Conductance of a multiterminal ballistic wire

JETP Letters - An experimental study of the two-, three-, and four-terminal resistance of a ballistic wire is carried out. The wire is fabricated on the basis of high-mobility 2D electron gas in an...     

Galactic Metrics

The paths of stars in galaxies have circular velocity independent of their distance from the centre of the galaxy. Newtonian mechanics with a logarithmic potential has such paths. In relativity these paths can be taken to be geodesics and this requirement places a restricting equation on the spacetime metric. This equation has a non-unique spherically symmetric solution that in the Newtonian limit has a logarithmic potential. It also can be solved in terms of a conformal factor. In particular it has solutions which are conformal to the vacuum-Einstein solutions and such spacetimes are solutions to the vacuum-Bach equations. Therefore it is suggested that the Bach equations describe dynamics on galactic length scales.     

α-Fe2O3-In2O3 mixed oxide nanoparticles synthesized under hydrothermal supercritical conditions

α-Fe₂O₃-In₂O₃ mixed oxide nanoparticles system has been synthesized by hydrothermal supercritical and postannealing route, starting with (1−x)Fe(NO₃)₃·9H₂O·xIn(NO₃)₃·5H₂O aqueous solution (x=0-1). X-ray diffraction and Mössbauer spectroscopy have been used to study the phase structure and substitutions in the nanosized samples. The concentration regions for the existence of the solid solutions in the α-Fe₂O₃-In₂O₃ nanoparticle system together with the solubility limits of In³⁺ ions in the hematite lattice and of Fe³⁺ ions in the cubic In₂O₃ structure have been evidenced. In general, the substitution level is considerably lower than the nominal concentration x. A justification of the processes leading to the formation of iron and indium phases in the investigated supercritical hydrothermal system has been given.     

Condensation of Isatoic Anhydride with Hetarylguanidines

Condensation of isatoic anhydride with 4-methylquinazolin-2-yl-, 2-benzoxazolyl-, 2-benzothiazolyl-, and 4,6-dimethylpyrimidin-2-ylguanidines leads to the corresponding 2-hetarylamino-4-hydroxyquinazolines as a result of cyclization of intermediate anthranilic acid hetarylguanidides. These intermediates can be isolated as individual compounds.     

WITCH: A Penning Trap Retardation Spectrometer Combination for Precision Studies of the Weak Interaction

We present data from three seasons of experimental field work designed to recreate ancient Andean coastal ceramic firing techniques. Based on the recent discovery of two different archaeological ceramic production sites in the La Leche river valley of northern coastal Peru, the opportunity arose to apply Mössbauer spectroscopy and other analytical methods to reconstruct ancient firing procedures. Two sets of firings took place in 1993 and 1997 in Batán Grande using a partially restored Formative kiln from about 800 BC, local hardwood and cow dung as fuel. A third experiment followed in 2000 after the discovery of a Middle Sicán ceramics workshop in use between ca. AD 950 and 1050 at Huaca Sialupe, where an exact replica of an ancient kiln was built from local clay, and fired with local wood and cow dung. Additionally, inverted urns found at Huaca Sialupe were tested for their potential use as furnaces for metal working. Mössbauer spectroscopy was used to compare the physical and chemical state of specimens produced in the field experiments with ancient ceramics and with specimens produced in controlled laboratory experiments.     

The Orevkov invariant of an affine plane curve

We show that although the fundamental group of the complement of an algebraic affine plane curve is not easy to compute, it possesses a more accessible quotient, which we call the Orevkov invariant.

     

InAs/GaAs quantum dot infrared photodetectors with different growth temperatures

InAs/GaAs quantum dot infrared photodetectors were fabricated with quantum dots grown at three different temperatures. Large detection wavelength shift (5–14.5 μm) was demonstrated by changing 40 degrees of the epitaxy temperature. The smaller quantum dots grown at lower temperature generate 14.5 μm responses. The detectivity of the normal incident 15 μm QDIP at 77 K is 3 × 10⁸ cm Hz^1/2/W. A three-color detector was also demonstrated with quantum dots grown at medium temperature. The three-color detection comes from two groups of different sizes of dots within one QD layer. This new type of multicolor detector shows unique temperature tuning behavior that was never reported before.