Electronicly controlled isolating autotransformer

The goal of this work was to build a universal fully controllable laboratory power supply with AC output voltage. Main emphasis has been put on the final quality and durability of the power supply. Output voltage regulation is based on the principle of serial switching of secondary windings. The intelligent microprocessor control with alphanumeric display is also integrated in power supply. Realized power supply is suitable for universal applications, not only in electrical laboratories. Three fuses, electronic current and voltage limiters allow usage of this power supply also in school laboratories. The galvanic isolation is provided by a safety isolation of main transformers

Community structure, picoplankton grazing and zooplankton control of heterotrophic nanoflagellates in a eutrophic reservoir during the summer phytoplankton maximum

An intensive 5 wk study was conducted to investigate the role of protists, especially heterotrophic nanoflagellates (HNF), in microbial food webs during the summer phytoplankton bloom in the epilimnion and metalimnion of the eutrophic Rimov reservoir (South Bohemia, Czech Republic). On average, protists consumed similar to 90% of bacterial production in both layers. The community composition of HNF and the relative importance of different HNF groups as picoplankton consumers were determined. Small HNF (<8 mu m), as chrysomonads, bodonids and choanoflagellates, usually accounted for <30% of total HNF biomass but numerically dominated the community in both layers. They consumed most of (similar to 70 to 85 %) the bacterioplankton as well as autotrophic picoplankton (APP, exclusively cyanobacteria) production in the reservoir, with the rest consumed by ciliates. Both ciliates and HNF had higher clearance rates on APP than on bacteria and their grazing was likely responsible for a sharp decrease in APP abundance (from 3-4 x 10(5) to <2 x 10(3) ml(-1)) and a very constant size structure of bacterioplankton in which short rods in the size class of 0.4 to 0.8 mu m constituted 55 to 80 % of the total bacterial biomass in both layers. The proportion of HNF to total picoplankton biomass in the epilimnion indicated that the picoplankton biomass was sufficiently high to support HNF growth for most of the study. Uptake of picoplankton by less numerous, but larger, HNF (kathablepharids, Goniomonas sp., and Streptomonas sp.) was negligible, while their biomass, especially in the metalimnion, exceeded that of small HNF and the total biomass of picoplankton. This suggested that food items other than picoplankton were consumed to meet their carbon requirements. Analyzing potential bottom-up and top-down factors controlling HNF numbers and biomass, we did not find a tight relationship between HNF and the concentration of bacteria and chlorophyll. Variability of HNF abundance and biomass in the epilimnion could largely be explained by cladocerans or by pooled abundances of all potential crustacean consumers of HNF. In the metalimnion, the mean cell volume of HNF was positively linked to chlorophyll but negatively to the abundance of Cyclopidae and to the pooled abundances of Ceriodaphnia quadrangula and Diaphanosoma brachyurum

Changes in bacterial community composition and dynamics and viral mortality rates associated with enhanced flagellate grazing in a mesoeutrophic reservoir

Bacterioplankton from a meso-eutrophic dam reservoir was size fractionated to reduce (80% of the total bacteria by the end of the experiment. Once again, BCC changed strongly and a significant fraction of the large filaments was detected using a FISH probe targeted to members of the Flectobacillus lineage. Shifts of BCC were also reflected in DGGE patterns and in the increases in the relative importance of both beta proteobacteria and members of the Cytophaga-Flavobacterium cluster, which consistently formed different parts of the bacterial flocs. Viral concentrations and frequencies of infected cells were highly significantly correlated with grazing rates, suggesting that protistan grazing may stimulate viral activity

Influence of C60 fullerenes on the glass formation of polystyrene

AbstractWe investigate the impact of fullerene C60 on the thermal properties and glass formation of polystyrene (PS) by differential scanning calorimetry (DSC) and dielectric spectroscopy (DS), for C60 concentrations up to 30% mass fraction. The miscibility and dispersibility thresholds of PS/C60 nanocomposites are first estimated by a combination of microscopy, small angle neutron scattering (SANS) and wide-angle X-ray scattering (WAXS) experiments, and these thresholds were found to be ≃1 mass% and ≃4 mass% C60, respectively. The addition of C60 increases the glass-transition temperature (Tg) of rapidly precipitated PS composites, up to a ‘threshold’ C60 concentration (≃4 wt%, in agreement with the dispersibility estimate). Beyond this concentration, the Tg reverts gradually towards the neat PS value. We present a comprehensive study for composites based on PS of molecular mass 270 kg/mol, and demonstrate the generality of the impact of C60 on Tg for PS matrices of 2 and 20 kg/mol. Thermal annealing or slowly evaporated composites largely reverse these effects, as the dispersion quality decreases. The dynamic fragility m of the composite is found to increase in the presence of C60, but the scaling of m with Tg for PS is retained. Similarly, physical ageing experiments show a reduction of relaxation enthalpy in the glass regime, which is largely accounted for by the increase of Tg with C60. The slowing down of the PS α-relaxation with C60 contrasts with the local ‘softening’ indicated by former Debye-Waller measurements and increase in fragility m. This effect is opposite to that of antiplasticizer additives, which both stiffen the material in the glassy state and reduce Tg, and simulations suggest this could be due to an increase in packing frustration. Finally, we review observations on the effect of nanoparticles on the Tg of PS and discuss the non-universal nature of Tg shifts by various types of nanoparticles

Fundus-DeepNet: Multi-Label Deep Learning Classification System for Enhanced Detection of Multiple Ocular Diseases through Data Fusion of Fundus Images

YesDetecting multiple ocular diseases in fundus images is crucial in ophthalmic diagnosis. This study introduces the Fundus-DeepNet system, an automated multi-label deep learning classification system designed to identify multiple ocular diseases by integrating feature representations from pairs of fundus images (e.g., left and right eyes). The study initiates with a comprehensive image pre-processing procedure, including circular border cropping, image resizing, contrast enhancement, noise removal, and data augmentation. Subsequently, discriminative deep feature representations are extracted using multiple deep learning blocks, namely the High-Resolution Network (HRNet) and Attention Block, which serve as feature descriptors. The SENet Block is then applied to further enhance the quality and robustness of feature representations from a pair of fundus images, ultimately consolidating them into a single feature representation. Finally, a sophisticated classification model, known as a Discriminative Restricted Boltzmann Machine (DRBM), is employed. By incorporating a Softmax layer, this DRBM is adept at generating a probability distribution that specifically identifies eight different ocular diseases. Extensive experiments were conducted on the challenging Ophthalmic Image Analysis-Ocular Disease Intelligent Recognition (OIA-ODIR) dataset, comprising diverse fundus images depicting eight different ocular diseases. The Fundus-DeepNet system demonstrated F1-scores, Kappa scores, AUC, and final scores of 88.56%, 88.92%, 99.76%, and 92.41% in the off-site test set, and 89.13%, 88.98%, 99.86%, and 92.66% in the on-site test set.In summary, the Fundus-DeepNet system exhibits outstanding proficiency in accurately detecting multiple ocular diseases, offering a promising solution for early diagnosis and treatment in ophthalmology.European Union under the REFRESH – Research Excellence for Region Sustainability and High-tech Industries project number CZ.10.03.01/00/22_003/0000048 via the Operational Program Just Transition. The Ministry of Education, Youth, and Sports of the Czech Republic - Technical University of Ostrava, Czechia under Grants SP2023/039 and SP2023/042

A general mechanism for controlling thin film structures in all-conjugated block copolymer : fullerene blends

Block copolymers have the potential to self-assemble into thermodynamically stable nanostructures that are desirable for plastic electronic materials with prolonged lifetimes. Fulfillment of this potential requires the simultaneous optimisation of the spatial organisation and phase behaviour of heterogeneous thin films at the nanoscale. We demonstrate the controlled assembly of an all-conjugated diblock copolymer blended with fullerene. The crystallinity, nanophase separated morphology, and microscopic features are characterised for blends of poly(3-hexylthiophene-block-3-(2-ethylhexyl) thiophene) (P3HT-b-P3EHT) and phenyl-C61-butyric acid methyl ester (PCBM), with PCBM fractions varying from 0–65 wt%. We find that PCBM induces the P3HT block to crystallise, causing nanophase separation of the block copolymer. Resulting nanostructures range from ordered (lamellae) to disordered, depending on the amount of PCBM. We identify the key design parameters and propose a general mechanism for controlling thin film structure and crystallinity during the processing of semicrystalline block copolymers

2‐Methyltetrahydrofuran (2‐MeTHF) as a versatile green solvent for the synthesis of amphiphilic copolymers via ROP, FRP, and RAFT tandem polymerizations

2‐methyltetrahydrofuran (2‐MeTHF) is a readily available, inexpensive, neoteric, bio‐based solvent. It has been adopted across a wide range of chemical processes including the batch manufacture of fine chemicals, enzymatic polycondensations and ring opening polymerizations. To reduce the environmental burden related to the synthesis of pharmaceutical‐grade polymers based on lactide and caprolactone, we envisaged the use of 2‐MeTHF. For the first time, we combined a series of metal‐free and enzymatic ROPs with free radical and controlled RAFT polymerizations (carried out separately and in tandem) in 2‐MeTHF, in order to easily tune the chemistry and the architecture of the final polymers. After a simple purification, the amphiphilic polymers were formulated into nanoparticles and tested for their cytocompatibility in three model cell lines, to assess their application as potential polymeric excipients for nanomedicines