Optimal complex field holographic projection

We describe a technique that uses complex field holograms to project three-dimensional light patterns. Holographic projection commonly uses phase-only encoding since accurately representing complex holograms using both amplitude and phase spatial light modulators reduces the optical throughput significantly. Here, we use a lossless projection via the generalized phase contrast method to produce the necessary amplitude pattern required for complex field holographic projection. We numerically evaluate the technique and demonstrate high optical throughput with reduced undesired high diffraction orders.     

Accuracy of image registration between MRI and light microscopy in the ex vivo brain

A multistep procedure was developed to register magnetic resonance imaging (MRI) and histological data from the same sample in the light microscopy image space, with the ultimate goal of allowing quantitative comparisons of the two datasets. The fixed brain of an owl monkey was used to develop and test the procedure. In addition to the MRI and histological data, photographic images of the brain tissue block acquired during sectioning were assembled into a blockface volume to provide an intermediate step for the overall registration process. The MR volume was first registered to the blockface volume using a combination of linear and nonlinear registration, and two dimensional (2D) blockface sections were registered to corresponding myelin-stained sections using a combination of linear and nonlinear registration. Before this 2D registration, two major types of tissue distortions were corrected: tissue tearing and independent movement of different parts of the brain, both introduced during histological processing of the sections. The correction procedure utilized a 2D method to close tissue tears and a multiple iterative closest point (ICP) algorithm to reposition separate pieces of tissue in the image. The accuracy of the overall MR to micrograph registration procedure was assessed by measuring the distance between registered landmarks chosen in the MR image space and the corresponding landmarks chosen in the micrograph space. The average error distance of the MR data registered to micrograph data was 0.324±0.277 mm, only 8% larger than the width of the MRI voxel (0.3 mm).     

Fractional weak discrepancy and split semiorders

The fractional weak discrepancywd_F(P) of a poset P=(V,?) was introduced in Shuchat et al. (2007) [6] as the minimum nonnegative k for which there exists a function f:V→R satisfying (i) if a?b then f(a)+1≤f(b) and (ii) if a∥b then |f(a)−f(b)|≤k. In this paper we generalize results in Shuchat et al. (2006, 2009) [5] and [7] on the range of wd_F for semiorders to the larger class of split semiorders. In particular, we prove that for such posets the range is the set of rationals that can be represented as r/s for which 0≤s−1≤r<2s.     

The orienteering problem with stochastic travel and service times

In this paper, we introduce a variant of the orienteering problem in which travel and service times are stochastic. If a delivery commitment is made to a customer and is completed by the end of the day, a reward is received, but if a commitment is made and not completed, a penalty is incurred. This problem reflects the challenges of a company who, on a given day, may have more customers than it can serve. In this paper, we discuss special cases of the problem that we can solve exactly and heuristics for general problem instances. We present computational results for a variety of parameter settings and discuss characteristics of the solution structure.     

The relationship among voice onset, voice quality, and fundamental frequency: a dynamical perspective

In dynamical motor theory, skill acquisition occurs as a modification of preexisting coordination patterns or attractor states. The purpose of this study was to assess how different levels of voice onset, voice quality, and fundamental frequency (F₀) combine to form the attractor states common to voice motor control. Three levels of voice onset (glottal, simultaneous, and breathy), voice quality (modal speech, mixed, and falsetto), and fundamental frequency (low, mid, and high) were manipulated by vocally untrained, female subjects. Percent correct of acquisition trials and self-report of effort were used as measures of stable phonations indicative of an attractor state. Using intensity as a covariate, the results provided support for two of the three predicted triads representing attractor states in female speakers: (1) glottal onset/modal speech quality/low F₀; and (2) breathy onset/falsetto quality/high F₀. The results of this study suggest that certain parameters of voice motor control, such as onset, quality, and F₀, exist as part of a dynamical system that can be identified and manipulated in voice motor acquisition and learning.     

Collisional electron transfer to photoexcited acceptor radical anions

In this article, we show that photoexcitation of radical anions facilitates electron transfer from sodium atoms in femtosecond encounters. Thus, excitation of 7,7,8,8-tetracyano-p-quinodimethane (TCNQ) and fluorinated TCNQ (TCNQ-F(4)) anions to the second optically active state at 478 nm led to increases in the yields of dianions of about 20% and 10%, respectively. Photoexcitation with a nanosecond-long laser pulse was done a few microseconds before the ions entered the sodium collision cell so that none of the ions would be in any of the initially reached doublet-excited states. We suggest an explanation for the higher electron capture cross section based on the formation of long-lived quartet state anions. Excitation of TCNQ anions within the lowest-energy absorption band, where there are no accessible quartet states, led instead to a lower yield of dianions. There are at least three explanations for the lower dianion yields: (1) Depletion of the monoanion beam due to photodetachment after the absorption of minimum two photons; (2) Formation of short-lived vibrationally excited dianions that decay by electron autodetachment prior to identification; and (3) Lower electron capture cross sections of vibrationally excited monoanions. Similar losses in dianion signal can occur at 478 nm so the actual yield of dianions at this wavelength due to the population of quartet states is therefore greater than that observed. Our methodology devises a more efficient route for the production of molecular dianions, and at the same time it may provide information on long-lived electronic states.     

Synthesis and Profiling of a Diverse Collection of Azetidine-Based Scaffolds for the Development of CNS-Focused Lead-like Libraries

The synthesis and diversification of a densely functionalized azetidine ring system to gain access to a wide variety of fused, bridged, and spirocyclic ring systems is described. The in vitro physicochemical and pharmacokinetic properties of representative library members are measured in order to evaluate the use of these scaffolds for the generation of lead-like molecules to be used in targeting the central nervous system. The solid-phase synthesis of a 1976-membered library of spirocyclic azetidines is also described.     

A rapid method for cross-species quantitation of apolipoproteins A1, B48 and B100 in plasma by ultra-performance liquid chromatography/tandem mass spectrometry

Apolipoprotein B100 (apoB100) and apolipoprotein A1 (apoA1) are the primary protein components of low density lipoprotein (LDL) and high density lipoprotein (HDL) particles, respectively, and plasma levels of these proteins are associated with risks of cardiovascular disease. Existing apoB100 quantitation methods for animal models have been limited to affinity capture techniques such as enzyme-linked immunosorbent assay (ELISA) and Western blot which require specialized reagents for each species and in many cases are not readily available. Here we demonstrate a single translatable ultra-performance liquid chromatography/tandem mass spectrometry (UPLC/MS/MS) assay that is fast and robust and can be used to measure apolipoprotein concentrations in plasma for six species. When possible, peptide sequences that are conserved across species were identified for this assay. The sample preparation is limited and can be carried out in 96-well microtiter plates and thus allows for multiplexed preparation of samples for analysis of large numbers of samples in a short time frame when combined with UPLC/MS/MS. Separation and quantitation of the tryptic peptides is carried out at 700 μL/min using a 1.7 μm core shell C18 column (2.1 × 50 mm). The chromatography is designed for the analysis of over 100 samples per day, and the UPLC run is less than 10 min. This assay is capable of supporting cardiovascular research by providing a single assay to measure critical biomarkers across multiple species without the need for antibodies, and does so in a high-throughput manner.     

Cationic polythiophene-surfactant self-assembly complexes: phase transitions, optical response, and sensing

The absorption and photoluminescence spectra of the cationic conjugated polyelectrolyte poly[3-(6-trimethylammoniumhexyl)thiophene] (P3TMAHT) were observed to be dramatically altered in the presence of anionic surfactants due to self-assembly through ionic complex formation. Small-angle neutron scattering (SANS), UV/vis, and photoluminescence spectroscopy were used to probe the relationship between the supramolecular complex organization and the photophysical response of P3TMAHT in the presence of industrially important anionic surfactants. Subtle differences in the surfactant mole fraction and chemical structure (e.g., chain length, headgroup charge density, perfluorination) result in marked variations in the range and type of complexes formed, which can be directly correlated to a unique colorimetric and fluorimetric fingerprint. Our results show that P3TMAHT has potential as an optical sensor for anionic surfactants capable of selectively identifying distinct structural subgroups through dual mode detection.     

Development and validation of a reversed-phase liquid chromatographic method for analysis of demeclocycline and related impurities

A simple, robust, and rapid reversedphase high-performance liquid chromatographic method for the analysis of demeclocycline and its impurities is described. Chromatographic separations were achieved on a Symmetry Shield RP8 (75 mm × 4.6 mm, 3.5 μm) column kept at 40°C. The mobile phase was a gradient mixture of acetonitrile, 0.06 M sodium edetate (pH 7.5), 0.06 M tetrapropylammonium hydrogen sulphate (pH 7.5) and water, A (2:35:35:28 v/v/v/v) and B (30:35:35:0 v/v/v/v) pumped at a flow rate of 1 mL/min. UV detection was performed at 280 nm. The developed method was validated according to the ICH guidelines for specificity, limit of detection, limit of quantification, linearity, precision, and robustness. An experimental design was applied for robustness study. Results show that the peak shape, chromatographic resolution between the impurities, and the total analysis time are satisfactory and better than previous methods. The method has been applied for the analysis of commercial demeclocycline bulk samples available on the market.