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Smoking is a risk factor for periodontitis, and the immune response of periodontal tissues in patients with periodontitis may be strongly affected by smoking. The purpose of this study was to elucidate the bioactivity and signal transduction of human gingival endothelial cells (HGECs) due to nicotinic stimulation using a cultured medium supplemented with lipopolysaccharide (LPS) as a model of periodontitis. HGECs were cultured in medium supplemented with LPS, nicotine, nicotine + LPS, and medium supplemented without nicotine or LPS (control). Cell proliferation was assessed using Alamar blue. Cytotoxicity was assessed by lactate dehydrogenase leakage. The expression of adhesion molecule-1 (ICAM-1, VCAM-1) was assessed by reverse transcription quantitative polymerase chain reaction (RT-qPCR) and enzyme-linked immunosorbent assay. The expression of nicotinic acetylcholine receptor (nAChR) subunits (α3, α5, α7, β2 and β4) was evaluated by RT-PCR. The involvement of p38 mitogen-activated protein kinase (p38MAPK) and protein kinase C (PKC) cell signaling pathways in ICAM-1 and VCAM-1 expression was investigated by RT-qPCR with specific inhibitors. HGECs stimulated with LPS, nicotine and nicotine + LPS showed inhibition of cell proliferation, increase of cell death, and increase of gene and protein expression of ICAM-1. Moreover, HGECs showed the presence of α5 and α7 nAChR subunits. The expression of ICAM-1 in HGECs stimulated with LPS, nicotine, and nicotine + LPS was significantly suppressed by p38MAPK inhibitor, but not by a PKC inhibitor. The nAChR subunits of HGECs are α5 and α7, and that HGECs stimulated with nicotine and LPS express ICAM-1 via p38MAPK pathway.

Objectives: This study aimed to clarify the effects of strontium (Sr2⁺), borate (BO33−), and silicate (SiO32−) on cell proliferative capacity, the induction of differentiation into odontoblast-like cells (OLCs), and substrate formation of human dental pulp stem cells (hDPSCs). Methods: Sr2+, BO33−, and SiO32− solutions were added to the hDPSC culture medium at three different concentrations, totaling nine experimental groups. The effects of these ions on hDPSC proliferation, calcification, and collagen formation after 14, 21, and 28 days of culture were evaluated using a cell proliferation assay, a quantitative alkaline phosphatase (ALP) activity assay, and Alizarin red S and Sirius red staining, respectively. Further, the effects of these ions on hDPSC differentiation into OLCs were assessed via real-time polymerase chain reaction and immunohistochemistry. Results: Sr2+ and SiO32− increased the expression of odontoblast markers; i.e., nestin, DMP-1, dentin sialophospholipoprotein, and ALP genes, compared with the control group. BO33− increased the ALP gene expression and activity. Significance: The results of this study suggested that Sr2+, BO33−, and SiO₃²− may induce hDPSC differentiation into OLCs.

Gars and bichirs develop scales and teeth with ancient actinopterygian characteristics. Their scale surface and tooth collar are covered with enamel, also known as ganoin, whereas the tooth cap is equipped with an enamel-like tissue, acrodin. Here, we investigated the formation and mineralization of the ganoin and acrodin matrices in spotted gar, and the evolution of the scpp5, ameloblastin (ambn), and enamelin (enam) genes, which encode matrix proteins of ganoin. Results suggest that, in bichirs and gars, all these genes retain structural characteristics of their orthologs in stem actinopterygians, presumably reflecting the presence of ganoin on scales and teeth. During scale formation, Scpp5 and Enam were initially found in the incipient ganoin matrix and the underlying collagen matrix, whereas Ambn was detected mostly in a surface region of the well-developed ganoin matrix. Although collagen is the principal acrodin matrix protein, Scpp5 was detected within the matrix. Similarities in timings of mineralization and the secretion of Scpp5 suggest that acrodin evolved by the loss of the matrix secretory stage of ganoin formation: dentin formation is immediately followed by the maturation stage. The late onset of Ambn secretion during ganoin formation implies that Ambn is not essential for mineral ribbon formation, the hallmark of the enamel matrix. Furthermore, Scpp5 resembles amelogenin that is not important for the initial formation of mineral ribbons in mammals. It is thus likely that the evolution of ENAM was vital to the origin of the unique mineralization process of the enamel matrix.

Dielectric-Barrier-Discharge (DBD) plasma actuators are one of the recent research topics that has caught worldwide attention. Plasma actuators are typically used in the aerospace field of study for their flow control and wide usage of different types of plasma actuators. DBD plasma actuator is an immobile actuator that able to be utilized for its flexibility and light weight parts. Due to the wide usage of DBD plasma, it is also able to be useful in the field of combustion in terms of air flow control. In this research, the DBD plasma actuator is tested on its ability to be applied in micro combustors based on the air flow controlling aspect, the temperature of plasma and effects of vibration of plasma. Experiments were performed in the wind tunnel with smoke generator to show the flow separation by DBD plasma actuator while infrared camera and accelerometer were used to sense the temperature and vibration respectively to investigate the effects of DBD plasma actuator on these aspects. Results shows that the plasma generated has minimal effects of the flow characteristics whereas the temperature of plasma has a maximum of 90?celcius when it is generated continuously. The vibration results indicate that generating plasma produces a small amount of vibration.

The first combustion experiments aboard the Japanese Experiment Module “Kibo” on the International Space Station, titled “Elucidation of Flame Spread and Group Combustion Excitation Mechanism of Randomly Distributed Droplet Clouds (Group Combustion)” were conducted in 2017 in order to bridge the gap between droplet combustion and spray combustion through flame spread over droplet arrays, droplet-cloud elements and randomly distributed droplet clouds. n-Decane droplets were distributed randomly on a SiC-fiber lattice, and the flame spread and group-combustion excitation were observed. During the flame spread near the group-combustion-excitation limit, two types of anomalous behavior appeared: large-scale ignition and re-burning by a slow flame propagation in a burned area. We successfully simulated similar phenomena by a flame-spread experiment using droplet-cluster arrays. The large-scale ignition phenomenon is caused by the ignition of a flammable mixture generated by heating multiple droplets existing outside the local flame-spread limit. The re-burning phenomenon by the slow flame propagation in a burned area is caused by the ignition of a flammable mixture diluted by the combustion products after the radiative extinction of the group flame. There is the possibility of a cool-flame appearance in both phenomena.

Among extant cetaceans, mysticetes are filter feeders that do not possess teeth and use their baleen for feeding, while most odontocetes are considered suction feeders, which capture prey by suction without biting or chewing with teeth. In the present study, we address the functionality of amelogenin (AMEL) genes in cetaceans. AMEL encodes a protein that is specifically involved in dental enamel formation and is located on the sex chromosomes in eutherians. The X-copy AMELX is functional in enamel-bearing eutherians, whereas the Y-copy AMELY appears to have undergone decay and was completely lost in some species. Consistent with these premises, we detected various deleterious mutations and/or non-canonical splice junctions in AMELX of mysticetes and four suction feeding odontocetes, Delphinapterus leucas, Monodon monoceros, Kogia breviceps, and Physeter macrocephalus, and in AMELY of mysticetes and odontocetes. Regardless of the functionality, both AMELX and AMELY are equally and unusually small in cetaceans, and even their functional AMELX genes presumably encode a degenerate core region, which is thought to be essential for enamel matrix assembly and enamel crystal growth. Furthermore, our results suggest that the most recent common ancestors of extant cetaceans had functional AMELX and AMELY, both of which are similar to AMELX of Platanista minor. Similar small AMELX and AMELY in archaic cetaceans can be explained by gene conversion between AMELX and AMELY. We speculate that common ancestors of modern cetaceans employed a degenerate AMELX, transferred from a decaying AMELY by gene conversion, at an early stage of their transition to suction feeders.

Fucoidans are sulfated polysaccharides that are found in marine algae and have many useful activities, including antitumor effects, promotion of apoptosis of cancer cells, and antiviral, anti-inflammatory, and antiallergic actions. In oral medicine, several case reports have shown that fucoidan-containing creams and tablets markedly improved recurrent aphthous stomatitis, symptomatic inflamed tongue, and recurrent oral herpes labialis. The aim of this study was to examine the properties of fucoidans for use in oral healthcare. The antimicrobial, anti-adhesion, endotoxin-neutralizing, and cyclooxygenase (COX)-1 and COX-2 inhibitory activities of fucoidans were examined. Four key results were obtained: fucoidans showed strong antimicrobial activity against Candida albicans, Streptococcus mutans, and Porphyromonas gingivalis; significantly inhibited the adhesion of S. mutans to bovine teeth and porcelain; were suggested to bind to and neutralize endotoxin (lipopolysaccharide) in an LAL assay; and showed COX-1 and/or COX-2 inhibitory activity. These results suggested that fucoidans may be useful in the field of oral healthcare.

This research conducted microgravity experiments on the flame spread over droplet-cloud elements with strong droplet interaction aboard Kibo on the ISS. The droplet-cloud element represents a local droplet pattern appearing in randomly distributed droplet clouds near the group-combustion-excitation limit and consists of small-droplet-spacing droplets and large-droplet-spacing droplets. As droplet-cloud elements, we used four n-decane droplets, Droplets C, B, A and L, placed at fiber intersections of two-dimensional SiC-fiber lattice with a 4-mm fiber interval in a combustion chamber. The flame spreads over the droplet-cloud element in order of Droplets C, B, A and L. The position of Droplet L relative to Droplet A was varied to investigate the flame-spread-limit distribution around burning Droplet A. The position of Droplet B relative to Droplet A was varied to investigate the effect of two-droplet interaction between Droplets B and A on the flame spread to Droplet L. The position of Droplet C relative to Droplet B was also varied to investigate the effect of three-droplet interaction among Droplets C, B and A. The results shows that in the case with the strong interaction by two or three interactive droplets, the high-temperature region is enlarged by the droplet interaction, centers near the center of mass of the interactive droplets and plays an important role in the flame-spread-limit distribution. Since the burning lifetime of Droplet A is finite, the flame-spread time from burning Droplet A to Droplet L is limited by burning lifetime of Droplet A and is less than 80% of the burning lifetime of Droplet A, which increases with the interactive effect. The flame-spread-limit distance from the center of mass of the interactive droplets increases with the burning lifetime.

This research investigates the flame-spread characteristics between two droplets, Droplets A and L, of different diameter. n-Decane droplets are placed at intersections of 14 µ SiC fibers. The flame spread from Droplet A to Droplet L was observed in microgravity. The results show that the flame-spread rate decreases with an increase in the droplet spacing or the initial diameter of Droplet L for a constant initial diameter of Droplet A. The flame-spread time is approximated as the summation of the thermal conduction time from the flame around Droplet A to Droplet L and the heating time of Droplet L, which is the time required to activate the vaporization of Droplet L. Both the thermal conduction time and the heating time of Droplet L increase with the droplet spacing. The latter also linearly increases with the squared initial droplet diameter of Droplet L. The results suggest that the ratio of the heating time of Droplet L to the thermal conduction time depends roughly on the droplet diameter of Droplet L alone for a constant initial diameter of Droplet A. The flame-spread-limit droplet spacing gradually decreases with an increase in the initial droplet diameter of Droplet L and increases sharply with the initial droplet diameter of Droplet A. The flame-spread time is limited by the burning lifetime of Droplet A and about 80% of the burning lifetime of Droplet A under the near-flame-spread-limit condition. The flame-spread limit is discussed considering the burning lifetime of Droplet A, the thermal conduction time, and the heating time of Droplet L.

形態: カラー図版あり, Physical characteristics: Original contains color illustrations, Accepted: 2018-06-19, 資料番号: PA1910043000

Secretory calcium-binding phosphoprotein (SCPP) genes are expressed in the skin and jaw during the formation of bone, teeth, and scales in osteichthyans (bony vertebrates). Among these mineralized skeletal units is the ganoid scale, found in various fossil actinopterygians (ray-finned fish) but confirmed only in Polypteriformes (bichirs, reedfish) and Lepisosteiformes (gars) among extant clades. Here, we examined SCPP genes in the genome of seven non-teleost actinopterygian species that possess or do not possess ganoid scales. As a result, 39-43 SCPP genes were identified in Polypteriformes and Lepisosteiformes, whereas 22-24 SCPP genes were found in Acipenseriformes (sturgeons, paddlefish) and Amiiformes (bowfin). Most of these genes form two clusters in the genome of Polypteriformes, Lepisosteiformes, and Amiiformes, and these two clusters are duplicated in Acipenseriformes. Despite their distant phylogenetic relationship, Polypteriformes and Lepisosteiformes retain many orthologous SCPP genes. These results imply that common ancestors of extant actinopterygians possessed a large repertoire of SCPP genes, and that many SCPP genes were lost independently in Acipenseriformes and Amiiformes. Notably, most SCPP genes originally located in one of the two SCPP gene clusters are retained in Polypteriformes and Lepisosteiformes but were secondarily lost in Acipenseriformes and Amiiformes. In Lepisosteiformes, orthologs of these lost genes show high or detectable expression levels in the skin but not in the jaw. We thus hypothesize that many SCPP genes located in this cluster are involved in the formation of ganoid scales in Polypteriformes and Lepisosteiformes, and that their orthologs and ganoid scales were convergently lost in Acipenseriformes and Amiiformes.

Stable operation of liquid-fueled combustors requires the group combustion of fuel spray. Our study employs a percolation approach to describe unsteady group-combustion excitation based on findings obtained from microgravity experiments on the flame spread of fuel droplets. We focus on droplet clouds distributed randomly in three-dimensional square lattices with a low-volatility fuel, such as n-decane in room-temperature air, where the pre-vaporization effect is negligible. We also focus on the flame spread in dilute droplet clouds near the group-combustion-excitation limit, where the droplet interactive effect is assumed negligible. The results show that the occurrence probability of group combustion sharply decreases with the increase in mean droplet spacing around a specific value, which is termed the critical mean droplet spacing. If the lattice size is at smallest about ten times as large as the flame-spread limit distance, the flame-spread characteristics are similar to those over an infinitely large cluster. The number density of unburned droplets remaining after completion of burning attained maximum around the critical mean droplet spacing. Therefore, the critical mean droplet spacing is a good index for stable combustion and unburned hydrocarbon. In the critical condition, the flame spreads through complicated paths, and thus the characteristic time scale of flame spread over droplet clouds has a very large value. The overall flame-spread rate of randomly distributed droplet clouds is almost the same as the flame-spread rate of a linear droplet array except over the flame-spread limit.

In order to compare its characteristics with those of jaw tooth collar enamel, normally developing and experimentally regenerating ganoine from ganoid scales of Lepisosteus oculatus (spotted gar), an actinopterygian fish species, was examined by Western blotting and immunohistochemistry. Amelogenin, a major enamel matrix protein (EMP), is widely found from sarcopterygian fish to mammals. Therefore, we used antimammalian amelogenin antibodies and antisera: an antibody against bovine amelogenin; antiserum against porcine amelogenin; and region-specific antibodies or antiserum against the C-terminus, middle region, or N-terminus of porcine amelogenin in this study. Positive immunoreactivity with the antibody against bovine amelogenin, antiserum against porcine amelogenin, and the middle and C-terminal region-specific antibodies was detected in both normally developing and regenerating ganoine matrix, as well as in granules found within inner ganoine epithelial cells. These immunohistochemical analyses indicated that the Lepisosteus ganoine matrix contains EMP-like proteins with epitopes similar to mammalian amelogenins. In Western blotting analyses of regenerating ganoid scales with the antibovine amelogenin antibody, two protein bands with molecular weights of approximately 78 and 65 kDa were detected, which were similar to those found in Lepisosteus tooth enamel. Our study suggests that in Lepisosteus, EMP-like proteins in the ganoine matrix corresponded to those in tooth enamel. However, it was revealed that the 78 and 65 kDa EMP-like proteins were different from 27 kDa bovine amelogenin.

The effect of polydisperse water droplet size distribution on the burning behavior and extinction condition of counterflow spray diffusion flame was investigated experimentally in this study. N-heptane as liquid fuel spray and nitrogen as a carrier gas were introduced from the lower duct while water spray and oxidizer consisting of oxygen and nitrogen was issued from the upper duct. The burning behavior of spray flame for different fuel droplet size with and without water spray was observed and the extinction condition of counterflow spray diffusion flame was characterized by oxygen concentration at extinction. The results show that the minimum value of oxygen concentration at extinction for counterflow spray diffusion flame with water spray is similar to the extinction condition without water spray for higher mean droplet diameter of water. The minimum value of oxygen concentration at extinction shifts to the smaller fuel droplet size when decreasing the water droplet size. For fuel droplet size higher than 48 μm, the optimum of water droplet size for suppressing counterflow spray diffusion flame was smaller than gaseous flame. The explanation of optimum water droplet size based on the coupled effect of Stokes number and vaporization Damkohler number can be used for prediction of the effectiveness of water droplet on the suppression of counterflow spray diffusion flame.

Enameloid is a well-mineralized tissue covering the tooth surface in fish and it corresponds to the outer-most layer of dentin. It was reported that both dental epithelial cells and odontoblasts are involved in the formation of enameloid. Nevertheless, the localization and timing of secretion of ectodermal enamel matrix proteins in enameloid are unclear. In the present study, the enameloid matrix during the stages of enameloid formation in spotted gar, Lepisosteus oculatus, an actinopterygian, was examined mainly by transmission electron microscopy-based immunohistochemistry using an anti-mammalian amelogenin antibody and antiserum. Positive immunoreactivity with the antibody and antiserum was found in enameloid from the surface to the dentin-enameloid junction just before the formation of crystallites. This immunoreactivity disappeared rapidly before the full appearance of crystallites in the enameloid during the stage of mineralization. Immunolabelling was usually found along the collagen fibrils but was not seen on the electron-dense fibrous structures, which were probably derived from matrix vesicles in the previous stage. In inner dental epithelial cells, the granules in the distal cytoplasm often showed positive immunoreactivity, suggesting that the enamel matrix protein-like proteins originated from inner dental epithelial cells. Enamel matrix protein-like proteins in the enameloid matrix might be common to the enamel matrix protein-like proteins previously reported in the collar enamel of teeth and ganoine of ganoid scales, because they exhibited marked immunoreactivity with the same anti-mammalian amelogenin antibodies. It is likely that enamel matrix protein-like proteins are involved in the formation of crystallites along collagen fibrils in enameloid.

Microstructural investigations are conducted with specimens taken from a product size 10Cr–1.5Mo–0.2V–0.05Nb–0.05N steel large trial forging to reveal the difference in microstructure between specimens creep-ruptured and creep-interrupted. There is a large difference in the hardness between those specimens. The degree of martensitic lath microstructure recovery on the ruptured samples is faster than that of the interrupted specimens as long as the microstructure is compared under the same time condition. The recovery accompanied by the preferential recovery in the vicinity of prior austenite grain boundaries is promoted in the acceleration creep region. In addition, there are some differences in the precipitation behaviour such as nucleation and coarsening between the specimens. It is concluded that the microstructural evolution of high Cr steels under creep deformation at a constant loading condition cannot be discussed by means of the microstructure change on the specimens ruptured under various applied stress conditions.

Tooth enameloid in bony fish is a well-mineralized tissue resembling enamel in mammals. It was assumed that the dental epithelial cells are deeply involved in the formation of enameloid. However, unlike enamel matrix which fully consists of several ectodermal enamel matrix proteins (EMPs), whether enameloid matrix contains ectodermal EMPs has been debated for a long time. In the present study, transmission electron microscopy-based immunohistochemical examinations, using the protein A-gold method with antibodies and antiserum against mammalian amelogenin, were performed in order to search for EMP-like proteins in the cap enameloid of basic actinopterygians, Polypterus and gar. Positive immunoreactivity was detected in the cap enameloid matrix just before the appearance of many crystallites along collagen fibrils, indicating that the cap enameloid contains EMP-like proteins. Immunolabelling was usually found along the collagen fibrils but was not seen on the electron-dense fibrous structures. Therefore, it is conceivable that the ectodermal EMP-like proteins in cap enameloid are involved in crystallite formation along collagen fibrils.

Although most fish have no enamel layer in their teeth, those belonging to Lepisosteus (gars), an extant actinopterygian fish genus, do and so can be used to study amelogenesis. In order to examine the collar enamel matrix in gar teeth, we subjected gar teeth to light and electron microscopic immunohistochemical examinations using an antibody against bovine amelogenin (27 kDa) and antiserum against porcine amelogenin (25 kDa), as well as region-specific antibodies and antiserum against the C-terminus and middle region, and N-terminus of porcine amelogenin, respectively. The enamel matrix exhibited intense immunoreactivity to the anti-bovine amelogenin antibody and the anti-porcine amelogenin antiserum in addition to the C-terminal and middle region-specific antibodies, but not to the N-terminal-specific antiserum. These results suggest that the collar enamel matrix of gar teeth contains amelogenin-like proteins and that these proteins possess domains that closely resemble the C-terminal and middle regions of porcine amelogenin. Western blot analyses of the tooth germs of Lepisosteus were also performed. As a result, protein bands with molecular weights of 78 kDa and 65 kDa were clearly stained by the anti-bovine amelogenin antibody as well as the antiserum against porcine amelogenin and the middle-region-specific antibody. It is likely that the amelogenin-like proteins present in Lepisosteus do not correspond to the amelogenins found in mammals, although they do possess domains that are shared with mammalian amelogenins.

The negative effects of hydrocarbon fuels are widely highlighted by increasing global warming and declining quality of human health. Therefore, it is important to reduce the level of emissions from liquid hydrocarbon combustion. Hydrogen addition to the combustion chamber is one of the proven methods to improve emssions level. In this research, an experiment was conducted on diesel fuel spray combustion with hydrogen addition. The effect of additional hydrogen was observed on CO, CO2, NO and THC exhaust gas emissions. A small hydrogen fraction (0~3 vol %) was added to the rich premixed spray combustion. The results show that increasing the hydrogen fraction reduced the emission indexes of CO and THC, and increased the emission index of CO2. Increasing the hydrogen fraction caused an increase in the emission index of NO, but the actual physical amount was insignificant. Increasing the atomizing air flow rate reduced the CO and THC emission indexes, but increased the CO2 and NO emission indexes.

Most available periodontal studies regarding the endothelial cell (EC) were investigated by using human umbilical vein endothelial cells (HUVECs); however, ECs can display remarkable heterogeneity in vascular beds of different origins. The aim of the present study, therefore, is to characterize microvascular ECs isolated from periodontal tissue and investigate their growth and gene expression compared to HUVECs (macrovascular).Periodontal ligament ECs (PDL-ECs) and gingiva ECs (G-ECs) were isolated by coupling to monoclonal anti-CD31 antibody magnetic beads. Both PDL-ECs and G-ECs were characterized to definitively demonstrate that the culture represented pure ECs. Their growth was determined by resazurin reduction assay. Interleukin (IL)-8, intercellular adhesion molecule 1 (ICAM-1), and E-selectin gene expression were determined by real-time quantitative reverse-transcription polymerase chain reaction after treatment with Escherichia coli lipopolysaccharide (LPS).PDL-ECs and G-ECs revealed specific EC characteristics but formed tube-like structures and had slower growth rates than HUVECs. After E. coli LPS treatment, PDL-ECs and G-ECs showed similar dose-dependently increased levels of IL-8, ICAM-1, and E-selectin mRNA expression; however, their expressions were in contrast to HUVECs. PDL-ECs and G-ECs showed obviously increased ICAM-1 mRNA expression, whereas HUVECs showed markedly increased E-selectin mRNA expression after treatment with 0.1 μg/mL E. coli LPS.ECs isolated from periodontal tissue show different growth and gene expression from those of HUVECs. Thus, these microvascular ECs appear to be a more valuable in vitro model system than HUVECs (macrovascular) to further study pathogenesis and angiogenesis of periodontal disease.

Recent findings regarding the structure and development of jaw teeth and ganoid scales in the basic actinopterygians Polypterus and Lepisosteus have been summarized in the present review. The relationship between cap enameloid, collar enamel in teeth, and ganoine in scales has been studied to understand the evolution of hard tissues in lower vertebrates. Enameloid is a well-mineralized tissue that is formed by both odontoblasts and dental epithelial cells and is found within the outermost layer of dentin. The inner dental epithelial cells surrounding the enameloid maintain the ability to produce amelogenin-like proteins; however, this may be a rudimentary function. The collar enamel of Polypterus and Lepisosteus exhibits marked immunoreactivity to anti-mammalian amelogenin antibodies, suggesting that it accommodates amelogenin-like proteins. It is likely that the collar enamel in basic actinopterygians corresponds to the enamel in sarcopterygians and amphibians. The recent fine structural and developmental studies have shown that the ganoine of ganoid scales in Polypterus and Lepisosteus is an enamel-like tissue. Positive immunoreactivity to the anti-mammalian amelogenin antibodies by the preganoine of both Polypteridae and Lepisosteidae supports that ganoine is a homolog of tooth enamel.

This study investigates the characteristics of combustion noise from a diesel engine with hydrogen added to intake air. The engine noise with hydrogen addition of 10 vol% to the intake air was lower than that with diesel fuel alone at late diesel-fuel injection timings. A transient combustion-noise-generation model was introduced to discuss noise characteristics based on energy conversion from combustion impact to noise via structure vibration. The results show that the maximum combustion impact energy had a predominant effect on the maximum engine noise power for each cycle. Therefore, the combustion noise largely contributed to the total engine noise in an early stage of the expansion stroke. The dependences of engine noise on the diesel-fuel injection timing for different hydrogen fractions are discussed considering the characteristics of maximum combustion impact energy for each frequency.

The antimicrobial peptide LL-37 is known to have a potent lipopolysaccharide (LPS)-neutralizing activity in various cell types. Because of observed heterogeneity within periodontopathogenic LPS, the authors hypothesized that LL-37 had specificity to neutralize such LPS activity. The present study, therefore, aims to investigate the LPS-neutralizing activity of LL-37 to various periodontopathogenic LPS in interleukin-8 (IL-8) production after challenging them in human oral fibroblasts.Human periodontal ligament fibroblasts (PDLF) and gingival fibroblasts (GF) were cultured from biopsies of periodontal ligament and gingival tissues. After cell confluence in 24-well plates, LPS (10 μg/mL) from Porphyromonas gingivalis, Prevotella intermedia, Fusobacterium nucleatum, and Aggregatibacter actinomycetemcomitans were added with or without LL-37 (10 μg/mL). After 18 hours, the supernatant was collected and analyzed in IL-8 production by enzyme-linked immunosorbent assay.All periodontopathogenic LPS statistically significantly induced IL-8 production in both PDLF and GF (P0.01). After neutralization with LL-37, both PDLF and GF showed a statistically significant reduction in IL-8 production compared with LPS-treated groups without LL-37 (P0.01), and the percentage of reduction in IL-8 production in PDLF appeared to be higher than in GF. In addition, the percentage of reduction in IL-8 production varied considerably according to each periodontopathogenic LPS.The antimicrobial peptide LL-37 had an ability to suppress periodontopathogenic LPS-induced IL-8 production in both PDLF and GF. Its LPS-neutralizing activity revealed specificity to periodontopathogenic LPS and seemed to be dependent on the heterogeneity within LPS between different genera.

Combustion of gaseous and liquid fuel in meso-scale tubes with wire mesh was studied experimentally. For C3H8/air mixtures, the flame can be stabilized near the mesh inside the tube without external heating even for smaller tube than the classical quenching diameter by heat recirculation from the burned gas to the unburned gas through heat conduction in the wall and mesh. The mesh enhances heat transfer from the heated wall to the unburned gas. For tubes larger than the classical quenching diameter, the flame can be stabilized inside the tube even outside the flashback limit by the heat recirculation. Within a specific range of flow velocity, the flame propagates at relatively high speed and extinction occurs near the mesh, but the flame can be stabilized near the mesh if the condition is gradually shifted from another condition with a stabilized flame. Therefore, the mesh can act as a combustion inhibitor or an enhancer. The two types of burning behavior are discussed based on two steady-state flames; normal flame and weak flame predicted by other researchers. Next, combustion of electro-sprayed ethanol/n-heptane mixtures inside a meso-scale tube with d = 3.5 mm with a single mesh and double meshes was studied. The flame can be stabilized near the mesh without external heating. If droplets passing through the mesh directly interact with the flame, heat loss and asymmetric flame shape occurs. The flame stabilization region with double meshes is larger than that with a single mesh and comparable to that for gaseous fuel combustor except for the wall wetting region.

The present study experimentally investigated the performance and emission characteristics of the diesel engine with hydrogen added to the intake air at late diesel-fuel injection timings. The diesel-fuel injection timing and the hydrogen fraction in the intake mixture were varied while the available heat produced by diesel-fuel and hydrogen per second of diesel fuel and hydrogen was kept constant at a certain value. NO showed minimum at specific hydrogen fraction. The maximum rate of incylinder pressure rise also showed minimum at 10 vol. % hydrogen fraction. However, it is desirable to set the maximum rate of incylinder pressure rise less than 0.5 MPa/deg. to realize low level of combustion noise and NO emission. We attempt to reduce further NO and smoke emissions by EGR. As the result, in the case of the diesel-fuel injection timing of −2 °. ATDC with 3.9 vol. % hydrogen addition, the smoke emission value was 0%, NO emission was low, the cyclic variation was low, and the maximum rate of incylinder pressure rise was acceptable under a nearly stoichiometric condition without sacrificing indicated thermal efficiency.