1,783 research outputs found
Raman and infrared studies of La_1-ySr_yMn_1-xM_xO_3 (M=Cr, Co, Cu, Zn, Sc or Ga): Oxygen disorder and local vibrational modes
We present results of our study of polarized Raman scattering and infrared
reflectivity of rhombohedral ceramic La_1-ySr_yMn_1-xM_xO_3 manganites in the
temperature range between 77 and 320K. In our samples, a part of the Mn atoms
is substituted by M = Cr, Co, Cu, Zn, Sc, or Ga with x in the range 0 -- 0.1.
The hole concentration was kept at the optimal value of about 32% by tuning the
Sr content y. We have monitored the distortions of the oxygen sublattice by the
presence of broad bands in the Raman spectra, the increase of d.c. resistivity
extracted from the infrared reflectivity, and the change of the critical
temperature of the ferromagnetic transition. Our results support the idea, that
these properties are mainly determined by the radius of the substituent ion,
its electronic and magnetic structure playing only a minor role. Furthermore,
the Raman spectra exhibit an additional A_g-like high frequency mode attributed
to the local breathing vibration of oxygens surrounding the substituent ion.
Its frequency and intensity strongly depend on the type of the substituent. In
the Co-substituted sample, the mode anomalously softens when going from 300 to
77K. The frequency of the bulk A_{1g} mode depends linearly on the angle of the
rhombohedral distortion.Comment: 11 pages, 11 Figures, best-fit values table added, a discussion adde
Optical properties of NaxV2O5
The optical properties of sodium-deficient NaxV2O5 (0.85 < x <1) single
crystals are analyzed in the wide energy range, from 0.012 to 4.5 eV, using
ellipsometry, infrared reflectivity, and Raman scattering techniques. The
material remains insulating up to the maximal achieved hole concentration of
about 15%. In sodium deficient samples the optical absorption peak associated
to the fundamental electronic gap develops at about 0.44 eV. It corresponds to
the transition between vanadium dxy and the impurity band, which forms in the
middle of the pure NaV2O5 gap. Raman spectra measured with incident photon
energy larger then 2 eV show strong resonant behavior, due to the presence of
the hole-doping activated optical transitions, peaked at 2.8 eV.Comment: 7 pages, 4 fugures, to be published in PR
First evidence for charge ordering in NaVO from Raman spectroscopy
We argue on the basis of symmetry selection rules and Raman scattering
spectra that NaVO undergoes a charge ordering phase transition at
T=34 K. Such a transition is characterized by the redistribution of the
charges at the phase transition and corresponds to the change of the vanadium
ions, from uniform V to two different V and V states. In
the low temperature phase the V ions are forming a "zig-zag" ladder
structure along the {\bf b}-axis, consistent with the symmetry of the P2/b
space group.Comment: to be published in solid state communication
Π ΠΎΠ»Ρ ΡΠ°ΠΊΡΠΎΡΠ° Π½Π΅ΠΊΡΠΎΠ·Π° ΠΎΠΏΡΡ ΠΎΠ»ΠΈ-Π°Π»ΡΡΠ° Π² ΠΏΡΠΎΠ³Π½ΠΎΠ·ΠΈΡΠΎΠ²Π°Π½ΠΈΠΈ ΡΡΠΆΠ΅ΡΡΠΈ ΠΈ ΠΈΡΡ ΠΎΠ΄Π° ΡΠ΅ΠΏΡΠΈΡΠ° Ρ ΠΏΠ°ΡΠΈΠ΅Π½ΡΠΎΠ² Π½Π΅ΠΎΡΠ»ΠΎΠΆΠ½ΠΎΠ³ΠΎ ΠΎΡΠ΄Π΅Π»Π΅Π½ΠΈΡ Ρ ΡΠΈΡΡΠ΅ΠΌΠ½ΡΠΌ Π²ΠΎΡΠΏΠ°Π»Π΅Π½ΠΈΠ΅ΠΌ
Aim of the study was to determine whether the TNF-a levels, proximal inflammatory mediator, in septic patients presenting to the emergency department (ED) and admitted to the intensive care unit (ICU) are associated with progression to severe sepsis, septic shock or death. Material and methods. A retrospective observational study was performed on a sample of one hundred adult subjects presenting to the ED with systemic inflammatory response syndrome of 2 etiologies: presumed (and later confirmed in the ICU and/or operating room) severe acute pancreatitis or generalized peritonitis. Blood TNF-a samples measurements were taken shortly after ED admission. TNF-a was measured by commercial ELISA test in plasma. Results. Mean values of TNF-a on admission (day zero, in ED) were 191,5-fold lower in group with septic shock compared to severe sepsis group and were 63-fold higher in survivors (p<0.01). The area under the curve (AUC) for the TNF-a plots for severity of clinical status was 0.813 and for outcome 0.834. Patients with TNF-a levels lower than 7.95 pg/mL had a 3.2-fold higher probability of septic shock development than those with higher values, at the cutoff level sensitivity was 83,9% and specificity 72,5%. Patients with TNF-a levels higher than 10.5 pg/mL had a 4.8-fold higher probability to survive than those with lower values, at the cutoff level sensitivity was 83,0% and specificity 77,4%. Conclusion: Decreasing in TNF-a concentration leads to the septic shock development and fatal outcome. TNF-a is very good predictor of sepsis severity and outcome. Key words: sepsis, tumor necrosis factor-alpha, emergency medical services, survival rate, severity of illness index.Π¦Π΅Π»Ρ ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΡ β ΠΎΠΏΡΠ΅Π΄Π΅Π»ΠΈΡΡ, ΡΠ²ΡΠ·Π°Π½Ρ Π»ΠΈ ΡΡΠΎΠ²Π½ΠΈ Π€ΠΠ-a, ΠΊΠ»ΡΡΠ΅Π²ΠΎΠ³ΠΎ ΠΌΠ΅Π΄ΠΈΠ°ΡΠΎΡΠ° Π²ΠΎΡΠΏΠ°Π»Π΅Π½ΠΈΡ, Ρ ΠΏΠ°ΡΠΈΠ΅Π½ΡΠΎΠ² Ρ ΡΠ΅ΠΏΡΠΈΡΠΎΠΌ, ΠΏΠΎΡΡΡΠΏΠ°ΡΡΠΈΡ
Π² ΠΎΡΠ΄Π΅Π»Π΅Π½ΠΈΠ΅ Π½Π΅ΠΎΡΠ»ΠΎΠΆΠ½ΠΎΠΉ ΠΏΠΎΠΌΠΎΡΠΈ ΠΈ ΠΏΠ΅ΡΠ΅Π²ΠΎΠ΄ΡΡΠΈΡ
ΡΡ Π² ΠΎΡΠ΄Π΅Π»Π΅Π½ΠΈΠ΅ ΡΠ΅Π°Π½ΠΈΠΌΠ°ΡΠΈΠΈ, Ρ ΠΏΡΠΎΠ³ΡΠ΅ΡΡΠΈΡΠΎΠ²Π°Π½ΠΈΠ΅ΠΌ Π΅Π³ΠΎ Π΄ΠΎ ΡΡΠΆΠ΅Π»ΠΎΠ³ΠΎ ΡΠ΅ΠΏΡΠΈΡΠ°, ΡΠ΅ΠΏΡΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΡΠΎΠΊΠ° ΠΈ ΡΠΌΠ΅ΡΡΠΈ. ΠΠ°ΡΠ΅ΡΠΈΠ°Π» ΠΈ ΠΌΠ΅ΡΠΎΠ΄Ρ. Π Π΅ΡΡΠΎΡΠΏΠ΅ΠΊΡΠΈΠ²Π½ΠΎΠ΅ ΠΎΠ±ΡΠ΅ΡΠ²Π°ΡΠΈΠΎΠ½Π½ΠΎΠ΅ ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΠ΅ Π±ΡΠ»ΠΎ Π²ΡΠΏΠΎΠ»Π½Π΅Π½ΠΎ Π½Π° Π²ΡΠ±ΠΎΡΠΊΠ΅ Π² 100 Π²Π·ΡΠΎΡΠ»ΡΡ
ΡΠ΅Π»ΠΎΠ²Π΅ΠΊ, ΠΏΠΎΡΡΡΠΏΠΈΠ²ΡΠΈΡ
Π² Π½Π΅ΠΎΡΠ»ΠΎΠΆΠ½ΠΎΠ΅ ΠΎΡΠ΄Π΅Π»Π΅Π½ΠΈΠ΅ Ρ ΠΏΡΠΈΠ·Π½Π°ΠΊΠ°ΠΌΠΈ ΡΠΈΡΡΠ΅ΠΌΠ½ΠΎΠ³ΠΎ Π²ΠΎΡΠΏΠ°Π»Π΅Π½ΠΈΡ Π΄Π²ΡΡ
Π²ΠΎΠ·ΠΌΠΎΠΆΠ½ΡΡ
ΡΡΠΈΠΎΠ»ΠΎΠ³ΠΈΠΉ: ΡΡΠΆΠ΅Π»ΡΠΉ ΠΎΡΡΡΡΠΉ ΠΏΠ°Π½ΠΊΡΠ΅Π°ΡΠΈΡ (ΠΏΡΠ΅Π΄ΠΏΠΎΠ»Π°Π³Π°Π΅ΠΌΡΠΉ, Π° Π·Π°ΡΠ΅ΠΌ ΠΏΠΎΠ΄ΡΠ²Π΅ΡΠΆΠ΄Π΅Π½Π½ΡΠΉ Π² ΠΎΡΠ΄Π΅Π»Π΅Π½ΠΈΠΈ ΡΠ΅Π°Π½ΠΈΠΌΠ°ΡΠΈΠΈ ΠΈ/ΠΈΠ»ΠΈ ΠΎΠΏΠ΅ΡΠ°ΡΠΈΠΎΠ½Π½ΠΎΠΉ) ΠΈΠ»ΠΈ ΠΎΠ±ΡΠΈΠΉ ΠΏΠ΅ΡΠΈΡΠΎΠ½ΠΈΡ. ΠΡΠΎΠΈΠ·Π²ΠΎΠ΄ΠΈΠ»ΠΈ ΠΈΠ·ΠΌΠ΅ΡΠ΅Π½ΠΈΡ Π€ΠΠ-a Π² ΠΊΡΠΎΠ²ΠΈ ΡΡΠ°Π·Ρ ΠΏΠΎΡΠ»Π΅ ΠΏΠΎΡΡΡΠΏΠ»Π΅Π½ΠΈΡ. Π€ΠΠ-a ΠΈΠ·ΠΌΠ΅ΡΡΠ»ΠΈ ΠΊΠΎΠΌΠΌΠ΅ΡΡΠ΅ΡΠΊΠΈ Π΄ΠΎΡΡΡΠΏΠ½ΡΠΌ ELISA-ΠΌΠ΅ΡΠΎΠ΄ΠΎΠΌ Π² ΠΏΠ»Π°Π·ΠΌΠ΅ ΠΊΡΠΎΠ²ΠΈ. Π Π΅Π·ΡΠ»ΡΡΠ°ΡΡ. Π‘ΡΠ΅Π΄Π½ΠΈΠ΅ ΡΡΠΎΠ²Π½ΠΈ Π€ΠΠ-a ΠΏΡΠΈ ΠΏΠΎΡΡΡΠΏΠ»Π΅Π½ΠΈΠΈ (Π΄Π΅Π½Ρ 0, Π² Π½Π΅ΠΎΡΠ»ΠΎΠΆΠ½ΠΎΠΌ ΠΎΡΠ΄Π΅Π»Π΅Π½ΠΈΠΈ) Π±ΡΠ»ΠΈ Π² 191,5 ΡΠ°Π· Π½ΠΈΠΆΠ΅ Π² Π³ΡΡΠΏΠΏΠ΅ Ρ ΡΠ΅ΠΏΡΠΈΡΠ΅ΡΠΊΠΈΠΌ ΡΠΎΠΊΠΎΠΌ ΠΏΠΎ ΡΡΠ°Π²Π½Π΅Π½ΠΈΡ Ρ Π³ΡΡΠΏΠΏΠΎΠΉ ΡΡΠΆΠ΅Π»ΠΎΠ³ΠΎ ΡΠ΅ΠΏΡΠΈΡΠ° ΠΈ Π² 63 ΡΠ°Π·Π° Π²ΡΡΠ΅ Ρ Π²ΡΠΆΠΈΠ²ΡΠΈΡ
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Lattice dynamics of FeSb2
The lattice dynamics of FeSb2 is investigated by the first-principles DFT
calculations and Raman spectroscopy. All Raman and infra-red active phonon
modes are properly assigned. The calculated and measured phonon energies are in
good agreement except for the B3g symmetry mode. We have observed strong mixing
of the Ag symmetry modes, with the intensity exchange in the temperature range
between 210 K and 260 K. The Ag modes repulsion increases by doping FeSb2 with
Co. There are no signatures of the electron-phonon interaction for these modes
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