194 research outputs found
Energy transfer in aggregated CuInS<sub>2</sub>/ZnS core-shell quantum dots deposited as solid films
No full textWe report on the morphology and optical properties of CuInS2/ZnS core-shell quantum dots in solid films by means of AFM, SEM, HRTEM, steady state and time-resolved photoluminescence (PL) spectroscopy. The amount of aggregation of the CuInS2/ZnS QDs was controlled by changing the preparation conditions of the films. A red-shift of the PL spectrum of CuInS2/ZnS core-shell quantum dots, deposited as solid films on silicon substrates, is observed upon increasing the amount of aggregation. The presence of larger aggregates was found to lead to a larger PL red-shift. Besides, as the degree of aggregation increased, the PL decay became slower. We attribute the observed PL red-shift to energy transfer from the smaller to the larger dots within the aggregates, with the emission being realized via a long decay recombination mechanism (100-200 ns), the origin of which is discussed.</p
Exploring Solvent and Substituent Effects on the Excited State Dynamics and Symmetry Breaking of Quadrupolar Triarylamine End-Capped Benzothiazole Chromophores by Femtosecond Spectroscopy
No full text: We investigate herein the excited state dynamics and symmetry breaking processes in three benzothiazole-derived two-photon absorbing chromophores by femtosecond fluorescence and transient absorption (fs-TA) spectroscopies in solvents of various polarity. The chromophores feature a quasi-quadrupolar D-π-A-π-D architecture comprised of an electron-withdrawing benzothiazole core and lateral triphenylamine donors (Qbtz-H), while the acceptor strength of the central unit is enforced by attached cyano groups (Qbtz-CN) and the electron-donating strength of the arylamine moieties by introduction of peripheral methoxy groups (Qbtz'-CN). Steady state spectroscopy reveals positive solvatochromism, which is mostly pronounced for Qbtz'-CN. Femtosecond spectroscopy of Qbtz-H reveals the coexistence of the Franck-Condon (FC) state and states populated after symmetry breaking (SB) in low-polarity solvents such as toluene and tetrahydrofuran, while the SB state becomes favorable in polar acetonitrile. For the other two molecules possessing a stronger electron-accepting unit and thus more polar excited state, SB takes place even in low-polarity solvents, as shown by fs-TA spectroscopy. Global fitting of the fs-TA spectra together with investigation of the evolution associated spectra (EAS) reveals the existence of an initial FC state in Qbtz-H, in all studied solvents, which relaxes toward Intermediate Charge Transfer (I-CT) and SB states. On the other hand, for Qbtz-CN and Qbtz'-CN in more polar solvents, the FC state undergoes ultrafast relaxation toward symmetry-broken charge transfer (SB-CT) states which in turn show very fast recombination to the ground state. Our measurements confirm that the extent of symmetry breaking is larger for D-π-A-π-D systems with the stronger acceptor core and increases further by increasing electron-donating strength of triarylamine moieties, giving rise to symmetry breaking in these nonionic quadrupolar molecules with ethynylene (triple bond) π-spacers also in less polar solvents
Fakis, A. (girl)
No full textPhotograph from the C.R. Savage Portrait Studio. Name associated with the photograph: A. Faki
Quantitative analysis of qualitative information from interviews: A systematic literature review
No full textAuthor(s) Pre or Post Print Version OnlyBackground: A systematic literature review was conducted on mixed methods area. Objectives: The overall aim was to explore how qualitative information from interviews has been analyzed using quantitative methods. Methods: A contemporary review was undertaken and based on a predefined protocol. The references were identified using inclusion and exclusion criteria and specific key terms in 11 search databases. Results: Evidence was synthesized from 14 references that included the methods used for quantifying qualitative information, analyzing it statistically and the rationale behind this. Gaps in the existing literature and recommendations for future research were identified. Conclusions: This review highlights the need for a new mixed method based on advanced statistical modeling method that will explore complex relationships arising from qualitative information
Fakis, A. (group)
No full textPhotograph from the C.R. Savage Portrait Studio. Name associated with the photograph: A. Faki
Character with a Benzothiazole Unit in Matched or Mismatched Orientation
No full textBenzothiazole is among prominent electron-withdrawing heteroarene moieties used in a variety of π-conjugated molecules. Its relative orientation with respect to the principal dipole vector(s) of chromophores derived thereof is crucial, affecting photophysical and nonlinear optical properties. Here we compare the photophysics and ultrafast dynamics of dipolar and octupolar molecules comprising a triphenylamine electron-donating core, ethynylene π-conjugated linker(s) and benzothiazole acceptor(s) having the matched or mismatched orientation (with respect to the direction of intramolecular charge transfer), while a carbaldehyde group is attached as an auxiliary acceptor. Among chromophores without the auxiliary acceptor, stronger fluorescence solvatochromism and faster excited state dynamics are exhibited for the derivatives with the mismatched geometry. On the contrary, introduction of the auxiliary acceptor to the benzothiazole unit enhances the intramolecular charge transfer ICT (featuring ultrafast dynamics of the excited state) for the matched geometry. The data confirm the crucial role of the relative orientation of asymmetric heteroaromatic unit (regioisomeric effect) in dipolar as well as in multipolar molecules in tuning linear and nonlinear optical properties as well as excited state dynamics
Religious men and literacy in Berti society
No full textThe thesis examines the use of traditional literacy promulgated
by the Koranic schools among the Berti in the Northern Darfur
Province of the Republic of the Sudan. This literacy is restricted
both in the scope of its use as well as in its social distribution,
which remains limited to religious specialists - fakis. Instead of
leading to a change in the traditional mode of thought, Berti
literacy contributes considerably to maintaining the homeostatic
tendency supposedly characteristic of oral societies.
Literacy plays an important role in the Berti religious life.
The words of God contained in the Koran and other books widely used
by the fakis are considered to be sacred, and an important aspect of
Berti religion is their internalisation in the form of memorisation,
drinking of erasure and the retaining of amulets (hijbat). The
repetition of sacred words is used as a means of invoking God in
communal rituals and the rites of passage. Literacy underlies book
divination practised by the fakis and its literate origin is the
ultimate sanction of sand divination which is primarily practised by
the illiterate Berti.
In their use of the sacred words in healing, divination,
communal rituals, rites of passage and the preparation of amulets
and erasure, Berti fakis impose their own meaning on the Koranic
text which differs considerably from its theological meaning.
The thesis includes translation and analysis of over 50
original texts pertaining to erasure writing, amulets, book
divination and communal rituals. Photocopies of 25 original amulets
are presented in the thesis and the majority of them are translated
and commented upon
Porphyrin oriented self-assembled nanostructures for efficient exciton dissociation in high-performing organic photovoltaics
No full textHerein we report on enhanced organic solar cell performance through the incorporation of cathode interfacial layers consisting of self-organized porphyrin nanostructures with a face-on configuration. In particular, a water/methanol-soluble porphyrin molecule, the free base meso-tetrakis(1- methylpyridinium-4-yl)porphyrin chloride, is employed as a novel cathode interlayer in bulk heterojunction organic photovoltaics. It is demonstrated that the self-organization of this porphyrin compound into aggregates in which molecules adopt a face-to-face orientation parallel to the organic semiconducting substrate induces a large local interfacial electric field that results in a significant enhancement of exciton dissociation. Consequently, enhanced photocurrent and open circuit voltage were obtained resulting in overall device efficiency improvement in organic photovoltaics based on bulk heterojunction mixtures of different polymeric donors and fullerene acceptors, regardless of the specific combination of donor-acceptor employed. To highlight the impact of molecular orientation a second porphyrin compound, the Zn-metallated meso-tetrakis(1-methylpyridinium-4-yl)porphyrin chloride, was also studied and it was found that it forms aggregates with an edge-to-edge molecular configuration inducing a smaller increase in the device performance.</p
Genotyping of single nucleotide polymorphisms of pharmacogenetic interest
No full textΒιβλιογραφία : σ. 69 - 72Για την επιτυχία ενός φαρμάκου, η ρύθμιση της δόσης είναι σημαντική για να θεραπευτεί η νόσος και να περιοριστούν οι παρενέργειες. Συνεπώς είναι χρήσιμο να προβλεφθεί η απόκριση ενός ασθενούς απέναντι σε ένα φάρμακο. Στον άνθρωπο το γονίδιο NAT2 καταλύει την ενεργοποίηση και απενεργοποίηση ξενοβιοτικών ουσιών. Έχουν εντοπιστεί διάφοροι πολυμορφισμοί στο γονίδιο NAT2 που σχετίζονται με τον μεταβολισμό και με τον τρόπο δράσης διάφορων φαρμάκων. Από τους πολυμορφισμούς του NAT2 μπορεί να βρεθεί ο απλότυπος του ατόμου που εξετάζεται και συνεπώς ο φαινότυπος του. Το άτομο ανάλογα με τους πολυμορφισμούς που φέρει θα έχει φαινότυπο αργού ακετυλιωτή, ενδιάμεσου ακετυλιωτή, ή γρήγορου ακετυλιωτή. Στην παρούσα πτυχιακή εργασία εφαρμόστηκαν τεχνικές γονοτύπησης PCR-RFLP. Μελετήθηκαν 4 μονονουκλεοτιδικοί πολυμορφισμοί (SNPs) του γονιδίου NAT2: c.481C>T (rs1799929), c.590G>A (rs1799930), c.857G>A (rs1799931) και c.341T>C (rs1801280). Οι πολυμορφισμοί αυτοί εκπροσωπούν τα ανθρώπινα αλληλόμορφα NAT2*5, NAT2*6, NAT2*7 και NAT2*5 αντίστοιχα. Αλληλόμορφα NAT2 που εμφανίζουν μειωμένη ακετυλίωση (π.χ. NAT2∗5, NAT2∗6, NAT2∗7) εμφανίζονται συχνά στους πληθυσμούς αφρικανικής και καυκάσιας φυλής. Τα 113 δείγματα που μελετήθηκαν προέρχονται από τον πληθυσμό στην περιοχή της Αλεξανδρούπολης. Το NAT2*5 βρέθηκε να είναι το συχνότερο αλληλόμορφο στον υπό μελέτη πλυθυσμό, με ποσοστό εμφάνισης 82.3%. Οι αργοί ακετυλιωτές αποτελούν το μεγαλύτερο μέρος του πληθυσμού (με ποσοστό 66%), ακολουθούμενοι έπειτα από τους ενδιάμεσους ακετυλιωτές (με ποσοστό 27%) και τέλος οι γρήγοροι ακετυλιωτές (με ποσοστό 6%). Τα αποτελέσματα αυτά είναι παρόμοια με στατιστικά που έχουν αναγραφεί σε άλλους πληθυσμούς της καυκάσιας φυλής.For a drug to work, it is important to regulate the dosage in order to cure the disease and limit the side effects. Therefore it is useful to predict how a patient will respond to a prescribed drug. In humans, the NAT2 gene catalyzes the activation and deactivation of xenobiotics. Many polymorphisms in the NAT2 gene have been identified, that are associated with the metabolism of various drugs. Using the polymorphisms of the NAT2 gene, the haplotype of an individual can be found and from there also the individual’s phenotype. Depending on which polymorphisms an individual carries, that individual will either be a slow acetylator, an intermediate acetylator, or a fast acetylator. In this thesis PCR-RFLP genotyping techniques were used. Specifically 4 single nucleotide polymorphisms (SNPs) of the NAT2 gene were studied: c.481C>T (rs1799929), c.590G>A (rs1799930), c.857G>A (rs1799931) and c.341T>C (rs1801280). These polymorphisms represent the human NAT2*5, NAT2*6, NAT2*7 and NAT2*5 alleles accordingly. Alleles of the NAT2 gene that are associated with slow acetylation (for example NAT2∗5, NAT2∗6, NAT2∗7) are frequently present in African and Caucasian populations. The 113 samples which were studied come from the population in the area of Alexandroupoli. NAT2*5 was the most frequent allele in the studied population, with an appearance rate of 82.3%. Slow acetylators are the majority of the population (with a percentage of 66%), followed by intermediate acetylators (with a percentage of 27%) and last where the fast acetylators (with a percentage of 6%). These results are similar to statistics reported in other Caucasian populations.72 σ
Γονοτύπηση των πέντε συχνότερων μονονουκλεοτιδικών πολυμορφισμών (SNPs) του γονιδίου της Ν-ακετυλοτρανσφεράσης των αρυλαμινών 2 (ΝΑΤ2)
No full textΒιβλιογραφία: σ. 94-96Οι Ν-ακετυλοτρανσφεράσες των αρυλαμινών (ΝΑΤ) είναι ένζυμα που εμπλέκονται στο μεταβολισμό των φαρμάκων αρυλαμίνης και υδραζίνης και των περιβαλλοντικών και βιομηχανικών ρύπων. Στους ανθρώπους υπάρχουν δύο λειτουργικά ένζυμα ΝΑΤ (ΝΑΤ1 και ΝΑΤ2). Τα δύο ένζυμα είναι ιδιαίτερα πολυμορφικά, αλλά το ΝΑΤ2 σχετίζεται με τον κλασικό φαινότυπο ακετυλίωσης (γρήγοροι, ενδιάμεσοι και αργοί ακετυλιωτές) και κατέχει σημαντικό ρόλο στα πεδία της φαρμακογενετικής και της χημικής καρκινογένεσης. Ο σκοπός της παρούσας έρευνας ήταν ο προσδιορισμός της συχνότητας των πολυμορφισμών του ΝΑΤ2 σε έναν πληθυσμό από την περιοχή της Αλεξανδρούπολης και η πρόβλεψη των αντίστοιχων φαινοτύπων ακετυλίωσης. Η στρατηγική της γονοτύπησης περιλάμβανε πέντε μονονουκλεοτιδικούς πολυμορφισμούς (SNPs), συγκεκριμένα τους c.191G>A (rs1801279), c.341T>C (rs1801280), c.481C>T (rs1799929), c.590G>A (rs1799930) και c.857G>A (rs1799931). Όλοι τους εδράζονται στην κωδική περιοχή και η γονοτύπηση αυτών βασίστηκε σε ανάλυση PCR-RFLP. Γενωμικό DNA απομονώθηκε από δείγματα αίματος από 62 ανώνυμα άτομα Πραγματοποιήθηκαν τρείς αντιδράσεις PCR για τον πολλαπλασιασμό προϊόντων DNA μεγέθους 999bp, 510bp και 360bp. Το προϊόν μεγέθους 999bp χρησιμοποιήθηκε περαιτέρω για τον προσδιορισμό των c.481C>T, c.590G>A και c.857G>A, με τη χρήση των περιοριστικών ενδονουκλεασών KpnI, TaqI και BamHI αντίστοιχα. Για να προσδιοριστεί η ύπαρξη του c.191G>A, έγιναν πέψεις με το ένζυμο HapII του προϊόντος μεγέθους 510bp. Για τον πολλαπλασιασμό του προϊόντος μεγέθους 360bp, χρησιμοποιήθηκε ένας μεταλλαξιγόνος εκκινητής που δημιουργούσε μία νέα θέση κοπής για το ένζυμο NcoI, με σκοπό την ταυτοποίηση του πολυμορφισμού c.341T>C. Τα κομμάτια των πέψεων διαχωρίστηκαν σε πήκτωμα αγαρόζης γενικής χρήσης, ή σε πήκτωμα αγαρόζης υψηλής ευκρίνειας, ή σε πήκτωμα πολυακρυλαμίδης, ανάλογα με τις ανάγκες. Οι c.341T>C, c.481C>T και c.590G>A ήταν συχνοί πολυμορφισμοί, ο c.857G>A ήταν σπάνιος και ο c.191G>A δεν βρέθηκε. Τα αποτελέσματα υποδεικνύουν ότι η πλειοψηφία των ατόμων στον υπό μελέτη πληθυσμό προβλέπονται ως αργοί ακετυλιωτές (61%), ακολουθούμενοι από τους ενδιάμεσους ακετυλιωτές (36%) και μόνο το 3% προβλέπονται ως γρήγοροι ακετυλιωτές. Η κατανομή αυτή είναι παρόμοια με αυτές που έχουν καταγραφεί σε άλλους καυκάσιους πληθυσμούς.Arylamine N-acetyltransferases (NATs) are enzymes involved in the metabolism of arylamine and hydrazine compounds which include drugs, as well as environmental and industrial pollutants. In humans, there are two functional NAT enzymes (NAT1 and NAT2). Both genes are highly polymorphic, but NAT2 is associated with the classic acetylation phenotype (rapid, intermediate and slow acetylators) and it plays an important role in pharmacogenetics and chemical carcinogenesis. The aim of the current study was to determine the frequency of the polymorphisms of NAT2 in a population from the Alexandroupolis area and to suggest the expected acetylator phenotype. The genotyping strategy included five single nucleotide polymorphisms (SNPs), namely c.191G>A (rs1801279), c.341T>C (rs1801280), c.481C>T (rs1799929), c.590G>A (rs1799930) and c.857G>A (rs1799931), all located in the coding region. The genotyping approach was based on PCR–RFLP analysis. Genomic DNA was isolated from blood samples from 62 anonymous individuals. Three PCRs were performed to amplify 999bp, 510bp and 360bp DNA products. The 999bp product was further used to determine the presence of c.481C>T, c.590G>A and c.857G>A using the restriction endonucleases KpnI, TaqI and BamHI respectively. The 510bp product was digested with HapII to determine the presence of c.191G>A. For the amplification of the 360bp product, a mutagenesis primer was used to generate a new NcoI site in order to identify c.341T>C. Digests were separated by electrophoresis either on general purpose agarose, or high resolution agarose, or polyacrylamide gels, depending on fragment sizes and required resolution. According to our results, the c.341T>C, c.481C>T and c.590G>A were common polymorphisms, while c.857G>A was rare and c.191G>A was not found. These results indicated that the majority of individuals in this population are predicted to be slow acetylators (61%), followed by intermediate acetylators (36%) and only 3% rapid acetylators. This distribution is similar to that reported for other Caucasian populations.96 σ
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