Polymorphism Control through a Single Nucleation Event

2014 ◽  
Vol 14 (3) ◽  
pp. 1493-1499 ◽  
Author(s):  
Samir A. Kulkarni ◽  
Hugo Meekes ◽  
Joop H. ter Horst
Keyword(s):  
Nucleation Event

scholarly journals Observation of a SO2 induced nucleation event in the atmosphere

1998 ◽  
Vol 29 ◽  
pp. S609-S610 ◽  
Author(s):  
Bart Verheggen ◽  
Michael Mozurkewich
Keyword(s):  
Nucleation Event

scholarly journals Characterization of air ions in boreal forest air during BIOFOR III campaign

2005 ◽  
Vol 5 (3) ◽  
pp. 2749-2790 ◽  
Author(s):  
U. Hõrrak ◽  
P. P. Aalto ◽  
J. Salm ◽  
J. M. Mäkelä ◽  
L. Laakso ◽  
...  
Keyword(s):  
Boreal Forest ◽  
Correlation Coefficient ◽  
Aerosol Particles ◽  
Ion Pairs ◽  
Ion Concentration ◽  
Cluster Ions ◽  
Statistical Characteristics ◽  
Nucleation Event ◽  
Air Ions ◽  
20 Nm

Abstract. The behavior of the concentration of positive small (or cluster) air ions and naturally charged nanometer aerosol particles (aerosol ions) has been studied on the basis of measurements carried out in a boreal forest at the Hyytiälä SMEAR station, Finland, during the BIOFOR III campaign in spring 1999. Statistical characteristics of the concentrations of cluster ions, two classes of aerosol ions of the sizes of 2.5–8 nm and 8–ca 20 nm and the quantities that determine the balance of small ions in the atmosphere have been given for the nucleation event days and non-event days. The dependence of small ion concentration on the ion loss (sink) due to aerosol particles was investigated applying a model of bipolar diffusion charging of particles by small ions. The small ion concentration and the ion sink were closely correlated (correlation coefficient 87%) when the fog events and the hours of high relative humidity (above 97%), as well as nocturnal calms and weak wind (wind speed<0.6 m s-1 had been excluded. In the case of nucleation burst events, variations in the concentration of small positive ions were in accordance with the changes caused by the ion sink due to aerosols; no clear indication of positive ion depletion by ion-induced nucleation was found. The estimated average ionization rate of air at the Hyytiälä station in early spring, when the ground was partly covered with snow, was about 4.8 ion pairs cm-3 s-1. The study of the charging state of nanometer aerosol particles (2.5–8 nm) revealed a strong correlation (correlation coefficient 88%) between the concentrations of particles and their charged fraction (positive air ions) during nucleation bursts. The estimated charged fraction of particles, which varied from 3% to 6% considering various nucleation event days, confirms that these particles are almost quasi-steady state charged. Also the particles and air ions in the size range of 8–ca 20 nm showed a good qualitative consistency; the correlation coefficient was 92%.

scholarly journals Characterization of positive air ions in boreal forest air at the Hyytiälä SMEAR station

2007 ◽  
Vol 7 (4) ◽  
pp. 9465-9517 ◽  
Author(s):  
U. Hõrrak ◽  
P. P. Aalto ◽  
J. Salm ◽  
K. Komsaare ◽  
H. Tammet ◽  
...  
Keyword(s):  
Boreal Forest ◽  
Correlation Coefficient ◽  
Aerosol Particles ◽  
Ion Pairs ◽  
Coniferous Forest ◽  
Ion Concentration ◽  
Statistical Characteristics ◽  
Nucleation Event ◽  
Air Ions ◽  
20 Nm

Abstract. The behavior of the concentration of positive small (or cluster) air ions and naturally charged nanometer aerosol particles (aerosol ions) has been studied on the basis of measurements carried out in a boreal forest at the Hyytiälä SMEAR station, Finland, during the BIOFOR III campaign in spring 1999. Statistical characteristics of the concentrations of cluster ions, two classes of aerosol ions of the sizes of 2.5–8 nm and 8–ca. 20 nm and the quantities that determine the balance of small ions in the atmosphere have been given for the nucleation event days and non-event days. The dependence of small ion concentration on the ion loss (sink) due to aerosol particles was investigated applying a model of bipolar diffusion charging of particles by small ions. The small ion concentration and the ion sink were closely correlated (correlation coefficient –87%) when the fog events and the hours of high relative humidity (above 95%), as well as nocturnal calms and weak wind (wind speed <0.6 m s−1) had been excluded. However, an extra ion loss term presumably due to small ion deposition on coniferous forest with a magnitude equal to the average ion loss to pre-existing particles is needed to explain the observations. Also the hygroscopic growth correction of measured aerosol particle size distributions was found to be necessary for proper estimation of the ion sink. In the case of nucleation burst events, variations in the concentration of small positive ions were in accordance with the changes caused by the ion sink due to aerosols; no clear indication of positive ion depletion by ion-induced nucleation was found. The estimated average ionization rate of the air at the Hyytiälä station in early spring, when the ground was partly covered with snow, was about 6 ion pairs cm−3 s−1. The study of the charging state of nanometer aerosol particles (2.5–8 nm) revealed a strong correlation (correlation coefficient 88%) between the concentrations of particles and positively charged particles (positive air ions) during nucleation bursts. The estimated charged fraction of particles, which varied from 3% to 6% considering various nucleation event days, confirms that these particles are almost quasi-steady state charged. Also the particles and air ions in the size range of 8–ca. 20 nm showed a good qualitative consistency; the correlation coefficient was 92%.

scholarly journals Concentrations and fluxes of aerosol particles during the LAPBIAT measurement campaign at Värriö field station

2007 ◽  
Vol 7 (14) ◽  
pp. 3683-3700 ◽  
Author(s):  
T. M. Ruuskanen ◽  
M. Kaasik ◽  
P. P. Aalto ◽  
U. Hõrrak ◽  
M. Vana ◽  
...  
Keyword(s):  
Kola Peninsula ◽  
Aerosol Particle ◽  
Aerosol Particles ◽  
Particle Formation ◽  
Nucleation Event ◽  
New Particle Formation ◽  
Air Ions ◽  
Field Station ◽  
Air Mass ◽  
Measurement Campaign

Abstract. The LAPBIAT measurement campaign took place in the Värriö SMEAR I measurement station located in Eastern Lapland in the spring of 2003 between 26 April and 11 May. In this paper we describe the measurement campaign, concentrations and fluxes of aerosol particles, air ions and trace gases, paying special attention to an aerosol particle formation event broken by a air mass change from a clean Arctic air mass with new particle formation to polluted one approaching from industrial areas of Kola Peninsula, Russia, lacking new particle formation. Aerosol particle number flux measurements show strong downward fluxes during that time. Concentrations of coarse aerosol particles were high for 1–2 days before the nucleation event (i.e. 28–29 April), very low immediately before and during the observed aerosol particle formation event (30 April) and increased moderately from the moment of sudden break of the event. In general particle deposition measurements based on snow samples show the same changes. Measurements of the mobility distribution of air ions showed elevated concentrations of intermediate air ions during the particle formation event. We estimated the growth rates in the nucleation mode size range. For particles <10 nm, the growth rate increases with size on 30 April. Dispersion modelling made with model SILAM support the conclusion that the nucleation event was interrupted by an outbreak of sulphate-rich air mass in the evening of 30 April that originated from the industry at Kola Peninsula, Russia. The results of this campaign highlight the need for detailed research in atmospheric transport of air constituents for understanding the aerosol dynamics.

scholarly journals Mechanical Modification of Al-6%Si By Semisolid Process

2016 ◽  
Vol 61 (3) ◽  
pp. 1689-1696
Author(s):  
Z. Sarajan
Keyword(s):  
Mechanical Property ◽  
Growth Temperature ◽  
Liquidus Temperature ◽  
Microstructure Characterization ◽  
Nucleation Temperature ◽  
Nucleation Event ◽  
Semisolid Processing ◽  
Globule Size ◽  
Semisolid Process

Abstract In this study by semisolid processing of Al-6%Si alloy, it has been found that small additions of Ti-6Al-4V shift the liquidus temperature up and the recalescence decreases. The nucleation event takes place at higher temperatures. Furthermore, the rate at which growth temperature increases is less than that of nucleation temperature and therefore more nuclei form with less potential for growth. In this processing refiner increases the α-Al percentage and reduces globule size. Improvement of mechanical property and microstructure characterization are the main advantages of this study.

In situSAXS studies of the formation of sodium jarosite

2013 ◽  
Vol 20 (4) ◽  
pp. 626-634 ◽  
Author(s):  
Helen E. A. Brand ◽  
Nicola V. Y. Scarlett ◽  
Ian E. Grey ◽  
Robert B. Knott ◽  
Nigel Kirby
Keyword(s):  
Powder Diffraction ◽  
Reaction Vessel ◽  
Scattering Data ◽  
Wide Angle ◽  
Powder Diffraction Data ◽  
Nucleation Event ◽  
Time Resolved ◽  
Angle Scattering ◽  
Co Precipitation

This paper reports the results of time-resolved synchrotron small-angle scattering and powder diffraction experiments where natrojarosites were synthesizedin situin order to observe the species produced at the earliest stages of nucleation. The sample temperatures were 333, 353 and 368 K. These compounds were synthesized by co-precipitation from solution on the Small and Wide Angle Scattering and Powder Diffraction beamlines at the Australian Synchrotron. Scattering data were collected continuously throughout the syntheses. The results presented here show that the first particles to form in solution appear to be amorphous and nucleate on the walls of the reaction vessel. Crucially, there is a single nucleation event which forms particles with an elliptical disc morphology which then grow uniformly before natrojarosite crystallization is observed in complementary powder diffraction data. This nucleation event may represent the key to controlling the growth of jarosites in industrial and environmental settings.

Combination of a Single Primary Nucleation Event and Secondary Nucleation in Crystallization Processes

2011 ◽  
Vol 11 (4) ◽  
pp. 1271-1277 ◽  
Author(s):  
Somnath S. Kadam ◽  
Herman J. M. Kramer ◽  
Joop H. ter Horst
Keyword(s):  
Nucleation Event ◽  
Secondary Nucleation ◽  
Primary Nucleation

scholarly journals A network theory of the origin of life

2016 ◽  
Author(s):  
Geoffrey W. Hoffmann
Keyword(s):  
Origin Of Life ◽  
Network Theory ◽  
High Probability ◽  
Volcanic Ash ◽  
Large Fraction ◽  
Nucleation Event ◽  
Primitive Earth ◽  
Low Probability ◽  
The Origin Of Life ◽  
Non Coding Rnas

AbstractThe origin of life may have been a low probability event that involved both RNA and polypeptides. While such an event would occur with low probability, the probability is not too low in the context of the number of nucleation opportunities on the primitive Earth. The probability for the nucleation event is too small if needed components occur as frequently as disruptive components do, without specific interactions between the two classes. However, if many of the needed components contribute by inhibiting otherwise disruptive components, a high probability for a complex nucleation as the beginning of life event emerges. RNA interference and long non-coding RNAs are ascribed roles in inhibiting components that would otherwise be disruptive in the context of a nucleation event. The theory likewise provides an inhibitory role for the large fraction of proteins (35% to 40%) that have no known function in both prokaryotes and eukaryotes. It is suggested that volcanic ash could provide the large number of random shapes needed as the basis for the nucleation event. Experiments based on that hypothesis are proposed.

scholarly journals Oligohistidine Tag Mutagenesis of the λ Holin Gene

1998 ◽  
Vol 180 (16) ◽  
pp. 4199-4211 ◽  
Author(s):  
David L. Smith ◽  
Ry Young
Keyword(s):  
Affinity Chromatography ◽  
Copy Number ◽  
Integral Membrane Proteins ◽  
Immobilized Metal Affinity Chromatography ◽  
Diverse Group ◽  
Nucleation Event ◽  
Wild Type ◽  
Hole Formation ◽  
Metal Affinity ◽  
Insight Into

ABSTRACT Holins are a diverse group of small integral membrane proteins elaborated by bacteriophages to lyse bacterial hosts and effect release of progeny phages in a precisely timed manner. Recently, the holinS gene of phage λ was overexpressed and the holin protein was purified to homogeneity by means of an oligohistidine tag procedure and immobilized metal affinity chromatography (D. L. Smith, D. K. Struck, J. M. Scholtz, and R. Young, J. Bacteriol. 180:2531–2540, 1998). Numerous locations within the S gene were tested as sites for an oligohistidine-tag-encoding insertion which preserves holin function. The lysis phenotypes of these alleles, expressed from moderate-copy-number transactivation plasmids, were characterized. A striking class of mutants, previously referred to as early-dominant, have been found to have severe lysis defects but are fully functional in the presence of wild-type protein. Results presented here reveal that the early-dominance phenotype is independent of S107 inhibitor function. The results provide insight into the mechanism of hole formation and indicate that, while oligomerization is required in the pathway to hole formation, a nucleation event may also be required.

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