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We have developed a system for remote Raman spectra detection in hypersonic wind tunnel, which can be used in extreme environments such as ultra‐high temperature, high pressure, and complex airflow to measure in situ Raman spectra of ceramic matrix composites during oxidation, phase transformation or ablation. The designed system avoids stray light generated by windows and airflow through oblique incidence of excitation light. The time‐resolved method combined with pulsed laser and intensified charge‐coupled device (ICCD) was used to reduce the thermal emission background. An optical structure design based on fiber bundle is adopted to suppress the influence of aero‐optical effects and mechanical vibration on Raman spectrum acquisition. We demonstrated the feasibility of in situ Raman spectra detection in a Mach 5 combustion wind tunnel system. The design of anti‐interference prevents Raman spectra intensity from the influence of wind tunnel testing conditions. [ABSTRACT FROM AUTHOR]

The continuous fiber reinforced porous resin‐based composites with integrated gradient fabric (CPIGF) were successfully prepared. From the bottom to the top surface, the fiber volume fraction of the integrated fabric gradually increased, as well as the fabric architecture changed, meanwhile the porosity of the resin gradually decreased. The temperature in the inner composite increased quite slowly during ablation, and the linear ablation rate ranged from 0.019 mm/s to 0.029 mm/s. The simulation results showed that the good heat insulation capacity of CPIGFs was attributed to the anisotropy properties of the fabric architecture. The microstructure analysis showed that the good ablation resistance came from both the thermal expansion of the integrated gradient fabric and the densification of the zone with 3D orthogonal woven fabric. This work is helpful for designing thermal protection materials having both heat insulation and ablation resistance for hypersonic aircrafts. [ABSTRACT FROM AUTHOR]

As two prominent natural hazards, tropical cyclone (TC) and heat compound events seem irrelevant on most occasions. TC generally leads to cooling, but could induce extreme heat days (EHD) and heat compound hazard under certain circumstances. An EHD along the southeastern coast of China (SECC) associated with Typhoon Lekima (2019) is documented with its major contributing factors. The formation and intensity of the EHD were found to be closely related to the outer circulation of Lekima by comparing a series of WRF simulations. Via a boundary layer heat budget, we found local sensible heat flux was a necessary, but not sufficient condition for this EHD. Aided by a backward trajectory analysis, we found that upstream surface sensible heat flux, subsidence induced by Typhoon Lekima, and foehn effect due to local topography played approximately equal roles to the occurrence of the EHD. The retreat of regional land‐sea breeze circulation was also beneficial to the appearance of the EHD. Such TC‐heat events might be more overwhelming due to more vigorous TCs with warming in the future. Plain Language Summary: Tropical cyclone (TC) and heat compound events pose a severe threat to human health and natural ecosystems. This paper documents an extreme heat days (EHD) along the southeastern coast of China associated with Typhoon Lekima (2019). Through a series of WRF simulations, we found that the formation and intensity of the EHD are closely related to the outer circulation of Lekima. The local sensible heat flux was necessary, but insufficient for the formation of the EHD. The upstream surface sensible heat flux, subsidence induced by Typhoon Lekima, and foehn effect due to local topography were the key factors to the occurrence of the EHD and the contributions of these three factors were approximately equal. Regional land‐sea breeze circulation influenced by Lekima was also beneficial for the EHD. Such TC‐heat events can be more widespread and severe due to increased intensity of tropical cyclones with warming. Key Points: An extreme heat event along the southeastern coast of China was closely related to the outer circulation of Typhoon Lekima (2019)Upstream surface sensible heat flux, subsidence induced by Typhoon Lekima, and foehn effect due to local topography played approximately equal roles for the eventRetreat of regional land‐sea breeze circulation also favored the event [ABSTRACT FROM AUTHOR]

The persistent two‐peaked vertical structure of the Martian ionosphere is created by extreme and far ultraviolet radiation whose energies, respectively, determine their ionization altitude. A third low‐altitude transient layer (previously referred to as M3 or Mm) has been observed by radio occultation techniques and attributed to meteor ablation. However, recent remote sensing and in situ observations disfavor a meteoric origin. Here we propose an alternative hypothesis for these apparent layers associated with impact ionization from penetrating solar wind ions, previously observed as proton aurora. Localized ionization, occurring nonglobally at a given altitude range, breaks the symmetry assumed by the radio occultation technique, and creates electron layers apparently lower in the ionosphere than their true altitude. This may occur when the upstream bow shock is altered by a radial interplanetary magnetic field configuration, which allows the solar wind to penetrate directly into the thermosphere. This localized ionization hypothesis provides an explanation for apparent layers' wide variation in heights and their transient behavior. Moreover, this hypothesis is testable with new observations by the Mars Atmospheric and Volatile EvolutioN Radio Occultation Science Experiment in future Mars years. This hypothesis has implications for the ionospheres of Venus and Titan, where similar transient layers have been observed. Plain Language Summary: The ionosphere of a planet couples the neutral atmosphere to the exosphere and solar wind. Created by solar ionizing radiation, the ionosphere on the dayside of planet is expected to be hemispherically symmetric. When Mars Express discovered transient low‐altitude ionospheric layers in 2005, they were initially predicted to be due to meteor ablation. However, recent observations indicate that they are due to a geometric observational effect related to local, not hemispheric, ionization. Observations from three instruments on Mars Atmospheric and Volatile EvolutioN are used concurrently to understand this phenomenon. These transient layers have been observed at Venus and Titan as well, and this hypothesis indicates novel physics for those ionospheric systems. Key Points: Low‐altitude transient ionospheric layers may be explained by a geometric observational effect from localized, not hemispheric, ionizationA radio occultation of a transient ionospheric layer was obtained with observations of variable proton aurora and penetrating solar windTransient layers observed at Mars, Venus, and Titan are consistent with the presence of solar wind impact ionization at those planets [ABSTRACT FROM AUTHOR]

Abstract: Recent emerged antibacterial agents provide enormous new possibilities to replace antibiotics in fighting bacterial infectious diseases. Although abundant types of nanoagents are developed for preventing pathogen colonization, however, rationally design of nonchemotherapic, robust, and clinical‐adaptable nanoagents with tunable bacterial trap and killing activities remains a major challenge. Here, a demonstration of controlling the trap, ablation, and release activities of pathogenic bacteria via stimulus‐responsive regulatory mechanism is reported. First, temperature‐sensitive polymer brush is chemically grown onto carbon nanotube–Fe3O4, whereby the synthesized nanoagents can transfer from hydrophilic dispersion to hydrophobic aggregation upon near‐infrared light irradiation, which thus controls the bacterial trap, killing, and detaching. In turn, the formed aggregations will serve as localized heating sources to enhance photothermal ablation of bacteria. Systematically antibacterial experiments and mouse wound disinfection demonstrate the ultrarobust and recyclable disinfection capability of nanoagents with nearly 100% killing ratio to Staphylococcus aureus. Overall, for the first time, we represent a pioneering study on designing nonchemotherapic and robust dual‐responsive nanoagents that can sensitively and reversibly trap, inactivate, and detach bacteria. We envision that such nanoagents will not only have potential applications in pathogenic bacteria prevention but also provide a new pathway for wound disinfection, implant sterilization, and also live bacteria transportation. [ABSTRACT FROM AUTHOR]

To improve the thermal properties of novolac resin, zirconium diboride (ZrB2) nanoparticles (ZNP) with different weight percentages (0, 2, 4 and 7) were introduced into novolac resin. ZrB2 nanoparticles modified carbon-novolac (C-N) composites were used to determine and compare the ablation performance, thermal stresses and cracks, and mechanical properties of these modified polymer composites. Thermal protection via ablation was achieved through a self-regulating heat and mass transfer process involving an insulator with low thermal conductivity and concomitant formation of a hard char on the insulator surface after 160 s exposure to the combustion environment. Anti-oxidation mechanisms for the novolac resin modified with nanoparticles at different weight percentage were compared and discussed. Ablation performance shows a steady increase with the filler content until a maximum, at 4 wt% of ZNP, and then it decreases. [ABSTRACT FROM AUTHOR]

This work concerns ZnO nanoparticles (NPs), with sizes of tens of nm, produced by ablation with a pulsed Nd:YAG laser of a Zn plate in H2O. TEM images evidence the formation of nanoparticles with sizes of tens of nm. Moreover, HRTEM images and Raman spectra show that the distance between the crystalline planes and the vibrational modes are consistent with ZnO nanocrystal in wurtzite structure. Their optical properties are characterized by two emission bands both excited above the energy gap (3.4 eV): the first at 3.3 eV is associated with excitons recombination, the second at 2.2 eV is proposed to originate from a singly ionized oxygen vacancy. The green emission is independent of water pH, thus suggesting that point defects lie inside NPs rather than at the surface. Thermal annealing at 300 °C in O2 and He atmosphere, produces a reduction of the A1(LO) Raman mode at 562 cm-1, which is related to the oxygen vacancies, and a consequent decrease of the defect luminescence, while the excitonic luminescence increases. These results indicate that the ZnO emissions can be controlled by thermal annealing, and are promising in view of optoelectronic applications. [ABSTRACT FROM AUTHOR]

Ablation of micrometeoroids during atmospheric entry yields volatile gases such as water, carbon dioxide, and sulfur dioxide, capable of altering atmospheric chemistry and hence the climate and habitability of the planetary surface. While laboratory experiments have revealed the yields of these gases during laboratory simulations of ablation, the reactions responsible for the generation of these gases have remained unclear, with a typical assumption being that species simply undergo thermal decomposition without engaging in more complex chemistry. Here, pyrolysis-Fourier transform infrared spectroscopy reveals that mixtures of meteorite-relevant materials undergo secondary reactions during simulated ablation, with organic matter capable of taking part in carbothermic reduction of iron oxides and sulfates, resulting in yields of volatile gases that differ from those predicted by simple thermal decomposition. Sulfates are most susceptible to carbothermic reduction, producing greater yields of sulfur dioxide and carbon dioxide at lower temperatures than would be expected from simple thermal decomposition, even when mixed with meteoritically relevant abundances of low-reactivity Type IV kerogen. Iron oxides were less susceptible, with elevated yields of water, carbon dioxide, and carbon monoxide only occurring when mixed with high abundances of more reactive Type III kerogen. We use these insights to reinterpret previous ablation simulation experiments and to predict the reactions capable of occurring during ablation of carbonaceous micrometeoroids in atmospheres of different compositions. [ABSTRACT FROM AUTHOR]

Well-defined starter cracks at preselected sites in the microstructures are needed for systematic investigation of the characteristic features of microstructure controlled growth of small cracks. A kinked ellipsoidal micronotch with very high notch factor at the trailing kink is proposed, which triggers controlled crack initiation along the notch contour. These micronotches can be machined by femtosecond laser ablation with virtually no heat-affected zone at the edges. Crack growth results obtained for an intermetallic γ-TiAl alloy are presented as an illustrative example. [ABSTRACT FROM AUTHOR]

An experimental analysis is presented to establish the thermal performance of a latent heat thermal storage ( LHTS) unit. Paraffin is used as the phase change material ( PCM) on the shell side of the shell and tube-type LHTS unit while water is used as the heat transfer fluid ( HTF) flowing through the inner tube. The fluid inlet temperature and the mass flow rate of HTF are varied and the temperature distribution of paraffin in the shell side is measured along the radial and axial direction during melting and solidification process. The total melting time is established for different mass flow rates and fluid inlet temperature of HTF. The motion of the solid-liquid interface of the PCM with time along axial and radial direction of the test unit is critically evaluated. The experimental results indicate that the melting front moves from top to bottom along the axial direction while the solidification front moves only in the radial direction. The total melting time of PCM increases as the mass flow rate and inlet temperature of HTF decreases. A correlation is proposed for the dimensionless melting time in terms of Reynolds number and Stefan number of HTF. © 2013 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library (). DOI 10.1002/htj.21120 [ABSTRACT FROM AUTHOR]

SUMMARY A meshless numerical method is proposed for the solution of the transient bioheat equation in two and three dimensions. The Pennes bioheat equation is extended in order to incorporate water evaporation, tissue damage, and temperature-dependent tissue properties during tumor ablation. The conductivity of the tissue is not assumed constant but is treated as a local function to simulate local variability due to the existence of usually unclear interfacing of healthy and pathological segments. In this way, one avoids the need for accurate identification of the boundaries between pathological and healthy regions, which is a typical problem in medical practice, and sidesteps, evidently, the corresponding mathematical treatment of such boundaries, which is usually a tedious procedure with some inevitable degree of approximation. The numerical results of the new method for test applications of the bioheat transfer equation are validated against analytical predictions and predictions of other numerical methods. 3D simulations are presented that involve the modeling of tumor ablation and account for metabolic heat generation, blood perfusion, and heat ablation using realistic values for the various parameters. An evaluation of the effective medium approximation to homogenize conductivity fields for use with the bioheat equation is also provided. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

ABSTRACT Seasonally, snow-covered forests are a critical source of water in the Western United States and are subject to major disturbances, including fire, harvest, disease and insect-caused mortality, that have relatively unknown effects on water availability. In this study, we investigated changes in winter season snow accumulation and ablation in a forest following the Las Conchas fire in the Jemez Mountains of New Mexico. We investigated two competing sets of processes that should determine the peak annual snowpack prior to snowmelt: (1) reduced interception by forest canopy results in greater new snow accumulation and (2) increased winter season ablation of the snowpack results in reduced peak snowpack volumes. These processes were evaluated with approximately 800 spatially distributed manual observations of new snow, 1500 manual observations of peak snowpack, and light detection and ranging-derived snow depth, vegetation and terrain datasets collected prior to the fire. A single snowfall event yielded significantly larger snow depths in the post-burn area versus the unburned area ( p < 0.001), with 25% to 45% interception in the unburned area and near zero in the post-burn area. Conversely, the peak snowpack depths were significantly larger in the unburned area compared with the post-burn area (mean of 55 and 47 cm, respectively), despite nearly identical peak snowpacks prior to the fire (72 and 72 cm, respectively). The lack of strong vegetation controls led to less variability at peak snowpack in the post-burn area and a shift towards topographically controlled variability, caused by differences in elevation and aspect, occurring at larger spatial scales. The unburned area had roughly 10% more water available for melt than the post-burn area, with winter season ablation reducing snowpacks by nearly 50% prior to melt in the post-burn area. The relative importance of shortwave radiation to the snowpack energy balance and sublimation suggests that the 10% reductions in peak snow water storage found in these north-facing areas could be a conservative estimate for winter season ablation following fire. Further work is necessary to assess the role that topography plays in altering water partitioning following forest disturbance and the potential implications for ecological health and downstream water resources. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Viscous flow behavior of silica melts on an uncooled carbon/silicon carbide composite nozzle was investigated in the combustion environment of a liquid-fueled rocket engine simulated by an ethanol/oxygen combustion gas generator. The results showed that severe ablation of the nozzle throat were attributed to flow downstream and blow-off of the silica scales derived from vigorous oxidation of the silicon carbide matrix. The viscous flow behavior of the silica was determined by both the intrinsic viscosity of silica melts and the external aerodynamic forces of the combustion gas. [ABSTRACT FROM AUTHOR]

- We investigated three-dimensional structures of comet Wild 2 coma particle impact tracks using synchrotron radiation (SR) X-ray microtomography at SPring-8 to elucidate the nature of comet Wild 2 coma dust particles captured in aerogel by understanding the capture process. All tracks have a similar entrance morphology, indicating a common track formation process near the entrance by impact shock propagation irrespective of impactor materials. Distributions of elements along the tracks were simultaneously measured using SR-XRF. Iron is distributed throughout the tracks, but it tends to concentrate in the terminal grains and at the bottoms of bulbs. Based on these results, we propose an impact track formation process. We estimate the densities of cometary dust particles based on the hypothesis that the kinetic energy of impacting dust particles is proportional to the track volume. The density of 148 cometary dust particles we investigated ranges from 0.80 to 5.96 g cm−3 with an average of 1.01 (±0.25) g cm−3. Moreover, we suggest that less fragile crystalline particles account for approximately 5 vol% (20 wt%) of impacting particles. This value of crystalline particles corresponds to that of chondrules and CAIs, which were transported from the inner region of the solar system to the outer comet-forming region. Our results also suggest the presence of volatile components, such as organic material and perhaps ice, in some bulbous tracks (type-C). [ABSTRACT FROM AUTHOR]

C/ZrB2–SiC composites were fabricated by polymer infiltration and pyrolysis combined with slurry impregnation method. Three kinds of coating structures for these composites were applied in order to improve their ablation resistance: pure silicon carbide coatings, ZrB2–SiC mixture coatings, and ZrC–SiC alternating multilayer coatings. The ablation experiments were carried out on an oxyacetylene torch flame with a temperature of about 3000°C. The ZrC–SiC alternating multilayer showed the best ablation resistance. The linear erosion rate for ZrC–SiC alternating multilayer coatings is half of that for ZrB2–SiC mixture and pure SiC coatings. A model was put forward to account for such a result. [ABSTRACT FROM AUTHOR]

The ablation properties of a three-dimensional carbon/silicon carbide composite nozzle were investigated via hot-fire testing by an ethanol/oxygen combustion gas generator simulating combustion environments of the liquid rocket engine. The linear ablation rate at the nozzle throat was 0.250±0.023 mm/s, and the overall mass ablation rate was 0.246 kg/(m2 s). The ablation in the divergent section, convergent section, and in the regions near the throat grew severe by degree. Ablation mechanisms of the composite nozzle were predominated by the oxidation of the composite, and volatilization of the silica scale derived from oxidation of silicon carbide resulted in further ablation of the nozzle. [ABSTRACT FROM AUTHOR]

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The article presents a study which evaluated several testing methods for carbon-carbon (C-C) oxidation resistance on ultra-high temperature ceramic (UHTC) coatings. C-C composites that are used in aerospace applications exhibit poor oxidation resistance. Liquid precursors to UHTCs used to provide oxidation protection to C-C composites are tested by subjecting the coated composite to high temperatures and heat flux using different methods including solar energy testing and Oxyacetylene Ablation Testing.

A dual-purpose probe applicable both to permittivity measurements and ablation of biological materials has been developed. For these purposes, a planar-type open-ended coaxial probe was used as an applicator due to its capabilities of broadband permittivity measurements and near-field ablation. In order to maintain highly efficient power transfer during ablation, an impedance matching network is designed. To verify the dual-purpose probe, the complex permittivity of several biological materials was measured, and a block of pork muscle was ablated. As a result, permittivity measurements were successfully achieved nearly up to 20 GHz, and the surface temperature of pork muscle was raised up to 70°C with only 31 dBm of incident power at 18 GHz. [ABSTRACT FROM AUTHOR]

For hepatocellular carcinomas, radiofrequency ablation is extensively used to alleviate primary and metastatic hepatic tumours. Common complications of this procedure include bleeding, infection, and hollow organ perforation. We present the case of a patient with hepatoma who underwent radiofrequency ablation. He had intractable cough with yellowish sputum, particularly while lying down, three weeks after treatment. Chest computed tomography demonstrated a right middle lobe consolidation with pleural effusion and right subphrenic fluid collection. Thoracoscopic decortication was performed under the diagnosis of empyema. The attending anaesthesiologist noted bile‐like fluid aspirated from the endotracheal tube. Therefore, we suspected bronchobiliary fistula. Percutaneous transhepatic drainage of the subphrenic fluid and simultaneous cholangiography confirmed bronchobiliary fistula. The patient was successfully treated using percutaneous drainage combined with endoscopic retrograde biliary drainage. An imaging finding of subphrenic fluid collection with right lower lung consolidation after radiofrequency ablation for hepatic tumours should raise the suspicion of bronchobiliary fistula. Chest computed tomography demonstrated right middle lobe consolidation with pleural effusion and right‐side subphrenic fluid collection. Percutaneous transhepatic drainage of the subphrenic fluid and simultaneous cholangiography proved the bronchobiliary fistula. Percutaneous drainage combined with endoscopic retrograde biliary drainage successfully treated the patient. [ABSTRACT FROM AUTHOR]

Review: 52 refs. [ABSTRACT FROM AUTHOR]