795 research outputs found
Surface modification of a polyether-urethane with RGD-containing peptides for enhanced cell attachment and signalling
Abstract of article examining the chemical modification of polyurethane with RGD-containing peptides offers a means of encouraging the adhesion, spreading and proliferation of cells cultured on its surface. This study assesses the efficacy of a modification procedure using surface analysis techniques and preliminary cell culture studies
Development and modification of National Instruments Data Acquisition hardware for use in the centrifuge environment
This paper details the modification of a commercial data acquisition system for use in a geotech-nical centrifuge. As with many ‘off-the-shelf’ components put into service within the harsh high stress centri-fuge environment, they are not originally conceived to operate under these extreme conditions and thus it is not uncommon for high failure rates to occur in standard hardware items. In many cases successful modification can be implemented to strengthen standard components to enhance their robustness and operation. In this re-spect, this paper reports on difficulties experienced in the operation of a National Instruments PXI chassis sys-tem and its failure in the high gravity environment. Specific problems identified relate to fragility of the cooling fan systems that generate fault conditions that trigger auto shut down sequence of the chassis. A bespoke solution is developed and documented that has been successfully implemented to circumnavigate and mitigate fan failures
Development and calibration of a sand pluviation device for preparation of model sand bed for centrifuge tests
A bespoke 0.068m3 (18.5 gallon) sand hopper is employed at the newly established 50gTon centrifuge facility at the University of Sheffield. The sand hopper employs a series of mesh inserts of different diameters which control the flow rate and thus the relative density of the model. A series of calibration tests on equivalent Fraction E and Fraction C sands were performed to calibrate the mesh diameter and drop height for a desired relative density. Result showed that the sand hopper is capable of delivering repeatable relative densities in the range of 30% to above 90%, for both kinds of sand grades. This wide range relative density is considered sufficient to satisfy the needs of researchers preparing dry sand models for testing in the center
Centrifuge Health Monitoring of the 50gTon beam centrifuge at the University of Sheffield
In order to fully understand scientific test data it is crucial that we first understand the back-ground centrifuge operational environment and its variation with time and centrifugal acceleration. For exam-ple, changes in ambient air temperature or relative humidity in the centrifuge chamber during operation can have a significant impact on the evaporation levels of water from the surface of a clay model. It is vital to un-derstand these temporal changes in order to mitigate drying out of the soil surface as this would have a detrimental impact on model performance. This paper details the development of a centrifuge health monitoring system capable of measuring environmental parameters over natural seasonal variations of the laboratory environment but also during test conditions. The results of a series of preliminary tests of different duration, acceleration and configuration are discussed to demonstrate the significant changes that occur in the scientific environment during operation
Development of a 25ton consolidation press at the Centre for Energy and Infrastructure Ground Research
1d consolidation frame has been designed and manufactured at the Centre for Energy and Infrastructure Ground Research (CEIGR), University of Sheffield. The consolidation frame allows static consolidation of soil beds. This system comprises of a 25 ton rated press that can accommodate a range of centrifuge payload strong box configurations. The consolidation force is delivered via a hydraulic piston rated to deliver 80 kN force at 10bar supply pressure with a stroke of 500mm. A series of vertical draw-wire transducers are implemented which monitor consolidation settlement. Combined with pore pressure transducers, the user can measure the pore water pressure at the top and at the bottom of the clay sample. A bespoke LabVIEW VI visual display is implemented which offers visual/graphical feedback to the user on the range of sensor information and a live update of consolidation progress; it also incorporates data entry to capture test specific in-formation
Scoping biological indicators of soil quality Phase II. Defra Final Contract Report SP0534
This report presents results from a field assessment of a limited suite of potential biological indicators of soil quality to investigate their suitability for national-scale soil monitoring
Strategies for Managing Soil Fertility and Health in Organic Orchards - A Fact Sheet
This fact sheet is a report of research to provide fruit growers with locally adapted advice and solutions for managing soil fertility in certified organic stone-fruits.It includes information of transitioning to organic management; building soil organic matter and providing appropriate nutrients, including phosphorus, potassium, seconary nutrients and trace elements; soil testing; cover crops; mulches; and possible organic management systems
Thrombospondin 1 is a key mediator of transforming growth factor β-mediated cell contractility in systemic sclerosis via a mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK)-dependent mechanism
BACKGROUND: The mechanism underlying the ability of fibroblasts to contract a collagen gel matrix is largely unknown. Fibroblasts from scarred (lesional) areas of patients with the fibrotic disease scleroderma show enhanced ability to contract collagen relative to healthy fibroblasts. Thrombospondin 1 (TSP1), an activator of latent transforming growth factor (TGF)β, is overexpressed by scleroderma fibroblasts. In this report we investigate whether activation of latent TGFβ by TSP1 plays a key role in matrix contraction by normal and scleroderma fibroblasts. METHODS: We use the fibroblast populated collagen lattices (FPCL) model of matrix contraction to show that interfering with TSP1/TGFβ binding and knockdown of TSP1 expression suppressed the contractile ability of normal and scleroderma fibroblasts basally and in response to TGFβ. Previously, we have shown that ras/mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) mediates matrix contraction basally and in response to TGFβ. RESULTS: During mechanical stimulation in the FPCL system, using a multistation tensioning-culture force monitor (mst-CFM), TSP1 expression and p-ERK activation in fibroblasts are enhanced. Inhibiting TSP1 activity reduced the elevated activation of MEK/ERK and expression of key fibrogenic proteins. TSP1 also blocked platelet-derived growth factor (PDGF)-induced contractile activity and MEK/ERK activation. CONCLUSIONS: TSP1 is a key mediator of matrix contraction of normal and systemic sclerosis fibroblasts, via MEK/ERK
Eta absorption by mesons
Using the chiral Lagrangian with hidden local
symmetry, we evaluate the cross sections for the absorption of eta meson () by pion (), rho (), omega (), kaon (), and kaon
star () in the tree-level approximation. With empirical masses and
coupling constants as well as reasonable values for the cutoff parameter in the
form factors at interaction vertices, we find that most cross sections are less
than 1 mb, except the reactions ,
, , and , which are a few mb, and the reactions and , which are more than 10 mb. Including these reactions in a kinetic model
based on a schematic hydrodynamic description of relativistic heavy ion
collisions, we find that the abundance of eta mesons likely reaches chemical
equilibrium with other hadrons in nuclear collisions at the Relativistic Heavy
Ion Collider.Comment: 29 pages, 10 figures, version to appear in Nucl. Phys.
ISO Spectroscopy of Young Stellar Objects
Observations of gas-phase and solid-state species toward
young stellar objects (YSOs) with the spectrometers
on board the Infrared Space Observatory
are reviewed. The excitation and abundances of
the atoms and molecules are sensitive to the changing
physical conditions during star-formation. In
the cold outer envelopes around YSOs, interstellar
ices contain a significant fraction of the heavy element
abundances, in particular oxygen. Different ice
phases can be distinguished, and evidence is found for
heating and segregation of the ices in more evolved
objects. The inner warm envelopes around YSOs are
probed through absorption and emission of gas-phase
molecules, including CO, CO_2, CH_4 and H_2O. An
overview of the wealth of observations on gas-phase
H_2O in star-forming regions is presented. Gas/solid
ratios are determined, which provide information on
the importance of gas-grain chemistry and high temperature
gas-phase reactions. The line ratios of molecules
such as H_2, CO and H_2O are powerful probes
to constrain the physical parameters of the gas. Together
with atomic and ionic lines such as [0 I]
63 µm, [S I] 25 µm and (Si II] 35 µm, they can also
be used to distinguish between photon- and shock-heated
gas. Finally, spectroscopic data on circumstellar
disks around young stars are mentioned. The
results are discussed in the context of the physical
and chemical evolution of YSOs
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