Synthetic aspects of host-guest chemistry

Imperial Users onl

Design of ternary signals for MIMO identification in the presence of noise and nonlinear distortion

A new approach to designing sets of ternary periodic signals with different periods for multi-input multi-output system identification is described. The signals are pseudo-random signals with uniform nonzero harmonics, generated from Galois field GF(q), where q is a prime or a power of a prime. The signals are designed to be uncorrelated, so that effects of different inputs can be easily decoupled. However, correlated harmonics can be included if necessary, for applications in the identification of ill-conditioned processes. A design table is given for q les 31. An example is presented for the design of five uncorrelated signals with a common period N = 168 . Three of these signals are applied to identify the transfer function matrix as well as the singular values of a simulated distillation column. Results obtained are compared with those achieved using two alternative methods

Two-stage clustering in genotype-by-environment analyses with missing data

Cluster analysis has been commonly used in genotype-by-environment (G x E) analyses, but current methods are inadequate when the data matrix is incomplete. This paper proposes a new method, referred to as two-stage clustering, which relies on a partitioning of squared Euclidean distance into two independent components, the G x E interaction and the genotype main effect. These components are used in the first and second stages of clustering respectively. Two-stage clustering forms the basis for imputing missing values in the G x E matrix so that a more complete data array is available for other GxE analyses. Imputation for a given genotype uses information from genotypes with similar interaction profiles. This imputation method is shown to improve on an existing nearest cluster method that confounds the G x E interaction and the genotype main effect

Design and Development of the Space Shuttle Tail Service Masts

The successful launch of a space shuttle vehicle depends on the proper operation of two tail service masts (TSMs). Reliable TSM operation is assured through a comprehensive design, development, and testing program. The results of the concept verification test (CVT) and the resulting impact on prototype TSM design are presented. The design criteria are outlined, and the proposed prototype TSM tests are described

Dipole-dipole interaction between a quantum dot and graphene nanodisk

We study theoretically the dipole-dipole interaction and energy transfer in a hybrid system consisting of a quantum dot and graphene nanodisk embedded in a nonlinear photonic crystal. In our model a probe laser field is applied to measure the energy transfer between the quantum dot and graphene nanodisk while a control field manipulates the energy transfer process. These fields create excitons in the quantum dot and surface plasmon polaritons in the graphene nanodisk which interact via the dipole-dipole interaction. Here the nonlinear photonic crystal acts as a tunable photonic reservoir for the quantum dot, and is used to control the energy transfer. We have found that the spectrum of power absorption in the quantum dot has two peaks due to the creation of two dressed excitons in the presence of the dipole-dipole interaction. The energy transfer rate spectrum of the graphene nanodisk also has two peaks due to the absorption of these two dressed excitons. Additionally, energy transfer between the quantum dot and the graphene nanodisk can be switched on and off by applying a pump laser to the photonic crystal or by adjusting the strength of the dipole-dipole interaction. We show that the intensity and frequencies of the peaks in the energy transfer rate spectra can be modified by changing the number of graphene monolayers in the nanodisk or the separation between the quantum dot and graphene. Our results agree with existing experiments on a qualitative basis. The principle of our system can be employed to fabricate nano-biosensors, optical nano-switches, and energy transfer devices

Properties of the Strange Axial Mesons in the Relativized Quark Model

We studied properties of the strange axial mesons in the relativized quark model. We calculated the $K_1$ decay constant in the quark model and showed how it can be used to extract the $K_1 (^3P_1) - K_1 (^1P_1)$ mixing angle ($\theta_K$) from the weak decay $\tau \to K_1 \nu_\tau$. The ratio $BR(\tau \to \nu_\tau K_1 (1270))/BR(\tau\to \nu_\tau K_1(1400))$ is the most sensitive measurement and also the most reliable since the largest of the theoretical uncertainties factor out. However the current bounds extracted from the TPC/Two-Gamma collaboration measurements are rather weak: we typically obtain $-30^o \lesssim \theta_K \lesssim 50^o$ at 68\% C.L. We also calculated the strong OZI-allowed decays in the pseudoscalar emission model and the flux-tube breaking model and extracted a $^3P_1 - ^1P_1$ mixing angle of $\theta_K \simeq 45^o$. Our analysis also indicates that the heavy quark limit does not give a good description of the strange mesons.Comment: Revised version to be published in Phys. Rev. D. Minor changes. Latex file uses revtex version 3 and epsfig, 4 postcript figures are attached. The full postcript version with embedded figures is available at ftp://ftp.physics.carleton.ca/pub/theory/godfrey/ocipc9512.ps.

LOFAR observations of 4C+19.44. On the discovery of low frequency spectral curvature in relativistic jet knots

We present the first LOFAR observations of the radio jet in the quasar 4C+19.44 (a.k.a. PKS 1354+19) obtained with the long baselines. The achieved resolution is very well matched to that of archival Jansky Very Large Array (JVLA) observations at higher radio frequencies as well as the archival X-ray images obtained with {\it Chandra}. We found that, for several knots along the jet, the radio flux densities measured at hundreds of MHz lie well below the values estimated by extrapolating the GHz spectra. This clearly indicates the presence of spectral curvature. Radio spectral curvature has been already observed in different source classes and/or extended radio structures and it has been often interpreted as due to intrinsic processes, as a curved particle energy distribution, rather than absorption mechanisms ({ Razin-Tsytovich} effect, free-free or synchrotron self absorption to name a few). Here we discuss our results according to the scenario where particles undergo stochastic acceleration mechanisms also in quasar jet knots.Comment: 13 pages, 4 tables, 4 figures, pre-proof version, published on the Astrophysical Journal (Harris, et al. 2019 ApJ, 873, 21

Equity of Inpatient Health Care in Rural Tanzania:\ud A Population- and Facility-Based Survey

To explore the equity of utilization of inpatient health care at rural Tanzanian health centers through the use of a short wealth questionnaire.Methods: Patients admitted to four rural health centers in the Kigoma Region of Tanzania from May 2008 to May 2009 were surveyed about their illness, asset ownership and demographics. Principal component analysis was used to compare the wealth of the inpatients to the wealth of the region’s general population, using data from a previous population-based survey. Among inpatients, 15.3% were characterized as the most poor, 19.6% were characterized as very poor, 16.5% were characterized as poor, 18.9% were characterized as less poor, and 29.7% were characterized as the least poor. The wealth distribution of all inpatients (p < 0.0001), obstetric inpatients (p < 0.0001), other inpatients (p < 0.0001), and fee-exempt inpatients (p < 0.001) were significantly different than the wealth distribution in the community population, with poorer patients underrepresented among inpatients. The wealth distribution of pediatric inpatients (p = 0.2242) did not significantly differ from the population at large. The findings indicated that while current Tanzanian health financing policies may have improved access to health care for children under five, additional policies are needed to further close the equity gap, especially for obstetric inpatients.\u

A Search for Biomolecules in Sagittarius B2 (LMH) with the ATCA

We have used the Australia Telescope Compact Array to conduct a search for the simplest amino acid, glycine (conformers I and II), and the simple chiral molecule propylene oxide at 3-mm in the Sgr B2 LMH. We searched 15 portions of spectrum between 85 and 91 GHz, each of 64 MHz bandwidth, and detected 58 emission features and 21 absorption features, giving a line density of 75 emission lines and 25 absorption lines per GHz stronger than the 5 sigma level of 110 mJy. Of these, 19 are transitions previously detected in the interstellar medium, and we have made tentative assignments of a further 23 features to molecular transitions. However, as many of these involve molecules not previously detected in the ISM, these assignments cannot be regarded with confidence. Given the median line width of 6.5 km/s in Sgr B2 LMH, we find that the spectra have reached a level where there is line confusion, with about 1/5 of the band being covered with lines. Although we did not confidently detect either glycine or propylene oxide, we can set 3 sigma upper limits for most transitions searched. We also show that if glycine is present in the Sgr B2 LMH at the level of N = 4 x 10^{14} cm^{-2} found by Kuan et al. (2003) in their reported detection of glycine, it should have been easily detected with the ATCA synthesized beam size of 17.0 x 3.4 arcsec^{2}, if it were confined to the scale of the LMH continuum source (< 5 arcsec). This thus puts a strong upper limit on any small-scale glycine emission in Sgr B2, for both of conformers I and II.Comment: 12 pages, 2 figures, 5 tables, accepted by MNRA