Properties of Alumina-Magnesia Cutting Tools

The  high speed cutting tools that made from ceramic materials, alumina based, it is very important for the machining process. It has a hot hardness and abrasive resistance and chemical stability at the high temperature, but it has a brittleness and low fracture strength. In this study, synthesis samples from the α-alumina(Al2O3) doping with magnesia (MgO) with different percentage (0.35, 0.75, 1.1 % wt.)  and compare with the pure alumina properties. It is using cold uniaxial pressing (200 MPa) and sintered at (1500ᵒC) remain three hours for this samples. The purpose was to study the effect of the doping on the mechanical and physical properties and the ability to enhancing it. Numerical simulation was worked for the contact and friction between  the ceramic cutting tool and the workpiece material (AISI 1006 steel). This numerical methods dependent on ABAQUS Ver.6.14 program. The results show that ability of cutting and chip formation and successfully  propagation through this type of cutting tools without failure it at high speed (150-250)m/min. Also, the stress and heat generated due to ceramic cutting tool was presented The result appeared increasing in the hardness and the density value by the doping with MgO. By increase the percentage of magnesia that given enhanced the properties. The MgO as a second phase reduce alumina grain size and increase the hardness and the wear resistance to cutting tools. Small amount of magnesia enhanced the densification rate grain growth and accelerate the sintering rate. The magnesia doping enable to sinter the mixture alumina-magnesia to near theoretical density. The best result was found with 0.75% MgO at 1500oC (HV 19GPa). Keywords: ceramic, cutting tool, Johnson cook, Abaqus ,numerical. DOI: 10.7176/IEL/9-3-05 Publication date: April 30th 201

Androgenic response from cultured anthers of a leguminous tree, Cassia siamea Lam

Anthers of Cassia siamea, on culture on B5 medium supplemented with coconut milk (15%, v/v), 2,4-D (2 mg/l), and kinetin (0.5 mg/l), split open after one to two weeks of inoculation and eject a callus mass. Microscopic examination of the anthers cultured at the late uninucleate or early bi-celled stages, after 7-14 days of culture, revealed many multicellular structures at various stages of development, thus indicating the pollen origin of callus. Callus cells also showed the haploid chromosome number (n=14)

Sodium chloride resistant cell line from haploid Datura innoxia mill. A resistance trait carried from cell to plantlet and vice versa in Vitro

A cell line resistant to sodium chloride was selected from callus cultures of haploid Datura innoxia by cloning under selective pressure. Cells of the resistant cell line retained their resistance even after subculture in absence of NaCl. Plantlets could be regenerated from resistant cells in the presence as well as absence of NaCl. In contrast, regeneration of plantlets was not possible from normal cells in the presence of NaCl, although regeneration readily occurred in the absence of NaCl. To examine the stability of the resistance in the long-term, callus cultures were initiated in presence of NaCl from stem expiants of the differentiated plantlets. All expiants of plantlets derived from resistant cells showed callus formation. This callus, derived from resistant explants, retained the trait of resistance upon subculture

High frequency production of embryos in Datura innoxia from isolated pollen grains by combined cold treatment and serial culture of anthers in liquid medium

This study concerns the development of pollen embryos as affected by various physical conditions of culture in media devoid of hormones. Freshly isolated pollen, from anthers of Datura, failed to form embryos regardless of whether they were cultured on liquid or solid medium. In contrast, pollen isolated from anthers precultured on solid medium did form embryos and the response could be increased by prior cold treatment of anthers at 4 °C for 4 days. However, the best results were obtained when anthers were cultured from the very beginning in liquid medium and transferred serially to fresh medium. Under such conditions, the anthers dehisced, allowing spontaneous shedding of pollen grains. It was thus possible to have several fractions of shed pollen continuing their development into embryos. When serial culture was started with anthers from cold-treated buds not only were embryos formed in all the fractions of shed pollen but the frequency was also considerably higher than in any mode of culturing

Calibrating PIRLS Test in Sultanate of Oman Using Item Response Theory

The study aimed to calibrate Oman data of the PIRLS test using the graded response model and to examine the psychometric properties of it, as well as identify the fit and unfit of its items. PIRLS2011 test booklets were used, which consisted of 146 test items (74 dichotomous and 72 polytomous). Items were divided into 13 booklets; each with two blocks (one literary and one informational). PIRLS test booklets were administered to 13 groups of fourth grade students in Sultanate of Oman with a total sample of 10394 students. Assumptions of IRT (unidimensionality and local independence) were examined and supported. Also, item fit was examined and supported using Samejima’s graded response model. The data was analyzed by Multilog7.03 program to estimate both item and ability parameters. Results indicated that the assumptions of IRT were proved. Also, IRT analysis revealed that 8 items showed unfit which represents only 5% of the test items. So, this result confirms that the test has good psychometric properties under the IRT

Isolation and culture of protoplasts of Capsicum annuum L. and their regeneration into plants flowering in vitro

Axenic shoot cultures of Capsicum annuum cv. California Wonder were used as the source for isolation of protoplasts from mesophyll cells. Protoplasts underwent sustained mitotic activity and proliferated to form callus masses on NT or DPD medium enriched with 2,4-D, NAA and BAP each at 1 mg/l level. The callus could be differentiated into whole plants on the differentiation media and plants floweredin vitro under long day conditions

Plantlets from mesophyll protoplasts of Solanum xanthocarpum

Young leaves of Solanum xanthocarpum from axenic shoot cultures released viable protoplasts when treated with appropriate enzymes. The protoplasts on culture in modified Murashige and Skoog (1962) medium supplemented with 2,4-dichlorophenoxy-acetic acid (0.5 mg/l), naphtha leneacetic acid (1 mg/l), kinetin (1 mg/l) and organic nutrients of KM (Kao and Michayluk 1975) regenerated to form callus tissue as a result of repeated divisions. Protoplast-derived calli differentiated into shoots on MS medium enriched with kinetin (0.5 mg/l) and rooting could be initiated by transferring the shoot-buds to basal medium