Pulse Amplitude Measurements Research Articles

Data analysis procedures to improve energy resolution in silicon detectors using GET electronics

This study primarily focuses on improving the energy resolution of Double-Sided Silicon Strip Detectors (DSSSD) through optimized data analysis procedures using General Electronics for Time Projection Chambers (GET). We introduce two edge identification algorithms that demonstrate comparable efficacy. These methods are subsequently integrated with various techniques for measuring pulse amplitude, including sample smoothing and pole-zero cancellation. Notably, sample smoothing significantly enhances performances, achieving a resolution of 0.33% with DSSSD α calibration data. Additionally, we describe and apply the trapezoidal filter, examining its impact on resolution improvement and obtaining comparable results. The study also evaluates how internal GET parameters, specifically the sampling frequency and the shaping time of the Sallen-Key (SK) low-pass filter, affect signal resolution. Higher sampling frequencies and lower values of the SK filter were found to increase performance.

Optimization of the position of TaOx:N-based barrier layer in TaOx RRAM devices

Resistive Random-Access Memory (RRAM) presents a transformative technology for diverse computing and artificial intelligence applications. However, variability in the high resistance state (HRS) has proved to be a challenge, impeding its widespread adoption. This study focuses on optimizing TaOx-based RRAMs by strategically placing a nitrogen-doped TaOx barrier-layer (BL) to mitigate variability in the HRS. Through comprehensive electrical characterization and measurements, we uncover the critical influence of BL positioning on HRS variability and identify the optimal location of the BL to achieve a 2x lowering of HRS variability as well as an expanded range of operating voltages. Incremental reset pulse amplitude measurements show that the TaOx:N maintains a low HRS variability even at higher operating voltages when the position of the BL is optimized. Our findings offer insights into stable and reliable RRAM operation, highlighting the potential of the proposed BL to enhance the functionality of TaOx-based RRAMs and elevate overall device performance.

(125) Measurement of Clitoral Pulse Amplitude with a Wearable Device

Abstract Introduction Penile erection is well understood and has been extensively studied. The Erectile Hardness Score is a commonly used tool to quantify the strength of an erection. Few such measurement tools exists for women. This study builds on the work done by Mechelmans et al exploring Clitoral Pulse Amplitude (CPA) as a marker for physical arousal in women. CPA has been shown to be related to clitoral blood volume, erection, and engorgement of the clitoris. The erection in the clitoris is homologous to penile erection. Objective To test a new, wearable, clitoral pulse sensor designed for at-home use for correlation with subjective arousal for proof of concept. To test the comfort and usability of such a device configured with an internal (vaginal) portion and a clitoral portion. Methods 20 healthy female participants were shipped the device and completed the study from their home with an online module which guided them through the study material. Participants wore the device while watching a control (non-arousing) video and during progressively more sexually arousing activities. They were allowed to choose their own materials to watch, read, or listen to for arousal. A masturbation phase was included for additional information. Participants also reported their subjective arousal after each phase. After the test, participants were also surveyed about the comfort and usability of the device. Results The pulse sensor successfully detected CPA. Results show that most participants had increasing levels of subjective arousal correlating with increasing CPA. Statistical correlation between CPA and arousal was positive but low, which could be attributed to differences of sensor calibration and/or device placement by participants. Overall, this positive relationship indicates that a commercially available pulse sensor could be integrated into a future device to measure physical arousal in women, a metric which was previously not widely available. Participants reported high satisfaction with the comfort and usability of the device. These insights validate that this device shape will be comfortable and usable in further iterations, with the ultimate goal of producing a device which would give clitoris-owners greater insight into their sexual health and provide valuable information to their healthcare providers. Conclusions This study showed a positive relationship between Clitoral Pulse Amplitude and subjective sexual arousal using an at-home wearable device, opening possibilities for future measurement devices. Participants felt the device was very comfortable and easy to use, suggesting this form factor with vaginal (internal) and clitoral (external) portions is a viable configuration for further development. We anticipate improving both the pulse sensing system and device usability as the device is further commercialized. Disclosure Yes, this is sponsored by industry/sponsor: FirmTech. Clarification: Industry initiated, executed and funded study. Any of the authors act as a consultant, employee or shareholder of an industry for: FirmTech.

Prediction of shunt response in idiopathic normal pressure hydrocephalus by combined lumbar infusion test and preoperative imaging scoring.

Idiopathic normal pressure hydrocephalus (iNPH) is a potentially treatable disorder, but prognostic tests or biomarkers are lacking. The aim was to study the predictive power of clinical, neuroimaging and lumbar infusion test parameters (resistance to outflow Rout , cardiac-related pulse amplitude PA and the PA to intracranial pressure ICP ratio). In all, 127 patients diagnosed with iNPH who had a lumbar infusion test, a subsequent ventriculo-peritoneal shunt operation and at least 2 months of postoperative follow-up were retrospectively included. Preoperative magnetic resonance images were visually scored for NPH features using the iNPH Radscale. Preoperative and postoperative assessment was performed using cognitive testing, as well as gait and incontinence scales. At follow-up (7.4 months, range 2-20 months), an overall positive response was seen in 82% of the patients. Gait was more severely impaired at baseline in responders compared to non-responders. The iNPH Radscale score was borderline significantly higher in responders compared with non-responders, whereas no significant differences in infusion test parameters were seen between responders and non-responders. Infusion test parameters performed modestly with high positive (75%-92%) but low negative (17%-23%) predictive values. Although not significant, PA and PA/ICP seemed to perform better than Rout , and the odds ratio for shunt response seemed to increase in patients with higher PA/ICP, especially in patients with lower iNPH Radscale scores. Although only indicative, lumbar infusion test results increased the likelihood of a positive shunt outcome. Pulse amplitude measures showed promising results that should be further explored in prospective studies.

Artificial neural network on-chip and in-pixel implementation towards pulse amplitude measurement

We present the design of an in-pixel artificial intelligence (AI) for extraction of an amplitude of a pulse generated in semiconductor detector. The AI is design with traditional multi-level perceptron scheme having 6 layers and the total number of 420 parameters. The implementation shows 0.34% measurement accuracy. The AI block is fed by the 6-bit ADC at 5 MHz sampling rate. Standard front-end is optimized for low-noise pulses carrying 1000–3000 electrons. The methodology was tested using FPGA and results are promising. The design is intended to be fabricated and verified in the prototype solution.

Zero retinal vein pulsation amplitude extrapolated model in non-invasive intracranial pressure estimation

Intracranial pressure (ICP) includes the brain, optic nerve, and spinal cord pressures; it influences blood flow to those structures. Pathological elevation in ICP results in structural damage through various mechanisms, which adversely affects outcomes in traumatic brain injury and stroke. Currently, invasive procedures which tap directly into the cerebrospinal fluid are required to measure this pressure. Recent fluidic engineering modelling analogous to the ocular vascular flow suggests that retinal venous pulse amplitudes are predictably influenced by downstream pressures, suggesting that ICP could be estimated by analysing this pulse signal. We used this modelling theory and our photoplethysmographic (PPG) retinal venous pulse amplitude measurement system to measure amplitudes in 30 subjects undergoing invasive ICP measurements by lumbar puncture (LP) or external ventricular drain (EVD). We estimated ICP from these amplitudes using this modelling and found it to be accurate with a mean absolute error of 3.0 mmHg and a slope of 1.00 (r = 0.91). Ninety-four percent of differences between the PPG and invasive method were between − 5.5 and + 4.0 mmHg, which compares favourably to comparisons between LP and EVD. This type of modelling may be useful for understanding retinal vessel pulsatile fluid dynamics and may provide a method for non-invasive ICP measurement.

A new approach for pulse amplitude measurement using Lagrange’s interpolation for radiation or particle detectors

In radiation detector signal processing, usually, the charge-sensitive preamplifier converts the small charge signal coming from the semiconductor-based detector into voltage form and then the signal is further amplified to measure the energy of the incoming radiation. The voltage pulse from a charge-sensitive preamplifier (CSPA) is amplified using a shaping amplifier which reduces the signal bandwidth. To achieve better energy resolution, precise measurement of the peak amplitude of shaping amplifier output is required. The signal processing methods are available in which the signal from the charge-sensitive preamplifier can be directly digitized using high-speed Analog to Digital Converters (ADC), and then further signal processing such as gain and shaping is carried out inside the Field Programmable Gate Arrays (FPGA). For multiple detector systems, digital signal processing methods are quite difficult to implement in Field Programmable Gate Arrays (FPGA). In this context, The development of an alternative technique is initiated that uses a charge-sensitive preamplifier, shaping amplifier, low sampling analog-to-digital converter, and FPGA, where LaGrange’s interpolation technique is implemented in FPGA to precisely measure the peak of the analog pulse. In this paper, the comparison of the proposed method with other pulse amplitude measurement techniques is discussed. Results show that the implemented technique gives similar energy resolution compared to digital pulse processing and standard peak detector-based techniques.

Effects of childhood obesity on ocular pulse amplitude and intraocular pressure.

To assess intraocular pressure and ocular pulse amplitude changes in obese children and adolescents using dynamic contour tonometry. 137 cases, 64 obese and 73 healthy children, who were both age-matched and gender-matched, comprised the study population in this cross-sectional study. Children with body mass index values >95% for sex and age were regarded as obese. Participants underwent detailed ophthalmological examinations, including intraocular pressure measurement using a Pascal dynamic contour tonometer. Relationships between intraocular pressure and ocular pulse amplitude measurements and age, sex, obesity, pubertal status, and insulin resistance were investigated. Bilateral ocular pulse amplitude was lower while intraocular pressure was higher in the obese group than in the control group (p<0.001). No significant relationship was observed between insulin resistance and intraocular pressure or ocular pulse amplitude (p>0.005). No correlation was determined between systolic and diastolic blood pressure, homeostasis model assessment for insulin resistance, or blood lipid levels and intraocular pressure and ocular pulse amplitude. Our results show that obesity caused an increase in intraocular pressure and a decrease in ocular pulse amplitude independently of insulin resistance in children and adolescents. Prospective studies involving long-term follow-up of cases are now needed to assess the probable adverse effects of these ocular findings in obese children.

Non-invasive Clinical Measurement of Ocular Rigidity and Comparison to Biomechanical and Morphological Parameters in Glaucomatous and Healthy Subjects.

Purpose: To assess ocular rigidity using dynamic optical coherence tomography (OCT) videos in glaucomatous and healthy subjects, and to evaluate how ocular rigidity correlates with biomechanical and morphological characteristics of the human eye.Methods: Ocular rigidity was calculated using Friedenwald's empirical equation which estimates the change in intraocular pressure (IOP) produced by volumetric changes of the eye due to choroidal pulsations with each heartbeat. High-speed OCT video was utilized to non-invasively measure changes in choroidal volume through time-series analysis. A control-case study design was based on 23 healthy controls and 6 glaucoma cases. Multiple diagnostic modalities were performed during the same visit including Spectralis OCT for nerve head video, Pascal Dynamic Contour Tonometry for IOP and ocular pulse amplitude (OPA) measurement, Corvis ST for measuring dynamic biomechanical response, and Pentacam for morphological characterization.Results: Combining glaucoma and healthy cohorts (n = 29), there were negative correlations between ocular rigidity and axial length (Pearson R = −0.53, p = 0.003), and between ocular rigidity and anterior chamber volume (R = −0.64, p = 0.0002). There was a stronger positive correlation of ocular rigidity and scleral stiffness (i.e., stiffness parameter at the highest concavity [SP-HC]) (R = 0.62, p = 0.0005) compared to ocular rigidity and corneal stiffness (i.e., stiffness parameter at the first applanation [SP-A1]) (R = 0.41, p = 0.033). In addition, there was a positive correlation between ocular rigidity and the static pressure-volume ratio (P/V ratio) (R = 0.72, p < 0.0001).Conclusions: Ocular rigidity was non-invasively assessed using OCT video and OPA in a clinic setting. The significant correlation of ocular rigidity with biomechanical parameters, SP-HC and P/V ratio, demonstrated the validity of the ocular rigidity measurement. Ocular rigidity is driven to a greater extent by scleral stiffness than corneal stiffness. These in vivo methods offer an important approach to investigate the role of ocular biomechanics in glaucoma.

CORRECTION OF THE METHOD FOR MEASURING THE AMPLITUDES OF THE CURRENT OF THE IMPULSE ALONG THE LONG EARTH ELECTRODE

An improved method for measuring the amplitude reduction of the lightning current impulse as it flows from the beginning to the end of long horizontal earthing arrangement using ferromagnetic recorders has been substantiated. Two existing methods of pulse amplitude measurements at high voltages, the magnetic recording method and the method using a shunt, are used in justification. It is noted that in a number of cases it becomes necessary to determine the decrease in the pulse amplitude as it flows on a long object. This leads to the need to develop a method for performing such measurements. As an example, a long horizontal earth electrode was investigated when a lightning current pulse moves on it. Based on experimental studies in natural conditions, an improved method for measuring the decrease in the amplitude of the lightning current impulse along a long earth electrode is proposed. The proposed method has a measurement error not exceeding 10 %, and allows simultaneous measurements of the amplitude of the current strength at given points of the object, which can amount to tens or even hundreds. This method is implemented in a simple design and has an affordable manufacturing cost. The results of the experiments performed make it possible to recommend the corrected measurement method for practical use on existing electrical installations. The use of ferromagnetic recorders for recording and measuring the lightning current in areas of complex earthing arrangements is relevant for practical reasons, which include the possibility of measuring during a long wait and long-term storage of measurement results, does not require additional power sources and provides the possibility of synchronous measurements at various points of the grounding device. An important feature of the method is safety for technical equipment and personnel.

The Successful Measurement of Clitoral Pulse Amplitude Using a New Clitoral Photoplethysmograph: A Pilot Study

BackgroundAlthough the clitoris is more sensitive to stimulation and its innervation more conducive to sensory feedback than the vagina, the field of sexual psychophysiology, which uses psychophysiological methods including genital response measures to study sexual arousal, relies heavily on the measurement of vaginal, rather than clitoral, pulse amplitude. AimTo develop and test a new clitoral photoplethysmograph for the measurement of clitoral pulse amplitude (CPA). Methods2 versions of the new device, which differed in the orientation of the sensor and light source (parallel vs angled), were tested in 15 premenopausal, sexually functional women. Vaginal pulse amplitude (VPA) was assessed simultaneously. The women viewed a 3-minute erotic and an anxiety-inducing film segment with each clitoral sensor, interspersed with neutral video excerpts. In addition, they were asked to indicate their subjective level of sexual arousal during and after erotic video presentations. OutcomesThe main outcome measures are CPA, VPA, and subjective sexual arousal. ResultsThe clitoral photoplethysmograph successfully detected CPA. The quality of the signals was best for the angled sensor. Main effects of the film and the interaction between the film and epoch were stronger for the clitoral than for the vaginal device. In addition, CPA followed more closely changes in intensity of sexual films than VPA. Within- and between-subject correlations between genital response and subjective sexual arousal were higher for the clitoral than for the vaginal device. Clinical TranslationComparison of CPA with other genital blood flow measures in clinical samples is indicated and may contribute to improved physiological assessments of sexual response in women. Strengths and LimitationsOur sample was small and consisted of healthy volunteers. Future research could examine test-retest reliability, by including multiple recording sessions, and further explore the specificity of CPA by comparing sexual and non-sexual stimuli with positive valence. ConclusionThis study presents the first instrument to successfully measure CPA.Mechelmans DJ, Sachtler WL, von Wiegand TE, et al. The Successful Measurement of Clitoral Pulse Amplitude Using a New Clitoral Photoplethysmograph: A Pilot Study. J Sex Med 2020;17:1118–1125.

Ocular Pulse Elastography: Imaging Corneal Biomechanical Responses to Simulated Ocular Pulse Using Ultrasound.

PurposeIn vivo evaluation of corneal biomechanics holds the potential for improving diagnosis and management of ocular diseases. We aimed to develop an ocular pulse elastography (OPE) technique to quantify corneal strains generated by naturally occurring pulsations of the intraocular pressure (IOP) using high-frequency ultrasound.MethodsSimulated ocular pulses were induced in whole porcine and human donor globes to investigate the effects of physiologic variations in baseline IOP, ocular pulse amplitude, and frequency on corneal strains. Ocular pulse–induced strains were measured in additional globes before and after UVA-riboflavin–induced corneal crosslinking. The central cornea in each eye was imaged with a 50-MHz ultrasound imaging system and correlation-based speckle tracking of radiofrequency data was used to calculate tissue displacements and strains.ResultsOcular pulse–induced corneal strains followed the cyclic changes of IOP. Both baseline IOP and ocular pulse amplitude had a significant influence on strain magnitude. Variations in pulse frequency within the normal human heart rate range did not introduce detectable changes in corneal strains. A significant decrease of corneal strain, as quantified by the OPE technique, was observed after corneal crosslinking. The extent of corneal stiffening (i.e., strain reduction) seemed to correlate with the initial strain magnitude.ConclusionsThis ex vivo study demonstrated the feasibility of the OPE method to quantify corneal strains generated by IOP pulsation and detect changes associated with corneal crosslinking treatment.Translational RelevanceIntegrating in vivo measurement of IOP and ocular pulse amplitude, the OPE method may lead to a new clinical tool for safe and quick biomechanical evaluations of the cornea.

Usefulness of Noninvasively Measured Pulse Amplitude Changes During the Valsalva Maneuver to Identify Hospitalized Heart Failure Patients at Risk of 30-Day Heart Failure Events (from the PRESSURE-HF Study)

The pulse amplitude ratio (PAR), the ratio of pulse pressure at the end of the Valsalva maneuver to before the onset, correlates with cardiac filling pressure. We have developed a handheld device that uses finger photoplethysmography to measure PAR and estimate left ventricular end diastolic pressure (LVEDP). Patients hospitalized with heart failure (HF) performed three 10-second trials of a standardized Valsalva maneuver (at 20 mm Hg measured via pressure transducer), while photoplethysmography waveforms were recorded, at admission and discharge. Combined primary outcome was 30-day HF hospitalization, intravenous diuresis, or death. Fifty-two subjects had discharge PAR testing; 12 met the primary outcome. Median PAR on admission was 0.55 (interquartile range: 0.40 to 0.70, n = 48) and on discharge was 0.50 (interquartile range: 0.36 to 0.69). Mean PAR-estimated LVEDP was significantly higher in subjects that had an event (20.2 vs 16.9 mm Hg, p = 0.043). Subjects with PAR-estimated LVEDP >19.5 mm Hg had an event rate hazard ratio of 4.57 (95% confidence interval 1.37, 15.19, p = 0.013) compared with patients with LVEDP 19.5 mm Hg or below, with significantly lower 30-day event-free survival (log-rank p = 0.006). In conclusion, noninvasively estimated LVEDP using the pulse amplitude response to a Valsalva maneuver in patients hospitalized for HF changes with diuresis and identifies patients at high risk for 30-day HF events. Detection of elevated filling pressures before hospital discharge may be useful in guiding HF management to reduce HF events.

Pulse Pileup Correction of Signals From a Pyroelectric Sensor for Phase-Insensitive Ultrasound Computed Tomography

This paper describes the application of a pulse pileup correction algorithm based on maximum likelihood estimation to simulated and experimentally acquired signals from a pyroelectric ultrasound sensor. The sensor forms part of a prototype phase-insensitive ultrasound computed tomography (piUCT) system for breast cancer detection that generates quantitative maps of acoustic attenuation. The effectiveness of the piUCT technique has been previously demonstrated through imaging of cylindrical, polyurethane phantoms. For the technique to be applied clinically, the system must be capable of measuring high acoustic attenuations (>30 dB) and completing a scan in a clinically acceptable time frame of approximately 5 min. High attenuations present a challenge because the sensor responds directly to acoustic power and therefore, an attenuation of 30 dB causes a drop in signal level of three orders of magnitude, resulting in a large dynamic range in the received signal set. Completion of a scan in 5 min requires a period between measurements shorter than the response time of the sensor, causing pyroelectric pulse pileup. The maximum likelihood estimation method recovers the amplitudes of closely spaced superimposed pyroelectric signals while improving the coefficient of variation of the measurement by a factor of two compared to direct pulse amplitude measurement, simultaneously increasing the maximum measurable attenuation and measurement rate of the system.

Quantifying the Delays Between Multi-Site Photoplethysmography Pulse and Electrocardiogram R-R Interval Changes Under Slow-Paced Breathing.

Objective: Objective assessment of autonomic function is important, including the investigation of slow-paced breathing to induce associated periodic changes in the cardiovascular system – such as blood pressure and heart rate. However, pulse changes across a range of peripheral body sites have seldom been explored with this challenge. The primary aim of this pilot study was to utilize multi-site photoplethysmography (MPPG) technology to quantify the phase delays, i.e., correlation lags, between changes in heart rate and changes in key pulse features with slow-paced breathing (0.1 Hz).Methods: Waveforms were collected simultaneously from the right and left ear lobes, thumbs, and great toes of 18 healthy adult subjects. Cross correlation lags between reference beat-to-beat changes in electrocardiogram (ECG) R-R wave interval and changes in pulse arrival time (foot of pulse; PATf) and also for pulse amplitude (foot-to-peak; AMP) were determined.Results: Relative to R-R changes, the median ear, thumb, and toe PATf correlation lags were 3.4, 2.9, and 2.1 beats, respectively; contrasting to AMP with 5.7, 6.0, and 6.9 beats, respectively. These PATf correlation lags in beats were significantly lower than for the AMP measure. Segmental differences between sites and timing measure variability have also been quantified.Conclusion: This pilot study has indicated bilateral similarity plus segmental differences for relative delays in PPG pulse timing and amplitude measures relative to R-R interval changes with paced breathing. These correlation and variability data are now available for comparison with cardiovascular patient groups to support development of autonomic function assessment techniques.

Investigating microchannel plate PMTs with TOFPET2 multichannel picosecond timing electronics

TOFPET2 is the second-generation design of a high-performance multichannel picosecond timing readout electronics ASIC produced by PETsys Electronics SA, Portugal. Originally developed for time-of-flight positron emission tomography using silicon photomultipliers, in this work we describe an experimental programme to evaluate the performance of TOFPET2 with pixelated microchannel plate (MCP) photomultiplier tube (PMT) detectors.Investigations were performed using various signal input methods; injected electronic stim signals, SiPM photodetectors, a single anode MCP photomultiplier detector and finally imaging with a demountable multi-anode MCP detector using a 16 x 16 pixelated multi-layer ceramic readout. The detector utilised an active anode plus image charge configuration to provide the positive signal pulses required by the electronics.Measurements were undertaken using the PETsys Time-of-Flight ASIC evaluation kit (mark2) operating in single photon counting mode. We present performance results for time resolution, cross channel coincidence time resolution and energy resolution using internal pulse amplitude measurement and time-over-threshold signal paths.Photodetector timing performance was evaluated using a 40 ps wide pulsed laser, operating at single photon level using a temperature stabilised setup within a dark enclosure. Amplitude walk correction was applied using the in-built time-over-threshold output from the TOFPET2 system. Single photon timing resolution of better than 110 FWHM was demonstrated. Preliminary results obtained using signal spread over adjacent pixels of a pixellated anode yield a coincidence timing resolution of ∼87 ps rms.

Do ocular pulse amplitude and choroidal thickness change in patients with thyroid eye disease?

ABSTRACTPurpose: The aim of this study was to evaluate whether orbital changes induced by thyroid eye disease affect the ocular pulse amplitude and choroidal perfusion.Materials and Methods: A total of 38 eyes of 38 patients with thyroid eye disease (Group 1) and 38 eyes of 38 control individuals (Group 2) with normal intraocular pressure were enrolled in this study. Thyroid eye disease activity was defined using clinical activity score. Intraocular pressure measurement with Goldmann applanation tonometer, axial length, central corneal thickness, Hertel exophthalmometry and systolic and diastolic blood pressure measurements were taken from each patient. Ocular pulse amplitude and intraocular pressure were measured using dynamic contour tonometry. Choroidal thickness was measured by enhanced depth imaging-optical coherence tomography at subfoveal, nasal and temporal 1000 μm area.Results: Intraocular pressures measured with Goldmann applanation tonometer and dynamic contour tonometry and mean ocular pulse amplitude were not statistically different between groups. However mean choroidal thicknesses were significantly lower when compared to control group. Ocular pulse amplitude and intraocular pressure measurement with dynamic contour tonometry did not change significantly with the increase in clinical activity score. There was not statistically significant correlation between ocular pulse amplitude and choroidal thicknesses in patients with thyroid eye disease.Conclusion: Ocular pulse amplitude and choroidal perfusion were not found to change with orbital involvement in thyroid eye disease and with disease activity, especially in patients with normal intraocular pressure. Although choroidal thickness was thinner than control group, choroidal perfusion did not change as a compensatory mechanism for maintaining ocular homeostasis.

Experimental investigation on the suitability of flexible pressure sensor for wrist pulse measurement

Pulse examination at the radial artery of the wrist is a most apparent diagnosis technique. Wrist pulse carries rich information about the cardiovascular system of human body. An investigation is made here to suggest suitable flexible type of thin film pressure sensor to measure the wrist pulse as per Ayurvedic medicine system. Primary objective of this work is to suggest a sensor which exhibits optimum spatial features and SNR values. Force Sensing Resistor (FSR), piezoresistive and piezoelectric thin film sensors are considered under this study. Piezoelectric sensor shows good performance in the quality of the pulse with 22 dB SNR. Further experimentation is conducted to find out transmissivity, repeatability and susceptibility to motion artifact. Trasnsmissivities of 0.91, 0.68 and 0.64 are obtained for piezoelectric, piezoresistive and FSR sensors respectively. Piezoresistive and FSR show repeatability error of ±8% and ± 7% while measuring pulse amplitude under standard force. Noise due to motion artifact for each type of sensors are recorded and compared with the standard Gaussian distribution function with the help of histogram. Collectively, piezoelectric sensor exhibits good spatial features, high transmissivity and comparatively low susceptibility to motion artifact.

Altitude of origin influences the responses of PSII photochemistry to heat waves in European beech (Fagus sylvatica L.)

The photosynthetic responses to the combined effect of drought and heat stress were studied in leaves of 19-years-old European beech (Fagus sylvatica L.) trees originating from five provenances in Central Europe differing by altitude (55–1250 m), and grown in the same experimental plot. The measurements were conducted at the beginning of heat waves, under two different conditions: during a dry period (middle of July) and after recovery in wetter period, at the beginning of August. The decreases of stomatal conductance (gs) and net photosynthesis rate (ACO2) during drought and heat wave stress were very similar in all provenances. However, we observed distinct response of PSII photochemistry on combined drought and high temperature stress, well associated with altitude of origin of the beech provenances. Measurements of pulse amplitude modulated (PAM) fluorescence identified maintenance of a high electron transport rate in beech provenances from high altitudes under drought and heat wave conditions, associated with some decrease of excitation pressure on PSII. This can be explained by enhanced capacity of alternative electron sinks to utilize the excess of electrons as a photoprotective mechanism. The analyses of fast chlorophyll fluorescence kinetics confirmed the differences in responses of PSII photochemistry between provenances originating from different altitudes. Compared with provenances at higher altitudes, we found more sensitive response (i.e. more limited electron transport at the PSII acceptor side and changes in the size of light harvesting complexes) to drought and heat stress, in those growing at low altitudes. Our results support the hypothesis that the provenances originating from higher altitudes possess enhanced phenotypic plasticity related to photoprotective responses, resulting from the long-term adaptation to marginal mountain conditions.

In situ continuous countercurrent cloud point extraction of microalgae cultures

Abstract Green microalgae are gaining increased interest due to their ability to accumulate high-value compounds such as pigments, oils, antioxidants, and aromatics. These hydrophobic compounds can be extracted from the culture by the means of the biocompatible surfactant-based in situ cloud point extraction. In this study, we developed a continuous cloud point extraction using the nonionic surfactant Triton X-114, in order to extract the lipophilic substances from a green microalgae culture and accumulate these in the surfactant-rich phase. Cinnamic acid was applied as tracer in order to determine the optimal operating conditions for the extraction in a stirred extraction column. This model substance shows satisfying partitioning in the micellar phase ( 10 log P CA = 1.2 ± 0.2) and the maximal yield of 79.1 ± 0.2% in a corresponding batch experiment. The process window for the continuous extraction was developed based on three parameter ranges: feed-to-solvent ratio of 6–10, a total column capacity of 1–2 l·h −1 , and a stirring speed of 20–60 rpm. Statistical experimental design utilizing a response surface method was applied to investigate the influence of the three process parameters mentioned above on the yield and productivity of cinnamic acid. The optimal conditions for the in situ extraction of the microalgae were validated with an Acutodesmus obliquus culture (cell dry weight = 1g·l −1 ). A total amount of 0.2 ± 0.1 g Algae product /kg Culture (0.2 ± 0.1 g Algae product /g cell dry weight ) accumulated in the extract phase. A good biocompatibility of the surfactant with the microalgae cells in raffinate was demonstrated by measuring the photosynthetic activity with a pulse amplitude measurement. This study demonstrated for the first time a successful application of a surfactant-based cloud point extraction of microalgae in a continuous mode. The presented results proved the potential of the in situ surfactant-based extraction of microalgae products as an alternative to conventional extraction techniques.