Optimal slit orientation for long multi-object spectroscopic exposures

Historically, long-slit spectroscopic observations were carried out using the parallactic angle for the slit orientation if slit loss was an important consideration (either to maximize the signal-to-noise or to do spectrophotometry). This requires periodic realignment of the slit position angle as the parallactic angle changes. This is not possible for multi-slit observations where one slit position angle must be chosen for the entire exposure. Common wisdom suggests using the parallactic angle at the meridian (HA=0). In this paper, I examine what the best strategy is for long, multi-slit exposures. I find that in extreme cases (very long exposure time) the best choice is to orient the slit \emph{perpendicular} to the parallactic angle at the meridian. There are two effects to consider: the increasing dispersion with increasing airmass and the changing angle between the parallactic angle and the slit. In the case of \emph{traditional} slit orientation, the two effects amplify each other, thus rendering a significant fraction of the observation useless. Using the perpendicular orientation, the two processes work against each other, thus most of the observation remains useful. I will use, as an example, our 8 hour Lockman Hole observations using the Keck telescope, but generic methods are given to evaluate a particular observation. I also make the tools available to the community.Comment: Accepted by A&A (20/06/2005

Az élethosszig tartó tanulás kihívásai: középpontban a tanuló szervezet

Margaret Mead 1960 körül a kultúrák válfajait úgy különböztette meg, hogy van „a posztfiguratív kultúra, amelyben a gyerekek elsősorban elődeiktől tanulnak, a konfiguratív kultúra, amelyben mind a gyerekek, mind a felnőttek a velük egykorúaktól és egyenrangúaktól tanulnak és a prefiguratív kultúra, amelyben a felnőttek gyerekeiktől is tanulnak …” (Nyíri, 2009

Simultaneous Multicolor Detection of Faint Galaxies in the Hubble Deep Field

We present a novel way to detect objects when multiband images are available. Typically, object detection is performed in one of the available bands or on a somewhat arbitrarily co-added image. Our technique provides an almost optimal way to use all the color information available. We build up a composite image of the N passbands where each pixel value corresponds to the probability that the given pixel is just sky. By knowing the probability distribution of sky pixels (a chi-square distribution with N degrees of freedom), the data can be used to derive the distribution of pixels dominated by object flux. From the two distributions an optimal segmentation threshold can be determined. Clipping the probability image at this threshold yields a mask, where pixels unlikely to be sky are tagged. After using a standard connected-pixel criterion, the regions of this mask define the detected objects. Applying this technique to the Hubble Deep Field data, we find that we can extend the detection limit of the data below that possible using linearly co-added images. We also discuss possible ways of enhancing object detection probabilities for certain well defined classes of objects by using various optimized linear combinations of the pixel fluxes (optimal subspace filtering).Comment: 8 pages, 5 figures (4 postscript, 1 JPEG). To be published in A

Correcting second-order contamination in low-resolution spectra

An empirical method for correcting low-resolution astronomical spectra for second-order contamination is presented. The method was developed for correcting spectra obtained with grism #4 of the ALFOSC spectrograph at the Nordic Optical Telescope and the performance is demonstrated on spectra of two nearby bright Type Ia supernovae.Comment: accepted for publication in Astronomical Notes (Astronomische Nachrichten

Calibration update of the COMBO-17 CDFS catalogue

We present an update to the photometric calibration of the COMBO-17 catalogue on the Extended Chandra Deep Field South, which is now consistent with the GaBoDS and MUSYC catalogues. As a result, photometric redshifts become slightly more accurate, with <0.01 rms and little bias in the delta_z/(1+z) of galaxies with R<21 and of QSOs with R<24. With increasing photon noise the rms of galaxies reaches 0.02 for R<23 and 0.035 at R~23.5. Consequences for the rest-frame colours of galaxies at z<1 are discussed.Comment: A&A research note, resubmitted 02 Oct 2008, 4 pages in print forma

A nemi különbségek és az életkor hatása az immunreaktivitásra a szervezetet ért sérülések után = Effect of age and the sexual differences on the immuno-reactivity following injury

A nemi különbségek és az életkor hatása az immunreaktivitásra a szervezetet ért sérülések után. A kutatásokban a vázizom iszkémia-reperfúzió hatását vizsgáltuk az immunsejtek funkcióváltozásaira és az oxidatív stressz paramétereire mind humán, mind állatkíséreltekben. Fontosabb kutatási eredmények: Az állatkísérletekben az egyes kísérleti csoportok között nem volt különbség a granulocyta funkciókat illetően sem az életkor sem pedig a nem tekintetében. A lipid peroxidáció mértéke nőstény állatokban fokozottabb volt, ugyanakkor az antioxidáns kapacitás is nagyobb volt a reperfúzió során. Az iszkémiás prekondícionálás nemtől és kortól függetlenül fokozta a plazma antioxidáns kapacitását a reperfúzió kezdetén és 24 óra után is. A humán mérésekben a granulocyta-thrombocyta komplexek száma csökken a reperfúzió kezdetén és függ az iszkémia időtartamától, ugyanakkor a thrombocyta aggregáció nem változott. Az oxidatív stressz paramétere nem változott a reperfúzió során, ugyanakkor az antioxidáns kapacitás a plazmában csökkent. Következtetések: A speciálisan kezelt (kasztrált, hormonkezelt) állatoknál lehet nemtől függő különbség a gyulladásos válaszban, de ezt a normál populáción végzett mérések nem igazolták. A humán mérések megerősítették az oxidatív stressz fontos szerepét az izom reperfúziós károsodásával járó állapotokban, bár ezt a védekező mechanizmusok kompenzálni képesek. | Role of age and gender differences on the immunoreactivity after injuries of the body. Effect of ischemia-reperfusion of the skeletal muscle on the immune cell functions and on the oxidative stress was investigated in animal and human studies. Main results: In the animal studies there were no major differences among the different experimental groups concerning gender and age differences. The extent of lipid peroxidation was higher in female animals, however, antioxidant capacity was also higher during reperfusion. Ischemic preconditioning increased plasma antioxidant capacity at early reperfusion and 24 hours later. In human studies the number of granulocyte-thrombocyte complexes decreased during early reperfusion and they were indirectly proportional with the duration of ischemia. Aggregation of thrombocytes did not change. Parameters of oxidative stress did not change during reperfusion and but antioxidant capacity decreased in plasma. No gender differences were seen in these parameters. Conclusions: In specially composed experimental conditions (castration, hormone treatment) there might be differences in various biological parameters, however, our studies carried out on normal populations, do not support this theory. Our human studies support the role of oxidative stress in muscle reperfusion injury, however, antioxidant mechanisms can compensate these changes

Az élethosszig tartó tanulás kihívásai: középpontban a tanuló szervezet

Margaret Mead 1960 körül a kultúrák válfajait úgy különböztette meg, hogy van „a posztfiguratív kultúra, amelyben a gyerekek elsősorban elődeiktől tanulnak, a konfiguratív kultúra, amelyben mind a gyerekek, mind a felnőttek a velük egykorúaktól és egyenrangúaktól tanulnak és a prefiguratív kultúra, amelyben a felnőttek gyerekeiktől is tanulnak …” (Nyíri, 2009

Modern wound treatment with devices working according to various physical principles

The prevalence of venous diseases in Europe is 25.2%. According to studies of the University of Bonn this number can be as high as 90%. Optimistic estimates suggest this number to be 27.5% in Hungary, 21.5% in Germany. Treatment costs of varicosis and its complications are covered by 2% of the annual healthcare expenditure in Western countries. Chronic venous insufficiency (CVI, or chronic venous disease, CVD) affects 1.7% of European population, and can lead to venous ulcers. In Hungary 0.5-1% of the population suffers from venous ulcers, which is a result of primary or secondary varicosity.Although an increasing number of modern wound dressings have appeared during the last decade, the treatment of ulcerous wounds in necrotic and exudative phases requires additional methods, either conventional or surgical. Infrared light is used to discover pathologic veins. Beside sclerotherapy and surgical treatment external and internal (so called intraluminal) methods are used. Leg ulcers of venous origin in various phases can be cleaned with ultrasound devices, vacuum therapy or high pressure water. Hyperbaric oxygen treatment, keratinocytes, magnetic treatment, laser wound care and skin transplantation can be used as adjuvant.Authors present the aforementioned procedures with examples. New devices and methods help to reduce healing time and to avoid amputation in cases that are often considered hopeless.Technical advancement and modern wound dressings permit successful treatment and healing of wounds that earlier were untreatable, however monetary shortage and the current status of healthcare. DOI: 10.17489/biohun/2013/1/0