In Vitro Effect of Crude Extract from Traganum Nudatum on Glucose-Uptake in Liver Slices Isolated from Westar Rats

Background: Diabetes mellitus is a metabolic disorder characterized by chronic hyperglycemia resulting from defects in insulin secretion, insulin action, or both. There are many classes of drugs used for treatment, and these include insulin sensitizers, insulin secretagogues, and agents that delay the absorption of carbohydrates from the bowel. This study intends to investigate the effect of crude extract from a plant from South Algeria Traganum nudatum (Chenopodiaceae) on glucose uptake in liver slices isolated from  Wistar rats. Methods: The liver slices were incubated for 90 min at 37° in normoglycaemic (1g/l of glucose)  and hyperglycaemic (3g/l of glucose) KRBA Krebs Ringer Bicarbonate Albumin 4% media using  24 well-polyethylene plates. In each, well different concentrations of insulin (10, 50 and 100µU/ml)  and hydromethanolic crude extract (100, 200 and 500µg/ml) were added. After every 30 minutes, aliquots of the culture media were assayed for the determination of glucose left. Results: Tests showed that the glucose left after 90 minutes in the media which contained insulin at 100µg/ml was the lowest (0.44 and 1.41 )g/l in the normo and hyperglycaemic media respectively, which reflect that insulin at this concentration was the most effective on the stimulation of glucose uptake. The extract had the highest effect at 500µg/ml, the concentrations of glucose left after 90 minutes of incubation were found to be (0.38 and 1.31)g/l in the normoglycaemic and hyperglycaemic media respectively. Conclusion: From the obtained results, it can be concluded that our extract seems to have an insulin-like effect on glucose uptake in liver slices isolated from Wistar rats

Absence of a structural transition up to 40 Gpa in MgB2 and the relevance of magnesium non-stoichiometry

We report measurements on MgB2 up to ~40GPa. Increasing pressure yields a monotonous decrease of the lattice parameters and of the c/a ratio, but no structural transition down to parameters smaller than those of AlB2. The transition superconducting temperature also decreases with temperature in a sample dependent way. The results are explained by an increase of the filling of the 2D pxy bands with pressure, the Mg stoichiometry determining the starting position of the Fermi level. Our measurements indicate that these hole bands are the relevant ones for superconductivity.Comment: submitted March 9th 2001, PRB accepte

Thermal equation of state of cubic boron nitride: Implications for a high-temperature pressure scale

The equation of state of cubic boron nitride (cBN) has been determined to a maximum temperature of 3300 K at a simultaneous static pressure of up to more than 70 GPa. Ab initio calculations to 80 GPa and 2000 K have also been performed. Our experimental data can be reconciled with theoretical results and with the known thermal expansion at 1 bar if we assume a small increase in pressure during heating relative to that measured at ambient temperature. The present data combined with the Raman measurements we presented earlier form the basis of a high-temperature pressure scale that is good to at least 3300 K

Deep carbon cycle constrained by carbonate solubility.

Earth's deep carbon cycle affects atmospheric CO2, climate, and habitability. Owing to the extreme solubility of CaCO3, aqueous fluids released from the subducting slab could extract all carbon from the slab. However, recycling efficiency is estimated at only around 40%. Data from carbonate inclusions, petrology, and Mg isotope systematics indicate Ca2+ in carbonates is replaced by Mg2+ and other cations during subduction. Here we determined the solubility of dolomite [CaMg(CO3)2] and rhodochrosite (MnCO3), and put an upper limit on that of magnesite (MgCO3) under subduction zone conditions. Solubility decreases at least two orders of magnitude as carbonates become Mg-rich. This decreased solubility, coupled with heterogeneity of carbon and water subduction, may explain discrepancies in carbon recycling estimates. Over a range of slab settings, we find aqueous dissolution responsible for mobilizing 10 to 92% of slab carbon. Globally, aqueous fluids mobilise [Formula: see text]% ([Formula: see text] Mt/yr) of subducted carbon from subducting slabs

Phase boundary between Na–Si clathrates of structures I and II at high pressures and high temperatures

Understanding of the covalent clathrate formation is a crucial point for the design of new superhard materials with intrinsic coupling of superhardness and metallic conductivity. It has been found that silicon clathrates have the archetype structures, which can serve an existent model compounds for superhard clathrate frameworks Si–B, Si–C, B–C and C with intercalated atoms (e.g., alkali metals or even halogens) that can assure the metallic properties. Here we report our in situ and ex situ studies of high-pressure formation and stability of clathrates Na₈Si₄₆ (structure I) and Na₂₄₊xSi₁₃₆ (structure II). Experiments have been performed using standard Paris–Edinburgh cells (opposite anvils) up to 6 GPa and 1500 K. We have established that chemical interactions in the Na–Si system and transition between two structures of clathrates occur at temperatures below silicon melting. The strong sensitivity of crystallization products to the sodium concentration has been observed. A tentative diagram of clathrate transformations has been proposed. At least up to ~ 6 GPa, Na₂₄₊xSi₁₃₆ (structure II) is stable at lower temperatures as compared to Na₈Si₄₆ (structure I).Изучен in situ и ex situ процесс образования при высоких давлениях и стабильности клатратов Na₈Si₄₆ (структура I) и Na₂₄₊xSi₁₃₆ (структура II). Эксперименты были проведены в стандартных Париж-Эдинбургских ячейках (opposite anvils) при давлениях и температурах до 6 ГПа и 1500 K соответственно. Установлено, что химическое взаимодействие в системе Na–Si и переходы между двумя структурами клатратов происходят при температурах ниже температуры плавления кремния. Предложено первое приближение диаграммы превращений клатратов. Отмечена большая чувствительность продуктов кристаллизации к концентрации натрия. Na₂₄₊xSi₁₃₆ (структура II) является стабильной при более низких температурах по сравнению с Na₈Si₄₆ (структура I), по крайней мере до ~ 6 ГПа.Вивчено in situ і ex situ процес утворення при високих тисках і стабільності клатратів Na₈Si₄₆ (структура I) і Na₂₄₊xSi₁₃₆ (структура II). Експерименти було проведено в стандартних Париж-Единбурзький комірках (opposite anvils) при тисках і температурах до 6 ГПа і 1500 K відповідно. Встановлено, що хімічна взаємодія в системі Na–Si і переходи між двома структурами клатратов відбуваються при температурах нижче температури плавлення кремнію. Запропоновано перше наближення діаграми перетворень клатратів. Відзначено велику чутливість продуктів кристалізації до концентрації натрію. Na₂₄₊xSi₁₃₆ (структура II) є стабільною при більш низьких температурах у порівнянні з Na₈Si₄₆ (структура I), принаймні до ~ 6 ГПа

High pressure behavior of CsC8 graphite intercalation compound

International audienceThe high pressure phase diagram of CsC8 graphite intercalated compound has been investigated at ambient temperature up to 32 GPa. Combining X-ray and neutron diffraction, Raman and X- ray absorption spectroscopies, we report for the first time that CsC8, when pressurized, undergoes phase transitions around 2.0, 4.8 and 8 GPa. Possible candidate lattice structures and the transition mechanism involved are proposed. We show that the observed transitions involve the structural re- arrangement in the Cs sub-network while the distance between the graphitic layers is continuously reduced at least up to 8.9 GPa. Around 8 GPa, important modifications of signatures of the electronic structure measured by Raman and X-ray absorption spectroscopies evidence the onset of a new transition

Structure and density of Fe-C liquid alloys under high pressure

International audienceThe density and structure of liquid Fe-C alloys have been measured up to 58 GPa and 3,200 K by in situ X-ray diffraction using a Paris-Edinburgh press and laser-heated diamond anvil cell. Study of the pressure evolution of the local structure inferred by X-ray diffraction measurements is important to understand the compression mechanism of the liquid. Obtained data show that the degree of compression is greater for the first coordination sphere than the second and third coordination spheres. The extrapolation of the measured density suggests that carbon cannot be the only light element alloyed to iron in the Earth's core, as 8-16 at % C (1.8-3.7 wt % C) would be necessary to explain the density deficit of the outer core relative to pure Fe. This concentration is too high to account for outer core velocity. The presence of other light elements (e.g., O, Si, S, and H) is thus required