Region S2 Research Articles

Hydrochemical Assessment of the Irrigation Water Quality of the El-Salam Canal, Egypt

The El-Salam canal in Egypt is considered an important stream of fresh water for the agricultural sector that extends from the Nile River to Sinai, while it is subjected to several anthropogenic stresses. In this study, five-georeferenced stations (named from S1 to S5) were monitored along the El-Salam Canal before El-Sahara of the Suez Canal, via the estimation of the WQ index based on major cations and anions analysis including salinity hazard, permeability index, residual sodium carbonate, magnesium hazard, sodium percentage, sodium adsorption ratio, Kelley index, potential salinity, total hardness, and irrigation water quality index (IWQI). The sequence of average concentration of cations in water were Na+ > Ca2+ > Mg2+ > K+. The major cations constitute around 60% of the total dissolved salts. While the sequence of major anions in water were SO42− > HCO3− > Cl− > CO32−. These cations and anions showed an increasing trend from S1 (intake of the canal) to S5 (before El-Sahara) of the El-Salam Canal. Moreover, the order of heavy metals was Zn < Cd < Cr < Ni < Fe < Mn < Co < Cu < Pb. According to the US EPA (1999) guidelines, the levels of Fe and Zn in the El-Salam Canal are within the permissible limits for drinking and irrigation purposes, while Mn, Pb, Cu, Co, Ni, Cr, and Cd were detected at higher concentrations than those recommended. The value of IWQI in water samples varied from 40.26 to 114.82. The samples of S1 showed good water, the samples of region S2 (after mixing with Faraskour drainage) showed poor water quality, samples of regions S3 (after mixing with the El-Serw drain waters) and S5 (before El-Sahara) fell under the very poor water category and samples of region S4 (after mixing with the Hadous drainage) showed unsuitable water. Croplands irrigated with such water will not be exposed to any alkaline risks but will be exposed to the risk of salinity, which is more severe after mixing at the S3 and S4 sites. It is recommended to treat the drainage water before mixing with the irrigation water of El-Salam Canal to raise the suitability of irrigation water for crops, particularly for the Hadous drain.

Rocking response of self-centring wall with viscous dampers under pulse-type excitations

self-centering wall (SCW) is a lateral resistant rocking system that incorporates posttensioned (PT) tendons to provide a self-centering capacity along with dampers to dissipate energy. This paper investigates the rocking responses of a SCW with base viscous dampers under a sinusoidal-type pulse considering yielding and fracture behaviour of the PT tendon. The differences in the overturning acceleration caused by different initial forces in the PT tendon are computed by the theoretical method. The exact analytical solution to the linear approximate equation of motion is also provided for slender SCWs. Finally, the effects of the ductile behaviour of PT tendons on the rocking response of a SCW are analysed. The results demonstrate that SCWs exhibit two overturning modes under pulse excitation. The overturning region with Mode 1 in the PT force cases separates the safe region of the wall into two parts: region S1 with an elastic tendon and region S2 with a fractured tendon. The minimum overturning acceleration of a SCW with an elastic-brittle tendon becomes insensitive to excitation frequency as the PT force increases. After the plastic behaviour of the PT tendon is considered, the minimum overturning acceleration of a SCW is increased significantly in the whole range of the studied wg/p

Multiple P–T–d–t paths reveal the evolution of the final Nuna assembly in northeast Australia

AbstractThe final assembly of the Mesoproterozoic supercontinent Nuna was marked by the collision of Laurentia and Australia at 1.60 Ga, which is recorded in the Georgetown Inlier of NE Australia. Here, we decipher the metamorphic evolution of this final Nuna collisional event using petrostructural analysis, major and trace element compositions of key minerals, thermodynamic modelling, and multi‐method geochronology. The Georgetown Inlier is characterised by deformed and metamorphosed 1.70–1.62 Ga sedimentary and mafic rocks, which were intruded by c. 1.56 Ga old S‐type granites. Garnet Lu–Hf and monazite U–Pb isotopic analyses distinguish two major metamorphic events (M1 at c. 1.60 Ga and M2 at c. 1.55 Ga), which allows at least two composite fabrics to be identified at the regional scale—c. 1.60 Ga S1 (consisting in fabrics S1a and S1b) and c. 1.55 Ga S2 (including fabrics S2a and S2b). Also, three tectono‐metamorphic domains are distinguished: (a) the western domain, with S1 defined by low‐P (LP) greenschist facies assemblages; (b) the central domain, where S1 fabric is preserved as medium‐P (MP) amphibolite facies relicts, and locally as inclusion trails in garnet wrapped by the regionally dominant low‐P amphibolite facies S2 fabric; and (c) the eastern domain dominated by upper amphibolite to granulite facies S2 foliation. In the central domain, 1.60 Ga MP–medium‐T (MT) metamorphism (M1) developed within the staurolite–garnet stability field, with conditions ranging from 530–550°C at 6–7 kbar (garnet cores) to 620–650°C at 8–9 kbar (garnet rims), and it is associated with S1 fabric. The onset of 1.55 Ga LP–high‐T (HT) metamorphism (M2) is marked by replacement of staurolite by andalusite (M2a/D2a), which was subsequently pseudomorphed by sillimanite (M2b/D2b) where granite and migmatite are abundant. P–T conditions ranged from 600 to 680°C and 4–6 kbar for the M2b sillimanite stage. 1.60 Ga garnet relicts within the S2 foliation highlight the progressive obliteration of the S1 fabric by regional S2 in the central zone during peak M2 metamorphism. In the eastern migmatitic complex, partial melting of paragneiss and amphibolite occurred syn‐ to post‐ S2, at 730–770°C and 6–8 kbar, and at 750–790°C and 6 kbar, respectively. The pressure–temperature–deformation–time paths reconstructed for the Georgetown Inlier suggest a c. 1.60 Ga M1/D1 event recorded under greenschist facies conditions in the western domain and under medium‐P and medium‐T conditions in the central domain. This event was followed by the regional 1.56–1.54 Ga low‐P and high‐T phase (M2/D2), extensively recorded in the central and eastern domains. Decompression between these two metamorphic events is ascribed to an episode of exhumation. The two‐stage evolution supports the previous hypothesis that the Georgetown Inlier preserves continental collisional and subsequent thermal perturbation associated with granite emplacement.

Two‐stage Variscan metamorphism in the Canigou massif: Evidence for crustal thickening in the Pyrenees

AbstractThe Variscan metamorphism in the Pyrenees is dominantly of the low‐pressure–high‐temperature (LP‐HT) type. The relics of an earlier, Barrovian‐type metamorphism that could be related to orogenic crustal thickening are unclear and insufficiently constrained. A microstructural and petrological study of micaschists underlying an Ordovician augen orthogneiss in the core of the Canigou massif (Eastern Pyrenees, France) reveals the presence of two syntectonic metamorphic stages characterized by the crystallization of staurolite (M1) and andalusite (M2), respectively. Garnet is stable during the two metamorphic stages with a period of resorption between M1 and M2. The metamorphic assemblages M1 and M2 record similar peak temperatures of 580°C at different pressure conditions of 5.5 and 3 kbar, respectively. Using chemical zoning of garnet and calculated P–T pseudosections, a prograde P–T path is constrained with a peak pressure at ~6.5 kbar and 550°C. This P–T path, syntectonic with respect to the first foliation S1, corresponds to a cold gradient (of ~9°C/km), suggestive of crustal thickening. Resorption of garnet between M1 and M2 can be interpreted either in terms of a simple clockwise P–T path or a polymetamorphic two‐stage evolution. We argue in favour of the latter, where the medium‐pressure (Barrovian) metamorphism is followed by a period of significant erosion and crustal thinning leading to decompression and cooling. Subsequent advection of heat, probably from the mantle, leads to a new increase in temperature, coeval with the development of the main regional fabric S2. LA‐ICP‐MS U–Th–Pb dating of monazite yields a well‐defined date at c. 300 Ma. Petrological evidence indicates that monazite crystallization took place close to the M1 peak pressure conditions. However, the similarity between this age and that of the extensive magmatic event well documented in the eastern Pyrenees suggests that it probably corresponds to the age of monazite recrystallization during the M2 LP‐HT event.

Roles of surface wind, NDVI and snow cover in the recent changes in Asian dust storm occurrence frequency

This paper describes the recent variations in dust outbreak during the period from 1996 to 2007 over the Asian dust source regions. The Asian dust source regions were divided into four sub-regions; S1, Taklamakan; S2, Gobi; S3, Inner Mongolia-Manchuria; and S4, Loess, and the WMO SYNOP observation and satellite data were employed to analyze the features of recently changed dust outbreak frequencies (DOFs). There was no particular variation in region S1, but the recent spatiotemporal variations in DOFs over S2–S4 were well characterized by a severe and widespread increase in 2001–2002, and significant decreasing in 2003–2004 over the most source regions, with a steadily increasing trend again during 2005–2007. Seasonal features showed that the highest DOFs occurred in March–April before 2002, but was delayed by a month toward April–May during the next five years because of the shift in the month of highest strong wind-speed frequencies (SWFs). A secondary peak of DOF was also found, occurring in October–November since the year 2000. Over all the source regions, the primary controlling factor for explaining the spatiotemporal DOF patterns was the SWF, with a pattern correlation coefficient (PCC) of 0.66–0.76. Other secondary controlling factors varied from region to region. For example, the DOFs observed in region S2–S3 showed relatively greater sensitivity to the snow-cover fraction, and region S4 showed a better correlation with the normalized difference vegetation index (NDVI) than the other regions. Other recent significant changes in DOFs over the Asian dust source regions and their causes are also discussed in this study.

Lithostratigraphic setting and P-T metamorphic evolution for the Dora Maira Massif along the Piedmont Zone boundary (middle Susa Valley, NW Alps)

A new structural and petrological study, associated with a detailed geological mapping, allowed to better understand the tectonic relationships between the Dora Maira Massif and the Piedmont Zone in the middle Susa Valley. In the study area, a thick sequence of calcschists, previously attributed to the stratigraphic cover of the Dora Maira, is interpreted as belonging to the Piedmont Zone. Four deformation phases were identified: D1 represents the eclogite facies stage, D2 developed under greenschist facies conditions, transposed the early foliation and was responsible for the development of the regional schistosity S2. D3 is characterized by close to open folds with N dipping axial surfaces and finally, D4 developed macro-scale folds with E-dipping axial planes. Structural analyses allow to infer a relative timing for the tectonic contact between the two nappes which were coupled after the eclogite facies metamorphism but before the development of the S2 foliation under greenschist facies conditions. Petrographic investigation into metapelite samples permitted to identify two main metamorphic assemblages within the Dora Maira polymetamorphic basement: M1 (Phe + Pg + Cld + Grt + ChlI + Qtz + Rt) assemblage defines the S1 relict foliation, while M2 (Ms + Pg + Ab + ChlII + Qtz + Ilm ± Bt) assemblage is related to the regional foliation S2. PERPLE_X pseudosection modelling allowed to reconstruct a P-T path for a garnet–chloritoid-bearing micaschist from the northern part of the Dora Maira Massif, which reached eclogite facies conditions at 18–20 kbar and 515–525°C (M1/S1 event) and then was exhumed during increasing T (10–11 kbar and 555–565°C). The M2 assemblage defining the S2 regional foliation developed at P < 7 kbar and T < 575°C. According to the structural evolution, the tectonic coupling between Dora Maira and Piedmont Zone took place during exhumation along the subduction channel.

Designing near-perfect invisibility cloaks

Invisibility cloaks are a favorite device used by science-fiction and fantasy authors. Yet, despite the fact that invisibility fascinates many people, its practical realization has rarely been treated as a serious research topic in science and technology. Very recently, researchers noticed that one can deduce the exact material requirement for making a completely passive cloaking device using the theory of transformation optics.1, 2 The basic principle is illustrated in Figure 1. Even for the simplest cylindrical cloak structure, however, the ideal material parameters prove difficult to match with current metamaterial fabrication technology. Therefore, one would prefer to simplify the material required for a cloak. Here we describe two promising approaches for constructing a simplified cylindrical invisibility cloak that should ease implementation while retaining good performance. In a cylindrical coordinate system (r, θ, z), one can simplify the cloak’s materials parameters ez, μθ , and μr for normal wave incidence—with a single transverse electric (TE) polarization (in which the electric field is solely aligned along the axial or z direction of the cloak)—by keeping intact the products ezμθ and ezμr. In the simplest case, a cylindrical cloak can be obtained through linear radial spatial mapping, i.e. r′ = (r− a) b b−a , where a and b are the cloak’s inner and outer radii, respectively, and r′ and r are the radial coordinates in electromagnetic and physical spaces, respectively. The corresponding ideal material parameters are shown in the left column of Table 1. Based on this ideal cloak, a simplified version, as proposed by John Pentry’s group3, has material parameters shown in the middle column in Table 1. However, such a simplified cloak still scatters electromagnetic fields considerably, largely due to its unmatched impedance to free space.4 Wepropose a new version of a simplified cylindrical cloak that restores impedance matching to the space outside the cloak. We do not vary the products ezμθ and ezμr. This improved set of Figure 1. Formatting a cloak of an arbitrary shape by transformation optics (a): and (b) depict correlated coordinates’ lines in electromagnetic space and physical space, respectively. A void region S2 in (b) has appeared, which is obtained by blowing up a point (or a line, if the structure is invariant along the paper-normal direction) of zero size in (a). The annular shape bounded by S1 and S2 in (b) is electromagnetically equivalent to the region bounded by S1 in (a). However the regions’ material parameters are different owing to a change of coordinate. The region bounded by S1 and S2 in (b) constitutes a cloak, whose interior can conceal objects. Notice that the coordinate changes only for a finite spatial region bounded by S1 in both panels. As a consequence, the material outside S1 (which we assume is air) remains the same in both panels.

Structural Controls on Gold Mineralization at the Burnt Timber Mine, Lynn Lake Greenstone Belt, Trans-Hudson Orogen, Manitoba

The Burnt Timber gold deposit is located in the Paleoproterozoic Lynn Lake greenstone belt of the Trans-Hudson Orogen, Manitoba. The deposit occurs along the Johnson shear zone, and is hosted by enriched and depleted tholeiitic volcanic arc basalts cut by feldspar porphyry dikes. The Johnson shear zone is a regional, belt-parallel structure characterized by the intensification of the regional S2 foliation. At the Burnt Timber deposit, S2 is folded by centimeter- to meter-scale, Z-shaped, F3 chevron folds that have an axial planar S3 crenulation cleavage. Within the 20 to 30 m-wide core zone of the shear zone, S2 and F3 are transposed parallel to S3 and the volcanic rocks are strongly sheared parallel to S3. The presence of a steeply plunging stretching lineation, together with dextral shear sense indicators along both S2 and S3 on horizontal surfaces, suggest that the Johnson shear zone is a dextral transpression zone. Gold was introduced in pyritic, biotitic, and carbonatized mafic volcanic rocks along the core of the shear zone. Mylonitic mafic volcanic rocks contain localized high-grade zones (≥10 g/t Au) that differ from wider carbonatized, low-grade zones (<3 g/t Au) by the presence of deformed gold-bearing quartz- pyrite veins. High-grade zones are also associated with swarms of quartz-pyrite veins that cut across sericitized and carbonatized feldspar porphyry dikes, which acted as brittle, competent bodies during shearing. Gold deposition in the high-grade zones was controlled by the channeling of hydrothermal fluid along the core of the shear zone during shearing of the volcanic rocks, and brittle fracturing of the porphyry dikes. © 2006 Canadian Institute of Mining, Metallurgy and Petroleum. All rights reserved.

Relative timing of deformational, metamorphic and mineralisation events at the Mt. Todd (Yimuyn Manjerr) Mine, Pine Creek Inlier, Northern Territory, Australia

The Mt. Todd Mine (also known as the Yimuyn Manjerr Mine), located approximately 40 km northwest of the township of Katherine, in the Northern Territory, Australia, is host to several discrete ore bodies that strike NNE within a broad NE-trending corridor of gold mineralisation. The mine lies in the southern region of the Central Domain of the Pine Creek Inlier (PCI) and is hosted by a Palaeoproterozoic sequence of rocks termed the Burrell Creek Formation, which is dominated by greywacke, siltstone, sandstone and shale that exhibit sedimentary features akin to those of a river-dominant delta front to prodelta environment. The formation is conformably overlain by volcanoclastic and volcanolithic sedimentary rocks of the Tollis Formation (∼1890 Ma). Three deformation events are recognised in the Mt. Todd region, D1, D2 and D3. The earliest deformation, D1, is characterised by close to tight, NE to N to NW-trending asymmetric folds (F1), and a continuous axial–planar cleavage (S1). The deformation is associated with the development of conjugate buck–quartz veins and was preceded by the emplacement of the Yenberrie Leucogranite, which produced contact metamorphism of the sedimentary rocks of the Burrell Creek Formation to hornblende–hornfels facies (H1), with the development of cordierite porphyroblasts (type C1). D1 was coincident with peak regional metamorphism to greenschist facies. D2 is associated with westerly trending open folds (F2), and a spaced disjunctive to fracture cleavage (S2) in transection to the folds. It was preceded by the emplacement of the Tennysons Leucogranite of the Cullen Batholith (1835–1820 Ma), which produced contact metamorphism of the Yenberrie Leucogranite and the sedimentary rocks of the Burrell Creek and Tollis formations to hornblende–hornfels facies (H2), with the development of cordierite porphyroblasts (type C2). D3 is characterised by the reactivation of strike-slip faults (mostly sinistral), a steeply dipping Type S3-C type foliation, and mesoscopic en échelon folds (F3) that trend oblique to the faults in a left stepping (sinistral) array. The age of emplacement of the Tennysons Leucogranite, and the timing of D1 and D2 are broadly constrained by the age of emplacement of the Cullen Batholith at 1835–1800 Ma. D1 and D2 are correlated with deformation during the Maud Creek Event (∼1850 Ma), while D3 is correlated with deformation during the Shoobridge Event (∼1780 Ma). The age of the Yenberrie Leucogranite is constrained to the age of emplacement of granite batholiths at 1870–1860 Ma. A temporal and broad structural relationship exists between D2 structures, the Tennysons Leucogranite, and the several gold-bearing quartz–sulphide veins and lode systems of the Mt. Todd Mine. The systems appear to have formed after peak thermal metamorphism associated with the emplacement of the pluton at about 1825 Ma, and early in D2, prior to the development of the regional S2 fabric. W–Mo–Sn–Bi–Cu greisen-type mineralisation in the carapace of the Yenberrie Leucogranite of the Yenberrie Wolfram Field constitutes a discrete mineralising event that preceded the emplacement of the Tennysons Leucogranite.

Delamerian Glenelg tectonic zone, western Victoria: Characterisation and synthesis of igneous rocks

Cambro‐Ordovician plutonic rocks of the Glenelg River Complex (western Victoria) are grouped into three structural associations based on intrusion timing relative to Delamerian deformational episodes. Early syn‐compressional plutons contain the regional S2 foliation and comprise the Wando, Wennicott and Deep Creek granitic types, which have low K affinity and are confined to the southwestern corner of the complex. Wando types include hornblende diorite to gneissic tonalite and contain numerous mafic igneous enclaves; high Al2O3 and increasing K2O with silica are characteristic. Hornblende tonalites of Wennicott type are less deformed and by contrast evolve towards lower K2O, whereas the geochemistry of Deep Creek type granodiorites suggests plagioclase accumulation. The nearby Caupaul Igneous Complex also developed at this time and encompasses hornblende tonalite through diorite, gabbronorite and pyroxenite. Tonalitic and dioritic rocks are geochemically equivalent and exhibit a steep increase in K2O with silica, implying compositional control by fractional crystallisation, though relationships to cumulate rocks are obscure. Crystallisation of foliated hornblende tonalites is estimated at ∼460–660 MPa from hornblende‐plagioclase geobarometry. These rocks were supplanted by late syn‐compressional plutons of the Tuloona, Harrow and Loftus Creek magma types, which post‐date D2, but are weakly deformed by D5. Tuloona types are predominantly tonalitic and comprise the elongate central granitic batholith. Mafic igneous enclaves are ubiquitous, although more felsic varieties have magmatic muscovite and are complexly interleaved with migmatites. Harrow type granitic rocks to the northeast contain abundant muscovite, metasedimentary enclaves and are transitional to migmatitic envelopes, consistent with derivation by in situ anatexis of the host metasedimentary sequence. The subsequent transition to higher K magmatism is marked by intrusion of Loftus Creek type hornblende granodiorite, of which biotite phenocrysts and a high Sr signature are diagnostic. Considerably shallower emplacement levels (∼200–360 MPa) require exhumation of up to 11 km of crust after formation of Tuloona types. Following cessation of compressional deformation, the final igneous activity in the Glenelg River Complex involved intrusion of distinctive K‐rich adamellite and granite in the far west. This coherent plutonic sequence is more elaborate than documented from the eastern Mt Lofty Ranges in South Australia and conveys a more dynamic impression of magmatism within the trans‐Gondwana Delamerian Orogen than has hitherto been appreciated.

Vacuolating cytotoxin (vacA) alleles of Helicobacter pylori comprise two geographically widespread types, m1 and m2, and have evolved through limited recombination.

Vacuolating cytotoxin (vacA) alleles of Helicobacter pylori vary, particularly in their mid region (which may be type m1 or m2) and their signal peptide coding region (type s1 or s2). We investigated nucleotide diversity among vacA alleles in strains from several locales in Asia, South America, and the USA. Phylogenetic analysis of vacA mid region sequences from 18 strains validated the division into two main groups (m1 and m2) and showed further significant divisions within these groups. Informative site analysis demonstrated one example of recombination between m1 and m2 alleles, and several examples of recombination among alleles within these groups. Recombination was not sufficiently extensive to destroy phylogenetic structure entirely. Synonymous nucleotide substitution rates were markedly different between regions of vacA, suggesting different evolutionary divergence times and implying horizontal transfer of genetic elements within vacA. Non-synonymous/synonymous rate ratios were greater between m1 and m2 sequences than among m1 sequences, consistent with m1 and m2 alleles encoding functions fitting strains for slightly different ecological niches.

Thermal evolution of the central Halls Creek Orogen, northern Australia

The Halls Creek Orogen in northern Australia records the Palaeoproterozoic collision of the Kimberley Craton with the North Australian Craton. Integrated structural, metamorphic and geochronological studies of the Tickalara Metamorphics show that this involved a protracted episode of high‐temperature, low‐pressure metamorphism associated with intense and prolonged mafic and felsic intrusive activity in the interval ca 1850–1820 Ma. Tectonothermal development of the region commenced with an inferred mantle perturbation event, probably at ca 1880 Ma. This resulted in the generation of mafic magmas in the upper mantle or lower crust, while upper crustal extension preceded the rapid deposition of the Tickalara sedimentary protoliths. An older age limit for these rocks is provided by a psammopelitic gneiss from the Tickalara Metamorphics, which yield a 207Pb/206Pb SHRIMP age of 1867 ± 4 Ma for the youngest detrital zircon suite. Voluminous layered mafic intrusives were emplaced in the middle crust at ca 1860–1855 Ma, prior to the attainment of lower granulite facies peak metamorphic conditions in the middle crust. Locally preserved layer‐parallel D1 foliations that were developed during prograde metamorphism were pervasively overprinted by the dominant regional S2 gneissosity coincident with peak metamorphism. Overgrowths on zircons record a metamorphic 207Pb/206Pb age of 1845 ± 4 Ma. The S2 fabric is folded around tight folds and cut by ductile shear zones associated with D3 (ca 1830 Ma), and all pre‐existing structures are folded around large‐scale, open F4 folds (ca 1820 Ma). Construction of a temperature‐time path for the mid‐crustal section exposed in the central Halls Creek Orogen, based on detailed SHRIMP zircon data, key field relationships and petrological evidence, suggests the existence of one protracted thermal event (>400–500°C for 25–30 million years) encompassing two deformation phases. Protoliths to the Tickalara Metamorphics were relatively cold (∼350°C) when intruded by the Fletcher Creek Granite at ca 1850 Ma, but were subsequently heated rapidly to 700–800°C during peak metamorphism at ca 1845 Ma. Repeated injection of mafic magmas caused multiple remelting of the metasedimentary wall rocks, with mappable increases in leucosome volume that show a strong spatial relationship to these intrusives. This mafic igneous activity prolonged the elevated geotherm and ensured that the rocks remained very hot (≥650°C) for at least 10 million years. The Mabel Downs Tonalite was emplaced during amphibolite facies metamorphism, with intrusion commencing at ca 1835 Ma. Its compositional heterogeneity, and the presence of mutual cross‐cutting relations between ductile shear zones and multiple injections of mingled magma suggest that it was emplaced syn‐D3. Broad‐scale folding attributable to F4 was accompanied by widespread intrusion of granitoids, and F4 fold limbs are truncated by large, mostly brittle retrograde S4 shear zones.

Typing of Helicobacter pylori vacA gene and detection of cagA gene by PCR and reverse hybridization.

The present report describes an analysis of two virulence genes of Helicobacter pylori. Parts of the cagA gene, as well as parts from the signal (s) and middle (m) regions of the mosaic vacA gene, were amplified with biotin-labelled PCR primers and the products were subsequently analyzed by a single-step reverse hybridization line probe assay (LiPA). This assay comprises a strip containing multiple specific probes for the vacA s region (sla, slb, and s2 alleles), the vacA m region (ml and m2 alleles), and the cagA gene. A total of 103 H. pylori-positive materials, including cultured isolates, gastric biopsy specimens, and surgical specimens from patients living in Portugal (n = 55) and The Netherlands (n = 48) were tested by the PCR-LiPA. cagA was detected in 84 and 73% of the Portuguese and Dutch patients, respectively. vacA typing results, as determined by reverse hybridization, were completely concordant with those of sequence analysis. Most Portuguese patients (72%) contained type slb, whereas most Dutch patients (61%) contained type sla (P < 0.001). The method is also very effective at detecting the presence of multiple genotypes in a single biopsy specimen. The prevalence of multiple strains in Portuguese patient samples was significantly higher (29%) than that in Dutch patient samples (8%) (P = 0.001). There was a significant association between the presence of ulcers or gastric carcinoma and the presence of vacA type sl (sla or slb; P = 0.008) and cagA (P = 0.003) genes.

Diachronous fluid release and veining associated with out‐of‐sequence thrusts in the north Scandinavian Caledonides

The Ose Thrust of northern Norway represents a major late Caledonian out‐of‐sequence thrust which duplicates a previously assembled nappe stack with inverted metamorphic gradient. Fluid flow along this thrust gave rise to retrogression of peak metamorphic porphyroblastic phases in both footwall and hangingwall. Chlorite pseudomorphs after garnet are not smeared out suggesting that retrogression largely post‐dates thrust movement. Dominated by vein quartz, the 0se Thrust and adjacent footwall and hangingwall rocks record three stages of veining in a protracted history of fluid flow; schistosity‐parallel, prograde and peak metamorphic veins (VA‐VB), and retrogression‐related (post‐D3) veins which cross‐cut the regional S2 schistosity (Vc). Vc veins contain similar highly saline fluid inclusions to those associated with early ductile thrusts from the region. This indicates that various thrusts in the north Scandinavian Caledonides acted passively as important fluid conduits for late‐stage fluid flow and retr...

Kinematic evolution of metre-scale shear zones in foliated low-grade tectonites: an example from the Bousquet gold district, Quebec

Small-scale subvertical shear zones developed parallel to a regional preexisting S2 schistosity exhibit evidence of a complex shearing history recorded by conflicting kinematic indicators in both crosssection and plan view. The concordant schistosity internal to the shear zones contains a steeply plunging stretching lineation. Coexisting kinematic indicators of non-coaxial deformation parallel to this lineation are compatible with reverse dip-slip. This earliest shearing event was characterized by (1) the development of several shear discontinuities along selected preexisting S2 foliation surfaces, (2) subvertical transposition of both bedding and the oldest (S1) flat-lying foliation, and (3) by the emplacement of shear veins along the S2 foliation planes. The youngest shearing event reactivated the foliation-parallel shear discontinuities as dextral shear planes, thereby causing concomitant subhorizontal retransposition, east–west subhorizontal stretching, and emplacement of en echelon extension veins. A single set of shear bands occurring at a clockwise acute angle to the slipping foliation indicates that small-scale shear zones were transpressional during the late dextral shearing.

Metamorphosed fragments of oceanic crust in the upper Paleozoic Chonos accretionary complex, southern Chile

A 15 km2 body of metabasite with occasional pillow structures occurs within the Paleozoic accretionary complex in Isla Italia and Isla Dring. Trace elements and REE geochemistry indicate similarities between the metabasites and either plume-related mid-oceannic ridge basalts (P-type MORB) or ocean-island tholeiite basalte. The chemistry of relict clinopyroxenes is also indicative of an ocean-floor basalt protolith. The metabasites exhibit very low-grade metamorphism (pumpellyite-stilpnomelane-actinolite assemblage), comparable to the grade of the sorrounding semi-pelitic mélange as determined by illite crystallinity studies. Isotopic modification of the Rb-Sr system in the metabasites occurred during high fluid-pressure metamorphism, probably by introduction of metamorphic fluids from the sorrounding metapelites. A relatively early tectonic emplacement of the body into the accretionary complex before metamorphism and the generation of the main regional S2 foliation is proposed to explain these characteristics, in contrast to its previous interpretation as a late intrusion into the sorrounding metamorphic rocks.

Some research problems about algebraic differential equations II

Twenty-four new research problems are posed, and their background and partial solutions are sketched. Many of these problems are in the (somewhat unexpected) area of interaction between algebraic differential equations, topology, and mathematical logic. Introduction. What has struck me most about the subject of algebraic differential equations (ADEs) is how easy it is to pose hard problems. Another way of saying the same thing is that the subject is still in a formative state, with many fundamental problems not even posed, much less solved. I am going to present the first part (Problems 1-3) of this paper as I first wrote it. Thereis a rather dramatic twist at its end, as you will see. Explanatory section. An algebraic differential equation (ADE) is just one where the left-hand side is a polynomial in everything. More specifically, let P(x0, xl,... ,xn+,) be a polynomial in n + 2 variables, not the zero polynomial, with complex coefficients, or with real coefficients according to the context. Then the equation (1) P(z, w(z), W'(Z),. . . ,W(n)(Z)) = 0 is called an ADE. We may write this as (1') P (Z, W)=O. In the real case, we prefer to write (2) P(x, y(x), y'(x),. . . ,y(n)(x)) = 0 or just (2') P(x, y) =0. In both of these contexts, we call P a differentialpolynomial. What we mean by a solution of an ADE depends somewhat on the context. In the complex case it will mean an analytic (or sometimes a meromorphic) function on a region S2 that satisfies (1). When this happens, we call w(z) a hypotranscendental function. If w(z) satisfies no ADE, then it is assigned the beautiful adjective transcendentally transcendental. (See [OST] for a good introduction to this subject. In Received by the editors January 14, 1982. 1980 Mathematics Subject Classification. Primary 34-XX, 34A34. The research of the author was partially supported by a grant from the National Science Foundation. ?1983 American Mathematical Society 0002-9947/83 $1.00 + $.25 per page

Analysis of the Newly Identified Neutralization Epitopes on VP7 of Human Rotavirus Serotype 1

Neutralizing monoclonal antibodies (MAbs) directed to the VP7 protein and neutralization-resistant mutants were used to analyse the antigenic structure of VP7 of human rotavirus serotype 1. Cross-neutralization tests using the MAbs and the resistant mutants indicated the existence of two functionally independent neutralization epitope regions (S1 and S2) on VP7. Region S1 corresponds to a single epitope domain of VP7 which has been detected previously. Two MAbs prepared in this study recognized the S1 region, and the resistant mutants they selected had amino acid substitutions at positions 94 or 213. On the other hand, region S2 is considered to be a novel epitope. Single or double amino acid substitutions were detected in the variable regions (amino acid positions 145, 217 and 221) and in the constant regions (positions 104, 201 and 291) of the VP7 protein of mutants selected by MAbs directed to the S2 region. It was suggested that the variable region E (amino acids 208 to 221) includes two independent neutralization sites, and that amino acid substitutions in the constant region of VP7 also affect serotype-specific neutralization epitopes. Neutralization epitopes on VP7 are considered to be highly dependent on the conformation of VP7.

Numerical solution of a three-part mixed boundary value problem of linear elastostatics

A three-part mixed boundary value problem for the half-space z ⩾ 0 (with Neumann conditions prescribed over a finite doubly connected region S2 and Dirichlet conditions prescribed over the remaining of the z = 0 plane) is formulated to result into a system of two coupled integral equations. A procedure is outlined for the approximate solution of the problem under consideration for an arbitrary shape of the region S2. For the special axisymmetric case when the region S2 is a circular annulus of inner and outer radii a and b, respectively, the system of integral equations is reduced to a Fredholm integral equation of the second kind with a continuous non-symmetric kernel. The resulting integral equation is solved numerically and the results are found to be in good agreement with those previously published.