The effect of the number of response cycles on the behaviour of reinforced concrete elements subject to cyclic loading

The development of damage in reinforced concrete (RC) structures is a cumulative process. Some damage indices used to quantify damage make use of the number of response cycles as an Engineering Demand Parameter (EDP) relating with damage development. Other indices make use of deformation in terms of displacement or chord rotation. These functions are generally a function of whether the response is monotonic or cyclic, and are insensitive to the number of major deflection cycles leading to that state of damage. Many such relations are derived from experimental data from low-cycle fatigue tests performed on RC elements. The loading in such tests generally consists of either a monotonic increase in load or a gradually increasing cyclic load. Since damage development is a cumulative process, and hence depends on the load history, the loading pattern in low-cycle fatigue tests for assessment purposes should reflect the response of an earthquake. This paper will discuss a procedure to determine a loading history for cyclic tests, based on earthquake demands. The preliminary results of a campaign of low-cycle fatigue tests on RC elements to investigate the effect of using different load histories are also discussed

Low cycle fatigue tests of reinforced concrete columns and joints built with ribbed reinforcement and plain stirrups

The majority of existing reinforced concrete (RC) buildings were built prior to the introduction of seismic codes. As observed in various recent earthquakes, due to their lack of structural capacity and ductility such structures are very vulnerable and have suffered considerable damage. The number of cyclic tests that have been carried out to investigate the behaviour of RC components with detailing typical of these buildings is very limited. Such tests are very relevant for seismic vulnerability assessment purposes. In this paper, a low-cycle fatigue testing campaign on RC columns and connections specifically devised to investigate various physical parameters that affect damage development, is presented. The campaign consists of 19 columns and 7 beam-column connections. Some of the preliminary results and observations are presented and discussed

The relationship between the concentration of total soluble salts and osmotic potential in soil, ground and surface waters for several regions of Western Australia

In Western Australia salinity data are commonly reported in milligrams of total soluble salts per litre of solution. Laws from solution chemistry and data on the soluble salt composition for various regions of the State were combined to derive a relationship between total soluble salt concentration (C) and osmotic potential (WO) for each region. For the south-west of Western Australia, which contains the most productive agricultural areas in the Sate, this relationship is WO = 0.075 C

The use of permeability, conductivity, conductance and resistance in the description of water movement in soils and plants

Permeability, conductivity, conductance and resistance are important parameters in the description of water movement in soils and plants. These terms are related, but not synonymous. Permeability is only a function of the flow pathgeometry of the medium, while conductivity also depends on the fluid involved. Conductance, in addition, takes the size of the medium into account. Resistance is simply the inverse ofconductance. By applying the definition of resistance, it isshown that Darcy\u27s law and Ohm\u27s law are equivalent. Conductance and resistance relate volume flow rate to a potential difference, but to relate volume flux (volume flowrate per unit area) to a potential difference an area specific conductance or an area specific resistance must be used. Permeability and conductivity can be used in both cases. Conductances and resistances are also employed in the description of vapour movement where they relate mass flow rate or mass flux to a concentration difference. Their dimensions are therefore different to those of the analogous terms in thedescription of water movement. However, they can be made identical by introducing proper conversion factors. By doing so, it is shown that Darcy\u27s law and Fink\u27s law are related

Hepatitis B immunisation : a survey of surgeons and theatre nurses

Acute viral hepatitis remains a serious condition. Its long-term sequelae include cirrhosis and hepatocellular carcinoma. Health workers constitute a high-risk group for contracting hepatitis B. A group of clinicians associated with invasive procedures and nurses working in operating theatres were invited to answer a confidential questionnaire concerning hepatitis B immunisation and the use of protective measures. A self-administered confidential questionnaire was sent to 152 clinicians and 97 theatre nurses, of whom 82 and 74 respectively responded, giving an overall response rate of 63 %. Whilst 91% of respondents considered their speciality as being of high risk for hepatitis B only 63% of them were fully immunised and of these only 51% had had their immunity tested. Out of those who checked their antibody status 19% did so following a needle stick injury. 60% of our respondents had had a needle stick injury over the past year. Even so barrier precaution techniques were used infrequently with only 17% always or at least frequently using double gloving and 10% wearing a visor during operations. Some respondents also commented on the poor availability of resources such as impermeable gowns or blunt needles which are established precautions against contamination from hepatitis B.peer-reviewe

Mean first passage time analysis reveals rate-limiting steps, parallel pathways and dead ends in a simple model of protein folding

We have analyzed dynamics on the complex free energy landscape of protein folding in the FOLD-X model, by calculating for each state of the system the mean first passage time to the folded state. The resulting kinetic map of the folding process shows that it proceeds in jumps between well-defined, local free energy minima. Closer analysis of the different local minima allows us to reveal secondary, parallel pathways as well as dead ends.Comment: 7 page

Compact phases of polymers with hydrogen bonding

We propose an off-lattice model for a self-avoiding homopolymer chain with two different competing attractive interactions, mimicking the hydrophobic effect and the hydrogen bond formation respectively. By means of Monte Carlo simulations, we are able to trace out the complete phase diagram for different values of the relative strength of the two competing interactions. For strong enough hydrogen bonding, the ground state is a helical conformation, whereas with decreasing hydrogen bonding strength, helices get eventually destabilized at low temperature in favor of more compact conformations resembling $\beta$-sheets appearing in native structures of proteins. For weaker hydrogen bonding helices are not thermodynamically relevant anymore.Comment: 5 pages, 3 figures; revised version published in PR

Scale Free Cluster Distributions from Conserving Merging-Fragmentation Processes

We propose a dynamical scheme for the combined processes of fragmentation and merging as a model system for cluster dynamics in nature and society displaying scale invariant properties. The clusters merge and fragment with rates proportional to their sizes, conserving the total mass. The total number of clusters grows continuously but the full time-dependent distribution can be rescaled over at least 15 decades onto a universal curve which we derive analytically. This curve includes a scale free solution with a scaling exponent of -3/2 for the cluster sizes.Comment: 4 pages, 3 figure

Protein structure validation and refinement using amide proton chemical shifts derived from quantum mechanics

We present the ProCS method for the rapid and accurate prediction of protein backbone amide proton chemical shifts - sensitive probes of the geometry of key hydrogen bonds that determine protein structure. ProCS is parameterized against quantum mechanical (QM) calculations and reproduces high level QM results obtained for a small protein with an RMSD of 0.25 ppm (r = 0.94). ProCS is interfaced with the PHAISTOS protein simulation program and is used to infer statistical protein ensembles that reflect experimentally measured amide proton chemical shift values. Such chemical shift-based structural refinements, starting from high-resolution X-ray structures of Protein G, ubiquitin, and SMN Tudor Domain, result in average chemical shifts, hydrogen bond geometries, and trans-hydrogen bond (h3JNC') spin-spin coupling constants that are in excellent agreement with experiment. We show that the structural sensitivity of the QM-based amide proton chemical shift predictions is needed to refine protein structures to this agreement. The ProCS method thus offers a powerful new tool for refining the structures of hydrogen bonding networks to high accuracy with many potential applications such as protein flexibility in ligand binding.Comment: PLOS ONE accepted, Nov 201