Dielectric properties of strontium titanate in the 1 MHz to 1.5 GHz frequency regions

Strontium Titanate, SrTiO3 samples were prepared using the conventional solid state reaction method. SrTiO3 samples were sintered at 1100°C, 1200°C, and 1300°C. XRD was used to determine the crystalline structure of the samples. The AFM showed the grain size was significantly increased with an increase in sintering temperatures. The dielectric properties of the sample were measured using Agilent 4291B Impedance/material Analyzer in the sub-microwave region in the frequency range 1 MHz to 1.5 GHz at room temperature. The dielectric constant and the average grain size were found to be the highest for the SrTiO3 sample sintered at 1200°C. Hence, greatest dielectric polarization occurred in the sample with the largest grain size

Effect of milling time on microstructure, crystallite size and dielectric properties of Srtio3 ceramic synthesized via mechanical alloying method

SrTiO3 sample has been successfully prepared by mechanical alloying (MA) method. The effect of milling time on microstructure, crystallite size and dielectric properties of SrTiO3 were studied. The results revealed that the mean crystallite size of milled powders decreased from 84.56 to 12.87 nm with increasing milling time. However, the average lattice strain of milled powders increased from 0.2 to 0.93% with increasing milling time. A single phase SrTiO3 could not be formed with milling alone and required annealing process. A transformation of anatase-TiO2 to rutile-TiO2 was observed at 16 h of milling. After the milled powders were subjected to sintering process at 1200°C, formation of single-phase SrTiO3-type cubic (Pm-3m) perovskite structure was observed. The peak intensities of the sintered SrTiO3 samples decreased as the milling time was increased. For microstructural observations, the average grain size of the sintered SrTiO3 sample milled for 8 h showed the largest. For dielectric measurements, the dielectric constant of the sintered SrTiO3 sample milled for 8 h showed the highest among others. This could be due to the largest grain size obtained for sintered SrTiO3 sample milled for 8 h. The decrease in the grain size with increasing milling time resulted to the decrease in dielectric constant

Integration of Use Case Formal Template Using Mapping Rules

The integration of use case and formal specification plays an essential role in addressing the issue of gaining the rigor and reliable software model such as formal model via easy and economic model such as object model. Although extensive research has been carried out on this Integration, however there is a huge challenge on bridging the gaps between natural language used In use case scenario and the mathematics model used in formal model. This Is mainly because of the differences In syntax and semantic of these two models. Natural language requirement is well documented that it is being inconsistent, inherently ambiguous, and incomplete even though natural language Is universal, widespread, and flexible. As a consequence, It may lead to misunderstanding and produce an incorrect and inaccurate analysis and design model. Therefore, this paper aims to propose a use case formal template and define a new set of mapping rules that Is used for formalizing UML use case by transforming use case scenarios which are written In natural language Into VDM++ formal specification. The formal verification for the generated VDM++ formal specification can be further conducted by adopting the existing support tool of VDM++ (i. e. VDM++ ToolBox) to verify the correctness of the specification

Sintesis dan pencirian poli(etilena glikol) bermetoksi-ko-poli(β-amino ester) yang dibentuk daripada heksilamina linear dan siklik sebagai misel polimer

Poli(etilena glikol) bermetoksi-ko-poli(β-amino ester) (MPEG-PbAE) telah disintesis dengan menggunakan poli(etilena glikol) bermetoksi yang mempunyai kumpulan hujung berfungsi akrilat (MPEG-ac), 1,6-heksanadiol diakrilat, heksilamina linear (A) dan heksilamina siklik (B) sebagai bahan reaktan. Kopolimer MPEG-PbAE A dan B dijangka akan membentuk misel dengan MPEG berfungsi sebagai bahagian luar yang hidrofilik dan PbAE yang mempunyai kumpulan heksil berfungsi sebagai bahagian dalam yang hidrofobik. MPEG-ac selepas diubah suai dan kopolimer MPEG-PbAE A dan B selepas disintesis telah dicirikan. Spektroskopi inframerah transformasi Fourier (FT-IR) dan spektroskopi resonans magnet nukleus jenis proton (1H-NMR) telah mengesahkan pengubahsuaian kumpulan hujung hidroksil di MPEG kepada kumpulan hujung akrilat. Didapati kopolimer A adalah lebih sesuai digunakan sebagai pembawa ubat berdasarkan perbandingan antara kopolimer A daripada heksilamina linear dan kopolimer B daripada heksilamina siklik. Kromatografi penelapan gel (GPC) menunjukkan bahawa nombor-purata berat molekul, Mn kopolimer A adalah 11216 dengan indeks kepoliserakan (PDI) 1.1925. Kepekatan misel kritikal (CMC) kopolimer A dalam larutan akueus pH7.4 adalah 84.6 mg/L. Purata saiz misel yang diperoleh daripada analisis penyerakan cahaya dinamik (DLS) adalah 26.25±0.149 nm

Development of dielectric material with ceramic matrix composite (CMC) produced from kaolinite and CaCu3Ti4O12 (CCTO)

Ceramic matrix composites (CMC) combine reinforcing ceramic phases, CaCu3Ti4O12 (CCTO) with a ceramic matrix, kaolinite to create materials with new and superior properties. 10% and 20% CCTO were prepared by using a conventional solid state reaction method. CMC samples were pre‐sintered at 800 °C and sintered at 1000 °C. The dielectric properties of samples were measured using HP 4192A LF Impedance Analyzer. Microstructures of the samples were observed using an optical microscope. XRD was used to determine the crystalline structure of the samples. The AFM showed the morphology of the samples. The results showed that the dielectric constant and dielectric loss factor of both samples are frequency dependent. At 10 Hz, the dielectric constant is 1011 for both samples. The CMC samples were independent with temperature with low dielectric constant in the frequency range of 104–106 Hz. Since the CMC samples consist of different amount of kaolinite, so each sample exhibit different defect mechanism. Different reaction may occur for different composition of material. The effects of processing conditions on the microstructure and electrical properties of CMC are also discussed

Development of dielectric material, CaCu3Ti4O12

CaCu3Ti4O12 (CCTO) was prepared by a conventional solid state reaction method. CCTO sample was pre-sintered at 900°C for 10 hours and sintered at 1075°C for 12 hours. The dielectric properties of the sample were measured using HP 4192A LF Impedance Analyzer. The complex permittivity was measured within the frequency range from 10 Hz to 106 Hz and the temperature ranging from 30°C to 400°C. The results showed that the dielectric constant and dielectric loss factor of the sample are frequency dependent and temperature dependent. CCTO sample exhibits a high dielectric constant which is around 105. Dielectric constant increases with decreasing frequency due to interfacial polarization. This could be explained by the Maxwell- Wagner effect

Entomologic and molecular investigation into Plasmodium vivax transmission in Singapore, 2009

<p>Abstract</p> <p>Background</p> <p>Singapore has been certified malaria free since November 1982 by the World Health Organization and despite occasional local transmission, the country has maintained the standing. In 2009, three clusters of malaria cases were reported in Singapore.</p> <p>Methods</p> <p>Epidemiological, entomological and molecular studies were carried out to investigate the three clusters, namely Mandai-Sungei Kadut, Jurong Island and Sembawang.</p> <p>Results</p> <p>A total of 29 malaria patients, with no recent travel history, were reported in the three clusters. Molecular analysis based on the <it>msp3α </it>and <it>msp1 </it>genes showed two independent local transmissions: one in Mandai-Sungei Kadut and another in Sembawang. Almost all cases within each cluster were epidemiologically linked. In Jurong Island cluster, epidemiological link remains uncertain, as almost all cases had a unique genetic profile. Only two cases shared a common profile and were found to be linked to the Mandai-Sungei Kadut cluster. Entomological investigation found <it>Anopheles sinensis </it>to be the predominant Anopheline in the two areas where local transmission of <it>P. vivax </it>was confirmed. <it>Anopheles sinensis </it>was found to be attracted to human bait and bites as early as 19:45 hrs. However, all <it>Anopheles </it>mosquitoes caught were negative for sporozoites and oocysts by dissection.</p> <p>Conclusion</p> <p>Investigation of <it>P. vivax </it>cases from the three cluster areas confirmed the occurrence of local transmission in two areas. Although <it>An. sinensis </it>was the predominant Anopheline found in areas with confirmed transmission, the vector/s responsible for the outbreaks still remains cryptic.</p

First Report from the Asian Rotavirus Surveillance Network

Rotavirus remains the most common cause of severe, dehydrating diarrhea among children worldwide. Several rotavirus vaccines are under development. Decisions about new vaccine introduction will require reliable data on disease impact. The Asian Rotavirus Surveillance Network, begun in 2000 to facilitate collection of these data, is a regional collaboration of 36 hospitals in nine countries or areas that conduct surveillance for rotavirus hospitalizations using a uniform World Health Organization protocol. We summarize the Network's organization and experience from August 2001 through July 2002. During this period, 45% of acute diarrheal hospitalizations among children 0–5 years were attributable to rotavirus, higher than previous estimates. Rotavirus was detected in all sites year-round. This network is a novel, regional approach to surveillance for vaccine-preventable diseases. Such a network should provide increased visibility and advocacy, enable more efficient data collection, facilitate training, and serve as the paradigm for rotavirus surveillance activities in other regions

Canagliflozin and renal outcomes in type 2 diabetes and nephropathy

BACKGROUND Type 2 diabetes mellitus is the leading cause of kidney failure worldwide, but few effective long-term treatments are available. In cardiovascular trials of inhibitors of sodium–glucose cotransporter 2 (SGLT2), exploratory results have suggested that such drugs may improve renal outcomes in patients with type 2 diabetes. METHODS In this double-blind, randomized trial, we assigned patients with type 2 diabetes and albuminuric chronic kidney disease to receive canagliflozin, an oral SGLT2 inhibitor, at a dose of 100 mg daily or placebo. All the patients had an estimated glomerular filtration rate (GFR) of 30 to &lt;90 ml per minute per 1.73 m2 of body-surface area and albuminuria (ratio of albumin [mg] to creatinine [g], &gt;300 to 5000) and were treated with renin–angiotensin system blockade. The primary outcome was a composite of end-stage kidney disease (dialysis, transplantation, or a sustained estimated GFR of &lt;15 ml per minute per 1.73 m2), a doubling of the serum creatinine level, or death from renal or cardiovascular causes. Prespecified secondary outcomes were tested hierarchically. RESULTS The trial was stopped early after a planned interim analysis on the recommendation of the data and safety monitoring committee. At that time, 4401 patients had undergone randomization, with a median follow-up of 2.62 years. The relative risk of the primary outcome was 30% lower in the canagliflozin group than in the placebo group, with event rates of 43.2 and 61.2 per 1000 patient-years, respectively (hazard ratio, 0.70; 95% confidence interval [CI], 0.59 to 0.82; P=0.00001). The relative risk of the renal-specific composite of end-stage kidney disease, a doubling of the creatinine level, or death from renal causes was lower by 34% (hazard ratio, 0.66; 95% CI, 0.53 to 0.81; P&lt;0.001), and the relative risk of end-stage kidney disease was lower by 32% (hazard ratio, 0.68; 95% CI, 0.54 to 0.86; P=0.002). The canagliflozin group also had a lower risk of cardiovascular death, myocardial infarction, or stroke (hazard ratio, 0.80; 95% CI, 0.67 to 0.95; P=0.01) and hospitalization for heart failure (hazard ratio, 0.61; 95% CI, 0.47 to 0.80; P&lt;0.001). There were no significant differences in rates of amputation or fracture. CONCLUSIONS In patients with type 2 diabetes and kidney disease, the risk of kidney failure and cardiovascular events was lower in the canagliflozin group than in the placebo group at a median follow-up of 2.62 years