Correlation Of Mg Research Articles

Mineral Content and Phytochemical Composition of Avocado var. Hass Grown Using Sustainable Agriculture Practices in Ecuador.

Avocado demand has increased in recent years due to the nutraceutical properties that this fruit has and its positive impacts on human health; however, avocado production also requires sustainable alternatives to improve its cultivation. The objective of this study was to carry out characterization of the mineral content and phytochemical compounds in avocado fruit of the Hass variety grown using sustainable agricultural practices in Ecuador. Our results show an increase in fruit quality traits, such as firmness, and in the content of soluble solids, protein, fiber, fat, carotenoids, Ca, Mg, Zn and stearic acid in the pulp of the avocado Hass variety, as well as an initial trend of yield increase with the application of sustainable practices. Moreover, antioxidant activity was associated with polyphenol content. There were positive correlations of Mg with K and Ca, and of flavonoids with linolelaidic, linoleic and linolenic acids. Overall, our results indicate that avocado can be used as a functional and nutritional food due to its phytochemical composition and the mineral content of its pulp, which contributes to the promotion of its consumption and encourages healthy eating. In addition, the use of sustainable practices, such as fertigation and the application of microorganisms, is also promoted for growing avocado.

CORRELATION BETWEEN MAGNESIUM & INSULIN RESISTANCE IN POLYCYSTIC OVARY SYNDROME (PCOS)

PCOS is a hormonal disorder common among women of reproductive age. Patients with PCOS are known to have a high incidence of insulin resistance. Serum magnesium (Mg) is often associated with insulin resistance among patients with PCOS. This case - control study was conducted at SRM Medical College Hospital and Research Centre, Tamil Nadu, India. Total of 62 participants between the age group of 20- 40 years were recruited in the study, in which 31 were healthy controls and 31 were cases with PCOS. FBG, HbA1c, lipid profile, serum magnesium, serum insulin was estimated. Students ‘t’ test was done to compare the mean levels between groups. Low serum magnesium, higher levels of insulin and insulin resistance is seen in PCOS compare to non-PCOS group. The correlation of analysed biochemical parameters were done among PCOS group. Negative correlation of mg with insulin, FBS and HOMA-IR was observed. The evidence showing that low serum magnesium is associated with insulin resistance in PCOS individuals.

Myasthenia gravis genome-wide association study implicates AGRN as a risk locus

BackgroundMyasthenia gravis (MG) is a rare autoimmune disorder affecting the neuromuscular junction (NMJ). Here, we investigate the genetic architecture of MG via a genome-wide association study (GWAS) of the largest...

Effects of acute oral lead exposure on the levels of essential elements of mice: a metallomics and dose-dependent study

Background and objectivesLead (Pb) has been reported to disturb the metabolism of essential elements, such as calcium (Ca), magnesium (Mg), iron (Fe) and zinc (Zn) in vivo. This study focused on the relationship between various dose of Pb and the essential elements. Methods50 healthy male C57BL/6 mice underwent oral administration of 0.2 mL lead acetate trihydrate solution (0, 20, 100, 500, and 1000 mg Pb/day/kg body weight) for 3 days. The concentrations of Pb and four essential elements (Ca, Zn, Fe and Mg) in the blood, kidney, liver, bone and brain were quantified with inductively coupled plasma mass spectrometry. ResultsVarious doses of Pb led to significant increases in the contents of Ca, Fe and Zn in the liver, and decreased contents of Mg and Fe in the blood in a dose-dependent pattern. The Pb dose of 20 mg/kg reduced the concentration of bone Ca, which did not continue to show an obvious decline with continued increases in the oral Pb dose. Pb also caused alterations in the Mg distribution pattern, and decreased the correlation of Mg, Ca and Zn in the brain, both findings were dose-dependent. In addition to the changes in metallomics, the related oxidative stress was exacerbated, but no significant changes were detected in hepatic and renal histopathological lesions after a short period of Pb exposure. ConclusionsThis study contributes to a thorough analysis of the Pb-poisoning mechanism, and indicates that the concentrations of essential elements could be used as sensitive toxicological indicators of Pb exposure.

Noble gas variations in ureilites and their implications for ureilite parent body formation

Ureilites are equilibrated carbon-rich olivine-pyroxene rocks from the partially melted mantle of a large (>500 km diameter) heterogeneous parent body. Recently the ureilite parent body was interpreted as an incomplete mixture of material from two carbon-rich chondritic reservoirs, one (Mg-rich) with reduced iron, low Δ17O and low δ13C, and the other with oxidised iron, high Δ17O and high δ13C. Here we analyse noble gases (Ar, Kr and Xe) in six equilibrated (unbrecciated) ureilites from Northwest Africa (NWA 2236, NWA 7686, NWA 8049, NWA 8172, NWA 11032 and NWA 11368). We observe weak positive and negative correlations of Δ17O and Mg# with the elemental ratios of Ar/Xe and Kr/Xe, respectively, as well as a weak positive correlation of Mg# with the heavy isotopes of Xe. These correlations broadly support the idea of the two-component mixing hypothesis. Our analyses further suggest that the Mg-rich endmember was rich in Xe from presolar grains (HL-Xe) while the Mg-poorer component may have contained solar-derived noble gases. The observed correlations are less straightforward to reconcile with a recent model for the origin of the ureilite parent body, involving oxidation of metal by H2O from accreted ice with ‘heavy’ oxygen isotopes.

Mental strain: Magnesium increase along with stress-markers is relative

Abstract. 17 male officer trainees (between 20 and 24 years of age) of the Theresan Military Academy in Wiener Neustadt (Austria) have been subjected to an interactive computer operated wargame. Before and after the test, ionized Mg, ionized pCO 2 , and RRsys were determined from capillary blood. Within 1 hour of mental strain, Mg and pCO 2 decreased significantly (Mg due to arbitrary choice), hence Mg decrease is obviously coupled to increased metabolic turnover. Linear correlations of Mg and its delta values show that due to mental strain, metabolism increases significantly along with Mg loss from tissues. The concomitant Mg increase along with changing stress markers like pCO 2 and RRsys seems to be not in accordance with the measured Mg loss. The discrepancy is cleared by showing that Mg increase is relative – the highest Mg values due to highest strain are seen in those subjects with the relative smallest Mg loss. Thus, the velocity of Mg loss depends upon mental strain (and up to a degree upon Mg tissue reserves) in a similar way as it does during physical load.

Thermal Behaviors and Their Correlations of Mg(BH4)2-Contained Explosives

ABSTRACTIn order to explore the effect of metal hydride on energetic materials’ thermal behaviors and their correlations, we studied the heats of combustion and detonation of RDX, TNT, and Mg(BH4)2-containing explosives both theoretically and experimentally. The results showed that Mg(BH4)2 can significantly improve the energy of explosive. As the mass fraction of Mg(BH4)2 increases, the combustion heat of composite explosives increases gradually, while the combustion efficiency decreases. When its mass fraction is about 30%, the theoretical heats of detonation of RDX/Mg(BH4)2 and TNT/Mg(BH4)2 reach maximum, which are 7418.47 and 7032.46 kJ/kg, respectively. When we compared the errors between calculation and experimental values, we found that L-C method is more accurate in calculating oxygen-enriched and oxygen-balanced explosives, and that minimum free energy method is more suitable for seriously negative oxygen-balanced explosive. For single explosive, there are three kinds of relationships between heat of combustion and detonation according to the oxygen balance. For Mg(BH4)2-containing explosives, the relationship is in accordance with Boltzmann function.

Relationships between degree of milling and loss of Vitamin B, minerals, and change in amino acid composition of brown rice

The effects of the degree of milling (DOM) on amino acid composition, thiamine, riboflavin, phytic acid (PA), and mineral (Mg, Fe, Zn, Mn, Cu, Ca, Se, and Pb) contents of japonica Xinfeng 2 and indica T-You 15 brown rice were investigated. Almost all amino acids slightly decreased as DOM increased. Quadratic and linear relationships were observed between DOM and milling time at 0–30 s and 30–100 s, respectively. Thiamine and riboflavin content decreased linearly as DOM increased. Approximately 57.6–65.4% of thiamine and 40.3–45.7% of riboflavin were removed after 30 s of milling (DOM = ca. 9%). Considerable losses were observed for PA, Mg, Mn, Fe, and Pb during milling (DOM = ca. 9%), whereas the losses of Ca, Cu, Zn, and Se were relatively lower. In addition, the linear correlations of Mg, Mn, Pb, and Fe levels with PA concentration were revealed. These results indicate that DOM should be supervised to improve nutrient utilization and appropriately control toxic metal contamination.

Holocene climate variability in Central Germany and a potential link to the polar North Atlantic: A replicated record from three coeval speleothems

Here, we present high-resolution trace element and stable isotope records from three coeval Holocene stalagmites from the Herbstlabyrinth cave system, Central Germany. All stalagmites were precisely dated using MC-ICPMS 230Th/U-dating. One stalagmite started to grow at 13.62 ± 0.13 ka BP, covering the late Glacial; the other two speleothems started to grow at 11.13 ± 0.08 and 10.26 ± 0.08 ka BP, respectively. The combined record covers the entire Holocene. The interpretation of the different climate proxies is supported by data from a detailed cave monitoring programme. Cold conditions during the Younger Dryas are reflected by intermittent stalagmite growth at the Herbstlabyrinth. The δ18O records are in general agreement with the NGRIP δ18O record on millennial time scales indicating that speleothem δ18O values at the Herbstlabyrinth reflect large-scale climate variability in the North Atlantic area. The 8.2 ka event is clearly visible as a pronounced negative excursion in the δ18O records. In all other proxies, it is not reflected as a major excursion. Correlation and principal component analysis enable us to disentangle the various processes affecting the stable isotope and trace element signals. Phases with higher P, Ba and U concentrations and more negative δ13C values are interpreted as reflecting more productive vegetation above the cave. The negative correlation of Mg with P, Ba and U and the positive correlation with δ13C indicate more recharge during phases of more productive vegetation, probably because of increased rainfall. The majority of the observed phases of reduced vegetation productivity and drier climate coincide with cooler periods in the polar North Atlantic as reflected by a higher abundance of hematite-stained grains (i.e. the Bond events), suggesting a close relationship between terrestrial climate in Central Europe and the polar North Atlantic.

δ18O, δ13C, elemental content and depositional features of a stalagmite from Yelang Cave reflecting climate and vegetation changes since late Pleistocene in central Guizhou, China

A 13.5-cm long stalagmite from Yelang Cave in central Guizhou provides another example of AMS 14C dating on stalagmites which are not suitable for 230Th/U dating due to very low U content and low 230Th/232Th ratio. This record duplicates the published stalagmite record of 20120824-13 from the same cave (Zhao et al., 2015) not only on δ18O and δ13C records, but also on major growth hiatuses, facilitating speleothem δ18O and δ13C as climate and vegetation proxies respectively. Based on the two stalagmite records, climate and vegetation conditions can be deciphered as follow: relatively cool and dry climates with C4 dominated plants during 33.4–36 ka; very cold and dry climates with poor vegetation coverage during the Last Glacial Maximum; cold and dry climates with poor vegetation during Younger Dryas; warming and very wet climates with the best vegetation (mainly C3 plants) coverage during 9–11.5 ka BP corresponding to a maximum insolation; drying climate and decreased vegetation intensity from 9 ka to 8 ka; relatively good vegetation coverage during 5–6 ka; the summer monsoon strength decreased from 5 ka to 1.5 ka BP, but increased during the Medieval Warm Period to produce wet climates and abundant vegetation; and strongly decadal variations in moisture budget and strong deforestation due to human impact during the past 600 years. High Fe, Mn and Al contents from detritus caused dark bands near the hiatuses. Strong positive correlation of Mg and Sr with high Mg/Sr values (>23 in this study) reflects source control on the Mg and Sr variations, so that Mg/Sr is not a function of cave temperature in such a case. For pure calcite without detrital influence, Mg/Sr may register changes in cave temperature with higher Mg/Sr indicating warmer temperature. This study calls for the attention to find out climatic conditions in central Guizhou during the Bølling–Ållerød warming and the middle Holocene (6–8 ka) intervals because of lacking deposition during these intervals in Yelang Cave. Using stalagmite δ18O alone to decipher climatic conditions on decadal-to-millennial scales needs to consider multiple factors such as amount, source, and temperature effects on the δ18O.

The relationship between concentrations of magnesium and oxidized low-density lipoprotein and Beta2-microglobulin in the serum of patients on the end-stage of renal disease.

The end-stage of renal disease is associated with increased oxidative stress and oxidative modification of low-density lipoproteins (LDLs). Beta2 microglobulin (beta2M) is accumulated in the serum of dialysis patients. Magnesium (Mg) plays a protective role in the development of oxidative stress in healthy subjects. We studied the relationship between concentrations of magnesium and oxidized LDL (ox-LDL) and beta2M in the serum of patients on the end stage of renal disease. In 96 patients on on-line- predilution hemodiafiltration, beta2M and intact parathormone were measured by radioimmunoassays. High-sensitivity C-reactive protein (hsCRP) and ox-LDL were measured using ΕLISA. Serum bicarbonate levels were measured in the blood gas analyser gas machine. We performed logistic regression analysis models to investigate Mg as an important independent predictor of elevated ox-LDL and high beta2M serum concentrations, after adjustment to traditional and specific for dialysis patients' factors. We observed a positive correlation of Mg with ox-LDL (r = 0.383, P = 0.001), but the association of Mg with beta2M, hsCRP, and serum bicarbonate levels was significantly inverse (r = -0.252, P = 0.01, r = -0.292, P = 0.004, and r = -0.282, P = 0.04 respectively). The built logistic-regression analysis showed that Mg act as a significant independent factor for the elevated ox-LDL and beta2M serum concentrations adjusting to traditional and specific factors for these patients. We observed a positive relationship between magnesium and acidosis status- related ox-LDL concentrations, but the inverse association between magnesium and beta2M serum concentrations in hemodialysis patients.

Fluid rock interactions as recorded by Cl-rich amphiboles from continental and oceanic crust of italian orogenic belts.

A number of samples of Cl-rich amphiboles coming from oceanic and sub-continental gabbro bodies has been studied in order to compare their microstructural and compositional peculiarities and to investigate the fluid-rock interactions in different geodynamic contexts. The development of a first group of amphiboles outcropping in the Northern Apennines was the result of an hydration event that has been ascribed to oceanic metamorphism. The second group was found in a slice of continental crust subducted during Alpine collision, in a subcontinental metagabbro from the Sesia-Lanzo Zone of Western Italian Alps. Their development has been ascribed to a hydrothermal event that took place after the exhumation of the metagabbro during pre-Alpine lithospheric extension. The Cl-amphiboles are either found in veins, as granoblastic aggregates in different microstructures or as rims of zoned amphiboles, where brown-amphibole cores (sometimes Ti-rich), and successive green amphibole, are rimmed by the Cl-rich amphibole. All amphiboles show edembergite to pargasite compositions up to glaucophane and crossites when reequilibrated under HP conditions, with a direct correlation between Fe and Na (A) vs. Cl content, and inverse correlation of Mg and Na (M4) vs. Cl. A comparison with other Cl-amphiboles that have been observed both in oceanic and continental settings, allow inferring the role played by Cl-rich fluids infiltration both in oceanic and continental crust, during lithospheric extension. The large variations in Si, Al IV , Al VI , Fe, Mg, K and Cl may be related to the combination of different factors, such as Cl-content and related cristal-chemical constraints, whole rock composition, PT conditions of reequilibration, the microdomains where the amphibole grows and the variable a HCl/fluid /a H2O/fluid ratio of the fluid in equilibrium with the amphiboles at various stages of the metamorphic evolution. Amphiboles that locally contain extremely high Cl contents (up to 4% wt) could have been in equilibrium with a locally enriched Cl-fluid. As suggested by the fact that the Cl content of amphibole into the veins is generally lower than in amphibole rims far from the veins, these equilibrium conditions probably were reached at places where the system was locally closed. In addition, hydration reaction consumed the H 2 O component of the fluid, leading to a re-equilibration of the crystallising amphibole with the remaining Cl-enriched fluid. Equilibration temperatures up to 350°C can be attributed to the Apennines amphiboles, and up to 550°C to the ones from the Sesia-Lanzo Zone.

Structure–performance correlations of Mg–Al hydrotalcite catalysts for the isomerization of glucose into fructose

Mg–Al hydrotalcites with different Mg-to-Al molar ratio, texture, and morphology were studied as catalysts for the isomerization of glucose into fructose. The properties of the hydrotalcites were tuned by varying the preparation procedure including pH during co-precipitation, ageing temperature, and solvent. The catalysts were characterized by ICP-OES, N2 sorption, sorption of acrylic acid, XRD, TG-DSC, and SEM. Tuning the conditions of synthesis enables controlling properties such as crystallite size, dispersion of primary particles, and morphology of the agglomerates. These structural parameters of the hydrotalcites critically influence their basicity, which in turn predominantly determines the catalytic performance. The best fructose yields of up to 30% with 89% selectivity were obtained over hydrotalcites synthesized by co-precipitation in (i) an aqueous medium at pH 10 and (ii) an aqueous-ethanol medium at pH 9.5. These synthesis conditions enabled materials with optimal textural properties and the highest amount of accessible basic centres. Although some leaching of magnesium occurred caused by lactic acid formed as by-product of carbohydrate degradation, the hydrotalcites could be recycled without loss of activity and selectivity.

Influence of mineral matter content on static burning rate of Virginia tobacco from different production areas in Serbia

The aim of this study was to determine the influence of particular element of the minerals complex in Virginia tobacco, from different production areas, on value of static burning rate (SBR). Large leaf tobacco, type Virginia from five production areas in Serbia during year 2013, was used as a research material. Mineral content was determined by the atomic absorption spectrophotometer. Static burning rate was determined by the device Free Burning Rate Meter. Resulthad confirmed that the most important factors for mineral matter content in tobacco leaves are soil pH, organic matter content in soil and vicinity of large industrial centers. A very strong positive correlation between the content of Ca and Pb, a positive correlation of Mg and Na, and a strong negative correlation of Cd and both SBR values has been found.Virginia tobacco type grown at Senta area had the highest values for both speeds of combustion (4.99mm/min for SBRl and 69.97mg/min for SBRm). Virginia tobacco type grown at Sremska Mitrovica area had the lowest values for both speeds of combustion (3.95mm/min for SBRl and 49.11mg/min for SBRm).

Mineral Elements in Root of Wild Saposhnikovia divaricata and Its Rhizosphere Soil

Mineral elements are important components of medicinal herbs, and their concentrations are affected by many factors. In this study, Ca, Mg, Na, K, Fe, Mn, Cu, and Zn concentrations in wild Saposhnikovia divaricata and its rhizosphere soil collected from seven locations at two different times in China were measured, and influences of rhizosphere soil on those minerals in plant were evaluated. The results showed that mean concentrations of eight minerals in plant samples decreased in the order: Ca > Mg > Na > K > Fe > Zn > Mn > Cu, and those in the soil samples followed the following order: Na > Fe > Ca > K > Mg > Mn > Zn > Cu. Mean concentrations of Ca, Na, Mg, and K in plants were higher than those in soils, while higher mean concentrations of the other four minerals were found in soils. It was found that there was a positive correlation of Mg, Na, and Cu concentrations in the plant with those in the soil respectively, but a negative correlation of Mn concentration in plant with that in the soil. Except Ca, K, and Mn, the other five minerals in plant were all directly affected by one or more chemical compositions of soil. The results also indicate that pH value and concentrations of total nitrogen, Mg, Mn, and Cu in soil had significant correlations with multimineral elements in plant. In a word, mineral elements uptake of S. divaricata can be changed by adjusting the soil fertility levels to meet the need of appropriate quality control of S. divaricata.

Serum Trace Elements Levels in Preeclampsia and Eclampsia: Correlation with the Pregnancy Disorder

Preeclampsia and eclampsia are fatal medical complications of pregnancy accounting for 20-80% of increased maternal death in developing countries. Their aetiologies are still under investigation. Serum trace elements have been suggested to be involved in the pathogenesis of preeclampsia. Aim of this study was to address the correlation of serum trace elements with preeclampsia and eclampsia. It was a comparative cross-sectional study conducted on conveniently recruited 44 preeclampsia, 33 eclampsia and 27 normotensive pregnant patients. Atomic absorption spectrometry was employed to analyse serum concentrations of Ca, Mg, Cu, Zn and Fe. Data were analysed by Student's t test, one-way analysis of variance and multinomial logistic and binary regression analyses. p < 0.05 was considered as a level of significance. In preeclampsia, the serum Ca and Mg were significantly lower than those in eclampsia, while Cu and Zn values were higher. Significant changes of Ca, Mg and Cu were noted among preeclampsia, eclampsia and pregnant control. Serum Ca and Mg indicated a positive association, and Cu gave a negative association in preeclampsia. Cu/Fe ratio was high in eclampsia. Significant correlations of Mg with Zn in eclampsia and Mg with Fe in preeclampsia and eclampsia were predicted. Significant changes in serum trace element levels were present in preeclampsia and eclampsia that may have a link with the pathogenesis of pregnancy disorder.

EFFECT OF KASNAZAN IMPOUNDMENT AND WELLWATER IN CHEMICAL PROPERTIES OF SOIL AND PLANT

Soil, plant, and water (Kasnazan impoundment and well water) samples were monthly collected from Kasnazan (10 Km north east of Erbil city) during August 2004 to February 2005. Chemical and statistical analysis indicated that the irrigation with well water resulted to decreases EC from 0.87 dS.m-1 to 0.49 dS.m-1, because of leaching and dilution effects. Statistically there is a positive significant correlation (P< 0.05) between SAR value of well water and irrigated soil with it, whereas, a negative correlation of Mg+2 concentrations observed between well water and soil irrigated with it. On the other hand, there was high content of Mg+2 and low content of K+1 for eucalyptus plant irrigated by well water in comparison to that irrigated with impoundment water.

Melt viscosity, temperature and transport processes, Troodos ophiolite, Cyprus

The lava section in the Troodos ophiolite, Cyprus, is chemically stratified and divided into a shallow lava sequence with low TiO 2 content and a deeper lava sequence with high TiO 2 content. We calculate the viscosity at magmatic temperature based on major element chemistry of lavas in Cyprus Crustal Study Project (CCSP) Holes CY-1 and 1A. We find that typical shallow low-Ti lavas have a magmatic viscosity that is two to three orders of magnitude lower than that of the deeper high-Ti lavas. This implies that, after eruption on-axis, Troodos low-Ti lavas would have been able to flow down the same slope faster and farther than high-Ti lavas. The calculated lava viscosity increases systematically from the lava–sediment interface to the bottom of the composite Hole CY-1/1A. This suggests that an efficient process of lava segregation by viscosity on the upper flanks of the paleo Troodos rise may have been responsible for the chemical stratification in the Troodos lava pile. Calculated magmatic temperature and molar Mg/(Mg+Fe), or Mg#, decrease systematically down-section, while SiO 2 content increases. Correlation of Mg# in the lavas with Mg# in the underlying, lower crustal plutonic rocks sampled by CCSP Hole CY-4 shows that the shallow lavas came from a high-temperature, lower crustal magma reservoir which is now represented by high-Mg# pyroxenite cumulates, while the deeper lavas were erupted from a lower-temperature, mid-crustal reservoir which is now represented by gabbroic cumulates with lower Mg#.

Rocky Cometary Particulates: Their Elemental, Isotopic and Mineralogical Ingredients

The determination of the chemical composition of solid cometary dust particles was one of the prime objectives of the three missions to Comet Halley in 1986. The dust analysis was performed by time-of-flight mass-spectrometry. Within the experimental uncertainty the mean abundances of the rock-forming elements in cometary dust particles are comparable to their abundances in CI-chondrites and in the solar photosphere, i.e. they are cosmic. H, C., and N, on the other hand, in cometary dust are significantly more abundant than in CI-chondrites, approach solar abundances, are to some extent related to O, and reside in an omnipresent refractory organic component dubbed CHON. Element variations between individual dust grains are characterized by correlations of Mg, Si, and O, and to a lesser extent of Fe and S. From particle-to-particle variations of the rock forming elements information on the mineralogy of cometary dust can be obtained. Cluster analysis revealed certain groups that partly match the classifications of stratospheric interplanetary dust particles. About half of Halley’s analyzed particles are characterized by anhydrous Fe-poor Mg-silicates, Fesulfides, and rarely Fe metal. The Fe-poor Mg-silicates link Halley’s dust to that of Hale-Bopp as shown by recent IR observations. No significant deviation from normal of the isotopic composition of the elements is unequivocally present with the notable exception carbon: 12C-rich grains with 12C/13C-ratios up to ≈ 5, 000 link cometary dust to presolar circumstellar grains identified in certain chondrites.

Ureilite smelting

Abstract— Ureilites containing homogeneous Fo76 olivine cores in intimate co‐existence with graphite must have recrystallized at pressures of at least ∼100 bars to suppress smelting of the fayalite component of the olivine to Fe metal. Smelting of olivine and pyroxene‐saturated magmatic liquids produces orthopyroxene‐without‐olivine crystalline derivatives unlike those in ureilites. Thus the Mg# compositional variation within the ureilite suite, which is commonly attributed to partial smelting, cannot plausibly be produced by assemblages rich in liquid. In situ smelting of graphitic olivine + pigeonite crystal mushes can produce the correct crystal assemblage, but fails to provide a plausible account for the removal of metal from ureilites or for the correlation of Mg# with Δ17O. Even if Mg# and Δ17O variations are established in the nebula, ureilite recrystallization with graphite must have occurred at pressures greater than the minima we have experimentally established, corresponding to parent objects not less than ∼100 km in radius.