The effects of froth depth and impeller speed on gas dispersion properties and metallurgical performance of an industrial self-aerated flotation machine

In self-aerated flotation machines, the gas rate depends on operational variables (e.g. froth depth and impeller speed), pulp properties (e.g. solid content and viscosity), and reagent addition (e.g. type and concentration of frother). The gas rate has a strong correlation with the flotation performance by influencing the gas dispersion properties and froth retention time. A factorial experimental design was used to study how the gas dispersion properties, the froth retention time, and the flotation performance respond to changes in froth depth and impeller speed (as the most common operational variables). An in-depth understanding of the effects of impeller speed and froth depth on the gas dispersion properties, especially the bubble surface area flux and froth retention time, is necessary to improve operating strategies for self-aerated flotation machines. All experiments were carried out in a 50 m(3) self-aerated flotation cell in an iron ore processing plant. The results showed that the froth depth affected the metallurgical performance mostly via changing the froth retention time. The impeller speed had two important impacts on the metallurgical performance via varying both the froth retention time and the bubble surface area flux in the froth and pulp zones, respectively. The interaction effects of the froth depth and impeller speed were also established. This allowed us to develop a strategy for operating self-aerated flotation machines based on varying the froth depth and impeller speed with regard to the cell duty

The acoustical signals produced by antibubble formation

An antibubble is an unusual object: a submerged water drop encapsulated in a thin shell of air that is stable underwater for 10–100 s. They are often thought of as the inverse of a soap bubble because they are a spherical shell of air in water in contrast to a shell of water in air. Antibubbles may be formed when water droplets impact the surface of surfactant-covered water, within a limited range of drop radius and drop impact velocity. In this paper, the range of drop size and impact velocity over which large antibubbles (radius 1–3 mm) are generated by the impact of falling drops is characterised, and the relationship of these parameters to the size of the antibubble formed is shown. Measurements of the two acoustical signals that may be produced as an antibubble is formed by drop impact are reported, and their relationship to the antibubble radius and shell thickness is established. Acoustical measurements taken are interpreted in the context of a modified Rayleigh-Plesset equation that provides a good fit to the frequency data for air shells greater than 100 μm in thickness. However, these results highlight the need for future work on the damping mechanisms associated with these larger antibubbles

Plankton composition and environmental parameters in the habitat of the Iranian cave barb (Iranocypris typhlops) in Iran

La composición planctónica y los parámetros ambientales en el hábitat del barbo cavernícola iraní Iranocypris typhlops El barbo cavernícola iraní, Iranocypris typhlops (Bruun & Kaiser, 1944) es una especie catalogada como “Vulnerable” en la Lista Roja de la IUCN. Endémica de una única localidad situada en las montañas Zagros, en Irán occidental. Se trata de una especie omnívora que depende del plancton para alimentarse. Se estudió la distribución espacial y estacional del plancton en el hábitat original del barbo cavernícola iraní entre mayo de 2012 y febrero de 2013. Se midieron varios parámetros ambientales y se relacionaron con la distribución del plancton. La comunidad planctónica comprendía 13 géneros y cinco especies. El filo Rotifera tenía el mayor número de géneros (4) y de especies (4), seguido por Arthropoda (3), Ochrophyta (3), Myzozoa (2), Charophyta (2), Chlorophyta (2), Ciliophora (1) y Cryptophyta (1). Por lo que respecta a la cantidad, las especies dominantes de fitoplancton y zooplancton fueron Achnanthidium sp. y Lecane sp. Los coeficientes de correlación de Pearson pusieron de manifiesto que la relación entre las comunidades de plancton y los parámetros ambientales era baja pero significativa. Entre los parámetros ambientales, el total de sólidos en suspensión y la turbidez parecieron ser los más influyentes en la distribución temporal de las especies de plancton. Asimismo, se observó que el oxígeno disuelto desempeñaba una función importante para la mayoría de las especies de plancton, al igual que la temperatura para la mayoría de las especies de zooplancton. La diversidad y la abundancia de fitoplancton y zooplancton eran bajas durante todo el año en la cueva con una media anual de 96,4 ind./l y no mostraron ningún máximo durante el año.La composición planctónica y los parámetros ambientales en el hábitat del barbo cavernícola iraní Iranocypris typhlops El barbo cavernícola iraní, Iranocypris typhlops (Bruun & Kaiser, 1944) es una especie catalogada como “Vulnerable” en la Lista Roja de la IUCN. Endémica de una única localidad situada en las montañas Zagros, en Irán occidental. Se trata de una especie omnívora que depende del plancton para alimentarse. Se estudió la distribución espacial y estacional del plancton en el hábitat original del barbo cavernícola iraní entre mayo de 2012 y febrero de 2013. Se midieron varios parámetros ambientales y se relacionaron con la distribución del plancton. La comunidad planctónica comprendía 13 géneros y cinco especies. El filo Rotifera tenía el mayor número de géneros (4) y de especies (4), seguido por Arthropoda (3), Ochrophyta (3), Myzozoa (2), Charophyta (2), Chlorophyta (2), Ciliophora (1) y Cryptophyta (1). Por lo que respecta a la cantidad, las especies dominantes de fitoplancton y zooplancton fueron Achnanthidium sp. y Lecane sp. Los coeficientes de correlación de Pearson pusieron de manifiesto que la relación entre las comunidades de plancton y los parámetros ambientales era baja pero significativa. Entre los parámetros ambientales, el total de sólidos en suspensión y la turbidez parecieron ser los más influyentes en la distribución temporal de las especies de plancton. Asimismo, se observó que el oxígeno disuelto desempeñaba una función importante para la mayoría de las especies de plancton, al igual que la temperatura para la mayoría de las especies de zooplancton. La diversidad y la abundancia de fitoplancton y zooplancton eran bajas durante todo el año en la cueva con una media anual de 96,4 ind./l y no mostraron ningún máximo durante el año.The Iranian cave barb (Iranocypris typhlops Bruun & Kaiser, 1944) is ‘Vulnerable’ in the IUCN Red List. It is an endemic species of ray–finned fish of the family Cyprinidae from a single locality in the Zagros Mountains, western Iran. This species is an omnivore that depends on plankton for food. We studied the spatial and seasonal distribution of plankton in the native habitat of the Iranian cave barb between May 2012 and February 2013. We measured various environmental parameters and related these to plankton distribution. The plankton assemblage included 13 genera and five species. Rotifera had the highest number of genera (4) and species (4), followed by Arthropoda (3), Ochrophyta (3), Myzozoa (2), Charophyta (2), Chlorophyta (2), Ciliophora (1) and Cryptophyta (1). In terms of numbers, the dominant species of phytoplankton and zooplankton were Achnanthidium sp. and Lecane sp. Pearson correlation coefficients showed a low but significant relationship between plankton communities and environmental parameters. Among the environmental parameters, total suspended solids and turbidity seemed to have the most important influence on the temporal distribution of plankton species. We also observed that dissolved oxygen played an important role for most plankton species, as did temperature for most zooplankton species. The diversity and abundance of phytoplankton and zooplankton were low throughout the year in the cave with an annual mean of 96.4 ind./l and they did not show any peaks during the year

Developing performance indicators for clinical governance in dimensions of risk management and clinical effectiveness

Objective: This study has been designed and conducted to develop domestic indicators for evaluating the performance of clinical governance in dimensions of risk management and clinical effectiveness. Design: This study implemented a 5-stage process including conducting a comprehensive literature review, expert panel (~1000 h per person per session, 11 experts), semi-structured interviews, a 2-round Delphi study (33 experts were in attendance) and a final expert panel (8 experts were in attendance). Setting: East Azerbaijan-Iran Province. Participants: Fifty-six specialists and experts in different fields of medical sciences. Main Outcome Measures: Importance and applicability of indicators. Results: Using a thorough literature review, 361 indicators (129 risk management indicators in 4 dimensions and 232 clinical effectiveness indicators in 18 dimensions) were found. After conducting expert panels and interviews, the number of indicators decreased to 168 cases (65 risk management indicators in 4 dimensions and 103 clinical effectiveness indicators in 12 dimensions). Two rounds of Delphi identified four indicators that were omitted. The members of the final expert panel agreed on 113 indicators (43 risk management indicators in 4 dimensions and 70 clinical effectiveness indicators in 11 dimensions). Conclusion: In this study, indicators for assessing clinical governance in domains of risk management and clinical effectiveness were designed that can be used by policy-makers and other authorities for improving the quality of services and evaluating the performance of clinical governance. Those indicators can be used with slight modifications in other countries having healthcare systems similar to that of Iran. © The Author 2015. Published by Oxford University Press in association with the International Society for Quality in Health Care; all rights reserved

Global burden of 288 causes of death and life expectancy decomposition in 204 countries and territories and 811 subnational locations, 1990–2021 : a systematic analysis for the Global Burden of Disease Study 2021

Background: Regular, detailed reporting on population health by underlying cause of death is fundamental for public health decision making. Cause-specific estimates of mortality and the subsequent effects on life expectancy worldwide are valuable metrics to gauge progress in reducing mortality rates. These estimates are particularly important following large-scale mortality spikes, such as the COVID-19 pandemic. When systematically analysed, mortality rates and life expectancy allow comparisons of the consequences of causes of death globally and over time, providing a nuanced understanding of the effect of these causes on global populations. Methods: The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2021 cause-of-death analysis estimated mortality and years of life lost (YLLs) from 288 causes of death by age-sex-location-year in 204 countries and territories and 811 subnational locations for each year from 1990 until 2021. The analysis used 56 604 data sources, including data from vital registration and verbal autopsy as well as surveys, censuses, surveillance systems, and cancer registries, among others. As with previous GBD rounds, cause-specific death rates for most causes were estimated using the Cause of Death Ensemble model—a modelling tool developed for GBD to assess the out-of-sample predictive validity of different statistical models and covariate permutations and combine those results to produce cause-specific mortality estimates—with alternative strategies adapted to model causes with insufficient data, substantial changes in reporting over the study period, or unusual epidemiology. YLLs were computed as the product of the number of deaths for each cause-age-sex-location-year and the standard life expectancy at each age. As part of the modelling process, uncertainty intervals (UIs) were generated using the 2·5th and 97·5th percentiles from a 1000-draw distribution for each metric. We decomposed life expectancy by cause of death, location, and year to show cause-specific effects on life expectancy from 1990 to 2021. We also used the coefficient of variation and the fraction of population affected by 90% of deaths to highlight concentrations of mortality. Findings are reported in counts and age-standardised rates. Methodological improvements for cause-of-death estimates in GBD 2021 include the expansion of under-5-years age group to include four new age groups, enhanced methods to account for stochastic variation of sparse data, and the inclusion of COVID-19 and other pandemic-related mortality—which includes excess mortality associated with the pandemic, excluding COVID-19, lower respiratory infections, measles, malaria, and pertussis. For this analysis, 199 new country-years of vital registration cause-of-death data, 5 country-years of surveillance data, 21 country-years of verbal autopsy data, and 94 country-years of other data types were added to those used in previous GBD rounds. Findings: The leading causes of age-standardised deaths globally were the same in 2019 as they were in 1990; in descending order, these were, ischaemic heart disease, stroke, chronic obstructive pulmonary disease, and lower respiratory infections. In 2021, however, COVID-19 replaced stroke as the second-leading age-standardised cause of death, with 94·0 deaths (95% UI 89·2–100·0) per 100 000 population. The COVID-19 pandemic shifted the rankings of the leading five causes, lowering stroke to the third-leading and chronic obstructive pulmonary disease to the fourth-leading position. In 2021, the highest age-standardised death rates from COVID-19 occurred in sub-Saharan Africa (271·0 deaths [250·1–290·7] per 100 000 population) and Latin America and the Caribbean (195·4 deaths [182·1–211·4] per 100 000 population). The lowest age-standardised death rates from COVID-19 were in the high-income super-region (48·1 deaths [47·4–48·8] per 100 000 population) and southeast Asia, east Asia, and Oceania (23·2 deaths [16·3–37·2] per 100 000 population). Globally, life expectancy steadily improved between 1990 and 2019 for 18 of the 22 investigated causes. Decomposition of global and regional life expectancy showed the positive effect that reductions in deaths from enteric infections, lower respiratory infections, stroke, and neonatal deaths, among others have contributed to improved survival over the study period. However, a net reduction of 1·6 years occurred in global life expectancy between 2019 and 2021, primarily due to increased death rates from COVID-19 and other pandemic-related mortality. Life expectancy was highly variable between super-regions over the study period, with southeast Asia, east Asia, and Oceania gaining 8·3 years (6·7–9·9) overall, while having the smallest reduction in life expectancy due to COVID-19 (0·4 years). The largest reduction in life expectancy due to COVID-19 occurred in Latin America and the Caribbean (3·6 years). Additionally, 53 of the 288 causes of death were highly concentrated in locations with less than 50% of the global population as of 2021, and these causes of death became progressively more concentrated since 1990, when only 44 causes showed this pattern. The concentration phenomenon is discussed heuristically with respect to enteric and lower respiratory infections, malaria, HIV/AIDS, neonatal disorders, tuberculosis, and measles. Interpretation: Long-standing gains in life expectancy and reductions in many of the leading causes of death have been disrupted by the COVID-19 pandemic, the adverse effects of which were spread unevenly among populations. Despite the pandemic, there has been continued progress in combatting several notable causes of death, leading to improved global life expectancy over the study period. Each of the seven GBD super-regions showed an overall improvement from 1990 and 2021, obscuring the negative effect in the years of the pandemic. Additionally, our findings regarding regional variation in causes of death driving increases in life expectancy hold clear policy utility. Analyses of shifting mortality trends reveal that several causes, once widespread globally, are now increasingly concentrated geographically. These changes in mortality concentration, alongside further investigation of changing risks, interventions, and relevant policy, present an important opportunity to deepen our understanding of mortality-reduction strategies. Examining patterns in mortality concentration might reveal areas where successful public health interventions have been implemented. Translating these successes to locations where certain causes of death remain entrenched can inform policies that work to improve life expectancy for people everywhere

A new charge-transfer complex in UHV co-deposited tetramethoxypyrene and tetracyanoquinodimethane

UHV-deposited films of the mixed phase of tetramethoxypyrene and tetracyanoquinodimethane (TMP1-TCNQ1) on gold have been studied using ultraviolet photoelectron spectroscopy (UPS), X-ray-diffraction (XRD), infrared (IR) spectroscopy and scanning tunnelling spectroscopy (STS). The formation of an intermolecular charge-transfer (CT) compound is evident from the appearance of new reflexes in XRD (d1= 0.894 nm, d2= 0.677 nm). A softening of the CN stretching vibration (red-shift by 7 cm-1) of TCNQ is visible in the IR spectra, being indicative of a CT of the order of 0.3e from TMP to TCNQ in the complex. Characteristic shifts of the electronic level positions occur in UPS and STS that are in reasonable agreement with the prediction of from DFT calculations (Gaussian03 with hybrid functional B3LYP). STS reveals a HOMO-LUMO gap of the CT complex of about 1.25 eV being much smaller than the gaps (>3.0 eV) of the pure moieties. The electron-injection and hole-injection barriers are 0.3 eV and 0.5 eV, respectively. Systematic differences in the positions of the HOMOs determined by UPS and STS are discussed in terms of the different information content of the two methods.Comment: 20 pages, 6 figure