Noise Filtering Algorithm Using Gaussian Mixture Models for High-Resolution Mass Spectra of Natural Organic Matter.

High-resolution mass spectra of natural organic matter (NOM) contain a large number of noise signals. These signals interfere with the correct molecular composition estimation during nontargeted analysis because formula-assignment programs find empirical formulas for such peaks as well. Previously proposed noise filtering methods that utilize the profile of the intensity distribution of mass spectrum peaks rely on a histogram to calculate the intensity threshold value.

Temporal compression of high-power IR laser pulses in a KDP crystal.

It is shown that a KDP crystal can be used for temporal compression of powerful pulses of the near-IR range. A method of searching for laser beam and crystal parameters suitable for compression is proposed. Temporal compression of laser pulses at a central wavelength of 1034 nm from 266 fs to 94 fs during propagation along the optical axis in a 21 cm thick KDP crystal is demonstrated experimentally.

Shaping of picosecond laser pulses with THz intensity modulation in the infrared, visible, and ultraviolet ranges.

The methods of shaping picosecond laser pulses with periodic intensity modulation tunable in frequency and depth are considered. Schemes for shaping modulated pulses "in-line" and with one output port are proposed. A picosecond modulation of the time envelope for IR laser pulses using a polarization interferometer is demonstrated experimentally.

Exoscope-based videocapillaroscopy system for skin microcirculation imaging of various body areas.

The capillary system immediately responds to many pathologies and environmental conditions. Accurate monitoring of its functioning often enables early detection of various diseases related to disorders in skin microcirculation. To expand the scope of capillaroscopy application, it is reasonable to visualize and assess blood microcirculation exactly in the areas of inflamed skin.

Highly efficient fourth harmonic generation of broadband laser pulses retaining 3D pulse shape.

A method for highly efficient fourth harmonic generation (FHG) retaining spatiotemporal intensity distribution of broadband chirped laser pulses is proposed. It is based on the use of pulses with linear frequency chirps of equal absolute magnitudes and opposite signs at the oo-e type noncollinear second harmonic generation. Fourth harmonic generation can by obtained by the classical method, since the second harmonic pulse is narrowband and spectrally limited.