Greater Dynamic Range Research Articles

Compressed Two's Complement Data Formats Provide Greater Dynamic Range and Improved Noise Performance [exploratory DSP

In this article, we present and analyze a new family of fixed-point data formats for signal processing applications. These formats represent compressed two's complement data formats where compression on the sign bit is undertaken on a sample by sample basis. The extra room provided by sign-bit compression is utilized to retain more bits of precision for each individual sample. Compressed two's complement data formats are shown to provide greater dynamic range and improved noise performance over traditional fixed-point data formats such as sign-magnitude, offset binary, and traditional two's complement. Traditional two's complement is shown to be a member of the compressed two's complement family where the compression factor (CF) is equal to one. The dynamic range of a compressed two's complement data format is shown to approach the dynamic range of a non compressed data format raised to the power of the CF. Improved performance for digital signal processing (DSP) applications such as digital filters and transforms is presented for specific instances of this family.

Metabolic Imaging: A Link between Lactate Dehydrogenase A, Lactate, and Tumor Phenotype

We compared the metabolic profiles and the association between LDH-A expression and lactate production in two isogenic murine breast cancer cell lines and tumors (67NR and 4T1). These cell lines were derived from a single mammary tumor and have different growth and metabolic phenotypes. LDH-A expression, lactate concentration, glucose utilization, and oxygen consumption were measured in cells, and the potential relationship between tumor lactate levels [measured by magnetic resonance spectroscopic imaging (MRSI)] and tumor glucose utilization [measured by [(18)F]2-deoxy-2-fluoro-D-glucose positron emission tomography ([(18)F]FDG-PET)] was assessed in orthotopic breast tumors derived from these cell lines. We show a substantial difference in LDH-A expression between 67NR and 4T1 cells under normoxia and hypoxia. We also show that small orthotopic 4T1 tumors generate 10-fold more lactate than corresponding 67NR tumors. The high lactate levels in small primary 4T1 tumors are associated with intense pimonidazole staining (a hypoxia indicator). Less-intense hypoxia staining was observed in the larger 67NR tumors and is consistent with the gradual increase and plateau of lactate concentration in enlarging 67NR tumors. Lactate-MRSI has a greater dynamic range than [(18)F]FDG-PET and may be a more sensitive measure with which to evaluate the aggressive and metastatic potential of primary breast tumors.

D4cpv-calsequestrin: a sensitive ratiometric biosensor accurately targeted to the calcium store of skeletal muscle.

Current fluorescent monitors of free [Ca2+] in the sarcoplasmic reticulum (SR) of skeletal muscle cells are of limited quantitative value. They provide either a nonratio signal that is difficult to calibrate and is not specific or, in the case of Forster resonant energy transfer (FRET) biosensors, a signal of small dynamic range, which may be degraded further by imperfect targeting and interference from endogenous ligands of calsequestrin. We describe a novel tool that uses the cameleon D4cpv, which has a greater dynamic range and lower susceptibility to endogenous ligands than earlier cameleons. D4cpv was targeted to the SR by fusion with the cDNA of calsequestrin 1 or a variant that binds less Ca2+. “D4cpv-Casq1,” expressed in adult mouse at concentrations up to 22 µmole/liter of muscle cell, displayed the accurate targeting of calsequestrin and stayed inside cells after permeabilization of surface and t system membranes, which confirmed its strict targeting. FRET ratio changes of D4cpv-Casq1 were calibrated inside cells, with an effective KD of 222 µM and a dynamic range [(Rmax − Rmin)/Rmin] of 2.5, which are improvements over comparable sensors. Both the maximal ratio, Rmax, and its resting value were slightly lower in areas of high expression, a variation that was inversely correlated to distance from the sites of protein synthesis. The average [Ca2+]SR in 74 viable cells at rest was 416 µM. The distribution of individual ratio values was Gaussian, but that of the calculated [Ca2+]SR was skewed, with a tail of very large values, up to 6 mM. Model calculations reproduce this skewness as the consequence of quantifiably small variations in biosensor performance. Local variability, a perceived weakness of biosensors, thus becomes quantifiable. It is demonstrably small in D4cpv. D4cpv-Casq1 therefore provides substantial improvements in sensitivity, specificity, and reproducibility over existing monitors of SR free Ca2+ concentration.

The HOIS recommended practice for in-service computed radiography of pipes

The comparatively new technology of computed radiography (CR) for NDT imaging has a number of advantages over traditional film-based radiography, including reduced exposure times and greater dynamic range. In addition, it does not require facilities for the developmentof radiographic film, which can be difficult to install and maintain given the often restricted deck facilities space in an offshore environment. However, the technology associated with CR is substantially more complex than film and, in the absence of any internationally recognised standards for in-service radiographic inspection, the quality of the resulting CR images can be variable. To improve the quality control of this form of inspection, the HOIS JIP has developed a recommended practice covering CR for the in-service inspection of pipes for wall loss type flaws (corrosion, erosion). This project involved a series of experimental trials to first develop and then validate the recommendations, and also quantitatively compare the characteristics of different commercially available CR systems. The results of the CR trials undertaken during this project and the main recommendations of the recommended practice are described.

Robust localization and identification method of moving sound sources based on worst-case performance optimization

Based on the passive synthetic aperture principle, a new robust high-resolution focused array signal processing method of moving sound source localization and identification is proposed in this paper. By means of the integrated optimization, this method generates the coordinates of a virtual array and the data matrix through the vector maximum likelihood focused algorithm, then utilizes the sparse virtual array focused algorithm based on the worst-case performance optimization to obtain the robust high-resolution localization and recognition effects. The theory and the simulation analysis show that this method is applicable to the complex experimental situations such as non-uniform motion and tipsy array, and the focused spatial spectrum indicates the greater dynamic range, the sharper focused peak, and the stronger ability to suppress the fluctuations of the background noise. The higher robustness and better results of this proposed method are verified in the lake experiment. Under the same experimental condition, the dynamic range of high-resolution MVDR focused algorithm is only 3.5dB, however, it can reach 50 dB by the proposed method.

In vivo kinetics of [F‐18]MEFWAY: A comparison with [C‐11]WAY100635 and [F‐18]MPPF in the nonhuman primate

[F-18]Mefway was developed to provide an F-18 labeled positron emission tomography (PET) neuroligand with high affinity for the serotonin 5-HT(1A) receptor to improve the in vivo assessment of the 5-HT(1A) system. The goal of this work was to compare the in vivo kinetics of [F-18]mefway, [F-18]MPPF, and [C-11]WAY100635 in the rhesus monkey. Each of four monkeys were given bolus injections of [F-18]mefway, [C-11]WAY100635, and [F-18]MPPF and scans were acquired with a microPET P4 scanner. Arterial blood was sampled to assay parent compound throughout the time course of the PET experiment. Time activity curves were extracted in the high 5-HT(1A) binding areas of the anterior cingulate cortex (ACG), mesial temporal cortex, raphe nuclei, and insula cortex. Time activity curves were also extracted in the cerebellum, which was used as a reference region. The in vivo kinetics of the radiotracers were compared based on the nondisplaceable distribution volume (V(ND) ) and binding potential (BP(ND) ). At 30 min, the fraction of radioactivity in the plasma due to parent compound was 19%, 28%, and 29% and cleared from the arterial plasma at rates of 0.0031, 0.0078, and 0.0069 (min⁻¹) ([F-18]mefway, [F-18]MPPF, [C-11]WAY100635). The BP(ND) in the brain regions were mesial temporal cortex: 7.4 ± 0.6, 3.1 ± 0.4, 7.0 ± 1.2, ACG: 7.2 ± 1.2, 2.1 ± 0.2, 7.9 ± 1.2; raphe nuclei: 3.7 ± 0.6, 1.3 ± 0.3, 3.3 ± 0.7; and insula cortex: 4.2 ± 0.6, 1.2 ± 0.1, 4.7 ± 1.0 for [F-18]mefway, [F-18]MPPF, and [C-11]WAY100635 respectively. In the rhesus monkey, [F-18]mefway has similar in vivo kinetics to [C-11]WAY100635 and yields greater than 2-fold higher BP(ND) than [F-18]MPPF. These properties make [F-18]mefway a promising radiotracer for 5-HT(1A) assay, providing higher counting statistics and a greater dynamic range in BP(ND).

Morphometric and Visual Evaluation of Fibrosis in Renal Biopsies

Interstitial fibrosis is an outcome measure of increasing importance in clinical trials of both renal transplantation and native disease, but data on the comparative advantages of fibrosis measurement methods are limited. We compared four morphometric techniques and contrasted these with two visual fibrosis-scoring methods on trichrome-stained slides. Two morphometric methods included whole-slide digital images: collagen III immunohistochemistry and a new technique using trichrome and periodic acid-Schiff subtraction morphometry; the other two methods included Sirius Red with and without polarization on multiple digital fields. We evaluated 10 serial sections from 15 renal biopsies with a range of fibrosis extent and diagnoses on duplicate sections with each method on separate days. Three pathologists performed visual scoring on whole-slide images. Visual and morphometric techniques had good to excellent interassay reproducibility (R(2) = 0.62 to 0.96) and interobserver reproducibility (R(2) = 0.75 to 0.99, all P < 0.001). Morphometry showed less variation between observers than visual assessment (mean of 1% to 5% versus 11% to 13%). Collagen III, Sirius Red unpolarized, and visual scores had the strongest correlations (R(2) = 0.78 to 0.89), the greatest dynamic range, and the best correlation with estimated GFR (R(2) = 0.38 to 0.50, P < 0.01 to 0.001). Considering efficiency, reproducibility, and functional correlation, two current techniques stand out as potentially the best for clinical trials: collagen III morphometry and visual assessment of trichrome-stained slides.

Abstract 2681: EWS-FLI1 as a molecular target: Small molecule inhibitors for a disordered protein

Abstract Ewing's sarcoma family of tumors are characterized by the EWS-FLI1 oncogenic fusion protein. Our previous studies show that RNA Helicase A (RHA) enhances EWS-FLI1 driven oncogenesis, and interruption of this protein-protein complex by small molecule inhibitors validate this interaction as a unique therapeutic target (NatMed 2009 Jul;15(7):750-6). EWS-FLI1 is a significantly hydrophobic disordered protein with unknown three-dimensional structure, which therefore precludes standard structure-based small molecule design. Given the challenges of drug design targeted to EWS-FLI1, we hypothesize that the optimization of a peptide displacement assay using small molecules can predict and direct the design of more potent analogs. Fluorescence polarization (FP) was originally used to measure RHA peptide displacement from EWS-FLI1, but is time consuming and reagent limiting. To identify new strategies for higher-throughput screening, a TECAN ULTRA 384 was used for assay detection in a 96-well plate format. However, this resulted in high background and low signal. A second approach, AlphaScreen (amplified luminescent proximity homogenous assay, PerkinElmer), uses a bead-based interaction system based on energy conversion and generation of chemiluminescence when acceptor and donor beads are brought together during binding. Results show a 6-fold dynamic range between bound and quenched beads, in comparison to just 2.5-fold for FP and less than two-fold for TECAN. Our small molecule, YK-4-279, is able to reduce the signal down to baseline, indicating that YK-4-279 dissociates the RHA peptide and EWS-FLI1. Key negative controls support specific binding between EWS-FLI1 and the RHA peptide. In addition, YK-4-279 was unable to quench the signal from a positive control using immunoglobulin, supporting the conclusion that YK-4-279 disrupts the specific protein-peptide binding rather than directly extinguishing the chemiluminescence. Data from the AlphaScreen will be used as input to a quantitative-structure activity relationship (QSAR) method. This QSAR method will predict biological activity from chemical structure and the knowledge gained from AlphaScreen will aid in the optimization and design of future analogs. In our initial work, we used the Free-Wilson QSAR method, converting the structure of the small molecules into a numerical format allowing for a mathematical comparison between structures, to populate a table with 32 small molecule analogs of YK-4-279. The AlphaScreen data may also be used with other QSAR methods, to which we may transition in later work. AlphaScreen technology provides a method to quantitatively compare binding of small molecules in a high-throughput screening system, yields a greater dynamic range with more specificity, and provides data that will help to predict the binding of other analogs with similar chemical structures. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2681.

Reversible Dimerization of Aequorea victoria Fluorescent Proteins Increases the Dynamic Range of FRET-Based Indicators

Fluorescent protein (FP)-based Forster resonance energy transfer (FRET) technology is useful for development of functional indicators to visualize second messenger molecules and activation of signaling components in living cells. However, the design and construction of the functional indicators require careful optimization of their structure at the atomic level. Therefore, routine procedures for constructing FRET-based indicators currently include the adjustment of the linker length between the FPs and the sensor domain and relative dipole orientation of the FP chromophore. Here we report that, in addition to these techniques, optimization of the dimerization interface of Aequorea FPs is essential to achieve the highest possible dynamic range of signal change by FRET-based indicators. We performed spectroscopic analyses of various indicators (cameleon, TN-XL, and ATeam) and their variants. We chose variants containing mutant FPs with different dimerization properties, i.e., no, weak, or enhanced dimerization of the donor or acceptor FP. Our findings revealed that the FPs that dimerized weakly yielded high-performance FRET-based indicators with the greatest dynamic range.

Variability in Automatically Generated Raw Activity Scores

The limitations in the use of raw activity scores in the analysis of conditioned fear are clearly stated by Anagnostaras et al. (2010): raw activity scores such as those provided by the Video-freeze system do exhibit more between-subject variability than freezing scores. Figure ​Figure11 shows distributions of automatically generated freezing and activity scores for 44 Swiss Webster mice, which have been transformed into z scores in order to allow comparisons in a common metric1: Although freezing during baseline was absent for most subjects, raw activity scores do indeed show considerable variance. Figure 1 Raw activity and freezing scores under baseline and conditioned stimulus conditions (n = 44). Raw activity end percent freezing scores (freezing threshold = 18), were automatically generated by the Video-freeze© ... This increased variance is not limited to baseline data, but extends to conditioned responding, as can be seen in the right-hand side of Figure ​Figure1,1, which compares freezing and raw activity scores for the presentation of a conditioned stimulus (blinking house light), after two light-shock pairings (0.7 mA, 2 s. scrambled foot-shock). This increased variability of raw activity scores in and of itself does not constitute a limitation of this type of data. On the contrary, it may offer a unique opportunity to model individual differences through fear-conditioning preparations: one of the distinctive features of anxiety disorders such as post-traumatic stress syndrome is precisely the variability in the response to stressors. Such between-subject variation has been successfully replicated in animal models (Bush et al., 2007; Walker et al., 2008). Raw activity scores may constitute better predictors of response to stressors precisely because of their greater dynamic range, especially when comparing several strains of mice. Incorporating baseline differences into preclinical modeling will indeed require slight departures from current practices in the data analysis of fear-conditioning data (see for example Robles and Vargas-Irwin, 2010), but may by achieved with procedures as straight forward as using raw baseline data as covariates. In summary, analyzing raw scores presents new computational challenges, and further modeling and analytical developments are needed to take advantage of these opportunities.

Potential of Nonlinear Ultrasonic Indicators for Nondestructive Testing of Concrete

In the context of a growing need for safety and reliability in Civil Engineering, acoustic methods of nondestructive testing provide answers to a real industrial need. Linear indicators (wave speed and attenuation) exhibit a limited sensitivity, unlike nonlinear ones which usually have a far greater dynamic range. This paper illustrates the potential of these indicators, and evaluates its potential for in situ applications. Concrete, a structurally heterogeneous and volumetrically, mechanically damaged material, is an example of a class of materials that exhibit strong multiple scattering as well as significant elastic nonlinear response. In the context of stress monitoring in pre-stressed structures, we show that intense scattering can be applied to robustly determine velocity changes at progressively increasing applied stress using coda wave interferometry and thereby extract nonlinear coefficients. In a second part, we demonstrate the high sensitivity of nonlinear parameters to thermal damage as regard with linear ones. Then, the influence of water content and porosity on these indicators is quantified allowing to uncouple the effect of damage from environmental or structural parameters.

Quantum cascade laser gain enhancement by front facet illumination

Optical gain enhancement is demonstrated in a standard mid-infrared quantum cascade laser in pulse operation, using a near infrared illumination on the laser facet. An increase in the laser emission is observed, as well as greater dynamic range, threshold reduction, and a blue shift in the laser cavity modes. The optically induced gain increase allows for optical switching of the laser. All the changes have a nonlinear dependency on the illumination optical power and are attributed to the free carrier concentration increase and the electron transport change in the active region due to the near infrared illumination.

Abstract B181: EWS-FLI1 as a molecular target: Identification of inhibitors for a disordered protein

Abstract Ewing's sarcoma family of tumors (ESFT) are characterized by the EWS-FLI1 oncogenic fusion protein which results from a t(11;22) chromosomal translocation. Our previous studies show that RNA Helicase A (RHA) enhances EWS-FLI1 driven oncogenesis, and interruption of this protein-protein complex by small molecule inhibitors validate this interaction as a unique therapeutic target (NatMed 2009 Jul;15(7):750-6). EWS-FLI1 is a significantly hydrophobic disordered protein with unknown three-dimensional structure, which therefore precludes standard structure-based small molecule design. Fortunately, disordered proteins have a greater potential for binding with small molecule inhibitors due to structural flexibility. Given the challenges of drug design targeted to EWS-FLI1, we hypothesize that the optimization of a peptide displacement assay using small molecules can predict and direct the design of more potent analogs. Our methods originally used fluorescence polarization (FP) to measure RHA peptide displacement from EWS-FLI1. FP is a time consuming and reagent-limiting assay, so we evaluated new strategies using a 96-well plate format with the goal of high-throughput data collection. The first approach used a TECAN ULTRA 384 for assay detection and resulted in readings with high background noise and low signal. A second approach, AlphaScreen (amplified luminescent proximity homogenous assay, PerkinElmer), uses a bead-based interaction system based on energy conversion and generation of chemiluminescence when acceptor and donor beads are brought together during binding. The AlphaScreen assay uses approximately 3 ug of EWS-FLI1 protein per assay well and binds the 6-histadine tagged protein to the nickel-chelated donor beads while anti-FITC acceptor beads detect the flouresceintagged peptide. Our results show a 6-fold dynamic range between bound and quenched beads, in comparison to just 2.5-fold for FP and less than two-fold for the TECAN platform. Our small molecule YK-4-279 is able to reduce the signal back down to baseline, indicating that YK-4-279 dissociates the RHA peptide and EWS-FLI1. Key negative controls support specific binding between EWS-FLI1 and the RHA peptide. In addition, YK-4-279 was unable to quench the signal from a positive control using immunoglobulin, supporting the conclusion that YK-4-279 does indeed disrupt the specific protein-peptide binding rather than directly extinguishing the chemiluminescence. Data from the AlphaScreen will be used as input to a quantitative-structure activity relationship (QSAR) method. This QSAR method will predict biological activity from chemical structure and the knowledge gained from AlphaScreen will aid in the optimization and design of future analogs. In our initial work, we used the Free-Wilson QSAR method, converting the structure of the small molecules into a numerical format which allows for a mathematical comparison between structures, to populate a table with 32 small molecule analogs of YK-4-279. The AlphaScreen data may also be used with other QSAR methods, to which we may transition in later work. The AlphaScreen technology provides a method to quantitatively compare binding of small molecules in a high-throughput screening system, yields a greater dynamic range with more specificity, and provides data that will help to predict the binding of other analogs with similar chemical structures. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):B181.

Cost Effective, Versatile, High Performance, Spectral Analysis in a Synthetic Instrument

This paper described a versatile block of signal conditioning options that process raw data samples from the A/D converter and deliver a filtered and resampled version of those data samples to a conventional FFT based spectrum analyzer. The conditioning performs a number of important processing functions. These include spectral translation to baseband, noise bandwidth reduction to signal bandwidth, and arbitrary resampling to obtain specified spectral spacing with available sized FFTs. The versatility of an FPGA based processor and signal conditioning block enables the use of the signal conditioner blocks to align sample rate with transform sizes without the need to vary input sample clock rate or the cut off bandwidth of analog anti-alias filters in the signal path. A straw man set of specifications for the spectrum analyzer was proposed and used as the basis of the simulations presented in this paper. The processing described here reflects the great versatility and flexibility available to the system designer. Broader bandwidths and greater dynamic range options can be quickly accommodated in the architecture presented here.

A new class of floating-point data formats with applications to 16-bit digital-signal processing systems

Sixteen-bit, programmable, digital-signal processors suffer from inadequate dynamic range and noise performance due in part to the use of standard data formats with few bits available for numeric precision. A solution to this problem is developed that involves the use of irregular data formats. A new class of irregular floating-point formats is developed. A specific format is derived from this class that provides greater dynamic range and improved noise performance for 16-bit DSP applications. An experiment with one of the new formats is conducted and analyzed, and improved performance is verified. The importance of our work and its potential applications are discussed.

Transcription-Based Reporters of Wnt/β-Catenin Signaling

INTRODUCTIONThe Wnt/β-catenin pathway is the best characterized Wnt pathway largely as a result of powerful assays that allow measurement of in vivo and in vitro pathway activation. Early assays for Wnt/β-catenin signaling included phenotypic assays in Drosophila, dorsal axis duplication in Xenopus, and proliferation of C57MG mammary epithelial cells. More recent characterizations rely on direct measurement of pathway activation. The Wnt/β-catenin signaling pathway culminates with T-cell factor/lymphoid enhancer factor (TCF/LEF)-dependent regulation of target gene transcription; assaying such transcription with reporters containing multimerized TCF/LEF DNA-binding sites is a reliable measure of pathway activation. These reporters have helped characterize the Wnt/β-catenin signaling pathway and will be critical to further studies of pathway regulation and in the development of therapeutic mechanisms to combat diseases arising from aberrant signaling. This protocol describes a variety of methods for using an improved Wnt/β-catenin reporter system, the β-catenin-activated reporter (BAR), and its accompanying control reporter system, found-unresponsive BAR (fuBAR). Procedures are presented for transient and stable transfection of the reporter. Transient transfection is very robust and does not require lentiviral production, although it has a slightly smaller dynamic range relative to stably integrated BAR. The stable transduction system can be used to generate stable reporter cell lines, assay Wnt/β-catenin signaling in cells that might be otherwise difficult to transfect, or assay signaling in vivo. The BAR system, with its improved sensitivity, greater dynamic range, and lentiviral-based reporter system, provides a vital tool for future studies of this signaling pathway.

A novel high-throughput cell-based method for integrated quantification of type I interferons and in vitro screening of immunostimulatory RNA drug delivery.

A hallmark of immune activation by certain RNA sequences is the generation of interferon responses. However, the study of immunostimulatory RNA (isRNA) has been hindered by costly and slow methods, particularly in vitro. We have developed a cell-based assay to detect human type I interferon (IFN) that reliably senses both IFN-alpha and IFN-beta simultaneously. The human 293T cell line was stably transfected with a fusion gene of monomeric red fluorescent protein (mRFP) under the transcriptional control of an interferon-stimulated response element (ISRE). High levels of mRFP are expressed following activation of the type I IFN receptor (IFNAR). Using this method, detection limits for IFN similar to that of ELISA can be achieved but with a greater dynamic range and in a high-throughput manner. As a proof of concept, we utilized this method to screen a library of cationic lipid-like materials that form nanoparticle complexes with RNA for induction of innate immune responses in vitro. We expect the screening and detection methods described herein may provide a useful tool in elucidating mechanisms that govern the delivery of RNA molecules to effector cells and receptors of the innate immune system. We apply this tool to investigate isRNA drug delivery, but it may also find use in other applications for which high-throughput detection of type 1 IFN is desired.

Comparison of upper tropospheric water vapor observations from the Microwave Limb Sounder and Atmospheric Infrared Sounder

We compare matched retrievals of upper tropospheric water vapor (UTWV) mixing ratios from the Microwave Limb Sounder (MLS) instrument on the Aura satellite, and the Atmospheric Infrared Sounder (AIRS) instrument on the Aqua satellite. Because each instrument's sampling is affected by tropical conditions, about half of mutually observed scenes in the tropics yield simultaneous successful retrievals from both systems. The fraction of mutually retrieved scenes drops to 30% at higher latitudes where clouds significantly inhibit AIRS sounding. Essentially all scenes observed by MLS in extratropical and polar regions yield successful retrievals. At 250 hPa in the tropics, measurements from the two instruments are highly correlated, the differences of their means (q) are smaller than 10%, and the standard deviations of their differences (σq) are 30% or less. At 300 hPa, MLS means are drier by 10–15%, and σq is 40–60%, indicating that responses of MLS and AIRS to UTWV perturbations are not one‐to‐one. Root mean square agreement is also poorer over the poles at 300 hPa and at 200 and 150 hPa at lower latitudes. In these regions, ∣q∣ = 10% or more, and σq = 40–70%. Correlations between the two data sets are 0.7–0.9 at 300 and 250 hPa globally and at 200 hPa in the tropics. This high correlation indicates that σq of 50% or greater comes mainly from systematic differences in sensitivity of the two instruments, especially for small and large UTWV amounts; larger values of σq are generally not due to large random errors from either instrument. An AIRS low‐end sensitivity threshold of 15–20 ppmv leads to poorer agreement under the driest conditions. Disagreement at 300 hPa likely comes from overestimation by MLS for the wettest conditions of &gt;400 ppmv. While MLS is biased slightly dry overall at 300 hPa, it is biased wet in the wettest regions, particularly those associated with deep convection. These sensitivity differences explain nonunity slopes of linear fits to the two data sets. MLS everywhere has a greater dynamic range than AIRS, with larger maxima and smaller minima. Good agreement at 250 hPa suggests AIRS uncertainties of 25% up to the reported 250–200 hPa layer in the tropics and extratropics, consistent with previous comparisons with balloon‐ and aircraft‐borne instruments. The agreement at 250 hPa also indicates that MLS is reliable from its reported 215‐hPa level upward in altitude.

X‐ray microscopy of plant cells by using LiF crystal as a detector

A lithium fluoride (LiF) crystal has been utilized as a new soft X-ray detector to image different biological samples at a high spatial resolution. This new type of image detector for X-ray microscopy has many interesting properties: high resolution (nanometer scale), permanent storage of images, the ability to clear the image and reuse the LiF crystal, and high contrast with greater dynamic range. Cells of the unicellular green algae Chlamydomonas dysosmos and Chlorella sorokiniana, and pollen grains of Olea europea have been used as biological materials for imaging. The biological samples were imaged on LiF crystals by using the soft X-ray contact microscopy and contact micro-radiography techniques. The laser plasma soft X-ray source was generated using a Nd:YAG/Glass laser focused on a solid target. The X-ray energy range for image acquisition was in the water-window spectral range for single shot contact microscopy of very thin biological samples (single cells) and around 1 keV for multishots microradiography. The main aim of this article is to highlight the possibility of using a LiF crystal as a detector for the biological imaging using soft X-ray radiation and to demonstrate its ability to visualize the microstructure within living cells.

Total Deviation Probability Plots for Stimulus Size V Perimetry

To compare empirical probability plots in patients with glaucoma for size V and III perimetry testing. We computed empirical probability plot percentile limits after testing 60 age-matched controls tested with both size III (Swedish interactive thresholding algorithm) and size V (full threshold) perimetry twice. Probability plots of 120 patients with glaucoma tested in the same way were computed. We compared the number of abnormal test locations in the 2 stimulus sizes; we then compared these results with those from size III StatPac software (Zeiss Humphrey Systems, Dublin, California) using 2-way repeated-measures analysis of variance. We found a similar number of abnormal test locations (P < or = .05) for the size III and size V testing conditions identified by the probability plots (no significant difference); there were significantly fewer abnormal locations using StatPac (size III) than from our size III database. When results were stratified by mean deviation, the mild visual loss group again did not show any significant differences between sizes III and V. Size V full-threshold testing gives a similar number of abnormal test locations in patients with glaucoma compared with the size III Swedish interactive thresholding algorithm standard test. Size V testing, with its greater dynamic range and lower variability, may be a viable alternative to size III testing in patients with glaucoma.