Silicon micromachined waveguides for millimeter-wave and submillimeter-wave frequencies

The development of micromachining techniques to create silicon-based waveguide circuits, which can operate up to high submillimeter-wave frequencies, is reported. As a first step, a WR-10 waveguide has been fabricated from (110) silicon wafers. Insertion loss measurements on a gold-plated silicon waveguide show performance comparable to that of standard metal waveguides. It is suggested that active devices and planar circuits can be integrated with the waveguides, solving the traditional mounting problems

Silicon micromachined waveguides for millimeter and submillimeter wavelengths

The majority of radio receivers, transmitters, and components operating at millimeter and submillimeter wavelengths utilize rectangular waveguides in some form. However, conventional machining techniques for waveguides operating above a few hundred GHz are complicated and costly. This paper reports on the development of silicon micromachining techniques to create silicon-based waveguide circuits which can operate at millimeter and submillimeter wavelengths. As a first step, rectangular WR-10 waveguide structures have been fabricated from (110) silicon wafers using micromachining techniques. The waveguide is split along the broad wall. Each half is formed by first etching a channel completely through a wafer. Potassium hydroxide is used to etch smooth mirror-like vertical walls and LPCVD silicon nitride is used as a masking layer. This wafer is then bonded to another flat wafer using a polyimide bonding technique and diced into the U-shaped half wavelengths. Finally, a gold layer is applied to the waveguide walls. Insertion loss measurements show losses comparable to those of standard metal waveguides. It is suggested that active devices and planar circuits can be integrated with the waveguides, solving the traditional mounting problems. Potential applications in terahertz instrumentation technology are further discussed

Photo-induced reduction of graphene oxide coating on optical waveguide and consequent optical intermodulation

Increased absorption of transverse-magnetic (TM) - polarised light by a graphene-oxide (GO) coated polymer waveguide has been observed in the presence of transverse-electric (TE) - polarised light. The GO-coated waveguide exhibits very strong photo-absorption of TE-polarised light - and acts as a TM-pass waveguide polariser. The absorbed TE-polarised light causes a significant temperature increase in the GO film and induces thermal reduction of the GO, resulting in an increase in optical-frequency conductivity and consequently increased optical propagation loss. This behaviour in a GO-coated waveguide gives the action of an inverted optical switch/modulator. By varying the incident TE-polarised light power, a maximum modulation efficiency of 72% was measured, with application of an incident optical power level of 57 mW. The GO-coated waveguide was able to respond clearly to modulated TE-polarised light with a pulse duration of as little as 100 μs. In addition, no wavelength dependence was observed in the response of either the modulation (TE-polarised light) or the signal (TM-polarised light)

The use of misoprostol in the active management of the third stage of labour

Ph.DDOCTOR OF MEDICIN

Comparison of high resolution computed tomography findings of thorax between smear negative pulmonary tuberculosis and non-pulmonary tuberculosis among patients with suspected pulmonary tuberculosis in Hospital Universiti Sains Malaysia

Background: Pulmonary tuberculosis (PTB) has been around for over 100 years since it was first discovered. Despite its long existence, medical practitioners still found it challenging to diagnose sputum smear negative PTB. The ability of high resolution computed tomography (HRCT) in diagnosing PTB is still under discussion and investigation in the sputum smear-negative setting. Thus, this study was conducted to determine the HRCT findings in diagnosing early stage of active smear negative PTB and to study specific HRCT findings in diagnosing smear negative PTB. Methods: A cross-sectional study was conducted in Hospital Universiti Sains Malaysia (USM), Kota Bharu, Kelantan, Malaysia on 22 patients whose sputum smears were negative, and had undergone HRCT thorax. HRCT findings were collected and described using descriptive statistic, count (n) and percentage (%); and comparative HRCT findings between smear negative PTB versus non-PTB was analysed using the Pearson chi-square test. Results: The tree-in-bud appearance showed a significant association with smear negative PTB, with p-value of 0.046. And this main findings of tree-in-bud appearance showed significant association with smear negative PTB at S5 (medial segment) of right middle lobe and S3 (anterior segment) of left upper lobe, with p-value of 0.025 on both sides. Conclusion: Tree-in-bud appearance which indicates the early stage of active PTB, had shown significant association with smear negative PTB, and can be detected in HRCT. Hence, HRCT could be used as an alternative method to detect active PTB in the background of sputum smear-negative setting among higher risk patients

Development Of Seismic Refraction Technique With Flexible Sources- Receivers Arrangement

Seismic refraction method is one of the most effective of all geophysical methods used to characterize ground subsurface. The restricted use of seismic refraction may due to some limitations associated with survey costs and inadequate flexibility of survey. This study outlines the development of a new approach in flexible sources-receivers arrangement for seismic refraction data acquisition technique. This new design is an innovative solution which implements only a few geophones to execute a full-length seismic refraction survey, with adequately similar data to pick first arrival time in order to overcome the limitations of coverage and inflexibility of the survey

Lactate dehydrogenase in the guppy fish (Poecilia reticulata) as a biomarker of heavy-metal pollution in freshwater ecosystems

Heavy metal concentrations and allozyme variations were determined in females of guppy fish (Poecilia reticulata) populations collected from polluted and unpolluted sites. the concentrations of Cu and Fe were significantly (P0.05) in the Zn concentrations between the polluted and the unpolluted populations indicated that Zn, as a major essential metal, was regulated in this freshwater fish. seven enzyme systems EST, G6PDH, LDH, MDH, PGI, PGM, and SDH were tested. Only LDH (lactate dehydrogenase) was found to be agood biomarker for the contamination of Cu and Fe in P. reticulata. The zymogram of teh unpolluted wild population showed the same monomorphic allele as the unpolluted domesticated guppies from a pet shop,thus, further confirming LDH in P. reticulata as agood biomarker of contamination by Cu

Allozyme polymorphisms in horseshoe crabs, Carcinoscorpius rotundicauda, collected from polluted and unpolluted intertidal areas in Peninsular Malaysia.

It has been widely reported that allozyme frequency variation is a potential indicator of heavy metal-induced impacts in aquatic populations. In the present study, wild populations of horseshoe crab (Carcinoscorpius rotundicauda) were collected from contaminated and uncontaminated sites of Peninsular Malaysia. By adopting horizontal starch gel electrophoresis, seven enzyme systems were used to study allozyme polymorphisms. Nine polymorphic loci were observed in C. rotundicauda. The relationships of allozyme variations with the concentrations of Cd, Cu, Ni, and Zn in sediments and in muscle tissues of horseshoe crabs were determined. Based on genetic distance, the lower mean value of Nei's D (0.017) indicated that both of the contaminated populations of Kg. Pasir Puteh and Kuala Juru were very closely related when compared to the relatively uncontaminated Pantai Lido population. Higher heterozygosities were shown by the contaminated populations when compared to the uncontaminated population. Different allelic frequencies could be observed for the aldolase (ALD; E.C. 2.7.5.1) locus between the contaminated and uncontaminated populations of C. rotundicauda. The dendrogram of genetic relationships of the three populations of C. rotundicauda showed the same clustering pattern as the dendrograms are based on heavy metals in the sediments and in the horseshoe crabs' abdominal muscles. From the F statistics, the present study showed that the three populations of horseshoe crabs were considered to have undergone moderate genetic differentiation with a mean F (ST) value of 0.092 .The current results suggest that allozyme polymorphism in horseshoe crabs is a potential biomonitoring tool for metal contamination, although further validation is required

Is there a role for remote ischemic conditioning in preventing 5-fluorouracil-induced coronary vasospasm?

Cardiac ischemia associated with chemotherapy has been linked to several anti-neoplastic agents and is multifactorial in etiology. Coronary artery vasospasm is one of the most commonly reported effects of cancer therapy that can lead to myocardial ischemia or infarction. The chemotherapy agent 5-fluorouracil (5-FU) or its oral pro-drug capecitabine can result in coronary vascular endothelial dysfunction causing coronary artery spasm, and possibly coronary thrombosis. These drugs have also been shown to be associated with myocardial infarction, malignant ventricular arrhythmias, heart failure, cardiogenic shock, and sudden death. The proposed mechanisms underlying cardiotoxicity induced by 5-FU are vascular endothelial damage followed by thrombus formation, ischemia secondary to coronary artery vasospasm, direct toxicity on myocardium, and thrombogenicity. There remains a pressing need to discover novel and effective therapies that can prevent or ameliorate 5-FU associated cardiotoxicity. To this point, promising overlap has been observed between proposed remote ischemic conditioning (RIC) cardioprotective mechanisms and 5FU-associated cardiotoxic cellular pathways. RIC, in which transient episodes of limb ischemia and reperfusion (induced by inflations and deflations of a pneumatic cuff placed on the upper arm or thigh), confer both cardioprotective and vasculoprotective effects, and may therefore prevent 5-FU coronary artery spasm/cardiotoxicity. In this review, we will be discussing the following potentially therapeutic aspects of RIC in ameliorating 5-FU associated cardiotoxicity: sequential phases of 5-FU cardiotoxicity as possible targets for dual windows of cardioprotection characteristic of RIC; protective effects of RIC on endothelial function and microvasculature in relation to 5-FU induced endothelial dysfunction/microvascular dysfunction; reduction in platelet activation by RIC in the context of 5-FU induced thrombogenicity; and the utility of improvement in mitochondrial function conferred by RIC in 5-FU induced cellular toxicity secondary to mitochondrial dysfunction

Sparse temporally dynamic resting-state functional connectivity networks for early MCI identification

In conventional resting-state functional MRI (R-fMRI) analysis, functional connectivity is assumed to be temporally stationary, overlooking neural activities or interactions that may happen within the scan duration. Dynamic changes of neural interactions can be reflected by variations of topology and correlation strength in temporally correlated functional connectivity networks. These connectivity networks may potentially capture subtle yet short neural connectivity disruptions induced by disease pathologies. Accordingly, we are motivated to utilize disrupted temporal network properties for improving control-patient classification performance. Specifically, a sliding window approach is firstly employed to generate a sequence of overlapping R-fMRI sub-series. Based on these sub-series, sliding window correlations, which characterize the neural interactions between brain regions, are then computed to construct a series of temporal networks. Individual estimation of these temporal networks using conventional network construction approaches fails to take into consideration intrinsic temporal smoothness among successive overlapping R-fMRI subseries. To preserve temporal smoothness of R-fMRI sub-series, we suggest to jointly estimate the temporal networks by maximizing a penalized log likelihood using a fused sparse learning algorithm. This sparse learning algorithm encourages temporally correlated networks to have similar network topology and correlation strengths. We design a disease identification framework based on the estimated temporal networks, and group level network property differences and classification results demonstrate the importance of including temporally dynamic R-fMRI scan information to improve diagnosis accuracy of mild cognitive impairment patients