The importance of crystalline phases in ice nucleation by volcanic ash

Volcanic ash is known to nucleate ice when immersed in supercooled water droplets. This process may impact the properties and dynamics of the eruption plume and cloud as well as those of meteorological clouds once the ash is dispersed in the atmosphere. However, knowledge of what controls the ice-nucleating activity (INA) of ash remains limited, although it has been suggested that crystalline components in ash may play an important role. Here we adopted a novel approach using nine pairs of tephra and their remelted and quenched glass equivalents to investigate the influence of chemical composition, crystallinity, and mineralogy on ash INA in the immersion mode. For all nine pairs studied, the crystal-bearing tephra nucleated ice at warmer temperatures than the corresponding crystal-free glass, indicating that crystalline phases are key to ash INA. Similar to findings for desert dust from arid and semi-arid regions, the presence of feldspar minerals characterizes the four most ice-active tephra samples, although a high INA is observed even in the absence of alkali feldspar in samples bearing plagioclase feldspar and orthopyroxene. There is evidence of a potential indirect relationship between chemical composition and ash INA, whereby a magma of felsic to intermediate composition may generate ash containing ice-active feldspar or pyroxene minerals. This complex interplay between chemical composition, crystallinity, and mineralogy could help to explain the variability in volcanic ash INA reported in the literature. Overall, by demonstrating the importance of crystalline phases in the INA of ash, our study contributes insights essential for better appraising the role of airborne ash in ice formation. Among these is the inference that glass-dominated ash emitted by the largest explosive volcanic eruptions might be less effective at impacting ice-nucleating particle populations than crystalline ash generated by smaller, more frequent eruptions.</p

The Influence of Chemical and Mineral Compositions on the Parameterization of Immersion Freezing by Volcanic Ash Particles

Volcanic ash (VA) from explosive eruptions contributes to aerosol loadings in the atmosphere. Aside from the negative impact of VA on air quality and aviation, these particles can alter the optical and microphysical properties of clouds by triggering ice formation, thereby influencing precipitation and climate. Depending on the volcano and eruption style, VA displays a wide range of different physical, chemical, and mineralogical properties. Here, we present a unique data set on the ice nucleation activity of 15 VA samples obtained from different volcanoes worldwide. The ice nucleation activities of these samples were studied in the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) cloud simulation chamber as well as with the Ice Nucleation Spectrometer of the Karlsruhe Institute of Technology (INSEKT). All VA particles nucleated ice in the immersion freezing mode from 263 to 238K with ice nucleation active site (INAS) densities ranging from ∼10$^{5}$ to 10$^{11}$ m$^{-2}$, respectively. The variabilities observed among the VA samples, at any given temperature, range over 3.5 orders of magnitude. The ice-nucleating abilities of VA samples correlate to varying degrees with their bulk pyroxene and plagioclase contents as a function of temperature. We combined our new data set with existing literature data to develop an improved ice nucleation parameterization for natural VA in the immersion freezing mode. This should be useful for modeling the impact of VA on clouds

The Influence of Chemical and Mineral Compositions on the Parameterization of Immersion Freezing by Volcanic Ash Particles

Funder: Helmholtz Association of German Research CentresAbstract: Volcanic ash (VA) from explosive eruptions contributes to aerosol loadings in the atmosphere. Aside from the negative impact of VA on air quality and aviation, these particles can alter the optical and microphysical properties of clouds by triggering ice formation, thereby influencing precipitation and climate. Depending on the volcano and eruption style, VA displays a wide range of different physical, chemical, and mineralogical properties. Here, we present a unique data set on the ice nucleation activity of 15 VA samples obtained from different volcanoes worldwide. The ice nucleation activities of these samples were studied in the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) cloud simulation chamber as well as with the Ice Nucleation Spectrometer of the Karlsruhe Institute of Technology (INSEKT). All VA particles nucleated ice in the immersion freezing mode from 263 to 238K with ice nucleation active site (INAS) densities ranging from ∼105 to 1011 m−2, respectively. The variabilities observed among the VA samples, at any given temperature, range over 3.5 orders of magnitude. The ice‐nucleating abilities of VA samples correlate to varying degrees with their bulk pyroxene and plagioclase contents as a function of temperature. We combined our new data set with existing literature data to develop an improved ice nucleation parameterization for natural VA in the immersion freezing mode. This should be useful for modeling the impact of VA on clouds

Second thoughts about implementing routine screening of cancer patients for distress

Recommendations for routine screening of cancer patients for distress lack evidence that screening improves patient outcomes. Settings contemplating screening should consider other options for using the same resources. This article reviews evidence relevant to decision making and calls attention to limits in using screening instruments cross-culturally and for triaging patients for receipt of services. Whether screening is the best option depends on the patient population, culture, and health system

The importance of crystalline phases in ice nucleation by volcanic ash

Volcanic ash is known to nucleate ice when immersed in supercooled water droplets. This process may impact the properties and dynamics of the eruption plume and cloud as well as those of meteorological clouds once the ash is dispersed in the atmosphere. However, knowledge of what controls the ice-nucleating activity (INA) of ash remains limited, although it has been suggested that crystalline components in ash may play an important role. Here we adopted a novel approach using nine pairs of tephra and their remelted and quenched glass equivalents to investigate the influence of chemical composition, crystallinity, and mineralogy on ash INA in the immersion mode. For all nine pairs studied, the crystal-bearing tephra nucleated ice at warmer temperatures than the corresponding crystal-free glass, indicating that crystalline phases are key to ash INA. Similar to findings for desert dust from arid and semi-arid regions, the presence of feldspar minerals characterizes the four most ice-active tephra samples, although a high INA is observed even in the absence of alkali feldspar in samples bearing plagioclase feldspar and orthopyroxene. There is evidence of a potential indirect relationship between chemical composition and ash INA, whereby a magma of felsic to intermediate composition may generate ash containing ice-active feldspar or pyroxene minerals. This complex interplay between chemical composition, crystallinity, and mineralogy could help to explain the variability in volcanic ash INA reported in the literature. Overall, by demonstrating the importance of crystalline phases in the INA of ash, our study contributes insights essential for better appraising the role of airborne ash in ice formation. Among these is the inference that glass-dominated ash emitted by the largest explosive volcanic eruptions might be less effective at impacting ice-nucleating particle populations than crystalline ash generated by smaller, more frequent eruptions

The Association of Departmental Quality Infrastructure and Positive Change

A vertically and horizontally well-integrated quality improvement team is essential for effective quality data collection and implementation of improvement measures. We outline the quality structure of a large academic pathology department and describe successful projects across multiple divisions made possible by this tightly integrated structure. The physician vice chair for quality organizes departmental quality efforts and provides representation at the hospital level. The department has an independent continuous quality improvement unit and each laboratory of the department has a staff quality improvement representative. Faculty and staff experts have interacted to produce improvements such as accurate container labeling, efficient triage of specimens, and reduction of unnecessary testing. Specialized task forces such as the Courier Task Force are producing concrete recommendations for process improvement. All phases of pathology patient care are represented by faculty and staff who are trained in quality improvement, and each position touches and communicates actively with levels above and below itself. The key to the department’s approach has been the daily attention to quality efforts in all of its activities and the close association of faculty and staff to accomplish the goals of greater efficiency, safety, and cost savings