Fraction Of Impurities Research Articles

Criteria for selecting electrons with energies above 50 GeV according to the PAMELA experiment data

To separate the particles such as electrons and positrons, which are insignificant in number, from the total particle flux of cosmic rays, reliable enough criteria of their selection should be found. The proposed selection technique based on such criteria as the interaction in the first calorimeter layers, difference in the energy release for protons and electrons, and the measured number of neutrons makes it possible to separate electrons from the total charged particle flux with an impurity fraction no larger than 2% of the electron flux.

The role of 3He impurities in the stress induced roughening of superclimbing dislocations in solid 4He

We analyze the stress induced and thermally assisted roughening of a forest of superclimbing dislocations in a Peierls potential in the presence of 3He impurities and randomly frozen in static stresses. It is shown that the temperature of the dip Td in the flow rate observed by Ray and Hallock (Phys. Rev. Lett. 105, 145301 (2010)) is determined by the energy of 3He activation from dislocation core. However, it is suppressed by, essentially, the logarithm of the impurity fraction. The width of the dip is determined by inhomogeneous fluctuations of the stresses and is shown to be much smaller than Td.

Characterization of impurities in tylosin using dual liquid chromatography combined with ion trap mass spectrometry

Investigation of unknown impurities in a tylosin sample was performed using liquid chromatography coupled to mass spectrometry (LC/MS). Separation was performed according to the recently described LC-UV method of Ashenafi et al. (2011) [14]. This method was reported to have a good selectivity as it was able to separate the four main components of tylosin from the already known and 23 unknown impurities. However, as this method uses a mobile phase with non-volatile constituents, direct characterization of these impurities using LC/MS was not possible. The impurity fractions were therefore first collected and then desalted before sending them to the MS. Identification of the impurities in the tylosin sample was performed with a quadruple ion trap (IT) MS, with an electrospray ionization (ESI) source in the positive ion mode. The structure of the impurities was deduced by comparing their fragmentation pattern with those of the main components of tylosin. As several peaks in the LC-UV method contained multiple compounds, using this method in total 41 new impurities were (partly) characterized.

Development of a new sodium diclofenac certified reference material using the mass balance approach and 1H qNMR to determine the certified property value

Certified reference materials (CRMs) are essential tools to guarantee the metrological traceability of measurement results to the International System of Units (SI), which means the accuracy and comparability of results over time and space. In the pharmaceutical area, only a few CRMs are available and the use of (non-certified) reference materials is a much more common practice. In this paper, the studies on a new candidate CRM of sodium diclofenac based on the ISO Guides 34:2009 and 35:2005 are described. The project steps included characterization, homogeneity test, stability studies, and uncertainties estimation. In the characterization, the mass fractions of organic, inorganic, and volatile impurities were determined, and the results were cross-checked by independent reference methods or interlaboratorial study. The API mass fraction was calculated by mass balance and cross-checked by quantitative proton nuclear magnetic resonance (1H qNMR). The paper also presents a Monte Carlo simulation to estimate the measurement uncertainty as an approach to validate the GUM results in 1H qNMR. The homogeneity between batch units was verified, and the candidate CRM stability under transport and storage conditions was evaluated in short- and long-term stability studies. The CRM certified property value and corresponding expanded uncertainty, obtained from the combined standard uncertainty multiplied by the coverage factor (k=2), for a confidence level of 95%, was (999.76+0.10)mgg−1.

Discontinuous and continuous purification of single-chain antibody fragments using immobilized metal ion affinity chromatography

This work describes the adsorption–desorption behavior of a histidine-tagged single-chain Fragment variable antibody (D1.3 scFv) on a commercial immobilized metal ion affinity chromatography (IMAC) column. A clarified cell culture supernatant originating from Bacillus megaterium was characterized using single column experiments in a pH-gradient elution mode. The cell culture supernatant containing the antibody fragment D1.3 scFv could be treated in the chromatographic separation process as a pseudo-binary mixture. Adsorption equilibrium constants of the antibody fragment fraction (ABF) and the non-specifically retained protein impurity fraction (IMP) were determined experimentally at constant pH by reinjecting pulses of pooled fractions collected in preliminary batch gradient elution runs. Based on the estimated adsorption equilibrium constants a possible multicolumn open-loop three-zone two-step pH-gradient simulated moving bed (SMB) process is suggested and designed, which possesses the potential to isolate continuously the antibody fragment fraction (ABF) containing the single-chain antibody fragment D1.3 scFv.

Impurity analysis of NSTX using a transmission grating-based imaging spectrometer

A transmission grating-based imaging spectrometer has recently been installed and operated on the National Spherical Torus Experiment (NSTX) at PPPL. This paper describes the spectral and spatial characteristics of impurity emission under different operating conditions of the experiment—neutral beam heated, ohmic heated and RF heated plasma. A typical spectrum from each scenario is analyzed to provide quantitative estimates of impurity fractions in the plasma.

Effects of Ca-doping on microstructure and Tc in Bi2201 system

In this article, a series of samples with the nominal composition of Bi2Sr2-xCaxCuO6 (x=0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0) are prepared by sol-gel method. By means of XRD, TEM and four point probe measurements, the effects of Ca doping on phase composition and lattice constant of Bi2201 superconductor are studied. It is shown that Ca element occupy and influence the modulation period and Tc. It has been found that b and c axes shortens firstly and then keeps constant with increasing of Ca. The introduction of Ca results in a decrease of Sr content as well as increase of the modulation wavelength and Tc. When the doping level of Ca is up to 0.7, a fraction of impurity appears gradually, which leads to a decrease in Tc.

Insulin Degradation by Acinar Cell Proteases Creates a Dysfunctional Environment for Human Islets Before/After Transplantation: Benefits of α-1 Antitrypsin Treatment

Pancreatic acinar cells are commonly cotransplanted along with islets during auto- and allotransplantations. The aims of this study were to identify how acinar cell proteases cause human islet cell loss before and after transplantation of impure islet preparations and to prevent islet loss and improve function with supplementation of α-1 antitrypsin (A1AT). Acinar cell protease activity, insulin levels, and percent islet loss were measured after culture of pure and impure clinical islet preparations. The effect of proteases on ultrastructure of islets and β-cell insulin granules were examined by transmission electron microscopy. The number of insulin granules and insulin-labeled immunogold particles were counted. The in vivo effect of proteases on islet function was studied by transplanting acinar cells adjacent to islet grafts in diabetic mice. The effects of A1AT culture supplementation on protease activity, insulin levels, and islet function were assessed in pure and impure islets. Islet loss after culture was significantly higher in impure relative to pure preparations (30% vs. 14%, P<0.04). Lower islet purity was associated with increased protease activity and decreased insulin levels in culture supernatants. Reduced β-cell insulin granules and insulin degradation by proteases were confirmed by transmission electron microscopy. Transplantations in mice showed delayed islet graft function when acinar cells were transplanted adjacent to the islets under the kidney capsule. Supplementation of A1AT to impure islet cultures maintained islet cell mass, restored insulin levels, and preserved islet functional integrity. Culture of impure human islet fractions in the presence of A1AT prevents insulin degradation and improves islet recovery.

Thermodynamic properties of neopentylbenzene over the range from T → (0 to 350) K

In the present research, the temperature dependence of heat capacity Cp,m∘=f(T) of neopentylbenzene C6H5–C5H11 has been measured between T=(6 and 350)K in the precision adiabatic vacuum calorimeter and reported for the first time. The temperature and enthalpy of fusion of neopentylbenzene and the total mole fraction of impurities have been determined. The experimental results have been used to calculate the standard (р°=0.1MPa) thermodynamic functions Cp,m∘/R,Δ0THm∘/RT,Δ0TSm∘/R and Φm∘/R=Δ0TSm∘/R-Δ0THm∘/RT (where R is the universal gas constant) of neopentylbenzene over the range from T→(0 to 350)K. The standard entropy of formation of the compound under study at T=298.15K has been calculated.

Impurity localization in aluminum oxide compounds

Heat-treatment products of commercial γ-Al(OH)3 (gibbsite) were characterized by X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray fluorescence spectrometry with the aim of localizing impurities in the parent material. The results suggest that at least a fraction (about half) of typical impurities in the form of readily soluble aluminates is localized in the surface layer of gibbsite particles.

Individual organelle pH determinations of magnetically enriched endocytic organelles via laser-induced fluorescence detection.

The analysis of biotransformations that occur in lysosomes and other endocytic organelles is critical to studies on intracellular degradation, nutrient recycling, and lysosomal storage disorders. Such analyses require bioactive organelle preparations that are devoid of other contaminating organelles. Commonly used differential centrifugation techniques produce impure fractions and may not be compatible with microscale separation platforms. Density gradient centrifugation procedures reduce the level of impurities but may compromise bioactivity. Here we report on simple magnetic setup and a procedure that produce highly enriched bioactive organelles based on their magnetic capture as they traveled through open tubes. Following capture, in-line laser-induced fluorecence detection (LIF) determined for the first time the pH of each magnetically retained individual endocytic organelle. Unlike bulk measurements, this method was suitable to describe the distributions of pH values in endocytic organelles from L6 rat myoblasts treated with dextran-coated iron oxide nanoparticles (for magnetic retention) and fluorescein/TMRM-conjugated dextran (for pH measurements by LIF). Their individual pH values ranged from 4 to 6, which is typical of bioactive endocytic organelles. These analytical procedures are of high relevance to evaluate lysosomal-related degradation pathways in aging, storage disorders, and drug development.

Comparison Studies between Hydrogenation and Oxidation of MWNTs Followed by Acid Treatment

MWNTs obtained using iron catalyst and ethylene as a carbon source were submitted to a purification procedure. To purify these materials from amorphous carbon two parallel methods--based on either hydrogen or air treatment--were applied. At the second purification stage iron particles were removed using 1 M or 5 M nitric or hydrochloric acids. The phase composition of the samples was determined using X-ray diffraction method. The sample morphology was characterized using a high resolution transmission electron microscopy. The relative fraction of impurities in the samples was estimated by Raman spectroscopy and the quantitative analysis of metal impurity content was validated by means of thermogravimetric analysis.

Recombinant protein purification using gradient-assisted simulated moving bed hydrophobic interaction chromatography. Part I: Selection of chromatographic system and estimation of adsorption isotherms

The design of gradient simulated moving bed (SMB) chromatographic processes requires an appropriate selection of the chromatographic system followed by the determination of adsorption isotherm parameters in the relevant range of mobile phase conditions. The determination of these parameters can be quite difficult for recombinant target proteins present in complex protein mixtures. The first part of this work includes the estimation of adsorption isotherm parameters for streptokinase and a lumped impurity fraction present in an Escherichia coli cell lysate for a hydrophobic interaction chromatography (HIC) matrix. Perturbation experiments were carried out using a Butyl Sepharose matrix with purified recombinant protein on buffer equilibrated columns as well as with crude cell lysate saturated columns. The Henry constants estimated for streptokinase were found to exhibit in a wide range a linear dependence on the salt concentration in the mobile phase. These parameters were applied in subsequent investigations to design a simulated moving bed (SMB) process capable to purify in a continuous manner recombinant streptokinase from the E. coli cell lysate.

Influence of phase segregation on the bulk and grain boundary conductivity of LSGM electrolytes

Electrolytes based on La 1 − x Sr x Ga 0.8Mg 0.2O 3 − δ (LSGM) are difficult to synthesise as single phase materials and secondary phases of LaSrGa 3O 7 and LaSrGaO 4 are usually found at temperatures as high as 1400 °C. Dense LSGM ceramics with different amounts of these impurities were prepared from freeze-dried powders. These ceramics were studied by impedance spectroscopy to evaluate the influence of phase segregation on the bulk and grain boundary contributions to the ionic conductivity. The bulk and specific grain boundary conductivities of dense LSGM samples resulted to be nearly independent on the fraction of impurities. Furthermore, the ionic and electronic conductivities are not seriously affected by the presence of minor secondary phases.

Diluted manganese on the bond-centered site in germanium

The functional properties of Mn-doped Ge depend to large extent on the lattice location of the Mn impurities. Here, we present a lattice location study of implanted diluted Mn by means of electron emission channeling. Surprisingly, in addition to the expected substitutional lattice position, a large fraction of the Mn impurities occupies the bond-centered site. Corroborated by ab initio calculations, the bond-centered Mn is related to Mn-vacancy complexes. These unexpected results call for a reassessment of the theoretical studies on the electrical and magnetic behavior of Mn-doped Ge, hereby including the possible role of Mn-vacancy complexes.

ChemInform Abstract: Thermodynamic Properties of Borazole at Temperatures from 0 to 310 K

The temperature dependence of the molar heat capacity C°p,m for borazole (c-B3N3H6) has been studied at temperatures from 13 K to 310 K in a vacuum adiabatic calorimetric cryostat within 0.002·Cp,m. The temperature and enthalpy of melting of borazole as well as the total mole fraction of impurities have been determined. From the values obtained the thermodynamic functions ΔT0H°m, ΔT0S°m and Φ°m have been calculated in the temperature range 0 to 310 K, and the thermochemical quantities of formation: ΔfH°m, ΔfS°m, and ΔfG°m for borazole have been estimated also at T = 298.15 K and p = 101.325 kPa. The properties of borazole have been compared with those of benzene.

Culture of Impure Human Islet Fractions in the Presence of Alpha-1 Antitrypsin Prevents Insulin Cleavage and Improves Islet Recovery

Background Exocrine tissue is commonly cotransplanted with islets in autografting and allotransplantation of impure preparations. Proteases and insulin are released by acinar cells and islets, respectively, during pretransplantation culture and also systemically after transplantation. We hypothesized that released proteases could cleave insulin molecules and that addition of alpha-1 antitrypsin (A1AT) to impure islet cultures would block this cleavage, improving islet recovery and function. Methods Trypsin, chymotrypsin, and elastase (TCE) activity and insulin levels were measured in culture supernates of pure (n = 5) and impure (n = 5) islet fractions, which were isolated from deceased donors. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was used to detect insulin after incubation with proteases. We assessed the effects of A1AT supplementation (0.5 mg/mL; n = 4] on TCE activity, insulin levels, culture recovery, and islet quality. The ultrastructure of islets exposed to TCE versus control medium was examined using electron microscopy (EM). Results Protease (TCE) activity in culture supernatants was indirectly proportional to the percentage purity of islets: pure, impure, or highly impure. Increasingly lower levels of insulin were detected in culture supernatants when higher protease activity levels were present. Insulin levels measured from supernatants of impure and highly impure islet preparations were 61 ± 23.7% and 34 ± 33% of that in pure preparations, respectively. Incubation with commercially available proteases (TCE) or exocrine acinar cell supernatant cleaved insulin molecules as assessed using SDS-PAGE. Addition of A1AT to impure islet preparations reduced protease activity and restored normal insulin levels as detected using enzyme-linked immunosorbent assay (ELISA) and SDS-PAGE of culture supernates. A1AT improved insulin levels to 98% ± 1.3% in impure and 78% ± 34.2% in highly impure fractions compared with pure islet fractions. A1AT supplementation improved postculture recovery of islets in impure preparations compared with nontreated controls (72% ± 9% vs 47% ± 15%). Islet viability as measured using membrane integrity assays was similar in both the control (98% ± 2%) and the A1AT-treated groups (99% ± 1%). EM results revealed a reduction or absence of secretory granules after exposure to proteases (TCE). Conclusion Culture of impure human islet fractions in the presence of A1AT prevented insulin cleavage and improved islet recovery. A1AT supplementation of islet culture media, therefore, may increase the proportion of human islet products that meet release criteria for transplantation.

Modeling of radiation transport in coupled atmosphere-snow-ice-ocean systems

A radiative transfer model for coupled atmosphere-snow-ice-ocean systems (CASIO-DISORT) is used to develop accurate and efficient tools for computing the bidirectional reflectance distribution function (BRDF) of sea ice for a wide range of situations occurring in nature. These tools include a method to generate sea ice inherent optical properties (IOPs: single-scattering albedo, extinction optical depth, and scattering asymmetry parameter) for any wavelength between 300 and 4000 nm as a function of sea ice physical parameters including real and imaginary parts of the sea ice refractive index, brine pocket concentration and effective brine pocket size, air bubble concentration and effective air bubble size, volume fraction of ice impurities and impurity absorption coefficient, and sea ice thickness. The CASIO-DISORT code was used to compute look-up tables (LUTs) of the Fourier expansion coefficients of the BRDF as a function of angles of illumination and observation, sea ice IOPs, and ocean albedo. By interpolation in the LUTs one efficiently obtains accurate BRDF values. To include snow on the ice we modified DISORT2 to accept Fourier expansion coefficients for the BDRF as input instead of the BRDF itself, thereby reducing the computation time by a factor of about 60. The BRDF computed by CASIO-DISORT or retrieved from the LUTs applies to diffuse light only. To remedy this shortcoming we added a specular Gaussian beam component to the new BRDF tool and verified that it works well for BRDFs for bare and snow-covered sea ice.

Statistical mechanics of bilayer membranes in troubled aqueous media

We consider a bilayer membrane surrounded by small impurities, assumed to be attractive or repulsive. The purpose is a quantitative study of the effects of these impurities on the statistical properties of the supported membrane. Using the replica trick combined with a variational method, we compute the membrane mean-roughness and the height correlation function for almost-flat membranes, as functions of the primitive elastic constants of the membrane and some parameter that is proportional to the volume fraction of impurities and their interaction strength. As results, the attractive impurities increase the shape fluctuations due to the membrane undulations, while repulsive ones suppress these fluctuations. Second, we compute the equilibrium diameter of (spherical) vesicles surrounded by small random particles starting from the curvature equation. Third, the study is extended to a lamellar phase composed of two parallel fluid membranes, which are separated by a finite distance. This lamellar phase undergoes an unbinding transition. We demonstrate that the attractive impurities increase the unbinding critical temperature, while repulsive ones decrease this temperature. Finally, we say that the presence of small impurities in an aqueous medium may be a mechanism to suppress or to produce an unbinding transition, even the temperature and polarizability of the aqueous medium are fixed, in lamellar phases formed by parallel lipid bilayers.

A Hierarchy of Self-Renewing Tumor-Initiating Cell Types in Glioblastoma

The neural stem cell marker CD133 is reported to identify cells within glioblastoma (GBM) that can initiate neurosphere growth and tumor formation; however, instances of CD133(-) cells exhibiting similar properties have also been reported. Here, we show that some PTEN-deficient GBM tumors produce a series of CD133(+) and CD133(-) self-renewing tumor-initiating cell types and provide evidence that these cell types constitute a lineage hierarchy. Our results show that the capacities for self-renewal and tumor initiation in GBM need not be restricted to a uniform population of stemlike cells, but can be shared by a lineage of self-renewing cell types expressing a range of markers of forebrain lineage.