Analytical procedures for the modelling of hopping transport in disordered semiconductors

The transient and steady-state electronic and optoelectronic properties of disordered semiconductors involve interactions of charge carriers with localized states distributed over a range of energies. Where the concentration of such states is sufficiently high, the transport mechanism can be dominated by hopping (quantum-mechanical tunnelling) transitions directly between them. In the analysis of the above situation, one easily applicable approach is to replace a continuous energy distribution with a 'ladder' of energetically discrete sets of traps. This can greatly simplify calculations, but a serious limitation is that the resulting properties depend extremely sensitively upon the slice width selected. In this letter, two variants of a new approach, based upon simple concepts of differential probability and detailed balance, and applicable to an arbitrary energy distribution of trapping centres, are introduced. The capabilities of the procedures are demonstrated by their application to the calculation of effective hopping rates in an exponential energy distribution of localized states. Finally, to illustrate the application of the techniques, the effective rates are coupled to the corresponding hopping distances. This allows the results to be employed (as a preliminary example) in the calculation of the time dependence of the transient photocurrent within an exponential band tail.     

Influence of temperature on the bioelectric conductivity of peripheral motor nerve]

14 persons were examined electro-neurographically before and after cooling with an ice bag. The following results were found. A slight decrease of the motor conductivity is verified. This decrease in function is shown most markedly in the slowly-conducting motor neurons. At the cooling borderlines reactions with increased function are discernible. For the clarification of the relevance of changes of the nerve conductivity, further investigations with methodic variants are necessary.     

Flexibility of information processing and the memory of field-independent and field-dependent learners

This study examined memory differences between 48 field-independent and 48 field-dependent learners, and it hypothesized that rigid information processing by field-dependent learners interferes with cue efficiency during memory recall. The field-independent and field-dependent learners were presented with paired associates in which the target recall words were homographs, and accompanying associates emphasized one of the homograph's two meanings. Homograph recall occurred under three conditions: (a) same cue recall, (b) different cue recall (emphasized other meaning of homograph), and (c) free recall. This study found memory differences favoring the field-independent learner and findings consistent with the rigid information processing hypothesis of field-dependent learners.     

A theoretical model of effective electrical conductivity and piezoresistivity of carbon nanotube composites

A theoretical model is developed to predict the electrical conductivity of polymer composites containing carbon nanotubes. It incorporates the effect of two conductivity mechanisms, electron hopping between adjacent nanotubes at the nanoscale and the transmission of electrons through conductive networks formed by nanotubes at the microscale. Based on the model, analytical expressions of both electrical conductivity and piezoresisitivity under stretching are established. The expressions are simple in form, without resorting to heavy computation, and able to give accurate estimations for both electrical conductivity and piezoresistivity.     

Estimation of density of charged defects in amorphous chalcogenides from a.c. conductivity: Random-walk approach for bipolarons based on correlated barrier hopping

Abstract

Although the pair approximation (PA) based on correlated bamer hopping (CBH) is now fairly well established to explain the a.c. conductivity of amorphous chalcogenides, the density of charged states deduced from PA is large compared with those estimated from other studies, namely light-induced electron spin resonance and drift mobility. We have used the continuous-time random-walk approximation based on CBH to estimate the density of charged defects and have applied it to experimental data for amorphous As₂Se₃, and a density of charged defects consistent with other measurements has been estimated.     

Individuality and mutuality in the language of families of field-dependent and field-independent children

The use of singular and plural first-person pronouns provided a measure of individuality and mutuality in families of 18 field-dependent and 20 field-independent children (19 boys and 19 girls). The families were observed in home and laboratory settings. Consistent with notions of a more differentiated sense of self, field-independent boys and girls used more I words; the greater social orientation of the field-dependent children was reflected in their more frequent use of we terms. Family members in the field-independent group were more varied in their use of these linguistic measures, especially in the lab. Fathers of field-independent children used more we words. These usages were discussed in terms of social control mechanisms. personal pronoun usage as indicators of separateness/connectedness in families was also discussed.     

The derivation of some tests for the rasch model from the multinomial distribution

The present paper is concerned with testing the fit of the Rasch model. It is shown that this can be achieved by constructing functions of the data, on which model tests can be based that have power against specific model violations. It is shown that the asymptotic distribution of these tests can be derived by using the theoretical framework of testing model fit in general multinomial and product-multinomial models. The model tests are presented in two versions: one that can be used in the context of marginal maximum likelihood estimation and one that can be applied in the context of conditional maximum likelihood estimation.I am indebted to Norman Verhelst and Niels Veldhuijzen for their helpful comments. Requests for reprints should be sent to Cees A. W. Glas, Cito, PO Box 1034, 6801 MG Arnhem, THE NETHERLANDS.     

Auditory reaction time and the derivation of equal loudness contours for the monkey

Monkeys were trained to release a telegraph key at the onset of a pure tone. Latency of the response was measured over a 70-db range of sound pressure (re 0.0002 dyn/cm(2)) at six frequencies (250 to 15,000 cps). Latency was found to be an inverse exponential function of intensity at all frequencies. Equal loudness was inferred from the equal latency contours which were constructed from the latency-intensity functions at each frequency. These data indicate peak auditory sensitivity for the monkey near 1000 cps. At the frequencies above and below 1000 cps consistently more sound energy was required for equal latency.     

A Hobbesian derivation of the principle of universalization

In this article, I derive a weak version of Kant’s categorical imperative within an informal game-theoretic framework. More specifically, I argue that Hobbesian agents would choose what I call the weak principle of universalization, if they had to decide on a rule of conflict resolution in an idealized but empirically defensible hypothetical decision situation. The discussion clarifies (i) the rationality requirements imposed on agents, (ii) the empirical conditions assumed to warrant the conclusion, and (iii) the political institutions that are necessary to implement the derived principle. The analysis demonstrates the moral significance of the weak principle of universalization and its epistemic advantage over the categorical imperative.     

On a derivation of the necessity of identity

The source, status, and significance of the derivation of the necessity of identity at the beginning of Kripke’s lecture “Identity and Necessity” is discussed from a logical, philosophical, and historical point of view.     

A note on the derivation of the general latent class model

A general formulation of the latent structure principle is suggested, from which it is possible to derive Lazarsfeld's accounting equations in their most general form. The basic equations of Gibson's latent profile model can thence be derived in a single step.     

Notes on Kant's derivation of the various formulae of the categorical imperative

Abstract

This article is concerned with examining Kant's derivation of the various formulae of his Categorical Imperative. It is in agreement with Paton in maintaining that Kant actually mentions five formulae. But it is not in agreement with him, and some others, in maintaining that they are ultimately reducible to three. Nor is it in agreement with those who maintain that they are ultimately reducible to just one. According to the present article, they are ultimately reducible to two: that about a moral law being a universal law; and that about a moral law involving treating human beings as ends in themselves.     

Theoretical and statistical derivation of a screener for the behavioral assessment of executive functions in children

The problem of valid measurement of psychological constructs remains an impediment to scientific progress, and the measurement of executive functions is not an exception. This study examined the statistical and theoretical derivation of a behavioral screener for the estimation of executive functions in children from the well-established Behavior Assessment System for Children (BASC). The original national standardization sample of the BASC-Teacher Rating Scales for children ages 6 through 11 was used (N = 2,165). Moderate-to-high internal consistency was obtained within each factor (.80-.89). A panel of experts was used for content validity examination. A confirmatory factor analysis model with 25 items loading on 4 latent factors (behavioral control, emotional control, attentional control, and problem solving) was developed, and its statistical properties were examined. The multidimensional model demonstrated adequate fit, and it was deemed invariant after configural, metric, and scalar measurement invariance tests across sex and age. Given its strong psychometric properties, with further tests of item validity, this instrument promises future clinical and research utility for the screening of executive functions in school-age children.     

A concise derivation of the contact conditions at a migrating sharp interface

A sharp interface model can be used to simulate the kinetics of diffusional phase transformations provided the transformation process is controlled by migration of the interface and by diffusion of components in the bulk phases only. The contact conditions at the migrating sharp interface can be derived by applying the principles of mass balance and maximum dissipation. A concise derivation of the contact conditions on this basis is presented in this work.