Displaying publications 41 - 60 of 157 in total

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  1. Fulltext Optimization of the cytogenetic protocol for Pangasianodon hypophthalmus (Sauvage, 1878) and Clarias gariepinus (Burchell, 1822)
    Okomoda VT, Koh ICC, Hassan A, Amornsakun T, Moh JHZ, Shahreza SM
    PeerJ, 2018;6:e5712.
    PMID: 30416879 DOI: 10.7717/peerj.5712
    To obtain well spread chromosomes, the cytogenetic protocol for Pangasianodon hypophthalmus and Clarias gariepinus were optimized. This includes, the colchicine concentration (0.01%, 0.025%, 0.05%)/exposure duration (1, 3, and 5 h), hypotonic solution (distilled water or 0.075M KCl solution)/exposure duration (30 min, 1, and 2 h), the time of cell suspension preparation (at hypotonic treatment or before slide preparation) and chromosome aging period (0, 3, and 7 days in Carnoy's fixative). In addition, the type (i.e., fin, gill or kidney) and the amount of tissue (10, 50, 100 or 150 mg) were also investigated. Regardless of the species, the result obtained showed that well-spread chromosomes could be obtained using the following optimized protocol: Juveniles are injected with 0.05% colchicine (at one ml kg-1) and allowed to swim for 3 h. Then, 50 mg of gill tissue is made into cell suspension in 0.075M KCl for 1 h. The cell suspension is treated in Carnoy's fixative (changed three times at 20 min interval) and then aged for 3 days. Finally, chromosome slides are made and stained with 10% Giemsa for 1 h.
  2. Fulltext Morphological characterization of the progenies of pure and reciprocal crosses of Pangasianodon hypophthalmus (Sauvage, 1878) and Clarias gariepinus (Burchell, 1822)
    Okomoda TV, Koh ICC, Hassan A, Amornsakun T, Shahreza SM
    Sci Rep, 2018 02 28;8(1):3827.
    PMID: 29491444 DOI: 10.1038/s41598-018-22149-4
    Twenty-five traditional and thirty-four geometric morphometric comparisons were carried out on pure and reciprocal crosses of Pangasianodon hypophthalmus (Sauvage, 1878) and Clarias gariepinus (Burchell, 1822). Thirty fish samples each of the C. gariepinus (CH), P. hypophthalmus (PH), Pangapinus (♀PH × ♂CG) and the two distinct morphotypes of the Clariothalmus (♀CG × ♂PH) (Clarias-like and Panga-like) between the ages of four and six months were used for this study. Phenotypically, the Clarias-like Clariothalmus and the Pangapinus progenies were indistinguishable from their maternal parents while the Panga-like Clariothalmus was a phenotypic intermediary of the putative parents but looks more closely to the paternal parent. Hence, both univariate proportion and multivariate analysis of the collected data successfully separated the different fishes into three multivariate spaces. The analysis of the dendrogram with complete linkage and Euclidean distance further showed the close relationship of the isolated Panga-like Clariothalmus progenies to the paternal parent, however, Clarias-like Clariothalmus and the Pangapinus were completely intermingled with their maternal parents. The most important index of discrimination of these fishes into different multivariate spaces was the fin characteristic which showed 100% exclusive ranges for the individual groups in many cases.
  3. Filth flies associated with municipal solid waste and impact of delay in cover soil application on adult filth fly emergence in a sanitary landfill in Pulau Pinang, Malaysia
    Nurita AT, Hassan AA
    Bull. Entomol. Res., 2013 Jun;103(3):296-302.
    PMID: 23302698 DOI: 10.1017/S0007485312000703
    Two types of municipal solid waste (MSW), newly arrived and 2 weeks old, were sampled from a sanitary landfill in Pulau Pinang, Malaysia at a fortnightly interval and kept under field conditions for 2 weeks. A total of 480 kg of each type of MSW was sampled to study species composition and impact of delays in cover soil applications on filth fly emergence. Out of 960 kg of MSW sampled, 9.2 ± 0.5 flies emerged per kilogram. Weekly adult fly emergence rates of newly arrived and 2-week-old waste did not differ significantly and MSW remained suitable for fly breeding for up to 1 month. Eight species of flies emerged from the MSW: namely, Musca domestica, Musca sorbens, Synthesiomyia nudiseta, Hydrotaea chalcogaster, Chrysomya megacephala, Lucilia cuprina, Hemipyrellia ligurriens and Sarcophaga sp. Newly arrived waste was determined to be the main source for M. domestica, C. megacephala and L. cuprina in the landfill owing to significantly higher mean emergence compared with 2-week-old waste. Musca sorbens was found in newly arrived waste but not in 2-week-old waste, suggesting that the species was able to survive transportation to landfill but unable to survive landfill conditions. Hemipyrellia ligurriens, H. chalcogaster and S. nudiseta were not imported into the landfill with MSW and pre-existing flies in and around the landfill itself may be their source. The results show that landfills can be a major source of fly breeding if cover soil or temporary cover is not applied daily or on a regular schedule.
  4. Fulltext Comparative performance of two commercial neonicotinoid baits against filth flies under field conditions
    Nurita AT, Abu Hassan A
    Trop Biomed, 2010 Dec;27(3):559-65.
    PMID: 21399598 MyJurnal
    Two performance (efficacy and attractiveness) comparisons of neonicotinoid baits QuickBayt® (imidacloprid) and Agita® (thiamethoxam) against filth flies were conducted under field conditions to determine suitability for use outdoors. The first experiment compared bait performance and the second compared effects of different applications on QuickBayt® performance. Applications compared were: (i) scattered in petri dish (SPD); (ii) wet-down in petri dish (WPD); (iii) scattered on cardboard (SCB) and (iv) painted on cardboards (PCB). Efficacy and attractiveness were assessed based on knockdown percentage (KD%) and number of flies feeding on baits, respectively. The KD% of QuickBayt® (34% ± 3.0%) was not significantly higher than Agita® (29% ± 1.3%) (t-test, P>0.05). Agita® (101 ± 5.7 flies) was significantly more attractive to flies than QuickBayt® (76 ± 4.8 flies) and the sugar solution (49 ± 7.2) (one-way ANOVA, P<0.05). The PCB and SCB applications were significantly more attractive to filth flies than WPD and SPD (One-way ANOVA, P<0.05), however differences in KD% were not significantly different (One-way ANOVA, P>0.05). The two baits provided the same level of efficacy in a wide-open area against filth flies of various species. QuickBayt® was more versatile; efficacy was not significantly affected by different applications. Surface area and moisture affects attractiveness of the bait.
  5. Fulltext Species composition surveys of synanthropic fly populations in northern peninsular Malaysia
    Nurita AT, Abu Hassan A, Nur Aida H
    Trop Biomed, 2008 Aug;25(2):145-53.
    PMID: 18948886 MyJurnal
    Three species composition surveys were conducted in a rural location in Kedah and an urban location in Pulau Pinang. Two of the surveys were conducted in November 2003, the first was at the Kedah site and the second was at the Pulau Pinang site. The third survey was conducted at the Pulau Pinang site again on the last week of April 2004. All these surveys were conducted one week prior to field evaluations of commercial chemical fly baits. The predominant species recovered from the surveys was the house fly, Musca domestica, which ranked first in prevalence in all three studies. Catches of Musca sorbens, Chrysoma megacephala and Lucillia cuprina were lower than M. domestica. Sarcophaga sp. was not present at the Kedah site and was only present at the Pulau Pinang site during the survey in April 2004. The other fly species present at the Kedah site were Megaselia sp., Psycoda sp., Piophila sp. and Fannia sp. These species were scarce and never exceeded 1% of the total catch.
  6. Fulltext Field evaluations of the granular fly bait, Quick Bayt and the paint-on fly bait, Agita against synanthropic flies
    Nurita AT, Abu Hassan A, Nur Aida H, Norasmah B
    Trop Biomed, 2008 Aug;25(2):126-33.
    PMID: 18948883
    The efficacy and residual efficacy of commercial baits, Quick Bayt (0.5% w/w imidacloprid) and Agita (10.0% w/w thiamethoxam) against synanthropic flies were evaluated under field conditions. Efficacy was evaluated based on knockdown percentage (KD %). The bait efficacy and residual efficacy evaluation were conducted for a period of 3 weeks and 6 weeks respectively. Baits were applied onto bait targets and placed on fly-count targets to facilitate the counting of flies. All baits were applied according to the manufacturer's recommended application rate. Three replicate treatments for each type of bait were placed at the study site each week. The number of flies feeding on baits and the knocked down flies were counted and collected. The efficacy of Agita and Quick Bayt did not differ significantly (t-test, P>0.05) over the 3-week period, even though Quick Bayt had a slightly higher KD% than Agita. In the residual efficacy evaluation, the (knockdown) KD% of Quick Bayt was consistent at around 36% for the first five weeks but dropped to 33.8 +/- 0.4% on the sixth week. The KD% for Agita on the first week was 33.6 +/- 12.2% and remained relatively consistent for the first 4 weeks at around 31%. KD% dropped to 16.7 +/- 3.3% on week 5 and to 15.7 +/- 1.2% on week 6. The difference in residual efficacy of the two baits was significant (t-test, p < 0.05).
  7. Fulltext Population analysis of Aedes albopictus (Skuse) (Diptera:Culicidae) under uncontrolled laboratory conditions
    Nur Aida H, Abu Hassan A, Nurita AT, Che Salmah MR, Norasmah B
    Trop Biomed, 2008 Aug;25(2):117-25.
    PMID: 18948882
    A semi laboratory experiment using 3 cohorts of Aedes albopictus adults was performed to obtain age-specific mortality and fecundity information and to derive statistical estimates of some population growth parameters. Life expectancy was calculated for both males and females. The following population parameters were estimated: intrinsic rate of increase (rm= 0.21), net reproductive (replacement) rate (Ro= 68.70), age at mean cohort reproduction (To=10.55 days), birth rate (B=0.23), death rate (D=0.02) and generation time (G=20.14 days). The high rm/B (0.91) and B/D (11.50) ratios indicated the high colonizing ability of Ae. albopictus in nature.
  8. Fulltext Daily foraging pattern and proteinaceous food preferences of Solenopsis geminata (Fabricius) (Hymenoptera:Formicidae)
    Norasmah B, Abu Hassan A, Che Salmah MR, Nurita AT, Nur Aida H
    Trop Biomed, 2006 Dec;23(2):134-9.
    PMID: 17322814
    A field study on foraging activity and proteinacous food preference was performed on the tropical fire ant (Solenopsis geminata) (Fabricius) at the School of Biological Sciences and Desasiswa Bakti Permai, Universiti Sains Malaysia (USM), Penang. Foraging activity studies of 4 colonies of S. geminata were conducted in the field for 24 hours. Foraging activity significantly increased 4 hours before sunset and maximum foraging occurred at midnight until early morning. Three types of proteinacous food; anchovy, meat and egg yolk were tested among the five colonies of S. geminata in the field. The egg yolk was the most preferred food (100%) followed by meat (31%) and anchovy (15%).
  9. Fulltext Phylogenetic analysis of human metapneumovirus among children with acute respiratory infections in Kuala Lumpur, Malaysia
    Nor'e SS, Sam IC, Mohamad Fakri EF, Hooi PS, Nathan AM, de Bruyne JA, et al.
    Trop Biomed, 2014 Sep;31(3):562-6.
    PMID: 25382484 MyJurnal
    Human metapneumovirus (HMPV) is a recently discovered cause of viral respiratory infections. We describe clinical and molecular epidemiology of HMPV cases diagnosed in children with respiratory infection at University of Malaya Medical Centre, Kuala Lumpur, Malaysia. The prevalence rate of HMPV between 2010 and 2012 was 1.1%, and HMPV contributed 6.5% of confirmed viral respiratory infections. The HMPV patients had a median age of 1.6 years, and a median hospital admission of 4 days. The most common clinical presentations were fever, rhinitis, pneumonia, vomiting/diarrhoea, and bronchiolitis. Based on the partial sequences of F fusion gene from 26 HMPV strains, 14 (54%) were subgenotype A2b, which was predominant in 2010; 11 (42%) were subgenotype B1, which was predominant in 2012; and 1 (4%) was subgenotype A2a. Knowledge of the circulating subgenotypes in Malaysia, and the displacement of predominant subgenotypes within 3 years, is useful data for future vaccine planning.
  10. Fulltext Ferrocene-Based Terpolyamides and Their PDMS-Containing Block Copolymers: Synthesis and Physical Properties
    Mushtaq I, Jabeen E, Akhter Z, Javed F, Hassan A, Khan MSU, et al.
    Polymers (Basel), 2022 Nov 23;14(23).
    PMID: 36501482 DOI: 10.3390/polym14235087
    Aromatic polyamides are well-known as high-performance materials due to their outstanding properties making them useful in a wide range of applications. However, their limited solubility in common organic solvents restricts their processability and becomes a hurdle in their applicability. This study is focused on the synthesis of processable ferrocene-based terpolyamides and their polydimethylsiloxane (PDMS)-containing block copolymers, using low-temperature solution polycondensation methodology. All the synthesized materials were structurally characterized using FTIR and 1H NMR spectroscopic techniques. The ferrocene-based terpolymers and block copolymers were soluble in common organic solvents, while the organic analogs were found only soluble in sulfuric acid. WXRD analysis showed the amorphous nature of the materials, while the SEM analysis exposed the modified surface of the ferrocene-based block copolymers. The structure-property relationship of the materials was further elucidated by their water absorption and thermal behavior. These materials showed low to no water absorption along with their high limiting oxygen index (LOI) values depicting their good flame-retardant behavior. DFT studies also supported the role of various monomers in the polycondensation reaction where the electron pair donation from HOMO of diamine monomer to the LUMO of acyl chloride was predicted, along with the calculation of various other parameters of the representative terpolymers and block copolymers.
  11. Fulltext Molecular basis of Rh blood group system in the Malaysian population
    Musa RH, Muhamad NA, Hassan A, Ayob Y, Yusoff NM
    Asian J Transfus Sci, 2015 Jan-Jun;9(1):48-54.
    PMID: 25722573 DOI: 10.4103/0973-6247.150951
    Rh molecular studies have been previously mainly conducted in Caucasians and African population. There is a limited data on the molecular basis for Rh genotypes among Asians.
  12. WITHDRAWN: Rh genotypes among Malaysian blood donors
    Musa RH, Hassan A, Ayob Y, Yusoff NM
    Transfus Apher Sci, 2014 Dec 12.
    PMID: 26144905 DOI: 10.1016/j.transci.2014.12.001
    This article has been withdrawn at the request of the author and editor. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at http://www.elsevier.com/locate/withdrawalpolicy.
  13. Fulltext Converting non-metallic printed circuit boards waste into a value added product
    Muniyandi SK, Sohaili J, Hassan A, Mohamad SS
    J Environ Health Sci Eng, 2013;11:2.
    PMID: 24764542 DOI: 10.1186/2052-336X-11-2
    The aim of this study was to investigate the feasibility of using nonmetallic printed circuit board (PCB) waste as filler in recycled HDPE (rHDPE) in production of rHDPE/PCB composites. Maleic anhydride modified linear low-density polyethylene (MAPE) was used as compatibilizer. In particular, the effects of nonmetallic PCB and MAPE on mechanical properties of the composites were assessed through tensile, flexural and impact testing. Scanning electron microscope (SEM) was used to study the dispersion of nonmetallic PCB and MAPE in the matrix. Nonmetallic PCB was blended with rHDPE from 0-30 wt% and prepared by counter-rotating twin screw extruder followed by molding into test samples via hot press for analysis. A good balance between stiffness, strength and toughness was achieved for the system containing 30 wt% PCB. Thus, this system was chosen in order to investigate the effect of the compatibilizer on the mechanical properties of the composites. The results indicate that MAPE as a compatiblizer can effectively promote the interfacial adhesion between nonmetallic PCB and rHDPE. The addition of 6 phr MAPE increased the flexural strength, tensile strength and impact strength by 71%, 98% and 44% respectively compared to the uncompatibilized composites.
  14. Fulltext METER (Mental health emergency response) program: Findings of psychological impact status and factors associated with depression, anxiety and stress among healthcare workers in public hospital in Malaysia during the COVID-19 pandemic
    Muhamad NA, Subhas N, Mustapha N, Abdullah N, Muhamad Rasat MA, Ab Ghani RM, et al.
    PLOS Glob Public Health, 2023;3(4):e0001823.
    PMID: 37058465 DOI: 10.1371/journal.pgph.0001823
    INTRODUCTION: The COVID-19 pandemic has become the greatest challenge of the new millennium. Most healthcare workers (HCWs) experienced unprecedented levels of workload since the pandemic. This study aims to identify the prevalence and factors of depression, anxiety and stress among HCWs in Malaysian healthcare facilities in the midst of the pandemic due to the SARs-CoV-2.

    METHODS: An emergency response programme on mental health was conducted from June to September 2020. A standardized data collection form was distributed among the HCWs in the government hospital in Klang Valley. The form contained basic demographic information and the self-reported Malay version of the Depression, Anxiety and Stress scale (BM DASS-21).

    RESULTS: Of the1,300 staff who attended the Mental Health and Psychosocial Support in Covid-19 (MHPSS COVID-19) programme, 996 staff (21.6% male, 78.4% female) completed the online survey (response rate: 76.6%). Result showed that staff aged above 40 years old were almost two times more likely to have anxiety (AOR = 1.632; 95% CI = 1.141-2.334, p:0.007) and depression (AOR = 1.637; 95% CI = 1.1.06-2.423, p:0.014) as compared to staff who were less than 40 years old. Those who had direct involvement with COVID-19 patients were likely to suffer stress (AOR = 0.596; 95% CI = 0.418-0.849, p:0.004), anxiety (AOR = 0.706; 95% Ci = 0.503-0.990, p:0.044) and depression (AOR = 0.630; 95% Ci = 0.427-0.928, p:0.019). HCWs with stress (AOR = 0.638; 95% CI of 0.476-0.856, p = 0.003), anxiety (AOR = 0.720; 95% CI 0.542-0.958, p = 0.024) and depression (AOR = 0.657; 95% CI 0.480-0.901, p = 0.009) showed less confidence to treat critically ill patients and need psychological help during outbreak.

    CONCLUSION: This study showed the importance of psychosocial support to reduce psychological distress among HCWs when working or coping during the COVID-19 pandemic or outbreak.

  15. Fulltext Chitosan dermal substitute and chitosan skin substitute contribute to accelerated full-thickness wound healing in irradiated rats
    Mohd Hilmi AB, Halim AS, Jaafar H, Asiah AB, Hassan A
    Biomed Res Int, 2013;2013:795458.
    PMID: 24324974 DOI: 10.1155/2013/795458
    Wounds with full-thickness skin loss are commonly managed by skin grafting. In the absence of a graft, reepithelialization is imperfect and leads to increased scar formation. Biomaterials can alter wound healing so that it produces more regenerative tissue and fewer scars. This current study use the new chitosan based biomaterial in full-thickness wound with impaired healing on rat model. Wounds were evaluated after being treated with a chitosan dermal substitute, a chitosan skin substitute, or duoderm CGF. Wounds treated with the chitosan skin substitute showed the most re-epithelialization (33.2 ± 2.8%), longest epithelial tongue (1.62 ± 0.13 mm), and shortest migratory tongue distance (7.11 ± 0.25 mm). The scar size of wounds treated with the chitosan dermal substitute (0.13 ± 0.02 cm) and chitosan skin substitute (0.16 ± 0.05 cm) were significantly decreased (P < 0.05) compared with duoderm (0.45 ± 0.11 cm). Human leukocyte antigen (HLA) expression on days 7, 14, and 21 revealed the presence of human hair follicle stem cells and fibroblasts that were incorporated into and surviving in the irradiated wound. We have proven that a chitosan dermal substitute and chitosan skin substitute are suitable for wound healing in full-thickness wounds that are impaired due to radiation.
  16. A Bilayer Engineered Skin Substitute for Wound Repair in an Irradiation-Impeded Healing Model on Rat
    Mohd Hilmi AB, Hassan A, Halim AS
    Adv Wound Care (New Rochelle), 2015 May 1;4(5):312-320.
    PMID: 26005597
    Objective: An engineered skin substitute is produced to accelerate wound healing by increasing the mechanical strength of the skin wound via high production of collagen bundles. During the remodeling stage of wound healing, collagen deposition is the most important event. The collagen deposition process may be altered by nutritional deficiency, diabetes mellitus, microbial infection, or radiation exposure, leading to impaired healing. This study describes the fabrication of an engineered bilayer skin substitute and evaluates its effectiveness for the production of collagen bundles in an impaired healing model. Approach: Rats were exposed to 10 Gy of radiation. Two months postirradiation, the wounds were excised and treated with one of three skin replacement products: bilayer engineered skin substitutes, chitosan skin templates, or duoderm(©). The collagen deposition was analyzed by hematoxylin and eosin staining. Results: On day 21 postwound, the irradiated wounds displayed increased collagen bundle deposition after treatment using bilayer engineered skin substitutes (3.4±0.25) and chitosan skin templates (3.2±0.58) compared with duoderm (2.0±0.63). Innovation: We provide the first report on the fabrication of bilayer engineered skin substitutes using high density human dermal fibroblasts cocultured with HFSCs on chitosan skin templates. Conclusion: The high density of fibroblasts significantly increases the penetration of cells into chitosan skin templates, contributing to the fabrication of bilayer engineered skin substitute.
  17. Fulltext Pattern of QTc prolongation in Methadone Maintenance Therapy (MMT) subjects receiving different methadone dosages: A prospective cohort study
    Mohamad N, Abdul Jalal MI, Hassan A, Abdulkarim Ibrahim M, Salehuddin R, Abu Bakar NH
    Pak J Med Sci, 2013 Sep;29(5):1132-6.
    PMID: 24353706
    OBJECTIVES: This study aimed to compare the QTc interval between low and high dose methadone groups and evaluate the pattern of QTc variation.
    METHODS: This is a prospective cohort study conducted from December 2010 till August 2011 at Malaysian University of Science's Hospital. Forty six subjects, grouped in high dose (>80mg) and low dose (<80mg) oral methadone, were followed-up at 4-weekly for QTc measurements. Relevant demographic and biochemical profiles were taken at intervals with concurrent QTc measurements.
    RESULTS: No significant QTc differences between methadone dosage groups were found at Week 0 (434ms vs 444ms, p = 0.166) and week 8 (446.5ms vs 459ms, p = 0.076), but not at week 4(435ms vs 450ms, p = 0.029). However, there were significant associations between the groups with QTc prolongation at week 0 and 4 (OR 4.29(95% CI 1.01, 18.72) p=0.044 and OR 5.18 (95% CI 1.34, 20.06) p =0.013, respectively) but not at week 8 (OR 2.44 (95% CI 0.74, 8.01) p=0.139). On multivariate analysis, dose group was the sole significant factor for QTc prolongation for week 0 and 4 (p values 0.047 and 0.017, respectively), but not at week 8.
    CONCLUSION: High-dose methadone group is more likely to develop prolonged QTc than low-dose group. However, such effects were inconsistent and occurred even during chronic methadone therapy, mandating judicious QTc and serum methadone monitoring.
    KEYWORDS: High Dose; Low Dose; Methadone; QTc
  18. Isolation and characterization of microcrystalline cellulose from oil palm biomass residue
    Mohamad Haafiz MK, Eichhorn SJ, Hassan A, Jawaid M
    Carbohydr Polym, 2013 Apr 2;93(2):628-34.
    PMID: 23499105 DOI: 10.1016/j.carbpol.2013.01.035
    In this work, we successfully isolated microcrystalline cellulose (MCC) from oil palm empty fruit bunch (OPEFB) fiber-total chlorine free (TCF) pulp using acid hydrolysis method. TCF pulp bleaching carried out using an oxygen-ozone-hydrogen peroxide bleaching sequence. Fourier transform infrared (FT-IR) spectroscopy indicates that acid hydrolysis does not affect the chemical structure of the cellulosic fragments. The morphology of the hydrolyzed MCC was investigated using scanning electron microscopy (SEM), showing a compact structure and a rough surface. Furthermore, atomic force microscopy (AFM) image of the surface indicates the presence of spherical features. X-ray diffraction (XRD) shows that the MCC produced is a cellulose-I polymorph, with 87% crystallinity. The MCC obtained from OPEFB-pulp is shown to have a good thermal stability. The potential for a range of applications such as green nano biocomposites reinforced with this form of MCC and pharmaceutical tableting material is discussed.
  19. Interspecific Cross-Mating Between Aedes aegypti and Aedes albopictus Laboratory Strains: Implication of Population Density on Mating Behaviors
    Marcela P, Hassan AA, Hamdan A, Dieng H, Kumara TK
    J Am Mosq Control Assoc, 2015 Dec;31(4):313-20.
    PMID: 26675452 DOI: 10.2987/moco-31-04-313-320.1
    Mating behavior between Aedes aegypti and Ae. albopictus, established colony strains were examined under laboratory conditions (30-cm(3) screened cages) for 5 consecutive days. The effect of selected male densities (30, 20, 10) and female density (20) on the number of swarming, mating pairs, eggs produced, and inseminated females were evaluated. Male densities significantly increased swarming behavior, mating pairs, and egg production of heterospecific females, but female insemination was reduced. Aedes aegypti males mate more readily with heterospecific females than do Ae. albopictus males. The current study suggests that Ae. aegypti males were not species-specific in mating, and if released into the field as practiced in genetically modified mosquito techniques, they may mate with both Ae. aegypti and Ae. albopictus females, hence reducing populations of both species by producing infertile eggs.
  20. Fulltext Mechanical and Thermal Properties of Montmorillonite-Reinforced Polypropylene/Rice Husk Hybrid Nanocomposites
    Majeed K, Ahmed A, Abu Bakar MS, Indra Mahlia TM, Saba N, Hassan A, et al.
    Polymers (Basel), 2019 Sep 25;11(10).
    PMID: 31557811 DOI: 10.3390/polym11101557
    In recent years, there has been considerable interest in the use of natural fibers as potential reinforcing fillers in polymer composites despite their hydrophilicity, which limits their widespread commercial application. The present study explored the fabrication of nanocomposites by melt mixing, using an internal mixer followed by a compression molding technique, and incorporating rice husk (RH) as a renewable natural filler, montmorillonite (MMT) nanoclay as water-resistant reinforcing nanoparticles, and polypropylene-grafted maleic anhydride (PP-g-MAH) as a compatibilizing agent. To correlate the effect of MMT delamination and MMT/RH dispersion in the composites, the mechanical and thermal properties of the composites were studied. XRD analysis revealed delamination of MMT platelets due to an increase in their interlayer spacing, and SEM micrographs indicated improved dispersion of the filler(s) from the use of compatibilizers. The mechanical properties were improved by the incorporation of MMT into the PP/RH system and the reinforcing effect was remarkable as a result of the use of compatibilizing agent. Prolonged water exposure of the prepared samples decreased their tensile and flexural properties. Interestingly, the maximum decrease was observed for PP/RH composites and the minimum was for MMT-reinforced and PP-g-MAH-compatibilized PP/RH composites. DSC results revealed an increase in crystallinity with the addition of filler(s), while the melting and crystallization temperatures remained unaltered. TGA revealed that MMT addition and its delamination in the composite systems improved the thermal stability of the developed nanocomposites. Overall, we conclude that MMT nanoclay is an effective water-resistant reinforcing nanoparticle that enhances the durability, mechanical properties, and thermal stability of composites.
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