Characterization of Expressed Genes Isolated From Oil Palm Vegetative, Normal and Abnormal Inflorescence Meristems Using EST Approach

Little is known about the function of genes expressed in oil palm vegetative meristem tissues, which are expressed during transition from vegetative to reproductive growth, and those expressed during the formation of abnormal inflorescence. This study was aimed at isolating sufficiently large numbers of expressed sequence tags (ESTs) from an oil palm vegetative meristem cDNA library so that the expression of genes in this tissue could be studied. The genes (or ESTs) that were specifically expressed in vegetative meristems at early stages of normal inflorescence meristem development, and in abnormal inflorescence meristems were isolated to study the transition from vegetative to reproductive growth and the formation of floral abnormalities from clonal palms. A random EST approach has been used to obtain vast amounts of genes from many organisms. However, the random EST approach may result in the isolation of clones that are highly repeated in proportion to their abundance in the mRNA population of the appropriate tissues. Therefore, cold-plaque screemng and suppression subtractive hybridization (SSH) techniques were employed in the EST approach to isolate as much unique transcripts as possible in this study. Based on the EST collections made from the vegetative meristem tissues, 1088 ESTs were isolated. The redundancy of the ESTs was reduced to about 18.9% where 81.1% out of 1088 oil palm vegetative meristem ESTs were unique due to the use of the cold-plaque screening approach. Classification of the putative function of ESTs provides an idea of the type of genes expressed in the vegetative meristem tissue. The expressed genes range from housekeeping genes to genes related to photosynthesis. About 44% of the ESTs were unknown and were not characterized in other species. Stage specific expressed genes were isolated from vegetative meristem, inflorescence meristem, normal and abnormal inflorescence meristem subtraction libraries. About 601 contigs were identified from these four subtraction libraries. More than 57% of the ESTs encoded unknown functions. Through the use of digital differential display calculations, the ESTs were expressed in a tissue specific manner. Reverse northern analysis confirmed that the the majority of the EST -contigs were tissue specific.This study reveals that the apical meristem devotes more cellular activity to the biosynthesis of cellular components than to photosynthesis which is predicted from the EST analysis and physiological experiments conducted on plants. This study also reveals profound changes in gene expression that are involved in the transitionfrom the vegetative meristem to an inflorescence meristem that is driven by the action of a series of genes expressed in a stage-specific manner. Significant differences in gene expression between normal and abnormal inflorescence meristems could not be detected with this EST approach. Transient changes in gene expression or epigenetic phenomenon have been proposed to explain the molecular basis of abnormal floral development

One reference genome is not enough.

A recent study on human structural variation indicates insufficiencies and errors in the human reference genome, GRCh38, and argues for the construction of a human pan-genome

A Simple Model for Cavity Enhanced Slow Lights in Vertical Cavity Surface Emission Lasers

We develop a simple model for the slow lights in Vertical Cavity Surface Emission Lasers (VCSELs), with the combination of cavity and population pulsation effects. The dependences of probe signal power, injection bias current and wavelength detuning for the group delays are demonstrated numerically and experimentally. Up to 65 ps group delays and up to 10 GHz modulation frequency can be achieved in the room temperature at the wavelength of 1.3 $\mu$m. The most significant feature of our VCSEL device is that the length of active region is only several $\mu$m long. Based on the experimental parameters of quantum dot VCSEL structures, we show that the resonance effect of laser cavity plays a significant role to enhance the group delays

Attenuation of Guided Wave Propagation by the Insulation Pipe

Pipeline systems are widely used in gas, refinery, chemical and petro-chemical industries, which usually carry high pressure, high temperature or even highly corrosive fluids. Cracks and corrosion are often found at the outer or inner surface of pipeline and can lead to a serious thinning of wall thickness. Leaks or sudden failures of pipes can cause injuries, fatalities and environmental damage. Ultrasonic nondestructive techniques are available for the detection of wall loss associated with defects in the pipe. Unfortunately, a high proportion in pipelines of these industrial are insulated, so that even external corrosion cannot readily be detected by the conventional ultrasonic testing (single position measurement) without the removal of the insulation, which in most case is time-consuming and cost expensive. Especially in typically industrial plants, there are hundreds of kilometers of pipelines can be in operation. Making inspection of full pipelines is virtually impossible in industrial plants. There is therefore a quick reliable method for the detection of corrosion under insulation (CUI). This technique, called guided wave, employs a pulseecho system applied at a single location of a pipe where only a small section of insulation need to be removed, using waves propagation along the pipe wall. The changes in the response signal indicate the presence of an impedance change in the pipe. The shape and axial location of defects and features in the pipe are also determined by reflected signals and their arrival times. Propagation distance of many tens of meters can readily be obtained in steel pipes [1-6]. Since these guided waves are cylindrical Lamb waves along the pipe, no lateral spreading can occur and the propagation is essentially one-dimensional. In a uniform pipe, their amplitude with propagation distance is therefore only reduced by the material attenuation of the steel [7]

Structural and Thermoelectric Properties Characterization of Individual Single Crystalline Nanowire

Herein, we report a method for structural characterization as well as TE properties measurements of individual single-crystalline Lead telluride (PbTe) NWs by employing a new microchip design. In this work, the single PbTe NW was characterized in four different types of measurement: structural characterization, Seebeck coefficient S, electrical conductivity σ, and thermal conductivity κ. The structural characterization by transmission electron microscope (TEM) revealed that the PbTe NWs were high-quality single crystals with a growth along the [100] direction. The TE properties S, σ, and κ measurement results of individual 75 nm PbTe NW at room temperature were −54.76 µV K−1, 1526.19 S m−1, and 0.96 W m−1 K−1, respectively. Refer to the result of S, σ and κ; the figure of merit ZT values of a 75 nm PbTe NW at the temperature range of 300‒350 K were 1.4‒4.3 x 10−3. Furthermore, it was observed that the κ value is size-dependent compared to previous reported, which indicates that thermal transport through the individual PbTe NWs is limited by boundary scattering of both electrons and phonons. The results show that this new technique measurement provided a reliable ZT value of individual NW yielded high accuracy for size-dependent studies