Increasing Contact Surface Area Research Articles

The role of cavity shapes in improving the performance of a heat sink incorporating nano-enhanced phase change material

Improving the cooling performance of heat sink is critical for providing better thermal management to compact electronic devices. Thus, analyzing various cavity shapes for a heat sink containing Nano-enhanced Phase Change Material is of utmost necessity. The present study focuses on a two-dimensional conjugate heat propagation in a Heat sink with Rectangular (HRC), Trapezoidal (HTC), and Wavy (HWC) cavities. Various cavity shapes are examined to identify the ideal shape for a heat sink containing nano-enhanced Phase Change Material (Ne-PCM). The copper oxide (CuO) nanoparticle enhanced paraffin is considered as Ne-PCM. The analysis encompasses identification of the potent cavity shape, its optimum geometric parameters, the dominant mode of heat transfer and ultimately the desirable thermophysical properties of the Ne-PCM. Among HRC, HTC, and HWC, the heat sink with HRC performs the best by maintaining the lowest base temperature. The HTC, has a better initial performance than the HRC, though HTC has low PCM content. Nevertheless, as time progresses, HTC fails to inhibit the base temperature rise. In contrast, due to increased contact surface area, PCM in HWC experiences a stronger opposing viscous force. Consequently, HWC has conduction-dominated heat transfer and the slowest melting of PCM that elevates the base temperature, accumulating heat near cavity walls. Shortening the relative pitch distance and elongating the relative height of the HRC further lowers the base temperature of the heat sink. Notably, the heat transfer mode analysis reveals that in the cavity with maximum height, heat diffusion dominates convective heat transfer. Heat diffusion increases away from the cavity walls towards the middle of the cavity. Ultimately, it is noted that a denser PCM with high thermal conductivity and low viscosity effectively maintains a low heat sink base temperature. A denser PCM imparts more sensible and latent heat absorption capability and maintains a lower base temperature. On complete melting, the convective heat transfer is much higher in a denser PCM. A PCM with higher thermal conductivity marginally lowers the base temperature with a small increase in PCM melting rate.

C. elegans Presenilin Mediates Inter-Organelle Contacts and Communication that Is Required for Lysosome Activity.

Compromised lysosome function is implicated in the pathology of many neurodegenerative diseases, including Alzheimer's disease (AD). Familial Alzheimer's disease (fAD) is caused primarily by mutations in the presenilin encoding genes, but the underlying mechanism remains obscure. Loss of the conserved C. elegans presenilin orthologue SEL-12 results in increased mitochondrial calcium, which promotes neurodegeneration. Here, we find that sel-12 mutant lysosomes, independent of SEL-12 proteolytic activity, are significantly enlarged and more alkaline due to increased ER-to-mitochondrial calcium signaling and concomitant mitochondrial oxidative stress. These defects and their dependence on mitochondrial calcium are recapitulated in human fAD fibroblasts, demonstrating a conserved role for mitochondrial calcium in presenilin-mediated lysosome dysfunction. sel-12 mutants also have increased contact surface area between the ER, mitochondria, and lysosomes, suggesting sel-12 has an additional role in modulating organelle contact and communication. Overall, we demonstrate that SEL-12 maintains lysosome acidity and lysosome health by controlling ER-to-mitochondrial calcium signaling.

Boosting the electrical output of cement-based triboelectric nanogenerator by surface treatment technique

Triboelectric nanogenerators have the potential to convert mechanical energy to electric energy through electrostatic induction thus they are promising alternative cleaning energy sources for human beings. The objective of this work is to increase the electrical outputs of cement-based triboelectric nanogenerators (C-TENGs) by using a surface polishing treatment technique. The hand-mixed cement pastes with water-to-cement ratios of 0.3, 0.4, and 0.5 by weight were cast in the molds and cured in saturated lime water. A study was conducted to investigate the electrical output, which included voltage and current, under a single vertical contract-separation mode with a constant force and a frequency of 3 Hz. To improve the electrical generating performance, all samples were subjected to a surface treatment by polishing with sandpaper. After electrical investigations, the electrical outputs were remeasured. The results showed that the modified surface samples have significantly higher electrical outputs than that of the pristine sample due to the increased contact surface area. Moreover, the cement paste with a water-to-cement ratio of 0.3 after a polished-surface treatment exhibits the highest power density for an external resistance of 10 MΩ, improving around 70% higher than the pristine sample. The study successfully presents a low-cost and simple technique for improving the performance of cement-based triboelectric nanogenerators.

Characterization of Wheat Straw Fiber Grown Around Jimma Zone, ETHIOPIA

ABSTRACT This specific study investigates the chemical and morphological properties of naturally treated wheat straw fiber growing around in Jimma zone. The chemical composition properties including cellulose 45.43%, hemicellulose 36.50%, and lignin 21.61% were determined. The physical properties of naturally treated wheat straw fibers, such as bulk density, particle density, moisture content, and ash content, are 0.037 g/cm3, 0.194 g/cm3, 10.04%, and 1.44%, respectively. The chemical functional group of naturally treated wheat straw fiber was established by Fourier transform infrared spectroscopy (FTIR), crystallinity index is calculated by X-ray powder diffraction (×RD) analysis, and the thermogravimetric analysis (TGA) result ensures that the naturally treated wheat straw has thermally withstood up to 314.35°C. A fiber’s surface morphology shows the presence of shallow pores, which increase the surface roughness of the fiber; this contributes to increased contact surface area, which ensures better fiber-matrix adherence in composite fabrication. We conclude that naturally treated wheat straw fiber has a significant value in fiber reinforced concrete technology as reinforcement materials in concrete composites formation by incorporating optimum percentage to reduce the limitation of concrete and to enhance the mechanical properties of concrete.

Effect of halloysite nanotubes and organically modified bentonite clay hybrid filler system on the properties of natural rubber

The versatility and potential have framed natural rubber (NR) nanocomposites as the focal point in the polymer research field and industry. Currently, NR nanocomposites filled with hybrid nanostructures is an interesting area than single filler or conventional filler systems. Halloysite nanotube (HNT) and bentonite clay are well-studied potential fillers of polymers. This work is an attempt to study the effect of hybrid filler system of HNT and organically modified bentonite nanoclay (NC) in the properties of NR. NR/HNT-NC systems with varied filler concentrations were prepared in a two-roll mixing mill. Properties such as cure characteristics, morphology, mechanical, thermal, and transport behavior were analyzed in detail. The prepared composites had better wear properties than gum vulcanizates. Improvement in physical properties was observed due to the increased contact surface area between the filler and the matrix. The nanocomposite with 2 wt% hybrid filler shows a 31% decrease in abrasion loss compared to neat NR composite. Apparently, 4 wt% of hybrid filler could improve modulus at 300% strain and tear by approximately 57% and 14%, respectively. The ability to withstand high strain was evident from the improved crack growth resistance as observed in micrographs. Lorenz–Park plots were employed to analyze the rubber–filler interaction. The activation energy of thermal degradation was calculated using Coats–Redfern equation.

Effect of structural design on the pullout strength of suture anchors for rotator cuff repair.

Various types of suture anchor designs are currently available for rotator cuff repair. The purpose of our study was to investigate the pullout strength of such anchors based on their structural design and the predominant geometric design factors affecting the pullout strength using finite element analysis. Finite element models were constructed using five cadaveric humeri and ten suture anchors with different designs. The pullout strength and distribution of bone stress around the anchor at three different directions of the applied force (0°, 45°, and 75°) were analyzed. The following geometric factors of suture anchor design were computed and their correlations with pullout strength assessed: Overall length, minor, and major diameters; number of threads; height of thread; distance between threads; helix angle; contact surface area between the anchor threads and surrounding bone; contact surface area between the cylindrical portion of the anchor; and surrounding bone and total contact surface area between the anchor and surrounding bone. The pullout strength and distribution of bone stress around the anchor varied according to the suture anchor designs and the direction of the applied force, respectively. The pullout strength had a strong positive correlation with the contact surface area between the anchor threads and surrounding bone, overall length, and the number and height of threads. This study demonstrated that suture anchor designs with increased contact surface area between the anchor threads and surrounding bone, overall length, and the number and height of threads can enhance the pullout strength during rotator cuff repair. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:3318-3327, 2018.

A three-dimensional numerical comparison of bearing capacity and settlement of tapered and under-reamed piles

Tapered piles by top cross sections larger than the toe cross sections and under-reamed piles by having one or more bulbs, have the potential for substantial major sides over conventional straight-sided piles. Most of the studies on tapered and under-reamed piles have been conducted on the experimental side, while, theoretical studies, such as finite element method, have been mainly confined to conventional straight-sided piles. On the other hand, although several field, laboratory and experimental studies have been conducted to study the behaviour of tapered and under-reamed piles, few numerical studies have been carried out to simulate the behaviour of the piles. In addition, there is no research to compare and evaluate behaviour of these two piles due to different geotechnical and geometrical properties. Therefore, the aim of this study was to numerically investigate bearing capacity and settlement of tapered and under-reamed piles by changing the soil type, cohesion, angle of internal friction, the length and diameter of piles, tapering degree and the number of bulbs using finite element method. Based on the FEM results, it was found that by increasing the values of geotechnical and geometrical properties, bearing capacity of the tapered pile was more than that of the under-reamed one (i.e. settlement of tapered pile was less than that of the under-reamed one). The reason for this trend could be attributed to increasing contact surface area, friction resistance and more adhesion between soil and the tapered pile. In addition, bulb number of under-reamed piles and tapering degree of tapered piles had significant effects on settlement and bearing capacity of the piles.

Remarkable Mechanical and Thermal Increments of Epoxy Composites by Graphene Nanosheets and Carbon Nanotubes Synergetic Reinforcement

Graphene nanosheets (GNSs) were modified with aqueous ammonia and hydrogen peroxide, to obtain amine (–NH2) functionalized GNSs (AFGNSs) and enhance the bondings between the GNSs and epoxy matrix. We report an easy and efficient approach to improve the mechanical properties and thermal conductivity of epoxy matrix composites by combining one dimensional multi-walled carbon nanotubes and two dimensional AFGNSs. The long and tortuous MWCNTs can bridge adjacent AFGNSs and inhibit their aggregation, resulting in an increased contact surface area between GNS/MWCNT structures and the polymer. A remarkable synergetic effect between the GNSs and MWCNTs on the enhanced mechanical properties and thermal conductivity of the epoxy composites was demonstrated. The addition of 2 wt.% MWCNT-GNS hybrid fillers improved the tensile strength and flexural strength of the pristine epoxy by 20.71% and 55.51%, respectively. Thermal conductivity increased by 93.71% using MWCNT-GNS hybrid fillers compared to non-derivatised epoxy. This study has demonstrated that 2-D GNSs and 1-D MWCNTs have an obvious synergetic reinforcing effect on the mechanical properties and a remarkable thermal conductivity enhancement in epoxy composites which provides an easy and effective way to design and improve the properties of composite materials.

Rheological and solid-state NMR assessments of copovidone/clotrimazole model solid dispersions

This study aims to assess several model solid dispersions by using dynamic oscillatory rheology, solid-state NMR and other solid phase characterization techniques, and correlate their viscoelastic responses with processing methods and microstructures. A model active pharmaceutical ingredient (API), clotrimazole, was compounded with copovidone to form solid dispersions via various techniques with different mixing capabilities. Physicochemical characterizations of the resulting solid dispersions demonstrated that simple physical mixing led to a poorly mixed blend manifested by existence of large API crystalline content and heterogeneous distribution. Cryogenic milling significantly improved mixing of two components as a result of reduced particle size and increased contact surface area, but produced limited amorphous content. In contrast, hot melt extrusion (HME) processing resulted in a homogenous amorphous solid dispersion because of its inherent mixing efficiency. Storage modulus and viscosities versus frequency of different solid dispersions indicated that the incorporation of API into the polymer matrix resulted in a plasticizing effect which reduced the viscosity. The crystalline/aggregated forms of API also exhibited more elastic response than its amorphous/dispersed counterpart. Temperature ramps of the physical mixture with high API concentration captured a critical temperature, at which a bump was observed in damping factor. This bump was attributed to the dissolution of crystalline API into the polymer. In addition, heating–cooling cycles of various solid dispersions suggested that cryomilling and HME processing could form a homogeneous solid dispersion at low API content, whereas high drug concentration led to a relatively unstable dispersion due to supersaturation of API in the polymer.

Development of PLGA–PEG encapsulated miltefosine based drug delivery system against visceral leishmaniasis

Targeted drug delivery systems are ideal technology to increase the maximum mechanism of action with smaller dose, we have developed miltefosine encapsulated PLGA–PEG nanoparticles (PPEM) to target macrophage of infected tissues against Leishmania donovani. The structural characterization of PLGA–PEG by transmission electron microscopy (TEM) has shown a size range of 10 to 15nm. Synthesis and drug encapsulation confirmed by dynamic light scattering (DLS) and Fourier transform infrared spectroscopy (FTIR) and confirmed NP encapsulation. The dose of nano encapsulated miltefosine decreased by fifty percent as compared to that of a conventional miltefosine and Amphoterecin B. The inhibition of amastigotes in the splenic tissue with nano encapsulated miltefosine (23.21±23) was significantly more than the conventional miltefosine (89.22±52.7) and Amphoterecin B (94.12±55.1). This study signifies that there is an increased contact surface area of the nano encapsulated drug and significant reduction in size, improved the efficacy in both in vitro and in vivo study than that of the conventional miltefosine, Amphoterecin B.

Preparation and Properties of Graphene and its Nanocomposites

This study proposed a method to improve the mechanical properties and thermal conductivity of epoxy composites by incorporating multi-walled carbon nanotubes (MWCNTs) and multi-graphene platelets (MGPs) hybrid materials. The MWCNT can bridge adjacent MGPs and inhibit their aggregation effectively, leading to an increased contact surface area between MGP/MWCNT hybrid materials and epoxy matrix. From observing the fractured surface of composite by scanning electron microscope, MWCNT/MGP hybrid materials exhibited better compatibility than individual MWCNT and MGP did.The tensile strength of GD400-MWCNT/MGP/epoxy composites was 35.4% higher than that of epoxy, compared to only a 0.9% increase in tensile strength for MGP/epoxy composites. Thermal conductivity enhanced by 146.9% through incorporating MWCNT/MGP hybrid materials and 23.9% for MGP fillers, compared to non-derivatised epoxy.

One-step synthesis of 3D flower-like Zn2SnO4 hierarchical nanostructures and their gas sensing properties

Zn2SnO4 three-dimensional (3D) flowerlike hierarchical nanostructures have been successfully synthesized via a simple one-step hydrothermal method. Field emission scanning electron microscopic (SEM) and transmission electron microscopic (TEM) results reveal that the Zn2SnO4 flowerlike structures are assembled with nanorods. To demonstrate the potential applications, gas sensor is fabricated based on the as-synthesized hierarchical Zn2SnO4. Gas sensing test results show that the hierarchical Zn2SnO4 sensor exhibits significantly better sensing properties compared with the compact Zn2SnO4 structures. The enhancement of sensing performance is attributed to the unique 3D hierarchical nanostructures, the increased contact surface area between Zn2SnO4 and target gases, and greater number of surface active sites on the surface of as-prepared gas-sensing material. The as-prepared Zn2SnO4 are significant for further exploitation of the potential applications in the future.

Heat transfer enhancement by multiple twisted tape inserts and TiO2/water nanofluid

The aim of this present work is to enhance thermal performance characteristics in a heat exchanger tube by studying: (i) multiple twisted tapes in different arrangements; (ii) TiO2 nanoparticles with different concentrations as the working fluid. The tube inserted the multiple twisted tapes showed superior thermal performance factor when compared with plain tube or the tube inserted a single twisted tape, due to continuous multiple swirling flow and multi-longitudinal vortices flow along the test tube. The higher number of twisted tape inserts led to an enhancement of thermal performance that resulted from increasing contact surface area, residence time, swirl intensity and fluid mixing with multi-longitudinal vortices flow. Moreover, arrangement of twisted tapes in counter current was superior energy saving devices for the practical use, particularly at low Reynolds number. This was especially the case for quadruple counter tapes in the cross directions (CC-QTs) where heat transfer enhancement with relatively low friction loss penalty was deserved. The use of CC-QTs led to the highest thermal performance factor up to 1.45. Using water with TiO2 nanoparticle as a working fluid yielded a higher thermal performance than using pure water. The tube inserted CC-QTs with TiO2/water nanofluid at concentration of 0.21% by volume provided the highest thermal performance factor 1.59, where heat transfer rate and friction factor increased to 3.52 times and 11.7 times of those in the plain tube with water as the working fluid.

Fabrication of iron oxide functionalized with PAMAM dendrimer and glycine for the development of drug delivery carrier against visceral leishmania

Background: Magnetic nanoparticles (MNPs) have been a subject of great interest in recent years due to their potential biomedical applications as carriers for drug delivery, AmongMNPs, superparamagneticmagnetite (Fe3O4) hasbeenparticularly attractive due to its unique magnetic properties and biocompatibility Thus we have developed the MNPs drug delivery carrier against visceral leishmania. Methods &Materials: The functionalization of Fe3O4 nanoparticles has been done with dendrimer and glycine was carried out in situ during co-precipitation of Fe 2+ and Fe 3+ ions in basic medium. The terminal amino acid on the shell of the magnetic nanocarriers allows us to create functionalized exteriors with high densities of organic moieties (both amine and carboxyl) for encapsulation of drug molecules. The drug-loading efficiency of the nanocarriers is investigated using amphoterecin B as a model drug to evaluate their potential as a carrier system. Results: Results andhigh loading affinity of nanocarriers for antileishmanial drug, their sustained release profile and during in vitro study, the mean 0.0801±0.0251 of extracellular promastigote of amphoterecin B is significantly higher than MNPs encapsulated amphoterecin B 0.1129±0.01499. Conclusion: Study signifies that there is an increased contact surface area of the drug and significant reduction in size, improved its efficacy than that of amphotericin B against visceral leishmania and invitro study also showinghigh affinity at lowdose,Further this nanoformulations will be also good candidate as drug carriers for other infectious disease.

Comparative Study between a Curved and a Wedge PEEK Cage for Single-level Anterior Cervical Discectomy and Interbody Fusion.

ObjectiveThis study evaluated the efficiency of a curved polyetheretherketone (PEEK) cage in comparison with a wedge PEEK cage according to radiologic and clinical outcomes in patients with cervical degenerative disease.MethodsA total of 37 patients who suffering from cervical disc disease with radiculopathy or myelopathy were reviewed retrospectively. Seventeen patients were underwent anterior cervical discectomy and interbody fusion with a curved shape PEEK cage (curved cage group), and twenty patients with wedge shape PEEK cage (wedge cage group). Clinical assessment was graded using Odom's criteria, NDI score and VAS score. For radiologic analysis, disc height (DH), segmental angle (SA), subsidence were measured at the preoperative and last follow up.ResultsA comparison of the preoperative and postoperative results revealed improvements after the surgery in the DH and SA in both cage groups. The change of postoperative DH between the preoperative and the last follow-up in wedge cage group and curved cage group was 6.85% and 25.5%, respectively. The change of postoperative SA was 1.75° and 0.95°, respectively. There was no statistically significant difference in the DH and SA between the 2 groups. The subsidence rate in the wedge cage group and curved cage group was 20% and 6%, respectively.ConclusionThe 2 different cage groups showed significant improvements in the disc height, segmental angle and clinical outcomes. However, the shape of PEEK Cage influences the tendency for subsidence. Increasing contact surface area and fitting into two adjacent vertebral body prevent significant subsidence.

Toner/Transfer Member Adhesion Response to Environment-Induced Material Property Changes, and Their Impact on Transfer Fields

Toner adhesion to substrates has been demonstrated to be a strong function of temperature. Previous work has suggested that particle deformation due to surface forces increases with reduced material stiffness at higher temperatures, thus increasing contact surface area and increasing adhesion. Toner Storage and Loss Modulus were measured for a variety of toners both on the individual toner scale and on the macro scale. These measurements showed material property changes in the region below the glass transition temperature that could account for the measured increase in toner adhesion. Toner adhesion measurements were then reconciled with transfer field forces to reveal an interaction between transfer fields, stored energy, and toner adhesion.

Effect of paste humidity on kinetics of carbothermal reduction of extruded barite and coke mixture

The effect of the moisture content of barite-coke paste on the kinetics of carbothermal reduction was investigated to understand the role of extrusion technique on this type of solid-gas reaction. The pastes were formulated using the typical natural barite and coke powders normally used in the industrial scale. 0.65 wt.% carboxyl methyl cellulose and different amounts of distilled water, ranging 24.3–34.4% were added to the mixed powders. The obtained pastes were then shaped by a laboratory extruder. The extrusion process was assessed by determining the total porosity of dry samples. The samples in the form of disc were isothermally heated at different temperatures in the range of 800–950 °C and the conversion of barite into barium sulfide was measured by the iodometry. The reduction data were analyzed by a modified kinetic model and the frequency factor and activation energy were calculated to evaluate the reduction mechanism. It was found that the moisture content of the paste significantly affects the active site density due to increasing contact surface area between coke and barite particles.

Self-cutting blades and their influence on primary stability of tapered dental implants in a simulated low-density bone model: a laboratory study

This study tested the hypothesis that there would be differences in primary stability due to the presence of self cutting blades. We investigated the effect of a self-cutting blade implant design on the primary stability of tapered dental implants in a simulated low-density bone model. Implant fixtures with 2 different designs, one with self-cutting blades and the other without self-cutting blades, were fabricated in the same implant system. Insertion torque, resonance frequency analysis, reverse torque, and pull-out and push-in tests were evaluated in grade no. 10 solid rigid polyurethane foam. All 5 assessments of the group without self-cutting blades were significantly higher than those of the self-cutting group (P < .001). The implants without self-cutting blades create a lateral compression with increased contact surface area and consequently improve the primary stability in a simulated low-density bone model.

Fabrication of silicon nanopillar arrays and application on direct methanol fuel cell

We present a simple method that combines self-assembled nanosphere lithography (SANL) and photo-assisted electrochemical etching (PAECE) to fabricate near-perfect and orderly arranged nanopillar arrays for the direct methanol fuel cells electrode (DMFCs) applications. The nanosphere arrays were fabricated by combining thin photoresist grid structure and ultrasonic vibration coating processes. The fabricated nanopillars are with 1.56μm in height and 250nm in diameter showing aspect ratio as high as 6.2. Furthermore, PAECE with applying various voltages to produce nanostructure arrays, resulting in different specific surface area for the electrode fabrication of fuel cell was investigated as well. Comparing with typical planar electrodes, the maximum power density of 58.4W/cm2 for nanopillar electrodes is 6.3 times of that for typical planar electrodes with maximum power density of 9.3W/cm2. These results indicated that the improved performance of the fuel cell is because of the increased contact surface area between the catalyst and fuel cell by utilizing nanopillar arrays.

Study on photocurrent of bilayers photoanodes using different combination of WO 3 and Fe 2O 3

Bilayer photoanodes were prepared onto glass substrates (FTO) in order to improve generated photocurrents using UV–vis light by water splitting process. A comparative study of photocatalytic was performed over the films surface using Fe 2O 3, WO 3 and mixture of bicomponents (Fe 2O 3:WO 3). Different types of films were prepared using Fe 2O 3, WO 3 and bicomponents (mixture) on FTO substrates. The films were grown by sol gel method with the PEG-300 as the structure-directing agent. The photo-generated of the samples were determined by measuring the currents and voltages under illumination of UV–vis light. The morphology, structure and related composition distribution of the films have been characterized by SEM, XRD and EDX respectively. Photocurrent measurements indicated surface roughness as the effective parameter in this study. The deposited surfaces by bicomponents or mixture are flat without any feature on the surface while the deposited surfaces by WO 3 appears rough surface as small round (egg-shaped particles) and cauliflower-like. The surface deposited by Fe 2O 3 show rough no as well as WO 3 surface. The deposited surfaces by WO 3 reveal the higher value of photocurrent measurement due to surface roughness. Indeed, the roughness can be effective in increasing contact surface area between film and electrolyte and diffuse reflection (light scattering effect). The solution (Fe 2O 3:WO 3) shows the low photocurrent value in compare to WO 3 and Fe 2O 3 hat it may be due to decomposition the compound at 450 ± 1 °C to iron-tungstate Fe 2(WO 4) 3.