In the literature, there was an exact analytical result for the splitting of hydrogen spectral lines in an electric field E rotating with a constant angular velocity Ω. In the reference frame rotating with the angular velocity of the field, the problem was reduced to a hydrogen atom in the static electric field crossed with a fictitious static magnetic field, the latter problem having an exact analytical solution. From the physical point of view, this was achieved by using the O4 symmetry of hydrogen atoms. In the present paper we provide an analytical solution for the splitting of hydrogen-like spectral lines in the situation where the rotating field represents a circularly polarized electromagnetic wave, but there is also a true, relatively strong magnetic field B that can be parallel or antiparallel to the angular velocity vector Ω. We show that by varying the true magnetic field, it is possible to diminish the splitting of hydrogenic spectral lines, which is a counterintuitive result. The most interesting case is where the true magnetic field completely cancels out the effect of the fictitious magnetic field, thus minimizing the splitting. In this case, the total intensity of the spectral line diminishes by 40

GigaGauss (GG) or even multi-GG magnetic fields are expected to develop during relativistic laser-plasma interactions. In our previous paper we proposed a method for measuring GG magnetic fields based on the phenomenon of Langmuir-wave-cased dips (L-dips) in x-ray line profiles. The L-dips were observed in several experimental spectroscopic studies of relativistic laser-plasma interactions. Ultra-strong magnetic fields affect the separation of the L-dips from one another, so that this separation can be used to measure such fields. In the present paper we provide some new results concerning the effect of the ultra-strong magnetic fields on the separation between the L-dips. But the primary focus of the present paper is at another effect of the GG magnetic fields on the L-dips: we study how these ultra-intense magnetic fields affect the halfwidth of the L-dips. One of the results turns out to be counterintuitive: for the case of the two-quantum resonance, the halfwidth of the L-dips is a non-monotonic function of the magnetic field. By advancing the results of the previous work, the present paper expands the possibilities for measuring super-strong magnetic fields up to ~ 10 GG expected to arise during relativistic laser-plasma interactions.

In this paper we introduce a new application that exploits the emerging imaging modality of full field optical coherence tomography (FFOCT) as a means of optical biopsy. The objective is to build a computer-aided diagnosis (CAD) tool that can speed up the detection of tumoral areas in skin excisions resulting from Mohs surgery. Since there is little prior knowledge about the appearance of cancer cell morphology in this type of imagery, deep learning techniques are applied. Using convolutional neural networks (CNN), we train a feature extractor able to find representative characteristics for FFOCT data and a classifier that learns a generalized distribution of the data. With a dataset of 40 high-resolution images, we obtained a classification accuracy of 95.93%.

The processes of photo-detachment or ionization of stable molecules are widely investigated in modern atomic physics. But the present work deals with the calculation of the photo-detachment cross-sections in the case of negative quasi-molecules formed during collisions. The reaction H + H− + ħω → H + H + e has been taken as an example of bound-free transitions in single-active-electron quasi-molecules. For simplicity, we discuss the one-dimensional case in the frame of the zero-range potential model.

Transurethral resections are commonly used for bladder cancer diagnosis, treatment and follow-up. Cancer staging relies largely on the analysis of muscle in the resections; however, muscle presence is uncertain at the time of the resection. An extemporaneous quality control tool would be of great use to certify the presence of muscle in the resection, and potentially formulate a primo-diagnosis, in order to ensure optimum patient care. Full-field optical coherence tomography (FFOCT) offers a fast and non-destructive method of obtaining images of biological tissues at ultrahigh resolution (1 mu m in all 3 directions), approaching traditional histological sections. This study aimed to evaluate the potential of FFOCT for the quality control and the primo-diagnosis of transurethral bladder resections. Over 70 transurethral bladder resections were imaged with FFOCT within minutes, shortly after excision, and before histological preparation. Side-by-side comparison with histology allowed to establish reading criteria for the presence of muscle and cancer in particular. Images of 24 specimens were read blindly by three non-pathologists readers: two resident urologists and a junior bio-medical engineer, who were asked to notify the presence of muscle and tumor. Results showed that after appropriate training, 96% accuracy could be obtained on both tumour and muscle detection. FFOCT is a fast and non-destructive imaging technique that provides analysis results concordant with histology. Its implementation as a quality control and primo-diagnosis tool for transurethral bladder resections in the urology suite is feasible and lets envision high value for the patient.

We review studies of two kinds of dips in spectral line profiles emitted by plasmas the dips that have been predicted theoretically and observed experimentally: Langmuir-wave-caused dips (L-dips) and charge-exchange caused dips (X-dips). There is a principal difference with respect to positions of L-dips and X-dips relative to the unperturbed wavelength of a spectral line: positions of L-dips scale with the electron density N-e roughly as N-e(1/2), while positions of X-dips are almost independent of N-e (the dependence is much weaker than for L-dips). L-dips and X-dips phenomena are important both fundamentally and practically. The fundamental importance is due to a rich physics behind each of these phenomena. As for important practical applications, they are as follows. Observations of L-dips constitute a very accurate method to measure the electron density in plasmas - the method that does not require the knowledge of the electron temperature. L-dips also allow measuring the amplitude of the electric field of Langmuir waves - the only one spectroscopic method available for this purpose. Observations of X-dips provide an opportunity to determine rate coefficient of charge exchange between multi-charged ions. This is an important reference data virtually inaccessible by other experimental methods. The rate coefficients of charge exchange are important.for magnetic fusion in Tokamaks, for population inversion in the soft x-ray and VIJV ranges, for ion storage devices, as well as for astrophysics (e.g., for the solar plasma and for determining the physical state of planetary nebulae).

We present X-ray spectroscopic diagnostics in femto-second laser-driven experiments revealing nonlinear phenomena caused by the strong coupling of the laser radiation with the created plasma. Among those nonlinear phenomena, we found the signatures of the Two Plasmon Decay (TPD) instability in a laser-driven CO2 cluster-based plasma by analyzing the Langmuir dips in the profile of the O VIII Lyε line, caused by the Langmuir waves created at the high laser intensity 3 1018Wcm-2. With similar laser intensities, we reveal also the nonlinear phenomenon of the Second Harmonic Generation (SHG) of the laser frequency by analyzing the nonlinear phenomenon of satellites of Lyman δ and ε lines of Ar XVII. In the case of relativistic laser-plasma interaction we discovered the Parametric Decay Instability (PDI)-induced ion acoustic turbulence produced simultaneously with Langmuir waves via irradiation of thin Si foils by laser intensities of 1021Wcm-2.

Transport phenomena in plasmas, such as, e.g., resistivity, can be affected by electrostatic turbulence that frequently occurs in various kinds of laboratory and astrophysical plasmas. Transport phenomena are affected most significantly by a low-frequency electrostatic turbulence—such as, e.g., ion acoustic waves, also known as ionic sound—causing anomalous resistivity. In this case, for computing profiles of spectral lines, emitted by plasma ions, by any appropriate code for diagnostic purposes, it is necessary to calculate the distribution of the total quasistatic field. For a practically important situation, where the average turbulent field is much greater than the characteristic ion microfield, we develop a robust computational method valid for any appropriate distribution of the ion microfield at a charged point. We show that the correction to the Rayleigh distribution of the turbulent field is controlled by the behavior of the ion microfield distribution at large fields—in distinction to the opposite (and therefore, erroneous) result in the literature. We also obtain a universal analytical expression for the correction to the Rayleigh distribution based on the asymptotic of the ion microfield distribution at large fields at a charged point. By comparison with various known distributions of the ion microfield, we show that our asymptotic formula has a sufficiently high accuracy. Also exact computations are used to verify the high accuracy of the method. This robust approximate, but accurate method yields faster computational results than the exact calculations and therefore should be important for practical situations requiring simultaneous computations of a large number of spectral lineshapes (e.g., for calculating opacities)—especially for laser-produced plasmas.

By analyzing profiles of experimental x-ray spectral lines of Si XIV and Al XIII, we found that both Langmuir and ion acoustic waves developed in plasmas produced via irradiation of thin Si foils by relativistic laser pulses (intensities ~1021 W/cm2). We prove that these waves are due to the parametric decay instability (PDI). This is the first time that the PDI-induced ion acoustic turbulence was discovered by the x-ray spectroscopy in laser-produced plasmas. These conclusions are also supported by PIC simulations. Our results can be used for laboratory modeling of physical processes in astrophysical objects and a better understanding of intense laser-plasma interactions.

Intra-Stark spectroscopy (ISS) is the spectroscopy within the quasistatic Stark profile of a spectral line. The present paper advances the ISS-based study of the relativistic laser–plasma interaction from our previous paper (Oks et al 2017 Opt. Express 25 1958). By improving the experimental conditions and the diagnostics, it provides an in-depth spectroscopic study of the simultaneous production of the Langmuir waves and of the ion acoustic turbulence at the surface of the relativistic critical density. It demonstrates a reliable reproducibility of the Langmuir-wave-induced dips at the same locations in the experimental profiles of Si XIV Ly-beta line, as well as of the deduced parameters (fields) of the Langmuir waves and ion acoustic turbulence in several individual 1 ps laser pulses and of the peak irradiances of 1–3 × 1020 W cm−2. Besides, this study employs for the first time the most rigorous condition of the dynamic resonance, on which the ISS phenomenon is based, compared to all previous studies in all kinds of plasmas in a wide range of electron densities. It shows how different interplays between the Langmuir wave field and the field of the ion acoustic turbulence lead to distinct spectral line profiles, including the disappearance of the Langmuir-wave-induced dips.

It is shown that the production of X-ray emission spectra in the interaction of high-intensity laser radiation with cluster targets may be affected by the bichromatic oscillating electric field arising from the generation of the second harmonic of laser radiation. A technique is proposed for diagnosing harmonic generation in laser - cluster interactions using the spectral line profiles of multiply charged helium ions. The efficiency of second harmonic generation at a laser intensity of 3 x 10(18) W cm(-2) is shown to amount to about 2 %.

Full-field optical coherence tomography (FFOCT) offers a fast and non-destructive method of obtaining images of biological tissues at ultrahigh resolution, approaching traditional histological sections. In the context of prostate cancer diagnosis involving multiple biopsies, FFOCT could be used to validate the cores just after they are obtained in order to guide the number of biopsies to be performed. The aim of the study was to define and test a training protocol for efficient FFOCT prostate biopsy assessment. Three readers (a pathologist with previous experience with FFOCT, a pathologist new to FFOCT, and a urologist new to FFOCT) were trained to read FFOCT images of prostate biopsies on a set of 20 commented zooms (1 mm field of view) and 25 complete images. They were later tested on a set of 115 anonymized and randomized images of prostate biopsies. The results showed that an extra 30 images were necessary for more complete training as compared to prior studies. After training, pathologists obtained 100% sensitivity on high-grade cancer detection and 96% overall specificity; the urologist obtained 88% sensitivity on high-grade cancer and 89% overall specificity. Overall, the readers obtained a mean of 93% accuracy of qualifying malignancy on prostate biopsies. Moreover, the two pathologists showed a steeper learning curve than the urologist. This study demonstrates that a training protocol for such a new imaging modality may be implemented and yield very high efficiency for the prehistologic detection of malignancy on prostate biopsies.

Previously we discovered a way for producing not-yet-available fundamental data on charge exchange between multicharged ions, virtually inaccessible by other experimental methods. It was based on the formation of dips (called x-dips) in spectral lines of hydrogen-like ions from laser-produced plasmas. At that time the x-dip phenomenon was considered to be possible only in spectral lines of hydrogenic systems: due to the existence of exact algebraic (higher than geometrical) symmetries relevant only to hydrogenic systems and to the corresponding two-Coulomb-centre systems (dicentres) having one electron. In the present paper, by engaging the concept of an approximate algebraic symmetry of two-electron dicentres (and of helium-like ions), we opened up the way to significantly broaden the scope of experimental studies of the x-dip phenomenon-to studies of possible x-dips in spectral line profiles emitted by He-like ions in laser-produced plasmas. We identified three prospective two-electron dicentres and calculated analytically theoretical positions of the x-dips in the corresponding He-like spectral lines (though future experimental and theoretical studies should not be limited to these three two-electron dicentres). Since future experimental and theoretical studies should not be limited to these three two-electron dicentres, we presented also a table containing 15 prospective He-like spectral lines and 10 corresponding solid targets for observing x-dips in laser-produced plasmas. For completeness we presented also a similar table for H-like lines. It presented 16 prospective H-like spectral lines and 11 corresponding solid targets for observing x-dips in laser-produced plasmas. From the shape of experimental x-dips it is possible to determine the rate coefficient of charge exchange in the corresponding dicentre, as demonstrated previously. Therefore the results of the present paper should very significantly extend the range of fundamental data on charge exchange between multicharged ions that can be obtained via the x-dip phenomenon, but not by any other method.

We present the first study of two kinds of dips (L-dips and X-dips) in spectral lines from femtosecond laser-driven cluster-based plasma. We found that the observed L-dips are caused by Langmuir waves resulting from the two-plasmon decay instability and our experiment constitutes the first observation of the signature of this instability in spectral line profiles. We also observed an X-dip caused by charge exchange and used it for the experimental determination of the rate of charge exchange between the hydrogenic oxygen and fully-stripped helium-an important fundamental reference data virtually inaccessible by other experimental methods.

The review covers theoretical and experimental studies of two kinds of dips (local depressions) in spectral line profiles emitted by plasmas: Langmuir-wave-caused dips (L-dips) and charge-exchange-caused dips (X-dips). Positions of L-dips (relative to the unperturbed wavelength of a spectral line) scale with the electron density N-e roughly as N-e(1/2), while positions of X-dips are almost independent of N-e. L-dips and X-dips phenomena are interesting and important both fundamentally and practically. The fundamental interest is due to a rich physics behind each of these phenomena. As for important practical applications, they are as follows. Observation of L-dips constitutes a very accurate method to measure the electron density in plasmas - the method that does not require the knowledge of the electron temperature. L-dips also allow measuring the amplitude of the electric field of Langmuir waves - the only one spectroscopic method available for this purpose. In the most recent laser plasma experiments, L-dips were found to be a spectroscopic signature of the two-plasmon decay instability. This instability causes hot-electron generation and is a critical part in laser-driven inertial confinement fusion program. As for observations of X-dips, they serve to determine rates of charge exchange between multicharged ions. This is an important reference data virtually inaccessible by other experimental methods. The rates of charge exchange are essential for magnetic fusion in tokamaks, for population inversion in the soft x-ray and VUV ranges, for ion storage devices, as well as for astrophysics (e.g., for the solar plasma and for determining the physical state of planetary nebulae).

Objectives. - To evaluate the value of full field optical coherence tomography (FFOCT) for cancer detection on prostate biopsiesPatients and methods. - Eight consecutive patients who underwent prostate biopsies for an elevated PSA or suspicious DRE findings were included in the study. For each patient, one to three biopsy cores were imaged with FFOCT immediately after sampling. Images obtained were analyzed by a pathologist blinded to the pathological results, and classified into three categories: non-cancerous tissue, suspicion of malignancy and prostate carcinoma. A pathological correlation analysis was further performed.Results. - Sixteen biopsy cores were analyzed. The median FFOCT procedure time was of 4 (3-5) minutes. No artifact was noted in subsequent pathological analysis. Six cores were involved with cancer and eight cores showed no evidence of cancer. On two cores, diagnosis was uncertain, and immuno-histochemical analysis confirmed cancer involvement in one of them. The agreement rate between standard histological analysis and FFOCT evaluation was of 81% (13/16). The three cases of disagreement were due to one false positive and two false negatives of FFOCT analysis.Conclusions. - FFOCT of prostate biopsy cores seemed to be feasible and to allow concordant results with those of pathological analysis in the majority of the cases. (C) 2013 Elsevier Masson SAS. All rights reserved.

Full-field OCT (FFOCT) has the ability to provide en-face images with a very good axial sectioning as well as a very high transverse resolution (about 1 microns in all directions). Therefore it offers the possibility to visualize biological tissues with very high resolution both on the axial native view, and on vertical reconstructed sections. Here we investigated the potential dermatological applications of in-vivo skin imaging with FFOCT. A commercial FFOCT device was adapted for the in-vivo acquisition of stacks of images on the arm, hand and finger. Several subjects of different benign and pathological skin conditions were tested. The images allowed measurement of the stratum corneum and epidermis thicknesses, measurement of the stratum corneum refractive index, size measurement and count of the keratinocytes, visualization of the dermal-epidermal junction, and visualization of the melanin granules and of the melanocytes. Skins with different pigmentations could be discriminated and skin pathologies such as eczema could be identified. The very high resolution offered by FFOCT both on axial native images and vertical reconstructed sections allows for the visualization and measurement of a set of parameters useful for cosmetology and dermatology. In particular, FFOCT is a potential tool for the understanding and monitoring of skin hydration and pigmentation, as well as skin inflammation.

Jets of energetic ions launched at laser-burnt-through foils represent an efficient tool for investigation of plasma interaction with solid surfaces (plasma-wall interaction, PWI) and for description of transient phenomena occurring close to the walls. Highly charged ions approaching the secondary target interpenetrate the near surface layer, collide with the counter-propagating matter and capture a large number of electrons. This results in a creation of atoms in highly excited Rydberg states or hollow ions with multiple inner vacancies; plasma jet and target ions may also undergo charge exchange (CE) processes. We report PWI experiments with Al/Si(PMMA) and Al/C targets irradiated at normal or oblique laser incidence. The distinct dip structures observed in red wings of Al Lyγ self-emission is interpreted in terms of CE between C6+ and Al12+ in the near-wall zone. The spectroscopic identification of CE phenomena is supported by results of analytical and numerical calculations.