Network Synthesis of Linear Dynamical Quantum Stochastic Systems

The purpose of this paper is to develop a synthesis theory for linear dynamical quantum stochastic systems that are encountered in linear quantum optics and in phenomenological models of linear quantum circuits. In particular, such a theory will enable the systematic realization of coherent/fully quantum linear stochastic controllers for quantum control, amongst other potential applications. We show how general linear dynamical quantum stochastic systems can be constructed by assembling an appropriate interconnection of one degree of freedom open quantum harmonic oscillators and, in the quantum optics setting, discuss how such a network of oscillators can be approximately synthesized or implemented in a systematic way from some linear and non-linear quantum optical elements. An example is also provided to illustrate the theory.Comment: Revised and corrected version, published in SIAM Journal on Control and Optimization, 200

Influence of convective transport on tropospheric ozone and its precursors in a chemistry-climate model

The impact of convection on tropospheric O₃ and its precursors has been examined in a coupled chemistry-climate model. There are two ways that convection affects O₃. First, convection affects O₃ by vertical mixing of O₃ itself. Convection lifts lower tropospheric air to regions where the O₃ lifetime is longer, whilst mass-balance subsidence mixes O₃-rich upper tropospheric (UT) air downwards to regions where the O₃ lifetime is shorter. This tends to decrease UT O₃ and the overall tropospheric column of O₃. Secondly, convection affects O₃ by vertical mixing of O₃ precursors. This affects O₃ chemical production and destruction. Convection transports isoprene and its degradation products to the UT where they interact with lightning NO_x to produce PAN, at the expense of NO_x. In our model, we find that convection reduces UT NO_x through this mechanism; convective down-mixing also flattens our imposed profile of lightning emissions, further reducing UT NO_x. Over tropical land, which has large lightning NO_x emissions in the UT, we find convective lofting of NO_x from surface sources appears relatively unimportant. Despite UT NO_x decreases, UT O₃ production increases as a result of UT HO_x increases driven by isoprene oxidation chemistry. However, UT O₃ tends to decrease, as the effect of convective overturning of O₃ itself dominates over changes in O₃ chemistry. Convective transport also reduces UT O₃ in the mid-latitudes resulting in a 13% decrease in the global tropospheric O₃ burden. These results contrast with an earlier study that uses a model of similar chemical complexity. Differences in convection schemes as well as chemistry schemes – in particular isoprene-driven changes are the most likely causes of such discrepancies. Further modelling studies are needed to constrain this uncertainty range

The Las Campanas Infra-red Survey. V. Keck Spectroscopy of a large sample of Extremely Red Objects

(Abridged) We present deep Keck spectroscopy, using the DEIMOS and LRIS spectrographs, of a large and representative sample of 67 ``Extremely Red Objects'' (EROs) to H=20.5, with I-H>3.0, in three of the Las Campanas Infrared Survey fields. Spectroscopic redshifts are determined for 44 sources, of which only two are contaminating low mass stars. When allowance is made for incompleteness, the spectroscopic redshift distribution closely matches that predicted earlier on the basis of photometric data. Our spectra are of sufficient quality that we can address the important question of the nature and homogeneity of the z>0.8 ERO population. A dominant old stellar population is inferred for 75% of our spectroscopic sample; a higher fraction than that seen in smaller, less-complete samples with broader photometric selection criteria (e.g. R-K). However, only 28% have spectra with no evidence of recent star formation activity, such as would be expected for a strictly passively-evolving population. More than ~30% of our absorption line spectra are of the `E+A' type with prominent Balmer absorption consistent, on average, with mass growth of 5-15% in the past Gyr. We use our spectroscopic redshifts to improve earlier estimates of the spatial clustering of this population as well as to understand the significant field-to-field variation. Our spectroscopy enables us to pinpoint a filamentary structure at z=1.22 in the Chandra Deep Field South. Overall, our study suggests that the bulk of the ERO population is an established population of clustered massive galaxies undergoing intermittent activity consistent with continued growth over the redshift interval 0.8<z<1.6.Comment: 27 pages, including 14 figures and appendix of spectra (at low resolution). Full resolution paper can be found at http://www.ast.cam.ac.uk/~md . To appear in MNRA

Study of radiation hazards to man on extended near earth missions

Radiation hazards to man on extended near earth mission

NASA's progress in nuclear electric propulsion technology

The National Aeronautics and Space Administration (NASA) has established a requirement for Nuclear Electric Propulsion (NEP) technology for robotic planetary science mission applications with potential future evolution to systems for piloted Mars vehicles. To advance the readiness of NEP for these challenging missions, a near-term flight demonstration on a meaningful robotic science mission is very desirable. The requirements for both near-term and outer planet science missions are briefly reviewed, and the near-term baseline system established under a recent study jointly conducted by the Lewis Research Center (LeRC) and the Jet Propulsion Laboratory (JPL) is described. Technology issues are identified where work is needed to establish the technology for the baseline system, and technology opportunities which could provide improvement beyond baseline capabilities are discussed. Finally, the plan to develop this promising technology is presented and discussed

Arkansas Cotton Variety Test 2004

The primary aim of the Arkansas Cotton Variety Test is to provide unbiased data regarding the agronomic performance of cotton varieties and advanced breeding lines in the major cotton-growing areas of Arkansas. This information helps seed dealers establish marketing strategies and assists producers in choosing varieties to plant

NHEJ protects mycobacteria in stationary phase against the harmful effects of desiccation

The physiological role of the non-homologous end-joining (NHEJ) pathway in the repair of DNA double-strand breaks (DSBs) was examined in Mycobacterium smegmatis using DNA repair mutants (DeltarecA, Deltaku, DeltaligD, Deltaku/ligD, DeltarecA/ku/ligD). Wild-type and mutant strains were exposed to a range of doses of ionizing radiation at specific points in their life-cycle. NHEJ-mutant strains (Deltaku, DeltaligD, Deltaku/ligD) were significantly more sensitive to ionizing radiation (IR) during stationary phase than wild-type M. smegmatis. However, there was little difference in IR sensitivity between NHEJ-mutant and wild-type strains in logarithmic phase. Similarly, NHEJ-mutant strains were more sensitive to prolonged desiccation than wild-type M. smegmatis. A DeltarecA mutant strain was more sensitive to desiccation and IR during both stationary and especially in logarithmic phase, compared to wild-type strain, but it was significantly less sensitive to IR than the DeltarecA/ku/ligD triple mutant during stationary phase. These data suggest that NHEJ and homologous recombination are the preferred DSB repair pathways employed by M. smegmatis during stationary and logarithmic phases, respectively

Utilising the ubiquity of the cell phone to record physiological activities

Lifelogging is a term used to describe recording different aspects of your daily life, in digital form, for your own exclusive personal use. It is a form of reverse surveillance, sometimes termed sousveillance, referring to us - the subjects - doing the watching, of ourselves. In today's healthcare world where we react to conditions that have already developed, lifelogging technologies may offer a glimpse into a future world of proactive healthcare where symptoms of conditions are detected at much earlier stages. At the end of last year it was estimated that there were 4 billion cell phones in the world, in comparison to just over 1 billon PCs. In this presentation I will discuss a framework, which leverages the ubiquity of the cell phone, to aggregate multiple wearable biological sensors. This physiological lifelogged data can then be easily queried via an interface which utilises contextual memory retrieval cues to assist people remember what type of activity they were doing at a particular time. This may be helpful for the diagnosis of potential medical conditions e.g. to explain that my heart rate was very high because I was at the gym, or that I had a disturbed night's sleep because I was in an unfamiliar hotel room