Effects of sample orientation on nonpiloted ignition of thin poly(methyl methacrylate) sheets by a laser: 2. Experimental results

The effect of the sample orientation angle on frontside (irradiated surface) ignition and subsequent backside (nonirradiated surface) flame appearance over thin poly(methyl methacrylate) (PMMA) sheets having thicknesses of 0.2 and 0.5 mm has been experimentally investigated, using a CO₂ laser as an external radiant source in quiescent normal gravity. The sample orientation angle was varied from θ=−90° (ceiling configuration) to +90° (floor configuration) at intervals of 15° under three different laser powers of 16.0, 17.3, and 26.1 W. The shortest frontside ignition delay time was observed for the ceiling configuration (θ=−90°) and frontside ignition delay time significantly varied with increase in sample orientation angle at a laser power of 16.0 W. As the laser power was increased, frontside ignition was observed at all angles and its delay time became less dependent on the sample orientation angle. The appearance of a backside flame was achieved after the formation of an open hole (due to local consumption of the sample) by two different processes: the onset of laser induced ignition over the backside sample (backside ignition) and a flame traveling from the frontside through an open hole to the backside (backside flame). The former process was observed for a limited number of cases only around the vertical configurations (−30°?θ?30°). The delay time for the appearance of backside flame tended to be longer for sample surfaces facing downward (θ°<0) than for the sample surface facing upward (θ?0°) regardless of the laser power. When the duration of laser irradiation was shortened from 10 to 4 s, as soon as the laser was shut off, the flame on the frontside immediately shrank, moved close to the sample surface, and then traveled rapidly to the backside. Therefore, the delay time of backside flame appearance (about 6 s) became longer with longer duration of laser irradiation after the onset of a frontside flame. The size of the hole (about 4 mm diameter) was large enough for the flame to travel through it, even after 4 s of laser irradiation to sample. These results indicate that the size of the hole appears to be not a critical parameter for the appearance of the backside flame.     

Nanotrap and mass analysis of aromatic molecules by phenyl group-modified nanoparticle

To functionalize the surface of nanoparticles with phenyl groups for subsequent cross-linking with aromatic molecules by mutual interactions, we prepared functional nanoparticles (d = 3 nm) by silanization with phenyl-triethoxysilane. The nanoparticles had Fe(2)O(3) cores conjugated to phenyl groups; this was confirmed by Fourier transform infrared (FT-IR) spectroscopy and absorption spectrophotometry. The typical C-H and C-C peaks and the absorption at 240 nm, which corresponds to aromatic rings, were detected in the spectroscopic results for the phenyl group-modified nanoparticles. The nanoparticles could ionize aromatic (colchicine, reserpine, and bradykinin peptide) and nonaromatic (L-α-phosphatidylethanolamine,dioleoyl, and polyethylene glycol) molecules by nanoparticle-assisted laser desorption/ionization mass spectrometry. The nanoparticles worked as a selective trap and an ionization-assisting reagent in mass spectrometry for the aromatic molecular targets.     

Noninvasive subsurface analysis using multiple miniaturized Raman probes, part I: basic study of thin-layered transparent models of biomedical tissues

This study describes a basic theory for reconstructing pure Raman signals of materials composing a multilayer sample from Raman spectra obtained using two types of miniaturized Raman probes. An illustrative example is demonstrated using a multilayer system of samples composed of the transparent plastics polymethylmethacrylate (PMMA) and polyethylene (PE) as a model of thin-layered biomedical tissues. When the same region of an object is measured using Raman probes with different focal properties, the Raman spectra provide different depth profile information depending on the level of light penetration. Thus, a detailed comparison of the spectra can provide an interesting opportunity to probe the differences between the layers. A simple analytic form is presented for reconstructing the pure Raman spectra of the embedded layer. The method applies an understanding of the Raman sampling volume in layered transparent materials to the interpretation of Raman spectra experimentally measured by multiple probes. The basic theory described here is necessary for the expansion of the technique to turbid media, such as biological samples, where light-scattering effects must be considered. The potential applications of the proposed method include material and catalyst subsurface probing through different embedded materials, such as assessment of silicon wafers, effective noninvasive screening for catalyst synthesis, and biomedical tissue research.     

Significance of the detection of staphylococcal enterotoxin A gene in low fat milk which caused a serious outbreak of food poisoning

In June 2000, there was a large-scale outbreak of food poisoning after consumption of Snow Brand low fat milk. In the evening of a day the incident made public, some cartons of low fat milk were brought to our laboratory for examination. Next day, we detected only staphylococcal enterotoxin (SE) A gene among SE (A-E) genes by PCR in left-over milk samples or samples from the same lots that patients had consumed. We presumed that the outbreak was caused by the intake of SEA. We subsequently confirmed the presence of SEA in these samples. To investigate the existence of SE (A-E) genes in milk, we examined 100 samples of commercial low fat milk and milk by PCR, but none of the genes was detected. We estimated the detection limit of SEA gene in low fat milk by PCR. Four strains of SEA-producing Staphylococcus aureus cultures were serially diluted in low fat milk. The SEA gene was detected at levels of 5.5 x 10(2) to 1.6 x 10(4) cfu/mL of S. aureus. These amounts of S. aureus are higher than the values in raw milk reported previously. Therefore we consider that SE genes in low fat milk should usually be undetectable by our PCR. This study shows that quick detection of SE genes by PCR is very helpful to analyze outbreaks, especially if no significant bacterium can be cultured.     

The citation system: Citation networks as repeatedly focusing on difference, continuous re-evaluation, and as persistent knowledge accumulation

It can be shown that claims of a lack of theories of citation are also indicative of a grate need for a theory which links science dynamics and measurement. There is a wide gap between qualitative (science dynamics) and quantitative (measurement) approaches. To link them, the present study proposes the use of the citation system, that potentially bridges a gap between measurement and epistemology, by applying system theory to the publication system.     

Network structures and dynamics of dry and swollen poly(acrylate)s. Characterization of high- and low-frequency motions as revealed by suppressed or recovered intensities (SRI) analysis of C NMR

We recorded temperature-dependent high-resolution ¹³C NMR spectra of dry and swollen poly(acrylate)s [poly(2-methoxyethyl acrylate) (PMEA), poly(2-hydroxyethyl methacrylate) (PHEMA), and poly(tetrahydrofurfuryl acrylate) (PTHFA)] by dipolar decoupled-magic angle spinning (DD-MAS) and cross-polarization-magic angle spinning (CP-MAS) methods, to gain insight into their network structures and dynamics. Suppressed or recovered intensities (SRI) analysis of ¹³C CP-MAS and DD-MAS NMR was successfully utilized, to reveal portions of dry and swollen polymers which undergo fast and slow motions with fluctuation frequencies in the order of 10⁸ Hz and 10⁴-10⁵ Hz, respectively. Fast isotropic motions with frequency higher than 10⁸ Hz at ambient temperature were located to the portions in which ¹³C CP-MAS NMR signals of swollen PMEA were selectively suppressed. In contrast, low-frequency motion was identified to the portions in which ¹³C DD-MAS (and CP-MAS) signals are most suppressed at the characteristic suppression temperature(s) T_s. Network of PMEA gels (containing 7 wt% of water) turns out to be formed by partial association of backbones only, as manifested from their T_s gradient at lowered temperature, whereas networks of PHEMA (containing 40 wt% of water) and PTHFA (9 wt% of water) gels are tightly formed through mutual inter-chain associations of both backbones and side-chains, as viewed from the raised T_s values for both near at ambient temperature. It is also interesting to note that flexibility of gel network (PMEA > PTHFA > PHEMA) characterized by the suppression temperature T_s (PMEA < PTHFA < PHEMA) is well related with a characteristic parameter for biocompatibility such as the production of TAT (thrombin-antithrombin III complex) as a marker of activation of the coagulation system.     

Novel Enantiocomplementary C2‐Symmetric Chiral Bis(imidazoline) Ligands: Highly Enantioselective Friedel–Crafts Alkylation of Indoles with Ethyl 3,3,3‐Trifluoropyruvate

Enantioselective Friedel–Crafts alkylations of a variety of indoles with ethyl 3,3,3‐trifluoropyruvate catalyzed by novel chiral m‐phenylenebis(imidazoline)‐copper(II) complexes or the bis(imidazoline)‐achiral acid combination afforded products with high enantioselectivity. Both enantiomers of indole derivatives can be prepared with high enantioselectivities by tuning the N‐substituents of the imidazoline.     

Effect of chloride on the formation of 3-monochloro-1,2-propanediol fatty acid diesters and glycidol fatty acid esters in fish,meats and acylglycerols during heating

The effects of the presence of chloride on the formation of 3-monochloro-1,2-propanediol fatty acid esters (3-MCPDEs) and glycidol fatty acid esters (GEs) in saltwater fish, meats and acylglycerols (diacylglycerol and triacylglycerol) during heating were investigated in this study. Five saltwater fish species (salmon, saury, yellowtail, mackerel and Spanish mackerel) were grilled with a fish griller. 3-MCPDEs and GEs were detected in all of the grilled fish samples. The total amount of GEs was higher than 3-MCPDEs. Beef and pork patties with or without sodium chloride (1.5%) were cooked using gaseous fuel. The formation of 3-MCPDEs was significantly increased by the addition of sodium chloride to the meat patties, whereas the concentration of GEs in the cooked meat patties was not changed by the content of sodium chloride. Hexadecane solutions of diacylglycerol or triacylglycerol containing FeCl₃ were heated at 240°C. The formation of 3-MCPDEs was greatly increased by adding FeCl₃ to the solutions of triacylglycerol. The amounts of 3-MCPDEs decreased with the extension of the heating time. From these results, it is suggested that 3-MCPDEs and GEs are formed in saltwater fish and meats by cooking, and that the formation of 3-MCPDEs was affected by chloride in foodstuffs.     

Effects of Phosphoryl Oligosaccharides of Calcium (POs-Ca) on Mycelial Growth and Fruiting Body Development of the Edible Mushroom,Pleurotus ostreatus

Phosphoryl oligosaccharides of calcium (POs-Ca) is a calcium salt of phosphoryl maltooligosaccharides made from potato starch. POs-Ca is highly water-soluble and can supply both the calcium ion and acidic oligosaccharides in an aqueous solution. In this study, we investigated the effects of POs-Ca on the mycelial growth and fruiting body yield of Pleurotus ostreatus , which is one of the most widely cultivated edible mushrooms in the world. We cultivated the mushroom using both potato dextrose agar (PDA) medium and sawdust-based medium, with added calcium salts. The addition of POs-Ca into the PDA medium with a calcium concentration of 10 mg increased mycelial growth significantly ( p < 0.05, vs . control). POs-Ca addition to the sawdust-based medium at concentrations of 1.0 to 3.0 g/100 g medium increased the amount of calcium in the fruiting bodies but did not affect the length of the cultivation period or the weight of the fruiting body. The calcium content in the fruiting body increased 12-fold when compared to the control. On the other hand, neither the CaHPO ₄ ･2H ₂ O group nor the CaHPO ₄ ･2H ₂ O with oligosaccharides group showed changes in the calcium content of the fruiting bodies. Our results indicate that the use of POs-Ca in mushroom cultivation allows for the possibility of developing new functional foods like calcium-enriched edible mushrooms. This is the first report describing the effects of POs-Ca on mushroom cultivation.     

Nitric Oxide and Reactive Oxygen Species in the Pathogenesis of Preeclampsia

Preeclampsia (PE) is characterized by disturbed extravillous trophoblast migration toward uterine spiral arteries leading to increased uteroplacental vascular resistance and by vascular dysfunction resulting in reduced systemic vasodilatory properties. Its pathogenesis is mediated by an altered bioavailability of nitric oxide (NO) and tissue damage caused by increased levels of reactive oxygen species (ROS). Furthermore, superoxide (O₂⁻) rapidly inactivates NO and forms peroxynitrite (ONOO⁻). It is known that ONOO⁻ accumulates in the placental tissues and injures the placental function in PE. In addition, ROS could stimulate platelet adhesion and aggregation leading to intravascular coagulopathy. ROS-induced coagulopathy causes placental infarction and impairs the uteroplacental blood flow in PE. The disorders could lead to the reduction of oxygen and nutrients required for normal fetal development resulting in fetal growth restriction. On the other hand, several antioxidants scavenge ROS and protect tissues against oxidative damage. Placental antioxidants including catalase, superoxide dismutase (SOD), and glutathione peroxidase (GPx) protect the vasculature from ROS and maintain the vascular function. However, placental ischemia in PE decreases the antioxidant activity resulting in further elevated oxidative stress, which leads to the appearance of the pathological conditions of PE including hypertension and proteinuria. Oxidative stress is defined as an imbalance between ROS and antioxidant activity. This review provides new insights about roles of oxidative stress in the pathophysiology of PE.