Astronomical Optical Interferometry. I. Methods and Instrumentation

Previous decade has seen an achievement of large interferometricprojects including 8-10m telescopes and 100m class baselines. Modern computerand control technology has enabled the interferometric combination of lightfrom separate telescopes also in the visible and infrared regimes. Imagingwith milli-arcsecond (mas) resolution and astrometry with micro-arcsecond($mu$as) precision have thus become reality. Here, I review the methods andinstrumentation corresponding to the current state in the field ofastronomical optical interferometry. First, this review summarizes thedevelopment from the pioneering works of Fizeau and Michelson. Next, thefundamental observables are described, followed by the discussion of the basicdesign principles of modern interferometers. The basic interferometrictechniques such as speckle and aperture masking interferometry, aperture synthesisand nulling interferometry are disscused as well. Using the experience ofpast and existing facilities to illustrate important points, I considerparticularly the new generation of large interferometers that has beenrecently commissioned (most notably, the CHARA, Keck, VLT and LBTInterferometers). Finally, I discuss the longer-term future of opticalinterferometry, including the possibilities of new large-scale ground-based projects and prospects for space interferometry

Astronomical optical interferometry, II: Astrophysical results

Optical interferometry is entering a new age with several ground- based long-baseline observatories now making observations of unprecedented spatial resolution. Based on a great leap forward in the quality and quantity of interferometric data, the astrophysical applications are not limited anymore to classical subjects, such as determination of fundamental properties of stars; namely, their effective temperatures, radii, luminosities and masses, but the present rapid development in this field allowed to move to a situation where optical interferometry is a general tool in studies of many astrophysical phenomena. Particularly, the advent of long-baseline interferometers making use of very large pupils has opened the way to faint objects science and first results on extragalactic objects have made it a reality. The first decade of XXI century is also remarkable for aperture synthesis in the visual and near-infrared wavelength regimes, which provided image reconstructions from stellar surfaces to Active Galactic Nuclei. Here I review the numerous astrophysical results obtained up to date, except for binary and multiple stars milliarcsecond astrometry, which should be a subject of an independent detailed review, taking into account its importance and expected results at microarcsecond precision level. To the results obtained with currently available interferometers, I associate the adopted instrumental settings in order to provide a guide for potential users concerning the appropriate instruments which can be used to obtain the desired astrophysical information

Wavefront outer scale deduced from interferometric dispersed fringes

Astronomy and Astrophysics, v. 448, p. 1225-1234, 2006. http://dx.doi.org/10.1051/0004-6361:20052806International audienc

Allergenic potency of kiwi fruit during fruit development

Food allergies, including kiwi fruit allergy, have been the subject of extensive research in the last few years. The aim of this study was to examine a possible relationship between the developmental stage of kiwi fruit and its allergenic potency. The protein and allergen patterns of kiwi fruit extracts in September, October, November and December fruit in the period from 2000-2002 were analysed. One of the factors that may contribute to the difficulties in proposing well-defined and standardized fruit extracts should also be the time of fruit harvesting. In this particular case, when the kiwi fruit was edible throughout November and December, we showed discrepancies in allergen content and potencies both in qualitative and quantitative terms. Two major allergens of kiwi fruit, Act c 1 and Act c 2, mainly accounted for the highest allergenic potential of November kiwi extract in vivo and in vitro. Not only the content of major allergens, but also the ratio of different proteins and even isoforms of the same allergen (Act c 2) change with fruit ripening. These findings should be taken into account during preparation of extracts for allergy diagnosis

Parcijalna karakterizacija antibakterijskog peptida koji proizvodi probiotska bakterija Lactobacillus plantarum G2

The aim of this study was the partial characterization of the antimicrobial peptide bacteriocin G, produced by probiotic bacteria Lactobacillus plantarum G(2), which was isolated from a clinical sample of a healthy person. Antimicrobial substance was secreted in the supernatant of an L. plantarum G(2) culture, and showed a diverse spectrum of antimicrobial activity of all the tested strains of the genera Lactobacillus and the pathogenic bacteria Staphylococcus aureus and Salmonella abony. Isoclectric focusing revealed that bacteriocin G(2) is a cationic peptide (pI about 10) with a molecular mass of 2.2 kDa according to tricine sodium dodecyl sulphate polyacrylamide gel electrophoresis, SDS-PAGE. The antimicrobial activity of bactcriocin G(2) was diminished by the proteolytic action of trypsin and proteinase K. Bacteriocin G(2) preserved its biological activity in the temperature range 40-60 degrees C (15 min), which was lost at 80 degrees C. Bacteriocin G(2) was stable in the pH range 2-9, while treatment with 1 % Tween 80 and 1 % urea resulted in increased antimicrobial activity. The probiotic strain L. plantarum G(2) produces the antimicrobial substance proteinaceous in nature with bacteriocin characteristics. Bacteriocin production is one of the key properties of probiotic bacteria with clinical potential as anti-infective agents, which will increase the likelihood of its in vivo efficacy.Cilj ovog istraživanja je bila parcijalna karakterizacija antimikrobnog peptida iz probiotske bakterija Lactobacillus plantarum G2 izolovane iz kliničkog uzorka zdrave osobe. Antimikrobno jedinjenje iz L. plantarum G2, označeno kao bakteriocin G2, dobijeno iz supernatanta bakterijske kulture, pokazalo je širok spektar antimikrobne aktivnosti, inhibirajići rast svih ispitivanh vrsta roda Lactobacillus, kao i patogenih bakterija Staphylococcus aureus i Salmonella abony. Bakteriocin G2 je osetljiv na proteolitičko dejstvo tripsina i proteinaze K. Antimikrobna aktivnost je stabilna u opsegu 40-60°C (15 min), ali se gubi na temperaturi od 80°C. Ustanovljeno je da je bakteriocin stabilan na pH vrednostima između 2 i 9. Dejstvo Tween-a 80 i uree je dovelo do povećane inhibitorne aktivnosti. Prema IEF, bakteriocin G2 je katjonski protein, sa pI vrednošću oko 10, a molekulaska masa određena na osnovu tricin-SDS-PAGE je 2,2 kDa. Probiotski soj L plantarum G2 produkuje antimikrobno jedinjenje proteinske strukture sa karakteristikama bakteriocina. Sinteza bakteriocina je jedna od ključnih osobina probiotskih bakterija koje imaju klinički potencijal kao antiinfektivni agensi, jer značajno povećava verovatnoću njihove in vivo efikasnosti

First VLTI/MIDI observations of a Be star: Alpha Ara

We present the first VLTI/MIDI observations of the Be star Alpha Ara, showing a nearly unresolved circumstellar disk in the N band. The interferometric measurements made use of the UT1 and UT3 telescopes. The projected baselines were 102 and 74 meters with position angles of 7 degres and 55 degres, respectively. These measurements put an upper limit to the envelope size in the N band under the Uniform disk approximation of $\phi_{\rm max}= 4\pm1.5$ mas, corresponding to 14 $R_{\star}$, assuming $R_{\star}$=4.8${\rm R}_\odot$ and the Hipparcos distance of 74pc. On the other hand the disk density must be large enough to produce the observed strong Balmer line emission. In order to estimate the possible circumstellar and stellar parameters we have used the SIMECA code developed by Stee (1995) and Stee & Bittar (2001). Optical spectra taken with the echelle instrument Heros and the ESO-50cm telescope, as well as infrared ones from the 1.6m Brazilian telescope have been used together with the MIDI spectra and visibilities. These observations put complementary constraints on the density and geometry of Alpha Ara circumstellar disk. We discuss on the potential truncation of the disk by a companion and we present spectroscopic indications of a periodic perturbation of some Balmer lines.Comment: Accepted in A&

Green analytical approach for extraction and chemical profiling of phenolic compounds from natural products: A case study of Teucrium chamaedrys L.

One of the main principles of green analytical chemistry is to eliminate or reduce the use of organic solvents and reagents, and therefore use of Natural Deep Eutectic Solvents (NADES) as medium in sample extraction was recognized as green alternative to conventional one. In this paper, 19 different natural deep eutectic solvents were used for the extraction of phenolic compounds from Teucrium chamaedrys L. Chemical profiles of the extracts were obtained by applying high-performance thin-layer chromatography (HPTLC), which is a green technique due to the simultaneous analysis of a large number of samples, using small amounts of extracts and minimal amounts of solvents. Greenness of proposed methodology was estimated by NEMI pictogram and analytical eco-scale.Jedan od glavnih ciljeva zelene analitičke hemije je eliminisanje ili smanjenje upotrebe organskih rastvarača i reagenasa i zbog toga je primena prirodnih eutektičkih smeša (NADES - natural deep eutectic solvents) kao medijuma za ekstrakciju uzoraka prepoznata kao zelena alternativa. U ovom radu je primenjeno 19 različitih prirodnih eutektičkih smeša za ekstrakciju fenolnih jedinjenja iz biljke podubice. Za hemijsko profilisanje ekstrakata korišćena je visoko-efikasna tankoslojna hromatografija (HPTLC – High-performance thin-layer chromatography) koja predstavlja zelenu tehniku zbog istovremene analize velikog broja uzoraka, uz upotrebu male količine ekstrakata i minimalnih količina rastvarača. Ekološka prihvatljivost predložene metodologije procenjena je primenom Nacionalnog indeksa uticaja metode na životnu sredinu i eko-skale

A new concept for the combination of optical interferometers and high-resolution spectrographs

The combination of high spatial and spectral resolution in optical astronomy enables new observational approaches to many open problems in stellar and circumstellar astrophysics. However, constructing a high-resolution spectrograph for an interferometer is a costly and time-intensive undertaking. Our aim is to show that, by coupling existing high-resolution spectrographs to existing interferometers, one could observe in the domain of high spectral and spatial resolution, and avoid the construction of a new complex and expensive instrument. We investigate in this article the different challenges which arise from combining an interferometer with a high-resolution spectrograph. The requirements for the different sub-systems are determined, with special attention given to the problems of fringe tracking and dispersion. A concept study for the combination of the VLTI (Very Large Telescope Interferometer) with UVES (UV-Visual Echelle Spectrograph) is carried out, and several other specific instrument pairings are discussed. We show that the proposed combination of an interferometer with a high-resolution spectrograph is indeed feasible with current technology, for a fraction of the cost of building a whole new spectrograph. The impact on the existing instruments and their ongoing programs would be minimal.Comment: 27 pages, 9 figures, Experimental Astronomy; v2: accepted versio