Comparison of a daily and alternate-day photobiomodulation protocol in the prevention of oral mucositis in patients undergoing radiochemotherapy for oral cancer: a triple-blind, controlled clinical trial.

BACKGROUND: Preventive Photobiomodulation Therapy (PBMT) significantly reduces oral mucositis (OM) severity in patients undergoing Radiochemotherapy (RCT) for the treatment of oral cancer, but daily applications generate cost, overload the dental team, and reduce the number of patients assisted.To evaluate the effectiveness of two PBMT protocols in preventing OM in patients undergoing RCT for oral cancer. MATERIAL AND METHODS: 16 patients diagnosed with oral cancer undergoing RCT were included, equally divided into two groups: a group treated daily with PBMT, and another group also submitted to daily treatment, however, performing the application of PBMT every three days, interspersed with a simulation of PBMT (placebo). A red laser was used (~660 nm), 0.1W power, 1J of energy applied per point, 9 points per area (labial mucosa, buccal mucosa, lateral borders of the tongue, body of the tongue, and floor of the mouth) from the beginning of RCT until the end of the oncological treatment. Daily assessments were performed regarding OM scores, the World Health Organization (WHO) pain scale, and the visual analog scale (VAS). Weight, salivary flow (SGAPP), OHIP-14, and DMFT were evaluated on the initial and final days of RT. OM incidence and clinical data were compared by Pearson's chi-square test or Fisher's exact test. Pain and other scale scores were compared using the Mann-Whitney and Friedman/Dunn tests (SPSS v20.0 p<0.05). RESULTS: In the group with PBMT on alternate days, there was an increase in the frequency of grade 2 and grade 3 oral mucositis and an increased risk of grade 2 oral mucositis, in addition to higher mean pain scores and greater reduction in salivary flow. CONCLUSIONS: The daily PBMT protocol proved more effective in controlling the frequency and severity of OM, pain, and salivary flow.

Is immunohistochemistry more sensitive than hematoxylin-eosin staining for identifying perineural or lymphovascular invasion in oral squamous cell carcinoma? A systematic review and meta-analysis.

BACKGROUND: This study aimed to analyze whether immunohistochemistry (IHC) is more sensitive than hematoxylin-eosin (H&E) staining for identifying perineural invasion (PNI) or lymphovascular invasion (LVI) in oral squamous cell carcinoma (OSCC). MATERIAL AND METHODS: In this systematic review and meta-analysis (Prospective Register of Systematic Reviews - CRD 42021256515), data were obtained from six databases (PubMed, Scopus, LILACS, Web of Science, EBSCO, LIVIVO, Embase) and the grey literature. Cross-sectional observational studies of the diagnostic sensitivity of IHC for PNI and LVI were included. Studies were selected in two phases: first collection and reference retrieval. The Quality Assessment of Diagnostic Accuracy Studies-2 tool assessed study quality, while the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) approach assessed evidence quality. The meta-analysis (random effects model) was performed using MedCalc 18.2.1 software (MedCalc®) (p<0.05). RESULTS: Four studies (560 patients with 295 biopsies) were analyzed. The combined sensitivity was 76% (95% confidence interval [CI], 44.30-97.19%) and specificity was 42% (95% CI, 23.40-62.02%). The positive predictive value (PPV) and negative predictive value (NPV) were 61% (95% CI, 49.78-71.53%) and 70% (95% CI, 37.63-94.43%). The overall accuracy was 58% (95% CI, 45.17-70.65%). The risk of bias was low, and GRADE analysis showed a very low certainty of evidence. CONCLUSIONS: Our data suggest that IHC staining to highlight PNI/LVI may be useful in cases in which H&E analysis results in a negative decrease in the prevalence of false-negative cases and underestimated treatment.

PMS2: a potential prognostic protein marker in oral squamous cell carcinoma.

BACKGROUND: An increase in oral squamous cell carcinoma (OSCC) cases was observed despite the reduction in exposure to classic risk factors. Although the exact cause of this trend remains unknown, epigenetic factors could be contributing to an increased occurrence of these tumors. This study aims to assess the influence of PMS2 protein immunoexpression on the prognosis of patients with OSCC. MATERIAL AND METHODS: This study comprised 76 cases of OSCC treated between 2011 and 2016. Immunohistochemical staining for PMS2 was performed. For evaluation, 10 fields per histological section were photographed at a 400x magnification and positively-stained cells were counted with Image J. Mann-Whitney and Kruskal-Wallis tests were used to compare the immunolabeling pattern with the clinical-pathological and prognostic characteristics. Survival analysis was performed with Chi-square, Long-Rank Mantel-Cox and Cox regression tests (p<0.05). RESULTS: An overexpression of PMS2 was observed in N0/1 tumors and in oral cancers found in unusual locations. In patients ≤60 years of age, high levels of PMS2 (>60%; p=0.041) were associated with low survival (p=0.029). In multivariate analysis, surgery combined with chemotherapy (p=0.030) and high PMS2 immunoexpression (p=0.042) significantly increased the risk of death for ≤60 years old patients. CONCLUSIONS: The findings of this study indicate that PMS2 can be a potential prognostic protein marker in OSCC patients 60 years of age and younger.

Clinical-pathological and sociodemographic factors associated with the distant metastasis and overall survival of oral cavity and oropharynx squamous cell carcinoma.

BACKGROUND: The objective of this study was to evaluate the influence of clinical-pathological and sociodemographic factors on the prevalence of distant metastasis (DM) and overall survival in patients with oral cavity and oropharynx squamous cell carcinoma (OOSCC). MATERIAL AND METHODS: Cross-sectional study based on the records of 404 OOSCC patients evaluated for DM, covering the period 2000-2014. We analysed the influence of age, sex, level of schooling, primary tumor subsite, treatment, marital status, family history of cancer, history of smoking and alcohol consumption, type of health care coverage (private vs. public) and overall survival. Findings were submitted to Fisher's exact test, Pearson's chi-squared test, Mantel-Cox log-rank testing and multinomial and Cox regression analysis (SPSS v. 20.0; p<0.05). RESULTS: The prevalence of DM was 5.4% (22/404). The respiratory tract was the most affected DM site (n=9; 40.9%). Male sex (p=0.049), oropharyngeal primary tumor (p=0.008), stage T3-4 (p=0.022), lymph node metastasis (N+) (p<0.001) and palliative treatment (p=0.005) were directly associated with DM. Patients with oral primary tumours (p=0.343) and primary oropharyngeal tumours (p=0.242) did not differ significantly with regard to the prevalence of DM. N+ was an independent risk factor for DM (p=0.017). Five variables independently reduced overall survival: male sex (p=0.035), age >65 years (p=0.046), indigenous/brown racial type (p=0.045), palliative treatment (p=0.035) and DM (p=0.048). CONCLUSIONS: Lymph node metastasis independently increased the prevalence of DM and, along with male sex, older age, brown racial type and palliative treatment, was independently associated with poor prognosis in patients with OOSCC.

In silico evaluation of the stress fields on the cortical bone surrounding dental implants: Comparing root-analogue and screwed implants.

Tooth loss is a problem that affects both old and young people. It may be caused by several conditions, such as poor oral hygiene, lifestyle choices or even diseases like periodontal disease, tooth grinding or diabetes. Nowadays, replacing a missing tooth by an implant is a very common process. However, many limitations regarding the actual strategies can be enumerated. Conventional screwed implants tend to induce high levels of stress in the peri-implant bone area, leading to bone loss, bacterial bio-film formation, and subsequent implant failure. In this sense, root-analogue dental implants are becoming promising solutions for immediate implantation due to their minimally invasive nature, improved bone stress distribution and because they do not require bone drilling, sinus lift, bone augmentation nor other traumatic procedures. The aim of this study was to analyse and compare, by means of FEA, the stress fields of peri-implant bone around root-analogue and screwed conventional zirconia implants. For that purpose, one root-analogue implant, one root-analogue implant with flaps, two conventional implants (with different threads) and a replica of a natural tooth were modelled. COMSOL was used to perform the analysis and implants were subjected to two simultaneous loads: 100 N axially and 100 N oblique (45°). RESULTS: revealed that root-analogue implants, namely with flaps, should be considered as promising alternatives for dental implant solutions since they promote a better stress distribution in the cortical bone when compared with conventional implants.

Sliding behavior of zirconia porous implant surfaces against bone.

Different zirconia porous layers were produced on zirconia dense zirconia substrates by slip casting using powder with different mean sizes: 40 µm (Z40), 70 µm (Z70), and 100 µm (Z100). The dynamic and static coefficients of friction against bovine femoral bone, mimicking the implantation process, were conducted using a ball-on-flat reciprocating sliding tribometer under 3 N of normal load. Additionally, the porous layers were assessed with regard to their low temperature degradation (aging). Results revealed that the porous layers were able to keep their integrity during the sliding testes against bone, with no zirconia particles being transferred to the bone. Results did not show significant differences (p > 0.05) in kinetic and static COF values for Z40, Z70, Z100, and GRAD specimens, ranging from 0.53 to 0.77 and 0.65 to 0.90, respectively. The aging tests revealed that all surfaces were prone to low temperature degradation (~49% of monoclinic content after 18 h). In conclusion, the cohesive integrity of the layers and relatively high COF observed reveled that zirconia porous layers may be considered for replacing the current implant surfaces, and are expected to improve their primary stability. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1113-1121, 2019.

Effect of HAp and ß-TCP incorporation on the tribological response of Ti6Al4V biocomposites for implant parts.

Titanium and its alloys have been widely used in many engineering areas due to their properties. Despite having a high implant-tissue osseointegration time, Ti6Al4V has been extensively used in prosthesis and articular implants. To promote a faster bone ingrowth and consequently reduce the implant fixation time, the addition of a bioactive phase to form a biocomposite seems to be an excellent solution. Because of their bioactivity and similarity in composition with the human bone, HAp and ß-TCP are two of the most widely used calcium phosphates in biomedical applications. To guarantee a strong adhesion of the previous bioactive materials in the implants surface, samples of Ti6Al4V, Ti6Al4V+HAp (10 vol %) and Ti6Al4V+ß-TCP (10 vol %) TCP were processed by the hot pressing technique. Tribological tests against Al2 O3, lubricated in PBS at 37°C were carried out on a ball-on-flat reciprocating sliding geometry. Loads in the range of 3 N to 30 N were applied and their effect on the friction behavior and wear resistance of the tested materials was evaluated. Values of the coefficient of friction as well as the wear rate tend to increase with the addition of a bioactive phase to the Ti alloy. Micrographs of the worn surfaces showed that abrasion and plastic deformation are the prevailing wear mechanisms in the studied tribosystems. For biocomposites, particularly in the case of Ti6Al4V+HAp, pull-out of bioactive particle clusters has a determinant role on the tribological response, increasing both the friction coefficient and the specific wear rate. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1010-1016, 2018.

In vitro and in vivo evaluation of sodium dodecyl sulfate (SDS) as an inactivator of caprine lentivirus (CLV) in colostrum and milk / Avaliação in vitro e in vivo do dodecil sulfato de sódio (SDS) como inativador do lentivírus caprino (LVC) em colostro e leite

The aim of this study was to evaluate in vitro and in vivo the effect of sodium dodecyl sulfate (SDS) on the caprine lentivirus (CLV) in colostrum and milk. This was performed to develop a practical and efficient method of blocking the lactogenic transmission of the virus. In the in vitro experiment, colostrum and milk were treated with 0.25%; 0.50% and 1% SDS. Then, somatic cells of colostrum and milk were submitted to co-culture with caprine synovial membrane cells (CSM). In the in vivo test, goats were fed with colostrum and milk provided from CLV-positive goats treated with SDS in the same concentrations used in the in vitro experiment. Animals were tested by nested polymerase chain reaction (nPCR) and Western blot (WB) assays. In the in vitro experiment, inhibitory activity against CLV without inactivation occurred in colostrum with all SDS concentrations. However, concentrations of 0.25 and 0.5% SDS presented only inhibitory activity against CLV in milk cells, and 1% concentration provided inactivation of the virus. In the in vivo tests, none of the three concentrations of SDS was effective in inactivating LVC in colostrum or goat milk, which was confirmed by seroconversion and presence of proviral DNA in animals afterwards.(AU)

O objetivo da pesquisa foi avaliar in vitro e in vivo o efeito do dodecil sulfato de sódio (SDS) sobre o lentivírus caprino (LVC) no colostro e no leite, a fim de desenvolver um método prático e eficiente no bloqueio da via de transmissão lactogênica do vírus. No experimento in vitro, o colostro e o leite de cabras positivas foram tratados com SDS a 0,25%, 0,50% e 1,0%. Em seguida, as células somáticas do colostro e do leite foram obtidas e direcionadas ao cocultivo com células de membrana sinovial caprina (MSC). No teste in vivo, os cabritos foram alimentados com colostro e leite providos de cabras positivas para LVC, tratados com SDS nas mesmas concentrações usadas no teste in vitro. Os animais foram acompanhados pelos testes de reação em cadeia da polimerase nested (nPCR) e western blot (WB). Nos resultados in vitro, no colostro, observou-se que, em todas as concentrações de SDS, ocorreu uma atividade inibitória contra o LVC, sem a inativação. Em relação às células do leite, o SDS apresentou, nas concentrações de 0,25 e 0,5%, atividade inibitória contra o LVC, e na concentração de 1%, houve inativação viral. Nos testes in vivo, as três concentrações de SDS testadas não foram efetivas na inativação do LVC no colostro e no leite caprino, o que se comprovou pela soroconversão e pela presença de DNA proviral nos animais.(AU)

Bioactive materials driven primary stability on titanium biocomposites.

The Ti6Al4V alloy constitutes an alternative choice to the most common metal-polymer solutions for total hip arthroplasty (THA) due to good biocompatibility, optimal mechanical properties and high load bearing capacity. However, as Ti6Al4V is not bioactive in its conventional form, hydroxyapatite (HAp) and tricalcium phosphate (TCP) have been widely used as coatings of metal prostheses due to their osteogenic properties and ability to form strong bonds with bone tissue. A promising approach consists in creating a bioactive surface metal matrix composite Ti6Al4V+ß-TCP or Ti6Al4V+HAp, obtained by hot pressing (HP) of powders. In this work, the tribological performance of Ti6Al4V+ß-TCP and Ti6Al4V+HAp composites is studied to evaluate the frictional response and surface damage representative of prosthesis implantation, key factors in bone fixation. Biocomposites with 10vol% ß-TCP and 10vol% Hap, as well as base titanium alloy, were prepared by HP with two surface finishing conditions - polished (Ra=0.3-0.5µm) and sandblasted (Ra=2.1-2.5µm) - for tribological testing against bovine cortical bone tissue. The static friction increases with surface roughness (from 0.20 to 0.60), whereas the kinetic regime follows an inverse trend for the biocomposites. In contrast with current knowledge, this study shows that an implant design solution based on Ti6Al4V+ß-TCP or Ti6Al4V+HAp biocomposites with polished surfaces results in an improved primary stability of implants, when compared to traditional rough surfaces. Moreover, it is also expected that the secondary stability will improve due to the adhesion between bone and HAp/ß-TCP, increasing the overall stability of the implant.

Inter- and Intra-Individual Analysis of Post-Exercise Hypotension Following a Single Bout of High-Intensity Interval Exercise and Continuous Exercise: A Pilot Study.

Recently, post-exercise blood pressure (BP) has been considered a predictive tool to identify individuals who are responsive or not to BP reductions with exercise training (i. e., "high" and "low responders"). This study aimed to analyze the inter- and intra-individual BP responsiveness following a single bout of high-intensity interval exercise (HIIE) and continuous exercise (CE) in normotensive men (n=14; 24.5±4.2 years). Mean change in BP during the 60 min period post-exercise was analyzed and minimal detectable change (MDC) was calculated to classify the subjects as "low" (no post-exercise hypotension [PEH]) and "high responders" (PEH occurrence) following each exercise protocol (inter-individual analysis). The MDC for systolic and diastolic BP was 5.8 and 7.0 mmHg. In addition, a difference equal/higher than MDC between the exercise protocols was used to define an occurrence of intra-individual variability in BP responsiveness. There were "low" and "high" PEH responders following both exercise protocols (inter-individual variability) as well as subjects who presented higher PEH following a specific exercise protocol (intra-individual variability between exercise protocols). These results were observed mainly for systolic BP. In summary, PEH is a heterogeneous physiological phenomenon and, for some subjects, seems to be exercise-protocol dependent. Further investigations are necessary to confirm our preliminary findings.

Leydig cell number and sperm production decrease induced by chronic ametryn exposure: a negative impact on animal reproductive health.

Ametryn is an herbicide used to control broadleaf and grass weeds and its acute and chronic toxicity is expected to be low. Since toxicological data on ametryn is scarce, the aim of this study was to evaluate rat reproductive toxicity. Thirty-six adult male Wistar rats (90 days) were divided into three groups: Co (control) and T1 and T2 exposed to 15 and 30 mg/kg/day of ametryn, respectively, for 56 days. Testicular analysis demonstrated that ametryn decreased sperm number per testis, daily sperm production, and Leydig cell number in both treated groups, although little perceptible morphological change has been observed in seminiferous tubule structure. Lipid peroxidation was higher in group T2, catalase activity decreased in T1 group, superoxide dismutase activity diminished, and a smaller number of sulphydryl groups of total proteins were verified in both exposed groups, suggesting oxidative stress. These results showed negative ametryn influence on the testes and can compromise animal reproductive performance and survival.

Avaliação imunohistoquímica e ultraestrutural de gametas e embriões caprinos infectados com o CAEV / Immunohistochemical and ultrastructural evaluation of gametes and embryos of goats infected with CAEV

O objetivo do presente estudo foi determinar a susceptibilidade dos folículos ovarianos, espermatozoides e embriões caprinos ao Vírus da Artrite Encefalite Caprina (CAEV). Para isto, foram analisados espermatozoides e folículos ovarianos pelas técnicas de imunohistoquímica e microscopia eletrônica de transmissão, antes e após protocolos de infecção in vitro com o CAEV. Foram submetidos à análise ultraestrutural, embriões caprinos produzidos in vivo, oriundos de cabras negativas e positivas para o CAEV. Nas amostras seminais, provenientes de animais tanto com infecção natural quanto dos artificialmente infectados, foi observada imunomarcação positiva dos espermatozoides, assim como alterações degenerativas na sua análise ultraestrutural. Já nas amostras de tecido ovariano, a imunomarcação foi mais discreta e identificada na região do estroma. No tocante à análise ultraestrutural, folículos e embriões se apresentaram íntegros. De acordo com esses resultados, pode-se concluir que os espermatozoides caprinos apresentaramse infectados, assinalando a susceptibilidade dessas células ao vírus, bem como a potencialidade do CAEV ser carreado ao cerne do oócito, originando embriões infectados.

The aim of this study was to determine the susceptibility of goat ovarian follicles, spermatozoa and embryos to caprine arthritis-encephalitis virus (CAEV). Spermatozoa and ovarian follicles were analyzed, before and after in vitro infection with CAEV, through immunohistochemistry and transmission electron microscopy techniques. Goat embryos, produced in vivo from infected and non-infected goats, were submitted to ultrastructural analysis. Immunohistochemical examination of seminal samples from goats naturally and artificially infected with CAEV revealed viral antigens in spermatozoa, while the ultrastructural analysis showed degenerative changes in these cells. Ovarian tissue samples presented a more discreet immunohistochemical positive reaction situated in the stroma region. Ultrastructural analysis revealed that the embryos and ovarian follicles were intact. These results indicate that the spermatozoa were infected, confirming the susceptibility of these cells to the virus, as well as the potential of CAEV entering the oocyte, giving rise to infected embryos.

Inibição dos lentivírus de pequenos ruminantes por drogas antivirais / Inhibition of small ruminant lentivirus by antiviral drugs

Inibidores da enzima transcriptase reversa e da protease foram avaliados quanto ao seu efeito inibitório na replicação do Vírus da Artrite Encefalite Caprina (CAEV) cepa CAEV Cork e do vírus Maedi-Visna (MVV) cepa K1514 cultivados em células fibroblásticas de caprinos. Os fármacos utilizados foram: lamivudina, didanosina, estavudina, zidovudina, efavirenz, atazanavir e lopinavir/ritonavir. A maior concentração utilizada para lamivudina, estavudina, zidovudina e efavirenz foi 500 ?M, para atazanavir foi 50 ?M e 5,0 ?M para lopinavir/r e didanosina. A atividade antiviral in vitro foi pesquisada por meio da avaliação da viabilidade celular através da redução do MTT e pela pesquisa de inibição dos efeitos citopáticos (CPE) dos vírus. A replicação dos vírus só não foi completamente bloqueada pelos inibidores de protease (IP) atazanavir e lopinavir/r enquanto os demais apresentaram eficácia antiviral significativa em diferentes concentrações. Os IP juntamente com o efavirenz, não mostraram atividade antiviral quando foram avaliados pela técnica de redução do MTT. Esses dados indicam que os fármacos inibidores da transcriptase reversa lamivudina, didanosina, estavudina e zidovudina são eficazes na inibição in vitro dos lentivírus de pequenos ruminantes.

Inhibitors of the reverse transcriptase and protease enzymes were evaluated for their inhibitory effect on the replication of caprine arthritis encephalitis virus (CAEV) strain CAEV Cork and of the Maedi-Visna virus (MVV) strain K1514 cultured in fibroblastic cells. The drugs lamivudine, didanosine, stavudine, zidovudine, efavirenz, atazanavir and lopinavir/ritonavir were used. The highest concentration used for lamivudine, stavudine, zidovudine and efavirenz was 500 ?M, for atazanavir it was 50 ?M and 5.0 ?M for lopinavir/r and didanosine. The in vitro antiviral activity was investigated by evaluating the cell viability by the MTT method and testing for inhibition of cytopathic effects (CPE) of the virus. The replication of the virus was not completely inhibited by the protease inhibitors atazanavir and lopinavir/r in the test for CPE, while the others drugs showed significant antiviral efficacy in different concentrations. The protease inhibitors together with the efavirenz did not show antiviral activity when they were assessed by the reduced MTT technique. These data showed that the reverse transcriptase inhibitor drugs lamivudine, didanosine, stavudine and zidovudine were effective in the in vitro inhibition of small ruminant lentivirus.

The use of microemulsions to remove chromium from industrial sludge.

In this work microemulsion systems were used to remove chromium from leather tannery sediments. The sludge was treated by a solid-liquid extraction process (acid digestion). The effects of particle size, digestion temperature and digestion time with regards to the efficiency of chromium removal were considered. The raw sludge (3 Mesh) was dried, grounded and sieved. Particles with 3, 14, 65, 100, 200, and 325 Mesh were evaluated. Sludge digestion solutions were prepared using each studied granule size at 25 degrees C, 70 degrees C, and 95 degrees C. Microemulsion extraction experiments to remove chromium III from the acid digestion solution were made according to a Scheffé Net experimental design methodology, using microemulsion systems inside the Winsor II region (System I) and inside the microemulsion region (Winsor IV--System II). A statistical treatment was used to obtain the isoresponse plots. Chromium extraction percentages were up to 73.3% for System I and up to 93.4% for System II.

Adsorption of bovine serum albumin on template-polymerized chitosan/poly(methacrylic acid) complexes.

Particulate systems composed of polyelectrolyte complexes (PEC) based on chitosan and poly(methacrylic acid) were obtained via template polymerization. The resultant particles were characterized as having regions with different charge densities: chitosan predominating in the core and poly(methacrylic acid) at the surface, the particles being negatively charged, as a consequence. Albumin was adsorbed on these particles (after cross-linking with glutardialdehyde), and pH was controlled to obtain two conditions: (i) adsorption of positively charged albumin and (ii) adsorption of albumin at its isoelectric point. Adsorption isotherms and zeta-potential measurements showed that albumin adsorption was controlled by hydrogen bonding/van der Waals interactions and that brush-like structures may enhance the adsorption of albumin on these particles. It was also found that shearing can induce desorption of albumin from the PEC surface, depending on the continuous phase albumin concentration.

Effect of molecular weight and ionic strength on the formation of polyelectrolyte complexes based on poly(methacrylic acid) and chitosan.

Chitosan/poly(methacrylic acid) complexes, CS/PMAA, were prepared via dropwise addition of a solution of PMAA to a solution of chitosan in acetic acid 2 wt %. The increase in molecular weight of PMAA inhibited the formation of insoluble complexes, while the increase in ionic strength first favored the formation of the complex followed by inhibiting it at higher concentrations. These observations were related to a description of polyelectrolyte complexation that was strongly dependent on macromolecular dimensions, both in terms of molecular weight and of coil expansion/contraction driven by polyelectrolyte effect.

Permeability studies in chitosan membranes. Effects of crosslinking and poly(ethylene oxide) addition.

Pure chitosan, glutaraldehyde crosslinked chitosan, and a blend of chitosan with poly(ethylene oxide) (PEO) membranes were prepared. The three membranes were characterized in terms of their swelling capacities as well as their permeabilities to a drug model (sulfamerazine sodium salt). For the permeation experiments, the variables analyzed were the type of membrane and the initial drug concentration in the liquid phase (from 0.1% to 1.5%). Permeability coefficients were calculated using UV spectroscopy. The results showed that for the three analyzed membranes, the permeability did not change with time (over the studied time interval). An increase in the permeability for CHI/PEO membranes compared to those made of pure chitosan was also observed, possibly due to microporous region formation and/or crystallinity reduction. For the crosslinked membrane, an even higher increase in the permeability coefficient was observed. In this case, the increase was attributed to free volume variation.

Evaluation and optimization of chromium removal from tannery effluent by microemulsion in the Morris extractor.

In this research a surfactant derived from a vegetable oil (coconut oil) was used to remove chromium from a tannery effluent. In the extraction process, a Morris extractor was used. Important variables used in assessing the optimization of the process included agitation speed, solvent rate and total flow rate. The experiments were conducted using a 2(3) factorial design. According to the response from the experimental design, the effects of each variable were calculated and the interactions between them determined. Response surface methodology was employed to study the effects of the studied variables. The optimum operational conditions were: agitation speed, 428 rpm; solvent rate, 0.37; total flow rate, 2.0 l h(-1). After extraction process, a re-extraction study was accomplished and the obtained results showed that chromium could be removed from the microemulsion phase by hydrochloric and sulphuric acidic solutions, what allows its reuse in the leather manufacturing process.

Heavy metals extraction by microemulsions.

The objective of this study is the heavy metal extraction by microemulsion, using regional vegetable oils as surfactants. Firstly, the main parameters, which have influence in the microemulsion region, such as: nature of cosurfactant, influence of cosurfactant (C)/surfactant (S) ratio and salinity were studied, with the objective of choosing the best extraction system. The extraction/reextraction process by microemulsion consists of two stages. In the first one, the heavy metal ion present in the aqueous phase is extracted by the microemulsion. In a second step, the reextraction process occurs: the microemulsion phase, rich in metal, is acidified and the metal is recovered in a new aqueous phase, with higher concentration. The used system had the following parameters: surfactant-saponified coconut oil; cosurfactant-n-butanol; oil phase-kerosene; C/S ratio=4; salinity-2% (NaCl); temperature of 27+/-1 degrees C; water phase-aqueous solution that varied according to the heavy metal in study (Cr, Cu, Fe, Mn, Ni and Pb). A methodology of experimental planning was used (Scheffé Net) to study the behavior of the extraction in a chosen domain. The extraction was accomplished in one step and yielded extraction percentage higher than 98% for all metals. In the reextraction HCl-8M was used as reextraction agent and the influence of the pH and time were verified. This work showed the great efficiency of the microemulsion, indicating that it is possible to extract selectively the heavy metals from the aqueous phase.

Gallium extraction by microemulsions.

In this work, the use of microemulsion in the extraction of gallium, with Bayer process, has been studied. The studied microemulsion systems were: systems I and II, with saponified coconut oil (SCO) and 4-ethyl,1-methyl,7-octyl,8-hydroxyquinoleine (Kelex-100) as extractants. The extraction essays by microemulsion were carried out by applying an experimental planning method whose microemulsion points were prepared within an experimental domain favorable to the extraction. Gallium and aluminum extraction percentages, in each point, were evaluated via a statistical treatment of the data, with the use of variance analysis and mathematical models. In system I (SCO), percentages of extraction of 85.5% for gallium and 35.4% for aluminum were achieved; in system II (Kelex-100), the yields were 100% for gallium and 99.9% for aluminum. The reextraction study with sulfuric acid presented the same behavior for both systems, with efficiency depending upon the concentration of the acid, and allowing for a selective reextraction of gallium and aluminum.