How many digits are needed?

Let $X_1,X_2,...$ be the digits in the base-$q$ expansion of a random variable $X$ defined on $[0,1)$ where $q\ge2$ is an integer. For $n=1,2,...$, we study the probability distribution $P_n$ of the (scaled) remainder $\sum_{k=n+1}^\infty X_qq^{n-k}$: If $X$ has an absolutely continuous CDF then $P_n$ converges in the total variation metric to Lebesgue measure on the unit interval; under certain smoothness conditions we establish exponentially fast convergence of $P_n$ and its PDF $f_n$; and we give examples of these results. The results are extended to the case of a multivariate random variable defined on a unit cube.Comment: 15 pages, 2 figure

Progress in Cherenkov femtosecond fiber lasers

We review the recent developments in the field of ultrafast Cherenkov fiber lasers. Two essential properties of such laser systems – broad wavelength tunability and high efficiency of Cherenkov radiation wavelength conversion are discussed. The exceptional performance of the Cherenkov fiber laser systems are highlighted - dependent on the realization scheme, the Cherenkov lasers can generate the femtosecond output tunable across the entire visible and even the UV range, and for certain designs more than 40 % conversion efficiency from the pump to Cherenkov signal can be achieved. The femtosecond Cherenkov laser with all-fiber architecture is presented and discussed. Operating in the visible range, it delivers 100–200 fs wavelength-tunable pulses with multimilliwatt output power and exceptionally low noise figure an order of magnitude lower than the traditional wavelength tunable supercontinuum-based femtosecond sources. The applications for Cherenkov laser systems in practical biophotonics and biomedical applications, such as bio-imaging and microscopy, are discussed

Nonlinearity-tailored fiber laser technology for low-noise, ultra-wideband tunable femtosecond light generation

Liu X, Laegsgaard J, Iegorov R, et al. Nonlinearity-tailored fiber laser technology for low-noise, ultra-wideband tunable femtosecond light generation. Photonics Research. 2017;5(6): 750

The effect of ionic strength on oil adhesion in sandstone - the search for the low salinity mechanism

Core flood and field tests have demonstrated that decreasing injection water salinity increases oil recovery from sandstone reservoirs. However, the microscopic mechanism behind the effect is still under debate. One hypothesis is that as salinity decreases, expansion of the electrical double layer decreases attraction between organic molecules and pore surfaces. We have developed a method that uses atomic force microscopy (AFM) in chemical force mapping (CFM) mode to explore the relationship between wettability and salinity. We functionalised AFM tips with alkanes and used them to represent tiny nonpolar oil droplets. In repeated measurements, we brought our “oil” close to the surface of sand grains taken from core plugs and we measured the adhesion between the tip and sample. Adhesion was constant in high salinity solutions but below a threshold of 5,000 to 8,000 ppm, adhesion decreased as salinity decreased, rendering the surface less oil wet. The effect was consistent, reproducible and reversible. The threshold for the onset of low salinity response fits remarkably well with observations from core plug experiments and field tests. The results demonstrate that the electric double layer force always contributes at least in part to the low salinity effect, decreasing oil wettability when salinity is low

Transcutaneous spinal direct current stimulation increases corticospinal transmission and enhances voluntary motor output in humans

Optimization of motor performance is of importance in daily life, in relation to recovery following injury as well as for elite sports performance. The present study investigated whether transcutaneous spinal direct current stimulation (tsDCS) may enhance voluntary ballistic activation of ankle muscles and descending activation of spinal motor neurons in able‐bodied adults. Forty‐one adults (21 men; 24.0 ± 3.2 years) participated in the study. The effect of tsDCS on ballistic motor performance and plantar flexor muscle activation was assessed in a double‐blinded sham‐controlled cross‐over experiment. In separate experiments, the underlying changes in excitability of corticospinal and spinal pathways were probed by evaluating soleus (SOL) motor evoked potentials (MEPs) following single‐pulse transcranial magnetic stimulation (TMS) over the primary motor cortex, SOL H‐reflexes elicited by tibial nerve stimulation and TMS‐conditioning of SOL H‐reflexes. Measures were obtained before and after cathodal tsDCS over the thoracic spine (T11‐T12) for 10 min at 2.5 mA. We found that cathodal tsDCS transiently facilitated peak acceleration in the ballistic motor task compared to sham tsDCS. Following tsDCS, SOL MEPs were increased without changes in H‐reflex amplitudes. The short‐latency facilitation of the H‐reflex by subthreshold TMS, which is assumed to be mediated by the fast conducting monosynaptic corticomotoneuronal pathway, was also enhanced by tsDCS. We argue that tsDCS briefly facilitates voluntary motor output by increasing descending drive from corticospinal neurones to spinal plantar flexor motor neurons. tsDCS can thus transiently promote within‐session CNS function and voluntary motor output and holds potential as a technique in the rehabilitation of motor function following central nervous lesions

Potassium, chlorine, and sulfur in ash, particles, deposits, and corrosion during wood combustion in a circulating fluidized-bed boiler

The effect of the addition of chlorine and/or sulfur to the fuel on fly ash composition, deposit formation, and superheater corrosion has been studied during biomass combustion in a circulating fluidized-bed boiler. The chlorine (HCl (aq)) and sulfur (SO2 (g)) were added in proportions of relevance for the potassium chemistry. The composition of the bottom and the fly ashes was analyzed. Gas and particle measurements were performed downstream of the cyclone before the convection pass and the flue gas composition was recorded in the stack with a series of standard instruments and an FTIR analyzer. At the position downstream of the cyclone, a deposit probe was situated, simulating a superheater tube. Deposits on the probe and initial corrosion were examined. It is concluded that addition of sulfur and chlorine increases the formation of submicron particles leading to deposition of potassium sulfate and chloride. The results compare well with earlier work based on laboratory-scale experiments concerning effects of chlorine and sulfur on potassium chemistry

Sudden cardiac death among persons with diabetes aged 1-49 years:a 10-year nationwide study of 14 294 deaths in Denmark

Aims The aim of this study was to compare nationwide incidence rate (IR) of sudden cardiac death (SCD) in persons aged 1–49 years with and without diabetes mellitus (DM). Methods and results The study population consisted of all persons in Denmark aged 1–49 years in 2000–09, which equals 27.1 million person-years. All 14 294 deaths in the 10-year period were included. By using the highly descriptive Danish death certificates, 1698 cases of sudden and unexpected death were identified. Through review of autopsy reports, discharge summaries, and the Danish registries, we identified 1363 cases of SCD. The Danish Register of Medicinal Product Statistics was used to identify persons with type 1 DM and type 2 DM. Among the 14 294 decedents, there were 669 with DM, of which 118 suffered SCD (9% of all SCD), making SCD the leading cause of death among young persons with DM. Among those aged 1–35 years, the IR of SCD-DM was 21.9 per 100 000 person-years compared to 2.6 per 100 000 person-years among persons without DM [IR ratio 8.6, 95% confidence interval (CI) 5.8–28.6]. Within the age range 36–49 years, the IR among persons with DM was 119.8 per 100 000 person-years compared to 19.7 per 100 000 person-years among persons without DM (IR ratio 6.1, 95% CI 4.7–7.8). Conclusion We found that young persons with DM aged 1–35 years had >8-fold higher SCD IR compared to young persons without DM. Our study highlights the need for early cardiovascular risk monitoring and assessment in young persons with DM.This work was supported by the Novo Nordisk Foundation, Copenhagen, Denmark [NNFOC140011573]. JS, reciewed salary from the Department of Forensic Medicine, Univiserty of Copenhagen

Ethnic disparities in out-of-hospital cardiac arrest:A population-based cohort study among adult Danish immigrants

BACKGROUND: Ethnicity might impact out-of-hospital cardiac arrest (OHCA) risk, but it has scarcely been studied in Europe. We aimed to assess whether ethnicity influenced the risk of OHCA of cardiac cause in Danish immigrants and its interplay with risk factors for OHCA and socioeconomic status. METHODS: This nationwide study included all immigrants between 18 and 80 years present in Denmark at some point between 2001 and 2020. Regions of origin were defined as Africa, Arabic countries, Asia, Eastern Europe, Latin America, and Western countries. OHCAs with presumed cardiac cause were identified from the Danish Cardiac Arrest Registry. FINDINGS: Overall, among 1,011,565 immigrants, a total of 1,801 (0.2%) OHCAs (median age 64 (Q1-Q3 53–72) years, 72% males) occurred. The age- and sex- standardized (reference: Western countries) incidence of OHCA (/1,00,000 person-years) was 34.6 (27.8–43.4) in African, 34.1 (30.4–38.4) in Arabic, 33.5 (29.3–38.2) in Asian, 35.6 (31.9–39.6) in Eastern European, and 16.2 (9.0–27.2) in Latin American immigrants. When selecting Western origin as a reference, and after adjusting on OHCA risk factors, Arabic (HR 1.18, 95%CI 1.04–1.35; P=0.01), Eastern European (HR 1.28, 95%CI 1.13–1.46; P<0.001), and African origin (HR 1.34, 95%CI 1.10–1.63; P<0.01) were associated with higher risk of OHCA, whereas Latin American origin (HR 0.58, 95%CI 0.35–0.0.96; P=0.03) was associated with lower risk of OHCA. Comparable results were observed when adjusting on education level and economic status. INTERPRETATION: This study emphasizes that ethnicity is associated with OHCA risk, even when considering traditional cardiac arrest risk factors. FUNDING: R Garcia received a grant from the Fédération Française de Cardiologie for his post-doctoral fellowship and this work was supported by the Novo Nordisk Foundation Tandem Programme 2022 (grant# 31364)

DNA methylome profiling of all-cause mortality in comparison with age-associated methylation patterns

Figure S1 PCA performed to identify batch effect, and ComBat correction using the SVA R-package with distributions of M-values before and after ComBat correction. (DOCX 571 kb