Water-based polyurethane dispersions: chemistry, technology and applications

Over the past few decades, polyurethane-polyurea aqueous dispersions (PUDs) have developed a solid reputation for high performance applications, particularly in the field of adhesives and coatings. PUDs are mostly environmentally compatible products; they are totally devoid or contain only low amounts of volatile organic compounds (VOC). This is an important feature in view of the present environmental policies where governments and internal agencies are placing emphasis on developing sustainable processes, improving work conditions and reducing emissions of toxic and polluting substances into the atmosphere. In the past years, our research group has been involved in the development of polyurethane-polyurea aqueous dispersions for two main applications (footwear and indirect food contact). With this work we intend to review this theme and describe some of the achieved developments. Characterization of commercial dispersions will be presented and examples of synthesis will be described, following a modified pre-polymer process developed in our group

Description of Lyme disease-like syndrome in Brazil: is it a new tick borne disease or Lyme disease variation?

An emerging clinical entity that reproduces clinical manifestations similar to those observed in Lyme disease (LD) has been recently under discussion in Brazil. Due to etiological and laboratory particularities it is named LD-like syndrome or LD imitator syndrome. The condition is considered to be a zoonosis transmitted by ticks of the genus Amblyomma, possibly caused by interaction of multiple fastidious microorganisms originating a protean clinical picture, including neurological, osteoarticular and erythema migrans-like lesions. When peripheral blood of patients with LD-like syndrome is viewed under a dark-field microscope, mobile uncultivable spirochete-like bacteria are observed. PCR carried out with specific or conservative primers to recognize Borrelia burgdorferi sensu stricto or the genus Borrelia has been negative in ticks and in biological samples. Two different procedures, respectively involving hematoxylin and eosin staining of cerebrospinal fluid and electron microscopy analysis of blood, have revealed spirochetes not belonging to the genera Borrelia, Leptospira or Treponema. Surprisingly, co-infection with microorganisms resembling Mycoplasma and Chlamydia was observed on one occasion by electron microscopy analysis. We discuss here the possible existence of a new tick-borne disease in Brazil imitating LD, except for a higher frequency of recurrence episodes observed along prolonged clinical follow-up

The Spin-Statistics Connection in Quantum Gravity

It is well-known that is spite of sharing some properties with conventional particles, topological geons in general violate the spin-statistics theorem. On the other hand, it is generally believed that in quantum gravity theories allowing for topology change, using pair creation and annihilation of geons, one should be able to recover this theorem. In this paper, we take an alternative route, and use an algebraic formalism developed in previous work. We give a description of topological geons where an algebra of "observables" is identified and quantized. Different irreducible representations of this algebra correspond to different kinds of geons, and are labeled by a non-abelian "charge" and "magnetic flux". We then find that the usual spin-statistics theorem is indeed violated, but a new spin-statistics relation arises, when we assume that the fluxes are superselected. This assumption can be proved if all observables are local, as is generally the case in physical theories. Finally, we also show how our approach fits into conventional formulations of quantum gravity.Comment: LaTeX file, 31 pages, 5 figure

Development of a modified pre-polymer method to produce NMP-free polyurethane-urea aqueous dispersions

A modified pre-polymer process was developed for the synthesis of NMP (N-methyl-2-pyrrolidone)-free polyurethane-urea aqueous dispersions. The pre-polymer process is based on the use of dimethylol propionic acid (DMPA, hydrophilizing diol), which requires dissolution in NMP to be introduced in the reactive mixture. NMP is difficult to remove from the dispersion remaining in the final product. In this work we present a modified pre-polymer process composed by four main stages: (1) pre-polymer synthesis in two stages: (i) reaction of the isocyanate with the polyol at 80ºC, and (ii) introduction of DMPA pre-neutralized in acetone and proceeding of the reaction at 50ºC, (2) Pre-polymer dispersion in water, (3) Chain extension with a diamine; and (4) Co-solvent removal. Several dispersions were synthesized using different DMPA contents (3.0, 4.0, 5.0%, keeping the pre-neutralization degree at 100.0%), and different DMPA pre-neutralization degree (100.0 and 90.0%, using 5.0 % of DMPA). The effect of these variables in the particle size and dispersion stability was evaluated. Based on the obtained results, the modified pre-polymer process is a feasible alternative to obtain NMP-free PUD, thus fulfilling the restrictions imposed by the European Union.POCI-01-0145-FEDER-006984 (LA LSRE-LCM), funded by FEDER, through POCI-COMPETE2020 and FCT; Project NORTE-01-0145-FEDER-000006, funded by NORTE2020 under PT2020.info:eu-repo/semantics/publishedVersio

Microencapsulation of ammodaucus leucotrichus essential oil using chitosan/ TPP/vanillin chemical system

A. leucotrichus (Coss. & Dur.) Coss. & Dur., known in Algeria as “Kammûnes-sofi”, is a medicinal plant that finds culinary use by indigenous populations. Among others, it is used against stomach pain, indigestion, diarrhea, vomiting, fever, and to combat high blood pressure. In this work, the essential oil of A. leucotrichus, obtained by steam distillation (3h) from fruits collected in March 2015 from Tassili n'Ajjer, a vast plateau in south-east Algeria (25°30'0" N and 9°0'0" E), was chemically and biologically characterized and thereafter microencapsulated using a chitosan/TPP/vanillin system.A. leucotrichus essential oil microparticles were produced using an atomization/coagulation technique with chitosan as the shell material, sodium tripolyphosphaste (TPP) and vanillin as crosslinking agents. Comparatively to the most used chemical systems, this one presents several advantages since all the raw materials are nontoxic and no organic solvents are required. Moreover, the used microencapsulation process allows the microparticles production in a single step, without having the constrains of the traditionally used oil-in-water (o/w) emulsion based techniques. The adopted procedure comprises the following stages: (1) Chitosan solution (CS) preparation (3.0%, w/v) in acidic medium (acetic acid 3%, v/v); (2) Oil-in-water (o/w) emulsion preparation by emulsifying the essential oil (O) with the chitosan solution at O/CS ratio of 0.025 (v/v) with Tween 80 (emulsifier of HLB=15.0, 1.5%, w/v). The emulsion was homogenized at 11000 rpm during 5 min with a CAT Unidrive X homogenizer; (3) Atomization of the o/w emulsion in a Nisco VarJ30 system (flow rate: 0.3 ml/min) under pressurized nitrogen; (4) Coagulation with TPP (10%, w/v at pH 6.0) followed by vanillin crosslinking (1.0% (w/v), 50ºC at 0.5 ml/min during 2 h). Microparticles were recovered by filtration under reduced pressure, washed with distilled water and stored in the hydrated form.info:eu-repo/semantics/publishedVersio

Chemical profile and bioactive properties of the essential oil isolated from Ammodaucus leucotrichus fruits growing in Sahara and its evaluation as a cosmeceutical ingredient

Ammodaucus leucotrichus is a medicinal plant commonly used in Algeria by the indigenous populations, especially due to its therapeutic effects. In this context, the aim of the present study was to chemically characterize the essential oil of A. leucotrichus fruits (EOALF) growing in Algerian Sahara, and to evaluate its bioactive properties (antimicrobial, antioxidant and anti-inflammatory). Considering the interest of the cosmetic industry for natural ingredients, and taking into account the obtained biological properties, the essential oil was also evaluated by incorporation in a base cosmetic (cream). The essential oil was extracted with a yield of 2.58 ± 0.17%, being perilla aldehyde identified as the main component, accounting for 85.6% of the total composition. Concerning the tested bioactivities, EOALF presented antioxidant potential, a strong anti-inflammatory activity, and was effective against the tested microbial strains (Staphylococcus aureus, Eschericia coli and Pseudomonas aeruginosa), being S. aureus the most sensitive bacteria. After incorporation in a base cosmetic, the developed formulation was able to preserve the EOALF bioactivities along 28 days under storage. The obtained results, with relevance for the strong-anti-inflammatory activity, pointed out the interest to exploit this essential oil as a cosmeceutical ingredient in the cosmetic industry.The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) and FEDER under Program PT2020 for financial support to CIMO (UID/AGR/00690/2013), S.A. Heleno (SFRH/ BPD/101413/2014) and P. Costa (SFRH/BPD/101413/2014). This work was also financially supported by Project POCI-01-0145-FEDER- 006984–Associate Laboratory LSRE-LCM funded by FEDER through COMPETE 2020 – Programa Operacional Competitividade e Internacionalização (POCI) – and by national funds through FCT and project NORTE-01-0145-FEDER-000006, supported by Norte Portugal Regional Operational Program (NORTE 2020), under the Portugal 2020 Partnership Agreement, through the European Regional Development Fund (ERDF).info:eu-repo/semantics/publishedVersio

Late coronary occlusion after intracoronary brachytherapy

BACKGROUND: Intracoronary brachytherapy appears to be a promising technology to prevent restenosis. Presently, limited data are available regarding the late safety of this therapeutic modality. The aim of the study was to determine the incidence of late (>1 month) thrombosis after PTCA and radiotherapy. METHODS AND RESULTS: From April 1997 to March 1999, we successfully treated 108 patients with PTCA followed by intracoronary beta-radiation. Ninety-one patients have completed at least 2 months of clinical follow-up. Of these patients, 6.6% (6 patients) presented with sudden thrombotic events confirmed by angiography 2 to 15 months after intervention (2 balloon angioplasty and 4 stent). Some factors (overlapping stents, unhealed dissection) may have triggered the thrombosis process, but the timing of the event is extremely unusual. Therefore, the effect of radiation on delaying the healing process and maintaining a thrombogenic coronary surface is proposed as the most plausible mechanism to explain such late events. CONCLUSIONS: Late and sudden thrombosis after PTCA followed by intracoronary radiotherapy is a new phenomenon in interventional cardiology

Geographic Miss

Background—A recognized limitation of endovascular ß-radiation therapy is the development of new stenosis at the edges of the irradiated area. The combination of injury and low-dose radiation may be the precursor of this phenomenon. We translated the radio-oncological concept of "geographic miss" to define cases in which the radiation source did not fully cover the injured area. The aims of the study were to determine the incidence and causes of geographic miss and evaluate the impact of this inadequate treatment on the outcome of patients treated with intracoronary ß-radiation. Methods and Results—We analyzed 50 consecutive patients treated with ß-radiation after percutaneous coronary intervention. The prescribed dose ranged between 12 and 20 Gy at 2 mm from the source axis. By means of quantitative coronary angiography, the irradiated segment (IRS) and both edges were studied before and after intervention and at 6-month follow-up. Edges that were injured during the procedure constituted the geographic miss edges. Twenty-two edges were injured during the intervention, mainly because of procedural complications that extended the treatment beyond the margins of the IRS. Late loss was significantly higher in geographic miss edges than in IRSs and uninjured edges (0.84±0.6 versus 0.15±0.4 and 0.09±0.4 mm, respectively; P<0.0001). Similarly, restenosis rate was significantly higher in the injured edges (10% within IRS, 40.9% in geographic miss edges, and 1.9% in uninjured edges; P<0.001). Conclusions—These data support the hypothesis that the combination of injury and low-dose ß-radiation induces deleterious outcome

Geographic miss: a cause of treatment failure in radio-oncology applied to intracoronary radiation therapy

BACKGROUND: A recognized limitation of endovascular beta-radiation therapy is the development of new stenosis at the edges of the irradiated area. The combination of injury and low-dose radiation may be the precursor of this phenomenon. We translated the radio-oncological concept of "geographic miss" to define cases in which the radiation source did not fully cover the injured area. The aims of the study were to determine the incidence and causes of geographic miss and evaluate the impact of this inadequate treatment on the outcome of patients treated with intracoronary beta-radiation. METHODS AND RESULTS: We analyzed 50 consecutive patients treated with beta-radiation after percutaneous coronary intervention. The prescribed dose ranged between 12 and 20 Gy at 2 mm from the source axis. By means of quantitative coronary angiography, the irradiated segment (IRS) and both edges were studied before and after intervention and at 6-month follow-up. Edges that were injured during the procedure constituted the geographic miss edges. Twenty-two edges were injured during the intervention, mainly because of procedural complications that extended the treatment beyond the margins of the IRS. Late loss was significantly higher in geographic miss edges than in IRSs and uninjured edges (0.84+/-0.6 versus 0.15+/-0.4 and 0.09+/-0.4 mm, respectively; P<0.0001). Similarly, restenosis rate was significantly higher in the injured edges (10% within IRS, 40.9% in geographic miss edges, and 1.9% in uninjured edges; P<0.001). CONCLUSIONS: These data support the hypothesis that the combination of injury and low-dose beta-radiation induces deleterious outcome

Symmetry breaking in numeric constraint problems

Symmetry-breaking constraints in the form of inequalities between variables have been proposed for a few kind of solution symmetries in numeric CSPs. We show that, for the variable symmetries among those, the proposed inequalities are but a specific case of a relaxation of the well-known LEX constraints extensively used for discrete CSPs. We discuss the merits of this relaxation and present experimental evidences of its practical interest.Postprint (author’s final draft