Two Hands Are Better Than One (up to constant factors): Self-Assembly In The 2HAM vs. aTAM

We study the difference between the standard seeded model (aTAM) of tile self-assembly, and the "seedless" two-handed model of tile self-assembly (2HAM). Most of our results suggest that the two-handed model is more powerful. In particular, we show how to simulate any seeded system with a two-handed system that is essentially just a constant factor larger. We exhibit finite shapes with a busy-beaver separation in the number of distinct tiles required by seeded versus two-handed, and exhibit an infinite shape that can be constructed two-handed but not seeded. Finally, we show that verifying whether a given system uniquely assembles a desired supertile is co-NP-complete in the two-handed model, while it was known to be polynomially solvable in the seeded model.National Science Foundation (U.S.) (NSF grant CDI-0941538

Two Heads Are Better Than One? Setting Realizable Goals in the Basic Course

Establishing goals is central to the success of the basic course. The degree to which those goals are realized depends, in large measure, upon the manner in which they are established and reviewed. This article assists course directors and instructional staff by examining the process of defining objectiveness, a process which encompasses goals, mission, and vision and which benefits from widespread, active involvement. This article presents sample objectives for consideration, and it notes the conditions under which the process of defining objectives thrives or is threatened

Four - Fermi Theories in Fewer Than Four Dimensions

Four-fermi models in dimensionality $2<d<4$ exhibit an ultra-violet stable renormalization group fixed point at a strong value of the coupling constant where chiral symmetry is spontaneously broken. The resulting field theory describes relativistic fermions interacting non-trivially via exchange of scalar bound states. We calculate the $O(1/N_f)$ corrections to this picture, where $N_f$ is the number of fermion species, for a variety of models and confirm their renormalizability to this order. A connection between renormalizability and the hyperscaling relations between the theory's critical exponents is made explicit. We present results of extensive numerical simulations of the simplest model for $d=3$, performed using the hybrid Monte Carlo algorithm on lattice sizes ranging from $8^3$ to $24^3$. For $N_f=12$ species of massless fermions we confirm the existence of a second order phase transition where chiral symmetry is spontaneously broken. Using both direct measurement and finite size scaling arguments we estimate the critical exponents $\beta$, $\gamma$, $\nu$ and $\delta$. We also investigate symmetry restoration at non-zero temperature, and the scalar two-point correlation function in the vicinity of the bulk transition. All our results are in excellent agreement with analytic predictions, and support the contention that the $1/N_f$ expansion is accurate for this class of models.Comment: CERN-TH.6557/92 ILL-(TH)-92-\# 19, 60 pages, 18 figures (not included

Better safe than sorry? Reliability policy in network industries

This report develops a roadmap for reliability policy in network industries. Based on economic theory, we analyse the relationship between reliability and various types of government policy: privatisation, liberalisation, regulation, unbundling, and 'commitment policy'. We let government policy depend on (1) the feasibility of competition between networks, (2) contractibility of reliability, and (3) the relation between profit maximisation and public interests. We test this roadmap on the basis of the empirical literature and case studies on electricity, natural gas, drinking water, wastewater, and railways.

"Women Are Better Than Men" - Public Beliefs on Gender Differences and Other Aspects in Multitasking.

Reports in public media suggest the existence of a stereotype that women are better at multitasking than men. The present online survey aimed at supporting this incidental observation by empirical data. For this, 488 participants from various ethnic backgrounds (US, UK, Germany, the Netherlands, Turkey, and others) filled out a self-developed online-questionnaire. Results showed that overall more than 50% of the participants believed in gender differences in multitasking abilities. Of those who believed in gender differences, a majority of 80% believed that women were better at multitasking. The main reasons for this were believed to be an evolutionary advantage and more multitasking practice in women, mainly due to managing children and household and/or family and job. Findings were consistent across the different countries, thus supporting the existence of a widespread gender stereotype that women are better at multitasking than men. Further questionnaire results provided information about the participants' self-rated own multitasking abilities, and how they conceived multitasking activities such as childcare, phoning while driving, and office work

Windows into Sensory Integration and Rates in Language Processing: Insights from Signed and Spoken Languages

This dissertation explores the hypothesis that language processing proceeds in "windows" that correspond to representational units, where sensory signals are integrated according to time-scales that correspond to the rate of the input. To investigate universal mechanisms, a comparison of signed and spoken languages is necessary. Underlying the seemingly effortless process of language comprehension is the perceiver's knowledge about the rate at which linguistic form and meaning unfold in time and the ability to adapt to variations in the input. The vast body of work in this area has focused on speech perception, where the goal is to determine how linguistic information is recovered from acoustic signals. Testing some of these theories in the visual processing of American Sign Language (ASL) provides a unique opportunity to better understand how sign languages are processed and which aspects of speech perception models are in fact about language perception across modalities. The first part of the dissertation presents three psychophysical experiments investigating temporal integration windows in sign language perception by testing the intelligibility of locally time-reversed sentences. The findings demonstrate the contribution of modality for the time-scales of these windows, where signing is successively integrated over longer durations (~ 250-300 ms) than in speech (~ 50-60 ms), while also pointing to modality-independent mechanisms, where integration occurs in durations that correspond to the size of linguistic units. The second part of the dissertation focuses on production rates in sentences taken from natural conversations of English, Korean, and ASL. Data from word, sign, morpheme, and syllable rates suggest that while the rate of words and signs can vary from language to language, the relationship between the rate of syllables and morphemes is relatively consistent among these typologically diverse languages. The results from rates in ASL also complement the findings in perception experiments by confirming that time-scales at which phonological units fluctuate in production match the temporal integration windows in perception. These results are consistent with the hypothesis that there are modality-independent time pressures for language processing, and discussions provide a synthesis of converging findings from other domains of research and propose ideas for future investigations

Rethinking Leadership, or Team LEaders Are Not Music Directors

Let us begin with a thought experiment. Think for a moment about one of the finest groups you have every seen—one that accomplished its work superbly, that got better and better as a performing unit over time, and whose members came away from the group experience wiser and more skilled than they were before. Next, think about a different group, one that failed to achieve its purposes, that deteriorated in performance capability over time, and whose members found the group experience far more frustrating than fulfilling

Are Female Workers Less Productive Than Male Workers?

This paper addresses whether there are productivity differences between men and women among blue-collar workers. We compare the wages under piece- and time-rate contracts of men and women working in the same occupation in the same establishment in three countries: the U.S., Norway, and Sweden. The findings are summarized in four points. First, the gender wage gap is smaller under piece- than under time-rate work. According to the interpretation put forth here, two thirds of the gap at the occupation–establishment level is due to productivity differences, while one third is not “accounted for”, but could be due to discrimination or experience or other factors. Productivity differences between sexes in typically male-dominated blue-collar industries are however very small, of 1– 3%: Sweden 1%, U.S. 2% and Norway 3%. Second, in age groups where women on average have extensive family obligations, the wage gap is larger than in other age groups. Third, under time-rate work, the wage gap is more or less independent of supposed occupation-based productivity differences between men and women, while under piece-rate work, the wage gap mirrors quite closely assumed productivity differences, with women receiving a wage premium in female-advantageous settings and a penalty in male-advantageous settings. Fourth, in contrast to Sweden, in Norway and the U.S. women sort more often into piece-rate work than men.

Target-the-two. A lab-in-the-field experiment on routinization

The paper investigates the cognitive determinants of routinization and creativity by means of a lab-in-the-field experiment run at the 20th edition of a mass gathering festival in Italy (“La Notte della Taranta”). Subjects play repeatedly the puzzle version of the Target-The-Two game (32 hands). In hands 1-16, the strategy that is optimal given the card distribution is always the same and it is the easiest to be discovered. Conversely, in hands 17-32, subjects are exposed to games where the optimal contextual strategy may differ from the one with which they have been made familiar. We investigate whether and how, in hands 17-32, subjects remain routinized on the familiar strategy, or creatively choose a different one. We define as “experts” those subjects who played the optimal contextual strategy in the overwhelming majority of hands 1-16. In hands 17-32, we find several subjects playing the familiar strategy even when it is not the optimal one, regardless of whether they are experts or not. This shows that routinization is deep-rooted in the cognitive individual process. Furthermore, routinization pays off only for inexpert subjects: creative inexpert subjects are slower and they fail to find the optimal contextual strategy in several hands. Among expert subjects instead, creative subjects, although still slower, need less moves than routinized ones to find the optimal contextual strategy