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GaN films have been grown on SiC substrates with an AlN nucleation layer by using a metal organic chemical vapor deposition technique. Micro-cracking of the GaN films has been observed in some of the grown samples. In order to investigate the micro-cracking and microstructure, the samples have been studied using various characterization techniques such as optical microscopy, atomic force microscopy, Raman spectroscopy, scanning electron microscopy and transmission electron microscopy (TEM). The surface morphology of the AlN nucleation layer is related to the stress evolution in subsequent overgrown GaN epilayers. It is determined via TEM evidence that, if the AlN nucleation layer has a rough surface morphology, this leads to tensile stresses in the GaN films, which finally results in cracking. Raman spectroscopy results also suggest this, by showing the existence of considerable tensile residual stress in the AlN nucleation layer. Based on these various observations and results, conclusions or propositions relating to the microstructure are presented.
In this work, a new compact, low profile, frequency, and end-fire pattern reconfigurable antenna is presented. The proposed antenna consists of four parasitic elements and an electric-inductive-capacitive (ELC) resonator enclosed with a closed ring resonator (CRR). The reconfigurability in the proposed antenna is achieved with the help of five PIN diodes (D1–D5) embedded on the top surface of the substrate. The diode (D1) is implanted between ELC and CRR resonators for frequency reconfigurability. The other four diodes (D2–D5) are implanted between the ground plane and four parasitic elements to control the electrical length of the ground plane to achieve pattern diversity. The ground plane and parasitic elements steer the primary omni-directional beam to bi-directional and uni-directional end-fire radiation at multiple frequencies. The proposed antenna exhibits multiband operation and end-fire pattern diversity depending upon the different states of PIN diodes. The overall size of the proposed antenna is 0.20λ0× 0.17λ0× 0.009λ0, where λ0 is calculated at the lowest resonance frequency. The impedance bandwidth of the antenna ranges from 1.45 to 26.22%, while peak gain varies from 0.86 to 3.86 dBi depending upon the state of operation. The measured results are in agreement with the simulated results, which confirm the frequency and pattern diversity performance of the antenna. The proposed antenna can be used in back-to-back repeater systems.
Organic light emitting diodes (OLEDs) have drawn great attention owing to their potential applications in high-quality flat display panels and smart solid-state lighting. Over the last three decades, numerous approaches have been made on material design and device physics to achieve high-efficiency and long-lifespan. Herein, we report a novel tactic to employ solution-processed hybrid metal oxide, molybdenum trioxide-tungsten trioxide (MoO3:WO3), as an efficient and stable hole injection/transport (HIL/HTL) and electron blocking layer for efficient OLEDs. By using phosphorescent orange-red emitter tris(2-phenylquinoline)-iridium(III) Ir(2-phq)3, MoO3:WO3 HIL based OLED device exhibits a power efficiency of 27.7 lm W-1 and 22.9 lm W-1 at 100 and 1000 cd m-2, respectively, which are 89% and 157% higher than that of conventional OLED device consisting of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) as an HIL. Moreover, the resulted device also displays 1.6 times lower turn-on voltage and 3.0 time higher brightness as compare to other counter part. The higher device performances of OLED device may be attributed to robust hole transporting ability, balanced charge carrier in the recombination zone and non-acidic nature of designed HIL. Our results demonstrate that a novel alternative approach based on transition metal oxide hybrid HIL/HTL as a substitute to PEDOT:PSS for high-efficiency solution process OLEDs.
Organic light-emitting diodes (OLEDs) have attracted huge concern because of their intrinsic characteristics and ability to reach the pinnacle in the field of high-quality flat-panel displays and energy-efficient solid-state lighting. High-efficiency is always a key crux for OLED devices being energy-saving and longer life-span. OLEDs have encountered enormous difficulties in meeting the requirements for large-sized devices due to a major limitation in vacuum thermal evaporation technology. In multilayered OLED devices, the characteristics of the charge injection/transport layer is a crucial factor for the operating-voltage, power-efficiency and stability of the device. Transition metal oxides have shown great potential owing to their wide range of possible energy level alignments, balanced charge injection, and improvement of carrier mobilities. In this study, we report a solution-processed blend V2O5-PEDOT:PSS hole-injection/hole-transport layer (HIL/HTL) for efficient orange phosphorescent OLEDs. The electroluminescent characteristics of blend V2O5-PEDOT:PSS based devices were studied with the structure ITO/V2O5-PEDOT:PSS/CBP:Ir(2-phq)3/TPBi/LiF/Al. The V2O5-PEDOT:PSS based OLEDs displayed relatively higher device performance and low roll-off than that of the counter PEDOT:PSS device in terms of a maximum luminance of 17,670 cd m-2, power efficiency of 19.4 lm W-1, external quantum efficiency of 8.7%, and more importantly, low turn-on voltage. These results demonstrate an alternative approach based on metal oxide/organic blend HIL/HTL as a substitute of PEDOT:PSS for high-efficiency solution process OLEDs.
Hydrilla is an invasive aquatic plant that has rapidly spread through many inland water bodies across the globe by outcompeting native aquatic plants. The negative impacts of hydrilla invasion have become a concern for water resource management authorities, power companies, and environmental scientists. The early detection of hydrilla infestation is very important to reduce the costs associated with control and removal efforts of this invasive species. Therefore, in this study, we aimed to develop a tool for rapid, frequent, and large-scale monitoring and predicting spatial extent of hydrilla habitat. This was achieved by integrating in situ and Landsat 8 Operational Land Imager satellite data for Lake J. Strom Thurmond, the largest US Army Corps of Engineers lake east of the Mississippi River, located on the border of Georgia and South Carolina border. The predictive model for presence of hydrilla incorporated radiometric and physical measurements, including remote-sensing reflectance, Secchi disk depth (SDD), light-attenuation coefficient (Kd), maximum depth of colonization (Zc), and percentage of light available through the water column (PLW). The model-predicted ideal habitat for hydrilla featured high SDD, Zc, and PLW values, low values of Kd. Monthly analyses based on satellite images showed that hydrilla starts growing in April, reaches peak coverage around October, begins retreating in the following months, and disappears in February. Analysis of physical and meteorological factors (i.e., water temperature, surface runoff, net inflow, precipitation) revealed that these parameters are closely associated with hydrilla extent. Management agencies can use these results not only to plan removal efforts but also to evaluate and adapt their current mitigation efforts.
Thin films of insulating Ti1−xNixO2 (x = 0.00, 0.05, 0.10, and 0.15) are synthesized by the spray pyrolysis technique. All the films are seen to crystallize into polycrystalline anatase phase of TiO2. However, weak signature of the NiTiO3 phase is also observed for the films having higher Ni ion concentration. Optical absorption analysis suggests nonmonotonous band gap decrease from 3.67 to 3.59 eV with respect to added concentration of Ni ions unto ‘x’ = 0.10 in the TiO2 matrix. The presence of ferromagnetic ordering at room temperature in Ni incorporated TiO2 films is revealed by M–H measurements. Calculated values of saturation magnetization indicate that the observed ferromagnetism is not due to the presence of Ni clusters or segregation of other ferromagnetic phase. Electrically insulating nature of the films suggests that the observed FM ordering is most probably due to the ferromagnetic interaction between bound magnetic polarons which formed due to the creation of oxygen vacancies or defects.
To evaluate effectiveness of point-of-use water treatment in improving treatment of children affected by severe acute malnutrition (SAM).
Programme sites were randomized to one of four intervention arms: (i) standard SAM treatment; (ii) SAM treatment plus flocculent/disinfectant water treatment; (iii) SAM treatment plus chlorine disinfectant; or (iv) SAM treatment plus ceramic water filter. Outcome measures were calculated based on participant status upon exit or after 120d of enrolment, whichever came first. Child anthropometric data were collected during weekly monitoring at programme sites. Child caregivers were interviewed at enrolment and exit. Use of water treatment products was assessed in a home visit 4–6 weeks after enrolment.
Dadu District, Sindh Province, Pakistan.
Children (n 901) aged 6–59 months with SAM and no medical complications.
Recovery rates were 16·7–22·2 % higher among children receiving water treatment compared with the control group. The adjusted odds of recovery were approximately twice as high for those receiving water treatment compared with controls. Mean length of stay until recovery was 73 (sd 24·6) d and mean rate of weight gain was 4·7 (sd 3·0) g/kg per d. Differences in recovery rate, length of stay and rate of weight gain between intervention groups were not statistically significant.
Incorporating point-of-use water treatment into outpatient treatment programmes for children with SAM increased nutritional recovery rates. No significant differences in recovery rates were observed between the different intervention groups, indicating that different water treatment approaches were equally effective in improving recovery.
Organic light-emitting diodes (OLEDs) have progressively attracted generous attention because of their versatile applications in solid state lighting and full color displays. High-efficiency is crucial for OLED devices being energy saving and to have a longer lifespan. Numerous approaches have been attempted to attain high-efficiency OLEDs via newly synthesized organic materials, light-extraction structure design and energy-efficient device architectures. The organic materials used in optoelectronic devices have inherently low dielectric constant. In this work, we demonstrate a comprehensive model to quantitatively investigate the role of dielectric constant of the electron transporting material on the electric field distribution, charge drift and exciton recombination probability across the emissive layer (EML) and electron transport layer (ETL) in organic light-emitting diode via commercialized electrical simulation package SETFOS.
To assess the quality of care provided by lady health workers (LHW) managing cases of uncomplicated severe acute malnutrition (SAM) in the community.
Cross-sectional quality-of-care study.
The feasibility of the implementation of screening and treatment for uncomplicated SAM in the community by LHW was tested in Sindh Province, Pakistan. An observational, clinical prospective multicentre cohort study compared the LHW-delivered care with the existing outpatient health facility model.
LHW implementing treatment for uncomplicated SAM in the community.
Oedema was diagnosed conducted correctly for 87·5 % of children; weight and mid upper-arm circumference were measured correctly for 60·0 % and 57·4 % of children, respectively. The appetite test was conducted correctly for 42·0 % of cases. Of all cases of SAM without complications assessed during the study, 68·0 % received the correct medical and nutrition treatment. The proportion of cases that received the correct medical and nutrition treatment and key counselling messages was 4·0 %.
This quality-of-care study supports existing evidence that LHW are able to identify uncomplicated SAM, and a majority can provide appropriate nutrition and medical treatment in the community. However, the findings also show that their ability to provide the complete package with an acceptable level of care is not assured. Additional evidence on the impact of supervision and training on the quality of SAM treatment and counselling provided by LHW to children with SAM is required. The study has also shown that, as in other sectors, it is essential that operational challenges are addressed in a timely manner and that implementers receive appropriate levels of support, if SAM is to be treated successfully in the community.
Under natural conditions, prey resources may fluctuate considerably in space and time; and predators are continuously faced with challenges of resource availability and use. In this study, effects of fluctuations (scarce/optimal/abundant) in biomass of pea aphid (Acyrthosiphon pisum (Harris); Hemiptera: Aphididae) during rearing and experimental conditions on certain predatory attributes (consumption rate/conversion, efficiency/growth rate) of two sympatric aphidophagous Coccinellidae (Coleoptera) were evaluated. Results revealed significant influence of rearing conditions on conversion efficiency and growth rate; and experimental conditions on all three predation attributes of Menochilus sexmaculatus (Fabricius) (Coleoptera: Coccinellidae). Larvae/adults of M. sexmaculatus had similar consumption rates per rearing condition, but exhibited highest and lowest consumption rates when abruptly shifted to abundant and scarce prey experimental conditions. Further, scarce prey reared larvae/adults of M. sexmaculatus displayed highest conversion efficiency and growth rate on optimal/abundant prey experimental condition(s). However, all three predation attributes of larvae/adults of Propylea dissecta (Mulsant) (Coleoptera: Coccinellidae) were influenced substantially by both the rearing and experimental conditions; and scarce prey reared larvae/adults exhibited highest predation attributes on optimal/abundant prey experimental condition(s). Moreover, predation attributes of M. sexmaculatus were higher than P. dissecta on the three experimental conditions. Therefore, this study suggests that M. sexmaculatus has a better compensatory ability to overcome prey resource fluctuation than P. dissecta.
Ion acceleration from submicron thick foil target irradiated by a circularly polarized laser is studied using multidimensional particle-in-cell simulations. Convex, flat, and concave target shapes are considered. Radius of curvature of curved target is of the order of laser width in transverse direction. Accelerated ion beam of highest peak energy and least energy spread is obtained from concave target, whereas total accelerated charge is highest in convex target. It is attributed to the change in the growth of transverse instabilities and geometrical effects due to target curvature in initial stages of acceleration process. The variation in the radius of curvature of the foil depends on the ratio of initial spot size to the radius of curvature. Faster reduction in curvature is achieved for tightly focused Gaussian pulses as conjectured by the model.
Metastases to the parotid region are relatively infrequent and originate primarily from head and neck cancer. Metastases of an infraclavicular origin are uncommon. Moreover, metastasis from the carcinoma of urinary bladder (CUB) to any part of the head and neck, including parotid gland, is rare. Surgery and chemotherapy are usually offered. We report a case of solitary parotid metastasis from CUB, who was successfully treated with stereotactic body radiotherapy (SBRT) using CyberKnife. SBRT is a safe alternative in cases unwilling/unfit for surgery.
Due to the high surface area and good bio-compatibility of nano structured ZnO, it finds good utility in biosensor applications. In this work we have fabricated highly dense ZnO nano bundles with the assistance of self assembled poly methylsilisesquoxane (PMSSQ) matrix which has been realized in a carpet like configuration with implanted ZnO nano-seeds. Such high aspect ratio structures (∼50) with carpet like layout have been realized for the first time using solution chemistry. Nanoparticles of PMMSQ are mixed with a nano-assembler Poly-propylene glycol (PPG) and Zinc Oxide nanoseeds (5-15 nm). The PPG acts by assembling the PMSSQ nanoparticles and evaporates from this film thus creating the highly porous nano-assembly of PMMSQ nanoparticles with implanted Zinc Oxide seeds. Nano-wire bundles with a high overall surface roughness are grown over this template by a daylong incubation of an aqueous solution of hexamethylene tetra amine and Zinc nitrate. Characterization of the fabricated structures has been extensively performed using FESEM, EDAX, and XRD. We envision these films to have potential of highly dense immobilization platforms for antibodies in immunosensors. The principle advantage in our case is a high aspect ratio of the nano-bundles and a high level of roughness in overall surface topology of the carpet outgrowing the zinc-oxide nanowire bundles. Antibody immobilization has been performed by modifying the surface with protein-G followed by Goat anti salmonella antibody. Antibody activity has been characterized by using 3D profiler, Bio-Rad Protein assay and UV-Visible spectrophotometer.
The bubble regime acceleration of electrons by a short pulse laser in a carbon nanotube (CNT) embedded plasma is investigated, employing two-dimensional Particle-in-Cell simulations. The laser converts the CNT placed on the laser axis into dense plasma and expels the electrons out, to form a co-moving positive charged sheet inside the bubble. The additional field generated due to sheet enhances the energy of the monoenergetic bunch by about 5% and their number by 5–20%. For a typical 40 fs, 7.5 × 1019 Wcm−2 pulse in an underdense plasma of density n0, CNT of thickness 25 nm and electron density 30n0, produces a monoenergetic bunch of 115 MeV with 5% energy spread. When CNT density is raised to 90n0, the energy gain, energy spread and accelerated charge increases further. The analytical framework supports these features.
A Ka-band carrier generator using phase-locked loop (PLL) frequency synthesizer is presented in this paper. The design uses integer-N PLL chip PE83336 as the important hardware support. The key idea of generating Ka-band frequency signal with low-phase noise is to generate a high-quality X-band frequency signal using PLL frequency synthesizer and employ a frequency multiplier to deliver the high-frequency output at the desired frequency band. Experimental measurements of the frequency synthesizer demonstrate the excellent performance, which is achieved with the Ka-band output with a frequency resolution of 5.7 MHz and phase noise better than −70 dBc/Hz at 1 kHz.
In this paper, the design analysis of a multi-way and high-power radial combiner is presented. This combiner incorporates a rigid stripline-type combining structure. This analysis, based on an equivalent circuit model and segmentation of the radial transmission line, provides simple design formulae. The developed methodology, after fine-tuning with the help of an electromagnetic full-wave simulator, is physically demonstrated by developing a high-power (16 kW average) and high combining-efficiency (98.9%) 16-way combiner at the center frequency of 505.8 MHz. Its efficient and repeatable performance, fabrication-friendly structure, and absence of the heat-related problem, caused by the isolation resistor, are the main features of this design.
Mega-dam building in India in the post-independence era became a major symbol of modernization. Even today, the mega-dam continues to be seen as a symbol of progress, of man's supremacy over nature, of prosperity and of pride. However, due to construction of dams, many indigenous communities are displaced involuntarily and compensated marginally. It severely damages the rich sociocultural fabric of the marginalized people. In this process, the indigenous people suffer from economic and social marginalization in many important areas of community life. The rehabilitation and resettlement policies have often further marginalized the already marginalized people from life's opportunities. This has deprived this segment of the population from the rights and privileges enjoyed by the dominant sections of society. Countless studies and reports have documented that the interests of ‘development oustees’ were rarely taken into consideration when mega projects were built (Oliver-Smith 1991; Thukral 1992 and 1996; Parasuraman 1993 and 1999; Scudder 1996; Colson 1999; WCD 2000). Indigenous people seldom understand the long-term implications of development projects, and hence fail in their efforts to devise measures to counter them.
Recognizing this problem, World Bank sociologist Michael Cernea developed the highly influential Impoverishment Risks and Reconstruction (IRR) model (see Cernea 1994, 1997, 1998, 1999, 2000) now widely used in resettlement research (for example, Mathur and Marsden 1998). This model has been key in showing how displacement goes hand in hand with physical, social and economic exclusion.
The objective of this study was to determine the mechanism of decarburization of alloy 617 by investigating the surface and bulk stabilities of the alloy in helium gas containing only CO and CO2 impurities over the temperature range 900-1000°C. For this purpose, the alloy was pre-oxidized at 900°C for 150h in He + 15 ppm CO + 1.6 ppm CO2 gas mixture and subsequently decarburized at 1000°C for additional 100h. The reaction mechanism was corroborated through gas phase analysis, microstructural examination and micro-probe measurements. It was determined that decarburization of the alloy occurred via a reaction between the porous Cr2O3 scale (formed during pre-oxidation) and carbon in the alloy, resulting in chromium metal and carbon monoxide. The chromium diffused back into the matrix, whereas the carbon monoxide escaped the sample through existing cracks and pores in the oxide. Therefore, this study shows that decarburization of alloy 617 occurs in a helium gas containing only CO and CO2 impurities.