scholarly journals Electric charge in clouds at temperatures above 0° C

MAUSAM ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 409-414
Author(s):  
ANNA MANI ◽  
M. V. SIVARAMAKRISHNAN ◽  
S. P. VENKITESHWARAN
Keyword(s):  
Electric Charge ◽  
Freezing Point ◽  
Heavy Rain ◽  
Initial Step ◽  
Direct Role ◽  
Change Of State ◽  
Lightning Discharges ◽  
Rain Drops ◽  
Cumulonimbus Clouds

It is well-established that heavy rain can fall under certain conditions, from clouds whose temperatures are nowhere below the freezing point and where the Bergeron mechanism is pot applicable, and coalescence of droplets can provide the initial step in the growth of rain drops. It is, however, generally believed that lightning discharges occur in heavy cumulus or cumulonimbus clouds in which glaciations has begun to be apparent, and most of the theories so far advanced on the development of electric charges in the clouds assume the change of state to play a direct role in the electrification of the cloud.

Continuous Measurement of Electric Charge Carried by Rain Drops in Case of Thunderstorm

1971 ◽  
Vol 30 (4) ◽  
pp. 1204-1204
Author(s):  
Shuichiro Kawamata ◽  
Satomi Kokubu ◽  
Yukio Edano ◽  
Noriki Kikusato
Keyword(s):  
Electric Charge ◽  
Continuous Measurement ◽  
Rain Drops

scholarly journals RdDM pathway is required for Tobamovirus-induced symptomatology production

2020 ◽  
Author(s):  
Melisa Leone ◽  
Diego Zavallo ◽  
Andrea Venturuzzi ◽  
Sebastián Asurmendi
Keyword(s):  
Dna Methylation ◽  
Viral Infection ◽  
Viral Infections ◽  
Expression Patterns ◽  
Initial Step ◽  
List Type ◽  
Direct Role ◽  
Transcriptional Changes ◽  
Virus Interactions

SummarySmall RNAs (sRNA) are important molecules for gene regulation in plants and play an essential role in plant-pathogen interactions. Researchers have evaluated the relationship between viral infections as well as the endogenous accumulation of sRNAs and the transcriptional changes associated with the production of symptoms, little is known about a possible direct role of epigenetics, mediated by 24-nt sRNAs, in the induction of these symptoms.With the use of different RNA directed DNA methylation pathway mutants and triple demethylase mutants, here we demonstrate that the disruption of RdDM pathway during viral infection produced alterations in the plant transcriptomic changes (because of the infection) and in symptomatology.This study represents the initial step in exposing that DNA methylation directed by endogenous sRNAs has an important role, uncoupled to defense, in the production of symptoms associated with plant-virus interactions.Significance statementThe crop yield losses induced by phytoviruses are mainly associated with the symptoms of the disease. DNA modifications as methylation, can modulate the information coded by the sequence, process named epigenetics. Viral infection can change the expression patterns of different genes linked to defenses and symptoms. This work represents the initial step to expose the role of epigenetic process, in the production of symptoms associated with plants-virus interactions.

scholarly journals VIII. The ionization of dilute solutions at the freezing point

1900 ◽  
Vol 194 (252-261) ◽  
pp. 321-360 ◽  
Keyword(s):  
Potassium Chloride ◽  
Electric Current ◽  
Sulphuric Acid ◽  
Electric Charge ◽  
Chemical Nature ◽  
Freezing Point ◽  
Barium Chloride ◽  
The Other ◽  
Dilute Solutions ◽  
The Subject

The existence of a relation between the depression of the freezing point, produced by dissolving an acid or a salt in water, and the electrolytic conductivity of the solution thus obtained was pointed out by Arrhenius in 1887, and has been the subject of much experiment and discussion since that date. As is well known, the facts of electrolysis indicate that an electric current, when passing through a solution, is associated with a passage in opposite directions of the constituents of the salt. Faraday called these mobile parts ions. The number of the ions depends on the chemical nature of the salt, and is usually indicated by its formula. Thus for one molecule of potassium chloride we have two ions, the potassium travelling in one direction and the chlorine in the other. For barium chloride or sulphuric acid we have three ions, and, since the electric charge of an ion is proportional to its valency, the electrically equivalent weights of these substances are represented by ½BaCl 2 and ½H 2 So 4 , respectively.

scholarly journals Raindrop Fall Velocities from an Optical Array Probe and 2D-video Disdrometer

2017 ◽  
Author(s):  
Viswanathan Bringi ◽  
Merhala Thurai ◽  
Darrel Baumgardner
Keyword(s):  
Heavy Rain ◽  
Terminal Velocity ◽  
Wind Speeds ◽  
Average Wind ◽  
Array Probe ◽  
High Turbulence ◽  
Rain Drops ◽  
The Mean ◽  
Fall Speed ◽  
Rain Events

Abstract. We report on fall speed measurements of rain drops in light-to-heavy rain events from two climatically different regimes (Greeley, Colorado, and Huntsville, Alabama) using the high resolution (50 microns) Meteorological Particle Spectrometer (MPS) and a 3rd generation (170 microns resolution) 2D-video disdrometer (2DVD). To mitigate wind-effects, especially for the small drops, both instruments were installed within a 2/3-scale Double Fence Intercomparison Reference (DFIR) enclosure. Two cases involved light-to-moderate wind speeds/gusts while the third case was a tornadic supercell that passed over the site with high wind speeds/gusts. As a proxy for turbulent intensity, maximum wind speeds from 10-m height at the instrumented site recorded every 3 s were differenced with the 5-min average wind speeds and then squared. The fall speed versus size from 0.1–2 mm were derived from the MPS data and the 2DVD was used for sizes > 0.7 mm. Consistency of fall speeds from the two instruments in the overlap region (0.7–2 mm) gave confidence in the data quality and processing methodologies. Our results indicate that under light-to-moderate wind gusts, the mean fall speeds agree well with fits to the terminal velocity measured in the laboratory by Gunn and Kinzer from 100 microns up to precipitation sizes. In the supercell case the very strong gusts and inferred high turbulence intensity caused a significant broadening of the fall speed distributions with the mean fall speeds about 25–30 % less than the terminal velocity of Gunn-Kinzer, i.e. sub-terminal fall speeds.

scholarly journals Inhibitors of signalling identify differential control processes responsible for selective effects of insulin on the expression of phosphoenolpyruvate carboxykinase and gene 33 in rat H4 hepatoma cells

1995 ◽  
Vol 310 (2) ◽  
pp. 375-378 ◽  
Author(s):  
S H Yang ◽  
A J Dickson
Keyword(s):  
Gene Expression ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Signal Transduction Pathway ◽  
Initial Step ◽  
Model Systems ◽  
Transduction Pathway ◽  
Regulation Of Expression ◽  
Direct Role ◽  
Control Of Gene Expression ◽  
Differential Control

Gene 33 and phosphoenolpyruvate carboxykinase (PEPCK) present excellent model systems for the analysis of the differential control of hepatic gene expression by the insulin-regulated signal-transduction pathway(s). We have analysed the importance of specific components in the insulin-regulated transduction pathway(s) towards enhanced gene expression (gene 33) and inhibited gene expression (PEPCK) by examination of the influence of selective inhibitors. Rapamycin, which inhibits the 70 kDa S6 kinase (p70rsk) does not influence the actions of insulin on gene 33 or PEPCK; thus the kinase p70rsk appears to play no direct role in the regulation of expression of these two hepatic genes. Wortmannin, an inhibitor of phosphatidylinositol 3-kinase, differentiates between processes involved in insulin regulation of gene 33 and PEPCK mRNA expression. Although the actions of insulin on gene 33 expression are abolished by wortmannin, the actions of insulin on PEPCK expression are insensitive to wortmannin. The existence of wortmannin-sensitive and rapamycin/wortmannin-insensitive pathways for transducing insulin signals to factors controlling gene expression, and the differential actions on specific genes, presents an initial step towards deciphering the linkage between signalling components and selective control of gene expression.

scholarly journals Numerical Model and Forecasting Potential of Aircraft Weather Hazards over Kenya

2018 ◽  
Vol 2 (1) ◽  
pp. 7
Author(s):  
Francis Jagero
Keyword(s):  
Numerical Model ◽  
Grid Point ◽  
Convective Available Potential Energy ◽  
Heavy Rain ◽  
Dew Point ◽  
Civil Aviation ◽  
Aviation Hazards ◽  
Strong Convection ◽  
Point Distance ◽  
Cumulonimbus Clouds

The study investigated the forecasting potential of aircraft weather hazards over Kenya using numerical model. The various causes of accidents/incidents were identified using analyzed investigated weather-related aviation hazards data obtained from Kenya Civil Aviation Authority database system from 2008 through 2014. The parameters analyzed included the Winds, Temperature, Relative humidity, Convective Available Potential Energy (CAPE), Lifted Index (LI) and Dew Point Temperature. Their combined effect was able to provide the means of identifying the areas of strong convection. The model was run on a grid point distance resolution of 10 km and runs finite differencing scheme, based on Taylor series. Grid Analysis and Display System (GrADS) which is embedded on the model upon installation, was used as the default post processing tool. Key findings revealed that Wind, Fog, Turbulence, Heavy rain showers, and low ceiling influenced aircraft operations. It was shown that the majority of the hazards were linked with cumulonimbus clouds. Landing phase of flight affected aviation most.

Preparation of Electron Transparent Metal-Matrix Composites

1968 ◽  
Vol 26 ◽  
pp. 334-335 ◽  
Author(s):  
M. R. Pinnel ◽  
A. Lawley
Keyword(s):  
Stainless Steel ◽  
Load Transfer ◽  
Volume Fraction ◽  
Steel Wire ◽  
Initial Step ◽  
Interfacial Region ◽  
Matrix Composites ◽  
Specific Test ◽  
The Matrix ◽  
The One

Numerous phenomenological descriptions of the mechanical behavior of composite materials have been developed. There is now an urgent need to study and interpret deformation behavior, load transfer, and strain distribution, in terms of micromechanisms at the atomic level. One approach is to characterize dislocation substructure resulting from specific test conditions by the various techniques of transmission electron microscopy. The present paper describes a technique for the preparation of electron transparent composites of aluminum-stainless steel, such that examination of the matrix-fiber (wire), or interfacial region is possible. Dislocation substructures are currently under examination following tensile, compressive, and creep loading. The technique complements and extends the one other study in this area by Hancock.The composite examined was hot-pressed (argon atmosphere) 99.99% aluminum reinforced with 15% volume fraction stainless steel wire (0.006″ dia.).Foils were prepared so that the stainless steel wires run longitudinally in the plane of the specimen i.e. the electron beam is perpendicular to the axes of the wires. The initial step involves cutting slices ∼0.040″ in thickness on a diamond slitting wheel.

HVEM Cryomicroscopy of Frozen Hydrated PTK1 Cells

1990 ◽  
Vol 48 (1) ◽  
pp. 500-501
Author(s):  
E.T. O’Toole ◽  
G.P. Wray ◽  
J.R. Kremer ◽  
J.R. Mcintosh
Keyword(s):  
Liquid Nitrogen ◽  
Phase Contrast ◽  
Culture Medium ◽  
Low Dose ◽  
Ammonium Acetate ◽  
Freezing Point ◽  
Voltage Electron ◽  
Cold Stage ◽  
Humidity Chamber ◽  
Coated Carbon

Ultrarapid freezing and cryomicroscopy of frozen hydrated material makes it possible to visualize samples that have never been exposed to chemical fixatives, dehydration, or stains. In principle, freezing and cryoimaging methods avoid artifacts associated with chemical fixation and processing and allow one to visualize the specimen in a condition that is close to its native state. Here we describe a way to use a high voltage electron microscope (HVEM) for the cryoimaging of frozen hydrated PTK1 cells.PTK1 cells were cultured on formvar-coated, carbon stabilized gold grids. After three days in culture, the grids were removed from the culture medium and blotted in a humidity chamber at 35° C. In some instances, the grids were rinsed briefly in 0.16 M ammonium acetate buffer (pH 7.2) prior to blotting. After blotting, the grids were transferred to a plunging apparatus and plunged into liquid ethane held directly above its freezing point. The plunging apparatus consists of a vertical slide rail that guides the fall of a mounted pair of forceps that clamp the specimen. The forceps are surrounded by a plexiglass humidity chamber mounted over a dewar of liquid nitrogen containing an ethane chamber. After freezing, the samples were transferred to liquid nitrogen and viewed in a JEOL JEM 1000 equipped with a top entry cold stage designed and built by Mr. George Wray (Univ. Colorado). The samples were routinely exposed to electron doses of 1 e/Å2/sec, and viewed at a temperature of −150° C. A GATAN video system was used to enhance contrast and to estimate the correct amount of underfocus needed to obtain phase contrast at various magnifications. Low dose micrographs were taken using two second exposures of Kodak 4463 film. The state of the solid water in the specimen was determined by diffraction using a 30/μm field limiting aperture and a camera length of 1 meter.

The Advantages of Cryotechniques: Application To Bioluminescent Cells

1990 ◽  
Vol 48 (1) ◽  
pp. 486-487
Author(s):  
Gisèle Nicolas ◽  
Jean-Marie Bassot ◽  
Marie-Thérèse Nicolas
Keyword(s):  
Endoplasmic Reticulum ◽  
Striated Muscle ◽  
Light Emission ◽  
Stable State ◽  
Freeze Substitution ◽  
Initial Step ◽  
Point Of Interest ◽  
Cell Components ◽  
Excellent Preservation ◽  
External Water

The use of fast-freeze fixation (FFF) followed by freeze-substitution (FS) brings substantial advantages which are due to the extreme rapidity of this fixation compared to the conventional one. The initial step, FFF, physically immobilizes most molecules and therefore arrests the biological reactions in a matter of milliseconds. The second step, FS, slowly removes the water content still in solid state and, at the same time, chemically fixes the other cell components in absence of external water. This procedure results in an excellent preservation of the ultrastructure, avoids osmotic artifacts,maintains in situ most soluble substances and keeps up a number of cell activities including antigenicities. Another point of interest is that the rapidity of the initial immobilization enables the capture of unstable structures which, otherwise, would slip towards a more stable state. When combined with electrophysiology, this technique arrests the ultrastructural modifications at a well defined state, allowing a precise timing of the events.We studied the epithelium of the elytra of the scale-worm, Harmothoe lunulata which has excitable, conductible and bioluminescent properties. The intracellular sites of the light emission are paracrystals of endoplasmic reticulum (PER), named photosomes (Fig.1). They are able to flash only when they are coupled with plasma membrane infoldings by dyadic or triadic junctions (Fig.2) basically similar to those of the striated muscle fibers. We have studied them before, during and after stimulation. FFF-FS showed that these complexes are labile structures able to diffentiate and dedifferentiate within milliseconds. Moreover, a transient network of endoplasmic reticulum was captured which we have named intermediate endoplasmic reticulum (IER) surrounding the PER (Fig.1). Numerous gap junctions are found in the membranous infoldings of the junctional complexes (Fig.3). When cryofractured, they cleave unusually (Fig.4-5). It is tempting to suggest that they play an important role in the conduction of the excitation.

E3 ubiquitin ligases

2005 ◽  
Vol 41 ◽  
pp. 15-30 ◽  
Author(s):  
Helen C. Ardley ◽  
Philip A. Robinson
Keyword(s):  
Protein Complexes ◽  
Loss Of Function ◽  
Direct Role ◽  
Cellular Processes ◽  
Substrate Protein ◽  
Protein Ubiquitination ◽  
C Terminus ◽  
Full Complement ◽  
Spatio Temporal ◽  
Eukaryotic Organisms

The selectivity of the ubiquitin–26 S proteasome system (UPS) for a particular substrate protein relies on the interaction between a ubiquitin-conjugating enzyme (E2, of which a cell contains relatively few) and a ubiquitin–protein ligase (E3, of which there are possibly hundreds). Post-translational modifications of the protein substrate, such as phosphorylation or hydroxylation, are often required prior to its selection. In this way, the precise spatio-temporal targeting and degradation of a given substrate can be achieved. The E3s are a large, diverse group of proteins, characterized by one of several defining motifs. These include a HECT (homologous to E6-associated protein C-terminus), RING (really interesting new gene) or U-box (a modified RING motif without the full complement of Zn2+-binding ligands) domain. Whereas HECT E3s have a direct role in catalysis during ubiquitination, RING and U-box E3s facilitate protein ubiquitination. These latter two E3 types act as adaptor-like molecules. They bring an E2 and a substrate into sufficiently close proximity to promote the substrate's ubiquitination. Although many RING-type E3s, such as MDM2 (murine double minute clone 2 oncoprotein) and c-Cbl, can apparently act alone, others are found as components of much larger multi-protein complexes, such as the anaphase-promoting complex. Taken together, these multifaceted properties and interactions enable E3s to provide a powerful, and specific, mechanism for protein clearance within all cells of eukaryotic organisms. The importance of E3s is highlighted by the number of normal cellular processes they regulate, and the number of diseases associated with their loss of function or inappropriate targeting.

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