Relationships of maternal grandparents to grandchildren: a study of attitudes and child rearing practices.

Thesis (M.S.)--Boston Universit

Multiwavelength study of the radio emission from a tight galaxy pair Arp 143

We present results of the recent low-frequency radio observations of a tight galaxy pair Arp 143 at 234 and 612 MHz. These data are analysed together with the archive data at 1490, 4860, 8440, and 14940 MHz. From the analysis of the radio emission we derive constraints on the age of the radio emitting structures as well as on the properties of their magnetic field. We show that the collisional ring of NGC 2445 hosts strong magnetic fields (reaching 12 $\mu$G in its northwestern part) manifesting as a steep--spectrum, nonthermal radiation at radio frequencies. The spectral age of this structure is higher than estimates derived for the star-forming regions from the H$\alpha$ distribution, suggesting that the radio emission might have a different origin. The galactic core is of a very young spectral age, suggesting an ongoing starburst activity. Additionally we identify a possible ridge of emission between the ring galaxy and its elliptical companion NGC 2444.Comment: 10 pages, 5 figures, 4 tables. Accepted for publication in MNRA

Discovery of a tidal dwarf galaxy in the Leo Triplet

We report discovery of a dwarf galaxy in the Leo Triplet. Analysis of the neutral hydrogen distribution shows that it rotates independently of the tidal tail of NGC 3628, with a radial velocity gradient of 35-40 km s$^{-1}$ over approximately 13 kpc. The galaxy has a very high neutral gas content, explaining large part of its total dynamic mass - suggesting small dark matter content. As it is located at the tip of the gaseous tail, this strongly suggests its tidal origin. Should it be the case, it would be one of the most confident and closest (to the Milky Way) detections of a tidal dwarf galaxy and, at the same time, a most detached from its parent galaxy ($\approx$140 kpc) object of this type.Comment: 6 pages, 4 figures; The Astrophysical Journal, in pres

The basis problem for subspaces of monotonically normal compacta

We prove, assuming Souslin's Hypothesis, that each uncountable subspace of each zero-dimensional monotonically normal compact space contains an uncountable subset of the real line with either the metric, the Sorgenfrey, or the discrete topology.Comment: 12 page

A search for extended radio emission from selected compact galaxy groups

Context. Studies on compact galaxy groups have led to the conclusion that a plenitude of phenomena take place in between galaxies that form them. However, radio data on these objects are extremely scarce and not much is known concerning the existence and role of the magnetic field in intergalactic space. Aims. We aim to study a small sample of galaxy groups that look promising as possible sources of intergalactic magnetic fields; for example data from radio surveys suggest that most of the radio emission is due to extended, diffuse structures in and out of the galaxies. Methods. We used the Effelsberg 100 m radio telescope at 4.85 GHz and NRAO VLA Sky Survey (NVSS) data at 1.40 GHz. After subtraction of compact sources we analysed the maps searching for diffuse, intergalactic radio emission. Spectral index and magnetic field properties were derived. Results. Intergalactic magnetic fields exist in groups HCG 15 and HCG 60, whereas there are no signs of them in HCG 68. There are also hints of an intergalactic bridge in HCG 44 at 4.85 GHz. Conclusions. Intergalactic magnetic fields exist in galaxy groups and their energy density may be comparable to the thermal (X-ray) density, suggesting an important role of the magnetic field in the intra-group medium, wherever it is detected.Comment: 13 pages, 4 figures, 3 tables, accepted for publication in A&

Influence of Structural Characteristics on the Mechanical Properties of FDM Printed PLA Material

The present study reports on the influence of printing process parameters, architecture, raster, infill orientation and filling on the density, macrostructure, and mechanical properties, including impact resistance, of biodegradable polymer parts fabricated in polylactide (PLA) on a desktop printer. It complements and considers phenomenologically the results of recently published similar studies, including the use of recycled filament. In our study, complex mechanical properties for the samples printed at the same time on a Replicator 2 printer were investigated. Three samples were printed for each test. Full mechanical characteristics (tensile, compression and bend strengths and impact resistance) of the printed PLA material are reported. This is the novelty in comparison to other studies, where the samples test were printed individually or in a series for each test. The shape and thickness of the layered macrostructure, the presence of holes inside the layers, the number of shell perimeters and the fill density all influenced the tensile properties of the printed materials. These results show the possibility of printing with a 0.3, i.e. shorter printing time than 0.1, 0.15 and 0.18 mm layer thicknesses also reported, without significant decrease in mechanical properties. It is interesting to note that the compressive strengths, the yield of 70–80 MPa and a UTS 113–120 MPa for the printed material with a fill density of 94–96% are comparable with those of aluminum

Delineation of wellhead protection area based on the analytical elements method (AEM) – a case study with comparative research

The delineation of protection zones for groundwater intakes is a difficult task resulting from the significant variability of regional and local environmental conditions. Different methods are used, both simple (analytical or graphic), giving estimated results, and the most reliable, but also the most time-consuming ones, based on numerical groundwater flow models. An alternative method for the delineation of protection zones is the analytical elements method (AEM), which gives solutions like those obtained using FDM/FEM modelling methods with a relatively low degree of complexity. The estimated ranges of protection zones obtained with the use of four methods are presented for the selected test area (groundwater intake around Olesno). Results obtained with the use of the FDM model were taken as reference and CFR and SimpleWHPA were used as simplified methods. Comparative studies indicate that the results obtained by the CFR method differ significantly from the results of other methods, and their reliability is low. The results of the SimpleWHPA method are satisfactory, given the relative simplicity of the method. On the other hand, the results obtained with the AEM are close to the results obtained with the FDM treated as a reference. Considering that AEM is less time-consuming than FDM (which requires the most effort for proper model preparation), the use of AEM in the practice of protection zone delineation seems to be an interesting alternative

Object Mapping in the OPC-UA Protocol for Statically and Dynamically Typed Programming Languages

Two or more object-oriented components located in networked computers can form a distributed system to exchange information and execute methods. The most known approaches include object request broker architectures (e.g. CORBA), messaging-service architecture (e.g. based on ZMQ or JMS) or some variant of Service Oriented Architecture (e.g. SOAP). One of new approaches in the field is the OPC-UA protocol. While having common parts with all aforementioned architectures, it brings very rich and extensible information modelling capabilities, versatility and dynamic address space model, among others. This paper proposes a mapping of information model (applicable in the OPC-UA protocol) into class and object structure of an object-oriented programming language. Special attention is paid to whether given programming language is statically or dynamically typed, with examples and applications in C++ for the former case and Python for the latter. The study also covers the cases of using the proposed mapping at both server- and client-side of OPC-UA software