19672 research outputs found
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Resonant Tunneling Diode (RTD) Terahertz Active Transmission Line Oscillator with Graphene-Plasma Wave and Two Graphene Antennas
No full textThis study describes the design of a resonant tunneling diode (RTD) oscillator (RTD oscillator) with a RTD-gated-graphene-2DEF (two dimensional electron fluid) and demonstrates the functioning of this RTD oscillator through a transmission line simulation model. Impedance of the RTD oscillator changes periodically when physical dimension of the device is of considerable fraction of the electrical wavelength. As long as impedance matching is achieved, the oscillation frequency is not limited by the size of the device. An RTD oscillator with a graphene film and negative differential resistance (NDR) will produce power amplification. The positive electrode of the DC power supply is modified and designed as an antenna. So, the reflected power can also be radiated to increase RTD oscillator output power. The output analysis shows that through the optimization of the antenna structure, it is possible to increase the RTD oscillator output to 22 mW at 1.9 THz and 20 mW at 6.1 THz respectively. Furthermore, the RTD oscillator has the potential to oscillate at 50 THz with a matching antenna
Investigation of surface plasmon resonance (SPR) in MoS2- and WS2-protected titanium side-polished optical fiber as a humidity sensor
No full textIn this paper, we report the effects of a side-polished fiber (SPF) coated with titanium (Ti) films in different thicknesses, namely 5 nm, 13 nm, and 36 nm, protected by a thin layer of transition metal dichalcogenides (TMDCs) such as molybdenum disulfide (MoS2) and tungsten disulfide (WS2), which provide ultra-sensitive sensor-based surface plasmon resonance (SPR) covering from the visible to mid-infrared region. The SPF deposited with Ti exhibits strong evanescent field interaction with the MoS2 and WS2, and good optical absorption, hence resulting in high-sensitivity performance. Incremental increases in the thickness of the Ti layer contribute to the enhancement of the intensity of transmission with redshift and broad spectra. The findings show that the optimum thickness of Ti with 36 nm combined with MoS2 causes weak redshifts of the longitudinal localized surface plasmon resonance (LSPR) mode, while the same thickness of Ti with WS2 causes large blueshifts. The redshifts are possibly due to a reduced plasmon-coupling effect with the excitonic region of MoS2. The observed blueshifts of the LSPR peak position are possibly due to surface modification between WS2 and Ti. Changing the relative humidity from 58% to 88% only elicited a response in Ti/MoS2. Thus, MoS2 shows more sensitivity on 36-nm thickness of Ti compared with WS2. Therefore, the proposed fiber-optic sensor with integration of 2D materials is capable of measuring humidity in any environment
English language and graduate employability
No full textPurpose: The purpose of this paper is to examine the perspectives of Malaysian employers and students on the need for English language proficiency and skills for employment. Design/methodology/approach: Interviews were conducted with employers from various organisations. Additionally, questionnaires were disseminated to undergraduates at four public universities in Malaysia. These were done to ascertain the perspectives of different stakeholders on the importance of English in securing employment, the effect of a marked regional accent or dialect on employability and industry’s expectations and requirements for new employees. Findings: Employers and students agree that English plays a major role in employability. Whilst there was general agreement by both parties that good grammar and a wide range of vocabulary are important, the findings indicated several mismatches in terms of students’ perceptions and employers’ expectations. Among them is the use of the colloquial form of English at the workplace which was not favoured by employers. Employers also generally felt that knowledge of different types of writing styles could be learnt on-the-job. Furthermore, employers pointed out other essential skills for employability: the ability to communicate in other languages, confidence and a good attitude. Practical implications: Cognisant of the fact that English is essential in improving employability, initiatives to improve the level of English among Malaysian students must continue to be put in place. University students should be made aware of the different language skills sought by employers early in their university education. The mismatches between the perceptions of university students and the expectations of employers should be considered when planning English language courses and degree programmes. More structured feedback from industry on both would help to better prepare students for the world of work and to ease the transition from campus to career. Social implications: In relation to graduate employability, these English-language elite groups would have an advantage in securing employment especially in multinational companies, and this will, in a long run, create a larger gap between students from the international and public schools. Originality/value: With the standpoint of two important parties, employers and students, a more comprehensive idea of the effect of English language on employability has been obtained
Review on space science research in Malaysia
No full textThe Malaysia in space science R & D is still in its infancy stage. Internationally, space science has a major role and has impacted our society over the last 50 years and will continue providing returns on investment. The Return on Investment (ROI) could be in the form of new knowledge that provides understanding to world problems such as those relating to the Earth-Sun relationship. These can be directly or indirectly beneficial. The main output from space science R & D is new knowledge which is "priceless". Other than that space science will provide economic opportunities as well as wealth creation and social well-being. In Malaysia, space science R & D has progressed but there are a lot of windows for improvement. This review article looked at several milestones in the Malaysian space science R & D program as well as at its current challenges. Recommendations are made for the improvement of the space science R & D program in Malaysia
Factors influencing childhood anaemia in Bangladesh: a two level logistic regression analysis
No full textBackground: Anemia is not only a major public health problem among children in developing countries, it is also an important predictor for their future growth and development. The objective of this study was to identify possible factors associated with anemia among pre-school children in Bangladesh after removing a cluster effect of the population, and to determine the prevalence of this condition. Methods: Data for this study was extracted from the 2011 Bangladesh Demographic and Health Survey (BDHS-2011). In this survey, data was collected using a two-stage stratified cluster sampling approach. The chi-square test and a two-level logistic regression model were used for further analysis. Results: Data from 2231 children aged 6-59 months were included for analysis. The prevalence of child anemia was noted to be 52.10%. Among these anemic children, 48.40% where from urban environment and 53.90% were from rural areas. The prevalence of mild, moderate and severe anemia among children was 57.10, 41.40 and 1.50% respectively. The two-level logistic regression model revealed that the following factors were associated with childhood anemia: children of anemic mothers (p < 0.01), undernourished children (p < 0.05), younger children (age < 2 years) (p < 0.01) and children from poor family (p < 0.05). Lastly, anemia was more common among children living in Barisal and Rangpur divisions compared to those from Dhaka division (p < 0.01), and among non-Muslims than Muslim (p < 0.05). Conclusions: Our study showed that prevalence of anemia among pre-school children in Bangladesh was very high (52.10%). We noted that young children of anemic mothers, from poor families, and being undernourished were at higher risk of developing anemia. Since most of these risk factors were related to socioeconomic conditions, they were potentially modifiable. Therefore, our findings may be useful for the health authorities to identify children at risk for remedial action and to plan for preventive measures
Low-Cost Integrated Zinc Oxide Nanorod-Based Humidity Sensors for Arduino Platform
No full textRealization of a simple integrated and low-cost intensity modulation/direct detection-based humidity and vapor detection system utilizing zinc oxide (ZnO) nanorods as the active material is demonstrated. The sensing device comprises of ZnO nanorods optimally grown on a glass substrate and mounted on 3D printed platform for the alignment with a green light-emitting diode setup for an edge excitation. An Arduino platform was used for the signal processing of the detection of the transmitted light. Both forward and backward scattering are affected due to light leakage while propagating through the glass substrate which are further attenuated in the presence of humidity. In this paper, backward scattering was found to be dominant, and thus, with increasing humidity, a reduction in the transmitted light was monitored. When the sensor was tested in a humidity controlled environment, it was found that the output voltage drops by approximately 750 mV upon changing the relative humidity (RH) level from 35% to 90% in a non-linear fashion. The average sensitivity of the sensor was observed to be-12 mV/% throughout the tested RH levels. Sensitivity was found to be higher at-24.6 mV/% for RH's beyond 70%. An average response time of 3.8 s was obtained for RH levels of 85% with respect to the standard ambient humidity conditions (RH 50%), which showed a quicker recovery time of 2.2 s. The proposed sensor device provides numerous advantages, including low-cost production, simplicity in design, ease of use, and stability during handling
Smart combination of β-cyclodextrin polymer-conjugated magnetic nanosorbent for potential adsorption of deoxyribonucleic acid
No full textWe reported the synthesis and characterization of Fe 3 O 4 magnetic nanoparticles modified β-cyclodextrin polymer (MNP@βCD-TDI) for the adsorption of deoxyribonucleic acid (DNA). The synthesized MNP@βCD-TDI was characterized by Fourier Transform Infra-Red spectroscopy and Vibrating Sample Magnetometer. Experiments were performed in a batch mode and parameters that affected the DNA adsorption were investigated. An evaluation of the adsorption behavior revealed that Freundlich model and pseudo-second-order fit the equilibrium data. The adsorption efficiency of DNA was found to be at 70 ± 5 % after being recycled three times. This study could be used as a general platform for future work on DNA adsorption and enrichment
An unexpected encounter with jejunal web after foreign bodies entrapment in a toddler
No full textWe present a very rare case of jejunal web discovered after a toddler presented with foreign bodies entrapment, following incidental ingestion. This is perhaps the first case reported in the English publication. Expectant management with spontaneous passage of foreign bodies failed. Serial abdominal radiographs failed to determine the site of the foreign bodies accurately. Endoscopic removal was unsuccessful. Surgical removal was warranted with unexpected intra-operative finding of a jejunal web with foreign body entrapment. Although rare, a congenital intestinal web must be considered in a child presents with failure of expectant management following foreign body ingestion as surgical intervention is necessary
Training size optimization with reduced complexity in cell-free massive MIMO system
No full textTraining sequence is used in multiple antenna systems to estimate channel state information and mitigate channel distortion between transmitter and receiver. However, the training sequence or pilot must be limited to a certain size in order to reduce the impact of overhead loss due to limited channel coherence length in mobile users. In this paper, we proposed to use training size optimization in cell-free massive MIMO system. In addition, we proposed and compared the performance of different training size optimization algorithms, namely exhaustive search optimization, bisection optimization and min–max optimization, with each method has different level of calculation complexities. The results showed that in general, all of the 3 training length optimization methods improved the downlink rate compared to the conventional pilot length method. We also showed that the training optimization methods are more effective when the coherence length is small or the number of users is very large. In the case of large number of users or small coherence length, the exhaustive search has the best median downlink rate, followed closely by min–max optimum and finally the bisection method. Even though the exhaustive search optimization has the best downlink rate, we showed that the proposed reduce optimization complexity methods has significantly less calculation complexity. In addition, the median downlink rate performance of min–max optimization method is only slightly less than that of the exhaustive search method for various number of users and coherence length. © 2018, Springer Science+Business Media, LLC, part of Springer Nature
Genomic analyses of two Alteromonas stellipolaris strains reveal traits with potential biotechnological applications
No full textThe Alteromonas stellipolaris strains PQQ-42 and PQQ-44, previously isolated from a fish hatchery, have been selected on the basis of their strong quorum quenching (QQ) activity, as well as their ability to reduce Vibrio-induced mortality on the coral Oculina patagonica. In this study, the genome sequences of both strains were determined and analyzed in order to identify the mechanism responsible for QQ activity. Both PQQ-42 and PQQ-44 were found to degrade a wide range of N-acylhomoserine lactone (AHL) QS signals, possibly due to the presence of an aac gene which encodes an AHL amidohydrolase. In addition, the different colony morphologies exhibited by the strains could be related to the differences observed in genes encoding cell wall biosynthesis and exopolysaccharide (EPS) production. The PQQ-42 strain produces more EPS (0.36 g l−1) than the PQQ-44 strain (0.15 g l−1), whose chemical compositions also differ. Remarkably, PQQ-44 EPS contains large amounts of fucose, a sugar used in high-value biotechnological applications. Furthermore, the genome of strain PQQ-42 contained a large non-ribosomal peptide synthase (NRPS) cluster with a previously unknown genetic structure. The synthesis of enzymes and other bioactive compounds were also identified, indicating that PQQ-42 and PQQ-44 could have biotechnological applications. © 2019, The Author(s)