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Sample records for gastric slow wave

  1. Detection of the Recovery Phase of in vivo Gastric Slow Wave Recordings

    PubMed Central

    Paskaranandavadivel, Niranchan; Pan, Xingzheng; Du, Peng; O’Grady, Gregory; Cheng, Leo K.

    2016-01-01

    Gastric motility is coordinated by bio-electrical events known as slow waves. Abnormalities in slow waves are linked to major functional and motility disorders. In recent years, the use of high-resolution (HR) recordings have provided a unique view of spatiotemporal activation profiles of normal and dysrhythmic slow wave activity. To date, in vivo studies of gastric slow wave activity have primarily focused on the activation phase of the slow wave event. In this study, the recovery phase of slow waves was investigated through the use of HR recording techniques. The recovery phase of the slow wave event was detected through the use of the signal derivative, computed via a wavelet transform. The activation to recovery interval (ARi) metric was computed as a difference between the recovery time and activation time. The detection method was validated with synthetic slow wave signals of varying morphologies with the addition of synthetic ventilator and high frequency noise. The methods was then applied to HR experimental porcine gastric slow wave recordings. Ventilator noise more than 10% of the slow wave amplitude affected the estimation of the ARi metric. Signal to noise ratio below 3 dB affected the ARi metric, but with minor deviation in accuracy. Experimental ARi values ranged from 3.7–4.7 s from three data sets, with significant differences across them. PMID:26737682

  2. Effects of body mass index on gastric slow wave: a magnetogastrographic study.

    PubMed

    Somarajan, S; Cassilly, S; Obioha, C; Richards, W O; Bradshaw, L A

    2014-02-01

    We measured gastric slow wave activity simultaneously with magnetogastrogram (MGG), mucosal electromyogram (EMG) and electrogastrogram (EGG) in human subjects with varying body mass index (BMI) before and after a meal. In order to investigate the effect of BMI on gastric slow wave parameters, each subject's BMI was calculated and divided into two groups: subjects with BMI ≤ 27 and BMI > 27. Signals were processed with Fourier spectral analysis and second-order blind identification (SOBI) techniques. Our results showed that increased BMI does not affect signal characteristics such as frequency and amplitude of EMG and MGG. Comparison of the postprandial EGG power, on the other hand, showed a statistically significant reduction in subjects with BMI > 27 compared with BMI ≤ 27. In addition to the frequency and amplitude, the use of SOBI-computed propagation maps from MGG data allowed us to visualize the propagating slow wave and compute the propagation velocity in both BMI groups. No significant change in velocity with increasing BMI or meal was observed in our study. In conclusion, multichannel MGG provides an assessment of frequency, amplitude and propagation velocity of the slow wave in subjects with differing BMI categories and was observed to be independent of BMI. PMID:24398454

  3. A System and Method for Online High-Resolution Mapping of Gastric Slow-Wave Activity

    PubMed Central

    Bull, Simon H.; O’Grady, Gregory; Du, Peng

    2015-01-01

    High-resolution (HR) mapping employs multielectrode arrays to achieve spatially detailed analyses of propagating bioelectrical events. A major current limitation is that spatial analyses must currently be performed “off-line” (after experiments), compromising timely recording feedback and restricting experimental interventions. These problems motivated development of a system and method for “online” HR mapping. HR gastric recordings were acquired and streamed to a novel software client. Algorithms were devised to filter data, identify slow-wave events, eliminate corrupt channels, and cluster activation events. A graphical user interface animated data and plotted electrograms and maps. Results were compared against off-line methods. The online system analyzed 256-channel serosal recordings with no unexpected system terminations with a mean delay 18 s. Activation time marking sensitivity was 0.92; positive predictive value was 0.93. Abnormal slow-wave patterns including conduction blocks, ectopic pacemaking, and colliding wave fronts were reliably identified. Compared to traditional analysis methods, online mapping had comparable results with equivalent coverage of 90% of electrodes, average RMS errors of less than 1 s, and CC of activation maps of 0.99. Accurate slow-wave mapping was achieved in near real-time, enabling monitoring of recording quality and experimental interventions targeted to dysrhythmic onset. This work also advances the translation of HR mapping toward real-time clinical application. PMID:24860024

  4. Rapid high-amplitude circumferential slow wave propagation during normal gastric pacemaking and dysrhythmias

    PubMed Central

    O'Grady, Gregory; Du, Peng; Paskaranandavadivel, Nira; Angeli, Timothy R.; Lammers, Wim JEP; Asirvatham, Samuel J.; Windsor, John A.; Farrugia, Gianrico; Pullan, Andrew J.; Cheng, Leo K.

    2012-01-01

    Background Gastric slow waves propagate aborally as rings of excitation. Circumferential propagation does not normally occur, except at the pacemaker region. We hypothesized that: i) the unexplained high-velocity, high-amplitude activity associated with the pacemaker region is a consequence of circumferential propagation; ii) rapid, high-amplitude circumferential propagation emerges during gastric dysrhythmias; iii) the driving network conductance might switch between ICC-MP and circular ICC-IM during circumferential propagation; iv) extracellular amplitudes and velocities are correlated. Methods An experimental-theoretical study was performed. HR gastric mapping was performed in pigs during normal activation, pacing and dysrhythmia. Activation profiles, velocities and amplitudes were quantified. ICC pathways were theoretically evaluated in a bidomain model. Extracellular potentials were modelled as a function of membrane potentials. Key Results High-velocity, high-amplitude activation was only recorded in the pacemaker region when circumferential conduction occurred. Circumferential propagation accompanied dysrhythmia in 8/8 experiments, was faster than longitudinal propagation (8.9 vs 6.9 mm/s; p=0.004), and of higher amplitude (739 vs 528 μV; p=0.007). Simulations predicted that ICC-MP could be the driving network during longitudinal propagation, whereas during ectopic pacemaking, ICC-IM could outpace and activate ICC-MP in the circumferential axis. Experimental and modeling data demonstrated a linear relationship between velocities and amplitudes (p<0.001). Conclusions & Inferences The high-velocity and high-amplitude profile of the normal pacemaker region is due to localized circumferential propagation. Rapid circumferential propagation also emerges during a range of gastric dysrhythmias, elevating extracellular amplitudes and organizing transverse wavefronts. One possible explanation for these findings is bidirectional coupling between ICC-MP and circular

  5. Biomagnetic and bioelectric detection of gastric slow wave activity in normal human subjects – a correlation study

    PubMed Central

    Somarajan, S; Muszynski, ND; Obioha, C; Richards, WO; Bradshaw, LA

    2012-01-01

    We measured gastric slow wave activity simultaneously with a Superconducting Quantum Interference Device (SQUID) magnetometer, mucosal electrodes, and cutaneous electrodes in 18 normal human subjects (11 women and 7 men). We processed signals with Fourier spectral analysis and SOBI blind-source separation techniques. We observed a high waveform correlation between mucosal electromyogram (EMG) and multichannel SQUID magnetogastrogram (MGG). There was a lower waveform correlation between mucosal EMG and cutaneous electrogastrogram (EGG), but the correlation improved with application of SOBI. There was also a high correlation between the frequency of the electrical activity recorded in MGG and in mucosal electrodes (r =0.97). We concluded that SQUID magnetometers noninvasively record gastric slow wave activity that is highly correlated with the activity recorded by invasive mucosal electrodes. PMID:22735166

  6. Development of gastric slow waves and effects of feeding in pre-term and full-term infants.

    PubMed

    Zhang, J; Ouyang, H; Zhu, H B; Zhu, H; Lin, X; Co, E; Hayes, J; Chen, J D Z

    2006-04-01

    The aims of this study were to investigate the difference in developmental process of gastric slow waves and the effects of feeding in pre-term and full-term infants. Twenty-six pre-term and 31 full-term infants were enrolled in the study. Gastric myoelectrical activity was recorded using electrogastrography (EGG) from birth to month 6. An increase in the % of 2-4 cpm slow waves was noted in both pre-term (P < 0.01) and full-term infants (P < 0.04) from birth to month 4. The pre-term infants showed a reduced dominant EGG power at certain points of the study. (3) Breast or formula feeding resulted in no difference in the EGG in the full-term infants and showed a difference in the postprandial dominant power of the EGG in the pre-term infants only at month 2 after birth (P < 0.05) but not at other times. The gastric slow wave in pre-term infants is of a significantly reduced amplitude but similar rhythmicity. The method of feeding has no effects on the EGG in full-term infants and minimal effects (may be of non-clinical significance) on the EGG in pre-term infants as the difference was noted only at one time point during the 6-month follow-up study. PMID:16553583

  7. A Framework for the Online Analysis of Multi-Electrode Gastric Slow Wave Recordings

    PubMed Central

    Bull, Simon H.; O’Grady, Greg; Cheng, Leo K.; Pullan, Andrew J.

    2014-01-01

    High resolution mapping of electrical activity is becoming an important technique for analysing normal and dysrhythmic gastrointestinal (GI) slow wave activity. Several methods are used to extract meaningful information from the large quantities of data obtained, however, at present these methods can only be used offline. Thus, all analysis currently performed is retrospective and done after the recordings have finished. Limited information about the quality or characteristics of the data is therefore known while the experiments take place. Building on these offline analysis methods, an online implementation has been developed that identifies and displays slow wave activations working alongside an existing recording system. This online system was developed by adapting existing and novel signal processing techniques and linking these to a new user interface to present the extracted information. The system was tested using high resolution porcine data, and will be applied in future high resolution mapping studies allowing researchers to respond in real time to experimental observations. PMID:22254663

  8. A miniature bidirectional telemetry system for in vivo gastric slow wave recordings.

    PubMed

    Farajidavar, Aydin; O'Grady, Gregory; Rao, Smitha M N; Cheng, Leo K; Abell, Thomas; Chiao, J-C

    2012-06-01

    Stomach contractions are initiated and coordinated by an underlying electrical activity (slow waves), and electrical dysrhythmias accompany motility diseases. Electrical recordings taken directly from the stomach provide the most valuable data, but face technical constraints. Serosal or mucosal electrodes have cables that traverse the abdominal wall, or a natural orifice, causing discomfort and possible infection, and restricting mobility. These problems motivated the development of a wireless system. The bidirectional telemetric system constitutes a front-end transponder, a back-end receiver and a graphical userinter face. The front-end module conditions the analogue signals, then digitizes and loads the data into a radio for transmission. Data receipt at the backend is acknowledged via a transceiver function. The system was validated in a bench-top study, then validated in vivo using serosal electrodes connected simultaneously to a commercial wired system. The front-end module was 35 × 35 × 27 mm3 and weighed 20 g. Bench-top tests demonstrated reliable communication within a distance range of 30 m, power consumption of 13.5 mW, and 124 h operation when utilizing a 560 mAh, 3 V battery. In vivo,slow wave frequencies were recorded identically with the wireless and wired reference systems (2.4 cycles min−1), automated activation time detection was modestly better for the wireless system (5% versus 14% FP rate), and signal amplitudes were modestly higher via the wireless system (462 versus 3 86μV; p<0.001). This telemetric system for slow wave acquisition is reliable,power efficient, readily portable and potentially implantable. The device will enable chronic monitoring and evaluation of slow wave patterns in animals and patients.0967-3334/ PMID:22635054

  9. Automated Gastric Slow Wave Cycle Partitioning and Visualization for High-resolution Activation Time Maps

    PubMed Central

    Erickson, Jonathan C.; O’Grady, Greg; Du, Peng; Egbuji, John U.; Pullan, Andrew J.; Cheng, Leo K.

    2014-01-01

    High-resolution (HR) multi-electrode mapping has become an important technique for evaluating gastrointestinal (GI) slow wave (SW) behaviors. However, the application and uptake of HR mapping has been constrained by the complex and laborious task of analyzing the large volumes of retrieved data. Recently, a rapid and reliable method for automatically identifying activation times (ATs) of SWs was presented, offering substantial efficiency gains. To extend the automated data-processing pipeline, novel automated methods are needed for partitioning identified ATs into their propagation cycles, and for visualizing the HR spatiotemporal maps. A novel cycle partitioning algorithm (termed REGROUPS) is presented. REGROUPS employs an iterative REgion GROwing procedure and incorporates a Polynomial-surface-estimate Stabilization step, after initiation by an automated seed selection process. Automated activation map visualization was achieved via an isochronal contour mapping algorithm, augmented by a heuristic 2-step scheme. All automated methods were collectively validated in a series of experimental test cases of normal and abnormal SW propagation, including instances of patchy data quality. The automated pipeline performance was highly comparable to manual analysis, and outperformed a previously proposed partitioning approach. These methods will substantially improve the efficiency of GI HR mapping research. PMID:20927594

  10. Slow frictional waves

    NASA Astrophysics Data System (ADS)

    Viswanathan, Koushik; Sundaram, Narayan; Chandrasekar, Srinivasan

    Stick-slip, manifest as intermittent tangential motion between two dry solid surfaces, is a friction instability that governs diverse phenomena from automobile brake squeals to earthquakes. We show, using high-speed in situ imaging of an adhesive polymer interface, that low velocity stick-slip is fundamentally of three kinds, corresponding to passage of three different surface waves -- separation pulses, slip pulses and the well-known Schallamach waves. These waves, traveling much slower than elastic waves, have clear distinguishing properties. Separation pulses and Schallamach waves involve local interface separation, and propagate in opposite directions while slip pulses are characterized by a sharp stress front and do not display any interface detachment. A change in the stick-slip mode from separation to slip pulse is effected simply by increasing the normal force. Together, these three waves constitute all possible stick-slip modes in adhesive friction and are shown to have direct analogues in muscular locomotory waves in soft bodied invertebrates. A theory for slow wave propagation is also presented which is capable of explaining the attendant interface displacements, velocities and stresses.

  11. Source modeling sleep slow waves

    PubMed Central

    Murphy, Michael; Riedner, Brady A.; Huber, Reto; Massimini, Marcello; Ferrarelli, Fabio; Tononi, Giulio

    2009-01-01

    Slow waves are the most prominent electroencephalographic (EEG) feature of sleep. These waves arise from the synchronization of slow oscillations in the membrane potentials of millions of neurons. Scalp-level studies have indicated that slow waves are not instantaneous events, but rather they travel across the brain. Previous studies of EEG slow waves were limited by the poor spatial resolution of EEGs and by the difficulty of relating scalp potentials to the activity of the underlying cortex. Here we use high-density EEG (hd-EEG) source modeling to show that individual spontaneous slow waves have distinct cortical origins, propagate uniquely across the cortex, and involve unique subsets of cortical structures. However, when the waves are examined en masse, we find that there are diffuse hot spots of slow wave origins centered on the lateral sulci. Furthermore, slow wave propagation along the anterior−posterior axis of the brain is largely mediated by a cingulate highway. As a group, slow waves are associated with large currents in the medial frontal gyrus, the middle frontal gyrus, the inferior frontal gyrus, the anterior cingulate, the precuneus, and the posterior cingulate. These areas overlap with the major connectional backbone of the cortex and with many parts of the default network. PMID:19164756

  12. FEL on slow cyclotron wave

    SciTech Connect

    Silivra, A.

    1995-12-31

    A physical mechanism of interaction of fast electromagnetic wave with slow cyclotron wave of relativistic electron beam in a FEL with helical wiggler field is described. It is shown that: (1) interaction is possible for both group of steady state electron trajectories (2) positive gain is achieved within certain interval of guide field strength (3) operation wavelength for group 1 trajectories ({Omega}{sub 0}/{gamma} < k{omega}{upsilon}{parallel}) is shorter than for the conventional FEL synchronism. A nonlinear analysis shows that efficiency of slow cyclotron FEL is restricted mainly by a breakdown of a single electron synchronism due to dependence of (modified) electron cyclotron frequency on an energy of electron. Nevertheless, as numerical simulation shows, typical efficiency of 15 % order is achieved in millimeter wavelength band for the midrelativistic ({gamma}= 3 {divided_by} 4) slow cyclotron wave FEL. Tapering of magnetic field results in a substantial increase of efficiency.

  13. Human Gamma Oscillations during Slow Wave Sleep

    PubMed Central

    Valderrama, Mario; Crépon, Benoît; Botella-Soler, Vicente; Martinerie, Jacques; Hasboun, Dominique; Alvarado-Rojas, Catalina; Baulac, Michel; Adam, Claude; Navarro, Vincent; Le Van Quyen, Michel

    2012-01-01

    Neocortical local field potentials have shown that gamma oscillations occur spontaneously during slow-wave sleep (SWS). At the macroscopic EEG level in the human brain, no evidences were reported so far. In this study, by using simultaneous scalp and intracranial EEG recordings in 20 epileptic subjects, we examined gamma oscillations in cerebral cortex during SWS. We report that gamma oscillations in low (30–50 Hz) and high (60–120 Hz) frequency bands recurrently emerged in all investigated regions and their amplitudes coincided with specific phases of the cortical slow wave. In most of the cases, multiple oscillatory bursts in different frequency bands from 30 to 120 Hz were correlated with positive peaks of scalp slow waves (“IN-phase” pattern), confirming previous animal findings. In addition, we report another gamma pattern that appears preferentially during the negative phase of the slow wave (“ANTI-phase” pattern). This new pattern presented dominant peaks in the high gamma range and was preferentially expressed in the temporal cortex. Finally, we found that the spatial coherence between cortical sites exhibiting gamma activities was local and fell off quickly when computed between distant sites. Overall, these results provide the first human evidences that gamma oscillations can be observed in macroscopic EEG recordings during sleep. They support the concept that these high-frequency activities might be associated with phasic increases of neural activity during slow oscillations. Such patterned activity in the sleeping brain could play a role in off-line processing of cortical networks. PMID:22496749

  14. Slow-wave synchronous pick-up and kicker

    SciTech Connect

    DiMassa, G.

    1988-01-01

    Slow-wave synchronous pick-up (PU) and Kicker (K) are proposed for the stochastic cooling of bunched beams in RHIC. A corrugated waveguide is used to support a slow wave that is synchronous with the beam.

  15. Sheet beam slow-wave amplifiers

    SciTech Connect

    Kirolous, H.; Joe, J.; Basten, M.A.; Booske, J.H.; Scharer, J.E.; Anderson, J.; True, R.; Scheitrum, G.

    1994-12-31

    Sheet electron beams used in conjunction with slow-wave (Cerenkov) structures are a promising way to realize higher average power millimeter-wave amplifiers. For example, a sheet beam with a meander line structure is proposed to obtain a 100 watt W-band power booster amplifier. A sheet beam with a tapered grating structure is also being considered as a wideband ({approximately} 10--20% instantaneous bandwidth) Ka-band amplifier with approximately 10 kW of average output power. The authors describe results of research that examine critical technological issues relevant to the realization of the proposed devices. The method of forming a sheet beam using magnetic quadrupole lenses and focusing it using periodically-cusped magnetic (PCM) fields are discussed. A pencil beam from a 10 kV, 0.25 A Pierce electron source is used for the initial investigations. The EGUN simulations with the measured magnetic field indicates that a thin (2 mm dia.) beam is available at the interaction region. Beam characterization has been performed using current density probes and an electrostatic velocity spread analyzer. Numerical modeling and cold test measurements of a tapered slow-wave structure together with the simulations and measurements of small-signal gain and bandwidth are also presented.

  16. Slow EIT waves as gravity modes

    SciTech Connect

    Vranjes, J.

    2011-06-15

    The EIT waves [named after the extreme-ultraviolet imaging telescope (EIT) onboard the solar and heliospheric observatory (SOHO)] are in the literature usually described as fast magneto-acoustic (FMA) modes. However, observations show that a large percentage of these events propagate with very slow speeds that may be as low as 20 km/s. This is far below the FMA wave speed which cannot be below the sound speed, the latter being typically larger than 10{sup 2} km/s in the corona. In the present study, it is shown that, to account for such low propagation speed, a different wave model should be used, based on the theory of gravity waves, both internal (IG) and surface (SG) ones. The gravity modes are physically completely different from the FMA mode, as they are essentially dispersive and in addition the IG wave is a transverse mode. Both the IG and the SG mode separately can provide proper propagation velocities in the whole low speed range.

  17. Slow Wave Sleep and Long Duration Spaceflight

    NASA Technical Reports Server (NTRS)

    Whitmire, Alexandra; Orr, Martin; Arias, Diana; Rueger, Melanie; Johnston, Smith; Leveton, Lauren

    2012-01-01

    While ground research has clearly shown that preserving adequate quantities of sleep is essential for optimal health and performance, changes in the progression, order and /or duration of specific stages of sleep is also associated with deleterious outcomes. As seen in Figure 1, in healthy individuals, REM and Non-REM sleep alternate cyclically, with stages of Non-REM sleep structured chronologically. In the early parts of the night, for instance, Non-REM stages 3 and 4 (Slow Wave Sleep, or SWS) last longer while REM sleep spans shorter; as night progresses, the length of SWS is reduced as REM sleep lengthens. This process allows for SWS to establish precedence , with increases in SWS seen when recovering from sleep deprivation. SWS is indeed regarded as the most restorative portion of sleep. During SWS, physiological activities such as hormone secretion, muscle recovery, and immune responses are underway, while neurological processes required for long term learning and memory consolidation, also occur. The structure and duration of specific sleep stages may vary independent of total sleep duration, and changes in the structure and duration have been shown to be associated with deleterious outcomes. Individuals with narcolepsy enter sleep through REM as opposed to stage 1 of NREM. Disrupting slow wave sleep for several consecutive nights without reducing total sleep duration or sleep efficiency is associated with decreased pain threshold, increased discomfort, fatigue, and the inflammatory flare response in skin. Depression has been shown to be associated with a reduction of slow wave sleep and increased REM sleep. Given research that shows deleterious outcomes are associated with changes in sleep structure, it is essential to characterize and mitigate not only total sleep duration, but also changes in sleep stages.

  18. Slow Wave Sleep and Long Duration Spaceflight

    NASA Technical Reports Server (NTRS)

    Orr, M.; Whitmire, A.; Arias, D.; Leveton, L.

    2011-01-01

    To review the literature on slow wave sleep (SWS) in long duration space flight, and place this within the context of the broader literature on SWS particularly with respect to analogous environments such as the Antarctic. Explore how SWS could be measured within the International Space Station (ISS) context with the aim to utilize the ISS as an analog for future extra-orbital long duration missions. Discuss the potential use of emergent minimally intrusive wireless technologies like ZEO for integrated prelaunch, flight, and return to Earth analysis and optimization of SWS (and general quality of sleep).

  19. Coupling between whistler waves and slow-mode solitary waves

    SciTech Connect

    Tenerani, A.; Califano, F.; Pegoraro, F.; Le Contel, O.

    2012-05-15

    The interplay between electron- and ion-scale phenomena is of general interest for both laboratory and space plasma physics. In this paper, we investigate the linear coupling between whistler waves and slow magnetosonic solitons through two-fluid numerical simulations. Whistler waves can be trapped in the presence of inhomogeneous external fields such as a density hump or hole where they can propagate for times much longer than their characteristic time scale, as shown by laboratory experiments and space measurements. Space measurements have detected whistler waves also in correspondence to magnetic holes, i.e., to density humps with magnetic field minima extending on ion-scales. This raises the interesting question of how ion-scale structures can couple to whistler waves. Slow magnetosonic solitons share some of the main features of a magnetic hole. Using the ducting properties of an inhomogeneous plasma as a guide, we present a numerical study of whistler waves that are trapped and transported inside propagating slow magnetosonic solitons.

  20. Slow waves in mutually inhibitory neuronal networks

    NASA Astrophysics Data System (ADS)

    Jalics, Jozsi

    2004-05-01

    A variety of experimental and modeling studies have been performed to investigate wave propagation in networks of thalamic neurons and their relationship to spindle sleep rhythms. It is believed that spindle oscillations result from the reciprocal interaction between thalamocortical (TC) and thalamic reticular (RE) neurons. We consider a network of TC and RE cells reduced to a one-layer network model and represented by a system of singularly perturbed integral-differential equations. Geometric singular perturbation methods are used to prove the existence of a locally unique slow wave pulse that propagates along the network. By seeking a slow pulse solution, we reformulate the problem to finding a heteroclinic orbit in a 3D system of ODEs with two additional constraints on the location of the orbit at two distinct points in time. In proving the persistence of the singular heteroclinic orbit, difficulties arising from the solution passing near points where normal hyperbolicity is lost on a 2D critical manifold are overcome by employing results by Wechselberger [Singularly perturbed folds and canards in R3, Thesis, TU-Wien, 1998].

  1. Superconducting niobium thin film slow-wave structures

    NASA Technical Reports Server (NTRS)

    Bautista, J. J.; Petty, S. M.; Allen, L. H.; Beasley, M. R.; Hammond, R. H.

    1983-01-01

    A superconducting comb structure as a slow-wave element in a traveling-wave maser will significantly improve maser noise temperature and gain by reducing the insertion loss. The results of the insertion loss measurements of superconducting niobium slow-wave structures subjected to maser operating conditions at X-Band frequencies are presented.

  2. Gastric emptying is slow in chronic fatigue syndrome

    PubMed Central

    Burnet, Richard B; Chatterton, Barry E

    2004-01-01

    Background Gastrointestinal symptoms are common in patients with Chronic Fatigue Syndrome (CFS). The objective of this study was to determine the frequency of these symptoms and explore their relationship with objective (radionuclide) studies of upper GI function. Methods Thirty-two (32) patients with CFS and 45 control subjects completed a questionnaire on upper GI symptoms, and the 32 patients underwent oesophageal clearance, and simultaneous liquid and solid gastric emptying studies using radionuclide techniques compared with historical controls. Results The questionnaires showed a significant difference in gastric (p > 0.01) symptoms and swallowing difficulty. Nocturnal diarrhoea was a significant symptom not previously reported. 5/32 CFS subjects showed slightly delayed oesophageal clearance, but overall there was no significant difference from the control subjects, nor correlation of oesophageal clearance with symptoms. 23/32 patients showed a delay in liquid gastric emptying, and 12/32 a delay in solid gastric emptying with the delay significantly correlated with the mean symptom score (for each p ≪ 0.001). Conclusions GI symptoms in patients with chronic fatigue syndrome are associated with objective changes of upper GI motility. PMID:15619332

  3. Review of slow-wave structures

    NASA Astrophysics Data System (ADS)

    Wallett, Thomas M.; Qureshi, A. Haq

    1994-06-01

    The majority of recent theoretical and experimental reports published in the literature dealing with helical slow-wave structures focus on the dispersion characteristics and their effects due to the finite helix wire thickness and attenuation, dielectric loading, metal loading, and the introduction of plasma. In many papers, an effective dielectric constant is used to take into account helix wire dimensions and conductivity losses, while the propagation constant of the signal and the interaction impedance of the structure are found to depend on the surface resistivity of the helix. Also, various dielectric supporting rods are simulated by one or several uniform cylinders having an effective dielectric constant, while metal vane loading and plasma effects are incorporated in the effective dielectric constant. The papers dealing with coupled cavities and folded or loaded wave guides describe equivalent circuit models, efficiency enhancement, and the prediction of instabilities for these structures. Equivalent circuit models of various structures are found using computer software programs SUPERFISH and TOUCHSTONE. Efficiency enhancement in tubes is achieved through dynamic velocity and phase adjusted tapers using computer techniques. The stability threshold of unwanted antisymmetric and higher order modes is predicted using SOS and MAGIC codes and the dependence of higher order modes on beam conductance, section length, and effective Q of a cavity is shown.

  4. Review of Slow-Wave Structures

    NASA Technical Reports Server (NTRS)

    Wallett, Thomas M.; Qureshi, A. Haq

    1994-01-01

    The majority of recent theoretical and experimental reports published in the literature dealing with helical slow-wave structures focus on the dispersion characteristics and their effects due to the finite helix wire thickness and attenuation, dielectric loading, metal loading, and the introduction of plasma. In many papers, an effective dielectric constant is used to take into account helix wire dimensions and conductivity losses, while the propagation constant of the signal and the interaction impedance of the structure are found to depend on the surface resistivity of the helix. Also, various dielectric supporting rods are simulated by one or several uniform cylinders having an effective dielectric constant, while metal vane loading and plasma effects are incorporated in the effective dielectric constant. The papers dealing with coupled cavities and folded or loaded wave guides describe equivalent circuit models, efficiency enhancement, and the prediction of instabilities for these structures. Equivalent circuit models of various structures are found using computer software programs SUPERFISH and TOUCHSTONE. Efficiency enhancement in tubes is achieved through dynamic velocity and phase adjusted tapers using computer techniques. The stability threshold of unwanted antisymmetric and higher order modes is predicted using SOS and MAGIC codes and the dependence of higher order modes on beam conductance, section length, and effective Q of a cavity is shown.

  5. Multi-channel wireless mapping of gastrointestinal serosal slow wave propagation

    PubMed Central

    Paskaranandavadivel, Niranchan; Wang, Rui; Sathar, Shameer; O’Grady, Gregory; Cheng, Leo K; Farajidavar, Aydin

    2015-01-01

    Background High-resolution (HR) extracellular mapping allows accurate profiling of normal and dysrhythmic slow wave patterns. A current limitation is that cables traverse the abdominal wall or a natural orifice, risking discomfort, dislodgement or infection. Wireless approaches offer advantages, but a multi-channel system is required, capable of recording slow waves and mapping propagation with high fidelity. Methods A novel multi-channel (n=7) wireless mapping system was developed and compared to a wired commercial system. Slow wave signals were recorded from the porcine gastric and intestinal serosa in-vivo. Signals were simultaneously acquired using both systems, and were filtered and processed to map activation wavefronts. For validation, the frequency and amplitude of detected events were compared, together with the speed and direction of mapped wavefronts. Key Results The wireless device achieved comparable signal quality to the reference device, and slow wave frequencies were identical. Amplitudes of the acquired gastric and intestinal slow wave signals were consistent between the devices. During normal propagation, spatiotemporal mapping remained accurate in the wireless system, however, during ectopic dysrhythmic pacemaking, the lower sampling resolution of the wireless device led to reduced accuracy in spatiotemporal mapping. Conclusions and Inferences A novel multichannel wireless device is presented for mapping slow wave activity. The device achieved high quality signals, and has the potential to facilitate chronic monitoring studies and clinical translation of spatiotemporal mapping. The current implementation may be applied to detect normal patterns and dysrhythmia onset, but HR mapping with finely spaced arrays currently remains necessary to accurately define dysrhythmic patterns. PMID:25599978

  6. Waves in low-beta plasmas - Slow shocks

    NASA Technical Reports Server (NTRS)

    Steinolfson, R. S.; Hundhausen, A. J.

    1989-01-01

    Results from wave theory and numerical simulation of the nonlinear MHD equations are used to study the response of a conducting fluid containing an embedded magnetic field with beta less than 1 to the sudden injection of material along the field lines. It is shown that the injection produces slow shocks with configurations which are concave toward the ejecta driver. Fast-mode waves which have not steepened into the shock precede the slow shock and alter the ambient medium. When beta equals 0.1, the fast mode becomes a transverse wave for parallel propagation, while the slow wave approaches a longitudinal, or sound, wave.

  7. Sharp Slow Waves in the EEG.

    PubMed

    Janati, A Bruce; AlGhasab, Naif Saad; Alshammari, Raed Ayed; saad AlGhassab, Abdulmohsen; Al-Aslami Yossef Fahad

    2016-06-01

    There exists a paucity of data in the EEG literature on characteristics of "atypical" interictal epileptiform discharges (IEDs), including sharp slow waves (SSWs). This article aims to address the clinical, neurophysiological, and neuropathological significance of SSW The EEGs of 920 patients at a tertiary-care facility were prospectively reviewed over a period of one year. Thirty-six patients had SSWs in their EEG. Of these, 6 patients were excluded because of inadequate clinical data. The clinical and neuroimaging data of the remaining 30 patients were then retrospectively collected and reviewed, and the findings were correlated. The data revealed that SSWs were rare and age-related EEG events occurring primarily in the first two decades of life. All patients with SSWs had documented epilepsy, presenting clinically with partial or generalized epilepsy. It is notable that one-third of the patients with SSWs had chronic or static central nervous system (CNS) pathology, particularly congenital CNS anomalies. Though more than one mechanism may be involved in the pathogenesis of SSWs, this research indicates that the most compelling theory is a deeply seated cortical generator giving rise to this EEG pattern. The presence of SSWs should alert clinicians to the presence of partial or generalized epilepsy or an underlying chronic or static CNS pathology, in particular congenital CNS anomalies, underscoring the significance of brain magnetic resonance imaging in the work-up of this population. PMID:27373055

  8. Enhancement of sleep slow waves: underlying mechanisms and practical consequences

    PubMed Central

    Bellesi, Michele; Riedner, Brady A.; Garcia-Molina, Gary N.; Cirelli, Chiara; Tononi, Giulio

    2014-01-01

    Even modest sleep restriction, especially the loss of sleep slow wave activity (SWA), is invariably associated with slower electroencephalogram (EEG) activity during wake, the occurrence of local sleep in an otherwise awake brain, and impaired performance due to cognitive and memory deficits. Recent studies not only confirm the beneficial role of sleep in memory consolidation, but also point to a specific role for sleep slow waves. Thus, the implementation of methods to enhance sleep slow waves without unwanted arousals or lightening of sleep could have significant practical implications. Here we first review the evidence that it is possible to enhance sleep slow waves in humans using transcranial direct-current stimulation (tDCS) and transcranial magnetic stimulation. Since these methods are currently impractical and their safety is questionable, especially for chronic long-term exposure, we then discuss novel data suggesting that it is possible to enhance slow waves using sensory stimuli. We consider the physiology of the K-complex (KC), a peripheral evoked slow wave, and show that, among different sensory modalities, acoustic stimulation is the most effective in increasing the magnitude of slow waves, likely through the activation of non-lemniscal ascending pathways to the thalamo-cortical system. In addition, we discuss how intensity and frequency of the acoustic stimuli, as well as exact timing and pattern of stimulation, affect sleep enhancement. Finally, we discuss automated algorithms that read the EEG and, in real-time, adjust the stimulation parameters in a closed-loop manner to obtain an increase in sleep slow waves and avoid undesirable arousals. In conclusion, while discussing the mechanisms that underlie the generation of sleep slow waves, we review the converging evidence showing that acoustic stimulation is safe and represents an ideal tool for slow wave sleep (SWS) enhancement. PMID:25389394

  9. Nonlinear slow magnetoacoustic waves in coronal plasma structures

    NASA Astrophysics Data System (ADS)

    Afanasyev, A. N.; Nakariakov, V. M.

    2015-01-01

    Context. There is abundant observational evidence of longitudinal waves in the plasma structures of the solar corona. These essentially compressive waves are confidently interpreted as slow magnetoacoustic waves. The use of the slow waves in plasma diagnostics and estimating their possible contribution to plasma heating and acceleration require detailed theoretical modelling. Aims: We investigate the role of obliqueness and magnetic effects in the evolution of slow magnetoacoustic waves, also called tube waves, in field-aligned plasma structures. Special attention is paid to the wave damping caused by nonlinear steepening. Methods: We considered an untwisted straight axisymmetric field-aligned plasma cylinder and analysed the behaviour of the slow magnetoacoustic waves that are guided by this plasma structure. We adopted a thin flux tube approximation. We took into account dissipation caused by viscosity, resistivity and thermal conduction, and nonlinearity. Effects of stratification and dispersion caused by the finite radius of the flux tube were neglected. Results: We derive the Burgers-type evolutionary equation for tube waves in a uniform plasma cylinder. Compared with a plane acoustic wave, the formation of shock fronts in tube waves is found to occur at a larger distance from the source. In addition, tube waves experience stronger damping. These effects are most pronounced in plasmas with the parameter β at about or greater than unity. In a low-β plasma, the evolution of tube waves can satisfactorily be described with the Burgers equation for plane acoustic waves. Conclusions:

  10. Electron heating and current drive by mode converted slow waves

    SciTech Connect

    Majeski, R.; Phillips, C.K.; Wilson, J.R.

    1994-08-01

    An approach to obtaining efficient single pass mode conversion at high parallel wavenumber from the fast magnetosonic wave to the slow ion Bernstein wave, in a two ion species tokamak plasma, is described. The intent is to produce localized electron heating or current drive via the mode converted slow wave. In particular, this technique can be adapted to off-axis current drive for current profile control. Modelling for the case of deuterium-tritium plasmas in TFTR is presented.

  11. Regional Slow Waves and Spindles in Human Sleep

    PubMed Central

    Nir, Yuval; Staba, Richard J.; Andrillon, Thomas; Vyazovskiy, Vladyslav V.; Cirelli, Chiara; Fried, Itzhak; Tononi, Giulio

    2011-01-01

    SUMMARY The most prominent EEG events in sleep are slow waves, reflecting a slow (<1 Hz) oscillation between up and down states in cortical neurons. It is unknown whether slow oscillations are synchronous across the majority or the minority of brain regions—are they a global or local phenomenon? To examine this, we recorded simultaneously scalp EEG, intracerebral EEG, and unit firing in multiple brain regions of neurosurgical patients. We find that most sleep slow waves and the underlying active and inactive neuronal states occur locally. Thus, especially in late sleep, some regions can be active while others are silent. We also find that slow waves can propagate, usually from medial prefrontal cortex to the medial temporal lobe and hippocampus. Sleep spindles, the other hallmark of NREM sleep EEG, are likewise predominantly local. Thus, intracerebral communication during sleep is constrained because slow and spindle oscillations often occur out-of-phase in different brain regions. PMID:21482364

  12. Slow waves, sharp waves, ripples, and REM in sleeping dragons.

    PubMed

    Shein-Idelson, Mark; Ondracek, Janie M; Liaw, Hua-Peng; Reiter, Sam; Laurent, Gilles

    2016-04-29

    Sleep has been described in animals ranging from worms to humans. Yet the electrophysiological characteristics of brain sleep, such as slow-wave (SW) and rapid eye movement (REM) activities, are thought to be restricted to mammals and birds. Recording from the brain of a lizard, the Australian dragon Pogona vitticeps, we identified SW and REM sleep patterns, thus pushing back the probable evolution of these dynamics at least to the emergence of amniotes. The SW and REM sleep patterns that we observed in lizards oscillated continuously for 6 to 10 hours with a period of ~80 seconds. The networks controlling SW-REM antagonism in amniotes may thus originate from a common, ancient oscillator circuit. Lizard SW dynamics closely resemble those observed in rodent hippocampal CA1, yet they originate from a brain area, the dorsal ventricular ridge, that has no obvious hodological similarity with the mammalian hippocampus. PMID:27126045

  13. Slow electrostatic solitary waves in Earth's plasma sheet boundary layer

    NASA Astrophysics Data System (ADS)

    Kakad, Amar; Kakad, Bharati; Anekallu, Chandrasekhar; Lakhina, Gurbax; Omura, Yoshiharu; Fazakerley, Andrew

    2016-05-01

    We modeled Cluster spacecraft observations of slow electrostatic solitary waves (SESWs) in the Earth's northern plasma sheet boundary layer (PSBL) region on the basis of nonlinear fluid theory and fluid simulation. Various plasma parameters observed by the Cluster satellite at the time of the SESWs were examined to investigate the generation process of the SESWs. The nonlinear fluid model shows the coexistence of slow and fast ion acoustic waves and the presence of electron acoustic waves in the PSBL region. The fluid simulations, performed to examine the evolution of these waves in the PSBL region, showed the presence of an extra mode along with the waves supported by the nonlinear fluid theory. This extra mode is identified as the Buneman mode, which is generated by relative drifts of ions and electrons. A detailed investigation of the characteristics of the SESWs reveals that the SESWs are slow ion acoustic solitary waves.

  14. Global intracellular slow-wave dynamics of the thalamocortical system.

    PubMed

    Sheroziya, Maxim; Timofeev, Igor

    2014-06-25

    It is widely accepted that corticothalamic neurons recruit the thalamus in slow oscillation, but global slow-wave thalamocortical dynamics have never been experimentally shown. We analyzed intracellular activities of neurons either from different cortical areas or from a variety of specific and nonspecific thalamic nuclei in relation to the phase of global EEG signal in ketamine-xylazine anesthetized mice. We found that, on average, slow-wave active states started off within frontal cortical areas as well as higher-order and intralaminar thalamus (posterior and parafascicular nuclei) simultaneously. Then, the leading edge of active states propagated in the anteroposterior/lateral direction over the cortex at ∼40 mm/s. The latest structure we recorded within the slow-wave cycle was the anterior thalamus, which followed active states of the retrosplenial cortex. Active states from different cortical areas tended to terminate simultaneously. Sensory thalamic ventral posterior medial and lateral geniculate nuclei followed cortical active states with major inhibitory and weak tonic-like "modulator" EPSPs. In these nuclei, sharp-rising, large-amplitude EPSPs ("drivers") were not modulated by cortical slow waves, suggesting their origin in ascending pathways. The thalamic active states in other investigated nuclei were composed of depolarization: some revealing "driver"- and "modulator"-like EPSPs, others showing "modulator"-like EPSPs only. We conclude that sensory thalamic nuclei follow the propagating cortical waves, whereas neurons from higher-order thalamic nuclei display "hub dynamics" and thus may contribute to the generation of cortical slow waves. PMID:24966387

  15. Shock Formation of Slow Magnetosonic Waves in Coronal Plumes

    NASA Technical Reports Server (NTRS)

    Cuntz, Manfred; Suess, Steven T.; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    We investigate the height of shock formation in coroner plumes for slow magnetosonic waves. The models take into account plume geometric spreading, heat conduction and radiative damping. The wave parameters as well as the spreading functions of the plumes and the base magnetic field strengths are given by empirical constraints mostly from Solar and Heliospheric Observatory/Ultraviolet Coronagraph Spectrometer (SOHO/UVCS). Our models show that shock formation occurs at low coronal heights, i.e., within 1.3 solar radius, depending on the model parameters. The shock formation is calculated using the well-established wave breaking condition given by the intersection of C+ characteristics in the space-time plane. Our models show that shock heating by slow magnetosonic waves is expected to be relevant at most heights in solar coronal plumes, although slow magnetosonic waves are most likely not a solely operating energy supply mechanism.

  16. Slow Magnetosonic Waves and Fast Flows in Active Region Loops

    NASA Technical Reports Server (NTRS)

    Ofman, L.; Wang, T. J.; Davila, J. M.

    2012-01-01

    Recent extreme ultraviolet spectroscopic observations indicate that slow magnetosonic waves are present in active region (AR) loops. Some of the spectral data were also interpreted as evidence of fast (approx 100-300 km/s) quasiperiodic flows. We have performed three-dimensional magnetohydrodynamic (3D MHD) modeling of a bipolar AR that contains impulsively generated waves and flows in coronal loops. The model AR is initiated with a dipole magnetic field and gravitationally stratified density, with an upflow-driven steadily or periodically in localized regions at the footpoints of magnetic loops. The resulting flows along the magnetic field lines of the AR produce higher density loops compared to the surrounding plasma by injection of material into the flux tubes and the establishment of siphon flow.We find that the impulsive onset of flows with subsonic speeds result in the excitation of damped slow magnetosonic waves that propagate along the loops and coupled nonlinearly driven fast-mode waves. The phase speed of the slow magnetosonic waves is close to the coronal sound speed. When the amplitude of the driving pulses is increased we find that slow shock-like wave trains are produced. When the upflows are driven periodically, undamped oscillations are produced with periods determined by the periodicity of the upflows. Based on the results of the 3D MHD model we suggest that the observed slow magnetosonic waves and persistent upflows may be produced by the same impulsive events at the bases of ARs.

  17. SLOW MAGNETOSONIC WAVES AND FAST FLOWS IN ACTIVE REGION LOOPS

    SciTech Connect

    Ofman, L.; Wang, T. J.; Davila, J. M.

    2012-08-01

    Recent extreme ultraviolet spectroscopic observations indicate that slow magnetosonic waves are present in active region (AR) loops. Some of the spectral data were also interpreted as evidence of fast ({approx}100-300 km s{sup -1}) quasi-periodic flows. We have performed three-dimensional magnetohydrodynamic (3D MHD) modeling of a bipolar AR that contains impulsively generated waves and flows in coronal loops. The model AR is initiated with a dipole magnetic field and gravitationally stratified density, with an upflow-driven steadily or periodically in localized regions at the footpoints of magnetic loops. The resulting flows along the magnetic field lines of the AR produce higher density loops compared to the surrounding plasma by injection of material into the flux tubes and the establishment of siphon flow. We find that the impulsive onset of flows with subsonic speeds result in the excitation of damped slow magnetosonic waves that propagate along the loops and coupled nonlinearly driven fast-mode waves. The phase speed of the slow magnetosonic waves is close to the coronal sound speed. When the amplitude of the driving pulses is increased we find that slow shock-like wave trains are produced. When the upflows are driven periodically, undamped oscillations are produced with periods determined by the periodicity of the upflows. Based on the results of the 3D MHD model we suggest that the observed slow magnetosonic waves and persistent upflows may be produced by the same impulsive events at the bases of ARs.

  18. Scattering resonance of elastic wave and low-frequency equivalent slow wave

    NASA Astrophysics Data System (ADS)

    Meng, X.; Liu, H.; Hu, T.; Yang, L.

    2015-12-01

    Transmitted wave occurs as fast p-wave and slow p-wave in certain conditions when seismic waves travel through inhomogeneous layers. Energy of slow p-waves is strongest at some frequency band, but rather weak at both high frequency band and low frequency band, called scattering resonance. For practical seismic exploration, the frequency of slow p-wave occurs is below 10Hz, which cannot be explained by Biot's theory which predicts existence of the slow p-wave at ultrasonic band in the porous media. The slow p-wave equation have been derived, but which only adapted to explaining slow p-wave in the ultrasonic band. Experimental observations exhibit that slow p-wave also exists in nonporous media but with enormous low-velocity interbeds. When vertical incidence, elastic wave is simplified as compressing wave, the generation of slow waves is independent on shear wave. In the case of flat interbed and gas bubble, Liu (2006) has studied the transmission of acoustic waves, and found that the slow waves below the 10Hz frequency band can be explained. In the case of general elastic anisotropy medium, the tiheoretical research on the generation of slow waves is insufficient. Aiming at this problem, this paper presents an exponential mapping method based on transmitted wave (Magnus 1954), which can successfully explain the generation of the slow wave transmission in that case. Using the prediction operator (Claerbout 1985) to represent the transmission wave, this can be derived as first order partial differential equation. Using expansions in the frequency domain and the wave number domain, we find that the solutions have different expressions in the case of weak scattering and strong scattering. Besides, the method of combining the prediction operator and the exponential map is needed to extend to the elastic wave equation. Using the equation (Frazer and Fryer 1984, 1987), we derive the exponential mapping solution for the prediction operator of the general elastic medium

  19. Signal reconstruction of the slow wave and spike potential from electrogastrogram.

    PubMed

    Qin, Shujia; Ding, Wei; Miao, Lei; Xi, Ning; Li, Hongyi; Yang, Chunmin

    2015-01-01

    The gastric slow wave and the spike potential can correspondingly represent the rhythm and the intensity of stomach motility. Because of the filtering effect of biological tissue, electrogastrogram (EGG) cannot measure the spike potential on the abdominal surface in the time domain. Thus, currently the parameters of EGG adopted by clinical applications are only the characteristics of the slow wave, such as the dominant frequency, the dominant power and the instability coefficients. The limitation of excluding the spike potential analyses hinders EGG from being a diagnosis to comprehensively reveal the motility status of the stomach. To overcome this defect, this paper a) presents an EGG reconstruction method utilizing the specified signal components decomposed by the discrete wavelet packet transform, and b) obtains a frequency band for the human gastric spike potential through fasting and postprandial cutaneous EGG experiments for twenty-five human volunteers. The results indicate the lower bound of the human gastric spike potential frequency is 0.96±0.20 Hz (58±12 cpm), and the upper bound is 1.17±0.23 Hz (70±14 cpm), both of which have not been reported before to the best of our knowledge. As an auxiliary validation of the proposed method, synchronous serosa-surface EGG acquisitions are carried out for two dogs. The frequency band results for the gastric spike potential of the two dogs are respectively 0.83-0.90 Hz (50-54 cpm) and 1.05-1.32 Hz (63-79 cpm). They lie in the reference range 50-80 cpm proposed in previous literature, showing the feasibility of the reconstruction method in this paper. PMID:26405915

  20. Properties of slow oscillation during slow-wave sleep and anesthesia in cats.

    PubMed

    Chauvette, Sylvain; Crochet, Sylvain; Volgushev, Maxim; Timofeev, Igor

    2011-10-19

    Deep anesthesia is commonly used as a model of slow-wave sleep (SWS). Ketamine-xylazine anesthesia reproduces the main features of sleep slow oscillation: slow, large-amplitude waves in field potential, which are generated by the alternation of hyperpolarized and depolarized states of cortical neurons. However, direct quantitative comparison of field potential and membrane potential fluctuations during natural sleep and anesthesia is lacking, so it remains unclear how well the properties of sleep slow oscillation are reproduced by the ketamine-xylazine anesthesia model. Here, we used field potential and intracellular recordings in different cortical areas in the cat to directly compare properties of slow oscillation during natural sleep and ketamine-xylazine anesthesia. During SWS cortical activity showed higher power in the slow/delta (0.1-4 Hz) and spindle (8-14 Hz) frequency range, whereas under anesthesia the power in the gamma band (30-100 Hz) was higher. During anesthesia, slow waves were more rhythmic and more synchronous across the cortex. Intracellular recordings revealed that silent states were longer and the amplitude of membrane potential around transition between active and silent states was bigger under anesthesia. Slow waves were mostly uniform across cortical areas under anesthesia, but in SWS, they were most pronounced in associative and visual areas but smaller and less regular in somatosensory and motor cortices. We conclude that, although the main features of the slow oscillation in sleep and anesthesia appear similar, multiple cellular and network features are differently expressed during natural SWS compared with ketamine-xylazine anesthesia. PMID:22016533

  1. Changes in cortical slow wave activity in healthy aging.

    PubMed

    Leirer, Vera Maria; Wienbruch, Christian; Kolassa, Stephan; Schlee, Winfried; Elbert, Thomas; Kolassa, Iris-Tatjana

    2011-09-01

    A number of studies have demonstrated enhanced slow wave activity associated with pathological brain function e.g. in stroke patients, schizophrenia, depression, Morbus Alzheimer, and post-traumatic stress disorder. However, the association between slow wave activity and healthy aging has remained largely unexplored. This study examined whether the frequency at which focal generators of delta waves appear in the healthy cerebral cortex changes with age and whether this measure relates to cognitive performance. We investigated 53 healthy individuals aged 18 to 89 years and assessed MEG during a resting condition. Generators of focal magnetic slow waves were localized. Results showed a significant influence of age: dipole density decreases with increasing age. The relationship between cognitive performance and delta dipole density was not significant. The results suggest that in healthy aging slow waves decrease with aging and emphasize the importance of age-matched control groups for further studies. Increased appearance of slow waves as a marker for pathological stages can only be detected in relation to a control group of the same age. PMID:21698438

  2. Finned-Ladder Slow-Wave Circuit for a TWT

    NASA Technical Reports Server (NTRS)

    Wilson, Jeffrey D.; Wintucky, Edwin G.; Kory, Carol L.

    2004-01-01

    A finned-ladder structure has been invented in an effort to improve the design of the slow-wave circuit of a traveling-wave tube (TWT). The point of departure for the design effort was a prototype TWT that contains a ring-plane slow-wave circuit (see Figure 1). The design effort was a response to the observation that despite the high-power capabilities of the ringplane TWT, its requirement for a high supply voltage and its low bandwidth have made it unacceptable for use outside a laboratory setting.

  3. Standing slow magnetosonic waves in a dipole-like plasmasphere

    NASA Astrophysics Data System (ADS)

    Leonovich, A. S.; Kozlov, D. A.; Edemskiy, I. K.

    2010-09-01

    A problem of the structure and spectrum of standing slow magnetosonic waves in a dipole plasmasphere is solved. Both an analytical (in WKB approximation) and numerical solutions are found to the problem, for a distribution of the plasma parameters typical of the Earth's plasmasphere. The solutions allow us to treat the total electronic content oscillations registered above Japan as oscillations of one of the first harmonics of standing slow magnetosonic waves. Near the ionosphere the main components of the field of registered standing SMS waves are the plasma oscillations along magnetic field lines, plasma concentration oscillation and the related oscillations of the gas-kinetic pressure. The velocity of the plasma oscillations increases dramatically near the ionospheric conductive layer, which should result in precipitation of the background plasma particles. This may be accompanied by ionospheric F2 region airglows modulated with the periods of standing slow magnetosonic waves.

  4. Slow Wave Excitation in the ICRF and HHFW Regimes

    SciTech Connect

    Phillips, C. K.; Valeo, E. J.; Hosea, J. C.; LeBlanc, B. P.; Wilson, J. R.; Jaeger, E. F.; Berry, L. A.; Ryan, P. M.; Bonoli, P. T.; Wright, J. C.; Smithe, D. N.

    2011-12-23

    Theoretical considerations and high spatial resolution numerical simulations of radio frequency (rf) wave heating in tokamaks and in spherical toruses (ST) indicate that fast waves launched into tokamaks in the ion cyclotron range of frequencies (ICRF) or into spherical toruses in the high harmonic fast wave (HHFW) regime may excite a short wavelength slow mode inside of the plasma discharge due to the presence of hot electrons that satisfy the condition {omega}wave frequency, k{sub ||} is the local parallel component of the wave vector, and v{sub te} is the local electron thermal speed. This excited slow wave may be related to the electrostatic ion cyclotron wave that propagates for frequencies above the fundamental ion cyclotron frequency in warm plasmas or to a high frequency version of a kinetic Alfven wave. This slow wave, if physically real, would provide another path for rf power absorption in tokamaks and ST devices.

  5. Laminar analysis of slow wave activity in humans

    PubMed Central

    Csercsa, Richárd; Dombovári, Balázs; Fabó, Dániel; Wittner, Lucia; Erőss, Loránd; Entz, László; Sólyom, András; Rásonyi, György; Szűcs, Anna; Kelemen, Anna; Jakus, Rita; Juhos, Vera; Grand, László; Magony, Andor; Halász, Péter; Freund, Tamás F.; Maglóczky, Zsófia; Cash, Sydney S.; Papp, László; Karmos, György; Halgren, Eric

    2010-01-01

    Brain electrical activity is largely composed of oscillations at characteristic frequencies. These rhythms are hierarchically organized and are thought to perform important pathological and physiological functions. The slow wave is a fundamental cortical rhythm that emerges in deep non-rapid eye movement sleep. In animals, the slow wave modulates delta, theta, spindle, alpha, beta, gamma and ripple oscillations, thus orchestrating brain electrical rhythms in sleep. While slow wave activity can enhance epileptic manifestations, it is also thought to underlie essential restorative processes and facilitate the consolidation of declarative memories. Animal studies show that slow wave activity is composed of rhythmically recurring phases of widespread, increased cortical cellular and synaptic activity, referred to as active- or up-state, followed by cellular and synaptic inactivation, referred to as silent- or down-state. However, its neural mechanisms in humans are poorly understood, since the traditional intracellular techniques used in animals are inappropriate for investigating the cellular and synaptic/transmembrane events in humans. To elucidate the intracortical neuronal mechanisms of slow wave activity in humans, novel, laminar multichannel microelectrodes were chronically implanted into the cortex of patients with drug-resistant focal epilepsy undergoing cortical mapping for seizure focus localization. Intracortical laminar local field potential gradient, multiple-unit and single-unit activities were recorded during slow wave sleep, related to simultaneous electrocorticography, and analysed with current source density and spectral methods. We found that slow wave activity in humans reflects a rhythmic oscillation between widespread cortical activation and silence. Cortical activation was demonstrated as increased wideband (0.3–200 Hz) spectral power including virtually all bands of cortical oscillations, increased multiple- and single-unit activity and

  6. Laminar analysis of slow wave activity in humans.

    PubMed

    Csercsa, Richárd; Dombovári, Balázs; Fabó, Dániel; Wittner, Lucia; Eross, Loránd; Entz, László; Sólyom, András; Rásonyi, György; Szucs, Anna; Kelemen, Anna; Jakus, Rita; Juhos, Vera; Grand, László; Magony, Andor; Halász, Péter; Freund, Tamás F; Maglóczky, Zsófia; Cash, Sydney S; Papp, László; Karmos, György; Halgren, Eric; Ulbert, István

    2010-09-01

    Brain electrical activity is largely composed of oscillations at characteristic frequencies. These rhythms are hierarchically organized and are thought to perform important pathological and physiological functions. The slow wave is a fundamental cortical rhythm that emerges in deep non-rapid eye movement sleep. In animals, the slow wave modulates delta, theta, spindle, alpha, beta, gamma and ripple oscillations, thus orchestrating brain electrical rhythms in sleep. While slow wave activity can enhance epileptic manifestations, it is also thought to underlie essential restorative processes and facilitate the consolidation of declarative memories. Animal studies show that slow wave activity is composed of rhythmically recurring phases of widespread, increased cortical cellular and synaptic activity, referred to as active- or up-state, followed by cellular and synaptic inactivation, referred to as silent- or down-state. However, its neural mechanisms in humans are poorly understood, since the traditional intracellular techniques used in animals are inappropriate for investigating the cellular and synaptic/transmembrane events in humans. To elucidate the intracortical neuronal mechanisms of slow wave activity in humans, novel, laminar multichannel microelectrodes were chronically implanted into the cortex of patients with drug-resistant focal epilepsy undergoing cortical mapping for seizure focus localization. Intracortical laminar local field potential gradient, multiple-unit and single-unit activities were recorded during slow wave sleep, related to simultaneous electrocorticography, and analysed with current source density and spectral methods. We found that slow wave activity in humans reflects a rhythmic oscillation between widespread cortical activation and silence. Cortical activation was demonstrated as increased wideband (0.3-200 Hz) spectral power including virtually all bands of cortical oscillations, increased multiple- and single-unit activity and powerful

  7. Shock Formation of Slow Magnetosonic Waves in Coronal Plumes

    NASA Technical Reports Server (NTRS)

    Cuntz, Manfred; Suess, Steve; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    We investigate the height of shock formation in coronal plumes for slow magnetosonic waves. The models take into account plume geometric spreading, heat conduction, and radiative damping. The wave parameters as well as the spreading functions of the plumes and the base magnetic field strengths are given by empirical constraints mostly from Solar and Heliospheric Observatory (SOHO)/ Ultraviolet Coronograph Spectrometer (UVCS), Extreme Ultraviolet Imaging Telescope (EIT), Michelson Doppler Imager (MDI), and Large Angle Spectrometric Coronagraph (LASCO). Our models show that shock formation occurs at relatively low coronal heights, typically within 1.2 RsuN, depending on the model parameters. The shock formation is calculated using the well-established wave breaking criterion given by the intersection of C+ characteristics in the space-time plane. Our models show that shock heating by slow magnetosonic waves is expected to be relevant at most heights in solar coronal plumes, although such waves are probably not the main energy supply mechanism.

  8. TeO2 slow surface acoustic wave Bragg cell

    NASA Astrophysics Data System (ADS)

    Yao, Shi-Kay

    1991-08-01

    A newly discovered slow acoustic surface wave (SAW) on a (-110) cut TeO2 surface is reported focusing on its properties studied using a PC based numerical method. It is concluded that the slow SAW is rather tolerant to crystal surface orientation errors and has unusually deep penetration of its shear component into the thickness of substrate, about 47 wavelengths for a half amplitude point. The deep shear field is considered to be beneficial for surface acoustooptic interaction with free propagating focused laser beams. Rotation of the substrate about the z-axis makes it possible to adjust a slow SAW velocity with the potential advantage of trading acoustic velocity for less acoustic attenuation. Wider-bandwidth long signal processing time Bragg cells may be feasible utilizing this trade-off. The slow SAW device is characterized by an extremely low power consumption which might be useful for compact portable or avionics signal processing equipment applications.

  9. High-resolution Mapping of In Vivo Gastrointestinal Slow Wave Activity Using Flexible Printed Circuit Board Electrodes: Methodology and Validation

    PubMed Central

    DU, PENG; O'GRADY, G.; EGBUJI, J. U.; LAMMERS, W. J.; BUDGETT, D.; NIELSEN, P.; WINDSOR, J. A.; PULLAN, A. J.; CHENG, L. K.

    2014-01-01

    High-resolution, multi-electrode mapping is providing valuable new insights into the origin, propagation, and abnormalities of gastrointestinal (GI) slow wave activity. Construction of high-resolution mapping arrays has previously been a costly and time-consuming endeavor, and existing arrays are not well suited for human research as they cannot be reliably and repeatedly sterilized. The design and fabrication of a new flexible printed circuit board (PCB) multi-electrode array that is suitable for GI mapping is presented, together with its in vivo validation in a porcine model. A modified methodology for characterizing slow waves and forming spatiotemporal activation maps showing slow waves propagation is also demonstrated. The validation study found that flexible PCB electrode arrays are able to reliably record gastric slow wave activity with signal quality near that achieved by traditional epoxy resin-embedded silver electrode arrays. Flexible PCB electrode arrays provide a clinically viable alternative to previously published devices for the high-resolution mapping of GI slow wave activity. PCBs may be mass-produced at low cost, and are easily sterilized and potentially disposable, making them ideally suited to intra-operative human use. PMID:19224368

  10. Acetazolamide for electrical status epilepticus in slow-wave sleep.

    PubMed

    Fine, Anthony L; Wirrell, Elaine C; Wong-Kisiel, Lily C; Nickels, Katherine C

    2015-09-01

    Electrical status epilepticus in slow-wave sleep (ESES) is characterized by nearly continuous spike-wave discharges during non-rapid eye movement (REM) sleep. ESES is present in Landau-Kleffner syndrome (LKS) and continuous spike and wave in slow-wave sleep (CSWS). Sulthiame has demonstrated reduction in spike-wave index (SWI) in ESES, but is not available in the United States. Acetazolamide (AZM) is readily available and has similar pharmacologic properties. Our aims were to assess the effect of AZM on SWI and clinical response in children with LKS and CSWS. Children with LKS or CSWS treated with AZM at our institution were identified retrospectively. Pre- and posttherapy electroencephalography (EEG) studies were evaluated for SWI. Parental and teacher report of clinical improvement was recorded. Six children met criteria for inclusion. Three children (50%) demonstrated complete resolution or SWI <5% after AZM. All children had improvement in clinical seizures and subjective improvement in communication skills and school performance. Five of six children had subjective improvement in hyperactivity and attention. AZM is a potentially effective therapy for children with LKS and CSWS. This study lends to the knowledge of potential therapies that can be used for these disorders, which can be challenging for families and providers. PMID:26230617

  11. Band formation in coupled-resonator slow-wave structures.

    PubMed

    Möller, Björn M; Woggon, Ulrike; Artemyev, Mikhail V

    2007-12-10

    Sequences of coupled-resonator optical waveguides (CROWs) have been examined as slow-wave structures. The formation of photonic bands in finite systems is studied in the frame of a coupled oscillator model. Several types of resonator size tuning in the system are evaluated in a systematical manner. We show that aperiodicities in sequences of coupled microspheres provide an additional degree of freedom for the design of photonic bands. PMID:19551030

  12. Conical slow wave antenna as a plasma source.

    PubMed

    Grubb, D P; Lovell, T

    1978-01-01

    A simple conical helix has been successfully employed as a slow wave structure to generate plasmas by electron cyclotron resonance heating (ECRH). The plasma is typical of plasmas created by ''Lisitano coil'' sources, n approximately 10(10)-10(12) cm(-3) with T(e) approximately 2-20 eV. This source, however, is much simpler to fabricate. The ease of fabrication allows the user some flexibility in designing the source to fit a specific plasma physics experiment. PMID:18698943

  13. Analysis of the power capacity of overmoded slow wave structures

    SciTech Connect

    Zhang, Dian; Zhang, Jun; Zhong, Huihuang; Jin, Zhenxing

    2013-07-15

    As the generated wavelength shortens, overmoded slow wave structures (SWSs) with large diameters are employed in O-type Cerenkov high power microwave (HPM) generators to achieve high power capacity. However, reported experimental results suggest that overmoded slow wave HPM generators working at millimeter wavelength output much lower power than those working at X-band do, despite the fact that the value of D/λ (here, D is the average diameter of SWSs and λ is the generated wavelength) of the former is much larger than that of the latter. In order to understand this, the characteristics of the power capacity of the TM{sub 0n} modes in overmoded SWSs are numerically investigated. Our analysis reveals the following facts. First, the power capacity of higher order TM{sub 0n} modes is apparently larger than that of TM{sub 01} mode. This is quite different from the conclusion got in the foregone report, in which the power capacity of overmoded SWSs is estimated by that of smooth cylindrical waveguides. Second, the rate at which the power capacity of TM{sub 01} mode in overmoded SWSs grows with diameter does not slow down as the TM{sub 01} field transforms from “volume wave” to “surface wave.” Third, once the diameter of overmoded SWSs and the beam voltage are fixed, the power capacity of TM{sub 01} wave drops as periodic length L shortens and the generated frequency rises, although the value of D/λ increases significantly. Therefore, it is necessary to investigate the capability of annular electron beam to interact efficiently with higher order TM{sub 0n} modes in overmoded SWSs if we want to improve the power capacity of overmoded O-type Cerenkov HPM generators working at high frequency.

  14. Propagation and damping of slow MHD waves in a flowing viscous coronal plasma

    NASA Astrophysics Data System (ADS)

    Kumar, Nagendra; Kumar, Anil; Murawski, K.

    2016-04-01

    We investigate the propagation of slow MHD waves in a flowing viscous solar coronal plasma. The compressive viscosity and steady flow along and opposite to the wave propagation are taken into account to study the damping of slow waves. We numerically solve the MHD equations by MacCormack method to examine the effect of steady flow on the damping of slow MHD waves in viscous solar coronal plasma. Amplitude of velocity perturbation and damping time of slow waves decrease with the increase in the value of Mach number. Flow causes a phase shift in the perturbed velocity amplitude and an increase in wave period. The damping of slow waves in flowing viscous plasma is stronger than the damping of waves in viscous plasma. Slow wave in backward flow damps earlier than the wave in forward flow.

  15. Slow magnetohydrodynamic waves in stratified and viscous plasmas

    SciTech Connect

    Ballai, Istvan; Erdelyi, Robert; Hargreaves, James

    2006-04-15

    The propagation of slow magnetohydrodynamic waves in vertical thin flux tubes embedded in a vertically stratified plasma in the presence of viscosity is shown here to be governed by the Klein-Gordon-Burgers (KGB) equation, which is solved in two limiting cases assuming an isothermal medium in hydrostatic equilibrium surrounded by a quiescent environment. The results presented here can be applied to, e.g., study the propagation of slow magnetohydrodynamic waves generated by the granular buffeting motion in thin magnetic photospheric tubes. When the variation in the reduced velocity occurs over typical lengths much larger than the gravitational scale height, the KGB equation can be reduced to a Klein-Gordon equation describing the propagation of an impulse followed by a wake oscillating with the frequency reduced by viscosity and the solution has no spatial or temporal decay. However, in the other limiting case, i.e., typical variations in the reduced velocity occur over characteristic lengths much smaller than the gravitational scale height, waves have a temporal and spatial decay.

  16. Compact FEL`s based on slow wave wigglers

    SciTech Connect

    Riyopoulos, S.

    1995-12-31

    Slow waves excited in magnetron-type cavities are attractive canditates as wigglers for compact Free Electron Lasers. Because of group velocities much below the speed of light, slow waves offer an order of magnitude increase in FEL gain under given circulating power in the wiggler resonator, compared to fast wave wigglers of similar period. In addition, they offer the versatility of operation either at modest beam energy via upshifing of the fundamental wavelength, or at low beam energy benefiting from the submillimeter wiggler harmonics. Because the main electron undulation is in the transverse direction for all spatial harmonics, the radiated power is increased by a factor {gamma}{sup 2} relative to the Smith-Purcell approach that relies on axial electron undulation. Technical advantages offered by magnetron-type wiggles are: the generation of the wiggler microwaves and the FEL interaction take place inside the same cavity, avoiding the issue of high power coupling between cavities; the excitation of wiggler microwaves relies on distributed electron emission from the cavity wall and does not require separate beam injection.

  17. Analysis of waves in the plasma guided by a periodical vane-type slow wave structure

    SciTech Connect

    Wu, T.J.; Kou, C.S.

    2005-10-01

    In this study, the dispersion relation has been derived to characterize the propagation of the waves in the plasma guided by a periodical vane-type slow wave structure. The plasma is confined by a quartz plate. Results indicate that there are two different waves in this structure. One is the plasma mode that originates from the plasma surface wave propagating along the interface between the plasma and the quartz plate, and the other is the guide mode that originally travels along the vane-type slow wave structure. In contrast to its original slow wave characteristics, the guide mode becomes a fast wave in the low-frequency portion of the passband, and there exists a cut-off frequency for the guide mode. The vane-type guiding structure has been shown to limit the upper frequency of the passband of the plasma mode, compared with that of the plasma surface wave. In addition, the passband of the plasma mode increases with the plasma density while it becomes narrower for the guide mode. The influences of the parameters of the guiding structure and plasma density on the propagation of waves are also presented.

  18. Spontaneous K-Complex Density in Slow-Wave Sleep

    PubMed Central

    Zannat, Wassilatul; Pandi-Perumal, Seithikurippu R.; BaHammam, Ahmed S.; Hussain, M. Ejaz

    2016-01-01

    Purpose To study spontaneous K-complex (KC) densities during slow-wave sleep. The secondary objective was to estimate intra-non-rapid eye movement (NREM) sleep differences in KC density. Materials and Methods It is a retrospective study using EEG data included in polysomnographic records from the archive at the sleep research laboratory of the Centre for Physiotherapy and Rehabilitation Sciences, Jamia Millia Islamia, India. The EEG records of 4459 minutes were used. The study presents a manual identification investigation of KCs in 17 healthy young adult male volunteers (age = 23.82±3.40 years and BMI = 23.42±4.18 kg/m2). Results N3 had a higher KC density than N2 (Z = -2.485, p = 0.013) for all of the probes taken together. Four EEG probes had a higher probe-specific KC density during N3. The inter-probe KC density differed significantly during N2 (χ2 = 67.91, p < .001), N3 (χ2 = 70.62, p < .001) and NREM (χ2 = 68.50, p < .001). The percent distribution of KC decreased uniformly with sleep cycles. Conclusion The inter-probe differences during N3 establish the fronto-central dominance of the KC density regardless of sleep stage. This finding supports one local theory of KC generation. The significantly higher KC density during N3 may imply that the neuro-anatomical origin of slow-wave activity and KC is the same. This temporal alignment with slow-wave activity supports the sleep-promoting function of the KC. PMID:26963714

  19. Propagated infra-slow intrinsic brain activity reorganizes across wake and slow wave sleep

    PubMed Central

    Mitra, Anish; Snyder, Abraham Z; Tagliazucchi, Enzo; Laufs, Helmut; Raichle, Marcus E

    2015-01-01

    Propagation of slow intrinsic brain activity has been widely observed in electrophysiogical studies of slow wave sleep (SWS). However, in human resting state fMRI (rs-fMRI), intrinsic activity has been understood predominantly in terms of zero-lag temporal synchrony (functional connectivity) within systems known as resting state networks (RSNs). Prior rs-fMRI studies have found that RSNs are generally preserved across wake and sleep. Here, we use a recently developed analysis technique to study propagation of infra-slow intrinsic blood oxygen level dependent (BOLD) signals in normal adults during wake and SWS. This analysis reveals marked changes in propagation patterns in SWS vs. wake. Broadly, ordered propagation is preserved within traditionally defined RSNs but lost between RSNs. Additionally, propagation between cerebral cortex and subcortical structures reverses directions, and intra-cortical propagation becomes reorganized, especially in visual and sensorimotor cortices. These findings show that propagated rs-fMRI activity informs theoretical accounts of the neural functions of sleep. DOI: http://dx.doi.org/10.7554/eLife.10781.001 PMID:26551562

  20. A Bi-Frequency Linear Slow Wave Device

    NASA Astrophysics Data System (ADS)

    Simon, David; Zhang, Peng; Lau, Y. Y.; Greening, Geoff; Gilgenbach, Ronald; Hoff, Brad

    2014-10-01

    Bi-frequency sources are of interest to plasma processing, diagnostics, RF heating, and defense electronics. The recirculating planar magnetron has been modified to produce two frequencies using two different slow wave structures in the planar regions. To highlight the coupling in the two frequencies, we consider here a linear TWT driven by a sheet beam inside such a structure. The cold tube dispersion is derived and is compared favorably with HFSS. The hot tube dispersion has also been derived, and is being compared with MAGIC simulations. Various nonlinear effects are explored, such as harmonic generation, parametric amplification, and intermodulation. This work was supported by ONR and AFOSR.

  1. Slow Wave Conduction Patterns in the Stomach: From Waller’s Foundations to Current Challenges

    PubMed Central

    2015-01-01

    This review provides an overview of our understanding of motility and slow wave propagation in the stomach. It begins by reviewing seminal studies conducted by Walter Cannon and Augustus Waller on in vivo motility and slow wave patterns. Then our current understanding of slow wave patterns in common laboratory animals and humans is presented. The implications of slow wave dysrhythmic patterns that have been recorded in animals and patients suffering from gastroparesis are discussed. Finally, current challenges in experimental methods and techniques, slow wave modulation and the use of mathematical models are discussed. PMID:25313679

  2. Energy and energy flux in axisymmetric slow and fast waves

    NASA Astrophysics Data System (ADS)

    Moreels, M. G.; Van Doorsselaere, T.; Grant, S. D. T.; Jess, D. B.; Goossens, M.

    2015-06-01

    Aims: We aim to calculate the kinetic, magnetic, thermal, and total energy densities and the flux of energy in axisymmetric sausage modes. The resulting equations should contain as few parameters as possible to facilitate applicability for different observations. Methods: The background equilibrium is a one-dimensional cylindrical flux tube model with a piecewise constant radial density profile. This enables us to use linearised magnetohydrodynamic equations to calculate the energy densities and the flux of energy for axisymmetric sausage modes. Results: The equations used to calculate the energy densities and the flux of energy in axisymmetric sausage modes depend on the radius of the flux tube, the equilibrium sound and Alfvén speeds, the density of the plasma, the period and phase speed of the wave, and the radial or longitudinal components of the Lagrangian displacement at the flux tube boundary. Approximate relations for limiting cases of propagating slow and fast sausage modes are also obtained. We also obtained the dispersive first-order correction term to the phase speed for both the fundamental slow body mode under coronal conditions and the slow surface mode under photospheric conditions. Appendix A is available in electronic form at http://www.aanda.org

  3. Sleep slow-wave activity regulates cerebral glycolytic metabolism.

    PubMed

    Wisor, Jonathan P; Rempe, Michael J; Schmidt, Michelle A; Moore, Michele E; Clegern, William C

    2013-08-01

    Non-rapid eye movement sleep (NREMS) onset is characterized by a reduction in cerebral metabolism and an increase in slow waves, 1-4-Hz oscillations between relatively depolarized and hyperpolarized states in the cerebral cortex. The metabolic consequences of slow-wave activity (SWA) at the cellular level remain uncertain. We sought to determine whether SWA modulates the rate of glycolysis within the cerebral cortex. The real-time measurement of lactate concentration in the mouse cerebral cortex demonstrates that it increases during enforced wakefulness. In spontaneous sleep/wake cycles, lactate concentration builds during wakefulness and rapid eye movement sleep and declines during NREMS. The rate at which lactate concentration declines during NREMS is proportional to the magnitude of electroencephalographic (EEG) activity at frequencies of <10 Hz. The induction of 1-Hz oscillations, but not 10-Hz oscillations, in the electroencephalogram by optogenetic stimulation of cortical pyramidal cells during wakefulness triggers a decline in lactate concentration. We conclude that cerebral SWA promotes a decline in the rate of glycolysis in the cerebral cortex. These results demonstrate a cellular energetic function for sleep SWA, which may contribute to its restorative effects on brain function. PMID:22767634

  4. The Propagation of Slow Wave Potentials in Pea Epicotyls.

    PubMed Central

    Stahlberg, R.; Cosgrove, D. J.

    1997-01-01

    Slow wave potentials are considered to be electric long-distance signals specific for plants, although there are conflicting ideas about a chemical, electrical, or hydraulic mode of propagation. These ideas were tested by comparing the propagation of hydraulic and electric signals in epicotyls of pea (Pisum sativum L). A hydraulic signal in the form of a defined step increase in xylem pressure (Px) was applied to the root of intact seedlings and propagated nearly instantly through the epicotyl axis while its amplitude decreased with distance from the pressure chamber. This decremental propagation was caused by a leaky xylem and created an axial Px gradient in the epicotyl. Simultaneously along the epicotyl surface, depolarizations appeared with lag times that increased acropetally with distance from the pressure chamber from 5 s to 3 min. When measured at a constant distance, the lag times increased as the size of the applied pressure steps decreased. We conclude that the Px gradient in the epicotyl caused local depolarizations with acropetally increasing lag times, which have the appearance of an electric signal propagating with a rate of 20 to 30 mm min-1. This static description of the slow wave potentials challenges its traditional classification as a propagating electric signal. PMID:12223601

  5. Comparing the Robustness of High-Frequency Traveling-Wave Tube Slow-Wave Circuits

    NASA Technical Reports Server (NTRS)

    Chevalier, Christine T.; Wilson, Jeffrey D.; Kory, Carol L.

    2007-01-01

    A three-dimensional electromagnetic field simulation software package was used to compute the cold-test parameters, phase velocity, on-axis interaction impedance, and attenuation, for several high-frequency traveling-wave tube slow-wave circuit geometries. This research effort determined the effects of variations in circuit dimensions on cold-test performance. The parameter variations were based on the tolerances of conventional micromachining techniques.

  6. SLOW MAGNETOACOUSTIC WAVES IN TWO-RIBBON FLARES

    SciTech Connect

    Nakariakov, V. M.; Zimovets, I. V.

    2011-04-01

    We demonstrate that disturbances observed to propagate along the axis of the arcade in two-ribbon solar flares at the speed of a few tens of km s{sup -1}, well below the Alfven and sound speeds, can be interpreted in terms of slow magnetoacoustic waves. The waves can propagate across the magnetic field, parallel to the magnetic neutral line, because of the wave-guiding effect due to the reflection from the footpoints. The perpendicular group speed of the perturbation is found to be a fraction of the sound speed, which is consistent with observations. The highest value of the group speed grows with the increase in the ratio of the sound and Alfven speeds. For a broad range of parameters, the highest value of the group speed corresponds to the propagation angle of 25 deg. - 28 deg. to the magnetic field. This effect can explain the temporal and spatial structure of quasi-periodic pulsations observed in two-ribbon flares.

  7. A slow slip event triggered by teleseismic surface waves

    NASA Astrophysics Data System (ADS)

    Itaba, Satoshi; Ando, Ryosuke

    2011-11-01

    In recent years slow slip events (SSE) have been observed to occur at regular intervals on the deep portions of subduction zone interfaces. These are accompanied by seismic tremor that occurs over their duration. It has been observed that tremor activity shows transient modulations in response to earth tides and the passage of seismic waves from distant earthquakes. Here we show, for the first time, geodetic evidence for the triggering of an interplate SSE itself by teleseismic surface waves. This SSE, in southwest Japan, which had an equivalent magnitude Mw 5.3 and duration of 1.5 days, was triggered by the surface waves of a Mw 7.6 earthquake in Tonga. This evidence was captured by a newly deployed sensitive strainmeter network. The triggered SSE occurred on a place on the plate interface where the recurrence time for such events had almost expired, whereas other regions, at up to 90% of the recurrence time, were not triggered. This provides information for the conditions for triggering and generation of SSEs and, perhaps, for regular earthquakes.

  8. Circadian regulation of slow waves in human sleep: Topographical aspects

    PubMed Central

    Lazar, Alpar S.; Lazar, Zsolt I.; Dijk, Derk-Jan

    2015-01-01

    Slow waves (SWs, 0.5–4 Hz) in field potentials during sleep reflect synchronized alternations between bursts of action potentials and periods of membrane hyperpolarization of cortical neurons. SWs decline during sleep and this is thought to be related to a reduction of synaptic strength in cortical networks and to be central to sleep's role in maintaining brain function. A central assumption in current concepts of sleep function is that SWs during sleep, and associated recovery processes, are independent of circadian rhythmicity. We tested this hypothesis by quantifying all SWs from 12 EEG derivations in 34 participants in whom 231 sleep periods were scheduled across the circadian cycle in a 10-day forced-desynchrony protocol which allowed estimation of the separate circadian and sleep-dependent modulation of SWs. Circadian rhythmicity significantly modulated the incidence, amplitude, frequency and the slope of the SWs such that the peaks of the circadian rhythms in these slow-wave parameters were located during the biological day. Topographical analyses demonstrated that the sleep-dependent modulation of SW characteristics was most prominent in frontal brain areas whereas the circadian effect was similar to or greater than the sleep-dependent modulation over the central and posterior brain regions. The data demonstrate that circadian rhythmicity directly modulates characteristics of SWs thought to be related to synaptic plasticity and that this modulation depends on topography. These findings have implications for the understanding of local sleep regulation and conditions such as ageing, depression, and neurodegeneration which are associated with changes in SWs, neural plasticity and circadian rhythmicity. PMID:25979664

  9. Circadian regulation of slow waves in human sleep: Topographical aspects.

    PubMed

    Lazar, Alpar S; Lazar, Zsolt I; Dijk, Derk-Jan

    2015-08-01

    Slow waves (SWs, 0.5-4Hz) in field potentials during sleep reflect synchronized alternations between bursts of action potentials and periods of membrane hyperpolarization of cortical neurons. SWs decline during sleep and this is thought to be related to a reduction of synaptic strength in cortical networks and to be central to sleep's role in maintaining brain function. A central assumption in current concepts of sleep function is that SWs during sleep, and associated recovery processes, are independent of circadian rhythmicity. We tested this hypothesis by quantifying all SWs from 12 EEG derivations in 34 participants in whom 231 sleep periods were scheduled across the circadian cycle in a 10-day forced-desynchrony protocol which allowed estimation of the separate circadian and sleep-dependent modulation of SWs. Circadian rhythmicity significantly modulated the incidence, amplitude, frequency and the slope of the SWs such that the peaks of the circadian rhythms in these slow-wave parameters were located during the biological day. Topographical analyses demonstrated that the sleep-dependent modulation of SW characteristics was most prominent in frontal brain areas whereas the circadian effect was similar to or greater than the sleep-dependent modulation over the central and posterior brain regions. The data demonstrate that circadian rhythmicity directly modulates characteristics of SWs thought to be related to synaptic plasticity and that this modulation depends on topography. These findings have implications for the understanding of local sleep regulation and conditions such as ageing, depression, and neurodegeneration which are associated with changes in SWs, neural plasticity and circadian rhythmicity. PMID:25979664

  10. Slow Wave Vane Structure with Elliptical Cross-Section Slots, an Analysis

    NASA Technical Reports Server (NTRS)

    Kosmahl, Henry G.

    1994-01-01

    Mathematical analysis of the wave equation in cylinders with elliptical cross-section slots was performed. Compared to slow wave structures with rectangular slots higher impedance and lower power dissipation losses are evident. These features could lead to improved designs of traveling wave magnetrons and gigahertz backward-wave oscillators as well as linear traveling wave tubes with relatively shallow slots.

  11. Nonlinear theory of slow cyclotron wave interaction in folded waveguide

    SciTech Connect

    Ganguly, A.K.; Choi, J.J.

    1995-12-31

    A three-dimensional non-linear theory is presented for the generation of broadband radiation from slow cyclotron wave interaction in a folded waveguide. The serpentine structure is formed by folding a rectangular waveguide so that the orientation of the magnetic changes (H-plane bend) instead of the conventional E-plane bend configuration where the orientation of the electric field changes. The H-plane bend structure can use larger beam tunnel without distorting the rf field structure and generate higher output power. Numerical results will be shown for the TE{sub 10} mode propagation in an unridged and a double ridged waveguide. For a 61.5 kV, 3 A beam with {alpha}=1.0 and {Delta}v{sub z}/v{sub z}=0, calculations show an efficiency of 25% with 20% bandwidth and an efficiency of 35% at 10% bandwidth. The efficiency and bandwidth is relatively unchanged up to a beam axial velocity spread of 2%. The bandwidth can be further increased by mode coalescing techniques. Multistage operation is necessary to avoid backward wave oscillation.

  12. SLOW MAGNETOACOUSTIC WAVES OBSERVED ABOVE A QUIET-SUN REGION IN A DARK CAVITY

    SciTech Connect

    Liu Jiajia; Zhou Zhenjun; Wang Yuming; Liu Rui; Liao Chijian; Shen Chenglong; Zheng Huinan; Miao Bin; Su Zhenpeng; Wang, S.; Wang Bin E-mail: ymwang@ustc.edu.cn

    2012-10-20

    Waves play a crucial role in diagnosing the plasma properties of various structures in the solar corona and coronal heating. Slow magnetoacoustic (MA) waves are one of the important types of magnetohydrodynamic waves. In past decades, numerous slow MA waves were detected above active regions and coronal holes, but were rarely found elsewhere. Here, we investigate a 'tornado'-like structure consisting of quasi-periodic streaks within a dark cavity at about 40-110 Mm above a quiet-Sun region on 2011 September 25. Our analysis reveals that these streaks are actually slow MA wave trains. The properties of these wave trains, including phase speed, compression ratio, and kinetic energy density, are similar to those of the reported slow MA waves, except that the period of these waves is about 50 s, much shorter than the typical reported values (3-5 minutes).

  13. A 0.14 THz relativistic coaxial overmoded surface wave oscillator with metamaterial slow wave structure

    SciTech Connect

    Guo, Weijie; Wang, Jianguo Chen, Zaigao; Cai, Libing; Wang, Yue; Wang, Guangqiang; Qiao, Hailiang

    2014-12-15

    This paper presents a new kind of device for generating the high power terahertz wave by using a coaxial overmoded surface wave oscillator with metamaterial slow wave structure (SWS). A metallic metamaterial SWS is used to avoid the damage of the device driven by a high-voltage electron beam pulse. The overmoded structure is adopted to make it much easy to fabricate and assemble the whole device. The coaxial structure is used to suppress the mode competition in the overmoded device. Parameters of an electron beam and geometric structure are provided. Particle-in-cell simulation results show that the high power terahertz wave at the frequency of 0.14 THz is generated with the output power 255 MW and conversion efficiency about 21.3%.

  14. Characterization of slow waves generated by myenteric interstitial cells of Cajal of the rabbit small intestine.

    PubMed

    Kito, Yoshihiko; Mitsui, Retsu; Ward, Sean M; Sanders, Kenton M

    2015-03-01

    Slow waves (slow wavesICC) were recorded from myenteric interstitial cells of Cajal (ICC-MY) in situ in the rabbit small intestine, and their properties were compared with those of mouse small intestine. Rabbit slow wavesICC consisted of an upstroke depolarization followed by a distinct plateau component. Ni(2+) and nominally Ca(2+)-free solutions reduced the rate-of-rise and amplitude of the upstroke depolarization. Replacement of Ca(2+) with Sr(2+) enhanced the upstroke component but decreased the plateau component of rabbit slow wavesICC. In contrast, replacing Ca(2+) with Sr(2+) decreased both components of mouse slow wavesICC. The plateau component of rabbit slow wavesICC was inhibited in low-extracellular-Cl(-)-concentration (low-[Cl(-)]o) solutions and by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), an inhibitor of Cl(-) channels, cyclopiazonic acid (CPA), an inhibitor of internal Ca(2+) pumps, or bumetanide, an inhibitor of Na(+)-K(+)-2Cl(-) cotransporter (NKCC1). Bumetanide also inhibited the plateau component of mouse slow wavesICC. NKCC1-like immunoreactivity was observed mainly in ICC-MY in the rabbit small intestine. Membrane depolarization with a high-K(+) solution reduced the upstroke component of rabbit slow wavesICC. In cells depolarized with elevated external K(+), DIDS, CPA, and bumetanide blocked slow wavesICC. These results suggest that the upstroke component of rabbit slow wavesICC is partially mediated by voltage-dependent Ca(2+) influx, whereas the plateau component is dependent on Ca(2+)-activated Cl(-) efflux. NKCC1 is likely to be responsible for Cl(-) accumulation in ICC-MY. The results also suggest that the mechanism of the upstroke component differs in rabbit and mouse slow wavesICC in the small intestine. PMID:25540230

  15. Enhanced traveling wave amplification of co-planar slow wave structure by extended phase-matching

    SciTech Connect

    Palm, Andrew; Sirigiri, Jagadishwar; Shin, Young-Min

    2015-09-15

    The electron beam co-propagating with slow waves in a staggered double grating array (SDGA) efficiently amplifies millimeter and sub-millimeter waves over a wide spectrum. Our theoretical and numerical analyses show that the power amplification in the fundamental passband is enhanced by the extended beam-wave phase-matching. Particle-in-cell simulations on the SDGA slow wave structure, designed with 10.4 keV and 50–100 mA sheet beam, indicate that maintaining beam-wave synchronization along the entire length of the circuit improves the gain by 7.3% leading to a total gain of 28 dB, corresponding to 62 W saturated power at the middle of operating band, and a 3-dB bandwidth of 7 GHz with 10.5% at V-band (73.5 GHz center frequency) with saturated peak power reaching 80 W and 28 dB at 71 GHz. These results also show a reasonably good agreement with analytic calculations based on Pierce small signal gain theory.

  16. Cortical thinning explains changes in sleep slow waves during adulthood.

    PubMed

    Dubé, Jonathan; Lafortune, Marjolaine; Bedetti, Christophe; Bouchard, Maude; Gagnon, Jean François; Doyon, Julien; Evans, Alan C; Lina, Jean-Marc; Carrier, Julie

    2015-05-20

    Sleep slow waves (SWs) change considerably throughout normal aging. In humans, SWs are generated and propagate on a structural backbone of highly interconnected cortical regions that form most of the default mode network, such as the insula, cingulate cortices, temporal lobe, parietal lobe, and medial frontal lobe. Regions in this network undergo cortical thinning and breakdown in structural and functional connectivity over the course of normal aging. In this study, we investigated how changes in cortical thickness (CT), a measure of gray matter integrity, are involved in modifications of sleep SWs during adulthood in humans. Thirty young (mean age = 23.49 years; SD = 2.79) and 33 older (mean age = 60.35 years; SD = 5.71) healthy subjects underwent a nocturnal polysomnography and T1 MRI. We show that, when controlling for age, higher SW density (nb/min of nonrapid eye movement sleep) was associated with higher CT in cortical regions involved in SW generation surrounding the lateral fissure (insula, superior temporal, parietal, middle frontal), whereas higher SW amplitude was associated with higher CT in middle frontal, medial prefrontal, and medial posterior regions. Mediation analyses demonstrated that thinning in a network of cortical regions involved in SW generation and propagation, but also in cognitive functions, explained the age-related decrease in SW density and amplitude. Altogether, our results suggest that microstructural degradation of specific cortical regions compromise SW generation and propagation in older subjects, critically contributing to age-related changes in SW oscillations. PMID:25995467

  17. Effects of aging on slow-wave sleep dynamics and human spatial navigational memory consolidation.

    PubMed

    Varga, Andrew W; Ducca, Emma L; Kishi, Akifumi; Fischer, Esther; Parekh, Ankit; Koushyk, Viachaslau; Yau, Po Lai; Gumb, Tyler; Leibert, David P; Wohlleber, Margaret E; Burschtin, Omar E; Convit, Antonio; Rapoport, David M; Osorio, Ricardo S; Ayappa, Indu

    2016-06-01

    The consolidation of spatial navigational memory during sleep is supported by electrophysiological and behavioral evidence. The features of sleep that mediate this ability may change with aging, as percentage of slow-wave sleep is canonically thought to decrease with age, and slow waves are thought to help orchestrate hippocampal-neocortical dialog that supports systems level consolidation. In this study, groups of younger and older subjects performed timed trials before and after polysomnographically recorded sleep on a 3D spatial maze navigational task. Although younger subjects performed better than older subjects at baseline, both groups showed similar improvement across presleep trials. However, younger subjects experienced significant improvement in maze performance during sleep that was not observed in older subjects, without differences in morning psychomotor vigilance between groups. Older subjects had sleep quality marked by decreased amount of slow-wave sleep and increased fragmentation of slow-wave sleep, resulting in decreased slow-wave activity. Across all subjects, frontal slow-wave activity was positively correlated with both overnight change in maze performance and medial prefrontal cortical volume, illuminating a potential neuroanatomical substrate for slow-wave activity changes with aging and underscoring the importance of slow-wave activity in sleep-dependent spatial navigational memory consolidation. PMID:27143431

  18. Slow wave activity and slow oscillations in sleepwalkers and controls: effects of 38 h of sleep deprivation.

    PubMed

    Perrault, Rosemarie; Carrier, Julie; Desautels, Alex; Montplaisir, Jacques; Zadra, Antonio

    2013-08-01

    Sleepwalkers have been shown to have an unusually high number of arousals from slow wave sleep and lower slow wave activity (SWA) power during the night than controls. Because sleep deprivation increases the frequency of slow wave sleep (SWS) arousals in sleepwalkers, it may also affect the expression of the homeostatic process to a greater extent than shown previously. We thus investigated SWA power as well as slow wave oscillation (SWO) density in 10 sleepwalkers and nine controls at baseline and following 38 h of sleep deprivation. There was a significant increase in SWA during participants' recovery sleep, especially during their second non-rapid eye movement (NREM) period. SWO density was similarly increased during recovery sleep's first two NREM periods. A fronto-central gradient in SWA and SWO was also present on both nights. However, no group differences were noted on any of the 2 nights on SWA or SWO. This unexpected result may be related to the heterogeneity of sleepwalkers as a population, as well as our small sample size. SWA pressure after extended sleep deprivation may also result in a ceiling effect in both sleepwalkers and controls. PMID:23398262

  19. Determination of S-wave slowness from a linear array of borehole receivers

    NASA Astrophysics Data System (ADS)

    Eisner, Leo; Fischer, Tomáš; Rutledge, James T.

    2009-01-01

    Locations of seismic events from a linear array of receivers may require determination of slowness vectors of arriving waves. In an isotropic medium, P waves are polarized along the slowness vector, which enables direct determination of backazimuth (i.e. azimuth to a source from a receiver) from P-wave polarization. In contrast, S waves usually have much larger signal-to-noise ratio than P waves, but are polarized in a plane perpendicular to their slowness vectors, which prevents direct determination of their backazimuth. We have developed a novel technique to determine the slowness vector of S waves detected in a linear array of receivers in an isotropic medium. We combine the S-wave polarization measurement with the derivative of the S-wave travel times along the array to obtain the full slowness vector and backazimuth. The proposed method allows one to determine direction to sources of seismic events from a single linear array of receivers, using only S waves. This technique is not affected by SV waves, which is shown by a test on a synthetic data set. We also test the method on two real microseismic data sets from hydraulic fracturing treatments and show that it outperforms the backazimuth determination from P waves and from horizontal polarization of S waves.

  20. Gastric dysrhythmias and the current status of electrogastrography

    NASA Technical Reports Server (NTRS)

    Koch, K. L.

    1989-01-01

    Myoelectrical activity recorded simultaneously from mucosal, serosal, and cutaneous electrodes has confirmed that the 3-cpm signal from such electrodes reflects gastric slow-wave activity. Now, the observation that patients with unexplained nausea and vomiting may have very rapid slow-wave frequencies (tachygastrias) and very slow, slow-wave frequencies (bradygastrias) suggests that electrogastrography, a reliable and noninvasive technique, may be useful in the diagnosis and management of patients with upper abdominal symptoms and gastroparesis.

  1. The occurrence of individual slow waves in sleep is predicted by heart rate.

    PubMed

    Mensen, Armand; Zhang, Zhongxing; Qi, Ming; Khatami, Ramin

    2016-01-01

    The integration of near-infrared spectroscopy and electroencephalography measures presents an ideal method to study the haemodynamics of sleep. While the cortical dynamics and neuro-modulating influences affecting the transition from wakefulness to sleep is well researched, the assumption has been that individual slow waves, the hallmark of deep sleep, are spontaneously occurring cortical events. By creating event-related potentials from the NIRS recording, time-locked to the onset of thousands of individual slow waves, we show the onset of slow waves is phase-locked to an ongoing oscillation in the NIRS recording. This oscillation stems from the moment to moment fluctuations of light absorption caused by arterial pulsations driven by the heart beat. The same oscillating signal can be detected if the electrocardiogram is time-locked to the onset of the slow wave. The ongoing NIRS oscillation suggests that individual slow wave initiation is dependent on that signal, and not the other way round. However, the precise causal links remain speculative. We propose several potential mechanisms: that the heart-beat or arterial pulsation acts as a stimulus which evokes a down-state; local fluctuations in energy supply may lead to a network effect of hyperpolarization; that the arterial pulsations lead to corresponding changes in the cerebral-spinal-fluid which evokes the slow wave; or that a third neural generator, regulating heart rate and slow waves may be involved. PMID:27445083

  2. The occurrence of individual slow waves in sleep is predicted by heart rate

    PubMed Central

    Mensen, Armand; Zhang, Zhongxing; Qi, Ming; Khatami, Ramin

    2016-01-01

    The integration of near-infrared spectroscopy and electroencephalography measures presents an ideal method to study the haemodynamics of sleep. While the cortical dynamics and neuro-modulating influences affecting the transition from wakefulness to sleep is well researched, the assumption has been that individual slow waves, the hallmark of deep sleep, are spontaneously occurring cortical events. By creating event-related potentials from the NIRS recording, time-locked to the onset of thousands of individual slow waves, we show the onset of slow waves is phase-locked to an ongoing oscillation in the NIRS recording. This oscillation stems from the moment to moment fluctuations of light absorption caused by arterial pulsations driven by the heart beat. The same oscillating signal can be detected if the electrocardiogram is time-locked to the onset of the slow wave. The ongoing NIRS oscillation suggests that individual slow wave initiation is dependent on that signal, and not the other way round. However, the precise causal links remain speculative. We propose several potential mechanisms: that the heart-beat or arterial pulsation acts as a stimulus which evokes a down-state; local fluctuations in energy supply may lead to a network effect of hyperpolarization; that the arterial pulsations lead to corresponding changes in the cerebral-spinal-fluid which evokes the slow wave; or that a third neural generator, regulating heart rate and slow waves may be involved. PMID:27445083

  3. Developmental aspects of sleep slow waves: linking sleep, brain maturation and behavior.

    PubMed

    Ringli, Maya; Huber, Reto

    2011-01-01

    Sleep slow waves are the major electrophysiological features of non-rapid eye movement (NREM) sleep. Although there is growing understanding of where slow waves originate and how they are generated during sleep, the function of slow waves is still largely unclear. A recently proposed hypothesis relates slow waves to the homeostatic regulation of synaptic plasticity. While several studies confirm a correlation between experimentally triggered synaptic changes and slow-wave activity (SWA), little is known about its association to synaptic changes occurring during cortical maturation. Interestingly, slow waves undergo remarkable changes during development that parallel the time course of cortical maturation. In a recent cross-sectional study including children and adolescents, the topographical distribution of SWA was analyzed with high-density electroencephalography. The results showed age-dependent differences in SWA topography: SWA was highest over posterior regions during early childhood and then shifted over central derivations to the frontal cortex in late adolescence. This trajectory of SWA topography matches the course of cortical gray maturation. In this chapter, the major changes in slow waves during development are highlighted and linked to cortical maturation and behavior. Interestingly, synaptic density and slow-wave amplitude increase during childhood are highest shortly before puberty, decline thereafter during adolescence, reaching overall stable levels during adulthood. The question arises whether SWA is merely reflecting cortical changes or if it plays an active role in brain maturation. We thereby propose a model, by which sleep slow waves may contribute to cortical maturation. We hypothesize that while there is a balance between synaptic strengthening and synaptic downscaling in adults, the balance of strengthening/formation and weakening/elimination is tilted during development. PMID:21854956

  4. Supplementing monosodium glutamate to partial enteral nutrition slows gastric emptying in preterm pigs

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Emerging evidence suggests that free glutamate may play a functional role in modulating gastroduodenal motor function. We hypothesized that supplementing monosodium glutamate (MSG) to partial enteral nutrition stimulates gastric emptying in preterm pigs. Ten-day-old preterm, parenterally fed pigs re...

  5. Enhancing the efficiency of slow-wave electron cyclotron masers with the tapered refractive index

    SciTech Connect

    Kong Lingbao; Hou Zhiling; Jing Jian; Jin Haibo; Du Chaohai

    2013-04-15

    The nonlinear analysis of slow-wave electron cyclotron masers (ECM) based on anomalous Doppler effect in a slab waveguide is presented. A method of tapered refractive index (TRI) is proposed to enhance the efficiency of slow-wave ECM. The numerical calculations show that the TRI method can significantly enhance the efficiency of slow-wave ECM with the frequency ranging from the microwave to terahertz band. The effect of beam velocity spread on the efficiency has also been studied. Although the velocity spread suppresses the efficiency significantly, a great enhancement of efficiency can still be introduced by the TRI method.

  6. Electrical slow waves in the mouse oviduct are dependent on extracellular and intracellular calcium sources

    PubMed Central

    Dixon, Rose Ellen; Britton, Fiona C.; Baker, Salah A.; Hennig, Grant W.; Rollings, Christina M.; Sanders, Kenton M.

    2011-01-01

    Spontaneous contractions of the myosalpinx are critical for oocyte transport along the oviduct. Slow waves, the electrical events that underlie myosalpinx contractions, are generated by a specialized network of pacemaker cells called oviduct interstitial cells of Cajal (ICC-OVI). The ionic basis of oviduct pacemaker activity is unknown. Intracellular recordings and Ca2+ imaging were performed to examine the role of extracellular and intracellular Ca2+ sources in slow wave generation. RT-PCR was performed to determine the transcriptional expression of Ca2+ channels. Molecular studies revealed most isoforms of L- and T-type calcium channels (Cav1.2,1.3,1.4,3.1,3.2,3.3) were expressed in myosalpinx. Reduction of extracellular Ca2+ concentration ([Ca2+]o) resulted in the abolition of slow waves and myosalpinx contractions without significantly affecting resting membrane potential (RMP). Spontaneous Ca2+ waves spread through ICC-OVI cells at a similar frequency to slow waves and were inhibited by reduced [Ca2+]o. Nifedipine depolarized RMP and inhibited slow waves; however, pacemaker activity returned when the membrane was repolarized with reduced extracellular K+ concentration ([K+]o). Ni2+ also depolarized RMP but failed to block slow waves. The importance of ryanodine and inositol 1,4,5 trisphosphate-sensitive stores were examined using ryanodine, tetracaine, caffeine, and 2-aminoethyl diphenylborinate. Results suggest that although both stores are involved in regulation of slow wave frequency, neither are exclusively essential. The sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) pump inhibitor cyclopiazonic acid inhibited pacemaker activity and Ca2+ waves suggesting that a functional SERCA pump is necessary for pacemaker activity. In conclusion, results from this study suggest that slow wave generation in the oviduct is voltage dependent, occurs in a membrane potential window, and is dependent on extracellular calcium and functional SERCA pumps. PMID:21881003

  7. Slow-Mode MHD Wave Penetration into a Coronal Null Point due to the Mode Transmission

    NASA Astrophysics Data System (ADS)

    Afanasyev, Andrey N.; Uralov, Arkadiy M.

    2016-05-01

    Recent observations of magnetohydrodynamic oscillations and waves in solar active regions revealed their close link to quasi-periodic pulsations in flaring light curves. The nature of that link has not yet been understood in detail. In our analytical modelling we investigate propagation of slow magnetoacoustic waves in a solar active region, taking into account wave refraction and transmission of the slow magnetoacoustic mode into the fast one. The wave propagation is analysed in the geometrical acoustics approximation. Special attention is paid to the penetration of waves in the vicinity of a magnetic null point. The modelling has shown that the interaction of slow magnetoacoustic waves with the magnetic reconnection site is possible due to the mode transmission at the equipartition level where the sound speed is equal to the Alfvén speed. The efficiency of the transmission is also calculated.

  8. Conventional, Bayesian, and Modified Prony's methods for characterizing fast and slow waves in equine cancellous bone

    PubMed Central

    Groopman, Amber M.; Katz, Jonathan I.; Holland, Mark R.; Fujita, Fuminori; Matsukawa, Mami; Mizuno, Katsunori; Wear, Keith A.; Miller, James G.

    2015-01-01

    Conventional, Bayesian, and the modified least-squares Prony's plus curve-fitting (MLSP + CF) methods were applied to data acquired using 1 MHz center frequency, broadband transducers on a single equine cancellous bone specimen that was systematically shortened from 11.8 mm down to 0.5 mm for a total of 24 sample thicknesses. Due to overlapping fast and slow waves, conventional analysis methods were restricted to data from sample thicknesses ranging from 11.8 mm to 6.0 mm. In contrast, Bayesian and MLSP + CF methods successfully separated fast and slow waves and provided reliable estimates of the ultrasonic properties of fast and slow waves for sample thicknesses ranging from 11.8 mm down to 3.5 mm. Comparisons of the three methods were carried out for phase velocity at the center frequency and the slope of the attenuation coefficient for the fast and slow waves. Good agreement among the three methods was also observed for average signal loss at the center frequency. The Bayesian and MLSP + CF approaches were able to separate the fast and slow waves and provide good estimates of the fast and slow wave properties even when the two wave modes overlapped in both time and frequency domains making conventional analysis methods unreliable. PMID:26328678

  9. Microfabrication of diamond-based slow-wave circuits for mm-wave and THz vacuum electronic sources

    NASA Astrophysics Data System (ADS)

    Lueck, M. R.; Malta, D. M.; Gilchrist, K. H.; Kory, C. L.; Mearini, G. T.; Dayton, J. A.

    2011-06-01

    Planar and helical slow-wave circuits for THz radiation sources have been made using novel microfabrication and assembly methods. A biplanar slow-wave circuit for a 650 GHz backward wave oscillator (BWO) was fabricated through the growth of diamond into high aspect ratio silicon molds and the selective metallization of the tops and sidewalls of 90 µm tall diamond features using lithographically created shadow masks. Helical slow-wave circuits for a 650 GHz BWO and a 95 GHz traveling wave tube were created through the patterning of trenches in thin film diamond, electroplating of gold half-helices, and high accuracy bonding of helix halves. The development of new techniques for the microfabrication of vacuum electronic components will help to facilitate compact and high-power sources for terahertz range radiation.

  10. Stick-slip at soft adhesive interfaces mediated by slow frictional waves.

    PubMed

    Viswanathan, Koushik; Sundaram, Narayan K; Chandrasekar, Srinivasan

    2016-06-28

    Stick-slip is a friction instability that governs diverse phenomena from squealing automobile brakes to earthquakes. At soft adhesive interfaces, this instability has long been attributed to Schallamach waves, which are a type of slow frictional wave. We use a contact configuration capable of isolating single wave events, coupled with high speed in situ imaging, to demonstrate the existence of two new stick-slip modes. It is shown that these modes also correspond to the passage of slow waves-separation pulse and slip pulse-with distinct nucleation and propagation characteristics. The slip pulse, characterized by a sharp stress front, propagates in the same direction as the Schallamach wave. In contrast, the separation pulse, involving local interface detachment and resembling a tensile neck, travels in exactly the opposite direction. A change in the stick-slip mode from the separation to the slip pulse is effected simply by increasing the normal force. Taken together, the three waves constitute all possible stick-slip modes in low-velocity sliding. The detailed observations enable us to present a phase diagram delineating the domains of occurrence of these waves. We suggest a direct analogy between the observed slow frictional waves and well known muscular locomotory waves in soft bodied organisms. Our work answers basic questions about adhesive mechanisms of frictional instabilities in natural and engineered systems, with broader implications for slow surface wave phenomena. PMID:27118236

  11. Propagation of Long-Wavelength Nonlinear Slow Sausage Waves in Stratified Magnetic Flux Tubes

    NASA Astrophysics Data System (ADS)

    Barbulescu, M.; Erdélyi, R.

    2016-05-01

    The propagation of nonlinear, long-wavelength, slow sausage waves in an expanding magnetic flux tube, embedded in a non-magnetic stratified environment, is discussed. The governing equation for surface waves, which is akin to the Leibovich-Roberts equation, is derived using the method of multiple scales. The solitary wave solution of the equation is obtained numerically. The results obtained are illustrative of a solitary wave whose properties are highly dependent on the degree of stratification.

  12. Slow Waves in Fractures Filled with Viscous Fluid

    SciTech Connect

    Korneev, Valeri

    2008-01-08

    Stoneley guided waves in a fluid-filled fracture generally have larger amplitudes than other waves, and therefore, their properties need to be incorporated in more realistic models. In this study, a fracture is modeled as an infinite layer of viscous fluid bounded by two elastic half-spaces with identical parameters. For small fracture thickness, I obtain a simple dispersion equation for wave-propagation velocity. This velocity is much smaller than the velocity of a fluid wave in a Biot-type solution, in which fracture walls are assumed to be rigid. At seismic prospecting frequencies and realistic fracture thicknesses, the Stoneley guided wave has wavelengths on the order of several meters and an attenuation Q factor exceeding 10, which indicates the possibility of resonance excitation in fluid-bearing rocks. The velocity and attenuation of Stoneley guided waves are distinctly different at low frequencies for water and oil. The predominant role of fractures in fluid flow at field scales is supported by permeability data showing an increase of several orders of magnitude when compared to values obtained at laboratory scales. These data suggest that Stoneley guided waves should be taken into account in theories describing seismic wave propagation in fluid-saturated rocks.

  13. Linear analysis of a backward wave oscillator with triangular corrugated slow wave structure

    NASA Astrophysics Data System (ADS)

    Saber, Md. Ghulam; Sagor, Rakibul Hasan; Amin, Md. Ruhul

    2016-05-01

    In this work, a backward wave oscillator (BWO) with triangularly corrugated periodic metallic slow wave structure (TrCSWS) driven by an infinitely thin annular electron beam is studied using linear theory. The electron beam is assumed to be guided by a strong magnetic field. The triangular axial profile of the SWS is approximated by a Fourier series in order to apply the linear Rayleigh-Fourier (R-F) theory that has long been used in the theoretical analysis of BWOs with sinusoidally corrugated SWS (SCSWS). The dispersion equation for various beam parameters has been solved and the temporal growth rate (TGR) of the electromagnetic wave for the fundamental TM_{01} mode is calculated numerically. The TGR values for different beam parameters have been compared with those of the BWO with SCSWS, semi-circularly corrugated SWS (SCCSWS) and trapezoidally corrugated SWS (TCSWS). In order to compare the TGR values, the amplitude of corrugation of the TrCSWS is varied so that its dispersion curve of TM_{01} mode almost coincides with that of the SCSWS and TCSWS. The study reveals that the performance (in terms of TGR) of the proposed BWO with TrCSWS is comparable to that of other BWOs with SCSWS and TCSWS for the same set of beam parameters and it provides significantly better performance than SCCSWS. So, the proposed TrCSWS that can easily be constructed may replace SCSWS, SCCSWS or TCSWS as their viable alternative.

  14. EEG slow-wave coherence changes in propofol-induced general anesthesia: experiment and theory.

    PubMed

    Wang, Kaier; Steyn-Ross, Moira L; Steyn-Ross, D A; Wilson, Marcus T; Sleigh, Jamie W

    2014-01-01

    The electroencephalogram (EEG) patterns recorded during general anesthetic-induced coma are closely similar to those seen during slow-wave sleep, the deepest stage of natural sleep; both states show patterns dominated by large amplitude slow waves. Slow oscillations are believed to be important for memory consolidation during natural sleep. Tracking the emergence of slow-wave oscillations during transition to unconsciousness may help us to identify drug-induced alterations of the underlying brain state, and provide insight into the mechanisms of general anesthesia. Although cellular-based mechanisms have been proposed, the origin of the slow oscillation has not yet been unambiguously established. A recent theoretical study by Steyn-Ross et al. (2013) proposes that the slow oscillation is a network, rather than cellular phenomenon. Modeling anesthesia as a moderate reduction in gap-junction interneuronal coupling, they predict an unconscious state signposted by emergent low-frequency oscillations with chaotic dynamics in space and time. They suggest that anesthetic slow-waves arise from a competitive interaction between symmetry-breaking instabilities in space (Turing) and time (Hopf), modulated by gap-junction coupling strength. A significant prediction of their model is that EEG phase coherence will decrease as the cortex transits from Turing-Hopf balance (wake) to Hopf-dominated chaotic slow-waves (unconsciousness). Here, we investigate changes in phase coherence during induction of general anesthesia. After examining 128-channel EEG traces recorded from five volunteers undergoing propofol anesthesia, we report a significant drop in sub-delta band (0.05-1.5 Hz) slow-wave coherence between frontal, occipital, and frontal-occipital electrode pairs, with the most pronounced wake-vs.-unconscious coherence changes occurring at the frontal cortex. PMID:25400558

  15. EEG slow-wave coherence changes in propofol-induced general anesthesia: experiment and theory

    PubMed Central

    Wang, Kaier; Steyn-Ross, Moira L.; Steyn-Ross, D. A.; Wilson, Marcus T.; Sleigh, Jamie W.

    2014-01-01

    The electroencephalogram (EEG) patterns recorded during general anesthetic-induced coma are closely similar to those seen during slow-wave sleep, the deepest stage of natural sleep; both states show patterns dominated by large amplitude slow waves. Slow oscillations are believed to be important for memory consolidation during natural sleep. Tracking the emergence of slow-wave oscillations during transition to unconsciousness may help us to identify drug-induced alterations of the underlying brain state, and provide insight into the mechanisms of general anesthesia. Although cellular-based mechanisms have been proposed, the origin of the slow oscillation has not yet been unambiguously established. A recent theoretical study by Steyn-Ross et al. (2013) proposes that the slow oscillation is a network, rather than cellular phenomenon. Modeling anesthesia as a moderate reduction in gap-junction interneuronal coupling, they predict an unconscious state signposted by emergent low-frequency oscillations with chaotic dynamics in space and time. They suggest that anesthetic slow-waves arise from a competitive interaction between symmetry-breaking instabilities in space (Turing) and time (Hopf), modulated by gap-junction coupling strength. A significant prediction of their model is that EEG phase coherence will decrease as the cortex transits from Turing–Hopf balance (wake) to Hopf-dominated chaotic slow-waves (unconsciousness). Here, we investigate changes in phase coherence during induction of general anesthesia. After examining 128-channel EEG traces recorded from five volunteers undergoing propofol anesthesia, we report a significant drop in sub-delta band (0.05–1.5 Hz) slow-wave coherence between frontal, occipital, and frontal–occipital electrode pairs, with the most pronounced wake-vs.-unconscious coherence changes occurring at the frontal cortex. PMID:25400558

  16. Discrete-State Simulated Annealing For Traveling-Wave Tube Slow-Wave Circuit Optimization

    NASA Technical Reports Server (NTRS)

    Wilson, Jeffrey D.; Bulson, Brian A.; Kory, Carol L.; Williams, W. Dan (Technical Monitor)

    2001-01-01

    Algorithms based on the global optimization technique of simulated annealing (SA) have proven useful in designing traveling-wave tube (TWT) slow-wave circuits for high RF power efficiency. The characteristic of SA that enables it to determine a globally optimized solution is its ability to accept non-improving moves in a controlled manner. In the initial stages of the optimization, the algorithm moves freely through configuration space, accepting most of the proposed designs. This freedom of movement allows non-intuitive designs to be explored rather than restricting the optimization to local improvement upon the initial configuration. As the optimization proceeds, the rate of acceptance of non-improving moves is gradually reduced until the algorithm converges to the optimized solution. The rate at which the freedom of movement is decreased is known as the annealing or cooling schedule of the SA algorithm. The main disadvantage of SA is that there is not a rigorous theoretical foundation for determining the parameters of the cooling schedule. The choice of these parameters is highly problem dependent and the designer needs to experiment in order to determine values that will provide a good optimization in a reasonable amount of computational time. This experimentation can absorb a large amount of time especially when the algorithm is being applied to a new type of design. In order to eliminate this disadvantage, a variation of SA known as discrete-state simulated annealing (DSSA), was recently developed. DSSA provides the theoretical foundation for a generic cooling schedule which is problem independent, Results of similar quality to SA can be obtained, but without the extra computational time required to tune the cooling parameters. Two algorithm variations based on DSSA were developed and programmed into a Microsoft Excel spreadsheet graphical user interface (GUI) to the two-dimensional nonlinear multisignal helix traveling-wave amplifier analysis program TWA3

  17. Slowing and stopping of wave in dispersive metamaterial loaded helical guide.

    PubMed

    Sharma, Dushyant K; Pathak, Surya K

    2016-02-01

    We propose a dispersive metamaterial loaded helical waveguide (DMLHG) structure that supports slowing and stopping of Electromagnetic (EM) wave. Analytical and computational characterizations have been done to visualize various modal characteristics in detail using the Drude model as a dispersive parameter. It is observed that metamaterial insertion enhances helical guide slow wave behaviour and it supports both forward wave (FW) and backward wave (BW) as well as mode degeneracy. Obtained mode degeneracy mechanism leads to trapping of EM wave. The proposed guide structure provides a dynamic control of wave velocity by varying its physical parameters. Two possible structures are designed and simulated using CST Microwave Studio Software. The simulation results verify the presence of similar characteristics as observed in analytical study such as FW, BW, mode-degeneracy, but in slightly shifted frequency spectrum. PMID:26906840

  18. Giant amplification in degenerate band edge slow-wave structures interacting with an electron beam

    NASA Astrophysics Data System (ADS)

    Othman, Mohamed A. K.; Veysi, Mehdi; Figotin, Alexander; Capolino, Filippo

    2016-03-01

    We propose a new amplification regime based on a synchronous operation of four degenerate electromagnetic (EM) modes in a slow-wave structure and the electron beam, referred to as super synchronization. These four EM modes arise in a Fabry-Pérot cavity when degenerate band edge (DBE) condition is satisfied. The modes interact constructively with the electron beam resulting in superior amplification. In particular, much larger gains are achieved for smaller beam currents compared to conventional structures based on synchronization with only a single EM mode. We demonstrate giant gain scaling with respect to the length of the slow-wave structure compared to conventional Pierce type single mode traveling wave tube amplifiers. We construct a coupled transmission line model for a loaded waveguide slow-wave structure exhibiting a DBE, and investigate the phenomenon of giant gain via super synchronization using the Pierce model generalized to multimode interaction.

  19. Sustained increase in hippocampal sharp-wave ripple activity during slow-wave sleep after learning

    PubMed Central

    Eschenko, Oxana; Ramadan, Wiâm; Mölle, Matthias; Born, Jan; Sara, Susan J.

    2008-01-01

    High-frequency oscillations, known as sharp-wave/ripple (SPW-R) complexes occurring in hippocampus during slow-wave sleep (SWS), have been proposed to promote synaptic plasticity necessary for memory consolidation. We recorded sleep for 3 h after rats were trained on an odor-reward association task. Learning resulted in an increased number SPW-Rs during the first hour of post-learning SWS. The magnitude of ripple events and their duration were also elevated for up to 2 h after the newly formed memory. Rats that did not learn the discrimination during the training session did not show any change in SPW-Rs. Successful retrieval from remote memory was likewise accompanied by an increase in SPW-R density and magnitude, relative to the previously recorded baseline, but the effects were much shorter lasting and did not include increases in ripple duration and amplitude. A short-lasting increase of ripple activity was also observed when rats were rewarded for performing a motor component of the task only. There were no increases in ripple activity after habituation to the experimental environment. These experiments show that the characteristics of hippocampal high-frequency oscillations during SWS are affected by prior behavioral experience. Associative learning induces robust and sustained (up to 2 h) changes in several SPW-R characteristics, while after retrieval from remote memory or performance of a well-trained procedural aspect of the task, only transient changes in ripple density were induced. PMID:18385477

  20. Noninvasive biomagnetic detection of intestinal slow wave dysrhythmias in chronic mesenteric ischemia

    PubMed Central

    Muszynski, N. D.; Cheng, L. K.; Bradshaw, L. A.; Naslund, T. C.; Richards, W. O.

    2015-01-01

    Chronic mesenteric ischemia (CMI) is a challenging clinical problem that is difficult to diagnose noninvasively. Diagnosis early in the disease process would enable life-saving early surgical intervention. Previous studies established that superconducting quantum interference device (SQUID) magnetometers detect the slow wave changes in the magnetoenterogram (MENG) noninvasively following induction of mesenteric ischemia in animal models. The purpose of this study was to assess functional physiological changes in the intestinal slow wave MENG of patients with chronic mesenteric ischemia. Pre- and postoperative studies were conducted on CMI patients using MENG and intraoperative recordings using invasive serosal electromyograms (EMG). Our preoperative MENG recordings showed that patients with CMI exhibited a significant decrease in intestinal slow wave frequency from 8.9 ± 0.3 cpm preprandial to 7.4 ± 0.1 cpm postprandial (P < 0.01) that was not observed in postoperative recordings (9.3 ± 0.2 cpm preprandial and 9.4 ± 0.4 cpm postprandial, P = 0.86). Intraoperative recording detected multiple frequencies from the ischemic portion of jejunum before revascularization, whereas normal serosal intestinal slow wave frequencies were observed after revascularization. The preoperative MENG data also showed signals with multiple frequencies suggestive of uncoupling and intestinal ischemia similar to intraoperative serosal EMG. Our results showed that multichannel MENG can identify intestinal slow wave dysrhythmias in CMI patients. PMID:25930082

  1. Two-channel gastric pacing in patients with diabetic gastroparesis

    PubMed Central

    Lin, Zhiyue; Sarosiek, Irene; Forster, Jameson; Ross, Robert A.; Chen, Jiande D.Z.; McCallum, Richard W.

    2011-01-01

    Background Our primary goals were to investigate the effects of two-channel gastric pacing on gastric myoelectrical activity, and energy consumption with the secondary intent to monitor gastric emptying and symptoms in patients with severe diabetic gastroparesis. Methods Four pairs of temporary pacing wires were inserted on the serosa of the stomach at the time of laparotomy to place the Enterra™ System in 19 patients with severe gastroparesis not responding to standard medical therapies. Two of the pairs were for electrical stimulation and the other two for recording. Five days after surgery the optimal pacing parameters for the entrainment of gastric slow waves in each patient were identified by serosal recordings. Two-channel gastric pacing was then initiated for 6 weeks using a newly developed external multi-channel pulse generator. Electrogastrogram (EGG), total symptom score (TSS), and a 4-hour gastric emptying test were assessed at baseline and after 6 weeks of active gastric pacing. Enterra™ device was turned OFF during the duration of this study. Key Results Two-channel gastric pacing at 1.1 times the intrinsic frequency entrained gastric slow waves and normalized gastric dysrhythmia. After 6 weeks of gastric pacing, tachygastria was decreased from 15±3 to 5±1% in the fasting state and from 10±2 to 5±1% postprandially (P<0.05), mean TSS was reduced from 21.3±1.1 to 7.0±1.5 (P<0.05) and mean 4-hour gastric retention improved from 42% to 28% (P=0.05). Conclusions& Inferences Two-channel gastric pacing is a novel treatment approach which is able to normalize and enhance gastric slow wave activity as well as accelerate gastric emptying in patients with diabetic gastroparesis with a good safety profile. PMID:21806741

  2. Kinetic Simulation of Slow Magnetosonic Waves and Quasi-Periodic Upflows in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Ruan, Wenzhi; He, Jiansen; Zhang, Lei; Vocks, Christian; Marsch, Eckart; Tu, Chuanyi; Peter, Hardi; Wang, Linghua

    2016-07-01

    Quasi-periodic disturbances of emission-line parameters are frequently observed in the corona. These disturbances propagate upward along the magnetic field with speeds of ∼100 km s‑1. This phenomenon has been interpreted as evidence of the propagation of slow magnetosonic waves or has been argued to be a signature of intermittent outflows superposed on the background plasmas. Here we aim to present a new “wave + flow” model to interpret these observations. In our scenario, the oscillatory motion is a slow-mode wave, and the flow is associated with a beam created by the wave–particle interaction owing to Landau resonance. With the help of a kinetic model, we simulate the propagation of slow-mode waves and the generation of beam flows. We find that weak periodic beam flows can be generated by to Landau resonance in the solar corona, and the phase with the strongest blueward asymmetry is ahead of that with the strongest blueshift by about 1/4 period. We also find that the slow wave damps to the level of 1/e after the transit time of two wave periods, owing to Landau damping and Coulomb collisions in our simulation. This damping timescale is similar to that resulting from thermal conduction in the MHD regime. The beam flow is weakened/attenuated with increasing wave period and decreasing wave amplitude since Coulomb collisions become more and more dominant over the wave action. We suggest that this “wave + flow” kinetic model provides an alternative explanation for the observed quasi-periodic propagating perturbations in various parameters in the solar corona.

  3. Fast and slow flexural waves in a deviated borehole in homogeneous and layered anisotropic formations

    NASA Astrophysics Data System (ADS)

    He, Xiao; Hu, Hengshan; Guan, Wei

    2010-04-01

    Dipole acoustic fields in an arbitrarily deviated well penetrating a homogeneous as well as a stratified transversely isotropic formation are simulated using a 3-D finite-difference time-domain algorithm in cylindrical coordinates. The modelling results show that a dipole source can excite a fast- and a slow-flexural mode due to the shear wave anisotropy when the borehole is inclined with respect to the symmetry axis of transverse isotropy. Both flexural slownesses change with the wellbore deviation angle. The splitting of flexural modes is prominent in full wave arrays when the shear anisotropy is strong enough. It is revealed that the dipole orientation influences the relative amplitudes of the fast- and slow-flexural waves but it has no effect on their slownesses or phases. In a vertical well parallel to the symmetry axis, the two flexural waves degenerate and propagate at the same speed. The degenerated flexural wave travels approximately at the shear speed along the borehole wall except in a few formations. Our study shows, for example, that it is about 10 per cent slower than the shear wave in Mesaverde clayshale 5501. Even in that kind of formations, however, extraction of the fast- and slow-shear velocities from the flexural modes is still possible if the borehole deviation is large enough. To examine the effect of layering, we modelled the full waves in a formation with a sandwich. When the well is perpendicular to the layer interfaces, reflection is obvious and can be recognized. It becomes weaker or even invisible as the deviation angle increases, so it is difficult to detect a thin layer embedded in a formation directly from reflected waves. The sandwich can, instead, be recognized from the irregularity in the spectra of the full waveforms displayed versus depth. [Correction added after online publication 25th February 2009; the original spelling of `homogenous' in the title has been corrected to `homogeneous'.[

  4. Slow-wave oscillations in a corticothalamic model of sleep and wake.

    PubMed

    Zhao, X; Kim, J W; Robinson, P A

    2015-04-01

    A physiologically-based corticothalamic neural field model is used to study slow wave oscillations including cortical UP and DOWN states in deep sleep by extending it to incorporate bursting dynamics of neurons in the thalamic reticular nucleus. The interplay of local bursting dynamics and network interactions produces the cortical UP and DOWN states of slow wave sleep while preserving previously verified model predictions in the wake state. Results show that EEG spectral features in wake and sleep are reproduced. The bursting is subthreshold but acts to intensify the amplitude of oscillations in slow wave sleep with deep UP/DOWN oscillations on the cortex emerging naturally. Furthermore, there is a continuous cycle between the two regimes, rather than a flip-flop between discrete states. PMID:25659479

  5. Effects of clonidine and sumatriptan on postprandial gastric volume response, antral contraction waves and emptying: an MRI study.

    PubMed

    Kwiatek, M A; Fox, M R; Steingoetter, A; Menne, D; Pal, A; Fruehauf, H; Kaufman, E; Forras-Kaufman, Z; Brasseur, J G; Goetze, O; Hebbard, G S; Boesiger, P; Thumshirn, M; Fried, M; Schwizer, W

    2009-09-01

    Gastric emptying (GE) may be driven by tonic contraction of the stomach ('pressure pump') or antral contraction waves (ACW) ('peristaltic pump'). The mechanism underlying GE was studied by contrasting the effects of clonidine (alpha(2)-adrenergic agonist) and sumatriptan (5-HT(1) agonist) on gastric function. Magnetic resonance imaging provided non-invasive assessment of gastric volume responses, ACW and GE in nine healthy volunteers. Investigations were performed in the right decubitus position after ingestion of 500 mL of 10% glucose (200 kcal) under placebo [0.9% NaCl intravenous (IV) and subcutaneous (SC)], clonidine [0.01 mg min(-1) IV, max 0.1 mg (placebo SC)] or sumatriptan [6 mg SC (placebo IV)]. Total gastric volume (TGV) and gastric content volume (GCV) were assessed every 5 min for 90 min, interspersed with dynamic scan sequences to measure ACW activity. During gastric filling, TGV increased with GCV indicating that meal volume dictates initial relaxation. Gastric contents volume continued to increase over the early postprandial period due to gastric secretion surpassing initial gastric emptying. Clonidine diminished this early increase in GCV, reduced gastric relaxation, decreased ACW frequency compared with placebo. Gastric emptying (GE) rate increased. Sumatriptan had no effect on initial GCV, but prolonged gastric relaxation and disrupted ACW activity. Gastric emptying was delayed. There was a negative correlation between gastric relaxation and GE rate (r(2 )=49%, P < 0.001), whereas the association between ACW frequency and GE rate was inconsistent and weak (r2=15%, P = 0.05). These findings support the hypothesis that nutrient liquid emptying is primarily driven by the 'pressure pump' mechanism. PMID:19413683

  6. Enhanced four-wave mixing in graphene-silicon slow-light photonic crystal waveguides

    SciTech Connect

    Zhou, Hao E-mail: tg2342@columbia.edu; Gu, Tingyi E-mail: tg2342@columbia.edu McMillan, James F.; Wong, Chee Wei E-mail: tg2342@columbia.edu; Petrone, Nicholas; Zande, Arend van der; Hone, James C.; Yu, Mingbin; Lo, Guoqiang; Kwong, Dim-Lee; Feng, Guoying; Zhou, Shouhuan

    2014-09-01

    We demonstrate the enhanced four-wave mixing of monolayer graphene on slow-light silicon photonic crystal waveguides. 200-μm interaction length, a four-wave mixing conversion efficiency of −23 dB is achieved in the graphene-silicon slow-light hybrid, with an enhanced 3-dB conversion bandwidth of about 17 nm. Our measurements match well with nonlinear coupled-mode theory simulations based on the measured waveguide dispersion, and provide an effective way for all-optical signal processing in chip-scale integrated optics.

  7. Slow Magnetosonic Waves Generated in the Plasmasphere by Ionospheric Terminator Motion

    NASA Astrophysics Data System (ADS)

    Leonovich, A. S.; Kozlov, D. A.

    2012-11-01

    A problem of the structure and spectrum of slow magnetosonic waves in a dipole plasmasphere is solved. The numerical solutions are found to the problem, for a distribution of the plasma parameters typical of the Earth's plasmasphere. The solutions allow us to treat the total electronic content oscillations registered above Japan as oscillations of one of the first harmonics of standing slow magnetosonic (SMS) waves. The results of numerical calculations of total electron content (TEC) oscillation amplitude are compared to the observations of the TEC oscillations and are shown to be in a good agreement with them.

  8. Shock Formation and Energy Dissipation of Slow Magnetosonic Waves in Coronal Plumes

    NASA Technical Reports Server (NTRS)

    Cuntz, M.; Suess, S. T.

    2003-01-01

    We study the shock formation and energy dissipation of slow magnetosonic waves in coronal plumes. The wave parameters and the spreading function of the plumes as well as the base magnetic field strength are given by empirical constraints mostly from SOHO/UVCS. Our models show that shock formation occurs at low coronal heights, i.e., within 1.3 bun, depending on the model parameters. In addition, following analytical estimates, we show that scale height of energy dissipation by the shocks ranges between 0.15 and 0.45 Rsun. This implies that shock heating by slow magnetosonic waves is relevant at most heights, even though this type of waves is apparently not a solely operating energy supply mechanism.

  9. Slow wave structures using twisted waveguides for charged particle applications

    SciTech Connect

    Kang, Yoon W.; Fathy, Aly E.; Wilson, Joshua L.

    2012-12-11

    A rapidly twisted electromagnetic accelerating structure includes a waveguide body having a central axis, one or more helical channels defined by the body and disposed around a substantially linear central axial channel, with central portions of the helical channels merging with the linear central axial channel. The structure propagates electromagnetic waves in the helical channels which support particle beam acceleration in the central axial channel at a phase velocity equal to or slower than the speed of light in free space. Since there is no variation in the shape of the transversal cross-section along the axis of the structure, inexpensive mechanical fabrication processes can be used to form the structure, such as extrusion, casting or injection molding. Also, because the field and frequency of the resonant mode depend on the whole structure rather than on dimensional tolerances of individual cells, no tuning of individual cells is needed. Accordingly, the overall operating frequency may be varied with a tuning/phase shifting device located outside the resonant waveguide structure.

  10. SDO/AIA Observation and Modeling of Flare-excited Slow Waves in Hot Coronal Loops

    NASA Astrophysics Data System (ADS)

    Wang, T.; Ofman, L.; Provornikova, E.; Sun, X.; Davila, J. M.

    2014-12-01

    The flare-excited standing slow waves were first detected by SOHO/SUMER as Doppler shift oscillations in hot (>6 MK) coronal loops. It has been suggested that they are excited by small or micro- flares at one loop's footpoint. However, the detailed excitation mechanism remains unclear. In this study, we report an oscillation event observed by SDO/AIA in the 131 channel. The intensity disturbances excited by a C-class flare propagated back and forth along a hot loop for about two period with a strong damping. From the measured oscillation period and loop length, we estimate the wave phase speed to be about 410 km/s. Using a regularized DEM analysis we determine the loop temperature and electron density evolution and find that the loop plasma is heated to a temperature of 8-12 MK with a mean about 9 MK. These measurements support the interpretation as slow magnetoacousic waves. Magnetic field extrapolation suggests that the flare is triggered by slipping and null-point-type reconnections in a fan-spine magnetic topology, and the injected (or impulsively evaporated) hot plasmas flowing along the large spine field lines form the oscillating hot loops. To understand why the propagating waves but not the standing waves as observed previously are excited in this event, we preform simulations using a 3D MHD model based on the observed magnetic configuration including full energy equation. Our simulations indicate that the nature of loop temperature structure is critical for the excitation of whether propagating or standing waves in a hot loop. Our result demonstrates that the slow waves may be used for heating diagnostics of coronal loops with coronal seismology. We also discuss the application of coronal seismology for estimating the average magnetic field strength in the hot loop based on the observed slow waves.

  11. Cut-off period for slow magnetoacoustic waves in coronal plasma structures

    NASA Astrophysics Data System (ADS)

    Afanasyev, A. N.; Nakariakov, V. M.

    2015-10-01

    Context. There is abundant observational evidence of longitudinal compressive waves in plasma structures of the solar corona, which are confidently interpreted in terms of slow magnetoacoustic waves. The uses of coronal slow waves in plasma diagnostics, as well as analysis of their possible contribution to coronal heating and the solar wind acceleration, require detailed theoretical modelling. Aims: We investigate the effects of obliqueness, magnetic field, and non-uniformity of the medium on the evolution of long-wavelength slow magnetoacoustic waves guided by field-aligned plasma non-uniformities, also called tube waves. Special attention is paid to the cut-off effect due to the gravity stratification of the coronal plasma. Methods: We study the behaviour of linear tube waves in a vertical untwisted straight field-aligned isothermal plasma cylinder. We apply the thin flux tube approximation, taking into account effects of stratification caused by gravity. The dispersion due to the finite radius of the flux tube is neglected. We analyse the behaviour of the cut-off period for an exponentially divergent magnetic flux tube filled in with a stratified plasma. The results obtained are compared with the known cases of the constant Alfven speed and the pure acoustic wave. Results: We derive the wave equation for tube waves and reduce it to the form of the Klein-Gordon equation with varying coefficients, which explicitly contains the cut-off frequency. The cut-off period is found to vary with height, decreasing significantly in the low-beta plasma and in the plasma with the beta of the order of unity. The depressions in the cut-off period profiles can affect the propagation of longitudinal waves along coronal plasma structures towards the higher corona and can form coronal resonators.

  12. Preliminary study of slow and fast ultrasonic waves using MR images of trabecular bone phantom

    NASA Astrophysics Data System (ADS)

    Solis-Najera, S. E.; Neria-Pérez, J. A.; Medina, L.; Garipov, R.; Rodríguez, A. O.

    2014-11-01

    Cancellous bone is a complex tissue that performs physiological and biomechanical functions in all vertebrates. It is made up of trabeculae that, from a simplified structural viewpoint, can be considered as plates and beams in a hyperstatic structure that change with time leading to osteoporosis. Several methods has been developed to study the trabecular bone microstructure among them is the Biot's model which predicts the existence of two longitudinal waves in porous media; the slow and the fast waves, that can be related to porosity of the media. This paper is focused on the experimental detection of the two Biot's waves of a trabecular bone phantom, consisting of a trabecular network of inorganic hydroxyapatite. Experimental measurements of both waves were performed using through transmission ultrasound. Results had shown clearly that the propagation of two waves propagation is transversal to the trabecular alignment. Otherwise the waves are overlapped and a single wave seems to be propagated. To validate these results, magnetic resonance images were acquired to assess the trabecular direction, and to assure that the pulses correspond to the slow and fast waves. This approach offers a methodology for non-invasive studies of trabecular bones.

  13. Preliminary study of slow and fast ultrasonic waves using MR images of trabecular bone phantom

    SciTech Connect

    Solis-Najera, S. E. E-mail: angel.perez@ciencias.unam.mx Neria-Pérez, J. A. E-mail: angel.perez@ciencias.unam.mx Medina, L. E-mail: angel.perez@ciencias.unam.mx; Garipov, R.; Rodríguez, A. O.

    2014-11-07

    Cancellous bone is a complex tissue that performs physiological and biomechanical functions in all vertebrates. It is made up of trabeculae that, from a simplified structural viewpoint, can be considered as plates and beams in a hyperstatic structure that change with time leading to osteoporosis. Several methods has been developed to study the trabecular bone microstructure among them is the Biot’s model which predicts the existence of two longitudinal waves in porous media; the slow and the fast waves, that can be related to porosity of the media. This paper is focused on the experimental detection of the two Biot’s waves of a trabecular bone phantom, consisting of a trabecular network of inorganic hydroxyapatite. Experimental measurements of both waves were performed using through transmission ultrasound. Results had shown clearly that the propagation of two waves propagation is transversal to the trabecular alignment. Otherwise the waves are overlapped and a single wave seems to be propagated. To validate these results, magnetic resonance images were acquired to assess the trabecular direction, and to assure that the pulses correspond to the slow and fast waves. This approach offers a methodology for non-invasive studies of trabecular bones.

  14. Midlife Decline in Declarative Memory Consolidation Is Correlated with a Decline in Slow Wave Sleep

    ERIC Educational Resources Information Center

    Backhaus, Jutta; Born, Jan; Hoeckesfeld, Ralf; Fokuhl, Sylvia; Hohagen, Fritz; Junghanns, Klaus

    2007-01-01

    Sleep architecture as well as memory function are strongly age dependent. Slow wave sleep (SWS), in particular, decreases dramatically with increasing age, starting already beyond the age of 30. SWS normally predominates during early nocturnal sleep and is implicated in declarative memory consolidation. However, the consequences of changes in…

  15. Neuronal Networks in Children with Continuous Spikes and Waves during Slow Sleep

    ERIC Educational Resources Information Center

    Siniatchkin, Michael; Groening, Kristina; Moehring, Jan; Moeller, Friederike; Boor, Rainer; Brodbeck, Verena; Michel, Christoph M.; Rodionov, Roman; Lemieux, Louis; Stephani, Ulrich

    2010-01-01

    Epileptic encephalopathy with continuous spikes and waves during slow sleep is an age-related disorder characterized by the presence of interictal epileptiform discharges during at least greater than 85% of sleep and cognitive deficits associated with this electroencephalography pattern. The pathophysiological mechanisms of continuous spikes and…

  16. Standing Slow-Mode Waves in Hot Coronal Loops: Observations, Modeling, and Coronal Seismology

    NASA Astrophysics Data System (ADS)

    Wang, Tongjiang

    2011-07-01

    Strongly damped Doppler shift oscillations are observed frequently associated with flarelike events in hot coronal loops. In this paper, a review of the observed properties and the theoretical modeling is presented. Statistical measurements of physical parameters (period, decay time, and amplitude) have been obtained based on a large number of events observed by SOHO/SUMER and Yohkoh/BCS. Several pieces of evidence are found to support their interpretation in terms of the fundamental standing longitudinal slow mode. The high excitation rate of these oscillations in small- or micro-flares suggest that the slow mode waves are a natural response of the coronal plasma to impulsive heating in closed magnetic structure. The strong damping and the rapid excitation of the observed waves are two major aspects of the waves that are poorly understood, and are the main subject of theoretical modelling. The slow waves are found mainly damped by thermal conduction and viscosity in hot coronal loops. The mode coupling seems to play an important role in rapid excitation of the standing slow mode. Several seismology applications such as determination of the magnetic field, temperature, and density in coronal loops are demonstrated. Further, some open issues are discussed.

  17. Social Exclusion in Middle Childhood: Rejection Events, Slow-wave Neural Activity and Ostracism Distress

    PubMed Central

    Crowley, Michael J.; Wu, Jia; Molfese, Peter J.; Mayes, Linda C.

    2010-01-01

    This study examined neural activity with event-related potentials (ERPs) in middle childhood during a computer-simulated ball-toss game, Cyberball. Experiencing fair play initially, children were ultimately excluded by the other players. We focused specifically on “not my turn” events within fair play and rejection events within social exclusion. Dense-array ERPs revealed that rejection events are perceived rapidly. Condition differences (“not my turn” vs. rejection) were evident in a posterior ERP peaking at 420 ms consistent, with a larger P3 effect for rejection events indicating that in middle childhood rejection events are differentiated in < 500 ms. Condition differences were evident for slow-wave activity (500–900 ms) in the medial frontal cortical region and the posterior occipital-parietal region, with rejection events more negative frontally and more positive posteriorly. Distress from the rejection experience was associated with a more negative frontal slow wave and a larger late positive slow wave, but only for rejection events. Source modeling with Geosouce software suggested that slow wave neural activity in cortical regions previously identified in functional imaging studies of ostracism, including subgenual cortex, ventral anterior cingulate cortex and insula was greater for rejection events vs. “not my turn” events. PMID:20628967

  18. Compressible turbulence with slow-mode waves observed in the bursty bulk flow of plasma sheet

    NASA Astrophysics Data System (ADS)

    Wang, Tieyan; Cao, Jinbin; Fu, Huishan; Meng, Xuejie; Dunlop, M.

    2016-03-01

    In this paper, we report the evidence of compressible turbulence with slow-mode waves in a bursty bulk flow of plasma sheet. This compressible turbulence is characterized by a multiscale (1-60 s) anticorrelation between plasma density and magnetic field strength. Besides, the magnetic compressibility spectrum stays nearly constant at all the measured frequencies. Furthermore, the turbulence energy distributions are anisotropic with k⊥ > k//, and the dispersion relation is consistent with slow-mode prediction. The fluctuations of density and magnetic field have similar double slope spectrum and kurtosis. These results suggest that the slow waves are involved in the intermittent turbulence cascade from MHD to ion kinetic scales, which may have significant implications for the energy transfer in the plasma sheet.

  19. Dynamic Analysis of the Conditional Oscillator Underlying Slow Waves in Thalamocortical Neurons

    PubMed Central

    David, François; Crunelli, Vincenzo; Leresche, Nathalie; Lambert, Régis C.

    2016-01-01

    During non-REM sleep the EEG shows characteristics waves that are generated by the dynamic interactions between cortical and thalamic oscillators. In thalamic neurons, low-threshold T-type Ca2+ channels play a pivotal role in almost every type of neuronal oscillations, including slow (< 1 Hz) waves, sleep spindles and delta waves. The transient opening of T channels gives rise to the low threshold spikes (LTSs), and associated high frequency bursts of action potentials, that are characteristically present during sleep spindles and delta waves, whereas the persistent opening of a small fraction of T channels, (i.e., ITwindow) is responsible for the membrane potential bistability underlying sleep slow oscillations. Surprisingly thalamocortical (TC) neurons express a very high density of T channels that largely exceed the amount required to generate LTSs and therefore, to support certain, if not all, sleep oscillations. Here, to clarify the relationship between T current density and sleep oscillations, we systematically investigated the impact of the T conductance level on the intrinsic rhythmic activities generated in TC neurons, combining in vitro experiments and TC neuron simulation. Using bifurcation analysis, we provide insights into the dynamical processes taking place at the transition between slow and delta oscillations. Our results show that although stable delta oscillations can be evoked with minimal T conductance, the full range of slow oscillation patterns, including groups of delta oscillations separated by Up states (“grouped-delta slow waves”) requires a high density of T channels. Moreover, high levels of T conductance ensure the robustness of different types of slow oscillations. PMID:26941611

  20. Beam-plasma amplifiers based on nonhomogeneous plasma-cavity slow-wave structure

    SciTech Connect

    Perevodchikov, V.I.; Mitin, L.A.; Shapiro, A.L.; Zavjalov, M.A.

    1995-11-01

    The investigation of interaction of E-beam with hybrid waves of nonhomogeneous plasma-cavity slow-wave structure have been carried out. It`s shown that depression of external magnetic field at out-put part of plasma-cavity structure may be used for decreasing of phase velocity of active waves and phase space synchronization ones with space charge fields, induced in plasma. This mode of operation of plasma TWT was calculated. The investigations carried out theoretically has been supported by experiments with plasma TWT.

  1. Simultaneous realization of negative group velocity, fast and slow acoustic waves in a metamaterial

    NASA Astrophysics Data System (ADS)

    Li, Xiao-juan; Xue, Cheng; Fan, Li; Zhang, Shu-yi; Chen, Zhe; Ding, Jin; Zhang, Hui

    2016-06-01

    An acoustic metamaterial is designed based on a simple and compact structure of one string of side pipes arranged along a waveguide, in which diverse group velocities are achieved. Owing to Fabry-Perot resonance of the side pipes, a negative phase time is achieved, and thus, acoustic waves transmitting with negative group velocities are produced near the resonant frequency. In addition, both fast and slow acoustic waves are also observed in the vicinity of the resonance frequency. The extraordinary group velocities can be explained based on spectral rephasing induced by anomalous dispersion on the analogy of Lorentz dispersion in electromagnetic waves.

  2. Calculation of coupling to slow and fast waves in the LHRF from phased waveguide arrays

    SciTech Connect

    Pinsker, R.I.; Duvall, R.E.; Fortgang, C.M.; Colestock, P.L.

    1986-04-01

    A previously reported algorithm for solving the problem of coupling electromagnetic energy in the LHRF from a phased array of identical rectangular waveguides to a plane-stratified, magnetized cold plasma is numerically implemented. The resulting computer codes are sufficiently general to allow for an arbitrary number of waveguides with finite dimensions in both poloidal and toroidal directions, and are thus capable of computing coupling to both slow and fast waves in the plasma. Some of the details of the implementation and the extension of the algorithm to allow study of the Fourier spectrum of slow and fast waves launched by the array are discussed. Good agreement is found with previously reported, less general work for the slow wave launching case. The effect of phasing multirow arrays in the poloidal direction is studied, and an asymmetry between phasing 'up' and 'down' is found that persists in the case where the plasma adjacent to the array is uniform. A 4 x 3 array designed to launch fast waves of high phase velocity is studied. By using the optimal poloidal phasing, low reflection coefficients (absolute value of R/sup 2/ less than or equal to 20%) are found under some not unrealistic edge plasma conditions, but most of the input power is trapped in the outermost layer of the plasma. Implications of our results for fast wave current drive experiments are discussed.

  3. Fast and slow magnetosonic waves in two-dimensional spin-1/2 quantum plasma

    SciTech Connect

    Mushtaq, A.; Vladimirov, S. V.

    2010-10-15

    Using the spin-1/2 resistive quantum magnetohydrodynamics model, linear and nonlinear relations for slow and fast magnetosonic modes are derived. Spin effects are incorporated via spin force and macroscopic spin magnetization current. The plasma resistivity is shown to play a role of dissipation in the system. With the aid of tanh method the traveling wave solution of Kadomstev-Petviashvili-Burgers is obtained. The solution shows a general shock wave profile superposed by a perturbative solitary-wave contribution. The dynamics of fast and slow magnetosonic shock and soliton, respectively, in the presence and absence of dissipation is investigated with respect to electron spin magnetization, quantum diffraction, and plasma statistic. It is found that results obtained from the spin quantum plasmas differ significantly from the nonspin quantum plasmas. The relevance of the present work to dense astrophysical plasmas such as pulsar magnetosphere is pointed out.

  4. Accurate Cold-Test Model of Helical TWT Slow-Wave Circuits

    NASA Technical Reports Server (NTRS)

    Kory, Carol L.; Dayton, J. A., Jr.

    1998-01-01

    Recently, a method has been established to accurately calculate cold-test data for helical slow-wave structures using the three-dimensional (3-D) electromagnetic computer code, MAFIA. Cold-test parameters have been calculated for several helical traveling-wave tube (TWT) slow-wave circuits possessing various support rod configurations, and results are presented here showing excellent agreement with experiment. The helical models include tape thickness, dielectric support shapes and material properties consistent with the actual circuits. The cold-test data from this helical model can be used as input into large-signal helical TWT interaction codes making it possible, for the first time, to design a complete TWT via computer simulation.

  5. Accurate Cold-Test Model of Helical TWT Slow-Wave Circuits

    NASA Technical Reports Server (NTRS)

    Kory, Carol L.; Dayton, James A., Jr.

    1998-01-01

    Recently, a method has been established to accurately calculate cold-test data for helical slow-wave structures using the three-dimensional (3-D) electromagnetic computer code, MAxwell's equations by the Finite Integration Algorithm (MAFIA). Cold-test parameters have been calculated for several helical traveLing-wave tube (TWT) slow-wave circuits possessing various support rod configurations, and results are presented here showing excellent agreement with experiment. The helical models include tape thickness, dielectric support shapes and material properties consistent with the actual circuits. The cold-test data from this helical model can be used as input into large-signal helical TWT interaction codes making It possible, for the first time, to design complete TWT via computer simulation.

  6. Numerical calculation of electromagnetic eigenfields and dispersion relations for slow-wave device simulation

    SciTech Connect

    Oslake, J.M.; Verboncoeur, J.P.; Birdsall, C.K.

    1996-12-31

    Slow-wave structures support microwave amplification via electromagnetic coupling with an injected electron beam. Critical in the design of such devices is the dependence of the dispersion relation on the geometry of the guiding structure. The dispersion relation provides phase and group velocities, and the fields provide the impedance as seen by the beam. To this end, a computer model is developed which first numerically solves a wave equation in finite difference form subject to boundary conditions periodic in z and conducting elsewhere. For decades, the desired dispersion and impedance have been obtained experimentally from cold tests (no beam) on slow-wave structures by varying structure dimensions. However, the numerical approach condenses this process to a few minutes of simulation.

  7. Accurate Cold-Test Model of Helical TWT Slow-Wave Circuits

    NASA Technical Reports Server (NTRS)

    Kory, Carol L.; Dayton, James A., Jr.

    1997-01-01

    Recently, a method has been established to accurately calculate cold-test data for helical slow-wave structures using the three-dimensional electromagnetic computer code, MAFIA. Cold-test parameters have been calculated for several helical traveling-wave tube (TWT) slow-wave circuits possessing various support rod configurations, and results are presented here showing excellent agreement with experiment. The helical models include tape thickness, dielectric support shapes and material properties consistent with the actual circuits. The cold-test data from this helical model can be used as input into large-signal helical TWT interaction codes making it possible, for the first time, to design a complete TWT via computer simulation.

  8. Effect of Helical Slow-Wave Circuit Variations on TWT Cold-Test Characteristics

    NASA Technical Reports Server (NTRS)

    Kory, Carol L.; Dayton, James A., Jr.

    1997-01-01

    Recent advances in the state of the art of computer modeling offer the possibility for the first time to evaluate the effect that slow-wave structure parameter variations, such as manufacturing tolerances, have on the cold-test characteristics of helical traveling-wave tubes (TWT's). This will enable manufacturers to determine the cost effectiveness of controlling the dimensions of the component parts of the TWT, which is almost impossible to do experimentally without building a large number of tubes and controlling several parameters simultaneously. The computer code MAFIA is used in this analysis to determine the effect on dispersion and on-axis interaction impedance of several helical slow-wave circuit parameter variations, including thickness and relative dielectric constant of the support rods, tape width, and height of the metallized films deposited on the dielectric rods. Previous computer analyses required so many approximations that accurate determinations of the effect of many relevant dimensions on tube performance were practically impossible.

  9. Effect of Helical Slow-Wave Circuit Variations on TWT Cold-Test Characteristics

    NASA Technical Reports Server (NTRS)

    Kory, Carol L.; Dayton, J. A., Jr.

    1998-01-01

    Recent advances in the state of the art of computer modeling offer the possibility for the first time to evaluate the effect that slow-wave structure parameter variations, such as manufacturing tolerances, have on the cold-test characteristics of helical traveling-wave tubes (TWT's). This will enable manufacturers to determine the cost effectiveness of controlling the dimensions of the component parts of the TWT, which is almost impossible to do experimentally without building a large number of tubes and controlling several parameters simultaneously. The computer code MAFIA is used in this analysis to determine the effect on dispersion and on-axis interaction impedance of several helical slow-wave circuit parameter variations, including thickness and relative dielectric constant of the support rods, tape width, and height of the metallized films deposited on the dielectric rods. Previous computer analyzes required so many approximations that accurate determinations of the effect of many relevant dimensions on tube performance were practically impossible.

  10. High-Intensity Continuous Wave Slow Positron Source at Jefferson Lab

    NASA Astrophysics Data System (ADS)

    Golge, Serkan; Vlahovic, Branislav; Wojtsekhowski, Bogdan

    2013-04-01

    We present a novel concept of an electron linac-based slow positron source with projected intensity on the order of 10^10 slow e^+/s. The key components of this concept are a Continuous Wave (CW) electron beam, a rotating positron-production target, a synchronized raster/anti-raster, a transport channel, and extraction of positrons into a field-free area through a magnetic field terminator plug for moderation in a solid Neon moderator. The feasibility calculations were completed in the framework of GEANT4 simulation and OPERA-3D magnetic field calculation code.

  11. Frequency-dependent damping in propagating slow magneto-acoustic waves

    SciTech Connect

    Prasad, S. Krishna; Banerjee, D.; Van Doorsselaere, T.

    2014-07-10

    Propagating slow magneto-acoustic waves are often observed in polar plumes and active region fan loops. The observed periodicities of these waves range from a few minutes to a few tens of minutes and their amplitudes were found to decay rapidly as they travel along the supporting structure. Previously, thermal conduction, compressive viscosity, radiation, density stratification, and area divergence were identified to be some of the causes for change in the slow wave amplitude. Our recent studies indicate that the observed damping in these waves is frequency-dependent. We used imaging data from the Solar Dynamics Observatory/Atmospheric Imaging Assembly to study this dependence in detail and for the first time via observations we attempted to deduce a quantitative relation between the damping length and frequency of these oscillations. We developed a new analysis method to obtain this relation. The observed frequency dependence does not seem to agree with the current linear wave theory and it was found that the waves observed in the polar regions show a different dependence from those observed in the on-disk loop structures despite the similarity in their properties.

  12. Estimation of material parameters from slow and fast shear waves in an incompressible, transversely isotropic material.

    PubMed

    Tweten, Dennis J; Okamoto, Ruth J; Schmidt, John L; Garbow, Joel R; Bayly, Philip V

    2015-11-26

    This paper describes a method to estimate mechanical properties of soft, anisotropic materials from measurements of shear waves with specific polarization and propagation directions. This method is applicable to data from magnetic resonance elastography (MRE), which is a method for measuring shear waves in live subjects or in vitro samples. Here, we simulate MRE data using finite element analysis. A nearly incompressible, transversely isotropic (ITI) material model with three parameters (shear modulus, shear anisotropy, and tensile anisotropy) is used, which is appropriate for many fibrous, biological tissues. Both slow and fast shear waves travel concurrently through such a material with speeds that depend on the propagation direction relative to fiber orientation. A three-parameter estimation approach based on directional filtering and isolation of slow and fast shear wave components (directional filter inversion, or DFI) is introduced. Wave speeds of each isolated shear wave component are estimated using local frequency estimation (LFE), and material properties are calculated using weighted least squares. Data from multiple finite element simulations are used to assess the accuracy and reliability of DFI for estimation of anisotropic material parameters. PMID:26476762

  13. Modeling of Reflective Propagating Slow-mode Wave in a Flaring Loop

    NASA Astrophysics Data System (ADS)

    Fang, X.; Yuan, D.; Van Doorsselaere, T.; Keppens, R.; Xia, C.

    2015-11-01

    Quasi-periodic propagating intensity disturbances have been observed in large coronal loops in extreme ultraviolet images over a decade, and are widely accepted to be slow magnetosonic waves. However, spectroscopic observations from Hinode/EIS revealed their association with persistent coronal upflows, making this interpretation debatable. We perform a 2.5D magnetohydrodynamic simulation to imitate the chromospheric evaporation and the following reflected patterns in a flare loop. Our model encompasses the corona, transition region, and chromosphere. We demonstrate that the quasi periodic propagating intensity variations captured by the synthesized Solar Dynamics Observatory/Atmospheric Imaging Assembly 131, 94 Å emission images match the previous observations well. With particle tracers in the simulation, we confirm that these quasi periodic propagating intensity variations consist of reflected slow mode waves and mass flows with an average speed of 310 km s‑1 in an 80 Mm length loop with an average temperature of 9 MK. With the synthesized Doppler shift velocity and intensity maps of the Solar and Heliospheric Observatory/Solar Ultraviolet Measurement of Emitted Radiation Fe xix line emission, we confirm that these reflected slow mode waves are propagating waves.

  14. Simulating Reflective Propagating Slow-wave/flow in a Flaring Loop

    NASA Astrophysics Data System (ADS)

    Fang, X.

    2015-12-01

    Quasi-periodic propagating intensity disturbances have been observed in large coronal loops in EUV images over a decade, and are widely accepted to be slow magnetosonic waves. However, spectroscopic observations from Hinode/EIS revealed their association with persistent coronal upflows, making this interpretation debatable. We perform a 2.5D magnetohydrodynamic simulation to imitate the chromospheric evaporation and the following reflected patterns in a post flare loop. Our model encompasses the corona, transition region, and chromosphere. We demonstrate that the quasi periodic propagating intensity variations captured by our synthesized AIA 131, 94~Å~emission images match the previous observations well. With particle tracers in the simulation, we confirm that these quasi periodic propagating intensity variations consist of reflected slow mode waves and mass flows with an average speed of 310 km/s in an 80 Mm length loop with an average temperature of 9 MK. With the synthesized Doppler shift velocity and intensity maps in SUMER Fe XIX line emission, we confirm that these reflected slow mode waves are propagating waves.

  15. Evaluation of Some Slow-wave Vane Structures for Aminiature Traveling-wave Tube at 30 Ghz

    NASA Technical Reports Server (NTRS)

    Kavanagh, Frank; Ebihara, Ben; Wallett, Thomas M.; Dayton, James A., Jr.

    1994-01-01

    The dispersion characteristics of six vane type slow wave structures were experimentally measured near 1 GHz to determine applicability in an electrostatically focused 30 GHz miniature traveling wave tube (TWT). From the measured results, the trapezoidal vane structure appeared to be the most promising exhibiting an interaction impedance equal to 337.9 ohms at beta(L)/pi equal to 0.3. A 30 GHz trapezoidal vane structure with coupling irises was fabricated using electrical discharge machining (EDM). This structure, however, was too lossy for a short electrostatically focused tube, but several of the structures are amenable to a tube with permanent magnetic focusing.

  16. Evidence of Biot Slow Waves in Electroseismic Measurementss on Laboratory-Scale

    NASA Astrophysics Data System (ADS)

    Devi, M. S.

    2015-12-01

    Electroseismic methods which are the opposite of seismo-electric methods have only been little investigated up to now especially in the near surface scale. These methods can generate the solid-fluid relative movement induced by the electric potential in fluid-filled porous media. These methods are the response of electro-osmosis due to the presence of the electrical double layer. Laboratory experiments and numerical simulations of electroseismic studies have been performed. Electroseismic measurements conducted in micro glass beads saturated with demineralized water. Pair of 37 x 37 mm square aluminium grids with 2 mm of aperture and 4 mm of spacing is used as the electric dipole that connected to the electric power source with the voltage output 150 V. A laser doppler vibrometer is the system used to measure velocity of vibrating objects during measurements by placing a line of reflective paper on the surface of media that scattered back a helium-neon laser. The results in homogeneous media shows that the compressional waves induced by an electric signal. We confirm that the results are not the effects of thermal expansion. We also noticed that there are two kinds of the compressional waves are recorded: fast and slow P-waves. The latter, Biot slow waves, indicate the dominant amplitude. Moreover, we found that the transition frequency (ωc) of Biot slow waves depends on mechanical parameters such as porosity and permeability. The ωc is not affected when varying conductivity of the fluid from 25 - 320 μS/cm, although the amplitude slightly changed. For the results in two layer media by placing a sandstone as a top layer shows that a large amount of transmission seismic waves (apparently as Biot slow waves) rather than converted electromagnetic-to-seismic waves. These properties have also been simulated with full waveform numerical simulations relying on Pride's (1994) using our computer code (Garambois & Dietrich, 2002). If it is true that the electric source in

  17. Efficiency enhancement of high power vacuum BWO's using nonuniform slow wave structures

    SciTech Connect

    Moreland, L.D.; Schamiloglu, E. . Pulsed Power and Plasma Science Lab.); Lemke, R.W. ); Korovin, S.D.; Rostov, V.V.; Roitman, A.M. . Inst. of High Current Electronics); Hendricks, K.J.; Spencer, T.A. . Advanced Weapons and Survivability Directorate)

    1994-10-01

    The Sinus-6, a high-power relativistic repetitively-pulsed electron beam accelerator, is used to drive various slow wave structures in a BWO configuration in vacuum. Peak output power of about 550 MW at 9.45 GHz was radiated in an 8-ns pulse. The authors describe experiments which study the relative efficiencies of microwave generation from a two-stage nonuniform amplitude slow wave structure and its variations without an initial stage. Experimental results are compared with 2.5 D particle-in-cell computer simulations. The results suggest that prebunching the electron beam in the initial section of the nonuniform BWO results in increased microwave generation efficiency. Furthermore, simulations reveal that, in addition to the backward propagating surface harmonic of the TM[sub 01] mode, backward and forward propagating volume harmonics with phase velocity twice that of the surface harmonic play an important role in high-power microwave generation and radiation.

  18. Slow-wave disruption enhances the accessibility of positive memory traces.

    PubMed

    Goldschmied, Jennifer R; Cheng, Philip; Kim, Hyang Sook; Casement, Melynda; Armitage, Roseanne; Deldin, Patricia J

    2015-11-01

    The purpose of this study was to explore the effects of slow-wave disruption on positive and negative word recognition in a sample of healthy control participants and those with major depressive disorder. Prior to sleep, participants learned a set of emotional and neutral words during an encoding task by responding whether or not the word described them. Following baseline sleep, participants underwent one night of selective slow-wave disruption by auditory stimuli. Accuracy and reaction time to a recognition word set, including both positive and negative words, was assessed in the morning. Repeated-measures ANOVA revealed a significant interaction between word valence and condition, with positive words recognized significantly faster than negative words after disruption, in only healthy control participants. There were no significant results in those with major depressive disorder, or with regard to accuracy. These results may add to the increasing body of literature suggesting a hedonic bias to positive stimuli following sleep disruption. PMID:26409320

  19. THE SLOW-MODE NATURE OF COMPRESSIBLE WAVE POWER IN SOLAR WIND TURBULENCE

    SciTech Connect

    Howes, G. G.; Klein, K. G.; TenBarge, J. M.; Bale, S. D.; Chen, C. H. K.; Salem, C. S.

    2012-07-01

    We use a large, statistical set of measurements from the Wind spacecraft at 1 AU, and supporting synthetic spacecraft data based on kinetic plasma theory, to show that the compressible component of inertial range solar wind turbulence is primarily in the kinetic slow mode. The zero-lag cross-correlation C({delta}n, {delta}B{sub ||}) between proton density fluctuations {delta}n and the field-aligned (compressible) component of the magnetic field {delta}B{sub ||} is negative and close to -1. The typical dependence of C({delta}n, {delta}B{sub ||}) on the ion plasma beta {beta}{sub i} is consistent with a spectrum of compressible wave energy that is almost entirely in the kinetic slow mode. This has important implications for both the nature of the density fluctuation spectrum and for the cascade of kinetic turbulence to short wavelengths, favoring evolution to the kinetic Alfven wave mode rather than the (fast) whistler mode.

  20. Over-reflection of slow magnetosonic waves by homogeneous shear flow: Analytical solution

    SciTech Connect

    Dimitrov, Z. D.; Maneva, Y. G.; Hristov, T. S.; Mishonov, T. M.

    2011-08-15

    We have analyzed the amplification of slow magnetosonic (or pseudo-Alfvenic) waves (SMW) in incompressible shear flow. As found here, the amplification depends on the component of the wave-vector perpendicular to the direction of the shear flow. Earlier numerical results are consistent with the general analytic solution for the linearized magnetohydrodynamic equations, derived here for the model case of pure homogeneous shear (without Coriolis force). An asymptotically exact analytical formula for the amplification coefficient is derived for the case when the amplification is sufficiently large.

  1. Numerical calculation of electromagnetic eigenfields and dispersion relation for slow-wave device simulation

    SciTech Connect

    Oslake, J.M.; Verboncoeur, J.P.; Birdsall, C.K.

    1996-12-31

    Slow-wave structures support microwave amplification via electromagnetic coupling with an injected electron beam. Critical in the design of such devices is the dependence of the dispersion relation on the geometry of the guiding structure. The dispersion relation provides phase and group velocities, and the fields provide the impedance as seen by the beam. To this end, a computer model is developed which first numerically solves a wave equation in finite difference from subject to boundary conditions periodic in z and conducting elsewhere. Here the direction of wave propagation is along the z-axis. The solution produces a sequence of eigenfrequencies and eigenfields beginning with cut-off. Fourier decomposition of each eigenfield along selected mesh lines coincident with the location of the electron beam is then performed to establish a correspondence between eigenfrequency and wave number. From this data the dispersion relation for the slow-wave structure can then be formed. An example showing the first two TM passbands and E{sub z} fields for a slotted waveguide in xz coordinates is demonstrated. The authors plan to incorporate plasma loading with space-time dependent dielectric constant.

  2. Slow Feature Analysis on Retinal Waves Leads to V1 Complex Cells

    PubMed Central

    Dähne, Sven; Wilbert, Niko; Wiskott, Laurenz

    2014-01-01

    The developing visual system of many mammalian species is partially structured and organized even before the onset of vision. Spontaneous neural activity, which spreads in waves across the retina, has been suggested to play a major role in these prenatal structuring processes. Recently, it has been shown that when employing an efficient coding strategy, such as sparse coding, these retinal activity patterns lead to basis functions that resemble optimal stimuli of simple cells in primary visual cortex (V1). Here we present the results of applying a coding strategy that optimizes for temporal slowness, namely Slow Feature Analysis (SFA), to a biologically plausible model of retinal waves. Previously, SFA has been successfully applied to model parts of the visual system, most notably in reproducing a rich set of complex-cell features by training SFA with quasi-natural image sequences. In the present work, we obtain SFA units that share a number of properties with cortical complex-cells by training on simulated retinal waves. The emergence of two distinct properties of the SFA units (phase invariance and orientation tuning) is thoroughly investigated via control experiments and mathematical analysis of the input-output functions found by SFA. The results support the idea that retinal waves share relevant temporal and spatial properties with natural visual input. Hence, retinal waves seem suitable training stimuli to learn invariances and thereby shape the developing early visual system such that it is best prepared for coding input from the natural world. PMID:24810948

  3. Fast and slow wave detection in bovine cancellous bone in vitro using bandlimited deconvolution and Prony's method.

    PubMed

    Wear, Keith; Nagatani, Yoshiki; Mizuno, Katsunori; Matsukawa, Mami

    2014-10-01

    Fast and slow waves were detected in a bovine cancellous bone sample for thicknesses ranging from 7 to 12 mm using bandlimited deconvolution and the modified least-squares Prony's method with curve fitting (MLSP + CF). Bandlimited deconvolution consistently isolated two waves with linear-with-frequency attenuation coefficients as evidenced by high correlation coefficients between attenuation coefficient and frequency: 0.997 ± 0.002 (fast wave) and 0.986 ± 0.013 (slow wave) (mean ± standard deviation). Average root-mean-squared (RMS) differences between the two algorithms for phase velocities were 5 m/s (fast wave, 350 kHz) and 13 m/s (slow wave, 750 kHz). Average RMS differences for signal loss were 1.6 dB (fast wave, 350 kHz) and 0.4 dB (slow wave, 750 kHz). Phase velocities for thickness = 10 mm were 1726 m/s (fast wave, 350 kHz) and 1455 m/s (slow wave, 750 kHz). Results show support for the model of two waves with linear-with frequency attenuation, successful isolation of fast and slow waves, good agreement between bandlimited deconvolution and MLSP + CF as well as with a Bayesian algorithm, and potential variations of fast and/or slow wave properties with bone sample thickness. PMID:25324100

  4. Resonant interaction between a localized fast wave and a slow wave with constant asymptotic amplitude

    SciTech Connect

    Zabolotskii, A. A.

    2009-11-15

    An integrable Yajima-Oikawa system is solved in the case of a finite density, which corresponds to a slowly varying (long-wavelength) wave with finite amplitude at infinity and a localized fast-oscillating (short-wavelength) wave. Application of the results to spinor Bose-Einstein condensates and other physical systems is discussed.

  5. Modeling "slow movements"—Auto waves of non-elastic deformation in ductile and brittle materials and media

    NASA Astrophysics Data System (ADS)

    Makarov, P. V.; Peryshkin, A. Yu.

    2015-10-01

    In this paper, a mathematical model of propagating slow waves of non-elastic deformation, whose velocities in magnitude are between the velocities of tectonic creep and sound velocities, is proposed. It is shown that the model describes both Lueders fronts and slow waves of deformation in geo-environments and in the faults. Our model is a related dynamic model of elasto-plastic deformation of loaded medium, where fast processes of dynamic medium response to loading develop together with the formation of slow deformational wave. These slow waves of deformation in the model are treated as auto-wave processes and they are a collective response to loading, i.e. they are the result of self-organization in the medium being deformed.

  6. Experimental observation of sub-terahertz backward-wave amplification in a multi-level microfabricated slow-wave circuit

    SciTech Connect

    Baik, Chan-Wook Ahn, Ho Young; Kim, Yongsung; Lee, Jooho; Hong, Seogwoo; Lee, Sang Hun; Choi, Jun Hee; Kim, Sunil; Kim, Jong Min; Hwang, Sungwoo; Jeon, So-Yeon; Yu, SeGi; Collins, George; Read, Michael E.; Lawrence Ives, R.

    2015-11-09

    In our earlier paper dealing with dispersion retrieval from ultra-deep, reactive-ion-etched, slow-wave circuits on silicon substrates, it was proposed that splitting high-aspect-ratio circuits into multilevels enabled precise characterization in sub-terahertz frequency regime. This achievement prompted us to investigate beam-wave interaction through a vacuum-sealed integration with a 15-kV, 85-mA, thermionic, electron gun. Our experimental study demonstrates sub-terahertz, backward-wave amplification driven by an external oscillator. The measured output shows a frequency downshift, as well as power amplification, from beam loading even with low beam perveance. This offers a promising opportunity for the development of terahertz radiation sources, based on silicon technologies.

  7. ORIGIN OF CORONAL SHOCK WAVES ASSOCIATED WITH SLOW CORONAL MASS EJECTIONS

    SciTech Connect

    Magdalenic, J.; Marque, C.; Zhukov, A. N.; Vrsnak, B.; Zic, T.

    2010-07-20

    We present a multiwavelength study of five coronal mass ejection/flare events (CME/flare) and associated coronal shock waves manifested as type II radio bursts. The study is focused on the events in which the flare energy release, and not the associated CME, is the most probable source of the shock wave. Therefore, we selected events associated with rather slow CMEs (reported mean velocity below 500 km s{sup -1}). To ensure minimal projection effects, only events related to flares situated close to the solar limb were included in the study. We used radio dynamic spectra, positions of radio sources observed by the Nancay Radioheliograph, GOES soft X-ray flux measurements, Large Angle Spectroscopic Coronagraph, and Extreme-ultraviolet Imaging Telescope observations. The kinematics of the shock wave signatures, type II radio bursts, were analyzed and compared with the flare evolution and the CME kinematics. We found that the velocities of the shock waves were significantly higher, up to one order of magnitude, than the contemporaneous CME velocities. On the other hand, shock waves were closely temporally associated with the flare energy release that was very impulsive in all events. This suggests that the impulsive increase of the pressure in the flare was the source of the shock wave. In four events the shock wave was most probably flare-generated, and in one event results were inconclusive due to a very close temporal synchronization of the CME, flare, and shock.

  8. Sharp wave-associated synchronized inputs from the piriform cortex activate olfactory tubercle neurons during slow-wave sleep

    PubMed Central

    Narikiyo, Kimiya; Manabe, Hiroyuki

    2013-01-01

    During slow-wave sleep, anterior piriform cortex neurons show highly synchronized discharges that accompany olfactory cortex sharp waves (OC-SPWs). The OC-SPW-related synchronized activity of anterior piriform cortex neurons travel down to the olfactory bulb and is thought to be involved in the reorganization of bulbar neuronal circuitry. However, influences of the OC-SPW-related activity on other regions of the central olfactory system are still unknown. Olfactory tubercle is an area of OC and part of ventral striatum that plays a key role in reward-directed motivational behaviors. In this study, we show that in freely behaving rats, olfactory tubercle receives OC-SPW-associated synchronized inputs during slow-wave sleep. Local field potentials in the olfactory tubercle showed SPW-like activities that were in synchrony with OC-SPWs. Single-unit recordings showed that a subpopulation of olfactory tubercle neurons discharged in synchrony with OC-SPWs. Furthermore, correlation analysis of spike activity of anterior piriform cortex and olfactory tubercle neurons revealed that the discharges of anterior piriform cortex neurons tended to precede those of olfactory tubercle neurons. Current source density analysis in urethane-anesthetized rats indicated that the current sink of the OC-SPW-associated input was located in layer III of the olfactory tubercle. These results indicate that OC-SPW-associated synchronized discharges of piriform cortex neurons travel to the deep layer of the olfactory tubercle and drive discharges of olfactory tubercle neurons. The entrainment of olfactory tubercle neurons in the OC-SPWs suggests that OC-SPWs coordinate reorganization of neuronal circuitry across wide areas of the central olfactory system including olfactory tubercle during slow-wave sleep. PMID:24108798

  9. The nonlinear theory of slow-wave electron cyclotron masers with inclusion of the beam velocity spread

    SciTech Connect

    Kong, Ling-Bao; Wang, Hong-Yu; Hou, Zhi-Ling; Jin, Hai-Bo; Du, Chao-Hai

    2013-12-15

    The nonlinear theory of slow-wave electron cyclotron masers (ECM) with an initially straight electron beam is developed. The evolution equation of the nonlinear beam electron energy is derived. The numerical studies of the slow-wave ECM efficiency with inclusion of Gaussian beam velocity spread are presented. It is shown that the velocity spread reduces the interaction efficiency. -- Highlights: •The theory of slow-wave electron cyclotron masers is considered. •The calculation of efficiency under the resonance condition is presented. •The efficiency under Gaussian velocity spreads has been obtained.

  10. Coronal Seismology of Flare-Excited Standing Slow-Mode Waves Observed by SDO/AIA

    NASA Astrophysics Data System (ADS)

    Wang, Tongjiang; Ofman, Leon; Davila, Joseph M.

    2016-05-01

    Flare-excited longitudinal intensity oscillations in hot flaring loops have been recently detected by SDO/AIA in 94 and 131 Å bandpasses. Based on the interpretation in terms of a slow-mode wave, quantitative evidence of thermal conduction suppression in hot (>9 MK) loops has been obtained for the first time from measurements of the polytropic index and phase shift between the temperature and density perturbations (Wang et al. 2015, ApJL, 811, L13). This result has significant implications in two aspects. One is that the thermal conduction suppression suggests the need of greatly enhanced compressive viscosity to interpret the observed strong wave damping. The other is that the conduction suppression provides a reasonable mechanism for explaining the long-duration events where the thermal plasma is sustained well beyond the duration of impulsive hard X-ray bursts in many flares, for a time much longer than expected by the classical Spitzer conductive cooling. In this study, we model the observed standing slow-mode wave in Wang et al. (2015) using a 1D nonlinear MHD code. With the seismology-derived transport coefficients for thermal conduction and compressive viscosity, we successfully simulate the oscillation period and damping time of the observed waves. Based on the parametric study of the effect of thermal conduction suppression and viscosity enhancement on the observables, we discuss the inversion scheme for determining the energy transport coefficients by coronal seismology.

  11. One dimensional full wave analysis of slow-to-fast mode conversion in lower hybrid frequencies

    SciTech Connect

    Jia, Guo-Zhang; Gao, Zhe

    2014-12-15

    The linear conversion from the slow wave to the fast wave in the lower hybrid range of frequencies is analyzed numerically by using the set of field equations describing waves in a cold plane-stratified plasma. The equations are solved as a two-point boundary value problem, where the polarizations of each mode are set consistently in the boundary conditions. The scattering coefficients and the field patterns are obtained for various density profiles. It is shown that, for large density scale length, the results agree well with the traditional cognitions. In contrast, the reflected component and the probable transmitted-converted component from the conversion region, which are neglected in the usual calculations, become significant when the scale length is smaller than the wavelength of the mode. The inclusion of these new components will improve the accuracy of the simulated propagation and deposition for the injected rf power when the conversion process is involved within a sharp-varying density profile. Meanwhile, the accessibility of the incident slow wave for the low frequency case is also affected by the scale length of the density profile.

  12. Is There a Relation between EEG-Slow Waves and Memory Dysfunction in Epilepsy? A Critical Appraisal

    PubMed Central

    Höller, Yvonne; Trinka, Eugen

    2015-01-01

    Is there a relationship between peri-ictal slow waves, loss of consciousness, memory, and slow-wave sleep, in patients with different forms of epilepsy? We hypothesize that mechanisms, which result in peri-ictal slow-wave activity as detected by the electroencephalogram, could negatively affect memory processes. Slow waves (≤4 Hz) can be found in seizures with impairment of consciousness and also occur in focal seizures without impairment of consciousness but with inhibited access to memory functions. Peri-ictal slow waves are regarded as dysfunctional and are probably caused by mechanisms, which are essential to disturb the consolidation of memory entries in these patients. This is in strong contrast to physiological slow-wave activity during deep sleep, which is thought to group memory-consolidating fast oscillatory activity. In patients with epilepsy, slow waves may not only correlate with the peri-ictal clouding of consciousness, but could be the epiphenomenon of mechanisms, which interfere with normal brain function in a wider range. These mechanisms may have transient impacts on memory, such as temporary inhibition of memory systems, altered patterns of hippocampal–neocortical interactions during slow-wave sleep, or disturbed cross-frequency coupling of slow and fast oscillations. In addition, repeated tonic–clonic seizures over the years in uncontrolled chronic epilepsy may cause a progressive cognitive decline. This hypothesis can only be assessed in long-term prospective studies. These studies could disentangle the reversible short-term impacts of seizures, and the impacts of chronic uncontrolled seizures. Chronic uncontrolled seizures lead to irreversible memory impairment. By contrast, short-term impacts do not necessarily lead to a progressive cognitive decline but result in significantly impaired peri-ictal memory performance. PMID:26124717

  13. Equivalence between fourth sound in liquid He II at low temperatures and the Biot slow wave in consolidated porous media

    NASA Astrophysics Data System (ADS)

    Johnson, David Linton

    1980-12-01

    The theory of acoustic propagation in porous fluid-filled media developed by Biot is applied to the case where superfluid 4He is in the pores (T<1.1 K where there is a negligible amount of normal fluid). For a consolidated (fused) matrix Biot's slow compressional wave is shown to be identical to the phenomenon known as fourth sound; V(slow wave/fourth sound)=V(fluid)/n. The index of refraction of fourth sound is related to the ''structure factor''α, of the Biot theory by n=α1/2, and so use of the superfluid provides a direct means of measuring α in a given sample. Predictions for the velocities of the fast wave, the shear wave, and the slow wave/fourth sound are made for fused gass bead samples in which Plona has previously reported seeing these three waves under the condition of water saturation.

  14. High performance tunable slow wave elements enabled with nano-patterned permalloy thin film for compact radio frequency applications

    NASA Astrophysics Data System (ADS)

    Farid Rahman, B. M.; Divan, Ralu; Zhang, Hanqiao; Rosenmann, Daniel; Peng, Yujia; Wang, Xuehe; Wang, Guoan

    2014-05-01

    Slow wave elements are promising structures to design compact RF (radio frequency) and mmwave components. This paper reports a comparative study on different types of coplanar wave-guide (CPW) slow wave structures (SWS). New techniques including the use of defected ground structure and the different signal conductor shape have been implemented to achieve higher slow wave effect with comparative loss. Results show that over 42% and 35% reduction in length is reported in the expense of only 0.3 dB and 0.1 dB insertion loss, respectively, which can end up with 66% and 58% area reduction for the design of a branch line coupler. Implementation of the sub micrometer patterned Permalloy (Py) thin film on top of the simple SWS has been demonstrated for the first time to increase the slow wave effect. Comparing with the traditional slow wave structure, with 100 nm thick Py patterns, the inductance per unit length of the SWS has been increased from 879 nH/m to 963 nH/m. The slow wave effect of the designed structure is also tunable by applied DC current. Measured results have shown that the phase shift can be changed from 94° to 90.5° by applying 150 mA DC current. This provides a solution in designing RF passive components which can work in multiple frequency bands.

  15. Validation of an Accurate Three-Dimensional Helical Slow-Wave Circuit Model

    NASA Technical Reports Server (NTRS)

    Kory, Carol L.

    1997-01-01

    The helical slow-wave circuit embodies a helical coil of rectangular tape supported in a metal barrel by dielectric support rods. Although the helix slow-wave circuit remains the mainstay of the traveling-wave tube (TWT) industry because of its exceptionally wide bandwidth, a full helical circuit, without significant dimensional approximations, has not been successfully modeled until now. Numerous attempts have been made to analyze the helical slow-wave circuit so that the performance could be accurately predicted without actually building it, but because of its complex geometry, many geometrical approximations became necessary rendering the previous models inaccurate. In the course of this research it has been demonstrated that using the simulation code, MAFIA, the helical structure can be modeled with actual tape width and thickness, dielectric support rod geometry and materials. To demonstrate the accuracy of the MAFIA model, the cold-test parameters including dispersion, on-axis interaction impedance and attenuation have been calculated for several helical TWT slow-wave circuits with a variety of support rod geometries including rectangular and T-shaped rods, as well as various support rod materials including isotropic, anisotropic and partially metal coated dielectrics. Compared with experimentally measured results, the agreement is excellent. With the accuracy of the MAFIA helical model validated, the code was used to investigate several conventional geometric approximations in an attempt to obtain the most computationally efficient model. Several simplifications were made to a standard model including replacing the helical tape with filaments, and replacing rectangular support rods with shapes conforming to the cylindrical coordinate system with effective permittivity. The approximate models are compared with the standard model in terms of cold-test characteristics and computational time. The model was also used to determine the sensitivity of various

  16. Slow, large scales from fast, small ones in dispersive wave turbulence

    NASA Astrophysics Data System (ADS)

    Smith, Leslie; Waleffe, Fabian

    2000-11-01

    Dispersive wave turbulence in systems of geophysical interest (beta-plane, rotating, stratified and rotating-stratified flows) has been simulated with random, isotropic small scale forcing and hyper-viscosity. This can be thought of as a Langevin model of the small space-time scales only with potential implications for climate modeling. In all cases, slow, coherent large scales are generated after long times of 2nd order in the nonlinear time scale. These slow, large scales ultimately dominate the flows. Beta-plane and rotating flow results were reported earlier [PoF 11, 1608]. In stratified flows, the energy accumulates in a 1D vertically sheared flow at selected large scales. As the rotation rate is increased, a progressive transition toward generation of all large scale vortical zero modes (quasi-geostrophic 3D flow) is observed. For yet higher rotation rate, energy accumulates primarily in a 2D quasi-geostrophic flow (cyclonic vortices) at all large scales.

  17. Generation of slow wave type action potentials in the mouse small intestine involves a non-L-type calcium channel.

    PubMed

    Malysz, J; Richardson, D; Farraway, L; Christen, M O; Huizinga, J D

    1995-10-01

    Intrinsic electrical activities in various isolated segments of the mouse small intestine were recorded (i) to characterize action potential generation and (ii) to obtain a profile on the ion channels involved in initiating the slow wave type action potentials (slow waves). Gradients in slow wave frequency, resting membrane potential, and occurrence of spiking activity were found, with the proximal intestine exhibiting the highest frequency, the most hyperpolarized cell membrane, and the greatest occurrence of spikes. The slow waves were only partially sensitive to L-type calcium channel blockers. Nifedipine, verapamil, and pinaverium bromide abolished spikes that occurred on the plateau phase of the slow waves in all tissues. The activity that remained in the presence of L-type calcium channel blockers, the upstroke potential, retained a similar amplitude to the original slow wave and was of identical frequency. The upstroke potential was not sensitive to a reduction in extracellular chloride or to the sodium channel blockers tetrodotoxin and mexiletine. Abolishment of the Na+ gradient by removal of 120 mM extracellular Na+ reduced the upstroke potential frequency by 13 - 18% and its amplitude by 50 - 70% in the ileum. The amplitude was similarly reduced by Ni2+ (up to 5 mM), and by flufenamic acid (100 mu M), a nonspecific cation and chloride channel blocker. Gadolinium, a nonspecific blocker of cation and stretch-activated channels, had no effect. Throughout these pharmacological manipulations, a robust oscillation remained at 5 - 10 mV. This oscillation likely reflects pacemaker activity. It was rapidly abolished by removal of extracellular calcium but not affected by L-type calcium channel blockers. In summary, the mouse small intestine has been established as a model for research into slow wave generation and electrical pacemaker activity. The upstroke part of the slow wave has two components, the pacemaker component involves a non-L-type calcium channel

  18. Laminar analysis of the slow wave activity in the somatosensory cortex of anesthetized rats.

    PubMed

    Fiáth, Richárd; Kerekes, Bálint Péter; Wittner, Lucia; Tóth, Kinga; Beregszászi, Patrícia; Horváth, Domonkos; Ulbert, István

    2016-08-01

    Rhythmic slow waves characterize brain electrical activity during natural deep sleep and under anesthesia, reflecting the synchronous membrane potential fluctuations of neurons in the thalamocortical network. Strong evidence indicates that the neocortex plays an important role in the generation of slow wave activity (SWA), however, contributions of individual cortical layers to the SWA generation are still unclear. The anatomically correct laminar profiles of SWA were revealed under ketamine/xylazine anesthesia, with combined local field potential recordings, multiple-unit activity (MUA), current source density (CSD) and time-frequency analyses precisely co-registered with histology. The up-state related negative field potential wave showed the largest amplitude in layer IV, the CSD was largest in layers I and III, whereas MUA was maximal in layer V, suggesting spatially dissociated firing and synaptic/transmembrane processes in the rat somatosensory cortex. Up-state related firing could start in virtually any layers (III-VI) of the cortex, but were most frequently initiated in layer V. However, in a subset of experiments, layer IV was considerably active in initiating up-state related MUA even in the absence of somatosensory stimulation. Somatosensory stimulation further strengthened up-state initiation in layer IV. Our results confirm that cortical layer V firing may have a major contribution to the up-state generation of ketamine/xylazine-induced SWA, however, thalamic influence through the thalamorecipient layer IV can also play an initiating role, even in the absence of sensory stimulation. PMID:27177594

  19. Direct evidence and generation conditions of triggered slow slip event by teleseismic surface waves

    NASA Astrophysics Data System (ADS)

    Itaba, S.; Ando, R.; Takeda, N.

    2011-12-01

    In recent years slow slip events (SSE) have been observed to occur at regular intervals on the deep portions of subduction zone interfaces. There are many evidence of triggered tremor with only transient excitation by the passage of seismic waves from distant earthquakes, however SSEs, which are much larger in sizes and continue longer after the transient excitation, have been yet to be identified. Here we found, for the first time, robust and direct geodetic evidence of an interplate SSE with tremor activity in southwest Japan triggered by an earthquake in strain records from our highly sensitive strainmeter network. This SSE, in southwest Japan, which had an equivalent magnitude Mw 5.3 and duration of 1.5 days, was triggered by the surface waves of a Mw 7.6 earthquake in Tonga. The triggered SSE occurred on a place on the plate interface where the recurrence time for such events had almost expired, whereas other regions, at up to 90% of the recurrence time, were not triggered. Therefore, it is suggested that the overall segment of the triggered SSE had been necessarily very close to the critical stress level due to tectonic loading, and the seismic wave gave only the last push. Our results provide physical constraints to elucidate how earthquakes start and growth not only for the slow earthquakes but also for regular earthquakes.

  20. Effect of Helical Slow-Wave Circuit Variations on TWT Cold-Test Characteristics

    NASA Technical Reports Server (NTRS)

    Kory, Carol L.; Dayton, James A., Jr.

    1998-01-01

    Recent advances in the state of the art of computer modeling offer the possibility for the first time to evaluate the effect that slow-wave structure parameter variations, such'as manufacturing tolerances, have on the cold-test characteristics of helical traveling-wave tubes (TWT's). This will enable manufacturers to determine the cost effectiveness of controlling the dimensions of the component parts of the TWT, which is almost impossible to do experimentally without building a large number of tubes and controlling several parameters simultaneously. The computer code MAxwell's equations by the Finite Integration Algorithm (MAFIA) is used in this analysis to determine the effect on dispersion and on-axis interaction impedance of several helical slow-wave circuit parameter variations, including thickness and relative dielectric constant of the support rods, tape width, and height of the metallized films deposited on the dielectric rods. Previous computer analyzes required so many approximations that accurate determinations of the effect of many relevant dimensions on tube performance were practically impossible.

  1. Synthetic spectral analysis of a kinetic model for slow-magnetosonic waves in solar corona

    NASA Astrophysics Data System (ADS)

    Ruan, Wenzhi; He, Jiansen; Zhang, Lei; Vocks, Christian; Marsch, Eckart; Tu, Chuanyi; Peter, Hardi; Wang, Linghua

    2016-03-01

    We propose a kinetic model of slow-magnetosonic waves to explain various observational features associated with the propagating intensity disturbances (PIDs) occurring in the solar corona. The characteristics of slow mode waves, e.g, inphase oscillations of density, velocity, and thermal speed, are reproduced in this kinetic model. Moreover, the red-blue (R-B) asymmetry of the velocity distribution as self-consistently generated in the model is found to be contributed from the beam component, as a result of the competition between Landau resonance and Coulomb collisions. Furthermore, we synthesize the spectral lines and make the spectral analysis, based on the kinetic simulation data of the flux tube plasmas and the hypothesis of the surrounding background plasmas. It is found that the fluctuations of parameters of the synthetic spectral lines are basically consistent with the observations: (1) the line intensity, Doppler shift, and line width are fluctuating in phase; (2) the R-B asymmetry usually oscillate out of phase with the former three parameters; (3) the blueward asymmetry is more evident than the redward asymmetry in the R-B fluctuations. The oscillations of line parameters become weakened for the case with denser surrounding background plasmas. Similar to the observations, there is no doubled-frequency oscillation of the line width for the case with flux-tube plasmas flowing bulkly upward among the static background plasmas. Therefore, we suggest that the "wave + beam flow" kinetic model may be a viable interpretation for the PIDs observed in the solar corona.

  2. Shear wave velocity structure of the Anatolian Plate: anomalously slow crust in southwestern Turkey

    NASA Astrophysics Data System (ADS)

    Delph, Jonathan R.; Biryol, C. Berk; Beck, Susan L.; Zandt, George; Ward, Kevin M.

    2015-07-01

    The Anatolian Plate is composed of different lithospheric blocks and ribbon continents amalgamated during the closure of the Paleotethys Ocean and Neotethys Ocean along a subduction margin. Using ambient noise tomography, we investigate the crustal and uppermost mantle shear wave velocity structure of the Anatolian Plate. A total of 215 broad-band seismic stations were used spanning 7 yr of recording to compute 13 778 cross-correlations and obtain Rayleigh wave dispersion measurements for periods between 8 and 40 s. We then perform a shear wave inversion to calculate the seismic velocity structure of the crust and uppermost mantle. Our results show that the overall crustal shear wave velocities of the Anatolian crust are low (˜3.4 km s-1), indicative of a felsic overall composition. We find that prominent lateral seismic velocity gradients correlate with Tethyan suture zones, supporting the idea that the neotectonic structures of Turkey are exploiting the lithospheric weaknesses associated with the amalgamation of Anatolia. Anomalously slow shear wave velocities (˜3.15 km s-1 at 25 km) are located in the western limb of the Isparta Angle in southwestern Turkey. In the upper crust, we find that these low shear wave velocities correlate well with the projected location of a carbonate platform unit (Bey Dağlari) beneath the Lycian Nappe complex. In the lower crust and upper mantle of this region, we propose that the anomalously slow velocities are due to the introduction of aqueous fluids related to the underplating of accretionary material from the underthrusting of a buoyant, attenuated continental fragment similar to the Eratosthenes seamount. We suggest that this fragment controlled the location of the formation of the Subduction-Transform Edge Propagator fault in the eastern Aegean Sea during rapid slab rollback of the Aegean Arc in early Miocene times. Lastly, we observe that the uppermost mantle beneath continental Anatolia is generally slow (˜4.2 km s-1

  3. Two features of sleep slow waves: homeostatic and reactive aspects--from long term to instant sleep homeostasis.

    PubMed

    Halász, Péter; Bódizs, Róbert; Parrino, Liborio; Terzano, Mario

    2014-10-01

    In this paper we reviewed results of sleep research that have changed the views about sleep slow wave homeostasis, which involve use-dependent and experience-dependent local aspects to understand more of the physiology of plastic changes during sleep. Apart from the traditional homeostatic slow-wave economy, we also overviewed research on the existence and role of reactive aspects of sleep slow waves. Based on the results from spontaneous and artificially evoked slow waves, we offer a new hypothesis on instant slow wave homeostatic regulation. This regulation compensates for any potentially sleep-disturbing events by providing instant "delta injections" to maintain the nightly delta level, thus protecting cognitive functions located in the frontal lobe. We suggest that this double (long-term /instant) homeostasis provides double security for the frontal lobes in order to protect cognitive functions. The incorporation of reactive slow wave activity (SWA) makes sleep regulation more dynamic and provides more room for the internalization of external influences during sleep. PMID:25192672

  4. Slow wave structures integrated with ferromagnetic and ferro-electric thin films for smart RF applications

    NASA Astrophysics Data System (ADS)

    Rahman, B. M. Farid

    Modern communications systems are following a common trend to increase the operational frequency, level of integration and number of frequency bands. Although 90-95% components in a cell phone are passives which take 80% of the total board area. High performance RF passive components play limited role and are desired towards this technological advancement. Slow wave structure is one of the most promising candidates to design compact RF and mm-Wave passive components. Slow wave structures are the specially designed transmission line realized by placing the alternate narrow and wide signal conductors in order to reduce the physical size of the components. This dissertation reports multiband slow wave structures integrated with ferromagnetic and ferroelectric thin films and their RF applications. A comparative study on different types of coplanar wave-guide (CPW) slow wave structures (SWS) has been demonstrated for the first time. Slow wave structures with various shapes have been investigated and optimized with various signal conductor shapes, ground conductor shapes and pitch of the sections. Novel techniques i.e. the use of the defected ground structure and the different signal conductor length has been implemented to achieve higher slow wave effect with minimum loss. The measured results have shown the reduction of size over 43.47% and 37.54% in the expense of only 0.27dB and 0.102dB insertion loss respectively which can reduce the area of a designed branch line coupler by 68% and 61% accordingly. Permalloy (Py) is patterned on top of the developed SWS for the first time to further increase the slow wave effect and provide tunable inductance value. High frequency applications of Py are limited by its ferro-magnetic resonance frequency since the inductance value decreases beyond that. Sub-micrometer patterning of Py has increased FMR frequency until 6.3GHz and 3.2GHz by introducing the shape anisotropy. For the SWS with patterned Py, the size of the quarter

  5. Enhancing Slow Wave Sleep with Sodium Oxybate Reduces the Behavioral and Physiological Impact of Sleep Loss

    PubMed Central

    Walsh, James K.; Hall-Porter, Janine M.; Griffin, Kara S.; Dodson, Ehren R.; Forst, Elizabeth H.; Curry, Denise T.; Eisenstein, Rhody D.; Schweitzer, Paula K.

    2010-01-01

    Study Objectives: To investigate whether enhancement of slow wave sleep (SWS) with sodium oxybate reduces the impact of sleep deprivation. Design: Double-blind, parallel group, placebo-controlled design Setting: Sleep research laboratory Participants: Fifty-eight healthy adults (28 placebo, 30 sodium oxybate), ages 18-50 years. Interventions: A 5-day protocol included 2 screening/baseline nights and days, 2 sleep deprivation nights, each followed by a 3-h daytime (08:00-11:00) sleep opportunity and a recovery night. Sodium oxybate or placebo was administered prior to each daytime sleep period. Multiple sleep latency test (MSLT), psychomotor vigilance test (PVT), Karolinska Sleepiness Scale (KSS), and Profile of Mood States were administered during waking hours. Measurements and Results: During daytime sleep, the sodium oxybate group had more SWS, more EEG spectral power in the 1-9 Hz range, and less REM. Mean MSLT latency was longer for the sodium oxybate group on the night following the first daytime sleep period and on the day following the second day sleep period. Median PVT reaction time was faster in the sodium oxybate group following the second day sleep period. The change from baseline in SWS was positively correlated with the change in MSLT and KSS. During recovery sleep the sodium oxybate group had less TST, SWS, REM, and slow wave activity (SWA) than the placebo group. Conclusions: Pharmacological enhancement of SWS with sodium oxybate resulted in a reduced response to sleep loss on measures of alertness and attention. In addition, SWS enhancement during sleep restriction appears to result in a reduced homeostatic response to sleep loss. Citation: Walsh JK; Hall-Porter JM; Griffin KS; Dodson ER; Forst EH; Curry DT; Eisenstein RD; Schweitzer PK. Enhancing slow wave sleep with sodium oxybate reduces the behavioral and physiological impact of sleep loss. SLEEP 2010;33(9):1217-1225. PMID:20857869

  6. Theoretical, Experimental, and Computational Evaluation of Several Vane-Type Slow-Wave Structures

    NASA Technical Reports Server (NTRS)

    Wallett, Thomas M.; Qureshi, A. Haq

    1994-01-01

    Several types of periodic vane slow-wave structures were fabricated. The dispersion characteristics were found by theoretical analysis, experimental testing, and computer simulation using the MAFIA code. Computer-generated characteristics agreed to approximately within 2 percent of the experimental characteristics for all structures. The theoretical characteristics, however, deviated increasingly as the width to height ratio became smaller. Interaction impedances were also computed based on the experimental and computer-generated resonance frequency shifts due to the introduction of a perturbing dielectric rod.

  7. Using COMSOL Multiphysics Software to Model Anisotropic Dielectric and Metamaterial Effects in Folded-Waveguide Traveling-Wave Tube Slow-Wave Circuits

    NASA Technical Reports Server (NTRS)

    Starinshak, David P.; Smith, Nathan D.; Wilson, Jeffrey D.

    2008-01-01

    The electromagnetic effects of conventional dielectrics, anisotropic dielectrics, and metamaterials were modeled in a terahertz-frequency folded-waveguide slow-wave circuit. Results of attempts to utilize these materials to increase efficiency are presented.

  8. Optimization of relativistic backward wave oscillator with non-uniform slow wave structure and a resonant reflector

    SciTech Connect

    Chen, Zaigao; Wang, Jianguo; Wang, Yue

    2015-01-15

    This letter optimizes synchronously 18 parameters of a relativistic backward wave oscillator with non-uniform slow wave structure (SWS) and a resonant reflector by using the parallel genetic algorithms and particle-in-cell simulation. The optimization results show that the generation efficiency of microwave from the electron beam has increased 32% compared to that of the original device. After optimization, the electromagnetic mode propagating in the resonant changes from the original TM{sub 020} mode of reflector to higher-order TM{sub 021} mode, which has a high reflection coefficient in a broader frequency range than that of the former. The modulation of current inside the optimized device is much deeper than that in the original one. The product of the electric field and current is defined. Observing this product, it is found that the interaction of the electron beam with the electromagnetic wave in the optimized device is much stronger than that in the original device, and at the rear part of SWS of the optimized device, the electron beam dominantly gives out the energy to the electromagnetic wave, leading to the higher generation efficiency of microwave than that of the original device.

  9. Hybrid metal-dielectric, slow wave structure with magnetic coupling and compensation

    NASA Astrophysics Data System (ADS)

    Smirnov, A. V.; Savin, E.

    2016-06-01

    A number of electron beam vacuum devices such as small radiofrequency (RF) linear accelerators (linacs) and microwave traveling wave tubes (TWTs) utilize slow wave structures which are usually rather complicated in production and may require multi-step brazing and time consuming tuning. Fabrication of these devices becomes challenging at centimeter wavelengths, at large number of cells, and when a series or mass production of such structures is required. A hybrid, metal-dielectric, periodic structure for low gradient, low beam current applications is introduced here as a modification of Andreev's disk-and-washer (DaW) structure. Compensated type of coupling between even and odd TE01 modes in the novel structure results in negative group velocity with absolute values as high as 0.1c-0.2c demonstrated in simulations. Sensitivity to material imperfections and electrodynamic parameters of the disk-and-ring (DaR) structure are considered numerically using a single cell model.

  10. All-metal metamaterial slow-wave structure for high-power sources with high efficiency

    SciTech Connect

    Wang, Yanshuai; Duan, Zhaoyun Tang, Xianfeng; Wang, Zhanliang; Zhang, Yabin; Gong, Yubin; Feng, Jinjun

    2015-10-12

    In this paper, we have proposed a metamaterial (MTM) which is suitable for the compact high-power vacuum electron devices. For example, an S-band slow-wave structure (SWS) based on the all-metal MTMs has been studied by both simulation and experiment. The results show that this MTM SWS is very helpful to miniaturize the high-power vacuum electron devices and largely improve the output power and the electronic efficiency. The simulation model of an S-band MTM backward wave oscillator (BWO) is built, and the particle-in-cell simulated results are presented here: a 2.454 GHz signal is generated and its peak output power is 4.0 MW with a higher electronic efficiency of 31.5% relative to the conventional BWOs.

  11. Transversal and longitudinal mode selections in double-corrugation coaxial slow-wave devices

    NASA Astrophysics Data System (ADS)

    Ge, Xingjun; Zhong, Huihuang; Qian, Baoliang; Liu, Lie; Liu, Yonggui; Li, Limin; Shu, Ting; Zhang, Jiande

    2009-06-01

    To reduce the dimensions of relativistic backward wave oscillators (RBWOs) operating in the low frequency regime of less than 2 GHz, the theory of transversal and longitudinal mode selections are introduced in this paper. The transversal mode selection is achieved using the property of "surface wave" of the coaxial slow-wave structure (SWS) to excite the quasi transverse electromagnetic (quasi-TEM) mode without the higher transverse magnetic (TM) modes and it is proved that the coaxial SWS may decrease the transversal dimension of the SWS sections. In addition, the S-parameter method is employed to investigate the longitudinal resonant characteristic of the finite-length SWS, and the scheme of longitudinal mode selection is put forward. It is proposed that the introduction of a well-designed coaxial extractor to slow-wave devices can help to achieve the longitudinal mode selection and reduce the period number of the SWS, which not only can make the devices more compact, but also can avoid the destructive competition between various longitudinal modes, therefore can enhance the efficiency and stabilize the frequency. To sum up, the physical mechanisms of transversal and longitudinal mode selections ensure that the microwave is produced with a single mode and a narrow band. Based on the above discussion, a compact L-band coaxial RBWO is investigated and optimized in detail with the particle-in-cell KARAT code (V. P. Tarakanov, Berkeley Research Associates, Inc., 1992). In simulation, the L-band coaxial RBWO, driven by a 700 kV, 11 kA electron beam, comes to a nonlinear steady state in 20 ns. High-power microwave of quasi-TEM mode is generated with an average power of 2.66 GW, a frequency of 1.6 GHz, and power conversion efficiency of 34.5% in durations of 30-60 ns.

  12. Transversal and longitudinal mode selections in double-corrugation coaxial slow-wave devices

    SciTech Connect

    Ge Xingjun; Zhong Huihuang; Qian Baoliang; Liu Lie; Liu Yonggui; Li Limin; Shu Ting; Zhang Jiande

    2009-06-15

    To reduce the dimensions of relativistic backward wave oscillators (RBWOs) operating in the low frequency regime of less than 2 GHz, the theory of transversal and longitudinal mode selections are introduced in this paper. The transversal mode selection is achieved using the property of ''surface wave'' of the coaxial slow-wave structure (SWS) to excite the quasi transverse electromagnetic (quasi-TEM) mode without the higher transverse magnetic (TM) modes and it is proved that the coaxial SWS may decrease the transversal dimension of the SWS sections. In addition, the S-parameter method is employed to investigate the longitudinal resonant characteristic of the finite-length SWS, and the scheme of longitudinal mode selection is put forward. It is proposed that the introduction of a well-designed coaxial extractor to slow-wave devices can help to achieve the longitudinal mode selection and reduce the period number of the SWS, which not only can make the devices more compact, but also can avoid the destructive competition between various longitudinal modes, therefore can enhance the efficiency and stabilize the frequency. To sum up, the physical mechanisms of transversal and longitudinal mode selections ensure that the microwave is produced with a single mode and a narrow band. Based on the above discussion, a compact L-band coaxial RBWO is investigated and optimized in detail with the particle-in-cell KARAT code (V. P. Tarakanov, Berkeley Research Associates, Inc., 1992). In simulation, the L-band coaxial RBWO, driven by a 700 kV, 11 kA electron beam, comes to a nonlinear steady state in 20 ns. High-power microwave of quasi-TEM mode is generated with an average power of 2.66 GW, a frequency of 1.6 GHz, and power conversion efficiency of 34.5% in durations of 30-60 ns.

  13. Reconstruction of multiple gastric electrical wave fronts using potential-based inverse methods

    NASA Astrophysics Data System (ADS)

    Kim, J. H. K.; Pullan, A. J.; Cheng, L. K.

    2012-08-01

    One approach for non-invasively characterizing gastric electrical activity, commonly used in the field of electrocardiography, involves solving an inverse problem whereby electrical potentials on the stomach surface are directly reconstructed from dense potential measurements on the skin surface. To investigate this problem, an anatomically realistic torso model and an electrical stomach model were used to simulate potentials on stomach and skin surfaces arising from normal gastric electrical activity. The effectiveness of the Greensite-Tikhonov or the Tikhonov inverse methods were compared under the presence of 10% Gaussian noise with either 84 or 204 body surface electrodes. The stability and accuracy of the Greensite-Tikhonov method were further investigated by introducing varying levels of Gaussian signal noise or by increasing or decreasing the size of the stomach by 10%. Results showed that the reconstructed solutions were able to represent the presence of propagating multiple wave fronts and the Greensite-Tikhonov method with 204 electrodes performed best (correlation coefficients of activation time: 90%; pacemaker localization error: 3 cm). The Greensite-Tikhonov method was stable with Gaussian noise levels up to 20% and 10% change in stomach size. The use of 204 rather than 84 body surface electrodes improved the performance; however, for all investigated cases, the Greensite-Tikhonov method outperformed the Tikhonov method.

  14. Properties of short-wavelength oblique Alfvén and slow waves

    SciTech Connect

    Zhao, J. S.; Wu, D. J.; Voitenko, Y.; Yu, M. Y.; Lu, J. Y.

    2014-10-01

    Linear properties of kinetic Alfvén waves (KAWs) and kinetic slow waves (KSWs) are studied in the framework of two-fluid magnetohydrodynamics. We obtain the wave dispersion relations that are valid in a wide range of the wave frequency ω and plasma-to-magnetic pressure ratio β. The KAW frequency can reach and exceed the ion-cyclotron frequency at ion kinetic scales, whereas the KSW frequency remains sub-cyclotron. At β ∼ 1, the plasma and magnetic pressure perturbations of both modes are in anti-phase, so that there is nearly no total pressure perturbations. However, these modes also exhibit several opposite properties. At high β, the electric polarization ratios of KAWs and KSWs are opposite at the ion gyroradius scale, where KAWs are polarized in the sense of electron gyration (right-hand polarized) and KSWs are left-hand polarized. The magnetic helicity σ ∼ 1 for KAWs and σ ∼ –1 for KSWs, and the ion Alfvén ratio R{sub Ai} << 1 for KAWs and R{sub Ai} >> 1 for KSWs. We also found transition wavenumbers where KAWs change their polarization from left-handed to right-handed. These new properties can be used to discriminate KAWs and KSWs when interpreting kinetic-scale electromagnetic fluctuations observed in various solar-terrestrial plasmas. This concerns, in particular, identification of modes responsible for kinetic-scale pressure-balanced fluctuations and turbulence in the solar wind.

  15. NON-WKB MODELS OF THE FIRST IONIZATION POTENTIAL EFFECT: THE ROLE OF SLOW MODE WAVES

    SciTech Connect

    Laming, J. Martin

    2012-01-10

    A model for element abundance fractionation between the solar chromosphere and corona is further developed. The ponderomotive force due to Alfven waves propagating through or reflecting from the chromosphere in solar conditions generally accelerates chromospheric ions, but not neutrals, into the corona. This gives rise to what has become known as the first ionization potential effect. We incorporate new physical processes into the model. The chromospheric ionization balance is improved and the effect of different approximations is discussed. We also treat the parametric generation of slow mode waves by the parallel propagating Alfven waves. This is also an effect of the ponderomotive force, arising from the periodic variation of the magnetic pressure driving an acoustic mode, which adds to the background longitudinal pressure. This can have subtle effects on the fractionation, rendering it quasi-mass independent in the lower regions of the chromosphere. We also briefly discuss the change in the fractionation with Alfven wave frequency, relative to the frequency of the overlying coronal loop resonance.

  16. Experimental and numerical evidences of the observation of the Biot slow wave thanks to its electrokinetic conversion

    NASA Astrophysics Data System (ADS)

    Bordes, C.; Garambois, S.; Brito, D.; Dietrich, M.; Holzhauer, J.

    2013-12-01

    As originally described by Biot in 1956, seismic propagation in fluid-filled porous media should include two longitudinal contributions: the fast and slow P waves, the latest being commonly referred to as the ';Biot slow wave'. This seismic wave has been seldom observed in natural rocks at laboratory frequencies due to its low amplitude properties and has never been recognized at seismic frequencies due to its diffusive properties. In porous media, a part of seismic energy may also be converted into electromagnetic fields by a coupling phenomenon of electrokinetic nature: the so-called seismoelectric effect. Most seismoelectric studies focus on the observation of co-seismic or depth-converted electric fields generated by the propagation of fast P-waves, mainly to detect or to image new physico-chemical contrasts. Based on Pride's theory (1994), numerical modeling of seismo-electromagnetic wave propagation suggests that the observation of the Biot slow wave could be boosted by its electrokinetic conversion, i.e. that it would be easier to record the electric fields accompanying Biot slow waves generated by a mechanical source rather than the seismic fields. In order to confirm these numerical predictions, we designed a specific laboratory experiment involving a silica sand tank excited by using a homemade pneumatic seismic source. The investigated frequency range [0.5-5kHz] contains the Biot (transition) frequency separating the diffusive from the propagation regimes of the slow wave. Numerical seismoelectromagnetic experiments were also performed at this scale to compute the seismoelectric response in homogeneous and partially saturated sand with this acquisition configuration. The comparison of these experimental data to numerical results provides new perspectives for the detection, study and potential use of the Biot slow wave.

  17. Slow wave sleep-inducing effects of first generation H1-antagonists.

    PubMed

    Saitou, K; Kaneko, Y; Sugimoto, Y; Chen, Z; Kamei, C

    1999-10-01

    The present study was performed to see if first-generation histamine H1-antagonists are useful sedative-hypnotic drugs. Increases in electroencephalogram (EEG) power spectra of the delta band (0-4 Hz) at the frontal cortex and theta band (4-8 Hz) at the hippocampus in rats were used as an indexes of sleep. The H1-antagonists used in this study resulted in a decrease in sleep latency and an increase in sleep duration (slow wave sleep). The rate of REM (rapid eye movement) sleep during slow wave sleep was decreased by H1-antagonists and brotizolam. The order of potency of H1-antagonists for the reduction in sleep latency (from greatest to least) was promethazine>chlorpheniramine>diphenhydramine and pyrilamine, and that for the increase in sleep duration was chlorpheniramine>promethazine>diphenhydramine and pyrilamine. Brotizolam was more potent than these H1-antagonists, with 14-18-fold and 4-14-fold greater effects on sleep latency and duration, respectively. These results clearly show that H1-antagonists are effective in mild to moderate insomnia as sedative-hypnotic drugs. PMID:10549859

  18. Targeted Memory Reactivation During Slow Wave Sleep Facilitates Emotional Memory Consolidation

    PubMed Central

    Cairney, Scott A.; Durrant, Simon J.; Hulleman, Johan; Lewis, Penelope A.

    2014-01-01

    Study Objectives: To investigate the mechanisms by which auditory targeted memory reactivation (TMR) during slow wave sleep (SWS) influences the consolidation of emotionally negative and neutral memories. Design: Each of 72 (36 negative, 36 neutral) picture-location associations were encoded with a semantically related sound. During a subsequent nap, half of the sounds were replayed in SWS, before picture-location recall was examined in a final test. Setting: Manchester Sleep Laboratory, University of Manchester. Participants: 15 adults (3 male) mean age = 20.40 (standard deviation ± 3.07). Interventions: TMR with auditory cues during SWS. Measurements and Results: Performance was assessed by memory accuracy and recall response times (RTs). Data were analyzed with a 2 (sound: replayed/not replayed) × 2 (emotion: negative/neutral) repeated measures analysis of covariance with SWS duration, and then SWS spindles, as the mean-centered covariate. Both analyses revealed a significant three-way interaction for RTs but not memory accuracy. Critically, SWS duration and SWS spindles predicted faster memory judgments for negative, relative to neutral, picture locations that were cued with TMR. Conclusions: TMR initiates an enhanced consolidation process during subsequent SWS, wherein sleep spindles mediate the selective enhancement of reactivated emotional memories. Citation: Cairney SA; Durrant SJ; Hulleman J; Lewis PA. Targeted memory reactivation during slow wave sleep facilitates emotional memory consolidation. SLEEP 2014;37(4):701-707. PMID:24688163

  19. High power microwave source with a three dimensional printed metamaterial slow-wave structure.

    PubMed

    French, David M; Shiffler, Don

    2016-05-01

    For over the last decade, the concept of metamaterials has led to new approaches for considering the interaction of radiation with complex structures. However, practical manifestations of such a device operating at high power densities have proven difficult to achieve due to the resonant nature of metamaterials and the resultant high electric fields, which place severe constraints on manufacturing the slow wave structures. In this paper, we describe the first experimental manifestation of a high power microwave device utilizing a metallic slow wave structure (metamaterial-like) fabricated using additive manufacturing. The feasibility of utilizing additive manufacturing as a technique for building these relatively complicated structures has thus been demonstrated. The MW class microwave source operates in the C-band and shows frequency tunablility with electron beam voltage. The basic electromagnetic characteristics of this device, the construction using additive manufacturing, and the basic performance as a microwave oscillator are considered. Due to the tunable nature of the device, it shows promise not only as an oscillator but also as a microwave amplifier. Therefore, the dispersive characteristics and a discussion of the anticipated gain is included as it relates to an amplifier configuration. PMID:27250415

  20. Attachment dismissal predicts frontal slow-wave ERPs during rejection by unfamiliar peers.

    PubMed

    White, Lars O; Wu, Jia; Borelli, Jessica L; Rutherford, Helena J V; David, Daryn H; Kim-Cohen, Julia; Mayes, Linda C; Crowley, Michael J

    2012-08-01

    Attachment representations are thought to provide a cognitive-affective template, guiding the way individuals interact with unfamiliar social partners. To examine the neural correlates of this process, we sampled event-related potentials (ERPs) during exclusion by unfamiliar peers to differentiate insecure-dismissing from securely attached youth, as indexed by the child attachment interview. Thirteen secure and 10 dismissing 11- to 15-year-olds were ostensibly connected with two peers via the Internet to play a computerized ball-toss game. Actually, peers were computer generated, first distributing the ball evenly, but eventually excluding participants. Afterward children rated their distress. As in previous studies, distress was related to a negative left frontal slow wave (500-900 ms) during rejection, a waveform implicated in negative appraisals and less approach motivation. Though attachment classifications were comparable in frontal ERPs and distress, an attachment-related dismissal dimension predicted a negative left frontal slow wave during rejection, suggesting that high dismissal potentially involves elevated anticipation of rejection. As expected, dismissal and self-reported distress were uncorrelated. Yet, a new approach to quantifying the dissociation between self-reports and rejection-related ERPs revealed that dismissal predicted underreporting of distress relative to ERPs. Our findings imply that evaluations and regulatory strategies linked to attachment generalize to distressing social contexts in early adolescence. PMID:22251047

  1. Slow-wave activity saturation and thalamocortical isolation during propofol anesthesia in humans.

    PubMed

    Ní Mhuircheartaigh, Róisín; Warnaby, Catherine; Rogers, Richard; Jbabdi, Saad; Tracey, Irene

    2013-10-23

    The altered state of consciousness produced by general anesthetics is associated with a variety of changes in the brain's electrical activity. Under hyperpolarizing influences such as anesthetic drugs, cortical neurons oscillate at ~1 Hz, which is measurable as slow waves in the electroencephalogram (EEG). We have administered propofol anesthesia to 16 subjects and found that, after they had lost behavioral responsiveness (response to standard sensory stimuli), each individual's EEG slow-wave activity (SWA) rose to saturation and then remained constant despite increasing drug concentrations. We then simultaneously collected functional magnetic resonance imaging and EEG data in 12 of these subjects during propofol administration and sensory stimulation. During the transition to SWA saturation, the thalamocortical system became isolated from sensory stimuli, whereas internal thalamocortical exchange persisted. Rather, an alternative and more fundamental cortical network (which includes the precuneus) responded to all sensory stimulation. We conclude that SWA saturation is a potential individualized indicator of perception loss that could prove useful for monitoring depth of anesthesia and studying altered states of consciousness. PMID:24154602

  2. Coronal seismology of flare-excited longitudinal slow magnetoacoustic waves in hot coronal loops

    NASA Astrophysics Data System (ADS)

    Wang, T.; Ofman, L.; Sun, X.; Provornikova, E. A.; Davila, J. M.

    2015-12-01

    The flare-excited longitudinal intensity oscillations in hot flaring loops have been recently detected by SDO/AIA in 94 and 131 bandpasses. These oscillations show similar physical properties (such as period, decay time, and trigger) as those slow-mode standing waves previously detected by the SOHO/SUMER spectrometer in Doppler shift of flare lines formed above 6 MK. The multi-wavelength AIA observations with high spatio-temporal resolution and wide temperature coverage enable us to measure both thermal and wave properties of the oscillating hot plasma with unprecedented accuracy. These new measurements can be used to diagnose the complicated energy transport processes in flare plasma by a technique called coronal seismology based on the combination of observations and MHD wave theory. From a detailed case study we have found evidence for thermal conduction suppression in hot loops by measuring the polytropic index and analyzing the phase relationship between the temperature and density wave signals. This result is not only crucial for better understanding the wave dissipation mechanism but also provides an alternative mechanism to explain the puzzles of long-duration events and X-ray loop-top sources which show much slower cooling than expected by the classical Spitzer conductive cooling. This finding may also shed a light on the coronal heating problem because weak thermal conductivity implies slower cooling of hot plasma in nanoflares, so increasing the average coronal temperature for the same heating rate. We will discuss the effects of thermal conduction suppression on the wave damping and loop cooling based on MHD simulations.

  3. Changes in gastric myoelectric activity during space flight

    NASA Technical Reports Server (NTRS)

    Harm, Deborah L.; Sandoz, Gwenn R.; Stern, Robert M.

    2002-01-01

    The purpose of the present study was to examine postprandial myoelectric activity of the stomach and gastric activity associated with space motion sickness using electrogastrography. Three crewmembers participated in this investigation. Preflight, subjects exhibited normal postprandial responses to the ingestion of a meal. Inflight, crewmembers exhibited an abnormal decrease in the power of the normal gastric slow wave after eating on flight day 1, but had a normal postprandial response by flight day 3. Prior to and during episodes of nausea and vomiting, the electrical activity of the stomach became dysrhythmic with 60-80% of the spectral power in the bradygastric and tachygastric frequency ranges. These findings indicate that gastric motility may be decreased during the first few days of space flight. In addition, changes in the frequency of the gastric slow wave associated with space motion sickness symptoms are consistent with those reported for laboratory-induced motion sickness.

  4. Investigation of Double-groove Loaded Folded-Waveguide Slow-wave Structure for Millimeter Traveling-wave Tubes

    NASA Astrophysics Data System (ADS)

    He, Jun; Wei, Yanyu

    2014-03-01

    To enhance the strength of beam-wave interaction and improve the performance of gain, the double-groove loaded folded-waveguide slow-wave structure (SWS) is proposed for millimeter traveling-wave tubes (TWTs). In the first part, the expressions for the dispersion and the interaction impedance of this novel structure are obtained by using matching conditions of the RF fields. Ansoft HFSS is also used to calculate the high frequency characteristics. The simulation results from HFSS agree with the theoretical results. Numerical calculation for different combinations of the groove width and depth is carried out to study the influence of groove loading on the properties of this novel circuit. In the second part, a linear theory of a double-groove loaded folded-waveguide TWT is developed and calculated for analyzing the effect of groove dimensions on the property of small signal gain. The investigation results indicate that the interaction impedance is obviously raised up and the small signal gain are enhanced by loading groove in the FWSWS.

  5. Statistical detection of slow-mode waves in solar polar regions with SDO/AIA

    SciTech Connect

    Su, J. T.

    2014-10-01

    Observations from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory are utilized to statistically investigate the propagating quasi-periodic oscillations in the solar polar plume and inter-plume regions. On average, the periods are found to be nearly equal in the three coronal channels of AIA 171 Å, 193 Å, and 211 Å, and the wavelengths increase with temperature from 171 Å, 193 Å, and 211 Å. The phase speeds may be inferred from the above parameters. Furthermore, the speed ratios of v {sub 193}/v {sub 171} and v {sub 211}/v {sub 171} are derived, e.g., 1.4 ± 0.8 and 2.0 ± 1.9 in the plume regions, respectively, which are equivalent to the theoretical ones for acoustic waves. We find that there are no significant differences for the detected parameters between the plume and inter-plume regions. To our knowledge, this is the first time that we have simultaneously obtained the phase speeds of slow-mode waves in the three channels in the open coronal magnetic structures due to the method adopted in the present work, which is able to minimize the influence of the jets or eruptions on wave signals.

  6. PROPAGATING SLOW MAGNETOACOUSTIC WAVES IN CORONAL LOOPS OBSERVED BY HINODE/EIS

    SciTech Connect

    Wang, T. J.; Ofman, L.; Davila, J. M.

    2009-05-10

    We present the first Hinode/EUV Imaging Spectrometer observations of 5 minute quasi-periodic oscillations detected in a transition-region line (He II) and five coronal lines (Fe X, Fe XII, Fe XIII, Fe XIV, and Fe XV) at the footpoint of a coronal loop. The oscillations exist throughout the whole observation, characterized by a series of wave packets with nearly constant period, typically persisting for 4-6 cycles with a lifetime of 20-30 minutes. There is an approximate in-phase relation between Doppler shift and intensity oscillations. This provides evidence for slow magnetoacoustic waves propagating upward from the transition region into the corona. We find that the oscillations detected in the five coronal lines are highly correlated, and the amplitude decreases with increasing temperature. The amplitude of Doppler shift oscillations decrease by a factor of about 3, while that of relative intensity decreases by a factor of about 4 from Fe X to Fe XV. These oscillations may be caused by the leakage of the photospheric p-modes through the chromosphere and transition region into the corona, which has been suggested as the source for intensity oscillations previously observed by Transition Region and Coronal Explorer. The temperature dependence of the oscillation amplitudes can be explained by damping of the waves traveling along the loop with multithread structure near the footpoint. Thus, this property may have potential value for coronal seismology in diagnostic of temperature structure in a coronal loop.

  7. Dielectric {hacek C}erenkov maser with a plasma column in a dielectric lined slow-wave waveguide

    SciTech Connect

    Jian-Qiang, W.

    1997-08-01

    Dielectric {hacek C}erenkov maser with a plasma column in a dielectric lined slow-wave waveguide is studied in the absence of a longitudinal guided magnetic field by use of a fully self-consistent and relativistic field theory. Determinantal dispersion equations of the interaction of a thin annular relativistic electron beam (TAREB) with the wave are derived for the TAREB inside and surrounding the plasma column, respectively. These dispersion equations show that the beam{endash}wave interaction results from the coupling of the transverse-magnetic (TM) mode in the dielectric lined slow-wave waveguide with the plasma column to the beam mode via the electron beam. Finally, the dispersion equations are directly solved numerically, and the cutoff frequency, the operation frequency, and the growth rate of the wave are obtained. {copyright} {ital 1997 American Institute of Physics.}

  8. Stimulating forebrain communications: Slow sinusoidal electric fields over frontal cortices dynamically modulate hippocampal activity and cortico-hippocampal interplay during slow-wave states.

    PubMed

    Greenberg, Anastasia; Whitten, Tara A; Dickson, Clayton T

    2016-06-01

    Slow-wave states are characterized by the most global physiological phenomenon in the mammalian brain, the large-amplitude slow oscillation (SO; ~1Hz) composed of alternating states of activity (ON/UP states) and silence (OFF/DOWN states) at the network and single cell levels. The SO is cortically generated and appears as a traveling wave that can propagate across the cortical surface and can invade the hippocampus. This cortical rhythm is thought to be imperative for sleep-dependent memory consolidation, potentially through increased interactions with the hippocampus. The SO is correlated with learning and its presumed enhancement via slow rhythmic electrical field stimulation improves subsequent mnemonic performance. However, the mechanism by which such field stimulation influences the dynamics of ongoing cortico-hippocampal communication is unknown. Here we show - using multi-site recordings in urethane-anesthetized rats - that sinusoidal electrical field stimulation applied to the frontal region of the cerebral cortex creates a platform for improved cortico-hippocampal communication. Moderate-intensity field stimulation entrained hippocampal slow activity (likely by way of the temporoammonic pathway) and also increased sharp-wave ripples, the signature memory replay events of the hippocampus, and further increased cortical spindles. Following cessation of high-intensity stimulation, SO interactions in the cortical-to-hippocampal direction were reduced, while the reversed hippocampal-to-cortical communication at both SO and gamma bandwidths was enhanced. Taken together, these findings suggest that cortical field stimulation may function to boost memory consolidation by strengthening cortico-hippocampal and hippocampo-cortical interplay at multiple nested frequencies in an intensity-dependent fashion. PMID:26947518

  9. Compact broadband slow wave system based on spoof plasmonic THz waveguide with meander grooves

    NASA Astrophysics Data System (ADS)

    Yang, Bao Jia; Zhou, Yong Jin

    2015-12-01

    Conformal surface plasmons (CSPs) on ultrathin corrugated metallic strips have been proposed to develop versatile spoof plasmonic subwavelength integrated devices at lower frequencies bands, especially at terahertz (THz) frequencies. However, the effects of the groove shapes have not been fully investigated. Here we have proposed the CSPs waveguide constructed by meander grooves on an ultrathin dielectric substrate. The dispersions and propagation characteristics of the CSPs on the proposed waveguide have been investigated in the THz frequencies. A very compact broadband slow wave system based on such waveguide has been demonstrated, whose lateral dimension decreases about 43.2% than that based on the conventional CSPs waveguide. To verify the performance of the THz plasmonic device, we implemented experimental validation in the microwave frequencies by scaling up its geometry structure. It is believed that the CSPs waveguide and device can find more applications in the surface plasmonic THz platform such as signal processing and optical communication system.

  10. Experimental observation of ultrasound fast and slow waves through three-dimensional printed trabecular bone phantoms.

    PubMed

    Mézière, F; Juskova, P; Woittequand, J; Muller, M; Bossy, E; Boistel, Renaud; Malaquin, L; Derode, A

    2016-02-01

    In this paper, ultrasound measurements of 1:1 scale three-dimensional (3D) printed trabecular bone phantoms are reported. The micro-structure of a trabecular horse bone sample was obtained via synchrotron x-ray microtomography, converted to a 3D binary data set, and successfully 3D-printed at scale 1:1. Ultrasound through-transmission experiments were also performed through a highly anisotropic version of this structure, obtained by elongating the digitized structure prior to 3D printing. As in real anisotropic trabecular bone, both the fast and slow waves were observed. This illustrates the potential of stereolithography and the relevance of such bone phantoms for the study of ultrasound propagation in bone. PMID:26936578

  11. Reactivation of emergent task-related ensembles during slow-wave sleep after neuroprosthetic learning.

    PubMed

    Gulati, Tanuj; Ramanathan, Dhakshin S; Wong, Chelsea C; Ganguly, Karunesh

    2014-08-01

    Brain-machine interfaces can allow neural control over assistive devices. They also provide an important platform for studying neural plasticity. Recent studies have suggested that optimal engagement of learning is essential for robust neuroprosthetic control. However, little is known about the neural processes that may consolidate a neuroprosthetic skill. On the basis of the growing body of evidence linking slow-wave activity (SWA) during sleep to consolidation, we examined whether there is 'offline' processing after neuroprosthetic learning. Using a rodent model, we found that, after successful learning, task-related units specifically experienced increased locking and coherency to SWA during sleep. Moreover, spike-spike coherence among these units was substantially enhanced. These changes were not present with poor skill acquisition or after control awake periods, demonstrating the specificity of our observations to learning. Notably, the time spent in SWA predicted the performance gains. Thus, SWA appears to be involved in offline processing after neuroprosthetic learning. PMID:24997761

  12. Fragmentation of slow wave sleep after onset of complete locked-in state.

    PubMed

    Soekadar, Surjo R; Born, Jan; Birbaumer, Niels; Bensch, Michael; Halder, Sebastian; Murguialday, Ander Ramos; Gharabaghi, Alireza; Nijboer, Femke; Schölkopf, Bernhard; Martens, Suzanne

    2013-09-15

    Locked-in syndrome (LIS) as a result of brainstem lesions or progressive neurodegenerative disorders, such as amyotrophic lateral sclerosis (ALS), is a severe medical condition in which a person is fully conscious but unable to move or talk. LIS can transition into complete locked-in syndrome (CLIS) in which residual abilities to communicate through muscle twitches are entirely lost. It is unknown how CLIS affects circadian rhythm and sleep/wake patterns. Here we report a 39-year-old ALS patient who transitioned from LIS to CLIS while brain activity was continuously recorded using electrocorticography (ECoG) over one month. While we found no circadian rhythm in heart rate and body temperature, transition into CLIS was associated with increased fragmentation of slow wave sleep (SWS) across the day. Total time in SWS did not change. SWS fragmentation might reflect progressive circadian system impairment and should be considered as a factor further limiting communication capabilities in these patients. PMID:23997708

  13. Neurons of visual cortex respond to visceral stimulation during slow wave sleep.

    PubMed

    Pigarev, I N

    1994-10-01

    It is hypothesized here that the same cortical areas which process signals from exteroreceptors (visual, acoustic, etc.) in wakefulness process signals from visceral organs during sleep. To check this hypothesis, the activity of 49 neurons (hypercomplex, complex and simple, as defined by conventional visual stimulation) was recorded from visual areas V1 and V2 in chronic cats at different stages of the sleep-waking cycle. Neuronal responses to electrical stimulation of the area of stomach and small intestine (single pulses of 100-500 microA. 0.5 ms duration) were investigated. It was found that intraperitoneal stimulation delivered during slow wave sleep evoked clear excitatory responses in most simple and complex cells. In hypercomplex cells, only inhibitory responses were observed. All these responses disappeared in wakefulness. These observations are compatible with the above hypothesis. PMID:7845596

  14. Altered Neural Responses to Sounds in Primate Primary Auditory Cortex during Slow-Wave Sleep

    PubMed Central

    Issa, Elias B.

    2011-01-01

    How sounds are processed by the brain during sleep is an important question for understanding how we perceive the sensory environment in this unique behavioral state. While human behavioral data have indicated selective impairments of sound processing during sleep, brain imaging and neurophysiology studies have reported that overall neural activity in auditory cortex during sleep is surprisingly similar to that during wakefulness. This responsiveness to external stimuli leaves open the question of how neural responses during sleep differ, if at all, from wakefulness. Using extracellular neural recordings in the primary auditory cortex of naturally sleeping common marmosets, we show that slow-wave sleep (SWS) alters neural responses in the primate auditory cortex in two specific ways. SWS reduced the sensitivity of auditory cortex such that quiet sounds elicited weak responses in SWS compared with wakefulness, while loud sounds evoked similar responses in SWS and wakefulness. Furthermore, SWS reduced the extent of sound-evoked response suppression. This pattern of alterations was not observed during rapid eye movement sleep and could not be easily explained by the presence of slow rhythms in SWS. The alteration of excitatory and inhibitory responses during SWS suggests limitations in auditory processing and provides novel insights for understanding why certain sounds are processed while others are missed during deep sleep. PMID:21414918

  15. A theoretical model of slow wave regulation using voltage-dependent synthesis of inositol 1,4,5-trisphosphate.

    PubMed Central

    Imtiaz, Mohammad S; Smith, David W; van Helden, Dirk F

    2002-01-01

    A qualitative mathematical model is presented that examines membrane potential feedback on synthesis of inositol 1,4,5-trisphosphate (IP(3)), and its role in generation and modulation of slow waves. Previous experimental studies indicate that slow waves show voltage dependence, and this is likely to result through membrane potential modulation of IP(3). It is proposed that the observed response of the tissue to current pulse, pulse train, and maintained current injection can be explained by changes in IP(3), modulated through a voltage-IP(3) feedback loop. Differences underlying the tissue responses to current injections of opposite polarities are shown to be due to the sequence of events following such currents. Results from this model are consistent with experimental findings and provide further understanding of these experimental observations. Specifically, we find that membrane potential can induce, abolish, and modulate slow wave frequency by altering the excitability of the tissue through the voltage-IP(3) feedback loop. PMID:12324409

  16. α Power Modulation and Event-Related Slow Wave Provide Dissociable Correlates of Visual Working Memory

    PubMed Central

    Mance, Irida; Vogel, Edward K.

    2015-01-01

    Traditionally, electrophysiological correlates of visual working memory (VWM) capacity have been characterized using a lateralized VWM task in which participants had to remember items presented on the cued hemifield while ignoring the distractors presented on the other hemifield. Though this approach revealed a lateralized parieto-occipital negative slow wave (i.e., the contralateral delay activity) and lateralized α power modulation as neural correlates of VWM capacity that may be mechanistically related, recent evidence suggested that these measures might be reflecting individuals' ability to ignore distractors rather than their ability to maintain VWM representations. To better characterize the neural correlates of VWM capacity, we had human participants perform a whole-field VWM task in which they remembered all the items on the display. Here, we found that both the parieto-occipital negative slow wave and the α power suppression showed the characteristics of VWM capacity in the absence of distractors, suggesting that they reflect the maintenance of VWM representations rather than filtering of distractors. Furthermore, the two signals explained unique portions of variance in individual differences of VWM capacity and showed differential temporal characteristics. This pattern of results clearly suggests that individual differences in VWM capacity are determined by dissociable neural mechanisms reflected in the ERP and the oscillatory measures of VWM capacity. SIGNIFICANCE STATEMENT Our work demonstrates that there exist event-related potential and oscillatory correlates of visual working memory (VWM) capacity even in the absence of task-irrelevant distractors. This clearly shows that the two neural correlates are directly linked to maintenance of task-relevant information rather than filtering of task-irrelevant information. Furthermore, we found that these two correlates show differential temporal characteristics. These results are inconsistent with proposals

  17. Ring-plane traveling-wave tube slow-wave circuit design simulations at V-Band frequencies

    SciTech Connect

    Kory, C.L.; Wilson, J.D.

    1995-06-01

    The V-Band frequency range of 59-64 GHz is a region of the millimeter-wave spectrum that has been designated for intersatellite communications. As a first effort to develop a high-efficiency V-band TWT, variations on a ring-plane slow-wave circuit were computationally investigated to develop an alternative to the more conventional ferruled coupled-cavity circuit. The ring-plane circuit was chosen because of its high interaction impedance, large beam aperture, and excellent thermal dissipation properties. Despite the high-power capabilities of the ring-plane TWT, disadvantages of low bandwidth and high voltage requirements have until now prevented its acceptance outside the laboratory. In this paper, the authors use the three-dimensional electromagnetic simulation code MAFIA to investigate methods of increasing the bandwidth and lowering the operating voltage. Dispersion, impedance, and attenuation calculations for various geometric variations and loading distributions were performed. Based on the results of the variations, a circuit termed the finned-ladder TWT slowwave circuit was designed and is compared here to the scaled ring-plane prototype and the conventional ferruled coupled-cavity TWT circuit over the V-band frequency range.

  18. Ring-plane traveling-wave tube slow-wave circuit design simulations at V-Band frequencies

    NASA Technical Reports Server (NTRS)

    Kory, Carol L.; Wilson, Jeffrey D.

    1995-01-01

    The V-Band frequency range of 59-64 GHz is a region of the millimeter-wave spectrum that has been designated for intersatellite communications. As a first effort to develop a high-efficiency V-band TWT, variations on a ring-plane slow-wave circuit were computationally investigated to develop an alternative to the more conventional ferruled coupled-cavity circuit. The ring-plane circuit was chosen because of its high interaction impedance, large beam aperture, and excellent thermal dissipation properties. Despite the high-power capabilities of the ring-plane TWT, disadvantages of low bandwidth and high voltage requirements have until now prevented its acceptance outside the laboratory. In this paper, we use the three-dimensional electromagnetic simulation code MAFIA to investigate methods of increasing the bandwidth and lowering the operating voltage. Dispersion, impedance, and attenuation calculations for various geometric variations and loading distributions were performed. Based on the results of the variations, a circuit termed the finned-ladder TWT slowwave circuit was designed and is compared here to the scaled ring-plane prototype and the conventional ferruled coupled-cavity TWT circuit over the V-band frequency range.

  19. Antidepressant Effects of Selective Slow Wave Sleep Deprivation in Major Depression: A High-Density EEG Investigation

    PubMed Central

    Landsness, Eric C.; Goldstein, Michael R.; Peterson, Michael J.; Tononi, Giulio; Benca, Ruth M.

    2011-01-01

    Sleep deprivation can acutely reverse depressive symptoms in some patients with major depression. Because abnormalities in slow wave sleep are one of the most consistent biological markers of depression, it is plausible that the antidepressant effects of sleep deprivation are due to the effects on slow wave homeostasis. This study tested the prediction that selectively reducing slow waves during sleep (slow wave deprivation; SWD), without disrupting total sleep time, will lead to an acute reduction in depressive symptomatology. As part of a multi-night, cross-over design study, participants with major depression (non-medicated; n = 17) underwent baseline, SWD, and recovery sleep sessions, and were recorded with high-density EEG (hdEEG). During SWD, acoustic stimuli were played to suppress subsequent slow waves, without waking up the participant. The effects of SWD on depressive symptoms were assessed with both self-rated and researcher-administered scales. Participants experienced a significant decrease in depressive symptoms according to both self-rated (p = .007) and researcher-administered (p = .010) scales, while vigilance was unaffected. The reduction in depressive symptoms correlated with the overnight dissipation of fronto-central slow wave activity (SWA) on baseline sleep, the rebound in right frontal all-night SWA on recovery sleep, and the amount of REM sleep on the SWD night. In addition to highlighting the benefits of hdEEG in detecting regional changes in brain activity, these findings suggest that SWD may help to better understand the pathophysiology of depression and may be a useful tool for the neuromodulatory reversal of depressive symptomatology. PMID:21397252

  20. Design and Experimental Demonstration of Cherenkov Radiation Source Based on Metallic Photonic Crystal Slow Wave Structure

    NASA Astrophysics Data System (ADS)

    Fu, Tao; Yang, Zi-Qiang; Ouyang, Zheng-Biao

    2016-06-01

    This paper presents a kind of Cherenkov radiation source based on metallic photonic crystal (MPC) slow-wave structure (SWS) cavity. The Cherenkov source designed by linear theory works at 34.7 GHz when the cathode voltage is 550 kV. The three-dimensional particle-in-cell (PIC) simulation of the SWS shows the operating frequency of 35.56 GHz with a single TM01 mode is basically consistent with the theoretically one under the same parameters. An experiment was implemented to testify the results of theory and PIC simulation. The experimental system includes a cathode emitting unit, the SWS, a magnetic system, an output antenna, and detectors. Experimental results show that the operating frequency through detecting the retarded time of wave propagation in waveguides is around 35.5 GHz with a single TM01 mode and an output power reaching 54 MW. It indicates that the MPC structure can reduce mode competition. The purpose of the paper is to show in theory and in preliminary experiment that a SWS with PBG can produce microwaves in TM01 mode. But it still provides a good experimental and theoretical foundation for designing high-power microwave devices.

  1. Radio-frequency sheath voltages and slow wave electric field spatial structure

    SciTech Connect

    Colas, Laurent Lu, Ling-Feng; Křivská, Alena; Jacquot, Jonathan

    2015-12-10

    We investigate theoretically how sheath radio-frequency (RF) oscillations relate to the spatial structure of the RF parallel electric field emitted by Ion Cyclotron (IC) wave launchers, using a simple model of Slow Wave (SW) evanescence coupled with Direct Current (DC) plasma biasing via sheath boundary conditions in a plasma-filled 2-dimensional (parallel, radial) rectangle. Within a “wide sheaths” asymptotic regime, valid for large-amplitude near RF fields, our model becomes partly linear: the sheath oscillating voltage at open field line boundaries is a linear combination of elementary contributions by every source point of the radiated RF field map. These individual contributions are all the more intense as the SW emission point is toroidally nearer to the sheath walls. A limit formula is given for a source infinitely close to the sheaths. The decay of sheath RF voltages with the sheath/source parallel distance is quantified as a function of two characteristic SW evanescence lengths. Decay lengths are smaller than antenna parallel extensions. The sheath RF voltages at an IC antenna side limiter are therefore mainly sensitive to SW emission near this limiter, as recent observations suggest. Toroidal proximity effects could also explain why sheath oscillations persist with antisymmetric strap toroidal phasing, despite the parallel anti-symmetry of the radiated field map. They could also justify current attempts at reducing the RF fields induced near antenna boxes to attenuate sheath oscillations in their vicinity.

  2. Strain waves, earthquakes, slow earthquakes, and afterslip in the framework of the Frenkel-Kontorova model.

    PubMed

    Gershenzon, N I; Bykov, V G; Bambakidis, G

    2009-05-01

    The one-dimensional Frenkel-Kontorova (FK) model, well known from the theory of dislocations in crystal materials, is applied to the simulation of the process of nonelastic stress propagation along transform faults. Dynamic parameters of plate boundary earthquakes as well as slow earthquakes and afterslip are quantitatively described, including propagation velocity along the strike, plate boundary velocity during and after the strike, stress drop, displacement, extent of the rupture zone, and spatiotemporal distribution of stress and strain. The three fundamental speeds of plate movement, earthquake migration, and seismic waves are shown to be connected in framework of the continuum FK model. The magnitude of the strain wave velocity is a strong (almost exponential) function of accumulated stress or strain. It changes from a few km/s during earthquakes to a few dozen km per day, month, or year during afterslip and interearthquake periods. Results of the earthquake parameter calculation based on real data are in reasonable agreement with measured values. The distributions of aftershocks in this model are consistent with the Omori law for temporal distribution and a 1/r for the spatial distributions. PMID:19518576

  3. Research of dynamical Characteristics of slow deformation Waves as Massif Responses on Explosions

    NASA Astrophysics Data System (ADS)

    Hachay, Olga; Khachay, Oleg; Shipeev, Oleg

    2013-04-01

    The research of massif state with use of approaches of open system theory [1-3] was developed for investigation the criterions of dissipation regimes for real rock massifs, which are under heavy man-caused influence. For realization of that research we used the data of seismic catalogue of Tashtagol mine. As a result of the analyze of that data we defined character morphology of phase trajectories of massif response, which was locally in time in a stable state: on the phase plane with coordinates released by the massif during the dynamic event energy E and lg(dE/dt) there is a local area as a ball of twisted trajectories and some not great bursts from that ball, which are not greater than 105 joules. In some time intervals that burst can be larger, than 105 joules, achieving 106 joules and yet 109 joules. [3]. Evidently there are two reciprocal depend processes: the energy accumulation in the attracted phase trajectories area and resonance fault of the accumulated energy. But after the fault the system returns again to the same attracted phase trajectories area. For analyzing of the thin structure of the chaotic area we decided to add the method of processing of the seismic monitoring data by new parameters. We shall consider each point of explosion as a source of seismic or deformation waves. Using the kinematic approach of seismic information processing we shall each point of the massif response use as a time point of the first arrival of the deformation wave for calculation of the wave velocity, because additionally we know the coordinates of the fixed response and the coordinates of explosion. The use of additional parameter-velocity of slow deformation wave propagation allowed us with use method of phase diagrams identify their hierarchic structure, which allow us to use that information for modeling and interpretation the propagation seismic and deformation waves in hierarchic structures. It is researched with use of that suggested processing method the thin

  4. On the Properties of Slow MHD Sausage Waves within Small-scale Photospheric Magnetic Structures

    NASA Astrophysics Data System (ADS)

    Freij, N.; Dorotovič, I.; Morton, R. J.; Ruderman, M. S.; Karlovský, V.; Erdélyi, R.

    2016-01-01

    The presence of magnetoacoustic waves in magnetic structures in the solar atmosphere is well-documented. Applying the technique of solar magneto-seismology (SMS) allows us to infer the background properties of these structures. Here, we aim to identify properties of the observed magnetoacoustic waves and study the background properties of magnetic structures within the lower solar atmosphere. Using the Dutch Open Telescope and Rapid Oscillations in the Solar Atmosphere instruments, we captured two series of high-resolution intensity images with short cadences of two isolated magnetic pores. Combining wavelet analysis and empirical mode decomposition (EMD), we determined characteristic periods within the cross-sectional (i.e., area) and intensity time series. Then, by applying the theory of linear magnetohydrodynamics (MHD), we identified the mode of these oscillations within the MHD framework. Several oscillations have been detected within these two magnetic pores. Their periods range from 3 to 20 minutes. Combining wavelet analysis and EMD enables us to confidently find the phase difference between the area and intensity oscillations. From these observed features, we concluded that the detected oscillations can be classified as slow sausage MHD waves. Furthermore, we determined several key properties of these oscillations such as the radial velocity perturbation, the magnetic field perturbation, and the vertical wavenumber using SMS. The estimated range of the related wavenumbers reveals that these oscillations are trapped within these magnetic structures. Our results suggest that the detected oscillations are standing harmonics, and this allows us to estimate the expansion factor of the waveguides by employing SMS. The calculated expansion factor ranges from 4 to 12.

  5. Aging and sleep in Williams syndrome: accelerated sleep deterioration and decelerated slow wave sleep decrement.

    PubMed

    Bódizs, Róbert; Gombos, Ferenc; Gerván, Patrícia; Szőcs, Katalin; Réthelyi, János M; Kovács, Ilona

    2014-12-01

    Specific developmental and aging trajectories characterize sleep electroencephalogram (EEG) of typically developing (TD) subjects. Williams syndrome (WS) is marked by sleep alterations and accelerated aging of several anatomo-functional and cognitive measures. Here we test the hypothesis of a premature aging of sleep in WS. Age-related changes of home recorded sleep EEG of 42 subjects (21 WS, 21 age- and gender matched TD subjects, age: 6-29 years) were tested by Pearson correlations and homogeneity-of-slopes analysis. Typical developmental/aging effects of sleep EEGs were observed in TD subjects. Accelerated aging in WS was confirmed by overall sleep/wake measures. Specifically, premature aging was evident in accelerated age-dependent declines in WS subjects' sleep efficiency, as well as in steeper age-related rises in wakefulness and wake after sleep onset (WASO) of the WS group. In contrast, NREM sleep-related measures indicated atypical decelerations of the developmental trends of WS subjects, characterized by the slowing down of the age-related slow wave sleep (SWS) declines mirrored by the lack of age-dependent increase in Stage 2 (S2) sleep. Age-effects in sleep EEG power spectra were not different among the groups. Objectively measured sleep disruption of subjects with WS is age-dependent and increasing with age. Moreover, these data suggest atypical pre- and postpubertal neural development in WS, with sleep/wake balance and REM sleep time indicating accelerated aging while NREM sleep composition revealing signs of an as yet unidentified, perhaps compensatory developmental delay. PMID:25178705

  6. The Effect of Slow Coronary Artery Flow on Microvolt T-Wave Alternans

    PubMed Central

    Surgit, Ozgur; Erturk, Mehmet; Akgul, Ozgur; Gul, Mehmet; Pusuroglu, Hamdi; Akturk, Ibrahim Faruk; Uzun, Fatih; Somuncu, Umut; Ayaz, Ahmet; Eksik, Abdurrahman

    2014-01-01

    Background Slow coronary artery flow (SCF) is characterized by angiographically confirmed delayed vessel opacification in the absence of any evidence of obstructive epicardial coronary artery disease. Microvolt T-wave alternans (MTWA) is defined as beat-to-beat changes in shape, amplitude, or timing of ST segments and T waves, and is utilized in predicting sudden cardiac death and life-threatening malign ventricular arrhythmias in high-risk patients. In our study, we aimed to evaluate the effects of slow coronary artery flow on MTWA. Methods Thirty-nine consecutive patients (SCF group: 6 women and 33 men; mean age, 49 ± 10 years) with angiographally documented SCF in at least 1 major epicardial artery and 39 patients (control group: 13 women and 26 men; mean age, 50 ± 10 years) with normal coronary arteries were included in the study. Coronary flow rates of all patients were calculated by thrombolysis in myocardial infarction frame count (TFC). The MTWAs of all patients were analyzed using the time-domain modified moving average method by means of a treadmill exercise stress test. Results The age distribution , body mass index, and diastolic and systolic blood pressure (BP) were similar in the SCF and control group. In the SCF group, the three epicardial coronary artery corrected TFCs and mean TFCs were significantly higher than in the control group (for all, p < 0.001). MTWA positivity in the SCF group was statistically significant compared to the control group (p = 0.006). Spearman’s correlation analysis, showed a positive correlation between MTWA and right coronary artery (RCA) TFC and mean TFC (r = 0.368, p = 0.001 and r = 0.271, p = 0.016, respectively). In linear regression analysis, only the right coronary artery TFC was correlated with positive MTWA (p = 0.001). Conclusions The results of our study suggest that diagnosed SCF is associated with MTWA positivity. Furthermore, we determined that only RCA TFC was predictive of positive MTWA. PMID:27122788

  7. Reflection of Propagating Slow Magneto-acoustic Waves in Hot Coronal Loops: Multi-instrument Observations and Numerical Modeling

    NASA Astrophysics Data System (ADS)

    Mandal, Sudip; Yuan, Ding; Fang, Xia; Banerjee, Dipankar; Pant, Vaibhav; Van Doorsselaere, Tom

    2016-09-01

    Slow MHD waves are important tools for understanding coronal structures and dynamics. In this paper, we report a number of observations from the X-Ray Telescope (XRT) on board HINODE and Solar Dynamic Observatory/Atmospheric Imaging Assembly (AIA) of reflecting longitudinal waves in hot coronal loops. To our knowledge, this is the first report of this kind as seen from the XRT and simultaneously with the AIA. The wave appears after a micro-flare occurs at one of the footpoints. We estimate the density and temperature of the loop plasma by performing differential emission measure (DEM) analysis on the AIA image sequence. The estimated speed of propagation is comparable to or lower than the local sound speed, suggesting it to be a propagating slow wave. The intensity perturbation amplitude, in every case, falls very rapidly as the perturbation moves along the loop and eventually vanishes after one or more reflections. To check the consistency of such reflection signatures with the obtained loop parameters, we perform a 2.5D MHD simulation, which uses the parameters obtained from our observation as inputs, and perform forward modeling to synthesize AIA 94 Å images. Analyzing the synthesized images, we obtain the same properties of the observables as for the real observation. From the analysis we conclude that a footpoint heating can generate a slow wave which then reflects back and forth in the coronal loop before fading. Our analysis of the simulated data shows that the main agent for this damping is anisotropic thermal conduction.

  8. β-amyloid disrupts human NREM slow waves and related hippocampus-dependent memory consolidation

    PubMed Central

    Mander, Bryce A.; Marks, Shawn M.; Vogel, Jacob W.; Rao, Vikram; Lu, Brandon; Saletin, Jared M.; Ancoli-Israel, Sonia; Jagust, William J.; Walker, Matthew P.

    2015-01-01

    Independent evidence associates β-amyloid pathology with both NREM sleep disruption and memory impairment in older adults. However, whether the influence of β-amyloid pathology on hippocampus-dependent memory is, in part, driven by impairments of NREM slow wave activity (SWA) and associated overnight memory consolidation is unknown. Here, we show that β-amyloid burden within medial prefrontal cortex (mPFC) is significantly correlated with the severity of impairment in NREM SWA generation. Moreover, reduced NREM SWA generation was further associated with impaired overnight memory consolidation and impoverished hippocampal-neocortical memory transformation. Furthermore, structural equation models revealed that the association between mPFC β-amyloid pathology and impaired hippocampus-dependent memory consolidation is not direct, but instead, statistically depends on the intermediary factor of diminished NREM SWA. By linking β-amyloid pathology with impaired NREM SWA, these data implicate sleep disruption as a novel mechanistic pathway through which β-amyloid pathology may contribute to hippocampus-dependent cognitive decline in the elderly. PMID:26030850

  9. Complementary roles of slow-wave sleep and rapid eye movement sleep in emotional memory consolidation.

    PubMed

    Cairney, Scott A; Durrant, Simon J; Power, Rebecca; Lewis, Penelope A

    2015-06-01

    Although rapid eye movement sleep (REM) is regularly implicated in emotional memory consolidation, the role of slow-wave sleep (SWS) in this process is largely uncharacterized. In the present study, we investigated the relative impacts of nocturnal SWS and REM upon the consolidation of emotional memories using functional magnetic resonance imaging (fMRI) and polysomnography (PSG). Participants encoded emotionally positive, negative, and neutral images (remote memories) before a night of PSG-monitored sleep. Twenty-four hours later, they encoded a second set of images (recent memories) immediately before a recognition test in an MRI scanner. SWS predicted superior memory for remote negative images and a reduction in right hippocampal responses during the recollection of these items. REM, however, predicted an overnight increase in hippocampal-neocortical connectivity associated with negative remote memory. These findings provide physiological support for sequential views of sleep-dependent memory processing, demonstrating that SWS and REM serve distinct but complementary functions in consolidation. Furthermore, these findings extend those ideas to emotional memory by showing that, once selectively reorganized away from the hippocampus during SWS, emotionally aversive representations undergo a comparably targeted process during subsequent REM. PMID:24408956

  10. Rats Housed on Corncob Bedding Show Less Slow-Wave Sleep

    PubMed Central

    Leys, Laura J; McGaraughty, Steve; Radek, Richard J

    2012-01-01

    Despite the reported advantages of corncob bedding, questions have emerged about how comfortable animals find this type of bedding as a resting surface. In this study, encephalography (EEG) was used to compare the effects of corncob and aspen-chip bedding on rat slow-wave sleep (SWS). According to a facility-wide initiative, rats that were weaned on aspen-chip bedding were switched to corncob bedding in home cages and EEG recording chambers. Spontaneous EEG recordings obtained for 5 wk after the switch to corncob bedding demonstrated that rats spent significantly less time in SWS as compared with levels measured on aspen chips just prior to the bedding switch. SWS remained low even after a 5-wk acclimation period to the corncob bedding. We then acutely switched back to aspen-chip bedding in EEG recording chambers. Acute reinstatement of aspen-chip bedding during EEG recording was associated with an average 22% increase in time spent in SWS, with overall levels of SWS comparable to the levels measured on aspen chips prior to the change to corncob bedding. Aspen-chip bedding subsequently was reinstated in both home cages and EEG recording chambers, and SWS baseline levels were restored. These data raise important concerns about the effects of corncob bedding on rodents used in research. PMID:23294881

  11. Development of the brain's default mode network from wakefulness to slow wave sleep.

    PubMed

    Sämann, Philipp G; Wehrle, Renate; Hoehn, David; Spoormaker, Victor I; Peters, Henning; Tully, Carolin; Holsboer, Florian; Czisch, Michael

    2011-09-01

    Falling asleep is paralleled by a loss of conscious awareness and reduced capacity to process external stimuli. Little is known on sleep-associated changes of spontaneously synchronized anatomical networks as detected by resting-state functional magnetic resonance imaging (rs-fMRI). We employed functional connectivity analysis of rs-fMRI series obtained from 25 healthy participants, covering all non-rapid eye movement (NREM) sleep stages. We focused on the default mode network (DMN) and its anticorrelated network (ACN) that are involved in internal and external awareness during wakefulness. Using independent component analysis, cross-correlation analysis (CCA), and intraindividual dynamic network tracking, we found significant changes in DMN/ACN integrity throughout the NREM sleep. With increasing sleep depth, contributions of the posterior cingulate cortex (PCC)/retrosplenial cortex (RspC), parahippocampal gyrus, and medial prefrontal cortex to the DMN decreased. CCA revealed a breakdown of corticocortical functional connectivity, particularly between the posterior and anterior midline node of the DMN and the DMN and the ACN. Dynamic tracking of the DMN from wakefulness into slow wave sleep in a single subject added insights into intraindividual network fluctuations. Results resonate with a role of the PCC/RspC for the regulation of consciousness. We further submit that preserved corticocortical synchronization could represent a prerequisite for maintaining internal and external awareness. PMID:21330468

  12. Analysis of the power capacity characteristics of coaxial slow-wave structures

    NASA Astrophysics Data System (ADS)

    Bai, Zhen; Zhang, Jun; Zhong, Huihuang; Zhang, Dian; Meng, Dong

    2016-06-01

    Coaxial O-type Cerenkov devices usually operate in the quasi-TEM or TM01 mode, but the power capacity characteristics of these modes in coaxial slow-wave structures (SWSs) have not been published thus far. This paper presents numerical studies of the power capacity characteristics of the quasi-TEM and TM01 modes in coaxial SWSs. The results suggest that the power capacity of the TM01 mode is not significantly higher than that of the quasi-TEM mode, unless the distance between the inner and outer conductors is less than a critical value. A comparison of the power capacities of the TM01 mode in coaxial and hollow SWSs is reported for the first time. When the distance between the inner and outer conductors of coaxial SWSs is small enough or the outer radius is large enough, the power capacity of the TM01 mode in coaxial SWSs is higher than that of the TM01 mode in hollow SWSs with the same outer radius.

  13. Increased frontal sleep slow wave activity in adolescents with major depression

    PubMed Central

    Tesler, Noemi; Gerstenberg, Miriam; Franscini, Maurizia; Jenni, Oskar G.; Walitza, Susanne; Huber, Reto

    2015-01-01

    Sleep slow wave activity (SWA), the major electrophysiological characteristic of deep sleep, mirrors both cortical restructuring and functioning. The incidence of Major Depressive Disorder (MDD) substantially rises during the vulnerable developmental phase of adolescence, where essential cortical restructuring is taking place. The goal of this study was to assess characteristics of SWA topography in adolescents with MDD, in order to assess abnormalities in both cortical restructuring and functioning on a local level. All night high-density EEG was recorded in 15 patients meeting DSM-5 criteria for MDD and 15 sex- and age-matched healthy controls. The actual symptom severity was assessed using the Children's Depression Rating Scale—Revised (CDRS-R). Topographical power maps were calculated based on the average SWA of the first non-rapid eye movement (NREM) sleep episode. Depressed adolescents exhibited significantly more SWA in a cluster of frontal electrodes compared to controls. SWA over frontal brain regions correlated positively with the CDRS-R subscore “morbid thoughts”. Self-reported sleep latency was significantly higher in depressed adolescents compared to controls whereas sleep architecture did not differ between the groups. Higher frontal SWA in depressed adolescents may represent a promising biomarker tracing cortical regions of intense use and/or restructuring. PMID:26870661

  14. β-amyloid disrupts human NREM slow waves and related hippocampus-dependent memory consolidation.

    PubMed

    Mander, Bryce A; Marks, Shawn M; Vogel, Jacob W; Rao, Vikram; Lu, Brandon; Saletin, Jared M; Ancoli-Israel, Sonia; Jagust, William J; Walker, Matthew P

    2015-07-01

    Independent evidence associates β-amyloid pathology with both non-rapid eye movement (NREM) sleep disruption and memory impairment in older adults. However, whether the influence of β-amyloid pathology on hippocampus-dependent memory is, in part, driven by impairments of NREM slow wave activity (SWA) and associated overnight memory consolidation is unknown. Here we show that β-amyloid burden in medial prefrontal cortex (mPFC) correlates significantly with the severity of impairment in NREM SWA generation. Moreover, reduced NREM SWA generation was further associated with impaired overnight memory consolidation and impoverished hippocampal-neocortical memory transformation. Furthermore, structural equation models revealed that the association between mPFC β-amyloid pathology and impaired hippocampus-dependent memory consolidation was not direct, but instead statistically depended on the intermediary factor of diminished NREM SWA. By linking β-amyloid pathology with impaired NREM SWA, these data implicate sleep disruption as a mechanistic pathway through which β-amyloid pathology may contribute to hippocampus-dependent cognitive decline in the elderly. PMID:26030850

  15. Regional scalp EEG slow-wave synchronization during sleep cyclic alternating pattern A1 subtypes.

    PubMed

    Ferri, Raffaele; Rundo, Francesco; Bruni, Oliviero; Terzano, Mario G; Stam, Cornelis J

    2006-09-01

    The levels of EEG synchronization, in the 0.25-2.5 Hz band, during the A1 subtypes of the sleep "cyclic alternating pattern" (CAP) were measured in five healthy subjects by means of the synchronization likelihood (SL) algorithm. SL was measured for seven electrode pairs (F4-F3, C4-C3, P4-P3 for the analysis of interhemispheric SL and F4-C4, C4-P4, F3-C3, and C3-P3, for the analysis of intrahemispheric SL). During the A1 CAP subtypes, SL tended to be highest between pairs of electrodes situated over different hemispheres; in particular, SL obtained from F4-F3 was the highest, followed by that of P4-P3. These results indicate that the transient high level of synchronization in the slow-wave EEG range, during the sleep A1 CAP subtypes, is a phenomenon involving mostly the anterior parts of the brain and is probably based on interhemispheric interactions, possibly mediated by transcallosal connections. PMID:16806696

  16. Characteristics and Management of Children with Continuous Spikes and Waves during Slow Sleep.

    PubMed

    Fatema, K; Rahman, M M; Begum, S

    2015-10-01

    This study was done to describe the clinical spectrum, EEG characteristics and treatment modalities in children with continuous spike and slow wave in sleep (CSWS). Ten patients with CSWS had been treated between 2012 and 2013. Mean age of the patients was 6.9 years; male female ratio was 3:2. The main etiologic group in this study was epilepsy (10), cerebral palsy (3) and brain lesion (arachnoid cyst). All the patients had prior seizure. Presenting features were abnormal behavior (4), agitation (4), aggression (4), eye blinking (2) and involuntary movement (2). Three patients had speech regression and 1 had motor regression. Regarding EEG finding, 7 out 10 cases had SWI>85% whereas, rest of them had SWI 50 to 80%. Most of the patients were resistant to two or more oral AED. The AED found to be efficacious were Midazolam drip, pulse methyl prednisolone and valproate. Eighty percent (80%) patient responded to midazolam drip. Methyl prednisolone caused 50% improvement in one patient but failed in 2 cases. In contrast to the previous studies where high dose valproic acid, levetiracetam, Injection ACTH was more efficacious, this study demonstrates significant positive result with midazolam drip. PMID:26620024

  17. Rats housed on corncob bedding show less slow-wave sleep.

    PubMed

    Leys, Laura J; McGaraughty, Steve; Radek, Richard J

    2012-11-01

    Despite the reported advantages of corncob bedding, questions have emerged about how comfortable animals find this type of bedding as a resting surface. In this study, encephalography (EEG) was used to compare the effects of corncob and aspen-chip bedding on rat slow-wave sleep (SWS). According to a facility-wide initiative, rats that were weaned on aspen-chip bedding were switched to corncob bedding in home cages and EEG recording chambers. Spontaneous EEG recordings obtained for 5 wk after the switch to corncob bedding demonstrated that rats spent significantly less time in SWS as compared with levels measured on aspen chips just prior to the bedding switch. SWS remained low even after a 5-wk acclimation period to the corncob bedding. We then acutely switched back to aspen-chip bedding in EEG recording chambers. Acute reinstatement of aspen-chip bedding during EEG recording was associated with an average 22% increase in time spent in SWS, with overall levels of SWS comparable to the levels measured on aspen chips prior to the change to corncob bedding. Aspen-chip bedding subsequently was reinstated in both home cages and EEG recording chambers, and SWS baseline levels were restored. These data raise important concerns about the effects of corncob bedding on rodents used in research. PMID:23294881

  18. [General statistical characteristics of the background firing in cat's cortical neurons during slow-wave sleep].

    PubMed

    Bibikov, N G; Pigarev, I N

    2013-03-01

    Background activity of 62 neurons in cat cerebral cortex was recorded in the state of slow-wave sleep for evaluation of the firing statistics. In according to their statistical characteristics neurons were subdivided in three groups. In the first group deviation from the Poisson process were comparatively small, and revealed as fragments of increased excitability following immediately after the refractory period. Second group demonstrated positive correlation of the neighbouring interspike intervals what was conditioned by the changes of the mean firing rate. In these neurons the number of spikes included into the bursts reduced after random permutation of the interspike intervals. The third group was characterized by the big number of spikes included into the bursts (> 15%), and number of bursts usually dropped down after random permutation. Some neurons of this group had constant interspike intervals within the bursts while in other units these intervals monotonically increased toward the end of the burst. Only limited number of neurons demonstrated maximums of the autocorrelation function corresponded to the frequency of the EEG delta activity. PMID:23789438

  19. "Slowing" Mechanical Waves with a Consumer-Type High-Speed Digital Camera

    ERIC Educational Resources Information Center

    Ng, Pun-hon; Chan, Kin-lok

    2015-01-01

    In most secondary physics textbooks, waves are first introduced with examples of mechanical waves because they can be illustrated by drawings and photographs. However, these illustrations are static and cannot reflect the dynamic nature of waves. Although many mechanical waves (e.g. water waves and vibrating strings) can be easily shown using…

  20. Consciousness Can Change the Output Signals of a Solar Cell and the Photoelectric Conversion Equation of Slow Mass Wave

    NASA Astrophysics Data System (ADS)

    Cao, Dayong

    2009-03-01

    The experiment's results show that human consciousness can change output signals such as Voc (open-circuit voltage) and Isc (short circuit current) of a solar cell placed some distance from a participant. For the first time, a consciousness signal is able to be recorded through the experiment conducted in Oct 2002. The order and rhythm of the changing wave pattern of Voc is related to the action of consciousness. The order and rhythm of slow brain signal of ERP and EEG are related to the cognized objects. Consciousness is independent and self-determined while brain signal is passive and driven. Consciousness is spiritual and Intelligence while brain signal is physical, corporality and mechanic. So consciousness is different from the brain signal. And consciousness effection is different from physical effection of light. Because consciousness can choose the object which it acts on. The light have a pairt of mass wave of low frequency and energy wave of high frequency. In photoelectric conversion process, We only use the energy wave to get the η (photoelectric transformation efficiency) which is little. If being used a pairt of wave, we will get a larger η. The photoelectric conversion equation of slow mass wave are being put forward.

  1. Magnetic resonance elastography of slow and fast shear waves illuminates differences in shear and tensile moduli in anisotropic tissue.

    PubMed

    Schmidt, J L; Tweten, D J; Benegal, A N; Walker, C H; Portnoi, T E; Okamoto, R J; Garbow, J R; Bayly, P V

    2016-05-01

    Mechanical anisotropy is an important property of fibrous tissues; for example, the anisotropic mechanical properties of brain white matter may play a key role in the mechanics of traumatic brain injury (TBI). The simplest anisotropic material model for small deformations of soft tissue is a nearly incompressible, transversely isotropic (ITI) material characterized by three parameters: minimum shear modulus (µ), shear anisotropy (ϕ=µ1µ-1) and tensile anisotropy (ζ=E1E2-1). These parameters can be determined using magnetic resonance elastography (MRE) to visualize shear waves, if the angle between the shear-wave propagation direction and fiber direction is known. Most MRE studies assume isotropic material models with a single shear (µ) or tensile (E) modulus. In this study, two types of shear waves, "fast" and "slow", were analyzed for a given propagation direction to estimate anisotropic parameters µ, ϕ, and ζ in two fibrous soft materials: turkey breast ex vivo and aligned fibrin gels. As expected, the speed of slow shear waves depended on the angle between fiber direction and propagation direction. Fast shear waves were observed when the deformations due to wave motion induced stretch in the fiber direction. Finally, MRE estimates of anisotropic mechanical properties in turkey breast were compared to estimates from direct mechanical tests. PMID:26920505

  2. FUNDAMENTAL AREAS OF PHENOMENOLOGY (INCLUDING APPLICATIONS): Linear Analysis of Folded Double-Ridged Waveguide Slow-Wave Structure for Millimeter Wave Traveling Wave Tube

    NASA Astrophysics Data System (ADS)

    He, Jun; Wei, Yan-Yu; Gong, Yu-Bin; Wang, Wen-Xiang

    2009-11-01

    A novel slow-wave structure (SWS), the folded double-ridged waveguide structure, is presented and its linear gain properties are investigated. The perturbed dispersion equation is derived and the small signal growth rate is calculated for dimensions of the ridge-loaded region and the parameters of the electron beam. The novel structure has potential applications in the production of high power and broad band radiation. For a cold beam, the linear theory predicts a gain of 1.1-1.27 dB/period and a 3-dB small-signal gain bandwidth of 30% in W-band. A comparison between the folded double-ridged waveguide SWS and folded waveguide SWS (FWSWS) shows that with the same physical parameters, the novel SWS has an advantage over the FWSWS on the bandwidth and electron efficiency.

  3. Reduction in cortical gamma synchrony during depolarized state of slow wave activity in mice

    PubMed Central

    Hwang, Eunjin; McNally, James M.; Choi, Jee Hyun

    2013-01-01

    EEG gamma band oscillations have been proposed to account for the neural synchronization crucial for perceptual integration. While increased gamma power and synchronization is generally observed during cognitive tasks performed during wake, several studies have additionally reported increased gamma power during sleep or anesthesia, raising questions about the characteristics of gamma oscillation during impaired consciousness and its role in conscious processing. Phase-amplitude modulation has been observed between slow wave activity (SWA, 0.5–4 Hz) and gamma oscillations during ketamine/xylazine anesthesia or sleep, showing increased gamma activity corresponding to the depolarized (ON) state of SWA. Here we divided gamma activity into its ON and OFF (hyperpolarized) state components based on the phase of SWA induced by ketamine/xylazine anesthesia and compared their power and synchrony with wake state levels in mice. We further investigated the state-dependent changes in both gamma power and synchrony across primary motor and primary somatosensory cortical regions and their interconnected thalamic regions throughout anesthesia and recovery. As observed previously, gamma power was as high as during wake specifically during the ON state of SWA. However, the synchrony of this gamma activity between somatosensory-motor cortical regions was significantly reduced compared to the baseline wake state. In addition, the somatosensory-motor cortical synchrony of gamma oscillations was reduced and restored in an anesthetic state-dependent manner, reflecting the changing depth of anesthesia. Our results provide evidence that during anesthesia changes in long-range information integration between cortical regions might be more critical for changes in consciousness than changes in local gamma oscillatory power. PMID:24379760

  4. Drosophila wing imaginal discs respond to mechanical injury via slow InsP3R-mediated intercellular calcium waves

    NASA Astrophysics Data System (ADS)

    Restrepo, Simon; Basler, Konrad

    2016-08-01

    Calcium signalling is a highly versatile cellular communication system that modulates basic functions such as cell contractility, essential steps of animal development such as fertilization and higher-order processes such as memory. We probed the function of calcium signalling in Drosophila wing imaginal discs through a combination of ex vivo and in vivo imaging and genetic analysis. Here we discover that wing discs display slow, long-range intercellular calcium waves (ICWs) when mechanically stressed in vivo or cultured ex vivo. These slow imaginal disc intercellular calcium waves (SIDICs) are mediated by the inositol-3-phosphate receptor, the endoplasmic reticulum (ER) calcium pump SERCA and the key gap junction component Inx2. The knockdown of genes required for SIDIC formation and propagation negatively affects wing disc recovery after mechanical injury. Our results reveal a role for ICWs in wing disc homoeostasis and highlight the utility of the wing disc as a model for calcium signalling studies.

  5. Drosophila wing imaginal discs respond to mechanical injury via slow InsP3R-mediated intercellular calcium waves.

    PubMed

    Restrepo, Simon; Basler, Konrad

    2016-01-01

    Calcium signalling is a highly versatile cellular communication system that modulates basic functions such as cell contractility, essential steps of animal development such as fertilization and higher-order processes such as memory. We probed the function of calcium signalling in Drosophila wing imaginal discs through a combination of ex vivo and in vivo imaging and genetic analysis. Here we discover that wing discs display slow, long-range intercellular calcium waves (ICWs) when mechanically stressed in vivo or cultured ex vivo. These slow imaginal disc intercellular calcium waves (SIDICs) are mediated by the inositol-3-phosphate receptor, the endoplasmic reticulum (ER) calcium pump SERCA and the key gap junction component Inx2. The knockdown of genes required for SIDIC formation and propagation negatively affects wing disc recovery after mechanical injury. Our results reveal a role for ICWs in wing disc homoeostasis and highlight the utility of the wing disc as a model for calcium signalling studies. PMID:27503836

  6. Drosophila wing imaginal discs respond to mechanical injury via slow InsP3R-mediated intercellular calcium waves

    PubMed Central

    Restrepo, Simon; Basler, Konrad

    2016-01-01

    Calcium signalling is a highly versatile cellular communication system that modulates basic functions such as cell contractility, essential steps of animal development such as fertilization and higher-order processes such as memory. We probed the function of calcium signalling in Drosophila wing imaginal discs through a combination of ex vivo and in vivo imaging and genetic analysis. Here we discover that wing discs display slow, long-range intercellular calcium waves (ICWs) when mechanically stressed in vivo or cultured ex vivo. These slow imaginal disc intercellular calcium waves (SIDICs) are mediated by the inositol-3-phosphate receptor, the endoplasmic reticulum (ER) calcium pump SERCA and the key gap junction component Inx2. The knockdown of genes required for SIDIC formation and propagation negatively affects wing disc recovery after mechanical injury. Our results reveal a role for ICWs in wing disc homoeostasis and highlight the utility of the wing disc as a model for calcium signalling studies. PMID:27503836

  7. Experimental evidence of dynamical propagation for solitary waves in ultra slow stochastic non-local Kerr medium.

    PubMed

    Louis, H; Tlidi, M; Louvergneaux, E

    2016-07-11

    We perform a statistical analysis of the optical solitary wave propagation in an ultra-slow stochastic non-local focusing Kerr medium such as liquid crystals. Our experimental results show that the localized beam trajectory presents a dynamical random walk whose beam position versus the propagation distance z depicts two different kind of evolutions A power law is found for the beam position standard deviation during the first stage of propagation. It obeys approximately z3/2 up to ten times the power threshold for solitary wave generation. PMID:27410886

  8. Experimental evidence of dynamical propagation for solitary waves in ultra slow stochastic non-local Kerr medium.

    PubMed

    Louis, H; Tlidi, M; Louvergneaux, E

    2016-07-11

    We perform a statistical analysis of the optical solitary wave propagation in an ultra-slow stochastic non-local focusing Kerr medium such as liquid crystals. Our experimental results show that the localized beam trajectory presents a dynamical random walk whose beam position versus the propagation distance z depicts two different kind of evolutions A power law is found for the beam position standard deviation during the first stage of propagation. It obeys approximately z3/2 up to ten times the power threshold for solitary wave generation. PMID:27410887

  9. Implementation of dispersion-free slow acoustic wave propagation and phase engineering with helical-structured metamaterials

    NASA Astrophysics Data System (ADS)

    Zhu, Xuefeng; Li, Kun; Zhang, Peng; Zhu, Jie; Zhang, Jintao; Tian, Chao; Liu, Shengchun

    2016-05-01

    The ability to slow down wave propagation in materials has attracted significant research interest. A successful solution will give rise to manageable enhanced wave-matter interaction, freewheeling phase engineering and spatial compression of wave signals. The existing methods are typically associated with constructing dispersive materials or structures with local resonators, thus resulting in unavoidable distortion of waveforms. Here we show that, with helical-structured acoustic metamaterials, it is now possible to implement dispersion-free sound deceleration. The helical-structured metamaterials present a non-dispersive high effective refractive index that is tunable through adjusting the helicity of structures, while the wavefront revolution plays a dominant role in reducing the group velocity. Finally, we numerically and experimentally demonstrate that the helical-structured metamaterials with designed inhomogeneous unit cells can turn a normally incident plane wave into a self-accelerating beam on the prescribed parabolic trajectory. The helical-structured metamaterials will have profound impact to applications in explorations of slow wave physics.

  10. Implementation of dispersion-free slow acoustic wave propagation and phase engineering with helical-structured metamaterials.

    PubMed

    Zhu, Xuefeng; Li, Kun; Zhang, Peng; Zhu, Jie; Zhang, Jintao; Tian, Chao; Liu, Shengchun

    2016-01-01

    The ability to slow down wave propagation in materials has attracted significant research interest. A successful solution will give rise to manageable enhanced wave-matter interaction, freewheeling phase engineering and spatial compression of wave signals. The existing methods are typically associated with constructing dispersive materials or structures with local resonators, thus resulting in unavoidable distortion of waveforms. Here we show that, with helical-structured acoustic metamaterials, it is now possible to implement dispersion-free sound deceleration. The helical-structured metamaterials present a non-dispersive high effective refractive index that is tunable through adjusting the helicity of structures, while the wavefront revolution plays a dominant role in reducing the group velocity. Finally, we numerically and experimentally demonstrate that the helical-structured metamaterials with designed inhomogeneous unit cells can turn a normally incident plane wave into a self-accelerating beam on the prescribed parabolic trajectory. The helical-structured metamaterials will have profound impact to applications in explorations of slow wave physics. PMID:27198887

  11. Electrophysiological and Mechanical Characteristics in Human Ileal Motility: Recordings of Slow Waves Conductions and Contractions, In vitro.

    PubMed

    Ryoo, Seung-Bum; Oh, Heung-Kwon; Moon, Sang Hui; Choe, Eun Kyung; Yu, Sung A; Park, Sung-Hye; Park, Kyu Joo

    2015-11-01

    Little human tissue data are available for slow waves and migrating motor complexes, which are the main components of small bowel motility. We investigated the electrophysiological and mechanical characteristics of human ileal motility, in vitro. Ileum was obtained from patients undergoing bowel resection. Electrophysiological microelectrode recordings for membrane potential changes and mechanical tension recordings for contraction from smooth muscle strips and ileal segments were performed. Drugs affecting the enteric nervous system were applied to measure the changes in activity. Slow waves were detected with a frequency of 9~10/min. There were no cross-sectional differences in resting membrane potential (RMP), amplitude or frequency between outer and inner circular muscle (CM), suggesting that electrical activities could be effectively transmitted from outer to inner CM. The presence of the interstitial cell of Cajal (ICC) at the linia septa was verified by immunohistochemistry. Contractions of strips and segments occurred at a frequency of 3~4/min and 1~2/min, respectively. The frequency, amplitude and area under the curve were similar between CM and LM. In segments, contractions of CM were associated with LM, but propagation varied with antegrade and retrograde directions. Atropine, N(W)-oxide-L-arginine, and sodium nitroprusside exhibited different effects on RMP and contractions. There were no cross-sectional differences with regard to the characteristics of slow waves in CM. The frequency of contractions in smooth muscle strips and ileal segments was lower than slow waves. The directions of propagation were diverse, indicating both mixing and transport functions of the ileum. PMID:26557020

  12. Involvement of Spindles in Memory Consolidation Is Slow Wave Sleep-Specific

    ERIC Educational Resources Information Center

    Cox, Roy; Hofman, Winni F.; Talamini, Lucia M.

    2012-01-01

    Both sleep spindles and slow oscillations have been implicated in sleep-dependent memory consolidation. Whereas spindles occur during both light and deep sleep, slow oscillations are restricted to deep sleep, raising the possibility of greater consolidation-related spindle involvement during deep sleep. We assessed declarative memory retention…

  13. Needleless transcutaneous electroacupuncture improves rectal distension-induced impairment in intestinal motility and slow waves via vagal mechanisms in dogs

    PubMed Central

    Song, Jun; Yin, Jieyun; Chen, Jiande

    2015-01-01

    Aim: This study was designed to compare the effects and mechanisms of transcutaneous electroacupuncture (TEA) on rectal distention (RD)-induced intestinal dysmotility with EA. Methods: six female dogs chronically implanted with a duodenal fistula, a proximal colon fistula and intestinal serosal electrodes were studied. EA and TEA were performed via needles and cutaneous electrodes placed at bilateral ST-36 (Zusanli) acupoints respectively; their effects on postprandial intestinal dysmotility (slow waves, contractions and transit) induced by RD, and autonomic functions were compared. Results: RD at a volume of 140 ml suppressed intestinal contractions; the motility index was reduced with RD (P = 0.001). Both EA and TEA ameliorated the suppressed contractions (P = 0.003 and 0.001) and their effects were comparable. RD reduced the percentage of normal intestinal slow waves (P = 0.002) that was increased with both EA and TEA (P = 0.005 and 0.035). No significant difference was noted between EA and TEA. EA and TEA reduced small bowel transit time (P = 0.001 and 0.007); these prokinetic effects were blocked by atropine. Both EA and TEA increased vagal activity assessed by the spectral analysis of heart rate variability (both P = 0.03). Conclusion: RD inhibits postprandial intestinal motility. Both EA and TEA at ST-36 are able to improve the RD-induced impairment in intestinal contractions, transit and slow waves mediated via the vagal mechanism. Needleless TEA is as effective as EA in ameliorating the intestinal hypomotility. PMID:26064396

  14. Reflectivity and Transmissivity of a Water-saturated Porous Plate: First Observations of Slow Biot Wave Conversions on Reflection

    NASA Astrophysics Data System (ADS)

    Bouzidi, Y.; Schmitt, D. R.

    2008-12-01

    Three distinct body wave modes, the fast and slow P and an S wave, propagate in a liquid saturated porous and permeable solid. The slow, or Biot, wave is highly attenuated and while it may be impossible to observe directly in the earth it does influence the energy budget available and as such influences both the seismic reflectivity and transmissivity of porous materials. There remain few experimental tests of wave propagation in such materials but there are still questions with regards to mechanisms of seismic attenuation and completely untested theories regarding the boundary conditions that control reflection and transmission at interfaces. To overcome this limitation, a series of pulse transmission and reflection tests were made through and from, respectively, a water-saturated plate of sintered glass beads. A novel ultrasonic goniometer system consisting of a large ultrasonic transmitter and a near-point source ultrasonic receiver were specially constructed for these tests. Despite the attempt to emulate plane wave behaviour, the finite diffraction effects of even the large aperture transducer influenced all the observations. This necessitated that the transducer response be fully modelled in order to eliminate misinterpretation, and these concepts were validated first on plates of simple isotropic glasses. The reflectivity and transmissivity of the plate were observed for incidence angles ranging from -50 ° to +50 °. The reflection responses were well modeled using the open pore boundary condition assumption. Additionally, the more complex transmission responses were successfully modeled but only once the viscoelastic response of the dry frame was included for the fast P and S waves. Notably, the slow P attenuation did not depend on the frame attenuation. Taken together, these results provide additional support for the dynamic poro-elastic theory of Biot in high porosity materials. An added serendipitous bonus of the reflectivity experiments is the first

  15. High-contrast 40 Gb/s operation of a 500 μm long silicon carrier-depletion slow wave modulator.

    PubMed

    Brimont, A; Thomson, D J; Gardes, F Y; Fedeli, J M; Reed, G T; Martí, J; Sanchis, P

    2012-09-01

    In this Letter, we demonstrate a highly efficient, compact, high-contrast and low-loss silicon slow wave modulator based on a traveling-wave Mach-Zehnder interferometer with two 500 μm long slow wave phase shifters. 40  Gb/s operation with 6.6 dB extinction ratio at quadrature and with an on-chip insertion loss of only 6 dB is shown. These results confirm the benefits of slow light as a means to enhance the performance of silicon modulators based on the plasma dispersion effect. PMID:22940930

  16. Implementation of dispersion-free slow acoustic wave propagation and phase engineering with helical-structured metamaterials

    PubMed Central

    Zhu, Xuefeng; Li, Kun; Zhang, Peng; Zhu, Jie; Zhang, Jintao; Tian, Chao; Liu, Shengchun

    2016-01-01

    The ability to slow down wave propagation in materials has attracted significant research interest. A successful solution will give rise to manageable enhanced wave–matter interaction, freewheeling phase engineering and spatial compression of wave signals. The existing methods are typically associated with constructing dispersive materials or structures with local resonators, thus resulting in unavoidable distortion of waveforms. Here we show that, with helical-structured acoustic metamaterials, it is now possible to implement dispersion-free sound deceleration. The helical-structured metamaterials present a non-dispersive high effective refractive index that is tunable through adjusting the helicity of structures, while the wavefront revolution plays a dominant role in reducing the group velocity. Finally, we numerically and experimentally demonstrate that the helical-structured metamaterials with designed inhomogeneous unit cells can turn a normally incident plane wave into a self-accelerating beam on the prescribed parabolic trajectory. The helical-structured metamaterials will have profound impact to applications in explorations of slow wave physics. PMID:27198887

  17. Fast and Slow Mode Solitary Waves in a Five Component Plasma

    NASA Astrophysics Data System (ADS)

    Sebastian, Sijo; Michael, Manesh; Varghese, Anu; Sreekala, G.; Venugopal, Chandu

    2016-07-01

    We have investigated fast and slow mode solitary profiles in a five component plasma consisting of positively and negatively charged pair ions, hydrogen ions and hotter and colder electrons. Of these, the heavier ions and colder photo-electrons are of cometary origin while the other components are of solar origin; the electrons being described by kappa distributions. The Zakharov-Kuznetzov (ZK) equation is derived and solutions for fast and slow mode solitary structures are plotted for parameters relevant to that of comet Halley. From the figures, it is seen that the presence of hydrogen ion determines the polarity of fast and slow mode solitary structures. Also different pair ions like He, C and O have significant effect on the width of the fast and slow mode solitary structures.

  18. Integrated fiber-coupled launcher for slow plasmon-polariton waves.

    PubMed

    Della Valle, Giuseppe; Longhi, Stefano

    2012-01-30

    We propose and numerically demonstrate an integrated fiber-coupled launcher for slow surface plasmon-polaritons. The device is based on a novel plasmonic mode-converter providing efficient power transfer from the fast to the slow modes of a metallic nanostripe. Total coupling efficiency with standard single-mode fiber approaching 30% (including ohmic losses) has been numerically predicted for a 25-µm long gold-based device operating at 1.55 µm telecom wavelength. PMID:22330553

  19. Novel high-gain, improved-bandwidth, finned-ladder V-band Traveling-Wave Tube slow-wave circuit design

    NASA Technical Reports Server (NTRS)

    Kory, Carol L.; Wilson, Jeffrey D.

    1994-01-01

    The V-band frequency range of 59-64 GHz is a region of the millimeter-wave spectrum that has been designated for inter-satellite communications. As a first effort to develop a high-efficiency V-band Traveling-Wave Tube (TWT), variations on a ring-plane slow-wave circuit were computationally investigated to develop an alternative to the more conventional ferruled coupled-cavity circuit. The ring-plane circuit was chosen because of its high interaction impedance, large beam aperture, and excellent thermal dissipation properties. Despite these advantages, however, low bandwidth and high voltage requirements have, until now, prevented its acceptance outside the laboratory. In this paper, the three-dimensional electrodynamic simulation code MAFIA (solution of MAxwell's Equation by the Finite-Integration-Algorithm) is used to investigate methods of increasing the bandwidth and lowering the operating voltage of the ring-plane circuit. Calculations of frequency-phase dispersion, beam on-axis interaction impedance, attenuation and small-signal gain per wavelength were performed for various geometric variations and loading distributions of the ring-plane TWT slow-wave circuit. Based on the results of the variations, a circuit termed the finned-ladder TWT slow-wave circuit was designed and is compared here to the scaled prototype ring-plane and a conventional ferruled coupled-cavity TWT circuit over the V-band frequency range. The simulation results indicate that this circuit has a much higher gain, significantly wider bandwidth, and a much lower voltage requirement than the scaled ring-plane prototype circuit, while retaining its excellent thermal dissipation properties. The finned-ladder circuit has a much larger small-signal gain per wavelength than the ferruled coupled-cavity circuit, but with a moderate sacrifice in bandwidth.

  20. Evidence of Thermal Conduction Suppression in a Solar Flaring Loop by Coronal Seismology of Slow-mode Waves

    NASA Astrophysics Data System (ADS)

    Wang, Tongjiang; Ofman, Leon; Sun, Xudong; Provornikova, Elena; Davila, Joseph M.

    2015-09-01

    Analysis of a longitudinal wave event observed by the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory is presented. A time sequence of 131 Å images reveals that a C-class flare occurred at one footpoint of a large loop and triggered an intensity disturbance (enhancement) propagating along it. The spatial features and temporal evolution suggest that a fundamental standing slow-mode wave could be set up quickly after meeting of two initial disturbances from the opposite footpoints. The oscillations have a period of ˜12 minutes and a decay time of ˜9 minutes. The measured phase speed of 500 ± 50 km s‑1 matches the sound speed in the heated loop of ˜10 MK, confirming that the observed waves are of slow mode. We derive the time-dependent temperature and electron density wave signals from six AIA extreme-ultraviolet channels, and find that they are nearly in phase. The measured polytropic index from the temperature and density perturbations is 1.64 ± 0.08 close to the adiabatic index of 5/3 for an ideal monatomic gas. The interpretation based on a 1D linear MHD model suggests that the thermal conductivity is suppressed by at least a factor of 3 in the hot flare loop at 9 MK and above. The viscosity coefficient is determined by coronal seismology from the observed wave when only considering the compressive viscosity dissipation. We find that to interpret the rapid wave damping, the classical compressive viscosity coefficient needs to be enhanced by a factor of 15 as the upper limit.

  1. Apolipoprotein E4 Causes Age-Dependent Disruption of Slow Gamma Oscillations during Hippocampal Sharp-Wave Ripples.

    PubMed

    Gillespie, Anna K; Jones, Emily A; Lin, Yuan-Hung; Karlsson, Mattias P; Kay, Kenneth; Yoon, Seo Yeon; Tong, Leslie M; Nova, Philip; Carr, Jessie S; Frank, Loren M; Huang, Yadong

    2016-05-18

    Apolipoprotein (apo) E4 is the major genetic risk factor for Alzheimer's disease (AD), but the mechanism by which it causes cognitive decline is unclear. In knockin (KI) mice, human apoE4 causes age-dependent learning and memory impairments and degeneration of GABAergic interneurons in the hippocampal dentate gyrus. Here we report two functional apoE4-KI phenotypes involving sharp-wave ripples (SWRs), hippocampal network events critical for memory processes. Aged apoE4-KI mice had fewer SWRs than apoE3-KI mice and significantly reduced slow gamma activity during SWRs. Elimination of apoE4 in GABAergic interneurons, which prevents learning and memory impairments, rescued SWR-associated slow gamma activity but not SWR abundance in aged mice. SWR abundance was reduced similarly in young and aged apoE4-KI mice; however, the full SWR-associated slow gamma deficit emerged only in aged apoE4-KI mice. These results suggest that progressive decline of interneuron-enabled slow gamma activity during SWRs critically contributes to apoE4-mediated learning and memory impairments. VIDEO ABSTRACT. PMID:27161522

  2. Epileptic encephalopathy with continuous spikes and waves in the occipito-temporal region during slow-wave sleep in two patients with acquired Kanji dysgraphia.

    PubMed

    Kuki, Ichiro; Kawawaki, Hisashi; Okazaki, Shin; Ikeda, Hiroko; Tomiwa, Kiyotaka

    2014-12-01

    We encountered two patients with acquired Kanji dysgraphia in whom continuous spikes and waves, dominant in the occipito-temporal region, were recorded during slow-wave sleep. Electrical status epileptics during sleep (ESES) was demonstrated on overnight electroencephalography, and dipoles clustered in and around the posterior inferior temporal cortex on magnetoencephalography. Functional neuroimaging suggested dysfunction in the left posterior temporal lobe, including the posterior inferior temporal cortex. The patients had normal intelligence with no problems in reading and writing Kana, as well as copying, reading aloud, and identifying Kanjis, but showed Kanji dysgraphia (morphological, phonemic, and semantic error) accompanied by impaired visual processing. ESES was resolved by sodium valproate, clonazepam, and acetazolamide in Patient 1, and by adrenocorticotropic hormone, sodium valproate, and clorazepate in Patient 2. The present cases had the unique cognitive dysfunction of Kanji dysgraphia, which is distinct from that of Landau-Kleffner syndrome and continuous spikes and waves during slow-wave sleep. However, the present cases also share common features with these two encephalopathies in terms of the clinical course, pathophysiology, neuroimaging, and response to steroids and antiepileptic drugs. In the context of the Japanese language, acquired Kanji dysgraphia may occur due to electrical dysfunction of left posterior inferior temporal cortex in patients with ESES. PMID:25333864

  3. Dispersion retrieval from multi-level ultra-deep reactive-ion-etched microstructures for terahertz slow-wave circuits

    SciTech Connect

    Baik, Chan-Wook Young Ahn, Ho; Kim, Yongsung; Lee, Jooho; Hong, Seogwoo; Hee Choi, Jun; Kim, Sunil; Hun Lee, Sang; Min Kim, Jong; Hwang, Sungwoo; Yeon Jun, So; Yu, SeGi; Lawrence Ives, R.

    2014-01-13

    A multi-level microstructure is proposed for terahertz slow-wave circuits, with dispersion relation retrieved by scattering parameter measurements. The measured return loss shows strong resonances above the cutoff with negligible phase shifts compared with finite element analysis. Splitting the circuit into multi levels enables a low aspect ratio configuration that alleviates the loading effect of deep-reactive-ion etching on silicon wafers. This makes it easier to achieve flat-etched bottom and smooth sidewall profiles. The dispersion retrieved from the measurement, therefore, corresponds well to the theoretical estimation. The result provides a straightforward way to the precise determination of dispersions in terahertz vacuum electronics.

  4. T-waves from a slow earthquake: analysis of hydroacoustic data from the July 17, 2006 Jawa

    NASA Astrophysics Data System (ADS)

    Salzberg, D.; Pulli, J.

    2006-12-01

    The July 17, 2006 Jawa earthquake (Mw=7.7) was a `slow' earthquake, with little high frequency energy. The T-waves from this earthquake were recorded at the IMS hydroacoustic station at Diego Garcia. Comparisons between this T-wave and the T-waves for the Dec. 26, 2004 (Mw=9.3) and March 28, 2005 (Mw=8.7) Northern Sumatra earthquakes provides potential T-wave markers that can be useful for tsunami warning. First, the T-wave amplitude from the July 2006 event was small compared with that of the December 2004 and March 2005 events; peak amplitudes from the time series are about 100x smaller for the July 2006 event when compared to the other events. That presumably results from the lack of high frequency energy in the slow earthquake. Thus, we conclude the T-wave amplitude is not a robust indicator of tsunamigenisis. Another potential marker is the T-wave duration. The duration of the T- wave results from a combination of source duration and a broad seismic-to-acoustic conversion region. The latter can be calibrated by comparing the T-wave to that of an aftershock, as the aftershock can act as an empirical Green's function for the main shock. Therefore, the difference between the aftershock duration and mainshock duration gives approximate source durations. The mainshock T-wave duration for the July 2006 event was about 400 seconds compared with 80 seconds for the aftershock the next day, yielding a source duration of about 300 seconds. For comparison, the measured duration of the two northern Sumatra T-waves was 700 seconds (2004) and 260 seconds (2005). Thus, the T-wave duration may be an indicator of tsunamigenisis (or at least extended source duration). A final marker is based on the spectral content , represented by the spectral slope. We previously demonstrated that the spectral content of a T-wave results from attenuation from the solid-earth propagation path. Therefore, a shallow spectral slope (in log-amplitude space) indicates a shallow rupture, which is

  5. SMALL-SCALE PRESSURE-BALANCED STRUCTURES DRIVEN BY OBLIQUE SLOW MODE WAVES MEASURED IN THE SOLAR WIND

    SciTech Connect

    Yao Shuo; He, J.-S.; Tu, C.-Y.; Wang, L.-H.; Marsch, E.

    2013-09-01

    Recently, small-scale pressure-balanced structures (PBSs) were identified in the solar wind, but their formation mechanism remains unclear. This work aims to reveal the dependence of the properties of small-scale PBSs on the background magnetic field (B{sub 0}) direction and thus to corroborate the in situ mechanism that forms them. We analyze the plasma and magnetic field data obtained by WIND in the quiet solar wind at 1 AU. First, we use a developed moving-average method to obtain B{sub 0}(s, t) for every temporal scale (s) at each time moment (t). By wavelet cross-coherence analysis, we obtain the correlation coefficients between the thermal pressure P{sub th} and the magnetic pressure P{sub B}, distributing against the temporal scale and the angle {theta}{sub xB} between B{sub 0}(s, t) and Geocentric Solar Ecliptic coordinates (GSE)-x. We note that the angle coverage of a PBS decreases with shorter temporal scale, but the occurrence of the PBSs is independent of {theta}{sub xB}. Suspecting that the isolated small PBSs are formed by compressive waves in situ, we continue this study by testing the wave modes forming a small-scale PBS with B{sub 0}(s, t) quasi-parallel to GSE-x. As a result, we identify that the cross-helicity and the compressibility attain values for a slow mode from theoretical calculations. The wave vector is derived from minimum variance analysis. Besides, the proton temperatures obey T < T{sub Parallel-To} derived from the velocity distribution functions, excluding a mirror mode, which is the other candidate for the formation of PBSs in situ. Thus, a small-scale PBS is shown to be driven by oblique, slow-mode waves in the solar wind.

  6. Odors enhance slow-wave activity in non-rapid eye movement sleep.

    PubMed

    Perl, Ofer; Arzi, Anat; Sela, Lee; Secundo, Lavi; Holtzman, Yael; Samnon, Perry; Oksenberg, Arie; Sobel, Noam; Hairston, Ilana S

    2016-05-01

    Most forms of suprathreshold sensory stimulation perturb sleep. In contrast, presentation of pure olfactory or mild trigeminal odorants does not lead to behavioral or physiological arousal. In fact, some odors promote objective and subjective measures of sleep quality in humans and rodents. The brain mechanisms underlying these sleep-protective properties of olfaction remain unclear. Slow oscillations in the electroencephalogram (EEG) are a marker of deep sleep, and K complexes (KCs) are an EEG marker of cortical response to sensory interference. We therefore hypothesized that odorants presented during sleep will increase power in slow EEG oscillations. Moreover, given that odorants do not drive sleep interruption, we hypothesized that unlike other sensory stimuli odorants would not drive KCs. To test these hypotheses we used polysomnography to measure sleep in 34 healthy subjects (19 women, 15 men; mean age 26.5 ± 2.5 yr) who were repeatedly presented with odor stimuli via a computer-controlled air-dilution olfactometer over the course of a single night. Each participant was exposed to one of four odorants, lavender oil (n = 13), vetiver oil (n = 5), vanillin (n = 12), or ammonium sulfide (n = 4), for durations of 5, 10, and 20 s every 9-15 min. Consistent with our hypotheses, we found that odor presentation during sleep enhanced the power of delta (0.5-4 Hz) and slow spindle (9-12 Hz) frequencies during non-rapid eye movement sleep. The increase was proportionate to odor duration. In addition, odor presentation did not modulate the occurrence of KCs. These findings imply a sleep-promoting olfactory mechanism that may deepen sleep through driving increased slow-frequency oscillations. PMID:26888107

  7. Roles of convective heating and boundary-layer moisture asymmetry in slowing down the convectively coupled Kelvin waves

    NASA Astrophysics Data System (ADS)

    Wang, Lu; Li, Tim

    2016-06-01

    Mechanisms for an in-phase relationship between convection and low-level zonal wind and the slow propagation of the convectively coupled Kelvin wave (CCKW) are investigated by analyzing satellite-based brightness temperature and reanalysis data and by constructing a simple theoretical model. Observational data analysis reveals an eastward shift of the low-level convergence and moisture relative to the CCKW convective center. The composite vertical structures show that the low-level convergence lies in the planetary boundary layer (PBL) (below 800 hPa), and is induced by the pressure trough above the top of PBL through an Ekman-pumping process. A traditional view of a slower eastward propagation speed compared to the dry Kelvin waves is attributed to the reduction of atmospheric static stability in mid-troposphere due to the convective heating effect. The authors' quantitative assessment of the heating effect shows that this effect alone cannot explain the observed CCKW phase speed. We hypothesize that additional slowing process arises from the effect of zonally asymmetric PBL moisture. A simple theoretical model is constructed to understand the relative role of the heating induced effective static stability effect and the PBL moisture effect. The result demonstrates the important role of the both effects. Thus, PBL-free atmosphere interaction is important in explaining the observed structure and propagation of CCKW.

  8. Long-term history and immediate preceding state affect EEG slow wave characteristics at NREM sleep onset in C57BL/6 mice.

    PubMed

    Cui, N; Mckillop, L E; Fisher, S P; Oliver, P L; Vyazovskiy, V V

    2014-01-01

    The dynamics of cortical activity across the 24-h day and at vigilance state transitions is regulated by an interaction between global subcortical neuromodulatory influences and local shifts in network synchrony and excitability. To address the role of long-term and immediate preceding history in local and global cortical dynamics, we investigated cortical EEG recorded from both frontal and occipital regions during an undisturbed 24-h recording in mice. As expected, at the beginning of the light period, under physiologically increased sleep pressure, EEG slow waves were more frequent and had higher amplitude and slopes, compared to the rest of the light period. Within discrete NREM sleep episodes, the incidence, amplitude and slopes of individual slow waves increased progressively after episode onset in both derivations by approximately 10-30%. Interestingly, at the beginning of NREM sleep episodes slow waves in the frontal and occipital derivations frequently occurred in isolation, as quantified by longer latencies between consecutive slow waves in the two regions. Notably, slow waves during the initial period of NREM sleep following REM sleep episodes were significantly less frequent, lower in amplitude and exhibited shallower slopes, compared to those that occurred in NREM episodes after prolonged waking. Moreover, the latencies between consecutive frontal and occipital NREM slow waves were substantially longer when they occurred directly after REM sleep compared to following consolidated wakefulness. Overall these data reveal a complex picture, where both time of day and preceding state contribute to the characteristics and dynamics of slow waves within NREM sleep. These findings suggest that NREM sleep initiates in a more "local" fashion when it occurs following REM sleep episodes as opposed to sustained waking bouts. While the mechanisms and functional significance of such a re-setting of brain state after individual REM sleep episodes remains to be

  9. Neuropsychological impairment in early-onset hydrocephalus and epilepsy with continuous spike-waves during slow-wave sleep: A case report and literature review

    PubMed Central

    Posar, Annio; Parmeggiani, Antonia

    2013-01-01

    Epilepsy with continuous spike-waves during slow-wave sleep (CSWS) is often characterized by a severe cognitive and behavioral impairment. Symptomatic cases also include patients with an early-onset hydrocephalus, but in literature detailed neuropsychological data on these subjects are not available. We describe the results of serial cognitive assessments in a girl with shunted early-onset hydrocephalus, followed by partial epilepsy complicated with CSWS at 4 years 10 months, in which a dramatic cognitive and behavioral deterioration occurred few months after CSWS onset. Adrenocorticotropic hormone treatment improved both clinical and electroencephalogram picture, but an impairment of visual perception, visual-motor coordination and executive functions persisted after CSWS disappearance. We hypothesize, in this case, an involvement of right occipital-parietal lobe and prefrontal lobe. PMID:24082936

  10. Site Response And Slow Basin Waves In The Sacramento/San Joaquin Delta

    NASA Astrophysics Data System (ADS)

    Fletcher, J. B.; Sell, R.

    2009-12-01

    About 1700 km of levees protect farmland and communities from inundation in the delta of the Sacramento/San Joaquin Rivers at the western edge of the Great Valley in California. These levees are made from dredged soils, such as peat, and are characterized by low shear-wave velocities (about 200m/s) and are vulnerable to breaking from major earthquakes in the greater San Francisco Bay area. We have investigated the seismic response of sites in the delta by deploying a set of broadband seismometers to record local moderate-sized earthquakes. Each of the 11 sites has a 30s broadband, 3-component seismograph digitized continuously at 100 sps/channel. In the summer of 2008 we expanded the original array, which covered a small area near Bethel Is., to cover a greater proportion of the delta, and it now extends from Tracy in the south to Bethel Is. in the northwest to Eight Mile Road in the northeast, an area of about 20 by 30 km. Several of the sites are on levees and the others are on farmland. One site is on a outcrop just west of the Clifton Court Forebay in the foothills. During the last year we have recorded nine events in the M 3 to 4 range with good signal to noise at the array. Site response was estimated with spectral ratios of S waves using Black Diamond Mine, a station in the UC Berkeley seismic network, as a reference station. Site responses at levee sites typically show large resonances in the 1-3 Hz range with amplifications greater than 10 for the Sept. 6, 2008 M4.1 Alamo event. Other sites show amplifications between 2 and 7 at various frequencies between 1 and 10 Hz. Sites within the delta show late-arriving Rayleigh waves with a period of about one second. A three-element array at the Holland Marina (spacing 180-290m) shows these waves to be traveling at about 610 m/s with a back azimuth about 20 degrees off the azimuth to the epicenter. Observations of well-developed, one-second surface waves across basins are not common, but they are similar to

  11. TWT Driven by a Large Diameter Annular Electron Beam in a Disk-on-Rod Slow-Wave Structure

    NASA Astrophysics Data System (ADS)

    Wong, P.; Simon, D. H.; Zhang, Peng; Lau, Y. Y.; Gilgenbach, R. M.; Hoff, B.

    2014-10-01

    This paper studies the viability of a high-power traveling wave tube (TWT) using a disk-on-rod slow-wave structure (SWS), which admits a large diameter, high current, annular electron beam. The annular electron beam would achieve much higher current than a pencil beam. The cold-tube as well as the hot-tube dispersion relations are analytically studied and compared to numerical simulations. The Pierce gain parameter, C , is calculated by two very different methods: the exact formulation of the space-charge wave on the disk-on-rod SWS, and the calculation of the action of the beam on the operating circuit mode. Both methods yield identical results of C. The so-called Pierce AC space charge effect parameter, QC, is calculated rigorously for the first time for the disk-on-rod SWS TWT. Proof-of-principle experiment is designed based on the combined analytic and simulation studies. This work is supported by AFOSR, and by L-3 Communications Electron Devices.

  12. Vessel heterogeneity of TIMI frame count and its relation to P-wave dispersion in patients with coronary slow flow

    PubMed Central

    Peng, You; Bardeesi, Adham Sameer A.; Bardisi, Ekhlas Samir A.; Liao, Xinxue

    2016-01-01

    Background The vessel heterogeneity of thrombolysis in myocardial infarction (TIMI) frame count (TFC) in patients with coronary slow flow (CSF) remains to be further evaluated, and the correlation between TFC heterogeneity and P-wave dispersion (PWD) has not been elucidated. We aim to investigate the vessel heterogeneity of TFC in coronary arteries, and its relation to PWD in patients with CSF and otherwise normal coronary arteries. Methods We studied 72 patients with angiographically documented CSF and 66 age- and gender-matched control subjects. The coefficient of variation (CV) and mean TFC of the three vessels were calculated. P-wave duration and PWD were measured on the standard electrocardiograms (ECGs). Results The mean TFC and CV were both significantly higher in CSF patients than in controls (P<0.001 for both comparisons). The maximum P-wave duration (Pmax) and PWD were found to be significantly higher in CSF patients than in controls (P<0.001 for both comparisons). In patients with CSF, both Pmax and PWD were mildly correlated to mean TFC (r=0.318, P=0.009; and r=0.307, P=0.010), and were more significantly correlated to CV (r=0.506, P<0.001; and r=0.579, P<0.001). Conclusions These data demonstrate that variability of TFC in three coronary arteries is increased in CSF patients, and that the vessel heterogeneity in coronary flow might be intimately associated with PWD. PMID:27076943

  13. Theoretical, Experimental, and Computational Evaluation of a Tunnel Ladder Slow-Wave Structure

    NASA Technical Reports Server (NTRS)

    Wallett, Thomas M.; Qureshi, A. Haq

    1994-01-01

    The dispersion characteristics of a tunnel ladder circuit in a ridged wave guide were experimentally measured and determined by computer simulation using the electromagnetic code MAFIA. To qualitatively estimate interaction impedances, resonance frequency shifts due to a perturbing dielectric rod along the axis were also measured indicating the axial electric field strength. A theoretical modeling of the electric and magnetic fields in the tunnel area was also done.

  14. Ion thermal effects on slow mode solitary waves in plasmas with two adiabatic ion species

    SciTech Connect

    Nsengiyumva, F. Hellberg, M. A. Mace, R. L.

    2015-09-15

    Using both the Sagdeev and Korteweg-de Vries (KdV) methods, ion thermal effects on slow mode ion acoustic solitons and double layers are investigated in a plasma with two adiabatic positive ion species. It is found that reducing the gap between the two ion thermal speeds by increasing the relative temperature of the cool ions increases the typical soliton/double layer speeds for all values of the ion-ion density ratio and reduces the range in the density ratio that supports double layers. The effect of increasing the relative cool ion temperature on the soliton/double layer amplitudes depends on the relative densities. For lower values of the ion density ratio, an increase in cool ion temperature leads to a significant decrease in soliton/double layer amplitude, so one may find that solitons of all permissible speeds lie within the range of KdV theory.

  15. Slow Modulations of Periodic Waves in Hamiltonian PDEs, with Application to Capillary Fluids

    NASA Astrophysics Data System (ADS)

    Benzoni-Gavage, S.; Noble, P.; Rodrigues, L. M.

    2014-08-01

    Since its elaboration by Whitham almost 50 years ago, modulation theory has been known to be closely related to the stability of periodic traveling waves. However, it is only recently that this relationship has been elucidated and that fully nonlinear results have been obtained. These only concern dissipative systems though: reaction-diffusion systems were first considered by Doelman et al. (Mem Am Math Soc 199(934):viii+105, 2009), and viscous systems of conservation laws have been addressed by Johnson et al. (Invent Math, 2013). Here, only nondissipative models are considered, and a most basic question is investigated, namely, the expected link between the hyperbolicity of modulated equations and the spectral stability of periodic traveling waves to sideband perturbations. This is done first in an abstract Hamiltonian framework, which encompasses a number of dispersive models, in particular the well-known (generalized) Korteweg-de Vries equation and the less known Euler-Korteweg system, in both Eulerian coordinates and Lagrangian coordinates. The latter is itself an abstract framework for several models arising in water wave theory, superfluidity, and quantum hydrodynamics. As regards its application to compressible capillary fluids, attention is paid here to untangle the interplay between traveling waves/modulation equations in Eulerian coordinates and those in Lagrangian coordinates. In the most general setting, it is proved that the hyperbolicity of modulated equations is indeed necessary for the spectral stability of periodic traveling waves. This extends earlier results by Serre (Commun Partial Differ Equ 30(1-3):259-282, 2005), Oh and Zumbrun (Arch Ration Mech Anal 166(2):99-166, 2003), and Johnson et al. (Phys D 239(23-24):2057-2065, 2010). In addition, reduced necessary conditions are obtained in the small-amplitude limit. Then numerical investigations are carried out for the modulated equations of the Euler-Korteweg system with two types of "pressure

  16. Ameliorating Effects of Auricular Electroacupuncture on Rectal Distention-Induced Gastric Dysrhythmias in Rats

    PubMed Central

    Zhang, Zhaohui; Yin, Jieyun; Chen, Jiande D. Z.

    2015-01-01

    Gastric slow waves (GSW) are known to regulate gastric motility and are impaired with rectal distention (RD). Electroacupuncture (EA) at body acupoints, such as ST 36, has been shown to improve gastric dysrhythmias; however, little is known about the possible effects of auricular electroacupuncture (AEA) on GSW. To study effects and possible mechanisms of AEA on RD-induced gastric dysrhythmias in rats, ten male Sprague-Dawley (SD) rats implanted with gastric serosal electrodes were studied in two different experiments in fed state. Four sessions were performed in experiment 1 as follows: control (RD, no stimulation), RD+AEA, RD+EA at body points and RD+sham AEA. Two sessions were included in experiment 2 to study mechanisms of AEA: RD + atropine and RD + atropine + AEA. It was found that 1) RD significantly decreased the percentage of normal GSW from 89.8±3.5% to 76.0±3.3% (P<0.05); 2) AEA increased the percentage of normal GSW during RD to 94.0±2.1% (P<0.05 vs. RD) via a reduction in the percentages of tachygastria and arrhythmia (P<0.05 vs. RD); 3) atropine blocked the ameliorating effect of AEA on RD-induced gastric dysrhythmias. Our results demonstrated that RD induces gastric dysrhythmias in fed state in rats. AEA improves RD-induced gastric dysrhythmias via the vagal pathway. AEA may have a therapeutic potential in treating gastric dysrhythmias. PMID:25643282

  17. A highly efficient CMOS nanoplasmonic crystal enhanced slow-wave thermal emitter improves infrared gas-sensing devices

    NASA Astrophysics Data System (ADS)

    Pusch, Andreas; de Luca, Andrea; Oh, Sang S.; Wuestner, Sebastian; Roschuk, Tyler; Chen, Yiguo; Boual, Sophie; Ali, Zeeshan; Phillips, Chris C.; Hong, Minghui; Maier, Stefan A.; Udrea, Florin; Hopper, Richard H.; Hess, Ortwin

    2015-12-01

    The application of plasmonics to thermal emitters is generally assisted by absorptive losses in the metal because Kirchhoff’s law prescribes that only good absorbers make good thermal emitters. Based on a designed plasmonic crystal and exploiting a slow-wave lattice resonance and spontaneous thermal plasmon emission, we engineer a tungsten-based thermal emitter, fabricated in an industrial CMOS process, and demonstrate its markedly improved practical use in a prototype non-dispersive infrared (NDIR) gas-sensing device. We show that the emission intensity of the thermal emitter at the CO2 absorption wavelength is enhanced almost 4-fold compared to a standard non-plasmonic emitter, which enables a proportionate increase in the signal-to-noise ratio of the CO2 gas sensor.

  18. A highly efficient CMOS nanoplasmonic crystal enhanced slow-wave thermal emitter improves infrared gas-sensing devices.

    PubMed

    Pusch, Andreas; De Luca, Andrea; Oh, Sang S; Wuestner, Sebastian; Roschuk, Tyler; Chen, Yiguo; Boual, Sophie; Ali, Zeeshan; Phillips, Chris C; Hong, Minghui; Maier, Stefan A; Udrea, Florin; Hopper, Richard H; Hess, Ortwin

    2015-01-01

    The application of plasmonics to thermal emitters is generally assisted by absorptive losses in the metal because Kirchhoff's law prescribes that only good absorbers make good thermal emitters. Based on a designed plasmonic crystal and exploiting a slow-wave lattice resonance and spontaneous thermal plasmon emission, we engineer a tungsten-based thermal emitter, fabricated in an industrial CMOS process, and demonstrate its markedly improved practical use in a prototype non-dispersive infrared (NDIR) gas-sensing device. We show that the emission intensity of the thermal emitter at the CO(2) absorption wavelength is enhanced almost 4-fold compared to a standard non-plasmonic emitter, which enables a proportionate increase in the signal-to-noise ratio of the CO(2) gas sensor. PMID:26639902

  19. A highly efficient CMOS nanoplasmonic crystal enhanced slow-wave thermal emitter improves infrared gas-sensing devices

    PubMed Central

    Pusch, Andreas; De Luca, Andrea; Oh, Sang S.; Wuestner, Sebastian; Roschuk, Tyler; Chen, Yiguo; Boual, Sophie; Ali, Zeeshan; Phillips, Chris C.; Hong, Minghui; Maier, Stefan A.; Udrea, Florin; Hopper, Richard H.; Hess, Ortwin

    2015-01-01

    The application of plasmonics to thermal emitters is generally assisted by absorptive losses in the metal because Kirchhoff’s law prescribes that only good absorbers make good thermal emitters. Based on a designed plasmonic crystal and exploiting a slow-wave lattice resonance and spontaneous thermal plasmon emission, we engineer a tungsten-based thermal emitter, fabricated in an industrial CMOS process, and demonstrate its markedly improved practical use in a prototype non-dispersive infrared (NDIR) gas-sensing device. We show that the emission intensity of the thermal emitter at the CO2 absorption wavelength is enhanced almost 4-fold compared to a standard non-plasmonic emitter, which enables a proportionate increase in the signal-to-noise ratio of the CO2 gas sensor. PMID:26639902

  20. Heightened Delta Power during Slow-Wave-Sleep in Patients with Rett Syndrome Associated with Poor Sleep Efficiency

    PubMed Central

    Ammanuel, Simon; Chan, Wesley C.; Adler, Daniel A.; Lakshamanan, Balaji M.; Gupta, Siddharth S.; Ewen, Joshua B.; Johnston, Michael V.; Marcus, Carole L.; Naidu, Sakkubai; Kadam, Shilpa D.

    2015-01-01

    Sleep problems are commonly reported in Rett syndrome (RTT); however the electroencephalographic (EEG) biomarkers underlying sleep dysfunction are poorly understood. The aim of this study was to analyze the temporal evolution of quantitative EEG (qEEG) biomarkers in overnight EEGs recorded from girls (2–9 yrs. old) diagnosed with RTT using a non-traditional automated protocol. In this study, EEG spectral analysis identified high delta power cycles representing slow wave sleep (SWS) in 8–9h overnight sleep EEGs from the frontal, central and occipital leads (AP axis), comparing age-matched girls with and without RTT. Automated algorithms quantitated the area under the curve (AUC) within identified SWS cycles for each spectral frequency wave form. Both age-matched RTT and control EEGs showed similar increasing trends for recorded delta wave power in the EEG leads along the antero-posterior (AP). RTT EEGs had significantly fewer numbers of SWS sleep cycles; therefore, the overall time spent in SWS was also significantly lower in RTT. In contrast, the AUC for delta power within each SWS cycle was significantly heightened in RTT and remained heightened over consecutive cycles unlike control EEGs that showed an overnight decrement of delta power in consecutive cycles. Gamma wave power associated with these SWS cycles was similar to controls. However, the negative correlation of gamma power with age (r = -.59; p<0.01) detected in controls (2–5 yrs. vs. 6–9 yrs.) was lost in RTT. Poor % SWS (i.e., time spent in SWS overnight) in RTT was also driven by the younger age-group. Incidence of seizures in RTT was associated with significantly lower number of SWS cycles. Therefore, qEEG biomarkers of SWS in RTT evolved temporally and correlated significantly with clinical severity. PMID:26444000

  1. Mortality salience modulates cortical responses to painful somatosensory stimulation: Evidence from slow wave and delta band activity.

    PubMed

    Valentini, Elia; Koch, Katharina; Nicolardi, Valentina; Aglioti, Salvatore Maria

    2015-10-15

    Social psychology studies show that awareness of one's eventual death profoundly influences human cognition and behaviour by inducing defensive reactions against end-of-life-related anxiety. Much less is known about the impact of reminders of mortality on brain activity. Here we tested whether reminders of mortality can induce a modulation of the slow electroencephalographic activity triggered by somatosensory nociceptive or auditory threatening stimulation and if this modulation is related to mood and anxiety as well as personality traits. We found a specific slow wave (SW) modulation only for nociceptive stimulation and only following mortality salience induction (compared to reminders of an important failed exam). The enhancement of SW negativity at the scalp vertex was associated with increased state anxiety and negative mood, whereas higher self-esteem was associated with reduced SW amplitude. In addition, mortality salience was linked to an increased amplitude of frontal delta band, which was correlated also with increased positive mood and higher self-esteem. The results indicate that SW and delta spectral activity may represent both proximal and distal defences associated with reminders of death and that neurophysiological correlates of somatosensory representation of painful and threatening stimuli may be useful for existential neuroscience studies. PMID:26188186

  2. Spectroscopic observations of propagating disturbances in a polar coronal hole: evidence of slow magneto-acoustic waves

    NASA Astrophysics Data System (ADS)

    Gupta, G. R.; Teriaca, L.; Marsch, E.; Solanki, S. K.; Banerjee, D.

    2012-10-01

    Aims: We focus on detecting and studying quasi-periodic propagating features that have been interpreted in terms of both slow magneto-acoustic waves and of high-speed upflows. Methods: We analyzed long-duration spectroscopic observations of the on-disk part of the south polar coronal hole taken on 1997 February 25 by the SUMER spectrometer onboard SOHO. We calibrated the velocity with respect to the off-limb region and obtained time-distance maps in intensity, Doppler velocity, and line width. We also performed a cross-correlation analysis on different time series curves at different latitudes. We studied average spectral line profiles at the roots of propagating disturbances and along the propagating ridges, and performed a red-blue asymmetry analysis. Results: We clearly find propagating disturbances in intensity and Doppler velocity with a projected propagation speed of about 60 ± 4.8 km s-1 and a periodicity of ≈14.5 min. To our knowledge, this is the first simultaneous detection of propagating disturbances in intensity as well as in Doppler velocity in a coronal hole. During the propagation, an intensity enhancement is associated with a blueshifted Doppler velocity. These disturbances are clearly seen in intensity also at higher latitudes (i.e., closer to the limb), while disturbances in Doppler velocity become faint there. The spectral line profiles averaged along the propagating ridges are found to be symmetric, to be well fitted by a single Gaussian, and have no noticeable red-blue asymmetry. Conclusions: Based on our analysis, we interpret these disturbances in terms of propagating slow magneto-acoustic waves.

  3. Slow Ca2+ wave stimulation using low repetition rate femtosecond pulsed irradiation

    NASA Astrophysics Data System (ADS)

    Iwanaga, S.; Smith, N. I.; Fujita, K.; Kawata, S.

    2006-01-01

    We demonstrated stimulation of Ca2+ in living cells by near-infrared laser pulses operated at sub-MHz repetition rates. HeLa cells were exposed to focused 780 nm femtosecond pulses, generated by a titanium-sapphire laser and adjusted by an electro-optical modulator. We found that the laser-induced Ca2+ waves could be generated over three orders of magnitude in repetition rates, with required laser pulse energy varying by less than one order of magnitude. Ca2+ wave speed and gradients were reduced with repetition rate, which allows the technique to be used to modulate the strength and speed of laser-induced effects. By lowering the repetition rate, we found that the laser-induced Ca2+ release is partially mediated by reactive oxygen species (ROS). Inhibition of ROS was successful only at low repetition rates, with the implication that ROS scavengers may in general be depleted in experiments using high repetition rate laser irradiation.

  4. Characterization of K-complexes and slow wave activity in a neural mass model.

    PubMed

    Weigenand, Arne; Schellenberger Costa, Michael; Ngo, Hong-Viet Victor; Claussen, Jens Christian; Martinetz, Thomas

    2014-11-01

    NREM sleep is characterized by two hallmarks, namely K-complexes (KCs) during sleep stage N2 and cortical slow oscillations (SOs) during sleep stage N3. While the underlying dynamics on the neuronal level is well known and can be easily measured, the resulting behavior on the macroscopic population level remains unclear. On the basis of an extended neural mass model of the cortex, we suggest a new interpretation of the mechanisms responsible for the generation of KCs and SOs. As the cortex transitions from wake to deep sleep, in our model it approaches an oscillatory regime via a Hopf bifurcation. Importantly, there is a canard phenomenon arising from a homoclinic bifurcation, whose orbit determines the shape of large amplitude SOs. A KC corresponds to a single excursion along the homoclinic orbit, while SOs are noise-driven oscillations around a stable focus. The model generates both time series and spectra that strikingly resemble real electroencephalogram data and points out possible differences between the different stages of natural sleep. PMID:25392991

  5. Characterization of K-Complexes and Slow Wave Activity in a Neural Mass Model

    PubMed Central

    Ngo, Hong-Viet Victor; Claussen, Jens Christian; Martinetz, Thomas

    2014-01-01

    NREM sleep is characterized by two hallmarks, namely K-complexes (KCs) during sleep stage N2 and cortical slow oscillations (SOs) during sleep stage N3. While the underlying dynamics on the neuronal level is well known and can be easily measured, the resulting behavior on the macroscopic population level remains unclear. On the basis of an extended neural mass model of the cortex, we suggest a new interpretation of the mechanisms responsible for the generation of KCs and SOs. As the cortex transitions from wake to deep sleep, in our model it approaches an oscillatory regime via a Hopf bifurcation. Importantly, there is a canard phenomenon arising from a homoclinic bifurcation, whose orbit determines the shape of large amplitude SOs. A KC corresponds to a single excursion along the homoclinic orbit, while SOs are noise-driven oscillations around a stable focus. The model generates both time series and spectra that strikingly resemble real electroencephalogram data and points out possible differences between the different stages of natural sleep. PMID:25392991

  6. Nonlinear waves in earth crust faults: application to regular and slow earthquakes

    NASA Astrophysics Data System (ADS)

    Gershenzon, Naum; Bambakidis, Gust

    2015-04-01

    The genesis, development and cessation of regular earthquakes continue to be major problems of modern geophysics. How are earthquakes initiated? What factors determine the rapture velocity, slip velocity, rise time and geometry of rupture? How do accumulated stresses relax after the main shock? These and other questions still need to be answered. In addition, slow slip events have attracted much attention as an additional source for monitoring fault dynamics. Recently discovered phenomena such as deep non-volcanic tremor (NVT), low frequency earthquakes (LFE), very low frequency earthquakes (VLF), and episodic tremor and slip (ETS) have enhanced and complemented our knowledge of fault dynamic. At the same time, these phenomena give rise to new questions about their genesis, properties and relation to regular earthquakes. We have developed a model of macroscopic dry friction which efficiently describes laboratory frictional experiments [1], basic properties of regular earthquakes including post-seismic stress relaxation [3], the occurrence of ambient and triggered NVT [4], and ETS events [5, 6]. Here we will discuss the basics of the model and its geophysical applications. References [1] Gershenzon N.I. & G. Bambakidis (2013) Tribology International, 61, 11-18, http://dx.doi.org/10.1016/j.triboint.2012.11.025 [2] Gershenzon, N.I., G. Bambakidis and T. Skinner (2014) Lubricants 2014, 2, 1-x manuscripts; doi:10.3390/lubricants20x000x; arXiv:1411.1030v2 [3] Gershenzon N.I., Bykov V. G. and Bambakidis G., (2009) Physical Review E 79, 056601 [4] Gershenzon, N. I, G. Bambakidis, (2014a), Bull. Seismol. Soc. Am., 104, 4, doi: 10.1785/0120130234 [5] Gershenzon, N. I.,G. Bambakidis, E. Hauser, A. Ghosh, and K. C. Creager (2011), Geophys. Res. Lett., 38, L01309, doi:10.1029/2010GL045225. [6] Gershenzon, N.I. and G. Bambakidis (2014) Bull. Seismol. Soc. Am., (in press); arXiv:1411.1020

  7. High-resolution entrainment mapping of gastric pacing: a new analytical tool.

    PubMed

    O'Grady, Gregory; Du, Peng; Lammers, Wim J E P; Egbuji, John U; Mithraratne, Pulasthi; Chen, Jiande D Z; Cheng, Leo K; Windsor, John A; Pullan, Andrew J

    2010-02-01

    Gastric pacing has been investigated as a potential treatment for gastroparesis. New pacing protocols are required to improve symptom and motility outcomes; however, research progress has been constrained by a limited understanding of the effects of electrical stimulation on slow-wave activity. This study introduces high-resolution (HR) "entrainment mapping" for the analysis of gastric pacing and presents four demonstrations. Gastric pacing was initiated in a porcine model (typical amplitude 4 mA, pulse width 400 ms, period 17 s). Entrainment mapping was performed using flexible multielectrode arrays (waves in spatiotemporal detail. In the second demonstration, slow-wave velocity was accurately determined with HR field analysis, and paced propagation was found to be anisotropic (longitudinal 2.6 +/- 1.7 vs. circumferential 4.5 +/- 0.6 mm/s; P < 0.001). In the third demonstration, a dysrhythmic episode that occurred during pacing was mapped in HR, revealing an ectopic slow-wave focus and uncoupled propagations. In the fourth demonstration, differences were observed between paced and native slow-wave amplitudes (0.24 +/- 0.08 vs. 0.38 +/- 0.14 mV; P < 0.001), velocities (6.2 +/- 2.8 vs. 11.5 +/- 4.7 mm/s; P < 0.001), and activated areas (20.6 +/- 1.9 vs. 32.8 +/- 2.6 cm(2); P < 0.001). Entrainment mapping enables an accurate quantification of the effects of gastric pacing on slow-wave activity, offering an improved method to assess whether pacing protocols are likely to achieve physiologically and clinically useful outcomes. PMID:19926815

  8. Dispersive characteristics and longitudinal resonance properties in a relativistic backward wave oscillator with the coaxial arbitrary-profile slow-wave structure

    NASA Astrophysics Data System (ADS)

    Ge, Xingjun; Zhong, Huihuang; Qian, Baoliang; Zhang, Jun; Fan, Yuwei; Shu, Ting; Liu, Jinliang

    2009-11-01

    The method for calculating the dispersion relations of the slow-wave structures (SWSs) with arbitrary geometrical structures is studied in detail by using the Fourier series expansion. In addition, dispersive characteristics and longitudinal resonance properties of the SWSs with the cosinusoidal, trapezoidal, and rectangular corrugations are analyzed by numerical calculation. Based on the above discussion, a comparison on an L-band coaxial relativistic backward wave oscillator (BWO) and an L-band coaxial BWO with a coaxial extractor is investigated in detail with particle-in-cell KARAT code (V. P. Tarakanov, Berkeley Research Associates, Inc., 1992). Furthermore, experiments are carried out at the TORCH-01 accelerator under the low guiding magnetic field. At diode voltage of 647 kV, beam current of 9.3 kA, and guiding magnetic field strength of 0.75 T, the microwave is generated with power of 1.07 GW, mode of TM01, and frequency of 1.61 GHz. That is the first experimental report of the L-band BWO.

  9. Dispersive characteristics and longitudinal resonance properties in a relativistic backward wave oscillator with the coaxial arbitrary-profile slow-wave structure

    SciTech Connect

    Ge Xingjun; Zhong Huihuang; Qian Baoliang; Zhang Jun; Fan Yuwei; Shu Ting; Liu Jinliang

    2009-11-15

    The method for calculating the dispersion relations of the slow-wave structures (SWSs) with arbitrary geometrical structures is studied in detail by using the Fourier series expansion. In addition, dispersive characteristics and longitudinal resonance properties of the SWSs with the cosinusoidal, trapezoidal, and rectangular corrugations are analyzed by numerical calculation. Based on the above discussion, a comparison on an L-band coaxial relativistic backward wave oscillator (BWO) and an L-band coaxial BWO with a coaxial extractor is investigated in detail with particle-in-cell KARAT code (V. P. Tarakanov, Berkeley Research Associates, Inc., 1992). Furthermore, experiments are carried out at the TORCH-01 accelerator under the low guiding magnetic field. At diode voltage of 647 kV, beam current of 9.3 kA, and guiding magnetic field strength of 0.75 T, the microwave is generated with power of 1.07 GW, mode of TM{sub 01}, and frequency of 1.61 GHz. That is the first experimental report of the L-band BWO.

  10. In vitro estimation of fast and slow wave parameters of thin trabecular bone using space-alternating generalized expectation-maximization algorithm.

    PubMed

    Grimes, Morad; Bouhadjera, Abdelmalek; Haddad, Sofiane; Benkedidah, Toufik

    2012-07-01

    In testing cancellous bone using ultrasound, two types of longitudinal Biot's waves are observed in the received signal. These are known as fast and slow waves and their appearance depend on the alignment of bone trabeculae in the propagation path and the thickness of the specimen under test (SUT). They can be used as an effective tool for the diagnosis of osteoporosis because wave propagation behavior depends on the bone structure. However, the identification of these waves in the received signal can be difficult to achieve. In this study, ultrasonic wave propagation in a 4mm thick bovine cancellous bone in the direction parallel to the trabecular alignment is considered. The observed Biot's fast and slow longitudinal waves are superimposed; which makes it difficult to extract any information from the received signal. These two waves can be separated using the space alternating generalized expectation maximization (SAGE) algorithm. The latter has been used mainly in speech processing. In this new approach, parameters such as, arrival time, center frequency, bandwidth, amplitude, phase and velocity of each wave are estimated. The B-Scan images and its associated A-scans obtained through simulations using Biot's finite-difference time-domain (FDTD) method are validated experimentally using a thin bone sample obtained from the femoral-head of a 30 months old bovine. PMID:22284937

  11. Single-subject-based whole-brain MEG slow-wave imaging approach for detecting abnormality in patients with mild traumatic brain injury.

    PubMed

    Huang, Ming-Xiong; Nichols, Sharon; Baker, Dewleen G; Robb, Ashley; Angeles, Annemarie; Yurgil, Kate A; Drake, Angela; Levy, Michael; Song, Tao; McLay, Robert; Theilmann, Rebecca J; Diwakar, Mithun; Risbrough, Victoria B; Ji, Zhengwei; Huang, Charles W; Chang, Douglas G; Harrington, Deborah L; Muzzatti, Laura; Canive, Jose M; Christopher Edgar, J; Chen, Yu-Han; Lee, Roland R

    2014-01-01

    Traumatic brain injury (TBI) is a leading cause of sustained impairment in military and civilian populations. However, mild TBI (mTBI) can be difficult to detect using conventional MRI or CT. Injured brain tissues in mTBI patients generate abnormal slow-waves (1-4 Hz) that can be measured and localized by resting-state magnetoencephalography (MEG). In this study, we develop a voxel-based whole-brain MEG slow-wave imaging approach for detecting abnormality in patients with mTBI on a single-subject basis. A normative database of resting-state MEG source magnitude images (1-4 Hz) from 79 healthy control subjects was established for all brain voxels. The high-resolution MEG source magnitude images were obtained by our recent Fast-VESTAL method. In 84 mTBI patients with persistent post-concussive symptoms (36 from blasts, and 48 from non-blast causes), our method detected abnormalities at the positive detection rates of 84.5%, 86.1%, and 83.3% for the combined (blast-induced plus with non-blast causes), blast, and non-blast mTBI groups, respectively. We found that prefrontal, posterior parietal, inferior temporal, hippocampus, and cerebella areas were particularly vulnerable to head trauma. The result also showed that MEG slow-wave generation in prefrontal areas positively correlated with personality change, trouble concentrating, affective lability, and depression symptoms. Discussion is provided regarding the neuronal mechanisms of MEG slow-wave generation due to deafferentation caused by axonal injury and/or blockages/limitations of cholinergic transmission in TBI. This study provides an effective way for using MEG slow-wave source imaging to localize affected areas and supports MEG as a tool for assisting the diagnosis of mTBI. PMID:25009772

  12. Single-subject-based whole-brain MEG slow-wave imaging approach for detecting abnormality in patients with mild traumatic brain injury

    PubMed Central

    Huang, Ming-Xiong; Nichols, Sharon; Baker, Dewleen G.; Robb, Ashley; Angeles, Annemarie; Yurgil, Kate A.; Drake, Angela; Levy, Michael; Song, Tao; McLay, Robert; Theilmann, Rebecca J.; Diwakar, Mithun; Risbrough, Victoria B.; Ji, Zhengwei; Huang, Charles W.; Chang, Douglas G.; Harrington, Deborah L.; Muzzatti, Laura; Canive, Jose M.; Christopher Edgar, J.; Chen, Yu-Han; Lee, Roland R.

    2014-01-01

    Traumatic brain injury (TBI) is a leading cause of sustained impairment in military and civilian populations. However, mild TBI (mTBI) can be difficult to detect using conventional MRI or CT. Injured brain tissues in mTBI patients generate abnormal slow-waves (1–4 Hz) that can be measured and localized by resting-state magnetoencephalography (MEG). In this study, we develop a voxel-based whole-brain MEG slow-wave imaging approach for detecting abnormality in patients with mTBI on a single-subject basis. A normative database of resting-state MEG source magnitude images (1–4 Hz) from 79 healthy control subjects was established for all brain voxels. The high-resolution MEG source magnitude images were obtained by our recent Fast-VESTAL method. In 84 mTBI patients with persistent post-concussive symptoms (36 from blasts, and 48 from non-blast causes), our method detected abnormalities at the positive detection rates of 84.5%, 86.1%, and 83.3% for the combined (blast-induced plus with non-blast causes), blast, and non-blast mTBI groups, respectively. We found that prefrontal, posterior parietal, inferior temporal, hippocampus, and cerebella areas were particularly vulnerable to head trauma. The result also showed that MEG slow-wave generation in prefrontal areas positively correlated with personality change, trouble concentrating, affective lability, and depression symptoms. Discussion is provided regarding the neuronal mechanisms of MEG slow-wave generation due to deafferentation caused by axonal injury and/or blockages/limitations of cholinergic transmission in TBI. This study provides an effective way for using MEG slow-wave source imaging to localize affected areas and supports MEG as a tool for assisting the diagnosis of mTBI. PMID:25009772

  13. Human longevity is associated with regular sleep patterns, maintenance of slow wave sleep, and favorable lipid profile

    PubMed Central

    Mazzotti, Diego Robles; Guindalini, Camila; Moraes, Walter André dos Santos; Andersen, Monica Levy; Cendoroglo, Maysa Seabra; Ramos, Luiz Roberto; Tufik, Sergio

    2014-01-01

    Some individuals are able to successfully reach very old ages, reflecting higher adaptation against age-associated effects. Sleep is one of the processes deeply affected by aging; however few studies evaluating sleep in long-lived individuals (aged over 85) have been reported to date. The aim of this study was to characterize the sleep patterns and biochemical profile of oldest old individuals (N = 10, age 85–105 years old) and compare them to young adults (N = 15, age 20–30 years old) and older adults (N = 13, age 60–70 years old). All subjects underwent full-night polysomnography, 1-week of actigraphic recording and peripheral blood collection. Sleep electroencephalogram spectral analysis was also performed. The oldest old individuals showed lower sleep efficiency and REM sleep when compared to the older adults, while stage N3 percentage and delta power were similar across the groups. Oldest old individuals maintained strictly regular sleep-wake schedules and also presented higher HDL-cholesterol and lower triglyceride levels than older adults. The present study revealed novel data regarding specific sleep patterns and maintenance of slow wave sleep in the oldest old group. Taken together with the favorable lipid profile, these results contribute with evidence to the importance of sleep and lipid metabolism regulation in the maintenance of longevity in humans. PMID:25009494

  14. A biphasic daily pattern of slow wave activity during a two-day 90-minute sleep wake schedule.

    PubMed

    Duncan, W C; Barbato, G; Fagioli, I; Garcia-Borreguero, D; Wehr, T A

    2009-12-01

    Twenty-four hour sleep patterns were measured in six healthy male volunteers during a 90-minute short sleep-wake (SW 30:60) cycle protocol for 48 hours. Sleep pressure estimates (amount of Slow Wave Sleep [SWS], SWA, and Rate of Synchronization [RoS: the rate of SWA build-up at the beginning of the NREM period]) were compared with the 24-hour patterns of body temperature (Tb24) and sleep propensity. A moderate sleep debt was incurred over the 48 hour study as indicated by decreased levels of 24 hour sleep. On day 1, ultradian patterns of REM and SWS sleep were prominent; on day 2, more prominent were circadian patterns of REM sleep, SWS, Sleep Latency, TST and Tb24. Also on Day 2, biphasic patterns of SWA and RoS were expressed, with peaks occurring during the falling and rising limbs of Tb24. The biphasic peaks in SWA and RoS may be associated with phase-specific interactions of the circadian pacemaker with the sleep homeostat during conditions of moderate sleep pressure. Further research is needed to replicate the finding and to identify biological factors that may underlie the twelve hour pattern in SWA. PMID:20162861

  15. Effect of gastric acid suppressants on human gastric motility

    PubMed Central

    Parkman, H; Urbain, J; Knight, L; Brown, K; Trate, D; Miller, M; Maurer, A; Fisher, R

    1998-01-01

    Background—The effect of histamine H2 receptor antagonists on gastric emptying is controversial. 
Aims—To determine the effects of ranitidine, famotidine, and omeprazole on gastric motility and emptying. 
Patients and methods—Fifteen normal subjects underwent simultaneous antroduodenal manometry, electrogastrography (EGG), and gastric emptying with dynamic antral scintigraphy (DAS). After 30 minutes of fasting manometry and EGG recording, subjects received either intravenous saline, ranitidine, or famotidine, followed by another 30 minutes recording and then three hours of postprandial recording after ingestion of a radiolabelled meal. Images were obtained every 10-15 minutes for three hours to measure gastric emptying and assess antral contractility. Similar testing was performed after omeprazole 20 mg daily for one week. 
Results—Fasting antral phase III migrating motor complexes (MMCs) were more common after ranitidine (9/15 subjects, 60%), famotidine (12/15, 80%), and omeprazole (8/12, 67%) compared with placebo (4/14, 29%; p<0.05). Postprandially, ranitidine, famotidine, and omeprazole slowed gastric emptying, increased the amplitude of DAS contractions, increased the EGG power, and increased the antral manometric motility index. 
Conclusions—Suppression of gastric acid secretion with therapeutic doses of gastric acid suppressants is associated with delayed gastric emptying but increased antral motility. 

 Keywords: gastric motility; gastric emptying; histamine H2 receptor antagonists; proton pump inhibitors; gastric acid secretion; scintigraphy PMID:9536950

  16. EDITORIAL: Slow light Slow light

    NASA Astrophysics Data System (ADS)

    Boyd, Robert; Hess, Ortwin; Denz, Cornelia; Paspalakis, Emmanuel

    2010-10-01

    Research into slow light began theoretically in 1880 with the paper [1] of H A Lorentz, who is best known for his work on relativity and the speed of light. Experimental work started some 60 years later with the work of S L McCall and E L Hahn [2] who explored non-linear self-induced transparency in ruby. This field of research has burgeoned in the last 10 years, starting with the work of L Vestergaard Hau and coworkers on slow light via electromagnetically induced transparency in a Bose-Einstein condensate [3]. Many groups are now able to slow light down to a few metres per second or even stop the motion of light entirely [4]. Today, slow light - or more often `slow and fast light' - has become its own vibrant field with a strongly increasing number of publications. In broad scope, slow light research can be categorized in terms of the sort of physical mechanism used to slow down the light. One sort of slow light makes use of material dispersion. This dispersion can be the natural dispersion of the ordinary refractive index or can be the frequency dependence of some nonlinear optical process, such as electromagnetically induced transparency, coherent population oscillations, stimulated light scattering, or four-wave mixing processes. The second sort of slow light makes use of the wavelength dependence of artificially structured materials, such as photonic crystals, optical waveguides, and collections of microresonators. Material systems in which slow light has been observed include metal vapours, rare-earth-doped materials, Raman and Brillioun gain media, photonic crystals, microresonators and, more recently, metamaterials. A common feature of all of these schemes is the presence of a sharp single resonance or multiple resonances produced by an atomic transition, a resonance in a photonic structure, or in a nonlinear optical process. Current applications of slow light include a series of attractive topics in optical information processing, such as optical data

  17. Theta-rhythmic drive between medial septum and hippocampus in slow-wave sleep and microarousal: a Granger causality analysis.

    PubMed

    Kang, D; Ding, M; Topchiy, I; Shifflett, L; Kocsis, B

    2015-11-01

    Medial septum (MS) plays a critical role in controlling the electrical activity of the hippocampus (HIPP). In particular, theta-rhythmic burst firing of MS neurons is thought to drive lasting HIPP theta oscillations in rats during waking motor activity and REM sleep. Less is known about MS-HIPP interactions in nontheta states such as non-REM sleep, in which HIPP theta oscillations are absent but theta-rhythmic burst firing in subsets of MS neurons is preserved. The present study used Granger causality (GC) to examine the interaction patterns between MS and HIPP in slow-wave sleep (SWS, a nontheta state) and during its short interruptions called microarousals (a transient theta state). We found that during SWS, while GC revealed a unidirectional MS→HIPP influence over a wide frequency band (2-12 Hz, maximum: ∼8 Hz), there was no theta peak in the hippocampal power spectra, indicating a lack of theta activity in HIPP. In contrast, during microarousals, theta peaks were seen in both MS and HIPP power spectra and were accompanied by bidirectional GC with MS→HIPP and HIPP→MS theta drives being of equal magnitude. Thus GC in a nontheta state (SWS) vs. a theta state (microarousal) primarily differed in the level of HIPP→MS. The present findings suggest a modification of our understanding of the role of MS as the theta generator in two regards. First, a MS→HIPP theta drive does not necessarily induce theta field oscillations in the hippocampus, as found in SWS. Second, HIPP theta oscillations entail bidirectional theta-rhythmic interactions between MS and HIPP. PMID:26354315

  18. Substance P and the neurokinin-1 receptor regulate electroencephalogram non-rapid eye movement sleep slow-wave activity locally

    PubMed Central

    Zielinski, Mark R.; Karpova, Svetlana A.; Yang, Xiaomei; Gerashchenko, Dmitry

    2014-01-01

    The neuropeptide substance P is an excitatory neurotransmitter produced by various cells including neurons and microglia that is involved in regulating inflammation and cerebral blood flow—functions that affect sleep and slow-wave activity (SWA). Substance P is the major ligand for the neurokinin-1 receptor (NK-1R), which is found throughout the brain including the cortex. The NK-1R is found on sleep-active cortical neurons expressing neuronal nitric oxide synthase whose activity is associated with SWA. We determined the effects of local cortical administration of a NK-1R agonist (substance P-fragment 1, 7) and a NK-1R antagonist (CP96345) on sleep and SWA in mice. The NK-1R agonist significantly enhanced SWA for several hours when applied locally to the cortex of the ipsilateral hemisphere as the electroencephalogram (EEG) electrode but not after application to the contralateral hemisphere when compared to saline vehicle control injections. In addition, a significant compensatory reduction in SWA was found after the NK-1R agonist-induced enhancements in SWA. Conversely, injections of the NK-1R antagonist into the cortex of the ipsilateral hemisphere of the EEG electrode attenuated SWA compared to vehicle injections but this effect was not found after injections of the NK-1R antagonist into contralateral hemisphere as the EEG electrode. Non-rapid eye movement sleep and rapid eye movement sleep duration responses after NK-1R agonist and antagonist injections were not significantly different from the responses to the vehicle. Our findings indicate that the substance P and the NK-1R are involved in regulating SWA locally. PMID:25301750

  19. Comparisons of shear-wave slowness in the Santa Clara Valley, California using blind interpretations of data from invasive and noninvasive methods

    USGS Publications Warehouse

    Boore, D.M.; Asten, M.W.

    2008-01-01

    Many groups contributed to a blind interpretation exercise for the determination of shear-wave slowness beneath the Santa Clara Valley. The methods included invasive methods in deep boreholes as well as noninvasive methods using active and passive sources, at six sites within the valley (with most investigations being conducted at a pair of closely spaced sites near the center of the valley). Although significant variability exists between the models, the slownesses from the various methods are similar enough that linear site amplifications estimated in several ways are generally within 20% of one another. The methods were able to derive slownesses that increase systematically with distance from the valley edge, corresponding to a tendency for the sites to be underlain by finer-grained materials away from the valley edge. This variation is in agreement with measurements made in the boreholes at the sites.

  20. Research the dynamical characteristics of slow deformation waves as a rock massif response to explosions during its outworking

    NASA Astrophysics Data System (ADS)

    Hachay, Olga; Khachay, Oleg; Shipeev, Oleg

    2015-04-01

    mine to estimate the changing state of the rock burst in the massif by its outworking. As a result we have selected a typical morphology of massif response phase trajectories, which were locally, over time, in a stable state: on the phase plane the local area presented as a ball of twisted trajectories with some not far removed points from the ball, which had not exceeded energy of more than 105 joules. For some time intervals those removed points exceeded 105 joules, achieving 106 joules and even 109 joules (Hachay et al., 2010). Introduction of the additional velocity parameter of slow deformation wave propagation allowed us, with the use of phase diagrams, to identify the hierarchic structure. Further, we can use that information for the modelling and interpretation of seismic and deformation waves in hierarchic structures (Hachay et al., 2012). That method can be useful in building-up an understanding of the resonance outshooting of catastrophic dynamic events and prevent these events. References 1.Chulichkov A. (2003) Mathematical models of nonlinear dynamics. Moscow: Phismatlit. 294p. 2.Hachay O., Khachay O.Yu., Klimko V., et al. (2010) Reflection of synergetic features of rock massif state under the man-caused influence from the data of a seismological catalogue. Mining Information-Analytic Bulletin, Moscow, Mining book, 6, pp.259-271. 3.Hachay O., Khachay A.Yu. (2012) Research of stress-deforming state of hierarchic medium. Proceedings of the Third Tectonics and Physics Conference at the Institute of the Physics of the Earth 8-12 October 2012, Moscow, IFZ RAS, pp.114-117. 4.Kurlenja M., Oparin V., Vostrikov V. (1993) About forming elastic wave trains by impulse excitation of block medium. Waves of pendulum type Uμ. DAN USSR, V.133, 4, pp.475-481. 5.Naimark Yu., Landa P. (2009). Stochastic and chaotic oscillations. Moscow, Knigniy dom ,'LIBROKOM', 424 p. 7.Oparin V., Vostrikov V., Tapsiev A. et al. (2006) About one kinematic criterion of forecasting of the

  1. Nonlinear Dynamical Systems Effects of Homeopathic Remedies on Multiscale Entropy and Correlation Dimension of Slow Wave Sleep EEG in Young Adults with Histories of Coffee-Induced Insomnia

    PubMed Central

    Bell, Iris R.; Howerter, Amy; Jackson, Nicholas; Aickin, Mikel; Bootzin, Richard R.; Brooks, Audrey J.

    2012-01-01

    Background Investigators of homeopathy have proposed that nonlinear dynamical systems (NDS) and complex systems science offer conceptual and analytic tools for evaluating homeopathic remedy effects. Previous animal studies demonstrate that homeopathic medicines alter delta electroencephalographic (EEG) slow wave sleep. The present study extended findings of remedy-related sleep stage alterations in human subjects by testing the feasibility of using two different NDS analytic approaches to assess remedy effects on human slow wave sleep EEG. Methods Subjects (N=54) were young adult male and female college students with a history of coffee-related insomnia who participated in a larger 4-week study of the polysomnographic effects of homeopathic medicines on home-based all-night sleep recordings. Subjects took one bedtime dose of a homeopathic remedy (Coffea cruda or Nux vomica 30c). We computed multiscale entropy (MSE) and the correlation dimension (Mekler-D2) for stage 3 and 4 slow wave sleep EEG sampled in artifact-free 2-minute segments during the first two rapid-eye-movement (REM) cycles for remedy and post-remedy nights, controlling for placebo and post-placebo night effects. Results MSE results indicate significant, remedy-specific directional effects, especially later in the night (REM cycle 2) (CC: remedy night increases and post-remedy night decreases in MSE at multiple sites for both stages 3 and 4 in both REM cycles; NV: remedy night decreases and post-remedy night increases, mainly in stage 3 REM cycle 2 MSE). D2 analyses yielded more sporadic and inconsistent findings. Conclusions Homeopathic medicines Coffea cruda and Nux vomica in 30c potencies alter short-term nonlinear dynamic parameters of slow wave sleep EEG in healthy young adults. MSE may provide a more sensitive NDS analytic method than D2 for evaluating homeopathic remedy effects on human sleep EEG patterns. PMID:22818237

  2. Slow-Wave Phase Shifters, Based on Thin Ferroelectric Films, for Reflectarray Antennas. Frequency-Agile Radio: Systems and Technlogies, WMG 139

    NASA Technical Reports Server (NTRS)

    Romanofsky, Robert R.

    2006-01-01

    We have developed relatively broadband K- and Ka-band phase shifters using synthetic (slow-wave) transmission lines employing coupled microstripline "varactors". The tunable coupled microstripline circuits are based on laser ablated BaSrTiO films on lanthanum aluminate substrates. A model and design criteria for these novel circuits will be presented, along with measured performance including anomalous phase delay characteristics. The critical role of phase shifter loss and transient response in reflectarray antennas will be emphasized.

  3. Comparison of shear-wave slowness profiles at 10 strong-motion sites from noninvasive SASW measurements and measurements made in boreholes

    USGS Publications Warehouse

    Brown, L.T.; Boore, D.M.; Stokoe, K.H., II

    2002-01-01

    The spectral-analysis-of-surface-waves (SASW) method is a relatively new in situ method for determining shear-wave slownesses. All measurements are made on the ground surface, making it much less costly than methods that require boreholes. The SASW method uses a number of active sources (ranging from a commercial Vibroseis truck to a small handheld hammer for the study conducted here) and different receiver spacings to map a curve of apparent phase velocity versus frequency. With the simplifying assumption that the phase velocities correspond to fundamental mode surface waves, forward modeling yields an estimate of the sub-surface shear-wave slownesses. To establish the reliability of this indirect technique, we conducted a blind evaluation of the SASW method. SASW testing was performed at 10 strong-motion stations at which borehole seismic measurements were previously or subsequently made; if previously made, the borehole results were not used for the interpretation of the SASW data, and vice-versa. Comparisons of the shear-wave slownesses from the SASW and borehole measurements are generally very good. The differences in predicted ground-motion amplifications are less than about 15% for most frequencies. In addition, both methods gave the same NEHRP site classification for seven of the sites. For the other three sites the average velocities from the downhole measurements were only 5-13 m/sec larger than the velocity defining the class C/D boundary. This study demonstrates that in many situations the SASW method can provide subsurface information suitable for site response predictions.

  4. Dual effects of trimebutine on electrical responses of gastric smooth muscles in the rat.

    PubMed

    Xue, L; Fukuta, H; Yamamoto, Y; Suzuki, H

    1995-12-27

    The effects of trimebutine on the electrical properties of smooth muscle membranes were studied in the isolated rat stomach, the objective being to elucidate the dual actions of this drug on gastric motility. Transmural nerve stimulation elicited a cholinergic excitatory junction potential (e.j.p.) and a nonadrenergic noncholinergic inhibitory junction potential (i.j.p.), and trimebutine inhibited the e.j.p. more than the i.j.p., with no significant change in the acetylcholine-induced depolarization. Trimebutine reduced the interval and, at high concentrations, the amplitude of slow waves. In enzymatically dispersed single cells, the Ca2+ current elicited by depolarization of the membrane was also inhibited by trimebutine. Thus, trimebutine increases slow wave frequency and inhibits cholinergic transmission and Ca2+ influx. The former would enhance while the latter two would depress gastric motility. PMID:8788418

  5. Dissociating the contributions of slow-wave sleep and rapid eye movement sleep to emotional item and source memory.

    PubMed

    Groch, S; Zinke, K; Wilhelm, I; Born, J

    2015-07-01

    Sleep benefits the consolidation of emotional memories, and this influence is commonly attributed to the rapid eye movement (REM) stage of sleep. However, the contributions of sleep stages to memory for an emotional episode may differ for the event per se (i.e., item memory), and the context in which it occurred (source memory). Here, we examined the effects of slow wave sleep (SWS) and REM sleep on the consolidation of emotionally negative and neutral item (picture recognition) and source memory (recall of picture-location and picture-frame color association) in humans. In Study 1, the participants (n=18) learned 48 negative and 48 neutral pictures which were presented at specific locations and preceded by colored frames that had to be associated with the picture. In a within-subject design, learning was either followed by a 3-h early-night SWS-rich or by a late-night REM sleep-rich retention interval, then retrieval was tested. Only after REM-rich sleep, and not after SWS-rich sleep, was there a significant emotional enhancement, i.e., a significantly superior retention of emotional over neutral pictures. On the other hand, after SWS-rich sleep the retention of picture-frame color associations was better than after REM-rich sleep. However, this benefit was observed only for neutral pictures; and it was completely absent for the emotional pictures. To examine whether this absent benefit reflected a suppressive effect of emotionality on associations of minor task relevance, in Study 2 we manipulated the relevance of the picture-frame color association by combining it with information about monetary reward, following otherwise comparable procedures. Here, rewarded picture-frame color associations were equally well retained over SWS-rich early sleep no matter if the frames were associated with emotional or neutral pictures. Results are consistent with the view that REM sleep favors the emotional enhancement of item memory whereas SWS appears to contribute primarily

  6. Exposure to extinction-associated contextual tone during slow-wave sleep and wakefulness differentially modulates fear expression.

    PubMed

    Ai, Si-Zhi; Chen, Jie; Liu, Jian-Feng; He, Jia; Xue, Yan-Xue; Bao, Yan-Ping; Han, Fang; Tang, Xiang-Dong; Lu, Lin; Shi, Jie

    2015-09-01

    Recent research has used context cues (odor or auditory cues) to target memories during sleep and has demonstrated that they can enhance declarative and procedural memories. However, the effects of external cues re-presented during sleep on emotional memory are still not fully understood. In the present study, we conducted a Pavlovian fear conditioning/extinction paradigm and examined the effects of re-exposure to extinction memory associated contextual tones during slow-wave sleep (SWS) and wakefulness on fear expression. The participants underwent fear conditioning on the first day, during which colored squares served as the conditioned stimulus (CS) and a mild shock served as the unconditioned stimulus (US). The next day, they underwent extinction, during which the CSs were presented without the US but accompanied by a contextual tone (pink noise). Immediately after extinction, the participants were required to take a nap or remain awake and randomly assigned to six groups. Four of the groups were separately exposed to the associated tone (i.e. SWS-Tone group and Wake-Tone group) or an irrelevant tone (control tone, CtrT) (i.e. SWS-CtrT group and Wake-CtrT group), while the other two groups were not (i.e. SWS-No Tone group and Wake-No Tone group). Subsequently, the conditioned responses to the CSs were tested to evaluate the fear expression. All of the participants included in the final analysis showed successful levels of fear conditioning and extinction. During the recall test, the fear responses were significantly higher in the SWS-Tone group than that in the SWS-No Tone group or the SWS-CtrT group, while the Wake-Tone group exhibited more attenuated fear responses than either the Wake-No Tone group or Wake-CtrT group. Otherwise, re-exposure to auditory tones during SWS did not affect sleep profiles. These results suggest that distinct conditions during which re-exposure to an extinction memory associated contextual cue contributes to differential effects on

  7. DUAL TRIGGER OF TRANSVERSE OSCILLATIONS IN A PROMINENCE BY EUV FAST AND SLOW CORONAL WAVES: SDO/AIA AND STEREO/EUVI OBSERVATIONS

    SciTech Connect

    Gosain, S.; Foullon, C.

    2012-12-20

    We analyze flare-associated transverse oscillations in a quiescent solar prominence on 2010 September 8-9. Both the flaring active region and the prominence were located near the west limb, with a favorable configuration and viewing angle. The full-disk extreme ultraviolet (EUV) images of the Sun obtained with high spatial and temporal resolution by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory show flare-associated lateral oscillations of the prominence sheet. The STEREO-A spacecraft, 81.{sup 0}5 ahead of the Sun-Earth line, provides an on-disk view of the flare-associated coronal disturbances. We derive the temporal profile of the lateral displacement of the prominence sheet by using the image cross-correlation technique. The displacement curve was de-trended and the residual oscillatory pattern was derived. We fit these oscillations with a damped cosine function with a variable period and find that the period is increasing. The initial oscillation period (P{sub 0}) is {approx}28.2 minutes and the damping time ({tau}{sub D}) {approx} 44 minutes. We confirm the presence of fast and slow EUV wave components. Using STEREO-A observations, we derive a propagation speed of {approx}250 km s{sup -1} for the slow EUV wave by applying the time-slice technique to the running difference images. We propose that the prominence oscillations are excited by the fast EUV wave while the increase in oscillation period of the prominence is an apparent effect, related to a phase change due to the slow EUV wave acting as a secondary trigger. We discuss implications of the dual trigger effect for coronal prominence seismology and scaling law studies of damping mechanisms.

  8. Parametric excitation of coupled fast and slow upper hybrid waves by counter-propagating circularly polarized lasers in a magnetized plasma

    NASA Astrophysics Data System (ADS)

    Verma, Kanika; Baliyan, Sweta; Sajal, Vivek; Kumar, Ravindra; Sharma, Navneet K.

    2016-07-01

    The parametric decay of large amplitude non-resonant beating mode of counter-propagating lasers (having a frequency difference ≥ 2 ω p ) into a pair of upper hybrid waves is studied in magnetized plasma. One of the excited upper hybrid waves (known as fast wave) having phase velocity close to c , can be utilized for electron acceleration. The coupled mode equations of fast and slow upper hybrid waves are modelled by solving equation of motion and continuity equation simultaneously (using the density perturbation technique) to derive the dispersion relation for two plasmon decay process. The growth rate of the present excitation process using right circularly polarized beating lasers is higher as compared with the growth rates of the excitation processes using ordinary and extraordinary beating lasers. However, the growth rate is not significant in the case of left circularly polarized beating lasers. The growth rate ˜ 0.15 ω p s - 1 is achieved for right circularly polarized beating lasers having v 1 , 2 / c = 0.1 for scattering angle θ s ˜ 160 ° and applied magnetic field ˜ 90 T. The growth rate of fast upper hybrid wave was reduced with the applied axial magnetic field in the present case. The present work is not only significant for the electron acceleration by fast upper hybrid wave but also for diagnostic purpose.

  9. Gastric Emptying in the Elderly.

    PubMed

    Soenen, Stijn; Rayner, Chris K; Horowitz, Michael; Jones, Karen L

    2015-08-01

    Aging is characterized by a diminished homeostatic regulation of physiologic functions, including slowing of gastric emptying. Gastric and small intestinal motor and humoral mechanisms in humans are complex and highly variable: ingested food is stored, mixed with digestive enzymes, ground into small particles, and delivered as a liquefied form into the duodenum at a rate allowing efficient digestion and absorption. In healthy aging, motor function is well preserved whereas deficits in sensory function are more apparent. The effects of aging on gastric emptying are relevant to the absorption of oral medications and the regulation of appetite, postprandial glycemia, and blood pressure. PMID:26195094

  10. Low-loss adiabatically-tapered high-contrast gratings for slow-wave modulators on SOI

    NASA Astrophysics Data System (ADS)

    Sciancalepore, Corrado; Hassan, Karim; Ferrotti, Thomas; Harduin, Julie; Duprez, Hélène; Menezo, Sylvie; Ben Bakir, Badhise

    2015-02-01

    In this communication, we report about the design, fabrication, and testing of Silicon-based photonic integrated circuits (Si-PICs) including low-loss flat-band slow-light high-contrast-gratings (HCGs) waveguides at 1.31 μm. The light slowdown is achieved in 300-nm-thick silicon-on-insulator (SOI) rib waveguides by patterning adiabatically-tapered highcontrast gratings, capable of providing slow-light propagation with extremely low optical losses, back-scattering, and Fabry-Pérot noise. In detail, the one-dimensional (1-D) grating architecture is capable to provide band-edge group indices ng ~ 25, characterized by overall propagation losses equivalent to those of the index-like propagation regime (~ 1-2 dB/cm). Such photonic band-edge slow-light regime at low propagation losses is made possible by the adiabatic apodization of such 1-D HCGs, thus resulting in a win-win approach where light slow-down regime is reached without additional optical losses penalty. As well as that, a tailored apodization optimized via genetic algorithms allows the flattening of slow-light regime over the wavelength window of interest, therefore suiting well needs for group index stability for modulation purposes and non-linear effects generation. In conclusion, such architectures provide key features suitable for power-efficient high-speed modulators in silicon as well as an extremely low-loss building block for non-linear optics (NLO) which is now available in the Si photonics toolbox.

  11. Role of the bound-state wave function in capture-loss rates: Slow proton in an electron gas

    SciTech Connect

    Alducin, M.; Nagy, I.

    2003-07-01

    Capture and loss rates for protons moving in an electron gas are calculated using many-body perturbation theory. The role of the form of the bound-state wave function for weakly bound states around the proton is analyzed. We find significant differences (up to a factor of 2 higher) in the values of Auger capture and loss rates when using Hulthen-type instead of hydrogenic wave functions. Its relevance in stopping power is briefly discussed.

  12. Percutaneous implantation of gastric electrodes - a novel technique applied in animals and in patients.

    PubMed

    Elfvin, A; Andersson, S; Abrahamsson, H; Edebo, A; Simrén, M; Lönroth, H

    2007-02-01

    Temporary electrodes implanted under general anaesthesia, or via an oral or percutaneous endoscopic gastrostomy route have been used for testing of gastric electrical stimulation (GES). We have developed a principle for percutaneous electrode implantation. Leads were constructed so that the tip could be anchored to the gastric submucosa under gastroscopic control. Acute experiments were performed in anaesthetized pigs. Three patients referred for nausea and/or vomiting and non-established indications for GES (chronic intestinal pseudo-obstruction, functional dyspepsia without gastroparesis) were evaluated. Electrode function was tested by recording and stimulation techniques. In the pigs, a slow-wave (SW) rhythm (3 min(-1)) was recorded with decrease in frequency at the end of the experiments. In the patients, implantation time from start of gastroscopy to end of electrode placement was 12-20 min. Electrode distance varied from 12 to 45 mm. Gastric electromyography showed a regular SW rhythm of about 3 min(-1). Antral pressure waves had intervals being multiples of the SW-to-SW time. With temporary GES for 7-9 days, weekly frequency of the referral symptoms decreased >80% in two patients and 33% in one patient. Temporary percutaneous gastric leads can easily be implanted and may be used for testing of GES and study of gastric electrophysiology. PMID:17244164

  13. Slow release delivery of rioprostil by an osmotic pump inhibits the formation of acute aspirin-induced gastric lesions in dogs and accelerates the healing of chronic lesions without incidence of side effects.

    PubMed

    Katz, L B; Shriver, D A

    1989-10-01

    Rioprostil, a primary alcohol prostaglandin E1 analog, inhibits gastric acid secretion and prevents gastric lesions induced by a variety of irritants in experimental animals. Because rioprostil is relatively short-acting, it would be of significant benefit clinically if its duration of action could be extended to allow once daily dosing. This investigation demonstrates that when administered via an osmotically driven pump (Osmet, Alza Corp.), rioprostil prevents the acute effects of aspirin on the gastric mucosa of dogs, accelerates the healing of aspirin-induced gastric lesions, and heals preexisting aspirin-induced gastric lesions during chronic administration of aspiring. The potency of rioprostil against acute gastric lesion formation was greatest when delivered from a 24-hr release pump (ED50 = 0.77 micrograms/kg/24 hr) and was 37 times greater than when administered as a single oral bolus. In addition, this activity occurred at doses which had little or no gastric antisecretory activity in betazole-stimulated Heidenhain pouch dogs. When delivered from a 24-hr pump, rioprostil (100 micrograms/kg/24 hr) healed preexisting aspirin-induced gastric lesions within 8 days after removal of aspirin, or after 15 days during continued daily aspirin administration. Additional studies determined that administration of rioprostil at doses of 720, 1440, or 2160 micrograms/kg/24 hr (935-2805 times the gastroprotective ED50 in 24 hr pumps) was well tolerated, with only slight, transient increases in body temperature, softening of the stools, and mild sedation at the highest dose. Administration of rioprostil daily for 5 days at 960 micrograms/kg/24 hr from 24-hr release pumps was also well tolerated by all dogs with no evidence of any accumulation of effect of rioprostil. In summary, administration of rioprostil via an osmotic pump increases its potency and duration of action against the gastric lesion-inducing effect of aspirin, and maintains a wide ratio of safety. PMID

  14. Oscillating square wave Transcranial Direct Current Stimulation (tDCS) delivered during slow wave sleep does not improve declarative memory more than sham: A randomized sham controlled crossover study

    PubMed Central

    Sahlem, Gregory L.; Badran, Bashar W.; Halford, Jonathan J.; Williams, Nolan R.; Korte, Jeffrey E.; Leslie, Kimberly; Strachan, Martha; Breedlove, Jesse L.; Runion, Jennifer; Bachman, David L.; Uhde, Thomas W.; Borckardt, Jeffery J.; George, Mark S.

    2015-01-01

    Background A 2006 trial in healthy medical students found that anodal slow oscillating tDCS delivered bi-frontally during slow wave sleep had an enhancing effect in declarative, but not procedural memory. Although there have been supporting animal studies, and similar findings in pathological groups, this study has not been replicated, or refuted, in the intervening years. We therefore tested these earlier results for replication using similar methods with the exception of current wave form (square in our study, nearly sinusoidal in the original). Objective/Hypothesis Our objective was to test the findings of a 2006 trial suggesting bi-frontal anodal tDCS during slow wave sleep enhances declarative memory. Methods Twelve students (mean age 25, 9 women) free of medical problems underwent two testing conditions (active, sham) in a randomized counterbalanced fashion. Active stimulation consisted of oscillating square wave tDCS delivered during early Non-Rapid Eye Movement (NREM) sleep. The sham condition consisted of setting-up the tDCS device and electrodes, but not turning it on during sleep. tDCS was delivered bi-frontally with anodes placed at F3/F4, and cathodes placed at mastoids. Current density was 0.517mA/CM2, and oscillated between zero and maximal current at a frequency of 0.75Hz. Stimulation occurred during five-five minute blocks with one-minute inter-block intervals (25 minutes total stimulation). The primary outcomes were both declarative memory consolidation measured by a paired word association test (PWA), and non-declarative memory, measured by a non-dominant finger-tapping test (FTT). We also recorded and analyzed sleep EEG. Results There was no difference in the number of paired word associations remembered before compared to after sleep [(active = 3.1±3.0SD more associations) (sham = 3.8±3.1S.D more associations)]. Finger tapping improved, (non-significantly) following active stimulation [(3.6±2.7 S.D. correctly typed sequences) compared to

  15. Electrogastrography in Adults and Children: The Strength, Pitfalls, and Clinical Significance of the Cutaneous Recording of the Gastric Electrical Activity

    PubMed Central

    Indrio, Flavia

    2013-01-01

    Cutaneous electrogastrography (EGG) is a non-invasive technique to record gastric myoelectrical activity from the abdominal surface. Although the recent rapid increase in the development of electrocardiography, EGG still suffers from several limitations. Currently, computer analysis of EGG provides few reliable parameters, such as frequency and the percentage of normal and altered slow wave activity (bradygastria and tachygastria). New EGG hardware and software, along with an appropriate arrangement of abdominal electrodes, could detect the coupling of the gastric slow wave from the EGG. At present, EGG does not diagnose a specific disease, but it puts in evidence stomach motor dysfunctions in different pathological conditions as gastroparesis and functional dyspepsia. Despite the current pitfalls of EGG, a multitasking diagnostic protocol could involve the EGG and the 13C-breath testing for the evaluation of the gastric emptying time—along with validated gastrointestinal questionnaires and biochemical evaluations of the main gastrointestinal peptides—to identify dyspeptic subgroups. The present review tries to report the state of the art about the pathophysiological background of the gastric electrical activity, the recording and processing methodology of the EGG with particular attention to multichannel recording, and the possible clinical application of the EGG in adult and children. PMID:23762836

  16. Learning-dependent, transient increase of activity in noradrenergic neurons of locus coeruleus during slow wave sleep in the rat: brain stem-cortex interplay for memory consolidation?

    PubMed

    Eschenko, Oxana; Sara, Susan J

    2008-11-01

    Memory consolidation during sleep is regaining attention due to a wave of recent reports of memory improvements after sleep or deficits after sleep disturbance. Neuromodulators have been proposed as possible players in this putative off-line memory processing, without much experimental evidence. We recorded neuronal activity in the rat noradrenergic nucleus locus coeruleus (LC) using chronically implanted movable microelectrodes while monitoring the behavioral state via electrocorticogram and online video recording. Extracellular recordings of physiologically identified noradrenergic neurons of LC were made in freely behaving rats for 3 h before and after olfactory discrimination learning. On subsequent days, if LC recording remained stable, additional learning sessions were made within the olfactory discrimination protocol, including extinction, reversals, learning new odors. Contrary to the long-standing dogma about the quiescence of noradrenergic neurons of LC, we found a transient increase in LC activity in trained rats during slow wave sleep (SWS) 2 h after learning. The discovery of learning-dependent engagement of LC neurons during SWS encourages exploration of brain stem-cortical interaction during this delayed phase of memory consolidation and should bring new insights into mechanisms underlying memory formation. PMID:18321875

  17. An Improved Method for the Estimation and Visualization of Velocity Fields from Gastric High-Resolution Electrical Mapping

    PubMed Central

    Paskaranandavadivel, Niranchan; O'Grady, Gregory; Du, Peng; Pullan, Andrew J; Cheng, Leo K

    2014-01-01

    High-resolution (HR) electrical mapping is an important clinical research tool for understanding normal and abnormal gastric electrophysiology. Analyzing velocities of gastric electrical activity in a reliable and accurate manner can provide additional valuable information for quantitatively and qualitatively comparing features across and within subjects, particularly during gastric dysrhythmias. In this study we compared three methods of estimating velocities from HR recordings to determine which method was the most reliable for use with gastric HR electrical mapping. The three methods were i) Simple finite difference ii) Smoothed finite difference and a iii) Polynomial based method. With synthetic data, the accuracy of the simple finite difference method resulted in velocity errors almost twice that of the smoothed finite difference and the polynomial based method, in the presence of activation time error up to 0.5s. With three synthetic cases under various noise types and levels, the smoothed finite difference resulted in average speed error of 3.2% and an average angle error of 2.0° and the polynomial based method had an average speed error of 3.3% and an average angle error of 1.7°. With experimental gastric slow wave recordings performed in pigs, the three methods estimated similar velocities (6.3-7.3 mm/s), but the smoothed finite difference method had a lower standard deviation in its velocity estimate than the simple finite difference and the polynomial based method, leading it to be the method of choice for velocity estimation in gastric slow wave propagation. An improved method for visualizing velocity fields is also presented. PMID:22207635

  18. Gastric suction

    MedlinePlus

    ... al. Position paper update: gastric lavage for gastrointestinal decontamination. Clin Toxicol (Phila) . 2013;51(3); 140-146. ... 2012:chap 49. Zeringe M, Fowler GC. Gastrointesinal decontamination. In: Pfenninger JL, Fowler GC, eds. Pfenninger & Fowler's ...

  19. Gastric Banding

    MedlinePlus

    ... gastric banding before deciding to have the procedure. Advertisements for a device or procedure may not include ... feeds Follow FDA on Twitter Follow FDA on Facebook View FDA videos on YouTube View FDA photos ...

  20. Gastric culture

    MedlinePlus

    ... test or procedure preparation (3 to 6 years) School age test or procedure preparation (6 to 12 ... immune system. The final results of the gastric culture test may take several weeks. Your provider will ...

  1. Amplitude inversion of fast and slow converted waves for fracture characterization of the Montney Formation in Pouce Coupe field, Alberta, Canada

    NASA Astrophysics Data System (ADS)

    MacFarlane, Tyler L.

    The Montney Formation of western Canada is one of the largest economically viable gas resource plays in North America with reserves of 449TCF. As an unconventional tight gas play, the well development costs are high due to the hydraulic stimulations necessary for economic success. The Pouce Coupe research project is a multidisciplinary collaboration between the Reservoir Characterization Project (RCP) and Talisman Energy Inc. with the objective of understanding the reservoir to enable the optimization of well placement and completion design. The work in this thesis focuses on identifying the natural fractures in the reservoir that act as the delivery systems for hydrocarbon flow to the wellbore. Characterization of the Montney Formation at Pouce Coupe is based on time-lapse multicomponent seismic surveys that were acquired before and after the hydraulic stimulation of two horizontal wells. Since shear-wave velocities and amplitudes of the PS-waves are known to be sensitive to near-vertical fractures, I utilize isotropic simultaneous seismic inversions on azimuthally-sectored PS1 and PS2 data sets to obtain measurements of the fast and slow shear-velocities. Specifically, I analyze two orthogonal azimuths that are parallel and perpendicular to the strike of the dominant fracture system in the field. These volumes are used to approximate the shear-wave splitting parameter (gamma(s*)) that is closely related to crack density. Since crack density has a significant impact on defining the percolation zone, the work presented in this thesis provides information that can be utilized to reduce uncertainty in the reservoirs fracture model. Isotropic AVO inversion of azimuthally limited PS-waves demonstrates sufficient sensitivity to detect contrast between the anisotropic elastic properties of the reservoir and is capable of identifying regions with high crack density. This is supported by integration with spinner production logs, hydraulic stimulation history of the field

  2. Slow wave changes in amygdala to visual, auditory, and social stimuli following lesions of the inferior temporal cortex in squirrel monkey (Saimiri sciureus).

    PubMed

    Kling, A S; Lloyd, R L; Perryman, K M

    1987-01-01

    Radiotelemetry of slow wave activity of the amygdala was recorded under a variety of conditions. Power, and the percentage of power in the delta band, increased in response to stimulation. Recordings of monkey vocalizations and slides of ethologically relevant, natural objects produced a greater increase in power than did control stimuli. The responses to auditory stimuli increased when these stimuli were presented in an unrestrained, group setting, yet the responses to the vocalizations remained greater than those following control stimuli. Both the natural auditory and visual stimuli produced a reliable hierarchy with regard to the magnitude of response. Following lesions of inferior temporal cortex, these two hierarchies are disrupted, especially in the auditory domain. Further, these same stimuli, when presented after the lesion, produced a decrease, rather than an increase, in power. Nevertheless, the power recorded from the natural stimuli was still greater than that recorded from control stimuli in that the former produced less of a decrease in power, following the lesion, than did the latter. These data, in conjunction with a parallel report on evoked potentials in the amygdala, before and after cortical lesions, lead us to conclude that sensory information, particularly auditory, available to the amygdala, following the lesion, is substantially the same, and that it is the interpretation of this information, by the amygdala, which is altered by the cortical lesion. PMID:3566692

  3. Diagnosis and treatment of gastric emptying disorders. Clinical usefulness of radionuclide measurements of gastric emptying

    SciTech Connect

    Pellegrini, C.A.; Broderick, W.C.; Van Dyke, D.; Way, L.W.

    1983-01-01

    We studied 53 patients with severe gastrointestinal symptoms thought to be due to a gastric motility disorder. Sixty-six percent had had a previous operation on the stomach, and 21 percent had insulin-dependent diabetes mellitus. Based on clinical, radiographic, and endoscopic findings, 48 patients were thought to have gastroparesis, 3 were thought to have dumping, and 2 had no diagnosis. Measurement of gastric emptying of solids showed that gastric emptying was normal in 12 patients, rapid in 15 patients, and slow in 26 patients. Further evaluation showed that half of the patients with normal gastric emptying, and one third of those with rapid gastric emptying had other diseases of the gastrointestinal tract that responded well to surgery. Of those patients with dumping, diet modification was effective in 40 percent, and half of those who did not respond to dietary manipulations did well after reoperation. Nineteen patients with delayed gastric emptying were treated with metoclopramide. Sixty percent of those without previous gastric surgery responded, whereas only 25 percent of those with previous gastric surgery had good results. The rate of gastric emptying improved following reoperation in 9 (90 percent) of 10 patients with delayed gastric emptying (4 who had not responded to metoclopramide). Gastric emptying was measured again in 15 patients after treatment. The changes after treatment paralleled the clinical response. These studies indicate that gastroparesis cannot be reliably diagnosed on the basis of clinical findings and standard tests. Gastric emptying studies are essential to diagnose and treat patients thought to have gastric motility disorders, and to evaluate the results of therapy.

  4. Hippocampal formation is involved in movement selection: evidence from medial septal cholinergic modulation and concurrent slow-wave (theta rhythm) recording.

    PubMed

    Oddie, S D; Kirk, I J; Whishaw, I Q; Bland, B H

    1997-11-01

    Hippocampal rhythmical slow-wave field activity which occurs in response to sensory stimulation is predominantly cholinergic (atropine-sensitive theta rhythm), can precede movement initiation, and co-occurs during non-cholinergic theta rhythm associated with ongoing movement (atropine-resistant). This relationship suggests that theta rhythm plays some role in movement control. The present naturalistic experiments tested the idea that atropine-sensitive theta rhythm plays a role in sensory integration and planning required for initiating appropriate movements. One of a pair of hungry rats, the victim, implanted with hippocampal field recording electrodes, a septal injection cannula, and a posterior hypothalamic stimulating electrode, was given food which the other, the robber, tries to steal. Since the victim dodges from the robber with a latency, distance, and velocity dependent upon the size of the food, elapsed eating time, and proximity of the robber, the movement requires sensory integration and planning. Although eating behavior seemed normal, atropine-sensitive theta rhythm and dodging were disrupted by an infusion of a cholinergic antagonist into the medial septum. When the victim in turn attempted to steal the food back, Type 1 theta rhythm was present and robbery attempts seemed normal. Prior to cholinergic blockade, posterior hypothalamic stimulation produced theta rhythm and dodges, even in the absence of the robber, but following injections, atropine-sensitive theta rhythm and dodging were absent as the animals dropped the food and ran. The results provide the first evidence to link atropine-sensitive theta rhythm and hippocampal structures to a role in sensory integration and planning for the initiation of movement. PMID:9404626

  5. The dream-lag effect: Selective processing of personally significant events during Rapid Eye Movement sleep, but not during Slow Wave Sleep.

    PubMed

    van Rijn, E; Eichenlaub, J-B; Lewis, P A; Walker, M P; Gaskell, M G; Malinowski, J E; Blagrove, M

    2015-07-01

    Incorporation of details from waking life events into Rapid Eye Movement (REM) sleep dreams has been found to be highest on the night after, and then 5-7 nights after events (termed, respectively, the day-residue and dream-lag effects). In experiment 1, 44 participants kept a daily log for 10 days, reporting major daily activities (MDAs), personally significant events (PSEs), and major concerns (MCs). Dream reports were collected from REM and Slow Wave Sleep (SWS) in the laboratory, or from REM sleep at home. The dream-lag effect was found for the incorporation of PSEs into REM dreams collected at home, but not for MDAs or MCs. No dream-lag effect was found for SWS dreams, or for REM dreams collected in the lab after SWS awakenings earlier in the night. In experiment 2, the 44 participants recorded reports of their spontaneously recalled home dreams over the 10 nights following the instrumental awakenings night, which thus acted as a controlled stimulus with two salience levels, high (sleep lab) and low (home awakenings). The dream-lag effect was found for the incorporation into home dreams of references to the experience of being in the sleep laboratory, but only for participants who had reported concerns beforehand about being in the sleep laboratory. The delayed incorporation of events from daily life into dreams has been proposed to reflect REM sleep-dependent memory consolidation. However, an alternative emotion processing or emotional impact of events account, distinct from memory consolidation, is supported by the finding that SWS dreams do not evidence the dream-lag effect. PMID:25683202

  6. Randomised clinical trial of the effects of prolonged-release melatonin, temazepam and zolpidem on slow-wave activity during sleep in healthy people.

    PubMed

    Arbon, Emma L; Knurowska, Malgorzata; Dijk, Derk-Jan

    2015-07-01

    Current pharmacological treatments for insomnia include benzodiazepine and non-benzodiazepine hypnotics targeting γ-aminobutyric acid (GABA)A receptors, as well as agonists of the melatonin receptors MT1 and MT2. Melatonin, temazepam and zolpidem are thought to exert their effect through different mechanisms of action, but whether this leads to differential effects on electroencephalogram (EEG) power spectra during sleep in middle-aged people is currently not known. To establish whether the effects of prolonged-release melatonin (2 mg) on the nocturnal sleep EEG are different to those of temazepam (20 mg) and zolpidem (10 mg). Sixteen healthy men and women aged 55-64 years participated in a double-blind, placebo-controlled, four-way cross-over trial. Nocturnal sleep was assessed with polysomnography and spectral analysis of the EEG. The effects of single oral doses of prolonged-release melatonin, temazepam and zolpidem on EEG slow-wave activity (SWA, 0.75-4.5 Hz) and other frequencies during nocturnal non-rapid eye movement (NREM) sleep were compared. In an entire night analysis prolonged-release melatonin did not affect SWA, whereas temazepam and zolpidem significantly reduced SWA compared with placebo. Temazepam significantly reduced SWA compared with prolonged-release melatonin. Prolonged-release melatonin only reduced SWA during the first third of the night compared with placebo. These data show that the effects of prolonged-release melatonin on the nocturnal sleep EEG are minor and are different from those of temazepam and zolpidem; this is likely due to the different mechanisms of action of the medications. PMID:25922426

  7. [Gastric Acid].

    PubMed

    Ruíz Chávez, R

    1996-01-01

    Gastric acid, a product of parietal cells secretion, full fills multiple biological roles which are absolutely necessary to keep corporal homeostasis. The production of the acid depends upon an effector cellular process represented in the first step by histamine, acetilcholine and gastrin, first messengers of the process. These interact with specific receptors than in sequence activate second messengers -cAMP and the calcium-calmodulin system- which afterwards activate a kinase. An specific protein is then phosphorilated by this enzyme, being the crucial factor that starts the production of acid. Finally, a proton bomb, extrudes the acid towards the gastric lumen. The secretion process mentioned above, is progressive lyactivated in three steps, two of which are stimulators -cephalic and gastric phases- and the other one inhibitor or intestinal phase. These stages are started by mental and neurological phenomena -thought, sight, smell or memory-; by food, drugs or other ingested substances; and by products of digestion. Changes in regulation of acid secretion, in the structure of gastro-duodenal mucosal barrier by a wide spectrum of factors and agents including food, drugs and H. pylori, are the basis of acid-peptic disease, entity in which gastric acid plays a fundamental role. From the therapeutic point of view, so at the theoretical as at the practical levels, t is possible to interfere with the secretion of acid by neutralization of some of the steps of the effector cellular process. An adequate knowledge of the basics related to gastric acid, allows to create strategies for the clinical handling of associated pathology, specifically in relation to peptic acid disease in all of the known clinical forms. PMID:12165790

  8. Gastric dysmotility in healthy first-degree relatives of patients with schizophrenia.

    PubMed

    Berger, Sandy; Hocke, Michael; Bär, Karl-Jürgen

    2010-10-01

    Gastric dysmotility has been reported in patients suffering from major depression or schizophrenia. An increased sympathetic activity modulating the gastric pacemaker located in the antrum of the stomach has been suggested as the underlying pathology. Similar to patients suffering from schizophrenia, their first-degree relatives showed alterations in cardiac autonomic modulation. Here we aimed to investigate gastric myoelectrical activity in healthy relatives of patients suffering from paranoid schizophrenia. Electrogastrography (EGG) was performed before and after test meal ingestion in 20 patients with paranoid schizophrenia, 20 of their first-degree relatives and 20 healthy matched controls. Autonomic and abdominal symptoms were assessed by the autonomic symptom score as previously reported. Autonomic parameters were correlated with the positive and negative syndrome scale (PANSS). Only minimal differences were observed before test meal ingestion between relatives and controls. In contrast, after test meal ingestion we observed a significantly increased tachygastria within the signal of the gastric pacemaker in relatives compared to controls, whereas normogastria was reduced. Significant difference between relatives and controls were also found for postprandial ICDF (instability coefficient of dominant frequency) and slow wave, which represents the dominant frequency of gastric pacemaker activity, indicating gastric dysmotility in relatives. Between relatives and patients just a difference for ICDP (instability coefficient of dominant power) was observed. After stimulation of the enteric nervous system we have observed an increased sympathetic modulation in first-degree relatives of patients suffering from schizophrenia. This result adds evidence to an ongoing debate on the genetic influence of autonomic dysfunction in the disease. PMID:20654673

  9. A biophysically based finite-state machine model for analyzing gastric experimental entrainment and pacing recordings.

    PubMed

    Sathar, Shameer; Trew, Mark L; Du, Peng; O'Grady, Greg; Cheng, Leo K

    2014-04-01

    Gastrointestinal motility is coordinated by slow waves (SWs) generated by the interstitial cells of Cajal (ICC). Experimental studies have shown that SWs spontaneously activate at different intrinsic frequencies in isolated tissue, whereas in intact tissues they are entrained to a single frequency. Gastric pacing has been used in an attempt to improve motility in disorders such as gastroparesis by modulating entrainment, but the optimal methods of pacing are currently unknown. Computational models can aid in the interpretation of complex in vivo recordings and help to determine optimal pacing strategies. However, previous computational models of SW entrainment are limited to the intrinsic pacing frequency as the primary determinant of the conduction velocity, and are not able to accurately represent the effects of external stimuli and electrical anisotropies. In this paper, we present a novel computationally efficient method for modeling SW propagation through the ICC network while accounting for conductivity parameters and fiber orientations. The method successfully reproduced experimental recordings of entrainment following gastric transection and the effects of gastric pacing on SW activity. It provides a reliable new tool for investigating gastric electrophysiology in normal and diseased states, and to guide and focus future experimental studies. PMID:24276722

  10. Gastric Carcinoids

    PubMed Central

    Borch, Kurt; Ahrén, Bo; Ahlman, Håkan; Falkmer, Sture; Granérus, Göran; Grimelius, Lars

    2005-01-01

    Objective: To analyze tumor biology and the outcome of differentiated treatment in relation to tumor subtype in patients with gastric carcinoid. Background: Gastric carcinoids may be subdivided into ECL cell carcinoids (type 1 associated with atrophic gastritis, type 2 associated with gastrinoma, type 3 without predisposing conditions) and miscellaneous types (type 4). The biologic behavior and prognosis vary considerably in relation to type. Methods: A total of 65 patients from 24 hospitals (51 type 1, 1 type 2, 4 type 3, and 9 type 4) were included. Management recommendations were issued for newly diagnosed cases, that is, endoscopic or surgical treatment of type 1 and 2 carcinoids (including antrectomy to abolish hypergastrinemia) and radical resection for type 3 and 4 carcinoids. Results: Infiltration beyond the submucosa occurred in 9 of 51 type 1, 4 of 4 type 3, and 7 of 9 type 4 carcinoids. Metastases occurred in 4 of 51 type 1 (3 regional lymph nodes, 1 liver), the single type 2 (regional lymph nodes), 3 of 4 type 3 (all liver), and 7 of 9 type 4 carcinoids (all liver). Of the patients with type 1 carcinoid, 3 had no specific treatment, 40 were treated with endoscopic or surgical excision (in 10 cases combined with antrectomy), 7 underwent total gastrectomy, and 1 underwent proximal gastric resection. Radical tumor removal was not possible in 2 of 4 patients with type 3 and 7 of 9 patients with type 4 carcinoid. Five- and 10-year crude survival rates were 96.1% and 73.9% for type 1 (not different from the general population), but only 33.3% and 22.2% for type 4 carcinoids. Conclusion: Subtyping of gastric carcinoids is helpful in the prediction of malignant potential and long-term survival and is a guide to management. Long-term survival did not differ from that of the general population regarding type 1 carcinoids but was poor regarding type 4 carcinoids. PMID:15973103

  11. Gastric infarction following gastric bypass surgery

    PubMed Central

    Do, Patrick H; Kang, Young S; Cahill, Peter

    2016-01-01

    Gastric infarction is an extremely rare occurrence owing to the stomach’s extensive vascular supply. We report an unusual case of gastric infarction following gastric bypass surgery. We describe the imaging findings and discuss possible causes of this condition. PMID:27200168

  12. The Effects of Banha-sasim-tang on Dyspeptic Symptoms and Gastric Motility in Cases of Functional Dyspepsia: A Randomized, Double-Blind, Placebo-Controlled, and Two-Center Trial

    PubMed Central

    Ko, Seok-Jae; Han, Gajin; Yeo, Inkwon; Ryu, Bongha; Kim, Jinsung

    2013-01-01

    Introduction. Functional dyspepsia (FD) is highly prevalent, and no standard treatments exist for this condition. Herbal prescriptions are widely used to treat FD. In traditional Korean medicine, Banha-sasim-tang (BST) is a famous herbal prescription for dyspepsia. This study aimed to evaluate the efficacy of BST and to examine the relationship between gastric slow waves and dyspeptic symptoms. Materials and Methods. In total, 100 FD patients were recruited; BST or placebo was administered for 6 weeks. The gastrointestinal symptom scale, FD-related quality of life scale, and frequency or power variables regarding gastric slow waves were measured at 0, 6, and 14 weeks. Results. There were no significant differences in the overall dyspeptic symptoms or quality of life between the BST and placebo groups. However, early satiety was significantly improved in the BST group (P = 0.009, at 6 weeks by intention-to-treat analysis). Abnormal gastric dysrhythmias and power ratios were also significantly improved by BST. Conclusion. BST had no significant effects on FD. However, early satiety appeared to improve after BST administration. Electrogastrography may be a useful technique for assessing changes in gastric motility dysfunction after interventions for FD. Further investigation focused on specific symptoms or subtypes of FD is required. PMID:23861702

  13. Differential gene expression in the murine gastric fundus lacking interstitial cells of Cajal

    PubMed Central

    Daigo, Yataro; Takayama, Ichiro; Ponder, Bruce AJ; Caldas, Carlos; Ward, Sean M; Sanders, Kenton M; Fujino, Masayuki A

    2003-01-01

    Background The muscle layers of murine gastric fundus have no interstitial cells of Cajal at the level of the myenteric plexus and only possess intramuscular interstitial cells and this tissue does not generate electric slow waves. The absence of intramuscular interstitial cells in W/WV mutants provides a unique opportunity to study the molecular changes that are associated with the loss of these intercalating cells. Method The gene expression profile of the gastric fundus of wild type and W/WV mice was assayed by murine microarray analysis displaying a total of 8734 elements. Queried genes from the microarray analysis were confirmed by semi-quantitative reverse transcription-polymerase chain reaction. Results Twenty-one genes were differentially expressed in wild type and W/WV mice. Eleven transcripts had 2.0–2.5 fold higher mRNA expression in W/WV gastric fundus when compared to wild type tissues. Ten transcripts had 2.1–3.9 fold lower expression in W/WV mutants in comparison with wild type animals. None of these genes have ever been implicated in any bowel motility function. Conclusions These data provides evidence that several important genes have significantly changed in the murine fundus of W/WV mutants that lack intramuscular interstitial cells of Cajal and have reduced enteric motor neurotransmission. PMID:12795813

  14. Slow Pseudotachylites

    NASA Astrophysics Data System (ADS)

    Pec, M.; Stunitz, H.; Heilbronner, R.

    2011-12-01

    Tectonic pseudotachylites as solidified, friction induced melts are believed to be the only unequivocal evidence for paleo-earthquakes. Earthquakes occur when fast slip (1 - 3 m/s) propagates on a localized failure plane and are always related with stress drops. The mechanical work expended, together with the rock composition and the efficiency of thermal dissipation, controls whether the temperature increase on a localized slip plane will be sufficient to induce fusion. We report the formation of pseudotachylites during steady-state plastic flow at slow bulk shear strain rates (~10^-3 to ~10^-5 /s corresponding to slip rates of ~10^-6 to ~10^-8 m/s) in experiments performed at high confining pressures (500 MPa) and temperatures (300°C) corresponding to a depth of ~15 km. Crushed granitioid rock (Verzasca gneiss), grain size ≤ 200 μm, with 0.2 wt% water added was placed between alumina forcing blocks pre-cut at 45°, weld-sealed in platinum jackets and deformed with a constant displacement rate in a solid medium deformation apparatus (modified Griggs rig). Microstructural observations show the development of a S-C-C' fabric with C' slip zones being the dominant feature. Strain hardening in the beginning of the experiment is accompanied with compaction which is achieved by closely spaced R1 shears pervasively cutting the whole gouge zone and containing fine-grained material (d < 100 nm). The peak strength is achieved at γ ~ 2 at shear stress levels of 1350-1450 MPa when compaction ceases. During further deformation, large local displacements (γ > 10) are localized in less densely spaced, ~10 μm thick C'-C slip zones which develop predominantly in feldspars and often contain micas. In TEM, they appear to have no porosity consisting of partly amorphous material and small crystalline fragments with the average grain size of 20 nm. After the peak strength, the samples weaken by ~20 MPa and continue deforming up to γ ~ 4 without any stress drops. Strain

  15. Stomach (Gastric) Cancer Screening

    MedlinePlus

    ... Treatment Stomach Cancer Prevention Stomach Cancer Screening Research Stomach (Gastric) Cancer Screening (PDQ®)–Patient Version What is ... These are called diagnostic tests . General Information About Stomach (Gastric) Cancer Key Points Stomach cancer is a ...

  16. Slow earthquakes coincident with episodic tremors and slow slip events.

    PubMed

    Ito, Yoshihiro; Obara, Kazushige; Shiomi, Katsuhiko; Sekine, Shutaro; Hirose, Hitoshi

    2007-01-26

    We report on the very-low-frequency earthquakes occurring in the transition zone of the subducting plate interface along the Nankai subduction zone in southwest Japan. Seismic waves generated by very-low-frequency earthquakes with seismic moment magnitudes of 3.1 to 3.5 predominantly show a long period of about 20 seconds. The seismicity of very-low-frequency earthquakes accompanies and migrates with the activity of deep low-frequency tremors and slow slip events. The coincidence of these three phenomena improves the detection and characterization of slow earthquakes, which are thought to increase the stress on updip megathrust earthquake rupture zones. PMID:17138867

  17. Mixed-mode bursting oscillations: dynamics created by a slow passage through spike-adding canard explosion in a square-wave burster.

    PubMed

    Desroches, Mathieu; Kaper, Tasso J; Krupa, Martin

    2013-12-01

    This article concerns the phenomenon of Mixed-Mode Bursting Oscillations (MMBOs). These are solutions of fast-slow systems of ordinary differential equations that exhibit both small-amplitude oscillations (SAOs) and bursts consisting of one or multiple large-amplitude oscillations (LAOs). The name MMBO is given in analogy to Mixed-Mode Oscillations, which consist of alternating SAOs and LAOs, without the LAOs being organized into burst events. In this article, we show how MMBOs are created naturally in systems that have a spike-adding bifurcation or spike-adding mechanism, and in which the dynamics of one (or more) of the slow variables causes the system to pass slowly through that bifurcation. Canards are central to the dynamics of MMBOs, and their role in shaping the MMBOs is two-fold: saddle-type canards are involved in the spike-adding mechanism of the underlying burster and permit one to understand the number of LAOs in each burst event, and folded-node canards arise due to the slow passage effect and control the number of SAOs. The analysis is carried out for a prototypical fourth-order system of this type, which consists of the third-order Hindmarsh-Rose system, known to have the spike-adding mechanism, and in which one of the key bifurcation parameters also varies slowly. We also include a discussion of the MMBO phenomenon for the Morris-Lecar-Terman system. Finally, we discuss the role of the MMBOs to a biological modeling of secreting neurons. PMID:24387585

  18. Mixed-mode bursting oscillations: Dynamics created by a slow passage through spike-adding canard explosion in a square-wave burster

    NASA Astrophysics Data System (ADS)

    Desroches, Mathieu; Kaper, Tasso J.; Krupa, Martin

    2013-12-01

    This article concerns the phenomenon of Mixed-Mode Bursting Oscillations (MMBOs). These are solutions of fast-slow systems of ordinary differential equations that exhibit both small-amplitude oscillations (SAOs) and bursts consisting of one or multiple large-amplitude oscillations (LAOs). The name MMBO is given in analogy to Mixed-Mode Oscillations, which consist of alternating SAOs and LAOs, without the LAOs being organized into burst events. In this article, we show how MMBOs are created naturally in systems that have a spike-adding bifurcation or spike-adding mechanism, and in which the dynamics of one (or more) of the slow variables causes the system to pass slowly through that bifurcation. Canards are central to the dynamics of MMBOs, and their role in shaping the MMBOs is two-fold: saddle-type canards are involved in the spike-adding mechanism of the underlying burster and permit one to understand the number of LAOs in each burst event, and folded-node canards arise due to the slow passage effect and control the number of SAOs. The analysis is carried out for a prototypical fourth-order system of this type, which consists of the third-order Hindmarsh-Rose system, known to have the spike-adding mechanism, and in which one of the key bifurcation parameters also varies slowly. We also include a discussion of the MMBO phenomenon for the Morris-Lecar-Terman system. Finally, we discuss the role of the MMBOs to a biological modeling of secreting neurons.

  19. Loss of Interstitial Cells of Cajal and Patterns of Gastric Dysrhythmia in Patients with Chronic Unexplained Nausea and Vomiting

    PubMed Central

    Angeli, Timothy R.; Cheng, Leo K.; Du, Peng; Wang, Tim Hsu-Han; Bernard, Cheryl E.; Vannucchi, Maria-Giuliana; Faussone-Pellegrini, Maria Simonetta; Lahr, Christopher; Vather, Ryash; Windsor, John A.; Farrugia, Gianrico; Abell, Thomas L.; O’Grady, Gregory

    2015-01-01

    Background & Aims Chronic unexplained nausea and vomiting (CUNV) is a debilitating disease of unknown cause. Symptoms of CUNV substantially overlap with those of gastroparesis, so the diseases therefore may share pathophysiologic features. We investigated this hypothesis by quantifying densities of interstitial cells of Cajal (ICCs) and mapping slow wave abnormalities in patients with CUNV vs controls. Methods Clinical data and gastric biopsy specimens were collected from 9 consecutive patients with at least 6 months of continuous symptoms of CUNV, but normal gastric emptying, treated at the University of Mississippi Medical Center, and from 9 controls (individuals undergoing bariatric surgery but free of gastrointestinal disease or diabetes). ICCs were counted and ultrastructural analyses were performed on tissue samples. Slow-wave propagation profiles were defined by high-resolution electrical mapping (256 electrodes; 36 cm2). Results from patients with CUNV were compared to those of controls as well as patients with gastroparesis who were previously studied by identical methods. Results Patients with CUNV had fewer ICCs than controls (mean 3.5 vs 5.6 bodies/field; P<.05), with mild ultrastructural abnormalities in the remaining ICCs. Slow-wave dysrhythmias were identified in all 9 subjects with CUNV vs only 1/9 controls. Dysrhythmias included abnormalities of initiation (stable ectopic pacemakers, unstable focal activities) and conduction (retrograde propagation, wave front collisions, conduction blocks, and re-entry), operating across bradygastric, normal (range 2.4−3.7 cycles/min), and tachygastric frequencies; dysrhythmias showed velocity anisotropy (mean 3.3 mm/s longitudinal vs 7.6 mm/s circumferential, P<.01). ICCs were less depleted in patients with CUNV than those with gastroparesis (mean 3.5 vs 2.3 bodies/field; P<.05), but slow-wave dysrhythmias were similar between groups. Conclusions This study defined cellular and bioelectrical abnormalities in

  20. H. Pylori in a gastric schwannoma: a case report.

    PubMed

    Lavy, Daniel S; Paulin, Ethan T; Parker, Mitchell I; Zhang, Bin; Parker, Glenn S; Schwartz, Mark R

    2016-04-01

    Schwannomas are benign, often asymptomatic, slow-growing tumors that originate from Schwann cells of the neural sheath. Although H. Pylori has been associated with gastric adenocarcinoma, there has never been a recorded association with schwannoma formation. We present a 64-year-old woman who underwent a laparoscopic partial wedge gastrectomy for an incidentally discovered gastric mass. Histologic examination was consistent with schwannoma; however, chronic inflammation with microorganisms morphologically consistent with H. Pylori was also present. This case suggests the first recorded case of H. Pylori in an immunohistochemically confirmed gastric schwannoma. PMID:27162787

  1. H. Pylori in a gastric schwannoma: a case report

    PubMed Central

    Paulin, Ethan T.; Parker, Mitchell I.; Zhang, Bin; Parker, Glenn S.; Schwartz, Mark R.

    2016-01-01

    Schwannomas are benign, often asymptomatic, slow-growing tumors that originate from Schwann cells of the neural sheath. Although H. Pylori has been associated with gastric adenocarcinoma, there has never been a recorded association with schwannoma formation. We present a 64-year-old woman who underwent a laparoscopic partial wedge gastrectomy for an incidentally discovered gastric mass. Histologic examination was consistent with schwannoma; however, chronic inflammation with microorganisms morphologically consistent with H. Pylori was also present. This case suggests the first recorded case of H. Pylori in an immunohistochemically confirmed gastric schwannoma. PMID:27162787

  2. Slow earthquakes triggered by typhoons.

    PubMed

    Liu, ChiChing; Linde, Alan T; Sacks, I Selwyn

    2009-06-11

    The first reports on a slow earthquake were for an event in the Izu peninsula, Japan, on an intraplate, seismically active fault. Since then, many slow earthquakes have been detected. It has been suggested that the slow events may trigger ordinary earthquakes (in a context supported by numerical modelling), but their broader significance in terms of earthquake occurrence remains unclear. Triggering of earthquakes has received much attention: strain diffusion from large regional earthquakes has been shown to influence large earthquake activity, and earthquakes may be triggered during the passage of teleseismic waves, a phenomenon now recognized as being common. Here we show that, in eastern Taiwan, slow earthquakes can be triggered by typhoons. We model the largest of these earthquakes as repeated episodes of slow slip on a reverse fault just under land and dipping to the west; the characteristics of all events are sufficiently similar that they can be modelled with minor variations of the model parameters. Lower pressure results in a very small unclamping of the fault that must be close to the failure condition for the typhoon to act as a trigger. This area experiences very high compressional deformation but has a paucity of large earthquakes; repeating slow events may be segmenting the stressed area and thus inhibiting large earthquakes, which require a long, continuous seismic rupture. PMID:19516339

  3. Synchronization Properties of Slow Cortical Oscillations

    NASA Astrophysics Data System (ADS)

    Takekawa, T.; Aoyagi, T.; Fukai, T.

    During slow-wave sleep, the brain shows slow oscillatory activity with remarkable long-range synchrony. Intracellular recordings show that the slow oscillation consists of two phases: an textit{up} state and a textit{down} state. Deriving the phase-response function of simplified neuronal systems, we examine the synchronization properties on slow oscillations between the textit{up} state and the textit{down} state. As a result, the strange interaction functions are found in some parameter ranges. These functions indicate that the states with the smaller phase lag than a critical value are all stable.

  4. Impaired gastric myoelectricity in patients with chronic pancreatitis: Role of maldigestion

    PubMed Central

    Lu, Ching-Liang; Chen, Chih-Yen; Luo, Jiing-Chyuan; Chang, Full-Young; Lee, Shou-Dong; Wu, Han-Chang; Chen, JDZ

    2005-01-01

    AIM: To investigate whether gastric myoelectrical activity was impaired in patients with chronic pancreatitis (CP) and to explore the role of pancreatic enzyme in regulating gastric myoelectrical activity. METHODS: Twenty CP patients and 20 controls participated in the study. Gastric myoelectrical activity was recorded by a homemade electrogastrography (EGG) device. Two experiments were carried out. In experiment one, EGG was recorded in both controls and CP patients. While in experiment two, either pancreatic enzymes or placebo was given together with test meals. Spectral analysis was used to generate various EGG parameters. RESULTS: The control subjects, but not the CP patients, showed typically increased postprandial dominant frequency. The postprandial dominant power (DP) increment (2.24±1.13 vs 5.35±0.96 dB, P = 0.04) and the percentage of normal 2-4 cpm slow waves (63.0±3.8% vs 77.4 ±3.1%, P<0.05) were lower in CP patients when compared with the control. In the 20 CP patients, the DP increment (4.76±1.02 vs 2.53±1.20 dB, P<0.05) and the postprandial percentage of normal 2-4 cpm (74.4±2.8% vs 64.8 ±5.7%, P<0.05) were significantly higher with pancreatic enzyme replacement than the placebo. CONCLUSION: CP patients have an abnormal postprandial stomach myoelectricity showing poor response in dominant frequency/power and regularity, whereas these abnormalities are corrected after pancreatic enzyme replacement. Maldigestion is likely to be the factor leading to abnormal postprandial gastric myoelectricity of CP patients. PMID:15637747

  5. Gastric tissue biopsy and culture

    MedlinePlus

    Culture - gastric tissue; Biopsy - gastric tissue ... of organisms that cause infection. A gastric tissue culture may be considered normal if it does not show certain bacteria. Stomach acids normally prevent too much bacteria from growing.

  6. OBSERVED DAMPING OF THE SLOW MAGNETOACOUSTIC MODE

    SciTech Connect

    Marsh, M. S.; Walsh, R. W.; De Moortel, I. E-mail: mmarsh@uclan.ac.uk

    2011-06-20

    Spectroscopic and stereoscopic imaging observations of slow magnetoacoustic wave propagation within a coronal loop are investigated to determine the decay length scale of the slow magnetoacoustic mode in three dimensions and the density profile within the loop system. The slow wave is found to have an e-folding decay length scale of 20,000{sup +4000}{sub -3000} km with a uniform density profile along the loop base. These observations place quantitative constraints on the modeling of wave propagation within coronal loops. Theoretical forward modeling suggests that magnetic field line divergence is the dominant damping factor and thermal conduction is insufficient, given the observed parameters of the coronal loop temperature, density, and wave mode period.

  7. Relation between gastric emptying rate and rate of intraluminal lipolysis.

    PubMed

    Maes, B D; Ghoos, Y F; Geypens, B J; Hiele, M I; Rutgeerts, P J

    1996-01-01

    The variable gastric emptying rate of a test meal is one of the major problems in evaluating accurately gastrointestinal physiological functions beyond the stomach. The aim of this study was to evaluate the effect of the gastric emptying rate on the rate of intraluminal lipolysis. Thirty four subjects without pancreatic disease (21 with a normal gastric emptying and 13 with a known slow gastric emptying) and 14 subjects with pancreatic disease (four without and 10 with pancreatic insufficiency) were studied using a dual labelled breath test. The test meal consisted of one egg, 60 grams of white bread, 10 grams of margarine, and 150 ml of water (350 kcal). The egg yolk was labelled with 91 mg of 13C-octanoic acid, the margarine was labelled with 296 kBq of distearyl-2-14C-octanoyl-glycerol. Breath samples were taken every 15 minutes during six hours and analysed for 13CO2 and 14CO2 content. The gastric emptying rate of the meal was evaluated by the gastric emptying coefficient, the half emptying time, and the lag phase; the rate of intraluminal lipolysis was evaluated by the six hours cumulative 14CO2 excretion. Despite a clear distinction in the rate of intraluminal lipolysis, no difference could be detected in gastric emptying rate of the test meal between subjects without and with pancreatic disease. In subjects with pancreatic insufficiency, intraluminal hydrolysis was the rate limiting process in fat assimilation; in patients without pancreatic insufficiency, however, gastric emptying could be rate limiting. Therefore, patients with known slow gastric emptying, displayed a significantly decreased rate of intraluminal lipolysis compared with normal controls. This decrease could be corrected for accurately using a correction factor based on the gastric emptying coefficient. In conclusion, the combined 13C-octanoic acid and 14C-mixed triglyceride breath test permits the measurement of gastric emptying rate and intraluminal lipolysis simultaneously in a minimally

  8. Update on gastric varices

    PubMed Central

    Triantafyllou, Maria; Stanley, Adrian J

    2014-01-01

    Although less common than oesophageal variceal haemorrhage, gastric variceal bleeding remains a serious complication of portal hypertension, with a high associated mortality. In this review we provide an update on the aetiology, classification and management of gastric varices, including acute bleeding, prevention of rebleeding and primary prophylaxis. We describe the optimum management strategies for gastric varices including drug, endoscopic and radiological therapies, focusing on recent published evidence. PMID:24891929

  9. Growth of Pollen Tubes of Papaver rhoeas Is Regulated by a Slow-Moving Calcium Wave Propagated by Inositol 1,4,5-Trisphosphate.

    PubMed Central

    Franklin-Tong, V. E.; Drobak, B. K.; Allan, A. C.; Watkins, PAC.; Trewavas, A. J.

    1996-01-01

    A signaling role for cytosolic free Ca2+ ([Ca2+]i) in regulating Papaver rhoeas pollen tube growth during the self-incompatibility response has been demonstrated previously. In this article, we investigate the involvement of the phosphoinositide signal transduction pathway in Ca2+-mediated pollen tube inhibition. We demonstrate that P. rhoeas pollen tubes have a Ca2+-dependent polyphosphoinositide-specific phospholipase C activity that is inhibited by neomycin. [Ca2+]i imaging after photolysis of caged inositol (1,4,5)-trisphosphate (Ins[1,4,5]P3) in pollen tubes demonstrated that Ins(1,4,5)P3 could induce Ca2+ release, which was inhibited by heparin and neomycin. Mastoparan, which stimulated Ins(1,4,5)P3 production, also induced a rapid increase in Ca2+, which was inhibited by neomycin. These data provide direct evidence for the involvement of a functional phosphoinositide signal-transducing system in the regulation of pollen tube growth. We suggest that the observed Ca2+ increases are mediated, at least in part, by Ins(1,4,5)P3-induced Ca2+ release. Furthermore, we provide data suggesting that Ca2+ waves, which have not previously been reported in plant cells, can be induced in pollen tubes. PMID:12239415

  10. Acoustic power absorption and enhancement generated by slow and fast MHD waves. Evidence of solar cycle velocity/intensity amplitude changes consistent with the mode conversion theory

    NASA Astrophysics Data System (ADS)

    Simoniello, R.; Finsterle, W.; García, R. A.; Salabert, D.; Jiménez, A.; Elsworth, Y.; Schunker, H.

    2010-06-01

    We used long duration, high quality, unresolved (Sun-as-a star) observations collected by the ground based network BiSON and by the instruments GOLF and VIRGO on board the ESA/NASA SOHO satellite to search for solar-cycle-related changes in mode characteristics in velocity and continuum intensity for the frequency range between 2.5 mHz <ν< 6.8 mHz. Over the ascending phase of solar cycle 23 we found a suppression in the p-mode amplitudes both in the velocity and intensity data between 2.5 mHz <ν< 4.5 mHz with a maximum suppression for frequencies in the range between 2.5 mHz <ν< 3.5 mHz. The size of the amplitude suppression is 13 ± 2 per cent for the velocity and 9 ± 2 per cent for the intensity observations. Over the range of 4.5 mHz <ν< 5.5 mHz the findings hint within the errors to a null change both in the velocity and intensity amplitudes. At still higher frequencies, in the so called High-frequency Interference Peaks (HIPs) between 5.8 mHz <ν< 6.8 mHz, we found an enhancement in the velocity amplitudes with the maximum 36 ± 7 per cent occurring for 6.3 mHz <ν< 6.8 mHz. However, in intensity observations we found a rather smaller enhancement of about 5 ± 2 per cent in the same interval. There is evidence that the frequency dependence of solar-cycle velocity amplitude changes is consistent with the theory behind the mode conversion of acoustic waves in a non-vertical magnetic field, but there are some problems with the intensity data, which may be due to the height in the solar atmosphere at which the VIRGO data are taken.

  11. Movement - uncontrolled or slow

    MedlinePlus

    ... leg movements - uncontrollable; Slow involuntary movements of large muscle groups; Athetoid movements ... The slow twisting movements of muscles (athetosis) or jerky muscle ... including: Cerebral palsy Drug side effects Encephalitis ...

  12. Lateral hypothalamic lesions cause gastric injury by stimulating gastric contractility.

    PubMed

    Garrick, T; Grijalva, C V; Trauner, M

    1993-07-01

    Changes in gastric contractility following lateral hypothalamic (LH) lesions with and without bilateral cervical vagotomy were measured in urethan-anesthetized rats. LH lesions were induced with direct current passed through stereotaxically placed electrodes. Gastric contractility was recorded continuously for 4 h with acutely implanted strain gauge force transducers and analyzed by computer. LH lesions consistently stimulated gastric contractility and caused more gastric mucosal injury than control conditions. Vagotomy blocked both gastric mucosal injury and high-amplitude gastric contractions. In rats with LH lesions and exogenously infused intragastric hydrochloric acid, atropine methyl nitrate inhibited high-amplitude gastric contractions and gastric erosions. These findings indicate that LH lesions stimulate vagally mediated high-amplitude gastric contractions, which, in the presence of hydrochloric acid, cause gastric mucosal erosions. PMID:8338162

  13. Treatment of gastric cancer

    PubMed Central

    Orditura, Michele; Galizia, Gennaro; Sforza, Vincenzo; Gambardella, Valentina; Fabozzi, Alessio; Laterza, Maria Maddalena; Andreozzi, Francesca; Ventriglia, Jole; Savastano, Beatrice; Mabilia, Andrea; Lieto, Eva; Ciardiello, Fortunato; De Vita, Ferdinando

    2014-01-01

    The authors focused on the current surgical treatment of resectable gastric cancer, and significance of peri- and post-operative chemo or chemoradiation. Gastric cancer is the 4th most commonly diagnosed cancer and the second leading cause of cancer death worldwide. Surgery remains the only curative therapy, while perioperative and adjuvant chemotherapy, as well as chemoradiation, can improve outcome of resectable gastric cancer with extended lymph node dissection. More than half of radically resected gastric cancer patients relapse locally or with distant metastases, or receive the diagnosis of gastric cancer when tumor is disseminated; therefore, median survival rarely exceeds 12 mo, and 5-years survival is less than 10%. Cisplatin and fluoropyrimidine-based chemotherapy, with addition of trastuzumab in human epidermal growth factor receptor 2 positive patients, is the widely used treatment in stage IV patients fit for chemotherapy. Recent evidence supports the use of second-line chemotherapy after progression in patients with good performance status PMID:24587643

  14. Not all gastric masses are gastric cancer.

    PubMed

    Del Rosario, Michael; Tsai, Henry

    2016-01-01

    Lung cancer metastasising to the gastrointestinal tract normally does not occur. However, as clinicians, we must be aware that lung adenocarcinoma, as in all cancers, can and will metastasise to any part of the body. We describe a case of a patient with a presumed primary gastric adenocarcinoma who presented with shortness of breath due to pleural effusion. Pathology from the pleural effusion was positive for primary lung adenocarcinoma. Further investigation revealed that the patient's gastric mass was misdiagnosed as gastric adenocarcinoma. We correctly diagnosed the mass as metastatic lung adenocarcinoma. This was very significant because the patient was transitioning to palliative care with possible tube feeding. After the correct diagnosis, her management drastically changed and her health improved. Clinical, pathological and medical management of lung cancer metastasis to the stomach are discussed. PMID:26976833

  15. Computing Slow Manifolds of Saddle Type

    NASA Astrophysics Data System (ADS)

    Guckenheimer, John; Kuehn, Christian

    2009-01-01

    Slow manifolds are important geometric structures in the state spaces of dynamical systems with multiple time scales. This paper introduces an algorithm for computing trajectories on slow manifolds that are normally hyperbolic with both stable and unstable fast manifolds. We present two examples of bifurcation problems where these manifolds play a key role and a third example in which saddle-type slow manifolds are part of a traveling wave profile of a partial differential equation. Initial value solvers are incapable of computing trajectories on saddle-type slow manifolds, so the slow manifold of saddle type (SMST) algorithm presented here is formulated as a boundary value method. We take an empirical approach here to assessing the accuracy and effectiveness of the algorithm.

  16. Tests of gastric neuromuscular function.

    PubMed

    Parkman, Henry P; Jones, Michael P

    2009-05-01

    Tests of gastric neuromuscular function are used to evaluate patients with symptoms referable to the upper digestive tract. These symptoms can be associated with alterations in the rates of gastric emptying, impaired accommodation, heightened gastric sensation, or alterations in gastric myoelectrical function and contractility. Management of gastric neuromuscular disorders requires an understanding of pathophysiology and treatment options as well as the appropriate use and interpretation of diagnostic tests. These tests include measures of gastric emptying; contractility; electrical activity; regional gastric motility of the fundus, antrum, and pylorus; and tests of sensation and compliance. Tests are also being developed to improve our understanding of the afferent sensory pathways from the stomach to the central nervous system that mediate gastric sensation in health and gastric disorders. This article reviews tests of gastric function and provides a basic description of the tests, the methodologies behind them, descriptions of the physiology that they assess, and their clinical utility. PMID:19293005

  17. [The influence of aging on autonomic nervous system activity and gastric myoelectric activity in humans].

    PubMed

    Thor, P J; Kolasińska-Kloch, W; Pitala, A; Janik, A; Kopp, B; Sibiga, W

    1999-01-01

    The study was performed on 84 healthy volunteers (33 women, 52 men) of age 20-71 years with no history of the circulatory or gastrointestinal system disease. The gastric myoelectrical activity (EGG) was recorded with the cutaneous electrodes--electrogastrography Synectics (Sweden). The activity of the cardiac autonomic nervous system was measured by HRV (heart rate variability) recorded with EGG and computer assisted programme Proster (Poland). Subject were divided into 5 groups according to the decade of age (20-70). Percentage of basal electrical rhythm (BER) dysrhythmias increased (1.9 +/- 0.5% vs 21.1 +/- 3.2% in fasting and 2.4 +/- 1.2% vs 24.6 +/- 5% postprandially but decrease of the EGG amplitude after the meal was observed (270 +/- 20% vs 90 +/- 7%) in youngest and oldest group respectively. With the ageing the cardiac sympathetic and parasympathetic activity (LF and HF) decreased in first and last group respectively. In the forth decade in man and women the sympathetic activity system prevalence expressed by the LF/HF rate increased (1.09 +/- 0.2 vs. 2.14 +/- 0.5) (p < 0.05). The results of our study suggest the deleterious influence of the ageing on the of autonomic system activity as shown by changes in HRV and dysrhythmia of the gastric slow waves in EGG. PMID:10909474

  18. Occupation and gastric cancer.

    PubMed

    Raj, A; Mayberry, J F; Podas, T

    2003-05-01

    Gastric cancer is a cause of significant morbidity and mortality. There are several risk factors, with occupation emerging as one of these. There is considerable evidence that occupations in coal and tin mining, metal processing, particularly steel and iron, and rubber manufacturing industries lead to an increased risk of gastric cancer. Other "dusty" occupations-for example, wood processing, or work in high temperature environments have also been implicated but the evidence is not strong. The mechanism of pathogenesis of gastric cancer is unclear and the identification of causative agents can be difficult. Dust is thought to be a contributor to the pathological process, but well known carcinogens such as N-nitroso compounds have been detected in some environments. Further research on responsible agents is necessary and screening for detection of precursor gastric cancer lesions at the workplace merits consideration. PMID:12782770

  19. Laparoscopic gastric banding

    MedlinePlus

    ... gastric banding is not a "quick fix" for obesity. It will greatly change your lifestyle. You must ... panel on weight loss surgery: executive report update. Obesity . 2009;17:842-62. PMID: 19396063 www.ncbi. ...

  20. Gastric Sleeve Surgery

    MedlinePlus

    ... or "sleeve" out of the rest. The new, banana-shaped stomach is much smaller than the original ... of your stomach, leaving you with a smaller banana-shaped stomach called the gastric sleeve. Because it's ...

  1. Occupation and gastric cancer

    PubMed Central

    Raj, A; Mayberry, J; Podas, T

    2003-01-01

    Gastric cancer is a cause of significant morbidity and mortality. There are several risk factors, with occupation emerging as one of these. There is considerable evidence that occupations in coal and tin mining, metal processing, particularly steel and iron, and rubber manufacturing industries lead to an increased risk of gastric cancer. Other "dusty" occupations—for example, wood processing, or work in high temperature environments have also been implicated but the evidence is not strong. The mechanism of pathogenesis of gastric cancer is unclear and the identification of causative agents can be difficult. Dust is thought to be a contributor to the pathological process, but well known carcinogens such as N-nitroso compounds have been detected in some environments. Further research on responsible agents is necessary and screening for detection of precursor gastric cancer lesions at the workplace merits consideration. PMID:12782770

  2. Hereditary Diffuse Gastric Cancer

    MedlinePlus

    ... with the syndrome is recommended. What are the estimated cancer risks associated with HDGC? Not everyone who ... the lifetime risk for diffuse gastric cancer is estimated to be 70% to 80% for men and ...

  3. Gastric bypass surgery

    MedlinePlus

    ... your legs to help prevent blood clots from forming. You will receive shots of medicine to prevent ... diversion with duodenal switch Dumping syndrome References Buchwald H. Laparoscopic Roux-en-Y gastric bypass. In: Buchwald ...

  4. Inhibitory effects of xylitol on gastric emptying and food intake

    SciTech Connect

    Shafer, R.B.; Levine, A.S.; Marlette, J.M.; Morley, J.E.

    1985-05-01

    The authors have previously shown, using a 99m-Tc scrambled egg meal, that pentose sugars (i.e. xylose and arabinose) markedly prolong gastric emptying. Others have reported that slowing of gastric emptying may decrease appetite and thus decrease food intake. In the present study, the authors utilized the effects of xylitol (an FDA-approved pentose sugar) on gastric emptying to study the correlation between gastric emptying and food intake. Initially, gastric emptying was measured in human volunteers utilizing a standardized 99m-Tc-scrambled egg meal washed with 50 cc tap water. Results demonstrated a significant reduction in food intake (892 +- 65 kcal with water vs 654 +- 26 kcal following the ingestion of 25 gm xylitol (p<0.05). We conclude that the effect of pentose sugars in prolonging gastric emptying directly influences food intake and contributes to early satiety. The data suggest a role of xylitol as an essentially non-caloric food additive potentially important in diet control.

  5. CT of Gastric Emergencies.

    PubMed

    Guniganti, Preethi; Bradenham, Courtney H; Raptis, Constantine; Menias, Christine O; Mellnick, Vincent M

    2015-01-01

    Abdominal pain, nausea, and vomiting are common presenting symptoms among adult patients seeking care in the emergency department, and, with the increased use of computed tomography (CT) to image patients with these complaints, radiologists will more frequently encounter a variety of emergent gastric pathologic conditions on CT studies. Familiarity with the CT appearance of emergent gastric conditions is important, as the clinical presentation is often nonspecific and the radiologist may be the first to recognize gastric disease as the cause of a patient's symptoms. Although endoscopy and barium fluoroscopy remain important tools for evaluating patients with suspected gastric disease in the outpatient setting, compared with CT these modalities enable less comprehensive evaluation of patients with nonspecific complaints and are less readily available in the acute setting. Endoscopy is also more invasive than CT and has greater potential risks. Although the mucosal detail of CT is relatively poor compared with barium fluoroscopy or endoscopy, CT can be used with the appropriate imaging protocols to identify inflammatory conditions of the stomach ranging from gastritis to peptic ulcer disease. In addition, CT can readily demonstrate the various complications of gastric disease, including perforation, obstruction, and hemorrhage, which may direct further clinical, endoscopic, or surgical management. We will review the normal anatomy of the stomach and discuss emergent gastric disease with a focus on the usual clinical presentation, typical imaging appearance, and differentiating features, as well as potential imaging pitfalls. PMID:26562229

  6. Slow liner fusion

    SciTech Connect

    Shaffer, M.J.

    1997-08-01

    {open_quotes}Slow{close_quotes} liner fusion ({approximately}10 ms compression time) implosions are nondestructive and make repetitive ({approximately} 1 Hz) pulsed liner fusion reactors possible. This paper summarizes a General Atomics physics-based fusion reactor study that showed slow liner feasibility, even with conservative open-line axial magnetic field confinement and Bohm radial transport.

  7. Gastric Adenocarcinoma Presenting with Gastric Outlet Obstruction in a Child

    PubMed Central

    Al-Hussaini, Abdulrahman; AlGhamdi, Salem; Al-Kasim, Fawaz; Habib, Zakaria; Ourfali, Nouri

    2014-01-01

    Gastric carcinoma is extremely rare in children representing only 0.05% of all gastrointestinal malignancies. Here, we report the first pediatric case of gastric cancer presenting with gastric outlet obstruction. Upper endoscopy revealed a markedly thickened antral mucosa occluding the pylorus and a clean base ulcer 1.5 cm × 2 cm at the lesser curvature of the stomach. The narrowed antrum and pylorus underwent balloon dilation, and biopsy from the antrum showed evidence of Helicobacter pylori gastritis. The biopsy taken from the edge of the gastric ulcer demonstrated signet-ring-cell type infiltrate consistent with gastric adenocarcinoma. At laparotomy, there were metastases to the liver, head of pancreas, and mesenteric lymph nodes. Therefore, the gastric carcinoma was deemed unresectable. The patient died few months after initiation of chemotherapy due to advanced malignancy. In conclusion, this case report underscores the possibility of gastric adenocarcinoma occurring in children and presenting with gastric outlet obstruction. PMID:24707411

  8. General Information about Gastric Cancer

    MedlinePlus

    ... Research Gastric Cancer Treatment (PDQ®)–Patient Version General Information About Gastric Cancer Go to Health Professional Version ... the PDQ Adult Treatment Editorial Board . Clinical Trial Information A clinical trial is a study to answer ...

  9. Gastric retention properties of superporous hydrogel composites.

    PubMed

    Chen, J; Blevins, W E; Park, H; Park, K

    2000-02-14

    In many applications, usefulness of conventional hydrogels is limited by their slow swelling. To improve the swelling property of the conventional hydrogels, we have synthesized superporous hydrogels (SPHs) which swell fast to equilibrium size in minutes due to water uptake by capillary wetting through numerous interconnected open pores. The swelling ratio was also large in the range of hundreds. The mechanical strength of the highly swollen SPHs was increased by adding a composite material during the synthesis. The composite material used in the synthesis of SPH composites was Ac-Di-Sol((R)) (croscarmellose sodium). The gastric retention property of the prepared SPH composites was tested in dogs both in fasted and fed conditions. The SPH composites were placed in a hard gelatin capsule (size 000) for oral administration. All dogs tested were fasted for 36 h before experiments. Under the fasted condition, the SPH composite remained in the stomach for 2-3 h after before breaking into two pieces and being emptied. When food was given before the experiment just once following 36 h of fasting, the SPH composite remained in the stomach for more than 24 h, even though the fed condition was maintained only for the first few hours. Our study indicated that SPH composites possessed three properties necessary for gastric retention: fast swelling; superswelling; and high mechanical strength. While more improvements need to be made, the SPH composites provide the basis for the development of effective long-term gastric retention devices. PMID:10640644

  10. GASTRIC MOTOR DISTURBANCES IN PATIENTS WITH IDIOPATHIC RAPID GASTRIC EMPTYING

    PubMed Central

    Bharucha, Adil E.; Manduca, Armando; Lake, David S.; Fidler, Jeff; Edwards, Phillip; Grimm, Roger C.; Zinsmeister, Alan R.; Riederer, Stephen J.

    2011-01-01

    Background and Aims The mechanisms of “idiopathic” rapid gastric emptying, which is associated with functional dyspepsia and functional diarrhea, are not understood. Our hypotheses were that increased gastric motility and reduced postprandial gastric accommodation contribute to rapid gastric emptying. Methods Fasting and postprandial (300kCal nutrient meal) gastric volumes were measured by magnetic resonance imaging (MRI) in 20 healthy people and 17 with functional dyspepsia; 7 had normal and 10 had rapid gastric emptying. In 17 healthy people and patients, contractility was analyzed by spectral analysis of a time-series of gastric cross-sectional areas. Logistic regression models analyzed whether contractile parameters, fasting volume, and postprandial volume change could discriminate between health and patients with normal or rapid gastric emptying. Results While upper gastrointestinal symptoms were comparable, patients with rapid emptying had a higher (p = 0.002) body mass index (BMI) than normal gastric emptying. MRI visualized propagating contractions at ~ 3 cpm in healthy people and patients. Compared to controls (0.16 ± 0.02, Mean ± SEM), the amplitude of gastric contractions in the entire stomach was higher (OR 4.1, 95% CI 1.2–14.0) in patients with rapid (0.24 ± 0.03) but not normal gastric emptying (0.10 ± 0.03). Similar differences were observed in the distal stomach. However, the propagation velocity, fasting gastric volume, and the postprandial volume change were not significantly different between patients and controls. Conclusions MRI provides a noninvasive and refined assessment of gastric volumes and contractility in humans. Increased gastric contractility may contribute to rapid gastric emptying in functional dyspepsia. PMID:21470342

  11. Transformer Industry Productivity Slows.

    ERIC Educational Resources Information Center

    Otto, Phyllis Flohr

    1981-01-01

    Annual productivity increases averaged 2.4 percent during 1963-79, slowing since 1972 to 1.5 percent; computer-assisted design and product standardization aided growth in output per employee-hour. (Author)

  12. Hypoglycaemia after gastric bypass: mechanisms and treatment.

    PubMed

    Ritz, P; Vaurs, C; Barigou, M; Hanaire, H

    2016-03-01

    Hypoglycaemia after gastric bypass can be severe, but is uncommon, and is sometimes only revealed through monitoring glucose concentrations. The published literature is limited by the heterogeneity of the criteria used for diagnosis, arguing in favour of the Whipple triad with a glycaemia threshold of 55 mg/dl as the diagnostic reference. Women who lost most of their excess weight after gastric bypass, long after the surgery was performed, and who did not have diabetes before surgery are at the greatest risk. In this context, hypoglycaemia results from hyperinsulinism, which is either generated by pancreas anomalies (nesidioblastosis) and/or caused by an overstimulation of β cells by incretins, mainly glucagon-like peptide-1 (GLP-1). Glucose absorption is both accelerated and increased because of the direct communication between the gastric pouch and the jejunum. This is a post-surgical exaggeration of a natural adaptation that is seen in patients who have not undergone surgery in whom glucose is infused directly into the jejunum. There is not always a correspondence between symptoms and biological traits; however, hyperinsulinism is constant if hypoglycaemia is severe and there are neuroglucopenic symptoms. The treatment relies firstly on changes in eating habits, splitting food intake into five to six daily meals, slowing gastric emptying, reducing the glycaemic load and glycaemic index of foods, using fructose and avoiding stress at meals. Pharmacological treatment with acarbose is efficient, but other drugs still need to be validated in a greater number of subjects (insulin, glucagon, calcium channel blockers, somatostatin analogues and GLP-1 analogues). Lastly, if the surgical option has to be used, the benefits (efficient symptom relief) and the risks (weight regain, diabetes) should be weighed carefully. PMID:26508374

  13. Slow medical education.

    PubMed

    Wear, Delese; Zarconi, Joseph; Kumagai, Arno; Cole-Kelly, Kathy

    2015-03-01

    Slow medical education borrows from other "slow" movements by offering a complementary orientation to medical education that emphasizes the value of slow and thoughtful reflection and interaction in medical education and clinical care. Such slow experiences, when systematically structured throughout the curriculum, offer ways for learners to engage in thoughtful reflection, dialogue, appreciation, and human understanding, with the hope that they will incorporate these practices throughout their lives as physicians. This Perspective offers several spaces in the medical curriculum where slowing down is possible: while reading and writing at various times in the curriculum and while providing clinical care, focusing particularly on conducting the physical exam and other dimensions of patient care. Time taken to slow down in these ways offers emerging physicians opportunities to more fully incorporate their experiences into a professional identity that embodies reflection, critical awareness, cultural humility, and empathy. The authors argue that these curricular spaces must be created in a very deliberate manner, even on busy ward services, throughout the education of physicians. PMID:25426738

  14. Immunotherapy in gastric cancer

    PubMed Central

    Matsueda, Satoko; Graham, David Y

    2014-01-01

    Gastric cancer is the second most common of cancer-related deaths worldwide. In the majority of cases gastric cancer is advanced at diagnosis and although medical and surgical treatments have improved, survival rates remain poor. Cancer immunotherapy has emerged as a powerful and promising clinical approach for treatment of cancer and has shown major success in breast cancer, prostate cancer and melanoma. Here, we provide an overview of concepts of modern cancer immunotherapy including the theory, current approaches, remaining hurdles to be overcome, and the future prospect of cancer immunotherapy in the treatment of gastric cancer. Adaptive cell therapies, cancer vaccines, gene therapies, monoclonal antibody therapies have all been used with some initial successes in gastric cancer. However, to date the results in gastric cancer have been disappointing as current approaches often do not stimulate immunity efficiently allowing tumors continue to grow despite the presence of a measurable immune response. Here, we discuss the identification of targets for immunotherapy and the role of biomarkers in prospectively identifying appropriate subjects or immunotherapy. We also discuss the molecular mechanisms by which tumor cells escape host immunosurveillance and produce an immunosuppressive tumor microenvironment. We show how advances have provided tools for overcoming the mechanisms of immunosuppression including the use of monoclonal antibodies to block negative regulators normally expressed on the surface of T cells which limit activation and proliferation of cytotoxic T cells. Immunotherapy has greatly improved and is becoming an important factor in such fields as medical care and welfare for human being. Progress has been rapid ensuring that the future of immunotherapy for gastric cancer is bright. PMID:24587645

  15. Highly Alfvenic Slow Solar Wind

    NASA Technical Reports Server (NTRS)

    Roberts, D. Aaron

    2010-01-01

    It is commonly thought that fast solar wind tends to be highly Alfvenic, with strong correlations between velocity and magnetic fluctuations, but examples have been known for over 20 years in which slow wind is both Alfvenic and has many other properties more typically expected of fast solar wind. This paper will present a search for examples of such flows from more recent data, and will begin to characterize the general characteristics of them. A very preliminary search suggests that such intervals are more common in the rising phase of the solar cycle. These intervals are important for providing constraints on models of solar wind acceleration, and in particular the role waves might or might not play in that process.

  16. Melanoma with gastric metastases.

    PubMed

    Wong, Katherine; Serafi, Sam W; Bhatia, Abhijit S; Ibarra, Irene; Allen, Elizabeth A

    2016-01-01

    An 81-year-old woman with a history of malignant melanoma who presented with dyspnea and fatigue was found to have metastases to the stomach detected on endoscopy. Primary cutaneous malignant melanoma with gastric metastases is a rare occurrence, and it is often not detected until autopsy because of its non-specific manifestations. PMID:27609722

  17. Models of gastric emptying.

    PubMed Central

    Stubbs, D F

    1977-01-01

    Some empirical and theoretical models of the emptying behaviour of the stomach are presented. The laws of Laplace, Hooke, and Poisseuille are used to derive a new model of gastric emptying. Published data on humans are used to test the model and evaluate empirical constants. It is shown that for meals with an initial volume of larger than or equal to 300 ml, the reciprocal of the cube root of the volume of meal remaining is proportional to the time the meal is in the stomach.For meals of initial volume of less than 300 ml the equation has to be corrected for the fact that the 'resting volume' of gastric contents is about 28 ml. The more exact formula is given in the text. As this model invokes no neural or hormonal factors, it is suggested that the gastric emptying response to the volume of a meal does not depend on these factors. The gastric emptying response to the composition of the meal does depend on such factors and a recent model of this process is used to evaluate an empirical constant. PMID:856678

  18. The release of histamine during gastric acid secretion in conscious rats

    PubMed Central

    el Munshid, H. A.; Lake, H. J.

    1974-01-01

    1. Conscious gastric-cannulated rats were given [3H]histidine and aminoguanidine by dosage procedures intended to build up fast-turnover and slow-turnover pools of tissue [3H]histamine. Acid secretion was stimulated by I.V. infusion of pentagastrin, and the [3H]histamine content of gastric juice and excretion in urine were determined at 30 min intervals. 2. The amount of [3H]histamine in gastric juice derived from either a slow-turnover or fast-turnover pool was very low in unstimulated animals, and was not altered during pentagastrin-stimulated acid secretion. 3. From a slow-turnover pool pentagastrin caused increased urinary excretion of [3H]histamine. This was abolished by gastrectomy, so that the [3H]histamine liberated by pentagastrin from this pool appears to have been derived from the stomach. Evidence was not found for the existence of a slow-turnover histamine pool in the glandular mucosa of the stomach, and the source within the stomach of this pentagastrin-liberated histamine is thus uncertain. 4. From a fast-turnover pool pentagastrin did not cause an increased urinary excretion of [3H]histamine. The amount of [3H]histamine excreted by gastrectomized rats was not different from that produced by gastric-cannulated animals. This suggests that a high proportion of urinary histamine derived from a fast-turnover pool was non-gastric in origin. 5. Differences in the time scale of [3H]histamine release and acid secretion were not found. In some experiments the urinary output of [3H]histamine was prolonged beyond the end of pentagastrin administration and gastric acid secretion. However, the overall data do not suggest that urinary histamine output and gastric acid secretion take different time courses. PMID:4141368

  19. Drugs Approved for Stomach (Gastric) Cancer

    MedlinePlus

    ... Professionals Questions to Ask about Your Treatment Research Drugs Approved for Stomach (Gastric) Cancer This page lists ... stomach (gastric) cancer that are not listed here. Drugs Approved for Stomach (Gastric) Cancer Cyramza (Ramucirumab) Docetaxel ...

  20. Gastric metastasis from salivary duct carcinoma mimicking primary gastric cancer

    PubMed Central

    Yamashita, Kanefumi; Takeno, Shinsuke; Nimura, Satoshi; Sugiyama, Yoshikazu; Sueta, Takayuki; Maki, Kenji; Kayashima, Yoshiyuki; Shiwaku, Hironari; Kato, Daisuke; Hashimoto, Tatsuya; Sasaki, Takamitsu; Yamashita, Yuichi

    2016-01-01

    Introduction We present a very rare case of gastric metastasis mimicking primary gastric cancer in a patient who had undergone surgery for salivary duct carcinoma. Presentation of case A 67-year-old man had been diagnosed as having right parotid cancer and had undergone a right parotidectomy and lymph node dissection. The histological diagnosis was salivary duct carcinoma. One year after the surgery, a positron emission tomography–computed tomography scan using fluorodeoxyglucose (FDG) revealed an abnormal uptake of FDG in the left cervical, mediastinal, paraaortic, and cardiac lymph nodes; stomach; and pancreas. On gastroduodenoscopy, there was a huge, easily bleeding ulcer mimicking primary gastric cancer at the upper body of the stomach. Biopsy revealed poorly differentiated adenocarcinoma. Therefore, we were unable to differentiate between the primary gastric cancer and the metastatic tumor using gastroduodenoscopy and biopsy. Because of the uncontrollable bleeding from the gastric cancer, we performed an emergency palliative total gastrectomy. On histological examination, the gastric lesion was found to be metastatic carcinoma originating from the salivary duct carcinoma. Discussion In the presented case, we could not diagnose the gastric metastasis originating from the salivary duct carcinoma even by endoscopic biopsy. This is because the histological appearance of salivary duct carcinoma is similar to that of high-grade adenocarcinoma, thus, resembling primary gastric cancer. Conclusion When we perform endoscopic examination of patients with malignant neoplasias, a possibility of metastatic gastric cancer should be taken into consideration. PMID:27085106

  1. Gastric Aspiration Models

    PubMed Central

    Davidson, Bruce A.; Alluri, Ravi

    2016-01-01

    The procedures described below are for producing gastric aspiration pneumonitis in mice with alterations for rats and rabbits described parenthetically. We use 4 different injury vehicles delivered intratracheally to investigate the inflammatory responses to gastric aspiration: Normal saline (NS) as the injury vehicle controlNS + HCl, pH = 1.25 (acid)NS + gastric particles, pH ≈ 5.3 (part.)NS + gastric particles + HCl, pH = 1.25 (acid + part.) The volume, pH, and gastric particle concentration all affect the resulting lung injury. In mice, we generally use an injury volume of 3.6 ml/kg (rat: 1.2 ml/kg, rabbit: 2.4 ml/kg), an injury pH (for the acid-containing vehicles) of 1.25, and a gastric particulate concentration (in the particulate-containing vehicles) of 10 mg/ml (rat: 40 mg/ml). In our hands this results in a maximal, non-lethal lung injury with ≤ 10% mortality for the most injurious vehicle (i.e., acid + part.) The maximum tolerable particulate concentration needs to be determined empirically for any new strains to be used, especially in genetically-altered mice, because an altered inflammatory response may have detrimental affects on mortality. We have extensive experience utilizing these procedures in the outbred strain, CD-1, as well as many genetically-altered inbred stains on the C57BL/6 background. Choice of strain should be carefully considered, especially in terms of strain-specific immune bias, to assure proper data interpretation. The size of the mouse should be ≥ 20 g at the time of injury. Smaller mice can be attempted, if necessary, but the surgical manipulation becomes increasingly more difficult and the surgery survival rate decreases substantially. There are no size or strain constraints for rat and rabbit models, but we generally use Long-Evans rats at 250–300 g and New Zealand White rats at ≈ 2 kg at the time of initial injury.

  2. Nonlinear dynamical triggering of slow slip

    SciTech Connect

    Johnson, Paul A; Knuth, Matthew W; Kaproth, Bryan M; Carpenter, Brett; Guyer, Robert A; Le Bas, Pierre - Yves; Daub, Eric G; Marone, Chris

    2010-12-10

    Among the most fascinating, recent discoveries in seismology have been the phenomena of triggered slip, including triggered earthquakes and triggered-tremor, as well as triggered slow, silent-slip during which no seismic energy is radiated. Because fault nucleation depths cannot be probed directly, the physical regimes in which these phenomena occur are poorly understood. Thus determining physical properties that control diverse types of triggered fault sliding and what frictional constitutive laws govern triggered faulting variability is challenging. We are characterizing the physical controls of triggered faulting with the goal of developing constitutive relations by conducting laboratory and numerical modeling experiments in sheared granular media at varying load conditions. In order to simulate granular fault zone gouge in the laboratory, glass beads are sheared in a double-direct configuration under constant normal stress, while subject to transient perturbation by acoustic waves. We find that triggered, slow, silent-slip occurs at very small confining loads ({approx}1-3 MPa) that are smaller than those where dynamic earthquake triggering takes place (4-7 MPa), and that triggered slow-slip is associated with bursts of LFE-like acoustic emission. Experimental evidence suggests that the nonlinear dynamical response of the gouge material induced by dynamic waves may be responsible for the triggered slip behavior: the slip-duration, stress-drop and along-strike slip displacement are proportional to the triggering wave amplitude. Further, we observe a shear-modulus decrease corresponding to dynamic-wave triggering relative to the shear modulus of stick-slips. Modulus decrease in response to dynamical wave amplitudes of roughly a microstrain and above is a hallmark of elastic nonlinear behavior. We believe that the dynamical waves increase the material non-affine elastic deformation during shearing, simultaneously leading to instability and slow-slip. The inferred

  3. Clinical epidemiology of gastric cancer

    PubMed Central

    Ang, Tiing Leong; Fock, Kwong Ming

    2014-01-01

    Gastric cancer is the second leading cause of cancer-related mortality and the fourth most common cancer globally. There are, however, distinct differences in incidence rates in different geographic regions. While the incidence rate of gastric cancer has been falling, that of gastric cardia cancers is reportedly on the rise in some regions. Helicobacter pylori (H. pylori) infection is a major risk factor of non-cardia gastric cancer, and data has emerged concerning the role of H. pylori eradication for primary prevention of gastric cancer. Dietary, lifestyle and metabolic factors have also been implicated. Although addressing these other factors may contribute to health, the actual impact in terms of cancer prevention is unclear. Once irreversible histological changes have occurred, endoscopic surveillance would be necessary. A molecular classification system offers hope for molecularly tailored, personalised therapies for gastric cancer, which may improve the prognosis for patients. PMID:25630323

  4. Gastric cancer review

    PubMed Central

    Carcas, Lauren Peirce

    2014-01-01

    Gastric cancer is an aggressive disease that continues to have a daunting impact on global health. Despite an overall decline in incidence over the last several decades, gastric cancer remains the fourth most common type of cancer and is the second leading cause of cancer-related death worldwide. This review aims to discuss the global distribution of the disease and the trend of decreasing incidence of disease, delineate the different pathologic subtypes and their immunohistochemical (IHC) staining patterns and molecular signatures and mutations, explore the role of the pathogen H. pylori in tumorgenesis, discuss the increasing incidence of the disease in the young, western populations and define the role of biologic agents in the treatment of the disease. PMID:25589897

  5. A gastric acid secretion model.

    PubMed Central

    de Beus, A M; Fabry, T L; Lacker, H M

    1993-01-01

    A theory of gastric acid production and self-protection is formulated mathematically and examined for clinical and experimental correlations, implications, and predictions using analytic and numerical techniques. In our model, gastric acid secretion in the stomach, as represented by an archetypal gastron, consists of two chambers, circulatory and luminal, connected by two different regions of ion exchange. The capillary circulation of the gastric mucosa is arranged in arterial-venous arcades which pass from the gastric glands up to the surface epithelial lining of the lumen; therefore the upstream region of the capillary chamber communicates with oxyntic cells, while the downstream region communicates with epithelial cells. Both cell types abut the gastric lumen. Ion currents across the upstream region are calculated from a steady-state oxyntic cell model with active ion transport, while the downstream ion fluxes are (facilitated) diffusion driven or secondarily active. Water transport is considered iso-osmotic. The steady-state model is solved in closed form for low gastric lumen pH. A wide variety of previously performed static and dynamic experiments on ion and CO2 transport in the gastric lumen and gastric blood supply are for the first time correlated with each other for an (at least) semiquantitative test of current concepts of gastric acid secretion and for the purpose of model verification. Agreement with the data is reported with a few outstanding and instructive exceptions. Model predictions and implications are also discussed. Images FIGURE 1 PMID:8396457

  6. Helicobacter pylori in gastric carcinogenesis.

    PubMed

    Ahn, Hyo Jun; Lee, Dong Soo

    2015-12-15

    Gastric cancer still is a major concern as the third most common cancer worldwide, despite declining rates of incidence in many Western countries. Helicobacter pylori (H. pylori) is the major cause of gastric carcinogenesis, and its infection insults gastric mucosa leading to the occurrence of atrophic gastritis which progress to intestinal metaplasia, dysplasia, early gastric cancer, and advanced gastric cancer consequently. This review focuses on multiple factors including microbial virulence factors, host genetic factors, and environmental factors, which can heighten the chance of occurrence of gastric adenocarcinoma due to H. pylori infection. Bacterial virulence factors are key components in controlling the immune response associated with the induction of carcinogenesis, and cagA and vacA are the most well-known pathogenic factors. Host genetic polymorphisms contribute to regulating the inflammatory response to H. pylori and will become increasingly important with advancing techniques. Environmental factors such as high salt and smoking may also play a role in gastric carcinogenesis. It is important to understand the virulence factors, host genetic factors, and environmental factors interacting in the multistep process of gastric carcinogenesis. To conclude, prevention via H. pylori eradication and controlling environmental factors such as diet, smoking, and alcohol is an important strategy to avoid H. pylori-associated gastric carcinogenesis. PMID:26690981

  7. Helicobacter pylori in gastric carcinogenesis

    PubMed Central

    Ahn, Hyo Jun; Lee, Dong Soo

    2015-01-01

    Gastric cancer still is a major concern as the third most common cancer worldwide, despite declining rates of incidence in many Western countries. Helicobacter pylori (H. pylori) is the major cause of gastric carcinogenesis, and its infection insults gastric mucosa leading to the occurrence of atrophic gastritis which progress to intestinal metaplasia, dysplasia, early gastric cancer, and advanced gastric cancer consequently. This review focuses on multiple factors including microbial virulence factors, host genetic factors, and environmental factors, which can heighten the chance of occurrence of gastric adenocarcinoma due to H. pylori infection. Bacterial virulence factors are key components in controlling the immune response associated with the induction of carcinogenesis, and cagA and vacA are the most well-known pathogenic factors. Host genetic polymorphisms contribute to regulating the inflammatory response to H. pylori and will become increasingly important with advancing techniques. Environmental factors such as high salt and smoking may also play a role in gastric carcinogenesis. It is important to understand the virulence factors, host genetic factors, and environmental factors interacting in the multistep process of gastric carcinogenesis. To conclude, prevention via H. pylori eradication and controlling environmental factors such as diet, smoking, and alcohol is an important strategy to avoid H. pylori-associated gastric carcinogenesis. PMID:26690981

  8. Role of Ih in differentiating the dynamics of the gastric and pyloric neurons in the stomatogastric ganglion of the lobster, Homarus americanus.

    PubMed

    Zhu, Lin; Selverston, Allen I; Ayers, Joseph

    2016-06-01

    The hyperpolarization-activated inward cationic current (Ih) is known to regulate the rhythmicity, excitability, and synaptic transmission in heart cells and many types of neurons across a variety of species, including some pyloric and gastric mill neurons in the stomatogastric ganglion (STG) in Cancer borealis and Panulirus interruptus However, little is known about the role of Ih in regulating the gastric mill dynamics and its contribution to the dynamical bifurcation of the gastric mill and pyloric networks. We investigated the role of Ih in the rhythmic activity and cellular excitability of both the gastric mill neurons (medial gastric, gastric mill) and pyloric neurons (pyloric dilator, lateral pyloric) in Homarus americanus Through testing the burst period between 5 and 50 mM CsCl, and elimination of postinhibitory rebound and voltage sag, we found that 30 mM CsCl can sufficiently block Ih in both the pyloric and gastric mill neurons. Our results show that Ih maintains the excitability of both the pyloric and gastric mill neurons. However, Ih regulates slow oscillations of the pyloric and gastric mill neurons differently. Specifically, blocking Ih diminishes the difference between the pyloric and gastric mill burst periods by increasing the pyloric burst period and decreasing the gastric mill burst period. Moreover, the phase-plane analysis shows that blocking Ih causes the trajectory of slow oscillations of the gastric mill neurons to change toward the pyloric sinusoidal-like trajectories. In addition to regulating the pyloric rhythm, we found that Ih is also essential for the gastric mill rhythms and differentially regulates these two dynamics. PMID:26912595

  9. Selexipag: a selective prostacyclin receptor agonist that does not affect rat gastric function.

    PubMed

    Morrison, Keith; Ernst, Roland; Hess, Patrick; Studer, Rolf; Clozel, Martine

    2010-10-01

    Selexipag [2-{4-[(5,6-diphenylpyrazin-2-yl)(isopropyl)amino]butoxy}-N-(methylsulfonyl)acetamide] is an orally available prostacyclin (PGI(2)) receptor (IP receptor) agonist that is chemically distinct from PGI(2) and is in clinical development for the treatment of pulmonary arterial hypertension. Selexipag is highly selective for the human IP receptor in vitro, whereas analogs of PGI(2) can activate prostanoid receptors other than the IP receptor. The goal of this study was to determine the impact of selectivity for the IP receptor on gastric function by measuring 1) contraction of rat gastric fundus ex vivo and 2) the rates of gastric emptying and intestinal transport in response to selexipag in comparison with other PGI(2) analogs. The rat gastric fundus expresses mRNA encoding multiple prostanoid receptors to different levels: prostaglandin E receptor 1 (EP(1)) > prostaglandin E receptor 3 (EP(3)), IP receptor > prostaglandin D(2) receptor 1, thromboxane receptor. Selexipag and metabolite {4-[(5,6-diphenylpyrazin-2-yl)(isopropyl)amino]butoxy}acetic acid (ACT-333679) did not contract gastric fundus at concentrations up to 10(-3) M. In contrast, the PGI(2) analogs iloprost and beraprost evoked concentration-dependent contraction of gastric fundus. Contraction to treprostinil was observed at high concentration (10(-4) M). Contraction to all PGI(2) analogs was mediated via activation of EP(3) receptors, although EP(1) receptors also contributed to the contraction of gastric fundus to iloprost and beraprost. Antagonism of IP receptors did not affect responses. Oral selexipag did not significantly alter gastric function in vivo, as measured by rates of stomach emptying and intestinal transport, whereas beraprost slowed gastrointestinal transport. The high functional selectivity of selexipag and ACT-333679 for the IP receptor precludes a stimulatory action on gastric smooth muscle and may help minimize gastric side effects such as nausea and vomiting. PMID:20660124

  10. The role of K+ conductances in regulating membrane excitability in human gastric corpus smooth muscle

    PubMed Central

    Lee, Ji Yeon; Ko, Eun-ju; Ahn, Ki Duck; Kim, Sung

    2015-01-01

    Changes in resting membrane potential (RMP) regulate membrane excitability. K+ conductance(s) are one of the main factors in regulating RMP. The functional role of K+ conductances has not been studied the in human gastric corpus smooth muscles (HGCS). To examine the role of K+ channels in regulation of RMP in HGCS we employed microelectrode recordings, patch-clamp, and molecular approaches. Tetraethylammonium and charybdotoxin did not affect the RMP, suggesting that BK channels are not involved in regulating RMP. Apamin, a selective small conductance Ca2+-activated K+ channel (SK) blocker, did not show a significant effect on the membrane excitability. 4-Aminopyridine, a Kv channel blocker, caused depolarization and increased the duration of slow wave potentials. 4-Aminopyridine also inhibited a delayed rectifying K+ current in isolated smooth muscle cells. End-product RT-PCR gel detected Kv1.2 and Kv1.5 in human gastric corpus muscles. Glibenclamide, an ATP-sensitive K+ channel (KATP) blocker, did not induce depolarization, but nicorandil, a KATP opener, hyperpolarized HGCS, suggesting that KATP are expressed but not basally activated. Kir6.2 transcript, a pore-forming subunit of KATP was expressed in HGCS. A low concentration of Ba2+, a Kir blocker, induced strong depolarization. Interestingly, Ba2+-sensitive currents were minimally expressed in isolated smooth muscle cells under whole-cell patch configuration. KCNJ2 (Kir2.1) transcript was expressed in HGCS. Unique K+ conductances regulate the RMP in HGCS. Delayed and inwardly rectifying K+ channels are the main candidates in regulating membrane excitability in HGCS. With the development of cell dispersion techniques of interstitial cells, the cell-specific functional significance will require further analysis. PMID:25591864

  11. Pathology and Genetics of Syndromic Gastric Polyps.

    PubMed

    Brosens, Lodewijk A A; Wood, Laura D; Offerhaus, G Johan; Arnold, Christina A; Lam-Himlin, Dora; Giardiello, Francis M; Montgomery, Elizabeth A

    2016-05-01

    Gastric polyps are found in 1% to 4% of patients undergoing gastroscopy. The vast majority are sporadic, but some gastric polyps indicate an underlying syndrome. Gastric polyps can manifest in each of the gastrointestinal polyposis syndromes, including the recently described gastric adenocarcinoma and proximal polyposis of the stomach syndrome. In addition, gastric polyps occur in Lynch syndrome and in a few rare conditions that are not primarily gastrointestinal. While some of these syndromes are clearly associated with an increased risk of gastric cancer, others are not. Interestingly, even in disorders with a well-established risk of gastric cancer, the neoplastic potential and the precursor status of these gastric polyps are not always clear. Although rare, recognition of syndromic gastric polyps is important for individual patient management. These conditions also serve as important models to study gastric homeostasis and gastric tumorigenesis. PMID:26721304

  12. miR-218 inhibits multidrug resistance (MDR) of gastric cancer cells by targeting Hedgehog/smoothened

    PubMed Central

    Zhang, Xiang-Liang; Shi, Hui-Juan; Wang, Ji-Ping; Tang, Hong-Sheng; Cui, Shu-Zhong

    2015-01-01

    Multidrug resistance (MDR) is the main obstacle to successful chemotherapy for patients with gastric cancer. The microRNA miR-218 influences various pathobiological processes in gastric cancer, and its down-regulation in this disease raises the question of whether it normally inhibits MDR. In this study we observed that two MDR gastric cancer cell lines showed lower expression of miR-218 compared with their chemosensitive parental cell line. Overexpressing miR-218 chemosensitizes gastric cancer cells, slowed efflux of adriamycin, and accelerated drug-induced apoptosis. We identified the smoothened (SMO) gene as a functional target of miR-218, and found that SMO overexpression counteracts the chemosensitizing effects of miR-218. These findings suggest that miR-218 inhibits MDR of gastric cancer cells by down-regulating SMO expression. PMID:26261515

  13. [Helicobacter pylori and gastric ulcer].

    PubMed

    Maaroos, H I

    1994-01-01

    In connection with longitudinal ulcer studies and the demonstration of Helicobacter pylori as the main cause of chronic gastritis, new aspects of gastric ulcer recurrences and healing become evident. This extends the possibilities to prognosticate the course of gastric ulcer and to use more effective treatment. PMID:7937016

  14. Effect of sucralfate on gastric emptying in duodenal ulcer patients

    SciTech Connect

    Petersen, J.M.; Caride, V.J.; Prokop, E.K.; Troncale, F.; McCallum, R.W.

    1985-05-01

    Duodenal ulcer (DU) patients may have accelerated gastric emptying (GE) suggesting that there is an increase in unbuffered gastric acid reaching the duodenum contributing to DU disease. Aluminum-containing antacids were shown to delay GE. The authors' aim was to investigate whether another aluminum-containing compound, Sucralfate, affects GE in normal and DU patients. Nine normal volunteers and 10 patients with documented DU disease were studied. For each test the subject ingested a meal composed of chicken liver Tc-99m-S-C mixed with beef stew and eaten with 4 oz. of water labelled with 100..mu..Ci of III-in-DTPA. On two separate days, subjects received 1 gram of Sucralfate (190 mg of aluminum per gram) or placebo in a randomized double-blind fashion one hour prior to the test meal. GE of liquids and solids in normal subjects was not significantly changed by Sucralfate. Sucralfate in the DU patients significantly slowed liquid emptying in the initial 40 min and solid food throughout the study compared to placebo (p<0.05). This paper summarizes that; GE of solids but not liquids is accelerated in DU patients compared to normal subjects; and sucralfate delays GE of both liquid and solid components of a meal in DU patients but has no effect on GE in normals. The authors conclude that a slowing of gastric emptying possibly mediated by aluminum ions, may be one mechanism by which Sucralfate enhances healing and decreases recurrence of DU.

  15. Variations of Weight Loss Following Gastric Bypass and Gastric Band

    PubMed Central

    Puzziferri, Nancy; Nakonezny, Paul A.; Livingston, Edward H.; Carmody, Thomas J.; Provost, David A.; Rush, A. John

    2016-01-01

    Objective To compare and describe the weight loss outcomes from gastric bypass and gastric band so as to define the variation of excess weight loss (EWL) among individual patients, the time to onset of effect, and the durability of weight loss in severely obese adults. Summary Background Data Gastric bypass and gastric band are the most common operations for obesity performed in the United States, but few reports have compared these 2 procedures. Methods Patients (N = 1733, aged 18–65 years) met National Institutes of Health criteria for obesity surgery and underwent either gastric bypass or gastric band between March 1997 and November 2006. The selection of bypass versus band was based on patient/surgeon discussion. The evaluable sample consisted of 1518 patients. The percentage of EWL was assessed over 2 years. Successful weight loss was defined a priori as ≥40% EWL in each of four 6-month postoperative measurement periods. The analyses included a mixed model and generalized estimating equation (GEE) model with repeated measures. Odds ratios and descriptive analyses were also provided. Results Gastric bypass was associated with less individual variation in weight loss than gastric band. Both procedures were associated with a significant EWL benefit (Treatment Group effect P < 0.0001), but they differed in terms of time to effect (Treatment Group × Period interaction effect P < 0.0001). The mean EWL for gastric bypass was greater at each measurement period (6, 12, 18, 24 months) compared with gastric band (P < 0.0001). Furthermore, at each of the postoperative measurement periods within each treatment group (bypass and band), the mean EWL was greater for those who had preoperative body mass index (BMI) ≤50 kg/m2 than for those who had preoperative BMI >50 kg/m2 (P < 0.0001). Gastric bypass was consistently associated with a greater likelihood of at least a 40% EWL in each of the 6-month postoperative measurement periods (GEE, P < 0.0001). The odds ratio

  16. Go, Slow, and Whoa Foods

    MedlinePlus

    ... quick tips for seasonal health, safety and fun Go, Slow, and Whoa Foods Past Issues / Summer 2007 ... of California and Flaghouse, Inc. 2002 Food Group GO Almost anytime foods SLOW Sometimes foods WHOA Once ...

  17. Primary Gastric Chorioadenocarcinoma.

    PubMed

    Baraka, Bahaaeldin A; Al Kharusi, Suad S; Al Bahrani, Bassim J; Bhathagar, Gunmala

    2016-09-01

    Primary gastric chorioadenocarcinoma (PGC) is a rare and rapidly invasive tumor. Choriocarcinoma is usually known to be of endometrial origin and gestational; however, it has been reported in other extragenital organs, such as the gall bladder, prostate, lung, liver, and the gastrointestinal tract. Human chorionic gonadotropin related neoplasms of the stomach are seldom discussed in the literature. We report a case of PGC in a 56-year-old man treated with a standard non-gestational choriocarcinoma chemotherapy regimen, EMA/CO (etoposide, methotrexate, actinomycin D, cyclophosphamide, vincristine), with a complete response and good tolerability. PMID:27602194

  18. Primary Gastric Chorioadenocarcinoma

    PubMed Central

    Baraka, Bahaaeldin A.; Al Kharusi, Suad S.; Al Bahrani, Bassim J.; Bhathagar, Gunmala

    2016-01-01

    Primary gastric chorioadenocarcinoma (PGC) is a rare and rapidly invasive tumor. Choriocarcinoma is usually known to be of endometrial origin and gestational; however, it has been reported in other extragenital organs, such as the gall bladder, prostate, lung, liver, and the gastrointestinal tract. Human chorionic gonadotropin related neoplasms of the stomach are seldom discussed in the literature. We report a case of PGC in a 56-year-old man treated with a standard non-gestational choriocarcinoma chemotherapy regimen, EMA/CO (etoposide, methotrexate, actinomycin D, cyclophosphamide, vincristine), with a complete response and good tolerability. PMID:27602194

  19. Two-wave propagation in in vitro swine distal ulna

    NASA Astrophysics Data System (ADS)

    Mano, Isao; Horii, Kaoru; Matsukawa, Mami; Otani, Takahiko

    2015-07-01

    Ultrasonic transmitted waves were obtained in an in vitro swine distal ulna specimen, which mimics a human distal radius, that consists of interconnected cortical bone and cancellous bone. The transmitted waveforms appeared similar to the fast waves, slow waves, and overlapping fast and slow waves measured in the specimen after removing the surface cortical bone (only cancellous bone). In addition, the circumferential waves in the cortical bone and water did not affect the fast and slow waves. This suggests that the fast-and-slow-wave phenomenon can be observed in an in vivo human distal radius.

  20. Demonstration of slow light in semiconductor optical amplifier

    NASA Astrophysics Data System (ADS)

    Patil, Anoop C.; Venkitesh, Deepa; Dexter, Karl; Anandarajah, Prince; Barry, Liam P.

    2011-08-01

    Slow light generation through four wave mixing is experimentally investigated in a non-linear semiconductor optical amplifier (SOA). The mechanism of slow-light generation is analyzed through gain saturation behavior of the SOA. The delay of the probe beam is controlled optically by pump-probe detuning. A delay of 260 ps is achieved for sinusoidal modulation at 0.5 GHz corresponding to a RF phase change of 0.26π.

  1. Demonstration of slow light in semiconductor optical amplifier

    NASA Astrophysics Data System (ADS)

    Patil, Anoop C.; Venkitesh, Deepa; Dexter, Karl; Anandarajah, Prince; Barry, Liam P.

    2010-12-01

    Slow light generation through four wave mixing is experimentally investigated in a non-linear semiconductor optical amplifier (SOA). The mechanism of slow-light generation is analyzed through gain saturation behavior of the SOA. The delay of the probe beam is controlled optically by pump-probe detuning. A delay of 260 ps is achieved for sinusoidal modulation at 0.5 GHz corresponding to a RF phase change of 0.26π.

  2. Slow earthquakes, preseismic velocity changes, and the origin of slow frictional stick-slip.

    PubMed

    Kaproth, Bryan M; Marone, C

    2013-09-13

    Earthquakes normally occur as frictional stick-slip instabilities, resulting in catastrophic failure and seismic rupture. Tectonic faults also fail in slow earthquakes with rupture durations of months or more, yet their origin is poorly understood. Here, we present laboratory observations of repetitive, slow stick-slip in serpentinite fault zones and mechanical evidence for their origin. We document a transition from unstable to stable frictional behavior with increasing slip velocity, providing a mechanism to limit the speed of slow earthquakes. We also document reduction of P-wave speed within the active shear zone before stick-slip events. If similar mechanisms operate in nature, our results suggest that higher-resolution studies of elastic properties in tectonic fault zones may aid in the search for reliable earthquake precursors. PMID:23950495

  3. Slow Transit Constipation.

    PubMed

    Wald, Arnold

    2002-08-01

    The diagnosis of slow transit functional constipation is based upon diagnostic testing of patients with idiopathic constipation who responded poorly to conservative measures such as fiber supplements, fluids, and stimulant laxatives. These tests include barium enema or colonoscopy, colonic transit of radio-opaque markers, anorectal manometry, and expulsion of a water-filled balloon. Plain abdominal films can identify megacolon, which can be further characterized by barium or gastrografin studies. Colonic transit of radio-opaque markers identifies patients with slow transit with stasis of markers in the proximal colon. However, anorectal function should be characterized to exclude outlet dysfunction, which may coexist with colonic inertia. Because slow colonic transit is defined by studies during which patients consume a high-fiber diet, fiber supplements are generally not effective, nor are osmotic laxatives that consist of unabsorbed sugars. Stimulant laxatives are considered first-line therapy, although studies often show a diminished colonic motor response to such agents. There is no evidence to suggest that chronic use of such laxatives is harmful if they are used two to three times per week. Polyethylene glycol with or without electrolytes may be useful in a minority of patients, often combined with misoprostol. I prefer to start with misoprostol 200 mg every other morning and increase to tolerance or efficacy. I see no advantage in prescribing misoprostol on a TID or QID basis or even daily because it increases cramping unnecessarily. This drug is not acceptable in young women who wish to become pregnant. An alternative may be colchicine, which is reported to be effective when given as 0.6 mg TID. Long-term efficacy has not been studied. Finally, biofeedback is a risk-free approach that has been reported as effective in approximately 60% of patients with slow transit constipation in the absence of outlet dysfunction. Although difficult to understand

  4. [Molecular Subtypes of Gastric Cancer].

    PubMed

    Hatogai, Ken; Doi, Toshihiko

    2016-03-01

    Gastric cancer has been classified based on the pathological characteristics including microscopic configuration and growth pattern. Although these classifications have been used in studies investigating prognosis and recurrence pattern, they are not considered for decisions regarding the therapeutic strategy. In the ToGA study, trastuzumab, an anti-HER2 monoclonal antibody, demonstrated clinical efficacy for gastric cancer with HER2 overexpression or HER2 gene amplification. Based on these findings of the ToGA study, the definition of HER2-positive gastric cancer was established. Thereafter, several molecular targeted agents, including agents targeting other receptor tyrosine kinases, have been investigated in gastric cancer. However, to date no biomarker, except HER2, has been established. Based on the recent technological development in the field of gene analysis, a comprehensive molecular evaluation of gastric cancer was performed as part of The Cancer Genome Atlas (TCGA) project, and a new molecular classification was proposed that divided gastric cancer into the following 4 subtypes: tumors positive for Epstein-Barr virus, microsatellite instability tumors, genomically stable tumors, and tumors with chromosomal instability. Each subtype has specific molecular alterations including gene mutation and amplification, DNA methylation, and protein overexpression. Additionally, some subtypes were suggested to be correlated with the clinicopathological characteristics or as targets of some molecular targeted agents that are currently under development. The new molecular classification is expected to be a roadmap for patient stratification and clinical trials on molecular targeted therapies in gastric cancer. PMID:27067842

  5. Other Helicobacters and gastric microbiota.

    PubMed

    De Witte, Chloë; Schulz, Christian; Smet, Annemieke; Malfertheiner, Peter; Haesebrouck, Freddy

    2016-09-01

    This article aimed to review the literature from 2015 dealing with gastric and enterohepatic non-Helicobacter pylori Helicobacter species (NHPH). A summary of the gastric microbiota interactions with H. pylori is also presented. An extensive number of studies were published during the last year and have led to a better understanding of the pathogenesis of infections with NHPH. These infections are increasingly reported in human patients, including infections with H. cinaedi, mainly characterized by severe bacteremia. Whole-genome sequencing appears to be the most reliable technique for identification of NHPH at species level. Presence of NHPH in laboratory animals may influence the outcome of experiments, making screening and eradication desirable. Vaccination based on UreB proteins or bacterial lysate with CCR4 antagonists as well as oral glutathione supplementation may be promising strategies to dampen the pathogenic effects associated with gastric NHPH infections. Several virulent factors such as outer membrane proteins, phospholipase C-gamma 2, Bak protein, and nickel-binding proteins are associated with colonization of the gastric mucosae and development of gastritis. The development of high-throughput sequencing has led to new insights in the gastric microbiota composition and its interaction with H. pylori. Alterations in the gastric microbiota caused by the pH-increasing effect of a H. pylori infection may increase the risk for gastric cancer. PMID:27531542

  6. Slow microwaves in left-handed materials

    NASA Astrophysics Data System (ADS)

    di Gennaro, E.; Parimi, P. V.; Lu, W. T.; Sridhar, S.; Derov, J. S.; Turchinetz, B.

    2005-07-01

    Remarkably slow propagation of microwaves in two different classes of left-handed materials (LHM’s) is reported from microwave-pulse and continuous-wave transmission measurements. Microwave dispersion in a composite LHM made of split-ring resonators and wire strips reveals group velocity vg˜c/50 , where c is the free-space light velocity. Photonic crystals (PhC’s) made of dielectric Al2O3 rods reveal vg˜c/10 . Group delay dispersion of both the composite LHM and PhC’s determined from the experiment is in complete agreement with that obtained from theory. The slow group velocities are quantitatively described by the strong dispersion observed in these materials.

  7. Slow Scan Telemedicine

    NASA Technical Reports Server (NTRS)

    1984-01-01

    Originally developed under contract for NASA by Ball Bros. Research Corporation for acquiring visual information from lunar and planetary spacecraft, system uses standard closed circuit camera connected to a device called a scan converter, which slows the stream of images to match an audio circuit, such as a telephone line. Transmitted to its destination, the image is reconverted by another scan converter and displayed on a monitor. In addition to assist scans, technique allows transmission of x-rays, nuclear scans, ultrasonic imagery, thermograms, electrocardiograms or live views of patient. Also allows conferencing and consultation among medical centers, general practitioners, specialists and disease control centers. Commercialized by Colorado Video, Inc., major employment is in business and industry for teleconferencing, cable TV news, transmission of scientific/engineering data, security, information retrieval, insurance claim adjustment, instructional programs, and remote viewing of advertising layouts, real estate, construction sites or products.

  8. Reduction of hexavalent chromium by fasted and fed human gastric fluid. II. Ex vivo gastric reduction modeling.

    PubMed

    Kirman, Christopher R; Suh, Mina; Hays, Sean M; Gürleyük, Hakan; Gerads, Russ; De Flora, Silvio; Parker, William; Lin, Shu; Haws, Laurie C; Harris, Mark A; Proctor, Deborah M

    2016-09-01

    To extend previous models of hexavalent chromium [Cr(VI)] reduction by gastric fluid (GF), ex vivo experiments were conducted to address data gaps and limitations identified with respect to (1) GF dilution in the model; (2) reduction of Cr(VI) in fed human GF samples; (3) the number of Cr(VI) reduction pools present in human GF under fed, fasted, and proton pump inhibitor (PPI)-use conditions; and (4) an appropriate form for the pH-dependence of Cr(VI) reduction rate constants. Rates and capacities of Cr(VI) reduction were characterized in gastric contents from fed and fasted volunteers, and from fasted pre-operative patients treated with PPIs. Reduction capacities were first estimated over a 4-h reduction period. Once reduction capacity was established, a dual-spike approach was used in speciated isotope dilution mass spectrometry analyses to characterize the concentration-dependence of the 2nd order reduction rate constants. These data, when combined with previously collected data, were well described by a three-pool model (pool 1 = fast reaction with low capacity; pool 2 = slow reaction with higher capacity; pool 3 = very slow reaction with higher capacity) using pH-dependent rate constants characterized by a piecewise, log-linear relationship. These data indicate that human gastric samples, like those collected from rats and mice, contain multiple pools of reducing agents, and low concentrations of Cr(VI) (<0.7 mg/L) are reduced more rapidly than high concentrations. The data and revised modeling results herein provide improved characterization of Cr(VI) gastric reduction kinetics, critical for Cr(VI) pharmacokinetic modeling and human health risk assessment. PMID:27396814

  9. What gastric cancer proteomic studies show about gastric carcinogenesis?

    PubMed

    Leal, Mariana Ferreira; Wisnieski, Fernanda; de Oliveira Gigek, Carolina; do Santos, Leonardo Caires; Calcagno, Danielle Queiroz; Burbano, Rommel Rodriguez; Smith, Marilia Cardoso

    2016-08-01

    Gastric cancer is a complex, heterogeneous, and multistep disease. Over the past decades, several studies have aimed to determine the molecular factors that lead to gastric cancer development and progression. After completing the human genome sequencing, proteomic technologies have presented rapid progress. Differently from the relative static state of genome, the cell proteome is dynamic and changes in pathologic conditions. Proteomic approaches have been used to determine proteome profiles and identify differentially expressed proteins between groups of samples, such as neoplastic and nonneoplastic samples or between samples of different cancer subtypes or stages. Therefore, proteomic technologies are a useful tool toward improving the knowledge of gastric cancer molecular pathogenesis and the understanding of tumor heterogeneity. This review aimed to summarize the proteins or protein families that are frequently identified by using high-throughput screening methods and which thus may have a key role in gastric carcinogenesis. The increased knowledge of gastric carcinogenesis will clearly help in the development of new anticancer treatments. Although the studies are still in their infancy, the reviewed proteins may be useful for gastric cancer diagnosis, prognosis, and patient management. PMID:27126070

  10. Gastric tissue biopsy and culture

    MedlinePlus

    ... laboratory test that examines the tissue sample for bacteria and other organisms that can cause disease. ... of organisms that cause infection. A gastric tissue culture may be ... Stomach acids normally prevent too much bacteria from growing.

  11. Gastric cancer pathogenesis.

    PubMed

    Berger, Hilmar; Marques, Miguel S; Zietlow, Rike; Meyer, Thomas F; Machado, Jose C; Figueiredo, Ceu

    2016-09-01

    Gastric cancer (GC) results from a multistep process that is influenced by Helicobacter pylori infection, genetic susceptibility of the host, as well as of other environmental factors. GC results from the accumulation of numerous genetic and epigenetic alterations in oncogenes and tumor suppressor genes, leading to dysregulation of multiple signaling pathways, which disrupt the cell cycle and the balance between cell proliferation and cell death. For this special issue, we have selected to review last year's advances related to three main topics: the cell of origin that initiates malignant growth in GC, the mechanisms of direct genotoxicity induced by H. pylori infection, and the role of aberrantly expressed long noncoding RNAs in GC transformation. The understanding of the molecular basis of GC development is of utmost importance for the identification of novel targets for GC prevention and treatment. PMID:27531537

  12. [Gastric duplication of 3 observations].

    PubMed

    Bugallo, M; Carauni, D; Serra, E; De los Reyes, C; Briend, S; Valdovinos, B; Lanari, A

    2000-01-01

    Gástric duplicación si an infrequent congenital malformation present in both, neonatal period and childhood, and exceptionally during adulthood. We present here there cases of gastric duplication from patients of different ages, in which it was not possible to make diagnosis before surgery. In all of them cystic form was the predominating one, without communication with gastric lumen (cavity). Diagnosis was performed after laparotomy and histopathological examination. PMID:11086515

  13. Slow, nondiffusive dynamics in concentrated nanoemulsions

    NASA Astrophysics Data System (ADS)

    Guo, H.; Wilking, J. N.; Liang, D.; Mason, T. G.; Harden, J. L.; Leheny, R. L.

    2007-04-01

    Using multispeckle x-ray photon correlation spectroscopy, we have measured the slow, wave-vector-dependent dynamics of concentrated, disordered nanoemulsions composed of silicone oil droplets in water. The intermediate scattering function possesses a compressed exponential line shape and a relaxation time that varies inversely with wave vector. We interpret this dynamics as strain in response to local stress relaxation. The motion includes a transient component whose characteristic velocity decays exponentially with time following a mechanical perturbation of the nanoemulsions and a second component whose characteristic velocity is essentially independent of time. The steady-state characteristic velocity is surprisingly insensitive to the droplet volume fraction in the concentrated regime, indicating that the strain motion is only weakly dependent on the droplet-droplet interactions.

  14. Gene methylation in gastric cancer.

    PubMed

    Qu, Yiping; Dang, Siwen; Hou, Peng

    2013-09-23

    Gastric cancer is one of the most common malignancies and remains the second leading cause of cancer-related death worldwide. Over 70% of new cases and deaths occur in developing countries. In the early years of the molecular biology revolution, cancer research mainly focuses on genetic alterations, including gastric cancer. Epigenetic mechanisms are essential for normal development and maintenance of tissue-specific gene expression patterns in mammals. Disruption of epigenetic processes can lead to altered gene function and malignant cellular transformation. Recent advancements in the rapidly evolving field of cancer epigenetics have shown extensive reprogramming of every component of the epigenetic machinery in cancer, including DNA methylation, histone modifications, nucleosome positioning, noncoding RNAs, and microRNAs. Aberrant DNA methylation in the promoter regions of gene, which leads to inactivation of tumor suppressor and other cancer-related genes in cancer cells, is the most well-defined epigenetic hallmark in gastric cancer. The advantages of gene methylation as a target for detection and diagnosis of cancer in biopsy specimens and non-invasive body fluids such as serum and gastric washes have led to many studies of application in gastric cancer. This review focuses on the most common and important phenomenon of epigenetics, DNA methylation, in gastric cancer and illustrates the impact epigenetics has had on this field. PMID:23669186

  15. Targeted therapy in gastric cancer.

    PubMed

    Thiel, Alexandra; Ristimäki, Ari

    2015-05-01

    Gastric cancer is often diagnosed at an advanced stage. Although chemotherapy prolongs survival and improves quality of life, the survival of gastric cancer patients with advanced disease is short. Thanks to recent insights into the molecular pathways involved in gastric carcinogenesis, new targeted treatment options have become available for gastric cancer patients. Trastuzumab, an antibody targeted to HER-2, was shown to improve survival of advanced gastric cancer patients harboring HER-2 overexpression due to gene amplification in their tumor cells, and is currently also explored in adjuvant and neoadjuvant settings. Another agent with promising results in clinical trials is ramucirumab, an antibody targeting VEGFR-2. No clear survival benefit, however, were experienced with agents targeting EGFR (cetuximab, panitumumab), VEGF-A (bevacizumab), or mTOR (everolimus). Drugs targeting c-MET/HGF are currently under investigation in biomarker-selected cohorts, with promising results in early clinical trials. This review will summarize the current status of targeted treatment options in gastric cancer. PMID:25706252

  16. Gastric control of food intake.

    PubMed

    Robinson, P H; McHugh, P R; Moran, T H; Stephenson, J D

    1988-01-01

    Inhibition of gastric emptying leads to enhanced satiety and this mechanism may contribute to the undereating observed after administration of cholecystokinin (CCK) and fenfluramine, and in patients with anorexia nervosa. Pyloric smooth muscle bears specific CCK receptors and the evidence suggests that a major site of action for CCK satiety is in the periphery. CCK receptors are widespread in the neonatal rat stomach but not in the brain and over the first two weeks of life binding in the stomach decreases and that in the brain increases. This and the finding that independent ingestion as well as gastric emptying are inhibited by CCK at birth suggest the stomach as its likely site of action in the neonatal rat. Fenfluramine inhibits feeding in animals and in patients with bulimia nervosa. In monkeys, fenfluramine inhibits gastric emptying and this action correlates with its feeding inhibition. Patients with anorexia nervosa who are acutely starving and rats maintained on a restricted diet have delayed gastric emptying. Anorexic patients showed abnormal reporting of both hunger and satiety, and, together with those with bulimia nervosa, often associated gastric contents with symptoms of eating disorder, indicating disturbed interpretation of gastric signals. PMID:3065484

  17. Genetics and gastric cancer susceptibility

    PubMed Central

    Lu, Yan; Lu, Fang; Zeng, Sha; Sun, Suqing; Lu, Li; Liu, Lifeng

    2015-01-01

    Gastric cancer has high morbidity and mortality in China. It is ranked first in malignant tumors of the digestive system. Its etiology and pathogenesis are still unclear, but they may be associated with a variety of factors. Genetic susceptibility genes have become a research hotspot in China. Elucidating the genetic mechanisms of gastric cancer can facilitate achieving individualized prevention and developing more effective methods to reduce clinical adverse consequences, which has important clinical significance. Genetic susceptibility results from the influence of genetic factors or specific genetic defects that endow an individual’s offspring with certain physiological and metabolic features that are prone to certain diseases. Currently, studies on the genetic susceptibility genes of gastric cancer have become a hotspot. The purpose is to screen for the etiology of gastric cancer, search for gene therapy methods, and ultimately provide a scientific basis for the prevention and control of gastric cancer. This article reviews the current progress of studies on genetic susceptibility genes for gastric cancer. PMID:26309491

  18. DBGC: A Database of Human Gastric Cancer.

    PubMed

    Wang, Chao; Zhang, Jun; Cai, Mingdeng; Zhu, Zhenggang; Gu, Wenjie; Yu, Yingyan; Zhang, Xiaoyan

    2015-01-01

    The Database of Human Gastric Cancer (DBGC) is a comprehensive database that integrates various human gastric cancer-related data resources. Human gastric cancer-related transcriptomics projects, proteomics projects, mutations, biomarkers and drug-sensitive genes from different sources were collected and unified in this database. Moreover, epidemiological statistics of gastric cancer patients in China and clinicopathological information annotated with gastric cancer cases were also integrated into the DBGC. We believe that this database will greatly facilitate research regarding human gastric cancer in many fields. DBGC is freely available at http://bminfor.tongji.edu.cn/dbgc/index.do. PMID:26566288

  19. Slow inactivation of Na(+) channels.

    PubMed

    Silva, Jonathan

    2014-01-01

    Prolonged depolarizing pulses that last seconds to minutes cause slow inactivation of Na(+) channels, which regulates neuron and myocyte excitability by reducing availability of inward current. In neurons, slow inactivation has been linked to memory of previous excitation and in skeletal muscle it ensures myocytes are able to contract when K(+) is elevated. The molecular mechanisms underlying slow inactivation are unclear even though it has been studied for 50+ years. This chapter reviews what is known to date regarding the definition, measurement, and mechanisms of voltage-gated Na(+) channel slow inactivation. PMID:24737231

  20. Progress of Photodynamic Therapy in Gastric Cancer

    PubMed Central

    Narahara, Hiroyuki; Otani, Toru; Okuda, Shigeru

    1999-01-01

    Progress of photodynamic therapy (PDT) in gastric cancer and the clinical outcome are described in this paper. (1) We included the whole lesion and a 5 mm margin in the field for irradiation. Marking by injection of India-ink showing the irradiation field was performed beforehand. (2) We established the standard light dose to be 90 J/cm2 for an argon dye laser and 60 J/cm2 for a pulse wave laser. (3) The size of cancerous lesion curable by PDT was expanded from 3 cm in diameter, i.e. 7 cm2 in area to 4 cm in diameter, i.e. 13 cm2 by employing a new excimer dye laser model, which could emit 4mJ/pulse with 80 Hz pulse frequency. (4) The depth of cancer invasion which could be treated by PDT was increased from about 4 mm, i.e. the superficial part of the submucosal layer (SM-1) to more than 10 mm in depth, i.e. the proper muscular layer. These improvements owe much to the pulse laser, the photodynamic action induced by which permits deeper penetration than that of a continuous wave laser. (5) We employed a side-viewing fiberscope for gastric PDT to irradiate the lesion from an angle of 90°. (6) We designed a simple cut quartz fiber for photoradiation with a spiral spring thickened toward the end. (7) We developed an endoscopic device for photoradiation in PDT which achieves accurate and efficient irradiation. As a result of these improvements a higher cure rate was obtained even with a lower light dose of irradiation. PMID:18493500

  1. Spontaneous neuronal burst discharges as dependent and independent variables in the maturation of cerebral cortex tissue cultured in vitro: a review of activity-dependent studies in live 'model' systems for the development of intrinsically generated bioelectric slow-wave sleep patterns.

    PubMed

    Corner, Michael A

    2008-11-01

    A survey is presented of recent experiments which utilize spontaneous neuronal spike trains as dependent and/or independent variables in developing cerebral cortex cultures when synaptic transmission is interfered with for varying periods of time. Special attention is given to current difficulties in selecting suitable preparations for carrying out biologically relevant developmental studies, and in applying spike-train analysis methods with sufficient resolution to detect activity-dependent age and treatment effects. A hierarchy of synchronized nested burst discharges which approximate early slow-wave sleep patterns in the intact organism is established as a stable basis for isolated cortex function. The complexity of reported long- and short-term homeostatic responses to experimental interference with synaptic transmission is reviewed, and the crucial role played by intrinsically generated bioelectric activity in the maturation of cortical networks is emphasized. PMID:18722470

  2. Pembrolizumab, Combination Chemotherapy, and Radiation Therapy Before Surgery in Treating Adult Patients With Locally Advanced Gastroesophageal Junction or Gastric Cardia Cancer That Can Be Removed by Surgery

    ClinicalTrials.gov

    2016-06-27

    Adenocarcinoma of the Gastroesophageal Junction; Gastric Cardia Adenocarcinoma; Stage IB Gastric Cancer; Stage IIA Gastric Cancer; Stage IIB Gastric Cancer; Stage IIIA Gastric Cancer; Stage IIIB Gastric Cancer

  3. Gastric lactobezoar - a rare disorder?

    PubMed Central

    2012-01-01

    Gastric lactobezoar, a pathological conglomeration of milk and mucus in the stomach of milk-fed infants often causing gastric outlet obstruction, is a rarely reported disorder (96 cases since its first description in 1959). While most patients were described 1975-1985 only 26 children have been published since 1986. Clinically, gastric lactobezoars frequently manifest as acute abdomen with abdominal distension (61.0% of 96 patients), vomiting (54.2%), diarrhea (21.9%), and/or a palpable abdominal mass (19.8%). Respiratory (23.0%) and cardiocirculatory (16.7%) symptoms are not uncommon. The pathogenesis of lactobezoar formation is multifactorial: exogenous influences such as high casein content (54.2%), medium chain triglycerides (54.2%) or enhanced caloric density (65.6%) of infant milk as well as endogenous factors including immature gastrointestinal functions (66.0%), dehydration (27.5%) and many other mechanisms have been suggested. Diagnosis is easy if the potential presence of a gastric lactobezoar is thought of, and is based on a history of inappropriate milk feeding, signs of acute abdomen and characteristic features of diagnostic imaging. Previously, plain and/or air-, clear fluid- or opaque contrast medium radiography techniques were used to demonstrate a mass free-floating in the lumen of the stomach. This feature differentiates a gastric lactobezoar from intussusception or an abdominal neoplasm. Currently, abdominal ultrasound, showing highly echogenic intrabezoaric air trapping, is the diagnostic method of choice. However, identifying a gastric lactobezoar requires an investigator experienced in gastrointestinal problems of infancy as can be appreciated from the results of our review which show that in not even a single patient gastric lactobezoar was initially considered as a possible differential diagnosis. Furthermore, in over 30% of plain radiographs reported, diagnosis was initially missed although a lactobezoar was clearly demonstrable on repeat

  4. Measurement of gastric emptying during and between meal intake in free-feeding Lewis rats.

    PubMed

    van der Velde, P; Koslowsky, I; Koopmans, H S

    1999-02-01

    A new scintigraphic measurement technique is described that allows accurate assessment of gastric emptying in between as well as during a number of successive meals. Measurements were made every minute of food intake, gastric nutrient filling, and gastric emptying over a 6 h, 40 min period in conscious, free-feeding, loosely restrained rats. Before receiving access to the food, the animals had been deprived for a period of 31 h. Over the full duration of the experiment, an average rate of gastric emptying of 2.46 +/- 0.18 (SE) kcal/h was established. During most meals, however, the gastric emptying rate was increased so that an average of 26.9 +/- 2.7% of the ingested calories was emptied while the animals were feeding, with an average emptying rate of 0.15 +/- 0.014 kcal/min or 8.88 +/- 0.84 kcal/h. This transient increase in the rate of gastric emptying was followed by a subsequent slowing of gastric emptying after meal termination; in the 10-min postmeal interval, an average emptying rate of 0.96 +/- 0.12 kcal/h was found. Despite these fluctuations during and immediately after meals, a relatively constant rate of caloric emptying is maintained over longer periods. There were no differences between the emptying rate during the first meal when the gastrointestinal tract was still empty, compared with later meals when the gastrointestinal tract had been filled with food. The emptying rate during the 10-min postmeal interval, however, was significantly reduced during later meals. The results suggest that gastric emptying is controlled by different mechanisms during and after the ingestion of food and that these mechanisms remain in effect at various degrees of gastrointestinal filling. PMID:9950942

  5. Memory improvement via slow-oscillatory stimulation during sleep in older adults.

    PubMed

    Westerberg, Carmen E; Florczak, Susan M; Weintraub, Sandra; Mesulam, M-Marsel; Marshall, Lisa; Zee, Phyllis C; Paller, Ken A

    2015-09-01

    We examined the intriguing but controversial idea that disrupted sleep-dependent consolidation contributes to age-related memory decline. Slow-wave activity during sleep may help strengthen neural connections and provide memories with long-term stability, in which case decreased slow-wave activity in older adults could contribute to their weaker memories. One prediction from this account is that age-related memory deficits should be reduced by artificially enhancing slow-wave activity. In young adults, applying transcranial current oscillating at a slow frequency (0.75 Hz) during sleep improves memory. Here, we tested whether this procedure can improve memory in older adults. In 2 sessions separated by 1 week, we applied either slow-oscillatory stimulation or sham stimulation during an afternoon nap in a double-blind, crossover design. Memory tests were administered before and after sleep. A larger improvement in word-pair recall and higher slow-wave activity was observed with slow-oscillatory stimulation than with sham stimulation. This is the first demonstration that this procedure can improve memory in older adults, suggesting that declarative memory performance in older adults is partly dependent on slow-wave activity during sleep. PMID:26116933

  6. Risks of Stomach (Gastric) Cancer Screening

    MedlinePlus

    ... Treatment Stomach Cancer Prevention Stomach Cancer Screening Research Stomach (Gastric) Cancer Screening (PDQ®)–Patient Version What is ... These are called diagnostic tests . General Information About Stomach (Gastric) Cancer Key Points Stomach cancer is a ...

  7. Aldioxa improves delayed gastric emptying and impaired gastric compliance, pathophysiologic mechanisms of functional dyspepsia

    PubMed Central

    Asano, Teita; Aida, Shuji; Suemasu, Shintaro; Tahara, Kayoko; Tanaka, Ken-ichiro; Mizushima, Tohru

    2015-01-01

    Delayed gastric emptying and impaired gastric accommodation (decreased gastric compliance) play important roles in functional dyspepsia (FD). Here we screen for a clinically used drug with an ability to improve delayed gastric emptying in rats. Oral administration of aldioxa (dihydroxyaluminum allantoinate) partially improved clonidine- or restraint stress-induced delayed gastric emptying. Administration of allantoin, but not aluminium hydroxide, restored the gastric emptying. Both aldioxa and allantoin inhibited clonidine binding to the α-2 adrenergic receptor, suggesting that antagonistic activity of the allantoin moiety of aldioxa on this receptor is involved in the restoration of gastric emptying activity. Aldioxa or aluminium hydroxide but not allantoin restored gastric compliance with restraint stress, suggesting that aluminium hydroxide moiety is involved in this restoration. We propose that aldioxa is a candidate drug for FD, because its safety in humans has already been confirmed and its ameliorating effect on both of delayed gastric emptying and impaired gastric compliance are confirmed here. PMID:26620883

  8. Novel insights into the effects of diabetes on gastric motility.

    PubMed

    Marathe, Chinmay S; Rayner, Christopher K; Jones, Karen L; Horowitz, Michael

    2016-01-01

    Recent data from the Diabetes Control and Complications Trial/Epidemiology of Diabetic Interventions and Complications cohort indicate that the disease burden of gastroparesis in diabetes remains high, consistent with the outcome of cross-sectional studies in type 1 and 2 diabetes. An improved understanding of the pathogenesis of diabetic gastroparesis at the cellular level has emerged in the last decade, particularly as a result of initiatives such as the National Institute of Health funded Gastroparesis Clinical Research Consortium in the US. Management of diabetic gastroparesis involves dietary and psychological support, attention to glycaemic control, and the use of prokinetic agents. Given that the relationship between upper gastrointestinal symptoms and the rate of gastric emptying is weak, therapies targeted specifically at symptoms, such as nausea or pain, are important. The relationship between gastric emptying and postprandial glycaemia is complex and inter-dependent. Short-acting glucagon-like peptide-1 agonists, that slow gastric emptying, can be used to reduce postprandial glycaemic excursions and, in combination with basal insulin, result in substantial reductions in glycated haemoglobin in type 2 patients. PMID:26647088

  9. Subtotal gastrectomy for gastric cancer

    PubMed Central

    Santoro, Roberto; Ettorre, Giuseppe Maria; Santoro, Eugenio

    2014-01-01

    Although a steady decline in the incidence and mortality rates of gastric carcinoma has been observed in the last century worldwide, the absolute number of new cases/year is increasing because of the aging of the population. So far, surgical resection with curative intent has been the only treatment providing hope for cure; therefore, gastric cancer surgery has become a specialized field in digestive surgery. Gastrectomy with lymph node (LN) dissection for cancer patients remains a challenging procedure which requires skilled, well-trained surgeons who are very familiar with the fast-evolving oncological principles of gastric cancer surgery. As a matter of fact, the extent of gastric resection and LN dissection depends on the size of the disease and gastric cancer surgery has become a patient and “disease-tailored” surgery, ranging from endoscopic resection to laparoscopic assisted gastrectomy and conventional extended multivisceral resections. LN metastases are the most important prognostic factor in patients that undergo curative resection. LN dissection remains the most challenging part of the operation due to the location of LN stations around major retroperitoneal vessels and adjacent organs, which are not routinely included in the resected specimen and need to be preserved in order to avoid dangerous intra- and postoperative complications. Hence, the surgeon is the most important non-TMN prognostic factor in gastric cancer. Subtotal gastrectomy is the treatment of choice for middle and distal-third gastric cancer as it provides similar survival rates and better functional outcome compared to total gastrectomy, especially in early-stage disease with favorable prognosis. Nonetheless, the resection range for middle-third gastric cancer cases and the extent of LN dissection at early stages remains controversial. Due to the necessity of a more extended procedure at advanced stages and the trend for more conservative treatments in early gastric cancer, the

  10. Acetaldehyde and gastric cancer.

    PubMed

    Salaspuro, Mikko

    2011-04-01

    Aldehyde dehydrogenase (ALDH2) and alcohol dehydrogenase (ADH) gene polymorphisms associating with enhanced acetaldehyde exposure and markedly increased cancer risk in alcohol drinkers provide undisputable evidence for acetaldehyde being a local carcinogen not only in esophageal but also in gastric cancer. Accordingly, acetaldehyde associated with alcoholic beverages has recently been classified as a Group 1 carcinogen to humans. Microbes are responsible for the bulk of acetaldehyde production from ethanol both in saliva and Helicobacter pylori-infected and achlorhydric stomach. Acetaldehyde is the most abundant carcinogen in tobacco smoke and it readily dissolves into saliva during smoking. Many foodstuffs and 'non-alcoholic' beverages are important but unrecognized sources of local acetaldehyde exposure. The cumulative cancer risk associated with increasing acetaldehyde exposure suggests the need for worldwide screening of the acetaldehyde levels of alcoholic beverages and as well of the ethanol and acetaldehyde of food produced by fermentation. The generally regarded as safe status of acetaldehyde should be re-evaluated. The as low as reasonably achievable principle should be applied to the acetaldehyde of alcoholic and non-alcoholic beverages and food. Risk groups with ADH-and ALDH2 gene polymorphisms, H. pylori infection or achlorhydric atrophic gastritis, or both, should be screened and educated in this health issue. L-cysteine formulations binding carcinogenic acetaldehyde locally in the stomach provide new means for intervention studies. PMID:21401890

  11. [Gastric cancer in Lima].

    PubMed

    Pilco, Paul; Payet, Eduardo; Cáceres, Eduardo

    2006-01-01

    Gastric cancer continues to be one of the most common malignant neoplasias in the world. Despite the decreasing incidence of this disease in developed countries, Eastern Europe and Latin America show the highest incidences. It accounted for 8.6% of all new cases of cancer in 2002. In Peru it has increased between 1990 and 1997 amounting to 24.3/100000 in men and 17.6/100000 in women, during the last period studied, thus it is considered a high risk area. Mortality: it is still the leading cause of death for both sexes, in men it is 19.3/100000 and in women 14.2/100000. Incidence is directly proportional to the place of origin in Metropolitan Lima, a city of almost 8 million inhabitants, and the districts with the highest incidences are Puente Piedra and Lince followed by Villa El Salvador, El Augustino, Breña and Rimac among others. These are districts with medium-low socioeconomic levels, whereas the lowest incidences are found in districts with high socioeconomic levels, such as San Isidro and Miraflores, among others. PMID:17211488

  12. Centrally driven slow oscillating potential of extrathoracic trachea.

    PubMed

    Kondo, T; Kobayashi, I; Hirokawa, Y; Ohta, Y; Yamabayashi, H; Arita, H

    1993-03-01

    Spontaneous electrical activity of extrathoracic trachea was recorded along with force developed by tracheal smooth muscle and phrenic nerve activity in decerebrated, paralyzed, and artificially ventilated dogs with pneumothorax. The tracheal electrical activity exhibited slow oscillating potentials that were coupled with spontaneous phasic contraction of trachea. Both rhythmic changes were synchronous with central respiratory rhythm represented by phrenic burst, independent of the respirator's rhythm. The dominant component of the slow oscillating potentials consisted of sinusoidal waves with large amplitude that occurred shortly after cessation of phrenic burst, i.e., in the postinspiratory phase. The concomitant small change in the slow oscillating potentials began in the late inspiratory phase just before the initiation of the tracheal contraction. This phase relationship was preserved after removal of intrathoracic vagal afferents from lungs. Such slow oscillating potentials were also observed during lung collapse produced by disconnecting the tube attached to the respirator. Transection of recurrent laryngeal nerves abolished the slow oscillating potentials. These results indicate that the slow oscillating potentials of the extrathoracic trachea are generated by a physiological process associated with the central respiratory rhythm. The dominant component of the slow oscillating potentials occurs in the postinspiratory phase. PMID:8482644

  13. Ingestion, gastric fill, and gastric emptying before and after withdrawal of gastric contents.

    PubMed

    Kaplan, J M; Siemers, W; Grill, H J

    1994-11-01

    The notion that satiation signals are derived from the stomach with no additional contribution of postgastric sources (J. A. Deutsch. In: Handbook of Behavioral Neuroscience, Food and Water Intake. 1990, vol. 10, p. 151-182) was evaluated in two experiments. In experiment 1, the gastric contents were withdrawn after the rat met the satiety criterion for an initial intraoral intake test (12.5% glucose delivered at 1.0 ml/min). Ten minutes later, the intraoral infusion was continued until the rat again met the satiety criterion. We found that rats reingested an amount closely corresponding to the amount withdrawn, in agreement with previous studies using spout-licking tests. Despite a lower gastric emptying rate during reingestion than during the initial test, the amount recovered from the stomach (both volume and solute content) after reingestion was significantly less (gastric volume 16% less; gastric glucose 18% less) than that withdrawn initially. In experiment 2, a portion (8 ml) of the gastric contents was removed after the end of an initial intraoral intake test and, after 10 min, rats were again given an opportunity to ingest to satiety. The procedure was repeated for a total of three withdrawals (24 ml) and three reingestion opportunities. Rats accurately replaced the amounts withdrawn such that net intake at the end of the experiment did not differ from that ingested during the initial test. In addition, the amount recovered from the stomach after the terminal test was considerably less (gastric volume 25% less; gastric glucose 29% less) than that recovered at the end of single-test control sessions.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7977874

  14. Slow bars in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Fridman, A. M.; Khoruzhii, O. V.

    2000-11-01

    Here we put forward some arguments in favour of the existence of slow bars. More then a half of spiral galaxies have in their central regions a bar - a structure in the form of triaxial ellipsoid. Historically two models of the bar were developed - those of the so called ``slow'' and ``fast'' bars. In both cases the bar is in some resonance with the galactic disc region near the bar ends - it is the corotation resonance for a fast bar and the inner Lindblad resonance for a slow bar. For the same angular velocity the fast bar would be larger then the slow bar. Alternatively, for the same size the fast bar would have much higher angular velocity, that being the reason for the terminology used. Up till now, the direct measurement of angular velocity of a bar has been an open problem. This is why all arguments on the nature of bar observed in some particular galaxy are inevitably indirect. Despite the fact that the model of slow bars was developed slightly earlier, the main part of attention was focused on the fast bars. Presently many researchers believe in the existence of the fast bars in real galaxies, while discussions on the existence of the slow bars continue so far. In this Letter we demonstrate that the bar detected in the grand design spiral galaxy NGC 157 is the slow bar.

  15. Epstein-Barr virus in gastric carcinomas and gastric stump carcinomas: a late event in gastric carcinogenesis

    PubMed Central

    zur Hausen, A; van Rees, B P; van Beek, J; Craanen, M E; Bloemena, E; Offerhaus, G J A; Meijer, C J L M; van den Brule, A J C

    2004-01-01

    Background: To determine at what stage during gastric carcinogenesis Epstein-Barr virus (EBV) enters the gastric epithelial cells, the presence of EBV was investigated in two pathogenetically related but distinct forms of adenocarcinoma of the stomach—gastric carcinoma of the intact stomach (GCIS) and gastric stump carcinoma (GSC)—and their presumed precursor lesions. Patients and methods: Eleven patients with EBV positive GCIS and eight patients with EBV positive GSC, demonstrated by the highly sensitive EBV encoded RNA 1/2 (EBER1/2) RNA in situ hybridisation (RISH) technique, were studied. Paraffin wax embedded tissue available from preoperative gastric biopsies and tumour adjacent tissue from the resection specimens containing normal gastric mucosa, inflamed gastric mucosa, and preneoplastic lesions (intestinal metaplasia and dysplasia) was investigated by EBER1/2 RISH, in addition to EBV nuclear antigen 1 (EBNA-1) and latent membrane protein 1 (LMP-1) immunohistochemistry (IHC). Results: In both GCIS and GSC and their precursor lesions EBER1/2 transcripts were restricted to the carcinoma cells. In addition, positivity of EBNA-1 IHC was also restricted to the tumour cells. IHC for LMP-1 was negative in all cases tested. Conclusions: The absence of EBER1/2 transcripts in preneoplastic gastric lesions (intestinal metaplasia and dysplasia) and their presence in two distinct types of gastric carcinoma strongly suggest that EBV can only infect neoplastic gastric cells and thus is a late event in gastric carcinogenesis. PMID:15113855

  16. Ghrelin and gastric acid secretion

    PubMed Central

    Yakabi, Koji; Kawashima, Junichi; Kato, Shingo

    2008-01-01

    Ghrelin, a novel growth hormone-releasing peptide, was originally isolated from rat and human stomach. Ghrelin has been known to increase the secretion of growth hormone (GH), food intake, and body weight gain when administered peripherally or centrally. Ghrelin is also known to stimulate the gastric motility and the secretion of gastric acid. In the previous studies, the action of ghrelin on acid secretion was shown to be as strong as that of histamine and gastrin in in-vivo experiment. In the studies, the mechanism for the action of ghrelin was also investigated. It was shown that vagotomy completely inhibited the action of ghrelin on the secretion of gastric acid suggesting that vagal nerve is involved in the mechanism for the action of ghrelin on acid secretion. As famotidine did not inhibit ghrelin-induced acid secretion in the study by Masuda et al, they concluded that histamine was not involved in the action of ghrelin on acid secretion. However, we have shown that famotidine completely inhibited ghrelin-induced acid secretion and histidine decarboxylase (HDC) mRNA was increased in gastric mucosa by ghrelin injection which is inhibited by vagotomy Our results indicate that histamine is involved in the action of ghrelin on acid secretion. Furthermore synergistic action of gastrin and ghrelin on gastric acid secretion was shown. Although gastrin has important roles in postprandial secretion of gastric acid, ghrelin may be related to acid secretion during fasting period or at night. However, further studies are needed to elucidate the physiological role of ghrelin in acid secretion. PMID:19009648

  17. MHD Wave in Sunspots

    NASA Astrophysics Data System (ADS)

    Sych, Robert

    2016-02-01

    The study of magnetohydrodynamic (MHD) waves and oscillations in the solar atmosphere is one of the fastest developing fields in solar physics, and lies in the mainstream of using solar instrumentation data. This chapter first addresses the spatial frequency morphology of sources of sunspot oscillations and waves, including their localization, size, oscillation periods, and height localization with the mechanism of cutoff frequency that forms the observed emission variability. Then, it presents a review dynamic of sunspot wave processes, provides the information about the structure of wave fronts and their time variations, and investigates the oscillation frequency transformation depending on the wave energy. The chapter also addresses the initializing solar flares caused by trigger agents like magnetoacoustic waves, accelerated particle beams, and shocks. Special attention is paid to the relation between the flare reconnection periodic initialization and the dynamics of sunspot slow magnetoacoustic waves.

  18. Reflected-wave maser. [low noise amplifier

    NASA Technical Reports Server (NTRS)

    Clauss, R. C. (Inventor)

    1976-01-01

    A number of traveling-wave, slow-wave maser structures, containing active maser material but absent the typical ferrite isolators, are immersed in a nonuniform magnetic field. The microwave signal to be amplified is inserted at a circulator which directs the signal to a slow-wave structure. The signal travels through the slow-wave structure, being amplified according to the distance traveled. The end of the slow-wave structure farthest from the circulator is arranged to be a point of maximum reflection of the signal traveling through the slow-wave structure. As a consequence, the signal to be amplified traverses the slow-wave structure again, in the opposite direction (towards the circulator) experiencing amplification equivalent to that achieved by a conventional traveling-wave maser having twice the length. The circulator directs the amplified signal to following like stages of amplification. Isolators are used in between stages to prevent signals from traveling in the wrong direction, between the stages. Reduced signal loss is experienced at each stage. The high gain produced by each slow-wave structure is reduced to a moderate value by use of a nonuniform magnetic field which also broadens the line width of the maser material. The resulting bandwidth can be exceptionally wide. Cascaded stages provide high gain, exceptionally wide bandwith and very low noise temperature.

  19. Recapitulating Human Gastric Cancer Pathogenesis: Experimental Models of Gastric Cancer.

    PubMed

    Ding, Lin; El Zaatari, Mohamad; Merchant, Juanita L

    2016-01-01

    This review focuses on the various experimental models to study gastric cancer pathogenesis, with the role of genetically engineered mouse models (GEMMs) used as the major examples. We review differences in human stomach anatomy compared to the stomachs of the experimental models, including the mouse and invertebrate models such as Drosophila and C. elegans. The contribution of major signaling pathways, e.g., Notch, Hedgehog, AKT/PI3K is discussed in the context of their potential contribution to foregut tumorigenesis. We critically examine the rationale behind specific GEMMs, chemical carcinogens, dietary promoters, Helicobacter infection, and direct mutagenesis of relevant oncogenes and tumor suppressor that have been developed to study gastric cancer pathogenesis. Despite species differences, more efficient and effective models to test specific genes and pathways disrupted in human gastric carcinogenesis have yet to emerge. As we better understand these species differences, "humanized" versions of mouse models will more closely approximate human gastric cancer pathogenesis. Towards that end, epigenetic marks on chromatin, the gut microbiota, and ways of manipulating the immune system will likely move center stage, permitting greater overlap between rodent and human cancer phenotypes thus providing a unified progression model. PMID:27573785

  20. Delayed gastric emptying in Parkinson's disease.

    PubMed

    Marrinan, Sarah; Emmanuel, Anton V; Burn, David J

    2014-01-01

    Gastrointestinal symptoms are evident in all stages of Parkinson's disease (PD). Most of the gastrointestinal abnormalities associated with PD are attributable to impaired motility. At the level of the stomach, this results in delayed gastric emptying. The etiology of delayed gastric emptying in PD is probably multifactorial but is at least partly related to Lewy pathology in the enteric nervous system and discrete brainstem nuclei. Delayed gastric emptying occurs in both early and advanced PD but is underdetected in routine clinical practice. Recognition of delayed gastric emptying is important because it can cause an array of upper gastrointestinal symptoms, but additionally it has important implications for the absorption and action of levodopa. Delayed gastric emptying contributes significantly to response fluctuations seen in people on long-term l-dopa therapy. Neurohormonal aspects of the brain-gut axis are pertinent to discussions regarding the pathophysiology of delayed gastric emptying in PD and are also hypothesized to contribute to the pathogenesis of PD itself. Ghrelin is a gastric-derived hormone with potential as a therapeutic agent for delayed gastric emptying and also as a novel neuroprotective agent in PD. Recent findings relating to ghrelin in the context of PD and gastric emptying are considered. This article highlights the pathological abnormalities that may account for delayed gastric emptying in PD. It also considers the wider relevance of abnormal gastric pathology to our current understanding of the etiology of PD. PMID:24151126

  1. Slow motion increases perceived intent.

    PubMed

    Caruso, Eugene M; Burns, Zachary C; Converse, Benjamin A

    2016-08-16

    To determine the appropriate punishment for a harmful action, people must often make inferences about the transgressor's intent. In courtrooms and popular media, such inferences increasingly rely on video evidence, which is often played in "slow motion." Four experiments (n = 1,610) involving real surveillance footage from a murder or broadcast replays of violent contact in professional football demonstrate that viewing an action in slow motion, compared with regular speed, can cause viewers to perceive an action as more intentional. This slow motion intentionality bias occurred, in part, because slow motion video caused participants to feel like the actor had more time to act, even when they knew how much clock time had actually elapsed. Four additional experiments (n = 2,737) reveal that allowing viewers to see both regular speed and slow motion replay mitigates the bias, but does not eliminate it. We conclude that an empirical understanding of the effect of slow motion on mental state attribution should inform the life-or-death decisions that are currently based on tacit assumptions about the objectivity of human perception. PMID:27482091

  2. Slow motion increases perceived intent

    PubMed Central

    Caruso, Eugene M.; Burns, Zachary C.; Converse, Benjamin A.

    2016-01-01

    To determine the appropriate punishment for a harmful action, people must often make inferences about the transgressor’s intent. In courtrooms and popular media, such inferences increasingly rely on video evidence, which is often played in “slow motion.” Four experiments (n = 1,610) involving real surveillance footage from a murder or broadcast replays of violent contact in professional football demonstrate that viewing an action in slow motion, compared with regular speed, can cause viewers to perceive an action as more intentional. This slow motion intentionality bias occurred, in part, because slow motion video caused participants to feel like the actor had more time to act, even when they knew how much clock time had actually elapsed. Four additional experiments (n = 2,737) reveal that allowing viewers to see both regular speed and slow motion replay mitigates the bias, but does not eliminate it. We conclude that an empirical understanding of the effect of slow motion on mental state attribution should inform the life-or-death decisions that are currently based on tacit assumptions about the objectivity of human perception. PMID:27482091

  3. Collisionless Reconnection with Weak Slow Shocks Under Anisotropic MHD Approximation

    NASA Astrophysics Data System (ADS)

    Hirabayashi, K.; Hoshino, M.

    2014-12-01

    Magnetic reconnection accompanied by a pair of slow-mode shock waves, known as Petschek's theory, has been widely studied as an efficient mechanism to convert magnetically stored energy to thermal and/or kinetic energy in plasmas. Satellite observations in the Earth's magnetotail, on the other hand, report that the detection of slow shocks is rare compared with the theory. As an important step to bridge the gap between the observational fact and the Petschek-type reconnection, we performed one- and two- dimensional collisionless magnetohydrodynamic (MHD) simulations of magnetic reconnection paying special attention to the effect of temperature anisotropy. In high-beta plasmas such as a plasma sheet in the magnetotail, it is expected that even weak temperature anisotropy can greatly modify the dynamics. We demonstrate that the slow shocks do exist in the reconnection layer even under the anisotropic temperature. The resultant shocks, however, are weaker than those in isotropic MHD in terms of plasma compression. In addition, the amount of magnetic energy released across the shock is extremely small, that is, the shock is no longer switch-off type. In spite of the weakness of the shocks, the reconnection rates measured by the inflow velocities are kept at the same level as the isotropic cases. Once the slow shock forms, the downstream plasma is heated in highly anisotropic manner, and the firehose-sense anisotropy affects the wave structure in the system. In particular, it is remarkable that the sequential order of propagation of slow shocks and rotational discontinuities reverses depending upon the magnitude of a superposed guide field. Our result is consistent with the rareness of the slow shock detection in the magnetotail, and implies that shocks do not necessarily play an important role. Furthermore, a variety of wave structure of a reconnection layer shown here will help interpretation of observational data in collisionless reconnection.

  4. Functional role of autophagy in gastric cancer

    PubMed Central

    2016-01-01

    Autophagy is a highly regulated catabolic pathway responsible for the degradation of long-lived proteins and damaged intracellular organelles. Perturbations in autophagy are found in gastric cancer. In host gastric cells, autophagy can be induced by Helicobacter pylori (or H. pylori) infection, which is associated with the oncogenesis of gastric cancer. In gastric cancer cells, autophagy has both pro-survival and pro-death functions in determining cell fate. Besides, autophagy modulates gastric cancer metastasis by affecting a wide range of pathological events, including extracellular matrix (ECM) degradation, epithelial-to-mesenchymal transition (EMT), tumor angiogenesis, and tumor microenvironment. In addition, some of the autophagy-related proteins, such as Beclin 1, microtubule-associated protein 1 light chain 3 (MAP1-LC3), and p62/sequestosome 1 (SQSTM1) have certain prognostic values for gastric cancer. In this article, we review the recent studies regarding the functional role of autophagy in gastric cancer. PMID:26910278

  5. Choroidal and cutaneous metastasis from gastric adenocarcinoma.

    PubMed

    Kawai, Shoichiro; Nishida, Tsutomu; Hayashi, Yoshito; Ezaki, Hisao; Yamada, Takuya; Shinzaki, Shinichiro; Miyazaki, Masanori; Nakai, Kei; Yakushijin, Takayuki; Watabe, Kenji; Iijima, Hideki; Tsujii, Masahiko; Nishida, Kohji; Takehara, Tetsuo

    2013-03-01

    Choroidal or cutaneous metastasis of gastric cancer is rare. Gastrointestinal cancer was found in only 4% in patients with uveal metastasis. Choroidal metastasis from gastric cancer was reported in two cases in earlier literature. The frequency of gastric cancer as a primary lesion was 6% in cutaneous metastasis of men, and cutaneous metastasis occurs in 0.8% of all gastric cancers. We report a patient with gastric adenocarcinoma who presented with visual disorder in his left eye and skin pain on his head as his initial symptoms. These symptoms were diagnosed to be caused by choroidal and cutaneous metastasis of gastric adenocarcinoma. Two cycles of chemotherapy consisted of oral S-1 and intravenous cisplatin (SPIRITS regimen); this was markedly effective to reduce the primary gastric lesion and almost all the metastatic lesions. PMID:23538460

  6. Traveling wave tube and method of manufacture

    NASA Technical Reports Server (NTRS)

    Vancil, Bernard K. (Inventor)

    2004-01-01

    A traveling wave tube includes a glass or other insulating envelope having a plurality of substantially parallel glass rods supported therewithin which in turn support an electron gun, a collector and an intermediate slow wave structure. The slow wave structure itself provides electrostatic focussing of a central electron beam thereby eliminating the need for focussing magnetics and materially decreasing the cost of construction as well as enabling miniaturization. The slow wave structure advantageously includes cavities along the electron beam through which the r.f. energy is propagated, or a double, interleaved ring loop structure supported by dielectric fins within a ground plane cylinder disposed coaxially within the glass envelope.

  7. Effects of gastric distension and infusion of umami and bitter taste stimuli on vagal afferent activity.

    PubMed

    Horn, Charles C; Murat, Chloé; Rosazza, Matthew; Still, Liz

    2011-10-24

    Until recently, sensory nerve pathways from the stomach to the brain were thought to detect distension and play little role in nutritional signaling. Newer data have challenged this view, including reports on the presence of taste receptors in the gastrointestinal lumen and the stimulation of multi-unit vagal afferent activity by glutamate infusions into the stomach. However, assessing these chemosensory effects is difficult because gastric infusions typically evoke a distension-related vagal afferent response. In the current study, we recorded gastric vagal afferent activity in the rat to investigate the possibility that umami (glutamate, 150 mM) and bitter (denatonium, 10 mM) responses could be dissociated from distension responses by adjusting the infusion rate and opening or closing the drainage port in the stomach. Slow infusions of saline (5 ml over 2 min, open port) produced no significant effects on vagal activity. Using the same infusion rate, glutamate or denatonium solutions produced little or no effects on vagal afferent activity. In an attempt to reproduce a prior report that showed distention and glutamate responses, we produced a distension response by closing the exit port. Under this condition, response to the infusion of glutamate or denatonium was similar to saline. In summary, we found little or no effect of gastric infusion of glutamate or denatonium on gastric vagal afferent activity that could be distinguished from distension responses. The current results suggest that sensitivity to umami or bitter stimuli is not a common property of gastric vagal afferent fibers. PMID:21925651

  8. Comparison of Gastric Microbiota Between Gastric Juice and Mucosa by Next Generation Sequencing Method

    PubMed Central

    Sung, Jihee; Kim, Nayoung; Kim, Jaeyeon; Jo, Hyun Jin; Park, Ji Hyun; Nam, Ryoung Hee; Seok, Yeong-Jae; Kim, Yeon-Ran; Lee, Dong Ho; Jung, Hyun Chae

    2016-01-01

    Background: Not much is known about the role of gastric microbiota except for Helicobacter pylori in human health and disease. In this study, we aimed to detect human gastric microbiota in both gastric mucosa and gastric juice by barcoded 454-pyrosequencing of the 16S rRNA gene and to compare the results from mucosa and juice. Methods: Gastric biopsies and stomach juices were collected from 4 subjects who underwent standard endoscopy at Seoul National University Bundang Hospital. Gastric microbiota of antral mucosa, corpus mucosa samples, and gastric fluids were analyzed by barcoded 454-pyrosequencing of the 16S rRNA gene. The analysis focused on bacteria, such as H. pylori and nitrosating or nitrate-reducing bacteria. Results: Gastric fluid samples showed higher diversity compared to that of gastric mucosa samples. The mean of operational taxonomic units was higher in gastric fluid than in gastric mucosa. The samples of gastric fluid and gastric mucosa showed different composition of phyla. The composition of H. pylori and Proteobacteria was higher in mucosa samples compared to gastric fluid samples (H. pylori, 66.5% vs. 3.3%, P = 0.033; Proteobacteria, 75.4% vs. 26.3%, P = 0.041), while Actinobacteria, Bacteroidetes, and Firmicutes were proportioned relatively less in mucosa samples than gastric fluid. However there was no significant difference. (Actinobacteria, 3.5% vs. 20.2%, P = 0.312; Bacteroidetes, 6.0% vs. 14.8%, P = 0.329; Firmicutes, 12.8% vs. 33.4%, P = 0.246). Conclusions: Even though these samples were small, gastric mucosa could be more effective than gastric fluid in the detection of meaningful gastric microbiota by pyrosequencing. PMID:27051651

  9. Waves in Solar Coronal Loops

    NASA Astrophysics Data System (ADS)

    Wang, T. J.

    2016-02-01

    The corona is visible in the optical band only during a total solar eclipse or with a coronagraph. Coronal loops are believed to be plasma-filled closed magnetic flux anchored in the photosphere. Based on the temperature regime, they are generally classified into cool, warm, and hot loops. The magnetized coronal structures support propagation of various types of magnetohydrodynamics (MHD) waves. This chapter reviews the recent progress made in studies based on observations of four types of wave phenomena mainly occurring in coronal loops of active regions, including: flare-excited slow-mode waves; impulsively excited kink-mode waves; propagating slow magnetoacoustic waves; and ubiquitous propagating kink (Alfvénic) waves. This review not only comprehensively discusses these waves and coronal seismology but also topics that are newly emerging or hotly debated in order to provide the reader with useful guidance on further studies.

  10. De Novo Gastric Cancer After Liver Transplantation.

    PubMed

    Gong, Chung-Sik; Yoo, Moon-Won; Kim, Beom-Su; Hwang, Shin; Kim, Ki-Hun; Yook, Jeong-Hwan; Kim, Byung-Sik; Lee, Sung-Gyu

    2016-01-01

    BACKGROUND In South Korea, which has a high incidence of gastric cancer, the most common de novo malignancy associated with liver transplantation is gastric cancer. This study sought to identify clinicopathologic characteristics in gastric cancer patients after liver transplantation, and to help manage these cases. MATERIAL AND METHODS We investigated gastric cancer patients after liver transplantation at Asan Medical Center. We analyzed sex, age, cause of liver transplantation, initiating immunosuppressant, pre-transplantation gastric fibroscopy findings, time interval between transplantation and gastric cancer occurrence, follow-up period, existence of gastric cancer screening, Helicobacter pylori infection, family cancer history, gastric cancer treatment, cancer location, size of tumor, macroscopic gross type, WHO histologic type, Lauren's classification, TNM stage, and survival. RESULTS Of 2968 adult liver transplantation patients at our hospital, 19 were diagnosed with gastric cancer. The mean age at the time of gastric cancer diagnosis was 60.2±6.8 (46-71) years and mean time interval between liver transplantation and diagnosis of gastric cancer was 56.0±30.7 (3.20-113) months. Endoscopic submucosal dissection was done for 10 patients, 4 of whom underwent surgical resection. Surgical resection as an initial treatment was done in 8 patients. One patient received chemotherapy first. The standard incidence ratio of gastric cancer in these patients was 1036 per 100 000 persons (95% CI, 623.7-1,619) in men and 318.9 per 100 000 (95% CI, 4.170-1,774) in women. CONCLUSIONS For long-term survival of liver transplant patients, early detection of de novo cancer is necessary. Therefore, annual screening for gastric cancer after liver transplantation is needed, especially in areas where the incidence of gastric cancer is high, such as South Korea. PMID:27334929

  11. Laboratory observations of slow earthquakes and the spectrum of tectonic fault slip modes.

    PubMed

    Leeman, J R; Saffer, D M; Scuderi, M M; Marone, C

    2016-01-01

    Slow earthquakes represent an important conundrum in earthquake physics. While regular earthquakes are catastrophic events with rupture velocities governed by elastic wave speed, the processes that underlie slow fault slip phenomena, including recent discoveries of tremor, slow-slip and low-frequency earthquakes, are less understood. Theoretical models and sparse laboratory observations have provided insights, but the physics of slow fault rupture remain enigmatic. Here we report on laboratory observations that illuminate the mechanics of slow-slip phenomena. We show that a spectrum of slow-slip behaviours arises near the threshold between stable and unstable failure, and is governed by frictional dynamics via the interplay of fault frictional properties, effective normal stress and the elastic stiffness of the surrounding material. This generalizable frictional mechanism may act in concert with other hypothesized processes that damp dynamic ruptures, and is consistent with the broad range of geologic environments where slow earthquakes are observed. PMID:27029996

  12. Laboratory observations of slow earthquakes and the spectrum of tectonic fault slip modes

    PubMed Central

    Leeman, J. R.; Saffer, D. M.; Scuderi, M. M.; Marone, C.

    2016-01-01

    Slow earthquakes represent an important conundrum in earthquake physics. While regular earthquakes are catastrophic events with rupture velocities governed by elastic wave speed, the processes that underlie slow fault slip phenomena, including recent discoveries of tremor, slow-slip and low-frequency earthquakes, are less understood. Theoretical models and sparse laboratory observations have provided insights, but the physics of slow fault rupture remain enigmatic. Here we report on laboratory observations that illuminate the mechanics of slow-slip phenomena. We show that a spectrum of slow-slip behaviours arises near the threshold between stable and unstable failure, and is governed by frictional dynamics via the interplay of fault frictional properties, effective normal stress and the elastic stiffness of the surrounding material. This generalizable frictional mechanism may act in concert with other hypothesized processes that damp dynamic ruptures, and is consistent with the broad range of geologic environments where slow earthquakes are observed. PMID:27029996

  13. Laboratory observations of slow earthquakes and the spectrum of tectonic fault slip modes

    NASA Astrophysics Data System (ADS)

    Leeman, J. R.; Saffer, D. M.; Scuderi, M. M.; Marone, C.

    2016-03-01

    Slow earthquakes represent an important conundrum in earthquake physics. While regular earthquakes are catastrophic events with rupture velocities governed by elastic wave speed, the processes that underlie slow fault slip phenomena, including recent discoveries of tremor, slow-slip and low-frequency earthquakes, are less understood. Theoretical models and sparse laboratory observations have provided insights, but the physics of slow fault rupture remain enigmatic. Here we report on laboratory observations that illuminate the mechanics of slow-slip phenomena. We show that a spectrum of slow-slip behaviours arises near the threshold between stable and unstable failure, and is governed by frictional dynamics via the interplay of fault frictional properties, effective normal stress and the elastic stiffness of the surrounding material. This generalizable frictional mechanism may act in concert with other hypothesized processes that damp dynamic ruptures, and is consistent with the broad range of geologic environments where slow earthquakes are observed.

  14. Effect of meal volume and calorie load on postprandial gastric function and emptying: studies under physiological conditions by combined fiber-optic pressure measurement and MRI.

    PubMed

    Kwiatek, Monika A; Menne, Dieter; Steingoetter, Andreas; Goetze, Oliver; Forras-Kaufman, Zsofia; Kaufman, Elad; Fruehauf, Heiko; Boesiger, Peter; Fried, Michael; Schwizer, Werner; Fox, Mark R

    2009-11-01

    This study assessed the effects of meal volume (MV) and calorie load (CL) on gastric function. MRI and a minimally invasive fiber-optic recording system (FORS) provided simultaneous measurement of gastric volume and pressure changes during gastric filling and emptying of a liquid nutrient meal in physiological conditions. The gastric response to 12 iso-osmolar MV-CL combinations of a multinutrient drink (MV: 200, 400, 600, 800 ml; CL: 200, 300, 400 kcal) was tested in 16 healthy subjects according to a factorial design. Total gastric volume (TGV) and gastric content volume (GCV = MV + secretion) were measured by MRI during nasogastric meal infusion and gastric emptying over 60 min. Intragastric pressure was assessed at 1 Hz by FORS. The dynamic change in postprandial gastric volumes was described by a validated three-component linear exponential model. The stomach expanded with MV, but the ratio of GCV:MV at t(0) diminished with increasing MV (P < 0.01). Postprandial changes in TGV followed those of GCV. Intragastric pressure increased with MV, and this effect was augmented further by CL (P = 0.02); however, the absolute pressure rise was <4 mmHg. A further postprandial increase of gastric volumes was observed early on before any subsequent volume decrease. This "early" increase in GCV was greater for smaller than larger MV (P < 0.01), indicating faster initial gastric emptying of larger MV. In contrast, volume change during filling and in the early postprandial period were unaffected by CL. In the later postprandial period, gastric emptying rate continued to be more rapid with high MVs (P < 0.001); however, at any given volume, gastric emptying was slowed by higher CL (P < 0.001). GCV half-emptying time decreased with CL at 18 +/- 6 min for each additional 100-kcal load (P < 0.001). These findings indicate that gastric wall stress (passive strain and active tone) provides the driving force for gastric emptying, but distal resistance to gastric outflow regulates

  15. Nonlinear theory of slow dissipative layers in anisotropic plasmas

    SciTech Connect

    Ballai, I.; Ruderman, M.S.; Erdelyi, R.

    1998-01-01

    The solar coronal plasma is a well-known example of a plasma with strongly anisotropic dissipative coefficients. The main dissipative processes in the solar corona are strongly anisotropic thermal conductivity and viscosity. Ruderman and Goossens [Astrophys. J. {bold 471}, 1015 (1996)] developed a linear theory of driven slow resonant waves in plasmas with strongly anisotropic viscosity and thermal conductivity. Linear theory shows that in the slow dissipative layer the amplitudes of oscillations become very large for high Reynolds and Pecklet numbers, so that nonlinearity may be important. In the present paper the nonlinear behavior of driven magnetohydrodynamic waves in the slow dissipative layer in plasmas with strongly anisotropic viscosity and thermal conductivity is studied. The nonlinear governing equation for wave variables in the dissipative layer is derived. The nonlinear connection formulae, which are extensions of the linear connection formulae first introduced in the theory of resonant magnetohydrodynamic waves by Sakurai, Goossens, and Hollweg [Solar Phys. {bold 133}, 127 (1991)], are derived. {copyright} {ital 1998 American Institute of Physics.}

  16. Advances in gastric cancer prevention

    PubMed Central

    Giordano, Antonio; Cito, Letizia

    2012-01-01

    Gastric cancer is a multifactorial neoplastic pathology numbering among its causes both environmental and genetic predisposing factors. It is mainly diffused in South America and South-East Asia, where it shows the highest morbility percentages and it is relatively scarcely diffused in Western countries and North America. Although molecular mechanisms leading to gastric cancer development are only partially known, three main causes are well characterized: Helicobacter pylori (H. pylori) infection, diet rich in salted and/or smoked food and red meat, and epithelial cadherin (E-cadherin) mutations. Unhealthy diet and H. pylori infection are able to induce in stomach cancer cells genotypic and phenotypic transformation, but their effects may be crossed by a diet rich in vegetables and fresh fruits. Various authors have recently focused their attention on the importance of a well balanced diet, suggesting a necessary dietary education starting from childhood. A constant surveillance will be necessary in people carrying E-cadherin mutations, since they are highly prone in developing gastric cancer, also within the inner stomach layers. Above all in the United States, several carriers decided to undergo a gastrectomy, preferring changing their lifestyle than living with the awareness of the development of a possible gastric cancer. This kind of choice is strictly personal, hence a decision cannot be suggested within the clinical management. Here we summarize the key points of gastric cancer prevention analyzing possible strategies referred to the different predisposing factors. We will discuss about the effects of diet, H. pylori infection and E-cadherin mutations and how each of them can be handled. PMID:23061031

  17. Time Slows Down during Accidents

    PubMed Central

    Arstila, Valtteri

    2012-01-01

    The experienced speed of the passage of time is not constant as time can seem to fly or slow down depending on the circumstances we are in. Anecdotally accidents and other frightening events are extreme examples of the latter; people who have survived accidents often report altered phenomenology including how everything appeared to happen in slow motion. While the experienced phenomenology has been investigated, there are no explanations about how one can have these experiences. Instead, the only recently discussed explanation suggests that the anecdotal phenomenology is due to memory effects and hence not really experienced during the accidents. The purpose of this article is (i) to reintroduce the currently forgotten comprehensively altered phenomenology that some people experience during the accidents, (ii) to explain why the recent experiments fail to address the issue at hand, and (iii) to suggest a new framework to explain what happens when people report having experiences of time slowing down in these cases. According to the suggested framework, our cognitive processes become rapidly enhanced. As a result, the relation between the temporal properties of events in the external world and in internal states becomes distorted with the consequence of external world appearing to slow down. That is, the presented solution is a realist one in a sense that it maintains that sometimes people really do have experiences of time slowing down. PMID:22754544

  18. Time Slows Down during Accidents.

    PubMed

    Arstila, Valtteri

    2012-01-01

    The experienced speed of the passage of time is not constant as time can seem to fly or slow down depending on the circumstances we are in. Anecdotally accidents and other frightening events are extreme examples of the latter; people who have survived accidents often report altered phenomenology including how everything appeared to happen in slow motion. While the experienced phenomenology has been investigated, there are no explanations about how one can have these experiences. Instead, the only recently discussed explanation suggests that the anecdotal phenomenology is due to memory effects and hence not really experienced during the accidents. The purpose of this article is (i) to reintroduce the currently forgotten comprehensively altered phenomenology that some people experience during the accidents, (ii) to explain why the recent experiments fail to address the issue at hand, and (iii) to suggest a new framework to explain what happens when people report having experiences of time slowing down in these cases. According to the suggested framework, our cognitive processes become rapidly enhanced. As a result, the relation between the temporal properties of events in the external world and in internal states becomes distorted with the consequence of external world appearing to slow down. That is, the presented solution is a realist one in a sense that it maintains that sometimes people really do have experiences of time slowing down. PMID:22754544

  19. 64Cu DOTA-Trastuzumab PET/CT in Studying Patients With Gastric Cancer

    ClinicalTrials.gov

    2016-06-27

    Adenocarcinoma of the Gastroesophageal Junction; Diffuse Adenocarcinoma of the Stomach; Intestinal Adenocarcinoma of the Stomach; Mixed Adenocarcinoma of the Stomach; Recurrent Gastric Cancer; Stage IA Gastric Cancer; Stage IB Gastric Cancer; Stage IIA Gastric Cancer; Stage IIB Gastric Cancer; Stage IIIA Gastric Cancer; Stage IIIB Gastric Cancer; Stage IIIC Gastric Cancer

  20. Molecular classification and prediction in gastric cancer

    PubMed Central

    Lin, Xiandong; Zhao, Yongzhong; Song, Won-min; Zhang, Bin

    2015-01-01

    Gastric cancer, a highly heterogeneous disease, is the second leading cause of cancer death and the fourth most common cancer globally, with East Asia accounting for more than half of cases annually. Alongside TNM staging, gastric cancer clinic has two well-recognized classification systems, the Lauren classification that subdivides gastric adenocarcinoma into intestinal and diffuse types and the alternative World Health Organization system that divides gastric cancer into papillary, tubular, mucinous (colloid), and poorly cohesive carcinomas. Both classification systems enable a better understanding of the histogenesis and the biology of gastric cancer yet have a limited clinical utility in guiding patient therapy due to the molecular heterogeneity of gastric cancer. Unprecedented whole-genome-scale data have been catalyzing and advancing the molecular subtyping approach. Here we cataloged and compared those published gene expression profiling signatures in gastric cancer. We summarized recent integrated genomic characterization of gastric cancer based on additional data of somatic mutation, chromosomal instability, EBV virus infection, and DNA methylation. We identified the consensus patterns across these signatures and identified the underlying molecular pathways and biological functions. The identification of molecular subtyping of gastric adenocarcinoma and the development of integrated genomics approaches for clinical applications such as prediction of clinical intervening emerge as an essential phase toward personalized medicine in treating gastric cancer. PMID:26380657

  1. Comparative Effects of Prolonged and Intermittent Stimulation of the Glucagon-Like Peptide 1 Receptor on Gastric Emptying and Glycemia

    PubMed Central

    Umapathysivam, Mahesh M.; Lee, Michael Y.; Jones, Karen L.; Annink, Christopher E.; Cousins, Caroline E.; Trahair, Laurence G.; Rayner, Chris K.; Chapman, Marianne J.; Nauck, Michael A.; Horowitz, Michael; Deane, Adam M.

    2014-01-01

    Acute administration of glucagon-like peptide 1 (GLP-1) and its agonists slows gastric emptying, which represents the major mechanism underlying their attenuation of postprandial glycemic excursions. However, this effect may diminish during prolonged use. We compared the effects of prolonged and intermittent stimulation of the GLP-1 receptor on gastric emptying and glycemia. Ten healthy men received intravenous saline (placebo) or GLP-1 (0.8 pmol/kg ⋅ min), as a continuous 24-h infusion (“prolonged”), two 4.5-h infusions separated by 20 h (“intermittent”), and a 4.5-h infusion (“acute”) in a randomized, double-blind, crossover fashion. Gastric emptying of a radiolabeled mashed potato meal was measured using scintigraphy. Acute GLP-1 markedly slowed gastric emptying. The magnitude of the slowing was attenuated with prolonged but maintained with intermittent infusions. GLP-1 potently diminished postprandial glycemia during acute and intermittent regimens. These observations suggest that short-acting GLP-1 agonists may be superior to long-acting agonists when aiming specifically to reduce postprandial glycemic excursions in the treatment of type 2 diabetes. PMID:24089511

  2. Overexpression of stathmin1 in the diffuse type of gastric cancer and its roles in proliferation and migration of gastric cancer cells

    PubMed Central

    Jeon, T-Y; Han, M-E; Lee, Y-W; Lee, Y-S; Kim, G-H; Song, G-A; Hur, G-Y; Kim, J-Y; Kim, H-J; Yoon, S; Baek, S-Y; Kim, B-S; Kim, J-B; Oh, S-O

    2010-01-01

    Background: Stathmin1 is a microtubule-regulating protein that has an important role in the assembly and disassembly of the mitotic spindle. The roles of stathmin1 in carcinogenesis of various cancers, including prostate and breast cancer, have been explored. However, its expression and roles in gastric cancer have not yet been described. Methods: Stathmin1 expression in paraffin-embedded tissue sections from 226 patients was analysed by immunohistochemistry. Roles of stathmin1 were studied using a specific small interfering RNA (siRNA). Results: The expression of stathmin1 was positively correlated with lymph node metastasis, TNM stages and vascular invasion, and negatively with recurrence-free survival, in the diffuse type of gastric cancer. The median recurrence-free survival in patients with a negative and positive expression of stathmin1 was 17.0 and 7.0 months, respectively (P=0.009). When the expression of stathmin1 was knocked down using siRNA, the proliferation, migration and invasion of poorly differentiated gastric cancer cells in vitro were significantly inhibited. Moreover, stathmin1 siRNA transfection significantly slowed the growth of xenografts in nude mice. Conclusion: These results suggest that stathmin1 can be a good prognostic factor for recurrence-free survival rate and is a therapeutic target in diffuse-type gastric cancer. PMID:20087351

  3. Phase II Study of Oxaliplatin, Irinotecan, and Capecitabine in Advanced Gastric/Gastroesophageal Junction Carcinoma

    ClinicalTrials.gov

    2015-04-15

    Adenocarcinoma of the Gastroesophageal Junction; Diffuse Adenocarcinoma of the Stomach; Intestinal Adenocarcinoma of the Stomach; Mixed Adenocarcinoma of the Stomach; Recurrent Gastric Cancer; Stage IIIA Gastric Cancer; Stage IIIB Gastric Cancer; Stage IIIC Gastric Cancer; Stage IV Gastric Cancer

  4. Irinotecan, Cisplatin, and Bevacizumab in Treating Patients With Unresectable or Metastatic Gastric or Gastroesophageal Junction Adenocarcinoma

    ClinicalTrials.gov

    2013-06-03

    Adenocarcinoma of the Gastroesophageal Junction; Diffuse Adenocarcinoma of the Stomach; Intestinal Adenocarcinoma of the Stomach; Mixed Adenocarcinoma of the Stomach; Recurrent Gastric Cancer; Stage IIIA Gastric Cancer; Stage IIIB Gastric Cancer; Stage IIIC Gastric Cancer; Stage IV Gastric Cancer

  5. Alpha-fetoprotein-producing hepatoid gastric adenocarcinoma in a child presenting with spontaneous gastric perforation.

    PubMed

    Emir, Suna; Karakurt, Neslihan; Karakuş, Esra; Şenel, Emrah; Kırsaçlıoğlu, Ceyda; Demir, Hacı Ahmet; Orhan, Diclehan

    2014-01-01

    Gastric adenocarcinoma is a rare entity in the pediatric population. Gastric hepatoid adenocarcinoma with elevated serum alpha-fetoprotein (AFP) is seen extremely rarely in children. A 12-year-old boy was admitted to the hospital with complaint of abdominal pain. X-ray revealed free air density below the diaphragm. Emergent laparotomy showed perforated stomach. Four weeks after the operation, he was readmitted with severe gastrointestinal obstruction symptoms. He underwent an explorative laparotomy, which revealed intestinal edema and diffuse small solid nodules covering the peritoneum. Serum AFP level was mildly elevated. Endoscopic evaluation of the upper gastrointestinal tract was performed, and a gastric mass was detected. All pathological findings were compatible with gastric carcinoma showing hepatoid differentiation. We report an unusual case of AFP-producing hepatoid gastric adenocarcinoma presenting with gastric perforation. This is, to the best of our knowledge, the first reported case of AFP- producing hepatoid gastric adenocarcinoma presenting with gastric perforation in a child. PMID:24827954

  6. Slow Images and Entangled Photons

    SciTech Connect

    Swordy, Simon

    2007-06-20

    I will discuss some recent experiments using slow light and entangled photons. We recently showed that it was possible to map a two dimensional image onto very low light level signals, slow them down in a hot atomic vapor while preserving the amplitude and phase of the images. If time remains, I will discuss some of our recent work with time-energy entangled photons for quantum cryptography. We were able to show that we could have a measurable state space of over 1000 states for a single pair of entangled photons in fiber.

  7. Slow Crack Growth of Germanium

    NASA Technical Reports Server (NTRS)

    Salem, Jon

    2016-01-01

    The fracture toughness and slow crack growth parameters of germanium supplied as single crystal beams and coarse grain disks were measured. Although germanium is anisotropic (A=1.7), it is not as anisotropic as SiC, NiAl, or Cu, as evidence by consistent fracture toughness on the 100, 110, and 111 planes. Germanium does not exhibit significant slow crack growth in distilled water. (n=100). Practical values for engineering design are a fracture toughness of 0.7 MPam and a Weibull modulus of m=6+/-2. For well ground and reasonable handled coupons, fracture strength should be greater than 30 MPa.

  8. Slow shocks around the sun

    NASA Technical Reports Server (NTRS)

    Whang, Y. C.

    1982-01-01

    It is inferred from this study that magnetohydrodynamic slow shocks can exist in the vicinity of the sun. The study uses a two-hole corona model, the sub-Alfvenic streams originating from the edge of the polar open-field regions are forced to turn towards equator in coronal space following the curved boundary of the closed field region. When the streamlines from the opposite poles merge at a neutral point, their directions become parallel to the neutral sheet. An oblique slow shock can develop near or at the neutral point, the shock extends polewards to form a surface of discontinuity around the sun.

  9. Slow light with electromagnetically induced transparency in optical fibre

    NASA Astrophysics Data System (ADS)

    Muhamad Hatta, Agus; Kamli, Ali A.; Al-Hagan, Ola A.; Moiseev, Sergey A.

    2015-08-01

    Slow light with electromagnetically induced transparency (EIT) in the core of optical fibre containing three-level atoms is investigated. The guided modes are treated in the weakly guiding approximation which renders the analysis into a manageable form. The transparency window and permittivity profile of the core due to the strong pump field in the EIT scheme is calculated. For a specific permittivity profile of the core due to EIT, the propagation constant of the weak signal field and spatial shape of fundamental guided mode are calculated by solving the vector wave equation using the finite difference method. It is found that the transparency window and slow light field can be controlled via the optical fibre parameters. The reduced group velocity of slow light in this configuration is useful for many technological applications such as optical memories, effective control of single photon fields, optical buffers and delay lines.

  10. Gastric partitioning gastrojejunostomy in unresectable distal gastric cancer patients.

    PubMed

    Kwon, Sung Joon; Lee, Ha Gyoon

    2004-04-01

    The main purpose of bypass surgery in patients with unresectable distal gastric cancer is to improve their quality of life (QoL). However, the result of conventional gastroenterostomy is dismal including continuous bleeding due to the contact of food material on the tumor surface and early obstruction of the stoma by tumor growth. Developing more effective surgery is warranted to improve the QoL of these patients. Among the 1158 patients with gastric cancer who underwent surgery from March 1993 to July 2002 at Hanyang University Medical Center, 54 (4.7%) had unresectable cancers. Various types of gastrojejunostomy (G-Jstomy), including conventional G-Jstomy (CGJ) (n = 18), antral exclusion G-Jstomy (n = 7), and gastric partitioning G-Jstomy (GPGJ) (n = 17), as well as exploratory laparotomy only (n = 12) were performed in these unresectable cases. In this study, survival and postoperative QoL were compared for the CGJ and GPGJ groups. The median survivals were 120 and 209 days for the CGJ and GPGJ groups, respectively (p = 0.046). The rates of postoperative body weight loss compared to the preoperative weight were 9.3% and 3.1% in the CGJ and GPGJ groups, respectively; the difference showed borderline significance (p = 0.067). The volume of blood transfusion was much less during the postoperative period than during the preoperative period in the GPGJ group but not in the CGJ group. The GPGJ procedure minimized food contact on the tumor surface, which was confirmed by an upper gastrointestinal barium meal series. GPGJ can be recommended as the procedure of choice for bypass surgery in patients with unresectable distal gastric cancer considering their improved survival and postoperative QoL compared to those who underwent CGJ. PMID:14994143

  11. Use of lectin microarray to differentiate gastric cancer from gastric ulcer

    PubMed Central

    Huang, Wei-Li; Li, Yang-Guang; Lv, Yong-Chen; Guan, Xiao-Hui; Ji, Hui-Fan; Chi, Bao-Rong

    2014-01-01

    AIM: To investigate the feasibility of lectin microarray for differentiating gastric cancer from gastric ulcer. METHODS: Twenty cases of human gastric cancer tissue and 20 cases of human gastric ulcer tissue were collected and processed. Protein was extracted from the frozen tissues and stored. The lectins were dissolved in buffer, and the sugar-binding specificities of lectins and the layout of the lectin microarray were summarized. The median of the effective data points for each lectin was globally normalized to the sum of medians of all effective data points for each lectin in one block. Formalin-fixed paraffin-embedded gastric cancer tissues and their corresponding gastric ulcer tissues were subjected to Ag retrieval. Biotinylated lectin was used as the primary antibody and HRP-streptavidin as the secondary antibody. The glycopatterns of glycoprotein in gastric cancer and gastric ulcer specimens were determined by lectin microarray, and then validated by lectin histochemistry. Data are presented as mean ± SD for the indicated number of independent experiments. RESULTS: The glycosylation level of gastric cancer was significantly higher than that in ulcer. In gastric cancer, most of the lectin binders showed positive signals and the intensity of the signals was stronger, whereas the opposite was the case for ulcers. Significant differences in the pathological score of the two lectins were apparent between ulcer and gastric cancer tissues using the same lectin. For MPL and VVA, all types of gastric cancer detected showed stronger staining and a higher positive rate in comparison with ulcer, especially in the case of signet ring cell carcinoma and intra-mucosal carcinoma. GalNAc bound to MPL showed a significant increase. A statistically significant association between MPL and gastric cancer was observed. As with MPL, there were significant differences in VVA staining between gastric cancer and ulcer. CONCLUSION: Lectin microarray can differentiate the different

  12. Gastric Hamartomatous Polyps—Review and Update

    PubMed Central

    Vyas, Monika; Yang, Xiu; Zhang, Xuchen

    2016-01-01

    Gastric polyps are frequently encountered on endoscopic examinations. While many of these represent true epithelial lesions, some of the polyps may result from underlying stromal or lymphoid proliferations or even heterotopic tissue. Histologic examination is essential for accurate typing of the polyps to predict malignant potential and underlying possible genetic abnormalities. The focus of this review is on gastric hamartomatous polyps, which are relatively rare and diagnostically challenging. Though most of the gastric hamartomatous polyps are benign, certain types are associated with increased malignant potential. These include certain polyps associated with specific genetic familial polyposis syndromes and gastric inverted hamartomatous polyps. Identification of these polyps can result in the prevention or early diagnosis of gastric carcinoma and also help in the identification of family members with polyposis syndromes. The aim of this review is to categorize gastric hamartomatous polyps and aid in the identification of high-risk categories. PMID:27081323

  13. [Intra-gastric penetration of an adjustable gastric band].

    PubMed

    Ablassmaier, B; Opitz, I; Jacobi, C A; Müller, J M

    2001-07-01

    Between November 1995 and August 2000 we performed adjustable silicone gastric banding laparoscopically in 252 patients. The body mass index varied from 37 to 86 kg/m2. We report on a 38-year-old woman who was operated on in 1997 with a body mass index of 47 kg/m2 (167 cm, 132 kg). The postoperative follow-up was uneventful until January 2000. The patient lost weight until she weighed 78 kg. Then she complained of diffuse epigastric pain. Gastroscopy revealed gastritis. Omeprazol was prescribed. No amelioration occurred. Endoscopic control showed partial intragastric migration of the band. After laparoscopic removal of the band, the patient was free of symptoms. Band erosion is a possible complication of adjustable gastric banding. As is known from intragastric penetration of the Angelchik prosthesis, the clinical symptoms of this complication may be mild. Since the follow-up of most patients with gastric banding is less than 5 years, more complications similar to that one described may be diagnosed in the future. PMID:11490764

  14. Human Gastric Epithelial Cells Contribute to Gastric Immune Regulation by Providing Retinoic Acid to Dendritic Cells

    PubMed Central

    Bimczok, Diane; Kao, John Y.; Zhang, Min; Cochrun, Steven; Mannon, Peter; Peter, Shajan; Wilcox, Charles M.; Mönkemüller, Klaus E.; Harris, Paul R.; Grams, Jayleen M.; Stahl, Richard D.; Smith, Phillip D.; Smythies, Lesley E.

    2014-01-01

    Despite the high prevalence of chronic gastritis caused by H. pylori, the gastric mucosa has received little investigative attention as a unique immune environment. Here, we analyzed whether retinoic acid (RA), an important homeostatic factor in the small intestinal mucosa, also contributes to gastric immune regulation. We report that human gastric tissue contains high levels of the RA precursor molecule, retinol, and that gastric epithelial cells express both RA biosynthesis genes and RA response genes, indicative of active RA biosynthesis. Moreover, primary gastric epithelial cells cultured in the presence of retinol synthesized RA in vitro and induced RA biosynthesis in co-cultured monocytes through an RA-dependent mechanism, suggesting that gastric epithelial cells may also confer the ability to generate RA on gastric DCs. Indeed, DCs purified from gastric mucosa had similar levels of aldehyde dehydrogenase activity and RA biosynthesis gene expression as small intestinal DCs, although gastric DCs lacked CD103. In H. pylori-infected gastric mucosa, gastric RA biosynthesis gene expression was severely disrupted, which may lead to reduced RA signaling and thus contribute to disease progression. Collectively, our results support a critical role for RA in human gastric immune regulation. PMID:25249167

  15. Diversity of the Gastric Microbiota in Thoroughbred Racehorses Having Gastric Ulcer.

    PubMed

    Dong, Hee-Jin; Ho, Hungwui; Hwang, Hyeshin; Kim, Yongbaek; Han, Janet; Lee, Inhyung; Cho, Seongbeom

    2016-04-28

    Equine gastric ulcer syndrome is one of the most frequently reported diseases in thoroughbred racehorses. Although several risk factors for the development of gastric ulcers have been widely studied, investigation of microbiological factors has been limited. In this study, the presence of Helicobacter spp. and the gastric microbial communities of thoroughbred racehorses having mild to severe gastric ulcers were investigated. Although Helicobacter spp. were not detected using culture and PCR techniques from 52 gastric biopsies and 52 fecal samples, the genomic sequences of H. pylori and H. ganmani were detected using nextgeneration sequencing techniques from 2 out of 10 representative gastric samples. The gastric microbiota of horses was mainly composed of Firmicutes (50.0%), Proteobacteria (18.7%), Bacteroidetes (14.4%), and Actinobacteria (9.7%), but the proportion of each phylum varied among samples. There was no major difference in microbial composition among samples having mild to severe gastric ulcers. Using phylogenetic analysis, three distinct clusters were observed, and one cluster differed from the other two clusters in the frequency of feeding, amount of water consumption, and type of bedding. To the best of our knowledge, this is the first study to investigate the gastric microbiota of thoroughbred racehorses having gastric ulcer and to evaluate the microbial diversity in relation to the severity of gastric ulcer and management factors. This study is important for further exploration of the gastric microbiota in racehorses and is ultimately applicable to improving animal and human health. PMID:26809803

  16. Effects of Dietary Factors and the NAT2 Acetylator Status on Gastric Cancer in Koreans

    PubMed Central

    Zhang, Yan Wei; Eom, Sang-Yong; Kim, Yong-Dae; Song, Young-Jin; Yun, Hyo-Yung; Park, Joo-Seung; Youn, Sei-Jin; Kim, Byung Sik; Kim, Heon; Hein, David W.

    2009-01-01

    Environmental dietary carcinogens and genetic polymorphisms in metabolic enzymes have been reported to be risk factors for gastric cancer. This study was undertaken to investigate the effects of the diet, the N-acetyltransferase (NAT) 2 acetylation status, and their interaction on gastric cancer risk. The study population consisted of 471 gastric cancer patients and 471 age- and sex-matched control subjects. NAT2 genotypes were identified using single-nucleotide primer extension reaction methods. Thirty-one alleles related to 12 polymorphism sites were assayed in this study. Significantly increased odds ratios were observed in former smokers (OR = 2.39, 95%CI = 1.57-3.62), heavy drinkers (OR = 1.28, 95%CI = 1.06-1.55), and individuals who eat well-done meat (OR = 1.24, 95%CI = 1.09-1.41). The odds ratios (95% CI) for high intake of kimchi, stews, and soybean paste were 3.27 (2.44-4.37), 1.96 (1.50-2.58), and 1.63 (1.24-2.14), respectively. The NAT2 genotype alone was not associated with gastric cancer risk. A significant gene-environment interaction was observed between environmental carcinogens and NAT2 genotypes. The odds ratios for kimchi, stews, and soybean paste were higher in slow/intermediate acetylators than in rapid acetylators. The odds ratios for slow/intermediate acetylators were 2.28 (95% CI: 1.29-4.04) for light smokers and 3.42 (95% CI: 2.06-5.68) for well-done meat intake. The NAT2 acetylator genotype may be an important modifier of the effects of environmental factors on gastric cancer risk. PMID:19350634

  17. The volume and energy content of meals as determinants of gastric emptying.

    PubMed Central

    Hunt, J N; Stubbs, D F

    1975-01-01

    1. Results were collected from thirty-three published and unpublished studies of gastric emptying. The volumes of the meals ranged from 50 to 1250 ml., and composition varied from pure carbohydrates to ordinary food. 2. From the published composition of the meals, their nutritive density, as kcal/ml. (4-18 KJ/ml.) was computed: it ranged from zero to 2-3 kcal/ml. 3. The volume of each meal, or test meal, delivered to the duodenum in 30 min was determined, assuming that gastric emptying was exponential. 4. The greater the nutritive density of a meal, the less was the volume transferred to the duodenum in 30 min. The original volume of meal given was not a determinant of the rate of emptying (ml./min). 5. The slowing of gastric emptying with a meal of high nutritive density was not sufficient to prevent an increased rate of delivery of energy to the duodenum (nutritive density times volume delivered in unit time) with a meal of high nutritive density. 6. Assuming an appropriate relationship for the interaction of a stimulus (kcal/ml.) and duodenal receptors, it was possible to predict a rate of gastric emptying for each meal, given its nutritive density. Knowing the initial volume of the meal, it was possible to predict the mean half time for its emptying. 7. There were eight sets of anomalous results: in four the volumes of meal given were less than 200 ml.; explanations of the anomalies in the other four results could not be provided. 8. The results are consistent with equal slowing of gastric emptying by the duodenal action of the products of digestion of isocaloric amounts of fat, protein and carbohydrate, for example, 4 g fat or 9 g carbohydrate, both 36 kcal, taking carbohydrate and protein as 4 kcal/g and fat as 9 kcal/g. PMID:1127608

  18. Gastric duplication cyst: a rare entity

    PubMed Central

    Doepker, Matthew P.; Ahmad, Syed A.

    2016-01-01

    Gastric duplication cysts are an uncommon finding, especially in the adult population. Presenting symptoms can be non-specific, but can include abdominal pain, nausea and emesis. In this report, we present a 28-year-old female diagnosed with a communicating gastric cyst with both gastric and duodenal mucosa, along with pancreatic tissue and no evidence of dysplasia or malignancy. The clinical picture, diagnosis and treatment are described and compared to findings in the literature. PMID:27150283

  19. Gastric duplication cyst: a rare entity.

    PubMed

    Doepker, Matthew P; Ahmad, Syed A

    2016-01-01

    Gastric duplication cysts are an uncommon finding, especially in the adult population. Presenting symptoms can be non-specific, but can include abdominal pain, nausea and emesis. In this report, we present a 28-year-old female diagnosed with a communicating gastric cyst with both gastric and duodenal mucosa, along with pancreatic tissue and no evidence of dysplasia or malignancy. The clinical picture, diagnosis and treatment are described and compared to findings in the literature. PMID:27150283

  20. Fast wandering of slow birds

    NASA Astrophysics Data System (ADS)

    Toner, John

    2011-12-01

    I study a single slow bird moving with a flock of birds of a different and faster (or slower) species. I find that every species of flocker has a characteristic speed γ≠v0, where v0 is the mean speed of the flock such that if the speed vs of the slow bird equals γ, it will randomly wander transverse to the mean direction of flock motion far faster than the other birds will: Its mean-squared transverse displacement will grow in d=2 with time t like t5/3, in contrast to t4/3 for the other birds. In d=3, the slow bird's mean-squared transverse displacement grows like t5/4, in contrast to t for the other birds. If vs≠γ, the mean-squared displacement of the slow bird crosses over from t5/3 to t4/3 scaling in d=2 and from t5/4 to t scaling in d=3 at a time tc that scales according to tc∝|vs-γ|-2.

  1. Reading and the Slow Learner.

    ERIC Educational Resources Information Center

    Ediger, Marlow

    Advocates of high standards and expectations usually believe that gaps in reading achievement can be eliminated with good teaching, but slow readers need a specially designed reading curriculum. The teacher first needs to use an informal reading inventory to determine the student's reading level. Functioning generally on a higher level than…

  2. Slow extraction at LAMPF II

    SciTech Connect

    Colton, E.P.

    1985-10-01

    Half-integer resonant extraction will be used to slow extract the 45 GeV proton beam from the LAMPF II main ring during a time spread of 1/6 sec. High extraction efficiency is obtained by performing the extraction in a high-beta long straight section and by utilizing an electrostatic wire septum and iron septum.

  3. Slow extraction at LAMPF II

    SciTech Connect

    Colton, E.P.

    1985-01-01

    Half-integer resonant extraction will be used to slow extract the 45 GeV proton beam from the LAMPF II main ring during a time spread of 1/6 sec. High extration efficiency is obtained by performing the extraction in a high-beta long straight section and by utilizing an electrostatic wire septum and iron septum. 3 refs., 4 figs.

  4. Gastric Syphilis and Membranous Glomerulonephritis.

    PubMed

    Roh, Min; Sohn, Joo Hyun; Kim, Tae Yeob; Kim, Sung Jong; Kim, Ji Soong; Chung, Sung Jun; Pyo, Ju Yeon; Oh, Young-Ha

    2015-05-01

    Syphilis is a chronic systemic infectious disease caused by the bacterium Treponema pallidum. Gastric involvement and nephrotic syndrome are uncommon but well documented complications of syphilis, but the co-occurrence of these two complications in the same patient is extremely rare. Thus, because of their nonspecific presentation, suspicion of gastric syphilis (GS) and nephrotic syndrome is essential for diagnosis. Patients should be investigated thoroughly and a diagnosis made based on clinical, endoscopic, and histological findings, in order to initiate appropriate therapy. We report of a 34-year-old male patient with a history of epigastric pain and a diagnosis of GS and syphilis-associated membranous glomerulonephritis confirmed by gastroscopy and kidney biopsy, who was treated successfully with penicillin G benzathine. This case report provides information on the typical features of GS that should help raise awareness of this rare disease entity among clinicians, resulting in earlier diagnosis and administration of appropriate therapy. PMID:26064828

  5. Gastric Syphilis and Membranous Glomerulonephritis

    PubMed Central

    Roh, Min; Kim, Tae Yeob; Kim, Sung Jong; Kim, Ji Soong; Chung, Sung Jun; Pyo, Ju Yeon; Oh, Young-Ha

    2015-01-01

    Syphilis is a chronic systemic infectious disease caused by the bacterium Treponema pallidum. Gastric involvement and nephrotic syndrome are uncommon but well documented complications of syphilis, but the co-occurrence of these two complications in the same patient is extremely rare. Thus, because of their nonspecific presentation, suspicion of gastric syphilis (GS) and nephrotic syndrome is essential for diagnosis. Patients should be investigated thoroughly and a diagnosis made based on clinical, endoscopic, and histological findings, in order to initiate appropriate therapy. We report of a 34-year-old male patient with a history of epigastric pain and a diagnosis of GS and syphilis-associated membranous glomerulonephritis confirmed by gastroscopy and kidney biopsy, who was treated successfully with penicillin G benzathine. This case report provides information on the typical features of GS that should help raise awareness of this rare disease entity among clinicians, resulting in earlier diagnosis and administration of appropriate therapy. PMID:26064828

  6. Involvement of leukotrienes in acute gastric damage.

    PubMed

    Boughton-Smith, N K

    1989-01-01

    The leukotrienes have potent inflammatory actions which could be of importance in gastric mucosal integrity. In animals, LTC4 produces vasoconstriction in the gastric mucosa. Furthermore, acute gastric damage produced by ethanol is accompanied by marked increases in the mucosal formation of LTC4 and LTB4. Depending on the extent of protection, prostaglandins either have no effect or prevent the increases in leukotriene formation which accompany ethanol-induced damage. Various non-specific inhibitors of leukotriene synthesis prevent ethanol and indomethacin-induced damage to the gastric mucosa. However, a novel selective 5-lipoxygenase inhibitor (BW A4C) had no effect on these models of acute gastric damage at doses which completely inhibited gastric mucosal leukotriene synthesis. These studies cast doubt on the role of the leukotrienes in these models of acute gastric damage. However, the potent biological actions of the leukotrienes may be of importance in the pathogenesis of other forms of gastric damage, or as mediators of chronic gastric ulceration or inflammation. PMID:2657289

  7. Ischemic Gastropathic Ulcer Mimics Gastric Cancer

    PubMed Central

    Daher, Saleh; Lahav, Ziv; Rmeileh, Ayman Abu; Mizrahi, Meir

    2016-01-01

    Gastric ulcer due to mesenteric ischemia is a rare clinical finding. As a result, few reports of ischemic gastric ulcers have been reported in the literature. The diagnosis of ischemic gastropathy is seldom considered in patients presenting with abdominal pain and gastric ulcers. In this case report, we describe a patient with increasing abdominal pain, weight loss, and gastric ulcers, who underwent extensive medical evaluation and whose symptoms were resistant to medical interventions. Finally he was diagnosed with chronic mesenteric ischemia, and his clinical and endoscopic abnormalities resolved after surgical revascularization of both the superior mesenteric artery and the celiac trunk. PMID:27579191

  8. The psyche and gastric functions.

    PubMed

    Nardone, Gerardo; Compare, Debora

    2014-01-01

    Although the idea that gastric problems are in some way related to mental activity dates back to the beginning of the last century, until now it has received scant attention by physiologists, general practitioners and gastroenterologists. The major breakthrough in understanding the interactions between the central nervous system and the gut was the discovery of the enteric nervous system (ENS) in the 19th century. ENS (also called 'little brain') plays a crucial role in the regulation of the physiological gut functions. Furthermore, the identification of corticotropin-releasing factor (CRF) and the development of specific CRF receptor antagonists have permitted to characterize the neurochemical basis of the stress response. The neurobiological response to stress in mammals involves three key mechanisms: (1) stress is perceived and processed by higher brain centers; (2) the brain mounts a neuroendocrine response by way of the hypothalamic-pituitary-adrenal axis (HPA) and the autonomic nervous system (ANS), and (3) the brain triggers feedback mechanisms by HPA and ANS stimulation to restore homeostasis. Various stressors such as anger, fear, painful stimuli, as well as life or social learning experiences affect both the individual's physiologic and gastric function, revealing a two-way interaction between brain and stomach. There is overwhelming experimental and clinical evidence that stress influences gastric function, thereby outlining the pathogenesis of gastric diseases such as functional dyspepsia, gastroesophageal reflux disease and peptic ulcer disease. A better understanding of the role of pathological stressors in the modulation of disease activity may have important pathogenetic and therapeutic implications. PMID:24732184

  9. Slow dynamics of the amphibian tympanic membrane

    NASA Astrophysics Data System (ADS)

    Bergevin, Christopher; Meenderink, Sebastiaan W. F.; van der Heijden, Marcel; Narins, Peter M.

    2015-12-01

    Several studies have demonstrated that delays associated with evoked otoacoustic emissions (OAEs) largely originate from filter delays of resonant elements in the inner ear. However, one vertebrate group is an exception: Anuran (frogs and toads) amphibian OAEs exhibit relatively long delays (several milliseconds), yet relatively broad tuning. These delays, also apparent in auditory nerve fiber (ANF) responses, have been partially attributed to the middle ear (ME), with a total forward delay of ˜0.7 ms (˜30 times longer than in gerbil). However, ME forward delays only partially account for the longer delays of OAEs and ANF responses. We used scanning laser Doppler vibrometery to map surface velocity over the tympanic membrane (TyM) of anesthetized bullfrogs (Rana catesbeiana). Our main finding is a circularly-symmetric wave on the TyM surface, starting at the outer edges of the TyM and propagating inward towards the center (the site of the ossicular attachment). This wave exists for frequencies ˜0.75-3 kHz, overlapping the range of bullfrog hearing (˜0.05-1.7 kHz). Group delays associated with this wave varied from 0.4 to 1.2 ms and correlated with with TyM diameter, which ranged from ˜6-16 mm. These delays correspond well to those from previous ME measurements. Presumably the TyM waves stem from biomechanical constraints of semi-aquatic species with a relatively large tympanum. We investigated some of these constraints by measuring the pressure ratio across the TyM (˜10-30 dB drop, delay of ˜0.35 ms), the effects of ossicular interruption, the changes due to physiological state of TyM (`dry-out'), and by calculating the middle-ear input impedance. In summary, we found a slow, inward-traveling wave on the TyM surface that accounts for a substantial fraction of the relatively long otoacoustic and neurophysiological delays previously observed in the anuran inner ear.

  10. Clinical implications of proliferation activity in T1 or T2 male gastric cancer patients

    PubMed Central

    Kim, Young-Woo; Eom, Bang Wool; Kook, Myeong-Cherl; Kim, Han-Seong; Kim, Mi-Kyung; Hwang, Hai-Li; Chandra, Vishal; Poojan, Shiv; Song, Yura; Koh, Jae-Soo; Bae, Chang-Dae; Ro, Jungsil; Hong, Kyeong-Man

    2015-01-01

    Proliferation activity has already been established as a prognostic marker or as a marker for anticancer drug sensitivity. In gastric cancer, however, the prognostic significance of proliferation activity is still being debated. Several studies evaluating proliferation activity using Ki-67 have shown controversial results in terms of the relationship between proliferation activity and overall survival (OS) or drug sensitivity in gastric cancer patients. Because cytoskeleton-associated protein 2 (CKAP2) staining has recently been introduced as a marker of proliferation activity, we analyzed 437 gastric cancer tissues through CKAP2 immunohistochemistry, and we evaluated the chromatin CKAP2-positive cell count (CPCC) for proliferation activity. Although the CPCC did not show any significant correlation with OS in the male, female or total number of cases, it did show a significant correlation in the T1 or T2 male patient subgroup, according to log-rank tests (P=0.001) and univariate analysis (P=0.045). Additionally, multivariate analysis with the Cox proportional hazard regression model showed a significant correlation between the CPCC and OS (P=0.039) for the co-variables of age, gender, T stage, N stage, histology, tumor location, tumor size and adjuvant chemotherapy. In male gastric cancer cell lines, faster-growing cancer cells showed higher sensitivity to cisplatin than slow-growing cells. Thus our study indicates that CPCC-measured proliferation activity demonstrates a significantly worse prognosis in T1 or T2 male gastric cancer patients. The CPCC will help to more precisely classify gastric cancer patients and to select excellent candidates for adjuvant chemotherapy, which in turn will facilitate further clinical chemotherapeutic trials. PMID:26542785

  11. Effects of chronic normovolemic anemia on gastric microcirculation and ethanol-induced gastric damage in rats.

    PubMed

    Marroni, N; Casadevall, M; Panés, J; Piera, C; Jou, J M; Pique, J M

    1994-04-01

    The effects of chronic normovolemic anemia on gastric microcirculation and gastric mucosal susceptibility to ethanol-induced gastric damage were investigated in anesthetized rats. Blood exchange by a plasma expander during four consecutive days rendered the animals anemic with a 34% decrease in the baseline hematocrit but without affecting blood volume. Chronic anemia induced a decrease in whole blood viscosity, an increase in gastric mucosal blood flow measured by hydrogen gas clearance, a decrease in gastric vascular resistance, and a decrease in gastric hemoglobin content without changes in the gastric oxygen content, the latter two parameters being measured by reflectance spectrophotometry. Gastric mucosal blood flow was lowered by intragastric administration of 100% ethanol in both anemic and control rats, but the final blood flow was significantly higher in anemic than in control animals. Macroscopic gastric damage induced by ethanol administration was significantly lower in anemic than in control rats. We conclude that chronic normovolemic anemia increases gastric mucosal blood flow and leads a protecting mechanism against gastric mucosal damage induced by absolute ethanol. PMID:8149840

  12. Slow Slip Events on a 760 mm Long Granite Sample

    NASA Astrophysics Data System (ADS)

    Mclaskey, G.; Yamashita, F.

    2015-12-01

    We describe slow slip events and dynamic rupture events generated on a newly constructed large-scale biaxial friction apparatus at Cornell University that provide insights into the mechanisms of aseismic and seismic slip. We find that, under nominally similar experimental conditions, the 760 mm long granite sample sometimes slips in dynamic stick-slip events and sometimes relieves accumulated shear stress through slow slip events. To provide insights into this curious behavior and the underlying mechanisms, fault slip and shear stress are each measured at 8 locations along the 760 mm long fault. This allows us to map slow slip fronts and the nucleation and propagation of dynamic fault rupture. The granite sample is also instrumented with an array of piezoelectric sensors that are the laboratory equivalent of a seismic network. When the sample is loaded relatively slowly, at 0.03 MPa/s, slow slip occurs on large sections of the fault and the slow slipping region soon expands to the sample boundary. In this case, stress is released in a slow slip event with peak slip velocities < 2 mm/s. Alternatively, when one end of the sample is loaded rapidly (4 MPa/s), or the sample is allowed to heal in stationary contact for a few minutes, slow slip initiates near the load point and accelerates to slip velocities exceeding 200 mm/s before the slow slipping region expands all the way to the sample boundary. This produces a dynamic slip event (stick-slip). The dynamic slip events radiate seismic waves equivalent to a M = -2.5 earthquake. In contrast, the laboratory-generated slow slip events are predominantly aseismic and produce only bursts of tiny and discrete seismic events (M = -6) reminiscent of swarms of microseismicity. The experiments illustrate how a single fault can slide slowly and aseismically or rapidly and dynamically depending on stress state and loading conditions. We compare the behavior observed on this Cornell apparatus to the behavior of other large

  13. Slow Conduction in Cardiac Muscle

    PubMed Central

    Lieberman, Melvyn; Kootsey, J. Mailen; Johnson, Edward A.; Sawanobori, Tohru

    1973-01-01

    Mechanisms of slow conduction in cardiac muscle are categorized and the most likely identified. Propagating action potentials were obtained experimentally from a synthetically grown strand of cardiac muscle (around 50 μm by 30 mm) and theoretically from a one-dimensional cable model that incorporated varying axial resistance and membrane properties along its length. Action potentials propagated at about 0.3 m/s, but in some synthetic strands there were regions (approximately 100 μm in length) where the velocity decreased to 0.002 m/s. The electrophysiological behavior associated with this slow conduction was similar to that associated with slow conduction in naturally occurring cardiac muscle (notches, Wenckebach phenomena, and block). Theoretically, reasonable changes in specific membrane capacitance, membrane activity, and various changes in geometry were insufficient to account for the observed slow conduction velocities. Conduction velocities as low as 0.009 m/s, however, could be obtained by increasing the resistance (ri) of connections between the cells in the cable; velocities as low as 0.0005 m/s could be obtained by a further increase in ri made possible by a reduction in membrane activity by one-fourth, which in itself decreased conduction velocity by only a factor of 1/1.4. As a result of these findings, several of the mechanisms that have been postulated, previously, are shown to be incapable of accounting for delays such as those which occur in the synthetic strand as well as in the atrioventricular (VA) node. ImagesFIGURE 1FIGURE 2FIGURE 3FIGURE 4 PMID:4709519

  14. Slow light and saturable absorption

    NASA Astrophysics Data System (ADS)

    Selden, A. C.

    2009-06-01

    Quantitative analysis of slow light experiments utilising coherent population oscillation (CPO) in a range of saturably absorbing media, including ruby and alexandrite, Er3+:Y2SiO5, bacteriorhodopsin, semiconductor quantum devices and erbium-doped optical fibres, shows that the observations may be more simply interpreted as saturable absorption phenomena. A basic two-level model of a saturable absorber displays all the effects normally associated with slow light, namely phase shift and modulation gain of the transmitted signal, hole burning in the modulation frequency spectrum and power broadening of the spectral hole, each arising from the finite response time of the non-linear absorption. Only where hole-burning in the optical spectrum is observed (using independent pump and probe beams), or pulse delays exceeding the limits set by saturable absorption are obtained, can reasonable confidence be placed in the observation of slow light in such experiments. Superluminal (“fast light”) phenomena in media with reverse saturable absorption (RSA) may be similarly explained.

  15. Lifting the Mist on Gastric Stem Cells.

    PubMed

    Varga, Julia; Greten, Florian R

    2016-01-01

    In a recent issue of Cancer Cell, Hayakawa et al. (2015) demonstrate that Mist1(+) gastric stem cells are supported by a specialized niche composed of Cxcl12(+) endothelium and Wnt5a-producing Cxcr4(+) innate lymphoid cells. In diffuse-type gastric cancer this perivascular stem cell niche is expanded and can be exploited for cancer therapy. PMID:26748749

  16. Gastric cancer with pregnancy: two case reports

    PubMed Central

    Mohamed, Sahar; Chakravarti, Seema

    2011-01-01

    Gastric cancer with pregnancy is quite rare, and is often diagnosed at advanced stages with poor prognosis. This highlights the need to improve diagnosis by means of early endoscopy. We herein report two cases of advanced gastric cancer during pregnancy who sadly died within five weeks of diagnosis, to alert clinicians to this rare disease.

  17. Helicobacter pylori infection and gastric cancer.

    PubMed

    Sugiyama, Toshiro; Asaka, Masahiro

    2004-09-01

    Helicobacter pylori infection has an association with histological gastritis, gastric atrophy, gastric cancer, and mucosa-associated lymphoid tissue (MALT) lymphoma in the stomach. Gastric cancer occurs in only a minority of infected individuals, however. Such clinical diversities are caused by variations of H. pylori pathogenicity, host susceptibility, environmental factors, and interactions of these factors. By three prospective epidemiological studies, the International Agency for Research on Cancer, World Health Organization (IARC/WHO) concluded in 1994 that H. pylori had a causal linkage to gastric carcinogenesis and is a definite carcinogen in humans. In addition, the Mongolian gerbil model with or without low-dose chemical carcinogens demonstrated that H. pylori infection could develop into gastric cancer. The experimental studies have elucidated that virulence factors of H. pylori have an interaction with gastric epithelial cell signaling related to carcinogenesis. The cag pathogenicity island (cagPAI) is a major virulence gene cluster and codes the type IV secretion machinery system, forming a cylinder-like structure. The CagA protein is translocated into target cells via this secretion system and induces a hummingbird morphology, growth factor-like effect. The other gene products are probably translocated into target cells and accelerate cellular proliferation and apoptosis. Understanding the molecular mechanism of the interaction between H. pylori and gastric epithelial cells will provide us with a new strategy for effective prevention of the development of gastric cancer induced by H. pylori infection. PMID:15449106

  18. Laparoscopic gastric band removal complicated by splenosis.

    PubMed

    Nicolas, Gregory; Schoucair, Ramy; Shimlati, Rasha; Rached, Linda; Khoury, George

    2016-08-01

    In any patient, the occurrence of postsplenectomy splenosis can complicate the planning of further surgeries. In our case, the gastric sleeve procedure was aborted, as it would have put the patient's life in danger. Therefore, only the gastric band was removed, eliminating future erosion. PMID:27525091

  19. Helicobacter pylori Diversity and Gastric Cancer Risk

    PubMed Central

    2016-01-01

    ABSTRACT Gastric cancer is a leading cause of cancer-related death worldwide. Helicobacter pylori infection is the strongest known risk factor for this malignancy. An important goal is to identify H. pylori-infected persons at high risk for gastric cancer, so that these individuals can be targeted for therapeutic intervention. H. pylori exhibits a high level of intraspecies genetic diversity, and over the past two decades, many studies have endeavored to identify strain-specific features of H. pylori that are linked to development of gastric cancer. One of the most prominent differences among H. pylori strains is the presence or absence of a 40-kb chromosomal region known as the cag pathogenicity island (PAI). Current evidence suggests that the risk of gastric cancer is very low among persons harboring H. pylori strains that lack the cag PAI. Among persons harboring strains that contain the cag PAI, the risk of gastric cancer is shaped by a complex interplay among multiple strain-specific bacterial factors as well as host factors. This review discusses the strain-specific properties of H. pylori that correlate with increased gastric cancer risk, focusing in particular on secreted proteins and surface-exposed proteins, and describes evidence from cell culture and animal models linking these factors to gastric cancer pathogenesis. Strain-specific features of H. pylori that may account for geographic variation in gastric cancer incidence are also discussed. PMID:26814181

  20. The journey of personalizing gastric cancer treatment.

    PubMed

    Yan, Li

    2016-01-01

    Gastric cancer ranks the fourth most prevalent malignancy yet it is the second leading cause of cancer-related death. Every year, gastric cancer adds nearly 1 million new cancer cases, and 723,000 or 10% of cancer deaths to the global cancer burden. Approximately, 405,000 or 43% of the new cases and 325,000 or 45% of the deaths are in China, making gastric cancer a particularly challenging malignancy. This thematic series discusses the molecular classifications of gastric cancer by the Cancer Genome Atlas (TCGA) and the Asian Cancer Research Group (ACRG) as well as the implications in personalized therapeutic choices; discusses the evolution of gastric surgery and presents perspectives on surgical techniques in treating gastric cancer; and reviews current and emerging targeted agents as well as immunotherapies in treating gastric cancer. With these advancements in molecular characterization, surgical intervention, and targeted and immunotherapies, gastric cancer will enter a personalized medicine era in the next 5 years. PMID:27581614

  1. A Simple Band for Gastric Banding.

    PubMed

    Broadbent

    1993-08-01

    The author has noted that flexible gastric bands have occasionally stenosed the gastric stoma or allowed it to dilate. A band was developed using a soft outer silicone rubber tube over a holding mechanism made out of a nylon cable tie passed within the silicone tube. This simple, easily applied band is rigid, resisting scar contracture and dilatation. PMID:10757939

  2. Nutrition and Gastric Cancer Risk: An Update

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Data from epidemiologic, experimental, and animal studies indicate that diet plays an important role in the etiology of gastric cancer. High intake of fresh fruit and vegetable, lycopene and lycopene-containing food products, and potentially vitamin C and selenium may reduce the risk for gastric can...

  3. Effects of simulated heat waves on ApoE-/- mice.

    PubMed

    Wang, Chunling; Zhang, Shuyu; Tian, Ying; Wang, Baojian; Shen, Shuanghe

    2014-02-01

    The effects of simulated heat waves on body weight, body temperature, and biomarkers of cardiac function in ApoE-/- mice were investigated. Heat waves were simulated in a meteorological environment simulation chamber according to data from a heat wave that occurred in July 2001 in Nanjing, China. Eighteen ApoE-/- mice were divided into control group, heat wave group, and heat wave BH4 group. Mice in the heat wave and BH4 groups were exposed to simulated heat waves in the simulation chamber. Mice in BH4 group were treated with gastric lavage with BH4 2 h prior to heat wave exposure. Results showed that the heat waves did not significantly affect body weight or ET-1 levels. However, mice in the heat wave group had significantly higher rectal temperature and NO level and lower SOD activity compared with mice in the control group (p < 0.01), indicating that heat wave had negative effects on cardiac function in ApoE-/- mice. Gastric lavage with BH4 prior to heat wave exposure significantly reduced heat wave-induced increases in rectal temperature and decreases in SOD activity. Additionally, pretreatment with BH4 further increased NO level in plasma. Collectively, these beneficial effects demonstrate that BH4 may potentially mitigate the risk of coronary heart disease in mice under heat wave exposure. These results may be useful when studying the effects of heat waves on humans. PMID:24477215

  4. Anticancer Effect of Lycopene in Gastric Carcinogenesis.

    PubMed

    Kim, Mi Jung; Kim, Hyeyoung

    2015-06-01

    Gastric cancer ranks as the most common cancer and the second leading cause of cancer-related death in the world. Risk factors of gastric carcinogenesis include oxidative stress, DNA damage, Helicobacter pylori infection, bad eating habits, and smoking. Since oxidative stress is related to DNA damage, smoking, and H. pylori infection, scavenging of reactive oxygen species may be beneficial for prevention of gastric carcinogenesis. Lycopene, one of the naturally occurring carotenoids, has unique structural and chemical features that contributes to a potent antioxidant activity. It shows a potential anticancer activity and reduces gastric cancer incidence. This review will summarize anticancer effect and mechanism of lycopene on gastric carcinogenesis based on the recent experimental and clinical studies. PMID:26151041

  5. Helicobacter pylori, Cancer, and the Gastric Microbiota.

    PubMed

    Wroblewski, Lydia E; Peek, Richard M

    2016-01-01

    Gastric adenocarcinoma is one of the leading causes of cancer-related death worldwide and Helicobacter pylori infection is the strongest known risk factor for this disease. Although the stomach was once thought to be a sterile environment, it is now known to house many bacterial species leading to a complex interplay between H. pylori and other residents of the gastric microbiota. In addition to the role of H. pylori virulence factors, host genetic polymorphisms, and diet, it is now becoming clear that components of the gastrointestinal microbiota may also influence H. pylori-induced pathogenesis. In this chapter, we discuss emerging data regarding the gastric microbiota in humans and animal models and alterations that occur to the composition of the gastric microbiota in the presence of H. pylori infection that may augment the risk of developing gastric cancer. PMID:27573782

  6. Anticancer Effect of Lycopene in Gastric Carcinogenesis

    PubMed Central

    Kim, Mi Jung; Kim, Hyeyoung

    2015-01-01

    Gastric cancer ranks as the most common cancer and the second leading cause of cancer-related death in the world. Risk factors of gastric carcinogenesis include oxidative stress, DNA damage, Helicobacter pylori infection, bad eating habits, and smoking. Since oxidative stress is related to DNA damage, smoking, and H. pylori infection, scavenging of reactive oxygen species may be beneficial for prevention of gastric carcinogenesis. Lycopene, one of the naturally occurring carotenoids, has unique structural and chemical features that contributes to a potent antioxidant activity. It shows a potential anticancer activity and reduces gastric cancer incidence. This review will summarize anticancer effect and mechanism of lycopene on gastric carcinogenesis based on the recent experimental and clinical studies. PMID:26151041

  7. Polyamines are Inhibitors of Gastric Acid Secretion

    NASA Astrophysics Data System (ADS)

    Ray, Tushar K.; Nandi, Jyotirmoy; Pidhorodeckyj, Nykolai; Meng-Ai, Zhou

    1982-03-01

    The naturally occurring organic polycations such as spermine and spermidine inhibit histamine-stimulated gastric acid secretion by bullfrog gastric mucosa in vitro; spermine is much more potent than spermidine. Unlike the H2 receptor antagonists, the polyamines are completely ineffective from the nutrient side and are effective only from the secretory side of the chambered mucosa. The polyamine effects could be reversed by increasing K+ concentration in the secretory solution. Studies with isolated gastric microsomal vesicles demonstrate that the polyamines do not inhibit the gastric H+,K+-ATPase but greatly decrease the ATPase-mediated uptake of H+ under appropriate conditions. For the latter effects the presence of polyamine within the vesicle interior was found to be essential. Our data strongly suggest an uncoupling of the gastric H+,K+-ATPase system by the polyamines. The therapeutic potential of these and similar compounds in the treatment of hyperacidity and peptic ulcer is discussed.

  8. Traveling-Wave Tubes

    NASA Technical Reports Server (NTRS)

    Kory, Carol L.

    1998-01-01

    The traveling-wave tube (TWT) is a vacuum device invented in the early 1940's used for amplification at microwave frequencies. Amplification is attained by surrendering kinetic energy from an electron beam to a radio frequency (RF) electromagnetic wave. The demand for vacuum devices has been decreased largely by the advent of solid-state devices. However, although solid state devices have replaced vacuum devices in many areas, there are still many applications such as radar, electronic countermeasures and satellite communications, that require operating characteristics such as high power (Watts to Megawatts), high frequency (below 1 GHz to over 100 GHz) and large bandwidth that only vacuum devices can provide. Vacuum devices are also deemed irreplaceable in the music industry where musicians treasure their tube-based amplifiers claiming that the solid-state and digital counterparts could never provide the same "warmth" (3). The term traveling-wave tube includes both fast-wave and slow-wave devices. This article will concentrate on slow-wave devices as the vast majority of TWTs in operation fall into this category.

  9. Isoprenaline Induces Periostin Expression in Gastric Cancer

    PubMed Central

    Liu, Guo-Xiao; Xi, Hong-Qing; Sun, Xiao-Yan; Geng, Zhi-Jun; Yang, Shao-Wei; Lu, Yan-Jie

    2016-01-01

    Purpose Periostin mediates critical steps in gastric cancer and is involved in various signaling pathways. However, the roles of periostin in promoting gastric cancer metastasis are not clear. The aim of this study was to investigate the relevance between periostin expression and gastric cancer progression and the role of stress-related hormones in the regulation of cancer development and progression. Materials and Methods Normal, cancerous and metastatic gastric tissues were collected from patients diagnosed with advanced gastric cancer. The in vivo expression of periostin was evaluated by in situ hybridization and immunofluorescent staining. Meanwhile, human gastric adenocarcinoma cell lines MKN-45 and BGC-803 were used to detect the in vitro expression of periostin by using quantitative real-time polymerase chain reaction (PCR) and western blotting. Results Periostin is expressed in the stroma of the primary gastric tumors and metastases, but not in normal gastric tissue. In addition, we observed that periostin is located mainly in pericryptal fibroblasts, but not in the tumor cells, and strongly correlated to the expression of α-smooth muscle actin (SMA). Furthermore, the distribution patterns of periostin were broader as the clinical staging of tumors progressed. We also identified a role of stress-related signaling in promoting cancer development and progression, and found that isoprenaline upregulated expression levels of periostin in gastric cancer cells. Conclusion These findings suggest that the distribution pattern of periostin was broader as the clinical staging of the tumor progressed and found that isoprenaline upregulated expression levels of periostin in gastric cancer cells. PMID:26996552

  10. Exsanguination due to gastric ulceration in a foal.

    PubMed

    Traub-Dagartz, J; Bayly, W; Riggs, M; Thomas, N; Pankowski, R

    1985-02-01

    An Arabian foal with a congenital heart disease died due to hemorrhage secondary to a large gastric ulcer. Previously, death of foals with gastric ulcers has been due to diffuse peritonitis resulting from gastric ulcer perforation. The foal in this case report died due to hemorrhage secondary to a large gastric ulcer. PMID:3972690

  11. Targeted therapy for gastric cancer.

    PubMed

    Smyth, Elizabeth C; Cunningham, David

    2012-09-01

    For patients with advanced gastric cancer, traditional double or triplet cytotoxic chemotherapy regimens result in a median survival of 9-11 months. As combination therapy is associated with increased survival, but also increased toxicity in a patient population whose performance status often compromised by their malignancy, development of more effective and less toxic treatment choices is mandated. Emerging data from gene expression profiling suggests that differences in pathological appearance and clinical behavior may be due the presence of unique molecular phenotypes. Characterization of the gastric cancer genomic landscape reveals the presence of multiple alterations in expression of receptor tyrosine kinases, which in conjunction with their ligands and downstream effector molecules represent potentially druggable pathways for future drug development. Treatment of HER2 positive gastric cancer with trastuzumab has led to significant gains in overall survival, and further manipulation of this pathway using the novel anti-HER2 directed agents pertuzumab and T-DM1 in addition to dual EGFR/HER2 blockade with lapatinib may yield positive results. In contrast, targeting of the EGFR pathway in combination with chemotherapy in unselected patients has not been fruitful to date, with no significant gains over standard chemotherapy yet demonstrated. Similarly, use of the anti-angiogenic monoclonal antibody bevacizumab was not successful in a large global randomized trial; however intriguing regional variations were seen with respect to efficacy of this drug, leading to calls for a second, regionally stratified study. Careful selection of patient subsets will become a key factor in future clinical trials, as novel targeted agents such as those targeting the MET/HGF and FGFR axes move forward into clinical development. It is hoped that treatment of patients in such molecularly defined groups is will lead to significant gains in survival compared to current treatment

  12. Triple gastric peptic ulcer perforation.

    PubMed

    Radojkovic, Milan; Mihajlovic, Suncica; Stojanovic, Miroslav; Stanojevic, Goran; Damnjanovic, Zoran

    2016-03-01

    Patients with advanced or metastatic cancer have compromised nutritional, metabolic, and immune conditions. Nevertheless, little is known about gastroduodenal perforation in cancer patients. Described in the present report is the case of a 41-year old woman with stage IV recurrent laryngeal cancer, who used homeopathic anticancer therapy and who had triple peptic ulcer perforation (PUP) that required surgical repair. Triple gastric PUP is a rare complication. Self-administration of homeopathic anticancer medication should be strongly discouraged when evidence-based data regarding efficacy and toxicity is lacking. PMID:27193988

  13. Biphasic nature of gastric emptying.

    PubMed

    Siegel, J A; Urbain, J L; Adler, L P; Charkes, N D; Maurer, A H; Krevsky, B; Knight, L C; Fisher, R S; Malmud, L S

    1988-01-01

    The existence of a lag phase during the gastric emptying of solid foods is controversial. It has been hypothesised that among other early events, the stomach requires a period of time to process solid food to particles small enough to be handled as a liquid. At present no standardised curve fitting techniques exist for the characterisation and quantification of the lag phase or the emptying rate of solids and liquids. We have evaluated the ability of a modified power exponential function to define the emptying parameters of two different solid meals. Dual labelled meals were administered to 24 normal volunteers. The subjects received meals consisting of either Tc-99m in vivo labelled chicken liver or Tc-99m-egg, which have different densities, and In-111-DTPA in water. The emptying curves were biphasic in nature. For solids, this represented an initial delay in emptying or lag phase followed by an equilibrium emptying phase characterised by a constant rate of emptying. The curves were analysed using a modified power exponential function of the form y(t) = 1-(1-e-kt)beta, where y(t) is the fractional meal retention at time t, k is the gastric emptying rate in min-1, and beta is the extrapolated y-intercept from the terminal portion of the curve. The length of the lag phase and half-emptying time increased with solid food density (31 +/- 8 min and 77.6 +/- 11.2 min for egg and 62 +/- 16 min and 94.1 +/- 14.2 min for chicken liver, respectively). After the lag phase, both solids had similar emptying rates, and these rates were identical to those of the liquids. In vitro experiments indicated that the egg meal disintegrated much more rapidly than the chicken liver under mechanical agitation in gastric juice, lending further support to the hypothesis that the initial lag in emptying of solid food is due to the processing of food into particles small enough to pass the pylorus. We conclude that the modified power exponential model permits characterisation of the biphasic

  14. Current Perspectives on Gastric Cancer.

    PubMed

    Marqués-Lespier, Juan M; González-Pons, María; Cruz-Correa, Marcia

    2016-09-01

    Gastric cancer (GC) is third leading cause of cancer-related death. Only 28.3% of new GC cases survive more than 5 years. Although incidence has declined in the United States, an increase is estimated for 2016. Risk factors include sex (risk is higher in men), Helicobacter pylori infection, heredity, and lifestyle. GC is usually diagnosed between the ages of 60-80 years. Prognosis of GC is largely dependent on the tumor stage at diagnosis and classification as intestinal or diffuse type; diffuse-type GC has worse prognosis. Chemoprevention has been shown to decrease risk, but is currently not used clinically. PMID:27546840

  15. Slow Lévy flights

    NASA Astrophysics Data System (ADS)

    Boyer, Denis; Pineda, Inti

    2016-02-01

    Among Markovian processes, the hallmark of Lévy flights is superdiffusion, or faster-than-Brownian dynamics. Here we show that Lévy laws, as well as Gaussian distributions, can also be the limit distributions of processes with long-range memory that exhibit very slow diffusion, logarithmic in time. These processes are path dependent and anomalous motion emerges from frequent relocations to already visited sites. We show how the central limit theorem is modified in this context, keeping the usual distinction between analytic and nonanalytic characteristic functions. A fluctuation-dissipation relation is also derived. Our results may have important applications in the study of animal and human displacements.

  16. Intense source of slow positrons

    NASA Astrophysics Data System (ADS)

    Perez, P.; Rosowsky, A.

    2004-10-01

    We describe a novel design for an intense source of slow positrons based on pair production with a beam of electrons from a 10 MeV accelerator hitting a thin target at a low incidence angle. The positrons are collected with a set of coils adapted to the large production angle. The collection system is designed to inject the positrons into a Greaves-Surko trap (Phys. Rev. A 46 (1992) 5696). Such a source could be the basis for a series of experiments in fundamental and applied research and would also be a prototype source for industrial applications, which concern the field of defect characterization in the nanometer scale.

  17. Glut, war slow Mideast activity

    SciTech Connect

    Not Available

    1984-07-20

    Oilpatch activity in the Middle East has been on the slow side recently, and with a heated-up war between Iran and Iraq throwing off violent sparks around the Arabian Gulf, it's difficult to keep one's mind on business-as-usual. The article deals with the rising cost of insurance for shipping because of the war and the effects on drilling, production and the environment (oil spills). The development and production of offshore oil and gas in Egypt, Saudi Arabia, and the United Arab Emirates is also discussed.

  18. Gabor Wave Packet Method to Solve Plasma Wave Equations

    SciTech Connect

    A. Pletzer; C.K. Phillips; D.N. Smithe

    2003-06-18

    A numerical method for solving plasma wave equations arising in the context of mode conversion between the fast magnetosonic and the slow (e.g ion Bernstein) wave is presented. The numerical algorithm relies on the expansion of the solution in Gaussian wave packets known as Gabor functions, which have good resolution properties in both real and Fourier space. The wave packets are ideally suited to capture both the large and small wavelength features that characterize mode conversion problems. The accuracy of the scheme is compared with a standard finite element approach.

  19. Influence of meal weight and caloric content on gastric emptying of meals in man

    SciTech Connect

    Moore, J.G.; Christian, P.E.; Brown, J.A.; Brophy, C.; Datz, F.; Taylor, A.; Alazraki, N.

    1984-06-01

    This study was designed to assess the relative influence of meal weight and caloric content on gastric emptying of liquid and solid meals in man. A dual radioisotopic method which permits noninvasive and simultaneous measurement of liquid- and solid-phase emptying by external gamma camera techniques was employed. Nine healthy volunteer subjects ingested 50-, 300-, and 900-g lettuce and water meals adjusted to either 68, 208, or 633 kcal with added salad oil. The following observations were made: (1) absolute emptying rates (grams of solid food emptied from the stomach per minute) increased directly and significantly with meal weight; (2) increasing meal total caloric content significantly slowed solid food gastric emptying but did not overcome the enhancing effect of meal weight; and (3) liquid emptying rates were uninfluenced by meal total kcal amount.

  20. A Mechanistic Model of Intermittent Gastric Emptying and Glucose-Insulin Dynamics following a Meal Containing Milk Components

    PubMed Central

    MacPherson, Jayden A. R.; Berends, Harma; Steele, Michael A.

    2016-01-01

    To support decision-making around diet selection choices to manage glycemia following a meal, a novel mechanistic model of intermittent gastric emptying and plasma glucose-insulin dynamics was developed. Model development was guided by postprandial timecourses of plasma glucose, insulin and the gastric emptying marker acetaminophen in infant calves fed meals of 2 or 4 L milk replacer. Assigning a fast, slow or zero first-order gastric emptying rate to each interval between plasma samples fit acetaminophen curves with prediction errors equal to 9% of the mean observed acetaminophen concentration. Those gastric emptying parameters were applied to glucose appearance in conjunction with minimal models of glucose disposal and insulin dynamics to describe postprandial glycemia and insulinemia. The final model contains 20 parameters, 8 of which can be obtained by direct measurement and 12 by fitting to observations. The minimal model of intestinal glucose delivery contains 2 gastric emptying parameters and a third parameter describing the time lag between emptying and appearance of glucose in plasma. Sensitivity analysis of the aggregate model revealed that gastric emptying rate influences area under the plasma insulin curve but has little effect on area under the plasma glucose curve. This result indicates that pancreatic responsiveness is influenced by gastric emptying rate as a consequence of the quasi-exponential relationship between plasma glucose concentration and pancreatic insulin release. The fitted aggregate model was able to reproduce the multiple postprandial rises and falls in plasma glucose concentration observed in calves consuming a normal-sized meal containing milk components. PMID:27253712