117,879 research outputs found
New peptide nucleic acids for biotechnological applications
No full textIn the present study was designed and realized a new similar to the PNA. It is a chiral nucleo-γ-peptide, dabPNA, isomer of the aegPNA unit and characterized by a 2,4-diaminobutyric acid (DABA)-based backbone carrying the carboxymethylated nucleobase on its α amino group.
Differently from aegPNA monomers, dabPNA presents a shorter backbone (3C between the nitrogen atom and the carbonyl) and an enhanced distance between the nucleobase and the backbone, i.e. 3 atoms (1N+2C) instead of 2C in aegPNAs. Furthermore, in comparison with ornPNA that binds to RNA forming a stable triplex, daba-based PNA has a methylene group less in the backbone.
To achieve dabPNA oligomers, the new monomers tL-dab, tD-dab, aL-dab and aD-dab were synthesized in good yield using suitable protected building blocks and characterized by NMR and ESI-MS techniques.
Initially, the homothymine oligomers (tL-dab)12 and (tD-dab)6 were synthesized, using a synthetic strategy that ensured the maintenance of chirality during the coupling steps, and tested for hybridization towards natural nucleic acids. No binding evidence with both DNA (dA12) and RNA (A12) was revealed by CD and UV experiments. Furthermore, the insertion of a single tL-dab unit in the middle or at N-terminus of a homothymine aegPNA chain leads to a decreased binding efficiency to the target DNA in comparison to full aegPNA.Since dabPNAs based on L- and D-DABA don’t bind natural nucleic acids, we explored the possibility that complementary nucleopeptides based on D or L-DABA could bind between themselves. This property would be interesting in order to develop novel DABA-based dendrimeric systems, as new materials, and also to realize new diagnostic tools, as for example new molecular beacon probe. To verify this interesting possibility, the monomers aL-dab and aD-dab were oligomerized to the homoadenine hexamers (aL-dab)6 and (aD,L-dab)6. In order to find the correct combination of chirality suitable for obtaining the binding, also the (tD,L-dab)6 oligomer were realized to perform the hybridization studies. From CD and UV experiments, binding evidence was revealed in the case of the complementary oligomers with alternate chirality, (aD,L-dab)6 and (tD,L-dab)6, even if the stability of the complex formed was not so high (Tm 11°C).
Furthermore, some interesting properties relative to the self-complementary oligomer (aL−dab-tD−dab)3 emerged from preliminary DLS experiments that evidenced the formation of multimeric aggregates for this system.
These results, together with the high serum stability of the DABA-based oligomers, suggest further studies on dabPNAs as new self-recognizing bio-inspired polymers, with the potentiality to develop new nanomaterials or new biotechnological tools in bioengineering and biomedical applications
The syntax of Moroccan Arabic/French and Moroccan Arabic/Standard Arabic code switching.
No full textContact between different speech communities represents one breeding ground for change and accommodation which can affect the forms as well as the functions of language. Code switching (CS), as one result of this contact situation, is an important site to display the dominance of one language over another, or to witness the resolve of a speech community to incorporate another language so as to satisfy their needs, be them syntactic, lexical or pragmatic. The aim of this thesis is to trace down the formal manifestations of this type of language negotiation whereby switching occurs between two or more languages. It will be shown that, in a CS situation, collision of languages is highly regularised by specific syntactic features. A number of different models to CS structural constraints are considered, and one particular approach based on the analysis of selectional properties of the functional heads is advocated; this I will call the Functional Parameter Constraint (FPC). The underlying assumption of the FPC, which owes it theoretical motivation to recent syntactic research (e. g. Abney 1986, Ouhalla 1991, Chomsky 1995), is that interlanguage parameters, as opposed to language universals, constrain CS. Parameters are restricted to the features of functional categories given that their lexical counterparts are conceptually selected entries which are drawn from an invariant universal vocabulary, and therefore, are not to be parameterised (Chomsky 1995). Following Ouhalla (1991), three selectional properties for which functional categories can be parameterised cross-linguistically are identified, namely c-selection, m-selection and grammatical features. A corpus consisting of naturally occurring data was gathered to test the empirical validity of the hypothesis set for the study. The results of the examination of Moroccan Arabic/French and Moroccan/Standard Arabic bilingual conversations provide the sought empirical support
Le Zaïre : de la république à l'Etat du citoyen / Daba E. L. Misamu
No full textContient une table des matièresAvec mode text
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Missione Archeologica Italiana a Daba al Bayah (Sultanato dell’Oman)
No full textIl sito di Daba consiste in un complesso funerario di grande importanza costituito da numerose tombe collettive di grandi dimensioni, contenenti centinaia di individui e migliaia oggetti di valore. Daba si trova sulla costa orientale della penisola di Musandam (Oman) ed è circondata da diversi siti dell'età del ferro tra cui insediamenti e complessi funerari di grande importanza come Tel Abrak, Masafi e Hili per gli insediamenti, Jebel Buhais, Shimal e Asimah per il complesso funerario.
Il sito archeologico è attualmente composto da due tombe a camera lunga, una tomba partica successiva e diverse fosse come offerta rituale. Tutta l'area era un tributo monumentale all'alleanza tribale risalente alla fine del II millennio a.C. Il primo monumento funerario ha una forma rettangolare, con una lunghezza di 14,75 m e una larghezza di 3,50 m con una superficie totale di 49 mq. All'interno della grande tomba sono stati rinvenuti resti umani riferibili a 188 individui e quasi duemila oggetti preziosi tra cui vasi in bronzo e steatite, pugnali, bracciali, punte di frecce e medaglioni.
La presenza di fosse rituali con centinaia d'oggetti di valore deposti all'interno rivela che l'area era considerata uno spazio sacro, in considerazione dell'esistenza delle grandi tombe collettive. La seconda tomba collettiva è più grande della prima ed è composta da lastre, pietre arrotondate e mattoni di fango, spesso rinforzati con intonaco e argilla bruciata. Migliaia di oggetti sono stati recuperati durante l'esplorazione della tomba, spesso associati a resti umani riferibili a centinaia di individui. Oltre alla tomba collettiva sono state identificate molte sepolture singole e altri edifici assemblati con mattoni di argilla.
La tomba produceva un'alta quantità di materiale tra cui vasellame, vasi di softstone, punte di freccia in bronzo, elementi di gioielli e perline di vario tipo. Questo materiale include elementi di date diverse, dalla tarda età del bronzo (1600-1350 a.C) fino alla tarda età del ferro (300 a.C.) a testimonianza di un lungo periodo di utilizzo.
Daba è un sito di fondamentale importanza per la conoscenza delle società tribali dell'età del ferro di tutta la penisola arabica e l'area, in base alle numerose testimonianze individuate, assume un ruolo di grande importanza per la comprensione del rituale funerario
Square Dancing with the Stars to Enhance Dynamic Hirschman Linkages?
No full textIn this Presidential Address, the author takes the reader on a reconnaissance of his life and time as a regional scientist. He points out scenery he found scintillating along the way, hoping that some may pick up the banner and chew on a few of the ideas for a while. He suggests a revisit to Albert O. Hirschman’s notion of key sectors and more empirical analysis related to Marcus Berliant’s and Masahisa Fujita’s notion of knowledge creation and transfer.Presidential Address, San Antonio, Texas, March 29, 2014 (53rd Meetings of the Southern Regional Science Association
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Selenium source in the selenosis area of the Daba region, South Qinling Mountain, China
No full textNaore Village in the Shuang'an countryside, Ziyang County, Shaanxi Province is located in the Daba region of South Qinling Mountain. It is one of two selenosis or selenium poisoning areas in China. Crops grown in the area are enriched in selenium. The soil is derived from high-selenium, pyritic, black carbonaceous slate and volcanic tuff of the Lujiaping Formation, Early Cambrian and Late Neoproterozoic in age, which is exposed in this area. The Lujiaping Formation is more than 40-m thick. Selenium content of the volcanic tuff averages 32 mg/kg Se and the black carbonaceous slate averages 22 mg/kg Se, which represent the highest concentrations recorded among all the strata and rocks sampled in the Daba region of South Qinling Mountain. This series of selenium-enriched rocks is also found in other places in the Daba region, South Qinling Mountain, where the soil contains about 10 to 30 mg/kg Se. These zones are latent selenosis zones in the Daba region. In addition, a selenium-enriched black carbonaceous shale, of Early Cambrian age, and containing 10 to 40 mg/kg Se, occurs in several other provinces in the south of China
Letter from unknown writer to Jesse L. Boyce
No full textLetter to Jesse L. Boyce from unknown author (possibly Jack) about the investigation into the powder magazine located in the Grand Canyon. Some personal news is included in the letter such as the writer's marriage to the daughter of C.A. Taylor, former Supervisor of Cochise County
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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