Presence Of Acceleration Research Articles

Late Second-Trimester Nonstress Test Characteristics in Preterm Delivery before 32 Weeks of Gestation

Objective: To clarify electronic fetal heart rate (FHR) monitoring characteristics in pregnancies with preterm delivery before 32 weeks of gestation, using the late second-trimester nonstress test. Methods: Among 953 children born from 1993 to 1996, we identified 100 singleton infants born before 32 weeks of gestation in whom second-trimester (24–27 weeks of gestation) electronic fetal monitoring (EFM) records were obtained. Individual components of the FHR patterns [baseline rate, baseline FHR variability, presence of acceleration (at least 10 beats/min for at least 10 s) and periodic or episodic deceleration (at least 25 beats/min for at least 15 s)] and birth characteristics were compared between pregnancy with or without second-trimester decelerations. Results: Among 100 infants, 65 had and 35 did not have second-trimester decelerations. There were no significant differences in gestational age at birth, birth weight, cord arterial blood pH, Apgar score and meconium staining between pregnancies with second-trimester decelerations and those without second-trimester decelerations. There were no significant differences in baseline rate and baseline variability between pregnancies with or without second-trimester decelerations. The number of accelerations in pregnancies with second-trimester decelerations was significantly more frequent than that in pregnancies without second-trimester decelerations (p < 0.001). There was a significant increase in the occurrence of premature rupture of the membranes (PROM; 60.0%) in pregnancies with second-trimester decelerations, when compared with events (37.1%) related to pregnancies without second-trimester decelerations (p < 0.05). There were no significant differences in the onset of breech presentation, cervical incompetency, preeclampsia and abnormal FHR pattern at birth between pregnancies with second-trimester decelerations and those without second-trimester decelerations. Pregnancies with PROM after second-trimester EFM were significantly more likely to have second-trimester decelerations than those without PROM (75.0 vs. 54.2%, p < 0.05). Conclusion: Periodic or episodic decelerations during late second-trimester EFM were associated with an increased risk of the occurrence of PROM in pregnancies with preterm delivery before 32 weeks of gestation.

Comparison of late–second-trimester nonstress test characteristics between small for gestational age and appropriate for gestational age infants

Objective: To compare electronic fetal heart rate (FHR) monitoring characteristics between appropriate for gestational age (AGA) fetuses and small for gestational age (SGA) fetuses and to determine whether SGA fetuses have specific abnormalities at second-trimester electronic fetal monitoring (EFM), using nonstress test. Methods: Among 953 children born from 1993–1996, we identified 500 singleton infants born after 36 weeks’ gestation of uncomplicated pregnancies in whom second-trimester (24–27 weeks’ gestation) EFM records were obtained. Individual components of FHR patterns (baseline rate, baseline FHR variability, presence of acceleration [at least 10 beats per minute for at least 10 seconds], and periodic or episodic deceleration [at least 25 beats per minute for at least 15 seconds]) and birth characteristics were compared between AGA and SGA infants, or between pregnancies with or without second-trimester decelerations. Results: Among 500 infants, 443 were AGA and 57 SGA; 105 had and 395 did not have second-trimester decelerations. Baseline FHR variability (12.9 ± 3.2 beats per minute) in SGA fetuses was significantly higher than variability (10.3 ± 3.4 beats per minute) in AGA fetuses ( P < .001). Small for gestational age fetuses were significantly more likely to have second-trimester decelerations than AGA fetuses (33.3% vs 19.4%, P < .05). There were no significant differences in baseline rate and accelerations between AGA and SGA infants. Small for gestational age infants were more frequent in pregnancies with second-trimester decelerations, compared with those without second-trimester decelerations (18.1% vs 9.6%, P < .05). Baseline FHR variability in pregnancies with second-trimester decelerations was significantly higher than in pregnancies without second-trimester decelerations (12.2 ± 3.7 vs 10.0 ± 3.1 beats per minute, P < .001). Conclusion: Periodic or episodic decelerations and increased FHR variability during late second-trimester EFMwere associated with an increased risk of SGA birth weight.

ASCA results on SS 433: a galactic astrophysical jet system

The ASCA observations of SS 433 revealed two important properties of SS 433. The X-ray emission from the central point source exhibited multi-temperature thermal spectra which have two velocity components corresponding to the two anti-parallel jets outflowing at 0.26 c. The detailed analysis of the spectra revealed that the kinetic luminosity of SS 433 far exceeds the Eddington luminosity for any stellar size objects. The X-ray lobes, which are distributed at a very large scale (tens of parsecs) were found to have non-thermal spectra, suggesting presence of acceleration of energetic particles. There are still essential problems awaiting to be addressed. For example, identification of the compact object underlying the jets requires sensitive and detailed spectroscopy which will be made possible with ASTRO-E.

Studies on the Reaction of Development-free Vapor Photolithography (DFVP).

Based on the reaction of vapor HF and SiO2 at a temperature of above 100°C, development-free vapor photolithography (DFVP) eliminates the development step in conventional process. Under the etching condition, only in the presence of accelerators can the etching reaction occur. The accelerators catalyze this nucleophilic reaction by raising the nucleophilic activity of HF or activating the leaving group in substrate. Photochemical reaction leads to the concentration difference of accelerators between exposed area and unexposed area and thus results in the area-selective etching.

Studies of the chemically amplified development-free vapor photolithography

Development-free vapor photolithography (DFVP) is a unique all-dry pattern transfer technique, which is based on the reaction of SiO 2 with HF vapor under a polymer film in the presence of accelerators at a temperature of above 100°C. In this paper, we found that the etching reaction could be catalyzed by superacids. Based on this discovery, a novel, chemically amplified, development-free vapor photolithography technique was developed, and has benn successfully applied to power electronic device manufacture.

Studies on a New Antireversion Agent for Sulfur Vulcanization of Diene Rubbers

Abstract The mechanism of biscitraconimides (BCI) as antireversion agents for sulfur vulcanized diene rubber was investigated choosing squalene as a model substrate. Curing of squalene with sulfur in the presence of accelerator, activator and BCI at 170°C gave BCI bridged adducts. The products were identified by spectroscopic methods as being results of a Diels-Alder reaction of BCI (dienophile) with conjugated polyenes that are formed as a result of reversion. The rate at which the sulfur network degrades is comparable to the rate in which BCI adduct is formed. As a result of this, a nearly constant crosslink density is obtained after optimum cure time (t90). Based on this concept, the advantage of using 1,3-bis-(citraconimidomethyl) benzene (BCI-MX), a representative of the BCI-class, in NR based compounds is examined.

Effect of polymer accelerators upon development-free vapor photolithography

Development-free vapor photolithography (DFVP) is a new technology, which is based on the reaction of SiO 2 with HF vapor under a polymer film in the presence of accelerators. This paper discusses the effect of functional groups of polymers, glass transition temperature ( T g), film thickness, and etching temperature on the reaction. The results demonstrate that polymers with carbonyl, nitro, amino, amino formacyl, and other polar functional groups act not only as film formers but also as accelerators of the etching reaction of SiO 2 with HF.

Vulcanization of Nitrile Rubber. Part III. Formulation and Study of Oil-Resisting Vulcanization, Based on Acrylonitrile-Butadiene Rubber

Abstract Acrylonitrile butadiene rubber (Krynac, 803) with the best system of vulcanization in presence of accelerators, and coaccelerators, is further modified by the addition of different quantities of melamine-formaldehyde resin. As compared with the blank sample without this resin, the values of optimum cure time and scorch time decrease with the addition of resin. The rate of vulcanization increases and then begins to decrease gradually at higher quantities. Higher values of tensile strength, modulus, and hardness are obtained for vulcanized samples. The elasticity and elongation at break, respectively, remain at 28% and 260% till 3.0 pphr. Even higher quantities of the added resin lead to slight decreases in the studied properties. Better properties were also obtained upon aging in fuel and in hydraulic oil.

Biomechanical exploration on dynamic modes of lifting.

Whatever the lifting method used, dynamic factors appear to have an effect on the safe realization of movement, and NIOSH guidelines recommend smooth lifting with no sudden acceleration effects. On the other hand, inertial forces may play an important role in the process of transfer of momentum to the load. The direction by which these inertial forces may affect the loadings on body structures and processes of energy transfers cannot be determined a priori. A biomechanical experiment was performed to examine if there were differences in the execution processes between a slow-continuous lift and an accelerated-continuous lift, and also between accelerated lifts either executed continuously or interrupted with a pause. The lifts were executed from a height of 15 cm to a height of 185 cm above the head and with two different loads (6.4 and 11.6 kg). Five experienced workers in manual materials handling were used as subjects. Films and force platforms recordings supplied the data; dynamic segmental analyses were performed to calculate net muscular moments at each joint; a planar single-muscle equivalent was used to estimate compression loadings at L5/S1; total mechanical work, joint work distribution, and energy transfers were determined from a kinetic approach based on the integration of joint power as a function of time. Analyses of variance with repeated measures were applied to the three treatments. The results showed that joint muscular moments, spinal loadings, mechanical work, and muscular utilization ratios were generally increased by the presence of acceleration without inducing benefits of improved energy transfers; therefore slower lifts with reduced acceleration may be safer when handling moderately heavy loads. The maximum values of kinematic and kinetic factors were generally not affected by the pause, but the occurrence of jerks in the movement (acceleration, ground forces, and muscular moments) suggests that the pause may not be indicated when considering total exposure to muscular exertion. Full consideration should be given to the dynamics of motion when assessing risk factors in working tasks.

Effect of Acceleration on the Heat Transfer Coefficient on a Film-Cooled Surface

Results are presented of an experimental investigation into the influence of mainstream acceleration on the heat transfer coefficient downstream of injection through a row of 35 deg holes in a flat plate. A mass transfer analogue technique was used, with two uniform acceleration parameters, K ( = v(du∞/dx)/u2∞, of 1.9 × 10−6 and 5.0×10−6 in addition to the zero acceleration baseline case. Two injectants, air and carbon dioxide, were employed to give coolant-to-mainstream density ratios of 1.0 and 1.52, respectively. The blowing rate varied from 0.5 to 2.0. The heat transfer coefficient beneath the film decreased progressively as the acceleration increased, with maximum reductions from the zero acceleration datum case of about 27 percent. In the presence of acceleration, the heat transfer coefficient at a given blowing rate was dependent on the density ratio, an increase in the density ratio leading to a decrease in the heat transfer coefficient. An empirical correlation of the data over most of the range of densities and blowing rates of the experiments has been developed.

Reliability of intrapartum fetal heart rate monitoring in the postterm fetus with meconium passage.

Fifty-six postterm fetuses with intrapartum meconium passage underwent routine scalp stimulation and scalp blood sampling. Fetal heart rate (FHR) patterns were compared with blood pH. Nine fetuses (16%) had a scalp pH less than 7.20. Twenty-nine fetuses (54%) demonstrated spontaneous or induced FHR accelerations; none were acidemic. Acidemia with normal variability was found only in conjunction with severe variable decelerations, and may represent respiratory acidosis. In this group, two of nine acidemic fetuses demonstrated no decelerations (pH 7.04) or mild variable decelerations only (pH 7.19). The absence of late decelerations was not as reliable as the presence of accelerations in the prediction of fetal well-being. Thirty-three percent of the fetuses who failed to exhibit spontaneous or provoked FHR accelerations were acidemic. These findings suggest that in this high-risk group of fetuses, the absence of spontaneous FHR accelerations should be followed by an attempt to induce accelerations, scalp pH assessment, or cesarean section.

The significance of antepartum variable decelerations

A total of 4886 nonstress tests were reviewed to establish the relationship between antepartum variable decelerations and perinatal outcome. The association between various fetal heart rate components and variable decelerations was also studied. The incidence of variable decelerations, defined as three or more decelerations greater than or equal to 15 bpm lasting at least 15 seconds in a 20-minute period, was 1.3%. The results suggest that in the presence of variable decelerations: there is a higher incidence of fetal distress in labor, low Apgar scores, neonatal intensive care unit admissions, and nuchal cord involvement; the presence of accelerations and normal variability is associated with good neonatal outcome, whereas their absence is associated with adverse outcome; the presence of accelerations or good variability is not independently correlated with neonatal outcome.

Acceleration of the fetal heart rate

Acceleration of the fetal heart rate during contractions was usually followed by deceleration, and evidence is presented to show that it results from increased sympathetic drive and may be associated with fetal tissue hypoxia. However, the presence of accelerations are not serious and merely warn the obstetrician of the possibility of the occurrence of subsequent decelerations. The mechanism thought most likely to produce accelerations is uterine compression of the umbilical vein during contractions.

Observer variability in assessment of antepartum cardiotocograms.

SummaryOne hundred cardiotocograms (CTGs) were marked twice independently by five observers to assess the inter‐ and intra‐observer reliability of the interpretation of the antepartum CTG. Scores given for basal heart rate, variability expressed in terms of oscillatory amplitude and frequency, the presence of accelerations and decelerations were studied, as well as a total score combining these variables. Assessment of CTGs with this scoring system was compared to subjective assessment using two sets of criteria. Both inter‐ and intra‐observer reliability was higher with the scoring system than in the subjective assessments. The highest intra‐ and inter‐observer consistency in interpretation, was found for basal heart rate followed by decelerations. Oscillatory frequency was slightly more reliable than oscillatory amplitude. Accelerations were so unreliable that it war necessary to clearly define these in terms of both amplitude and duration. It is concluded that the interpretation of the antepartum CTG is not as easy nor as reproducible as one may wish. In this respect the scoring system, which is easy to use, offers major advantages when compared to subjective assessment.

Complementary domain pyroelectric detectors with reduced sensitivity to mechanical vibrations and temperature changes

LiTaO3 pyroelectric detectors have been fabricated in a novel complementary domain configuration that reduces the interference from vibrational noise sources and from changes in ambient temperature by over an order of magnitude relative to the performance of conventional pyroelectric detectors. Detectors made in this complementary domain configuration exhibit D’s in excess of 109 cm Hz1/2 W−1, and the measured D’s degrade less than 10% in the presence of accelerations as great as 0.05g in a 1-Hz bandwidth, or temperature changes of 10 °C/min.

Combustion of aluminized condensed systems under acceleration loading

1. As the acceleration increases, so do the burning rate and the mass of the slaggy residue, the more rapidly burning compositions being less sensitive to acceleration loading. 2. As the length of the specimen increases, so does the mass of the slag, whereas the mean burning rate decreases. 3. The proposed theoretical model of the combustion of aluminized systems in the presence of acceleration is in good agreement with the data of our experiments and those of other authors. 4. The maximum and minimum increases in the burning rate and the duration of the transition regime can be theoretically predicted from the acceleration and the characteristics of the system together with the size of the entrained particles and the mass of the slag in the steady-state combustion regime.

On the trajectories of particles in an isochronous cyclotron in the presence of acceleration. III

On the trajectories of particles in an isochronous cyclotron in the presence of acceleration. III

Particle trajectories in an isochronous cyclotron in the presence of acceleration. II

Particle trajectories in an isochronous cyclotron in the presence of acceleration. II

On the trajectories of particles in an isochronous cyclotron in the presence of acceleration

On the trajectories of particles in an isochronous cyclotron in the presence of acceleration

The Television Camera System Used in Apollo 7 and 8 Command Modules

Spaceborne television has been principally used in a remote instrumentation role. In the Apollo 7 and 8 flights an important additional function was that of public information, which required the use of design methods not customarily employed in spaceborne instrumentation television. The need to minimize the power for the communication link resulted in the choice of modified standards of scanning rates and resolution, which involved a consideration of trade-offs between picture quality and operating bandwidth. The nature of the mission dictated a design for minimum camera weight and minimum volume, with liberal use of integrated circuits. The possibility of operating the camera during the launch phase made it necessary to design for acceptable camera operation in the presence of acceleration and vibration. Since the busy schedule of the astronaut could not include time for camera adjustments, a highly reliable camera with fixed parameters was required.