The structural and dielectric properties of SrBi
2−
x
Ce
x
Nb
2
O
9
(
x
= 0, 0.2, 0.35) oxides prepared by a solid state method have been examined. The samples are characterized by means of scanning ...electron microscopy, energy dispersive x-ray spectroscopy, x-ray powder diffraction and Fourier-transform infrared spectroscopy. The results obtained from different experiments correlated well to reveal the structure–property relationship. The impact of cerium substitution on the dielectric properties of the SrBi
2-
x
Ce
x
Nb
2
O
9
is elucidated. Ce-doped SrBi
2
Nb
2
O
9
ceramics have low dielectric loss values and the flattening of the dielectric constant at higher frequencies. The dielectric loss decreased for doped compositions compared to SrBi
2
Nb
2
O
9
at room temperature, whereas the dielectric constant was higher for doped ceramics due the possible incorporation of Ce
4+
and Ce
3+
ions into the Bi
2
O
2
layers. A significant increase in diffusiveness was observed with increasing Ce.
Structure and dielectric properties of Eu-doped SrBi2Nb2O9 ceramics (with 0,
20 and 35 at.% of Eu), prepared by the solid-state method and sintering,
were investigated. XRD, FTIR and SEM measurements ...were provided to validate
the characteristic structural features of the obtained ceramics. For all
samples, the orthorhombic structure was identified through XRD analysis. SEM
results confirmed that the fabricated samples have relatively dense
structure with rod- and plate-like grains typical for Aurivillius layered
structures. Dielectric results showed that the doping with Eu decreases
dielectric constant and reduces dielectric loss. Movement of the dielectric
peak towards higher temperatures appearing at about 400?C with increase of
frequency indicates on relaxor behaviour of the sample with 35 at.% of Eu.
nema
We present the dielectric properties study of the ceramic SrBi
2
Nb
2
O
9
single-phase matrix as well as the SrBi
2
Nb
2
O
9
+ (%)La
2
O
3
composite. The SrBi
2
Nb
2
O
9
was doped with lanthanum ...oxide (La
2
O
3
) with 3%, 5%, 10% and 15% proportions. Structural characterization by x-ray diffraction was carried out. The dielectric properties in the radio frequency and microwave ranges are presented. The
τ
f
temperature coefficient of the composite samples was obtained experimentally. The Hakki–Coleman method has been used to obtain the microwave properties and HFSS software has been used to obtain the far field properties in order to view possible applications of SrBi
2
Nb
2
O
9
+ La
2
O
3
as a dielectric resonant antenna.
► The piezoelectric properties of SBN are enhanced by (Bi, Na) modification. ► The d33 and Tc of SBNBN4 are 22pC/N and 586.5°C, respectively. ► The d33 of SBNBN4 have better temperature stability. ► ...The better piezoelectric activities are induced by larger lattice distortion.
Sr1−x(Bi, Na)x/2Bi2Nb2O9 (SBNBNO, x=0, 0.2, 0.4 and 0.6) ceramics were prepared by the conventional solid-state route. X-ray diffraction analyses (XRD) and Raman spectroscopy indicated that all specimens have a single phase with perovskite-type orthorhombic structure. The piezoelectric activity and Curie temperature of SrBi2Nb2O9 (SBN) ferroelectric ceramics are significantly improved by bismuth and sodium modification. The piezoelectric coefficient d33 of the Sr0.6(Bi, Na)0.2Nb2O9 (SBNBN4) specimen was found to be 22pC/N, which is higher than the d33 values (about 12pC/N) of SBN specimen. Moreover, the SBNBN4 specimen exhibited the excellent temperature stability of piezoelectric properties. In order to confirm the nature of the piezoelectric properties enhanced, the relationship between the structure and electrical properties was discussed.
Gestational diabetes mellitus (GDM) is a common complication of pregnancy that is characterized by glucose intolerance, leads to dyslipidemia, and is aggravated by obesity. Cholesterol is taken up by ...the placenta as part of lipoproteins through the scavenger receptor class B type I receptor (SRBI), low-density lipoprotein receptor (LDLR), and very low density lipoprotein receptor (VLDLR), and its efflux is then mediated by ABCA1 and ABCG1. PCSK9 is involved in the degradation of LDLR and VLDLR. The goal of this study was to evaluate the impact of GDM and prepregnancy body mass index (BMI) on cholesterol transport through the modulation of the expression of several key players. Human full-term placenta, maternal, and venous cord blood samples were obtained at delivery from normal-weight women without GDM (n = 10), normal-weight women with GDM (n = 6), and overweight/obese women with GDM (n = 6). Lipids (total cholesterol, high-density lipoprotein, low-density lipoprotein, triglycerides, free fatty acids, apolipoprotein A1, apolipoprotein B100) levels were evaluated in blood samples. Messenger RNA and protein expression levels (LDLR, VLDLR, SRBI, ABCA1, ABCG1, proprotein convertase subtilisin/kexin type 9, liver x receptors, peroxisome proliferator-activated receptors) were assessed in human full-term placenta, respectively, by real-time RT-PCR and Western blots. Lipoprotein lipase activity was evaluated using a commercial kit on tissue homogenates. Overall, our study demonstrates that GDM affects the maternal and neonatal lipid profiles as well as different key players of placental cholesterol transfer from the maternal to the fetal circulation, depending on the maternal BMI. These changes could affect the fetal metabolism and predispose the fetus to future metabolic diseases.
The room temperature structures of the five layer Aurivillius phases
A
2Bi
4Ti
5O
18 (
A=Ca, Sr, Ba and Pb) have been refined from powder neutron diffraction data using the Rietveld method. The ...structures consist of Bi
2O
2
2+ layers interleaved with perovskite-like
A
2Bi
2Ti
5O
16
2− blocks. The structures were refined in the orthorhombic space group
B2eb (SG. No. 41),
Z
=
4
, and the unit cell parameters of the oxides are
a
=
5.4251
(
2
)
,
b
=
5.4034
(
1
)
,
c
=
48.486
(
1
)
;
a
=
5.4650
(
2
)
,
b
=
5.4625
(
3
)
,
c
=
48.852
(
1
)
;
a
=
5.4988
(
3
)
,
b
=
5.4980
(
4
)
,
c
=
50.352
(
1
)
;
a
=
5.4701
(
2
)
,
b
=
5.4577
(
2
)
,
c
=
49.643
(
1
)
for
A
=
Ca
, Sr, Ba and Pb, respectively. The structural features of the compounds were found similar to
n
=
2
–
4
layers bismuth oxides. The strain caused by mismatch of cell parameter requirements for the Bi
2O
2
2+ layers and perovskite-like
A
2Bi
2Ti
5O
16
2− blocks were relieved by tilting of the TiO
6 octahedra. Variable temperature synchrotron X-ray studies for Ca and Pb compounds showed that the orthorhombic structure persisted up to 675 and 475
K, respectively. Raman spectra of the compounds are also presented.
The origin of the ferroelectric behavior in the five-layer Aurivillius oxides BaBi
4Ti
5O
18 is discussed in light of accurate structural studies
Display omitted .
An Aurivillius perovskite nano-structure of SrBi
4
Ti
4
O
15
-catalyzed cyclocondensation reaction of 2-amino-4,5-dihydronaphtho1,2-
b
thiophene-3-carboxamide and aldehydes has been carried out by ...HSBM technique under mild conditions for obtaining 9-aryl-5,8-dihydronaphtho2′,1′:4,5thieno2,3-
d
pyrimidin-7(6H)-ones in good to excellent yields.
This paper presents a study of the structure and dielectric properties of
Eu-doped SrBi2Nb2O9 ceramics prepared by co-precipitation route and sintered
at 850?C. The materials were examined using XRD ...and FTIR methods. XRD data
indicated the formation of well crystallized structure of the pure and doped
SrBi2Nb2O9, without the presence of undesirable phases. FTIR spectra do not
bring a significant shift in the band positions. Moreover, the AC
conductivity, dielectric constant and dielectric loss of the ceramics were
determined through the frequency range 50 kHz-1MHz. In particular, the
dielectric constant (??) and dielectric losses (tan ?) of the SrBi2Nb2O9 and
SrBi1.6Eu0.4Nb2O9 ceramics were measured as a function of temperature at
various frequencies.
nema
U radu se analiziraju članci objavljeni u
kulturno-političkom časopisu
Srđ
iz Dubrovnika tijekom njegova izlaženja (1902.
– 1908.) kojima je glavna preokupacija jezik. Autor polazi od imaginarija ...Srba
katolika u Dubrovniku da bi pokazao kako su se jezična pitanja problematizirala,
odnosno kakva su bila stajališta uredništva i autora prema dubrovačkom govoru
te prema dubrovačkoj književnosti – u prošlosti i danas. Na takav se način
pokušava razumjeti uloga jezika u određivanju nacionalnog identiteta grada.
Analiziraju se svi članci koji su relevantni za to pitanje, napose polemike i
pregledi književnosti. Autor se fokusira ne samo na iznesene teze nego i na
modele argumentiranja, čime želi istaknuti neke nedosljednosti tih koncepcija
te posljedice njihove primjene.
In this study, the articles published in the Dubrovnik
cultural-political journal
Srđ
throughout the whole period of its publication
(1902–1908) which deal with linguistic questions are taken into consideration.
Beginning with an overview of the imagery of the movement of ‘Serbs Catholics
in Dubrovnik, the researcher aims to demonstrate how linguistic issues were
conceptualized, i.e. how the editors and published authors referred to the
Dubrovnik vernacular and literature – now and in the past. In this way, the
researcher aims at understanding the role of language in the determination of
the national identity of the city. In the study, all articles which are
relevant to this issue are analyzed, in particular polemics and companions to
literature. The researcher focuses not only on the theses but also on the modes
of argumentation to single out inconsistencies of the ideas in question and
hence the outcomes of their use.
Strontium bismuth tantalate (SrBi
2
Ta
2
O
9
) was synthesized by a co-precipitation method. The sample was characterized by x-ray powder diffraction patterns (XRD), Fourier-transform infrared ...spectroscopy (FTIR) and scanning electron microscopy (SEM). The results of the dielectric properties are reported at room temperature. No secondary phases were found while heating the powder at 850°C and the pure SrBi
2
Ta
2
O
9
phase was formed, as revealed by XRD. The characteristic bands for SrBi
2
Ta
2
O
9
were observed by FTIR at approximately 619 cm
−1
and 810 cm
−1
. SEM micrographs for the sample displayed thin plate-like grains. The grain size was less than 1
μ
m and the crystallite size of about 24 nm. Dielectric response at room temperature shows that the SrBi
2
Ta
2
O
9
ceramic has low loss values, and the flattening of the dielectric constant at higher frequencies. The observed Curie temperature is comparable with those reported in the literature.
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