scholarly journals THE KILLING OF CERTAIN BACTERIA BY X-RAYS

1930 ◽  
Vol 52 (3) ◽  
pp. 435-446 ◽  
Author(s):  
Ralph W. G. Wyckoff
Keyword(s):  
Cell Death ◽  
X Rays ◽  
Sensitive Cell ◽  
Peak Voltage ◽  
X Ray ◽  
Destructive Action ◽  
Air Ionization

Both copper K X-rays and the soft general radiation from a tungsten tube operated at 12 KV kill B. coli and B. aertryke in a linearly exponential fashion. Within the experimental limits, the two organisms appear to be equally sensitive to these radiations. By making use of the fact that X-ray energy is absorbed in quanta, an approximate picture can be formed of the mechanism of this destructive action. If the average numbers of quanta (α) absorbed per bacterium per second are calculated from measurements of air ionization using the quantities outlined in the text, survival ratios for these bacilli can be approximately represented by the equations See PDF for Equation for filtered copper rays and See PDF for Equation for unfiltered copper rays (peak voltage = 34 KV). In terms of the foregoing interpretation this means that when death results, it is caused by the absorption of a single X-ray quantum of energy. Since only about one in twenty of the absorbed quanta kills, the sensitive cell constituents whose destruction leads to cell death must have a volume which is less than 0.06 of the bacterium itself.

scholarly journals Exposure of the cytoplasm to low-dose X-rays modifies ataxia telangiectasia mutated-mediated DNA damage responses

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Munetoshi Maeda ◽  
Masanori Tomita ◽  
Mika Maeda ◽  
Hideki Matsumoto ◽  
Noriko Usami ◽  
...  
Keyword(s):  
Dna Damage ◽  
Cell Death ◽  
Ataxia Telangiectasia ◽  
Kinase Inhibitor ◽  
Surrogate Marker ◽  
X Rays ◽  
Ataxia Telangiectasia Mutated ◽  
Whole Cell ◽  
X Ray ◽  
Dna Damage Responses

AbstractWe recently showed that when a low X-ray dose is used, cell death is enhanced in nucleus-irradiated compared with whole-cell-irradiated cells; however, the role of the cytoplasm remains unclear. Here, we show changes in the DNA damage responses with or without X-ray microbeam irradiation of the cytoplasm. Phosphorylated histone H2AX foci, a surrogate marker for DNA double-strand breaks, in V79 and WI-38 cells are not observed in nucleus irradiations at ≤ 2 Gy, whereas they are observed in whole-cell irradiations. Addition of an ataxia telangiectasia mutated (ATM) kinase inhibitor to whole-cell irradiations suppresses foci formation at ≤ 2 Gy. ABL1 and p73 expression is upregulated following nucleus irradiation, suggesting the induction of p73-dependent cell death. Furthermore, CDKN1A (p21) is upregulated following whole-cell irradiation, indicating the induction of cell cycle arrest. These data reveal that cytoplasmic radioresponses modify ATM-mediated DNA damage responses and determine the fate of cells irradiated at low doses.

scholarly journals Effect of Backscattered Radiation on X-Ray Image Contrast

2017 ◽  
Vol 9 (1) ◽  
pp. 105
Author(s):  
A. T. Naji ◽  
M. S. Jaafar ◽  
E. A. Ali ◽  
S. K. J. Al-Ani
Keyword(s):  
Radiation Exposure ◽  
Image Contrast ◽  
X Rays ◽  
Peak Voltage ◽  
X Ray ◽  
Geometrical Design ◽  
Remarkable Effect ◽  
Test Tool ◽  
Different Types

This paper assesses the effect of backscattered radiation on X-ray image contrast by evaluating the effect of backscatter reduction on X-ray image contrast. Contrast test tool RMI Densitometer, and different types of fabricated anti backscattered grids have been utilized in this study. The measurements are recorded at different exposure parameters such as X-ray tube peak voltage (kVp), and X-rays intensities (mAs). For each exposure, the contrast of the image is evaluated by measuring the variation in optical densities for aluminium steps wedge. The results showed that the x-ray image contrast can be enhanced by decreasing the amount of backscattered radiation, also the fabricated anti backscattered grids have a remarkable effect in the improvement of X-ray image contrast according to grid’s capability in reducing backscattered radiation. In addition, the effectiveness of fabricated grids in improving image contrast depends on the grid’s material and the geometrical design, as well as the radiation exposure parameters. The image contrast enhancements increased up to 36% with the use of crossed iron steel grid which placed under the film screen combination during exposure.

scholarly journals Laser-Driven Ultrashort Pulsed Electron Beam Radiation at Doses of 0.5 and 1.0 Gy Induces Apoptosis in Human Fibroblasts

2019 ◽  
Vol 20 (20) ◽  
pp. 5140 ◽  
Author(s):  
Nelly Babayan ◽  
Bagrat Grigoryan ◽  
Lusine Khondkaryan ◽  
Gohar Tadevosyan ◽  
Natalya Sarkisyan ◽  
...  
Keyword(s):  
Cell Death ◽  
Electron Beam ◽  
Human Fibroblasts ◽  
Lung Fibroblasts ◽  
Particle Accelerators ◽  
X Rays ◽  
Beam Radiation ◽  
X Ray ◽  
Pulsed Electron Beam ◽  
Γh2ax Foci

Rapidly evolving laser technologies have led to the development of laser-generated particle accelerators as an alternative to conventional facilities. However, the radiobiological characteristics need to be determined to enhance their applications in biology and medicine. In this study, the radiobiological effects of ultrashort pulsed electron beam (UPEB) and X-ray radiation in human lung fibroblasts (MRC-5 cell line) exposed to doses of 0.1, 0.5, and 1 Gy are compared. The changes of γH2AX foci number as a marker of DNA double-strand breaks (DSBs) were analyzed. In addition, the micronuclei induction and cell death via apoptosis were studied. We found that the biological action of UPEB-radiation compared to X-rays was characterized by significantly slower γH2AX foci elimination (with a dose of 1 Gy) and strong apoptosis induction (with doses of 0.5 and 1.0 Gy), accompanied by a slight increase in micronuclei formation (dose of 1 Gy). Our data suggest that UPEB radiation produces more complex DNA damage than X-ray radiation, leading to cell death rather than cytogenetic disturbance.

scholarly journals THE PRODUCTION OF PERSISTENT ALOPECIA IN RABBITS BY X-RAYS OF VARIOUS DEGREES OF HARDNESS

1925 ◽  
Vol 42 (4) ◽  
pp. 517-522 ◽  
Author(s):  
Harry Clark ◽  
Ernest Sturm
Keyword(s):  
X Rays ◽  
Abdominal Skin ◽  
X Ray ◽  
Minimum Dose ◽  
Air Ionization ◽  
High Degree

1. The minimum dose of x-ray, of each of three degrees of hardness, required to produce persistent alopecia of the abdominal skin of normal white rabbits has been studied. 40 kilovolt rays filtered by 0.5 mm., 50 kilovolt rays filtered by 1 mm., and 70 kilovolt rays filtered by 1.5 mm. of aluminium were employed. The 70 kilovolt work is unfinished. 2. Under constant conditions of treatment, the animals were found to react with a high degree of consistency. 3. The values of the critical minimum doses expressed in terms of air ionization (pair of ions per gm. of air divided by 1015), for rays produced at 30, 40, 50, and 70 kilovolt peak, are 2.04, 3.7, 4.5, and over 5.1 respectively. The 30 kilovolt value is taken from a previous paper. 4. It is shown that the alopecia reaction does not run parallel to the erythema and pigmentation reactions.

scholarly journals THE KILLING OF COLON BACILLI BY X-RAYS OF DIFFERENT WAVE LENGTHS

1930 ◽  
Vol 52 (5) ◽  
pp. 769-780 ◽  
Author(s):  
Ralph W. G. Wyckoff
Keyword(s):  
Cell Volume ◽  
Biological Action ◽  
Experimental Results ◽  
X Rays ◽  
X Ray ◽  
Linear Fashion ◽  
Air Ionization

X-ray beams of wave lengths lying in the range between 4 A and 0.5 A all kill B. coli in a semilogarithmically linear fashion. Interpreted in terms of the known quantized absorption of X-rays, this means that one absorption of any of these radiations is sufficient to kill. Though death results from a single absorption, only about one hit in four with Ag K and one in sixty with Ag L radiation is deadly. The course of curves constructed from these experimental results suggests that the portion of this bacterium which is essential to its continued life has a total of approximately 0.01 of the cell volume. For copper and harder radiations the biological action of the rays is proportional to their measured air ionization. The same biological change with the softer chromium K. and silver L X-rays seems to require a somewhat more intensely ionizing beam.

scholarly journals Stochastic multicellular modeling of x-ray irradiation, DNA damage induction, DNA free-end misrejoining and cell death

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Jake C. Forster ◽  
Michael J. J. Douglass ◽  
Wendy M. Phillips ◽  
Eva Bezak
Keyword(s):  
Dna Damage ◽  
Cell Death ◽  
Cell Killing ◽  
Track Structure ◽  
Linear Component ◽  
X Rays ◽  
Dna Double Strand Breaks ◽  
Cell Nuclei ◽  
Strand Breaks ◽  
X Ray

AbstractThe repair or misrepair of DNA double-strand breaks (DSBs) largely determines whether a cell will survive radiation insult or die. A new computational model of multicellular, track structure-based and pO2-dependent radiation-induced cell death was developed and used to investigate the contribution to cell killing by the mechanism of DNA free-end misrejoining for low-LET radiation. A simulated tumor of 1224 squamous cells was irradiated with 6 MV x-rays using the Monte Carlo toolkit Geant4 with low-energy Geant4-DNA physics and chemistry modules up to a uniform dose of 1 Gy. DNA damage including DSBs were simulated from ionizations, excitations and hydroxyl radical interactions along track segments through cell nuclei, with a higher cellular pO2 enhancing the conversion of DNA radicals to strand breaks. DNA free-ends produced by complex DSBs (cDSBs) were able to misrejoin and produce exchange-type chromosome aberrations, some of which were asymmetric and lethal. A sensitivity analysis was performed and conditions of full oxia and anoxia were simulated. The linear component of cell killing from misrejoining was consistently small compared to values in the literature for the linear component of cell killing for head and neck squamous cell carcinoma (HNSCC). This indicated that misrejoinings involving DSBs from the same x-ray (including all associated secondary electrons) were rare and that other mechanisms (e.g. unrejoined ends) may be important. Ignoring the contribution by the indirect effect toward DNA damage caused the DSB yield to drop to a third of its original value and the cDSB yield to drop to a tenth of its original value. Track structure-based cell killing was simulated in all 135306 viable cells of a 1 mm3 hypoxic HNSCC tumor for a uniform dose of 1 Gy.

White-Light Coronal Structures: Streamers and CMEs

1994 ◽  
Vol 144 ◽  
pp. 82
Author(s):  
E. Hildner
Keyword(s):  
Emission Line ◽  
Electron Density ◽  
White Light ◽  
Coronal Mass Ejections ◽  
X Rays ◽  
Solar Cycles ◽  
Temperature Function ◽  
X Ray ◽  
Eclipse Observations ◽  
Coronal Structures

AbstractOver the last twenty years, orbiting coronagraphs have vastly increased the amount of observational material for the whitelight corona. Spanning almost two solar cycles, and augmented by ground-based K-coronameter, emission-line, and eclipse observations, these data allow us to assess,inter alia: the typical and atypical behavior of the corona; how the corona evolves on time scales from minutes to a decade; and (in some respects) the relation between photospheric, coronal, and interplanetary features. This talk will review recent results on these three topics. A remark or two will attempt to relate the whitelight corona between 1.5 and 6 R⊙to the corona seen at lower altitudes in soft X-rays (e.g., with Yohkoh). The whitelight emission depends only on integrated electron density independent of temperature, whereas the soft X-ray emission depends upon the integral of electron density squared times a temperature function. The properties of coronal mass ejections (CMEs) will be reviewed briefly and their relationships to other solar and interplanetary phenomena will be noted.

Chemical Species Identification in an SEM by Changes in Emitted X-Ray Energies

1974 ◽  
Vol 32 ◽  
pp. 570-571
Author(s):  
R. H. Duff
Keyword(s):  
Species Identification ◽  
Valence Electron ◽  
Chemical Species ◽  
X Rays ◽  
Chemical Bonds ◽  
Small Shift ◽  
X Ray ◽  
Electron Transitions ◽  
Peak Energy ◽  
Chemical Combination

A material irradiated with electrons emits x-rays having energies characteristic of the elements present. Chemical combination between elements results in a small shift of the peak energies of these characteristic x-rays because chemical bonds between different elements have different energies. The energy differences of the characteristic x-rays resulting from valence electron transitions can be used to identify the chemical species present and to obtain information about the chemical bond itself. Although these peak-energy shifts have been well known for a number of years, their use for chemical-species identification in small volumes of material was not realized until the development of the electron microprobe.

Influence of X-Ray Induced Fluorescence on Energy Dispersive X-Ray Analysis of Thin Foils

1977 ◽  
Vol 35 ◽  
pp. 328-329
Author(s):  
E. A. Kenik ◽  
J. Bentley
Keyword(s):  
Thin Foil ◽  
Electron Excitation ◽  
Simple Approach ◽  
Foil Thickness ◽  
X Rays ◽  
X Ray ◽  
Hole Spectrum ◽  
Illumination System ◽  
Thin Foils ◽  
Intensity Ratios

Cliff and Lorimer (1) have proposed a simple approach to thin foil x-ray analy sis based on the ratio of x-ray peak intensities. However, there are several experimental pitfalls which must be recognized in obtaining the desired x-ray intensities. Undesirable x-ray induced fluorescence of the specimen can result from various mechanisms and leads to x-ray intensities not characteristic of electron excitation and further results in incorrect intensity ratios.In measuring the x-ray intensity ratio for NiAl as a function of foil thickness, Zaluzec and Fraser (2) found the ratio was not constant for thicknesses where absorption could be neglected. They demonstrated that this effect originated from x-ray induced fluorescence by blocking the beam with lead foil. The primary x-rays arise in the illumination system and result in varying intensity ratios and a finite x-ray spectrum even when the specimen is not intercepting the electron beam, an ‘in-hole’ spectrum. We have developed a second technique for detecting x-ray induced fluorescence based on the magnitude of the ‘in-hole’ spectrum with different filament emission currents and condenser apertures.

X-ray micro tomography in the scanning electron microscope

1978 ◽  
Vol 36 (1) ◽  
pp. 106-107 ◽  
Author(s):  
W. Brünger
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Target Surface ◽  
The Body ◽  
X Rays ◽  
Cross Sectional ◽  
X Ray ◽  
Micro Tomography ◽  
Scanning Electron

Reconstructive tomography is a new technique in diagnostic radiology for imaging cross-sectional planes of the human body /1/. A collimated beam of X-rays is scanned through a thin slice of the body and the transmitted intensity is recorded by a detector giving a linear shadow graph or projection (see fig. 1). Many of these projections at different angles are used to reconstruct the body-layer, usually with the aid of a computer. The picture element size of present tomographic scanners is approximately 1.1 mm2.Micro tomography can be realized using the very fine X-ray source generated by the focused electron beam of a scanning electron microscope (see fig. 2). The translation of the X-ray source is done by a line scan of the electron beam on a polished target surface /2/. Projections at different angles are produced by rotating the object.During the registration of a single scan the electron beam is deflected in one direction only, while both deflections are operating in the display tube.

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