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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. 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…

  3. Intensity perception. VIII. Loudness comparisons between different types of stimuli.

    PubMed

    Lim, J S; Rabinowtiz, W M; Braida, L D; Durlach, N I

    1977-11-01

    In this paper, we describe an extension of our preliminary theory of intensity resolution [Durlach and Braida, J. Acoust. Soc. Am. 46, 372-383 (1969)] to include loudness comparisons among different types of stimuli. The extended theory relates mean loudness matches to discrimination and provides a framework for the interpretation of results on the intrasubject variability of loudness comparisons. The predicted relation between mean loudness matches and discrimination is essentially the same as that proposed by Riesz [J. Acoust. Soc. Am. 5, 211-216 (1933)]. With regard to the variability of loudness comparisons, the extended model is essentially the same as the preliminary model except that a new term is included in the trace-mode memory variance to account for the dissimilarity of the stimuli being compared. The model is compared to some published data on loudness matching and discrimination and to some new data of our own on the variability of loudness comparisons obtained in a two-interval, roving-level, loudness-discrimination experiment. PMID:915119

  4. Performance Characterization of Watson Ahumada Motion Detector Using Random Dot Rotary Motion Stimuli

    PubMed Central

    Jain, Siddharth

    2009-01-01

    The performance of Watson & Ahumada's model of human visual motion sensing is compared against human psychophysical performance. The stimulus consists of random dots undergoing rotary motion, displayed in a circular annulus. The model matches psychophysical observer performance with respect to most parameters. It is able to replicate some key psychophysical findings such as invariance of observer performance to dot density in the display, and decrease of observer performance with frame duration of the display. Associated with the concept of rotary motion is the notion of a center about which rotation occurs. One might think that for accurate estimation of rotary motion in the display, this center must be accurately known. A simple vector analysis reveals that this need not be the case. Numerical simulations confirm this result, and may explain the position invariance of MST(d) cells. Position invariance is the experimental finding that rotary motion sensitive cells are insensitive to where in their receptive field rotation occurs. When all the dots in the display are randomly drawn from a uniform distribution, illusory rotary motion is perceived. This case was investigated by Rose & Blake previously, who termed the illusory rotary motion the omega effect. Two important experimental findings are reported concerning this effect. First, although the display of random dots evokes perception of rotary motion, the direction of motion perceived does not depend on what dot pattern is shown. Second, the time interval between spontaneous flips in perceived direction is lognormally distributed (mode≈2 s). These findings suggest the omega effect fits in the category of a typical bistable illusion, and therefore the processes that give rise to this illusion may be the same processes that underlie much of other bistable phenomenon. PMID:19225571

  5. 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.

  6. Comparisons of memory for nonverbal auditory and visual sequential stimuli.

    PubMed

    McFarland, D J; Cacace, A T

    1995-01-01

    Properties of auditory and visual sensory memory were compared by examining subjects' recognition performance of randomly generated binary auditory sequential frequency patterns and binary visual sequential color patterns within a forced-choice paradigm. Experiment 1 demonstrated serial-position effects in auditory and visual modalities consisting of both primacy and recency effects. Experiment 2 found that retention of auditory and visual information was remarkably similar when assessed across a 10s interval. Experiments 3 and 4, taken together, showed that the recency effect in sensory memory is affected more by the type of response required (recognition vs. reproduction) than by the sensory modality employed. These studies suggest that auditory and visual sensory memory stores for nonverbal stimuli share similar properties with respect to serial-position effects and persistence over time.

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

    PubMed

    Swisher, Melissa; Urcuioli, Peter J

    2013-07-01

    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.

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

    PubMed

    Swisher, Melissa; Urcuioli, Peter J

    2013-07-01

    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

  9. The merger and development of equivalence classes by unreinforced conditional selection of comparison stimuli.

    PubMed Central

    Saunders, R R; Saunders, K J; Kirby, K C; Spradlin, J E

    1988-01-01

    Three experiments assessed the likelihood that subjects with histories of equivalence class development would respond conditionally on new discriminations in the absence of differential consequences for responses. In the first two experiments, two groups of subjects with different experimental histories, but whose performances showed four equivalence classes, responded on trials without explicit reinforcement involving samples from two of the classes and comparisons from the other two classes, in a two-choice matching-to-sample format. Subjects consistently selected a particular comparison in the presence of a particular sample. Subsequent tests showed the emergence of equivalence relations between stimuli from classes linked by the unreinforced conditional selections. Subsequently, in Experiment II, the subjects' responses in the conditional selection trials were reinforced if the selection was reversed from that made previously. Although reversed selection was maintained, 2 of the 3 subjects continued to perform on equivalence relation trials according to their original unreinforced selections. In the third experiment, these 2 subjects responded on a series of conditional discriminations involving three new pairs of sample stimuli and one new pair of comparison stimuli. No explicit reinforcement followed responses on any trial in this experiment. Subsequent tests for equivalence between sample stimuli revealed the development of two equivalence classes. PMID:3193052

  10. 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

  11. 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.

  12. 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. PMID:7598675

  13. 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.

  14. 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. PMID:18316314

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

    PubMed Central

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

    2014-01-01

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

  16. 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

  17. 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…

  18. Tones and numbers: a combined EEG-MEG study on the effects of musical expertise in magnitude comparisons of audiovisual stimuli.

    PubMed

    Paraskevopoulos, Evangelos; Kuchenbuch, Anja; Herholz, Sibylle C; Foroglou, Nikolaos; Bamidis, Panagiotis; Pantev, Christo

    2014-11-01

    This study investigated the cortical responses underlying magnitude comparisons of multisensory stimuli and examined the effect that musical expertise has in this process. The comparative judgments were based on a newly learned rule binding the auditory and visual stimuli within the context of magnitude comparisons: "the higher the pitch of the tone, the larger the number presented." The cortical responses were measured by simultaneous MEG\\EEG recordings and a combined source analysis with individualized realistic head models was performed. Musical expertise effects were investigated by comparing musicians to non-musicians. Congruent audiovisual stimuli, corresponding to the newly learned rule, elicited activity in frontotemporal and occipital areas. In contrast, incongruent stimuli activated temporal and parietal regions. Musicians when compared with nonmusicians showed increased differences between congruent and incongruent stimuli in a prefrontal region, thereby indicating that music expertise may affect multisensory comparative judgments within a generalized representation of analog magnitude.

  19. Tones and numbers: a combined EEG-MEG study on the effects of musical expertise in magnitude comparisons of audiovisual stimuli.

    PubMed

    Paraskevopoulos, Evangelos; Kuchenbuch, Anja; Herholz, Sibylle C; Foroglou, Nikolaos; Bamidis, Panagiotis; Pantev, Christo

    2014-11-01

    This study investigated the cortical responses underlying magnitude comparisons of multisensory stimuli and examined the effect that musical expertise has in this process. The comparative judgments were based on a newly learned rule binding the auditory and visual stimuli within the context of magnitude comparisons: "the higher the pitch of the tone, the larger the number presented." The cortical responses were measured by simultaneous MEG\\EEG recordings and a combined source analysis with individualized realistic head models was performed. Musical expertise effects were investigated by comparing musicians to non-musicians. Congruent audiovisual stimuli, corresponding to the newly learned rule, elicited activity in frontotemporal and occipital areas. In contrast, incongruent stimuli activated temporal and parietal regions. Musicians when compared with nonmusicians showed increased differences between congruent and incongruent stimuli in a prefrontal region, thereby indicating that music expertise may affect multisensory comparative judgments within a generalized representation of analog magnitude. PMID:24916460

  20. A comparison of neural responses to appetitive and aversive stimuli in humans and other mammals.

    PubMed

    Hayes, Dave J; Duncan, Niall W; Xu, Jiameng; Northoff, Georg

    2014-09-01

    Distinguishing potentially harmful or beneficial stimuli is necessary for the self-preservation and well-being of all organisms. This assessment requires the ongoing valuation of environmental stimuli. Despite much work on the processing of aversive- and appetitive-related brain signals, it is not clear to what degree these two processes interact across the brain. To help clarify this issue, this report used a cross-species comparative approach in humans (i.e. meta-analysis of imaging data) and other mammals (i.e. targeted review of functional neuroanatomy in rodents and non-human primates). Human meta-analysis results suggest network components that appear selective for appetitive (e.g. ventromedial prefrontal cortex, ventral tegmental area) or aversive (e.g. cingulate/supplementary motor cortex, periaqueductal grey) processing, or that reflect overlapping (e.g. anterior insula, amygdala) or asymmetrical, i.e. apparently lateralized, activity (e.g. orbitofrontal cortex, ventral striatum). However, a closer look at the known value-related mechanisms from the animal literature suggests that all of these macroanatomical regions are involved in the processing of both appetitive and aversive stimuli. Differential spatiotemporal network dynamics may help explain similarities and differences in appetitive- and aversion-related activity.

  1. A comparison of neural responses to appetitive and aversive stimuli in humans and other mammals.

    PubMed

    Hayes, Dave J; Duncan, Niall W; Xu, Jiameng; Northoff, Georg

    2014-09-01

    Distinguishing potentially harmful or beneficial stimuli is necessary for the self-preservation and well-being of all organisms. This assessment requires the ongoing valuation of environmental stimuli. Despite much work on the processing of aversive- and appetitive-related brain signals, it is not clear to what degree these two processes interact across the brain. To help clarify this issue, this report used a cross-species comparative approach in humans (i.e. meta-analysis of imaging data) and other mammals (i.e. targeted review of functional neuroanatomy in rodents and non-human primates). Human meta-analysis results suggest network components that appear selective for appetitive (e.g. ventromedial prefrontal cortex, ventral tegmental area) or aversive (e.g. cingulate/supplementary motor cortex, periaqueductal grey) processing, or that reflect overlapping (e.g. anterior insula, amygdala) or asymmetrical, i.e. apparently lateralized, activity (e.g. orbitofrontal cortex, ventral striatum). However, a closer look at the known value-related mechanisms from the animal literature suggests that all of these macroanatomical regions are involved in the processing of both appetitive and aversive stimuli. Differential spatiotemporal network dynamics may help explain similarities and differences in appetitive- and aversion-related activity. PMID:25010558

  2. The role of spatial attention in nonconscious processing: a comparison of face and nonface stimuli.

    PubMed

    Finkbeiner, Matthew; Palermo, Romina

    2009-01-01

    Recent findings from the masked priming paradigm have revealed a surprising influence of higher-level cognitive systems (i.e., attention) on nonconscious cognitive processes. These data have effectively undermined the long-standing assumption in cognitive science that nonconscious processes are carried out independently of attention and have quickly led to the opposite view that attention is a prerequisite for nonconscious processes. Here we present evidence for a middle position by showing that the dependence of nonconscious processes on attention varies with the type of information to be processed. Specifically, we found that nonconsciously perceived faces engaged cognitive processes regardless of attention, whereas nonface stimuli engaged cognitive processes only when attended. These qualitatively different patterns suggest two distinct processing routes: one that is modulated by visual attention and one that is not.

  3. Signal transduction in insulin secretion: comparison between fuel stimuli and receptor agonists.

    PubMed

    Wollheim, C B; Biden, T J

    1986-01-01

    The initial events in signal transduction in insulin-secreting cells are summarized in FIGURE 8. Both nutrient stimuli, such as glucose and amino acids and the muscarinic agonist carbachol (carbamylcholine) raise [Ca2+]i. Although the rise in [Ca2+]i precedes the stimulation of insulin release, it is not a moment-to-moment regulator of release. The metabolizable fuel stimuli cause Ca2+ influx through voltage-dependent Ca2+ channels following depolarization of the membrane potential. In contrast, carbachol, which does not depolarize, elicits Ptd Ins 4,5-P2 hydrolysis, a reaction catalyzed by phospholipase C. The generation of Ins 1,4,5-P3 in this instance is Ca2+ independent, but appears to involve a GTP-binding protein. However, this protein is not a substrate for pertussis toxin. The levels of Ins 1,4,5-P3, which releases Ca2+ from an ATP-dependent Ca2+ pool of the endoplasmic reticulum, are increased prior to the rise in [Ca2+]i. The mitochondria may take up Ca2+ after large increases in [Ca2+]i. A previously proposed second messenger, arachidonic acid, is much less selective than Ins 1,4,5-P3 in that it releases Ca2+ from mitochondria as well as from the endoplasmic reticulum in a slow and irreversible manner. As Ins 1,4,5-P3 is also generated during glucose stimulation of islets, albeit in a Ca2+-dependent manner, this metabolite could mediate not only the action of carbachol but also contribute to amplifying the [Ca2+]i rise in response to glucose.

  4. The bank of standardized stimuli (BOSS): comparison between French and English norms.

    PubMed

    Brodeur, Mathieu B; Kehayia, Eva; Dion-Lessard, Geneviève; Chauret, Mélissa; Montreuil, Tina; Dionne-Dostie, Emmanuelle; Lepage, Martin

    2012-12-01

    Throughout the last decades, numerous picture data sets have been developed, such as the Snodgrass and Vanderwart (1980) set, and have been normalized for variables such as name and familiarity; however, due to cultural and linguistic differences, norms can vary from one country to another. The effect due specifically to culture has already been demonstrated by comparing samples from different countries where the same language is spoken. On the other hand, it is still not clear how differences between languages may affect norms. The present study explores this issue by collecting and comparing norms on names and many other features from French Canadian speakers and English Canadian speakers living in Montreal, who thus live in similar cultural environments. Norms were collected for the photos of objects from the Bank of Standardized Stimuli (BOSS) by asking participants to name the objects, to categorize them, and to rate their familiarity, visual complexity, object agreement, viewpoint agreement, and manipulability. Names and ratings from the French speakers are available in Appendix A, available in the supplemental materials. The results show that most of the norms are comparable across linguistic groups and also that the ratings given are correlated across linguistic groups. The only significant group differences were found in viewpoint agreement and visual complexity. Overall, there was good concordance between the norms collected from French and English native speakers living in the same cultural setting.

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

    PubMed Central

    Kolchinsky, Artemy; Puce, Aina

    2014-01-01

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

  6. What a difference a parameter makes: a psychophysical comparison of random dot motion algorithms.

    PubMed

    Pilly, Praveen K; Seitz, Aaron R

    2009-06-01

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

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

    PubMed Central

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

    2011-01-01

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

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

    PubMed

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

    2016-09-01

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

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

    PubMed

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

    2016-09-01

    Several methods that are promising for studying the neurophysiology of fear conditioning (e.g., EEG, MEG) require a high number of trials to achieve an adequate signal-to-noise ratio. While electric shock and white noise burst are among the most commonly used unconditioned stimuli (US) in conventional fear conditioning studies with few trials, it is unknown whether these stimuli are equally well suited for paradigms with many trials. Here, N = 32 participants underwent a 260-trial differential fear conditioning and extinction paradigm with a 240-trial recall test 24 h later and neutral faces as conditioned stimuli. In a between-subjects design, either white noise bursts (n = 16) or electric shocks (n = 16) served as US, and intensities were determined using the most common procedure for each US (i.e., a fixed 95 dB noise burst and a work-up procedure for electric shocks, respectively). In addition to differing US types, groups also differed in closely linked US-associated characteristics (e.g., calibration methods, stimulus intensities, timing). Subjective ratings (arousal/valence), skin conductance, and evoked heart period changes (i.e., fear bradycardia) indicated more reliable, extinction-resistant, and stable conditioning in the white noise burst versus electric shock group. In fear conditioning experiments where many trials are presented, white noise burst should serve as US. PMID:27286734

  10. 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.

  11. 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.

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

    SciTech Connect

    Shahzadeh, Mohammadreza; Sabaeian, Mohammad

    2014-06-15

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

  13. The late positive potential (LPP) in response to varying types of emotional and cigarette stimuli in smokers: a content comparison.

    PubMed

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

    2013-07-01

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

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

    PubMed

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

    2011-10-01

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

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

    PubMed Central

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

    2016-01-01

    Measurements of blood volume pulse (BVP) and skin conductance are commonly used as indications of psychological arousal in affective computing and human–machine interfaces. To date, palmar surfaces remain the primary site for these measurements. Placement of sensors on palmar surfaces, however, is undesirable when recordings are fraught with motion and pressure artifacts. These artifacts are frequent when the human participant has involuntary movements as in hyperkinetic cerebral palsy. This motivates the use of alternative measurement sites. The present study examined the correlation between measurements of blood volume pulse and skin conductance obtained from three different sites on the body (fingers, toes and ear for BVP; fingers, toes and arch of the foot for skin conductance) in response to cognitive and affective stimuli. The results of this pilot study indicated significant inter-site correlation among signal features derived from different sites, with the exception of BVP amplitude, the number of electrodermal reactions and the slope of the electrodermal activity response. We attribute these differences in part to inter-site discrepancies in local skin conditions, such as skin temperature. Despite these differences, significant changes from baseline were present in the responses to the cognitive and affective stimuli at non-palmar sites, suggesting that these sites may provide viable signal measurements for use in affective computing and human–machine interface applications. PMID:21849720

  16. 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.

  17. Comparison of V[Combining Dot Above]O2peak Performance on a Motorized vs. a Nonmotorized Treadmill.

    PubMed

    Morgan, Amy L; Laurent, C Matthew; Fullenkamp, Adam M

    2016-07-01

    Morgan, AL, Laurent, CM, and Fullenkamp, AM. Comparison of V[Combining Dot Above]O2peak performance on a motorized vs. a nonmotorized treadmill. J Strength Cond Res 30(7): 1898-1905, 2016-Despite growing popularity of nonmotorized treadmills (NMTs), little data exist regarding responses during exercise testing using this equipment, which is important when providing an appropriate exercise prescription. The purpose of this study was to evaluate physiological and perceptual responses during peak graded exercise tests (GXTs) on a motorized treadmill (MT) vs. NMT. Volunteers (12 men and 12 women aged 18-35 years) performed 2 peak GXT sessions (1 MT and 1 NMT). Respiratory gases and heart rate (HR) were collected each minute; perceptual response was estimated (Borg's 6-20 rating of perceived exertion [RPE] scale) during the final 10 seconds of each stage. Peak values (i.e., V[Combining Dot Above]O2, HR, speed) were determined during the final 10 seconds of each test; ventilatory threshold (VT) was assessed using the V-slope method. Paired t-tests matching variables measured at each stage of the GXT identified significantly higher values on the NMT for V[Combining Dot Above]O2 83% of the time, HR 67% of the time, and RPE 25% of the time. Interestingly though, neither peak V[Combining Dot Above]O2 (48.6 ± 9.2 ml·kg·min vs. 47.8 ± 8.9 ml·kg·min), peak HR (185 ± 9 b·min vs. 188 ± 10 b·min; p = 0.90), nor VT (72.7 ± 5.7% vs. 73.8 ± 5.4%) were significantly different on the NMT vs. the MT. However, significant differences were identified between NMT and MT tests for time to exhaustion (9:55 ± 1:49 vs. 12:05 ± 2:48; p < 0.01) and peak speed (8.0 ± 0.9 mph vs. 9.2 ± 1.4 mph; p < 0.01). Thus, although peak values obtained were similar between testing sessions on the NMT and MT, the majority of submaximal data were significantly different between trials. These differences are important when designing exercise prescriptions using submaximal values from NMT testing

  18. Comparison of V[Combining Dot Above]O2peak Performance on a Motorized vs. a Nonmotorized Treadmill.

    PubMed

    Morgan, Amy L; Laurent, C Matthew; Fullenkamp, Adam M

    2016-07-01

    Morgan, AL, Laurent, CM, and Fullenkamp, AM. Comparison of V[Combining Dot Above]O2peak performance on a motorized vs. a nonmotorized treadmill. J Strength Cond Res 30(7): 1898-1905, 2016-Despite growing popularity of nonmotorized treadmills (NMTs), little data exist regarding responses during exercise testing using this equipment, which is important when providing an appropriate exercise prescription. The purpose of this study was to evaluate physiological and perceptual responses during peak graded exercise tests (GXTs) on a motorized treadmill (MT) vs. NMT. Volunteers (12 men and 12 women aged 18-35 years) performed 2 peak GXT sessions (1 MT and 1 NMT). Respiratory gases and heart rate (HR) were collected each minute; perceptual response was estimated (Borg's 6-20 rating of perceived exertion [RPE] scale) during the final 10 seconds of each stage. Peak values (i.e., V[Combining Dot Above]O2, HR, speed) were determined during the final 10 seconds of each test; ventilatory threshold (VT) was assessed using the V-slope method. Paired t-tests matching variables measured at each stage of the GXT identified significantly higher values on the NMT for V[Combining Dot Above]O2 83% of the time, HR 67% of the time, and RPE 25% of the time. Interestingly though, neither peak V[Combining Dot Above]O2 (48.6 ± 9.2 ml·kg·min vs. 47.8 ± 8.9 ml·kg·min), peak HR (185 ± 9 b·min vs. 188 ± 10 b·min; p = 0.90), nor VT (72.7 ± 5.7% vs. 73.8 ± 5.4%) were significantly different on the NMT vs. the MT. However, significant differences were identified between NMT and MT tests for time to exhaustion (9:55 ± 1:49 vs. 12:05 ± 2:48; p < 0.01) and peak speed (8.0 ± 0.9 mph vs. 9.2 ± 1.4 mph; p < 0.01). Thus, although peak values obtained were similar between testing sessions on the NMT and MT, the majority of submaximal data were significantly different between trials. These differences are important when designing exercise prescriptions using submaximal values from NMT testing

  19. Comparison of DOT-ELISA and Standard-ELISA for Detection of the Vibrio cholerae Toxin in Culture Supernatants of Bacteria Isolated from Human and Environmental Samples.

    PubMed

    Meza-Lucas, Antonio; Pérez-Villagómez, María-Fernanda; Martínez-López, José-Patricio; García-Rodea, Ricardo; Martínez-Castelán, María-Guadalupe; Escobar-Gutiérrez, Alejandro; de-la-Rosa-Arana, Jorge-Luis; Villanueva-Zamudio, Altagracia

    2016-09-01

    A comparison of DOT-ELISA and Standard-ELISA was made for detection of Vibrio cholerae toxin in culture supernatants of bacteria isolated from human and environmental samples. A total of 293 supernatants were tested in a double blind assay. A correlation of 100 % was obtained between both techniques. The cholera toxin was found in 20 Inaba and 3 Ogawa strains. Positive samples were from seafood (17 samples), potable water (1 sample) and sewage (5 samples). The DOT-ELISA was useful as the standard-ELISA to confirm the presence of cholera toxin in the environmental samples.

  20. Comparison of DOT-ELISA and Standard-ELISA for Detection of the Vibrio cholerae Toxin in Culture Supernatants of Bacteria Isolated from Human and Environmental Samples.

    PubMed

    Meza-Lucas, Antonio; Pérez-Villagómez, María-Fernanda; Martínez-López, José-Patricio; García-Rodea, Ricardo; Martínez-Castelán, María-Guadalupe; Escobar-Gutiérrez, Alejandro; de-la-Rosa-Arana, Jorge-Luis; Villanueva-Zamudio, Altagracia

    2016-09-01

    A comparison of DOT-ELISA and Standard-ELISA was made for detection of Vibrio cholerae toxin in culture supernatants of bacteria isolated from human and environmental samples. A total of 293 supernatants were tested in a double blind assay. A correlation of 100 % was obtained between both techniques. The cholera toxin was found in 20 Inaba and 3 Ogawa strains. Positive samples were from seafood (17 samples), potable water (1 sample) and sewage (5 samples). The DOT-ELISA was useful as the standard-ELISA to confirm the presence of cholera toxin in the environmental samples. PMID:27407304

  1. Comparison of three empirical force fields for phonon calculations in CdSe quantum dots.

    PubMed

    Kelley, Anne Myers

    2016-06-01

    Three empirical interatomic force fields are parametrized using structural, elastic, and phonon dispersion data for bulk CdSe and their predictions are then compared for the structures and phonons of CdSe quantum dots having average diameters of ˜2.8 and ˜5.2 nm (˜410 and ˜2630 atoms, respectively). The three force fields include one that contains only two-body interactions (Lennard-Jones plus Coulomb), a Tersoff-type force field that contains both two-body and three-body interactions but no Coulombic terms, and a Stillinger-Weber type force field that contains Coulombic interactions plus two-body and three-body terms. While all three force fields predict nearly identical peak frequencies for the strongly Raman-active "longitudinal optical" phonon in the quantum dots, the predictions for the width of the Raman peak, the peak frequency and width of the infrared absorption peak, and the degree of disorder in the structure are very different. The three force fields also give very different predictions for the variation in phonon frequency with radial position (core versus surface). The Stillinger-Weber plus Coulomb type force field gives the best overall agreement with available experimental data.

  2. 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.

  3. Comparison of two methods for describing the strain profiles in quantum dots

    SciTech Connect

    Pryor, C.; Kim, J.; Wang, L.W.; Williamson, A.J.; Zunger, A.

    1998-03-01

    The electronic structure of interfaces between lattice-mismatched semiconductors is sensitive to the strain. We compare two approaches for calculating such inhomogeneous strain{emdash}continuum elasticity [(CE), treated as a finite difference problem] and atomistic elasticity. While for {ital small} strain the two methods must agree, for the large strains that exist between lattice-mismatched III-V semiconductors (e.g., 7{percent} for InAs/GaAs outside the linearity regime of CE) there are discrepancies. We compare the strain profile obtained by both approaches (including the approximation of the correct C{sub 2} symmetry by the C{sub 4} symmetry in the CE method) when applied to C{sub 2}-symmetric InAs pyramidal dots capped by GaAs. {copyright} {ital 1998 American Institute of Physics.}

  4. 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

  5. Binocular coordination in response to stereoscopic stimuli

    NASA Astrophysics Data System (ADS)

    Liversedge, Simon P.; Holliman, Nicolas S.; Blythe, Hazel I.

    2009-02-01

    Humans actively explore their visual environment by moving their eyes. Precise coordination of the eyes during visual scanning underlies the experience of a unified perceptual representation and is important for the perception of depth. We report data from three psychological experiments investigating human binocular coordination during visual processing of stereoscopic stimuli.In the first experiment participants were required to read sentences that contained a stereoscopically presented target word. Half of the word was presented exclusively to one eye and half exclusively to the other eye. Eye movements were recorded and showed that saccadic targeting was uninfluenced by the stereoscopic presentation, strongly suggesting that complementary retinal stimuli are perceived as a single, unified input prior to saccade initiation. In a second eye movement experiment we presented words stereoscopically to measure Panum's Fusional Area for linguistic stimuli. In the final experiment we compared binocular coordination during saccades between simple dot stimuli under 2D, stereoscopic 3D and real 3D viewing conditions. Results showed that depth appropriate vergence movements were made during saccades and fixations to real 3D stimuli, but only during fixations on stereoscopic 3D stimuli. 2D stimuli did not induce depth vergence movements. Together, these experiments indicate that stereoscopic visual stimuli are fused when they fall within Panum's Fusional Area, and that saccade metrics are computed on the basis of a unified percept. Also, there is sensitivity to non-foveal retinal disparity in real 3D stimuli, but not in stereoscopic 3D stimuli, and the system responsible for binocular coordination responds to this during saccades as well as fixations.

  6. 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.

  7. Detection and typing of human papillomavirus using the Vira Type "in situ" kit: comparison with a conventional dot blot technique.

    PubMed Central

    Faulkner-Jones, B E; Bellomarino, V M; Borg, A J; Orzeszko, K; Garland, S M

    1990-01-01

    A new commercial kit (Vira Type "in situ", Life Technologies, Inc., Molecular Diagnostics Division, Guithersburg, Maryland, USA) for the detection of human papillomavirus (HPV) types 6, 11, 16, 18, 31, 33 and 35 in routinely processed human anogenital tissue was compared with a conventional dot blot assay for HPV 6, 11, 16 and 18. Both systems use double-stranded genomic DNA probes for the detection of type specific HPV DNA. The probes used on the dot blots were labelled with 32P and visualised autoradiographically. The Vira Type probes were labelled with biotin and visualised using a streptavidin-alkaline phosphatase conjugate with NBT-BCIP substrate. Biopsy specimens from the cervix, vagina, and vulva of 46 women were processed by both methods and compared. The histological diagnoses ranged from benign changes, to dysplasia, and invasive carcinoma. Overall, 50% of biopsy specimens were positive for HPV DNA by dot blot hybridisation; only 39% were positive by Vira Type in situ hybridisation. Three of the specimens positive by the Vira Type "in situ" kit showed no cross hybridisation and were the same HPV type as the dot blot. A further 13 showed hybridisation, but the showed cross hybridisation, but the to the dot blot results. One biopsy specimen was positive for different HPV types by the two tests and one was positive by Vira Type and negative by dot blot. Six biopsy specimens were negative by Vira Type but positive by dot blot. It is concluded that the Vira Type "in situ" kit has a similar specificity but lower sensitivity than the dot blot hybridisation method for the detection of HPV DNA. Images PMID:2175755

  8. Comparison of Gated Audiovisual Speech Identification in Elderly Hearing Aid Users and Elderly Normal-Hearing Individuals: Effects of Adding Visual Cues to Auditory Speech Stimuli.

    PubMed

    Moradi, Shahram; Lidestam, Björn; Rönnberg, Jerker

    2016-01-01

    The present study compared elderly hearing aid (EHA) users (n = 20) with elderly normal-hearing (ENH) listeners (n = 20) in terms of isolation points (IPs, the shortest time required for correct identification of a speech stimulus) and accuracy of audiovisual gated speech stimuli (consonants, words, and final words in highly and less predictable sentences) presented in silence. In addition, we compared the IPs of audiovisual speech stimuli from the present study with auditory ones extracted from a previous study, to determine the impact of the addition of visual cues. Both participant groups achieved ceiling levels in terms of accuracy in the audiovisual identification of gated speech stimuli; however, the EHA group needed longer IPs for the audiovisual identification of consonants and words. The benefit of adding visual cues to auditory speech stimuli was more evident in the EHA group, as audiovisual presentation significantly shortened the IPs for consonants, words, and final words in less predictable sentences; in the ENH group, audiovisual presentation only shortened the IPs for consonants and words. In conclusion, although the audiovisual benefit was greater for EHA group, this group had inferior performance compared with the ENH group in terms of IPs when supportive semantic context was lacking. Consequently, EHA users needed the initial part of the audiovisual speech signal to be longer than did their counterparts with normal hearing to reach the same level of accuracy in the absence of a semantic context. PMID:27317667

  9. Comparison of Gated Audiovisual Speech Identification in Elderly Hearing Aid Users and Elderly Normal-Hearing Individuals: Effects of Adding Visual Cues to Auditory Speech Stimuli.

    PubMed

    Moradi, Shahram; Lidestam, Björn; Rönnberg, Jerker

    2016-06-17

    The present study compared elderly hearing aid (EHA) users (n = 20) with elderly normal-hearing (ENH) listeners (n = 20) in terms of isolation points (IPs, the shortest time required for correct identification of a speech stimulus) and accuracy of audiovisual gated speech stimuli (consonants, words, and final words in highly and less predictable sentences) presented in silence. In addition, we compared the IPs of audiovisual speech stimuli from the present study with auditory ones extracted from a previous study, to determine the impact of the addition of visual cues. Both participant groups achieved ceiling levels in terms of accuracy in the audiovisual identification of gated speech stimuli; however, the EHA group needed longer IPs for the audiovisual identification of consonants and words. The benefit of adding visual cues to auditory speech stimuli was more evident in the EHA group, as audiovisual presentation significantly shortened the IPs for consonants, words, and final words in less predictable sentences; in the ENH group, audiovisual presentation only shortened the IPs for consonants and words. In conclusion, although the audiovisual benefit was greater for EHA group, this group had inferior performance compared with the ENH group in terms of IPs when supportive semantic context was lacking. Consequently, EHA users needed the initial part of the audiovisual speech signal to be longer than did their counterparts with normal hearing to reach the same level of accuracy in the absence of a semantic context.

  10. 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

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

    PubMed

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

    2002-04-01

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

  12. Comparison of duplex to austenitic stainless steels for DOT 407 and 412 cargo tanks in liquid chemical service

    SciTech Connect

    Staebler, R.R.

    1998-12-31

    U.S. Highway transportation of liquid chemicals has depended upon austenitic stainless steels (316 and 304) since the 1940`s. This paper will compare these austenitics to the duplex stainless steels (UNS S31803 and S32205 both commonly known as 2205 and UNS S32304 commonly known as 2304) from various aspects such as: composition, mechanical and physical properties; corrosion resistance; design, manufacturing and welding of vessel; heating panel application on the bottom of the vessel; surface finish; DOT Regulations; and cost. Some actual experience with 2205 will be explained.

  13. 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

  14. Comparison of Burrowing and Stimuli-Evoked Pain Behaviors as End-Points in Rat Models of Inflammatory Pain and Peripheral Neuropathic Pain

    PubMed Central

    Muralidharan, Arjun; Kuo, Andy; Jacob, Meera; Lourdesamy, Jacintha S.; Carvalho, Lara Melo Soares Pinho De; Nicholson, Janet R.; Corradini, Laura; Smith, Maree T.

    2016-01-01

    Establishment and validation of ethologically-relevant, non-evoked behavioral end-points as surrogate measures of spontaneous pain in rodent pain models has been proposed as a means to improve preclinical to clinical research translation in the pain field. Here, we compared the utility of burrowing behavior with hypersensitivity to applied mechanical stimuli for pain assessment in rat models of chronic inflammatory and peripheral neuropathic pain. Briefly, groups of male Sprague-Dawley rats were habituated to the burrowing environment and trained over a 5-day period. Rats that burrowed ≤ 450 g of gravel on any 2 days of the individual training phase were excluded from the study. The remaining rats received either a unilateral intraplantar injection of Freund's complete adjuvant (FCA) or saline, or underwent unilateral chronic constriction injury (CCI) of the sciatic nerve- or sham-surgery. Baseline burrowing behavior and evoked pain behaviors were assessed prior to model induction, and twice-weekly until study completion on day 14. For FCA- and CCI-rats, but not the corresponding groups of sham-rats, evoked mechanical hypersensitivity developed in a temporal manner in the ipsilateral hindpaws. Although burrowing behavior also decreased in a temporal manner for both FCA-and CCI- rats, there was considerable inter-animal variability. By contrast, mechanical hyperalgesia and mechanical allodynia in the ipsilateral hindpaws of FCA- and CCI-rats respectively, exhibited minimal inter-animal variability. Our data collectively show that burrowing behavior is altered in rodent models of chronic inflammatory pain and peripheral neuropathic pain. However, large group sizes are needed to ensure studies are adequately powered due to considerable inter-animal variability. PMID:27242458

  15. NESSTI: Norms for Environmental Sound Stimuli

    PubMed Central

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

    2013-01-01

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

  16. Comparison of a dot immunobinding assay, latex agglutination, and cytotoxin assay for laboratory diagnosis of Clostridium difficile-associated diarrhea.

    PubMed

    Woods, G L; Iwen, P C

    1990-05-01

    C. diff-CUBE, a dot immunobinding assay (DIA) (Difco Laboratories, Ann Arbor, Mich.) for detection of Clostridium difficile toxin A in stool specimens, was compared with latex agglutination (LA) (Marion Laboratories, Kansas City, Mo.) and cytotoxin assay (CTA) for the laboratory diagnosis of C. difficile-associated diarrhea. A total of 200 stool specimens collected from 169 patients with suspected C. difficile diarrhea were tested. Of the 198 specimens evaluated by all three methods, 36 (18%) from 36 patients were positive by one or more of the tests. Twenty-five, 26, and 23 specimens were positive by CTA, DIA, and LA, respectively; 14 were positive by all three methods. Eight specimens yielded nonspecific LA test results; all eight were negative by CTA, and one was positive by DIA. DIA results agreed with CTA results in 183 (92%) cases and with LA results in 175 (88%) cases. CTA and LA results agreed in 179 (90%) cases. Freezing of the specimen did not appear to adversely affect either the DIA or LA test. These preliminary results suggest that C. diff-CUBE may be useful as a rapid screen for the diagnosis of C. difficile-associated diarrhea. However, for optimum laboratory diagnosis, further testing of all stools that are negative by DIA is warranted.

  17. Accommodation for flickering stimuli.

    PubMed

    Owens, D A; Wolfe, J M

    1985-01-01

    A laser optometer was used to measure accommodative responses of three observers for sinusoidal gratings presented in Maxwellian view at optical distances ranging from 0 to 4 diopters. Contrast of the stimuli was modulated spatially at 1.0, 4.2 and 6.5 cycles deg.-1 (cpd), and temporally at six frequencies ranging from 3.0 to 40 Hz. Accommodation was consistently more accurate for the 4.2 cpd than for either the 1.0 or 6.5 cpd gratings. Furthermore, accommodative responsiveness for the 4.2 cpd was not affected by temporal modulation, while that for the other spatial frequencies improved monotonically as a function of temporal frequency. These results reinforce earlier reports that accommodation is most responsive for contrast of intermediate spatial frequencies and they indicate that stimulus flicker generally degrades accommodation for spatial contrast.

  18. Attentional orienting towards smoking-related stimuli.

    PubMed

    Hogarth, L C; Mogg, K; Bradley, B P; Duka, T; Dickinson, A

    2003-03-01

    According to incentive salience theory, conditioned stimuli (CS+) associated with drug reinforcement acquire the capacity to elicit a conditioned attentional orienting response, which controls drug-seeking and drug-taking behaviour. We sought evidence for this proposal by measuring visual attentional orienting towards smoking pictures presented briefly in the periphery of the visual field, versus control pictures likewise presented, in smokers versus non-smokers. In each trial, smokers and non-smokers responded manually to a dot probe stimulus that appeared in a location previously occupied by either a smoking picture or a control picture. Attentional bias scores were calculated by subtracting the median reaction time (RT) in the former condition from the median RT in the latter condition. In two experiments, light-smokers (smokers of fewer than 20 cigarettes/day) produced a mean bias score that was significantly greater than that of heavy-smokers (smokers of 20 or more cigarettes/day) and non-smokers. In addition, when smokers from the two experiments were pooled, a significant quadratic relationship was found between cigarettes/day and the attentional bias for the smoking stimuli. These findings are consistent with incentive salience theories and dual-process theories of addiction.

  19. 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

  20. 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.

  1. [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.

  2. Fluorescent carbon dot (C-dot) nanoclusters.

    PubMed

    Wang, Guan; Pan, Xiaoyong; Gu, Liuqun; Ren, Wei; Cheng, Weiren; Kumar, Jatin N; Liu, Ye

    2014-09-19

    Fluorescent carbon dot (C-dot) nanoclusters composed of C-dot-loaded hollow silica spheres are obtained via the dehydration of mannose, which is adsorbed onto hollow silica spheres or poly(ethylene glycol)-graft-hollow silica spheres (PEG-g-hollow silica). The structure of C-dot nanoclusters are confirmed using 1H NMR, FTIR, TEM and TGA. C-dot nanoclusters show a redshifted fluorescence emission with an increased excitation wavelength. Passivation with PEG diamines improve the quantum yields to ∼2%. Confocal laser scanning microscopy (CLSM) results reflect the fact that C-dot nanoclusters can provide good cytoplasm imaging of live Hep G2 cells and live MCF-7 cells, and the imaging obtained is brighter and more even than those from free C-dots. With their combination of good photostability and low cytotoxicity, C-dot nanoclusters are promising for the production of higher quality bioimaging.

  3. 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…

  4. 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…

  5. 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.

  6. Crowding of biological motion stimuli.

    PubMed

    Ikeda, Hanako; Watanabe, Katsumi; Cavanagh, Patrick

    2013-01-01

    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.

  7. Event-related brain potentials in selective listening to frequent and rare stimuli.

    PubMed

    Alho, K; Lavikainen, J; Reinikainen, K; Sams, M; Näätänen, R

    1990-01-01

    Our previous event-related brain potential (ERP) results suggest that during selective listening, relevant stimuli are selected for further processing by comparing each stimulus to an "attentional trace," a neuronal representation of the physical features of the relevant stimuli that distinguish them from the irrelevant stimuli. This comparison process is reflected by the early component of the processing negativity (PN), which is largest and longest to the relevant stimuli (perfectly matching with the trace). In the present study, the subjects selectively listened to designated tone stimuli which randomly appeared among irrelevant tones of a different pitch. The probability of relevant stimuli in a block was varied. The processing negativity elicited by relevant stimuli was smaller the less frequent they were. The results support the attentional-trace theory of selective attention, which proposes that, in addition to active maintenance, the trace also depends on the rate of sensory reinforcement provided by the relevant stimuli.

  8. Comparison of chemical assay, bioassay, enzyme-linked immunosorbent assay, and dot blot hybridization for detection of aerobactin in members of the family Enterobacteriaceae.

    PubMed Central

    Le Roy, D; Bouchet, A; Saulnier, P; Pecquet, S; Andremont, A

    1993-01-01

    In order to determine the best strategy for detection of aerobactin in members of the family Enterobacteriaceae, we compared the results of three phenotypic assays, including a chemical assay, a cross-feeding bioassay, and an enzyme-linked immunosorbent assay (ELISA), with the results of a dot blot hybridization assay using a specific probe for the aerobactin genes. The sensitivity and specificity of the ELISA were better than those of the chemical and cross-feeding assays, but the results of dot blot hybridization were the most reproducible. However, none of the Serratia and Enterobacter cloacae strains which produced aerobactin hybridized with the probe. We concluded that the best strategy for aerobactin detection is a two-step procedure that combines screening by dot blot hybridization with an ELISA for negative strains. PMID:8481015

  9. Transitive responding in hooded crows requires linearly ordered stimuli.

    PubMed Central

    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 order the stimuli along a physical dimension. For the other 4 birds, the circles corresponding to the colored cards had the same diameter (constant feedback group). In later testing, a novel choice pair (BD) was presented. Reinforcement history involving stimuli B and D was controlled so that the reinforcement/nonreinforcement ratios for the latter would be greater than for the former. If, during the BD test, the crows chose between stimuli according to these reinforcement/nonreinforcement ratios, then they should prefer D; if they chose according to the diameter of the feedback stimuli, then they should prefer B. In the ordered feedback group, the crows strongly preferred B over D; in the constant feedback group, the crows' choice did not differ significantly from chance. These results, plus simulations using associative models, suggest that the orderability of the postchoice feedback stimuli is important for crows' transitive responding. PMID:15484868

  10. 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.

  11. How do people order stimuli?

    PubMed

    Kemp, Simon; Grace, Randolph C

    2014-08-01

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

  12. 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

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

    PubMed

    Lopez-Garcia, Pilar; 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

    2016-02-01

    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.

  14. Stimuli-responsive polymer films.

    PubMed

    Zhai, Lei

    2013-09-01

    Stimuli-responsive polymer films undergo interesting structural and property changes upon external stimuli. Their applications have extended from smart coatings to controlled drug release, smart windows, self-repair and other fields. This tutorial review summarizes non-covalent bonding, reversible reactions and responsive molecules that have played important roles in creating stimuli-responsive systems, and presents the recent development of three types of responsive polymer systems: layer-by-layer polymer multilayer films, polymer brushes, and self-repairing polymer films, with a discussion of their response mechanism. Future research efforts include comprehensive understanding of the response mechanism, producing polymer systems with controlled response properties regarding single or multiple external signals, combining polymer film fabrication with nanotechnology, improving the stability of polymer films on substrates, and evaluating the toxicity of the degradation products. PMID:23749141

  15. 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.

  16. 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…

  17. Comparison of low frequency charge noise in identically patterned Si/SiO2 and Si/SiGe quantum dots

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

    We investigate and compare the charge noise in Si/SiO2 and Si/SiGe gate defined quantum dots with identically patterned gates by measuring the low frequency 1/f current noise through the biased quantum dots in the coulomb blockade regime. The current noise is normalized and used to extract a measurement of the potential energy noise in the system. Additionally, the temperature dependence of this noise is investigated. The measured charge noise in Si/SiO2 compares favorably with that of the SiGe device as well as previous measurements made on other substrates suggesting Si/SiO2 is a potential candidate for spin based quantum computing.

  18. 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.

  19. 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.

  20. Behavioral and ERP measures of attentional bias to threat in the dot-probe task: poor reliability and lack of correlation with anxiety

    PubMed Central

    Kappenman, Emily S.; Farrens, Jaclyn L.; Luck, Steven J.; Proudfit, Greg Hajcak

    2014-01-01

    The dot-probe task is often considered a gold standard in the field for investigating attentional bias to threat. However, serious issues with the task have been raised. Specifically, a number of studies have demonstrated that the traditional reaction time (RT) measure of attentional bias to threat in the dot-probe task has poor internal reliability and poor test-retest reliability. In addition, although threatening stimuli capture attention in other paradigms, attentional bias to threat has not usually been found in typical research participants in the dot-probe task. However, when attention is measured in the dot-probe task with the N2pc component of the event-related potential waveform, substantial attentional orienting to threat is observed, and the internal reliability is moderate. To provide a rigorous comparison of the reliability of this N2pc measure and the conventional behavioral measure, as well as to examine the relationship of these measures to anxiety, the present study examined the N2pc in conjunction with RT in the dot-probe task in a large sample of participants (N = 96). As in previous studies, RT showed no bias to threatening images across the sample and exhibited poor internal reliability. Moreover, this measure did not relate to trait anxiety. By contrast, the N2pc revealed a significant initial shift of attention to threat, and this measure was internally reliable. However, the N2pc was not correlated with trait anxiety, indicating that it does not provide a meaningful index of individual differences in anxiety in the dot-probe task. Together, these results indicate a serious need to develop new tasks and methods to more reliably investigate attentional bias to threat and its relationship to anxiety in both clinical and non-clinical populations. PMID:25538644

  1. 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

  2. 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.

  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. PMID:26268965

  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. Effects of complex aural stimuli on mental performance.

    PubMed

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

    2003-06-01

    The objective of this study is to investigate the effect of complex aural stimuli on mental performance. A series of experiments were designed to obtain data for two different analyses. The first analysis is a "Stimulus" versus "No-stimulus" comparison for each of the four dependent variables, i.e. quantitative ability, reasoning ability, spatial ability and memory of an individual, by comparing the control treatment with the rest of the treatments. The second set of analysis is a multi-variant analysis of variance for component level main effects and interactions. The two component factors are tempo of the complex aural stimuli and sound volume level, each administered at three discrete levels for all four dependent variables. Ten experiments were conducted on eleven subjects. It was found that complex aural stimuli influence the quantitative and spatial aspect of the mind, while the reasoning ability was unaffected by the stimuli. Although memory showed a trend to be worse with the presence of complex aural stimuli, the effect was statistically insignificant. Variation in tempo and sound volume level of an aural stimulus did not significantly affect the mental performance of an individual. The results of these experiments can be effectively used in designing work environments. PMID:15176128

  6. 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…

  7. Extended cortical activations during evaluating successive pain stimuli.

    PubMed

    Lötsch, Jörn; Walter, Carmen; Felden, Lisa; Preibisch, Christine; Nöth, Ulrike; Martin, Till; Anti, Sandra; Deichmann, Ralf; Oertel, Bruno G

    2012-08-01

    Comparing pain is done in daily life and involves short-term memorizing and attention focusing. This event-related functional magnetic resonance imaging study investigated the short-term brain activations associated with the comparison of pain stimuli using a delayed discrimination paradigm. Fourteen healthy young volunteers compared two successive pain stimuli administered at a 10 s interval to the same location at the nasal mucosa. Fourteen age- and sex-matched subjects received similar pain stimuli without performing the comparison task. With the comparison task, the activations associated with the second pain stimulus were significantly greater than with the first stimulus in the anterior insular cortex and the primary somatosensory area. This was observed on the background of a generally increased stimulus-associated brain activation in the presence of the comparison task that included regions of the pain matrix (insular cortex, primary and secondary somatosensory area, midcingulate cortex, supplemental motor area) and regions associated with attention, decision making, working memory and body recognition (frontal and temporal gyri, inferior parietal lobule, precuneus, lingual cortices). This data provides a cerebral correlate for the role of pain as a biological alerting system that gains the subject's attention and then dominates most other perceptions and activities involving pain-specific and non-pain-specific brain regions.

  8. Luminescent Quantum Dots as Ultrasensitive Biological Labels

    NASA Astrophysics Data System (ADS)

    Nie, Shuming

    2000-03-01

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

  9. Dot-immunobinding assay (Dot-Iba).

    PubMed

    Surendran, Sumi; Mathai, Annamma; Radhakrishnan, Vishnampet Venkataraman

    2015-01-01

    Dot-immunobinding assay (Dot-Iba) is a simple and highly reproducible immunodiagnostic method. Antibody or antigen is dotted directly onto nitrocellulose membrane (NCM) discs. The diagnostic material to be checked can be incubated on this disc. Presence of antigen-antibody complex in NCM discs can be directly demonstrated with enzyme-conjugated antiglobulins and substrate. Development of a purple-pink colored, insoluble substrate product in the nitrocellulose membrane will be considered a positive result in the assay. This assay allows the processing of multiple specimens at a time and the entire operational procedures required only 4-6 h. Dot-IBA is rapid and the technical steps involved in the assay are much simpler than the other immunoassays such as enzyme-linked immunosorbent assay in detecting circulating antigen and antibody in clinical samples. The Dot-Iba showed an overall sensitivity of 60 % for tuberculous meningitis diagnosis and no false positive results were encountered. Hence this assay is highly specific for the diagnosis of paucibacillary diseases like extrapulmonary tuberculosis. Dot-Iba is best suited to laboratories in developing world where there are constraints in laboratory resources.

  10. Decimetric radio dot emissions

    NASA Astrophysics Data System (ADS)

    Mészárosová, H.; Karlický, M.; Sawant, H. S.; Fernandes, F. C. R.; Cecatto, J. R.; de Andrade, M. C.

    2008-11-01

    Context: We study a rare type of solar radio bursts called decimetric dot emissions. Aims: In the period 1999-2001, 20 events of decimetric dot emissions observed by the Brazilian Solar Spectroscope (BSS) in the frequency range 950-2640 MHz are investigated statistically and compared with radio fine structures of zebras and fibers. Methods: For the study of the spectral characteristics of the dot emissions we use specially developed Interactive Data Language (IDL) software called BSSView and basic statistical methods. Results: We have found that the dm dot emissions, contrary to the fine structures of the type IV bursts (i.e. zebras, fibers, lace bursts, spikes), are not superimposed on any background burst emission. In the radio spectrum, in most cases the dot emissions form chains that appear to be arranged in zebra patterns or fibers. Because some zebras and fibers, especially those observed with high time and high spectral resolutions, also show emission dots (but superimposed on the background burst emission), we compared the spectral parameters of the dot emissions with the dots being the fine structure of zebras and fibers. For both these dots, similar spectral characteristics were found. Some similarities of the dot emissions can be found also with the lace bursts and spikes. For some events the dot emissions show structural evolution from patterns resembling fibers to patterns resembling zebras and vice versa, or they evolve into fully chaotic patterns. Conclusions: For the first time, we present decimetric dot emissions that appear to be arranged in zebra patterns or fibers. We propose that these emissions are generated by the plasma emission mechanism at the locations in the solar atmosphere where the double resonance condition is fulfilled.

  11. Body image concern and selective attention to disgusting and non-self appearance-related stimuli.

    PubMed

    Onden-Lim, Melissa; Wu, Ray; Grisham, Jessica R

    2012-09-01

    Although selective attention to one's own appearance has been widely documented in studies of body dysmorphic disorder (BDD), little is known about attentional bias toward non-self appearance-related stimuli in BDD. Furthermore, despite reports of heightened experience of disgust in BDD, it is unknown whether these individuals differentially attend to disgusting stimuli and whether disgust is important in processing of unattractive stimuli. We used a dot probe procedure to investigate the relationship between dysmorphic concern, a defining feature of BDD, and selective attention to faces, attractive, unattractive and disgusting images in a female heterosexual student population (N=92). At the long stimulus presentation (1000 ms), dysmorphic concern was positively associated with attention to faces in general and attractive appearance-related images. In contrast, at the short stimulus presentation (200 ms), there was a positive association between dysmorphic concern and disgusting images. Implications for theoretical models of BDD are discussed.

  12. 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.

  13. A brain-derived metric for preferred kinetic stimuli.

    PubMed

    Zeki, Semir; Stutters, Jonathan

    2012-02-01

    We here address the question of whether there is any correlation between subjective preference for simple configurations within a specific visual domain such as motion and strength of activity in visual areas in which that domain is emphasized. We prepared several distinctive patterns of dots in motion with various characteristics and asked humans to rate them according to their preference, before and while scanning the activity in their brains with functional magnetic resonance imaging. For simplicity, we restricted ourselves to motion in the fronto-parallel plane. Moving patterns produced activity in areas V1, V2, the V3 complex (V3, V3A, V3B) and V5, but only in areas V5, V3A/B and parietal cortex did the preferred kinetic patterns produce stronger activity when compared with the non-preferred ones. In addition, preferred patterns produced activity within field A1 of medial orbito-frontal cortex (mOFC), which is not otherwise activated by kinetic stimuli. Hence, for these areas, stronger neural activity correlated with subjective preference. We conclude that configurations of kinetic stimuli that are subjectively preferred correlate with stronger activity within early visual areas and within mOFC. This opens up the possibility of more detailed studies to relate subjective preferences to strength of activity in early visual areas and to relate activity in them to areas whose activity correlates with the subjective experience of beauty.

  14. Quantum Dot Solar Cells

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

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

  15. 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. 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.

  17. Comparison between dot-immunoblotting assay and clinical sign determination method for quantifying avian infectious bronchitis virus vaccine by titration in embryonated eggs.

    PubMed

    Yuk, Seong-su; Kwon, Jung-Hoon; Noh, Jin-Yong; Hong, Woo-tack; Gwon, Gyeong-Bin; Jeong, Jei-Hyun; Jeong, Sol; Youn, Ha-Na; Heo, Yong-Hwan; Lee, Joong-Bok; Park, Seung-Yong; Choi, In-Soo; Song, Chang-Seon

    2016-04-01

    A sensitive and specific method for measuring the vaccine titer of infectious bronchitis virus (IBV) is important to commercial manufacturers for improving vaccine quality. Typically, IBV is titrated in embryonated chicken eggs, and the infectivity of the virus dilutions is determined by assessing clinical signs in the embryos as evidence of viral propagation. In this study, we used a dot-immunoblotting assay (DIA) to measure the titers of IBV vaccines that originated from different pathogenic strains or attenuation methods in embryonated eggs, and we compared this assay to the currently used method, clinical sign evaluation. To compare the two methods, we used real-time reverse transcription-PCR, which had the lowest limit of detection for propagated IBV. As a clinical sign of infection, dwarfism of the embryo was quantified using the embryo: egg (EE) index. The DIA showed 9.41% higher sensitivity and 15.5% higher specificity than the clinical sign determination method. The DIA was particularly useful for measuring the titer of IBV vaccine that did not cause apparent stunting but propagated in embryonated chicken eggs such as a heat-adapted vaccine strain. The results of this study indicate that the DIA is a rapid, sensitive, reliable method for determining IBV vaccine titer in embryonated eggs at a relatively low cost.

  18. Comparison of magneto-optical properties of various excitonic complexes in CdTe and CdSe self-assembled quantum dots

    NASA Astrophysics Data System (ADS)

    Kobak, J.; Smoleński, T.; Goryca, M.; Rousset, J.-G.; Pacuski, W.; Bogucki, A.; Oreszczuk, K.; Kossacki, P.; Nawrocki, M.; Golnik, A.; Płachta, J.; Wojnar, P.; Kruse, C.; Hommel, D.; Potemski, M.; Kazimierczuk, T.

    2016-07-01

    We present a comparative study of two self-assembled quantum dot (QD) systems based on II-VI compounds: CdTe/ZnTe and CdSe/ZnSe. Using magneto-optical techniques we investigated a large population of individual QDs. The systematic photoluminescence studies of emission lines related to the recombination of neutral exciton X, biexciton XX, and singly charged excitons (X+, X-) allowed us to determine average parameters describing CdTe QDs (CdSe QDs): X-XX transition energy difference 12 meV (24 meV); fine-structure splitting δ1=0.14 meV (δ1=0.47 meV); g-factor g  =  2.12 (g  =  1.71) diamagnetic shift γ=2.5 μeV T-2 (γ =1.3 μeV T-2). We find also statistically significant correlations between various parameters describing internal structure of excitonic complexes.

  19. Nociceptive stimuli induce changes in somatosensory responses of rat dorsal column nuclei neurons.

    PubMed

    Costa-García, Miguel; Nuñez, Angel

    2004-10-29

    Accumulating evidence suggest that the dorsal column nuclei (DCN) neurons play a role in nociception. To evaluate DCN neuronal responses to nociceptive stimuli, unit recordings were performed in urethane-anesthesized rats. Neurons selected for this analysis displayed a low spontaneous firing rate and some of them were antidromically activated by electrical stimulation of the ventral posterolateral thalamic nucleus. Formalin injections into receptive fields (RFs) of DCN cells, or applications of short-lasting and long-lasting thermal nociceptive stimuli were used. DCN neurons displayed smaller responses when long-lasting nociceptive thermal stimuli were applied to their RFs in comparison with values obtained from the innocuous cutaneous stimulation (5.2+/-1.0 and 4.0+/-0.6 spikes/stimuli, respectively; p=0.02). Formalin also decreased the responses to innocuous cutaneous stimuli when these stimuli were applied to the formalin injection site (2.6+/-0.3 spikes/stimuli in control conditions and 1.8+/-0.3 spikes/stimuli 20 min after formalin; p=0.002). In contrast, responses to sensory stimuli applied at the periphery of the RF after formalin injection increased (2.2+/-0.2 to 2.8+/-0.3 spikes/stimuli; p=0.005). In some cases, DCN neurons expanded their RF. Fiber input to the DCN did not modify their somatosensory responses when nociceptive stimuli were applied. Results demonstrate that thermal and formalin nociceptive stimuli modify the somatosensory responses of DCN neurons. Thus, decreasing somatosensory responses at the pain induction site or the generation of allodynia may be due to the activity of DCN neurons.

  20. Visual stimuli: past and present

    NASA Astrophysics Data System (ADS)

    Westheimer, Gerald

    2013-03-01

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

  1. Cardiorespiratory interactions to external stimuli.

    PubMed

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

    2005-09-01

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

  2. Exposition of visual stimuli in an aversive situation and self-exposure to light in rats.

    PubMed

    Matysiak, J

    1978-01-01

    The aim of the work presented was to test the effect of associating visual stimuli with an aversive situation on later self-exposure to these stimuli. Forty-five male albino rats (Wistar) aged approximately 90 days were divided into three groups; visual trained in avoidance response to visual stimuli; auditory trained in avoidance response to auditory stimuli; and neutral untrained in avoidance response. In part two of the experiment all the rats were tested in a chamber for self-exposure to light. A statistically significant increase in the rewarding value of visual stimulation was found in the visual group in comparison with the remaining groups. This effect is interpreted as a result of extinction of anxiety response to visual stimuli as a result of which relaxation begins to positively reinforce the response leading to switching on the light.

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

    PubMed Central

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

    2012-01-01

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

  4. 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

  5. Priming effects on the perceived grouping of ambiguous dot patterns.

    PubMed

    Kurylo, Daniel D; Bukhari, Farhan

    2015-09-01

    For ambiguous stimuli, complex dynamics guide processes of perceptual grouping. Previous studies have suggested two opposing effects on grouping that are produced by the preliminary stimulus state: one that enhances grouping towards the existing structure, and another that opposes this structure. To examine effects of the preliminary state on grouping directly, measurements were made of perceived grouping of dot patterns that followed a visual prime. Three stimuli were presented in sequence: prime, target, and mask. Targets were composed of an evenly spaced dot grid in which grouping was established by similarity in luminance. Subjects indicated the dominant perceived grouping. The prime either corresponded to or opposed the prevailing organization of the target. Contrary to the hypothesis, solid-line primes biased grouping away from the structure of the prime, even when the prevailing organization of dot patterns strongly favored the primes' structure. This effect occurred, although to a lesser extent, when primes did not occupy the same location of targets, but were presented in a marginal area surrounding the grid. Priming effects did not occur for primes constructed of dot patterns. Effects found here may be attributed to a forward masking effect by primes, which more effectively disrupts grouping of patterns matched to the prime. Effects may also be attributed to a type of pattern contrast, in which a grouped pattern dissimilar to primes gains salience. For the pattern contrast model, the partial activation of multiple grouped configurations is compared to the pattern of the solid-line primes. PMID:25281427

  6. Priming effects on the perceived grouping of ambiguous dot patterns.

    PubMed

    Kurylo, Daniel D; Bukhari, Farhan

    2015-09-01

    For ambiguous stimuli, complex dynamics guide processes of perceptual grouping. Previous studies have suggested two opposing effects on grouping that are produced by the preliminary stimulus state: one that enhances grouping towards the existing structure, and another that opposes this structure. To examine effects of the preliminary state on grouping directly, measurements were made of perceived grouping of dot patterns that followed a visual prime. Three stimuli were presented in sequence: prime, target, and mask. Targets were composed of an evenly spaced dot grid in which grouping was established by similarity in luminance. Subjects indicated the dominant perceived grouping. The prime either corresponded to or opposed the prevailing organization of the target. Contrary to the hypothesis, solid-line primes biased grouping away from the structure of the prime, even when the prevailing organization of dot patterns strongly favored the primes' structure. This effect occurred, although to a lesser extent, when primes did not occupy the same location of targets, but were presented in a marginal area surrounding the grid. Priming effects did not occur for primes constructed of dot patterns. Effects found here may be attributed to a forward masking effect by primes, which more effectively disrupts grouping of patterns matched to the prime. Effects may also be attributed to a type of pattern contrast, in which a grouped pattern dissimilar to primes gains salience. For the pattern contrast model, the partial activation of multiple grouped configurations is compared to the pattern of the solid-line primes.

  7. 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.

  8. 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

  9. 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.

  10. Dots and Cubes

    ERIC Educational Resources Information Center

    Eaton, Bryan L.

    1974-01-01

    Illustrated is the mathematical analysis of a three-dimensional game using techniques from the calculus of finite differences. This game is an analog of the familiar two-dimensional game, Dots and Squares. (JP)

  11. 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

  12. Effective Stimuli for Constructing Reliable Neuron Models

    PubMed Central

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

    2011-01-01

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

  13. 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…

  14. 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.)

  15. 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

  16. 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

  17. Learning about categories that are defined by object-like stimuli despite impaired declarative memory.

    PubMed

    Reed, J M; Squire, L R; Patalano, A L; Smith, E E; Jonides, J

    1999-06-01

    Exposure to members of a category facilitates later categorization of similar but novel instances of the category. Past studies have suggested that category knowledge can be acquired implicitly and independently of declarative memory. However, these studies have relied on dot pattern stimuli that, unlike most real-world objects, are difficult to verbalize and cannot be broken into component features. It is therefore unclear how relevant such studies are to an understanding of everyday categorization. In the present studies, category learning in amnesic patients was tested with stimuli that both exhibit discrete features and are easy to describe (namely, cartoon animals). Amnesic patients were as competent as healthy volunteers in learning to categorize these animals, despite their impairment in recalling the animals' features. The results suggest that the implicit acquisition of category knowledge is a common process in everyday experience, and that it can occur whenever individuals encounter a large group of related items.

  18. [Segmentation, grouping and accentuation during stimuli perception].

    PubMed

    Sokolov, E N; Nezlina, N I

    2009-01-01

    The paper is concerned with grouping, segmentation and accentuation occurring in the processes of stimuli perception. An universal model of these events is based on vector coding in neuronal networks. Grouping is unification of objects or events into collections according to their similarity. Segmentation is separation of such groups up to small ensembles of units. In neuroscience grouping and segmentation are regarded as referred to neural mechanisms underlying perceptual and semantic processes resulting in a phenomenal attachment or separation. It is assumed that stimuli in neuronal nets are encoded by combinations of excitations of cardinal neurons constituting excitation vectors. Differences among stimuli are formed as absolute values of their excitation vector differences. The more different are stimuli the separate are their perceptual and semantic representations. The more similar are respective stimuli, the less is their separation. It suggests that stimuli having similar excitation vectors would be grouped together. On the contrary stimuli with opposed excitation vectors would be segmented and pushed to different ensembles. The vector encoding is expressed also for location in space. Thus spatial separation of objects is increasing with the increasing of their spatial excitation vector differences. The universal principle of vector encoding of differences can be illustrated by color contrast: differences of contrast colors rise with increase of their excitation vector differences. Objects having similar excitation vectors constitute a group accentuated due to summation of their excitation vectors. Groups of objects characterized by different excitation vectors are mutually accentuated by a contrast mechanism. A plastic accentuation depends on novelty of stimulation being habituated during repeated stimulus presentations.

  19. Short term memory for tactile stimuli.

    PubMed

    Gallace, Alberto; Tan, Hong Z; Haggard, Patrick; Spence, Charles

    2008-01-23

    Research has shown that unreported information stored in rapidly decaying visual representations may be accessed more accurately using partial report than using full report procedures (e.g., [Sperling, G., 1960. The information available in brief visual presentations. Psychological Monographs, 74, 1-29.]). In the 3 experiments reported here, we investigated whether unreported information regarding the actual number of tactile stimuli presented in parallel across the body surface can be accessed using a partial report procedure. In Experiment 1, participants had to report the total number of stimuli in a tactile display composed of up to 6 stimuli presented across their body (numerosity task), or else to detect whether or not a tactile stimulus had previously been presented in a position indicated by a visual probe given at a variable delay after offset of a tactile display (i.e., partial report). The results showed that participants correctly reported up to 3 stimuli in the numerosity judgment task, but their performance was significantly better than chance when up to 5 stimuli were presented in the partial report task. This result shows that short-lasting tactile representations can be accessed using partial report procedures similar to those used previously in visual studies. Experiment 2 showed that the duration of these representations (or the time available to consciously access them) depends on the number of stimuli presented in the display (the greater the number of stimuli that are presented, the faster their representation decays). Finally, the results of a third experiment showed that the differences in performance between the numerosity judgment and partial report tasks could not be explained solely in terms of any difference in task difficulty. PMID:18083147

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

    PubMed

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

    2015-11-11

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

  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. 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.

  3. Stimuli-responsive materials in analytical separation.

    PubMed

    Lorenzo, Rosa A; Carro, Antonia M; Concheiro, Angel; Alvarez-Lorenzo, Carmen

    2015-07-01

    This review focuses on the fundamentals of stimuli-responsive materials and their applications to three common separation techniques, namely extraction, chromatography, and electrophoresis. Although still little investigated, materials that switch their affinity for the analyte on and off as a function of tiny changes in physical and biochemical variables offer relevant advantages for analyte extraction, concentration, and separation. Temperature and/or pH-responsive polymers in the form of chains or networks, which are dispersed in the sample as free entities or after being grafted onto beads (which may incorporate magnetic cores), enable quantitative capture and/or elution of the analyte under mild conditions and without needing organic solvents. Regarding liquid-chromatography separation, responsive stationary phases enable the implementation of "all-in-water" procedures in which retention times are modulated by means of temperature or pH gradients. Other stimuli that can be externally applied, for example light or magnetic fields, can also be used for efficient extraction or separation of the target substance without altering the composition of the sample matrix. Moreover, stimuli-responsiveness enables straightforward recycling of solid and/or stationary phases for a prolonged lifetime. Improved understanding of the phase transitions of stimuli-responsive materials and design of suitable formats for analytical applications should enable wider and more successful application of stimuli-responsive materials in analytical separations. PMID:25910881

  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. 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.

  6. Threat ≠ prevention, challenge ≠ promotion: the impact of threat, challenge and regulatory focus on attention to negative stimuli.

    PubMed

    Sassenberg, Kai; Sassenrath, Claudia; Fetterman, Adam K

    2015-01-01

    The purpose of the current experiment was to distinguish between the impact of strategic and affective forms of gain- and loss-related motivational states on the attention to negative stimuli. On the basis of the counter-regulation principle and regulatory focus theory, we predicted that individuals would attend more to negative than to neutral stimuli in a prevention focus and when experiencing challenge, but not in a promotion focus and under threat. In one experiment (N = 88) promotion, prevention, threat, or challenge states were activated through a memory task, and a subsequent dot probe task was administered. As predicted, those in the prevention focus and challenge conditions had an attentional bias towards negative words, but those in promotion and threat conditions did not. These findings provide support for the idea that strategic mindsets (e.g., regulatory focus) and hot emotional states (e.g., threat vs. challenge) differently affect the processing of affective stimuli.

  7. Magnitude processing in non-symbolic stimuli

    PubMed Central

    Leibovich, Tali; Henik, Avishai

    2013-01-01

    Dot arrays are often used to study basic numerical skills across cultures, species and development. Researchers investigate the ability of subjects to discriminate between dot arrays, as a function of the ratio or distance between their numerosities. Such studies have contributed significantly to the number sense theory (i.e., that humans are born with the ability to process numerosities, and share this ability with various species)—possibly the most influential theory in numerical cognition literature today. However, a dot array contains, in addition to numerosity, continuous properties such as the total surface area of the dots, their density, etc. These properties are highly correlated with numerosity and therefore might influence participants' performance. Different ways in which different studies choose to deal with this confound sometimes lead to contradicting results, and in our opinion, do not completely eliminate the confound. In this work, we review these studies and suggest several possible reasons for the contradictions in the literature. We also suggest that studying continuous properties, instead of just trying to control them, may contribute to unraveling the building blocks of numerical abilities. PMID:23805121

  8. Structural analysis of site-controlled InAs/InP quantum dots

    NASA Astrophysics Data System (ADS)

    Fain, B.; Elvira, D.; Le Gratiet, L.; Largeau, L.; Beaudoin, G.; Troadec, D.; Abram, I.; Beveratos, A.; Robert-Philip, I.; Patriarche, G.; Sagnes, I.

    2011-11-01

    We present atomic-scale characterization of site-controlled InAs/InP(001) quantum dots grown by metal-organic chemical vapor deposition using nano-area selective area growth. We have developed for this purpose a process combining e-beam lithography, inductively coupled-plasma etching and focused ion beam etching to isolate a few quantum dots. The size, the shape and the composition of the quantum dots are investigated by Scanning Transmission Electron Microscopy. A comparison with the well-known single self-assembled quantum dots highlights the specificities of our growth mode compared to the Stranski-Krastanov growth mode.

  9. 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

  10. Verbal Establishing Stimuli: Testing the Motivative Effect of Stimuli in a Derived Relation with Consequences

    ERIC Educational Resources Information Center

    Ju, Winifred C.; Hayes, Steven C.

    2008-01-01

    The present study examined whether the presentation of stimuli in equivalence relations with consequences increases the operant behavior that produces these consequences. In Experiment 1, both normal words and experimentally trained equivalence stimuli did so with young children. In Experiment 2, results were similar with college students. Here, a…

  11. Stark effect in ensembles of polar (0001) Al{sub 0.5}Ga{sub 0.5}N/GaN quantum dots and comparison with semipolar (11−22) ones

    SciTech Connect

    Leroux, M.; Brault, J.; Kahouli, A.; Damilano, B.; Mierry, P. de; Korytov, M.; Maghraoui, D.; Kim, Je-Hyung; Cho, Yong-Hoon

    2014-07-21

    This work presents a continuous-wave photoluminescence study of Al{sub 0.5}Ga{sub 0.5}N/GaN quantum dots grown by ammonia-assisted molecular beam epitaxy on sapphire, either on the wurtzite polar (0001) or the semipolar (11−22) plane. Due to interface polarization discontinuities, the polar dots are strongly red-shifted by the Stark effect and emit in the visible range. Carrier injection screening of the polarization charges has been studied. A model relying on average dot heights and dot height variances, as measured by transmission electron microscopy, is proposed. It can account for the injection dependent luminescence energies and efficiencies. The electric field discontinuity deduced from the fittings is in good agreement with theoretical expectations for our barrier composition. On the contrary, semipolar quantum dot ensembles always emit above the gap of GaN strained to Al{sub 0.5}Ga{sub 0.5}N. Their luminescence linewidth is significantly lower than that of polar ones, and their energy does not shift with injection. Our study then confirms the expected strong decrease of the Stark effect for (11−22) grown (Al,Ga)N/GaN heterostructures.

  12. Electrocortical evidence for rapid allocation of attention to threat in the dot-probe task.

    PubMed

    Kappenman, Emily S; MacNamara, Annmarie; Proudfit, Greg Hajcak

    2015-04-01

    Threatening stimuli have been shown to preferentially capture attention using a range of tasks and measures. However, attentional bias to threat has not typically been found in unselected individuals using behavioral measures in the dot-probe task, one of the most common ways of examining attention to threat. The present study leveraged event-related potentials (ERPs) in conjunction with behavioral measures in the dot-probe task to examine whether more direct measures of attention might reveal an attentional bias to threat in unselected individuals. As in previous dot-probe studies, we found no evidence of an attentional bias to threat using reaction time; additionally, this measure exhibited poor internal reliability. In contrast, ERPs revealed an initial shift of attention to threat-related stimuli, reflected by the N2pc, which showed moderate internal reliability. However, there was no evidence of sustained engagement with the threat-related stimuli, as measured by the late positive potential (LPP). Together, these results demonstrate that unselected individuals do initially allocate attention to threat in the dot-probe task, and further, that this bias is better characterized by neural measures of attention than traditional behavioral measures. These results have implications for the study of attention to threat in both unselected and anxious populations.

  13. Potential bronchoconstrictor stimuli in acid fog.

    PubMed

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

  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. 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.

  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. 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.

  19. Responsiveness of human nasal mucosa to trigeminal stimuli depends on the site of stimulation.

    PubMed

    Frasnelli, Johannes; Heilmann, Stefan; Hummel, Thomas

    2004-05-13

    There is evidence that functionally different areas can be distinguished within the nasal mucosa with regard to stimulation site and stimulus properties. The aim of the present study was the comparison of electrophysiological and psychophysical measures obtained in response to mechanical and chemosomatosensory stimulation of two different regions of the nasal mucosa. A total of 40 volunteers participated in this study (age range 21-36 years). Chemosomatosensory event-related potentials (ERPs) were recorded using gaseous CO2 as stimulant, while somatosensory ERPs were recorded in response to intranasal mechanical stimuli (air puffs). Stimuli were released to the anterior portion and to the posterior portion of the nasal cavity. A significant interaction between stimulus properties and site of stimulation could be detected after analysis of ERP parameters and intensity ratings. Thus, the chemosensory stimulus was perceived as stronger in the anterior portion of the nasal cavity whereas this was not the case for mechanosensory stimuli. In addition, mechanosensory stimuli were found to evoke ERPs with shorter latencies. These results underline the idea that the respiratory mucosa should not be seen as a homogeneous tissue. It exhibits varying sensitivities to trigeminal stimulation depending on stimulus quality and site of stimulation. Hence, perception of chemosensory stimuli seems to be most accurate in the anterior portion of the nasal cavity, while sensitivity to mechanical stimuli appears to be highest in the posterior portion. In addition, these differences within the respiratory mucosa may contribute to differences in the perception of orthonasal and retronasal odorous stimulation.

  20. Matching- and nonmatching-to-sample concept learning in rats using olfactory stimuli.

    PubMed

    April, L Brooke; Bruce, Katherine; Galizio, Mark

    2011-09-01

    Previous research has shown that rats can learn matching-to-sample relations with olfactory stimuli; however, the specific characteristics of this relational control are unclear. In Experiment 1, 6 rats were trained to either match or nonmatch to sample in a modified operant chamber using common household spices as olfactory stimuli. After matching or nonmatching training with 10 exemplars, the contingencies were reversed with five new stimuli such that subjects trained on matching were shifted to nonmatching and vice versa. Following these reversed contingencies, the effects of the original training persisted for many trials with new exemplars. In Experiment 2, 9 rats were trained with matching procedures in an arena that provided for 18 different spatial locations for comparison stimuli. Five subjects were trained with differential reinforcement outcomes and 4 with only one type of reinforcer. Differential outcomes and multiple exemplars facilitated learning, and there was strong evidence for generalization to new stimuli for most rats that acquired several conditional discriminations. Performances with novel samples were generally above chance, but rarely reached the high levels obtained during baseline with well-trained stimulus relations. However, taken together, the data from the two experiments extend previous work, show that rats can learn both match and nonmatch relations with different experimental protocols, and demonstrate generalization to novel sample stimuli.

  1. Appetitive responses to computer-generated visual stimuli by the praying mantis Sphodromantis lineola (Burr.).

    PubMed

    Prete, F R; Mahaffey, R J

    1993-01-01

    Tethered adult female praying mantises, Sphodromantis lineola (Burr.), were presented with various computer-generated visual stimuli that moved against patterned or homogeneous white backgrounds in predetermined patterns and at predetermined speeds. The degrees to which the stimulus configurations elicited appetitive behaviors (attempting to approach and/or striking) indicated the relative degrees to which the stimuli were classified as prey. Mantises readily struck at cartoon "crickets" that subtended visual angles as great as 24.5 deg x 62.5 deg, but response rate was suppressed if the stimuli were superimposed on horizontally moving patterned backgrounds. Mantises also displayed appetitive behaviors to moving black squares (edge lengths = 10-47 deg) that moved in predetermined "erratic" paths; however, their response rates were affected by several factors: (1) response rate declined as edge length increased over 10 deg; (2) striking was emitted to stimuli viewed from 23 mm (but not farther) away; and (3) both stimulus displacement rate (distance moved between video frames) and apparent speed (video frame rate) dramatically affected the releasing strength of the stimuli. Finally, mantises responded appetitively to random dot patterns moving synchronously against identically patterned backgrounds and to pairs of black squares moving synchronously against a white background. However, in the latter case, response rate declined as the squares were moved farther apart horizontally or vertically. These and previous results from our laboratory on mantises are congruent with behavioral results obtained from other insects such as flies (Diptera) and dragon flies (Odonata) and suggest that there are neuroanatomical similarities between these groups. PMID:8338803

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

    PubMed

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

    2012-01-01

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

  3. 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.

  4. Influence of recall procedures on the modality effect with numbers and enumerated stimuli.

    PubMed

    Gibbons, Jeffrey A; Velkey, Andrew K; Partin, Kathren T

    2008-01-01

    Experiment 1 extended J. S. Nairne and W. L. McNabb's (1985) counting procedure for presenting numerical stimuli to examine the modality effect. The present authors presented participants with dots and beeps and instructed participants to count the items to derive to-be-remembered numbers. In addition, the authors presented numbers as visual and auditory symbols, and participants recalled items by using free-serial written recall. Experiment 1 demonstrated primacy effects, recency effects, and modality effects for visual and auditory symbols and for counts of dots and beeps. Experiment 2 replicated the procedure in Experiment 1 using strict-serial written recall instead of free-serial written recall. The authors demonstrated primacy and recency effects across all 4 presentation conditions and found a modality effect for numbers that the authors presented as symbols. However, the authors found no modality effect when they presented numbers as counts of beeps and dots. The authors discuss the implications of the results in terms of methods for testing modality effects.

  5. Towards Engineered Energy Flows in Quantum Dot Assemblies

    NASA Astrophysics Data System (ADS)

    Crooker, Scott A.

    2003-03-01

    Communication, coupling, and coherence between quantum dots are central themes in numerous scientific efforts of present physical and technological interest. In the limit of large numbers of coupled dots, colloidal semiconductor nanocrystal quantum dots (NQDs) are promising building blocks for the bottom-up assembly of macroscopic Â"artificial materialsÂ" having engineered functionality. Although NQDs offer size-tunable optical properties and ease of chemical manipulation into structures of varied complexity, strong inter-dot coupling (e.g., via electron tunneling) requires close proximity and a high degree of structural order, conditions which are difficult to achieve in practice. In this work [1] we investigate an alternative approach involving NQD coupling via long-range dipolar interactions, which allow inter-dot communication via resonant (Förster) energy transfer. We present studies of the dynamics of resonant energy transfer in monodisperse, mixed-size, and energy gradient (layered) assemblies of CdSe NQDs. Time- and spectrally-resolved photoluminescence data directly reveal the energy-dependent transfer rate of excitons from smaller to larger dots, showing sub-nanosecond energy transfer directly across a large tens-of-meV energy gap (i.e., between dots of disparate size). Results from layered NQD assemblies demonstrate unidirectional energy flows, a first step towards artificial light-harvesting structures. In comparison with some of Nature's most efficient energy transfer complexes -- chlorophylls -- the data suggest that inter-dot energy transfer can approach picosecond time scales in structurally optimized systems. [1] S. A. Crooker, J. A. Hollingsworth, S. Tretiak, and V. I. Klimov, Phys. Rev. Lett. v89, p186802 (2002).

  6. 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.

  7. 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

  8. 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.

  9. Quantum Dots as Cellular Probes

    SciTech Connect

    Alivisatos, A. Paul; Gu, Weiwei; Larabell, Carolyn

    2004-09-16

    Robust and bright light emitters, semiconductor nanocrystals[quantum dots (QDs)] have been adopted as a new class of fluorescent labels. Six years after the first experiments of their uses in biological applications, there have been dramatic improvements in understanding surface chemistry, biocompatibility, and targeting specificity. Many studies have shown the great potential of using quantum dots as new probes in vitro and in vivo. This review summarizes the recent advances of quantum dot usage at the cellular level, including immunolabeling, cell tracking, in situ hybridization, FRET, in vivo imaging, and other related technologies. Limitations and potential future uses of quantum dot probes are also discussed.

  10. Self-assembly drives quantum dot photoluminescence.

    PubMed

    Plain, J; Sonnefraud, Y; Viste, P; Lérondel, G; Huant, S; Royer, P

    2009-03-01

    Engineering the spectral properties of quantum dots can be achieved by a control of the quantum dots organization on a substrate. Indeed, many applications of quantum dots as LEDs are based on the realization of a 3D architecture of quantum dots. In this contribution, we present a systematic study of the quantum dot organization obtained on different chemically modified substrates. By varying the chemical affinity between the quantum dots and the substrate, the quantum dot organization is strongly modified from the 2D monolayer to the 3D aggregates. Then the photoluminescence of the different obtained samples has been systematically studied and correlated with the quantum dot film organization. We clearly show that the interaction between the substrate and the quantum dot must be stronger than the quantum dot-quantum dot interaction to avoid 3D aggregation and that these organization strongly modified the photoluminescence of the film rather than intrinsic changes of the quantum dot induced by pure surface chemistry.

  11. 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.

  12. Photonic water dynamically responsive to external stimuli.

    PubMed

    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

  13. 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.

  14. 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.

  15. 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

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

    PubMed Central

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

    2013-01-01

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

  17. Observing of chain-schedule stimuli.

    PubMed

    Slezak, Jonathan M; Anderson, Karen G

    2014-06-01

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

  18. Anagrus breviphragma Soyka Short Distance Search Stimuli

    PubMed Central

    Chiappini, Elisabetta; Berzolla, Alessia; Oppo, Annalisa

    2015-01-01

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

  19. 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. PMID:25201983

  20. Stimuli-responsive polymersomes for cancer therapy.

    PubMed

    Thambi, Thavasyappan; Park, Jae Hyung; Lee, Doo Sung

    2016-01-01

    Cancer is the leading cause of mortality and remains a major challenge for modern chemotherapy. Recent advances in cancer therapy have made a modest impact on patient survival. Nanomedicine represents an innovative field with significant potential to improve cancer treatment. Nanomedicine utilizes numerous nanoconstructs, including polymersomes, micelles, and drug conjugates, to deliver therapeutic agents at the target site of interest. In particular, polymeric vesicles, also known as polymersomes, are self-assembled amphiphilic polymers in which an aqueous compartment is enclosed by a thick bilayer membrane. Unlike liposomes, polymersomes consist of high-molecular-weight amphiphilic polymer analogues. Since polymersomes are prepared using synthetic amphiphilic polymers, the bilayer membrane thickness can be readily altered by tuning the molecular weight of hydrophobic blocks. As a consequence, the polymersomes prepared from high-molecular-weight amphiphiles strengthen their membranes, making them inherently more stable than liposomes. The intriguing aggregation of polymersomes offers numerous advantages, including stability, tunable membrane properties, and the capability of encapsulating hydrophilic and hydrophobic agents. Owing to these properties, polymersomes are attractive candidates for various applications such as drug delivery, gene therapy, and tissue engineering. Although these properties have placed polymersomes at the forefront of drug delivery applications, to attain an enhanced therapeutic effect polymersomes are supposed to rapidly release the drug at the target site. To fulfill this requirement, stimuli-responsive polymersomes that respond to various internal or external stimuli have been developed. This review focuses on recently developed stimuli-responsive polymersomes and their potential application in cancer therapy.

  1. 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.

  2. 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.

  3. Finding Areas on Dot Paper

    ERIC Educational Resources Information Center

    Pagni, David L.

    2007-01-01

    This article contains investigative activities to assist students in constructing formulas out of an understanding of the area of geometric shapes. Included with this article are a "Finding Areas on Square Dot Paper Activity Sheet" and a "Finding Areas on Triangle Dot Paper Activity Sheet." (Contains 1 table and 11 figures.)

  4. 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

  5. Quantum dot cascade laser

    PubMed Central

    2014-01-01

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

  6. Visualization Dot Com

    SciTech Connect

    Bethel, Wes

    2000-02-09

    In this article, we explore the seemingly well-worn subject of distance-based, or remote visualization. Current practices in remote visualization tend to clump into two broad categories. One approach, which we'll call render-remote, is to render an image remotely, then transmit the data to the user. Another option, render-local, transfers raw data to the user, where it is then visualized and rendered on the local workstation. With advances in networking and graphics technology, we can explore a class of approaches from a new, third category. With this third category, which we'll called shared, or ''dot com'' visualization, we stand to reap the best of both worlds; minimized data transfers and workstation-accelerated rendering. We will describe a prototype system called Visapult currently under development at Lawrence Berkeley National Laboratory (LBNL) that strikes such a balance, achieving a blended, scalable visualization tool. ''Dot com'' visualization means that remote and local resources collaborate and negotiate, combining capabilities to produce a final product.

  7. Selective attentional processing to fall-relevant stimuli among older adults who fear falling.

    PubMed

    Brown, Lesley A; White, Patti; Doan, Jonathan B; de Bruin, Natalie

    2011-05-01

    Fear of falling is known to affect more than half of community-dwelling older adults over 60 years of age. This fear is associated with physical and psychological effects that increase the risk of falling. The authors' theory is that attentional processing biases may exist in this population that serve to perpetuate fear of falling and subsequently increase fall risk. As a starting point in testing this proposition, the authors examined selective attentional processing bias to fall-relevant stimuli among older adults. Thirty older adult participants (M(age) = 70.8 ± 5.8), self-categorized to be Fearful of Falling (FF, n = 15) or Non-Fearful of Falling (NF, n = 15) completed a visual dot-probe paradigm to determine detection latencies to fall-threatening and general-threat stimuli. Attentional processing was defined using three index scores: attentional bias, congruency index, and incongruency index. Bias indicates capture of attention, whereas congruency and incongruency imply vigilance and disengagement difficulty, respectively. Both groups showed an attentional bias to fall-threat words but those who were fearful of falling also showed an incongruency effect for fall-threat words. These findings confirm that selective attentional processing profiles for fall-relevant stimuli differ between older adults who exhibit fear of falling and those who do not have this fear. Moreover, in accordance with current interpretations of selective attentional processing, the incongruency effect noted among fall-fearful older adults presents a possibility for a difficulty disengaging from fall-threatening stimuli.

  8. Children's Preference for Stimuli Associated with Being Imitated.

    ERIC Educational Resources Information Center

    Parton, David A.; Priefert, Maria J.

    Forty-eight preschool children were run under a classical conditioning paradigm in which some neutral stimuli were repeatedly associated with an adult matching the behavior of the subject, and other neutral stimuli were associated with the same adult mismatching the behavior of the subject. Preference for the stimuli associated with being matched…

  9. 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…

  10. 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

  11. 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.

  12. 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

  13. Mimicking biophysical stimuli within bone tumor microenvironment*

    PubMed Central

    Marturano-Kruik, A.; Yeager, K.; Bach, D.; Villasante, A.; Cimetta, E.; Vunjak-Novakovic, G.

    2016-01-01

    In vivo, cells reside in a complex environment regulating their fate and function. Most of this complexity is lacking in standard in vitro models, leading to readouts falling short of predicting the actual in vivo situation. The use of engineering tools, combined with deep biological knowledge, leads to the development and use of bioreactors providing biologically sound niches. Such bioreactors offer new tools for biological research, and are now also entering the field of cancer research. Here we present the development and validation of a modular bioreactor system providing: (i) high throughput analyses, (ii) a range of biological conditions, (iii) high degree of control, and (iv) application of physiological stimuli to the cultured samples. The bioreactor was used to engineer a three-dimensional (3D) tissue model of cancer, where the effects of mechanical stimulation on the tumor phenotype were evaluated. Mechanical stimuli applied to the engineered tumor model activated the mechanotransduction machinery and resulted in measurable changes of mRNA levels towards a more aggressive tumor phenotype. PMID:26737062

  14. Dynamic stimuli: accentuating aesthetic preference biases.

    PubMed

    Friedrich, Trista E; Harms, Victoria L; Elias, Lorin J

    2014-01-01

    Despite humans' preference for symmetry, artwork often portrays asymmetrical characteristics that influence the viewer's aesthetic preference for the image. When presented with asymmetrical images, aesthetic preference is often given to images whose content flows from left-to-right and whose mass is located on the right of the image. Cerebral lateralization has been suggested to account for the left-to-right directionality bias; however, the influence of cultural factors, such as scanning habits, on aesthetic preference biases is debated. The current research investigates aesthetic preference for mobile objects and landscapes, as previous research has found contrasting preference for the two image types. Additionally, the current experiment examines the effects of dynamic movement on directionality preference to test the assumption that static images are perceived as aesthetically equivalent to dynamic images. After viewing mirror-imaged pairs of pictures and videos, right-to-left readers failed to show a preference bias, whereas left-to-right readers preferred stimuli with left-to-right directionality regardless of the location of the mass. The directionality bias in both reading groups was accentuated by the videos, but the bias was significantly stronger in left-to-right readers. The findings suggest that scanning habits moderate the leftward bias resulting from hemispheric specialization and that dynamic stimuli further fluent visual processing.

  15. Escape from serial stimuli leading to food

    PubMed Central

    Dinsmoor, James A.; Lee, Diana M.; Brown, Marceline M.

    1986-01-01

    If the functional relations governing the strength of a conditioned reinforcer correspond to those obtained with other Pavlovian procedures (e.g., Kaplan, 1984), the termination of stimuli appearing early in the interval between successive food deliveries should be reinforcing. During initial training we presented four key colors, followed by food, in a recurrent sequence to each of 6 pigeons. This established a baseline level of autoshaped pecking. In later sessions, we terminated each of these colors or only the first color for a brief period following each peck, replacing the original color with a standard substitute to avoid darkening the key. Pecking decreased in the presence of the last color in the sequence but increased in the presence of the first. In accord with contemporary models of Pavlovian conditioning, these and other data suggest that the behavioral effects of stimuli in a chain may be better understood in terms of what each stimulus predicts, as measured by relative time to the terminal reinforcer, than in the exclusively positive terms of the traditional formulation (Skinner, 1938). The same model may also account for the initial pause under fixed-interval and fixed-ratio schedules of reinforcement. PMID:16812462

  16. Illusory movement of dotted lines

    PubMed Central

    Ito, Hiroyuki; Anstis, Stuart; Cavanagh, Patrick

    2013-01-01

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

  17. Dual-monitor deterministic hardware for visual stimuli generation in neuroscience experiments.

    PubMed

    Gazziro, Mario; Almeida, Lirio

    2010-01-01

    This article describes the development of a dual-monitor visual stimulus generator that is used in neuroscience experiments with invertebrates such as flies. The experiment consists in the visualization of two fixed images that are displaced horizontally according to the stimulus data. The system was developed using off-the-shelf FPGA kits and it is capable of displaying 640x480 pixels with 256 intensity levels at 200 frames per second (FPS) on each monitor. A Raster plot of the experiment with the superimposed stimuli was generated as the result of this work. A novel architecture was developed, using the same DOT Clock for both monitors, and its implementation generates a perfect synchronism in both devices.

  18. Dual-monitor deterministic hardware for visual stimuli generation in neuroscience experiments.

    PubMed

    Gazziro, Mario; Almeida, Lirio

    2010-01-01

    This article describes the development of a dual-monitor visual stimulus generator that is used in neuroscience experiments with invertebrates such as flies. The experiment consists in the visualization of two fixed images that are displaced horizontally according to the stimulus data. The system was developed using off-the-shelf FPGA kits and it is capable of displaying 640x480 pixels with 256 intensity levels at 200 frames per second (FPS) on each monitor. A Raster plot of the experiment with the superimposed stimuli was generated as the result of this work. A novel architecture was developed, using the same DOT Clock for both monitors, and its implementation generates a perfect synchronism in both devices. PMID:21096378

  19. Acquisition of matching-to-sample performance in rats using visual stimuli on nose keys.

    PubMed

    Iversen, I H

    1993-05-01

    Steady and blinking white lights were projected on three nose keys arranged horizontally on one wall. The procedure was a conditional discrimination with a sample stimulus presented on the middle key and comparison stimuli on the side keys. Three rats acquired simultaneous "identity matching." Accuracy reached 80% in about 25 sessions and 90% or higher after about 50 sessions. Acquisition progressed through several stages of repeated errors, alteration between comparison keys from trial to trial, preference of specific keys or stimuli, and a gradual lengthening of strings of consecutive trials with correct responses. An analysis of the acquisition curves for individual trial configurations indicated that the matching-to-sample performance possibly consisted of separate discriminations. PMID:8315365

  20. 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.

  1. The development of quantum dot calibration beads and quantitative multicolor bioassays in flow cytometry and microscopy.

    PubMed

    Wu, Yang; Campos, Samuel K; Lopez, Gabriel P; Ozbun, Michelle A; Sklar, Larry A; Buranda, Tione

    2007-05-15

    The use of fluorescence calibration beads has been the hallmark of quantitative flow cytometry. It has enabled the direct comparison of interlaboratory data as well as quality control in clinical flow cytometry. In this article, we describe a simple method for producing color-generalizable calibration beads based on streptavidin functionalized quantum dots. Based on their broad absorption spectra and relatively narrow emission, which is tunable on the basis of dot size, quantum dot calibration beads can be made for any fluorophore that matches their emission color. In an earlier publication, we characterized the spectroscopic properties of commercial streptavidin functionalized dots (Invitrogen). Here we describe the molecular assembly of these dots on biotinylated beads. The law of mass action is used to readily define the site densities of the dots on the beads. The applicability of these beads is tested against the industry standard, namely commercial fluorescein calibration beads. The utility of the calibration beads is also extended to the characterization surface densities of dot-labeled epidermal growth factor ligands as well as quantitative indicators of the binding of dot-labeled virus particles to cells.

  2. Exposure to oscillating magnetic fields influences sensitivity to electrical stimuli. I. Experiments on pigeons.

    PubMed

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

    1995-01-01

    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 behavioral patterns.

  3. 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.

  4. Quantum dots: Rethinking the electronics

    NASA Astrophysics Data System (ADS)

    Bishnoi, Dimple

    2016-05-01

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

  5. Stimuli dependent impedance of conductive magnetorheological elastomers

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

  6. Termination of pinned spirals by local stimuli

    NASA Astrophysics Data System (ADS)

    Chen, Jiang-Xing; Guo, Ming-Ming; Ma, Jun

    2016-02-01

    The termination of pinned spirals on a defect by means of local stimuli is studied. On a completely unexcitable defect, the elimination process is discussed and its corresponding mechanism is presented. Especially, the mechanism of unpinning spirals on a partially unexcitable defect, which has not been investigated so far, is explored. With fixed pacing frequency ω L , there exists a maximal radius R max above which the pinned spiral cannot be removed. It is found that the value of R max does not increase as ω L in a dynamical regime, forming a platform in the R\\textit{max}\\text-ωL curves. Based on analyzing the dispersion relation on the spiral tip around the obstacle, the underlying mechanism is clarified. Also, it is found that when multiple spirals are pinned, the value of R max decreases on a partially unexcitable defect while the change is very slight on a completely unexcitable one.

  7. Working memory of emotional stimuli: Electrophysiological characterization.

    PubMed

    Kessel, Dominique; García-Rubio, María J; González, E Kirstin; Tapia, Manuel; López-Martín, Sara; Román, Francisco J; Capilla, Almudena; Martínez, Kenia; Colom, Roberto; Carretié, Luis

    2016-09-01

    Memorizing emotional stimuli in a preferential way seems to be one of the adaptive strategies brought on by evolution for supporting survival. However, there is a lack of electrophysiological evidence on this bias in working memory. The present study analyzed the influence of emotion on the updating component of working memory. Behavioral and electrophysiological indices were measured from a 3-back task using negative, neutral, and positive faces. Electrophysiological data evidenced an emotional influence on the working memory sensitive P3 component, which presented larger amplitudes for negative matching faces compared to neutral ones. This effect originated in the superior parietal cortex, previously reported to be involved in N-back tasks. Additionally, P3 results showed a correlation with reaction times, where higher amplitudes were associated with faster responses for negative matching faces. These findings indicate that electrophysiological measures seem to be very suitable indices of the emotional influence on working memory.

  8. MULTIFUNCTIONAL AND STIMULI-SENSITIVE PHARMACEUTICAL NANOCARRIERS

    PubMed Central

    Torchilin, Vladimir

    2011-01-01

    Currently used pharmaceutical nanocarriers, such as liposomes, micelles, and polymeric nanoparticles, demonstrate a broad variety of useful properties, such as longevity in the body; specific targeting to certain disease sites; enhanced intracellular penetration; contrast properties allowing for direct carrier visualization in vivo; stimili-sensitivity, and others. Some of those pharmaceutical carriers have already made their way into clinic, while others are still under preclinical development. In certain cases, the pharmaceutical nanocarriers combine several of the listed properties. Long-circulating immunoliposomes capable of prolonged residence in the blood and specific target recognition represent one of examples of this kind. The engineering of multifunctional pharmaceutical nanocarriers combining several useful properties in one particle can significantly enhance the efficacy of many therapeutic and diagnostic protocols. This paper considers the current status and possible future directions in the emerging area of multifunctional nanocarriers with primary attention on the combination of such properties as longevity, targetability, intracellular penetration, contrast loading, and stimuli sensitivity. PMID:18977297

  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. Quantum Dots in Cell Biology

    PubMed Central

    Barroso, Margarida M.

    2011-01-01

    Quantum dots are semiconductor nanocrystals that have broad excitation spectra, narrow emission spectra, tunable emission peaks, long fluorescence lifetimes, negligible photobleaching, and ability to be conjugated to proteins, making them excellent probes for bioimaging applications. Here the author reviews the advantages and disadvantages of using quantum dots in bioimaging applications, such as single-particle tracking and fluorescence resonance energy transfer, to study receptor-mediated transport. PMID:21378278

  11. A procedure for generating differential "sample" responding without different exteroceptive stimuli.

    PubMed Central

    Lionello-DeNolf, Karen M; Urcuioli, Peter J

    2003-01-01

    Sidman (1994, 2000) suggested that responses as well as stimuli can join equivalence classes, a hypothesis difficult to test because differential responding typically requires different stimuli. The present experiments describe a procedure with pigeons that avoids this potential confounding effect. In Experiment 1, spacing two responses 3 s apart (a differential-reinforcement-of-low-rate [DRL] schedule) to a white stimulus on some trials produced food or the comparison stimuli in a matching task, whereas pecking 10 or more times with no temporal restrictions (a fixed-ratio [FR] schedule) produced the same effect on other trials. Completing the alternative (unscheduled) requirement terminated the white stimulus and repeated the trial. Following such errors, pigeons learned to switch to the alternative response pattern on the repeat trials. In addition, the correct response pattern functioned as a conditional cue for comparison choice. In Experiment 2, mixed DRL-FR training was preceded by two-sample/two-alternative matching-to-sample with DRL and FR sample-response requirements. In a subsequent transfer test in which the correct response pattern to white served as the sample, pigeons preferentially chose the comparison previously reinforced following that pattern in the baseline task. This "unsignaled response" procedure may be useful for assessing whether differential responses can be members of acquired equivalence classes. PMID:12696739

  12. 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.

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

    PubMed

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

    1989-01-01

    Two experiments were conducted in order to investigate the possible effects of X-inactivation (Lyon, 1961) on female carriers of colorblindness. The results of the first experiment, like those of Grützner et al. (1976), were consistent with the prediction of the Lyon (1961) hypothesis that the retinas of female carriers are composed of mosaic patches of colorblind and normal areas. In this first experiment, rows and columns of colored spots were presented tachistoscopically, and subjects were asked to identify the colors of the spots. In the second experiment, plates from the Ishihara test of colorblindness were presented tachistoscopically and subjects were asked to identify the number which was embedded in the pattern of colored dots. Both experiments support the Lyon hypothesis in that female carriers were found to have more difficulty in perceiving patterns of colored stimuli than did control subjects, and they suggest that the amount of time that a carrier has to scan colored stimuli plays an important role in her ability to accurately perceive them. PMID:2800352

  14. Stimuli-Responsive Materials for Controlled Release of Theranostic Agents

    PubMed Central

    Wang, Yucai; Shim, Min Suk; Levinson, Nathanael S.; Sung, Hsing-Wen

    2014-01-01

    Stimuli-responsive materials are so named because they can alter their physicochemical properties and/or structural conformations in response to specific stimuli. The stimuli can be internal, such as physiological or pathological variations in the target cells/tissues, or external, such as optical and ultrasound radiations. In recent years, these materials have gained increasing interest in biomedical applications due to their potential for spatially and temporally controlled release of theranostic agents in response to the specific stimuli. This article highlights several recent advances in the development of such materials, with a focus on their molecular designs and formulations. The future of stimuli-responsive materials will also be explored, including combination with molecular imaging probes and targeting moieties, which could enable simultaneous diagnosis and treatment of a specific disease, as well as multi-functionality and responsiveness to multiple stimuli, all important in overcoming intrinsic biological barriers and increasing clinical viability. PMID:25477774

  15. Gating of attention towards food stimuli in binge eating disorder.

    PubMed

    Schmitz, Florian; Naumann, Eva; Biehl, Stefanie; Svaldi, Jennifer

    2015-12-01

    Cognitive models of eating disorders propose that attentional biases for disorder-relevant stimuli contribute to eating disorder pathology. Empirical evidence of a contribution of attentional biases for binge eating disorder (BED) is still scarce. The aim of the present study was to assess attention engagement towards, and disengagement from, food stimuli in overweight females with BED (n = 25) and a group of overweight and obese women without BED (OW; n = 30). Participants completed a rapid serial visual presentation (RSVP) paradigm with food and neutral words as target stimuli. This task can be used to decompose an attentional bias for food stimuli into its stimulus engagement and stimulus disengagement components. Findings indicate that facilitated stimulus engagement for food stimuli over neutral stimuli was more pronounced in the BED group compared to the OW group. Conversely, there were no substantial disengagement effects in either group. Thereby, results support the idea that early attentional processes are biased in BED.

  16. Gating of attention towards food stimuli in binge eating disorder.

    PubMed

    Schmitz, Florian; Naumann, Eva; Biehl, Stefanie; Svaldi, Jennifer

    2015-12-01

    Cognitive models of eating disorders propose that attentional biases for disorder-relevant stimuli contribute to eating disorder pathology. Empirical evidence of a contribution of attentional biases for binge eating disorder (BED) is still scarce. The aim of the present study was to assess attention engagement towards, and disengagement from, food stimuli in overweight females with BED (n = 25) and a group of overweight and obese women without BED (OW; n = 30). Participants completed a rapid serial visual presentation (RSVP) paradigm with food and neutral words as target stimuli. This task can be used to decompose an attentional bias for food stimuli into its stimulus engagement and stimulus disengagement components. Findings indicate that facilitated stimulus engagement for food stimuli over neutral stimuli was more pronounced in the BED group compared to the OW group. Conversely, there were no substantial disengagement effects in either group. Thereby, results support the idea that early attentional processes are biased in BED. PMID:26212270

  17. Quantum dot loaded immunomicelles for tumor imaging

    PubMed Central

    2010-01-01

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

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

    PubMed Central

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

    2015-01-01

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

  19. 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. PMID:27397012

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

    PubMed

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

    2016-08-26

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

  1. 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.

  2. 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…

  3. Methodological Issues in the Study of Age Differences in Infants' Attention to Stimuli Varying in Movement and Complexity.

    ERIC Educational Resources Information Center

    Ames, Elinor W.; Silfen, Carole K.

    Pioneering research has shown that infants are capable of perceptual discrimination and has provided some indication of the nature of the discrimination; that is, what stimuli are differentiable. Studies have demonstrated that significant effects exist, in stimulus-pair comparisons, for age of infant, speed of movement of stimulus during…

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

    PubMed

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

    2014-09-01

    The cerebral cortex responds to stimuli of a wide range of intensities. Previous studies have demonstrated that undetectably weak somatosensory stimuli cause a functional deactivation or inhibition in somatosensory cortex. In the present study, we tested whether invisible visual stimuli lead to similar responses, indicated by an increase in EEG alpha-band power-an index of cortical excitability. We presented subliminal and supraliminal visual stimuli after estimating each participant's detection threshold. Stimuli consisted of peripherally presented small circular patches that differed in their contrast to a background consisting of a random white noise pattern. We demonstrate that subliminal and supraliminal stimuli each elicit specific neuronal response patterns. Supraliminal stimuli evoked an early, strongly phase-locked lower-frequency response representing the evoked potential and induced a decrease in alpha-band power from 400 ms on. By contrast, subliminal visual stimuli induced an increase of non-phase-locked power around 300 ms that was maximal within the alpha-band. This response might be due to an inhibitory mechanism, which reduces spurious visual activation that is unlikely to result from external stimuli. PMID:24872526

  5. 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

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

    PubMed

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

    2014-09-01

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

  7. Predator and heterospecific stimuli alter behaviour in cattle.

    PubMed

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

    2009-05-01

    Wild and domestic ungulates modify their behaviour in the presence of olfactory and visual cues of predators but investigations have not exposed a domestic species to a series of cues representing various predators and other ungulate herbivores. We used wolf (Canis lupus), mountain lion (Puma concolor), and mule deer (Odocoileus hemionus) stimuli (olfactory and visual), and a control (no stimuli) to experimentally test for differences in behaviour of cattle (Bos taurus) raised in Arizona. We measured (1) vigilance, (2) foraging rates, (3) giving up density (GUD) of high quality foods and (4) time spent in high quality forage locations in response to location of stimuli treatments. In general, we found a consistent pattern in that wolf and deer treatments caused disparate results in all 4 response variables. Wolf stimuli significantly increased cattle vigilance and decreased cattle foraging rates; conversely, deer stimuli significantly increased cattle foraging rate and increased cattle use of high quality forage areas containing stimuli. Mountain lion stimuli did not significantly impact any of the 4 response variables. Our findings suggest that domestic herbivores react to predatory stimuli, can differentiate between stimuli representing two predatory species, and suggest that cattle may reduce antipredatory behaviour when near heterospecifics. PMID:19429201

  8. 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.

  9. Happiness increases distraction by auditory deviant stimuli.

    PubMed

    Pacheco-Unguetti, Antonia Pilar; Parmentier, Fabrice B R

    2016-08-01

    Rare and unexpected changes (deviants) in an otherwise repeated stream of task-irrelevant auditory distractors (standards) capture attention and impair behavioural performance in an ongoing visual task. Recent evidence indicates that this effect is increased by sadness in a task involving neutral stimuli. We tested the hypothesis that such effect may not be limited to negative emotions but reflect a general depletion of attentional resources by examining whether a positive emotion (happiness) would increase deviance distraction too. Prior to performing an auditory-visual oddball task, happiness or a neutral mood was induced in participants by means of the exposure to music and the recollection of an autobiographical event. Results from the oddball task showed significantly larger deviance distraction following the induction of happiness. Interestingly, the small amount of distraction typically observed on the standard trial following a deviant trial (post-deviance distraction) was not increased by happiness. We speculate that happiness might interfere with the disengagement of attention from the deviant sound back towards the target stimulus (through the depletion of cognitive resources and/or mind wandering) but help subsequent cognitive control to recover from distraction. PMID:26302716

  10. 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.

  11. Stereotypic vision: how stereotypes disambiguate visual stimuli.

    PubMed

    Correll, Joshua; Wittenbrink, Bernd; Crawford, Matthew T; Sadler, Melody S

    2015-02-01

    Three studies examined how participants use race to disambiguate visual stimuli. Participants performed a first-person-shooter task in which Black and White targets appeared holding either a gun or an innocuous object (e.g., a wallet). In Study 1, diffusion analysis (Ratcliff, 1978) showed that participants rapidly acquired information about a gun when it appeared in the hands of a Black target, and about an innocuous object in the hands of a White target. For counterstereotypic pairings (armed Whites, unarmed Blacks), participants acquired information more slowly. In Study 2, eye tracking showed that participants relied on more ambiguous information (measured by visual angle from fovea) when responding to stereotypic targets; for counterstereotypic targets, they achieved greater clarity before responding. In Study 3, participants were briefly exposed to targets (limiting access to visual information) but had unlimited time to respond. In spite of their slow, deliberative responses, they showed racial bias. This pattern is inconsistent with control failure and suggests that stereotypes influenced identification of the object. All 3 studies show that race affects visual processing by supplementing objective information. PMID:25603373

  12. 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

  13. Anchoring in Numeric Judgments of Visual Stimuli.

    PubMed

    Langeborg, Linda; Eriksson, Mårten

    2016-01-01

    This article investigates effects of anchoring in age estimation and estimation of quantities, two tasks which to different extents are based on visual stimuli. The results are compared to anchoring in answers to classic general knowledge questions that rely on semantic knowledge. Cognitive load was manipulated to explore possible differences between domains. Effects of source credibility, manipulated by differing instructions regarding the selection of anchor values (no information regarding anchor selection, information that the anchors are randomly generated or information that the anchors are answers from an expert) on anchoring were also investigated. Effects of anchoring were large for all types of judgments but were not affected by cognitive load or by source credibility in either one of the researched domains. A main effect of cognitive load on quantity estimations and main effects of source credibility in the two visually based domains indicate that the manipulations were efficient. Implications for theoretical explanations of anchoring are discussed. In particular, because anchoring did not interact with cognitive load, the results imply that the process behind anchoring in visual tasks is predominantly automatic and unconscious. PMID:26941684

  14. Anchoring in Numeric Judgments of Visual Stimuli.

    PubMed

    Langeborg, Linda; Eriksson, Mårten

    2016-01-01

    This article investigates effects of anchoring in age estimation and estimation of quantities, two tasks which to different extents are based on visual stimuli. The results are compared to anchoring in answers to classic general knowledge questions that rely on semantic knowledge. Cognitive load was manipulated to explore possible differences between domains. Effects of source credibility, manipulated by differing instructions regarding the selection of anchor values (no information regarding anchor selection, information that the anchors are randomly generated or information that the anchors are answers from an expert) on anchoring were also investigated. Effects of anchoring were large for all types of judgments but were not affected by cognitive load or by source credibility in either one of the researched domains. A main effect of cognitive load on quantity estimations and main effects of source credibility in the two visually based domains indicate that the manipulations were efficient. Implications for theoretical explanations of anchoring are discussed. In particular, because anchoring did not interact with cognitive load, the results imply that the process behind anchoring in visual tasks is predominantly automatic and unconscious.

  15. Stereotypic vision: how stereotypes disambiguate visual stimuli.

    PubMed

    Correll, Joshua; Wittenbrink, Bernd; Crawford, Matthew T; Sadler, Melody S

    2015-02-01

    Three studies examined how participants use race to disambiguate visual stimuli. Participants performed a first-person-shooter task in which Black and White targets appeared holding either a gun or an innocuous object (e.g., a wallet). In Study 1, diffusion analysis (Ratcliff, 1978) showed that participants rapidly acquired information about a gun when it appeared in the hands of a Black target, and about an innocuous object in the hands of a White target. For counterstereotypic pairings (armed Whites, unarmed Blacks), participants acquired information more slowly. In Study 2, eye tracking showed that participants relied on more ambiguous information (measured by visual angle from fovea) when responding to stereotypic targets; for counterstereotypic targets, they achieved greater clarity before responding. In Study 3, participants were briefly exposed to targets (limiting access to visual information) but had unlimited time to respond. In spite of their slow, deliberative responses, they showed racial bias. This pattern is inconsistent with control failure and suggests that stereotypes influenced identification of the object. All 3 studies show that race affects visual processing by supplementing objective information.

  16. 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

  17. Dynamic observing tonometry (DOT)

    NASA Astrophysics Data System (ADS)

    Kanngiesser, Hartmut E.; Robert, Yves C.

    1999-06-01

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

  18. 49 CFR 178.345 - General design and construction requirements applicable to Specification DOT 406 (§ 178.346), DOT...

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... applicable to Specification DOT 406 (§ 178.346), DOT 407 (§ 178.347), and DOT 412 (§ 178.348) cargo tank....345 General design and construction requirements applicable to Specification DOT 406 (§ 178.346), DOT 407 (§ 178.347), and DOT 412 (§ 178.348) cargo tank motor vehicles....

  19. 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.

  20. 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…

  1. Inhibition of premature ventricular extrastimuli by subthreshold conditioning stimuli.

    PubMed

    Skale, B T; Kallok, M J; Prystowsky, E N; Gill, R M; Zipes, D P

    1985-07-01

    The purpose of this study was to determine whether trains of subthreshold high frequency conditioning stimuli (333 Hz, 1 ms duration, 2 ms interval) delivered to the canine ventricle inhibited the response to a premature stimulus (S2) more effectively than did a single subthreshold conditioning stimulus. It was found that trains of conditioning stimuli (mean 1.21 mA) inhibited the response to S2 152 ms beyond expiration of the ventricular effective refractory period, whereas a single conditioning stimulus inhibited S2 only 20 ms or less beyond the ventricular effective refractory period. In late diastole, trains of conditioning stimuli failed to inhibit S2 when the train of stimuli caused ventricular depolarization or the latter occurred in response to the next sinus impulse. Trains of conditioning stimuli did not induce ventricular arrhythmias. Lidocaine or autonomic blockade did not alter the response to trains of conditioning stimuli. Trains of conditioning stimuli or a single conditioning stimulus inhibited the response to S2 only when they were delivered at the same electrode site. By lengthening the ventricular effective refractory period, trains of conditioning stimuli could prevent or terminate tachycardias, but this possibility is constrained, at present, by the spatial limitations of the technique.

  2. Conditional Reinforcers and Informative Stimuli in a Constant Environment

    ERIC Educational Resources Information Center

    Boutros, Nathalie; Davison, Michael; Elliffe, Douglas

    2009-01-01

    Five pigeons responded on steady-state concurrent variable-interval variable-interval schedules of food presentation in which half of the foods were removed and replaced with nonfood stimuli. Across conditions, the stimuli were either paired or unpaired with food, and the correlation between the ratio of food deliveries on the two alternatives and…

  3. 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…

  4. Logical Rules and the Classification of Integral-Dimension Stimuli

    ERIC Educational Resources Information Center

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

    2013-01-01

    A classic distinction in perceptual information processing is whether stimuli are composed of separable dimensions, which are highly analyzable, or integral dimensions, which are processed holistically. Previous tests of a set of logical-rule models of classification have shown that separable-dimension stimuli are processed serially if the…

  5. 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.

  6. 14 CFR 323.13 - DOT actions.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 4 2010-01-01 2010-01-01 false DOT actions. 323.13 Section 323.13... REGULATIONS TERMINATIONS, SUSPENSIONS, AND REDUCTIONS OF SERVICE § 323.13 DOT actions. (a) If an objection has been filed under this part, DOT will dispose of the objection by order. (b) If no objection has...

  7. 49 CFR 199.5 - DOT procedures.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 3 2010-10-01 2010-10-01 false DOT procedures. 199.5 Section 199.5 Transportation... DOT procedures. The anti-drug and alcohol programs required by this part must be conducted according to the requirements of this part and DOT Procedures. Terms and concepts used in this part have...

  8. 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

  9. Optimal Decision Stimuli for Risky Choice Experiments: An Adaptive Approach.

    PubMed

    Cavagnaro, Daniel R; Gonzalez, Richard; Myung, Jay I; Pitt, Mark A

    2013-02-01

    Collecting data to discriminate between models of risky choice requires careful selection of decision stimuli. Models of decision making aim to predict decisions across a wide range of possible stimuli, but practical limitations force experimenters to select only a handful of them for actual testing. Some stimuli are more diagnostic between models than others, so the choice of stimuli is critical. This paper provides the theoretical background and a methodological framework for adaptive selection of optimal stimuli for discriminating among models of risky choice. The approach, called Adaptive Design Optimization (ADO), adapts the stimulus in each experimental trial based on the results of the preceding trials. We demonstrate the validity of the approach with simulation studies aiming to discriminate Expected Utility, Weighted Expected Utility, Original Prospect Theory, and Cumulative Prospect Theory models. PMID:24532856

  10. Optimal Decision Stimuli for Risky Choice Experiments: An Adaptive Approach

    PubMed Central

    Cavagnaro, Daniel R.; Gonzalez, Richard; Myung, Jay I.; Pitt, Mark A.

    2014-01-01

    Collecting data to discriminate between models of risky choice requires careful selection of decision stimuli. Models of decision making aim to predict decisions across a wide range of possible stimuli, but practical limitations force experimenters to select only a handful of them for actual testing. Some stimuli are more diagnostic between models than others, so the choice of stimuli is critical. This paper provides the theoretical background and a methodological framework for adaptive selection of optimal stimuli for discriminating among models of risky choice. The approach, called Adaptive Design Optimization (ADO), adapts the stimulus in each experimental trial based on the results of the preceding trials. We demonstrate the validity of the approach with simulation studies aiming to discriminate Expected Utility, Weighted Expected Utility, Original Prospect Theory, and Cumulative Prospect Theory models. PMID:24532856

  11. 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. PMID:26179894

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

    SciTech Connect

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

    2015-03-21

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

  14. 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

  15. Attentional biases and memory for emotional stimuli in men and male rhesus monkeys.

    PubMed

    Lacreuse, Agnès; Schatz, Kelly; Strazzullo, Sarah; King, Hanna M; Ready, Rebecca

    2013-11-01

    We examined attentional biases for social and non-social emotional stimuli in young adult men and compared the results to those of male rhesus monkeys (Macaca mulatta) previously tested in a similar dot-probe task (King et al. in Psychoneuroendocrinology 37(3):396-409, 2012). Recognition memory for these stimuli was also analyzed in each species, using a recognition memory task in humans and a delayed non-matching-to-sample task in monkeys. We found that both humans and monkeys displayed a similar pattern of attentional biases toward threatening facial expressions of conspecifics. The bias was significant in monkeys and of marginal significance in humans. In addition, humans, but not monkeys, exhibited an attentional bias away from negative non-social images. Attentional biases for social and non-social threat differed significantly, with both species showing a pattern of vigilance toward negative social images and avoidance of negative non-social images. Positive stimuli did not elicit significant attentional biases for either species. In humans, emotional content facilitated the recognition of non-social images, but no effect of emotion was found for the recognition of social images. Recognition accuracy was not affected by emotion in monkeys, but response times were faster for negative relative to positive images. Altogether, these results suggest shared mechanisms of social attention in humans and monkeys, with both species showing a pattern of selective attention toward threatening faces of conspecifics. These data are consistent with the view that selective vigilance to social threat is the result of evolutionary constraints. Yet, selective attention to threat was weaker in humans than in monkeys, suggesting that regulatory mechanisms enable non-anxious humans to reduce sensitivity to social threat in this paradigm, likely through enhanced prefrontal control and reduced amygdala activation. In addition, the findings emphasize important differences in

  16. 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

  17. 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

  18. Quantum Dots for Molecular Pathology

    PubMed Central

    True, Lawrence D.; Gao, Xiaohu

    2007-01-01

    Assessing malignant tumors for expression of multiple biomarkers provides data that are critical for patient management. Quantum dot-conjugated probes to specific biomarkers are powerful tools that can be applied in a multiplex manner to single tissue sections of biopsies to measure expression levels of multiple biomarkers. PMID:17251330

  19. 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…

  20. Vertical asymmetric double quantum dots

    NASA Astrophysics Data System (ADS)

    Roßbach, R.; Reischle, M.; Beirne, G. J.; Schweizer, H.; Jetter, M.; Michler, P.

    2007-01-01

    Two layers of differently sized self-assembled InP-quantum dots (QDs) separated by a GaInP spacer layer with varying thickness were grown by metal organic vapor phase epitaxy (MOVPE). Photoluminescence measurements of the QD ensembles and of individual asymmetric double QDS show coupling due to the tunnelling of carriers.

  1. 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

  2. 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. PMID:25891121

  3. 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.

  4. Dot-ELISA in diagnosis of schistosomiasis.

    PubMed

    Madwar, M A; Hassan, M M

    1989-12-01

    One microliter of S. mansoni egg antigen was dotted directly on the nitrocellulose paper sheet acting as the adsorbent surface (9 dots/paper). The sera of 25 Egyptian patients and 15 healthy persons (2 microliters of each) were dotted over the antigen dots, then 2 ml of each of the blocking, washing, HRP-conjugated IgG and DAB adding procedures, were added over the nitrocellulose paper in the petri-dish at room temperature. An intact brown circle (by naked-eye) indicates a positive in Dot-ELISA. There is an insignificant dot colour intensities in different clinical stages of S. mansoni infected Egyptians whereas, a direct relation was obtained between egg count and the colour intensity of the dots. The test had 100% sensitivity and 86% specificity thus it appears to be useful for both laboratory and field studies. PMID:2794577

  5. Numerosity judgments for tactile stimuli distributed over the body surface.

    PubMed

    Gallace, Alberto; Tan, Hong Z; Spence, Charles

    2006-01-01

    A large body of research now supports the claim that two different and dissociable processes are involved in making numerosity judgments regarding visual stimuli: subitising (fast and nearly errorless) for up to 4 stimuli, and counting (slow and error-prone) when more than 4 stimuli are presented. We studied tactile numerosity judgments for combinations of 1-7 vibrotactile stimuli presented simultaneously over the body surface. In experiment 1, the stimuli were presented once, while in experiment 2 conditions of single presentation and repeated presentation of the stimulus were compared. Neither experiment provided any evidence for a discontinuity in the slope of either the RT or error data suggesting that subitisation does not occur for tactile stimuli. By systematically varying the intensity of the vibrotactile stimuli in experiment 3, we were able to demonstrate that participants were not simply using the 'global intensity' of the whole tactile display to make their tactile numerosity judgments, but were, instead, using information concerning the number of tactors activated. The results of the three experiments reported here are discussed in relation to current theories of counting and subitising, and potential implications for the design of tactile user interfaces are highlighted. PMID:16583769

  6. Psychophysical definition of S-cone stimuli in the macaque

    PubMed Central

    Hall, Nathan; Colby, Carol

    2013-01-01

    We used the perceptual reports of nonhuman primates to perform psychophysical calibrations of S-cone isolating stimuli. S-cone stimuli were calibrated separately at several spatial locations for each monkey. To do this we exploited the effect of transient tritanopia, which causes a selective decrease of sensitivity in the observer's S-cone channel. At the start of each transient tritanopia trial monkeys were visually adapted to a bright yellow background. This type of adaptation is known to induce transient tritanopia. Calibrated S-cone isolating stimuli were determined by finding a near S-cone stimulus whose detection threshold was maximally elevated during transient tritanopia. At the start of each control trial, monkeys were adapted to a bright white background. In these trials, monkeys' detection thresholds for near S-cone stimuli were unchanged. We found that S-cone isolating stimuli could be determined at most locations tested in each monkey. Calibrated S-cone stimuli were particular to both spatial location and animal. To understand the visual system as a whole in vivo requires physiological methods not possible in human subjects. The present results open the door to novel behavioral and physiological experiments by showing that S-cone isolating stimuli can be calibrated in monkeys. PMID:23412341

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

    SciTech Connect

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

    2014-02-14

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

  8. 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

  9. 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

  10. 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.

  11. 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. PMID:25408428

  12. 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.

  13. CLE Peptide Signaling and Crosstalk with Phytohormones and Environmental Stimuli.

    PubMed

    Wang, Guodong; Zhang, Guohua; Wu, Mengyao

    2015-01-01

    The CLE (CLAVATA3/Endosperm surrounding region-related) peptide family is one of the best-studied secreted peptide families in plants. Accumulated data have revealed that CLE genes play vital roles on stem cell homeostasis in different types of meristems. Additionally, CLE genes have been found to perform various biological roles in plant growth and development, and in response to environmental stimuli. With recent advances on our understanding of CLE peptide function, it is showing that the existence of potential crosstalks of CLE peptides with phytohormones and external stimuli. Complex interactions exist in which CLE petides coordinate with hormones to regulate plant growth and development, and in response to external stimuli. In this article, we present recent advances in cell-cell communication that is mediated by CLE peptides combining with phytohormones and external stimuli, and suggest additional Arabidopsis CLE genes that are likely to be controlled by hormones and environmental cues. PMID:26779239

  14. Do extraverts process social stimuli differently from introverts?

    PubMed Central

    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. PMID:21738558

  15. 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. PMID:24788961

  16. 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.

  17. 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.

  18. Prism adaptation contrasts perceptual habituation for repetitive somatosensory stimuli.

    PubMed

    Torta, D M; Tatu, M K; Cotroneo, D; Alamia, A; Folegatti, A; Trojan, J

    2016-03-01

    Prism adaptation (PA) is a non-invasive procedure that requires performing a visuo-motor pointing task while wearing prism goggles inducing a visual displacement of the pointed target. This procedure involves a reorganization of sensorimotor coordination, and induces long-lasting effects on numerous higher-order cognitive functions in healthy volunteers and neglect patients. Prismatic displacement (PD) of the visual field can be induced when prisms are worn but no sensorimotor task is required. In this case, it is unlikely that any subsequent reorganization takes place. The effects of PD are short-lived in the sense that they last as long as prisms are worn. In this study we aimed, to the best of our knowledge for the first time, at investigating whether PA and PD induce changes in the perception of intensity of nociceptive and non- nociceptive somatosensory stimuli. We induced, in healthy volunteers, PD (experiment 1), or PA (experiment 2) and asked participants to rate the intensity of the stimuli applied to the hand undergoing the visuo-proprioceptive conflict (experiment 1) or adaptation (experiment 2). Our results indicate that: 1) the visuo-proprioceptive conflict induced by PD does not reduce the perceived intensity of the stimuli, 2) PA prevents perceptual habituation for both nociceptive and non-nociceptive somatosensory stimuli. Moreover, to investigate the possible underlying mechanisms of the effects of PA we conducted a third experiment in which stimuli were applied both at the adapted and the non-adapted hand. In line with the results of experiment 2, we found that perceptual habituation was prevented for stimuli applied onto the adapted hand. Moreover, we observed the same finding for stimuli applied onto the non-adapted hand. This result suggests that the detention of habituation is not merely driven by changes in spatial attention allocation. Taken together, these data indicate that prisms can affect the perceived intensity of somatosensory stimuli

  19. Multisensory numerosity judgments for visual and tactile stimuli.

    PubMed

    Gallace, Alberto; Tan, Hong Z; Spence, Charles

    2007-05-01

    To date, numerosity judgments have been studied only under conditions of unimodal stimulus presentation. It is therefore unclear whether the same limitations on correctly reporting the number of unimodal visual or tactile stimuli presented in a display might be expected under conditions in which participants have to count stimuli presented simultaneously in two or more different sensory modalities. In Experiment 1, we investigated numerosity judgments using both unimodal and bimodal displays consisting of one to six vibrotactile stimuli (presented over the body surface) and one to six visual stimuli (seen on the body via mirror reflection). Participants had to count the number of stimuli regardless of their modality of presentation. Bimodal numerosity judgments were significantly less accurate than predicted on the basis of an independent modality-specific resources account, thus showing that numerosity judgments might rely on a unitary amodal system instead. The results of a second experiment demonstrated that divided attention costs could not account for the poor performance in the bimodal conditions of Experiment 1. We discuss these results in relation to current theories of cross-modal integration and to the cognitive resources and/or common higher order spatial representations possibly accessed by both visual and tactile stimuli. PMID:17727102

  20. 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

  1. Bitter Taste Stimuli Induce Differential Neural Codes in Mouse Brain

    PubMed Central

    Wilson, David M.; Boughter, John D.; Lemon, Christian H.

    2012-01-01

    A growing literature suggests taste stimuli commonly classified as “bitter” induce heterogeneous neural and perceptual responses. Here, the central processing of bitter stimuli was studied in mice with genetically controlled bitter taste profiles. Using these mice removed genetic heterogeneity as a factor influencing gustatory neural codes for bitter stimuli. Electrophysiological activity (spikes) was recorded from single neurons in the nucleus tractus solitarius during oral delivery of taste solutions (26 total), including concentration series of the bitter tastants quinine, denatonium benzoate, cycloheximide, and sucrose octaacetate (SOA), presented to the whole mouth for 5 s. Seventy-nine neurons were sampled; in many cases multiple cells (2 to 5) were recorded from a mouse. Results showed bitter stimuli induced variable gustatory activity. For example, although some neurons responded robustly to quinine and cycloheximide, others displayed concentration-dependent activity (p<0.05) to quinine but not cycloheximide. Differential activity to bitter stimuli was observed across multiple neurons recorded from one animal in several mice. Across all cells, quinine and denatonium induced correlated spatial responses that differed (p<0.05) from those to cycloheximide and SOA. Modeling spatiotemporal neural ensemble activity revealed responses to quinine/denatonium and cycloheximide/SOA diverged during only an early, at least 1 s wide period of the taste response. Our findings highlight how temporal features of sensory processing contribute differences among bitter taste codes and build on data suggesting heterogeneity among “bitter” stimuli, data that challenge a strict monoguesia model for the bitter quality. PMID:22844505

  2. 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

  3. Quantum Dot Light Emitting Diode

    SciTech Connect

    Kahen, Keith

    2008-07-31

    The project objective is to create low cost coatable inorganic light emitting diodes, composed of quantum dot emitters and inorganic nanoparticles, which have the potential for efficiencies equivalent to that of LEDs and OLEDs and lifetime, brightness, and environmental stability between that of LEDs and OLEDs. At the end of the project the Recipient shall gain an understanding of the device physics and properties of Quantum-Dot LEDs (QD-LEDs), have reliable and accurate nanocrystal synthesis routines, and have formed green-yellow emitting QD-LEDs with a device efficiency greater than 3 lumens/W, a brightness greater than 400 cd/m{sup 2}, and a device operational lifetime of more than 1000 hours. Thus the aim of the project is to break the current cost-efficiency paradigm by creating novel low cost inorganic LEDs composed of inorganic nanoparticles.

  4. 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

  5. Quantum Dot Light Emitting Diode

    SciTech Connect

    Keith Kahen

    2008-07-31

    The project objective is to create low cost coatable inorganic light emitting diodes, composed of quantum dot emitters and inorganic nanoparticles, which have the potential for efficiencies equivalent to that of LEDs and OLEDs and lifetime, brightness, and environmental stability between that of LEDs and OLEDs. At the end of the project the Recipient shall gain an understanding of the device physics and properties of Quantum-Dot LEDs (QD-LEDs), have reliable and accurate nanocrystal synthesis routines, and have formed green-yellow emitting QD-LEDs with a device efficiency greater than 3 lumens/W, a brightness greater than 400 cd/m2, and a device operational lifetime of more than 1000 hours. Thus the aim of the project is to break the current cost-efficiency paradigm by creating novel low cost inorganic LEDs composed of inorganic nanoparticles.

  6. 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

  7. Saccadic latency is modulated by emotional content of spatially filtered face stimuli.

    PubMed

    Bannerman, Rachel L; Hibbard, Paul B; Chalmers, Kirsty; Sahraie, Arash

    2012-12-01

    Models of attention and emotion assign a special status to the processing of threat. While evidence for threat-related attentional bias in highly anxious individuals is robust, effects in the normal population are mixed. An important explanation for the absence of threat-related attentional bias in nonanxious individuals may relate to the spatial frequency components of stimuli. Here we report behavioral data from two experiments examining the relationship between spatial frequency components of emotional and neutral faces and fast saccadic orienting behavior. In Experiment 1 participants had to saccade toward a single face, filtered to include mostly low, high or broad spatial frequencies (LSF, HSF or BSF), posing a fearful, happy or neutral expression presented for 20 ms in the periphery. At BSF a general emotional effect was found whereby saccadic responses were faster for fearful and happy faces relative to neutral, with no significant differences between fearful and happy faces. At LSF both fearful and happy faces had shorter saccadic latencies in comparison to neutral, demonstrating an emotional bias consistent with the BSF data. However, at LSF fearful faces resulted in significantly faster saccades than happy faces indicating that this bias was stronger for threat-related faces. There was no difference in saccadic responses between any emotions at HSF. Experiment 2 showed that the emotional bias diminished for inverted stimuli suggesting that the results were not attributable to low-level image properties. The findings suggest an overall advantage in the oculomotor system for orientation to emotional stimuli and at LSF in particular, a significantly faster localization of threat conveyed by the face stimuli in all individuals.

  8. 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.

  9. The Blue Dots Initiative and Roadmapping Exercise

    NASA Astrophysics Data System (ADS)

    Coudé du Foresto, V.

    2010-10-01

    The Blue Dots initiative (a grassroot effort to build a scientific community in Europe around the exoplanet theme) is introduced. The Blue Dots activities include the elaboration of a roadmap towards the spectroscopic characterization of habitable exoplanets, a summary of which is presented here. While the roadmap will need to be updated regularly, it is expected that the methodology developed within Blue Dots will provide a durable framework for the elaboration of future revisions.

  10. Biexciton induced refractive index changes in a semiconductor quantum dot

    NASA Astrophysics Data System (ADS)

    Shojaei, S.

    2015-06-01

    We present a detailed theoretical study of linear and third order nonlinear refractive index changes in a optically driven disk-like GaN quantum dot. In our numerical calculations, we consider the three level system containing biexciton, exciton, and ground states and use the compact density matrix formalism and iterative method to obtain refractive index changes. Variational method through effective mass approximation are employed to calculate the ground state energy of biexciton and exciton states. The evolution of refractive index changes around one, two and three photon resonance is investigated and discussed for different quantum dot sizes and light intensities. Size-dependent three-photon nonlinear refractive index change versus incident photon energy compared to that of two-photon is obtained and analyzed. As main result, we found that around resonance frequency at exciton-biexciton transition the quantum confinement has great influence on the linear change in refractive index so that for very large quantum dots, it decreases. Moreover, it was found that third order refractive index changes for three photon process is strongly dependent on QD size and light intensity. Our study reveals that considering our simple model leads to results which are in good agreement with other rare numerical results. Comparison with experimental results has been done.

  11. DOTS in China - removing barriers or moving barriers?

    PubMed

    Xu, B; Dong, H J; Zhao, Q; Bogg, L

    2006-09-01

    In 1992, China initiated its modern National TB Control Programme (NTP) with DOTS strategy through a project funded by a World Bank loan. Key motives for the revised NTP-DOTS were to reduce financial barriers to patients by removing fee charges for diagnosis and treatment, and to address regressive suppliers' incentives for appropriate referrals. This study aims to assess to what extent China's NTP subsidies are achieving the objective of removing financial barriers to care in terms of patients' expenditure. One county with NTP-DOTS - Jianhu - and one county without - Funing - were selected. A cohort of 493 tuberculosis patients newly diagnosed in 2002 was interviewed by questionnaire. The main outcome measure was tuberculosis patients' expenditure on medical care and transportation/accommodation from the onset of symptoms to treatment completion. During the follow-up period, Funing started implementing NTP-DOTS, which offered a possibility of longitudinal comparison both between counties and within county. Ninety-four per cent (465/493) of subjects were followed-up. The mean total patient's expenditure on TB medical care and transportation/accommodation before TB diagnosis was higher in Jianhu than in Funing (715 vs. 256CNY), whereas it was higher in Funing (835 vs. 157CNY) after diagnosis. After implementing NTP-DOTS in Funing, expenditure after diagnosis decreased slightly whereas expenditure before diagnosis increased remarkably. We found that the market incentive structures in the reformed health system appear to have a stronger regressive effect and may result in prolonged delays before effective treatment can be given. We believe that doctors adapt to new incentive structures, with bonus income being linked to the hospitals' fee-for-service revenue, and find new ways of keeping revenue at the old levels, which reduce or eliminate the intended effect of the subsidies. TB patients suffer a heavy economic burden even in counties where NTP-DOTS treatment is

  12. 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.

  13. Quantum dot enabled high color gamut LCDs

    NASA Astrophysics Data System (ADS)

    Chen, Jian; Kan, Shihai; Lee, Ernie; Gensler, Steve; Hartlove, Jason

    2015-03-01

    Quantum dots are a new generation of phosphor material that have high photon conversion efficiency, narrow spectral line-widths and can be continuously tuned in their emission wavelengths. Since 2013, quantum dots have been adopted by the consumer electronics industry into LCDs to significantly increase their color performance. Compared to the OLED solution, quantum dot LCDs have higher energy efficiency, larger color gamut, longer lifetime, and are offered at a fraction of the cost of OLED panels. In this paper, we demonstrate that quantum-dot based LCDs can achieve more than 90% coverage of the ultra-wide color gamut, Rec. 2020, which is the new color standard for UHDTV.

  14. Thermoelectric energy harvesting with quantum dots.

    PubMed

    Sothmann, Björn; Sánchez, Rafael; Jordan, Andrew N

    2015-01-21

    We review recent theoretical work on thermoelectric energy harvesting in multi-terminal quantum-dot setups. We first discuss several examples of nanoscale heat engines based on Coulomb-coupled conductors. In particular, we focus on quantum dots in the Coulomb-blockade regime, chaotic cavities and resonant tunneling through quantum dots and wells. We then turn toward quantum-dot heat engines that are driven by bosonic degrees of freedom such as phonons, magnons and microwave photons. These systems provide interesting connections to spin caloritronics and circuit quantum electrodynamics.

  15. 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.

  16. Differing ERP patterns caused by suction and puff stimuli.

    PubMed

    Choi, Mi-Hyun; Kim, Hyung-Sik; Baek, Ji-Hye; Lee, Jung-Chul; Park, Sung-Jun; Jeong, Ul-Ho; Gim, Seon-Young; You, Ji Hye; Kim, Sung-Pil; Lim, Dae-Woon; Kim, Hyun-Jun; Chung, Soon-Cheol

    2015-05-01

    The present study compared event-related potential (ERP) patterns for two stimuli types, puff and suction, by applying these stimuli to the fingers; ERP patterns for the two stimuli were compared at C3, an area related to somatosensory perception, and at FC5, an area related to motor function. Participants were 12 healthy males in their 20s (mean age=23.1±2.0 years). One session consisted of a Control Phase (3s), a Stimulation Phase (3s), and a Rest Phase (9s). During the Stimulation Phase, a 4-psi suction or puff stimulus was applied to the first joint of the right index finger. After completion of the session, a subjective magnitude test was presented. In all phases, electroencephalography signals were recorded. We extracted maximum positive amplitude and minimum negative amplitude as well as relevant latency values for C3 and FC5 signals. Suction and puff stimuli had similar subjective magnitude scores. For both C3 and FC5, the maximum and minimum amplitude latency was reached earlier for the suction stimulus than for the puff stimulus. In conclusion, when suction and puff stimuli of the same intensity were applied to the fingers, the suction stimulus caused a more sensitive response in the somatosensory area (C3) and motor area (FC5) than did the puff stimulus.

  17. Individual mouse taste cells respond to multiple chemical stimuli

    PubMed Central

    Caicedo, Alejandro; Kim, Kyung-Nyun; Roper, Stephen D

    2002-01-01

    Sensory organs are specialized to detect and decode stimuli in terms of intensity and quality. In the gustatory system, the process of identifying and distinguishing taste qualities (e.g. bitter versus sweet) begins in taste buds. A central question in gustatory research is how information about taste quality is extracted by taste receptor cells. For instance, whether and how individual taste cells respond to multiple chemical stimuli is still a matter for debate. A recent study showed that taste cells expressing bitter-responsive taste receptors do not also express sweet-responsive taste receptors and vice versa. These results suggest that the gustatory system may use separate cellular pathways to process bitter and sweet signals independently. Results from electrophysiological studies, however, reveal that individual taste receptor cells respond to stimuli representing multiple taste qualities. Here we used non-invasive Ca2+ imaging in slices of lingual tissue containing taste buds to address the issue of quality detection in murine taste receptor cells. We recorded calcium transients elicited by chemical stimuli representing different taste qualities (sweet, salty, sour and bitter). Many receptor cells (38 %) responded to multiple taste qualities, with some taste cells responding to both appetitive (‘sweet’) and aversive (‘bitter’) stimuli. Thus, there appears to be no strict and separate detection of taste qualities by distinct subpopulations of taste cells in peripheral gustatory sensory organs in mice. PMID:12381822

  18. 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

  19. siRNA Delivery by Stimuli-Sensitive Nanocarriers.

    PubMed

    Salzano, Giuseppina; Costa, Daniel F; Torchilin, Vladimir P

    2015-01-01

    Since its discovery in the late 1990, small interfering RNA (siRNA) have quickly crept into the biopharmaceutical research as a new and powerful tool 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, de-regulated levels of enzymes, altered redox potential and magnetic field are examples of stimuli exploit to design stimuli-sensitive nanoparticles. In this review, we discuss on recent stimulisensitive 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

  20. Quantum dot-encoded mesoporous beads with high brightness and uniformity: rapid readout using flow cytometry.

    PubMed

    Gao, Xiaohu; Nie, Shuming

    2004-04-15

    A new generation of optically encoded beads has been prepared by using mesoporous polystyrene beads and surfactant-coated semiconductor quantum dots. In comparison with nonporous beads of similar sizes and chemical compositions, the encoded porous beads are approximately 1000 times brighter and 5 times more uniform in fluorescence intensities. Using both absolute intensity and ratiometric fluorescence coding, we show that the beads can be identified with a standard flow cytometer at 1000 beads/s. This result indicates that the multiple excited-state lifetimes and relaxation pathways of quantum dots do not limit their applications in high-speed optical detection and imaging.

  1. Anticipation of emotionally aversive visual stimuli activates right insula.

    PubMed

    Simmons, Alan; Matthews, Scott C; Stein, Murray B; Paulus, Martin P

    2004-10-01

    Understanding the neural substrates of anticipation is required for a comprehensive model of the ways in which anxiety influences information processing. While it is apparent that the insula and medial frontal cortex are involved in processing anticipation of physical (i.e., painful) stimuli, their role in processing anticipation of aversive affective stimuli has yet to be determined. Twenty-eight healthy non-phobic volunteers observed aversive affective images (spiders and snakes) that were preceded by an auditory signal. The insula, dorsolateral prefrontal cortex, and parahippocampal gyrus activated during anticipation of aversive affective images. These findings indicate that common neural circuitry is involved in the anticipation of (and, perhaps, the subjective experience of anticipating) aversive affective and noxious physical stimuli. PMID:15371746

  2. 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. PMID:26683083

  3. Odor of taste stimuli in conditioned "taste" aversion learning.

    PubMed

    Capaldi, Elizabeth D; Hunter, Martin J; Privitera, Gregory J

    2004-12-01

    The present research addresses whether rats can express odor aversions to the odor of taste stimuli. In Experiment 1, saccharin or salt were either mixed in distilled water, so the rats could taste and smell them, or presented on disks attached to the tubes' metal spouts so the rats could only smell them. Aversions were established to taste stimuli under both conditions. The results of Experiment 2 indicate that conditioning was to the odor of the tastes when they were presented on disks in Experiment 1, hence both taste and odor aversions were established by means of "taste" stimuli. Taste aversion learning thus may more properly be termed flavor aversion learning, with flavor referring to both taste and odor components.

  4. 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

  5. Nitrogen-Doped Carbon Dots for "green" Quantum Dot Solar Cells.

    PubMed

    Wang, Hao; Sun, Pengfei; Cong, Shan; Wu, Jiang; Gao, Lijun; Wang, Yun; Dai, Xiao; Yi, Qinghua; Zou, Guifu

    2016-12-01

    Considering the environment protection, "green" materials are increasingly explored for photovoltaics. Here, we developed a kind of quantum dots solar cell based on nitrogen-doped carbon dots. The nitrogen-doped carbon dots were prepared by direct pyrolysis of citric acid and ammonia. The nitrogen-doped carbon dots' excitonic absorption depends on the N-doping content in the carbon dots. The N-doping can be readily modified by the mass ratio of reactants. The constructed "green" nitrogen-doped carbon dots solar cell achieves the best power conversion efficiency of 0.79 % under AM 1.5 G one full sun illumination, which is the highest efficiency for carbon dot-based solar cells.

  6. Single-dot optical emission from ultralow density well-isolated InP quantum dots

    SciTech Connect

    Ugur, A.; Hatami, F.; Masselink, W. T.; Vamivakas, A. N.; Lombez, L.; Atatuere, M.

    2008-10-06

    We demonstrate a straightforward way to obtain single well-isolated quantum dots emitting in the visible part of the spectrum and characterize the optical emission from single quantum dots using this method. Self-assembled InP quantum dots are grown using gas-source molecular-beam epitaxy over a wide range of InP deposition rates, using an ultralow growth rate of about 0.01 atomic monolayers/s, a quantum-dot density of 1 dot/{mu}m{sup 2} is realized. The resulting isolated InP quantum dots embedded in an InGaP matrix are individually characterized without the need for lithographical patterning and masks on the substrate. Such low-density quantum dots show excitonic emission at around 670 nm with a linewidth limited by instrument resolution. This system is applicable as a single-photon source for applications such as quantum cryptography.

  7. 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

  8. 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

  9. STED nanoscopy with fluorescent quantum dots

    PubMed Central

    Hanne, Janina; Falk, Henning J.; Görlitz, Frederik; Hoyer, Patrick; Engelhardt, Johann; Sahl, Steffen J.; Hell, Stefan W.

    2015-01-01

    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. PMID:25980788

  10. STED nanoscopy with fluorescent quantum dots

    NASA Astrophysics Data System (ADS)

    Hanne, Janina; Falk, Henning J.; Görlitz, Frederik; Hoyer, Patrick; Engelhardt, Johann; Sahl, Steffen J.; Hell, Stefan W.

    2015-05-01

    The widely popular class of quantum-dot molecular labels could so far not be utilized as standard fluorescent probes in STED (stimulated emission depletion) nanoscopy. This is because broad quantum-dot excitation spectra extend deeply into the spectral bands used for STED, thus compromising the transient fluorescence silencing required for attaining super-resolution. Here we report the discovery that STED nanoscopy of several red-emitting commercially available quantum dots is in fact successfully realized by the increasingly popular 775 nm STED laser light. A resolution of presently ~50 nm is demonstrated for single quantum dots, and sub-diffraction resolution is further shown for imaging of quantum-dot-labelled vimentin filaments in fibroblasts. The high quantum-dot photostability enables repeated STED recordings with >1,000 frames. In addition, we have evidence that the tendency of quantum-dot labels to blink is largely suppressed by combined action of excitation and STED beams. Quantum-dot STED significantly expands the realm of application of STED nanoscopy, and, given the high stability of these probes, holds promise for extended time-lapse imaging.

  11. 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.

  12. STED nanoscopy with fluorescent quantum dots.

    PubMed

    Hanne, Janina; Falk, Henning J; Görlitz, Frederik; Hoyer, Patrick; Engelhardt, Johann; Sahl, Steffen J; Hell, Stefan W

    2015-05-18

    The widely popular class of quantum-dot molecular labels could so far not be utilized as standard fluorescent probes in STED (stimulated emission depletion) nanoscopy. This is because broad quantum-dot excitation spectra extend deeply into the spectral bands used for STED, thus compromising the transient fluorescence silencing required for attaining super-resolution. Here we report the discovery that STED nanoscopy of several red-emitting commercially available quantum dots is in fact successfully realized by the increasingly popular 775 nm STED laser light. A resolution of presently ∼ 50 nm is demonstrated for single quantum dots, and sub-diffraction resolution is further shown for imaging of quantum-dot-labelled vimentin filaments in fibroblasts. The high quantum-dot photostability enables repeated STED recordings with >1,000 frames. In addition, we have evidence that the tendency of quantum-dot labels to blink is largely suppressed by combined action of excitation and STED beams. Quantum-dot STED significantly expands the realm of application of STED nanoscopy, and, given the high stability of these probes, holds promise for extended time-lapse imaging.

  13. 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.

  14. Orienting Toward Face-Like Stimuli in Early Childhood.

    PubMed

    Shah, Punit; Happé, Francesca; Sowden, Sophie; Cook, Richard; Bird, Geoffrey

    2015-01-01

    Newborn infants orient preferentially toward face-like or "protoface" stimuli and recent studies suggest similar reflexive orienting responses in adults. Little is known, however, about the operation of this mechanism in childhood. An attentional-cueing procedure was therefore developed to investigate protoface orienting in early childhood. Consistent with the extant literature, 5- to 6-year-old children (n = 25) exhibited orienting toward face-like stimuli; they responded faster when target location was cued by the appearance of a protoface stimulus than when location was cued by matched control patterns. The potential of this procedure to investigate the development of typical and atypical social perception is discussed. PMID:26435013

  15. CdS QDs-chitosan microcapsules with stimuli-responsive property generated by gas-liquid microfluidic technique.

    PubMed

    Chen, Yanjun; Yao, Rongyi; Wang, Yifeng; Chen, Ming; Qiu, Tong; Zhang, Chaocan

    2015-01-01

    This article describes a straightforward gas-liquid microfluidic approach to generate uniform-sized chitosan microcapsules containing CdS quantum dots (QDs). CdS QDs are encapsulated into the liquid-core of the microcapsules. The sizes of the microcapsules can be conveniently controlled by gas flow rate. QDs-chitosan microcapsules show good fluorescent stability in water, and exhibit fluorescent responses to chemical environmental stimuli. α-Cyclodextrin (α-CD) causes the microcapsules to deform and even collapse. More interestingly, α-CD induces obvious changes on the fluorescent color of the microcapsules. However, β-cyclodextrin (β-CD) has little influence on the shape and fluorescent color of the microcapsules. Based on the results of scanning electron microscopy, the possible mechanism about the effects of α-CD on the chitosan microcapsules is analyzed. These stimuli-responsive microcapsules are low-cost and easy to be prepared by gas-liquid microfluidic technique, and can be applied as a potential micro-detector to chemicals, such as CDs.

  16. Substitutional impurity in the graphene quantum dots

    NASA Astrophysics Data System (ADS)

    Sierański, K.; Szatkowski, J.

    2015-09-01

    The process of formation of the localized defect states due to substitutional impurity in sp2-bonded graphene quantum dot is considered using a simple tight-binding-type calculation. We took into account the interaction of the quantum dot atoms surrounding the substitutional impurity from the second row of elements. To saturate the external dangling sp2 orbitals of the carbon additionally 18 hydrogen atoms were introduced. The chemical formula of the quantum dot is H18C51X, where X is the symbol of substitutional atom. The position of the localized levels is determined relative to the host-atoms (C) εp energies. We focused on the effect of substitutional doping by the B, N and O on the eigenstate energies and on the total energy change of the graphene dots including for O the effect of lattice distorsion. We conclude that B, N, and O can form stable substitutional defects in graphene quantum dot.

  17. 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.

  18. Model-based clustered-dot screening

    NASA Astrophysics Data System (ADS)

    Kim, Sang Ho

    2006-01-01

    I propose a halftone screen design method based on a human visual system model and the characteristics of the electro-photographic (EP) printer engine. Generally, screen design methods based on human visual models produce dispersed-dot type screens while design methods considering EP printer characteristics generate clustered-dot type screens. In this paper, I propose a cost function balancing the conflicting characteristics of the human visual system and the printer. By minimizing the obtained cost function, I design a model-based clustered-dot screen using a modified direct binary search algorithm. Experimental results demonstrate the superior quality of the model-based clustered-dot screen compared to a conventional clustered-dot screen.

  19. Photoluminescence of a quantum-dot molecule

    SciTech Connect

    Kruchinin, Stanislav Yu.; Rukhlenko, Ivan D.; Baimuratov, Anvar S.; Leonov, Mikhail Yu.; Turkov, Vadim K.; Baranov, Alexander V.; Fedorov, Anatoly V.; Gun'ko, Yurii K.

    2015-01-07

    The coherent coupling of quantum dots is a sensitive indicator of the energy and phase relaxation processes taking place in the nanostructure components. We formulate a theory of low-temperature, stationary photoluminescence from a quantum-dot molecule composed of two spherical quantum dots whose electronic subsystems are resonantly coupled via the Coulomb interaction. We show that the coupling leads to the hybridization of the first excited states of the quantum dots, manifesting itself as a pair of photoluminescence peaks with intensities and spectral positions strongly dependent on the geometric, material, and relaxation parameters of the quantum-dot molecule. These parameters are explicitly contained in the analytical expression for the photoluminescence differential cross section derived in the paper. The developed theory and expression obtained are essential in interpreting and analyzing spectroscopic data on the secondary emission of coherently coupled quantum systems.

  20. Pigeons may not remember the stimuli that reinforced their recent behavior.

    PubMed Central

    Schaal, D W; Odum, A L; Shahan, T A

    2000-01-01

    In two experiments the conditioned reinforcing and delayed discriminative stimulus functions of stimuli that signal delays to reinforcement were studied. Pigeons' pecks to a center key produced delayed-matching-to-sample trials according to a variable-interval 60-s (or 30-s in 1 pigeon) schedule (Experiment 1) or a multiple variable-interval 20-s variable-interval 120-s schedule (Experiment 2). The trials consisted of a 2-s illumination of one of two sample key colors followed by delays ranging across phases from 0.1 to 27.0 s followed in turn by the presentation of matching and nonmatching comparison stimuli on the side keys. Pecks to the key color that matched the sample were reinforced with 4-s access to grain. Under some conditions of Experiment 1, pecks to nonmatching comparison stimuli produced a 4-s blackout and the start of the next interval. Under other conditions of Experiment 1 and each condition of Experiment 2, pecks to nonmatching stimuli had no effect and trials ended only when pigeons pecked the other, matching stimulus and received food. The functions relating pretrial response rates to delays differed markedly from those relating matching-to-sample accuracy to delays. Specifically, response rates remained relatively high until the longest delays (15.0 to 27.0 s) were arranged, at which point they fell to low levels. Matching accuracy was high at short delays, but fell to chance at delays between 3.0 and 9.0 s. In Experiment 2, both matching accuracy and response rates remained high over a wider range of delays in the variable-interval 120-s component relative to the variable-interval 20-s component. The difference in matching accuracy between the components was not due to an increased tendency in the variable-interval 20-s component toward proactive interference following short intervals. Thus, under these experimental conditions the conditioned reinforcing and the delayed discriminative functions of the sample stimulus depended on the same

  1. 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

  2. Direct interband light absorption in the cylindrical quantum dot with modified Pöschl-Teller potential

    NASA Astrophysics Data System (ADS)

    Hayrapetyan, D. B.; Kazaryan, E. M.; Tevosyan, H. Kh.

    2012-09-01

    In this paper the direct interband light absorption in cylindrical quantum dot with modified Pöschl-Teller potential made of GaAs is studied. For the regime of strong size quantization analytical expressions for the particle energy spectrum, absorption coefficient and dependencies of effective threshold frequencies of absorption on the geometrical sizes of quantum dot are obtained. The selection rules corresponding to different transitions between quantum levels are found. To facilitate the comparison of obtained results with the probable experimental data, size dispersion distribution of growing quantum dots by the geometrical sizes using two experimentally realizing distribution functions has been taken into account. Distribution functions of Lifshits-Slezov and Gaussian have been considered.

  3. 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.

  4. 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.

  5. Blood Compatibility Evaluations of Fluorescent Carbon Dots.

    PubMed

    Li, Sha; Guo, Zhong; Zhang, Yi; Xue, Wei; Liu, Zonghua

    2015-09-01

    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.

  6. Validation of an automated punctate mechanical stimuli delivery system designed for fMRI studies in rodents.

    PubMed

    Governo, Ricardo Jose Moylan; Prior, Malcolm John William; Morris, Peter Gordon; Marsden, Charles Alexander; Chapman, Victoria

    2007-06-15

    Functional magnetic resonance imaging (fMRI) is increasingly being used for animal studies studying the transmission of nociceptive information. Application of noxious mechanical stimuli is widely used for animal and human assessment of pain processing. Any accessory hardware used in animal imaging studies must, however, be sufficiently small to fit in the magnet bore diameter and be non-magnetic. We have developed a system that can apply mechanical stimuli simultaneously with fMRI. This system consists of a standardized instrument to deliver mechanical stimuli (VonFrey monofilament) and a gas-pressured mechanical transducer. These components were integrated with a computer console that controlled the period of stimuli to match acquisition scans. Preliminary experiments demonstrated that the force-stimulus transducer did not influence MRI signal to noise ratio. Mechanical stimulation of the hindpaw significantly increased blood oxygen level dependent (BOLD) signal intensity in several midbrain regions involved in the processing of nociceptive information in the rat (p<0.001, uncorrected for multiple comparisons). This system can be applied to both animal and human imaging studies and has a wide range of applications for studies of nociceptive processing. PMID:17368787

  7. 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.

  8. Neglect for low luminance contrast stimuli but not for high colour contrast stimuli: a behavioural and electrophysiological case study.

    PubMed

    Doricchi, F; Angelelli, P; De Luca, M; Spinelli, D

    1996-05-31

    We describe a patient with a right hemisphere lesion involving the frontal lobe, the post-central gyrus and the superior parietal lobule. Behavioural testing demonstrated severe left unilateral neglect to low luminance contrast stimuli, but not to high colour contrast stimuli. Evoked potentials to low contrast luminance gratings presented in the left hemifield were not reliable. However, equiluminant coloured gratings presented in the same hemifield evoked reliable electrophysiological responses, although longer in latency than those evoked in the right hemifield. These findings suggest that the patient has severe damage of the high contrast sensitivity magnocellular pathway in the right hemisphere, with minor involvement of the parvocellular pathway.

  9. Effect of shells on photoluminescence of aqueous CdTe quantum dots

    SciTech Connect

    Yuan, Zhimin; Yang, Ping

    2013-07-15

    Graphical abstract: Size-tunable CdTe coated with several shells using an aqueous solution synthesis. CdTe/CdS/ZnS quantum dots exhibited high PL efficiency up to 80% which implies the promising applications for biomedical labeling. - Highlights: • CdTe quantum dots were fabricated using an aqueous synthesis. • CdS, ZnS, and CdS/ZnS shells were subsequently deposited on CdTe cores. • Outer ZnS shells provide an efficient confinement of electron and hole inside the QDs. • Inside CdS shells can reduce the strain on the QDs. • Aqueous CdTe/CdS/ZnS QDs exhibited high stability and photoluminescence efficiency of 80%. - Abstract: CdTe cores with various sizes were fabricated in aqueous solutions. Inorganic shells including CdS, ZnS, and CdS/ZnS were subsequently deposited on the cores through a similar aqueous procedure to investigate the effect of shells on the photoluminescence properties of the cores. In the case of CdTe/CdS/ZnS quantum dots, the outer ZnS shell provides an efficient confinement of electron and hole wavefunctions inside the quantum dots, while the middle CdS shell sandwiched between the CdTe core and ZnS shell can be introduced to obviously reduce the strain on the quantum dots because the lattice parameters of CdS is situated at the intermediate-level between those of CdTe and ZnS. In comparison with CdTe/ZnS core–shell quantum dots, the as-prepared water-soluble CdTe/CdS/ZnS quantum dots in our case can exhibit high photochemical stability and photoluminescence efficiency up to 80% in an aqueous solution, which implies the promising applications in the field of biomedical labeling.

  10. Updating Positive and Negative Stimuli in Working Memory in Depression

    ERIC Educational Resources Information Center

    Levens, Sara M.; Gotlib, Ian H.

    2010-01-01

    Difficulties in the ability to update stimuli in working memory (WM) may underlie the problems with regulating emotions that lead to the development and perpetuation of mood disorders such as depression. To examine the ability to update affective material in WM, the authors had diagnosed depressed and never-disordered control participants perform…

  11. 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…

  12. 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. PMID:25487054

  13. 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.

  14. Stimuli-Responsive Nanoparticles for siRNA Delivery.

    PubMed

    Eloy, Josimar O; Petrilli, Raquel; Lopez, Renata F V; Lee, Robert J

    2015-01-01

    Nanoparticles have been extensively employed to deliver many drugs, including siRNA, for the treatment of a variety of diseases, particularly cancer. Lately, there has been a great deal of effort to design nanoparticles with materials that are able to respond to intrinsic or extrinsic stimuli for "on demand" delivery of siRNA. These nanoparticles are able to trigger siRNA release upon different stimuli, such as a pH decrease, redox gradient, enzyme, light, magnetic field, temperature, ultrasound or electric current. Frequently, the stimuli cause the nanoparticles to undergo protonation, hydrolytic breakdown or phase transition for triggered release of siRNA, resulting in decreased side effects and better therapeutic outcome. While studies have demonstrated efficient in vitro and in vivo delivery, these "smart" nanoparticles have not yet reached the clinic. In this review, we address different classes of nanoparticles, such as polyplexes, lipoplexes, liposomes, polymeric micelles, polymeric, lipid and inorganic nanoparticles, that are able to respond to specific stimuli for siRNA triggered-release, emphasizing their application and discussing the latest advances. PMID:26323434

  15. Reward contexts extend dopamine signals to unrewarded stimuli.

    PubMed

    Kobayashi, Shunsuke; Schultz, Wolfram

    2014-01-01

    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.

  16. 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…

  17. 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. PMID:27080081

  18. Stimuli-responsive polymersomes for programmed drug delivery.

    PubMed

    Meng, Fenghua; Zhong, Zhiyuan; Feijen, Jan

    2009-02-01

    In the past decade, polymersomes (also referred to as polymeric vesicles) have attracted rapidly growing interest based on their intriguing aggregation phenomena, cell and virus-mimicking dimensions and functions, as well as tremendous potential applications in medicine, pharmacy, and biotechnology. Unlike liposomes self-assembled from low molecular weight lipids, polymersomes are in general prepared from macromolecular amphiphiles of various architectures including amphiphilic diblock, triblock, graft and dendritic copolymers. Polymersomes exhibit very unique features highlighted with high stability, tunable membrane properties, versatility, and capacity of transporting hydrophilic as well as hydrophobic species such as anticancer drugs, genes, proteins, and diagnostic probes. Recently, much effort has been directed to the development of intelligent polymersomes that respond to internal or external stimuli, in particular, pH, temperature, redox potential, light, magnetic field, and ultrasound, either reversibly or nonreversibly. Stimuli-sensitive polymersomes have emerged as novel programmable delivery systems in which the release of the encapsulated contents can be readily modulated by the stimulus. The stimuli-responsive release may result in significantly enhanced therapeutic efficacy and minimized possible side effects. It is also feasible to form and disassemble polymersomes in water simply by applying an appropriate stimulus. In this article, recent advances in stimuli-sensitive polymersomes have been reviewed, and perspectives on future developments have been discussed.

  19. 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 tested the…

  20. 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…

  1. Gradient Shifts with Naturally Occurring Human Face Stimuli

    ERIC Educational Resources Information Center

    Derenne, Adam; Breitstein, R. Michael

    2006-01-01

    The present research examined stimulus generalization and gradient shifts on a dimension involving human faces. Twenty undergraduates were instructed to examine the proportion of the total face length that lay between the tip of the nose and the end of the chin. The face stimuli were images of actual people shown on a computer screen; no face was…

  2. 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…

  3. 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.

  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. Joint Control and the Selection of Stimuli from Their Description

    ERIC Educational Resources Information Center

    Lowenkron, Barry

    2006-01-01

    This research examined the role the two constituents of joint control, the tact and the echoic, play in producing accurate selections of novel stimuli in response to their spoken descriptions. Experiment 1 examined the role of tacts. In response to unfamiliar spoken descriptions, children learned to select from among six successively presented…

  6. Probability of Equivalence Formation: Familiar Stimuli and Training Sequence

    ERIC Educational Resources Information Center

    Arntzen, Erik

    2004-01-01

    The present study was conducted to show how responding in accord with equivalence relations changes as a function of position of familiar stimuli, pictures, and with the use of nonsense syllables in an MTO-training structure. Fifty college students were tested for responding in accord with equivalence in an AB, CB, DB, and EB training structure.…

  7. 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.

  8. 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

  9. Positive mood broadens visual attention to positive stimuli

    PubMed Central

    Wadlinger, Heather A.; Isaacowitz, Derek M.

    2010-01-01

    In an attempt to investigate the impact of positive emotions on visual attention within the context of Fredrickson's (1998) broaden-and-build model, eye tracking was used in two studies to measure visual attentional preferences of college students (n=58, n=26) to emotional pictures. Half of each sample experienced induced positive mood immediately before viewing slides of three similarly-valenced images, in varying central-peripheral arrays. Attentional breadth was determined by measuring the percentage viewing time to peripheral images as well as by the number of visual saccades participants made per slide. Consistent with Fredrickson's theory, the first study showed that individuals induced into positive mood fixated more on peripheral stimuli than did control participants; however, this only held true for highly-valenced positive stimuli. Participants under induced positive mood also made more frequent saccades for slides of neutral and positive valence. A second study showed that these effects were not simply due to differences in emotional arousal between stimuli. Selective attentional broadening to positive stimuli may act both to facilitate later building of resources as well as to maintain current positive affective states. PMID:20431711

  10. 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…

  11. 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…

  12. 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)

  13. Avoidance of affective pain stimuli predicts chronicity in patients with acute low back pain.

    PubMed

    Sharpe, Louise; Haggman, Sonia; Nicholas, Michael; Dear, Blake F; Refshauge, Kathryn

    2014-01-01

    This prospective study of acute and sub-acute low back pain (LBP) patients was conducted to assess whether attentional biases predicted chronic pain status 3 and 6 months later. The attentional biases of 100 LBP patients were assessed within 3 months of developing pain and 6 months later. Participants also completed measures associated with outcome at 3 assessment points: baseline, 3 and 6 months later. Current pain status was assessed at follow-ups. Patients were classified as those that met standard criteria for chronic pain or those who did not (i.e., the comparison group). At baseline, participants demonstrated a bias toward sensory pain words. However, biases toward sensory pain words did not differentiate those who subsequently developed chronic pain and those who did not at either follow-up. The same bias was observed 6 months later, but again it failed to distinguish between the chronic pain and comparison groups. However, subjects who developed chronic pain at both 3 (n=22) and 6 (n=21) months demonstrated biases away from affective pain words at baseline but not 6 months later, in comparison to other participants. These results remained significant in multivariate analyses. These findings are consistent with patterns observed in the previous research, and suggest that avoidance of emotionally laden pain-related stimuli (i.e., affective pain words) is associated with negative outcomes for LBP patients in the acute and sub-acute phase. This research suggests that attentional biases in relation to pain-related stimuli are important for the development of chronic pain, but are more complex than initially thought. PMID:24028848

  14. Two-photon absorption in CdSe colloidal quantum dots compared to organic molecules.

    PubMed

    Makarov, Nikolay S; Lau, Pick Chung; Olson, Christopher; Velizhanin, Kirill A; Solntsev, Kyril M; Kieu, Khanh; Kilina, Svetlana; Tretiak, Sergei; Norwood, Robert A; Peyghambarian, Nasser; Perry, Joseph W

    2014-12-23

    We discuss fundamental differences in electronic structure as reflected in one- and two-photon absorption spectra of semiconductor quantum dots and organic molecules by performing systematic experimental and theoretical studies of the size-dependent spectra of colloidal quantum dots. Quantum-chemical and effective-mass calculations are used to model the one- and two-photon absorption spectra and compare them with the experimental results. Currently, quantum-chemical calculations are limited to only small-sized quantum dots (nanoclusters) but allow one to study various environmental effects on the optical spectra such as solvation and various surface functionalizations. The effective-mass calculations, on the other hand, are applicable to the larger-sized quantum dots and can, in general, explain the observed trends but are insensitive to solvent and ligand effects. Careful comparison of the experimental and theoretical results allows for quantifying the range of applicability of theoretical methods used in this work. Our study shows that the small clusters can be in principle described in a manner similar to that used for organic molecules. In addition, there are several important factors (quality of passivation, nature of the ligands, and intraband/interband transitions) affecting optical properties of the nanoclusters. The larger-size quantum dots, on the other hand, behave similarly to bulk semiconductors, and can be well described in terms of the effective-mass models. PMID:25427158

  15. Neurexin/neuroligin interaction kinetics characterized by counting single cell-surface attached quantum dots.

    PubMed

    Saint-Michel, Edouard; Giannone, Grégory; Choquet, Daniel; Thoumine, Olivier

    2009-07-22

    We report what to our knowledge is a new method to characterize kinetic rates between cell-surface-attached adhesion molecules. Cells expressing specific membrane receptors are surface-labeled with quantum dots coated with their respective ligands. The progressive diminution in the total number of surface-diffusing quantum dots tracked over time collectively reflects intrinsic ligand/receptor interaction kinetics. The probability of quantum dot detachment is modeled using a stochastic analysis of bond formation and dissociation, with a small number of ligand/receptor pairs, resulting in a set of coupled differential equations that are solved numerically. Comparison with the experimental data provides an estimation of the kinetic rates, together with the mean number of ligands per quantum dot, as three adjustable parameters. We validate this approach by studying the calcium-dependent neurexin/neuroligin interaction, which plays an important role in synapse formation. Using primary neurons expressing neuroligin-1 and quantum dots coated with purified neurexin-1beta, we determine the kinetic rates between these two binding partners and compare them with data obtained using other techniques. Using specific molecular constructs, we also provide interesting information about the effects of neurexin and neuroligin dimerization on the kinetic rates. As it stands, this simple technique should be applicable to many types of biological ligand/receptor pairs.

  16. Stimuli-sensitive nanopreparations for combination cancer therapy.

    PubMed

    Jhaveri, Aditi; Deshpande, Pranali; Torchilin, Vladimir

    2014-09-28

    Nanocarriers have revolutionized drug delivery practices over the past couple of decades, primarily due to the advances in materials chemistry, nanotechnology and nanomedicine. This in turn, has spurred the development of a number of novel nanocarrier-based platforms and treatment strategies for cancer. It is now clear that to manage a disease as complex as cancer, a single or stand-alone treatment strategy may not suffice. Present day drug delivery strategies progressively lean towards "multi-pronged" combination approaches to make cancer treatments more effective. To that end, nanocarriers which simultaneously incorporate multiple drugs that affect different pathways and act through different mechanisms, or combinations of drugs with biological therapeutics like genes, antibodies, proteins or siRNAs have been the focus of recent active research. Furthermore, nanocarriers which respond to a variety of intrinsic cues afforded by the tumor microenvironment like low pH, elevated redox potential, over-expressed enzymes and hyperthermia as well as to externally applied stimuli such as magnetic field, ultrasound or light have been developed to trigger site-specific drug release. In this review, we focus specifically on nanocarriers that simultaneously exhibit stimuli-sensitivity and incorporate various combinations of conventional small molecule chemotherapeutic agents and biologics. We provide an overview of the different internal and external stimuli most relevant to cancer, and discuss selected examples of stimuli-sensitive combination nanopreparations from the recent literature with respect to each stimulus. Finally, we discuss multifunctional stimuli-sensitive nanopreparations which incorporate various combinations of drugs, biologics and targeting ligands within a single carrier that form so-called "smart" nanopreparations. PMID:24818767

  17. 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.

  18. 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

  19. 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

  20. 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. PMID:24392130

  1. 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.

  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. Quantum Dots in Gated Nanowires and Nanotubes

    NASA Astrophysics Data System (ADS)

    Churchill, Hugh Olen Hill

    This thesis describes experiments on quantum dots made by locally gating one-dimensional quantum wires. The first experiment studies a double quantum dot device formed in a Ge/Si core/shell nanowire. In addition to measuring transport through the double dot, we detect changes in the charge occupancy of the double dot by capacitively coupling it to a third quantum dot on a separate nanowire using a floating gate. We demonstrate tunable tunnel coupling of the double dot and quantify the strength of the tunneling using the charge sensor. The second set of experiments concerns carbon nanotube double quantum dots. In the first nanotube experiment, spin-dependent transport through the double dot is compared in two sets of devices. The first set is made with carbon containing the natural abundance of 12C (99%) and 13C (1%), the second set with the 99% 13C and 1% 12C. In the devices with predominantly 13C, we find evidence in spin-dependent transport of the interaction between the electron spins and the 13C nuclear spins that was much stronger than expected and not present in the 12C devices. In the second nanotube experiment, pulsed gate experiments are used to measure the timescales of spin relaxation and dephasing in a two-electron double quantum dot. The relaxation time is longest at zero magnetic field and goes through a minimum at higher field, consistent with the spin-orbit-modified electronic spectrum of carbon nanotubes. We measure a short dephasing time consistent with the anomalously strong electron-nuclear interaction inferred from the first nanotube experiment.

  4. Magnon-driven quantum dot refrigerators

    NASA Astrophysics Data System (ADS)

    Wang, Yuan; Huang, Chuankun; Liao, Tianjun; Chen, Jincan

    2015-12-01

    A new model of refrigerator consisting of a spin-splitting quantum dot coupled with two ferromagnetic reservoirs and a ferromagnetic insulator is proposed. The rate equation is used to calculate the occupation probabilities of the quantum dot. The expressions of the electron and magnon currents are obtained. The region that the system can work in as a refrigerator is determined. The cooling power and coefficient of performance (COP) of the refrigerator are derived. The influences of the magnetic field, applied voltage, and polarization of two leads on the performance are discussed. The performances of two different magnon-driven quantum dot refrigerators are compared.

  5. Clocking an Array of Quantum Dots

    NASA Astrophysics Data System (ADS)

    Khatun, Mahfuza; Mandell, Eric

    2000-10-01

    Preferred Session: Condensed Matter Physics Clocking an Array of Quantum Dots* Eric Mandell and M. Khatun, Ball State University. We report a theoretical analysis of the time-dependent electric field due to a line of charged rods. The effects of both the real and image charge are taken into account. The rods are biased electrostatically to study the dynamical behavior of an array of quantum dots. The barrier heights between the quantum dots are controlled by the electric field. *Supported in part by the Indiana Academy of Science, Center for Energy Research/Education/Services(CERES) and the Office of Academic Research and Sponsored Programs, Ball State University.

  6. Nanometer distance measurements between multicolor quantum dots.

    PubMed

    Antelman, Josh; Wilking-Chang, Connie; Weiss, Shimon; Michalet, Xavier

    2009-05-01

    Quantum dot dimers made of short double-stranded DNA molecules labeled with different color quantum dots at each end were imaged using multicolor stage-scanning confocal microscopy. This approach eliminates chromatic aberration and color registration issues usually encountered in other multicolor imaging techniques. We demonstrate nanometer accuracy in individual distance measurement by suppression of quantum dot blinking and thoroughly characterize the contribution of different effects to the variability observed between measurements. Our analysis opens the way to accurate structural studies of biomolecules and biomolecular complexes using multicolor quantum labeling.

  7. 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

  8. Electronic Structure of Few-Electron Quantum Dot Molecules

    NASA Astrophysics Data System (ADS)

    Popsueva, V.; Hansen, J. P.; Caillat, J.

    2007-12-01

    We present a study of strongly correlated few-electron quantum dots, exploring the spectra of various few-electron quantum dot molecules: a double (diatomic) structure a quadruple two-electron quantum dot, and a three-electron double dot. Electron energy spectra are computed for different values of dot separation. All spectra show clear band structures and can be understood from asymptotical properties of the system.

  9. Instability-driven quantum dots

    NASA Astrophysics Data System (ADS)

    Aqua, Jean-Noël; Frisch, Thomas

    2015-10-01

    When a film is strained in two dimensions, it can relax by developing a corrugation in the third dimension. We review here the resulting morphological instability that occurs by surface diffusion, called the Asaro-Tiller-Grinfel'd instability (ATG), especially on the paradigmatic silicon/germanium system. The instability is dictated by the balance between the elastic relaxation induced by the morphological evolution, and its surface energy cost. We focus here on its development at the nanoscales in epitaxial systems when a crystal film is coherently deposited on a substrate with a different lattice parameter, thence inducing epitaxial stresses. It eventually leads to the self-organization of quantum dots whose localization is dictated by the instability long-time dynamics. In these systems, new effects, such as film/substrate wetting or crystalline anisotropy, come into play and lead to a variety of behaviors. xml:lang="fr"

  10. Quantum dots and prion proteins

    PubMed Central

    Sobrova, Pavlina; Blazkova, Iva; Chomoucka, Jana; Drbohlavova, Jana; Vaculovicova, Marketa; Kopel, Pavel; Hubalek, Jaromir; Kizek, Rene; Adam, Vojtech

    2013-01-01

    A diagnostics of infectious diseases can be done by the immunologic methods or by the amplification of nucleic acid specific to contagious agent using polymerase chain reaction. However, in transmissible spongiform encephalopathies, the infectious agent, prion protein (PrPSc), has the same sequence of nucleic acids as a naturally occurring protein. The other issue with the diagnosing based on the PrPSc detection is that the pathological form of prion protein is abundant only at late stages of the disease in a brain. Therefore, the diagnostics of prion protein caused diseases represent a sort of challenges as that hosts can incubate infectious prion proteins for many months or even years. Therefore, new in vivo assays for detection of prion proteins and for diagnosis of their relation to neurodegenerative diseases are summarized. Their applicability and future prospects in this field are discussed with particular aim at using quantum dots as fluorescent labels. PMID:24055838

  11. Visualizing phase transition behavior of dilute stimuli responsive polymer solutions via Mueller matrix polarimetry.

    PubMed

    Narayanan, Amal; Chandel, Shubham; Ghosh, Nirmalya; De, Priyadarsi

    2015-09-15

    Probing volume phase transition behavior of superdiluted polymer solutions both micro- and macroscopically still persists as an outstanding challenge. In this regard, we have explored 4 × 4 spectral Mueller matrix measurement and its inverse analysis for excavating the microarchitectural facts about stimuli responsiveness of "smart" polymers. Phase separation behavior of thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) and pH responsive poly(N,N-(dimethylamino)ethyl methacrylate) (PDMAEMA) and their copolymers were analyzed in terms of Mueller matrix derived polarization parameters, namely, depolarization (Δ), diattenuation (d), and linear retardance (δ). The Δ, d, and δ parameters provided useful information on both macro- and microstructural alterations during the phase separation. Additionally, the two step action ((i) breakage of polymer-water hydrogen bonding and (ii) polymer-polymer aggregation) at the molecular microenvironment during the cloud point generation was successfully probed via these parameters. It is demonstrated that, in comparison to the present techniques available for assessing the hydrophobic-hydrophilic switch over of simple stimuli-responsive polymers, Mueller matrix polarimetry offers an important advantage requiring a few hundred times dilute polymer solution (0.01 mg/mL, 1.1-1.4 μM) at a low-volume format. PMID:26287499

  12. Compound stimuli in emergent stimulus relations: Extending the scope of stimulus equivalence

    PubMed Central

    Markham, Michael R.; Dougher, Michael J.

    1993-01-01

    Three experiments were conducted to investigate stimulus relations that might emerge when college students are taught relations between compound sample stimuli and unitary comparison stimuli using match-to-sample procedures. In Experiment 1, subjects were taught nine AB-C stimulus relations, then tested for the emergence of 18 AC-B and BC-A relations. All subjects showed the emergence of all tested relations. Twelve subjects participated in Experiment 2. Six subjects were taught nine AB-C relations and were then tested for symmetrical (C-AB) relations. Six subjects were taught nine AB-C and three C-D relations and were then tested for nine AB-D (transitive) relations. Five of 6 subjects demonstrated the emergence of symmetrical relations, and 6 subjects showed the emergence of transitivity. In Experiment 3, 5 college students were taught nine AB-C and three C-D relations and were then tested for nine equivalence (D-AB) relations and 18 AD-B and BD-A relations. Three subjects demonstrated all tested relations. One subject demonstrated the AD-B and BD-A relations but not the D-AB relations. One subject did not respond systematically during testing. The results of these experiments extend stimulus equivalence research to more complex cases. PMID:16812718

  13. Basic Emotions in the Nencki Affective Word List (NAWL BE): New Method of Classifying Emotional Stimuli

    PubMed Central

    Wierzba, Małgorzata; Riegel, Monika; Wypych, Marek; Jednoróg, Katarzyna; Turnau, Paweł; Grabowska, Anna; Marchewka, Artur

    2015-01-01

    The Nencki Affective Word List (NAWL) has recently been introduced as a standardized database of Polish words suitable for studying various aspects of language and emotions. Though the NAWL was originally based on the most commonly used dimensional approach, it is not the only way of studying emotions. Another framework is based on discrete emotional categories. Since the two perspectives are recognized as complementary, the aim of the present study was to supplement the NAWL database by the addition of categories corresponding to basic emotions. Thus, 2902 Polish words from the NAWL were presented to 265 subjects, who were instructed to rate them according to the intensity of each of the five basic emotions: happiness, anger, sadness, fear and disgust. The general characteristics of the present word database, as well as the relationships between the studied variables are shown to be consistent with typical patterns found in previous studies using similar databases for different languages. Here we present the Basic Emotions in the Nencki Affective Word List (NAWL BE) as a database of verbal material suitable for highly controlled experimental research. To make the NAWL more convenient to use, we introduce a comprehensive method of classifying stimuli to basic emotion categories. We discuss the advantages of our method in comparison to other methods of classification. Additionally, we provide an interactive online tool (http://exp.lobi.nencki.gov.pl/nawl-analysis) to help researchers browse and interactively generate classes of stimuli to meet their specific requirements. PMID:26148193

  14. Basic Emotions in the Nencki Affective Word List (NAWL BE): New Method of Classifying Emotional Stimuli.

    PubMed

    Wierzba, Małgorzata; Riegel, Monika; Wypych, Marek; Jednoróg, Katarzyna; Turnau, Paweł; Grabowska, Anna; Marchewka, Artur

    2015-01-01

    The Nencki Affective Word List (NAWL) has recently been introduced as a standardized database of Polish words suitable for studying various aspects of language and emotions. Though the NAWL was originally based on the most commonly used dimensional approach, it is not the only way of studying emotions. Another framework is based on discrete emotional categories. Since the two perspectives are recognized as complementary, the aim of the present study was to supplement the NAWL database by the addition of categories corresponding to basic emotions. Thus, 2902 Polish words from the NAWL were presented to 265 subjects, who were instructed to rate them according to the intensity of each of the five basic emotions: happiness, anger, sadness, fear and disgust. The general characteristics of the present word database, as well as the relationships between the studied variables are shown to be consistent with typical patterns found in previous studies using similar databases for different languages. Here we present the Basic Emotions in the Nencki Affective Word List (NAWL BE) as a database of verbal material suitable for highly controlled experimental research. To make the NAWL more convenient to use, we introduce a comprehensive method of classifying stimuli to basic emotion categories. We discuss the advantages of our method in comparison to other methods of classification. Additionally, we provide an interactive online tool (http://exp.lobi.nencki.gov.pl/nawl-analysis) to help researchers browse and interactively generate classes of stimuli to meet their specific requirements.

  15. A Novel Method of Brainstem Auditory Evoked Potentials Using Complex Verbal Stimuli

    PubMed Central

    Kouni, Sophia N; Koutsojannis, Constantinos; Ziavra, Nausika; Giannopoulos, Sotirios

    2014-01-01

    Background: The click and tone-evoked auditory brainstem responses are widely used in clinical practice due to their consistency and predictability. More recently, the speech-evoked responses have been used to evaluate subcortical processing of complex signals, not revealed by responses to clicks and tones. Aims: Disyllable stimuli corresponding to familiar words can induce a pattern of voltage fluctuations in the brain stem resulting in a familiar waveform, and they can yield better information about brain stem nuclei along the ascending central auditory pathway. Materials and Methods: We describe a new method with the use of the disyllable word “baba” corresponding to English “daddy” that is commonly used in many other ethnic languages spanning from West Africa to the Eastern Mediterranean all the way to the East Asia. Results: This method was applied in 20 young adults institutionally diagnosed as dyslexic (10 subjects) or light dyslexic (10 subjects) who were matched with 20 sex, age, education, hearing sensitivity, and IQ-matched normal subjects. The absolute peak latencies of the negative wave C and the interpeak latencies of A-C elicited by verbal stimuli “baba” were found to be significantly increased in the dyslexic group in comparison with the control group. Conclusions: The method is easy and helpful to diagnose abnormalities affecting the auditory pathway, to identify subjects with early perception and cortical representation abnormalities, and to apply the suitable therapeutic and rehabilitation management. PMID:25210677

  16. Stimuli-responsive supramolecular polymers in aqueous solution.

    PubMed

    Ma, Xiang; Tian, He

    2014-07-15

    CONSPECTUS: Aiming to construct various novel supramolecular polymeric structures in aqueous solution beyond small supramolecular self-assembly molecules and develop functional supramolecular polymeric materials, research interest on functional supramolecular polymers has been prevailing in recent years. Supramolecular polymers are formed by bridging monomers or components together via highly directional noncovalent interactions such as hydrogen bonding, hydrophobic interaction, π-π interaction, metal-ligand coordination, electrostatic interaction, and so forth. They can be easily functionalized by employing diverse building components with specific functions besides the traditional polymeric properties, a number of which are responsive to such external stimuli as pH variance, photoirradiation, chemically or electrochemically redox with the controllable conformation or construction switching, polymerization building and rebuilding, and function adjustment reversibly owing to the reversibility of noncovalent interactions. Supramolecular polymers are "soft matters" and can be functionalized with specific properties such as morphology adjustment, controllable luminescence, shape memory, self-healing, and so forth. Supramolecular polymers constructed based on macrocycle recognition and interlocked structures represent one typical branch of the supramolecular polymer family. Cyclodextrin (CD), cucurbituril (CB), and hydrophilic calixarene derivatives are usually employed to construct hydrophilic supramolecular polymers in aqueous solution. Stimuli-responsive hydrophilic supramolecular polymers, constructed in aqueous solution particularly, can be promising candidates for mimicking biocompatible or vital functional materials. This Account mainly focuses on the recent stimuli-responsive supramolecular polymers based on the host-guest interaction in aqueous solution. We describe the hydrophilic supramolecular polymers constructed via hydrophobic effects, electrostatic

  17. Detecting collinear dots in noise.

    PubMed

    Tripathy, S P; Mussap, A J; Barlow, H B

    1999-01-01

    We estimated the sensitivity for detecting a row of collinear target elements (usually dots) by measuring the maximum density of randomly positioned noise elements that allowed 75% correct detection of the orientation of alignment (binary choice: horizontal versus vertical) of the target elements. We varied the number of target elements, their mode of generation, and their accuracy of positioning. As reported previously (Moulden (1994) Higher-order processing in the visual system. Ciba Foundation Symposium 184. Chichester: Wiley), target detection improved rapidly until the number of target elements reached about seven, and then improved more slowly beyond this point. However, this break was reduced (and often removed entirely) when the target array was formed by repositioning pre-existing noise elements lying close to the target location, rather than by superimposition of additional target elements onto the noise array. This almost linear slope of improvement, coupled with the observation that target detection was disrupted more by random jitter of target elements at right angles to their axis of alignment than by jittering along this axis, argues against a two-stage process of perceptual grouping (Moulden, 1994) and supports instead an explanation based on the operation of a single mechanism. This single mechanism explanation is further supported by the observation that intrinsic positional uncertainty (estimated from the results of jitter experiments) was independent of target element number. Additional experiments showed that target detection is facilitated by aperiodic noise dots that fall close to the target axis. The results are discussed in relation to alternative explanations of perceptual grouping.

  18. 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

  19. 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

  20. On wildebeests and humans: the preferential detection of negative stimuli.

    PubMed

    Dijksterhuis, Ap; Aarts, Henk

    2003-01-01

    On the basis of a functional perspective, we hypothesized that negative stimuli are detected faster than positive stimuli. In Experiment 1, participants were subliminally presented with positive and negative words or with no words at all. After each presentation, participants were asked whether they had seen a word. They detected negative words more accurately than positive words. In Experiment 2, participants were subliminally presented with negative or positive words. After each presentation, they were asked whether the presented word was positive or negative. Negative words were correctly categorized more often than positive words. Experiment 3 showed that although participants correctly categorized negative words more often than positive words. they could not guess the meaning of the words better than would be expected by chance. The results are discussed against the background of recent findings on basic affective processes. PMID:12564748

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

    PubMed

    Torchilin, Vladimir P

    2014-11-01

    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

  2. The automatic orienting of attention to goal-relevant stimuli.

    PubMed

    Vogt, Julia; De Houwer, Jan; Moors, Agnes; Van Damme, Stefaan; Crombez, Geert

    2010-05-01

    It is often assumed that attention is automatically allocated to stimuli relevant to one's actual goals. However, the existing evidence for this idea is limited in several ways. We investigated whether words relevant to a person's current goal influence the orienting of attention even when an intention to attend to the goal-relevant stimuli is not present. In two experiments, participants performed a modified spatial cueing paradigm combined with a second task that induced a goal. The results of the experiments showed that the induced goal led to the orientation of attention to goal-relevant words in the spatial cueing task. This effect was not found for words semantically related to the goal-relevant words. The results provide evidence for motivational accounts of attention, which state that the automatic allocation of attention is guided by the current goals of a person.

  3. Interactions of auditory and visual stimuli in space and time.

    PubMed

    Recanzone, Gregg H

    2009-12-01

    The nervous system has evolved to transduce different types of environmental energy independently, for example light energy is transduced by the retina whereas sound energy is transduced by the cochlea. However, the neural processing of this energy is necessarily combined, resulting in a unified percept of a real-world object or event. These percepts can be modified in the laboratory, resulting in illusions that can be used to probe how multisensory integration occurs. This paper reviews studies that have utilized such illusory percepts in order to better understand the integration of auditory and visual signals in primates. Results from human psychophysical experiments where visual stimuli alter the perception of acoustic space (the ventriloquism effect) are discussed, as are experiments probing the underlying cortical mechanisms of this integration. Similar psychophysical experiments where auditory stimuli alter the perception of visual temporal processing are also described. PMID:19393306

  4. 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. PMID:23426680

  5. Functional stimuli responsive hydrogel devices by self-folding

    NASA Astrophysics Data System (ADS)

    Yoon, ChangKyu; Xiao, Rui; Park, JaeHyun; Cha, Jaepyeong; Nguyen, Thao D.; Gracias, David H.

    2014-09-01

    We describe a photolithographic approach to create functional stimuli responsive, self-folding, microscale hydrogel devices using thin, gradient cross-linked hinges and thick, fully cross-linked panels. The hydrogels are composed of poly (N-isopropylacrylamide-co-acrylic acid) (pNIPAM-AAc) with reversible stimuli responsive properties just below physiological temperatures. We show that a variety of three-dimensional structures can be formed and reversibly actuated by temperature or pH. We experimentally characterized the swelling and mechanical properties of pNIPAM-AAc and developed a finite element model to rationalize self-folding and its variation with hinge thickness and swelling ratio. Finally, we highlight applications of this approach in the creation of functional devices such as self-folding polymeric micro-capsules, untethered micro-grippers and thermally steered micro-mirror systems.

  6. 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.

  7. 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.

  8. Nanomaterials: Earthworms lit with quantum dots

    NASA Astrophysics Data System (ADS)

    Tilley, Richard D.; Cheong, Soshan

    2013-01-01

    Yeast, bacteria and fungi have been used to synthesize a variety of nanocrystals. Now, the metal detoxification process in the gut of an earthworm is exploited to produce biocompatible cadmium telluride quantum dots.

  9. Luminescence blinking of a reacting quantum dot.

    PubMed

    Routzahn, Aaron L; Jain, Prashant K

    2015-04-01

    Luminescence blinking is an inherent feature of optical emission from individual fluorescent molecules and quantum dots. There have been intense efforts, although not with complete resolution, toward the understanding of the mechanistic origin of blinking and also its mitigation in quantum dots. As an advance in our microscopic view of blinking, we show that the luminescence blinking of a quantum dot becomes unusually heavy in the temporal vicinity of a reactive transformation. This stage of heavy blinking is a result of defects/dopants formed within the quantum dot on its path to conversion. The evolution of blinking behavior along the reaction path allows us to measure the lifetime of the critical dopant-related intermediate in the reaction. This work establishes luminescence blinking as a single-nanocrystal level probe of catalytic, photocatalytic, and electrochemical events occurring in the solid-state or on semiconductor surfaces.

  10. Quantum dots: A charge for blinking

    NASA Astrophysics Data System (ADS)

    Krauss, Todd D.; Peterson, Jeffrey J.

    2012-01-01

    No accepted description of luminescent blinking in quantum dots is currently available. Now, experiments probing the connection between charge and fluorescence intensity fluctuations unveil an unexpected source of blinking, significantly advancing our fundamental understanding of this baffling phenomenon.

  11. 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.

  12. 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. PMID:20099307

  13. 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.

  14. An fMRI Study Of The Perception Of Noisy Visual Stimuli

    NASA Astrophysics Data System (ADS)

    Simonotto, E.; Spanó, F.; Riani, M.; Ferrari, A.; Levrero, F.; Pilot, A.; Vitali, P.; Parodi, R. C.; Renzetti, P.; Sardanelli, F.; Twitty, J.; Moss, F.

    1998-03-01

    We have demonstrated that Stochastic Resonance can be used as a tool to quantify the ability of human observers to detect details in a noisy visual stimulation(E. Simonotto, et al., Phys. Rev. Lett.) 78, 1186 (1997). This technique gives consistently reproducible results and allows a quantitative comparison between different subjects. We have begun fMRI studies to investigate the underlying processes used by the visual system to extract information from noisy visual stimulations. Healthy human observers in a MRI scanner are presented animations treated with and without the addition of noise and threshold filtering. The functional areas activated during the noisy visual stimulation are compared to the case of noiseless visual stimuli. Preliminary results will be given.

  15. 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.

  16. Feedback and Feedforward Control of Frequency Tuning to Naturalistic Stimuli

    PubMed Central

    Chacron, Maurice J.; Maler, Leonard; Bastian, Joseph

    2016-01-01

    Sensory neurons must respond to a wide variety of natural stimuli that can have very different spatiotemporal characteristics. Optimal responsiveness to subsets of these stimuli can be achieved by devoting specialized neural circuitry to different stimulus categories, or, alternatively, this circuitry can be modulated or tuned to optimize responsiveness to current stimulus conditions. This study explores the mechanisms that enable neurons within the initial processing station of the electrosensory system of weakly electric fish to shift their tuning properties based on the spatial extent of the stimulus. These neurons are tuned to low frequencies when the stimulus is restricted to a small region within the receptive field center but are tuned to higher frequencies when the stimulus impinges on large regions of the sensory epithelium. Through a combination of modeling and in vivo electrophysiology, we reveal the respective contributions of the filtering characteristics of extended dendritic structures and feedback circuitry to this shift in tuning. Our results show that low-frequency tuning can result from the cable properties of an extended dendrite that conveys receptor-afferent information to the cell body. The shift from low- to high-frequency tuning, seen in response to spatially extensive stimuli, results from increased wide-band input attributable to activation of larger populations of receptor afferents, as well as the activation of parallel fiber feedback from the cerebellum. This feedback provides a cancellation signal with low-pass characteristics that selectively attenuates low-frequency responsiveness. Thus, with spatially extensive stimuli, these cells preferentially respond to the higher-frequency components of the receptor-afferent input. PMID:15944380

  17. Brain response to visual sexual stimuli in homosexual pedophiles

    PubMed Central

    Schiffer, Boris; Krueger, Tillmann; Paul, Thomas; de Greiff, Armin; Forsting, Michael; Leygraf, Norbert; Schedlowski, Manfred; Gizewski, Elke

    2008-01-01

    Objective The neurobiological mechanisms of deviant sexual preferences such as pedophilia are largely unknown. The objective of this study was to analyze whether brain activation patterns of homosexual pedophiles differed from those of a nonpedophile homosexual control group during visual sexual stimulation. Method A consecutive sample of 11 pedophile forensic inpatients exclusively attracted to boys and 12 age-matched homosexual control participants from a comparable socioeconomic stratum underwent functional magnetic resonance imaging during a visual sexual stimulation procedure that used sexually stimulating and emotionally neutral photographs. Sexual arousal was assessed according to a subjective rating scale. Results In contrast to sexually neutral pictures, in both groups sexually arousing pictures having both homosexual and pedophile content activated brain areas known to be involved in processing visual stimuli containing emotional content, including the occipitotemporal and prefrontal cortices. However, during presentation of the respective sexual stimuli, the thalamus, globus pallidus and striatum, which correspond to the key areas of the brain involved in sexual arousal and behaviour, showed significant activation in pedophiles, but not in control subjects. Conclusions Central processing of visual sexual stimuli in homosexual pedophiles seems to be comparable to that in nonpedophile control subjects. However, compared with homosexual control subjects, activation patterns in pedophiles refer more strongly to subcortical regions, which have previously been discussed in the context of processing reward signals and also play an important role in addictive and stimulus-controlled behaviour. Thus future studies should further elucidate the specificity of these brain regions for the processing of sexual stimuli in pedophilia and should address the generally weaker activation pattern in homosexual men. PMID:18197269

  18. 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.

  19. 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. PMID:20117179

  20. 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…

  1. 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

  2. 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.

  3. 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.

  4. Renormalization in Periodically Driven Quantum Dots.

    PubMed

    Eissing, A K; Meden, V; Kennes, D M

    2016-01-15

    We report on strong renormalization encountered in periodically driven interacting quantum dots in the nonadiabatic regime. Correlations between lead and dot electrons enhance or suppress the amplitude of driving depending on the sign of the interaction. Employing a newly developed flexible renormalization-group-based approach for periodic driving to an interacting resonant level we show analytically that the magnitude of this effect follows a power law. Our setup can act as a non-Markovian, single-parameter quantum pump. PMID:26824557

  5. Electron Spin Dynamics in Semiconductor Quantum Dots

    SciTech Connect

    Marie, X.; Belhadj, T.; Urbaszek, B.; Amand, T.; Krebs, O.; Lemaitre, A.; Voisin, P.

    2011-07-15

    An electron spin confined to a semiconductor quantum dot is not subject to the classical spin relaxation mechanisms known for free carriers but it strongly interacts with the nuclear spin system via the hyperfine interaction. We show in time resolved photoluminescence spectroscopy experiments on ensembles of self assembled InAs quantum dots in GaAs that this interaction leads to strong electron spin dephasing.

  6. Electrophysiological responses to bitter stimuli in primate cortex.

    PubMed

    Scott, T R; Giza, B K; Yan, J

    1998-11-30

    Studies investigating fine details of gustatory coding in the domain of each basic taste quality have been completed for sweet, salt, and sour stimuli. In the present experiment, we used chemicals that humans describe as predominantly bitter. We recorded the activity of 50 taste neurons in insular cortex of two cynomolgus macaques. Stimuli were water, fruit juice, glucose, NaCl, HCl, and 16 bitter solutions. In a multidimensional taste space the 16 bitter stimuli formed a coherent cluster composed of three main subgroups: (1) QHCl, phenylalanine, theophylline, caffeine, propyl-thiouracil (PROP), and phenylthiocarbamide (PTC), all of which humans describe as rather purely bitter, (2) MgCl2, CaCl2, NH4Cl, and arginine, which humans describe as salty-bitter, and (3) urea, cysteine, and vitamin B1, which are described as sour-bitter. Vitamin B2, histidine and nicotine were in the center of the bitter cluster. Human descriptions of taste qualities conformed well to the presumed quality of each stimulus as inferred from its position in the multidimensional space (MDS), reinforcing the use of the macaque as a neural model for human gustation.

  7. 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. PMID:15176615

  8. 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

  9. Resistance to extinction following habituation to behaviourally disruptive novel stimuli.

    PubMed

    Haggbloom, S J; Brewer, V R

    1989-11-01

    Three experiments tested the prediction, derived from generalized frustration theory (Amsel, 1972), that habituation to behaviourally disruptive stimuli increases resistance to extinction in the runway. In each experiment, rats received initial consistent reinforcement (CRF) training and then either continued CRF (Groups C), partial reinforcement (PRF) training (Groups P), or CRF accompanied by presentations of a novel tactile, tone, or obstacle stimulus (Groups D) in Experiments 1-3, respectively. PRF increased resistance to extinction whether non-reinforcement disrupted behaviour (Experiment 1) or not (Experiments 2 and 3). The tactile and obstacle stimuli very substantially disrupted behaviour, and the tone produced a modest disruption of behaviour. All subjects habituated to the disruptive effects of these stimuli, but Group D was not more resistant to extinction than Group C in any experiment. The results suggest that non-reinforcement has unique stimulus properties, a consequence of which is that habituation to other sources of disruptive stimulation does not promote responding to non-reinforcement in extinction.

  10. Endogenous sequential cortical activity evoked by visual stimuli.

    PubMed

    Carrillo-Reid, Luis; Miller, Jae-Eun Kang; Hamm, Jordan P; Jackson, Jesse; Yuste, Rafael

    2015-06-10

    Although the functional properties of individual neurons in primary visual cortex have been studied intensely, little is known about how neuronal groups could encode changing visual stimuli using temporal activity patterns. To explore this, we used in vivo two-photon calcium imaging to record the activity of neuronal populations in primary visual cortex of awake mice in the presence and absence of visual stimulation. Multidimensional analysis of the network activity allowed us to identify neuronal ensembles defined as groups of cells firing in synchrony. These synchronous groups of neurons were themselves activated in sequential temporal patterns, which repeated at much higher proportions than chance and were triggered by specific visual stimuli such as natural visual scenes. Interestingly, sequential patterns were also present in recordings of spontaneous activity without any sensory stimulation and were accompanied by precise firing sequences at the single-cell level. Moreover, intrinsic dynamics could be used to predict the occurrence of future neuronal ensembles. Our data demonstrate that visual stimuli recruit similar sequential patterns to the ones observed spontaneously, consistent with the hypothesis that already existing Hebbian cell assemblies firing in predefined temporal sequences could be the microcircuit substrate that encodes visual percepts changing in time. PMID:26063915

  11. Endogenous Sequential Cortical Activity Evoked by Visual Stimuli

    PubMed Central

    Miller, Jae-eun Kang; Hamm, Jordan P.; Jackson, Jesse; Yuste, Rafael

    2015-01-01

    Although the functional properties of individual neurons in primary visual cortex have been studied intensely, little is known about how neuronal groups could encode changing visual stimuli using temporal activity patterns. To explore this, we used in vivo two-photon calcium imaging to record the activity of neuronal populations in primary visual cortex of awake mice in the presence and absence of visual stimulation. Multidimensional analysis of the network activity allowed us to identify neuronal ensembles defined as groups of cells firing in synchrony. These synchronous groups of neurons were themselves activated in sequential temporal patterns, which repeated at much higher proportions than chance and were triggered by specific visual stimuli such as natural visual scenes. Interestingly, sequential patterns were also present in recordings of spontaneous activity without any sensory stimulation and were accompanied by precise firing sequences at the single-cell level. Moreover, intrinsic dynamics could be used to predict the occurrence of future neuronal ensembles. Our data demonstrate that visual stimuli recruit similar sequential patterns to the ones observed spontaneously, consistent with the hypothesis that already existing Hebbian cell assemblies firing in predefined temporal sequences could be the microcircuit substrate that encodes visual percepts changing in time. PMID:26063915

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

    PubMed

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

    2015-10-28

    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. PMID:26400734

  13. Fertility of beef cattle females with mating stimuli around insemination.

    PubMed

    Rodriguez, R O; Rivera, M J

    1999-01-29

    An experiment was conducted to test the hypothesis that sterile mounts around insemination improves pregnancy rate to artificial insemination (AI) and to define the effects of age, season, time to complete AI and time of day of insemination. A total of 178 Simbrah females were randomly assigned by calving date and body condition to one of three treatments during two consecutive years: (1) mating stimuli with a sterile bull at the time the cows were detected in estrus; (2) mating stimuli immediately after completing AI; (3) without mating stimuli. All cows and heifers were maintained under the same conditions of handling and feeding within the two breeding seasons (winter 1995 and summer 1996). Vasectomized bulls were used for the sterile mounts. Cows and heifers that were given a sterile mount at the time of detection of estrus, had an increased pregnancy rate (60.0%) compared with females given a sterile mount after completing AI (25.4%) or females without the sterile mount (35.6%) (P < 0.01). Age, season, time to complete AI and time of day of AI were all non-significant (P > 0.05). Therefore, there is a biostimulatory effect of mating at the time beef cattle females are detected in estrus, on pregnancy rates to AI.

  14. Neural Conflict–Control Mechanisms Improve Memory for Target Stimuli

    PubMed Central

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

    2015-01-01

    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. PMID:24108799

  15. 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.

  16. 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.

  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. PMID:18843371

  18. Expectations accelerate entry of visual stimuli into awareness.

    PubMed

    Pinto, Yair; van Gaal, Simon; de Lange, Floris P; Lamme, Victor A F; Seth, Anil K

    2015-01-01

    How do expectations influence transitions between unconscious and conscious perceptual processing? According to the influential predictive processing framework, perceptual content is determined by predictive models of the causes of sensory signals. On one interpretation, conscious contents arise when predictive models are verified by matching sensory input (minimizing prediction error). On another, conscious contents arise when surprising events falsify current perceptual predictions. Finally, the cognitive impenetrability account posits that conscious perception is not affected by such higher level factors. To discriminate these positions, we combined predictive cueing with continuous flash suppression (CFS) in which the relative contrast of a target image gradually increases over time. In four experiments we established that expected stimuli enter consciousness faster than neutral or unexpected stimuli. These effects are difficult to account for in terms of response priming, pre-existing stimulus associations, or the attentional mechanisms that cause asynchronous temporal order judgments (of simultaneously presented stimuli). Our results further suggest that top-down expectations play a larger role when bottom-up input is ambiguous, in line with predictive processing accounts of perception. Taken together, our findings support the hypothesis that conscious access depends on verification of perceptual predictions. PMID:26114676

  19. Fertility of beef cattle females with mating stimuli around insemination.

    PubMed

    Rodriguez, R O; Rivera, M J

    1999-01-29

    An experiment was conducted to test the hypothesis that sterile mounts around insemination improves pregnancy rate to artificial insemination (AI) and to define the effects of age, season, time to complete AI and time of day of insemination. A total of 178 Simbrah females were randomly assigned by calving date and body condition to one of three treatments during two consecutive years: (1) mating stimuli with a sterile bull at the time the cows were detected in estrus; (2) mating stimuli immediately after completing AI; (3) without mating stimuli. All cows and heifers were maintained under the same conditions of handling and feeding within the two breeding seasons (winter 1995 and summer 1996). Vasectomized bulls were used for the sterile mounts. Cows and heifers that were given a sterile mount at the time of detection of estrus, had an increased pregnancy rate (60.0%) compared with females given a sterile mount after completing AI (25.4%) or females without the sterile mount (35.6%) (P < 0.01). Age, season, time to complete AI and time of day of AI were all non-significant (P > 0.05). Therefore, there is a biostimulatory effect of mating at the time beef cattle females are detected in estrus, on pregnancy rates to AI. PMID:10090564

  20. 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.

  1. 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. PMID:22822244

  2. Bears “Count” Too: Quantity Estimation and Comparison in Black Bears (Ursus Americanus)

    PubMed Central

    Vonk, Jennifer; Beran, Michael J.

    2012-01-01

    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. PMID:22822244

  3. 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.

  4. Evolution of a distinct genomic domain in Drosophila: comparative analysis of the dot chromosome in Drosophila melanogaster and Drosophila virilis.

    PubMed

    Leung, Wilson; Shaffer, Christopher D; Cordonnier, Taylor; Wong, Jeannette; Itano, Michelle S; Slawson Tempel, Elizabeth E; Kellmann, Elmer; Desruisseau, David Michael; Cain, Carolyn; Carrasquillo, Robert; Chusak, Tien M; Falkowska, Katazyna; Grim, Kelli D; Guan, Rui; Honeybourne, Jacquelyn; Khan, Sana; Lo, Louis; McGaha, Rebecca; Plunkett, Jevon; Richner, Justin M; Richt, Ryan; Sabin, Leah; Shah, Anita; Sharma, Anushree; Singhal, Sonal; Song, Fine; Swope, Christopher; Wilen, Craig B; Buhler, Jeremy; Mardis, Elaine R; Elgin, Sarah C R

    2010-08-01

    The distal arm of the fourth ("dot") chromosome of Drosophila melanogaster is unusual in that it exhibits an amalgamation of heterochromatic properties (e.g., dense packaging, late replication) and euchromatic properties (e.g., gene density similar to euchromatic domains, replication during polytenization). To examine the evolution of this unusual domain, we undertook a comparative study by generating high-quality sequence data and manually curating gene models for the dot chromosome of D. virilis (Tucson strain 15010-1051.88). Our analysis shows that the dot chromosomes of D. melanogaster and D. virilis have higher repeat density, larger gene size, lower codon bias, and a higher rate of gene rearrangement compared to a reference euchromatic domain. Analysis of eight "wanderer" genes (present in a euchromatic chromosome arm in one species and on the dot chromosome in the other) shows that their characteristics are similar to other genes in the same domain, which suggests that these characteristics are features of the domain and are not required for these genes to function. Comparison of this strain of D. virilis with the strain sequenced by the Drosophila 12 Genomes Consortium (Tucson strain 15010-1051.87) indicates that most genes on the dot are under weak purifying selection. Collectively, despite the heterochromatin-like properties of this domain, genes on the dot evolve to maintain function while being responsive to changes in their local environment.

  5. Electrical control of quantum dot spin qubits

    NASA Astrophysics Data System (ADS)

    Laird, Edward Alexander

    This thesis presents experiments exploring the interactions of electron spins with electric fields in devices of up to four quantum dots. These experiments are particularly motivated by the prospect of using electric fields to control spin qubits. A novel hyperfine effect on a single spin in a quantum dot is presented in Chapter 2. Fluctuations of the nuclear polarization allow single-spin resonance to be driven by an oscillating electric field. Spin resonance spectroscopy revealed a nuclear polarization built up inside the quantum dot device by driving the resonance. The evolution of two coupled spins is controlled by the combination of hyperfine interaction, which tends to cause spin dephasing, and exchange, which tends to prevent it. In Chapter 3, dephasing is studied in a device with tunable exchange, probing the crossover between exchange-dominated and hyperfine-dominated regimes. In agreement with theoretical predictions, oscillations of the spin conversion probability and saturation of dephasing are observed. Chapter 4 deals with a three-dot device, suggested as a potential qubit controlled entirely by exchange. Preparation and readout of the qubit state are demonstrated, together with one out of two coherent exchange operations needed for arbitrary manipulations. A new readout technique allowing rapid device measurement is described. In Chapter 5, an attempt to make a two-qubit gate using a four-dot device is presented. Although spin qubit operation has not yet been possible, the electrostatic interaction between pairs of dots was measured to be sufficient in principle for coherent qubit coupling.

  6. Formation and ordering of epitaxial quantum dots

    NASA Astrophysics Data System (ADS)

    Atkinson, Paola; Schmidt, Oliver G.; Bremner, Stephen P.; Ritchie, David A.

    2008-10-01

    Single quantum dots (QDs) have great potential as building blocks for quantum information processing devices. However, one of the major difficulties in the fabrication of such devices is the placement of a single dot at a pre-determined position in the device structure, for example, in the centre of a photonic cavity. In this article we review some recent investigations in the site-controlled growth of InAs QDs on GaAs by molecular beam epitaxy. The method we use is ex-situ patterning of the GaAs substrate by electron beam lithography and conventional wet or dry etching techniques to form shallow pits in the surface which then determine the nucleation site of an InAs dot. This method is easily scalable and can be incorporated with marker structures to enable simple post-growth lithographic alignment of devices to each site-controlled dot. We demonstrate good site-control for arrays with up to 10 micron spacing between patterned sites, with no dots nucleating between the sites. We discuss the mechanism and the effect of pattern size, InAs deposition amount and growth conditions on this site-control method. Finally we discuss the photoluminescence from these dots and highlight the remaining challenges for this technique. To cite this article: P. Atkinson et al., C. R. Physique 9 (2008).

  7. Children's identity matching and oddity: assessing control by specific and general sample-comparison relations.

    PubMed Central

    Stromer, R; Stromer, J B

    1989-01-01

    After children in Experiments 1 and 2 learned identity matching or oddity, control by sample-comparison relations was assessed. Tests for generalized control displayed novel samples and two comparison stimuli, one identical to the sample. Specific relations were tested with identical or nonidentical sample-comparison stimuli from one set of stimuli and substitute comparisons from either the other training set or from a novel set. When tests displayed identical stimuli, patterns of comparison selection suggested control by generalized identity and oddity. However, selection patterns varied when stimuli were nonidentical and familiar or novel substitute comparisons were used. Therefore, control by specific relations is not a precondition for generalized identity and oddity. One set of training stimuli was used in Experiment 3, and generalized performances occurred again. Moreover, control by specific relations was shown by the oddity subjects and 2 of 6 identity subjects. Generalized and specific control may therefore exist simultaneously. In Experiment 4, selections were irregular on tests displaying substitute comparisons and samples and familiar comparison stimuli; this finding supported the relational account of specific sample-comparison control found in Experiment 3. PMID:2921587

  8. 49 CFR 40.227 - May employers use the ATF for non-DOT tests, or non-DOT forms for DOT tests?

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 1 2010-10-01 2010-10-01 false May employers use the ATF for non-DOT tests, or non-DOT forms for DOT tests? 40.227 Section 40.227 Transportation Office of the Secretary of..., Equipment and Supplies Used in Alcohol Testing § 40.227 May employers use the ATF for non-DOT tests, or...

  9. Taste coding of complex naturalistic taste stimuli and traditional taste stimuli in the parabrachial pons of the awake, freely licking rat.

    PubMed

    Sammons, Joshua D; Weiss, Michael S; Victor, Jonathan D; Di Lorenzo, Patricia M

    2016-07-01

    Several studies have shown that taste-responsive cells in the brainstem taste nuclei of rodents respond to sensory qualities other than gustation. Such data suggest that cells in the classical gustatory brainstem may be better tuned to respond to stimuli that engage multiple sensory modalities than to stimuli that are purely gustatory. Here, we test this idea by recording the electrophysiological responses to complex, naturalistic stimuli in single neurons in the parabrachial pons (PbN, the second neural relay in the central gustatory pathway) in awake, freely licking rats. Following electrode implantation and recovery, we presented both prototypical and naturalistic taste stimuli and recorded the responses in the PbN. Prototypical taste stimuli (NaCl, sucrose, citric acid, and caffeine) and naturalistic stimuli (clam juice, grape juice, lemon juice, and coffee) were matched for taste quality and intensity (concentration). Umami (monosodium glutamate + inosine monophosphate) and fat (diluted heavy cream) were also tested. PbN neurons responded to naturalistic stimuli as much or more than to prototypical taste stimuli. Furthermore, they convey more information about naturalistic stimuli than about prototypical ones. Moreover, multidimensional scaling analyses showed that across unit responses to naturalistic stimuli were more widely separated than responses to prototypical taste stimuli. Interestingly, cream evoked a robust and widespread response in PbN cells. Collectively, these data suggest that natural foods are more potent stimulators of PbN cells than purely gustatory stimuli. Probing PbN cells with pure taste stimuli may underestimate the response repertoire of these cells.

  10. Taste coding of complex naturalistic taste stimuli and traditional taste stimuli in the parabrachial pons of the awake, freely licking rat.

    PubMed

    Sammons, Joshua D; Weiss, Michael S; Victor, Jonathan D; Di Lorenzo, Patricia M

    2016-07-01

    Several studies have shown that taste-responsive cells in the brainstem taste nuclei of rodents respond to sensory qualities other than gustation. Such data suggest that cells in the classical gustatory brainstem may be better tuned to respond to stimuli that engage multiple sensory modalities than to stimuli that are purely gustatory. Here, we test this idea by recording the electrophysiological responses to complex, naturalistic stimuli in single neurons in the parabrachial pons (PbN, the second neural relay in the central gustatory pathway) in awake, freely licking rats. Following electrode implantation and recovery, we presented both prototypical and naturalistic taste stimuli and recorded the responses in the PbN. Prototypical taste stimuli (NaCl, sucrose, citric acid, and caffeine) and naturalistic stimuli (clam juice, grape juice, lemon juice, and coffee) were matched for taste quality and intensity (concentration). Umami (monosodium glutamate + inosine monophosphate) and fat (diluted heavy cream) were also tested. PbN neurons responded to naturalistic stimuli as much or more than to prototypical taste stimuli. Furthermore, they convey more information about naturalistic stimuli than about prototypical ones. Moreover, multidimensional scaling analyses showed that across unit responses to naturalistic stimuli were more widely separated than responses to prototypical taste stimuli. Interestingly, cream evoked a robust and widespread response in PbN cells. Collectively, these data suggest that natural foods are more potent stimulators of PbN cells than purely gustatory stimuli. Probing PbN cells with pure taste stimuli may underestimate the response repertoire of these cells. PMID:27121585

  11. 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

  12. Lateral Quantum Dots for Quantum Information Processing

    NASA Astrophysics Data System (ADS)

    House, Matthew Gregory

    The possibility of building a computer that takes advantage of the most subtle nature of quantum physics has been driving a lot of research in atomic and solid state physics for some time. It is still not clear what physical system or systems can be used for this purpose. One possibility that has been attracting significant attention from researchers is to use the spin state of an electron confined in a semiconductor quantum dot. The electron spin is magnetic in nature, so it naturally is well isolated from electrical fluctuations that can a loss of quantum coherence. It can also be manipulated electrically, by taking advantage of the exchange interaction. In this work we describe several experiments we have done to study the electron spin properties of lateral quantum dots. We have developed lateral quantum dot devices based on the silicon metal-oxide-semiconductor transistor, and studied the physics of electrons confined in these quantum dots. We measured the electron spin excited state lifetime, which was found to be as long as 30 ms at the lowest magnetic fields that we could measure. We fabricated and characterized a silicon double quantum dot. Using this double quantum dot design, we fabricated devices which combined a silicon double quantum dot with a superconducting microwave resonator. The microwave resonator was found to be sensitive to two-dimensional electrons in the transistor channel, which we measured and characterized. We developed a new method for extracting information from random telegraph signals, which are produced when we observe thermal fluctuations of electrons in quantum dots. The new statistical method, based on the hidden Markov model, allows us to detect spin-dependent effects in such fluctuations even though we are not able to directly observe the electron spin. We use this analysis technique on data from two experiments involving gallium arsenide quantum dots and use it to measure spin-dependent tunneling rates. Our results advance the

  13. (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.

  14. 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.

  15. Understanding electronic systems in semiconductor quantum dots

    NASA Astrophysics Data System (ADS)

    Ciftja, Orion

    2013-11-01

    Systems of confined electrons are found everywhere in nature in the form of atoms where the orbiting electrons are confined by the Coulomb attraction of the nucleus. Advancement of nanotechnology has, however, provided us with an alternative way to confine electrons by using artificial confining potentials. A typical structure of this nature is the quantum dot, a nanoscale system which consists of few confined electrons. There are many types of quantum dots ranging from self-assembled to miniaturized semiconductor quantum dots. In this work we are interested in electrostatically confined semiconductor quantum dot systems where the electrostatic confining potential that traps the electrons is generated by external electrodes, doping, strain or other factors. A large number of semiconductor quantum dots of this type are fabricated by applying lithographically patterned gate electrodes or by etching on two-dimensional electron gases in semiconductor heterostructures. Because of this, the whole structure can be treated as a confined two-dimensional electron system. Quantum confinement profoundly affects the way in which electrons interact with each other, and external parameters such as a magnetic field. Since a magnetic field affects both the orbital and the spin motion of the electrons, the interplay between quantum confinement, electron-electron correlation effects and the magnetic field gives rise to very interesting physical phenomena. Thus, confined systems of electrons in a semiconductor quantum dot represent a unique opportunity to study fundamental quantum theories in a controllable atomic-like setup. In this work, we describe some common theoretical models which are used to study confined systems of electrons in a two-dimensional semiconductor quantum dot. The main emphasis of the work is to draw attention to important physical phenomena that arise in confined two-dimensional electron systems under various quantum regimes.

  16. 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.

  17. 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.

  18. 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

  19. 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…

  20. 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.

  1. Teaching children with autism to engage in conversational exchanges: script fading with embedded textual stimuli.

    PubMed Central

    Sarokoff, R A; Taylor, B A; Poulson, C L

    2001-01-01

    A multiple baseline across three sets of stimuli was used to assess the effects of a script-fading procedure using embedded text to teach 2 children with autism to engage in conversation statements about the stimuli. Both students stated all the scripted statements, and unscripted statements also increased. Generalization was assessed with novel peers and with untrained stimuli. PMID:11317993

  2. Evaluating Preference for Familiar and Novel Stimuli across a Large Group of Children with Autism

    ERIC Educational Resources Information Center

    Kenzer, Amy L.; Bishop, Michele R.

    2011-01-01

    This study examined relative preference for familiar and novel stimuli for 31 children with autism. Preference surveys, completed by 39 staff members, identified high and low preference familiar stimuli for each participant. Novel stimuli were selected by experimenters and included items that were not reported on a preference survey for that…

  3. Beyond the classical receptive field: The effect of contextual stimuli.

    PubMed

    Spillmann, Lothar; Dresp-Langley, Birgitta; Tseng, Chia-Huei

    2015-01-01

    Following the pioneering studies of the receptive field (RF), the RF concept gained further significance for visual perception by the discovery of input effects from beyond the classical RF. These studies demonstrated that neuronal responses could be modulated by stimuli outside their RFs, consistent with the perception of induced brightness, color, orientation, and motion. Lesion scotomata are similarly modulated perceptually from the surround by RFs that have migrated from the interior to the outer edge of the scotoma and in this way provide filling-in of the void. Large RFs are advantageous to this task. In higher visual areas, such as the middle temporal and inferotemporal lobe, RFs increase in size and lose most of their retinotopic organization while encoding increasingly complex features. Whereas lower-level RFs mediate perceptual filling-in, contour integration, and figure-ground segregation, RFs at higher levels serve the perception of grouping by common fate, biological motion, and other biologically relevant stimuli, such as faces. Studies in alert monkeys while freely viewing natural scenes showed that classical and nonclassical RFs cooperate in forming representations of the visual world. Today, our understanding of the mechanisms underlying the RF is undergoing a quantum leap. What had started out as a hierarchical feed-forward concept for simple stimuli, such as spots, lines, and bars, now refers to mechanisms involving ascending, descending, and lateral signal flow. By extension of the bottom-up paradigm, RFs are nowadays understood as adaptive processors, enabling the predictive coding of complex scenes. Top-down effects guiding attention and tuned to task-relevant information complement the bottom-up analysis. PMID:26200888

  4. Parasympathetic Stimuli on Bronchial and Cardiovascular Systems in Humans

    PubMed Central

    Zannin, Emanuela; Pellegrino, Riccardo; Di Toro, Alessandro; Antonelli, Andrea; Dellacà, Raffaele L.; Bernardi, Luciano

    2015-01-01

    Background It is not known whether parasympathetic outflow simultaneously acts on bronchial tone and cardiovascular system waxing and waning both systems in parallel, or, alternatively, whether the regulation is more dependent on local factors and therefore independent on each system. The aim of this study was to evaluate the simultaneous effect of different kinds of stimulations, all associated with parasympathetic activation, on bronchomotor tone and cardiovascular autonomic regulation. Methods Respiratory system resistance (Rrs, forced oscillation technique) and cardio-vascular activity (heart rate, oxygen saturation, tissue oxygenation index, blood pressure) were assessed in 13 volunteers at baseline and during a series of parasympathetic stimuli: O2 inhalation, stimulation of the carotid sinus baroreceptors by neck suction, slow breathing, and inhalation of methacholine. Results Pure cholinergic stimuli, like O2 inhalation and baroreceptors stimulation, caused an increase in Rrs and a reduction in heart rate and blood pressure. Slow breathing led to bradycardia and hypotension, without significant changes in Rrs. However slow breathing was associated with deep inhalations, and Rrs evaluated at the baseline lung volumes was significantly increased, suggesting that the large tidal volumes reversed the airways narrowing effect of parasympathetic activation. Finally inhaled methacholine caused marked airway narrowing, while the cardiovascular variables were unaffected, presumably because of the sympathetic activity triggered in response to hypoxemia. Conclusions All parasympathetic stimuli affected bronchial tone and moderately affected also the cardiovascular system. However the response differed depending on the nature of the stimulus. Slow breathing was associated with large tidal volumes that reversed the airways narrowing effect of parasympathetic activation. PMID:26046774

  5. Intact emotion facilitation for nonsocial stimuli in autism: is amygdala impairment in autism specific for social information?

    PubMed

    South, Mikle; Ozonoff, Sally; Suchy, Yana; Kesner, Raymond P; McMahon, William M; Lainhart, Janet E

    2008-01-01

    Atypical amygdala development may play a key role in the emergence of social disability and other symptoms of autism (Baron-Cohen et al., 2000; Schultz, 2005). The mechanisms by which this may occur have received little attention, however, and most support from behavioral and imaging studies has been concerned with socially relevant stimuli such as faces. Given the complexity of amygdala function and its known role in many other emotional tasks, we examined whether individuals with autism would demonstrate impaired performance on several tasks that have been shown to require activation of the amygdala but that do not have any explicit social meaning. Relative to a typical comparison group matched for age and IQ, our sample of 37 adolescents and adults with autism (mean age=19.7 years) demonstrated equivalent facilitation for perception and learning of emotionally relevant stimuli. On each of four tasks, there were significant main effects of emotion condition on performance for both groups. Future research regarding atypical amygdala function and emotion processing in autism should consider whether the response to nonsocial emotion factors (including negative valence or high arousal) may be intact, despite difficulties in responding to socially relevant stimuli. PMID:18078530

  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. 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.

  8. Induced Pluripotent Stem Cell Labeling Using Quantum Dots

    PubMed Central

    Yukawa, Hiroshi; Suzuki, Kaoru; Kano, Yuki; Yamada, Tatsuya; Kaji, Noritada; Ishikawa, Tetsuya; Baba, Yoshinobu

    2013-01-01

    Induced pluripotent stem (iPS) cells have received remarkable attention as the cell sources for clinical applications of regenerative medicine including stem cell therapy. Additionally, labeling technology is in high demand for tracing transplanted cells used in stem cell therapy. In this study, we used quantum dots (QDs), which have distinct fluorescence abilities in comparison with traditional probes, as the labeling materials and investigated whether iPS cells could be labeled with QDs with no cytotoxicity. iPS cells could not be labeled with QDs alone but required the use of cell-penetrating peptides such as octaarginine (R8). No significant cytotoxicity to iPS cells was confirmed by up to 8 nM QDs, and the iPS cells labeled with QDs maintained their undifferentiated state and pluripotency. These data suggest that QDs can be used for fluorescence labeling of iPS cells. PMID:26858884

  9. 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

  10. Peptide-mediated cellular delivery of semiconductor quantum dots

    NASA Astrophysics Data System (ADS)

    Gemmill, Kelly Boeneman; Muttenthaler, Markus; Delehanty, James; Deschamps, Jeff; Susumu, Kimihiro; Stewart, Michael; Dawson, Philip; Huston, Alan; Medintz, Igor

    2013-05-01

    CdSe/ZnS semiconductor quantum dots (QDs) are ideal materials for biological sensing and cellular imaging applications due to their superior photophysical properties in comparison to fluorescent proteins or dyes and their ease of conjugation to biological materials. We have previously developed a number of in vitro FRET based biosensors in the laboratory for detection of proteases and biological and chemical agents. We would like to expand these biosensing capabilities into cellular systems, requiring development of QD cellular delivery techniques. Peptide mediated cellular delivery of QDs is ideal as peptides are small, easily conjugated to QDs, easily manipulated and synthesized, and can be designed with "handles" for further chemical conjugation with other cargo. Here we discuss four cell delivery peptides that facilitate QD uptake in live cells. Understanding these peptides will help us design better nanoparticle cellular delivery systems and advance our capabilities for in vivo biosensing.

  11. 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.

  12. Dorsal horn spatial representation of simple cutaneous stimuli.

    PubMed

    Brown, P B; Millecchia, R; Lawson, J J; Stephens, S; Harton, P; Culberson, J C

    1998-02-01

    A model of lamina III-IV dorsal horn cell receptive fields (RFs) has been developed to visualize the spatial patterns of cells activated by light touch stimuli. Low-threshold mechanoreceptive fields (RFs) of 551 dorsal horn neurons recorded in anesthetized cats were characterized by location of RF center in cylindrical coordinates, area, length/width ratio, and orientation of long axis. Best-fitting ellipses overlapped actual RFs by 90%. Exponentially smoothed mean and variance surfaces were estimated for these five variables, on a grid of 40 points mediolaterally by 20/segment rostrocaudally in dorsal horn segments L4-S1. The variations of model RF location, area, and length/width ratio with map location were all similar to previous observations. When elliptical RFs were simulated at the locations of the original cells, the RFs of real and simulated cells overlapped by 64%. The densities of cell representations of skin points on the hindlimb were represented as pseudocolor contour plots on dorsal view maps, and segmental representations were plotted on the standard views of the leg. Overlap of modeled and real segmental representations was at the 84% level. Simulated and observed RFs had similar relations between area and length/width ratio and location on the hindlimb: r(A) = 0.52; r(L/W) = 0.56. Although the representation of simple stimuli was orderly, and there was clearly only one somatotopic map of the skin, the representation of a single point often was not a single cluster of active neurons. When two-point stimuli were simulated, there usually was no fractionation of response zones or addition of new zones. Variation of stimulus size (area of skin contacted) produced less variation of representation size (number of cells responding) than movement of stimuli from one location to another. We conclude that stimulus features are preserved poorly in their dorsal horn spatial representation and that discrimination mechanisms that depend on detection of such

  13. 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

  14. Searching for optimal stimuli: ascending a neuron's response function.

    PubMed

    Koelling, Melinda Evrithiki; Nykamp, Duane Q

    2012-12-01

    Many methods used to analyze neuronal response assume that neuronal activity has a fundamentally linear relationship to the stimulus. However, some neurons are strongly sensitive to multiple directions in stimulus space and have a highly nonlinear response. It can be difficult to find optimal stimuli for these neurons. We demonstrate how successive linear approximations of neuronal response can effectively carry out gradient ascent and move through stimulus space towards local maxima of the response. We demonstrate search results for a simple model neuron and two models of a highly selective neuron. PMID:22580579

  15. Photoluminescence of carbon dots from mesoporous silica

    NASA Astrophysics Data System (ADS)

    Nelson, D. K.; Razbirin, B. S.; Starukhin, A. N.; Eurov, D. A.; Kurdyukov, D. A.; Stovpiaga, E. Yu; Golubev, V. G.

    2016-09-01

    Photophysical properties of carbon dots were investigated under various excitation conditions and over a wide temperature region - from room to liquid helium temperatures. The carbon dots (CDs) were synthesized using mesoporous silica particles as a reactor and (3-aminopropyl)triethoxysilane (APTES) as a precursor. The photoluminescence spectra of CDs exhibit a strong dependence on the excitation wavelength and demonstrate a significant inhomogeneous broadening. Lowering sample temperature reveals the doublet structure of the spectra, which is associated with the vibronic structure of radiative transitions. The vibration energy ∼1200 cm-1 is close to the energy of Csbnd O stretching vibration. Long-lived phosphorescence of carbon dots with its decay time ∼0.2 s at T = 80 K was observed. The fluorescence and phosphorescence spectra are shown to be spectrally separated. The long-lived component of the emission was ascribed to optically forbidden triplet-singlet transitions. The value of the singlet-triplet splitting was found to be about 0.3 eV. Photo-induced polarization of the luminescence of carbon dots was revealed. The degree of the linear polarization is dependent on the wavelengths of both excitation and emitted light. The effect indicates a hidden anisotropy of optical dipole transitions in the dots and demonstrates the loss of the dipole orientation during the electron energy relaxation.

  16. Electronic structure and electron correlation in weakly confining spherical quantum dot potentials

    NASA Astrophysics Data System (ADS)

    Kimani, Peter Borgia Ndungu

    The electronic structure and electron correlations in weakly confining spherical quantum dots potentials are investigated. Following a common practice, the investigation starts with the restricted Hartree-Fock (HF) approximation. Then electron correlation is added in steps in a series of approximations based on the single particle Green's function approach: (i) Second-order Green function (GF) (ii) 2ph-Tamm-Dancoff approximation (TDA) and (iii) an extended version thereof (XTDA) which introduces ground-state correlation into the TDA. The study includes as well Hartree-Fock V (N-1) potential approximation in which framework the Hartree-Fock virtual orbitals are calculated in the field of the N-1 electrons as opposed to the regular but unphysical N-electron field Hartree-Fock calculation of virtual orbitals. For contrast and comparison, the same approximation techniques are applied to few-electron closed-shell atoms and few-electron negative ions for which pertinent data is readily available. The results for the weakly confining spherical quantum dot potentials and the standard atomic systems exhibit fundamental similarities as well as significant differences. For the most part the results of these calculations are in favor of application of HF, GF, and TDA techniques in the modeling of three-dimensional weakly confining quantum dot potentials. The observed differences emphasize the significance of confinement and electronic features unique to quantum dots such as the increased binding of electrons with higher angular momentum and the modified shell filling sequences.

  17. Neural responses to smoking stimuli are influenced by smokers' attitudes towards their own smoking behaviour.

    PubMed

    Stippekohl, Bastian; Winkler, Markus H; Walter, Bertram; Kagerer, Sabine; Mucha, Ronald F; Pauli, Paul; Vaitl, Dieter; Stark, Rudolf

    2012-01-01

    An important feature of addiction is the high drug craving that may promote the continuation of consumption. Environmental stimuli classically conditioned to drug-intake have a strong motivational power for addicts and can elicit craving. However, addicts differ in the attitudes towards their own consumption behavior: some are content with drug taking (consonant users) whereas others are discontent (dissonant users). Such differences may be important for clinical practice because the experience of dissonance might enhance the likelihood to consider treatment. This fMRI study investigated in smokers whether these different attitudes influence subjective and neural responses to smoking stimuli. Based on self-characterization, smokers were divided into consonant and dissonant smokers. These two groups were presented smoking stimuli and neutral stimuli. Former studies have suggested differences in the impact of smoking stimuli depending on the temporal stage of the smoking ritual they are associated with. Therefore, we used stimuli associated with the beginning (BEGIN-smoking-stimuli) and stimuli associated with the terminal stage (END-smoking-stimuli) of the smoking ritual as distinct stimulus categories. Stimulus ratings did not differ between both groups. Brain data showed that BEGIN-smoking-stimuli led to enhanced mesolimbic responses (amygdala, hippocampus, insula) in dissonant compared to consonant smokers. In response to END-smoking-stimuli, dissonant smokers showed reduced mesocortical responses (orbitofrontal cortex, subcallosal cortex) compared to consonant smokers. These results suggest that smoking stimuli with a high incentive value (BEGIN-smoking-stimuli) are more appetitive for dissonant than consonant smokers at least on the neural level. To the contrary, smoking stimuli with low incentive value (END-smoking-stimuli) seem to be less appetitive for dissonant smokers than consonant smokers. These differences might be one reason why dissonant smokers

  18. 49 CFR 15.15 - SSI disclosed by DOT.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... document issued by DOT. (2) Security background check. Prior to providing SSI to a person under paragraph... the Secretary of DOT, a security background check. (e) Other conditional disclosure. The Secretary...

  19. 49 CFR 15.15 - SSI disclosed by DOT.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... document issued by DOT. (2) Security background check. Prior to providing SSI to a person under paragraph... the Secretary of DOT, a security background check. (e) Other conditional disclosure. The Secretary...

  20. 49 CFR 15.15 - SSI disclosed by DOT.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... document issued by DOT. (2) Security background check. Prior to providing SSI to a person under paragraph... the Secretary of DOT, a security background check. (e) Other conditional disclosure. The Secretary...

  1. 49 CFR 15.15 - SSI disclosed by DOT.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... document issued by DOT. (2) Security background check. Prior to providing SSI to a person under paragraph... the Secretary of DOT, a security background check. (e) Other conditional disclosure. The Secretary...

  2. 49 CFR 15.15 - SSI disclosed by DOT.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... document issued by DOT. (2) Security background check. Prior to providing SSI to a person under paragraph... the Secretary of DOT, a security background check. (e) Other conditional disclosure. The Secretary...

  3. 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.

  4. 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.

  5. 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

  6. 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. PMID:26958463

  7. 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.

  8. Genetically engineered protein in hydrogels tailors stimuli-responsive characteristics

    NASA Astrophysics Data System (ADS)

    Ehrick, Jason D.; Deo, Sapna K.; Browning, Tyler W.; Bachas, Leonidas G.; Madou, Marc J.; Daunert, Sylvia

    2005-04-01

    Certain proteins undergo a substantial conformational change in response to a given stimulus. This conformational change can manifest in different manners and result in an actuation, that is, catalytic or signalling event, movement, interaction with other proteins, and so on. In all cases, the sensing-actuation process of proteins is initiated by a recognition event that translates into a mechanical action. Thus, proteins are ideal components for designing new nanomaterials that are intelligent and can perform desired mechanical actions in response to target stimuli. A number of approaches have been undertaken to mimic nature's sensing-actuating process. We now report a new hybrid material that integrates genetically engineered proteins within hydrogels capable of producing a stimulus-responsive action mechanism. The mechanical effect is a result of an induced conformational change and binding affinities of the protein in response to a stimulus. The stimuli-responsive hydrogel exhibits three specific swelling stages in response to various ligands offering additional fine-tuned control over a conventional two-stage swelling hydrogel. The newly prepared material was used in the sensing, and subsequent gating and transport of biomolecules across a polymer network, demonstrating its potential application in microfluidics and miniaturized drug-delivery systems.

  9. Nonconvulsive status epilepticus in rats: impaired responsiveness to exteroceptive stimuli.

    PubMed

    Mikulecká, A; Krsek, P; Hlinák, Z; Druga, R; Mares, P

    2000-12-20

    An animal model of human complex partial status epilepticus induced by lithium chloride and pilocarpine administration was developed in our laboratory. The objective of the study was to provide a detailed analysis of both ictal and postictal behavior and to quantify seizure-related morphological damage. In order to determine the animal's responsiveness to either visual or olfactory stimuli, adult male rats were submitted to the following behavioral paradigms: the object response test, the social interaction test, and the elevated plus-maze test. The rotorod test was used to evaluate motor performance. Two weeks after status epilepticus, brains were morphologically examined and quantification of the brain damage was performed. Profound impairment of behavior as well as responsiveness to exteroceptive stimuli correlated with the occurrence of epileptic EEG activity. When the epileptic EEG activity ceased, responsiveness of the pilocarpine-treated animals was renewed. However, remarkable morphological damage persisted in the cortical regions two weeks later. This experimental study provides support for the clinical evidence that even nonconvulsive epileptic activity may cause brain damage. We suggest that the model can be used for the study of both functional and morphological consequences of prolonged nonconvulsive seizures. PMID:11099755

  10. Food-associated stimuli enhance barrier properties of gastrointestinal mucus.

    PubMed

    Yildiz, Hasan M; Speciner, Lauren; Ozdemir, Cafer; Cohen, David E; Carrier, Rebecca L

    2015-06-01

    Orally delivered drugs and nutrients must diffuse through mucus to enter the circulatory system, but the barrier properties of mucus and their modulation by physiological factors are generally poorly characterized. The main objective of this study was to examine the impact of physicochemical changes occurring upon food ingestion on gastrointestinal (GI) mucus barrier properties. Lipids representative of postprandial intestinal contents enhanced mucus barriers, as indicated by a 10-142-fold reduction in the transport rate of 200 nm microspheres through mucus, depending on surface chemistry. Physiologically relevant increases in [Ca(2+)] resulted in a 2-4-fold reduction of transport rates, likely due to enhanced cross-linking of the mucus gel network. Reduction of pH from 6.5 to 3.5 also affected mucus viscoelasticity, reducing particle transport rates approximately 5-10-fold. Macroscopic visual observation and micro-scale lectin staining revealed mucus gel structural changes, including clumping into regions into which particles did not penetrate. Histological examination indicated food ingestion can prevent microsphere contact with and endocytosis by intestinal epithelium. Taken together, these results demonstrate that GI mucus barriers are significantly altered by stimuli associated with eating and potentially dosing of lipid-based delivery systems; these stimuli represent broadly relevant variables to consider upon designing oral therapies. PMID:25907034

  11. Spatio-temporal processing of tactile stimuli in autistic children.

    PubMed

    Wada, Makoto; Suzuki, Mayuko; Takaki, Akiko; Miyao, Masutomo; Spence, Charles; Kansaku, Kenji

    2014-08-07

    Altered multisensory integration has been reported in autism; however, little is known concerning how the autistic brain processes spatio-temporal information concerning tactile stimuli. We report a study in which a crossed-hands illusion was investigated in autistic children. Neurotypical individuals often experience a subjective reversal of temporal order judgments when their hands are stimulated while crossed, and the illusion is known to be acquired in early childhood. However, under those conditions where the somatotopic representation is given priority over the actual spatial location of the hands, such reversals may not occur. Here, we showed that a significantly smaller illusory reversal was demonstrated in autistic children than in neurotypical children. Furthermore, in an additional experiment, the young boys who had higher Autism Spectrum Quotient (AQ) scores generally showed a smaller crossed hands deficit. These results suggest that rudimentary spatio-temporal processing of tactile stimuli exists in autistic children, and the altered processing may interfere with the development of an external frame of reference in real-life situations.

  12. Empathic behavioral and physiological responses to dynamic stimuli in depression.

    PubMed

    Schneider, Daniel; Regenbogen, Christina; Kellermann, Thilo; Finkelmeyer, Andreas; Kohn, Nils; Derntl, Birgit; Schneider, Frank; Habel, Ute

    2012-12-30

    Major depressive disorder (MDD) is strongly linked to social withdrawal and interpersonal problems which characterize the disorder and further aggravate symptoms. Investigating the nature of impaired emotional-social functioning as a basis of interpersonal functioning in MDD has been widely restricted to static stimuli and behavioral emotion recognition accuracy. The present study aimed at examining higher order emotional processes, namely empathic responses and its components, emotion recognition accuracy and affective responses in 28 MDD patients and 28 healthy control participants. The dynamic stimulus material included 96 short video clips depicting actors expressing basic emotions by face, voice prosody, and sentence content. Galvanic skin conductance measurements revealed implicit processes in the multimethod assessment of empathy. Overall, patients displayed lower empathy, emotion accuracy, and affective response rates than controls. Autonomous arousal was higher in patients. A generalized emotion processing deficit is in line with the "emotional context insensitivity" (ECI) theory which proposes decreased overall responsiveness to emotional stimuli. The dissociation between hypo-reactivity in explicit and hyper-reactivity in implicit measures of emotion processing can be related to the "limbic-cortical dysregulation" model of depression. Our findings support the dissociation of autonomic and subjective emotional responses which may account for interpersonal as well as emotional deficits in depression. PMID:22560057

  13. Event-related desynchronization evoked by auditory stimuli.

    PubMed

    Krause, C M; Lang, H A; Laine, M; Helle, S I; Kuusisto, M J; Pörn, B

    1994-01-01

    Event-Related Desynchronization (ERD) and Synchronization (ERS) of several EEG alpha frequencies was studied in 19 subjects during the presentation of linguistic and/or melodic auditory stimuli. The stimulus length was 1300 msec (+/-100 msec) and the interstimulus interval was 2000 msec. A significant ERD was found during auditory stimulation in the 8-10 Hz and 10-12 Hz alpha frequency bands, and there were also significant differences in the spatiotemporal pattern of the ERD between these frequency bands. Significant ERD was elicited also in the 10-11 and 11-12 Hz frequency bands by auditory stimulation. There were no significant differences between these one-hertz frequency bands. The subjects were assigned to two analysis groups according to their individual alpha peak frequency (10-11 or 11-12 Hz) at rest. The ERD in these groups reached statistical significance and there were significant differences between the groups. The ERD of the two groups differed significantly also when their EEG data was studied in the 10-12 Hz frequency band. The results from this study show that ERD is not modality-specific, i.e., it can be elicited also by auditory stimuli. Moreover, they indicate that it is important to control over interindividual variation in the EEG when studying the ERD phenomenon.

  14. 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.

  15. Simplification of olfactory stimuli in pseudo-gustatory displays.

    PubMed

    Narumi, Takuji; Miyaura, Masaaki; Tanikawa, Tomohiro; Hirose, Michitaka

    2014-04-01

    In this paper, we propose a technique that simplifies pseudo-gustatory systems by using the cross-modal effect between vision and olfaction to change only the visual and olfactory stimuli without altering the ingredients of the food. Conventional pseudo-gustatory simulations require one olfactory stimulus for each flavor. In contrast, we hypothesize that the cross-modal effect between vision and olfaction in a pseudo-gustatory presentation can be utilized to reduce the required number of olfactory stimuli, and verify this hypothesis using a pseudo-gustatory display with our proposed method. This pseudo-gustatory display uses the visual-olfactory cross-modal effect and the key scent components decided on the basis of similarity analysis of olfactory perception. We also investigate how users perceive the taste of a drink under various visual and olfactory conditions, both with and without the visual-olfactory interactions. Our results indicate that the cross-modal effect between vision and olfaction can effectively simplify pseudo-gustatory simulations.

  16. 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

  17. Advances in stimuli responsive nanobiomaterials for cancer therapy.

    PubMed

    Sampathkumar, Kaarunya; Arulkumar, Shylaja; Ramalingam, Murugan

    2014-03-01

    Cancer has become one of the major reasons for disease mortality with drastic increase of death rate in recent years. The reason for most of these deaths is due to the inefficacy and failure of the current methods of treatments or due to the unavailability of treatment options. Even after extensive research that has been carried out in the field, there is no gold standard in cancer therapy. With the advancement of the field of nanomedicine and materials science, many research works are being aimed at developing micro and nanocarriers for site-specific delivery of anticancer drugs. As a further advancement in the field, smart carriers, based on nanobiomaterials, which respond to various external and internal stimuli and act locally are being developed to improve the efficacy of current treatments. These smart nanobiomaterials act as carriers for not only anticancer drugs but also for gene and other biomolecules. Keeping the importance and advancement of smart carrier anticancer drug delivery system (AcDDS) in view, this review focuses on stimuli responsive nanobiomaterials that are currently being studied for cancer therapy. PMID:24730233

  18. MEG brain activities reflecting affection for visual food stimuli.

    PubMed

    Kuriki, Shinya; Miyamura, Takahiro; Uchikawa, Yoshinori

    2010-01-01

    This study aimed to explore the modulation of alpha rhythm in response to food pictures with distinct affection values. We examined the method to discriminate subject's state, i.e., whether he/she liked the article of food or not, from MEG signals detected over the head. Pictures of familiar foods were used as affective stimuli, while those pictures with complementary color phase were used as non-affective stimuli. Alpha band signals in a narrow frequency window around the spectral peak of individual subjects were wavelet analyzed and phase-locked component to the stimulus onset was obtained as a complex number. The amplitude of the phase-locked component was averaged during 0-1 s after stimulus onset for 30 epochs in a measurement session and across 76 channels of MEG sensor. In statistical test of individual subjects, significant difference was found in the real part of the averaged phase-locked amplitude between the normal-color and reverse-color pictures. These results suggest that affective information processing of food pictures is reflected in the synchronized component of narrow band alpha rhythm. PMID:21096510

  19. 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.

  20. Escape and aggregation responses of three echinoderms to conspecific stimuli.

    PubMed

    Campbell, A C; Coppard, S; D'Abreo, C; Tudor-Thomas, R

    2001-10-01

    In marine invertebrates, waterborne chemical stimuli mediate responses including prey detection and predator avoidance. Alarm and flight, in response to damaged conspecifics, have been reported in echinoderms, but the nature of the stimuli involved is not known. The responses of Asterias rubens Linnaeus, Psammechinus miliaris (Gmelin), and Echinus esculentus Linnaeus to conspecifics were tested in a choice chamber against a control of clean seawater (no stimulus). All three species showed statistically significant movement toward water conditioned by whole animals or homogenate of test epithelium. P. miliaris and E. esculentus displayed a statistically significant avoidance reaction, moving away from conspecific coelomic fluid, gut homogenate, and gonad homogenate. A. rubens was indifferent to conspecific coelomic fluid, pyloric cecum homogenate, and gonad homogenate but moved away from cardiac gut homogenate. P. miliaris was indifferent to gametes, but the other two species were significantly attracted to them. No species showed preference for one particular side of the chamber during trials to balance water flow. These echinoderms can distinguish between homogenates of conspecific tissues that might be exposed when a predator damages the test, and those that may emanate from the exterior surface during normal activities. PMID:11687389

  1. Effects of olfactory stimuli on urge reduction in smokers.

    PubMed

    Sayette, M A; Parrott, D J

    1999-05-01

    This study examined the possibility that exposure to olfactory stimuli can reduce self-reported urge to smoke. After an initial assessment of self-reported urge, nicotine-deprived smokers evaluated the pleasantness of a series of 8 odors. Facial expressions during odor presentations were coded with P. Ekman and W. V. Friesen's (1978a) Facial Action Coding System. After odor administration, participants were exposed to smoking cues. Next, participants were administered their most pleasant, least pleasant, or a control odor (water) and reported their urge to smoke. Results indicated that sniffing either a pleasant or unpleasant odor reduced reported urge to smoke relative to the control odor. Reported pleasantness of the odors did not differentially affect urge reduction. Odors eliciting negative-affect-related expressions, however, were less effective than odors that did not elicit negative-affect-related expressions in reducing reported urge. Results of this preliminary investigation provide support for the consideration of odor stimuli as an approach to craving reduction.

  2. Response of Morris-Lecar neurons to various stimuli

    NASA Astrophysics Data System (ADS)

    Wang, Hengtong; Wang, Longfei; Yu, Lianchun; Chen, Yong

    2011-02-01

    We studied the responses of three classes of Morris-Lecar neurons to sinusoidal inputs and synaptic pulselike stimuli with deterministic and random interspike intervals (ISIs). It was found that the responses of the output frequency of class 1 and 2 neurons showed similar evolution properties by varying input amplitudes and frequencies, whereas class 3 neuron exhibited substantially different properties. Specifically, class 1 and 2 neurons display complicated phase locking (p : q, p>q, denoting output action potentials per input spikes) in low-frequency sinusoidal input area when the input amplitude is above their threshold, but a class 3 neuron does not fire action potentials in this area even if the amplitude is much higher. In the case of the deterministic ISI synaptic injection, all the three classes of neurons oscillate spikes with an arbitrary small frequency. When increasing the input frequency (both sinusoidal and deterministic ISI synaptic inputs), all neurons display 1 : 1 phase locking, whereas the response frequency decreases even fall to zero in the high-frequency input area. When the random ISI synaptic pulselike stimuli are injected into the neurons, one can clearly see the low-pass filter behaviors from the return map. The output ISI distribution depends on the mean ISI of input train as well as the ISI variation. Such different responses of three classes of neurons result from their distinct dynamical mechanisms of action potential initiation. It was suggested that the intrinsic dynamical cellular properties are very important to neuron information processing.

  3. 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

  4. Large crowding zones in peripheral vision for briefly presented stimuli.

    PubMed

    Tripathy, Srimant Prasad; Cavanagh, Patrick; Bedell, Harold E

    2014-12-30

    When a target is flanked by distractors, it becomes more difficult to identify. In the periphery, this crowding effect extends over a wide range of target-flanker separations, called the spatial extent of interaction (EoI). A recent study showed that the EoI dramatically increases in size for short presentation durations (Chung & Mansfield, 2009). Here we investigate this duration-EoI relation in greater detail and show that (a) it holds even when visibility of the unflanked target is equated for different durations, (b) the function saturates for durations shorter than 30 to 80 ms, and (c) the largest EoIs represent a critical spacing greater than 50% of eccentricity. We also investigated the effect of same or different polarity for targets and flankers across different presentation durations. We found that EoIs for target and flankers having opposite polarity (one white, the other black) show the same temporal pattern as for same polarity stimuli, but are smaller at all durations by 29% to 44%. The observed saturation of the EoI for short-duration stimuli suggests that crowding follows the locus of temporal integration. Overall, the results constrain theories that map crowding zones to fixed spatial extents or to lateral connections of fixed length in the cortex.

  5. 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.

  6. Pairwise agonist scanning predicts cellular signaling responses to combinatorial stimuli.

    PubMed

    Chatterjee, Manash S; Purvis, Jeremy E; Brass, Lawrence F; Diamond, Scott L

    2010-07-01

    Prediction of cellular response to multiple stimuli is central to evaluating patient-specific clinical status and to basic understanding of cell biology. Cross-talk between signaling pathways cannot be predicted by studying them in isolation and the combinatorial complexity of multiple agonists acting together prohibits an exhaustive exploration of the complete experimental space. Here we describe pairwise agonist scanning (PAS), a strategy that trains a neural network model based on measurements of cellular responses to individual and all pairwise combinations of input signals. We apply PAS to predict calcium signaling responses of human platelets in EDTA-treated plasma to six different agonists (ADP, convulxin, U46619, SFLLRN, AYPGKF and PGE(2)) at three concentrations (0.1, 1 and 10 x EC(50)). The model predicted responses to sequentially added agonists, to ternary combinations of agonists and to 45 different combinations of four to six agonists (R = 0.88). Furthermore, we use PAS to distinguish between the phenotypic responses of platelets from ten donors. Training neural networks with pairs of stimuli across the dose-response regime represents an efficient approach for predicting complex signal integration in a patient-specific disease milieu. PMID:20562863

  7. Contrast polarity preservation's role in perception: explained and unexplained stimuli.

    PubMed

    McCormick, Meghan C; Hon, Alice J; Huang, Abigail E; Altschuler, Eric L

    2012-01-01

    Roncato and Casco (2003, Perception & psychophysics 65 1252-1272) had shown that in situations where the Gestalt principle of good continuity is put into conflict with preservation of contrast polarity (CP) the perception that preserves CP prevails. Parlangeli and Roncato (2010, Perception 39 255-259) have studied this question of preservation of CP more closely and have added an addendum to the rule. They have used stimuli consisting of a checkerboard of perpendicularly arranged rectangular bricks (white, gray, or black) and draughtsmen white, gray, or black disks placed at the corners of the bricks. This study has caused them to add an addendum to the rule of CP-preserved path-conjunction binding: if there are two contour completions that preserve the CP, the one with the higher contrast will prevail. Parlangeli and Roncato find that, for certain shades of the disks and bricks, the perpendicular lines of the checkerboard appear strikingly to be slanted or undulating. Here we consider all possible arrangements of relative magnitudes of checkerboards consisting of bricks of two different shades and disks of two shades as well, as such arrangements with widely varying differences in the magnitude of brightness. We have found a number of cases where the perception is not explained by the rule and addendum of Roncato and Casco, and Parlangeli and Roncato, and a case where preservation of "distant" as well as local CP plays a role in perception. The previously known cases, and the new exceptional unexplained stimuli we have found, warrant further study.

  8. 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

  9. 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. PMID:27375410

  10. Spatio-temporal processing of tactile stimuli in autistic children

    PubMed Central

    Wada, Makoto; Suzuki, Mayuko; Takaki, Akiko; Miyao, Masutomo; Spence, Charles; Kansaku, Kenji

    2014-01-01

    Altered multisensory integration has been reported in autism; however, little is known concerning how the autistic brain processes spatio-temporal information concerning tactile stimuli. We report a study in which a crossed-hands illusion was investigated in autistic children. Neurotypical individuals often experience a subjective reversal of temporal order judgments when their hands are stimulated while crossed, and the illusion is known to be acquired in early childhood. However, under those conditions where the somatotopic representation is given priority over the actual spatial location of the hands, such reversals may not occur. Here, we showed that a significantly smaller illusory reversal was demonstrated in autistic children than in neurotypical children. Furthermore, in an additional experiment, the young boys who had higher Autism Spectrum Quotient (AQ) scores generally showed a smaller crossed hands deficit. These results suggest that rudimentary spatio-temporal processing of tactile stimuli exists in autistic children, and the altered processing may interfere with the development of an external frame of reference in real-life situations. PMID:25100146

  11. 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.

  12. Multiple sensitivity to chemical stimuli in single human taste papillae.

    PubMed

    Bealer, S L; Smith, D V

    1975-06-01

    The sensitivities of 15 human fungiform papillae were tested using a 5-alternative forced-choice procedure. Subjects were aked to recognize which of the following stimuli was presented to a papilla on each of 250 trials: 5.0 M NaCl, 0.5 N citric acid, 1.0 M quinine hydrochloride, and distilled H2O. Solution droplets were delivered to individual papillae from 0.5 mm diameter platinum wire loops. Based on each subject's responses to distilled H2O, corrections were made for individual response biases. Of the papillae tested, 33 percent responded to all four compounds, 33 percent to three, none to only two, 20 percent to only one, and 13 percent to none of the chemical stimuli. These results are contradictory to earlier work, in which it was suggested that taste quality is encoded by chemically specific papillae, but are consistent with the electrophysiological data suggesting multiple sensitivity of mammalian gustatory receptor cells and first-order neurons. The data suggested that the narrow range of sensitivity reported by von Békésy [2] was determined by the reciprocal relationship between the size of the stimulated area and the concentration necessary to elicit a threshold sensation. PMID:1187834

  13. Nanoparticle role on the repeatability of stimuli-responsive nanocomposites.

    PubMed

    Ahn, Sungsook; Lee, Sang Joon

    2014-10-15

    Repeatability of the responsiveness with time is one important concern for effective durable functions of stimuli-responsive materials. Although the increase in the yield and tensile strength of the hybrid composite materials by nanoparticle (NP) incorporation has been reported, exact NP effect on stimuli-responsiveness is rarely reported. In this study, a set of nanoscale actuating system is demonstrated by a thermo-sensitive process operated by polyethylene glycol (PEG) linked by gold nanoparticle (AuNP). This designed nanocomposite exclusively provides an artificial on/off gate function for selective passages of permeate molecules. The results demonstrate high repetition efficiency with sharp responding in a timely manner. In terms of the morphology changes induced by repeated swelling-deswelling mechanics, the nanocomposite exhibits phase separation between AuNP clusters and PEG domains. This leads to a delay in responsiveness in a cumulative way with time. Acting as stable junction points in the nanocomposite network structures, the incorporated AuNPs contribute to maintain repeatability in responsiveness. This study contributes to new-concept smart material design and fundamental understanding on the hybrid nanomaterials for various applications in terms of a dynamic mechanical behavior.

  14. Optical and structural properties of InP quantum dots embedded in (AlxGa1-x)0.51In0.49P

    NASA Astrophysics Data System (ADS)

    Schulz, W.-M.; Roßbach, R.; Reischle, M.; Beirne, G. J.; Bommer, M.; Jetter, M.; Michler, P.

    2009-01-01

    Within this work we present optical and structural properties of InP quantum dots embedded in (AlxGa1-x)0.51In0.49P barriers. Atomic force microscopy measurements show a mainly bimodal height distribution with aspect ratios (ratio of width to height) of about 10:1 and quantum dot heights of around 2 nm for the smaller quantum dot class (type A) and around 4 nm for the larger quantum dot class (type B). From ensemble-photoluminescence measurements we estimated thermal activation energies of up to 270 meV for the type-A quantum dots, resulting in a 300 times higher luminescence intensity at 200 K in comparison to our InP quantum dots in Ga0.51In0.49P at the same emission wavelength. Photon statistic measurements clearly display that InP quantum dots in (Al0.20Ga0.80)0.51In0.49P emit single photons up to 80 K, making them promising candidates for high-temperature single-photon emitters.

  15. [Development and perspectives of community DOTS].

    PubMed

    Narita, Tomoyo; Kobayashi, Noriko

    2009-04-01

    The Japanese version of DOTS seems to have established itself. However, there is criticism that the primary purpose of DOTS expansion has often been supplanted by pressure to meet a quota. In this symposium, we returned to the starting point of DOTS, i.e., seeking a total cure of TB patients, and rededicated ourselves to our ultimate goal--TB elimination. In order to promote community DOTS more effectively, we should endeavor to build a community DOTS network with unified related information systems backed by government commitments. In so doing, we must continue to provide patients with support while respecting their rights and emphasizing their improved quality of life. 1. Achievements and challenges of DOTS conference: Yukiko SAITO (Fukujuji Hospital, JATA). We conduct face-to-face DOTS for all patients from the time of their admission until the time they are discharged. The DOTS conference is a place where hospitals and public health centers can share patient information, linking hospital DOTS with community DOTS. This meeting is an indispensable process in order to prevent patients' defaulting and irregular treatment. The ultimate goal of DOTS is treatment completion of tuberculosis patients, and in order to achieve that goal, a partnership among clinical, public health, and social services is crucial. The DOTS conference provides an opportunity for several public health centers to come together and share information. Conducting hospital DOTS and the DOTS conference in parallel facilitates providing comprehensive patient support. Continuing to hold regular DOTS conferences is both a sign of achievement of DOTS and a challenge for the future. 2. Achievements and challenges of cohort meeting in the TB control program in Kobe: Noriko TANAKA (Kobe City Public Health Office) The TB control program of Kobe City is based on the Second Five-Year TB strategy targeting the reduction of the TB incidence rate. It has five policy pillars, prevention and IEC, early case

  16. Reconstruction of Sensory Stimuli Encoded with Integrate-and-Fire Neurons with Random Thresholds

    PubMed Central

    Lazar, Aurel A.; Pnevmatikakis, Eftychios A.

    2013-01-01

    We present a general approach to the reconstruction of sensory stimuli encoded with leaky integrate-and-fire neurons with random thresholds. The stimuli are modeled as elements of a Reproducing Kernel Hilbert Space. The reconstruction is based on finding a stimulus that minimizes a regularized quadratic optimality criterion. We discuss in detail the reconstruction of sensory stimuli modeled as absolutely continuous functions as well as stimuli with absolutely continuous first-order derivatives. Reconstruction results are presented for stimuli encoded with single as well as a population of neurons. Examples are given that demonstrate the performance of the reconstruction algorithms as a function of threshold variability. PMID:24077610

  17. TOPICAL REVIEW: Polar and nonpolar GaN quantum dots

    NASA Astrophysics Data System (ADS)

    Daudin, Bruno

    2008-11-01

    Growth, structural and optical properties of GaN quantum dots are reviewed, with a special emphasis on plasma-assisted molecular beam epitaxy. The versatility of this technique makes it particularly adapted to growth of quantum dots, either polar (c-plane) or nonpolar (a-plane and m-plane). After describing in detail the growth process and analyzing the morphology of the dots, we review the optical properties of these nanostructures and discuss the properties of single dots.

  18. Slow electron cooling in colloidal quantum dots.

    PubMed

    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 approximately 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.

  19. PRISM3 DOT1 Atlantic Basin Reconstruction

    USGS Publications Warehouse

    Dowsett, Harry; Robinson, Marci; Dwyer, Gary; Chandler, Mark; Cronin, Thomas

    2006-01-01

    PRISM3 DOT1 (Pliocene Research, Interpretation and Synoptic Mapping 3, Deep Ocean Temperature 1) provides a three-dimensional temperature reconstruction for the mid-Pliocene Atlantic basin, the first of several regional data sets that will comprise a global mid-Pliocene reconstruction. DOT1 is an alteration of modern temperature values for the Atlantic Ocean in 4 degree x 5 degree cells in 13 depth layers for December 1 based on Mg/Ca-derived BWT estimates from seventeen DSDP and ODP Sites and SST estimates from the PRISM2 reconstruction (Dowsett et al., 1999). DOT1 reflects a vaguely modern circulation system, assuming similar processes of deep-water formation; however, North Atlantic Deep Water (NADW) production is increased, and Antarctic Bottom Water (AABW) production is decreased. Pliocene NADW was approximately 2 degreesC warmer than modern temperatures, and Pliocene AABW was approximately 0.3 degreesC warmer than modern temperatures.

  20. Quantum Dot-Based Cell Motility Assay

    SciTech Connect

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

    2005-06-06

    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.

  1. Low Frequency Noise in Mesoscopic Magnetic Dots

    NASA Astrophysics Data System (ADS)

    Dahlberg, E. Dan

    2014-03-01

    Measurements of random telegraph noise (RTN) in individual mesoscopic sized NiFe alloy dots will be presented; the dots dimensions are as small as 200nm x 200nm x 10nm. The temperature and magnetic field dependence of the RTN are explained by the energy landscape in the dots; the energy landscape RTN was independently measured [Appl. Phys. Lett. 103, 042409 (2013)]. The research was motivated by questions raised in understanding magnetic noise in magnetic tunnel junctions and giant magnetoresistance devices [Appl. Phys. Lett. 95, 062512 (2009) and Phys. Rev. B 88, 014409 (2013)]. This work was supported primarily by ONR Grant N00014-11-1-0850 and the MRSEC Program of the NSF under Grant No. DMR-0819885. Additional support for work done using the University of Minnesota Nanofabrication Center and Characterization Facility was provided by the NSF NNIN network. Reseach performed in collaboration with Dan Endean, Feng Guo, C. T. Weigelt and R. H. Victora.

  2. Isotopically enhanced triple-quantum-dot qubit.

    PubMed

    Eng, Kevin; Ladd, Thaddeus D; Smith, Aaron; Borselli, Matthew G; Kiselev, Andrey A; Fong, Bryan H; Holabird, Kevin S; Hazard, Thomas M; Huang, Biqin; Deelman, Peter W; Milosavljevic, Ivan; Schmitz, Adele E; Ross, Richard S; Gyure, Mark F; Hunter, Andrew T

    2015-05-01

    Like modern microprocessors today, future processors of quantum information may be implemented using all-electrical control of silicon-based devices. A semiconductor spin qubit may be controlled without the use of magnetic fields by using three electrons in three tunnel-coupled quantum dots. Triple dots have previously been implemented in GaAs, but this material suffers from intrinsic nuclear magnetic noise. Reduction of this noise is possible by fabricating devices using isotopically purified silicon. We demonstrate universal coherent control of a triple-quantum-dot qubit implemented in an isotopically enhanced Si/SiGe heterostructure. Composite pulses are used to implement spin-echo type sequences, and differential charge sensing enables single-shot state readout. These experiments demonstrate sufficient control with sufficiently low noise to enable the long pulse sequences required for exchange-only two-qubit logic and randomized benchmarking. PMID:26601186

  3. Three-terminal quantum-dot refrigerators

    NASA Astrophysics Data System (ADS)

    Zhang, Yanchao; Lin, Guoxing; Chen, Jincan

    2015-05-01

    Based on two capacitively coupled quantum dots in the Coulomb-blockade regime, a model of three-terminal quantum-dot refrigerators is proposed. With the help of the master equation, the transport properties of steady-state charge current and energy flow between two quantum dots and thermal reservoirs are revealed. It is expounded that such a structure can be used to construct a refrigerator by controlling the voltage bias and temperature ratio. The thermodynamic performance characteristics of the refrigerator are analyzed, including the cooling power, coefficient of performance (COP), maximum cooling power, and maximum COP. Moreover, the optimal regions of main performance parameters are determined. The influence of dissipative tunnel processes on the optimal performance is discussed in detail. Finally, the performance characteristics of the refrigerators operated in two different cases are compared.

  4. A hybrid double-dot in silicon

    SciTech Connect

    Gonzalez-Zalba, M. F.; Heiss, D.; Ferguson, A. J.

    2013-12-04

    We report electrical measurements of a single arsenic dopant atom in the tunnel barrier of a silicon single-electron transistor (SET). In addition to performing the electrical characterisation of the individual dopants, we study the series electrical transport through the dopant and SET. We measure the bias triangles of this hybrid double-dot and show that we can tune the electrostatic coupling between the two sub-systems. Additionally, we measured SET in which an additional plunger gate allows the reduction of the electron number in the SET down to the few-electron regime where the dot presents well-defined spin configurations. Finally, we discuss the challenges of operating a dopant-dot hybrid system in the few-electron regime.

  5. Isotopically enhanced triple-quantum-dot qubit

    PubMed Central

    Eng, Kevin; Ladd, Thaddeus D.; Smith, Aaron; Borselli, Matthew G.; Kiselev, Andrey A.; Fong, Bryan H.; Holabird, Kevin S.; Hazard, Thomas M.; Huang, Biqin; Deelman, Peter W.; Milosavljevic, Ivan; Schmitz, Adele E.; Ross, Richard S.; Gyure, Mark F.; Hunter, Andrew T.

    2015-01-01

    Like modern microprocessors today, future processors of quantum information may be implemented using all-electrical control of silicon-based devices. A semiconductor spin qubit may be controlled without the use of magnetic fields by using three electrons in three tunnel-coupled quantum dots. Triple dots have previously been implemented in GaAs, but this material suffers from intrinsic nuclear magnetic noise. Reduction of this noise is possible by fabricating devices using isotopically purified silicon. We demonstrate universal coherent control of a triple-quantum-dot qubit implemented in an isotopically enhanced Si/SiGe heterostructure. Composite pulses are used to implement spin-echo type sequences, and differential charge sensing enables single-shot state readout. These experiments demonstrate sufficient control with sufficiently low noise to enable the long pulse sequences required for exchange-only two-qubit logic and randomized benchmarking. PMID:26601186

  6. 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.

  7. 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. PMID:26238406

  8. 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.

  9. [The P300-based brain-computer interface: presentation of the complex "flash + movement" stimuli].

    PubMed

    Ganin, I P; Kaplan, A Ia

    2014-01-01

    The P300 based brain-computer interface requires the detection of P300 wave of brain event-related potentials. Most of its users learn the BCI control in several minutes and after the short classifier training they can type a text on the computer screen or assemble an image of separate fragments in simple BCI-based video games. Nevertheless, insufficient attractiveness for users and conservative stimuli organization in this BCI may restrict its integration into real information processes control. At the same time initial movement of object (motion-onset stimuli) may be an independent factor that induces P300 wave. In current work we checked the hypothesis that complex "flash + movement" stimuli together with drastic and compact stimuli organization on the computer screen may be much more attractive for user while operating in P300 BCI. In 20 subjects research we showed the effectiveness of our interface. Both accuracy and P300 amplitude were higher for flashing stimuli and complex "flash + movement" stimuli compared to motion-onset stimuli. N200 amplitude was maximal for flashing stimuli, while for "flash + movement" stimuli and motion-onset stimuli it was only a half of it. Similar BCI with complex stimuli may be embedded into compact control systems requiring high level of user attention under impact of negative external effects obstructing the BCI control.

  10. Late Positive Potential ERP Responses to Social and Nonsocial Stimuli in Youth with Autism Spectrum Disorder.

    PubMed

    Benning, Stephen D; Kovac, Megan; Campbell, Alana; Miller, Stephanie; Hanna, Eleanor K; Damiano, Cara R; Sabatino-DiCriscio, Antoinette; Turner-Brown, Lauren; Sasson, Noah J; Aaron, Rachel V; Kinard, Jessica; Dichter, Gabriel S

    2016-09-01

    We examined the late positive potential (LPP) event related potential in response to social and nonsocial stimuli from youths 9 to 19 years old with (n = 35) and without (n = 34) ASD. Social stimuli were faces with positive expressions and nonsocial stimuli were related to common restricted interests in ASD (e.g., electronics, vehicles, etc.). The ASD group demonstrated relatively smaller LPP amplitude to social stimuli and relatively larger LPP amplitude to nonsocial stimuli. There were no group differences in subjective ratings of images, and there were no significant correlations between LPP amplitude and ASD symptom severity within the ASD group. LPP results suggest blunted motivational responses to social stimuli and heightened motivational responses to nonsocial stimuli in youth with ASD. PMID:27344337

  11. 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.

  12. 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…

  13. Resonant tunneling in graphene pseudomagnetic quantum dots.

    PubMed

    Qi, Zenan; Bahamon, D A; Pereira, Vitor M; Park, Harold S; Campbell, D K; Neto, A H Castro

    2013-06-12

    Realistic relaxed configurations of triaxially strained graphene quantum dots are obtained from unbiased atomistic mechanical simulations. The local electronic structure and quantum transport characteristics of y-junctions based on such dots are studied, revealing that the quasi-uniform pseudomagnetic field induced by strain restricts transport to Landau level- and edge state-assisted resonant tunneling. Valley degeneracy is broken in the presence of an external field, allowing the selective filtering of the valley and chirality of the states assisting in the resonant tunneling. Asymmetric strain conditions can be explored to select the exit channel of the y-junction.

  14. Potential clinical applications of quantum dots

    PubMed Central

    Medintz, Igor L; Mattoussi, Hedi; Clapp, Aaron R

    2008-01-01

    The use of luminescent colloidal quantum dots in biological investigations has increased dramatically over the past several years due to their unique size-dependent optical properties and recent advances in biofunctionalization. In this review, we describe the methods for generating high-quality nanocrystals and report on current and potential uses of these versatile materials. Numerous examples are provided in several key areas including cell labeling, biosensing, in vivo imaging, bimodal magnetic-luminescent imaging, and diagnostics. We also explore toxicity issues surrounding these materials and speculate about the future uses of quantum dots in a clinical setting. PMID:18686776

  15. Bilayer graphene quantum dot defined by topgates

    SciTech Connect

    Müller, André; Kaestner, Bernd; Hohls, Frank; Weimann, Thomas; Pierz, Klaus; Schumacher, Hans W.

    2014-06-21

    We investigate the application of nanoscale topgates on exfoliated bilayer graphene to define quantum dot devices. At temperatures below 500 mK, the conductance underneath the grounded gates is suppressed, which we attribute to nearest neighbour hopping and strain-induced piezoelectric fields. The gate-layout can thus be used to define resistive regions by tuning into the corresponding temperature range. We use this method to define a quantum dot structure in bilayer graphene showing Coulomb blockade oscillations consistent with the gate layout.

  16. Ambipolar quantum dots in intrinsic silicon

    SciTech Connect

    Betz, A. C. Gonzalez-Zalba, M. F.; Podd, G.; Ferguson, A. J.

    2014-10-13

    We electrically measure intrinsic silicon quantum dots with electrostatically defined tunnel barriers. The presence of both p- and n-type ohmic contacts enables the accumulation of either electrons or holes. Thus, we are able to study both transport regimes within the same device. We investigate the effect of the tunnel barriers and the electrostatically defined quantum dots. There is greater localisation of charge states under the tunnel barriers in the case of hole conduction, leading to higher charge noise in the p-type regime.

  17. 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.

  18. 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.

  19. 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.

  20. Identifying selective visual attention biases related to fear of pain by tracking eye movements within a dot-probe paradigm.

    PubMed

    Yang, Zhou; Jackson, Todd; Gao, Xiao; Chen, Hong

    2012-08-01

    This research examined selective biases in visual attention related to fear of pain by tracking eye movements (EM) toward pain-related stimuli among the pain-fearful. EM of 21 young adults scoring high on a fear of pain measure (H-FOP) and 20 lower-scoring (L-FOP) control participants were measured during a dot-probe task that featured sensory pain-neutral, health catastrophe-neutral and neutral-neutral word pairs. Analyses indicated that the H-FOP group was more likely to direct immediate visual attention toward sensory pain and health catastrophe words than was the L-FOP group. The H-FOP group also had comparatively shorter first fixation latencies toward sensory pain and health catastrophe words. Conversely, groups did not differ on EM indices of attentional maintenance (i.e., first fixation duration, gaze duration, and average fixation duration) or reaction times to dot probes. Finally, both groups showed a cycle of disengagement followed by re-engagement toward sensory pain words relative to other word types. In sum, this research is the first to reveal biases toward pain stimuli during very early stages of visual information processing among the highly pain-fearful and highlights the utility of EM tracking as a means to evaluate visual attention as a dynamic process in the context of FOP. PMID:22717101