Transfer Elements Research Articles

Heat transfer enhancement by a circumferentially non-uniform array of longitudinal fins assembled inside a circular channel

Circular channels are one of the most common tools used in several types of heat exchangers. When available energy for supplying pumping power is a constraint, improving the design of heat transfer elements, such as longitudinal fins, becomes significant. In this paper, a new array of fins is introduced, in which the longitudinal fins are assembled non-uniformly along the internal circumference of a circular channel. A numerical model is used for calculating the pressure drop, required pumping power, and heat transfer of finned-tube laminar flow. Three cases including smooth channels, uniformly finned channels, and non-uniformly finned channels, sharing the same pumping power, are compared to each other according to their heat transfer capacity. It is proved that the proposed non-uniform configuration of fins improves the thermal performance up to 46% in comparison with smooth channels and traditional uniformly finned channels, depending on the magnitude of the required pumping power. Finally, the effects of geometrical parameters such as the number of fins, relative fin heights, and length to diameter ratios on the thermal performance of the fins' assembly are reported.

Alevi ve Bektaşi Sözlü Kültüründeki Değer Kavramları

The meeting of the Turks with Alawism coincides with the beginning of the introduction of Islam. For this reason, Alawism has started to spread among the Turks living in rural areas or living innomads. Written transfer was not very common in these communities because of their way of life. Accordingly, Alawism culture and teachings have been taught and passed on to the next generationsby means of oral transmission. Although this situation creates the impression that some cultural elements belonging to Alawism have disappeared, it is understood that these transfer elements have been preserved to a great extent due to their strength and public acceptance. Gulbank is the strongestof these cultural transfer elements with different forms such as poetry and saying. Gulbank, which is a kind of prayer in Alawi and Bektashi oral culture, also contains strong moral advice. Gulbank often refers to the value patterns that are considered important in the Turkish culture and Islamic tradition.In this study, value patterns on basic topics such as “belief, people, education and science, the place of women in society, friendship, love, affection, modesty, bravery, truthfulness” which are included in the Alawi and Bektashi gulbanks, are discussed. In addition, the concepts of ‘value’ in other oral cultural elements were also investigated. Accordingly, theoretical works and interviews with opinion leaders were examined. The pattern of the study was created in accordance with qualitative research methods. The findings were constructed using a critical point of view and interpretation technique.The main argument of this study is that the concepts of ‘value’, which take a strong place in the Alawi and Bektashi oral culture, are compatible with universal and Islamic values, and at the same time,these values play a vital function in the formation of Turkish culture. Even this claim alone makes the subject important and worthy of investigation.

Resource and Infrastructure-Appropriate Management of ST-Segment Elevation Myocardial Infarction in Low- and Middle-Income Countries.

The 143 low- and middle-income countries (LMICs) of the world constitute 80% of the world's population or roughly 5.86 billion people with much variation in geography, culture, literacy, financial resources, access to health care, insurance penetration, and healthcare regulation. Unfortunately, their burden of cardiovascular disease in general and acute ST-segment-elevation myocardial infarction (STEMI) in particular is increasing at an unprecedented rate. Compounding the problem, outcomes remain suboptimal because of a lack of awareness and a severe paucity of resources. Guideline-based treatment has dramatically improved the outcomes of STEMI in high-income countries. However, no such focused recommendations exist for LMICs, and the unique challenges in LMICs make directly implementing Western guidelines unfeasible. Thus, structured solutions tailored to their individual, local needs, and resources are a vital need. With this in mind, a multicountry collaboration of investigators interested in LMIC STEMI care have tried to create a consensus document that extracts transferable elements from Western guidelines and couples them with local realities gathered from expert experience. It outlines general operating principles for LMICs focused best practices and is intended to create the broad outlines of implementable, resource-appropriate paradigms for management of STEMI in LMICs. Although this document is focused primarily on governments and organizations involved with improvement in STEMI care in LMICs, it also provides some specific targeted information for the frontline clinicians to allow standardized care pathways and improved outcomes.

“Honor thy father and thy mother” or not: uncertain family aid and the design of social long term care insurance

We study the role and the design of long-term care insurance programs when informal care is uncertain; with and without active actuarially-fair private insurance markets against dependency. Three types of public insurance policies are considered: (1) a topping-up scheme, (2) an opting-out scheme, and (3) an opting-out-cum-transfer scheme which combines elements of the first two. A topping-up scheme can never do better than private insurance; opting out and opting-out-cum-transfer schemes can because they provide some insurance against the default of informal care. Long-term care policies have different implications for crowding out. A topping-up policy entails crowding out at both intensive and extensive margins and an opting-out policy leads to crowding out solely at the extensive margin. The opting-out feature of an opting-out-cum-transfer policy too leads to crowding out at the extensive margin, but its transfer element leads to crowding out at the intensive margin and crowding in at the extensive margin.

Model Capacity Building Pada Pesantren Perbatasan Binaan Dinas Pendidikan Dayah Provinsi Aceh

The era of globalization demands education institution to be adaptive, creative, and innovative, including Islamic boarding schools as the institutions of Islamic education which become the national cultural heritage. One of the innovative programs is capacity building as a series of strategies aimed at increasing efficiency, effectiveness, and responsiveness of performance. This study was directed to explore capacity building implementation at Darul Amin Islamic modern boarding school Southeast Aceh. A qualitative research approach with a case study as the research strategy was implemented. The results of the study showed that capacity building focused on three dimensions, namely (1) human resource development; (2) organizational strengthening, and (3) institutional reform. The principle of Darul Amin capacity building contained the elements of participation, repetition, relevance, transfer, and feedback. In the process of capacity building, there were four stages, namely (1) pre-formal stage (pilot education organization); (2) formal stage (potential education organization); (3) transitional stage (national standard education organization); and (4) autonomous stage (international standard education organization). Towards the existence of the institution, Darul Amin also made various efforts at various levels, namely the system level, organizational level, and individual level.

Colistin Resistance Burden among Clinical Isolates of Gram-negative Rods: A Systematic Review and Meta-analysis

Introduction: In recent decades, the inappropriate use of antibiotics and the existence of transferable resistant elements have caused the emergence of multidrug-resistant (MDR) gram-negative organisms. Antimicrobial resistance is becoming one of the major challenges to public health and has caused morbidity and mortality worldwide. The purpose of this study was the assessment of the prevalence and frequency of colistin resistance among gram-negative bacilli (Enterobacteriaceae, Acinetobacter spp., and Pseudomonas spp.) in Iran and around the world. Methods: For this systematic review and meta-analysis, we searched international and national databases, including PubMed, Google Scholar, SID, and Magiran, from 1998 to 2018 for articles and abstracts describing colistin resistance among gram-negative bacilli. We have included 92 studies that met our inclusion criteria, and the outcomes were combined using a random-effects model to derive the event rate of colistin resistance among gram-negative bacilli. Data were analyzed by the Comprehensive Meta-Analysis Software (V2), and the heterogeneity of the studies was assessed using the I2 index. Results: Out of the 11050 papers identified, 92 studies met the strict inclusion criteria and were finally included. The overall event rate of colistin resistance among gram-negative bacilli (GNB) was about 6.6%, while the event rate of colistin resistance among Acinetobacter spp. (n = 18504) was 2.8% (summary: 95% confidence interval (CI): [0.02, 0.041], P = 0.001, I2 = 70, df (Q) = 36, Q-value = 121.924). The colistin resistance among Pseudomonas spp. (n = 15094) was 3% (95% CI: [0.022, 0.041], P = 0.001, I2 = 68.3, df (Q) = 25, Q-value = 85.648), and the colistin resistance among Enterobacteriaceae spp. (n = 44772) was 0.8% (95% CI: [0.004, 0.014], P = 0.001, I2 = 87.6, df (Q) = 15, Q-value = 71.291). Therefore, the event rate of resistance to colistin among GNB was relatively low (6.6%). Conclusion: The event rate of resistance to colistin among GNB was low. Therefore, this antimicrobial agent can still be administered as a suitable option against GNB that are resistant to other antibiotics such as carbapenems.

On the role of acoustic reflections from duct boundaries in fan flutter

The role that acoustic reflections from duct boundaries play in aeroengine fan flutter is theoretically investigated. To make a systematic parametric study attainable, a three-dimensional semi-analytical approach is employed. Based on the transfer element method combined with a boundary integral equation method, this approach effectively captures the acoustic coupling effect of an annular rotor undergoing incipient oscillation and a finite-length non-rigid duct in subsonic flow. For a given vibration mode, the disturbances generated both inside and outside the duct are determined by a simultaneous solution. The flutter likelihood is subsequently evaluated through the energy method. Results reveal that near the flutter boundary, the aeroelastic impact of duct boundary reflections becomes evident and critical when propagating (cut-on or weakly damped) acoustic modes exist in the flow duct. Under such condition the aerodynamic interaction between both duct openings strongly affects the sound field distribution, thus contributing to the notable installation effect on aeroelastic stability. Moreover, the flutter-driven acoustic field is also susceptible to the sound reflection effect of the partially lined duct wall. It is found that the variation of the blade aerodynamic damping with the liner impedance is markedly different when the duct end reflections come into play. Under appropriate conditions the mutual effect of the lined wall and the duct openings significantly strengthens their acoustic couplings with the ducted fan, where a reasonable estimate of aeroelastic stability can only be provided with an adequate consideration of the realistic acoustic boundary conditions for the entire duct.

Chlorine disinfection promotes the exchange of antibiotic resistance genes across bacterial genera by natural transformation

Chlorine disinfection to drinking water plays an important role in preventing and controlling waterborne disease outbreaks globally. Nevertheless, little is known about why it enriches the antibiotic resistance genes (ARGs) in bacteria after chlorination. Here, ARGs released from killed antibiotic-resistant bacteria (ARB), and culturable chlorine-injured bacteria produced in the chlorination process as the recipient, were investigated to determine their contribution to the horizontal transfer of ARGs during disinfection treatment. We discovered Escherichia coli, Salmonella aberdeen, Pseudomonas aeruginosa and Enterococcus faecalis showed diverse resistance to sodium hypochlorite, and transferable RP4 could be released from killed sensitive donor consistently. Meanwhile, the survival of chlorine-tolerant injured bacteria with enhanced cell membrane permeabilisation and a strong oxidative stress-response demonstrated that a physiologically competent cell could be transferred by RP4 with an improved transformation frequency of up to 550 times compared with the corresponding untreated bacteria. Furthermore, the water quality factors involving chemical oxygen demand (CODMn), ammonium nitrogen and metal ions (Ca2+ and K+) could significantly promote above transformation frequency of released RP4 into injured E. faecalis. Our findings demonstrated that the chlorination process promoted the horizontal transfer of plasmids by natural transformation, which resulted in the exchange of ARGs across bacterial genera and the emergence of new ARB, as well as the transfer of chlorine-injured opportunistic pathogen from non-ARB to ARB. Considering that the transfer elements were quite resistant to degradation through disinfection, this situation poses a potential risk to public health.

Unravelling the menace: detection of antimicrobial resistance in aquaculture.

One of the major problems to be addressed in aquaculture is the prominence of antimicrobial resistance (AMR). The occurrence of bacterial infections in cultured fishes promotes the continuous use of antibiotics in aquaculture, which results in the selection of proliferated antibiotic-resistant bacteria and increases the possibility of transfer to the whole environment through horizontal gene transfer. Hence, the accurate cultivation-dependent and cultivation-independent detection methods are very much crucial for the immediate and proper management of this menace. Antimicrobial resistance determinants carrying mobile genetic transfer elements such as transposons, plasmids, integrons and gene cassettes need to be specifically analysed through molecular detection techniques. The susceptibility of microbes to antibiotics should be tested at regular intervals along with various biochemical assays and conjugation studies so as to determine the extent of spread of AMR. Advanced omic-based and bioinformatic tools can also be incorporated for understanding of genetic diversity. The present review focuses on different detection methods to unearth the complexity of AMR in aquaculture. This monitoring helps the authorities to curb the use of antibiotics, commencement of appropriate management measures and adequate substitute strategies in aquaculture. The long battle of AMR could be overcome by the sincere implementation of One Health approach. SIGNIFICANCE AND IMPACT OF THE STUDY: The use of antibiotics and increased antimicrobial resistance (AMR) are of major concerns in aquaculture industry. This could result in global health risks through direct consumption of cultured fishes and dissemination of AMR to natural environment through horizontal gene transfer. Hence, timely detection of the antimicrobial-resistant pathogens and continuous monitoring programmes are inevitable. Advanced microbiological, molecular biological and omic-based tools can unravel the menace to a great extent. This will help the authorities to curb the use of antibiotics and implement appropriate management measures to overcome the threat.

Role of Nuclear Receptor Condensates in Ligand Induced Co‐operative Gene Regulation

Enhancers are transferable DNA elements that regulate target genes within the confines of Topologically Associated Domains (TADs) through Cohesin‐dependent looping. However, the potential regulatory functions and mechanisms of long‐distance, inter‐TAD enhancer associations remain largely unexplored. We report that 17β‐estradiol (E2) rapidly increases the spatial proximity of a fraction of E2‐responsive enhancers located in widely separated TADs. These enhancers are characterized by the recruitment of mega‐dalton sized multi transcription factor complex and high enhancer RNA (eRNA) induction. Optimal activation of these enhancer targets requires their co‐localization with phase‐separated interchromatin granules (ICGs). Chemical disruption of phase‐separated structures abolishes enhancer complex assembly and, specifically deactivates the most robust signal induced enhancers. Surprisingly, the physical property of the enhancer complex alters with the duration of hormone stimulation. In support of the long distance enhancer cooperativity model, the deletion of the most robust E2 induced enhancers resulted in a quantifiable decrease in the transcriptional activity of homotypic enhancers in the same chromosome. These data reveal previously unappreciated mechanisms for co‐ordinated gene regulation: (i) The biophysical properties of enhancer complex is critical for transcriptional output (ii) Phase separation mediated long‐distance enhancer cooperativity is required for optimal transcriptional activation by acute signaling programs. These findings reveal a new, generalizable model for the acute spatial gene regulation.Support or Funding InformationResearch support for S.J.N include postdoctoral fellowship from American Heart Association (14POST19860025), T32 Fellowship (5T32DK007044), and KO1 career grant (1K01DK121871). D.M. was supported by NIH‐NIDDK Grant 5F32DK112682. MGR is supported by Howard Hughes Medical Institute.Model of E2‐induced changes in the chromatin architecture. E2 stimulation results in ERa dependent recruitment of MegaTrans complex, Condensin complex, and enhancer RNA as phase‐separated ribonucleoprotein condensates. Spatial enhancer association results from “megaloops” formation between the most robust enhancers (E.g. TFF1e1 and NRIP1e3). Maximal cooperative enhancer activation occurs with the co‐localization of the enhancers in the interchromatin granule (ICG).Figure 1

A comparative experimental investigation on thermal performance for two types of vacuum tube solar air collectors based on flat micro-heat pipe arrays (FMHPA)

Two types of solar air collectors (SACs), namely, a conventional-tube collector (C-TC) and a transparent-tube collector (T-TC), are designed on the basis of flat micro-heat pipe arrays (FMHPA) and are compared. FMHPA is used as the core heat transfer element for both collectors. Absorption coatings are located at different places. It is located at, namely, on the inner wall of vacuum tube and on the FMHPA evaporation section in the C-TC and the T-TC. A large volumetric flow rate of air contributes to high efficiency. Results of the comparative experiment show that even if the thermal efficiency of the C-TC (77.6%) is smaller than that of the T-TC (85.0%), the useful energy of the C-TC (641 W) is larger than that of the T-TC (497 W). Moreover, the COP values of the C-TC and T-TC are 11.4 and 8.9, respectively. The unit initial investments are 0.15 and 0.21 $/W. Hence, considering the heating capability and price advantage, the C-TC is a better collector form than the T-TC in the same collector gross area. The collector pressure drop does not exceed 19.1 Pa. These results can serve as a reference for the selection and design of SACs for heating applications and crop drying.

Impact Analysis of Intermediate Heat Carrier on Heat Transfer in Furnace

Intermediate heat carriers have been applied in engineering as enhanced heat transfer elements, but their theoretical analysis still needs to be improved. Therefore, an intermediate heat carrier is added to establish the quaternary model of the furnace gas under nongray radiation characteristics. Based on this model, an analytical expression of heat flux on the surface of the billet is derived. General rule of the impact of intermediate heat carrier on the thermal efficiency in the furnace can be properly derived by analytical calculation from a theoretical point of view. The results show that the longer the length of the intermediate heat carrier located at the top of the furnace, the greater the heat exchange capacity on the surface of the billet. Meanwhile, when the intermediate heat carrier is located in the center of the furnace top, the billet gets higher heat flux; the closer to both sides, the lower the heat flux. In addition, the influence that the surface emissivity of the intermediate heat carrier has on the heat transfer of the billet surface is related to the values of εg and αgw. Comparison with previous literature shows that adding intermediate heat carrier can improve the heat exchange capacity of billet.

Complex thermodynamic analysis of the heat-technological complex of sugar production: analysis method

The object of research is the heat-technological systems of sugar production and the heat-technological complex as a whole. A modern sugar factory is a complex hierarchical system of inextricably interconnected elements, and its basis – a heat-technological complex – combines the elements of technological, heat transfer, and mechanical equipment, in which complex physicochemical processes are simultaneously realized, closely interacting. Given the complexity of the internal relationships of processes, their parameters and characteristics, it is necessary to systematically approach the analysis of real functioning, performance evaluation and the solution of optimization problems of the complex as a whole, as well as its individual subsystems and elements.In this work, it is proposed a method for thermodynamic analysis of the heat-technological complex of sugar production as a single thermodynamic system, which allows to analyze the main factors influencing the energy efficiency of the complex regardless of the course of processes implemented within the system. The methodology is based on a joint analysis of the general synthetic and analytical balances of mass, energy and entropy. This model has a deep physical foundation, because the material balance equation is an integral form of the law of conservation of the quantity of matter, the energy balance equation is an integral form of the first law of thermodynamics, and the entropy balance equation is an integral form of the second law of thermodynamics. The main objective of the methodology is a quick assessment of the excellence of the heat-technological complex and its definition of “energy-saving potential”. Also, the application of the principle of energy compensation of irreversibility and entropy criteria allows to determine the sources and causes of system imperfections, and imperfections are compiled to help develop a system of measures to increase the efficiency of the optimal sequence complex. Therefore, the proposed methodology of thermodynamic analysis, in contrast to the methods based on exergy characteristics, provides a comprehensive analysis, operating only with the fundamental laws and principles of classical thermodynamics. It can also be used both to optimize the energy characteristics of existing ones and to design new sugar industry enterprises

Numerical investigation on the effects of the fracture network pattern on the heat extraction capacity for dual horizontal wells in enhanced geothermal systems

In an enhanced geothermal system (EGS), fractures and fracture networks are the predominant elements for fluid flow and heat transfer through the artificial reservoir. In this work, different conceptual discrete fracture networks were generated by characterizing the fracture number, fracture bifurcation and fracture connectivity of the fracturing area. A thermal–hydraulic (TH) coupled mathematical model was applied to evaluate the EGS thermal recovery process. Heat extraction capacity was appraised in terms of the temperature production, net power generation and thermal recovery rate. The results show that an interconnected fracture network with considerable bifurcation results in high heat production and power generation, however the energy efficiency is not optimized due to water loss. The effect of fracture connectivity is more significant than that of fracture spacing. The more fractures (bifurcations) the higher the overall and local heat recovery rates near the production well. For the case with connected fractures without bifurcation, the less characteristic length in the direction of flow results in a lower heat production and power generation.

Organizational Learning: The Missing Link to Promote Nurses' Professional Self-Efficacy.

Nurses are one of the important sources of organizational learning, and the main elements of knowledge transfer in hospitals. They can play a major role in the process of organizational learning. One of the factors affecting nurses' learning is self-efficacy. The aim of this study was to evaluate the association between organizational learning and professional self-efficacy among nurses. A cross-sectional study was conducted among 150 nurses in Ali Ibn Abitaleb Hospital in Zahedan City, Iran in 2018, selected by simple randomized sampling. Tools used were the Neefe Organizational Learning Questionnaire (Neefe, 2001), and Riggs and Knight's Self-Efficacy Questionnaire (1994). The results showed a significant positive correlation (p <0.05) between self-efficacy scores and the organizational learning dimensions of systems thinking, team learning, and shared vision. Linear regression analysis showed that these three dimensions of organizational learning predicted 16.1% of the professional self-efficacy variations. Organizational learning has a direct relationship with nurses' professional self-efficacy. Promotion of organizational learning characteristics in hospitals will enhance nurses' self-efficacy.

ПІДВИЩЕННЯ ЕФЕКТИВНОСТІ ОЧИЩЕННЯ ОХОЛОДЖУВАЧА ПРОДУВНОГО ПОВІТРЯ ДИЗЕЛЬНОГО ДВИГУНА

In order to increase the mass of the air charge, one has to increase its density. Therefore, the density of the air may be increased by increasing the air pressure and reducing its temperature. The temperature of the purge air is being decreased in the air cooler. With the lapse of time, its performance efficiency drops due to the contaminant pollution of heat transfer elements, which as a consequence, leads to the diesel engine power reduction. The established procedure for cleaning the air cooler does not ensure a complete cleaning of heat exchangers, especially in hard-to-reach places, and manual mechanical cleaning is rather time consuming and requires engine cutoff over a protracted period of time. Thus, improving the efficiency and simplifying the complexity of the air cooler cleaning procedure is considered to be an urgent task to complete. In order to reduce those shortcomings, the modernization of the air cooler cleaning system is being considered. The upgrade being suggested involves an installation of auxiliary atomizing devices on both sides of the cooling element, i.e., in those places where the air cooler is being polluted the most. The purge air temperature increase leads to a decrease in the engine power, increased fuel consumption and accumulation of deposits in the exhaust manifold and flue pass, which consequently may contribute to a spontaneous combustion. Taking into consideration the demand for regular cleaning procedure of the cooling element, the serial system is time consuming. In addition to cleaning by means of atomizers, it also involves systematic disassembly of the cooler and manual cleaning of the elements. The modernization being suggested allows to increase the cleaning efficiency of the blower air cooler of the diesel engine by installing additional atomizers of detergent near the side surfaces of the cooling element. Modernization procedure is not a complicated one and its implementation is possible on existing vessels by the engine crew taking into account the necessity of a long-term stopover of the vessel for maintenance and repair. The solution is universal and may be implemented on ships with the gas-turbocharged engines with purge air cooling system. The application of an upgraded system will also reduce the complexity of the cleaning procedure of the air cooler cooling elements by avoiding manual mechanical cleaning of hard-to-reach cooling surfaces.

Mediation of resonance energy transfer by two polarisable particles.

The molecular quantum electrodynamics theory is employed to calculate the matrix element and Fermi golden rule rate for resonant transfer of electronic excitation energy between a donor and an acceptor in the vicinity of two neutral electric dipole polarizable particles, which play the role of bridging species. The emitter and absorber couple linearly to the electric displacement field via their electric dipole moments, while each mediator interacts quadratically with this field through its dynamic polarizability. This form of interaction Hamiltonian enables fourth-order perturbation theory to be used to compute the probability amplitude together with summation over 24 time-ordered diagrams representing a single virtual photon exchange between each pair of coupled particles. Expressions for the migration rate mediated by two inert molecules are obtained for an arbitrary arrangement of the four species that are in fixed mutual orientation or are freely tumbling. These formulae are valid for all interparticle separation distances outside the orbital overlap region. From the general result, rate equations applicable to an equidistant collinear configuration of the four bodies are evaluated. Near- and far-zone limiting forms of the transfer rate for the relay pathway are also calculated and exhibit inverse sixth and inverse square dependences on relative separation distances between pairs of particles, confirming the short-range (radiationless) and long-range (radiative) energy transfer mechanisms associated with two-body theory. The distance behavior of interference terms between two-, three-, and four-body terms is also examined, and the relative importance of each contribution to the total transfer rate is discussed.

A novel ultra-thin vapor chamber for heat dissipation in ultra-thin portable electronic devices

Ultra-thin vapor chamber (UTVC) is an efficient heat transfer element that meets the heat dissipation requirement of miniaturized electronics. In this study, a novel UTVC (0.5 mm thick) with four spiral woven meshes and one bottom mesh composite wick was designed for cooling portable electronic devices. The UTVCs were manufactured using a cost-effective process suitable for mass production. The heat transfer performance of the UTVCs with different filling ratios were tested and the maximum heat transfer capacity of the UTVCs with filling ratios of 90%, 100%, 110% and 120% were 5.10 W, 7.58 W, 6.58 W and 6.33 W, respectively. Furthermore, the maximum heat transfer capacity of the optimal filling ratio UTVC (100%) in five representative placement states: horizontal state, gravity state, anti-gravity state, side state and inverted state were 7.58 W, 9.06 W, 6.33 W, 7.33 W and 7.58 W, respectively. The maximum effective thermal conductivity of the UTVC was found to be about 20900 W/(m·K) in horizontal state and 25200 W/(m·K) in gravity state, which were about 52 times and 63 times higher than that of pure copper, respectively. The proposed novel UTVC is promising for solving the heat dissipation problem of high performance ultra-thin portable electronic devices.

The visualized investigation on flow and heat transfer characteristics of flat-plate heat pipe with micro rectangular grooves

With the development of information technology, the heating power of data transmission equipment (mobile phones, notebook computers, data center processors, etc) continues to rise, and the high temperature failure has become a major cause of equipment damage. At present, the heat flux of high-power chips has reached 2 ´ 106 W/m2. Therefore, the traditional single-phase heat transfer is unable to meet the heat dissipation requirements of new data equipment, and more efficient heat exchange methods are urgently needed to ensure the normal operation of the equipment. As a highly efficient phase change heat transfer element, the thin plate grooved heat pipe is researched in the order of millimeters or even micrometers. Therefore, flat grooved heat pipes simultaneously satisfy the heat dissipation and packaging requirements of high power data transmission equipment, and thus have been extensively studied. In the present study, the phase change characteristics and heat transfer performance of flat-plate heat pipes with rectangular grooves were experimentally studied. Each micro heat pipe test section consisted of twenty parallel grooves with the same total length of 90 mm. The cross-sectional area of G-400 heat pipe and G-800 heat pipe were 400 μm ´ 400 μm and 800 μm ´ 800 μm, respectively. The evaporation section, adiabatic section and condensation section had the same size of 30 mm, and vapor space height was equal to 3.6 mm. The flat-plate was sealed on its upper face with transparent plate, and the phase change phenomenon in the grooves could be observed. A high speed camera was used to visualize the phase change phenomenon in evaporation and condensation regimes. The experiments were carried out with the same cooling water temperature of 30°C under the conditions comprising the heat power range of 18–90 W and filling ratio of 150%–400%, respectively. In order to systematically investigate the performance of flat heat pipes with different dimensions of micro grooves, the analysis was focused on the heat resistance and phase change phenomenon in evaporation section and condensation section. The results showed that the heat pipe with wide grooves was able to maintain stable heat transfer performance at higher heat power, while heat pipes with narrow grooves would dry out at lower heat power. The optimal liquid filling rate of G-400 heat pipe was 400%, and the optimal liquid filling ratio of G-800 heat pipe was 150%. Furthermore, the heat transfer in the evaporation section of flat heat pipe with narrow grooves was mainly dominated by liquid film evaporation. Comparatively, the heat transfer phenomenon in the evaporation section of a heat pipe with wide grooves was affected by the liquid filling ratio. The liquid film evaporation was the main solution at low liquid filling ratio, and continuous bubble behavior was visualized in high filling ratio. In addition, the phase change behaviors in the condensation section of rectangular-grooved flat heat pipe not only occured at the gas-liquid interface, but also had droplet condensation phenomenon on the top surface of the groove rib. The cycle of condensation consisted of three stages: Droplet growth, droplet coalescence, and droplet department.

From farm to fork: identical clones and Tn6674-like elements in linezolid-resistant Enterococcus faecalis from food-producing animals and retail meat.

Increasing numbers of linezolid-resistant Enterococcus carrying optrA are being reported across different niches worldwide. We aimed to characterize the first optrA-carrying Enterococcus faecalis obtained from food-producing animals and retail meat samples in Tunisia. Seven optrA-carrying E. faecalis obtained from chicken faeces (n=3, August 2017) and retail chicken meat (n=4, August 2017) in Tunisia were analysed. Antimicrobial susceptibility was determined by disc diffusion, broth microdilution and Etest against 13 antibiotics, linezolid and tedizolid, respectively (EUCAST/CLSI). optrA stability (∼600 bacterial generations), transfer (filter mating) and location (S1-PFGE/hybridization) were characterized. WGS (Illumina-HiSeq) was done for four representatives that were analysed through in silico and genomic mapping tools. Four MDR clones carrying different virulence genes were identified in chicken faeces (ST476) and retail meat (the same ST476 clone plus ST21 and ST859) samples. MICs of linezolid and tedizolid were stably maintained at 8 and 1-2 mg/L, respectively. optrA was located in the same transferable chromosomal Tn6674-like element in ST476 and ST21 clones, similar to isolates from pigs in Malaysia and humans in China. ST859 carried a non-conjugative plasmid of ∼40 kb with an impB-fexA-optrA segment, similar to plasmids from pigs and humans in China. The same chromosomal and transferable Tn6674-like element was identified in different E. faecalis clones from humans and animals. The finding of retail meat contaminated with the same linezolid-resistant E. faecalis strain obtained from a food-producing animal highlights the potential role of the food chain in the worrisome dissemination of optrA that can be stably maintained without selective pressure over generations.