Search

In order to obtain the in-situ stress field characteristics and analyze tectonic stability in the Motuo key area of the eastern Himalayan syntaxis, the in-situ stress measurement of one in-situ stress hole and 11 test sections of the Xirang section of the Motuo fault zone were carried out by the hydraulic fracturing method. The results show that the maximum and minimum horizontal principal stress values (SH, Sh) in the test section of 61.43−121.34 m are 3.05−14.50 MPa and 2.16−9.87 MPa, respectively, and the vertical principal stress values (Sv) are 1.63−3.31 MPa, namely, SH>Sh>Sv. The in-situ stress field at the measuring point is dominated by horizontal compression, and all of them belong to the in-situ stress state of reverse fault. The principal stress values gradually increase with the increase of depth, and the dominant direction of the maximum principal stress is NEE. In the whole range of in-situ stress depth, the lateral pressure coefficients (Kav) are 1.39−4.38, the maximum horizontal stress coefficients (KHv) are greater than 1, and the ratio increases with the increase of depth. The regional stress field of this key area is dominated by horizontal stress and it is highly directional. The horizontal stress coefficients (KHh) of all test sections are 1.23−1.66, which are similar to the calculation results of in-situ stress characteristic parameters in Linzhi−Tongmai section. The horizontal tectonic stress of the shallow level at 98 m is relatively small, and the stress accumulation level is low. The friction coefficient required to maintain fault stability is smaller than the critical friction coefficient of actual fault, and the tectonic environment is relatively stable. When the depth exceeds 98 m, the friction coefficient required to maintain fault stability is close to the critical friction coefficient value of the actual fault due to the dominant role of horizontal tectonic stress, and there is a small risk of fault instability slip. The superposition of the Coulomb stress change in the sinistral strike-slip direction and the thrust direction caused by the strong regional earthquakes on the fault plane of the Motuo fault zone in the study area are all negative numbers, which inhibits fault slip and does not increase the risk of fault activity in the study area.

The Namjag Barwa syntaxis is in the eastern Himalayan syntaxis area with the most intensive neotectonic activity. There are many late Quaternary active fault belts and strong seismicities. The tectonic stability of these active fault belts, such as the Jiali, Dongjiu-Milin, and Motuo fault belts, may influence the project's construction. In-situ stress is a critical parameter for estimating regional tectonic stability. Currently, there is a lack of abundant in-situ stress results about the Namjag Barwa syntaxis. It is challenging to assess geological safety risks for major projects. Based on focal mechanism solutions, the paper reveals the orientation of the maximum principal stress surrounding the Namjag Barwa syntaxis using the stress tensor inversion method. According to the critical condition of fault instability, the magnitudes of principal stresses around the Namjag Barwa syntaxis are also estimated by combining the inversion of the stress shape ratio and the frictional coefficient. The results indicate that the maximum principal stress direction in the Namjag Barwa syntaxis area is NE-NNE. The maximum and minimum horizontal principal stresses increase linearly with depth at a gradient of 0.032~0.0355 MPa/m and 0.0227~0.0236 MPa/m, respectively. Heterogeneous features of the in-situ stress field still exist. Generally, the results estimated in this study are in good concordance with the in-situ stress measurements. They can provide reliable in-situ stress parameters for evaluating the tectonic stability in the Namcha Barwa region.

Copyright of Journal of Geomechanics is the property of Journal of Geomechanics Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Severe corneal ulcerations, causing major keratolysis with large perforation of the cornea or extending to the limbal region, are an ophthalmic emergency. In these cases, a larger corneoscleral graft can be transplanted to restore tectonic integrity, alleviate pain, save vision, and prevent loss of the eye. Chart review of 34 patients with a corneoscleral graft ≥9.5 mm was conducted. Primary endpoints of the study were tectonic stability defined as no need for another keratoplasty or enucleation. In addition, visual acuity, postoperative complications, and secondary procedures were analyzed. In total, 12 patients (35%) were female. The mean age at transplantation was 65 ± 19 years. The underlying disease was a perforated infectious corneal ulcer in 30 cases (88%). Mean follow up was 675 ± 789 days. Tectonic stability at the end of the follow-up was maintained with a probability of 56% in a Kaplan–Meier analysis. Another penetrating keratoplasty was necessary in six cases (17%) and enucleation in five cases (15%). A corneoscleral transplant remains a viable treatment option to prevent enucleation in severe keratolysis. In our study, this was possible in about half of the cases. Postoperative complications, secondary surgeries, and markedly reduced visual acuity put the advantages into perspective.

Copyright of Acta Geoscientica Sinica is the property of Acta Geoscientica Sinica Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Colombian Caribbean is an active margin characterized by constant and intense tectonic activity since the Cretaceous. Nonetheless, recent studies have reported a period of relative stability during the early Oligocene for some Caribbean basins. We have studied the biostratigraphic and well-log record of a 143-m sedimentary succession from the ANH San Jacinto-1 well in the Sinú-San Jacinto Basin. We present the first astrobiochronological age model constructed for the early Oligocene (32-28 Ma) based on the integrated use of planktonic foraminifer biostratigraphy and the gamma-ray record (GR). Rhythmic GR alternations, associated with changes in clay/organic matter concentration, exhibit a regular pattern of 1:2:5:20 and are correlated in amplitude and intensity with orbital cycles, being the eccentricity-related alternations, the most prominent signal imprinted in the GR record. The correlation with the astronomical target curves allowed us to establish a robust age model for the early Oligocene, which will be instrumental for defining future high-resolution correlations in the Colombian Caribbean basins. Orbitally driven GR patterns indicate that changes in sediment yield are associated with seasonal climatic changes, revealing that during eccentricity maxima (likely precession minima), enhanced humid climate conditions existed in the Caribbean area. At the same time, reduced precipitations persisted over eccentricity minima (likely precession maxima). The GR record amplitude also suggests that at times of reduced precession-driven Equatorial insolation, the obliquity exerted a larger control over the clay-rich sediment input, likely via enhanced humid conditions. • Astrobiochronological tuned chronology from 32 to 28 Ma in the SSJB. • GR signals show a preferent eccentricity parameter (405–413 kyr and 100-kyr). • Obliquity (28.5, 41, 54 kyr) and precession cycles (22 kyr) are present in the ANH-SJ-1. • In eccentricity maxima runoff leading to higher clay/organic matter supply. • Obliquity had a larger effect at times of insolation minima. [ABSTRACT FROM AUTHOR]

Severe corneal ulcerations, causing major keratolysis with large perforation of the cornea or extending to the limbal region, are an ophthalmic emergency. In these cases, a larger corneoscleral graft can be transplanted to restore tectonic integrity, alleviate pain, save vision, and prevent loss of the eye. Chart review of 34 patients with a corneoscleral graft ≥9.5 mm was conducted. Primary endpoints of the study were tectonic stability defined as no need for another keratoplasty or enucleation. In addition, visual acuity, postoperative complications, and secondary procedures were analyzed. In total, 12 patients (35%) were female. The mean age at transplantation was 65 ± 19 years. The underlying disease was a perforated infectious corneal ulcer in 30 cases (88%). Mean follow up was 675 ± 789 days. Tectonic stability at the end of the follow-up was maintained with a probability of 56% in a Kaplan-Meier analysis. Another penetrating keratoplasty was necessary in six cases (17%) and enucleation in five cases (15%). A corneoscleral transplant remains a viable treatment option to prevent enucleation in severe keratolysis. In our study, this was possible in about half of the cases. Postoperative complications, secondary surgeries, and markedly reduced visual acuity put the advantages into perspective.

Abstract: The plant diversity of the Cape Floristic Region is regarded as being exceptional in an ecological and evolutionary context. The region supports about double the number of species predicted by models based on water-energy variables for regional floras globally. However, contemporary diversity patterns are profoundly influenced by evolutionary processes contingent upon idiosyncrasies of history and geography. The relatively recent appearance of dated molecular phylogenies, and their optimization in relation to habitat and geography, has provided hitherto unsurpassed opportunities to generate knowledge about the evolution of the Cape flora. Almost all studies invoke climatic deterioration during the Mio-Pliocene as the major trigger of radiations and subsequent speciation of Cape clades. While some do show the importance of edaphic heterogeneity for clade radiation, the evolution of this heterogeneity is not considered. Here, we review the literature on the late Cenozoic geomorphic evolution of the Cape in order to assess the extent to which the changing nature of scenery and soils could act as a stimulus for plant diversification. Despite dating uncertainties associated with both the phylogenetic and geomorphic data, it appears that moderate uplift in the early and late Miocene, which significantly increased the topo-edaphic heterogeneity of the Cape was an important driver of plant diversification. In particular, the massive increase in heterogeneity after the late Miocene event probably acted in synergy with rapid climatic deterioration, to produce the extraordinarily rapid diversification recorded for some Cape clades at that time. A comparison of the plant diversity and palaeoenvironmetal patterns of mediterranean-climate regions provide insights regarding the “remarkable environmental conditions” of the Cape that have generated the high diversification and low extinction rates necessary to produce such a rich flora. These conditions are a gradual increase in topo-edaphic heterogeneity and relative climatic stability during the late Cenozoic. [Copyright &y& Elsevier]

A series of dynamic penetration tests were performed up to a maximum depth of 2 m along sandy coastlines of Sardinia and Latium, Italy, in order to examine the change in resistance showed by sands. A maximum of resistance appears at the depth where the current sea level varies with tide fluctuations; this maximum resistance is due to capillary forces, which occur and disappear two times a day. A second maximum of sand resistance was found about half a meter under the first. In two cases where it was possible to attribute an age to the sands showing this more ancient level, the ages were before 37 AD and about 1700 AD. The features of this compact sand level suggest that between these two ages the sea level must have been practically constant, and unchanged until 300 years ago. These results were compared with tide gauge data recorded in the Netherlands, northern Italy and France. The data from the Amsterdam region, the oldest ones in the world, were reinterpreted as follows: the site of the Amsterdam tide gauge station is recognised as having undergone local settlements, while the entire region is denied to have been, as previously claimed, subject to a regional subsidence in the period of interest. As a consequence, also in the Amsterdam region the sea level maintained nearly the same position at least from 1700 up to about 1800. Then this level, which as from now can be labelled as “pre-industrial”, rose more and more rapidly, in agreement with the accelerated character of the increase of CO2 in the atmosphere. In the Netherlands, northern Italy and France the amount of sea level rise in the last 200 years seems to be slightly smaller (20–23 cm) than the mean sea rise in the world (about 27 cm), while in the study area (central Mediterranean) the sea rise is shown to be about twice as much. Another result of this study regards the tendency of sea level change. The study showed that, of the two peaks of sand resistance found, the most recent peak is not coincident with the present sea level at the moment of the tests: it is about 10 cm higher. This difference is possibly due to an actual lowering of the sea, a countertendence likely to have begun in the year 2000. If this interpretation is true, it would mean that the pattern of the sea level rise, which up to now had been found to follow an upward accelerated movement, has presently ceased, to possibly invert its movement. [Copyright &y& Elsevier]