Symmetrised Characterisation of Noisy Quantum Processes

A major goal of developing high-precision control of many-body quantum systems is to realise their potential as quantum computers. Probably the most significant obstacle in this direction is the problem of "decoherence": the extreme fragility of quantum systems to environmental noise and other control limitations. The theory of fault-tolerant quantum error correction has shown that quantum computation is possible even in the presence of decoherence provided that the noise affecting the quantum system satisfies certain well-defined theoretical conditions. However, existing methods for noise characterisation have become intractable already for the systems that are controlled in today's labs. In this paper we introduce a technique based on symmetrisation that enables direct experimental characterisation of key properties of the decoherence affecting a multi-body quantum system. Our method reduces the number of experiments required by existing methods from exponential to polynomial in the number of subsystems. We demonstrate the application of this technique to the optimisation of control over nuclear spins in the solid state.Comment: About 12 pages, 5 figure

β ‐ sheet assembly in amyloidogenic glutamic acid nanostructures: insights from X‐ray scattering and infrared nanospectroscopy

Glutamic acid–rich peptides are crucial to a variety of biological processes, including glutamatergic neurotransmission and immunological defense. Glutamic acid sequences often exhibit unusual organization into β2‐type sheets, where bifurcated H bonds formed between glutamic acid side chains and NH in amide bonds on adjacent β‐strands play a paramount role for stabilizing the molecular assembly. Herein, we investigate the self‐assembly and supramolecular structure of simplified models consisting of alternating glutamic acid/phenylalanine residues. Small‐angle X‐ray scattering and atomic force microscopy show that the aggregation pathway is characterized by the formation of small oligomers, followed by coalescence into nanofibrils and nanotapes. Amyloidogenic features are further demonstrated through fiber X‐ray diffraction, which reveal molecular packing according to cross‐β patterns, where β‐strands appear perpendicularly oriented to the long axis of nanofibrils and nanotapes. Nanoscale infrared spectroscopy from individual nanoparticles on dried samples shows a remarkable decrease of β2‐sheet content, accompanied by growth of standard β‐sheet fractions, indicating a β2‐to‐β1 transition as a consequence of the release of solvent from the interstices of peptide assemblies. Our findings highlight the key role played by water molecules in mediating H‐bond formation in β2‐sheets commonly found in amyloidogenic glutamic acid–rich aggregates

Sequence length dependence in arginine/phenylalanine oligopeptides: Implications for self-assembly and cytotoxicity

We present a detailed study on the self-assembly and cytotoxicity of arginine-rich fragments with general form [RF]n (n = 1–5). These highly simplified sequences, containing only two l-amino acids, provide suitable models for exploring both structure and cytotoxicity features of arginine-based oligopeptides. The organization of the sequences is revealed over a range of length scales, from the nanometer range down to the level of molecular packing, and their cytotoxicity toward C6 rat glioma and RAW264.7 macrophage cell lines is investigated. We found that the polymorphism is dependent on peptide length, with a progressive increase in crystalline ordering upon increasing the number of [RF] pairs along the backbone. A dependence on length was also found for other observables, including critical aggregation concentrations, formation of chiral assemblies and half maximum inhibitory concentrations (IC50). Whereas shorter peptides self-assemble into fractal-like aggregates, clear fibrillogenic capabilities are identified for longer sequences with octameric and decameric chains exhibiting crystalline phases organized into cross-β structures. Cell viability assays revealed dose-dependent cytotoxicity profiles with very similar behavior for both glioma and macrophage cell lines, which has been interpreted as evidence for a nonspecific mechanism involved in toxicity. We propose that structural organization of [RF]n peptides plays a paramount role regarding toxicity due to strong increase of local charge density induced by self-assemblies rich in cationic groups when interacting with cell membranes

Structural behaviour and gene delivery in complexes formed between DNA and arginine-containing peptide amphiphiles

We describe in depth the structure of complexes formed between DNA and two classes of arginine-containing peptide amphiphiles, namely, the lipopeptide PRW–C16 (P = proline, R = arginine, W = tryptophan, C16 = C16 : 0 alkyl chain) and the bolaamphiphile RFL4FR (R = arginine, F = phenylalanine, L = leucine). A combination of X-ray and neutron scattering provided unprecedented insights into the local structure of these complexes. Lipopeptide-based complexes self-assembled into layered structures with large-scale fractal features, hosting DNA in the interstices. Bola-amphiphile scaffolds were characterized by planar structures with DNA strands presumably sandwiched in-between peptide nanotapes. Importantly, complexation did not affect the structural integrity of DNA in either of the two complexes. The bolaamphiphile conjugates displayed high levels of molecular ordering in contrast to the liquid-crystalline features observed in lipopeptide assemblies. Peptide–DNA complexes were assessed for their potential as a means to deliver the reporter vector pEGFP-N1 into SW480 human colon carcinoma cells. Successfully transfected cells expressed green fluorescent protein. The potentiating effect of PRW–C16 on the cellular uptake of ectopic DNA was found to be much greater than that observed with RFL4FR. In contrast to the bolaamphiphile-based conjugate, the liquid-crystalline nature of the lipopeptide complex is likely to play a key role in DNA release and transfection efficiency since these weakly bound structures require lower energy expenditure during disassembly and load release

Simplificações para Redução do Custo Computacional da Pré-ênfase de Voz na Plataforma Arduino

Atualmente, existe um crescente interesse por aplicações em que a interação homem-máquina seja realizada via a voz humana. No entanto, alguns equipamentos, como telefones celulares e eletrodomésticos, possuem limitações de armazenamento e processamento, dificultando a implementação deste tipo de sistema. Neste trabalho, foram utilizadas simplificações em uma das etapas do processo de reconhecimento da fala, as quais foram comparadas e analisadas em relação à implementação tradicional. Diante das mesmas, foi obtida uma redução de até 1/5 do tempo de execução e número de ciclos de clock

Benefits of Entomophile Pollination in Crops of Brassica napus and Aspects of Plant Floral Biology

Rapeseed (Brassica napus L. var. oleifera) is an oleaginous species of the Brassicaceae family, being the third most produced oleaginous in the world. Rapeseed can produce fruits and seeds from both self-pollination and cross-pollination. However, cross-pollination rate is approximately 30% and may suffer variations due to the abundance and diversity of pollinator insects, cultivar and meteorological conditions. Different researchers have reported that pollination by insects, especially Apis mellifera honeybee, on rapeseed flowers provides an increase in productivity, improving yield and contributing to the uniformity and initial pod establishment. It is estimated that the economic value of A. mellifera honeybees for rapeseed cultivation in Brazil is US$ 8.2 million. The objective of this chapter is gathering data for a compilation of information regarding rapeseed culture and the importance of A. mellifera in Brassica napus pollination

Efeito hipolipemiante da suplementação dietética com a farinha do cubiu (solanum sessiliforum dunal) em ratos hipercolesterolêmicos

Studies with fruit and vegetables rich in dietary fber have shown lowering effects on the blood concentrations of total cholesterol (TC), acting preventively against hypercholesterolemia. The aim of this study was to analyze the chemical composition of cocona and evaluate the effect of the consumption of cocona four on lipemia of Wistar rats with hypercholesterolemia. Eight animals were used for each treatment, in 7 groups: control; 3 experimental groups with 5%, 25% and 50% of the recommended fber (AIN-93) from cocona four; 3 groups per feeding with pectin and cellulose as source of dietary fber, in the same proportions of the experimental groups. At the end of the assay, we verifed that there were not signifcant variations in the consumption of the animals and the body weight during the experiment. Treatments with cocna four were responsible for reducing the concentrations of total cholesterol (-21.6%), LDL-c (-56.8%), increasing the excretion of fecal cholesterol (+116%) and lowering the liver cholesterol (-32.1%). None of the treatments signifcantly altered the triglyceride concentrations. Treatments using pectin and cellulose show results similar to cocona. The observed results can be used in further studies aimed at the biotechnological exploitation of this fruit. © 2015, Instituto de Biociencias. All rights reserved

On the reaction time of some synchronous systems

This paper presents an investigation of the notion of reaction time in some synchronous systems. A state-based description of such systems is given, and the reaction time of such systems under some classic composition primitives is studied. Reaction time is shown to be non-compositional in general. Possible solutions are proposed, and applications to verification are discussed. This framework is illustrated by some examples issued from studies on real-time embedded systems.Comment: In Proceedings ICE 2011, arXiv:1108.014