Atomic effects on β-decay

1988 ◽  
Vol 420 (1859) ◽  
pp. 277-321 ◽  
Keyword(s):  
Half Life ◽  
Electronic Configuration ◽  
Bound State ◽  
The Other ◽  
Initial State ◽  
Β Decay ◽  
Point Energy ◽  
Chemical Effects ◽  
Chemically Induced ◽  
Induced Changes

Factors leading to the dependence of the β-decay half-life on the atomic electron environment are discussed. An expression for the rate of allowed β-decay of a nucleus embedded in a multielectron atom having an arbitrary electronic configuration is derived. This is then used to obtain a new expression for the ratio of decay constants for bound and continuum decays from a general electron state. This expression fully incorporates exchange of the β-electron with the other bound electrons. It also includes the inhibition of the decay rate, which originates from the total or partial occupation of orbitals by electrons in the initial state. Specific expressions are presented for bound-state decay of an initial-state atomic system having open or closed s-shell configurations. The magnitudes of chemical effects on low-energy β-decays are demonstrated by calculations on 106 Ru. This isotope appears to represent a particularly favourable case for experimental study of chemical effects. Two main chemical effects are found. One arises from the change in bound-state decays, which, although they constitute a small fraction (less than 1%) of total decays, are very sensitive to chemical effects. The other factor arises from the effect on continuum decays of chemically induced changes in the end-point energy. For 106 Ru both effects lead to changes of order 0.1% in the total decay half-life when the ionicity is changed by one unit. However, both effects tend to partially cancel one another, with the result that the net difference in half-life is in the range 0.01–0.1%.

Modification of microelectrode arrays: new microelectrochemical devices for sensor applications

1987 ◽  
Vol 316 (1176) ◽  
pp. 13-30 ◽  
Keyword(s):  
Active Material ◽  
Microelectrode Arrays ◽  
State Of Charge ◽  
The Other ◽  
Redox Polymer ◽  
Active Materials ◽  
Sensor Applications ◽  
Redox Active ◽  
Chemically Induced ◽  
Induced Changes

Microelectrode arrays consisting of two or eight closely spaced ( ca. 1 μm) gold or platinum microelectrodes (approximate dimensions 2 μm wide x 50 μm long x 0.1 μm high) can be modified with a variety of redox-active materials in a way that leads to microelectrochemical devices that may be useful as sensors. In general, a pair of microelectrodes connected by a redox-active material represents a device, because the current, I d , passing from one microelectrode (source) to the other (drain) at a fixed potential between them, V d , can be modulated by electrically or chemically induced changes in the state of charge of the redox material. The fundamental issues associated with pH-sensitive devices based on poly(3-methylthiophene), poly(4-vinylpyridine), a viologen—quinone redox polymer and WO 3 are described to illustrate generic concepts that underlie the development of microelectrochemical sensors.

Turnover and Distribution of 131Iodine-Labelled Human Fibrinogen

1964 ◽  
Vol 11 (02) ◽  
pp. 404-422 ◽  
Author(s):  
Annemarie Amris ◽  
C. J Amris
Keyword(s):  
Body Weight ◽  
Cancer Patient ◽  
Distribution Ratio ◽  
Half Life ◽  
Fibrinolytic Activity ◽  
The Other ◽  
Turnover Rates ◽  
Human Fibrinogen ◽  
Coagulation Defects ◽  
Fractional Turnover

Summary14 patients (5 diabetics with arteriosclerotic complications, 4 patients with thrombo-embolic disease, 4 with cirrhosis, coagulation defects and increased fibrinolytic activity, and 1 cancer patient) and 3 control patients were subjected to turnover studies with 13iodine labelled human fibrinogen.Half-life times in the control patients were found to be 4 days, the fractional turnover rates 19–23 per cent, of intravascular fibrinogen per day, and the absolute turnover 0.02 to 0.06 gm per day per kg. body weight. The other patient’s half-life times and turnover rates varied considerably from 0.9–5.5 days, 13–160 per cent, per day of intravascular fibrinogen and 0.02–0.4 gm per day per kg. body weight respectively.As fibrinogen unlike other proteins subjected to turnover studies, is converted to fibrin, it is not possible to measure the true intra-extravascular distribution ratio of fibrinogen. But intravascular fibrinogen could be approximated to constitute 68–99 per cent, of the total fibrinogen. There is justification in believing that fibrinogen is degradated through a continuous coagulation in equilibrium with fibrinolysis, and that the organism contains a greater mass of fibrin, the “fibrin pool”. Considerations of the turnover mechanism can however only be hypothetical.

Investigation of bound state β− decay half-lives of bare atoms

2021 ◽  
Vol 104 (2) ◽  
Author(s):  
Shuo Liu ◽  
Chao Gao ◽  
Chang Xu
Keyword(s):  
Bound State ◽  
Β Decay

scholarly journals A Discontinuity of the Energy of Quantum Walk in Impurities

Symmetry ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1134
Author(s):  
Kenta Higuchi ◽  
Takashi Komatsu ◽  
Norio Konno ◽  
Hisashi Morioka ◽  
Etsuo Segawa
Keyword(s):  
Unit Circle ◽  
Stationary State ◽  
Discrete Time ◽  
Quantum Walk ◽  
Time Limit ◽  
The Other ◽  
Unitary Matrix ◽  
Initial State ◽  
Time Quantum ◽  
Long Time

We consider the discrete-time quantum walk whose local dynamics is denoted by a common unitary matrix C at the perturbed region {0,1,⋯,M−1} and free at the other positions. We obtain the stationary state with a bounded initial state. The initial state is set so that the perturbed region receives the inflow ωn at time n(|ω|=1). From this expression, we compute the scattering on the surface of −1 and M and also compute the quantity how quantum walker accumulates in the perturbed region; namely, the energy of the quantum walk, in the long time limit. The frequency of the initial state of the influence to the energy is symmetric on the unit circle in the complex plain. We find a discontinuity of the energy with respect to the frequency of the inflow.

Tensor correlations and the β-decay half-life of 132Sn

2015 ◽  
Vol 12 (4) ◽  
pp. 494-497 ◽  
Author(s):  
E. O. Sushenok ◽  
A. P. Severyukhin
Keyword(s):  
Half Life ◽  
Β Decay

scholarly journals Comparison of Two Methods of Producing Adaptation of Saccade Size and Implications for the Site of Plasticity

1998 ◽  
Vol 79 (2) ◽  
pp. 704-715 ◽  
Author(s):  
Charles A. Scudder ◽  
Ekatherina Y. Batourina ◽  
George S. Tunder
Keyword(s):  
Relative Size ◽  
Neural Mechanisms ◽  
The Other ◽  
Rapid Adaptation ◽  
Adaptive Mechanisms ◽  
Saccade Size ◽  
Orbital Position ◽  
One Step ◽  
Induced Changes ◽  
Visual Error

Scudder, Charles A., Ekatherina Y. Batourina, and George S. Tunder. Comparison of two methods of producing adaptation of saccade size and implications for the site of plasticity. J. Neurophysiol. 79: 704–715, 1998. Saccade accuracy is known to be maintained by adaptive mechanisms that progressively reduce any visual error that consistently exists at the end of saccades. Experimentally, the visual error is induced using one of two paradigms. In the first, the horizontal and medial recti of trained monkeys are tenectomized and allowed to reattach so that both muscles are paretic. After patching the unoperated eye and forcing the monkey to use the “paretic eye,” saccades initially undershoot the intended target, but gradually increase in size until they almost acquire the target in one step. In the second, the target of a saccade is displaced in midsaccade so that the saccade cannot land on target. Again saccade size adapts until the target can be acquired in one step. Because adaptation with the latter paradigm is very rapid but adaptation using the former is slow, it has frequently been questioned whether or not the two forms of adaptation depend on the same neural mechanisms. We show that the rate of adaptation in both paradigms depends on the number of possible visual targets, so that when this variable is equated, adaptation occurs at similar rates in both paradigms. To demonstrate further similarities between the result of the two paradigms, an experiment using intrasaccadic displacements was conducted to show that rapid adaptation possesses the capacity to produce gain changes that vary with orbital position. The relative size of intrasaccadic displacements were graded with orbital position so as to mimic the position-dependent dysmetria initially produced by a single paretic extraocular muscle. Induced changes in saccade size paralleled the size of the displacements, being largest for saccades into one hemifield and being negligible for saccades into the other hemifield or in the opposite direction. Collectively, the data remove the rational for asserting that adaptation produced by the two paradigms depends on separate neural mechanisms. We argue that adaptation produced by both paradigms depends on the cerebellum.

scholarly journals UJI FOTOSTABILITAS PIGMEN BIXIN PADA BENTONIT DAN BENTONIT TERPILAR-TiO2

2020 ◽  
Vol 8 (2) ◽  
Author(s):  
Nelly - Wahyuni
Keyword(s):  
Half Life ◽  
The Other ◽  
Uv C

One of the characteristics of the bixin pigment is its low photostability, which causes its limitations. There are many methods to improve the photostability of bixin. This study aims to study the rate of degradation of bixin in the form of an extract that will be impregnated in bentonite and TiO2 pillared bentonite. The photostability test was carried out by continuously illuminating the sample with ultraviolet (UV C) light for nine h. Bixin concentration was observed using a UV-spectrophotometer. The results showed that the impregnation of bixin extract on bentonite could increase the photostability of bixin from 14.4 h to 138.6 h. On the other, impregnation of bixin on TiO2 pillared bentonite increases the rate of bixin degradation. The half-life of bixin offered to this material is only 3.7 h. TiO2 pillared bentonite enrolls as a photocatalyst, which is enhanced photodegradation of bixin pigment. Keywords: bixin, bentonite, photostability, pigment, TiO2-pillared bentonite 

scholarly journals Balanced networks under spike-time dependent plasticity

2021 ◽  
Vol 17 (5) ◽  
pp. e1008958
Author(s):  
Alan Eric Akil ◽  
Robert Rosenbaum ◽  
Krešimir Josić
Keyword(s):  
Spike Timing ◽  
Recurrent Networks ◽  
Spike Time ◽  
Weight Changes ◽  
Initial State ◽  
Dependent Plasticity ◽  
Plausible Mechanism ◽  
Spike Time Dependent Plasticity ◽  
Induced Changes ◽  
Balanced Networks

The dynamics of local cortical networks are irregular, but correlated. Dynamic excitatory–inhibitory balance is a plausible mechanism that generates such irregular activity, but it remains unclear how balance is achieved and maintained in plastic neural networks. In particular, it is not fully understood how plasticity induced changes in the network affect balance, and in turn, how correlated, balanced activity impacts learning. How do the dynamics of balanced networks change under different plasticity rules? How does correlated spiking activity in recurrent networks change the evolution of weights, their eventual magnitude, and structure across the network? To address these questions, we develop a theory of spike–timing dependent plasticity in balanced networks. We show that balance can be attained and maintained under plasticity–induced weight changes. We find that correlations in the input mildly affect the evolution of synaptic weights. Under certain plasticity rules, we find an emergence of correlations between firing rates and synaptic weights. Under these rules, synaptic weights converge to a stable manifold in weight space with their final configuration dependent on the initial state of the network. Lastly, we show that our framework can also describe the dynamics of plastic balanced networks when subsets of neurons receive targeted optogenetic input.

A BGK MODEL FOR CHEMICAL PROCESSES: THE REACTION-DIFFUSION APPROXIMATION

1994 ◽  
Vol 04 (01) ◽  
pp. 35-47 ◽  
Author(s):  
RENATO SPIGLER ◽  
DAMIÁN H. ZANETTE
Keyword(s):  
Kinetic Model ◽  
Diffusion Approximation ◽  
Reaction Diffusion ◽  
Chemical Processes ◽  
Reaction Diffusion Equations ◽  
The Other ◽  
Diffusion Equations ◽  
Bgk Model ◽  
Chemical Substances ◽  
Chemical Effects

A BGK-type kinetic model is derived for describing the interaction of chemical substances. The ensuing equation is then solved asymptotically on certain space-time scales on which an appreciable interplay between kinetic and chemical effects, or the prevailing of one on the other, can be observed. The description of the interaction at the macroscopic level consists of a hierarchy of reaction-diffusion equations satisfied by the densities. Comparison is made with similar results previously obtained from certain phenomenological models, and illustrative examples are given.

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