Gut microbiota of patients with type 2 diabetes and gastrointestinal intolerance to metformin differs in composition and functionality from tolerant patients.

OBJECTIVE: Metformin modifies the gut microbiome in type 2 diabetes and gastrointestinal tolerance to metformin could be mediated by the gut microbiome. METHODS: We enrolled 35 patients with type 2 diabetes not receiving treatment with metformin due to suspected gastrointestinal intolerance. Metformin was reintroduced at 425 mg, increasing 425 mg every two weeks until reaching 1700 mg per day. According to the occurrence of metformin-related gastrointestinal symptoms, patients were classified into three groups: early intolerance, non-tolerant, and tolerant. Gut microbiota was profiled with 16 S rRNA. This sequencing aimed to determine the differences in the baseline gut microbiota in all groups and prospectively in the tolerant and non-tolerant groups. RESULTS: The classification resulted in 15 early intolerant, 10 tolerant, and 10 non-tolerant subjects. Early tolerance was characterized by a higher abundance of Subdoligranulum; while Veillonella and Serratia were higher in the non-tolerant group. The tolerant group showed enrichment of Megamonas, Megamonas rupellensis, and Phascolarctobacterium spp; Ruminococcus gnavus was lower in the longitudinal analysis. At the end point Prevotellaceae, Prevotella stercorea, Megamonas funiformis, Bacteroides xylanisolvens, and Blautia producta had a higher relative abundance in the tolerant group compared to the non-tolerant group. Subdoligranulum, Ruminococcus torques_1, Phascolarctobacterium faecium, and Eubacterium were higher in the non-tolerant group. The PICRUSt analysis showed a lower activity of the amino acid biosynthesis pathways and a higher sugar degradation pathway in the intolerant groups. CONCLUSIONS: Gut microbiota of subjects with gastrointestinal intolerance depicted taxonomic and functional differences compared to tolerant patients, and this changed differently after metformin administration.

Extruded PLA Nanocomposites Modified by Graphene Oxide and Ionic Liquid.

Polylactic acid (PLA)-based nanocomposites were prepared by twin-screw extrusion. Graphene oxide (GO) and an ionic liquid (IL) were used as additives separately and simultaneously. The characterization of the samples was carried out by means of Fourier transform infrared (FT-IR) and Raman spectroscopies, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The viscoelastic behavior was determined using dynamic mechanical analysis (DMA) and rheological measurements. IL acted as internal lubricant increasing the mobility of PLA chains in the solid and rubbery states; however, the effect was less dominant when the composites were melted. When GO and IL were included, the viscosity of the nanocomposites at high temperatures presented a quasi-Newtonian behavior and, therefore, the processability of PLA was highly improved.

Graphene-Ionic Liquid Thin Film Nanolubricant.

Graphene (0.5 wt.%) was dispersed in the hydrophobic room-temperature ionic liquid 1-octyl-3-methylimidazolium bis(trifluoromethanesulfonyl) imide (IL) to obtain a new non-Newtonian (IL + G) nanolubricant. Thin layers of IL and (IL + G) lubricants were deposited on stainless steel disks by spin coating. The tribological performance of the new thin layers was compared with those of full fluid lubricants. Friction coefficients for neat IL were independent of lubricant film thickness. In contrast, for (IL + G) the reduction of film thickness not only afforded 40% reduction of the friction coefficient, but also prevented wear and surface damage. Results of surface profilometry, scanning and transmission electron microscopy (SEM and TEM), energy dispersive analysis (EDX), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy were discussed.

Extrusion of Polymer Nanocomposites with Graphene and Graphene Derivative Nanofillers: An Overview of Recent Developments.

This review is focused on the recent developments of nanocomposite materials that combine a thermoplastic matrix with different forms of graphene or graphene oxide nanofillers. In all cases, the manufacturing method of the composite materials has been melt-processing, in particular, twin-screw extrusion, which can then be followed by injection molding. The advantages of this processing route with respect to other alternative methods will be highlighted. The results point to an increasing interest in biodegradable matrices such as polylactic acid (PLA) and graphene oxide or reduced graphene oxide, rather than graphene. The reasons for this will also be discussed.

New Alkylether-Thiazolium Room-Temperature Ionic Liquid Lubricants: Surface Interactions and Tribological Performance.

The use of newly synthesized alkylether-thiazolium ionic liquids as lubricants is described for the first time. Two ionic liquids composed of a thiazolium cation and a bis(trifluoromethanesulfonyl)amide ([Th][Tf2N]) or dicyanamide ([Th][(NC)2N]) anion have been studied, and their tribological behavior has been compared with that of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide ([Im][Tf2N]) in pin-on-disk tests using sapphire balls against AISI 52100 or AISI 316L steels. All ionic liquids show higher contact angles on AISI 316L steel than on AISI 52100, the lowest values found for ([Im][Tf2N]) on both steel surfaces. AISI 52100 shows similar friction coefficients for all lubricants, and negligible wear rates for the ionic liquids containing the bis(trifluoromethanesulfonyl)amide anion. Immersion tests show no corrosion of AISI 52100 in imidazolium or thiazolium bis(trifluoromethanesulfonyl)amide ionic liquids. AISI 316L shows similar friction coefficients for both bis(trifluoromethanesulfonyl)amide ionic liquids, but the lowest wear rate is obtained for [Th][Tf2N]. An increase in friction coefficient and wear rate is observed for thiazolium dicyanamide. This increase is related to a tribocorrosion process due to decomposition of the thiazolium cation. XPS shows the formation of iron sulfide on the wear track on AISI 316L after lubrication with thiazolium dicyanamide. No tribocorrosion processes take place for the [Tf2N] ionic liquids.

Static and kinetic friction force and surface roughness of different archwire-bracket sliding contacts.

The aim of this study was to determine the static and kinetic friction forces of the contact bracket-archwire with different dental material compositions in order to select those materials with lower resistance to sliding. We carried out sliding friction tests by means of a universal testing machine following an experimental procedure as described in ASTM D1894 standard. We determined the static and kinetic friction forces under dry and lubricating conditions using an artificial saliva solution at 36.5ºC. The bracket-archwire pairs studied were: stainless steel-stainless steel; stainless steel-glass fiber composite; stainless steel-Nitinol 60; sapphire-stainless steel; sapphire-glass fiber composite; and sapphire-Nitinol 60. The best performance is obtained for Nitinol 60 archwire sliding against a stainless steel bracket, both under dry and lubricated conditions. These results are in agreement with the low surface roughness of Nitinol 60 with respect to the glass fiber composite archwire. The results described here contribute to establishing selection criteria for materials for dental archwire-brackets.

Surface coating from phosphonate ionic liquid electrolyte for the enhancement of the tribological performance of magnesium alloy.

A chronoamperometric method has been applied for the growth of a surface coating on AZ31B magnesium alloy, using the imidazolium alkylphosphonate room-temperature ionic liquid 1-ethyl-3-methylimidazolium ethylphosphonate ([EMIM][EtPO3H]) as electrolyte. A surface coating layer is obtained after 4 h under a constant voltage bias of -0.8 V with respect to the standard electrode. The coating nucleation and growth process correlates well with a 3D progressive mechanism. X-ray photoelectron spectrometry (XPS) analysis of [EMIM][EtPO3H] shows new P 2p and O 1s peaks after its use as electrolyte, as a consequence of reaction between the phosphonate anion and the magnesium substrate. Angle-resolved XPS (ARXPS) analysis of [EMIM][EtPO3H] did not show any change in the composition of the surface before and after chronoamperometry, since the sampling depth (1.5 nm at the highest emission angle) is larger than the cation and anion sizes (ca. 7 and 5 Å, respectively). Characterization of the coating was made by scanning electron microscopy (SEM), focussed ion beam SEM, energy dispersive X-ray spectroscopy, XPS, and ARXPS. FIB-SEM shows that the coating presents a mean thickness of 374 (±36) nm and contains magnesium and aluminum phosphates. Linear reciprocating tribological tests under variable load show that the presence of the coating can reduce friction coefficients of the coated AZ31B against steel up to 32% and wear rates up to 90%, with respect to the uncoated alloy.

Scratch resistance of polycarbonate containing ZnO nanoparticles: effects of sliding direction.

Abrasive wear resistance of injection molded polycarbonate (PC) and polycarbonate + zinc oxide nanocomposites containing 0.5 wt% ZnO nanoparticles was determined as a function of the sliding direction with respect to injection flow. First we have performed single scratch testing under progressively increasing the load applied. Then sliding wear testing consisting of 15 successive scratches along the same groove was performed. Neat PC shows anisotropic behavior, with instantaneous penetration depth more than 50% higher in the direction parallel to the melt injection flow than in the transverse direction. Viscoelastic recovery after scratching of neat PC is also higher in the longitudinal than in the transverse direction, hence final residual depth values are similar in both directions. The addition of ZnO nanoparticles reduces the instantaneous penetration depth in the longitudinal direction but lowers viscoelastic recovery so that the residual depth is large. In the transverse direction, the scratch resistance is similar for neat PC and the nanocomposite. Dynamic mechanical analysis, SEM/FIB results and wear mechanisms from SEM observations of wear scars are discussed. Below the glass transition region the nanocomposite has distinctly higher storage modulus E' than PC--a clear reinforcement effect. However, the addition of ZnO nanoparticles to the polymer increases the material brittleness at room temperature by a factor of 2.72.

Liquid crystals in tribology.

Two decades ago, the literature dealing with the possible applications of low molar mass liquid crystals, also called monomer liquid crystals (MLCs), only included about 50 references. Today, thousands of papers, conference reports, books or book chapters and patents refer to the study and applications of MLCs as lubricants and lubricant additives and efforts are made to develop new commercial applications. The development of more efficient lubricants is of paramount technological and economic relevance as it is estimated that half the energy consumption is dissipated as friction. MLCs have shown their ability to form ordered boundary layers with good load-carrying capacity and to lower the friction coefficients, wear rates and contact temperature of sliding surfaces, thus contributing to increase the components service life and to save energy. This review includes the use of MLCs in lubrication, and dispersions of MLCs in conventional polymers (PDMLCs). Finally, new lubricating system composed of MLC blends with surfactants, ionic liquids or nanophases are considered.

Ionic liquids as advanced lubricant fluids.

Ionic liquids (ILs) are finding technological applications as chemical reaction media and engineering fluids. Some emerging fields are those of lubrication, surface engineering and nanotechnology. ILs are thermally stable, non-flammable highly polar fluids with negligible volatility, these characteristics make them ideal candidates for new lubricants under severe conditions, were conventional oils and greases or solid lubricants fail. Such conditions include ultra-high vacuum and extreme temperatures. Other very promising areas which depend on the interaction between IL molecules and material surfaces are the use of ILs in the lubrication of microelectromechanic and nanoelectromechanic systems (MEMS and NEMS), the friction and wear reduction of reactive light alloys and the modification of nanophases.

Índice de Charlson versus índice de Barthel como predictor de mortalidad e institucionalización en una unidad geriátrica de agudos y media estancia / Barthel and Charlson indexes for the prognosis of mortality and institutionalization in hospitalized geriatric patients

Introducción Comparar la validez del índice de Barthel (IB), el índice de comorbilidad de Charlson (ICC) y, una variante de este último, el índice de comorbilidad de Charlson corregido por la edad (ICCE) en el pronóstico de mortalidad e institucionalización en pacientes geriátricos hospitalizados.Material y métodos Se realiza un estudio retrospectivo de todos los pacientes ingresados durante el año 2006 en una unidad de agudos y media estancia de un servicio de geriatría (n=343). Como variables independientes se recogieron el IB al ingreso (registrado en la historia clínica de los pacientes) y el ICC e ICCE recogidos a posteriori con la información disponible. La variable resultado fue la ocurrencia de muerte o la institucionalización al alta del paciente, recogiéndose valores de sensibilidad y especificidad para cada uno de los puntos de corte seleccionados de las escalas evaluadas, y elaborando una curva ROC para cada una de ellas, calculando el área bajo la curva (ABC) con su intervalo de confianza (IC) del 95%. Resultados La muestra tenía una edad media de 82,3 años, con el 58,6% de mujeres. El ABC correspondiente al IB fue de 0,736 (IC del 95%=0,68–0,79), para el ICC fue de 0,61 (IC del 95%=0,55–0,67) y para el ICCE fue de 0,625 (IC del 95%=0,56–0,69), encontrándose diferencias estadísticamente significativas entre el ABC del IB frente al ABC de los otros dos índices (p<0,01).Conclusiones Como predictores de mortalidad e institucionalización, la validez del IB fue superior a la de los ICC (original y corregido por la edad). Por este motivo, el IB puede tener una mayor utilidad para el uso más adecuado de los recursos sanitarios disponibles(AU)

Introduction To compare the validity of the Barthel (BI) and Charlson comorbidity index (CCI) as well as the age-adjusted CCI for the prognosis of mortality and institutionalization in hospitalized geriatric patients.Material and methods A retrospective study was conducted to evaluate patients admitted to an acute care geriatric ward and mid-term care facility in 2006 (n=343). The independent variables were the admission BI (registered in the clinical history in all patients) and the CCI and the age-adjusted CCI, which were registered “a posteriori” using the available information. The outcome variable was mortality or institutionalization when the patient was discharged. The sensitivity and specificity values for each of the cut-off points selected from the scales analyzed were recorded and ROC curves were constructed for each of these points; the area under the curve (AUC) with a confidence interval (CI) of up to 95% was calculated.Results The mean age was 82.3 years (58.6% women). The AUC was 0.736 (95% CI=0.68–0.79) for the BI, 0.61 (95% CI=0.55–0.67) for the CCI and 0.625 (95% CI=0.56–0.69) for the age-adjusted CCI. Statistically significant differences were found among the AUC of the BI compared with that of the other two indexes (p<0.01).Conclusions As predictors of mortality and institutionalization, the BI was superior to the CCI and the age-adjusted CCI. The BI could therefore be more useful than the other two indexes when considering an adequate use of healthcare services (AU)

[Barthel and Charlson indexes for the prognosis of mortality and institutionalization in hospitalized geriatric patients]. / Indice de Charlson versus índice de Barthel como predictor de mortalidad e institucionalización en una unidad geriátrica de agudos y media estancia.

INTRODUCTION: To compare the validity of the Barthel (BI) and Charlson comorbidity index (CCI) as well as the age-adjusted CCI for the prognosis of mortality and institutionalization in hospitalized geriatric patients. MATERIAL AND METHODS: A retrospective study was conducted to evaluate patients admitted to an acute care geriatric ward and mid-term care facility in 2006 (n=343). The independent variables were the admission BI (registered in the clinical history in all patients) and the CCI and the age-adjusted CCI, which were registered "a posteriori" using the available information. The outcome variable was mortality or institutionalization when the patient was discharged. The sensitivity and specificity values for each of the cut-off points selected from the scales analyzed were recorded and ROC curves were constructed for each of these points; the area under the curve (AUC) with a confidence interval (CI) of up to 95% was calculated. RESULTS: The mean age was 82.3 years (58.6% women). The AUC was 0.736 (95% CI=0.68-0.79) for the BI, 0.61 (95% CI=0.55-0.67) for the CCI and 0.625 (95% CI=0.56-0.69) for the age-adjusted CCI. Statistically significant differences were found among the AUC of the BI compared with that of the other two indexes (p<0.01). CONCLUSIONS: As predictors of mortality and institutionalization, the BI was superior to the CCI and the age-adjusted CCI. The BI could therefore be more useful than the other two indexes when considering an adequate use of healthcare services.

Reliability of preoperative duplex scanning in designing a therapeutic strategy for chronic lower limb ischemia.

The objective of this study was to compare the treatment plan designed on the basis of preoperative duplex scanning evaluation of the critical limb ischemia with the treatment plan finally carried out, after assessing the findings obtained during surgical or endovascular treatment. Over a period of 51 months a preoperative duplex scanning study was carried out in 335 consecutive patients with chronic critical ischemia, to design the best therapeutic strategy. Agreement between both plans were as follows: 80%, 82,7% and 59% in the examinations of the iliac arteries, femoropopliteal or tibial arteries respectively. The operation plan was more frequently modified due to a duplex scanning failure in procedures involving the the distal vessels(10 of 44 [22.7%], p < 0.01). In conclusion, duplex scanning evaluation of patients with occlusive arterial disease of the lower limbs permits the design of both a medical and a surgical or endovascular treatment plan with a high level of agreement with the findings obtained during the revascularization procedure.