Symmetrological review of the ornamental patterns of the Chiprovtsi hand-woven carpets

Especially suitable for the study of 2-dimensional symmetry, antisymmetry and colored symmetry is the large number of geometric patterns executed in textile. The tradition of carpet-making in Chiprovtsi, NW Bulgaria is selected for inscription on the Representative List of the Intangible Cultural Heritage of humanity in 2014 by UNESCO. The town of Chiprovtsi is rich in history and was also famous all over the Balkan Peninsula for its goldsmiths. The earliest information about Chiprovtsi carpets dates back from the 17th century. The hand-woven technique,preserving the ancient way of weaving, is used to produce two-sided flat carpets and nowadays. The present investigation arose from a desire to clarify contradictory statements regarding the decorative ornaments which are to be found on the carpeting from different regions in Bulgaria and in the Chiprovtsi carpets particularly. It is well known that there are 17 classes of symmetry groups of planar ornaments which repeat in at least two nonparallel directions; these are known as crystallographic plane groups. When each set is denoted by a color, the geometrical pattern becomes a color pattern (Senechal, 1975). In this respect, preliminary analysis can be made on symmetry patterns (Shubnikov and Koptsik, 2004). Characteristic for the composition of the oldest carpets is a rim orbiting a square or rectangular field consisting of one or more strips. The traditional carpet ornamentations of the Chiprovtsi region are symmetrically organized with highly stylizing geometric forms. The first ornamental shape which is determined by the technique of weaving is a triangle (Stankov, 1964). In different models were documented several typical ornaments with specific names as “kanatitsa”, “makaz”, “kamulka”, “karakachka”, etc. According to the symmetry elements and operations in different ornaments are recognized p1, pm, cm, pmm, p4, p4mm and other plane groups arrangements. From each uncolored group of symmetry several colored groups can be derived if different choices of color-changing symmetry operators are made. In such manner some late models, from ornamental period, have received and formed an exceptionally rich decorated style. Twinning phenomenon, as in crystalline nature, was not failed to be recognized from the Chiprovtsi masters and the beauty of the principle was used in the model composing. It applied in majority with an ornamental match of two or several patterns. Adding of black-and-white (anti-) symmetry to the p4mm plane group led to the design expressivity of the oldest carpet example, exposed nowadays in the museum of Chiprovtsi town. The Arabic geometrical art with its preponderance of hexagonal or trigonal patterns stands unique in the history of ornamental art, while the two-dimensional geometrical patterns of antique Greece and Rome in the great majority were based on orthogonal axial systems(Makovicky and Makovicky, 1977). The rhombohedric-like motifs in Chiprovtsi models known from older carpets apparently borrowed itsdecorative form from the Orient. It is obvious also from semantic point of view that some of the ornaments have foreign origin, such as “makaz” from Arabic and others. The most distinctive feature of the Chiprovtsi carpets can be mentioned as use of the simplified triangular forms and the stylized models. In addition, the most popular motif “kanatitsa” is regularly used in internal and external architectural decoration of different parts of local public and private building

Tennantite-tetrahedrite series from the Madan Pb-Zn deposits, Central Rhodopes, Bulgaria

Minerals from the tennantite-tetrahedrite series (fahlores) are found as single euhedral crystals and crustiform aggregates in hydrothermal veins of the Gradishte and Petrovitsa Pb-Zn deposits of the Madan ore field, southern Bulgaria. Unusually large compositional variations and fine oscillatory crystal zoning were investigated with electron microprobe analysis. The Gradishte samples correspond dominantly to tennantite, while Petrovitsa crystals have exclusively tetrahedrite composition. Fahlore compositions at Madan correspond to zincian varieties (1.6–1.95 apfu), with low Fe-content (<0.45 apfu). Minor silver is characteristic only for the Petrovitsa samples, reaching a maximum of 0.30 apfu. The (Cu+Ag) content of the Petrovitsa tennantites and the Cu content of the Gradishte tetrahedrites systematically exceed 10 apfu resulting in compensation of the excess Cu in the structure by Fe3+. Textural characteristics, mineral relationships and available fluid inclusion and stable isotope data suggest that fahlores precipitated in the late stages of mineralization at Madan, at temperature interval of 300–200 °C from oxidizing fluids with mixed (magmatic-meteoric) signatures

Genesis of filamentary pyrite associated with calcite crystals.

The calcite of the hydrothermal Surneshko Kladenche copper vein deposit from the Rossen ore field, Bulgaria, sometimes encloses peculiar filamentary pyrite crystals. Three successive calcite generations were observed belonging to a low-temperature (<235°C) carbonate paragenesis formed in open cavities of the ore veins after the main chalcopyrite mineralisation. Three generations of pyrite crystals are associated with these calcite crystals: pyrite 1, with [001] elongated columnar crystals which crystallised in open space; pyrite 2, in groups of long (up to 10 mm) sub-parallel tortuous filaments of varying thickness (3-20 µm) which are oriented nearly perpendicular to the surfaces of a transient w{315} scalenohedral calcite crystal zone; and pyrite 3, made of slightly elongated small crystals, located in the outermost v{211} zone of the same scalenohedral calcite crystals. The columnar pyrite 1 is formed by subsequent thickening of thin straight whiskers rapidly grown under diffusional regime, whereas the filamentary pyrite 2 and 3 grew contemporaneously with the enclosing calcite crystal.Peer reviewe

Calcite interaction with acidic sulphate solutions: a vertical scanning interferometry and energy-dispersive XRF study

Calcite dissolution on (10 (1) over bar4) cleavage surface was investigated by means of ex situ vertical scanning interferometry (VSI) measurements using flow-through and batch experiments at ambient pCO(2), pH 1-7 and room temperature in metal (Fe(II), Zn, Cu and Cd) and metal-free chloride solutions, and metal sulphate and metal-free sulphate solutions, undersaturated with respect to calcite and undersaturated or in equilibrium with respect to gypsum.Based on the VSI measurements, surface retreat was quantified at different pH and Delta G(r) < -8.1 kcal mol(-1), yielding intrinsic dissolution rate constants of calcite. These rates were used to derive an empirical rate law that takes into account the pH effect on calcite dissolution at room temperature and far from equilibrium with respect to calcite and is expressed asRate(calcite)(mol . cm(-2) . s(-1)) = 3.3 +/- 1. 8 x 10(-6) . (a(H+))(0.94+0.08) + k(2)where a(H+) is the proton activity and k(2) equals 2.5 +/- 0.8 x 10(-11) mol cm(-2) s(-1). The rhombic etch pit morphology changes at very low pH (pH < 3) due to the catalytic effect of pH on calcite dissolution, yielding rounded pseudo-rhombic etch pits.The presence of Fe(II), Cu, Zn and Cd inhibits calcite dissolution at pH 3, in contrast to the presence of sulphate, which does not affect calcite dissolution. The presence of Zn affected the etch pit morphology, yielding triangular etch pits. Under gypsum saturation conditions, gypsum (or other metal-bearing sulphate phases) precipitated on calcite as calcite dissolved, yielding a decrease in dissolution rate with time due to loss of calcite reactivity. Based on energy-dispersive X-ray fluorescence (EDXRF) measurements the precipitation rates of Zn4SO4(OH)(6) center dot 5H(2)O and Cu4SO4(OH)(6) center dot 2H(2)O were calculated to be between 1 x 10(-7) and 6 x 10(-7) mol m(-2)s(-1).This work was financially supported by the CYCIT Project CGL2010-20984-C02-01, by Fundacio´n Ciudad de la Energı´a (Spanish Government) (project ALM11/009) and by the European Union through the ‘‘European Energy Programme for Recovery’’ and the Compostilla OXYCFB300 project and by the PANACEA project (European Community’s Seventh framework Programme FP7/2007-2013 under grant agreement number 282900). The first author is grateful to the National Science Fund of the Bulgarian Ministry of Education and Science (NZMU-1503 and DO1-904).Peer Reviewe

A Generalized Net Model of the Prostate Gland&rsquo;s Functioning

Over the last 20 years, many Generalized Net (GN) models of the ways of functioning of the different systems and organs in the human body and models related to the description of biomedical processes in living organisms have been constructed. In this paper, a GN model of the prostate gland&rsquo;s functioning was developed, as a continuation of the previous research. The model provides the possibility to trace the logical relations of the interactions of the prostate gland and various individual organs in the human body. The model shows the possibility for the existence of currently unknown feedback loops