Mean Molar Research Articles

Effect of Surface Charge on the Interfacial Orientation and Conformation of FB1 in Model Membranes

The toxicity of FB1 is usually explained through the enzymatic disruption of lipidic metabolism. However, it may lie in the thermodynamics of the membrane and its cooperative phase behavior rather than in the activity of individual proteins. Here, we investigate the effects of FB1 at the molecular and mesoscopic levels in FB1-phospholipid mixed Langmuir films. Mean molecular area vs FB1 molar fractions (x(FB1)) and phase diagram analysis allowed us to define miscibility conditions and phase states at different x(FB1). Surface potential measurements, evaluated as a function of the molecular packing and x(FB1), revealed the FB1-induced change in the collective dipolar reorientation leaded to neutralization of charged films. Size, shape, and distribution of 2D-domain analysis from epifluorescence data suggested the increase in the mixing entropy and film relaxation rate. Finally, PM-IRRAS revealed the orientation of FB1 with the amine end (zwitterionic and negatively charged monolayers) or the tricarballylic acid end (positively charged monolayers) pointing to the air. The globular-extended conformational equilibrium of FB1 is dynamically defined by the membrane charge becoming a toxicity enhancing factor. The specificity of the toxin-protein interaction might also be perturbed by the FB1-induced remodeling of the membrane topography by affecting the raft-like platforms where membrane enzymes are considered to be located.

Tadpoles enhance microbial activity and leaf decomposition in a neotropical headwater stream

Summary1. Relationships between biodiversity and ecosystem function are of increasing interest, particularly in freshwater ecosystems where species losses are occurring at unprecedented rates. Amphibian declines have been associated with a loss of ecosystem function in neotropical streams, but little is known of the potential roles of stream‐dwelling tadpoles in leaf decomposition. Leaf litter is an important energy source to streams, and the breakdown of this material to fine particulate organic matter (FPOM) is a key ecosystem function.2. We used mesocosms in a natural stream setting to quantify the effects of grazing tadpoles, shredding macroinvertebrates and a combination of the two on leaf decomposition and associated microbial activity. We measured respiration rates of decomposing leaves, particulate organic matter (POM) and leaf biofilm biomass and C : N : P ratios, and leaf area loss in 4 treatments: Control, tadpole only (TP), tadpole and shredding macroinvertebrates (TP + INV) and shredding macroinvertebrates only (INV). We hypothesised that tadpoles would enhance leaf decomposition by changing nutrient availability and stimulating microbial activity.3. Respiration rates ranged from 3.1 to 6.0 mg O2 dry mass−1 h−1 and were significantly higher in the TP and TP + INV treatments than in the control. The TP + INV treatment had significantly higher POM in chambers than the control and INV treatments. The TP treatment had significantly lower leaf biofilm biomass than the control and INV treatments.4. Tadpoles influenced the elemental balance of C and N in POM and leaf biofilm. In contrast to our prediction, molar C : N ratios were higher in the TP + INV treatment than in the control. Mean molar N : P ratios in POM were higher in the TP + INV treatment than in any other treatment. Leaf biofilm followed a similar pattern, but both TP and TP + INV had significantly higher N : P ratios than the control and INV treatments. Leaf area loss was greatest when tadpoles and invertebrates were together (TP + INV = 0.6% leaf area loss per mg organism) than separate (TP = 0.1%, INV = 3%), indicating facilitation.5. Tadpoles indirectly affected leaf decomposition by influencing microbial communities and macroinvertebrate feeding. As such, ongoing amphibian declines may adversely affect a critical ecosystem function in freshwater habitats.

Estimation of phase composition and size of asphaltene colloidal particles in mixtures of asphaltene + polystyrene + toluene at 293 K and atmospheric pressure

Mixtures of asphaltene+polystyrene+toluene were recently shown to separate into asphaltene-rich and polystyrene-rich liquid phases over a broad range of global compositions at 293K and atmospheric pressure, for polystyrene mean molar masses of Mw=393,400 and Mw=700,000g/mol. In this work, a model based on the lever rule is used to estimate the binodal curves and the critical points. Measured speed of sound values were compared with values calculated from estimated compositions and speed of sound mixing rules. Large deviations were obtained but the introduction of a parameter γ, interpreted as the fraction of asphaltenes causing phase separation, improved the agreement between experimental and calculated speeds of sound in the coexisting phases. The best agreement was obtained for γ=0.63 and 0.49 for polystyrene molar masses Mw=393,400 and Mw=700,000g/mol, respectively. A model for the depletion flocculation mechanism for mixtures of solvent (toluene), monodispersed colloidal particles and a non-adsorbing polymer (polystyrene) was used to calculate critical loci for cases of theta and good solvents. The mean radii of asphaltene particles active in the phase separation was estimated to fall in the 6–11nm range. Exogenous SAXS measurements for related asphaltene+aromatic solvent binary mixtures place 1/3–2/3 of asphaltene particles in this nominal size range. The need for coordinated phase equilibrium and asphaltene particle size measurements is underscored.

Dental functional traits of mammals resolve productivity in terrestrial ecosystems past and present

We have recently shown that rainfall, one of the main climatic determinants of terrestrial net primary productivity (NPP), can be robustly estimated from mean molar tooth crown height (hypsodonty) of mammalian herbivores. Here, we show that another functional trait of herbivore molar surfaces, longitudinal loph count, can be similarly used to extract reasonable estimates of rainfall but also of temperature, the other main climatic determinant of terrestrial NPP. Together, molar height and the number of longitudinal lophs explain 73 per cent of the global variation in terrestrial NPP today and resolve the main terrestrial biomes in bivariate space. We explain the functional interpretation of the relationships between dental function and climate variables in terms of long- and short-term demands. We also show how the spatially and temporally dense fossil record of terrestrial mammals can be used to investigate the relationship between biodiversity and productivity under changing climates in geological time. The placement of the fossil chronofaunas in biome space suggests that they most probably represent multiple palaeobiomes, at least some of which do not correspond directly to any biomes of today's world.

Liquid–Liquid Phase Equilibria in Asphaltene + Polystyrene + Toluene Mixtures at 293 K

The phase behavior of hydrocarbon mixtures where one of the constituents self-aggregates is a subject of significant industrial and academic interest. Here, a nonintrusive acoustic phased-array technique operated in pulse echo mode is used to investigate the phase behavior of asphaltenes, a well-known self-aggregating species, in mixtures with polystyrene and toluene at 293 K and atmospheric pressure. This mixture exhibits liquid–liquid phase behavior where both liquids are opaque to visible light, are of uniform composition, and are stable over broad ranges of composition. One phase is asphaltene rich and the other phase is polystyrene rich. Varying the polystyrene mean molar mass had little impact on the liquid to liquid–liquid phase boundaries. Liquid–liquid critical points were identified and phase compositions were confirmed for a fixed global composition using the UV–visible spectrophotometry and mass balance equations. This is the first report of liquid–liquid phase behavior for such mixtures. Depl...

The Impact of Stirring Rate on the Crystallinity and Bioactivity of 58S Bioactive Glass

In most biphasic composite systems consisting of sol-gel derived bioactive glass and a second system that is usually used as a reinforcing agent, thorough stirring is necessary to prevent the precipitation of the grains of the second system. Consequently, the aim of this work is to investigate the impact of various stirring rates on the crystallinity and bioactivity of a bioactive glass in the system 58S. Sol-gel-derived bioactive glass (58S) was produced as described in literature. During the gelation, stirring rates of 0, 200, 400, 600 and 800 rpms were applied producing, respectively, the corresponding glass powders. The in vitro bioactivity of the powders was tested in Simulated Body Fluid (SBF) for various immersion times, while the solution was renewed after 6h, 24h and then every 2 days. Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and X-ray Diffractometry (XRD) were used to characterize all materials before and after immersion in SBF solution. FTIR and XRD measurements of all powders revealed mainly the formation of an amorphous glass, while the main crystalline phase was identified to be Ca2SiO4. After immersion in SBF solution for 12h, SEM microphotographs revealed apatite formation on the surface of all samples, while FTIR and XRD confirmed the aforementioned findings. Furthermore, since EDS analysis proved a mean molar Ca/P ratio of about1.7 after 6 days of immersion of all samples- besides those stirred at 400 and 600rpm- it can be assumed that a thick apatite layer was formed covering the whole surface.

Using General Estimating Equations to Analyze Oral Health in the Moche Valley of Perú

ABSTRACTThis study introduces a new method for analyzing oral health indicators and thus reconstructing diet. To this end, we examined the dental remains of 173 individuals recovered from the site of Cerro Oreja in the Moche Valley of Perú, who lived during the Salinar (400–1 BC) or Gallinazo (AD 1–200) phases. The infectious and degenerative conditions analyzed include: dental caries, dental wear, dental abscess, antemortem tooth loss and dental calculus, all of which have been used to track dietary and thus subsistence‐related economic and sociopolitical changes. Data were analyzed using generalized estimating equations, an extension of generalized linear models. Significant changes in the frequency of occurrence of most dental conditions suggest that during the period of study, there was an increase in the consumption of agricultural products. However, these changes in oral health did not equally affect females and males. By the end of the Gallinazo phase, significant sex differences developed, with females more often affected by dental caries and males displaying greater mean molar wear scores. Copyright © 2011 John Wiley & Sons, Ltd.

Gingival changes and secondary tooth eruption in adolescents and adults: A longitudinal retrospective study

Our aim was to investigate 8 years of vertical changes of the gingival margin and tooth displacement of maxillary molars and incisors in adolescents and adults. Twenty-five adolescents and 10 adults were included in this study, with dental casts taken 2 and 10 years after orthodontic treatment. The gingival contour of the teeth was traced digitally using calibrated photographs of the 2 dental casts, and gingival changes were measured on crown superimposition. Eruption of the central incisors and first molar were measured on dental casts after scanning and superimposition on the palatal vault. Adults and adolescents presented a mean molar eruption of 0.27 and 0.34 mm and a mean incisor eruption of 0.39 and 0.73 mm, respectively. Adults and adolescents presented a mean molar gingival displacement of respectively 0.34 and 0.77 mm, and the adolescents a mean incisor gingival displacement of 0.44 mm. Correlation between secondary tooth eruption and gingival displacement was obtained only for the incisors in the adolescent group. Adolescents and adults presented apical displacement of the gingival contour of the maxillary first molars, as was the case for maxillary incisors in adolescents. Secondary eruption of maxillary first molars and central incisors continues in adolescents and adults.

Fe‐Mn systematics of type IIA chondrules in unequilibrated CO, CR, and ordinary chondrites

Abstract– We have examined Fe/Mn systematics of 34 type IIA chondrules in eight highly unequilibrated CO, CR, and ordinary chondrites using new data from this study and prior studies from our laboratory. Olivine grains from type IIA chondrules in CO chondrites and unequilibrated ordinary chondrites (UOC) have significantly different Fe/Mn ratios, with mean molar Fe/Mn = 99 and 44, respectively. Olivine analyses from both these chondrite groups show well‐defined trends in Mn versus Fe (afu) and molar Fe/Mn versus Fe/Mg diagrams. In general, type IIA chondrules in CR chondrites have properties intermediate between those in UOC and CO chondrites. In most UOC and CR type IIA chondrules, the Fe/Mn ratio of olivine decreases during crystallization, whereas in CO chondrites the Fe/Mn ratio does not appear to change. It is difficult to interpret the observed Fe/Mn trends in terms of differing moderately volatile element depletions inherited from precursor materials. Instead, we suggest that significant differences in the abundances of silicates and sulfides ± metals in the precursor material, as well as open‐system behavior during chondrule formation, were responsible for establishing the different Fe/Mn trends. Using Fe‐Mn‐Mg systematics, we are able to identify relict grains in type IIA chondrules, which could be derived from previous generations of chondrules, including chondrules from other chondrite groups, and possibly chondritic reservoirs that have not been sampled previously.

Evaluation of buccolingual inclination of posterior teeth in different facial patterns using computed tomography

Buccolingual inclination of teeth is an essential factor in establishing good occlusion. The objective of this study was to evaluate the buccolingual inclination of molar teeth in different vertical skeletal patterns by using computed tomography scans. Coronal section of the jaws obtained from computed tomograms were used to measure the buccolingual inclination of the long axis of the molars relative to their skeletal base. Forty male adult individuals with class I dental occlusion were selected. They were classified as short (Group 1), average (Group II), and long faced (Group III) as per their skeletal patterns measured by GoGn-SN, FH-MP, Y-axis and facial height index in cephalograms. ANOVA and Tukey HSD tests were applied to calculate if there were any significant differences in the mean molar inclination between the groups. Pearson's coefficients of correlation were calculated between the facial parameters and tooth inclination. The differences in the mean molar inclination between the short, average, and long faced groups is significant for mandibular 1 st and 2 nd molars and maxillary 2 nd molars. Variations in mean molar inclination values are observed between short, average, and long faced groups.

Possibility to use Ademetionine for the treatment of psoriaticpatients with a pathology of the hepatobiliary system

The endogenous intoxication syndrome manifested in the form of excessive accumulation of low and mean molar mass substances in plasma and urine as well as increased blood plasma concentrations of malonic dialdehyde against the background of reduced alpha-tocopherol was revealed in psoriatic patients with the concomitant hepatobiliary system pathology. Application of Ademetionine in the dose of 800 mg per day for 15 days as a part of the complex therapy for such patients as opposed to the patients receiving standard therapy resulted in reliable reduction in the severity of clinical manifestations of the disease and PASI value as well as decrease in the concentration of low and mean molecular mass substances in plasma and erythrocytes, reduction in the blood plasma malonic dialdehyde concentration and increase in alpha-tocopherol.

Correlation and toxicological inference of trace elements in tissues from stranded and free-ranging bottlenose dolphins (Tursiops truncatus)

The significance of metal concentrations in marine mammals is not well understood and relating concentrations between stranded and free-ranging populations has been difficult. In order to predict liver concentrations in free-ranging dolphins, we examined concentrations of trace elements (Al, As, Ba, Be, Cd, Co, Cu, Fe, Li, Mn, Ni, Pb, Sb, Se, Sn, total Hg (THg), V, Zn) in skin and liver of stranded bottlenose dolphins (Tursiops truncatus) from the South Carolina (SC) coast and the Indian River Lagoon, Florida (FL) during 2000–2008. Significantly higher concentrations of Zn, Fe, Se, Al, Cu and THg were found in skin while liver exhibited significantly higher Cu, Fe, Mn and THg concentrations for both study sites. Mean skin concentrations of Cu and Mn were significantly higher in SC dolphins while higher concentrations of THg and V were found in FL dolphins. In addition, liver tissues in SC dolphins exhibited significantly higher As concentrations while higher Fe, Pb, Se, THg, and V levels were found in FL dolphins. Two elements (Cu and THg) showed significant age-related correlations with skin concentration while five elements (Cu, Se, THg, Zn and V) showed age-related correlations with liver concentrations. Geographic location influenced age-related accumulation of several trace elements and age-related accumulation of THg in hepatic tissue was observed for both sites to have the highest correlations (r2=0.90SC; r2=0.69FL). Mean THg concentration in liver was about 10 times higher in FL dolphins (330μgg−1dw) than those samples from SC dolphins (34.3μgg−1dw). The mean molar ratio of Hg to Se was 0.93±0.32 and 1.08±0.38 for SC and FL dolphins, respectively. However, the Hg:Se ratio varied with age as much lower ratios (0.2–0.4) were found in younger animals. Of the 18 measured elements, only THg was significantly correlated in skin and liver of stranded dolphins and skin of free-ranging dolphins from both sites suggesting that skin may be useful in predicting Hg concentrations in liver tissue of free-ranging dolphins. Results indicate that 33% of the stranded and 15% of the free-ranging dolphins from FL exceed the minimum 100μgg−1 wet weight (ww) (∼400dw) Hg threshold for hepatic damage while none from SC reached this level. Hepatic concentrations of As in SC dolphins and V in FL dolphins were also highly correlated with skin concentrations which may have some regional specificity predictive value. The present study provides the first application of trace element concentrations derived from stranded bottlenose dolphins to predict liver concentrations in free-ranging populations.

Purification of crude fatty acids using a PDMS-based composite membrane

Crude FA obtained by acid hydrolysis of used frying oils was purified using a PDMS based composite membrane. During processing crude FA, FA preferentially permeated through the membrane increasing FA content from 86.5% to 90% while color compounds were substantially reduced (92.8%) improving the overall purity of FA. Studies with crude FA-used frying oil system showed that a good correlation existed between reciprocal of viscosity and permeate flux, both total as well as FA fluxes. As expected, FA flux showed a significant improvement in crude FA–hexane system besides improving the FA content to the extent of 97% without significantly affecting reduction of color (83–88%). Increase in pressure as well as hexane dilution improved the FA flux but marginally affected purity and color reduction. Preferential permeation was observed over a wide of hexane dilution almost throughout the entire range of X (weight ratio of FA in feed) but to a varying degree and the positive coupling was strong at very low and high concentrations of hexane and FA. A maximal J FA (FA flux) of 4.4 kg/(m 2 h) was obtained at X = 0.3 demonstrating an improvement of 11 fold achievable with appropriate hexane dilution at 1 MPa. In both crude FA-used frying oil and crude FA–hexane systems, the mean molar total permeate flux [ln( J m)] showed a linear dependency on the mean molar volume [ V m] of permeate, which is in agreement with solution-diffusion or regular solution model.

Investigating the potential role of ammonia in ion chemistry of fine particulate matter formation for an urban environment

To investigate the potential role of ammonia in ion chemistry of PM 2.5 aerosol, measurements of PM 2.5 (particulate matter having aerodynamic diameter < 2.5 µm) along with its ionic speciation and gaseous pollutants (sulfur dioxide (SO 2), nitrogen oxides (NO x ), ammonia (NH 3) and nitric acid (HNO 3)) were undertaken in two seasons (summer and winter) of 2007–2008 at four sampling sites in Kanpur, an urban-industrial city in the Ganga basin, India. Mean concentrations of water-soluble ions were observed in the following order (i) summer: SO 4 2− (26.3 µg m − 3 ) > NO 3 − (16.8) > NH 4 + (15.1) > Ca 2+ (4.1) > Na + (2.4) > K + (2.1 µg m − 3 ) and (ii) winter: SO 4 2− (28.9 µg m − 3 ) > NO 3 − (23.0) > NH 4 + (16.4) > Ca 2+(3.4) > K +(3.3) > Na + (3.2 µg m − 3 ). The mean molar ratio of NH 4 + to SO 4 2− was 2.8 ± 0.6 (mostly >2), indicated abundance of NH 3 to neutralize H 2SO 4. The excess of NH 4 + was inferred to be associated with NO 3 − and Cl −. Higher sulfur conversion ratio ( F s: 58%) than nitrogen conversion ratio ( F n: 39%) indicated that SO 4 2− was the preferred secondary species to NO 3 −. The charge balance for the ion chemistry of PM 2.5 revealed that compounds formed from ammonia as precursor are (NH 4) 2SO 4, NH 4NO 3 and NH 4Cl. This study conclusively established that while there are higher contributions of NH 4 +, SO 4 2− to PM 2.5 in summer but for nitrates (in particulate phase), it is the winter season, which is critical because of low temperatures that drives the reaction between ammonia and HNO 3 in forward direction for enhanced nitrate formation. In summary, inorganic secondary aerosol formation accounted for 30% mass of PM 2.5 and any particulate control strategy should include optimal control of primary precursor gases including ammonia.

A model of reduced kinetics for alkane oxidation using constituents and species: Proof of concept for n-heptane

A methodology for deriving a reduced kinetic mechanism for alkane oxidation is described and applied to n-heptane. The model is based on partitioning the species of the skeletal kinetic mechanism into lights, defined as those having a carbon number smaller than 3, and heavies, which are the complement in the species ensemble. For modeling purposes, the heavy species are mathematically decomposed into constituents, which are similar but not identical to groups in the group additivity theory. From analysis of the LLNL skeletal mechanism in conjunction with CHEMKIN II, it is shown that a similarity variable can be formed such that the appropriately scaled global constituent molar density exhibits a self-similar behavior over a very wide range of equivalence ratios, initial pressures and initial temperatures that is of interest for predicting n-heptane oxidation. Furthermore, the oxygen and water molar densities are shown to display a quasi-linear behavior with respect to the similarity variable. The light species ensemble is partitioned into quasi-steady and unsteady species. The concept is tested by using tabular information from the LLNL skeletal mechanism in conjunction with CHEMKIN II. The test reveals that the similarity concept is indeed justified and that the combustion temperature is well predicted, but that the ignition time is overpredicted. To palliate this deficiency, functional modeling is incorporated into our conceptual reduction. Due to the reduction process, models are also included for the global constituent molar density, the kinetics-induced enthalpy evolution of the heavy species, the contribution to the reaction rate of the unsteady lights from the heavies, the molar density evolution of oxygen and water, the mole fractions of the quasi-steady light species and the mean molar heat capacity of the heavy species. The model is compact in that there are only nine species-related progress variables. Results are presented comparing the performance of the model for predicting the temperature and species evolution with that of the skeletal mechanism. The model reproduces the ignition time over a wide range of equivalence ratios, initial pressure and initial temperature.

A new variant of saponite‐rich micrometeorites recovered from recent Antarctic snowfall

Abstract– Eight saponite‐rich micrometeorites with very similar mineralogy were found from the recent surface snow in Antarctica. They might have come to Earth as a larger meteoroid and broke up into pieces on Earth, because they were recovered from the same layer and the same location of the snow. Synchrotron X‐ray diffraction (XRD) analysis indicates that saponite, Mg‐Fe carbonate, and pyrrhotite are major phases and serpentine, magnetite, and pentlandite are minor phases. Anhydrous silicates are entirely absent from all micrometeorites, suggesting that their parental object has undergone heavy aqueous alteration. Saponite/serpentine ratios are higher than in the Orgueil CI chondrite and are similar to the Tagish Lake carbonaceous chondrite. Transmission electron microscope (TEM) observation indicates that serpentine occupies core regions of fine‐grained saponite, pyrrhotite has a low‐Ni concentration, and Mg‐Fe carbonate shows unique concentric ring structures and has a mean molar Mg/(Mg + Fe) ratio of 0.7. Comparison of the mineralogy to hydrated chondrites and interplanetary dust particles (IDPs) suggests that the micrometeorites are most similar to the carbonate‐poor lithology of the Tagish Lake carbonaceous chondrite and some hydrous IDPs, but they show a carbonate mineralogy dissimilar to any primitive chondritic materials. Therefore, they are a new variant of saponite‐rich micrometeorite extracted from a primitive hydrous asteroid and recently accreted to Antarctica.

Significant mid-latitude aridity in the middle Miocene of East Asia

The East Asian climate history during the Neogene is a complicated and contentious issue, in particular because of its bearing on the development of the East Asian monsoon and Tibetan uplift chronology. Here we present a paleoprecipitation analysis based on mean molar tooth height (hypsodonty) of large herbivorous mammals to investigate the spatial pattern of climate zonation in East Asia during the middle Miocene. We show a generally humid and uniform situation before the late middle Miocene, replaced by a mid-latitude arid belt from the late middle Miocene, into the earlier part of the late Miocene. These findings are concordant with the global phenomena of the middle Miocene climate optimum and the subsequent cooling, and suggest that the predominant climate in East Asia for most of the Miocene was planetary rather than monsoonal. Our results support a late initiation of the East Asian summer monsoon, coincidentally with the beginning of eolian red clay deposition in the later late Miocene at 7–8 Ma.

Electrochemical and XPS study of polyethyleneimines of different molecular sizes as corrosion inhibitors for AISI 430 stainless steel in near-neutral chloride media

Polyethyleneimines (PEI) with different mean molar mass (from 1300 to 750,000 g mol −1) were studied as potential corrosion inhibitors for AISI 430 stainless steel in a 3% NaCl solution. Linear polarization measurements and immersion tests showed that all of the selected polymers protect this stainless steel against uniform corrosion. PEI with a mean molar mass of 2000 g mol −1 provides the best protection against localized corrosion, as demonstrated by cyclic polarization measurements. A closer insight into the polymer adsorption was obtained by XPS technique. PEI molecules most probably physisorb on the metal surface since no peak shift was observed that would indicate C–N–metal connection. PEI probably acts as a diffusion barrier by preventing an attack by the chloride of the salt solution.

Nitrogen dilution effect on the flammability limits for hydrocarbons

Theoretical models to predict the upper/lower flammability limits of hydrocarbons diluted with inert nitrogen gas are proposed in this study. It is found that there are linear relations between the reciprocal of the upper/lower flammability limits and the reciprocal of the molar fraction of hydrocarbon in the hydrocarbon/inert nitrogen mixture. Such linearity is examined by experimental data reported in the literature, which include the cases of methane, propane, ethylene and propylene. The R-squared values ( R 2) of the regression lines of the cases explored are all greater than 0.989 for upper flammability limit (UFL). The theoretical slope of the predictive line for lower flammability limit (LFL) is found to be very close to zero for all explored cases; and this result successfully explains the experimental fact that adding inert nitrogen to a flammable material has very limited effect on LFL. Because limit oxygen concentration (LOC) could be taken as the intersectional point of the UFL curve and LFL curve, a LOC-based method is proposed to predict the slope of the UFL curve when experimental data of UFL are not available. This LOC-based method predicts the UFL with average error ranging from 2.17% to 5.84% and maximum error ranging from 8.58% to 12.18% for the cases explored. The predictive models for inert gas of nitrogen are also extended to the case of inert gas other than nitrogen. Through the extended models, it was found that the inert ability of an inert gas depends on its mean molar heat capacity at the adiabatic flame temperature. Theoretical calculation shows that the inert abilities of carbon dioxide, steam, nitrogen and helium are in the following order: carbon dioxide > steam > nitrogen > helium; and this sequence conforms to the existing experimental data reported in the literature.

Ferritin Contains Less Iron (59Fe) in Cells When the Protein Pores Are Unfolded by Mutation

Ferric minerals in ferritins are protected from cytoplasmic reductants and Fe2+ release by the protein nanocage until iron need is signaled. Deletion of ferritin genes is lethal; two critical ferritin functions are concentrating iron and oxidant protection (consuming cytoplasmic iron and oxygen in the mineral). In solution, opening/closing (gating) of eight ferritin protein pores controls reactions between external reductant and the ferritin mineral; pore gating is altered by mutation, low heat, and physiological urea (1 mm) and monitored by CD spectroscopy, protein crystallography, and Fe2+ release rates. To study the effects of a ferritin pore gating mutation in living cells, we cloned/expressed human ferritin H and H L138P, homologous to the frog open pore model that was unexpressable in human cells. Human ferritin H L138P behaved like the open pore ferritin model in vitro as follows: (i) normal protein cage assembly and mineralization, (ii) increased iron release (t1/2) decreased 17-fold), and (iii) decreased alpha-helix (8%). Overexpression (> 4-fold), in HeLa cells, showed for ferritin H L138P equal protein expression and total cell 59Fe but increased chelatable iron, 16%, p < 0.01 (59Fe in the deferoxamine-containing medium), and decreased 59Fe in ferritin, 28%, p < 0.01, compared with wild type. The coincidence of decreased 59Fe in open pore ferritin with increased chelatable 59Fe in cells expressing the ferritin open pore mutation suggests that ferritin pore gating influences to the amount of iron (59Fe) in ferritin in vivo.