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PubMed2006

Systematic front distortion and presence of consecutive fronts in a precipitation system.

A new simple reaction-diffusion system is presented focusing on pattern formation phenomena as consecutive precipitation fronts and distortion of the precipitation front. The chemical system investigated here is based on the amphoteric property of aluminum hydroxide and exhibits two unique phenomena. Both the existence of consecutive precipitation fronts and distortion are reported for the first time. The precipitation patterns could be controlled by the pH field, and the distortion of the precipitation front can be practical for microtechnological applications of reaction-diffusion systems.

Letter↗

PubMed2005

Synthesis and purification of oxide nanoparticle dispersions by modified emulsion precipitation.

ZrO2 and Fe2O3 precursor nanoparticles are synthesized, well-dispersed in decane, via a modified emulsion precipitation (MEP) method. This method starts with preparing two thermostable water-in-oil (w/o) emulsions with nonylphenol tetra(ethylene glycol) ether (Arkopal-40) as the main surfactant, didodecyldimethylammonium bromide (DiDAB) as the cosurfactant, decane as the continuous oil phase, and either a metal salt solution or a hexamethylenetetramine (HMTA) precipitation agent solution as the dispersed water phase. After mixing of the two emulsions, individual precursor particles are formed by precipitation in the confinement of the aqueous solution droplets. Excess water is removed by azeotropic distillation, and steric stabilization of the particles in the remaining oil medium is achieved with poly(octadecyl methacrylate) (PODMA), initially present dissolved in the oil phase. A purification process is conducted to remove the precipitation reaction byproduct and excess surfactants from the nanoparticle dispersions. Transmission electron microscopy (TEM) characterization shows that the ZrO2 and Fe2O3 precursor nanoparticles are both non-agglomerated, spherical, and have a narrow particle size distribution, centered at 4 nm in diameter. The precipitation from the dispersion of byproduct NH4Cl after water removal, and insoluble surfactant DiDAB after dilution with pure decane, is confirmed by X-ray diffraction (XRD). NMR results show that most of the oil-soluble surfactant Arkopal-40 can be removed from the dispersion by a 3x repeated dead-end pressure filtration process. It is shown that, after purification, the nanoparticle dispersions can be used for the preparation of homogeneous nanostructured coatings. The purification procedure as discussed provides guidelines for up-scaling the process and reuse of emulsifiers.

Journal Article↗

PubMed2005

Effect of the structures of ionic liquids and alkylbenzene-derived amphiphiles on the inhibition of asphaltene precipitation from CO2-injected reservoir oils.

The inhibition of asphaltene precipitation from high-pressure, CO(2)-injected reservoir oils by ionic and nonionic amphiphiles, the ionic liquids based on p-alkylpyridinium ([C(n)()py](+)) and N-butylisoquinolinium ([C(4)iql](+)) cations, and the alkylbenzene-derived amphiphiles p-alkylphenol (C(n)()phol), p-alkylbenzenesulfonic acid (C(n)()bsa), and sodium p-alkylbenzenesulfonate (C(n)()bsNa) was investigated for the first time. The influences of the structures of these compounds and the effect of the combination of their cations and anions were studied. The results show that the inhibition abilities of the alkylbenzene-derived amphiphiles first increase when n = 2-8 and then remain almost constant when n >/=8 and that the effectiveness follows the order C(n)()phol < C(n)()bsa approximately C(n)()bsNa. The inverse trend is observed for the ionic liquids [C(n)()py][Cl]; that is, their inhibition abilities decrease as n increases from 4 to 8 to 12. [C(4)iql][Cl] is more effective than [C(4)py][Cl], but [C(n)()py][BF(4)] and [C(n)()py][PF(6)] have almost no effect on the stabilization of asphaltenes. It was found that the effectiveness of an alkylbenzene-derived amphiphile on the inhibition of asphaltene precipitation from reservoir oils relies on its ability to form a stable steric-stabilization layer around asphaltenes, which is controlled by the polarity of its headgroup and the length of its alkyl tail. The novel mechanism of inhibiting asphaltene precipitation using the ionic liquids [C(n)()py] ([Cl], [BF(4)], and [PF(6)]) and [C(4)iql][Cl] was proposed. The mechanism states that the ionic liquids can effectively prevent asphaltene precipitation from the reservoir oils by breaking the asphaltene associations, which are due to the local nonneutrality of the charge densities of the cation and the anion. The ionic liquids that are based on an anion with high charge density, in connection with cations with sufficiently low charge densities, can effectively inhibit asphaltene precipitation from the reservoir oils. This mechanism is also important for studying the thermodynamic properties and phase behavior of the ionic liquids.

Journal Article↗

PubMedDate not supplied

Solubilization of trichloroacetic acid (TCA) precipitated microbial proteins via naOH for two-dimensional electrophoresis.

In preparing intracellular microbial samples for one- or two-dimensional electrophoresis, trichloroacetic acid (TCA) precipitation is frequently used to remove interfering compounds. Solubilization of TCA precipitate typically requires the addition of a number of chaotropes or detergents, in a multistep process, that requires hours to carry out. In this study, a simple, rapid, one-step method to solubilize TCA precipitated proteins is presented. Precipitated proteins are pretreated with 0.2 M NaOH for less than 5 min, followed by addition of standard sample solubilization buffer (SSSB). When compared to solubilization with SSSB alone, NaOH pretreatment of TCA-precipitated intracellular protein from Aspergillus oryzae and Escherichia coli shows an approximate 5-fold increase in soluble protein. In addition, two-dimensional gel electrophoresis on resolubilized proteins shows an equivalent number of proteins in samples with and without NaOH pretreatment.

Aspergillus oryzae↗

PubMed2002

Transport of phenolic compounds from leaf surface of creosotebush and tarbush to soil surface by precipitation.

During the last 100 years, many desert grasslands have been replaced by shrublands. One possible mechanism by which shrubs outcompete grasses is through the release of compounds that interfere with neighboring plants. Our objective was to examine the movement of secondary compounds from the leaf surface of creosotebush and tarbush to surrounding soil surfaces via precipitation. Units consisting of a funnel and bottle were used to collect stemflow, throughfall, and interspace precipitation samples from 20 creosotebush (two morphotypes) and 10 tarbush plants during three summer rainfall events in 1998. Precipitation samples were analyzed for total phenolics (both species) and nordihydroguaiaretic acid (creosotebush only). Phenolics were detected in throughfall and stemflow of both species with stemflow containing greater concentrations than throughfall (0.088 and 0.086 mg/ml for stemflow and 0.022 and 0.014 mg/ml for throughfall in creosotebush morphotypes U and V, respectively: 0.044 and 0.006 mg/ml for tarbush stemflow and throughfall, respectively). Nordihydroguaiaretic acid was not found in any precipitation collections. The results show that phenolic compounds produced by creosotebush and tarbush can be transported to the soil surface by precipitation, but whether concentrations are ecologically significant is uncertain. Nordihydroguaiaretic acid was not present in the runoff from creosotebush.

Asteraceae↗

PubMed2006

Precipitants of partner aggression.

Self-reported precipitants of psychological and physical partner aggression were examined in a community sample of 453 cohabiting couples with 3- to 7-year-old children. Partners precipitated most partner aggression. Men, but not maritally discordant men, were more likely than women to cite physical partner aggression as the precipitant of their own aggression. Women, including maritally discordant women, were more likely to endorse partner verbal than partner physical aggression as a precipitant for their own mild physical aggression, which is consistent with women's aggression escalation. Nonaggressive partner precipitants were common and deserve future research attention.

Aggression↗

PubMed2006

Complex precipitation pathways in multicomponent alloys.

One usual way to strengthen a metal is to add alloying elements and to control the size and the density of the precipitates obtained. However, precipitation in multicomponent alloys can take complex pathways depending on the relative diffusivity of solute atoms and on the relative driving forces involved. In Al-Zr-Sc alloys, atomic simulations based on first-principle calculations combined with various complementary experimental approaches working at different scales reveal a strongly inhomogeneous structure of the precipitates: owing to the much faster diffusivity of Sc compared with Zr in the solid solution, and to the absence of Zr and Sc diffusion inside the precipitates, the precipitate core is mostly Sc-rich, whereas the external shell is Zr-rich. This explains previous observations of an enhanced nucleation rate in Al-Zr-Sc alloys compared with binary Al-Sc alloys, along with much higher resistance to Ostwald ripening, two features of the utmost importance in the field of light high-strength materials.

Journal Article↗

PubMed2001

Desert dust suppressing precipitation: a possible desertification feedback loop.

The effect of desert dust on cloud properties and precipitation has so far been studied solely by using theoretical models, which predict that rainfall would be enhanced. Here we present observations showing the contrary; the effect of dust on cloud properties is to inhibit precipitation. Using satellite and aircraft observations we show that clouds forming within desert dust contain small droplets and produce little precipitation by drop coalescence. Measurement of the size distribution and the chemical analysis of individual Saharan dust particles collected in such a dust storm suggest a possible mechanism for the diminished rainfall. The detrimental impact of dust on rainfall is smaller than that caused by smoke from biomass burning or anthropogenic air pollution, but the large abundance of desert dust in the atmosphere renders it important. The reduction of precipitation from clouds affected by desert dust can cause drier soil, which in turn raises more dust, thus providing a possible feedback loop to further decrease precipitation. Furthermore, anthropogenic changes of land use exposing the topsoil can initiate such a desertification feedback process.

Journal Article↗

PubMed2003

The inhibition of calcium phosphate precipitation by fetuin is accompanied by the formation of a fetuin-mineral complex.

The present studies show that the previously reported ability of fetuin to inhibit the precipitation of hydroxyapatite from supersaturated solutions of calcium and phosphate in vitro is accompanied by the formation of the fetuin-mineral complex, a high molecular mass complex of calcium phosphate mineral and the proteins fetuin and matrix Gla protein that was initially discovered in the serum of rats treated with etidronate and that appears to play a critical role in inhibiting calcification in vivo. Rat serum potently inhibited the precipitation of calcium phosphate mineral when the concentration of calcium and phosphate were increased by 10 mm each, and the modified serum was incubated at 37 degrees C for 9 days; in the absence of serum, precipitation occurred in seconds. Large amounts of the fetuin-mineral complex were generated in the first 3 h of this incubation and remained throughout the 9-day incubation. Purified bovine fetuin inhibited the precipitation of mineral for over 14 days in a solution containing 5 mM calcium and phosphate at pH 7.4 at 22 degrees C, whereas precipitation occurred in minutes without fetuin. There was a biphasic drop in ionic calcium in the fetuin solution, however, from 5 to 3 mM in the first hour and from 3 to 0.9 mM between 20 and 24 h; these changes in ionic calcium are due to the formation of complexes of calcium, phosphate, and fetuin. The complex found at 24 h to 14 days is identical to the fetuin-mineral complex found in the serum of etidronate-treated rats, whereas the complex found between 1 and 20 h is less stable.

Animals↗

PubMed1984

Precipitates found around Schistosoma haematobium eggs from human urine prior to circumoval precipitin test.

Schistosoma haematobium eggs were recovered in urine from schoolchildren in Mwachinga Village, Kwale District, Kenya. The surface of the eggs showed a pattern similar to that observed in a circumoval precipitin (COP) test. Observed precipitates were removed by treatment of the eggs with pepsin, but were not affected by trypsin. Similar precipitates occurred after incubating the pepsin-treated eggs with urine supernatants from the same children. Attempts were made to identify the components that might contribute to observed bleb (precipitate) formation. The fluorescent antibody test revealed both IgG and IgM in the precipitate, while urine examination by immunodiffusion revealed IgG, IgM, IgA and C3. These components probably participated in the bleb formation. This possibility seemed more likely because of the presence of anti-egg antibodies in the immunoglobulins identified in the urine, and agrees well with the expected activity of pepsin on these immunoglobulins. These results, therefore, suggest that S. haematobium eggs recovered in urine contain precipitates formed mainly by immunoglobulins; it is necessary to treat such eggs with pepsin before carrying out a COP test. The relevance of these findings to the immunodiagnosis of Schistosomiasis haematobium in man is discussed.

Adolescent↗

PubMed1980

Dense precipitate of brain tubulin with skeletal muscle myosin.

Purified tubulin from porcine brain formed a dense precipitate at 37 degrees C with muscle myosin filaments from rabbit skeletal muscle; this effect was greater than that with partially purified tubulin. ATP or GTP, which prevented the myosin filaments from precipitating, inhibited the formation of the dense precipitate, but did not dissociate the dense precipitate once formed. The dense precipitate was found by thin-section electron microscopy to be composed to side-by-side aggregates of myosin filaments whose projections might be decorated by tubulin. The decoration was also seen by negative-stain electron microscopy. The binding of tubulin to myosin filaments decreased the Mg2+- and Ca2+-GTPase activity of the myosin by about half, but did not affect either Mg2+- or Ca2+-ATPase activity. The binding ratio of tubulin to myosin in the presence of 5 mM MgCl2 was 2.2 mol/mol using purified tubulin and 1.8 mol/mol using partially purified tubulin. Five mM ATP and GTP in the presence of 5 mM MgCl2 decreased the tubulin binding by 1.6-2.0 and 1.1-1.3 mol/mol, respectively, when added before an encounter of tubulin with myosin filaments, but did not cause any decrease when added after such an encounter.

Adenosine Triphosphatases↗

PubMed2005

The influence of extraction and precipitation pH on the dry matter yield of broiler dark meat.

In recent years, demand for white meat products has resulted in excess supplies and depressed prices of leg meat in the United States. One approach to increasing the utilization of dark meat is to extract the pigments and fat to make the resulting product more acceptable for the production of further-processed meat products. To date, such technologies have been inefficient (low yields) or have resulted in products of limited use. Three replicate trials were conducted to determine the effects of extraction pH and precipitation pH on the wet and dry extract yields of boneless, skinless broiler leg meat. Broiler leg meat was chopped with added water and extracted by adjusting the pH to 8.0, 8.5, 9.0, 9.5, 10.0, 10.5, 11.0, 11.5, and 12.0 while mixing. After determination of extraction yields, each extraction was adjusted to pH 3.8, 4.0, 4.2, 4.4, 4.6, 4.8, 5.0, and 5.2 to determine the effect of precipitate pH on total wet and dry yields. Dry yield increased with extraction pH and precipitation pH. However, the greatest yields, over 70%, were at extraction pH values above 10.5, which have been associated with the production of potentially harmful by-products. Combinations of extraction pH values between 9 and 10.5 and precipitation pH values above 4.4 resulted in dry yields of approximately 65%. These results indicate that pH extraction and precipitation may result in economically viable yields. Further research is needed to determine the optimal conditions of yield, composition, and functionality.

Animals↗

PubMed1999

Risk factors and precipitating neck movements causing vertebrobasilar artery dissection after cervical trauma and spinal manipulation.

STUDY DESIGN: Potential precipitating events and risk factors for vertebrobasilar artery dissection were reviewed in an analysis of the English language literature published before 1993. OBJECTIVES: To assess the literature pertaining to precipitating neck movements and risk factors for vertebrobasilar artery dissection in an attempt to determine whether the incidence of these complications can be minimized. SUMMARY OF BACKGROUND DATA: Vertebrobasilar artery dissection and occlusion leading to brain stem and cerebellar ischemia and infarction are rare but often devastating complications of cervical, manipulation and neck trauma. Although various investigators have suggested potential risk factors and precipitating events, the basis for these suggestions remains unclear. METHODS: A detailed search of the literature using three computerized bibliographic databases was performed to identify English language articles from 1966 to 1993. Literature before 1966 was identified through a hand search of Index Medicus. References of articles obtained by database search were reviewed to identify additional relevant articles. Data presented in all articles meeting the inclusion criteria were summarized. RESULTS: The 367 case reports included in this study describe 160 cases of spontaneous onset, 115 cases of onset after spinal manipulation, 58 cases associated with trivial trauma, and 37 cases caused by major trauma (3 cases were classified in two categories). The nature of the precipitating trauma, neck movement, or type of manipulation that was performed was poorly defined in the literature, and it was not possible to identify a specific neck movement or trauma that would be considered the offending activity in the majority of cases. There were 208 (57%) men and 158 (43%) women (gender data not reported in one case) with an average age of 39.3 +/- 12.9 years. There was an overall prevalence of 13.4% hypertension, 6.5% migraines, 18% use of oral contraception (percent of female patients), and 4.9% smoking. In only isolated cases was specific vascular disease such as fibromuscular hyperplasia noted. CONCLUSIONS: The literature does not assist in the identification of the offending mechanical trauma, neck movement, or type of manipulation precipitating vertebrobasilar artery dissection or the identification of the patient at risk. Thus, given the current status of the literature, it is impossible to advise patients or physicians about how to avoid vertebrobasilar artery dissection when considering cervical manipulation or about specific sports or exercises that result in neck movement or trauma.

Aortic Dissection↗

PubMed2002

Predictions of extreme precipitation and sea-level rise under climate change.

Two aspects of global climate change are particularly relevant to river and coastal flooding: changes in extreme precipitation and changes in sea level. In this paper we summarize the relevant findings of the IPCC Third Assessment Report and illustrate some of the common results found by the current generation of coupled atmosphere-ocean general circulation models (AOGCMs), using the Hadley Centre models. Projections of changes in extreme precipitation, sea-level rise and storm surges affecting the UK will be shown from the Hadley Centre regional models and the Proudman Oceanographic Laboratory storm-surge model. A common finding from AOGCMs is that in a warmer climate the intensity of precipitation will increase due to a more intense hydrological cycle. This leads to reduced return periods (i.e. more frequent occurrences) of extreme precipitation in many locations. The Hadley Centre regional model simulates reduced return periods of extreme precipitation in a number of flood-sensitive areas of the UK. In addition, simulated changes in storminess and a rise in average sea level around the UK lead to reduced return periods of extreme high coastal water events. The confidence in all these results is limited by poor spatial resolution in global coupled models and by uncertainties in the physical processes in both global and regional models, and is specific to the climate change scenario used.

Altitude↗

PubMed1987

Rat C3 conversion by rat anti-2,4,dinitrophenyl (DNP) hapten IgA immune precipitates.

Monomeric (m-) and polymeric (p-) anti-DNP monoclonal (MC) rat IgA antibodies (Ab) were tested for precipitation with DNP-bovine serum albumin (DNP-BSA) and C3 conversion in rat serum, with rat MC anti-DNP IgG2b used as reference. At equivalence, p-IgA rapidly precipitated DNP-BSA, with little antigen (Ag) left in the supernatant. In contrast, m-IgA at five-fold higher concentration precipitated Ag very slowly, with less than 50% of Ag precipitated at equivalence. The Ag/Ab weight ratio at equivalence was 0.13 for both m- and p-IgA, but the molar ratio was 0.3 for m-IgA and close to 1.0 for p-IgA, suggesting a higher avidity of p-IgA. Rat C3 conversion by rat IgA immune precipitates (IP) was about 20% with m-IgA and 40% with p-IgA. EGTA did not significantly affect these figures. Therefore, rat MC IgA IP activated the rat alternative C pathway. Neither rat nor mouse IgA anti-DNP IP activated C3 in normal human serum.

Animals↗

PubMed1987

Chemical synthesis of phosphoseryl-phosphoserine, a partial analogue of human salivary statherin, a protein inhibitor of calcium phosphate precipitation in human saliva.

Human salivary secretions are supersaturated with respect to basic calcium phosphates but spontaneous precipitation of these salts from saliva, or surface-induced precipitation of calcium phosphates onto dental enamel, does not normally occur. This unexpected stability has been attributed to the inhibitory activities of two kinds of salivary phosphoproteins: statherin and the acidic, proline-rich phosphoproteins (PRP). Investigation of the structure-function relationships of statherin, the most potent inhibitor of primary (spontaneous) and secondary (seeded) precipitation of calcium phosphate salts in human saliva has been limited to studies of peptide segments obtained from the native peptide by specific proteolysis. Solid phase peptide synthesis (SPPS) is a useful and potentially more flexible alternative. Phosphoserine residues (positions 2 & 3) play critically important roles in the precipitation-inhibition activities of statherin, but SPP synthesis of these phosphorylated peptides is precluded because of the instability of phosphoserine residues in the presence of HF. Thus, this peptide was synthesized by solution-phase methods. The dipeptide possessed substantial inhibitory activity in assays for inhibition of both primary and secondary precipitation of calcium phosphate salts, but was not as active as either N-terminal tryptic hexapeptide of statherin or intact statherin. Syntheses of other model phosphorylated peptides are underway to expand the structure-function relationships.

Calcium Phosphates↗

PubMed1995

Suppression of naloxone-precipitated withdrawal jumps in morphine-dependent mice by stimulation of prostaglandin EP3 receptor.

1. We have shown that intracisternal (i.c.) administration of interleukin-1 beta (IL-1 beta) attenuates naloxone-precipitated withdrawal jumps in morphine-dependent mice, and the effect was partly mediated by the corticotropin-releasing factor. To elucidate further other possible mechanisms involved in the inhibitory effect of IL-1 beta on morphine withdrawal jumping behaviour, in this study, we examined the involvement of the prostaglandin-synthesis pathway, because prostaglandins have been shown to mediate the several central effects of IL-1. Furthermore, we examined the effects of subtype-selective prostaglandin receptor agonists on morphine withdrawal jumping behaviour. 2. Mice were rendered morphine-dependent by subcutaneous implantation of a pellet containing 11.5 +/- 0.3 mg morphine hydrochloride for 48 h. Morphine withdrawal syndromes were precipitated by intraperitoneal (i.p.) injection of naloxone (10 mg kg-1). The degree of physical dependence on morphine was estimated by counting the number of jumps, one of the typical withdrawal signs in mice, for 40 min. 3. The inhibitory effect of IL-1 beta (1 ng/mouse) administered intracisternally 30 min before naloxone (10 mg kg-1, i.p.) was significantly blocked by pretreatment with sodium salicylate (a cyclo-oxygenase inhibitor, 10 ng or 30 ng/mouse) administered intracisternally 15 min before IL-1 beta, while i.c. administration of sodium salicylate alone (3 ng, 10 ng or 30 ng/mouse) followed by i.c. administration of vehicle instead of IL-1 beta did not significantly change the number of jumps precipitated by naloxone. 4. Intracisternal administration of M&B28,767 (an EP3-receptor agonist, 1 fg-30 ng/mouse) and sulprostone (an EP1/EP3-receptor agonist, 10 fg-100 ng/mouse) 30 min before naloxone (10 mg kg,-1 i.p.) attenuated withdrawal jumps with a U-shaped dose-response, reaching a peak at 10 pg/mouse and 100 pg/mouse, respectively. On the other hand, i.c. administration of iloprost (an EP1/IP-receptor agonist, 10 fg-100 ng/mouse), butaprost (an EP2-receptor agonist, 10 fg-100 ng/mouse) or prostaglandin F2 alpha (a FP-receptor agonist, 10 fg-100 ng/mouse) 30 min before naloxone (10 mg kg-1, i.p.) did not significantly change the number of jumps precipitated by naloxone. 5. These results indicate that the prostaglandin-synthesis pathway is, at least in part, involved in the inhibitory effect of IL-1 beta on naloxone-precipitated withdrawal jumps in morphine-dependent mice, and that the prostaglandin synthesized in the brain suppresses the morphine withdrawal jumping behaviour via the EP3-receptor, but not via the EP1-, EP2-, IP- or FP-receptor.

Alprostadil↗

PubMed1992

The partners' views on precipitant stressors in suicide.

All suicides (n = 1397) in Finland during 1 year were studied by thorough interviews with the surviving next of kin. We included 388 suicides after which a spouse's or a cohabiting partner's subjective views of precipitant stressors in suicide process during the last 3 months and earlier in life were determined. In 82% of the cases the partner considered life events as precipitant stressors for the suicide. Among men, the most common stressors considered as suicide precipitants were somatic illness (25%), interpersonal discord (22%) and separation (14%). Among women these were mental disorder (28%), interpersonal discord (18%) and death of a significant other (17%). Somatic illness and retirement were more commonly considered as precipitants among older men, whereas interpersonal discord, separation and financial trouble were more common among younger men. Among women, job problems were more commonly considered as precipitants for younger subjects. Among both sexes, childhood adversity was more commonly reported among the younger subjects.

Adult↗