Catálogo de publicaciones - revistas

<jats:p>Amidst international tensions and military posturing, the Demilitarized Zone (DMZ) separating North and South Korea has, for 45 years, provided sanctuary to endangered and threatened animals and plants. The DMZ has been rigidly enforced: It is uninhabited by humans, and its inaccessibility has allowed damaged forests to rehabilitate and farmlands that are thousands of years old to return to a natural state. The DMZ has, in fact, become a unique nature reserve containing the last vestiges of Korea's natural heritage. The Korean Peace Bioreserves System provides a strategy to preserve the rich biodiversity of the DMZ. Joint development of the Korean Peace Bioreserves System will foster trust, understanding, and respect between the Democratic People's Republic of Korea in the north and the Republic of Korea in the south.</jats:p>

<jats:p> Bovine spongiform encephalopathy (BSE) and human Creutzfeldt-Jakob disease (CJD) are among the most notable central nervous system degenerative disorders caused by prions. CJD may present as a sporadic, genetic, or infectious illness. Prions are transmissible particles that are devoid of nucleic acid and seem to be composed exclusively of a modified protein (PrP <jats:sup>Sc</jats:sup> ). The normal, cellular prion protein (PrP <jats:sup>C</jats:sup> ) is converted into PrP <jats:sup>Sc</jats:sup> through a posttranslational process during which it acquires a high β-sheet content. It is thought that BSE is a result of cannibalism in which faulty industrial practices produced prion-contaminated feed for cattle. There is now considerable concern that bovine prions may have been passed to humans, resulting in a new form of CJD. </jats:p>

<jats:p>Molecules of benzene-1,4-dithiol were self-assembled onto the two facing gold electrodes of a mechanically controllable break junction to form a statically stable gold-sulfur-aryl-sulfur-gold system, allowing for direct observation of charge transport through the molecules. Current-voltage measurements at room temperature demonstrated a highly reproducible apparent gap at about 0.7 volt, and the conductance-voltage curve showed two steps in both bias directions. This study provides a quantative measure of the conductance of a junction containing a single molecule, which is a fundamental step in the emerging area of molecular-scale electronics.</jats:p>

<jats:p>Seismic tomography and wave form inversion revealed that very slow velocity anomalies (5 to 7 percent) beneath the active Lau spreading center extend to 100-kilometer depth and are connected to moderately slow anomalies (2 to 4 percent) in the mantle wedge to 400-kilometer depth. These results indicate that geodynamic systems associated with back-arc spreading are related to deep processes, such as the convective circulation in the mantle wedge and deep dehydration reactions in the subducting slab. The slow regions associated with the Tonga arc and the Lau back arc are separated at shallow levels but merge at depths greater than 100 kilometers, suggesting that slab components of back-arc magmas occur through mixing at these depths.</jats:p>

<jats:p>The diffusion of carbon monoxide molecules on the (110) surface of copper was investigated in the temperature range between 42 and 53 kelvin. The activation energy for thermal motion was determined directly by imaging individual molecular displacements with a scanning tunneling microscope. An attractive interaction between carbon monoxide molecules gave rise to the formation of dimers and longer chains. Carbon monoxide chains diffused substantially faster than isolated molecules although the chains moved by a sequence of single-molecule jumps. A higher preexponential factor in the Arrhenius law was found to be responsible for the observed efficiency of chain hopping.</jats:p>

<jats:p> Chemical reactions that break alkane carbon-hydrogen (C–H) bonds are normally carried out under conditions of high temperature and pressure because these bonds are extremely strong (∼100 kilocalories per mole), but certain metal complexes can activate C–H bonds in alkane solution under the mild conditions of room temperature and pressure. Time-resolved infrared experiments probing the initial femtosecond dynamics through the nano- and microsecond kinetics to the final stable products have been used to generate a detailed picture of the C–H activation reaction. Structures of all of the intermediates involved in the reaction of Tp*Rh(CO) <jats:sub>2</jats:sub> (Tp* = HB–Pz <jats:sub>3</jats:sub> *, Pz* = 3,5-dimethylpyrazolyl) in alkane solution have been identified and assigned, and energy barriers for each reaction step from solvation to formation of the final alkyl hydride product have been estimated from transient lifetimes. </jats:p>

<jats:p>Macroscopic orientational ordering of the pores of condensed hexagonal mesostructured silica (MCM-41) was achieved through alignment of an unpolymerized, hexagonal, lyotropic silicate-surfactant liquid crystal in a high magnetic field. This alignment was preserved after polymerization of the silicate species by acid treatment. Subsequent calcination to remove the surfactant yielded a mesoporous silica solid that retained both macroscopic pore alignment and mesoscale periodicity. Potential applications of such liquid crystal processing strategies range from the formation of anisotropic silica-based bulk ceramics to the production of oriented mesoporous thin films for chemical sensors, separations, catalysis, or host-guest applications.</jats:p>

<jats:p>A 6-month-long monitoring campaign of the Io plasma torus and neutral cloud was conducted to determine the characteristics of their interaction. During the observations, a large outburst of material from Io—inferred to be caused by the eruption of a volcanic plume on Io—caused a transient increase in the neutral cloud and plasma torus masses. The response of the plasma torus to this outburst shows that the interaction between Io and Jupiter's magnetosphere is stabilized by a feedback mechanism in which increases in the plasma torus mass cause a nonlinear increase in loss from the plasma torus, limiting plasma buildup.</jats:p>

<jats:p> Five absorption features are reported at wavelengths of 3.4, 3.88, 4.05, 4.25, and 4.57 micrometers in the surface materials of the Galilean satellites Callisto and Ganymede from analysis of reflectance spectra returned by the Galileo mission near-infrared mapping spectrometer. Candidate materials include CO <jats:sub>2</jats:sub> , organic materials (such as tholins containing C≡N and C-H), SO <jats:sub>2</jats:sub> , and compounds containing an SH-functional group; CO <jats:sub>2</jats:sub> , SO <jats:sub>2</jats:sub> , and perhaps cyanogen [(CN) <jats:sub>2</jats:sub> ] may be present within the surface material itself as collections of a few molecules each. The spectra indicate that the primary surface constituents are water ice and hydrated minerals. </jats:p>