12 research outputs found
Strengths of Exaggerated Tsunami-Originated Placenames : Disaster Subculture in Sanriku Coast, Japan
Disaster-originated placename is a kind of disaster subculture that is used for a practical purpose of identifying a location while reminding the past disaster experience. They are expected to transmit the risks and knowledge of high-risk low-frequency natural hazards, surviving over time and generations. This paper compares the perceptions to tsunami-originated placenames in local communities having realistic and exaggerated origins in Sanriku Coast, Japan. The reality of tsunami-originated placenames is first assessed by comparing the tsunami run-ups indicated in the origins and that of the tsunami in the Great East Japan Earthquake 2011 using GIS and digital elevation model. Considerable proportions of placenames had exaggerated origins, but the group interviews to local communities revealed that origins indicating unrealistic tsunami run-ups were more believed than that of the more realistic ones. We discuss that accurate hazard information will be discredited if it contradicts to the peopleās everyday life and the desire for safety, and even imprecise and ambiguous information can survive if it is embedded to a system of local knowledge that consistently explains the various facts in a local area that requires explanation
Trace analysis of nitrite ion in seawater using ion chromatography
An ion chromatographic method of separating and detecting nitrite in sea water is described. The system includes precolumn, new hydrophilic separation column, suppressor and two-valve system. Nitrite was diverted, trapped and separeted in a 2.6-ml sample loop using 6- and 4-port valves. The eluent used was 14.4 mM sodium hydrogen carbonate at flow-rate oflml/min while the scanvenger was 14 mM sulfuric acid. Nitrite recovery achieved was 100Ā±2%. The minimum detection limit was 0.15 ppm with the signal-to-noise set 2.5 Nitrite recovery obtained using different mixing ratios of sodium hydrogen carbonate and sodium carbonate were lower. Eluent ph and compoosition affected both peak heights and retention timed of nitrite and other anions
Ion chromatography of inorganic anions in brine samples
An ion chromatographic method for separating and detecting anions in brine samples is described. Nitrite, bromide, nitrate, and sulfate ions in brine samples are well separated when chloride ion concentration in the sample solution is below 2000 ppm. However, at higher chloride concentrations, nitrite and chloride peaks are not resolved. Low level nitrite ion in the brine sample is separated from a major chloride ion by a heart-cutting and recycling system. After elution, the unresolved portion, including the nitrite ion, is cut and trapped in a 10-mL sample collecting loop and reinjected on the column by using 6- and 4-port valve systems. The detection limit of nitrite spiked in the seawater samples is 0.5 ppm
Involvement of a sensory afferent pathway in human discogenic low back pain-Comparison of upper and lower spinal nerve block effects on discogenic low back pain
Molecular Mechanism of the Reaction Specificity in Threonine Synthase: Importance of the Substrate Conformations
Threonine
synthase (ThrS) catalyzes the final chemical reaction
of l-threonine biosynthesis from its precursor, <i>O</i>-phospho-l-homoserine. As the phosphate ion generated in
its former half reaction assists its latter reaction, ThrS is recognized
as one of the best examples of product-assisted catalysis. In our
previous QM/MM study, the chemical reactions for the latter half reactions,
which are critical for the product-assisted catalysis, were revealed.
However, accurate free energy changes caused by the conformational
ensembles and entrance of water molecules into the active site are
unknown. In the present study, by performing long-time scale MD simulations,
the free energy changes by the divalent anions (phosphate or sulfate
ions) and conformational states of the intermediate states were theoretically
investigated. We found that the calculated free energy double differences
are in good agreement with the experimental results. We also revealed
that the phosphate ion contributes to forming hydrogen bonds that
are suitable for the main reaction progress. This means that the conformation
of the active site amino acid residues and the substrate, and hence,
the tunable catalysis, are controlled by the product phosphate ion,
and this clearly demonstrates a molecular mechanism of the product-assisted
catalysis in ThrS
A QM/MM Study of the lāThreonine Formation Reaction of Threonine Synthase: Implications into the Mechanism of the Reaction Specificity
Threonine
synthase catalyzes the most complex reaction among the
pyridoxal-5ā²-phosphate (PLP)-dependent enzymes. The important
step is the addition of a water molecule to the CĪ²āCĪ±
double bond of the PLPāĪ±-aminocrotonate aldimine intermediate.
Transaldimination of this intermediate with Lys61 as a side reaction
to form Ī±-ketobutyrate competes with the normal addition reaction.
We previously found that the phosphate ion released from the <i>O</i>-phospho-l-homoserine substrate plays a critical
role in specifically promoting the normal reaction. In order to elucidate
the detailed mechanism of this āproduct-assisted catalysisā,
we performed comparative QM/MM calculations with an exhaustive search
for the lowest-energy-barrier reaction pathways starting from PLPāĪ±-aminocrotonate
aldimine intermediate. Satisfactory agreements with the experiment
were obtained for the free energy profile and the UV/vis spectra when
the PLP pyridine N1 was unprotonated and the phosphate ion was monoprotonated.
Contrary to an earlier proposal, the base that abstracts a proton
from the attacking water was the Īµ-amino group of Lys61 rather
than the phosphate ion. Nevertheless, the phosphate ion is important
for stabilizing the transition state of the normal transaldimination
to form l-threonine by making a hydrogen bond with the hydroxy
group of the l-threonine moiety. The absence of this interaction
may account for the higher energy barrier of the side reaction, and
explains the mechanism of the reaction specificity afforded by the
phosphate ion product. Additionally, a new mechanism, in which a proton
temporarily resides at the phenolate O3ā² of PLP, was proposed
for the transaldimination process, a prerequisite step for the catalysis
of all the PLP enzymes