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2. Academic Writing at Babeş-Bolyai University. A Case Study

Author

Moraru, Camelia, Aluaş, Mihaela, Kelemen, Andrei, Lung, Rodica, Cramarenco, Romana Emilia, Pavlenko, Sonia, Schuster, Christian, Bojan, Cristina, Balazsi, Robert, Kirkpatrick, Andy, Series Editor, Adamson, Bob, Series Editor, Chitez, Mădălina, editor, Doroholschi, Claudia Ioana, editor, Kruse, Otto, editor, Salski, Łukasz, editor, and Tucan, Dumitru, editor

Published
2018
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10. CHHC and [superscript 1]H–[superscript 1]H magnetization exchange: Analysis by experimental solid-state NMR and 11-spin density-matrix simulations

Author

Aluas, Mihaela, Tripon, Carmen, Griffin, John M., Filip, Xenia, Ladizhansky, Vladimir, Brown, Steven P., Filip, Claudiu, Griffin, Robert Guy, Massachusetts Institute of Technology. Department of Chemistry, Francis Bitter Magnet Laboratory (Massachusetts Institute of Technology), and Griffin, Robert Guy

Abstract

A protocol is presented for correcting the effect of non-specific cross-polarization in CHHC solid-state MAS NMR experiments, thus allowing the recovery of the [superscript 1]H–[superscript 1]H magnetization exchange functions from the mixing-time dependent buildup of experimental CHHC peak intensity. The presented protocol also incorporates a scaling procedure to take into account the effect of multiplicity of a CH[subscript 2] or CH[subscript 3] moiety. Experimental CHHC buildup curves are presented for l-tyrosine·HCl samples where either all or only one in 10 molecules are U–[superscript 13]C labeled. Good agreement between experiment and 11-spin SPINEVOLUTION simulation (including only isotropic [superscript 1]H chemical shifts) is demonstrated for the initial buildup (t[subscript mix] < 100 μs) of CHHC peak intensity corresponding to an intramolecular close (2.5 Å) H–H proximity. Differences in the initial CHHC buildup are observed between the one in 10 dilute and 100% samples for cases where there is a close intermolecular H–H proximity in addition to a close intramolecular H–H proximity. For the dilute sample, CHHC cross-peak intensities tended to significantly lower values for long mixing times (500 μs) as compared to the 100% sample. This difference is explained as being due to the dependence of the limiting total magnetization on the ratio N[subscript obs]/N[subscript tot] between the number of protons that are directly attached to a [superscript 13]C nucleus and hence contribute significantly to the observed [superscript 13]C CHHC NMR signal, and the total number of [superscript 1]H spins into the system. [superscript 1]H–[superscript 1]H magnetization exchange curves extracted from CHHC spectra for the 100% l-tyrosine·HCl sample exhibit a clear sensitivity to the root sum squared dipolar coupling, with fast buildup being observed for the shortest intramolecular distances (2.5 Å) and slower, yet observable buildup for the longer intermolecular distances (up to 5 Å)., National Institutes of Health (U.S.) (Grant EB-001960), National Institutes of Health (U.S.) (Grant EB-003151), National Institutes of Health (U.S.) (Grant EB-002026)

Published
2009

11. CHHC and H-1-H-1 magnetization exchange:analysis by experimental solid-state NMR and 11-spin density-matrix simulations

Author

Aluas, Mihaela, Tripon, Carmen, Griffin, John M., Filip, Xenia, Ladizhansky, Vladimir, Griffin, Robert G., Brown, Steven P., Filip, Claudiu, Aluas, Mihaela, Tripon, Carmen, Griffin, John M., Filip, Xenia, Ladizhansky, Vladimir, Griffin, Robert G., Brown, Steven P., and Filip, Claudiu

Abstract

A protocol is presented for correcting the effect of non-specific cross-polarization in CHHC solid-state MAS NMR experiments, thus allowing the recovery of the H-1-H-1 magnetization exchange functions front the mixing-time dependent buildup of experimental CHHC peak intensity. The presented protocol also incorporates a Scaling Procedure to take into account the effect Of multiplicity of a CH2 or CH3 moiety. Experimental CHHC buildup Curves are presented for L-tyrosine center dot HCl samples where either all OF only one in 10 molecules are U-C-13 labeled. Good agreement between experiment and 11-spin SPINEVOLUTION simulation (including only isotropic H-1 chemical shifts) is demonstrated for the initial buildup (t(mix) <100 mu s) of CHHC peak intensity corresponding to an intramolecular close (2.5 degrees) H-H proximity. Differences in the initial CHHC buildup are observed between the one in 10 dilute and 100% samples for cases where there is a close intermolecular H-H proximity in addition to a close intramolecular H-H proximity. For the dilute sample, CHHC cross-peak intensities tended to significantly lower values for long mixing times (500 mu s) as compared to the 100% sample. This difference is explained as being due to the dependence of the limiting total magnetization on the ratio N-obs/N-tot between the number of protons that are directly attached to a C-13 nucleus and hence contribute significantly to the observed C-13 CHHC NMR signal, and the total number of H-1 spins into the system. H-1-H-1 magnetization exchange Curves extracted from CHHC spectra for the 100% L-tyrosine HCI sample exhibit a clear sensitivity to the root sum squared dipolar coupling, with fast buildup being observed for the shortest intramolecular distances (2.5 angstrom) and slower, yet observable buildup for the longer intermolecular distances (up to 5 angstrom). (C) 2009 Elsevier Inc. All rights reserved.

Published
2009

15. Academic Writing.

Author

PAVLENKO, SONIA, BOJAN, CRISTINA, KELEMEN, ANDREI, and ALUAS, MIHAELA

Subjects
ACADEMIC discourse, UNIVERSITIES & colleges, TECHNICAL writing, HISTORICAL distance, AWARENESS
Abstract

Academic writing is a field not sufficiently explored nor investigated in Romania to date. This article aims at offering the fundamental characteristics of academic writing by analyzing global views and contrasting them to Romanian perspectives. It discusses the main-stream approaches to academic writing, looking at its development from a historical perspective and then analyzing comparatively contemporary approaches. Furthermore, it investigates Romanian efforts in the direction of developing academic writing awareness and suggests a possible path to be taken by Romanian higher education institutions. [ABSTRACT FROM AUTHOR]

Published
2014

16. Physico-chemical comparison of betulinic acid, betulin and birch bark extract and in vitro investigation of their cytotoxic effects towards skin epidermoid carcinoma (A431), breast carcinoma (MCF7) and cervix adenocarcinoma (HeLa) cell lines.

Author

Şoica, CodrutaM., Dehelean, CristinaA., Peev, Camelia, Aluas, Mihaela, Zupkó, I., Kása, P., and Alexa, Ersilia

Abstract

Betulin and betulinic acid are pentacyclic triterpenes present in the bark of the birch tree and other vegetal sources. Quantitatively, in birch bark betulin is more significant than betulinic acid; therefore, birch can be a large and feasible source of raw material for betulin extraction. Betulin can be used as extracted or, after chemical modification, as a starting compound for its acid, betulinic acid, with both substances possessing various interesting pharmacological properties. The purpose of this study is to analyse the betulin and betulinic acid content of a birch tree bark extract, as well as its cytotoxic activity. The extraction was done using a Soxhlet extractor and chloroform/dichlormethane/methanol (1 : 1 : 1) as solvent. The betulin and betulinic acid content of the extract was estimated using standards of pure betulin and betulinic acid, by thermal analysis as opposed to pure substance (thermogravimetric and differential thermal analysis). The extract and the main compounds were also analysed by NMR. The results indicated a high amount of betulin in the final extract (up to 50%), and an important quantity of betulinic acid: over 3%. The cytotoxic activity indicated a high proliferation inhibition for the birch tree extract but was still comparable with betulinic acid and betulin. [ABSTRACT FROM PUBLISHER]

Published
2012
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