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In this study, condensation heat transfer of water vapor in a minichannel heat exchanger on smooth and pin fins surfaces was investigated experimentally. The experimental study was carried out to evaluate heat transfer coefficient, overall heat transfer coefficient, and Nusselt number over different ranges of vapor mass flux from 0.0064 to 0.0368 kg m−2 s−1 and cold-water flow rate range between 0.0013 kg s−1 to 0.0057 kg s−1. The minichannel has a rectangular shape with a hydraulic diameter of 1.3 mm. The experimental testing is carried out on aluminum surface with a channel that has a length of 270, width of 30 mm, and height of 1.3 mm. The pin fins surface is on the bottom of the condensing channel and the fins are circular and have diameter, height, and spacing of 1 mm, and are in-inline arrangement. It is found that condensation heat transfer coefficient on pin fins surface is about 15 % higher than that on smooth surface. It is found that the condensation heat transfer coefficient increases significantly with increasing the vapor mass flux. In addition, the effect of increasing the cold fluid flow rate is lower than that of the hot vapor flow rate, but it becomes more significant for higher vapor flux.

A MEMS heat sink having straight microchannels integrating sidewall cavities in staggered pattern is conceptualized in this work and its thermal resistance and pumping power characterized for Reynolds number ranging from 100 to 750. Over this Reynolds number range, the thermal resistance and pumping power of the proposed MEMS heat sink are lower than that of a MEMS heat sink having straight microchannels. With increase in Reynolds number, the relative reduction of thermal resistance varied from 1.8% to 23.4% while the relative reduction of pumping power varied between 18.6% and 6.5%. The proposed MEMS heat sink achieves reduction in thermal resistance with reduced pumping power and this is its novelty. The Nusselt and Poiseuille numbers of the straight microchannel integrating sidewall cavities are higher and lower than that of a straight microchannel without sidewall cavities, respectively. With increase in Reynolds number, the relative increase of Nusselt number ranged between 6.6% and 46.5% while the relative reduction of Poiseuille number ranged from 18.6% to 6.5%. The influence of the geometric features of the MEMS heat sink having straight microchannels integrating sidewall cavities is examined in this study. It is identified that there is a threshold value for the length of the sidewall cavities below which sidewall cavities do not influence thermal resistance and pumping power; above this threshold value, increase in the length of the sidewall cavities lead to reduction in thermal resistance and pumping power as well as increase and decrease in Nusselt and Poiseuille numbers, respectively. Increase in length of sidewall cavities led to the relative reduction of thermal resistance and pumping power varied from 1% and 19% at the lowest Reynolds number to 23.2% and 7.3% at the highest Reynolds number. With increase in the length of sidewall cavities, the relative increase of Nusselt number and relative reduction of Poiseuille number ranged from 2.3% and 19%, for Reynolds number of 100, to 38.9% and 7.3%, for Reynolds number of 750. It is identified that for every Reynolds number there exists an optimal value for the width of the sidewall cavities at which thermal resistance and Nusselt number are minimum and maximum, respectively; similar observation is made regarding the relationship between hydraulic diameter and thermal resistance while Nusselt and Poiseuille numbers decrease and increase with hydraulic diameter, respectively. Also, increase in the number of sidewall cavities lead to reduction in thermal resistance and pumping power; increase in the number sidewall cavities leads to increase and decrease in both Nusselt and Poiseuille numbers, respectively. With increase in the number of sidewall cavities, the relative reduction of thermal resistance at the lowest and highest Reynolds numbers are 1.4% and 1.8%, respectively; the relative reduction of pumping power at the lowest and highest Reynolds numbers are 12.6% and 7.1%, respectively. The relative increase of Nusselt number at the lowest and highest Reynolds numbers are 29.2% and 23.6%, respectively; the relative reduction of Poiseuille number at the lowest and highest Reynolds numbers are 12.6% and 7.1%, respectively. The model is validated using data from literature.INDEX TERMS Electronics cooling, microfluidics, numerical simulation, thermal resistance.

This paper investigates the thermal performance of straight microchannel heat sinks featuring square-shaped fins on the sidewalls using a CFD developed model. The study evaluates the performance of the heat sink in terms of the total thermal resistance (Rth) and pumping power (PPf). The results show that incorporating square-shaped fins improves thermal performance, however at the penalty of increased pressure drop. To combine heat transfer enhancement with increased pressure drop, the study uses the Figure of Merit (FOM) approach. The study finds that increasing the size of the fins reduces thermal resistance by an average of 53.5%, but Design 1, which has smaller fins, offers a higher FOM. Similarly, reducing the spacing between fins lowers thermal resistance by an average of 61.95%, but Design 5 with smaller spacing than Design 4 offers a higher FOM. Furthermore, smaller channel sizes reduce thermal resistance by an average of 51.43%, but Design 6, which has larger channel sizes than Design 7, provides a higher FOM. Additionally, reducing channel spacing reduces thermal resistance by an average of 62.2% without affecting the pumping power, and Design 8 with smaller spacing than Design 9 offers a higher FOM.

This study investigates pressure drop and heat transfer characteristics in a minichannel heat exchanger experimentally. The experimental testing was carried out on a minichannel with a hydraulic diameter of about 2.5 mm, with smooth and embedded with circular pin-fins. The testing was conducted with different hot fluids, air and water, over different Reynolds numbers ranges, and over different heat capacity ratios (0.25, 0.5, 0.75, and 1). The experimental study of the pressure drop covers a Reynolds number range between 100-1900 for the hot water, and Reynolds number range between 500-10,000 for the hot air. The hot fluid flows through a channel with an inline arrangement with a 1750 pin fin, while the cold fluid flows through a smooth channel. Increasing flow rates resulted in an increase in pressure drop and heat transfer coefficients. When using pin-fins surface instead of smooth surface, the overall heat transfer coefficient (U) increased by 190% when water is used as the heat transfer fluid (HTF), and the same coefficient increased by 42% when air is used as the heat transfer fluid. Similarly, the difference in pressure drop is low in the case of water-water, while in the case of air-water, the difference in pressure drop is more substantial as Reynolds number increases.

Simulation based work carried out in order to understand the thermohydraulic characteristics of fluid flow in helical microchannel, with circular cross-section, that is subjected to constant heat flux is detailed in this work. Water is used as the fluid in this study and the study is carried out for Reynolds number ranging from 50 to 500. The helical path of the fluid increases the heat transfer coefficient and pressure drop for a specific Reynolds number in comparison with that in a straight microchannel. The increase in heat transfer coefficient and pressure drop associated with the helical microchannel manifests as increased Nusselt number and Poiseuille number. At Reynolds number of 50, the Nusselt number of the helical microchannel is 1.36 times higher than that of the straight microchannel while at Reynolds number of 500, this enhancement increases to 2.33. Regarding Poiseuille number of helical microchannel, it is higher than that of the Poiseuille number of straight microchannel by 1.02 and 1.72 at Reynolds number of 50 and 500, respectively. It is identified from this study that by shifting from straight microchannel to helical microchannel, the enhancement in Nusselt number is higher than the associated penalty, i.e. increase in Poiseuille number.

MEMS heat sink having wavy microchannels integrating circular pin-fins for cooling of microelectronic chips is proposed and analyzed in this work; the pin-fins are placed at the valleys and peaks of the wavy structure. The pumping power and thermal resistance of the proposed MEMS heat sink is higher and lower than that of MEMS heat sink having straight microchannels. At Reynolds number of 250, the maximum temperature of the microelectronic chip, generating 106 W/m2, when using the proposed MEMS heat sink is only 0.77 of that when using MEMS heat sink having straight microchannels; this ratio lowers to 0.6 at Reynolds number of 1250. The thermal resistance of the proposed MEMS heat sink is only 0.72 and 0.43 of that of the MEMS heat sink having straight microchannels at Reynolds numbers of 250 and 1250, respectively. Regarding the pumping power of the proposed MEMS heat sink, it is higher than that of the MEMS heat sink having straight microchannels by 2 and 3.7 at the lowest and highest Reynolds numbers, respectively. This work also analyzes the contribution of geometric features on the behavior of the proposed MEMS heat sink in terms of maximum temperature of the microelectronic chip, thermal resistance, and pumping power as well as that of microchannel employed in the proposed MEMS heat sink in terms of Poiseuille and Nusselt numbers. Maximum temperature of the microelectronic chip and thermal resistance decrease along with increase in pumping power with increase in amplitude, diameter of pin-fins, and hydraulic diameter of microchannel as well as with decrease in wavelength. Poiseuille and Nusselt numbers increased with rise in amplitude, diameter of pin-fins, and hydraulic diameter as well as decrease in wavelength. In addition, experiments have been conducted on two designs of the proposed MEMS heat sink to generate data for purposes of validating the model. The experimental data are compared with data from simulations and the difference between the two are within the uncertainty of experimental data thereby validating the model.

This work explains the simulation-based study to understand the thermohydraulic characteristics (thermal resistance and pumping power) of a MEMS heat sink using serpentine microchannels employed for thermal management of concentrated photovoltaic cells; the planar dimensions of both are 1 cm by 1 cm. In this study, water is the coolant and the MEMS heat sink is constructed in silicon. Over the Reynolds number varying from 50 to 1000 and for concentration ratio of 20, the thermal resistance and pumping power of a MEMS heat sink using serpentine microchannel, in comparison with that using straight microchannel, is lower and higher, respectively; the benefit of switching microchannels outweigh the cost as up to 64% reduction in thermal resistance is achieved with just 126% rise in pumping power. Studies are done for understanding the contribution of geometry of the serpentine microchannel on the characteristics of the MEMS heat sink. Irrespective of the geometry, rise in Reynolds number leads to the rise and decrease in the pumping power and thermal resistance, respectively. For a particular Reynolds number, decrease in hydraulic diameter, rise in offset width, and decrease in offset length led to rise in pumping power and decrease in thermal resistance. The contribution of concentration ratio on characteristics of MEMS heat sink using serpentine microchannel is investigated and found to be independent of concentration ratio. Nusselt and Poiseuille numbers of serpentine microchannel are provided for the benefit of heat sink designers; these parameters are higher for serpentine microchannel in comparison with a similar straight microchannel.

This article investigates fluid distribution in multichannel microfluidic devices with U-shaped manifolds. The parameters investigated include Reynolds number, microchannel width, microchannel spacing width, and microchannel length. The study is carried out using a microfluidic device having 50 microchannels employing water as the working fluid. The flow distribution in the microfluidic device is investigated for microchannel widths between 100 µm to 500 µm and for Reynolds number ranging between 0.04 to 100. The effect of channel spacing width on flow distribution is investigated for microchannel spacing widths between 100 µm to 500 µm. The increase in Reynolds number affects the flow distribution by increasing the non-uniformity of the flow. It is found that increasing the microchannel width causes more non-uniformity in the flow. It is also found that increasing the microchannel spacing width decreased the non-uniformity of the flow distribution. It is found that increasing the channel width from 100 µm to 300 µm increased the flow maldistribution by 83%, and increasing the microchannel spacing width from 100 µm to 300 µm decreased the flow maldistribution by 42%. It is observed that the microchannel width has a stronger influence on the flow distribution compared with microchannel spacing width. The study is useful for examining the flow maldistribution in microfluidic devices as their performance is dependent on flow rate.

This article details the mathematical modeling and experimental validation of a liquid based MEMS heat sink using wavy microchannels with pin-fins for cooling of microelectronic chips with heat flux of 1000 kW/m2. The characteristics of the heat sink are evaluated using thermal resistance, pumping power, Poiseuille number, and Nusselt number. Investigations are done for Reynolds number varying from 250 to 1500 for understanding the working of the proposed MEMS heat sink as well as to evaluate the contribution of different geometric parameters (amplitude, wavelength, hydraulic diameter, and diameter of pin-fins) on its performance. Over this Reynolds number range, the thermal resistance of MEMS heat sinks using wavy microchannel with pin-fins is 7–10% lower than that of MEMS heat sinks using wavy microchannel while the corresponding pumping power increased by 66–148%; at the lowest Reynolds number, the proposed MEMS heat sink reduced the maximum substrate temperature by 5 °C compared with that of MEMS heat sinks employing wavy microchannels and at the highest Reynolds number, this temperature difference is 2 °C. The influence of geometric parameters is the highest at the low Reynolds number and their influence reduces with rise in Reynolds number. It is established based on the studies that increase in amplitude, hydraulic diameter, and diameter of pin-fins lead to decrease in thermal resistance and rise in pumping power; however, rise in wavelength raises and decreases the thermal resistance and pumping power, respectively. The contribution of hydraulic diameter and wavelength to thermal resistance and pumping power is greater than that of amplitude and diameter of pin-fins. The average Poiseuille number and Nusselt number associated with many combinations of dimensions of MEMS heat sinks using wavy microchannels with pin-fins are provided in this work and this information is particularly useful for designers of the proposed MEMS heat sink.

This work carries out an investigation on the performance of a MEMS microchannel heatsink with multiple zig-zag microchannels (MCHSzz). The heat sink is realized in silicon and uses water as the coolant. The study is conducted by employing Fluent module of Ansys Workbench. The performance of zig-zag and straight MCHS are compared for Reynolds number (Re) from 250 to 1500. The performance of the MCHS is quantified in terms of total thermal resistance (Rth) and pumping power (PPf) where Rth of zig-zag MCHS is better than that with straight microchannel; the enhanced thermal performance is achieved at the cost of increased PPf. Based on the cases studied in this work, it is observed that the relative change in Rth varied from 26% to 51% with increase in Re and the corresponding relative change in PPf varied from 40% to 120% with increase in Re. By employing zig-zag microchannels, it is possible to significantly reduce convective thermal resistance (Rth,cov), for a particular Re. Additionally, the influence of microchannel hydraulic diameter, orientation of microchannel, number of repeating units, and microchannel spacing are studied in this work. It is identified that the Rth and PPf over the considered range of Re decreased and increased, respectively, regardless of the geometric parameters. Additionally, Rth decreased with increase in geometric parameters for a specific Reynolds value until a threshold value beyond which no changes occur.

This paper conceptualizes and mathematically models a dielectrophoretic microdevice with planar corrugated electrodes for focusing micro-particles at any lateral location along the width of the micro-scale flow passage; two of these electrodes are placed on the top and bottom surfaces of the micro-scale flow passage with the electrodes on the top and bottom aligned with each other to form a pair. The mathematical model includes equations of motion, Navier-Stokes equations, and equations of electric voltage and field and considers the influence of several phenomena, including inertia, sedimentation, drag, virtual mass and dielectrophoresis on the focusing of micro-particles. The mathematical model is solved using the finite difference method. The mathematical model is used for parametric study, thereby revealing that the performance metrics related to focusing depend on the geometric (micro-scale flow passage and electrode dimensions) and operating (applied electric voltages and volumetric flow rate) parameters of the microdevice. The mathematical model allows for determining the operating and geometric parameters for achieving the desired performance metrics based on constraints. The mathematical model is validated using experimental data from the literature.

This article proposes a novel a magnetophoretic microfluidic device for separation of magnetic microparticles based on size and subsequently carries out simulation-based parametric analysis of the same. The microfluidic device is constructed with two inlets as well as two outlets and employs a soft magnetic element subjected to a uniform magnetic field to create the desired spatially varying magnetic field inside the microchannel. The first inlet introduces the sample while the second inlet is for introducing sheath flow to focus the microparticles close to the microchannel’s bottom surface prior to being deflected by magnetophoresis to the appropriate outlets. Parameters such as location of outlets, microchannel height, fluid velocity, and ratio of inlet and of outlet flow rates influence the movement of microparticles inside the microchannel and the associated performance metrics. Parametric study, carried out using 1 and 10 µm magnetic microparticle suspended in water, revels that the best performance metrics occur when flow rate ratios are maintained as low as possible. In addition, the performance metrics are examined for different designs to determine the optimal value of the location of the outlet associated with large microparticles.

This work proposes implementation of a passive heat transfer enhancement technique in MEMS two-fluid parallel flow heat exchangers as well as model based investigation of the same; the technique involves embedding square in-line pin-fins in the microchannels of the heat exchanger. Model based study is conducted using MEMS two-fluid heat exchangers, with and without pin fins, for a wide range of Reynolds number and two heat capacity ratios. With increase in Reynolds number, the effectiveness of heat exchangers with pin fins increases in comparison with those without pin fins for all heat capacity ratios; moreover, at low Reynolds number the effectiveness of both types of heat exchangers are equal. The power consumption in heat exchangers with pin-fins is higher than in those without pin-fins; the difference in the power consumption increases with increase in Reynolds number irrespective of the heat capacity ratio. This enhancement technique allows MEMS two-fluid parallel flow heat exchangers operate at higher throughput without compromising the effectiveness. For purposes of simulation, microchannel dimensions are kept at 150 μm (width) by 150 μm (height) by 2 cm (length) and pin fin dimensions are held at 75 μm (width) by 500 μm (pitch) while the Reynolds number is varied between 50 and 1500 for heat capacity ratios of unity and 0.5. For the cases considered for simulation, the maximum increase in effectiveness, relative to the baseline case, achieved is 84% and 66% for balanced and unbalanced flow conditions, respectively.

The 7th edition of the Textbook of Neonatal Resuscitation recommends administration of epinephrine via an umbilical venous catheter (UVC) inserted 2–4 cm below the skin, followed by a 0.5-mL to 1-mL flush for severe bradycardia despite effective ventilation and chest compressions (CC). This volume of flush may not be adequate to push epinephrine to the right atrium in the absence of intrinsic cardiac activity during CC. The objective of our study was to evaluate the effect of 1-mL and 2.5-mL flush volumes after UVC epinephrine administration on the incidence and time to achieve return of spontaneous circulation (ROSC) in a near-term ovine model of perinatal asphyxia induced cardiac arrest. After 5 min of asystole, lambs were resuscitated per Neonatal Resuscitation Program (NRP) guidelines. During resuscitation, lambs received epinephrine through a UVC followed by 1-mL or 2.5-mL normal saline flush. Hemodynamics and plasma epinephrine concentrations were monitored. Three out of seven (43%) and 12/15 (80%) lambs achieved ROSC after the first dose of epinephrine with 1-mL and 2.5-mL flush respectively (p = 0.08). Median time to ROSC and cumulative epinephrine dose required were not different. Plasma epinephrine concentrations at 1 min after epinephrine administration were not different. From our pilot study, higher flush volume after first dose of epinephrine may be of benefit during neonatal resuscitation. More translational and clinical trials are needed.

There is variability in practice among care providers on feeding infants admitted with neonatal hypoglycemia (NH) for parenteral dextrose. We compared clinical outcomes in infants who were fed (NH-Fed) and hypoglycemic infants who were kept nothing per os (NPO) (NH-NPO) at the time of initiation of intravenous (IV) dextrose. We performed a retrospective review of all newborn infants admitted to the neonatal intensive care unit with NH for IV dextrose. Infants were grouped as per the feeding approach at initiation of IV dextrose: NH-Fed or NH-NPO infants. We found that infants in the NH-Fed group had lower maximum glucose infusion rate, less duration of glucose infusion therapy compared with the NH-NPO group, and significantly less number of days of hospital stay compared with the NH-NPO group (5.87 ± 1.4 days vs 4.9 ± 1.4 days, P < .006). In conclusion, feeding infants with hypoglycemia who require IV dextrose offers tangible benefits of shorter duration of parenteral dextrose and shorter length of hospitalization.

Resuscitation with 21% O2 may not achieve target oxygenation in preterm infants and in neonates with persistent pulmonary hypertension of the newborn (PPHN). Inhaled nitric oxide (iNO) at birth can reduce pulmonary vascular resistance (PVR) and improve PaO2. We studied the effect of iNO on oxygenation and changes in PVR in preterm lambs with and without PPHN during resuscitation and stabilization at birth. Preterm lambs with and without PPHN (induced by antenatal ductal ligation) were delivered at 134 d gestation (term is 147–150 d). Lambs without PPHN were ventilated with 21% O2, titrated O2 to maintain target oxygenation or 21% O2 + iNO (20 ppm) at birth for 30 min. Preterm lambs with PPHN were ventilated with 50% O2, titrated O2 or 50% O2 + iNO. Resuscitation with 21% O2 in preterm lambs and 50%O2 in PPHN lambs did not achieve target oxygenation. Inhaled NO significantly decreased PVR in all lambs and increased PaO2 in preterm lambs ventilated with 21% O2 similar to that achieved by titrated O2 (41 ± 9% at 30 min). Inhaled NO increased PaO2 to 45 ± 13, 45 ± 20 and 76 ± 11 mmHg with 50% O2, titrated O2 up to 100% and 50% O2 + iNO, respectively, in PPHN lambs. We concluded that iNO at birth reduces PVR and FiO2 required to achieve target PaO2.

This article details the mathematical model of a microfluidic device aimed at separating any binary heterogeneous sample of microparticles into two homogeneous samples based on size with sub-micron resolution. The device consists of two sections, where the upstream section is dedicated to focusing of microparticles, while the downstream section is dedicated to separation of the focused stream of microparticles into two samples based on size. Each section has multiple planar electrodes of finite size protruding into the microchannel from the top and bottom of each sidewall; each top electrode aligns with a bottom electrode and they form a pair leading to multiple pairs of electrodes on each side. The focusing section subjects all microparticles to repulsive dielectrophoretic force, from each set of the electrodes, to focus them next to one of the sidewalls. This separation section pushes the big microparticles toward the interior, away from the wall, of the microchannel using repulsive dielectrophoretic force, while the small microparticles move unaffected to achieve the desired degree of separation. The operating frequency of the set of electrodes in the separation section is maintained equal to the cross-over frequency of the small microparticles. The working of the device is demonstrated by separating a heterogeneous mixture consisting of polystyrene microparticles of different size (radii of 2 and 2.25 μm) into two homogeneous samples. The mathematical model is used for parametric study, and the performance is quantified in terms of separation efficiency and separation purity; the parameters considered include applied electric voltages, electrode dimensions, outlet widths, number of electrodes, and volumetric flowrate. The separation efficiencies and separation purities for both microparticles are 100% for low volumetric flow rates, a large number of electrode pairs, large electrode dimensions, and high differences between voltages in both sections.

This article conceptualizes and mathematically models a dielectrophoretic microfluidic device with two sets of interdigitated transducer vertical electrodes for separation of a binary heterogeneous mixture of particles based on size; each set of electrodes is located on the sidewalls and independently controllable. To achieve separation in the proposed microfluidic device, the small microparticles are subjected to positive dielectrophoresis and the big microparticles do not experience dielectrophoresis. The mathematical model consists of equations describing the motion of each microparticle, fluid flow profile, and electric voltage and field profiles, and they are solved numerically. The equations of motion take into account the influence of phenomena, such as inertia, drag, dielectrophoresis, gravity, and buoyancy. The model is used for a parametric study to understand the influence of parameters on the performance of the microfluidic device. The parameters studied include applied electric voltages, electrode dimensions, volumetric flow rate, and number of electrodes. The separation efficiency of the big and small microparticles is found to be independent of and dependent on all parameters, respectively. On the other hand, the separation purity of the big and small microparticles is found to be dependent on and independent of all parameters, respectively. The mathematical model is useful in designing the proposed microfluidic device with the desired level of separation efficiency and separation purity.

BackgroundEpinephrine administered by low umbilical venous catheter (UVC) or endotracheal tube (ETT) is indicated in neonates who fail to respond to positive pressure ventilation and chest compressions at birth. Pharmacokinetics of ETT epinephrine via fluid‐filled lungs or UVC epinephrine in the presence of fetal shunts is unknown. We hypothesized that epinephrine administered by ETT or low UVC results in plasma epinephrine concentrations and rates of return of spontaneous circulation (ROSC) similar to right atrial (RA) epinephrine. Methods and ResultsForty‐four lambs were randomized into the following groups: RA epinephrine (0.03 mg/kg), low UVC epinephrine (0.03 mg/kg), postcompression ETT epinephrine (0.1 mg/kg), and precompression ETT epinephrine (0.1 mg/kg). Asystole was induced by umbilical cord occlusion. Resuscitation was initiated following 5 minutes of asystole. Thirty‐eight of 44 lambs achieved ROSC (10/11, 9/11, and 12/22 in the RA, UVC, and ETT groups, respectively; subsequent RA epinephrine resulted in a total ROSC of 19/22 in the ETT groups). Median time (interquartile range) to achieve ROSC was significantly longer in the ETT group (including those that received RA epinephrine) compared to the intravenous group (4.5 [2.9–7.4] versus 2 [1.9–3] minutes; P=0.02). RA and low UVC epinephrine administration achieved comparable peak plasma epinephrine concentrations (470±250 versus 450±190 ng/mL) by 1 minute compared to ETT values of 130±60 ng/mL at 5 minutes; P=0.03. Following ROSC with ETT epinephrine alone, there was a delayed peak epinephrine concentration (652±240 ng/mL). ConclusionsThe absorption of ETT epinephrine is low and delayed at birth. RA and low UVC epinephrine rapidly achieve high plasma concentrations resulting in ROSC.

PURPOSE:Current knowledge about pulmonary/systemic hemodynamics and gas exchange during neonatal resuscitation in a model of transitioning fetal circulation with fetal shunts and fluid-filled alveoli is limited. Using a fetal lamb asphyxia model, we sought to determine whether hemodynamic or gas-exchange parameters predicted successful return of spontaneous circulation (ROSC). METHODS:The umbilical cord was occluded in 22 lambs to induce asphyxial cardiac arrest. Following five minutes of asystole, resuscitation as per AHA-Neonatal Resuscitation Program guidelines was initiated. Hemodynamic parameters and serial arterial blood gases were assessed during resuscitation. RESULTS:ROSC occurred in 18 lambs (82%) at a median (IQR) time of 120 (105-180) seconds. There were no differences in hemodynamic parameters at baseline and at any given time point during resuscitation between the lambs that achieved ROSC and those that did not. Blood gases at arrest prior to resuscitation were comparable between groups. However, lambs that achieved ROSC had lower PaO2, higher PaCO2, and lower lactate during resuscitation. Increase in diastolic blood pressures induced by epinephrine in lambs that achieved ROSC (11 ±4 mmHg) did not differ from those that were not resuscitated (10 ±6 mmHg). Low diastolic blood pressures were adequate to achieve ROSC. CONCLUSIONS:Hemodynamic parameters in a neonatal lamb asphyxia model with transitioning circulation did not predict success of ROSC. Lactic acidosis, higher PaO2 and lower PaCO2 observed in the lambs that did not achieve ROSC may represent a state of inadequate tissue perfusion and/or mitochondrial dysfunction.

An experimentally validated mathematical model of a microfluidic device with nozzle-shaped electrode configuration for realizing dielectrophoresis based 3D-focusing is presented in the article. Two right-triangle shaped electrodes on the top and bottom surfaces make up the nozzle-shaped electrode configuration. The mathematical model consists of equations describing the motion of microparticles as well as profiles of electric potential, electric field, and fluid flow inside the microchannel. The influence of forces associated with inertia, gravity, drag, virtual mass, dielectrophoresis, and buoyancy are taken into account in the model. The performance of the microfluidic device is quantified in terms of horizontal and vertical focusing parameters. The influence of operating parameters, such as applied electric potential and volumetric flow rate, as well as geometric parameters, such as electrode dimensions and microchannel dimensions, are analyzed using the model. The performance of the microfluidic device enhances with an increase in applied electric potential and reduction in volumetric flow rate. Additionally, the performance of the microfluidic device improves with reduction in microchannel height and increase in microparticle radius while degrading with increase in reduction in electrode length and width. The model is of great benefit as it allows for generating working designs of the proposed microfluidic device with the desired performance metrics.

This paper presents focusing of microparticles in multiple paths within the direction of the flow using dielectrophoresis. The focusing of microparticles is realized through partially perforated electrodes within the microchannel. A continuous electrode on the top surface of the microchannel is considered, while the bottom side is made of a circular meshed perforated electrode. For the mathematical model of this microfluidic channel, inertia, buoyancy, drag and dielectrophoretic forces are brought up in the motion equation of the microparticles. The dielectrophoretic force is accounted for through a finite element discretization taking into account the perforated 3D geometry within the microchannel. An ordinary differential equation is solved to track the trajectories of the microparticles. For the case of continuous electrodes using the same mathematical model, the numerical simulation shows a very good agreement with the experiments, and this confirms the validation of focusing of microparticles within the proposed perforated electrode microchannel. Microparticles of silicon dioxide and polystyrene are used for this analysis. Their initial positions and radius, the Reynolds number, and the radius of the pore in perforated electrodes mainly conduct microparticles trajectories. Moreover, the radius of the pore of perforated electrode is the dominant factor in the steady state levitation height.

The current guidelines recommend the use of 100% O2 during resuscitation of a neonate requiring chest compressions (CC). Studies comparing 21% and 100% O2 during CC were conducted in postnatal models and have not shown a difference in incidence or timing of return of spontaneous circulation (ROSC). The objective of this study is to evaluate systemic oxygenation and oxygen delivery to the brain during CC in an ovine model of perinatal asphyxial arrest induced by umbilical cord occlusion. Pulseless cardiac arrest was induced by umbilical cord occlusion in 22 lambs. After 5 min of asystole, lambs were resuscitated with 21% O2 as per Neonatal Resuscitation Program (NRP) guidelines. At the onset of CC, inspired O2 was either increased to 100% O2 (n = 25) or continued at 21% (n = 9). Lambs were ventilated for 30 min post ROSC and FiO2 was gradually titrated to achieve preductal SpO2 of 85–95%. All lambs achieved ROSC. During CC, PaO2 was 21.6 ± 1.6 mm Hg with 21% and 23.9 ± 6.8 mm Hg with 100% O2 (p = 0.16). Carotid flow was significantly lower during CC (1.2 ± 1.6 mL/kg/min in 21% and 3.2 ± 3.4 mL/kg/min in 100% oxygen) compared to baseline fetal levels (27 ± 9 mL/kg/min). Oxygen delivery to the brain was 0.05 ± 0.06 mL/kg/min in the 21% group and 0.11 ± 0.09 mL/kg/min in the 100% group and was significantly lower than fetal levels (2.1 ± 0.3 mL/kg/min). Immediately after ROSC, lambs ventilated with 100% O2 had higher PaO2 and pulmonary flow. It was concluded that carotid blood flow, systemic PaO2, and oxygen delivery to the brain are very low during chest compressions for cardiac arrest irrespective of 21% or 100% inspired oxygen use during resuscitation.

In this article, thermal performance of different waste materials and by-products of industrial processes is investigated experimentally. A geopolymer concrete block with 7.5 cm thickness and cross-sectional area of 5 × 5 cm was considered as a reference model to measure heat transmission across the two opposite surfaces while all four remnant surfaces were perfectly insulated. For all other samples, a sandwich concrete block was developed by taking two pieces of the geopolymer concrete with 2.5 cm thickness each on either side and insulation material of 2.5 cm thickness in between. The sandwich materials investigated were air cavity, expanded polystyrene foam, polyurethane foam, rubber tire, date palm, PCM-30, and PCM-42. Experimental investigations revealed that the investigated green materials and industrial by-products have comparable insulation performance with respect to the traditional insulations such as expanded polystyrene foam. It is found that polyurethane foam and date palm can reduce indoor cooling demand by 46.6% each in hot conditions while rubber tire can reduce indoor heating demand by 59.2% in cold climatic conditions at the maximum. The research results confirm and encourage the effective utilization of waste materials in building walls for reducing indoor air-conditioning demand in the extreme climatic conditions.

Persistent pulmonary hypertension of the newborn (PPHN) is a syndrome of failed circulatory adaptation at birth due to delay or impairment in the normal fall in pulmonary vascular resistance (PVR) that occurs following birth. The fetus is in a state of physiological pulmonary hypertension. In utero, the fetus receives oxygenated blood from the placenta through the umbilical vein. At birth, following initiation of respiration, there is a sudden precipitous fall in the PVR and an increase of systemic vascular resistance (SVR) due to the removal of the placenta from circulation. There is dramatic increase in pulmonary blood flow with a decrease in, and later reversal of shunts at the foramen ovale and ductus arteriosus. The failure of this normal physiological pulmonary transition leads to the syndrome of PPHN. PPHN presents with varying degrees of hypoxemic respiratory failure. Survival of infants with PPHN has significantly improved with the use of gentle ventilation, surfactant and inhaled nitric oxide (iNO). PPHN is associated with significant mortality and morbidity among survivors. Newer agents that target different enzymatic pathways in the vascular smooth muscle are in different stages of development and testing. Further research using these agents is likely to further reduce morbidity and mortality associated with PPHN.

This work proposes and demonstrates the novel idea of using Fe _3 O _4 @SiO _2 core/shell structure nanoparticles (NPs) to improve the solar thermal conversion efficiency. Magnetite (Fe _3 O _4 ) NPs are synthesized by controlled co-precipitation method. Fe _3 O _4 @SiO _2 NPs are prepared based on sol–gel approach, then characterized. Water-based Fe _3 O _4 @SiO _2 nanofluid is prepared and usedto illustrate the photo-thermal conversion characteristics of a solar collector under solar simulator. The temperature rise characteristics of the nanofluids are investigated at different heights of the solar collector, for duration of 300 min, under a solar intensity of 1000 W m ^−2 . The experimental results show that Fe _3 O _4 @SiO _2 NPs have a core/shell structure with spherical morphology and size of about 400 nm. Fe _3 O _4 @SiO _2 /H _2 O nanofluid enhances the photo-thermal conversion efficiency compared with base fluid and Fe _3 O _4 /H _2 O nanofluid, since the silica coating improves both the thermodynamic stability of the nanofluid and the light absorption effectiveness of the NPs. At a concentration of 1 mg/1 ml of Fe _3 O _4 @SiO _2 /H _2 O, and with the utilization of kerosene into the solar collector, and exposure for radiation for 5 min, the photo-thermal conversion efficiency has shown an enhancement at the bottom of the collector of about 32.9% compared to the base fluid.

High seroprevalence rates for Anaplasma phagocytophilum (8.8%), Coxiella burnetii (6.4%), Bartonella henselae (9.6%), and Rickettsia typhi (4.1%) in 365 farm workers near Tianjin, People’s Republic of China, suggest that human infections with these zoonotic bacteria are frequent and largely unrecognized. Demographic features of seropositive persons suggest distinct epidemiology, ecology, and risks.