Exact Placement Research Articles

IBD Patients with Primary or Secondary Nonresponse to Ustekinumab Benefit from Dose Escalation or Reinduction.

Ustekinumab is a monoclonal antibody approved for the treatment of IBD. This drug has a well-established efficacy; however, patients may not respond or lose response. The availability of other biological therapies prompts the need for comparative data between different agents to suggest first- or second-line strategies. Aim of this review is to compare the effectiveness of ustekinumab to other biologics in Crohn's disease and ulcerative colitis, as well as report the available data on dose escalation and reinduction. A systematic electronic search of the English literature was performed up to November 2023, using Medline (PubMed), Web of Science, Scopus and the Cochrane Library. Conference proceedings were also screened. Out of 659 citations, 80 relevant articles were selected and included in the present narrative review. Head-to-head comparisons of different biological drugs are relatively scarce, mostly deriving from indirect comparison or retrospective studies. Overall available data indicate similar effectiveness in the treatment of IBD patients. Dose escalation and reinduction strategies are well documented, but the optimal treatment schedule is still to be defined. Response and remission rates vary in different studies, and a proportion of patients fail to achieve clinical and endoscopic outcomes. However, both approaches are effective and safe in nonresponders and secondary loss of response. IBD patients may benefit from dose escalation or reinduction. Both strategies prove effective in regaining response in a proportion of patients, avoiding unnecessary early switch. Head-to-head trials are still needed to determine the exact placement of this drug compared to other biologics.

Foveapeltis gen. nov., an unusual cleroid genus with large hypomeral cavities from mid-Cretaceous amber (Coleoptera: Cleroidea).

Beetles have a remote evolutionary history dating back to the Carboniferous, with Mesozoic fossils playing a pivotal role in elucidating the early evolution of extant families. Despite their exceptional preservation in amber, deciphering the systematic positions of Mesozoic trogossitid-like beetles remains challenging. Here, we describe and illustrate a new trogossitid-like lineage from mid-Cretaceous Kachin amber, Foveapeltis rutai Li, Kolibáč, Liu & Cai, gen. et sp. nov. Foveapeltis stands out within the Cleroidea due to the presence of a significant large cavity on each hypomeron. While the exact phylogenetic placement of Foveapeltis remains uncertain, we offer a discussion on its potential affinity based on our constrained phylogenetic analyses.

Magnetic Susceptibility Modeling of Magic-Angle Spinning Modules for Part Per Billion Scale Field Homogeneity

Magic-angle spinning (MAS) solid-state NMR methods are crucial in many areas of biology and materials science. Conventional probe designs have often been specified with 0.1 part per million (ppm) or 100 part per billion (ppb) magnetic field resolution, which is a limitation for many modern scientific applications. Here we describe a novel 5-mm MAS module design that significantly improves the linewidth and line shape for solid samples by an improved understanding of the magnetic susceptibility of probe materials and geometrical symmetry considerations, optimized to minimize the overall perturbation to the applied magnetic field (B0). The improved spinning module requires only first and second order shimming adjustments to achieve a sub-Hz resolution of 13C resonances of adamantane at 150 MHz Larmor frequency (14.1Tesla magnetic field). Minimal use of third and higher order shims improves experimental reproducibility upon sample changes and the exact placement within the magnet. Furthermore, the shimming procedure is faster, and the required gradients smaller, thus minimizing thermal drift of the room temperature (RT) shims. We demonstrate these results with direct polarization (Bloch decay) and cross polarization experiments on adamantane over a range of sample geometries and with multiple superconducting magnet systems. For a direct polarization experiment utilizing the entire active sample volume of a 5-mm rotor (90 µl), we achieved full width at half maximum (FWHM) of 0.76 Hz (5 ppb) and baseline resolved the 13C satellite peaks for adamantane as a consequent of the 7.31 Hz (59 ppb) width at 2% intensity. We expect these approaches to be increasingly pivotal for high-resolution solid-state NMR spectroscopy at and above 1 GHz 1H frequencies.

Dynamic beam steering for wireless optical power transfer in IoT applications.

The alignment of a receiver with a pencil beam in a wireless optical power transfer (WOPT) system employing a resonance beam charging (RBC) technology limits the establishment of a resonance cavity. Accurate tracking necessitates precise and dependable monitoring, which requires the exact placement of transmitting and receiving devices. Herein, we present a concept of a two-dimensional (2D) beam steering mechanism for RBC-based WOPT systems utilizing dispersed laser beams. The proposed approach allows a significant improvement, including reduction of scanning times and minimization of errors, in relation to conventional pencil-beam-based systems. Experimental results reveal 14% faster acquisition time efficiency, an 18% improvement in pointing accuracy, and a 24% enhancement in tracking accuracy. These results establish the prerequisites for the implementation of dispersed beam steering in the RBC-based WOPT system. This capability empowers the system to charge movable devices and Internet of Things devices consistently in smart factories.

Visuospatial cognition predicts performance on an obstructed vision obstacle walking task in older adults

Walking performance and cognitive function demonstrate strong associations in older adults, with both declining with advancing age. Walking requires the use of cognitive resources, particularly in complex environments like stepping over obstacles. A commonly implemented approach for measuring the cognitive control of walking is a dual-task walking assessment, in which walking is combined with a second task. However, dual-task assessments have shortcomings, including issues with scaling the task difficulty and controlling for task prioritization. Here we present a new assessment designed to be less susceptible to these shortcomings while still challenging cognitive control of walking: the Obstructed Vision Obstacle (OBVIO) task. During the task, participants hold a lightweight tray at waist level obstructing their view of upcoming foam blocks, which are intermittently spaced along a 10 m walkway. This forces the participants to use cognitive resources (e.g., attention and working memory) to remember the exact placement of upcoming obstacles to facilitate successful crossing. The results demonstrate that adding the obstructed vision board significantly slowed walking speed by an average of 0.26 m/s and increased the number of obstacle strikes by 8-fold in healthy older adults (n = 74). Additionally, OBVIO walking performance (a score based on both speed and number of obstacle strikes) significantly correlated with computer-based assessments of visuospatial working memory, attention, and verbal working memory. These results provide initial support that the OBVIO task is a feasible walking test that demands cognitive resources. This study lays the groundwork for using the OBVIO task in future assessment and intervention studies.

Tool for estimating scope of building damage based on results of geometric operations between elements in building information models

ABSTRACT As a building ages, various types of problem caused by issues such as water leakage become more likely. Building information models (BIMs) are becoming more commonly used in the design and construction phases. Effort has been expended to also make them more effective in the maintenance phase. This study develops an add-on tool for predicting the scope of water leakage using the results of geometric operations between different elements in a BIM. A case study of water leakage associated with deteriorating rooftop waterproofing is presented. The development of the tool is based on interviews and a literature survey. The process of water spreading from a starting spot is described using multiple stages. A drawing on a plan view and calculation results based on the number of elements are presented to the user. The developed add-on tool is evaluated using a case study on some rooms in a BIM. The proposed tool can represent the knowledge and experience related to facility management using BIM technology. The novelty of the proposed tool is that it focuses on the detailed geometry and exact placement of elements in a BIM used for maintenance purposes and uses these elements in edited form.

Incidence of brachial plexus injury after cardiac surgery: a retrospective study

Background: Brachial plexopathy is a rare but debilitating injury associated with cardiac surgery. The reported incidence varies widely. Several risk factors have been described, including both patient and surgical factors. Objectives: The aim of this study is to (1) investigate the incidence of brachial plexus injury in cardiac surgery in a three-year period in our hospital, (2) give an overview of risk factors and possible mechanisms of brachial plexopathy, and (3) consider the legal ramifications of these injuries. Design and setting: single centre retrospective study Methods: Data were collected retrospectively from all patients undergoing cardiac surgery in a major hospital in a three-year year period (N = 1305). Hospital records were screened for patients who underwent an electromyography after their surgery. Those cases were further investigated for brachial plexus injury. Patient characteristics and data applying to known risk factors for peroperative nerve injury were obtained. Results: Brachial plexus injury was observed in 7 out of 1305 patients (0.54%). All patients with brachial plexus injury underwent coronary artery bypass surgery with internal mammary artery harvesting at the side of the injury. No further analysis concerning risk factors was performed since only seven cases were identified and underreporting was suspected. Conclusion: Our data suggest that brachial plexus injury in cardiac surgery might be associated with asymmetrical sternal retraction during internal mammary artery harvesting. These findings correspond with previous reports, although it would be interesting to further investigate the importance of the exact placement and type of retractor used.

Detection and Localization of Tea Bud Based on Improved YOLOv5s and 3D Point Cloud Processing

Currently, the detection and localization of tea buds within the unstructured tea plantation environment are greatly challenged due to their small size, significant morphological and growth height variations, and dense spatial distribution. To solve this problem, this study applies an enhanced version of the YOLOv5 algorithm for tea bud detection in a wide field of view. Also, small-size tea bud localization based on 3D point cloud technology is used to facilitate the detection of tea buds and the identification of picking points for a renowned tea-picking robot. To enhance the YOLOv5 network, the Efficient Channel Attention Network (ECANet) module and Bi-directional Feature Pyramid Network (BiFPN) are incorporated. After acquiring the 3D point cloud for the region of interest in the detection results, the 3D point cloud of the tea bud is extracted using the DBSCAN clustering algorithm to determine the 3D coordinates of the tea bud picking points. Principal component analysis is then utilized to fit the minimum outer cuboid to the 3D point cloud of tea buds, thereby solving for the 3D coordinates of the picking points. To evaluate the effectiveness of the proposed algorithm, an experiment is conducted using a collected tea image test set, resulting in a detection precision of 94.4% and a recall rate of 90.38%. Additionally, a field experiment is conducted in a tea experimental field to assess localization accuracy, with mean absolute errors of 3.159 mm, 6.918 mm, and 7.185 mm observed in the x, y, and z directions, respectively. The average time consumed for detection and localization is 0.129 s, which fulfills the requirements of well-known tea plucking robots in outdoor tea gardens for quick identification and exact placement of small-sized tea shoots with a wide field of view.

Use of a scent-detection dog for sea turtle nest monitoring of three sea turtle species in Florida.

Sea turtles are threatened with extinction around the world and rely on sandy beaches for laying their eggs. To protect eggs and locate them for calculation of reproductive success, beach surveyors must find the exact placement of each clutch. Eggs may be buried up to one meter deep under a nest mound several square meters in area. To locate sea turtle eggs, beach surveyors might spend hours searching for these eggs hidden in the sand, especially for difficult-to-locate leatherback (Dermochelys coriacea) and green turtle (Chelonia mydas) eggs. Scent-detection dogs (Canis lupus familiaris) are a novel tool that could provide a means to more accurately identify nests and efficiently locate eggs that need assessment, protection, or relocation. We assessed the effectiveness and feasibility of using a detection dog to locate sea turtle eggs buried in beach sand as compared to the traditional method using human beach surveyors. The detection dog was significantly more accurate in detecting loggerhead sea turtle (Caretta caretta) eggs and more efficient (less time spent and fewer holes dug) in assisting with locating the eggs. This case study presents results on the performance of one detection dog only, and additional research is needed with multiple detection dogs and handlers.

Borel complexity and Ramsey largeness of sets of oracles separating complexity classes

AbstractWe prove two sets of results concerning computational complexity classes. First, we propose a new variation of the random oracle hypothesis, originally posed by Bennett and Gill after they showed that relative to a randomly chosen oracle, with probability 1. Their original hypothesis was quickly disproven in several ways, most famously in 1992 with the result that , in spite of the classes being shown unequal with probability 1. Here we propose a variation of what it means to be “large” using the Ellentuck topology. In this new context, we demonstrate that the set of oracles separating and is not small, and obtain similar results for the separation of from along with the separation of from . We also show that the set of oracles equating with is large in this new sense. We demonstrate that this version of the hypothesis provides a sufficient condition for unrelativized relationships, at least in the cases considered here. Second, we examine the descriptive complexity of the classes of oracles providing the separations for these various classes, and determine their exact placement in the Borel hierarchy.

ID: 213194 Optimizing Deep Brain Stimulation Parameters in Drug Resistant Epilepsy: An EEG Oriented Approach

Deep brain stimulation (DBS) of anterior thalamic nucleus (ATN) is establishing as an effective adjunctive therapy for patients with drug resistant epilepsy (DRE) not suitable for epilepsy brain surgery and/or vagal nerve stimulation. The success of ATN-DBS is dependent upon exact placement of the DBS electrodes and judicious selection of DBS parameters (DBSPs) and patients; even then, the success has been observed to be limited to mainly one form of intractable seizures (IS), namely complex partial seizures with other forms of IS failing to respond satisfactorily. Furthermore, the conventional mode of selection of DBSPs is by trial and error and the required adjustments in the DBSPs are governed by the clinical response in the seizure profile over the course of multiple sessions and hospital visits, thus, warranting a strong need for optimization of the DBSPs. We present an EEG-guided novel and superior approach to the selection of effective DBSPs that induces EEG-desynchronization which is known to possess potent antiepileptic property with possibly possession of an additional anti-kindling effect that can suppress and even arrest the ongoing process of epileptogenesis in the patients with DRE in addition to its primary role in exercising control over the IS. It is further claimed that the innovative EEG-guided approach can successfully optimize the DBSPs resulting in minimum sessions of DBSP adjustments reducing the frequency of hospital visits, minimum side effects and minimum consumption of the device battery thus prolonging its life. Preliminary results of the clinical application of the novel approach in the selection of the DBSPs in a small case series have been promising and encouraging despite which it is strongly recommended that well designed large sized studies are required for its validation and successful clinical outcome.

Using augmented reality to guide bone conduction device implantation

Exact placement of bone conduction implants requires avoidance of critical structures. Existing guidance technologies for intraoperative placement have lacked widespread adoption given accessibility challenges and significant cognitive loading. The purpose of this study is to examine the application of augmented reality (AR) guided surgery on accuracy, duration, and ease on bone conduction implantation. Five surgeons surgically implanted two different types of conduction implants on cadaveric specimens with and without AR projection. Pre- and postoperative computer tomography scans were superimposed to calculate centre-to-centre distances and angular accuracies. Wilcoxon signed-rank testing was used to compare centre-to-centre (C-C) and angular accuracies between the control and experimental arms. Additionally, projection accuracy was derived from the distance between the bony fiducials and the projected fiducials using image guidance coordinates. Both operative time (4.3 ± 1.2 min. vs. 6.6 ± 3.5 min., p = 0.030) and centre-to-centre distances surgery (1.9 ± 1.6 mm vs. 9.0 ± 5.3 mm, p < 0.001) were significantly less in augmented reality guided surgery. The difference in angular accuracy, however, was not significantly different. The overall average distance between the bony fiducial markings and the AR projected fiducials was 1.7 ± 0.6 mm. With direct intraoperative reference, AR-guided surgery enhances bone conduction implant placement while reduces operative time when compared to conventional surgical planning.

V12-04 PELVIC FLOOR EXAM &amp; TRIGGER POINT INJECTIONS: A CADAVERIC AND ANIMATED DEMONSTRATION

You have accessJournal of UrologyCME1 Apr 2023V12-04 PELVIC FLOOR EXAM & TRIGGER POINT INJECTIONS: A CADAVERIC AND ANIMATED DEMONSTRATION Jacquelyn Booher and Grace Shenhar Jacquelyn BooherJacquelyn Booher More articles by this author and Grace ShenharGrace Shenhar More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000003347.04AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Pelvic pain is a complex phenomenon for which many women seek treatment from urologists. If pelvic floor trigger point injections are not taught in residency or fellowship, a urologist may not feel comfortable offering this treatment therefore referring the patient to another specialty or urologic subspecialist. This video aims to be an all-encompassing video one can watch to familiarize oneself with the pelvic floor anatomy, positioning, specific distances, and pitfalls for transvaginal pelvic floor injections by the use of animations, cadaveric model, and needles into specific proposed injection sites. Once watching this video one will feel comfortable performing this therapy. METHODS: A single female cadaver was dissected by the authors to identify specific pelvic structures relevant to pelvic floor trigger point injections. A video recording was taken demonstrating a standard pelvic floor injection template as described by Gupta et al. Spinal needles were placed into the proposed area of injection. Voice over and picture in picture cartoon animations were used for enhanced visual aid. RESULTS: The location of the spinal needles in the cadaver model shows exact placement into the pelvic floor muscles that are being targeted for pelvic floor injections. This video demonstrates the close proximity of the obturator nerve and vessels 1-o’clock injection sites. It also highlights the close proximity of injection in relation to the sacrospinous ligament and pudendal vessels. CONCLUSIONS: Pelvic pain is a complex phenomenon for which many women seek treatment from urologists. If pelvic floor trigger point injections are not taught in residency or fellowship, a urologist may not feel comfortable offering this treatment therefore referring the patient to another specialty or urologic subspecialist. Once watching this video one will feel comfortable performing this therapy. Source of Funding: None © 2023 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 209Issue Supplement 4April 2023Page: e1065 Advertisement Copyright & Permissions© 2023 by American Urological Association Education and Research, Inc.MetricsAuthor Information Jacquelyn Booher More articles by this author Grace Shenhar More articles by this author Expand All Advertisement PDF downloadLoading ...

Effects of mode of heat transfer on puffing quality of rice grain: A modeling and simulation analysis

AbstractCereal grains can be puffed by heating in hot sand bed or domestic microwave oven. The purpose of this study was to explore and compare the reasons of transformational changes in preconditioned rice during its sand bed heating and microwave heating in domestic microwave oven. Mathematical modeling and simulation techniques were used to estimate the changes in microwave power absorption density and temperature of rice with the heating methods. Sand puffing, initiated from the tips of rice, progressed toward the central region of the rice following the change in temperature profile of rice and outcomes were completely puffed rice. The rice grains, placed in the different radial zones on the turntable of oven cavity, experienced nonuniform and inconsistent rate of microwave power absorption within the rice due to its placement and rotation, the oven factors, grain's shape, size, and dielectric properties. Microwave puffing, initiated from the central region of rice, progressed toward the tips of the rice. The slow rate of heating resulted in evaporative cooling of rice and most of the rice were unable to puff completely. However, the rate of microwave heating of rice was comparable with that of sand heating and about 92.0 ± 2.3% puffed was observed when rice was place in radial zone of 5.0 cm. Hence, the exact placement of rice in the oven cavity was required for achieving good puffing quality of rice.Practical applicationsThe present study helps to understand the reasons for uneven puffing of rice in domestic microwave oven. This understanding of puffing process in domestic microwave oven provides an opportunity to develop strategy for microwave puffing of rice or design a specific microwave puffing equipment suitable for achieving quantitative and qualitative puffing of rice.

Coccoloba-associated xerocomoid boletes (Boletaceae) from the Caribbean and Mexico: Tropicoboletus ruborculus gen. et comb. nov., revision of Xerocomus coccolobae, phylogenetic assessment of Singerocomus guadelupae comb. nov., and type studies of Xerocomus caeruleonigrescens, X. cuneipes, and X. pseudoboletinus var. pini-caribaeae

Only two Coccoloba-associated xerocomoid boletes with smooth basidiospores are currently known from the Dominican Republic, namely Boletus ruborculus and Xerocomus coccolobae. A multilocus phylogenetic analysis of four gene markers (ITS, LSU, RPB2, TEF1) reveals that B. ruborculus forms an autonomous clade in the Boletaceae corresponding to a novel genus, which is introduced here as Tropicoboletus gen. nov., whereas X. coccolobae is confirmed as a member of Xerocomus s. str. Tropicoboletus is sister to subfamily Xerocomoideae in the combined RPB2/TEF1 Boletaceae-wide analysis. Accurate morphological descriptions of the two species based on well-annotated samples are provided, accompanied by color photographs of fresh specimens in habitat and line drawings of their main anatomical features. The holotype collections of B. ruborculus and X. coccolobae were successfully sequenced and re-examined anatomically. The distribution range of Tropicoboletus ruborculus comb. nov. is extended from the original locality in Puerto Rico to the Dominican Republic and Mexico where its presence is reported for the first time. Similarly, the Dominican collections of X. coccolobae represent the first documented occurrence of this species for the Island of Hispaniola. Based on molecular and morphological evidence, we conclude that the Belizean species Xerocomus olivaceus is conspecific with X. coccolobae and is therefore reduced into synonymy. In addition, the holotypes of Xerocomus caeruleonigrescens, Xerocomus cuneipes, and Xerocomus pseudoboletinus var. pini-caribaeae were microscopically re-studied, although their exact taxonomic placement remains unresolved in the absence of any phylogenetic inference. Molecular investigation of a paratype of Boletus guadelupae resulted in a conspecificity with the recently described Singerocomus atlanticus from Brazil, extending the biogeographic coverage of Singerocomus to the Caribbean. Accordingly, the new combination Singerocomus guadelupae is proposed and S. atlanticus is synonymized. Finally, a putative novel Xerocomus s. str. species is discovered from the Dominican Republic but not formally described for the time being due to the paucity of material available.

Impacts of Taxon-Sampling Schemes on Bayesian Tip Dating Under the Fossilized Birth-Death Process.

Evolutionary timescales can be inferred by molecular-clock analyses of genetic data and fossil evidence. Bayesian phylogenetic methods such as tip dating provide a powerful framework for inferring evolutionary timescales, but the most widely used priors for tree topologies and node times often assume that present-day taxa have been sampled randomly or exhaustively. In practice, taxon sampling is often carried out so as to include representatives of major lineages, such as orders or families. We examined the impacts of different densities of diversified sampling on Bayesian tip dating on unresolved fossilized birth-death (FBD) trees, in which fossil taxa are topologically constrained but their exact placements are averaged out. We used synthetic data generated by simulations of nucleotide sequence evolution, fossil occurrences, and diversified taxon sampling. Our analyses under the diversified-sampling FBD process show that increasing taxon-sampling density does not necessarily improve divergence-time estimates. However, when informative priors were specified for the root age or when tree topologies were fixed to those used for simulation, the performance of tip dating on unresolved FBD trees maintains its accuracy and precision or improves with taxon-sampling density. By exploring three situations in which models are mismatched, we find that including all relevant fossils, without pruning off those that are incompatible with the diversified-sampling FBD process, can lead to underestimation of divergence times. Our reanalysis of a eutherian mammal data set confirms some of the findings from our simulation study, and reveals the complexity of diversified taxon sampling in phylogenomic data sets. In highlighting the interplay of taxon-sampling density and other factors, the results of our study have practical implications for using Bayesian tip dating to infer evolutionary timescales across the Tree of Life. [Bayesian tip dating; eutherian mammals; fossilized birth-death process; phylogenomics; taxon sampling.].

High-efficiency silicon metasurface mirror on a sapphire substrate

For a possible implementation of high-efficiency Si-nanosphere metasurface mirrors functioning at telecom wavelengths in future gravitational wave detectors, exact dimensional and configuration parameters of the total system, including substrate and protective coating, have to be determined a priori. The reflectivity of such multi-layer metasurfaces with embedded Si nanoparticles and their potential limitations need to be investigated. Here we present the results on how the substrate and protective layer influence optical properties and demonstrate how dimensional and material characteristics of the structure alter light reflectivity. Additionally, we consider the impact of manufacturing imperfections, such as fluctuations of Si nanoparticle sizes and their exact placement, on the metasurface reflectivity. Finally, we demonstrate how high reflectivity of the system can be preserved under variations of the protective layer thickness, incident angle of light, and its polarization.

Autocorrelation and Parameter Estimation in a Bayesian Change Point Model

A piecewise function can sometimes provide the best fit to a time series. The breaks in this function are called change points, which represent the point at which the statistical properties of the model change. Often, the exact placement of the change points is unknown, so an efficient algorithm is required to combat the combinatorial explosion in the number of potential solutions to the multiple change point problem. Bayesian solutions to the multiple change point problem can provide uncertainty estimates on both the number and location of change points in a dataset, but there has not yet been a systematic study to determine how the choice of hyperparameters or the presence of autocorrelation affects the inference made by the model. Here, we propose Bayesian model averaging as a way to address the uncertainty in the choice of hyperparameters and show how this approach highlights the most probable solution to the problem. Autocorrelation is addressed through a pre-whitening technique, which is shown to eliminate spurious change points that emerge due to a red noise process. However, pre-whitening a dataset tends to make true change points harder to detect. After an extensive simulation study, the model is applied to two climate applications: the Pacific Decadal Oscillation and a global surface temperature anomalies dataset.

Controlling the gelation time of sodium silicate gelants for fluid management in hydrocarbon reservoirs

An efficient gel-based treatment of fractures and high-permeability layers requires the precise placement of the gelant within the formation, which is highly dependent on the gelation time. This study proposes an optimal method that reduces the uncertainties associated with the exact placement of sodium silicate gelants in a formation. This method is based on the control of the gelation time, so that these potent and eco-friendly blocking agents can be used more effectively in water shut-off, profile modification, and carbon storage projects. We proposed a new pre-flush operation and gelation protocol for sodium silicate gelants; gelation time experiments were conducted using a rheometer and through characterization of gel strength codes. To improve the pre-flush operation, the masking potential of citric acid is examined in this study. We show that citric acid is capable of complexing formation water ions, thus small amounts of citric acid can delay the gelation time by up to 8 h. In previous studies, silica nanoparticles were used as nucleation promoters in sodium silicate gelants, which required large amounts of surfactant for their stabilization. As an alternative, we propose a new gelation mechanism that is based on the adsorption tendency and nucleation ability of silica nanoparticles. We show that, based on their adsorption tendency, silica nanoparticles initially form an H+ layer around themselves and do not participate in the gelation reaction. At the same time, they can reduce the reaction rate of silicates, which postpones the gelation time by up to 14% (at 0.15 wt% of silica nanoparticles in defined concentrations of sodium silicate and acid). However, we observed that adding silica nanoparticles at a concentration less than 0.15 wt% or greater than 0.3 wt% accelerates gelation. But when the H+ layer breaks down, the nanoparticles intensify the gelation process through nucleation. The mechanistic insights are derived from an experimental study in which the concentrations of silica nanoparticles, sodium silicate, and gelling agent are varied. Also, experiments in a wide range of temperatures and concentrations of silica nanoparticles, sodium silicate, and citric acid showed that shielding silica nanoparticles with H+ ions released from the gelling agent keeps the nanoparticles stable in the gelant without the use of other additives. Accordingly, this mechanism, in addition to having the ability to decrease the gelation rate, increases the nucleation capacity, and reduces the complexity and cost of the system. The results of this work provide guidelines for preparing sodium silicate gelants and optimizing their gelation process.

Update: Endoprothetik am oberen Sprunggelenk

The ankle joint has to bear the entire body weight on arelatively small joint surface. Incongruities, instabilities and deformities lead to painful arthrosis and considerable restrictions in everyday life. For many years, arthrodesis has proven to be the gold standard for end stage arthrosis; however, considering modern endoprostheses for the ankle joint it is no longer appropriate to offer only arthrodesis. The very good results of the 3rd generation 3‑component prostheses and the 4th generation 2‑component prostheses show how much the surgical treatment options for the ankle joint are currently changing. The simplified implantation techniques enable access to arthroplasty of the ankle joint for abroader spectrum of surgeons and explain the increasing implantation rates in recent years. Decisive for postoperative success are correct planning with knowledge of the leg axes and foot position, correct patient selection and exact surgical placement of the components.