Increased length-dependent activation of human engineered heart tissue after chronic α1A-adrenergic agonist treatment: testing a novel heart failure therapy.

Chronic stimulation of cardiac α1A-adrenergic receptors (α1A-ARs) improves symptoms in multiple preclinical models of heart failure. However, the translational significance remains unclear. Human engineered heart tissues (EHTs) provide a means of quantifying the effects of chronic α1A-AR stimulation on human cardiomyocyte physiology. EHTs were created from thin slices of decellularized pig myocardium seeded with human induced pluripotent stem cell (iPSC)-derived cardiomyocytes and fibroblasts. With a paired experimental design, EHTs were cultured for 3 wk, mechanically tested, cultured again for 2 wk with α1A-AR agonist A61603 (10 nM) or vehicle control, and retested after drug washout for 24 h. Separate control experiments determined the effects of EHT age (3-5 wk) or repeat mechanical testing. We found that chronic A61603 treatment caused a 25% increase of length-dependent activation (LDA) of contraction compared with vehicle treatment (n = 7/group, P = 0.035). EHT force was not increased after chronic A61603 treatment. However, after vehicle treatment, EHT force was increased by 35% relative to baseline testing (n = 7/group, P = 0.022), suggesting EHT maturation. Control experiments suggested that increased EHT force resulted from repeat mechanical testing, not from EHT aging. RNA-seq analysis confirmed that the α1A-AR is expressed in human EHTs and found chronic A61603 treatment affected gene expression in biological pathways known to be activated by α1A-ARs, including the MAP kinase signaling pathway. In conclusion, increased LDA in human EHT after chronic A61603 treatment raises the possibility that chronic stimulation of the α1A-AR might be beneficial for increasing LDA in human myocardium and might be beneficial for treating human heart failure by restoring LDA.NEW & NOTEWORTHY Chronic stimulation of α1A-adrenergic receptors (α1A-ARs) is known to mediate therapeutic effects in animal heart failure models. To investigate the effects of chronic α1A-AR stimulation in human cardiomyocytes, we tested engineered heart tissue (EHT) created with iPSC-derived cardiomyocytes. RNA-seq analysis confirmed human EHT expressed α1A-ARs. Chronic (2 wk) α1A-AR stimulation with A61603 (10 nM) increased length-dependent activation (LDA) of contraction. Chronic α1A-AR stimulation might be beneficial for treating human heart failure by restoring LDA.

Multi-wavelength high-energy gas-filled fiber Raman laser spanning from 1.53 µm to 2.4 µm.

In this work, we present a high-pulse-energy multi-wavelength Raman laser spanning from 1.53 µm up to 2.4 µm by employing the cascaded rotational stimulated Raman scattering effect in a 5 m hydrogen (H2)-filled nested anti-resonant fiber, pumped by a linearly polarized Er/Yb fiber laser with a peak power of ∼13kW and pulse duration of ∼7ns in the C-band. The developed Raman laser has distinct lines at 1683 nm, 1868 nm, 2100 nm, and 2400 nm, with pulse energies as high as 18.25 µJ, 14.4 µJ, 14.1 µJ, and 8.2 µJ, respectively. We demonstrate how the energy in the Raman lines can be controlled by tuning the H2 pressure from 1 bar to 20 bar.

High pulse energy and quantum efficiency mid-infrared gas Raman fiber laser targeting CO2 absorption at 4.2 µm.

In this Letter, we demonstrate a high pulse energy and linearly polarized mid-infrared Raman fiber laser targeting the strongest absorption line of ${\rm CO}_2$CO2 at $\sim{4.2}\;\unicode {x00B5} {\rm m}$∼4.2µm. This laser was generated from a hydrogen (${\rm H}_2$H2)-filled antiresonant hollow-core fiber, pumped by a custom-made 1532.8 nm Er-doped fiber laser delivering 6.9 ns pulses and 11.6 kW peak power. A quantum efficiency as high as 74% was achieved, to yield 17.6 µJ pulse energy at 4.22 µm. Less than 20 bar ${\rm H}_2$H2 pressure was required to maximize the pulse energy since the transient Raman regime was efficiently suppressed by the long pump pulses.

Observation on temperature and strain dependency of Brillouin dynamic grating in a few-mode fiber with a ring-cavity configuration.

We experimentally conduct Brillouin dynamic grating (BDG) operation using a 1-km-long four-mode fiber. By employing a simplified ring-cavity configuration with single-end pumping, the BDG is effectively generated in $ {{\rm LP}_{01}} $LP01 mode within a range of 250 m, and three higher-order modes, namely, $ {{\rm LP}_{11b}} $LP11b, $ {{\rm LP}_{21a}} $LP21a, and $ {{\rm LP}_{02}} $LP02, are chosen as probes to analyze the BDG with a spatial resolution of 1 m. To the best of our knowledge, this is the first time to characterize the responses of BDG frequency to temperature and strain for different modes in a conventional few-mode fiber. By employing the pump-probe pair of $ {{\rm LP}_{01}}{{\rm - LP}_{02}} $LP01-LP02 mode, the highest temperature and strain sensitivities of 3.21 MHz/°C and $ - 0.0384\;{\rm MHz}/{\unicode{x00B5}}{\unicode{x03B5}} $-0.0384MHz/µÎµ have been achieved. Also, the performance of simultaneously distributed temperature and strain sensing based on BDG is evaluated.

Mode-selective few-mode Brillouin fiber lasers based on intramodal and intermodal SBS.

Mode-selective fiber lasers have advantages in a number of applications. Here we propose and experimentally demonstrate a transverse mode-selective few-mode Brillouin fiber laser using the mode-selective photonic lantern. We generated the lowest three orders of linearly polarized (LP) modes based on both intramodal and intermodal stimulated Brillouin scattering (SBS). Their slope efficiencies, optical spectra, mode profiles, and linewidths were measured.

Single-mode, low loss hollow-core anti-resonant fiber designs.

In this paper, we numerically investigate various hollow-core anti-resonant (HC-AR) fibers towards low propagation and bend loss with effectively single-mode operation in the telecommunications window. We demonstrate how the propagation loss and higher-order mode modal contents are strongly influenced by the geometrical structure and the number of the anti-resonant cladding tubes. We found that 5-tube nested HC-AR fiber has a wider anti-resonant band, lower loss, and larger higher-order mode extinction ratio than designs with 6 or more anti-resonant tubes. A loss ratio between the higher-order modes and fundamental mode, as high as 12,000, is obtained in a 5-tube nested HC-AR fiber. To the best of our knowledge, this is the largest higher-order mode extinction ratio demonstrated in a hollow-core fiber at 1.55 µm. In addition, we propose a modified 5-tube nested HC-AR fiber, with propagation loss below 1 dB/km from 1330 to 1660 nm. This fiber also has a small bend loss of ~15 dB/km for a bend radius of 1 cm.

Low-crosstalk few-mode EDFAs using retro-reflection for single-mode fiber trunk lines and networks.

Few-mode EDFAs with low channel crosstalk can replace multiple parallel single-mode EDFAs in single-mode fiber trunk lines and networks. Here we proposed a low-crosstalk few-mode EDFA by exploiting the unitary property of the coupling matrix of a symmetric photonic lantern. We experimentally demonstrated a 3-channel few-mode EDFA using retro-reflection of a 3-mode symmetric photonic lantern. The small signal gain for all three channels are measured to be larger than 25 dB over the entire C-band and the crosstalks are below -10 dB.

Multioctave supercontinuum from visible to mid-infrared and bend effects on ultrafast nonlinear dynamics in gas-filled hollow-core fiber.

Broadband supercontinuum generation is numerically investigated in a Xe-filled nested hollow-core antiresonant (HC-AR) fiber pumped at 3 µm with pulses of 100 fs duration and 15 µJ energy. For a 25 cm long fiber, under 7 bar pressure, the supercontinuum spectrum spans multiple octaves from 400 nm to 5000 nm. Furthermore, the influence of bending on ultrafast nonlinear pulse propagation dynamics is investigated for two types of HC-AR fibers (nested and non-nested capillaries). Our results predict similar nonlinear dynamics for both fiber types and a significant reduction of the spectral broadening under tight bending conditions.

Psychometric assessment of the cultural capacity scale Spanish version in Chilean nursing students.

AIM: To assess the psychometric properties of the Cultural Capacity Scale Spanish version in Chilean nursing students. BACKGROUND: The increased diversity in healthcare facilities and the current shortage of local nursing workforce in Chile present a significant challenge to the nursing education to train future competent local nurses. To facilitate cultural competence development among Chilean nursing students, it is necessary to regularly assess their cultural competence, which necessitates a culturally adapted valid and reliable tool. METHODS: A convenience sample of 502 Chilean nursing students was surveyed in this cross-sectional study using the culturally adapted scale. Reliability of the instrument was established by internal consistency and stability reliability, while validity was established by content and construct. RESULTS: The Cronbach's α value of the entire scale was 0.95, and the test-retest reliability was 0.85. The Corrected Item-Total Correlations ranged from 0.45 to 0.78. The tool manifested an excellent content and construct validity. The exploratory factor analysis confirmed a single factor of the scale. DISCUSSION: The tool demonstrated evidence of internal consistency, stability reliability, content validity and construct validity. The study provided cross-cultural evidence for the potential application of this scale in Chile and other Spanish-speaking countries. CONCLUSION: The Cultural Capacity Scale Spanish version demonstrated sound psychometric properties for assessing the cultural competence of Chilean nursing students. LIMITATIONS: The sample was restricted to one university, and the tool was only used in Chilean nursing students. IMPLICATIONS FOR NURSING POLICY: The establishment of the Spanish version of the tool will facilitate accurate and timely monitoring of the cultural competence among Chilean nursing students and other Spanish-speaking nursing students and nurses, which can inform the creation of nursing policies aimed at ensuring cultural competence development.

All-fiber few-mode multicore photonic lantern mode multiplexer.

The emergence of space division multiplexing (SDM) for ultrahigh capacity networks has heralded pioneering Petabit-class optical transmission systems. In parallel to novel SDM fibers, a new class of components to enable scalable, low-loss schemes for unlocking fiber capacity is being developed. In this work, an all-fiber mode selective photonic lantern mode multiplexer designed for launching into few-mode multicore fibers is demonstrated. This device is capable of selectively exciting LP01, LP11a and LP11b modes in a seven-core configuration, resulting in 21 spatial channels, with less than 38 dB core-to-core crosstalk and insertion loss below 0.4 dB. The multicore photonic lantern multiplexer is scalable to larger number of cores and modes per core, and can be easily integrated with emerging ultra-high bandwidth few-mode multicore optical communication systems.

Tailoring frequency generation in uniform and concatenated multimode fibers.

We demonstrate that frequency generation in multimode parabolic-index fibers can be precisely engineered through appropriate fiber design. This is accomplished by exploiting the onset of a geometric parametric instability that arises from resonant spatiotemporal compression. By launching the output of an amplified Q-switched microchip laser delivering 400 ps pulses at 1064 nm, we observe a series of intense frequency sidebands that strongly depend on the fiber core size. The nonlinear frequency generation is analyzed in three fiber samples with 50 µm, 60 µm, and 80 µm core diameters. We further demonstrate that by cascading fibers of different core sizes, a desired frequency band can be generated from the frequency lines parametrically produced in each section. The observed frequency shifts are in good agreement with analytical predictions and numerical simulations. Our results suggest that core scaling and fiber concatenation can provide a viable avenue in designing optical sources with tailored output frequencies.

Reduced-symmetry LMA rod-type fiber for enhanced higher-order mode delocalization.

We present a novel design of a micro-structured large-pitch, large-mode-area (LMA) asymmetric rod-type fiber. By reducing the cladding symmetry through six high-refractive index germanium-doped silica inclusions, the fiber features strong higher-order mode (HOM) delocalization, leading to a potentially enhanced preferential gain for the fundamental mode in active fibers. In addition, high resolution spatially and spectrally (S2) resolved mode analysis measurements confirm HOM contributions below 1% and LP1m-like HOM contributions below the detection limit. This proposed fiber design enables single-mode operation, with near-diffraction-limited beam quality of M2=1.3 and an effective mode area of 2560 µm2 at 1064 nm. This design opens new insights into improving the threshold-like onset of modal instabilities in high-power fiber lasers and fiber amplifiers by efficiently suppressing LP11 modes.

Instant and efficient second-harmonic generation and downconversion in unprepared graded-index multimode fibers.

We show that germanium-doped graded-index multimode silica fibers can exhibit relatively high conversion efficiencies (∼6.5%) for second-harmonic generation when excited at 1064 nm. This frequency-doubling behavior is also found to be accompanied by an effective downconversion. As opposed to previous experiments carried out in single- and few-mode fibers where hours of preparation were required, in our system, these χ(2) related processes occur almost instantaneously. The efficiencies observed in our experiments are, to the best of our knowledge, among the highest ever reported in unprepared fibers.

Blood feeding of Ornithodoros turicata larvae using an artificial membrane system.

An artificial membrane system was adapted to feed Ornithodoros turicata (Ixodida: Argasidae) larvae from a laboratory colony using defibrinated swine blood. Aspects related to larval feeding and moulting to the first nymphal instar were evaluated. A total of 55.6% of all larvae exposed to the artificial membrane in two experimental groups fed to repletion and 98.0% of all fed larvae moulted. Mortality rates of first instar nymphs differed significantly depending on the sorting tools used to handle engorged larvae (χ2 = 35.578, P < 0.0001): engorged larvae handled with featherweight forceps showed significantly higher mortality (odds ratio = 4.441) than those handled with a camel-hair brush. Differences in the physical properties of the forceps and camel-hair brush may affect the viability of fragile soft tick larvae even when care and the same technique are used to sort them during experimental manipulations. The current results represent those of the first study to quantify successful feeding to repletion, moulting and post-moulting mortality rates in O. turicata larvae using an artificial membrane feeding system. Applications of the artificial membrane feeding system to fill gaps in current knowledge of soft tick biology and the study of soft tick-pathogen interactions are discussed.

Modal analysis of antiresonant hollow core fibers using S2 imaging.

We analyze the higher-order core mode content in various designs of antiresonant hollow core fibers using spatially and spectrally resolved imaging. Hollow core fibers have great potential for a variety of applications, and understanding their mode content is crucial for many of these. Two different designs of hollow core fibers are considered, the first with eight nontouching rings and the second with eight touching rings forming a closed boundary core. The mode content of each fiber is measured as a function of length and bending diameter. Low amounts of higher-order modes were found in both hollow core fibers, and mode specific and bending-dependent losses have been determined. This study aids in understanding the core modes of hollow core fibers and possible methods of controlling them.

Few-mode erbium-doped fiber amplifier with photonic lantern for pump spatial mode control.

We demonstrate a few-mode erbium-doped fiber amplifier employing a mode-selective photonic lantern for controlling the modal content of the pump light. Amplification of six spatial modes in a 5 m long erbium-doped fiber to ∼6.2 dBm average power is obtained while maintaining high modal fidelity. Through mode-selective forward pumping of the two degenerate LP21 modes operating at 976 nm, differential modal gains of <1 dB between all modes and signal gains of ∼16 dB at 1550 nm are achieved. In addition, low differential modal gain for near-full C-band operation is demonstrated.

Bending sensor combining multicore fiber with a mode-selective photonic lantern.

A bending sensor is demonstrated using the combination of a mode-selective photonic lantern (PL) and a multicore fiber. A short section of three-core fiber with strongly coupled cores is used as the bend sensitive element. The supermodes of this fiber are highly sensitive to the refractive index profiles of the cores. Small bend-induced changes result in drastic changes of the supermodes, their excitation, and interference. The multicore fiber is spliced to a few-mode fiber and excites bend dependent amounts of each of the six linearly polarized (LP) modes guided in the few-mode fiber. A mode selective PL is then used to demultiplex the modes of the few-mode fiber. Relative power measurements at the single-mode PL output ports reveal a high sensitivity to bending curvature and differential power distributions according to bending direction, without the need for spectral measurements. High direction sensitivity is demonstrated experimentally as well as in numerical simulations. Relative power shifts of up to 80% have been measured at radii of approximately 20 cm, and good sensitivity was observed with radii as large as 10 m, making this sensing system useful for applications requiring both large and small curvature measurements.

Compact fiber-optic curvature sensor based on super-mode interference in a seven-core fiber.

A compact, low loss, and highly sensitive optical fiber curvature sensor is presented. The device consists of a few-millimeter-long piece of seven-core fiber spliced between two single-mode fibers. When the optical fiber device is kept straight, a pronounced interference pattern appears in the transmission spectrum. However, when the device is bent, a spectral shift of the interference pattern is produced, and the visibility of the interference notches changes. This allows for using either visibility or spectral shift for sensor interrogation. The dynamic range of the device can be tailored through the proper selection of the length of the seven-core fiber. The effects of temperature and refractive index of the external medium on the response of the curvature sensor are also discussed. Linear sensitivity of about 3000 nm/mm(-1) for bending was observed experimentally.

Six mode selective fiber optic spatial multiplexer.

Low-loss all-fiber photonic lantern (PL) mode multiplexers (MUXs) capable of selectively exciting the first six fiber modes of a multimode fiber (LP01, LP11a, LP11b, LP21a, LP21b, and LP02) are demonstrated. Fabrication of the spatial mode multiplexers was successfully achieved employing a combination of either six step or six graded index fibers of four different core sizes. Insertion losses of 0.2-0.3 dB and mode purities above 9 dB are achieved. Moreover, it is demonstrated that the use of graded index fibers in a PL eases the length requirements of the adiabatic tapered transition and could enable scaling to large numbers.

Comparison of the accuracy of CT colonography and colonoscopy in the diagnosis of colorectal cancer.

AIM: The available evidence was reviewed to compare the effectiveness of CT colonography with that of colonoscopy for colorectal cancer (CRC) screening. METHOD: An electronic search was conducted using PubMed, EMBASE, the Cochrane Library and Centre for Reviews and Dissemination databases, from inception to July 2009. Studies were included if investigations used CT colonography for CRC screening in asymptomatic populations. Studies were excluded if investigations were conducted for the diagnosis of CRC or in elderly, high-risk or symptomatic populations. RESULTS: Of the 213 references identified, nine studies were included. The specificity of CT colonography in screening for CRC was high, although it decreased with decreasing diameter of polyp to be detected. The sensitivity of CT colonography for the detection of polyps < 6 mm in diameter was low and heterogeneous, although it was higher for polyps > 10 mm. The main factors contributing to a greater sensitivity of CT colonography were the inclusion of only populations with an average CRC risk and colonic insufflation with CO2 . The incidence of adverse effects was very low for both tests. CONCLUSION: CT colonography has high specificity but heterogeneous sensitivity, although in most cases it is not as sensitive or specific as conventional colonoscopy. CT colonography could therefore be useful as a screening test for populations with an average risk of CRC.