Adsorption of cationic monomeric and gemini surfactants on montmorillonite and adsolubilization of vitamin E

Adsorption of a cationic gemini surfactant (1,2-bis(dodecyldimethylammonio) ethane dibromide, 12-2-12) and the corresponding monomeric surfactant (dodecyltrimethylammonium bromide, DTAB) on montmorillonite has been characterized with a combination of adsorption isotherm, interlayer spacing and FT-IR spectroscopic data. Adsolubilization of vitamin E into the adsorbed surfactant layers has also been studied. The adsorption isotherm data reveal that the adsorption of the two surfactants is driven by the two factors: one is the cation exchange that occurs on the interlayer basal planes and the other is the hydrophobic interaction between hydrocarbon chains of the surfactants. Although the adsorbed amount measured in the saturation region (in mol g(-1)) is almost identical for the two surfactants, the conformation of the intercalated surfactant molecules differs significantly from each other. The adsorption of DTAB results in a lateral bilayer arrangement in the limited interlayer space, whereas 12-2-12 gives a normal bilayer arrangement in the expanded interlayer space. Adsolubilization of vitamin E takes place into the adsorbed surfactant layers, and interestingly, all the vitamin E molecules added in the montmorillonite suspensions are hybridized at lower surfactant concentrations due to the great specific surface area of the clay material. Since the maximum adsolubilization amount is usually obtained just below the critical micelle concentration, the gemini surfactant is deemed to be more efficient than the corresponding monomeric one to achieve the great adsolubilization amount.     

Influence of heating and laser irradiation on the Raman D band in single-wall carbon nanotubes

Fine structure of the Raman D band in single-wall carbon nanotubes (SWNTs) was investigated by heating and laser irradiation. It is shown that the D band is composed of three components at ～ 1313, 1340, and 1355 cm^? 1, denoted by D₁, D₂, and D₃, respectively. The D₁ and D₂ intensities significantly increase with laser irradiation in air and vacuum, respectively. The D₃ intensity drastically increases with heating in air. From these results, it is suggested that the fine structure of the D band is attributed to different kinds of defects introduced in SWNTs.     

Intra-body data transmission for the personal area network

Intra-body communication is a wireless means of exchanging information within a personal area network (PAN) between wearable electronic sensors and devices. The feasibility of intra-body communication is confirmed through several experiments on signal propagation within the human body, and a human phantom is designed and used to obtain reproducible results over repeated experiments. Based on the results of these experiments, a prototype transmission system is constructed using aluminum electrodes powered by 3 V DC and operating in the 10.7 MHz frequency modulation (FM) band. This prototype is demonstrated to be capable of transmitting analog signals through the human subjects in the presence of external noise. Digital data transmission at 9600 bps is also achieved using newly fabricated 10.7 MHz frequency shift keying (FSK) transmitter and receiver devices. The carrier frequency of 10.7 MHz is the intermediate frequency of FM radio receivers, meaning that the proposed system can make use of a wide selection of inexpensive, commercial radio frequency devices.     

Mechanical characteristics of a contact optical head slider operating on a metal-layered medium

 Advances in a digital network society require both higher density and higher transfer rates in all sorts of storage systems. Even in optical recording, the trend toward higher density and larger capacity requires novel surface-recording technologies that can drastically diminish head-to-medium spacing, resulting in an improvement in spatial resolution and, finally, a higher recording density. In this paper, we propose a novel contact optical head slider that is able to almost cancel the suspension load by generating hydrodynamic pressure, thus realizing a lower net contact force. A trial-manufactured contact slider being processed four sliding pads on air-bearing surfaces has indicated a gentle variation of both the acoustic emission signal intensity and the friction force as the circumferential velocity changes. Furthermore, a time-domain simulation was performed to investigate the effects of the damping of a medium surface (lubricant) both on slider bouncing and on contact force. Received: 5 July 2001/Accepted: 1 November 2001     

Monte Carlo simulation of circular double-stranded polymers

Double-helix structure of DNA provides an appropriate model system for studying equilibrium properties of macromolecule. In contrast to the models of linear polymers, the secondary structure as well as most of interaction parameters can be introduced into the model. We present studies of double-stranded twisted circular polymer chain by mean of computer simulation. The attention was focused on the effect of polymer chain twisting on the properties of macromolecule. We found that the number of double helical turns affects the scaling of the polymer chain and markedly changes system properties, for example, coil to globule transition temperature.     

Prediction of the capacity of a heat exchanger by a thermal network method: Modified effective specific heat model considering the influence of static pressure distributions of refrigerants

In this paper, we proposed a method to predict the capacity of a heat exchanger by considering static pressure distributions of refrigerants. The thermal network method was modified by adding an equivalent heat generation term into a heat balance equation that was connected with calculated 1D static pressure distributions of refrigerants. An experiment was performed with a heat exchanger having two rows and two passes to verify the accuracy of the proposed method. The result showed the error of the predicted capacity to be less than 1% for an evaporator and less than 2% for a condenser. © 2002 Wiley Periodicals, Inc. Heat Trans Asian Res, 31(5): 376–390, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10039     

Depression among cancer patients

OBJECTIVE: To identify important causes of premature mortality among Aboriginal adults in the Northern Territory (NT), 1979-1991. METHODS: All deaths of NT Aboriginal residents aged 15-64 years which occurred in the NT between 1979 and 1991 and which were recorded by the Registry of Births, Deaths and Marriages were included. Standardised mortality ratios (SMRs) were used to compare the number of deaths observed among Aboriginals in the NT to those expected, based on overall Australian rates. Years of potential life lost before age 65 (YPLL65) were estimated for specific causes of death. RESULTS: Aboriginal women (overall SMR, 5.5) and Aboriginal men (SMR, 4.7) experienced a high burden of excess mortality from almost every cause of death. This excess increased over time, especially for Aboriginal women. Among Aboriginal men, the most important causes of premature death were motor vehicle accidents (11% of excess deaths and 17% of YPLL65), ischaemic heart disease (10% of excess deaths and 10% of YPLL65), pneumonia and influenza (8% of excess deaths and 6% of YPLL65), and homicide (7% of excess deaths and 8% of YPLL65). For Aboriginal women, the most important causes included homicide (7% of excess deaths and 11% of YPLL65), chronic obstructive pulmonary disease (10% of excess deaths and 5% of YPLL65), rheumatic heart disease (7% of excess deaths and 8% of YPLL65), and ischaemic heart disease (6% of excess deaths and 5% of YPLL65). CONCLUSIONS: The wide variety of causes of excess mortality will require an equally wide variety of solutions, both medical and non-medical, and a long term commitment will be necessary to achieve reductions in premature mortality among NT Aboriginal adults.     

Fabrication of low-loss single-mode fibres

Low-loss single-mode fibres with GeO2-doped SiO2 cores have been made by the c.v.d. method and the loss spectrum from 0.6 to 1.8 ?m measured. The minimum loss of the fibre with suitably designed parameters, characterised by the refractive-index difference and the core diameter, was 0.75 dB/km at 1.05 ?m.     

Development of coincidence transmission electron microscope. III. Incorporation with gamma-type imaging energy filter

We have developed a new analytical transmission electron microscope (TEM), called coincidence TEM, which, in principle, enables observation of elemental mapping images at a high signal-to-noise ratio. We have previously reported the successful observation of an elemental mapping image of a specimen, but over a very long period of time (168 h). To solve this inefficiency, we installed a gamma-type imaging energy filter in the coincidence TEM to remove the no-loss electrons, which are mainly transmitted electrons. This has enabled the intensity of the background signals in the coincidence measurement to be markedly reduced. The coincidence TEM with a gamma-type imaging energy filter allows the coincidence image to be observed in 3 h, thus, the measurement time is shortened by two orders of magnitude. Moreover, the use of a silicon drift detector (SDD) will shorten the measurement time.