scholarly journals Changes in the charge of an α-Particle passing through matter

1923 ◽  
Vol 102 (717) ◽  
pp. 496-506 ◽  
Keyword(s):  
Initial Velocity ◽  
Rapid Decrease ◽  
Number Of Particles

It is remarkable that investigations on the velocity of α -particles have hitherto failed to detect with certainty particles of velocity less than about 8 x 10 8 cm. per second (0.4V 0 , where V 0 is the initial velocity of α -particles from RaC). Geiger believed he had found a-particles with velocities as low as 0.3V 0 . However, later work of Marsden and Taylor showed that when the velocity of an α -ray beam had fallen to about 0.45V 0 , any further increase of absorption caused a rapid decrease in the number of particles; the number fell to zero when the velocity had decreased to about 0.4V 0 . Thus the minimum observed energy was that which would be acquired by the α -particle in falling through about 600,000 volts. It is surprising that particles with such enormous energy should vanish, leaving no trace. Positive rays of much less energy have of course been detected in several ways.

scholarly journals Commonly available but highly effective protection against SARS-CoV-2 during gastrointestinal endoscopies

PLoS ONE ◽  
2021 ◽  
Vol 16 (7) ◽  
pp. e0254979
Author(s):  
Radan Keil ◽  
Štěpán Hlava ◽  
Petr Stanovský ◽  
Vladimír Ždímal ◽  
Jan Šťovíček ◽  
...  
Keyword(s):  
Health Problem ◽  
Initial Velocity ◽  
Effective Protection ◽  
Endoscopic Procedures ◽  
Protective Cover ◽  
Fluid Particles ◽  
Pass Through ◽  
Control Body ◽  
Made In ◽  
Number Of Particles

Background and aims SARS-CoV-2 is a worldwide serious health problem. The aim of this study was to demonstrate the number of potentially infectious particles present during endoscopic procedures and find effective tools to eliminate the risks of SARS-CoV-2 infection while performing them. Methods An experimental model which focused on aerosol problematics was made in a specialized laboratory. This model simulated conditions present during endoscopic procedures and monitored the formation of potentially infectious fluid particles from the patient’s body, which pass through the endoscope and are then released into the environment. For this reason, we designed and tested a prototype of a protective cover for the endoscope’s control body to prevent the release and spread of these fluid particles from its working channel. We performed measurements with and without the protective cover of the endoscope’s control body. Results It was found that liquid coming through the working channel of the endoscope with forceps or other instruments inside generates droplets with a diameter in the range of 0.1–1.1 mm and an initial velocity of up to 0.9 m/s. The average number of particles per measurement per whole measured area without a protective cover on the endoscope control body was 51.1; with this protective cover on, the measurement was 0.0, p<0.0001. Conclusions Our measurements proved that fluid particles are released from the working channel of an endoscope when forceps are inserted. A special protective cover for the endoscope control body, made out of breathable material (surgical cap) and designed by our team, was found to eliminate this release of potentially infectious fluid particles.

Stereo Electron Microscopy Applied to High Resolution Freeze-Etch Replicas

1970 ◽  
Vol 28 ◽  
pp. 306-307
Author(s):  
L. Andrew Staehelin
Keyword(s):  
Electron Microscopy ◽  
Plastic Deformation ◽  
High Resolution ◽  
Smooth Surfaces ◽  
Small Particles ◽  
Membrane Surfaces ◽  
Wide Acceptance ◽  
New Information ◽  
Number Of Particles ◽  
Small Holes

Freeze-etched membranes usually appear as relatively smooth surfaces covered with numerous small particles and a few small holes (Fig. 1). In 1966 Branton (1“) suggested that these surfaces represent split inner mem¬brane faces and not true external membrane surfaces. His theory has now gained wide acceptance partly due to new information obtained from double replicas of freeze-cleaved specimens (2,3) and from freeze-etch experi¬ments with surface labeled membranes (4). While theses studies have fur¬ther substantiated the basic idea of membrane splitting and have shown clearly which membrane faces are complementary to each other, they have left the question open, why the replicated membrane faces usually exhibit con¬siderably fewer holes than particles. According to Branton's theory the number of holes should on the average equal the number of particles. The absence of these holes can be explained in either of two ways: a) it is possible that no holes are formed during the cleaving process e.g. due to plastic deformation (5); b) holes may arise during the cleaving process but remain undetected because of inadequate replication and microscope techniques.

Angular Calibration of Ribosomal Subuntts in Factor Space

1990 ◽  
Vol 48 (1) ◽  
pp. 462-463
Author(s):  
Minakhi Pujari ◽  
Joachim Frank
Keyword(s):  
Three Dimensional ◽  
Carbon Layer ◽  
Uranyl Acetate ◽  
Particle Analysis ◽  
Factor Space ◽  
Multivariate Statistical ◽  
Ribosomal Subunits ◽  
Layer Method ◽  
Dimensional Reconstruction ◽  
Number Of Particles

In single-particle analysis of macromolecule images with the electron microscope, variations of projections are often observed that can be attributed to the changes of the particle’s orientation on the specimen grid (“rocking”). In the multivariate statistical analysis (MSA) of such projections, a single factor is often found that expresses a large portion of these variations. Successful angle calibration of this “rocking factor” would mean that correct angles can be assigned to a large number of particles, thus facilitating three-dimensional reconstruction.In a study to explore angle calibration in factor space, we used 40S ribosomal subunits, which are known to rock around an axis approximately coincident with their long axis. We analyzed micrographs of a field of these particles, taken with 20° tilt and without tilt, using the standard methods of alignment and MSA. The specimen was prepared with the double carbon-layer method, using uranyl acetate for negative staining. In the MSA analysis, the untilted-particle projections were used as active, the tilted-particle projections as inactive objects. Upon tilting, those particles whose rocking axes are parallel to the tilt axis will change their appearance in the same way as under the influence of rocking. Therefore, each vector, in factor space, joining a tilted and untilted projection of the same particle can be regarded as a local 20-degree calibration bar.

A Sensitive On-Grid Immunoelectron Microscopic Procedure for Diagnosis of Rotavirus Infection

1980 ◽  
Vol 38 ◽  
pp. 506-507
Author(s):  
M. F. Miller ◽  
A. R. Rubenstein
Keyword(s):  
Electron Microscopy ◽  
Specific Antibody ◽  
Immune Complexes ◽  
Acute Gastroenteritis ◽  
Plant Viruses ◽  
Aggregation Process ◽  
Microscopic Technique ◽  
Fecal Material ◽  
Present Communication ◽  
Number Of Particles

Studies of rotavirus particles in humans, monkeys and various non-primates with acute gastroenteritis have involved detection of virus in fecal material by electron microscopy. The EM techniques most commonly employed have been the conventional negative staining (Fig. 1) and immune aggregation (Fig. 2) procedures. Both methods are somewhat insensitive and can most reliably be applied to samples containing large quantities of virus either naturaLly or as a result of concentration by ultracentrifugation. The formation of immune complexes by specific antibody in the immune aggregation procedures confirms the rotavirus diagnosis, but the number of particles per given microscope field is effectively reduced by the aggregation process. In the present communication, we describe use of an on-grid immunoelectron microscopic technique in which rotavirus particles are mounted onto microscope grids that were pre-coated with specific antibody. The technique is a modification of a method originalLy introduced by Derrick (1) for studies of plant viruses.

140: Systemic Nitric Oxide Augmentation Leads to a Rapid Decrease of the Bladder Outlet Resistance in Heal thy Men

2005 ◽  
Vol 173 (4S) ◽  
pp. 38-38
Author(s):  
Michael Muentener ◽  
Brigitte Schurch ◽  
Bjoem Wefer ◽  
Andre Reitz
Keyword(s):  
Nitric Oxide ◽  
Rapid Decrease

Stimulated Glanzmann’s Thrombasthenia Platelets Produce Microvesicles

1995 ◽  
Vol 74 (06) ◽  
pp. 1533-1540 ◽  
Author(s):  
Pål André Holme ◽  
Nils Olav Solum ◽  
Frank Brosstad ◽  
Nils Egberg ◽  
Tomas L Lindahl
Keyword(s):  
Complement System ◽  
Shape Change ◽  
Annexin V ◽  
Platelet Surface ◽  
Glanzmann’S Thrombasthenia ◽  
Large Numbers ◽  
Glanzmann's Thrombasthenia ◽  
Series Of Experiments ◽  
The Complement System ◽  
Number Of Particles

SummaryThe mechanism of formation of platelet-derived microvesicles remains controversial.The aim of the present work was to study the formation of microvesicles in view of a possible involvement of the GPIIb-IIIa complex, and of exposure of negatively charged phospholipids as procoagulant material on the platelet surface. This was studied in blood from three Glanzmann’s thrombasthenia patients lacking GPIIb-IIIa and healthy blood donors. MAb FN52 against CD9 which activates the complement system and produces microvesicles due to a membrane permeabilization, ADP (9.37 μM), and the thrombin receptor agonist peptide SFLLRN (100 μM) that activates platelets via G-proteins were used as inducers. In a series of experiments platelets were also preincubated with PGE1 (20 μM). The number of liberated microvesicles, as per cent of the total number of particles (including platelets), was measured using flow cytometry with FITC conjugated antibodies against GPIIIa or GPIb. Activation of GPIIb-IIIa was detected as binding of PAC-1, and exposure of aminophospholipids as binding of annexin V. With normal donors, activation of the complement system induced a reversible PAC-1 binding during shape change. A massive binding of annexin V was seen during shape change as an irreversible process, as well as formation of large numbers of microvesicles (60.6 ±2.7%) which continued after reversal of the PAC-1 binding. Preincubation with PGE1 did not prevent binding of annexin V, nor formation of microvesicles (49.5 ± 2.7%), but abolished shape change and PAC-1 binding after complement activation. Thrombasthenic platelets behaved like normal platelets after activation of complement except for lack of PAC-1 binding (also with regard to the effect of PGE1 and microvesicle formation). Stimulation of normal platelets with 100 μM SFLLRN gave 16.3 ± 1.2% microvesicles, and strong PAC-1 and annexin V binding. After preincubation with PGE1 neither PAC-1 nor annexin V binding, nor any significant amount of microvesicles could be detected. SFLLRN activation of the thrombasthenic platelets produced a small but significant number of microvesicles (6.4 ± 0.8%). Incubation of thrombasthenic platelets with SFLLRN after preincubation with PGE1, gave results identical to those of normal platelets. ADP activation of normal platelets gave PAC-1 binding, but no significant annexin V labelling, nor production of microvesicles. Thus, different inducers of the shedding of microvesicles seem to act by different mechanisms. For all inducers there was a strong correlation between the exposure of procoagulant surface and formation of microvesicles, suggesting that the mechanism of microvesicle formation is linked to the exposure of aminophospholipids. The results also show that the GPIIb-IIIa complex is not required for formation of microvesicles after activation of the complement system, but seems to be of importance, but not absolutely required, after stimulation with SFLLRN.

APPLICATION OF THE METHOD SPRINGY DEFORMATIONS OF BARREL DURING SHOT FOR DETERMINING THE INITIAL VELOCITY OF THE SHELL (MINE)

2019 ◽  
Vol 1 (12) ◽  
pp. 75-80
Author(s):  
Ye. Didenko ◽  
O. Stepanenko
Keyword(s):  
Strain Gauge ◽  
Initial Velocity ◽  
Radial Direction ◽  
Fire Control ◽  
Automatic Control Systems ◽  
Measurement Results ◽  
Initial Resistance ◽  
The Moment ◽  
The Many ◽  
Effective Use

One of the indicators of the effective use of artillery is the accuracy of the fire impact on the objects of enemy. The accuracy of the artillery is achieved by completing the implementation of all measures for the preparation of shooting and fire control. Main measures of ballistic preparation are to determine and take into account the summary deviation of the initial velocity. The existing procedure for determining the summary deviation of the initial velocity for the check (main) cannon of battery leads to accumulation of ballistic preparation errors. The supply of artillery units with means of determining the initial speed of the projectile is insufficient. Among the many known methods for measuring the initial velocity, not enough attention was paid to the methods of analyzing the processes that occur during a shot in the "charge-shell-barrel" system. Under the action of the pressure of the powder gases in the barrel channel and the forces of the interaction of the projectile with the barrel there are springy deformations in the radial direction. To measure springy deformations it is advisable to use strain gauge sensors. Monitoring of deformation in a radial direction by time can be used to determine the moment of passing a projectile past the strain gauge mounted on the outer surface of the barrel. In the case of springy deformations, the initial resistance of the sensor varies in proportion to its value. The speed of the shell (mine) in the barrel can be determined by time between pulses of signals obtained from strain gauges located at a known distance from each other. The simplicity of the proposed method for measuring the initial velocity of an artillery shell provides an opportunity for equipping each cannon (mortar) with autonomous means for measuring the initial velocity. With the simultaneous puting into action of automatic control systems can be automatically taking into account the measurement results. This will change the existing procedure for determining the total deviation of the initial velocity and improve the accuracy, timeliness and suddenness of the opening of artillery fire, which are components of its efficiency.

First passage time for the state of exact chemical equilibrium

1980 ◽  
Vol 45 (3) ◽  
pp. 777-782 ◽  
Author(s):  
Milan Šolc
Keyword(s):  
Chemical Equilibrium ◽  
First Passage Time ◽  
Passage Time ◽  
The State ◽  
Recurrence Time ◽  
First Passage ◽  
First Order ◽  
The Mean ◽  
Passage Times ◽  
Number Of Particles

The establishment of chemical equilibrium in a system with a reversible first order reaction is characterized in terms of the distribution of first passage times for the state of exact chemical equilibrium. The mean first passage time of this state is a linear function of the logarithm of the total number of particles in the system. The equilibrium fluctuations of composition in the system are characterized by the distribution of the recurrence times for the state of exact chemical equilibrium. The mean recurrence time is inversely proportional to the square root of the total number of particles in the system.

Kinetic theory

2018 ◽  
Author(s):  
Nathalie Deruelle ◽  
Jean-Philippe Uzan
Keyword(s):  
Distribution Function ◽  
Kinetic Theory ◽  
Liouville Equation ◽  
Vlasov Equation ◽  
Particle Distribution ◽  
Equations Of Motion ◽  
Poisson Brackets ◽  
Hamiltonian Form ◽  
First Order ◽  
Number Of Particles

This chapter covers the equations governing the evolution of particle distribution and relates the macroscopic thermodynamical quantities to the distribution function. The motion of N particles is governed by 6N equations of motion of first order in time, written in either Hamiltonian form or in terms of Poisson brackets. Thus, as this chapter shows, as the number of particles grows it becomes necessary to resort to a statistical description. The chapter first introduces the Liouville equation, which states the conservation of the probability density, before turning to the Boltzmann–Vlasov equation. Finally, it discusses the Jeans equations, which are the equations obtained by taking various averages over velocities.

scholarly journals Dynamic Indoor Localization Using Maximum Likelihood Particle Filtering

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1090
Author(s):  
Wenxu Wang ◽  
Damián Marelli ◽  
Minyue Fu
Keyword(s):  
Maximum Likelihood ◽  
Particle Filtering ◽  
Indoor Localization ◽  
Real Data ◽  
High Accuracy ◽  
Classical Particle ◽  
Popular Approach ◽  
Filtering Method ◽  
Essential Idea ◽  
Number Of Particles

A popular approach for solving the indoor dynamic localization problem based on WiFi measurements consists of using particle filtering. However, a drawback of this approach is that a very large number of particles are needed to achieve accurate results in real environments. The reason for this drawback is that, in this particular application, classical particle filtering wastes many unnecessary particles. To remedy this, we propose a novel particle filtering method which we call maximum likelihood particle filter (MLPF). The essential idea consists of combining the particle prediction and update steps into a single one in which all particles are efficiently used. This drastically reduces the number of particles, leading to numerically feasible algorithms with high accuracy. We provide experimental results, using real data, confirming our claim.

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