The diversity of globin-coupled sensors

AbstractThe recently discovered globin-coupled sensors (GCSs) are heme-containing two-domain transducers distinct from the PAS domain superfamily. We have identified an additional 22 GCSs with varying multi-domain C-terminal transmitters through a search of the complete and incomplete microbial genome datasets. The GCS superfamily is composed of two major subfamilies: the aerotactic and gene regulators. We postulate the existence of protoglobin in Archaea as the predecessor to the chimeric GCS

Waterproofing 3D-Printed Parts

Team Operation: Watertight has been given the task to design a technique for printing or a post process application for treating fused deposition modeled parts to become impermeable to water. The final design report shows the progress made over the past academic year in order to create this process. In the fall, the team brainstormed many possible solutions and was able to narrow them down with the support of our sponsors, accompanied by a lot of research. This research consisted of many literature searches and patent searches to ensure there was not a process already designed for this application. Last semester, four concepts were selected and tested: resin injection, resin vacuum in filtration, XTC-3D, and Gelcoat. Each concept was applied to 3D printed ABS parts and then submerged in water. The change in mass after submersion for varying lengths of time allowed for the evaluation of each process. From the results seen, XTC-3D and resin injection proved to be the most promising out of the four. With this knowledge, the two methods were combined and tested in the Spring semester. They were not only tested by submergence, but pressure and strength tests were done as well. The original goal for the pressure test was to create a vessel to withstand 100 psi. With the methods applied, this goal was surpassed by 200 psi. The strength test was completed to see the effects of each method on the structural integrity of the 3D printed part

Chemical Power for Microscopic Robots in Capillaries

The power available to microscopic robots (nanorobots) that oxidize bloodstream glucose while aggregated in circumferential rings on capillary walls is evaluated with a numerical model using axial symmetry and time-averaged release of oxygen from passing red blood cells. Robots about one micron in size can produce up to several tens of picowatts, in steady-state, if they fully use oxygen reaching their surface from the blood plasma. Robots with pumps and tanks for onboard oxygen storage could collect oxygen to support burst power demands two to three orders of magnitude larger. We evaluate effects of oxygen depletion and local heating on surrounding tissue. These results give the power constraints when robots rely entirely on ambient available oxygen and identify aspects of the robot design significantly affecting available power. More generally, our numerical model provides an approach to evaluating robot design choices for nanomedicine treatments in and near capillaries.Comment: 28 pages, 7 figure

Gravitational wave background from Population III black hole formation

We study the generation of a stochastic gravitational wave (GW) background produced from a population of core-collapse supernovae, which form black holes in scenarios of structure formation. We obtain, for example, that the formation of a population (Population III) of black holes, in cold dark matter scenarios, could generate a stochastic GW background with a maximum amplitude of $h_{\rm BG} \simeq 10^{-24}$ and corresponding closure energy density of $\Omega_{\rm{GW}}\sim 10^{-7}$, in the frequency band $\nu_{\rm{obs}} \simeq 30-470 {\rm Hz}$ (assuming a maximum efficiency of generation of GWs, namely, $\epsilon_{\rm GW_{\rm max}} = 7\times 10^{-4}$) for stars forming at redshifts $z\simeq 30-10.$ We show that it will be possible in the future to detect this isotropic GW background by correlating signals of a pair of `advanced' LIGO observatories (LIGO III) at a signal-to-noise ratio of $\simeq 40$. We discuss what astrophysical information could be obtained from a positive (or even a negative) detection of such a GW background generated in scenarios such as those studied here. One of them is the possibility of obtaining the initial and final redshifts of the emission period from the observed spectrum of GWs.Comment: 10 pages (mn2e Latex), 3 eps figures, MNRAS (in press

Stochastic backgrounds of gravitational waves from cosmological sources - The role of dark energy

[Abridged] We investigate the detectability of the gravitational stochastic background produced by cosmological sources in scenarios of structure formation. The model considers the coalescences of three kind of binary systems: double neutron stars, the neutron star-black hole binaries, and the black hole-black hole systems. We also included the core-collapse supernovae leaving black holes as compact remnants. We use two different dark-energy scenarios, cosmological constant and Chaplygin gas, in order to verify their influence on the cosmic star formation rate, the coalescence rates, and on the gravitational wave backgrounds. We calculate the gravitational wave signals separately for each kind of source as well as we determine their collective contribution for the stochastic background of gravitational waves. Concerning to the compact binary systems, we verify that these sources produce stochastic backgrounds with signal-to-noise ratios (S/N) ~ 1.5 (~ 0.90) for NS-NS, ~ 0.50 (~ 0.30) for NS-BH, ~ 0.20 (~ 0.10) for BH-BH for a pair of advanced LIGO detectors in the cosmological constant (Chaplygin gas) cosmology. Particularly, the sensitivity of the future third generation of detectors as the Einstein Telescope (ET) could increase the present signal-to-noise ratios by a high-factor (~ 300 - 1000) when compared to the (S/N) calculated for advanced LIGO detectors. Thus, the third generation of gravitational wave detectors could be used to reconstruct the history of star formation in the Universe as well as for contributing with the characterization of the dark energy, for example, identifying if there is evidence for the evolution of the dark energy equation-of-state parameter w(a).Comment: Accepted for publication in MNRA

Non-perturbative effective field theory for two-leg antiferromagnetic spin ladders

We study the long wavelength limit of a spin 1/2 Heisenberg antiferromagnetic two-leg ladder, treating the interchain coupling in a non-perturbative way. We perform a mean field analysis and then include exactly the fluctuations. This allows for a discussion of the phase diagram of the system and provides an effective field theory for the low energy excitations. The coset fermionic Lagrangian obtained corresponds to a perturbed SU(4)_1/U(1) Conformal Field Theory (CFT). This effective theory is naturally embedded in a SU(2)_2 x Z_2 CFT, where perturbations are easily identified in terms of conformal operators in the two sectors. Crossed and zig-zag ladders are also discussed using the same approach.Comment: 14 pages LaTeX, 5 PostScript figures included using epsfig.sty; minor corrections and a few references adde

Identifying Vessel Branching from Fluid Stresses on Microscopic Robots

Objects moving in fluids experience patterns of stress on their surfaces determined by the geometry of nearby boundaries. Flows at low Reynolds number, as occur in microscopic vessels such as capillaries in biological tissues, have relatively simple relations between stresses and nearby vessel geometry. Using these relations, this paper shows how a microscopic robot moving with such flows can use changes in stress on its surface to identify when it encounters vessel branches.Comment: Version 2 has minor clarification

Kinematical structure of the circumstellar environments of galactic B[e]-type stars

High resolution line profiles are presented for selected forbidden and permitted emission lines of a sample of galactic B[e]-type stars. The spectral resolution corresponds to 5-7 km/s with the exception of some line profiles which were observed with a resolution of 9-13 km/s. All Ha profiles are characterized by a narrow split or single emission component with a width of about 150-250 km/s (FWHM) and broad wings with a full width of ~1000-2000 km/s. The Ha profiles can be classified into three groups: double-peaked profiles representing the majority, single-peaked emission-line profiles, and normal P Cygni-type profiles. The forbidden lines exhibit in most cases double-peaked profiles. The split forbidden line profiles have peak separations of as little as 10 km/s. The ratio of violet to red emission peak intensities, V/R, is predominantly smaller or equal to 1. Theoretical profiles were calculated for the optically thin case. A latitude-dependent stellar wind with a radial expansion and a velocity decreasing from the pole to the equator was adopted. In addition an equatorial dust ring with various optical depths was assumed. This model can explain split lines and line asymmetries observed in some stars. Moreover, the V/R ratios can be understood in terms of this model. The comparison of the observed line profiles with the models thus confirms the assumption of disk-like line-formation regions as commonly adopted for B[e]-type stars.Comment: Astronomy & Astrophysics, in pres

Dust temperature and density profiles of AGB and post-AGB stars from mid-infrared observations

First mid-infrared images of a sample of AGB and post-AGB carbon stars (V Hya, IRC +10216, CIT 6 and Roberts 22) obtained at La Silla Observatory (ESO, Chile) are reported. CIT 6 presents a cometary-like feature clearly seen in the 9.7$\mu$m image, Roberts 22 shows an envelope slightly elongated in the north-east direction while images of V Hya and IRC+10216 are roughly spherically symmetric. Using inversion technique, the dust emissivity was derived from the observed intensity profiles, allowing a determination of the grain temperature and density distributions inside the envelope for these stars. Dust masses and mass-loss rates were estimated for V Hya and IRC +10216. Our results are comparable to those obtained in previous studies if dust grains have dimensions in the range $\sim$ 0.01 - 0.2 $\mu$m. Color maps suggest the presence of temperature inhomogeneities in the central regions of the dust envelopes. In the case of V Hya, an eccentric hot point, which direction coincides with the jet previously seen in [SII] emission, suggest that we are observing a material ejected in a previous mass-loss event. Bipolar lobes are clearly seen in the color maps of Roberts 22 and IRC +10216.Comment: accepted for publication in Astronomy and Astrophysic

A timeband framework for modelling real-time systems

Complex real-time systems must integrate physical processes with digital control, human operation and organisational structures. New scientific foundations are required for specifying, designing and implementing these systems. One key challenge is to cope with the wide range of time scales and dynamics inherent in such systems. To exploit the unique properties of time, with the aim of producing more dependable computer-based systems, it is desirable to explicitly identify distinct time bands in which the system is situated. Such a framework enables the temporal properties and associated dynamic behaviour of existing systems to be described and the requirements for new or modified systems to be specified. A system model based on a finite set of distinct time bands is motivated and developed in this paper