The human nose serves vital physiological functions, including warming, filtration, humidification, and olfaction. These functions are based on transport phenomena that depend on nasal airflow ...patterns and turbulence. Accurate prediction of these airflow properties requires careful selection of computational fluid dynamics models and rigorous validation. The validation studies in the past have been limited by poor representations of the complex nasal geometry, lack of detailed airflow comparisons, and restricted ranges of flow rate. The objective of this study is to validate various numerical methods based on an anatomically accurate nasal model against published experimentally measured data under breathing flow rates from 180 to 1100ml/s. The numerical results of velocity profiles and turbulence intensities were obtained using the laminar model, four widely used Reynolds-averaged Navier-Stokes (RANS) turbulence models (i.e., k-ε, standard k-ω, Shear Stress Transport k-ω, and Reynolds Stress Model), large eddy simulation (LES) model, and direct numerical simulation (DNS). It was found that, despite certain irregularity in the flow field, the laminar model achieved good agreement with experimental results under restful breathing condition (180ml/s) and performed better than the RANS models. As the breathing flow rate increased, the RANS models achieved more accurate predictions but still performed worse than LES and DNS. As expected, LES and DNS can provide accurate predictions of the nasal airflow under all flow conditions but have an approximately 100-fold higher computational cost. Among all the RANS models tested, the standard k-ω model agrees most closely with the experimental values in terms of velocity profile and turbulence intensity.
Nasal airflow is essential for the functioning of the human nose. Given individual variation in nasal anatomy, there is yet no consensus what constitutes normal nasal airflow patterns. We attempt to ...obtain such information that is essential to differentiate disease-related conditions.
Computational fluid dynamics (CFD) simulated nasal airflow in 22 healthy subjects during resting breathing. Streamline patterns, airflow distributions, velocity profiles, pressure, wall stress, turbulence, and vortical flow characteristics under quasi-steady state were analyzed. Patency ratings, acoustically measured minimum cross-sectional area (MCA), and rhinomanometric nasal resistance (NR) were examined for potential correlations with morphological and airflow-related variables.
Common features across subjects included: >50% total pressure drop reached near the inferior turbinate head; wall shear stress, NR, turbulence energy, and vorticity were lower in the turbinate than in the nasal valve region. However, location of the major flow path and coronal velocity distributions varied greatly across individuals. Surprisingly, on average, more flow passed through the middle than the inferior meatus and correlated with better patency ratings (r = -0.65, p < 0.01). This middle flow percentage combined with peak postvestibule nasal heat loss and MCA accounted for >70% of the variance in subjective patency ratings and predicted patency categories with 86% success. Nasal index correlated with forming of the anterior dorsal vortex. Expected for resting breathing, the functional impact for local and total turbulence, vorticity, and helicity was limited. As validation, rhinomanometric NR significantly correlated with CFD simulations (r = 0.53, p < 0.01).
Significant variations of nasal airflow found among healthy subjects; Key features may have clinically relevant applications.
Aiming at substantially improving the electrochemical sensing performance for guanine, we bring out a novel high-efficiency electrocatalyst composed of hierarchical sea urchin-like Prussian ...blue@palladium core–shell heterostructures supported on nitrogen-doped reduced graphene oxide (PB–U@Pd/N-RGO). The said PB-U@Pd/N-RGO was synthesized by a new and facile wet-chemistry method without using any surfactant and template. More impressively, we demonstrate a new strategy for morphology-controlled synthesis of Prussian blue via simply tuning the ratio of N,N′-dimethyl formamide and H2O in the mixed solvent. In-depth electrochemical characterizations demonstrate the superior electrocatalytic performance of PB-U@Pd/N-RGO toward the oxidation of guanine, which benefits from the synergistic effect of component materials and its unique core–shell heterostructure. Consequently, the constructed PB-U@Pd/N-RGO-based electrochemical sensor displays superb comprehensive performance for the guanine assay. To be specifical, the developed sensor exhibits wide detection range (0.01–85.0 μM), low detection limit (2.6 nM), good reproducibility, long-term stability, high sensitivity and selectivity together with acceptable recovery (97.0–104.0%) for the assay of guanine in biological samples. Such outstanding comprehensive performance is amongst the top of reports for the electrochemical sensing of guanine, promising practical applications in biosensing fields.
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•Novel sea urchin-like PB has been prepared by tuning the ratio of DMF and H2O.•Sea urchin-like PB exhibits superb load performance for Pd nanoparticles.•PB-U@Pd/N-RGO displays excellent catalytic properties for guanine oxidation.•Advantages for guanine assay include wide detection range and low detection limit.
Well-dispersed Pd nanoparticles were facilely anchored on graphene oxide (Pd/GO) via a one-pot chemical reduction of the Pd2+ precursor without any surfactants and templates. The morphology and ...composition of the Pd/GO nanocomposite were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and energy dispersive analysis of X-ray (EDX). The stepwise fabrication process of the Pd/GO modified electrode and its electrochemical sensing performance towards paracetamol was evaluated using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The experimental results indicate that the as-synthesized Pd nanoparticles are relatively uniform in size (5–10nm) without large aggregation and uniformly distributed in the carbon matrix with the overall Pd content of 28.77wt% in Pd/GO. Compared with the GO modified electrode, the Pd/GO modified electrode shows a better electrocatalytic activity to the oxidation of paracetamol with lower oxidation potential and larger peak current, so the Pd/GO nanocomposite can be used as an enhanced sensing platform for the electrochemical determination of paracetamol. The kinetic parameters of the paracetamol electro-oxidation at Pd/GO electrode were studied in detail, and the determination conditions were optimized. Under the optimal conditions, the oxidation peak current is linear to the paracetamol concentration in the ranges of 0.005–0.5μM and 0.5–80.0μM with a detection limit of 2.2nM. Based on the high sensitivity and good selectivity of the Pd/GO modified electrode, the proposed method was successfully applied to the determination of paracetamol in commercial tablets and human urines, and the satisfactory results confirm the applicability of this sensor in practical analysis.
•A well-dispersed Pd/GO nanocomposite was fabricated via a facile one-step chemical reduction method.•This nanocomposite displays excellent comprehensive performances for the electrochemical detection of paracetamol.•This proposed method was successfully applied to detect paracetamol in commercial tablets and human urines.
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N-doped carbon coated TiO2 nanoparticles (TiO2@NC) were synthesized through a simple two-step route, in which dopamine was simultaneously utilized as both nitrogen and carbon sources. ...With TiO2@NC applied in the Na-ion battery (SIB) anodes, the continuous and uniform N-doped carbon layer can not only enhance the electrical conductivity of TiO2 and facilitate the surface pseudocapacitive process, but also serve as a buffer layer to accommodate the volume expansion during the sodiation–desodiation processes. The as-prepared TiO2@NC exhibits excellent electrochemical performance when utilized as the SIB anodes, which delivers a remarkably high reversible capacity of 250.2 mAh g−1 at a rate of 0.25C (84 mA g−1) after 200 cycles and still retains 122.1 mAh g−1 at 10C (3.35 A g−1) even after 3000 cycles accompanied with a 95.3% retention of the maximum capacity, outperforming most of the reported TiO2/C-based composites as SIB anodes. To our best knowledge, the preparation of TiO2@NC with dopamine as both nitrogen and carbon sources and its application in the SIB anodes are reported for the first time.
Adequate perception of nasal airflow (i.e., nasal patency) is an important consideration for patients with nasal sinus diseases. The perception of a lack of nasal patency becomes the primary symptom ...that drives these patients to seek medical treatment. However, clinical assessment of nasal patency remains a challenge because we lack objective measurements that correlate well with what patients perceive. The current study examined factors that may influence perceived patency, including air temperature, humidity, mucosal cooling, nasal resistance, and trigeminal sensitivity. Forty-four healthy subjects rated nasal patency while sampling air from three facial exposure boxes that were ventilated with untreated room air, cold air, and dry air, respectively. In all conditions, air temperature and relative humidity inside each box were recorded with sensors connected to a computer. Nasal resistance and minimum airway cross-sectional area (MCA) were measured using rhinomanometry and acoustic rhinometry, respectively. General trigeminal sensitivity was assessed through lateralization thresholds to butanol. No significant correlation was found between perceived patency and nasal resistance or MCA. In contrast, air temperature, humidity, and butanol threshold combined significantly contributed to the ratings of patency, with mucosal cooling (heat loss) being the most heavily weighted predictor. Air humidity significantly influences perceived patency, suggesting that mucosal cooling rather than air temperature alone provides the trigeminal sensation that results in perception of patency. The dynamic cooling between the airstream and the mucosal wall may be quantified experimentally or computationally and could potentially lead to a new clinical evaluation tool.
The role of procalcitonin in diagnosing severe acute pancreatitis has not been clearly assessed. This meta-analysis aims to evaluate the overall diagnostic accuracy of procalcitonin as a biomarker ...for severe acute pancreatitis. Medline (via PubMed), Embase, Web of Science, Cochrane Library, China National Knowledge Infrastructure, and China WanFang Data were searched systematically for prospective studies reporting procalcitonin as a diagnostic marker of severe acute pancreatitis before August 31, 2021. Sensitivity, specificity, and other measures of the accuracy of procalcitonin in the diagnosis of severe acute pancreatitis were pooled by Stata 15.0 software. Heterogeneity was evaluated by I.sup.2 test, and the quality of included studies was evaluated by using the Quality Assessment of Diagnostic Accuracy Studies-2 system. Further, the sources of heterogeneity were verified using meta-regression and subgroup analysis, and the publication bias was evaluated by the Deeks' funnel plot. A total of 18 studies meeting the inclusion criteria were included, containing 1764 patients. The pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, diagnostic odds ratio, and area under the receiver operating characteristic curve of procalcitonin for diagnosing severe acute pancreatitis were as follows: 0.80 (95% CI: 0.73-0.86), 0.84 (95% CI: 0.78-0.88), 4.95 (95% CI: 3.46-7.09), 0.23 (95% CI: 0.16-0.34), 21.26 (95% CI: 11.09-40.74), 0.89 (95% CI: 0.86-0.92). Also, P > .05 suggested no significant publication bias. Current evidence indicates that procalcitonin has good sensitivity and diagnostic accuracy for severe acute pancreatitis. However, the findings should be carefully used as routine evidence in diagnosing patients with severe acute pancreatitis alone because of the limited number of included studies and high heterogeneity. Keywords: Diagnosis, meta-analysis, procalcitonin, severe acute pancreatitis
With the advancement of artificial intelligence technology, memristors show great potential in serving as artificial synapses to imitate diverse biological learning behaviors. In this study, we ...present the implementation of an artificial nociceptor using a threshold switching memristor device based on zinc oxide. The memristor device with threshold switching demonstrates volatile resistance switching properties, offering an on/off ratio of 10
5
. This feature enables the emulation of learning patterns observed in biological synapses. The synaptic plasticity of the Al/ZnO/FTO memristor encompasses spike rate-dependent plasticity, paired-pulse facilitation, spike timing-dependent plasticity, and long-term potentiation/depression. In addition, the threshold switching memristor consisting of Al/ZnO/FTO has a similar function to that of a nociceptor, which is a specialized receptor found in sensory neurons responsible for detecting harmful stimuli and transmitting signals to the central nervous system for protective measures. The device demonstrates several important characteristics resembling nociceptors, such as the occurrence of threshold, relaxation, and sensitization phenomena associated with allodynia and hyperalgesia. These responses are influenced by factors, such as the intensity, duration, and frequency of the external stimuli. This study demonstrates the potential use of this device in alarm systems for humanoid robots, specifically designed to enhance their artificial sensory capabilities.
Tailored designs/fabrications of hierarchical porous advanced electrode materials are of great importance for developing high-performance electrochemical sensors. Herein, we demonstrate a simple and ...low-cost in situ chemical approach for the facile synthesis of MnO2-embedded hierarchical porous carbon microspheres (MnO2/CM). By the characterizations of scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray powder diffraction and energy dispersive spectroscopy, we evidenced that the synthesized product were flower-like carbon microspheres (CM) assembled by the bent flakes with thickness of about several nanometers and MnO2 nanorods were highly dispersed and successfully decorated on the CM layers, resulting in a rough surface and three-dimensional microstructure. The greatest benefit from the combined porous CM with MnO2 nanorods is that the MnO2/CM modified electrode has the synergetic catalysis effect on the electro-oxidation of caffeic acid, leading to the remarkable increase in the electron transfer rate and significant decrease in the over-potential for the caffeic acid oxidation in contrast to the bare electrode and CM modified electrode. This implies that the prepared MnO2/CM can be employed as an enhanced electrocatalyst for the sensitive detection of caffeic acid. Under the optimum conditions, the anodic peak current of caffeic acid is linear with its concentration in the range of 0.01–15.00 μmol L−1, and a detection limit of 2.7 nmol L−1 is achieved based on S/N = 3. The developed sensor shows good selectivity, sensitivity, reproducibility, and also excellent recovery in the detections of real samples, revealing the promising practicality of the sensor for the caffeic acid detection.
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•The novel hybrid of flower-like porous MnO2/MC was fabricated by a simple strategy.•MnO2/MC shows superior electrocatalytic properties for the oxidation of caffeic acid.•The MnO2/MC-based sensor shows excellent performance for the caffeic acid detection.•This proposed method was successfully used to detect caffeic acid in tablets and fruits.
Because of the promising corrosion resistance and load-bearing capacity, titanium-clad (TC) bimetallic steel has gained increasing attention in ocean/coastal civil and structural engineering. Due to ...the double-layer nature of TC bimetallic steel, the characteristics of the structural member’s geometry and weld details are considerably different from that of conventional steel members. Even though previous studies have conducted systematical clarifications on parent material of TC bimetallic steels, the mechanical behaviors of weld joints are still vague. This paper firstly describes the manufacture features of TC bimetallic steel welded joints and welded members. Subsequently, the type II and type III butt-welded joints provided by GB/T 13149-2009 are selected to study the corresponding tensile mechanical behavior. Two butt-welded TC bimetallic steel plates were fabricated from hot-rolled bonding TA2 + Q355B TC bimetallic steel and welding wire of ER55-Ni1 and ERTA2ELI. Eight tensile coupons were then extracted from the two welded plates and loaded to failure monotonically. The failure mechanism, stress–strain curves and key mechanical properties are studied and compared with that of parent material. It is found that both types of welded joints possess two fracture points. The first one refers to the fracture of weld joint between the clad layer and titanium cover plate, whilst the second one is the eventual fracture of substrate metal. When the first fracture point is reached, the stress–strain relation exhibits a sharp drop in stress value. Thereafter, a strain-hardening behavior can still be observed prior to the ultimate strength point. The first fracture-induced stress drop of type II joint is less than that of type III joint, whilst the strain-hardening amount of type II joint is more outstanding than that of type III joint. The fracture elongations of type II joint and type III joint are respectively 37% and 57% that of the parent material, whilst the proportions between the ultimate strengths of welded joints and parent material are, respectively, 90% and 93%. In general, the two types of TC bimetallic steel weld joints investigated herein exhibit favorable load-bearing capacity but unfavorable ductility and deformability. Based upon the experimental results, the structural design methodology of welded TC bimetallic steel structure is discussed. The investigations conducted in this paper can provide reference for development of structural design theory of welded TC bimetallic steel structure.
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