96 research outputs found
Effect of Air Injection on Nucleation Rates: An Approach from Induction Time Statistics
From
disruption of the supersaturated solution to improved mass
transfer in the crystallizing suspension, the introduction of a moving
gas phase in a crystallizer could lead to improved rates of nucleation
and crystal growth. In this work, saturated air has been injected
to batch crystallizers to study the effects on formation of the first
crystal and subsequent turbidity buildup. To account for the typically
large sample-to-sample variation, nucleation rates were evaluated
for a large number of replicates using probability distributions of
induction times. The slope and the intercept of the distributions
were studied independently, allowing the simultaneous determination
of the mean induction time and a certain detection delay related to
the rate of crystal growth after formation of the first nucleus. When
saturated air was injected in aqueous glycine solutions, the average
detection delay was reduced from 69 to 13 min, and the mean induction
time decreased from 128 to 36 min. The effect on aqueous solutions
of l-arginine was less apparent, with a detection delay reduction
from 15 to 3 min, and no significant changes on the rate of primary
nucleation. These results demonstrate the potential of this technique
for reduction in nucleation induction time and improved mass deposition
rates in crystallization operations
Osmosis in a minimal model system
Osmosis plays a central role in the function of living and soft matter
systems. While the thermodynamics of osmosis is well understood, the underlying
microscopic dynamical mechanisms remain the subject of discussion. Unraveling
these mechanisms is a crucial prerequisite for eventually understanding osmosis
in non-equilibrium systems. Here, we investigate the microscopic basis of
osmosis, in a system at equilibrium, using molecular dynamics simulations of a
minimal model in which repulsive solute and solvent particles differ only in
their interactions with an external potential. For this system, we can derive a
simple virial-like relation for the osmotic pressure. Our simulations support
an intuitive picture in which the solvent concentration gradient, at osmotic
equilibrium, arises from the balance between an outward force, caused by the
increased total density in the solution, and an inward diffusive flux caused by
the decreased solvent density in the solution. While more complex effects may
occur in other osmotic systems, they are not required for a description of the
basic physics of osmosis in this minimal model.Comment: 10 pages, 8 figure
Comparative Genomic Characterization of Francisella tularensis Strains Belonging to Low and High Virulence Subspecies
Tularemia is a geographically widespread, severely debilitating, and occasionally lethal disease in humans. It is caused by infection by a gram-negative bacterium, Francisella tularensis. In order to better understand its potency as an etiological agent as well as its potential as a biological weapon, we have completed draft assemblies and report the first complete genomic characterization of five strains belonging to the following different Francisella subspecies (subsp.): the F. tularensis subsp. tularensis FSC033, F. tularensis subsp. holarctica FSC257 and FSC022, and F. tularensis subsp. novicida GA99-3548 and GA99-3549 strains. Here, we report the sequencing of these strains and comparative genomic analysis with recently available public Francisella sequences, including the rare F. tularensis subsp. mediasiatica FSC147 strain isolate from the Central Asian Region. We report evidence for the occurrence of large-scale rearrangement events in strains of the holarctica subspecies, supporting previous proposals that further phylogenetic subdivisions of the Type B clade are likely. We also find a significant enrichment of disrupted or absent ORFs proximal to predicted breakpoints in the FSC022 strain, including a genetic component of the Type I restriction-modification defense system. Many of the pseudogenes identified are also disrupted in the closely related rarely human pathogenic F. tularensis subsp. mediasiatica FSC147 strain, including modulator of drug activity B (mdaB) (FTT0961), which encodes a known NADPH quinone reductase involved in oxidative stress resistance. We have also identified genes exhibiting sequence similarity to effectors of the Type III (T3SS) and components of the Type IV secretion systems (T4SS). One of the genes, msrA2 (FTT1797c), is disrupted in F. tularensis subsp. mediasiatica and has recently been shown to mediate bacterial pathogen survival in host organisms. Our findings suggest that in addition to the duplication of the Francisella Pathogenicity Island, and acquisition of individual loci, adaptation by gene loss in the more recently emerged tularensis, holarctica, and mediasiatica subspecies occurred and was distinct from evolutionary events that differentiated these subspecies, and the novicida subspecies, from a common ancestor. Our findings are applicable to future studies focused on variations in Francisella subspecies pathogenesis, and of broader interest to studies of genomic pathoadaptation in bacteria
Inequity in healthcare use among older people after 2008: The case of Southern European Countries
Despite the sizeable cuts in public healthcare spending, part of the austerity measures recently undertaken in Southern European countries, little attention has been devoted to monitoring distributional aspects of healthcare usage. This study aims at measuring socioeconomic inequities in primary and secondary healthcare experienced some time after the crisis onset in Italy, Spain and Portugal. The analysis, based on data drawn from the Survey of Health, Ageing and Retirement in Europe (SHARE), focuses on older people, who generally face significantly higher healthcare needs, and whose health appeared to have worsened in the aftermath of the crisis. The Horizontal Inequity indexes reveal remarkable socioeconomic inequities in older people’s access to secondary healthcare in all three countries. In Portugal, the one country facing most severe healthcare budget cuts and where user charges apply also to GP visits, even access to primary care exhibits a significant pro-rich concentration. If reducing inequities in older people’s access to healthcare remains a policy objective, austerity measures maybe pulling the Olive belt countries further way
from achieving it
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