RESUMO
Single crystals of silicon double salt (NH4)3SiF7 = (NH4)2SiF6·NH4F = (NH4)3[SiF6]F were grown and studied by the methods of polarization optics, X-ray diffraction and calorimetry. A sequence of symmetry transformations with the temperature change was established: P4/mbm (Z = 2) (G1) â Pbam (Z = 4) (G2) â P21/c (Z = 4) (G3) â P1[combining macron] (Z = 4) (G4) â P21/c (Z = 8) (G5). Crystal structures of different phases were determined. The experimental data were also interpreted by a group-theoretical analysis of the complete condensate of order parameters taking into account critical and noncritical atomic displacements. Strengthening of the N-HF hydrogen bonds can be a driving force of the observed phase transitions.
RESUMO
Single crystals of germanium double salt (NH4)3GeF7 = (NH4)2GeF6·NH4F = (NH4)3[GeF6]F were grown and studied by the methods of polarization optics and X-ray diffraction. The birefringence Δn = (no - ne), the rotation angle of the optical indicatrix Ï(T) and unit cell parameters were measured in the temperature range 100-400 K. Three structural phase transitions were found at the temperatures: T1↓ = 279.2 K (T1↑ = 279.4 K), T2↑ = 270 K (T2↓ = 268.9 K), T3↓ = 218 K (T3↑ = 227 K). An unusual sequence of symmetry transformations with temperature change was established: P4/mbm (Z = 2) (G1) â Pbam (Z = 4) (G2) â P21/c (Z = 4) (G3) â Pa3[combining macron] (Z = 8) (G4). The crystal structures of different phases were determined. The experimental data were additionally interpreted by a group-theoretical analysis of the complete condensate of order parameters taking into account the critical and noncritical atomic displacements. Strengthening of the N-HF hydrogen bonds can be a driving force of the observed phase transitions.
Assuntos
Infecções por Helicobacter , Helicobacter pylori , Cirrose Hepática/complicações , Gastropatias , Anti-Infecciosos/administração & dosagem , Anti-Infecciosos/uso terapêutico , Quimioterapia Combinada , Feminino , Fármacos Gastrointestinais/administração & dosagem , Fármacos Gastrointestinais/uso terapêutico , Infecções por Helicobacter/complicações , Infecções por Helicobacter/tratamento farmacológico , Infecções por Helicobacter/epidemiologia , Infecções por Helicobacter/microbiologia , Helicobacter pylori/efeitos dos fármacos , Helicobacter pylori/isolamento & purificação , Humanos , Cirrose Hepática/epidemiologia , Masculino , Gastropatias/complicações , Gastropatias/tratamento farmacológico , Gastropatias/epidemiologia , Gastropatias/microbiologiaRESUMO
Experiment on male rats has shown that acute stress suppressed amylase and superoxide dismutase activity in the submandibular salivary glands. The influence of short repeated stresses weakened the inhibiting effect of the acute stress on the activity of enzymes. A conclusion is drawn about the high sensibility of salivary glands to stress influences.
