Rapid sync acquisition system Patent

System designed to reduce time required for obtaining synchronization in data communication with spacecraft utilizing pseudonoise code

Design for a Rapid Automatic Sync Acquisition System

System provides rapid command sync acquisition between widely separated transmitter-receivers. It is based on a rapid, automatic range-adjustment approach rather than the time-consuming cycle slipping or stepping techniques of conventional phase-locked loops

Double dynamical regime of confined water

The Van Hove self correlation function of water confined in a silica pore is calculated from Molecular Dynamics trajectories upon supercooling. At long time in the $\alpha$ relaxation region we found that the behaviour of the real space time dependent correlators can be decomposed in a very slow, almost frozen, dynamics due to the bound water close to the substrate and a faster dynamics of the free water which resides far from the confining surface. For free water we confirm the evidences of an approach to a crossover mode coupling transition, previously found in Q space. In the short time region we found that the two dynamical regimes are overimposed and cannot be distinguished. This shows that the interplay between the slower and the faster dynamics emerges in going from early times to the $\alpha$ relaxation region, where a layer analysis of the dynamical properties can be performed.Comment: 6 pages with 9 figures. RevTeX. Accepted for pulbication in J. Phys. Cond. Mat

Lanthanide(III) complexes of rhodamine-DO3A conjugates as agents for dual-modal imaging

Two novel dual-modal MRI/optical probes based on a rhodamine-DO3A conjugate have been prepared. The bis aqua-Gd(III) complex Gd.L1 and mono aqua-Gd(III) complex Gd.L2 behave as dual-modal imaging probes (r1 = 8.5 and 3.8 mM-1s-1 for Gd.L1 and Gd.L2 respectively; λex = 560 nm and λem = 580 nm for both complexes). The rhodamine fragment is pH sensitive and upon lowering of pH an increase in fluorescence intensity is observed as the spirolactam ring opens to give the highly fluorescent form of the molecule. The ligands are bimodal when coordinated to Tb(III) ions, inducing fluorescence from both the lanthanide center and the rhodamine fluorophore, on two independent time-frames. Confocal imaging experiments were carried out to establish the localization of Gd.L2 in HEK cells. Co-localisation with MitoTracker® Green confirmed that Gd.L2 compartmentalizes in the mitochondria. Gd.L2 was also evaluated as an MRI probe for imaging tumors in BALB/c nude mice bearing M21 xenografts. A 36.5% decrease in T1 within the tumor was observed 30 minutes post injection showing that Gd.L2 is preferentially up taken in the tumor. Gd.L2 is the first small molecule MR/fluorescent dual-modal imaging agent to display an off-on pH switch upon its preferential uptake within the more acidic micro-environment of tumor cells

Discovery of the Narrow-Line Seyfert 1 galaxy Mkn 335 in an historical low X-ray flux state

We report the discovery of the Narrow-Line Seyfert 1 galaxy Mkn 335 in an extremely low X-ray state. A comparison of Swift observations obtained in May and June/July 2007 with all previous X-ray observations between 1971 to 2006 show the AGN to have diminished in flux by a factor of more than 30, the lowest X-ray flux Mkn 335 has ever been observed in. The Swift observations show an extremely hard X-ray spectrum at energies above 2 keV. Possible interpretations include partial covering absorption or X-ray reflection from the disk. In this letter we consider the partial covering interpretation. The Swift observations can be well fit by a strong partial covering absorber with varying absorption column density N_H= 1-4 x 10^{23} cm-2 and a covering fraction f_c=0.9 - 1. When corrected for intrinsic absorption, the X-ray flux of Mkn 335 varies by only factors of 4-6. In the UV Mkn 335 shows variability in the order of 0.2 mag. We discuss the similarity of Mkn 335 with the highly variable NLS1 WPVS007, and speculate about a possible link between NLS1 galaxies and broad-absorption line quasars.Comment: ApJ Letter accepted; 8 pages, 2 figures; The new version has three more sentences in the introduction and three references added to the discussio

Tuning the relaxation rates of dual-mode T?/T? nanoparticle contrast agents: a study into the ideal system

Magnetic resonance imaging (MRI) is an excellent imaging modality. However the low sensitivity of the technique poses a challenge to achieving an accurate image of function at the molecular level. To overcome this, contrast agents are used; typically gadolinium based agents for T? weighted imaging, or iron oxide based agents for T? imaging. Traditionally, only one imaging mode is used per diagnosis although several physiological situations are known to interfere with the signal induced by the contrast agents in each individual imaging mode acquisition. Recently, the combination of both T? and T? imaging capabilities into a single platform has emerged as a tool to reduce uncertainties in MR image analysis. To date, contradicting reports on the effect on the contrast of the coupling of a T? and T? agent have hampered the application of these specialised probes. Herein, we present a systematic experimental study on a range of gadolinium-labelled magnetite nanoparticles envisioned to bring some light into the mechanism of interaction between T? and T? components, and advance towards the design of efficient (dual) T? and T? MRI probes. Unexpected behaviours observed in some of the constructs will be discussed. In this study, we demonstrate that the relaxivity of such multimodal probes can be rationally tuned to obtain unmatched potentials in MR imaging, exemplified by preparation of the magnetite-based nanoparticle with the highest T? relaxivity described to date