A GPS-enabled seabed sediment sampler: Recovery efficiency and efficacy.

The design, manufacture, and commissioning of a global positioning system enabled sampler instrument conceived for the retrieval of seabed sediments are described. This system was designed for sampling in environmental assessment applications and, especially, those requirements that might include insoluble, anthropogenic radioactivity derived from the effluent from nuclear facilities. Once triggered, the sampler operates autonomously for the recovery of samples by settling in the sampling environment, and it is compatible with submersion in fresh water and also with an off-the-shelf, submersible, remotely operated vehicle. A number of tests have been carried out to determine the efficiency and efficacy of the sample recovery performed by the system and the extent to which the recovery of samples disturbs neighboring sediments.

Depicting corrosion-born defects in pipelines with combined neutron/γ ray backscatter: a biomimetic approach.

The identification of corrosion, cracks and defects in pipelines used for transporting oil and gas can reduce the possibility of leaks, and consequently, it can limit the extent of an environmental disaster, public hazard and the associated financial impact of such events. Typically, corrosion in oil pipelines is measured with non-destructive ultrasonic or electromagnetic techniques, on the basis that corrosion and defects are often manifest as a change of thickness in the steel from which pipelines are made. However, such approaches are not practical for underground pipelines and their deployment can be complicated for the case of pipelines covered by insulation. In this paper, we present an innovative, non-destructive testing technique, which exploits the backscatter of a combination of fast-neutron and γ radiation from steel samples of a variety of thicknesses consistent with changes that might arise due to corrosion of a pipe wall. Our research demonstrates the potential to measure and characterise different steel thicknesses by detecting both the elastic, fast-neutron backscatter and the Compton-scattered γ radiations, simultaneously. Further, we demonstrate that the presence of insulation yields a consistent and separable influence on the experimental, wall-thickness measurements. The data from experimental measurements are supported by a comprehensive Monte Carlo computer simulation study.

Passive, non-intrusive assay of depleted uranium.

The ability to detect neutrons from the spontaneous fission of 238U in samples of depleted uranium with organic liquid scintillation detectors is presented. In this paper we introduce a small modular organic liquid scintillator detector array that can detect changes in mass of 238U between 3.69 g and 14.46 g. To do this, 18-h assays of various masses of 0.3% wt. of depleted uranium dioxide were assessed using four EJ-309 detectors, a mixed field analyser operated in pulse gradient analysis mode, and associated counting components. We observe a background-corrected fast neutron count sensitivity of (2.0 ±â€¯0.3) × 10-4 n g-1 s-1 per detector. This research demonstrates a proof of concept for depleted uranium quantity to be assessed passively on a non-intrusive basis via its spontaneous fission decay.

A remotely triggered fast neutron detection instrument based on a plastic organic scintillator.

A detector system for the characterization of radiation fields of both fast neutrons and γ rays is described comprising of a gated photomultiplier tube (PMT), an EJ299-33 solid organic scintillator detector, and an external trigger circuit. The objective of this development was to conceive a means by which the PMT in such a system can be actuated remotely during the high-intensity bursts of pulsed γ-ray contamination that can arise during active interrogation procedures. The system is used to detect neutrons and γ rays using established pulse-shape discrimination (PSD) techniques. The gating circuit enables the PMT to be switched off remotely. This is compatible with use during intense radiation transients to avoid saturation and the disruption of the operation of the PMT during the burst. Data are presented in the form of pulse-height spectra and PSD scatter plots for the system triggered with a strobed light source. These confirm that the gain of the system and the throughput for both triggered and un-triggered scenarios are as expected, given the duty cycle of the stimulating radiation. This demonstrates that the triggering function does not perturb the system response of the detector.

Characterisation of the TRIUMF neutron facility using a Monte Carlo simulation code.

Here, the characterisation of the high-energy neutron field at TRIUMF (The Tri Universities Meson Facility, Vancouver, British Columbia) with Monte Carlo simulation software is described. The package used is MCNPX version 2.6.0, with the neutron fluence rate determined at three locations within the TRIUMF Thermal Neutron Facility (TNF), including the exit of the neutron channel where users of the facility can test devices that may be susceptible to the effects of this form of radiation. The facility is often used to roughly emulate the field likely to be encountered at high altitudes due to radiation of galactic origin and thus the simulated information is compared with the energy spectrum calculated to be due to neutron radiation of cosmic origin at typical aircraft altitudes. The calculated values were also compared with neutron flux measurements that were estimated using the activation of various foils by the staff of the facility, showing agreement within an order of magnitude.

Sector-shaped fast organic liquid scintillation detectors based neutron coincidence counter.

A simulation based on the Monte Carlo method is described which has been performed using MCNPX 2.6.0, to model the geometry of a sector-shaped liquid scintillation detector in response to coincident neutron events. The detection of neutrons from a mixed-oxide (MOX) fuel pellet has been simulated for different thicknesses of scintillators. A layer of lead has been used to reduce the gamma-ray fluence reaching the scintillator and, the effect of lead for neutron detection has also been estimated by considering different thicknesses of lead layers.

Repeat endocarditis: analysis of risk factors based on the International Collaboration on Endocarditis - Prospective Cohort Study.

Repeat episodes of infective endocarditis (IE) can occur in patients who survive an initial episode. We analysed risk factors and 1-year mortality of patients with repeat IE. We considered 1874 patients enrolled in the International Collaboration on Endocarditis - Prospective Cohort Study between January 2000 and December 2006 (ICE-PCS) who had definite native or prosthetic valve IE and 1-year follow-up. Multivariable analysis was used to determine risk factors for repeat IE and 1-year mortality. Of 1874 patients, 1783 (95.2%) had single-episode IE and 91 (4.8%) had repeat IE: 74/91 (81%) with new infection and 17/91 (19%) with presumed relapse. On bivariate analysis, repeat IE was associated with haemodialysis (p 0.002), HIV (p 0.009), injection drug use (IDU) (p < 0.001), Staphylococcus aureus IE (p 0.003), healthcare acquisition (p 0.006) and previous IE before ICE enrolment (p 0.001). On adjusted analysis, independent risk factors were haemodialysis (OR, 2.5; 95% CI, 1.2-5.3), IDU (OR, 2.9; 95% CI, 1.6-5.4), previous IE (OR, 2.8; 95% CI, 1.5-5.1) and living in the North American region (OR, 1.9; 95% CI, 1.1-3.4). Patients with repeat IE had higher 1-year mortality than those with single-episode IE (p 0.003). Repeat IE is associated with IDU, previous IE and haemodialysis. Clinicians should be aware of these risk factors in order to recognize patients who are at risk of repeat IE.

Accelerated aging during chronic oxidative stress: a role for PARP-1.

Oxidative stress plays a major role in the pathophysiology of chronic inflammatory disease and it has also been linked to accelerated telomere shortening. Telomeres are specialized structures at the ends of linear chromosomes that protect these ends from degradation and fusion. Telomeres shorten with each cell division eventually leading to cellular senescence. Research has shown that poly(ADP-ribose) polymerase-1 (PARP-1) and subtelomeric methylation play a role in telomere stability. We hypothesized that PARP-1 plays a role in accelerated aging in chronic inflammatory diseases due to its role as coactivator of NF-κb and AP-1. Therefore we evaluated the effect of chronic PARP-1 inhibition (by fisetin and minocycline) in human fibroblasts (HF) cultured under normal conditions and under conditions of chronic oxidative stress, induced by tert-butyl hydroperoxide (t-BHP). Results showed that PARP-1 inhibition under normal culturing conditions accelerated the rate of telomere shortening. However, under conditions of chronic oxidative stress, PARP-1 inhibition did not show accelerated telomere shortening. We also observed a strong correlation between telomere length and subtelomeric methylation status of HF cells. We conclude that chronic PARP-1 inhibition appears to be beneficial in conditions of chronic oxidative stress but may be detrimental under relatively normal conditions.

Mild oxidative damage in the diabetic rat heart is attenuated by glyoxalase-1 overexpression.

Diabetes significantly increases the risk of heart failure. The increase in advanced glycation endproducts (AGEs) and oxidative stress have been associated with diabetic cardiomyopathy. We recently demonstrated that there is a direct link between AGEs and oxidative stress. Therefore, the aim of the current study was to investigate if a reduction of AGEs by overexpression of the glycation precursor detoxifying enzyme glyoxalase-I (GLO-I) can prevent diabetes-induced oxidative damage, inflammation and fibrosis in the heart. Diabetes was induced in wild-type and GLO-I transgenic rats by streptozotocin. After 24-weeks of diabetes, cardiac function was monitored with ultrasound under isoflurane anesthesia. Blood was drawn and heart tissue was collected for further analysis. Analysis with UPLC-MSMS showed that the AGE Nε-(1-carboxymethyl)lysine and its precursor 3-deoxyglucosone were significantly elevated in the diabetic hearts. Markers of oxidative damage, inflammation, and fibrosis were mildly up-regulated in the heart of the diabetic rats and were attenuated by GLO-I overexpression. In this model of diabetes, these processes were not accompanied by significant changes in systolic heart function, i.e., stroke volume, fractional shortening and ejection fraction. This study shows that 24-weeks of diabetes in rats induce early signs of mild cardiac alterations as indicated by an increase of oxidative stress, inflammation and fibrosis which are mediated, at least partially, by glycation.

Telomere length, oxidative stress, and antioxidant status in elderly men in Zutphen and Crete.

The incidence of chronic diseases such as cardiovascular diseases is lower in Mediterranean Southern Europe than Northern Europe. This may be due to a lower level of oxidative stress and a higher antioxidant status in people living around the Mediterranean Sea. Oxidative stress may influence the rate of shortening of telomeres, the nucleoprotein structures at the ends of chromosomes. We compared leukocyte telomere length (LTL) in elderly men from Northern and Southern Europe and investigated the possible relationship between LTL and indicators of oxidative stress and antioxidant status. We examined 143 elderly Dutch men (mean age 83.9 years) and 109 Greek elderly men (mean age 84.6 years) and found that the Greek men had significantly longer telomeres (geometric mean 4.95 kbp, 95% confidence interval (CI): 4.71-5.23 kbp) compared to the men from the Netherlands (4.76 kbp, 95% CI: 4.55-4.98 kbp; P=0.001). Age was inversely associated with LTL (ß=-0.10, P=0.31 in Cretan men and ß=-0.19, P=0.02 in Dutch men). In all men LTL was not related to indicators of oxidative stress and plasma antioxidants. However, the endogenous antioxidants serum albumin (ß=0.18, P=0.007) and uric acid (ß=0.13, P=0.045) were positively associated with LTL. The age-adjusted difference between Crete and Zutphen was reduced by 25% after adjustment for serum albumin and uric acid. We conclude that Greek elderly men have significantly longer LTL compared to Dutch counterparts. The endogenous antioxidants albumin and uric acid were positively associated with longer telomeres.

A digital approach to neutron-γ imaging with a narrow tungsten collimator aperture and a fast organic liquid scintillator detector.

A digital neutron-γ imaging technique for mixed radiation field is described. The imaging system is based upon an organic liquid scintillator detector, a narrow tungsten collimator, fast digitiser and adjustable equatorial mount. Radioactive sources have been attached to a vertical plane and the digitiser has been used to digitise neutron and γ events. The digitised events have been discriminated using pulse gradient analysis and images have been generated of the count distribution in the source plane.

Telomere length and mental well-being in elderly men from the Netherlands and Greece.

Telomeres, repetitive DNA sequences that promote chromosomal stability, have been related to different measures of mental well-being and self-rated health, but mainly in women during adulthood. We aimed to investigate whether accelerated telomere shortening is associated with poor mental well-being and poor self-rated health in community-dwelling elderly men. Leukocyte telomere length was measured using quantitative PCR in two different samples of 203 elderly men (mean age 78 years) from the Netherlands in 1993, and 123 elderly men (mean age 84 years) from Greece in 2000. We also obtained follow-up data in 2000 from 144 Dutch subjects, of whom 75 had paired telomere length data in 1993 and 2000. Mental well-being was conceptualized as dispositional optimism, depressive symptoms, cognitive functioning, and loneliness. Linear regression analyses were used to study the association between telomere length, measures of mental well being, and self-rated health, while adjusting for potential confounders. In cross-sectional analyses, leukocyte telomere length was not associated with measures of mental well-being and self-rated health, neither in the Netherlands nor in Greece. Also, the rate of leukocyte telomere shortening (mean decrease: 0.28 kbp over 7 years) in the 75 Dutch participants with longitudinal data was not associated with changes in different measures of mental well-being and self-rated health. Thus, our results provide no support for a relationship between leukocyte telomere length and mental well-being in elderly community-dwelling men.

An analytical approach to γ-ray self-shielding effects for radioactive bodies encountered nuclear decommissioning scenarios.

A novel analytical approach is described that accounts for self-shielding of γ radiation in decommissioning scenarios. The approach is developed with plutonium-239, cobalt-60 and caesium-137 as examples; stainless steel and concrete have been chosen as the media for cobalt-60 and caesium-137, respectively. The analytical methods have been compared MCNPX 2.6.0 simulations. A simple, linear correction factor relates the analytical results and the simulated estimates. This has the potential to greatly simplify the estimation of self-shielding effects in decommissioning activities.

Telomere length and mortality in elderly men: the Zutphen Elderly Study.

Telomere shortening is a marker of aging and therefore telomere length might be related to disease progression and survival. To address these questions, we measured leukocyte telomere length (LTL) in male participants from the Zutphen Elderly Study. LTL was measured by quantitative polymerase chain reaction in 203 men: mean aged 78 years in 1993 and 75 surviving participants mean aged 83 years in 2000. During 7 years of follow-up, 105 men died. Cox proportional hazards models were used to estimate hazard ratios for all-cause and cause-specific mortality. We found that LTL declined with a mean of 40.2 bp/year, and LTL values measured in 1993 and 2000 correlated significantly (r = .51, p < .001). Longer telomeres at baseline were not predictive for all-cause mortality, cardiovascular mortality, or cancer mortality. These results suggest that LTL decreases with increasing age and that LTL is not related to mortality in men aged more than 70 years.

Telomere shortening in chronic obstructive pulmonary disease.

Chronic oxidative stress and systemic inflammation contribute to the pathology of several chronic diseases, one among which is chronic obstructive pulmonary disease (COPD). In addition, increased oxidative stress and inflammation have been observed to be negatively associated with telomere length (TL). Our aim was to investigate the TL in COPD patients in relation to pulmonary and extrapulmonary disease severity. Furthermore, based on experimental evidence suggesting the effects of oxidative stress on telomere shortening, we studied the association of TL with the antioxidant enzyme superoxide dismutase (SOD). One hundred and two COPD patients with moderate to severe COPD were studied and compared with 19 healthy age-matched controls. Patients were characterized by elevated levels of inflammatory markers (CRP, sTNF-receptors) and lower SOD-activity than the controls (p<0.001), irrespective of the SOD genotype. TL was negatively associated with age (p<0.01) and was significantly shorter in COPD patients than controls (p<0.05). Within the patient group age-adjusted TL variability could not be explained by lung function and smoking history but a modest association was found with the percentage of fat mass (p<0.05). These data provide evidence for a relationship between a disturbed oxidant/antioxidant balance and telomere shortening and indicate that preservation of fat mass may be protective in delaying telomere shortening in COPD patients.

The "mini brain" appearance of plasmacytoma in the appendicular skeleton.

We report on the case of a 70-year-old woman presenting with right hip pain. Radiographs of the right hip demonstrated a well-defined large lytic lesion in the proximal right femur, with prominent trabeculae situated peripherally and extending into the lesion in a "spoke-wheel" pattern. Magnetic resonance imaging (MRI) demonstrated solid enhancing marrow-replacing lesion, with intervening linear nonenhancing areas of low T2 signal intensity. The MRI appearance resembled that of a small brain or "mini brain". Biopsy specimen demonstrated predominantly mature plasma cells, with occasional admixed immature forms. A diagnosis of plasmacytosis, consistent with myeloma, was made. This case illustrates a rare but seemingly characteristic "mini brain" appearance of plasmacytoma, which, to date, has only been reported in the spine and has not been observed in other bony lesions.

A portable energy-sensitive cosmic neutron detection instrument.

The construction and testing of a portable energy-sensitive neutron instrument are described. This instrument has been designed and constructed for the primary purpose of characterizing cosmic-ray neutron fields in the upper atmosphere and in cosmic reference field facilities. The instrument comprises a helium-3 proportional counter surrounded by 15 mm of lead and 140 mm of polyethylene creating a spherical structure with a diameter of 34 cm. The instrument also incorporates 12 boron-coated diodes, six on the outside of the polyethylene layer with six placed within the structure. The dimensions, materials, and arrangement of these in the instrument have previously been optimized with the MCNPX Monte Carlo simulation software to provide a compromise between the requirements of portability and spectral response. Testing took place at several locations and experimental data from the instrument's operation at the high-altitude Jungfraujoch laboratory in the Swiss alps are presented.

Telomere length assessment: biomarker of chronic oxidative stress?

Telomeres are nucleoprotein structures, located at the ends of chromosomes and are subject to shortening at each cycle of cell division. They prevent chromosomal ends from being recognized as double strand breaks and protect them from end to end fusion and degradation. Telomeres consist of stretches of repetitive DNA with a high G-C content and are reported to be highly sensitive to damage induced by oxidative stress. The resulting DNA strand breaks can be formed either directly or as an intermediate step during the repair of oxidative bases. In contrast to the majority of genomic DNA, there is evidence that telomeric DNA is deficient in the repair of single strand breaks. Since chronic oxidative stress plays a major role in the pathophysiology of several chronic inflammatory diseases, it is hypothesized that telomere length is reducing at a faster rate during oxidative stress. Therefore, assessment of telomere length might be a useful biomarker of disease progression. In this review several features of telomere length regulation, their relation with oxidative stress, and the potential application of measurement of telomere length as biomarker of chronic oxidative stress, will be discussed.

The role of glutathione in the regulation of nucleotide excision repair during oxidative stress.

Nucleotide excision repair (NER) mainly repairs bulky DNA adducts and helix distorting lesions, but is additionally considered to be a back-up system for base excision repair to remove oxidative stress induced DNA damage. Therefore, it can be speculated that NER is up-regulated or primed by oxidative stress. Exposure of human pulmonary epithelial cells (A549) to non-toxic doses of 100muM H(2)O(2) indeed showed a 2 to 4.5-fold increase in expression of XPA, XPC, ERCC4, and ERCC5, whereas the expression of ERCC1 was 5-fold decreased. Phenotypical assessment of NER capacity (i.e. recognition and incision of benzo[a]pyrene-DNA adducts) showed a significant decrease to less than 50% after H(2)O(2) exposure, which paralleled the effects of H(2)O(2) on ERCC1 expression. To study the possible involvement of glutathione (GSH) in the regulation of NER, cells were pre-incubated with 0.5mM BSO, resulting in total GSH depletion and increased intracellular oxidative stress. In GSH-depleted cells, the down-regulation of ERCC1 expression by H(2)O(2) was completely abolished and the up-regulation of ERCC4 expression was potentiated from 2.5-fold to >10-fold. Similarly, the H(2)O(2)-induced decrease in NER capacity was absent in GSH-depleted cells. Overall, our data suggest that NER capacity as well as the expression of NER related genes can be modulated by oxidative stress. ERCC1 expression and NER capacity correlated strongly (R(2)=0.85, P<0.01) after oxidant exposure, indicating ERCC1 as a specific target for oxidative stress induced modification of NER.

The design of a portable cosmic ray three-band neutron detector.

The design of a portable three-band cosmic-ray neutron detector is reported in this article. This instrument has been designed to characterise cosmic ray neutron fields in the upper atmosphere and in cosmic reference field facilities. The design utilises a spherical moderator with a layer of spallation material covering a central (3)He proportional counter. The instrument incorporates twelve lithium-coated diodes, six on the outside of the polyethylene layer and six placed within the structure. The dimensions, materials and arrangement of these in the instrument have been optimised with MCNPX to provide a compromise between the requirements of portability and spectral response.