Infrared spectroscopy of Landau levels in graphene

We report infrared studies of the Landau level (LL) transitions in single layer graphene. Our specimens are density tunable and show \textit{in situ} half-integer quantum Hall plateaus. Infrared transmission is measured in magnetic fields up to B=18 T at selected LL fillings. Resonances between hole LLs and electron LLs, as well as resonances between hole and electron LLs are resolved. Their transition energies are proportional to $\sqrt{B}$ and the deduced band velocity is $\tilde{c}\approx1.1\times10^6$ m/s. The lack of precise scaling between different LL transitions indicates considerable contributions of many-particle effects to the infrared transition energies.Comment: 4 pages, 3 figures, to appear in Phys. Rev. Let

Prenatal antidepressant exposure and child behavioural outcomes at 7 years of age: a study within the Danish National Birth Cohort

Objective: To investigate the impact of prenatal antidepressant exposure on behavioural problems in children at 7 years of age. Design: Nationwide population-based study. Setting: Danish National Birth Cohort. Population: A cohort of 49 178 pregnant women recruited between 1996 and 2002. Methods: Data obtained from computer-assisted telephone interviews twice during pregnancy were used to identify children born to: (i) depressed women who took antidepressants during pregnancy (n = 210); (ii) depressed women who did not take any antidepressants during pregnancy (n = 231); and (iii) healthy women who were not depressed (n = 48 737). Childhood behavioural problems at 7 years of age were examined using the validated Danish parent-report version of the Strengths and Difficulties Questionnaire (SDQ). Main outcome measures: SDQ scores. Results: No associations were observed between prenatal antidepressant exposure and abnormal SDQ scores for overall problem behaviour (adjusted relative risk, aRR 1.00; 95% confidence interval, 95% CI 0.49–2.05), hyperactivity/inattention (aRR 0.99; 95% CI 0.56–1.75), or peer problems (aRR 1.04; 95% CI 0.57–1.91). Although prenatal antidepressant exposure appeared to be associated with abnormal SDQ scores on the subscales of emotional symptoms (aRR 1.68; 95% CI 1.18–2.38) and conduct problems (aRR 1.58; 95% CI 1.03–2.42), these associations were significantly attenuated following adjustment for antenatal mood status (aRR 1.20; 95% CI 0.85–1.70 and aRR 1.19; 95% CI 0.77 1.83, respectively). Untreated prenatal depression was associated with an increased risk of all behavioural outcomes evaluated, compared with unexposed children, with significant attenuation following adjustment for antenatal mood status. Conclusions: The results of this study suggest that independent of maternal illness, prenatal antidepressant exposure is not associated with an increased risk of behavioural problems in children at 7 years of age.LE Grzeskowiak, JL Morrison, TB Henrikse, BH Bech, C Obel, J Olsen, LH Pederse

Fish Consumption Measured during Pregnancy and Risk of Cardiovascular Diseases Later in Life: An Observational Prospective Study

Previous studies have indicated a protective effect of long chain n-3 PUFAs against cardiovascular disease; however, the overall evidence remains uncertain, and there is a general lack of knowledge in the field of cardiovascular epidemiology in women. Therefore, the objective of this study was to explore the association between fish intake and cardiovascular disease among 7429 women from a prospective pregnancy cohort in Aarhus, Denmark, who were followed for 12–17 years. Exposure information derived from a questionnaire sent to the women in gestation week 16, and daily fish consumption was quantified based on assumptions of standard portion sizes and food tables. Information on admissions to hospital was obtained from the Danish National Patient Registry and diagnoses of hypertensive, cerebrovascular and ischaemic heart disease were used to define the outcome: cardiovascular disease. During the follow-up period 263 events of cardiovascular disease were identified. Overall, there was no association between cardiovascular disease and fish intake, confidence intervals for effect estimates in the different fish intake groups were wide, overlapped and for all but one they encompassed unity. Restricting the analysis to women who had reported the same fish intake in a questionnaire in gestation week 30 did not alter these findings. In conclusion, our data from a prospective cohort of relatively young and initially healthy women from Aarhus linked with information from registries could not substantiate a protective effect of fish intake against cardiovascular disease

Norwegian lakes show widespread recovery from acidification; results from national surveys of lakewater chemistry 1986-1997

International audienceSurveys of 485 lakes in Norway conducted in 1986 and again in 1995 reveal widespread chemical recovery from acidification. Sulphate concentrations in lakes have decreased by 40% in acidified areas in southern Norway. This decrease has been compensated about 25% by decreases in concentrations of base cations and of 75% by increased Acid Neutralising Capacity (ANC). The increased ANC in turn reflects lower concentrations of acidic cations Aluminum (ALn+) and Hydrogen (H+). A sub-set of 78 of the 485 lakes sampled yearly between 1986 and 1997 shows that, at first most of the decrease in non-marine sulphate (SO4*) was compensated by a decrease in base cations, such that ANC remained unchanged. Then as SO4* continued to decrease, the concentrations of non- marine calcium and magnesium ((Ca+Mg)*) levelled out. Consequently, ANC increased, and H+ and Aln+ started to decrease. In eastern Norway, this shift occurred in 1989?90, and came slightly later in southern and western Norway. Similar shifts in trends in about 1991?92 can also be seen in the non-acidified areas in central and northern Norway. This shift in trends is not as pronounced in western Norway, perhaps because of the confounding influence of sea-salt episodes on water chemistry. This is the first documented national-scale recovery from acidification due to reduced acid deposition. Future climate warming and potentially increased N-leaching can counteract the positive trends in recovery from acidification

A framework for hierarchical, object-oriented simulation modeling of a steel manufacturing enterprise

This is the final report of a two-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The objective of the project is to combine detailed physical models of industrial processes with unit operations and business-level models. This would allow global and individual process control schemes to be implemented that would facilitate improved overall system performance. Intelligent decision support that employs expert system concepts (knowledge base and rules) could then also be incorporated. This project is innovative because it attempts to incorporate all levels of production-related activities from atoms to enterprise, and to integrate those activities into one comprehensive decision support tool. This project is an interdisciplinary effort requiring enterprise modeling and simulation model integration; process modeling and control; process control and optimization; chemical process modeling; and detailed molecular-level models. It represents the state of the art in enterprise modeling and simulation and incorporates cutting edge process modeling, process control, and system optimization techniques

A complete classification of spherically symmetric perfect fluid similarity solutions

We classify all spherically symmetric perfect fluid solutions of Einstein's equations with equation of state p/mu=a which are self-similar in the sense that all dimensionless variables depend only upon z=r/t. For a given value of a, such solutions are described by two parameters and they can be classified in terms of their behaviour at large and small distances from the origin; this usually corresponds to large and small values of z but (due to a coordinate anomaly) it may also correspond to finite z. We base our analysis on the demonstration that all similarity solutions must be asymptotic to solutions which depend on either powers of z or powers of lnz. We show that there are only three similarity solutions which have an exact power-law dependence on z: the flat Friedmann solution, a static solution and a Kantowski-Sachs solution (although the latter is probably only physical for a1/5, there are also two families of solutions which are asymptotically (but not exactly) Minkowski: the first is asymptotically Minkowski as z tends to infinity and is described by one parameter; the second is asymptotically Minkowski at a finite value of z and is described by two parameters. A complete analysis of the dust solutions is given, since these can be written down explicitly and elucidate the link between the z>0 and z<0 solutions. Solutions with pressure are then discussed in detail; these share many of the characteristics of the dust solutions but they also exhibit new features.Comment: 63 pages. To appear in Physical Review