Pronounced fibres are formed through simple shearing of a dense calcium caseinate dispersion. Both mechanical tests and scanning electron microscopy images demonstrate that the material is ...anisotropic. It is hypothesised that calcium caseinate aggregates, under shear, align into micro-fibres and bundle further into a hierarchical structure. Yet no direct evidence at the sub-micron length scale can support the assumption. Small angle neutron scattering (SANS) experiments were conducted on calcium caseinate samples prepared at different conditions. Analysis of the SANS data revealed that the micro-fibres have a diameter of ∼100nm and a length of ∼300nm. The addition of enzyme and air contributed to longer and thinner micro-fibres. Furthermore, the extent of fibre alignment at the micro-scale and the macroscopic anisotropy index followed the same trends with varying processing conditions. It is concluded that the material does indeed possess a hierarchical structure and the micro-fibres are responsible for the anisotropy on the macro-scale.
Display omitted
•Micro-fibres in calcium caseinate were studied by small angle neutron scattering.•The micro-fibres have a diameter of ∼100nm and a length of ∼300nm.•The addition of enzyme and air contributed to longer and thinner fibres.•The micro-fibres are responsible for the mechanical properties at the macro-scale.
The formation of calcium carbonate (CaCO3) nanoparticles (NPs) in the presence of polystyrene sulfonate (PSS) as an additive was examined by time‐resolved small‐angle X‐ray scattering (SAXS) in a ...flow system that mimics experimental conditions used at home facilities where the precipitation can be achieved in a beaker. The experiments were carried out at low concentrations to remain in the dilute regime. A model‐independent analysis was performed using the Porod invariant which defines the scale factor, leaving only the distribution of radii as the adjustable parameter. The presence of the PSS additive strongly retards the precipitation of CaCO3 NPs. The formation of NPs reaches a state of equilibrium after a few minutes. Here, it is shown that the concentration of precursors at a fixed PSS concentration plays a key role in determining the size of the NPs obtained. A full analysis of the SAXS patterns was carried out using the Hurd–Flower model to account for the weaker intensity decay than the classical Porod behaviour. The temporal evolution of the particle radii was determined. Wide‐angle X‐ray scattering experiments carried out simultaneously show that the particles formed have the structure of vaterite with growth consistent with the evolution of the Porod invariant.
The kinetics of precipitation of CaCO3 particles in the presence of polystyrene sulfonate was studied by small‐ and wide‐angle X‐ray scattering. Employment of the Porod invariant and the Hurd–Flower model provides essential information on the kinetics.
Uvod: Zdravstveno osebje ima velik vpliv na doživljanje staršev ob rojstvu nedonošenega otroka. Namen raziskave je bil preučiti in predstaviti doživljanje mater ob rojstvu nedonošenega otroka.Metode: ...Uporabljena je bila deskriptivna fenomenološka analiza. Na namenskem vzorcu enajstih mater, ki so imele izkušnjo rojstva nedonošenega otroka, rojenega med 24. in 35. tednom gestacije, so bili izvedeni delno strukturirani intervjuji. Najmlajša intervjuvanka je bila ob porodu stara 24 let in najstarejša 36. Za osem izmed njih je bil porod nedonošenega otroka prvi porod. Raziskava je potekala med majem in junijem 2017. Podatki so bili analizirani s pomočjo Giorgijevega pristopa, značilnega za fenomenološko raziskavo.Rezultati: Strukturo opisa sestavljajo štiri tematske skupine, ki opredeljujejo doživljanje mater ob rojstvu nedonošenega otroka: (1) potek poroda: želje in pričakovanja; (2) reprezentacijo materinstva: čustvovanje, navezanost, empatijo, spomine; (3) čustvovanje in skrb za nedonošenega otroka v poporodnem obdobju ter (4) (ne)profesionalnost zdravstvenih delavcev.Diskusija in zaključek: Izsledki raziskave kažejo, da je večina mater iskala vzroke prezgodnjega poroda. Veliko jim je pomenila podpora svojcev, zdravstvenih delavcev ter »sotrpink« z oddelka. Večina mater se je med porodom in hospitalizacijo soočala z negativnimi občutki; empatičen odnos zaposlenih jih je spodbujal in navdajal z upanjem ter zaupanjem.
Controlling particle dispersity is of huge importance for practical applications in nanoscience and technology. The analysis of small‐angle scattering of X‐rays and neutrons for strongly polydisperse ...particulate systems is considered from the point of view of describing the type of size distribution function without applying classical regularization approaches. This article presents the development of a method for determining the polydispersity parameters of nanoobjects, based on the analysis of the ratio of various moments of the size distribution function, which are proportional to different invariants of the scattering curve. The use of the unified exponential/power‐law approximation to describe small‐angle scattering data makes it possible to determine the type of distribution, the average size and the spread. The possibilities of the method were tested for several hydrosols of metallic nanoparticles.
This article introduces a generalized approach to determine polydispersity characteristics from small‐angle scattering analysis based on the Beaucage model without numerical integration of experimental data.
The concave behaviour of the Porod invariant observed during the calcination of CaCO3 powder samples suggests the following picture of the evolving internal structure of the samples. The outset ...sample is formed by a crystalline CaCO3 phase and a void phase. During the calcination, the first phase shrinks in volume at fixed density since the temperature increase breaks down the crystalline structure at the interface, leading to the formation of an amorphous phase comprising an equal number of CO2 and CaO atomic groups. The last groups gradually condense, forming a third phase of solid CaO of constant density and increasing volume fraction, while the companion CO2 groups flow out of the sample. The amorphous phase occupies, with a variable density, all the volume left free by the other two phases. At the end of the calcination, both the volume fraction of the first phase and the density of the amorphous phase vanish so that the sample will again be made up of two phases: the voids and the solid CaO. Best‐fitting the resulting theoretical expressions of the Porod invariant and of the Porod law coefficient to the observed values, one can determine the matter densities, volume fractions and specific surface areas of the phases.
The chemical structures of the phases of CaCO3 samples undergoing a calcination process, as well as the volume fractions and matter densities of those phases, are determined by the Porod invariant behaviour.
A new method to estimate the size distribution of non‐interacting colloidal particles from small‐angle scattering data is presented. The method demonstrates that the distribution can be efficiently ...retrieved through features of the scattering data when plotted in the Porod representation, thus avoiding the standard fitting procedure of nonlinear least squares. The present approach is elaborated using log‐normal and Weibull distributions. The method can differentiate whether the distribution actually follows the functionality of either of these two distributions, unlike the standard fitting procedure which requires a prior assumption of the functionality of the distribution. After validation with various simulated scattering profiles, the formalism is used to estimate the size distribution from experimental small‐angle X‐ray scattering data from two different dilute dispersions of silica. At present the method is limited to monomodal distributions of dilute spherical particles only.
A new and efficient method for the estimation of particle‐size distribution from small‐angle scattering data is presented. This method is based on features of the Porod plot.
Uvod: Vpliv porodnega položaja na tveganje za poškodbo presredka, ki je odvisen od lokalnih in regionalnih babiških praks, kot so ročna tehnika zaščite presredka, razne stopnje epiziotomije in ...operativnih porodov itd., še ni zadostno raziskan. Namen raziskave je bil v eni od slovenskih porodnišnic preučiti morebitno povezavo med porodnim položajem ob iztisu ploda in pojavnostjo poškodbe presredka.Metode: V retrospektivno kohortno raziskavo smo vključili 625 porodnic, ki so leta 2021 rodile v Splošni bolnišnici Jesenice. Izključili smo večplodne nosečnosti, prezgodnje porode, porode s plodom v medenični ali okcipito-posteriorni vstavi, vakuumske ekstrakcije ploda in epiziotomije. Z multiplo logistično regresijo smo preučili, ali je bil položaj porodnice ob iztisu ploda (leže na hrbtu (n = 66), leže na boku (n = 404) ali vsi ostali položaji (n = 155)) neodvisno povezan s pojavnostjo poškodbe presredka.Rezultati:Pri 363 porodnicah (58 %) ni prišlo do poškodbe presredka. Pri 192 (73 %) je prišlo do poškodbe prve stopnje, pri 59 (23 %) do poškodbe druge stopnje in pri 11 (4 %) do poškodbe presredka tretje ali četrte stopnje. Porodni položaj ob iztisu ploda ob upoštevanju drugih potencialnih dejavnikov tveganja ni bil statistično pomembno povezan s tveganjem za poškodbo presredka: razmerje obetov (RO) 0,691, 95% interval zaupanja (IZ) – 0,401–1,191 za položaj na boku; RO 0,710, 95% IZ – 0,386–1,306 za ostale položaje v primerjavi s porajanjem leže na hrbtu.Diskusija in zaključek: V slovenski porodnišnici z visokim odstotkom porodnic, ki ne rodijo leže na hrbtu, porodni položaj ob iztisu ploda ni neodvisni dejavnik tveganja za nastanek poškodbe presredka
Cilj je ovoga preglednog rada ukazati na moguće rizike prijevremenoga poroda za daljnji razvoj djece te prikazati rezultate recentnih istraživanja psihofizičkoga zdravlja roditelja prijevremeno ...rođene djece. Istraživanja pokazuju da posljedice koje prijevremeno rođenje ima za djecu mogu biti ozbiljne, pri čemu rizik od neurorazvojnih poremećaja raste s nižom gestacijskom dobi djeteta i nižom porodnom težinom. Rizici prijevremenoga rođenja djeteta za roditelje mogu se očitovati neposredno i/ili dugoročno, od akutne stresne reakcije do poslijetraumatskoga stresnog sindroma, poteškoća u razvoju privrženosti, perzistirajuće intenzivne brige i straha za dijete, što je dodatno naglašeno prelaskom djeteta iz bolničkoga okruženja na kućnu njegu. Inicijalna emocionalna i informativna podrška medicinskoga osoblja, prakticiranje tzv. klokanske njege, dostupnost stručnjaka za mentalno zdravlje te neformalni izvori podrške izuzetno su važni čimbenici prilagodbe roditelja. Pregled suvremenih istraživanja upućuje na potrebu za daljnjim ispitivanjima čimbenika koji se dovode u vezu s (ne)uspješnom psihofizičkom prilagodbom roditelja na prijevremeno rođenje djeteta i skrb o nedonoščetu. Budući da je adekvatno suočavanje roditelja važan preduvjet razvojnih ishoda kod neurorizične djece, bitno je osigurati programe podrške roditeljima da bi se osnažila njihova znanja i kompetencije.
The aim of this review is to highlight possible risks preterm birth can have for the development of children and to present the results of recent research on psychophysical health of parents of prematurely born children. Research shows that, for children, the consequences of preterm birth can be serious, with the risk of neurodevelopmental disorders increasing with lower gestational age of the child as well as birth weight. For parents, the effects of child’s preterm birth can manifest immediately and/or long-term, and range from an acute stress reaction, to post-traumatic stress syndrome, difficulties in the development of attachment, persistent intense worry and fear for the child, which is further emphasized by the child’s transition from a hospital environment to home care. Initial emotional and informative support of the medical staff, practicing kangaroo care, as well as the availability of mental health experts and informal support sources are extremely important for parents’ adaptation. A review of contemporary research points to the need for further investigation of factors associated with the (un)successful psychophysical adaptation of parents to the premature birth of a child and the care of a premature infant. Since adequate parental coping is an important prerequisite for developmental outcomes in neuro-risk children, it is important to provide support programs for parents in order to strengthen their knowledge and competences.
SHORT CERVIX – WHAT NOW? Faris Mujezinović
Zdravniški vestnik (Ljubljana, Slovenia : 1992),
02/2018, Volume:
78
Journal Article
Peer reviewed
Open access
Background: It is possible to predict preterm delivery (PD) before 34 weeks by ultrasound measurement of uterine cervical length (CL). This is the reason why this screening method is more frequently ...used in clinical practice. Methods: I extracted from PubMed database Crane’s sistematic review and articles about association of CL with PD and instructions what is necessary to take into consideration and what to do in case of a short cervix. Results: Majority of studies suggested CL of 25 mm as a cut-off point for selecting pregnancy as high risk for PD. Minority of studies also used 15 mm as a cut-off point. This inconsistency in selecting an unique cut-off point, as some authors showed, is a result of ignoring gestational age when measurement of CL is made. CL is usually measured until 24 weeks of pregnancy and value of US measurement of CL made later in pregnancy or role of follow-up measure- ments are still unclear. In cases with threatened preterm labour where CL is measured there was 66 % reduction of unnecessary tocolysis. US measurement of CL is of a little value if there is a progressive dilatation of cervix (Bishop score > 6). Shirodkar cerclage in women with short cervix does not reduce the risk for PD. Vaginal progesteron causes a 50 % decrease of incidence of PD in women with short cervix (CL < 15 mm). We do not know which form of vaginal progesteron is most effective. Progesteron is uneffective in women with PD in previous pregnancy and CL > 25 mm. Conclusions: US measurement of CL becomes reliable criteria for detecting pregnancies with increased risk for PD before 34 weeks of pregnancy. It enables individual risk calculation for PD with consideration of other risk factors.
Small‐angle X‐ray scattering (SAXS) is an accurate nondestructive method that requires a minimum of sample preparation and is employed to study porosity, morphology and hierarchical structures. ...Zeolites and silica are among the porous materials that are widely investigated by SAXS. However, studies of covalent organic frameworks (COFs) are still scarce. In the present study, SAXS was employed to investigate meso‐ and microporous COFs, affording insightful information about their nanostructure textural properties. SAXS is especially useful when combined with other characterization techniques, such as powder X‐ray diffraction and N2 adsorption isotherms, emerging as an efficient tool to further characterize COFs. For microporous COFs, SAXS was used mainly to obtain quantitative values of surface roughness as a function of fractal parameters, in all cases indicating surface fractals of the large‐scale scattering object, namely the `grain'. Mesoporous COF studies allowed elucidation of their hexagonal structure on the basis of their structure peaks; however, the main result lies in the distinction between the pore and the grain, which are described as a hierarchical structure by the Beaucage model and evaluated according to their fractality. These COFs generally exhibit pores with mass fractal features and grains with surface fractal features when they are submitted to post‐functionalization, which may be due to the poor diffusivity of the functionalizing agents into the pores. In addition, a proposed aggregation description of the porous scattering objects was envisioned, based on small‐angle scattering premises, which was confirmed for a microporous COF by high‐resolution transmission electron microscopy.
Small‐angle X‐ray scattering models are applied to covalent organic frameworks in order to analyse fractal parameters and structure–scattering relationships.
PDF
