Graphene-TiO2 hybrids for photocatalytic aided removal of VOCs and nitrogen oxides from outdoor environment.

Outdoor and indoor air pollution has become a global concern in modern society. Although many policies and regulations on air quality have been promulgated worldwide over the past decades, airborne pollution still negatively affects health and therefore the life-style of human beings. One of the strategies to challenge this problem might be reducing the amount of airborne pollutant by mineralising them via photoinduced reactions. Photocatalytic oxidation of gaseous pollutants via titanium dioxide is one of the most promising solar photochemical reactions. In this research work, by means of a green sol-gel procedure, we have coupled titania to graphene (0.5 and 1.0 wt%) aiming to increase the solar photocatalytic activity of the produced hybrid materials. Transient paramagnetic species formed upon UV-A irradiation were detected by means of EPR spectroscopy. The photocatalytic reactions were assessed by monitoring the removal of nitrogen oxides and two different volatile organic compounds (benzene and isopropanol), which has never been assessed before. Our results highlight the exceptional characteristics of the TiO2/graphene hybrid material synthesised with 1.0 wt% graphene, and its excellent suitability for multi-purpose applications in the field of environmental remediation. Compared to unmodified titania, it shows a clear enhancement in the photocatalytic removal of those hazardous pollutants, having a photocatalytic degradation rate twice higher. In addition, the same material is highly stable and shows fully recyclability over repeated tests. Hybrid titania-graphene materials could thus be exploited to grant safer outdoor and indoor environments, having thus a beneficial impact on public health and on the quality of our lives.

How Does the Accuracy of Intracranial Volume Measurements Affect Normalized Brain Volumes? Sample Size Estimates Based on 966 Subjects from the HUNT MRI Cohort.

BACKGROUND AND PURPOSE: The intracranial volume is commonly used for correcting regional brain volume measurements for variations in head size. Accurate intracranial volume measurements are important because errors will be propagated to the corrected regional brain volume measurements, possibly leading to biased data or decreased power. Our aims were to describe a fully automatic SPM-based method for estimating the intracranial volume and to explore the practical implications of different methods for obtaining the intracranial volume and normalization methods on statistical power. MATERIALS AND METHODS: We describe a method for calculating the intracranial volume that can use either T1-weighted or both T1- and T2-weighted MR images. The accuracy of the method was compared with manual measurements and automatic estimates by FreeSurfer and SPM-based methods. Sample size calculations on intracranial volume-corrected regional brain volumes with intracranial volume estimates from FreeSurfer, SPM, and our proposed method were used to explore the benefits of accurate intracranial volume estimates. RESULTS: The proposed method for estimating the intracranial volume compared favorably with the other methods evaluated here, with mean and absolute differences in manual measurements of -0.1% and 2.2%, respectively, and an intraclass correlation coefficient of 0.97 when using T1-weighted images. Using both T1- and T2-weighted images for estimating the intracranial volume slightly improved the accuracy. Sample size calculations showed that both the accuracy of intracranial volume estimates and the method for correcting the regional volume measurements affected the sample size. CONCLUSIONS: Accurate intracranial volume estimates are most important for ratio-corrected regional brain volumes, for which our proposed method can provide increased power in intracranial volume-corrected regional brain volume data.

Novel 3,6-bis(imidazolidine)acridines as effective photosensitizers for photodynamic therapy.

The photoeffect of new proflavine derivatives with DNA-binding and antitumour activities, 3,6-bis((1-alkyl-5-oxo-imidazolidin-2-yliden)imino)acridine hydrochlorides (AcrDIMs), was studied to evaluate them as potential photosensitizers for photodynamic antitumor therapy. EPR measurements showed that superoxide radical anion and singlet oxygen were produced upon irradiation of AcrDIMs with UV-A light (>300nm) in the presence of molecular oxygen. This indicates that AcrDIMs may act as photosensitizers. The most active pentyl-AcrDIM and hexyl-AcrDIM displayed photocytotoxic effect toward the mouse lymphocytic leukemia cell line L1210 and human ovarian cancer cells A2780. Antitumor activity of pentyl-AcrDIM increased as high as about 12 times (72h incubation) after irradiation of A2780 cells (365nm, 1.05J/cm(2)). The photocytotoxicity seems to be associated with oxidative stress. Concerning the cell cycle, flow cytometry showed an arrest in the S-phase already 4h after irradiation. In a comet assay, no genotoxicity of AcrDIMs was found. Typical morphologic changes and formation of DNA-ladders indicated induction of apoptotic cell death, though no activation of caspase-3 was observed. Investigation of intracellular localization of pentyl-AcrDIM confirmed its partial accumulation in mitochondria and lysosomes. After irradiation of the A2780 cells, colocalization of pentyl-AcrDIM with monodansylcadaverine, a lysosomal dye, was proven, suggesting that lysosomes in the irradiated cells may be involved in the cell death.

The MRI volumetry of the posterior fossa and its substructures in trigeminal neuralgia: a validated study.

PURPOSE: Our aim was to determine whether the anatomical configuration of the posterior fossa and its substructures might represent a predisposition factor for the occurrence of clinical neurovascular conflict in trigeminal neuralgia (TN). METHODS: We used MRI volumetry in 18 patients with TN and 15 controls. The volume of the pontomesencephalic cistern, Meckel's cave and the trigeminal nerve on the clinical and non-affected sides was compared. The reliability has been assessed in all measurements. RESULTS: The posterior fossa volume was not different in the clinical and control groups; there was no difference between the affected and non-affected sides when measuring the pontomesencephalic cistern and Meckel's cave volume either. The volume of the clinically affected trigeminal nerve was significantly reduced, but with a higher error of measurement. CONCLUSIONS: We did not find any association between the clinical neurovascular conflict (NVC) and the size of the posterior fossa and its substructures. MRI volumetry may show the atrophy of the affected trigeminal nerve in clinical NVC.

Antioxidant properties of carotenoids: QSAR prediction of their redox potentials.

There is a great need to predict the antioxidant properties of molecules such as carotenoids. These compounds are of great interest due to their contribution to various important biological and industrial processes, including toxicity and fate. In our study, redox potentials were compiled from several literature sources. Redox potential values ranged from 537.2 mV for zeaxanthin up to 691.5 mV for beta-carotene; they correspond to the formation of cation radicals, using the standard calomel electrode (SCE). The redox potential values were measured using conventional electrochemical techniques, cyclic voltammetry and Osteryoung square-wave voltammetry. A quantitative structure-activity relationship (QSAR) was developed to model and consequently to predict the values of redox potential. The predicted values of redox potential for four external carotenoids, namely beta-carotene, zeaxanthin, cantaxanthin and astaxanthin, are presented and discussed. They indicate the dependence of redox potential on structure, donor and acceptor groups and polarisability.

Photoinduced electron transfer between C70 fullerene and 3,3',5,5'-tetramethylbenzidine studied by electron paramagnetic resonance.

Electron paramagnetic resonance (EPR) in situ spectroscopy was applied in the study of photoinduced electron transfer between 3,3',5,5'-tetramethylbenzidine (TMB) and C70 in different solvent systems. The changes found in UV-vis spectra pointed at ground state charge transfer complex formation [C70-TMB] in benzonitrile. Upon selective excitation of C70 using steady-state monochromatic irradiation with a wavelength of 546 nm, two EPR singlets were observed, which were assigned to C70 mono- and di-anion. In the photochemical and cathodic in situ reductions, identical EPR spectra of anion radicals were obtained. C70 mono-anion was investigated also in frozen 1,2-dichlorobenzene solutions within the temperature range from 110 to 210 K, and at 110 K the anisotropic EPR spectrum of C70 mono-anion was simulated assuming an axially symmetric g-matrix with gparallel - gperpendicular = 0.00165.

Reactive radical intermediates formed from illuminated nifedipine.

Nifedipine, (1,4-dihydro-2,6,dimethyl-4-(2-nitrophenyl)-3, 5-pyridinedicarboxylic acid dimethyl ester) a calcium channel blocker widely used in treatment of hypertension, is strongly photolabile. This may represent a problem in patients taking nifedipine and in handling of nifedipine samples. Reactive radical intermediates were determined and characterized in the process of nifedipine illumination using EPR spectroscopy. On illumination of nifedipine by daylight or by a mercury lamp, a nitroxide radical, RIIL-NIFNO.X was observed (in the first step), in various solvents like benzene, cyclohexane, methanol, acetonitrile, dimethylsulphoxide, or aqueous suspensions of liposomes. RIIL-NIF represents the nifedipine skeleton centered with phenyl group, and X is an EPR silent substituent. The generation of RIIL-NIFNO.X is coupled with the formation of nitroso compound, RIIL-NIFNO, as characterized by UV-visible spectroscopy. In a further step, RIIL-NIFNO abstracts hydrogen from nifedipine skeleton under the formation of RIIL-NIFNO.H radical. In addition to this, in system containing RIIL-NIFNO and unsaturated lipids, nitroxide radicals RIIL-NIFNO.RLIPIDS are formed probably via a pseudo Diels-Alder mechanism (RLIPIDS represents lipidic skeleton). The unusually easy photochemical activation of nifedipine is probably stimulated by photosensitization of its nitro group interacting with suitably positioned hydrogen or carboxylic methyl ester group from the pyridinyl ring.

Radical intermediates in the redox reactions of tetrazolium salts in aprotic solvents (cyclovoltammetric, EPR and UV-VIS study).

Tetrazolium Blue (TBCl2) and Nitrotetrazolium Blue (NTBCl2) cathodically reduced in non aqueous solvents form radicals with the center of unpaired electron on the tetrazolyl ring (TBH., NTBH.) as detected by EPR spectroscopy. After prolonged reduction, formazans (TBH2, NTBH2) are formed and are then further reduced to the nitro-centered anion radical (from NTBH2) and the azogroup-centered anion radical (from TBH2). The first cathodic peak in the cyclovoltammetric study in the region from -0.3 to -0.6 V vs. SCE (saturated calomel electrode) is irreversible and indicates an adsorption and diffusion process on the platinum and mercury electrodes. Formation of TBH+ and NTBH+ is assumed. The second peak, in the region from -0.8 to -1.3 V vs. SCE, is nearly reversible and coupled with the formation of TBH. and NTBH. radicals. UV-VIS spectra measured during the reduction show isosbestic points at the conversions: TB++-->TBH+, NTB++-->NTBH+; further, TBH+-->TBH2 and NTBH+-->NTBH2. The characteristic colours of the solutions observed can be used to characterise the reduction state of tetrazolium salts.

Reaction kinetics of alpha-tocopheroxyl radical with biologically and pharmacologically active substances.

The alpha-tocopheroxyl radical (alpha TR.)generated in the reaction with 1,1-diphenyl-2-picrylhydrazyl in n-butanol decayed according to second-order kinetics with a rate constant k alpha = 3 x 10(3) M-1s-1 as determined by EPR spectroscopy. Various biologically and pharmacologically active substances like isoprenaline (ISO), epinephrine (EPI), histamine (HIS), stobadine (STO), nafazatrom (NAF) and Kampo C medicine (KMC) accelerated the decay rate of alpha TR(.). The whole process is formally a third-order reaction with the rate constants (in 10(9) M-2s-1): ks(ISO) = 1.28, ks(NAF) = 1.25, ks(EPI) = 0.6, ks(HIS) = 0.4, and ks(STO) = 0.1. In the kinetics of the reaction mechanism, bimolecular intermediates are assumed and the rate constants of their formation were determined.