Methylthiolate-induced reconstruction of Ag(1 1 1): A medium energy ion scattering study

Medium energy ion scattering (MEIS), using 100 keV H+ incident ions, has been used to investigate the structure of the Ag(1 1 1)(√7 × √7)R19° –CH3S surface phase. The results provide the first direct evidence that this structure does involve substantial reconstruction of the Ag surface layer. The measured absolute scattered ion yields and blocking curves are in generally good agreement with a specific structural model of the surface based on a reconstructed layer containing 3/7 ML Ag atoms, previously suggested on the basis of scanning tunnelling microscopy (STM) and normal incidence X-ray standing wave (NIXSW) studies. However, the MEIS data indicate that any rumpling of the thiolate layer, is small, and probably 0.2 Å. This value is smaller than the amplitude suggested in the STM and NIXSW studies, but could be entirely consistent with the earlier experimental data

グァテマラにおけるテメホス剤を用いた広域でのブユ防除法の検討

金沢大学留学生センターグァテマラのオンコセルカ症流行地域における媒介ブユ幼虫の防除方法を改良する目的で, テメホスの各種剤型を用いて, 雨季にグアチピリン水系で広範囲にわたる野外実験を行った。その結果, 0.2∿2.0ppm/10minの範囲では有効距離に薬剤濃度は無関係で, 流水量が関係していた。テメホスの固型剤, 水和剤, 乳剤, 油剤の間, および瞬時投入と10分間投入との間には顕著な差は認められなかった。したがって, グァテマラにおけるオンコセルカ症媒介ブユ対策の作業は, テメホス水和剤1.0∿1.5g入りの袋を流水量とは無関係に, 50∿100mおきに瞬時投入するのが適切と考えられた。 In order to investigate an effective control method of blackfly larvae in an onchocerciasis endemic area of Guatemala, large scale stream tests were done in the rainy season using various formulations of temephos. The concentration of temephos had no relationship with its carry within a range of 0.2-2.0ppm/10min. There existed a clear tendency in that the larger the water discharge, the longer was the carry of the insecticide. No distinct difference was observed in efficacy among the four formulations, i.e. solid, water dispersible powders (wdp), emulsifiable concentrates (EC) and oil solution, as also between the two application methods, instantaneous pouring and pouring during a 10min period. It is recommended that in future vector control operations of Guatemalan onchocerciasis temephos wdp packed in a bag containing 1.0-1.5g of the active ingredient should be poured into a stream immediately after mixing it with stream water, regardless of the water discharge of stream. With this mode of application, 50-100m carry would be expected in streams infested with Simulium ochraceum, the principal vector of onchocerciasis

Notes on the age determination, ovariole changes and gonotrophic cycle of Simulium ochraceum in Guatemala

金沢大学留学生センター室内および野外個体の解剖観察をもとに, S. ochraceumの羽化から吸血までの最短期間を2日, 吸血から産卵までを5日, 産卵後まもなく2回目の吸血をすると仮定すると, 吸血-産卵-吸血(gonotrophic cycle)の最短期間は5日と考えられた。調査4地点(1977年10月∿12月)の平均産卵経験率はS. ochraceum 48.7%, S. callidum 46.9%, S. metallicum 41.2%, S. mexicanum 38.9%であった。産卵経験率およびsac-like relic率は日変化を示し, 午後に高い傾向を示した。以上のことからS. ochraceumの日生存率は0.866と計算され, 羽化後1回目の吸血でO. volvulusのMf.を取り込んだとして, これが感染型に発育し, 伝播可能になる吸血後9日目の生存率は27.3%と推定された。 Of the S. ochraceum in Guatemala, the shortest duration from emergence to blood-feeding, from blood-feeding to oviposition (both at 22℃) and from oviposition to next blood-feeding (under the field condition) were presumed to be 2 days, 5 days and 0 day, respectively. One gonotrophic cycle of this species was to be 5 days in the shortest case. The average parous rate observed in the blackflies collected at four locations from October to December, 1977 were 48.7% for S. ochraceum, 41.2% for S. metallicum, 46.9% for S. callidum and 38.9% for S. mexicanum. The parous rate showed diurnal change, those of which captured in the afternoon being somewhat higher. The survival rate of S. ochraceum for 9 days after blood-feeding when this species become infective, was estimated at 27.3%

Duration of blood feeding of Simulium ochraceum in relation to intake of Onchocerca volvulus microfilariae

金沢大学留学生センターグアテマラにおけるオンコセルカ症の主要媒介種Simulium ochraceumのOnchocerca volvulus仔虫のとりこみに関して実験を行った。仔虫のとりこみは, ブユが体表にとまってから30秒で始まった。3∿4分後には65%のブユが吸血を完了し, とりこまれる仔虫数が最高に達した。それ以後は吸血時間がのびても, とりこみ量は増加しなかった。仔虫密度が皮膚10(mm)^2あたり55∿116匹の中程度に感染した人にあっては, とりこまれる仔虫の数は皮膚中の仔虫の密度と関連していた。しかし仔虫密度が1.8と非常に低い人の場合に, 異常に高い仔虫のとりこみが観察された。このことは, 皮膚中の仔虫密度が低い場合には, 仔虫がブユの吸血時に誘引あるいは何らかの刺激を受けることを示唆するものかもしれない。 Intake of microfilariae of Onchocerca volvulus by Simulium ochraceum, the main vector of onchocerciasis in Guatemala, was studied. The initiation of intake of microfilariae was around 30sec after landing. Thereafter, the number of microfilariae taken by flies increased as the feeding time increased. After 3 to 4min of landing, 69% of flies finished their blood meal, and the intake of microfilariae reached the highest. Thereafter, increase of feeding time did not increase the intake. With the volunteers of moderate density of microfilariae (55-116 Mf per 10(mm)^2), the number of microfilariae taken by the flies was correlated with the density of microfilariae in human skin. With a volunteer of very low density (1.8 Mf per 10(mm)^2), however, an extraordinarily high intake of microfilariae was observed. This suggested the possibility of the flies attracting or stimulating the microfilariae in the skin of low density carriers

Magnetic Interactions and Transport in (Ga,Cr)As

The magnetic, transport, and structural properties of (Ga,Cr)As are reported. Zincblende Ga$_{1-x}$Cr$_{x}$As was grown by low-temperature molecular beam epitaxy (MBE). At low concentrations, x$\sim$0.1, the materials exhibit unusual magnetic properties associated with the random magnetism of the alloy. At low temperatures the magnetization M(B) increases rapidly with increasing field due to the alignment of ferromagnetic units (polarons or clusters) having large dipole moments of order 10-10$^2$$\mu_B$. A standard model of superparamagnetism is inadequate for describing both the field and temperature dependence of the magnetization M(B,T). In order to explain M(B) at low temperatures we employ a distributed magnetic moment (DMM) model in which polarons or clusters of ions have a distribution of moments. It is also found that the magnetic susceptibility increases for decreasing temperature but saturates below T=4 K. The inverse susceptibility follows a linear-T Curie-Weiss law and extrapolates to a magnetic transition temperature $\theta$=10 K. In magnetotransport measurements, a room temperature resistivity of $\rho$=0.1 $\Omega$cm and a hole concentration of $\sim10^{20}$ cm$^{-3}$ are found, indicating that Cr can also act as a acceptor similar to Mn. The resistivity increases rapidly for decreasing temperature below room temperature, and becomes strongly insulating at low temperatures. The conductivity follows exp[-(T$_1$/T)$^{1/2}$] over a large range of conductivity, possible evidence of tunneling between polarons or clusters.Comment: To appear in PRB 15 Mar 200

Distribution of airway narrowing responses across generations and at branching points, assessed in vitro by anatomical optical coherence tomography

Background: Previous histological and imaging studies have shown the presence of variability in the degree of bronchoconstriction of airways sampled at different locations in the lung (i.e., heterogeneity). Heterogeneity can occur at different airway generations and at branching points in the bronchial tree. Whilst heterogeneity has been detected by previous experimental approaches, its spatial relationship either within or between airways is unknown.Methods: In this study, distribution of airway narrowing responses across a portion of the porcine bronchial tree was determined in vitro. The portion comprised contiguous airways spanning bronchial generations (#3-11), including the associated side branches. We used a recent optical imaging technique, anatomical optical coherence tomography, to image the bronchial tree in three dimensions. Bronchoconstriction was produced by carbachol administered to either the adventitial or luminal surface of the airway. Luminal cross sectional area was measured before and at different time points after constriction to carbachol and airway narrowing calculated from the percent decrease in luminal cross sectional area.Results: When administered to the adventitial surface, the degree of airway narrowing was progressively increased from proximal to distal generations (r = 0.80 to 0.98, P < 0.05 to 0.001). This 'serial heterogeneity' was also apparent when carbachol was administered via the lumen, though it was less pronounced. In contrast, airway narrowing was not different at side branches, and was uniform both in the parent and daughter airways.Conclusions: Our findings demonstrate that the bronchial tree expresses intrinsic serial heterogeneity, such that narrowing increases from proximal to distal airways, a relationship that is influenced by the route of drug administration but not by structural variations accompanying branching sites

Search for dinucleon decay into pions at Super-Kamiokande

A search for dinucleon decay into pions with the Super-Kamiokande detector has been performed with an exposure of 282.1 kiloton-years. Dinucleon decay is a process that violates baryon number by two units. We present the first search for dinucleon decay to pions in a large water Cherenkov detector. The modes $^{16}$O$(pp) \rightarrow$ $^{14}$C$\pi^{+}\pi^{+}$, $^{16}$O$(pn) \rightarrow$ $^{14}$N$\pi^{+}\pi^{0}$, and $^{16}$O$(nn) \rightarrow$ $^{14}$O$\pi^{0}\pi^{0}$ are investigated. No significant excess in the Super-Kamiokande data has been found, so a lower limit on the lifetime of the process per oxygen nucleus is determined. These limits are: $\tau_{pp\rightarrow\pi^{+}\pi^{+}} > 7.22 \times 10^{31}$ years, $\tau_{pn\rightarrow\pi^{+}\pi^{0}} > 1.70 \times 10^{32}$ years, and $\tau_{nn\rightarrow\pi^{0}\pi^{0}} > 4.04 \times 10^{32}$ years. The lower limits on each mode are about two orders of magnitude better than previous limits from searches for dinucleon decay in iron.Comment: 20 pages, 17 figures. Accepted for publication in Physical Review D on March 30, 201