bluuebunny/crossref_metadata_2025 huggingface dataset:
Is the thin layer of methyl aminolevulinate used during photodynamic therapy sufficient?
Authors: Wiegell Stine R. , Lerche Catharina M. , Wulf Hans Christian
Published: November 2015

Background

If the recommended 1.0 mm layer of methyl aminolevulinate (MAL) is used during photodynamic therapy (PDT) of large areas with multiple actinic keratoses (AK) huge amounts of cream are needed.

Objectives

To report the amount of MAL used for PDT of AK and basal cell carcinomas (BCC) in daily routine. The association of protoporphyrin IX (PpIX) fluorescence and thickness of MAL was investigated in a randomized paired study in healthy volunteers.

Methods

Amount of cream used per cm2 during conventional and daylight PDT was recorded. In 16 healthy volunteers, 0.1 mm, 0.2 mm, 0.5 mm and 1.0 mm MAL cream were applied for 3 h on tape‐stripped areas on each forearm randomized to light‐permeable or light‐impermeable occlusion. PpIX fluorescence was measured.

Results

Less than 0.4 mm MAL was used during PDT of BCC and 0.2 mm for AK. No difference in PpIX fluorescence was found between the different thicknesses of MAL using light‐impermeable occlusion.

Conclusion

In daily routine <0.4 mm MAL was used during PDT of BCC and 0.1–0.2 mm MAL during PDT of AK. The recommended 1.0 mm MAL did not result in a higher accumulation of PpIX compared to thinner MAL layers after light‐impermeable occlusion for 3 h.
Mast cells: new therapeutic target in helminth immune modulation
Authors: Vukman K. V. , Lalor R. , Aldridge A. , O'Neill S. M.
Published: November 2015

Helminth infection and their secreted antigens have a protective role in many immune‐mediated inflammatory disorders such as inflammatory bowel disease, rheumatoid arthritis and multiple sclerosis. However, studies have focused primarily on identifying immune protective mechanisms of helminth infection and their secreted molecules on dendritic cells and macrophages. Given that mast cells have been shown to be implicated in the pathogenesis and progression of many inflammatory disorders, their role should also be examined and considered as cellular target for helminth‐based therapies. As there is a dearth of studies examining the interaction of helminth‐derived antigens and mast cells, this review will focus on the role of mast cells during helminth infection and examine our current understanding of the involvement of mast cells inTH1/TH17‐mediated immune disorders. In this context, potential mechanisms by which helminths could target theTH1/TH17 promoting properties of mast cells can be identified to unveil novel therapeutic mast cell driven targets in combating these inflammatory disorders.
Development of an intraoral device for social inclusion of a physically disabled patient
Authors: de Mesquita‐Guimarães Késsia Suênia Fidelis , Ferreira Danielly Cunha Araújo , da Silva Raquel Assed Bezerra , Díaz‐Serrano Kranya Victoria , de Queiroz Alexandra Mussolino , Mantovani Carolina Paes Torres , De Rossi Andiara
Published: November 2015

The aim of this study is to describe the use of an intraoral assistive technology for a patient with idiopathic generalized muscular dystonia, presenting temporomandibular disorder and severe anterior tooth mobility and diastema. A multidisciplinary team developed an intraoral device to provide typing and painting functions, and promote relaxation of masticatory muscles without compromising the teeth and supporting tissue structures. The occlusal splint associated with the device promoted muscle relaxation and relief of the signs and symptoms of temporomandibular dysfunction, in this case with generalized muscle dystonia, allowing typing and painting with her mouth without causing tooth mobility or occlusal alteration. This intraoral device has low cost, easy adaptation and was efficient in TMD symptoms. Furthermore, the patient returned to her rehabilitation allowing performance of her duties without compromising dental structures, facilitating the social and the digital inclusion.
Human leucocyte antigen alloimmunisation in repeatedly transfused thalassemic Egyptian children and its relation to febrile non‐haemolytic transfusion reactions
Authors: Mourad Z. , Hassab H. , Younan D. , Abdo A.
Published: November 2015

ABSTRACT

Objectives

To document the incidence of lymphocytotoxic antibodies (LCA) in chronically transfused children with β thalassemia major and the relationship between alloimmunisation and febrile non‐haemolytic transfusion reactions. We also compared the effect of leucoreduced‐packed red blood cells (RBCs) by bed‐side filtration and washed RBCs in preventing FNHTRs and in inducing haemoglobin rise.

Background

Alloimmunisation to human leucocytic antigens is one of the common complications of transfusions, particularly in chronically transfused patients as those with thalassemia major, a common disease in Northern Egypt.

Methods/Materials

LCA were screened for in 45 chronically transfused β thalassemia major children (group I), 20 splenectomised ones (group II) and 20 healthy controls (group III), using qualitative lymphocytotoxic antibody (LCA) enzyme‐linked immunosorbent assay (ELISA) kit.

Results

Nine out of 65 thalassemic children (∼14%) were positive for LCA antibodies. Frequency of transfusions and LCA positivity were significantly higher in group I than group II (p = 0·036 and 0·014). There was no statistically significant difference between LCA positive and negative cases regarding age of starting transfusion, frequency of transfusions or FNHTRs. There was no statistically significant difference between washed and filtered RBCs in reducing FNHTRs (p = 1·000) and in inducing haemoglobin rise in positive LCA cases (p = 0·409).

Conclusion

Human leukocyte antigen (HLA) alloimmunisation was only 14% in the children with β thalassemia major we studied. Surprisingly FNHTRs were not more common in those with HLA antibodies. Splenectomy plays a role in reducing the frequency of transfusion and HLA alloimmunisation. Washed and filtered RBCs are comparable in reducing FNHTRs and in inducing haemoglobin rise.
The status of occupational blood and infectious body fluids exposures in five blood centres in China: a 5‐year review
Authors: Wang Y.‐J. , Meng Z.‐H. , Zheng X.‐F. , Tang X.‐X. , Sang L.‐Y. , Du X.‐M. , Cheng Y.‐Z.
Published: November 2015

Background

Little information about the occupational exposures to blood and body fluid (BBF) among blood service workers (BSWs) in blood stations in China is available currently.

Objectives

To assess current status of occupational exposure to BBF and assess the knowledge about occupational blood‐borne pathogen exposures and universal precaution among BSWs in blood donations in China. To understand the incidence of occupational exposure in five blood centres in China.

Methods

A cross‐sectional study was conducted from January 2008 to December 2013.

Results

There were a total of 99 BBF exposures reported during the study period. The total incidence of BBF exposures was 4·4 per 100 person‐years. Higher rates were observed for persons employed less than five years and persons less than 45 years old. Nurses have the highest percentage (49·5%) of BBF exposures. BBF exposures occurred most commonly during the afternoon (62·7%). Percutaneous injuries were the most common BBF exposures. Most incidents occurred during sharps use (73·4%). The major cause of occupational exposure was that there was no continuous training (48·4%) and improper use of equipment (23·2%). Only 56·6% of BBF exposures had appropriate first aid measures. During this research work, one staff member was reported to have seroconverted to syphilis after BBF exposure.

Conclusions

To reduce BBF exposures, it is urgent to take several effective actions in China, including improved occupational health systems, adequate education, administrative support, increased use of standard precautions, better safety devices/products and work practices.
Seasonal malaria chemoprevention in an area of extended seasonal transmission in Ashanti, Ghana: an individually randomised clinical trial
Authors: Tagbor Harry , Antwi Gifty Dufie , Acheampong Princess Ruhama , Bart Plange Constance , Chandramohan Daniel , Cairns Matthew
Published: November 2015

Objective

To investigate the effectiveness of seasonal malaria chemoprevention (SMC) and community case management with long‐acting artemisinin‐based combination therapies (ACTs) for the control of malaria in areas of extended seasonal malaria transmission.

Method

Individually randomised, placebo‐controlled trial in the Ashanti Region of Ghana. A total of 2400 children aged 3–59 months received either: (i) a short‐acting ACT for case management of malaria (artemether‐lumefantrine, AL) plus placebo SMC, or (ii) a long‐acting ACT (dihydroartemisinin‐piperaquine, DP) for case management plus placebo SMC or (iii) AL for case management plus active SMC with sulphadoxine‐pyrimethamine and amodiaquine. SMC or placebo was delivered on five occasions during the rainy season. Malaria cases were managed by community health workers, who used rapid diagnostic tests to confirm infection prior to treatment.

Results

The incidence of malaria was lower in children given SMC during the rainy season. Compared to those given placebo SMC and AL for case management, the adjusted hazard ratio (aHR) was 0.62 (95% CI: 0.41, 0.93), P = 0.020 by intention to treat and 0.53 (95% CI: 0.29, 0.95), P = 0.033 among children given five SMC courses. There were no major differences between groups given different ACTs for case management (aHR DP vs. AL 1.18 (95% CI 0.83, 1.67), P = 0.356).

Conclusion

SMC may have an important public health impact in areas with a longer transmission season, but further optimisation of SMC schedules is needed to maximise its impact in such settings.
Histone acetyltransferase GCN5 is essential for heat stress‐responsive gene activation and thermotolerance in Arabidopsis
Authors: Hu Zhaorong , Song Na , Zheng Mei , Liu Xinye , Liu Zhenshan , Xing Jiewen , Ma Junhua , Guo Weiwei , Yao Yingyin , Peng Huiru , Xin Mingming , Zhou Dao‐Xiu , Ni Zhongfu , Sun Qixin
Published: November 2015

Exposure to temperatures exceeding the normal optimum levels, or heat stress (HS), constitutes an environmental disruption for plants, resulting in severe growth and development retardation. Here we show that loss of function of the Arabidopsis histone acetyltransferase GCN5 results in serious defects in terms of thermotolerance, and considerably impairs the transcriptional activation of HS‐responsive genes. Notably, expression of several key regulators such as the HS transcription factors HSFA2 and HSFA3, Multiprotein Bridging Factor 1c (MBF1c) and UV‐HYPERSENSITIVE 6 (UVH6) is down‐regulated in the gcn5 mutant under HS compared with the wild‐type. Chromatin immunoprecipitation (ChIP) assays indicated that GCN5 protein is enriched at the promoter regions of HSFA3 and UVH6 genes, but not in HSFA2 and MBF1c, and that GCN5 facilitates H3K9 and H3K14 acetylation, which are associated with HSFA3 and UVH6 activation under HS. Moreover, constitutive expression of UVH6 in the gcn5 mutant partially restores heat tolerance. Taken together, our data indicate that GCN5 plays a key role in the preservation of thermotolerance via versatile regulation in Arabidopsis. In addition, expression of the wheat TaGCN5 gene re‐establishes heat tolerance in Arabidopsis gcn5 mutant plants, suggesting that GCN5‐mediated thermotolerance may be conserved between Arabidopsis and wheat.
Highly efficient heritable plant genome engineering using Cas9 orthologues from Streptococcus thermophilus and Staphylococcus aureus
Authors: Steinert Jeannette , Schiml Simon , Fauser Friedrich , Puchta Holger
Published: November 2015

The application of the clustered regularly interspaced short palindromic repeats (CRISPR)/Cas system of Streptococcus pyogenes (SpCas9) is currently revolutionizing genome engineering in plants. However, synthetic plant biology will require more complex manipulations of genomes and transcriptomes. The simultaneous addressing of different specific genomic sites with independent enzyme activities within the same cell is a key to this issue. Such approaches can be achieved by the adaptation of additional bacterial orthologues of the CRISPR/Cas system for use in plant cells. Here, we show that codon‐optimised Cas9 orthologues from Streptococcus thermophilus (St1Cas9) and Staphylococcus aureus (SaCas9) can both be used to induce error‐prone non‐homologous end‐joining‐mediated targeted mutagenesis in the model plant Arabidopsis thaliana at frequencies at least comparable to those that have previously been reported for the S. pyogenes CRISPR/Cas system. Stable inheritance of the induced targeted mutations of the ADH1 gene was demonstrated for both St1Cas9‐ and SaCas9‐based systems at high frequencies. We were also able to demonstrate that the SaCas9 and SpCas9 proteins enhance homologous recombination via the induction of double‐strand breaks only in the presence of their species‐specific single guide (sg) RNAs. These proteins are not prone to inter‐species interference with heterologous sgRNA expression constructs. Thus, the CRISPR/Cas systems of S. pyogenes and S. aureus should be appropriate for simultaneously addressing different sequence motifs with different enzyme activities in the same plant cell.
Design of Automatic Landing Systems Using the H-inf Control and the Dynamic Inversion
Authors: Lungu Romulus , Lungu Mihai
Published: November 2015

This paper focuses on the automatic control of aircraft in the longitudinal plane, during landing, by using the linearized dynamics of aircraft, taking into consideration the wind shears and the errors of the sensors. A new robust automatic landing system (ALS) is obtained by means of the H-inf control, the dynamic inversion, an optimal observer, and two reference models providing the aircraft desired velocity and altitude. The theoretical results are validated by numerical simulations for a Boeing 747 landing; the simulation results are very good (Federal Aviation Administration (FAA) accuracy requirements for Category III are met) and show the robustness of the system even in the presence of wind shears and sensor errors. Moreover, the designed control law has the ability to reject the sensor measurement noises and wind shears with low intensity.
Wall Effects on the Brownian Movement, Thermophoresis, and Deposition of Nanoparticles in Liquids
Authors: Michaelides Efstathios E.
Published: November 2015

It is well known that the hydrodynamic drag on particles is significantly enhanced close to a plane or curved boundary. This enhancement impedes the movement of the particles in both the parallel and the normal directions with respect to the wall. In the presence of a temperature gradient, the Brownian movement of particles induces the phenomenon of thermophoresis, which results in the steady motion of the particles toward the colder domains of the flow field. This paper examines the effect of the enhanced wall drag on the thermophoretic movement of the nanoparticles in a Newtonian fluid, at short distances (0–10 radii) from a flat, horizontal wall. The effect of the flow shear lift on the thermophoretic motion of the particles close to a horizontal wall is also examined. It is observed that the movement of the particles toward the plane wall is significantly retarded because of the enhanced drag and that it, actually, causes particle accumulation close to the plane wall. It is also observed that the lift, which is induced by the relative Brownian movement, does not have an effect on the average motion of particles toward the wall and does not play an important role on the deposition of particles.
Lattice Boltzmann Simulations on the Charging Procedure of a Solar Storage Tank With Immersed Phase Change Materials
Authors: Su Yan
Published: November 2015

The transient charging procedure of a rectangular solar storage tank with immersed tubes filled by phase change materials (PCM) have been simulated by a Lattice Boltzmann Method (LBM). The energy charge speeds for the storage tank with and without the PCM have been compared. The transient temperature and flow fields including melting of the PCM are also presented. The transient interfaces between fluid and solid are clearly shown. The enhancement of the energy storage capability due to the PCM is calculated based on the simulation results. Also the effects of the arrangement of the PCM are discussed.
Comprehensive Two Fluid Model Simulation of Critical Two-Phase Flow Through Short Tube Orifices
Authors: Javidmand Puya , Hoffmann Klaus A.
Published: November 2015

Small-diameter tubes are utilized widely as expansion devices in refrigeration systems. They are employed in either kinds of short-tube orifices or long capillary tubes. Performance of these tubes is reliant upon critical flashing of the two-phase flow that controls the mass flow rate of the refrigeration system resulting in a steep reduction in pressure and temperature. The critical flow condition is approached whenever the mass flow rate increases to an amount whereby the choked-flow phenomenon occurs at the outlet of the tube. Due to their very small tube diameter, the evaporating two-phase flow, and the choked-flow condition, numerical analysis of flow through short-tube orifices is challenging. Accordingly, all available numerical analyses of such flows are performed as one-dimensional and in the majority of them, auxiliary correlations are applied to simplify the solution procedure. Typical approaches include homogeneous flow models and separated flow models, both of which consider the two-phase region in thermal equilibrium. The most comprehensive method for analyzing such flows is the two-fluid model in which there is no assumption of equilibrium between phases. Because of the complicated nature of this model, it has been used in a very limited number of previous investigations. Furthermore, two-phase flow calculations at the entrance and vena contracta region were eliminated. In the current investigation, additional steps utilized to improve the accuracy of computations include the following: (1) applying the most comprehensive two-fluid model including the effect of various two-phase flow patterns and the metastability of liquid phase, and (2) performing a two-phase analysis of the evaporating flow through the entrance and vena contracta regions which involves simulating the region as a converging diverging tube and performing a quasi-one-dimensional solution of governing equations through this region. Results showed more compatibility with experimental data in comparison with those of previous investigations for predicting the critical flow condition of common refrigerants HFC-134a and HFC-410a through short-tube orifices and long capillary tubes.
Numerical-Based Comparison Among Critical Flow Properties of HFC-134a and its New Alternatives HFO-1234yf and HFO-1234ze Through Short-Tube Orifices
Authors: Javidmand Puya , Koffmann Klaus A.
Published: November 2015

Although HFC-134a is a common refrigerant for residential and mobile refrigeration systems, investigators are dealing with replacing it with new alternatives because of its harmful environmental and global warming effects. Recently HFO-1234yf and HFO-1234ze have been introduced as suitable alternative refrigerants because they have zero ozone depletion potential (ODP) and low global warming potential (GWP) and possess thermophysical properties similar to those of HFC-134a. Because there is no experimental data on the performance of these new refrigerants in capillary tubes and short-tube orifices, a recently developed numerical model for analysis of critical two-phase flow through these tubes is used to predict the critical mass flow rate and pressure distribution of HFO-1234yf and HFO-1234ze under various operating conditions. The applied numerical model is based on a comprehensive two-fluid model including the effects of two-phase flow patterns and liquid-phase metastability. The numerical method has been validated by comparing numerical results of the critical flows of HFC-134a, R-410A, and HCFC-22 with available experimental data. The developed numerical simulation is applied in order to develop comparison and selection charts for short-tube orifices based on the common refrigerant HFC-134a and the alternative new refrigerants HFO-1234yf and HFO-1234ze.
Application of Microchannel Condensers for Small Scale Kalina Waste Heat Recovery Systems
Authors: Fronk Brian M. , Zada Kyle R.
Published: November 2015

Thermally driven ammonia/water Kalina cycles have shown some promise for improving the efficiency of electricity production from low temperature reservoirs (T < 200°C). However, there has been limited application of these systems to exploiting widely available, disperse, waste heat streams for smaller scale power production (∼ 1 kWe). Factors limiting increased deployment of these systems include large, costly heat exchangers, and concerns over safety of the working fluid. The use of mini and microchannel (D < 1 mm) heat exchangers has the potential to decrease system size and cost, while also reducing the working fluid inventory, enabling penetration of Kalina cycles into these new markets.

To demonstrate this potential, a detailed heat exchanger model for a liquid-coupled microchannel ammonia/water condenser is developed. The heat exchanger is sized to provide the required heat transfer area for a 1 kWe Kalina system with a source and sink temperature of 150° and 20°C, respectively. An additional constraint on heat exchanger size is that the fluid pressure loss is maintained below some threshold value. A parametric analysis is conducted to assess the effect of different correlations/models for predicting the underlying heat and mass transfer and pressure drop of the ammonia/water mixture on the calculated heat exchanger area. The results show that accurately minimizing the size of the overall system is dependent upon validated zeotropic heat and mass transfer models at low mass fluxes and in small channels.
Multiphase Approach on Heat Transfer Performance of Micro-Channel Using Hybrid Carbon Nanofluid
Authors: Nimmagadda Rajesh , Venkatasubbaiah K.
Published: November 2015

Laminar forced convection flow of nanofluids in a rectangular micro-channel has been numerically studied. The study is carried out to investigate the flow and heat transfer characteristics of hybrid single walled carbon nanotube (SWCNT) and Copper (Cu) nanofluid in a micro-channel. Hybridization of SWCNT and Cu nanoparticles are varied with different proportions such as 50% - 50%, 70% - 30% and 30% - 70% using sphericity based effective thermal conductivity evaluation. A two-dimensional multiphase mixture model has been developed and the effects of Reynolds number, nanoparticles mixture volume concentration on the flow and heat transfer characteristics of hybrid (SWCNT + Cu) nanofluids are reported. The accuracy of present numerical model has been validated with the experimental and numerical results available in the literature. The results show that the average convective heat transfer coefficient increases with increase in Reynolds number. It is also observed that 1 vol.% hybrid nanofluid (0.7 vol.% SWCNT + 0.3 vol.% Cu) significantly enhances the average convective heat transfer coefficient than that of pure water. Moreover, the multiphase mixture approach showed better enhancement in terms of heat transfer when compared with single phase homogenous model. The study concludes that hybrid nanofluids with suitable volume concentration of carbon (SWCNT) nanoparticles can be used as modern working fluid based on cooling requirement. Further, hybridizing nanoparticles at higher volume concentrations will minimize the working fluid cost and also enhances the heat transfer characteristics in comparison with pure metal based nanofluids.
Effect of Tube Diameter on Flow Phenomena of Gas-Liquid Two-Phase Flow in Microchannels
Authors: Ide Hideo , Kinoshita Eiji , Kuroshima Ryo , Ohtaka Takeshi , Shibata Yuichi , Kawaji Masahiro
Published: November 2015

Gas-liquid two-phase flows in minichannels and microchannels display a unique flow pattern called ring film flow, in which stable waves of relatively large amplitudes appear at seemingly regular intervals and propagate in the flow direction. In the present work, the velocity characteristics of gas slugs, ring films, and their features such as the gas slug length, flow phenomena and frictional pressure drop for nitrogen-distilled water and nitrogen-30 wt% ethanol water solution have been investigated experimentally. Four kinds of circular microchannels with diameters of 100 μm, 150 μm, 250 μm and 518 μm were used. The effects of tube diameter and physical properties, especially the surface tension and liquid viscosity, on the flow patterns, gas slug length and the two-phase frictional pressure drop have been investigated by using a high speed camera at 6,000 frames per second. The flow characteristics of gas slugs, liquid slugs and the waves of ring film are presented in this paper.
Study on the Motion of Magnetic Particles Contained in a Liquid Slug in a Microtube
Authors: Shibata Yuichi , Okamoto Osamu , Ide Hideo , Kawaji Masahiro
Published: November 2015

The field of microfluidics is fast developing with advances in MEMS, biotechnology and μ-TAS technologies. In various devices, controlling the flow rate of liquid or gas accurately at micro or nanoliter volume levels is required. By using a magnet the flow of a liquid slug containing magnetized particles or gas in a microtube can be controlled by the driving power exerted on the magnetized particles. Also magnetic particles and alginate microbeads can be applied to a study of transfer technologies in a bioreactor and DDS (Drug Delivery System). In this field, controlling the motions of magnetic particles and microbeads is required. In the present study, an unsteady flow of a liquid slug containing magnetic particles under the driving force exerted by a permanent magnet ring has been investigated in a microtube. The motion and behavior of the microbeads were observed. In addition, we examined the motion and stopping position, and analyzed the velocity of microbeads experimentally and theoretically.
Evaluating the Efficacy of Hollow Fiber Pre-Concentrator for Water Quality Monitoring
Authors: Dasgupta Saumyadeb , Chavali Ravi , Gunda Naga Siva Kumar , Mitra Sushanta Kumar
Published: November 2015

Simple, efficient and compact concentrating systems are of prime importance to the development of portable biosensor based testing solutions for bacterial contamination in potable water. Bacteria are non-uniformly distributed in drinking water and hence testing with small sample volumes does not provide an accurate estimation. Hence bacteria have to be concentrated from large volumes of water of the order of 100 mL as recommended by United States Environmental Protection Agency (USEPA) to a few hundred microliters to accommodate within portable biosensor platforms like Lab on a Chip (LOC), paper microfluidics and micro-cantilever systems. In the present work, we have developed a simplified, rapid, handheld and field deployable concentrating module which involves filtration of contaminated water through a hollow fiber filter using tangential flow filtration and a subsequent elution step to facilitate the transfer of the concentrated mixture on to a portable biosensor platform. The process involves the collection of water sample in a 5 mL syringe. With the aid of two other syringes, the sample volume is concentrated by passing it through the hollow fiber a couple of times. For improved efficiency, bacteria recovery is performed using 1 mL of a non-ionic surfactant (Tween 20) solution as an elution fluid which is administered by another syringe. The bacteria along with the elution fluid form the required concentrated mixture. This elution strategy was found to be very efficient and the product recovery was close to 85%. With further modification to the current configuration, the system can be developed into a highly efficient pre-concentrating module compatible with any microfluidics based platform.
High Flow Rate Micro Orifice Dispersion of Gas-Liquid Flow
Authors: Tollkoetter Alexander , Kockmann Norbert , Schirmbeck Florian , Wesholowski Jens
Published: November 2015

The flow of microbubbles in millichannels with typical dimensions in the range of few millimeters offers a reduced pressure loss with simultaneous large specific contact surface. By flowing through micro orifices, the transformation of pressure into kinetic energy creates a desired secondary flow pattern, which results in continuous dispersion. Differences in velocity and pressure act on the phase boundary of the bubbles and lead to deformations and break-up.

In this work, bubble dispersion and bubbly flow in different orifices and channel modules with widths up to 7 mm are studied experimentally and by CFD simulations. The effect of the orifice dimensions on bubble sizes are evaluated for hydraulic diameters of 0.25 to 0.5 mm with different aspect ratios. Several channel structures are analyzed to offer less coalescence and larger residence times. The modules are arranged in a holder and are fixed under a view glass for optical characterization via high-speed camera. Volume flow rates of 10 to 250 mL/min are studied with various phase ratios.

Bubble diameters are generated in the range of less than 0.1 to 0.7 mm with narrow size distributions depending on the entire flow rate through the device. The first break-up point is shifted closer to the outlet of the orifices for increasing velocities and smaller hydraulic diameters, but the whole break-up region stays nearly constant for each orifice indicating stronger velocity oscillations acting on the bubble surface. Generally, a linear relation of smaller bubble diameters with larger energy input was identified.

Opening angles of the orifices above 6° resulted in flow detachments and recirculation zones around the effluent jet. Independence of the Reynolds number was determined contrary to existing literature models. Flow detachment and coalescence in curves was avoided by an additional bend within the curve based on systematically varied geometrical dimensions.
Measurement of Equivalent Pore Radius and Contact Angle Within Porous Media
Authors: Ravi Saitej , Horner David , Moghaddam Saeed
Published: November 2015

The equivalent pore radius (i.e. capillary radius) and contact angle determine the capillary pressure generated in a porous medium. The most common method to determine these two parameters is through measurement of the capillary pressure generated by a test liquid and a reference liquid (i.e. a liquid with near-zero contact angle). The rate of rise technique commonly used to determine the capillary pressure results in significant uncertainties. In this study, we utilize our recently developed technique for independent measurement of the capillary pressure and permeability to determine the equivalent capillary radii and contact angle of water within micropillar wick structures. In this method, the experimentally measured dryout threshold of a wick structure at different wicking lengths is fit to Darcy’s law to extract the capillary pressure generated by the test liquid. The equivalent capillary radii of different wick geometries are determined by measuring the capillary pressures generated using n-hexane as the working fluid. It is found that the equivalent capillary radius is dependent on the diameter of pillars as well as the spacing between pillars. The equivalent capillary radii of micropillar wicks determined using the new method are found to be up to 7 times greater than the current geometry-based first order estimates. The contact angle subtended by water at the walls of the micropillars was determined by measuring the capillary pressure generated by water within the arrays and the measured capillary radii for the different geometries. This contact angle was determined to be 52.7°.
Single Phase and Two Phase Flow Characteristics and Heat Transfer in Micro-Fin Tubes
Authors: Li Jun-ye , Guo Si-pu , Zhang Jing , Li Wei , Wei Jin-jia , Simon Terrence
Published: November 2015

An experimental investigation was performed with R22 and R410a for single-phase flow, evaporation and condensation inside five micro-fin tubes of various geometries to obtain pressure drop and heat transfer characteristics. The results suggest single-phase flow heat transfer coefficients are increased by 46% to 64% compared with smooth tubes values. Tube geometries that had higher evaporation heat transfer coefficients or higher condensation heat transfer coefficients were identified. Condensation pressure drop characteristics also varied with tube geometry. Based on experiment data, a new correlation which contains the characteristics of a liquid film in annular flow is established. The new correlation can predict the experimental data within an error band of 15% and, for 77% of the data from the literature, within an error band of 30%. The Choi et al. correlation can predict the present condensation pressure drop data within a 20% error band and the Yu and Koyama correlation can predict the present condensation heat transfer coefficient data within 25%.
Thermal Transport Property of Silicon Membranes With Asymmetric Porous Structure
Authors: Hagino Harutoshi , Miyazaki Koji
Published: November 2015

The size effect on thermal conduction due to phonon boundary scattering in films was studied as controlling heat conduction. Thermal rectifier was proposed as a new heat control concept by a ballistic rectifier relies on asymmetric scattering of phonons in asymmetric linear structure. We focus on the thermal rectification effect in membrane with asymmetric pores. We discussed on the thermal rectification effect from the calculation and thermal conductivity measurement of asymmetric structured membrane. Thermal conduction was calculated by using radiation calculation of ANSYS Fluent based on Boltzmann transport theory which is development of equation of phonon radiative transfer from view point of phonon mean free path and boundary scattering condition. In-plane thermal conductivities of free standing membranes with microsized asymmetric pores were measured by periodic laser heating measurement. From the result of calculation, phonons were transition to ballistic transport in the membranes with asymmetric shaped pores and thermal rectification effect was obtained on the condition of specular scattering because of the asymmetric back-scattering of ballistic phonons from asymmetric structure. The thermal rectification effect was increased with decreasing thickness of membrane shorter and shorter than mean free path of phonon. From the result of measurements, we were able to confirm the reduction of thermal conductivity based on ballistic phonon transport theory, but the strong thermal rectification effect was not confirmed.
Effect of Mechanical Vibration on Heat Transfer Characteristics of Liquid Film in Rectangular Microgrooves
Authors: Guo Chaohong , Yu Dong , Hu Xuegong , Jiang Yuyan , Wang Tao , Tang Dawei
Published: November 2015

The effects of vertical mechanical vibration on the heat characteristics of liquid film in vertical rectangular microgrooves are observed. The vibration frequencies are 6Hz, 10Hz and 30Hz, respectively; the vibration amplitudes are in the range of 1.95∼3.23mm. Three sizes of rectangular microgrooved plate are used in experiments. The microgrooved plate is vertically mounted on a vibration plane; DC heat load is added on the back wall of the microgrooved plate. Vibration of the liquid film in the microgroove is observed by a high-speed digital camera, and temperature on the back of the plate is recorded by a data acquisition. The experimental results show that temperature on the plate back decreases obviously with the increase of the vibration frequency or amplitude, heat transfer of the microgrooved plate is intensively enhanced. The main reason is that the forced convections on the groove surface and in the liquid film, caused by the mechanical vibration, enhance the heat transfer. The investigation provides more information for the application of the micro-configuration heat sink under fierce vibration conditions.
Pressure Loss of Water Flow and Flow Boiling Heat Transfer in Microtubes
Authors: Okamoto Takeya , Ohtake Hiroyasu , Hasegawa Koji
Published: November 2015

The phase change heat transfer is one of the most effective cooling methods. Therefore, investigations for the phase change heat transfer and the two-phase flow have been performed by many researchers in the past. This study provided the frictional drop of single-phase flow and flow boiling heat transfer in microchannels. An internal diameter of the present micro pipes for our research was 161 μm, 86 μm and 54 μm, respectively. Test liquid was commercial pure water. A range of Reynolds number was 20 < Re < 2.7×103: the range of liquid velocity was 0.21 < u < 12 m/s. The correlation between a heat flux and a temperature difference between the wall temperature and the bulk temperature with a 161 μm internal diameter was higher than the conventional correlations for turbulent flow about single phase heat transfer. The correlation between a heat flux and a temperature difference between the wall temperature and the bulk temperature with an 86 μm internal diameter was also higher than the conventional correlations for laminar flow. However, the correlation between a heat flux and a temperature difference between the wall temperature and the bulk temperature with a 54 μm internal diameter was in good agreement with the conventional correlations for laminar flow. CHF was increased with increasing the internal diameter. Moreover, critical heat flux depends on velocity of flow. The CHF in the case of a 161 μm internal diameter in turbulent flow was approximately 20 MW/m2; the CHF in the case of an 86 μm internal diameter in laminar flow was approximately 6.9 MW/m2 and a 54 μm internal diameter in laminar flow was approximately 3.1 MW/m2. As a result, the CHF in case of an 86 μm internal diameter in laminer flow was in good agreement with conventional value calculated by Ivey-Morris equation.
Molecular Dynamics Study on Explosive Boiling of Thin Liquid Argon Film on Nanostructured Surface Under Different Wetting Conditions
Authors: Shavik Sheikh Mohammad , Hasan Mohammad Nasim , Morshed A. K. M. Monjur
Published: November 2015

Molecular dynamics (MD) simulations have been performed to investigate the boiling phenomena of thin liquid film adsorbed on a nanostructured solid surface with particular emphasis on the effect of wetting condition of the solid surface. The molecular system consists of liquid and vapor argon, and solid platinum wall. The nanostructures which reside on top of the solid wall have shape of rectangular block. The solid-liquid interfacial wettability, in other words whether the solid surface is hydrophilic or hydrophobic has been altered for different cases to examine its effect on boiling phenomena. The initial configuration of the simulation domain comprised a three phase system (solid platinum, liquid argon and vapor argon) which was equilibrated at 90 K. After equilibrium period, the wall temperature was suddenly increased from 90 K to 250 K which is far above the critical point of argon and this initiates rapid or explosive boiling. The spatial and temporal variation of temperature and density as well as the variation of system pressure with respect to time were closely monitored for each case. The heat flux normal to the solid surface was also calculated to illustrate the effectiveness of heat transfer for different cases of wetting conditions of solid surface. The results show that the wetting condition of surface has significant effect on explosive boiling of the thin liquid film. The surface with higher wettability (hydrophilic) provides more favorable conditions for boiling than the low-wetting surface (hydrophobic) and therefore, liquid argon responds quickly and shifts from liquid to vapor phase faster in case of hydrophilic surface.
Thermal Convection and Stress Analysis of the Cooling System for a Terahertz Radiation Detector
Authors: Wu Angela , Pacheco-Vega Arturo , Cobian Jeanette
Published: November 2015

Detailed three-dimensional numerical simulations have been carried out to find the velocity and temperature fields, in combination with shear and normal stresses, of the fluid flow inside a rectangular channel with large aspect-ratio. The channel under analysis is aimed to cool a thermochromic liquid crystal material (TLC) that is able to capture laser irradiation in the terahertz range. The TLC is manufactured on an extremely-thin substrate. The overall objective of the cooling system is to maintain a nearly-homogeneous temperature of the TLC-domain that is not exposed to the direct laser irradiation, while minimizing the deformation in the TLC caused by the fluid-solid interaction. The fluid flow, stress-strain and heat transfer simulations are carried out on the basis of three-dimensional Navier-Stokes and energy equations for an incompressible flow, coupled with the stress-strain equation for the TLC-layer, to determine values of velocity, pressure and temperature for the fluid inside the channel and the stresses and deformation of the TLC layer, under different operating conditions. These values are then used to find, from a specific set, the value of the channel gap that enables a nearly-uniform temperature distribution in the fluid and the least amount of deformation in the solid layer, within the expected operating conditions. Results from this analysis indicate that, for all the inlet velocities considered, there is a common value of the channel gap, that represents the optimum for the cooling system.
Two-Phase Flow and Mass Transfer in Helical Capillary Flow Reactors With Alternating Bends
Authors: Kurt Safa Kutup , Nigam Krishna Deo Prasad , Kockmann Norbert
Published: November 2015

Microstructured devices have gained much attention in R&D and industry as they offer large specific surface area with enhanced mass and heat transfer. Helically coiled tubular devices in micro-scale can further increase the performance in terms of transport phenomena, as secondary flow (Dean vortices) enhances the radial mixing along the tube. In the content of this work liquid-liquid mass transfer of different helical capillary flow reactors was investigated and compared with straight capillaries by using water/acetone/butyl acetate test systems for liquid extraction. Helically flow capillary reactors with alternating bends and straight capillaries were fabricated by using FEP tubes (fluorinated ethylene propylene) with inner diameter of 1 mm. Slug flow was introduced within the reactors by utilizing T-shaped mixing elements at the inlet. In order to obtain robust and precise downstream analyses, a continuously working, in-line phase splitter was fabricated and connected to the outlets of the reactors. It instantaneously splits the organic and aqueous phases depending on their wettability characteristics. Total volumetric flow rate was varied in the range of 1–8 mL min−1 and volumetric flow ratios (aq/org) in the range of 0.5–2.0. Effects of contact time, volumetric flow ratio, and the reactor geometry on extraction efficiency were investigated for the experiments at ambient temperature by generating slug flow patterns. Experimental results revealed that the helical capillary flow reactors offer higher extraction efficiency up to 20 % compared to straight capillaries at constant contact times. Hence, these types of reactors can be applied for liquid-liquid mass transfer processes, which require longer residence time due to slow mass transfer rates.
Microchannel Flow Enhancement by Microplasma Actuation
Authors: Shivkumar Gayathri , Tholeti Siva Sashank , Alexeenko Alina A.
Published: November 2015

Microscale plasma actuators operate at lower voltages than their macroscale counterparts and allow easy integration into microsystems. Field-emission driven microplasma actuators can be applied for gas flow enhancement in microchannels for pumping and microcombustion applications. The present work studies the feasibility of microplasma actuation as a pump for gaseous microchannel flow. We use 2D Particle-In-Cell / Monte Carlo Collisions (PIC/MCC) method to calculate the volumetric force generated by field-emission driven micro dielectric barrier discharge (DBD). The simulations show that the induced volumetric force and heat source scale inversely with the dielectric thickness. A volumetric force of 1000 μN/mm3 with Joule heat source of 6 W/mm3 for an input power of 16 mW/m was obtained for a dielectric thickness of 3 μm per DBD. This force couples with the momentum flow in the microchannel in the solution of the Navier-Stokes equations. The flow enhancement increased with the decreasing Reynolds number (Re). In a long microchannel (40 mm) at Re = 73, the actuation lead to 22% increase in mass flow rate. However the vorticity induced by heating reduced this gain by 0.03%. In a short microchannel (1.5 mm) without pressure gradient, the actuator induced flow rate was found to be higher than that of a conventional DBD pump. The inclusion of heat source further enhanced the flow by 0.05% in the short channels.
Geometric Evaporator Enhancements of an Oscillating Heat Pipe
Authors: Hoesing Mitchell P. , Michna Gregory J.
Published: November 2015

The oscillating heat pipe (OHP) is a passive two-phase cooling device that is capable of transferring large amounts of thermal energy. Previous research conducted on OHPs indicates that it is a viable option for developing high-heat flux cooling requirements, particularly in the field of electronics cooling. OHPs consist of evaporator, adiabatic, and condenser sections connected by multiple interconnected meandering channels. A two-phase working fluid, in this study acetone, fills the channels and acts as the heat transfer medium. The focus of this study is to further the development of OHPs to improve performance and operation by conducting a comparison between two different evaporator geometries. The first was a traditional straight channel geometry. The second consisted of circular pins centered in the channels with circular cavities surrounding the pins to allow fluid flow. The results of this study showed that the traditional straight channel configuration preformed best. The lowest fill ratio, 35%, performed best for all cases. The lowest thermal resistance observed was 0.11 K/W for the straight channels, and 0.16 K/W for the enhanced channels. The enhanced channels likely did not improve the performance because of an increase in pressure drop through the evaporator section.
Effects of Fabrication Imperfections on Fully Developed Flow in Rectangular Micro-Channels
Authors: Florindo I. , Puccetti G. , Sphaier L. A. , Morini G. L.
Published: November 2015

Over the past few decades, the microfluidics field has been established itself as an emerging technology, serving as a tool for many areas both in science and in industry. As a result, research involving the analysis of micro-flows has been growing dramatically and is acting in the advancement of new technologies and microfluidic devices. As small diameters are considered, on most occasion laminar flow occurs, which allows simpler numerical solution of the problem to be carried-out. In fact, for fully developed velocity profiles the advective terms become unimportant and the problem becomes linear, which allows analytical solutions to be carried out if regular geometries are considered. While for macro-channel flows, the fabrication of channels with regular geometries such as circular or rectangular is fairly simple, when micro-fabrication is considered the resulting channels geometry in many occasions cannot be treated as regular, even if the nominal profile is so. On such example is seen channels with rectangular nominal geometries. For this type of channels, on many occasions the resulting cross-section geometry is somewhat trapezoidal with slightly rounded corners. While for large scale channels these imperfections can be neglected in micro channels they may be of notable influence on the flow field. In this context, the purpose of the paper is to analyze the influence that the aforementioned fabrication imperfections has on the fully developed flow field in nominally rectangular microchannels. The solution methodology is based on the Generalized Integral Transform Technique applied to irregular geometries.