112 research outputs found
Comparative Study on Pantothenic Acid Separation by Reactive Extraction with Tri-n-octylamine and Di-(2-ethylhexyl) Phosphoric Acid
The mechanism of reactive extraction of pantothenic acid with tri-n-octylamine and di-(2-ethylhexyl) phosphoric acid was analysed for three solvents in the presence or absence of 1-octanol. In the absence of 1-octanol, the stoichiometric ratio between the solute and tri-n-octylamine was 1:1 for dichloromethane, 1:2 for butyl acetate, and 1:4 for n-heptane. In the presence of 1-octanol, the formation of aminic adducts was restricted, the stoichiometries for the interfacial reaction between the acid and tri-n-octylamine becoming 1:1 for dichloromethane and butyl acetate, 1:2 for n-heptane. A similar effect has been observed for extraction with di-(2-ethylhexyl) phosphoric acid, the structure of the interfacial compound being changed for n-heptane and butyl acetate from HAE2 in the absence of 1-octanol to HAE by addition of this alcohol. The highest extraction constants were obtained when extractant associates were formed. However, when the extraction mechanism was the same, the increase in organic phase polarity influenced positively the value of extraction constant
Inelastic scattering of broadband electron wave packets driven by an intense mid-infrared laser field
Intense, 100 fs laser pulses at 3.2 and 3.6 um are used to generate, by
multi-photon ionization, broadband wave packets with up to 400 eV of kinetic
energy and charge states up to Xe+6. The multiple ionization pathways are well
described by a white electron wave packet and field-free inelastic cross
sections, averaged over the intensity-dependent energy distribution for (e,ne)
electron impact ionization. The analysis also suggests a contribution from a 4d
core excitation in xenon
Eco-friendly Production of Chemicals 1. Improvement of Enzymatic Production of Acetophenone by Direct Extraction
Acetophenone can be enzymatically produced by conversion of methylbenzylamine using transaminase. The enzymatic process
is strongly affected by the product inhibition, thus requiring the acetophenone removal from the media during its synthesis. In
this purpose, the individual and selective extraction of acetophenone and methylbenzylamine with the biocompatible solvent nheptane containing 1-octanol, D2EHPA or TOA has been analyzed at three values of pH (5, 7, and 9). Regardless of the solvent
used and pH-value, the highest efficiency has been reached for extraction of acetophenone, the difference between the extraction
yields of acetophenone and methylbenzylamine being amplified during the separation of these compounds from their mixture. On
the basis of the experimental selectivity factors and taking into consideration both the possible loss of substrate from the media
and the pH required for enzymatic reaction, pH = 7, it has been concluded that the optimum solvent combination is the mixture
between n-heptane and 1-octanol. This solvent mixture allowed reaching high selectivity factor of 315, corresponding to the
extraction yield of acetophenone of 94.5 % and of methylbenzylamine of only 0.3 %
THE STATE OF VEGETATION IN THE STANDS ESTABLISHED ON DEGRADATED LANDU IN THE HILLY AREA OF TRANSILVANIA
In the past, Transylvania was an area of high afforestation, in 1919 having a surface of about four million hectares.
Due to the need to expand agricultural areas, accessible ones have been deforested, with some of them degrading as a
result of intense and irrational grazing.
In order to ensure that the degraded areas are not totally unproductive, in the 1970s, they have been afforested, many
of them being made with resinous, even in situations where the ecological group provided for other solutions.
A number of six sample surfaces were taken into study, in which measurements were taken to track the growth of stands
on degraded lands. These stands suffer from isolated windfall and crown breaks, due to the fact that the silvicultural
operations are performed at a lower frequency than the production stands.
Comparing the data obtained, it was found that the most healthy stands are in the SÄvÄdisla, Sic and SÄrmaĆu areas,
while in the Filitelnic area the trees are affected by isolated windfall and tops and crowns breaks. For tree damage to
occur at the lowest possible frequency, strict silvicultural operations required for each stage of development is
necessary
Nonlinear stability analysis of the Emden-Fowler equation
In this paper we qualitatively study radial solutions of the semilinear
elliptic equation with and on the
positive real line, called the Emden-Fowler or Lane-Emden equation. This
equation is of great importance in Newtonian astrophysics and the constant
is called the polytropic index. By introducing a set of new variables, the
Emden-Fowler equation can be written as an autonomous system of two ordinary
differential equations which can be analyzed using linear and nonlinear
stability analysis. We perform the study of stability by using linear stability
analysis, the Jacobi stability analysis (Kosambi-Cartan-Chern theory) and the
Lyapunov function method. Depending on the values of these different
methods yield different results. We identify a parameter range for where
all three methods imply stability.Comment: 12 pages; new reference added; 3 new references added; fully revised
versio
Factors associated with Toxoplasma gondii infection in confined farrow-to-finish pig herds in western France: an exploratory study in 60 herds
Background: Infection by Toxoplasma gondii postnatally can occur after ingestion of contaminated meat or water (tissue cysts/oocysts). In Europe, percentage of meat borne infections is estimated between 30 and 63 %, out of which pork makes the most important source. The aim of this study was to (i) investigate the seroprevalence of T. gondii in intensive pig farms from western France; and (ii) identify the risk factors associated with seropositivity. Methods: Data were collected between November 2006 and February 2008 in 60 intensive farrow-to-finish farms, where sera were taken from 3595 fattening pigs, weaned and suckling piglets. Information about three classes of potential seropositivity risk factors were obtained through a questionnaire concerning: (i) breeding characteristics; (ii) farm management; and (iii) husbandry and hygiene. The modified agglutination test (MAT) was used for detection of specific anti T. gondii antibodies in pig sera, starting from 1/6 dilution. Results: The overall proportion of seropositive animals was 6.9 %, but the proportion of herds with at least one positive pig was 100 %. Multivariate logistic mixed model showed an increased seropositivity risk in weaned compared to suckling piglets, and a decreasing risk for mid-sized and large farms. The presence of a Danish entry facility, that clearly separates clean and dirty areas, had a protective effect on T. gondii seropositivity as well. Conclusions: The observed proportion of herds with at least one T. gondii seropositive animal provides further evidence that even in confined conditions of pig breeding, infection occurs, and is common. The highest risk for acquiring T. gondii is at the end of weaning period. Smaller confined pig farms demonstrate higher T. gondii seropositivity levels. This study also showed that Danish entry on farm buildings provides effective protection against T. gondii
On Some Geometric Structures Associated to a k-Symplectic Manifold
A canonical connection is attached to any k-symplectic manifold. We study the
properties of this connection and its geometric applications to k-symplectic
manifolds. In particular we prove that, under some natural assumption, any
ksymplectic manifold admits an Ehresmann connection, discussing some
corollaries of this result, and we find vanishing theorems for characteristic
classes on a k-symplectic manifold.Comment: To appear on J. Phys. A: Math. Theo
Clocking Auger electrons
Intense X-ray free-electron lasers (XFELs) can rapidly excite matter, leaving it in inherently unstable states that decay on femtosecond timescales. The relaxation occurs primarily via Auger emission, so excited-state observations are constrained by Auger decay. In situ measurement of this process is therefore crucial, yet it has thus far remained elusive in XFELs owing to inherent timing and phase jitter, which can be orders of magnitude larger than the timescale of Auger decay. Here we develop an approach termed âself-referenced attosecond streakingâ that provides subfemtosecond resolution in spite of jitter, enabling time-domain measurement of the delay between photoemission and Auger emission in atomic neon excited by intense, femtosecond pulses from an XFEL. Using a fully quantum-mechanical description that treats the ionization, core-hole formation and Auger emission as a single process, the observed delay yields an Auger decay lifetime of 2.2_â0.3^+0.2 fs for the KLL decay channel
Clocking Auger Electrons
Intense X-ray free-electron lasers (XFELs) can rapidly excite matter, leaving
it in inherently unstable states that decay on femtosecond timescales. As the
relaxation occurs primarily via Auger emission, excited state observations are
constrained by Auger decay. In situ measurement of this process is therefore
crucial, yet it has thus far remained elusive at XFELs due to inherent timing
and phase jitter, which can be orders of magnitude larger than the timescale of
Auger decay. Here, we develop a new approach termed self-referenced attosecond
streaking, based upon simultaneous measurements of streaked photo- and Auger
electrons. Our technique enables sub-femtosecond resolution in spite of jitter.
We exploit this method to make the first XFEL time-domain measurement of the
Auger decay lifetime in atomic neon, and, by using a fully quantum-mechanical
description, retrieve a lifetime of fs for the KLL
decay channel. Importantly, our technique can be generalised to permit the
extension of attosecond time-resolved experiments to all current and future FEL
facilities.Comment: Main text: 20 pages, 3 figures. Supplementary information: 17 pages,
6 figure
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