Radiocarbon: detection, contamination, and determination

My PhD research deals with radiocarbon, the natural radioactive isotope of carbon, known for its application in dating. The first and main part was the exploration of the capabilities of a new, potentially revolutionary technique to measure radiocarbon. This technique, ICOGS (IntraCavity OptoGalvanic Spectroscopy), much cheaper and easier than the accelerators presently in use, was first published as successful for radiocarbon detection by the Murnick group, Rutgers University, USA. Motivated by their results, we collaborated with them in the development and improvement of ICOGS in Groningen. However, after more than two years of experiments, we had to conclude that the results claimed by the Murnick group were not real. We have finally published these -negative- results in the journal Analytical Chemistry ("ICOGS Not Suitable for Ambient Level Radiocarbon Detection"), to discredit the technique and warn other research groups. So far, however, Murnick et al have not given up their claim. The second project aimed at improving the accuracy of radiocarbon measurements close to the age limit of the method (>40,000 years). We learned that samples stored in certain form and condition could be severely affected by contamination with "modern" carbon. We published our understandings and recommendations concerning ways to minimize sample contamination in the journal Radiocarbon. The third project demonstrated radiocarbon measurements on ultra-small stratospheric CO2 samples (altitude 12-28 km) collected using an ingenious new sampling method, "AirCore", developed at NOAA. We successfully demonstrated that extraction and radiocarbon measurements of such small samples are feasible and that the sampling method is promising

Glassy carbon as a novel mould material for replicative forming of precision glass optics.

Replicative forming of precision glass optics has been fast emerging as a rapid, net shape process chain for mobile camera lenses, CD/DVD pickup lenses, microscope objectives, night vision lenses, Fresnel lenses and so on. The process involves moulding a glass gob at high temperatures exceeding the glass transition temperature using a predefined loading and thermal cycle. Typically, the mould material is required to have high strength, low thermal expansion, chemical inertness and anti-adhesion properties, especially at high temperatures. Traditional mould materials, such as, invar or tungsten carbide are difficult to machine which adversely affects the cost of the entire process. In the present work, glassy carbon mould has been developed using p-tolune sulfonic acid (PTSA) cured phenolic resin by a process of carbonization where the composition ratio of phenolic resin and PTSA solution was standardised accompanied by the pyrolysing conditions. Detailed characterisation of the phase evolution, surface compositions, morphology and mechanical parameters of the glassy carbon has been conducted by X-Ray diffraction (XRD) technique, Raman Spectral (RS) analysis, X-ray Photoelectron Spectroscopy (XPS), Field Emission Scanning Electron microscope (FESEM), Energy Dispersive Spectroscopy (EDX) and Nanomechanical testing which reveal an optimal combination of properties of the glassy carbon that makes it an attractive low cost mould material for replicative forming process chain of glass optics fabrication

Synthesis of ultra-high temperature silicon oxycarbide (SiOC) glass by an organic-inorganic hybrid route

Silicon oxycarbide is a new generation amorphous glassy ceramic possessing unique electrical, mechanical, optical properties and ultra-high temperature stability upto 2730°C. It has numerous engineering applications in additive manufacturing, lithium-ion batteries, brake disks for sports car, ultra-fast and high voltage LEDs, MOSFETs, thyristors for high power switching, astronomical telescope, nuclear power reactor etc. In this work, SiOC was prepared by sol-gel technique using organic-inorganic hybrids as precursors. Tetraethoxysilane (TEOS) and Polydimethylsiloxane (PDMS) were used as silica and carbon sources respectively. SiOC sols were formed through hydrolysis of TEOS and PDMS. The used chemicals in this process involved isopropanol, distilled water and hydrochloric acid, which is used here as solvent, hydrolytic agent and catalyst respectively, at different refluxing condition, alkoxide to water ratios, pH levels etc. The sols thus formed were allowed to gel over a varying period (up to maximum of 10 days). After drying the gels for 24 hours, the same was pyrolysed at 1100°C under inert nitrogen atmosphere to yield SiOC. Phase formation was carried out by X-Ray Diffraction (XRD) technique, X-ray Photoelectron Spectroscopy (XPS) analysis and Raman Spectroscopic analysis. XRD data showed formation of a broad peak at 2θ~22 degrees indicating formation of amorphous SiOC and absence of any crystalline peaks indicating no SiC or Si was formed during pyrolysis. XPS data shows the presence of Si, O and C peaks in the range 100-200 eV, 530 eV and 285 eV, respectively, confirming formation of SiOC. It was revealed that within the random network of Si-O tetrahedra, islands of only C-C bonds were responsible for coloring the SiOC glass black. The estimation of mechanical properties revealed that the hardness value and Young’s modulus, of the synthesized SiOC ceramic sample, was determined to be 11.67 GPa and 75.79 respectively which indicating the better mechanical properties than other reported SiOC systems

Complement factor I deficiency: a potentially treatable cause of fulminant cerebral inflammation

Objective To raise awareness of complement factor I (CFI) deficiency as a potentially treatable cause of severe cerebral inflammation. Methods Case report with neuroradiology, neuropathology, and functional data describing the mutation with review of literature. Results We present a case of acute, fulminant, destructive cerebral edema in a previously well 11-year-old, demonstrating massive activation of complement pathways on neuropathology and compound heterozygote status for 2 pathogenic mutations in CFI which result in normal levels but completely abrogate function. Conclusions Our case adds to a very small number of extant reports of this phenomenon associated with a spectrum of inflammatory histopathologies including hemorrhagic leukoencephalopathy and clinical presentations resembling severe acute disseminated encephalomyelitis. CFI deficiency can result in uncontrolled activation of the complement pathways in the brain resulting in devastating cerebral inflammation. The deficit is latent, but the catastrophic dysregulation of the complement system may be the result of a C3 acute phase response. Diagnoses to date have been retrospective. Diagnosis requires a high index of suspicion and clinician awareness of the limitations of first-line clinical tests of complement activity and activation. Simple measurement of circulating CFI levels, as here, may fail to diagnose functional deficiency with absent CFI activity. These diagnostic challenges may mean that the CFI deficiency is being systematically under-recognized as a cause of fulminant cerebral inflammation. Complement inhibitory therapies (such as eculizumab) offer new potential treatment, underlining the importance of prompt recognition, and real-time whole exome sequencing may play an important future role

Methylsiloxanes from Vehicle Emissions Detected in Aerosol Particles

Methylsiloxanes have gained growing attention as emerging pollutants due to their toxicity to organisms. As man-made chemicals with no natural source, most research to date has focused on volatile methylsiloxanes from personal care or household products and industrial processes. Here, we show that methylsiloxanes can be found in primary aerosol particles emitted by vehicles based on aerosol samples collected in two tunnels in São Paulo, Brazil. The aerosol samples were analyzed with thermal desorption-proton transfer reaction-mass spectrometry (TD-PTR-MS), and methylsiloxanes were identified and quantified in the mass spectra based on the natural abundance of silicon isotopes. Various methylsiloxanes and derivatives were found in aerosol particles from both tunnels. The concentrations of methylsiloxanes and derivatives ranged 37.7–377 ng m–3, and the relative fractions in organic aerosols were 0.78–1.9%. The concentrations of methylsiloxanes exhibited a significant correlation with both unburned lubricating oils and organic aerosol mass. The emission factors of methylsiloxanes averaged 1.16 ± 0.59 mg kg–1 of burned fuel for light-duty vehicles and 1.53 ± 0.37 mg kg–1 for heavy-duty vehicles. Global annual emissions of methylsiloxanes in vehicle-emitted aerosols were estimated to range from 0.0035 to 0.0060 Tg, underscoring the significant yet largely unknown potential for health and climate impacts

Microbleeds in dementia with Lewy bodies

Funder: Avid Radiopharmaceuticals; doi: http://dx.doi.org/10.13039/100014392Abstract: Introduction: Microbleeds are associated with the development of dementia in older people and are common in Alzheimer’s disease (AD). Their prevalence and clinical importance in dementia with Lewy bodies (DLB) is unclear. The objective of this study was to compare the rates of microbleeds in DLB with those in AD and healthy older people, and investigate associations between microbleeds and amyloid deposition, vascular risk and disease severity in DLB. Methods: DLB (n = 30), AD (n = 18) and control (n = 20) participants underwent clinical assessment at baseline and 1 year in this longitudinal observational study. 3T MRI (including T2* susceptibility weighted imaging) and florbetapir PET were carried out at baseline. Microbleeds were rated visually and a standardised uptake value ratio (SUVR) was calculated from florbetapir PET scans. Results: 40% of DLB subjects had microbleeds compared with 50% of AD and 15% of controls. Compared to DLB without microbleeds, those with microbleeds had higher systolic BP (156 ± 26 v. 135 ± 19 mmHg; p = 0.03), but did not have greater levels of vascular disease or amyloid deposition (SUVR 1.25 ± 0.24 v. 1.25 ± 0.22; p = 0.33). There was evidence of less severe dementia in DLB participants with microbleeds, but these differences may have been driven by a shorter disease duration in those with microbleeds. Conclusion: The presence of microbleeds in DLB is associated with higher blood pressure, but not with other measures of vascular disease or amyloid deposition. The relationship between microbleeds and clinical presentation remains unclear