Mixed Hemimicelles Solid phase Extraction of Atrazine and Simazine from Environmental Water Samples Using Alumina-Coated Magnetite Composite Material

Journal of Analytical Chemistry - A sensitive and selective mixed hemimicelles solid phase extraction magnetic material based on sodium dodecyl sulfate-coated magnetite (Fe3O4)/alumina (Al2O3) is...     

DNA Damage and Apoptosis Induced by Photosensitization of 5,10,15,20-Tetrakis (N-methyl-4-pyridyl)-21H,23H-porphyrin via Singlet Oxygen Generation

Cancer photodynamic therapy (PDT) requires photosensitizers that efficiently and selectively destroy tumor cells. We investigated 5,10,15,20-tetrakis ( N -methyl-4-pyridyl)-21 H ,23 H -porphyrin (TMPyP) as a potential cancer treatment. Confocal fluorescence microscopy showed that TMPyP was localized in the nuclei, whereas 5-aminolevulinic acid (ALA)-derived protoporphyrin IX (PPIX) was localized diffusely in the cytoplasm of human leukemia (HL-60) cells. In HL-60 cells under UVA irradiation, TMPyP effectively induced apoptosis. Moreover, 8-oxo-7,8-dihydro-2'-deoxyguanosine, an oxidative product of 2'-deoxyguanosine, was accumulated in the DNA of cells treated with photoirradiated TMPyP, whereas only small amounts were observed in ALA-treated cells in the presence of UVA light. TMPyP and UVA caused extensive damage at every guanine residue in DNA fragments obtained from the human p 53 tumor suppressor gene and the c-Ha- ras -1 proto-oncogene, whereas PPIX induced little DNA damage under these conditions. Electron spin resonance spectroscopy using a singlet oxygen (¹O₂) probe and D₂O showed that photoexcited TMPyP generated ¹O₂. These results suggest that photoexcited TMPyP reacts with oxygen to generate ¹O₂, which in turn, oxidizes guanine residues. Taken together, the results demonstrated that TMPyP was localized in the nucleus where it was photosensitized to induce DNA damage, suggesting that TMPyP may have clinical utility as a nucleus-targeted PDT.     

Adaptive neural network-based saturated control of robotic exoskeletons

In this paper, novel adaptive neural network (NN) controllers with input saturation are presented for n-link robotic exoskeletons. The controllers consist of a state feedback controller and an output feedback controller. Through utilizing auxiliary dynamics, the controllers provide a new framework for input saturated control of these robotic systems which can feature the global stability for state feedback control. To compensate for the unknown dynamics of the system, adaptive schemes based on NNs are exploited. Furthermore, adaptive robust terms are utilized to deal with unknown external disturbances. Stability studies show that the closed-loop system is globally uniformly ultimately bounded (UUB) with the state feedback controller, where the global property of the NN-based controller is achieved exploiting a smooth switching function and a robust control term. Also, the system is semi-globally UUB with the output feedback controller. Effectiveness of the controllers is validated by simulations and experimental tests.     

Measurement of small chirp-parameter for Mach-Zehnder-type optical modulator

A new measurement method of chirp-parameters is proposed for electro-optic (EO) intensity modulators with the Mach-Zehnder (MZ) waveguide interferometer. This method is suitably applied for the measurement of the small chirp with operation at a specific RF-frequency. To determine the chirp-parameter, optical spectrum components of the modulated light are observed with varying the relative optical phase difference between the two arms of the MZ waveguide interferometer. The chirp-parameter of 0.17, which is a value small enough for EO intensity modulation, was successfully measured by the experiment.     

Region Division Assignment: A New OVSF Code Reservation and Assignment Scheme for Downlink Capacity in W-CDMA Systems

This work focuses on the efficient management of orthogonal-variable-spreading-factor (OVSF) codes for multimedia communications in the W-CDMA systems. Because these systems must assign only OVSF codes that are mutually orthogonal, even if they have sufficient transmission capacity they block connections for which no orthogonal OVSF codes are available. This code blocking can, with extra overhead, be eliminated by reassigning codes, but in this paper we propose an OVSF code management scheme designed to not reassign codes. This scheme, called Region Division Assignment, cannot eliminate code blocking but can reduce the overhead for code assignment. Computer simulations based on the multiple access protocol in UMTS/IMT-2000 show that the proposed scheme can efficiently provide variable-rate services as well as low-rate services. This paper was presented in part at the IEEE Vehicular Technology Conference Fall 2001, October 7-11, 2001, Atlantic City, NJ USA. Rujipun Assarut received his BE from Chularongkorn University, Thailand, in 1997 and his MS from Gunma University, Japan, in 2002. Currently, he is working as a software engineer for NEC communication systems. His current project is the development of IP phone for enterprise applications. Ken’ichi Kawanishi is a research associate with Gunma University, Japan. His current research interests include queueing theory and stochastic processes. He is a member of ORSJ, JSIAM and IEICE. Ushio Yamamoto received a bachelor’s degree in information engineering, and a master’s degree and Ph.D. degree in information science from Tohoku University in 1992, 1994 and 1997, respectively. He is now an associate professor in Dept. of Computer Science, Gunma University. He has been engaged in research on wireless ad hoc networks, multimedia communication networks, load balancing on computer networks and intelligent agents. He is a member of IPSJ and JSAI. Yoshikuni Onozato is a Professor with Gunma University. His research interests are in satellite systems, computer communication networks and distributed computing systems and span the entire spectrum from the design and performance evaluation of these systems to their implementation. He is a member of IEEE, ACM, IPSJ, ORSJ and IEICE.     

AlGaAs transverse junction stripe laser with distributed Bragg reflector

A new longitudinal mode stabilised AlGaAs transverse junction stripe laser with distributed Bragg reflector has been fabricated. Stabilised single longitudinal mode operation was obtained; temperature dependence of the lasing wavelength for the d.b.r. t.j.s. laser was 0.5 ?/°C.     

1.544-Mbits/s Transmission of TV Signals by Interframe Coding System

As a powerful tool for economizing on the digital transmission of videotelephone signals, interframe coding techniques have drawn increasing attention, and various interframe coding schemes have been proposed recently. However, many problems remain to be studied in establishing technical feasibility for these techniques and schemes. This concise paper reports on field trial in which a 1.544-Mbits/s digital transmission of videotelephone signals was conducted over Nippon Telegraph and Telephone Public Corporation's (NTT's) PCM100M digital repeatered line between Tokyo and Yokohama, Japan. The experimental interframe codec is based on the well-understood conditional picture element replenishment algorithm. The object of the field trial was to demonstrate, not the validity of the algorithm itself, but the technical feasibility of the interframe coding system as an entity. Experimental results are satisfactory enough to assure us of the system's practicality in the near future.     

Asymptotic formalism for ultraflat optical frequency comb generation using a Mach-Zehnder modulator

We theoretically prove that a conventional Mach-Zehnder modulator can generate an optical frequency comb with excellent spectral flatness. The modulator is asymmetrically dual driven by large amplitude sinusoidal signals with different amplitudes. The driving condition to obtain spectral flatness is analytically derived and optimized, yielding a simple formula. This formula also predicts the conversion efficiency and bandwidth of the generated frequency comb.     

Guanine-specific DNA oxidation photosensitized by the tetraphenylporphyrin phosphorus(V) complex via singlet oxygen generation and electron transfer

The photosensitized DNA damage caused by dihydroxoP(V)tetraphenylporphyrin (P(V)TPP), a cationic water-soluble porphyrin, was examined. The study of near-infrared emission measurements demonstrated the photosensitized singlet oxygen ((1)O(2)) generation by P(V)TPP (quantum yield: 0.28 in ethanol). The fluorescence quenching of P(V)TPP by DNA showed the electron transfer (ET) from nucleobases to photoexcited P(V)TPP. These results have shown that P(V)TPP has ability to damage DNA through dual mechanisms, (1)O(2) generation and ET. Under aerobic conditions, P(V)TPP photosensitized damage was more severe for single-stranded DNA compared to its double-stranded counterpart. Photoexcited P(V)TPP damaged every guanine residue in single-stranded DNA. HPLC measurements confirmed the formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo), an oxidized product of 2'-deoxyguanosine, and showed that the yield of 8-oxodGuo in single-stranded DNA is larger than that in double-stranded DNA. The guanine-specific DNA damage and the enhancement in single-stranded DNA suggest that the (1)O(2) generation mainly contributes to the mechanism of DNA photodamage by P(V)TPP. Absorption spectrum measurements suggested the interaction between P(V)TPP and DNA. This interaction is expected to enhance the (1)O(2)-mediated DNA damage since the lifetime of (1)O(2) is very short. On the other hand, for double-stranded DNA, photosensitized damage at consecutive guanines was much less pronounced. Because the consecutive guanines act as a hole trap, this DNA-damaging pattern suggests the partial involvement of photoinduced ET. However, DNA damage by ET was not a main mechanism, possibly due to the reverse ET. In conclusion, P(V)TPP induces guanine specific photooxidation mainly via (1)O(2) generation. The interaction with DNA and the energy level of the photoexcited porphyrin may be advantageous for (1)O(2)-mediated DNA damage rather than ET mechanism.