ATP-independent Control of Vac8 Palmitoylation by a SNARE Subcomplex on Yeast Vacuoles

Yeast vacuole fusion requires palmitoylated Vac8. We previously showed that Vac8 acylation occurs early in the fusion reaction, is blocked by antibodies against Sec18 (yeast N-ethylmaleimide-sensitive fusion protein (NSF)), and is mediated by the R-SNARE Ykt6. Here we analyzed the regulation of this reaction on purified vacuoles. We show that Vac8 acylation is restricted to a narrow time window, is independent of ATP hydrolysis by Sec18, and is stimulated by the ion chelator EDTA. Analysis of vacuole protein complexes indicated that Ykt6 is part of a complex distinct from the second R-SNARE, Nyv1. We speculate that during vacuole fusion, Nyv1 is the classical R-SNARE, whereas the Ykt6-containing complex has a novel function in Vac8 palmitoylation

Quantum gate characterization in an extended Hilbert space

We describe an approach for characterizing the process of quantum gates using quantum process tomography, by first modeling them in an extended Hilbert space, which includes non-qubit degrees of freedom. To prevent unphysical processes from being predicted, present quantum process tomography procedures incorporate mathematical constraints, which make no assumptions as to the actual physical nature of the system being described. By contrast, the procedure presented here ensures physicality by placing physical constraints on the nature of quantum processes. This allows quantum process tomography to be performed using a smaller experimental data set, and produces parameters with a direct physical interpretation. The approach is demonstrated by example of mode-matching in an all-optical controlled-NOT gate. The techniques described are non-specific and could be applied to other optical circuits or quantum computing architectures.Comment: 4 pages, 2 figures, REVTeX (published version

Fluxes of microbes, organic aerosols, dust, sea-salt Na ions, non-sea-salt Ca ions, and methanesulfonate onto Greenland and Antarctic ice

Using a spectrofluorimeter with 224-nm laser excitation and six emission bands from 300 to 420 nm to measure fluorescence intensities at 0.3-mm depth intervals in ice cores, we report results of the first comparative study of concentrations of microbial cells (using the spectrum of protein-bound tryptophan (Trp) as a proxy) and of aerosols with autofluorescence spectra different from Trp (denoted "non-Trp") as a function of depth in ice cores from West Antarctica (WAIS Divide and Siple Dome) and Greenland (GISP2). The ratio of fluxes of microbial cells onto West Antarctic (WAIS Divide) versus Greenland sites is 0.13±0.06; the ratio of non-Trp aerosols onto WAIS Divide versus Greenland sites is 0.16±0.08; and the ratio of non-sea-salt Ca<sup>2+</sup> ions (a proxy for dust grains) onto WAIS Divide versus Greenland sites is 0.06±0.03. All of these are roughly comparable to the ratio of fluxes of dust onto Antarctic versus Greenland sites (0.08±0.05). By contrast to those values, which are considerably lower than unity, the ratio of fluxes of methanesulfonate (MSA) onto Antarctic versus Greenland sites is 1.9±0.4 and the ratio of sea-salt Na<sup>2+</sup> ions onto WAIS Divide versus Greenland sites is 3.0±2. These ratios are more than an order of magnitude higher than those in the first grouping. We infer that the correlation of microbes and non-Trp aerosols with non-sea-salt Ca and dust suggests a largely terrestrial rather than marine origin. The lower fluxes of microbes, non-Trp aerosols, non-sea-salt Ca and dust onto WAIS Divide ice than onto Greenland ice may be due to the smaller areas of their source regions and less favorable wind patterns for transport onto Antarctic ice than onto Greenland ice. The correlated higher relative fluxes of MSA and marine Na onto Antarctic versus Greenland ice is consistent with the view that both originate largely on or around sea ice, with the Antarctic sea ice being far more extensive than that around Greenland

Efeito de aditivos em substrato de arroz para produção de conídios de Metarhizium anisopliae (Metsch.) Sorok. e Beauveria bassiana (Bals.) Vuill.

O incremento de meios de cultura com diversas fontes de carbono e nitrogênio, principalmente de meios a base de produtos vegetais, tem sido estudado com o objetivo de aumentar a produtividade de fungos entomopatogênicos. Assim, o presente trabalho teve como objetivo avaliar o efeito de aditivos na produção dos fungos entomopatogênicos Metarhizium anisopliae e Beauveria bassiana em substrato de arroz. A produção e a viabilidade de conídios em meio sólido de arroz foi avaliada utilizando os diferentes aditivos: caldo de batata (5%; 10%: 15% e 20%), lactose (1 g; 2 g; 3 g e 4 g;), extrato de levedura (0,005 g; 0,01 g e 0,1 g), além dos sais: nitrato de sódio; cloreto de potássio; cloreto de cálcio; sulfato de magnésio e ácido ascórbico na concentração 0,01 g. Cada tratamento teve quatro repetições, sendo o tratamento testemunha constituído apenas por substrato de arroz. Os dados foram submetidos à análise de variância e as médias comparadas por regressão e teste de Tukey (P≤0,05). Verificou-se que o aumento da concentração de aditivos no meio de cultura de arroz causou uma pequena redução na produção de conídios de ambos os fungos avaliados, exceto no tratamento extrato de levedura 0,005 g e lactose 1 g onde houve um incremento na produção do fungo M. anisopliae (2,31×108 e 1,89×108 conídios.g-1, respectivamente). A viabilidade dos conídios não foi afetada pelos aditivos no meio de cultura. A adição de 0,01 g de cloreto de potássio aumentou significativamente a produção de M. anisopliae e os demais tratamentos não afetaram a produção deste fungo. A adição de sais minerais ao meio de cultivo não afetou a produção de B. bassiana. A germinação dos conídios de M. anisopliae não foi afetada pela adição de sais minerais ao meio de cultura. Já para B. bassiana o tratamento nitrato de sódio diferiu estatisticamente dos tratamentos sulfato de magnésio e cloreto de potássio, os demais tratamentos não apresentaram diferenças significativas em relação ao tratamento testemunha

Optical quantum computing with photons of arbitrarily low fidelity and purity

Linear optics quantum computing (LOQC) is a leading candidate for the implementation of large scale quantum computers. Here quantum information is encoded into the quantum states of light and computation proceeds via a linear optics network. It is well known that in such schemes there are stringent requirements on the spatio-temporal structure of photons -- they must be completely indistinguishable and of very high purity. We show that in the Boson-sampling model for LOQC these conditions may be significantly relaxed. We present evidence that by increasing the size of the system we can implement a computationally hard algorithm even if our photons have arbitrarily low fidelity and purity. These relaxed conditions make Boson-sampling LOQC within reach of present-day technology.Comment: Version submitted to Phys. Rev.

Simultaneous Matrix Diagonalization for Structural Brain Networks Classification

This paper considers the problem of brain disease classification based on connectome data. A connectome is a network representation of a human brain. The typical connectome classification problem is very challenging because of the small sample size and high dimensionality of the data. We propose to use simultaneous approximate diagonalization of adjacency matrices in order to compute their eigenstructures in more stable way. The obtained approximate eigenvalues are further used as features for classification. The proposed approach is demonstrated to be efficient for detection of Alzheimer's disease, outperforming simple baselines and competing with state-of-the-art approaches to brain disease classification

Error tolerance of the BosonSampling model for linear optics quantum computing

Linear optics quantum computing (LOQC) is a promising approach to implementing scalable quantum computation (QC). However, this approach has very demanding physical resource requirements. Recently, Aaronson & Arkhipov showed that a simplified model, which avoids the requirement for fast feed-forward and post-selection, while likely not capable of solving BQP-complete problems efficiently, can solve an interesting sampling problem, believed to be classically hard. Loss and mode-mismatch are the dominant sources of error in such systems. We provide evidence that even lossy systems, or systems with mode-mismatch, are likely to be classically hard to simulate. This is of practical interest to experimentalists wishing to demonstrate such systems, since it suggests that even with errors in their implementation, they are likely implementing an algorithm which is classically hard to simulate. Our results also equivalently apply to the multi-walker quantum walk model.Comment: 6 pages, 3 figure