Analysis of debris from Spacelab Space Life Sciences-1

Airborne microbiological and particulate contamination generated aboard Spacelab modules is a potential safety hazard. In order to shed light on the characteristics of these contaminants, microbial and chemical/particulate analyses were performed on debris vacuumed from cabin and avionics air filters in the Space Life Sciences-1 (SLS-1) module of the Space Transportation System 40 (STS-40) mission 1 month after landing. The debris was sorted into categories (e.g., metal, nonmetal, hair/fur, synthetic fibers, food particles, insect fragments, etc.). Elemental analysis of particles was done by energy dispersive analysis of x rays (metals) and Fourier transform infrared spectroscopy (nonmetals). Scanning electron micrographs were done of most particles. Microbiological samples were grown on R2A culture medium and identified. Clothing fibers dominated the debris by volume. Other particles, all attributed to the crew, resulted from abrasions and impacts during missions operations (e.g., paint chips, plastic, electronic scraps and clothing fibers). All bacterial species identified are commonly found in the atmosphere or on the human body. Bacillus sp. was the most frequently seen bacterium. One of the bacterial species, Enterobacter agglomerans, could cause illness in crew members with depressed immune systems

Cyclic Fluctuations, Climatic Changes and Role of Noise in Planktonic Foraminifera in the Mediterranean Sea

The study of Planktonic Foraminifera abundances permits to obtain climatic curves on the basis of percentage ratio between tropical and temperate/polar forms. Climatic changes were controlled by several phenomena as: (i) Milankovitch's cycles, produced by variations of astronomical parameters such as precession, obliquity and eccentricity; (ii) continental geodynamic evolution and orogenic belt; (iii) variations of atmospheric and oceanic currents; (iv) volcanic eruptions; (v) meteor impacts. But while astronomical parameters have a quasi-regular periodicity, the other phenomena can be considered as "noise signal" in natural systems. The interplay between cyclical astronomical variations, the "noise signal" and the intrinsic nonlinearity of the ecologic system produces strong glacial or interglacial period according to the stochastic resonance phenomenon.Comment: 6 pages, 4 figure

Determining the labour force status of Aboriginal people using a multinomial logit model

It is well documented that Aboriginal people are less likely to be in employment and more likely to be unemployed or not in the labour force than are other Australians. The aim of this paper is to consider some of the reasons for these differences in the statistical framework of a multinomial regression equation. Using 1986 Census data, results are presented for males and females on the effect of Aboriginality, education, age, family characteristics and location of residence on the probability of being in full-time employment, part-time employment, unemployment or not in the labour force. Major results include the negative effect of Aboriginality on the probability of being in full-time employment and the positive effect of more education on the probability of being in full-time employment. This latter result was particularly strong for Aboriginal women. These results will provide an important benchmark for comparing results from a similar exercise using 1991 Census data

A comparative study on low-temperature sol-gel ga-doped zinc oxide inverted PSCs

A low-temperature sol-gel Ga-doped ZnO (ZnO:Ga) thin film as the electron transport layer (ETL) for high efficiency inverted polymer solar cells (PSCs) has been realised. The ZnO:Ga precursor was prepared by dissolving zinc acetate and ethanolamine in the 2-methoxyethanol with Ga(NO3)3 at different concentration. Doped ZnO thin films were deposed on indium tin oxide (ITO)/glass substrates by spin-coating technique and the films annealed at 150°C for 5 minutes in air. To check performances of ZnO:Ga thin film were realized inverted polymer solar cells with the configuration ITO/ZnO:Ga/photoactive layer/MoO3/Ag. The photoactive layer was a blend of poly[(4,8-bis-(2-ethylhexyloxy)-benzo(1,2-b:4,5-b′)dithiophene)-2,6-diyl-alt-(4-(2-octanoyl)-3-fluorothieno[3,4-b]thiophene-)-2-6-diyl)] (PBDTTT-CF) and [6,6]-phenyl C71 butyric acid methyl ester ([70]PCBM) (1:1.5 w/w). In this work was investigated the effect of gallium concentration on the photovoltaic behavior of PSCs. The best efficiency of 7.7% was reached by using a 6 at% ZnO:Ga film as ETL

Quantum diffusion with disorder, noise and interaction

Disorder, noise and interaction play a crucial role in the transport properties of real systems, but they are typically hard to control and study both theoretically and experimentally, especially in the quantum case. Here we explore a paradigmatic problem, the diffusion of a wavepacket, by employing ultra-cold atoms in a disordered lattice with controlled noise and tunable interaction. The presence of disorder leads to Anderson localization, while both interaction and noise tend to suppress localization and restore transport, although with completely different mechanisms. When only noise or interaction are present we observe a diffusion dynamics that can be explained by existing microscopic models. When noise and interaction are combined, we observe instead a complex anomalous diffusion. By combining experimental measurements with numerical simulations, we show that such anomalous behavior can be modeled with a generalized diffusion equation, in which the noise- and interaction-induced diffusions enter in an additive manner. Our study reveals also a more complex interplay between the two diffusion mechanisms in regimes of strong interaction or narrowband noise.Comment: 11 pages, 10 figure

Exciton Dynamics in Photosynthetic Complexes: Excitation by Coherent and Incoherent Light

In this paper we consider dynamics of a molecular system subjected to external pumping by a light source. Within a completely quantum mechanical treatment, we derive a general formula, which enables to asses effects of different light properties on the photo-induced dynamics of a molecular system. We show that once the properties of light are known in terms of certain two-point correlation function, the only information needed to reconstruct the system dynamics is the reduced evolution superoperator. The later quantity is in principle accessible through ultrafast non-linear spectroscopy. Considering a direct excitation of a small molecular antenna by incoherent light we find that excitation of coherences is possible due to overlap of homogeneous line shapes associated with different excitonic states. In Markov and secular approximations, the amount of coherence is significant only under fast relaxation, and both the populations and coherences between exciton states become static at long time. We also study the case when the excitation of a photosynthetic complex is mediated by a mesoscopic system. We find that such case can be treated by the same formalism with a special correlation function characterizing ultrafast fluctuations of the mesoscopic system. We discuss bacterial chlorosom as an example of such a mesoscopic mediator and propose that the properties of energy transferring chromophore-protein complexes might be specially tuned for the fluctuation properties of their associated antennae.Comment: 12 page

Unsupplemented Artemia Diet Results in Reduced Growth and Jaw Dysmorphogenesis in Zebrafish

The number of laboratories using zebrafish as an experimental animal model has risen tremendously over the past two decades (Craig et al., 2006). As a result, the number of zebrafish facilities around the world has dramatically increased to meet the elevated demand for proper animal care and maintenance. In order to meet this demand, aquaculture facilities must employ husbandry protocols designed to produce a constant supply of healthy, viable eggs. Surprisingly, many husbandry strategies, particularly feeding protocols, are frequently passed down from members of one lab to another in a colloquial fashion without rigorous experimental validation. An ideal diet should consist of a minimal variety of foodstuffs designed to be nutritionally complete, simple to prepare, non-fouling, and cost-effective. Previous studies aimed at streamlining adult zebrafish feeding strategies in large aquaculture facilities have emphasized cost-effective, single-food models, but such diets lead to diminished survivorship and reproductive capacity (Goolish et al., 1999; Meinelt et al., 1999; Barnard & Bagatto, 2002), suggesting that these diets are lacking in some key nutritional component(s). Restricting adult fish diets to single foodstuffs, while desirable from a time and cost perspective, may not provide the trace mineral balance needed for adequate hormone and enzyme production, proper skeletal formation, and other biochemical or physiological needs. Nonetheless, given the intense breeding schedules many facilities are forced to adopt to meet research needs, a sin

Distribution of entanglement in light-harvesting complexes and their quantum efficiency

Recent evidence of electronic coherence during energy transfer in photosynthetic antenna complexes has reinvigorated the discussion of whether coherence and/or entanglement has any practical functionality for these molecular systems. Here we investigate quantitative relationships between the quantum yield of a light-harvesting complex and the distribution of entanglement among its components. Our study focusses on the entanglement yield or average entanglement surviving a time scale comparable to the average excitation trapping time. As a prototype system we consider the Fenna-Matthews-Olson (FMO) protein of green sulphur bacteria and show that there is an inverse relationship between the quantum efficiency and the average entanglement between distant donor sites. Our results suggest that longlasting electronic coherence among distant donors might help modulation of the lightharvesting function.Comment: Version accepted for publication in NJ

Dephasing-induced diffusive transport in anisotropic Heisenberg model

We study transport properties of anisotropic Heisenberg model in a disordered magnetic field experiencing dephasing due to external degrees of freedom. In the absence of dephasing the model can display, depending on parameter values, the whole range of possible transport regimes: ideal ballistic conduction, diffusive, or ideal insulating behavior. We show that the presence of dephasing induces normal diffusive transport in a wide range of parameters. We also analyze the dependence of spin conductivity on the dephasing strength. In addition, by analyzing the decay of spin-spin correlation function we discover a presence of long-range order for finite chain sizes. All our results for a one-dimensional spin chain at infinite temperature can be equivalently rephrased for strongly-interacting disordered spinless fermions.Comment: 15 pages, 9 PS figure

Motional effects on the efficiency of excitation transfer

Energy transfer plays a vital role in many natural and technological processes. In this work, we study the effects of mechanical motion on the excitation transfer through a chain of interacting molecules with application to biological scenarios of transfer processes. Our investigation demonstrates that, for various types of mechanical oscillations, the transfer efficiency is significantly enhanced over that of comparable static configurations. This enhancement is a genuine quantum signature, and requires the collaborative interplay between the quantum-coherent evolution of the excitation and the mechanical motion of the molecules; it has no analogue in the classical incoherent energy transfer. This effect may not only occur naturally, but it could be exploited in artificially designed systems to optimize transport processes. As an application, we discuss a simple and hence robust control technique.Comment: 25 pages, 11 figures; completely revised; version accepted for publicatio