Physical and mechanical properties of flame retardant urea formaldehyde medium density fiberboard

Medium density fiberboard (MDF) is one of the widely used wood-based panels to manufacture building components such as furniture units for interior applications. Although MDF is an excellent product it is prone to fire hazard which should be enhanced using flame retardants during its manufacture. Properties of the flame retardant urea formaldehyde (UF) MDF made using a dry process from rubberwood fibers were investigated. Flame retardant chemicals that were evaluated include sodium aluminate, zinc borate and aluminum trihydrate, which were incorporated with rubberwood fibers to manufacture experimental MDF. Four concentration levels, 10%, 15%, 20% and 30% of fire retardants and 15% urea formaldehyde resin based on oven dry fiber weight were used to manufacture experimental panels. Physical and mechanical properties including thickness swelling, water absorption, bending characteristics, and internal bond strength of the samples were determined. Flame retardant properties of the panels were also investigated using a Cabinet Method along with char index, weight loss and size of ellipse area. Finally, thermogravimetry method was employed to analyze thermal properties of the MDF panels. The results showed that thickness swell and water absorption decreased as the flame retardant increased. The MOR was not affected by the flame retardant treatment for boards bonded with urea formaldehyde resin. The internal bond strength showed a small reduction compared with the controls as the flame retardant chemicals increased but not for boards treated with 5% aluminum trihydrate. When the concentration of flame retardant chemicals increased to 30%, the internal bond generally decreased. Char index, area of ellipse and weight loss reduced as the percentage of flame retardant increased. Sodium aluminate showed the best performance in reducing thermal degradation followed by aluminum trihydrate and zinc borate. Aluminum trihydrate cured closely resemble that of the control during the gelation test.     

Enhancement of stack ventilation in hot and humid climate using a combination of roof solar collector and vertical stack

In the hot and humid climate, stack ventilation is inefficient due to small temperature difference between the inside and outside of naturally ventilated buildings. Hence, solar induced ventilation is a feasible alternative in enhancing the stack ventilation. This paper aims to investigate the effectiveness of a proposed solar induced ventilation strategy, which combines a roof solar collector and a vertical stack, in enhancing the stack ventilation performance in the hot and humid climate. The methodology selected for the investigation is physical experimental modelling which was carried out in the actual environment. The results are presented and discussed in terms of two performance variables: air temperature and air velocity. The findings indicate that the proposed strategy is able to enhance the stack ventilation, both in semi-clear sky and overcast sky conditions. The highest air temperature difference between the air inside the stack and the ambient air (T_i−T_o) is achieved in the semi-clear sky condition, which is about 9.9 °C (45.8 °C–35.9 °C). Meanwhile, in the overcast sky condition, the highest air temperature difference (T_i−T_o) is 6.2 °C (39.3 °C–33.1 °C). The experimental results also indicate good agreement with the theoretical results for the glass temperature, the air temperature in the roof solar collector’s channel and the absorber temperature. The findings also show that wind has significant effect to the induced air velocity by the proposed strategy.     

Electronic properties of polyaniline doped with dodecylbenzenesulphonic acid (PANI-DBSA) and poly(methyl methacrylate) (PMMA) blends in the presence of hydroquinone

Films of polyaniline doped with dodecylbenzenesulphonic acid (DBSA) and poly(methyl methacrylate) (PMMA) blends were studied with and without compatibilising agent “hydroquinone”. Hydroquinone was used to maximize solubility and to make it compatible with polymethylmethacrylate (PMMA) to get uniform and homogenous films on indium tin oxide ITO coated glass. Current density measurement as a function of voltage (J–V) and capacitance voltage (C–V) measurements at different temperature were carried out. The observed J–V and C–V characteristics can be satisfactorily fitted using the modified Schottky equations. The junction parameters were strongly influenced by hydroquinone. From C–V characteristics, the built-in voltage and charge carriers concentration were also calculated and discussed.     

Agreement and clinical utility of 2 techniques for measuring cardiac output in patients with low cardiac output

BACKGROUND: The reliability of cardiac output obtained with the bolus technique is a problem. OBJECTIVES: To compare measurements of cardiac output measured with bolus and continuous techniques in patients with low cardiac output and to determine if measurements obtained with the continuous technique increased the number of subsequent clinical decisions. METHODS: In 60 intensive care patients, a nurse recorded a single continuous cardiac output measurement and then obtained the mean of 3 consecutive bolus determinations. The medical records of these 60 patients (experimental group) for the next 48 hours and of 60 other patients with regular or mixed venous oximetry catheters (control group) were reviewed to assess the occurrence of cardiac output events and the frequency of clinical decisions based on the events. RESULTS: Mean cardiac output was 4.46 L/min by the continuous technique and 5.20 L/min by the bolus technique (P = .011) for the experimental group. Median bias between the 2 types of measurements was -0.10 L/min (P = .79). Twenty-three of the pairs (38%) had an absolute percent difference greater than 15%. Of these, 18 (78%) had a higher bolus reading. Treatment decisions per 48 hours were 9.9 for the experimental group and 8.6 for the control group (P = .014). Median length of stay was 2 days less in the experimental group (P = .02), and mean highest cardiac output was 0.81 L/min higher (P = .009). CONCLUSIONS: Measurements of cardiac output determined with the continuous technique may be more precise than measurements determined with the bolus technique. Continuous cardiac output information increases the number of treatment decisions and actions that may shorten hospital length of stay.     

Essential oils of Zingiber officinale var. rubrum Theilade and their antibacterial activities

The essential oils obtained by hydrodistilation of the leaves and rhizomes of Zingiber officinale var. rubrum Theilade were analysed by capillary GC and GC–MS. Forty-six constituents were identified in the leaf oil, while 54 were identified in the oil from the rhizomes. The leaf oil was clearly dominated by β-caryophyllene (31.7%), while the oil from the rhizomes was predominantly monoterpenoid, with camphene (14.5%), geranial (14.3%), and geranyl acetate (13.7%) the three most abundant constituents. The evaluation of antibacterial activities using the micro-dilution technique revealed that both the leaf and rhizome oils were moderately active against the Gram-positive bacteria Bacilluslicheniformis, Bacillus spizizenii and Staphylococcus aureus, and the Gram-negative bacteria Escherichia coli, Klebsiella pneumoniae and Pseudomonas stutzeri.     

Combustion characteristics of biomass in SouthEast Asia

Gas emission during combustion of mixed tropical wood, bamboo, oil palm trunk, acacia, and rubber wood have been investigated by using TG–MS in presence of oxygen as well as FTIR. The weight decreasing profiles and the gas formation rates of oil palm trunk was significantly different among the samples although their elemental composition was almost the same from biomass samples. It was found that H₂O is the main product formed for all samples. The evolving rates of the gaseous products during the combustion and infrared spectrums such as CO, H₂O, CO₂, CH₄ and COOH⁺ were found. The DTG curves spectrums for biomass present four overlapping peaks.     

Dopamine D3 receptor mutant mice exhibit increased behavioral sensitivity to concurrent stimulation of D1 and D2 receptors

The dopamine D3 receptor is expressed primarily in regions of the brain that are thought to influence motivation and motor functions. To specify in vivo D3 receptor function, we generated mutant mice lacking this receptor. Our analysis indicates that in a novel environment, D3 mutant mice are transiently more active than wild-type mice, an effect not associated with anxiety state. Moreover, D3 mutant mice exhibit enhanced behavioral sensitivity to combined injections of D1 and D2 class receptor agonists, cocaine and amphetamine. However, the combined electrophysiological effects of the same D1 and D2 agonists on single neurons within the nucleus accumbens were not altered by the D3 receptor mutation. We conclude that one function of the D3 receptor is to modulate behaviors by inhibiting the cooperative effects of postsynaptic D1 and other D2 class receptors at systems level.