Ahsan Habib

Passive air monitoring of PCBs and PCNs across East Asia: A comprehensive congener evaluation for source characterization

A comprehensive congener specific evaluation of polychlorinated biphenyls (PCBs) and polychlorinated naphthalenes (PCNs) in the atmosphere was conducted across East Asia in spring 2008, applying polyurethane foam (PUF) disk passive air sampler (PAS) as monitoring device. Mean concentrations derived for Japan, China and Korea were 184 ± 24, 1100 ± 118, and 156 ± 20 pg m(-3) for ∑(202) PCBs, and 9.5 ± 1.5, 61 ± 6, and 16 ± 2.4 pg m(-3) for ∑(63) PCNs, respectively. Relative to reported data from 2004, the present results suggest that air PCBs concentrations have not changed much in Japan and Korea, while it has increased by one order of magnitude in China. From principal component analysis, combustion emerged highly culpable in contemporary emissions of both PCBs and PCNs across the East Asian sub-region. Another factor derived as important to air PCBs was re-emissions/volatilization. Signals from PCBs formulations were also picked, but their general importance was virtually consigned to the re-emissions/volatilization tendencies. On the contrary, counterpart PCNs formulations did not appear to contribute much to air PCNs.

Synthesis and characterization of ZnO-TiO2 nanocomposites and their application as photocatalysts

Nanocomposite ZnO-TiO2 powders of varying ZnO/TiO2 molar ratios have been prepared from their salt/compound by heating at 600°C and 900°C and characterized using scanning electron microscope and X-ray diffraction techniques. The nanosized powders can decolorize/degrade brilliant golden yellow (BGY), an azo dye extensively used in textile industries, in water under solar irradiation. The effects of various parameters such as photocatalyst loading, molar ratio of ZnO/TiO2, pH of the solution, initial dye concentration, and irradiation time on the photodecolorization have been investigated. ZnO-TiO2 nanocomposite (6 g/L) in the molar ratio of 1:1 or 3:1, prepared at 900°C, can efficiently decolorize about 98% of 20 mg/L BGY at pH of about 7 by 2-h illumination in sunlight. The initial dye decolorization follows pseudo-first-order kinetics. Finally, trial experiments were done using real textile wastewater to find out the effectiveness of the photocatalysts to a more complex system.

Photocatalytic decolorization of crystal violet in aqueous nano-ZnO suspension under visible light irradiation

Nanosized ZnO was prepared through hydrothermal process and characterized by scanning electron microscopy, X-ray diffraction and laser-induced breakdown spectra measurement techniques. The as-prepared nanosized ZnO was used to investigate the decolorization/degradation of crystal violet, a cationic dye which is extensively used in dyeing/textile industries, under visible light through adsorption studies of the dye solution with ZnO in the dark. The results show that the adsorption of CV on ZnO takes about 200 min to reach equilibrium, and the equilibrium time at a certain concentration of the dye seems to be independent of temperatures that are used for the preparation of ZnO samples. The adsorption data follow the pseudo-first-order kinetic model (Lagergren), and the adsorption pattern follows the Langmuir model.Prepared ZnO (300°C) was found to be a more efficient photocatalyst among others including pristine ZnO, to decolorize/degrade the dye. The decolorization rate is increased with the decreasing of the initial dye concentration and reached at a limiting value. The catalyst loading also influences the decolorization/degradation of the dye, and decolorization rate is increased with increasing the catalyst loading and reached at a limiting value. ZnO was found to be stable under visible light irradiation at solution pH = 6. The photocatalytic degradation of the dye followed zero-order kinetics, and the Langmuir-Hinshelwood mechanism was found to be valid.

Zinc oxide-mediated photocatalytic decolorization of Ponceau S in aqueous suspension by visible light

ZnO, comprising nanosize particles (approximately 40 nm) has been prepared by heating (300°C) ZnCO3, which was obtained as precipitate by mixing ZnSO4 and (NH4)2CO3 solutions. The prepared ZnO was characterized by X-ray diffraction, scanning electron microscopy (SEM), laser-induced breakdown spectroscopy, and adsorption studies. It has been used to catalyze the decolorization of Ponceau S (PS), a model diazo dye, in an aqueous suspension under visible light (I ≈ 1.8 × 10−4 W cm−2). This ZnO was found to be more efficient as a photocatalyst compared to pristine ZnO. ZnO samples with higher temperatures (500°C and 700°C) show less catalytic activity. SEM images show that the particle size of ZnO increases with the increase in calcined temperature of ZnO through agglomeration, resulting in a decrease in surface area. Photodecolorization of PS is affected by its and ZnO concentrations, but unaffected by the initial pH of the solutions in the range of 4 to 7. Illumination for a sufficiently long time completely mineralizes the dye, but no Zn2+ can be detected in the clear solution.Photodegradation kinetics in the ZnO suspension obeys the Langmuir-Hinshelwood equation, and some activation of the ZnO surface by light is indicated.

Impact of earnings management on value‐relevance of accounting information: empirical evidence from Japan

This paper investigates the impact of earnings management on value relevance of accounting information in the context of Japan. Researchers carrying out earnings management research usually rely on the Jones (1991) or the modified Jones model (1995) to disaggregate accruals into its discretionary and non‐discretionary components. However, because of criticisms leveled against extant models of discretionary accruals, this study instead uses earnings management measures constructed by Leuz et al. (2001) and Bhattacharya et al. (2001) and examines the relationship between these measures and their impact on the value‐relevance of accounting information. The latter is operationalized by the explanatory power of book values and earnings (combined model) and earnings alone (earnings model) for stock price. Results based on 5,318 consolidated firm‐year observations over 1992‐1999 show that, both earnings management measures and aggregate earnings management measures (combination of both earnings smoothing and earnings management measures) are significantly negatively associated with the combined value relevance of book values of equity and earnings (combined model) and value relevance of earnings (earnings model).

Detection of explosives using a hollow cathode discharge ion source.

RATIONALE For public security and safety, it is highly desirable to develop an ion source for the detection of explosives that is highly sensitive, compact in size, robust, and does not use any special carrier gases such as helium. In this work, a hollow cathode discharge (HCD) ion source was developed for the detection of explosives using ambient air as a carrier gas. METHODS To detect nonvolatile and thermally unstable explosives with high sensitivities, a new HCD ion source was designed and coupled with an ion trap mass spectrometer. RESULTS Five explosives--hexamethylene triperoxide diamine (HMTD), 1,3,5-trinitroperhydro-1,3,5-triazine (RDX), pentaerythritol tetranitrate (PETN), nitroglycerin (NG) and trinitrotoluene (TNT)--were detected with limits of detection of lower than ng. The intensities of the NO3(-) adduct ions with RDX, PETN, and NG showed a marked increase with increase in ion source pressure in the range of 1-28 Torr. CONCLUSIONS Because the major NOx(-) ions (x = 2, 3) produced in the plasma act as reagent ions in ion-molecule reactions of explosives, air is best suited as a carrier gas for the detection of explosives. It is proposed that the NOx(-) (x = 2, 3) and O3 contributed to the formation of [TNT-H](-) and [TNT-NO](-) ions, via the reactions NOx(-) + TNT → [TNT-H](-) + HNOx and [TNT](-) + O3 → [TNT-NO](-) + NO2 + O2.

Attitudes towards disability and inclusion in Bangladesh: from theory to practice

Along with the development of global consciousness, the campaign for an inclusive society is gaining momentum. An inclusive society based on social justice ensures individual rights and social welfare for each and everybody. On the contrary, the conventional disability paradigm categorizes people with many different labels which exclude people from society. For many years, people have been labelled as being ‘normal’, ‘disabled’ and ‘handicapped’ around the world. The theoretical developments around understanding disability have influenced professional knowledge and policy-making. During the twentieth century, social sciences show that disability is a socially created phenomenon rather than the individuals fault. This article represents a discussion based on the learning aims of the module ‘Inclusive Society–Inclusive School’ within the Erasmus Mundus Special Education Needs study programme (EMSEN), and raises a number of perspectives and potential problems and concerns related to new disability paradigms. The article offers the authors’ reflection through the EMSEN programme, a programme that constitutes an opportunity and opens up space to practise and understand ‘inclusion’ through a multicultural environment across diverse geographical contexts.

Optimizing coverage performance of multiple random path-planning robots

This paper presents a new approach to the multi-agent coverage path-planning problem. An efficient multi-robot coverage algorithm yields a coverage path for each robot, such that the union of all paths generates an almost full coverage of the terrain and the total coverage time is minimized. The proposed algorithm enables multiple robots with limited sensor capabilities to perform efficient coverage on a shared territory. Each robot is assigned to an exclusive route which enables it to carry out its tasks simultaneously, e.g., cleaning assigned floor area with minimal path overlapping. It is very difficult to cover all free space without visiting some locations more than once, but the occurrence of such events can be minimized with efficient algorithms. The proposed multi-robot coverage strategy directs a number of simple robots to cover an unknown area in a systematic manner. This is based on footprint data left by the randomized path-planning robots previously operated on that area. The developed path-planning algorithm has been applied to a simulated environment and robots to verify its effectiveness and performance in such an application.

Accounting‐Based Equity Valuation Techniques and the Value Relevance of Dividend Information: Empirical Evidence from Japan

This paper empirically examines whether dividends are value‐relevant in Japan by employing Ohlson’s (1995) accounting‐based equity valuation technique. The substantial U.S.‐based literature on dividends has confirmed the signalling role of dividends in mitigating information asymmetry between managers and investors, and is consistent with an environment characterized by dispersion of ownership. However, the most important corporate governance characteristic that distinguishes Japan from the U.S. is the predominance of inter‐corporate, interlocking ownership in Japan, which reduces information asymmetry and is therefore likely to diminish the role of dividends in mitigating such asymmetries. Pooled regression results provide evidence consistent with this hypothesis. However, even in such an environment, dividends are value relevant for firms that incur losses whilst paying dividends, and also for firms with permanent earnings.