CFD Simulations on the Heating Capability in a Human Nasal Cavity

The air conditioning capability of the nose is dependent on the nasal mucosal temperature and the airflow dynamics caused by the airway geometry. A computational model of a human nasal cavity obtained through CT scans was produced and CFD techniques were applied to study the effects of morphological differences in the left and right nasal cavity on the airflow and heat transfer of inhaled air. A laminar steady flow of 10L/min was applied and two inhalation conditions were investigated: normal conditions, 25°C, 35% relative humidity and cold dry air conditions, 12°C, 13% relative humidity. It was found that the frontal regions of the nasal cavity exhibited greater secondary cross flows compared to the middle and back regions. The left cavity in the front region had a smaller cross-sectional area compared to the right which allowed greater heating as the heat source from the wall was closer to the bulk flow regions. Additionally it was found that the residence time of the inhaled air was important for the heating ability in laminar flows

A combined experimental and numerical study on upper airway dosimetry of inhaled nanoparticles from an electrical discharge machine shop

Backgrounds: Exposure to nanoparticles in the workplace is a health concern to occupational workers with increased risk of developing respiratory, cardiovascular, and neurological disorders. Based on animal inhalation study and human lung tumor risk extrapolation, current authoritative recommendations on exposure limits are either on total mass or number concentrations. Effects of particle size distribution and the implication to regional airway dosages are not elaborated. Methods: Real time production of particle concentration and size distribution in the range from 5.52 to 98.2 nm were recorded in a wire-cut electrical discharge machine shop (WEDM) during a typical working day. Under the realistic exposure condition, human inhalation simulations were performed in a physiologically realistic nasal and upper airway replica. The combined experimental and numerical study is the first to establish a realistic exposure condition, and under which, detailed dose metric studies can be performed. In addition to mass concentration guided exposure limit, inhalation risks to nano-pollutant were reexamined accounting for the actual particle size distribution and deposition statistics. Detailed dosimetries of the inhaled nano-pollutants in human nasal and upper airways with respect to particle number, mass and surface area were discussed, and empirical equations were developed. Results: An astonishing enhancement of human airway dosages were detected by current combined experimental and numerical study in the WEDM machine shop. Up to 33 folds in mass, 27 folds in surface area and 8 folds in number dosages were detected during working hours in comparison to the background dosimetry measured at midnight. The real time particle concentration measurement showed substantial emission of nano-pollutants by WEDM machining activity, and the combined experimental and numerical study provided extraordinary details on human inhalation dosimetry. It was found out that

Assessment of Cropland Changes Due to New Canals in Vientiane Prefecture of Laos using Earth Observation Data

The lower catchment area of a Mak Hiao river system is vulnerable to flash floods and water stress. So it is important to construct irrigation structures in this area to minimize floods during the rainy season and store water for the winter season. The Asian Development Bank (ADB) has been supporting the Government of Laos in constructing such small reservoirs like Donkhuay schemes 1 & 2, Mak Hiao, Nalong 3 and Sang Houabor projects in lower catchment areas. Our study evaluated the impacts of small irrigation schemes in terms of land-use/landcover (LULC), crop intensity, and productivity changes, using high resolution satellite imagery, socioeconomic, and ground data. We analyzed the temporal cropping pattern in the Vientiane prefecture of Laos using Planet and Sentinel-2 data. On the other hand, crop intensity and cropland changes were mapped using Sentinel-2 data and spectral matching techniques (SMTs). The crop classification accuracy based on field-plot data was 88.6%. Our results show that irrigation projects in the lower catchment areas brought about significant on-site changes in terms of cropland expansion and increased crop intensity. Remarkable changes in LULC were observed especially in the command areas owing to an increase of about 300% in crop area with access to irrigation and increase of water bodies by 31%. Our study found that interventions at the level of the command area do improved on-site soil, water and environmental services. They study emphasized underline the role of land-use regulations in reducing pressure on natural land-use systems and thereby serving the major goal of up-scaling sustainable natural resource management. The study documented the vital role of small/medium irrigation projects in restoring ecosystem services such as cropping patterns and LULC conversio

Safety and efficacy of GABAA α5 antagonist S44819 in patients with ischaemic stroke: a multicentre, double-blind, randomised, placebo-controlled trial

Background: S44819, a selective GABAA α5 receptor antagonist, reduces tonic post-ischaemic inhibition of the peri-infarct cortex. S44819 improved stroke recovery in rodents and increased cortical excitability in a transcranial magnetic stimulation study in healthy volunteers. The Randomized Efficacy and Safety Trial of Oral GABAA α5 antagonist S44819 after Recent ischemic Event (RESTORE BRAIN) aimed to evaluate the safety and efficacy of S44819 for enhancing clinical recovery of patients with ischaemic stroke. Methods: RESTORE BRAIN was an international, randomised, double-blind, parallel-group, placebo-controlled, multicentre phase 2 trial that evaluated the safety and efficacy of oral S44189 in patients with recent ischaemic stroke. The study was done in specialised stroke units in 92 actively recruiting centres in 14 countries: ten were European countries (Belgium, Czech Republic, France, Germany, Hungary, Italy, Netherlands, Poland, Spain, and the UK) and four were non-European countries (Australia, Brazil, Canada, and South Korea). Patients aged 18–85 years with acute ischaemic stroke involving cerebral cortex (National Institute of Health Stroke Scale [NIHSS] score 7–20) without previous disability were eligible for inclusion. Participants were randomly assigned to receive 150 mg S44819 twice a day, 300 mg S44819 twice a day, or placebo twice a day by a balanced, non-adaptive randomisation method with a 1:1:1 ratio. Treatment randomisation and allocation were centralised via the interactive web response system using computer-generated random sequences with a block size of 3. Blinding of treatment was achieved by identical appearance and taste of all sachets. Patients, investigators and individuals involved in the analysis of the trial were masked to group assignment. The primary endpoint was the modified Rankin Scale (mRS) score 90 days from onset of treatment, evaluated by shift analysis (predefined main analysis) or by dichotomised analyses using 0–1 versus 2–6 and 0–2 versus 3–6 cutoffs (predefined secondary analysis). Secondary endpoints were the effects of S44819 on the NIHSS and Montreal Cognitive Assessment (MoCA) scores, time needed to complete parts A and B of the Trail Making Test, and the Barthel index. Efficacy analyses were done on all patients who received at least one dose of treatment and had at least one mRS score taken after day 5 (specifically, on or after day 30). Safety was compared across treatment groups for all patients who received at least one dose of treatment. The study was registered at ClinicalTrials.gov, NCT02877615. Findings: Between Dec 19, 2016, and Nov 16, 2018, 585 patients were enrolled in the study. Of these, 197 (34%) were randomly assigned to receive 150 mg S44819 twice a day, 195 (33%) to receive 300 mg S44819 twice a day, and 193 (33%) to receive placebo twice a day. 189 (96%) of 197 patients in the 150 mg S44819 group, 188 (96%) of 195 patients in the 300 mg S44819 group, and 191 (99%) patients in the placebo group received at least one dose of treatment and had at least one mRS score taken after day 5, and were included in efficacy analyses. 195 (99%) of 197 patients in the 150 mg S44819 group, 194 (99%) of 195 patients in the 300 mg S44819 group, and 193 (100%) patients in the placebo group received at least one dose of treatment, and were included in safety analyses. The primary endpoint of mRS at day 90 did not differ between each of the two S44819 groups and the placebo group (OR 0·91 [95% CI 0·64–1·31]; p=0·80 for 150 mg S44819 compared with placebo and OR 1·17 [95% CI 0·81–1·67]; p=0·80 for 300 mg S44819 compared with placebo). Likewise, dichotomised mRS scores at day 90 (mRS 0–2 vs 3–6 or mRS 0–1 vs 2–6) did not differ between groups. Secondary endpoints did not reveal any significant group differences. The median NIHSS score at day 90 did not differ between groups (4 [IQR 2–8] in 150 mg S44819 group, 4 [2–7] in 300 mg S44819 group, and 4 [2–6] in placebo group), nor did the number of patients at day 90 with an NIHSS score of up to 5 (95 [61%] of 156 in 150 mg S44819 group, 106 [66%] of 161 in 300 mg S44819 group, and 104 [66%] of 157 in placebo group) versus more than 5 (61 [39%] in 150 mg S44819 group, 55 [34%] in 300 mg S44819 group, and 53 [34%] in placebo group). Likewise, the median MoCA score (22·0 [IQR 17·0–26·0] in 150 mg S44819 group, 23·0 [19·0–26·5] in 300 mg S44819 group, and 22·0 [17·0–26·0] in placebo group), time needed to complete parts A (50 s [IQR 42–68] in 150 mg S44819 group, 49 s [36–63] in 300 mg S44819 group, and 50 s [38–68] in placebo group) and B (107 s [81–144] in 150 mg S44819 group, 121 s [76–159] in 300 mg S44819 group, and 130 s [86–175] in placebo group) of the Trail Making Test, and the Barthel index (90 [IQR 60–100] in 150 mg S44819 group, 90 [70–100] in 300 mg S44819 group, and 90 [70–100] in placebo group) were similar in all groups. Number and type of adverse events were similar between the three groups. There were no drug-related adverse events and no drug-related deaths. Interpretation: There was no evidence that S44819 improved clinical outcome in patients after ischaemic stroke, and thus S44819 cannot be recommended for stroke therapy. The concept of tonic inhibition after stroke should be re-evaluated in humans. Funding: Servier

A numerical investigation of wind environment around a walking human body

Human-induced wake flow characteristics and its interaction with thermal conditions was investigated by performing CFD simulations with dynamic-meshing of a moving manikin model. The manikin motion with and without swinging limbs was achieved by the re-meshing method to update the grid with each time step. The results focused on determining what discrepancies are produced in the flow field by a simplified geometry in the form of a cylinder, swinging limbs and thermal conditions; and whether such assumptions can be made for larger multi-body analysis. Using a cylinder showed differences in the velocity field behind the head and leg gap. The flow field between the rigid motion and swinging limb motion, showed significant discrepancies which corresponded to the gait phase. There were increased airflow disturbances at the hands and ankles (furthest body parts from the pivot point). The influence of thermal plume on the wake flow was minor during walking motion because of the walking speed of 1.2 m/s which dominated the buoyant thermal plume velocity. However, after the manikin stopped moving the thermal plume velocity became comparable to the residual wake

Surface mapping for visualisation of wall stresses during inhalation in a human nasal cavity

Airflow analysis can assist in better understanding the physiology however the human nasal cavity is an extremely complicated geometry that is difficult to visualize in 3D space, let alone in 2D space. In this paper, an anatomically accurate 3D surface of the nasal passages derived from CT data was unwrapped and transformed into a 2D space, into a UV-domain (where u and v are the coordinates) to allow a complete view of the entire wrapped surface. This visualization technique allows surface flow parameters to be analyzed with greater precision. A UV-unwrapping tool is developed and a strategy is presented to allow deeper analysis to be performed. This includes (i) the ability to present instant comparisons of geometry and flow variables between any number of different nasal cavity models through normalization of the 2D unwrapped surface; (ii) visualization of an entire surface in one view and; (iii) a planar surface that allows direct 1D and 2D analytical solutions of diffusion of inhaled vapors and particles through the nasal walls. This work lays a foundation for future investigations that correlates adverse and therapeutic health responses to local inhalation of gases and particles

Dynamic meshing modelling for particle resuspension caused by swinging manikin motion

Human-induced wake flow characteristics and its impact on particle re-dispersion from the floor was investigated by performing CFD simulations of a moving thermal manikin model. The manikin moved with realistic kinematic motion which included swinging arms and legs. This was performed using dynamic-meshing which updated the grid with each time step to represent the manikin motion. The wake flow and fluid dynamics generated from three walking speeds (0.8 m/s, 1.2 m/s and 1.8 m/s) were compared. Particle transport from the floor and its re-dispersion was tracked by the Lagrangian approach. The results showed that the flow field had a strong dependence on the walking motion. For example the flow behind the body showed a downwash flow originating from the head, at mid-height the flow followed the manikin, and at the leg and feet, there was slight upwards flow. At the front of the body, flow streamlines showed the flow was pushed out and was pulled back around the body into the wake. These flow patterns provided the basis for particle re-suspension from the floor and dispersion through the air. After the manikin stopped walking, the wake continued forwards and passed over the manikin body. When the wake momentum dissipated, thermal plume effects became significant which influenced the airborne particles to spread over time. The particle concentration entering the frontal zones of the body during the walking was evaluated to show the level of occupants exposure to contaminants

Experimental and numerical investigation on a new type of heat exchanger in ground source heat pump system

Based on deficiencies of existing underground heat exchangers, a new design is proposed which consists of one outlet and three inlet pipes. Experimental measurements to evaluate the performance of single-U, double-U, and the new design referred to as 3I, for three inlet pipes, were carried out which showed superior performance of the 3I design. Experimental results showed that when under a constant heating load, the average circulating water temperature (ACWT) of the 3I-type was 3.7 and 1 °C lower than that of single-U and double-U, respectively. The thermal resistance of the 3I-type was 15.8 and 31.1 % lower than that of double-U and single-U type. In addition, numerical simulations were performed to further investigate the heat transfer performance over a very long operating time. Numerical results showed that for long-term operation under constant heating load, the ACWT of the 3I-type was 6.6 and 5.8 % lower than that of double-U type. Under a constant inlet water temperature that mimics a condenser output, the heat exchange per unit borehole depth of 3I-type was 17.1 and 11.6 % higher than that of double-U type in different operation conditions

Detailed micro-particle deposition patterns in the human nasal cavity influenced by the breathing zone

The breathing region connects the nasal cavity with the outside environmental air where flow is accelerated through the nostrils. Particles introduced into the nasal cavity without considering the breathing region neglect the influence of facial features and realistic boundary conditions at the nostrils. In this study, a new nasal cavity model is reconstructed combining facial features and an ambient environment focusing on the breathing region. The inhaled air from outside the nose is investigated and compared with a model that consists of the nasal cavity alone. An improved 2D surface mapping technique is applied to the 3D nasal cavity to visualize the particle deposition patterns onto a planar geometry. Using this technique, deposition of micron particles from 0.4 μm to 30 μm were investigated, and trajectories of 2.5 μm, 10 μm and 20 μm were compared with the 'nasal-only' case. Particle deposition efficiency curves and particle trajectories are plotted to show that the inclusion of the external nose and breathing region causes: (i) a change in the fluid flow within the anterior nasal cavity half but the flow patterns regulate in the posterior half; (ii) minimal difference for 2.5 μm particle deposition patterns; (iii) significant differences in 10 and 20 μm particle deposition patterns where more particles are deposited in the posterior nasal regions

Application of surface mapping to visualize wall shear stress and particles deposition in a realistic human nasal cavity

Nasal cavity is an important component of respiration system for the various physiological functions (Elad et al., 2008; Lee, 2010). By using a commercial CFD software Ansys-Fluent and a surface mapping software Unfold3D, wall shear stress (WSS) distribution and particle deposition patterns on the nasal cavity wall were simulated and transformed into a normalized UV domain (where U and V denote coordinate axes of a 2D space) to present a complete view of an entire wrapped surface, therefore to be analyzed with better precision and to allow direct comparisons between left and right cavities. In this paper, applications of surface mapping methods on a nasal cavity are demonstrated, and results for WSS distribution and time dependent particle deposition on UV domain during steady inhalation are analyzed