Coherent Optomechanical State Transfer between Disparate Mechanical Resonators

Hybrid quantum systems have been developed with various mechanical, optical and microwave harmonic oscillators. The coupling produces a rich library of interactions including two mode squeezing, swapping interactions, back-action evasion and thermal control. In a multimode mechanical system, coupling resonators of different scales (both in frequency and mass) leverages the advantages of each resonance. For example: a high frequency, easily manipulated resonator could be entangled with a low frequency massive object for tests of gravitational decoherence. Here we demonstrate coherent optomechanical state swapping between two spatially and frequency separated resonators with a mass ratio of 4. We find that, by using two laser beams far detuned from an optical cavity resonance, efficient state transfer is possible through a process very similar to STIRAP (Stimulated Raman Adiabatic Passage) in atomic physics. Although the demonstration is classical, the same technique can be used to generate entanglement between oscillators in the quantum regime

Experimental exploration of the optomechanical attractor diagram and its dynamics

We demonstrate experimental exploration of the attractor diagram of an optomechanical system where the optical forces compensate for the mechanical losses. In this case stable self-induced oscillations occur but only for specific mirror amplitudes and laser detunings. We demonstrate that we can amplify the mechanical mode to an amplitude 500 times larger than the thermal amplitude at 300K. The lack of unstable or chaotic motion allows us to manipulate our system into a non-trivial steady state and explore the dynamics of self-induced oscillations in great detail.Comment: 6 pages, 4 figure

Vibration isolation with high thermal conductance for a cryogen-free dilution refrigerator

We present the design and implementation of a mechanical low-pass filter vibration isolation used to reduce the vibrational noise in a cryogen-free dilution refrigerator operated at 10 mK, intended for scanning probe techniques. We discuss the design guidelines necessary to meet the competing requirements of having a low mechanical stiffness in combination with a high thermal conductance. We demonstrate the effectiveness of our approach by measuring the vibrational noise levels of an ultrasoft mechanical resonator positioned above a SQUID. Starting from a cryostat base temperature of 8 mK, the vibration isolation can be cooled to 10.5 mK, with a cooling power of 113 $\mu$W at 100 mK. We use the low vibrations and low temperature to demonstrate an effective cantilever temperature of less than 20 mK. This results in a force sensitivity of less than 500 zN/$\sqrt{\mathrm{Hz}}$, and an integrated frequency noise as low as 0.4 mHz in a 1 Hz measurement bandwidth

COEXPRESSION OF CYTOCHROME P4502A6 AND HUMAN NADPH-P450 OXIDOREDUCTASE IN THE BACULOVIRUS SYSTEM

ABSTRACT: Heterologous expression using baculovirus vectors has become a popular method for the production of catalytically active cytochrome P450s (CYPs). We have systematically optimized the multiplicity of infection (MOI) for a coinfection approach for the coexpression of CYP2A6 (viral vector designated v2A6) and NADPH-P450 oxidoreductase (OR; viral vector designated vOR) using Sf9 insect cells. A 3000-fold range of MOI was examined in stationary culture and stirred suspension culture. Surprisingly, our results indicate that the best CYP2A6 catalytic activity (850-1300 pmol/ min/mg total lysate protein as measured by coumarin 7-hydroxylase activity) was obtained only when using a low MOI of v2A6 (1.5-3 ؋ 10 ؊2 ) and a vOR of 10-to 20-fold less. This activity was ϳ7-to 11-fold higher than the best activity obtained when infecting cells with v2A6 alone. At this level of coinfection, the P450 content ranged from 180 to 250 pmol/mg total lysate protein, and the NADPH cytochrome c reductase activity ranged from 350 to 520 nmol/min/mg total lysate protein. Increasing the MOI of both viruses to 50-fold higher resulted in lower overall activity with the optimum (250 pmol/min/mg total lysate protein) being seen earlier postinfection (60 vs. 72 hr). Increasing the MOI of vOR to levels comparable with those of v2A6, decreased coumarin 7-hydroxylase activity 14-fold. These results suggest that the best CYP2A6 catalytic activity depends on properly posttranslationally modified proteins accumulating in a right ratio as a result of primary, secondary, and possibly tertiary infection of both viruses. These results also suggest that high OR expression results in degradation of P450. CYPs 1 are a multienzyme, membrane-bound system that metabolizes many drugs and other xenobiotics (1). The catalytic activity of CYP enzymes requires the presence of NADPH-CYP OR. In addition, cytochrome b 5 stimulates catalytic activity for some CYP forms (2). Several efficient systems for the heterologous expression of mammalian CYP enzymes have been developed, including bacterial, yeast, and mammalian and baculovirus/insect cell-based systems (reviewed in ref. 2). Of the systems available, the baculovirus system has distinct advantages for the production of high levels of active, native CYP enzyme. Although efficient mammalian CYP expression is possible in bacterial systems, modification of the amino acid sequence is usually required for high level expression (2). Three distinct approaches have been taken for production of catalytically active CYP enzymes using baculovirus system. Expression of the CYP enzyme alone and then reconstitution with OR using purified P450s or total cell lysate (3-5), coexpression of the CYP and OR using a single virus (6), and coinfection with independent viruses containing CYP or OR (7). Each approach has unique advantages and disadvantages. Purification/reconstitution provides flexibility in controlling the CYP to OR ratio, but is time-and labor-intensive because of the need for column purifications. The single virus approach is more time-and labor-efficient (simple cell lysate can be used), but, because of the small number of promoters characterized for baculovirus expression, the ability to control the CYP to OR ratio is limited The human CYP2A6 is the only enzyme known to date responsible for coumarin 7-hydroxylase activity in human liver (9, 10). CYP2A6 also metabolically activates certain carcinogens and promutagens (for review, see refs. 1, 9, and 10). It has the highest activity for activation of the mutagen N-nitrosodiethylamine among all human P450s studied (9, 11). It also activates tobacco-specific nitrosamines 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, 1-(N-methyl-N-nitrosamino)-1-(3-pyridinyl)-4-butanal, n-nitrosonornicotine (12, 13), and the mycotoxin aflatoxin B1 In this study, we describe a systematic characterization of a coinfection approach using CYP2A6 and human OR. To obtain an overall phenomena for coexpression of P450 and OR proteins in the baculovirus system, we examined a wide range of MOI for both v2A6 and vOR, with different ratios for coinfection to determine the best ratio for optimal coumarin 7-hydroxylase catalytic activity in insect cell lysate. Materials and Methods Rabbit anti-rat 2A1 (16) and rabbit anti-rat OR (17) antibodies were described in the previous studies. Recombinant baculoviruses v2A6 and vOR This study was supported in part by SBIR Contract N43-ES-31001 from the National Institute of Environmental Health Sciences. 1 Abbreviations used are: CYP, cytochrome P450; OR, NADPH-P450 oxidoreductase; P450, cytochrome P450; MOI, multiplicity of infection (the number of virus used per cell); v2A6, a recombinant baculovirus containing the human CYP2A6 cDNA; vOR, a recombinant baculovirus containing the human OR cDNA; Sf9, Spodoptera frugiperda; pfu, plaque-forming units (measurement of infectivity of a virus); AcMNPV, Autographa californica nuclear polyhedrosis virus. Send reprint requests to: Dr. Liping Chen

XML-based genetic rules for scene boundary detection in a parallel processing environment

Genetic programming is based on Darwinian evolutionary theory that suggests that the best solution for a problem can be evolved by methods of natural selection of the fittest organisms in a population. These principles are translated into genetic programming by populating the solution space with an initial number of computer programs that can possibly solve the problem and then evolving the programs by means of mutation, reproduction and crossover until a candidate solution can be found that is close to or is the optimal solution for the problem. The computer programs are not fully formed source code but rather a derivative that is represented as a parse tree. The initial solutions are randomly generated and set to a certain population size that the system can compute efficiently. Research has shown that better solutions can be obtained if 1) the population size is increased and 2) if multiple runs are performed of each experiment. If multiple runs are initiated on many machines the probability of finding an optimal solution are increased exponentially and computed more efficiently. With the proliferation of the web and high speed bandwidth connections genetic programming can take advantage of grid computing to both increase population size and increasing the number of runs by utilising machines connected to the web. Using XML-Schema as a global referencing mechanism for defining the parameters and syntax of the evolvable computer programs all machines can synchronise ad-hoc to the ever changing environment of the solution space. Another advantage of using XML is that rules are constructed that can be transformed by XSLT or DOM tree viewers so they can be understood by the GP programmer. This allows the programmer to experiment by manipulating rules to increase the fitness of a rule and evaluate the selection of parameters used to define a solution

The macroecology of airborne pollen in Australian and New Zealand urban areas

The composition and relative abundance of airborne pollen in urban areas of Australia and New Zealand are strongly influenced by geographical location, climate and land use. There is mounting evidence that the diversity and quality of airborne pollen is substantially modified by climate change and land-use yet there are insufficient data to project the future nature of these changes. Our study highlights the need for long-term aerobiological monitoring in Australian and New Zealand urban areas in a systematic, standardised, and sustained way, and provides a framework for targeting the most clinically significant taxa in terms of abundance, allergenic effects and public health burden

Non-metric multidimensional scaling ordination (nMDS) of the major pollen taxa in Australia and New Zealand.

<p>(<b>A</b>) Distribution of urban areas using a matrix of percentage representation of major pollen taxa (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0097925#pone-0097925-t002" target="_blank">Table 2</a> and using top eight pollen taxa at each site). The pie charts depict the relative contribution of the most abundant pollen taxa in each urban area. (<b>B</b>) Distribution of pollen taxa contributing to the differentiation of aerobiology of each urban area Note: coloured squares associated with each taxa depicted in (B) match the pie chart colours shown in (A), with diamonds showing taxa with a low percentage representation. The vectors (dotted lines) for the environmental variables show positions for each variable within the environmental space. Longer vectors (higher r² values, see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0097925#pone-0097925-t003" target="_blank">Table 3</a>) indicate a stronger association of the environmental variable with site/species variation in the ordination space.</p