The diffusion of polymers in porous materials as studied by dynamic light scattering/

The diffusion of polymers in porous materials as studied by dynamic light scattering

BOOTSTRAPPING YOUR FISH OR FISHING FOR BOOTSTRAPS?: PRECISION OF WELFARE LOSS ESTIMATES FROM A GLOBALLY CONCAVE INVERSE DEMAND MODEL OF COMMERCIAL FISH LANDINGS IN THE U.S. GREAT LAKES

Replaced with revised version of paper 06/30/04.Demand and Price Analysis, Resource /Energy Economics and Policy,

The role of PRNP codon 129 genotype in defining strain transmission properties of human transmissible spongiform encephalopathy

The human prion protein (PrP) gene (PRNP) codon 129 (M/V) polymorphism is a susceptibility factor for variant Creutzfeldt-Jakob Disease (vCJD) and a major determinant of clinico-pathological phenotype in sporadic CJD. The role of codon 129 in defining susceptibility and strain transmission properties has been investigated in three lines of transgenic mice that express human PrP. The human PRNP gene has directly replaced the murine version, by gene targeting, and variation at codon 129 has given the three genotype lines (HuMM, HuMV, and HuVV). The genetics of these three mouse lines are otherwise identical, and therefore differences in transmission properties can be directly attributable to the codon 129 genotype. vCJD inoculation has shown that all three codon 129 genotype mice are susceptible with a ranking of transmission efficiency of HuMM>HuMV>HuVV. HuMM mice develop the most widespread neuropathology with features similar to human vCJD. Subclinical infection was noted in each mouse line. These data suggest that the vCJD strain is transmissible to humans of each of the three codon 129 genotypes, implying that non-MM cases of human infection with bovine spongiform encephalopathy (BSE) may exist but with long subclinical incubation periods. Inoculation of material from blood transfusion associated vCJD showed no change in transmission properties suggesting that the threat of a future epidemic of human-to-human vCJD infection has not been increased by adaptation of the vCJD strain. However the route of infection, for example via blood transfusion or surgery, may be more efficient that the original oral route of BSE infection. sCJD is classified into six subgroups according to clinico-pathological features, and defined by codon 129 genotype and electrophoretic mobility type (1 or 2) of disease associated PrPSc (MM1, MM2, MV1, MV2, VV1, VV2). Typical cases from each subgroup have shown specific transmission properties suggesting that the subgrouping is defining separate disease strains. The commonest subgroup (MM1) was the most transmissible and the HuVV mouse line the most susceptible host. These data outline the transmission risk from all sCJD types to recipients of each codon 129 genotype should an infection event occur, and show the significant role of recipient codon 129 genotype in defining the clinical or subclinical state and the success or failure of transmission. This is important for determining individual risk following known exposure, and for modelling the potential of iatrogenic infection from sCJD patients

The Association Between the Long-Term Change in Directly Measured Cardiorespiratory Fitness and Mortality Risk

Introduction: There is a strong inverse association between cardiorespiratory fitness (CRF) and mortality outcomes. This relationship has predominantly been assessed cross-sectionally, however low CRF is a modifiable risk factor, thus assessing this association using a single baseline measure may be sub-optimal. Purpose: To examine the association of the long-term change in CRF, measured using cardiopulmonary exercise testing (CPX) with all-cause and disease-specific mortality. Methods: Participants included 833 apparently healthy men and women (42.9±10.8 years) who underwent two maximal CPXs, the second CPX being ≥ 1 year following the baseline assessment. Participants were followed for 17.7 ± 11.8 years for allcause, cardiovascular disease (CVD), and cancer mortality. Cox-proportional hazard models were performed to determine the association between the change in CRF, computed as visit 1 (V1) peak oxygen consumption (VO2peak (ml·kg-1·min-1)) – visit 2 (V2) VO2peak, and mortality outcomes. Results: During follow-up, 172 participants died. Overall, the change in CPX-derived CRF was inversely related to all-cause, CVD, and cancer mortality (p\u3c0.05). Each 1 ml·kg-1·min-1 increase was associated with a 10.8, 14.7, and 15.9% reductions in allcause, CVD, and cancer mortality, respectively. The inverse relationship between CRF and all-cause mortality remained significant (p\u3c0.05) when men and women were examined independently, after adjusting for years since first CPX, baseline VO2peak, and age. Conclusion: Long-term changes in CRF were inversely related to mortality outcomes, and mortality was better predicted by CRF measured at subsequent examination than baseline CRF. These findings support the recent American Heart Association scientific statement advocating CRF as a clinical vital sign that should be assessed routinely in clinical practice, as well as support regular participation in physical activity to maintain adequate CRF levels across the lifespan

Single-source precursor deposition of low-toxicity sulphides for thin film photovoltaic devices

Solar power has long been considered as an environmentally friendly method of energy generation, enjoying continued development and implementation. However, silicon solar cells (the most commercially successful type of solar cell) require high energy input for the extraction of silicon, high material quality, and is an economically expensive technology. This thesis investigates the use of alternative solar cells, namely: hybrid solar cells, using both organic and inorganic semiconductors, with an additional study focusing on utilising non-toxic materials for fabricating thin film inorganic solar cells. Overcoming obstacles associated with the future commercialisation of these techniques (i.e. associated toxicity and fabrication challenges) is the main purpose of this work. A key focus will be placed on metal xanthates, utilised as the inorganic precursor for each of these devices, as they have been proven to be effective, low temperature precursors for metal sulphide deposition. Initially, it was important to determine that the synthesised metal xanthates (cadmium ethyl xanthate, copper ethyl xanthate, tin ethyl xanthate and zinc ethyl xanthate) were effective precursors for deposition (decomposing to the appropriate metal sulphide) and to check the thermal stability of the purchased polymer (Poly(3-hexylthiophene-2,5-diyl)(P3HT)). It was demonstrated that all metal xanthate precursors had the expected mass loss after decomposition, elemental ratios and crystal structures, proving the feasibility of these precursor materials. It was also shown that P3HT had no significant mass loss up until 300 \textsuperscript{o}C, allowing for metal xanthate precursors to be deposited in conjunction with P3HT. Overall, the feasibility of each precursor, to be utilised within this work, was demonstrated . The main focus of this work was on overcoming the obstacles for the commercialisation of hybrid Bulk Heterojunctions (BHJs) and Cu\textsubscript{2}ZnSnS\textsubscript{4} (CZTS) based photovoltaic devices, respectively. Three keys areas were addressed as obstacles to be investigated, these were: \textbf{(i)} the use of CdS (a highly toxic material) as an acceptor material within photovoltaic devices, \textbf{(ii)} investigating the use of spray coating for creating these devices (a technique that allows for easy up-scale to commercialisation), and \textbf{(iii)} investigating potential routes to improve the efficiencies of these devices. To address the toxicity associated with the use of CdS, the chemical composition of the acceptor material was altered by incorporating ZnS into the layer, to form functional photovoltaic devices with reduced toxicity. This was conducted systematically for hybrid BHJs, investigating how the efficiency of a device alters while reducing the toxicity. It was shown that a toxicity reduction of up to 25 \% for human toxicity (HT) and 19 \% for the terrestrial ecotoxicity (TET) could be achieved while actually enhancing the performance of the device. Although, higher ZnS loaded devices performed worse compared to their more toxic counterparts. This CdS:ZnS mix (the highest performing ratio from work conducted into hybrid BHJs) was used an alternative acceptor material for CZTS based photovoltic devices, showing a minor improvement in the efficiency of the device (with a Power Conversion Efficiency (PCE) of 0.16 and 0.15 \% respectively) while reducing the toxicity of the device. To investigate the use of spray coating P3HT:ZnS and CZTS based photovoltaic devices were fabricated and tested. The PCE of P3HT:ZnS bulk heterojunctions significantly outperformed the P3HT:ZnS devices previously presented using spin coating and matched the previously optimised P3HT:CdS devices. This shows the potential of completely replacing CdS with ZnS, reducing the toxicity of up to 99 \% and 73 \% for HT and TET respectively, while maintaining the same performance. For CZTS devices, an effective fabrication route for spray coating metal xanthate precursors is unknown. To decipher this, different precursor ratios were deposited. It was shown that the tin rich sample (CZT2) displayed the most accurate overlap with CZTS. This observation was explained via a kinetic investigation into the decomposition of the metal xanthate precursors, showing that the decomposition of copper and zinc precursors aligned very well, at 1.26 and 1.24 s\textsuperscript{-1} respectively, while the rate constant for the tin precursor was calculated to be 1.09 s\textsuperscript{-1}. Therefore, in order to form a material with the correct ratio, a tin rich precursor mixture was required. The versatile nature of spray coating was further exploited, utilising the flexibility of this method to fabricate graded CZTS:CdS devices, forming areas with an overlapping architecture similar to that of a bulk heterojunction. However, it was noted that these graded interfaces resulted in chemical changes in the photoactive materials. This in turn resulted in devices with a graded interface of more than 20 \% of the total deposition time to show no photoactivity and display no characteristic features of a CZTS device. However, it was shown that photoactive devices with a graded overlap performed three times better than the ungraded or spin coated samples, demonstrating the feasibility of this technique. To further show the utility of P3HT:ZnS devices, carbon nanotubes (CNTs) were incorporated into the active layer for spin-coated devices. It was shown that PCEs of the devices significantly improved after just a 5 wt\% addition of any CNT. It was also shown that incorporating CNTs into the devices allowed for similar PCEs to be achieved compared to the P3HT:CdS device, demonstrating how a dopant can allow for ZnS to completely replace CdS, while maintaining a similar PCE

Environmental assessment of the near-net-shape electrochemical metallisation process and the Kroll-electron beam melting process for titanium manufacture

The enforcement of environmental policies, in recent years, has become one of the major driving forces for industrial upgrading. Therefore, this study is focused on the evaluation of the environmental impact of a newly proposed titanium additive manufacturing process, including its in-depth comparison with the conventional method. This new method, referred to as Near-net-shape Electrochemical Metallisation, is based on the in-situ metallisation (via the FFC-Cambridge Process) of 3D-printed titanium oxide precursors (using Direct Ink Writing Process). In order to evaluate the main contributors to the environmental damage and to compare them with the conventional route for titanium manufacturing, the gate-to-gate Life Cycle Assessment has been conducted following established international standards. From this, the main contributors within the Near-net-shape Electrochemical Metallisation process were identified to be electricity and synthetic rutile, with medium impacts from argon and nickel. It was found that major impacts were challenging to be reduced without affecting the properties of the final product. However, the medium impacts can theoretically be modified, yielding potential improvements in the sustainability of the process by 10%. When compared to the conventional route (consisting of the Kroll Process, Free Fall Gas Atomisation and Electron Beam Melting), the end point results demonstrated that, by adopting the Near-net-shape Electrochemical Metallisation Process, the overall impact of titanium fabrication was dramatically reduced. Specifically, an average reduction of 68% for the ecosystem, human health and resources was observed

Development of the Fray-Farthing-Chen Cambridge Process: towards the sustainable production of titanium and its alloys

The Kroll process has been employed for titanium extraction since the 1950s. It is a labour and energy intensive multi-step semi-batch process. The post-extraction processes for making the raw titanium into alloys and products are also excessive, including multiple remelting steps. Invented in the late 1990s, the Fray-Farthing-Chen (FFC) Cambridge process extracts titanium from solid oxides at lower energy consumption via electrochemical reduction in molten salts. Its ability to produce alloys and powders, while retaining the cathode shape also promises energy and material efficient manufacturing. Focusing on titanium and its alloys, this article reviews the recent development of the FFC-Cambridge process in two aspects, (i) resource and process sustainability and (ii) advanced post-extraction processing

Network Harmonisation of Physical Activity Variables Through Indirect Validation

Harmonisation of data for pooled analysis relies on the principle of inferential equivalence between variables from different sources. Ideally, this is achieved using models of the direct relationship with gold standard criterion measures, but the necessary validation study data are often unavailable. This study examines an alternative method of network harmonisation using indirect models. Starting methods were self-report or accelerometry, from which we derived indirect models of relationships with doubly labelled water (DLW)-based physical activity energy expenditure (PAEE) using sets of two bridge equations via one of three intermediate measures. Coefficients and performance of indirect models were compared to corresponding direct models (linear regression of DLW-based PAEE on starting methods). Indirect model beta coefficients were attenuated compared to direct model betas (10-63%), narrowing the range of PAEE values; attenuation was greater when bridge equations were weak. Directly and indirectly harmonised models had similar error variance but most indirectly derived values were biased at group-level. Correlations with DLW-based PAEE were identical after harmonisation using continuous linear but not categorical models. Wrist acceleration harmonised to DLW-based PAEE via combined accelerometry and heart rate sensing had lowest error variance (24.5%) and non-significant mean bias 0.9 (95%CI: -1.6; 3.4) kJ•day-1•kg-1. Associations between PAEE and BMI were similar for directly and indirectly harmonised values, but most fell outside the confidence interval of the criterion PAEE-to-BMI association. Indirect models can be used for harmonisation. Performance depends on the measurement properties of original data, variance explained by available bridge equations, and similarity of population characteristics.This work was funded by UK Medical Research Council (MC_UU_12015/3) and the NIHR Biomedical Research Centre in Cambridge (IS-BRC-1215-20014). UK Biobank is acknowledged for contributing to the costs of the fieldwork. Newcastle University and MedImmune are acknowledged for contributing to the costs of the doubly labelled water measurements. The funders had no role in the design, conduct, analysis, and decision to publish results from this study

Locating Boosted Kerr and Schwarzschild Apparent Horizons

We describe a finite-difference method for locating apparent horizons and illustrate its capabilities on boosted Kerr and Schwarzschild black holes. Our model spacetime is given by the Kerr-Schild metric. We apply a Lorentz boost to this spacetime metric and then carry out a 3+1 decomposition. The result is a slicing of Kerr/Schwarzschild in which the black hole is propagated and Lorentz contracted. We show that our method can locate distorted apparent horizons efficiently and accurately.Comment: Submitted to Physical Review D. 12 pages and 22 figure

The Association between the Change in Directly Measured Cardiorespiratory Fitness across Time and Mortality Risk

Background: The relationship between cardiorespiratory fitness (CRF) and mortality risk has typically been assessed using a single measurement, though some evidence suggests the change in CRF over time influences risk. This evidence is predominantly based on studies using estimated CRF (CRFe). The strength of this relationship using change in directly measured CRF over time in apparently healthy men and women is not well understood. Purpose: To examine the association of change in CRF over time, measured using cardiopulmonary exercise testing (CPX), with all-cause and disease-specific mortality and to compare baseline and subsequent CRF measurements as predictors of all-cause mortality. Methods: Participants included 833 apparently healthy men and women (42.9 ± 10.8 years) who underwent two maximal CPXs, the second CPX being ≥1 year following the baseline assessment (mean 8.6 years, range 1.0 to 40.3 years). Participants were followed for up to 17.7 (SD 11.8) years for all-cause-, cardiovascular disease- (CVD), and cancer mortality. Cox-proportional hazard models were performed to determine the association between the change in CRF, computed as visit 1 (CPX1) peak oxygen consumption (VO2peak [mL·kg−1·min−1]) – visit 2 (CPX2) VO2peak, and mortality outcomes. A Wald-Chi square test of equality was used to compare the strength of CPX1 to CPX2 VO2peak in predicting mortality. Results: During follow-up, 172 participants died. Overall, the change in CPX-CRF was inversely related to all-cause, CVD, and cancer mortality (p \u3c 0.05). Each 1 mL·kg−1·min−1 increase was associated with a ~11, 15, and 16% (all p \u3c 0.001) reduction in all-cause, CVD, and cancer mortality, respectively. The inverse relationship between CRF and all-cause mortality was significant (p \u3c 0.05) when men and women were examined independently, after adjusting for years since first CPX, baseline VO2peak, and age. Further, the Wald Chi-square test of equality found CPX2 VO2peak to be a significantly stronger predictor of all-cause mortality than CPX1 VO2peak (p \u3c 0.05). Conclusion: The change in CRF over time was inversely related to mortality outcomes, and mortality was better predicted by CRF measured at subsequent test than CPX1 CRF. These findings emphasize the importance of adopting lifestyle behaviors that promote CRF, as well as support the need for routine assessment of CRF in clinical practice to better assess risk