Universal Control of Nuclear Spins Via Anisotropic Hyperfine Interactions

We show that nuclear spin subsystems can be completely controlled via microwave irradiation of resolved anisotropic hyperfine interactions with a nearby electron spin. Such indirect addressing of the nuclear spins via coupling to an electron allows us to create nuclear spin gates whose operational time is significantly faster than conventional direct addressing methods. We experimentally demonstrate the feasibility of this method on a solid-state ensemble system consisting of one electron and one nuclear spin.Comment: RevTeX4, 8 pages, 8 figure

Trapped ion mobility spectrometry and PASEF enable in-depth lipidomics from minimal sample amounts

A comprehensive characterization of the lipidome from limited starting material remains very challenging. Here we report a high-sensitivity lipidomics workflow based on nanoflow liquid chromatography and trapped ion mobility spectrometry (TIMS). Taking advantage of parallel accumulation-serial fragmentation (PASEF), we fragment on average 15 precursors in each of 100 ms TIMS scans, while maintaining the full mobility resolution of co-eluting isomers. The acquisition speed of over 100 Hz allows us to obtain MS/MS spectra of the vast majority of isotope patterns. Analyzing 1 mu L of human plasma, PASEF increases the number of identified lipids more than three times over standard TIMS-MS/MS, achieving attomole sensitivity. Building on high intra- and inter-laboratory precision and accuracy of TIMS collisional cross sections (CCS), we compile 1856 lipid CCS values from plasma, liver and cancer cells. Our study establishes PASEF in lipid analysis and paves the way for sensitive, ion mobility-enhanced lipidomics in four dimensions

Direct Observation of Quantum Coherence in Single-Molecule Magnets

Direct evidence of quantum coherence in a single-molecule magnet in frozen solution is reported with coherence times as long as T2 = 630 ns. We can strongly increase the coherence time by modifying the matrix in which the single-molecule magnets are embedded. The electron spins are coupled to the proton nuclear spins of both the molecule itself and interestingly, also to those of the solvent. The clear observation of Rabi oscillations indicates that we can manipulate the spin coherently, an essential prerequisite for performing quantum computations.Comment: 5 Pages, 4 Figures, final version published in PR

Transport and recombination through weakly coupled localized spin pairs in semiconductors during coherent spin excitation

Semi-analytical predictions for the transients of spin-dependent transport and recombination rates through localized states in semiconductors during coherent electron spin excitation are made for the case of weakly spin-coupled charge carrier ensembles. The results show that the on-resonant Rabi frequency of electrically or optically detected spin-oscillation doubles abruptly as the strength of the resonant microwave field gamma B_1 exceeds the Larmor frequency separation within the pair of charge carrier states between which the transport or recombination transition takes place. For the case of a Larmor frequency separation of the order of gamma B_1 and arbitrary excitation frequencies, the charge carrier pairs exhibit four different nutation frequencies. From the calculations, a simple set of equations for the prediction of these frequencies is derived

T1T_1- and T2T_2-spin relaxation time limitations of phosphorous donor electrons near crystalline silicon to silicon dioxide interface defects

A study of donor electron spins and spin--dependent electronic transitions involving phosphorous ($^{31}$P) atoms in proximity of the (111) oriented crystalline silicon (c-Si) to silicon dioxide (SiO$_{2}$) interface is presented for [$^{31}$P] = 10$^{15}$ $\mathrm{cm}^{-3}$ and [$^{31}$P] = 10$^{16}$ $\mathrm{cm}^{-3}$ at about liquid $^4$He temperatures ($T = 5$ $\mathrm{K} - 15$ $\mathrm{K}$). Using pulsed electrically detected magnetic resonance (pEDMR), spin--dependent transitions between the \Phos donor state and two distinguishable interface states are observed, namely (i) \Pb centers which can be identified by their characteristic anisotropy and (ii) a more isotropic center which is attributed to E$^\prime$ defects of the \sio bulk close to the interface. Correlation measurements of the dynamics of spin--dependent recombination confirm that previously proposed transitions between \Phos and the interface defects take place. The influence of these electronic near--interface transitions on the \Phos donor spin coherence time $T_2$ as well as the donor spin--lattice relaxation time $T_1$ is then investigated by comparison of spin Hahn--echo decay measurements obtained from conventional bulk sensitive pulsed electron paramagnetic resonance and surface sensitive pEDMR, as well as surface sensitive electrically detected inversion recovery experiments. The measurements reveal that both $T_2$ and $T_1$ of \Phos donor electrons spins in proximity of energetically lower interface states at $T\leq 13$ K are reduced by several orders of magnitude

Optimizing sampling effort and information content of biodiversity surveys: a case study of alpine grassland

Aims: Current rates of biodiversity loss do not allow for inefficient monitoring. Optimized monitoring maximizes the ratio between information and sampling effort (i.e., time and costs). Sampling effort increases with the number and size of sampling units. We hypothesize that an optimal size and number of sampling units can be determined providing maximal information via minimal effort. We apply an approach that identifies the optimal size and number of sampling quadrats. The approach can be adapted to any study system. Here we focus on alpine grassland, a diverse but threatened ecosystem. Location: Gran Paradiso National Park, Italy. Methods: We sampled nine 20 m 7 20 m-plots. Each plot consisted of 100 2 m 7 2 m-subplots. Species richness and Shannon diversity were quantified for different sizes and quantities of subplots. We simulated larger subplot sizes by unifying adjacent 2 m 7 2 m-subplots. Shannon's information entropy was used to quantify information content among richness and diversity values resulting from different subplot sizes and quantities. The optimal size and number of subplots is the lowest size and number of subplots returning maximal information. This optimal subplot size and number was determined by Mood's median test and segmented linear regression, respectively. Results: The information content among richness values increased with subplot size, irrespective of the number of subplots. Therefore, the largest subplot size available is the optimal size for information about richness. Information content among diversity values increased with subplot size if 18 or less subplots were considered, and decreased if at least 27 subplots were sampled. The subplot quantity consequently determined whether the smallest or largest subplot size available is the optimal size, and whether the optimal size can be generalized across richness and diversity. Given a 2 m 7 2 m size, we estimated an optimal quantity of 54. Given a size of 4 m 7 4 m, we estimated an optimal number of 36. The optimal number of plots can be generalized across both indices because it barely differed between the indices given a fixed subplot size. Conclusions: The information content among richness and diversity values depends on the sampling scale. Shannon's information entropy can be used to identify the optimal number and size of plots that return most information with least sampling effort. Our approach can be adapted to other study systems to create an efficient in-situ sampling design, which improves biodiversity monitoring and conservation under rapid environmental change

Pulmonary Toxoplasmosis, a Rare but Severe Manifestation of a Common Opportunistic Infection in Late HIV Presenters: Report of Two Cases

Abstract : Pulmonary toxoplasmosis is rare, particularly in the era of highly active antiretroviral therapy (HAART). Here, we describe two severe cases in patients not known to be HIV-infected. In both patients, early diagnosis and therapy led to a favourable outcome. Pulmonary toxoplasmosis should be considered in the differential diagnosis in potentially HIV-infected patients with respiratory symptom

Sustainability assessment of organic dairy farms in mountainous areas of Austria

Dairy farming plays a major role in mountainous regions of Austria, mostly due to high proportion of grasslands. In general, Austria’s dairy farming faces challenges regarding sustainability, e.g. environmental impacts, but specifically for alpine areas low productivity and dependency on direct payments are lowering sustainability. Organic farming is considered as a strategy to overcome these challenges. Considering this general background, we analysed the sustainability performance and its main drivers of organic dairy farms in mountainous regions of Austria

Time-optimal synthesis of unitary transformations in coupled fast and slow qubit system

In this paper, we study time-optimal control problems related to system of two coupled qubits where the time scales involved in performing unitary transformations on each qubit are significantly different. In particular, we address the case where unitary transformations produced by evolutions of the coupling take much longer time as compared to the time required to produce unitary transformations on the first qubit but much shorter time as compared to the time to produce unitary transformations on the second qubit. We present a canonical decomposition of SU(4) in terms of the subgroup SU(2)xSU(2)xU(1), which is natural in understanding the time-optimal control problem of such a coupled qubit system with significantly different time scales. A typical setting involves dynamics of a coupled electron-nuclear spin system in pulsed electron paramagnetic resonance experiments at high fields. Using the proposed canonical decomposition, we give time-optimal control algorithms to synthesize various unitary transformations of interest in coherent spectroscopy and quantum information processing.Comment: 8 pages, 3 figure

Data on alpine grassland diversity in Gran Paradiso National Park, Italy

The diversity of alpine grassland species and their functional traits constitute alpine ecosystem functioning and services that support human-wellbeing. However, alpine grassland diversity is threatened by land use and climate change. Field surveys and monitoring are necessary to understand and preserve such endangered ecosystems. Here we describe data on abundances (percentage cover) of 247 alpine plant species (including mosses and lichens) inside nine 20 m by 20 m plots that were subdivided into 2 m by 2 m subplots. The nine plots are located in Gran Paradiso National Park, Italy. They cover three distinct alpine vegetation subtypes (\u2018pure\u2019 natural grassland, sparsely vegetated \u2018rocky\u2019 grassland, and wetland) in each of three valleys (Bardoney, Colle de Nivolet and Levionaz) between 2200 and 2700 m a.s.l., i.e. above the treeline. The vegetation survey was conducted in 2015 at the peak of vegetation development during August. The dataset is provided as supplementary material and associated with the research article \u201cOptimizing sampling effort and information content of biodiversity surveys: a case study of alpine grassland\u201d [1]. See [1] for data interpretation