Blowing Flow Research Articles

Reduced Cerebral Blood Flow in Benign Oligemia Relates to Poor Clinical Outcome in Acute Ischemic Stroke Patients.

The imaging of cerebral blow flow (CBF) has shown great promise in predicting the tissue outcome or functional outcome of acute ischemic stroke patients. Arterial spin labeling (ASL) provides a noninvasive tool for quantitative CBF measurement and does not require a contrast agent, which makes it an attractive technology for perfusion imaging in clinical settings. Previous studies have shown the feasibility of using ASL for acute stroke imaging and its potential in stroke outcome prediction. However, the relationship between the tissue-level CBF reduction in hypoperfused region and clinical outcome in acute stroke patients remains not well understood. In this study, we obtained the quantitative measurements of CBF in acute ischemic stroke patients (N = 18) using pseudocontinuous ASL (pCASL) perfusion imaging technology. The tissue-level CBF changes were evaluated and their correlations with patient clinical outcome were explored. Our results showed different CBF values between hypoperfused tissues recruited into infarction and those that survived. Moreover, a significant correlation was found specifically between the CBF reduction in benign oligemia area and patient neurological deficit severity. These findings showed the validity of pCASL perfusion imaging in the assessment of tissue-level CBF information in acute stroke. The association of CBF with patient clinical outcome might provide useful insights in early diagnosis of acute stroke patients.

Research of bottom blowing and slag layer thickness on bath stirring in a 120t ladle

The relationship between mixing time, ladle kinetic energy and bottom blowing radial position, bottom blowing flow rate, slag layer thickness and a series of operating variables are studied. The mixing time has been measured in a 1:6 scale model, and the method of adding tracers has been improved to obtain more accurate results. In addition, the kinetic energy in the bath is calculated through the VOF+DPM coupling model. The experimental results show that the mixing time in the bath decreases with the increase of the bottom blowing rate or the decrease of the thickness of the oil layer. Compared with the bottom blowing radial position of 0.55R and 0.65R, 0.45R is more conducive to mixing in the bath. As the radial position of the bottom blowing approached the wall, the gas-liquid phase zone began to tilt toward the ladle wall. The kinetic energy in the bath is not necessarily related to the mixing time, but when the bottom blowing flow rate and position are the same, the kinetic energy decreases with the increase of the oil layer thickness. When the thickness of the oil layer is 1 cm, 2 cm and 3 cm, the kinetic energy compared with the thickness of the oil-free layer decreases by 24.07%, 30.56% and 36.30%, respectively.

Utility of topic agents in post cervical uterine fibroids removal

Uterine fibroids represent the most commonly encountered uterine tumors in women worldwide which can develop at the level of any segment of the uterus and can pose different problems in regard to the most appropriate therapeutic strategy especially in young women which deserve fertility preservation. Meanwhile in certain cases they can impede the development of a normal pregnancy due to their location or can show significant enlargement in volume during pregnancy due to the increased blow flow at this level. In all cases in which they induce the apparition of symptoms or impede the apparition or development of a normal pregnancy they should be removed. In cases in which the fibroids are located at the level of the uterine cervix attention should be focused on providing a correct and efficient postoperative healing. The aim of this paper is to review the most important aspects related to uterine cervix fibroid symptoms, treatment and postoperative healing, particular attention being given to Cerviron, a topic agent which seems to provide an efficient healing at this level.

A green all-polysaccharide hydrogel platform for sensing and electricity harvesting/storage

Multi-functional polysaccharide-based gels have gained increasing interest for various applications because of their biodegradability, flexibility and porous structure. This paper focuses on the exploration of an all-polysaccharide hydrogel platform for sensing and electricity harvesting/storage, with hydrogels consisting of cationic guar gum (CGG) and chitosan (CS). The gelling and crosslinking are due to the imine and acetal formations between carbonyl groups in polysaccharides, which are in-situ generated via the sodium periodate (NaIO4) oxidation, and their hydroxyl/amine groups. Consequently, CS/CGG hydrogel is fabricated without any crosslinking agents, and it exhibits injectability, conductivity, adhesiveness, etc. Thanks to its pressure responsiveness, the CS/CGG hydrogel accurately detects human motions. More importantly, it generates an output voltage of 32.1 mV upon moist air flow blowing, due to the abundant hydrophilic groups. Furthermore, the aerogel obtained by freeze-drying of CS/CGG hydrogel produces a voltage up to 162.2 mV, demonstrating its good electricity harvesting capacity. The carbon aerogel obtained from the calcination of CS/CGG aerogel exhibits good electrochemical performance with a high capacity and capacitance retention (ca. 90% after 10,000 consecutive cycles). Thus, this work provides a novel strategy to design a sustainable hydrogel platform for many applications, which may provide inspiration for all-natural functional material development.

Carboxyhemglobin and Drainage Pressure During Venovenous Extracorporeal Membrane Oxygenation.

To the Editor: We read with interest the article1 recently published by Nisar et al. on ASAIO Journal. The authors describe the frequent development of carboxyhemoglobinemia in patients treated with venovenous (V-V) extracorporeal membrane oxygenation (ECMO). As highlighted in the article, high carboxyhemoglobin levels cause significant discrepancies between pulse oximetry and actual oxyhemoglobin levels. This may lead to erroneous interpretation of patient oxygenation when the latter is assessed noninvasively. Carboxyhemoglobinemia has been described since 19492 as a marker for hemolysis. Hemolysis during V-V ECMO occurs in up to 18% of patients.3 The principal causes of mechanical hemolysis during ECMO support include circuit components (oxygenator, pump,4 cannula size) as well as patient’s characteristics.5 Centrifugal pump could be a major source of hemolysis when rotating in unsuitable conditions. High rotation speed (e.g., >3000 rpm) may result in high negative pressures at the pump head, thus promoting hydrodynamic cavitation and a high level of hemolysis.6 We performed a retrospective analysis of prospectively collected data of our historical cohort of acute respiratory distress syndrome patients treated with V-V ECMO, to compare our findings with Nisar et al. We included adult patients admitted to our ECMO unit (Rianimazione Generale, ASST Monza, Italy) between 2014 and 2020. We excluded patients with veno-venoarterial ECMO and COVID-19 patients, who may present coagulopathy as a part of the underlying disease.7 Arterial blood gas (ABG) analysis was performed with the RAPIDPoint 500e System (Siemens Healthcare, Erlangen, Germany). Elevated carboxyhemoglobin was defined according to the authors’ threshold (i.e., >3%).1 Eighty-four patients (39% females, 53 ± 10 years) were included in our analysis. ECMO configuration was femoro-femoral (86% of patients) or femoro-jugular. Median duration of ECMO support was 20 days, ranging from 3 to 83 days. Average blow flow was 3.5 ± 0.5 (2,520 ± 287 rpm), whereas mean drainage pressure was −42 ± 14 mm Hg. Overall, mean carboxyhemoglobin level was 1.1 ± 0.8%. Carboxyhemoglobin level at ECMO connection was 0.6 ± 0.5%%, and its average increase was 0.011% for each ECMO day. Among 1,653 ABG analyses, carboxyhemoglobin was >3% in only 23 samples (1.4%). A carboxyhemoglobin higher than 3% occurred at least once in eight (9.5%) patients. In our study, we found a lower incidence of hemolysis compared with Nisar et al.1 This finding may have different explanations. First, at our institution, we are used to carefully monitor the drainage pressure and adjusting the ECMO blood flow to avoid drainage pressures lower than −60/−70 mm Hg. This may limit hemolysis due to hydrodynamic cavitation. Moreover, a minor difference due to technical reason (i.e., two different blood gas analyzers) cannot be excluded. In absence of recirculation, a BF of 3–4 L/min usually allows achieving a safe oxygenation in adult patients.8 If adequate drainage cannulae are used (i.e., 21–25 Fr), this blood flow range can be usually achieved with drainage pressure of −30 to −60 mm Hg.9,10 Therefore, we hypothesize that limiting the blood flow rate to maintain “safe” drainage pressures may help in reducing the increase of carboxyhemoglobinemia during the ECMO course.

Flow-induced vibration suppression of elastic square cylinder using windward-suction-leeward-blowing approach

This article covers the application of the windward-suction-leeward-blowing concept in the reduction of flow-induced vibration of an elastically-mounted square-section cylinder in the active open-loop control framework. Certain slots with equal length are devised on the front and rear surfaces of the cylinder to perform flow suction and flow blowing. These slots have the same actuation velocity. To study the effectiveness of the present flow control approach, fluid-structure interaction simulations for both the lock-in (85 < Reynolds Number < 95) and galloping (Reynolds Number > 170) regions are conducted based on a finite volume code. According to the plots of maximum cylinder cross-flow displacement, planar orbital trajectories and snapshots of vorticity contours, the success of this control approach in complete suppression of vortex shedding and thus the flow-induced oscillations in both mentioned regions is shown. Also, increasing the actuation velocity and slot length improves the performance of windward-suction-leeward-blowing in flow control and vibration attenuation. The minimum actuation velocity required for attenuation of cylinder oscillations in the galloping zone is higher than that of the lock-in region. Moreover, with increasing actuation velocity and slot length, the shear layer is stretched, suppressing the vortex-shedding and changing the mode of wake structure from 2S (for lock-in region) and 2S+2P (for galloping zone) to a vortex-free symmetric wake. Also, the proposed control approach alters the orbital pattern diagrams of the cylinder that are in the form of figure-8-shaped plots and transfers them to a bounded region commensurate to the small transverse and in-line displacements of the cylinder.

Effects of nozzle geometry and active blowing on lift enhancement for upper surface blowing configuration

Upper Surface Blowing (USB) has been regarded as a promising lift enhancement technique for short-take-off and landing (STOL) applications. The present study conducted numerical investigations to further explore the potential capability of USB technique by passive and active flow control strategies. Computations were accomplished by a Reynolds-averaged Navier-Stokes solver enclosed by the two-equation k-ω shear stress transport turbulence model. The propulsion effect of the up-mounted engine was represented by the Turbine Powered Simulator (TPS). Results show that aerodynamic lift of using USB system is significantly enhanced due to the attenuation of plume edge roll-up vortex which is beneficial to the Coanda effect. Varying nozzle geometries can augment lift by alleviating the three-dimensional edge effect and thus delaying the rollup of plume with a thinner jet sheet. Compared to the passive flow control method by nozzle geometry modification, active constant blowing flow control technique shows a more promising potential for lift enhancement for USB powered system. Within the test cases, a 50% lift increment can be achieved by using constant blowing on the USB system.

Lower cerebral oxygen utilization is associated with Alzheimer’s disease‐related neurodegeneration on MRI and poorer cognitive performances among apolipoprotein E ε4 carriers

AbstractBackgroundOxygen extraction fraction (OEF) and the cerebral metabolic rate of oxygen (CMRO2) are markers of oxygen utilization and neuronal energy demands that may offer insights into normal and abnormal changes in aging. This study cross‐sectionally related OEF and CMRO2 to cognitive and structural neuroimaging variables among older adults. Because apolipoprotein E (APOE)‐ε4 status is an Alzheimer’s disease (AD) genetic risk factor and a molecular mediator of vascular damage, we tested whether APOE‐ε4 status modified associations.MethodVanderbilt Memory and Aging Project participants free of stroke and dementia (n=237, 75±7 years, 37% female) underwent neuropsychological testing and multimodal 3T brain MRI, including T 1‐weighted imaging (grey matter volumes/thickness), fluid attenuated inversion recovery (white matter hyperintensities (WMHs)), T2‐relaxation‐under‐spin‐tagging (venous oxygenation (Yv)), and pseudo‐continuous arterial spin‐labeling (cerebral blow flow (CBF)). Participant‐specific Yv, arterial oxygenation, and hematocrit were used to calculate OEF, which multiplied by CBF yielded CMRO2. Linear regressions related OEF and CMRO2 individually to cognition, grey matter volumes, an AD imaging signature (Schwarz et al., 2016), and WMHs adjusting for age, sex, race/ethnicity, education, Framingham Stroke Risk Profile, Clinical Dementia Rating, APOE‐ε4 status, and (as appropriate) intracranial volume. Follow‐up models tested predictor x APOE‐ε4 status interactions on outcomes followed by APOE‐ε4 status stratification.ResultMain effects were mostly null (p‐values&gt;0.04). APOE‐ε4 status interacted with both OEF and CMRO2 on language (p‐values&lt;0.04), episodic memory (p&lt;0.04), hippocampal volume (p‐values&lt;0.03), and Schwarz AD signature (p‐values&lt;0.05). APOE‐ε4 status also interacted with CMRO2 on total grey matter volume (p=0.04), inferior lateral ventricle volume (p=0.01), executive function (p=0.05), and visuospatial skills (p=0.01). For all interactions, lower OEF and CMRO2 related to worse cognitive performances and smaller regional grey matter structures in APOE‐ε4 carriers only.Conclusion APOE‐ε4 status modifies associations linking cerebral oxygen metabolism markers (CMRO2, OEF) to worse episodic memory performance and smaller neuroimaging variables in regions susceptible to AD‐related neurodegeneration. Consistently, results are present in APOE‐ε4 carriers only. Congruence between cognitive and neuroimaging findings suggests that oxygen metabolism and APOE‐ε4 may interact early in the pathogenesis of AD and related neurodegeneration with important clinical consequences.

Effect of a self-rotating oxygen lance system on mass transfer between slag and molten steel

To improve the efficiency of the steelmaking process, a system of self-rotating lance was designed, and corresponding cold simulation mechanism was developed. The influence of the self-rotating lance on the mass transfer rate between slag and molten steel was investigated by comparing this novel system with the traditional oxygen lance. The results show that the self-rotating lance can stably rotate with a gas jet as the power source. The mass transfer rate increases with an increase in the top and bottom blow flow rates and with a decline in the lance position. Approximately 13.7% of the top blow flow rate is converted to stirring energy, which is approximately twice that of the traditional oxygen lance, and the mass transfer rate can increase by over 30%. Furthermore, the impact energy can be concentrated at different depths of the molten bath by adjusting the rotational speed. With the same energy density, the mass transfer rate produced by the self-rotating lance is higher; however, the influence of the energy density on the mass transfer rate is low when the rotational speed is 30–50 r/min.

Impact of Flow Blowing and Suction strategies on the establishment of an aerodynamic barrier for solar cavity receivers

This study compares two aerodynamic approaches to minimize convective losses from cavity receivers, namely blowing and suction. A laboratory-scale cavity receiver was operated in a large wind tunnel at varying wind speed and tilt angle. The inner surface of the cavity was heated to a constant temperature of 300 °C by finely controlled electrical heaters. The measured electric energy required to maintain the heaters at the same temperature was used to provide a direct measure of losses from the receiver. An air curtain was engineered to provide curtain of air blown either downward or upwards across the aperture. Suction was alternatively applied through a nozzle positioned below the aperture for a series of suction flowrates. A numerical study was also conducted using a commercial CFD package and validated with available data. It was found that the upward blowing air curtain performs better than the downward curtain for the buoyancy dominant conditions. Moreover, the measured effectiveness of the downward blowing air curtain at tilt angle of the cavity of 45° showed that the application of air curtain with higher velocities increases the convective heat losses over the case with no air curtain. When comparing the performance of air curtain with air suction, it was found that for the low range of relative momentum ratio of curtain to wind flow, suction performs better than blown air. Finally, this study highlights the need for adaptable strategies, based on operating condition, to minimize heat losses and improve the thermal efficiency of cavity receivers.

Exercise with blood flow restriction as a new tool for health improvement in hypertensive elderly women: the role of purinergic enzymes.

Purinergic signaling has been considered one of the mechanisms by which exercise exerts its antihypertensive effects; and research on the effects of blow flow restriction (BFR) exercise has increased as an alternative for elderly hypertensive patients. We analyzed the acute responses of NTPDase and adenosine deaminase (ADA) activities to low intensity aerobic exercise (LIAE) with BFR in lymphocytes of hypertensive elderly women. Sixteen hypertensive elderly women performed three exercise protocols: LIAE; high intensity aerobic exercise (HIAE) and LIAE+BFR. Blood pressure, heart rate and blood collection were carried out before exercise, immediately after exercise and 30 min after exercise. NTPDase and ADA activities were measured in lymphocytes. Our results showed that LIAE+BFR triggered the same stimuli when compared to HIAE exercise regarding to NTPDases activities, suggesting that both protocols trigger an augment of these enzyme activities in response to: 1) increase in ATP release during exercise; and 2) need of adenosine generation to promotes anti-inflammatory responses in the recovery period. HIAE protocol was more effective than the others to trigger combined hypotensive and anti-inflammatory effects in the recovery period. This study showed that BFR is a good tool to promote anti-inflammatory effects similar (not equal) to HIAE. Moreover, LIAE+BFR promotes much more stimuli and adaptations related to immune functions than low intensity protocols, bringing more benefits for the hypertensive elderly population.

Metalized solid propellant combustion under high-speed blowing flow

This study presents a mathematical model and a calculation method of the nonstationary combustion rate of metalized solid propellant (nitroglycerin powder with aluminum particle additives) under blowing conditions. The combustion of metalized fuel flat surface under unlimited blowing flow is investigated. The mathematical model describes the erosion effects of solid fuel through boundary layer approximation. The blowing effect is considered in turbulent heat-mass transfer. Results of theoretical and numerical analyses show the influence of aluminum powder additives on the burning rate of solid propellant under blowing flow. This study provides data on the dependence of propellant burning rate on blowing flow speed and dispersion of metal particles in the solid propellant.

The complementary effects of galvanic current electrical stimulation associated with conservative treatment to increase vasodilation in patients with Raynaud’s phenomenon: a randomized trial

Objective: To analyze the effectiveness of an electrotherapy intervention with galvanic current on symptoms associated with Raynaud’s phenomenon. Design: Single-blind randomized controlled trial, parallel design (1:1 ratio) and intention-to-treat analysis. Setting: Virgen de las Nieves Hospital, Granada, Spain. Subjects: Thirty-four participants with Raynaud’s phenomenon, with a mean (SD) age of 43.43 (17.62) years. Interventions: The patients were randomly assigned to a control group with conservative treatment (anti-inflammatory, vasodilatory and analgesic drugs) or an intervention group that received conservative treatment and vasodilatory electrical stimulation during seven weeks, three times/week for a total of 20 sessions. Main measures: The primary outcome was the number of attacks. Secondary outcomes were pain, peripheral blow flow, oxygen saturation, upper limb disability, central sensitization, pain catastrophizing and temperature recovery. All outcomes were assessed at baseline, posttreatment and at two months of follow-up. Results: The galvanic current electrotherapy group showed significantly greater improvements in the number of attacks (mean difference = 26.3, 95% confidence interval (CI) = 14.4 to 38.3), pre-cold stress pain (95% CI = 0.6 to 2.4), radial artery blood flow (95% CI = −7.8 ⩾ x ⩽ 1.3), ulnar artery blood flow (95% CI = −8.63 to 0.60), oxygen saturation (95% CI = −1.7 ⩾ x ⩽ −0.29), upper limb disability (95% CI = 1.1 to 22.3), central sensitization (95% CI = 6.7 to 18.2) and temperature recovery (95% CI = −5.7 ⩾ x ⩽ −0.32) than the conservative treatment group. Conclusion: This study suggests that a complementary treatment with galvanic current in combination to conservative approach is superior to conservative applied as isolate, in reducing the clinical manifestations and disability in Raynaud’s phenomenon.

Examination of the comfort and pain experienced with blood flow restriction training during post-surgery rehabilitation of anterior cruciate ligament reconstruction patients: A UK National Health Service trial

ObjectiveExamine the comfort and pain experienced with blow flow restriction resistance training (BFR-RT) compared to standard care heavy load resistance training (HL-RT) during anterior cruciate ligament reconstruction (ACLR) patient rehabilitation. DesignRandomised controlled trial. SettingUnited Kingdom National Health Service. ParticipantsTwenty eight patients undergoing unilateral ACLR surgery with hamstring autograft were recruited. Following surgery participants were block randomised to either HL-RT at 70% repetition maximum (1RM) (n = 14) or BFR-RT (n = 14) at 30% 1RM and completed 8 weeks of twice weekly unilateral leg press training on both limbs. Main outcome measuresPerceived knee pain, muscle pain and rating of perceived exertion (RPE) were assessed using Borg’s (1998) RPE and pain scales during training. Knee pain was also assessed 24 h post-training. ResultsThere were no adverse events. Knee pain was lower with BFR-RT during (p < 0.05) and at 24 h post-training (p < 0.05) with BFR-RT for all sessions. Muscle pain was higher (p < 0.05) with BFR-RT compared to HL-RT during all sessions. RPE remained unchanged (p > 0.05) for both BFR-RT and HL-RT. ConclusionACLR patients experienced less knee joint pain and reported similar ratings of perceived exertion during and following leg press exercise with BFR-RT compared to traditional HL-RT. BFR-RT may be more advantageous during the early phases of post-surgery ACLR rehabilitation.

ANALISA KERJA BLOWER PADA ALAT VENTILATOR

Ventilator is a mechanical aid that functions to provide breathing assistance so that patients breathe easier. this study aims to determine how the blower works in mixing oxygen and what is the rotational speed of the blower when mixing. This research was conducted by the integrated laboratory of USM-I. The research method used was descriptive with the from of quantitative survey implementation. Which aims to analyze the working principle of the blower on the ventolator. This research was conducted using a Hamilton C2 ventilator. in the blower flow measurement is done from the preassure setting points 5, 15, 25, 35, 55. The results of this study indicate that the blower works welol on the ventilator and the measurement results of each blower flow value reading does not exceed the predetermined standard limit of ±10%.

An increase in bed temperature on gasification of dual reactor fluidized bed

One of the main issues using biomass as fuel in air gasification is the dilution of its product gas by the nitrogen in the air. A dual reactor fluidized bed (DRFB) overcomes this problem in which the gasification and combustion reactions are decoupled and conducted in two separate fluidized bed reactors connected by circulating bed material. The DFRB unit made of 304 stainless steel pipe with a height of 100 and 150 cm, and inner diameters (i.d.) of 15.2 and 5.1 cm for gasifier and combustor respectively. The rice husk as fuel and quartz sand as bed material having the same size of 0.4 - 0.6 mm were applied in this investigation. Since the gasification process is an endothermic reaction, gasification temperatures are varied at 600°C to 700°C while combustion reactor were kept at 600°C using the electric heaters enclosed in ceramic cover. The superficial gas velocity in this study was kept constant at 17 m/s using the external air volumetric flux of the blower flow entering the DRFB loop. Gas gasification samples are then examined by gas chromatography to determine syngas content (CO, CH4 and H2). The test results showed that by the increasing temperature of the gasification reactor there was an increase in syngas especially CO gas conentration. The temperature increases in the gasification reactor (600°C, 650°C, 700°C) is able to increase the endothermic reaction in the gasification process which is dominated by CO gas production. The syngas efficiency was found to increase from 40.95% to 43.77%.as the temperature of the gasification reactor increased.

Suction and Blowing Flow Control on Airfoil for Drag Reduction in Subsonic Flow

Lift force is produced from a pressure difference between the pressures acting in upper and lower surfaces. Therefore, flow becomes detached from the surface of the airfoil at separation point and form vortices. These vortices affect the aerodynamic performance of the airfoil in term of lift and drag coefficient. Therefore, this study is investigating the effect of suction and jet blowing in boundary layer separation control on NACA 0012 airfoil in a subsonic wind tunnel. The experiment examined both methods at the position of 25% of the chord-length of the airfoil at Reynolds number 1.2 × 105. The findings show that suction and jet blowing affect the aerodynamic performance of NACA 0012 airfoil and can be an effective means for boundary layer separation control in subsonic flow.

Dual-echo ASL contributes to decrypting the link between functional connectivity and cerebral blow flow.

Arterial spin labeling (ASL) MRI with a dual-echo readout module (DE-ASL) enables noninvasive simultaneous acquisition of cerebral blood flow (CBF)-weighted images and blood oxygenation level dependent (BOLD) contrast. Up to date, resting-state functional connectivity (FC) studies based on CBF fluctuations have been very limited, while the BOLD is still the method most frequently used. The purposes of this technical report were (i) to assess the potentiality of the DE-ASL sequence for the quantification of resting-state FC and brain organization, with respect to the conventional BOLD (cvBOLD) and (ii) to investigate the relationship between a series of complex network measures and the CBF information. Thirteen volunteers were scanned on a 3T scanner acquiring a pseudocontinuous multislice DE-ASL sequence, from which the concomitant BOLD (ccBOLD) simultaneously to the ASL can be extracted. In the proposed comparison, the brain FC and graph-theoretical analysis were used for quantifying the connectivity strength between pairs of regions and for assessing the network model properties in all the sequences. The main finding was that the ccBOLD part of the DE-ASL sequence provided highly comparable connectivity results compared to cvBOLD. As expected, because of its different nature, ASL sequence showed different patterns of brain connectivity and graph indices compared to BOLD sequences. To conclude, the resting-state FC can be reliably detected using DE-ASL, simultaneously to CBF quantifications, whereas a single fMRI experiment precludes the quantitative measurement of BOLD signal changes. Hum Brain Mapp 38:5831-5844, 2017. © 2017 Wiley Periodicals, Inc.

Simulations of an aircraft with constant and pulsed blowing flow control at the engine/wing junction

In high-lift and especially landing conditions, the vortices emerging from the engine strake and pylon as well as from the inboard and outboard slat tips of civil aircraft configurations can be the cause of the so-called nacelle wake flow separation. This phenomenon might be responsible for the wing stall and sudden lift loss; the effect is expected to increase with the coming up of enlarged nacelles and larger slat cutouts typical of Ultra High Bypass Ratio turbofan engines. In the framework of the European project AFLoNext, DLR and ONERA performed numerical studies focused on a realistic aircraft in high-lift configuration. Structured and unstructured grids were generated to perform Reynolds Averaged Navier–Stokes computations aimed at analyzing the baseline flow without control and determining relevant location and settings for active flow control systems. Constant blowing devices with different slot sizes, types and injection velocities were evaluated with RANS simulations over complete lift polars. The gains in CLmax were quantified; they range from 1 to 3% for actuator capacities compatible with manufacturer requirements, the nacelle wake separation appears at angles of attack one to two degrees higher than without control and the lift levels in post-stall conditions are significantly improved. Finally, unsteady RANS computations were carried out to investigate the potential of a pulsed blowing device. The gains in CLmax and flow separation containment obtained with the latter are similar to those of constant blowing devices which yet exhibit greater momentum coefficient and mass flow rate values.

Utility of Arterial Spin Labeling MRI in Pediatric Neuroimaging: A Pictorial Essay

With advances in magnetic field strength, multichannel coils and parallel imaging, arterial spin labeling (ASL) magnetic resonance imaging (MRI) is now widely available for clinical use. There is a growing body of literature on the utility of ASL in a variety of pediatric diseases that feature alterations in blood flow as part of the pathophysiologic process. ASL can help discriminate high-grade tumors from low-grade tumors, and is especially useful to identify characteristic hyperperfusion seen in hemangioblastoma and choroid plexus tumors. In moyamoya, ASL coupled with acetazolamide challenge provides quantitative cerebral blow flow data that can inform decisions regarding revascularization surgery. In both migraine headaches and hypoxic ischemic injury (HII), there is early hypoperfusion on ASL imaging followed by hyperperfusion. Global or medial occipital hyperperfusion in the setting of HII is a poor prognostic factor. ASL can identify hypoperfusion in seizure foci, but is more useful for seizure localization with hyperperfusion in the acute setting. ASL perfusion imaging is a useful adjunct to conventional brain MRI in children, and should be applied in a wide variety of clinical scenarios.