Burning velocity measurement of fluorinated compounds by the spherical-vessel method

Burning velocity has been measured using the spherical-vessel (SV) method for four hydrofluorocarbons (HFCs), i.e., difluoromethane (HFC-32), 1,1,2-trifluoroethane (HFC-143), 1,1,1-trifluoroethane (HFC-143a), and 1,1-difluoroethane (HFC-152a). Experiments were conducted for initial pressures in the range 78-108 kPa and initial temperatures in the range 280-330 K, over wide ranges of HFC-air equivalence ratios. The burning velocities were determined from the rate of pressure increase by applying a spherical-flame propagation model. Flame propagation behavior was observed in a cylindrical vessel equipped with optical windows by employing schlieren photography. It was found that the values of burning velocity derived from the spherical-vessel method are in good agreement with the ones obtained with schlieren method. It is found that the SV method is adequate for determining the burning velocity for weakly flammable HFCs as well as for moderately flammable compounds. The burning velocity of each HFC was obtained as a function of temperature, pressure, and equivalence ratio. The maximum burning velocities of HFC-32, HFC-143, HFC-143a, and HFC-152a were determined to be 6.7, 13.1, 7.1, and 23.6 cm s⁻¹, respectively. The maximum burning velocity occurred for slightly fuel-rich concentrations. The magnitude of the burning velocity is strongly dependent on the ratio of H atoms to F atoms in the HFC molecules.     

Enhanced Phonon Scattering Below T c Caused by Zn and Ni Substitution in La1.85Sr0.15CuO4

The thermal conductivity has been measured for La _2-X Sr _X CuO ₄ and La _1.85 Sr _0.15 Cu _0.98 M _0.02 O ₄ (M; Zn, Ni). The characteristic enhancement in below T _c was confirmed for La _1.85 Sr _0.15 CuO ₄ . The phonon scattering mechanisms were analyzed in detail and the electron-phonon coupling constant was estimated to be 0.05. The enhancement becomes indetectable on Zn or Ni substitution for Cu, which indicated survival of the phonon scattering by charge carriers down to lower temperatures as a result of reduced T _c .     

Interaction between coal and liquefaction catalysts studied by high temperature electron spin resonance

The high temperature electron spin resonance technique has been used to obtain in situ information on the behaviour of liquefaction catalysts during coal pyrolysis. The spin concentration in coal was induced in the presence of a catalyst at the pyrolysis temperature. ZnCl₂ drastically increased the spin concentration of coal. The order of activity of the catalysts with respect to the increase in spin concentration was: ZnCl₂ (impregnated) ?ZnCl₂ (dispersed) >ZnCl₂/KCl>SnCl₂ > SbCl₃≈AlCl₃ ≈CaCl₂ > coal alone.     

Analytical Expression of Maximum Throughput for Long-Frame Communications in One-way String Wireless Multihop Networks

It is important to obtain analytical expressions of the maximum throughput in IEEE 802.11 Distributed Coordination Function multi-hop networks. In the previous works, the analytical expressions of the maximum throughput for one-way string multi-hop networks taking into account the signal capture effect were obtained. In other researches, the analytical expressions of the maximum throughput for one-way string multi-hop networks were also obtained, which are, however, valid only for short-frame communications. There is no analytical expression for maximum throughput, which is valid for long-frame communications. This paper presents an analytical expression of the maximum throughput for long-frame communications. For the long-frame-communication analysis, we make different assumptions from those in the previous-analyses. In the short-frame-communication analyses, it is assumed that all nodes always have frames. In the long-frame-communication analysis, however, it should be assumed that every equal to or more than three nodes in a string-topology network have frames. The comprehension of this behavior is the most important progression in this paper. The assumptions and the analytical expression are validated by the simulation results.     

Adrenomedullary hyperplasia associated with cortisol producing adenoma

We report a case of a 58-year-old man with adrenal medullary hyperplasia associated with cortisol producing adenoma. Preoperative examination showed both adrenocortical and adrenomedullary hyperfunction. No Cushingoid sign was present and pheochromocytoma-like symptoms were predominant. Abdominal computerized tomography revealed a left adrenal tumor stained by contrast medium. Histologically, the adrenal tumor was found to be a cortical adenoma, and medullary hyperplasia was observed in the remaining parenchyma.     

Radiotherapy for carcinoma of the buccal mucosa: analysis of prognostic factors]

The radiotherapeutic results of 55 patients with carcinoma of the buccal mucosa were analyzed to determine the prognostic factors and appropriate treatment modality. They were classified into 5 groups according to treatment modality: group A (preoperative radiotherapy followed by surgery), group B (interstitial implant), group C (electron therapy), group D (mainly external radiotherapy) and group E (external radiotherapy followed by mold therapy with remote afterloading system). The overall 5-year survival rates for groups A, B, C, D, E and the entire group were 50%, 61%, 67%, 29%, 25% and 48%, respectively. The cumulative 5-year local control rates for groups A through E were 81%, 94%, 75%, 33% and 25%, respectively. In univariate analysis, T stage (T1-2 vs. T3-4), N stage (N0 vs. N1-3), clinical stage (II vs. III-IV), histologic grade (well differentiated vs. moderately and poorly differentiated) and treatment modality (A-C vs. D-E) were significantly related to overall survival (p < 0.05). Multivariate analysis revealed that treatment modality (groups A-C) and N0 stage were significantly associated with favorable prognosis (p < 0.05). These results suggest that interstitial implants are comparable with surgery for T1 to early T3 lesions, with or without slight invasion to the bucco-alveolar sulci or retromolar areas, that can be treated with a single-plane implant.     

Reduction of AC flashover strength by the attachment of insulating strings on the insulator surfaces

AC flashover voltage in air (ACFOV) decreases when nylon string is attached on the PMMA insulator surface which has a backside electrode. The decrease in ACFOV by the attachment is explained by the generation and the propagation of the negative surface leader along the string. When the contact angle between the HV electrode and the insulator surface is in a range from 90° to 120°, some of the negative surface leaders generated proceed along the string to the grounded counterelectrode. The magnitude of the negative leader along the string is stronger than that of the leader on the insulator without a string. In the range of the contact angle from 120° to 180°, the negative surface leader which does not appear on the insulator without a string is generated along the string by the attachment. In both ranges of the contact angle, the negative leader along the string promotes the flashover.     

Extraction of rice-planted area using a self-organizing feature map

We introduce a neural network of self-organizing feature map (SOM) to classify remote-sensing data, including microwave and optical sensors, for the estimation of areas of planted rice. This method is an unsupervised neural network which has the capability of nonlinear discrimination, and the classification function is determined by learning. The satellite data are observed before and after rice planting in 1999. Three sets of RADARSAT and one set of SPOT/HRV data were used in Higashi–Hiroshima, Japan. The RADARSAT image has only one band of data and it is difficult to extract the rice-planted area. However, the SAR back-scattering intensity in a rice-planted area decreases from April to May and increases from May to June. Therefore, three RADARSAT images from April to June were used in this study. The SOM classification was applied the RADARSAT and SPOT data to evaluate the rice-planted area estimation. It is shown that the SOM is useful for the classification of satellite data.     

Derivatization for stabilizing sialic acids in MALDI-MS

While matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is useful in oligosaccharide analysis, the sialic acid, or N-acetylneuraminic acid (NANA), moiety of an oligosaccharide is liable to dissociation in- or postsource during mass measurement. In this study, we tried to stabilize the moiety by amidation, as in the case of peptides (Sekiya, S.; Wada, Y. Tanaka, K. Anal. Chem. 2004, 76, 5894-5902), and found 4-(4,6-dimethoxy-1,3,5-triazin-2yl)-4-methylmorpholinium chloride to be a desirable condensing agent. Amidation stabilized the glycosidic bond with NANA and suppressed its preferential cleavage by in-source decay, postsource decay, or collision-induced dissociation. In addition, the suppressed dissociation considerably improved the yield of the B/Y type ions for structural analysis by MS/MS. These results demonstrate that amidation is an effective derivatization to reinforce the structural analysis of sialylated oligosaccharides by MALDI-MS. In addition, amidation with (15)N-labeled ammonium chloride decreases the mass shift from the acid to amide form to just 0.013, reducing the complexity of mass spectral interpretation and database searching.