Quantum state tomography of molecular rotation

We show how the rotational quantum state of a linear or symmetric top rotor can be reconstructed from finite time observations of the polar angular distribution under certain conditions. The presented tomographic method can reconstruct the complete rotational quantum state in many non-adiabatic alignment experiments. Our analysis applies for measurement data available with existing measurement techniques.Comment: 7 pages, 1 figur

Principal components of thermal regimes in mountain river networks

Description of thermal regimes in flowing waters is key to understanding physical processes, enhancing predictive abilities, and improving bioassessments. Spatially and temporally sparse data sets, especially in logistically challenging mountain environments, have limited studies on thermal regimes, but inexpensive sensors coupled with crowd-sourced data collection efforts provide efficient means of developing large data sets for robust analyses. Here, thermal regimes are assessed using annual monitoring records compiled from several natural resource agencies in the northwestern United States that spanned a 5-year period (2011–2015) at 226 sites across several contiguous montane river networks. Regimes were summarized with 28 metrics and principal component analysis (PCA) was used to determine those metrics which best explained thermal variation on a reduced set of orthogonal axes. Four principal components (PC) accounted for 93.4&thinsp;% of the variation in the temperature metrics, with the first PC (49&thinsp;% of variance) associated with metrics that represented magnitude and variability and the second PC (29&thinsp;% of variance) associated with metrics representing the length and intensity of the winter season. Another variant of PCA, T-mode analysis, was applied to daily temperature values and revealed two distinct phases of spatial variability – a homogeneous phase during winter when daily temperatures at all sites were &lt;3&thinsp;∘C and a heterogeneous phase throughout the year's remainder when variation among sites was more pronounced. Phase transitions occurred in March and November, and coincided with the abatement and onset of subzero air temperatures across the study area. S-mode PCA was conducted on the same matrix of daily temperature values after transposition and indicated that two PCs accounted for 98&thinsp;% of the temporal variation among sites. The first S-mode PC was responsible for 96.7&thinsp;% of that variance and correlated with air temperature variation (r=0.92), whereas the second PC accounted for 1.3&thinsp;% of residual variance and was correlated with discharge (r=0.84). Thermal regimes in these mountain river networks were relatively simple and responded coherently to external forcing factors, so sparse monitoring arrays and small sets of summary metrics may be adequate for their description. PCA provided a computationally efficient means of extracting key information elements from the temperature data set used here and could be applied broadly to facilitate comparisons among more diverse stream types and develop classification schemes for thermal regimes.</p

Anomalous magneto-oscillations in two-dimensional systems

The frequencies of Shubnikov-de Haas oscillations have long been used to measure the unequal population of spin-split two-dimensional subbands in inversion asymmetric systems. We report self-consistent numerical calculations and experimental results which indicate that these oscillations are not simply related to the zero-magnetic-field spin-subband densities.Comment: 4 pages, 3 figures; changed content (clarifications

The traveling heads 2.0: multicenter reproducibility of quantitative imaging methods at 7 Tesla

OBJECT: This study evaluates inter-site and intra-site reproducibility at ten different 7 T sites for quantitative brain imaging. MATERIAL AND METHODS: Two subjects - termed the "traveling heads" - were imaged at ten different 7 T sites with a harmonized quantitative brain MR imaging protocol. In conjunction with the system calibration, MP2RAGE, QSM, CEST and multi-parametric mapping/relaxometry were examined. RESULTS: Quantitative measurements with MP2RAGE showed very high reproducibility across sites and subjects, and errors were in concordance with previous results and other field strengths. QSM had high inter-site reproducibility for relevant subcortical volumes. CEST imaging revealed systematic differences between the sites, but reproducibility was comparable to results in the literature. Relaxometry had also very high agreement between sites, but due to the high sensitivity, differences caused by different applications of the B1 calibration of the two RF coil types used were observed. CONCLUSION: Our results show that quantitative brain imaging can be performed with high reproducibility at 7 T and with similar reliability as found at 3 T for multicenter studies of the supratentorial brain

Repeat Composition of CenH3-chromatin and H3K9me2-marked heterochromatin in Sugar Beet (Beta vulgaris)

Kowar T, Zakrzewski F, Macas J, et al. Repeat Composition of CenH3-chromatin and H3K9me2-marked heterochromatin in Sugar Beet (Beta vulgaris). BMC Plant Biology. 2016;16(1): 120.Background Sugar beet (Beta vulgaris) is an important crop of temperate climate zones, which provides nearly 30 % of the world’s annual sugar needs. From the total genome size of 758 Mb, only 567 Mb were incorporated in the recently published genome sequence, due to the fact that regions with high repetitive DNA contents (e.g. satellite DNAs) are only partially included. Therefore, to fill these gaps and to gain information about the repeat composition of centromeres and heterochromatic regions, we performed chromatin immunoprecipitation followed by sequencing (ChIP-Seq) using antibodies against the centromere-specific histone H3 variant of sugar beet (CenH3) and the heterochromatic mark of dimethylated lysine 9 of histone H3 (H3K9me2). Results ChIP-Seq analysis revealed that active centromeres containing CenH3 consist of the satellite pBV and the Ty3-gypsy retrotransposon Beetle7, while heterochromatin marked by H3K9me2 exhibits heterogeneity in repeat composition. H3K9me2 was mainly associated with the satellite family pEV, the Ty1-copia retrotransposon family Cotzilla and the DNA transposon superfamily of the En/Spm type. In members of the section Beta within the genus Beta, immunostaining using the CenH3 antibody was successful, indicating that orthologous CenH3 proteins are present in closely related species within this section. Conclusions The identification of repetitive genome portions by ChIP-Seq experiments complemented the sugar beet reference sequence by providing insights into the repeat composition of poorly characterized CenH3-chromatin and H3K9me2-heterochromatin. Therefore, our work provides the basis for future research and application concerning the sugar beet centromere and repeat rich heterochromatic regions characterized by the presence of H3K9me2

Simple rules describe bottom-up and top-down control in food webs with alternative energy pathways

Many human influences on the world’s ecosystems have their largest direct impacts at either the top or the bottom of the food web. To predict their ecosystem-wide consequences we must understand how these impacts propagate. A long-standing, but so far elusive, problem in this endeavour is how to reduce food web complexity to a mathematically tractable, but empirically relevant system. Simplification to main energy channels linking primary producers to top consumers has been recently advocated. Following this approach, we propose a general framework for the analysis of bottom-up and top-down forcing of ecosys- tems by reducing food webs to two energy pathways originating from a limiting resource shared by com- peting guilds of primary producers (e.g. edible vs. defended plants). Exploring dynamical models of such webs we find that their equilibrium responses to nutrient enrichment and top consumer harvesting are determined by only two easily measurable topological properties: the lengths of the component food chains (odd-odd, odd-even, or even-even) and presence vs. absence of a generalist top consumer reconnecting the two pathways (yielding looped vs. branched webs). Many results generalise to other looped or branched web structures and the model can be easily adapted to include a detrital pathway

Ontogenetic diet shifts promote predator-mediated coexistence

It is widely believed that predation moderates interspecific competition and promotes prey diversity. Still, in models of two prey sharing a resource and a predator, predator-mediated coexistence occurs only over narrow ranges of resource productivity. These models have so far ignored the widespread feature of ontogenetic diet shifts in predators. Here, we theoretically explore the consequences of a diet shift from juvenile to adult predator stages for coexistence of two competing prey. We find that only very minor deviations from perfectly identical diets in juveniles and adults destroy the ‘‘traditional’’ mechanism of predator- mediated coexistence, which requires an intrinsic trade-off between prey defendedness and competitive ability. Instead, predator population structure can create an ‘‘emergent’’ competition-predation trade-off between prey, where a bottleneck in one predator stage enhances predation on the superior competitor and relaxes predation on the inferior competitor, irrespective of the latter’s intrinsic defendedness. Pronounced diet shifts therefore greatly enlarge the range of prey coexistence along a resource gradient. With diet shifts, however, coexistence usually occurs as one of two alternative states and, once lost, may not be easily restored