238 research outputs found
Spectrophotometric Determination of Stability Constants of Lactato and B-Hydroxypropionato Complexes of Cobalt(ll), Nickel(II), and Copper(II)
Stability constants for lactato and B-hydroxypropionato complexes
of Co(II), Ni(II), and Cu(II) were obtained from spectrophotometric
data, using Bjerrum\u27s method of corresponding solutions.
Measurements were made in the visible range and the
results plotted for graphical evaluation by Fronaeus\u27 method.
Graphically determined values for each stability constant were
utilized for averaging and least-squares calculations with a digital
computer programmed according to R. S. Tobias (»Gauss Z« program)
Muon-spin rotation measurements of the penetration depth of the Mo_3Sb_7 superconductor
Measurements of the magnetic field penetration depth \lambda in
superconductor Mo_3Sb_7 (T_c~2.1 K) were carried out by means of
muon-spin-rotation. The absolute values of \lambda, the Ginzburg-Landau
parameter \kappa, the first H_{c1} and the second H_{c2} critical fields at T=0
are \lambda(0)=720(100)nm, \kappa(0)=55(9), \mu_0H_{c1}(0)=1.8(3)mT, and
\mu_0H_{c2}(0)=1.9(2)T. The zero temperature value of the superconducting
energy gap \Delta(0) was found to be 0.35(1)meV corresponding to the ratio
2\Delta(0)/k_BT_c=3.83(10). At low temperatures \lambda^{-2}(T) saturates and
becomes constant below T~0.3T_c, in agreement with what is expected for s-wave
BCS superconductors. Our results suggest that Mo_3Sb_7 is a BCS superconductor
with the isotropic energy gapComment: 5 pages, 4 figure
Investigations of the Changes in the Bentonite Structure Caused by the Different Treatments
Abstract: Th
Reintroduction of the European beaver (Castor fiber L.) into Serbia and return of its parasite: The case of Stichorchis subtriquetrus
After becoming extinct in the second half of the 20th century, the European beaver (Castor fiber L., 1758) was successfully reintroduced from Bavaria into Serbia during 2004-2005. In the necropsy of an adult female beaver (found dead in December of 2007), we discovered some parasites identified as Stichorchis subtriquetrus in the colon and peritoneal area. This is the first occurrence of the given specific parasite of beavers in Serbia. Decoding of a subcutaneous implanted microchip has confirmed that our specimen was one of the released beavers. We therefore conclude that the parasite in question was reintroduced into Serbia with the beavers originating from Bavaria.Nakon nestanka u drugoj polovini XX veka, evropski dabar (Castor fiber L. 1758) je tokom 2004-2005. godine, uspešno reintrodukovan sa područja Bavarske u Srbiju. Tokom obdukcije jedne adultne ženke(pronađena mrtva u decembru 2006) pronašli smo parazite u želucu koji su identifikovani kao Stichorchis subtriquetrus. To je prvi nalaz ovog specifičnog parazita dabra u Srbiji. Dekodiranjem subkutano implantiranog mikročipa, potvrđeno je da pronađena ženka jedna od 20 jedinki koje su decembra 2004. godine naseljene na području Specijalnog rezervata prirode Obedska bara. Ova činjenica nam sugeriše da je parazit neželjeno reintrodukovan u Srbiju zajedno sa dabrovima koji su poreklom iz Bavarske naseljavani u Srbiju.Projekat ministarstva br. TR 2001
Memory Effects of Benzodiazepines: Memory Stages and Types Versus Binding-Site Subtypes
Benzodiazepines are well established as inhibitory modulators of memory processing. This effect is
especially prominent when applied before the acquisition phase of a memory task. This minireview
concentrates on the putative subtype selectivity of the acquisition-impairing action of
benzodiazepines. Namely, recent genetic studies and standard behavioral tests employing subtype-selective
ligands pointed to the predominant involvement of two subtypes of benzodiazepine binding
sites in memory modulation. Explicit memory learning seems to be affected
through the GABAA receptors containing the α1 and α1
subunits, whereas the effects on procedural memory can be mainly mediated by
the α1 subunit. The pervading involvement of the α1 subunit in
memory modulation is not at all unexpected because this subunit is the major
subtype, present in 60% of all GABAA receptors. On
the other hand, the role of α5 subunits, mainly expressed in the
hippocampus, in modulating distinct forms of memory gives promise of selective pharmacological coping
with certain memory deficit states
Mesoscopic phase separation in NaCoO ()
NMR, EPR and magnetization measurements in NaCoO for are presented. While the EPR signal arises from Co magnetic
moments ordering at K, Co NMR signal originates from
cobalt nuclei in metallic regions with no long range magnetic order and
characterized by a generalized susceptibility typical of strongly correlated
metallic systems. This phase separation in metallic and magnetic insulating
regions is argued to occur below ( K). Above an
anomalous decrease in the intensity of the EPR signal is observed and
associated with the delocalization of the electrons which for were
localized on Co orbitals. It is pointed out that the in-plane
antiferromagnetic coupling cannot be the driving force for the phase
separation.Comment: 14 figure
Magnetic field dependence of the oxygen isotope effect on the magnetic penetration depth in hole-doped cuprate superconductors
The magnetic field dependence of the oxygen-isotope (^{16}O/^{18}O) effect
(OIE) on the in-plane magnetic field penetration depth \lambda_{ab} was studied
in the hole-doped high-temperature cuprate superconductors YBa_2Cu_4O_8,
Y_0.8Pr_0.2Ba_2Cu_3O_7-\delta, and Y_0.7Pr_0.3Ba_2Cu_3O_7-\delta. It was found
that \lambda_ab for the ^{16}O substituted samples increases stronger with
increasing magnetic field than for the ^{18}O ones. The OIE on \lambda_ab
decreases by more than a factor of two with increasing magnetic field from
\mu_0H=0.2 T to \mu_0H=0.6 T. This effect can be explained by the isotope
dependence of the in-plane charge carrier mass m^\ast_{ab}.Comment: 4 pages, two figure
Correlation between oxygen isotope effects on the transition temperature and the magnetic penetration depth in high-temperature superconductors close to optimal doping
The oxygen-isotope (^{16}O/^{18}O) effect (OIE) on the in-plane magnetic
penetration depth \lambda_{ab}(0) in optimally-doped YBa_2Cu_3O_{7-\delta} and
La_{1.85}Sr_{0.15}CuO_4, and in slightly underdoped YBa_2Cu_4O_8 and
Y_{0.8}Pr_{0.2}Ba_2Cu_3O_{7-\delta} was studied by means of muon-spin rotation.
A substantial OIE on \lambda_{ab}(0) with an OIE exponent
\beta_O=-d\ln\lambda_{ab}(0)/d\ln M_O\approx - 0.2 (M_O is the mass of the
oxygen isotope), and a small OIE on the transition temperature T_c with an OIE
exponent \alpha_O=-d\ln T_{c}/d \ln M_O\simeq0.02 to 0.1 were observed. The
observation of a substantial isotope effect on \lambda_{ab}(0), even in
cuprates where the OIE on T_c is small, indicates that lattice effects play an
important role in cuprate HTS.Comment: 6 pages, 4 figure
- …