The morphology of WO
3 aggregates formed by irregular nanoparticles (
D∼40
nm) and nanowires of different aspect ratios (2, 4, 6, and 10
μm nominal lengths) dispersed in commonly used polar solvents ...without dispersant agents is investigated using a small-angle light scattering technique and by means of fractal theory. Nanoparticles form compact spherical aggregates (
D
f∼2.6), whereas 2
μm nanowires with low aspect ratio (
L/
D∼10) follow a slow cluster–cluster aggregation mechanism with no discernable change in fractal dimension (
D
f=2.1) monitored in an extended period of 6 months, despite a notable growth in size (
R
g
=2.3–3.1
μm). For higher aspect ratio nanowires, scattered intensity profiles, which migrate towards the Porod regime, qualitatively obey the Lorenz–Mie theory predictions. The 10
μm nanowires with very high aspect ratio (
L/
D∼250) are observed to form stable dispersions in a time span of 6 days. Analytical methods based on spherical primary particle formulations predict
D
f=1.9, 1.7, and 1.4 for 4, 6, and 10
μm nanowires, respectively.
This combined study using small‐angle neutron scattering (SANS), X‐ray powder diffraction (XRPD), transmission electron microscopy (TEM) and adsorption isotherm techniques demonstrates radical ...changes in the microstructure of porous hematite (α‐Fe2O3) nanoparticles upon calcination in air. TEM images of the as‐synthesized hematite sample show that it consists of subrounded nanoparticles 50 (8)–61 (11) nm in average minimum and maximum diameters with an apparent porous structure of nanosized pores/channels or cracks. SANS data confirm the presence of two characteristic sizes, one originating from the particle size and the other from the pore/void structure. Furthermore, the TEM images show that the particle sizes are nearly unaffected by calcination at 623 K, whereas their pore/void structure changes radically to an apparently pitted or spongy microstructure with cavities or/and voids. The change in microstructure also causes a reduction in the surface area as calculated by gaseous adsorption. The XRPD and SANS data show that the crystallite and SANS particle sizes are virtually unchanged by calcination at 623 K. Calcination at 973 K induces a significant alteration of the sample. The XRPD data reveal that the crystallite size increases significantly, and the SANS and adsorption isotherm studies suggest that the specific surface area decreases by a factor of ∼5–6. The TEM images show that the particles are sintered into larger agglomerates, but they also show that parts of the porous microstructure observed in the sample calcined at 623 K are retained in the sample calcined at 973 K.
Iako se nalazimo u 21. stoljeću ipak u Republici Hrvatskoj porod kod kuće još uvijek nije adekvatno zakonski reguliran te gotovo sve žene rađaju u bolničkom okruženju. Cilj ovog istraživanja bio je ...utvrditi stavove prvostupnica primaljstva u Republici Hrvatskoj o porodu kod kuće. U istraživanju su sudjelovale 73 prvostupnice primaljstva u registru članova Hrvatske komore primalja. Istraživanje se provodilo u svibnju 2021. godine putem on-line anonimnog anketnog upitnika koji je izrađen specifično za ovo istraživanje. Rezultati su pokazali kako dvije trećine ispitanika smatra da je mogućnost komplikacija u porodu niža ako se porod odvija u bolnici, dok trećina ispitanika smatra da se porodi ne trebaju isključivo obavljati u bolnici. Gotovo trećina ispitanika navodi kako bi vodili porode kod kuće u slučaju njihove adekvatne zakonske regulacije i najveći udio je u dobi od 21 do 31 godine s manje od pet godina radnog staža. Tek 27% prvostupnica primaljstva smatra da ima dovoljno znanja i vještina za vođenje kućnih poroda, a 18% bi uz više edukacije i radnog staža bilo spremno voditi kućne porode. Zbog sve više stope kućnih poroda u Hrvatskoj, od važnosti je osigurati ženama mogućnost stručnog vođenja takvih poroda. Prvostupnici/ce primaljstva Republike Hrvatske najadekvatnije su zdravstveno osoblje za vođenje poroda kod kuće s ciljem što boljih ishoda, i za žene i za njihovu djecu.
The internal nanostructure of the diatoms
Cyclotella meneghiniana
,
Seminavis robusta
and
Achnanthes subsessilis
was investigated using small angle neutron scattering (SANS) to examine thin biosilica ...samples, consisting of isotropic (powder) from their isolated cell walls. The interpretation of SANS data was assisted by several other measurements. The N
2
adsorption, interpreted within the Branuer–Emmet–Teller isotherm, yielded the specific surface area of the material. Fourier transform infrared (FTIR) and Raman spectroscopy indicates that the isolated material is amorphous silica with small amounts of organic cell wall materials acting as a filling material between the silica particles. A two-phase (air and amorphous silica) model was used to interpret small angle neutron scattering data. After correction for instrumental resolution, the measurements on two SANS instruments covered an extended range of scattering vectors 0.0011 nm
−1
<
q
< 5.6 nm
−1
, giving an almost continuous SANS curve over a range of scattering vectors,
q
, on an
absolute scale of intensity
for each sample. Each of the samples gave a characteristic scattering curve where log (intensity) versus log (
q
) has a −4 dependence, with other features superimposed. In the high-
q
regime, departure from this behaviour was observed at a length-scales equivalent to the proposed unitary silica particle. The limiting Porod scattering law was used to determine the specific area per unit of volume of each sample illuminated by the neutron beam. The Porod behaviour, and divergence from this behaviour, is discussed in terms of various structural features and the proposed mechanisms for the bio-assembly of unitary silica particles in frustules.
We consider a procedure for coarse-graining polymer molecules from the atomistic level of description to the reptation level for entangled polymers. The coarse-grained polymer model obtained with a ...competing-spring construction belongs to a class of models, referred to as tapeworms, for which a straightforward solution scheme based on generating functions is discussed and illustrated. The significance of the results and several perspectives for nonequilibrium simulations of entangled polymers are discussed.
LIJEČENJE PRIJETEĆEG PRIJEVREMENOG PORODA Prodan, Mirko; Petrović, Oleg
Gynaecologia et perinatologia (Zagreb, Croatia),
12/2008, Letnik:
17, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Sažetak. Prijevremeni porod je vodeći uzrok neonatalnog mortaliteta i morbiditeta i još uvijek jedan od najvećih problema i izazova suvremene perinatologije. Njegovo sprječavanje i liječenje je ...otežano zbog postojanja većeg broja uzročnih i rizičnih čimbenika koji su dijelom i nepoznati. U ovom prikazu razmotreni su različiti postupci i lijekovi za sprječavanje i liječenje prijetećeg prijevremenoga poroda. Posebno su analizirane pojedine skupine tokolitika, njihova učinkovitost i nedostatci. Oni mogu odgoditi porod za najviše 48 sati do sedam dana, ali bitno ne poboljšavaju perinatalni i neonatalni ishod. Taj vremenski period je, međutim, dovoljan za transport u tercijarni perinatološki centar i sprovođenje kortikosteroidne profilakse. Smatra se da je to jedini dokazan učinak tokolitičke terapije. Za sada, dok se ne otkriju bolji i učinkovitiji lijekovi i metode, kvalitetna i pravodobna antenatalna skrb, hospitalizacija pa i preventivna, u odabranim rizičnim slučajevima još uvijek najdjelotvornije smanjuju učestalost prematuriteta i njegovih neželjenih posljedica.
An analytical method to estimate the thickness of the interface between two phases from small‐angle scattering (SAS) data has been developed using Porod's law modified by a triangular smoothing ...function. The convolution with a `top‐hat' function describing a sharp density profile results in a semi‐sigmoidal density profile. This analytical method allows an interfacial layer thickness to be estimated from the negative slope of a Porod plot. The interfacial layer thickness (T) obtained from this model is related to similar models, namely a linear (E) and a sigmoidal density profile (σ) model, as follows: T = 21/2E = 2(61/2)σ, where σ is the standard deviation of the Gaussian function and does not represent the boundary thickness itself. The interfacial layer thickness obtained from any convolution method is a model‐dependent parameter.
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