DG Values Research Articles

Valuation of Distributed Solar: A Qualitative View

A critical evaluation of the arguments used by solar DG advocates shows that those arguments may often overvalue solar DG. It is time to reassess the value of solar DG from production to dispatch and to calibrate our pricing policies to make certain that our efforts are equitable and carrying us in the right direction.

Comparison of mean glandular dose values provided by a digital breast tomosynthesis system in Brazil

Studies are needed to determine the radiation dose of patients that are undergoing Digital breast tomosynthesis (DBT) procedures. Mean glandular dose (DG) values were derived from the incident air kerma (Ki) measurements and tabulated conversion coefficients. Ki values were obtained through an ionization chamber positioned in a Hologic Selenia Dimensions system using appropriate exposure parameters. This work contributes to determine the reliable radiation dose received by the patients and compare DG values provided by this DBT system images.

Mesoporous Silica Nanoparticles for the Adsorptive Removal of Cu(II), Mn(II), and U(VI) from Acid Mine Drainage

The adsorption of Cu(II), Mn(II), and U(VI) ions by mesoporous silica nanoparticles (NPs) was inves- tigated by batch experiments to assess the potential using NPs to remediate acid mine drainage (AMD) contaminated water. Adsorption reactions were found to be rapid, attaining equilibrium within 5 min for Cu and less than a minute for Mn and U. Calculated adsorption rates based on the pseudo-second order model (R 2 = 0.99) showed that Mn adsorption was (3 times faster than Cu and 7 times faster than U. Adsorption increased with pH and temper- ature, and DG and DH values indicate that the process was spontaneous and endothermic. Isotherm data were best described by the Freundlich and Temkin models (R 2 = 0.99), with chemisorption responsible for the removal of Cu and Mn, and adsorption and precipitation for U removal. Importantly, Fe 3? , Mn, and SO4 2- ions increased adsorption from 52, 56, and 49 % to 77, 66, and 76 % for Cu, Mn, and U, respectively. Cu removal was, however, inhibited in 1:2 Cu:Mn solutions. NPs were then applied to actual AMD-contaminated ground and surface water. As in simulated AMD, adsorption was higher for Mn than Cu and removal efficiencies of up to 60 % for Mn and 34 % for Cu were attained. These NPs therefore offer an alternative for Mn removal that precludes pH adjustment and the copious amounts of lime required for that. Importantly, they can be used for cost-effective treatment of AMD-contaminated water.

Properties of PAN-TBP extraction chromatographic material

Three production routes of the preparation of a solid extractant based on tributylphosphate (TBP) embedded in the polyacrylonitrile matrix (PAN) have been studied. The method of direct PAN coagulation with TBP was found to be not viable due to the significant TBP solubility in the coagulation bath. The most suitable PAN-TBP solid extractant was prepared by the well-known impregnation method of ready-made neat PAN beads. The kinetics of uranium extraction from 3 mol L−1 HNO3, the effect of nitrate and nitric acids concentrations on the value of weight distribution coefficients Dg as well as the uranium “extraction isotherm” were determined for this material. Uranium extraction was rather fast, approximately 1 h was sufficient for the equilibrium achievement. Capacity for the uranium uptake, measured in batch experiments on PAN-TBP for 0.048 mol L−1 of uranium in 3 mol L−1 nitric acid, was found to be q = 0.363 mmol g−1 (58 % of the theoretical capacity). It was concluded that PAN-TBP material behaves like TBP in liquid–liquid extraction. Extraction capacity determined in column experiments was lower (by about 23 %) than expected from the “extraction isotherm” due to the TBP leaching out of the column. The thus prepared material is therefore not very suitable for multicycle extraction and stripping and can be used once, particularly for the analytical purposes.

Influence of Temperature and pH on the Transfer of SO2 from Water to Air by Inverse Gas Chromatography

Reversed-flow gas chromatography, a version of inverse gas chromatography, was applied for the study of the transfer of sulfur dioxide from pure and artificial sea water to the atmospheric environment. Using suitable mathematical equation rate coefficients, the transfer of SO2 from water to air (k c) as well as diffusion coefficients of SO2 vapors into nitrogen (D g) was determined. The rate coefficients increase with increasing temperature and decrease with increasing pH of the liquid phase. Moreover, they depend on the water environment, being bigger for the transfer of SO2 from pure water than those from artificial sea water. Finally, the values of D g and k c are compared with those given in the literature or calculated theoretically.

Competitive adsorption of dye species from aqueous solution onto melon husk in single and ternary dye systems

Polluted water may contain more than one dye species. Consequently, the behavior of a particular dye in a water system may be affected by the presence of the others. In this study, the adsorption of methylene blue (MB) in single dye system (SDS) and in ternary dye system (TDS) comprising of MB, congo red and methyl orange onto formaldehyde-treated melon husk (FMH) was investigated as a function of pH, contact time and species concentra- tions. Surface studies of FMH were investigated by Fourier transform infrared and scanning electron microscopy. The dye species adsorption equilibria were rapidly attained after 60 (SDS) and 90 min (TDS) of contact times. The adsorption kinetics were analyzed using pseudo first-order, pseudo second-order and intraparticle diffusion models and the adsorption data were well described by the pseudo second-order model. The equilibrium adsorption data were interpreted in terms of the Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, Harkin-Jura and Halsey isotherm models and the goodness of fittings were inspected using linear regression analysis (R 2 ). Our results indicated that the Langmuir model was best fitted, suggesting monolayer adsorption. Thermodynamic study showed that the adsorptions in SDS and TDS on FMH are favourable. The change in entropy (DS) and heat of adsorption (DH )o f dye species on FMH in TDS were estimated as 82.2 J/ mol K and 17.95 kJ/mol. respectively while in SDS, they were respectively -43.76 J/mol K and -21.84 kJ/mol. The sorption process in both systems was thermodynami- cally feasible with negative DG values.

Longitudinal assessment of grip strength using bulb dynamometer in Duchenne Muscular Dystrophy.

BACKGROUND:Grip strength is used to infer functional status in several pathological conditions, and the hand dynamometer has been used to estimate performance in other areas. However, this relationship is controversial in neuromuscular diseases and studies with the bulb dynamometer comparing healthy children and children with Duchenne Muscular Dystrophy (DMD) are limited.OBJECTIVE:The evolution of grip strength and the magnitude of weakness were examined in boys with DMD compared to healthy boys. The functional data of the DMD boys were correlated with grip strength.METHOD:Grip strength was recorded in 18 ambulant boys with DMD (Duchenne Group, DG) aged 4 to 13 years (mean 7.4±2.1) and 150 healthy volunteers (Control Group, CG) age-matched using a bulb dynamometer (North Coast- NC70154). The follow-up of the DG was 6 to 33 months (3-12 sessions), and functional performance was verified using the Vignos scale.RESULTS:There was no difference between grip strength obtained by the dominant and non-dominant side for both groups. Grip strength increased in the CG with chronological age while the DG remained stable or decreased. The comparison between groups showed significant difference in grip strength, with CG values higher than DG values (confidence interval of 95%). In summary, there was an increment in the differences between the groups with increasing age. Participants with 24 months or more of follow-up showed a progression of weakness as well as maintained Vignos scores.CONCLUSIONS:The amplitude of weakness increased with age in the DG. The bulb dynamometer detected the progression of muscular weakness. Functional performance remained virtually unchanged in spite of the increase in weakness.

Characterization of Amide Bond Conformers for a Novel Heterocyclic Template of N-acylhydrazone Derivatives

Herein we describe NMR experiments and structural modifications of 4-methyl-2-phenylpyrimidine-N-acylhydrazone compounds (aryl-NAH) in order to discover if duplication of some signals in their 1H- and 13C-NMR spectra was related to a mixture of imine double bond stereoisomers (E/Z) or CO-NH bond conformers (syn and anti-periplanar). NMR data from NOEdiff, 2D-NOESY and 1H-NMR spectra at different temperatures, and also the synthesis of isopropylidene hydrazone revealed the nature of duplicated signals of a 4-methyl-2-phenylpyrimidine-N-acylhydrazone derivative as a mixture of two conformers in solution. Further we investigated the stereoelectronic influence of substituents at the ortho position on the pyrimidine ring with respect to the carbonyl group, as well as the electronic effects of pyrimidine by changing it to phenyl. The conformer equilibrium was attributed to the decoplanarization of the aromatic ring and carbonyl group (generated by an ortho-alkyl group) and/or the electron withdrawing character of the pyrimidine ring. Both effects increased the rotational barrier of the C-N amide bond, as verified by the ΔG≠ values calculated from dynamic NMR. As far as we know, it is the first description of aryl-NAH compounds presenting two CO-NH bond- related conformations.

Improved Estimation of Protein-Ligand Binding Free Energy by Using the Ligand-Entropy and Mobility of Water Molecules

We previously developed the direct interaction approximation (DIA) method to estimate the protein-ligand binding free energy (ΔG). The DIA method estimates the ΔG value based on the direct van der Waals and electrostatic interaction energies between the protein and the ligand. In the current study, the effect of the entropy of the ligand was introduced with protein dynamic properties by molecular dynamics simulations, and the interaction between each residue of the protein and the ligand was also weighted considering the hydration of each residue. The molecular dynamics simulation of the apo target protein gave the hydration effect of each residue, under the assumption that the residues, which strongly bind the water molecules, are important in the protein-ligand binding. These two effects improved the reliability of the DIA method. In fact, the parameters used in the DIA became independent of the target protein. The averaged error of ΔG estimation was 1.3 kcal/mol and the correlation coefficient between the experimental ΔG value and the calculated ΔG value was 0.75.

Mean glandular dose for different angles of the X-ray tube using different glandularity phantoms

Digital breast tomosynthesis (DBT) is a three-dimensional radiographic technique that is beginning to be used as part of an imaging diagnostic program in some of Brazilian clinical practices. Studies are needed to evaluate the performance and to determine the radiation dose of patients that are undergoing this new procedure. The aim of this work is to present results of the mean glandular dose (DG) for different angles of the X-ray tube using a computed radiography (CR) mammography unit and different glandularity standard breast phantoms. DG values were derived from measurements of the incident air kerma (Ki) and tabulated conversion coefficients that are dependent on the half-value layer (HVL) of the X-ray spectrum. Irradiations were done in a 3000 Nova model Siemens MAMMOMAT mammography unit with the X-ray tube angle ranging from −30° to 30°. The protocol with 28kV was used for Mo/Mo combination. The distance between focus and the 90×5–6M model Radcal ionization chamber was 60.5cm and the tube loading (PIt) used was 50mAs. Exposures were done for DG determination using the semi-automatic exposure control mode and the 45mm Computerized Imaging Reference Systems, Inc phantoms which approximately simulate a standard breast with glandularities of 0, 30, 50, 70 and 100%. DG values ranged from 1.3±0.1 to 7.6±0.7mGy. The results are in according to the reference level of 3mGy established by the International Basic Safety Standards (BSS115) to breast with 45mm of thickness, 50% of glandularity and for the X-ray tube positioned in 0°. The results showed that DG increases with the glandularity and with the rotation of the X-ray tube. This work contributes to begin in Brazil the dosimetry in DBT equipments using different protocols and target/filter combinations.

The concept of RNA-assisted protein folding: Representation of amino acid kinetics at the tRNA level

Transfer RNA molecules (tRNA) have the thermodynamic potential to interact with each other to form dimers (hybridization energy, dG=−33.2±6.7kcal/mole, compared to the folding energy of the cloverleaf configuration, dG=−25±4.4kcal/mole, p<0.0001). The dG values have a strong negative correlation with the frequency of co-locations and substitutions of associated amino acids. We suggest that tRNA interactions participate in determining amino acid interactions (co-locations) and consequently the 3D structures of peptides.

Association of Base Excision Repair Gene Polymorphisms with ESRD Risk in a Chinese Population

The base excision repair (BER) pathway, containing OGG1, MTH1 and MUTYH, is a major protector from oxidative DNA damage in humans, while 8-oxoguanine (8-OHdG), an index of DNA oxidation, is increased in maintenance hemodialysis (HD) patients. Four polymorphisms of BER genes, OGG1 c.977C > G (rs1052133), MTH1 c.247G > A (rs4866), MUTYH c.972G > C (rs3219489), and AluYb8MUTYH (rs10527342), were examined in 337 HD patients and 404 healthy controls. And the 8-OHdG levels in leukocyte DNA were examined in 116 HD patients. The distribution of MUTYH c.972 GG or AluYb8MUTYH differed between the two groups and was associated with a moderately increased risk for end-stage renal disease (ESRD) (P = 0.013 and 0.034, resp.). The average 8-OHdG/106 dG value was significantly higher in patients with the OGG1 c.977G, MUTYH c.972G or AluYb8MUTYH alleles (P < 0.001 via ANOVA). Further analysis showed that combination of MUTYH c.972GG with OGG1 c.977GG or AluYb8MUTYH increased both the risk for ESRD and leukocyte DNA 8-OHdG levels in HD patients. Our study showed that MUTYH c.972GG, AluYb8MUTYH, and combination of OGG1 c.977GG increased the risk for ESRD development in China and suggested that DNA oxidative damage might be involved in such process.

Transmit–receive diversity for 2×2 multiple-input multiple-output channel in body area networks

Body-centric communication is an important part of 4G personal communication systems. The principal goal of this study is to investigate the effect of multiple-input multiple-output (MIMO)-diversity for on-body communication channels. The MIMO-diversity gain (DG) is calculated by plotting the cumulative distribution functions. The DG values for 2×2 MIMO system are calculated, which are equivalent to the DGs achievable by an equivalent diversity system of order 4. The power imbalance and the correlation among the subchannels is also presented and a comparison of 2×2, 2×1 and 1×2 systems is done on the basis of diversity performance.

Preparation of TiO2 nanoparticles by sonochemical method, isotherm, thermodynamic and kinetic studies on the sorption of strontium

The objective of this study is to evaluate the use of titanium dioxide nanoparticles which were prepared by novel sonochemical method as an ion exchange material for the removal of Sr from aqueous solution. The pH effect on the Sr 2? sorption was investigated. The data obtained have been correlated with Freundlich, Temkin and Dubi- nin-Radushkevich (D-R) isotherm models. Thermody- namic parameters fort he sorption system have been determined at four temperatures. Simple kinetic models have been applied to the rate and isotherm sorption data and the relevant kinetic parameters were determined from the graphical presentation of these models at 298K. Results explained that the pseudo second-order sorption mechanism is predominant and the overall rate constant of sorption process appears to be controlled by chemical sorption process. The value of sorption energy E = 13 kJ/ mol at 298K and the value of Gibbs free energy DG = 3,222 kJ/mol at 298K prove that the sorption of strontium on titanium dioxide nanoparticles is an endo- thermic and non-spontaneous process.

Relationship between structure, morphology, and carbon isotopic composition of graphite in marbles: Implications for calcite-graphite carbon isotope thermometry

Carbon isotope exchange between calcite and graphite is a useful and reliable geothermometer for medium- to high-grade marbles. However, in rare instances, such as at Naxos, Greece, apparent disequilibrium carbon isotope fractionation between calcite and graphite has been previously reported. In this study, new results are presented on the morphological features, X-ray diffraction studies, Raman spectroscopic studies, and carbon isotope studies of graphite. Three morphologically distinct graphite types are identified. The first type is fine grained with distinct polygonal crystal aggregates having smooth pinacoid faces. The second type consists of large botryoidal aggregates with typical crystal overgrowth features, and the third type is “normal” large platy crystals associated with phlogopite. Graphite morphological features using an FE-SEM suggests that the botryoidal aggregates are composed of complexly intergrown and stacked graphite layers, comprised of cone-helix structures. Different types of graphite display distinct Lc(002) and DG values as well as a sharp first-order Raman peak at ~1580 cm −1 with disordered bands. The presence of Raman disordered bands in fine-grained well-crystallized graphite is attributed to edge effects. Carbon isotope analysis of graphite reveals that marble with fine-grained well-crystallized graphite show a consistent isotope fractionation with the calcite, which perfectly match temperature estimates based on the mineral isograds. In contrast, coarse botryoidal graphite gives heterogeneous carbon isotope values (about a few per mill) and show anomalous carbon isotope fractionation between the calcite and graphite. The graphite associated with phlogopite also shows variations in the carbon isotope values. Combining morphologic, crystallographic, and carbon isotopic data we conclude that the variations in carbon isotopic composition were caused by the overgrowth of graphite on the preexisting grain and that morphological observations and structural characterizations of graphite crystals is a key for predicting isotopic equilibration during metamorphism.

Study of HDEHP-PAN solid extractants for the determination of 90Sr

Solid extractants containing di-(2-ethylhexyl)phosphoric acid (HDEHP) in the support based on modified polyacrylonitrile (PAN) were studied for the determination of 90Sr by means of measuring the activity of its separated 90Y daughter. In this paper, 152Eu and 133Ba were used as chemical homologues of 90Y and 90Sr. For these radionuclides, dependences of mass distribution coefficients (D g) on the nitric acid concentration were measured for several types of HDEHP-PAN solid extractants. The mechanism of the Eu3+ and Ba2+ ions extraction was confirmed to follow the theoretical two-phase equation for the chelating extractants. Further, the influences of the presence of nitrates, calcium and iron ions on the values of D g(Ba, Eu) were determined concentrating on the possibility of masking the iron ions by the addition of the ascorbic acid. This method was tested on the solution simulating the leachate of ashed green plant sample. The results obtained make the application of solid extractants containing HDEHP in PAN support prospective for 90Sr determination.

Properties of isotactic polypropylene irradiated in various atmospheres

In this paper, changes in structure and physical properties of stabilized isotactic polypropylene (iPP) were created by gamma irradiation, up to a dose of 700 kGy, in different media: air, deionized distilled (DD) water and acetylene. Two main effects occur when polyolefins, such as iPP, are subjected to ionizing radiation: crosslinking and scission of macromolecules. The domination of one or the other of these competitive processes is determined by both the structural peculiarities of the polymers and the experimental irradiation conditions. Gel and infrared (IR) spectroscopy measurements were used to determine the changes in the degree of network formation and oxidative degradation, respectively. Sol-gel analysis was studied in detail using the Charlesby-Pinner (C-P) equation. The radiation-induced changes in the structure and evolution of oxygen-containing species were also studied through dielectric loss (tan ?) analysis in a wide temperature and/or frequency range. Evolution of low temperature dielectric relaxations with gamma irradiation was investigated. The results showed that degradation was the major reaction in the initial step of irradiation, no matter what the atmosphere was. The C-P equation seemed applicable when stabilized iPP was irradiated within a certain dose range in various atmospheres. The iPP irradiated in acetylene/air had the lowest/highest values for oxidation level, dielectric losses, Dg and G(s)/G(x) values. The calculated Dg values are 1.5 and 5 times larger for the irradiation in DD water and air than for the acetylene. Furthermore, our data confirm that oxidation strongly affects the gel point but has a much lower effect on the G(S)/G(X) ratio. In the case of dielectric relaxation measurements, the connection between the oxidative degradation and dielectric properties is well established and is in good agreement with IR spectroscopy measurements. The amount of carbonyl, hydroperoxide and other polar groups is much higher for the irradiation in air than in other media, leading to higher dielectric losses. Disappearance of low temperature (? and ?) relaxations with gamma radiation confirmed great sensitivity of iPP structure to radiation-induced changes. Complete ?vanishing? of the ? relaxation in iPP samples irradiated in air is connected with a large radiation-induced oxidative degradation in this medium. Similar crosslinking, oxidation and dielectric behaviour was observed for the samples irradiated in water and acetylene, indicating DD water as a good crosslinking medium.

Equilibrium and Thermodynamic Studies of Cesium Adsorption on Natural Vermiculite and Optimization of Operation Conditions

Removal of cesium from synthetic aqueous solution through adsorption on vermiculite, under batch equilibrium experimental condition at six initial values of pH (3, 4, 6, 9, 11 and 12) and five temperatures (25, 50, 75, 85 and 95 °C) has been investigated. It is necessary to propose a suitable model for a better understanding of the mechanism of cesium adsorption on vermiculite. For this propose the suitability of the Langmiur, Freundlich and Redlich-Peterson (R-P) adsorption models for equilibrium data were investigated. The parameters in the adopted adsorption isotherm models were determined by Eviews software. The study of equilibrium isotherm shows that the best model for analysis of experimental data is Redlich-Peterson model with correlation coefficient higher than 0.99(both for temperature and pH). The results showed that increasing of pH and temperature increased the adsorption ability of vermiculite. Optimum conditions for adsorption were determined as T=75 °C, pH=9, vermiculite dose=1.5 g and contact time of 24 hr. Finally the thermodynamic constants of adsorption phenomena, DH° and DS° were found to be 2.672 kJ/mol and 0.563 kJ/mol K in the range of 25-95 °C respectively. The negative value of the Gibbs free energy DG demonstrates the spontaneous nature of cesium adsorption onto vermiculite.

Twenty-four Hour and Spot Urine Metabolic Evaluations: Correlations Versus Agreements

To investigate the correlations and agreements between the solute/creatinine ratios from the 24-hour and early morning spot urine samples for metabolic evaluation in stone-formers given the various pitfalls with the 24-hour urinary metabolic evaluation in stone-formers. 30 urinary stone-formers out of an initial 62 recruited provided a complete 24-hour urine and early morning spot urine samples for metabolic evaluation. Pearson correlation and Bland and Altman Test were used to assess the correlations and agreements. Significant correlations were established between the 24-hour urinary solute excretions and the corresponding early morning spot urine solute/creatinine ratios for calcium, magnesium, urate, potassium, oxalate, citrate, and the Differential Gibb's free energy value of calcium oxalate DG(CaOx) values. However, all these solute/creatinine measurements between the 24-hour and early morning spot urine samples were judged to be not within the acceptable limits based on the estimated "limit of agreement" by the Bland and Altman Test of Agreement. Diurnal circadian rhythm and postprandial excretion surge are thought to be responsible for the disagreements. Thus, the early morning spot urine is not suitable to be used interchangeably to replace the 24-hour urine collection in the evaluation of urinary metabolic abnormalities in stone-formers. A good correlation does not translate to an agreement between the 2 measurements.

Gibbs Free Energy Difference in Bulk Metallic Glass Forming Alloys

The Gibbs Free Energy Difference between the solid and liquid phases (DG) is related to nucleation frequency and has played an important role in predicting the glass forming ability (GFA) of multicomponent metallic alloys. This is due to the fact that the maximum energy for nucleus formation i.e. the activation barrier for nucleation has an inverse square relation with DG. The Gibbs Free Energy Difference of three multi-component bulk metallic glasses namely Mg65Cu25Y10, Zr57Cu15.4Ni12.6Al10Nb5 and Zr52.5Cu17.9Ni14.6Al10Ti5 have been evaluated using two new expressions. The results show that the DG values calculated assuming DCp to be constant lie closer to the experimental values for the Mg based system while in the case of two Zr based systems, DG computed using the hyperbolic variation of DCp show improved agreement with the experimental data.