In this work, the effect of using zirconium(IV) hydroxide (Zr(OH) 4 ) nanoparticles in the enhancement of the thermal stability and viscoelastic properties of organically cross-linked polyacrylamide (PAM) hydrogels using hydroquinone (HQ) and hexamethylenetetramine (HMT) was studied. The thermal stability and viscoelastic properties of the PAM gels were studied by DSC and DMA, respectively. From the DSC analysis, the bound and free water contents were analyzed along with the degradation enthalpy to give a preliminary clue about the direct vs indirect interactions taking place in the gel. With the addition of 0.2−0.8 wt % Zr(OH) 4 , the thermal stability of the PAM hydrogel improved by 3−5 °C (reaching 187 °C) compared to PAM alone. Moreover, the elasticity of the PAM hydrogel increased with the addition of Zr(OH) 4 which was also supported by the strong interaction bond formed as demonstrated from the higher degradation enthalpy and free water recorded. These interactions were further explained using FTIR and optical microscope images. The TGA results also revealed the functionalization of PAM gel and showed that the gel was thermally stable even at 400 °C. In addition, the effects of calcination, organic cross-linker, salinity, and pH on the gel properties were investigated. From DSC and DMA analysis, it was found that the optimal conditions for the polymer gel were as follows: PAM at 4 wt %, Zr(OH) 4 at 0.2−0.8 wt %, organic cross-linkers (OrgCL) at 0.3 wt %, and KCl or MgCl 2 at 2 wt %.
We report what is believed to be the first demonstration of diode-pumped continuous-wave (CW) thin-disk Yb3+-doped Gd2SiO5 (Yb:GSO) laser at 1048 nm. With a 3.8% output coupler, the maximum output power is 1.38 W under a pump power of 17.8 W. Moreover, intracavity second-harmonic generation (SHG) has also been achieved with a power of 337 mW at 524 nm by using a LiB3O5 (LBO) nonlinear crystal. At the output power level of 337 mW, the green power stability is better than 5% and the ellipticity of spot is 0.97.
Phenyl acetic acid, a metabolite of 2—phenyl ethylamine, acts as a neuromodulator in the nigrostriatal dopaminergic pathway neuromodulator stimulating the release of dopamine. The evaluation of phenyl acetic acid concentration in the biological fluid reflects phenyl ethylamine levels thus allowing the assessment of the modulatory role of this endogenous substance. Changes in biological fluids levels of 2—phenylethylamine and/or in its metabolite have been reported in affective disorders, such as depression and schizophrenia. Recently, the occurrence of the “attention deficit hyperactivity syndrome” has been frequently reported in childhood population and involvement of dopaminergic dysfunction in this disease has been suspected. A fast, reliable and reproducible method for the determination of phenyl acetic acid in human blood, is therefore needed in order to have a screening tool for monitoring both healthy childhood population and suspected “attention deficit hyperactivity syndrome” patients. The gas chromatographicmass spectrometric method here described makes use of a deuterated internal standard in order to overcome problems related to the lack of reproducibility often encountered when a derivatization step is performed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.