T1, 5–10 years of exposure-T2, and >10 years of exposure-T3). Group 2 (control group) consisted of 20 individuals (40 ears). Absolute latency and amplitude of waves I, III, and V were compared between the two groups for both click and CE-chirp stimuli. T1, T2, and T3 groups were compared for the same parameters to see the effect of noise exposure duration on CE-chirp and click ABR. Result: In Click ABR, while both the parameters for wave III were significantly poorer for the experimental group, wave V showed a significant decline in terms of amplitude only. There was no significant difference obtained for any of the parameters for wave I. In CE-Chirp ABR, the latencies for all three waves were significantly prolonged in the experimental group. However, there was a significant decrease in terms of amplitude in only wave V for the same group. Discussion: Compared to click evoked ABR, CE-Chirp ABR was found to be more sensitive in comparison of latency parameters in individuals with occupational noise exposure. Monitoring of early pathological changes at the brainstem level can be studied effectively by using CE-Chirp stimulus in comparison to click stimulus. Conclusion: This study indicates that ABR's obtained with CE-chirp stimuli serves as an effective tool to identify the early pathological changes due to occupational noise exposure when compared to click evoked ABR. PMID:27762255

  16. Improved dot size uniformity and luminescense of InAs quantum dots on InP substrate

    NASA Technical Reports Server (NTRS)

    Qiu, Y.; Uhl, D.

    2002-01-01

    InAs self-organized quantum dots have been grown in InGaAs quantum well on InP substrates by metalorganic vapor phase epitaxy. Atomic Force Microscopy confirmed of quantum dot formation with dot density of 3X10(sup 10) cm(sup -2). Improved dot size uniformity and strong room temperature photoluminescence up to 2 micron were observed after modifying the InGaAs well.

  17. PREFACE: Stimuli Stimuli

    NASA Astrophysics Data System (ADS)

    Queisser, Hans J.

    2011-01-01

    Tributes are paid to Zhores Alferov by presenting personal anecdotes from the fields, where Alferov performed his pioneering research: masers, lasers, solar cells and heterojunctions. What a pleasure and honor to pay tribute to Zhores Alferov in this Festschrift. Member of a remarkable laboratory and originator of imaginative and useful ideas for semiconductor physics and technology; a happy birthday! I would like to use this opportunity to ramble a little about the physics of masers, lasers, heterojunctions, solar cells— all themes of such vital importance in Alferov's career—and also tangible in my own endeavors. I start out with an anecdote of a colloquium presentation in my youthful days at Göttingen. The Physics Colloquium at Göttingen University presented a serious weekly meeting. Werner Heisenberg and Carl Friedrich von Weizsäcker attended, often Wolfgang Pauli visited from Zurich; Otto Hahn always sat in the first row, on the left corner— and he smoked his cigar. I had just obtained my doctorate [1]— it was 1958, and my boss Rudolf Hilsch ordered me to contribute a colloquium talk. He hoped that I would report on color centers in alkali halides or review experiments on quenched amorphous bismuth, a surprising superconductor [2], or on my own dissertation [1], all recent results of our team. I, however, being an avid reader of the latest American physics literature, begged to differ. The English language gave me no problems because I had in 1951/52 spent a year at the University of Kansas. This experience in the friendly American Midwest provided me with a definite linguistic advantage over most of my German fellow students. I was fascinated by those very first reports on the maser, this molecular amplifier using ammonia for stimulated emission, and therefore decided, quite to the chagrin of my boss Hilsch, to choose this particular topic for a report at the Colloquium. So I went to the rostrum in the small auditorium 'Hörsaal II' and delivered a well-rehearsed talk. The audience was intrigued by this new principle of stimulated coherent microwave radiation [3]. Friedrich Hund, famous for his 'rule' was then our theory professor, he sat in the second row. He was very surprised, and asked me in the discussion if he had understood correctly. If it were true what I had just suggested, then the maser coherence length would go from the Earth to the Moon. I paused a little, pondered and observed my microwave-conscious friends in the audience nodding encouragingly. 'Yes, sir; I think so!' 'I don't believe it', Hund retorted. How could a youngster react? I remained silent and obediently, quite imperceptibly shrugged my shoulders. After the talk, Professor Lamla, an editor of a science journal came to congratulate me and asked for a manuscript. I delivered [4]. This item on my early publication list may have contributed to the fact that I was hired in 1959 by William Shockley to join his fledgling company Shockley Transistor in this old apricot barn on 391 South San Antonio Road in Mountain View, California [5]. I knew that it would be extremely difficult to extend the frequency into the optical regime, you have to fight against the square of the frequency. Nevertheless, I refrained from making the statement in my paper that reaching an optical maser might be hopeless [4]. 'Never say never' is an appropriate adage, not only for seniors. A young colleague, who had also written a review paper, dared to support a more pessimistic view [6]. He anticipated in his very last sentence that stimulated emission would probably prevail merely in the microwave regime. This defeatist attitude seemed to have ruled throughout Germany, as already preached in the famous textbooks by Pohl [7], and also assumed by physics Professor Hellwege at Darmstadt, who was the leading expert regarding luminescence of materials such as ruby crystals; yet Maiman and others surpassed him [8]. Silicon came next for me, working, for example, with Shockley on the theory of maximal efficiency for solar cells, not really a topic regarding coherent radiation [9]. Once, however, a discussion evolved during one of those nearly dreaded hamburger lunches with Shockley at Kirk's charcoal restaurant on El Camino Real in Mountain View. Those frugal lunches ended with a demanding one-on-one interrogation, stricter and tougher than any doctoral oral examination. 'What, you do not know of Einstein's A and B coefficients?' Next afternoon I dutifully looked them up in the Stanford physics library. My first, rather indirect contacts with semiconductor heterojunctions occurred in this former apricot barn of Shockley's. Improving junction transistors required a maximum of the emitter efficiency. The emitter-to-base junction should carry only a forward current, no particles should flow from base to emitter [10]. This requirement can be met with a heterojunction: some other semiconductor material covering the silicon. Shockley had already contemplated this possibility while still at Bell Laboratories [11]. One day, a physicist by the name of Herbert Krömer visited us. This young man had also studied at Göttingen, especially with the memorable theoretician Richard Becker, whom we all admired. Krömer had in Princeton contributed to the theoretical understanding [12] of such wide-gap emitter/base junctions, and Shockley urgently wanted to hire him. But Herb preferred to join Varian Associates, just up the road in Palo Alto. Later, it was my great pleasure to attend the Nobel Festivities for Herb and Zhores Alferov in Stockholm. In the early sixties, I became a Member of Technical Staff at the Bell Laboratories in Murray Hill, New Jersey. Now, compound semiconductors, such as gallium arsenide, had to attract my interest. By the time of the mid-sixties, helium/neon-lasers were quite the vogue; Bell Labs actually established a little workshop with a production line to fabricate them and spread them throughout the departments. 'The solution in search of a problem', as sceptics joked about this new light source, was of vital interest to us because of the high frequencies to carry plenty of information channels. Transmission of laser light straight through the air, from Building 1 to Building 2 at Murray Hill, however, showed that the atmosphere was by far too unstable. We discussed silver-plated tubes and glass fibers, which eventually became so unbelievably pure that nowadays they provide a wealth of inexpensive communication channels. A gas laser did not appear to emerge into a viable, convenient engineering solution, nor did the ruby. A diode laser source had to be developed. I used laser-induced photoluminescence to search for more efficient GaAs materials, which resulted in detecting crystals with amphoteric silicon doping of very high output in the near-infrared [13]. This invention was patented in 37 countries and provided millions of diodes, such as for TV remote control devices. I had to sign off my inventor's reward for one US dollar, which I actually did not even receive. (In earlier years, patentors obtained one silver dollar; but not anymore!) Yet my little diodes, however efficient, could not be stimulated to emit coherent light, alas! Together with my colleagues and friends Morton Panish and Craig Casey, later famous textbook authors on diode lasers [14], we searched for solutions, although colleagues at the famed RCA Laboratories in Princeton had predicted that a laser diode was impossible [15]. I remember one morning when Mort told us of a talk he had just heard at a meeting in New York City, where our friendly competitors at the IBM Labs in Yorktown Heights, NY had suggested that heterojunctions could nicely confine and concentrate carriers, maybe also photons. Such heterojunctions were then tried in Panish's lab to be grown via liquid-phase epitaxy, Stan Sumski being the expert technician. At that time, the Leningraders, under leadership of Zhores Alferov were working hard and highly successfully with this crystal growth technique. We were very much impressed by the success in Leningrad. Liquid-phase epitaxy yields, in principle, exceedingly pure crystals, but we were unhappy about the principal lack of direct monitoring during this growth process, which we deemed absolutely necessary for obtaining reproducible heterojunctions with tightly controlled small dimensions. Ultrahigh-vacuum epitaxy seemed to be the inescapable solution. Delicate molecular beams had to be gently used and monitored! What a costly proposition! I clearly remember the day when Mort and I went to the Laboratory director John Galt. A little bit fearful and subdued, we explained our project. No, not expensive, rather a very expensive idea! We anxiously watched John with his usual stern demeanour; he paused and contemplated: 'All right, we do it—go ahead!' Construction for equipment needed for the Molecular Beam Epitaxy (MBE) began, and in Al Cho, an excellent new employee was hired for this task. A little later I left Bell Labs, this fabulous 'Mecca of Solid State' for a physics professorship at the Goethe University in Frankfurt-on-the-Main in Germany. Meanwhile, successful work on semiconductor lasers bore ample fruit worldwide. In Frankfurt, I used gas laser sources for photoluminescence diagnostics of elemental and compound semiconductors. With my astute doctoral student 'Teddy' Güttler, for example, we observed impurity photoluminescence in Au-doped silicon and concluded that doping of solar cells with deep impurities would not be beneficial for cell efficiency; just the opposite would happen because of increased carrier recombination [16]. In 1968, Western Germany experienced an ultra-left-wing student rebellion. Frankfurt students violently attacked me and accused me of war research since I used lasers, obviously a deadly weapon of mass destruction. Dieter Bimberg, our co-editor of this Festschrift, will undoubtedly remember those happenings when he was a doctoral candidate. In 1968, we all assembled in Moscow for the International Conference on the Physics of Semiconductors; what a unique opportunity to meet so many Russian colleagues, including this intellectual elite from the most remarkable Joffe Institute, with Zhores Alferov a major player. In 1970, I became a founding director of the Max-Planck-Institute for Solid State Research at Stuttgart, in the Southwest of Germany. There I eventually succeeded—against massive opposition—to establish a group for MBE, which became truly successful under the very capable leadership of Klaus Ploog [17], to whom was bestowed a prize of the Seibold-Foundation for Japan-Germany Science Cooperation. Klaus von Klitzing's group in our Max-Planck-Institute in Stuttgart relies on MBE to the present day for research on the quantum Hall effect [18]. Equally, my former doctoral student Horst Stormer had to utilize excellent MBE for his Nobel-Prize winning research on the fractional quantum Hall effect [18]. We fondly remember one congenial dinner party at our Stuttgart house, with Zhores Alferov and Helmut Lotsch as our valued guests; it must have been in the mid-seventies. My wife Inge had prepared a dessert in the shape of the title page of the Springer journal Applied Physics, with chocolate and orange cream. Herr Lotsch had won Alferov to become part of our board of editors, a most valuable connection to the excellence of Soviet semiconductor research! Many Japanese colleagues, especially from industrial electronics labs came to learn the tricks of MBE from us in Stuttgart; the German electronics industry, however, was reluctant and remained completely disinterested—but the French equipment maker RIBER was our staunch ally, and this company grew with the international acceptance of MBE for small, high-frequency devices. One diligent young visitor at my Stuttgart laboratories, Ozamu Kumagai from the SONY Corporation, did especially well. Back at home, he most cleverly devised novel technologies for efficient and low-cost production of laser diodes and thus earned a promotion to Vice Presidency. One of the most recent, gratifying encounters with Zhores Alferov happened to me in a cozy retreat in the forests near Madrid, with Antonio Luque being our gracious host for a solar cell symposium. We Stuttgarters had hoped to use multi-pair generation in perfected silicon solar cells [19], but a better chance to capture more photons from the solar spectrum exists most likely in multi-junction cells [20], with fancy tunnel-contacts interconnecting between heterojunctions. We shall see if this approach might eventually lead to more efficient, yet still economical solar energy conversion. Semiconductor heterojunctions for communications and consumers! Many of Alferov's present activities in St Petersburg and Berlin are governed by this magic modern prefix nano, which might one day also provide some applications in solar cells; but we have yet to carefully investigate [21]! References [1] Queisser H J 1958 Z.Physik 152 507 and 495 [2] Buckel W and Hilsch R 1956 Z. Physik 146 27 [3] Wittke J P 1957 Proc. IRE 45 291 with references to earlier work [4] Queisser H J 1959 Naturwiss. 46 394 [5] Queisser H J 1988 The Conquest of the Microchip (Cambridge, MA: Harvard University Press) [6] Wolf H C and Agnew Z 1958 Physik 10 480 [7] Pohl R W Optik (Heidelberg: Springer) [8] Yariv A 1968 Quantum Electronics (New York: Wiley) [9] Shockley W and Queisser H J 1961 J. Appl. Phys. 32 510 [10] For details, see Sze S M and Ng K K 2007 Physics of Semiconductor Devices 3rd edn (Hoboken, NJ: Wiley) [11] Shockley W 1951 US Patent Specification 2.569.347 [12] Krömer H 1957 Proc. IRE 45 1535 [13] Queisser H J 1966 J. Appl. Phys. 37 2909 (this paper was withheld internally for some time due to the patent application: US Pat.3.387.163) [14] Panish M B and Casey C H 1978 Heterostructure Lasers (New York: Academic) [15] Kressel H Private communications [16] Güttler G and Queisser H J 1996 J. Appl. Phys. 40 4994 [17] Ploog K and Graf K 1984 MBE of III-V Compounds (Berlin: Springer) [18] For recent coverage, see Chakraborty T and Pietiläinen P 1995 The Quantum Hall Effect (Berlin: Springer) [19] Werner J H, Kolodinski S and Queisser H J 1993 Phys. Rev. Lett. 72 3851 [20] Yamaguchi M 2002 Physica E 14 84 [21] Queisser H J 2002 Physica E 14 1 and many other contributions in this issue

  18. Stroking or Buzzing? A Comparison of Somatosensory Touch Stimuli Using 7 Tesla fMRI

    PubMed Central

    van der Zwaag, Wietske; Gruetter, Rolf; Martuzzi, Roberto

    2015-01-01

    Studying body representations in the brain helps us to understand how we humans relate to our own bodies. The in vivo mapping of the somatosensory cortex, where these representations are found, is greatly facilitated by the high spatial resolution and high sensitivity to brain activation available at ultra-high field. In this study, the use of different stimulus types for somatotopic mapping of the digits at ultra-high field, specifically manual stroking and mechanical stimulation, was compared in terms of sensitivity and specificity of the brain responses. Larger positive responses in digit regions of interest were found for manual stroking than for mechanical stimulation, both in terms of average and maximum t-value and in terms of number of voxels with significant responses to the tactile stimulation. Responses to manual stroking were higher throughout the entire post-central sulcus, but the difference was especially large on its posterior wall, i.e. in Brodmann area 2. During mechanical stimulation, cross-digit responses were more negative than during manual stroking, possibly caused by a faster habituation to the stimulus. These differences indicate that manual stroking is a highly suitable stimulus for fast somatotopic mapping procedures, especially if Brodmann area 2 is of interest. PMID:26285027

  19. A Comparison of Cognitive Teaching Stimuli in a First Grade Classroom.

    ERIC Educational Resources Information Center

    Sigrest, Christine E.

    A study assessed the effectiveness of three cognitive levels of instruction with first graders--three-dimensional (3-D) instruction using real objects, two-dimensional (2-D) instruction using picture representations, and verbal instruction. The study population included 18 first-grade students between the ages of 6 and 8 at a small elementary city…

  20. Fashion advertisements: a comparison of viewers' perceptual and affective responses to illustrated and photographed stimuli.

    PubMed

    Kimle, P A; Fiore, A M

    1992-12-01

    The perceptual and affective responses of 44 women to actual illustrated and photographed fashion advertisements during focused interviews were explored. Content analysis methods identified categories of response; frequency of response categories for the two media were compared using Fisher's z tests. Significant differences in perceptual responses included greater visual interest created by the use of color in photographs, greater interest in layout and design features of the illustrations, and interest in characteristics of the models in the photographs. Affective response differences included greater preference for photographic advertisements and the garments in them. Contrary to suggestions from professionals in fashion advertising, no significant differences were found in viewers' perceptions of information about the products in the advertisements or perceptions of meaning and aesthetic response.