We have developed a method of calculating the average local absorbance (ALA) of a nucleus from the integrated nuclear absorbance and area. One can use the ALA, along with nuclear areas measured at different point absorbance thresholds, to determine whether a nucleus is stained too lightly or too darkly for accurate absorption measurements; this allows selection of an optimal light wavelength for the performance of these measurements. The ALA can also be used for automatic and instantaneous correction of integrated absorbance values from darkly stained cells. This allows the rapid measurement of the integrated absorbances of a large number of nuclei that are heterogeneous in stain intensity. Coefficients of variation of approximately 3% are obtained for the integrated absorbances of nuclei of nontransformed G0/G1 cells. This correction method can be applied with any image densitometer that generates both integrated absorbance and area values.

The 3C 273 and RX J1230.8+0115 sight lines probe the outskirts of the Virgo Cluster at physical separations between the sight lines of 200 and 500 h70-1 kpc. We present an analysis of available Hubble Space Telescope STIS echelle and Far-Ultraviolet Spectroscopic Explorer (FUSE) UV spectroscopy of RX J1230.8+ 0115, in which we detect five Lyα absorbers at Virgo distances. One of these absorbers is a blend of two strong metal-line absorbers at a recession velocity coincident with the highest neutral hydrogen column density absorber in the 3C 273 sight line, ∼350 h70-1 kpc away. The consistency of the metal-line column density ratios in the RX J1230.8+0115 sight line allows us to determine the ionization mechanism (photoionization) for these absorbers. While the low signal-to-noise ratio of the FUSE spectrum limits our ability to model the neutral hydrogen column density of these absorbers precisely, we are able to constrain them to be in the range 1016-1017 cm -2. The properties of these absorbers are similar to those obtained for the nearby 3C 273 absorber studied by Tripp and collaborators. However, the inferred line-of-sight size for the 3C 273 absorber is only 70 pc, much smaller than those inferred in RX J1230.8+0115, which are 10-30 h70-1 kpc. The small sizes of all three absorbers are at odds with the ≥ 350 h70-1 kpc minimum transverse size implied by an application of the standard QSO line-pair analysis. On the basis of absorber associations between these two sight lines we conclude that a large-scale structure filament produces a correlated, not contiguous, gaseous structure in this region of the Virgo Supercluster. These data may indicate that we are detecting overdensities in the large-scale structure filaments in this region. Alternatively, the presence of a galaxy 71 h70-1 kpc from a 3C 273 absorber may indicate that we have probed outflowing, starburst-driven shells of gas associated with nearby galaxies.

We present Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS) and Far Ultraviolet Spectroscopic Explorer (FUSE) spectra of the QSO PG 1211+143 (zem = 0.081) and a galaxy survey of the surrounding field. This sight line shows two strong intergalactic absorption systems at cz ≃ 15,300 and 19,300 km s-1. This sight line addresses the nature and origin of the O VI absorbers and their connection to galaxies. We explore the relationship of these absorbers to the nearby galaxies and compare them to other O VI-bearing absorbers in diverse environments. At 15,300 km s-1, we find four distinct H I components and associated C II, C III, C IV, Si II, Si III, Si IV, N V, and O VI, lying near a spiral-dominated galaxy group with a bright member galaxy 137 h 70-1 kpc from the sight line. The observed ions of C, Si, and N are likely to be photoionized, but the O VI is more consistent with collisional ionization. The ion ratios in this absorber resemble the highly ionized Galactic high-velocity clouds (HVCs); it may also trace the hot intragroup medium gas or the unbound wind of an undiscovered dwarf galaxy. At 19,300 km s-1, we find five H I components and associated C III, Si III, and collisionally ionized O VI lying 146 h70-1 kpc from an isolated galaxy. The properties of the O VI-bearing gas are consistent with an origin in strong shocks between low-metallicity gas (≥2%-6% solar) and one or more of the warm photoionized components. It is likely that these absorbers are related to the nearby galaxies, perhaps by outflows or gas stripped from unseen satellite galaxies by interactions. However, we cannot reject completely the hypothesis that they reside in the same large-scale structure in which the galaxies are embedded but are otherwise not directly related.

We provide an in-depth analysis of the He II and H I absorption in the intergalactic medium (IGM) at redshifts z = 2.3-2.9 toward HE 2347-4342, using spectra from the Far Ultraviolet Spectroscopic Explorer and the Ultraviolet-Visual Echelle Spectrograph on the Very Large Telescope. Following up on our earlier study, we focus here on two major topics: (1) small-scale variability (Δz ≈ 10-3) in the ratio η = N(He II)/N(H I) and (2) an observed correlation of high-η absorbers (soft radiation fields) with voids in the (H I) Lyα distribution. These effects may reflect fluctuations in the ionizing sources on scales of 1 Mpc, together with radiative transfer through a filamentary IGM whose opacity variations control the penetration of 1-5 ryd radiation over 30-40 Mpc distances. Given the photon statistics and backgrounds, we can measure optical depths over the ranges 0.1 < τHe II < 2.3 and 0.02 < τH I < 3.9 and reliably determine values of η ≈ 4τHe II/τH I over the range 0.1-460. Values η = 20-200 are consistent with models of photoionization by quasars with observed spectral indices α s = 0-3. Values η > 200 may require additional contributions from starburst galaxies, heavily filtered quasar radiation, or density variations. Regions with η < 30 may indicate the presence of local hard sources. We find that η is higher in "void" regions, where H I is weak or undetected and ∼80% of the path length has η > 100. These voids may be ionized by local soft sources (dwarf starbursts) or by QSO radiation softened by escape from the active galactic nucleus cores or transfer through the "cosmic web." The apparent differences in ionizing spectra may help to explain the 1.45 Gyr lag between the reionization epochs of H I (zH I ∼ 6.2 ± 0.2) and He II (zHe II ∼ 2.8 ± 0.2).

This paper presents and evaluates a new terahertz metamaterial absorber (MMA) for sensing applications. Because of its unique properties, metamaterial-based sensors are widely employed in a variety of applications. The reported structure comprises of two identical metallic patches, a dielectric spacer and a ground metal plane. The finite element approach has been utilized to simulate and analyse the design. It is found that the MMA offered a prominent resonant peak with near 100% absorbance at frequency 4.5 THz due to the resultant effect of coupling between the two identical patches. In addition, surface current distribution, absorption mechanism and structural parametric analysis has also been investigated. The peak is designated as 'A', with a line width of 0.02 THz and a quality factor (Q-factor) of 225, which is sensitive to the refractive index of the environment (RI). As a result of its highly sensitive sensing capabilities, the proposed design can be employed as a sensor for refractive index, having 1.6 THz per refractive index unit (RIU) sensitivity and figure of merit (FoM) of 80 in terms of change in RI of the environment. The majority of biomedical samples have RI of 1.3 to 1.36, which is worth highlighting. Thus, biomedical applications may be possible with the suggested sensor.

The gastrointestinal tract has a large functional reserve. This is particularly true of the small intestine, and early studies by Flint in 1912, showed that dogs could withstand 50%-70% small intestinal resection, returning to normal health after an initial period of weight loss and malabsorption. No doubt, this reserve is in part due to the very high rate of epithelial proliferation in small bowel mucosa. Intestinal adaptation is the result of morphological and functional changes, and while these parameters can be accurately appreciated, the mechanisms by which these changes take place, are still under active investigation. This section summarises the changes, both structural and functional, in the adaptive process, and this is followed by a review of the background work done on the possible mechanism of adaptation. The normal anatomy of intestinal mucosa is however, considered first. Most of the work done to date in the field of intestinal adaptation, involves the small bowel, and this part of the gut will be discussed predominantly, but data available on colonic growth will be mentioned.

The current period of human history is considered to be the plastics age due to its versatile characteristics, especially the lightweight, durability and low production cost. Plastics can be manufactured to suit multifarious functions, for example, for personal care products, food/drink storage and medical purposes. Thus, the use of plastics is unavoidable now, finally contributing to the severe pollution worldwide. In 2018 alone, the global plastics production amount has exceeded 359 million tons, around 10% of which ultimately become waste persisting in the environment. When plastic wastes exposed to the sun's radiation, climate change and mechanic abrasion, degradation and fragmentation may occur. Once the size of the fragmentation products is less than 5 mm, they are commonly defined as microplastics (MPs) by the National Oceanographic and Atmospheric Administration. Currently, microplastics have been regarded as the most pervasive environmental pollution problems, not only because of their physical hazards but also due to their interactions with other pollutants in the environment. Pollution can be attributed by the release of additives from MPs, as well as the MPs with adsorbed toxic contaminants. Moreover, MPs additives together with adsorbed chemicals can be easily uptaken by animals, which may cause further propagated effects on the ambient ecosystem. Through the bioaccumulation and biomagnification effect, MPs can even be accumulated in the organisms from different trophic levels and cause serious impacts on aquatic ecology and human health. Despite growing number of evidences that have confirmed the presence and consequential effects of microplastics, researches on microplastic pollution are still lacking. Investigations on occurrence, determination and environmental fate of MPs in aquatic systems are clearly needed. Therefore, the major objective of this study is to elucidate the distribution of MPs in natural environment, to develop novel determination methods to characterize the micro-(nano-)plastics (MNPs), and to study the interactions of MPs with other contaminants in different conditions, as well as their consequential fate in different matrices (e.g. freshwater, cold-blooded intestine, and warm-blooded intestine). The spatial-temporal distribution of the MPs along the Maozhou River was investigated for both the surface water and sediments from 17 sites. Results showed that MPs were widely and unevenly distributed along the river. The MP abundances in dry season ranged from 4.0 ± 1.0 to 25.5 ± 3.5 items·L-1 in water and 35 ± 15 to 560 ± 70 item·kg-1 in sediments, which were relatively higher than those observed in wet season (water: 3.5 ± 1.0 to 10.5 ± 2.5 items·L-1; sediments: 25 ± 5 to 360 ± 90 item·kg-1; p value < 0.05). The dominant types of MPs were identified as: polyethylene (PE, water: 45.0%, sediments: 42.0%), polypropylene (PP, water and sediments: 12.5%), polystyrene (PS, water: 34.5%; sediments 14.5%) and polyvinyl chloride (PVC, water: 2.0%; sediments: 15%). Moreover, metals such as Al, Si, Ca were discovered on the rough surface of the MPs, indicating the interactions between the MPs and the aquatic environment. After obtaining the occurrence of the MPs in the aquatic systems, we proposed an accurate method for MNPs identification and quantification with the employment of the matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS). By optimizing the conditions (e.g. the laser energy, matrix, analyte, cationization agent and their ratio), the peaks of PS and polyethylene terephthalate (PET) were successfully identified. A quantitative correlation was built between the normalized signal intensity and ln[polymer concentration], with a correlation coefficient above 0.96 for low-molecular-weight (LM-) polymers and 0.98 for high-molecular-weight (HM-) polymers. Furthermore, two types of environmental MPs samples were prepared, including the particles of an aviation cup as the fresh plastics and the aged MPs extracted from river sediment. By using MALDI-TOF MS, the PS-related micro-(nano-)plastics (in both aviation cup and sediment) consisted of C8H8 and C16H16O oligomers, while the PET-related MNPs (only found in sediment) were identified with compositions of C10H8O4 and C12H12O4. The contents of PS and PET MNPs in sediment were quantified as 8.56 ± 0.04 and 28.71 ± 0.20 mg·kg-1, respectively. Also, the interaction between MPs and bisphenols was investigated. PVC was selected as the representative target because it is comparatively easy to decompose into MPs with the release of additives, especially the bisphenols. The released bisphenols may then be readsorbed by the PVC MPs and cause consequential pollution to the ecosystem. To elaborate on the interactions mechanism, a systematic study was carried out to determine the adsorption mechanisms of five bisphenol analogues (BPA, BPS, BPF, BPB, and BPAF) on PVC MPs. The equilibrium adsorption numbers of the bisphenols on PVC MPs are 0.19 ± 0.02 mg/g (BPA), 0.15 ± 0.01 mg/g (BPS), 0.16 ± 0.01 mg/g (BPF), 0.22 ± 0.01 (BPB), 0.24 ± 0.02 mg/g (BPAF), respectively. Intraparticle diffusion modeling (kinetics) divided the adsorption process into three stages: external mass transport, intraparticle diffusion and dynamic equilibrium. The isotherm results showed a better fit of the adsorption to the Freundlich model. Furthermore, the adsorption mechanisms of the five bisphenol analogues were explored intensively, with respect to hydrophobic interaction, electrostatic force and noncovalent bonds. Besides the adsorption process, the transfer and release behaviors of contaminated MPs are of critically importance in the exploration of their role as culprits and/or vectors for the aforementioned toxicity. Therefore, experiments were performed to examine desorption behaviors and cytotoxicity performance of contaminated MPs in aquatic surroundings and intestinal environment after ingestion by organisms (cold-/warm-blooded). The kinetic study showed that the rate of desorption for bisphenols could be enhanced threefold under simulated warm intestinal conditions. The Freundlich isotherms indicated multiple-layer desorption of the bisphenols on the heterogeneous surfaces of PVC MPs. Hysteresis was detected in the adsorption/desorption of bisphenols in a water environment, but no adsorption/desorption hysteresis was observed in the simulated intestinal conditions of warm-blooded organisms. Due to the enhanced bioaccessibility, the desorption results implied that the environmental risk of contaminated PVC MPs might be significantly increased after ingestion at a high bisphenols dosage. Although with different IC50, the five bisphenols released under the intestinal conditions of warm-blooded organisms can cause higher proliferation reduction in fish and human cell lines than the bisphenols released in water. In summary, this study elucidated the spatial-temporal distribution behaviors of MPs, developed effective determination methods for MNPs revealed the interactions mechanisms of MPs with other contaminants, and explored their consequential fate in different environments. The obtained results are helpful of better understanding on the land-based input of MPs from the intensively affected inland waters, realizing the role of microplastics as both source and carrier for emerging organic pollutants, and providing a novel alternative for MPs determination in future studies.

The main objective was to develop a procedure based on differential optical absorption spectroscopy (DOAS) to measure atmospheric total column of ozone, using the automated instrument developed at the University of North Texas (UNT) by Nebgen in 2006. This project also explored the ability of this instrument to provide measurements of atmospheric total column nitrogen dioxide. The instrument is located on top of UNT’s Environmental Education, Science and Technology Building. It employs a low cost spectrometer coupled with fiber optics, which are aimed at the sun to collect solar radiation. Measurements taken throughout the day with this instrument exhibited a large variability. The DOAS procedure derives total column ozone from the analysis of daily DOAS Langley plots. This plot relates the measured differential column to the airmass factor. The use of such plots is conditioned by the time the concentration of ozone remains constant. Observations of ozone are typically conducted throughout the day. Observations of total column ozone were conducted for 5 months. Values were derived from both DOAS and Nebgen’s procedure and compared to satellite data. Although differences observed from both procedures to satellite data were similar, the variability found in measurements was reduced from 70 Dobson units, with Nebgen’s procedure, to 4 Dobson units, with the DOAS procedure.A methodology to measure atmospheric nitrogen dioxide using DOAS was also investigated. Although a similar approach to ozone measurements could be applied, it was found that such measurements were limited by the amount of solar radiation collected by the instrument. Observations of nitrogen dioxide are typically conducted near sunrise or sunset, when solar radiation experiences most of the atmospheric absorption.

A new detector for atomic spectroscopy was developed based on the photoacoustic principle. A simple system was constructed based on this detector and applied to the trace analysis of mercury. The detection limit was found to be about 0.2 ug/1 of mercury with a one milliliter sample.

The objectives of this work were (i) to develop a new methodfor the preparation of thin cellulose model films, (ii) to usethese model films for swelling measurements and (iii) to relatethe swelling of fibers and films to the dry strength ofpaper. In the new film preparation method, NMMO(N-methylmorpholine-N-oxide) was used to dissolve cellulose andDMSO (dimethyl sulfoxide) was added to control the viscosity ofthe cellulose solution. A dilute solution of the cellulose wasspin-coated onto a silicon oxide wafer and the cellulose filmthus prepared was then precipitated in deionised water. Asaturated layer of glyoxalated-polyacrylamide was used toanchor the film onto the silicon oxide wafer. This proceduregave films with thicknesses in the range of 20-270 nm. Thefilms were cleaned in deionised water and were found by ESCAanalysis and contact angle measurements (θ&lt;20°)to be free from solvents. Solid state NMR measurements onfibers spun from NMMO also indicated that the model filmconsisted of about 50% crystalline material and that thecrystalline structure was of the cellulose II type.Determination of the molecular weight distribution of thecellulose surface material showed that the NMMO treatmentcaused only a minor breakdown of the cellulose chains and thatlow molecular mass oligomers of glucose were not created. It was further shown that atomic force microscopy (AFM)measurements could be used to determine the thicknessof thecellulose films, in both the dry and wet states. The thicknesswas determined as the height difference between the top surfaceand the underlying silica wafer measured at a position where anincision had been made in the cellulose film. The cellulosesolutions were also directly spin-coated onto the crystal usedin the Quartz crystal microbalance (QCM-D), pre-treated withthe same type of anchoring polymer. With this application,these model surfaces were shown to be suitable for swellingmeasurements with the QCM-D. The extent of swelling and theswelling kinetics in the presence of electrolytes, such asNaCl, CaCl2 and Na2SO4, and at different pH were measured inthis way. The films were found to be very stable during thesemeasurements and the results were comparable to the swellingresults obtained for the corresponding pulps. The swelling ofboth fibers and films followed the general behavior ofpolyelectrolyte gels in the presence of electrolytes and was inaccordance with the Donnan equilibrium theory. The films havebeen shown to differ from fibers with regard to the absence ofa covalent interior network. This influences the evaluation ofthe deswelling effects measured on the model films. Theswelling effect seen with different electrolytes has also beenconsidered in relation to the tensile strength of paperprepared from a kraftliner-pulp. In this study, it was foundthat there was no direct relationship between the swelling ofthe fibers, measured as WRV, and the strength of the paper inthe presence of different electrolytes at pH 5. KEYWORDS:absorption, carboxymethyl cellulose,cellulose, cellulose fibers, dissolving pulps, donnanequilibrium, electrolytes, film, ion exchange, ionization,kinetics, liner boards, microscopy, spinning, surfaces,swelling, tensile strength, water, water retention value. / <p>NR 20140805</p>