712 research outputs found
Enantioseparation of the four nadolol stereoisomers by fixed-bed and simulated moving bed chromatography
In the last decades, the separation and purification of high added value products by liquid chromatography has been a very popular technique. The development of more stable and efficient stationary phases, together with the design of innovative and more flexible separation processes, enhanced the use of chromatographic processes, particularly at preparative and industrial scales through simulated moving bed (SMB) technology and allied techniques. Nowadays, preparative and SMB related techniques are more and more used in the separation of a wide range of high added value products of interest for the pharmaceutical, fine chemistry, biotechnology and food industries.
In this context, one of the actual main challenges concerns the design and optimization of these chromatographic processes for multicomponent separations. This includes the development of new and innovative chromatographic processes, combining different design strategies and modes of operation, with different types of stationary and mobile phases.
This communication will introduce the multicomponent separation challenge using the commercial pharmaceutical drug of nadolol stereoisomers. The nadolol represents a very interesting case-study of multicomponent chiral separation since it is composed by four stereoisomers, arranged in two pairs of enantiomers. In this way, it introduces the possibility of alternative strategies, using different kind of separation sequences and techniques, the use of different packings (chiral and achiral stationary phases), and the correspondent mobile phase optimization at both normal and reversed phase modes.
An extensive set of experimental results obtained at fixed-bed and SMB operations will be presented. The complete methodology will be explained and applied for the pseudo-binary enantioseparation of the more retained and active stereoisomer (1+2+3)/(4), and for the (2)/(3) and (1)/(4) binary enantioseparations after a first achiral pseudo-binary separation of the two nadolol racemates.Financed by projects: NORTE-01-0145-FEDER-000006 - funded by NORTE2020 through PT2020
and ERDF; Associate Laboratory LSRE-LCM - UID/EQu/50020/2019 - funded by national funds
through FCT/MCTES (PIDDAC). Rami S. Arafah gratefully acknowledges his Ph.D. scholarship from
Funda~ao para a Ciencia e Tecnologia (FCT) SFRH/BD/137966/201B.info:eu-repo/semantics/publishedVersio
Separation of nadolol racemates by high pH reversed-phase preparative chromatography
The separation of nadolol racemates under high pH reversed-phase preparative chromatography is presented for
the first time.
Three Waters C18 adsorbents (XBridge, Shield and XSelect) are compared for the separation of nadolol racemates
using ethanol:water:diethylamine solvent mixtures. Experimental and simulation results are presented
to compare the separation performances at preparative scale using both the fixed-bed and the simulated moving
bed operations.
The Waters XBridge C18 adsorbent and an ethanol:water:diethylamine solvent mixture are selected as a good
option for the separation of nadolol racemates. The validated methodology allows the separation of a multicomponent
nadolol feed mixture composed by four stereoisomers into two pure racemates (two pairs of enantiomers).
This work introduces the potential of using an initial achiral separation step in the global strategy for
the complete multicomponent separation of the four nadolol stereoisomers.This work is a result of: Project âAIProcMat@N2020 - Advanced
Industrial Processes and Materials for a Sustainable Northern Region of
Portugal 2020â, with the reference NORTE-01-0145-FEDER-000006,
supported by Norte Portugal Regional Operational Programme (NORTE
2020), under the Portugal 2020 Partnership Agreement, through the
European Regional Development Fund (ERDF); Associate Laboratory
LSRE-LCM - UID/EQU/50020/2019 - funded by national funds through
FCT/MCTES (PIDDAC).
Rami S. Arafah is supported by a PhD Grant of Fundação para a
CiĂȘncia e a Tecnologia (SFRH/BD/137966/2018).info:eu-repo/semantics/publishedVersio
Metal-insulator transition in two-dimensional disordered systems with power-law transfer terms
We investigate a disordered two-dimensional lattice model for noninteracting
electrons with long-range power-law transfer terms and apply the method of
level statistics for the calculation of the critical properties. The
eigenvalues used are obtained numerically by direct diagonalization. We find a
metal-insulator transition for a system with orthogonal symmetry. The exponent
governing the divergence of the correlation length at the transition is
extracted from a finite size scaling analysis and found to be . The critical eigenstates are also analyzed and the distribution of the
generalized multifractal dimensions is extrapolated.Comment: 4 pages with 4 figures, printed version: PRB, Rapid Communication
An exercise on transition systems
Labelled transition systems admit different but equivalent characterizations either as relational structures or coalgebras for the powerset functor, each of them with their own merits. Notions of simulation and bisimulation, for example, are expressed in the pointfree relational calculus in a very concise and precise way. On the other hand, the coalgebraic perspective regards processes as inhabitants of a final universe and allows for an intuitive definition of the semantics of processâ combinators.
This paper is an exercise on such a dual characterisation. In particular, it discusses how a notion of weak bisimilarity can be lifted from the relational to the coalgebraic level, to become an effective reasoning tool on coinductively defined process algebras.(undefined
The cyclooxigenase-2 inhibitor parecoxib prevents epidermal dysplasia in HPV16-transgenic mice: efficacy and safety observations
Carcinogenesis induced by high-risk human papillomavirus (HPV) involves inflammatory
phenomena, partially mediated by cyclooxigenase-2. In pre-clinical models of HPV-induced cancer,
cyclooxygenase-2 inhibitors have shown significant e cacy, but also considerable toxicity. This study
addresses the chemopreventive e ect and hepatic toxicity of a specific cyclooxigensase-2 inhibitor,
parecoxib, in HPV16-transgenic mice. Forty-three 20 weeks-old female mice were divided into four
groups: I (HPV16+/-, n = 10, parecoxib-treated); II (HPV16+/- n = 11, untreated); III (HPV16+/-,
n = 11, parecoxib-treated) and IV (HPV16+/- n = 11, untreated). Parecoxib (5.0 mg/kg once daily)
or vehicle was administered intraperitoneally for 22 consecutive days. Skin lesions were classified
histologically. Toxicological endpoints included genotoxic parameters, hepatic oxidative stress,
transaminases and histology. Parecoxib completely prevented the onset of epidermal dysplasia in
HPV16+/- treated animals (0% versus 64% in HPV16+/- untreated, p = 0.027). Parecoxib decreases
lipid peroxidation (LPO) and superoxide dismutase (SOD) activity and increases the GSH:GSSG
ratio in HPV16+/- treated animals meaning that oxidative stress is lower. Parecoxib increased
genotoxic stress parameters in wild-type and HPV16-transgenic mice, but didnât modify histological or biochemical hepatic parameters. These results indicate that parecoxib has chemopreventive e ects
against HPV16-induced lesions while maintaining an acceptable toxicological profile in this model.This work is supported by National Funds by FCTâPortuguese Foundation for Science and Technology,
under the projects UID/AGR/04033/2019, UID/CVT/00772/2019 and UID/EQU/00511/2019 - Laboratory for Process
Engineering, Environment, Biotechnology and EnergyâLEPABE funded by national funds through FCT/MCTES
(PIDDAC); Project âLEPABE-2-ECO-INNOVATIONââNORTE-01-0145-FEDER-000005, funded by Norte Portugal
Regional Operational Programme (NORTE 2020), under PORTUGAL 2020 Partnership Agreement, through the
European Regional Development Fund.info:eu-repo/semantics/publishedVersio
Search for the standard model Higgs boson decaying into two photons in pp collisions at sqrt(s)=7 TeV
A search for a Higgs boson decaying into two photons is described. The
analysis is performed using a dataset recorded by the CMS experiment at the LHC
from pp collisions at a centre-of-mass energy of 7 TeV, which corresponds to an
integrated luminosity of 4.8 inverse femtobarns. Limits are set on the cross
section of the standard model Higgs boson decaying to two photons. The expected
exclusion limit at 95% confidence level is between 1.4 and 2.4 times the
standard model cross section in the mass range between 110 and 150 GeV. The
analysis of the data excludes, at 95% confidence level, the standard model
Higgs boson decaying into two photons in the mass range 128 to 132 GeV. The
largest excess of events above the expected standard model background is
observed for a Higgs boson mass hypothesis of 124 GeV with a local significance
of 3.1 sigma. The global significance of observing an excess with a local
significance greater than 3.1 sigma anywhere in the search range 110-150 GeV is
estimated to be 1.8 sigma. More data are required to ascertain the origin of
this excess.Comment: Submitted to Physics Letters
- âŠ