Publications by authors named "Hadi Ghasemi"

33 Publications

Evaporation in nano/molecular materials.

Adv Colloid Interface Sci 2021 Apr 23;290:102385. Epub 2021 Feb 23.

Department of Mechanical Engineering, University of Houston, 4726 Calhoun Rd, Houston, TX 77204, USA. Electronic address:

Evaporation is a physical phenomenon with fundamental significance to both nature and technology ranging from plant transpiration to DNA engineering. Various analytical and empirical relationships have been proposed to characterize evaporation kinetics at macroscopic scales. However, theoretical models to describe the kinetics of evaporation from nano and sub-nanometer (molecular) confinements are absent. On the other hand, the fast advancements in technology concentrated on development of nano/molecular-scale devices demand appropriate models that can accurately predict physics of phase-change in these systems. A thorough understanding of the physics of evaporation in nano/molecular materials is, thus, of critical importance to develop the required models. This understanding is also crucial to explain the intriguing evaporation-related phenomena that only take place when the characteristic length of the system drops to several nanometers. Here, we comprehensively review the underlying physics of evaporation phenomenon and discuss the effects of nano/molecular confinement on evaporation. The role of liquid-wall interface-related phenomena including the effects of disjoining pressure and flow slippage on evaporation from nano/molecular confinements are discussed. Different driving forces that can induce evaporation in small confinements, such as heat transfer, pressure drop, cavitation and density fluctuations are elaborated. Hydrophobic confinement induced evaporation and its potential application for synthetic ion channels are discussed in detail. Evaporation of water as molecular clusters rather than isolated molecules is discussed. Despite the lack of experimental investigations on evaporation at nanoscale, there exist an extensive body of literature that have applied different simulation techniques to predict the phase change behavior of liquids in nanoconfinements. We infer that exploring the effect of electrostatic interactions and flow slippage to enhance evaporation from nanoconduits is an interesting topic for future endeavors. Further future studies could be devoted to developing nano/molecular channels with evaporation-based gating mechanism and utilization of 2D materials to tune energy barrier for evaporation leading to enhanced evaporation.
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http://dx.doi.org/10.1016/j.cis.2021.102385DOI Listing
April 2021

The potential of hydrogen hydrate as a future hydrogen storage medium.

iScience 2021 Jan 9;24(1):101907. Epub 2020 Dec 9.

Department of Mechanical Engineering, University of Houston, 4726 Calhoun Road, Houston, TX 77204, USA.

Hydrogen is recognized as the "future fuel" and the most promising alternative of fossil fuels due to its remarkable properties including exceptionally high energy content per unit mass (142 ), low mass density, and massive environmental and economical upsides. A wide spectrum of methods in production, especially carbon-free approaches, purification, and storage have been investigated to bring this energy source closer to the technological deployment. Hydrogen hydrates are among the most intriguing material paradigms for storage due to their appealing properties such as low energy consumption for charge and discharge, safety, cost-effectiveness, and favorable environmental features. Here, we comprehensively discuss the progress in understanding of hydrogen clathrate hydrates with an emphasis on charging/discharging rate of (i.e. hydrate formation and dissociation rates) and the storage capacity. A thorough understanding on phase equilibrium of the hydrates and its variation through different materials is provided. The path toward ambient temperature and pressure hydrogen batteries with high storage capacity is elucidated. We suggest that the charging rate of in this storage medium and long cyclic performance are more immediate challenges than storage capacity for technological translation of this storage medium. This review and provided outlook establish a groundwork for further innovation on hydrogen hydrate systems for promising future of hydrogen fuel.
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http://dx.doi.org/10.1016/j.isci.2020.101907DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7770607PMC
January 2021

Transport Phenomena in Nano/Molecular Confinements.

ACS Nano 2020 Nov 30. Epub 2020 Nov 30.

Department of Mechanical Engineering, University of Houston, 4726 Calhoun Road, Houston, Texas 77204, United States.

The transport of fluid and ions in nano/molecular confinements is the governing physics of a myriad of embodiments in nature and technology including human physiology, plants, energy modules, water collection and treatment systems, chemical processes, materials synthesis, and medicine. At nano/molecular scales, the confinement dimension approaches the molecular size and the transport characteristics deviates significantly from that at macro/micro scales. A thorough understanding of physics of transport at these scales and associated fluid properties is undoubtedly critical for future technologies. This compressive review provides an elaborate picture on the promising future applications of nano/molecular transport, highlights experimental and simulation metrologies to probe and comprehend this transport phenomenon, discusses the physics of fluid transport, tunable flow by orders of magnitude, and gating mechanisms at these scales, and lists the advancement in the fabrication methodologies to turn these transport concepts into reality. Properties such as chain-like liquid transport, confined gas transport, surface charge-driven ion transport, physical/chemical ion gates, and ion diodes will provide avenues to devise technologies with enhanced performance inaccessible through macro/micro systems. This review aims to provide a consolidated body of knowledge to accelerate innovation and breakthrough in the above fields.
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http://dx.doi.org/10.1021/acsnano.0c07372DOI Listing
November 2020

Hydrophilic polymer-based anti-biofouling coatings: Preparation, mechanism, and durability.

Adv Colloid Interface Sci 2020 Oct 9;284:102264. Epub 2020 Sep 9.

Department of Mechanical Engineering, University of Houston, 4726 Calhoun Road, Houston, TX 77204-4006, United States. Electronic address:

Anti-biofouling materials that combat microorganism attachment have been intensively studied due to the ever-growing demand on smart and durable coatings. Although various hydrophilic polymer surfaces demonstrated superior anti-biofouling properties, their practical application was hampered by the undesired mechanical vulnerability and complicated fabrication process. In this review, we summarized the mechanically and chemically robust anti-biofouling coatings into six strategies namely (i) 3D-grafted coatings, (ii) hierarchical spheres-based coatings, (iii) inorganic nanomaterials-reinforced coatings, (iv) hydrolysis-based coating, (v) semi-interpenetrating structure-based coatings, and (vi) layer-by-layer (LbL) assembled coatings. The anti-biofouling efficacy and durability of these coatings over a series of challenges were also comprehensively presented. The purpose of this review is to inspire researchers to develop novel anti-biofouling coatings for future practical applications.
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http://dx.doi.org/10.1016/j.cis.2020.102264DOI Listing
October 2020

Overexpression of reactive oxygen species modulator 1 is associated with advanced grades of bladder cancer.

Mol Biol Rep 2020 Sep 8;47(9):6497-6505. Epub 2020 Aug 8.

Department of Pathology, School of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran.

Reactive Oxygen Species Modulator 1 (ROMO1) plays a pivotal role in the regulation of mitochondrial structure integrity, and the production of reactive oxygen species (ROS). Increased ROMO1 expression was reported in various cancer cell lines; however, the possible association between ROMO1 expression and bladder cancer was not well studied. The present study aimed to investigate the rate of ROMO1 expression and the correlation of oxidative stress with the development of bladder cancer. In this study, a total of 35 cancerous and healthy adjacent tissues were examined using quantitative real-time polymerase chain reaction (qRT-PCR) to analyze the gene expression of ROMO1. Also, we evaluated the serum level of ROMO1 and Total Antioxidant Capacity (TAC), as well as Total Oxidant Status (TOS) in patients with bladder cancer along with age- and sex-matched healthy individuals. The ROMO1 gene was significantly higher in cancerous tissues than that of adjacent healthy tissues. Also, the serum levels of ROMO1, TAC, TOS, and Oxidative Stress Index (OSI) were increased in patients with bladder cancer compared with healthy subjects. It can be concluded that the overexpression of the ROMO1 gene is associated with advanced grades of bladder cancer as well as an increase in oxidative stress conditions. Our findings also suggest that the serum level of ROMO1 might be a promising tumor marker for bladder cancer.
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http://dx.doi.org/10.1007/s11033-020-05702-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7414271PMC
September 2020

On interfacial viscosity in nanochannels.

Nanoscale 2020 Jul 2;12(27):14626-14635. Epub 2020 Jul 2.

Department of Mechanical Engineering, University of Houston, 4726 Calhoun Rd, Houston, Texas 77204, USA.

Capillary driven transport of liquids in nanoscopic channels is an omnipresent phenomenon in nature and technology including fluid flow in the human body and plants, drug delivery, nanofluidic devices, and energy/water systems. However, the kinetics of this mass transport mechanism remains in question as the well-known Lucas-Washburn (LW) model predicts significantly faster flow rates compared to the experimental observations. We here showed the role of interfacial viscosity in capillary motion slowdown in nanochannels through a combination of experimental, analytical and molecular dynamics techniques. We showed that the slower liquid flow is due to the formation of a thin liquid layer adjacent to the channel walls with a viscosity substantially greater than the bulk liquid. By incorporating the effect of the interfacial layer, we presented a theoretical model that accurately predicts the capillarity kinetics in nanochannels of different heights. Non-equilibrium molecular dynamics simulation confirmed the obtained interfacial viscosities. The viscosities of isopropanol and ethanol within the interfacial layer were 9.048 mPa s and 4.405 mPa s, respectively (i.e. 279% and 276% greater than their bulk values). We also showed that the interfacial layers are 6.4 nm- and 5.3 nm-thick for isopropanol and ethanol, respectively.
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http://dx.doi.org/10.1039/d0nr02294bDOI Listing
July 2020

Tissue stiffness contributes to YAP activation in bladder cancer patients undergoing transurethral resection.

Ann N Y Acad Sci 2020 08 19;1473(1):48-61. Epub 2020 May 19.

Urology & Nephrology Research Center, Hamadan University of Medical Sciences, Hamadan, Iran.

Changes in the cellular microenvironment play a critical role in the development of bladder cancer (BC). Yes-associated protein (YAP), a central mediator of the Hippo pathway, functions as a nuclear sensor of mechanotransduction that can be induced by stiffness of the extracellular matrix (ECM), including stiffness resulting from surgical manipulations. We aimed to clarify the possible association between surgically-related ECM stiffness and YAP activation in BC patients. We compared 30 bladder cancer tissues with grade II (n = 15 recurrent and n = 15 newly diagnosed) with 30 adjacent healthy tissues. Atomic force microscopy showed that patients with recurrent BC had stiffer ECM than newly diagnosed patients (P < 0.05). Gene expression profiles showed that β1 integrin (ITGB1), focal adhesion kinase (FAK), CDC42, and YAP were upregulated in cancerous tissues (P < 0.05); additionally, β1 integrin activation was confirmed using a specific antibody. Nuclear localization of YAP was higher in recurrent cancerous tissues compared with newly diagnosed and it was positively associated with higher stiffness (P < 0.05). Our results suggest that postsurgery-induced ECM stiffness can influence integrin-FAK-YAP activity and thereby YAP trafficking to the nucleus where it contributes to BC progression and relapse.
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http://dx.doi.org/10.1111/nyas.14358DOI Listing
August 2020

Concentrations of Heavy Metals in Wastewater of One of the Largest Dentistry Schools in Iran.

Int J Occup Environ Med 2020 04;11(2):113-114

Department of Community Oral Health, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran.

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http://dx.doi.org/10.34172/ijoem.2020.1917DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7205512PMC
April 2020

Stress-localized durable anti-biofouling surfaces.

Soft Matter 2019 Jul;15(29):6014-6026

Department of Mechanical Engineering, University of Houston, 4726 Calhoun Rd, Houston, Texas 77204-4006, USA.

Growing demands for bio-friendly antifouling surfaces have stimulated the development of new and ever-improving material paradigms. Despite notable progress in bio-friendly coatings, the biofouling problem remains a critical challenge. In addition to biofouling characteristics, mechanically stressed surfaces such as ship hulls, piping systems, and heat exchangers require long-term durability in marine environments. Here, we introduce a new generation of anti-biofouling coatings with superior characteristics and high mechanical, chemical and environmental durability. In these surfaces, we have implemented the new physics of stress localization to minimize the adhesion of bio-species on the coatings. This polymeric material contains dispersed organogels in a high shear modulus matrix. Interfacial cavitation induced at the interface of bio-species and organogel particles leads to stress localization and detachment of bio-species from these surfaces with minimal shear stress. In a comprehensive study, the performance of these surfaces is assessed for both soft and hard biofouling including Ulva, bacteria, diatoms, barnacles and mussels, and is compared with that of state-of-the-art surfaces. These surfaces show Ulva accumulation of less than 1%, minimal bacterial biofilm growth, diatom attachment of 2%, barnacle adhesion of 0.02 MPa and mussel adhesion of 7.5 N. These surfaces promise a new physics-based route to address the biofouling problem and avoid adverse effects of biofouling on the environment and relevant technologies.
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http://dx.doi.org/10.1039/c9sm00790cDOI Listing
July 2019

Icephobic surfaces: Definition and figures of merit.

Adv Colloid Interface Sci 2019 Jul 27;269:203-218. Epub 2019 Apr 27.

Department of Mechanical Engineering, University of Houston, 4726 Calhoun Rd, Houston, TX 77204-4006, USA. Electronic address:

Icephobic surfaces have a critical footprint on human daily lives ranging from aviation systems and infrastructures to energy systems, but creation of these surfaces for low-temperature applications remains elusive. Non-wetting, liquid-infused and hydrated surfaces have inspired routes for development of icephobic surfaces. However, high freezing temperature, high ice adhesion strength and subsequent ice accretion, low mechanical durability, and high production cost have restricted their practical applications. In this review, we provide a comprehensive definition for icephobicity through thermodynamics, heat transfer and mechanics of ice/water-material interface and elucidate physic-based routes through which nano-scale could help to achieve exceptional icephobic surfaces. Based on conservation laws, mathematical models are developed that accurately predict ice growth rate on various substrates and wind conditions. Through physics of fracture at ice-icephobic material interface, we cast a standard method for ice adhesion measurement that has the potential to eliminate discrepancies between reported ice adhesion from different laboratories. To assure long-time performance of icephobic surfaces, durability metrics need to be defined. We provide standard methods to examine mechanical, chemical, and environmental durability of icephobic surfaces. In the developed comprehensive framework on icephobicity in this review, performance of state-of-the-art icephobic surfaces are compared and main deficiencies in this field are highlighted.
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http://dx.doi.org/10.1016/j.cis.2019.04.005DOI Listing
July 2019

Nanostructured polymer films with metal-like thermal conductivity.

Nat Commun 2019 04 16;10(1):1771. Epub 2019 Apr 16.

Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.

Due to their unique properties, polymers - typically thermal insulators - can open up opportunities for advanced thermal management when they are transformed into thermal conductors. Recent studies have shown polymers can achieve high thermal conductivity, but the transport mechanisms have yet to be elucidated. Here we report polyethylene films with a high thermal conductivity of 62 Wm K, over two orders-of-magnitude greater than that of typical polymers (~0.1 Wm K) and exceeding that of many metals and ceramics. Structural studies and thermal modeling reveal that the film consists of nanofibers with crystalline and amorphous regions, and the amorphous region has a remarkably high thermal conductivity, over ~16 Wm K. This work lays the foundation for rational design and synthesis of thermally conductive polymers for thermal management, particularly when flexible, lightweight, chemically inert, and electrically insulating thermal conductors are required.
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http://dx.doi.org/10.1038/s41467-019-09697-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6467866PMC
April 2019

An in situ method on kinetics of gas hydrates.

Rev Sci Instrum 2019 Mar;90(3):035111

Department of Mechanical Engineering, University of Houston, 4726 Calhoun Rd, Houston, Texas 77204-4006, USA.

Gas hydrate formation is a high-risk and common flow assurance problem in subsea oil production plants. The modern strategies to mitigate hydrate formation have switched from thermodynamic inhibition to risk management. In this new mitigation strategy, hydrate formation is allowed as long as it does not lead to plugging of pipelines. Thus, understanding the growth kinetics of gas hydrates plays a critical role in risk management strategies. Here, we report a new accurate and in situ approach to probe the kinetics of gas hydrate formation. This approach is based on the hot-wire method, which probes the thermal properties of the medium surrounding the hot-wire. As the thermal properties of gas hydrate and its initial constituents are different, variation in these properties is used to probe kinetics of hydrate growth front. Through this in situ method, we determine kinetics of cyclopentane hydrate formation in both mixing and flow conditions. The findings show that at ambient pressure and a temperature of 1-2 °C, the hydrate formation rate under mixing condition varies between 1.9 × 10 and 3.9 × 10 kg m s, while in flow condition, this growth rate drops to 4.5 × 10 kg m s. To our knowledge, this is the first reported growth rate of cyclopentane hydrate. This in situ approach allows us to probe kinetics of hydrate formation where there is no optical access and provides a tool to rationally design risk management strategies for subsea infrastructures.
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http://dx.doi.org/10.1063/1.5082333DOI Listing
March 2019

Ultrahigh Evaporative Heat Fluxes in Nanoconfined Geometries.

Langmuir 2019 01 28;35(1):78-85. Epub 2018 Dec 28.

Department of Mechanical Engineering , University of Houston , 4726 Calhoun Road , Houston , Texas 77204-4006 , United States.

Advancement in high-performance photonics/electronics devices has boosted generated thermal energy, making thermal management a bottleneck for accelerated innovation in these disciplines. Although various methods have been used to tackle the thermal management problem, evaporation with nanometer fluid thickness is one of the most promising approaches for future technological demands. Here, we studied thin-film evaporation in nanochannels under absolute negative pressure in both transient and steady-state conditions. We demonstrated that thin-film evaporation in nanochannels can be a bubble-free process even at temperatures higher than boiling temperature, providing high reliability in thermal management systems. To achieve this bubble-free characteristic, the dimension of nanochannels should be smaller than the critical nucleolus dimension. In transient evaporative conditions, there is a plateau in the velocity of liquid in the nanochannels, which limits the evaporative heat flux. This limit is imposed by liquid viscous dissipation in the moving evaporative meniscus. In contrast, in steady-state condition, unprecedented average interfacial heat flux of 11 ± 2 kW cm is achieved in the nanochannels, which corresponds to liquid velocity of 0.204 m s. This ultrahigh heat flux is demonstrated for a long period of time. The vapor outward transport from the interface is both advective and diffusion controlled. The momentum transport of liquid to the interface is the limiting physics of evaporation at steady state. The developed concept and platform provide a rational route to design thermal management technologies for high-performance electronic systems.
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http://dx.doi.org/10.1021/acs.langmuir.8b03463DOI Listing
January 2019

Evaporation Mass Flux: A Predictive Model and Experiments.

Langmuir 2018 10 19;34(39):11676-11684. Epub 2018 Sep 19.

Department of Mechanical Engineering , University of Houston , 4726 Calhoun Rd , Houston , Texas 77204-4006 , United States.

Evaporation is a fundamental and core phenomenon in a broad range of disciplines including power generation and refrigeration systems, desalination, electronic/photonic cooling, aviation systems, and even biosciences. Despite its importance, the current theories on evaporation suffer from fitting coefficients with reported values varying in a few orders of magnitude. Lack of a sound model impedes simulation and prediction of characteristics of many systems in these disciplines. Here, we studied evaporation at a planar liquid-vapor interface through a custom-designed, controlled, and automated experimental setup. This experimental setup provides the ability to accurately probe thermodynamic properties in vapor, liquid, and close to the liquid-vapor interface. Through analysis of these thermodynamic properties in a wide range of evaporation mass fluxes, we cast a predictive model of evaporation based on nonequilibrium thermodynamics with no fitting parameters. In this model, only the interfacial temperatures of liquid and vapor phases along with the vapor pressure are needed to predict evaporation mass flux. The model was validated by the reported study of an independent research group. The developed model provides a foundation for all liquid-vapor phase change studies including energy, water, and biological systems.
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http://dx.doi.org/10.1021/acs.langmuir.8b02289DOI Listing
October 2018

Polymorphisms of DNA repair genes XRCC1 and LIG4 and idiopathic male infertility.

Syst Biol Reprod Med 2017 Dec 9;63(6):382-390. Epub 2017 Oct 9.

d Urology & Nephrology Research Center , Hamadan University of Medical Sciences , Hamadan , Iran.

Sperm DNA damage is one of the associated factors of idiopathic male infertility and abnormal spermatogenesis. This study was conducted to assess possible association between risk of male infertility with X-ray repair cross complementing group 1 (XRCC1) Arg399Gln (G to A) and DNA ligase 4 (LIG4) Thr9Ile (C to T) gene polymorphisms which are involved in different DNA repair pathways. In this case-control study 191 fertile and 191 infertile men (29-40 years old) were enrolled. The single-nucleotide polymorphism genotypes and alleles of XRCC1 Arg399Gln and LIG4 Thr9Ile were assessed using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique. There was no significant association between XRCC1 Arg399Gln polymorphism and risk of male infertility. The frequency of LIG4 Thr9Ile genotypes and alleles were statistically different between fertile and infertile men (p<0.001). We found that the CT genotype increased infertility risk more than threefold (OR, 3.12; 95% CI, 1.803-5.407). The LIG4 TT genotype carriers had decreased progressive motile sperm (p<0.05) and increased non-progressive motile sperm (p<0.001) compared with the CC genotype. Moreover, sperm concentration in subjects carrying the CT genotype was lower than that observed in CC carriers (p<0.05). The results revealed that the GG/CT and GA/CT combinations of genotypes increase the risk of infertility 3.5 and fourfold, respectively (p=0.021 and 0.004, respectively). This study demonstrated that there was an association between LIG4 Thr9Ile polymorphism and male infertility and suggests CT genotype as a risk factor for male infertility.
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http://dx.doi.org/10.1080/19396368.2017.1374488DOI Listing
December 2017

Antiscaling Magnetic Slippery Surfaces.

ACS Appl Mater Interfaces 2017 Jun 6;9(24):21025-21033. Epub 2017 Jun 6.

Department of Mechanical Engineering, University of Houston , 4726 Calhoun Road, Houston, Texas 77204-4006, United States.

Scale formation is a common problem in a wide range of industries such as oil and gas, water desalination, and food processing. Conventional solutions for this problem including mechanical removal and chemical dissolution are inefficient, costly, and sometimes environmentally hazardous. Surface modification approaches have shown promises to address this challenge. However, these approaches suffer from intrinsic existence of solid-liquid interfaces leading to high rate of scale nucleation and high adhesion strength of the formed scale. Here, we report a new surface called magnetic slippery surface in two forms of Newtonian fluid (MAGSS) and gel structure (Gel-MAGSS). These surfaces provide a liquid-liquid interface to elevate the energy barrier for scale nucleation and minimize the adhesion strength of the formed scale on the surface. Performance of these new surfaces in both static and dynamic (under fluid flow) configurations is examined. These surfaces show superior antiscaling properties with an order of magnitude lower scale accretion compared to the solid surfaces and offer longevity and stability under high shear flow conditions. We envision that these surfaces open a new path to address the scale problem in the relevant technologies.
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http://dx.doi.org/10.1021/acsami.7b05564DOI Listing
June 2017

Decoupled Hierarchical Structures for Suppression of Leidenfrost Phenomenon.

Langmuir 2017 03 2;33(10):2541-2550. Epub 2017 Mar 2.

Department of Mechanical Engineering, University of Houston , 4726 Calhoun Road, Houston, Texas 77204-4006, United States.

Thermal management of high temperature systems through cooling droplets is limited by the existence of the Leidenfrost point (LFP), at which the formation of a continuous vapor film between a hot solid and a cooling droplet diminishes the heat transfer rate. This limit results in a bottleneck for the advancement of the wide spectrum of systems including high-temperature power generation, electronics/photonics, reactors, and spacecraft. Despite a long time effort on development of surfaces for suppression of this phenomenon, this limit has only shifted to higher temperatures, but still exists. Here, we report a new multiscale decoupled hierarchical structure that suppress the Leidenfrost state and provide efficient heat dissipation at high temperatures. The architecture of these structures is composed of a nanomembrane assembled on top of a deep micropillar structure. This architecture allows to independently tune the involved forces and to suppress LFP. Once a cooling droplet contacts these surfaces, by rerouting the path of vapor flow, the cooling droplet remains attached to the hot solid substrates even at high temperatures (up to 570 °C) for heat dissipation with no existence of Leidenfrost phenomenon. These new surfaces offer unprecedented heat dissipation capacity at high temperatures (2 orders of magnitude higher than the other state-of-the-art surfaces). We envision that these surfaces open a new avenue in thermal management of high-temperature systems through spray cooling.
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http://dx.doi.org/10.1021/acs.langmuir.7b00163DOI Listing
March 2017

Magnetic slippery extreme icephobic surfaces.

Nat Commun 2016 11 8;7:13395. Epub 2016 Nov 8.

Department of Mechanical Engineering, University of Houston, 4726 Calhoun Road, Houston, Texas 77204-4006, USA.

Anti-icing surfaces have a critical footprint on daily lives of humans ranging from transportation systems and infrastructure to energy systems, but creation of these surfaces for low temperatures remains elusive. Non-wetting surfaces and liquid-infused surfaces have inspired routes for the development of icephobic surfaces. However, high freezing temperature, high ice adhesion strength, and high cost have restricted their practical applications. Here we report new magnetic slippery surfaces outperforming state-of-the-art icephobic surfaces with a ice formation temperature of -34 °C, 2-3 orders of magnitude higher delay time in ice formation, extremely low ice adhesion strength (≈2 Pa) and stability in shear flows up to Reynolds number of 10. In these surfaces, we exploit the magnetic volumetric force to exclude the role of solid-liquid interface in ice formation. We show that these inexpensive surfaces are universal and can be applied to all types of solids (no required micro/nano structuring) with no compromise to their unprecedented properties.
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http://dx.doi.org/10.1038/ncomms13395DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5105164PMC
November 2016

Offspring sex ratio of Iranian dentists.

Environ Health Prev Med 2016 Nov 21;21(6):446-449. Epub 2016 Jun 21.

Dental Research Institute, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran.

Objective: To assess the impact of occupational factors on the sex ratio of dentists' children.

Methods: A randomly selected 501 Iranian dentists participated in a telephone interview. The participants were contacted by their mobile number to answer questions about demographic variables (gender, age, marriage status), practice-related variables (year of graduation as general or specialist dentist, years of clinical work, working hours, average number of radiographs taken in a day, and spouse's job), and questions about their children (number, gender and date of birth of each child). Kruskal-Wallis and Chi-square tests served for statistical evaluation.

Results: Of all participating dentists, 71 % were men, about two-thirds were 35- to 50-year olds, and 89 % were married. In total, the dentists had 768 children; about 21 % had no child. Of all the children, 54 % were boys (overall sex ratio = 1.17). The offspring sex ratio was 1.13 among male dentists, 1.50 for female dentists, and 1.44 when both parents were dentists. Higher percentages of boys were prevalent among female dentists, younger dentists, and general dental practitioners (p < 0.008).

Conclusion: Demographic and practice-related factors showed some impact on proportions of both sexes of dentists' children in this study. However, the result needs evaluation in further studies.
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http://dx.doi.org/10.1007/s12199-016-0546-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5112190PMC
November 2016

Does Smoking Hamper Oral Self-Care Among Dental Professionals?

J Dent (Tehran) 2015 May;12(5):333-9

Adjunct Professor, Department of Oral Public Health, Institute of Dentistry, University of Helsinki, Helsinki, Finland.

Objectives: Smoking may impact oral self-care (OSC). This study aimed to analyze the role of smoking in OSC among Iranian dental health professionals.

Materials And Methods: The cross-sectional data were collected at two annual dental meetings and seven randomly selected dental schools in Iran. A total of 1,459 respondents composed of 967 general dental practitioners (GDPs), 229 dental educators (DE), and 263 senior dental students (DS) anonymously completed a self-administered questionnaire inquiring about smoking status and OSC.

Results: Thirty percent of the male and 12% of the female dental health professionals reported smoking tobacco. There was no difference between their professional status. Women reported better OSC than did men, but only 26% of the women and 17% of the men followed the three most important recommendations for OSC. Smoking was associated with infrequent tooth brushing and flossing, irregular use of fluoride containing toothpaste, consumption of sugary snacks and weak adherence to the recommended OSC guidelines.

Conclusion: Dental health education should place more emphasis on smoking counseling and cessation among dental health professionals.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4749097PMC
May 2015

Social Determinants of Tooth Loss among a Group of Iranian Female Heads of Household.

J Dent Res Dent Clin Dent Prospects 2015 10;9(2):126-30. Epub 2015 Jun 10.

Assistant Professor of Pediatric Dentistry, Dental Material Research Center, Department of Community Oral Health, School of Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran.

Background and aims. Tooth loss may lead to mastication disability, which in turn has important impact on individual's quality of life. Social and psychological factors have been shown to be associated with tooth loss. This study aimed to investigate the social determinants and prevalence of tooth loss, and presence of functional dentition among female heads of household under support of Welfare Organization in Mashhad, Iran. Materials and methods. In current study 556 participants aged 16-76 years were recruited. Sociodemographic characteristics (age, level of education, family size, and monthly income) were collected using interviewer-led questionnaire. Data about number of teeth and functional dentition were obtained by oral examination. The data were analyzed using Chi-square, Kruskal-Wallis, T-test and binary logistic regression analysis. Results. Four percent of participants were edentulous. Tooth loss was significantly associated with level of education, age and family size (P < 0.001). There was no significant association between level of income and tooth loss (P = 0.88). Only 37.5% of dentate subjects had functional dentition (anterior and premolar teeth). Women older than 40 years were 0.63 times less likely to have functional dentition than those younger than 40 years. Females with at least a high-school diploma were six times more likely to have functional dentition than their illiterate counterparts. Conclusion. Social determinants of functional dentition should be taken into account when planning oral health promoting programs for female heads of household. For reducing oral health inequalities access to dental services should be facilitated.
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http://dx.doi.org/10.15171/joddd.2015.025DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4517306PMC
August 2015

Health education in primary school textbooks in iran in school year 2010-2011.

J Dent (Tehran) 2014 Sep 30;11(5):536-44. Epub 2014 Sep 30.

Assistant Professor, Department of Community Oral Health, Faculty of Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran.

Objectives: Health education in schools is one of the most effective ways of promoting health in a society. Studies have shown the effectiveness of health interventions aimed at improving students' knowledge, attitude, and behaviors about health issues. The aim of this study was to evaluate health issues in primary school textbooks in Iran.

Materials And Methods: In school year 2010-2011, the contents of all primary school textbooks in Iran were assessed in accordance to their health-related teachings. Health lessons of these 27 textbooks in the form of picture and text were retrieved and analyzed using content analysis method.

Results: In total, 502 health-related lessons were found. The textbooks of the third grade contained the highest (144) and those of the fourth grade had the lowest (26) number of health lessons. Among health-related issues, the largest number (87) of lessons were about personal hygiene, while prevention of high risk behaviors comprised the least number (8). Some important health issues such as nutrition, oral health, and prevention of high-risk behaviors were not adequately discussed in the textbooks.

Conclusion: The potential of primary school textbooks in delivering health messages has been neglected in Iran. Taking the critical importance of school ages into account, incorporating health issues in textbooks should be more strongly emphasized.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4290773PMC
September 2014

Charging-free electrochemical system for harvesting low-grade thermal energy.

Proc Natl Acad Sci U S A 2014 Dec 17;111(48):17011-6. Epub 2014 Nov 17.

Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139;

Efficient and low-cost systems are needed to harvest the tremendous amount of energy stored in low-grade heat sources (<100 °C). Thermally regenerative electrochemical cycle (TREC) is an attractive approach which uses the temperature dependence of electrochemical cell voltage to construct a thermodynamic cycle for direct heat-to-electricity conversion. By varying temperature, an electrochemical cell is charged at a lower voltage than discharge, converting thermal energy to electricity. Most TREC systems still require external electricity for charging, which complicates system designs and limits their applications. Here, we demonstrate a charging-free TREC consisting of an inexpensive soluble Fe(CN)6(3-/4-) redox pair and solid Prussian blue particles as active materials for the two electrodes. In this system, the spontaneous directions of the full-cell reaction are opposite at low and high temperatures. Therefore, the two electrochemical processes at both low and high temperatures in a cycle are discharge. Heat-to-electricity conversion efficiency of 2.0% can be reached for the TREC operating between 20 and 60 °C. This charging-free TREC system may have potential application for harvesting low-grade heat from the environment, especially in remote areas.
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http://dx.doi.org/10.1073/pnas.1415097111DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4260536PMC
December 2014

Membrane-free battery for harvesting low-grade thermal energy.

Nano Lett 2014 Nov 16;14(11):6578-83. Epub 2014 Oct 16.

Department of Mechanical Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.

Efficient and low-cost systems are desired to harvest the tremendous amount of energy stored in low-grade heat sources (<100 °C). An attractive approach is the thermally regenerative electrochemical cycle (TREC), which uses the dependence of electrode potential on temperature to construct a thermodynamic cycle for direct heat-to-electricity conversion. By varying the temperature, an electrochemical cell is charged at a lower voltage than discharged; thus, thermal energy is converted to electricity. Recently, a Prussian blue analog-based system with high efficiency has been demonstrated. However, the use of an ion-selective membrane in this system raises concerns about the overall cost, which is crucial for waste heat harvesting. Here, we report on a new membrane-free battery with a nickel hexacyanoferrate (NiHCF) cathode and a silver/silver chloride anode. The system has a temperature coefficient of -0.74 mV K(-1). When the battery is discharged at 15 °C and recharged at 55 °C, thermal-to-electricity conversion efficiencies of 2.6% and 3.5% are achieved with assumed heat recuperation of 50% and 70%, respctively. This work opens new opportunities for using membrane-free electrochemical systems to harvest waste heat.
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http://dx.doi.org/10.1021/nl5032106DOI Listing
November 2014

Solar steam generation by heat localization.

Nat Commun 2014 Jul 21;5:4449. Epub 2014 Jul 21.

Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.

Currently, steam generation using solar energy is based on heating bulk liquid to high temperatures. This approach requires either costly high optical concentrations leading to heat loss by the hot bulk liquid and heated surfaces or vacuum. New solar receiver concepts such as porous volumetric receivers or nanofluids have been proposed to decrease these losses. Here we report development of an approach and corresponding material structure for solar steam generation while maintaining low optical concentration and keeping the bulk liquid at low temperature with no vacuum. We achieve solar thermal efficiency up to 85% at only 10 kW m(-2). This high performance results from four structure characteristics: absorbing in the solar spectrum, thermally insulating, hydrophilic and interconnected pores. The structure concentrates thermal energy and fluid flow where needed for phase change and minimizes dissipated energy. This new structure provides a novel approach to harvesting solar energy for a broad range of phase-change applications.
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http://dx.doi.org/10.1038/ncomms5449DOI Listing
July 2014

An electrochemical system for efficiently harvesting low-grade heat energy.

Nat Commun 2014 May 21;5:3942. Epub 2014 May 21.

1] Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA [2] Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA.

Efficient and low-cost thermal energy-harvesting systems are needed to utilize the tremendous low-grade heat sources. Although thermoelectric devices are attractive, its efficiency is limited by the relatively low figure-of-merit and low-temperature differential. An alternative approach is to explore thermodynamic cycles. Thermogalvanic effect, the dependence of electrode potential on temperature, can construct such cycles. In one cycle, an electrochemical cell is charged at a temperature and then discharged at a different temperature with higher cell voltage, thereby converting heat to electricity. Here we report an electrochemical system using a copper hexacyanoferrate cathode and a Cu/Cu(2+) anode to convert heat into electricity. The electrode materials have low polarization, high charge capacity, moderate temperature coefficients and low specific heat. These features lead to a high heat-to-electricity energy conversion efficiency of 5.7% when cycled between 10 and 60 °C, opening a promising way to utilize low-grade heat.
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http://dx.doi.org/10.1038/ncomms4942DOI Listing
May 2014

Number of tracts or stone size: which influences outcome of percutaneous nephrolithotomy for staghorn renal stones?.

Urol Int 2012 24;89(1):103-6. Epub 2012 May 24.

Hasheminejad Clinical Research Development Center, Tehran, Iran.

Introduction: Percutaneous nephrolithotomy (PCNL) is the recommended first-line treatment for staghorn stones. To achieve complete stone clearance, PCNL may require using multiple tracts.

Objective: To evaluate outcome of PCNL in patients with staghorn calculi and its correlation with the number of tracts and stone features.

Materials And Methods: One hundred consecutive patients with staghorn renal stone who underwent PCNL were included in the study. Perioperative and postoperative features were recorded. Correlation of the variables with number of tracts and stone size was assessed.

Results: Mean age (± SD) was 49.6 ± 14.7 years. Our patients were ASA class I. The mean cumulative stone burden was 365.9 ± 156.5 mm(2). The mean number of tracts was 2.4 (range: 1-7), and stone-free rate was 83%. The stone-free rate (p = 0.026) and hospital stay (p = 0.005) correlated with stone size, but not with number of tracts. Postoperative fever correlated with stone size (p = 0.017) and number of tracts (p = 0.037).

Conclusion: PCNL using multiple tracts seem to be effective and safe in treatment of staghorn calculi. Most outcome measures correlated with stone size rather than number of tracts.
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http://dx.doi.org/10.1159/000338645DOI Listing
December 2012

Outcomes of tubeless percutaneous nephrolithotomy in patients with chronic renal insufficiency.

Iran J Kidney Dis 2012 May;6(3):216-8

Tehran University of Medical Sciences, Tehran, Iran.

We evaluated the outcomes of percutaneous nephrolithotomy in patients with chronic renal insufficiency. A total of 60 patients with a creatinine level greater than 1.5 mg/dL who underwent PCNL were included. Serum creatinine level, as a kidney function index, was assessed before and after the operation. The mean calculus size was 31.13 ± 9.38 mm. The mean pre-operative and 2-week postoperative serum creatinine levels were 2.43 ± 0.75 mg/dL and 2.08 ± 0.78 mg/dL, respectively. There was a significant difference between the pre-operative and postoperative creatinine levels in all postoperative days (days 1, 2, and 14). Fifty of the 60 patients (83.3%) were stone free. Ten patients (16.6%) developed postoperative fever. We can conclude that percutaneous nephrolithotomy seems to be a safe and effective therapeutic option for kidney calculi in patients with chronic kidney disease.
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May 2012

Determinants of Iranian dentists' behaviour regarding infection control.

Int Dent J 2011 Apr;61(2):85-9

Department of Community Oral Health, Dental faculty, Mashhad University of Medical Sciences, Mashhad.

Aim: To evaluate the determinants of Iranian dentists' behaviour regarding infection control (IC).

Design:   A cross-sectional questionnaire survey.

Setting: Iranian general dental practitioners (GDP) participating in a national dental congress.

Methods: The GDPs filled in a self-administered questionnaire containing questions regarding their attitudes towards and their behaviour on several aspects of IC. Background factors included GDP's year of birth, gender, and work-related factors. Statistical evaluation employed the Chi-square test, Cronbach alpha, and regression analysis.

Results:   In total, 479 GDPs returned the questionnaire. Their mean age was 38.6years (SD=9.4) and 53% were men. The vast majority of the GDPs had positive attitudes towards the inquired after IC criteria with no statistical difference based on the GDP's background characteristics. Of all respondents, >70% reported that they inform the laboratory about the infection status of the sent items, disinfect impressions before sending to the laboratory, and wash patients' mouths before working with high-speed or ultrasonic devices. Adherence to all the studied IC criteria was reported by 10% of the respondents; more frequently by younger GDPs and those with fewer experience years (P<0.05).

Conclusion: Greater emphasis on infection control programmes in dentists' education is called for especially in continuing education.
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http://dx.doi.org/10.1111/j.1875-595X.2011.00019.xDOI Listing
April 2011

Perceived barriers to the provision of preventive care among Iranian dentists.

Oral Health Prev Dent 2009 ;7(4):339-46

Department of Oral Public Health, University of Helsinki, Helsinki, Finland.

Purpose: The aim of this study was to examine the perceived barriers to preventive dental practice among Iranian dentists.

Materials And Methods: A questionnaire survey was performed among the dentists who participated in two annual dental meetings (conducted in December 2004 and in July 2005) in Tehran, Iran. The dentists who attended the meeting completed the self-administered questionnaire anonymously. The questionnaire included 12 statements with answer alternatives rated on a 5-point scale to which the dentists were asked to indicate how much each of the 12 items, later classified as three barriers (practice-, dentist- and patient-related), impedes them from practising preventive care. The sum of the scores of the four items in each barrier served as an indicator of each dentist's perception of the strength of each barrier. The background data included dentists' personal and professional characteristics. In total, 1033 dentists completed the questionnaire, of whom 980 (64% men) were eligible. Statistical evaluation was performed using analysis of variance, t test and Pearson's correlation coefficient.

Results: Of the respondents, 29% to 66% rated the items of the practice-related barrier as very strong impediments. Corresponding figures for the dentist- and the patient-related barriers were 20% to 54% and 70% to 77%, respectively. The highest mean of the score sum was for the patient-related barrier (11.9) and the lowest mean was for the dentist-related barrier (7.9). For both practice- and dentist-related barriers, male dentists reported significantly higher scores than the female dentists (P < 0.001).

Conclusions: The perceived barriers to the provision of preventive care should be meticulously explored and tackled to enhance oral health in Iran.
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March 2010