1,022 research outputs found

    Verrucous Carcinoma of the Esophagus

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75147/1/j.1572-0241.1984.tb11856.x.pd

    Numerical investigation of stability and settlement of tunnels in undrained clay

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    This thesis describes the development, verification and use of a numerical model for investigating circular tunnels in cohesive soils. Using this model, important problems relating to tunnel construction can be studied. In particular, it studies the stability and settlement problems that arise during the construction of single and twin tunnels using tunnel-boring machines (TBM’s). The developed numerical model simulates the movement and relaxation of the soil around the shield and tail void that occurs due to overcutting and the time delay to lining installation and back grouting. Using this numerical model, a parametric study is conducted which covers most of the practical range. Settlement and stability data is collected for single and twin tunnels. The settlement data is analysed using a regression of the commonly used Gaussian equation on the settlement data. This approach allows a settlement parameter (ix) to be estimated reliably and accurately for each case. The results of this study are quite positive, settlement results compare well with previous experimental and observational results. Design charts using dimensionless ratios have therefore been presented, which allow the prediction of a settlement profile based on geometry, volume loss, and material properties. Stability is analysed using the widely used Broms-Bennermark stability number (N). This approach allows an N to be calculated for each case, which defines the differential between surface and internal pressure. By determining the collapse stage during the relaxation method, an envelope for the critical N is developed. This stability envelope is then compared to the rigorous upper and lower bound solutions computed by the finite-element limit analysis approach developed by the University of Newcastle Geotechnical group. The results are quite positive, with the stability results from this study remaining within 5% of the upper and lower bound solutions. Design charts using dimensionless ratios have therefore been presented. These calculated stability numbers are also considered with the settlement results, which allows some correlation between N and volume loss

    Biochemical and Structural Effects of Rigor Mortis-Accelerating Treatments in Broiler \u3ci\u3ePectoralis\u3c/i\u3e

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    This study was conducted to elucidate the mechanism of action of two selected rigor mortis-accelerating treatment systems employed in the prevention of the toughness associated with early-harvested (1 h post-mortem) broiler Pectoralis muscle. The treatments included 14 min of low voltage electrical stimulation (110 V, 1 A, pulsing 1 s on and 1 s off) combined with high temperature conditioning (39 C) and muscle tensioning (LV + HTC + MT); a 15-s high voltage stimulation (440 V, 1 A pulsing 2 s on and 1 s off) combined with muscle tensioning (HV + MT); and a control simulating commercial broiler processing practices. The rigor-accelerating treatments reduced pH and increased R-value (inosine:adenosine ratio) at 1 h post-mortem, but only the LV + HTC + MT treatment reduced sarcomere shortening. Both rigor treatments reduced the amount of measurable myofibrillar fragmentation. Cathepsin B and B + L activities were not affected by the rigor treatments. Calpain I activity was not detectable in any 24-h post-mortem sample. Calpain II activity at 24 h post-mortem was greater in muscles receiving HV + MT than from the LV + HTC + MT or control carcasses, but was reduced in all muscles by 24 h postmortem. An SDS-PAGE indicated a 30-kDa polypeptide that was absent at death and appeared in control and LV + HTC + MT muscles but to a lesser extent in HV + MT muscles. These results suggested that the LV + HTC + MT treatment has a greater tenderizing effect than the HV + MT treatment because the former achieves a better balance between reduced sarcomere shortening and myofibrillar fragmentation

    Biochemical and Structural Effects of Rigor Mortis-Accelerating Treatments in Broiler \u3ci\u3ePectoralis\u3c/i\u3e

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    This study was conducted to elucidate the mechanism of action of two selected rigor mortis-accelerating treatment systems employed in the prevention of the toughness associated with early-harvested (1 h post-mortem) broiler Pectoralis muscle. The treatments included 14 min of low voltage electrical stimulation (110 V, 1 A, pulsing 1 s on and 1 s off) combined with high temperature conditioning (39 C) and muscle tensioning (LV + HTC + MT); a 15-s high voltage stimulation (440 V, 1 A pulsing 2 s on and 1 s off) combined with muscle tensioning (HV + MT); and a control simulating commercial broiler processing practices. The rigor-accelerating treatments reduced pH and increased R-value (inosine:adenosine ratio) at 1 h post-mortem, but only the LV + HTC + MT treatment reduced sarcomere shortening. Both rigor treatments reduced the amount of measurable myofibrillar fragmentation. Cathepsin B and B + L activities were not affected by the rigor treatments. Calpain I activity was not detectable in any 24-h post-mortem sample. Calpain II activity at 24 h post-mortem was greater in muscles receiving HV + MT than from the LV + HTC + MT or control carcasses, but was reduced in all muscles by 24 h postmortem. An SDS-PAGE indicated a 30-kDa polypeptide that was absent at death and appeared in control and LV + HTC + MT muscles but to a lesser extent in HV + MT muscles. These results suggested that the LV + HTC + MT treatment has a greater tenderizing effect than the HV + MT treatment because the former achieves a better balance between reduced sarcomere shortening and myofibrillar fragmentation

    Widespread Infilling of Tidal Channels and Navigable Waterways in the Human-Modified Tidal Deltaplain of Southwest Bangladesh

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    Since the 1960s, ~5000 km2 of tidal deltaplain in southwest Bangladesh has been embanked and converted to densely inhabited, agricultural islands (i.e., polders). This landscape is juxtaposed to the adjacent Sundarbans, a pristine mangrove forest, both well connected by a dense network of tidal channels that effectively convey water and sediment throughout the region. The extensive embanking in poldered areas, however, has greatly reduced the tidal prism (i.e., volume of water) transported through local channels. We reveal that \u3e600 km of these major waterways have infilled in recent decades, converting to land through enhanced sedimentation and the direct blocking of waterways by embankments and sluice gates. Nearly all of the observed closures (~98%) have occurred along the embanked polder systems, with no comparable changes occurring in channels of the Sundarbans (2 of new land in the last 40–50 years, the rate of which, ~2 km2/yr, offsets the 4 km2/yr that is eroded at the coast, and is equivalent to ~20% of the new land produced naturally at the Ganges-Brahmaputra tidal rivermouth. Most of this new land, called ‘khas’ in Bengali, has been reclaimed for agriculture or aquaculture, contributing to the local economy. However, benefits are tempered by the loss of navigable waterways for commerce, transportation, and fishing, as well as the forced rerouting of tidal waters and sediments necessary to sustain this low-lying landscape against rising sea level. A more sustainable delta will require detailed knowledge of the consequences of these hydrodynamic changes to support more scientifically-grounded management of water, sediment, and tidal energy distribution

    Comment on "Radiative forcings for 28 potential Archean greenhouse gases" by Byrne and Goldblatt (2014)

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    In the recent article by Byrne and Goldblatt, "Radiative forcing for 28 potential Archean greenhouse gases", Clim. Past. 10, 1779–1801 (2014), the authors employ the HITRAN2012 spectroscopic database to evaluate the radiative forcing of 28 Archean gases. As part of the evaluation of the status of the spectroscopy of these gases in the selected spectral region (50–1800 cm−1), the cross sections generated from the HITRAN line-by-line parameters were compared with those of the PNNL database of experimental cross sections recorded at moderate resolution. The authors claimed that for NO2, HNO3, H2CO, H2O2, HCOOH, C2H4, CH3OH and CH3Br there exist large or sometimes severe disagreements between the databases. In this work we show that for only three of these eight gases a modest discrepancy does exist between the two databases and we explain the origin of the differences. For the other five gases, the disagreements are not nearly at the scale suggested by the authors, while we explain some of the differences that do exist. In summary, the agreement between the HITRAN and PNNL databases is very good, although not perfect. Typically differences do not exceed 10 %, provided that HITRAN data exist for the bands/wavelengths of interest. It appears that a molecule-dependent combination of errors has affected the conclusions of the authors. In at least one case it appears that they did not take the correct file from PNNL (N2O4 (dimer)+ NO2 was used in place of the monomer). Finally, cross sections of HO2 from HITRAN (which do not have a PNNL counterpart) were not calculated correctly in BG, while in the case of HF misleading discussion was presented there based on the confusion by foreign or noise features in the experimental PNNL spectra
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