5 research outputs found
Kinetic Limitation to Inorganic Ion Diffusivity and to Coalescence of Inorganic Inclusions in Viscous Liquid–Liquid Phase-Separated Particles
Mixed
organic/inorganic aerosols may undergo liquid–liquid phase
separation (LLPS) when the relative humidity drops in the atmosphere.
Phase-separated particles adopt different morphologies, which will
have different consequences for atmospheric chemistry and climate.
Recent laboratory studies on submicron particles led to speculation
whether LLPS observed for larger drops might actually be suppressed
in smaller droplets. Here, we report on micron-sized droplets of a
ternary mixture of ammonium sulfate (AS), carminic acid, and water
at different temperatures, which were exposed to typical atmospheric
drying rates ranging from 0.34 to 5.0% RH min<sup>–1</sup>.
Our results reveal that increasing the drying rate and lowering the
temperature results in different morphologies after LLPS and may suppress
the growth and coalescence of the inorganic-rich phase inclusions
due to kinetic limitations in a viscous matrix. The coalescence time
was used to estimate the viscosity of the organic-rich phase within
a factor of 20, and based on the Stokes–Einstein relationship,
we estimated AS diffusivity. Furthermore, we evaluated the initial
growth of inclusions to quantitatively determine the AS diffusivity
in the organic-rich phase, which is about 10<sup>–8</sup> cm<sup>2</sup> s<sup>–1</sup> at room temperature. Extrapolation
of diffusivity to lower temperatures using estimations for the diffusion
activation energy leads us to conclude that the growth of the inorganic
phase is not kinetically impeded for tropospheric submicron particles
larger than 100 nm
Kinetic Limitation to Inorganic Ion Diffusivity and to Coalescence of Inorganic Inclusions in Viscous Liquid–Liquid Phase-Separated Particles
Mixed
organic/inorganic aerosols may undergo liquid–liquid phase
separation (LLPS) when the relative humidity drops in the atmosphere.
Phase-separated particles adopt different morphologies, which will
have different consequences for atmospheric chemistry and climate.
Recent laboratory studies on submicron particles led to speculation
whether LLPS observed for larger drops might actually be suppressed
in smaller droplets. Here, we report on micron-sized droplets of a
ternary mixture of ammonium sulfate (AS), carminic acid, and water
at different temperatures, which were exposed to typical atmospheric
drying rates ranging from 0.34 to 5.0% RH min<sup>–1</sup>.
Our results reveal that increasing the drying rate and lowering the
temperature results in different morphologies after LLPS and may suppress
the growth and coalescence of the inorganic-rich phase inclusions
due to kinetic limitations in a viscous matrix. The coalescence time
was used to estimate the viscosity of the organic-rich phase within
a factor of 20, and based on the Stokes–Einstein relationship,
we estimated AS diffusivity. Furthermore, we evaluated the initial
growth of inclusions to quantitatively determine the AS diffusivity
in the organic-rich phase, which is about 10<sup>–8</sup> cm<sup>2</sup> s<sup>–1</sup> at room temperature. Extrapolation
of diffusivity to lower temperatures using estimations for the diffusion
activation energy leads us to conclude that the growth of the inorganic
phase is not kinetically impeded for tropospheric submicron particles
larger than 100 nm
Kinetic Limitation to Inorganic Ion Diffusivity and to Coalescence of Inorganic Inclusions in Viscous Liquid–Liquid Phase-Separated Particles
Mixed
organic/inorganic aerosols may undergo liquid–liquid phase
separation (LLPS) when the relative humidity drops in the atmosphere.
Phase-separated particles adopt different morphologies, which will
have different consequences for atmospheric chemistry and climate.
Recent laboratory studies on submicron particles led to speculation
whether LLPS observed for larger drops might actually be suppressed
in smaller droplets. Here, we report on micron-sized droplets of a
ternary mixture of ammonium sulfate (AS), carminic acid, and water
at different temperatures, which were exposed to typical atmospheric
drying rates ranging from 0.34 to 5.0% RH min<sup>–1</sup>.
Our results reveal that increasing the drying rate and lowering the
temperature results in different morphologies after LLPS and may suppress
the growth and coalescence of the inorganic-rich phase inclusions
due to kinetic limitations in a viscous matrix. The coalescence time
was used to estimate the viscosity of the organic-rich phase within
a factor of 20, and based on the Stokes–Einstein relationship,
we estimated AS diffusivity. Furthermore, we evaluated the initial
growth of inclusions to quantitatively determine the AS diffusivity
in the organic-rich phase, which is about 10<sup>–8</sup> cm<sup>2</sup> s<sup>–1</sup> at room temperature. Extrapolation
of diffusivity to lower temperatures using estimations for the diffusion
activation energy leads us to conclude that the growth of the inorganic
phase is not kinetically impeded for tropospheric submicron particles
larger than 100 nm
European Emissions of Halogenated Greenhouse Gases Inferred from Atmospheric Measurements
European emissions of nine representative halocarbons (CFC-11, CFC-12, Halon 1211, HCFC-141b, HCFC-142b, HCFC-22, HFC-125, HFC-134a, HFC-152a) are derived for the year 2009 by combining long-term observations in Switzerland, Italy, and Ireland with campaign measurements from Hungary. For the first time, halocarbon emissions over Eastern Europe are assessed by top-down methods, and these results are compared to Western European emissions. The employed inversion method builds on least-squares optimization linking atmospheric observations with calculations from the Lagrangian particle dispersion model FLEXPART. The aggregated halocarbon emissions over the study area are estimated at 125 (106–150) Tg of CO<sub>2</sub> equiv/y, of which the hydrofluorocarbons (HFCs) make up the most important fraction with 41% (31–52%). We find that chlorofluorocarbon (CFC) emissions from banks are still significant and account for 35% (27–43%) of total halocarbon emissions in Europe. The regional differences in per capita emissions are only small for the HFCs, while emissions of CFCs and hydrochlorofluorocarbons (HCFCs) tend to be higher in Western Europe compared to Eastern Europe. In total, the inferred per capita emissions are similar to estimates for China, but 3.5 (2.3–4.5) times lower than for the United States. Our study demonstrates the large benefits of adding a strategically well placed measurement site to the existing European observation network of halocarbons, as it extends the coverage of the inversion domain toward Eastern Europe and helps to better constrain the emissions over Central Europe
Easy to Apply Polyoxazoline-Based Coating for Precise and Long-Term Control of Neural Patterns
Arranging
cultured cells in patterns via surface modification is a tool used
by biologists to answer questions in a specific and controlled manner.
In the past decade, bottom-up neuroscience emerged as a new application,
which aims to get a better understanding of the brain via reverse
engineering and analyzing elementary circuitry in vitro. Building
well-defined neural networks is the ultimate goal. Antifouling coatings
are often used to control neurite outgrowth. Because erroneous connectivity
alters the entire topology and functionality of minicircuits, the
requirements are demanding. Current state-of-the-art coating solutions
such as widely used poly(l-lysine)-<i>g</i>-poly(ethylene
glycol) (PLL-<i>g</i>-PEG) fail to prevent primary neurons
from making undesired connections in long-term cultures. In this study,
a new copolymer with greatly enhanced antifouling properties is developed,
characterized, and evaluated for its reliability, stability, and versatility.
To this end, the following components are grafted to a poly(acrylamide)
(PAcrAm) backbone: hexaneamine, to support spontaneous electrostatic
adsorption in buffered aqueous solutions, and propyldimethylethoxysilane,
to increase the durability via covalent bonding to hydroxylated culture
surfaces and antifouling polymer poly(2-methyl-2-oxazoline) (PMOXA).
In an assay for neural connectivity control, the new copolymer’s
ability to effectively prevent unwanted neurite outgrowth is compared
to the gold standard, PLL-<i>g</i>-PEG. Additionally, its
versatility is evaluated on polystyrene, glass, and poly(dimethylsiloxane)
using primary hippocampal and cortical rat neurons as well as C2C12
myoblasts, and human fibroblasts. PAcrAm-<i>g</i>-(PMOXA,
NH<sub>2</sub>, Si) consistently outperforms PLL-<i>g</i>-PEG with all tested culture surfaces and cell types, and it is the
first surface coating which reliably prevents arranged nodes of primary
neurons from forming undesired connections over the long term. Whereas
the presented work focuses on the proof of concept for the new antifouling
coating to successfully and sustainably prevent unwanted connectivity,
it is an important milestone for in vitro neuroscience, enabling follow-up
studies to engineer neurologically relevant networks. Furthermore,
because PAcrAm-<i>g</i>-(PMOXA, NH<sub>2</sub>, Si) can
be quickly applied and used with various surfaces and cell types,
it is an attractive extension to the toolbox for in vitro biology
and biomedical engineering