120 research outputs found
A study of thermoassociative gelation of aqueous cationic poly(N-isopropyl acrylamide) graft copolymer solutions
No full textIn this work thermoassociative gel formation of a new family of aqueous temperature-responsive copolymer solutions has been investigated. This was achieved using a cationic poly(N-isopropyl acrylamide) (PNIPAm) graft copolymer recently prepared [Liu R, De Leonardis P, Cellesi F, Tirelli N, Saunders BR. Langmuir 2008;24:7099]. The PDMA+x-g-(PNIPAmn)y copolymers have x and y values that originate from the macroinitiator; the value for n corresponds to the PNIPAm arm length. DMA+ is quarternarized N,N-dimethylaminoethyl methacrylate. The copolymer solutions exhibited cloud point temperatures (Tclpt) of about 33 °C, which were not significantly affected by x/y ratio or the value for n. Thermoassociative gel formation occurred above Tclpt at copolymer concentrations (Ccopol) greater than or equal to 4 wt.%. This is a reasonably low Ccopol value and is a consequence of the graft copolymer architecture employed. We investigated the effect of temperature, Ccopol and copolymer structure on gelation and gel elasticity using variable - temperature dynamic rheology. For PDMA+30-g-(PNIPAm210)14 solutions at 39 °C it was found that G′ (elastic modulus) scales with Ccopol according to G′ ∼ Ccopol3.85. The data suggested that a significant proportion of PNIPAm units is not directly involved in network formation. Thermoassociative gel formation and the gel properties for these systems appear to be governed by a balance between electrostatic repulsion involving the DMA+ units (favouring spatial extension of the copolymer backbones) and attractive hydrophobic interactions between PNIPAm side chains (favouring associative crosslink formation). © 2009 Elsevier Ltd. All rights reserved
Outbreak and persistence of Chlamydia pneumoniae infection in a Italian family
No full textWe describe an outbreak of familial infection of Chlamydia pneumoniae, an etiological agent for respiratory tract infections. In a family member detection of C. pneumoniae on a pharyngeal swab by polymerase chain reaction was positive until four months after the onset of symptoms, despite a course of antibiotics known to be effective against Chlamydia specie
Human bocavirus detection in an atopic child affected by pneumonia associated with wheezing
No full textBackground: Human bocavirus (HBoV) is a newly discovered human parvovirus. HBoV was detected in respiratory samples by PCR, but its aetiologic role in the pathogenesis of acute respiratory infectious diseases is still unclear. Results: In this report, we describe an atopic child affected by pneumonia, with a past history of wheezing. A panel of bacteria and respiratory viruses were searched in the nasopharyngeal swab, only human bocavirus was detected by PCR. Conclusions: Detection of HboV, as the only microbial agent, in samples from children with wheezing and acute respiratory diseases supports the assumption that this emerging virus could have an aetiologic role in the pathogenesis of respiratory diseases. © 2007 Elsevier B.V. All rights reserved
Muscular-skeletal cryptococcosis in a patient with idiopathic CD4+ lymphopenia
No full textA healthy 27-year-old woman presented, four months after childbirth, ingravescent pain and claudication of the left lower limb. Magnetic Resonance Imaging of the lumbosacral and iliac regions showed widespread muscular-skeletal lesions. The patient underwent surgery; Cryptococcus neoformans was isolated from surgical samples. Liposomal amphotericin B, fluconazole and itraconazole were administered. Laboratory findings showed lymphocytopenia, with reduction of CD4+ lymphocytes (23 cells per cubic millimeter) in the absence of HIV infection and any other defined immunodeficiency. This is a rare case of muscular-skeletal cryptococcal infection isolated in a subject affected with idiopathic CD4+ lymphocytopenia
Water-Dispersible, Ligand-Free, and Extra-Small (< 10 nm) Titania Nanoparticles: Control Over Primary, Secondary, and Tertiary Agglomeration Through a Modified "Non-Aqueous" Route
No full textNon-aqueous routes to inorganic nanoparticles are supposedly based on the absence of water; here, this view is partially challenged, showing that the presence of water (or moisture) is probably necessary, and is surely useful to achieve a precise control over the growth/aggregation phenomena leading to titanium dioxide nanoparticles.This study is focused on the preparation of size-controlled and ligand-free titania (anatase) nanoparticles in water dispersion. This is achieved through a three-step process: 1) production of primary (3-4 nm) nanoparticles from titanium alkoxides (Ti(OnPr)(4), Ti(OnBu)(4) or Ti((OPr)-Pr-i)(4)) in benzyl alcohol through the controlled addition of water; 2) thermal growth phase, where the aggregation of primary nanoparticles at 80 degrees C leads to secondary nanoparticles with a typical fractal dimension of 2.2-2.4; the primary particles are still identifiable as the individual crystallites composing the secondary nanoparticles; 3) precipitation/re-dispersion in water, where secondary nanoparticles further agglomerate to yield tertiary nanoparticles. The size of the latter and their photocatalytic efficiency is primarily controlled by the nature of residual alkoxide chains; in particular, isopropoxide groups allow to produce anatase nanoparticles with an average size of 7-8 nm in water dispersion and in the absence of any stabilizing ligand, which is an unprecedented result
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