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Visar resultat 1 - 5 av 240 avhandlingar som matchar ovanstående sökkriterier.

1. 1. Mid- and near-infrared NICE-OHMS : techniques for ultra-sensitive detection of molecules in gas phase

   Författare :Thomas Hausmaninger; Ove Axner; Kyle Crabtree; Umeå universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; spectrometry; NICE-OHMS; trace gas detection; acetylene; methane; isotopologues; near-infrared; mid-infrared; shot-noise; optical parametric oscillator; teknisk fysik med inriktningen mikrosystemteknik; engineering science with specialization in microsystems technology;

   Sammanfattning : Noise-immune cavity-enhanced optical heterodyne molecular spectrometry (NICE-OHMS) is a technique for ultra-sensitive detection of molecular absorption and dispersion. For highest performance, the technique combines cavity enhancement (CE) with frequency modulation (FM); while the former increases the effective interaction length between the light and the analyte by several orders of magnitudes, the latter removes the in-coupling of 1/f noise and makes the signals background free. LÄS MER

3. 2. Measurement of trace components in aqueous solutions with near and mid infrared Fourier transform spectroscopy

   Författare :Peter Snoer Jensen; Atomfysik; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Near-infrared; Temperature dependency; Dual-beam; Optical null; Optimal pathlength Haemodialysis liquid; Urea; Glucose; Phosphate; Atom- och molekylärfysik; Atomic and molecular physics; Infrared; Water absorption; Fourier transform spectroscopy; Fysicumarkivet A:2003:Snoer Jensen;

   Sammanfattning : This thesis treats various aspects of the measurement of trace components in aqueous solutions with Fourier transform infrared spectroscopy. This technique has several applications from such diverse fields as dairy industry and biomedical optics. LÄS MER

4. 3. Ultrafast spin, lattice, and electron dynamics in thin metallic films : in the terahertz, near-infrared, and extreme ultraviolet regimes

   Författare :Vivek Unikandanunni; Stefano Bonetti; Andreas Rydh; Jurgen Lindner; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Terahertz; near-infrared; extreme ultraviolet; epitaxial cobalt; transient grating; field emission; gold; platinum; electron-phonon coupling; magneto-crystalline anisotropy; nanoscale dynamics; ultrafast spin dynamics; magnetic inertia; nutation; pump-probe; two-temperature model; Fowler-Nordheim tunneling; fysik; Physics;

   Sammanfattning : In this thesis, we studied the ultrafast spin and electron dynamics triggered by electromagnetic radiation belonging to three different regions of the electromagnetic spectrum, namely terahertz, near-infrared and extreme ultraviolet. By performing pump–probe measurements, we explored the role of the lattice in ultrafast spin and electron dynamics in metallic thin films. LÄS MER

5. 4. Stream monitoring using near-infrared spectroscopy of epilithic material

   Författare :Jan Persson; Ingemar Renberg; Umeå universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Streams; environmental monitoring; Water Framework Directive; water quality; biological impact; epilithic material; near-infrared spectroscopy; diatoms; Earth sciences; Geovetenskap;

   Sammanfattning : The European Union Water Framework Directive (WFD), with initiatives to manage surface water resources, has increased the need for fast and inexpensive methods for monitoring conditions in streams. The objective of this thesis is to assess the potential of near-infrared spectroscopy (NIRS) of epilithic material to become such method. LÄS MER

7. 5. Damage mechanisms for near-infrared radiation induced cataract

   Författare :Zhaohua Yu; Per Söderberg; Konstantin Galichanin; Masami Kojima; Uppsala universitet; []
   Nyckelord :MEDICIN OCH HÄLSOVETENSKAP; MEDICAL AND HEALTH SCIENCES; infrared radiation; photochemical; thermal; forward light scattering; lens; cataract; temperature; Arrhenius equation; heat diffusion;

   Sammanfattning : Purpose: 1) To estimate the threshold dose and the time evolution for cataract induction by near infrared radiation (IRR) in seconds exposure time domain; 2) to determine the ocular temperature development during the threshold exposure; 3) to investigate if near IRR induces cumulative lens damage considering irradiance exposure time reciprocity; 4) to experimentally estimate the temperature in the lens indirectly from the measurement of temperature-induced light scattering increase.Methods: Before exposure, 6-weeks-old albino rats were anesthetized and the pupils of both eyes were dilated. LÄS MER