1,183 research outputs found
New sulfoglycophoshoramidates as phosphoinositide mimetics
No full textProtein kinases are enzymes involved in the regulation of many crucial cellular processes like proliferation, differentiation and apoptosis. Among them, the serine/threonine protein kinase B (PKB), also known as Akt, plays a key role as a component of the phosphoinositide 3-kinase (PI3K)-Akt-mTOR axis, which is implicated in aberrant tumor cell signaling. Inappropriate activation of the Akt kinase is a common event in human tumors and Akt is a critical player in cell survival. Thus, inhibitors that target PI3Ks and its downstream effectors, including PKB are potentially relevant for cancer therapy. PI3K activation generates 3-phosphorylated phosphatidylinositols [PI(3)P] that bind PKB pleckstrin homology (PH) domain promoting PKB activation through its translocation from the cytosol to the plasma membrane, conformational change and final phosphorylation. New glucose-based inositol analogues are currently investigated as potential Akt inhibitors and the structure of PI(3)P, natural ligand of PKB PH domain, can be easily reconducted to a suitably modified d-glucose scaffold as in phosphoramidate. Here, the synthesis of a set of unnatural sulphoglycophosphoramidate as PI(3)P analogues targeting the PKB PH domain will be reported. In particular, we synthesized a series of analogues of natural sulfoquinovosylacylglycerols (SQAG) in which sulfoquinovose is beta-linked to a phosphoramidate moiety with different alkyl chains
A lower limit for Newtonian-noise models of the Einstein Telescope
No full textThe Einstein Telescope (ET) is a proposed third-generation gravitational-wave (GW) underground observatory. It will have greatly increased sensitivity compared to current GW detectors, and it is designed to extend the observation band down to a few Hz. At these frequencies, a major limitation of the ET sensitivity is predicted to be due to gravitational fluctuations produced by the environment, most importantly by the seismic field, which give rise to the so-called Newtonian noise (NN). Accurate models of ET NN are crucial to assess the compatibility of an ET candidate site with the ET sensitivity target also considering a possible reduction in NN by noise cancellation. With NN models becoming increasingly complex as they include details of geology and topography, it is crucial to have tools to make robust assessments of their accuracy. For this purpose, we derive a lower bound on seismic NN spectra, which is weakly dependent on geology and properties of the seismic field. As a first application, we use the lower limit to compare it with NN estimates recently calculated for the Sardinia and Euregio Meuse-Rhine (EMR) candidate sites. We find the utility of the method, which shows an inconsistency with the predictions for the EMR site, which indicates that ET NN models require further improvement
BIOELECTROCHEMICAL SYSTEM FOR REMOVING HEXAVALENT CHROMIUM FROM WATERS
No full textBES include a set of technologies that exploit the ability of certain microorganisms to use electrodes as the electrons acceptors/donors and to catalyze redox reactions in order to promote a flow of electrons. In the present study, we have assessed the possibility to remove Cr(VI) in a biocathodic chamber of a dual-chamber (2C) Microbial Electrolysis Cell (MEC) with cathode as the sole electron donor. The cathode was first put into the anodic compartment of a 2CMicrobial Fuel Cell (MFC) inoculated with sludge from an anaerobic digester. After the acclimation period, the electrode was transferred into the cathodic chamber to work at -300 mV (vs. Standard Hydrogen Electrode - SHE) as the biocathode in a Cr(VI)-reducing MEC with 2000 μg Cr(VI)/L. The acclimation phase in the 2C-MFC allowed to shorten the time for the electroactive-biofilm growth, and to increase the efficiency of the Cr(VI)-reducing MEC. The bioelectrochemical system ensured higher removal efficiency than the pure chemical process
Aikidô: Caminho para promoção de saúde e educação dialógica?
No full textTrabalho de Conclusão de Curso - Universidade Federal de Santa Catarina. Curso de Medicina. Departamento de Saúde Pública
Erratum: Energy-momentum tensor for a Casimir apparatus in a weak gravitational field [Phys. Rev. D 74, 085011 (2006)]
No full textAdvanced oxidation processes (AOPs) for the mineralization of azo-dyes from wastewaters: homogeneous vs. heterogeneous photocatalytic processes
No full textAdvanced oxidation processes (AOPs) for the mineralization of azo-dyes from wastewaters: homogeneous vs. heterogeneous photocatalytic processes
Francesco Conte 1, Cristina Calloni 2, Ilenia Rossetti 3 and Gianguido Ramis 4*
1 Chemical Plants and Industrial Chemistry Group, Dipartimento di Chimica, Università degli Studi di Milano, Milan, Italy
2 Chemical Plants and Industrial Chemistry Group, Dipartimento di Chimica, Università degli Studi di Milano, Milan, Italy
3 Chemical Plants and Industrial Chemistry Group, Dipartimento di Chimica, Università degli Studi di Milano, Milan, Italy
4* DICCA, Università degli Studi di Genova, Genoa, Italy, presenting author, corr. author ([email protected])
INTRODUCTION
Textiles industries huge production determines a strong environmental impact: the yearly total impact per person is estimated to be 1.3 tonnes of raw material and over 100 m3 of water. Ca. 700,000 – 1,000,000 tons/years of dyes are produced and more than 280,000 tons are lost in the effluent and often remain as persistent pollutants. Heterogeneous and homogeneous phototreatments can be efficiently used as Advanced Oxidation Processes to degrade such contaminants and a comparison between different technologies has been carried out on the azo-dye Dystar’s Levafix Brilliant Red E-6BA.
EXPERIMENTAL
Oas a model molecule for this study because it is characterized by low biodegradability
TiO2 P25 was employed as a commercial nanostructured material supplied by Evonik and compared with TiO2 FSP, prepared through a homemade flame spray pyrolysis apparatus. Metallic co-catalysts were deposited over the surface by wet impregnation and then reduced at different temperature (Ag, Au, Pt, Pd, Fe).
The catalysts were characterised by XRD, N2 physisorption and DR-UV-VIS analyses.
The photo-degradation tests were carried out in different cylinder-type double-wall glass reactors of 300-1000 mL capacity, open to air and equipped with a suitable lamp in case of photocatalyzed processes.
The Fenton process was carried out either in light or dark conditions by adding Fe salts and H2O2 and compared with UV/H2O2 and Heterogeneous photodegradation processes with the above described catalysts.
The light sources employed were characterized by different emission wavelength and power output: a LED-type lamp (white light, 30 W, 2700 lm), an external UV lamp (200W, maximum emission at 365 nm) and two different low power immersed-UV lamp (125 W, maximum emission at 365 nm); natural sunlight. The average irradiance was measured for the different setups through a photo-radiometer sensitive to the UVA fraction and were 116 W/m2 in case of the external-UV lamp and respectively 60 and 260 W/m2 for the low irradiance (lamp 1) and high irradiance (lamp 2) immersed-UV lamp. The progress of the reaction was monitored by UV-Vis and Total Organic Carbon (TOC).
Toxicity tests on the treated solutions were also carried out using the Crustacean Daphnia magna.
RESULTS AND DISCUSSION
The fastest degradation process was Photo-Fenton with the highest power immersion UV lamp (10 min to 97.4% conversion), strictly followed by the UV/H2O2 process (20 min to 100% conversion). The degradation time increased with the other light sources, i.e. sun and LED, but overall, the total reaction time did not exceed 30 min. On the other hand, when it comes to the heterogeneous process, the titania synthetized via flame pyrolysis takes longer time to reach full conversion. At first glance it seems that the homogeneous treatment outperforms the heterogeneous ones, however, in the first case these results were achieved using a large amount of hydrogen peroxide, about 3.5 equivalents, which of course boost the reaction and lowers the time required to achieve a good conversion of the substrate.
Figure 9: Degradation of Levafix dye: comparison.
No organic carbon was detected after the treatment, except when employing gold deposited catalyst. Acute toxicity tests revealed that the Levafix Briliant Red resulted in a 48h-LC50 of 117 mg/L. The toxic response was dramatic in case of the solutions treated with UV/H2O2 and (Photo)Fenton processed, since a higher mortality of Daphnia magna specimens was observed due to the residual amounts of hydrogen peroxide. Overall, the best toxicity results were achieved in case of the samples treated with titania photocatalyst (P25), since the toxicity of the solutions was lower than the ones containing the bare dye.
CONCLUSION
Photo-degradation of Levafix Brilliant Red was compared for different AOPs. The homogeneous treatments were more efficient in the degradation of the selected dye, but the main advantages of employing solid nanostructured photocatalyst is that it is not compulsory to add hydrogen peroxide (low toxicity) and the catalyst can be recovered easily
Energy-momentum tensor for a Casimir apparatus in a weak gravitational field.
No full textThe influence of the gravity acceleration on the regularized energy-momentum tensor of the quantized electromagnetic field between two plane-parallel conducting plates is derived. We use Fermi coordinates and work to first order in the constant acceleration parameter. A perturbative expansion, to this order, of
the Green functions involved and of the energy-momentum tensor is derived by means of the covariant geodesic point-splitting procedure. In correspondence to the Green functions satisfying mixed and gaugeinvariant boundary conditions, andWard identities, the energy-momentum tensor is covariantly conserved and satisfies the expected relation between gauge-breaking and ghost parts, while a new simple formula
for the trace anomaly is obtained to first order in the constant acceleration. A more systematic derivation is therefore obtained of the theoretical prediction according to which the Casimir device in a weak gravitational field will experience a tiny push in the upwards direction
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