Studies on proton exchange membranes-based SPEEK Chitosan crosslinked via ultraviolet curing method / Nazli Ahmad Aini

The use of proton exchange membrane (PEM) is very significant component in PEMFC and DMFC. It functions to separate anode and cathode, prevents fuel gas crossover, and transports protons from anode to the cathode through it. Nation is widely used as a PEM material in commercial PEMFC due to high proton conductivity, good mechanical, chemical stability and excellent thermal stability. However, seeking for new materials as an alternative to Nation is needed due to its expensive, low proton conductivity when temperature operation above 100 oC and high fuel permeability. As an alternative, sulfonated poly(ether ether ketone) (SPEEK) based membrane is a potential candidate due to low cost, exhibit good chemical and thermal stabilities. However, SPEEK with high degree of sulfonation (DS) exhibits gradually deterioration of the mechanical properties, excessive water uptakes at elevated temperatures and methanol permeability that leads to the reduction in cell voltage performance. The use of hybrid membrane is one opportunity to overcome the SPEEK drawbacks. SPEEK and Chitosan can be crosslinked through sulfonic (-S03H) and amine (-NH2) functional groups. Introduction of Chitosan into SPEEK membrane can modify SPEEK properties particularly by improving its swelling ability. Several series of cross-linked membranes of SPEEK with a chitosan were prepared by solution cast technique. SPEEK and Chitosan was dissolved in DMSO and acetic acid, respectively. They were then mixed together and stirred until homogenous solution obtained. The solution was then exposed and treated under ultra violet (UV) light for curing process. Only six samples were prepared with different composition

Resting-state fMRI: comparing default mode network connectivity between normal and low auditory working memory groups

The relationship between resting effective connectivity (EC) among default mode network (DMN) regions and auditory working memory (AWM) performance is still poorly understood. In this work, resting-state functional magnetic resonance imaging (rsfMRI) was used to determine the optimum connectivity model between posterior cingulate cortex (PCC) and medial prefrontal cortex (mPFC) in 40 healthy male volunteers. in low and normal working memory groups of subjects. Correlation between EC with AWM performance and AWM-capacity was also studied. The participants were divided into two groups which are normal and low AWM-capacity groups based on Malay Version Auditory Verbal Learning Test. The AWM performance was assessed using a word-based backward recall task. Both assessments were conducted outside the MRI scanner. The participants were scanned using a 3-T MRI system and the data were analyzed using statistical parametric mapping (SPM12) and spectral Dynamic Causal Modelling (spDCM). Results revealed that PCC and mPFC were significantly interconnected in both groups. Group analyses showed that the connection between PCC and mPFC exhibits an anti-correlated network. The results also indicated that the AWM performance and AWM-capacity were not associated with EC. These findings suggest that EC at rest between the two regions may not significantly influence cognitive abilities important for this AWM task

Whole genome sequence analysis showing unique SARS-CoV-2 lineages of B.1.524 and AU.2 in Malaysia

SARS-CoV-2 has spread throughout the world since its discovery in China, and Malaysia is no exception. WGS has been a crucial approach in studying the evolution and genetic diversity of SARS-CoV-2 in the ongoing pandemic. Despite considerable number of SARS-CoV-2 genome sequences have been submitted to GISAID and NCBI databases, there is still scarcity of data from Malaysia. This study aims to report new Malaysian lineages of the virus, responsible for the sustained spikes in COVID-19 cases during the third wave of the pandemic. Patients with nasopharyngeal and/or oropharyngeal swabs confirmed COVID-19 positive by real-time RT-PCR with CT value < 25 were chosen for WGS. The selected SARS-CoV-2 isolates were then sequenced, characterized and analyzed along with 986 sequences of the dominant lineages of D614G variants currently circulating throughout Malaysia. The prevalence of clade GH and G formed strong ground for the presence of two Malaysian lineages of AU.2 and B.1.524 that has caused sustained spikes of cases in the country. Statistical analysis on the association of gender and age group with Malaysian lineages revealed a significant association (p <0.05). Phylogenetic analysis revealed dispersion of 41 lineages, of these, 22 lineages are still active. Mutational analysis showed presence of unique G1223C missense mutation in transmembrane domain of the spike protein. For better understanding of the SARS-CoV-2 evolution in Malaysia especially with reference to the reported lineages, large scale studies based on WGS are warranted

Whole Genome Sequencing Analysis of Spike D614G Mutation Reveals Unique SARS-CoV-2 Lineages of B.1.524 and AU.2 in Malaysia

The SARS-CoV-2 has spread throughout the world since its discovery in China, and Malaysia is no exception. WGS has been a crucial approach in studying the evolution and genetic diversity of SARS-CoV-2 in the ongoing pandemic, and while an exceptional number of SARS-CoV-2 complete genomes have since been submitted to GISAID and NCBI, there is a scarcity of data from Malaysia. This study aims to report new Malaysian lineages responsible for the sustained spikes in COVID-19 cases during the third wave of the pandemic. Patients whose nasopharyngeal and oropharyngeal swabs were confirmed positive by real-time RT-PCR with Ct-value < 25 were chosen for WGS. The 10 SARS-CoV-2 isolates obtained were then sequenced, characterized and analyzed, including 1356 sequences of the dominant lineages of D614G variant currently circulating throughout Malaysia. The prevalence of clade GH and G formed strong ground of the discovery of two Malaysian lineages that caused sustained spikes of cases locally. Statistical analysis on the association of gender and age group with Malaysian lineages revealed a significant association (p < 0.05). Phylogenetic analysis revealed dispersion of 41 lineages, for which 22 lineages are still active. Mutational analysis observed unique G1223C missense mutation in Transmembrane Domain of Spike protein. Thus, calls for the large-scale WGS analysis of strains found around the world for greater understanding of viral evolution and genetic diversity especially in addressing the question of the effect of deleterious substitution mutation in transmembrane region of Spike protein

Perbandingan Ketelapan Awal Bagi Bahan Ferit Lembut Nixzn(1-x)Fe2O4, Mgxzn(1-x)Fe2O4 dan Cuxzn(1-x)Fe2O4

Desakan ke arah pengecilan litar elektronik dan anjakan frekuensi operasi yang lebih tinggi telah menghalakan penghasilan ferit dengan ketelapan awal yang tinggi serta kehilangan tenaga yang rendah. Untuk memenuhi permintaan dan keperluan teknologi semasa itu, beberapa keperluan seperti mikrostruktur yang homogen, suhu Curie yang tinggi, kehilangan tenaga yang rendah serta kos pengeluaran yang kompetetif mesti dipenuhi. Untuk menghasilkan bahan yang sedemikian, faktor ektrinsik dan intrinsik yang mempengaruhi ketelapan awal harus dikenalpasti. Untuk mencapai matlamat tersebut ferit berasaskan NiZn, MgZn dan CuZn digunakan. Ferit ini mengandungi Zn sebanyak 60%, 70% dan 80% dari keseluruhan ion dwivalen. Julat suhu pensinteran adalah di antara 1050oC hingga 1300oC. Hasilnya mendapati ketelapan awal ferit meningkat tinggi apabila kandungan Zn tidak melebihi 50% dan menyusut dengan cepat apabila melebihi 60%. Ketelapan awal adalah bertambah apabila suhu Curie tinggi dan faktor kehilangan relatif (FKR) rendah. Kandungan Zn yang melebihi 60% menyaksikan perubahan kerintangan dan pertumbuhan butir yang berbeza-beza dan tidak selanjar terhadap ketelapan awal

Marine Traffic Density Over Port Klang, Malaysia Using Statistical Analysis of AIS Data: A Preliminary Study

Port Klang Malaysia is the 13th busiest port in the world, the capacity at the port expected to be able to meet the demand until 2018. It is one of the busiest ports in the world and also the busiest port in Malaysia. Even though there are statistics published by Port Klang Authority showing that a lot of ships using this port, this number is only based on ships that entering Port Klang. Therefore, no study has been done to investigate on how dense the traffic is in Port Klang, Malaysia the surrounding sea including Strait of Malacca . This paper has investigated on traffic density over Port Klang Malaysia and its surrounding sea using statistical analysis from AIS data. As a preliminary study, this study only collected AIS data for 7 days to represent daily traffic weekly. As a result, an hourly number of vessels, daily number of vessels, vessels classification and sizes and also traffic paths will be plotted

Structural and electronic properties of orthorhombic phase Bi₂Se₃ based on first-principles study / Muhammad Zamir Mohyedin ... [et al.]

Bi₂Se₃ is one of the promising materials in thermoelectric devices and is environmentally friendly due to its efficiency to perform in room temperature. Structural and electronic properties of Bi2Se3 were investigated based on the first-principles calculation of density functional theory (DFT) using CASTEP computer code. The calculation is conducted within the exchange-correlation of local density approximation (LDA) and generalised gradient approximation within the revision of Perdew-Burke-Ernzerhof (GGA-PBE) functional. A comparative study is carried out between the electronic properties of LDA and GGA-PBE. Lattice parameter and band gap are consistent with the other reports. Calculation from LDA is more accurate and has a better agreement than GGA-PBE in describing the lattice parameter of Bi2Se3. Band gap and density of states of LDA show higher electrical conductivity than GGA-PBE. Both LDA and GGA-PBE have same degree of thermal conductivity due to the occurrence of indirect band gap at same range of wave vector

Low intensity white noise improves performing in auditory working memory taks: an FMRI study

Research suggests that white noise may facilitate auditory working memory performance via stochastic resonance. Stochastic resonance is quantified by plotting cognitive performance as a function of noise intensity. The plot would appear as an inverted U-curve, that is, a moderate noise is beneficial for performance whereas too low and too much noise attenuates performance. However, knowledge about the optimal signal-to-noise ratio (SNR) needed for stochastic resonance to occur in the brain, particularly in the neural network of auditory working memory, is limited and demand further investigation. In the present study, we extended previous works on the impact of white noise on auditory working memory performance by including multiple background noise levels to map out the inverted U-curve for the stochastic resonance. Using functional magnetic resonance imaging (fMRI), twenty healthy young adults performed a word-based backward recall span task under four signal-to-noise ratio conditions: 15, 10, 5, and 0-dB SNR. Group results show significant behavioral improvement and increased activation in frontal cortices, primary auditory cortices, and anterior cingulate cortex in all noise conditions, except at 0-dB SNR, which decreases activation and performance. When plotted as a function of signal-to-noise ratio, behavioral and fMRI data exhibited a noise-benefit inverted U-shaped curve. Additionally, a significant positive correlation was found between the activity of the right superior frontal gyrus (SFG) and performance in 5- dB SNR. The predicted phenomenon of SR on auditory working memory performance is confirmed. Findings from this study suggest that the optimal signal-to-noise ratio to enhance auditory working memory performance is within 10 to 5-dB SNR and that the right SFG may be a strategic structure involved in enhancement of auditory working memory performance