166 research outputs found
A Myometric Evaluation of Certain Aspects of the Perioral Musculature in Individuals with Demonstrable Adverse Swallowing Patterns
The forces exerted by the perioral musculature and the effects observed in subjects with adverse swallowing patterns accompanied by demonstrable mentalis habits were compared with a control group of normal subjects by the following methods:
1. Study casts of upper and lower arches were obtained for a morphological evaluation of denial structures.
2. Measurements of lip pressures against the teeth were recorded for the following:
a. Drinking water
b. Volitional and spontaneous swallows
c. Designated speech sounds
d. Maximum effort pressure
3. Measurements of inter-lip pressures were recorded at the center and corner of the mouth for the following:
a. Maximum pressures
b. Volitional swallow
The recording instrument consisted of a cast rubber pressure sensing cushion coupled to a pressure-sensitive transducer by small, relatively inelastic tubing. The system was hydraulically activated. The signals from the transducer were recorded by a two-channel recorder equipped with strain gauge amplifiers.
From the records accumulated, this investigation has shown evidences that point to the following: Persons with a normal swallowing pattern generally exert greater pressures of lips against teeth and gums in both upper and lower arches during speaking and swallowing. The pressures resulting from the pill exerted by the mentalis and associated muscles is not primarily against the mandibular incisors and adjacent gum area. Persons with abnormal swallowing patters accompanied by mentalis habit exert greater inter-lip pressures. Since malocclusion is such a constant accompaniment of the mentalis habit, it is thought possible that the repetitive eversion of the lower lip associated with the mentalis habit may be contributory
On measuring the gravitational-wave background using Pulsar Timing Arrays
Long-term precise timing of Galactic millisecond pulsars holds great promise
for measuring the long-period (months-to-years) astrophysical gravitational
waves. Several gravitational-wave observational programs, called Pulsar Timing
Arrays (PTA), are being pursued around the world. Here we develop a Bayesian
algorithm for measuring the stochastic gravitational-wave background (GWB) from
the PTA data. Our algorithm has several strengths: (1) It analyses the data
without any loss of information, (2) It trivially removes systematic errors of
known functional form, including quadratic pulsar spin-down, annual modulations
and jumps due to a change of equipment, (3) It measures simultaneously both the
amplitude and the slope of the GWB spectrum, (4) It can deal with unevenly
sampled data and coloured pulsar noise spectra. We sample the likelihood
function using Markov Chain Monte Carlo (MCMC) simulations. We extensively test
our approach on mock PTA datasets, and find that the algorithm has significant
benefits over currently proposed counterparts. We show the importance of
characterising all red noise components in pulsar timing noise by demonstrating
that the presence of a red component would significantly hinder a detection of
the GWB. Lastly, we explore the dependence of the signal-to-noise ratio on the
duration of the experiment, number of monitored pulsars, and the magnitude of
the pulsar timing noise. These parameter studies will help formulate observing
strategies for the PTA experiments.Comment: 10 pages, 12 figure
Influence of myocardial oxygen demand on the coronary vascular response to arterial blood gas changes in humans
It remains unclear if the human coronary vasculature is inherently sensitive to changes in arterial PO2 and PCO2 or if coronary vascular responses are the result of concomitant increases in myocardial O2 consumption/demand (MVO2). We hypothesized that the coronary vascular response to PO2 and PCO2 would be attenuated in healthy men when MVO2 was attenuated with β1-adrenergic receptor blockade. Healthy men (n=11; age: 25 {plus minus} 1 years) received intravenous esmolol (β1-adrenergic receptor antagonist) or volume-matched saline in a double-blind, randomized, crossover study, and were exposed to poikilocapnic hypoxia, isocapnic hypoxia, and hypercapnic hypoxia. Measurements made at baseline and following 5-min of steady state at each gas manipulation included left anterior descending coronary blood velocity (LADV; Doppler echocardiography), heart rate and arterial blood pressure. LADV values at the end of each hypoxic condition were compared between esmolol and placebo. Rate pressure product (RPP) and left-ventricular mechanical energy (MELV) were calculated as indices of MVO2. All gas manipulations augmented RPP, MELV, and LADV but only RPP and MELV were attenuated (4-18%) following β1-adrenergic receptor blockade (P<0.05). Despite attenuated RPP and MELV responses, β1-adrenergic receptor blockade did not attenuate the mean LADV vasodilatory response when compared to placebo during poikilocapnic hypoxia (29.4{plus minus}2.2 vs. 27.3{plus minus}1.6 cm/s) and isocapnic hypoxia (29.5{plus minus}1.5 vs. 30.3{plus minus}2.2 cm/s). Hypercapnic hypoxia elicited a feed-forward coronary dilation that was blocked by β1-adrenergic receptor blockade. These results indicate a direct influence of arterial PO2 on coronary vascular regulation that is independent of MVO2
The independent effects of hypovolemia and pulmonary vasoconstriction on ventricular function and exercise capacity during acclimatisation to 3800 m
We aimed to determine the isolated and combined contribution of hypovolemia and hypoxic pulmonary vasoconstriction in limiting left ventricular (LV) function and exercise capacity under chronic hypoxemia at high altitude. In a double‐blinded, randomized and placebo‐controlled design, twelve healthy participants underwent echocardiography at rest and during submaximal exercise before completing a maximal test to exhaustion at sea level (SL; 344 m) and after 5–10 days at 3800 m. Plasma volume was normalised to SL values, and hypoxic pulmonary vasoconstriction was reversed by administration of Sildenafil (50 mg) to create four unique experimental conditions that were compared with SL values; high altitude (HA), Plasma Volume Expansion (HA‐PVX), Sildenafil (HA‐SIL) and Plasma Volume Expansion with Sildenafil (HA‐PVX‐SIL). High altitude exposure reduced plasma volume by 11% (P < 0.01) and increased pulmonary artery systolic pressure (19.6 ± 4.3 vs. 26.0 ± 5.4, P < 0.001); these differences were abolished by PVX and SIL respectively. LV end‐diastolic volume (EDV) and stroke volume (SV) were decreased upon ascent to high altitude, but were comparable to sea level in the HA‐PVX. LV EDV and SV were also elevated in the HA‐SIL and HA‐PVX‐SIL trials compared to HA, but to a lesser extent. Neither PVX or SIL had a significant effect on the LV EDV and SV response to exercise, or the maximal oxygen consumption or peak power output. In summary, at 3800 m both hypovolemia and hypoxic pulmonary vasoconstriction contribute to the decrease in LV filling, however, restoring LV filling does not confer an improvement in maximal exercise performance
Extending gravitational wave burst searches with pulsar timing arrays
Pulsar timing arrays (PTAs) are being used to search for very low frequency
gravitational waves. A gravitational wave signal appears in pulsar timing
residuals through two components: one independent of and one dependent on the
pulsar's distance, called the 'Earth term' (ET) and 'pulsar term' (PT),
respectively. The signal of a burst (or transient) gravitational wave source in
pulsars' residuals will in general have the Earth and pulsar terms separated by
times of the order of the time of flight from the pulsar to the Earth.
Therefore, both terms are not observable over a realistic observation span, but
the ETs observed in many pulsars should be correlated. We show that pairs (or
more) of pulsars can be aligned in such a way that the PTs caused by a source
at certain sky locations can arrive at Earth within a time window short enough
to be captured during a realistic observation span. We find that for the
pulsars within the International Pulsar Timing Array (IPTA) ~67 per cent of the
sky produces such alignments for pulsars terms separated by less than 10 years.
We compare estimates of the source event rate that would be required to observe
one signal in the IPTA if searching for the correlated ETs, or in searching via
the PTs, and find that event rates would need to be about two orders of
magnitude higher to observe an event with the PTs than the ETs. We also find
that an array of hundreds of thousands of pulsars would be required to achieve
similar numbers of observable events in PT or ET searches. This disfavours PTs
being used for all-sky searches, but they could potentially be used target
specific sources and be complementary to ET only searches.Comment: version accepted for MNRA
Effects of 1 year of exercise training versus combined exercise training and weight loss on body composition, low-grade inflammation and lipids in overweight patients with coronary artery disease:a randomized trial
Liraglutide improves the beta-cell function without increasing insulin secretion during a mixed meal in patients, who exhibit well-controlled type 2 diabetes and coronary artery disease
Investigating ultra-long gravitational waves with measurements of pulsars rotational parameters
A method is suggested to explore the gravitational wave background (GWB) in
the frequency range from to \hbox{ Hz}. That method is
based on the precise measurements of pulsars' rotational parameters: the
influence of the gravitational waves (GW) in the range will affect them and
therefore some conclusions about energy density of the GWB can be made using
analysis of the derivatives of pulsars' rotational frequency. The calculated
values of the second derivative from a number of pulsars limit the density of
GWB as follows: . Also, the time
series of the frequency of different pulsars in pulsar array can be
cross-correlated pairwise in the same manner as in anomalous residuals analysis
thus providing the possibility of GWB detection in ultra-low frequency range.Comment: 5 pages, submitted to MNRAS; changes of content in Section 3,
reference added for section 1; changes in content in Section 3, refernce
added, generally matches MNRAS versio
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