scholarly journals Charging of ice-vapor interfaces: applications to thunderstorms

2003 ◽  
Vol 3 (4) ◽  
pp. 1237-1252 ◽  
Author(s):  
J. Nelson ◽  
M. Baker
Keyword(s):  
Contact Region ◽  
Spatial Separation ◽  
The Other ◽  
Surface Charges ◽  
High Concentration ◽  
Ice Surface ◽  
Moving Interface ◽  
Ice Films ◽  
Electromagnetic Emissions ◽  
Ice Surfaces

Abstract. The build-up of intrinsic Bjerrum and ionic defects at ice-vapor interfaces electrically charges ice surfaces and thus gives rise to many phenomena including thermoelectricity, ferroelectric ice films, sparks from objects in blizzards, electromagnetic emissions accompanying cracking in avalanches, glaciers, and sea ice, and charge transfer during ice-ice collisions in thunderstorms. Fletcher's theory of the ice surface in equilibrium proposed that the Bjerrum defects have a higher rate of creation at the surface than in the bulk, which produces a high concentration of surface D defects that then attract a high concentration of OH- ions at the surface. Here, we add to this theory the effect of a moving interface caused by growth or sublimation. This effect can increase the amount of ionic surface charges more than 10-fold for growth rates near 1 mm s-1 and can extend the spatial separation of interior charges in qualitative agreement with many observations. In addition, ice-ice collisions should generate sufficient pressure to melt ice at the contact region and we argue that the ice particle with the initially sharper point at contact loses more mass of melt than the other particle. A simple analytic model of this process with parameters that are consistent with observations leads to predicted collisional charge exchange that semiquantitatively explains the negative charging region of thunderstorms. The model also has implications for snowflake formation, ferroelectric ice, polarization of ice in snowpacks, and chemical reactions in ice surfaces

Assessment of micro and macro nutrients in poultry feeds available in Dhaka city, Bangladesh.

2017 ◽  
Vol 1 ◽  
pp. 264
Author(s):  
Md Didarul Islam ◽  
Ashiqur Rahaman ◽  
Fahmida Jannat
Keyword(s):  
Heavy Metals ◽  
Adverse Effect ◽  
The Other ◽  
Nutrient Level ◽  
Dhaka City ◽  
Toxic Heavy Metals ◽  
High Concentration ◽  
Low Concentration ◽  
Feed Formulation ◽  
Macro Nutrients

This study was based on to determine the concentration of macro and micro nutrients as well as toxic and nontoxic heavy metals present in the chicken feed available in Dhaka city of Bangladesh. All macro nutrients, if present in the feed at high concentration have some adverse effect, at the same time if this nutrient present in the feed at low concentration this have some adverse effect too. So that this nutrient level should be maintained at a marginal level. On the other side toxic heavy metals if present in the feed at very low concentration those can contaminate the total environment of the ecosystem. In this study six brand samples (starter, grower, finisher and layer) which was collected from different renowned chicken feed formulation industry in Bangladesh. Those samples were prepared for analysis by wet ashing and then metals were determined by Atomic Absorption Spectroscopy. It was found that 27.7 to 68.4, 57.3 to 121.9, 0.21 to 4.1, 0.32 to 2.1, 0.11 to 1.58, 0.28 to 2.11 and 0.28 to 1.78 for zinc, iron, copper, mercury, cadmium, nickel and cobalt respectively. It was found that essential macro and micro nutrients were present in the feed in low concentration on the other side mercury was present in high concentration in the feed samples.

scholarly journals STUDIES ON THE BACTERIOPHAGE OF D'HERELLE

1925 ◽  
Vol 42 (4) ◽  
pp. 483-497 ◽  
Author(s):  
Jacques J. Bronfenbrenner ◽  
Charles Korb
Keyword(s):  
Quantitative Evaluation ◽  
Bacterial Species ◽  
Relative Concentration ◽  
Serial Dilution ◽  
The Other ◽  
Resistant Bacteria ◽  
Dilution Method ◽  
High Concentration ◽  
Average Size ◽  
Broth Dilution

The experiments reported above confirm the fact that lytic principle is distributed in active solution in a state of indivisible units. This permits its quantitative evaluation by serial dilution, as well as by plating on agar. The latter method, however, often gives readings considerably lower than those obtained by the broth dilution method of titration. By varying the concentration of agar it has been possible to show that the discrepancy is due to adsorption of the lytic agent on agar. When the concentration of the latter is increased from 0.3 per cent to 2.5 per cent the number of plaques of lysis is reduced more than 100 times. At the same time the average size of the plaques also decreases approximately to one-tenth of the original. The size, as well as the number of plaques, has been found to depend also on the condition of the culture employed in titration. Thus, when the culture exposed to the action of lytic agent is composed of young susceptible bacteria, the greater the concentration of bacteria, the smaller the plaques. When the culture is composed partly of young and partly of old susceptible bacteria, both the size and the number of the plaques are diminished with the increase in the relative concentration of old bacteria. On the other hand, presence in the culture of resistant bacteria does not affect either the size or the number of the plaques so long as the relative concentration of susceptible bacteria in the culture is sufficient to allow formation of them. The plaques appearing in the presence of a high concentration of resistant variants in the culture are relatively indistinct owing to overgrowth. Under carefully controlled conditions the size of plaques is found to be determined by the character of the lytic filtrate. Thus in the case of lytic agents which act upon more than one bacterial species the size of the plaques remains constant, irrespective of the bacterial substratum used for the production of the active filtrate.

Synthesis of Fructose Biosensors and Progressing Their Efficiency Using Californium Colloidal Nanoparticles for Detecting Fructose and Triglycerides

2020 ◽  
Vol 12 (8) ◽  
pp. 1002-1017
Author(s):  
Alireza Heidari
Keyword(s):  
Carbon Paste Electrode ◽  
Enzyme Reaction ◽  
The Other ◽  
Current Paper ◽  
Modified Carbon Paste Electrode ◽  
Colloidal Nanoparticles ◽  
Carbon Paste ◽  
High Concentration ◽  
Oxidase Enzyme ◽  
Paste Electrode

In the current paper, fructose–oxidase enzyme is used as stabilization medium due to its more efficiency, ability for more accurate controlling the enzyme reaction, protecting against wasting of enzyme as well as simple and easy use and exchange of enzyme medium after performing some levels of surface modification and developing multi–walled carbon nanotubes (MWCNTs) on Californium plate. For better connecting and stabilizing the enzyme on the medium, the prepared medium is washed by high concentration sulfuric acid and nitric acid and a large volume of deionized water and for protecting enzyme from devastating effect of Californium and prohibiting them to become inactive, surface is covered with cystamine before stabilization. Regarding the large size of fructose–oxidase enzyme compared to surface of medium, a connective material with amid at one end and pyrine at the other end is used as transfer agent and for stabilizing this connection, the prepared medium is placed into dimethylformamide (DMF) solution for a couple of hours. Activity of stabilized enzyme at 460 (nm) wavelength recorded by spectroscope was depicted against time to evaluate its stability in various times. The prepared medium, which have a large amount of fructose–oxidase enzyme, can be used as electrode in sensors. Furthermore, fructose–oxidase electrochemical sensor is one of the best methods for detecting low amount of fructose and applying Californium colloidal nanoparticles as a supplementary material in the structure of biosensor can be effective for progressing its efficiency and optimum efficiency. On the other hand, in the current study, electrode biosensor entitled as modified carbon paste electrode with Californium colloidal nanoparticles (Cfnano/CPE) is produced by carbon graphite powder, paraffin oil and Californium colloidal nanoparticles (24 nm) and it is compared with carbon paste electrode (CP). In semi–permeable membranes, a combination of 1 (ml) of 0.1 (M) phosphate buffer with specified pH and 10 (mg) of fructose–oxidase enzyme is placed around each electrode. In the same potential of 0.7 (V), biosensors are tested with fructose in concentration range of (0−1) (mM) and various amounts of pH (4,6,8) which lead to producing the maximum current and tracing fructose in pH=6 and concentration of 1 (M) as the optimum condition. Currentmetry induced from both biosensors are compared and it is confirmed that using Californium colloidal nanoparticles in the structure of (Cfnano/CPE) electrode leads to increasing the conductivity and currentmerty of biosensor. In addition, qualitative and quantitative measurement of food components is of great importance due to high cost of traditional methods, in addition to tendency for more accurate and sensitive detecting of these components. Fructose and triglycerides are such compounds that they frequently measure. Various methods are used to detect these food elements. However, the necessity for accurate measurement of these two compounds with high sensitivity, especially for food health issue, leads to developing biological methods, especially biosensors. Among them, biosensors based on conductive polymer nanostructures, especially Polypyrrole and Polythiophene, have been recently interested due to their unique characteristics. The current paper aims to introduce and investigate the previously performed studies about Polypyrrole and Polythiophene–based biosensors for detecting fructose and triglycerides.

Morphologies of Silver Films Fabricated by Thermal Decomposition of Silver Behenate

2006 ◽  
Vol 11-12 ◽  
pp. 481-484
Author(s):  
Xian Hao Liu ◽  
Shu Xia Lu ◽  
Wei Liang Cao ◽  
Jing Chang Zhang
Keyword(s):  
Thermal Decomposition ◽  
Thick Film ◽  
Silver Film ◽  
The Other ◽  
Silver Particles ◽  
High Concentration ◽  
Decomposition Products ◽  
Silver Films ◽  
Triangular Shape ◽  
Thermal Decomposition Products

Various morphologies of silver films fabricated by the thermal decomposition of silver behenate have been studied. The morphological structures of silver behenate films at different heating temperatures are characterized by using SEM, IR and XRD. It is found that, while heating the silver behenate films, the formed silver particles are stabilized by the other thermal decomposition products in the range of 193°C∼320°C. The influence of silver behenate concentration in organic solvent on the formation and packing density of as-fabricated silver films by thermal treatment on the silver behenate films at 500°C has been studied. The results show that the silver film fabricated by a millimolar solution of silver behenate possesses a silver monolayer; the silver thick film can be formed at high concentration, and interestingly, silver particles with regular triangular or truncated triangular shape in the silver thick film are also obtained.

scholarly journals Changes in the sensitivity to glucagon of lipolysis in adipocytes from pregnant and lactating rats

1988 ◽  
Vol 254 (3) ◽  
pp. 661-665 ◽  
Author(s):  
V A Zammit
Keyword(s):  
Adipose Tissue ◽  
The Other ◽  
High Concentration ◽  
Response Curves ◽  
Pregnant Rats ◽  
Adipose Tissue Lipolysis ◽  
The Right ◽  
Peak Lactation ◽  
Stimulation Of

1. Rates of lipolysis were measured at different concentrations of glucagon in adipocytes prepared from parametrial adipose tissue of fed or starved rats in different reproductive states. All experiments were performed in the presence of a high concentration of adenosine deaminase (1 unit/ml). 2. Maximal rates of lipolysis (elicited by 25 nM-glucagon in each instance) were higher in adipocytes from peak-lactating rats than those from pregnant animals in both the fed and starved states. 3. Of adipocytes from fed animals, those from peak-lactating rats were the most sensitive to glucagon, whereas those from late-pregnant and early-lactating rats were 1-2 orders of magnitude less sensitive. 4. Adipocytes from 24 h-starved rats showed a much smaller stimulation of lipolysis by glucagon, making the assessment of sensitivity difficult. Therefore, rates of lipolysis were also measured in the presence of a maximally anti-lipolytic dose of insulin. The presence of insulin did not alter the relative sensitivities to glucagon of adipocytes from fed animals in different reproductive states, although all dose-response curves were shifted to the right. When lipolysis in adipocytes from starved animals was measured in the presence of insulin, it became evident that starvation for 24 h markedly increased the sensitivity of adipocytes from late-pregnant rats to glucagon, but did not affect that of cells from animals in the other reproductive states. 5. It is concluded that the large changes in sensitivity to glucagon that occurred during the reproductive cycle may enable the modulation of adipose-tissue lipolysis in vivo to satisfy the different metabolic requirements of the animal in the transition from pregnancy to peak lactation.

scholarly journals Functional interrelationship between calponin and caldesmon

1991 ◽  
Vol 280 (1) ◽  
pp. 33-38 ◽  
Author(s):  
R Makuch ◽  
K Birukov ◽  
V Shirinsky ◽  
R Dabrowska
Keyword(s):  
Skeletal Muscle ◽  
Smooth Muscle ◽  
Atpase Activity ◽  
Smooth Muscle Contraction ◽  
The Other ◽  
High Concentration ◽  
Thin Filaments ◽  
Actomyosin Atpase ◽  
Molar Excess ◽  
Low Concentrations

Calponin and caldesmon, constituents of smooth-muscle thin filaments, are considered to be potential modulators of smooth-muscle contraction. Both of them interact with actin and inhibit ATPase activity of smooth- and skeletal-muscle actomyosin. Here we show that calponin and caldesmon could bind simultaneously to F-actin when used in subsaturating amounts, whereas each one used in excess caused displacement of the other from the complex with F-actin. Calponin was more effective than caldesmon in this competition: when F-actin was saturated with calponin the binding of caldesmon was eliminated almost completely, whereas even at high molar excess of caldesmon one-third of calponin (relative to the saturation level) always remained bound to actin. The inhibitory effects of low concentrations of calponin and caldesmon on skeletal-muscle actomyosin ATPase were additive, whereas the maximum inhibition of the ATPase attained at high concentration of each of them was practically unaffected by the other one. These data suggest that calponin and caldesmon cannot operate on the same thin filaments. CA(2+)-calmodulin competed with actin for calponin binding, and at high molar excess dissociated the calponin-actin complex and reversed the calponin-induced inhibition of actomyosin ATPase activity.

Boldo, Its Secondary Metabolites and their Derivatives

2019 ◽  
Vol 5 (1) ◽  
pp. 31-65 ◽  
Author(s):  
Bruce K. Cassels ◽  
Gonzalo Fuentes-Barros ◽  
Sebastián Castro-Saavedra
Keyword(s):  
Antioxidant Activity ◽  
The Other ◽  
Herbal Remedies ◽  
Medical Applications ◽  
High Concentration ◽  
Active Constituent ◽  
Research Papers ◽  
Scientific Support ◽  
Natural Insecticide ◽  
The Subject

Boldo leaves (Boldo folium, from Peumus boldus Mol.) are very frequently used as a medicinal herb in Chile and are exported to many countries to be used in teas or as extracts included in herbal remedies, primarily as an aid to digestion and as a mild sedative. Scientific support for these uses is scanty, and boldine, an alkaloid viewed as characteristic of the tree and present in high concentration in the bark, is extracted by specialized companies and sold as the supposed main active constituent. Consequently, boldine has been the subject of a considerable number of research papers, while some of the other alkaloids present to a greater extent in the leaves have been relatively neglected except when found in large amounts in other species. These studies range from assays of antioxidant activity to anti-inflammatory, antineoplastic and other medical applications. The essential oil, usually containing a large percentage of the toxic ascaridole, was once used as a vermifuge and is now regarded with caution, but is still of interest as a possible natural insecticide, fungicide, antiparasitic and herbicide. The last decade has seen an explosive increase in papers pointing to possible uses of boldo and its constituents. This review attempts to bring these publications together in a comprehensive way with the purpose of stimulating and orienting further research into the useful properties of this Chilean endemic tree.

Microthrix parvicella foaming at the Fusina WWTP

2002 ◽  
Vol 46 (1-2) ◽  
pp. 499-502 ◽  
Author(s):  
P. Miana ◽  
L. Grando ◽  
G. Caravello ◽  
M. Fabris
Keyword(s):  
Activated Sludge ◽  
Microscopic Observation ◽  
Industrial Wastewater ◽  
The Other ◽  
Physical Parameters ◽  
High Concentration ◽  
Strong Connection ◽  
Mixed Liquor ◽  
Microthrix Parvicella

The Fusina WWTP receives civil and industrial wastewater from Venice and its hinterland. Its treatment capacity is in the range of 4,000–5,000 m3/h. In winter the Fusina WWTP is subjected to brown and viscous foams developed on the surface of the aeration basins and of the clarifiers. The microscopic observation of biological foams and activated sludge samples showed high concentration of the filamentous organism Microthrix parvicella. This paper investigates the growth of M. parvicella from January 1998 to January 1999 and relates it to foams developed on the aeration basins and clarifiers, to temperature, surfactants, BOD5, NH4, NO3, NO2, DO, PO4 and pH of the wastewater influent, to SVI and the other species of filamentous organisms of mixed liquor. The results demonstrate the strong connection of the foams developed with M. parvicella abundance, the synergic action with surfactants, the dependence of M. parvicella on temperature and no relation to the other chemical and physical parameters investigated.

scholarly journals Comparison of three methods for rendering plant fat transesterification

2013 ◽  
Vol 59 (No. 2) ◽  
pp. 51-55
Author(s):  
A. Prošková ◽  
J. Kučera ◽  
Z. Kopicová ◽  
L. Škarková
Keyword(s):  
Fatty Acids ◽  
Free Acid ◽  
The Other ◽  
Alkaline Media ◽  
Optimum Temperature ◽  
Optimum Conditions ◽  
High Concentration ◽  
Reaction Velocity ◽  
Catalysed Reaction ◽  
The Difference

Three most frequently used methods for fat transesterification were compared using rendering plant fat (RPF) as model. Acid-catalysed transesterification was found to be the most effective (conversion 90%) at optimum conditions (fat: methanol ratio 1:10, sulphuric acid amount of 2% v/v, temperature 95°C). Base-catalysed transesterification of RPF on the other hand, results in much lower conversion (45%) at optimum conditions (fat:methanol ratio 1:20, NaOH amount 8% w/v, optimum temperature 95°C). The difference is done (among others) by the fact that RPF has high concentration of free acid (high acidity number) compared with the fats usually used for transesterification and that free acids are not esterified in alkaline media. Enzyme-(lipase) catalysed reaction could lead to partial esterification of free fatty acids, but with much lower reaction velocity. This fact leads to higher conversion in the case of enzyme-catalysed transesterification of RPF compared with base-catalysed reaction; nevertheless, even in this case the conversion is much lower in comparison with acid-catalysed reaction. The optimum conversion in enzyme-catalysed reaction was 55%.  

scholarly journals A Chemical Marker Proposal for the Lantana genus: Composition of the Essential Oils from the Leaves of Lantana radula and L. canescens

2010 ◽  
Vol 5 (4) ◽  
pp. 1934578X1000500
Author(s):  
José G. Sena Filho ◽  
Haroudo S. Xavier ◽  
José M. Barbosa Filho ◽  
Jennifer M. Duringer
Keyword(s):  
Quality Control ◽  
Chemical Analysis ◽  
Essential Oil ◽  
Essential Oils ◽  
The Other ◽  
Chemical Markers ◽  
Chemical Marker ◽  
High Concentration ◽  
Minor Compounds ◽  
Prior Analysis

Essential oil extracts from the leaves of two Lantana species ( L. radula Sw. and L. canescens Kunth), for which no prior analysis has been reported, were analyzed by GC-MS. This information was utilized to propose chemical markers for Lantana species so that identification between physically similar plant species can be achieved through chemical analysis. Results showed 33 constituents for L. canescens, among which β-caryophyllene (43.9%), β-cubebene (10.1%), elixene (8.6%), β-phellandrene (6.1%), α-caryophyllene (2.6%) and dehydro-aromadendrene (2.6%) were the principle components. L. radula revealed the presence of 21 compounds, the most abundant of which were β-cubebene (31.0%), β-caryophyllene (20.8%), elixene (10.0%), α-salinene (6.4%), β-phellandrene (6.1%), copaene (4.9%) cadinene (1.4%) and psi-limonene (1.4%). The high concentration of β-caryophyllene in the samples tested here and those in the literature make it a good candidate for a chemical marker for Lantana species, with β-cubebene, elixene and β-phellandrene following as minor compounds identified more sporadically in this genus. On the other hand, Lippia species, which are morphologically similar to those from the Lantana genus, would contain limonene, citral, carvacrol, β-myrcene, camphor and thymol as the main chemical markers. These chemical markers would be a powerful tool for maintaining quality control in the extraction of essential oils for use in medicinal applications, as well as in identification of plant specimens to a taxonomist.

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