Generation of intense and coherent sub-femtosecond X-ray pulses in electron storage rings.

Temporally short X-ray pulses are an indispensable tool for the study of electron transitions close to the Fermi energy and structural changes in molecules undergoing chemical reactions which take place on a time-scale of hundreds of femtoseconds. The time resolution of experiments at 3rd generation light sources which produce intense synchrotron radiation is limited fundamentally by the electron-bunch length in the range of tens of picoseconds. Here we propose a new scheme for the generation of intense and coherent sub-femtoseconds soft X-ray pulses in storage rings by applying the Echo-Enabled Harmonic Generation (EEHG) method. Many issues for obtaining the EEHG structure such as two modulators and a radiator are solved by a paradigm shift in an achromatic storage ring cell. Numerical demonstration of the feasibility of the scheme for the BESSY II beam parameters is presented.

The expression and distribution of deoxyribonucleic acid repair and apoptosis markers in testicular germ cells of infertile varicocele patients resembles that of old fertile men.

OBJECTIVE: To explore the expression and distribution of DNA damage repair and apoptosis marker proteins in human testicular germ cells of infertile varicocele patients; and to compare the expression and distribution with that of young and old fertile men. DESIGN: Retrospective case-control study. SETTING: Academic institutions. PATIENT(S): Testicular specimens were obtained from 8 infertile varicocele patients aged 20-30 years and from 16 fertile volunteers aged 20-82 years. INTERVENTION(S): Testicular germ cell DNA repair markers were assessed using immunohistochemical staining for the cell proliferation marker (proliferating cell nuclear antigen), DNA repair markers [poly(ADP-ribose) polymerase-1 (PARP-1), poly(ADP-ribose), X-ray repair cross-complementing 1, and apurinic/apyrimidinic endonuclease 1], and apoptosis markers (caspase 9, active caspase 3, and cleaved PARP-1). MAIN OUTCOME MEASURE(S): The prevalence and cellular localization of the above markers in testicular tissues of varicocele patients and fertile men of varying ages. RESULT(S): Statistically significant differences in DNA damage repair-associated proteins and apoptosis markers were observed in infertile men with varicocele compared with fertile young men. Old fertile men showed similar expression of the same markers when compared with infertile varicocele patients. CONCLUSION(S): The study demonstrates that there is an increase in human testicular germ cell DNA repair and apoptosis in infertile varicocele patients and that their profile resembles that of premature aging.

Deoxyribonucleic acid repair and apoptosis in testicular germ cells of aging fertile men: the role of the poly(adenosine diphosphate-ribosyl)ation pathway.

OBJECTIVE: To explore the relationship between men's age and DNA damage repair proteins related to apoptosis in human testicular germ cells. DESIGN: Retrospective case-control study. SETTING: Academic institutions. PATIENT(S): Testicular specimens were obtained from 22 fertile volunteers aged 20-82 years. INTERVENTION(S): Deoxyribonucleic acid repair markers were assessed using immunohistochemical staining for the cell proliferation marker [proliferating cell nuclear antigen (PCNA)]; DNA repair markers [poly(adenosine diphosphate-ribose) polymerase-1 (PARP-1), poly(adenosine diphosphate-ribose) (PAR), X-ray repair cross-complementing1(XRCC1), and apurinic/apyrimidinic endonuclease 1 (APE1)]; and apoptosis-associated markers (caspase 9, active caspase 3, and cleaved PARP-1). MAIN OUTCOME MEASURE(S): The prevalence and cellular localization of the above markers in testicular tissues of young, middle aged, and old men. RESULT(S): Statistically significant differences in DNA damage repair-associated proteins (PARP-1, PAR, XRCC1, and APE1), and apoptosis markers (caspase 9, active caspase 3, and cleaved PARP-1) were observed in testicular samples from older men. These differences were most marked in spermatocytes. CONCLUSION(S): The study demonstrates that there is an age-related increase in human testicular germ cell DNA break repair and apoptosis with age.

A model describing stable coherent synchrotron radiation in storage rings.

We present a model describing high power stable broadband coherent synchrotron radiation (CSR) in the terahertz frequency region in an electron storage ring. The model includes distortion of bunch shape from the synchrotron radiation (SR), which enhances higher frequency coherent emission, and limits to stable emission due to an instability excited by the SR wakefield. It gives a quantitative explanation of several features of the recent observations of CSR at the BESSY II storage ring. We also use this model to optimize the performance of a source for stable CSR emission.

Determination of the optical properties of a two-layer tissue model by detecting photons migrating at progressively increasing depths.

We have investigated a method for solving the inverse problem of determining the optical properties of a two-layer turbid model. The method is based on deducing the optical properties (OPs) of the top layer from the absolute spatially resolved reflectance that results from photon migration within only the top layer by use of a multivariate calibration model. Then the OPs of the bottom layer are deduced from relative frequency-domain (FD) reflectance measurements by use of the two-layer FD diffusion model. The method was validated with Monte Carlo FD reflectance profiles and experimental measurements of two-layer phantoms. The results showed that the method is useful for two-layer models with interface depths of >5 mm; the OPs were estimated, within a relatively short time (<1 min), with a mean error of <10% for the Monte Carlo reflectance profiles and with errors of <25% for the phantom measurements.

Brilliant, coherent far-infrared (THz) synchrotron radiation.

A new technology for generating steady state, brilliant, broadband, coherent, far-infrared (FIR) radiation in electron storage rings is presented, suitable for FIR spectroscopy. An FIR power increase of up to 100 000 compared to the normal, incoherent synchrotron radiation in the range of approximately 5 to approximately 40 cm(-1) could be achieved. The source is up to 1000 times more brillant compared to a standard Hg arc lamp. The coherent synchrotron radiation is produced in a "low alpha" optics mode of the synchrotron light source BESSY, by bunch shortening and non-Gaussian bunch deformation.

Steady-state far-infrared coherent synchrotron radiation detected at BESSY II.

At BESSY II it is demonstrated that far-infrared coherent synchrotron radiation (CSR) can be generated by a controlled, steady-state process at storage rings. As an indication for coherent emission, the radiated power grows with the square of the beam current. The spectrum was analyzed by an interferometer in the 1-mm to 0.3-mm wavelength range. The CSR was enhanced more than 3000 times above background; the incoherent radiation remained below the background level. Steady-state and bursting CSR were discriminated by time resolved analysis from micro seconds to seconds.