A Laboratory Investigation on Thermal Properties of the Opalinus Claystone

Some aspects of the thermal behavior of the Opalinus claystone are investigated through laboratory tests conducted on a new hollow cylinder triaxial apparatus specially designed for studying the thermo-hydro-mechanical behavior of very low permeable materials. Two hollow cylinder samples are first resaturated under isotropic stress state equal to the mean effective in situ one in order to minimize swelling and induced damage during the resaturation phase. Two drained heating-cooling cycles are performed on the first sample of Opalinus claystone. During the first cycle, a thermo-elasto-plastic response similar to that of plastic clays with low overconsolidation ratio is obtained. The thermal hardening of the sample is demonstrated by the quasi-reversible behavior of the sample during the second heating-cooling cycle. An undrained heating test performed on the second sample of Opalinus claystone induces an excess pore pressure in this sample. This induced pore pressure is attributed to the higher thermal expansion coefficient of pore water compared to that of the solid phase. It is shown that the excess pore pressure generated in the sample by undrained heating cannot be modeled by considering the free water thermal expansion coefficient. The thermal expansion coefficient of the Opalinus claystone water is back-analyzed from the experimental results which show a higher value than free wate

Effect of particle size on the measurement of the apparent contact angle in sand of varying wettability under air-dried conditions

Session: Advances in Experimental Methods: Mechanical PropertiesChanges in the wettability of soil are known to affect several processes such as infiltration and the shear strength of soil. In this study, the wettability of a medium to fine sand was chemically modified by using different concentrations of dimethyldichlorosilane (DMDCS). The sessile drop method (SDM) was used for the assessment of wettability of hydrophobised Leighton Buzzard Sand (LBS). The results demonstrate that beyond a concentration of 2 g per kg of LBS, the finer fraction had its apparent contact angle (ACA) increased up to 115° while the maximum ACA attained by the coarser fractions was 100°. At such high concentration of DMDCS, the effect of trapped air, which is known to increase the ACA, was found to be either small or insignificant. The standard deviations of the ACAs agreed well with past studies. The most important factors contributing to the water-repellent behaviour of chemically synthesised sand were attributed to the characteristics of the particles; these include surface area and particle shape.published_or_final_versio

Testing surfactants as additives for clay improvement: compaction and suction effects

Environmental Geotechnics (Joint TC106-TC215 Session)This paper presents an exploratory study on surfactants as additives to improve soil properties. It is hypothesized that surfactant molecules populate the air-water interfaces reducing surface tension and suction thus allowing a control of the mechanical response of the soil. Suction measurements by means of a high suction tensiometer, compaction tests and Atterberg limits were conducted in mixtures of sand and kaolin, with and without a surfactant solution. The results revealed a prominent effect on suction, but to a lesser extent on the Atterberg limits and compaction behavior (the maximum dry density). This targeted effect of the surfactants suggests its molecules populate, not only the air-water interfaces decreasing surface tension, but may be adsorbing to the clay particles and forming micelles in the pore water as well. Therefore the interplay between the three may influence the soil behavior.published_or_final_versio

Enquête sur l'infection naturelle du chien militaire au Maroc par le virus de Rubarth

Petrov Y.-J.-M., Delage B., Martin L.- A. Enquête sur l'infection naturelle du Chien militaire au Maroc par le virus de Rubarth. In: Bulletin de l'Académie Vétérinaire de France tome 111 n°7, 1958. pp. 341-346

Fractal Conductance Fluctuations in a Soft Wall Stadium and a Sinai Billiard

Conductance fluctuations have been studied in a soft wall stadium and a Sinai billiard defined by electrostatic gates on a high mobility semiconductor heterojunction. These reproducible magnetoconductance fluctuations are found to be fractal confirming recent theoretical predictions of quantum signatures in classically mixed (regular and chaotic) systems. The fractal character of the fluctuations provides direct evidence for a hierarchical phase space structure at the boundary between regular and chaotic motion.Comment: 4 pages, 4 figures, data on Sinai geometry added to Fig.1, minor change

PENGARUH ATOPI TERHADAP TIMBULNYA DERMATITIS KONTAK PADA MAHASISWIRNPENDIDIKAN DOKTER FAKULTAS KEDOKTERAN UNIVERSITAS SYIAH KUALA RNBANDA ACEH

Dermatitis kontak adalah inflamasi non infeksi pada kulit yang disebabkan karena pemaparan dengan suatu zat tertentu yang dapat mengiritasi kulit atau menyebabkan reaksi alergi. Perempuan lebih sering mengalami dermatitis kontak dibandingkan laki-laki. Atopi merupakan salah satu faktor predisposisi timbulnya dermatitis kontak. Penelitian ini bertujuan untuk mengetahui pengaruh atopi terhadap timbulnya dermatitis kontak pada mahasiswi Pendidikan Dokter Fakultas Kedokteran Universitas Syiah Kuala Banda Aceh. Penelitian ini bersifat analitik dengan pendekatan cross sectional. Data yang digunakan adalah data primer yang diperoleh dengan wawancara langsung pada responden. Uji statistik dengan menggunakan Chi Square diperoleh nilai p yang signifikan sebesar 0,00, ini berarti p < 0,05 maka secara statistik didapatkan hubungan antara atopi dengan dermatitis kontak dengan rasio prevalensi 2,17, artinya seseorang yang menderita atopi memiliki peluang sebesar 2,17 kali untuk mengalami dermatitis kontak dibandingkan dengan orang yang tidak menderita atopi. Bahan yang paling sering menyebabkan dermatitis kontak pada mahasiswi adalah deterjen dan kosmetik. Hasil penelitian yang diperoleh ada pengaruh atopi terhadap timbulnya dermatitis kontak pada mahasiswi Pendidikan Dokter FK Unsyiah Banda Aceh, dimana mahasiswi yang menderita atopi cenderung mengalami dermatitis kontak.Kata kunci: Atopi, Dermatitis kontak Alergi, Dermatitis kontak iritanBanda Ace

Influence of effective stress on swelling pressure of expansive soils

The volume change and shear strength behaviour of soils are controlled by the effective stress. Recent advances in unsaturated soil mechanics have shown that the effective stress as applicable to unsaturated soils is equal to the difference between the externally applied stress and the suction stress. The latter can be established based on the soil-water characteristic curve (SWCC) of the soil. In the present study, the evolution of swelling pressure in compacted bentonite-sand mixtures was investigated. Comparisons were made between magnitudes of applied suction, suction stress, and swelling pressure

The macro-and micro-fossil record of the Cambrian priapulid Ottoia

The stem-group priapulid Ottoia Walcott, 1911, is the most abundant worm in the mid-Cambrian Burgess Shale, but has not been unambiguously demonstrated elsewhere. High-resolution electron and optical microscopy of macroscopic Burgess Shale specimens reveals the detailed anatomy of its robust hooks, spines and pharyngeal teeth, establishing the presence of two species: Ottoia prolifica Walcott, 1911, and Ottoia tricuspida sp. nov. Direct comparison of these sclerotized elements with a suite of shale-hosted mid-to-late Cambrian microfossils extends the range of ottoiid priapulids throughout the middle to upper Cambrian strata of the Western Canada Sedimentary Basin. Ottoiid priapulids represented an important component of Cambrian ecosystems: they occur in a range of lithologies and thrived in shallow water as well as in the deep-water setting of the Burgess Shale. A wider survey of Burgess Shale macrofossils reveals specific characters that diagnose priapulid sclerites more generally, establishing the affinity of a wide range of Small Carbonaceous Fossils and demonstrating the prominent role of priapulids in Cambrian seas