Ionic calcium levels during pregnancy, at delivery and in the first hours of life

Free calcium ion concentration (mmol/l) and pH were determined in whole blood using a semiautomatic electrode system (ICA-1 Radiometer, Copenhagen, Denmark) in 37 normal women, 90 pregnant women (30 from each trimester of gestation), 28 mothers at delivery and their respective newborns. The blood samples from normal controls, pregnant women, umbilical cord and 40-50-hour-old infants were collected anaerobically in vacuum tubes. Duplicate samples drawn from newborns shortly after birth by heel puncture were collected in special heparinized capillary tubes. We observed that Ca2+ concentrations in the second (1.20 +/- 0.04) and third (1.20 +/- 0.05) trimesters of pregnancy, and at delivery (1.18 +/- 0.05), were lower than in the control group (1.23 +/- 0.04). The [Ca2+] in samples from the umbilical vein (1.44 +/- 0.11) and artery (1.45 +/- 0.08) and from newborns 2-5 min after birth (1.34 +/- 0.12) was greater than in control samples. The [Ca2+] in newborns 40-50 hours after birth was lower (1.16 +/- 0.14) than in the control group.     

Relative bioavailability of calcium from calcium formate, calcium citrate, and calcium carbonate

Calcium is an essential nutrient required in substantial amounts, but many diets are deficient in calcium making supplementation necessary or desirable. The objective of this study was to compare the oral bioavailability of calcium from calcium formate, a new experimental dietary calcium supplement, to that of calcium citrate and calcium carbonate. In a four-way crossover study, either a placebo or 1200 mg of calcium as calcium carbonate, calcium citrate, or calcium formate were administered orally to 14 healthy adult female volunteers who had fasted overnight. After calcium carbonate, the maximum rise in serum calcium ( approximately 4%) and the fall in serum intact parathyroid hormone 1-84 (iPTH) (approximately 20-40%) did not differ significantly from placebo. After calcium citrate, the changes were modestly but significantly (p < 0.05) greater, but only at 135 to 270 min after ingestion. In contrast, within 60 min after calcium formate serum calcium rose by approximately 15% and serum iPTH fell by 70%. The mean increment in area under the plasma concentration-time curve (0-270 min) for serum calcium after calcium formate (378 mg . min/dl) was double that for calcium citrate (178 mg . min/dl; p < 0.01), whereas the latter was only modestly greater than either placebo (107; p < 0.05) or calcium carbonate (91; p < 0.05). In this study, calcium formate was clearly superior to both calcium carbonate and calcium citrate in ability to deliver calcium to the bloodstream after oral administration. Calcium formate may offer significant advantages as a dietary calcium supplement.     

An Automated Low Ionic Antiglobulin Test

An automated antihuman globulin test has been performed by continuous flow analysis. Cell washing in acidic low ionic medium achieved sedimentation of aggregated cells and removal of supernatant fluid without centrifugation. These cells were subsequently disaggregated with hypertonic antihuman globulin serum, but human antibody-coated cells remained aggregated and were removed. Remaining red blood cells were hemolyzed, and their hemoglobin concentration was measured colorimetrically. This automated method detected antibodies of the Kell, Duffy, Kidd, and Lewis blood group systems.     

Ionic liquid-based liposome for selective SERS detection

An ionic liquid (IL)-based liposome was utilized as a substrate to construct a SERS platform. The isotropy of the IL outer surface together with its ion-exchange property led to the array-like growth of Au nanoparticles (NPs), generating hot-spots and resulting in anionic probes being present on the hot-spot regions. The simultaneous strategy of enrichment and localization endowed the platform with ability to detect trace amounts of anionic probes.

SERS platform of IL-based liposome@Au NPs for selective recognition of anionic probes located in hot-spot regions.     

Ionic conductivity of melt-frozen LiBH4 films

The fast Li conductivity of LiBH₄ envisages its use in all-solid-state batteries. Powders are commonly applied. But here, we study the formation of dense micrometer films by melting, spinning and subsequent solidifying. Characterized by electron microscopy, and spectroscopy (EDX/XPS/impedance), a reversible phase transformation is confirmed as well as a maximum conductivity of 10³ S cm⁻¹.

LiBH₄ melt-frozen film as solid state electrolyte.

Li ion batteries exhibit a high gravimetric and volumetric capacity as well as a high power density.¹ To overcome the drawbacks of liquid electrolytes such as safety concerns, leakage and limitations for miniaturization, solid state batteries are a suggested alternative.² In this context, complex hydrides have attracted much interest as candidates for solid state electrolytes. Lithium borohydride (LiBH₄) is a promising representative of this group.³Conventionally, LiBH₄ is applied as reducing agent, while recent research focuses on its energy functions such as solid state hydrogen storage, electrochemical Li storage and fast Li-ionic conductivity. When Matsuo et al. discovered the fast ionic conductivity of LiBH₄ in 2007,⁴ the research on its potential application as electrolyte was initiated.The electrical properties of LiBH₄ are related to its crystal structure. The low-temperature (LT) orthorhombic phase (space group Pnma) causes Li ionic conductivities in the range of 10⁻⁸ to 10⁻⁶ S cm⁻¹. At 110 °C, the transformation to the hexagonal high-temperature (HT) phase (space group P6₃mc) induces a discontinuous jump in the conductivity⁴ to 10³ S cm⁻¹, which is in the same range as offered by liquid electrolytes. The fast Li ionic conduction in LiBH₄ was theoretically justified.⁵ It was experimentally studied with pelletized samples (≈2 mm thickness) made of pressed LiBH₄ powder⁴ and with nanoconfined LiBH₄ in pores of ordered silica scaffolds.⁶ Due to its hygroscopicity, handling of LiBH₄ is restricted to protected atmosphere. In contact with steam and oxygen, the compound reacts spontaneously to hydroxides and oxides and a large amount of hydrogen is released.^7,8Xiong et al. prepared LiBH₄ films by pulsed laser deposition under hydrogen atmosphere from a LiB target to investigate the hydrolysis of the material.⁹ However, the electrochemical characterization of LiBH₄ films has not yet been reported. Thin films are advantageous for studying diffusion coefficients as well as the interfaces with different electrodes. Thin films may also open a way to improve the intimate contact between solid electrolyte and electrode. Currently, LiPON (lithium phosphorous oxynitride) is the most often applied thin film electrolyte, which shows conductivities of 10⁻⁶ S cm⁻¹ at RT and could be prepared with a thickness¹⁰ down to 12 nm.The purpose of the present study is preparing thin films of LiBH₄ and characterizing their microstructure and ionic conductivity. Melting of LiBH₄ powder and solidifying in layer geometry turns out to be a promising process. The method is enhanced by spin coating of the molten LiBH₄ aiming for thinner films. Electron microscopy (SEM) is used for measuring the thickness of the films. Photoelectron and energy dispersive X-ray spectroscopy (XPS, EDX) are used for chemical analysis while impedance spectroscopy (EIS) characterizes the ionic conductivity.Substrates were cut from silicon (Si) wafers with a thickness of (675 ± 15) μm and an orientation (111), which were previously oxidized by annealing for 5 hours at 1200 °C under air. On top, 50 nm of different current collectors, copper (Cu), platinum (Pt) or tantalum (Ta), were deposited by ion beam sputtering (IBS) in a custom-built UHV chamber with a DC ion source (KF/F 40, Ion-Tech GmbH). The LiBH₄ powder was purchased from Albemarle. Due to the sensitivity of LiBH₄ to oxygen and moisture, all experiments were conducted in protecting Ar atmosphere in a glove box (contents of oxygen and water ≤ 0.5 ppm) and the transfer to other instruments was protected when possible. For the melting process, the substrate with the powder was placed on a heating plate set to 290 °C (inside the glove box) and afterwards the LiBH₄ melt was flattened with a spatula. A notch in the spatula served as mechanical spacer to control the thickness of the film. Alternative spin coating was carried out on a KLM spin coater SCE (Schaefer) inside the glove box, with a custom-made sample holder that could be heated on a hot plate and offered sufficient heat capacity to keep the ion conductor liquid during the subsequent spinning.Upon the LiBH₄ layer, the upper current collector was deposited by IBS in a dotted electrode pattern to create multiple cells on a single sample wafer. The dots were of 1 mm diameter and the current collector thickness on top was varied between 50–150 nm. The samples were transported from the glove box to the IBS sputter chamber in an argon filled container.Electrical impedance spectroscopy was carried out directly after the film preparation, inside the glove box with the potentiostat VSP-300 (BioLogic). Samples were electrically contacted by gold coated stainless steel tips (Bürklin: 11H5560). Conductivity was measured at temperatures between room temperature and 150 °C. The frequency range was 3 MHz to 1 Hz and voltage amplitude up to 2.5 V.For microstructure imaging and EDX analysis, a DualBeam microscope (ThermoFischer Scios) was utilized for which protected transfer from the glove box was achieved with the vacuum shuttle LEICA EM VCT500. The XPS measurements were conducted with a Theta Probe ARXPS (ThermoFischer Scientific) for which mounting of the samples required a few seconds of atmosphere contact.A sketch of the layer preparation is shown in Fig. 1(a) and the geometric layer setup for the impedance measurements in Fig. 1(b). The samples were heated inside a glove box to 290 °C to ensure melting but avoiding decomposition of the hydride. The thickness of multiple electrolyte films flattened with the spatula was measured by FIB cross-sections to an average thickness of (18.6 ± 6.5) μm. This shows that layers with a reasonably reproducible thickness can be prepared by this method. An exemplary cross-section is shown in Fig. 2(a), where the upper and lower Cu current collectors are also visible. Pores visible in the layer are attributed to hydrogen loss by the ion beam cutting, which is observed also in other even more stable hydrides.¹¹ On the cross-section, EDX analyses were carried out as depicted in Fig. 2(b). In both spectra similar amount of boron is detected. Spectrum 1, measured at the surface of the layer, reveals a more significant contribution of oxygen (O). This indicates a slight surface reaction, taking place during sample transfer from the glove box to the ion beam sputter chamber. This observation confirms the high sensitivity of the material to the atmosphere (also discussed in Fig. 4(a)). Oxygen compounds are the typical products obtained when the borohydride comes into contact with air.^7,8 Additionally, Si from the substrate is visible in the second spectrum due to the tilt of the sample for cross section – EDX analysis. Chlorine also visible in both spectra is an impurity present in the purchased LiBH₄ powder.Open in a separate windowFig. 1(a) Sketch of the preparation of LiBH₄ layer on the heating plate by flattening the melt with a spatula containing a cut with a depth of 0.7 mm. (b) Final sample design. The current collectors were prepared by ion beam sputter-deposition. Different current collector materials are compared: Cu, Pt or Ta.Open in a separate windowFig. 2Investigations of a LiBH₄ layer prepared by melt-freezing of LiBH₄ powder on a SiO₂ substrate with ion beam sputter-deposited Cu 50 nm as current collector: (a) SEM image (5 kV, 0.8 nA) of a FIB cross-section with the positions of the EDX analyses marked. (b) EDX spectra of the two positions marked in a: 1 – closer to the surface and 2 – deeper in the layer volume. (c) XPS measurement showing the B 1s peak at 188.3 eV confirming the major presence of LiBH₄.^12,13 (d) XRD spectrum of the pristine LiBH₄ powder used and the melt-frozen film. All major (indexed) reflexions are understood by the crystalline LT phase of LiBH₄.Open in a separate windowFig. 4(a) SEM picture (5 kV, 1.6 nA) of a FIB cross-section trough a LiBH₄ layer spin coated with 30 rps on a Pt current collector. Overlaid EDX line scans discover an increased O content in the surface layer of the LiBH₄. (b) Top view on a LiBH₄ layer, spin coated with 90 rps on Cu a current collector imaged with backscattered electrons (5 kV, 0.8 nA). The bright spots are uncoated Cu areas. (c) Nyquist plot of the LT and the HT phase of a LiBH₄ layer prepared by spin coating with 30 rps on a Pt current collector. (d) Arrhenius plots of LiBH₄ layer prepared by spin coating with 30 rps with different current collectors. Fig. 2(c) shows the XPS characterization of the produced LiBH₄ layer. Despite the oxide also visible in the EDX analyses, the peak at 188.3 eV corresponds to LiBH₄,^12,13 clearly confirming that the desired compound is present to a major fraction after melting and solidification. The peak at 192.6 eV is attributed to LiB₄O₇ which probably represents the oxidation product formed during the transport of the sample to the XPS. The effect this oxidation layer has on hydrogen desorption was previously reported,^12,15,16 however its effect on the ionic conductivity in battery applications has not yet been considered. XRD characterization of the melt-frozen samples was performed to confirm their crystallinity after melting and cooling. The XRD is shown in Fig. 2(d) revealing the crystalline nature of the sample. The peaks identify the LT phase of LiBH₄. For comparison the XRD of the pristine powder used for the preparation is given and additional EDX of the powder is shown in the ESI.^†Nyquist plots of the impedance spectroscopy are presented in Fig. 3(a). The LT phase response appears with a complete semi-circle, while the HT phase does not start at the origin, an observation also visible in the work of Matsuo et al.⁴ It can be attributed to the high frequency limit of the potentiostat.Open in a separate windowFig. 3(a) Nyquist plots of the LT and the HT phase of LiBH₄ layers prepared by flattening the melt with a spatula and contacted with a Cu current collector. Model curves of the replacement circuit in red dashed. (b) Arrhenius plots of ≈18 μm LiBH₄ layers prepared by flattening the melt with a spatula on a 50 nm Cu current collector as bottom contact but different thicknesses of the upper Cu current collector as labelled.The calculated conductivities of three independent samples are provided in Fig. 3(b). In these measurements, the thickness of the upper Cu current collector was stepwise increased: 50 nm, 100 nm and 150 nm. The impedance spectroscopy of the sample with the 50 nm thin upper current collector, shown in black squares, could only be operated in the LT phase. At higher temperature no impedance could be measured. Increasing the thickness of the upper current collector to 100 or 150 nm, enabled reliable measurements of both the LT and the HT phases. This suggests damaging of the upper current collector layer or its interface towards the electrolyte during the phase transition. On the other hand, repetition of the heating cycle of the sample with an upper current collector of 150 nm in thickness (see triangles) demonstrates the reproducibility of the measurements and so the microstructure stability during phase transition. For later measurements the thickness of the upper current collector was chosen to be 150 nm.All resistivity measurements show the discontinuous jump of two to three orders of magnitude in conductivity at around 110 °C indicating the phase transition from orthorhombic to hexagonal. Below and above this discontinuity, the temperature dependence shows the expected Arrhenius behavior. In the LT phase, the conductivity ranges from 10⁻⁷ to 10⁻⁸ S cm⁻¹ at room temperature to 10⁻⁵ to 10⁻⁶ S cm⁻¹ before phase transition. The HT phase reaches values of ≈10⁻³ S cm⁻¹. These observations are in accordance with the measurements of Matsuo et al.⁴ at compressed powders, which demonstrated a maximum conductivity of 10⁻³ S cm⁻¹ at the HT phase. They confirm the presence of LiBH₄ in the melt-frozen layers and demonstrate the fast ionic conductivity in the HT phase which is comparable to the conductivities of liquid electrolytes. The activation energies for the conductivity in the LT and HT phase amount to (0.89 ± 0.1) eV and (0.60 ± 0.1) eV, respectively. They are slightly higher than the values of 0.69 eV for the LT and 0.53 eV for the HT phase reported for the powder.⁴ The difference is probably due to the more compact material in the molten films with less pores and grain boundaries in comparison to the compressed powders.Since these layers could be applied as thin film membranes in solid state batteries, improvement of the process could result in thinner layers, which was attempted by spin coating of the LiBH₄ melt. Indeed, the method can decrease the layer thickness. The following values were found for coating on Cu: (5.3 ± 0.8) μm for 30 rps, (2.3 ± 0.3) μm for 60 rps, (1.5 ± 0.2) μm for 90 rps, (1.3 ± 0.2) μm for 120 rps. Fig. 4(a) shows a cross-section of a sample coated with 30 rps with an overlaid EDX scan. Similar to the EDX spectra shown before, the O content is significantly elevated near the surface of the LiBH₄ layer. A sharp contrast visible in the secondary electron image between the contaminated surface layer with increased O content and the LiBH₄ volume underneath is partly marked by a dashed line. This indicates a clear reaction front between the surface oxide and the remaining LiBH₄ volume. Platinum (Pt) and silicon (Si) are detected because they are the current collector and the substrate, respectively in this case. (The apparent decrease in the Boron content is a consequence of different sample tilt during the EDX measurement.) The sharp contrast in oxygen intensity as well as the contrast in the electron image strongly indicates that in this case indeed a “second” surface phase has formed. In the case of the thinner spin-coated films, this layer also affects the impedances spectra as it will be further discussed hereafter.As a drawback, the spin-coated LiBH₄ layers do not completely cover the current collector, as it is seen in the top view of the backscattered electrons image in Fig. 4(b). Furthermore, the fraction of uncoated substrate area increases with increasing rotation speed, discovering this way a decisive disadvantage of the spin coating method. Since the upper current collector is sputter-deposited upon the LiBH₄ layer, holes in the ion conductor layer lead to short circuits. Due to these short circuits, only layers coated with 30 rps could be measured by impedance spectroscopy, which formed fewer short circuits. In the case of the Cu current collector only 4.1% of the contact dots examined did not reveal a short circuit. In order to check, whether the fraction of coating can be improved by better wetting of different metals, Pt and Ta were also tested as current collectors (upper and lower). Their higher melting temperature and therefore higher surface tension promise better wetting. This however did not improve the problem significantly. In the case of Pt, 5.3% of the dots examined on different samples did not reveal a short circuit. In the case of Ta, the quote was even worse, only 1.6%.Representative Nyquist diagrams of the LT and the HT phase are shown in Fig. 4(c). The measurement of the LT phase differs to that of the layers flattened with the spatula (compare Fig. 3(b)). This time, two semi-circles are visible showing that an additional resistance is present. By using an equivalent circuit with 2 resistances in series the fitting and interpretation of these two semi-circles is possible. The corresponding fit is shown in blue for the first semi-circle and in red for the second semi-circle. Expecting the lower conductivity for the thicker LiBH₄ film, we can conclude that the ionic conductivity of the main LiBH₄ is represented by the blue semicircle at higher frequency, while the second red one is attributed to the surface layer observed in Fig. 4(a). Naturally, in the case of the spin coated samples where the total thickness of the layer is smaller, the oxide surface layer plays a more important role. At the HT phase, only one semi-circle is visible but it is overlapped partly by the interface response. Also an inductive contribution becomes visible in comparison to the low absolute resistance. Thus, the accuracy of the HT conductivity of the spin-coated films is limited.Arrhenius plots of the conductivity measured for the different current collectors are provided in Fig. 4(d). The measurements with Cu and Pt show the characteristic shape and in the HT phase a conductivity of 10⁻³ S cm⁻¹ is reached. Nevertheless, the conductivity is slightly lower than observed for the thicker films of the spatula-flattening method. This might be attributed to the discussed surface reaction during the sample transfer from the glove box to the sputter chamber. Since the spin coated layers are one order of magnitude thinner, a surface reaction of similar reaction depth affects the conductivity of the spin coated layers more significantly. In the case of Ta, the conductivity stays below 10⁻⁵ S cm⁻¹ in the entire temperature range. From literature it is found that Ta surfaces develop a passivating tantalum pentoxide film¹⁴ with which, most likely, the LiBH₄ reacted in this case, resulting in the lower conductivity and the many short circuits of these samples. This indicates Ta as a bad candidate for a current collector in contact to LiBH₄. The ESI^† presents an additional comparison to pressed powder pellets showing a very similar temperature dependence of the conductivity.LiBH₄ has recently shown ionic conductivity comparable to the current liquid electrolytes used in Li-ion batteries. While powders are in the focus of interest to produce all-solid-state full cells, thin films can be a favourite tool to investigating the Li transport in these materials and promise more reliable dense structure at lower thicknesses. Two methods for preparing LiBH₄ layers for solid-state electrolyte testing from LiBH₄ melt with reproducible layer thickness were established during this work. Flattening the melt with a spatula leads to a thickness of 18.6 ± 6.5 μm. Additional spin-coating reduces the thicknesses to 5.3 ± 0.8 μm and even to 1.3 ± 0.2 μm depending on the rotation speed. However, frequent short circuits in the EIS measurements of the spin coated layers were induced because the LiBH₄ layer did not wet the bottom metallization completely. Different current collectors such as Cu, Pt and Ta were tested as substrate in pursuit of improvement. Nonetheless a high amount of short circuits was always visible. By contrast, the layers flattened with a spatula revealed a high reversibility and reliability in electrical measurement.The ionic conductivity of the layers flattened with a spatula reached in the HT phase ≈10⁻³ S cm⁻¹, a value comparable to liquid electrolytes. Nevertheless, high temperatures of 110 °C are necessary for the transformation into the conductive HT phase, which is a rather high temperature for applications. The spin-coated layers showed a reduced conductivity due to a surface reaction that takes place during the transfer between tools. The oxidation product layer is clearly visible in the SEM cross section and its additional resistance is observed with a second semi-circle in the EIS measurements. The high amount of oxygen in the contamination layer, is visible in the EDX and oxides are also detected by XPS measurements. Despite the presence of oxygen, XPS measurement and the characteristic temperature dependence of the conductivity confirm that the produced layers consist dominantly of LiBH₄. This work establishes an auspicious method for creating solid state thin film batteries with this hydride.     

Meta-analysis of calcium bioavailability: a comparison of calcium citrate with calcium carbonate

OBJECTIVE: To perform a meta-analysis of data from available published trials comparing the bioavailability of calcium carbonate with that of calcium citrate. DATA SOURCES: The whole set was comprised of 15 studies involving 184 subjects who underwent measurement of calcium absorption from calcium carbonate and calcium citrate. Category A excluded four studies for lack of physiological relevance, use of a mixed preparation with low content of calcium carbonate, or wide variability in results. Category B was comprised of five studies (from Category A) involving 71 subjects who took calcium supplements on an empty stomach. Category C was comprised of six studies (from Category A) involving 65 subjects who took calcium preparations with meals. METHOD: The meta-analysis of calcium absorption data from calcium carbonate and calcium citrate, with calculation of effect size and 95% confidence intervals. RESULTS: Calcium absorption from calcium citrate was consistently significantly higher than that from calcium carbonate by 20.0% in the whole set, by 24.0% in Category A, by 27.2% on an empty stomach, and by 21.6% with meals. CONCLUSION: Calcium citrate is better absorbed than calcium carbonate by approximately 22% to 27%, either on an empty stomach or co-administered with meals.     

Comparison of serum total calcium, albumin-corrected total calcium, and ionized calcium in 1213 patients with suspected calcium disorders

The correlations between serum ionized calcium, serum total calcium, total calcium corrected for albumin and calculated ionized calcium were investigated in a prospective multicentre investigation of 1213 patients suspected of having calcium metabolic disease. Diagnostic discordance between serum total calcium and measured ionized calcium was found in 31% of the patients. With the calculation of albumin-corrected total calcium or calculated ionized calcium the discordance decreased to 17.9%. The diagnostic discordance which could be ascribed to the analytical imprecision (CV = 1.5%) amounted to only 6.7%. Although we found highly significant correlations between the parameters, a considerable scatter around the regression line made prediction of ionized calcium from albumin-corrected total calcium unreliable in many patients.     

Ionic self-assembled organogel polyelectrolytes for energy storage applications

High performance organogel polyelectrolytes were synthesized by super acid catalyst step-growth polycondensation of isatin and the non-activated multiring aromatic p-terphenyl. Subsequently, a chemical modification reaction was carried out to obtained quaternary ammonium functionalized polyelectrolytes through a nucleophilic substitution reaction with (3-bromopropyl)trimethylammonium bromide and potassium carbonate at room temperature. Different functionalization degrees were obtained by controlling the molar ratio of the polymer and the modification agent. The organogel polyelectrolytes were formed due to the high phase segregation and self-assembling observed owing to the amphiphilic character of the material (hydrophobic backbone and hydrophilic fragment grafted). The organogel polyelectrolytes were used to fabricate supercapacitors using two commercial graphite electrodes. These polyelectrolytes displayed good ionic conductivity without the use of another doping agent such as salts, acids or ionic liquids. In this work, a strong correlation of functionalization degree and ionic conductivity of the polyelectrolytes and capacitance of the supercapacitors was observed. The ionic conductivity of the polyelectrolytes reached 0.46 mS cm⁻¹ for the 100% functionalization degree, meanwhile the polyelectrolyte with the 10% functionalization degree shows 0.036 mS cm⁻¹. Li-doped polyelectrolytes showed higher ionic conductivity due the presence of extra ionic charges (2.26 and 0.2 mS cm⁻¹ for the polyelectrolytes with the 100% and 10% of functionalization degree, respectively). The principal novelty of this work lies in the possibility of modulating the ionic conductivity of organogels and the capacitance of supercapacitors by chemical modifications. The capacitance of the supercapacitors was 1.17 mF cm⁻² for the 100% functionalized polyelectrolyte and is higher in comparison with the polyelectrolyte with 10% functionalization degree (0.68 mF cm⁻²) measured at a discharge current of 52 μA cm⁻² by galvanostatic charge discharge technique. Additionally, when lithium salt (lithium triflate) was added, the polyelectrolytes retained a gel consistency, increasing the ionic conductivity and capacitance. For the doped polyelectrolytes, the areal capacitance reaches 1.37 mF cm⁻² for the 100% functionalization degree polyelectrolyte with lithium triflate. These organogel polyelectrolytes open the possibility to design flexible and all solid-state supercapacitors without the risk of leakage.

High performance organogel polyelectrolytes were synthesized by super acid catalyst step-growth polycondensation of isatin and the non-activated multiring aromatic p-terphenyl.     

Receptor-regulated calcium entry

A wide variety of hormones and neurotransmitters activate cellular responses by mobilizing cellular Ca2+. In general, this Ca2+ mobilization response is comprised of a release of Ca2+ from intracellular stores, as well as increased entry of Ca2+ into the cytoplasm from the extracellular space. The mechanism for release of intracellular Ca2+ results from the Ca2(+)-mobilizing actions of a second messenger, D-myo-inositol 1,4,5-trisphosphate. Inositol polyphosphates appear also to be involved in the activation of Ca2+ entry, but the mechanism by which this is accomplished is less clear. According to the capacitative model for Ca2+ entry, the depletion of the agonist-regulated intracellular Ca2+ pool by the action of D-myo-inositol 1,4,5-trisphosphate is somehow coupled to the activation of Ca2+ entry. The evidence for this model comes from the demonstration, by diverse strategies, that the same Ca2+ entry mechanism normally activated by Ca2(+)-mobilizing agonists can be equally well triggered by depletion of the intracellular Ca2+ pool, even in the absence of receptor activation or elevated cellular levels of inositol polyphosphates.     

Cerebral calcium embolism

A new‐onset neurological deficit after calcified aortic valve replacement and an hyperdense image on the computed tomography raised suspicion of an stroke of unusual etiology.     

Nonspecific Ionic Inhibition of Ethambutol Binding by Mycobacterium smegmatis

Magnesium sulfate and spermidine were tested for their effects on binding of (14)C-ethambutol by Mycobacterium smegmatis. Concentrations were used that protected the organism from ethambutol inhibition. Sodium salts were examined as possible ethambutol antagonists to test the previously reported specificity of the divalent cation salt effect. Consistent with growth-protection experiments, 20 mM MgSO(4) or 2.0 mM spermidine prevented and reversed (14)C binding by cells shaken with 0.2 mug of (14)C-ethambutol per ml of Sauton medium at 37 C. Sodium salts were not effective ethambutol antagonists when tested at 20 mM, but at concentrations equivalent in ionic strength (mu) to that provided by 20 mM MgSO(4) they were effective. Thus, 20 mM MgSO(4), 80 mM NaCl, or 27 mM Na(2)SO(4) (mu = 0.08) all gave similar results in growth protection and binding experiments, suggesting that MgSO(4) antagonism is a nonspecific ionic effect. Because spermidine (mu 相似文献   

人工骨材料磷酸钙及硫酸钙在腱-骨愈合中的作用

背景：有关促进腱-骨愈合的方法文献报道很多,主要方法就是给腱-骨间隙添加一些刺激物质,以此促进腱骨的愈合。磷酸钙盐作为生物活性材料具有骨传导性,已广泛应用于临床骨缺损的替代和填充。而硫酸钙作为人工材料,具有潜在的骨诱导活性。目的：在自体腘绳肌肌腱移植重建膝关节前交叉韧带过程中,观察人工骨材料磷酸钙及硫酸钙促进腱-骨愈合的效应。方法：选用36条雄性成熟比格犬,先行切断双侧膝关节前交叉韧带,取同侧后肢趾长屈肌腱作为移植物,采用悬吊式固定重建前交叉韧带。按随机数字表法分为3组,磷酸钙组于股骨腱骨隧道中注入磷酸钙,硫酸钙组注入硫酸钙,空白组韧带重建结束后不添加任何填充物。分别于重建后1,2,3,4,6个月取材行大体观察、组织学和生物力学观测。结果与结论：前交叉韧带重建后1,2,3,4个月时,磷酸钙组及硫酸钙组腱骨界面纤维连接明显强于空白组,而磷酸钙组、硫酸钙组差异无显著性意义。6个月时,各组愈合程度相似。生物力学方面,重建后1个月时,磷酸钙组及硫酸钙组腱骨界面的抗拉脱强度均高于空白组（P〈0.05）,而磷酸钙组、硫酸钙组差异无显著性意义（P〉0.05）。提示磷酸钙及硫酸钙均能促进腱-骨愈合,两者之间无明显差异。     

人工骨材料磷酸钙及硫酸钙在腱-骨愈合中的作用

背景:有关促进腱-骨愈合的方法文献报道很多,主要方法就是给腱-骨间隙添加一些刺激物质,以此促进腱骨的愈合.磷酸钙盐作为生物活性材料具有骨传导性,已广泛应用于临床骨缺损的替代和填充.而硫酸钙作为人工材料,具有潜在的骨诱导活性.目的:在自体腘绳肌肌腱移植重建膝关节前交叉韧带过程中,观察人工骨材料磷酸钙及硫酸钙促进腱-骨愈合的效应.方法:选用36条雄性成熟比格犬,先行切断双侧膝关节前交叉韧带,取同侧后肢趾长屈肌腱作为移植物,采用悬吊式固定重建前交叉韧带.按随机数字表法分为3组,磷酸钙组于股骨腱骨隧道中注入磷酸钙,硫酸钙组注入硫酸钙,空白组韧带重建结束后不添加任何填充物.分别于重建后1,2,3,4,6个月取材行大体观察、组织学和生物力学观测.结果与结论:前交叉韧带重建后1,2,3,4个月时,磷酸钙组及硫酸钙组腱骨界面纤维连接明显强于空白组,而磷酸钙组、硫酸钙组差异无显著性意义.6个月时,各组愈合程度相似.生物力学方面,重建后1个月时,磷酸钙组及硫酸钙组腱骨界面的抗拉脱强度均高于空白组(P < 0.05),而磷酸钙组、硫酸钙组差异无显著性意义(P > 0.05).提示磷酸钙及硫酸钙均能促进腱-骨愈合,两者之间无明显差异.