Effect of aspect ratio on flow boiling characteristics in microchannels Al-Zaidi, Ali H.; Mahmoud, Mohamed M.; Karayiannis, Tassos G.
International Journal of Heat and Mass Transfer/International journal of heat and mass transfer,
January 2021, 2021-01-00, 20210101, Letnik:
164
Journal Article
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Odprti dostop
•Bubble size in nucleate boiling region increased with decreasing aspect ratio.•Wall heat transfer rates increases at high aspect ratio.•Base heat flux increases with decreasing aspect ratio.•The ...pressure drop increased with increasing aspect ratio.•Effect of aspect ratio on pumping power was not significant.
The effect of channel aspect ratio on flow boiling characteristics (flow patterns, heat transfer and pressure drop) of HFE-7100 in copper multi-microchannel heat sinks was investigated experimentally. Three heat sinks with base area 500 mm2, channel hydraulic diameter 0.46 mm and channel aspect ratio (ratio of channel width to channel height) of 0.5, 1.0 and 2.0 were tested. The average surface roughness of the channel bottom surface was nearly the same in the three heat sinks and the measured values were 0.271, 0.286 and 0.304 µm. The local heat transfer rates were determined simultaneously with flow visualisation at mass flux ranging from 50 to 250 kg/m2s, wall heat flux from 9.6 to 191.6 kW/m2, system pressure of 1 bar and low inlet sub-cooling of 5 K. The results showed that, when the channel aspect ratio increased, the heat transfer coefficient increased, while the flow boiling pressure drop decreased. However, the heat transfer rate calculated using the heat sink base area was higher in the heat sink with the smallest channel aspect ratio, indicating an enhancement due to the largest surface area.
•Flow boiling study of HFE-7100 in multi-microchannels.•Flow patterns, pressure drop and heat transfer rates in microchannel evaporator.•The heat transfer coefficient increased with heat flux and did ...not depend on mass flux.•The present data were compared with existing correlations.
The main objective of this research was the design and test of a multi-microchannels heat sink for electronics cooling applications, which operates at system pressure near atmospheric and low mass flow rates. HFE-7100, a dielectric and eco-friendly coolant, was chosen as the working fluid. Twenty five rectangular microchannels, of width 0.7 mm and height 0.35 mm giving a hydraulic diameter of 0.46 mm, were fabricated from oxygen-free copper with a base area of 500 mm2. The channels in-between wall was 0.1 mm thick. Five mass fluxes ranging from 50 to 250 kg/m2 s were tested at fixed inlet sub-cooling near 5 K. The effect of heat flux, mass flux and vapour quality on the local heat transfer coefficient was investigated. Four flow patterns namely; bubbly, slug, churn and annular flow, were visualized using a high-speed camera mounted on a microscope. In this study, the maximum flow boiling heat transfer coefficient was 12.71 kW/m2 K at mass flux of 250 kg/m2 s. A comprehensive comparison with experimental results was conducted including flow pattern maps, heat transfer and pressure drop correlations. Some of the correlations, proposed for conventional channels and microchannels, showed good agreement with the present results.
OBJECTIVE:The aim of this study was to assess the impact of chemoradiation on the immune microenvironment to influence and optimally design future neoadjuvant clinical trials.
SUMMARY BACKGROUND ...DATA:Programmed death (PD)-1 inhibitors in metastatic gastroesophageal cancer have demonstrated response rates of approximately 25% in programmed death ligand-1 (PD-L1+) tumors. Unfortunately, the majority of patients do not respond. Therefore, a rationale strategy of combining immunotherapeutic agents with chemoradiation in earlier stage esophageal cancer may prevent metastatic disease in patients.
METHODS:To determine the effects of chemoradiation on resected esophageal adenocarcinomas, we examined the immune microenvironment pre- and post-chemoradiation using immunohistochemistry, quantitative reverse transcriptase polymerase chain reaction (qRT-PCR), and functional analysis of tumor-infiltrating lymphocytes. Additionally, to assess the duration and dependency of radiation-induced PD-L1 upregulation, a surgical rat reflux model of esophageal adenocarcinoma is used. First, tumor-bearing animals were dosed with single-fraction 13Gy or 16Gy radiation to determine safety, dose correlation, and PD-L1 upregulation using qRT-PCR post-radiation. Next, longitudinal PD-L1 expression levels within individual animals were determined using serial endoscopic biopsies at baseline, 1, 5, and 9 weeks post 16Gy radiation.
RESULTS:The majority of cancers displayed enhanced interferon γ and activated CD8+ T lymphocytes at the tumor stroma interface. These tumors also demonstrated enhanced upregulation of PD-L1 and multiple other immune checkpoints including TIM3, GITR, IDO1, LAG3, OX40, and KIR. The animal model results indicated PD-L1 upregulation is dose-dependent and transiently elevated post radiation exposure.
CONCLUSIONS:Collectively, these findings provide insights into the evolving immune landscape after chemoradiation and have significant implications for neoadjuvant trial designs that will combine radiotherapy with immune checkpoint inhibitors.
Efforts to quantify the global burden of enteric fever are valuable for understanding the health lost and the large-scale spatial distribution of the disease. We present the estimates of typhoid and ...paratyphoid fever burden from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2017, and the approach taken to produce them.
For this systematic analysis we broke down the relative contributions of typhoid and paratyphoid fevers by country, year, and age, and analysed trends in incidence and mortality. We modelled the combined incidence of typhoid and paratyphoid fevers and split these total cases proportionally between typhoid and paratyphoid fevers using aetiological proportion models. We estimated deaths using vital registration data for countries with sufficiently high data completeness and using a natural history approach for other locations. We also estimated disability-adjusted life-years (DALYs) for typhoid and paratyphoid fevers.
Globally, 14·3 million (95% uncertainty interval UI 12·5–16·3) cases of typhoid and paratyphoid fevers occurred in 2017, a 44·6% (42·2–47·0) decline from 25·9 million (22·0–29·9) in 1990. Age-standardised incidence rates declined by 54·9% (53·4–56·5), from 439·2 (376·7–507·7) per 100 000 person-years in 1990, to 197·8 (172·0–226·2) per 100 000 person-years in 2017. In 2017, Salmonella enterica serotype Typhi caused 76·3% (71·8–80·5) of cases of enteric fever. We estimated a global case fatality of 0·95% (0·54–1·53) in 2017, with higher case fatality estimates among children and older adults, and among those living in lower-income countries. We therefore estimated 135·9 thousand (76·9–218·9) deaths from typhoid and paratyphoid fever globally in 2017, a 41·0% (33·6–48·3) decline from 230·5 thousand (131·2–372·6) in 1990. Overall, typhoid and paratyphoid fevers were responsible for 9·8 million (5·6–15·8) DALYs in 2017, down 43·0% (35·5–50·6) from 17·2 million (9·9–27·8) DALYs in 1990.
Despite notable progress, typhoid and paratyphoid fevers remain major causes of disability and death, with billions of people likely to be exposed to the pathogens. Although improvements in water and sanitation remain essential, increased vaccine use (including with typhoid conjugate vaccines that are effective in infants and young children and protective for longer periods) and improved data and surveillance to inform vaccine rollout are likely to drive the greatest improvements in the global burden of the disease.
Bill & Melinda Gates Foundation.
Currently, there is no clinically relevant non-invasive biomarker for early detection of esophageal squamous cell carcinoma (ESCC). Herein, we established and evaluated a circulating microRNA ...(miRNA)-based signature for the early detection of ESCC using a systematic genome-wide miRNA expression profiling analysis.
We performed miRNA candidate discovery using three ESCC tissue miRNA datasets (n = 108, 238, and 216) and the candidate miRNAs were confirmed in tissue specimens (n = 64) by qRT-PCR. Using a serum training cohort (n = 408), we conducted multivariate logistic regression analysis to develop an ESCC circulating miRNA signature and the signature was subsequently validated in two independent retrospective and two prospective cohorts.
We identified eighteen initial miRNA candidates from three miRNA expression datasets (n = 108, 238, and 216) and subsequently validated their expression in ESCC tissues. We thereafter confirmed the overexpression of 8 miRNAs (miR-103, miR-106b, miR-151, miR-17, miR-181a, miR-21, miR-25, and miR-93) in serum specimens. Using a serum training cohort, we developed a circulating miRNA signature (AUC:0.83 95%CI:0.79-0.87) and the diagnostic performance of the miRNA signature was confirmed in two independent validation cohorts (n = 126, AUC:0.80 95%CI:0.69-0.91; and n = 165, AUC:0.89 95%CI:0.83-0.94). Finally, we demonstrated the diagnostic performance of the 8-miRNA signature in two prospective cohorts (n = 185, AUC:0.92, 95%CI:0.87-0.96); and (n = 188, AUC:0.93, 95%CI:0.88-0.97). Importantly, the 8-miRNA signature was superior to current clinical serological markers in discriminating early stage ESCC patients from healthy controls (p < 0.001).
We have developed a novel and robust circulating miRNA-based signature for early detection of ESCC, which was successfully validated in multiple retrospective and prospective multinational, multicenter cohorts.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Introduction
Abnormal DeMeester score on pH monitoring is a well-established predictor of favorable outcome after antireflux surgery (ARS). Esophageal pH monitoring also facilitates analysis of the ...temporal association between symptoms and reflux episodes. This association can be expressed with several symptom–reflux association indices with symptom association probability (SAP) being the most reliable. SAP is often used as an adjunct to DeMeester score during preoperative assessment of patients seeking ARS. However, data on the utility of SAP in predicting ARS outcome is limited. The aim of this study was to determine the utility of SAP as an adjunct to DeMeester score in predicting outcomes after fundoplication.
Methods
Records of patients who underwent primary fundoplication from 2015 to 2021 were reviewed. Patients with a preoperative DeMeester score >14.7 on Bravo pH monitoring were included. A SAP >95% was considered SAP-positive. Favorable outcome was defined as freedom from proton pump inhibitors (PPIs) and patient satisfaction at 1 year postoperatively. Outcomes were compared based on the presence and number of SAP-positive symptoms, individual typical and atypical SAP-positive symptoms, and within demographic, clinical, and reflux severity subgroups.
Results
The final study population consisted of 597 patients (71.4% female) with a median (IQR) age of 59.0 (49–67). At a mean (SD) follow-up of 10.5 (8) months, 82.0% patients achieved favorable outcome (satisfaction and freedom from PPI), freedom from PPI was 91.7%, and satisfaction was 87.4%. SAP was positive in 430 (72.0%) patients, of which 221 (37.0%) had one SAP-positive symptom, 164 (27.5%) had two SAP-positive symptoms, and 45 (7.5%) had all three SAP-positive symptoms. There was no association between having at least one SAP-positive symptom and favorable outcome (
p
=0.767). There was no difference in favorable outcome between patients with one, two, or all SAP-positive symptoms (0.785). Outcomes were comparable for SAP-positive typical (
p
=0.873) and atypical symptoms (
p
=1.000) and all individual symptoms (
p
>0.05). Outcomes were also comparable within all subgroups (
p
>0.05).
Conclusion
Symptom association probability with an abnormal DeMeester score did not enhance the prediction of antireflux surgery outcome. These findings suggest that SAP should not be used in surgical decision-making in patients with objective evidence of reflux.
Graphical Abstract
Somatic mutations are a hallmark of tumorigenesis and may be useful for non-invasive diagnosis of cancer. We analyzed whole-genome sequencing data from 2,511 individuals in the Pan-Cancer Analysis of ...Whole Genomes (PCAWG) study as well as 489 individuals from four prospective cohorts and found distinct regional mutation type-specific frequencies in tissue and cell-free DNA from patients with cancer that were associated with replication timing and other chromatin features. A machine-learning model using genome-wide mutational profiles combined with other features and followed by CT imaging detected >90% of patients with lung cancer, including those with stage I and II disease. The fixed model was validated in an independent cohort, detected patients with cancer earlier than standard approaches and could be used to monitor response to therapy. This approach lays the groundwork for non-invasive cancer detection using genome-wide mutation features that may facilitate cancer screening and monitoring.
•Experimental study of HFE-710 condensing in a small rectangular channel of 0.57mm hydraulic diameter.•Local heat transfer coefficient increases with increasing mass flux and decreases with ...decreasing vapour quality.•The interfacial shear stress is the dominant regime at this scale and with this particular fluid.•The main flow regime is annular flow.•Comparisons with existing flow pattern maps and heat transfer correlations were performed.
An experimental investigation was carried out to study the effect of refrigerant mass flux, local vapour quality, coolant flow rate and inlet coolant temperature on the local condensation heat transfer coefficient. Flow visualization was also conducted to capture flow patterns during flow condensation using a high-speed camera integrated with a microscope. HFE-7100, a dielectric and eco-friendly refrigerant was used in rectangular multi-microchannels with a hydraulic diameter of 0.57mm. Experiments were performed at a saturation temperature of 60°C, mass flux range 48–126kg/(m2s), coolant flow rate range 0.5–1.1L/min and inlet coolant temperature range 20–40°C. The results showed that the local condensation heat transfer coefficient increases with increasing mass flux and decreases with decreasing local vapour quality. A negligible effect of the coolant side conditions, saturation-to-wall temperature difference, on the local condensation heat transfer coefficient was found. The main flow regime was annular flow, while slug and bubbly flow were found at some operating conditions. The experimental results were compared with the existing correlations for heat transfer rates. Also, two existing flow pattern maps, for conventional and mini/microchannels, were used to compare the current flow pattern results.
Peritoneal carcinomatosis (PC) is a complex manifestation of abdominal cancers, with a poor prognosis and limited treatment options. Recent work identifying high concentrations of the cytokine ...interleukin-6 (IL-6) and its soluble receptor (sIL-6-Rα) in the peritoneal cavity of patients with PC has highlighted this pathway as an emerging potential therapeutic target. This review article provides a comprehensive overview of the current understanding of the potential role of IL-6 in the development and progression of PC. We discuss mechansims by which the IL-6 pathway may contribute to peritoneal tumor dissemination, mesothelial adhesion and invasion, stromal invasion and proliferation, and immune response modulation. Finally, we review the prospects for targeting the IL-6 pathway in the treatment of PC, focusing on common sites of origin, including ovarian, gastric, pancreatic, colorectal and appendiceal cancer, and mesothelioma.
Topical drug delivery is preferable route over systemic delivery in case of Cutaneous leishmaniasis (CL). Among the available agents, amphotericin B (AmB) and pentamidine (PTM) showed promising ...result against CL. However, monotherapy is associated with incidences of reoccurrence and resistance. Combination therapy is therefore recommended. Thin film hydration method was employed for amphotericin B-pentamidine loaded niosomes (AmB-PTM-NIO) preparation followed by their incorporation into chitosan gel. The optimization of AmB-PTM-NIO was done via Box Behnken Design method and in vitro and ex vivo analysis was performed. The optimized formulation indicated 226 nm particle size (PS) with spherical morphology, 0.173 polydispersity index (PDI), −36 mV zeta potential (ZP) and with entrapment efficiency (EE) of 91% (AmB) and 79% (PTM), respectively. The amphotericin B-pentamidine loaded niosomal gel (AmB-PTM-NIO-Gel) showed desirable characteristics including physicochemical properties, pH (5.1 ± 0.15), viscosity (31870 ± 25 cP), and gel spreadability (280 ± 26.46%). In vitro release of the AmB and PTM from AmB-PTM-NIO and AmB-PTM-NIO-Gel showed more prolonged release behavior as compared to their respective drug solution. Higher skin penetration, greater percentage inhibition and lower IC50 against the promastigotes shows that AmB-PTM-NIO has better antileishmanial activity. The obtained findings suggested that the developed AmB-PTM-NIO-Gel has excellent capability of permeation via skin layers, sustained release profile and augmented anti-leishmanial outcome of the incorporated drugs.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
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