Evaluation of the dispersion properties of graphene oxide/cetyltrimethylammonium bromide for application in nanocomposite materials

The properties of thermal diffusivity and Z potential of the GONPs/CTAB nanofluid were studied as a function of GO concentration (in the range between 4 and 12% w/v), temperature (35 and 50 °C) and time (30 and 60 min) under ultrasound. In turn, the structural properties of GONPs/CTAB were measured by XRD, Raman, SEM and TEM. The GO previously modified with CTAB was used to obtain a PLA/GO nanocomposite. It was found that the behavior of thermal diffusivity provides information in situ on the dispersion properties of the nanofluid, finding values from 0.0013 to 0.0024 cm2 s-1. The hydrodynamic diameter of the GONP dispersions was also determined to range from 75.83 to 360.3 nm with an increase in Z potential from 17 to 30 mV. The most stable GONPs/CTAB dispersion conditions were 6% w/v GO, 50 °C and 30 min. Under these conditions, the GONPs/CTAB materials present an increase in the spacing between GO layers, associated with a greater multilayer stacking of the GO and CTAB layers. The Raman spectrum allowed us to demonstrate that the modification with CTAB did not affect the crystallinity of GO, which was verified by the intensity ratio of the D band and the G band (ID/IG) for the GO/CTAB samples, with the exception of the GO 6% sample, where an increase in the ID/IG ratio (0.9) was observed compared to GO (0.82), associated with greater intercalation of CTAB between the GO sheets. Finally, an SEM analysis of the PLA/GO nanocomposite was carried out and the homogeneous distribution of GO in PLA was demonstrated when it is used as a filler in proportions of 0.1%. This treatment, in turn, contributed to improving the mechanical flexural properties of the nanocomposite materials.

Lumbar plexus terminal branch block, a safe alternative for transfemoral aortic valve implantation. Case report

Transcatheter aortic valve implantation is an alternative treatment for patients with severe aortic stenosis, it is conventionally performed under general anaesthesia or local anaesthesia plus sedation. We present the first case of trans-femoral, trans-catheter aortic valve implantation, performed in our hospital in a patient with severe aortic stenosis, who was a high surgical risk. Anaesthesia consisted of a combination of bilateral selective blockade of the iliohypogastric, ilioinguinal and genitofemoral nerves with the patient awake without sedation, using an ultrasound-guided approach. Transcatheter aortic valve implantation was successful and passed without incident, the patient remained immobile, calm, did not report pain, and sedation or hypnotics were not necessary during dilation of the vascular accesses with the introducer. Standard monitoring demonstrated haemodynamic stability, without cardiovascular repercussions and did not necessitate vasopressor or inotropic drug support. After the intervention, the patient was sent to the Cardiac Intensive Care Unit, where he remained asymptomatic and stable. Subsequently, the patient was admitted to the cardiology ward from where he was discharged without complications.

Application of thermal lens microscopy (TLM) for measurement of Cr(VI) traces in wastewater

In this work, we demonstrate for the first time that Thermal Lens Microscopy technique (TLM) can be applied to monitor the dynamics of a photocatalytic process in-situ. The photocatalytic reduction of hexavalent chromium -Cr(VI)- in aqueous solution using CdS and irradiated with visible light is monitored by TLM. Since the values of Cr(VI) concentration obtained after the photocatalytic process were close to those imposed by the international regulations for drinking water, the use of TLM allowed its measurement with a better reliability than with UV spectroscopy, usually used in this kind of analysis.