Direct Intensity Measurements Research Articles

Phase analysis of biphoton joint spectra by interference between different SPDC sources

In spontaneous parametric down-conversion, the spectral correlations between the signal and the idler are expressed by the joint spectral amplitude (JSA) function. However, in the standard coincidence measurements, the phase information of the JSA is lost, and only the square of the absolute value of the JSA is recorded, thus preventing full characterization of the biphoton state. Here, we present an experimental technique to investigate the interference of biphoton joint spectral amplitudes, unlocking new avenues in quantum photonics research. Our method explores phase-dependent phenomena within entangled biphoton spectra. This is achieved by simultaneously pumping two structured nonlinear photonic crystals and observing their interference, which reveals previously inaccessible effects with direct intensity measurements. We demonstrate the versatility of our technique by analyzing two types of joint spectra: one exhibiting a two-lobe shape and the other a three-lobe shape. Additionally, we reconstruct the joint spectral amplitudes for both scenarios and observe good agreement with theoretical predictions. These results pave the way for developing advanced quantum communication and information processing technologies using biphoton spectra.

Quantum estimation of tripartite coupling in spin-magnon-mechanical hybrid systems

Tripartite interactions play a fundamental role in the quantum information processing and quantum technology. However, it is generally difficult to realize strong tripartite coupling. We investigate the estimation of a tripartite coupling strength in a hybrid setup composed of a single nitrogen-vacancy (NV) center and a micromagnet. A time-independent parametric drive can be utilized to increase the estimation precision of the tripartite coupling strength. By calculating the quantum Fisher information (QFI), we can obtain the optimal estimation precision by measuring the eigenstate of the tripartite system. At the critical position, the QFI is divergent due to that the preparation time of the eigenstate is divergent. When the system is subjected to a dissipation, the QFI near the critical point of the driven-dissipation phase transition is analytically obtained. The direct intensity measurement is the optimal measurement near the dissipation phase transition point. In addition, we quantify the robustness of an imperfect measurement operator by the measurement noise susceptibility based on the error propagation formula. We find that the direct intensity measurement is robust enough against small measurement disturbance from a coherent drive. But it can be disturbed by the nonlinear anti-harmonic measurement noise, especially near the critical point.

NuSTAR and Swift observations of two supergiant fast X-ray transients: AX J1841.0−0536 and SAX J1818.6−1703

ABSTRACT Supergiant fast X-ray transients are wind-fed binaries hosting neutron star accretors, which display a peculiar variability in the X-ray domain. Different models have been proposed to explain this variability and the strength of the compact object magnetic field is generally considered a key parameter to discriminate among possible scenarios. We present here the analysis of two simultaneous observational campaigns carried out with Swift and NuSTAR targeting the supergiant fast X-ray transient sources AX J1841.0−0536 and SAX J1818.6−1703. A detailed spectral analysis is presented for both sources, with the main goal of hunting for cyclotron resonant scattering features that can provide a direct measurement of the neutron star magnetic field intensity. AX J1841.0−0536 was caught during the observational campaign at a relatively low flux. The source broad-band spectrum was featureless and could be well-described by using a combination of a hot blackbody and a power-law component with no measurable cut-off energy. In the case of SAX J1818.6−1703, the broad-band spectrum presented a relatively complex curvature which could be described by an absorbed cut-off power law (including both a cut-off and a folding energy) and featured a prominent edge at ∼7 keV, compatible with being associated to the presence of a ‘screen’ of neutral material partly obscuring the X-ray source. The fit to the broad-band spectrum also required the addition of a moderately broad (∼1.6 keV) feature centred at ∼14 keV. If interpreted as a cyclotron resonant scattering feature, our results would indicate for SAX J1818.6−1703 a relatively low-magnetized neutron star (∼1.2 × 1012 G).

Noise-resistant phase imaging with intensity correlation.

Interferometric methods form the basis of highly sensitive measurement techniques from astronomy to bioimaging. Interferometry typically requires high stability between the measured and reference beams. The presence of rapid phase fluctuations washes out interference fringes, making phase profile recovery impossible. This challenge can be addressed by shortening the measurement time. However, such an approach reduces photon-counting rates, precluding applications in low-intensity imaging. We introduce a phase imaging technique which is immune to time-dependent phase fluctuations. Our technique, relying on intensity correlation instead of direct intensity measurements, allows one to obtain high interference visibility for arbitrarily long acquisition times. We prove the optimality of our method using the Cramér-Rao bound in the extreme case when no more than two photons are detected within the time window of phase stability. Our technique will broaden prospects in phase measurements, including emerging applications such as in infrared and x-ray imaging and quantum and matter-wave interferometry.

Real-Time Ellipsometric Surface Plasmon Resonance Sensor Using Polarization Camera May Provide the Ultimate Detection Limit.

Ellipsometric Surface Plasmon Resonance (SPR) sensors are known for their relatively simple optical configuration compared to interferometric and optical heterodyne phase interrogation techniques. However, most of the previously explored ellipsometric SPR sensors based on intensity measurements are limited by their real-time applications because phase or polarization shifts are conducted serially. Here we present an ellipsometric SPR sensor based on a Kretschmann-Raether (KR) diverging beam configuration and a pixelated microgrid polarization camera. The proposed methodology has the advantage of real-time and higher precision sensing applications. The short-term stability of the measurement using the ellipsometric parameters tanψ and cos(Δ) is found to be superior over direct SPR or intensity measurements, particularly with fluctuating sources such as laser diodes. Refractive index and dynamic change measurements in real-time are presented together with Bovine Serum Albumin (BSA)-anti-BSA antibody binding to demonstrate the potential of the developed sensor for biological sensing applications with a resolution of sub-nM and down to pM with additional optimization. The analysis shows that this approach may provide the ultimate detection limit for SPR sensors.

Resolution Limit of Correlation Plenoptic Imaging between Arbitrary Planes

Correlation plenoptic imaging (CPI) is an optical imaging technique based on intensity correlation measurement, which enables detecting, within fundamental physical limits, both the spatial distribution and the direction of light in a scene. This provides the possibility to perform tasks such as three-dimensional reconstruction and refocusing of different planes. Compared with standard plenoptic imaging devices, based on direct intensity measurement, CPI overcomes the problem of the strong trade-off between spatial and directional resolution. Here, we study the resolution limit in a recent development of the technique, called correlation plenoptic imaging between arbitrary planes (CPI-AP). The analysis, based on Gaussian test objects, highlights the main properties of the technique, as compared with standard imaging, and provides an analytical guideline to identify the limits at which an object can be considered resolved.

Positron Emission Intensity in the Decay of 86gY for Use in Dosimetry Studies.

The β+-emitting radionuclide 86gY (t1/2 = 14.7 h) forms a matched-pair with the β−-emitting therapeutic radionuclide 90Y (t1/2 = 2.7 d) for theranostic application in medicine. This approach demands a precise knowledge of the positron emission probability of the PET nuclide which was until recently rather uncertain for 86gY. In this work, an 86gY source of high radionuclidic purity was prepared and a direct measurement of the positron emission intensity per 100 decay of the parent (hereafter “positron emission intensity”) was performed using high-resolution HPGe detector γ-ray spectroscopy. The electron capture intensity was also determined as an additional check by measuring the Kα and Kβ X-rays of energies 14.1 and 15.8 keV, respectively, using a low energy HPGe detector. From those measurements, normalized values of 27.2 ± 2.0% for β+-emission and 72.8 ± 2.0% for EC were obtained. These results are in excellent agreement with values recently reported in the literature based on a detailed decay scheme study.

Slope and distance from buildings are easy-to-retrieve proxies for estimating livestock site-use intensity in alpine summer pastures.

Regardless of the issue, most of the research carried out on summer pastures of European Alps had to consider the effects of grazing management, as it is an intrinsic component of alpine environment. The management intensity of grazing livestock is measured in terms of livestock stocking rate, but not always a direct measure of it is easily retrievable. Therefore, the aim of the research was to test the reliability of proxies easily retrievable from open data sources (i.e. slope and distance from buildings) in approximating the pastoral site-use intensity. To test the proxies' effectiveness two different approaches were used. With the first one, the proxies' reliability was assessed in a case-study conducted at farm scale by using the number of positions gathered with GPS collars, which are a reliable measure of livestock site-use intensity. With the second, the proxies' reliability was assessed by means of five Vegetation Ecological Groups (VEGs), used as a tool for indirect quantification of livestock site-use intensity at regional scale (thirty-two alpine valleys of the Western Italian Alps, Piedmont Region-Italy). At farm scale, distance from buildings and slope were both reliable predictors of the number of GPS locations as assessed with a Generalized Additive Model. Results of Generalized Linear Models at the regional scale showed that the values of both the slope and the distance from buildings were able to separate VEGs along the same site-use intensity gradient assessed by modelling the number of GPS locations at farm scale. By testing proxies' reliability both with a direct (i.e. GPS collar positions) and indirect (i.e. VEGs) measurement of livestock site-use intensity, results indicated that slope and distance from buildings can be considered effective surrogates of site-use intensity gradient in alpine grasslands managed under livestock grazing. Therefore, when the level of site-use intensity in research carried out in alpine summer pastures is not directly available, a reliable solution consists in the use of the terrain slope and the distance from buildings, which are also easily retrievable from open data sources or computable.

Interpretable tropical cyclone intensity estimation using Dvorak-inspired machine learning techniques

The intensity of a tropical cyclone is correlated strongly to the damage it causes when it makes landfall. Most of the time, tropical cyclones are located over the open ocean, where direct intensity measurements are difficult to obtain. An alternative approach is to estimate the tropical cyclone intensity indirectly from satellite images. In this case, there are two key points to consider: spatial and temporal relationships. For spatial relationships, the basic assumption is that cyclones with similar intensities have similar patterns. Thus, researchers can estimate intensity using pattern extraction and investigating similarities. For temporal relationships, the intensity of the cyclone is assumed to change smoothly, as a tropical cyclone is a continuous weather phenomenon. Thus, satellite images belonging to the same tropical cyclone should have a temporal (chronological) relationship with one another, meaning that the estimated intensity value of subsequent images should not change too drastically. In this research, we take advantage of these two key points and use random walk with a restart model to discover hidden correlations between target and historical cyclone images to estimate their intensity. We then use machine learning models to determine the temporal relationships among cyclone images, smoothing the prediction of the tropical cyclone event as a whole. Finally, our results show 15.77-knot root-mean-square error (RMSE) for the intensity estimation of tropical cyclones in the West Pacific Basin area.

Evaluation of the lighting system in drawing studio at the E12 building, Faculty of Engineering UNNES

A room can be said to be a good one if the lighting following the requirements of needs depends on the function of the room. The room studied in this study was a drawing studio room in E12 Building, Faculty of Engineering UNNES. This room has a condition where the spread of light entering from the window is uneven so during the day the lights must always be turned on. The purpose of this study is to measure and evaluate the lighting intensity of the drawing studio space. This research was conducted using descriptive and evaluative methods. The data obtained is sourced from the results of direct light intensity measurements on the object of research conducted in the morning, afternoon, and evening for three days using a lux meter and measurements made referring to SNI 16-7062-2004 about measuring the intensity of lighting at work. The results of the measurement of lighting intensity in the image studio room will be compared with the SNI recommended standards. According to SNI 03-6575-2001, the standard requirement for a lux studio drawing space is 750 lux. The result, both when the lamp is turned on and the lamp turns off the measurement results do not meet the standards. It is recommended to increase the intensity of artificial lighting (lights) in the drawing studio until it meets the SNI 750 lux standard. From the results of calculations with the lumen method, it is recommended to replace each lamp with a lamp that has a light current of 9360 lumens.

Focal-shape effects on the efficiency of the tunnel-ionization probe for extreme laser intensities

We examine the effect of laser focusing on the effectiveness of a recently discussed scheme [M. F. Ciappina et al., Phys. Rev. A 99, 043405 (2019) and M. F. Ciappina and S. V. Popruzhenko, Laser Phys. Lett. 17, 025301 (2020)] for in situ determination of ultrahigh intensities of electromagnetic radiation delivered by multi-petawatt laser facilities. Using two model intensity distributions in the focus of a laser beam, we show how the resulting yields of highly charged ions generated in the process of multiple sequential tunneling of electrons from atoms depend on the shapes of these distributions. Our findings lead to the conclusion that an accurate extraction of the peak laser intensity can be made either in the near-threshold regime, when the production of the highest charge state happens only in a small part of the laser focus close to the point where the intensity is maximal or through the determination of the points where the ion yields of close charges become equal. We show that for realistic parameters of the gas target, the number of ions generated in the central part of the focus in the threshold regime should be sufficient for a reliable measurement with highly sensitive time-of-flight detectors. Although the positions of the intersection points generally depend on the focal shape, they can be used to localize the peak intensity value in certain intervals. Finally, the slope of the intensity-dependent ion yields is shown to be robust with respect to both the focal spot size and the spatial distribution of the laser intensity in the focus. When these slopes can be measured, they will provide the most accurate determination of the peak intensity value within the considered tunnel ionization scheme. In addition to this analysis, we discuss the method in comparison with other recently proposed approaches for direct measurement of extreme laser intensities.

Study of Light Intensity in Riparian Zone of Teak Production Forest in KHDTK Cemoro Modang

Vegetation is one of the factors that influence the protection function of the riparian zone. Riparian vegetation in teak production forests is dominated by teak plantation with low species diversity. Rehabilitation is needed to increase the role of vegetation in protecting riparian zone. Data and information of light intensity is required to support the success of rehabilitation. Light intensity is a significant factor for photosynthesis which impacts on the survival, growth and adaptation of a vegetation. The varying light intensity in the riparian zone due to diverse land cover becomes a challenge in rehabilitating this area. This study aims to identify light intensity in riparian zone of Modang River and Cemoro River in the teak production forest. Recognizing light characteristics will help in species selection to rehabilitate this area. Primary and secondary data were used in this study. Direct measurement of light intensity was carried out along riparian zone of the Modang and Cemoro Rivers by systematic sampling. A sampling plot measuring 20 x 20 meter was used as the location of the sampling point with a total of 36 plots. Climate data are obtained from field observations through the nearest climatology station. The results showed that different canopy cover causing light intensity of Modang and Cemoro rivers varies. Canopy cover in this area can be divided into canopy cover of teak forest of various ages (production plants), johar (previous rehabilitation plants), and logged-over areas. The selection of tolerant and intolerant trees is important to use as consideration for rehabilitation, in addition to other silvicultural and socio-economic considerations of the local community.

Study of Light Intensity in Riparian Zone of Teak Production Forest in KHDTK Cemoro Modang

Vegetation is one of the factors that influence the protection function of the riparian zone. Riparian vegetation in teak production forests is dominated by teak plantation with low species diversity. Rehabilitation is needed to increase the role of vegetation in protecting riparian zone. Data and information of light intensity is required to support the success of rehabilitation. Light intensity is a significant factor for photosynthesis which impacts on the survival, growth and adaptation of a vegetation. The varying light intensity in the riparian zone due to diverse land cover becomes a challenge in rehabilitating this area. This study aims to identify light intensity in riparian zone of Modang River and Cemoro River in the teak production forest. Recognizing light characteristics will help in species selection to rehabilitate this area. Primary and secondary data were used in this study. Direct measurement of light intensity was carried out along riparian zone of the Modang and Cemoro Rivers by systematic sampling. A sampling plot measuring 20 x 20 meter was used as the location of the sampling point with a total of 36 plots. Climate data are obtained from field observations through the nearest climatology station. The results showed that different canopy cover causing light intensity of Modang and Cemoro rivers varies. Canopy cover in this area can be divided into canopy cover of teak forest of various ages (production plants), johar (previous rehabilitation plants), and logged-over areas. The selection of tolerant and intolerant trees is important to use as consideration for rehabilitation, in addition to other silvicultural and socio-economic considerations of the local community. Keywords: light, riparian, teak production forest

Multi-resolution convolutional neural networks for inverse problems

Inverse problems in image processing, phase imaging, and computer vision often share the same structure of mapping input image(s) to output image(s) but are usually solved by different application-specific algorithms. Deep convolutional neural networks have shown great potential for highly variable tasks across many image-based domains, but sometimes can be challenging to train due to their internal non-linearity. We propose a novel, fast-converging neural network architecture capable of solving generic image(s)-to-image(s) inverse problems relevant to a diverse set of domains. We show this approach is useful in recovering wavefronts from direct intensity measurements, imaging objects from diffusely reflected images, and denoising scanning transmission electron microscopy images, just by using different training datasets. These successful applications demonstrate the proposed network to be an ideal candidate solving general inverse problems falling into the category of image(s)-to-image(s) translation.

Towards an in situ, full-power gauge of the focal-volume intensity of petawatt-class lasers.

About 50 years ago, Sarachick and Schappert [Phys. Rev. D. 1, 2738-2752 (1970)] showed that relativistic Thomson scattering leads to wavelength shifts that are proportional to the laser intensity. About 28 years later, Chen et al. [Nature 396, 653-655 (1998)] used these shifts to estimate their laser intensity near 1018 W/cm 2. More recently, there have been several theoretical studies aimed at exploiting nonlinear Thomson scattering as a tool for direct measurement of intensities well into the relativistic regime. We present the first quantitative study of this approach for intensities between 1018 and 1019 W/cm 2. We show that the spectral shifts are in reasonable agreement with estimates of the peak intensity extracted from images of the focal area obtained at reduced power. Finally, we discuss the viability of the approach, its range of usefulness and how it might be extended to gauge intensities well in excess of 1019 W/cm 2.

Quantitative Detection and Real-Time Monitoring of Endogenous mRNA at the Single Live Cell Level Using a Ratiometric Molecular Beacon.

Messenger ribonucleic acid (mRNA) plays an important role in various cellular processes. however, traditional techniques cannot realize mRNA detections in live cells as they rely on mRNA purification or cell fixation. To achieve real-time and quantitative mRNA detections at a single live cell level, a single-strand stem-loop-structured ratiometric molecular beacon (RMB) composed of the phosphorothioate-modified loop domain on the 2'-O-methyl RNA backbone with a reporter dye, quencher, and reference dye is proposed to detect the Hsp27 mRNA as a modeled endogenous mRNA. When the RMB hybridizes with the target, the stem-loop structure opens, causing separation of the reporter dye and the quencher and restores the reporter fluorescent signals; therefore, the Hsp27 mRNA can be quantitatively detected according to the ratio of the reporter fluorescent signal to the reference fluorescent signal. Both the phosphorothioate and 2'-O-methyl RNA modifications obviously reduce the nonspecific opening, and the additional reference dye ensures the detection precision using co-localization analysis. Not only does this remove the false-positive signal caused by the nuclease degradation-generated RMB fragment, but it also corrects variations caused by direct measurement of reporter fluorescence intensities at a single cell level owing to inhomogeneity in probe delivery. The designed RMB could detect the Hsp27 mRNA with high signal-to-noise ratio and sensitivity as well as excellent specificity and antidegradation capability proved in vitro and in live cells. Furthermore, it was successfully adopted in subcellular localization, quantitative copy number measurements, and even real-time monitoring of Hsp27 mRNA in live cells, demonstrating that the proposed RMB can be a potential quantitative endogenous mRNA detection tool, especially at a single live cell level.

Analiza wpływu zmienności natężenia ruchu na poziom hałasu na drogach

The paper presents the results of analyses concerning the annual variability of the road traffic noise level calculated in the reference point. Because of the large differences between the average noise values and the maximum ones, scaling factors enabling one to convert annual average values into the highest annual averages have been developed. The time range favourable for conducting sampling measurements ensuring the reliable estimation of annual average and highest annual average of the road traffic noise level has been determined. Moreover, factors for scaling the annual average daily traffic (for all vehicles and heavy vehicles, respectively), with a division into two daily periods, have been developed. The scaling factors make it possible to determine the noise level when no direct measurement of traffic intensity can be carried out. The analyses were made using data from 25 automatic traffic recorders (ATRs), equipped with state-of-the-art SICK and Golden river vehicle counters, located on national interurban expressways (class A and S roads).

Experimental investigation of environment-induced entanglement using an all-optical setup

We investigate the generation of entanglement between two non interacting qubits coupled to a common reservoir. An experimental setup was conceived to encode one qubit on the polarization of an optical beam and another qubit on its transverse mode. The action of the reservoir is implemented as conditional operations on these two qubits, controlled by the longitudinal path as an ancillary degree of freedom. An entanglement witness and the two-qubit concurrence are easily evaluated from direct intensity measurements showing an excellent agreement with the theoretical prediction.

Highly Efficient Electrochemiluminescence of Cyanovinylene-Contained Polymer Dots in Aqueous Medium and Its Application in Imaging Analysis.

Luminescent semiconducting polymer dots (Pdots) have attracted intense attention in the field of electrochemiluminescence (ECL) due to their nontoxic features. For utilizing the nontoxic Pdots to achieve sensitive ECL bioimaging detection, this work studied the ECL behaviors of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-(1-cyanovinylene-1,4-phenylene)] (CN-PPV) Pdots in aqueous solution, which introduced an electron-withdrawing cyano group to p-phenylenevinylene for enhancing the luminescent efficiency. The CN-PPV Pdots could be both electrochemically oxidized to a positively charged state and electrochemically reduced to a negatively charged state, which led to annihilation of ECL emission. The order of oxidation and reduction greatly influenced the annihilation behavior. In the presence of tri-n-propylamine (TPrA) or S2O82- as a coreactant, the CN-PPV Pdots showed strong band gap ECL emission at 602 nm, which followed two different routes and gave ECL efficiencies of 11.22% and 1.84% (vs Ru(bpy)32+/TPrA), respectively. The high ECL efficiency allowed CN-PPV Pdots/TPrA system for ECL imaging analysis. As a proof-of-methodology, an ECL imaging method was designed via the chelating interaction of metal ions and Pdots to achieve high selectivity. The proposed ECL imaging chip-based sensor exhibited excellent analytical performance for Fe3+ with a wide linear range from 100 pM to 100 μM and a detection limit of 67 pM. Compared with the ECL methods based on the direct intensity measurement, the developed ECL imaging method possesses the advantages of simplicity, rapid, and high-throughput and has application potential in monitoring water and food quality.

Determination of Quercetin and Luteolin in Paprika Samples by Voltammetry and Partial Least Squares Calibration

AbstractQuercetin and luteolin are flavonoids with beneficious properties, which are present in paprika. In this work, both have been determined in paprika by using electrochemistry combined with chemometrics. The electrochemical oxidation mechanisms of both analytes have been studied through sampled direct current (DC) voltammetry, differential pulse voltammetry (DPV) and Square Wave Voltammetry (SWV), making use of a glassy carbon electrode. The final technique selected for the quantification was DPV due to its high repeatability with respect SWV. The chemical variables and the instrumental parameters were optimized and the final conditions employed were ethanol: water (20 : 80), 0.75 mol dm−3 of HCl, and a pulse amplitude of 50 mV. Due to the facts that oxidation potential of both analytes were quite similar, their DPV peaks were overlapped, and also because the analytes interaction during the electrochemical process causes a non‐additivity of the signals, they could not be quantified separately by direct measurement of peak intensity. For this reason, a chemometric algorithm was applied (partial least squares (PLS) regression in its modality PLS‐2). In the case of validation samples, appropriate sets of calibration and validation were built and good results were obtained. This methodology was applied to real paprika samples and the results were similar to those obtained with a HPLC method previously reported.