Understanding the nature of electronic effective mass in double-doped SrTiO3_{3}

We present an approach to tune the effective mass in an oxide semiconductor by a double doping mechanism. We demonstrate this in a model oxide system Sr$_{1-x}$La$_x$TiO$_{3-\delta}$, where we can tune the effective mass ranging from 6--20$\mathrm{m_e}$ as a function of filling or carrier concentration and the scattering mechanism, which are dependent on the chosen lanthanum and oxygen vacancy concentrations. The effective mass values were calculated from the Boltzmann transport equation using the measured transport properties of thin films of Sr$_{1-x}$La$_x$TiO$_{3-\delta}$. Our method, which shows that the effective mass decreases with carrier concentration, provides a means for understanding the nature of transport processes in oxides, which typically have large effective mass and low electron mobility, contrary to the tradional high mobility semiconductors.Comment: 5 pages with 4 figure

The problematic issues concerning modern well drilling technologies

Well drilling is the leading technological cycle that makes it possible to carry out prospecting and mining operations within different mineral deposits. Numerous operations as for construction of different industrial and civil purposes are impossible without well drilling technologies. It should be noted that wells are constructed in the rocks differing with their mechanical properties; in addition, those wells vary greatly in their depths. These are the reasons why the construction periods for the majority of wells are rather long-term with the resulting significant deceleration in completing the current operation

2,25-Dioxo-27,28-diphenyl-30-oxa-29-thia-3,10,17,24-tetra­aza­penta­cyclo­[24.2.1.112,15.04,9.018,23]triaconta-5,7,9(4),10,12,14,16,18,20,22,26,28-dodeca­ene chloro­form disolvate

The macrocycle of the title compound, C36H24N4O3S·2CHCl3, contains a rigid framework with the nitro­gen and oxygen heteroatoms pointing in towards the center of the macrocyclic cavity. The macrocycle is essentially planar (r.m.s. deviation = 0.027 Å) except for the thio­phene ring. The dihedral angle between the thio­phene ring plane and the mean plane of the central macrocyclic core including all atoms except sulfur is 21.6 (1)°. Four intra­molecular hydrogen bonds occur: two are between the amide hydrogen atoms and the Schiff base nitro­gen atoms, while the others are between the amide hydrogen atoms and the sulfur atom of the thio­phene. The two solvate chloro­form mol­ecules are bound to the carbonyl oxygen atoms of the ligand by weak C—H⋯O hydrogen bonding. In addition, the structure reveals inter­molecular Cl⋯Cl close contacts [3.308 (2), 3.404 (2) and 3.280 (2) Å] between the chloro­form solvate mol­ecules. In the crystal, the macrocycles form layers parallel to (101), with an inter­layer distance of 3.362 (3) Å. This short distance is determined by the stacking inter­actions between the amide carbonyl and imine fragments of neighboring ligands

N,N′-Bis(2-amino­phen­yl)-3,4-diphenyl­thio­phene-2,5-dicarboxamide acetonitrile solvate

In the title solvate, C30H24N4O2S·CH3CN, the substituted thiophene possesses approximate Cs(m) intrinsic symmetry, with the mirror plane passing through the S atom and the mid-point of the (Ph)C—C(Ph) bond. Despite the main backbone of the mol­ecule being a long chain of conjugated bonds, it adopts a non-planar conformation due to the presence of various intra- and inter­molecular hydrogen bonds. The hydrogen bonds result in twist configurations for both the amido and amino­phenyl fragments relative to the central thio­phene ring. There are two intra­molecular Namine—H⋯O hydrogen bonds within the thio­phene-2,5-dicarboxamide mol­ecule that form seven-membered rings. In the crystal, the thio­phene-2,5-dicarboxamide mol­ecules form inversion dimers by four amide–amine N—H⋯N hydrogen bonds. The dimers are further linked into layers propagating in (100) both directly (via Namine—H⋯O hydrogen bonds) and through the acetonitrile solvate mol­ecules (via amine–cyano N—H⋯N and CMe—H⋯O inter­actions)

rac-Ethyl 6-hy­droxy-6-methyl-3-oxo-4-phenyl-1,3,4,5,6,7-hexa­hydro­benzo[c][1,2]oxazole-5-carboxyl­ate

In the title compound, C17H19NO5, the cyclo­hexene ring is in a half-chair conformation and the isoxazole ring in an envelope conformation with the N atom as the flap. The C atoms in the 4- and 6-positions are of the same absolute configuration, whereas the C atom in the 5-position is of the opposite configuration, i.e. (4S*,5R*,6S*). The methyl fragment of the eth­oxy­carbonyl group at position 5 is disordered over two sets of sites in a 0.60:0.40 ratio. The crystal packing displays inter­molecular N—H⋯O and O—H⋯O hydrogen bonds

rac-5-Acetyl-6-hy­droxy-3,6-dimethyl-4-phenyl-2H-4,5,6,7-tetra­hydro­indazol-1-ium chloride

The structure of the title compound, C17H21N2O2 +·Cl−, is of inter­est with respect to its biological activity. The title compound comprises an organic cation and a chloride anion in the asymmetric unit. The positive charge is localized in a pyrazole moiety forming a pyrazolium cation. The structure displays inter­molecular O—H⋯Cl and N—H⋯Cl hydrogen bonding

Negative magneto-resistance of electron gas in a quantum well with parabolic potential

We have studied the electrical conductivity of the electron gas in parallel electric and magnetic fields directed along the plane of a parabolic quantum well (across the profile of the potential). We found a general expression for the electrical conductivity applicable for any magnitudes of the magnetic field and the degree of degeneration of the electron gas. A new mechanism of generation of the negative magnetoresistance has been revealed. It has been shown that in a parabolic quantum well with a non-degenerated electron gas the negative magnetoresistance results from spin splitting of the levels of the size quantization.Comment: 15 pages, 3 figure