Application of classical versus bayesian statistical control charts to on-line radiological monitoring

False positive and false negative incidence rates of radiological monitoring data from classical and Bayesian statistical process control chart techniques are compared. The on-line monitoring for illicit radioactive material with no false positives or false negatives is the goal of homeland security monitoring, but is unrealistic. However, statistical fluctuations in the detector signal, short detection times, large source to detector distances, and shielding effects make distinguishing between a radiation source and natural background particularly difficult. Experimental time series data were collected using a 1″ × 1″ LaCl₃(Ce) based scintillation detector (Scionix, Orlando, FL) under various simulated conditions. Experimental parameters include radionuclide (gamma-ray) energy, activity, density thickness (source to detector distance and shielding), time, and temperature. All statistical algorithms were developed using MATLAB™. The Shewhart (3-σ) control chart and the cumulative sum (CUSUM) control chart are the classical procedures adopted, while the Bayesian technique is the Shiryayev–Roberts (S–R) control chart. The Shiryayev–Roberts method was the best method for controlling the number of false positive detects, followed by the CUSUM method. However, The Shiryayev–Roberts method, used without modification, resulted in one of the highest false negative incidence rates independent of the signal strength. Modification of The Shiryayev–Roberts statistical analysis method reduced the number of false negatives, but resulted in an increase in the false positive incidence rate.     

Formation of peptide aggregates during ESI: Size, charge, composition, and contributions to noise

Ion mobility/time-of-flight techniques have been used to examine the onset of aggregation in model systems of Gly-Xxx (where Xxxx = Ala, Asn, Asp, Gln, Glu, His, Leu, Ser, Thr, and Trp) dipeptides. Under the experimental conditions employed, there is evidence that simple binary and quaternary mixtures of these dipeptides produce clusters containing as many as 16 to 75 peptide units (and 1 to 7 charges). In some systems, cluster compositions appear to come about largely from statistical association of peptide units; other dipeptide mixtures (and generally for small clusters) show evidence for nonstatistical behavior which could arise from some differences in gas-phase or solution thermochemistry. The minimum aggregate size appears to be largely determined by the charge state. Average thresholds for aggregate formation in the z = 2, 3, and 4 charge state families occur at m/z ∼500, 660, and 875, respectively. We briefly consider the idea that aggregates formed during electrospray ionization (ESI) may contribute to the background signal observed in the analysis of complex peptide mixtures.     

Time-average measurement of velocity, density, temperature, and turbulence velocity fluctuations using Rayleigh and Mie scattering

Measurement of time-averaged velocity, density, temperature, and turbulence velocity fluctuations in sparsely seeded gas flows using a non-intrusive, point-wise technique based on Rayleigh and Mie scattering is discussed. A Fabry-Perot interferometer (FPI) is used to spectrally resolve laser light scattered by molecules and particulates in gas flows. The spectral content of the scattered light provides information about velocity, density, and temperature of the gas. A CCD camera is used to record images of the fringes formed by scattered light passing through the interferometer. Models of the spectral components are used in a least squares fitting routine to estimate the parameters from fringe images. Flow measurements are presented for subsonic and supersonic jet flows. The application range for this technique is mostly for high velocity situations (>25 m/s). Velocity, density, temperature, and turbulence velocity fluctuations were determined with accuracies within 5 m/s, 4%, 2%, and 5 m/s, respectively.     

Thermoresponsive copolymer nanofilms for controlling cell adhesion, growth, and detachment

This study reports the development and use of a novel thermoresponsive polymeric nanofilm for controlling cell adhesion and growth at 37 °C, and then cell detachment for cell recovery by subsequent temperature drop to the ambient temperature, without enzymatic cleavage or mechanical scraping. A copolymer, poly(N-isopropylacrylamide-co-hydroxypropyl methacrylate-co-3-(trimethoxysilyl)propyl methacrylate) (abbreviated PNIPAAm copolymer), was synthesized by free radical polymerization. The thermoresponses of the copolymer in aqueous solution were demonstrated by dynamic light scattering (DLS) through detecting the sensitive changes of copolymer aggregation against temperature. The DLS measurements revealed the lower critical solution temperature (LCST) at approximately 30 °C. The PNIPAAm film stability and robustness was provided through silyl cross-linking within the film and with the hydroxyl groups on the substrate surface. Film thickness, stability, and reversibility with respect to temperature switches were examined by spectroscopic ellipsometry (SE), atomic force microscopy (AFM), and contact angle measurements. The results confirmed the high extent of thermosensitivity and structural restoration based on the alterations of film thickness and surface wettability. The effective control of adhesion, growth, and detachment of HeLa and HEK293 cells demonstrated the physical controllability and cellular compatibility of the copolymer nanofilms. These PNIPAAm copolymer nanofilms could open up a convenient interfacial mediation for cell film production and cell expansion by nonenzymatic and nonmechanical cell recovery.     

Biocompatible copper(I) catalysts for in vivo imaging of glycans

The Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) is the standard method for bioorthogonal conjugation. However, current Cu(I) catalyst formulations are toxic, hindering their use in living systems. Here we report that BTTES, a tris(triazolylmethyl)amine-based ligand for Cu(I), promotes the cycloaddition reaction rapidly in living systems without apparent toxicity. This catalyst allows, for the first time, noninvasive imaging of fucosylated glycans during zebrafish early embryogenesis. We microinjected embryos with alkyne-bearing GDP-fucose at the one-cell stage and detected the metabolically incorporated unnatural sugars using the biocompatible click chemistry. Labeled glycans could be imaged in the enveloping layer of zebrafish embryos between blastula and early larval stages. This new method paves the way for rapid, noninvasive imaging of biomolecules in living organisms.     

Identification of candidate biomarkers in ovarian cancer serum by depletion of highly abundant proteins and differential in‐gel electrophoresis

Ovarian cancer is the fifth leading cause of cancer death for women in the US, yet survival rates are over 90% when it is diagnosed at an early stage, highlighting the need for biomarkers for early detection. To enhance the discovery of tumor‐specific proteins that could represent novel serum biomarkers for ovarian cancer, we depleted serum of highly abundant proteins which can mask the detection of proteins present in serum at low concentrations. Three commercial immunoaffinity columns were used in parallel to deplete the highly abundant proteins in serum from 60 patients with serous ovarian carcinoma and 60 non‐cancer controls. Medium and low abundance serum proteins from each serum pool were then evaluated by the quantitative proteomic technique of differential in‐gel electrophoresis. The number of protein spots that were elevated in ovarian cancer sera by at least twofold ranged from 36 to 248, depending upon the depletion and separation methods. From the 33 spots picked for MS analysis, nine different proteins were identified, including the novel candidate ovarian cancer biomarkers leucine‐rich α2 glycoprotein‐1 and ficolin 3. Western blotting validated the relative increases in serum protein levels for three of the proteins identified, demonstrating the utility of this approach for the identification of novel serum biomarkers for ovarian cancer.     

Continuous-wave mid-infrared frequency conversion in silicon nanowaveguides

We report the first demonstration of cw wavelength conversion from the telecommunications band to the mid-IR (MIR) region via four-wave mixing in silicon nanowaveguides. We measure a parametric bandwidth of 748 nm by converting a 1636 nm signal to produce a 2384 nm idler and show continuously tunable wavelength conversion from 1792 to 2116 nm. This report indicates that the advantages of silicon photonics may be leveraged to create devices for a large range of MIR applications that require cw operation.     

Adjusting for confounding by cluster using generalized linear mixed models

We show how to use generalized linear mixed models to adjust for confounding by cluster of the effect of a within-cluster covariate. We derive estimators for both a cluster-specific causal effect and a population-averaged causal effect.