Numerical study of the optical nonlinearity of doped and gapped graphene: From weak to strong field excitation

Numerically solving the semiconductor Bloch equations within a phenomenological relaxation time approximation, we extract both the linear and nonlinear optical conductivities of doped graphene and gapped graphene under excitation by a laser pulse. We discuss in detail the dependence of second harmonic generation, third harmonic generation, and the Kerr effects on the doping level, the gap, and the electric field amplitude. The numerical results for weak electric fields agree with those calculated from available analytic perturbation formulas. For strong electric fields when saturation effects are important, all the effective third order nonlinear response coefficients show a strong field dependence.Comment: 12 pages with 9 figure

Third order nonlinearity of graphene: effects of phenomenological relaxation and finite temperature

We investigate the effect of phenomenological relaxation parameters on the third order optical nonlinearity of doped graphene by perturbatively solving the semiconductor Bloch equation around the Dirac points. An analytic expression for the nonlinear conductivity at zero temperature is obtained under the linear dispersion approximation. With this analytic formula as starting point, we construct the conductivity at finite temperature and study the optical response to a laser pulse of finite duration. We illustrate the dependence of several nonlinear optical effects, such as third harmonic generation, Kerr effects and two photon absorption, parametric frequency conversion, and two color coherent current injection, on the relaxation parameters, temperature, and pulse duration. In the special case where one of the electric fields is taken as a dc field, we investigate the dc-current and dc-field induced second order nonlinearities, including dc-current induced second harmonic generation and difference frequency generation.Comment: 23+ pages, 10 figures. In this version we correct a sign typo in Eq. (25), for which we thank the discussion in the work http://arxiv.org/abs/1506.00534v

The AMC Linear Disability Score in patients with newly diagnosed Parkinson disease

Objective: The aim of this study was to examine the clinimetric properties of the AMC Linear Disability Score (ALDS), a new generic disability measure based on Item Response Theory, in patients with newly diagnosed Parkinson disease (PD).\ud \ud Methods: A sample of 132 patients with PD was evaluated using the Hoehn and Yahr (H&Y), the Unified PD Rating Scale motor examination, the Schwab and England scale (S&E), the Short Form–36, the PD Quality of Life Questionnaire, and the ALDS.\ud \ud Results: The internal consistency reliability of the ALDS was good ([alpha] = 0.95) with 55 items extending the sufficient item-total correlation criterion (r > 0.20). The ALDS was correlated with other disability measures (r = 0.50 to 0.63) and decreasingly associated with measures reflecting impairments (r = 0.36 to 0.37) and mental health (r = 0.23 to -0.01). With regard to know-group validity, the ALDS indicated that patients with more severe PD (H&Y stage 3) were more disabled than patients with mild (H&Y stage 1) or moderate PD (H&Y stage 2) (p < 0.0001). The ALDS discriminated between more or less severe extrapyramidal symptoms (p = 0.001) and patients with postural instability showed lower ALDS scores compared to patients without postural instability (p = < 0.0001). Compared to the S&E (score 100% = 19%), the ALDS showed less of a ceiling effect (5%).\ud \ud Conclusion: The AMC Linear Disability Score is a flexible, feasible, and clinimetrically promising instrument to assess the level of disability in patients with newly diagnosed Parkinson disease

Dutch disease and the mitigation effect of migration: Evidence from Canadian provinces

This paper looks at whether immigration can mitigate the Dutch disease effects associated with booms in natural resource sectors. We first derive predicted changes in the size of the non-tradable sector from a small general-equilibrium model à la Obstfeld-Rogoff, supplemented by a resource income and a varying labour supply. Using data for Canadian provinces, we test for the existence of a mitigating effect of immigration in terms of an increase in the size of the non-tradable sector triggered by the positive resource shock in booming regions. We find evidence of such an effect for the aggregate inflow of migrants. Disentangling those flows by type of migrants, we find that the mitigation effect is due mostly to interprovincial migration and temporary international migration. There is no evidence of such an effect for permanent international immigration. Nevertheless, interprovincial migration also results in a spreading effect of Dutch disease from booming to non-booming provinces

Verkenning mogelijkheden om energie-efficiëntie in de rozenteelt te verbeteren. Een modelstudie

Energie is verreweg de grootste kostenpost in de rozenteelt (ca. 40%) en is de afgelopen jaren sterk toegenomen door de toename van de belichtingsintensiteit en van het aantal belichtingsuren. De rentabiliteit staat de laatste jaren onder druk. Met als doel energiebesparing met behoud van rendabiliteit en als uitgangspunt geen grote aanpassingen in kasuitrusting of technologie zijn op basis van divers onderzoek een viertal alternatieve teeltstrategieën beschreven met potentie de energie'input in MJ per tak te verlagen. Om inzicht te geven in de te bereiken energiebesparing en in de consequenties voor de productie, de kwaliteit, en het economisch rendement zijn de strategieën na bepaling van de uitgangspunten met energetische en economische berekeningen vergelegen met een referentieteelt (KWIN 2008). De gehanteerde prijzen voor gas en elektriciteit zijn gebaseerd op het prijsniveau van december 200

Understanding life together: A brief history of collaboration in biology

AbstractThe history of science shows a shift from single-investigator ‘little science’ to increasingly large, expensive, multinational, interdisciplinary and interdependent ‘big science’. In physics and allied fields this shift has been well documented, but the rise of collaboration in the life sciences and its effect on scientific work and knowledge has received little attention. Research in biology exhibits different historical trajectories and organisation of collaboration in field and laboratory – differences still visible in contemporary collaborations such as the Census of Marine Life and the Human Genome Project. We employ these case studies as strategic exemplars, supplemented with existing research on collaboration in biology, to expose the different motives, organisational forms and social dynamics underpinning contemporary large-scale collaborations in biology and their relations to historical patterns of collaboration in the life sciences. We find the interaction between research subject, research approach as well as research organisation influencing collaboration patterns and the work of scientists

Machine Body Language: Expressing a Smart Speaker’s Activity with Intelligible Physical Motion

People’s physical movement and body language implicitly convey what they think and feel, are doing or are about to do. In contrast, current smart speakers miss out on this richness of body language, primarily relying on voice commands only. We present QUBI, a dynamic smart speaker that leverages expressive physical motion – stretching, nodding, turning, shrugging, wiggling, pointing and leaning forwards/backwards – to convey cues about its underlying behaviour and activities. We conducted a qualitative Wizard of Oz lab study, in which 12 participants interacted with QUBI in four scripted scenarios. From our study, we distilled six themes: (1) mirroring and mimicking motions; (2) body language to supplement voice instructions; (3) anthropomorphism and personality; (4) audio can trump motion; (5) reaffirming uncertain interpretations to support mutual understanding; and (6) emotional reactions to QUBI’s behaviour. From this, we discuss design implications for future smart speakers