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Institution

Tokyo University of Science

EducationTokyo, Japan
About: Tokyo University of Science is a education organization based out in Tokyo, Japan. It is known for research contribution in the topics: Thin film & Enantioselective synthesis. The organization has 15800 authors who have published 24147 publications receiving 438081 citations. The organization is also known as: Tōkyō Rika Daigaku & Science University of Tokyo.


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Book ChapterDOI
TL;DR: The investigation of dioxin formation from the combustion of various waste-simulated samples, including different kinds of paper, various kinds of wood, fallen leaves, food samples, polyethylene (PE), polystyrene (PS), polyvinyl chloride (PVC),polyvinylidene chloride,polyethylene tetraphthalate (PET), andVarious kinds of plastic products found no significant relationship between dioxIn formation and chamber temperatures.
Abstract: There has been great concern about dioxins-polychlorinated dibenzo dioxins (PCDDs), polychlorinated dibenzo furans (PCDFs), and polychlorinated biphenyls (PCBs)-causing contamination in the environment because the adverse effects of these chemicals on human health have been known for many years. Possible dioxin-contamination has received much attention recently not only by environmental scientists but also by the public, because dioxins are known to be formed during the combustion of industrial and domestic wastes and to escape into the environment via exhaust gases from incinerators. Consequently, there is a pressing need to investigate the formation mechanisms or reaction pathways of these chlorinated chemicals to be able to devise ways to reduce their environmental contamination. A well-controlled small-scale incinerator was used for the experiments in the core references of this review. These articles report the investigation of dioxin formation from the combustion of various waste-simulated samples, including different kinds of paper, various kinds of wood, fallen leaves, food samples, polyethylene (PE), polystyrene (PS), polyvinyl chloride (PVC), polyvinylidene chloride, polyethylene tetraphthalate (PET), and various kinds of plastic products. These samples were also incinerated with inorganic chlorides (NaCl, KCl, CuCI2, MgCl2, MnCl2, FeCl2, CoCl2, fly ash, and seawater) or organic chlorides (PVC, chlordane, and pentachlorophenol) to investigate the role of chlorine content and/or the presence of different metals in dioxin formation. Some samples, such as newspapers, were burned after they were impregnated with NaCl or PVC, as well as being cocombusted with chlorides. The roles of incineration conditions, including chamber temperatures, O2 concentrations, and CO concentrations, in dioxin formation were also investigated. Dioxins (PCDDs, PCDFs, and coplanar-PCBs) formed in the exhaust gases from a controlled small-scale incinerator, where experimental waste samples were burned, were analyzed by gas chromatography/mass spectrometry. Formation of total PCDFs was much higher than that of PCDDs in all samples. The total PCDFs comprised 70%-90% of the total dioxin formed. The amount of total PCDFs formed ranged from 0.78 ng/g (newspaper) to 8,490ng/g (PVC burned in high CO concentration). The amount of total PCDDs formed ranged from 0.02ng/g (newspaper) to 430ng/g (PVC). Coplanar PCBs were found at the lowest level of the dioxins formed. Their formation levels ranged from 0ng/g (newspaper) to 77.6ng/g (PVC). It is obvious that the samples with either inorganic or organic chlorides produced much more dioxins than the sample without chlorides when incinerated under similar conditions. It is not clear how inorganic and organic chloride contribute differently to dioxin formation. Among the metals examined, copper seems to have higher activity toward dioxin formation than other metals. It acted not only as a catalyst but also as a transmitter of heterogeneous chlorine. The toxicity equivalence quantity (TEQ) values generally correlated with the amount of chlorine content in the samples and the amount of dioxin formed in exhaust gases from an incinerator. When the same sample was incinerated at different temperatures, however, the sample burned at low temperature yielded a higher TEQ value than did the sample burned at high temperature. The samples that did not contain chlorine or were not combusted with chlorides exhibited low TEQ values. In contrast, samples with high chlorine content, such as PVC (51.3%), gave high TEQ values. Combustion temperatures may play an important role in dioxin formation in exhaust gases from the incineration of waste materials. However, no significant relationship between dioxin formation and chamber temperatures was reported in the core articles. However, It is obvious that dioxin formation occurred at temperatures above 450'C and was reduced significantly at temperatures above 850 degrees C. The reaction occurring in an incinerator is extremely complex, and there are many factors in addition to combustion temperature influencing dioxin formation. Even though it is possible to hypothesize reasonable formation mechanisms of dioxins produced in exhaust gases according to the results obtained from experiments in classical chemistry, the reactions involved in an incinerator are extremely complex and heterogeneous. More detailed investigation of the many individual factors influencing dioxin formation is needed to find ways to reduce their formation in individual and municipal incinerators.

119 citations

Journal ArticleDOI
TL;DR: It was found that mercury and selenium exist in the form of HgSe in the liver of northern fur seal and the existence of a solid solution Hg(Se, S) as granules in black-footed albatross was disclosed.
Abstract: Marine mammals and seabirds tend to exhibit high accumulations of mercury, cadmium, and selenium in their livers and kidneys. In this study, chemical forms of mercury, cadmium, and selenium accumul...

119 citations

Journal ArticleDOI
TL;DR: The authors show that the Lotus japonicus transcription factor NRSYM1 activates the production of CLE-RS2 in nitrogen-sufficient conditions to prevent nodulation, providing the genetic basis for how plants respond to the nitrogen environment and control symbiosis to achieve proper plant growth.
Abstract: Legumes and rhizobia establish symbiosis in root nodules. To balance the gains and costs associated with the symbiosis, plants have developed two strategies for adapting to nitrogen availability in the soil: plants can regulate nodule number and/or stop the development or function of nodules. Although the former is accounted for by autoregulation of nodulation, a form of systemic long-range signaling, the latter strategy remains largely enigmatic. Here, we show that the Lotus japonicus NITRATE UNRESPONSIVE SYMBIOSIS 1 (NRSYM1) gene encoding a NIN-LIKE PROTEIN transcription factor acts as a key regulator in the nitrate-induced pleiotropic control of root nodule symbiosis. NRSYM1 accumulates in the nucleus in response to nitrate and directly regulates the production of CLE-RS2, a root-derived mobile peptide that acts as a negative regulator of nodule number. Our data provide the genetic basis for how plants respond to the nitrogen environment and control symbiosis to achieve proper plant growth.

119 citations

Journal ArticleDOI
TL;DR: In this paper, the authors demonstrate optical driving at a petahertz frequency in the wide-bandgap semiconductor gallium nitride, which corresponds to instantaneous light-induced switching from insulator to conductor.
Abstract: Experiments showing that electron dynamics can be controlled on attosecond timescales suggest that wide-bandgap semiconductors could be exploited for petahertz signal processing technologies. High-speed photonic and electronic devices at present rely on radiofrequency electric fields to control the physical properties of a semiconductor1, which limits their operating speed to terahertz frequencies (1012 Hz; ref. 2). Using the electric field from intense light pulses, however, could extend the operating frequency into the petahertz regime (1015 Hz; ref. 3). Here we demonstrate optical driving at a petahertz frequency in the wide-bandgap semiconductor gallium nitride. Few-cycle near-infrared pulses are shown to induce electric interband polarization though a multiphoton process. Dipole oscillations with a periodicity of 860 as are revealed in the gallium nitride electron and hole system by using the quantum interference between the two transitions from the valence and conduction band states, which are probed by an extremely short isolated attosecond pulse with a coherent broadband spectrum. In principle, this shows that the conductivity of the semiconductor can be manipulated on attosecond timescales, which corresponds to instantaneous light-induced switching from insulator to conductor. The resultant dipole frequency reaches 1.16 PHz, showing the potential for future high-speed signal processing technologies based on wide-bandgap semiconductors.

119 citations

Journal ArticleDOI
TL;DR: Analysis of the photoelectron transfer kinetics proved both the output of electrons from PSI and the effectiveness of the molecular wire.
Abstract: Nach Anregung mit Licht ubertragt das P700 des Photosystems I (PS I) Elektronen auf eine Goldoberflache (siehe Bild). Dabei kommt ein neuartiges molekulares Verbindersystem zum Einsatz, in dem ein kunstlicher molekularer Draht, der auf der Goldoberflache angeordnet ist, durch Rekonstitution mit PS I verbunden wurde. Die Analyse der Kinetik des Photoelektronentransfers belegt die Abgabe von Elektronen aus PS I sowie die Effektivitat des molekularen Drahts.

118 citations


Authors

Showing all 15878 results

NameH-indexPapersCitations
Kazunori Kataoka13890870412
Yoichiro Iwakura12970564041
Kouji Matsushima12459056995
Masaki Ishitsuka10362439383
Shinsuke Tanabe9872237445
Tatsumi Koi9741150222
Hirofumi Akagi9461843179
Clifford A. Lowell9125823538
Teruo Okano9160528346
László Á. Gergely8942660674
T. Sumiyoshi8885562277
Toshinori Nakayama8640525275
Akihiko Kudo8632839475
Hans-Joachim Gabius8569928085
Motohide Tamura85100732725
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
202356
2022137
20211,357
20201,481
20191,510
20181,429