Tinnitus is the experience of sounds without an appropriate external auditory source. These auditory sensations are intertwined with emotional and attentional processing. Drawing on theories of mental control, we predicted that suppressing an affectively negative sound mimicking the psychoacoustic features of tinnitus would result in decreased persistence in a mentally challenging task (mental arithmetic) that required participants to ignore the same sound, but that receiving a mindfulness exercise would reduce this effect. Normal hearing participants (N = 119) were instructed to suppress an affectively negative sound under cognitive load or were given no such instructions. Next, participants received either a mindfulness induction or an attention control task. Finally, all participants worked with mental arithmetic while exposed to the same sound. The length of time participants could persist in the second task served as the dependent variable. As hypothesized, results indicated that an auditory suppression rationale reduced time of persistence relative to no such rationale, and that a mindfulness induction counteracted this detrimental effect. The study may offer new insights into the mechanisms involved in the development of tinnitus interference. Implications are also discussed in the broader context of attention control strategies and the effects of emotional sound on task performance. The ironic processes of mental control may have an analog in the experience of sounds. / <p>On the day of the defence date the status of this article was <em>Manuscript</em>.</p>

A multi band orthogonal frequency division multiplexing (MB-OFDM) compatible ultra wideband (UWB) receiver with narrowband interference (NBI) suppression capability is presented. The average transmit power of UWB system is limited to -41.3 dBm/MHz in order to not interfere existing narrowband systems. Moreover, it must operate even in the presence of unintentional radiation of FCC Class-B compatible devices. If this unintentional radiation resides in the UWB band, it can jam the communication. Since removing the interference in digital domain requires higher dynamic range of analog front-end than removing it in analog domain, a programmable analog notch filter is used to relax the receiver requirements in the presence of NBI. The baseband filter is placed before the variable gain amplifier (VGA) in order to reduce the signal swing at the VGA input. The frequency hopping period of MB-OFDM puts a lower limit on the settling time of the filter, which is inverse proportional to notch bandwidth. However, notch bandwidth should be low enough not to attenuate the adjacent OFDM tones. Since these requirements are contradictory, optimization is needed to maximize overall performance. Two different NBI suppression schemes are tested. In the first scheme, the notch filter is operating for all sub-bands. In the second scheme, the notch filter is turned on during the sub-band affected by NBI. Simulation results indicate that the UWB system with the first and the second suppression schemes can handle up to 6 dB and 14 dB more NBI power, respectively. The results of this work are not limited to MB-OFDM UWB system, and can be applied to other frequency hopping systems.

In todays highly maneuverable jet aircraft designs, aircraft are required to have a propulsion system that can operate during sudden accelerations and rapid changes in angle-of-attack. Consequently, the compressor of the jet engine occasionally must operate at low-flow rates and rapid changes in inlet conditions. The high angle-of-attack and low-flow regime of compressor operation is often plagued by rotating stall and surge. Rotating stall and surge can result in loss of engine performance, rapid heating of the blades, and severe mechanical stresses. Traditional methods for suppressing rotating stall and surge only partially protect against rotating stall or reduce compressor efficiency. The objective of this research is to design a stall suppression system that will introduce oscillatory blowing into one of the rotor blade (stall suppression blade). This oscillatory blowing method has been tested on a wing section in a wind tunnel and has shown to increase the stall angle-of-attack by several degrees.\cite{gilarranzetal02} This increase in stall angle-of-attack will eliminate stall cells as they form in the compressor. The goal of this research is to design a single stage axial compressor that will incorporate the new oscillatory blowing stall suppression system; moreover, this research will design, build, and test a scaled down version of this suppression system.

No description available.

Recent studies have discovered that LPS-treated Sprague-Dawley rats induced a reduction (phase I), followed by an augmentation (phase II), and decrease again (phase III) in the power density of the vasomotor component (0-0.8 Hz) in systemic arterial pressure (SAP). It was reported that the vasomotor components were related to the brain stem, even closely related to the rostral ventrolateral medulla (RVLM). But the molecular mechanism involved in the death progression of rat brain stem is mostly unknown. We used suppression subtractive hybridization (SSH) and library construction to find differentially expressed genes between phase I and phase II of LPS-treated RVLM. At present, we have found some genes that are differentially expressed between phase I and phase II of LPS-treated RVLM. Some genes are up-regulation expression and others are down-regulation expression. Thus, these genes may be involved in the molecular mechanism of the death progression in the rat brain stem.

Modern satellite, wireless communications, and radar systems often demand wideband performance for multi-channel and multi-function operations. Among these applications, phased array antennas play an important role. This dissertation covers two wideband phased array antennas, one produces linear polarization and one produces circular polarization. The main difference between these two phased array antennas is the antenna array. For the linearly polarized array, a wideband microstrip line to slotline transition is used to feed a Vivaldi antenna. For the circularly polarized array, a wideband microstrip line to parallel stripline transition is used to feed a spiral antenna. From 3 to 12 GHz, the linearly polarized beam is steered over ± 15º. Since the electromagnetic spectrum is limited and has to be shared, interference is getting serious as more and more wireless applications emerge. Filters are key components to prevent harmonic interference. The harmonic signals can be suppressed by cascading additional lowpass filters or bandstop filters. A bandstop filter combining shunt open stubs and a spurline is proposed for a compact size and a deeper rejection. Two lowpass filters with interdigital capacitors and slotted ground structures are also studied. Harmonic suppression can also be achieved with the modification of bandpass filters. Three conventional bandpass filters with spurious passbands are investigated. The first one is a dual-mode patch bandpass filter. The second passband of the proposed filter is at 2.88fo, where fo is the fundametal frequency. The second filter is an open-loop bandpass filter. Two open stubs are added to achieve high suppression in the second harmonic signal. The suppression of 35 dB at the second harmonic is obtained. For the third filter using half-wavelength open stubs, a T-shaped line is used to replace the quarter-wavelength connecting line. The T-shaped line has the same response with the connecting line in the passband. Furthermore, the T-shaped line works as a bandstop filter at the second harmonic. Finally, a new compact slow-wave resonator and bandpass filters are presented. A simple transmission-line model is used to predict the resonant frequency. Compared with the conventional uniform half-wavelength resonator, the slow-wave resonator shows a 25% size reduction.

Recent investigations have suggested that the use of emotion-avoidance or emotion- suppression strategies to cope with anxiety contributes to the development and maintenance of anxiety disorders, and that substituting these strategies with emotional acceptance can lead to effective symptom reduction. We wished to consider whether attempts to suppress the negative emotions associated with exposure therapy would serve to impede emotional processing and symptom reduction, and conversely, whether acceptance of these emotions would augment treatment efficacy. Fifty-nine participants displaying marked claustrophobic fear were assigned to receive 30 minutes of exposure (enclosure in a small chamber) while receiving, A) instructions to accept and allow the experience of unpleasant emotions (ACC), B) instructions to control and suppress the experience of unpleasant emotions (SUP), or C) no instructions regarding emotion regulation (exposure only; EO). Outcome assessments were conducted prior to treatment, immediately following treatment, and at one-month follow-up, and included fear and heart rate reactivity in response to a behavioral approach test. We predicted that ACC participants would display greater reductions in claustrophobic fear than EO participants, and that EO participants would in turn display greater reductions in claustrophobic fear than SUP participants. These hypotheses were not supported. In addition, a detailed analysis of treatment process data was conducted. Peak fear ratings, claustrophobic threat expectancies, self-efficacy, and acceptance of anxiety were collected over the course of the treatment session, and hierarchical linear modeling (HLM) was used to produce individual growth curves for these variables. Three hypotheses were formulated: 1) ACC participants would display a more rapid improvement in these measures than SUP and EO participants, 2) threat expectancies, self-efficacy and anxiety would mediate reductions in fear over the course of treatment, and 3) mediational pathways would be moderated by treatment condition. Though no support was found for our first process hypothesis, treatment specific mediation was found. Among ACC participants, self-efficacy and suffocation expectancies mediated the session-fear relationship, and among EO participants, entrapment expectancies mediated this relationship. Among SUP participants, no significant mediators were identified. / text

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Intrusive cognitions are a natural occurrence within our stream of consciousness, however, when they become repetitive, negative, distressing, and difficult to control, they may warrant clinical concern. Thought suppression is a common control strategy used to manage intrusive thoughts even though research suggests it may actually exacerbate the problem. Conversely, acceptance-based interventions have gained recent attention as an alternative strategy for managing distressing internal experiences. Only preliminary research has focused on the psycho- and neurophysiological bases of intrusive cognitions, and their relationship to cognitive control strategies. Evidence suggests that the anterior cingulate cortex (ACC) may be a brain region critically involved in this process. The present investigation compared the subjective, behavioral, and physiological effects of a thought suppression and acceptance strategy in a sample of university students with high or low obsessive-compulsive (OC) characteristics who were exposed to an emotion-evoking film clip. Participants were instructed either to suppress or accept any intrusive cognitions during a rest period after the film clip, while monitoring for the number of intrusions. Next, psychophysiological signals and reaction times were measured while participants performed a variant of the Stroop task. The commission of errors during a forced choice task generates an error-related negativity (ERN), which is believed to index activity in the ACC. Results showed that self-reported intrusions during the rest interval were greater for the acceptance group and the high-OC group. Correlations suggested that participants who reported more effort at suppression also indicated more distress about their thoughts, whereas those who reported more acceptance indicated less distress. During Stroop task errors, the ERN was apparent as a maximal frontal negativity, and was larger for the suppression group than the acceptance group at a frontal scalp site (Fz), but not a central scalp site (Cz). Correlations between self-reported intrusions at rest and ERN amplitude indicated that participants who reported fewer intrusions demonstrated enhanced ERNs, a marker for increased ACC activity. These findings may be interpreted as supporting the hypothesis that thought suppression is associated with increased ACC activity and greater self-reported discomfort with the intrusions.

No description available.