MICROMECHANICAL CHARACTERIZATION OF CEMENT PASTE MODIFIED BY NANOCLAYS

This work deals with the comparison of micromechanical properties and microstructure of cement pastes with additives used in concrete to reduce the lateral pressure on the formwork. This work is a steppingstone for broader investigation of the lateral pressures on different cement mixtures. The work focused on two additives used for the purpose, namely calcined clay (metakaolin) and a type of nanoclay sepiolite. A scanning electron microscope was used to describe their microstructure. Micromechanical properties of both cement composites were investigated by nanoindentation. Large statistical grids of indents were performed on three sample types: plain cement paste and two mixtures containing the enhancing additive of metakaolin and nanoclay. From the evaluated results in the form of property histograms, the modulus of elasticity, hardness and creep parameter were derived. It was found that in the cement paste with metakaolin the amount of C-S-H gel increased compared to the control mixture. Increased portlandite and the amount of unhydrous clinker was found in the cement paste with nanoclay. Nanomechanical response of individual phases was derived from overall property histograms by statistical deconvolution. The results were confirmed by electron microscopy. The micromechanical research was supplemented with the measurement of the compressive strength on cubes at the macroscopic level

EXPERIMENTAL STUDIES OF ACCELERATED CHLORIDE TRANSPORT IN CONCRETE

This contribution deals with the efficiency of electromigration of chlorides used as a repair method for reinforced concrete structures. Experimental studies of accelerated chloride transport tests were performed on samples of concrete without chlorides and with admixed sodium chloride during concreting. Two concrete types from Portland cement characterized with normal and low compressive strengths were studied. The electromigration was applied to penetrate chlorides into the chloride-free sample and for extraction of chlorides from the sample. The effectiveness of the chloride extraction process for rehabilitation of reinforced concrete in terms of lowering the chloride concentration in different concrete types and surface concentration was observed. Electrical extraction was found to be effective for lowering of initial chloride concentration by 15-20% after 24 hours. The decrease in surface concentrations was found in the range of 40-50%. The extraction process was found to be feasible and effective for both concrete types

Diversity and Distribution of Mites (Acari: Ixodida, Mesostigmata, Trombidiformes, Sarcoptiformes) in the Svalbard Archipelago

Svalbard is a singular region to study biodiversity. Located at a high latitude and geographically isolated, the archipelago possesses widely varying environmental conditions and unique flora and fauna communities. It is also here where particularly rapid environmental changes are occurring, having amongst the fastest increases in mean air temperature in the Arctic. One of the most common and species-rich invertebrate groups in Svalbard is the mites (Acari). We here describe the characteristics of the Svalbard acarofauna, and, as a baseline, an updated inventory of 178 species (one Ixodida, 36 Mesostigmata, 43 Trombidiformes, and 98 Sarcoptiformes) along with their occurrences. In contrast to the Trombidiformes and Sarcoptiformes, which are dominated in Svalbard by species with wide geographical distributions, the Mesostigmata include many Arctic species (39%); it would thus be an interesting future study to determine if mesostigmatid communities are more affected by global warming then other mite groups. A large number of new species (42 spp.) have been described from Svalbard, including 15 that have so far been found exclusively there. It is yet uncertain if any of these latter species are endemic: six are recent findings, the others are old records and, in most cases, impossible to verify. That the Arctic is still insufficiently sampled also limits conclusions concerning endemicity.publishedVersio

An oribatid mite (Arachnida: Acari) from the Oxford Clay (Jurassic: Upper Callovian) of South Cave Station Quarry, Yorkshire, UK

A single specimen of a new species of oribatid mite belonging to the genus Jureremus Krivolutsky, in Krivolutsky and Krassilov 1977, previously described from the Upper Jurassic of the Russian Far East, is described as J. phippsi sp. nov. The mite is preserved by iron pyrite replacement, and was recovered by sieving from the Oxford Clay Formation (Jurassic: Upper Callovian) of South Cave, Yorkshire. It is the first record of a pre-Pleistocene mite, and the second species record of the family Cymbaeremaeidae, from the British Isles; also, it is only the third record of Acari from the Jurassic Period. The presence of a terrestrial mite in a sedimentary sequence of open marine origin is noteworthy, and suggestions for its mode of transport to the site of deposition are discussed

The predatory rhagidiid mites (Acari: Prostigmata: Rhagidiidae) in stony debris

Miloslav Zachard

Foveacheles halltalensis Zacharda 2000, n. sp.

<i>Foveacheles halltalensis</i> n. sp. <p>(®gures 4±6)</p> <p> <i>Material examined</i></p> <p> All from Austria, Tyrol Alps. HOLOTYPE: adult female, deposited in the Canadian National Collection of Insects and Arachnids, Ottawa, in micropreparations, Type No. 22,404; Oetztal Alps, Obergurgl (11ss02¾E, 46ss52¾N), Neue Karlsruher HuÈ tte, about 2440 m altitude, under stones at foot of talus slope partly covered with soil and <i>Salix herbacea</i> and <i>Polytrichum</i> spp., 8 September 1993. PARATYPES: two adult females and two adult males, same data as holotype; two adult females, Festkogl mt, top plateau, 3000 m altitude, lower nival zone with sporadically occurring single plants of <i>Ranunculus glacialis</i>, <i>Silene acaulis</i> or <i>Cerastium cerastoides</i>; under stones covered with snow with springtails, 6 September 1993, otherwise same data as holotype; two adult females, Gurgler Schartl-mountain range, W of Obergurgl, upper border of alpine subnival zone about 2700 m altitude, under stones on talus slope covered with wet soil with <i>Polytrichum</i> spp., moss and <i>Salix herbacea</i>, 7 September 1993; one female, Halltal valley, collected in pitfall trap left in subterranean spaces of a talus slope from 23 June 1991 to 25 June 1992. All collected by M. Zacharda.</p> <p> <i>D iagnosis</i></p> <p> Chelicerae with elongated and attenuated digits and with lyri®ssure-like structure on ®xed digit positioned laterally and slightly distad of articulation of movable digit. Dorsal surface of ®xed digit with distinct narrow rim. Proximal cheliceral seta inserted distinctly distad of articulation of movable digit. Tip of proximal cheliceral seta not reaching insertion of distal seta. Rhagidial organ II consists of three rhagidial solenidia lying in tandem in conūent depressions and small spiniform famulus, <i>e</i>, subtending proximal rhagidial solenidion. Bothridial setae sc 1 short, not overlapping disjugal suture. Spiniform solenidion on genu I dorsodistal, on genu II dorsodistomedial and on genu III laterodorsal, medial. Solenidion on tibia IV medioproximal, dorsal.</p> <p> <i>D escription</i></p> <p> Adult female (eight examined). Length of idiosoma 1294(1040±1632) <i>m</i> m. Ratio of leg I length to idiosomal length 1.12(0.92±1.43).</p> <p> <i>Gnathosoma.</i> Subcapitulum broadly oval, subtriangular (®gure 5E); ratio of length to breadth 1.27(1.13±1.37); distal hypostomal lips with spiniform internal malar and external malar processes; adoral setae nude; proximal subcapitular setae ciliate, external pair slightly longer than internal pair. Chelicerae robust, dorsal surface with distinct broad saddle-shaped depression anterior to bases of digits (®gure 5A); cheliceral digits long, robust; dorsal surface of ®xed digit with distinct narrow rim; ®xed digit smooth along masticatory surface and with distinct laterodorsal longitudinal slit-like structure positioned slightly distad of articulation of movable digit; movable digit ®nely serrated along approximately distal third of masticatory surface. Chelicerae with two setae inserted distad of articulation of movable digit; tip of proximal seta not reaching insertion of distal seta; tip of distal seta overlaps apex of ®xed digit. Length of chelicera 307(287±333), dorsoventral width 132 (118±158), length of movable digit 108 (99±119), length of proximal and distal cheliceral setae 31 (26±36) and 42(39±46) <i>m</i> m, respectively, distance between their insertions 36(30±39) <i>m</i> m. Ratios: cheliceral length to dorsoventral width 2.33 (2.02±2.47); length of movable digit to length of chelicera 0.35(0.31±0.37); length of movable digit to dorsoventral width of chelicera 0.80 (0.75±0.89). Palpus robust, with relatively slender tarsus (®gure 5D); ratio of length to width of tarsus 2.75 (2.46±2.85). Length of palpal trochanter, femorogenu, tibia and tarsus 42 (39±46), 152 (145±158), 66 (59±76) and 125 (105±138) <i>m</i> m, respectively. Number of setae and solenidia (in brackets) on palpal trochanter, femorogenu, tibia and tarsus 0-2-3-10(1), respectively; tarsal solenidion spiniform, erect.</p> <p> <i>Prodorsum.</i> Naso well-developed, with pair of internal vertical setae v 1. Bothridial setae sc 1 ®liform, ®nely pubescent, relatively short, not reaching disjugal suture (®gure 4A). Length of setae: v 1 70 (69±73), v 2 53 (46±63), sc 1 99 (89±112), sc 2 133 (122±142) <i>m</i> m. A pair of eyes visible beside bases of setae sc 2.</p> <p> <i>Opisthosomal dorsum.</i> Complement and arrangement of dorsal setae and cupules typical for Rhagidiidae (®gure 4A); three pairs of cupules; ia positioned laterally at level about midway between setae c 1 and d 1, im lateral and anterior to setae e 1, ip lateral and anterior to setae f 2. Setae c 1, d 1, e 1 and f 1 reach about 0.35, 0.31, 0.28 and 0.62 of distance to insertion of successive seta, respectively. Length of setae: c 1 58 (53±66), c 2 139 (125±152), d 1 55 (46±63), e 1 54 (46±63), f 1 73 (46±86), f 2 59 (53±72), h 1 124(115±128), h 2 77 (69±86) <i>m</i> m.</p> <p> <i>Podosoma.</i> Coxisternal plates (epimeres) I, II, IV with 3-1-3 ®nely pubescent setae, respectively. Coxisternal plates III either symmetrically or asymmetrically with four to six setae (®gure 4B).</p> <p> <i>Genital region.</i> Genital valves each with usually ®ve ®nely pubescent setae of similar length, <i>ca</i> 31 (26±39) <i>m</i> m, arranged evenly along medial edge of valve (sometimes only four setae on one valve) (®gure 4B). Five pairs of aggenital (paragenital) setae of similar length, <i>ca</i> 46(36±49) <i>m</i> m. Length of genital valves 135(132±168) <i>m</i> m. Cupules ih positioned ventrolaterally, almost laterad of posteriormost pair of pseudanals.</p> <p> <i>L egs.</i> Leg I 1438 (1360±1520) <i>m</i> m long, 1.12 (0.92±1.43) as long as idiosoma. Empodia of all legs setulose, broadly oval in dorsoventral view, slightly longer than claws; no ventrobasal clawlets on claws. Number of setae and solenidia (solenidia and famulus, <i>e</i>, bracketed), respectively, on legs I-II-III-IV: trochanters 1-1-2-2; basif emora +telofemora 6 +5-6 +5-4 +4-4 +4; genua 11(1)-9(1)-7 (1)-6; tibiae 11 (2)-7 (2)-8(2)-7 (1); tarsi 19 (4 + <i>e</i>)-16(3 + <i>e</i>)-14-14 (®gure 6). Genu I with one erect dorsodistal spiniform solenidion, genu II with one dorsodistomedial spiniform solenidion, genu III with one laterodorsal medial spiniform solenidion. Tibia I with one dorsomedioproximal erect spiniform solenidion, and one dorsodistal rhagidial solenidion; tibia II with one laterodorsal, proximal spiniform solenidion, and one lanceolate dorsodistal solenidion recessed in deep pit with small surface pore; tibia III with two erect spiniform laterodorsal medial solenidia arranged in tandem; tibia IV with one erect spiniform dorsomedial solenidion. Tarsus I robust, its tip abruptly truncated in lateral view, ratio length to width 4.56(3.90±5.33), with four rhagidial solenidia lying obliquely in separate depressions, stellate famulus, <i>e</i>, subtends second proximal rhagidial solenidion antaxially (®gure 5B); tarsus II with three rhagidial solenidia lying in tandem in conūent depressions, small spiniform famulus, <i>e</i>, subtends proximal rhagidial solenidion (®gure 5C).</p> <p> <i>A nities</i></p> <p> See A nities for <i>Foveacheles gigantea</i> n. sp. and key to species of the <i>gigantea</i> - species group.</p> <p> <i>Etymology</i></p> <p> The name <i>halltalensis</i> refers to the region of Halltal, Northern Tyrol Alps, E of Innsbruck, Tyrol, where the ®rst specimen of this newly discovered species was collected in a talus formation.</p>Published as part of <i>Zacharda, Miloslav, 2000, New species of the rhagidiid genus Foveacheles (Acari: Prostigmata: Eupodoidea) with a lyri ® ssure-like structure on the chelicerae, pp. 247-265 in Journal of Natural History 34 (2)</i> on pages 253-258, DOI: 10.1080/002229300299624, <a href="http://zenodo.org/record/4747477">http://zenodo.org/record/4747477</a&gt