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Bernacchi CJ, Portis AR, Nakano H, von Caemmerer S, Long SP. Temperature response of mesophyll conductance. Implications for the determination of Rubisco enzyme kinetics and for limitations to photosynthesis in vivo. PLANT PHYSIOLOGY 2002; 130:1992-8. [PMID: 12481082 PMCID: PMC166710 DOI: 10.1104/pp.008250] [Citation(s) in RCA: 448] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2002] [Revised: 06/16/2002] [Accepted: 08/17/2002] [Indexed: 05/18/2023]
Abstract
CO(2) transfer conductance from the intercellular airspaces of the leaf into the chloroplast, defined as mesophyll conductance (g(m)), is finite. Therefore, it will limit photosynthesis when CO(2) is not saturating, as in C3 leaves in the present atmosphere. Little is known about the processes that determine the magnitude of g(m). The process dominating g(m) is uncertain, though carbonic anhydrase, aquaporins, and the diffusivity of CO(2) in water have all been suggested. The response of g(m) to temperature (10 degrees C-40 degrees C) in mature leaves of tobacco (Nicotiana tabacum L. cv W38) was determined using measurements of leaf carbon dioxide and water vapor exchange, coupled with modulated chlorophyll fluorescence. These measurements revealed a temperature coefficient (Q(10)) of approximately 2.2 for g(m), suggesting control by a protein-facilitated process because the Q(10) for diffusion of CO(2) in water is about 1.25. Further, g(m) values are maximal at 35 degrees C to 37.5 degrees C, again suggesting a protein-facilitated process, but with a lower energy of deactivation than Rubisco. Using the temperature response of g(m) to calculate CO(2) at Rubisco, the kinetic parameters of Rubisco were calculated in vivo from 10 degrees C to 40 degrees C. Using these parameters, we determined the limitation imposed on photosynthesis by g(m). Despite an exponential rise with temperature, g(m) does not keep pace with increased capacity for CO(2) uptake at the site of Rubisco. The fraction of the total limitations to CO(2) uptake within the leaf attributable to g(m) rose from 0.10 at 10 degrees C to 0.22 at 40 degrees C. This shows that transfer of CO(2) from the intercellular air space to Rubisco is a very substantial limitation on photosynthesis, especially at high temperature.
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Pei Y, Wang H, Snyder GJ. Band engineering of thermoelectric materials. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2012; 24:6125-35. [PMID: 23074043 DOI: 10.1002/adma.201202919] [Citation(s) in RCA: 402] [Impact Index Per Article: 30.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2012] [Revised: 08/16/2012] [Indexed: 05/02/2023]
Abstract
Lead chalcogenides have long been used for space-based and thermoelectric remote power generation applications, but recent discoveries have revealed a much greater potential for these materials. This renaissance of interest combined with the need for increased energy efficiency has led to active consideration of thermoelectrics for practical waste heat recovery systems-such as the conversion of car exhaust heat into electricity. The simple high symmetry NaCl-type cubic structure, leads to several properties desirable for thermoelectricity, such as high valley degeneracy for high electrical conductivity and phonon anharmonicity for low thermal conductivity. The rich capabilities for both band structure and microstructure engineering enable a variety of approaches for achieving high thermoelectric performance in lead chalcogenides. This Review focuses on manipulation of the electronic and atomic structural features which makes up the thermoelectric quality factor. While these strategies are well demonstrated in lead chalcogenides, the principles used are equally applicable to most good thermoelectric materials that could enable improvement of thermoelectric devices from niche applications into the mainstream of energy technologies.
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Shahil KMF, Balandin AA. Graphene-multilayer graphene nanocomposites as highly efficient thermal interface materials. NANO LETTERS 2012; 12:861-7. [PMID: 22214526 DOI: 10.1021/nl203906r] [Citation(s) in RCA: 380] [Impact Index Per Article: 29.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
We found that the optimized mixture of graphene and multilayer graphene, produced by the high-yield inexpensive liquid-phase-exfoliation technique, can lead to an extremely strong enhancement of the cross-plane thermal conductivity K of the composite. The "laser flash" measurements revealed a record-high enhancement of K by 2300% in the graphene-based polymer at the filler loading fraction f = 10 vol %. It was determined that the relatively high concentration of the single-layer and bilayer graphene flakes (~10-15%) present simultaneously with the thicker multilayers of large lateral size (~1 μm) were essential for the observed unusual K enhancement. The thermal conductivity of the commercial thermal grease was increased from an initial value of ~5.8 W/mK to K = 14 W/mK at the small loading f = 2%, which preserved all mechanical properties of the hybrid. Our modeling results suggest that graphene-multilayer graphene nanocomposite used as the thermal interface material outperforms those with carbon nanotubes or metal nanoparticles owing to graphene's aspect ratio and lower Kapitza resistance at the graphene-matrix interface.
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Cai W, Moore AL, Zhu Y, Li X, Chen S, Shi L, Ruoff RS. Thermal transport in suspended and supported monolayer graphene grown by chemical vapor deposition. NANO LETTERS 2010; 10:1645-51. [PMID: 20405895 DOI: 10.1021/nl9041966] [Citation(s) in RCA: 343] [Impact Index Per Article: 22.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Graphene monolayer has been grown by chemical vapor deposition on copper and then suspended over a hole. By measuring the laser heating and monitoring the Raman G peak, we obtain room-temperature thermal conductivity and interface conductance of (370 + 650/-320) W/m K and (28 + 16/-9.2) MW/m(2) K for the supported graphene. The thermal conductivity of the suspended graphene exceeds (2500 + 1100/-1050) W/m K near 350 K and becomes (1400 + 500/-480) W/m K at about 500 K.
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Eriksson RA, Albrektsson T. The effect of heat on bone regeneration: an experimental study in the rabbit using the bone growth chamber. J Oral Maxillofac Surg 1984; 42:705-11. [PMID: 6593442 DOI: 10.1016/0278-2391(84)90417-8] [Citation(s) in RCA: 291] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
A dividable titanium implant that, after insertion in the tibial metaphysis of an experimental animal, permits a numerical estimation of ingrowing bone was used to evaluate the effects of a defined temperature rise on bone regeneration. Heating the test implants to 47 degrees C or 50 degrees C for 1 minute caused significantly reduced bone formation in the implants, while no significant effects were observed after heating to 44 degrees C for 1 minute. The results reflect the importance of controlling the heat produced during surgery to avoid impaired bone regeneration.
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Chen S, Wu Q, Mishra C, Kang J, Zhang H, Cho K, Cai W, Balandin AA, Ruoff RS. Thermal conductivity of isotopically modified graphene. NATURE MATERIALS 2012; 11:203-7. [PMID: 22231598 DOI: 10.1038/nmat3207] [Citation(s) in RCA: 278] [Impact Index Per Article: 21.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2011] [Accepted: 11/21/2011] [Indexed: 05/20/2023]
Abstract
In addition to its exotic electronic properties graphene exhibits unusually high intrinsic thermal conductivity. The physics of phonons--the main heat carriers in graphene--has been shown to be substantially different in two-dimensional (2D) crystals, such as graphene, from in three-dimensional (3D) graphite. Here, we report our experimental study of the isotope effects on the thermal properties of graphene. Isotopically modified graphene containing various percentages of 13C were synthesized by chemical vapour deposition (CVD). The regions of different isotopic compositions were parts of the same graphene sheet to ensure uniformity in material parameters. The thermal conductivity, K, of isotopically pure 12C (0.01% 13C) graphene determined by the optothermal Raman technique, was higher than 4,000 W mK(-1) at the measured temperature T(m)~320 K, and more than a factor of two higher than the value of K in graphene sheets composed of a 50:50 mixture of 12C and 13C. The experimental data agree well with our molecular dynamics (MD) simulations, corrected for the long-wavelength phonon contributions by means of the Klemens model. The experimental results are expected to stimulate further studies aimed at a better understanding of thermal phenomena in 2D crystals.
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Svaasand LO, Boerslid T, Oeveraasen M. Thermal and optical properties of living tissue: application to laser-induced hyperthermia. Lasers Surg Med 1985; 5:589-602. [PMID: 4088001 DOI: 10.1002/lsm.1900050607] [Citation(s) in RCA: 240] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
This report discusses the thermal distribution in living tissue during hyperthermic treatment with visible or infrared electromagnetic irradiation. The underlying physical mechanisms that determine the transient as well as the steady-state temperature distribution are discussed. Results from the treatment of a murine tumor model, C3H/Tif mammary adenocarcinoma in C3D2F1/Bom mouse strain, are reported. Total cure, defined by a nonrecurrent tumor, was obtained in 30% of the cases.
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Bakken GS. A heat transfer analysis of animals: unifying concepts and the application of metabolism chamber data to field ecology. J Theor Biol 1976; 60:337-84. [PMID: 957719 DOI: 10.1016/0022-5193(76)90063-1] [Citation(s) in RCA: 206] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Sun Y, Sheng P, Di C, Jiao F, Xu W, Qiu D, Zhu D. Organic thermoelectric materials and devices based on p- and n-type poly(metal 1,1,2,2-ethenetetrathiolate)s. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2012; 24:932-937. [PMID: 22250047 DOI: 10.1002/adma.201104305] [Citation(s) in RCA: 192] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2011] [Revised: 12/08/2011] [Indexed: 05/28/2023]
Abstract
A series of metal coordination polymers containing 1,1,2,2-ethenetetrathiolate (ett) linking bridge (poly[Ax(M-ett)]) are synthesized. The Seebeck coefficients of these conducting materials are high, and vary according to the center metals and counter cations. The TE device fabricated demonstrates the great potentials of these materials for TE applications.
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Cline HE, Schenck JF, Hynynen K, Watkins RD, Souza SP, Jolesz FA. MR-guided focused ultrasound surgery. J Comput Assist Tomogr 1992; 16:956-65. [PMID: 1430448 DOI: 10.1097/00004728-199211000-00024] [Citation(s) in RCA: 189] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Magnetic resonance guided focused ultrasound surgery provides a minimally invasive controlled method for selectively destroying deep-lying tissue. A thermal analysis of focused ultrasound provides an estimate of the time-dependent temperature distribution and thermal dose required for ultrasound surgery. The temperature distribution is estimated by accumulating heat sources, considering the effects of thermal conductivity, heat content, and perfusion. In this study, both gel phantoms and excised in vitro bovine muscle specimens were imaged in a 1.5 T MR system while heated with a 5 cm diameter, 10 cm focal length, 1.1 MHz transducer. During sonication, the thermal effects were observed with T1-weighted pulse sequences. Below a critical temperature, the heat zone appeared as a dark spot that moved with the focal spot. Above a critical thermal dose, the in vitro tissue was irreversibly altered and the focal lesion was observed on both the MR image and the specimen slice.
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Zhong H, Zhu Z, Lin J, Cheung CF, Lu VL, Yan F, Chan CY, Li G. Reusable and Recyclable Graphene Masks with Outstanding Superhydrophobic and Photothermal Performances. ACS NANO 2020; 14:6213-6221. [PMID: 32329600 DOI: 10.1021/acsnano.0c02250] [Citation(s) in RCA: 186] [Impact Index Per Article: 37.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
The 2019 coronavirus outbreak (COVID-19) is affecting over 210 countries and territories, and it is spreading mainly by respiratory droplets. The use of disposable surgical masks is common for patients, doctors, and even the general public in highly risky areas. However, the current surgical masks cannot self-sterilize in order to reuse or be recycled for other applications. The resulting high economic and environmental costs are further damaging societies worldwide. Herein, we reported a unique method for functionalizing commercially available surgical masks with outstanding self-cleaning and photothermal properties. A dual-mode laser-induced forward transfer method was developed for depositing few-layer graphene onto low-melting temperature nonwoven masks. Superhydrophobic states were observed on the treated masks' surfaces, which can cause the incoming aqueous droplets to bounce off. Under sunlight illumination, the surface temperature of the functional mask can quickly increase to over 80 °C, making the masks reusable after sunlight sterilization. In addition, this graphene-coated mask can be recycled directly for use in solar-driven desalination with outstanding salt-rejection performance for long-term use. These roll-to-roll production-line-compatible masks can provide us with better protection against this severe virus. The environment can also benefit from the direct recycling of these masks, which can be used for desalinating seawater.
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Song SH, Park KH, Kim BH, Choi YW, Jun GH, Lee DJ, Kong BS, Paik KW, Jeon S. Enhanced thermal conductivity of epoxy-graphene composites by using non-oxidized graphene flakes with non-covalent functionalization. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2013; 25:732-7. [PMID: 23161437 DOI: 10.1002/adma.201202736] [Citation(s) in RCA: 172] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Revised: 09/24/2012] [Indexed: 05/20/2023]
Abstract
Homogeneous distribution of graphene flakes in a polymer matrix, still preserving intrinsic material properties, is key to successful composite applications. A novel approach is presented to disperse non-oxidized graphene flakes with non-covalent functionalization of 1-pyrenebutyric acid and to fabricate nanocomposites with outstanding thermal conductivity (∼1.53 W/mK) and mechanical properties (∼1.03 GPa).
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Rossmann C, Haemmerich D. Review of temperature dependence of thermal properties, dielectric properties, and perfusion of biological tissues at hyperthermic and ablation temperatures. Crit Rev Biomed Eng 2014; 42:467-92. [PMID: 25955712 PMCID: PMC4859435 DOI: 10.1615/critrevbiomedeng.2015012486] [Citation(s) in RCA: 171] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The application of supraphysiological temperatures (>40°C) to biological tissues causes changes at the molecular, cellular, and structural level, with corresponding changes in tissue function and in thermal, mechanical and dielectric tissue properties. This is particularly relevant for image-guided thermal treatments (e.g. hyperthermia and thermal ablation) delivering heat via focused ultrasound (FUS), radiofrequency (RF), microwave (MW), or laser energy; temperature induced changes in tissue properties are of relevance in relation to predicting tissue temperature profile, monitoring during treatment, and evaluation of treatment results. This paper presents a literature survey of temperature dependence of electrical (electrical conductivity, resistivity, permittivity) and thermal tissue properties (thermal conductivity, specific heat, diffusivity). Data of soft tissues (liver, prostate, muscle, kidney, uterus, collagen, myocardium and spleen) for temperatures between 5 to 90°C, and dielectric properties in the frequency range between 460 kHz and 3 GHz are reported. Furthermore, perfusion changes in tumors including carcinomas, sarcomas, rhabdomyosarcoma, adenocarcinoma and ependymoblastoma in response to hyperthmic temperatures up to 46°C are presented. Where appropriate, mathematical models to describe temperature dependence of properties are presented. The presented data is valuable for mathematical models that predict tissue temperature during thermal therapies (e.g. hyperthermia or thermal ablation), as well as for applications related to prediction and monitoring of temperature induced tissue changes.
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Mehta RJ, Zhang Y, Karthik C, Singh B, Siegel RW, Borca-Tasciuc T, Ramanath G. A new class of doped nanobulk high-figure-of-merit thermoelectrics by scalable bottom-up assembly. NATURE MATERIALS 2012; 11:233-240. [PMID: 22231596 DOI: 10.1038/nmat3213] [Citation(s) in RCA: 170] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2011] [Accepted: 11/23/2011] [Indexed: 05/31/2023]
Abstract
Obtaining thermoelectric materials with high figure of merit ZT is an exacting challenge because it requires the independent control of electrical conductivity, thermal conductivity and Seebeck coefficient, which are often unfavourably coupled. Recent works have devised strategies based on nanostructuring and alloying to address this challenge in thin films, and to obtain bulk p-type alloys with ZT>1. Here, we demonstrate a new class of both p- and n-type bulk nanomaterials with room-temperature ZT as high as 1.1 using a combination of sub-atomic-per-cent doping and nanostructuring. Our nanomaterials were fabricated by bottom-up assembly of sulphur-doped pnictogen chalcogenide nanoplates sculpted by a scalable microwave-stimulated wet-chemical method. Bulk nanomaterials from single-component assemblies or nanoplate mixtures of different materials exhibit 25-250% higher ZT than their non-nanostructured bulk counterparts and state-of-the-art alloys. Adapting our synthesis and assembly approach should enable nanobulk thermoelectrics with further increases in ZT for transforming thermoelectric refrigeration and power harvesting technologies.
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Dresselhaus MS, Dresselhaus G, Charlier JC, Hernández E. Electronic, thermal and mechanical properties of carbon nanotubes. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2004; 362:2065-2098. [PMID: 15370472 DOI: 10.1098/rsta.2004.1430] [Citation(s) in RCA: 170] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
A review of the electronic, thermal and mechanical properties of nanotubes is presented, with particular reference to properties that differ from those of the bulk counterparts and to potential applications that might result from the special structure and properties of nanotubes. Both experimental and theoretical aspects of these topics are reviewed.
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Cline HE, Hynynen K, Hardy CJ, Watkins RD, Schenck JF, Jolesz FA. MR temperature mapping of focused ultrasound surgery. Magn Reson Med 1994; 31:628-36. [PMID: 8057815 DOI: 10.1002/mrm.1910310608] [Citation(s) in RCA: 170] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Deep lying soft tissue tumors may be treated by a nonincisional surgical procedure executed inside an MR imaging system using a thermal effect delivered by a focused ultrasound transducer. A prototype system is constructed to assess MRI thermal monitoring and the localization of the heat zone in muscle. The temperature distribution of the focal spot is imaged with MRI while mechanically moving the transducer with an hydraulic 3-axis positioner. Acoustic power is applied with a spherical shell transducer using 1- to 10-s duration pulses at frequencies of 1.5 MHz to selectively coagulate tissue at 60-70 degrees C. The procedure is monitored with a series of fast second gradient echo, T1-weighted, temperature sensitive MR sequences. Acquisitions are optimized for high temperature sensitive images that yield the thermal diffusivity, heat flow time constant and the focal spot size in muscle. MR temperature maps of muscle provide localization and dosimetry both in the focal region and near field.
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Hannig M, Bott B. In-vitro pulp chamber temperature rise during composite resin polymerization with various light-curing sources. Dent Mater 1999; 15:275-81. [PMID: 10551096 DOI: 10.1016/s0109-5641(99)00047-0] [Citation(s) in RCA: 166] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
OBJECTIVES The purpose of this in vitro study was to measure the pulp chamber temperature increase induced during composite resin polymerization with various visible light-curing units. METHODS A Class II cavity was prepared in an extracted molar tooth, leaving a dentin layer 1 mm thick between pulp chamber and proximal cavity wall. A 2 mm composite resin layer was applied to the proximal box and light-cured with the selected curing units: Heliolux II (H; 320 mW/cm2), QHL 75 (Q; 505 mW/cm2), Astralis 5 (A; 515 mW/cm2), Optilux 500 (O; 670 mW/cm2), Elipar Highlight (EH; 730 mW/cm2), ADT 1000 PAC (P; 1196 mW/cm2). Light-curing took place for 40 s (H, A, Q, O, EH), 5 and 10 s (P). Measurement of pulp chamber temperature changes (starting temperature: 37.0 +/- 0.1 degrees C) during polymerization was performed with a K-type thermocouple positioned at the pulp-dentin junction. Mean values were calculated from 10 measurements with each light-curing unit. ANOVA and Dunnett t-test were used for statistical analyses. RESULTS Maximum temperature changes varied significantly depending on the light-curing unit used: 2.9 +/- 0.3 degrees C (H), 4.7 +/- 0.5 degrees C (A), 5.4 +/- 0.3 degrees C (P, 5 s), 5.6 +/- 0.4 degrees C (Q), 6.1 +/- 0.2 degrees C (EH, 2-step mode: 100 mW/cm2 over 10 s, 730 mW/cm2 over 30 s), 6.9 +/- 0.4 degrees C (EH), 7.3 +/- 0.3 degrees C (O), 7.8 +/- 0.9 degrees C (P, 10 s). SIGNIFICANCE It is concluded that light-polymerization with curing units characterized by high energy output (A,EH,O,P,Q) causes significantly higher pulp chamber temperature changes as compared to the conventional curing light (H). Therefore, clinicians should be aware of the potential thermal hazard to the pulp which might result from visible-light curing of composite resins.
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Collins CM, Liu W, Wang J, Gruetter R, Vaughan JT, Ugurbil K, Smith MB. Temperature and SAR calculations for a human head within volume and surface coils at 64 and 300 MHz. J Magn Reson Imaging 2004; 19:650-6. [PMID: 15112317 DOI: 10.1002/jmri.20041] [Citation(s) in RCA: 165] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
PURPOSE To examine relationships between specific energy absorption rate (SAR) and temperature distributions in the human head during radio frequency energy deposition in MRI. MATERIALS AND METHODS A multi-tissue numerical model of the head was developed that considered thermal conductivity, heat capacity, perfusion, heat of metabolism, electrical properties, and density. Calculations of SAR and the resulting temperature increase were performed for different coils at different frequencies. RESULTS Because of tissue-dependent perfusion rates and thermal conduction, there is not a good overall spatial correlation between SAR and temperature increase. When a volume coil is driven to induce a head average SAR level of either 3.0 or 3.2 W/kg, it is unlikely that a significant temperature increase in the brain will occur due to its high rate of perfusion, although limits on SAR in any 1 g of tissue in the head may be exceeded. CONCLUSION Attempts to ensure RF safety in MRI often rely on assumptions about local temperature from local SAR levels. The relationship between local SAR and local temperature is not, however, straightforward. In cases where high SAR levels are required due to pulse sequence demands, calculations of temperature may be preferable to calculations of SAR because of the more direct relationship between temperature and safety.
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Research Support, U.S. Gov't, P.H.S. |
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Yan J, Kim MH, Elle JA, Sushkov AB, Jenkins GS, Milchberg HM, Fuhrer MS, Drew HD. Dual-gated bilayer graphene hot-electron bolometer. NATURE NANOTECHNOLOGY 2012; 7:472-8. [PMID: 22659611 DOI: 10.1038/nnano.2012.88] [Citation(s) in RCA: 162] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2012] [Accepted: 05/01/2012] [Indexed: 05/06/2023]
Abstract
Graphene is an attractive material for use in optical detectors because it absorbs light from mid-infrared to ultraviolet wavelengths with nearly equal strength. Graphene is particularly well suited for bolometers-devices that detect temperature-induced changes in electrical conductivity caused by the absorption of light-because its small electron heat capacity and weak electron-phonon coupling lead to large light-induced changes in electron temperature. Here, we demonstrate a hot-electron bolometer made of bilayer graphene that is dual-gated to create a tunable bandgap and electron-temperature-dependent conductivity. The bolometer exhibits a noise-equivalent power (33 fW Hz(-1/2) at 5 K) that is several times lower, and intrinsic speed (>1 GHz at 10 K) three to five orders of magnitude higher than commercial silicon bolometers and superconducting transition-edge sensors at similar temperatures.
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Prasher R, Phelan PE, Bhattacharya P. Effect of aggregation kinetics on the thermal conductivity of nanoscale colloidal solutions (nanofluid). NANO LETTERS 2006; 6:1529-34. [PMID: 16834444 DOI: 10.1021/nl060992s] [Citation(s) in RCA: 162] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
The thermal conductivity, k, of nanoscale colloidal suspensions (also known as nanofluid), consisting of nanoparticles suspended in a base liquid, is much higher than the thermal conductivity of the base liquid at very small volume fractions of the nanoparticles. However, experimental results from various groups all across the world have shown various anomalies such as a peak in the enhancement of k with respect to nanoparticle size, an increase as well as a decrease in the ratio of k of these colloidal solutions with the k of the base fluid with increasing temperature, and a dependence of k on pH and time. In this paper, the aggregation kinetics of nanoscale colloidal solutions are combined with the physics of thermal transport to capture the effects of aggregation on k. Results show that the observed anomalies reported in experimental work can be well described by taking aggregation kinetics into account. Finally, we show that colloidal chemistry plays a significant role in deciding the k of colloidal nanosuspensions.
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See KC, Feser JP, Chen CE, Majumdar A, Urban JJ, Segalman RA. Water-processable polymer-nanocrystal hybrids for thermoelectrics. NANO LETTERS 2010; 10:4664-4667. [PMID: 20923178 DOI: 10.1021/nl102880k] [Citation(s) in RCA: 161] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We report the synthesis and thermoelectric characterization of composite nanocrystals composed of a tellurium core functionalized with the conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). Solution processed nanocrystal films electronically out perform both PEDOT:PSS and unfunctionalized Te nanorods while retaining a polymeric thermal conductivity, resulting in a room temperature ZT ∼ 0.1. This combination of electronic and thermal transport indicates the potential for tailored transport in nanoscale organic/inorganic heterostructures.
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Cline HE, Schenck JF, Watkins RD, Hynynen K, Jolesz FA. Magnetic resonance-guided thermal surgery. Magn Reson Med 1993; 30:98-106. [PMID: 8371680 DOI: 10.1002/mrm.1910300115] [Citation(s) in RCA: 152] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
A demonstration of MR guided thermal surgery involved experiments with imaging of focused ultrasound in an MRI system, measurements of the thermal transients and a thermal analysis of the resulting images. Both the heat distribution and the creation of focused ultrasound lesions in gel phantoms, in vitro bovine muscle and in vivo rabbit muscle were monitored with magnetic resonance imaging. Thermal surgical procedures were modeled by an elongated gaussian heat source where heat flow is controlled by tissue thermal properties and tissue perfusion. Temperature profiles were measured with thermocouples or calculated from magnetic resonance imaging in agreement with the model. A 2-s T1-weighted gradient-refocused acquisition provided thermal profiles needed to localize the heat distribution produced by a 4-s focused ultrasound pulse. Thermal analysis of the images give an effective thermal diffusion coefficient of 0.0015 cm2/s in gel and 0.0033 cm2/s in muscle. The lesions were detected using a T2-weighted spin-echo or fast spin-echo pulse sequence in agreement with muscle tissue sections. Potential thermal surgery applications are in the prostate, liver, kidney, bladder, breast, eye and brain.
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Meng C, Liu C, Fan S. A promising approach to enhanced thermoelectric properties using carbon nanotube networks. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2010; 22:535-539. [PMID: 20217749 DOI: 10.1002/adma.200902221] [Citation(s) in RCA: 152] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
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Marconnet AM, Yamamoto N, Panzer MA, Wardle BL, Goodson KE. Thermal conduction in aligned carbon nanotube-polymer nanocomposites with high packing density. ACS NANO 2011; 5:4818-4825. [PMID: 21598962 DOI: 10.1021/nn200847u] [Citation(s) in RCA: 151] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Nanostructured composites containing aligned carbon nanotubes (CNTs) are very promising as interface materials for electronic systems and thermoelectric power generators. We report the first data for the thermal conductivity of densified, aligned multiwall CNT nanocomposite films for a range of CNT volume fractions. A 1 vol % CNT composite more than doubles the thermal conductivity of the base polymer. Denser arrays (17 vol % CNTs) enhance the thermal conductivity by as much as a factor of 18 and there is a nonlinear trend with CNT volume fraction. This article discusses the impact of CNT density on thermal conduction considering boundary resistances, increased defect concentrations, and the possibility of suppressed phonon modes in the CNTs.
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