Electron density in the quiet solar coronal transition region from SoHO/SUMER measurements of S VI line radiance and opacity

Context: The sharp temperature and density gradients in the coronal transition region are a challenge for models and observations. Aims: We set out to get linearly- and quadratically-weighted average electron densities in the region emitting the S VI lines, using the observed opacity and the emission measure of these lines. Methods: We analyze SoHO/SUMER spectroscopic observations of the S VI lines, using the center-to-limb variations and radiance ratios to derive the opacity. We also use the Emission Measure derived from radiance at disk center. Results: We get an opacity at S VI line center of the order of 0.05. The resulting average electron density is 2.4 10^16 m^-3 at T = 2 10^5 K. This value is higher than the values obtained from radiance measurements. Conversely, taking a classical value for the density leads to a too high value of the thickness of the emitting layer. Conclusions: The pressure derived from the Emission Measure method compares well with previous determinations and implies a low opacity of 5 10^-3 to 10^-2. The fact that a direct derivation leads to a much higher opacity remains unexplained, despite tentative modeling of observational biases. Further measurements need to be done, and more realistic models of the transition region need to be used.Comment: 11 pages, 9 figure

Ribonucleoparticle-independent transport of proteins into mammalian microsomes

There are at least two different mechanisms for the transport of secretory proteins into the mammalian endoplasmic reticulum. Both mechanisms depend on the presence of a signal peptide on the respective precursor protein and involve a signal peptide receptor on the cis-side and signal peptidase on the trans-side of the membrane. Furthermore, both mechanisms involve a membrane component with a cytoplasmically exposed sulfhydryl. The decisive feature of the precursor protein with respect to which of the two mechanisms is used is the chain length of the polypeptide. The critical size seems to be around 70 amino acid residues (including the signal peptide). The one mechanism is used by precursor proteins larger than about 70 amino acid residues and involves two cytosolic ribonucleoparticles and their receptors on the microsomal surface. The other one is used by small precursor proteins and relies on the mature part within the precursor molecule and a cytosolic ATPase

ipso-Substitution – A Novel Pathway for Microbial Metabolism of Endocrine-Disrupting 4-Nonylphenols, 4-Alkoxyphenols, and Bisphenol A

Our studies with Sphingobium xenophagum Bayram show that this bacterial strain degrades ?-quaternary 4-nonylphenols by an ipso-substitution mechanism, whereby the nonylphenol substrates are initially hydroxylated at the ipso position to form 4-hydroxy-4-nonylcyclohexa-2,5-dienones (quinols). Subsequently, the ?-quaternary side chains are able to detach as short-living cations from these intermediates. Alkyl branches attached to the carbocation help to delocalize and thereby stabilize the positive charge through inductive and hyperconjugative effects, which explains why only alkyl moieties of ?-quaternary nonylphenols are released. This view is corroborated by experiments with S. xenophagum Bayram, in which the alkyl chains of the non-?-quaternary 4-(1-methyloctyl) phenol (4-NP2) and 4-n-nonylphenol (4-NP1) were not released, so that the bacterium was unable to utilize these isomers as growth substrates. Analysis of dead end metabolites and experiments with 18O labeled H2O and O2 clearly show that in the main degradation pathway the nonyl cation derived from ?-quaternary quinols preferentially combines with a molecule of water to yield the corresponding alcohol and hydroquinone. However, the incorporation of significant amounts of O2-derived oxygen into the nonanol metabolites derived from degradation of certain ?,?-dimethyl substituted nonylphenols by strain Bayram strongly indicates the existence of a minor pathway in which the cation undergoes an alternative reaction and attacks the ipso-hydroxy group, yielding a 4-alkoxyphenol as an intermediate. Additional growth experiments with strain Bayram revealed that also the two alkoxyphenols 4-tert-butoxyphenol and 4-n-octyloxyphenol promote growth. Furthermore, strain Bayram's ipso-hydroxlating activity is able to transform also bisphenol A

Pavement Design and Materials Research 2003-2005 Activities

This report documents the workthat has been completed under the NDOT-UNR cooperative agreement for Pavement Design and Materials Research for the 2003-2005 time period

Disuse rescues the age-impaired adaptive response to external loading in mice

UNLABELLED: We aimed to determine whether aged bones diminished response to mechanical loading could be rescued by modulating habitual activity. By reducing background loading, aged bones response to loading increased to a level no different to young mice. This suggests, given the right stimulus, that ageing bone can respond to mechanical loading. INTRODUCTION: Age-related decline in bone mass has been suggested to represent an impaired ability of bone to adapt to its mechanical environment. In young mice, the tibias response to external mechanical loading has been shown to increase when habitual activity is reduced by sciatic neurectomy. Here we investigate if neurectomy can rescue bones response to loading in old mice. METHODS: The effect of tibial disuse, induced by unilateral sciatic neurectomy (SN), on the adaptive response to a single peak magnitude of dynamic load-engendered mechanical strain was assessed in 19-month-old (aged) mice. In a second experiment, a range of peak loads was used to assess the load magnitude-related effects of loading on a background of disuse in young adult and aged mice. Bone architecture was analysed using micro-computed tomography (μCT) and dynamic histomorphometry. RESULTS: In the first experiment, SN in aged mice was associated with a significant periosteal osteogenic response to loading not observed in sham-operated mice (7.98 ± 1.7 vs 1.02 ± 2.2 % increase in periosteally enclosed area, p < 0.05). In the second experiment, SN abrogated the expected age-related difference in the bones osteogenic response to peak strain magnitude (p > 0.05). CONCLUSIONS: These data suggest that bones age-related decline in osteogenic responsiveness to loading does not originate in bone cells to either assess, or appropriately respond to strain, but rather is likely to be due to inhibitory averaging effects derived from the habitual strains to which the bone is already adapted. If such strain averaging is applicable to humans, it suggests that gentle exercise may degrade the beneficially osteogenic effects of short periods of more vigorous activity

Dermatoglyphic Patterns of Autistic Children in Nigeria

Dermatoglyphic patterns have positive correlation in a number of genetic diseases. This research was carried out to determine any possible relationship between dermatoglyphics and autism in Nigeria using digital and palmar patterns, total ridge count, a-b ridge count and crease pattern. The digital and palmar prints of 20 autistic subjects from an autistic centre in Port Harcourt, Rivers state Nigeria were taken with parental guidance. The percentage frequency distribution of the digital pattern of the autistic subject was 49.5% for the arch, 18.5% for the whorl, 28.5% for the ulnar loop and 3.5% for the radial loop against 44% for the ulnar loop, 25.5% for the arch, 22% for the whorl and 8.5% for the radial loop for normal subjects. The mean values of the a –b ridge counts on the right and left hands of autistic male were 34.66 and 33.33 against 36.40 and 31.33  in non-autistic children respectively while in  female they were 38.6 and 35.8 against 41.40 and 38.6 respectively. Though no statistical significant difference was observed when the two groups were compared (P>0.05). It was, however, observed that the number of the total ridge counts in the right and left hands of the autistic children were lower than those of the normal subjects. Thus, there is need for further investigation using larger sample size. The data from this study will serve as a good reference for future study on this subject in Nigeria. Key Words: Dermatoglyphics and Autis

Quantification of Alterations in Cortical Bone Geometry Using Site Specificity Software in Mouse models of Aging and the Responses to Ovariectomy and Altered Loading

Investigations into the effect of (re)modelling stimuli on cortical bone in rodents normally rely on analysis of changes in bone mass and architecture at a narrow cross-sectional site. However, it is well established that the effects of axial loading produce site-specific changes throughout bones’ structure. Non-mechanical influences (e.g. hormones) can be additional to or oppose locally-controlled adaptive responses and may have more generalized effects. Tools currently available to study site-specific cortical bone adaptation are limited. Here we applied novel Site-Specificity software to measure bone mass and architecture at each 1% site along the length of the mouse tibia from standard micro-computed tomography (μCT) images. Resulting measures are directly comparable to those obtained through μCT analysis (R2 > 0.96). Site-Specificity Analysis was used to compare a number of parameters in tibiae from young adult (19-week-old) versus aged (19-month-old) mice; ovariectomized and entire mice; limbs subjected to short periods of axial loading or disuse induced by sciatic neurectomy. Age was associated with uniformly reduced cortical thickness and site-specific decreases in cortical area most apparent in the proximal tibia. Mechanical loading site-specifically increased cortical area and thickness in the proximal tibia. Disuse uniformly decreased cortical thickness and decreased cortical area in the proximal tibia. Ovariectomy uniformly reduced cortical area without altering cortical thickness. Differences in polar moment of inertia between experimental groups were only observed in the proximal tibia. Ageing and ovariectomy also altered eccentricity in the distal tibia. In summary, Site-Specificity Analysis provides a valuable tool for measuring changes in cortical bone mass and architecture along the entire length of a bone. Changes in the (re)modelling response determined at a single site may not reflect the response at different locations within the same bone

Engine Performances of Lean Iso-Octane Mixtures in a Glow Plug Heated Sub-Chamber SI Engine

The overreliance on fossil fuels to generate energy is not sustainable because of their carbon emissions that are harming our environment. To substitute the fossil fuels with a more sustainable options, alternative fuels, such as carbon-free ammonia has been gaining worldwide attention. To allow the application of ammonia in internal combustion engines, its performance as an engine fuel need to be investigated. Ammonia as fuel has some shortcomings that can be outlined as slow combustion rate and corrosion due to the generation of hydrogen which makes it difficult to utilize in conventional internal combustion engines. In this study, an engine equipped with sub-chamber feature was used to overcome slow combustion rate of lean-burn condition of iso-octane/air mixture. Iso-octane was chosen as the fuel specifically since in lean-burn conditions, where the excess air ratio is near 1.8, its laminar burning velocity is similar to that of ammonia. The study was conducted using a single cylinder modified diesel engine which features spark plug and glow plug in a sub-chamber. The investigations varied the engine speeds (1000 and 1500 RPMs), glow plug voltages (6 V and 10 V), excess air ratios (1.4 to 1.8), and ignition timings (362 °CA to 365 °CA). The results suggested improved engine performances with a lower excess air ratio and higher glow plug voltage due to more complete and stable combustion. By increasing the engine speed, the lean burn limit was extended as seen from the improved engine performances. Because of the sub chamber feature, advancing the ignition timing, with respect to the after top dead centre, resulted in lower engine performances. Larger excess air ratio was found to increase the sensitivity of the engine performances with the ignition timing. The brake mean effective pressure for all conditions has a coefficient of variation of less than 5%, indicating stable combustion. The results suggested that the current setup can be used to investigate ammonia blended fuel and direct ammonia combustion in future works