Climate change and the urgency of decarbonizing the built environment are driving technological innovation in the way we deliver thermal comfort to occupants. These changes, in turn, seem to be ...setting the directions for contemporary thermal comfort research. This article presents a literature review of major changes, developments, and trends in the field of thermal comfort research over the last 20 years. One of the main paradigm shift was the fundamental conceptual reorientation that has taken place in thermal comfort thinking over the last 20 years; a shift away from the physically based determinism of Fanger's comfort model toward the mainstream and acceptance of the adaptive comfort model. Another noticeable shift has been from the undesirable toward the desirable qualities of air movement. Additionally, sophisticated models covering the physics and physiology of the human body were developed, driven by the continuous challenge to model thermal comfort at the same anatomical resolution and to combine these localized signals into a coherent, global thermal perception. Finally, the demand for ever increasing building energy efficiency is pushing technological innovation in the way we deliver comfortable indoor environments. These trends, in turn, continue setting the directions for contemporary thermal comfort research for the next decades.
In the context of airborne infection control, it is critical that the ventilation system is able to extract the contaminated exhaled air within the shortest possible time. To minimize the spread of ...contaminated air exhaled by occupants efficiently, a novel personalized ventilation (PV)–personalized exhaust (PE) system has been developed, which aims to exhaust the exhaled air as much as possible from around the infected person (IP). The PV–PE system was studied experimentally for a particular healthcare setting based on a typical consultation room geometry and four different medical consultation positions of an IP and a healthy person (HP). Experiments using two types of tracer gases were conducted to evaluate two types of PE: Top‐PE and Shoulder‐PE under two different background ventilation systems: Mixing Ventilation and Displacement Ventilation. Personalized exposure effectiveness, intake fraction (iF) and exposure reduction (ε) were used as indices to evaluate the PV–PE system. The results show that the combined PV‐PE system for the HP achieves the lowest intake fraction; and the use of PE system for the IP alone shows much better performance than using PV system for the HP alone.
•Effective distribution of airflow for indoor built environments is research focus.•Theory and practical applications of air distribution methods are reviewed.•Measuring and evaluating methods of air ...distribution are discussed.
Ventilation and air distribution methods are important for indoor thermal environments and air quality. Effective distribution of airflow for indoor built environments with the aim of simultaneously offsetting thermal and ventilation loads in an energy efficient manner has been the research focus in the past several decades. Based on airflow characteristics, ventilation methods can be categorized as fully mixed or non-uniform. Non-uniform methods can be further divided into piston, stratified and task zone ventilation. In this paper, the theory, performance, practical applications, limitations and solutions pertaining to ventilation and air distribution methods are critically reviewed. Since many ventilation methods are buoyancy driving that confines their use for heating mode, some methods suitable for heating are discussed. Furthermore, measuring and evaluating methods for ventilation and air distribution are also discussed to give a comprehensive framework of the review.
A novel air distribution principle of cooler air near the floor level being propelled upward via four fans mounted at each corner of a chair was developed to enhance the performance of conventional ...displacement ventilation (DV) system. Experiments were conducted in a well-controlled climate chamber with DV and constant heat load at different supply air temperatures, namely 20, 22, and 24 °C and room air temperatures, 22, 24, and 26 °C. Subjective assessments were carried out with 32 tropically-acclimatized college students who were given the choice to adjust the fan speed. Subjects' thermal comfort and the implication of personal usage pattern of the enhanced DV system were studied. The results revealed that at the ambient temperature of 26 °C, subjects preferred higher air movement and were satisfied with the cooling provided by the fans. However, the subjects felt cooler at the waists at room air temperatures of 22 and 24 °C when the fans were in operation. It was also found that the Whole Body Thermal Sensation (WBTS) reported by the subjects was correlated with the Local Thermal Sensation (LTS) at the waist, the arms, the calf and the feet when the novel DV system was employed. An expression which allows predicting WBTS based on the LTS was developed. Recommendations for fan speed at different room air temperatures were derived.
► The use of the fans in a DV room improved significantly the thermal sensation. ► The subjects did not frequently change the fan speed. ► The air movement around occupants could help to offset the warm thermal sensation.
The main objective of the study is to quantify the mass concentration exposure levels of fine traffic-generated particles (PM
2.5) at various heights of typical multi-storey public housing buildings ...located in close proximity, i.e. within 30
m and along a busy major expressway in Singapore. The secondary objective is to compare the potential health risks of occupants in the buildings, associated with inhalation exposure of fine traffic-generated particulate matter, based on estimated dose rates and the lowest observed adverse effect levels (loael) at the various floors of these buildings. Two typical public housing buildings, both naturally ventilated residential apartment blocks, of point block configuration (22-storey) and slab block configuration (16-storey) were selected for the study. Particulate samples were collected for both mass and chemical analysis (OC/EC ratio) at three representative floors: the lower, the mid, and upper floors of the buildings. Key meteorological parameters such as wind speed, wind direction, ambient temperature, and relative humidity were also concurrently measured at the sampling locations. For the potential health risk analysis, the occupants have been divided into four age categories namely, infants, children (1 year), children (8–10 years) and adults. The analysis takes into account age-specific breathing rates, body weights for different age categories. Experimental results explicitly showed that PM
2.5 mean particle mass concentration was highest at the midfloors of both buildings when compared to those measured at upper and lower floors during a typical day. Although the lower floors were closest to traffic emissions, the mean particle mass concentration was lower there than that at the midfloors, which could presumably be due to the interception of PM
2.5 particles by tree leaves or the inflow of clean and drier air from higher altitude with lower aerosol burden mixing with the traffic-polluted air at the lower levels thus lowering the concentration at the lower floors similar to induced chimney effect or both. The upper floors had the least fine particulate matter mass concentration due to dilution following pronounced mixing of traffic-polluted air with ambient air. The only difference between both blocks is that at corresponding floors, the mass concentration levels for slab block is much higher than that of point block. This could be attributed to the configuration of the blocks. Observational data show the slab block tends to slow down the approaching wind thus allowing the accumulation of the fine traffic-generated particulate matter in front of the building. For point block, the HR values at the mid and lower floors suggest that occupants living in these floors experience 1.81 and 1.34 times more health risk, respectively, in contracting respiratory diseases when compared to those living at the upper floors for all age categories. Similarly, for the slab block, occupants living in the mid and lower floors had 1.62 and 1.28 times more risk, respectively, in contracting respiratory diseases when compared to those living at the upper floors for all age categories.
This paper presents a study of local thermal sensation (LTS) and comfort in a field environmental chamber (FEC) served by displacement ventilation (DV) system. The FEC, 11.12
m (
L)×7.53
m (
W)×2.60
...m (
H), simulates a typical office layout. A total of 60 tropically acclimatized subjects, 30 male and 30 female, were engaged in sedentary office work for 3
h. Subjects were exposed to three vertical air temperature gradients, nominally 1, 3 and 5
K/m, between 0.1 and 1.1
m heights and three room air temperatures of 20, 23 and 26
°C at 0.6
m height. The objective of this study is to investigate the mutual effect of local and overall thermal sensation (OTS) and comfort in DV environment. The results show that in a space served by DV system, at OTS close to neutral, local thermal discomfort decreased with the increase of room air temperature. The OTS of occupants was mainly affected by LTS at the arm, calf, foot, back and hand. Local thermal discomfort was affected by both LTS and OTS. At overall cold thermal sensation, all body segments prefer slightly warm sensation. At overall slightly warm thermal sensation, all body segments prefer slightly cool sensation.
In patients with community-onset acute pyelonephritis (CO-APN), assessing the risk factors for poor clinical response after 72 h of antibiotic treatment (early clinical failure) is important. The ...objectives of this study were to define those risk factors, and to assess whether early clinical failure influences mortality and treatment outcomes. We prospectively collected the clinical and microbiological data of women with CO-APN in South Korea from March 2010 to February 2012. The numbers of cases in the early clinical success and early clinical failure groups were 840 (79.1%) and 222 (20.9%), respectively. Final clinical failure and mortality were higher in the early clinical failure group than in the early clinical success group (14.9% vs 2.3%, p <0.001; 6.8% vs 0.1%, p 0.001, respectively). In a multiple logistic regression model, the risk factors for early clinical failure among the total 1062 patients were diabetes mellitus (OR 1.5; 95% CI 1.1-2.1), chronic liver diseases (OR 3.3; 95% CI 1.6-6.7), malignancy (OR 2.2; 95% CI 1.1-4.4), Pitt score ≥2 (OR 2.5; 95% CI 1.6-3.8), presence of azotaemia (OR 1.8; 95% CI 1.2-2.7), white blood cell count ≥20 000/mm3 (OR 2.5; 95% CI 1.6-4.0), serum C-reactive protein level ≥20 mg/dL (OR 1.7; 95% CI 1.2-2.4), and history of antibiotic usage within the previous year (OR 1.5; 95% CI 1.1-2.2). Analysing the subgroup of 743 patients with CO-APN due to Enterobacteriaceae, fluoroquinolone resistance of the uropathogen was another factor associated with early clinical failure (OR 1.7; 95% CI 1.1-2.5). Simple variables of underlying diseases, previous antibiotic usage and initial laboratory test outcomes can be used to decide on the direction of treatment in CO-APN.
This paper investigates the airflow and pollutant distribution patterns in a “negative pressure” isolation room by means of objective measurement and computational fluid dynamics (CFD) modeling based ...on three ventilation strategies. An effective ventilation system is crucial to protect doctors, nurses and other health-care workers from patients with infectious disease. In the preliminary study with Strategy 1, the isolation room has two air supply diffusers and two extract grilles mounted on the ceiling. Strategy 2 retains the air supply diffusers in Strategy 1 but relocates the two extract grilles to the wall behind the bed at 0.3
m above the floor level. Strategy 3 has the same layout as Strategy 2 except the ceiling diffusers are replaced by supply grilles and relocated closer to the wall behind the bed.
The results show that the low-level extraction technique adopted in Strategies 2 and 3 is very effective in removing pollutant at the human breathing zone as compared to extraction at ceiling level in Strategy 1. It is found that Strategy 3 has the best pollutant removal efficiency with the supply air grilles delivering a laminar flow of outside air to the occupant with minimal entrainment of the air in the room. It is observed that the ventilation strategies and furniture layout have great influence on the airflow and pollutant distribution patterns in the isolation room. Design strategies of isolation room are formulated based on the results and observations made in this study.
•We address the validity of Dynamic Causal Modelling (DCM) for 7T fMRI at two levels.•We evaluate reproducibility and efficiency of DCM estimates across field strengths.•High reproducibility of ...effective connectivity between 3T and 7T was observed.•Posterior entropy of 7T parameter estimates was less than that of 3T estimates.•DCM enables inference about effective connectivity from 7T reliably and efficiently.
There is growing interest in ultra-high field magnetic resonance imaging (MRI) in cognitive and clinical neuroscience studies. However, the benefits offered by higher field strength have not been evaluated in terms of effective connectivity and dynamic causal modelling (DCM).
In this study, we address the validity of DCM for 7T functional MRI data at two levels. First, we evaluate the predictive validity of DCM estimates based upon 3T and 7T in terms of reproducibility. Second, we assess improvements in the efficiency of DCM estimates at 7T, in terms of the entropy of the posterior distribution over model parameters (i.e., information gain).
Using empirical data recorded during fist-closing movements with 3T and 7T fMRI, we found a high reproducibility of average connectivity and condition-specific changes in connectivity – as quantified by the intra-class correlation coefficient (ICC = 0.862 and 0.936, respectively). Furthermore, we found that the posterior entropy of 7T parameter estimates was substantially less than that of 3T parameter estimates; suggesting the 7T data are more informative – and furnish more efficient estimates.
In the framework of DCM, we treated field-dependent parameters for the BOLD signal model as free parameters, to accommodate fMRI data at 3T and 7T. In addition, we made the resting blood volume fraction a free parameter, because different brain regions can differ in their vascularization.
In this paper, we showed DCM enables one to infer changes in effective connectivity from 7T data reliably and efficiently.
Objectives
The aim of this study was to determine the risk factors and clinical characteristics of community-acquired acute pyelonephritis (CA-APN) caused by extended-spectrum β-lactamase ...(ESBL)-producing organisms.
Methods
From March 2010 to February 2011, patients with CA-APN were recruited in 11 hospitals in South Korea. Clinical and microbiological data were collected prospectively, and the ESBLs and multilocus sequence types of the ESBL-producing
Escherichia coli
were characterized. Comparison between CA-APN caused by ESBL-producing Enterobacteriaceae and those by non-ESBL-producing organisms was performed.
Results
A total of 566 patients were recruited. Enterobacteriaceae were detected in 526 patients. Forty-six isolates (46/526, 8.7 %) were positive for ESBLs. Clinical and microbiological failure did not differ between the two groups, despite there being fewer patients with ESBL-positive isolates provided with appropriate antibiotics initially (19.6 vs. 93.8 %,
p
< 0.001). However, the duration of hospitalization was longer in the ESBL group (10.5 vs. 7.0 days,
p
= 0.012). In a logistic regression model, Charlson score ≥1 point odds ratio (OR) 3.4, 95 % confidence interval (CI) 1.6–7.0,
p
= 0.001, antibiotics usage during the previous year (OR 3.1, 95 % CI 1.4–7.2,
p
= 0.008), and urinary catheterization during the previous month (OR 4.4, 95 % CI 1.1–17.6,
p
= 0.035) were associated with the risks of CA-APN by ESBL producers. CTX-M-15 (48 %) and CTX-M-14 (38 %) were the most common ESBLs. ST131 was the most common clone (7/24, 29.1 %), which was more frequently resistant to cefepime, fosfomycin, and temocillin.
Conclusions
The risk factors for CA-APN by ESBL producers were Charlson score ≥1 point, antibiotics usage during the previous year, and urinary catheterization during the previous month.
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