Evaluating the prognostic performance of candidate markers for future disease onset or progression is one of the major goals in medical research. A marker's prognostic performance refers to how well ...it separates patients at the high or low risk of a future disease state. Often the discriminative performance of a marker is affected by the patient characteristics (covariates). Time‐dependent receiver operating characteristic (ROC) curves that ignore the informativeness of the covariates will lead to biased estimates of the accuracy parameters. We propose a time‐dependent ROC curve that accounts for the informativeness of the covariates in the case of censored data. We propose inverse probability weighted (IPW) estimators for estimating the proposed accuracy parameters. We investigate the performance of the IPW estimators through simulation studies and real‐life data analysis.
Structural health monitoring (SHM) techniques have been studied for several years. An effective approach for SHM is to choose the parameters that are sensitive to the damage occurring in the ...structure but not sensitive to operational or environmental damages. This paper deals with a comparative study among the different vibration-based damage detection methods: fundamental modal examination, local diagnostic method, non-probabilistic methodology and the time series method. All these strategies contemplate different parameters of a structure to recognize damage. Out of the study made, time series analysis proves to more successfully in damage identification than the rest of the methods.
The electrical resistance change of a highly extensible composite consisting of a network of entangled multi-wall carbon nanotubes in a thermoplastic polyurethane elastomer is tested. The composite ...is prepared by taking a non-woven polyurethane filter membrane, enmeshing it with carbon nanotubes and melding them together. Testing has shown that the material can be elongated as much as 400% during which the resistance is increased more than 270 times. It indicates favorable properties of the composite for its use as a highly-deformation strain sensing element, a strain-electric signal transducer, electromagnetic field shielding and protection against lightning. As an example of its use as a strain sensor, human knee flexion and knee cyclic movement has been monitored. This may be of use in orthopedics and rehabilitation.
Cancer patients, chronic kidney disease patients, and subjects infected with HIV are routinely monitored over time using biomarkers that represent key health status indicators. Furthermore, ...biomarkers are frequently used to guide initiation of new treatments or to inform changes in intervention strategies. Since key medical decisions can be made on the basis of a longitudinal biomarker, it is important to evaluate the potential accuracy associated with longitudinal monitoring. To characterize the overall accuracy of a time‐dependent marker, we introduce a summary ROC curve that displays the overall sensitivity associated with a time‐dependent threshold that controls time‐varying specificity. The proposed statistical methods are similar to concepts considered in disease screening, yet our methods are novel in choosing a potentially time‐dependent threshold to define a positive test, and our methods allow time‐specific control of the false‐positive rate. The proposed summary ROC curve is a natural averaging of time‐dependent incident/dynamic ROC curves and therefore provides a single summary of net error rates that can be achieved in the longitudinal setting.
Sodium alginate (SA) and gelatine (G) based hydrogels with various SA/G ratios, crosslinked with calcium ions (Ca2+) and glutaraldehyde (GTA), respectively, were developed. Scanning electron ...microscopy, Fourier transform infrared spectroscopy (FTIR), and dynamic mechanical analysis (DMA) were applied to determine their physicochemical characterization. The swelling studies, conducted in phosphate-buffered saline with a pH ranging from 1 to 11 at 37°C, were utilized for an evaluation of their absorption ability. FTIR spectra of the Ca2+ crosslinked SA/G hydrogels revealed a small shift in symmetric stretching carboxyl groups, indicating an ionic binding between the Ca2+ ions and the SA. Increasing the G content in hydrogels crosslinked with GTA significantly changed the shapes of the amide I and II bands in the FTIR spectra, thus confirming the G–GTA crosslink formation. After crosslinking, a DMA study proved the enhanced viscoelastic properties and improved thermal stability of the prepared samples. The obtained data indicated that Ca2+ crosslinked hydrogels with a SA/G 50/50 ratio provide a good balance of swelling and viscoelastic properties, making them applicable as a potential nontoxic wound dressing material capable of adequately assuring a moist environment, elasticity and mechanical strength for comfortable wound healing.
Background Practice guidelines reflect published literature. Because of the ever changing literature base, it is necessary to update and revise guideline recommendations from time to time. The ...Society of Thoracic Surgeons recommends review and possible update of previously published guidelines at least every three years. This summary is an update of the blood conservation guideline published in 2007. Methods The search methods used in the current version differ compared to the previously published guideline. Literature searches were conducted using standardized MeSH terms from the National Library of Medicine PUBMED database list of search terms. The following terms comprised the standard baseline search terms for all topics and were connected with the logical ‘OR’ connector—Extracorporeal circulation (MeSH number E04.292), cardiovascular surgical procedures (MeSH number E04.100), and vascular diseases (MeSH number C14.907). Use of these broad search terms allowed specific topics to be added to the search with the logical ‘AND’ connector. Results In this 2011 guideline update, areas of major revision include: 1) management of dual anti-platelet therapy before operation, 2) use of drugs that augment red blood cell volume or limit blood loss, 3) use of blood derivatives including fresh frozen plasma, Factor XIII, leukoreduced red blood cells, platelet plasmapheresis, recombinant Factor VII, antithrombin III, and Factor IX concentrates, 4) changes in management of blood salvage, 5) use of minimally invasive procedures to limit perioperative bleeding and blood transfusion, 6) recommendations for blood conservation related to extracorporeal membrane oxygenation and cardiopulmonary perfusion, 7) use of topical hemostatic agents, and 8) new insights into the value of team interventions in blood management. Conclusions Much has changed since the previously published 2007 STS blood management guidelines and this document contains new and revised recommendations.
As the COVID-19 is still growing throughout the globe, a thorough investigation into the specific immunopathology of SARS-CoV-2, its interaction with the host immune system and pathogen evasion ...mechanism may provide a clear picture of how the pathogen can breach the host immune defenses in elderly patients and patients with comorbid conditions. Such studies will also reveal the underlying mechanism of how children and young patients can withstand the disease better. The study of the immune defense mechanisms and the prolonged immune memory from patients population with convalescent plasma may help in designing a suitable vaccine candidate not only for the current outbreak but also for similar outbreaks in the future. The vital drug candidates, which are being tested as potential vaccines or therapeutics against COVID-19, include live attenuated vaccine, inactivated or killed vaccine, subunit vaccine, antibodies, interferon treatment, repurposing existing drugs, and nucleic acid-based vaccines. Several organizations around the world have fast-tracked the development of a COVID-19 vaccine, and some drugs already went to phase III of clinical trials. Hence, here, we have tried to take a quick glimpse of the development stages of vaccines or therapeutic approaches to treat this deadly disease.
Here, we have demonstrated strong size dependency of quasi-equilibrium and nonequilibrium carrier and photon dynamics in InGaN/GaN single nanowalls using photoluminescence and transient absorption ...spectroscopy. We demonstrate that two-dimensional carrier confinement, strain relaxation, and modified density of states lead to a reduced Stokes shift, smaller full width at half-maxima, increased exciton binding energy, and reduced nonradiative recombination. The ultrafast transient spectroscopy shows that carrier capture is a two-step process dominated by optical phonons and carrier–carrier scattering in succession. The carrier capture is a strongly size-dependent process and becomes slower due to modulation of the density of available states for progressively decreasing nanowall sizes. The slowest process is the electron–hole recombination, which is also extremely size-dependent and the rate increases by almost an order of magnitude in comparison to that of quantum-well structures. Electron–hole wave function overlap and modified density of states are among the key aspects in determining all the properties of these structures.
The sensitivity of multi-wall carbon nanotube (MWCNT) networks of randomly entangled pure nanotubes and those oxidized with acidic KMnO
4 to various organic solvent vapors (iso-pentane, diethyl ...ether, acetone and methanol) has been investigated by resistance measurements. The solvents had different polarities given by Hansen solubility parameters and different volume fractions of saturated vapors defined by the vapor pressure. The results show that the network electrical resistance increases when exposed to organic solvent vapors, and a reversible reaction is observed when the network is removed from the vapors. The reaction with KMnO
4 increases oxygen content on the nanotube surface and causes lower porosity of MWCNT network as well as higher electrical resistance, which improves the network selectivity to polar solvents. The investigated MWCNT networks could be potentially used as sensing elements for sensitive and selective organic vapor switches.
PDF
