Convective and evaporative heat transfer coefficients during drying of ivy gourd under natural and forced convection solar dryer

In the present work, a study on convective heat, mass transfer coefficients and evaporative heat transfer coefficient of the thin layer drying process of ivy gourd is performed. The experiment was conducted in three drying modes such as natural, forced convection solar dryer and open sun drying. The hourly data for the rate of moisture removal, sample temperature, relative humidity inside and outside the solar and ambient air temperature for complete drying have been recorded. The drying air temperature varied from 55, 65, 70 and 75 °C, and the air velocity was 1, 1.5 and 2 m/s. All the drying experiments had shown a falling rate period. The data obtained from experimentation have been used to evaluate the experimental constant values of C and n by simple regression analysis. Based on the values of "C" and "n", convective and evaporative heat transfer coefficients for ivy gourd were determined. The average convective heat and mass transfer coefficients varied between 2.64 and 8.30 W/m² °C and 0.0025 to 0.0076 m/s for temperature ranges, at the different air velocities, respectively. The average evaporative heat transfer coefficient for ivy gourd varied from 181.89 to 421.84 W/m² °C. It was observed that convective and evaporative heat transfer coefficients increase with the increase in drying air temperature. The rate of increment of evaporative heat transfer coefficient is higher than the convective heat transfer coefficient. The intensity of heat and mass transfer during solar drying depends on the drying air temperature and velocity.

Study of activation energy and moisture diffusivity of various dipping solutions of ivy gourd using solar dryer

The study is aimed to enhance the shelf life of ivy gourd through the solar drying method in open, forced, and natural convection mode. Ivy gourd is treated as the primary agent to prepare medicines and the stems, leaves and flowers are used to cure diseases related to diabetics, ulcer and skin. The normal shelf life is 2-3 days and it can be increased up to 6 months with an effective drying process. The experiment is intended to find the best drying process among the open, natural, and forced convection mode with an initial dipping method with ascorbic acid, lemon juice, sugar solution, honey solutions individually, and a control sample (without dipping). A 3 kg sample of ivy gourd is dipped in 10 g/L of each of the solutions and it is used for the three drying processes individually. The obtained results are indicating that the forced convection method for ascorbic acid is best among the other drying method, with the highest moisture diffusivity is 7.88 × 10^-8 m²/s and the lowest activation energy of 21.12 kJ/mol. The lemon juice sample is found to have better sensory appeal in terms of colour (darkness) and shrinkage followed by honey, ascorbic acid, and control sample, whereas the honey-dipped sample offers a better taste followed by lemon juice-dipped samples, control, and ascorbic acid-dipped samples, respectively. The influence of dipping solution and drying mechanisms on the functionalities of drying are discussed with suitable illustrations.

Thermal convection in rotating spherical geometry: A numerical overview of the transitions from periodic axisymmetric to temporally complex three-dimensional flows

The aim of this work is to elucidate the type of transitions that take place when the periodic axisymmetric flows, which can set up at the onset of thermal convection in rotating fluid spheres, lose stability and to study the behavior of the new stable velocity fields until the flows become temporally chaotic. The computations for Prandtl numbers Pr=0.715, 0.1, and 0.01 show that when it decreases, the range of stability of these flows becomes narrower because the kinetic energy of the axisymmetric periodic solutions increases very fast, favoring their instability. From the stability analysis and direct three-dimensional simulations it is found that the transition to stable quasiperiodic flows through Neimark-Sacker bifurcations is supercritical when Pr≥0.01. For Pr=0.1 two branches of stable periodic flows emerging from the conduction state have been found due to the proximity to a double Hopf bifurcation. However, only the branches bifurcating from the azimuthal rotating waves are stable at large Rayleigh numbers. Far from this bifurcation the stable flows keep the influence of the axisymmetric dynamics up to large Rayleigh numbers. For small Pr they behave as repeated transients of mixed dynamics, controlled by the azimuthal wave numbers m=0, m=1, and m=2.

Dimensionally consistent learning with Buckingham Pi

In the absence of governing equations, dimensional analysis is a robust technique for extracting insights and finding symmetries in physical systems. Given measurement variables and parameters, the Buckingham Pi theorem provides a procedure for finding a set of dimensionless groups that spans the solution space, although this set is not unique. We propose an automated approach using the symmetric and self-similar structure of available measurement data to discover the dimensionless groups that best collapse these data to a lower dimensional space according to an optimal fit. We develop three data-driven techniques that use the Buckingham Pi theorem as a constraint: (1) a constrained optimization problem with a non-parametric input-output fitting function, (2) a deep learning algorithm (BuckiNet) that projects the input parameter space to a lower dimension in the first layer and (3) a technique based on sparse identification of nonlinear dynamics to discover dimensionless equations whose coefficients parameterize the dynamics. We explore the accuracy, robustness and computational complexity of these methods and show that they successfully identify dimensionless groups in three example problems: a bead on a rotating hoop, a laminar boundary layer and Rayleigh-Bénard convection.

Chronic convection-enhanced delivery of topotecan for patients with recurrent glioblastoma: a first-in-patient, single-centre, single-arm, phase 1b trial

BACKGROUND

Topotecan is cytotoxic to glioma cells but is clinically ineffective because of drug delivery limitations. Systemic delivery is limited by toxicity and insufficient brain penetrance, and, to date, convection-enhanced delivery (CED) has been restricted to a single treatment of restricted duration. To address this problem, we engineered a subcutaneously implanted catheter-pump system capable of repeated, chronic (prolonged, pulsatile) CED of topotecan into the brain and tested its safety and biological effects in patients with recurrent glioblastoma.

METHODS

We did a single-centre, open-label, single-arm, phase 1b clinical trial at Columbia University Irving Medical Center (New York, NY, USA). Eligible patients were at least 18 years of age with solitary, histologically confirmed recurrent glioblastoma showing radiographic progression after surgery, radiotherapy, and chemotherapy, and a Karnofsky Performance Status of at least 70. Five patients had catheters stereotactically implanted into the glioma-infiltrated peritumoural brain and connected to subcutaneously implanted pumps that infused 146 μM topotecan 200 μL/h for 48 h, followed by a 5-7-day washout period before the next infusion, with four total infusions. After the fourth infusion, the pump was removed and the tumour was resected. The primary endpoint of the study was safety of the treatment regimen as defined by presence of serious adverse events. Analyses were done in all treated patients. The trial is closed, and is registered with ClinicalTrials.gov, NCT03154996.

FINDINGS

Between Jan 22, 2018, and July 8, 2019, chronic CED of topotecan was successfully completed safely in all five patients, and was well tolerated without substantial complications. The only grade 3 adverse event related to treatment was intraoperative supplemental motor area syndrome (one [20%] of five patients in the treatment group), and there were no grade 4 adverse events. Other serious adverse events were related to surgical resection and not the study treatment. Median follow-up was 12 months (IQR 10-17) from pump explant. Post-treatment tissue analysis showed that topotecan significantly reduced proliferating tumour cells in all five patients.

INTERPRETATION

In this small patient cohort, we showed that chronic CED of topotecan is a potentially safe and active therapy for recurrent glioblastoma. Our analysis provided a unique tissue-based assessment of treatment response without the need for large patient numbers. This novel delivery of topotecan overcomes limitations in delivery and treatment response assessment for patients with glioblastoma and could be applicable for other anti-glioma drugs or other CNS diseases. Further studies are warranted to determine the effect of this drug delivery approach on clinical outcomes.

FUNDING

US National Institutes of Health, The William Rhodes and Louise Tilzer Rhodes Center for Glioblastoma, the Michael Weiner Glioblastoma Research Into Treatment Fund, the Gary and Yael Fegel Foundation, and The Khatib Foundation.

Constant Pressure Convection-Enhanced Delivery Increases Volume Dispersed With Catheter Movement in Agarose

Convection-enhanced delivery (CED) has been extensively studied for drug delivery to the brain due to its inherent ability to bypass the blood-brain barrier. Unfortunately, CED has also been shown to inadequately distribute therapeutic agents over a large enough targeted tissue volume to be clinically beneficial. In this study, we explore the use of constant pressure infusions in addition to controlled catheter movement as a means to increase volume dispersed (Vd) in an agarose gel brain tissue phantom. Constant flow rate and constant pressure infusions were conducted with a stationary catheter, a catheter retracting at a rate of 0.25 mm/min, and a catheter retracting at a rate of 0.5 mm/min. The 0.25 mm/min and 0.5 mm/min retracting constant pressure catheters resulted in significantly larger Vd compared to any other group, with a 105% increase and a 155% increase compared to the stationary constant flow rate catheter, respectively. These same constant pressure retracting infusions resulted in a 42% and 45% increase in Vd compared to their constant flow rate counterparts. Using constant pressure infusions coupled with controlled catheter movement appears to have a beneficial effect on Vd in agarose gel. Furthermore, constant pressure infusions reveal the fundamental limitation of flow-driven infusions in both controlled catheter movement protocols as well as in stationary protocols where maximum infusion volume can never be reliably obtained.

Convection-enhanced delivery with controlled catheter movement: A parametric finite element analysis

Convection-enhanced delivery (CED) is an investigational method for delivering therapeutics directly to the brain for the treatment of glioblastoma. However, it has not become a common clinical therapy due to an inability of CED treatments to deliver therapeutics in a large enough tissue volume to fully saturate the target region. We have recently shown that the combination of controlled catheter movement and constant pressure infusions can be used to significantly increase volume dispersed (Vd ) in an agarose gel brain tissue phantom. In the present study, we develop a computational model to predict Vd achieved by various retraction rates with both constant pressure and constant flow rate infusions. An increase in Vd is achieved with any movement rate, but increase in Vd between successive movement rates drops off at rates above 0.3-0.35 mm/min. Finally, we found that infusions with retraction result in a more even distribution in concentration level compared to the stationary catheter, suggesting a potential increased ability for moving catheters to have a therapeutic impact regardless of the required therapeutic concentration level.

Convection Driven Ultrarapid Protein Detection via Nanobody-Functionalized Organic Electrochemical Transistors

Conventional biosensors rely on the diffusion-dominated transport of the target analyte to the sensor surface. Consequently, they require an incubation step that may take several hours to allow for the capture of analyte molecules by sensor biorecognition sites. This incubation step is a primary cause of long sample-to-result times. Here, alternating current electrothermal flow (ACET) is integrated in an organic electrochemical transistor (OECT)-based sensor to accelerate the device operation. ACET is applied to the gate electrode functionalized with nanobody-SpyCatcher fusion proteins. Using the SARS-CoV-2 spike protein in human saliva as an example target, it is shown that ACET enables protein recognition within only 2 min of sample exposure, supporting its use in clinical practice. The ACET integrated sensor exhibits better selectivity, higher sensitivity, and lower limit of detection than the equivalent sensor with diffusion-dominated operation. The performance of ACET integrated sensors is compared with two types of organic semiconductors in the channel and grounds for device-to-device variations are investigated. The results provide guidelines for the channel material choice in OECT-based biochemical sensors, and demonstrate that ACET integration substantially decreases the detection speed while increasing the sensitivity and selectivity of transistor-based sensors.

In vitro bioaccessibility and activity of basil (Ocimum basilicum L.) phytochemicals as affected by cultivar and postharvest preservation method - Convection drying, freezing, and freeze-drying

The effects of convection drying, freezing, and freeze-drying, on phytochemicals content, in vitro activity and bioaccessibility of sweet basil, cinnamon basil, red rubin basil, and lemon basil were investigated. For evaluation of bioaccessibility, rosmarinic acid content, phenolic content, and antioxidant potential of samples before and after gastric and intestinal steps of digestion were determined. Results showed that the content, activity and bioaccessibility of basil phytochemicals varied depending on the cultivar as well as the applied postharvest preservation. It was found that the frozen and freeze-dried plant materials were characterized by a higher phenolic level and antioxidant activity compared to the convection dried. However, in general, convection drying allows obtaining samples with higher bioaccessibility of phytochemicals compared to the low-temperature processed samples. These findings highlight the need for evaluation of basil cultivars and postharvest preservation methods regarding phytochemicals bioaccessibility, which might help in the classification in terms of pro-health quality.

Optimization of convection-enhanced evaporation (CEE) using generalized cost ratios

Brine is a byproduct of desalination plants and several industrial processes which can have an adverse impact on the environment if not managed properly. Conventional brine management technologies are energy intensive and costly which limit their adoption. This study presents the first cost optimization of convection-enhanced evaporation (CEE) system to achieve a modular, cost-effective brine management and on-site treatment option for decentralized desalination plants and small-volume industries. CEE involves evaporating water from saline liquid films, released on evaporation surfaces, by the difference in vapor pressure created by forced air convection. The optimization identifies the optimal operating settings (brine flow rates, brine temperatures, and air speeds) and enables comprehensive investigation of the effect of various operational decisions on operating (energy) cost, capital cost, and footprint area. The objective functions are formulated using two cost ratios that relate material, thermal, and electrical energy costs, effectively generalizing the optimization results to be independent of location-specific cost parameters. The optimization reveals two distinct operation modes, "all-electric mode" and "heating mode". The "all-electric mode" corresponds to a lower total specific cost, ranging from $1.4 to $5 per m³, and higher footprint area, ranging from 0.5 to 1.8 m² per m³ of evaporated volume. The "heating mode" corresponds to a higher total specific cost, up to $6.5 per m³; at low energy cost ratios, a compact footprint area ranging from 0.072 to 0.5 m² per m³ of evaporated volume is achieved. Proposed designs were found to have lower costs than technologies available in the literature.

Experimental Study on Solidification Characteristics of Sessile Urine Droplets on a Horizontal Cold Plate Surface under Natural Convection

As the human excreta, urine is often used as one of the test materials in medical research due to its composition and content directly reflecting the health status of the body. Considering that the substances in urine may show different effects on its freezing process, solidification characteristics of sessile urine droplets on a horizontal cold plate surface under natural convection were experimentally investigated by comparing with those of water droplets under same conditions. To make the conclusion analysis more reasonable, the urine of a human without any diseases, especially metabolic diseases, was treated and used. The characteristics include nucleation location, dynamic variation of droplet color, and temperatures at different heights inside the droplet, and so forth. It was found that, similar to that of a water droplet, the solidification process of a urine droplet also experiences the following four stages: supercooling, recalescence, freezing, and cooling, in chronological order. Differently, the urine droplet changes from transparent to blur white at the supercooling stage due to the precipitation of inorganic salts. For nucleation locations, 46.67% cases are at the bottom, while others are at the top and middle of urine droplets. For a 10 μL droplet on a surface of -30 °C, urine has a 0.95 s freezing duration shorter than water, and a 5.31 °C lower phase-transition temperature. Results of this study are expected to reflect the content of substances in urine and thus provide references for urinalysis of patients with metabolic diseases.

Large-scale flow in a cubic Rayleigh-Bénard cell: long-term turbulence statistics and Markovianity of macrostate transitions

We investigate the large-scale circulation (LSC) in a turbulent Rayleigh-Bénard convection flow in a cubic closed convection cell by means of direct numerical simulations at a Rayleigh number Ra = 10⁶. The numerical studies are conducted for single flow trajectories up to 10⁵ convective free-fall times to obtain a sufficient sampling of the four discrete LSC states, which can be summarized to one macrostate, and the two crossover configurations which are taken by the flow in between for short periods. We find that large-scale dynamics depends strongly on the Prandtl number Pr of the fluid which has values of 0.1, 0.7, and 10. Alternatively, we run an ensemble of 3600 short-term direct numerical simulations to study the transition probabilities between the discrete LSC states. This second approach is also used to probe the Markov property of the dynamics. Our ensemble analysis gave strong indication of Markovianity of the transition process from one LSC state to another, even though the data are still accompanied by considerable noise. It is based on the eigenvalue spectrum of the transition probability matrix, further on the distribution of persistence times and the joint distribution of two successive microstate persistence times. This article is part of the theme issue 'Mathematical problems in physical fluid dynamics (part 1)'.

Stabilized convection in a ternary mixture with two Soret coefficients of opposite sign

We performed ground-based experiments on the sample polystyrene-toluene-cyclohexane in order to complement the experimental activities in microgravity conditions related to the ESA projects DCMIX4 and Giant Fluctuations. After applying a stabilizing thermal gradient by heating from above a layer of the fluid mixture, we studied over many hours the density variations in the bidimensional horizontal field by means of a Shadowgraph optical setup. The resulting images evidence the appearance of convective instability after a diffusive time associated with the binary molecular solvent consisting of toluene and cyclohexane, confirming the negative sign of the Soret coefficient of this mixture. After a larger diffusive time related to mass diffusion of the polystyrene in the binary solvent, convection was suppressed by the increasing stabilizing density gradient originated by the Soret-induced concentration gradient of the polymer. This is compatible with a positive sign of the Soret coefficient of the polymer in the binary solvent.

Recent progress in melting heat phenomenon for bioconvection transport of nanofluid through a lubricated surface with swimming microorganisms

The cooling of numerous microelectronic devices has become a need in today's world. Nanofluids, a novel type of heat transport fluid containing nano-sized particles embedded in a host liquid, were developed a few years ago. Impact of ultra-fine nanoparticles with oil, water, or ethylene glycol produces these fluids. Nano-liquids have a variety of applications, including engine cooling, electronic devices, biomedicine, and the manufacture of thermal exchangers. The main objective of current research article is to scrutinizes theoretically, the effects of axisymmetric magnetohydrodynamic flow of bio-convective nanoliquid through a moving surface in the occurrence of swimming microorganisms. The idea of the envisaged model is improved by considering the consequence of thermal radiation, activation energy with generalized slip effects under convective boundaries. The present analysis is developed in the form of mathematical formulation and then solved numerically. The governing flow equations are transmuted into dimensionless nonlinear ODEs system by compatible similarity transformations and then integrated this so-formulated highly nonlinear problem numerically via bvp4c built-in scheme in MATLAB. The significance of influential parameters versus velocity field, temperature profile, concentration field and motile density of microorganism's profile are examined with the aid of graphs and tabular data. The physical interpretation of outcomes highlight that the velocity receives increment for amplified mixed convection parameter. The thermal profile is found to be reducing with a greater Prandtl number. The concentration profile of nanoparticle boosts up for greater activation energy parameter. The microorganism's profile is reduced via bioconvection Lewis number. This investigation contains the significance of bioconvection phenomenon, thermal radiation, slip effects and activation energy under convective boundary conditions. These impacts are used in axisymmetric, stagnation point flow of bioconvective magnetized nanofluid containing swimming gyrotactic motile microorganisms over a lubricated surface. The present analysis is not yet published.

Applications of bioconvection for tiny particles due to two concentric cylinders when role of Lorentz force is significant

The bioconvection flow of tiny fluid conveying the nanoparticles has been investigated between two concentric cylinders. The contribution of Lorenz force is also focused to inspect the bioconvection thermal transport of tiny particles. The tiny particles are assumed to flow between two concentric cylinders of different radii. The first cylinder remains at rest while flow is induced due to second cylinder which rotates with uniform velocity. Furthermore, the movement of tiny particles follows the principle of thermophoresis and Brownian motion as a part of thermal and mass gradient. Similarly, the gyro-tactic microorganisms swim in the nanofluid as a response to the density gradient and constitute bio-convection. The problem is modeled by using the certain laws. The numerical outcomes are computed by using RKF -45 method. The graphical simulations are performed for flow parameters with specific range like 1≤Re≤5, 1≤Ha≤5, 0.5≤Nt≤2.5, 1≤Nb≤3, 0.2≤Sc≤1.8, 0.2≤Pe≤1.0 and 0.2≤Ω≤1.0. It is observed that the flow velocity decreases with the increase in the Hartmann number that signifies the magnetic field. This outcome indicates that the flow velocity can be controlled externally through the magnetic field. Also, the increase in the Schmidt numbers increases the nanoparticle concentration and the motile density.

The flow, thermal and mass properties of Soret-Dufour model of magnetized Maxwell nanofluid flow over a shrinkage inclined surface

A mathematical model of 2D-double diffusive layer flow model of boundary in MHD Maxwell fluid created by a sloping slope surface is constructed in this paper. The numerical findings of non-Newtonian fluid are important to the chemical processing industry, mining industry, plastics processing industry, as well as lubrication and biomedical flows. The diversity of regulatory parameters like buoyancy rate, magnetic field, mixed convection, absorption, Brownian motion, thermophoretic diffusion, Deborah number, Lewis number, Prandtl number, Soret number, as well as Dufour number contributes significant impact on the current model. The steps of research methodology are as followed: a) conversion from a separate matrix (PDE) to standard divisive calculations (ODEs), b) Final ODEs are solved in bvp4c program, which developed in MATLAB software, c) The stability analysis part also being developed in bvp4c program, to select the most effective solution in the real liquid state. Lastly, the numerical findings are built on a system of tables and diagrams. As a result, the profiles of velocity, temperature, and concentration are depicted due to the regulatory parameters, as mentioned above. In addition, the characteristics of the local Nusselt, coefficient of skin-friction as well as Sherwood numbers on the Maxwell fluid are described in detail.

Density stratification and double-diffusive convection in mine pools of flooded underground mines - A review

Layering of water bodies with different physico-chemical properties is called stratification. This physical effect is known from lakes or oceans but also occurs in flooded underground mines and has been studied in the past. This review gives a summary of their investigation methods, flow dynamics, stratification development and breakdown. Furthermore, the barrier effect of stratification is discussed, meaning that less mineralized water bodies (CF water bodies) on the top are separated from higher mineralized water bodies (WM water bodies) in the lower parts of the mine. This separation causes less mineralized water to discharge from the flooded mine and mine water treatment can be reduced or omitted. Various options to study mine water stratification will be discussed, thereunder tracer tests, camera-aided depth profile measurements and depth dependant mine water sampling. Studies about free convection and natural stratification as well as those about using artificial stratification to encapsulate the lower quality water in the deeper mine parts will be presented. No forecasting tool for the existence or development of stratification in flooded mines was found in the literature. References and a discussion about the long-term stability of the stratification and its potential implementation will be given. The conclusions show that precise predictions of mine water stratification are currently not possible in all detail, but wherever stratification occurs, it is mostly stable over a longer period of time as the density difference between the CF and WM layers prevents their mixing.

Thermal management of photovoltaic panel with nano-enhanced phase change material at different inclinations

Photovoltaic (PV) panel, coupled with phase change material (PCM), has attracted broad attention for the panel's thermal management. Despite the higher energy storage capability of PCMs, the main disadvantage is their low thermal conductivity which is compensated to an extent with the nano-enhanced PCMs (NEPCMs). In this study, numerical simulations are carried out to compare the heat transfer phenomena and thermal response of PV-NEPCM with simple PV-PCM for various tilt angles. CuO nanoparticles with mass concentrations of 1%, 3% and 5% are selected for NEPCM. The thermal performance of PV-NEPCM at inclinations of 0°, 15°, 30° and 45 [Formula: see text] is compared with a simple PV-PCM system to know the effect of mass concentration of nanoparticles and inclination. The average temperature of PV, liquid fraction and thermal energy stored in PCM, the pattern of isotherms and streamlines and performance of PV are compared for PV-PCM and PV-NEPCM systems. Results show that the loading of nanoparticles increases the heat transfer rate to PCM in all the configurations. It has also been shown that at lower inclinations, the use of NEPCM is more effective due to the presence of conduction heat transfer. At higher tilt angles, heat transfer from the PV module takes place by natural convection. By using NEPCM, the maximum decrease in PV temperature of 1.26 [Formula: see text] and maximum improvement in the liquid fraction of 8.25% are achieved when [Formula: see text] with 5% mass concentration of nanoparticles compared to simple PCM. Enhancement of thermal energy stored in PCM increases upon adding nanoparticles, and the highest improvement is obtained for [Formula: see text] Maximum enhancement of efficiency of PV module is found to be 1.75% for [Formula: see text] inclination on adding nanoparticles of 5% mass concentration.

Seasonal to sub-seasonal variations of the Asian Tropopause Aerosols Layer affected by the deep convection, surface pollutants and precipitation

The Asian Tropopause Aerosols Layer (ATAL) refers to an accumulation of aerosols in the upper troposphere and lower stratosphere during boreal summer over Asia, which has a fundamental impact on the monsoon system and climate change. In this study, we primarily analyze the seasonal to sub-seasonal variations of the ATAL and the factors potentially influencing those variations based on MERRA2 reanalysis. The ability of the reanalysis to reproduce the ATAL is well validated by CALIPSO observations from May to October 2016. The results reveal that the ATAL has a synchronous spatiotemporal pattern with the development and movement of the Asian Summer Monsoon. Significant enhancement of ATAL intensity is found during the prevailing monsoon period of July-August, with two maxima centered over South Asia and the Arabian Peninsula. Owing to the fluctuations of deep convection, the ATAL shows an episodic variation on a timescale of 7-12 days. Attribution analysis indicates that deep convection dominates the variability of the ATAL with a contribution of 62.7%, followed by a contribution of 36.6% from surface pollutants. The impact of precipitation is limited. The ATAL further shows a clear diurnal variation: the peak of ATAL intensity occurs from 17:30 to 23:30 local time (LT), when the deep convection becomes strongest; the minimum ATAL intensity occurs around 8:30 LT owing to the weakened deep convection and photochemical reactions in clouds. The aerosol components of the ATAL show different spatiotemporal patterns and imply that black carbon and organic carbon come mainly from India, whereas sulfate comes mainly from China during the prevailing monsoon period.

On the role of rock matrix to heat transfer in a fracture-rock matrix system

In this study, a fully coupled analytical model is developed for thermal energy transfer in a single fracture-rock matrix system where the coupling implies that the governing equations of thermal transfer in the fracture and rock matrix are supplemented with the continuity conditions of temperature and thermal flux at the interfaces of the fracture-rock matrix. The proposed model accounts for thermal convection, longitudinal thermal conduction and thermal dispersion in the fracture, and transverse thermal conduction in the rock matrix. The fully coupled two-dimensional model is established to investigate the thermal energy transfer processes, assess the spatiotemporal temperature distribution in the fracture and rock matrix system and investigate the role of the rock matrix. The solutions are verified with the existing studies and proven to be accurate and robust. The present study demonstrates that: 1) thermal dispersion in the fracture plays an important role in the temperature distribution in the fracture and rock matrix domains, and longitudinal thermal conduction in the fracture has minor effects on the temperature distribution in the system; 2) transverse thermal conduction in the rock matrix is a critical parameter that determines the spatiotemporal temperature distribution in both the fracture and the rock matrix domains. Ignoring thermal conduction in the rock matrix will lead to a significant overestimation of temperature in the short and long terms; 3) the sensitivity analysis implies that thermal energy transfer in the system is sensitive to the fluid velocity in the fracture, thermal dispersivity in the fracture and thermal conductivity in the rock matrix, and less sensitive to thermal conductivity in the fracture.

Exploring the photo-thermal conversion behavior and extinction coefficient of activated carbon nanofluids for direct absorption solar collector applications

This work aims to explore the optical and thermal conversion characteristics of activated carbon-solar glycol nanofluids with various volume fractions namely 0.2, 0.4, and 0.6%, respectively. Kigelia africana leaves were synthesized into porous activated carbon nanomaterials by using the high-temperature sintering process and the pyrolysis process in a muffle furnace. The experimental investigation was carried out with different nanofluid concentrations by using the solar simulator. Nanofluids were heated with the assistance of a solar simulator test system and the convection/conduction heat loss was decreased by using the glass as an insulating material around the test section. Prepared nanofluid with 0.6 vol% activated carbon augmented the thermal conductivity by 14.36% at 60°C. The maximum temperature difference of 10°C was attained at 0.6% volume concentrations of nanofluid as compared with base fluid (solar glycol). In addition, maximum receiver efficiency of 94.51% was attained at 0.6% volume fractions of activated carbon-based nanofluid compared with solar glycol thru a light radiation time of 600 s. Moreover, activated carbon-based nanofluid exhibited significantly higher absorption efficiency as the majority of the radiation was absorbed by the nanofluid. It is concluded that activated carbon-based nanofluids could be a suitable low-cost highly stable material for developing working fluid for direct absorbance solar collector-based applications.

Drying rate of latex coating affected by the deformability of resin particles in convection drying

Latex paints are widely used, and many researchers pointed out that the film formation process depends on the deformability of dispersed polymer particles. However, the relationship between the film formation process and drying rate has not been totally understood due to the lack of accurate data on drying rate throughout the drying process. In the present study, we measured the drying rate of latex coating by the temperature change method proposed by Imakoma in convective drying. We revealed that the drying process significantly depends on particle deformability, especially in the former stage of the falling drying rate period. At a low drying temperature, the close-packed structure of polymer particles is formed throughout the film at the end of the constant drying rate period. On the other hand, partially deformed soft particles due to wet sintering inhibit the drying rate even under high moisture content at high drying temperatures. In either case, after forming the closest-packed structure, the shrinkage of the gap space between particles due to capillary deformation decreases the drying rate, proportional to the moisture content.

Experimental studies on natural convection open and closed solar drying using external reflector

For low temperature agricultural crop and meat drying, dryers utilizing the renewable energy source (solar energy) appear to be an efficient technique as it is ecofriendly, energy efficient, and available in free of cost. This work presents the experimental investigation on a solar food dryer equipped with external reflectors to enhance the rate of drying efficiency by removing the moisture content available in the anchovy fish. A comparison of conventional open solar drying is carried out to assess the parameters such as drying efficiency, moisture removal rate, and heat energy required for drying the anchovy fish using the modified solar dryer using the natural convection technique. From the experimental results it is observed that the relative humidity greatly influence the rate of drying. The average relative humidity during the experiments using open solar drying is found as 50-65% whereas, the using solar dryer the average relative humidity inside the chamber is found as 20-35%. The relative humidity of the fish using open solar drying is higher as compared to solar dryer drying as the drying products are kept in open atmosphere. The physical examination results on the dried products proved that using a modified solar dryers, the dried product is free from insects, and dust. Also, it is found that the loss of color from the product is a minimum while compared to conventional open solar drying. The results showed that the thermal efficiency of top tray (dryer 1) and bottom tray (dryer 2) is comparatively higher as compared to that of conventional open solar drying and found as 16.73 and 19.34 %, respectively. Results also showed that nearly 20.05% of the energy could be saved using the modified solar dryer as compared to the open solar drying technique.

Convection-Enhanced Delivery in Children: Techniques and Applications

Since its first description in 1994, convection-enhanced delivery (CED) has become a reliable method of administering drugs directly into the brain parenchyma. More predictable and effective than simple diffusion, CED bypasses the challenging boundary of the blood brain barrier, which has frustrated many attempts at delivering large molecules or polymers into the brain parenchyma. Although most of the clinical work with CED has been carried out on adults with incurable neoplasms, principally glioblastoma multiforme, an increasing number of studies have recognized its potential for paediatric applications, which now include treatment of currently incurable brain tumours such as diffuse intrinsic pontine glioma (DIPG), as well as metabolic and neurotransmitter diseases. The roadmap for the development of hardware and use of pharmacological agents in CED has been well-established, and some neurosurgical centres throughout the world have successfully undertaken clinical trials, admittedly mostly early phase, on the basis of in vitro, small animal and large animal pre-clinical foundations. However, the clinical efficacy of CED, although theoretically logical, has yet to be unequivocally demonstrated in a clinical trial; this applies particularly to neuro-oncology.This review aims to provide a broad description of the current knowledge of CED as applied to children. It reviews published studies of paediatric CED in the context of its wider history and developments and underlines the challenges related to the development of hardware, the selection of pharmacological agents, and gene therapy. It also reviews the difficulties related to the development of clinical trials involving CED and looks towards its potential disease-modifying opportunities in the future.

Heat source and sink effects on periodic mixed convection flow along the electrically conducting cone inserted in porous medium

The system of partial differential equations governing the unsteady hydromagnetic boundary-layer flow along an electrically conducting cone embedded in porous medium in the presence of thermal buoyancy, magnetic field, heat source and sink effects are formulated. These equations are solved numerically by using an implicit Finite-Difference Method. The effects of the various parameters that are source/sink parameter, porous medium parameter, Prandtl number, mixed convection parameter and magnetic Prandtl number on the velocity, temperature profiles, transverse magnetic field are predicted. The effects of heat source and sink parameter on the time-mean value as well as on transient skin friction; heat transfer and current density rate are delineated especially in each plot. The extensive results reveal the existence of periodicity and show that periodicity becomes more distinctive for source and sink in the case of the electrically conducting cone. As the source and sink contrast increases, the periodic convective motion is invigorated to the amplitude and phase angle as reflect in the each plot. The dimensionless forms of the set of partial differential equations is transform into primitive form by using primitive variable formulation and then are solved numerically by using Finite Difference Scheme which has given in literature frequently. Physical interpretations of the overall flow and heat transfer along with current density are highlighted with detail in results and discussion section. The main novelty of the obtained numerical results is that first we retain numerical results for steady part and then used in unsteady part to obtain transient skin friction, rate of heat transfer and current density. The intensity of velocity profile is increased for increasing values of porosity parameter Ω, the temperature and mass concentration intensities are reduced due heat source effects.