Infection with the parasitic nematode Strongyloides stercoralis is characteristic for tropical and subtropical regions of the world, but autochthonous cases have been reported in European countries as well. Here we present the first nation-wide survey of S. stercoralis seroprevalence in Croatian individuals presenting with eosinophilia, and evaluate the fraction of positive microscopy rates in stool specimens of seropositive individuals. In our sample of 1407 patients tested between 2018 and 2021, the overall prevalence of strongyloidiasis was 9.31%, with significantly higher rates in those older than 60 years of age (P = 0.005). Of those, one-quarter (25.95%) were also positive following microscopy examination of faeces after using the merthiolate–iodine–formaldehyde concentration method. Our findings reinforce the notion of endemic strongyloidiasis transmission in Croatia, particularly in older individuals, and highlight the need to consider the presence of S. stercoralis in patients with eosinophilia.

The helminth infection caused by Strongyloides stercoralis is widespread in tropical regions, but rare in European countries. Unfamiliarity with the disease and diagnostic obstacles could contribute to its lethal outcome. Frequent use of corticosteroids during the COVID-19 pandemic could increase its significance. The aim of this retrospective descriptive study was to explore disease patterns and discuss clinical dilemmas in patients with S. stercoralis hyperinfection treated at the University Hospital for Infectious Diseases ‘Dr. Fran Mihaljević’ in Zagreb, Croatia, between 2010 and 2021. Five out of 22 (22.7%) immunosuppressed patients treated due to strongyloidiasis developed hyperinfection. All patients were male, median 64 years; four were immunosuppressed by corticosteroids (although ileum resection could have been the trigger in one) and one by rituximab. The diagnosis was established after a median of 1.5 months of symptom duration, accidentally in all patients, by visualizing the parasite in the gastric/duodenal mucosa in four cases, and bronchial aspirate in one. All patients were cachectic, four out of five had severe hypoalbuminemia and all suffered secondary bacterial/fungal infection. Despite combined antibiotic, antifungal and antihelmintic therapy, three out of five of the patients died, after failing to clear living parasites from stool samples. We can conclude that significant delays in diagnosis and lack of clinical suspicion were observed among our patients with the most severe clinical presentations of strongyloidiasis. Although being beyond diagnostic recommendations for strongyloidiasis, an early upper gastrointestinal endoscopy with mucosal sample analysis could expedite diagnosis in severe, immunosuppressed patients. The persistence of viable parasites in the stool despite antihelmintic therapy should be further investigated.

Coatings of plasma sprayed hydroxyapatite (HAp), incubated in simulated body fluid for periods varying from 1 to 56 days, were characterized using conventional laboratory X rays. Quantitative phase analysis, employing TOPAS software, showed an opposite trend in the two main phases of the coating, viz., HAp and tetracalcium phosphate (TTCP). The former increased within the first 7 days of incubation whilst the latter decreased during the same period; both phases stabilized with further incubation. The crystallinity of the coatings exhibited a trend similar to that of HAp i.e., an increase in the early stages of incubation stabilization with further incubation. Results of residual stress determined with Bruker’s D8 Discover and analyzed with LEPTOS software, showed both the normal stress tensor components, σ11 and σ22, to be tensile, relaxing significantly in the early stages of incubation before stabilizing with further incubation.

In order to improve light trapping in thin-film silicon solar cells two novel approaches are investigated in this article: angle-selective management of light scattering inside the solar cell and wavelength-selective manipulation of high reflectance or transmittance of light. Diffraction gratings are analyzed as a representative of the first approach. Haze and angular distribution function of scattered (diffracted) light in reflection are measured for aluminum-based rectangular periodic gratings with different period and height of the rectangles. High haze values in specific wavelength region and scattering angles of the investigated gratings measured in air and water agree very well with the theoretical predictions. Considering the actual optical situation in microcrystalline silicon solar cells, optimal period and height of the rectangular gratings applied as a back reflector are calculated for obtaining the total reflection at the front interfaces. In the frame of the second approach, photonic-crystal-like structures are introduced. By means of optical simulations photonic-crystal-like structures are investigated for two possible applications: an intermediate reflector in a micromorph silicon solar cell with wavelength-selective reflectivity and a dielectric back reflector with a high reflectance in the long-wavelength region. The photonic crystal structure consisting of sequences of n-doped amorphous silicon and ZnO layers is designed for the efficient intermediate reflector. For the back reflector with a high reflectance the structures with intrinsic amorphous silicon, SiO2, MgF2 and TiO2 are proposed.

The descriptive scattering parameters, haze and angular distribution functions of textured ZnO:Al transparent conductive oxides with different surface roughness are measured. An approach to determine the scattering parameters of all internal interfaces in p-i-n a-Si:H solar cells deposited on the glass/ZnO:Al substrates is presented. Using the determined scattering parameters as the input parameters of the optical model, a good agreement between the measured and simulated quantum efficiencies of the p-i-n a-Si:H solar cells with different interface roughness is achieved.

Using numerical simulator, the operational principle of two-terminal a-Si:H based three-color detectors with the multi-layer multi-bandgap PIN or PIIiN structure is investigated. Two different approaches, which lead to bias-controlled three-color detection, are described and evaluated in terms of spectral response, rejection ratio, color suppression, illumination intensity and bias-light. For both PIIN and PIIN structure, bias-light dependence and intensity dependence is investigated. Numerical simulation results showed strong negative correlation between color separation and bias-light sensitivity. The importance of the transparent conducting oxide for the three-color detection limits is demonstrated.

Using suitable simplifying approximations inside the particular regions of a p-i a-Si/n c-Si heterojunction solar cell, the analytical expressions for the solar cell current-voltage characteristics are derived showing clearly the dominating first-order effects on solar cell performance. The derived closed form solutions indicate that in the useful forward voltage range the largest dark current component of this cell is the interface recombination current and that the main contribution to the photocurrent comes from the light generated holes in the c-Si substrate layer. The transfer of holes across the intrinsic layer and over the ΔEv barrier is strongly suppressed resulting in an attenuation of solar cell dark and photocurrent.