Constrained action selection in children with developmental coordination disorder

The effect of advance (‘precue’) information on short aiming movements was explored in adults, high school children, and primary school children with and without developmental coordination disorder (n = 10, 14, 16, 10, respectively). Reaction times in the DCD group were longer than in the other groups and were more influenced by the extent to which the precue constrained the possible action space. In contrast, reaction time did not alter as a function of precue condition in adults. Children with DCD showed greater inaccuracy of response (despite the increased RT). We suggest that the different precue effects reflect differences in the relative benefits of priming an action prior to definitive information about the movement goal. The benefits are an interacting function of the task and the skill level of the individual. Our experiment shows that children with DCD gain a benefit from advance preparation in simple aiming movements, highlighting their low skill levels. This result suggests that goal-directed RTs may have diagnostic potential within the clinic

Evaluating the participation of an ethnic minority group in informal employment: a product of exit or exclusion?

This paper critically evaluates competing explanations for the participation of ethnic minority groups in informal employment. These interpret their participation either through a structuralist lens arising out of “exclusion” from formal employment or through a neo-liberal and/or post-structuralist lens driven by voluntary “exit” from formal institutions. To evaluate critically these competing explanations, this paper reports a survey of the experiences of Pakistani immigrants in informal employment in Sheffield, including fifty face-to-face interviews and two focus groups. The findings highlight informal employment amongst this Pakistani ethnic minority group is neither universally driven by exclusion nor exit. Instead, some participate mostly due to exclusion, others mostly for exit rationales and some for a combination of the two, with different mixtures across different groups and types of informal employment. The outcome is a call for greater appreciation of the multifarious character of undeclared work and a move beyond simplistic explanations and policy responses

Beyond the formal/informal enterprise dualism : explaining the level of (in)formality of entrepreneurs

Rather than portray formal and informal sector entrepreneurs as discrete groups, an emergent scholarship has conceptualized a continuum from wholly formal to wholly informal entrepreneurs. The aim of the paper is to advance a degree of (in)formality approach by evaluating whether the institutional determinants found to explain whether an enterprise is formal or informal are also valid when explaining the level of (in)formality of enterprises. To do so, a 2017 survey of 500 retail micro-enterprises in the city of Lahore in Pakistan is reported. The finding is that higher levels of formality are more significantly associated with individual-level characteristics of the entrepreneur and enterprise, such as educational level and sales, than with formal and informal institutional conditions, as proposed by institutional theory. The paper thus concludes by offering new theoretical implications and exploring some innovative policy measures to tackle informal entrepreneurship

Fighting for mates: the importance of individual size in mating contests in rocky shore littorinids

Studies of mating contests have reported how traits (e.g. body size) related to resource holding potential (RHP) and strategies to assess RHP and resource value influence contest outcome in many taxa but are rare in the Gastropoda. The influence of male size (as an index of RHP) and female size (as a measure of resource value) on contest outcome were investigated in two littorinid snails, Echinolittorina malaccana and E. radiata, in Hong Kong during May－June 2013. In these snails, contests between males take the form of a 'challenger' attempting to take over the copulation position occupied by a 'defender'. Both challengers and defenders were, generally, smaller than the females in both species. In both species, the larger the challenger relative to the defender, the more likely he would replace the defender in the copulation position. The challengers were, however, more successful in E. radiata, as they generally challenged defenders that were smaller than themselves, suggesting an ability to detect rival size before entering into a contest in this species. When sizes of the contestants were similar, defenders were more likely to win contests in E. malaccana but not in E. radiata. Evidence for pure self-assessment of RHP and the ability to assess resource value in challengers was found in E. malaccana. Different fighting strategies appear to have evolved in these congeneric marine snail species and decisions based on male and female sizes play an important role in determining male reproductive success

Sampling scale can cause bias in positive assortative mating estimates: The first evidence in two intertidal snails

Assortative mating in the wild is commonly estimated by correlating between traits in mating pairs (e.g. size of males and females). Unfortunately such an approach may suffer from considerable sampling bias when the distribution of different expressions of a trait in the wild is non-random; for example, when segregation of different size classes of individuals occur in different microhabitats or areas. Consequently, any observed trait correlation in the wild can be an artifact of pooling heterogeneous samples of mating pairs from different microhabitats or areas rather than true non-random matings. This bias in estimating trait correlations due to sampling scale is termed the scale-of-choice effect (SCE). Here we use two intertidal littorinid species from Hong Kong to show how the SCE can bias size-assortative mating estimates from mating pairs captured in the wild, empirically demonstrating the influence of this effect on measures of positive assortative mating. This finding cautions that studies that have overlooked SCE may have misinterpreted the magnitude and the cause of assortative mating, and we provide a new analytical approach to protect against this potential bias in future studies

Controlled Growth, Patterning and Placement of Carbon Nanotube Thin Films

Controlled growth, patterning and placement of carbon nanotube (CNT) thin films for electronic applications are demonstrated. The density of CNT films is controlled by optimizing the feed gas composition as well as the concentration of growth catalyst in a chemical vapor deposition process. Densities of CNTs ranging from 0.02 CNTs/{\mu}m^2 to 1.29 CNTs/{\mu}m^2 are obtained. The resulting pristine CNT thin films are then successfully patterned using either pre-growth or post-growth techniques. By developing a layered photoresist process that is compatible with ferric nitrate catalyst, significant improvements over popular pre-growth patterning methods are obtained. Limitations of traditional post-growth patterning methods are circumvented by selective transfer printing of CNTs with either thermoplastic or metallic stamps. Resulting as-grown patterns of CNT thin films have edge roughness (< 1 {\mu}m) and resolution (< 5 {\mu}m) comparable to standard photolithography. Bottom gate CNT thin film devices are fabricated with field-effect mobilities up to 20 cm^2/Vs and on/off ratios of the order of 10^3. The patterning and transfer printing methods discussed here have a potential to be generalized to include other nanomaterials in new device configurations

New coins from old, smoothly

Given a (known) function $f:[0,1] \to (0,1)$, we consider the problem of simulating a coin with probability of heads $f(p)$ by tossing a coin with unknown heads probability $p$, as well as a fair coin, $N$ times each, where $N$ may be random. The work of Keane and O'Brien (1994) implies that such a simulation scheme with the probability $\P_p(N<\infty)$ equal to 1 exists iff $f$ is continuous. Nacu and Peres (2005) proved that $f$ is real analytic in an open set $S \subset (0,1)$ iff such a simulation scheme exists with the probability $\P_p(N>n)$ decaying exponentially in $n$ for every $p \in S$. We prove that for $\alpha>0$ non-integer, $f$ is in the space $C^\alpha [0,1]$ if and only if a simulation scheme as above exists with $\P_p(N>n) \le C (\Delta_n(p))^\alpha$, where \Delta_n(x)\eqbd \max \{\sqrt{x(1-x)/n},1/n \}. The key to the proof is a new result in approximation theory: Let \B_n be the cone of univariate polynomials with nonnegative Bernstein coefficients of degree $n$. We show that a function $f:[0,1] \to (0,1)$ is in $C^\alpha [0,1]$ if and only if $f$ has a series representation $\sum_{n=1}^\infty F_n$ with F_n \in \B_n and $\sum_{k>n} F_k(x) \le C(\Delta_n(x))^\alpha$ for all $x \in [0,1]$ and $n \ge 1$. We also provide a counterexample to a theorem stated without proof by Lorentz (1963), who claimed that if some \phi_n \in \B_n satisfy $|f(x)-\phi_n(x)| \le C (\Delta_n(x))^\alpha$ for all $x \in [0,1]$ and $n \ge 1$, then $f \in C^\alpha [0,1]$.Comment: 29 pages; final version; to appear in Constructive Approximatio

Relativistic many-body calculations of electric-dipole matrix elements, lifetimes and polarizabilities in rubidium

Electric-dipole matrix elements for ns-n'p, nd-n'p, and 6d-4f transitions in Rb are calculated using a relativistic all-order method. A third-order calculation is also carried out for these matrix elements to evaluate the importance of the high-order many-body perturbation theory contributions. The all-order matrix elements are used to evaluate lifetimes of ns and np levels with n=6, 7, 8 and nd levels with n=4, 5, 6 for comparison with experiment and to provide benchmark values for these lifetimes. The dynamic polarizabilities are calculated for ns states of rubidium. The resulting lifetime and polarizability values are compared with available theory and experiment.Comment: 8 pages, 2 figure