Effects of different levels of physical activity on arterial stiffness and physical fitness performance in firefighters.

Background: Firefighters have lower levels of physical activity while on call. It is critical to understand the impact of firefighters' physical activity on arterial stiffness. This study classified groups by physical activity level and combined peripheral vascular monitor measurement to explore the relationships between the level of physical activity and cardiovascular (CV) risk and physical fitness (PF) of firefighters, as well as the acute response to arterial stiffness (AS) following maximal aerobic exercise test (MAET) intervention. Methods: The International Physical Activity Questionnaire (IPAQ) was used to classify the participants into 3 groups: low, moderate, and high level of physical activity group, respectively. A total of 36 participants were recruited, 12 in each group. Participants were assessed for body composition, rest brachial-ankle pulse wave velocity (baPWV), handgrip strength (HGS), maximal oxygen uptake (V̇O2max), and MAET baPWV. Results: In the three groups, significant differences were observed in V̇O2max, HGS, relative fat mass (%FM), body mass index (BMI), muscle mass ratio (MMR), and Rest baPWV (p < 0.05). After maximal aerobic exercise, the MAET baPWV values decreased significantly in all groups (all p < 0.001). Rest baPWV was significantly correlated with firefighters' age, seniority, metabolic equivalents (METs), height and muscle mass (MM) (p < 0.05). Conclusions: Firefighters with high levels of physical activity had better body composition and physical fitness and lower Rest baPWV. In all three groups, baPWV was lower after the MAET than before it. Therefore, regardless of a firefighter's level of physical activity, high-intensity aerobic exercise may have a beneficial effect on arterial stiffness.

Contactless ultrasound droplet manipulation system for mixing chemical reagents.

Green chemistry has been a rising topic in environmental sustainability, with a focus on the waste and consumption reduction of chemical and biomedical industries. Traditional chemical handling processes require tools that contact chemical reagents to produce vast amounts of residues and disposals. This study presents a contactless chemical mixing system that integrates acoustic droplet ejection and levitation techniques. First, the acoustic droplet ejection system creates a droplet in mid-air from a designated liquid reservoir by focusing acoustic energy at the liquid-air junction. The droplet levitation system captures and transports the droplet along a predetermined path by shifting the focal points of the acoustic standing waves. This facilitates contactless mixing of chemicals in a defined ratio. Notably, this study employs piezoelectric discs in an acoustic droplet ejection system to eject droplets from liquids. The relationship between the duration of the driving bursts and height and size of ejected droplets was also investigated. The proposed acoustic standing wave levitation system captures droplets with weights between 2.8 and 5.2 mg. To assess the reliability of the proposed system, 25 droplets were sequentially generated and transported to the mixing well without failure. The root mean square error between the collected and expected liquid weights was only 0.098 mg. The proposed system offers a promising solution for reducing waste and promoting environmentally friendly practices in chemical and biomedical laboratories.

Compensation for Electrode Detachment in Electrical Impedance Tomography with Wearable Textile Electrodes.

Electrical impedance tomography (EIT) is a radiation-free and noninvasive medical image reconstruction technique in which a current is injected and the reflected voltage is received through electrodes. EIT electrodes require good connection with the skin for data acquisition and image reconstruction. However, detached electrodes are a common occurrence and cause measurement errors in EIT clinical applications. To address these issues, in this study, we proposed a method for detecting faulty electrodes using the differential voltage value of the detached electrode in an EIT system. Additionally, we proposed the voltage-replace and voltage-shift methods to compensate for invalid data from the faulty electrodes. In this study, we present the simulation, experimental, and in vivo chest results of our proposed methods to verify and evaluate the feasibility of this approach.

Investigation of a Novel Acoustic Levitation Technique Using the Transition Period Between Acoustic Pulse Trains and Electrical Driving Signals.

Acoustic levitation is considered one of the most effective noncontact particle manipulation methods, along with aerodynamic, ferromagnetic, and optical levitation techniques. It is not restricted by the material properties of the target. However, existing acoustic levitation techniques have some drawbacks that limit their potential applications. Therefore, in this article, an innovative approach is proposed to manipulate objects more intuitively and freely. By taking advantage of the transition periods between the acoustic pulse trains and electrical driving signals, acoustic traps can be created by switching the acoustic focal spots rapidly. Since the high-energy-density points are not formed simultaneously, the computation of the acoustic field distribution with complicated mutual interference can be eliminated. Therefore, compared to the existing approaches that created acoustic traps by solving pressure distributions using iterative methods, the proposed method simplifies the computation of time delay and makes it possible to be solved even with a microcontroller. In this work, three experiments have been demonstrated successfully to prove the capability of the proposed method including lifting a Styrofoam sphere, transportation of a single target, and suspending two objects. Besides, simulations of the distributions of acoustic pressure, radiation force, and Gor'kov potential were conducted to confirm the presence of acoustic traps in the scenarios of lifting one and two objects. The proposed tactic should be considered effective since the results of the practical experiments and simulations support each other.

Targeting Chondroitin Sulfate Reduces Invasiveness of Glioma Cells by Suppressing CD44 and Integrin ß1 Expression.

Chondroitin sulfate (CS) is a major component of the extracellular matrix found to be abnormally accumulated in several types of cancer tissues. Previous studies have indicated that CS synthases and modification enzymes are frequently elevated in human gliomas and are associated with poor prognosis. However, the underlying mechanisms of CS in cancer progression and approaches for interrupting its functions in cancer cells remain largely unexplored. Here, we have found that CS was significantly enriched surrounding the vasculature in a subset of glioma tissues, which was akin to the perivascular niche for cancer-initiating cells. Silencing or overexpression of the major CS synthase, chondroitin sulfate synthase 1 (CHSY1), significantly regulated the glioma cell invasive phenotypes and modulated integrin expression. Furthermore, we identified CD44 as a crucial chondroitin sulfate proteoglycan (CSPG) that was modified by CHSY1 on glioma cells, and the suppression of CS formation on CD44 by silencing the CHSY1-inhibited interaction between CD44 and integrin ß1 on the adhesion complex. Moreover, we tested the CS-specific binding peptide, resulting in the suppression of glioma cell mobility in a fashion similar to that observed upon the silencing of CHSY1. In addition, the peptide demonstrated significant affinity to CD44, promoted CD44 degradation, and suppressed integrin ß1 expression in glioma cells. Overall, this study proposes a potential regulatory loop between CS, CD44, and integrin ß1 in glioma cells, and highlights the importance of CS in CD44 stability. Furthermore, the targeting of CS by specific binding peptides has potential as a novel therapeutic strategy for glioma.

Dry Wearable Textile Electrodes for Portable Electrical Impedance Tomography.

Electrical impedance tomography (EIT), a noninvasive and radiation-free medical imaging technique, has been used for continuous real-time regional lung aeration. However, adhesive electrodes could cause discomfort and increase the risk of skin injury during prolonged measurement. Additionally, the conductive gel between the electrodes and skin could evaporate in long-term usage and deteriorate the signal quality. To address these issues, in this work, textile electrodes integrated with a clothing belt are proposed to achieve EIT lung imaging along with a custom portable EIT system. The simulation and experimental results have verified the validity of the proposed portable EIT system. Furthermore, the imaging results of using the proposed textile electrodes were compared with commercial electrocardiogram electrodes to evaluate their performance.

An Acoustic Hotspot Tracking Algorithm for Highly Centralized Gas Temperature Distribution.

Acoustic pyrometer is expected to be a useful noninvasive method for monitoring gas temperature distribution inside a steel-making furnace. On the superficial layer above the burden of a blast furnace, most of the high-temperature gas is concentrated near the center, and tracking the position of the hotspot is critical for productivity. However, most of the existing acoustic temperature distribution reconstruction algorithms are developed with relatively uniform temperature distribution environments. Besides, their capabilities of tracking the pinnacle of temperature distribution in the region of interest (ROI) are rarely discussed. In this research, a reconstruction method of acoustic temperature tomography dedicated for highly centralized gas temperature distribution is proposed and demonstrated. The key metrics include the reproducibility of 2-D temperature distribution, the sensitivity of hotspot shift, and the accuracy of point-to-point (P2P)/peak temperature. To optimize the result of each metric, previous approaches of acoustic temperature tomography have been first evaluated. Then, the investigation of effects from the shape and size of meshes is proceeded to improve the performance. After that, a novel method to address convergence issues while using the iterative method is introduced. Consequently, the reconstruction method proposed in this article could effectively visualize the temperature map while hotspot moves to different locations. It could also sense the occurrence of a hotspot (2.56% of ROI) traveled from center to 1% of ROI's diameter. Moreover, a competitive accuracy with 5.89% and 1.46% error at P2P root-mean-square (rms) and peak temperature is achieved, respectively. Finally, a practical acoustic 2-D pyrometer consisted of 12 ultrasonic transducers arranged in a circular pattern with a 1-m width of ROI successfully detected the shift of a hotspot when the displacement of a heater reaches 5 cm.

Fluid balance correlates with clinical course of multiple organ dysfunction syndrome and mortality in patients with septic shock.

INTRODUCTION: Positive fluid balance is a prognostic factor for mortality in patients with sepsis; however, the association between cumulated fluid balance (CFB) and sepsis-induced multi-organ dysfunction syndrome (MODS) has yet to be elucidated. In this study, we sought to determine whether CFB is correlated with MODS and mortality in cases of septic shock. METHODS: The study retrospectively recruited patients with septic shock from the intensive care unit of a tertiary care hospital. Multiple organ dysfunction syndrome (MODS) was identified as sequential organ failure assessment (SOFA) score ≥ 2 in more than one organ system. The CFB is the sum of all daily intake and output. An independent t-test, single and multivariate logistic regression, the receiver operating characteristic (ROC) curves, and the Pearson correlation coefficient were used to determine whether a relationship exists between CFB and the development of MODS and mortality. RESULTS: Among the 104 patients enrolled in the study, 58 (55.8%) survived more than 28 days, and 73 (70.2%) developed MODS on day 3. The values of CFB in the first 24 hours and 72 hours after diagnosis of septic shock in patients with MODS were higher than these in patients without MODS (1086.6 ± 176.3 vs. 325.5 ± 205.7 ml, p = 0.013 and 2408 ± 361 vs. 873.1 ± 489 ml, p < 0.0001). In a multivariate logistic regression, the independent factors associated with the development of MODS on day 3 were APACHE II score at ICU admission (27.6 ± 7.6 in patients with MODS vs. 20.5 ± 6.4 in those without; O.R. 1.18; 95% C.1 I. 1.08-1.30; p < 0.001), disseminated intravascular coagulopathy (DIC) (n = 28; 38.4% vs. n = 2; 6.5%; O.R. 23.67; 95% C.I. 3.58-156.5; p = 0.001), and CFB in the first 72 hours (72-hr CFB) > median (1767.50ml) (n = 41; 56.2% vs. n = 11; 35.5%; O.R. 3.67; 95% C.I., 1.18-11.40; p = 0.024). Moreover, a multivariate logistic regression also identified neoplasm (n = 25; 54.3% vs. n = 17; 29.3%; O.R. 3.45; 95% C.I. 1.23-10.0; p = 0.019) and 72-hr CFB > median (n = 30; 65.2% vs. n = 21; 36.2%; O.R. 4.13; 95% C.I. 1.34-12.66; p = 0.013) as independent factors associated with 28-day mortality. 72-hr CFB values were strongly correlated with the SOFA score (r = 0.445, p < 0.0001). The area under the ROC curve revealed that 72-hr CFB has good discriminative power in associating the development of MODS (0.644, p = 0.002) and predicting subsequent 28-day mortality (0.704, p < 0.0001). CONCLUSIONS: 72-hr CFB appears to be correlated with the likelihood of developing MODS and mortality in patients with septic shock. Thus, it appears that 72-hr CFB could perhaps be used as an indicator for MODS and a predictor for mortality in those patients.

High-speed photoacoustic microscopy of mouse cortical microhemodynamics.

We applied high-speed photoacoustic microscopy (PAM) for both cortical microenvironment studies and dynamic brain studies, with micrometer-level optical resolution and a millisecond-level cross-sectional imaging speed over a millimeter-level field of view. We monitored blood flow redistribution in mini-stroke mouse models and cerebral autoregulation induced by a vasoactive agent. Our results collectively suggest that high-speed PAM is a promising tool for understanding dynamic neurophysiological phenomena, complementing conventional imaging modalities.

In vivo label-free photoacoustic flow cytography and on-the-spot laser killing of single circulating melanoma cells.

Metastasis causes as many as 90% of cancer-related deaths, especially for the deadliest skin cancer, melanoma. Since hematogenous dissemination of circulating tumor cells is the major route of metastasis, detection and destruction of circulating tumor cells are vital for impeding metastasis and improving patient prognosis. Exploiting the exquisite intrinsic optical absorption contrast of circulating melanoma cells, we developed dual-wavelength photoacoustic flow cytography coupled with a nanosecond-pulsed melanoma-specific laser therapy mechanism. We have successfully achieved in vivo label-free imaging of rare single circulating melanoma cells in both arteries and veins of mice. Further, the photoacoustic signal from a circulating melanoma cell immediately hardware-triggers a lethal pinpoint laser irradiation to kill it on the spot in a thermally confined manner without causing collateral damage. A pseudo-therapy study including both in vivo and in vitro experiments demonstrated the performance and the potential clinical value of our method, which can facilitate early treatment of metastasis by clearing circulating tumor cells from vasculature.

High-speed label-free functional photoacoustic microscopy of mouse brain in action.

We present fast functional photoacoustic microscopy (PAM) for three-dimensional high-resolution, high-speed imaging of the mouse brain, complementary to other imaging modalities. We implemented a single-wavelength pulse-width-based method with a one-dimensional imaging rate of 100 kHz to image blood oxygenation with capillary-level resolution. We applied PAM to image the vascular morphology, blood oxygenation, blood flow and oxygen metabolism in both resting and stimulated states in the mouse brain.

Photoacoustic lymphatic imaging with high spatial-temporal resolution.

Despite its critical function in coordinating the egress of inflammatory and immune cells out of tissues and maintaining fluid balance, the causative role of lymphatic network dysfunction in pathological settings is still understudied. Engineered-animal models and better noninvasive high spatial-temporal resolution imaging techniques in both preclinical and clinical studies will help to improve our understanding of different lymphatic-related pathologic disorders. Our aim was to take advantage of our newly optimized noninvasive wide-field fast-scanning photoacoustic (PA) microcopy system to coordinately image the lymphatic vasculature and its flow dynamics, while maintaining high resolution and detection sensitivity. Here, by combining the optical-resolution PA microscopy with a fast-scanning water-immersible microelectromechanical system scanning mirror, we have imaged the lymph dynamics over a large field-of-view, with high spatial resolution and advanced detection sensitivity. Depending on the application, lymphatic vessels (LV) were spectrally or temporally differentiated from blood vessels. Validation experiments were performed on phantoms and in vivo to identify the LV. Lymphatic flow dynamics in nonpathological and pathological conditions were also visualized. These results indicate that our newly developed PA microscopy is a promising tool for lymphatic-related biological research.

A water-immersible 2-axis scanning mirror microsystem for ultrasound andha photoacoustic microscopic imaging applications.

Fast scanning is highly desired for both ultrasound and photoacoustic microscopic imaging, whereas the liquid environment required for acoustic propagation limits the usage of traditional microelectromechanical systems (MEMS) scanning mirrors. Here, a new water-immersible scanning mirror microsystem has been designed, fabricated and tested. To achieve reliable underwater scanning, flexible polymer torsion hinges fabricated by laser micromachining were used to support the reflective silicon mirror plate. Two efficient electromagnetic microactuators consisting of compact RF choke inductors and high-strength neodymium magnet disc were constructed to drive the silicon mirror plate around a fast axis and a slow axis. The performance of this water-immersible scanning mirror microsystem in both air and water were tested using the laser tracing method. For the fast axis, the resonance frequency reached 224 Hz in air and 164 Hz in water, respectively. The scanning angles in both air and water under ±16 V DC driving were ±12°. The scanning angles in air and water under ±10 V AC driving (at the resonance frequencies) were ±13.6° and ±10°. For the slow axis, the resonance frequency reached 55 Hz in air and 38 Hz in water, respectively. The scanning angles in both air and water under ±10 V DC driving were ±6.5°. The scanning angles in air and water under ±10 V AC driving (at the resonance frequencies) were ±8.5° and ±6°. The feasibility of using such a water-immersible scanning mirror microsystem for scanning ultrasound microscopic imaging has been demonstrated with a 25-MHz ultrasound pulse/echo system and a target consisting of three optical fibers.

Wide-field fast-scanning photoacoustic microscopy based on a water-immersible MEMS scanning mirror.

By offering images with high spatial resolution and unique optical absorption contrast, optical-resolution photoacoustic microscopy (OR-PAM) has gained increasing attention in biomedical research. Recent developments in OR-PAM have improved its imaging speed, but have to sacrifice either the detection sensitivity or field of view or both. We have developed a wide-field fast-scanning OR-PAM by using a water-immersible microelectromechanical systems (MEMS) scanning mirror (MEMS-OR-PAM). In MEMS-OR-PAM, the optical and acoustic beams are confocally configured and simultaneously steered, which ensures the uniform detection sensitivity. A B-scan imaging speed as high as 400 Hz can be achieved over a 3 mm scanning range. Using the system, we imaged the flow dynamics of both red blood cells and carbon particles in a mouse ear in vivo. Presented results show that MEMS-OR-PAM could be a powerful tool for studying highly dynamic and time-sensitive biological phenomena.

Spontaneous emission dynamics in an omnidirectional waveguide made of photonic crystals.

The spontaneous emission dynamics of atoms embedded in an omnidirectional waveguide (ODWG), a novel optical waveguide, is studied on the basis of the complete reflection of one-dimensional photonic crystals. With the dispersion curve of the single waveguide mode within the photonic band gap and various extents of background dissipation, we characterize the photon-atom interaction in the ODWG. The photon emitter of the system is a two-level atom embedded in the low-index medium of the multilayer-film ODWG or the atom-ODWG system. Fractional calculus, an innovative mathematical method in optical systems, is applied to solve the equation of motion for this atom-ODWG system. Two kinds of states with different group velocities exhibit totally distinctive dynamical behavior. The high frequency waveguide mode with a fast group velocity shows fast exponential decay in propagation while the band-edge mode with a slow group velocity displays non-Markovian dynamics with non-exponential oscillating time evolution. We therefore suggest different functions of this atom-ODWG system for these two kinds of states. The richness of the physical content of the system is also revealed through investigating the dynamical behavior of the band-edge mode. These results aid in further application and fundamental understanding of the atom-ODWG system.

Modulation instability in nonlinear coupled resonator optical waveguides and photonic crystal waveguides.

Modulation instability (MI) in a coupled resonator optical waveguide (CROW) and photonic-crystal waveguide (PCW) with nonlinear Kerr media was studied by using the tight-binding theory. By considering the coupling between the defects, we obtained a discrete nonlinear evolution equation and termed it the extended discrete nonlinear Schrödinger (EDNLS) equation. By solving this equation for CROWs and PCWs, we obtained the MI region and the MI gains, G(p,q), for different wavevectors of the incident plane wave (p) and perturbation (q) analytically. In CROWs, the MI region, in which solitons can be formed, can only occur for pa being located either before or after pi/2, where a is the separation of the cavities. The location of the MI region is determined by the number of the separation rods between defects and the sign of the Kerr coefficient. However, in the PCWs, pa in the MI region can exceed the pi/2. For those wavevectors close to pi/2, the MI profile, G(q), can possess two gain maxima at fixed pa. It is quite different from the results of the nonlinear CROWs and optical fibers. By numerically solving the EDNLS equation using the 4th order Runge-Kutta method to observe exponential growth of small perturbation in the MI region, we found it is consistent with our analytic solutions.