19672 research outputs found
Sort by
One-photon Absorption Characterizations, Dipole Polarizabilities and Second Hyperpolarizabilities of Chlorophyll a and Crocin
No full textThe dispersion-free dipole polarizability (α) computations for chlorophyll a (1) and crocin (2) have been achieved by density functional theory (DFT) at B3LYP/ 6-31G(d) level. The measured one-photon absorption (OPA) wavelengths are quite consistence with the theoretically obtained values. Ab-initio quantum chemical calculations (time-dependent Hartree-Fock (TDHF)) have been implemented to reveal the static second hyperpolarizabilities (γ) and dynamic dipole polarizabilities of the title molecules. The examined compounds display γ with non-zero values, introducing their third-order nonlinear optical (NLO) phenomena. The first and second frontier molecular orbitals of the investigated molecules have been also derived from DFT
Load forecasting using combination model of multiple linear regression with neural network for Malaysian City
No full textForecasting a multiple seasonal data is differ from a usual seasonal data since it contains more than one cycle in a data. Multiple linear regression (MLR) models have been used widely in load forecasting because of its usefulness in the forecast a linear relationship with other factors but MLR has a disadvantage of having difficulties in modelling a nonlinear relationship between the variables and influencing factors. Neural network (NN) model, on the other hand, is a good model for modelling a nonlinear data. Therefore, in this study, a combination of MLR and NN models has proposed this combination to overcome the problem. This hybrid model is then compared with MLR and NN models to see the performance of the hybrid model. RMSE is used as a performance indicator and a proposed graphical error plot is introduce to see the error graphically. From the result obtained this model gives a better forecast compare to the other two models
Prevalence, transitions and factors predicting transition between frailty states among rural community-dwelling older adults in Malaysia
No full textObjectives This study aims to describe the prevalence and transitions of frailty among rural-community dwelling older adults in Malaysia and to analyse factors associated with different states of frailty transition. Frailty was conceptualized using modified Fried phenotype from the Cardiovascular Health Study. Design This is a prospective longitudinal study with 12-months follow up among older adults in Malaysia. Setting Kuala Pilah, a district in Negeri Sembilan, which is one of the fourteen states in Malaysia. Participants 2,324 community-dwelling older Malaysians aged 60 years and older. Results The overall prevalence of frailty in this study was 9.4% (95% CI 7.8–11.2). The prevalence increased at least three-fold with every 10 years of age. This increase was seen higher in women compared to men. Being frail was significantly associated with older age, women, and respondents with a higher number of chronic diseases, poor cognitive function and low socioeconomic status (p<0.05). During the 12-months follow-up, our study showed that the transition towards greater frailty states were more likely (22.9%) than transition toward lesser frailty states (19.9%) while majority (57.2%) Remained unchanged. Multivariate logistic regression analysis showed that presence of low physical activity increased the likelihood of worsening transition towards greater frailty states by three times (OR 2.9, 95% CI 2.2–3.7) and lowered the likelihood of transition towards lesser frailty states (OR 0.3, 95% CI 0.2–0.4). Conclusion Frailty is reported among one in every eleven older adults in this study. The prevalence increased across age groups and was higher among women than men. Frailty possesses a dynamic status due to its potential reversibility. This reversibility makes it a cornerstone to delay frailty progression. Our study noted that physical activity conferred the greatest benefit as a modifiable factor in frailty prevention
Mixed Transition Metal Dichalcogenide as Saturable Absorber in Ytterbium, Praseodymium, and Erbium Fiber Laser
No full textIn this paper, a Mo(1-x)WxS2 thin film saturable absorber (SA) is proposed and fabricated and its performance over a wavelength region of 1.0 to 1.5 μ {m} investigated. The few layer MoWS2 is obtained by hydrothermal exfoliation and fabricated into thin film with a host polymer. The SA is tested in a ring laser cavity with different gain media consisting of Ytterbium, Praseodymium, and Erbium doped fibers for Q-switching operation at 1.0, 1.3, and $1.56~ μ m. In all cases, the SA performs admirably with the mixed transition metal composition of the MoWS2 thin film allowing the optical properties of the SA to be altered by changing the composition ratio and the number of layers. The proposed SA has high potential as a new optical material to cater the needs of many optoelectronics application
High responsivity, self-powered carbon–zinc oxide hybrid thin film based photodetector
No full textA self-powered n-Si/C–ZnO/SiO2/p-Si heterojunction photodetector (PD) which comprises of carbon (C) and zinc oxide (ZnO) nanostructures on a n-type silicon (n-Si) substrate was prepared via vapor phase transport method. Excellent photodetection under 468 nm light illumination for powers ranging from 2.78 to 2910 µW delivered a quick response of about 9.5 µs. A high photoresponsivity of 2.082/AW and external quantum efficiency about 551% were obtained. The mechanism involved for the generation of a photocurrent at a zero bias voltage was discussed for future energy efficient optoelectronics devices. The morphology and composition of C, Zn and O were confirmed by field emission scanning electron microscope, energy dispersive X-ray and Raman scattering analysis. The formation of ZnO nanowires range from 10 to 100 nm, aided by the photoconduction mechanism. The Raman E2 high mode of 437/cm of ZnO and the presence of D and G bands show the formation of a hybrid C–ZnO thin film. The calculated rectifying ratio is found to shift as the direct current bias voltage and light power increased. The deposition of C particles on the ZnO surface creates point defects and sub-energy levels in the ZnO bandgap which favour fast responsivity in the PD
Q-switched laser generation using MoWS2-rGO in Erbium-doped fiber laser cavity
No full textA saturable absorber (SA) consisting of a Mo (1−x) W x S 2 -rGO composite is proposed and fabricated, and its performance demonstrated. The fabricated Mo (1−x) W x S 2 -rGO has an x composition of 0.2 and is incorporated into a polymer composite thin film. Nonlinear optical characterization of the SA reveals that the Mo (1−x) W x S 2 -rGO/PVA thin film exhibits a relatively high modulation depth of ∼5.9% and low saturation intensity of 0.003 MW/cm 2 . The Mo (1−x) W x S 2 -rGO/PVA thin film SA has an improved optical absorption as well as enhanced photo response, allowing it to generate tunable Q-switched outputs over a range of 56 nm from 1518 nm to 1574 nm in Erbium-doped fiber laser systems. At the optimum lasing wavelength of ∼1560 nm, the highest pulse repetition rate, narrowest pulse width, highest output power and highest pulse energy is achieved at 64.82 kHz, 1.47 μs, 0.37 mW and 5.98 nJ, respectively. The proposed laser would have significant applications in biomedical imaging, material processing environmental sensing and range finding
S+/S band passively Q-switched thulium-fluoride fiber laser based on using gallium selenide saturable absorber
No full textA Q-switched thulium-fluoride fiber (TFF) laser using gallium selenide (GaSe) as a passive saturable absorber (SA) for operation in the S+/S band is demonstrated. The generated pulses can be tuned from 1454 nm to 1512 nm, giving a tuning range of 58 nm. At 1502 nm, stable Q-switching operation is obtained from a pump power of 76.2 mW and is observed until the maximum pump power of 133.6 mW is reached, with the repetition rate varying from 16.5 kHz to 33.3 kHz and having a narrowest pulse width at 2.7 µs. The highest pulse energy obtained in this work is 51.4 nJ and this is, to the knowledge of the authors, the first time that Q-switching operation in the S+/S band region is obtained from a TFF laser using a GaSe based SA
Acrylate polymer coated side-polished fiber with graphene oxide nanoparticles for ultrafast fiber laser operation
No full textIn this work, a mode-locked fiber laser with a side-polished fiber coated with graphene oxide nanoparticles as a saturable absorber (SA) is proposed and demonstrated. The SA is further coated with an acrylate polymer layer to add strength and durability, thus enabling real-world applications to be realized. The coated SA is capable of generated a pulsed output with a pulse width, pulse energy and pulse peak power of 1.09 ps, 0.013 nJ and 0.012 kW respectively. The cavity has a threshold power of 131.7 mW, and the output signals have a constant signal-to-noise ratio of about 33 dB over a test period of 1 h, indicating a highly stable output. The protective polymer coating allows a simple way to manufacture a rugged device with no penalty to performance
A rare case of solitary unifocal Langerhans cell histiocytosis with orbital extension: Diagnostic dilemma
No full textLangerhans cell histiocytosis (LCH) is rarely encountered in ophthalmology practice. It is a spectrum of disorder characterized by accumulation of histiocytes in various tissues. Diagnosis is challenging as it may simulate periorbital hematoma, rhabdomyosarcoma, and neuroblastoma. We report a case of unifocal LCH with orbital extension. Diagnosis was obtained from incisional biopsy, and histopathological examination showed numerous histiocytes with eosinophilic infiltrations. The presence of Langerhans cells was confirmed by the presence of protein S-100, CD1a, and/or Langerin (CD207). Treatment depends on the degree of organ involvement. She responded well to cytotoxic drugs and steroids. This emphasized that prompt tissue diagnosis is crucial for early management
Automated detection and classification of liver fibrosis stages using contourlet transform and nonlinear features
No full textBackground and objective: Liver fibrosis is a type of chronic liver injury that is characterized by an excessive deposition of extracellular matrix protein. Early detection of liver fibrosis may prevent further growth toward liver cirrhosis and hepatocellular carcinoma. In the past, the only method to assess liver fibrosis was through biopsy, but this examination is invasive, expensive, prone to sampling errors, and may cause complications such as bleeding. Ultrasound-based elastography is a promising tool to measure tissue elasticity in real time; however, this technology requires an upgrade of the ultrasound system and software. In this study, a novel computer-aided diagnosis tool is proposed to automatically detect and classify the various stages of liver fibrosis based upon conventional B-mode ultrasound images. Methods: The proposed method uses a 2D contourlet transform and a set of texture features that are efficiently extracted from the transformed image. Then, the combination of a kernel discriminant analysis (KDA)-based feature reduction technique and analysis of variance (ANOVA)-based feature ranking technique was used, and the images were then classified into various stages of liver fibrosis. Results: Our 2D contourlet transform and texture feature analysis approach achieved a 91.46% accuracy using only four features input to the probabilistic neural network classifier, to classify the five stages of liver fibrosis. It also achieved a 92.16% sensitivity and 88.92% specificity for the same model. The evaluation was done on a database of 762 ultrasound images belonging to five different stages of liver fibrosis. Conclusions: The findings suggest that the proposed method can be useful to automatically detect and classify liver fibrosis, which would greatly assist clinicians in making an accurate diagnosis