Chikusaku-eki and Mokusaku-eki are natural resources and acidic liquid by-products of bamboo and broad leaved trees charcoal burner. These products contain more than 200 ingredients, including phenols, poly phenols and acetic acids. These by-products were tested for their fungicidal activity against sapstaining fungi. There are no studies about the antifungal activity of Chikusaku-eki and Mokusaku-eki against wood staining fungi in the literature. According to the recent findings, this is the first report about the antifungal activity of Chikusaku-eki and Mokusaku-eki against wood staining fungi. These extracts were more effective against sapstaining fungi at minimum concentrations (0.10-1.0 %) used in 2 % (malt extract agar) medium. Three Chikusaku-eki (Chikusakueki-I, Chikusaku-eki-II and Chikusaku-eki-III) and 2 Mokusaku-eki (Mokusaku-eki-I, Mokusaku-eki-II) extracts were tested against 4 sapstaining fungal samples to evaluate the inhibition range on sapstaining fungal growth. Ophiostoma flexuosum, Ophiostoma tetropii, Ophiostoma polonicum and Ophiostoma ips were the sapstaining fungi used in this study against bamboo and wood extracts. The initial calibration of extracts was done by calculating the specific gravity, tar calculation and total organic content. The chloroform fractions of these extracts were analyzed by gas chromatographymass spectrometry and both the extracts contained 2,6 dimethoxy phenol, dehydroacetic acid and 2,3,5 trimethoxytoluene. Results revealed that compounds of Chikusaku-eki and Mokusaku-eki markedly inhibited fungal growth at lower concentration. The Chikusaku-eki and Mokusaku-eki have both antifungal, antioxidant properties and a potential to be used as natural preservative in wood industries. Wood slice tests displayed the effective role of both extracts in laboratory level.
Surface morphology of green InGaN/GaN multi-quantum wells (MQWs) on a sapphire substrate with various high temperature grown GaN barriers has been evaluated. Keeping the InGaN well growth temperature constant at 740 °C, a series of MQWs were grown with GaN barrier temperatures varied up to 910 °C. GaN barriers grown below 800 °C lead to the generation of a high density of V-defects and inclusions embedded within V-defects as observed by atomic force microscopy. Scanning electron microscopy and cathodoluminescence (CL) studies revealed that the embedded inclusions are of two kinds: one of them appears as bright spots in CL mapping while the other appears as the surrounding region. Temperature ramping and subsequent interruption for GaN barrier growth suppresses both kinds of inclusion defects and also significantly reduces the V-defect density. An inclusion-free smooth surface is obtained for green emitting InGaN/GaN MQWs with the GaN barrier grown at 910 °C.
Sesamum indicum L. was used as an important oil crop in the world. An efficient protocol for in vitro plant regeneration via adventitious shoot formation from deembryonated cotyledon explants isolated from mature seeds of sesame is developed. Optimal medium for direct adventitious shoot formation was Murashige and Skoog (MS) medium with 22.2 μM 6-benzylaminopurin (BA) and 5.7 μM indole-3-acetic acid (IAA). Abscisic acid (3.8 μM ABA) and AgNO 3 (29.4 μM) were effective in enhancing the frequency of adventitious shoot formation. Preculture of cotyledon explants on high sucrose concentration (6-9%) for 2 wk and subsequent transfer to 3% sucrose enhanced the frequency of adventitious shoot induction. Root formation from the adventitious shoots was easily achieved on MS medium containing 2.7 μM of !-naphthalene acetic acid (NAA). Regenerated plantlets were acclimatized on sand and peat moss (1:1), showing 95% survival with subsequent flowering and seed set. We established the high-frequency plant regeneration via adventitious shoot formation in S. indicum L.
Mg-doped and In-Mg co-doped p-type GaN epilayers were grown using the metal organic chemical vapour deposition technique. The effect of In co-doping on the physical properties of p-GaN layer was examined by high resolution x-ray diffraction (HRXRD), transmission electron microscopy (TEM), Hall effect, photoluminescence (PL) and persistent photoconductivity (PPC) at room temperature. An improved crystalline quality and a reduction in threading dislocation density are evidenced upon In doping in p-GaN from HRXRD and TEM images. Hole conductivity, mobility and carrier density also significantly improved by In co-doping. PL studies of the In-Mg co-doped sample revealed that the peak position is blue shifted to 3.2 eV from 2.95 eV of conventional p-GaN and the PL intensity is increased by about 25%. In addition, In co-doping significantly reduced the PPC effect in p-type GaN layers. The improved electrical and optical properties are believed to be associated with the active participation of isolated Mg impurities.
In recent years the majority of the high density plasma etching of group III nitrides has been performed using an inductively coupled plasma (ICP) etch system because of its superior uniformity, control, and lower cost of ownership. [1][2][3] The main applications of the IIInitrides are photonic devices such as laser diodes and light-emitting diodes (LEDs). [4][5][6][7][8][9][10][11][12][13][14][15][16] Currently, all of the LEDs and a majority of the lasers are mesa-type structures in which the mesas are formed by dry etching. 16 Shul et al. 16,17 first reported the ICP etching of GaN in Cl 2 /H 2 /Ar ICP-generated plasmas with etch rates as high as ϳ6900 Å/min. Vartuli et al. 18 were the first to report the ICP etching of GaN, InN, and AlN with CH 4 //H 2 /Ar and CH 4 //H 2 /N 2 chemistries, and obtained etch rates ϳ2500 Å/min, which were approximately two times faster in the CH 4 //H 2 /Ar. Hahn et al. reported first the ICland IBr-based plasma chemistries for ICP etching of GaN, InN, and AlN. 19,20 They obtained maximum selectivities of ϳ30 for InN/AlN and ϳ14 for InN/GaN. They also reported the effect of additive noble gases (He, Ar, Xe) in Cl 2 -based ICP etching of GaN, InN, and AlN,21,22 in which they concluded efficient breaking of the III-nitrogen bond is crucial for higher etch rates.In this paper we report on a parametric study of ICP etching of undoped, n-and p-type GaN films in Cl 2 -based plasmas, especially in terms of varying the rf frequency of the capacitively coupled plasma source (or the rf chuck power source), which is applied to control ion energy. The effects of ICP source power, rf chuck power, and reactor pressure on etch rates have been investigated and results were discussed in terms of etch rates, dc bias voltage, surface morphology, and surface chemistry of the etched samples.Experimental The GaN films were grown at 1100ЊC on Al 2 O 3 substrates by metallorganic chemical vapor deposition (MOCVD). The total layer thickness was 1.5 m, and carrier concentrations were 7.9 ϫ 10 16 /cm 3 for p-GaN (Mg doping) and 1.0 ϫ 10 17 /cm 3 for n-GaN (Si doping).Etching was performed in a planar-type Vacuum Science ICP system (VSICP-1250A), in which the ICP source operates at 13.56 MHz. The temperature of the back-side cooled chuck was held at 20ЊC. The ion energy was controlled by the applied rf chuck power in different excitation frequencies of 100 kHz and 13.56 MHz. The Cl 2 /Ar mixture with total gas loads of 20 standard cubic centimeters per minute (sccm) was injected into the reactor through electronic mass flow controllers. For etch rate experiments, samples were masked with Apiezon wax; etch depths were obtained from stylus profilometry measurements of etched samples after removal of the wax. The error of these measurements is approximately Ϯ5%. It is worthwhile to note that selectivities of about 12-16 for the GaN films over SiO 2 was obtained with both frequencies in our experimental conditions, indicating that SiO 2 is a mask materal for pattern transfer. Surface morphology and near-s...
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