scholarly journals The decrease in velocity of α-particles in passing through matter

1913 ◽  
Vol 88 (605) ◽  
pp. 443-454 ◽  
Keyword(s):  
Magnetic Field ◽  
Internal Structure ◽  
Opposite Sign ◽  
Zinc Sulphide ◽  
Sources Of Information ◽  
Before And After ◽  
Complete Investigation ◽  
Equal Thickness ◽  
Different Parts ◽  
Α Particles

It is becoming recognised that one of the most fruitful sources of information as to the internal structure of atoms is provided by the phenomena attending the passage of swift electrified particles through them. In particular from a consideration of the scattering α-particles it has been found that the atom consists essentially of a very concentrated charge at the centre of the atom surrounded by eletricity of the opposite sign, probably electrons, distributed throughout the remainder of the atom. Further, Darwin and Bohr have attempted to obtain information as to the number and distribution of electrons in the atom by a consideration of the absorption or loss of velocity of the α-particles in passing through matter. The only data for this purpose so far obtainable are provided by the velocity curves, or relations between velocity and thickness of matter traversed, in aluminium as determined by Rutherford, and in mica as determined by Geiger. It seemed, therefore, of interest to make a more complete investigation of the velocity curves in various substances, more particularly as the earlier observations are subject to slight errors due to the assumption that equal thickness of matter have the same air equivalent at different parts of the range of α particles. In the present experiments the velocity curves in gold, copper, aluminium, mica and air have been determined, using as source the α-particles of radium C as in the experiments of Rutherford and of Geiger. The velocities of the α-particles before and after passing through sheets of matter of various thickness were measured by the deflection of the α-particles in a known magnetic field. The apparatus used is shown in fig. 1. It consists essentially of a source of radiation D, a series of absorption foils T, a slit L, to form a pencil of the α-particles, and a zinc sulphide screen M on which the position of the pencil could be observed, the whole being enclosed in an evacuated chamber C between the poles of a large electromagnet.

A study of the magnetic fatigue properties of a magnetorheological elastomer

2018 ◽  
Vol 30 (5) ◽  
pp. 749-754 ◽  
Author(s):  
Chenglong Lian ◽  
Kwang-Hee Lee ◽  
Seung-Bok Choi ◽  
Chul-Hee Lee
Keyword(s):  
Magnetic Field ◽  
Mechanical Properties ◽  
Shear Modulus ◽  
Internal Structure ◽  
Fatigue Properties ◽  
Fatigue Cycle ◽  
Repeated Application ◽  
Magnetorheological Elastomer ◽  
Before And After ◽  
Microscopy Images

In this study, the magnetic fatigue properties of a magnetorheological elastomer were evaluated with and without a magnetic field. To accomplish the process, a magnetic fatigue tester and magnetorheological elastomer samples were designed and fabricated. The mechanical properties of the magnetorheological elastomer were determined under various fatigue cycle numbers and fatigue frequencies with and without a magnetic field. The shear modulus of the magnetorheological elastomer was also measured before and after the test to evaluate its mechanical properties. The results show that the shear modulus of the magnetorheological elastomer was larger in the presence of a magnetic field and decreased as the number of fatigue cycles increased because the internal structure became loose. Scanning electron microscopy images showed that the internal structure of the magnetorheological elastomer was loose under repeated application of magnetic fields.

The Capture of Electrons by α-Particles

1931 ◽  
Vol 27 (1) ◽  
pp. 116-130 ◽  
Author(s):  
H. C. Webster ◽  
E. Rutherford
Keyword(s):  
Magnetic Field ◽  
Zinc Sulphide ◽  
Electron Stream ◽  
Magnetic Deflection ◽  
Α Particles

Davis and Barnes have recently reported new and unexpected phenomena concerning the capture of electrons by swift α-particles. A beam of α-particles from a polonium source was passed through a stream of electrons emitted from an oxide-coated filament and accelerated by a known voltage so as to move in directions roughly parallel to those of the α-particles. The α-particles were then deflected by a magnetic field, and finally fell on a zinc sulphide screen, where the scintillations were counted. If any of the α-particles captured electrons while passing through the electron stream, they would fall on a different part of the screen, since the magnetic deflection is proportional to the charge. Any capture could thus easily be detected, and its dependence on the accelerating voltage examined.

Print Media and the Political Reform in Ethiopia

2019 ◽  
Vol 14 ◽  
pp. 3356-3371
Author(s):  
Negesse Gessese
Keyword(s):  
Social Changes ◽  
Analysis Method ◽  
Sources Of Information ◽  
Attribution Of Responsibility ◽  
Societal Issues ◽  
Content Selection ◽  
Period 2 ◽  
Content Analysis Method ◽  
Before And After ◽  
Issue Frames

This research examines the agenda and frames used by the Reporter newspaper editorial coverage of issues and actors before and after the reform in Ethiopia. The study applies a quantitative content analysis method and examined 99 (Period 1 = 57 and Period 2 = 42) editorials in all periods. The source of data and the period of data collection were purposely selected. The results indicated that societal issues, government, and party issues were frequent in both periods. The professional journalist was the only Author in both periods. More government criticism and more reforms were mentioned before the reform. Compared with editorials published before and after the reform, noticeable changes were observed in government critique, attribution of responsibility frames, human interest frames and economic issue frames. However, content selection, sources of information, mentioned reforms, conflict relationship frames, and ideological frames didn’t have relationship with the date of publication. Finally, the Reporter editorials coverage did change significantly in many respects, although it is difficult to determine the causes of the changes—economic factors, reduced political control, social changes or globalization forces.

scholarly journals A simulation study investigating potential diffusion-based MRI signatures of microstrokes

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Rafat Damseh ◽  
Yuankang Lu ◽  
Xuecong Lu ◽  
Cong Zhang ◽  
Paul J. Marchand ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Statistical Power ◽  
Barrel Cortex ◽  
Signal Loss ◽  
Nuclear Spins ◽  
Directional Diffusion ◽  
Ischemic Tissue ◽  
Significant Difference ◽  
Before And After ◽  
Experimental Validations

AbstractRecent studies suggested that cerebrovascular micro-occlusions, i.e. microstokes, could lead to ischemic tissue infarctions and cognitive deficits. Due to their small size, identifying measurable biomarkers of these microvascular lesions remains a major challenge. This work aims to simulate potential MRI signatures combining arterial spin labeling (ASL) and multi-directional diffusion-weighted imaging (DWI). Driving our hypothesis are recent observations demonstrating a radial reorientation of microvasculature around the micro-infarction locus during recovery in mice. Synthetic capillary beds, randomly- and radially-oriented, and optical coherence tomography (OCT) angiograms, acquired in the barrel cortex of mice (n = 5) before and after inducing targeted photothrombosis, were analyzed. Computational vascular graphs combined with a 3D Monte-Carlo simulator were used to characterize the magnetic resonance (MR) response, encompassing the effects of magnetic field perturbations caused by deoxyhemoglobin, and the advection and diffusion of the nuclear spins. We quantified the minimal intravoxel signal loss ratio when applying multiple gradient directions, at varying sequence parameters with and without ASL. With ASL, our results demonstrate a significant difference (p < 0.05) between the signal-ratios computed at baseline and 3 weeks after photothrombosis. The statistical power further increased (p < 0.005) using angiograms measured at week 4. Without ASL, no reliable signal change was found. We found that higher ratios, and accordingly improved significance, were achieved at lower magnetic field strengths (e.g., B0 = 3T) and shorter echo time TE (< 16 ms). Our simulations suggest that microstrokes might be characterized through ASL-DWI sequence, providing necessary insights for posterior experimental validations, and ultimately, future translational trials.

scholarly journals Mobility Trends before and after the Pandemic Outbreak: Analyzing the Metropolitan Area of Barcelona through the Lens of Equality and Sustainability

2021 ◽  
Vol 13 (14) ◽  
pp. 7908
Author(s):  
Lucía Mejía-Dorantes ◽  
Lídia Montero ◽  
Jaume Barceló
Keyword(s):  
Metropolitan Area ◽  
Spatial Arrangement ◽  
Individual Characteristics ◽  
Sources Of Information ◽  
Mobility Patterns ◽  
Multiple Sources ◽  
Temporal Dimension ◽  
Population Groups ◽  
Highly Educated ◽  
Before And After

The spatial arrangement of a metropolis is of utmost importance to carry out daily activities, which are constrained by space and time. Accessibility is not only shaped by the spatial and temporal dimension, but it is also defined by individual characteristics, such as gender, impairments, or socioeconomic characteristics of the citizens living or commuting in this area. This study analyzes mobility trends and patterns in the metropolitan area of Barcelona before and after the COVID-19 pandemic outbreak, with special emphasis on gender and equality. The study draws on multiple sources of information; however, two main datasets are analyzed: two traditional travel surveys from the transport metropolitan area of Barcelona and two coming from smartphone data. The results show that gender plays a relevant role when analyzing mobility patterns, as already highlighted in other studies, but, after the pandemic outbreak, some population groups were more likely to change their mobility patterns, for example, highly educated population groups and those with higher income. This study also highlights that e-activities may shape new mobility patterns and living conditions for some population segments, but some activities cannot be replaced by IT technologies. For all these reasons, city and transport planning should foster sustainable development policies, which will provide the maximum benefit for society.

scholarly journals Diurnal variation effect in marine magnetometric surveys: clues from surveys in southeast Brazil

2021 ◽  
Vol 42 (3) ◽  
Author(s):  
Paula Possamai Sergipe ◽  
Yára Regina Marangoni ◽  
Roberto Paulo Zanon dos Santos ◽  
Denise Silva de Moura ◽  
Luigi Jovane
Keyword(s):  
Magnetic Field ◽  
Continental Shelf ◽  
Diurnal Variation ◽  
Brazilian Coast ◽  
Observatory Data ◽  
Before And After ◽  
Corrected Data ◽  
Well Correlation ◽  
The Magnetic Field ◽  
Magnetic Observatories

AbstractThe diurnal variation of the magnetic field cannot be predicted or modeled and for that reason, it is monitored during the magnetic surveys, usually by a stationary magnetometer. However, marine surveys have a practical issue with diurnal monitoring, owing to the distance between the survey, stationary magnetometers, and magnetic observatories. This work aims to verify the use of nearby magnetic observatories to estimate the diurnal variation correction in different marine surveys and evaluate its effectiveness. In this study, we selected surveys at the continental shelf near Santos city (Survey 1), continental slope next to the first survey location (Survey 2), continental shelf near Ubatuba city (Survey 3), and Mamanguá ria in the Paraty city (Survey 4), all southeast to the Brazilian coast. The crossing points were implemented to compare the magnetic field values at different times and days at the same measurement point, before and after the correction. Afterwards, we measure the Pearson’s Correlation of the raw data and the diurnal corrected data in all crossing points of each survey which showed an improvement after correction by the value approximating to 1, which indicates a very well correlation. The Ubatuba and Mamanguá surveys allowed comparing the observatory correction results with the base magnetometer results that were rather similar. Our analyses indicate a satisfactory diurnal correction using the observatory data and the crossing points approach, which can be used for every marine magnetometric survey worldwide placed near the coast (< 280 km) that do not have a stationary magnetometer available.

Planet Earth – our oasis in space

2004 ◽  
Vol 12 (1) ◽  
pp. 111-119
Author(s):  
SIEGFRIED J. BAUER
Keyword(s):  
Magnetic Field ◽  
Solar System ◽  
Internal Structure ◽  
Solid Surface ◽  
Liquid Water ◽  
Atmospheric Environment ◽  
Suitable Habitat ◽  
The Earth

Planet Earth is unique in our solar system as an abode of life. In contrast to its planetary neighbours, the presence of liquid water, a benign atmospheric environment, a solid surface and an internal structure providing a protective magnetic field make it a suitable habitat for man. While natural forces have shaped the Earth over millennia, man through his technological prowess may become a threat to this oasis of life in the solar system.

Study dearomatization of diesel fuel under the infulence of magnetic field by IR spectroscopy

2021 ◽  
pp. 2150122
Author(s):  
B. G. Abdulov ◽  
A. A. Hasanov
Keyword(s):  
Magnetic Field ◽  
Polycyclic Aromatic Hydrocarbons ◽  
Sulfuric Acid ◽  
Ir Spectroscopy ◽  
Aromatic Hydrocarbons ◽  
Diesel Fraction ◽  
Oil Refining ◽  
Purification Process ◽  
Before And After ◽  
Polycyclic Aromatic

The purification process of polycyclic aromatic hydrocarbons was carried out by extraction of diesel fraction from the primary oil refining using the effect of magnetic field. A mixture of N-methylpyrrolidone with sulfuric acid was used as an extractant. The content of aromatic hydrocarbons in the diesel fraction decreased by 39.8% under normal conditions and by 50.8% under the influence of magnetic field after extraction. The samples were investigated by infrared (IR) spectroscopy method before and after extraction. Vibartional modes corresponding to different atomic bonds have been observed. Deodorization of diesel was determined by interpreting obtained modes.

scholarly journals Energy Correlations of α-Particles in the 8Be-Nucleus Ground-State Formation Channel of the 12C(γ,3α) and 16O(γ,4α) Reactions

2019 ◽  
Vol 64 (9) ◽  
pp. 787
Author(s):  
S. N. Afanasyev
Keyword(s):  
Magnetic Field ◽  
Photon Energy ◽  
Relative Motion ◽  
Cross Sections ◽  
Ground State ◽  
Diffusion Chamber ◽  
Mechanism Of Interaction ◽  
The Magnetic Field ◽  
Maximum Photon ◽  
Α Particles

The method of diffusion chamber in the magnetic field making use of a bremsstrahlung beam with a maximum photon energy of 150 MeV is applied to study the 12C(y,3a) and 16O(y,4a) reactions. A resonance identified as the ground state of 8Be nucleus is found in the distribution of events over the energy of the relative motion of two a-particles. The partial cross-sections of the 8Be nucleus formation channels are measured. It is shown that the mechanism of interaction between a y-quantum and a virtual a-particle pair takes place in this case.

scholarly journals The ring current: a short biography

2012 ◽  
Vol 3 (2) ◽  
pp. 131-142 ◽  
Author(s):  
A. Egeland ◽  
W. J. Burke
Keyword(s):  
Magnetic Field ◽  
Ring Current ◽  
Energy Content ◽  
Spectral Characteristics ◽  
Direct Access ◽  
Sufficient Evidence ◽  
Mass Spectrometers ◽  
Before And After ◽  
Magnetic Signatures ◽  
Collective Plasma

Abstract. The "ring current'' grows in the inner magnetosphere during magnetic storms and contributes significantly to characteristic perturbations to the Earth's field observed at low-latitudes. This paper outlines how understanding of the ring current evolved during the half-century intervals before and after humans gained direct access to space. Its existence was first postulated in 1910 by Carl Størmer to explain the locations and equatorward migrations of aurorae under stormtime conditions. In 1917 Adolf Schmidt applied Størmer's ring-current hypothesis to explain the observed negative perturbations in the Earth's magnetic field. More than another decade would pass before Sydney Chapman and Vicenzo Ferraro argued for its necessity to explain magnetic signatures observed during the main phases of storms. Both the Størmer and Chapman–Ferraro models had difficulties explaining how solar particles entered and propagated in the magnetosphere to form the ring current. During the early 1950s Hannes Alfvén correctly argued that the ring current was a collective plasma effect, but failed to explain particle entry. The discovery of a weak but persistent interplanetary magnetic field embedded in a continuous solar wind provided James Dungey with sufficient evidence to devise the magnetic merging-reconnection model now regarded as the basis for understanding magnetospheric and auroral activity. In the mid-1960s Louis Frank showed that ions in the newly discovered plasma sheet had the energy spectral characteristics needed to explain the ring current's origin. The introduction of ion mass spectrometers on space missions during the 1970s revealed that O+ ions from the ionosphere contribute large fractions of the ring current's energy content. Precisely how cold O+ ions in the ionosphere are accelerated to ring-current energies still challenges scientific understanding.

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