Frequency-Modulated, Continuous-Wave Laser Ranging Using Photon-Counting Detectors

Optical ranging is a problem of estimating the round-trip flight time of a phase- or amplitude-modulated optical beam that reflects off of a target. Frequency- modulated, continuous-wave (FMCW) ranging systems obtain this estimate by performing an interferometric measurement between a local frequency- modulated laser beam and a delayed copy returning from the target. The range estimate is formed by mixing the target-return field with the local reference field on a beamsplitter and detecting the resultant beat modulation. In conventional FMCW ranging, the source modulation is linear in instantaneous frequency, the reference-arm field has many more photons than the target-return field, and the time-of-flight estimate is generated by balanced difference- detection of the beamsplitter output, followed by a frequency-domain peak search. This work focused on determining the maximum-likelihood (ML) estimation algorithm when continuous-time photoncounting detectors are used. It is founded on a rigorous statistical characterization of the (random) photoelectron emission times as a function of the incident optical field, including the deleterious effects caused by dark current and dead time. These statistics enable derivation of the Cramr-Rao lower bound (CRB) on the accuracy of FMCW ranging, and derivation of the ML estimator, whose performance approaches this bound at high photon flux. The estimation algorithm was developed, and its optimality properties were shown in simulation. Experimental data show that it performs better than the conventional estimation algorithms used. The demonstrated improvement is a factor of 1.414 over frequency-domainbased estimation. If the target interrogating photons and the local reference field photons are costed equally, the optimal allocation of photons between these two arms is to have them equally distributed. This is different than the state of the art, in which the local field is stronger than the target return. The optimal processing of the photocurrent processes at the outputs of the two detectors is to perform log-matched filtering followed by a summation and peak detection. This implies that neither difference detection, nor Fourier-domain peak detection, which are the staples of the state-of-the-art systems, is optimal when a weak local oscillator is employed

Characterization of wheat varieties by seed storageprotein electrophoresis

Wheat grains of thirteen varieties were collected from different ecological regions of Pakistan. The variability of seed storage-proteins was analyzed by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Electrophorogram for each variety were scored and Jaccard‘s similarity index (JSI) was calculated. Genetic diversity of wheat was evaluated by constructing the dendrogram for high molecular weight (HMW) and low molecular weight (LMW) gluten subunit bands. It is concludedthat seed storage protein profiles could be useful markers in the studies of genetic diversity and classification of adapted cultivars, thereby improving the efficiency of wheat breeding programs in cultivar development especially in a developing country like Pakistan

17-(Pyrimidin-2-yl)-8,16-dioxa-17-aza­tetra­cyclo­[7.7.1.02,7.010,15]hepta­deca-2,4,6,10,12,14-hexa­ene

In the title compound, C18H13N3O2, the benzene rings form a dihedral angle of 78.49 (9)°. The dihedral angles between the benzene rings and the pyrimidine ring are 76.53 (10) and 27.73 (11)°. The two cis-fused six-membered heterocyclic rings adopt half-chair confirmations. In the crystal, mol­ecules are linked by C—H⋯O hydrogen bonds, forming chains parallel to the b axis

Nutraceutical therapies for atherosclerosis

Atherosclerosis is a chronic inflammatory disease affecting large and medium arteries and is considered to be a major underlying cause of cardiovascular disease (CVD). Although the development of pharmacotherapies to treat CVD has contributed to a decline in cardiac mortality in the past few decades, CVD is estimated to be the cause of one-third of deaths globally. Nutraceuticals are natural nutritional compounds that are beneficial for the prevention or treatment of disease and, therefore, are a possible therapeutic avenue for the treatment of atherosclerosis. The purpose of this Review is to highlight potential nutraceuticals for use as antiatherogenic therapies with evidence from in vitro and in vivo studies. Furthermore, the current evidence from observational and randomized clinical studies into the role of nutraceuticals in preventing atherosclerosis in humans will also be discussed

Mechanical and Optical Properties of ZrO₂ Doped Silicate Glass Ceramics

In the present study, we report the physical and optical properties of low-cost glass (soda-lime silicate glass) fabricated from local minerals, obtained from Hazara division Khyber Pakhtunkhwa, Pakistan. Zirconium dioxide (1–3%) was added as a nucleating agent to investigate its effect on phase, density, hardness, and optical properties of soda-lime silicate glass. In the obtained glass-ceramic materials, the major crystalline phase was cristobalite. It was found that an increase in ZrO2 content and heat treatment of the samples, resulted in an increase in bulk crystallization of the samples. The mechanical properties were found to be improved with ZrO2 addition. The bandgap of the sample was in the range 3.78–4.09 eV

{5-Chloro-2-[(2-hy­droxy­benzyl­idene)amino]­phen­yl}(phen­yl)methanone

The title Schiff base compound, C20H14ClNO2, adopts an E configuration about the azomethine bond. The phenol and chloro­benzene rings form dihedral angles of 84.71 (9) and 80.70 (8)°, respectively, with the phenyl ring and are twisted by 15.32 (8)° with respect to one another. The mol­ecular conformation is stabilized by an intra­molecular O—H⋯N hydrogen bond, which forms an S(6) ring motif. In the crystal, mol­ecules are linked by C—H⋯O hydrogen bonds, forming columns parallel to the a axis

Manifold-Topology from K-Causal Order

To a significant extent, the metrical and topological properties of spacetime can be described purely order-theoretically. The $K^+$ relation has proven to be useful for this purpose, and one could wonder whether it could serve as the primary causal order from which everything else would follow. In that direction, we prove, by defining a suitable order-theoretic boundary of $K^+(p)$, that in a $K$-causal spacetime, the manifold-topology can be recovered from $K^+$. We also state a conjecture on how the chronological relation $I^+$ could be defined directly in terms of $K^+$.Comment: v2: 9 pages, 2 figures. Minor change