Margin Of Zone Research Articles

Long recurrence interval of faulting beyond the 2005 Kashmir earthquake around the northwestern margin of the Indo-Asian collision zone

The 2005 Kashmir earthquake in Pakistan occurred on a previously mapped active fault around the northwest margin of the Indo-Asian collision zone. To address the quantitative contribution of the earthquake to plate convergence, we performed paleoseismological trench excavations at Nisar Camp site near Muzaffarabad across the middle section of the 2005 surface rupture. The fault strands exposed in the trench cut late Holocene fluvial deposits and record evidence of both the 2005 and a penultimate event, supported by the presence of colluvial deposits and a downdip increase in displacement along the fault strands. The 2005 event produced a net slip of 5.4 m, and the penultimate earthquake exhibits a similar amount of slip. Radiocarbon ages and historical accounts loosely constrain the timing of the penultimate event between 500 and 2200 yr B.P.; however, the exposed section encompasses ~4 k.y. of stratigraphy, suggesting an average interevent interval of ~2 k.y. for the 2005 type events. We thus conclude that the 2005 event did not occur on the plate boundary megathrusts, but on intraplate active faults within the Sub-Himalaya. Consequently, the accumulated elastic strain around the complex northwestern margin of the Indo-Asian collision zone has not been significantly released by the 2005 earthquake.

Sensitivity Analysis to Operation Margin of Zone 3 Impedance Relays With Bus Power and Shunt Susceptance

Zone 3 impedance relays are sensitive to power-flow distribution due to their overreaching property, and may undesirably operate in stressed system conditions with reactive power shortages or neighboring faults. In this paper, the distance of the apparent impedance to the protection boundary on the R-X plane is defined by the operation margin, which is expressed as the function of bus voltages. The sensitivities of the operation margin to bus voltages, bus powers, and shunt susceptances quantify the influence of various disturbances on the relay performance. The numerical results show: (1) the operation margin is quantified by the sensitivities with satisfying accuracy and less computation effort compared with power-flow schemes; (2) the variation of bus powers and shunt susceptances at different locations may improve or decrease the operation margin; and (3) the variation of active and reactive powers at the same bus may yield opposite effects on the operation margin.

Developmental regulation of muscleblind‐like (MBNL) gene expression in the chicken embryo retina

Muscleblind-like (MBNL) is a CCCH zinc finger-containing RNA-binding protein required for the development of both muscle and photoreceptors in Drosophila; it is conserved evolutionarily, and it is associated in humans with the muscular disease myotonic dystrophy. Its role in the development of vertebrate retinal cells, however, remains unknown. As an initial approach to its investigation, we have cloned three chick muscleblind genes, characterized their isoforms, and examined their expression patterns in the chick embryo retina. The relative levels of expression of the MBNL genes increased during embryonic development. In situ hybridization (ISH) showed that the three MBNL mRNAs had widespread patterns of expression at all the developmental stages examined. Of interest, the temporal and spatial patterns of protein expression, detected by immunocytochemistry with antibodies against MBNL1 and MBNL2, were much more restricted than those seen by ISH. At early stages (ED5-7), for example, MBNL1 and MBNL2 mRNAs were present throughout the retina, but immunoreactivity for the corresponding proteins was largely restricted to the periphery of the optic cup (presumptive iris/ciliary epithelium/ciliary margin zone). MBNL1 and MBNL2 immunoreactivity became detectable at the fundus at later stages, but was limited to a very small subset of the cells that had ISH signals for the cognate mRNAs (particularly ganglion cells and photoreceptors). Within photoreceptors, MBNL1 and MBNL2 immunoreactivity first appeared in their inner segments; MBNL2 remained there, but MBNL1 became subsequently localized to their synaptic terminals. These expression patterns are consistent with the possibility that MBNLs may regulate photoreceptor development in the chick retina, much as MBL does in Drosophila, and suggest that the expression of MBNL1 and MBNL2 may be regulated posttranscriptionally.

Tethyan and Indian subduction viewed from the Himalayan high- to ultrahigh-pressure metamorphic rocks

The Himalayan range is one of the best documented continent-collisional belts and provides a natural laboratory for studying subduction processes. High-pressure and ultrahigh-pressure rocks with origins in a variety of protoliths occur in various settings: accretionary wedge, oceanic subduction zone, subducted continental margin and continental collisional zone. Ages and locations of these high-pressure and ultrahigh-pressure rocks along the Himalayan belt allow us to evaluate the evolution of this major convergent zone. (1) Cretaceous (80–100 Ma) blueschists and possibly amphibolites in the Indus Tsangpo Suture zone represent an accretionary wedge developed during the northward subduction of the Tethys Ocean beneath the Asian margin. Their exhumation occurred during the subduction of the Tethys prior to the collision between the Indian and Asian continents. (2) Eclogitic rocks with unknown age are reported at one location in the Indus Tsangpo Suture zone, east of the Nanga Parbat syntaxis. They may represent subducted Tethyan oceanic lithosphere. (3) Ultrahigh-pressure rocks on both sides of the western syntaxis (Kaghan and Tso Morari massifs) formed during the early stage of subduction/exhumation of the Indian northern margin at the time of the Paleocene–Eocene boundary. (4) Granulitized eclogites in the Lesser Himalaya Sequence in southern Tibet formed during the Paleogene underthrusting of the Indian margin beneath southern Tibet, and were exhumed in the Miocene. These metamorphic rocks provide important constraints on the geometry and evolution of the India–Asia convergent zone during the closure of the Tethys Ocean. The timing of the ultrahigh-pressure metamorphism in the Tso Morari massif indicates that the initial contact between the Indian and Asian continents likely occurred in the western syntaxis at 57 ± 1 Ma. West of the western syntaxis, the Higher Himalayan Crystallines were thinned. Rocks equivalent to the Lesser Himalayan Sequence are present north of the Main Central Thrust. Moreover, the pressure metamorphism in the Kaghan massif in the western part of the syntaxis took place later, 7 m.y. after the metamorphism in the eastern part, suggesting that the geometry of the initial contact between the Indian and Asian continents was not linear. The northern edge of the Indian continent in the western part was 300 to 350 km farther south than the area east of the Nanga Parbat syntaxis. Such “en baionnette” geometry is probably produced by north-trending transform faults that initially formed during the Late Paleozoic to Cretaceous Gondwana rifting. Farther east in the southern Tibet, the collision occurred before 50.6 ± 0.2 Ma. Finally, high-pressure to ultrahigh-pressure rocks in the western Himalaya formed and exhumed in steep subduction compared to what is now shown in tomographic images and seismologic data.

Through the eye of a book... on the eye

The retina is perhaps our most intricate and well-studied sensory structure. It receives visual information from the outside world and interprets this information as color, shape and movement, and then transmits it to visual centers in the brain in the form of coded impulses. The embryonic and early

Microstructural evolution within a partitioned midcrustal transpression zone, northeast Greenland Caledonides

The thrust‐related Imbricate Zone and the sinistral strike‐slip Storstrømmen Shear Zone (SSZ) are two major orogen‐parallel ductile shear zones that mark the western limit of intense Caledonian deformation in northeast Greenland and transect the orogenic hinterland, respectively. Detailed microstructural analysis of associated mylonitic fault rocks from Dronning Louise Land and Hertugen af Orléans Land has been carried out to provide insights into the evolution of these structures and to constrain the relative timing of movement. Amphibolite‐facies mylonites were developed across the entire ca. 8‐km‐wide SSZ and are currently exposed across an area ca. 3–4 km wide within the center of the shear zone. In contrast, retrograde greenschist‐facies mylonites are concentrated within a ca. 2‐ to 4‐km‐wide belt along the western margin of the shear zone. This metamorphic pattern is interpreted to reflect progressive localization of strain associated with exhumation and syntectonic cooling. The ca. 15‐km‐wide Imbricate Zone consists of numerous east‐dipping ductile thrust sheets. At low structural levels, mylonitic fabrics indicate that thrust‐related deformation occurred at middle‐greenschist facies. Toward higher levels, however, microstructures suggest that the metamorphic grade progressively increases. We propose that ductile thrusting across the Imbricate Zone was synchronous with uplift and exhumation of the orogenic hinterland and SSZ, accounting for the observed metamorphic variations. This implies that both structures were active broadly contemporaneously during regional partitioned transpression, an inference supported by scattered 40Ar/39Ar and recent U‐Pb zircon ages. The microstructural observations therefore support models that involve sinistrally oblique Silurian‐Devonian collision between Laurentia and Baltica.

Mapping of Epicardial Activation in a Rabbit Model of Chronic Myocardial Infarction:

This study examines the consequences of a large transmural apical infarct on the epicardial electrical activity in isolated rabbit hearts. Hearts were isolated 8 weeks after coronary artery ligation. Membrane voltage from the epicardial surface of the left ventricle (LV) including the infarct was monitored using the voltage sensitive dye RH237. Optical action potentials were detected from the epicardial surface of the infarct; the signal amplitude was approximately 20% of those in the noninfarcted zone (NZ). Epicardial activation mapping of the LV free wall showed that during right atrial (RA) pacing, the activation sequence was not significantly different between infarcted and sham-operated groups. However, direct stimulation of the epicardium in the NZ revealed an area of slow conduction velocity (CV approximately 5 cm/s(-1), approximately 10% of normal values) at the margin of the infarct zone (IZ). Within the IZ, CV was approximately 50% of normal. A prominent endocardial rim of myocardium in the infarct was not the source of epicardial optical signals because chemical ablation of the endocardium did not affect the epicardial activation pattern. Therefore, remnant groups of myocytes in the mid-wall and epicardium of the infarct scar support normal electrical activation during RA pacing. Areas of delayed conduction emerge only on epicardial stimulation.

Gravel extraction and planform change in a wandering gravel-bed river: The River Wear, Northern England

Within-channel alluvial gravel extraction is one of the most important forms of anthropogenically induced morphological change in river channels. In British rivers commercial gravel extraction was widespread between the 1930s and 1960s, and limited gravel extraction operations to reduce flood risk or maintain navigation continue to the present day. Despite this, gravel extraction has received little attention in UK river studies. This paper examines the significance of within-channel gravel extraction, during the period 1945–1960, on the planform of the River Wear in northern England. The study focuses on two 3 km piedmont reaches at Wolsingham and Harperley Park, located at the margin of the upland zone. Examination of detailed archival accounts of the gravel extraction operations, supplemented by the analysis of aerial photographs has enabled the impact of gravel extraction on the channel of the River Wear to be determined. Sediment budget calculations suggest large sediment deficits in both study reaches, however, assessing potential impacts simply in terms of a sediment deficit may be misleading as channel adjustments depend on local factors and a detailed consideration of the reach-scale sediment budget. Differences in the nature of channel adjustments of both reaches were found to be primarily a function of the method of gravel extraction employed. Overall patterns of channel change along the extraction reaches, over the past 150 years, were similar to reaches where gravel extraction was not practiced. This highlights the difficulty of trying to establish the significance of different processes where both local (gravel extraction) and catchment-scale factors (climate and land use) are operating.

Genetic structure of hybrid zones betweenSilene latifoliaandSilene dioica(Caryophyllaceae): evidence for introgressive hybridization

Natural hybrid zones provide a valuable tool to study introgressive hybridization, because they can contain a wide variety of genotypes that result from many generations of recombination. Here we used molecular markers and morphological variation to describe the structure of two natural hybrid zones between Silene latifolia and Silene dioica in the Swiss Alps. Populations in both hybrid zones consisted of few intermediate hybrids and were dominated by backcross hybrids. The latter were also found in the parental populations at the margins of the hybrid zones. Out of 209 amplified fragment length polymorphism (AFLP) markers scored in 390 individuals, only 7 (3.3%) were species specific. These results indicate that introgression between S. dioica and S. latifolia is extensive, and that hybrid zones act as bridges to gene flow between these two species. Analysis of linkage disequilibrium identified few populations in which hybridization is ongoing, whereas in most populations linkage disequilibrium has eroded. Where hybridization is ongoing, strong changes in species-specific marker frequencies and morphological traits were observed. Plastid introgression into the hybrid zone was found to be bidirectional, but only the S. latifolia plastid haplotype was found in a nuclear S. dioica background. This unidirectional plastid introgression from S. latifolia into S. dioica is most likely due to pollen-flow from S. dioica onto S. latifolia, and results in plastid capture. Comparisons between the molecular and the morphological hybrid indices revealed that morphology in this study system is useful for identifying hybrids, but not for detailed analysis of hybrid zone structure.

Late Neoproterozoic to Early Palaeozoic palaoegeography of the Holy Cross Mountains (Central Europe): an integrated approach

Study of geochemistry, examination of isotope ages of detrital minerals, palaeomagnetic analysis, and a study of the trilobites were performed to provide constraints on the palaeogeographical position of the Holy Cross Mountains in Late Ediacaran–Early Palaeozoic time. The geochemical results indicate an active continental margin or continental island arc provenance of the Ediacaran sediments. Sediments from a passive continental margin were deposited here during the Cambrian and Ordovician. The palaeomagnetic pole isolated from Cambrian rocks of the Małopolska region of the Holy Cross Mountains corresponds to the Cambrian segment of the Baltic apparent polar wander path. Isotope age estimations indicate that Cambrian sediments of the Małopolska region contain detritus not only from a latest Neoproterozoic source but also from sources with ages of c . 0.8–0.9 Ga, 1.5 Ga and 1.8 Ga. The Małopolska, Brunosilesia, Dobrugea and Moesia terranes, which originally developed near the present southern edge of Baltica and were partly involved in the Cadomian orogen, were dextrally relocated along its Trans-European Suture Zone margin. The first stage of this movement took place as early as latest Ediacaran time, while Baltica rotated anticlockwise. Anticlockwise rotation of Baltica at the Cambrian–Ordovician boundary implies further dextral movement of the Małopolska block.

The Tianger (Bingdaban) shear zone hosted gold deposit, west Tianshan, NW China: Petrographic and geochemical characteristics

The Wangfeng–Tianger–Saridala ore district consists of over 20 orebodies with total proven gold reserves exceeding 15 tonnes. The district is located on the EW-striking Tianger (Bingdaban) shear zone in west Tianshan Mountains, northwest China. The lensoid orebodies are distributed along the shear zone in a region about 25 km in length and 1 km in width. Enhanced fluid flow and fracturing controlled location and orientation of mineralized zones during deformation along narrow shear bands oriented oblique to the overall shear zone margins. Fabrics in fractures and strain shadow overgrowths generally plunge steeply, parallel to the lineation in the surrounding cataclasite matrix consisting of new grains of quartz and minor amounts of micas. Native gold occurs in mylonitized granites or mylonitized sulfide–mica–quartz veins. Gold grade is closely related with the occurrence of sulfide–quartz veins. Pyrite and pyrrhotite in gold-bearing sulfide–quartz veins contain inclusions of native gold. Chondrite-normalized rare earth element (REE) distribution patterns for pyrite from the orebodies show light REE enrichments and negative Eu anomalies. Relationships between gold contents and Th/U, Zr/Hf and (La/Yb) N values for pyrites imply that gold-rich pyrites are different from gold-poor pyrites, thus indicate that the pyrites in the orebodies have a different origin compared with those in wall rocks. A Rb–Sr isochron for the mylonitized Au-bearing quartz veins indicates an age of 224 ± 14 Ma with an initial 87Sr/ 86Sr ratio of 0.7294 ± 0.0089 (MSWD = 1.1). This age is conformed by 40Ar/ 39Ar dating on muscovites (220.9 to 222.5 Ma), which is interpreted as the age of ore-formation in the Tianger deposit. High initial 87Sr/ 86Sr ratios (0.7294), high δ 34S values (+ 11.2 to + 16.5‰), low δ 18O H2O values (1.67 to 3.07‰) and low δD values (− 84 to − 104‰) indicate that the ore-forming fluid was unrelated to any magmatic process.

Synergistic Fusion of Interferometric and Speckle-Tracking Methods for Deriving Surface Velocity From Interferometric SAR Data

This letter presents a technique to adjust and unify disconnected interferogram fringe regions for the derivation of accurate surface-velocity measurements. The interferogram from repeat-pass interferometric synthetic aperture radar data is often partitioned by shear margins of ice streams and other low-coherence zones into many small disconnected fringe regions. Although these isolated fringe regions can be unwrapped separately, the unwrapped phase for each region is referenced to a different seed point. Our technique exploits absolute range-offset measurements from the speckle-tracking method to bridge the isolated fringe regions in the interferogram. In this way, the unwrapped phases in these regions can be adjusted into consistent surface-displacement measurements with a common reference point. Using Radarsat interferometric data in Antarctica, we demonstrated that the synergetic fusion of the measurements from the interferometric and speckle-tracking methods can produce a highly accurate two-dimensional velocity field

Controllability Analysis for Operation Margin of Zone 3 Impedance Relay

Controllability Analysis for Operation Margin of Zone 3 Impedance Relay

Are there Middle Jurassic contourites in the Tarnovo depression (Southern Moesian platform margin)?

Abstract The first boreholes in the Tarnovo depression, located in the central Southern Moesian platform margin zone (Bulgaria), drilled at the end of the 1970s, display intervals of unusually thin, irregular and lens-like interbedding of shales and siltstones in the Middle Jurassic succession. Their specific lithological, log and seismic features, which resemble or distinguish them from contourites, have been studied and described in detail. The depositional setting in the Tarnovo depression during the Late Aalenian-Early Bajocian was favourable for the accumulation of deeper-water sediments, influenced by bottom currents. These were deposited along the hanging walls of major growth faults, which have a decisive geodynamic importance for Early-Middle Jurassic basin evolution throughout the Southern Moesian platform margin zone. Some lithological characteristics of the studied sediments correspond to diagnostic criteria for contourites. However, some other features, such as tractive indications, thin fine-grained laminae and wavy facies alternation, are also indicative of fine-grained turbidites and/or reworked bottom-current deposits.

No evidence of disease after radiofrequency ablation in delayed nephrectomy specimens

Objectives Computed tomography and magnetic resonance imaging are routinely used during follow-up of radiofrequency ablation (RFA) of renal masses. Widespread acceptance of needle ablation is limited by the need to rely on radiographic criteria to confirm effective ablation. In this report, we correlated the long-term radiographic appearance of RFA with the histologic findings in three delayed nephrectomy specimens. This should enhance our understanding of the histopathologic features of successful RFA and highlight potential shortcomings of modern imaging after ablation. Methods Radiographic and histologic data were analyzed in 3 patients who underwent delayed partial or total nephrectomy after RFA, performed for complications or misinterpretation of postablation surveillance imaging findings. Results Two delayed nephrectomies were performed for new enhancement at the periphery of the ablation zone margin and one for RFA-related ureteropelvic junction obstruction. At the initial ablation, all 3 patients had biopsy-proven renal cell carcinoma, and the mean time to delayed nephrectomy was 18 months. Histologically, all three demonstrated absence of residual cancer within the ablation zone. In the patients with enhancement at the periphery of the ablation zone, a granulomatous foreign body giant cell reaction was found. Conclusions RFA is an effective technology for eradicating small renal cell carcinomas. However, proper image interpretation after ablation is a crucial component of patient care. New enhancement at the peripheral margin of the tumor ablation zone does not invariably suggest malignant recurrence, but a benign granulomatous reaction. Additional experience with interpretation of cross-sectional imaging is required to better understand the radiographic evolution of radiofrequency-ablated renal tumors.

Mechanical deformation model of the western United States instantaneous strain-rate field

Summary We present a relationship between the long-term fault slip rates and instantaneous velocities as measured by Global Positioning System (GPS) or other geodetic measurements over a short time span. The main elements are the secularly increasing forces imposed by the bounding Pacific and Juan de Fuca (JdF) plates on the North American plate, viscoelastic relaxation following selected large earthquakes occurring on faults that are locked during their respective interseismic periods, and steady slip along creeping portions of faults in the context of a thin-plate system. In detail, the physical model allows separate treatments of faults with known geometry and slip history, faults with incomplete characterization (i.e. fault geometry but not necessarily slip history is available), creeping faults, and dislocation sources distributed between the faults. We model the western United States strain-rate field, derived from 746 GPS velocity vectors, in order to test the importance of the relaxation from historic events and characterize the tectonic forces imposed by the bounding Pacific and JdF plates. Relaxation following major earthquakes (Mγ 8.0) strongly shapes the present strain-rate field over most of the plate boundary zone. Equally important are lateral shear transmitted across the Pacific–North America plate boundary along ∼1000 km of the continental shelf, downdip forces distributed along the Cascadia subduction interface, and distributed slip in the lower lithosphere. Post-earthquake relaxation and tectonic forcing, combined with distributed deep slip, constructively interfere near the western margin of the plate boundary zone, producing locally large strain accumulation along the San Andreas fault (SAF) system. However, they destructively interfere further into the plate interior, resulting in smaller and more variable strain accumulation patterns in the eastern part of the plate boundary zone. Much of the right-lateral strain accumulation along the SAF system is systematically underpredicted by models which account only for relaxation from known large earthquakes. This strongly suggests that in addition to viscoelastic-cycle effects, steady deep slip in the lower lithosphere is needed to explain the observed strain-rate field.

Regional Tropical Precipitation Change Mechanisms in ECHAM4/OPYC3 under Global Warming*

Abstract Mechanisms of global warming impacts on regional tropical precipitation are examined in a coupled atmosphere–ocean general circulation model (ECHAM4/OPYC3). The pattern of the regional tropical precipitation changes, once established, tends to persist, growing in magnitude as greenhouse gases increase. The sulfate aerosol induces regional tropical precipitation anomalies similar to the greenhouse gases but with opposite sign, thus reducing the early signal. Evidence for two main mechanisms, the upped-ante and the anomalous gross moist stability (M′) mechanisms (previously proposed in an intermediate complexity model), is found in this more comprehensive coupled general circulation model. Preferential moisture increase occurs in convection zones. The upped-ante mechanism signature of dry advection from nonconvective regions is found in tropical drought regions on the margins of convection zones. Here advection in both the atmospheric boundary layer and lower free troposphere are found to be important, with an additional contribution from horizontal temperature transport in some locations. The signature of the M′ mechanism—moisture convergence due to increased moisture in regions of large mean vertical motion—enhances precipitation within strong convective regions. Ocean dynamical feedbacks can be assessed by net surface flux, the main example being the El Niño–like shift of the equatorial Pacific convection zone. Cloud–radiative feedbacks are found to oppose precipitation anomalies over ocean regions.

Ultra high temperature-metamorphism and its significance in the Central Indian Tectonic Zone

In the present study from the southern margin of the Central Indian Tectonic Zone, it is demonstrated how the metamorphic P– T path of ultrahigh-temperature granulite terranes can be reconstructed using the metamorphic transition in corundum granulites from early biotite melting to later FMAS solid–solid reaction. The extreme metamorphism in these rocks caused two-stage biotite melting, resulting in initial porphyroblastic garnet 1 and later sapphirine–spinel 1 incongruent solid mineral assemblages. During this process, the leucocratic and melanocratic layers in the corundum granulites evolved from an initial silica-oversaturated to a later silica-undersaturated domain. In the melanocratic layer, this allowed localized concentration of sapphirine-spinel 1 and residual sillimanite 1, producing an extremely restitic assemblage, at the culmination of peak metamorphism, BM 1. BM 1 is constrained at ∼ 1000 °C at relatively deep crustal levels ( P ∼ 9 kbar) from the stability of ferroaugite in a co-metamorphosed Iron Formation granulite. During subsequent metamorphism (BM 2), the reaction path and history in the corundum granulites shifted to the restitic domain allowing reacting sapphirine, spinel 1 and sillimanite to produce coronal garnet 2–corundum assemblage via a FMAS univariant reaction. In the final stages of reaction history, biotite 2–sillimanite 2–spinel 2 assemblage was produced after garnet 2–corundum due to localized melt–crystal interaction. The metamorphic sequence, when interpreted with the help of a newly constructed, qualitative KFMASH petrogenetic grid, reveals successive stages of heating, increasing pressure and cooling around the KFMASH invariant point, [Opx,Crd], which is consistent with a counterclockwise metamorphic P– T path. The near isobaric nature of post-peak cooling (Δ T ∼ 250–300 °C) is also evident from multistage pyroxene exsolution and by the appearance of lamellar and coronal garnets in the Iron Formation granulites. This study provides the first tight constraint for ultrahigh- T metamorphism along a counter clockwise P– T trajectory in the Central Indian Tectonic zone, and has important bearing for terrane correlations in this part of East Gondwanaland. In addition, the new KFMASH grid allows evaluation of metamorphic phase relations in ultrahigh- T, corundum-bearing and corundum-absent aluminous granulites.

Foraminiferal biodiversity and Holocene evolution of the Phetchaburi coastal area (Thailand Gulf)

Twenty three surface sediments were collected in May 2002, in the Phetchaburi coastal area (Thailand Gulf) starting from the outer margin of the vegetated zone, to a depth of about 20 m, covering an area of about 800 km 2. One core was taken in the north-eastern area of the Mae Khlong delta plain to investigate the recent paleoenvironmental evolution of this zone, thirteen core levels were collected for micropaleontological (foraminifers) investigation. This highly populated area is characterized by the inflow of the Mae Khlong, the second major river in Thailand, and the Khlong Ban Labun River. Empty tests pertaining to the thanathocoenosis are dominant and, as for the few living specimens, are most frequently represented by Ammonia spp. The collected species are typically of brackish-water settings. Foraminiferal diversity is rather low and increases from the northern part to the central-southern part of the studied area, where taxa typical of the Indo-Pacific realm (such as Miliolids and Schackoinella globosa) are more abundant than the cosmopolitan species such as Ammonia tepida and Gaudryina exilis. The geographic distribution of the four foraminiferal assemblages, defined on the basis of the cluster analysis, indicates that the northern sector is affected by severe environmental conditions. Since this area is affected by the Mae Khlong River input, the salinity fluctuation is probably a controlling factor on the foraminifers distribution. Ammonia tepida, A. inflata, Murrayinella murrayi and Miliolinella sp.1 are the most opportunistic species, able to tolerate wide environmental variability. As regards to the Holocene data, the study carried out on the core located on the Mae Khlong delta plain, indicates that the tidal flat paleoenvironment has been subject to different fresh-water influence, with a general prograding trend.

Assessment of epidermal subpopulations and proliferation in healthy skin, symptomless and lesional skin of spreading psoriasis

The margin zone in spreading psoriatic lesions has frequently been used as a model to study the changes in epidermal proliferation, keratinization and inflammation during the transition from symptomless to lesional skin. However, the dynamics of the changes in the epidermal subpopulations-basal cells, transit amplifying cells and differentiated cells-have not been studied in the transition between symptomless and lesional skin. To quantify in a dynamic model of the margin zone in psoriasis the characteristics of these subpopulations with respect to epidermal proliferation and differentiation. From seven patients with active psoriasis, biopsies were taken from the distant uninvolved skin, outer margin, inner margin and centre of a spreading psoriatic plaque. Frozen sections were labelled immunofluorescently using direct immunofluorescence for Ki-67 and beta1 integrin and the Zenon labelling technique for keratin 6, 10 and 15. Digital photographs of the stained sections were quantitatively analysed. In the distant uninvolved skin the expression of beta1 integrin was decreased and keratin 15 expression was lost. In this area suprabasal cells expressed beta1 integrin and in the outer margin suprabasal cells expressed Ki-67. From the outer to the inner margin of the psoriasis plaque, which coincided with the appearance of the clinical lesion, there was a significant change in the various markers. The patchy expression of keratin 6 in the inner margin became homogeneous in the centre of the psoriasis plaque and here was also coexpression of keratin 6 and keratin 10 in a single cell. The present study provides additional evidence that the distant uninvolved skin has a prepsoriatic phenotype, which is the first step in a psoriatic cascade. The cascade between symptomless and lesional skin comprises first an abnormality in inflammation with involvement of beta1 integrin-dim cells (transit amplifying cells) subsequently eliciting an enlarged germinative compartment with increased recruitment of cycling epidermal cells and focal expression of proliferation-associated keratins, ultimately culminating in a more-or-less homogeneous epidermis with massive recruitment of cycling epidermal cells and proliferation-associated keratinization.