Liquid-core waveguide TCSPC sensor for high-accuracy fluorescence lifetime analysis.

Liquid-core waveguide (LCW) has many advantages such as the elimination of optical artifacts typically exhibited in systems employing lenses and filters. However, due to the effect of temporal dispersion, LCWs are typically employed in steady-state fluorescence detection microsystems rather than in fluorescence lifetime measurement (FLM) systems. In this paper, we present a compact liquid-core waveguide time-correlated single-photon counting (LCW-TCSPC) sensor for FLM. The propagation of excitation within the LCW is analyzed both analytically and in simulations, with results in agreement with experimental characterization. Results reveal an optimal region within the LCW for highly accurate FLM. The proposed prototype achieves excellent excitation rejection and low temporal dispersion as a result of optimization of the propagation length of the excitation within the LCW. The prototype achieves a detection limit of 5 nM for Coumarin 6 in dimethyl sulfoxide with < 3% lifetime error. The techniques proposed for analyzing the LCW for TCSPC based FLM and prototype demonstration pave the way for developing high-performance fluorescence lifetime measurement for microfluidics and point-of-care applications. Graphical abstract A compact liquid-core waveguide time-correlated single-photon counting (LCW-TCSPC) sensor for fluorescence lifetime measurement (FLM) is presented. Results reveal an optimal propagation length region within the LCW for highly accurate FLM. The prototype achieves a detection limit of 5 nM for Coumarin 6 in dimethyl sulfoxide with < 3% lifetime error.

Recent Advances in Fluorescence Lifetime Analytical Microsystems: Contact Optics and CMOS Time-Resolved Electronics.

Fluorescence spectroscopy has become a prominent research tool with wide applications in medical diagnostics and bio-imaging. However, the realization of combined high-performance, portable, and low-cost spectroscopic sensors still remains a challenge, which has limited the technique to the laboratories. A fluorescence lifetime measurement seeks to obtain the characteristic lifetime from the fluorescence decay profile. Time-correlated single photon counting (TCSPC) and time-gated techniques are two key variations of time-resolved measurements. However, commercial time-resolved analysis systems typically contain complex optics and discrete electronic components, which lead to bulkiness and a high cost. These two limitations can be significantly mitigated using contact sensing and complementary metal-oxide-semiconductor (CMOS) implementation. Contact sensing simplifies the optics, whereas CMOS technology enables on-chip, arrayed detection and signal processing, significantly reducing size and power consumption. This paper examines recent advances in contact sensing and CMOS time-resolved circuits for the realization of fully integrated fluorescence lifetime measurement microsystems. The high level of performance from recently reported prototypes suggests that the CMOS-based contact sensing microsystems are emerging as sound technologies for application-specific, low-cost, and portable time-resolved diagnostic devices.

Cuffless and Continuous Blood Pressure Estimation from the Heart Sound Signals.

Cardiovascular disease, like hypertension, is one of the top killers of human life and early detection of cardiovascular disease is of great importance. However, traditional medical devices are often bulky and expensive, and unsuitable for home healthcare. In this paper, we proposed an easy and inexpensive technique to estimate continuous blood pressure from the heart sound signals acquired by the microphone of a smartphone. A cold-pressor experiment was performed in 32 healthy subjects, with a smartphone to acquire heart sound signals and with a commercial device to measure continuous blood pressure. The Fourier spectrum of the second heart sound and the blood pressure were regressed using a support vector machine, and the accuracy of the regression was evaluated using 10-fold cross-validation. Statistical analysis showed that the mean correlation coefficients between the predicted values from the regression model and the measured values from the commercial device were 0.707, 0.712, and 0.748 for systolic, diastolic, and mean blood pressure, respectively, and that the mean errors were less than 5 mmHg, with standard deviations less than 8 mmHg. These results suggest that this technique is of potential use for cuffless and continuous blood pressure monitoring and it has promising application in home healthcare services.

Dual Defocused Laser Pyrolysis: A Lasing-Centric Strategy for Defect and Morphological Optimization in Microsupercapacitor Electrodes.

Laser-induced graphene (LIG) has shown great potential for controllable and scalable realization of microsupercapacitors (MSCs). However, as is well-known, LIG electrodes suffer from low charge storage capacity and conductance. In this paper, a lasing-centric method is presented for defect control and morphological enhancement in LIG electrodes through unique dual laser pyrolysis. This method encompasses dual lasing pyrolysis, one for the synthesis of defocused LIG, and another for the decoration of Ru nanoparticles to enhance electrochemical performance. Fundamentally, the investigation simultaneously optimizes for defocused lasing distance and lasing speed, which to the best of the author's knowledge, has not been previously reported. The defocused LIG electrode exhibits a remarkably improved electrochemical capacitance of over 25 times (114 mF cm-2 ) compared to the one based on focused laser-induced graphene (FLIG). As a device demonstration, a flexible and self-healable MSC has been fabricated based on DFLIG/Ru-PEDOT/Au electrodes, exhibiting a high areal specific capacitance (25.7 mF cm-2 ), excellent electrochemical stability (91% retention of specific capacitance after 8000 cycles), and good self-healing performance (85.6% retention of specific capacitance after two cut-heal cycles). By enhancing material properties via dual defocused laser pyrolysis, this work presents a strategy for highly controllable and scalable realization of electrodes in micro-energy storage devices.

A correlation study of beat-to-beat R-R intervals and pulse arrival time under natural state and cold stimulation.

Beat-to-beat R-R intervals (RRI) and pulse arrival time (PAT) provide pivotal information to evaluate cardiac autonomic functions for predicting arrhythmias and cardiovascular morbidity. However, their relationship has not been clearly understood. In this study, we simultaneously recorded electrocardiograms and photoplethysmograms on 34 subjects in the natural state, and on 55 subjects under the cold stimulation. The RRI and the PAT were calculated and then analyzed using Pearson correlation coefficient. The results showed that the RRI and the PAT were strongly correlated (r = 0.562) and the RRI series were 2.18 ± 0.40 beats advanced to the PAT series. After smoothing, the RRI and the PAT were more correlated in the low frequency than in the high frequency. Furthermore, when involving RRI with the phase effect, the proposed PAT based model showed better performance for blood pressure estimation. We think these results are helpful to understand the underlying regulatory mechanisms of the two cardiovascular factors, and would provide useful suggestions for non-invasive cuffless blood pressure estimation.

Bean Pod-Inspired Ultrasensitive and Self-Healing Pressure Sensor Based on Laser-Induced Graphene and Polystyrene Microsphere Sandwiched Structure.

Flexible pressure sensors are currently at the center stage of wearable electronics. Despite tremendous progress in the recent years, flexible pressure sensors with high sensitivity, high stability, and mechanical robustness are still challenging. In this paper, as inspired by the bean pod structure, a sensor architecture consisting a microspacer core layer of polystyrene (PS) microspheres, sandwiched between two laser-induced graphene/polyurethane (LIG/PU) films, is presented. A flexible and self-healable pressure sensor is prepared, achieving ultrahigh sensitivity, improved linearity, wide sensing range up to 100 kPa, and excellent stability (for over 1000 loading-unloading cycles). Specifically, the pressure sensor achieves high sensitivities of 149, 659, and 2048 kPa-1 for the pressure ranges of 0-1, 1-10, and 10-100 kPa, respectively. Upon three cut-heal cycles at room temperature, severely damaged devices are self-healed and are able to maintain high sensitivity. The sensors have been further verified in stringent applications, such as human arterial pulse monitoring and gait detection. The novel device architecture enabling facile fabrication and high performance paves the way to the scalable production of pressure sensors for human physiological diagnostics and other advanced wearable applications.

[Identification and analysis of genuine and false Flos Rosae Rugosae by FTIR and 2D correlation IR spectroscopy].

The genuine and false Flos Rosae Rugosae (Flos Rosae Chinensis and Flos Rosa multiflora) were examined in terms of their differences by using Fourier transform infrared spectroscopy (FTIR) combined with two-dimensional (2D) correlation IR spectroscopy. The three species were shown very similar in FTIR spectra. The peak of 1318 cm(-1) of genuine Flos Rosae Rugosae is not obvious but this peak could be found sharp in Flos Rosae Chinensis and Flos Rosa multiflora. Generally, the second derivative IR spectrum can clearly enhance the spectral resolution. Flos Rosae Rugosae and Flos rosae Chinensis have aromatic compounds distinct fingerprint characteristics at 1 617 and 1 618 cm(-1), respectively. Nevertheless, FlosRosa multiflora has the peak at 1612 cm(-1). There is a discrepancy of 5 to 6 cm(-1). FlosRosa multiflora has glucide's distinct fingerprint characteristics at 1 044 cm(-1), but Flos Rosae Rugosae and Flos Rosae Chinensis don't. The second derivative infrared spectra indicated different fingerprint characteristics. Three of them showed aromatic compounds with autopeaks at 1620, 1560 and 1460 cm(-1). Flos Rosae Chinensis and Flos Rosa multiflora have the shoulder peak at 1660 cm(-1). In the range of 850-1250 cm(-1), three of them are distinct different, Flos Rosae Rugosae has the strongest autopeak, Flos Rosae Chinensis has the feeble autopeak and Flos Rosa multiflora has no autopeak at 1050 cm(-1). In third-step identification, the different contents of aromatic compounds and glucide in Flos Rosae Rugosae, Flos Rosae Chinensis and Flos Rosa multiflora were revealed. It is proved that the method is fast and effective for distinguishing and analyzing genuine Flos Rosae Rugosae and false Flos Rosae Rugosae (Flos Rosae Chinensis and Flos Rosa multiflora).

[Effects of seeds irradiation with 60Cogamma-ray on shoot growth and physiological status of Carthamus tinctorius].

OBJECTIVE: To provide the radiation-induced technical reference and theoretical basis for safflower and other medicinal plants. METHOD: Seeds of Carthamus tinctorius were irradiated with 60Cogamma-ray, and germination rate of seeds, germination, seedling rate and seedling height, root length, fresh weight, root activity and peroxide catalase (CAT), peroxidase (POD), superoxide dismutase (SOD) activity were determined. RESULT AND CONCLUSION: The LD50 of radiation dose is about 300 Gy, effects of seeds irradiation with 6Co-gamma-ray on shoot growth and physiological status of C. tinctorius are obtained.

Time-frequency analysis of heart rate variability during the cold pressor test using a time-varying autoregressive model.

Heart rate variability is a useful clinical tool for autonomic function assessment and cardiovascular disease diagnosis. To investigate the dynamic changes of sympathetic and parasympathetic activities during the cold pressor test, we used a time-varying autoregressive model for the time-frequency analysis of heart rate variability in 101 healthy subjects. We found that there were two sympathetic peaks (or two parasympathetic valleys) when the abrupt changes of temperature (ACT) occurred at the beginning and the end of the cold stimulus and that the sympathetic and parasympathetic activities returned to normal in about the last 2 min of the cold stimulus. These findings suggested that the ACT rather than the low temperature was the major cause of the sympathetic excitation and parasympathetic withdrawal. We also found that the onsets of the sympathetic peaks were 4-26 s prior to the ACT and the returns to normal were 54-57 s after the ACT, which could be interpreted as the feedforward and adaptation of the autonomic regulation process in the human body, respectively. These results might be helpful for understanding the regulatory mechanisms of the autonomic system and its effects on the cardiovascular system.