118,162 research outputs found
Nanostructure-Based Fluorescent Biosensors
No full textNanostructure-Based Fluorescent Biosensors
Shivaram K. a, Gunnella R. a, Giuliodori A. M.b, Spurio R.b, Fabbretti A. b, Perrozzi F.c
Ottaviano L.c
aSchool of Science and Technology, Physics Division, University of Camerino, Via Madonna delle Carceri 9, 62032 Camerino; e-mail: [email protected]
bSchool of Biosciences and Veterinary Medicine, Biology Division, University of Camerino, Via Gentile III da Varano, 62032 Camerino
cDipartimento di Scienze Fisiche e Chimiche, Universita' dell'Aquila Via Vetoio, 67100 L'Aquila
We have investigated a fluorescent biosensor based on graphene oxide (GO) for the measurement of interaction between a fluorophore FAM (Carboxyfluorescein)-labeled single-stranded DNA with its complementary single-stranded DNA oligonucleotide (target). The graphene oxide adsorbs the FAM-labeled single stranded DNA (probe) and quenches its fluorescence. Upon addition of the complementary single stranded DNA oligonucleotide, the probe hybridizes to its target [1] thus producing a double- stranded DNA, which detaches from the GO. The release of the double helix leads to the recovery of dye fluorescence that can be monitored by fluorimetric techniques. Pristine GO [2,3] flakes were prepared using a modified Hummers method and dispersed in water with a concentration of 0.5 mg/mL. The samples were prepared by drop casting, the GO and DNA with buffered solution [1] on 300 nm SiO2 /Si(100) at room temperature. AFM image of the GO flakes,) shows the typical AFM image of the DNA-GO complex, where the bright areas on the GO surface might be due to the adsorption of DNA. In this complex the thickness is about 3 nm.This observation indicates that GO can strongly adsorb ssDNA and can efficiently quench its fluorescence. The fluorescently labeled ssDNA-GO complex displayed significant fluorescence enhancement upon addition of complementary target DNA oligonucleotide (Figure 1b). This recovery of fluorescence increases with increasing concentration of the target DNA added to the mixture.
References
1. Lu, C.-H., Angew. Chem. Int. Ed. 48: 4785–4787 (2009). doi: 10.1002/anie.200901479.
2. Nan-Fu Chiu et al. M. Aliofkhazraei (Ed.), ISBN: 978-953-51-1182-5, InTech (2013). DOI: 10.5772/56221.
3. F. Perrozzi et al., J. Phys.: Condens. Matter 27, 013002 (2015) doi:10.1088/0953-8984/27/1/013002 Graphene oxide: from fundamentals to applications
Measurement of the Inclusive Cross Section \sigma(pp\rightarrow b\bar{b}X\rightarrow \mu\mu \mbox{X}^\prime) at TeV with the CMS Experiment at the LHC
No full textBeauty quarks are produced with a large cross section at a previously unreached center-of-mass energy at the Large Hadron Collider (LHC), enabling precision measurements to improve our understanding of heavy flavor physics.
This thesis presents the measurement of the inclusive cross section .
Di-muon events are selected in the pseudo-rapidity range
GeV or \pt>6 GeV. The amount of signal events is determined with a fit to the di-muon transverse impact parameter distribution.
The analysis is applied to data recorded by the CMS detector during proton-proton collisions at TeV centre-of-mass energies in the second half of year 2010, corresponding to an integrated luminosity of pb.
The -quark production cross section is determined and compared to leading-order and next-to-leading-order QCD predictions.Nel collisore adronico LHC i quark beauty sono prodotti
con un'elevata sezione d'urto ad una energia nel centro di massa mai raggiunta finora, consentendo misure di precisione in grado di migliorare la nostra comprensione della fisica del sapore.
Il presente lavoro di tesi riporta uno studio della misura della
produzione inclusiva dei quark tramite il processo .
Eventi di di-muoni sono selezionati nell'intervallo di pseudo-rapidità GeV or \pt>6 GeV. La frazione di eventi di segnale è determinata mediante un'interpolazione della distribuzione di parametro d'impatto trasverso. L'analisi e' applicata ai dati raccolti dal rivelatore CMS durante la fase di presa dati di collisioni ad energia di TeV nel centro di massa, avvenuta nella seconda metà del 2010, corrispondenti ad una luminosità integrata di pb.
La sezione d'urto di produzione dei -quark è misurata e confrontata cno le predizioni QCD al {\it leading-order} e
{\it next-to-leading-order}
XPS study of graphene oxide reduction induced by (100) and (111)-oriented Si substrates
No full textThe reduction of graphene oxide (GO) has been extensively studied in literature in order to let GO partially recover the properties of graphene. Most of the techniques proposed to reduce GO are based on high temperature annealing or chemical reduction. A new procedure, based on the direct reduction of GO by etched Si substrate, was recently proposed in literature. In the present work, we accurately investigated the Si-GO interaction with x-ray photoelectron spectroscopy. In order to avoid external substrate oxidation factors we used EtOH as the GO solvent instead of water, and thermal annealing was carried out in UHV. We investigated the effect of Si(100), Si(111) and Au substrates on GO, to probe the role played by both the substrate composition and substrate orientation during the reduction process. A similar degree of GO reduction was observed for all samples but only after thermal annealing, ruling out the direct reduction effect of the substrate
Tunable sulfur desorption in exfoliated MoS2 by means of thermal annealing in ultra-high vacuum
No full textThe effects of thermal annealing in ultra-high vacuum on the electronic structures of bulk and liquid exfoliated MoS2 have been studied by core level and valence band X-ray photoemission spectroscopy. A quantitative analysis of core level spectra demonstrates, in the case of exfoliated MoS2, that, upon annealing above 200 C, defect formation occurs in the form of sulfur single and double vacancies. Sulfur vacancies introduce surface states in the band gap (determined by the analysis of the valence band spectra). This determines a rigid shift of the core levels to lower binding energies, as a consequence of an upward band bending
Exfoliated black phosphorus gas sensing properties at room temperature
No full textRoom temperature gas sensing properties of chemically exfoliated black phosphorus (BP) to oxidizing (NO2, CO2) and reducing (NH3, H-2, CO) gases in a dry air carrier have been reported. To study the gas sensing properties of BP, chemically exfoliated BP flakes have been drop casted on Si3N4 substrates provided with Pt comb-type interdigitated electrodes in N2 atmosphere. Scanning electron microscopy and x-ray photoelectron spectroscopy characterizations show respectively the occurrence of a mixed structure, composed of BP coarse aggregates dispersed on BP exfoliated few layer flakes bridging the electrodes, and a clear 2p doublet belonging to BP, which excludes the occurrence of surface oxidation. Room temperature electrical tests in dry air show a p-type response of multilayer BP with measured detection limits of 20 ppb and 10 ppm to NO2 and NH3 respectively. No response to CO and CO2 has been detected, while a slight but steady sensitivity to H-2 has been recorded. The reported results confirm, on an experimental basis, what was previously theoretically predicted, demonstrating the promising sensing properties of exfoliated BP
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
In situ syntheses of hydroxyapatite-grafted graphene oxide composites
No full textIn this study, we examined three different syntheses of hydroxyapatite (HAp) and graphene oxide-hydroxyapatite (GO-HAp) composites with a GO content of 9, 33, and 43% wt. The materials were prepared from various precursors of calcium and phosphate ions, using an in situ synthesis method, with mild conditions to avoid reducing the GO. In situ bonding technology proposed that calcium ions bond with GO at first and then HAp nanoflakes in situ grow on GO sheets, forming GO-HAp nanocomposite. The aim of the present work was to analyze the differences due to the use of different starting reagents and verify, with the addition of increasing amounts of GO, the changes in morphology, crystallinity, and solubility of the obtained HAp composites. Detailed structural and morphological characterization studies of the composites were carried out using scanning electron microscopy, energy dispersive X-ray spectrometry, X-ray powder diffraction, Raman spectroscopy, and Fourier transform infrared spectroscopy. We found that GO sheets act as a nucleation site for HAp mineralization, but we observed a loss of the crystallographic order due to the intercalation of the graphenic sheets between the HAp particles
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
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