629 research outputs found
Recommended from our members
Disaggregation of soil during slurry pipe jacking
Pipe jacking is an environmentally friendly technique for the installation of services and utilities, which leads to minimum disturbance during installation. It is an
important construction method for urban environments where disruption to transport is expensive. The need to tunnel through varying geologies requiring support during
tunnelling has led to the increased use of slurry tunnel boring machines. The slurry is used to stabilise the tunnel face and transport the excavated spoil to the surface.
The research detailed in this dissertation assesses the magnitude of soil disaggregation during the excavation and pumping of the arisings within the slurry to the separation plant. The two main objectives were to create a mixing test that would allow the disaggregation of the soil to be predicted prior to specification of the
separation plant and to link the results of this test to typical soil properties. In addressing the second objective efforts have also been made to characterise the
different mechanisms of disaggregation observed in the mixing tests. The typical soil testing methods used to classify the soil samples were; Atterberg limits, particle size distributions, unconfined compressive strength, mineralogy (XRD) and chemical analysis (XRF).
A mixing test has been designed using a Hobart planetary mixer to classify the amount of soil cuttings that disaggregate during mixing with a slurry fluid. This test
was found to produce repeatable results using Speswhite Kaolin samples and then used to assess the differences in disaggregation rates of London Clay, Upper Mottled
Beds and Fleetwood Silts. In total 71 mixing tests were completed during the development of the test and the classifying of the soils. The test involved mixing
distilled water with 10 clay cuttings for varying times. The resulting solid particles were then sized through a series of sieves and sedimentation tests carried out to
produce a particle size distribution of the resulting soil.
The mixing tests showed the Upper Mottled Beds to have the highest rate of disaggregation, with the Fleetwood Silts displaying the least. This has been attributed
to the level of cementing within the soil and the microstructure of the clay and silt sized particles.
The liquidity index and initial soil strength were not found to be important factors in the predicting the rate of disaggregation of a particular soil type, but were significant for some soils. The Fleetwood Silts had the lowest unconfined compressive strengths but also produced the least amount of disaggregated soil. The soil macrofabric, although not quantified, also appeared to have an effect on the rate of disaggregation of a particular soil. An increase in discontinuities within the sample produced more cuttings larger than 4.75 mm but a lower amount of 63 μm sized fraction disaggregated.
In addition to the mixing tests carried out using water, a series of tests were completed using a polymer based slurry, HydroCut CF. This showed mixed results;
The polymer prevented any clay or silt sized particles from passing through the 63 μm sieve. However, there was no overall reduction in disaggregation and a significant increase in the time it took to sieve the slurry
Recommended from our members
Mechanisms for the disaggregation of soil cuttings in slurries
A series of tests has been undertaken on a variety of different soils to understand how soil cuttings disaggregate when pumped from the tunnel face to the separation plant during slurry tunnelling for pipe jacked tunnels. It is important to understand this process to ensure that the separation plant can be optimised to remove the maximum amount of soil from the slurry prior to the reuse of the liquid. In pipe-jacking operations this liquid is normally water, which is recirculated after the soil has been re-moved to minimise and if possible eliminate the production of liquid waste. The paper will present results from a series of “mixing tests”, devised by the authors to investigate disaggregation, and also from standard laboratory tests undertaken to establish basic soil properties such as soil strength. The “mixing tests” simulate the softening of the cuttings due to the presence of water and the shear forces applied to the slurry by the pumps and have al-ready allowed the effect of these factors to be quantified. This series of tests will demonstrate how the mechanism of disaggregation varies with strength resulting in different proportions of disaggregated soil particles in slurries subjected to the same mixing time and shear forces
The first long-read nuclear genome assembly of Oryza australiensis, a wild rice from northern Australia
Oryza australiensis is a wild rice native to monsoonal northern Australia. The International Oryza Map Alignment Project emphasises its significance as the sole representative of the EE genome clade. Assembly of the O. australiensis genome has previously been challenging due to its high Long Terminal Repeat (LTR) retrotransposon (RT) content. Oxford Nanopore long reads were combined with Illumina short reads to generate a high-quality ~ 858 Mbp genome assembly within 850 contigs with 46× long read coverage. Reference-guided scaffolding increased genome contiguity, placing 88.2% of contigs into 12 pseudomolecules. After alignment to the Oryza sativa cv. Nipponbare genome, we observed several structural variations. PacBio Iso-Seq data were generated for five distinct tissues to improve the functional annotation of 34,587 protein-coding genes and 42,329 transcripts. We also report SNV numbers for three additional O. australiensis genotypes based on Illumina re-sequencing. Although genetic similarity reflected geographical separation, the density of SNVs also correlated with our previous report on variations in salinity tolerance. This genome re-confirms the genetic remoteness of the O. australiensis lineage within the O. officinalis genome complex. Assembly of a high-quality genome for O. australiensis provides an important resource for the discovery of critical genes involved in development and stress tolerance.Aaron L. Phillips, Scott Ferguson, Nathan S. Watson, Haigh, Ashley W. Jones, Justin O. Borevitz, Rachel A. Burton, Brian J. Atwel
Spontaneous symmetry breaking in gauge theories via Bose-Einstein condensation
We propose a mechanism naturally leading to the spontaneous symmetry breaking
in a gauge theory. The Higgs field is assumed to have global and gauged
internal symmetries. We associate a non zero chemical potential to one of the
globally conserved charges commuting with all of the gauge transformations.
This induces a negative mass squared for the Higgs field triggering the
spontaneous symmetry breaking of the global and local symmetries. The mechanism
is general and we test the idea for the electroweak theory in which the Higgs
sector is extended to possess an extra global Abelian symmetry. To this
symmetry we associate a non zero chemical potential. The Bose-Einstein
condensation of the Higgs leads, at tree level, to modified dispersion
relations for the Higgs field while the dispersion relations of the gauge
bosons and fermions remain undisturbed. The latter are modified through higher
order corrections. We have computed some corrections to the vacuum
polarizations of the gauge bosons and fermions. To quantify the corrections to
the gauge boson vacuum polarizations with respect to the Standard Model we
considered the effects on the T parameter. We finally derive the one loop
modified fermion dispersion relations.Comment: RevTeX 4, 13 pages. Added references and corrected typo
Developing a core outcome set for fistulising perianal Crohn's disease
OBJECTIVE: Lack of standardised outcomes hampers effective analysis and comparison of data when comparing treatments in fistulising perianal Crohn's disease (pCD). Development of a standardised set of outcomes would resolve these issues. This study provides the definitive core outcome set (COS) for fistulising pCD. DESIGN: Candidate outcomes were generated through a systematic review and patient interviews. Consensus was established via a three-round Delphi process using a 9-point Likert scale based on how important they felt it was in determining treatment success culminating in a final consensus meeting. Stakeholders were recruited nationally and grouped into three panels (surgeons and radiologists, gastroenterologists and IBD specialist nurses, and patients). Participants received feedback fromtheir panel(in the second round) andall participants(in the third round) to allow refinement of their scores. RESULTS: A total of 295 outcomes were identified from systematic reviews and interviews that were categorised into 92 domains. 187 stakeholders (response rate 78.5%) prioritised 49 outcomes through a three-round Delphi study.The final consensus meeting of 41 experts and patients generated agreement on an eight domain COS. The COS comprised three patient-reported outcome domains (quality of life, incontinence and a combined score of patient priorities) and five clinician-reported outcome domains (perianal disease activity, development of new perianal abscess/sepsis, new/recurrent fistula, unplanned surgery and faecal diversion). CONCLUSION: A fistulising pCD COS has been produced by all key stakeholders. Application of the COS will reduce heterogeneity in outcome reporting, thereby facilitating more meaningful comparisons between treatments, data synthesis and ultimately benefit patient care
Global Search for New Physics with 2.0/fb at CDF
Data collected in Run II of the Fermilab Tevatron are searched for
indications of new electroweak-scale physics. Rather than focusing on
particular new physics scenarios, CDF data are analyzed for discrepancies with
the standard model prediction. A model-independent approach (Vista) considers
gross features of the data, and is sensitive to new large cross-section
physics. Further sensitivity to new physics is provided by two additional
algorithms: a Bump Hunter searches invariant mass distributions for "bumps"
that could indicate resonant production of new particles; and the Sleuth
procedure scans for data excesses at large summed transverse momentum. This
combined global search for new physics in 2.0/fb of ppbar collisions at
sqrt(s)=1.96 TeV reveals no indication of physics beyond the standard model.Comment: 8 pages, 7 figures. Final version which appeared in Physical Review D
Rapid Communication
Observation of Orbitally Excited B_s Mesons
We report the first observation of two narrow resonances consistent with
states of orbitally excited (L=1) B_s mesons using 1 fb^{-1} of ppbar
collisions at sqrt{s} = 1.96 TeV collected with the CDF II detector at the
Fermilab Tevatron. We use two-body decays into K^- and B^+ mesons reconstructed
as B^+ \to J/\psi K^+, J/\psi \to \mu^+ \mu^- or B^+ \to \bar{D}^0 \pi^+,
\bar{D}^0 \to K^+ \pi^-. We deduce the masses of the two states to be m(B_{s1})
= 5829.4 +- 0.7 MeV/c^2 and m(B_{s2}^*) = 5839.7 +- 0.7 MeV/c^2.Comment: Version accepted and published by Phys. Rev. Let
Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector
A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results
- …