Duration-controllable mid-infrared pulse from bias-pumped Er:ZBLAN fiber laser

We experimentally demonstrate the generation of duration-controllable pulses at 2.8 µm based on bias-pump technique for the first time. Bias-pumped by a 976 nm continuous-wave (CW)-pulsed combined laser, duration-controllable pulses are produced from an Er:ZBLAN fiber laser and the duration is entirely determined by the duration of pump pulse. Numerical simulations agree with experimental results well, and further predict that the temporal profile of output pulse from bias-pumped Er:ZBLAN fiber laser can also be identical with that of pump pulse under certain conditions. The pump-controlled mid-infrared pulse may have more applications in various areas due to its manageable temporal characteristics.

The Surface Photogalvanic and Photon Drag Effects in Ag/Pd Metal-Semiconductor Nanocomposite

We performed the investigation of the polarization-sensitive photocurrent generated in silver-palladium metal-semiconductor nanocomposite films under irradiation with nanosecond laser pulses at the wavelength of 2600 nm. It is shown that in both the transverse and the longitudinal configuration, the surface photogalvanic (SPGE) and photon drag effects (PDE) contribute to the observed photocurrent. However, the temporal profile of the transverse photocurrent pulse is monopolar at any polarization and angle of incidence, while the temporal profile of the longitudinal photocurrent pulse depends on the polarization of the excitation beam. Specifically, the irradiation of the film with the s-polarized excitation beam produces a monopolar photoresponse, while at p-polarized excitation, the photoresponse is bipolar, having a short front and long tail. Obtained experimental results are in agreement with the developed phenomenological theory, which describes transverse and longitudinal photocurrents due to SPGE and PDE in terms of relevant second-order nonlinear susceptibilities and allows us to obtain their dependences on the angle of incidence and polarization of the excitation laser beam. The pronounced dependence of the photocurrent on the angle of incidence and polarization of the excitation beam opens avenues toward the development of polarization- and position-sensitive detectors for industrial and space applications.

Temporal Profile of Pneumonia After Stroke

Background and Purpose: The occurrence of pneumonia after stroke is associated with a higher risk of poor outcome or death. We assessed the temporal profile of pneumonia after stroke and its association with poor outcome at several time points to identify the most optimal period for testing pneumonia prevention strategies. Methods: We analyzed individual patient data stored in the VISTA (Virtual International Stroke Trials Archive) from randomized acute stroke trials with an inclusion window up to 24 hours after stroke onset and assessed the occurrence of pneumonia in the first 90 days after stroke. Adjusted odds ratios and hazard ratios were calculated for the association between pneumonia and poor outcome and death by means of logistic and Cox proportional hazard regression, respectively, at different times of follow-up. Results: Of 10 821 patients, 1017 (9.4%) had a total of 1076 pneumonias. Six hundred eighty-nine (64.0%) pneumonias occurred in the first week after stroke. The peak incidence was on the third day and the median time of onset was 4.0 days after stroke (interquartile range, 2–12). The presence of a pneumonia was associated with an increased risk of poor outcome (adjusted odds ratio, 4.8 [95% CI, 3.8–6.1]) or death (adjusted hazard ratio, 4.1 [95% CI, 3.7–4.6]). These associations were present throughout the 90 days of follow-up. Conclusions: Two out of 3 pneumonias in the first 3 months after stroke occur in the first week, with a peak incidence on the third day. The most optimal period to assess pneumonia prevention strategies is the first 4 days after stroke. However, pneumonia occurring later was also associated with poor functional outcome or death.

Engaging stories eradicate age effects in dip-listening

Fluctuating background masking sounds facilitate speech intelligibility by providing speech ‘glimpses’ (masking release). Older adults benefit less from glimpses, but masking release is typically investigated using isolated sentences. Recent work indicates that naturalistic speech (spoken stories) may qualitatively alter speech-in-noise listening. Moreover, neural sensitivity to different amplitude envelopes profiles (ramped vs. damped) changes with age, but whether this impacts speech listening is unknown. In three experiments, we investigate how masking release in younger and older adults differs for masked disconnected sentences and stories, and how intelligibility varies with masker temporal profile. Intelligibility was generally greater for damped compared to ramped maskers for both age groups and speech types. Masking release was reduced in older relative to younger adults for disconnected sentences (Experiment 1), and stories with a randomized sentence order (Experiment 3). When listening to stories with a coherent narrative, older adults demonstrated equal (Experiment 3) or greater (Experiment 2) masking release compared to younger adults. Reduced masking release previously observed in older adults does not appear to generalize to sounds with an engaging, connected narrative: this reinforces the idea that the listening materials qualitatively change listening behavior and that standard intelligibility paradigms may underestimate speech-listening abilities in older adults.

ECG Ventricular Repolarization Dynamics during Exercise: Temporal Profile, Relation to Heart Rate Variability and Effects of Age and Physical Health

Periodic repolarization dynamics (PRD) is a novel electrocardiographic marker of cardiac repolarization instability with powerful risk stratification capacity for total mortality and sudden cardiac death. Here, we use a time-frequency analysis approach to continuously quantify PRD at rest and during exercise, assess its dependence on heart rate variability (HRV) and characterize the effects of age (young adults/middle-aged adults/older adults), body mass index (non-overweight/overweight) and cardiorespiratory fitness level (fit/unfit). Sixty-six male volunteers performed an exercise test. RR and dT variabilities (RRV, dTV), as well as the fraction of dT variability unrelated to RR variability, were computed based on time-frequency representations. The instantaneous LF power of dT (PdTV), representing the same concept as PRD, and of its RRV-unrelated component (PdTVuRRV) were quantified. dT angle was found to mostly oscillate in the LF band. Overall, 50–70% of PdTV was linearly unrelated to RRV. The onset of exercise caused a sudden increase in PdTV and PdTVuRRV, which returned to pre-exercise levels during recovery. Clustering analysis identified a group of overweight and unfit individuals with significantly higher PdTV and PdTVuRRV values at rest than the rest of the population. Our findings shed new light on the temporal profile of PRD during exercise, its relationship to HRV and the differences in PRD between subjects according to phenotypic characteristics.