The Influence of MMA Esterification on Interfacial Adhesion and Mechanical Properties of Hybrid Kenaf Bast/Glass Fiber Reinforced Unsaturated Polyester Composites

The demand for natural fiber hybrid composites for various applications has increased, which is leading to more research being conducted on natural fiber hybrid composites due to their promising mechanical properties. However, the incompatibility of natural fiber with polymer matrix limits the performance of the natural fiber hybrid composite. In this research work, the mechanical properties and fiber-to-matrix interfacial adhesion were investigated. The efficiency of methyl methacrylate (MMA)-esterification treatments on composites’ final product performance was determined. The composite was prepared using the hand lay-up method with varying kenaf bast fiber (KBF) contents of 10, 15, 20, 25, 30, 35 (weight%) and hybridized with glass fiber (GF) at 5 and 10 (weight%). Unsaturated polyester (UPE) resin and methyl ethyl ketone peroxide (MEKP) were used as binders and catalysts, respectively. Scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR) were used to examine the effects of MMA-esterification treatment on tensile strength and morphology (tensile fracture and characterization of MMA-esterification treatment) of the composite fabricated. The tensile strength of MMA-treated reinforced UPE and hybrid composites are higher than that of untreated composites. As for MMA treatment, 90 min of treatment showed the highest weight percent gain (WPG) and tensile strength of KBF-reinforced UPE composites. It can be concluded that the esterification of MMA on the KBF can lead to better mechanical properties and adhesion between the KFB and the UPE matrix. This research provides a clear reference for developing hybrid natural fibers, thus contributing to the current field of knowledge related to GF composites, specifically in transportation diligences due to their properties of being lightweight, superior, and involving low production cost.     

Severe α-Thalassemia Intermedia Due to a Compound Heterozygosity for the Highly Unstable Hb Adana (HBA2: c.179G>A) and a Novel Codon 24 (HBA2: c.75T>A) Mutation

We report a novel mutation at codon 24 of the α2-globin gene (HBA2: c.75T?>?A) found in a Sundanese family. This novel mutation was detected during prenatal diagnosis. The couple already had a 7-year-old boy who exhibited clinically severe α-thalassemia intermedia (α-TI), and he was found to be a compound heterozygote for the novel mutation at codon 24 and the previously described Hb Adana (HBA2: c.179G?>?A) at codon 59 of the α2-globin gene. The father was a carrier of the novel point mutation and showed normal hemoglobin (Hb) and a low mean corpuscular volume (MCV) and mean corpuscular Hb (MCH) value.     

Intestinal parasitic infections in Likupang, North Sulawesi, Indonesia.

A parasitological survey was conducted on the inhabitants of 6 villages of Likupang, Minahasa Peninsula, North Sulawesi, Indonesia, in August 1991. A total of 419 fecal samples were examined by using direct smear, flotation, formalin ether concentration, Harada-Mori culture and agar-plate culture techniques. Five nematode and 7 protozoan parasites were detected, while trematode and cestode infection was not observed. Soil-transmitted nematode infections were predominant. Among the younger inhabitants aged less than 15, positive rates of Ascaris, Trichuris and hookworm infections were almost same, namely 45.7, 45.3 and 47.7%, respectively. Among the elder people aged 15 or more, positive rate of hookworm infection (89.4%) was much higher than Ascaris and Trichuris infections (19.3 and 26.1%, respectively). Village to village differences in parasite prevalence, probably due to socio-economic and sanitary-environmental differences were observed. Both Necator americanus and Ancylostoma duodenale were detected. The agar-plate culture was proved to be an efficient method for detection of hookworm as well as Strongyloides stercoralis.     

The hemoglobin O mutation in Indonesia: distribution and phenotypic expression

We have investigated hemoglobin O Indonesia (HbO_Ina) in related ethnic populations of the Indonesian archipelago: 1725 individuals of the five ethnic populations of South Sulawesi (Bugis, Toraja, Makassar, Mandar, and Kajang) and 959 individuals of the neighboring islands, who were divided into five phylogenetic groups: (a) Batak; (b) Malay from Padang, Pakanbaru, and Palembang in the island of Sumatra; (c) Javanese-related populations (Java, Tengger, and Bali) from the islands of Java and Bali; (d) populations of the Lesser Sunda Islands of Lombok, Sumba, and Sumbawa; and (e) the Papuan-language-speaking population of Alor Island. Nineteen individuals heterozygous for HbO_Ina were identified from the Bugis, Toraja, Makassar, and Kajang ethnic populations, but none from the other populations. In all cases, the underlying mutation was found to be in codon 116 (GAG to AAG) of the α₁-globin gene, resulting in the Glu116Lys amino acid change. The level of HbO in the 17 individuals plus 12 additional family members carrying the mutation was found to be 11.6 ± 1.0%, significantly lower than the expected 17%–22%, indicating the instability of HbO. Received: February 19, 2001 / Accepted: June 4, 2001