Generation and characterisation of few-pulse attosecond pulse trains at 100 kHz repetition rate

The development of attosecond pump-probe experiments at high repetition rate requires the development of novel attosecond sources maintaining a sufficient number of photons per pulse. We use 7 fs, 800 nm pulses from a non-collinear optical parametric chirped pulse amplification laser system to generate few-pulse attosecond pulse trains (APTs) with a flux of >106 photons per shot in the extreme ultraviolet at a repetition rate of 100 kHz. The pulse trains have been fully characterised by recording frequency-resolved optical gating for complete reconstruction of attosecond bursts (FROG-CRAB) traces with a velocity map imaging spectrometer. For the pulse retrieval from the FROG-CRAB trace a new ensemble retrieval algorithm has been employed that enables the reconstruction of the shape of the APTs in the presence of carrier envelope phase fluctuations of the few-cycle laser system. © 2020 The Author(s). Published by IOP Publishing Ltd

Generation and characterisation of few-pulse attosecond pulse trains at 100 kHz repetition rate

The development of attosecond pump–probe experiments at high repetition rate requires the development of novel attosecond sources maintaining a sufficient number of photons per pulse. We use 7 fs, 800 nm pulses from a non-collinear optical parametric chirped pulse amplification laser system to generate few-pulse attosecond pulse trains (APTs) with a flux of >106 photons per shot in the extreme ultraviolet at a repetition rate of 100 kHz. The pulse trains have been fully characterised by recording frequency-resolved optical gating for complete reconstruction of attosecond bursts (FROG-CRAB) traces with a velocity map imaging spectrometer. For the pulse retrieval from the FROG-CRAB trace a new ensemble retrieval algorithm has been employed that enables the reconstruction of the shape of the APTs in the presence of carrier envelope phase fluctuations of the few-cycle laser system

Generation and characterization of isolated attosecond pulses at 100 kHz repetition rate

The generation of coherent light pulses in the extreme ultraviolet (XUV) spectral region with attosecond pulse durations constitutes the foundation of the field of attosecond science. Twenty years after the first demonstration of isolated attosecond pulses, they continue to be a unique tool enabling the observation and control of electron dynamics in atoms, molecules, and solids. It has long been identified that an increase in the repetition rate of attosecond light sources is necessary for many applications in atomic and molecular physics, surface science, and imaging. Although high harmonic generation (HHG) at repetition rates exceeding 100 kHz, showing a continuum in the cutoff region of the XUV spectrum, was already demonstrated in 2013, the number of photons per pulse was insufficient to perform pulse characterization via attosecond streaking, let alone to perform a pump-probe experiment. Here we report on the generation and full characterization of XUV attosecond pulses via HHG driven by near-single-cycle pulses at a repetition rate of 100 kHz. The high number of 106 XUV photons per pulse on target enables attosecond electron streaking experiments through which the XUV pulses are determined to consist of a dominant single attosecond pulse. These results open the door for attosecond pump-probe spectroscopy studies at a repetition rate 1 or 2 orders of magnitude above current implementations

The impact of PTEN tumor suppressor gene on acquiring resistance to tamoxifen treatment in breast cancer patients

Tamoxifen is a standard therapeutical treatment in patients with estrogen receptor positive breast carcinoma. However, less than 50% of estrogen receptor positive breast cancers do not respond to tamoxifen treatment whereas 40% of tumors that initially respond to treatment develop resistance over time. The underlying mechanisms for tamoxifen resistance are probably multifactorial but remain largely unknown. The primary aim of this study was to investigate the impact of PTEN tumor suppressor gene on acquiring resistance to tamoxifen by analyzing loss of heterozygosity (LOH) and immunohystochemical expression of PTEN in 49 primary breast carcinomas of patients treated with tamoxifen as the only adjuvant therapy. The effect of PTEN inactivation on breast cancer progression and disease outcome was also analyzed. Reduced or completely lost PTEN expression was observed in 55.1% of samples, while 63.3% of samples displayed LOH of PTEN gene. Inactivation of PTEN immunoexpression significantly correlated with the PTEN loss of heterozygosity, suggesting LOH as the most important genetic mechanism for the reduction or complete loss of PTEN expression in primary breast carcinoma. Most importantly, LOH of PTEN and consequential reduction of its immunoexpression showed significant correlation with the recurrence of the disease. Besides, our study revealed that LOH of PTEN tumor suppressor was significantly associated with shorter disease free survival, breast cancer specific survival and overall survival. In summary, our results imply that LOH of PTEN could be used as a good prognostic characteristic for the outcome of breast cancer patients treated with tamoxifen

Assessment of natural environment for the purposes of recreational tourism-example on drina river flow (Serbia)

The role of applied geography has been increasing in interdisciplinary research due to the advantage of knowing spatial processes and relations. This role has reflected in the geo-ecological evaluations of a particular geographical area used for different social purposes. This paper represents the GIS analysis of the natural environment of a part of the Drina River flow in wider terms so to apply in recreational tourism. The quantitative V-Wert diversification method has used for the study with the focus on identification of the area that might be favorable for recreation. The analysis is based on the knowledge of natural geographical elements. Criteria taken into consideration are the edges of the forest and water, the relief energy, the manner in which the landscape is used and the climate factor. According to the benefits of the said purpose, the unfavorable areas amount to 1,520 km2 (34.43%), conditionally favorable areas amount to 2,418 km2 (54.77%), favorable areas amount to 310.33 km2 (7.03%), very favorable areas amount to 163 km2 (3.69%) and the most favorable areas amount to 3.67 km2 (0.08%). The category of very favorable recreation contains a large area (167 km2) from the total amount of 4245 km2

Assessment of natural environment for the purposes of recreational tourism-example on drina river flow (Serbia)

The role of applied geography has been increasing in interdisciplinary research due to the advantage of knowing spatial processes and relations. This role has reflected in the geo-ecological evaluations of a particular geographical area used for different social purposes. This paper represents the GIS analysis of the natural environment of a part of the Drina River flow in wider terms so to apply in recreational tourism. The quantitative V-Wert diversification method has used for the study with the focus on identification of the area that might be favorable for recreation. The analysis is based on the knowledge of natural geographical elements. Criteria taken into consideration are the edges of the forest and water, the relief energy, the manner in which the landscape is used and the climate factor. According to the benefits of the said purpose, the unfavorable areas amount to 1,520 km2 (34.43%), conditionally favorable areas amount to 2,418 km2 (54.77%), favorable areas amount to 310.33 km2 (7.03%), very favorable areas amount to 163 km2 (3.69%) and the most favorable areas amount to 3.67 km2 (0.08%). The category of very favorable recreation contains a large area (167 km2) from the total amount of 4245 km2

Two-layer reconstruction of Raman spectra in diffusive media based on an analytical model in the time domain

We derive and validate an analytical model that describes the migration of Raman scattered photons in two-layer diffusive media, based on the diffusion equation in the time domain. The model is derived under a heuristic approximation that background optical properties are identical on the excitation and Raman emission wavelengths. Methods for the reconstruction of two-layer Raman spectra have been developed, tested in computer simulations and validated on tissue-mimicking phantom measurements data. Effects of different parameters were studied in simulations, showing that the thickness of the top layer and number of detected photon counts have the most significant impact on the reconstruction. The concept of quantitative, mathematically rigorous reconstruction using the proposed model was finally proven on experimental measurements, by successfully separating the spectra of silicone and calcium carbonate (calcite) layers, showing the potential for further development and eventual application in clinical diagnostics