Estimated Heating Rates Research Articles

Ferromagnetic resonance-based heat dissipation in dumbbell-like Au–Fe3O4 nanoparticles

Ferromagnetic resonance (FMR) holds promise for heating magnetic nanoparticles (MNPs) in cancer therapy, especially for rapidly heating MNPs. This study aims to enhance the FMR-based heating efficiency of multifunctional hybrid gold and iron oxide nanoparticles (Au-Fe3O4 NPs) as theranostic agents. We experimentally investigate the FMR-based heating properties of newly developed dumbbell-like Au-Fe3O4 NPs, which feature ∼5 nm gold and 15 nm iron oxide components, in comparison to our previously developed Au-coated Fe3O4 NPs (Fe3O4 core ∼5.2 nm, Au shell thickness ∼0.5 nm). For comparison, we also synthesize pure Fe3O4 NPs (∼11 nm) under the same experimental conditions as the dumbbell-like Au-Fe3O4 NPs but without 5 nm Au seeds. Temperature measurements are taken at various DC fields (HDC = 0‒1600 Oe) under a radiofrequency (RF) field (fAC = 4 GHz, HAC = 1.265 Oe) for ∼13s. The results reveal a rapid temperature rise during RF field ON, followed by a decline upon RF field OFF. Remarkably, dumbbell-like Au-Fe3O4 NPs achieve a peak temperature increase of 23.4 °C, corresponding to a heating rate of 1.73 °C/s at HDC = 400 Oe, surpassing the combined values of ∼11 nm Fe3O4 NPs (11.0 °C, i.e., 0.83 °C/s at HDC = 1000 Oe) and ∼5 nm Au NPs (3.5 °C). Comparing these results to our previously developed Au-coated Fe3O4 NPs, which achieved a heating rate of 1.29 °C/s (temperature rise 16.9 °C) under HDC = 1200 Oe with an RF field at fAC = 4 GHz and a significantly higher HAC = 4 Oe (i.e. for HAC = 1.265 Oe, the estimated heating rate was 0.129 °C/s with a temperature rise of 1.69 °C), the dumbbell-shaped Au-Fe3O4 NPs demonstrate a substantially higher temperature increase by 13.4 times. These findings highlight the exceptional potential of dumbbell-shaped Au-Fe3O4 NPs for application in magnetic hyperthermia.

Differences between in-situ ozonesonde observations and satellite retrieved ozone vertical profiles across Antarctica

In situ ozonesonde observations across nine Antarctic stations were used to validate the vertical profiles retrieved by the satellite-based Microwave Limb Sounder (MLS) instrument from 2004 to 2019. Intra-annual variations in the ozone concentration, along with the shape of the vertical profiles are well reproduced by the MLS with differences in the range of ±20%, although seasonally the differences were as high as 60%. The largest differences were also observed during the spring (September-October-November), when largescale ozone depletion takes place over Antarctica, with MLS overestimating concentrations at almost all the stations, except the northernmost stations of Marambio and Dumont d’Urville. This has implications for the estimations of ozone recovery over Antarctica based on MLS. The under-estimation or over-estimation in the MLS data caused differences up to ±1 K day−1 in the estimated heating rate. For the whole dataset, a good correlation (R2 > 0.9, p < 0.001) was seen at all the stations except at Maitri, where the correlation coefficient was lower but still significant (R2 = 0.77, p < 0.001). These results show that although the MLS data match the in-situ observations over longer averaging periods, for individual profiles the discrepancies are much higher and need to be considered when computing the ozone impacts using MLS data.

Turbulent Proton Heating Rate in the Solar Wind from 5–45 R ⊙

Abstract Various remote sensing observations have been used so far to probe the turbulent properties of the solar wind. Using the recently reported density modulation indices that are derived using angular broadening observations of Crab Nebula during 1952–2013, we measured the solar wind proton heating using the kinetic Alfvén wave dispersion equation. The estimated heating rates vary from ≈1.58 × 10−14 to 1.01 × 10−8 erg cm−3 s−1 in the heliocentric distance range of 5–45 R ⊙. Further, we found that heating rates vary with the solar cycle in correlation with density modulation indices. The models derived using in situ measurements (for example, electron/proton density, temperature, and magnetic field) that the recently launched Parker Solar Probe observations (planned closest perihelia 9.86 R ⊙ from the center of the Sun) are useful in the estimation of the turbulent heating rate precisely. Further, we compared our heating rate estimates with the one derived using previously reported remote sensing and in situ observations.

Wave‐Particle Interactions Associated With Io's Auroral Footprint: Evidence of Alfvén, Ion Cyclotron, and Whistler Modes

AbstractThe electrodynamic coupling between Io and Jupiter gives rise to wave‐particle interactions across multiple spatial scales. Here we report observations during Juno's 12th perijove (PJ) high‐latitude northern crossing of the flux tube connected to Io's auroral footprint. We focus on plasma wave measurements, clearly differentiating between magnetohydrodynamic (MHD), ion, and electron scales. We find (i) evidence of Alfvén waves undergoing a turbulent cascade, suggesting Alfvénic acceleration processes together with observations of bi‐directional, broadband electrons; (ii) intense ion cyclotron waves with an estimated heating rate that is consistent with the generation of ion conics reported by Clark et al. (2020, https://doi.org/10.1029/2020GL090839); and (iii) whistler‐mode auroral hiss radiation excited by field‐aligned electrons. Such high‐resolution wave and particle measurements provide an insight into satellite interactions in unprecedented detail. We further anticipate that these spatially well‐constrained results can be more broadly applied to better understand processes of Jupiter's main auroral oval.

Optical and physical properties of aerosols during active fire events occurring in the Indo-Gangetic Plains: Implications for aerosol radiative forcing

The climatological characteristics of biomass burning over the western Indo-Gangetic Plain (IGP) are examined during the post-monsoon (October-November) season from 2001-2018 using the Moderate resolution Imaging Spectrometer (MODIS) fire products. The intensity of the biomass burning are estimated from the fire pixels detected by the MODIS satellites in the form of fire counts, surface brightness temperature, and fire radiative power. Such biomass burning are mostly affected over Lahore and Patiala region of the western IGP. These fire products are examined along with optical and physical properties of aerosols and its radiative forcing estimated from AErosol RObotic NETwork (AERONET) data. Due to non-availability of long-term aerosol data, the study was performed only at Lahore (AERONET) and Patiala (MODIS) of the western IGP region. The current study shows increasing trends of average brightness temperature by 16% year−1 over Patiala and 14% year−1 over Lahore, which enhances the aerosol optical depth (AOD) by 3%–7% year−1 over the study region. The sphericity of the fine-mode aerosols are rising from 23% to 61% during non-fire to fire events and the dominance of fine-mode aerosols are observed during the active fire events. Further, the absorptivity of AOD (at 440 nm) has enhanced from 0.07 to 0.14 during non-fire to fire events. Asymmetric parameter (AS) of fine-mode aerosol increases from 0.65 to 0.68 during non-fire to active fire events. The characteristics of elevated aerosol layers due to the active fire events are clearly distinguished from the non-fire events within 0-2 km above the surface as noticed from high aerosol extinction and attenuated back scatter coefficients, obtained from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). Absorbing aerosols associated from biomass-burning contribute to the surface radiative forcing by -173.96 ± 47 W m−2 and atmospheric forcing by 123.57 ± 41 W m−2 over Lahore. The impact of the biomass-burning over Lahore has making the atmosphere more warming by 3.50 ± 1.14 K Day−1. The estimated heating rates (HR) in the atmosphere are rising during both fire and non-fire events by 3.79% and 3.44% per year, respectively.

Poly-L-lysine designed magnetic nanoparticles for combined hyperthermia, magnetic resonance imaging and cancer cell detection

Abstract The aim of this study was to test the suitability of poly-L-lysine coated magnetic nanoparticles for combined magnetic hyperthermia and magnetic resonance imaging (MRI) to unify the therapeutic and diagnostic approach. For this purpose, we have synthetized magnetic iron oxide (Fe3O4) nanoparticles of core diameter ∼10 nm and modified with Poly-L-lysine (PLL) to stabilize the particles and improve their biocompatibility. These modified nanoparticles (MFPLL) were tested for magnetic hyperthermia suitability by calorimetric measurements. Based on the estimated heating rates the specific absorption rates (SAR) for MFPLL particles were calculated. The SAR values of MFPLL particles were about 14–15 Wg−1 at frequency 190 kHz and applied field ∼8 kAm−1. In the MRI parametric mapping measurements we demonstrated the significant effect of MFPLL on transversal relaxation time T2 with the relaxivity r2 equal to 487.94 mM−1 s−1. The combination of the heating properties with the cytotoxic activities of MFPLL and MRI parameters holds great promise for the future development of targeted synergistic cancer treatment. Furthermore, as our previous results confirmed the cytotoxic activities of MFPLL in a cell type-dependent manner and the binding to cells expressing carbonic anhydrase (CA IX) when conjugated with the CA IX-specific antibody we have studied the antibody conjugated MFPLL nanoparticles in 3D spheroidal culture.

MAVEN NGIMS observations of atmospheric gravity waves in the Martian thermosphere

AbstractGravity waves have a significant impact on both the dynamics and energy budget of the Martian thermosphere. Strong density variations of spatial scales indicative of gravity waves have previously been identified in this region by using in situ observations. Here we use observations from the Neutral Gas and Ion Mass Spectrometer (NGIMS) mass spectrometer on Mars Atmosphere and Volatile EvolutioN Mission to identify such waves in the observations of different atmospheric species. The wave signatures seen in CO2 and Ar are almost identical, whereas the wave signature seen in N2, which is lighter and has a larger scale height, is generally smaller in amplitude and slightly out of phase with those seen in CO2 and Ar. Examination of the observed wave properties in these three species suggests that relatively long vertical wavelength atmospheric gravity waves are the likely source of the waves seen by NGIMS in the upper thermosphere. A two‐fluid linear model of the wave perturbations in CO2 and N2 has been used to find the best fit intrinsic wave parameters that match the observed features in these two species. We report the first observationally based estimate of the heating and cooling rates of the Martian thermosphere created by the waves observed in this region. The observed wave density amplitudes are anticorrelated with the background atmospheric temperature. The estimated heating rates show a weak positive correlation with the wave amplitude, whereas the cooling rates show a clearer negative correlation with the wave amplitude. Our estimates support previous model‐based findings that atmospheric gravity waves are a significant source of both heating and cooling.

Equatorial stratospheric thermal structure and ozone variations during the sudden stratospheric warming of 2013

Ozone mass mixing ratio (OMMR) obtained from both European Centre for Medium Range Weather Forecasting (ECMWF) Reanalysis (ERA)-Interim and Sounding of Atmosphere by Broadband Emission Radiometry (SABER) instrument onboard Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics (TIMED) satellite shows large values in the equatorial upper stratosphere during the occurrence of a major stratospheric sudden warming (SSW) in January 2013 preceded by a large reduction of planetary wave activity. However, surprisingly equatorial stratospheric temperature is found to decrease at pressure levels where the ozone mixing ratio is larger. The computed radiative heating rate using Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model also shows positive heating rate indicating that the temperature should increase in response to the ozone accumulation over equator. In addition to radiative heating due to ozone, heating rate due to other dominant factors, namely, ascending motion and convergence of meridional heat flux, which could influence the thermal structure of the equatorial stratosphere, are estimated. It is found that the observed low temperature during SSW is mainly due to large upward motions. The estimated heating rates agree reasonably well with the observed heating rates at 10-8hPa indicating the dominance of transport at lower stratosphere. The large discrepancy between the estimated and observed heating rates in the upper stratosphere may be due to the dominance of photochemistry.

Temperature enhancements and vertical winds in the lower thermosphere associated with auroral heating during the DELTA campaign

[1] A coordinated observation of the atmospheric response to auroral energy input in the polar lower thermosphere was conducted during the Dynamics and Energetics of the Lower Thermosphere in Aurora (DELTA) campaign. N2 rotational temperature was measured with a rocket-borne instrument launched from the Andoya Rocket Range, neutral winds were measured from auroral emissions at 557.7 nm with a Fabry-Perot Interferometer (FPI) at Skibotn and the KEOPS, and ionospheric parameters were measured with the European Incoherent Scatter (EISCAT) UHF radar at Tromso. Altitude profiles of the passive energy deposition rate and the particle heating rate were estimated using data taken with the EISCAT radar. The local temperature enhancement derived from the difference between the observed N2 rotational temperature and the MSISE-90 model neutral temperature were 70–140 K at 110–140 km altitude. The temperature increase rate derived from the estimated heating rates, however, cannot account for the temperature enhancement below 120 km, even considering the contribution of the neutral density to the estimated heating rate. The observed upward winds up to 40 m s �1 seem to respond nearly instantaneously to changes in the heating rates. Although the wind speeds cannot be explained by the estimated heating rate and the thermal expansion hypothesis, the present study suggests that the generation mechanism of the large vertical winds must be responsible for the fast response of the vertical wind to the heating event.

Using analysis increments to estimate atmospheric heating rates following volcanic eruptions

By using the analysis increments of the temperatures from atmospheric re‐analyses it is possible to roughly estimate the stratospheric radiative heating rates from volcanic eruption. The method is applied to the 30 hPa temperature from the 15 years of the ECMWF‐reanalysis. After the influence from the Quasi Biennial Oscillation is subtracted maximum values of the zonal mean radiative heating rates related to El Chichón and Pinatubo volcanic eruptions are estimated to 0.30 K/day and 0.25 K/day, respectively. The estimated heating rates are not solely due to aerosol heating but includes the effects of ozone reduction and geostrophic adjustment as well.

Ultra-Fast Biomass Pyrolysis in a High-Temperature (2200° C), Fluid-Wall Reactor

The pyrolysis of pine sawdust has been carried out in a High-Temperature Fluid-Wall Reactor. This unit has been specially designed to withstand working temperatures of up to 2200° C. The biomass is fed to the top of the reactor after sieving to the appropriate size, at a rate of 1.0 to 1.8 kg/min. The feed falls and, at the same time is very quickly heated by radiation to the reaction temperature. The estimated heating rate is on the order of 106° C/s for reactant surfaces. The fluid-wall, produced by a nitrogen flow through the 30 cm diameter porous reactor core, prevents both reactants and products from reaching the reactor wall. The product distribution at the reactor exit has been determined for different operating conditions. The influence of reactor temperature, biomass feed rate, and biomass particle size on the product distribution and on the heating value of the exit gas has been investigated.

Parametric study of the effects of arctic soot on solar radiation

A numerical radiative transfer model has been used to simulate the possible effects of carbonaceous aerosol on the Arctic climate. Because of uncertainties in aerosol properties in the Arctic, the sensitivity of modeled components of the solar radiation budget to ranges in aerosol parameters was determined. It was found that differences in assumed aerosol absorption, concentration and vertical distribution were more important than differences in aerosol size distribution. Aerosol absorption was parameterized through the index of refraction assuming an aerosol composed of soot and sulfates. Modeling the radiative effects of the springtime phenomena of Arctic soot leads to an increase in average heating rates of 0.01–0.06 K day −1 in the lowest 1–5 km of the atmosphere under cloud free conditions. The higher value is similar to estimated heating rates at northern latitudes that would result from doubling atmospheric CO 2 concentrations. The hemispheric average temperature change due to the Arctic soot is, however, estimated to be almost two orders of magnitude less than for doubling of CO 2 concentrations.

Black Carbon Aerosol Characteristics and Its Radiative Impact over Nainital: A High-Altitude Station in the Central Himalayas

Ground-based measurements of aerosol black carbon (BC), from a high altitude location at Nainital in the central Himalayas (during June 2006 to May 2007), were used to study its temporal variability and impact on the atmospheric radiative forcing. Diurnal variation of BC mass concentration shows single enhanced peak in the late afternoon hour. The peak is rather pronounced in winter months due to shallow and stable boundary layer condition, which is largely associated with low surface temperature. The mean BC mass concentrations were found to be as ~0.6 (±0.2), 1.4 (±0.1), 1.2 (±0.3) and 1.5 (±0.2) μg m-3 during monsoon, post-monsoon, winter and spring periods, respectively while its maximum value was ~1.8 (±0.8) μg m-3 during April. The prevailing winds revealed to facilitates the transport of BC from the distant sources to the observing site. A radiative transfer model was used in conjunction with an aerosol optical model to estimate the BC radiative forcing over the station. Results show BC forcing at the top-of-atmosphere (TOA), surface and in the atmosphere varies between about +3 to +7, -6 to -14 and +8 to +21 Wm-2, respectively which is more pronounced during spring then during monsoon depending upon BC mass loading. The positive atmosphere forcing represents a considerable amount of heating to the lower atmosphere and has been conjectured as potential factor causing global warming. The estimated heating rate of the lower atmosphere over the station was found to be ranging from 0.24 Kday-1 during monsoon to 0.58 Kday-1 during spring season. DOI: http://dx.doi.org/10.3126/jie.v8i3.5926 JIE 2011; 8(3): 1-10