SU(2) Cosmological Solitons

We present a class of numerical solutions to the SU(2) nonlinear $\sigma$-model coupled to the Einstein equations with cosmological constant $\Lambda\geq 0$ in spherical symmetry. These solutions are characterized by the presence of a regular static region which includes a center of symmetry. They are parameterized by a dimensionless ``coupling constant'' $\beta$, the sign of the cosmological constant, and an integer ``excitation number'' $n$. The phenomenology we find is compared to the corresponding solutions found for the Einstein-Yang-Mills (EYM) equations with positive $\Lambda$ (EYM$\Lambda$). If we choose $\Lambda$ positive and fix $n$, we find a family of static spacetimes with a Killing horizon for $0 \leq \beta < \beta_{max}$. As a limiting solution for $\beta = \beta_{max}$ we find a {\em globally} static spacetime with $\Lambda=0$, the lowest excitation being the Einstein static universe. To interpret the physical significance of the Killing horizon in the cosmological context, we apply the concept of a trapping horizon as formulated by Hayward. For small values of $\beta$ an asymptotically de Sitter dynamic region contains the static region within a Killing horizon of cosmological type. For strong coupling the static region contains an ``eternal cosmological black hole''.Comment: 20 pages, 6 figures, Revte

A comparison of the utility of data mining algorithms in an open distance learning context

The use of data mining within the higher education context has, increasingly, been gaining traction. A parallel examination of the accuracy, robustness and utility of the algorithms applied within data mining is argued as a necessary step toward entrenching the use of EDM. This paper provides a comparative analysis of various classification algorithms within an Open Distance Learning institution in South Africa. The study compares the performance of the ZeroR, OneR, Naïve Bayes, IBk, Simple Logistic Regression and the J48 in classifying students within a cohort over an 8 year timespan. The initial results appear to show that, given the data quality and structure of the institution under study, the J48 most consistently performed with the highest levels of accuracy

Examining properties of arc sprayed nanostructured coatings

The article presents the results of examining properties of arc sprayed coating obtained with nano-alloy on the iron matrix with a high amount of fine carbide precipitates sprayed on non-alloyed steel plates intended for high temperature operation. Powder metal cored wire EnDOtec DO*390N 1,6 mm diameter, was used to produce, dense, very high abrasion and erosion resistant coatings approx. 1,0 mm thick. Nano-material coatings characterization was done to determine abrasion resistance, erosion resistance, adhesion strength, hardness as well as metallographic examinations. Results have proved high properties of arc sprayed nano-material coatings and have shown promising industrial applications

Effect of Milling Conditions on Microstructure and Properties of AA6061/halloysite Composites

AbstractIn this work, AA6061 matrix composites reinforced with halloysite nanotubes (HNT) were fabricated using respectively, mechanical alloying and uniaxial pressing and hot extrusion. Halloysite, being a clayey mineral of volcanic origin which is characterized by large specific surface, high porosity, high ion exchange and easy mechanical and chemical treatment can be used as alternative reinforcement of metal matrix composite materials. Halloysite nanotubes have recently become the subject of research attention as a new type of reinforcement for improving the mechanical, thermal and fire-retardant performance of polymers. Application of halloysite as the reinforcement in metal matrix composites is the original invention of the authors and it has been patented (PL Patent 216257). The powders morphology, particle size and apparent density of newly developed nanostructural composites were studied as a function of milling time, ball-to-powder ratio and milling speed. Obtained composite powders of aluminium alloy matrix reinforced with 10wt.% of halloysite nanotubes were characterized by SEM analysis. Microstructural observation reveals that mechanical alloying generate a uniform dispersion of nanoparticles in the AA6061 matrix. AA6061 reinforced with 10wt.% HNT composite powder has been fabricated at vial rotation speed of 400rpm within only 6h of ball milling. It has been proven that milling speed and ball-to-powder ratio has a significant effect on the time required to achieve a morphological change in the powder being mechanically alloyed. Moreover, it has been confirmed that the use of mechanical alloying leads to high degree of deformation, which – coupled with a decrease in grain size below 100nm and the dispersion of the reinforcing refined particles – causing increase of composite hardness. Manufacturing conditions allow to achieve an improvement of mechanical properties compared with the base material

Current state and development of Airbnb accommodation offer in 167 countries

The paper examines the size, structure, distribution, dynamics, and use of Airbnb accommodation offer in 167 countries. Web-scrapping Airbnb website in fall 2018 and 2019 resulted in a datasets on 5.7 million listings, including 3.6 million active listings which have been rented out (reviewed) during the last year. Listings are divided into four groups based on types of properties and numbers of offers hosted by one platform user. The results show that the platform is most commonly used to rent out entire apartments by multi-hosts. The numbers of Airbnb listings in countries depend on the level of economic development and size of inbound tourism. One third of Airbnb supply is located in big cities, another one third near seacoasts. Airbnb offer grows most quickly in its relatively new markets, while in primary urban destinations of some European countries it is stable or decreases. The offer of professional hosts is growing more quickly than of peer-to-peer hosts. Differences in the frequency of use and prices of listings exaggerate the geographical unevenness in benefits and impacts of Airbnb activity. Airbnb supply is not a uniform segment of tourist accommodation and its effects on destinations should be considered in relation to territorial context

The results of breast conservative therapy in early breast cancer in Greatpoland Cancer Centre

We are presenting results of our treatment during 3 years (1993–1995) in Greatpoland Cancer Centre.We treated 67 women with early breast cancer performing breast conservative surgery and radiation therapy. For treatment we chose women with breast tumor up to 3 cm in diameter and unpalpable axillary lymph nodes. The therapy consisted of quadrantectomy and axillary dissection and then radiation therapy.Chemotherapy was used for patients with histologically positive lymph nodes metastases. Due to the local recurrence the mastectomy was performed in four patients. Five women were treated with cytostatics because of metastases to the liver and bones.Three women died. The other women remain in the periodical observation in our hospital. These results have a preliminary character, because of the short follow up

Zmiany w sposobie leczenia operacyjnego wysiłkowego nietrzymania moczu u kobiet – obserwacje ostatnich dwudziestu dwóch lat

Objectives: The aim of this study was to analyze the changing trends in surgical treatment of female urinary incontinence (UI). Material and methods: Medical records of all women admitted to II Department of Gynecology from 1985 to 2006 were analyzed in order to find out how the female SUI treatment changed over these years. Results: During analyzed time 36819 patients were hospitalized in our Department and 77.6% (28568) of them were operated because of various indications. The number of SUI surgeries among all hospitalized women steadily rose from 1.93% in 1985 to 10.96% in 2006 reaching maximum in 2005 (13.73%). Clinical effectiveness of SUI surgeries markedly improved from 35% for anterior colporrhaphy to almost 90 % for suburethral slings. Conclusions: Introduction into clinical practice modern suburethral slings improved clinical efficacy of SUI treatment. The percentage of women admitted and treated surgically because of SUI steadily increased over the last years.Cel pracy: Celem pracy było przeprowadzenie retrospektywnej analizy metod operacyjnego leczenia wysiłkowego nietrzymania moczu (WNM) u kobiet na przestrzeni ostatnich dwudziestu dwóch lat. Materiał i metody: Dane do analizy pozyskano z archiwum medycznego II Kliniki Ginekologii i na ich podstawie przedstawiono zmiany w operacyjnym leczeniu WNM u kobiet od 1985 do 2006 roku. Wyniki: W analizowanym okresie, w II Klinice hospitalizowanych było 36819 kobiet, z czego 77,6% (28568) było operowanych z powodu różnych wskazań. Liczba pacjentek operowanych z powodu WNM stale rosła od 1,93% w 1985r. do 10,96% w 2006r. ze szczytem w 2005r. (13,73%). Również skuteczność zabiegów znacznie wzrosła z 35% w przypadku różnych modyfikacji plastyki przedniej ściany pochwy do niemal 90% przy zastosowaniu taśm podcewkowych. Wnioski: Wprowadzenie nowoczesnych, małoinwazyjnych taśm podcewkowych znacząco zwiększyło efektywność operacyjnego leczenia WNM. Wydaje się to być jedną z przyczyn stałego wzrostu liczby kobiet decydujących się na tą metodę leczenia tej dolegliwości

58. Influence of total time of surgery and postoperative radiotherapy on the outcome patients with advanced laryngeal carcinoma

AimTo evaluate influence of total time of combined treatment on locoregional outcome of treatment in group patients with larynx cancer.Material/MethodsWe performed retrospective analysis of 254 patients with with stage III or IV squamous cell carcinoma of larynx who were treated between 1993 and 1996. There were 236 men, 18 women, median age was 56.3 years. Surgery consisted of total laryngectomy and elective/selective neck dissection. Patients postoperativly were irradiated in coventional way with total dose of 60 Gy. We used shrinking field technique with lateral opposed photon fields to tumor bed and upper-mid neck nodes. Supraclavicular regions (lower neck lymph nodes) were treated with an anterior field. Total time of combined treatment (from the surgery to the end of radiotherapy) was an average 92 days (range, 65–131 days). The interval between surgery and the beginning of radiotherapy was an average 45 days (range, 22–78 days) and time of irradiation was an average 45 day (range, 40–74 days).ResultsProlongation overall time of combined treatment beyond 90 days is strongly correlated with decreasing of locoregional outcome of treatment (p=0.00036). Also decreasing in outcome of treatment was noted when interval time between surgery and beginning of radiotherapy was more than 50 days (p=0.022) and when the time of irradiation was longer than 44 days (p=0.0026).ConclusionsDecreasing of total time of combined treatment (surgery and postoperative radiotherapy) is crucial in patients with advanced cancer of larynx

Metabolomic and high-throughput sequencing analysis—modern approach for the assessment of biodeterioration of materials from historic buildings

Preservation of cultural heritage is of paramount importance worldwide. Microbial colonization of construction materials, such as wood, brick, mortar and stone in historic buildings can lead to severe deterioration. The aim of the present study was to give modern insight into the phylogenetic diversity and activated metabolic pathways of microbial communities colonized historic objects located in the former Auschwitz II-Birkenau concentration and extermination camp in Oświęcim, Poland. For this purpose we combined molecular, microscopic and chemical methods. Selected specimens were examined using Field Emission Scanning Electron Microscopy (FESEM), metabolomic analysis and high-throughput Illumina sequencing. FESEM imaging revealed the presence of complex microbial communities comprising diatoms, fungi and bacteria, mainly cyanobacteria and actinobacteria, on sample surfaces. Microbial diversity of brick specimens appeared higher than that of the wood and was dominated by algae and cyanobacteria, while wood was mainly colonized by fungi. DNA sequences documented the presence of 15 bacterial phyla representing 99 genera including Halomonas, Halorhodospira, Salinisphaera, Salinibacterium, Rubrobacter, Streptomyces, Arthrobacter and 9 fungal classes represented by 113 genera including Cladosporium, Acremonium, Alternaria, Engyodontium, Penicillium, Rhizopus and Aureobasidium. Most of the identified sequences were characteristic of organisms implicated in deterioration of wood and brick. Metabolomic data indicated the activation of numerous metabolic pathways, including those regulating the production of primary and secondary metabolites, for example, metabolites associated with the production of antibiotics, organic acids and deterioration of organic compounds. The study demonstrated that a combination of electron microscopy imaging with metabolomic and genomic techniques allows to link the phylogenetic information and metabolic profiles of microbial communities and to shed new light on biodeterioration processes