MyMedR

Fulltext Stable and null current hysteresis perovskite solar cells based nitrogen doped graphene oxide nanoribbons hole transport layer

Kim J, Mat Teridi MA, Mohd Yusoff AR, Jang J

Sci Rep, 2016 06 09;6:27773.

PMID: 27277388 DOI: 10.1038/srep27773

Perovskite solar cells are becoming one of the leading technologies to reduce our dependency on traditional power sources. However, the frequently used component poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (

PEDOT: PSS) has several shortcomings, such as an easily corroded indium-tin-oxide (ITO) interface at elevated temperatures and induced electrical inhomogeneity. Herein, we propose solution-processed nitrogen-doped graphene oxide nanoribbons (NGONRs) as a hole transport layer (HTL) in perovskite solar cells, replacing the conducting polymer

PEDOT: PSS. The conversion efficiency of NGONR-based perovskite solar cells has outperformed a control device constructed using

PEDOT: PSS. Moreover, our proposed NGONR-based devices also demonstrate a negligible current hysteresis along with improved stability. This work provides an effective route for substituting

PEDOT: PSS as the effective HTL.

PVDF-ErGO-GRC electrode: A single setup electrochemical system for separation, pre-concentration and detection of lead ions in complex aqueous samples

Hamsawahini K, Sathishkumar P, Ahamad R, Yusoff AR

Talanta, 2016 Feb 1;148:101-7.

PMID: 26653429 DOI: 10.1016/j.talanta.2015.10.044

An effective electrode was developed based on electromembrane extraction (EME) and square wave voltammetry (SWV) for simultaneous separation, pre-concentration and determination of lead (II) (Pb(II)) ions in complex aqueous samples. Electrochemically reduced graphene oxide-graphite reinforced carbon (ErGO-GRC) was utilized in conjunction with the SWV. Pb(II) ions were extracted from an aqueous sample solution into an acidic acceptor phase (1M HCl) in the lumen of the polyvinylidene fluoride (PVDF) membrane bag by the application of voltage of maximum 6 V across the supported liquid membrane (SLM), consisting of organic solvent and di-(2-ethylhexyl)phosphoric acid (D2EHPA). The parameters affecting the EME were optimized for Pb(II) ions. The optimum EME conditions were found to be 20% D2EHPA in 1-octanol impregnated in the wall of PVDF membrane (PVDF17) as the SLM, extraction time of 20 min, pH of sample solution of 8 and a voltage of 5 V. The PVDF-ErGO-GRC electrode system attained enrichment factors of 40 times and 80% of extraction with relative standard deviations (n=5) of 8.3%. Good linearity ranging from 0.25 to 2 nM with coefficients correlation of 0.999 was obtained. The Pb(II) ions detection limit of PVDF-ErGO-GRC electrode was found to be 0.09 nM. The newly developed single setup electrochemical system was applied to complex aqueous samples such as tap, river and sea water to evaluate the feasibility of the method for applications.

A new sensitive electrochemical method for the determination of vanadium(IV) and vanadium(V) in Benfield sample

Qureshi MS, Mohd Yusoff AR, Shah A, Nafady A, Sirajuddin

Talanta, 2015 Jan;132:541-7.

PMID: 25476342 DOI: 10.1016/j.talanta.2014.10.005

Vanadium(IV) and vanadium(V) can be determined by using differential pulse cathodic stripping voltammetry technique (DPCSV). Cupferron (ammonium N-nitrosophenylhydroxylamine) was used as ligand to form complex compounds with vanadium ions in Britton-Robinson buffer (BRB) solution. At concentration lower than 1.0×10(-6) M, both V(IV) and V(V) cupferron complexes showed a single cathodic peak at -0.576 V in BRB of pH 4; thus V(IV) and V(V) ions cannot be differentiated at low concentration. However, the ionic species of vanadium can be differentiated at high concentration in the presence of cupferron. Parameters including pH of BRB solution, initial potential and accumulation potential were optimized. Under the optimized parameters, the limit of detection (LOD) was 0.09 nM, and the peak current was linear in the concentration range 0.01-0.9 µM total vanadium ions. The determination of V(IV) and V(V) ions was carried out at higher concentration in the sample using calibration plot method. At higher concentration range of 10-60 µM V(IV) and V(V) ions were determined with LOD of 1.2 and 1.1 µM, respectively. The developed method was successfully applied to 10,00,000 fold diluted Benfield sample and 0.6227 M total vanadium ions were determined. The determination of V(IV) and V(V) ions were also successfully carried out in artificial sample as well as Benfield sample (dilution factor, 10,000). The concentration of V(IV) and V(V) ions was 22.52 µM and 38.91 µM, respectively, giving total vanadium concentration of 0.6143 M in Benfield sample.

Mercury contamination in the estuaries and coastal sediments of the Strait of Malacca

Looi LJ, Aris AZ, Yusoff FM, Hashim Z

Environ Monit Assess, 2015 Jan;187(1):4099.

PMID: 25380712 DOI: 10.1007/s10661-014-4099-5

Sediment is a great indicator for assessing coastal mercury contamination. This work profiled the magnitude of mercury pollution in the tropical estuaries and coastal sediments of the Strait of Malacca. Mercury was extracted through the ultrasound-assisted mercury extraction method and analyzed using the flow injection mercury system. The mean concentration of mercury in the sediment samples was 61.43 ± 23.25 μg/kg, ranging from 16.55 ± 0.61 to 114.02 ± 1.54 μg/kg. Geoaccumulation index revealed that a total of 13% of sampling sites were moderately enriched with mercury. The northern part of the Strait of Malacca had the highest mean mercury (Hg) concentration (76.36 ± 27.25 μg/kg), followed by the southern (64.59 ± 16.09 μg/kg) and central (39.33 ± 12.91 μg/kg) parts. Sediment mercury concentration in the current study was lower than other regions like Japan, China, Indian, east Mediterranean, and Taiwan. When compared to the Canadian interim marine and freshwater sediment, China's soil interim environmental guidelines, mercury contamination in the Strait of Malacca was found to be below these permissible limits. Sediment organic matter content was found to have significant correlation with sediment mercury concentration. This study could provide the latest benchmark of mercury pollution and prove beneficial to future pollution studies in relation to monitoring works in tropical estuaries and coastal sediments.

Availability and Utilization of Pigments from Microalgae

Begum H, Yusoff FM, Banerjee S, Khatoon H, Shariff M

Crit Rev Food Sci Nutr, 2016 Oct 02;56(13):2209-22.

PMID: 25674822 DOI: 10.1080/10408398.2013.764841

Microalgae are the major photosynthesizers on earth and produce important pigments that include chlorophyll a, b and c, β-carotene, astaxanthin, xanthophylls, and phycobiliproteins. Presently, synthetic colorants are used in food, cosmetic, nutraceutical, and pharmaceutical industries. However, due to problems associated with the harmful effects of synthetic colorants, exploitation of microalgal pigments as a source of natural colors becomes an attractive option. There are various factors such as nutrient availability, salinity, pH, temperature, light wavelength, and light intensity that affect pigment production in microalgae. This paper reviews the availability and characteristics of microalgal pigments, factors affecting pigment production, and the application of pigments produced from microalgae. The potential of microalgal pigments as a source of natural colors is enormous as an alternative to synthetic coloring agents, which has limited applications due to regulatory practice for health reasons.

Fulltext Effect of the antihypertensive drug enalapril on oxidative stress markers and antioxidant enzymes in kidney of spontaneously hypertensive rat

Chandran G, Sirajudeen KN, Yusoff NS, Swamy M, Samarendra MS

Oxid Med Cell Longev, 2014;2014:608512.

PMID: 25254079 DOI: 10.1155/2014/608512

Oxidative stress has been suggested to play a role in hypertension and hypertension induced organ damage. This study examined the effect of enalapril, an antihypertensive drug, on oxidative stress markers and antioxidant enzymes in kidney of spontaneously hypertensive rat (SHR) and Nω -nitro-L-arginine methyl ester (L-NAME) administered SHR. Male rats were divided into four groups (SHR, SHR+enalapril, SHR+L-NAME, and SHR+enalapril+L-NAME). Enalapril (30 mg kg(-1) day(-1)) was administered from week 4 to week 28 and L-NAME (25 mg kg(-1) day(-1)) was administered from week 16 to week 28 in drinking water. Systolic blood pressure (SBP) was measured during the experimental period. At the end of experimental periods, rats were sacrificed; urine, blood, and kidneys were collected for the assessment of creatinine clearance, total protein, total antioxidant status (TAS), thiobarbituric acid reactive substances (TBARS), superoxide dismutase (SOD), and catalase (CAT), as well as histopathological examination. Enalapril treatment significantly enhanced the renal TAS level (P < 0.001) and SOD activity (P < 0.001), reduced the TBARS levels (P < 0.001), and also prevented the renal dysfunction and histopathological changes. The results indicate that, besides its hypotensive and renoprotective effects, enalapril treatment also diminishes oxidative stress in the kidneys of both the SHR and SHR+L-NAME groups.

Fulltext A review of norms and normative multiagent systems

Mahmoud MA, Ahmad MS, Yusoff MZ, Mustapha A

ScientificWorldJournal, 2014;2014:684587.

PMID: 25110739 DOI: 10.1155/2014/684587

Norms and normative multiagent systems have become the subjects of interest for many researchers. Such interest is caused by the need for agents to exploit the norms in enhancing their performance in a community. The term norm is used to characterize the behaviours of community members. The concept of normative multiagent systems is used to facilitate collaboration and coordination among social groups of agents. Many researches have been conducted on norms that investigate the fundamental concepts, definitions, classification, and types of norms and normative multiagent systems including normative architectures and normative processes. However, very few researches have been found to comprehensively study and analyze the literature in advancing the current state of norms and normative multiagent systems. Consequently, this paper attempts to present the current state of research on norms and normative multiagent systems and propose a norm's life cycle model based on the review of the literature. Subsequently, this paper highlights the significant areas for future work.

The effects of aging on the brain activation pattern during a speech perception task: an fMRI study

Manan HA, Franz EA, Yusoff AN, Mukari SZ

Aging Clin Exp Res, 2015 Feb;27(1):27-36.

PMID: 24906677 DOI: 10.1007/s40520-014-0240-0

In the present study, brain activation associated with speech perception processing was examined across four groups of adult participants with age ranges between 20 and 65 years, using functional MRI (fMRI). Cognitive performance demonstrates that performance accuracy declines with age. fMRI results reveal that all four groups of participants activated the same brain areas. The same brain activation pattern was found in all activated areas (except for the right superior temporal gyrus and right middle temporal gyrus); brain activity was increased from group 1 (20-29 years) to group 2 (30-39 years). However, it decreased in group 3 (40-49 years) with further decreases in group 4 participants (50-65 years). Result also reveals that three brain areas (superior temporal gyrus, Heschl's gyrus and cerebellum) showed changes in brain laterality in the older participants, akin to a shift from left-lateralized to right-lateralized activity. The onset of this change was different across brain areas. Based on these findings we suggest that, whereas all four groups of participants used the same areas in processing, the engagement and recruitment of those areas differ with age as the brain grows older. Findings are discussed in the context of corroborating evidence of neural changes with age.

Does gamma irradiation affect physicochemical properties of honey?

Hussein SZ, Yusoff KM, Makpol S, Mohd Yusof YA

Clin Ter, 2014;165(2):e125-33.

PMID: 24770820 DOI: 10.7471/CT.2014.1695

Honey is a supersaturated solution of sugars, enriched with proteins, minerals, vitamins, organic acids and polyphenols. Gamma irradiation is a physical technique of food preservation which protects the honey from insects' and microbial contamination during storage. We investigated the effect of gamma irradiation on physicochemical properties in two types of Malaysian honey, Gelam and Nenas.

Fulltext N-[Eth-yl(2-hy-droxy-eth-yl)carbamo-thio-yl]-2-methyl-benzamide

Yamin BM, Hizam SM, Yusoff SF, Hasbullah SA

Acta Crystallogr Sect E Struct Rep Online, 2014 May 1;70(Pt 5):o602.

PMID: 24860396 DOI: 10.1107/S1600536814008952

The title compound, C13H18N2O2S, adopts a cis conformation between the methyl-benzoyl and thiono groups across their thio-urea C-N bond. However, the methyl-benzoyl group and N2CS thio-urea moiety are twisted by 15.03 (3)°. In the molecule there is an N-H⋯O hydrogen bond. In the crystal, mol-ecules are linked by O-H⋯O inter-actions, generating chains extending along the c-axis direction.

Fulltext N-[Eth-yl(2-hy-droxy-eth-yl)carbamo-thio-yl]-3-fluoro-benzamide

Awang NW, Hasbullah SA, Yusoff SF, Yamin BM

Acta Crystallogr Sect E Struct Rep Online, 2014 May 1;70(Pt 5):o570.

PMID: 24860375 DOI: 10.1107/S1600536814008174

In the title compound, C12H15FN2O2S, the mol-ecule adopts a cis configuration of the fluoro-benzoyl group with respect to the thiono group about their C-N bond. The dihedral angle between the fluoro-benzoyl group and the thio-urea N2CS fragment is 69.60 (11)°. An intra-molecular N-H⋯O hydrogen bond occurs. In the crystal, mol-ecules form chains along the b-axis direction via O-H⋯S and C-H⋯O hydrogen bonds.

Fulltext Seropositive status of dengue virus infection among blood donors in North Malaysia

Harif NF, Kader ZS, Joshi SR, Yusoff NM

Asian J Transfus Sci, 2014 Jan;8(1):64.

PMID: 24678182 DOI: 10.4103/0973-6247.126702

Estimation of optimum specific light intensity per cell on a high-cell-density continuous culture of Chlorella zofingiensis not limited by nutrients or CO₂

Imaizumi Y, Nagao N, Yusoff FM, Taguchi S, Toda T

Bioresour Technol, 2014 Jun;162:53-9.

PMID: 24747382 DOI: 10.1016/j.biortech.2014.03.123

To determine the optimum light intensity per cell required for rapid growth regardless of cell density, continuous cultures of the microalga Chlorella zofingiensis were grown with a sufficient supply of nutrients and CO2 and were subjected to different light intensities in the range of 75-1000 μE m(-2) s(-1). The cell density of culture increased over time for all light conditions except for the early stage of the high light condition of 1000 μE m(-2) s(-1). The light intensity per cell required for the high specific growth rate of 0.5 day(-1) was determined to be 28-45 μE g-ds(-1) s(-1). The specific growth rate was significantly correlated to light intensity (y=0.721×x/(66.98+x), r(2)=0.85, p<0.05). A high specific growth rate was maintained over a range of light intensities (250-1000 μE m(-2) s(-1)). This range of light intensities suggested that effective production of C. zofingiensis can be maintained outdoors under strong light by using the optimum specific light intensity.

Preparation and quantification of radioactive particles for tracking hydrodynamic behavior in multiphase reactors

Yunos MA, Hussain SA, Yusoff HM, Abdullah J

Appl Radiat Isot, 2014 Sep;91:57-61.

PMID: 24907683 DOI: 10.1016/j.apradiso.2014.05.015

Radioactive particle tracking (RPT) has emerged as a promising and versatile technique that can provide rich information about a variety of multiphase flow systems. However, RPT is not an off-the-shelf technique, and thus, users must customize RPT for their applications. This paper presents a simple procedure for preparing radioactive tracer particles created via irradiation with neutrons from the TRIGA Mark II research reactor. The present study focuses on the performance evaluation of encapsulated gold and scandium particles for applications as individual radioactive tracer particles using qualitative and quantitative neutron activation analysis (NAA) and an X-ray microcomputed tomography (X-ray Micro-CT) scanner installed at the Malaysian Nuclear Agency.

Fulltext (4-Fluoro-phen-yl)thio-urea-1,10-phenanthroline (1/1)

Yamin BM, Salem HF, Yusoff SF

Acta Crystallogr Sect E Struct Rep Online, 2013;69(Pt 9):o1468.

PMID: 24427090 DOI: 10.1107/S1600536813023222

Refluxing a mixture of 1,10-phenanthroline, (4-fluoro-phen-yl)thio-urea and cadmium(II) chloride did not produce the expected mixed-ligand complex but formed a co-crystal of the two ligands, C12H8N2·C7H7FN2S. The asymmetric unit consists of two pairs of the co-crystal mol-ecules. In each (4-fluoro-phen-yl)thio-urea mol-ecule, the planes of the N2CS thio-urea units are almost perpendicular to the corresponding fluoro-benzene rings, subtending angles of 76.53 (7) and 85.25 (7)°. In the crystal, N-H⋯N and N-H⋯S hydrogen bonds form inversion dimers from the co-crystal pairs. A weak π-π inter-action between the phenanthroline rings [centroid-centroid distance = 3.7430 (15)Å] is also observed.

Fulltext 1-(4-Chlorophenyl)-3-(3-chloro-pro-pionyl)thio-urea

Yamin BM, Soh SK, Yusoff SF

Acta Crystallogr Sect E Struct Rep Online, 2013 Oct 23;69(Pt 11):o1696.

PMID: 24454122 DOI: 10.1107/S1600536813028511

In the title compound, C10H10Cl2N2OS, the mol-ecule adopts a trans-cis conformation with respect to the position of the carbonyl group and the chloro-phenyl groups relative to the thiono group across the C-N bonds. The mol-ecule is stabilized by an N-H⋯O hydrogen bond. In the crystal, mol-ecules are linked by N-H⋯S and C-H⋯O hydrogen bonds, forming zigzag chains along the b-axis direction. C-H⋯π inter-actions are also present.

Fulltext N-(2-Chloro-5-nitro-phen-yl)-N'-(3-chloro-propion-yl)thio-urea

Yamin BM, Soh SK, Yusoff SF

Acta Crystallogr Sect E Struct Rep Online, 2014 Jan 01;70(Pt 1):o34.

PMID: 24526981 DOI: 10.1107/S1600536813032662

The title compound, C10H9Cl2N3O3S, adopts a trans-cis conformation with respect to the position of chloropropionyl and chloronitrobenzene groups respectively, against the thiono about their C-N bonds. The conformation is stabilized by an intra-molecular N-H⋯O hydrogen bond. In the crystal, there is a short Cl⋯Cl contact with a distance of 3.386 (13) Å.

Adopting programmatic feedback to enhance the learning of complex skills

Yusoff MS, Hadie SN, Abdul Rahim AF

Med Educ, 2014 Feb;48(2):108-10.

PMID: 24528391 DOI: 10.1111/medu.12403

Fulltext Four products from Escherichia coli pseudogenes increase hydrogen production

Mohd Yusoff MZ, Hashiguchi Y, Maeda T, Wood TK

Biochem Biophys Res Commun, 2013 Oct 4;439(4):576-9.

PMID: 24025676 DOI: 10.1016/j.bbrc.2013.09.016

Pseudogenes are considered to be nonfunctional genes that lack a physiological role. By screening 3985 Escherichia coli mutants using chemochromic membranes, we found four pseudogenes involved in hydrogen metabolism. Knockouts of pseudogenes ydfW and ypdJ had a defective hydrogen phenotype on glucose and formate, respectively. Also, the knockout of pseudogene yqiG formed hydrogen from formate but not from glucose. For the yqiG mutant, 100% hydrogen recovery was obtained by the complementation of YqiG via a plasmid. The knockout of pseudogene ylcE showed hydrogen deficiency in minimal media which suggested that the role of YlcE is associated with cell growth. Hence, the products of these four pseudogenes play an important physiological role in hydrogen production in E. coli.

On the missing links in quantum dot solar cells: a DFT study on fluorophore oxidation and reduction processes in sensitized solar cells

Muzakir SK, Alias N, Yusoff MM, Jose R

Phys Chem Chem Phys, 2013 Oct 14;15(38):16275-85.

PMID: 24000052 DOI: 10.1039/c3cp52858h

The possibility of achieving many electrons per absorbed photon of sufficient energy by quantum dots (QDs) drives the motivation to build high performance quantum dot solar cells (QDSCs). Although performance of dye-sensitized solar cells (DSCs), with similar device configuration as that of QDSCs, has significantly improved in the last two decades QDSCs are yet to demonstrate impressive device performances despite the remarkable features of QDs as light harvesters. We investigated the fundamental differences in the optical properties of QDs and dyes using DFT calculations to get insights on the inferior performance of QDSCs. The CdSe QDs and the ruthenium bipyridyl dicarboxylic acid dye (N3) were used as typical examples in this study. Based on a generalized equation of state correlating material properties and photoconversion efficiency, we calculated ground and excited state properties of these absorbers at the B3LYP/lanl2dz level of DFT and analyzed them on the basis of the device performance. Five missing links have been identified in the study which provides numerous insights into building high efficiency QDSCs. They are (i) fundamental differences in the emitting states of the QDs in the strong and weak confinement regimes were observed, which explained successfully the performance differences; (ii) the crucial role of bifunctional ligands that bind the QDs and the photo-electrode was identified; in most cases use of bifunctional ligands does not lead to a QD enabled widening of the absorption of the photo-electrode; (iii) wide QDs size distribution further hinders efficient electron injections; (iv) wide absorption cross-section of QDs favours photon harvesting; and (v) the role of redox potential of the electrolyte in the QD reduction process.

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