Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Elementary Particles”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4Linked to original sources
PubMedDate not supplied

[Molecular computer. Biological physics and physics of the real world].

Any mind (man or computer) using Physical laws is a part of physical world, and thus it is necessary to correct physical laws for taking into account influence of the work of real limited computer on the predicted result. If we suppose that univerce was constructed to be supreme regular for mind, then this correction is negligible and on principle there is possibility to calculate relation between fundamental physical and biophysical constants. Two main principle are proposed: 1. The principle of minimum action and uncontrole influence of mind. 2. The maximum asymmetry of elementary particles, which are allowed by first principle. The first principle requires the upper and the lower limits for all physical values, and first of all the upper limit for velocity (c) and the lower limit for action (h). The second principle allows to construct the minimal physical elements for mind.

Biophysical Phenomena↗
PubMed1980

[Cutaneous argyria: an electron microscopic study of four eases with microanalysis X study of one case (author's transl)].

This study was done in order to follow the fate of silver in the dermis of chronic argyria. Silver was easily recognizable in the tissue as irregular aggregates of elementary granules round or ovoid in shape, ranging from 30 to 40 mm in size. The microanalysis X showed that the metal was bound with sulfur. In the cases of recent intoxication, the main location of silver was intracellular: the granules were found in the lysosomes as elementary particle or as dense heterogen bodies. In the cases where intoxication had been stopped a long time ago, silver was found either on fibrillar component of the connective tissue or in the basal material of sweat glands. The results show that silver is at first phagocytized by macrophages but this cell is unable to perform complete degradation of the silver salt or metal. Then silver is found on connective fibers where it remains on sulfated glycoproteins.

Aged↗
PubMedDate not supplied

[Is the "biopsychosocial model" a helpful construct?].

In 1977, G. L. Engel proposed a biopsychosocial model, applicable to all illness and disease. It was based on systems theory which orders the world into a ladder (of systems) from the most elementary particles to social phenomena and the cosmos. Systems theory was proposed to combat reductionism and to deal with complexity and order. Central to that theory is the concept of emergence that the properties of each "higher" or more complex system are not explainable either by their components nor by those at a lower level. However, no one form of complexity exists. Some forms of complexity arise out of the interactions of the components, especially as the result of feed-back, which in turn allows us to understand order, and sudden change. Living systems are characterized by genetic programs, self-replication, self-organization and adaptability. These properties exist at every "level", and thus make systems theory and its hierarchies no longer necessary, and also eliminate the concept of emergence.

Adaptation, Psychological↗
PubMed1976

[Basic changes in neurons in the peripheral regions of the human nervous system during pathologic processes (electron microscopic study)].

Compensatory-adaptational and reparative reactions were studied in bodies, processes, receptors and synapses of the human peripheral nervous system and in the innervated substrate (myocardium, kidney, liver) by means of electron microscopy. An extreme increase of the electron density of macromolecular protein formations of specific elementary particles was revealed, in particular, in the outer layers of the hypertrophid mitochondria cryst membranes at 50000.000 magnification. These particles are considered as mitochondria precursors.

Cell Nucleus↗
PubMed1982

Physical and biologic aspects on the optimum choice of radiation modality.

The most generally used radiation modalities, low energy photon and electron beams, have been gradually optimized with regard to their physical properties during the last decade. The advantages of increasing the energy range of these beams as high as 50 MeV are discussed based on the assumption that high quality beam flattening systems are used. Possible further developments of the conventional low LET electron and photon beams using grid irradiation and ultra short pulses are also indicated. The dose distributional properties of high quality electron and photon beams are compared with those of heavy particle beams indicating that in several cases only marginal advantages should be expected for the heavy charged particle beams.

Alpha Particles↗
PubMed1977

Particle radiation therapy: experimental basis and clinical application.

Conventional radiation therapy can eradicate cancers within tissues of their origin and regional spread with conservation of anatomic structure, thus preserving function and cosmesis. New treatment methods may improve the therapeutic ratio either by increasing the frequency of tumor control or lessening the treatment-related morbidity, or both. There are several physical and biological reasons why particle radiation therapy may increase tumor cell killing without increasing normal tissue sequelae. After preliminary basic research, clinical trials of fast neutron and proton teletherapy were started. Over 700 patients were treated with fast neutron beams in 3 U.S. research programs. These studies will be extended to include negative pi mesons and heavy particles.

Elementary Particles↗
PubMed1979

Sources of Atomic and Nuclear Data for Biomedical Purposes.

Users of nuclear and atomic data for biomedical purposes often have difficulty in identifying the most up-to-date and appropriate sources of such data. The biomedical Subcommittee of the UK Nuclear Data Committee have prepared a list of recommended data sources available at the beginning of 1978 on radioactive decay schemes; neutron cross-sections and data for neutron activation analysis; excitation functions for the production of radionuclides by charged particles; W-values for neutron and electron dosimetry; X- and gamma-ray cross-sections; stopping powers and ranges for charged particles; and dose deposition by electrons and beta particles.

Alpha Particles↗
PubMed1994

Alpha-cluster description of excitation energies in 12C(12C,3 alpha)X at 2.1A GeV.

An alpha-cluster expansion of the Glauber multiple scattering [correction of scatteirng] series is used to calculate the energy transfer spectrum to the 12C projectile in the 12C(12C,3 alpha)X reaction at 2.1A GeV. Cluster-abrasion response functions are defined in terms of alpha-cluster wave function and the collision dynamics appropriate for heavy-ion reactions. Comparisons are made to recent quasiexclusive experimental data with good agreement found. Calculations indicate that substructures in a 12C projectile are likely to be true spectators in fragmentation, however, with virtual states of excitation in the projectile ground state making a significant contribution to the fragmentation cross section.

Alpha Particles↗
PubMed1990

On the use of the pion stopping distribution and the lesion additivity concept for the calculation of effective doses in pion treatment planning.

The large spatial variation in LET, and hence in RBE, is one of the main obstacles in the development of routine treatment planning of charged particle beams. Since the biological effect distribution of plans cannot be realistically measured for each patient, a simple scheme of relating effect to basic empirical physical measurement is required. For the case of a pion beam, the high LET dose distribution is correlated with that of the pion stopping density, which can be indirectly measured using several techniques. A scheme based on this spatial correlation has been developed. In this method, after partitioning the local dose into a high and a low LET fraction, the local effective dose is computed using a simple formula extracted from a recent analysis of radiobiological results for mixtures of radiations of different LET. This simple formula can also be derived from a mechanistic model of mixed radiation action developed using the hypothesis of additivity of common intermediate lesions. In this paper, the concept of spatial correlation between the high LET dose and the pion stars is merged with the concept of lesion additivity for mixed radiation, from which a simple computational scheme is formulated for the calculation of effective doses in the treatment planning of pions. Similar schemes can also be developed for other charged particle beams.

Elementary Particles↗