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Results for “extreme rays”

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At least 235 records · Page 13Linked to original sources
PubMed1998

Reduced quadriceps strength relative to body weight: a risk factor for knee osteoarthritis in women?

OBJECTIVE: To determine whether baseline lower extremity muscle weakness is a risk factor for incident radiographic osteoarthritis (OA) of the knee. METHODS: This prospective study involved 342 elderly community-dwelling subjects (178 women, 164 men) from central Indiana, for whom baseline and followup (mean interval 31.3 months) knee radiographs were available. Lower extremity muscle strength was measured by isokinetic dynamometry and lean tissue (i.e., muscle) mass in the lower extremities by dual x-ray absorptiometry. RESULTS: Knee OA was associated with an increase in body weight in women (P = 0.0014), but not in men. In both sexes, lower extremity muscle mass exhibited a strong positive correlation with body weight. In women, after adjustment for body weight, knee extensor strength was 18% lower at baseline among subjects who developed incident knee OA than among the controls (P = 0.053), whereas after adjustment for lower extremity muscle mass, knee extensor strength was 15% lower than in the controls (P not significant). In men, in contrast, adjusted knee extensor strength at baseline was comparable to that in the controls. Among the 13 women who developed incident OA, there was a strong, highly significant negative correlation between body weight and extensor strength (r = -0.740, P = 0.003), that is, the more obese the subject, the greater the reduction of quadriceps strength. In contrast, among the 14 men who developed incident OA, a modest positive correlation existed between weight and quadriceps strength (r = 0.455, P = 0.058). No correlation between knee flexor (hamstring) strength and knee OA was seen in either sex. CONCLUSION: Reduced quadriceps strength relative to body weight may be a risk factor for knee OA in women.

Aged↗
PubMed2004

CT angiography in complex upper extremity reconstruction.

Computed tomography angiography is a new technique that provides high-resolution, three-dimensional vascular imaging as well as excellent bone and soft tissue spatial relationships. The purpose of this study was to examine the use of computed tomography angiography in planning upper extremity reconstruction. Seventeen computed tomography angiograms were obtained in 14 patients over a 20-month period. All studies were obtained on an outpatient basis with contrast administered through a peripheral vein. All the studies demonstrated the pertinent anatomy and the intraoperative findings were as demonstrated in all cases. Information from two studies significantly altered pre-operative planning. The average charge for computed tomography angiography was 1,140 dollars, compared to 3,900 dollars for traditional angiography.

Adolescent↗
PubMed1962

Comparison of stimulus energies required to elicit the ERG in response to x-rays and to light.

The retina of Rana pipiens, the leopard frog or grass frog, is shown to be an extremely sensitive detector of x-rays. Its sensitivity to x-rays equals in some respects its sensitivity to visible light. The energy required for the response to visible light is so low that the reaction has long been known as one of the most sensitive in biological systems. An exact comparison is made of the amount of energy required in the stimulus to elicit an electroretinogram (ERG) in response to x-rays and in response to light. ERG's from threshold responses to maximal responses obtainable with x-rays and with light are reproduced. The rods of the retina are shown to be responsible for the production of the ERG. The actual amount of energy absorbed in the rhodopsin from x-ray and from light stimulation over a wide range of intensities and durations has been determined and has been related to the amplitude of the ERG. To the question whether light or x-rays are more efficient in eliciting an ERG, no simple or unequivocal answer can be given. The three dimensional relationship of amplitude of response, intensity of stimulus, and duration of stimulus shows rather unexpectedly that in certain regions light is more efficient while in other regions x-rays are more efficient.

Animals↗
PubMed1979

Chromosomal mobilization from a recA mutant of Pseudomonas putida.

A methyl methane sulfonate sensitive mutant of P. putida strain PpG1 is also extremely sensitive to UV-rays, compared to parent wild type cells. This mutant behaves typically as recombination less (recA) mutants of Escherichia coli and Pseudomonas aeruginosa, since as a recipient, it exhibits extremely low frequency of recombination following conjugational, transductional, and transformational gene transfer. Sex factor plasmids such as K-XYL or TOL can mobilize chromosomal genes equally well both from recA+ and recA801 donor cells, suggesting that host recombination functions are not necessary for mobilization of chromosomal genes by such plasmids.

Bacterial Proteins↗
PubMedDate not supplied

[X-ray semeiotics of changes in the soft tissues and bones of the lower extremities in disorders of the venous outflow].

In order to improve radiodiagnosis of chronic and venous insufficiency of the lower limbs, the soft tissues and skeleton of the affected limbs were x-rayed in 120 patients with disturbed venous outflow (60 with varicosity and 60 with the post-thrombophlebitic syndrome - PTPS). The limb soft tissue changes in this disease were shown to be of one type and looked like the thickening of subcutaneous fat; obscure boundaries of the muscles with subcutaneous fat, the narrowing of intermuscular layers, the absence of differentiation of separate muscular groups, visible varices, calcifications of soft tissues and phleboliths. Bone changes appeared later than the clinical signs of disease and were as follows: regional and diffuse osteoporosis, various kinds of periostoses (scaled or partially assimilated linear, multilayer and pectiniform) and hyperostosis. Longitudinal platypodia and transverse foot flattening caused by dysfunction of the musculoligamentous apparatus and increasing venous congestion in the lower limbs were seen in most of the patients.

Humans↗
PubMed1998

Adhesive capsulitis of the shoulder (frozen shoulder) produces bone loss in the affected humerus, but long-term bony recovery is good.

The objective of the study was to assess the short- and long-term effects of adhesive capsulitis (frozen shoulder) on the bone mineral density (BMD) of the affected extremity. BMD and clinical status of 22 patients (group A) with active-phase unilateral adhesive capsulitis and 31 patients (group B) with a previous adhesive capsulitis (average 9 years before the examination) were determined. BMD was measured from the proximal humerus, humeral shaft, radial shaft, ulnar shaft, and distal forearm of both upper extremities using dual-energy X-ray absorptiometry (DXA). In group A, the mean BMD of the affected extremity, as compared with that of the unaffected side, was significantly lower in the proximal humerus (-5.6%; p = 0.001) and humeral shaft (-3.0%; p = 0.008). The radial shaft, ulnar shaft, and distal forearm showed no significant side-to-side differences. In contrast, in group B, the affected-to-unaffected side BMD differences were small and statistically insignificant. Compared with the 31 patients in group B, the relative side-to-side BMD difference of the 22 patients with active-phase disease (group A) was significantly lower in the proximal humerus (-5.6% vs. -1.5%, p = 0.009). In the other sites, groups A and B showed no significant differences. In conclusion, this study indicates that adhesive capsulitis of the shoulder results in significant bone loss in the humerus of the affected extremity, but in the long term, capsulitis-induced bone loss shows good recovery.

Aged↗
PubMed2001

High-resolution X-ray spectroscopy of rare events: a different look at local structure and chemistry.

The combination of large-acceptance high-resolution X-ray optics with bright synchrotron sources permits quantitative analysis of rare events such as X-ray fluorescence from very dilute systems, weak fluorescence transitions or X-ray Raman scattering. Transition-metal Kbeta fluorescence contains information about spin and oxidation state; examples of the characterization of the Mn oxidation states in the oxygen-evolving complex of photosystem II and Mn-consuming spores from the marine bacillus SG- are presented. Weaker features of the Kbeta spectrum resulting from valence-level and 'interatomic' ligand to metal transitions contain detailed information on the ligand- atom type, distance and orientation. Applications of this spectral region to characterize the local structure of model compounds are presented. X-ray Raman scattering (XRS) is an extremely rare event, but also represents a unique technique to obtain bulk-sensitive low-energy (<600 eV) X-ray absorption fine structure (XAFS) spectra using hard (approximately 10 keV) X-rays. A photon is inelastically scattered, losing part of its energy to promote an electron into an unoccupied level. In many cases, the cross section is proportional to that of the corresponding absorption process yielding the same X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) features. XRS finds application for systems that defy XAFS analysis at low energies, e.g. liquids or highly concentrated complex systems, reactive compounds and samples under extreme conditions (pressure, temperature). Recent results are discussed.

Bacillus↗
PubMed1992

Chromosome bands, their chromatin flavors, and their functional features.

To show that the input pattern of chromosomal mutations is highly organized relative to the band patterns along human chromosomes, a new term, "metaphase chromatin flavor," is introduced. Five different flavors of euchromatic metaphase bands are cytologically identified along a human ideogram. These are G-bands and, based upon combinations of extreme Alu richness and GC richness, four different R-band flavors. The two flavors with extremely GC-rich components, traditionally called "T-bands," represent only 15% of all bands. However, they contain 65% of mapped genes, 19 of 25 mapped oncogenes, most cancer-associated rearrangements, evolutionary rearrangements, meiotic chiasmata, and X-ray-induced breaks. Flavors with extremely Alu-rich flavors are also involved in melphalan-induced rearrangements, pachytene stretching, and mitotic chiasmata. Frequencies of CpG islands, CCGCCC boxes, retroposon families, and genes are characteristic to each chromatin flavor and will facilitate alignment of genome sequences onto ideograms of chromatin flavor. The influence of chromatin flavor on the evolution of a gene's sequence is so strong that one can infer the flavor of the band in which a gene resides from the sequence of the gene itself. Correlation coefficients for many pairs of mapped genetic variables, while globally high, are quite low within bands of one flavor, implicating a concerted mode of evolution for bands of one chromatin flavor.

Biological Evolution↗
PubMed2003

[Comparative study of muscular tonus in spastic tetraparetic cerebral palsy in children with predominantly cortical and subcortical lesions in computerized tomography of the skull].

OBJECTIVE: To compare distribution and intensity of muscular tonus in spastic tetraparetic cerebral palsy (CP), correlating the clinical data with lesion location in the central nervous system. METHOD: Twelve children aged two to four years old with predominantly cortical lesions (six children) and subcortical lesions (six children) were included. The tonus was analyzed in the upper (UULL) and lower limbs (LLLL) based on Durigon and Piemonte protocol. RESULT: There was no significant difference regarding tonus intensity and distribution in the UULL and LLLL in both groups. Comparing the upper and lower limbs of subjects in the same group, the LLLL presented more asymmetry and higher tonus intensity than the UULL. CONCLUSION: In this study children with CP as a result of predominantly cortical or subcortical lesions present a similar deficit in tonus modulation, causing a symmetric and homogeneous distribution of hypertonicity, which is predominant in the LLLL.

Cerebral Cortex↗
PubMed2000

Multiple Sub-Jet Model of Gamma-Ray Bursts and Possible Origin of X-Ray Precursors and Postcursors.

We assume that internal shocks of gamma-ray bursts (GRBs) consist of multiple sub-jets with a collimation half-angle of about several times gamma-1i, where gammai is the Lorentz factor of each sub-jet. If by chance a sub-jet is first emitted off-axis from the line of sight, the observed peak energy can be in the X-ray region. Next, if by chance a subsequent sub-jet is emitted along the line of sight, then the peak energy will be in the gamma-ray region and the gamma ray may arrive after the X-ray precursor from the former sub-jet depending on parameters. This model predicts a new class of GRBs with extremely weak and short gamma-ray emission but X-ray precursors and/or postcursors as well as an afterglow.

Journal Article↗
PubMed2002

The Chandra Deep Field-North Survey and the cosmic X-ray background.

Chandra has performed a 1.4 Ms survey centred on the Hubble Deep Field-North (HDF-N), probing the X-ray Universe 55-550 times deeper than was possible with pre-Chandra missions. We describe the detected point and extended X-ray sources and discuss their overall multi-wavelength (optical, infrared, submillimetre and radio) properties. Special attention is paid to the HDF-N X-ray sources, luminous infrared starburst galaxies, optically faint X-ray sources and high-to-extreme redshift active galactic nuclei. We also describe how stacking analyses have been used to probe the average X-ray-emission properties of normal and starburst galaxies at cosmologically interesting distances. Finally, we discuss plans to extend the survey and argue that a 5-10 Ms Chandra survey would lay key groundwork for future missions such as XEUS and Generation-X.

Journal Article↗
PubMed2002

Large-scale extragalactic jets powered by very-high-energy gamma rays.

The radiative cooling of electrons responsible for the nonthermal synchrotron emission of large-scale jets of radiogalaxies and quasars requires quasicontinuous (in time and space) production of relativistic electrons throughout the jets over the scales exceeding 100 kpc. While in the standard paradigm of large-scale jets this implies in situ acceleration of electrons, we propose a different "nonacceleration" origin of these electrons, assuming that they are implemented all over the length of the jet through effective development of electromagnetic cascades initiated by extremely high-energy gamma rays injected into the jet from the central object.

Journal Article↗