Efficacy and safety of Lacticaseibacillus paracasei Lpc-37® in students facing examination stress: A randomized, triple-blind, placebo-controlled clinical trial (the ChillEx study)

Lacticaseibacillus paracasei Lpc-37 (Lpc-37) has previously shown to reduce perceived stress in healthy adults. The ChillEx study investigated whether Lpc-37 reduces stress in a model of chronic examination stress in healthy students. One hundred ninety university students (18-40 y) were randomized to take 1.56 × 1010 colony-forming units of Lpc-37 or placebo (1:1) each day for 10 weeks, in a triple-blind, parallel, multicenter clinical trial consisting of six visits: two screening visits, a baseline visit, and visits at 4, 8, and 10 weeks after baseline. The primary objective was to demonstrate that Lpc-37 reduces stress, as measured by the change in state anxiety from baseline to just before the first examination, after 8 weeks using the State Trait Anxiety Inventory (STAI-state). Secondary objectives aimed to demonstrate that Lpc-37 modulates psychological stress-induced symptoms and biomarkers related to mood and sleep. An exploratory analysis of fecal microbiota composition was also conducted. There was no difference between Lpc-37 and placebo groups in the change of STAI-state score (estimate 1.03; 95% confidence interval [CI]: -1.62, 3.67; p = 0.446). None of the secondary outcomes resulted in significant results when corrected for multiplicity, but exploratory results were notable. Results showed an improvement in sleep-disturbance scores (odds ratio 0.30; 95% CI: 0.11, 0.82; p = 0.020) and reduction in duration of sleep (odds ratio 3.52; 95% CI: 1.46, 8.54; p = 0.005) on the Pittsburgh Sleep Quality Index questionnaire after 8 weeks in the Lpc-37 group compared to placebo. A reduction in Bond Lader VAS-alertness was also demonstrated in the Lpc-37 group compared to placebo (estimate -3.97; 95% CI: -7.78, -0.15; p = 0.042) just prior to the examination. Analysis of fecal microbiota found no differences between study groups for alpha and beta diversity or microbiota abundance. Adverse events were similar between groups. Vital signs, safety-related laboratory measures, and gastrointestinal parameters were stable during the trial. In conclusion, probiotic Lpc-37 was safe but had no effect on stress, mood, or anxiety in healthy university students in this model of chronic academic stress. ClinicalTrials.gov: NCT04125810.

Reduction formula for cross-spectral purity of nonstationary light fields

We examine cross-spectral purity of random, nonstationary (pulsed), scalar light fields with arbitrary spectral bandwidth. In particular, we derive a reduction formula in terms of time-integrated coherence functions, which ensures cross-spectral purity of interfering fields having identical normalized spectra. We further introduce fields that are cross-spectrally pure in either a global or local sense. Our analysis is based on an ideal field superposition realizable with all-reflective wavefront-shearing interferometers. Such devices avoid certain problems related to Young's interferometer, which is the framework customarily employed in assessing cross-spectral purity. We show that any partially coherent beam can be transformed into a locally cross-spectrally pure beam whose cross-spectral density is specular. On the other hand, lack of space-frequency (and space-time) coupling ensures cross-spectral purity in the global sense, i.e., across an entire transverse plane, regardless of the spectral bandwidth or the temporal shape of the pulses.

Feasibility of neural network metamodels for emulation and sensitivity analysis of radionuclide transport models

In this paper we compare the outputs of neural network metamodels with numerical solutions of differential equation models in modeling cesium-137 transportation in sand. Convolutional neural networks (CNNs) were trained with differential equation simulation results. Training sets of various sizes (from 5120 to 163,840) were used. First order and total order Sobol methods were applied to both models in order to test the feasibility of neural network metamodels for sensitivity analysis of a radionuclide transport model. Convolutional neural networks were found to be capable of emulating the differential equation models with high accuracy when the training set size was 40,960 or higher. Neural network metamodels also gave similar results compared with the numerical solutions of the partial differential equation model in sensitivity analysis.

On the inclusion of forest exposure pathways into a stylized lake-farm scenario in a geological repository safety analysis

Geological disposal of radioactive waste has been recognized as the 'reference solution' to ensure the safety required for the present and future society and environment. To study the possible exposure pathways from groundwater to humans, radioactive transport modelling is used. One of the ecosystems that may play a significant role when assessing the dose conversion factor (i.e. the dose resulting from a nominal release of 1 Bq/year of each radionuclide) for humans is forest. In this paper we have developed a model of a lake-farm system with a forest component. The biosphere system used in this study represents a typical agricultural scenario in Finland, amended with a typical forest. A lake is assumed to form due to post-glacial land uplift. The main features of this future lake have been obtained from our probabilistic shoreline displacement model. Both deterministic calculations and sensitivity analysis were carried out to simulate the model. The deterministic simulation demonstrates the behaviour of the studied radionuclides (36Cl, 135Cs, 129I, 237Np, 90Sr, 99Tc and 238U) and the proportions of different exposure pathways to humans. Particularly for 135Cs and 129I, forest pathways make a notable contribution to the dose conversion factor. The sensitivity analysis was done using two methods: EFAST and Sobol'. With both methods, the parameters related to the farm contribute the most to the variance of the dose conversion factor for humans. The study demonstrates that the exposure pathways related to forest products may make a considerable contribution to the dose conversion factor in a lake-farm-forest system. It is also confirmed that an advanced sensitivity analysis for a radionuclide transport and dose assessment model on such a landscape scale is feasible even with moderate computational efforts.

Measurement of spatial coherence of light [Invited]

The most frequently used experimental techniques for measuring the spatial coherence properties of classical light fields in the space-frequency and space-time domains are reviewed and compared, with some attention to polarization effects. In addition to Young's classical two-pinhole experiment and several of its variations, we discuss methods that allow the determination of spatial coherence at higher data acquisition rates and also permit the characterization of lower-intensity light fields. These advantages are offered, in particular, by interferometric schemes that employ only beam splitters and reflective elements, and thereby also facilitate spatial coherence measurements of broadband fields.

Psychotherapy and change in mental health-related work disability - A prospective population level register-based study in Finland

Introduction

Mental disorders are a major cause of work disability among working age population. Psychotherapy has been shown to be an effective treatment for mental disorders, but the evidence mainly comes from small scale randomised trials with a relatively short follow-up.

Objectives

We used population-based register data to examine the association between statutory rehabilitative psychotherapy and change in depression or anxiety related work disability using a quasi-experimental interrupted time series analysis.

Methods

All those who started rehabilitative psychotherapy in 2011-2014 comprised the study group. The study group included 10436 participants who were followed from three years prior to four years after the onset of rehabilitative psychotherapy, resulting in 83488 observations. Annual total number of mental health related work disability months was calculated based on total number of annual compensated sickness absence and disability pension days.

Results

The onset of rehabilitative psychotherapy marked a decline in depression or anxiety related work disability as compared to the counterfactual trend. Specifically, a 20% decrease in the level (incidence rate ratio, IRR 0.80; 95% CI 0.76-0.85) as well as a 48% decrease in the slope (IRR 0.52; 95% CI 0.50-0.54) of work disability was detected. The decline was steepest in the oldest age-group

Conclusions

Providing statutory psychotherapy may decrease work disability at the population level. Further evidence for causal inference and the potential heterogeneity of the association is required.

Psychotherapy – A Sound Investments In (Mental) Health Capital?

Introduction

The concept of health capital views health as a form of capital that produces healthy time to individual. This stock of capital - health that is - can decrease or increase. The potential of psychotherapy as individual's investment to (mental) health capital has been rarely studied in population level.

Objectives

The aim of our study is to shed light on the returns on individual-level investments in health capital. We consider the use of psychotherapy as an investment in health capital. This investment offers potential returns for individual as a higher level of subsequent income. However, these returns are potentially heterogenous: we aim to show to whom the use of psychotherapy is a sound investment in health capital.

Methods

We model the effects of mental health, and subsequent treatments such as the use of psychotropics and psychotherapy on income using two-way fixed effects regression.

Results

Preliminary results show that different parts of working-age population seem to have different potential returns related to the use of psychotherapy. These heterogenous effects are related to previously reported socioeconomic status related disparities: the level of human capital i.e. income and education play a role in the profitability of the individual level investment made in the health capital by the use of psychotherapy.

Conclusions

The use of psychotherapy has heterogenous effects on the income of individuals. The potential of this investment to produce health capital varies with education, the level of income prior to the use of psychotherapy.

Socioeconomic factors affecting psychotherapy use rates

Objectives

Previous studies indicate socioeconomic inequalities in psychotherapy utilization. The aim of this study was to assess the associations of individual annual incomes with the utilization of long-term rehabilitative psychotherapy during nine-year follow-up in men and women. As secondary analyses we assessed the association of main activity with the utilization of psychotherapy.

Methods

For this study, we selected those from a random sample of the working-age population (18-55 years) with information about income at each time point during the follow-up from 2011 to 2019 (N = 736 613). Psychotherapy usa during the follow-up period served as dependent variable and sosiodemographic variables, annual incomes and main activity (employed, unemployed, studying, other) were used as independent variables. To examine change in the psychotherapy use rates over time, we used sex-stratified generalized estimating equations logistic regression models with predicted marginal probabilities.

Results

Psychotherapy use rate was constantly higher among women than in men (in 2011 0.8% and 0.2%) and increased from 2011 to 2019 among both genders and income quartiles (among women 174% - 231% and among men 213% - 248% increase between quartiles). Among men, psychotherapy use rate was highest among lowest income quartile throughout the study interval. Among women such difference was not observed. Among women, studentś psychotherapy use increased significantly when compared to other groups from 2011 to 2019 (299% increase vs 89% - 210% increase among other groups). A similar pattern was seen among studying men versus other groups.

Conclusions

Between 2011 and 2019 the probability of having psychotherapy increased among both genders. Unexpectedly, pro-rich psychotherapy use rate was not observed. The highest probability to use psychotherapy in lowest income quartile might be linked with differences in health care systems for students and for other.

Pulse modulation by Bloch surface wave excitation

Considering dielectric multilayers with N identical bilayers and an additional terminating layer, we address the effect of Bloch surface wave excitation on the temporal characteristics of short optical pulses. When such a resonant excitation occurs within the spectrum of the incident pulse, the reflected pulse splits into leading and trailing parts, the latter having an exponentially decaying tail. The role of the number of bilayers and the level of absorption in the multilayer stack is illustrated.

Pulse shaping by spectral-domain polarization gratings

We consider the spectral-domain counterparts of spatial-domain polarization gratings and study their effect on the temporal evolution of femtosecond-scale light pulses. These devices divide an incident light pulse to several orders via spectral polarization modulation, permitting pulse splitting and shaping with controlled time-domain polarization dynamics.

Azimuthally periodic and radially quasi-periodic Bessel-correlated fields

We introduce a class of partially coherent sources, which are capable of producing beams with radially quasi-periodic and azimuthally fully periodic intensity profiles. The physical properties of the source, as well as the propagation of the intensity distribution and the complex degree of spatial coherence of the ensuing beams are investigated and interpreted. It is shown that the shape and symmetry of the intensity and the degree of spatial coherence are generally adjustable and modulated by the parameters related to the beam source. Moreover, the periodic changes of intensity arise from the discontinuity of the phase. The results provide a method for synthesizing fields with peculiar periodic intensity distributions in polar coordinates.

Propagation of Bessel-correlated specular and antispecular beams

We address the specular properties of Bessel-correlated fields, generated by illuminating a tilted rotating plane-parallel glass plate with a coherent Gaussian beam and passing the output beam though a mirror-based wavefront folding interferometer. This device allows us to produce beams whose specular properties are preserved in propagation. In the far zone, the specular nature of these partially coherent fields is shown to produce intensity-profile oscillations in the sub-diffraction-limit scale. The analytical results at various propagation distances are verified experimentally by using another wavefront-folding interferometer for coherence measurements.

Coherence Switching with Metamaterials

We demonstrate, theoretically, how the insertion of an enhanced epsilon-near-zero (EENZ) mirror in a laser cavity grants exceptional control over the coherence properties of the emitted light beam. By exploiting the peculiar sensitivity to polarization of EENZ materials, we achieve superior control over the spatial coherence of the emitted laser light, which can be switched at will between nearly incoherent and fully coherent, solely by means of polarization optics. Our EENZ cavity design is expected to be an efficient, compact, reconfigurable, and easily scalable source of light for illumination and speckle contrast imaging, as well as any other application that benefits from controlled spatial coherence.

Measuring therapeutic engagement in finnish adult acute psychiatric in-patient care units using the finnish version of therapeutic engagement questionnaire (TEQ)

Introduction

The Therapeutic Engagement Questionnaire (TEQ) has been developed and validated in partnership with service users (SUs), registered mental health nurses (RMHNs) and nurse academics in the UK in accordance with psychometric theory. The TEQ is highly relevant and useful to clinical practice. The TEQ measures therapeutic engagement (TE) in two contexts - 1-1 interactions between SUs and RMHNs, as well as the overall environment and atmosphere of the units - from the perspective of both SUs and RMHNs. The TEQ has been translated into Finnish by two expert panels and was pre-tested and validated in ten adult acute psychiatric in-patient units in two hospitals in Finland.

Objectives

To measure TE in Finnish adult acute in-patient psychiatric settings from the perspectives of both SUs and RMHNs.

Methods

The Finnish version of the TEQ (Hoidollinen yhteistyö) will be completed by RMHNs and SUs in 15 adult acute psychiatric in-patient units. Nine of the units are within the University Hospital and six in a municipal psychiatric hospital. The data will be collected within a 3-month period (October - December 2020). The coordinating nurse of each unit will organise the operational side of the study including obtaining consent from SUs. The nurses will participate in the survey via Webropol which includes nurses’ consent. Sociodemographic information will be collected from the SUs and nurses.

Results

The results of the measurement study will be reported at the 29th European Congress of Psychiatry.

Conclusions

The conclusions of the measurement study will be reported at the 29th European Congress of Psychiatry.

Conflict of interest

This study is supported by the National Institute for Health Research (NIHR) Applied Research Collaboration South London (NIHR ARC South London).

Correlated and uncorrelated parts of scalar fields in two-beam optical interferometry

We show that in the interference of two partially correlated scalar light beams, the fields can be divided into parts that are mutually completely correlated (coherent) and parts that are fully uncorrelated with the correlated parts and with each other. Such correlated and uncorrelated parts cannot, in general, be unambiguously specified, but with a certain additional constraint, the partition becomes unique and can be determined. We demonstrate experimentally that the uncorrelated contribution can be physically isolated with the help of a spatial unitary transformation, such as a nonabsorbing beam splitter. Our findings constitute foundational results on optical two-beam interferometry.

Hydroxychloroquine in the treatment of adult patients with Covid-19 infection in a primary care setting (LIBERTY): A structured summary of a study protocol for a randomised controlled trial

Objectives

The primary objective of this study is to evaluate the therapeutic potential of hydroxychloroquine (HCQ) in the treatment of adult patients with PCR-confirmed Covid-19 infection in a primary open-care setting, as compared to placebo. The study hypothesis is that treatment with HCQ will reduce the risk of hospitalization because of Covid-19 infection, and the sample size estimate of the study is based on the need to test this hypothesis.

The secondary objectives of the study are:

to evaluate the safety and tolerability of HCQ in the treatment of adult patients with PCR-confirmed Covid-19 infection in a primary open-care setting, as compared to placebo;

to collect experience of the use of HCQ in the treatment of Covid-19 infection in outpatients, in order to be able to identify patient characteristics that predict specific treatment responses (favourable or unfavourable); this objective will also be addressed by post-hoc subgroup analysis of the study results and by meta-analysis of pooled patient data from other clinical trials of HCQ in outpatients; and

to evaluate the impact of Covid-19 infection and its treatment on the mental health and well-being of the study participants.

In addition, if the data allow, the study has the following exploratory objectives:

to evaluate the extent and duration of SARS-CoV-2 viral shedding by PCR testing of nasopharyngeal swab samples in study subjects treated with HCQ, as compared to placebo;

to evaluate the extent and time course of SARS-CoV-2 virus-specific antibody responses in serum of study subjects treated with HCQ, as compared to placebo;

to evaluate other possible biomarker changes in blood in study subjects treated with HCQ, as compared to placebo;

to explore the possible effects of genetic variation in drug metabolizing enzymes on HCQ-related outcomes in the study population;

to explore the associations of HCQ-related outcome variables with other patient characteristics, e.g. HLA haplotypes, HCQ concentrations, demographic variables, disease history and concomitant medications.

Trial design

This is a phase 2, placebo-controlled, double-blind, randomized, parallel-group treatment trial comparing HCQ with placebo in outpatients with Covid-19 infection. Participants will be randomized in a 1:1 ratio to the two treatment arms.

Participants

Main inclusion criteria:

Males and females >40 years of age, or 18-40 years of age with one or both of the following: i. diabetes mellitus (type 1 or type 2); ii. BMI > 35 kg/m²;

Valid independent informed consent obtained;

Symptoms typical of Covid-19 infection, according to criteria specified in the study protocol. The onset of symptoms must be within 5 days of enrolment;

Positive SARS-CoV-2 PCR test result of a nasopharyngeal swab sample.

Main exclusion criteria:

1. Suspected severe or moderately severe pneumonia, presenting with any of the following: respiratory rate > 26 breaths/min; significant respiratory distress; or SpO₂ ≤94% on room air;

2. Requiring treatment in the hospital, according to the treating physician’s judgement;

3. Any contraindication to treatment with HCQ;

4. Pregnancy or lactation.

The trial will be conducted at seven study sites in a primary public health care setting in the region of Satakunta, Finland.

Intervention and comparator

Participants will be randomized to receive either HCQ capsules at 300 mg twice a day for one day and then 200 mg twice a day for 6 days, or placebo capsules for 7 days.

Main outcomes

The primary endpoint of the study is the number of hospitalizations due to Covid-19 infection within four weeks of entry into the study.

The secondary endpoints of the study include the following:

duration and severity of Covid-19-related symptoms, as reported by daily self-assessments;

number of Intensive Care Unit treatment episodes due to Covid-19 infection within four weeks of entry into the study;

number of deaths due to Covid-19 infection within four weeks of entry into the study;

number of treatment-related adverse events (AEs) and serious AEs (SAEs);

all-cause hospitalizations and mortality within six months of entry into the study; and

self-assessed symptoms of anxiety, as assessed with repeated administration of the Generalized Anxiety Disorder 7-item scale (GAD-7).

The exploratory endpoints of the study include the following:

extent and duration of SARS-CoV-2 viral shedding and virus-specific antibody responses in serum; and

possible other blood biomarker changes.

Randomisation

Eligible study participants are randomly allocated into two treatment arms (1:1 ratio). The randomization list has been generated using Viedoc™ (Viedoc Technologies AB, Uppsala, Sweden) that is used as an electronic data capture system for this study.

Blinding (masking)

The participants and all study personnel remain blinded to the treatment allocation by having both IMPs packed in identical containers. Masking of the treatments was performed by re-formulation of the IMPs so that the HCQ capsules and the placebo capsules have identical appearance.

Numbers to be randomised (sample size)

600 participants are to be randomised with 300 in each arm.

Trial Status

Protocol version 2, dated 14 July 2020; recruitment is expected to start in December, 2020, and to be completed in June, 2021.

Trial registration

EudraCT 2020-002038-33, registered 26 June 2020

Full protocol

The full protocol is attached as an additional file, accessible from the Trials website (Additional file 1). The protocol has been redacted to conform with privacy regulations by deleting the names and contact information of individuals mentioned in the protocol but not listed as authors in this communication. In the interest of expediting dissemination of this material, the familiar formatting has been eliminated; this Letter serves as a summary of the key elements of the full protocol.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-020-04989-6.

Comparison of absorption simulation in semiconductor nanowire and nanocone arrays with the Fourier modal method, the finite element method, and the finite-difference time-domain method

For the design of nanostructured semiconductor solar cells and photodetectors, optics modelling can be a useful tool that reduces the need of time-consuming and costly prototyping. We compare the performance of three of the most popular numerical simulation methods for nanostructure arrays: the Fourier modal method (FMM), the finite element method (FEM) and the finite-difference time-domain (FDTD) method. The difference between the methods in computational time can be three orders of magnitude or more for a given system. The preferential method depends on the geometry of the nanostructures, the accuracy needed from the simulations, whether we are interested in the total, volume-integrated absorption or spatially resolved absorption, and whether we are interested in broadband or narrowband response. Based on our benchmarking results, we provide guidance on how to choose the method.

Genuine-field modeling of partially coherent X-ray imaging systems

A genuine representation of the cross-spectral density function as a superposition of mutually uncorrelated, spatially localized modes is applied to model the propagation of spatially partially coherent light beams in X-ray optical systems. Numerical illustrations based on mode propagation with VirtualLab software are presented for imaging systems with ideal and non-ideal grazing-incidence mirrors.

Mirror-based scanning wavefront-folding interferometer for coherence measurements

We demonstrate a modification to the traditional prism-based wavefront-folding interferometer that allows the measurement of spatial and temporal coherence, free of distortions and diffraction caused by the prism corners. In our modified system, the two prisms of the conventional system are replaced with six mirrors. The whole system is mounted on a linear XY-translation stage, with an additional linear stage in the horizontal arm. This system enables rapid and exact measurement of the full four-dimensional degree of coherence, even for relatively weak signals. The capabilities of our system are demonstrated by measuring the spatial coherence of two inhomogeneous and non-Schell model light sources with distinct characteristics.

Large-angle beaming from asymmetric nanoslit-corrugation structures

The beaming effect in single apertures surrounded by periodic corrugations and the manipulation of beaming directions from such structures has gained considerable attention since discovery. Different materials and structural profiles have been studied in this context but directional beaming at angles larger than 45° has not been achieved. We design and demonstrate nanoslits in a gold film flanked by corrugations, which give rise to beaming angles ranging from 45° to 60°. While the previous designs are based on achieving constructive interference at the aimed beaming angle, our approach complements such constructive interference with destructive interference at 0° and, as a result, enhances the directional beaming effect at angles larger than 45°. The structures are fabricated by electron beam lithography with two consecutive lift-off processes. The experimental far-field intensity distributions agree well with the designs.

Temporal coherence and polarization modulation of pulse trains by resonance gratings

We analyze the effects of subwavelength-period resonance gratings on temporally partially coherent optical plane-wave pulse trains. The interaction of the grating with pulses is simulated with the Fourier modal method and finite-difference time-domain method whose performances are compared. Both TE and TM linearly polarized Gaussian Schell-model pulse trains are examined, and partial temporal coherence is modeled with the identical elementary-pulse method. The polarization-dependent response of the grating is seen to lead to significant variations in the average intensity, polarization properties, and degree of temporal coherence of the reflected (and transmitted) pulse trains when the coherence time and polarization state of the incident field are altered. As an important example, we demonstrate that a fully polarized incident pulse train can become partially polarized in grating reflection. The results find use in tailoring of random electromagnetic pulse trains.

Labor market outcomes before and after first episode of part-time sickness absence

Background

Previous research suggests that part-time sickness absence (PTSA) results in better work participation compared to full-time sickness absence (FTSA), but few studies have examined trends in FTSA and unemployment before and after PTSA.

Methods

This Finnish population-based cohort study included 3406 individuals with first episode (>30 days) of PTSA in 2011 (=PTSA group), 42 510 individuals with FTSA (>30 days) in 2011 (=FTSA group), and 25 167 individuals with no sickness absence (>30 days) in 2011 from the general working-age population. Annual days of FTSA from 2007 to 2015 and unemployment from 2012 to 2015 were measured for the participants of each group. We modeled trends and relative risks for these labor market outcomes using negative binomial regression with generalized estimation equations.

Results

For the PTSA group, the adjusted mean annual number of FTSA days was 3 in the beginning of the follow-up, 15 a year before the index year, and 8-10 after the index year. The adjusted risk ratio (RR) of FTSA days after versus before PTSA was 1.95 (95% CI 1.75-2.17). For the FTSA group, mean of sickness absence days was 4 in the beginning, 13 a year before the index year and 9-19 after the index year. The mean of FTSA was 1-2 throughout the follow-up in the general population. An increasing slope in unemployment after the index year was observed in all groups, the absolute level of unemployment being highest among FTSA group and lowest among the general population group.

Conclusions

Long-term PTSA marks a decline in labour market participation. In absolute terms this decline is smaller than that in employees with long-term FTSA.

Key messages

Part-time sickness absence lasting >30 days marked an increase in full-time sickness absence although the absence levels did not reach those observed after full-time sickness absence of > 30 days. Our results show smaller impairment in labour market outcomes in employees granted a long-term part-time sickness absence than in those with long-term full-time sickness absence.

Temporal coherence modulation of pulsed, scalar light with a Fabry-Pérot interferometer

We analyze the effect of a high-finesse Fabry-Pérot interferometer on the temporal coherence properties of scalar optical plane-wave pulse trains. We focus on the cases of single-peak and double-peak transmissions of Gaussian Schell-model (GSM) and supercontinuum (SC) pulses. For the GSM light, we show how the characteristics of the average intensity and temporal degree of coherence of the transmitted pulses depend on the coherence parameters of the incident field. Regarding the SC light, the output is found to depend specifically on the location of the transmission peak(s) within the average spectrum. The results demonstrate that a Fabry-Pérot etalon can act as a simple passive element for tailoring the temporal (and spectral) coherence properties of optical pulse trains.

Imaging-quality 3D-printed centimeter-scale lens

Three-dimensional (3D) printing of imaging-quality optics has been challenging due to the tight tolerances on surface shape and roughness. We report on manufacturing such optics with Print optical Technology, which is based on modified ink-jet printing. We demonstrate for the first time a 3D-printed singlet lens with a surface profile deviation of ±500 nm within a 12-mm aperture diameter. Its RMS surface roughness is below 1 nm without surface polishing. The printed lens exhibits an imaging resolution of some 140 lp mm ^-1 at 100-mm focal length in the visible region.

Scanning wavefront folding interferometers

We present modified scanning-type wavefront folding interferometers (WFIs), which allow spatial coherence measurements of non-uniformly correlated fields, where the degree of coherence is a function of two absolute spatial coordinates instead of coordinate separation only (Schell model). As an alternative to conventional prism-based WFI implementations, we introduce a scheme based on reflections by three mirrors. This setup allows us to avoid obstructions due to prism corners, and it is remarkably robust to polarization effects. Experimental results on measurement of fields that do not obey the Schell model are provided with the three-mirror WFI, and the results are compared to those obtained with a Young's interferometer realized using a digital micromirror device.

Interferometry and coherence of nonstationary light

We consider temporally integrating interferometric measurements and their relation to the coherence properties of nonstationary light. We find that performing such experiments as a function of time delay is equivalent to spectrally resolving the interference patterns, and time-domain coherence information can be obtained from field autocorrelation only if the source is of the Schell-model type. In an analogy to autocorrelation, we introduce field cross-correlation, which can be used to determine the complete complex field of unknown signal pulses if suitable probe pulses are available. We demonstrate our findings with simulated supercontinuum and free-electron laser ensembles, and discuss the prospect of carrying out experiments.

Temporal modes of stationary and pulsed quasistationary electromagnetic beams

We present a novel time-domain coherent-mode representation for random, stationary electromagnetic beams. We subsequently introduce random, quasistationary pulsed electromagnetic beams and develop an analogous (pseudo) mode decomposition for them as well. The former decomposition is valid provided the time window in which the field is considered is much longer than the coherence time, while the latter requires the field to vanish outside the window. For stationary beams, the theory is demonstrated by an example illustrating the role of polarization in the representation. In both cases, the data needed for the construction of the mode decomposition are straightforward to measure. The formalisms enable us to treat random vector-light beams in the time domain in terms of deterministic fields. We expect that the modal representations will find a wide range of applications in problems involving spatiotemporal propagation of temporally partially coherent light in optical systems.

Paraxial propagation of a class of Bessel-correlated fields

The propagation of a novel class of paraxial spatially partially coherent beams exhibiting Bessel-type correlations is studied in free space and in paraxial optical systems. We show that, under certain conditions, such beams can have functionally identical forms of the absolute value of the complex degree of spatial coherence not only at the source plane and in the far zone, but also at all finite propagation distances. Under these conditions the degree of spatial coherence properties of the field is a shape-invariant quantity, but the spatial intensity distribution is only approximately shape-invariant. The main properties of this class of model beams are demonstrated experimentally by passing a coherent Gaussian beam through a rotating wedge and measuring the coherence of the ensuing beams with a Young-type interferometer realized with a digital micromirror device.

Iterative design of diffractive elements made of lossy materials

Diffractive surface relief elements made of lossy materials exhibit phase-dependent absorption, which not only reduces the efficiency but also distorts the signal if the surface profile is realized on the basis of a phase-only design. We introduce an extension of the iterative Fourier transform algorithm, which accounts for such phase-dependent absorption, and present examples of its application to the design of diffractive beam splitters. The operator required for taking absorption into account is chosen to maximize the efficiency of the found design.

Bessel-correlated supercontinuum fields

We examine the spatial coherence properties of supercontinuum fields generated by illuminating rotating bulk media with intense pulsed beams. Theoretical models are presented, which indicate the possibility of generating a class of Bessel-correlated fields (in time-averaged sense) using tilted plane-parallel glass plates and wedges as media for generation of supercontinuum radiation. In special cases, the ensuing fields have a strictly identical functional form in the spatial and angular domains. Some of the main results are verified experimentally by measuring the spatial coherence properties of bulk-generated supercontinuum fields using a wavefront-folding interferometer.

Quasi-monochromatic modes of quasi-stationary, pulsed scalar optical fields

We investigate the temporal coherence of random, pulsed, quasi-stationary scalar light fields and introduce a new type of expansion for the mutual coherence function in terms of fully coherent frequency-shifted quasi-monochromatic modes of identical shape. The mode representation is valid provided the pulse length is shorter and the coherence time is much shorter than the width of the time window in which the field is considered. The construction of the expansion is particularly straightforward since information is required only on the average spectrum and the average temporal intensity. The method enables us to assess the coherence properties of quasi-stationary light by analyzing the behavior of deterministic quasi-monochromatic fields. The frequency-domain counterpart of the representation is also given. The method is illustrated by application to a pulsed free-electron laser source.

Self-focusing of a partially coherent beam with circular coherence

In a recent publication [Opt. Lett.42, 1512 (2017)OPLEDP0146-959210.1364/OL.42.001512], a novel class of partially coherent sources with circular coherence was introduced. In this paper, we examine the propagation behavior of the spectral density and the spectral degree of spatial coherence of a beam generated by such a source in free space and in oceanic turbulent media. It is found that the beam exhibits self-focusing, which is dependent on the initial coherence and the parameters of oceanic turbulence. The self-focusing phenomenon disappears when the initial coherence is high enough or the oceanic turbulence is strong. The area of high coherence appears in the center and along two diagonal lines. With increasing turbulence, the coherence area reduces gradually along one diagonal line and is retained along the other one. A physical interpretation of the self-focusing phenomenon is presented, and potential applications in optical underwater communication and beam shaping are considered.

Grating interferometer for light-efficient spatial coherence measurement of arbitrary sources

We present a theoretical analysis and experimental verification of a z-scanning double-grating interferometer for spatial coherence measurements in space-frequency and space-time domains. This interferometer permits the measurement of spatial coherence between an arbitrary pair of points along a one-dimensional line, and in favorable conditions, it has a high light efficiency compared to the classical Young's two-pinhole experiment. The scheme is applicable to both quasi-monochromatic and broadband sources that need not obey the Schell model. We first provide experimental results with several narrowband primary and secondary sources, and then apply the technique to broadband sources with discrete and continuous spectra. In the latter case, the complex degree of (time-domain) spatial coherence is retrieved from spectrally resolved measurements using the Friberg-Wolf theorem [Opt. Lett.20, 623 (1995)OPLEDP0146-959210.1364/OL.20.000623]. We compare all results to those obtained with Young's interferometer realized using a digital micromirror device.

Dielectric V-ridge gratings: transition from antireflection to retroreflection

We present a systematic study of the optical properties of dielectric gratings with symmetric V-shaped ridges having a 90 degree apex angle and refractive index n. Such structures exhibit completely different optical properties if the dimensions are scaled with respect to the vacuum wavelength λ₀ of light. In the subwavelength domain, where the grating period d is less than λ₀/n, the grating behaves as an antireflection layer. In the large-period domain d≫λ₀ (with normal incidence from the dielectric side), the grating turns into a micro-retroreflector array. The transition between these well-known domains is studied using rigorous diffraction theory. The results are verified experimentally by fabricating and characterizing V-profile gratings with the aid of wet etching of silicon using a process that defines a 90 degree apex angle and replication into a polymer.

Upper bound of signal-relevant efficiency of constrained diffractive elements

We define the signal-relevant efficiency (SRE) of a diffractive optical element as a measure of the proportion of the incident field power that ends up in the desired output signal. An upper bound for SRE is determined in the presence of arbitrary constraints imposed on the element, such as phase-dependent loss due to absorption within the microstructure and quantization of the surface profile. We apply the theory to the important class of diffractive elements that contain only one desired diffraction order (such as diffractive lenses) and derive the surface profile that provides the highest efficiency allowed by the constraints.

Probabilistic assessment of the influence of lake properties in long-term radiation doses to humans

The assessment processes concerning the safety of nuclear waste repositories include the modelling of radionuclide transport in biosphere and the evaluation of the doses to the most affected humans. In this paper, a scenario, in which a contaminated lake is the water source for drinking water, irrigation water and watering of livestock, is presented. The objective of the paper is to probabilistically study the influence of lake properties as parameters in the assessment scenario. The properties of the lake are a result of previously conducted probabilistic studies, where the land uplift of the terrain surrounding the repositories and the formation of water bodies were studied in a 10,000-year time span using Monte Carlo simulation. The lake is formed at 3000 years from present day and the changing properties of the lake have been used in the study. The studied radionuclides ³⁶Cl, ¹³⁵Cs, ¹²⁹I, ²³⁷Np, ⁹⁰Sr, ⁹⁹Tc and ²³⁸U enter the lake with a rate of 1 Bq/year. The transport process from the lake water to humans is described and the doses (dose conversion factors) to adult humans are evaluated based on a study on average food consumption. Sensitivity analysis is used for identifying the parameters having the most influence on the outcome of the dose. Based on the results from the sensitivity analysis, the volumetric outflow rate of the lake and the volume of the lake were taken into closer consideration. The results show the influence of probabilistically derived geomorphic lake input parameters on the dose.

Percutaneous transcatheter renal embolization with absolute ethanol for uncontrolled nephrotic syndrome: Case reports

Purpose: To retrospectively evaluate renal ethanol embolization in 2 patients with uncontrolled nephrotic syndrome.

Material and Methods: Three kidneys in 2 patients with uncontrolled nephrotic syndrome were embolized with absolute ethanol. The embolization technique, patient outcome and complications were analyzed retrospectively.

Results: The treatment was successful in both patients, with angiography-verified exclusion of blood flow to the renal arteries. Elimination of proteinuria was achieved in both patients and their body weight decreased by 25 and 10 kg, respectively. Hospitalization and protein substitution were no longer needed. No complications occurred.

Conclusion: Permanent bilateral ethanol embolization of the renal arteries is a feasible method of managing a treatment-resistant nephrotic syndrome in selected patients. Non-target embolization can be avoided by using a balloon occlusion catheter.

Experimental Measurement of the Second-Order Coherence of Supercontinuum

We measure experimentally the second-order coherence properties of supercontinuum generated in a photonic crystal fiber. Our approach is based on measuring separately the quasicoherent and quasistationary contributions to the cross-spectral density and mutual coherence functions using a combination of interferometric and nonlinear gating techniques. This allows us to introduce two-dimensional coherence spectrograms which provide a direct characterization and convenient visualization of the spectrotemporal coherence properties. The measured second-order coherence functions are in very good agreement with numerical simulations based on the generalized nonlinear Schrödinger equation. Our results pave the way towards the full experimental characterization of supercontinuum coherence properties. More generally, they provide a generic approach for the complete experimental measurement of the coherence of broadband sources.

On spectral and temporal coherence of x-ray free-electron laser beams

A model for the coherence properties of free-electron lasers (FELs) in time and frequency domains is introduced within the framework of classical second-order coherence theory of nonstationary light. An iterative phase-retrieval algorithm is applied to construct an ensemble of field realizations in both domains, based on single-pulse spectra measured at the Linac Coherent Light Source (LCLS) in self-amplified spontaneous emission mode. Such an ensemble describes the specific FEL pulse train in a statistically averaged sense. Two-time and two-frequency correlation functions are constructed, demonstrating that the hard X-ray free-electron laser at LCLS in this case behaves as a quasistationary source with low spectral and temporal coherence. We also show that the Gaussian Schell model provides a good description of this FEL.

Temporal coherence characterization of supercontinuum pulse trains using Michelson's interferometer

Temporal coherence properties of supercontinuum pulse trains generated in nonlinear fibers are analyzed within the framework of the second-order coherence theory of nonstationary light. Time-resolved Michelson's interference patterns are simulated, from which the full two-time mutual coherence function can (at least in principle) be determined experimentally. Standard time-integrated Michelson's interferograms are also simulated and shown to provide a rough estimate for the coherence time of the quasi-stationary contribution. A simple but illustrative analytical model representing supercontinuum pulse trains is presented, and numerically simulated realizations of such pulse trains are considered.

Experimental Demonstration of Spectral Intensity Optical Coherence Tomography

We demonstrate experimentally spectral-domain intensity optical coherence tomography using a Mach-Zehnder interferometer with balanced detection. We show that the technique allows for a point spread function with reduced full-width at half maximum compared to conventional optical coherence tomography. The method further provides benefits similar to those of chirped-pulse interferometry in terms of dispersion cancellation but only requires a broadband incoherent source and standard detectors. The measurements are in excellent agreement with the theoretical predictions. Finally, we propose an approach that enables the elimination of potential artefacts arising from multiple interfaces.

Conversion electron spectrometry of Pu isotopes with a silicon drift detector

An electron spectrometry set-up was built at IRMM consisting of a vacuum chamber with a moveable source holder and windowless Peltier-cooled silicon drift detector (SDD). The SDD is well suited for measuring low-energy x rays and electrons emitted from thin radioactive sources with low self-absorption. The attainable energy resolution is better than 0.5keV for electrons of 30keV. It has been used to measure the conversion electron spectra of three plutonium isotopes, i.e. (238)Pu, (239)Pu, (240)Pu, as well as (241)Am (being a decay product of (241)Pu). The obtained mixed x-ray and electron spectra are compared with spectra obtained with a close-geometry set-up using another SDD in STUK and spectra measured with a Si(Li) detector at IRMM. The potential of conversion electron spectrometry for isotopic analysis of mixed plutonium samples is investigated. With respect to the (240)Pu/(239)Pu isotopic ratio, the conversion electron peaks of both isotopes are more clearly separated than their largely overlapping peaks in alpha spectra.

Specular and antispecular light beams

We consider a class of spatially partially coherent light beams, which are generated by passing a Gaussian Schell-model beam though a wavefront-folding interferometer. In certain cases these beams are shape-invariant on propagation and can exhibit sharp internal structure with a central peak (specular beam) or a central dip (antispecular beam) whose dimensions depend on the spatial coherence area. Such beams are demonstrated experimentally and their cross-like distributions of the complex degree of spatial coherence are measured with a digital micromirror device.

Imaging with partially coherent light: elementary-field approach

Numerical modeling of bright-field and dark-field imaging with spatially partially coherent light is considered. The illuminating field is expressed as a superposition of transversely shifted fully coherent elementary fields of identical form. Examples of imaging under variable coherence conditions demonstrate the computational feasibility of the model even when the coherence area of the illumination is in the wavelength scale.

Two-time coherence of pulse trains and the integrated degree of temporal coherence

We examine the temporal coherence properties of trains of nonidentical short optical pulses in the framework of the second-order coherence theory of nonstationary light. Considering Michelson's interferometric measurement of temporal coherence, we demonstrate that time-resolved interferograms reveal the full two-time temporal coherence function of the partially coherent pulse train. We also show that the result given by the time-integrated Michelson interferogram equals the true degree of temporal coherence only when the pulse train is quasi-stationary, i.e., the coherence time is a small fraction of the pulse duration. True two-time and integrated coherence functions produced by specific models representing perturbed trains of mode-locked pulses and supercontinuum pulse trains produced in nonlinear fibers are illustrated.