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Modelling commercial vehicle handling and rolling stability
YesThis paper presents a multi-degrees-of-freedom non-linear multibody dynamic
model of a three-axle heavy commercial vehicle tractor unit, comprising a subchassis, front
and rear leaf spring suspensions, steering system, and ten wheels/tyres, with a semi-trailer
comprising two axles and eight wheels/tyres. The investigation is mainly concerned with the
rollover stability of the articulated vehicle. The models incorporate all sources of compliance,
stiffness, and damping, all with non-linear characteristics, and are constructed and simulated
using automatic dynamic analysis of mechanical systems formulation. A constant radius turn
test and a single lane change test (according to the ISO Standard) are simulated. The constant
radius turn test shows the understeer behaviour of the vehicle, and the single lane change
manoeuvre was conducted to show the transient behaviour of the vehicle. Non-stable roll
and yaw behaviour of the vehicle is predicted at test speeds .90 km/h. Rollover stability of
the vehicle is also investigated using a constant radius turn test with increasing speed.
The articulated laden vehicle model predicted increased understeer behaviour, due to higher
load acting on the wheels of the middle and rear axles of the tractor and the influence of the
semi-trailer, as shown by the reduced yaw rate and the steering angle variation during the constant
radius turn. The rollover test predicted a critical lateral acceleration value where complete
rollover occurs. Unstable behaviour of the articulated vehicle is also predicted in the single lane
change manoeuvre
Solving the Corner-Turning Problem for Large Interferometers
The so-called corner turning problem is a major bottleneck for radio
telescopes with large numbers of antennas. The problem is essentially that of
rapidly transposing a matrix that is too large to store on one single device;
in radio interferometry, it occurs because data from each antenna needs to be
routed to an array of processors that will each handle a limited portion of the
data (a frequency range, say) but requires input from each antenna. We present
a low-cost solution allowing the correlator to transpose its data in real time,
without contending for bandwidth, via a butterfly network requiring neither
additional RAM memory nor expensive general-purpose switching hardware. We
discuss possible implementations of this using FPGA, CMOS, analog logic and
optical technology, and conclude that the corner turner cost can be small even
for upcoming massive radio arrays.Comment: Revised to match accepted MNRAS version. 7 pages, 4 fig
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Strontium Isotopic Variations of Neoproterozoic Seawater: Implications for Crustal Evolution
We report high precision Sr isotopic data on carbonates from the Neoproterozoic Shaler Group, Victoria Island, Northwest Territories, Canada. Lithostratigraphic correlations with the relatively well-dated Mackenzie Mountains Supergroup constrain Shaler deposition to approximately 770-880 Ma, a range corroborated by 723 +/- 3 Ma lavas that disconformably overlie Shaler carbonates and by Late Riphean microfossils within the section. Samples with low Rb-87/Sr-86 ratios (< 0.01) were selected for Sr isotopic analysis. delta-O-18, Mn, Ca, Mg, and Sr data were used to recognize altered samples. The altered samples are characterized by high Mn/Sr (greater-than-or-equal-to 2) and variable delta-O-18; most are dolomites. The data indicate that between ca. 790-850 Ma the Sr-87/Sr-86 ratio of seawater varued between 0.70676 and 0.70561. The samples show smooth and systematic variation, with the lowest Sr-87/Sr-86 value of 0.70561 at ca. 830 Ma. The low Sr-87/Sr-86 ratio of carbonates from the lower parts of our section is similar to a value reported for one sample from the Adrar of Mauritania (almost-equal-to 900 Ma), West African Craton. Isotopic ratios from the upper part of the Shaler section are identical to values from the lower part of the Neoproterozoic Akademikerbreen Group, Spitsbergen. Although a paucity of absolute age determinations hinders attempts at the precise correlation of Neoproterozoic successions, it is possible to draw a broad outline of the Sr isotopic composition of seawater for this period. Indeed, the Sr isotope data themselves provide a stratigraphic tool of considerable potential. Data from this study and the literature are used to construct a curve of the Sr-87/Sr-86 ratio of Neoproterozoic seawater. The new data reported in this study substantially improve the isotopic record of Sr in seawater for the period 790-850 Ma. The Sr isotope composition of seawater reflects primarily the balance between continental Sr input through river input and mantle input via hydrothermal circulation of seawater through mid-ocean ridges. Coupling of Nd and Sr isotopic systems allows us to model changes in seafloor spreading rates (or hydrothermal flux) and continental erosion. The Sr hydrothermal flux and the erosion rate (relative to present-day value) are modeled for the period 500-900 Ma. The results indicate that the hydrothermal flux reached a maximum value at ca. 830 Ma. In contrast, a large peak in erosion rate is indicated at ca. 570 Ma. The peaks in hydrothermal flux and erosion rate are most likely related to developments in the Pan-African and related orogenic events, whose initial development is characterized by production of juvenile crust during supercontinental break up and rifting. The time ca. 570 Ma is characterized by continent-continent collision and production of recycled crust. Sr isotope data from Proterozoic carbonates offer a valuable resource for understanding large-scale crust dynamics.Earth and Planetary SciencesOrganismic and Evolutionary Biolog
Can variability in the effect of opioids on refractory breathlessness be explained by genetic factors?
© 2015, BMJ Publishing Group. All rights reserved. Objectives: Opioids modulate the perception of breathlessness with a considerable variation in response, with poor correlation between the required opioid dose and symptom severity. The objective of this hypothesis-generating, secondary analysis was to identify candidate single nucleotide polymorphisms (SNP) from those associated with opioid receptors, signalling or pain modulation to identify any related to intensity of breathlessness while on opioids. This can help to inform prospective studies and potentially lead to better tailoring of opioid therapy for refractory breathlessness. Setting: 17 hospice/palliative care services (tertiary services) in 11 European countries. Participants: 2294 people over 18 years of age on regular opioids for pain related to cancer or its treatment. Primary outcome measures: The relationship between morphine dose, breathlessness intensity (European Organisation for Research and Treatment of Cancer Core Quality of Life Questionnaire; EORTCQLQC30 question 8) and 112 candidate SNPs from 25 genes (n=588). Secondary outcome measures: The same measures for people on oxycodone (n=402) or fentanyl (n=429). Results: SNPs not in Hardy-Weinberg equilibrium or with allele frequencies ( < 5%) were removed. Univariate associations between each SNP and breathlessness intensity were determined with Benjamini-Hochberg false discovery rate set at 20%. Multivariable ordinal logistic regression, clustering over country and adjusting for available confounders, was conducted with remaining SNPs. For univariate morphine associations, 1 variant on the 5-hydroxytryptamine type 3B (HTR3B) gene, and 4 on the β-2-arrestin gene (ARRB2) were associated with more intense breathlessness. 1 SNP remained significant in the multivariable model: people with rs7103572 SNP (HTR3B gene; present in 8.4% of the population) were three times more likely to have more intense breathlessness (OR 2.86; 95% CIs 1.46 to 5.62; p=0.002). No associations were seen with fentanyl nor with oxycodone. Conclusions: This large, exploratory study identified 1 biologically plausible SNP that warrants further study in the response of breathlessness to morphine therapy
Correlations between the Electronic Properties of \u3cem\u3eShewanella oneidensis\u3c/em\u3e Cytochrome \u3cem\u3ec\u3c/em\u3e Nitrite Reductase (ccNiR) and Its Structure: Effects of Heme Oxidation State and Active Site Ligation
The electrochemical properties of Shewanella oneidensis cytochrome c nitrite reductase (ccNiR), a homodimer that contains five hemes per protomer, were investigated by UV–visible and electron paramagnetic resonance (EPR) spectropotentiometries. Global analysis of the UV–vis spectropotentiometric results yielded highly reproducible values for the heme midpoint potentials. These midpoint potential values were then assigned to specific hemes in each protomer (as defined in previous X-ray diffraction studies) by comparing the EPR and UV–vis spectropotentiometric results, taking advantage of the high sensitivity of EPR spectra to the structural microenvironment of paramagnetic centers. Addition of the strong-field ligand cyanide led to a 70 mV positive shift of the active site’s midpoint potential, as the cyanide bound to the initially five-coordinate high-spin heme and triggered a high-spin to low-spin transition. With cyanide present, three of the remaining hemes gave rise to distinctive and readily assignable EPR spectral changes upon reduction, while a fourth was EPR-silent. At high applied potentials, interpretation of the EPR spectra in the absence of cyanide was complicated by a magnetic interaction that appears to involve three of five hemes in each protomer. At lower applied potentials, the spectra recorded in the presence and absence of cyanide were similar, which aided global assignment of the signals. The midpoint potential of the EPR-silent heme could be assigned by default, but the assignment was also confirmed by UV–vis spectropotentiometric analysis of the H268M mutant of ccNiR, in which one of the EPR-silent heme’s histidine axial ligands was replaced with a methionine
The cell cycle regulator p27kip1 contributes to growth and differentiation of osteoblasts
The cyclin-dependent kinase (cdk) inhibitors are key regulators of cell cycle progression. p27 and p21 are members of the Cip/Kip family of cdk inhibitors and regulate cell growth by inactivating cell cycle stage-specific CDK-cyclin complexes. Because down-regulation of osteoprogenitor proliferation is a critical step for osteoblast differentiation, we investigated expression of p27 and p21 during development of the osteoblast phenotype in rat calvarial osteoblasts and in proliferating and growth-inhibited osteosarcoma ROS 17/2.8 cells. Expression of these proteins indicates that p21, which predominates in the growth period, is related to proliferation control. p27 levels are maximal postproliferatively, suggesting a role in the transition from cell proliferation to osteoblast differentiation. We directly examined the role of p27 during differentiation of osteoprogenitor cells derived from the bone marrow (BM) of p27-/- mice. BM cells from p27 null mice exhibited increased proliferative activity compared with BM cells from wild-type mice and formed an increased number and larger size of osteoblastic colonies, which further differentiated to the mineralization stage. Although p27-/- adherent marrow cells proliferate faster, they retain competency for differentiation, which may result, in part, from observed higher p21 levels compared with wild type. Histological studies of p27-/- bones also showed an increased cellularity in the marrow cavity compared with the p27+/+. The increased proliferation in bone does not lead to tumorigenesis, in contrast to observed adenomas in the null mice. Taken together, these findings indicate that p27 plays a key role in regulating osteoblast differentiation by controlling proliferation-related events in bone cells
Integrated chronostratigraphy of Proterozoic-Cambrian boundary beds in the western Anabar region, northern Siberia
Carbonate-rich sedimentary rocks of the western Anabar region, northern Siberia, preserve an
exceptional record of evolutionary and biogeochemical events near the Proterozoic/Cambrian boundary.
Sedimentologically, the boundary succession can be divided into three sequences representing successive
episodes of late transgressive to early highstand deposition; four parasequences are recognized in the
sequence corresponding lithostratigraphically to the Manykai Formation. Small shelly fossils are abundant
and include many taxa that also occur in standard sections of southeastern Siberia. Despite this coincidence
of faunal elements, biostratigraphic correlations between the two regions have been controversial because
numerous species that first appear at or immediately above the basal Tommotian boundary in southeastern
sections have first appearances scattered through more than thirty metres of section in the western Anabar.
Carbon- and Sr-isotopic data on petrographically and geochemically screened samples collected at one- to
two-metre intervals in a section along the Kotuikan River, favour correlation of the Staraya Reckha
Formation and most of the overlying Manykai Formation with sub-Tommotian carbonates in southeastern
Siberia. In contrast, isotopic data suggest that the uppermost Manykai Formation and the basal 26 m of the
unconformably overlying Medvezhya Formation may have no equivalent in the southeast; they appear to
provide a sedimentary and palaeontological record of an evolutionarily significant time interval represented
in southeastern Siberia only by the sub-Tommotian unconformity. Correlations with radiometrically dated
horizons in the Olenek and Kharaulakh regions of northern Siberia suggest that this interval lasted approximately
three to six million years, during which essentially all 'basal Tommotian' small shelly fossils
evolved
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