Focussed ultrasonic fields in inhomogeneous media.

The simplest source of focussed ultrasound used in medicine is the spherical cap transducer. It appeared that the theory of O'Neil, invariably used for predictions had not been previously tested comprehensively under narrowband low amplitude conditions. Extensive measurements on four weakly focussed transducers in water have shown that this theory is a poor predictor of the field actually radiated under these conditions. If the nominal geometrical parameters of a transducer are replaced in the theory by effective values derived from pressure amplitude extrema, a greatly improved fit between theory and experiment can be realised. A reliable protocol for the determination of effective parameters has been proposed. It has been shown that the effective parameters defined from measurements in water can be used with comparable success to predict the fields in castor oil. A novel method, using a spherical cap transducer and a miniature hydrophone, has been developed for the measurement of ultrasonic attenuation in penetrable media. Use of the technique for measuring the frequency dependence of the coherent scattering component of the attenuation in a suspension of polystyrene beads in a castor oil matrix, presenting refractive index variations of 35%, gave results in good agreement with the theory of Waterman and Truell. Amplitude measurements in the suspension have shown that the coherent part of the field is not defocussed. The defocussing observed in soft human tissue such as breast, by Poster and Hunt, appears to be largely due to the incoherent scattering contribution and its quantification is identified as the subject of future investigation

Focussed ultrasonic fields in inhomogeneous media.

The simplest source of focussed ultrasound used in medicine is the spherical cap transducer. It appeared that the theory of O'Neil, invariably used for predictions had not been previously tested comprehensively under narrowband low amplitude conditions. Extensive measurements on four weakly focussed transducers in water have shown that this theory is a poor predictor of the field actually radiated under these conditions. If the nominal geometrical parameters of a transducer are replaced in the theory by effective values derived from pressure amplitude extrema, a greatly improved fit between theory and experiment can be realised. A reliable protocol for the determination of effective parameters has been proposed. It has been shown that the effective parameters defined from measurements in water can be used with comparable success to predict the fields in castor oil. A novel method, using a spherical cap transducer and a miniature hydrophone, has been developed for the measurement of ultrasonic attenuation in penetrable media. Use of the technique for measuring the frequency dependence of the coherent scattering component of the attenuation in a suspension of polystyrene beads in a castor oil matrix, presenting refractive index variations of 35%, gave results in good agreement with the theory of Waterman and Truell. Amplitude measurements in the suspension have shown that the coherent part of the field is not defocussed. The defocussing observed in soft human tissue such as breast, by Poster and Hunt, appears to be largely due to the incoherent scattering contribution and its quantification is identified as the subject of future investigation

Chemical modificaton of nanodiamond powders produced by detonation method

Nanodiamonds are diamond particles measured in nanometers. The ideal nanodiamond molecule should have surface ability to bind with many organic groups. They are also susceptible to chemical modifications. Nanodiamonds due to their biocompatibility and low toxicity, can be used for biological materials or in medicine. They can also be used as drug carriers and as covalent and electrostatic binding to the active biomolecules. This review describes the chemical modification of nanodiamond powders. This research work aimed and gain new knowledge, understanding and interpretation of the phenomena occure during the chemical functionalization of nanodiamond powders. An observation and an analysis of the mechanisms of chemical bonds formation or physical interactions will broaden the knowledge in this field. An examination of the impact of organic groups on the nanodiamond surface and onto its physical and chemical properties contribute to the selection of the best method of modification. An implementation research allows to broaden the knowledge in the field of chemical surface modification of nanodiamonds powders

Problematyka wyznaczania wielkości filarów oporowych wyrobisk kapitalnych w głębokich kopalniach rud miedzi

This article describes stability issues of main excavations in deep copper mines in Poland, from the perspective of mining work safety. To protect main transportation and ventilation routes, parts of rock are left untaken to form so-called protective pillars. The problem was to determine the size of main excavations protective pillars in deep underground copper mines in which provide stability of main excavations. The results of numerical simulations of the stability of protective pillars under specific geological and mining conditions are presented, covering: underground depth and width of protective pillar, number, size and layout geometry of protected excavations, as well as the impact of parameters of surrounding gob areas. Problem was solved applying numerical simulations based on the finite element method which were performed in a plane state of strain by means of Phase2 v. 8.0 software. The behavior of the rock mass under load was described by an elastic-plastic model. The Mohr-Coulomb criterion was used to assess the stability of the rock mass. The results of numerical modeling have practical applications in the designing of protective pillars primarily in determining their width. These results were used to prepare new guidelines for protective pillars in Polish copper mines in the Legnica-Glogow Copper District.W artykule pisano problematykę stateczności wyrobisk kapitalnych w głębokich kopalniach rud miedzi w Polsce, która jest bardzo ważnym zagadnieniem w aspekcie bezpieczeństwa prowadzonych robót górniczych. W celu ochrony głównych dróg komunikacyjnych i wentylacyjnych pozostawia się fragmenty calizny tworzące tak zwane filary oporowe. Następnie przedstawiono wyniki symulacji numerycznych stateczności filarów oporowych w określonych warunkach geologiczno-górniczych ich użytkowania, które objęły: głębokość zalegania i szerokość filara, liczbę i wielkości oraz geometrię rozmieszczenia wyrobisk chronionych, a także oddziaływanie parametrów pól zrobów w otoczeniu. Symulacje numeryczne wykonano w płaskim stanie odkształcenia za pomocą programu Phase2 v. 8.0, w oparciu o metodę elementów skończonych. Zachowanie górotworu pod obciążeniem opisano modelem sprężysto-plastycznym. Zastosowano kryterium wytrzymałościowe Coulomba-Mohra. Wyniki modelowania numerycznego mają zastosowanie praktyczne przy projektowaniu filarów oporowych. Zostały wykorzystane przy opracowaniu nowych wytycznych dla filarów ochronnych w polskich kopalniach rud miedzi w Legnicko-Głogowskim Okręgu Miedziowym

Dissolution rate of point mass sources in porous bodies

Badano szybkość rozpuszczania źródeł masy (tabletek) dla różnych geometrii ich rozkładu w złożu ziarnistym. Wykazano wzrost szybkości rozpuszczania ze wzrostem natężenia przepływu cieczy. Zaobserwowano niewielkie zmniejszenie szybkości rozpuszczania substancji wraz ze wzrostem skupienia tabletek. Badano zmianę powierzchni tabletek w czasie: początkowo jedynie zmniejszają one swoje rozmiary, po pewnym czasie stają się porowate, pokruszone, co powoduje chwilowy wzrost powierzchni wymiany masy.Substance migration from a mass sources (tablets) placed in different geometrical configurations was investigated. An increase of fluid flow rate caused quicker tablets dissolution. A little lower dissolution rate was observed for a more then symmetrical clustered placement. The estimation of tablets' surface change in time was examined. Tablets' size decreased only in the beginning. Later the tablets become porous and crushed which caused the bigger interface surface

An attempt at evaluation of the remnant influence on the occurrence of seismic phenomena in a room-and-pillar mining system with roof deflection

Experience gained until now underground mining worldwide and in Poland indicates that remnants may have an impact on the occurrence of seismic phenomena. Remnants are stress concentration sites encompassing both the deposit and the layers of rock mass located above and below the undisturbed rock. In the case where stresses in the remnant exceed its strength, it may collapse, and under unfavourable geomechanical conditions, stress-induced rockburst may occur. Remnants may also cause breaking of strong roof layers above their edges, which results in the occurrence of high-energy shocks (Salustowicz [30], Adach [3], Adach and Butra [4]). This article presents the possibility of utilizing numerical modeling to evaluate the influence of remnant upon the occurrence of seismic phenomena. The results of numerical calculations performed for a model room-and-pillar mining system with roof deflection under the conditions of copper ore mines in the Legnica-Głogów Copper District (LGOM) are presented. Numerical calculations in a plane strain state were performed by means of Phase2 v. 8.0 software for the analyzed mining system in which remnant was left behind. The results of numerical modeling showed that sudden fracturing of roof layers above the mined out space may occur on the edge of the remnant. This may cause a shock with very high energy, and under the appropriate conditions, this may lead to the rockburst phenomenon

Roztwory wodne sterycznie specyficznych surfaktantów jako modelowe ekologiczne ciecze obróbkowe

From the large group of surfactants with branched chains, sulfosuccinate derivatives obtained based on 2-ethylhexyl alcohol were selected. The surfactant of reference was ethoxylated sulfosuccinate with an alkyl chain (C12-C14). Tests regarding foam-forming ability (V0) and foam stability (V10) for selected solutions of the three surfactants were performed. Foam stability of the solutions of sterically specific surfactants (P13, P14) decreased by up to a factor of ten as compared with the equivalent linear alkyl chain (P19). This was achieved with the high surface activity of the solutions of these compounds as represented by surface tension and wettability of the surface of the bearing steel. The consequence of the high surface activity of the compounds were low friction and wear in tribological tests at constant load and excellent anti-seizure properties. On the cooperating friction pairs, adsorption layers were formed, effectively separating the two materials and able to transfer the high loads [L. 3]. Summing up, there is the possibility of using solutions of sterically specific surfactants as model cutting fluids with low foaming ability.Z licznej grupy surfaktantów o rozgałęzionych łańcuchach wybrano pochodne sulfobursztynianowe otrzymane na bazie oksyalkinelowego alkoholu 2-etyloheksylowego. Surfaktantem odniesienia był etoksylowany sulfobursztynian posiadający łańcuch alkilowy (C12-C14). Wykonano testy określające zdolność pianotwórczą (V0) i trwałość piany (V20) wytypowanych roztworów trzech surfaktantów. Trwałość piany roztworów sterycznie specyficznych ZPC (P13, P14) zmniejszyła się nawet dziesięciokrotnie w stosunku do ich odpowiedników z liniowym łańcuchem alkilowym (P19). Efekt ten uzyskano przy wysokiej aktywności powierzchniowej roztworów tych związków, której miarą było napięcie powierzchniowe i zwilżalność powierzchni stali łożyskowej. Konsekwencją wysokiej aktywności powierzchniowej związków były niskie opory ruchu i zużycie w testach tribologicznych przy stałym obciążeniu oraz doskonałe właściwości przeciwzatarciowe. Na współpracujących tarciowo parach ciernych tworzą się warstwy adsorpcyjne skutecznie oddzielające materiały oraz przenoszące wysokie obciążenia. Reasumując, udokumentowano możliwość stosowania roztworów sterycznie specyficznych surfaktantów jako modelowych cieczy obróbkowych o niskiej pianotwórczości

The influence of crop production system on the contents of bioactive substances in the strawberry fruits

Celem pracy przedstawionej w artykule jest charakterystyka substancji bioaktywnych występujących w owocach truskawki i omówienie wpływu czynników związanych z systemem produkcji rolnej na ich występowanie i zawartość. Truskawki są niezwykle cennym surowcem, zawierającym dużo witaminy C, kwasów fenolowych i flawonoidów, w tym głównie z grupy antocyjanów. Z przeglądu literatury wynika, że ekologiczny system produkcji sprzyja gromadzeniu większej ilości substancji bioaktywnych w porównaniu do systemu konwencjonalnego. Jednak na zawartość tych związków w owocach truskawki wpływa nie tylko system uprawy, ale także odmiana, stopień dojrzałości, warunki zbioru i przechowywania. Najnowsze wyniki badań wskazują, że owoce pochodzące z upraw ekologicznych należy polecać jako produkty o charakterze prozdrowotnym.The aim of the article was to characterize of bioactive substances occurring in strawberry fruits and description of the impact of factors related to the agricultural production system on their presence and contents. Strawberries are an extremely valuable fruits that contains a lot of vitamin C, phenolic acids and flavonoids, mainly from the anthocyanins group. A review of the literature shows that the organic production system favors the synthesis of more bioactive substances in comparison to the conventional ones. However, the content of these compounds in the strawberry fruits affects not only the cultivation system but also the variety, degree of maturity, harvest and storage conditions. Based on the newest research results we can conclude that the fruit from organic farming should be recommended as pro-healthy products