Dynamics in the ordered and disordered phases of barocaloric adamantane.

High-entropy order-disorder phase transitions can be used for efficient and eco-friendly barocaloric solid-state cooling. Here the barocaloric effect is reported in an archetypal plastic crystal, adamantane. Adamantane has a colossal isothermally reversible entropy change of 106 J K-1 kg-1. Extremely low hysteresis means that this can be accessed at pressure differences less than 200 bar. Configurational entropy can only account for about 40% of the total entropy change; the remainder is due to vibrational effects. Using neutron spectroscopy and supercell lattice dynamics calculations, it is found that this vibrational entropy change is mainly caused by softening in the high-entropy phase of acoustic modes that correspond to molecular rotations. We attribute this difference in the dynamics to the contrast between an 'interlocked' state in the low-entropy phase and sphere-like behaviour in the high-entropy phase. Although adamantane is a simple van der Waals solid with near-spherical molecules, this approach can be leveraged for the design of more complex barocaloric molecular crystals. Moreover, this study shows that supercell lattice dynamics calculations can accurately map the effect of orientational disorder on the phonon spectrum, paving the way for studying the vibrational entropy, thermal conductivity, and other thermodynamic effects in more complex materials.

A robust regression analysis method to determine the significance of trends in concentrations of heavy metals in UK ambient air and improve network design and emission inventories.

A novel application of the Theil-Sen robust regression method for determining the temporal trends in the concentration of heavy metals in UK ambient air over the period 2005-2020 is presented and compared to other regression methods. We have demonstrated improvements over non-robust methods of regression, proving the ability to tease out trends that are small with respect to the variability of the concentration measurement. The method is used to identify, in general, large and significant trends in the concentrations of Ni, As, Pb and V over the period 2005-2020, either across the UK as a whole or at groupings of site classifications in the UK. These trends have been compared to trends in emission data determined in the same manner. Although the results for most metals provide confidence that the UK metal network of monitoring sites is successful in appropriately capturing changes in emissions, a key finding of this work is the disagreement between trends in measured concentrations and emissions for Cu, Mn and Ni, for which we suggest improvements in future network design. The results also indicate that UK emission data for V should be reviewed, as we propose that the rate of reduction of V emissions is likely to have been overestimated.

Progress in pre-treatment and extraction of organic and inorganic pollutants by layered double hydroxide for trace-level analysis.

Continuous release of pollutants into the environment poses serious threats to environmental sustainability and human health. For trace-level analysis of pollutants, layered double hydroxide (LDH) is an attractive option to impart enhanced sorption capability and sensitivity toward pollutants because of its unique layered structure, tunable interior architecture, high anion-exchange capacities, and high porosity (e.g., Zn/Cr LDH/DABCO-IL, Ni/Al LDH, CS-Ni/Fe LDH, SDS-Fe3O4@SiO2@Mg-Al LDH, Boeh/Mg/Al LDH/pC, and Fe@NiAl LDH). In concert with the well-defined analytical methodologies (e.g., HPLC and GC), the LDH materials can be employed to detect trace-level targets (e.g., as low as âˆ¼ 20 fg/L for phenols) in aqueous environments. This review highlights LDH as a promising material for pre-treatment of a variety of organic and inorganic target pollutants in complex real matrices. Challenges and future requirements for research into LDH-based analytical methods are also discussed.

Plant-based remediation of air pollution: A review.

Humans face threats from air pollutants present in both indoor and outdoor environments. The emerging role of plants in remediating the atmospheric environment is now being actively investigated as a possible solution for this problem. Foliar surfaces of plants (e.g., the leaves of cotton) can absorb a variety of airborne pollutants (e.g., formaldehyde, benzene, trimethylamine, and xylene), thereby reducing their concentrations in indoor environments. Recently, theoretical and experimental studies have been conducted to offer better insights into the interactions between plants and the surrounding air. In our research, an overview on the role of plants in reducing air pollution (often referred to as phytoremediation) is provided based on a comprehensive literature survey. The major issues for plant-based research for the reduction of air pollution in both outdoor and indoor environments are discussed in depth along with future challenges. Analysis of the existing data confirms the effectiveness of phytoremediation in terms of the absorption and purification of pollutants (e.g., by the leaves and roots of plants and trees), while being controlled by different variables (e.g., pore characteristics and planting patterns). Although most lab-scale studies have shown that plants can effectively absorb pollutants, it is important for such studies to reflect the real-world conditions, especially with the influence of human activities. Under such conditions, pollutants are to be replenished continually while the plant surface area to ambient atmosphere volume ratio vastly decreases (e.g., relative to lab-based experiments). The replication of such experimental conditions is the key challenge in this field of research. This review is expected to offer valuable insights into the innate ability of various plants in removing diverse pollutants (such as formaldehyde, benzene, and particulate matter) under different environmental settings.

International travel to obtain medical treatment for primary retinoblastoma: A global cohort study.

Early diagnosis and treatment of retinoblastoma (Rb), the most common intraocular malignancy, can save both the child's life and vision. However, access to services and hence chances for survival and preserving the eye and its vision vary widely across the globe. Some families have to, or make a choice to, leave their home country to seek planned medical treatment abroad. We aimed to investigate how frequently this cross-border travel occurs and the factors associated with it. A total of 278 Rb centres in 153 countries were recruited to participate in a global cross-sectional analysis of newly diagnosed Rb patients in 2017. Number and proportions of children who travelled from their home country for treatment were analysed by country, continent, socioeconomic stratum and clinical and demographic features. The cohort included 4351 new patients of whom 223 [5.1%, 95% confidence interval 4.5-5.8] were taken across country borders for planned medical treatment. Independently significant predictors of travelling across borders included: being from a country with a smaller population, being from a country classified as low socioeconomic status, having bilateral Rb and having intraocular disease without extraocular spread. The factors that determine international travel for Rb treatment are complex and deserve further investigation. We may need to rethink the way services are delivered in the light of the threat of severe curtailment of international travel from pandemics like corona virus disease 2019.

Redefinition of the Mole in the Revised International System of Units and the Ongoing Importance of Metrology for Accurate Chemical Measurements.

This Feature highlights the role of metrology, the science of measurement, in maintaining the infrastructure we all rely on for accurate chemical measurements. In particular, the recent change to the definition of the mole, the unit of chemistry, is explained.

Strategic design of wall envelopes for the enhancement of building thermal performance at reduced air-conditioning costs.

A strategy is proposed for the design of wall envelopes to improve unsteady thermal performance in non-air-conditioned buildings and to reduce energy costs in air-conditioned buildings. The thermophysical properties of building materials (e.g., burnt bricks, mud bricks, laterite stone, cinder concrete, and expanded polystyrene) were measured experimentally using a thermal analyzer. A total of 28 combinations for composite walls were designed with expanded polystyrene as an insulation material based on seven criteria and were subjected to 8 different external surface heat transfer coefficients, which were tested for unsteady thermal performance parameters and air-conditioning cost-saving potential. In this paper, unsteady thermal transmittance obtained from admittance method has been employed to compute cost saving potential of air-conditioning for the various wall envelopes. The use of C-H5 design at a 2 m/s wind speed was found to increase the decrement lag of burnt brick, mud brick, laterite stone, and cinder concrete composite wall envelopes by 48.1%, 49.0%, 59.5%, and 47.0%, respectively, relative to the common wall design (C-H1) in non-air-conditioned buildings. The laterite with a C-H5 design offers the highest annual energy cost savings (1.71 $/m2 at 2 m/s), the highest life cycle cost savings (18.32 $/m2 at 2 m/s), and the lowest payback period (4.03 yrs at 2 m/s) in all tested building materials for air-conditioned buildings. The overall results of this study are expected to open new paths to deliver simple design strategies for energy-efficient buildings.

Measuring measurement - What is metrology and why does it matter?

Metrology remains a uniquely important endeavour. A sign of its success and robustness as an infra-technology is that it usually goes unnoticed. This means that it is in danger of being under-valued and under-appreciated. The sure-footing that metrology provides to the quality infrastructure will be especially important as the world grapples with the aftereffects of the COVID-19 pandemic, rebuilding global economies and also re-focusing on addressing global grand challenges and exploiting emerging technologies. In this context it is important and timely to re-examine the concept of metrology and how it relates to the quality infrastructure that it serves, but differs to measurement in general. The concept of metrology as 'measuring measurement' is proposed, emphasising the characteristic meta-thought associated with the discipline that distinguishes it from routine measurement.

Breakthrough in Negating the Impact of Adsorption in Gas Reference Materials.

We have shown that an exchange dilution preparation method reduces the impact of surface adsorption of the target component in high-pressure gas mixtures used for underpinning measurements of amount-of-substance fraction. Gas mixtures are diluted in the same cylinder by releasing an aliquot of the parent mixture. Additional matrix gas is then added to the cylinder. This differs from conventional methods where dilutions are achieved by transferring the parent mixture to another cylinder, which then stores the final reference material. The benefit of this revolutionary approach is that losses due to adsorption to the walls of the cylinder and the valve are reduced as the parent mixture pacifies the surface with only a negligible relative change in amount-of-substance fraction. This development allows for preparation of gas reference materials with unprecedented uncertainties beyond the existing state of the art. It has significant implications for the preparation of high accuracy gas reference materials which underpin a broad range of requirements, particularly in atmospheric monitoring of carbon dioxide, where understanding the adsorption effects is the major obstacle to advancing the measurement science. It has the potential to remove the reliance on proprietary surface pretreatments as the method provides an in situ and consistent alternative.

Concentration trends of metals in ambient air in the UK: a review.

The monitoring of metals in ambient air has been undertaken for over 40 years on a national basis in the UK. During this period, the UK pollution landscape has continued to evolve in terms of emission sources, and the measurement framework for metals in ambient air, the UK Heavy Metals Monitoring Network, has also been subject to significant configuration changes. Therefore, this work provides a timely review of more recent concentration trends in the context of current emission profiles. Overall, throughout this time period, there has been a significant downward trend in the emissions and consequently, the measured concentrations of most metals in UK ambient air. Ambient concentrations were generally found to be well correlated with emission estimates. Analysis of the sensitivity of measured concentrations to emissions suggests that concentrations have fallen faster than the reduction in emission estimates would have predicted at typical median urban background sites.

Influence of Pressure on the Composition of Gaseous Reference Materials.

We have shown that the amount fraction of carbon dioxide in a nitrogen or synthetic air matrix stored in cylinders increases as the pressure of the gas mixture reduces, while the amount fraction of methane remains unchanged. Our measurements show the initial amount fraction of carbon dioxide to be lower than the gravimetric value after preparation, which we attribute to the adsorption of a proportion of the molecules to active sites on the internal surface of the cylinder and the valve. As the mixture is consumed, the pressure in the cylinder reduces and the amount fraction of the component is observed to increase. The effect is less pronounced in the presence of water vapor. More dramatic effects have been observed for hydrogen chloride. These findings have significant implications for the preparation of high accuracy gaseous reference materials with unprecedented uncertainties which underpin a broad range of requirements, in particular atmospheric monitoring of high impact greenhouse gases.

Optimization of the Magnetocaloric Effect in Low Applied Magnetic Fields in LnOHCO3 Frameworks.

This study probes the structure and magnetocaloric effect of the LnOHCO3 (Ln = Gd3+, Tb3+, Dy3+, Ho3+, and Er3+) frameworks. The combination of single crystal X-ray and neutron powder diffraction indicates that these materials solely adopt the P212121 structure under these synthetic conditions and magnetic susceptibility measurements indicate they remain paramagnetic down to 2 K. We show that the magnetocaloric effects of TbOHCO3 and DyOHCO3 have peak entropy changes of 30.99 and 33.34 J kg-1 K-1 for a 2-0 T field change, respectively, which are higher than that of the promising GdOHCO3 framework above 4 K in moderate magnetic fields. The magnetic entropy changes of TbOHCO3 and DyOHCO3 above 4 K for smaller than 2 T field changes also exceed those of Gd3Ga5O12 and Dy3Ga5O12, making them suitable magnetic cooling materials for use at liquid helium temperatures using the low applied magnetic fields accessible using permanent magnets, advantageous for efficient practical cooling devices.

Airborne volatile aromatic hydrocarbons at an urban monitoring station in Korea from 2013 to 2015.

The concentrations of C6-C10 volatile aromatic hydrocarbons (AHCs) in air were measured at an urban air quality monitoring station in Jong-Ro, Seoul, Korea, between 2013 and 2015. Their temporal patterns (e.g., diurnal, intraweek, daily) were assessed individually and collectively as groups of benzene, toluene, ethylbenzene, styrene, and xylene (BTESX); total aliphatic hydrocarbon (TALHC: C2-C12); total aromatic hydrocarbon (TARHC: C6-C10); and total hydrocarbon (THC: C2-C12). The highest mean AHC concentrations over the 3-year study (in ppb (v/v)) were observed for toluene (6.0 ±â€¯4.3), followed by the xylenes (1.5 ±â€¯1.3), ethylbenzene (0.85 ±â€¯0.93), benzene (0.73 ±â€¯0.77), and styrene (0.16 ±â€¯0.30) nL/L. The mean ppbC ((v/v), nL∙atm∙C/nL∙atm) values for BTESX, TALHC, TARHC, and THC were 65.8, 113, 77.7, and 191 ppbC, respectively. For most AHC species (e.g., toluene, styrene, and BTESX), only weak seasonal trends were observed in contrast to temporally varying species like nitric oxide (NO) (e.g., 26.3 ppb (January-February) vs. 8.5 ppb (July-August) during weekdays in 2013). Furthermore, toluene and NO concentrations were much higher (up to a factor 3) on weekdays than on Sunday for most weeks. This might reflect reduced anthropogenic activities on Sunday.

Monitoring of airborne particulate matter at mountainous urban sites.

Concentrations of various size fractions (TSP, PM10, PM2.5, and PM1.0) of particulate matter (PM) were measured at two mountainous sites, Buk Han (BH) and Gwan AK (GA), along with one ground reference site at Gwang Jin (GJ), located in Seoul, South Korea for the 4 years from 2010 to 2013. The daily average concentrations of TSP, PM10, PM2.5, and PM1.0 at BH were 47.9 ± 32.5, 37.0 ± 24.6, 20.6 ± 12.9, and 15.3 ± 9.53 µg m(-3), respectively. These values were slightly larger than those measured at GA while much lower than those measured at the reference site (GJ). Seasonal variations in PM concentrations were consistent across all locations with a relative increase in concentrations observed in spring and winter. Correlation analysis showed clear differences in PM concentrations between the mountainous sites and the reference site. Analysis of these PM concentrations indicated that the distribution of PM in the mountainous locations was affected by a number of manmade sources from nearby locations, including both traffic and industrial emissions.

Cataract surgery outcomes in bangladeshi children.

PURPOSE: To measure visual acuity (VA) outcomes, complication rates, and the social impact of cataract surgery in a cohort who underwent surgery as children in Bangladesh. DESIGN: Case series. PARTICIPANTS: A total of 471 of 850 children from 6 Bangladeshi districts who had been identified as cataract blind using key informants (KIs) between 2004 and 2009 during the Bangladesh Childhood Cataract Campaign (BCCC) together with all those children not included in the BCCC database but in the Child Sight Foundation (CSF) database who had been identified as cataract blind. METHODS: The subjects and families were contacted again by KIs and transported to local examination centers, where parents and subjects were administered a questionnaire and subjects underwent full ocular examination. Where operative data were available (15%), they were analyzed in conjunction with questionnaire and examination findings. Statistical analysis was performed using SPSS Statistics (IBM, Armonk, NY). MAIN OUTCOME MEASURES: Presenting and best-corrected visual acuities (BCVAs), cause(s) of poor outcome, postoperative refraction, and school attendance. RESULTS: A total of 407 of the participants had undergone bilateral surgery as children, with a mean follow-up of 8.8 years. The mean age at examination was 16 years (range, 5-28 years; standard deviation [SD], 4.6 years); 63% of those examined were male; 22% had a binocular presenting VA of >20/60; and 53% were severely visually impaired or blind (VA <20/200). After refraction, 33% had VA >20/60 in their better eye and 33% had VA <20/200. Factors that predicted poor VA in multivariate logistic regression analysis were nystagmus (P < 0.001), longer delay in presentation (P < 0.001), and magnitude of absolute spherical equivalent refractive error (P<0.001). Some 50% had nystagmus, and 69% of those currently aged ≤16 years were attending school. Better acuity was associated with school attendance (P < 0.001), whereas gender was not. CONCLUSIONS: Approximately one third of all participants had a BCVA of ≥20/60 in their better eye. Amblyopia and nystagmus limited visual outcome, indicating the need for earlier detection and treatment. This is the first study to show the link between pediatric cataract outcome and access to education, a millennium development goal.

International system of units traceable results of Hg mass concentration at saturation in air from a newly developed measurement procedure.

Data most commonly used at present to calibrate measurements of mercury vapor concentrations in air come from a relationship known as the "Dumarey equation". It uses a fitting relationship to experimental results obtained nearly 30 years ago. The way these results relate to the international system of units (SI) is not known. This has caused difficulties for the specification and enforcement of limit values for mercury concentrations in air and in emissions to air as part of national or international legislation. Furthermore, there is a significant discrepancy (around 7% at room temperature) between the Dumarey data and data calculated from results of mercury vapor pressure measurements in the presence of only liquid mercury. As an attempt to solve some of these problems, a new measurement procedure is described for SI traceable results of gaseous Hg concentrations at saturation in milliliter samples of air. The aim was to propose a scheme as immune as possible to analytical biases. It was based on isotope dilution (ID) in the liquid phase with the (202)Hg enriched certified reference material ERM-AE640 and measurements of the mercury isotope ratios in ID blends, subsequent to a cold vapor generation step, by inductively coupled plasma mass spectrometry. The process developed involved a combination of interconnected valves and syringes operated by computer controlled pumps and ensured continuity under closed circuit conditions from the air sampling stage onward. Quantitative trapping of the gaseous mercury in the liquid phase was achieved with 11.5 µM KMnO4 in 2% HNO3. Mass concentrations at saturation found from five measurements under room temperature conditions were significantly higher (5.8% on average) than data calculated from the Dumarey equation, but in agreement (-1.2% lower on average) with data based on mercury vapor pressure measurement results. Relative expanded combined uncertainties were estimated following a model based approach. They ranged from 2.2% to 2.8% (k = 2). The volume of air samples was traceable to the kilogram via weighing of water for the calibration of the sampling syringe. Procedural blanks represented on average less than 0.1% of the mass of Hg present in 7.4 cm(3) of air, and correcting for these blanks was not an important source of uncertainty.

Preparation and validation of fully synthetic standard gas mixtures with atmospheric isotopic composition for global CO2 and CH4 monitoring.

We report the preparation and validation of the first fully synthetic gaseous reference standards of CO2 and CH4 in a whole air matrix with an isotopic distribution matching that is in the ambient atmosphere. The mixtures are accurately representative of the ambient atmosphere and were prepared gravimetrically. The isotopic distribution of the CO2 was matched to the abundance in the ambient atmosphere by blending (12)C-enriched CO2 with (13)C-enriched CO2 in order to avoid measurement biases introduced by measurement instrumentation detecting only certain isotopologues. The reference standards developed here have been compared with standards developed by the National Institute of Standards and Technology and standards from the WMO scale. They demonstrate excellent comparability.