2,485 research outputs found
Grouted jetted precast concrete sheet piles: Method, experiments, and applications
This paper introduces an innovative technology - grouted jetted precast concrete piling - that increases the efficiency of piling operations in coastal regions. The technology includes the following steps: (i) casting concrete piles factory-designed especially for jetting and grouting; (ii) jetting to drive the concrete piles with a crane on a floating ship or platform into soil; and (iii) grouting to enhance the sheet pile connections and to increase the pile bearing capacity. This technology was applied to a number of piling construction projects at the mouth of the Yellow River Delta in China, and this experience demonstrated that it is a robust, fast track, cost-effective, and environmentally friendly piling method. Ā© 2006 NRC Canada.published_or_final_versio
Yet another breakdown point notion: EFSBP - illustrated at scale-shape models
The breakdown point in its different variants is one of the central notions
to quantify the global robustness of a procedure. We propose a simple
supplementary variant which is useful in situations where we have no obvious or
only partial equivariance: Extending the Donoho and Huber(1983) Finite Sample
Breakdown Point, we propose the Expected Finite Sample Breakdown Point to
produce less configuration-dependent values while still preserving the finite
sample aspect of the former definition. We apply this notion for joint
estimation of scale and shape (with only scale-equivariance available),
exemplified for generalized Pareto, generalized extreme value, Weibull, and
Gamma distributions. In these settings, we are interested in highly-robust,
easy-to-compute initial estimators; to this end we study Pickands-type and
Location-Dispersion-type estimators and compute their respective breakdown
points.Comment: 21 pages, 4 figure
On spherical twisted conjugacy classes
Let G be a simple algebraic group over an algebraically closed field of good
odd characteristic, and let theta be an automorphism of G arising from an
involution of its Dynkin diagram. We show that the spherical theta-twisted
conjugacy classes are precisely those intersecting only Bruhat cells
corresponding to twisted involutions in the Weyl group. We show how the
analogue of this statement fails in the triality case. We generalize to good
odd characteristic J-H. Lu's dimension formula for spherical twisted conjugacy
classes.Comment: proof of Lemma 6.4 polished. The journal version is available at
http://www.springerlink.com/content/k573l88256753640
Boundaries of Disk-like Self-affine Tiles
Let be a disk-like self-affine tile generated by an
integral expanding matrix and a consecutive collinear digit set , and let be the characteristic polynomial of . In the
paper, we identify the boundary with a sofic system by
constructing a neighbor graph and derive equivalent conditions for the pair
to be a number system. Moreover, by using the graph-directed
construction and a device of pseudo-norm , we find the generalized
Hausdorff dimension where
is the spectral radius of certain contact matrix . Especially,
when is a similarity, we obtain the standard Hausdorff dimension where is the largest positive zero of
the cubic polynomial , which is simpler than
the known result.Comment: 26 pages, 11 figure
Design, Identification, and Evolution of a Surface Ruthenium(II/III) Single Site for CO Activation
RuII compounds are widely used in catalysis, photocatalysis, and medical applications. They are usually obtained in a reductive environment as molecular O2 can oxidize RuII to RuIII and RuIV. Here we report the design, identification and evolution of an airāstable surface [bipyāRuII(CO)2Cl2] site that is covalently mounted onto a polyphenylene framework. Such a RuII site was obtained by reduction of [bipyāRuIIICl4]ā with simultaneous ligand exchange from Clā to CO. This structural evolution was witnessed by a combination of inā
situ Xāray and infrared spectroscopy studies. The [bipyāRuII(CO)2Cl2] site enables oxidation of CO with a turnover frequency of 0.73Ć10ā2ā
sā1 at 462ā
K, while the RuIII site is completely inert. This work contributes to the study of structureāactivity relationship by demonstrating a practical control over both geometric and electronic structures of singleāsite catalysts at molecular level
Prevalence and Predictors of Vitamin D Insufficiency in Children: A Great Britain Population Based Study
Objectives
To evaluate the prevalence and predictors of vitamin D insufficiency (VDI) in children In Great Britain.
Design
A nationally representative cross-sectional study survey of children (1102) aged 4ā18 years (999 white, 570 male) living in private households (January 1997ā1998). Interventions provided information about dietary habits, physical activity, socio-demographics, and blood sample. Outcome measures were vitamin D insufficiency (<50 nmol/L).
Results
Vitamin D levels (mean = 62.1 nmol/L, 95%CI 60.4ā63.7) were insufficient in 35%, and decreased with age in both sexes (p<0.001). Young People living between 53ā59 degrees latitude had lower levels (compared with 50ā53 degrees, p = 0.045). Dietary intake and gender had no effect on vitamin D status. A logistic regression model showed increased risk of VDI in the following: adolescents (14ā18 years old), odds ratio (OR) = 3.6 (95%CI 1.8ā7.2) compared with younger children (4ā8 years); non white children (OR = 37 [95%CI 15ā90]); blood levels taken December-May (OR = 6.5 [95%CI 4.3ā10.1]); on income support (OR = 2.2 [95%CI 1.3ā3.9]); not taking vitamin D supplementation (OR = 3.7 [95%CI 1.4ā9.8]); being overweight (OR 1.6 [95%CI 1.0ā2.5]); <1/2 hour outdoor exercise/day/week (OR = 1.5 [95%CI 1.0ā2.3]); watched >2.5 hours of TV/day/week (OR = 1.6[95%CI 1.0ā2.4]).
Conclusion
We confirm a previously under-recognised risk of VDI in adolescents. The marked higher risk for VDI in non-white children suggests they should be targeted in any preventative strategies. The association of higher risk of VDI among children who exercised less outdoors, watched more TV and were overweight highlights potentially modifiable risk factors. Clearer guidelines and an increased awareness especially in adolescents are needed, as there are no recommendations for vitamin D supplementation in older children
Skyrmion Multi-Walls
Skyrmion walls are topologically-nontrivial solutions of the Skyrme system
which are periodic in two spatial directions. We report numerical
investigations which show that solutions representing parallel multi-walls
exist. The most stable configuration is that of the square -wall, which in
the limit becomes the cubically-symmetric Skyrme crystal. There is
also a solution resembling parallel hexagonal walls, but this is less stable.Comment: 7 pages, 1 figur
Macrophage Subset Sensitivity to Endotoxin Tolerisation by Porphyromonas gingivalis
Macrophages (MĪ¦s) determine oral mucosal responses; mediating tolerance to commensal microbes and food whilst maintaining the capacity to activate immune defences to pathogens. MĪ¦ responses are determined by both differentiation and activation stimuli, giving rise to two distinct subsets; pro-inflammatory M1- and anti-inflammatory/regulatory M2- MĪ¦s. M2-like subsets predominate tolerance induction whereas M1 MĪ¦s predominate in inflammatory pathologies, mediating destructive inflammatory mechanisms, such as those in chronic P.gingivalis (PG) periodontal infection. MĪ¦ responses can be suppressed to benefit either the host or the pathogen. Chronic stimulation by bacterial pathogen associated molecular patterns (PAMPs), such as LPS, is well established to induce tolerance. The aim of this study was to investigate the susceptibility of MĪ¦ subsets to suppression by P. gingivalis. CD14hi and CD14lo M1- and M2-like MĪ¦s were generated in vitro from the THP-1 monocyte cell line by differentiation with PMA and vitamin D3, respectively. MĪ¦ subsets were pre-treated with heat-killed PG (HKPG) and PG-LPS prior to stimulation by bacterial PAMPs. Modulation of inflammation was measured by TNFĪ±, IL-1Ī², IL-6, IL-10 ELISA and NFĪŗB activation by reporter gene assay. HKPG and PG-LPS differentially suppress PAMP-induced TNFĪ±, IL-6 and IL-10 but fail to suppress IL-1Ī² expression in M1 and M2 MĪ¦s. In addition, P.gingivalis suppressed NFĪŗB activation in CD14lo and CD14hi M2 regulatory MĪ¦s and CD14lo M1 MĪ¦s whereas CD14hi M1 pro-inflammatory MĪ¦s were refractory to suppression. In conclusion, P.gingivalis selectively tolerises regulatory M2 MĪ¦s with little effect on pro-inflammatory CD14hi M1 MĪ¦s; differential suppression facilitating immunopathology at the expense of immunity
In situ visualization by X-Ray computed tomography on sulfur stabilization and lithium polysulfides immobilization in S@HCS/MnOā cathode
The lithium-sulfur (Li-S) batteries have high theoretical energy density, exceeding that of the lithium-ion batteries. However, their practical applications are hindered by the capacity decay due to lithium polysulfide shuttle effect and sulfur volume expansion. Here, we design a S@hollow carbon with porous shell/MnOx (S@HCS/MnOx) cathode to accommodate and immobilize sulfur and polysulfides, and develop a non-destructive technique X-ray computed tomography (X-ray CT) to in situ visualize the volume expansion of Li-S cathode. The designed cathode achieves a specific capacity of ā¼1100 mAh g-1 at 0.2āÆC with a fade rate of 0.18% per cycle over 300 cycles. The X-ray CT shows that only 16% volume expansion and 70% volume fraction of solid sulfur remaining in the S@HCS/MnOx cathode, superior to the commercial cathode with 40% volume expansion and 5% volume remaining of solid sulfur particles. This is the first reported visualization evidence for the effectiveness of hollow carbon structure in accommodating cathode volume expansion and immobilizing sulfur shuttling. X-ray CT can serve as a powerful in situ tool to trace the active materials and then feedback to the structure design, which helps develop efficient and reliable energy storage systems
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