Cross-Linked Thermally Rearranged Poly(benzoxazole-<i>co</i>-imide) Membranes for Gas Separation

Calle, Mariola,Doherty, Cara M.,Hill, Anita J.,Lee, Young Moo American Chemical Society 2013 Macromolecules Vol.46 No.20

<P>A novel strategy to tune the cavity size and free volume of thermally rearranged polybenzoxazole (TR-PBO) copolymer membranes by transesterification cross-linking reaction of <I>o</I>-hydroxy polyimide precursors with 1,4-butylene glycol in the solid state is demonstrated in this study. During the thermal rearrangement (TR) process at high temperatures, loose diester interchain cross-linkers are prone to degrade while formation of a much more rigid cross-linked structure occurs following or alongside the imide-to-benzoxazole rearrangement. As a result, a synergistic effect of high permeability and high selectivity appeared to be created in one step, and the newly synthesized cross-linked TR-PBO membranes exhibited outstanding gas separation performance, surpassing the so-called 2008 upper bound for CO<SUB>2</SUB>/CH<SUB>4</SUB> separation.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/mamobx/2013/mamobx.2013.46.issue-20/ma4014115/production/images/medium/ma-2013-014115_0012.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ma4014115'>ACS Electronic Supporting Info</A></P>

Characterization of Large Structural Genetic Mosaicism in Human Autosomes

Machiela, Mitchell J.,Zhou, W.,Sampson, Joshua N.,Dean, Michael C.,Jacobs, Kevin B.,Black, A.,Brinton, Louise A.,Chang, I.S.,Chen, C.,Chen, C.,Chen, K.,Cook, Linda S.,Crous Bou, M.,De Vivo, I.,Doherty University of Chicago Press [etc.] 2015 American journal of human genetics Vol.96 No.3

Analyses of genome-wide association study (GWAS) data have revealed that detectable genetic mosaicism involving large (>2 Mb) structural autosomal alterations occurs in a fraction of individuals. We present results for a set of 24,849 genotyped individuals (total GWAS set II [TGSII]) in whom 341 large autosomal abnormalities were observed in 168 (0.68%) individuals. Merging data from the new TGSII set with data from two prior reports (the Gene-Environment Association Studies and the total GWAS set I) generated a large dataset of 127,179 individuals; we then conducted a meta-analysis to investigate the patterns of detectable autosomal mosaicism (n = 1,315 events in 925 [0.73%] individuals). Restricting to events >2 Mb in size, we observed an increase in event frequency as event size decreased. The combined results underscore that the rate of detectable mosaicism increases with age (p value = 5.5 x 10<SUP>-31</SUP>) and is higher in men (p value = 0.002) but lower in participants of African ancestry (p value = 0.003). In a subset of 47 individuals from whom serial samples were collected up to 6 years apart, complex changes were noted over time and showed an overall increase in the proportion of mosaic cells as age increased. Our large combined sample allowed for a unique ability to characterize detectable genetic mosaicism involving large structural events and strengthens the emerging evidence of non-random erosion of the genome in the aging population.

Asian medical students: quality of life and motivation to learn

Marcus A. Henning,Susan J. Hawken,Christian Krageloh,Yipin Zhao,Iain Doherty 서울대학교 교육연구소 2011 Asia Pacific Education Review Vol.12 No.3

Issues linked with the notions of quality of life (QOL) and motivation to learn among Asian medical students have not been well documented. This is true in both the international and the New Zealand contexts. Our paper addresses this lack of research by focusing on the QOL of international and domestic Asian students studying in New Zealand, where Asian students form a significant proportion of tertiary students. Although there is evidence to suggest that Asian students do well academically, it was felt that an investigation into their QOL would be instructive as QOL will likely have an impact on cognition, behavior, general well-being, and motivation. The present study surveyed fourth- and fifth-year medical students to examine the relationship between QOL and motivation to learn and to consider how Asian medical students compare against European medical and non-medical student peers. The study utilized the World Health Organization-Quality of Life questionnaire (BREF version) and a shortened version of the Motivated Strategies for Learning Questionnaire. The results show that the Asian medical students in this study generated significantly lower scores in terms of their satisfaction with social relationships compared with their non-Asian peers. In addition, international Asian medical students appear to be more at risk than domestic Asian students with respect to test anxiety. The paper considers the findings and the implications for quality of life, motivation to learn, medical education, and the Asian student community.

Hydrochlorofluorocarbon and hydrofluorocarbon emissions in East Asia determined by inverse modeling

Stohl, A.,Kim, J.,Li, S.,O&,apos,Doherty, S.,Mü,hle, J.,Salameh, P. K.,Saito, T.,Vollmer, M. K.,Wan, D.,Weiss, R. F.,Yao, B.,Yokouchi, Y.,Zhou, L. X. Copernicus GmbH 2010 Atmospheric Chemistry and Physics Vol.10 No.8

<P>Abstract. The emissions of three hydrochlorofluorocarbons, HCFC-22 (CHClF2), HCFC-141b (CH3CCl2F) and HCFC-142b (CH3CClF2) and three hydrofluorocarbons, HFC-23 (CHF3), HFC-134a (CH2FCF3) and HFC-152a (CH3CHF2) from four East Asian countries and the Taiwan region for the year 2008 are determined by inverse modeling. The inverse modeling is based on in-situ measurements of these halocarbons at the Japanese stations Cape Ochi-ishi and Hateruma, the Chinese station Shangdianzi and the South Korean station Gosan. For every station and every 3 h, 20-day backward calculations were made with the Lagrangian particle dispersion model FLEXPART. The model output, the measurement data, bottom-up emission information and corresponding uncertainties were fed into an inversion algorithm to determine the regional emission fluxes. The model captures the observed variation of halocarbon mixing ratios very well for the two Japanese stations but has difficulties explaining the large observed variability at Shangdianzi, which is partly caused by small-scale transport from Beijing that is not adequately captured by the model. Based on HFC-23 measurements, the inversion algorithm could successfully identify the locations of factories known to produce HCFC-22 and emit HFC-23 as an unintentional byproduct. This lends substantial credibility to the inversion method. We report national emissions for China, North Korea, South Korea and Japan, as well as emissions for the Taiwan region. Halocarbon emissions in China are much larger than the emissions in the other countries together and contribute a substantial fraction to the global emissions. Our estimates of Chinese emissions for the year 2008 are 65.3±6.6 kt/yr for HCFC-22 (17% of global emissions extrapolated from Montzka et al., 2009), 12.1±1.6 kt/yr for HCFC-141b (22%), 7.3±0.7 kt/yr for HCFC-142b (17%), 6.2±0.7 kt/yr for HFC-23 (>50%), 12.9±1.7 kt/yr for HFC-134a (9% of global emissions estimated from Velders et al., 2009) and 3.4±0.5 kt/yr for HFC-152a (7%). </P>

Inverse modelling of CF4 and NF3 emissions in East Asia

Arnold, Tim,Manning, Alistair J.,Kim, Jooil,Li, Shanlan,Webster, Helen,Thomson, David,Mü,hle, Jens,Weiss, Ray F.,Park, Sunyoung,O&,apos,Doherty, Simon Copernicus GmbH 2018 Atmospheric Chemistry and Physics Vol.18 No.18

<P>Abstract. Decadal trends in the atmospheric abundances of carbon tetrafluoride (CF4) and nitrogen trifluoride (NF3) have been well characterised and have provided a time series of global total emissions. Information on locations of emissions contributing to the global total, however, is currently poor. We use a unique set of measurements between 2008 and 2015 from the Gosan station, Jeju Island, South Korea (part of the Advanced Global Atmospheric Gases Experiment network), together with an atmospheric transport model, to make spatially disaggregated emission estimates of these gases in East Asia. Due to the poor availability of good prior information for this study, our emission estimates are largely influenced by the atmospheric measurements. Notably, we are able to highlight emission hotspots of NF3 and CF4 in South Korea due to the measurement location. We calculate emissions of CF4 to be quite constant between the years 2008 and 2015 for both China and South Korea, with 2015 emissions calculated at 4.3±2.7 and 0.36±0.11 Gg yr−1, respectively. Emission estimates of NF3 from South Korea could be made with relatively small uncertainty at 0.6±0.07 Gg yr−1 in 2015, which equates to ∼1.6 % of the country's CO2 emissions. We also apply our method to calculate emissions of CHF3 (HFC-23) between 2008 and 2012, for which our results find good agreement with other studies and which helps support our choice in methodology for CF4 and NF3. </P>

Global emissions of HFC-143a (CH3CF3) and HFC-32 (CH2F2) from in situ and air archive atmospheric observations

O&,apos,Doherty, S.,Rigby, M.,Mü,hle, J.,Ivy, D. J.,Miller, B. R.,Young, D.,Simmonds, P. G.,Reimann, S.,Vollmer, M. K.,Krummel, P. B.,Fraser, P. J.,Steele, L. P.,Dunse, B.,Salameh, P. K.,Harth, Copernicus GmbH 2014 Atmospheric chemistry and physics Vol.14 No.17

<P>Abstract. High-frequency, in situ observations from the Advanced Global Atmospheric Gases Experiment (AGAGE), for the period 2003 to 2012, combined with archive flask measurements dating back to 1977, have been used to capture the rapid growth of HFC-143a (CH3CF3) and HFC-32 (CH2F2) mole fractions and emissions into the atmosphere. Here we report the first in situ global measurements of these two gases. HFC-143a and HFC-32 are the third and sixth most abundant hydrofluorocarbons (HFCs) respectively and they currently make an appreciable contribution to the HFCs in terms of atmospheric radiative forcing (1.7 ± 0.04 and 0.7 ± 0.02 mW m−2 in 2012 respectively). In 2012 the global average mole fraction of HFC-143a was 13.4 ± 0.3 ppt (1σ) in the lower troposphere and its growth rate was 1.4 ± 0.04 ppt yr−1; HFC-32 had a global mean mole fraction of 6.2 ± 0.2 ppt and a growth rate of 1.1 ± 0.04 ppt yr−1 in 2012. The extensive observations presented in this work have been combined with an atmospheric transport model to simulate global atmospheric abundances and derive global emission estimates. It is estimated that 23 ± 3 Gg yr−1 of HFC-143a and 21 ± 11 Gg yr−1 of HFC-32 were emitted globally in 2012, and the emission rates are estimated to be increasing by 7 ± 5% yr−1 for HFC-143a and 14 ± 11% yr−1 for HFC-32. </P>

Architecturing Nanospace via Thermal Rearrangement for Highly Efficient Gas Separations

Thornton, Aaron W.,Doherty, Cara M.,Falcaro, Paolo,Buso, Dario,Amenitsch, Heinz,Han, Sang Hoon,Lee, Young Moo,Hill, Anita J. American Chemical Society 2013 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.117 No.46

<P>The ability to monitor free volume formation during space-making treatments is critical for the ultrafine tuning of nanospace for efficient gas separation. Here, investigating the polymer thermal rearrangement using synchrotron in situ small-angle X-ray scattering for the first time and combining this information with transport theory, we elucidate the evolution of nanospace features in polymer-based gas separation membranes. The proposed nanospace monitoring technique encompasses the structure–property relationships, therefore offering a powerful tool for tuning the polymer properties for particular gas-related clean energy applications. These results demonstrate that the fine control of the nanospace dimension and magnitude leads to a drastic improvement in gas separation performance above any material to date.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2013/jpccck.2013.117.issue-46/jp410025b/production/images/medium/jp-2013-10025b_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp410025b'>ACS Electronic Supporting Info</A></P>

Thermally rearranged (TR) bismaleimide-based network polymers for gas separation membranes

Do, Y.,Lee, W.,Seong, J.,Kim, J.,Wang, H.,Doherty, C.,Hill, A.,Lee, Y. Royal Society of Chemistry 2016 Chemical communications Vol.52 No.93

<P>Highly permeable, thermally rearranged polymer membranes based on bismaleimide derivatives that exhibit excellent CO2 permeability up to 5440 Barrer with a high BET surface area (1130 m(2) g(-1)) are reported for the first time. In addition, the membranes can be easily used to form semi-interpenetrating networks with other polymers endowing them with superior gas transport properties.</P>

Global and regional emissions estimates of 1,1-difluoroethane (HFC-152a, CH3CHF2) from in situ and air archive observations

Simmonds, P. G.,Rigby, M.,Manning, A. J.,Lunt, M. F.,O&,apos,Doherty, S.,McCulloch, A.,Fraser, P. J.,Henne, S.,Vollmer, M. K.,Mü,hle, J.,Weiss, R. F.,Salameh, P. K.,Young, D.,Reimann, S.,Wenger Copernicus GmbH 2016 Atmospheric Chemistry and Physics Vol.16 No.1

<P>Abstract. High frequency, in situ observations from 11 globally distributed sites for the period 1994-2014 and archived air measurements dating from 1978 onward have been used to determine the global growth rate of 1,1-difluoroethane (HFC-152a, CH3CHF2). These observations have been combined with a range of atmospheric transport models to derive global emission estimates in a top-down approach. HFC-152a is a greenhouse gas with a short atmospheric lifetime of about 1.5 years. Since it does not contain chlorine or bromine, HFC-152a makes no direct contribution to the destruction of stratospheric ozone and is therefore used as a substitute for the ozone depleting chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs). The concentration of HFC-152a has grown substantially since the first direct measurements in 1994, reaching a maximum annual global growth rate of 0.84 ± 0.05 ppt yr−1 in 2006, implying a substantial increase in emissions up to 2006. However, since 2007, the annual rate of growth has slowed to 0.38 ± 0.04 ppt yr−1 in 2010 with a further decline to an annual average rate of growth in 2013-2014 of −0.06 ± 0.05 ppt yr−1. The annual average Northern Hemisphere (NH) mole fraction in 1994 was 1.2 ppt rising to an annual average mole fraction of 10.1 ppt in 2014. Average annual mole fractions in the Southern Hemisphere (SH) in 1998 and 2014 were 0.84 and 4.5 ppt, respectively. We estimate global emissions of HFC-152a have risen from 7.3 ± 5.6 Gg yr−1 in 1994 to a maximum of 54.4 ± 17.1 Gg yr−1 in 2011, declining to 52.5 ± 20.1 Gg yr−1 in 2014 or 7.2 ± 2.8 Tg-CO2 eq yr−1. Analysis of mole fraction enhancements above regional background atmospheric levels suggests substantial emissions from North America, Asia, and Europe. Global HFC emissions (so called “bottom up” emissions) reported by the United Nations Framework Convention on Climate Change (UNFCCC) are based on cumulative national emission data reported to the UNFCCC, which in turn are based on national consumption data. There appears to be a significant underestimate ( > 20 Gg) of “bottom-up” reported emissions of HFC-152a, possibly arising from largely underestimated USA emissions and undeclared Asian emissions. </P>

History of atmospheric SF6 from 1973 to 2008

Rigby, M.,Mü,hle, J.,Miller, B. R.,Prinn, R. G.,Krummel, P. B.,Steele, L. P.,Fraser, P. J.,Salameh, P. K.,Harth, C. M.,Weiss, R. F.,Greally, B. R.,O&,apos,Doherty, S.,Simmonds, P. G.,Vollmer, M Copernicus GmbH 2010 Atmospheric Chemistry and Physics Vol.10 No.21

<P>Abstract. We present atmospheric sulfur hexafluoride (SF6) mole fractions and emissions estimates from the 1970s to 2008. Measurements were made of archived air samples starting from 1973 in the Northern Hemisphere and from 1978 in the Southern Hemisphere, using the Advanced Global Atmospheric Gases Experiment (AGAGE) gas chromatographic-mass spectrometric (GC-MS) systems. These measurements were combined with modern high-frequency GC-MS and GC-electron capture detection (ECD) data from AGAGE monitoring sites, to produce a unique 35-year atmospheric record of this potent greenhouse gas. Atmospheric mole fractions were found to have increased by more than an order of magnitude between 1973 and 2008. The 2008 growth rate was the highest recorded, at 0.29 ± 0.02 pmolmol−1 yr−1. A three-dimensional chemical transport model and a minimum variance Bayesian inverse method was used to estimate annual emission rates using the measurements, with a priori estimates from the Emissions Database for Global Atmospheric Research (EDGAR, version 4). Consistent with the mole fraction growth rate maximum, global emissions during 2008 were also the highest in the 1973-2008 period, reaching 7.4 ± 0.6 Gg yr−1 (1-σ uncertainties) and surpassing the previous maximum in 1995. The 2008 values follow an increase in emissions of 48 ± 20% since 2001. A second global inversion which also incorporated National Oceanic and Atmospheric Administration (NOAA) flask measurements and in situ monitoring site data agreed well with the emissions derived using AGAGE measurements alone. By estimating continent-scale emissions using all available AGAGE and NOAA surface measurements covering the period 2004-2008, with no pollution filtering, we find that it is likely that much of the global emissions rise during this five-year period originated primarily from Asian developing countries that do not report detailed, annual emissions to the United Nations Framework Convention on Climate Change (UNFCCC). We also find it likely that SF6 emissions reported to the UNFCCC were underestimated between at least 2004 and 2005. </P>