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1.
Phys Rev E Stat Nonlin Soft Matter Phys ; 84(3 Pt 1): 032601, 2011 Sep.
Article in English | MEDLINE | ID: mdl-22060436

ABSTRACT

We present quantitative evidence for x-ray-induced water vaporization: water is vaporized at a rate of 5.5 pL/s with the 1-Å-wavelength x-ray irradiation of ~0.1 photons per Å(2); moreover, water vapor is reversibly condensed during pauses in irradiation. This result fundamentally suggests that photoionization induces vaporization. This phenomenon is attributed to surface-tension reduction by ionization and would be universally important in radiological and electrohydrodynamic situations.

2.
Phys Rev Lett ; 107(1): 018301, 2011 Jul 01.
Article in English | MEDLINE | ID: mdl-21797577

ABSTRACT

We show direct evidence that focused x rays enable us to merge polymer colloidal particles at room temperature. This phenomenon is ascribed to the photochemical scission of colloids with x rays, reducing the molecular weight, glass transition temperature, surface tension, and viscosity of colloids. The observation of the neck bridge growth with time shows that the x-ray-induced colloid coalescence is analogous to viscoelastic coalescence. This finding suggests a feasible protocol of photonic nanofabrication by sintering or welding of polymers, without thermal damage, using x-ray photonics.

3.
J Synchrotron Radiat ; 17(6): 817-20, 2010 Nov.
Article in English | MEDLINE | ID: mdl-20975231

ABSTRACT

Synchrotron phase-contrast hard X-ray imaging is used to provide highly efficient direct visualization of landslide dynamics and granular flows in fully wet granular piles. High penetration capability and phase-contrast enhancement of hard X-rays offer marked advantages in the precise tracking of individual granular movements through a thick water medium. It is revealed that the stress accumulation follows a power-law evolution while the relaxation follows an exponential one. The onset of landslide emerges at the trade-off of the two evolutions.

4.
J Synchrotron Radiat ; 15(Pt 6): 660-2, 2008 Nov.
Article in English | MEDLINE | ID: mdl-18955775

ABSTRACT

A quantitative application of microradiology with coherent X-rays to the real-time study of microbubble and microdroplet coalescence phenomena, with specific emphasis on the size relations in three-body events, is presented. The results illustrate the remarkable effectiveness of coherent X-ray imaging in delineating interfaces in multiphase systems, in accurately measuring their geometric properties and in monitoring their dynamics.


Subject(s)
Algorithms , Gases/chemistry , Microfluidics/methods , Solutions/chemistry , Surface Properties , Synchrotrons , Tomography, Optical Coherence/methods , X-Ray Diffraction/methods
5.
Phys Rev Lett ; 100(21): 217403, 2008 May 30.
Article in English | MEDLINE | ID: mdl-18518633

ABSTRACT

We discovered that intense irradiation by hard-x-ray strongly decreases the effects of natural surface tension of water in droplets and capillary tubes. The effect was revealed by direct experimental observations with phase contrast microradiology. A model based on ionization and surface charging explains this so far undetected phenomenon. The effect can impact the results of many experimental techniques based on x rays. This is an example of the largely unexplored effects that can be produced by extreme intense x-ray irradiation-an important issue due to current development of x-ray free-electron-lasers with unprecedented brilliance.

6.
Neuroimage ; 32(2): 566-9, 2006 Aug 15.
Article in English | MEDLINE | ID: mdl-16766209

ABSTRACT

Parkinson's disease (PD), defined as a neurodegenerative disorder, is characterized by the loss of dopaminergic neurons and the presence of Lewy bodies in neurons. Morphological study of Lewy bodies is important to identify the causes and the processes of PD. Here, we investigate a possibility of phase contrast radiography using coherent synchrotron X-rays to explore the microscopic details of Lewy bodies in thick (approximately 3 mm) midbrain tissues. Autopsied midbrain tissues of a PD patient were sliced in 3 mm thickness and then examined using synchrotron X-rays from the 7B2 beamline of the Pohang Light Source. Refraction-enhanced phase contrast radiography and microtomography were adopted to identify dark core and dim edge of Lewy bodies in neurons. The morphology of Lewy bodies was clearly revealed by the phase contrast radiography in very thick (3 mm) midbrain tissues without any staining treatment. Three-dimensional volume rendered microtomography of the autopsied midbrain tissues demonstrates striking evidence that several Lewy bodies are agglomerated by dim edges in a neuron. We suggest that the phase contrast radiography could be a useful tool to morphologically investigate the causes or the processes in PD.


Subject(s)
Image Enhancement/instrumentation , Image Processing, Computer-Assisted/instrumentation , Imaging, Three-Dimensional/instrumentation , Lewy Bodies/diagnostic imaging , Mesencephalon/diagnostic imaging , Microscopy, Phase-Contrast/instrumentation , Parkinson Disease/diagnostic imaging , Radiography/instrumentation , Synchrotrons , Tomography, X-Ray Computed/instrumentation , Dopamine/metabolism , Equipment Design , Humans , Lewy Bodies/pathology , Male , Mathematical Computing , Middle Aged , Nerve Degeneration/pathology , Parkinson Disease/pathology , Photography/instrumentation , Sensitivity and Specificity , Substantia Nigra/pathology
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