scholarly journals INFLUENCE OF DEATH CRITERIA ON THE X-RAY SURVIVAL CURVES OF THE FUNGUS, NEUROSPORA

1934 ◽  
Vol 17 (4) ◽  
pp. 577-590 ◽  
Author(s):  
Fred M. Uber ◽  
David R. Goddard
Keyword(s):  
Survival Curve ◽  
X Rays ◽  
Survival Curves ◽  
Single Spore ◽  
Accurate Analysis ◽  
Single Well ◽  
Growth Production ◽  
Multiple Hit ◽  
Neurospora Tetrasperma ◽  
Ascospore Production

1. When ascospores of Neurospora tetrasperma were irradiated with 11 kv. X-rays, the single spore cultures obtained displayed a wide variety of mutated forms. 2. Control germinations of ascospores showed uniform behavior, ranging from 92–95 per cent germination. 3. The shape of the survival curves was found to be a function of the criterion of death. The following criteria were used: germination, growth, production of mature ascospores, and the production of normal perithecia. 4. The germination survival curve exhibited a rhythmic variation with dosage. Germination is not a significant criterion of death. 5. Half-survival dosages for growth and ascospore production were approximately 30,000 and 20,000 roentgens, respectively. 6. Multiple hit-to-kill relations were found on the basis of the quantum hit theory; no accurate analysis was possible. 7. The studies indicate that ascospore death does not result from a single well defined reaction, but rather from the integrated effects of several deleterious processes initiated by the radiation.

scholarly journals Modelling Dose Effects from Space Irradiations: Combination of High-LET and Low-LET Radiations with a Modified Microdosimetric Kinetic Model

Life ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 161 ◽  
Author(s):  
Alejandro Bertolet ◽  
Alejandro Carabe
Keyword(s):  
Kinetic Model ◽  
Poisson Distribution ◽  
Survival Curve ◽  
X Rays ◽  
Linear Quadratic ◽  
Survival Curves ◽  
Survival Fraction ◽  
High Let ◽  
Combined Action ◽  
High Linear Energy Transfer

The Microdosimetric Kinetic Model (MKM) to predict the effects of ionizing radiation on cell colonies is studied and reformulated for the case of high-linear energy transfer (LET) radiations with a low dose. When the number of radiation events happening in a subnuclear domain follows a Poisson distribution, the MKM predicts a linear-quadratic (LQ) survival curve. We show that when few events occur, as for high-LET radiations at doses lower than the mean specific energy imparted to the nucleus, zF,n, a Poisson distribution can no longer be assumed and an initial pure linear relationship between dose and survival fraction should be observed. Predictions of survival curves for combinations of high-LET and low-LET radiations are produced under two assumptions for their comparison: independent and combined action. Survival curves from previously published articles of V79 cell colonies exposed to X-rays, α particles, Ar-ions, Fe-ions, Ne-ions and mixtures of X-rays and each one of the ions are predicted according to the modified MKM. We conclude that mixtures of high-LET and low-LET radiations may enhance the effect of individual actions due to the increase of events in domains provided by the low-LET radiation. This hypothesis is only partially validated by the analyzed experiments.

scholarly journals The bactericidal action of ultra-violet light

1940 ◽  
Vol 40 (2) ◽  
pp. 162-171 ◽  
Author(s):  
D. E. Lea ◽  
R. B. Haines
Keyword(s):  
Survival Curve ◽  
Wave Length ◽  
Chemical Change ◽  
Monochromatic Light ◽  
Ultra Violet ◽  
X Rays ◽  
Bactericidal Action ◽  
Survival Curves ◽  
Ultra Violet Light ◽  
Violet Light

Experiments on the bactericidal action of ultra-violet light have been made to determine the shape of the survival curve and the dependence upon radiation intensity of the rate of death.Bact. coli, Bact. prodigiosumand spores ofB. mesentericuswere irradiated with approximately monochromatic light of wave-length 2537 A. The survival curves obtained were exponential and the rate of death was accurately proportional to the intensity over an intensity range of 500:1.By comparing these results with data previously obtained of the action of X-rays on the same organisms it was established that one ionization produced by X-rays is as effective as some hundreds of ultra-violet quanta. This is interpreted to mean that the quantum yield in whatever chemical change leads to the loss of viability in the irradiated bacteria is, for 2537 A., between 0·01 and 0·001.

Use of a Modified Gompertz Equation to Predict the Effects of Temperature, pH, and NaCl on the Inactivation of Listeria monocytogenes Scott A Heated in Infant Formula

1996 ◽  
Vol 59 (1) ◽  
pp. 16-23 ◽  
Author(s):  
R. H. LINTON ◽  
W. H. CARTER ◽  
M. D. PIERSON ◽  
C. R. HACKNEY ◽  
J. D. EIFERT
Keyword(s):  
Listeria Monocytogenes ◽  
Infant Formula ◽  
Nonlinear Regression ◽  
Survival Curve ◽  
Interactive Effects ◽  
Parameter Estimates ◽  
Survival Curves ◽  
Gompertz Equation ◽  
Nacl Concentration ◽  
Effects Of Temperature

The heat resistance of Listeria monocytogenes was determined in infant formula for all possible combinations of temperature (50, 55, and 60°C), pH level (5, 6, and 7), and NaCl concentration (0, 2, and 4%). Survival curves were fit using nonlinear regression with a Gompertz equation. The Gompertz equation was flexible enough to fit the three most commonly observed survival curves: linear curves, those with an initial lag region followed by a linear region, and sigmoidal shaped. Parameter estimates obtained by the method of nonlinear least squares were used to describe the effect(s) of different heating treatments on the lag region, death rate, and tailing region of survival curves. These estimates were further used to predict single and interactive effects of temperature, pH, and percentage of NaCl on the log of the surviving fraction (LSF) of bacteria. Interactions among these variables significantly (P ≤ .05) affected the LSF. Generally, increased pH or NaCl concentration lead to an increased LSF, whereas increased time or temperature lead to a decreased LSF. All multiple-factor interactions significantly (P ≤ .05) affected the LSF. The correlation of observed LSF versus predicted LSF (R2 = .92) indicated that the estimated Gompertz equation was in close agreement with the observation. This study demonstrated that the Gompertz equation and nonlinear regression can be used as an effective means to predict survival curve shape and response to heat of L. monocytogenes under many different environmental conditions.

A unified degree day model describes survivorship of Copitarsia corruda Pogue & Simmons (Lepidoptera: Noctuidae) at different constant temperatures

2008 ◽  
Vol 99 (1) ◽  
pp. 65-72 ◽  
Author(s):  
N.N. Gómez ◽  
R.C. Venette ◽  
J.R. Gould ◽  
D.F. Winograd
Keyword(s):  
Survival Curve ◽  
The United States ◽  
Physiological Age ◽  
Alien Invasive Species ◽  
Temperature Threshold ◽  
Base Temperature ◽  
Survival Curves ◽  
Degree Day ◽  
Effects Of Temperature ◽  
Lepidoptera Noctuidae

AbstractPredictions of survivorship are critical to quantify the probability of establishment by an alien invasive species, but survival curves rarely distinguish between the effects of temperature on development versus senescence. We report chronological and physiological age-based survival curves for a potentially invasive noctuid, recently described as Copitarsia corruda Pogue & Simmons, collected from Peru and reared on asparagus at six constant temperatures between 9.7 and 34.5°C. Copitarsia spp. are not known to occur in the United States but are routinely intercepted at ports of entry. Chronological age survival curves differ significantly among temperatures. Survivorship at early age after hatch is greatest at lower temperatures and declines as temperature increases. Mean longevity was 220 (±13 SEM) days at 9.7°C. Physiological age survival curves constructed with developmental base temperature (7.2°C) did not correspond to those constructed with a senescence base temperature (5.9°C). A single degree day survival curve with an appropriate temperature threshold based on senescence adequately describes survivorship under non-stress temperature conditions (5.9–24.9°C).

scholarly journals Survival Curves and Age Response Functions for Chinese Hamster Cells Exposed to X-Rays or High LET Alpha-Particles

1972 ◽  
Vol 52 (1) ◽  
pp. 88 ◽  
Author(s):  
E. J. Hall ◽  
W. Gross ◽  
R. F. Dvorak ◽  
A. M. Kellerer ◽  
H. H. Rossi
Keyword(s):  
Chinese Hamster ◽  
Alpha Particles ◽  
X Rays ◽  
Response Functions ◽  
Survival Curves ◽  
Chinese Hamster Cells ◽  
High Let

Calculating Salmonella Inactivation in Nonisothermal Heat Treatments from Isothermal Nonlinear Survival Curves

2001 ◽  
Vol 64 (5) ◽  
pp. 606-613 ◽  
Author(s):  
K. L. MATTICK ◽  
J. D. LEGAN ◽  
T. J. HUMPHREY ◽  
M. PELEG
Keyword(s):  
Differential Equation ◽  
Heat Treatment ◽  
Mathematical Models ◽  
Survival Curve ◽  
Survival Ratio ◽  
Survival Curves ◽  
Time Intervals ◽  
Heat Treated ◽  
Rich Media ◽  
Nonisothermal Conditions

Salmonella cells in two sugar-rich media were heat treated at various constant temperatures in the range of 55 to 80°C and their survival ratios determined at various time intervals. The resulting nonlinear semilogarithmic survival curves are described by the model log10S(t) = −b(T)tn(T), where S(t) is the momentary survival ratio N(t)/N0, and b(T) and n(T) are coefficients whose temperature dependence is described by two empirical mathematical models. When the temperature profile, T(t), of a nonisothermal heat treatment can also be expressed algebraically, b(T) and n(T) can be transformed into a function of time, i.e., b[T(t)] and n[T(t)]. If the momentary inactivation rate primarily depends on the momentary temperature and survival ratio, then the survival curve under nonisothermal conditions can be constructed by solving a differential equation, previously suggested by Peleg and Penchina, whose coefficients are expressions that contain the corresponding b[T(t)] and n[T(t)] terms. The applicability of the model and its underlying assumptions was tested with a series of eight experiments in which the Salmonella cells, in the same media, were heated at various rates to selected temperatures in the range of 65 to 80°C and then cooled. In all the experiments, there was an agreement between the predicted and observed survival curves. This suggests that, at least in the case of Salmonella in the tested media, survival during nonisothermal inactivation can be estimated without assuming any mortality kinetics.

Plasma Diagnostics of Microflares observed by STIX and AIA

2021 ◽  
Author(s):  
Jonas Saqri ◽  
Astrid Veronig ◽  
Ewan Dickson ◽  
Säm Krucker ◽  
Andrea Francesco Battaglia ◽  
...  
Keyword(s):  
Solar Flares ◽  
Magnetic Energy ◽  
Emission Measure ◽  
Transport Processes ◽  
X Rays ◽  
Solar Dynamics Observatory ◽  
Energy Bands ◽  
Accurate Analysis ◽  
Great Opportunity ◽  
Wide Range

<p>Solar flares are generally thought to be the impulsive release of magnetic energy giving rise to a wide range of solar phenomena that influence the heliosphere and in some cases even conditions of earth. Part of this liberated energy is used for particle acceleration and to heat up the solar plasma. The Spectrometer/Telescope for Imaging X-rays (STIX) instrument onboard the Solar Orbiter mission launched on February 10th 2020 promises advances in the study of solar flares of various sizes. It is capable of measuring X-ray spectra from 4 to 150 keV with 1 keV resolution binned into 32 energy bins before downlinking. With this energy range and sensitivity, STIX is capable of sampling thermal plasma with temperatures of≳10 MK, and to diagnose the nonthermal bremsstrahlung emission of flare-accelerated electrons. During the spacecraft commissioning phase in the first half of the year 2020, STIX observed 68 microflares. Of this set, 26 events could clearly be identified in at least two energy channels, all of which originated in an active region that was also visible from earth. These events provided a great opportunity to combine the STIX observations with the multi-band EUV imagery from the Atmospheric Imaging Assembly (AIA) instrument on board the earth orbiting Solar Dynamics Observatory (SDO). For the microflares that could be identified in two STIX science energy bands, it was possible to derive the temperature and emission measure (EM) of the flaring plasma assuming an isothermal source. For larger events where more detailed spectra could be derived, a more accurate analysis was performed by fitting the spectra assuming various thermal and nonthermal sources. These results are compared to the diagnostics derived from AIA images. To this aim, the Differential EmissionMeasure (DEM) was reconstructed from AIA observations to infer plasma temperatures and EM in the flaring regions. Combined with the the relative timing between the emission seen by STIX and AIA, this allows us to get deeper insight into the flare energy release and transport processes.</p>

scholarly journals A simple model for calculating relative biological effectiveness of X-rays and gamma radiation in cell survival

2020 ◽  
Vol 93 (1112) ◽  
pp. 20190949 ◽  
Author(s):  
Oleg N. Vassiliev ◽  
Christine B. Peterson ◽  
David R. Grosshans ◽  
Radhe Mohan
Keyword(s):  
Experimental Data ◽  
Cell Survival ◽  
Relative Biological Effectiveness ◽  
Survival Curve ◽  
Linear Functions ◽  
Model Parameters ◽  
High Dose ◽  
X Rays ◽  
Γ Radiation ◽  
Biological Effectiveness

Objectives: The relative biological effectiveness (RBE) of X-rays and γ radiation increases substantially with decreasing beam energy. This trend affects the efficacy of medical applications of this type of radiation. This study was designed to develop a model based on a survey of experimental data that can reliably predict this trend. Methods: In our model, parameters α and β of a cell survival curve are simple functions of the frequency-average linear energy transfer (LF) of delta electrons. The choice of these functions was guided by a microdosimetry-based model. We calculated LF by using an innovative algorithm in which LF is associated with only those electrons that reach a sensitive-to-radiation volume (SV) within the cell. We determined model parameters by fitting the model to 139 measured (α,β) pairs. Results: We tested nine versions of the model. The best agreement was achieved with [Formula: see text] and β being linear functions of [Formula: see text] .The estimated SV diameter was 0.1–1 µm. We also found that α, β, and the α/β ratio increased with increasing [Formula: see text] . Conclusions: By combining an innovative method for calculating [Formula: see text] with a microdosimetric model, we developed a model that is consistent with extensive experimental data involving photon energies from 0.27 keV to 1.25 MeV. Advances in knowledge: We have developed a photon RBE model applicable to an energy range from ultra-soft X-rays to megaelectron volt γ radiation, including high-dose levels where the RBE cannot be calculated as the ratio of α values. In this model, the ionization density represented by [Formula: see text] determines the RBE for a given photon spectrum.

Array-type universal profile function for powder pattern fitting

1990 ◽  
Vol 23 (6) ◽  
pp. 485-491 ◽  
Author(s):  
H. Toraya
Keyword(s):  
Peak Position ◽  
Powder Pattern ◽  
Mathematical Form ◽  
X Rays ◽  
Unknown Parameters ◽  
Profile Function ◽  
Accurate Analysis ◽  
Array Type ◽  
Profile Fitting ◽  
Fitting In

An array-type universal profile function for powder-pattern fitting is described. It is defined as an array of unknown parameters representing the profile heights at discrete angular steps. The unknown parameters are determined during least-squares fitting together with the integrated intensity, the peak position, the peak width and background parameters. The function has been applied to profile fitting in a small 20 range, and has better R-factors than the pseudo-Voigt and Pearson VII functions. This new function has some important advantages: it can model any complex profile shape, which would be difficult to describe by a smoothly varying analytical-type function; it generally gives a better fit and thus more precise and accurate analysis than currently used analytical-type functions; and it can be applied to the data of all radiation sources including conventional X-rays, synchrotron radiation and time-of-flight and fixed-wavelength neutrons without changing the mathematical form. The optimized use of the function and the accuracy of deduced parameters are also discussed.

Death rate of populations of Bact. lactis aerogenes III. Interpretation of survival curves

1953 ◽  
Vol 141 (902) ◽  
pp. 137-145 ◽  
Keyword(s):  
Molecular Species ◽  
Death Rate ◽  
Critical Level ◽  
Survival Curve ◽  
Survival Times ◽  
Survival Curves ◽  
Independent Events ◽  
Random Events ◽  
Decline Curves ◽  
Frequent Observation

Most theories of the survival curve postulate either a progressive action of the lethal agent on cells with large inherent differences of resistance, or random events such as encounters between the agent and a sensitive region of the cells. A survey of the experimental evidence, however, suggests that death of the bacterial cell involves not only a progressive destruction of essential cell activities, but may also be conditioned at some stage by a random combina­tion of various independent events. The form of the survival curve depends essentially on the speed of the former process in relation to the probability of the latter. Factors modifying this form are: (1) intrinsic differences between individual cells, which, however, appear not to be the major cause of variation of survival times, and (2) the occurrence, in favourable circumstances, of adaptive adjustments. It is the element of chance in survival that accounts for the frequent observation of extremely skew distributions of survival times (and in the limit nearly logarithmic decline curves). It probably arises from the fact that the concentrations of various molecular species show complex fluctuations, at the appropriate phase of which certain cell activities fall below a critical level for viability.

Sign in / Sign up

Export Citation Format

Share Document