Metal Ions Implantation‐Induced Effects in GaN Thin Films

MOCVD-grown GaN n-type epilayers were implanted with 150keV Co+ and Cr+ ions at different fluences at room temperature. Co+ was implanted at 3x1016 and 5×1016 ions/cm2 and samples rapid-thermal-annealed at 700, 800 and 900°C for 5 minutes, while Cr+ was implanted at 3x1016 ions/cm2 and annealed at 800 and 900°C for 2 minutes. Diffraction patterns of implanted samples showed satellite peaks at the lower side of the main GaN (0002) reflection and these were assigned to implantation induced-damage and the formation of Ga1−xCoxN or Ga1−xCrxN phases. The coercivity (Hc) at 5K from SQUID for Co+ implanted GaN at 3x1016 ions/cm2 was 275 Oe and that at 5x1016 ions/cm2 was 600 Oe. For Cr+ implanted GaN at 3x1016 ions/cm2, Hc was 175 Oe. At the same dose of Cr+ and Co+ implanted ions, the saturation magnetization (Ms) values were almost similar. But after annealing at 900°C, the Ms value of Cr+ implanted GaN was higher than that of Co+ implanted at 5K. For Co+ implanted GaN, magnetization was retained up to 370K while in Cr+ implanted GaN, magnetization was retained above 380K. These findings are the highest reported Curie temperatures for Co+ and Cr+ implanted GaN diluted magnetic semiconductors

In-vitro Production of Cabbage and Cauliflower

Background: An efficient method of artificial mass propagation was optimized for two very nutritious vegetables of Pakistan, the cabbage and cauliflower. Being an agrarian economy, Pakistan’s more than half of the population depends directly or indirectly on agricultural products.Methodology: Hypocotyls of germinating of seeds (5-7 days old seedlings) were used as explants. Murashige and Skoog basal medium was supplemented with different concentrations of auxin (2,4 Dichlorophenoxy acetic  acid) and cytokinin (benzyl amino purine) in combination to study the callus forming tendency of cabbage and cauliflower; and found better if used in ratio of 2:1 (at least) respectively.Results: For evaluation of regeneration potential Kinetin, Zeatin, Gibrellic acid-3, and Indole acetic acid were found good in combination with benzyl amino purine. Higher (than auxin) concentration of cytokinin was found essential to obtain good regeneration response of callus.Conclusion:  Effectively concluded that these techniques can be used to raise the disease free stock of cabbage and cauliflower for genetic improvement of in-vitro bulk of varieties on commercial scale in a very brief time span

Proposed Model for Wastewater Treatment in Lahore using Constructed Wetlands

In developing countries, huge quantities of wastewater are disposed into water bodies without any treatment. Process complexity, high energy consumption, and high capital and operational costs have made the conventional treatment methods difficult to adopt in these countries. Lack of trained and skilled personnel to operate these highly sophisticated and complex systems is also a key problem associated with the conventional treatment methods. Constructed wetlands (CW) are engineered systems that have been designed and constructed to utilize the natural processes involving wetland vegetation, soils and the associated microbial assemblages to assist in treating wastewaters. It is a low cost and energy efficient option for a country like Pakistan which faces increased power shortages-an essential requirement for the majority of treatment methods. Therefore, its application for the treatment of wastewater of Lahore city was investigated in this study. A local plant, Reed (Phragmites) was evaluated for its potential use in constructed wetland. A lab scale wetland (using an earth pot) was used with reed as vegetation. Removal efficiency of the system was evaluated at different detention times ranging from 1-5 days. The results demonstrated 90% removal for TSS, 75% removal for BOD and 80% removal for COD at 5 days detention time. The mean effluent concentration of 10 mg/L, 40 mg/L and 68 mg/L for TSS, BOD and COD, respectively was obtained at 5-days detention period, thus complying with effluent standards of Pakistan. The results of the study support the suitability of CW for Lahore and also motivate for detailed pilot plant studies

EFFECT OF HUDIARA DRAIN ON THE QUALITY OF GROUNDWATER IN THE HOUSING SCHEMES OF LAHORE

A study was carried out to assess the effect of Hudiara Drain on groundwater quality in its vicinity, particularly some well planned residential neighborhoods such as Khayaban-e-Amin and Valencia in the city of Lahore (Qadeer, 2011). A total of eleven sampling points were selected. Three samples were collected from Hudiara Drain and eight samples were drawn from deep and shallow groundwater wells. Eight physical, chemical and biological parameters including pH, turbidity, total dissolved solids, total hardness, chloride, total iron, lead and total coliforms were examined and compared with the desired values mentioned in National Standards for Drinking Water Quality (NSDWQ) and World Health Organization (WHO) guidelines. The test results indicated that physical quality of all groundwater sources was satisfactory. Chemical quality of all groundwater sources was satisfactory for total dissolved solids (TDS), total hardness, and chlorides, however for total iron and lead the water quality was not meeting NSDWQ and WHO guidelines. Bacteriological contamination was also detected in almost all groundwater samples. The presence of higher concentrations of lead in groundwater certainly indicates that there is an external effect on groundwater. It is recommended that release of industrial wastewater in Hudiara Drain should be controlled and strictly monitored. In addition, proper disinfection should be practiced at the tube wells to ensure safe drinking water at the consumers end

Probability of Conjunction Estimation for Analyzing the Electromagnetic Environment Based on a Space Object Conjunction Methodology

The introduction of the space object conjunction method in electromagnetic compatibility modeling and simulation is quite a novel concept. It is useful for the stochastic analysis of an electromagnetic (EM) environment which is based on the probability of conjunction assessment. The space conjunction methodology is anticipated as the frontline defense for the protection of active satellites in space. EM congestion occurs in an environment with the increase in the number of operational EM devices. In a theoretical sense, this congestion is analogous to the space conjunction. Therefore, the space conjunction model can be applied in the EM scenarios. In this paper, we have investigated the application of the defined conjunction model by using the analytical expression of the probability of electromagnetic conjunction, which is based on the orbital parameters of the system under test. Additionally, we have elaborated the influence of these orbital parameters on the probability of conjunction. The simulations have been performed by considering different EM scenarios and the results are validated by using Monte Carlo simulations. The results show that errors in the analytical and Monte Carlo simulations are within a 1% range, which makes the analytical model effective. Computationally, the proposed analytical model is cost effective as compared to the numerical method, i.e., Monte Carlo. Moreover, from the results, it has been validated that the probability of conjunction increases with the increase in transmitted power and decreases with the compatible threshold limit of the receiving system, thus, making this method useful for analyzing the electromagnetic environment and as a frontline safety tool for electromagnetic systems

Elemental, structural and optical properties of nanocrystalline Zn1−xCuxSe films deposited by close spaced sublimation technique

The elemental composition, film thickness and concentration depth profiles of as-deposited and annealed Zn1−xCuxSe films were studied by the Rutherford backscattering spectrometer (RBS) technique. The films were deposited on glass substrates by close spaced sublimation (CSS) technique. As-deposited films of about 250–300 nm thickness were then annealed in air at temperatures of 200 °C and 400 °C for 1 h. Structural characterization including crystal structure, crystal orientation, stacking fault energy (ҮSFE) and surface morphology were carried out by using X-ray diffraction (XRD) and atomic force microscopy (AFM). XRD studies revealed that the fabricated films are polycrystalline with a zinc-blende structure and a strong (111) texture plane. Surface roughness was observed to be enhanced with annealing temperature with a decrease in stacking fault energy (ҮSFE). Spectroscopic ellipsometry has been utilized for the estimation of band gap energy (Eg) and dielectric constant (ε1). Band gap energy of the film increased with increasing annealing temperature while the dielectric constant decreased

Microparticle self-assembly induced by travelling surface acoustic waves

International audienceWe present an acoustofluidic method based on travelling surface acoustic waves (TSAWs) to induce self-assembly of microparticles inside a microfluidic channel. The particles are trapped above an interdigitated transducer, placed directly beneath the microchannel, by the TSAW-based direct acoustic radiation force (ARF). This approach was applied to trap 10 mm polystyrene particles, which were pushed towards the ceiling of the microchannel by 72 MHz TSAWs to form single-and multiple-layer colloidal structures. The repair of cracks and defects within the crystal lattice occurs as part of the self-assembly process. The sample flow through the first inlet can be switched with a buffer flow through the second inlet to control the number of particles assembled in the crystalline structure. The constant flow-induced Stokes drag force on the particles is balanced by the opposing TSAW-based ARF. This force balance is essential for the acoustics-based self-assembly of microparticles inside the microchannel. Moreover, we studied the effects of varying input voltage and fluid flow rate on the position and shape of the colloidal structure. The active self-assembly of microparticles into crystals with multiple layers can be used in the bottom-up fabrication of colloidal structures with dimensions greater than 500 mm  500 mm, which is expected to have important applications in various fields

Sheathless Focusing and Separation of Microparticles Using Tilted-Angle Traveling Surface Acoustic Waves

Sheathless focusing and separation of microparticles is an important preprocessing step in various biochemical assays in which enriched sample isolation is critical. Most of the previous microfluidic particle separation techniques have used sheath flows to achieve efficient sample focusing. The sheath flow dilutes the analyte and requires additional microchannels and accurate flow control. We demonstrated a tilted-angle traveling surface acoustic wave (taTSAW)-based sheathless focusing and separation of particles in a continuous flow. The proposed device consists of a piezoelectric substrate with a pair of interdigitated transducers (IDTs) deposited at two different angles relative to the flow direction. A Y-shaped polydimethylsiloxane (PDMS) microchannel having one inlet and two outlet ports was positioned on top of the IDTs such that the acoustic energy coupling into the fluid was maximized and wave attenuation by the PDMS walls was minimized. The two IDTs independently produced high-frequency taTSAWs, which propagated at ±30° with respect to the flow direction and imparted a direct acoustic radiation force onto the target particles. A sample mixture of 4.8 and 3.2 μm particles was focused and then separated by the actuation of the IDTs at 194 and 136 MHz frequencies, respectively, without using an additional sheath flow. The proposed taTSAW-based particle separation device offered a high purity >99% at the both outlets over a wide range of flow speeds (up to 83.3 mm/s)