H2 formation via the UV photo-processing of a-C:H nano-particles

Context. The photolysis of hydrogenated amorphous carbon, a-C(:H), dust by UV photon-irradiation in the laboratory leads to the release of H2 as well as other molecules and radicals. This same process is also likely to be important in the interstellar medium. Aims. To investigate molecule formation arising from the photo-dissociatively-driven, regenerative processing of a-C(:H) dust. Methods. We explore the mechanism of a-C(:H) grain photolysis leading to the formation of H2 and other molecules/radicals. Results. The rate constant for the photon-driven formation of H2 from a-C(:H) grains is estimated to be 2x10^-17 cm^3 s^-1. In intense radiation fields photon-driven grain decomposition will lead to fragmentation into daughter species rather than H2 formation. Conclusions. The cyclic re-structuring of arophatic a-C(:H) nano-particles appears to be a viable route to formation of H2 for low to moderate radiation field intensities (1 < G_0 < 10^2), even when the dust is warm (T ~ 50 - 100 K).Comment: 7 pages, 2 figures, accepted for publication in A&

Electronic Types of Marketing

Obsahem této bakalářské práce je analýza marketingu společnosti. Ve své práci se budu zabývat, zda společnost dostatečně využívá zejména elektronického marketingu, shrnu nejvýznamnější druhy elektronického marketingu, jeho trendy a vyberu pro společnost nejlépe vyhovující.The content of my bachelor thesis is analysis of company’s marketing. In my study I am going to consider if company adequately use especially electronic types of marketing, summarize the most important types of e-marketing, its trends and finally set of optimal solution.

Spatially resolved PAH emission in the inner disks of Herbig Ae/Be stars

We present adaptive optics high angular resolution (\sim0.1\arcsec) spectroscopic observations in the 3 \um region of eight well known Herbig Ae/Be stars with circumstellar disks. We detect the aromatic emission feature at 3.3 \um for four out of six of our objects with flared disks (HD 169142, HD 97048, HD 100453, HD 100546), some weaker additional features at 3.4 and 3.46 $\mu$m and nanodiamond features at 3.43 and 3.53 \um in two of our flared object (HD 100546 and HD 97048 respectively). We also detect hydrogen recombination line at 3.74 \um in practically all objects. The emission in the polycyclic aromatic hydrocarbons (PAHs) feature at 3.3 \um, additional and nanodiamond features in the 3.4-3.5 \um region is, for the first time, spatially resolved in all the sources where the features are detected. The full-width at half-maximum sizes that we derive are typical of emission arising in a circumstellar disk. On the other hand, the continuum emission is unresolved, with the exception of HD 97048 where it is marginally resolved. We compare the observed spatial distribution of the 3.3 $\mu$m PAH feature and the adjacent continuum to the predictions of a disk model that includes transiently heated small grains and PAHs in addition to large grains in thermal equilibrium \cite[]{habart2004a}. The model predicts that, as observed, the 3.3 $\mu$m PAH emission feature is significantly broader than that of the adjacent continuum and that about 50% of its integrated intensity comes from a radius $R<$ 30 AU. We find that the predicted brightness profiles reproduce very well the observed ones. This proves beyond doubt that the energetic 3.3 $\mu$m PAH emission feature takes its origin in the inner disk regions.Comment: 7 figures, accepted to A&

Diamonds in HD 97048

We present adaptive optics high angular resolution (\sim0\farcs1) spectroscopic observations in the 3 $\mu$m region of the Herbig Ae/Be star HD 97048. For the first time, we spatially resolve the emission in the diamond features at 3.43 and 3.53 $\mu$m and in the adjacent continuum. Using both the intensity profiles along the slit and reconstructed two-dimensional images of the object, we derive full-width at half-maximum sizes consistent with the predictions for a circumstellar disk seen pole-on. The diamond emission originates in the inner region ($R \lesssim 15$ AU) of the disk.Comment: ApJLetter, in pres

Evolution of PAHs in protoplanetary disks

Depending on whom you ask, PAHs are either the smallest dust particles or the largest gas-phase molecules in space. Whether referred to as gas or dust, these PAHs can contain up to 20% of the total cosmic carbon abundance and as such also play an important role in the carbon chemistry of protoplanetary disks. The interpretation of PAH bands is often a complex procedure involving not only gas physics to determine their ionization stage and temperature, but also radiative transfer effects that can bury these bands in a strong thermal continuum from a population of larger dust particles. PAHs are most readily seen in the spectral energy distributions (SEDs) of disks around Herbig AeBe stars where they are photoprocessed by the stellar radiation field. Resolved images taken in the PAH bands confirm their origin in the flaring surfaces of circumstellar disks: if the SED is consistent with a flat disk structure (less illuminated), there is little or no evidence of PAH emission. The very low detection rates in the disks around T Tauri stars often require an overall lower abundance of PAHs in these disk surface as compared to that in molecular clouds. In this review, I will adress three aspects of PAHs in protoplanetary disks: (1) Do PAHs form in protoplanetary disks or do they originate from the precursor molecular cloud? (2) Is the presence of PAH features in SEDs a consequence of the disk structure or do PAHs in fact shape the disk structure? (3) How can we use PAHs as tracers of processes in protoplanetary disks?Comment: 13 pages, 3 figures, invited review at the conference "PAHs and the Universe", C. Joblin and A.G.G.M Tielens Eds, EAS Publications Series vol. 46, 201

H2 formation and excitation in the diffuse interstellar medium

We use far-UV absorption spectra obtained with FUSE towards three late B stars to study the formation and excitation of H2 in the diffuse ISM. The data interpretation relies on a model of the chemical and thermal balance in photon-illuminated gas. The data constrain well the nR product between gas density and H2 formation rate on dust grains: nR = 1 to 2.2 e-15 s-1. For each line of sight the mean effective H2 density n, assumed uniform, is obtained by the best fit of the model to the observed N(J=1)/N(J=0) ratio, since the radiation field is known. Combining n with the nR values, we find similar H2 formation rates for the three stars of about R = 4 e-17 cm3/s. Because the target stars do not interact with the absorbing matter we can show that the H2 excitation in the J>2 levels cannot be accounted for by the UV pumping of the cold H2 but implies collisional excitation in regions where the gas is much warmer. The existence of warm H2 is corroborated by the fact that the star with the largest column density of CH+ has the largest amount of warm H2.Comment: 7 pages, 4 figures, to be published in Astronomy & Astrophysic

Molecular hydrogen in the disk of the Herbig Ae star HD97048

We present high-resolution spectroscopic mid-infrared observations of the circumstellar disk around the Herbig Ae star HD97048 obtained with the VLT Imager and Spectrometer for the mid-InfraRed (VISIR). We conducted observations of mid-infrared pure rotational lines of molecular hydrogen (H2) as a tracer of warm gas in the disk surface layers. In a previous paper, we reported the detection of the S(1) pure rotational line of H2 at 17.035 microns and argued it is arising from the inner regions of the disk around the star. We used VISIR on the VLT for a more comprehensive study based on complementary observations of the other mid-infrared molecular transitions, namely S(2) and S(4) at 12.278 microns and 8.025 microns respectively, to investigate the physical properties of the molecular gas in the circumstellar disk around HD97048. We do not detect neither the S(2) line nor the S(4) H2 line from the disk of HD97048, but we derive upper limits on the integrated line fluxes which allows us to estimate an upper limit on the gas excitation temperature, T_ex < 570 K. This limit on the temperature is consistent with the assumptions previously used in the analysis of the S(1) line, and allows us to set stronger contraints on the mass of warm gas in the inner regions of the disk. Indeed, we estimate the mass of warm gas to be lower than 0.1 M_Jup. We also discuss the probable physical mechanisms which could be responsible of the excitation of H2 in the disk of HD97048.Comment: accepted for publication in Ap

Effect of inhibitory neuron subtypes on neural population dynamics

Canonical models of neural circuits rarely differentiate between inhibitory population subtypes. Due to the recent development of optogenetic techniques, the effect of distinct inhibitory classes may now be analysed. This thesis adapts a neural population model of the mouse visual cortex and analyses the stability of equilibria with overall connectivity of the network as a bifurcation parameter. A stability result for small values of the parameter is obtained. 1Standardní modely neuronových obvodů málokdy rozlišují mezi druhy inhibičních neuronů. Díky nedávnému rozvoji optogenetických nástrojů lze v současné době analyzo- vat efekt odlišných ihibičních populací. Tato práce modifikuje existující populační model vizuální kůry u myší a provádí analýzu stability stacionárních bodů s celkovou konek- tivitou jako bifurkačním parametrem. Podařilo se dokázat stabilitu pro malé hodnoty parametru. 1Department of Software and Computer Science EducationKatedra softwaru a výuky informatikyFaculty of Mathematics and PhysicsMatematicko-fyzikální fakult

Survey of purchasing behaviour and preferences of Czech ice hockey goalies on the ice hockey goalie equipment market

Title: Survey of purchasing behaviour and preferences of Czech ice hockey goalies on the ice hockey goalie equipment market Objectives: The main objective of this work is to identify and describe the buying behaviour and preferences of Czech pure amateur hockey goalies on the hockey goalie gloves market. Other objectives were: to identify the factors that are crucial in the purchase of goalie gloves and that influence goalies the most, to find out the usual places of purchase of goalie gloves, the most used brands of goalie gloves among "hobby" goalies and the loyalty of these goalies to the brand of goalie gloves. The final objective is to identify the price sensitivity of "hobby" goalkeepers in their purchases. Methods: In our thesis, we used a combination of quantitative and qualitative research methods. The quantitative method represented by a questionnaire survey was used to obtain a large amount of data (195 responses received in total), which was then compared with the responses of three interviews representing the qualitative method. The interviews were used to obtain more developed and accurate answers on the subject matter. Results: The results of the questionnaires and interviews showed that hockey "hobby" goalies are most concerned about the functionality of the goalie gloves, and they...Název: Průzkum nákupního chování a preferencí českých hokejových brankářů na trhu s hokejovou brankářskou výstrojí Cíle: Hlavním cílem práce je zjistit a popsat nákupní chování a preference českých hokejových čistě amatérských brankářů na trhu s hokejovými brankářskými lapačkami. Dalším vytyčeným cílem bylo: poznat faktory, které jsou při koupi lapaček zásadní a které brankáře nejvíce ovlivňují, zjistit obvyklá místa nákupu brankářských lapaček, nejpoužívanější značky lapaček mezi "hobby" brankáři a loajalitu těchto brankářů ke značkám lapaček. Posledním cílem je identifikovat cenovou citlivost "hobby" brankářů při jejich nákupech. Metody: V práci byla využita kombinace kvantitativních a kvalitativních metod výzkumu. Kvantitativní metoda reprezentována dotazníkovým šetřením byla použita pro získání velkého množství dat (celkem 195 získaných odpovědí), která byla následně porovnávána s odpověďmi tří rozhovorů reprezentujících metodu kvalitativní. Rozhovory sloužily k získání rozvinutějších a přesnějších odpovědí na danou problematiku. Výsledky: Z výsledků dotazníků a rozhovorů vyplynulo, že hokejovým "hobby" brankářům nejvíce záleží na funkčnosti lapaček, přičemž lapačky nejčastěji nakupují na internetových bazarech. Nejužívanější značkou je značka Bauer, jež má méně loajální zákazníky než jiné...Katedra managementu sportuDepartment of Sport ManagementFaculty of Physical Education and SportFakulta tělesné výchovy a sport