Conditions Of Low Oxygen Concentration Research Articles

Experimental study on the fragmentation behavior of coal particles during gasification process in drop-tube furnace

Studying the fragmentation characteristics of coal particles is important for enhancing furnace gasification efficiency. Based on the processing method of visualization imaging technology, this study investigated the proportion of particle fragmentation, fragmentation mode, surface temperature, and other characteristics of the Fuhua Indonesian Coal (FIC) gasification process at different temperatures and oxygen concentrations in a drop-tube furnace. The results show that the proportion of fragmentation at the center was higher than the proportion of fragmentation at the outer zone under experimental conditions. The most significant difference between the two phenomena was the length of the fragmentation period and the overall structural changes. The proportion of fragmentation at the center positively correlated with an increase in temperature and negatively correlated with an increase in oxygen concentration. Under high-temperature and low-oxygen concentration conditions, FIC tends to be in the high fragmentation mode. The temperature at the time of FIC fragmentation increased with increasing particle size. Compared with the temperature, the change in oxygen concentration had a more remarkable effect on the fragmentation temperature, specifically in the outer zone. Elevating the oxygen concentration and temperature both promoted particle fragmentation. Temperature had a greater effect on fragmentation in the outer zone, while fragmentation at the center was more sensitive to changes in oxygen concentration.

Effect of oxygen concentration on the split injection combustion process of diesel spray injected into 2D piston cavity

The exhaust gas recirculation (EGR) technique effectively reduces NOx emissions, and the split injection can lower engine emissions. There is little research on the formation and oxidation of soot during fuel combustion by combining EGR and split injection. Therefore, the effect of oxygen concentration on the split injection strategies' flame characteristics was investigated by analyzing the integrated KL factor, the mean flame temperature, and the soot evolution. The experiment combines various conditions of single main injection, double main injection, high injection pressure, and low injection pressure, with pre-injection and without pre-injection, to discuss the influence of oxygen concentration on combustion characteristics. The 2D piston cavity has been used to form the impingement spray flame, and the two-color method has been used to analyze the combustion characteristics. Results reveal that there will not be fuel accumulation along the cavity groove between the first and the second main injection under low oxygen concentration with pre-injection conditions. Pre-injection reduces the soot oxidation rate under double main injection with low oxygen concentration. The ignition timing of the first main injection under double main injection with pre-injection conditions occurred in advance, even under low oxygen concentration conditions. The effect of oxygen concentration on the total flame area is not as significant as that of pre-injection or without pre-injection conditions. Considering all conditions, split injection (D160_50:50) without pre-injection has higher soot oxidation rate under 15% O2. The injection strategy (S160) without pre-injection can minimize soot and NOx emissions at a concentration of 15% O2.

Experimental study on coal combustion by using the ilmenite ore as active bed material in a 0.3 MWth circulating fluidized bed

The oxygen-carrier aided combustion (OCAC) technology which improves the uniformity of oxygen distribution in the fluidized bed and subsequently enhances the combustion efficiency has attracted more and more attention. However, the existing studies on OCAC mainly focused on the combustion of methane or biomass. There were few studies on low-volatile fuels (such as coal), especially pilot-scale studies that have not been reported. In this work, the effectiveness of OCAC technology on coal combustion has been comprehensively evaluated in a 0.3 MWth pilot-scale circulating fluidized bed (CFB) combustor. The experimental parameters including oxygen carrier (OC) proportion, primary air ratio (A) and oxygen concentration have been carefully investigated. The CO, NOx, SO2 and particulate matter (PM) were measured in real-time from the outlet of the cyclone separator by a gas analyzer and electrical low pressure impactor (ELPI). The results showed that the CO emission from the exit of the cyclone was reduced when the inert bed materials were replaced with the ilmenite ore, especially under the conditions of low oxygen concentration and A. The OCAC technology exhibited good thermal buffering capacity and oxygen buffering capacity. Compared to sand as bed material, the SO2 and NOx emission in flue gas under OCAC decreased and increased, respectively, which is attributed to the more uniform oxygen distribution with more available oxygen in the combustor. Such properties also promoted the self-desulfurization reaction of coal ash. However, it also reduces the reducibility area in the combustor and thus weakens the reduction of NOx. Compared to the sand case, the PM emission under OCAC case is more diminutive, especially in the size of 0–0.4 μm, the PM concentration under OCAC case is much lower than that under sand case.

Role of Epigenetic Mechanisms in Regulating the Activity of 2-OGDH and MDH in Maize Leaves (Zea mays L.) during Hypoxia

Molecular and epigenetic ways of regulating the activity of key TCA enzymes, 2-oxoglutarate dehydrogenase (2-OGDH) and malate dehydrogenase (MDH), in maize (Zea mays L.) leaves under hypoxic conditions were studied. It has been shown that regulation of the rate of enzyme functioning under stress conditions is caused not by conformational transformations of protein molecules but by changes in the transcriptional activity of their genes. Analysis into the level of transcripts of genes encoding 2-OGDH and MDH revealed a correlation with changes in the total enzymatic activity. When plants were incubated under hypoxic conditions, a decrease in the expression of the 2-OGDH and MDH genes was observed. It was found that fluctuations in the content of gene transcripts ogdh-1 and ogdh-3 is associated with a change in the methyl status of CG-dinucleotides in their promoters. An increase in the expression of these genes is associated with a decrease in the degree of methylation of their promoters. Conversely, a decrease in the relative level of transcripts is caused by an increase in the amount of methylated CG-dinucleotides. It is concluded that regulating the functioning of 2-oxoglutarate dehydrogenase and malate dehydrogenase under conditions of low oxygen concentrations takes place by means of an epigenetic mechanism, that is, by changing the methyl status of their gene promoters.

Experimental study on in-situ denitration using catalyst in fluidized bed reactor

This work proposed a process route for in-situ denitration in circulating fluidized bed (CFB) reactor through adding catalyst, and the feasibility has been verified through a bubbling FB reactor, a 6 kWth FB combustor and a 75 t/h CFB boiler. The effect of bed temperature, atmosphere and addition amount of catalyst on NO conversion rate were studied in the bubbling FB reactor. It was found that the increasing bed temperature, CO concentration and addition amount of catalyst can enhance the conversion efficiency of NO, and increasing concentration of SO2 and H2O have the opposite effect. The results from 20 h test suggested that a high SO2 and H2O atmosphere did not deactivate the catalyst. The continuous combustion experiments on a 6 kWth FB combustor showed that the catalyst addition not only can significant reduce NOx emission (>20%, even under conditions of low oxygen concentration and low ratio of primary air), but also does not have any adverse effect on the combustion characteristics. Similar results were also obtained from the 75 t/h CFB boiler. It was also found in the industrial scale tests that the addition of catalysts combined with the use of SNCR system would achieve better denitration effects.

Optical study on spray combustion characteristics of PODE/diesel blends in different ambient conditions

Polyoxymethylene dimethyl ethers (PODE) have been reported as a promising alternative fuel for the potential to reduce soot, CO and HC emissions of the diesel engine and improve the engine performance of gasoline compression ignition and dual-fuel engines. However, the fundamental data of spray and combustion characteristics of fuels with PODE are still deficient. In this study, the ignition delay, flame lift-off length (LOL) and soot distribution of diesel/PODE blends with PODE volume fraction of 0–100% were studied using high-speed OH chemiluminescence and planar laser-induced incandescence under different ambient temperature and oxygen concentration conditions. Results show that the ignition delay decreases and the flame LOL increases with the increase in PODE content. The increase in LOL is more distinct in lower ambient temperature conditions, whereas the decrease in ignition delay is relatively larger in higher temperature and lower oxygen concentration conditions. The total soot amount in the tested region decreases more than 50% and 95% when PODE volume fraction reaches 20% and 50%, respectively. When the PODE fraction is larger than 50%, nearly no soot can be observed in all the tested cases. The influence of PODE on soot reduction is more significant in higher ambient oxygen concentration and lower ambient temperature conditions. The soot distribution profile of the soot shows that the addition of PODE can not only reduce the soot formation but also accelerate the soot oxidation.

Mathematical modeling of regeneration of coked Cr-Mg catalyst in fixed bed reactors

On the base of two-dimensional (bed length and pellet radius coordinates) two-temperature (gas and catalyst phases) mathematical model the coked CrF3/MgF2 catalyst regeneration process in the adiabatic reactor of gas-phase perchloroethylene hydrofluorination to pentafluoroethane (Freon 125) is studied. The parameters of the mathematical model such as coke burning rate constant, temperature of the coke burning beginning T* (ignition point), heat of the reaction and activation energy were determined from experiments in lab-scale reactor and from the thermal analysis data. The influence of process parameters, e.g. oxygen and coke concentrations, initial gas and catalyst temperatures and pellet size was investigated. The simulation was carried out under conditions of low oxygen concentration (oxygen shortage) and showed that if the inlet gas temperature Tgo is lower than initial catalyst temperature Tp0 (Tgo<Tp0, Tpo≥T*), the coke burning occurs only near the outer surface of catalyst pellet, because the bed is “cooled” by the inlet gas flow. This leads to the dramatic rise of temperature in a narrow “peak burning wave” and to an unexpected bed overheating that exceeds the adiabatic heating. This effect was not discussed in publications but was detected in industrial reactor during the coked chromium–magnesium catalyst regeneration. This result is very significant for industrial applications since it helps to avoid the catalyst overheating and the following catalyst activity decreasing during the regeneration.

Ignition and combustion characteristics of coal particles under high-temperature and low-oxygen environments mimicking MILD oxy-coal combustion conditions

The experiments of coal particles combustion were conducted to mimic moderate and intense low-oxygen dilution (MILD) oxy-coal combustion on a diffusion-flamelet-based Hencken burner under different O2/CO2 and O2/N2 environments with the coflow temperatures of 1400–1800 K and oxygen concentrations of 5%–20%. The images of coal particles combustion flame were captured by a digital camera to determine the ignition standoff distances of coal particles. The radiation spectrums of burning coal particles at different coflow temperatures and oxygen concentrations were measured by a fiber optic spectrometer and the temperatures of burning coal particles were deduced with the two-color method. It is found that either increasing the coflow temperature or the oxygen concentration leads to brighter flame luminosity, shorter ignition standoff distance and higher burning particles temperature. The ignition standoff distance of coal particles is increased by 0.07–0.49 cm when carbon dioxide is used as diluent gas instead of nitrogen. The temperatures of the burning coal particles under O2/CO2 environments are lower by 51–185 K than those under O2/N2 environments at the same conditions due to the combined physicochemical properties of CO2 with higher heat capacity and the endothermic reaction of char gasification. Moreover, a method based on the coal particles temperature uniformity coefficient is proposed to quantitatively identify the combustion modes of MILD coal combustion and MILD oxy-coal combustion. All coal combustion flames are visible under both O2/CO2 and O2/N2 environments, and the MILD coal combustion flames under high-temperature and low-oxygen concentration conditions are weaker and more uniform with dark red color.

Effects of oxygen concentrations on the ignition and quasi-steady processes of n-heptane spray flames using large eddy simulation

Exhaust Gas Recirculation (EGR) is a frequently used technique to reduce the production of NOx. The effect of EGR on the early flame evolution, two-stage ignition process and spray flame structures for n-heptane spray flames are investigated using large eddy simulation. The two-stage ignition process is identified based on the formation of key species and early heat release process. Results demonstrate that a longer ignition delay (ID) and flame lift-off length (LOL) under lower oxygen concentration conditions could increase the mixing time for fuel and air. However, the first-stage ignition still initiates in fuel-richer regions for the cases with higher EGR rates due to the lack of oxygen. In contrast, compared to the case with the same initial oxygen content but at a higher gas temperature of 1000 K, the first-stage ignition moves to stoichiometric mixture fraction regions at 900 K. The combustion mode analysis based on hydroxyl and formaldehyde is conducted to distinguish between the low- and high-temperature combustion regions. Most importantly, to study the stabilization mechanism, the chemical explosive mode analysis (CEMA) is conducted based on analysis on the local flow time scale and the chemical time scale. During the early stage of ignition, a balance between reaction and mixing implies that cool flame propagates from the ignition spots through the entire flow field. And during the quasi-steady state, autoignition plays a dominant role.

In situ FTIR study on real-time changes of active groups during lignite reaction under low oxygen concentration conditions

Coal spontaneous combustion is essentially the reaction of active groups, which usually occurs in low oxygen atmospheres. This paper studied the real-time changes of active groups during coal reaction at low oxygen concentrations by in situ FTIR. The results show that the active groups have different reactive activities and changing trends, i.e. continuously increase, continuously decrease, decrease at first and then increase. Both the quantity and changing trends are influenced by oxygen supply. The oxygen-containing groups having small reactive activity increase with temperature rise. The active groups having large reactive activity have two vibrational types. The bending vibration groups change with temperature rise as the same style, while the stretching vibration ones change in different styles. For the same group, the quantity and reactive activity of stretching vibration ones are greater than bending vibration ones. The active groups still can react with oxygen even under an oxygen atmosphere of 5%, but pyrolysis is the main reaction form under this condition. It will provide active groups or sites for coal self-heating. Therefore, it's better to control the oxygen concentration below 5% for fire prevention. The results will be helpful for further understanding the mechanism of coal self-heating.

Ignition and combustion characteristics of n-pentanol–diesel blends in a constant volume chamber

Pentanol is considered as one of the most promising alternative biofuels due to its excellent physicochemical properties. The objective of this work was to compare the ignition and combustion characteristics of different n-pentanol/diesel blends in an optical constant volume combustion chamber. The tested fuels included 20% (D80P20) and 40% (D60P40) of n-pentanol blended with diesel in volume, and pure diesel (D100). Broadband chemiluminescence technique was used to measure the timing and location of spray ignition. A high-speed CCD camera with two ND8 dimmer lenses was used to capture the incandescence radiated from the soot particles during combustion. A wide range of experimental conditions was investigated. The ambient temperature ranged from 800K to 1200K and the oxygen concentration ranging from 10% to 21%, covering both the conventional and low temperature combustion regimes. The results show that pure diesel has shorter ignition delay and distance comparing to pentanol blends. A larger blending proportion of pentanol D60P40 advances the ignition phase more than the D80P20 in low oxygen concentration conditions. Due to the fuel-borne oxygen and the dilution effect, the natural flame luminosity is reduced significantly with the increase of pentanol ratio in most conditions except under the intermediate temperature region of 1000K. In that condition, the shorter ignition delay and flame lift-off length of pentanol blends cause a slightly increase in the natural flame luminosity. The natural flame luminosity images showed that the oxygen-contained structure of pentanol could accelerate soot oxidation under all conditions. This indicates that pentanol blends could decrease final soot emissions in internal combustion engines.

Thermodynamic characteristics of coal reaction under low oxygen concentration conditions

In order to further understand the characteristics of coal reaction under low oxygen concentration atmosphere, this study tested the thermodynamic characteristics during reaction processes under low oxygen concentrations. The kinetic factors were also analyzed based on testing results. The results show that there are some characteristic temperatures during coal spontaneous combustion and the influences of oxygen concentration on these temperatures are different. The influences of oxygen concentration on the mechanism function and kinetic parameters depend on the coal ranks and the reaction stages. They are different at different reaction stages for the same coal, and at the same reaction stage for different coals. This phenomenon is essentially resulted from the different influences of oxygen concentration on the micro reaction sequences during coal spontaneous combustion. The study will be helpful for further understanding of the actual development process of coal spontaneous combustion.

Optical soot measurement of bio-butanol upstream product, ABE (Acetone–Butanol–Ethanol), under diesel-like conditions

ABE (Acetone–Butanol–Ethanol), the upstream product of bio-butanol, is considered as a promising alternative fuel for IC engine. Two-dimensional soot distribution and soot mass of spray combustion of ABE and diesel was measured by forward illumination light extinction (FILE) technology. The ambient temperature and oxygen concentration of injection was varied from 1200K to 900K and 21% to 11% to represent normal temperature combustion and low temperature combustion modes respectively. It was found that soot distribution area and intensity of ABE, especially ABE with a high acetone fraction, is much lower than that of diesel. The soot clouds area and intensity increase with increasing ambient temperature and decreasing oxygen concentration, but the increased scale of soot for ABE is much lower than that of diesel. Quantitative results of soot mass for ABE show that the soot increases rapidly with increasing ambient temperature at lower oxygen concentration conditions because the soot producing rate is largely increased when elevating temperature, while the soot oxidation rate remained slow due to the insufficient oxygen. Based on analysis, it was found that clean combustion of ABE benefited from a lean air–fuel mixture because of the great volatility and low stoichiometric ratio of the fuel, and the competition of Carbon atom between CO and C2H2 in the pyrolysis reactions that reduced the soot source materials. Overall, as an alternative IC fuel, ABE is able to achieve much lower soot than diesel and is able to maintain clean combustion in a large range of environmental conditions.

A Reduced Chemical Kinetic Mechanism for Low Temperature Diesel Combustion and Soot Emissions

A reduced diesel surrogate fuel chemical kinetic mechanism of n-heptane/toluene/1-hexene including poly-aromatic hydrocarbons (PAHs) formation was developed for prediction of the diesel combustion process and soot emissions. The proposed mechanism, which includes 60 species and 123 reactions, agrees well with experimental ignition delays in shock tubes. The proposed mechanism was coupled with the KIVA-3V Release 2 computational fluid dynamics (CFD) code to predict the combustion process and soot emissions in constant volume spray chamber and diesel direct injection combustion cases. The simulation results predict the combustion processes for diesel fuel under various conditions well. However, the predicted soot emissions have notable deviations compared to the experimental data when C2H2 or phenanthrene (A3) were chosen as precursors in the soot model at lower oxygen concentration conditions. The predicted soot emissions at different oxygen concentrations have better agreement with the experimental data when pyrene (A4) was chosen as the soot precursor. Compared to C2H2 or A3, A4 is a more suitable precursor for soot predictions in the LTC simulations. The overall results show that the present mechanism can be used to predict the combustion process and soot emissions of low temperature diesel combustion.

An Experimental and Numerical Study on the Effects of Fuel Properties on the Combustion and Emissions of Low-Temperature Combustion Diesel Engines

Experimental and numerical investigations on the effects of fuel properties on combustion and soot emissions under both conventional and premixed low-temperature combustion (LTC) conditions have been conducted. Three different fuels, diesel, gasoline, and n-butanol, were used to formulate five fuels with different fuel properties. Computational fluid dynamic (CFD) simulations were conducted to predict the combustion processes and soot emissions of the various fuels. The results show that under both conventional and premixed combustion conditions, the cetane number (CN) has the dominant effect on the ignition delay; the volatility, aromatic, and oxygen contents only have a minor influence on ignition delay. High CN fuels need much higher exhaust gas recirculation (EGR) to provide a sufficiently long ignition delay compared to the fuels with lower CN. As a result, the carbon monoxide (CO) and unburned hydrocarbon (UHC) emissions of the high CN fuels are higher than the low CN fuels due to the lower intake oxygen concentrations. The volatility can be important under high, mixing-controlled, conventional combustion conditions, and the high volatility and oxygen content are also beneficial for CO and UHC reduction under high EGR premixed LTC conditions. The CN plays a dominant role in soot emissions, followed by the oxygen content and the volatility under low oxygen concentration conditions. The experiments show that the trade-off between NOx and soot can be totally eliminated by optimizing the diesel/gasoline/butanol blended fuel. A reduced primary reference fuel (PRF)-n-butanol-polycyclic aromatic hydrocarbon (PAH) mechanism was formulated to predict the combustion and soot emissions of the tested fuels, and the effects of fuel chemistry properties on the combustion processes and soot emissions were well predicted. The simulation results show that the mixing process can be greatly improved by adjusting the fuel chemistry properties, which leads to improved combustion and low soot emissions.

Volumetric combustion of biomass for CO2 and NOx reduction in coal-fired boilers

To meet the urgent environmental targets, substituting coal with biomass has been considered to be an effective and promising method over the last decades. In this paper, a new concept of volumetric combustion is proposed and further developed to achieve 100% fuel switching to biomass in large scale coal-fired boilers. Volumetric combustion not only changes the in-furnace flow but also affects the combustion reactions by the intensive mixing and internal recirculation of the flue gases. Firstly, the volumetric combustion properties of the wood pellets were investigated experimentally. An Aspen model was then used to thermodynamically describe and study the volumetric combustion with three different types of fuel, and the emission properties of CO2 and NOx were compared. Finally, two applications of volumetric combustion were discussed. It is concluded that the wood pellets ignited and combusted much faster than the coal pellets and had a larger combustion volume when combusted under lower oxygen concentration conditions, and the ignition time was almost independent of the oxygen concentration when the oxidizer was preheated to 1000°C. In addition, the NOx emissions decreased as the recirculation ratio of the flue gas increased, and as the percentage of biomass used in co-firing increased, the amount of flue gas that needs to be recycled for reduction of NOx decreased. Thus, the volumetric combustion is beneficial as it reduces the operation cost of NOx reduction. The volumetric combustion would be an attractive technology for co-firing a large proportion of biomass in coal-fired boilers with high boiler efficiency and effective emissions reduction.

PH and biogeochemical processes in the Gotland Basin of the Baltic Sea

The Baltic Sea is a semi-enclosed sea characterized by a limited water exchange, large input of river runoff and a low salinity. Data collected in 1995 and 2008 in the Gotland Deep have been evaluated with the objective to assess how pH couples to biogeochemical processes. One result of the density stratification between 60 and ~ 100 m, is the difference in dominating biogeochemical reactions in the surface layer compared to those in the bottom water. In the surface layer, distributions of seawater constituents were mainly determined by the seasonal balance between primary production and respiration. Chemical composition in the bottom water was governed by the availability of oxygen and the frequency of bottom-water intrusions. In 1995, oxygen was present throughout the water column and, as a consequence, nitrate concentrations were high (~ 10 μmol/kg) also in the bottom water. In contrast, there was no oxygen or nitrate in the bottom water in 2008, while hydrogen sulfide was detected at significant concentrations (up to ~ 100 μmol/kg). The largest decrease in pH was observed in the layer where oxygen decreased from ~ 300 μmol/kg to about zero. When oxygen was low or hydrogen sulfide was present pH was nearly constant both in 1995 and 2008 at a low level of ~ 7.2. The distributions of chemical constituents with depth in the water column showed that a major fraction of organic matter mineralization was caused by oxygen and sulfate as electron acceptors, while nitrate played a minor role in the low oxygen or anoxic environment. The small variability in pH under conditions of low oxygen concentrations indicated that Fe- and Mn-oxides were of minor importance as electron acceptors during organic matter mineralization at this site. In oxic environments, observed data were consistent with mineralization of the model substance (CH 2O) 45(CH 2) 44(NHCH 2CO) 16(CHPO 4Me). Under anoxic conditions, however, the observed changes in pH and DIC could be explained by mineralization of organic matter with significantly lower lipid content, e.g. material of terrestrial origin. In parallel, denitrification of preformed nitrate in the bottom layer may have contributed to changes in pH and DIC.

Cytochrome P450 BM3, NO binding and real-time NO detection

Nitric oxide is known to coordinate to ferrous heme proteins very tightly, following which it is susceptible to reaction with molecular oxygen or free NO. Its coordination to ferric heme is generally weaker but the resultant complexes are more stable in the presence of oxygen. Here we report determination of the binding constants of Cytochrome P450 BM3 for nitric oxide in the ferric state in the presence and absence of substrate. Compared to other 5-coordinate heme proteins, the K d values are particularly low at 16 and 40 nM in the presence and absence of substrate respectively. This most likely reflects the high hydrophobicity of the active site of this enzyme. The binding of NO is tight enough to enable P450 BM3 oxygenase domain to be used to determine NO concentrations and in real-time NO detection assays, which would be particularly useful under conditions of low oxygen concentration, where current methods break down.

Hypoxia-inducible Factor-1-mediated Regulation of Semaphorin 4D Affects Tumor Growth and Vascularity

Tumor progression and metastasis depend on the ability of cancer cells to initiate angiogenesis to ensure delivery of oxygen, nutrients, and growth factors to tumor cells and provide access to the systemic circulation. Hypoxia-inducible factor-1 (HIF-1) can activate expression of a broad range of genes that mediate many of the adaptive responses to decreased oxygen concentration, such as enhanced glucose uptake and formation of new blood vessels. Acting through Plexin-B1 on endothelial cells, Semaphorin 4D (Sema4D) has been shown to promote angiogenesis and enhance invasive growth and proliferation in some tumors. Here we show that the gene for Sema4D, the product of which is elevated in head and neck squamous cell carcinoma (HNSCC) cells, contains upstream hypoxia response elements (HRE) and is strongly induced in hypoxia in a HIF-1-dependent manner. Knocking down Sema4D expression with short hairpin (sh) RNA reduces in vitro endothelial cell migration and growth and vascularity of HNSCC xenografts expressing a degradation resistant HIF-1alpha subunit. We also demonstrate a correlation between HIF-1 activity and Sema4D expression in HNSCC specimens. These findings indicate that Sema4D is induced by hypoxia in a HIF-1-dependent manner and influences endothelial cell migration and tumor vascularity. Expression of Sema4D may be a strategy by which carcinomas promote angiogenesis and therefore could represent a therapeutic target for these malignancies.

Development of rapid mixing fuel nozzle for premixed combustion

Combustion in high-preheat and low oxygen concentration atmosphere is one of the attractive measures to reduce nitric oxide emission as well as greenhouse gases from combustion devices, and it is expected to be a key technology for the industrial applications in heating devices and furnaces. Before proceeding to the practical applications, we need to elucidate combustion characteristics of non-premixed and premixed flames in high-preheat and low oxygen concentration conditions from scientific point of view. For the purpose, we have developed a special mixing nozzle to create a homogeneous mixture of fuel and air by rapid mixing, and applied this rapidmixing nozzle to a Bunsen-type burner to observe combustion characteristics of the rapid-mixture. As a result, the combustion of rapid-mixture exhibited the same flame structure and combustion characteristics as the perfectly prepared premixed flame, even though the mixing time of the rapid-mixing nozzle was extremely short as a few milliseconds. Therefore, the rapid-mixing nozzle in this paper can be used to create preheated premixed flames as far as the mixing time is shorter than the ignition delay time of the fuel.