A double molecular disc in the triple-barred starburst galaxy NGC 6946: structure and stability

The late-type spiral galaxy NGC 6946 is a prime example of molecular gas dynamics driven by "bars within bars". Here we use data from the BIMA SONG and HERACLES surveys to analyse the structure and stability of its molecular disc. Our radial profiles exhibit a clear transition at distance R ~ 1 kpc from the galaxy centre. In particular, the surface density profile breaks at R ~ 0.8 kpc and is well fitted by a double exponential distribution with scale lengths R_1 ~ 200 pc and R_2 ~ 3 kpc, while the 1D velocity dispersion sigma decreases steeply in the central kpc and is approximately constant at larger radii. The fact that we derive and use the full radial profile of sigma rather than a constant value is perhaps the most novel feature of our stability analysis. We show that the profile of the Q stability parameter traced by CO emission is remarkably flat and well above unity, while the characteristic instability wavelength exhibits clear signatures of the nuclear starburst and inner bar within bar. We also show that CO-dark molecular gas, stars and other factors can play a significant role in the stability scenario of NGC 6946. Our results provide strong evidence that gravitational instability, radial inflow and disc heating have driven the formation of the inner structures and the dynamics of molecular gas in the central kpc.Comment: MNRAS, in pres

Application of morphometry, static DNA ploidy analysis, and steroid receptor expression in diagnosis and prognosis of Libyan breast cancer

The aim of this study was to describe the demographic, clinicopathological, biological and morphometric features of Libyan breast cancer patients. The supporting value of nuclear morphometry and static image cytometry in the sensitivity for detecting breast cancer in conventional fine-needle aspiration biopsies were estimated. The findings were compared with findings in breast cancer in Finland and Nigeria. In addation, the value of ER and PR were evaluated. There were 131 histological samples, 41 cytological samples, and demographic and clinicopathological data from 234 Libyan patients. The Libyan breast cancer is dominantly premenopausal and in this feature it is similar to breast cancer in sub-Saharan Africans, but clearly different from breast cancer in Europeans, whose cancers are dominantly postmenopausal in character. At presention most Libyan patients have locally advanced disease, which is associated with poor survival rates. Nuclear morphometry and image DNA cytometry agree with earlier published data in the Finnish population and indicate that nuclear size and DNA analysis of nuclear content can be used to increase the cytological sensitivity and specificity in doubtful breast lesions, particularly when free cell sampling method is used. Combination of the morphometric data with earlier free cell data gave the following diagnostic guidelines: Range of overlap in free cell samples: 55 μm2 -71 μm2. Cut-off values for diagnostic purposes: Mean nuclear area (MNA) >54 μm2 for 100% detection of malignant cases (specificity 84 %), MNA < 72 μm2 for 100% detection of benign cases (sensitivity 91%). Histomorphometry showed a significant correlation between the MNA and most clinicopathological features, with the strongest association observed for histological grade (p <0.0001). MNA seems to be a prognosticator in Libyan breast cancer (Pearson’s test r = - 0.29, p = 0.019), but at lower level of significance than in the European material. A corresponding relationship was not found in shape-related morphometric features. ER and PR staining scores were in correlation with the clinical stage (p= 0.017, and 0.015, respectively), and also associated with lymph node negative patients (p=0.03, p=0.05, respectively). Receptor-positive (HR+) patients had a better survival. The fraction of HR+ cases among Libyan breast cancers is about the same as the fraction of positive cases in European breast cancer. The study suggests that also weak staining (corresponding to as few as 1% positive cells) has prognostic value. The prognostic significance may be associated with the practice to use antihormonal therapy in HR+ cases. The low survival and advanced presentation is associated with active cell proliferation, atypical nuclear morphology and aneuploid nuclear DNA content in Libyan breast cancer patients. The findings support the idea that breast cancer is not one type of disease, but should probably be classified into premenopausal and post menopausal types.Morfometria, staattinen DNA sytometria, ja steroidireseptorit libyalaisen rintasyövän diagnostiikassa ja ennusteen arvioinnissa Väitöskirja kuvaa rintasyöpää sairastavien libyalaisten naisten elinoloja, ja heidän rintasyöpänsä kliinispatologisia, biologisia ja morfometrisia piirteitä. Tutkimuksessa arvioitiin, miten tumamorfometria ja staattinen DNA sytometriä lisäävät ohutneulabiopsian herkkyyttä löytää syöpäkasvain. Löydöksiä verrattiin suomalaisten ja nigerialaisten rintasyöpäpotilaiden tietoihin. Työssä arvioitiin myös steroidireseptorin merkitystä rintasyöpämateriaalissa. 131 histologista ja 41 sytologista näytettä analysoitiin, ja 234 libyalaisen potilaan kliinispatologiset ja väestötiedot tutkittiin. Libyalainen rintasyöpä on etupäässä premenopausaalista, ja eroaa siksi eurooppalaisesta rintasyövästä, joka on pääosin postmenopausaalista. Saharan eteläpuolinen rintasyöpä Afrikassa on myös selvästi premenopausaalista. Taudin toteamisvaiheessa useimmilla libyalaisilla naisilla oli paikallisesti levinnyt rintasyöpä johon liittyy huonompi ennuste kuin vain maitorauhasen sisäiseen syöpään. Tumamorfometrian ja DNA sytometrian tulokset ovat yhteneväisiä suomalaisesta rintasyöpämateriaalista julkaistujen tulosten kanssa. Menetelmiä voidaan käyttää lisäämään ohutneulabiopsiatutkimuksen herkkyyttä ja spesifisyyttä. Kun aikaisempien tutkimusten tulokset yhdistetään tässä tutkimuksessa havaittuihin, saadaan diagnostiikassa käytettäviksi tuloksiksi: hyvänlaatuisten ja rintasyöpäsolujen yhteinen kokoalue oli 55-71 neliömikrometriä. Kaikki syöpätapaukset löydettiin niiden näytteiden joukosta, joissa tumien alojen keskiarvo oli yli 54 neliömikrometriä. Tämä vastaa 100%:n herkkyyttä. Vastaava spesifisyys oli 84%. Kaikki hyvänlaatuiset näytteet sisältyivät tapauksiin, joissa tuman keskimääräinen ala oli alle 72 neliömikrometriä. Tällä alueella rintasyövän toteamisen herkkyys oli 91%. Rintasyöpäsolun keskimääräinen tuman pinta-ala oli suhteessa useimpiin ennusteellisiin kliinispatologisiin tietoihin. Vahvin korrelaatio oli suhteessa histologiseen erilaistumisasteeseen (gradus). Tilastollinen merkitsevyys ei kuitenkaan ollut libyalaisessa materiaalissa samaa luokkaa kuin aikaisemmin julkaistussa suomalaisessa materiaalissa. Kasvainsolun tuman muotoon liittyvillä tekijöillä ei ollut ennusteellista merkitystä. Steroidireseptorien värjäytyvyyttä arvioitiin histologisesti. Värjäytyvyydellä oli selvä yhteys kliiniseen levinneisyysasteeseen ja imusolmuke-etäpesäkkeiden esiintymiseen. Steroidireseptoripositiiviset syövät liittyivät pitempään keskimääräiseen eloonjäämisaikaan. Steroidireseptoripositiivisten potilaiden osuus libyalaisessa materiaalissa oli sama kuin suomalaisessa materiaalissa. Tutkimus osoitti, että myös heikko värjäytyminen oli ennusteellisesti merkitsevä. Reseptorien ennusteellinen merkitys voi liittyä siihen, että positiivisia potilaita hoidetaan antiestrogeenihoidolla. Rintasyövän heikompi ennuste Libyassa ja taudin levinneisyys diagnoosivaiheessa näyttää liittyvän lisääntyneeseen proliferaatioaktiivisuuteen, poikkeavaan tumarakenteeseen ja aneuploidiseen DNA pitoisuuteen. Löydökset tukevat ajatusta, että rintasyöpää ei välttämättä ole pidettävä yhtenäisenä biologisena tautina, vaan se voitaisiin ehkä jakaa premenopausaaliseen ja postmenopausaaliseen rintasyöpään.Siirretty Doriast

Relation entre fracturation et morphologie et leurs implications hydrogéologiques : Exemple des calcaires fissurés de la région de Chéria, (NE Algérien)

La région de Chéria est située au NE Algérien, à 45 kilomètres au Sud- Ouest de la ville de Tébessa. Le bassin versant à étudier s’étend sur une surface de 720 km2, abrite plus de 74300 habitants et caractérisé par un climat semi-aride. La région est formée essentiellement par des calcaires Maestrichtiens et Eocènes qui sont fissurés karstiques et qui constituent le potentiel aquifère de la région. Cette étude tente de conformer les relations entre la morphologie et la fracturation dans les calcaires et les confronter aux écoulements des nappes de ces derniers.Mots-clés: Cheria, Tébessa, calcaire, morphologie, fracturation. Relation fracturing-morpholo- structural and them implications hydrogeologiques. Example of limestones cracks of the area of Chéria (NE Algeria)The area of Chéria is located at Algerian, with 45 kilometers in the South-west of the town of Tébessa.The area catchment to study extends on a surface from 720 km2, shelters more than 74300 inhabitants and characterized by a semi-arid climate.The area is formed primarily by limestones of Maestrichtien and Eocene which are fissured karstic and which constitute the aquiferous potential of the area.This study tries to conform the relations between morphology and the fracturing in limestones and to confront them with the flows of the tablecloths of the latter.Keywords: Chéria, Tébessa, limestone, morphology, fracturing

Optical Emission Spectroscopy and Electrical Study of High Power Thermal Arc Plasma Switching Device

In this work, an atmospheric thermal plasma arc generated from a laboratory scale high power arc switching device was investigated. In the presented study the typical voltage and current profiles from the arc switching device were measured by a high voltage probe and a Rogowski coil. It was shown that the volt-ampere characteristic of the arc plasma is directly related to the distance between electrodes. This switching device has a pulse width range of approximately 120 ns. Furthermore, the optical emis-sion spectroscopy techniques were used to measurement of the arc temperature and to identify the plasma active species. The calculated arc temperature is about 14000 K

Periodic orbits of period 3 in the disc

Let f be an orientation preserving homeomorphism of the disc D2 which possesses a periodic point of period 3. Then either f is isotopic, relative the periodic orbit, to a homeomorphism g which is conjugate to a rotation by 2 pi /3 or 4 pi /3, or f has a periodic point of least period n for each n in N*.Comment: 7 page

Topological Entropy of Braids on the Torus

A fast method is presented for computing the topological entropy of braids on the torus. This work is motivated by the need to analyze large braids when studying two-dimensional flows via the braiding of a large number of particle trajectories. Our approach is a generalization of Moussafir's technique for braids on the sphere. Previous methods for computing topological entropies include the Bestvina--Handel train-track algorithm and matrix representations of the braid group. However, the Bestvina--Handel algorithm quickly becomes computationally intractable for large braid words, and matrix methods give only lower bounds, which are often poor for large braids. Our method is computationally fast and appears to give exponential convergence towards the exact entropy. As an illustration we apply our approach to the braiding of both periodic and aperiodic trajectories in the sine flow. The efficiency of the method allows us to explore how much extra information about flow entropy is encoded in the braid as the number of trajectories becomes large.Comment: 19 pages, 44 figures. SIAM journal styl

Patent foramen ovale and neurosurgery in sitting position: a systematic review

We have conducted a systematic review of air embolism complications of neurosurgery in the sitting position and patent foramen ovale (PFO) closure. It assesses the risk and benefit of PFO closure before neurosurgery in the sitting position. The databases Medline, Embase, and Cochrane Controlled Trial Register were systematically searched from inception to November 2007 for keywords in both topics separately. In total, 4806 patients were considered for neurosurgery in sitting position and 5416 patients underwent percutaneous PFO closure. The overall rate of venous air embolism during neurosurgery in sitting position was 39% for posterior fossa surgery and 12% for cervical surgery. The rate of clinical and transoesophageal echocardiography detected paradoxical air embolism was reported between 0% and 14%. The overall success rate for PFO closure using new and the most common closure devices was reported 99%, whereas the average risk of major complications is <1%. On the basis of our systematic review, we recommend screening for PFO and considering closure in cases in which the sitting position is the preferred neurosurgical approach. Our proposed management including the time of PFO closure according to available data is presented. However, the conclusions from our systematic review may be limited due to the lack of level A evidence and from using data from observational cohort studies. Thus, definite evidence-based recommendations require prospective evaluation of the issue in well-designed studie

Particle dynamics inside shocks in Hamilton-Jacobi equations

Characteristics of a Hamilton-Jacobi equation can be seen as action minimizing trajectories of fluid particles. For nonsmooth "viscosity" solutions, which give rise to discontinuous velocity fields, this description is usually pursued only up to the moment when trajectories hit a shock and cease to minimize the Lagrangian action. In this paper we show that for any convex Hamiltonian there exists a uniquely defined canonical global nonsmooth coalescing flow that extends particle trajectories and determines dynamics inside the shocks. We also provide a variational description of the corresponding effective velocity field inside shocks, and discuss relation to the "dissipative anomaly" in the limit of vanishing viscosity.Comment: 15 pages, no figures; to appear in Philos. Trans. R. Soc. series