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PubMed1990

[20 years of experience in using high-energy electron accelerators].

The authors summed up their 20-year experience in the clinical use of a linear accelerator of electrons and a Siemens betatron (42 MeV) in the Research Institute of Oncology and Radiology, Ministry of Health of the Byelorussian SSR. Comparative advantages and shortcomings of both accelerators and the results of their technical modifications were considered. A section in the paper, devoted to the clinical aspects of tumor therapy, is concerned with the description of a number of methods of irradiation with various types of therapeutic beams, energies, field sizes, directions, various regimens of dose fractionation in time and irradiated volume. Long-term results of radiotherapy with accelerators were assessed and compared with the results of gamma-beam therapy on cobalt units. A conclusion was made that by 1991-2000 the Republic would need 10 medical accelerators.

Cobalt Radioisotopes↗

PubMed1990

Positive pressure breathing for acceleration protection and its role in prevention of inflight G-induced loss of consciousness.

That pressure breathing for G protection (PBG) can improve both tolerance and endurance to high sustained +Gz acceleration is now well established. It is not surprising, therefore, that the undoubted potential benefits of PBG in an operational environment have been greeted with enthusiasm by aircrew and their commanders. In some quarters, the use of positive pressure breathing (PPB) during periods of high sustained +Gz acceleration is being hailed as a potential cure for the problem of G-induced loss of consciousness (G-LOC). We believe, however, that confidence in the technique for this purpose in modern, highly agile fighter aircraft is misplaced. This article reviews PPB's background and present use as protection against +Gz acceleration, and summarizes the physiologic basis for its effectiveness, before relating it to its undoubted role in support of other anti-G strategies. From theoretical considerations supported by published evidence, we conclude that while PPB, if used correctly and when combined with other strategies, can enhance tolerance to +Gz acceleration, its principal influence on the occurrence of G-LOC will be by virtue of its ability to increase endurance by decreasing aircrew fatigue.

Acceleration↗

PubMed1989

[Accelerated irradiation of bone metastases].

In a prospective study, accelerated irradiation was performed over 60 portals in 34 tumor patients with peripheral bone metastases. During a period of three days, three daily fractions of 3 Gy each were applied with intervals of four hours, resulting in a total dose of 27 Gy. Using this fractionation schedule introduced by Ammon, a reduction of metastasis-associated pain was achieved in 90% of cases (54/60). The onset of pain reduction was observed earlier than seen with conventional fractionation schedules (five fractions of 2 Gy each per week, total dose 40 Gy). With regard to objective treatment effects, no significant difference was found between accelerated irradiation and conventional fractionation, the rate of remineralization being 43% (26/60), and the rate of stabilization of formerly progressive bone destructions being 55% (33/60). Accelerated irradiation was tolerated well usually. Marked acute side reactions occurred in only one case with metastatic involvement of joint and reaction of synovia. The major advantage of accelerated irradiation is the shortening of the total treatment period and the consequent reduction of treatment stress in patients with advanced cancer.

Adult↗

PubMedDate not supplied

[Effect of linear, impact and vibration accelerations on the accuracy of performance of force load programs by an operator].

The factors that influence the accuracy with which motor commands are actualized were investigated. The study concentrated on linear acceleration of different sign (produced by rocking a heavy metal platform), vibration at a frequency of about 23 Hz, and impact acceleration resulting from the platform or the rotating chair being suddenly stopped. The force applied to hand sticks or foot levers was recorded by means of electromechanical sensors. It was demonstrated that smoothly varying and in particular impact acceleration caused normal men to subjectively underestimate their own muscle efforts. As a rule, this led to a greater than prescribed strength applied. It is very important to note that acceleration acting from right to left or from left to right (in the frontal plane) produced nonsymmetric pressure by the right and left limbs.

Acceleration↗

PubMed1985

[The management of particle accelerators in radiotherapy].

In this multicentric survey, the management costs and the technical problems connected with the use of electron accelerators in Radiotherapy are studied. The data were collected by a proper questionnaire and concern 11/35 accelerators in use in Italy, in public hospitals, during the period 1982-1983. The average purchase cost of an accelerator was 1113 milions lire and the amortization cost is 111 milions lire per year. The expenses for the amortization of the cost of the bunker, for ordinary and extraordinary maintenance, for the employed staff and for the electric power respectively, represent the 22%, 5%, 43% and 2% of the total management cost (395 milions lire per year). In 1983 the load per machine was 400 patients and the cost per patient was 1 milion lire. On the average, 4 years are needed from the order to the beginning of the treatments with large differences among centers. The machines average use is 7.1 hours a day and keep 2.8 technicians busy per week. The time wasted by repairs or maintenances increases (+7%) the average duration of stay in hospital of patients. An attentive evaluation of the studied parameters allows us to single out the most significant variables on which is possible to work to increase the efficiency and to reduce the management costs of an accelerator.

Cost-Benefit Analysis↗

PubMed1985

Effects of exercise-heat acclimation on fluid, electrolyte, and endocrine responses during tilt and +Gz acceleration in women and men.

Plasma fluid, electrolyte, protein, renin, and vasoactive hormone (epinephrine, norepinephrine, vasopressin) responses were measured in six women (21-23 yr) and four men (21-38 yr) before and immediately following an orthostatic tolerance test (70 degrees head-up tilt) and a +Gz (head-to-foot) acceleration tolerance test (0.5 G X min-1 linear ramp to grayout). These tests were conducted before and after 12 consecutive days of exercise-heat acclimation when the subjects exercised on a cycle ergometer at a relative oxygen uptake of 44% to 49% peak oxygen uptake in a hot environment (Ta = 40 degrees C, 42% rh). During acclimation plasma volume increased by 10.6% (p less than 0.05) in the women and by 11.9% (p less than 0.05) in the men; in both groups exercise heart rate decreased significantly. After acclimation, acceleration tolerance was unchanged in both groups (range 3.1 to 3.4 G); the women's tilt tolerance was unchanged (range 33.6 to 39.5 min), but the men's tilt tolerance increased from 30.4 min before to 58.3 min (delta = 91%, p less than 0.05) after acclimation. Since the pattern of fluid, electrolyte, and protein shifts and acceleration tolerances in the women and men were virtually the same, the hormone responses were highly variable, and the men's tilt tolerance increased significantly after acclimation, it is clear that responses to tilting cannot be used to predict responses to acceleration. Analysis of data from the present study and the literature suggests that current exercise training regimes should be unrestricted for astronauts who have not previously been highly endurance trained.(ABSTRACT TRUNCATED AT 250 WORDS)

Acceleration↗

PubMed1978

Predictive model of dynamic response of the human head/neck system to -Gx impact acceleration.

This paper describes the mathematical framework, underlying an empirical model, that predicts human head response using only the motion present at vertebra T1. Based on this framework, a model for --Gx impact acceleration was developed from data obtained on six volunteer subjects participating in the NAMRL impact acceleration experiments. Model performance was evaluated by comparing the errors in the predicted head responses with the normal variations observed between the responses of different subjects under identical impact accelerations. Independent sets of data were used for building and testing the model. The results of the evaluation indicate that the model will be useful in subsequent studies of human response to impact acceleration.

Acceleration↗

PubMed1983

[The first linear electron accelerator, the Therac 15 Saturne, in clinical service. I. Technical data and measurements in photon radiation].

A report is given about the linear electron accelerator operating at the Alfried Krupp Krankenhaus in Essen. This is the first accelerator of the type Therac Saturne supplied for 15 MeV. Besides a description of the most important technical data and the service instructions, dosimetric data for 12 MV photon radiation are presented. The authors communicate the clinical experiences gained hitherto with the accelerator and the patient-orientated verification and recording system which has still to be improved, especially as far as the recording part is concerned. The accelerator meets the requirements of radiologic oncology.

Documentation↗

PubMedDate not supplied

[Neuron-vascular connections in the superior geniculate body and anterior bigeminal body of cats after acceleration].

Thirty-nine cats were exposed to acceleration of 10 g for one or several days. Their neuronal-vascular relations in the subcortical optic centers were investigated using ink-gelatin injections and Nissl's method. During one-day back-to-chest, chest-to-back and head-to-feet acceleration and many-day head-to-feet and chest-to-back acceleration neuronal-vascular relations decreased, whereas during one-day feet-to-head and many-day, chest-to-back and feet-to-head acceleration they increased. During one-day centrifugation edematous neurons and during many-day centrifugation swollen neurons may occur.

Acceleration↗

PubMed1983

[Body acceleration measurement and oxygen uptake during jumping].

The integral of the positive acceleration per unit time was defined as physical activity. The device that measured physical activity during jumping was developed and the relationship between physical activity by acceleration measurement and energy expenditure was evaluated. Acceleration wave forms of back were measured with strain gauge type accelerometer. After amplification and rectification, the positive acceleration wave forms integrated. When the output of the integrator reached the threshold of comparator, the output of the comparator contained trigger signal. The physical activity was determined by the total counts of the trigger signal. 10 males jumped at four jumping cycles (20, 40, 60 min-1 and random) and 24 children jumped at random jumping. Oxygen uptake, physical activity and heart rate were simultaneously measured. The results showed the oxygen uptake, physical activity and heart rate of males were linearly related to jumping cycle. However, oxygen uptake of random jumping was less than one of 60 min-1 jumping in spite of the greater physical activity. This result indicated that the random jumping was operated efficiency due to the effect of elastic bounce. The oxygen uptake/body weight of males had good correlation to physical activity (r = 0.922), and heart rate (r = 0.902). Also the oxygen uptake/body weight of males and children had good correlation to physical activity (r = 0.953). The difference of ages and weights was not significant during jumping. These results mentioned to be useful in providing an objective evaluation of the physical activity of human subjects during jumping.

Acceleration↗

PubMed1978

Endolymph flow-pressure patterns in models of semicircular canals. Effects of angular accelerations in one or two spatial planes.

The effects of angular accelerations in one or two spatial planes over the pressure exerted on the cupule of the semicircular canals, was studied using hydraulic models of the canals. The models were accelerated using a torsion pendulum and the resulting flow was monitored. The relative position of the model modifies the direction and magnitude of the flow in each canal and in the equivalent of the utricle where the canals join each other. When simultaneous accelerations in two spatial planes were used, a coriolic effect was observed, which could be significant to explain some vestibular symptoms that occur under similar conditions. From the information obtained with the models, the excitation-inhibition patterns in each of the six semicircular canals can be predicted for accelerations in any given spatial plane or combination of planes.

Acceleration↗

PubMed1995

[With maintaining equilibrium: experimental study of the limits of acceleration which the human body can endure without losing postural balance].

OBJECTIVE: To explore the limits of acceleration to which a human organism can be exposed without loss of postural balance. DESIGN: Experimental study. SETTING: TNO Human Factors Research Institute, Soesterberg, and the public transport, Amsterdam. METHOD: Volunteers underwent accelerations of the underground in the laboratory. The acceleration that could be tolerated without extra support, was under investigation. In this way, conditions could be determined that cause loss of postural balance. RESULTS: A comparison of data obtained in the laboratory with measurements during public transportation proved that in tram, bus and tube, the 'jerk' and the level of acceleration are both in principle unmanageable without extra support. CONCLUSION: A built-in limitation of the jerk component in vehicles of the public transport could offer a substantial contribution to solving the problem of loss of postural balance by the passengers.

Acceleration↗

PubMedDate not supplied

[Potassium transport from Infusoria Tetrahymena pyriformis GL, immobilized by accelerations of 80-260 g].

The effects of direct influence of gravity on a cell have been studied. Potassium transport from infusoria. Tetrahymena pyriformis GL induced by the high gravitational levels which immobilize the cell (80, 140, 260 g) was examined. A minimum acceleration level at which the cells become motionless is 80 g. Kinetics of potassium output can be described as containing "fast" and "slow" component. The rate of potassium output relating to fast component does not depend on an acceleration level but is a function of the age and density of culture. The potassium output rate associated with slow component increases as acceleration is increased. It also rises in the course of time which points to a change of internal structure of the cells occurring the more rapidly the higher level of acceleration is. Direct effect of gravity on the cell is realized by two ways: 1) effect which results from difference of densities of cell and its environment; 2) effect on intracellular structures due to difference of their densities. It is supposed that the observed effects in main are being developed at the cost of a 2nd type of gravity effect.

Acceleration↗

PubMed1977

Motion sickness and otolith sensitivity: a pilot study of habituation to linear acceleration.

Astronauts, particularly in Skylab flights, experienced varying degrees of motion sickness lasting 3-5 d. One possible mechanism for this motion sickness adaptation is believed to be a reduction in otolith sensitivity with an attendant reduction in sensory conflict. In an attempt to determine if this hypothesis is valid, a ground-based pilot study was conducted on a vertical linear accelerator. The extent of habituation to accelerations which initially produced motion sickness was evaluated, along with the possible value of habituation training to minimize the space motion sickness problem. Results showed that habituation occurred for 6 of the 8 subjects tested. However, in tests designed to measure dynamic and static otolith function, no significant differences between pre- and post-habituation tests were observed. Cross habituation effects to a standard Coriolis acceleration test were not significant. It is unlikely that ground-based pre-habituation to linear accelerations of the type examined would alter susceptibility to space motion sickness.

Acceleration↗

PubMedDate not supplied

[Tolerance of +Gz acceleration by pilots with tendencies to hypotensive reactions in hot climate conditions].

During acrobatic flying the acceleration tolerance of healthy and hypotensive pilots was studied under hot climate conditions. From the professional point of view pilots were very similar. The tolerance was determined on the basis of indirect indices derived from flight accelerograms (maximum and median acceleration values, number of peaks over 4 g. time of flying). The maximum value and the number of peaks of acceleration (+Gz) over 4 g can be recommended as practically indicative of the tolerance. The observations showed an adverse effect of initial hypotension occurring in hot climate on the acceleration tolerance. As compared with the controls, the tolerance decline in 12 hypotensive pilots was I.I. g and 0.6 g of the maximum and median values, respectively.

Acceleration↗

PubMed1999

Influence of acceleration voltages on relative ion intensities in the post-source decay fragmentation of isomeric cyclic oligosaccharides by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

The isomeric sugar-branched cyclodextrin (CD) derivatives of 6-O-glucosyl-betaCD (G1-betaCD) and 6,6-di-O-glucosyl-alphaCD (G1, G1-alphaCD) were analyzed by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry at the different acceleration voltages of 20 and 8 kV. In the post-source decay (PSD) fragment spectra of G1-betaCD and G1, G1-alphaCD under the reduced acceleration voltage 8 kV, the relative intensity ratios of one-site cleavage ions [M - G1](+) to two-site cleavage ions [M - G2 approximately 5](+) were much larger than at 20 kV. This change in the intensity ratio in the spectra of G1, G1-alphaCD was much larger than in the spectra of G1-betaCD. The measurements under the reduced acceleration voltage were useful to distinguish easily between the otherwise very similar PSD fragment spectra of G1-betaCD and G1, G1-alphaCD. It was concluded that the acceleration energy is one of the most effective parameters controlling relative ion intensities in PSD, and that distinction between these oligosaccharide isomers is facilitated by manipulation of this parameter.

Carbohydrate Sequence↗

PubMed1988

Characteristics of accelerated disease in chronic myelogenous leukemia.

Determination of the characteristics of accelerated disease in chronic myelogenous leukemia (CML) helps in individual prognostication, and in the introduction and analysis of investigative approaches based on risk-benefit ratios. The outcome of 357 patients with Philadelphia chromosome-positive CML was analysed from the time of development of suspected features of accelerated disease. Median survivals shorter than 18 months were associated with the appearance of any of the following: cytogenetic clonal evolution; extramedullary disease; peripheral blasts greater than or equal to 15%, peripheral blasts and promyelocytes greater than or equal to 30%, or peripheral basophils greater than or equal to 20%; platelet count less than 1.0 X 10(5)/microliters; marrow blasts greater than or equal to 15%, marrow blasts and promyelocytes greater than or equal to 30%, or marrow basophils greater than or equal to 20%. Relative hazard ratios, or risk of death per unit time, were calculated based on the relative survivals of patients who did or did not develop the particular feature of accelerated disease, after accounting for the time to development of the characteristic. Further analysis identified five features that have additive independent prognostic importance: cytogenetic clonal evolution; peripheral blasts greater than or equal to 15%; peripheral basophils greater than or equal to 20%; peripheral blasts and promyelocytes greater than or equal to 30%; and thrombocytopenia. By providing an objective estimate of prognosis in accelerated disease, the model identifies patients in need of different therapeutic interventions before the development of blastic crisis.

Follow-Up Studies↗

PubMed1996

Accelerated generation of CD14+ monocyte-lineage cells from the bone marrow of rheumatoid arthritis patients.

OBJECTIVE: To examine the capacity of bone marrow progenitor cells to generate CD14+ cells, in order to assess the role of bone marrow in the pathogenesis of rheumatoid arthritis (RA). METHODS: CD14- cells purified from bone marrow specimens of 11 patients with active RA and 8 control patients (osteoarthritis or trauma) were cultured in the presence or absence of granulocyte-macrophage colony-stimulating factor (GM-CSF; 100 pg/ml). After incubation for various lengths of time, the cells were analyzed by flow cytometry for expression of CD14 and HLA-DR. RESULTS: The spontaneous generation of CD14+ cells from bone marrow CD14- progenitor cells was accelerated in RA patients compared with control patients. Moreover, the expression of HLA-DR on the bone marrow-derived CD14+ cells was also accelerated in RA patients compared with controls. GM-CSF significantly enhanced the generation of CD14+ cells, as well as the expression of HLA-DR, on CD14+ cells of control patients, but not those of RA patients. GM-CSF levels in the culture supernatants of bone marrow CD14- cells were not significantly different between RA patients and control patients (undetectable in most cases). CONCLUSION: These observations strongly support the hypothesis that the accelerated generation of CD14+ cells from bone marrow progenitor cells and the accelerated maturation of such CD14+ cells into HLA-DR+ cells play an important role in the pathogenesis of RA. Moreover, the data suggest a functional alteration of RA bone marrow CD14- cells in their responsiveness to GM-CSF.

Adult↗