Upconversion assisted self-pulsing in a high-concentration erbium doped fiber laser

We report results on experimental and theoretical characterisation of self-pulsing in high concentration erbium doped fibre laser which is free from erbium clusters. Unlike previous models of self-pulsing accounting for pair-induced quenching (PIQ) on the clustered erbium ions, new model has been developed with accounting for statistical nature of the excitation migration and upconversion and resonance-like pumpto-signal intensity noise transfer. The obtained results are in a good agreement with the experimental data

Multi-scale polarisation phenomena

Multi-scale methods that separate different time or spatial scales are among the most powerful techniques in physics, especially in applications that study nonlinear systems with noise. When the time scales (noise and perturbation) are of the same order, the scales separation becomes impossible. Thus, the multi-scale approach has to be modified to characterise a variety of noise-induced phenomena. Here, based on stochastic modelling and analytical study, we demonstrate in terms of the fluctuation-induced phenomena and Hurst R/S analysis metrics that the matching scales of random birefringence and pump–signal states of polarisation interaction in a fibre Raman amplifier results in a new random birefringence-mediated phenomenon, which is similar to stochastic anti-resonance. The observed phenomenon, apart from the fundamental interest, provides a base for advancing multi-scale methods with application to different coupled nonlinear systems ranging from lasers (multimode, mode-locked, random, etc.) to nanostructures (light-mediated conformation of molecules and chemical reactions, Brownian motors, etc.)

Predictors of Serum Dioxins and PCBs among Peripubertal Russian Boys

Background: Although sources and routes of exposure to dioxins and polychlorinated biphenyls (PCBs) have been studied, information regarding exposure among children is limited. Breast-feeding and diet are two important contributors to early life exposure. To further understand other significant contributors to childhood exposure, we studied a cohort of children from a city with high environmental dioxin levels. Objectives: We investigated predictors of serum concentrations of polychlorinated dibenzo-p-dioxins (PCDDs)/polychlorinated dibenzofurans (PCDFs)/co-planar PCBs (C-PCBs), toxic equivalents (TEQs), and PCBs among 8- to 9-year-old boys in Chapaevsk, Russia. Methods: We used general linear regression models to explore associations of log10-transformed serum concentrations of PCDDs/PCDFs/C-PCBs, TEQs, and PCBs at study entry with anthropometric, demographic, geographic, and dietary factors in 482 boys in Chapaevsk, Russia. Results: The median (25th, 75th percentile) concentration for total 2005 TEQs was 21.1 pg/g lipid (14.4, 33.2). Boys who were older, consumed local foods, were breast-fed longer, and whose mothers were employed at the Khimprom chemical plant (where chlorinated chemicals were produced) or gardened locally had significantly higher serum dioxins and PCBs, whereas boys with higher body mass index or more educated parents had significantly lower serum dioxins and PCBs. Boys who lived less than 2 km from Khimprom had higher total TEQs (picograms per gram lipid) [adjusted mean = 30.6; 95% confidence interval (CI), 26.8–35.0] than boys who lived greater than 5 km away (adjusted mean = 18.8; 95% CI, 17.2–20.6). Conclusions: Our findings suggest that there are specific local sources of dioxin and PCB exposure among children in Chapaevsk including maternal gardening, consumption of locally grown food, and residential proximity to the Khimprom plant

АПРИОРНАЯ ОЦЕНКА МЕТРОЛОГИЧЕСКИХ ХАРАКТЕРИСТИК РЕНТГЕНОФЛУОРЕСЦЕНТНЫХ ОПРЕДЕЛЕНИЙ СОДЕРЖАНИЯ ЭЛЕМЕНТОВ И СНИЖЕНИЯ ВЕЛИЧИНЫ МЕЖЭЛЕМЕНТНЫХ ВЛИЯНИЙ ПРИ РАЗБАВЛЕНИИ ПРОБ

A method for a priori estimation of improving the metrological characteristics of X-ray fluorescent definitions of the elements’ content and reducing the inter-elemental influences when diluting the analyzed samples by "heavy" or "light" diluents was demonstrated. The metrological characteristics were evaluated by modeling the measurement process on the scanning X-ray spectrometer using experimentally measured analytical characteristics of the spectrometer. The calculations were performed for the following models: molybdenum with the content of 1 to 80% mas. in light, neutral and heavy fillers, iron in iron ore concentrate at different degrees of dilution with lithium tetra borate and chromium oxide and uranium in corium material at different degrees of dilution with lithium tetra borate and zinc oxide. For the calculations, a method that allowed a priori estimation of the metrological characteristics of quantitative X-ray fluorescence analysis was used. The following metrological characteristics were evaluated: statistical limit of C0 detection using the 3σ criterion, differential sensitivity (η-speed estimates of the analytical line for the percentage of changes in the content of the element) and the average quadratic deviation of the measuring the σC element result content through the basic analytical parameters of the X-ray spectrometer such as integral sensitivity (I0 - experimental analysis line count speed on a single-cell sample), contrast (K-ratio of integral sensitivity to the background score speed), limit of basic hardware error A0 and theoretical coefficients (P-absorption factors) for the material under the known conditions of fluorescence excitation and measurement conditions (T-exposure). It was demonstrated that in the case of small degree of samples dilution with the heavy diluent, the effect of improving the metrological characteristics of X-ray fluorescent content definition was achieved. The same effect was achieved with more dilution by the light diluent. The proposed method of analysis could be used in planning methodical works for the selection of the degree of dilution in the analysis of solvents and powder materials.Keywords: X-ray fluorescent analysis, metrological characteristics, analytical parameters, light diluted, heavy dilutedDOI: http://dx.doi.org/10.15826/analitika.2020.24.1.006  B.D. Kalinin1, S.K. Saveliev2, J.I. Sergeyev3 1“Pretsizion Tekhnologies” Co. Lt, ul. Altai, 12, St. Petersburg, 196066, Russian Federation2Baltic State Technical University, ul.1st Krasnoarmeyskaya, 1, St. Petersburg, 195001, Russian Federation3“Spectron”, NPO LTD, ul. Tsiolkovsky, 10a, St. Petersburg, 190103, Russian FederationПредлагается способ априорной оценки улучшения метрологических характеристик рентгенофлуоресцентных определений содержания элементов и снижения межэлементных влияний при разбавлении анализируемых проб «тяжелым» или «легким» разбавителем. Метрологические характеристики оценивали путем моделирования процесса измерений на сканирующем рентгеновском спектрометре с использованием экспериментально измеренных аналитических характеристик спектрометра. Расчет метрологических характеристик был проведен для моделей: молибден при содержаниях от 1 до 80 % мас. в легком, нейтральном и тяжелом наполнителях, железо в железорудном концентрате при разных кратностях разбавления тетраработатом лития и оксидом хрома и уран в кориумном материале при разных кратностях разбавления тетраборатом лития и оксидом цинка. Для расчета был использован способ, позволяющий априорно оценивать метрологические характеристики количественного рентгенофлуоресцентного анализа: статистический предел обнаружения C0 по критерию 3s, дифференциальную чувствительность (h-скорость счета аналитической линии на процент изменения содержания элемента) и среднее квадратическое отклонение результата измерения содержания элемента sС через основные аналитические параметры рентгеновского спектрометра: интегральную чувствительность (I0 – экспериментальная скорость счета аналитической линии на одноэлементном образце), контрастность (K – отношение интегральной чувствительности к скорости счета фона), предел основной аппаратурной погрешности A0 и теоретические коэффициенты (P – абсорбционные факторы) для исследуемого материала при известных условиях возбуждения флуоресценции и условиях измерения (Т – экспозиция). В результате проведенных исследований показано, что при разбавлении проб тяжелым разбавителем при сравнительно небольшой кратности разбавления достигается эффект улучшения метрологических характеристик рентгенофлуоресцентного определения содержаний элементов и снижения величины межэлементных влияний такой же, как и при большей кратности разбавления легким разбавителем. Предлагаемый способ оценки может быть применен при планировании методических работ для выбора разбавителя и кратности разбавления при анализе растворов и порошковых материалов.Ключевые слова: рентгенофлуоресцентный анализ, метрологические характеристики, аналитические параметры, легкий разбавитель, тяжелый разбавительDOI: http://dx.doi.org/10.15826/analitika.2020.24.1.00

Trapping polarization of light in nonlinear optical fibers: An ideal Raman polarizer

The main subject of this contribution is the all-optical control over the state of polarization (SOP) of light, understood as the control over the SOP of a signal beam by the SOP of a pump beam. We will show how the possibility of such control arises naturally from a vectorial study of pump-probe Raman interactions in optical fibers. Most studies on the Raman effect in optical fibers assume a scalar model, which is only valid for high-PMD fibers (here, PMD stands for the polarization-mode dispersion). Modern technology enables manufacturing of low-PMD fibers, the description of which requires a full vectorial model. Within this model we gain full control over the SOP of the signal beam. In particular we show how the signal SOP is pulled towards and trapped by the pump SOP. The isotropic symmetry of the fiber is broken by the presence of the polarized pump. This trapping effect is used in experiments for the design of new nonlinear optical devices named Raman polarizers. Along with the property of improved signal amplification, these devices transform an arbitrary input SOP of the signal beam into one and the same SOP towards the output end. This output SOP is fully controlled by the SOP of the pump beam. We overview the sate-of-the-art of the subject and introduce the notion of an "ideal Raman polarizer"

The CRESST Experiment: Recent Results and Prospects

The CRESST experiment seeks hypothetical WIMP particles that could account for the bulk of dark matter in the Universe. The detectors are cryogenic calorimeters in which WIMPs would scatter elastically on nuclei, releasing phonons. The first phase of the experiment has successfully deployed several 262 g sapphire devices in the Gran Sasso underground laboratories. A main source of background has been identified as microscopic mechanical fracturing of the crystals, and has been eliminated, improving the background rate by up to three orders of magnitude at low energies, leaving a rate close to one count per day per kg and per keV above 10 keV recoil energy. This background now appears to be dominated by radioactivity, and future CRESST scintillating calorimeters which simultaneously measure light and phonons will allow rejection of a great part of it.Comment: To appear in the proceedings of the CAPP2000 Conference, Verbier, Switzerland, July, 2000 (eds J. Garcia-Bellido, R. Durrer, and M. Shaposhnikov

Association of Blood Lead Levels with Onset of Puberty in Russian Boys

Background: Epidemiologic studies suggest a temporal trend of earlier onset and longer duration of puberty, raising concerns regarding the potential impact of environmental factors on pubertal development. Lead exposure has been associated with delayed pubertal onset in girls; however, epidemiologic data in boys are limited. Methods: We used multivariable logistic regression models to explore the cross-sectional association of blood lead levels with growth and pubertal onset based on physician-assessed testicular volume (TV) and pubertal staging in 489 boys 8–9 years of age from Chapaevsk, Russia. We used multivariable linear regression models to assess associations of blood lead levels with somatic growth at the study entry visit. Results: The median (25th–75th percentile) blood lead level was 3 μg/dL (2–5 μg/dL). Height, weight, body mass index, birth weight, and gestational age were predictive of the onset of puberty as assessed either by TV (greater than 3 mL), genitalia stage (G2), or both. Blood lead level was inversely associated with height (p less than 0.001) and weight (p = 0.06) after adjustment for birth weight, gestational age, and age at examination. In multivariable adjusted analyses, boys with blood lead levels ≥ 5 μg/dL had 43% reduced odds of having entered G2 compared with those with lower levels (odds ratio = 0.57; 95% confidence interval, 0.34–0.95, p = 0.03). Conclusions: Relatively low environmental blood lead levels were associated with decreased growth and differences in pubertal onset in periadolescent Russian boys. Future analyses of this prospective cohort will address pubertal onset and progression in relation to lead and other environmental chemicals

Polarisation dynamics of vector soliton molecules in mode locked fibre laser

Two fundamental laser physics phenomena - dissipative soliton and polarisation of light are recently merged to the concept of vector dissipative soliton (VDS), viz. train of short pulses with specific state of polarisation (SOP) and shape defined by an interplay between anisotropy, gain/loss, dispersion, and nonlinearity. Emergence of VDSs is both of the fundamental scientific interest and is also a promising technique for control of dynamic SOPs important for numerous applications from nano-optics to high capacity fibre optic communications. Using specially designed and developed fast polarimeter, we present here the first experimental results on SOP evolution of vector soliton molecules with periodic polarisation switching between two and three SOPs and superposition of polarisation switching with SOP precessing. The underlying physics presents an interplay between linear and circular birefringence of a laser cavity along with light induced anisotropy caused by polarisation hole burning

Time delay between images of the lensed quasar UM673

We study brightness variations in the double lensed quasar UM673 (Q0142-100) with the aim of measuring the time delay between its two images. In the paper we combine our previously published observational data of UM673 obtained during the 2003 - 2005 seasons at the Maidanak Observatory with archival and recently observed Maidanak and CTIO UM673 data. We analyze the V, R and I-band light curves of the A and B images of UM673, which cover ten observational seasons from August 2001 to November 2010. We also analyze the time evolution of the difference in magnitudes between images A and B of UM673 over more than ten years. We find that the quasar exhibits both short-term (with amplitude of \sim 0.1 mag in the R band) and high-amplitude (\sim 0.3 mag) long-term variability on timescales of about several months and several years, respectively. These brightness variations are used to constrain the time delay between the images of UM673. From cross-correlation analysis of the A and B quasar light curves and error analysis we measure the mean time delay and its error of 89 \pm11 days. Given the input time delay of 88 days, the most probable value of the delay that can be recovered from light curves with the same statistical properties as the observed R-band light curves of UM673 is 95{+5/-16}{+14/-29} days (68 and 95 % confidence intervals). Analysis of the V - I color variations and V, R and I-band magnitude differences of the quasar images does not show clear evidence of the microlensing variations between 1998 and 2010.Comment: Submitted to A&A, 11 pages, 9 figure

Time delays in PG1115+080: new estimates

We report new estimates of the time delays in the quadruple gravitationally lensed quasar PG1115+080, obtained from the monitoring data in filter R with the 1.5-m telescope at the Maidanak Mountain (Uzbekistan, Central Asia) in 2004-2006. The time delays are 16.4 days between images C and B, and 12 days between C and A1+A2, with image C being leading for both pairs. The only known estimates of the time delays in PG1115 are those based on observations by Schechter et al. (1997) -- 23.7 and 9.4 days between images C and B, C and A1+A2, respectively, as calculated by Schechter et al., and 25 and 13.3 days as revised by Barkana (1997) for the same image components with the use of another method. The new values of time delays in PG 1115+080 may be expected to provide larger estimates of the Hubble constant thus decreasing a diversity between the H_0 estimates taken from gravitationally lensed quasars and with other methods.Comment: 5 pages, 2 figures, Accepted for publication in MNRAS Letter