IMPORTANCE: Clinically apparent atrial fibrillation increases the risk of ischemic stroke. In contrast, perioperative atrial fibrillation may be viewed as a transient response to physiological ...stress, and the long-term risk of stroke after perioperative atrial fibrillation is unclear. OBJECTIVE: To examine the association between perioperative atrial fibrillation and the long-term risk of stroke. DESIGN, SETTING, AND PARTICIPANTS: Retrospective cohort study using administrative claims data on patients hospitalized for surgery (as defined by surgical diagnosis related group codes), and discharged alive and free of documented cerebrovascular disease or preexisting atrial fibrillation from nonfederal California acute care hospitals between 2007 and 2011. Patients undergoing cardiac vs other types of surgery were analyzed separately. MAIN OUTCOMES AND MEASURES: Previously validated diagnosis codes were used to identify ischemic strokes after discharge from the index hospitalization for surgery. The primary predictor variable was atrial fibrillation newly diagnosed during the index hospitalization, as defined by previously validated present-on-admission codes. Patients were censored at postdischarge emergency department encounters or hospitalizations with a recorded diagnosis of atrial fibrillation. RESULTS: Of 1 729 360 eligible patients, 24 711 (1.43%; 95% CI, 1.41%-1.45%) had new-onset perioperative atrial fibrillation during the index hospitalization and 13 952 (0.81%; 95% CI, 0.79%-0.82%) experienced a stroke after discharge. At 1 year after hospitalization for cardiac surgery, cumulative rates of stroke were 0.99% (95% CI, 0.81%-1.20%) in those with perioperative atrial fibrillation and 0.83% (95% CI, 0.76%-0.91%) in those without atrial fibrillation. At 1 year after noncardiac surgery, cumulative rates of stroke were 1.47% (95% CI, 1.24%-1.75%) in those with perioperative atrial fibrillation and 0.36% (95% CI, 0.35%-0.37%) in those without atrial fibrillation. In a Cox proportional hazards analysis accounting for potential confounders, perioperative atrial fibrillation was associated with subsequent stroke both after cardiac surgery (hazard ratio, 1.3; 95% CI, 1.1-1.6) and noncardiac surgery (hazard ratio, 2.0; 95% CI, 1.7-2.3). The association was significantly stronger for perioperative atrial fibrillation after noncardiac vs cardiac surgery (P < .001 for interaction). CONCLUSIONS AND RELEVANCE: Among patients hospitalized for surgery, perioperative atrial fibrillation was associated with an increased long-term risk of ischemic stroke, especially following noncardiac surgery.
BACKGROUND—Age-related dementia, most commonly caused by Alzheimer disease or cerebrovascular factors (vascular dementia), is a major public health threat. Chronic arterial hypertension is a ...well-established risk factor for both types of dementia, but the link between hypertension and its treatment and cognition remains poorly understood. In this scientific statement, a multidisciplinary team of experts examines the impact of hypertension on cognition to assess the state of the knowledge, to identify gaps, and to provide future directions.
METHODS—Authors with relevant expertise were selected to contribute to this statement in accordance with the American Heart Association conflict-of-interest management policy. Panel members were assigned topics relevant to their areas of expertise, reviewed the literature, and summarized the available data.
RESULTS—Hypertension disrupts the structure and function of cerebral blood vessels, leads to ischemic damage of white matter regions critical for cognitive function, and may promote Alzheimer pathology. There is strong evidence of a deleterious influence of midlife hypertension on late-life cognitive function, but the cognitive impact of late-life hypertension is less clear. Observational studies demonstrated a cumulative effect of hypertension on cerebrovascular damage, but evidence from clinical trials that antihypertensive treatment improves cognition is not conclusive.
CONCLUSIONS—After carefully reviewing the literature, the group concluded that there were insufficient data to make evidence-based recommendations. However, judicious treatment of hypertension, taking into account goals of care and individual characteristics (eg, age and comorbidities), seems justified to safeguard vascular health and, as a consequence, brain health.
Cancer patients face an increased risk of arterial thromboembolism; however, it is uncertain when this excess risk begins. This study evaluated the risk of arterial thromboembolism before cancer ...diagnosis. Using the population-based Surveillance Epidemiology and End Results-Medicare linked dataset, we identified 374 331 patients ≥67 years of age with a new primary diagnosis of breast, lung, prostate, colorectal, bladder, uterine, pancreatic, gastric cancer, or non-Hodgkin lymphoma from 2005 through 2013. Cancer patients were individually matched by demographics and comorbidities to Medicare beneficiaries without cancer, who served as controls. Validated diagnosis codes were used to identify arterial thromboembolic events, defined as a composite of myocardial infarction or ischemic stroke. The Mantel-Haenszel estimator was used to compare risks of arterial thromboembolic events between cancer and noncancer groups during 30-day periods in the 360 days before date of cancer diagnosis. From 360 to 151 days before cancer diagnosis, the 30-day interval risks of arterial thromboembolic events were similar between cancer patients and matched controls. From 150 to 1 day before cancer diagnosis, the interval 30-day risks of arterial thromboembolic events were higher in cancer patients vs matched controls, progressively increasing as the cancer diagnosis date approached and peaking during the 30 days immediately before cancer diagnosis, when 2313 (0.62%) cancer patients were diagnosed with an arterial thromboembolic event vs 413 (0.11%) controls (odds ratio, 5.63; 95% confidence interval, 5.07-6.25). In conclusion, the risk of arterial thromboembolic events begins to increase 150 days before the date of cancer diagnosis in older persons and peaks in the 30 days before.
•Among 748 662 Medicare beneficiaries, the risk of arterial thromboembolic events was increased 69% in the year before cancer diagnosis.•The increased risk of arterial thromboembolic events began 5 months before cancer was officially diagnosed and peaked in the month prior.
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In concentrated solar power (CSP) plants built in dry and arid areas, natural draft dry cooling tower (NDDCT) are commonly employed to dissipate waste heat into the atmosphere. The cooling ...performance of NDDCT mainly depends on the induced air flow caused by the buoyancy effect. However, the high ambient temperature in summers reduce the cooling efficiency of dry cooling towers and cause significant power loss for CSP plants. To address this problem, spray cooling system utilizing water evaporation was developed to pre-cool the inlet hot air. Different designs of spray cooling systems were proposed and tested on a 20 m high experimental tower. Experimental data were collected to evaluate the performance of the spray cooling system. To our knowledge, this is the world's first attempt to practice spray cooling on a full-scale natural draft dry cooling tower. This study confirms the feasibility and effectiveness of employing spray cooling for cooling performance enhancement of NDDCT. With the goal of maximal cooling effect with least water consumption, the optimal design was proposed, which consists of 3 upward injections at the low level (Height = 2 m), 2 counterflow injections at the middle level (H = 3 m) and 3 counterflow injections at the high level (H = 4 m). The cooling capacity of NDDCT increases from 789 kW to 841.73 kW, as the result of an intensified natural convection. Moreover, in the spray zone, the presence of a low-temperature area is featured by high relative humidity (70%–80%). The intensified natural convection caused by pre-cooled air and the presence of high vapour concentration are attributed to spray evaporation, which confirms the necessity to introduce the spray cooling system.
Cooling capacity recovery for spray-assisted cooling tower. Display omitted
•Designed spray cooling system of eight nozzles for natural draft dry cooling towers.•Demonstrated the precooling effect on the 20 m real tower for the first time in the world.•Temperature distributions were obtained to study flow field inside the tower.•Increase tower performance by 6.68% with optimized spray cooling.•The mechanism for improved natural convection was revealed.
Upstream therapy of atrial remodeling may decrease atrial fibrillation and associated thromboembolism. We examined the impact of intensive BP lowering on ECG-defined left atrial abnormalities in the ...SPRINT. SPRINT was a randomized clinical trial comparing outcomes when a systolic BP of <120 mmHg (standard treatment) was the target. We included SPRINT participants without baseline atrial fibrillation who had a technically interpretable baseline ECG and at least one follow-up ECG. The primary outcome was incident left atrial abnormality, defined as P-wave terminal force in V
(PTFV
) > 4000 μV × ms. Secondary outcomes were regression of the left atrial abnormality and the change in PTFV
from baseline across follow-up ECGs. Cox regression was used to examine the associations between treatment assignment and incident left atrial abnormality and its regression. We used linear mixed models to examine the changes in PTFV
. Of 9361 SPRINT participants, 7738 qualified for this analysis, of whom 5544 did not have baseline left atrial abnormalities. Intensive BP management was not associated with incident left atrial abnormality (HR, 0.96; 95% CI, 0.87-1.07) or regression of the baseline left atrial abnormality (HR, 1.09; 95% CI, 0.98-1.21). The change in PTFV
from baseline through follow-up did not differ significantly between treatment groups (difference in μV × ms per year, 6; 95% CI, -67 to 79). Thus, among patients in a randomized clinical trial, we found no difference in the progression or regression of ECG-defined left atrial abnormalities with intensive BP management compared to standard BP management.
Air cooling systems are widely used in current data centers owing to their low capital costs and high reliability. To satisfy the increasing rack power density, the optimal air-cooling technology and ...an economic analysis should be carefully discussed. Therefore, this study discusses four airflow management technologies: Case 1: raised floor and cold aisle containment supply/computer room air conditioning (CRAC) direct return; Case 2: CRAC direct supply/hot aisle containment (HAC) return; Case 3: overhead duct supply/CRAC direct return; and Case 4: overhead duct supply/HAC return. Using a validated model, the thermal and economic performances of each case were compared. Results showed that Case 4 exhibited the best thermal performance, followed by Cases 3, 2, and 1. Case 1 cannot satisfy the heat dissipation requirement when the rack power density is larger than 12.5 kW; whereas only Case 4 can be used when the power density is larger than 15 kW. Regarding location within China, owing to the high ambient temperature, Shenzhen showed the highest annual cost value and power usage effectiveness, followed by Shanghai, Xi'an, Beijing, and Harbin. Finally, Cases 3 and 4 are recommended for application when the rack power density is greater than 10 kW.
Purpose - The aim of this paper is to introduce a new technique for convection visualization. This is similar to Bejan's heatlines and is even an exact match to Landau and Lifshitz's energy ...streamlines for two-dimensional geometries.Design methodology approach - The work benefits from a combination of numerical and analytical tools to show that, in two-dimensional space, heatlines and energy streamlines are effectively the same. More importantly, the energy flux vectors are tracing both of them accurately; as verified for some cases of free and forced convection problems in this paper.Findings - The new technique is easier to implement compared to the existing counterparts which are available in the literature. More specifically, the advantage of this new technique is that, contrary to heatlines and energy streamlines, it does not require further numerical analysis in addition to solving momentum and energy equations.Originality value - Energy flux vectors offer higher resolution compared to existing visualization tools.
A passive method with phase change material (PCM) is an appropriate technique in electronic cooling. But, due to its poor thermal conductivity, many enhancers are employed to reduce the thermal ...resistance offered by the PCM. A partial filling strategy to reduce the cost and weight of foams with fins is used in this study. A hybrid heat sink with a combination of fins placed at the sidewalls of the enclosure and foams filled at certain heights such as 10, 20, and 30 mm is considered in this present work. A two-dimensional numerical model with n-eicosane as PCM is developed in ANSYS Fluent 19. A multi-objective optimization is carried out using a reliable multi criteria decision making approach. Different weightage is distributed to the objective functions in this method depending on the choice of the user. The pore size and density vary for various filling heights, and 60 cases are investigated for both charging and discharging cycles. The pore size of 0.8-0.95 and pore density of 5-25 pores per inch with a broad range is considered. From the discussions, guidelines for selecting a preferable pore size and pore density can be determined based on the filling height and applied weightage.
NO
x
emission reduction from gas boilers has become a key issue in improving air quality. Combustion air humidification technology is gradually being used to reduce NO
x
emissions. However, the NO
x
...emission reduction effect of gas boilers at a higher combustion air humidity has been studied less. A flue gas with low NO
x
emissions and a waste heat recovery system using combustion air humidification technology are proposed in this study. In the ultra-low NO
x
mode, the effect of high combustion air humidity on NO
x
emission reduction and efficiency of the gas boiler were studied experimentally. In the waste heat recovery mode, the effects of the heat network backwater temperature on the NO
x
emission reduction and system efficiency were studied experimentally. Results showed that an increase in air humidity can significantly reduce the NO
x
concentration formed by combustion. The ultra-low NO
x
mode reduces NO
x
emissions from 130 mg/m
3
to 23.3 mg/m
3
and affects the boiler efficiency slightly. In the waste heat recovery mode, NO
x
emissions can be reduced to 39.9 mg/m
3
when the backwater temperature of the heat network is 55 °C. This condition improves the efficiency to 93.8%. The analysis results provide suggestions for the selection of the operation modes.
•A review of the PCM-based LTES systems for refrigerated transport and cold distribution applications is presented.•For the refrigerated vehicles, three different PCM-based LTES are proposed: ...supplementing the insulation wall, included in the refrigeration equipment, or as eutectic plates.•The LTES system is able to drastically reduce the greenhouse gas emissions and the operational costs.•The research path to be followed aiming at filling the existing gap is suggested.
Foodstuff has to be transported from where it is produced or packaged to the market. It is important to control the temperature and humidity of the delivered food to minimize the waste and ensure customer satisfaction. At the same time, unfortunately, the transport sector is among the polluting sectors. Therefore, innovative solutions have been proposed such as the adoption of Latent Thermal Energy Storage (LTES) systems based on Phase Change Materials (PCMs) to control the food temperature. Such systems minimize the fuel consumption and thereby reduce the emission. LTES systems rely on the phase change process to absorb and store heat in a more sustainable way while ensuring a nearly constant temperature for the foodstuff while being transported.
Hence, we first present a general overview of the application of PCMs at low temperatures. Then, the literature on the adoption of PCMs in the refrigerated transport sector is critically surveyed. Different proposals offered in the literature are recovered, compared, and critically assessed based on their merits. Despite the differences between the proposed technologies, significant advantages in terms of temperature uniformity in the refrigerated space, product thermal stress reduction, product quality, energy consumption, and pollutant emissions reduction are reported in the literature as surveyed in this paper.
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