Interpretation of fluid inclusions in quartz deformed by weak ductile shearing: reconstruction of differential stress magnitudes and pre-deformation fluid properties

A well developed theoretical framework is available in which paleofluid properties, such as chemical composition and density, can be reconstructed from fluid inclusions in minerals that have undergone no ductile deformation. The present study extends this framework to encompass fluid inclusions hosted by quartz that has undergone weak ductile deformation following fluid entrapment. Recent experiments have shown that such deformation causes inclusions to become dismembered into clusters of irregularly shaped relict inclusions surrounded by planar arrays of tiny, new-formed (neonate) inclusions. Comparison of the experimental samples with a naturally sheared quartz vein from Grimsel Pass, Aar Massif, Central Alps, Switzerland, reveals striking similarities. This strong concordance justifies applying the experimentally derived rules of fluid inclusion behaviour to nature. Thus, planar arrays of dismembered inclusions defining cleavage planes in quartz may be taken as diagnostic of small amounts of intracrystalline strain. Deformed inclusions preserve their pre-deformation concentration ratios of gases to electrolytes, but their H2O contents typically have changed. Morphologically intact inclusions, in contrast, preserve the pre-deformation composition and density of their originally trapped fluid. The orientation of the maximum principal compressive stress (σ1σ1) at the time of shear deformation can be derived from the pole to the cleavage plane within which the dismembered inclusions are aligned. Finally, the density of neonate inclusions is commensurate with the pressure value of σ1σ1 at the temperature and time of deformation. This last rule offers a means to estimate magnitudes of shear stresses from fluid inclusion studies. Application of this new paleopiezometer approach to the Grimsel vein yields a differential stress (σ1–σ3σ1–σ3) of ∼300 MPa∼300 MPa at View the MathML source390±30°C during late Miocene NNW–SSE orogenic shortening and regional uplift of the Aar Massif. This differential stress resulted in strain-hardening of the quartz at very low total strain (<5%<5%) while nearby shear zones were accommodating significant displacements. Further implementation of these experimentally derived rules should provide new insight into processes of fluid–rock interaction in the ductile regime within the Earth's crust.

Registration And Visualisation Of Deformation Maps From Terrestrial Radar Interferometry Using Photogrammetry And Structure From Motion

This paper describes a general workflow for the registration of terrestrial radar interferometric data with 3D point clouds derived from terrestrial photogrammetry and structure from motion. After the determination of intrinsic and extrinsic orientation parameters, data obtained by terrestrial radar interferometry were projected on point clouds and then on the initial photographs. Visualisation of slope deformation measurements on photographs provides an easily understandable and distributable information product, especially of inaccessible target areas such as steep rock walls or in rockfall run-out zones. The suitability and error propagation of the referencing steps and final visualisation of four approaches are compared: (a) the classic approach using a metric camera and stereo-image photogrammetry; (b) images acquired with a metric camera, automatically processed using structure from motion; (c) images acquired with a digital compact camera, processed with structure from motion; and (d) a markerless approach, using images acquired with a digital compact camera using structure from motion without artificial ground control points. The usability of the completely markerless approach for the visualisation of high-resolution radar interferometry assists the production of visualisation products for interpretation.

Blackfolds, plane waves and minimal surfaces

Minimal surfaces in Euclidean space provide examples of possible non-compact horizon geometries and topologies in asymptotically flat space-time. On the other hand, the existence of limiting surfaces in the space-time provides a simple mechanism for making these configurations compact. Limiting surfaces appear naturally in a given space-time by making minimal surfaces rotate but they are also inherent to plane wave or de Sitter space-times in which case minimal surfaces can be static and compact. We use the blackfold approach in order to scan for possible black hole horizon geometries and topologies in asymptotically flat, plane wave and de Sitter space-times. In the process we uncover several new configurations, such as black helicoids and catenoids, some of which have an asymptotically flat counterpart. In particular, we find that the ultraspinning regime of singly-spinning Myers-Perry black holes, described in terms of the simplest minimal surface (the plane), can be obtained as a limit of a black helicoid, suggesting that these two families of black holes are connected. We also show that minimal surfaces embedded in spheres rather than Euclidean space can be used to construct static compact horizons in asymptotically de Sitter space-times.

Distributed transpressive continental deformation: The Varto Fault Zone, eastern Turkey

The convergence between the Eurasian and Arabian plates has created a complicated structural setting in the Eastern Turkish high plateau (ETHP), particularly around the Karlıova Triple Junction (KTJ) where the Eurasian, Arabian, and Anatolian plates intersect. This region of interest includes the junction of the North Anatolian Shear Zone (NASZ) and the East Anatolian Shear Zone (EASZ), which forms the northern border of the westwardly extruding Anatolian Scholle and the western boundary of the ETHP, respectively. In this study, we focused on a poorly studied component of the KTJ, the Varto Fault Zone (VFZ), and the adjacent secondary structures, which have complex structural settings. Through integrated analyses of remote sensing and field observations, we identified a widely distributed transpressional zone where the Varto segment of the VFZ forms the most northern boundary. The other segments, namely, the Leylekdağ and Çayçatı segments, are oblique-reverse faults that are significantly defined by uplifted topography along their strikes. The measured 515 and 265 m of cumulative uplifts for Mt. Leylek and Mt. Dodan, respectively, yield a minimum uplift rate of 0.35 mm/a for the last 2.2 Ma. The multi-oriented secondary structures were mostly correlated with “the distributed strike-slip” and “the distributed transpressional” in analogue experiments. The misfits in strike of some of secondary faults between our observations and the experimental results were justified by about 20° to 25° clockwise restoration of all relevant structures that were palaeomagnetically measured to have happened since ~ 2.8 Ma ago. Our detected fault patterns and their true nature are well aligned as being part of a transpressional tectonic setting that supports previously suggested stationary triple junction models.

Minimal residual disease in cancer therapy - Small things make all the difference

Minimal residual disease (MRD) is a major hurdle in the eradication of malignant tumors. Despite the high sensitivity of various cancers to treatment, some residual cancer cells persist and lead to tumor recurrence and treatment failure. Obvious reasons for residual disease include mechanisms of secondary therapy resistance, such as the presence of mutant cells that are insensitive to the drugs, or the presence of cells that become drug resistant due to activation of survival pathways. In addition to such unambiguous resistance modalities, several patients with relapsing tumors do not show refractory disease and respond again when the initial therapy is repeated. These cases cannot be explained by the selection of mutant tumor cells, and the precise mechanisms underlying this clinical drug resistance are ill-defined. In the current review, we put special emphasis on cell-intrinsic and -extrinsic mechanisms that may explain mechanisms of MRD that are independent of secondary therapy resistance. In particular, we show that studying genetically engineered mouse models (GEMMs), which highly resemble the disease in humans, provides a complementary approach to understand MRD. In these animal models, specific mechanisms of secondary resistance can be excluded by targeted genetic modifications. This allows a clear distinction between the selection of cells with stable secondary resistance and mechanisms that result in the survival of residual cells but do not provoke secondary drug resistance. Mechanisms that may explain the latter feature include special biochemical defense properties of cancer stem cells, metabolic peculiarities such as the dependence on autophagy, drug-tolerant persisting cells, intratumoral heterogeneity, secreted factors from the microenvironment, tumor vascularization patterns and immunosurveillance-related factors. We propose in the current review that a common feature of these various mechanisms is cancer cell dormancy. Therefore, dormant cancer cells appear to be an important target in the attempt to eradicate residual cancer cells, and eventually cure patients who repeatedly respond to anticancer therapy but lack complete tumor eradication.

Synchronous carotid and coronary bypass surgery using minimal extracorporeal circulation does not increase the risk of in-hospital stroke compared to isolated carotid endarterectomy under general anaesthesia

Gebiet: Chirurgie Abstract: Introduction: Carotid endarterectomy (CEA) and coronary artery bypass grafting (CABG) could be approached in a combined or a staged fashion. Some crucial studies have shown no significant difference in peri-operative stroke and death rate in combined versus staged CEA/CABG. At present conventional extracorporeal circulation (CECC) is regarded as the gold standard for performing on-pump coronary artery bypass grafting. On contrary, the use of minimized extracorporeal circulation (MECC) for CABG diminishes hemodilution, blood-air contact, foreign surface contact and inflammatory response. At the same time, general anaesthesia (GA) is a potential risk factor for higher perioperative stroke rate after isolated CEA, not only for the ipsilateral but also for the contralateral side especially in case of contralateral high-grade stenosis or occlusion. The aim of the study was to analyze if synchronous CEA/CABG using MECC (CEA/CABG group) allows reducing the perioperative stroke risk to the level of isolated CEA performed under GA (CEA-GA group). – Methods: A retrospective analysis of all patients who underwent CEA at our institution between January 2005 and December 2012 was performed. We compared outcomes between all patients undergoing CEA/CABG to all isolated CEA-GA during the same time period. The CEA/CABG group was additionally compared to a reference group consisting of patients undergoing isolated CEA in local anaesthesia. Primary outcome was in-hospital stroke. – Results: A total of 367 CEAs were performed, from which 46 patients were excluded having either off-pump CABG or other cardiac surgery procedures than CABG combined with CEA. Out of 321 patients, 74 were in the CEA/CABG and 64 in the CEA-GA group. There was a significantly higher rate of symptomatic stenoses among patients in the CEA-GA group (p<0.002). Three (4.1%) strokes in the CEA/CABG group were registered, two ipsilateral (2.7%) and one contralateral (1.4%) to the operated side. In the CEA-GA group 2 ipsilateral strokes (3.1%) occurred. No difference was noticed between the groups (p=1.000). One patient with stroke in each group had a symptomatic stenosis preoperatively. – Conclusions: Outcome with regard to mortality and neurologic injury is very good in both -patients undergoing CEA alone as well as patients undergoing synchronous CEA and CABG using the MECC system. Although the CEA/CABG group showed slightly increased risk of stroke, it can be considered as combined treatment in particular clinical situations.

Use of minimal invasive extracorporeal circulation in cardiac surgery: principles, definitions and potential benefits. A position paper from the Minimal invasive Extra-Corporeal Technologies international Society (MiECTiS).

Minimal invasive extracorporeal circulation (MiECC) systems have initiated important efforts within science and technology to further improve the biocompatibility of cardiopulmonary bypass components to minimize the adverse effects and improve end-organ protection. The Minimal invasive Extra-Corporeal Technologies international Society was founded to create an international forum for the exchange of ideas on clinical application and research of minimal invasive extracorporeal circulation technology. The present work is a consensus document developed to standardize the terminology and the definition of minimal invasive extracorporeal circulation technology as well as to provide recommendations for the clinical practice. The goal of this manuscript is to promote the use of MiECC systems into clinical practice as a multidisciplinary strategy involving cardiac surgeons, anaesthesiologists and perfusionists.

Minimal invasive extracorporeal circulation should become the standard practice in coronary revascularization surgery†.

We read with great interest the large-scale network meta-analysis by Kowalewski et al. comparing clinical outcomes of patients undergoing coronary artery bypass grafting (CABG) operated on using minimal invasive extracorporeal circulation (MiECC) or off-pump (OPCAB) with those undergoing surgery on conventional cardiopulmonary bypass (CPB) [1]. The authors actually integrated into single study two recently published meta-analysis comparing MiECC and OPCAB with conventional CPB, respectively [2, 3] into a single study. According to the results of this study, MiECC and OPCAB are both strongly associated with improved perioperative outcomes following CABG when compared with CABG performed on conventional CPB. The authors conclude that MiECC may represent an attractive compromise between OPCAB and conventional CPB. After carefully reading the whole manuscript, it becomes evident that the role of MiECC is clearly undervalued. Detailed statistical analysis using the surface under the cumulative ranking probabilities indicated that MiECC represented the safer and more effective intervention regarding all-cause mortality and protection from myocardial infarction, cerebral stroke, postoperative atrial fibrillation and renal dysfunction when compared with OPCAB. Even though no significant statistical differences were demonstrated between MiECC and OPCAB, the superiority of MiECC is obvious by the hierarchy of treatments in the probability analysis, which ranked MiECC as the first treatment followed by OPCAB and conventional CPB. Thus, MiECC does not represent a compromise between OPCAB and conventional CPB, but an attractive dominant technique in CABG surgery. These results are consistent with the largest published meta-analysis by Anastasiadis et al. comparing MiECC versus conventional CPB including a total of 2770 patients. A significant decrease in mortality was observed when MiECC was used, which was also associated with reduced risk of postoperative myocardial infarction and neurological events [4]. Similarly, another recent meta-analysis by Benedetto et al. compared MiECC versus OPCAB and resulted in comparable outcomes between these two surgical techniques [5]. As stated in the text, superiority of MiECC observed in the current network meta-analysis, when compared with OPCAB, could be attributed to the fact that MiECC offers the potential for complete revascularization, whereas OPCAB poses a challenge for unexperienced surgeons; especially when distal marginal branches on the lateral and/or posterior wall of the heart need revascularization. This is reflected by a significantly lower number of distal anastomoses performed in OPCAB when compared with conventional CPB. Therefore, taking into consideration the literature published up to date, including the results of the current article, we advocate that MiECC should be integrated in the clinical practice guidelines as a state-of-the-art technique and become a standard practice for perfusion in coronary revascularization surgery.