Investigation of polyurethane electrospinning process efficiency

The electrospinning process efficiency of different PUs has been investigated. Specific attention has been paid to understand the role of PU soft segments and synthesis type on the stability of the PU solution and electrospinning process as well as on the quality/property changes of the produced nanofibres. PU samples before and after the process were analyzed rheologicaly and relaxation spectra were determined for all of them from frequency dependent loss and storage moduli measurements. It has been found that rheological analysis of PU, which is used for electrospinning process, can be useful tool from electrospinning process efficiency and optimization point of view. Nanolayers homogeneity during several hours of manufacture in optimized electrospinning process is proved by selected properties from aerosol filtration. © 2009 American Institute of Physics

Enterohemorrhagic Escherichia coli as Causes of Hemolytic Uremic Syndrome in the Czech Republic

Background: Enterohemorrhagic Escherichia coli (EHEC) cause diarrhea-associated hemolytic uremic syndrome (D+ HUS) worldwide, but no systematic study of EHEC as the causative agents of HUS was performed in the Czech Republic. We analyzed stools of all patients with D+ HUS in the Czech Republic between 1998 and 2012 for evidence of EHEC infection. We determined virulence profiles, phenotypes, antimicrobial susceptibilities and phylogeny of the EHEC isolates. Methodology/Principal Findings: Virulence loci were identified using PCR, phenotypes and antimicrobial susceptibilities were determined using standard procedures, and phylogeny was assessed using multilocus sequence typing. During the 15-year period, EHEC were isolated from stools of 39 (69.4%) of 56 patients. The strains belonged to serotypes [fliC types] O157:H7/NM[fliCH7] (50% of which were sorbitol-fermenting; SF), O26:H11/NM[fliCH11], O55:NM[fliCH7], O111:NM[fliCH8], O145:H28[fliCH28], O172:NM[fliCH25], and Orough:NM[fliCH25]. O26:H11/NM[fliCH11] was the most common serotype associated with HUS (41% isolates). Five stx genotypes were identified, the most frequent being stx2a (71.1% isolates). Most strains contained EHEC-hlyA encoding EHEC hemolysin, and a subset (all SF O157:NM and one O157:H7) harbored cdt-V encoding cytolethal distending toxin. espPα encoding serine protease EspPα was found in EHEC O157:H7, O26:H11/NM, and O145:H28, whereas O172:NM and Orough:NM strains contained espPγ. All isolates contained eae encoding adhesin intimin, which belonged to subtypes β (O26), γ (O55, O145, O157), γ2/θ (O111), and ε (O172, Orough). Loci encoding other adhesins (efa1, lpfAO26, lpfAO157OI-141, lpfAO157OI-154, iha) were usually associated with particular serotypes. Phylogenetic analysis demonstrated nine sequence types (STs) which correlated with serotypes. Of these, two STs (ST660 and ST1595) were not found in HUS-associated EHEC before. Conclusions/Significance: EHEC strains, including O157:H7 and non-O157:H7, are frequent causes of D+ HUS in the Czech Republic. Identification of unusual EHEC serotypes/STs causing HUS calls for establishment of an European collection of HUS-associated EHEC, enabling to study properties and evolution of these important pathogens

Pressure sensor and process for producing thereof

Tlakový senzor má soudržnou laminátovou strukturu, je tvořena plošným nosičem o tloušťce v rozmezí desítek až tisíc .mi.m, vytvořeným na bázi termoplastického polymeru, na němž je ukotvena senzorická vrstva tloušťky v rozmezí jednotek až stovek .mi.m, sestávající z navzájem propletených vícevrstevnatých uhlíkových nanotrubiček s průměrem 5 až 100 nm a délkou 1-20 .mi.m, s porozitou 0,5 až 0,9 a měrným odporem 0,01 až 1 .OMEGA./cm, a tato senzorická vrstva je zapojena do elektrického obvodu vybaveného snímačem odporu připojeným na výstup opatřený relevantní signalizací hodnoty tlaku. Způsob výroby tlakového senzoru podle vynálezu spočívá v tom, že z termoplastického polymeru se elektrostatickým zvlákňováním vyrobí filtrační membrána, z uhlíkových nanotrubiček a alespoň jednoho surfaktantu se připraví vodná disperze, nejlépe mícháním ultrazvukem, tato vodná disperze se rovnoměrně nanese na filtrační membránu porozity 0.1 a tloušťky v řádu 50 .mi.m až 2 cm, provede se filtrace vodné báze, promytí, sušení načež následuje zalisování vrstvy uhlíkových nanotrubiček s filtrační membránou za teploty zvýšené nad teplotu tání polymeru, vzniklý soudržný laminát se skrze senzorickou vrstvu začlení do elektrického obvodu se snímačem odporu s výstupem na signalizaci, načež se působením jmenovitého tlaku na senzorickou vrstvu provede kalibrace této signalizace na hodnoty tlaku

The effect of PVAc solution viscosity on diameter of PVAc nanofibres prepared by technology of electrospinning

Polyvinyl acetate (PVAc) nanofibers were prepared by technology of electrospinning with help of multi-jets electrospinning machine from acetic acid/water solvent system. The stability of the process was tested in a broad concentration region from 5 to 40 wt. % of PVAc. The main attention was carried out to study the effect of polyvinyl acetate solution concentration/viscosity onto mean diameter of prepared nanofibers. It was found that increased solution viscosity leads to increase of fibers diameters from appox. 60 nm at viscosity similar to 0.04 Pa.s to appox. 1000 nm at viscosity similar to 6-7 Pa.s. The PVAc nanofibres can be considered as a potential precursor for preparation of inorganic fibrous nanoparticles. Their dimensions can be effectively controlled by PVAc nanofibers diameter by easy diameter - concentration/viscosity optimalization

Isolation of Members of the Staphylococcus sciuri Group from Urine and Their Relationship to Urinary Tract Infections

During a 3-year study period, 32,741 urine samples were analyzed for the presence of members of the Staphylococcus sciuri group (S. sciuri, S. lentus, and S. vitulinus), and 13 isolates were identified. They presented 0.79% of the total number of coagulase-negative staphylococci isolated. One case of symptomatic urinary tract infection and five possible cases of asymptomatic bacteriuria caused by these bacteria were established. It is noteworthy, however, that over 50% of the isolates originated from hospitalized patients

A flexible multifunctional sensor based on carbon nanotube/polyurethane composite

A sensor was made of a polymer composite composed of electrically- conductive carbon nanotubes embedded in elastic polyurethane. The composite was prepared using a polyurethane filter membrane, enmeshing it, and melding together with carbon nanotubes. Testing has shown that the composite can be elongated as much as 400% during which the electrical resistance is increased 270 times. The composite is also sensitive to compression and to organic solvent vapors. These properties indicate the composite could have applications as a highly-deformable strain and chemical vapors sensing element and also as flexible electromagnetic shielding or protection against lightning. As an example of the use of the composite as a strain sensor, the pressure variation between a shoe and floor during walking and knee flexion during cycling has been monitored. © 2013 IEEE

Polyurethane/MWCNT nanowebs prepared by electrospinning process

Polyuretan, PU, a PU/MWCNT nanokompozitní nanovlákna obojí s průměry 350 nm byly připraveny technologií elektrostatického zvlákňování z roztoku v dimethyl formamidu. SEM analýzou byla pozorována existence nanosítěk u PU/MWCNT kompozitu s průměry vláken 20-40 nm. Předpokládá se existence sekundárního elektrického pole vlivem elektricky vodivých MWCNT částic které způsobuje tento efekt růstu síťové struktury mezi vlákny. Podle našich znalostí je toto první report popisující vznik těchto nanosítěk ze syntetických polymerů.Polyurethane, PU, and PU/MWCNT (Multi Wall Carbon Nanotubes) nanocomosite nanofibers both with diameter 350 nm were prepared by electrospinning process from PU dimethyl formamide solutions. Appearance of nanowebs in PU/MWCNT nanofibers structure containing polyurethane fibers with diameter 20-40 nm was observed. The existence of these structures can be based on the occurrence of strong secondary electric fields which are created between individual conducting MWCNTs (distributed in PU/MWCNT nanocomposite) which start to behave as the local moving nanoelectrodes promoting creation of additional very fine nanowebs during electrospinning processes. To our knowledge, this is the first report describing nanowebs from synthetic polymers prepared by electrospinning process