DNA entropy reveals a significant difference in complexity between housekeeping and tissue specific gene promoters

BACKGROUND The complexity of DNA can be quantified using estimates of entropy. Variation in DNA complexity is expected between the promoters of genes with different transcriptional mechanisms; namely housekeeping (HK) and tissue specific (TS). The former are transcribed constitutively to maintain general cellular functions, and the latter are transcribed in restricted tissue and cells types for specific molecular events. It is known that promoter features in the human genome are related to tissue specificity, but this has been difficult to quantify on a genomic scale. If entropy effectively quantifies DNA complexity, calculating the entropies of HK and TS gene promoters as profiles may reveal significant differences. RESULTS Entropy profiles were calculated for a total dataset of 12,003 human gene promoters and for 501 housekeeping (HK) and 587 tissue specific (TS) human gene promoters. The mean profiles show the TS promoters have a significantly lower entropy (p<2.2e-16) than HK gene promoters. The entropy distributions for the 3 datasets show that promoter entropies could be used to identify novel HK genes. CONCLUSION Functional features comprise DNA sequence patterns that are non-random and hence they have lower entropies. The lower entropy of TS gene promoters can be explained by a higher density of positive and negative regulatory elements, required for genes with complex spatial and temporary expression

MICRO PHOTO IONIZATION DETECTOR FOR VOLATILE ORGANIC COMPOUNDS

International audienc

MICRO PHOTO IONIZATION DETECTOR FOR BTEX ANALYSIS: REVIEW REPORT OF PERFORMANCE INFLUENCING PARAMETERS

International audienceVolatile Organic Compounds (VOCs) are gaseous chemical species emitted from solids and liquids that may cause short and long term adverse health effects. They are present in both outdoor and indoor air. In open environments, automotive exhausts and industrial waste are major sources of VOCs. They are also emitted from building materials, varnishes, paints, solvents, etc. [1]. Within the VOCs, BTEX (benzene, toluene, ethylbenzene, xylenes) are of greatest concern due to their health effects. Benzene, for example, is highly carcinogenic and the World Health Organization reports no safe level of exposure [2]. Gas chromatographs (GC) monitor air quality and can detect VOCs, these equipment are heavy, lab-based and non-portable. In 2016, Nasreddine [3] reported a miniaturized gas analyzer that can detect BTEX at ppb levels and weights 4 kg. In order to further reduce the size of this equipment and the consumption of carrier gas, its main components must be miniaturized and operate under low gas flow rate. The detector is one of the main components of the gas chromatograph, responsible for quantifying the chemicals sampled. This paper is centered on the type of detector named photo ionization detector (PID). The objective of this work is to present the main factors that affect the analytical PID performance. The information summarized here should be used as guidelines to design a future micro PID.Fig. 1 shows the basic elements of a photo ionization detector. In this device, a gas sample containing the chemicals flows through the ionization chamber, where photons emitted by the ionization source (UV lamp and window) reach the sample molecules. As a general rule, if the ionization energy of the photon is greater than the ionization potential of the molecule, ionization occurs. The electrodes establish then an electric field in the ionization chamber where the ionized molecules generate an ionization current proportional to the concentration of molecules in the gas sample.The performance of the PID is affected by design choices at the ionization source, ionization chamberand electrodes. The ionization source is selected according to the desired photon energy output,considering the target compounds to be detected. In theory, an ionization source with energy greater orequal to 9.3 ionizes all the BTEX molecules. However, Driscoll and Duffy [4] suggests to use the 10.2eV ionization source since it has the highest photon flux resulting in high PID sensitivity. The ionizationchamber should ensure uniform flow, otherwise the sensitivity of the PID is reduced [5]. Besides that,the ionization chamber volume should be as low as possible to reduce response time, thereby increasingsensitivity. A small volume also avoids remixing of organic species that have been previously separatedin the gas chromatograph and ensures uniform ionization of the sample, contributing positively to thelinearity and sensitivity of the signal. The electrodes inside the ionization chamber directly influencethe ion collection efficiency, which affects the sensitivity of the PID. Important electrode design aspectsinfluencing the ions collection efficiency are the electric field in the ionization chamber, the area of theelectrodes and the position of the electrodes in the ionization chamber [5].Micro and nanofabrication techniques can be used to miniaturize the PID with the possibility to improveits performance [5,6]. In the future, a micro PID design will be proposed and the most suitable microand nanofabrication technique for its fabrication will be evaluated. The new design will be based on themajor guidelines presented in this work with focus in diminishing both the ionization chamber volumeand the associated gas flow rate while maintaining low detection limit. The prototype will be evaluatedand compared to commercial PIDs

Convergence and Interdependence at the Civil-Military Interface

http://deepblue.lib.umich.edu/bitstream/2027.42/50870/1/91.pd

The structure of calcium metaphosphate glass obtained from x-ray and neutron diffraction and reverse Monte Carlo modelling

The short range structure of (CaO)(0.5)(P2O5)(0.5) glass has been studied using x-ray and neutron diffraction and modelled using the reverse Monte Carlo method. Using this combination of techniques has allowed six interatomic correlations to be distinguished and fitted to obtain a set of bond lengths and coordination numbers that describe the structure of the glass. The glass consists of metaphosphate chains of phosphate tetrahedra and each phosphate unit has two non-bridging oxygen atoms available for coordination with Ca. The Ca-O correlation was fitted with two peaks at 2.35 and 2.86 angstrom, representing a broad distribution of bond lengths. The total Ca-O coordination is 6.9 and is consistent with distorted polyhedral units such as capped octahedra or capped trigonal prisms. It is found that most non-bridging oxygen atoms are bonded to two calcium atoms. All of these observations are consistent with Hoppe's model for phosphate glasses. Furthermore, the medium range order is revealed to consist of phosphate chains intertwined with apparently elongated clusters of Ca ions, and the Ca-O and Ca-P correlations contributed significantly to the first sharp diffraction peak in x-ray diffraction

MICROFLUIDIC PHOTOIONIZATION DETECTOR: CHANNEL GEOMETRY AND SIGNAL EVALUATION

International audienc

Experimental Evaluation of Wireless Simulation Assumptions

All analytical and simulation research on ad hoc wireless networks must necessarily model radio propagation using simplifying assumptions. We provide a comprehensive review of six assumptions that are still part of many ad hoc network simulation studies, despite increasing awareness of the need to represent more realistic features, including hills, obstacles, link asymmetries, and unpredictable fading. We use an extensive set of measurements from a large outdoor routing experiment to demonstrate the weakness of these assumptions, and show how these assumptions cause simulation results to differ significantly from experimental results. We close with a series of recommendations for researchers, whether they develop protocols, analytic models, or simulators for ad hoc wireless networks

Embodying the illusion of a strong, fit back in people with chronic low back pain. A pilot proof-of-concept study

Objective: This proof-of-concept pilot study aimed to investigate if a visual illusion that altered the size and muscularity of the back could be embodied and alter perception of the back. Methods: The back visual illusions were created using the MIRAGE multisensory illusion system. Participants watched real-time footage of a modified version of their own back from behind. Participants undertook one experimental condition, in which the image portrayed a muscled, fit-looking back (Strong), and two control conditions (Reshaped and Normal) during a lifting task. Embodiment, back perception as well as pain intensity and beliefs about the back during lifting were assessed. Results: Two participants with low back pain were recruited for this study: one with altered body perception and negative back beliefs (Participant A) and one with normal perception and beliefs (Participant B). Participant A embodied the Strong condition and pain and fear were less and both perceived strength and confidence were more than for the Normal or the Reshaped condition. Participant B did not embody the Strong condition and reported similar levels of pain, fear strength and confidence across all three conditions. Discussion: An illusion that makes the back look strong successfully induced embodiment of a visually modified back during a lifting task in a low back pain patient with altered body perception. Both participants tolerated the illusion, there were no adverse effects, and we gained preliminary evidence that the approach may have therapeutic potential

Synthesis, characterisation and performance of (TiO2)(0.18)(SiO2)(0.82) xerogel catalysts

The synthesis of high surface area xerogels has been achieved using the sol-gel route. Heptane washing was used during the stages of drying to minimise capillary pressures and hence preserve pore structure and maximise the surface area. SAXS data have identified that heptane washing during drying, in general, results in a preservation of the pore structure and surface areas of up to 450 m(2) g(-1). O-17 NMR showed that Ti is fully mixed into the silica network in all of the samples. XANES data confirm that reversible 4-fold Ti sites are more prevalent in samples with high surface areas, as expected. The calcined xerogels were tested for their catalytic activity using the epoxidation of cyclohexene with tert-butyl hydroperoxide (TBHP) as a test reaction, with excellent selectivities and reasonable percentage conversions. FT-IR spectroscopy has revealed that the catalytic activity is correlated with the intensity of the Si-O-Ti signal, after accounting for variations in Si-OH and Si-O-Si. The most effective catalyst was produced with heptane washing, a calcination temperature of 500 degreesC, and a heating rate of 5 degreesC min(-1)