Release flux of heavy metals from river sediments at different flow rates

This paper simulates sediment motion under different hydrodynamic conditions, aiming to investigate the release flux of heavy metals in river sediments. During the lab experiments, carried out in a circular rectangular flume device, water velocity in the flume was altered by controlling the gate switch, and the flow rate was controlled from 0 to 1 m/s. Sediment from the Le'an River and chlorine-removed tap water were used as experimental sediment and water, respectively. Through analyses of Cu, Zn, Cd, and Pb concentration in water at different flow rates, the relationship between the release flux (y) of Cu, Zn, Cd, and Pb and the flow rate (x) was established with a fitting error of less than 15%. In order to judge the reliability of the conclusions, experimental results were verified outdoors. The results showed when the sediment particle size is between 0 and 250 μm, within 1 hour, a quadratic polynomial correlation between the release flux of Cu, Cd, and Pb from river sediments and water velocity when the water pH is 5–9 and the flow rate is 0–65 cm/s; when the water pH is 5–9, the flow rate is 0–35 cm/s, the release flux of Zn from river sediments was shown to have a quadratic polynomial relationship with water velocity. The error between the calculated and measured values of heavy metals released from sediment in the Le'an River were within 5–30%. Our results can provide a theoretical reference for the control and treatment of heavy metal pollution in rivers and further improve corresponding water quality models.

Characterization and Release of Ibuprofen in Proniosome System (Ibuprofen-Span 60-Cholesterol)

The aim of this research was to determine influence of proniosome system which consists of ibuprofen-span 60-cholesterol with molar ratio of 2:1:0.75. The proniosome system was made by Coacervation Phase Separation Method,using ethanol 96% as solvent and glycerol 0.1% as aqueous phase. There were two formulas in this research formula I was ibuprofen non proniosome in HPMC gel base and formula II was ibuprofen proniosome in HPMC gel base. Characterization of formulas included organoleptic and pH of ibuprofen gel. Drug release was determined using diffusion cell and cellophane membrane in phosphate buffer pH 6.0 ± 0.05 at temperature 32 ± 0.5 oC for 7 hours. The drug release (flux) of ibuprofen from formula I and II were 28.3067 ± 3.0852 µg/cm2/min½ and 23.1900 ± 1.7658 µg/cm2/min½, respectively. The statistical result using independent sample T-test on degree of confident of 95% (α = 0.05) concluded that there was significant value of their fluxs. Research result revealed that release of ibuprofen proniosome system was lower than ibuprofen nonproniosome system in HPMC 4000 gel base..

Composition, mineralization potential and release risk of nitrogen in the sediments of Keluke Lake, a Tibetan Plateau freshwater lake in China

The lakes distributed in the Tibetan Plateau constitute a lake group with the highest altitude, largest lakes and largest area in the world and are important in global climate and environmental effects. Freshwater lakes in the Tibetan Plateau possess high ecological values and high vulnerability. The migration and transformation of nitrogen in sediments are critical to lake ecosystems, but information on sedimentary nitrogen in the freshwater lakes in the Tibetan Plateau is limited. A case study was conducted in Keluke Lake, China, to reveal the effects of sedimentary nitrogen on water quality in plateau freshwater lakes. Nitrogen speciation, mineralization potential and release flux were analysed through a sequential extraction method, waterlogged incubation experiment and Fick's first diffusion law, respectively. The content of total nitrogen (TN) was 1295.75–6151.69 mg kg −1 , and 94.2% of TN was organic nitrogen (ON). The contents of three nitrogen fractions were in the order of hydrolysable nitrogen > residual nitrogen > exchangeable nitrogen. Ammonia nitrogen ( N H 4 + − N ) was the main mineralization product, and hydrolysable ON was the most significant contributor. The sediments showed a great mineralization potential, with a potentially mineralizable nitrogen value of 408.76 mg N kg −1 of sediment, that was mainly affected by hydrolysable ammonium nitrogen. The N H 4 + − N diffusion flux ranged from 24.14 to 148.75 mg m −2 d −1 , and the sediments served as an internal nitrogen source. Nitrogen release from sediments was considerably influenced by exchangeable ammonia nitrogen. The sediments in Keluke Lake pose a potential nitrogen release risk and threaten the water quality of the lake. The total content, speciation, mineralization of ON and the release flux at sediment–water interface should be considered comprehensively to evaluate the effects of nitrogen in sediments to water quality.

OPTIMIZATION OF CARBOPOL 940 AND OLEIC ACID IN DICLOFENAC SODIUM BASE GEL USING FACTORIAL DESIGN 22 METHOD

<em>The aim of the present study was to determine the effect of carbopol 940, oleic acid and interaction of both in the value of viscosity and release rate and to find optimum formula of diclofenac sodium base gel which can produced viscoisity between 20 dPa.s - 200 dPa.s and rate release 50μg/cm².menit^1/2 - 150μg/cm².menit^1/2 using factorial design 2². The level of carbopol 940 were 1,3% and 0,8% while the level of oleic acid were 5% and 20%. Analysis of the research used Design Expert 10 software.The results showed that carbopol 940 and oleic acid had significant effect in determining the viscosity response and the release rate. The addition of carbopol 940 and oleic acid l increased the viscosity response and the addition of carbopol 940 and oleic acid decreased the release flux response. There were 100 optimum compositions of combination of carbopol 940 between 0.8% to 1,194% and oleic acid between 5% and 19.95% which can be used to obtain sodium diclofenac base gel preparation with viscosity responses between 76,042 dPa.s -199,570 dPa.s and flux release responses from 101,000 μg/cm².minute^1/2until 124,250 μg/cm².minute^1/2.</em>

The voltage sensor of excitation–contraction coupling in mammals: Inactivation and interaction with Ca2+

In skeletal muscle, the four-helix voltage-sensing modules (VSMs) of CaV1.1 calcium channels simultaneously gate two Ca2+ pathways: the CaV1.1 pore itself and the RyR1 calcium release channel in the sarcoplasmic reticulum. Here, to gain insight into the mechanism by which VSMs gate RyR1, we quantify intramembrane charge movement associated with VSM activation (sensing current) and gated Ca2+ release flux in single muscle cells of mice and rats. As found for most four-helix VSMs, upon sustained depolarization, rodent VSMs lose the ability to activate Ca2+ release channels opening; their properties change from a functionally capable mode, in which the mobile sensor charge is called charge 1, to an inactivated mode, charge 2, with a voltage dependence shifted toward more negative voltages. We find that charge 2 is promoted and Ca2+ release inactivated when resting, well-polarized muscle cells are exposed to low extracellular [Ca2+] and that the opposite occurs in high [Ca2+]. It follows that murine VSMs are partly inactivated at rest, which establishes the reduced availability of voltage sensing as a pathogenic mechanism in disorders of calcemia. We additionally find that the degree of resting inactivation is significantly different in two mouse strains, which underscores the variability of voltage sensor properties and their vulnerability to environmental conditions. Our studies reveal that the resting and activated states of VSMs are equally favored by extracellular Ca2+. Promotion by an extracellular species of two states of the VSM that differ in the conformation of the activation gate requires the existence of a second gate, inactivation, topologically extracellular and therefore accessible from outside regardless of the activation state.

Altered Ca2+ signaling in skeletal muscle fibers of the R6/2 mouse, a model of Huntington’s disease

Huntington’s disease (HD) is caused by an expanded CAG trinucleotide repeat within the gene encoding the protein huntingtin. The resulting elongated glutamine (poly-Q) sequence of mutant huntingtin (mhtt) affects both central neurons and skeletal muscle. Recent reports suggest that ryanodine receptor–based Ca2+ signaling, which is crucial for skeletal muscle excitation–contraction coupling (ECC), is changed by mhtt in HD neurons. Consequently, we searched for alterations of ECC in muscle fibers of the R6/2 mouse, a mouse model of HD. We performed fluorometric recordings of action potentials (APs) and cellular Ca2+ transients on intact isolated toe muscle fibers (musculi interossei), and measured L-type Ca2+ inward currents on internally dialyzed fibers under voltage-clamp conditions. Both APs and AP-triggered Ca2+ transients showed slower kinetics in R6/2 fibers than in fibers from wild-type mice. Ca2+ removal from the myoplasm and Ca2+ release flux from the sarcoplasmic reticulum were characterized using a Ca2+ binding and transport model, which indicated a significant reduction in slow Ca2+ removal activity and Ca2+ release flux both after APs and under voltage-clamp conditions. In addition, the voltage-clamp experiments showed a highly significant decrease in L-type Ca2+ channel conductance. These results indicate profound changes of Ca2+ turnover in skeletal muscle of R6/2 mice and suggest that these changes may be associated with muscle pathology in HD.