237 research outputs found
Theory of the Optical Conductivity in the Cuprate Superconductors
We present a study of the normal state optical conductivity in the cuprate
superconductors using the nearly antiferromagnetic Fermi liquid (NAFL)
description of the magnetic interaction between their planar quasiparticles. We
find that the highly anisotropic scattering rate in different regions of the
Brillouin zone, both as a function of frequency and temperature, a benchmark of
NAFL theory, leads to an average relaxation rate of the Marginal Fermi Liquid
form for overdoped and optimally doped systems, as well as for underdoped
systems at high temperatures. We carry out numerical calculations of the
optical conductivity for several compounds for which the input spin fluctuation
parameters are known. Our results, which are in agreement with experiment on
both overdoped and optimally doped systems, show that NAFL theory explains the
anomalous optical behavior found in these cuprate superconductors.Comment: REVTEX file, 8 PostScript figure
Weak Pseudogap Behavior in the Underdoped Cuprate Superconductors
We report on an exact solution of the nearly antiferromagnetic Fermi liquid
spin fermion model in the limit \pi T << \omega_{sf}, which demonstrates that
the broad high energy features found in ARPES measurements of the spectral
density of the underdoped cuprate superconductors are determined by strong
antiferromagnetic (AF) correlations and precursor effects of an SDW state. We
show that the onset temperature, T^{cr}, of weak pseudo-gap (pseudoscaling)
behavior is determined by the strength, \xi, of the AF correlations, and obtain
the generic changes in low frequency magnetic behavior seen in NMR experiments
with \xi(T^{cr}) \approx 2, confirming the Barzykin and Pines crossover
criterion.Comment: REVTEX, 4 pages, 3 EPS figure
Zinc oxide-based materials with enhanced sunlight-driven photo- and photo-electro-catalytic activity
Current trend in photocatalysis is to develop efficient semiconductors which can be activated by absorbing sunlight. Which wavelength of sunlight will be absorbed depends on the semiconductor band gap; semiconductors with a wide band gap (> 3 eV) can absorb only UV light (5% of sunlight), while those with a narrow band gap (< 3 eV) can be activated by visible light (45% of sunlight). Zinc oxide (ZnO) is promising semiconductor with band gap of 3.37 eV. Various approaches have been applied to modify its optical properties, for example: incorporation of different metal and nonmetal ions or defects into the crystal structure, particlesā surface sensitization or hydrogenation. In this study, we examined the influence of different defects present in ZnO particles on their photo- and photo-electro-catalytic properties. Processing of ZnO particles were carried out in order to introduce: (1) lattice defects, through microwave procedure, (2) surface defects, through mechanical activation, and (3) surface defects, trough composite with polyethylene oxide. Synthesized particles were characterized by XRD, FESEM, laser diffraction particle size analyzer, Raman, UV-Vis diffuse reflectance and photoluminescence spectroscopy. The results of achieved photo- and photo-electro-catalytic tests indicate that both, structural and surface, defects enhanced sunlight-driven activity of ZnO particles
Optical Conductivity and Hall Coefficient in High-Tc Superconductors: Significant Role of Current Vertex Corrections
We study AC conductivities in high-Tc cuprates, which offer us significant
information to reveal the true electronic ground states. Based on the
fluctuation-exchange (FLEX) approximation, current vertex corrections (CVC's)
are correctly taken into account to satisfy the conservation laws. We find the
significant role of the CVC's on the optical Hall conductivity in the presence
of strong antiferromagnetic (AF) fluctuations. This fact leads to the failure
of the relaxation time approximation (RTA). As a result, experimental highly
unusual behaviors, (i) prominent frequency and temperature dependences of the
optical Hall coefficient, and (ii) simple Drude form of the optical Hall andge
for wide range of frequencies, are satisfactorily reproduced. In conclusion,
both DC and AC transport phenomena in (slightly under-doped) high-Tc cuprates
can be explained comprehensively in terms of nearly AF Fermi liquid, if one
take the CVC's into account.Comment: 5 page
Zeolit kao faktor poboljŔanja nekih proizvodnih osobina kod krava muzara
Milk yield and milk chemical composition are largely affected by diet quality. Natural zeolite has been successfully used in livestock production as a feed supplement for some types and categories of domestic animals. This experiment was conducted over a period of 15 months involving Domestic Spotted dairy cattle. The test animals were assigned to three groups, each receiving different levels of supplemental zeolite. The control group comprised cows that received no zeolite supplement. Experimental groups I and II were fed compound feeds supplemented with 4% and 2% zeolite, respectively. The production traits studied included the following milk performance traits: whole lactation length, milk and fat yields over whole lactations, milk and fat yields over standard lactations. The results obtained suggest that zeolite supplementation affects some production traits, depending on the zeolite level present in livestock feed.Kontrolna grupa krava imala je proseÄno trajanje laktacije od 312 dana, sa varijacijama od 300 do 360 dana. Ova grupa se po dobijenim rezultatima nalazi izmeÄu ostale dve grupe krava. StatistiÄke razlike u trajanju celih laktacija meÄu grupama su znaÄajne (P (lt) 0,05). Najniža proizvodnja mleka u celim laktacijama zabeležena je kod krava Kgrupe (6395,20 kg), viÅ”a kod krava I-O grupe (6714,13 kg) i najviÅ”a kod krava II-O grupe (6934,13 kg) koja je dobijala 2% zeolita preko krmnih smeÅ”a. StatistiÄke razlike u proizvodnji mleka u celim laktacijama meÄu grupama su vrlo znaÄajne (P (lt) 0,01). Najmanja proseÄna produkcija mleka zabeležena je kod krava K-grupe (6342,33 kg). Znatno veÄa proizvodnja je bila kod krava koje su dobijale zeolit. Krave I-O grupe dobijale su 4% zeolita i postigle su proseÄnu mleÄnost od 6690.86 kg. Krave II-O grupe dobijale su 2% zeolita i postigle su najveÄu proseÄnu mleÄnost od 6711.80 kg. Krave II-O grupe imale su najveÄu proseÄnu proizvodnju mleka u standardnim laktacijama i najniži koeficijent varijacije meÄu grupama. StatistiÄke razlike u proizvodnji mleka u standardnim laktacijama meÄu grupama su vrlo znaÄajne (P (lt) 0,01). Krave K-grupe imale su najmanju proseÄnu priozvodnju mleÄne masti u mleku, a krave II-O grupe najveÄu. StatistiÄke razlike u koliÄini mleÄne masti u celim laktacijama meÄu grupama su vrlo znaÄajne (P (lt) 0,01). TakoÄe su vrlo znaÄajne (P (lt) 0,01) i statistiÄke razlike meÄu grupama u koliÄini mleÄne masti u standardnim laktacijama
Pentoxifylline Prevents Autoimmune Mediated Inflammation in Low Dose Streptozotocin Induced Diabetes
Xanthine derivative, pentoxifylline (PTX), has been recently shown to exert a protective effects
in certain animal models of autoimmunity, including diabetes in NOD mice. In the present
study, the immunomodulatory potential of PTX was investigated in autoimmune diabetes
induced by multiple low doses of streptozotocin (MLD-SZ) in genetically susceptible CBA/H
mice (tested with 40 mg SZ/kg b.w. for 5 days) and DA rats (tested with 20 mg/kg b.w. for 5
days). In both species, 2 ā 3 weeks following the MLD-SZ treatment, sustained hyperglycemia
developed, as an outcome of inflammatory reaction with endothelial cell activation and accumulation
of mononuclear cells. Although there was no evidence of typical insulitis in early disease
development (day 10), in both rats and mice, macrophages, CD4+ and CD8+ cells were present in the islets of Langerhans as diffuse mononuclear infiltrates with the expression of
IFN-Ī³ and inducible NO synthase (iNOS). Administration of PTX (200 mg/kg/day for 10 days)
in combination with MLD-SZ reduced insulitis and the production of mediators tested, and prevented
the development of hyperglycemia. These results suggest that beneficial effects of PTX
involve down-regulation of local proinflammatory cytokine-mediated NO synthase pathway.
They also demonstrate that in addition to ameliorating spontaneous autoimmunity in NOD
mice, PTX may be effective in downregulating an inflammatory autoimmune process triggered
in susceptible host by an external agents, such as streptozotocin
Magnetoresistance in Heavily Underdoped YBa_2Cu_3O_{6+x}: Antiferromagnetic Correlations and Normal-State Transport
We report on a contrasting behavior of the in-plane and out-of-plane
magnetoresistance (MR) in heavily underdoped antiferromagnetic (AF)
YBa_2Cu_3O_{6+x} (x<0.37). The out-of-plane MR (I//c) is positive over most of
the temperature range and shows a sharp increase, by about two orders of
magnitude, upon cooling through the Neel temperature T_N. A contribution
associated with the AF correlations is found to dominate the out-of-plane MR
behavior for H//c from far above T_N, pointing to the key role of spin
fluctuations in the out-of-plane transport. In contrast, the transverse
in-plane MR (I//a(b);H//c) appears to be small and smooth through T_N, implying
that the development of the AF order has little effect on the in-plane
resistivity.Comment: 4 pages, 5 figures, accepted for publication in Phys.Rev.Let
Levels of Presepsin and Midregion-Proadrenomedullin in Septic Patients with End-Stage Renal Disease after Cardiovascular Surgery: 1-Year Follow Up Study
Background: Procalcitonin (PCT) is a marker for sepsis diagnosis, identification of bacterial infection and monitoring of antibiotic therapy. It has been shown that PCT is not a good choice in patients with hemodialysis. Therefore, we have explored two biomarkers: a) presepsin, and, b) midregion-proadrenomedullin (MR-proADM) in patients having End-Stage Renal Disease (ESRD). Patients and Methods: We prospectively enlisted 20 patients, who underwent cardiovascular surgery and had been on dialysis. The diagnosis of sepsis has been established clinically and confirmed by PCT. Blood samples were taken before and after dialysis. Additionally, plasma and sera of 10 healthy blood donors without any complications were used as controls. Results: Presepsin plasma concentrations (4368 Ā± 3088 vs. 694.1 Ā± 239.1 pg/mL) were significantly higher in patients with sepsis compared with controls (p0.05) with no significance between alive and deceased (p=0.53) patients. Adjustments have shown that the difference for MR-proADM level is due to the random sampling variability (p=0.989), whereas difference for presepsin remained highly significant (p<0.001). Conclusions: Our results indicate that the accuracy of new biomarkers is equal to that of PCT in patients with ESRD. Presepsin might be as good marker in repeated measurements, before and after dialysis, as it is PCT. Ā© 2014 Maravic-Stojkovic V, et al
PCR amplification of seven single copy nuclear genes from the Belgrade mummy
Here we report a DNA analysis of a human mummy dated approximately 2300 years BC. We extracted the DNA and used it for further PCR amplification of the following genes: c-fms proto-oncogene for CSF-1 receptor gene (CSF1PO); coagulation factor XIII a subunit gene (F13A01); c-fes/fps proto-oncogene (FESFPS); tyrosine hydroxylase gene (TH01); thyroid peroxidase gene (TPOX), von Willebrand factor gene (vWA) and Y chromosome specific sequence. The alleles from Belgrade mummy do not differ from the most frequent alleles of all present human populations. The exception is FESFPS gene. Belgrade mummy is homozygous for this locus which contains alleles with 7 motif repeats while such allele is found in less than 0.38% of living humans.U ovom radu dati su rezultati analiza molekula DNK izolovanih iz uzorka mumije Äoveka stare 2300 godina. Genomska DNK je izolovana i koriÅ”Äena za PCR amplifikaciju sledeÄih gena: c-fms protoonkogen za CSF-l receptor gen (CSF1PO), gen za a subjedinicu humanog faktora koagulacije XIII (F13A01), c-fes/fps protoonkogen (FESFPS), gen za tirozin hidroksilazu (TH01), gen za tiroidnu peroksidazu (TROH), gen za von Willebrand-ov faktor(vWA) i specifiÄne sekvence za Y hromozom. Aleli beogradske mumije se ne razlikuju od najuÄestalijih alela sadaÅ”anje humane populacije. Izuzetak je FESFPS gen. Beogradska mumija je homozigotna za ovaj lokus i ima alele sa motivom od 7 ponovaka. UÄestalost ovog alela u danaÅ”njoj humanoj populaciji je manja od 0.38%.nul
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