Soap film catastrophes

Earlier systematic experimental studies of bursting soap films by McEntee & Mysels (J. Phys. Chem., vol. 73, 1969, pp. 3018–3028) revealed the existence of a precursor shock wave preceding the expanding hole in a punctured film, with a disturbed region of shrinking film material in between known as the ‘aureole’. In the present work we report and interpret new phenomena associated with the aureole – the formation of folds on the surface of soap films. In search of the theoretical explanation of the experimentally identified conditions under which the folds appear, we establish that they correspond to catastrophes of collapsing soap films.

The occurrence of eleven elements in dairy cow´s milk, feed, and soil from three different regions of Slovakia

The objective of this study was to measure the concentrations of eleven essential, potentially toxic and toxic elements (arsenic – As, calcium – Ca, cadmium – Cd, copper – Cu, iron – Fe, mercury – Hg, magnesium – Mg, nickel – Ni, lead – Pb, selenium – Se, zinc- Zn) in raw cow’s milk (spring, summer, and autumn season), feed (spring and autumn season) and soil (spring season) from three different environments by routine methods in the certified testing laboratory. The samples were collected in the undisturbed region around Novoť, the moderately disturbed region around Tulčík, and the strongly disturbed region around Čečejovce. The concentrations of all toxic elements (As, Cd, Hg, Ni, Pb) and two essential elements (Cu, Se) in milk were under the limits of quantification (LOQ) from all investigated areas and during all seasons. Concentrations of other elements in milk from the undisturbed and disturbed areas were significantly different, generally with the highest levels in summer. In soil samples, the significantly highest concentrations of Ca, Cu, Ni were found in a strongly disturbed area, Mg and As in moderately disturbed area, and Fe, Se, Zn, Hg, and Pb in an undisturbed area. Cadmium was under the LOQ. In feed, the concentrations of essential elements, except of Se, were higher in the autumn. The significantly highest concentration of As, Ni were recorded in a moderately disturbed area and Pb in the undisturbed area in both seasons. Cadmium and Hg were under the LOQ. Despite the higher level of some elements in soil (Fe, Mg, Ca) from all regions, there were not elevated concentrations of any element in feed or milk. The concentrations of all toxic elements in milk were under the permitted limits. Thus, the milk from all investigated areas was not contaminated with the elements posing a health risk for consumers and it is considered safe for human consumption.

ANALISIS REGANGAN BAJA TULANGAN PADA STRUKTUR PILE CAP EMPAT TIANG METODE STRUT AND TIE MODEL

ABSTRACTPile cap is one of the many types of structures that are entirely Disturbed-region. The structure undergoes a non-linear strain because it was meeting point of the pile and column with centralized forces. In addition, geometry changes occur at the meeting between the column, pile cap, and pile, so the Bernoulli concept is no longer suitable for this condition. Pile cap testing consists of two groups of specimens and each group consists of three specimens. The first group was designed using the STM method (SNI 2847: 2013 Appendix A) and the second group was designed using conventional methods (SNI 2847: 2013 Article 15). Loading is the application of a centralized static load that is channeled through a centric column until the pile cap structure has collapsed. The results show that: (1) The flexural reinforcement which experiences the first yield condition both on the pile cap testing of the STM method and in the conventional method was the X direction flexural reinforcement (outsidest flexural reinforcement). (2) The average strain of the yield conditions and load on the pile cap STM method were 2242 με and 528.97 kN, whereas the conventional method were 2436 με and 437.03 kN. (3) Increasing the load capacity of the yield conditions (Py) of the pile cap STM method and conventional method on the plan load (Pn) were 32.2% and 9.3%.Keywords: pile cap, four piles, Strut and Tie Model (STM) ABSTRAK Pile cap merupakan salah satu dari jenis struktur yang sepenuhnya merupakan daerah terganggu (Disturbed-region). Struktur tersebut mengalami regangan non-linear karena merupakan titik pertemuan pile dan kolom dengan gaya-gaya terpusat. Selain itu, terjadi perubahan geometri pada pertemuan antara kolom, pile cap, dan pile, sehingga konsep Bernoulli tidak cocok lagi pada kondisi tersebut. Pengujian pile cap terdiri dari dua kelompok benda uji dan masing-masing kelompok terdiri dari tiga buah benda uji. Kelompok pertama dirancang menggunakan metode STM (SNI 2847:2013 Lampiran A) dan kelompok kedua dirancang menggunakan metode konvensional (SNI 2847:2013 Pasal 15). Pembebanan berupa penerapan beban statik terpusat yang disalurkan melalui kolom sentris sampai struktur pile cap mengalami keruntuhan. Hasil menunjukkan bahwa: (1) Tulangan lentur yang mengalami kondisi leleh terlebih dahulu baik pada pengujian benda uji pile cap metode STM maupun pada metode konvensional adalah tulangan lentur arah X (tulangan lentur terluar). (2) Rata-rata regangan kondisi leleh dan beban pada benda uji pile cap metode STM adalah 2242 με dan 528,97 kN, sedangkan pada metode konvensional adalah 2436 με dan 437,03 kN . (3) Peningkatan kapasitas beban kondisi leleh (Py) pada benda uji pile cap metode STM dan metode konvensional terhadap beban rencana (Pn) adalah 32,2 % dan 9,3 %. Kata kunci: pile cap, empat tiang, Strut-and-Tie Model (STM)