Monitoring of land use change is crucial for sustainable resource management and development planning. Up-to-date land use change information is important to understand its pattern and identify the drivers. Remote sensing and geographic information system (GIS) have proven as a useful tool to measure and analyze land use changes. Recent advances in remote sensing technology with digital image processing provide unprecedented possibilities for detecting changes in land use over large areas, with less costs and processing time. Thus, the objective of this study was to assess the land use changes in upper Prek Thnot watershed in Cambodia from 2006 until 2018. Geospatial tools such as remote sensing and GIS were used to process and produce land use maps from Landsat 5 TM, Landsat 7 ETM+ and Landsat 8. The post-classification comparison was conducted for analysing the land use changes. Results show forest area was greatly decreased by 1,162.06 km2 (33.67%) which was converted to rubber plantation (10.55 km2 ), wood shrub (37.65 km2 ), agricultural land (1,099.71 km2 ), built-up area (17.76 km2 ), barren land (3.65 km2 ), and water body (14.69 km2 ). Agricultural land increased by 1,258.99 km2 (36.48%), while wood shrub declined by 161.88 km2 (4.69%). Rubber plantation, built-up area, barren land, and water bodies were increased by 10.55 km2 (0.31%), 33.64 km2 (0.97%), 4.87 km2 (0.14%) and 15.89 km2 (0.46%), respectively. The decrease of forest and wood shrub had resulted due to population growth (1.8% from 2008 to 2019) and land conversion for agricultural purposes. Hence, this study may provide vital information for wise sustainable watershed’s land management, especially for further study on the effect of land use change on runoff in this area.
In this study, the asymmetry of the main effects of action, background and tonal frequency during a pitch memory processing
were investigated by means of brain activation. Eighteen participants (mean age 27.6 years) were presented with low and
high frequency tones in quiet and in noise. They listen, discriminate and recognize the target tone against the final tone
in a series of four distracting tones. The main effects were studied using the analysis of variance (ANOVA) with action (to
wring (rubber bulb) vs. not to wring), background (in quiet vs. in noise) and frequency (low vs. high) as the factors (and
levels respectively). The main effect of action is in the right pre-central gyrus (PCG), in conformation with its contralateral
behavior. The main effect of background indicated the bilateral primary auditory cortices (PAC) and is right lateralized,
attributable to white noise. The main effect of frequency is also observed in PAC but bilaterally equal and attributable to
low frequency tones. Despite the argument that the temporo-spectral lateralization dichotomy is not especially rigid as
revealed by the main effect of frequency, right lateralization of PAC for the respective main effect of background clearly
demonstrates its functional asymmetry suggesting different perceptual functionality of the right and left PAC.
Orthodontic elastic bands are an important iatrogenic etiologic factor in the causation of periodontal attachment apparatus breakdown. Appropriate diagnosis and a well constructed treatment plan tailor-made to suit the requirements of the particular patient is imperative for management of periodontal lesions induced by subgingival retention of rubber band. There are conflicting reports regarding the reattachment and regeneration of lost periodontal supporting tissues in such cases. The present case report highlights the spontaneous reversal and correction of periodontal destruction due to iatrogenic orthodontic elastic band displacement deep into the subgingival tissues.
Aedes albopictus larvae obtained from different types of agricultural and non-agricultural localities in Peninsular Malaysia were subjected to several larvicides at World Health Organization (WHO) recommended dosages. Upon 24 h of WHO larval bioassay using two organochlorines and six organophosphates, high resistance against dichlorodiphenyltrichloroethane (DDT), temephos, chlorpyrifos and bromophos were demonstrated among all larval populations. Aedes albopictus larvae from both paddy growing areas (92.33% mortality) and rubber estates (97.00% mortality) were moderately resistant to dieldrin while only Ae. albopictus larvae from dengue prone residential areas (89.00% mortality) showed high resistance against dieldrin. All Ae. albopictus larval populations also developed either incipient or high resistance to both malathion (33.67%-95.33% mortality) and fenitrothion (73.00%-92.67% mortality). Only Ae. albopictus larvae from fogging-free residential areas that were tolerant to fenthion (97.33% mortality), whereas Ae. albopictus larvae from dengue prone residential areas were highly resistant to the same organophosphate (88.33% mortality). Cross resistance between intraclass and interclass larvicides of organochlorines and organophosphates were also exhibited in this study. The present study provided baseline data on various susceptibility levels of Ae. albopictus larval populations from different types of agricultural and non-agricultural localities against organochlorines and organophosphates at WHO recommended dosages. Nevertheless, further susceptibility investigations are suggested using revised doses of larvicides established from the local reference strain of Ae. albopictus to prevent the underestimation or overestimation of insecticide resistance level among Ae. albopictus field strains of larvae.
The impacts of rubber variations (clonal, seasonal, and pre-treatment) were investigated to assess changes in the composition of volatile organic compounds (VOCs) emitted during rubber processing. VOC emissions from 14 different rubber types were evaluated by headspace micro-chamber (μ-TEC) extraction coupled with gas chromatography-mass spectrometry (GC-MS). Headspace extracted at 120 °C, which is equivalent to the drying temperature during rubber processing, revealed a significant number of odorants in terms of concentrations as well as odorant type. Volatile fatty acids (VFAs) such as acetic, propanoic, butanoic, pentanoic and hexanoic acids, were frequently detected at concentrations greater than their odour detection thresholds. Other odorous compounds including trimethylamine, p-cresol, butanone, indole, and phenol, were also detected. Emissions collected at ambient conditions represent odorants released during material storage (or maturation) and were dominated by benzene derivatives followed by ketones, aldehydes, esters, and acids. Emission composition during storage appeared to be governed by specific rubber properties such as protein and rubber moisture content. Seasonal variations revealed greater impacts on the concentration of VOCs for all studied clones, compared to pre-treatment variations, suggesting that the VOCs composition was seasonally dependent and may represents the 'potential' emissions from rubber as they are processed. A combination of sensorial and analytical measurements were used to produce odour wheels which may be used as tool to identify key malodours in onsite rubber processing. The linking of odours and odorants can facilitate communication between receptors (the public) and plant operators inorder to minimise odour impact and develop effective abatement and on-site management practices.
Different extraction procedures were evaluated to assess their potential for measuring volatile organic compounds (VOCs) from raw rubber materials. Four headspace sampling techniques (SHS, DHS, HS-SPME and µ-CTE) were studied. Each method was firstly optimised to ensure their reliability in performance. Passive sampling was also compared as a rapid identification of background VOCs. 352 VOCs were identified, 71 from passive sampling and 281 from active headspace sampling, with 62 not previously reported (hexanenitrile, octanone, decanal, indole, aniline, anisole, alpha-pinene as well as pentanol and butanol). The volatiles belonged to a broad range of chemical classes (ketones, aldehydes, aromatics, acids, alkanes, alcohol and cyclic) with their thermal effects (lower boiling points) greatly affecting their abundance at a higher temperature. Micro-chamber (µ-CTE) was found to be the most suitability for routine assessments due to its operational efficiency (rapidity, simplicity and repeatability), identifying 115 compounds from both temperatures (30 °C and 60 °C). Whereas, HS-SPME a widely applied headspace technique, only identified 75 compounds and DHS identified 74 VOCs and SHS only 17 VOCs. Regardless of the extraction technique, the highest extraction efficiency corresponded to aromatics and acids, and the lowest compound extraction were aldehyde and hydrocarbon. The interaction between techniques and temperature for all chemical groups were evaluated using two-way ANOVA (p-value is 0.000197) explaining the highly significant interactions between factors.
Poor performance of wet scrubbers in rubber processing plants due to breakthrough of specific volatile organic compounds (VOCs) causes odour impact events. The performance of wet scrubbers in the rubber drying process to remove VOCs was investigated in order to determine the responsible odorants. VOC emissions originating at the inlet and outlet of wet scrubbers were quantified using gas chromatography-mass spectrometry/olfactometry (GC-MS/O). Critical VOCs were identified alongside seasonal and daily variations of those VOCs. Altogether, 80 VOCs were detected in rubber emissions with 16 classified as critical VOCs based on their chemical concentration, high odour activity value (OAV) and unpleasant odour. Volatile fatty acids (VFAs) were the dominant VOCs with seasonal variations affecting emission composition. Results demonstrated the ineffectiveness of the wet scrubbers to mitigate odorous VOCs whereas the removal of some VOCs could be improved based on their polarity and solubility. It was found that there is a correlation between the wet scrubber performance and VFAs concentration in the emissions. The findings demonstrated that combining quantitative and sensory analyses improved accuracy in identifying odorous VOCs, which can cause odour annoyance from rubber processing. A VOC identification framework was proposed using both analyses approaches.
Methyl esters from the triglyceride fraction of the neutral lipids of natural rubber latex were found by gas liquid chromatography to contain about 90% of a furanoid acid. Spectroscopic analysis identified the acid as 10,13-epoxy-11-methyloctadeca-10,12-dienoic acid.
Streptomyces sp. strain CFMR 7, which naturally degrades rubber, was isolated from a rubber plantation. Whole genome sequencing and assembly resulted in 2 contigs with total genome size of 8.248 Mb. Two latex clearing protein (lcp) genes which are responsible for rubber degrading activities were identified.
Rubber materials have greatly contributed to human civilization. However, being a polymeric material does not decompose easily, it has caused huge environmental problems. On the other hand, only few bacteria are known to degrade rubber, with studies pertaining them being intensively focusing on the mechanism involved in microbial rubber degradation. The Streptomyces sp. strain CFMR 7, which was previously confirmed to possess rubber-degrading ability, was subjected to whole genome sequencing using the single molecule sequencing technology of the PacBio® RS II system. The genome was further analyzed and compared with previously reported rubber-degrading bacteria in order to identify the potential genes involved in rubber degradation. This led to the interesting discovery of three homologues of latex-clearing protein (Lcp) on the chromosome of this strain, which are probably responsible for rubber degrading activities. Genes encoding oxidoreductase α-subunit (oxiA) and oxidoreductase β-subunit (oxiB) were also found downstream of two lcp genes which are located adjacent to each other. In silico analysis reveals genes that have been identified to be involved in the microbial degradation of rubber in the Streptomyces sp. strain CFMR 7. This is the first whole genome sequence of a clear-zone-forming natural rubber- degrading Streptomyces sp., which harbours three Lcp homologous genes with the presence of oxiA and oxiB genes compared to the previously reported Gordonia polyisoprenivorans strain VH2 (with two Lcp homologous genes) and Nocardia nova SH22a (with only one Lcp gene).
As the living cytoplasm of laticiferous cells, Hevea brasiliensis latex is a rich blend of organic substances that include a mélange of proteins. A small number of these proteins have given rise to the problem of latex allergy. The salient characteristics of H. brasiliensis latex allergens that are recognized by the International Union of Immunological Societies (IUIS) are reviewed. These are the proteins associated with the rubber particles, the cytosolic C-serum proteins and the B-serum proteins that originate mainly from the lutoids. Procedures for the isolation and purification of latex allergens are discussed, from latex collection in the field to various preparative approaches adopted in the laboratory. As interest in recombinant latex allergens increases, there is a need to validate recombinant proteins to ascertain equivalence with their native counterparts when used in immunological studies, diagnostics, and immunotherapy.
Malaysia, with her tropical jungles, mangroves and seas, is blessed with riches in biodiversity, being one of the twelve megabiodiversity countries on earth. Genetics has contributed substantially to the success of our country's agricultural production especially of rubber and palm oil. Hence, it should play a pivotal role in helping Malaysia fulfill her responsibility to identify, characterize and sustainably utilize her numerous indigenous bioresources for the benefit of humanity.
Cellulose nanofibers (CNF) isolated from plant biomass have attracted considerable interests in polymer engineering. The limitations associated with CNF-based nanocomposites are often linked to the time-consuming preparation methods and lack of desired surface functionalities. Herein, we demonstrate the feasibility of preparing a multifunctional CNF-zinc oxide (CNF-ZnO) nanocomposite with dual antibacterial and reinforcing properties via a facile and efficient ultrasound route. We characterized and examined the antibacterial and mechanical reinforcement performances of our ultrasonically induced nanocomposite. Based on our electron microscopy analyses, the ZnO deposited onto the nanofibrous network had a flake-like morphology with particle sizes ranging between 21 to 34 nm. pH levels between 8-10 led to the formation of ultrafine ZnO particles with a uniform size distribution. The resultant CNF-ZnO composite showed improved thermal stability compared to pure CNF. The composite showed potent inhibitory activities against Gram-positive (methicillin-resistant Staphylococcus aureus (MRSA)) and Gram-negative Salmonella typhi (S. typhi) bacteria. A CNF-ZnO-reinforced natural rubber (NR/CNF-ZnO) composite film, which was produced via latex mixing and casting methods, exhibited up to 42% improvement in tensile strength compared with the neat NR. The findings of this study suggest that ultrasonically-synthesized palm CNF-ZnO nanocomposites could find potential applications in the biomedical field and in the development of high strength rubber composites.
Biodegradable polymeric films, obtained from chitosan/natural rubber latex (CS/NRL) blends with different compositions, have been prepared by wetting process. The blends were characterized by dynamic mechanical thermal analysis (DMTA) and found that the CS/NRL blends are thermodynamically incompatible. This is evident from the presence of two glass transitions, corresponding to CS and NRL phases in the blend. The mechanical properties of the CS/NRL blends were improved with increasing the amount of chitosan and after surface treatment with sulphuric acid due to the sulfonate ionic interaction. The dielectric properties was determined using Precision LCR meter in the frequency range 75 kHz up to 30 MHz. After CS/NRL surface treatment with sulphuric acid at high content of chitosan showed the highest dielectric constant. The surface properties of the CS/NRL blend films before and after surface treatment were confirmed by atomic force microscopy (AFM), respectively.
Background: Majority of root canal treatment in Malaysia was provided by general dental practitioner. The purpose of this study was to evaluate the knowledge and practice (canal’s preparation, use of materials) by them. Methods: A questionnaire was structured and distributed to 120 registered general dental practitioners in selected areas in Perak, Johor and Klang Valley regarding the provision of root canal therapy in their practices. The questionnaires were hand delivered and collected after 1 to 2 weeks. Results: Reply rate was 95% (n=114). The result demonstrated that 62% respondents indicated that they performed the root canal therapy (RCT) themselves. Out of these only 26% included molars in the treatment. Three quarters of them (77%) used step-back technique and 54% used stainless steel instruments to prepare the canals. The majority of the respondents (69%) used calcium hydroxide as intracanal medicaments. Only 30% used rubber dam for isolation whereas the rest used cotton rolls. The numbers of routine radiographs taken were two for anterior teeth and three for molar. Half of the respondents indicated that they usually completed the RCT for the anterior tooth within two visits whereas three visits were needed for the molar tooth. The results were analyzed descriptively. Conclusions: This study indicates that most of the general dental practitioners’ do not comply with quality standards guidelines such as use of rubber dam as isolation. Cotton roll was the most popular isolation method. In spite of this, most of the respondents tend to update their knowledge and practices with current techniques and materials.
Potato starch nanocrystals were found to serve as an effective reinforcing agent for natural rubber (NR). Starch nanocrystals were obtained by the sulfuric acid hydrolysis of potato starch granules. After mixing the latex and the starch nanocrystals, the resulting aqueous suspension was cast into film by solvent evaporation method. The composite samples were successfully prepared by varying filler loadings, using a colloidal suspension of starch nanocrystals and NR latex. The morphology of the nanocomposite prepared was analyzed by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). FESEM analysis revealed the size and shape of the crystal and their homogeneous dispersion in the composites. The crystallinity of the nanocomposites was studied using XRD analysis which indicated an overall increase in crystallinity with filler content. The mechanical properties of the nanocomposites such as stress-strain behavior, tensile strength, tensile modulus and elongation at break were measured according to ASTM standards. The tensile strength and modulus of the composites were found to improve tremendously with increasing nanocrystal content. This dramatic increase observed can be attributed to the formation of starch nanocrystal network. This network immobilizes the polymer chains leading to an increase in the modulus and other mechanical properties.
For the diagnosis of IgE-mediated (immediate) hypersensitivity to natural rubber latex (NRL), skin prick testing with extracts of latex gloves has been widely used, but such extracts are difficult to standardize. The present study aimed to produce on an industrial scale an NRL extract from freshly collected NRL and to evaluate, calibrate, and standardize the extract by both in vivo and in vitro testing. The source material, latex of the rubber tree, Hevea brasiliensis (clone RRIM 600), was frozen immediately after collection in Malaysia and shipped in dry ice to Stallergènes SA, France. Protein and allergen profiles were analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), immunoblotting, isoelectric focusing (IEF), crossed immunoelectrophoresis (CIE), and crossed radioimmunoelectrophoresis (CRIE). Allergen quantification was effected by RAST inhibition. The capacity of the preparation to elicit immediate hypersensitivity reactions in vivo was measured by skin prick testing in 46 latex-allergic patients and 76 nonallergic control subjects. SDS-PAGE and immunoblot profiles of the extract and an NRL standard (E8) provided by the US Food and Drug Administration were almost identical, disclosing several distinct IgE-binding proteins with apparent molecular weights of 14, 20, 27, 30, and 45 kDa, conforming to reported molecular weights of several significant NRL allergens. An arbitrary index of reactivity (IR) of 100 was assigned to the extract at 1:200 dilution (w/v), having a protein content of 22 micrograms/ml. Skin prick testing of latex-allergic patients and controls using the extract at 100 IR revealed 93% sensitivity, 100% specificity, 100% negative predictive value, and 96% positive predictive value. In conclusion, a skin prick test reagent for diagnosis of type I NRL allergy was successfully standardized. The reagent was demonstrated to contain most, if not all, of the currently known clinically significant NRL allergens, and it showed high sensitivity and specificity.
Carbonyl iron particles (CIPs) is one of the key components in magnetic rubber, known as magnetorheological elastomer (MRE). Apart from the influence of their sizes and concentrations, the role of the particle' shape is pronounced worthy of the attention for the MRE performance. However, the usage of CIPs in MRE during long-term applications may lead to corrosion effects on the embedded CIPs, which significantly affects the performance of devices or systems utilizing MRE. Hence, the distinctions between the two types of MRE embedded in different shapes of spherical and plate-like CIPs, at both conditions of non-corroded and corroded CIPs were investigated in terms of the field-dependent rheological properties of MRE. The plate-like shape was produced from spherical CIPs through a milling process using a rotary ball mill. Then, both shapes of CIPs individually subjected to an accelerated corrosion test in diluted hydrochloric (HCl) at different concentrations, particularly at 0.5, 1.0, and 1.5 vol.% for 30 min of immersion time. Eight samples of CIPs, including non-corroded for both CIPs shapes, were characterized in terms of a morphological study by field emission scanning electron microscope (FESEM) and magnetic properties via vibrating sample magnetometer (VSM). The field-dependent rheological properties of MREs were analyzed the change in the dynamic modulus behavior of MREs via rheometer. From the application perspective, this finding may be useful for the system to be considered that provide an idea to prolong the performance MRE by utilizing the different shapes of CIPs even when the material is fading.
The influence of hydraulic retention time (HRT, 24, 12, and 6h) on the physical characteristics of granules and performance of a sequencing batch reactor (SBR) treating rubber wastewater was investigated. Results showed larger granular sludge formation at HRT of 6h with a mean size of 2.0±0.1mm, sludge volume index of 20.1mLg(-1), settling velocity of 61mh(-1), density of 78.2gL(-1) and integrity coefficient of 9.54. Scanning electron microscope analyses revealed different morphology of microorganisms and structural features of granules when operated at various HRT. The results also demonstrated that up to 98.4% COD reduction was achieved when the reactor was operated at low HRT (6h). Around 92.7% and 89.5% removal efficiency was noted for ammonia and total nitrogen in the granular SBR system during the treatment of rubber wastewater.