Physical Factors Determining Ultraviolet Radiation Flux into Ecosystems

The dynamics of the cold atomic and molecular gas, on which we focus here, is strongly affected by non equilibrium heating and cooling processes. We give two different examples, in which the breaking of the thermal balance is due respectively to variations of the incident ultraviolet radiation flux, and non equilibrium abundances of H2 molecules in molecular clouds envelopes. Fluctuations of the ultraviolet radiation flux in clumpy molecular cloud envelopes result in the formation or the destruction of dense regions. Large density contrasts, greater than one order of magnitude, are easily achieved in cloud regions of moderate visual extinction. Condensation or expansion develop on quite short time scales, of the order of a few tenth of million year, and induce collective motions which can feed turbulence.Another example of the importance of out of equilibrium thermochemical processes is furnished by the study of the H — H2 transition layers in molecular clouds envelopes. They turn out to be unstable against convection-like motions, driven by the energy released by H2 photodestruction. The gas velocities involved in these motions are, again, typical of the observed turbulent velocity in clouds envelopes.

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Cumulative ultraviolet radiation flux in adulthood and risk of incident skin cancers in women

British Journal of Cancer ◽

10.1038/bjc.2014.43 ◽

2014 ◽

Vol 110 (7) ◽

pp. 1855-1861 ◽

Cited By ~ 28

Author(s):

S Wu ◽

J Han ◽

R A Vleugels ◽

R Puett ◽

F Laden ◽

...

Keyword(s):

Ultraviolet Radiation ◽

Radiation Flux ◽

Skin Cancers

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Thermal processes in molecular gas

Symposium - International Astronomical Union ◽

10.1017/s0074180900198900 ◽

1991 ◽

Vol 147 ◽

pp. 197-204

Author(s):

J.P. Chièze ◽

C. de Boisanger

Keyword(s):

Ultraviolet Radiation ◽

Molecular Clouds ◽

Radiation Flux ◽

Molecular Gas ◽

Heating And Cooling ◽

Collective Motions ◽

Thermochemical Processes ◽

Order Of Magnitude ◽

Short Time ◽

Non Equilibrium

The dynamics of the cold atomic and molecular gas, on which we focus here, is strongly affected by non equilibrium heating and cooling processes. We give two different examples, in which the breaking of the thermal balance is due respectively to variations of the incident ultraviolet radiation flux, and non equilibrium abundances of H2 molecules in molecular clouds envelopes. Fluctuations of the ultraviolet radiation flux in clumpy molecular cloud envelopes result in the formation or the destruction of dense regions. Large density contrasts, greater than one order of magnitude, are easily achieved in cloud regions of moderate visual extinction. Condensation or expansion develop on quite short time scales, of the order of a few tenth of million year, and induce collective motions which can feed turbulence.Another example of the importance of out of equilibrium thermochemical processes is furnished by the study of the H — H2 transition layers in molecular clouds envelopes. They turn out to be unstable against convection-like motions, driven by the energy released by H2 photodestruction. The gas velocities involved in these motions are, again, typical of the observed turbulent velocity in clouds envelopes.

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Análisis de interferencia de parámetros físicos del agua, en desinfección por radiación UV

Revista de Tecnología ◽

10.18270/rt.v14i2.1874 ◽

2016 ◽

Vol 14 (2) ◽

Author(s):

Pedro Mauricio Acosta Castellanos ◽

Carlos Andrés Caro Camargo ◽

Néstor Rafael Perico Granados

Keyword(s):

Escherichia Coli ◽

Ultraviolet Radiation ◽

Environmental Conditions ◽

Water Samples ◽

Evaluation Research ◽

Uv Disinfection ◽

Physical Parameters ◽

Physical Factors ◽

Static Test ◽

Microbiological Parameters

Este artículo presenta los resultados de investigación de la evaluación en la eficacia de la remoción de parámetros microbiológicos del agua por medio de radiación ultravioleta. Se hizo mediante ensayos estáticos en un banco de pruebas donde se irradiaron nueve muestras de agua, en las que se variaron las condiciones del medio y del agua. Los parámetros microbiológicos analizados fueron echerichia coli, coliformes totales y mesófilos.Se analizaron las muestras de agua, a partir de variar de manera controlada sus parámetros físicos, los que influyen en la inactivación, como turbiedad, tiempo de exposición y volumen de agua tratada y concentración microbiológica. Se infirió cuáles son los factores físicos que más tienen influencia en la inactivación y se comprobó la importancia de tratamientos primarios previos a la desinfección por radiación ultravioleta.Se construyeron las curvas dosis-respuesta de cada uno de los parámetros microbiológicos y su relación con el parámetro físico analizado. A partir de éstas se determinó la dosificación necesaria para la inactivación. Las muestras de agua fueron analizadas mediante los métodos de número más probable, sustrato definido y recuento en placa.Abstract This paper presents the results of evaluation research on the effectiveness of the removal of microbiological parameters water by ultraviolet radiation. It was made by a static test where nine water samples, in which environmental conditions and water were varied irradiated trials. The microbiological parameters analyzed were Escherichia coli, total coliforms and mesophilic. Water samples were analyzed from controllably vary its physical parameters, which influence the inactivation, as turbidity, exposure time and volume of treated water and microbiological concentration. Inferred what physical factors that influence the importance of inactivation and prior to UV disinfection are primary treatments was tested.

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Reproduction and Dissemination of the Units of Radiation Flux and Irradiance Using Standard Ultraviolet Radiation Detectors

Measurement Techniques ◽

10.1007/s11018-005-0129-6 ◽

2005 ◽

Vol 48 (3) ◽

pp. 232-236

Author(s):

O. A. Minaeva

Keyword(s):

Ultraviolet Radiation ◽

Radiation Flux ◽

Radiation Detectors

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Applications of Photoelectron Microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100092499 ◽

1976 ◽

Vol 34 ◽

pp. 506-507

Author(s):

William J. Baxter

Keyword(s):

Electron Microscopy ◽

Thermal Decomposition ◽

Chemical Composition ◽

Ultraviolet Radiation ◽

Thin Layer ◽

Edge Effects ◽

Electron Optics ◽

Surface Layers ◽

Crystalline Orientation ◽

Fluorescent Screen

In this form of electron microscopy, photoelectrons emitted from a metal by ultraviolet radiation are accelerated and imaged onto a fluorescent screen by conventional electron optics. image contrast is determined by spatial variations in the intensity of the photoemission. The dominant source of contrast is due to changes in the photoelectric work function, between surfaces of different crystalline orientation, or different chemical composition. Topographical variations produce a relatively weak contrast due to shadowing and edge effects.Since the photoelectrons originate from the surface layers (e.g. ∼5-10 nm for metals), photoelectron microscopy is surface sensitive. Thus to see the microstructure of a metal the thin layer (∼3 nm) of surface oxide must be removed, either by ion bombardment or by thermal decomposition in the vacuum of the microscope.

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