999 resultados para Potassium Fluoride
Resumo:
The structures of the hydrated sodium salts of 4-chloro-3-nitrobenzoic acid {poly[aqua(μ4-4-chloro-3-nitrobenzoato)sodium(I)], [Na(C7H3ClNO4)(H2O)]n, (I)} and 2-amino-4-nitrobenzoic acid {poly[μ-aqua-aqua(μ3-2-amino-4-nitrobenzoato)sodium(I)], [Na(C7H5N2O4)(H2O)2]n, (II)}, and the hydrated potassium salt of 2-amino-4-nitrobenzoic acid {poly[μ-aqua-aqua(μ5-2-amino-4-nitrobenzoato)potassium(I)], [K(C7H5N2O4)(H2O)]n, (III)} have been determined and their complex polymeric structures described. All three structures are stabilized by intra- and intermolecular hydrogen bonding and strong π–π ring interactions. In the structure of (I), the distorted trigonal bipyrimidal NaO5 coordination polyhedron comprises a monodentate water molecule and four bridging carboxylate O-atom donors, generating a two-dimensional polymeric structure lying parallel to (001). Intra-layer hydrogen-bonding associations and strong inter-ring π–π interactions are present. Structure (II) has a distorted octahedral NaO6 stereochemistry, with four bridging O-atom donors, two from a single carboxylate group and two from a single nitro group and three from the two water molecules, one of which is bridging. Na centres are linked through centrosymmetric four-membered duplex water bridges and through 18-membered duplex head-to-tail ligand bridges. Similar centrosymmetric bridges are found in the structure of (III), and in both (II) and (III) strong inter-ring π–π interactions are found. A two-dimensional layered structure lying parallel to (010) is generated in (II), whereas in (III) the structure is three-dimensional. With (III), the irregular KO7 coordination polyhedron comprises a doubly bridging water molecule, a single bidentate bridging carboxylate O-atom donor and three bridging O-atom donors from the two nitro groups. A three-dimensional structure is generated. These coordination polymer structures are among the few examples of metal complexes of any type with either 4-chloro-3-nitrobenzoic acid or 4-nitroanthranilic acid.
Resumo:
Piezoelectric energy harvesters can be used to convert ambient energy into electrical energy and power small autonomous devices. In recent years, massive effort has been made to improve the energy harvesting ability in piezoelectric materials. In this study, reduced graphene oxide was added into poly(vinylidene fluoride) to fabricate the piezoelectric nanocomposite films. Open-circuit voltage and electrical power harvesting experiments showed remarkable enhancement in the piezoelectricity of the fabricated poly(vinylidene fluoride)/reduced graphene oxide nanocomposite, especially at an optimal reduced graphene oxide content of 0.05 wt%. Compared to pristine poly(vinylidene fluoride) films, the open-circuit voltage, the density of harvested power of alternating current, and direct current of the poly(vinylidene fluoride)/reduced graphene oxide nanocomposite films increased by 105%, 153%, and 233%, respectively, indicating a great potential for a broad range of applications.
Resumo:
The thermal decomposition process of kaolinite–potassium acetate intercalation complex has been studied using simultaneous thermogravimetry coupled with Fourier-transform infrared spectroscopy and mass spectrometry (TG-FTIR-MS). The results showed that the thermal decomposition of the complex took place in four temperature ranges, namely 50–100, 260–320, 320–550, and 650–780 °C. The maximal mass losses rate for the thermal decomposition of the kaolinite–potassium acetate intercalation complex was observed at 81, 296, 378, 411, 486, and 733 °C, which was attributed to (a) loss of the adsorbed water, (b) thermal decomposition of surface-adsorbed potassium acetate (KAc), (c) the loss of the water coordinated to potassium acetate in the intercalated kaolinite, (d) the thermal decomposition of intercalated KAc in the interlayer of kaolinite and the removal of inner surface hydroxyls, (e) the loss of the inner hydroxyls, and (f) the thermal decomposition of carbonate derived from the decomposition of KAc. The thermal decomposition of intercalated potassium acetate started in the range 320–550 °C accompanied by the release of water, acetone, carbon dioxide, and acetic acid. The identification of pyrolysis fragment ions provided insight into the thermal decomposition mechanism. The results showed that the main decomposition fragment ions of the kaolinite–KAc intercalation complex were water, acetone, carbon dioxide, and acetic acid. TG-FTIR-MS was demonstrated to be a powerful tool for the investigation of kaolinite intercalation complexes. It delivers a detailed insight into the thermal decomposition processes of the kaolinite intercalation complexes characterized by mass loss and the evolved gases.
Resumo:
This paper relates to the importance of impact of the chosen bottle-point method when conducting ion exchange equilibria experiments. As an illustration, potassium ion exchange with strong acid cation resin was investigated due to its relevance to the treatment of various industrial effluents and groundwater. The “constant mass” bottle-point method was shown to be problematic in that depending upon the resin mass used the equilibrium isotherm profiles were different. Indeed, application of common equilibrium isotherm models revealed that the optimal fit could be with either the Freundlich or Temkin equations, depending upon the conditions employed. It could be inferred that the resin surface was heterogeneous in character, but precise conclusions regarding the variation in the heat of sorption were not possible. Estimation of the maximum potassium loading was also inconsistent when employing the “constant mass” method. The “constant concentration” bottle-point method illustrated that the Freundlich model was a good representation of the exchange process. The isotherms recorded were relatively consistent when compared to the “constant mass” approach. Unification of all the equilibrium isotherm data acquired was achieved by use of the Langmuir Vageler expression. The maximum loading of potassium ions was predicted to be at least 116.5 g/kg resin.
Resumo:
The structures of the isomorphous potassium and rubidium polymeric coordination complexes with 4-nitrobenzoic acid, poly[mu2-aqua-aqua-mu3-(4-nitrobenzoato)-potassium], [K(C7H4N2O2)(H2O)2]n, (I) and poly[mu3-aqua-aqua-mu5-(4-nitrobenzoato)-rubidium], [Rb(C7H4N2O2)(H2O)2]n, (II) have been determined. In (I) the very distorted KO6 coordination sphere about the K+ centres in the repeat unit comprise two bridging nitro O-atom donors, a single bridging carboxyl O-atom donor and two water molecules, one of which is bridging. In the the Rb complex (II), the same basic MO6 coordination is found in the repeat unit but is expanded to RbO9 through a slight increase in the accepted Rb-O bond length range and includes an additional Rb-O(carboxyl) bond, completing a bidentate O,O'-chelate interaction, and additional bridging Rb-Onitro) and Rb-O(water) bonds. The comparative K-O and Rb-O bond length ranges are 2.738(3)-3.002(3)Ang. (I) and 2.884(2)-3.182(2)Ang. (II). The structure of (II) is also isomorphous as well as isostructural with the known structure of the nine-coordinate caesium 4-nitrobenzoate analogue, [Cs(C7H4N2O~2~)(H~2~O)2]n, (III) in which the Cs---O range is 3.047(4)-3.338(4)Ang. In all three complexes, common basic polymeric extensions are found, including two different centrosymmetric bridging interactions through both water and nitro groups as well as extensions along c through the p-related carboxyl group, giving a two-dimensional structure in (I). In (II) and (III), three-dimensional structures are generated through additional bridges through the nitro and water O-atoms. In all structures, both water molecules are involved in similar intra-polymer O-H...O hydrogen-bonding interactions to both carboxyl as well as water O-atom acceptors. A comparison of the varied coordination behaviour of the full set of Li-Cs salts with 4-nitrobenzoic acid is also made.
Resumo:
The mineral lamprophyllite is fundamentally a silicate based upon tetrahedral siloxane units with extensive substitution in the formula. Lamprophyllite is a complex group of sorosilicates with general chemical formula given as A2B4C2Si2O7(X)4, where the site A can be occupied by strontium, barium, sodium, and potassium; the B site is occupied by sodium, titanium, iron, manganese, magnesium, and calcium. The site C is mainly occupied by titanium or ferric iron and X includes the anions fluoride, hydroxyl, and oxide. Chemical composition shows a homogeneous phase, composed of Si, Na, Ti, and Fe. This complexity of formula is reflected in the complexity of both the Raman and infrared spectra. The Raman spectrum is characterized by intense bands at 918 and 940 cm−1. Other intense Raman bands are found at 576, 671, and 707 cm−1. These bands are assigned to the stretching and bending modes of the tetrahedral siloxane units.
Resumo:
The two-dimensional coordination polymeric structures of the hydrated potassium and rubidium salts of (3,5-dichlorophenoxy)acetic acid, (3,5-D) namely, poly[mu-aqua-bis[mu3-2-(3,5-dichlorophenoxy)acetato]potassium, [K2(C8H5Cl2O3)2 (H2O)]n (I) and poly[mu-aqua-bis[mu3-2-(3,5-dichlorophenoxy)acetato]dirubidium] [Rb2(C8H5Cl2O3)2 (H2O)]n (II), respectively have been determined and are described. The two compounds are isotypic and the polymer is based on centrosymmetric dinuclear bridged complex units. The irregular six-coordination about the metal centres comprises a bridging water molecule lying on a twofold rotation axis, the phenoxy O-atom donor and and a triple bridging carboxylate O-atom of the oxoacetate side chain of the 3,5-D ligand in a bidentate chelate mode, the second carboxy O-donor, also bridging. The K-O and Rb-O bond-length ranges are 2.7238(15)--2.9459(14) and 2.832(2)--3.050(2) \%A respectively and the K...K and Rb...Rb separations in the dinuclear unit are 4.0214(7) and 4.1289(6) \%A, respectively. Within the two-dimensional layers which lie parallel to (100), the coordinated water molecule forms an O---H...O hydrogen bond to the single bridging carboxylate O atom.
Resumo:
Patients with anorexia nervosa (AN) have low body weight, depleted fat stores, and reduced muscle mass. Both total body potassium (TBK) and bioelectrical impedance analysis (BIA) have been used to measure the body composition of these patients.1–4 Whereas TBK accurately measures body cell mass, the metabolically active compartment of the body, whole body potassium counters are expensive and not readily available. The purpose of this study was to investigate the potential of multiple frequency BIA (MFBIA) to monitor changes in body compartments in patients with AN.
Resumo:
Malnutrition is a common problem in children with end-stage liver disease (ESLD), and accurate assessment of nutritional status is essential in managing these children. In a retrospective study, we compared nutritional assessment by anthropometry with that by body composition. We analyzed all consecutive measurements of total body potassium (TBK, n = 186) of children less than 3 years old with ESLD awaiting transplantation found in our database. The TBK values obtained by whole body counting of 40K were compared with reference TRK values of healthy children. The prevalence of malnutrition, as assessed by weight (weight Z score < -2) was 28%, which was significantly lower (chi-square test, p < 0.0001) than the prevalence of malnutrition (76%) assessed by TBK (< 90% of expected TRK for age). These results demonstrated that body weight underestimated the nutritional deficit and stressed the importance of measuring body composition as part of assessing nutritional status of children with ESLD.
Resumo:
Objective: To investigate measures aimed at defining the nutritional status of cystic fibrosis (CF) populations, this study compared standard anthropometric measurements and total body potassium (TBK) as indicators of malnutrition. Methods: Height, weight, and TBK measurements of 226 children with CF from Royal Children's Hospital, Brisbane, Australia, were analyzed. Z scores for height for age, weight for age, and weight for height were analyzed by means of the National Centre for Health Statistics reference. TBK was measured by means of whole body counting and compared with predicted TBK for age. Two criteria were evaluated with respect to malnutrition: (1) a z score < -2.0 and (2) a TBK for age <80% of predicted. Results: Males and females with CF had lower mean height-for-age and weight-for-age z scores than the National Centre for Health Statistics reference (P < .01), but mean weight-for-height z score was not significantly different. There were no significant gender differences. According to anthropometry, only 7.5% of this population were underweight and 7.6% were stunted. However, with TBK as an indicator of nutritional status, 29.9% of males and 22.0% of females were malnourished. Conclusion: There are large differences in the percentage of patients with CF identified as malnourished depending on whether anthropometry or body composition data are used as the nutritional indicator. At an individual level, weight-based indicators are not sensitive indicators of suboptimal nutritional status in CF, significantly underestimating the extent of malnutrition. Current recommendations in which anthropometry is used as the indicator of malnutrition in CF should be revised.
Resumo:
In our earlier study, we have observed that hypokalemia in langur monkeys, following gossypol acetic acid (GAA) treatment (5 mg dose level) when used as an antispermatogenic agent, and potassium salt supplementation partially maintained body potassium level of the animals. The aims of the present investigation was to confirm further occurrence of hypokalemia in the monkey (comparatively at two higher dose levels) and the role of potassium salt in preventing occurrence of gossypol-induced hypokalemia. Highly purified gossypol acetic acid alone at two dose levels (7.5 and 10 mg/animal/day; oral) and in combination with potassium chloride (0.50 and 0.75 mg/animal/day; oral) was given for 180 days. Treatment with gossypol alone as well as with the supplementation of potassium salt resulted in severe oligospermia and azoospermia. Animals receiving gossypol alone showed significant potassium deficiency with signs of fatigue at both dose levels. Enhanced potassium loss through urine was found in potassium-deficient animals, whereas animals receiving gossypol acetic acid plus potassium salt showed normal serum potassium with a less significant increase in urine potassium level during treatment phases. Other parameters of the body remained within normal range except gradual and significant elevation in serum transaminases activity. The animals gradually returned to normalcy following 150 and 180 days of termination of the treatment.
Resumo:
We report the ferroelectric and pyroelectric properties of the composite films of lithium tantalate (LT) nanoparticle in poly(vinylidene fluoride) PVDF matrix at different volume fractions of LT (f(LT) = 0.047, 0.09 and 0.17). For an applied electric field of 150 kV cm(-1) the nonvolatile polarization of the composite was observed to increase from 0.014 mu C cm(-2) at f(LT) = 0 to 2.06 mu C cm(-2) at f(LT) = 0.17. For f(LT) = 0.17, the composite films exhibit a saturated ferroelectric hysteresis loop with a remanent polarization (2P(r) = 4.13 mu C cm(-2)). Compared with pure poled PVDF the composite films also showed a factor of about five enhancement in the pyroelectric coefficient at f(LT) = 0.17. When used in energy detection mode the pyroelectric voltage sensitivity of the composite films was found to increase from 3.93 to 18.5 VJ(-1) with an increase in f(LT) from 0.0 to 0.17.
Resumo:
The cr~¢stal structure of [potassium(benzo-15-crown-5)](picrate) shows that in the complex the metal is sandwiched between two crowns andhas no interaction with plcrate.