The Complemented System Approach: A Novel Method for Calculating the X-ray Scattering from Computer Simulations

In this paper, we review the main problem concerning the calculation of X-ray scattering of simulated model systems, namely their finite size. A novel method based on the Rayleigh-Debye-Gans approximation was derived, which allows sidestepping this issue by complementing the missing surroundings of each particle with an average image of the system. The method was designed to operate directly on particle configurations without an intermediate step (e.g., calculation of pair distribution functions): in this way, all information contained in the configurations was preserved. A comparison of the results against those of other known methods showed that the new method combined several favourable properties: an arbitrary q-scale, scattering curves free of truncation artifacts and good behaviour down to the theoretical lower limit of the q-scale. A test of computational efficiency was also performed to establish a relative scale between the speeds of all known methods: the reciprocal lattice approach, the brute force method, the Fourier transform approach and the newly presented complemented system approach.Comment: 6 pages, 5 figures. Copyright 2010 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in The Journal of Chemical Physics and may be found at http://link.aip.org/link/?jcp/133/17412

Solvation of Nonionic Poly(Ethylene Oxide) Surfactant Brij 35 in Organic and Aqueous-Organic Solvents

Hypothesis: By combining the experimental small- and wide-angle x-ray scattering (SWAXS) method with molecular dynamics simulations and the theoretical 'complemented-system approach' it is possible to obtain detailed information about the intra- and inter-molecular structure and dynamics of the solvation and hydration of the surfactant in organic and mixed solvents, e.g., of the nonionic surfactant Brij 35 (C12E23) in alcohols and aqueous alcohol-rich ternary systems. This first application of the complemented-system approach to the surfactant system will promote the use of this powerful methodology that is based on experimental and calculated SWAXS data in studies of colloidal systems. By applying high-performance computing systems, such an approach is readily available for studies in the colloidal domain. Experiments: SWAXS experiments and MD simulations were performed for binary Brij 35/alcohol and ternary Brij 35/water/alcohol systems with ethanol, n-butanol and n-hexanol as the organic solvent component at 25 {\deg}C. Findings: We confirmed the presence of solvated Brij 35 monomers in the studied organic media, revealed their preferential hydration and discussed their structural and dynamic features at the intra- and inter-molecular levels. Anisotropic effective surfactant molecular conformations were found. The influence of the hydrophobicity of the organic solvent on the hydration phenomena of surfactant molecules was explained.Comment: 31 pages, 6 figures, 1 tabl

COLOUR DOPPLER SONOGRAPHY OF FACIAL AND OCCIPITAL ARTERIES IN PATIENTS WITH GIANT CELL ARTERITIS

Background: Giant cell arteritis (GCA) is the most common systemic large and medium size artery vasculitis in Western countries. Colour Doppler Sonography (CDS) allows the study of involvement of cranial arteries other than the temporal arteries, which are inconvenient to biopsy, such as the facial (FaA), and occipital (OcA) arteries. Objectives: We aimed to estimate the frequency of the FaA, and OcA involvement in GCA; and to explore the clinical characteristics of these subgroups of patients. Methods: From 1 January 2014 to 31 December 2016, we prospectively performed a CDS of the FaA, and OcA in addition to the temporal (TA), and the extracranial supra-aortic arteries in all newly diagnosed patients suspected of having GCA. We used a Philips IU22 with a 5–17.5 MHz multi-frequency linear probe from January 2014 to August 2016 and a Philips Epiq 7 with a 5–18 MHz multi-frequency linear probe from September 2016 to December 2016. All the arteries were evaluated in two planes for the highly specific halo-sign. Results: During the 36-month observation period we performed a CDS of the cranial and extra-cranial arteries in 93 GCA (66.7% female) patients. The patients’ median (IQR) age was 73.7 (66.1–79.1) years, and they had a median (IQR) symptom duration of 30 (21–90) days. We observed the halo-sign on the FaA, and OcA in 38 (40.9%), and 29 (31.2%) cases, respectively. The FaA, and OcA were simultaneously affected in 18/93 (19.4%) cases. Either FaA, or OcA were affected in 4/22 (18.2%) patients with a negative TA CDS. FaA involvement significantly correlated with jaw claudication and with severe visual manifestations, including permanent visual loss. Patients with OcA involvement least commonly had extracranial large vessel disease. Conclusions: A fifth of patients with a negative CDS of the TAs had signs of vasculitis on the CDS of the FaA, or OcA. Th e addition of FaA and OcA CDS to the routine CDS of the TAs could identify 4.3% more patients and thus further improve the sensitivity of the CDS in the suspected GCA. References: 1. Ješe R, Rotar Ž, Tomšič M, Hočevar A. Th e role of colour doppler ultrasonography of facial and occipital arteries in patients with giant cell arteritis: A prospective study. European Journal of Radiology. 2017;95:9–12

Short-term outcome of patients with adult IgA vasculitis: a single-center experience

BackgroundFollow-up data on IgA vasculitis (IgAV) in adults are scarce. We aimed to investigate the outcome of adult IgAV in a well-defined cohort.MethodsData from histologically proven patients diagnosed between January 2010 and July 2022 with at least a 3-month follow-up were analyzed. The frequency and type of relapses and information on kidney function were extracted. Risk factors for IgAV relapse and decline in renal function were studied using the Cox hazards regression analysis. Mortality in IgAV was assessed using the Kaplan–Meier analysis and the standardized mortality ratio (SMR).ResultsIn total, 265 patients were followed for a median of 24 months. At baseline, 38.9, 29.8, and 44.5% had articular, gastrointestinal, and renal involvement, respectively. Initially, 189 (71.3%) patients received systemic glucocorticoids, and 32 (12.1%) patients received an additional immunomodulator. During follow-up, 42 (15.8%) patients relapsed. Relapses were more common in younger patients (HR 1.03 [95%CI 1.01–1.05]) and those without baseline glucocorticoid treatment (HR 3.70 [95%CI 2.0–6.67]). Furthermore, 74 (27.9%) patients had persistent abnormal urinalysis and a substantial (≥20%) decline in glomerular filtration rate (eGFR) was recorded in 41 (15.5%) patients. The factors associated with persistent abnormal urinalysis were an absence of IgAV joint involvement and baseline immunomodulatory treatment. Pre-existent chronic kidney disease and heart failure were associated with eGFR decline. The overall SMR was 1.4 (95%CI 1.14–1.71) compared to the Slovenian general population.ConclusionIgAV relapses occurred in 15% of patients, with younger patients with symptomatically managed IgAV experiencing it more frequently. Heart failure emerged as a predictor of persistent abnormal urinalysis and a decline in eGFR. Adults with IgAV had increased mortality compared to the general population

Structural, Rheological and Dynamic Aspects of Hydrogen-Bonding Molecular Liquids: Aqueous Solutions of Hydrotropic tert-Butyl Alcohol

Hypothesis: The structural details, viscosity trends and dynamic phenomena in t-butanol/water solutions are closely related on the molecular scales across the entire composition range. Utilizing the experimental small- and wide-angle x-ray scattering (SWAXS) method, molecular dynamics (MD) simulations and the ‘complemented-system approach’ method developed in our group it is possible to comprehensively describe the structure-viscosity-dynamics relationship in such structurally versatile hydrogen-bonded molecular liquids, as well as in similar, self-assembling systems with pronounced molecular and supramolecular structures at the intra-, inter-, and supra-molecular scales. Experiments: The SWAXS and x-ray diffraction experiments and MD simulations were performed for aqueous t-butanol solutions at 25 °C. Literature viscosity and self-diffusion data were also used. Findings: The interpretive power of the proposed scheme was demonstrated by the extensive and diverse results obtained for aqueous t-butanol solutions across the whole concentration range. Four composition ranges with qualitatively different structures and viscosity trends were revealed. The experimental and calculated zero-shear viscosities and molecular self-diffusion coefficients were successfully related to the corresponding structural details. The hydrogen bonds 2 that were, along with hydrophobic effects, recognized as the most important driving force for the formation of t-butanol aggregates, show intriguing lifetime trends and thermodynamic properties of their formation

Koga, kdaj in kako napotiti k revmatologu

V Sloveniji kljub pomanjkanju revmatologov in s tem daljšimi čakalnimi dobami revmatološkim bolnikom zagotavljamo sodobno obravnavo, ki je primerljiva z delom v najbolj priznanih svetovnih ustanovah. Da visoko raven obravnave tudi vprihodnosti ohranimo, je bistvenega pomena, da so poslane napotnice primerno izpolnjene in opremljene z vsemi podatki, ki jih potrebujemo za ustrezno razvrščanje v čakalno knjigo glede na resnost in vrsto bolezni (triažiranje). V prispevku podajamo osnovna navodila glede napotitev v revmatološko ambulanto s strokovno ustreznimi stopnjami nujnosti

Epidemiologija i dijagnostika primarnoga Sjögrenovog sindroma

This review paper contains selected aspects of Sjögren’s syndrome. It consists of epidemiology, ultrasound of salivary glands and antimuscarinic antibodies. The first part present studies aimed to determine the prevalence and the incidence of the disease with special emphasize on epidemiological studies performed in Slovenia. This is followed by the demonstration of the role of ultrasound of salivary glands in the diagnosis of Sjögren’s syndrome and the value of antimuscarinic antibodies in global assesment of the secretory failure.U preglednom su članku opisani epidemiologija, ultrazvučni nalaz slinovnica i antimuskarinska antitijela u Sjögrenovom syndromu. U prvomu su dijelu rada prikazani prevalencija i incidencija bolesti u odnosu na epidemiološke studije u Sloveniji. Prikazana je uloga ultrazvučne pretrage slinovnica u dijagnozi Sjögrenova sindroma i vrijednost antimuskarinskih antitijela u općoj procjeni sekrecijske poremetnje