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Metal organic chemical vapor deposition of m-plane GaN epi-layer using a three-step approach towards enhanced surface morphology
No full textSpecular m-plane (101¯0) gallium nitride (m-GaN) epi-layer are grown on m-plane (101¯0) sapphire substrates by metal organic chemical vapor deposition using a three-step approach. A two-step approach was used to grow m-GaN buffer layer (BL), while a three-step approach was applied to improve the surface morphology of the top m-GaN epi-layer at high temperature. The three-step approach started with growing m-aluminum nitride nucleation layer with an optimized ammonia flux during the growth of aluminum nitride. Then the temperature was ramped up during the recrystallization step before the m-GaN BL deposition at low-temperature and the growth of m-GaN layer at high-temperature for the final step. Unexpectedly, when ammonia flow was intentionally halted during the recrystallization step, the surface morphology of the BL drastically changed from three- to two- dimensional with an abrupt cross-sectional structure. This in turn facilitated the complete coalescence of the m-GaN layer as revealed by field emission scanning electron microscopy. The three-step technique was found to affect the quality of m-GaN epi-layer as the samples exhibit improved crystallinity with X-ray diffraction rocking curves widths of 4680 and 1980 arcsec along the azimuth, perpendicular and parallel to [101¯0] directions, respectively
Productivity Changes of Pharmaceutical Industry in Bangladesh: Does Process Patent Matter?
No full textThe large pharmaceutical companies in Bangladesh have currently expertise in process patent activities rather than in product patent. Such industry condition can easily generate a high profile in production and sales. However, achieving sustainability in the long run using automation and purchase of the patent only seems unsuitable. In the last two decades, it is found that both the medium and big size companies have leaned on introducing automation in their existing product plants, improving them in nothing but production. The article measures technical efficiency using data envelopment analysis (DEA) over the period of 2009–2013. We use one output—annual sales—and three inputs, namely, (a) fixed asset, (b) raw material cost and (c) cost of salary to run Malmquist total factor productivity (TFP) index. The major contributor of TFP growth is found due to the technological positive growth with a value of 10.8 per cent annually. Moreover, all changes of technical efficiency, pure efficiency and scale efficiency have regressed with values of 5.5 per cent, 2.1 per cent and 3.5 per cent, respectively. Thus, the gains in productivity are entirely due to technological advancements and not for technical improvements. The main source of inefficiency in pharmaceutical industry is scale inefficiency rather than pure technical inefficiency. Limitations and policy implications are addressed
Half-Metallic Ferrimagnetic Characteristics of Co2YZ (Z = P, As, Sb, and Bi) New Full-Heusler Alloys: a DFT Study
No full textThe full-Heusler alloys Co2YZ (Z = P, As, Sb, and Bi) were investigated by using the state-of-the-art full-potential linearized augmented plane wave plus local orbital (FP-LAPW + lo) method within the framework of density functional theory (DFT), to understand the structural, electronic, and magnetic properties of these new Heusler alloys. The generalized gradient approximation (GGA) was chosen to define the exchange-correlation potential for studying the structural properties, whereas electronic and magnetic properties were developed by using the GGA + U scheme, where U is the Hubbard term, which explains the Coulomb repulsion and was applied to describe the “d” electrons. The structural properties indicated that the ferromagnetic states of these compounds are energetically more favorable than the paramagnetic states. Through results on the electronic structures (band structures and densities of states), it is found that all these alloys exhibit a complete half-metallic nature, with half-metallic gaps (EHM) of 0.632, 0.605, 1.223, and 0.922 eV for Co2YP, Co2YAs, Co2YSb, and Co2YBi alloys, respectively. The magnetic properties indicated that the total spin magnetic moments of these Heusler alloys obey the Slater-Pauling rule around value 2 µBapproximately. The local magnetic moments of Co and Y transition elements have opposite signs with different intensities, thus revealing the ferromagnetic character. Our study of both electronic and magnetic properties demonstrates in detail that Co2YZ (Z = P, As, Sb, and Bi) full-Heusler alloys are complete half-metallic ferrimagnetic materials
Towards a Better Approach for Link Breaks Detection and Route Repairs Strategy in AODV Protocol
No full textThis paper describes a parameterized approach to the Ad Hoc On-Demand Distance Vector (AODV) routing protocol using a network-simulator 2 (ns2). By utilizing two AODV's protocol functions, which are HELLO messages and local route repair, we explore the more flexible approach on these two important functions, rather than a fixed setting within the default AODV protocol. HELLO message is used to detect the broken link, while the local route repair in AODV is used to fix and discover alternative routes in the event of route failure. In this paper, two functions to optimize AODV performance have been utilized. The first is link break detection time (Llb), using the HELLO message to detect link failure, and the second is link break position parameter (Lbp) for AODV's local route repair. The results show that the default AODV setting does not yield the best results for most defined network scenarios. In some cases, improvement compared to the default setting can be as high as 38%, for local route repair strategies. This paper presents a potential flexible and parameterized approach for dealing with link breaks and route repairing strategies for AODV protocol
Identification of crocin, crocetin and zeaxanthin in Crocus sativus grown under controlled environment in Malaysia
No full textPurpose: The purpose of the study is to identify the high valuable compounds which are crocin, crocetin and zeaxanthin in the stigmas and stamens of Crocus sativus grown under controlled environment in Malaysia. Design/methodology/approach: Spectrophotometry and high-performance liquid chromatography (HPLC) analysis were used to identify and measure crocin, crocetin and zeaxanthin content qualitatively and quantitatively in the stigmas and stamens of C. sativus grown under controlled environment in Malaysia. Findings: The results of this study showed that crocin, crocetin and zeaxanthin were detected in the stigmas. However, among those three compounds, only crocetin was detected in the stamens. In the stigmas, the detectable level of crocin was high compared to crocetin and zeaxanthin. It was also found that crocetin was higher in the stamens compared to in the stigmas. Originality/value: This is the first attempt in Malaysia that the stigmas and stamens were directly purified from the natural sources by means of no addition of preservatives as C. sativus has never been grown here before. Furthermore, limited reports are available regarding the identification of compounds in saffron stamens
Deoxyelephantopin ameliorates lipopolysaccharides (LPS)-induced memory impairments in rats: Evidence for its anti-neuroinflammatory properties
No full textAim: Neuroinflammation is a critical pathogenic mechanism of most neurodegenerative disorders especially, Alzheimer's disease (AD). Lipopolysaccharides (LPS) are known to induce neuroinflammation which is evident from significant upsurge of pro-inflammatory mediators in in vitro BV-2 microglial cells and in vivo animal models. In present study, we investigated anti-neuroinflammatory properties of deoxyelephantopin (DET) isolated from Elephantopus scaber in LPS-induced neuroinflammatory rat model. Materials and methods: In this study, DET (0.625. 1.25 and 2.5 mg/kg, i.p.) was administered in rats for 21 days and those animals were challenged with single injection of LPS (250 μg/kg, i.p.) for 7 days. Cognitive and behavioral assessment was carried out for 7 days followed by molecular assessment on brain hippocampus. Statistical significance was analyzed with one-way analysis of variance followed by Dunnett's test to compare the treatment groups with the control group. Key findings: DET ameliorated LPS-induced neuroinflammation by suppressing major pro-inflammatory mediators such as iNOS and COX-2. Furthermore, DET enhanced the anti-inflammatory cytokines and concomitantly suppressed the pro-inflammatory cytokines and chemokine production. DET treatment also reversed LPS-induced behavioral and memory deficits and attenuated LPS-induced elevation of the expression of AD markers. DET improved synaptic-functionality via enhancing the activity of pre- and post-synaptic markers, like PSD-95 and SYP. DET also prevented LPS-induced apoptotic neurodegeneration via inhibition of PARP-1, caspase-3 and cleaved caspase-3. Significance: Overall, our studies suggest DET can prevent neuroinflammation-associated memory impairment and neurodegeneration and it could be developed as a therapeutic agent for the treatment of neuroinflammation-mediated and neurodegenerative disorders, such as AD
Impulse noise detection technique based on fuzzy set
No full textIn this study, a new fuzzy-based technique is introduced for denoising images corrupted by impulse noise. The proposed method is based on the intuitionistic fuzzy set (IFS), in which the degree of hesitation plays an important role. The degree of hesitation of the pixels is obtained from the values of memberships of the object and the background of the image. After minimising the obtained hesitation function, the IFS is constructed and the noisy pixels are detected outside the neighbourhood of mean intensity of the object and the background of an image. Denoised images are relatively analysed with five other methods: modified decision-based unsymmetric trimmed median filter, noise adaptive fuzzy switched median filter, adaptive fuzzy switching weighted average filter, adaptive weighted mean filter, iterative alpha trimmed mean filter. Performances of the proposed method along with these five state-of the-art methods are evaluated using a peak signal-to-noise ratio and error rate along with the time for computation. Experimentally, derived denoising method showed an improved performance than five other existing techniques in filtering noise in images due to the reduction of uncertainty while choosing the noisy pixels
Brain Lipopolysaccharide Preconditioning-Induced Gene Reprogramming Mediates a Tolerance State in Electroconvulsive Shock Model of Epilepsy
No full textThere is increasing evidence pointing toward the role of inflammatory processes in epileptic seizures, and reciprocally, prolonged seizures induce more inflammation in the brain. In this regard, effective strategies to control epilepsy resulting from neuroinflammation could be targeted. Based on the available data, preconditioning (PC) with low dose lipopolysaccharide (LPS) through the regulation of the TLR4 signaling pathway provides neuroprotection against subsequent challenge with injury in the brain. To test this, we examined the effects of a single and chronic brain LPS PC, which is expected to lead to reduction of inflammation against epileptic seizures induced by electroconvulsive shock (ECS). A total of 60 male Sprague Dawley rats were randomly assigned to five groups: control, vehicle (single and chronic), and LPS PC (single and chronic). We first recorded the data regarding the behavioral and histological changes. We further investigated the alterations of gene and protein expression of important mediators in relation to TLR4 and inflammatory signaling pathways. Interestingly, significant increased presence of NFκB inhibitors [Src homology 2-containing inositol phosphatase-1 (SHIP1) and Toll interacting protein (TOLLIP)] was observed in LPS-preconditioned animals. This result was also associated with over-expression of IRF3 activity and anti-inflammatory markers, along with down-regulation of pro-inflammatory mediators. Summarizing, the analysis revealed that PC with LPS prior to seizure induction may have a neuroprotective effect possibly by reprogramming the signaling response to injury
Lubricated Conditions Imposed on Coating Multi-layer on Wear Resistance Under Cr2O3 Effect
No full textLubricated pin-on-disk sliding wear tests were performed on applied to Al-0.1Mg-0.35Ni-Si Alloy by using the spray coating method has been investigated. Different loads were 5, 10, and 15 N at a sliding velocity, 1.32 m/s at room temperature and 60% relative humidity. The surfaces were analyzed by using X-ray diffraction the residual (XRD), energy dispersive (EDS), scanning of (SEM) and (AFM), respectively. The results have showed that the thickness of Cr 2 O 3 coating was significantly related under the identical cold spray condition. These methods have contributed much of the understanding of quality and properties of surfaces. The (Cr 2 O 3 ) coating has great potential as a wear-resistant. The hardness increased from 102 ± 5 HV to 116.4 ± 2.5 HV at coating thickness 45 µm and friction coefficient reduced from 0.29 to 0.24; and the wear rate was about 2.11X10 -13 m 3 N -1 m -1 while hardness was increased from 102 ± 5 HV to 108 ± 3.5 HV at coating thickness 15 µm. The friction reduced from 0.31 to 0.29 at same coating thickness alloys, and the wear rate was about 2.73X10 -13 m 3 N -1 m -1 . The tribological properties of Cr 2 O 3 coating have exhibited low friction and beneficial to improve the adhesion which was clear on worn surfaces of Cr 2 O 3 coating. Crack, powder flocculation and powder formation are caused by the wear mode of the surface. Brittle fracture was found; while, adhesion and oxidation are the main mechanism of wear during the test
Neural activation patterns and connectivity in visual attention during Number and Non-number processing: An ERP study using the Ishihara pseudoisochromatic plates
No full textVisual cognitive function is important in the construction of executive function in daily life. Perception of visual number form (e.g. Arabic digits) and numerosity (numeric magnitude) is of interest to cognitive neuroscientists. Neural correlates and the functional measurement of number representations are complex events when their semantic categories are assimilated together with concepts of shape and color. Color perception can be processed further to modulate visual cognition. The Ishihara pseudoisochromatic plates are one of the best and most common screening tools for basic red-green color vision testing. However, there has been little study of visual cognitive function assessment using such pseudoisochromatic plates. 25 healthy normal trichromat volunteers were recruited and studied using a 128-sensor net to record event-related electroencephalogram. Subjects were asked to respond by pressing numbered buttons when they saw the number and non-number plates of the Ishihara color vision test. Amplitudes and latencies of N100 and P300 event related potential components were analyzed from 19 electrode sites in the international 10-20 system. A brain topographic map, cortical activation patterns, and Granger causation (effective connectivity) were analyzed from 128 electrode sites. No significant differences between N100 event related potential components for either stimulus indicates early selective attention processing was similar for number and non-number plate stimuli, but non-number plate stimuli evoked significantly higher amplitudes, longer latencies of the P300 event related potential component with a slower reaction time compared to number plate stimuli imply the allocation of attentional load was more in non-number plate processing. A different pattern of the asymmetric scalp voltage map was noticed for P300 components with a higher intensity in the left hemisphere for number plate tasks and higher intensity in the right hemisphere for non-number plate tasks. Asymmetric cortical activation and connectivity patterns revealed that number recognition occurred in the occipital and left frontal areas where as the consequence was limited to the occipital area during the non-number plate processing. Finally, results demonstrated that the visual recognition of numbers dissociates from the recognition of non-numbers at the level of defined neural networks. Number recognition was not only a process of visual perception and attention, but was also related to a higher level of cognitive function, that of language