Synergistic Effect Of Heat Research Articles

Interface/Dipole Polarized Antibiotics-Loaded Fe3O4/PB Nanoparticles for Non-Invasive Therapy of Osteomyelitis Under Medical Microwave Irradiation.

Due to their poor light penetration, photothermal therapy and photodynamic therapy are ineffective in treating deep tissue infections, such as osteomyelitis caused by Staphylococcus aureus (S. aureus). Here, a microwave (MW)-responsive magnetic targeting composite system consisting of ferric oxide (Fe3O4)/Prussian blue (PB) nanoparticles, gentamicin (Gent), and biodegradable poly(lactic-co-glycolic acid) (PLGA) is reported. The PLGA/Fe3O4/PB/Gent complex is used in combination with MW thermal therapy (MTT), MW dynamic therapy (MDT), and chemotherapy (CT) to treat acute osteomyelitis infected with S. aureus-infected. The powerful antibacterial effect of the PLGA/Fe3O4/PB/Gent is determined by the synergistic effects of heat and reactive oxygen species (ROS) generation by the Fe3O4/PB nanoparticles under MW irradiation and the effective release of Gent at the infection site via magnetic targeting. The antibacterial mechanism of the PLGA/Fe3O4/PB/Gent under MW irradiation is analyzed using bacterial transcriptome RNA sequencing. The MW heat and ROS reduce the activity of the protein transporters on the bacterial membrane, along with the transport of various ions and the acceleration of phosphate metabolism, which can lead to increased permeability of the bacterial membrane, damage the ribosome and DNA, and accompany the internal protein efflux of the bacteria, thus effectively killing the bacteria.

Effect modification of air pollution on the association between heat and mortality in five European countries

BackgroundEvidence suggests that air pollution modifies the association between heat and mortality. However, most studies have been conducted in cities without rural data. This time-series study examined potential effect modification of particulate matter (PM) and ozone (O3) on heat-related mortality using small-area data from five European countries, and explored the influence of area characteristics. MethodsWe obtained daily non-accidental death counts from both urban and rural areas in Norway, England and Wales, Germany, Italy, and the Attica region of Greece during the warm season (2000–2018). Daily mean temperatures and air pollutant concentrations were estimated by spatial-temporal models. Heat effect modification by air pollution was assessed in each small area by over-dispersed Poisson regression models with a tensor smoother between temperature and air pollution. We extracted temperature-mortality relationships at the 5th (low), 50th (medium), and 95th (high) percentiles of pollutant distributions. At each air pollution level, we estimated heat-related mortality for a temperature increase from the 75th to the 99th percentile. We applied random-effects meta-analysis to derive the country-specific and overall associations, and mixed-effects meta-regression to examine the influence of urban-rural and coastal typologies and greenness on the heat effect modification by air pollution. ResultsHeat-related mortality risks increased with higher PM levels, rising by 6.4% (95% CI: −2.0%–15.7%), 10.7% (2.6%–19.5%), and 14.1% (4.4%–24.6%) at low, medium, and high PM levels, respectively. This effect modification was consistent in urban and rural regions but more pronounced in non-coastal regions. In addition, heat-mortality associations were slightly stronger at high O3 levels, particularly in regions with low greenness. ConclusionOur analyses of both urban and rural data indicate that air pollution may intensify heat-related mortality, particularly in non-coastal and less green regions. The synergistic effect of heat and air pollution implies a potential pathway of reducing heat-related health impacts by improving air quality.

The synergistic effect of high temperature and relative humidity on non-accidental deaths at different urbanization levels

Numerous studies have examined the impact of temperature on mortality, yet research on the combined effect of temperature and humidity on non-accidental deaths remains limited. This study investigates the synergistic impact of high temperature and humidity on non-accidental deaths in China, assessing the influence of urban development and urbanization level. Utilizing the distributed lag nonlinear model (DLNM) of quasi-Poisson regression, we analyzed the relationship between Wet Bulb Globe Temperature (WBGT) and non-accidental deaths in 30 Chinese cities from 2010 to 2016, including Guangzhou during 2012–2016. We stratified temperature and humidity across these cities to evaluate the influence of varying humidity levels on deaths under high temperatures. Then, we graded the duration of heat and humidity in these cities to assess the impact of deaths with different durations. Additionally, the cities were categorized based on gross domestic product (GDP), and a vulnerability index was calculated to examine the impact of urban development and urbanization level on non-accidental deaths. Our findings reveal a pronounced synergistic effect of high temperature and humidity on non-accidental deaths, particularly at elevated humidity levels. The synergies of high temperature and humidity are extremely complex. Moreover, the longer the duration of high temperature and humidity, the higher the risk of non-accidental death. Furthermore, areas with higher urbanization exhibited lower relative risks (RR) associated with the synergistic effects of heat and humidity. Consequently, it is imperative to focus on damp-heat related mortality among vulnerable populations in less developed regions.

High‐strength unidirectional cellulose long filament‐reinforced polymer composite for structural engineering applications

AbstractGreen polymer composites that are strong and stiff are desirable across various engineering fields to replace synthetic plastics, hence meeting the requirements for net zero demands. Nanocellulose, a natural and abundant biopolymer, is a promising candidate for the engineering and designing of novel composites with strengths surpassing petroleum‐based derivatives. In this work, we demonstrate the fabrication of a high‐strength, environmentally friendly and hydrophobic biocomposite using a lignin‐based resin and wet‐spun unidirectional cellulose long filaments (CLFs) as reinforcements. The wet‐spun CLFs were knit in the conformation of unidirectional mats and infused with the green hydrogen‐bonded lignin resin to form the prepreg. The unidirectional prepreg was densified using hot pressing whereby the synergistic effect of heat and pressure and the post‐curing process impacted the biocomposite with unique, fascinating features, including excellent flexural strength (389.9 MPa), modulus (38.5 GPa), hydrophobicity (101.0°), antioxidant properties (93.1%), and superior thermal stability. Our design strategy dispenses new insights into engineering lightweight and strong cellulosic materials that can substitute unsustainable plastics used across various engineering fields. Future aspects of this biocomposite include structural and automotive engineering.Highlights All‐green and sustainable unidirectional polymer biocomposite is fabricated. The biocomposite achieves higher strength and modulus than that of plastics. It has outstanding thermal stability, hydrophobicity, and antioxidant properties. The biocomposite is suitable for the replacement of synthetic plastics.

Synergistic Strategies of Heat and Peroxyacetic Acid Disinfection Treatments for Salmonella Control.

The food industry has recognized a pressing need for highly effective disinfection protocols to decrease the risk of pathogen emergence and proliferation in food products. The integration of antimicrobial treatments in food production has occurred as a potential strategy to attain food items of superior quality with respect to microbiological safety and sensory attributes. This study aims to investigate the individual and synergistic effects of heat and peroxyacetic acid on the inactivation of bacterial cells, considering various contact times and environmental conditions. Four Salmonella serotypes, isolated from industrial meat production surfaces, were employed as model organisms. By systematically assessing the impacts of individual factors and synergistic outcomes, the effectiveness of bacterial cell inactivation and the efficiency of heat and peroxyacetic acid could be predicted. To better approximate real-world food processing conditions, this study also incorporated a bovine albumin-rich condition as a simulation of the presence of organic loads in processing steps. The findings revealed the essential need for a synergistic interplay of investigated parameters with the following optimized values: 1.5% concentration of peroxyacetic acid, temperature range of 60-65 °C, and contact time of 3 min for the complete effect regardless of the degree of contamination.

Synergistic effects of heat and carbon on sustainable urban development: Case study of the Wuhan Urban Agglomeration

The rapid pace of urbanization has resulted in pressing climatic challenges, notably an escalation in carbon emissions and rising urban temperatures. Urban expansion frequently coincides with heightened carbon emissions, releasing substantial quantities of greenhouse gases such as CO2. This exacerbates the urban heat island (UHI) effect and poses a threat to urban living conditions. To shed light on the intricate relationship between land surface temperature (LST) and carbon emissions and provide novel insights into the synergistic regulation of “heat” and “carbon” in sustainable urban development, we conducted an in-depth investigation of the Wuhan Urban Agglomeration spanning from 2003 to 2018. Employing data on impervious surface fraction (ISF), LST, and carbon emissions, we harnessed weighted center and standard deviation ellipse analyses to explore the spatiotemporal expansion patterns of ISF, LST, and carbon emissions. We examined the relationship between LST and carbon emissions using spatial correlation analysis. The results revealed that regions with high carbon emissions and elevated LST were predominantly concentrated in the central urban areas of each city, aligned with the distribution of high-density impervious surfaces. The weighted centers of ISF, LST, and carbon emissions exhibited a progressive shift toward the central region of Wuhan, intensifying spatial clustering effects. The global Moran's I index for LST and carbon emissions increased from 0.33 in 2003 to 0.48 in 2018, signifying a strong positive correlation between LST and carbon emissions. In the clustering maps of LST and carbon emissions, the high-high clustering trend persistently expanded, signifying a shift from “dispersion” to “agglomeration” in urban heat and carbon effects. In regions marked by consistent carbon emission growth, the correlation coefficient (R) between carbon emissions and LST was 0.4, and the Pearson coefficient was 0.64, both higher than those in areas with gradual carbon emission growth. Within stable carbon emission growth areas, every 0.1-ton increase in carbon emissions has a 40% probability of a 1.33 °C temperature rise. As the rate of carbon emissions increased, the positive synergistic effect between carbon emissions and LST continued to increase. This study provides empirical support and academic groundwork to reduce urban emissions and mitigate the effects of UHIs.

Temperature-entropy and energy utilization diagrams for energy, exergy, and energy level analysis in solar water splitting reactions

Solar hydrogen production by water splitting reaction is an important route to realize the storage of solar energy. The involvement of light and chemical energy can reduce the high reaction temperature of direct thermochemical water splitting reactions, but the pivotal issues such as energy, exergy, and energy level relationships behind the temperature reduction remain under-researched. A graphic analysis of water splitting reactions using the temperature-entropy and energy utilization diagrams is proposed to research the energy, exergy, and energy level relationships. The energy composition and conversion mechanisms with the light and chemical energy are presented in the diagrams by comparing with direct thermochemical water splitting reactions. Three cases, including the photocatalytic, photo-thermochemical, and methane steam reforming reactions, are studied to explain the effect of light, the synergistic effect of heat and light, and the effect of chemical energy in reducing the temperature of water splitting reactions. The energy levels of light and methane are higher than those of hydrogen, thus lowering the energy level of heat and reducing reaction temperatures. The discovery of the energy level required for hydrogen production will provide guidance for reducing its temperature.

Ultra-lean dynamics of holder-stabilized hydrogen-enriched flames in a preheated mesoscale combustor near the laminar critical limit

This work experimentally investigates the ultra-lean dynamics of a 40% H2–60% CH4 flame near the laminar critical limit in a preheated mesoscale combustor with a flame holder. These experiments are conducted to verify a conjecture we proposed in a previous publication and reveal the ultra-lean flame dynamics under the synergistic effects of heat and flow recirculation. Notably, not only is our conjecture confirmed, but also some novel flame behaviors are found. As the equivalence ratio ϕ is decreased from 0.500 to 0.320, the conventional stable flame, stable residual flame, periodic residual flame with repetitive local extinction and re-ignition (periodic RFRER), and periodic oscillating residual flame are observed in sequence. For the stable residual flame (0.370 ≥ ϕ ≥ 0.355), the left and right flame roots reside directly behind the flame holder, and the flame tip stays near the combustor exit. For the periodic RFRER (0.350 ≥ ϕ ≥ 0.340), observed experimentally for the first time, the flame roots reside at almost the same location, but the flame tip oscillates up and down over time with pinch-off events. For the periodic oscillating residual flame (0.335 ≥ ϕ ≥ 0.320), found for the first time, the stable flame roots also reside at almost the same location, but the residual flame tip oscillates up and down over time without a pinch-off event. When ϕ decreases to 0.315, the oscillating residual flame extinguishes, and its blow-off dynamics are revealed in detail.

High-throughput profiling volatiles in edible oils by cooling assisted solid-phase microextraction technique for sensitive discrimination of edible oils adulteration

In this study, a cooling assisted solid-phase microextraction technique (CA-SPME) was proposed and used for identifying volatile and semi-volatile compounds in edible oil innovatively coupled to gas chromatography-mass spectrometry. Compared with regular SPME technique, CA-SPME presented significantly higher extraction efficiencies for analytes in edible oil due to its synergistic effect of heating and cooling. After optimization of the extraction conditions including heating temperature, cooling temperature, extraction time, and added amount of edible oil, thirty-eight, thirty-six, twenty-nine, and thirty-three kinds of compounds in peanut oil, olive oil, canola oil, and soybean oil were successfully identified, respectively, using DVB/CAR/PDMS coating with extraction time of 30 min and edible oil amounts of 20 μL. Principal component analysis, partial least squares discriminant analysis, and hierarchical clustering analysis (HCA) were performed to evaluate the potential of proposed method in discriminating edible oils adulteration (peanut oil adulterated with canola oil, peanut oil adulterated with soybean oil, olive oil adulterated with canola oil) subsequently. Results demonstrated that the method was useful in successful discrimination of pure and adulterated edible oils with adulteration percentages ranging from 0.5 to 10%. Furthermore, volatiles contributing to classifications between pure and adulterated edible oils were also illustrated based on variable importance for the projection analysis and distributions of volatiles in HCA heatmaps. The proposed method provided a novel strategy for sensitive detection of edible oil adulteration without any other sample pretreatment.

Mechanisms of heat and hypoxia defense in hard clam: Insights from transcriptome analysis

With global changes and anthropogenic activities, heat and hypoxia have become frequent stressors in aquatic environments. However, the molecular defense mechanisms of aquatic organisms, especially bivalves, against the synergistic effects of heat and hypoxia have not been fully elucidated. In this study, we analyzed transcriptomic data of the gills of Mercenaria mercenaria, an economically and ecologically important bivalve, under several stress challenges: high temperature (heat), low dissolved oxygen (hypoxia), and heat plus hypoxia. GO and KEGG enrichment analyses were performed on the differentially expressed gene sets of heat-induced genes under various dissolved oxygen (DO) solubilities, hypoxia-induced genes under different (normal and high) temperatures and common heat plus hypoxia stress-induced genes. We found that protein-folding item was significantly enriched in common differentially expressed heat-induced genes comparisons, with a high expression of molecular chaperones HSP90 and TCP1. Moreover, microtubule-related GO terms were significantly enriched in differentially expressed hypoxia-induced genes under different temperatures, and kinesin and dynein-related genes were commonly upregulated in the hypoxia challenge groups. Protein processing in endoplasmic reticulum and ubiquitin-mediated proteolysis were the most significantly enriched pathways in common heat plus hypoxia stress-induced genes. Furthermore, correctly-folding related genes, luminal chaperones, and ER-associated degradation related genes were upregulated under heat plus hypoxia stresses. Altogether, our results provided new insights on understanding the molecular defense mechanisms against heat and hypoxia stress in hard clams.

Hotter droughts alter resource allocation to chemical defenses in pi\xf1on pine

Heat and drought affect plant chemical defenses and thereby plant susceptibility to pests and pathogens. Monoterpenes are of particular importance for conifers as they play critical roles in defense against bark beetles. To date, work seeking to understand the impacts of heat and drought on monoterpenes has primarily focused on young potted seedlings, leaving it unclear how older age classes that are more vulnerable to bark beetles might respond to stress. Furthermore, we lack a clear picture of what carbon resources might be prioritized to support monoterpene synthesis under drought stress. To address this, we measured needle and woody tissue monoterpene concentrations and physiological variables simultaneously from mature piñon pines (Pinus edulis) from a unique temperature and drought manipulation field experiment. While heat had no effect on total monoterpene concentrations, trees under combined heat and drought stress exhibited ~ 85% and 35% increases in needle and woody tissue, respectively, over multiple years. Plant physiological variables like maximum photosynthesis each explained less than 10% of the variation in total monoterpenes for both tissue types while starch and glucose + fructose measured 1-month prior explained ~ 45% and 60% of the variation in woody tissue total monoterpene concentrations. Although total monoterpenes increased under combined stress, some key monoterpenes with known roles in bark beetle ecology decreased. These shifts may make trees more favorable for bark beetle attack rather than well defended, which one might conclude if only considering total monoterpene concentrations. Our results point to cumulative and synergistic effects of heat and drought that may reprioritize carbon allocation of specific non-structural carbohydrates toward defense.

Synergistic bactericidal nanofibers with photothermal controlled release of antibiotics triggered by near infrared

Herein, a type of nanofibrous membrane was prepared by co-electrospinning of polycaprolactone, poly(methyl methacrylate), polyaniline, and roxithromycin. The temperature of the nanofibers increased by 20 °C with 1 min of near infrared (NIR) radiation, and then the drug release was accelerated significantly. The bactericidal rate toward Staphylococcus aureus reached 99% with the synergistic effect of heat and antibiotics. This study provides a new approach to solving the problem of bacterial resistance by synergistic strategies involving photothermal and on-demand release of drugs.

Trapped radical behavior of electron beam irradiated polytetrafluoroethylene fine powder at various temperatures

Polytetrafluoroethylene (PTFE) fine powder with 93% crystallinity was irradiated by an electron beam (EB) at various temperatures under a nitrogen atmosphere. Trapped free radicals in PTFE were studied using electron spin resonance (ESR) spectroscopy. The observed spectra of the samples exposed to air after irradiation at various temperatures showed asymmetrical signals, which are middle-chain type peroxide macroradicals derived from fluoroalkyl radicals. The radical yields at each irradiation temperature increased with increasing absorbed dose, and eventually saturated. The higher irradiation temperature resulted in higher radical yields when compared at the same exposed dose. Furthermore, the G-value of the radicals (G(R·)) increases with increasing irradiation temperatures corresponding to each relaxation and transition temperature. It is concluded that the chain reaction by the fluorine extraction from the main chain due to the end-chain radical generated via β-scission after dissociative electron attachment (DEA) is enhanced by the synergistic effect of heat and radiation.

Anomalous blow-off behavior of a holder-stabilized premixed flame in a preheated mesoscale combustor

The present study investigates the blow-off limits of a laminar methane–air premixed flame under the synergistic effect of heat and flow recirculation by means of experimentation and three-dimensional numerical simulation. An anomalous blow-off phenomenon (the blow-off limit decreases with the decrease in Reynolds number (Re)) is experimentally observed and reproduced via simulation. First, the flame base structures for various Re values are studied. Subsequently, the underlying mechanisms are revealed in terms of flow field, stretch effect, preferential transport effect, and conjugate heat transfer. The main causes of the present anomalous blow-off phenomenon are the flow recirculation effect, preferential transport effect, and conjugate heat transfer, rather than the stretch effect. Specifically, a weaker flow recirculation effect, a weaker preferential transport effect, a larger heat loss ratio from the combustor to the ambient environment, and a lower preheated temperature of the fresh mixture altogether lead to a smaller blow-off limit at a smaller Re. In addition, the sharp reductions in both the local equivalence ratio and preheated temperature of the fresh fuel-oxidizer mixture explain why the blow-off limit sharply decreases from Re = 80 to 40. This work offers insights into flame blow-off behaviors under the synergistic effect of heat and flow recirculation in many practical combustors.

Ultra-lean blow-off dynamics of a holder-stabilized premixed flame in a preheated mesoscale combustor near laminar critical condition

The present work experimentally illustrates and analyzes the ultra-lean flame blow-off dynamics near laminar critical condition under the synergistic effect of heat and flow recirculation which exists in many practical combustors (such as aero-engine). The results indicate that the flame blow-off process can be divided into three stages at Reynolds number Re = 240. In the first stage, the flame initially becomes thinner over time. In the second stage, the residual flame with repetitive local extinction and re-ignition (RFRER) appears (the second stage), which is experimentally found for the first time for the methane/air premixed mixture of Lewis number Le = 1.0. The analysis indicates that the local extinction of the flame is mainly caused by the stretch effect on two sides. In the final stage, the residual flame with oscillation appears. The oscillating residual flame is finally carried convectively upstream and extinguishes within the recirculation zone as the present Lewis number effect is small. The analysis also indicates that the residual flame of hydrocarbon fuel cannot be maintained, but this issue can be solved via adding enough fast-diffusing species (such as hydrogen). This mechanism for suppressing or preventing the local extinction of the residual flame may be also suitable for the turbulent flames in many practical combustors. The present study provides the theoretical basis for predicting the flame status and suppressing the unstable flames at extreme operating conditions.

Laminar non-premixed flame patterns in compact micro disc-combustor with annular step and radial preheated channel

The study presents the laminar methane-air non-premixed flame patterns under the synergistic effect of heat and flow recirculation in a radial microchannel, as obtained through a numerical simulation. A regime diagram of the flame behaviors for various operating conditions was obtained. It was observed that the flame always remained stable until it was extinguished, which implies that the flame stability was strong. In addition, the flame patterns at small, moderate, and large Reynolds numbers (Re) were revealed. For a small Re, the flame could be well-anchored in a very upstream channel at a large global equivalence ratio (ϕ). At a moderate ϕ, the upstream part of the flame was anchored by a minor recirculation zone (RZ) near the inlet of the combustion chamber. At a small ϕ (i.e., 0.6), the flame became completely flat, and its upstream part was anchored by the major RZ behind the annular step. For a moderate Re, the flame roots were remarkably anchored by the minor and/or major RZs. For a large Re, for the first time. It was observed that the whole stable flame split into two parts in the radial channel at ϕ = 0.8 and 0.7, namely the upstream minor flame engulfed in the minor RZ and the downstream major flame anchored by the major RZ. However, when ϕ was further decreased to 0.6, the minor flame was extinguished and only the large major flame existed. The transformation mechanism of the aforementioned flame behaviors was also revealed in detail. Furthermore, this study has yielded abundant information on flame patterns in the current radial microchannel with the annular step and the radial preheated channel, which could help us gain further insights into the flame propagation characteristics in a radial channel.

Ultra-rich fuel dynamics of a holder-stabilized premixed flame in a preheated mesoscale combustor

The present work experimentally studies the laminar premixed flame dynamics at fuel ultra-rich condition under the synergistic effect of heat and flow recirculation, which take place in many practical combustors, such as aero engines. The normal, anomalous, and low speed blow-off phenomena are observed. Furthermore, the anomalous standoff distance between the flame root and the holder is found for the first time at fuel rich condition. Interestingly, with an increase in the equivalence ratio, the oscillating flame appears before blow-off at Reynolds number Re ≥ 60. The stability limit first increases and then decreases with a decrease in Re, which is also reported for the first time. If the equivalence ratio is increased further, the oscillating flame at Re ≥ 60 blows off with a small timescale, while the stable flame at Re < 60 gradually acquires a flat behavior, and then shifts downstream at a very slow speed.

Determination of Ferulic Acid in Angelica sinensis by Temperature-Controlled Hydrophobic Ionic Liquids-Based Ultrasound/Heating-Assisted Extraction Coupled with High Performance Liquid Chromatography.

Hydrophilic ionic liquids are often used to extract the active ingredients of medicinal plants, while hydrophobic ionic liquids are rarely used to directly extract solid samples. In this paper, a simple, novel and efficient temperature-controlled hydrophobic ionic liquids-based ultrasound/heating-assisted extraction (TC-ILs-UHAE) procedure coupled with high-performance liquid chromatography (HPLC) was developed and applied to the determination of ferulic acid (FA) in Chinese herbal medicine Angelica sinensis. During the extraction procedure, hydrophobic ionic liquids (ILs) were dispersed into water to form cloudy solution (fine droplets) with the aid of ultrasound and heating simultaneous. After extraction, phase separation was easily achieved by centrifuging at 0 °C. Among all ILs used, 1-butyl-3-methylimidazolium bis(trifluoromethanesulphonyl)imide ([C4mim]NTf2) exhibited the highest extraction ability and the possible extraction mechanism was discussed. Additionally, the synergistic effect of heating and ultrasound on the extraction efficiency was investigated. Under the optimized conditions, a good linearity was observed with correlation coefficient (r) of 0.9995. The limit of detection of FA (LOD, S/N = 3) was 9.6 µg/L and the spiked recoveries of FA for real samples were in the range of 91.67 to 102.00% with relative standard deviation (RSD) lower than 3.87%. Compared with the traditional extraction methods, the proposed method gave the highest yield of FA and had the shortest extraction time. Therefore, this method is a potential simple, green and highly efficient technique and expected to be applied to the extraction of other bioactive ingredients in medicinal plants.

Numerical investigation of the local extinction and re-ignition mechanisms of premixed flame in a micro combustor with a flame holder and preheating channels

A novel combustor with a flame holder and preheating channels, which takes advantage of heat and flow recirculation, was developed to improve the stability of the micro flame in our previous work. The results demonstrated that the lean methane/air premixed flame could be stabilized within a wide operating range. Certainly, the flame blows off when the equivalence ratio of the fuel mixture becomes too small or too big or the Reynolds number is too large. The present work reports and analyzes the blow-off dynamics of a methane/air laminar premixed flame at a relatively large Reynolds number under the synergistic effect of heat and flow recirculation. Interestingly, a flame with local extinction and re-ignition appears, which is first found in the micro combustor. The underlying mechanisms of this interesting phenomenon are systematically discussed in terms of the flow recirculation effect, stretch effect, conjugate heat exchange, and preferential transport effect. We find that the counter flow in the recirculation zone and stretch effect induce the local extinction of the flame. The smaller heat loss from the residual flame to the flame holder and the better preferential transport effect contribute to the re-ignition of the fuel mixture. The preheating effect on the unburned fuel mixture is not expected to be insignificant for the local extinction and re-ignition phenomenon. These results mean that the generated mechanism of the flame with local extinction and re-ignition in the micro combustor is different from that in the conventional combustors.

Sanitization of packaging and machineries in the food industry: Effect of hydrogen peroxide on ascospores and conidia of filamentous fungi

In the food industry, sterilization of packaging and filling machines by hydrogen peroxide (HP) is a widespread practice. Its effectiveness is usually tested by means of inactivation tests on selected test microorganisms that were any case chosen without taking into account that food products could be also spoiled by microorganisms presumably resistant to HP. For this reason, the aim of this work was to assess the resistance of different ascospore-forming moulds (Talaromyces bacillisporus, Aspergillus hiratsukae, Chaetomium globosum) to HP, in order to find the most resistant to this kind of chemical stress, and to compare their resistance with that registered for other moulds, including test microorganism Aspergillus brasiliensis ATCC 16404. Tests were carried out from 50 to 60 °C on spores or conidia, depending on the strain, either by immersing inoculated strips (aluminium, tin-plate, HDPE, PET) in HP, or by directly inoculating cells in the sanitizing medium. In both tests, T. bacillisporus proved the most resistant strain, followed by A. hiratsukae, C. globosum and A. brasiliensis at all temperatures tested. In test without a supporting material, D values of T. bacillisporus varied from 6 to 23 s. In test with metallic or plastic strips, D values of T. bacillisporus were higher on plastic materials, compared to those obtained on metallic ones up to 53 °C, whereas at higher temperatures D values proved similar. For A. hiratsukae, D values were similar if different materials were compared, except for D50 on aluminium and HDPE, which proved slightly higher (3.1–3.4 s) than those obtained on tin-plate and PET (2.7–2.8 s). Analogously, ascospores of C. globosum behaved in a similar way if different materials were compared, except for D50 values that varied in a wide range (from 2.9 s on tin-plate to 4.0 s on HDPE). A. brasiliensis was rapidly inactivated by the synergistic effect of heat and hydrogen peroxide, so for this strain it was not possible to calculate any D value. Based on the results obtained in this paper, tested ascospore-forming moulds proved to be sensibly more resistant to HP than other heat-sensitive strains tested, their D values always being significantly higher, regardless of the strain considered and the supporting material assessed. Ascospore-forming moulds could be furtherly investigated, as for practical purposes they seemed most suitable as target microorganisms than heat-sensitive microorganisms such as Aspergillus brasiliensis ATCC 16404, their use during bio-validations of sanitizing processes on machineries used for refrigerated products (pH > 4.5) or non-refrigerated acid products (pH ≤ 4.5) leading to more performing results.