2,764 research outputs found
Hydrothermal Au mineralisation caused by fluid decompression and cooling in dilatational cavities
It has been demonstrated that numerous hydrothermal mineralised (Au) quartz veins are related to seismic faulting (Wilkinson and Johnston, 1996; Weatherly and Henley, 2013). Dilatational cavities created during seismic faulting will result in (1) rapid fluid flow from the host rock into the cavities and (2) instantaneous fluid decompression under near-adiabatic and near-isenthalpic conditions (Fig. 1). Adiabatic-isenthalpic decompression of the fluid can either result in fluid heating or cooling (Fig. 1). Calculations demonstrate that for an initial lithostatic fluid pressures of 3-4 kbar and an initial fluid temperature ranging between 400 and 500°C, a CO2-bearing aqueous fluid has the ability to cool more than 100°C during decompression. The decrease in temperature will reduce the metal solubility largely due to its effect on the sulphur and oxygen fugacity
Modelling of hydrothermal fluid compositions in the crust and upper mantle
Carbon-oxygen-hydrogen (COH) fluids are integral to the formation of many hydrothermal ore deposits (including orogenic gold, graphite), and diamond. Typically, a crustal/upper mantle COH fluid comprises H2O, CO2, CH4, H2, CO, C2H6, and O2. Crustal and upper mantle fluid compositions are constrained by pressure, temperature and redox state, and can be calculated if: (1) A reliable equation of state for fluid mixtures is available for the relevant pressure-temperature conditions is available for the calculation of fugacity coefficients; (2) Reliable thermodynamic variables including enthalpy, entropy and isobaric heat capacity can be obtained. Here, we used the equation of state by Zhang and Duan (2009) in conjunction with the NIST reference dataset to develop a user-friendly Excel spread sheet that allows the calculation of fluid compositions for a pressure-temperature range of > 0.5 kbar and 300-1500°C, respectively. Data manipulation and modelling was achieved with a combination of VBA, Python and SQL scripting and allowed us to validate the model calculations in the Excel spread sheet. Here, we used the equation of state by Zhang and Duan (2009) in conjunction with the NIST reference dataset to develop a user-friendly Excel spread sheet that allows the calculation of fluid compositions for a pressure-temperature range of > 0.5 kbar and 300-1500°C, respectively. Data manipulation and modelling was achieved with a combination of VBA, Python and SQL scripting and allowed us to validate the model calculations in the Excel spread sheet
Inflation, quantum fields, and CMB anisotropies
Inflationary cosmology has proved to be the most successful at predicting the
properties of the anisotropies observed in the cosmic microwave background
(CMB). In this essay we show that quantum field renormalization significantly
influences the generation of primordial perturbations and hence the expected
measurable imprint of cosmological inflation on the CMB. However, the new
predictions remain in agreement with observation, and in fact favor the
simplest forms of inflation. In the near future, observations of the influence
of gravitational waves from the early universe on the CMB will test our new
predictions.Comment: 11 pages, 1 figure, Awarded with the fourth prize in the Gravity
Research Foundation 2009 Essay Competitio
Regular order reductions of ordinary and delay-differential equations
We present a C program to compute by successive approximations the regular
order reduction of a large class of ordinary differential equations, which
includes evolution equations in electrodynamics and gravitation. The code may
also find the regular order reduction of delay-differential equations.Comment: 4 figure
Enhanced local-type inflationary trispectrum from a non-vacuum initial state
We compute the primordial trispectrum for curvature perturbations produced
during cosmic inflation in models with standard kinetic terms, when the initial
quantum state is not necessarily the vacuum state. The presence of initial
perturbations enhances the trispectrum amplitude for configuration in which one
of the momenta, say , is much smaller than the others, . For those squeezed configurations the trispectrum acquires the
so-called local form, with a scale dependent amplitude that can get values of
order . This amplitude can be larger than the
prediction of the so-called Maldacena consistency relation by a factor ,
and can reach the sensitivity of forthcoming observations, even for
single-field inflationary models.Comment: 11 pages, 1 figure. References added, typos corrected, minor change
Computationally Efficient Implementation of Convolution-based Locally Adaptive Binarization Techniques
One of the most important steps of document image processing is binarization.
The computational requirements of locally adaptive binarization techniques make
them unsuitable for devices with limited computing facilities. In this paper,
we have presented a computationally efficient implementation of convolution
based locally adaptive binarization techniques keeping the performance
comparable to the original implementation. The computational complexity has
been reduced from O(W2N2) to O(WN2) where WxW is the window size and NxN is the
image size. Experiments over benchmark datasets show that the computation time
has been reduced by 5 to 15 times depending on the window size while memory
consumption remains the same with respect to the state-of-the-art algorithmic
implementation
Efficacy and Safety of Radium-223 Dichloride in Symptomatic Castration-resistant Prostate Cancer Patients With or Without Baseline Opioid Use From the Phase 3 ALSYMPCA Trial
Background: The phase 3 ALSYMPCA trial enrolled metastatic castration-resistant prostate
cancer patients with or without baseline opioid use.
Objective: To assess the efficacy and safety of radium-223 dichloride (radium-223) versus
placebo in ALSYMPCA patients by baseline opioid use.
Design, setting, and participants: Nine hundred and twenty one patients enrolled at 136 centers
globally.
Intervention: Radium-223 (50 kBq/kg, intravenous injection) every 4 wk for six cycles or
matching placebo, each plus best standard of care.
Outcome measurements and statistical analysis: Primary endpoint (overall survival [OS]),
main secondary efficacy endpoints, and safety were evaluated by baseline opioid use.
Additional analyses included time to first opioid use, time to first external beam radiation
therapy for bone pain, and safety of concomitant external beam radiation therapy.
Results and limitations: At baseline, 408 (44%) patients had no pain and no analgesic use or
mild pain with nonopioid therapy (World Health Organization ladder pain score 0–1 [nonopioid
subgroup]), and 513 (56%) had moderate pain with occasional opioids or severe pain
with regular daily opioids (World Health Organization ladder pain score 2–3 [opioid subgroup]).
Radium-223 significantly prolonged OS versus placebo in nonopioid (hazard ratio
[HR] = 0.70; 95% confidence interval [CI]: 0.52–0.93; p = 0.013) and opioid (HR = 0.68; 95% CI:
0.54–0.86; p = 0.001) subgroups, and significantly reduced risk of symptomatic skeletal events
versus placebo, regardless of baseline opioid use (nonopioid subgroup: HR = 0.56, 95% CI: 0.39–
0.82, p = 0.002; opioid subgroup: HR = 0.72, 95% CI: 0.53–0.98, p = 0.038). Time to first opioid
use for bone pain was significantly delayed with radium-223 versus placebo (HR = 0.62, 95% CI:
0.46–0.85, p = 0.002). Adverse event incidences were similar between opioid subgroups.
Conclusions: Radium-223 versus placebo significantly prolonged OS and reduced symptomatic
skeletal event risk with a favorable safety profile in castration-resistant prostate cancer
patients with symptomatic bone metastases, regardless of baseline opioid use.
Patient summary: In this ALSYMPCA opioid subgroup analysis, baseline symptom levels did
not appear to impact radium-223 dichloride efficacy or safet
The effects of anthropogenic sound and artificial light exposure on microbiomes: ecological and public health implications
Globally, anthropogenic sound and artificial light pollution have increased to alarming levels. Evidence suggests that these can disrupt critical processes that impact ecosystems and human health. However, limited focus has been given to the potential effects of sound and artificial light pollution on microbiomes. Microbial communities are the foundations of our ecosystems. They are essential for human health and provide myriad ecosystem services. Therefore, disruption to microbiomes by anthropogenic sound and artificial light could have important ecological and human health implications. In this mini-review, we provide a critical appraisal of available scientific literature on the effects of anthropogenic sound and light exposure on microorganisms and discuss the potential ecological and human health implications. Our mini-review shows that a limited number of studies have been carried out to investigate the effects of anthropogenic sound and light pollution on microbiomes. However, based on these studies, it is evident that anthropogenic sound and light pollution have the potential to significantly influence ecosystems and human health via microbial interactions. Many of the studies suffered from modest sample sizes, suboptimal experiments designs, and some of the bioinformatics approaches used are now outdated. These factors should be improved in future studies. This is an emerging and severely underexplored area of research that could have important implications for global ecosystems and public health. Finally, we also propose the photo-sonic restoration hypothesis: does restoring natural levels of light and sound help to restore microbiomes and ecosystem stability
Water-exchange MRI detects subtle blood-brain barrier breakdown in Alzheimer's disease rats
Blood-brain barrier (BBB) breakdown has been hypothesized to play a key role in the onset and progression of Alzheimer's disease (AD). However, the question of whether AD itself contributes to loss of BBB integrity is still uncertain, as many in-vivo studies have failed to detect signs of AD-related BBB breakdown. We hypothesize AD-related BBB damage is subtle, and that these negative results arise from a lack of measurement sensitivity. With the aim of developing a more sensitive measure of BBB breakdown, we have designed a novel MRI scanning protocol to quantify the trans-BBB exchange of endogenous water. Using this method, we detect increased BBB water permeability in a rat model of AD that is associated with reduced expression of the tight junction protein occludin. BBB permeability to MRI contrast agent, assessed using dynamic contrast-enhanced (DCE)-MRI, did not differ between transgenic and wild-type animals and was uncorrelated with occludin expression. Our data supports the occurrence of AD-related BBB breakdown, and indicates that such BBB pathology is subtle and may be undetectable using existing ‘tracer leakage’ methods. Our validated water-exchange MRI method provides a new powerful tool with which to study BBB damage in-vivo
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