Late Light Curves of Normal Type Ia Supernovae

We present late-epoch optical photometry (BVRI) of seven normal/super-luminous Type Ia supernovae: SN 2000E, SN 2000ce, SN 2000cx, SN 2001C, SN 2001V, SN 2001bg, SN 2001dp. The photometry of these objects was obtained using a template subtraction method to eliminate galaxy light contamination during aperture photometry. We show the optical light curves of these supernovae out to epochs of up to ~640 days after the explosion of the supernova. We show a linear decline in these data during the epoch of 200-500 days after explosion with the decline rate in the B,V,& R bands equal to about 1.4 mag/100 days, but the decline rate of the I-band is much shallower at 0.94 mag/100 days.Comment: 33 pages, 11 figures, Accepted for publication in The Astronomical Journa

Analysing the impact of compaction of soil aggregates using X-ray microtomography and water flow simulations

Soil aggregates are structural units of soil, which create complex pore systems controlling gas and water storage and fluxes in soil. Aggregates can be destroyed during swelling and shrinking or by external forces like mechanical compaction and yet, the knowledge of how physical impact alters aggregate structure remains limited. The aim of the study was to quantify the impact of compaction on macroaggregates, mainly on the pore size distribution and water flow. In this study, aggregates (2–5 mm) were collected by dry sieving in grassland of the Fuchsenbigl–Marchfeld Critical Zone Observatory (Austria). The structural alterations of these soil aggregates under controlled compaction were investigated with a non-invasive 3D X-ray microtomography (XMT). The detailed changes in pore size distribution between aggregates (interpores, diameter >90 μm) and within the aggregates (intrapores, diameter ≤90 μm) in pre- and post-compacted soils were revealed at two soil moisture (9.3% and 18.3% w/w) and two bulk density increments (0.28 and 0.71 g cm−3 from the initial values). The soil permeability was simulated using lattice Boltzmann method (LBM) based on 3D images. Soil compaction significantly reduced total pores volume and the proportion of interpores volume and surface area, while total pore surface area and the proportion of intrapores volume and surface area increased. The increases in soil moisture tended to reduce the effects of compaction on interpores and intrapores, while the high compaction increment drastically changed the pore size distribution. The aggregate compaction decreased water penetration potential due to the increase of small intra-aggregate pores and cavities as demonstrated by LBM. Notably, the LBM results showed a significant linear correlation between the water flow rate and bulk density of soil aggregates and predicted that the water flow could be reduced by up to 97–99% at bulk density of ≥1.6 g cm−3 with soil water content of 18.3% w/w. Thus, a combination of imaging and modelling provided new insights on the compaction effects on aggregates, underpinning the importance of protecting soil structure from mechanical compaction to minimise environmental impacts of soil compaction and maintain water infiltration and percolation in arable soils

Soil food web assembly and vegetation development in a glacial chronosequence in Iceland

Worldwide human activities threaten soil quality in terms of the soil's ability to deliver ecosystem services. This ongoing process of land degradation asks for effective strategies of soil protection. In this context, it is important to understand processes that build up and regenerate soil. The present study investigated how the soil ecosystem, including soil organisms, vegetation and soil ecological processes, develops during the process of soil formation in a chronosequence in a glacier forefield in Iceland. We hypothesised that along successional age we see increases in nutrient content, vegetation cover, and plant species richness linked to increases in soil food webs biomass and complexity. In line with our expectations all measured pools of carbon and nitrogen, and vegetation cover increased with age in the glacial forefield, but plant species richness levelled off after 30 years. Soil organisms generally increased in biomass with successional age, although some of the groups of soil organisms peaked at an intermediate successional stage. In contrast to our expectations, some of the calculated food web complexity metrics such as the number of trophic groups and trophic chain length did not increase linearly, but showed an intermediate peak or even decreased with successional age. However, plant cover and pools of carbon and nitrogen still increased after 120 years. From these results we conclude that soil ecosystem development takes more than a century under Icelandic climatic conditions to fully develop in terms of vegetation succession, food web structure and biogeochemical cycling.</p

Designing all-graphene nanojunctions by covalent functionalization

We investigated theoretically the effect of covalent edge functionalization, with organic functional groups, on the electronic properties of graphene nanostructures and nano-junctions. Our analysis shows that functionalization can be designed to tune electron affinities and ionization potentials of graphene flakes, and to control the energy alignment of frontier orbitals in nanometer-wide graphene junctions. The stability of the proposed mechanism is discussed with respect to the functional groups, their number as well as the width of graphene nanostructures. The results of our work indicate that different level alignments can be obtained and engineered in order to realize stable all-graphene nanodevices

Type Ia Supernovae as Stellar Endpoints and Cosmological Tools

Empirically, Type Ia supernovae are the most useful, precise, and mature tools for determining astronomical distances. Acting as calibrated candles they revealed the presence of dark energy and are being used to measure its properties. However, the nature of the SN Ia explosion, and the progenitors involved, have remained elusive, even after seven decades of research. But now new large surveys are bringing about a paradigm shift --- we can finally compare samples of hundreds of supernovae to isolate critical variables. As a result of this, and advances in modeling, breakthroughs in understanding all aspects of SNe Ia are finally starting to happen.Comment: Invited review for Nature Communications. Final published version. Shortened, update

Prevalence of the metabolic syndrome in Luxembourg according to the Joint Interim Statement definition estimated from the ORISCAV-LUX study

ABSTRACT: BACKGROUND: The prevalence of the metabolic syndrome (MS) has been determined in many countries worldwide but never in Luxembourg. This research aimed to 1) establish the gender- and age-specific prevalence of MS and its components in the general adult population of Luxembourg, according to the most recent Joint Interim Statement (JIS) definition, by using both the high and low cut-off points to define abdominal obesity, and 2) compare and assess the degree of agreement with the Revised National Cholesterol Education Programme-Adult Treatment Panel III (R-ATPIII) and the International Diabetes Federation (IDF) definitions. METHODS: A representative stratified random sample of 1349 European subjects, aged 18-69 years, participated to ORISCAV-LUX survey. Logistic regression and odds ratios (OR) were used to study MS prevalence with respect to gender and age. The Framingham risk score (FRS) to predict the 10-year coronary heart disease (CHD) risk was calculated to compare the proportion of MS cases below or above 20%, according to both high and low waist circumference (WC) thresholds. Cohen's kappa coefficient (kappa) was utilized to measure the degree of agreement between MS definitions. RESULTS: The prevalence of the MS defined by the JIS was 28.0% and 24.7% when using the low (94/80) and the high (102/88) WC cut-off points, respectively. The prevalence was significantly higher in men than in women (OR = 2.6 and 2.3 for the low and high WC thresholds), as were all components of the MS except abdominal obesity measured by both thresholds. It also increased with age (OR values in age categories ranging from 2.7 to 28 when compared to the younger subjects for low WC and from 3.3 to 31 for the high WC cut-offs). The 10-year predicted risk of CHD by FRS did not depend on the threshold used. Globally, excellent agreement was observed between the three definitions of MS (kappa= 0.89), in particular between JIS and IDF (kappa = 0.93). Agreement was significantly higher in women than in men, and differed between age groups. CONCLUSION: Regardless of the definition used, the adult population of Luxembourg reveals a high MS prevalence. Our findings contribute to build evidence regarding the definitive construct of the MS, to help selecting the waist circumference thresholds for Europid populations, and to support the need to revise the guidelines for abdominal obesity levels

Effect of sampling effort and sampling frequency on the composition of the planktonic crustacean assemblage: a case study of the river Danube

Although numerous studies have focused on the seasonal dynamics of riverine zooplankton, little is known about its short-term variation. In order to examine the effects of sampling frequency and sampling effort, microcrustacean samples were collected at daily intervals between 13 June and 21 July of 2007 in a parapotamal side arm of the river Danube, Hungary. Samples were also taken at biweekly intervals from November 2006 to May 2008. After presenting the community dynamics, the effect of sampling effort was evaluated with two different methods; the minimal sample size was also estimated. We introduced a single index (potential dynamic information loss; to determine the potential loss of information when sampling frequency is reduced. The formula was calculated for the total abundance, densities of the dominant taxa, adult/larva ratios of copepods and for two different diversity measures. Results suggest that abundances may experience notable fluctuations even within 1 week, as do diversities and adult/larva ratios