958 resultados para ZN2 IONS
Resumo:
The study of the effect of radiation on living tissues is a rather complex task to address mainly because they are made of a set of complex functional biological structures and interfaces. Particularly if one is looking for where damage is taking place in a first stage and what are the underlying reaction mechanisms. In this work a new approach is addressed to study the effect of radiation by making use of well identified molecular hetero-structures samples which mimic the biological environment. These were obtained by assembling onto a solid support deoxyribonucleic acid (DNA) and phospholipids together with a soft water-containing polyelectrolyte precursor in layered structures and by producing lipid layers at liquid/air interface with DNA as subphase. The effects of both ultraviolet (UV) radiation and carbon ions beams were systematically investigated in these heterostructures, namely damage on DNA by means vacuum ultraviolet (VUV), infrared (IR), X-Ray Photoelectron (XPS) and impedance spectroscopy. Experimental results revealed that UV affects furanose, PO2-, thymines, cytosines and adenines groups. The XPS spectrometry carried out on the samples allowed validate the VUV and IR results and to conclude that ionized phosphate groups, surrounded by the sodium counterions, congregate hydration water molecules which play a role of UV protection. The ac electrical conductivity measurements revealed that the DNA electrical conduction is arising from DNA chain electron hopping between base-pairs and phosphate groups, with the hopping distance equal to the distance between DNA base-pairs and is strongly dependent on UV radiation exposure, due loss of phosphate groups. Characterization of DNA samples exposed to a 4 keV C3+ ions beam revealed also carbon-oxygen bonds break, phosphate groups damage and formation of new species. Results from radiation induced damage carried out on biomimetic heterostructures having different compositions revealed that damage is dependent on sample composition, with respect to functional targeted groups and extent of damage. Conversely, LbL films of 1,2-dipalmitoyl-sn-Glycero-3-[Phospho-rac-(1-glycerol)] (Sodium Salt) (DPPG) liposomes, alternated with poly(allylamine hydrochloride) (PAH) revealed to be unaffected, even by prolonged UV irradiation exposure, in the absence of water molecules. However, DPPG molecules were damaged by the UV radiation in presence of water with cleavage of C-O, C=O and PO2- bonds. Finally, the study of DNA interaction with the ionic lipids at liquid/air interfaces revealed that electrical charge of the lipid influences the interaction of phospholipid with DNA. In the presence of DNA in the subphase, the effects from UV irrladiation were seen to be smaller, which means that ionic products from biomolecules degradation stabilize the intact DPPG molecules. This mechanism may explain why UV irradiation does not cause immediate cell collapse, thus providing time for the cellular machinery to repair elements damaged by UV.
Resumo:
The incorporation of fly ash (FA) in cementitious matrices have been frequently used in order to make the matrix more resistant to the action of chlorides. On the other hand, it is known that Ca (OH)2 existing in the matrix is partially consumed by the pozzolanic reactions, which facilitates the advancement of carbonation. Given that the combined action between carbonation and chloride penetration is a fact little known, we speculate about the behaviour of the matrix in this context. This study investigates the influence of the presence of chlorides on the carbonation in mortars with FA. Samples with 0% and 40% replacement of cement CEM I 42.5 R for FA were molded with water/binder 0.56 and 0.52 respectively. After 90 days of curing the specimens were subjected to cycles of immersion/drying for 56 days. Half of the samples was subjected to the following cycle: two days in a solution containing NaCl (concentration equal to 3.5 %); 12 days in the carbonation chamber (4% of CO2). The other half was: two days in water; 12 days in the carbonation chamber. Then, the development of carbonation was evaluated. The results indicate that the presence of chlorides influences the carbonation. The specimens submitted to the exclusive action of CO2 showed a greater depth of carbonation compared to that presented by the specimens subjected to combined action. This may be related to changes in properties of the matrix which may lead to further refinement of the pores and related to the presence of the salt that can lead to partial filling of the pores and the increase in moisture content.
Resumo:
The use of buffers to maintain the pH within a desired range is a very common practice in chemical, biochemical and biological studies. Among them, zwitterionic N-substituted aminosulfonic acids, usually known as Good's buffers, although widely used, can complex metals and interact with biological systems. The present work reviews, discusses and updates the metal complexation characteristics of thirty one commercially available buffers. In addition, their impact on biological systems is also presented. The influences of these buffers on the results obtained in biological, biochemical and environmental studies, with special focus on their interaction with metal ions, are highlighted and critically reviewed. Using chemical speciation simulations, based on the current knowledge of the metal-buffer stability constants, a proposal of the most adequate buffer to employ for a given metal ion is presented.
Resumo:
OBJECTIVE: To test the hypothesis that short periods of ischemia may increase the myocardial protection obtained with intermittent crossclamping of the aorta. METHODS: In the control group (18 patients), surgery was performed with systemic hypothermia at 32C and intermittent crossclamping of the aorta. Extracorporeal circulation was used. In the preconditioning group (17 patients), 2 crossclampings of the aorta lasting 3min each were added prior to the intermittent crossclamping of the conventional technique with an interval of 2min of reperfusion between them. Blood samples for analyses of pH, pCO2, pO2, sodium, potassium, calcium, and magnesium were obtained from the coronary sinus at the beginning of extracorporeal circulation (time 1), at the end of the first anastomosis (time 2), and at the end of extracorporeal circulation (time 3). RESULTS: No difference was observed in the results of the 2 groups, except for a variation in the ionic values in the different times of blood withdrawal; sodium values, however, remained stable. All patients had a good clinical outcome. CONCLUSION: The results of intermittent crossclamping of the aorta with moderate hypothermia were not altered by the use of ischemic preconditioning.
Resumo:
Results of analysis of variations of sum light ions concentration and their connections with radon, galactic cosmic rays intensity and content of sub-micron aerosols by diameter 0.1 micron in surface boundary layer of Tbilisi city are given.
Resumo:
, 2009-2010 .
Resumo:
In Tbilisi according to the data of the complex monitoring of light ions concentration, radon and sub-micron aerosols the effect of feedback of intensity of ionizing radiation with the light ions content in atmosphere is discovered.
Resumo:
The results of the stationary and expeditionary investigations of the light ions content in surface boundary layer in the urban and ecologically clean locality for different regions of Georgia are represented.
Resumo:
Foram estudados os efeitos do tempo de contato e das quantidades de Zn aplicadas sobre a fixao desse ction por 6 solos do Municpio de Piracicaba, usando o 65Zn como elemento traador. As principais concluses obtidas foram: a - em todos os solos as quantidades de Zn fixadas diminuram do 10 para o 20 dias de incubao; b - as quantidades de Zn fixadas cresceram medida que as quantidades aplicadas foram aumentadas.
Resumo:
Estudi elaborat a partir duna estada al Stony Brook University al juliol del 2006. El RbTiOPO4 (RTP) monocristall s un material d' ptica no lineal molt rellevant i utilitzat en la tecnologia lser actual, qumicament molt estable i amb unes propietats fsiques molt destacades, entre elles destaquen els alts coeficients electro-ptics i l'alt llindar de dany ptic que presenta. En els ltims anys sest utilitzant tecnolgicament en aplicacions d'ptica no lineal en general i electro-ptiques en particular. En alguns casos ja ha substitut, millorant prestacions, a materials tals com el KTP o el LNB(1). Dopant RTP amb ions lantnids (Ln3+) (2-4), el material es converteix en un material lser auto-doblador de freqncia, combinant les seves propietats no lineals amb les de matriu lser. El RTP genera radiaci de segon harmnic (SHG) a partir dun feix fonamental amb longituds dona inferiors a 990 nm, que s el lmit que presenta el KTP.La determinaci de la ubicaci estructural i lestudi de l'entorn local del ions actius lser s de fonamental importncia per a la correcta interpretaci de les propietats espectroscpiques daquest material. Mesures de difracci de neutrons sobre mostra de pols cristall mostren que els ions Nb5+ i Ln3+ noms substitueixin posicions de Ti4+ (8-9). Estudis molt recents d'EPR (electron paramagnetic resonance) semblen indicar que quan la concentraci d'i Ln3+ es baixa, aquest i presenta la tendncia a substituir l'i alcal present a l'estructura (10).Desprs dels resultats obtinguts en el present treball a partir de la tcnica EXAFS a la installaci sincrot del Brookhaven National Laboratory/State University of New York (Stony Brook) es pot concloure definitivament que els ions Nb subiquen en la posici Ti (1) i que els ions Yb3+ es distribueixen paritariament en les dues posicions del Ti (1 i 2). Aquests resultats aporten una valuosa informaci per a la correcta interpretaci dels espectres, tant dabsorci com demissi, del material i per la avaluaci dels parmetres del seu comportament durant l'acci lser.
Resumo:
Les vidences s'accumulent concernant des problmes de corrosion touchant les prothses col modulaires. Plusieurs tudes rcentes rvlent des taux d'ions mtalliques levs. Le but de cette tude tait de comparer les taux d'ions mtalliques (Co, Cr, Mo, Ti), dans le srum, chez des porteurs de prothses col modulaire, tige monobloc, ainsi que sans implant. Mthodes Nous avons recrut 60 patients, dont 50 porteurs d'une PTH, unilatrale, sans aucun autre implant, non-cimente, avec tte en cramique, minimum 1 anne postopratoire. Quarante avaient une tige SPS (Symbios) (Ti6Al4 V) modulaire (col en CoCr) et 10 une SPS monobloc (non-modulaire). Les cupules taient toutes en alliage de Ti (Ti6Al4 V) avec insert cramique ou PE. Nous avons constitu un groupe tmoin sans aucun implant. Dans le groupe o modulaires O, le col a t choisi en propratoire sur la base d'une planification 3D et assembl sec avant implantation. Nous avons prlev un chantillon srique, un autre sanguin, qui ont t analyss par spectromtrie de masse, permettant une dtermination atomique quantitative. Le rsultat clinique a t estim l'aide du o Oxford Hip Score O. Rsultats Nous avons trouv un Co srique moyen 1,54 Ig L dans le groupe O modulaires O et 0,32 Ig L dans le groupe o monobloc O avec un p < 0,001. Pour le Cr, on a 1,12 Ig L (modulaires) vs 0,60 Ig L (monoblocs) avec un p < 0,001, pour le Ti 31 Ig L (modulaires) vs 22 Ig L (monoblocs) avec p < 0,001 et pour le Mo, 0,96 Ig L (modulaires) vs 0,74 (monoblocs) avec p = 0,254. Deux patients avaient des valeurs de Co suprieures 7 Ig L et 11 taient au-dessus de 1 Ig L, valeur considre comme limite. Les valeurs dans le sang complet taient similaires. Nous n'avons pas trouv de diffrence significative selon les types de col modulaires (longs vs courts et rtro vs normaux). Curieusement, le taux de Cr tait significativement plus lev chez les patients sans aucun implant que chez les porteurs de SPS monobloc, par contre les diffrences n'taient pas significatives pour les autres lments. Conclusion Les taux sriques et sanguins de ions Co, Cr et Ti taient significativement plus levs dans le groupe des patients avec col modulaire, avec 2 valeurs 40 extrmement hautes et plus de la moiti (11 40) anormalement hautes. Bien que ces valeurs soient infrieures celles d'autres tudes, nous avons arrter d'utiliser de tiges cols modulaires, et avons initi un suivi annuel des patients porteurs, similaire celui instaur pour les grosses ttes mtal-mtal.
Resumo:
We have been able to label the excretory system of cercariae and all forms of schistosomula, immature and adult worms with the highly fluorescent dye resorufin. We have shown that the accumulation of the resorufin into the excretory tubules and collecting ducts of the male adult worm depends on the presence of extracellular calcium and phosphate ions. In the adult male worms, praziquantel (PZQ) prevents this accumulation in RPMI medium and disperses resorufin from tubules which have been prelabelled. Female worms and all other developmental stages are much less affected either by the presence of calcium and phosphate ions, or the disruption caused by PZQ. The male can inhibit the excretory system in paired female. Fluorescent PZQ localises in the posterior gut (intestine) region of the male adult worm, but not in the excretory system, except for the anionic carboxy fluorescein derivative of PZQ, which may be excreted by this route. All stages of the parasite can recover from damage by PZQ treatment in vitro. The excretory system is highly sensitive to damage to the surface membrane and may be involved in vesicle movement and damage repair processes. In vivo the adult parasite does not recover from PZQ treatment, but what is inhibiting recovery is unknown, but likely to be related to immune effector molecules.
Resumo:
The incidence of fungal infections in immuno-compromised patients increased considerably over the last 30 years. New treatments are therefore needed against pathogenic fungi. With Candida albicans as a model, study of host-fungal pathogen interactions might reveal new sources of therapies. Transcription factors (TF) are of interest since they integrate signals from the host environment and participate in an adapted microbial response. TFs of the Zn2-Cys6 class are specific to fungi and are important regulators of fungal metabolism. This work analyzed the importance of the C. albicans Zn2-Cys6 TF for mice kidney colonization. For this purpose, 77 Zn2-Cys6 TF mutants were screened in a systemic mice model of infection by pools of 10 mutants. We developed a simple barcoding strategy to specifically detect each mutant DNA from mice kidney by quantitative PCR. Among the 77 TF mutant strains tested, eight showed a decreased colonization including mutants for orf19.3405, orf19.255, orf19.5133, RGT1, UGA3, orf19.6182, SEF1 and orf19.2646, and four an increased colonization including mutants for orf19.4166, ZFU2, orf19.1685 and UPC2 as compared to the isogenic wild type strain. Our approach was validated by comparable results obtained with the same animal model using a single mutant and the revertant for an ORF (orf19.2646) with still unknown functions. In an attempt to identify putative involvement of such TFs in already known C. albicans virulence mechanisms, we determined their in vitro susceptibility to pH, heat and oxidative stresses, as well as ability to produce hyphae and invade agar. A poor correlation was found between in vitro and in vivo assays, thus suggesting that TFs needed for mice kidney colonization may involve still unknown mechanisms. This large-scale analysis of mice organ colonization by C. albicans can now be extended to other mutant libraries since our in vivo screening strategy can be adapted to any preexisting mutants.
Resumo:
Degut a la gran demanda tecnolgica, actualment hi ha un gran inters en desenvolupar medis magntics amb entitats ferromagntiques de dimensions nanomtriques. Aquesta demanda promou la investigaci i el desenvolupament de nous materials i processos de fabricaci que permetin controlar duna manera ms precisa les propietats magntiques i estructurals. Entre els mtodes de litografia convencionals (per exemple deposici fsica a travs de mscares, deposici qumica en fase vapor i electrodeposici), recentment sha demostrat que la irradiaci amb ions a travs de mscares prelitografiades, sembla ser un bon mtode per a la fabricaci destructures ferromagntiques de lordre dels nanmetres. Aquesta tcnica pot ser aplicada per aprofitar la transici paramagnticaferromagntica que presenten alguns materials al ser desordenats estructuralment (per exemple FeAl, FePt3, Ni3Sn2). En el treball que es presenta a continuaci sutilitza laliatge Fe60Al40 per a fabricar estructures ferromagntiques embegudes en una matriu paramagntica mitjanant irradiaci amb ions darg a travs duna membrana de polimetil metacrilat (PMMA) prviament litografiada amb feixos delectrons (EBL). La fabricaci daquest sistema t com a objectiu destudiar levoluci de la morfologia i el gruix de PMMA (a partir de SEM i AFM) i del comportament magntic de les estructures fabricades (MFM i MOKE), quan s irradiat consecutivament a diferents energies. Per a completar lestudi shan utilitzat simulacions per a determinar les condicions dirradiaci (TRIM), com per a una millor comprensi dels resultats (simulacions micromagntiques). El contingut de la memria inclou una breu introducci histrica i conceptual sobre el magnetisme. A continuaci sexposen les tcniques necessries per a la fabricaci, preparaci i caracteritzaci de la mostra. Finalment es presenta una discussi dels resultats obtinguts i les conclusions.
Resumo:
En aquest treball de recerca, shan estudiat les dues isoformes de metallotionena CnMT1 i CnMT2 presents en el fong patogen Cryptococcus neoformans. Recentment sha descobert que aquest fong t com a factor de virulncia, els nivells de coure del medi on es troba. Les dues isoformes produdes en medis rics en Zn(II) shan utilitzat per a fer valoracions amb Cu(I) i Cd(II), i sha seguit levoluci dels experiments mitjanant les tcniques DC, UV-vis, i ESI-MS. Sha pogut observar que les dues isoformes tenen preferncia per enllaar Cu(I). Per altra banda tamb sha establert una gran homologia entre les dues seqncies.
