Dark Background Research Articles

Impacto del envase de la leche de soja natural en la intención de compra del consumidor

The objective of this work was to evaluate the intention to purchase plain soymilk by correlating it with packaging characteristics through the conjoint analysis. Survey of attributes occurred by focus group (41 participants) and five samples of Brazilian original soymilk. Main attributes that interfered in the purchase decision: brand, presence of nutritional appeal, type of illustration of glass containing beverage and background color. Attributes were combined to generate eight packaging proposals, evaluated by 86 participants. SAS was used for data analysis, 85 of which were consistent. Participants were grouped by similarities/dissimilarities in three groups: G1 (48 participants), G2 (31) and G3 (6). G1 preferred packaging containing nutritional appeal and light background, being influenced by the brand. G2 opted for packaging containing nutritional appeal, lesser-known brand and filled glass. G3 preferred the presence of nutritional appeal, lesser known brand, full glass and dark background. Presence of nutritional appeal is the factor that most impacts the purchase decision, but the brand, type of glass illustration and background color are relevant. Packaging with the presence of nutritional appeal, glass with full filling and clear background is more likely to be of interest to consumers.

FORMULATION DEVELOPMENT AND EVALUATION OF SITE SPECIFIC PERIODONTAL GELS

Periodontal pockets act as a natural reservoir filled with gingival crevicular fluid for the controlled release of antimicrobials directly. This work reflects the present status of nonsurgical controlled local intrapocket delivery of antimicrobials in the treatment of periodontitis. These sites have specialty in terms of anatomy, permeability and their ability to retain a delivery system for a desired length of time. A number of antimicrobial products and the composition of the delivery systems, its use, clinical results, and their release are summarized. In the present study development of site specific periodontal drug delivery system was developed for Metronidazole and Minocycline HCl. Metronidazole is an important active substance that has been widely used in the treatment of some protozoal and anaerobic bacterial infections. Minocycline hydrochloride is a semi synthetic tetracycline, which has been primarily indicated for the treatment of Acne vulgaris. Polarizing photographs of gel lacking CMC, PVP and a gel encircling 10% CMC and 5% PVP are naked. Photographs demonstrated a dark background in the instance of plain gel, though some fan like formations were supposed in the polarizing photograph of the P5C10 formulation. The consequence of drug(s) concentration on gelation and gel melting is done. The gelation temperature was miserable in the company of drug(s) and conical linearly with its growing concentration, while the melting temperature amended with the concentration of drug(s). The mechanical properties of the augmented formulations for the supervision of periodontal disease were resolute.

Quantitative analysis of urea in serum by synchronous modulation and demodulation fluorescence spectroscopy

High-precision spectral data is a necessary prerequisite for quantitative analysis of complex solution components. In order to improve the accuracy of spectral data, this paper proposes a method of synchronous modulation and demodulation. This article also combines the “M + N” theory, cleverly uses the excitation fluorescence of the components in the serum and its self-absorption phenomenon, collects the fluorescence spectrum of the serum sample, and then uses the partial least squares (PLS) method and the cubic optimization model method to establish a model to analyze the urea concentration of serum. At the same time, in order to verify the effectiveness of synchronous modulation and demodulation method, the unmodulated fluorescence spectrum is used to establish the regression model of urea concentration. Compared with the unmodulated fluorescence spectrum modeling results, the fluorescence spectrum modeling results after modulation and demodulation have been significantly improved. In the modeling results of fluorescence spectrum after synchronous modulation and demodulation, the Rc is 0.916753, the RMSEC is 2.05848 mmol/L, the Rp is 0.79663, and the RMSEP is 3.16812 mmol/L, the Rp-all is 0.88879, and the RMSEP-all is 2.32114 mmol/L. The results show that the method of synchronous modulation and demodulation proposed in this paper not only reduces the influence of dark current, ambient light and background noise on the signal-to-noise ratio of the spectral data, but also effectively avoids the error caused by the non-synchronization of the chopper and the spectrometer. Therefore, the method used in this paper not only improves the signal-to-noise ratio and accuracy of spectral data, but also improves the accuracy of spectral quantitative analysis of complex solutions.

Highly sensitive and rapid detection of protein kinase C based on liquid crystal biosensor

Protein kinase C (PKC), a protein which is widely present in organisms, plays a pivotal role in the pathogenesis of many diseases, and has become a target for the diagnosis and treatment of many illness. In this study, a rapid method based on liquid crystal (LC) biosensor and nano-modified signal amplification technology for PKC detection is demonstrated. Glutaraldehyde (GA) was used to fix the PKC antibody/gold nanoparticles (anti-PKC/AuNPs) conjugations to the substrate mixed self-assembled with (3-aminopropyl)-triethoxysilane/N, N-dimethyl-N-octadecyl-(3-aminopropyl)-trimethoxysilyl chloride (APTES/DMOAP). The above processing maintained the LC molecules to arrange vertically and induced a dark background under polarized light. When PKC was presented, it would be fixed on substrate through binding with anti-PKC of the complex specifically. The specific binding event resulted in the change in morphology of the substrate, arrangement of the LC molecules and brightness of the LC film, thereby the sensitive detection of PKC was achieved. The developed biosensor present a good linear relationship between the average gray intensity of the optical imaging and the PKC concentration in a wide linear range of 10–250 ng·mL−1, the correlation coefficient was 0.997, and has a very low detection limit of 1.680 ± 0.005 ng·mL−1. The findings of this work provided a potential application for the high sensitivity and simple detection of protein kinases.

Seeing the world through the eyes of a butterfly: visual ecology of the territorial males of Pararge aegeria (Lepidoptera: Nymphalidae)

Combining studies of animal visual systems with exact imaging of their visual environment can get us a step closer to understand how animals see their “Umwelt”. Here, we have combined both methods to better understand how males of the speckled wood butterfly, Pararge aegeria, see the surroundings of their perches. These males are well known to sit and wait for a chance to mate with a passing females, in sunspot territories in European forests. We provide a detailed description of the males' body and head posture, viewing direction, visual field and spatial resolution, as well as the visual environment. Pararge aegeria has sexually dimorphic eyes, the smallest interommatidial angles of males are around 1°, those of females 1.5°. Perching males face the antisolar direction with their retinal region of the highest resolution pointing at an angle of about 45° above the horizon; thus, looking at a rather even and dark background in front of which they likely have the best chance to detect a sunlit female passing through the sunspot.

Arabic Sign Language Recognition System for Alphabets Using Machine Learning Techniques

In recent years, the role of pattern recognition in systems based on human computer interaction (HCI) has spread in terms of computer vision applications and machine learning, and one of the most important of these applications is to recognize the hand gestures used in dealing with deaf people, in particular to recognize the dashed letters in surahs of the Quran. In this paper, we suggest an Arabic Alphabet Sign Language Recognition System (AArSLRS) using the vision-based approach. The proposed system consists of four stages: the stage of data processing, preprocessing of data, feature extraction, and classification. The system deals with three types of datasets: data dealing with bare hands and a dark background, data dealing with bare hands, but with a light background, and data dealing with hands wearing dark colored gloves. AArSLRS begins with obtaining an image of the alphabet gestures, then revealing the hand from the image and isolating it from the background using one of the proposed methods, after which the hand features are extracted according to the selection method used to extract them. Regarding the classification process in this system, we have used supervised learning techniques for the classification of 28-letter Arabic alphabet using 9240 images. We focused on the classification for 14 alphabetic letters that represent the first Quran surahs in the Quranic sign language (QSL). AArSLRS achieved an accuracy of 99.5% for the K-Nearest Neighbor (KNN) classifier.

Combined Laparoscopic-Assisted Robotic-Hysteroscopic Isthmoplasty Using Near-Infra Red Technology: A Novel Approach

<h3>Study Objective</h3> To demonstrate a surgical technique of isthmoplasty for the treatment of symptomatic caesarean scar defect. The authors present a standardised approach using combined minimally invasive techniques and Near-Infra-Red technology (NIRT) to perform the procedure in a systematic manner. <h3>Design</h3> Step-by-step oral presentation of the surgical technique. <h3>Setting</h3> Macquarie University Hospital (MUH), Australia. <h3>Patients or Participants</h3> MUH Gynaecology Clinic. <h3>Interventions</h3> A 44-years-old with three previous Caesarean sections presented with intermenstrual bleeding and pelvic pain. Transvaginal ultrasound diagnosed a grade-3 (>25mm) isthmocoele. A combined robotic-assisted-laparoscopic-hysteroscopic isthmoplasty was performed using the Da-Vinci-Xi-robot. The procedure began with hysteroscopy to explore the uterine cavity and identify the caesarean scar defect. At laparoscopy, the abdomino-pelvic cavity was explored systematically. To expose the isthmocoele, sharp dissection of the visceral peritoneal layer overlying the uterine isthmus was performed. The hysteroscopic light was directed cephalad and the laparoscopic light was then switched off to demonstrate the "Halloween sign", helping to identify the upper and lower limits of the isthmocoele. NIRT mode was then activated, the green fluorescence of the scar defect in a dark background further demarcated the surgical margins. A colpotomiser was inserted; the cup stabilised the cervix relative to the uterine body while the central cannula defined the cervical canal and aligned the defect for excision and repair. The scar tissue was excised robotically with removal of all edges of the pseudo-cavity. The myometrium was repaired in two layers with continuous barbed 2-0 suture ensuring a tension-free repair. NIRT was again activated to check for integrity of repair. <h3>Measurements and Main Results</h3> Operative time was 60 minutes. Patient was discharged same day with symptoms resolution. <h3>Conclusion</h3> Combined Laparoscopic-assisted-robotic-hysteroscopic isthmoplasty is safe and effective, giving the surgeon a comprehensive evaluation of the anatomy of the isthmocoele, and increasing the accuracy of complete resection and restoration of the anatomy. NIRT technology demarcates the resection margins and confirms complete closure of the defect.

Combined Robotic-Assisted Laparoscopic-Hysteroscopic Isthmoplasty Using Near-Infra Red Technology: A Novel Approach

<h3>Study Objective</h3> To demonstrate a surgical technique of isthmoplasty for the treatment of symptomatic caesarean scar defect. The authors present a standardised approach using combined minimally invasive techniques and Near-Infra-Red technology (NIRT) to perform the procedure in a systematic manner. <h3>Design</h3> Step-by-step Video demonstration of the surgical technique. <h3>Setting</h3> Macquarie University Hospital (MUH), Australia. <h3>Patients or Participants</h3> MUH Gynaecology Clinic. <h3>Interventions</h3> A 44-years-old with three previous Caesarean sections presented with intermenstrual bleeding and pelvic pain. Transvaginal ultrasound diagnosed a grade-3 (>25mm) isthmocoele. A combined robotic-assisted-laparoscopic-hysteroscopic isthmoplasty was performed using the Da-Vinci-Xi-robot. The procedure began with hysteroscopy to explore the uterine cavity and identify the caesarean scar defect. At laparoscopy, the abdomino-pelvic cavity was explored systematically. To expose the isthmocoele, sharp dissection of the visceral peritoneal layer overlying the uterine isthmus was performed. The hysteroscopic light was directed cephalad and the laparoscopic light was then switched off to demonstrate the "Halloween sign", helping to identify the upper and lower limits of the isthmocoele. NIRT mode was then activated, the green fluorescence of the scar defect in a dark background further demarcated the surgical margins. A colpotomiser was inserted; the cup stabilised the cervix relative to the uterine body while the central cannula defined the cervical canal and aligned the defect for excision and repair. The scar tissue was excised robotically with removal of all edges of the pseudo-cavity. The myometrium was repaired in two layers with continuous barbed 2-0 suture ensuring a tension-free repair. NIRT was again activated to check for integrity of repair. <h3>Measurements and Main Results</h3> Operative time was 60 minutes. Patient was discharged same day with symptoms resolution. <h3>Conclusion</h3> Combined robotic-assisted-laparoscopic-hysteroscopic isthmoplasty is safe and effective, giving the surgeon a comprehensive evaluation of the anatomy of the isthmocoele, and increasing the accuracy of complete resection and restoration of the anatomy. NIRT technology demarcates the resection margins and confirms complete closure of the defect.

Retinal OFF-Pathway Overstimulation Leads to Greater Accommodation-Induced Choroidal Thinning

PurposeTo examine the interactions between accommodation and overstimulation of the retinal ON- and OFF-pathways, and their association with changes in choroidal thickness (ChT) and vascularity.MethodsOptical coherence tomography imaging of the choroid of twenty young adults (ages 25 ± 5 years) was performed before and after a series of 30-minute-long viewing tasks, including reading a bright text on dark background (ON-pathway overstimulation) and dark text on bright background (OFF-pathway overstimulation), and a control task of viewing a movie with unbiased ON-/OFF-pathway activation. The viewing tasks were performed with relaxed, and 5 diopter (D) accommodation (induced by soft contact lenses) demands. Both reading texts were matched for the mean luminance (35 cd/m2), luminance contrast (87%), and letter size (approximately 11.8 arc minutes). The change in ChT from baseline associated with contrast polarity and accommodation was examined using linear mixed model analysis.ResultsThe subfoveal ChT decreased significantly by −7 ± 1 µm with 5 D accommodation compared with relaxed accommodation (−3 ± 1 µm; P < 0.001), and by −9 ± 1 µm with OFF-pathway compared with ON-pathway overstimulation (−4 ± 1 µm; P = 0.002) and the control condition (−2 ± 1 µm; P < 0.001). Overstimulation of the OFF-pathway, but not the ON-pathway, resulted in a significantly greater choroidal thinning compared with the control condition, both at relaxed (−7 ± 1 µm; P = 0.003) and 5 D (−11 ± 1 µm; P = 0.005) accommodation levels. Similar changes were also observed for macular total, stromal, and luminal ChT.ConclusionsRetinal OFF-pathway stimulation enhanced the choroidal thinning associated with accommodation, thereby providing a potential mechanism that involves accommodation and the retinal OFF-signaling pathway, linking near work and myopia.

Dependence of perceptual saccadic suppression on peri-saccadic image flow properties and luminance contrast polarity

Perceptual detectability of brief visual stimuli is strongly diminished across saccades. Recent work showed that this perceptual suppression phenomenon is jumpstarted in the retina (Idrees et al., 2020), suggesting that the phenomenon might be significantly more visual in nature than normally acknowledged. Here, we explored the details of visual-visual interactions underlying saccadic suppression, and we did so by comparing suppression strength when saccades were made across a uniform image of constant luminance versus when saccades were made across image patches of different luminance, width, and trans-saccadic luminance polarity. In 6 human subjects, we measured perceptual contrast thresholds for brief peri-saccadic flashes of positive (luminance increments) or negative (luminance decrements) polarity. In different conditions, gaze crossed a luminance edge or stripe before landing on a uniform background like in the control condition. Perceptual thresholds were >6-7 times higher when saccades translated a luminance stripe or edge across the retina than when the movements were made over a completely uniform image patch. Moreover, both background luminance and flash luminance polarity relative to the background strongly modulated peri-saccadic contrast thresholds: dark backgrounds were associated with the strongest suppression, and negative polarity flashes over dark backgrounds caused stronger suppression than positive polarity flashes over the same backgrounds. Most importantly, we repeated the same experiments on all subjects with rapid image translations (simulating saccadic visual flows on the retina) without any real saccades. All of the image dependencies that we observed with real saccades (e.g. suppression with gaze crossing an edge or stripe versus suppression with a uniform background) also occurred. Our results indicate that perceptual saccadic suppression may be fundamentally a visual phenomenon. They also strongly motivate revisiting both the movement-related and visual components of saccadic suppression, and investigating how saccade movement commands may interact with visual-visual interactions in shaping trans-saccadic visual perception.

Mapping of biophysical and biochemical properties of coastal tidal wetland habitats with Landsat 8

Coastal tidal wetlands are significant and vulnerable aquatic ecosystems. Quantitative remote sensing of biophysical and biochemical properties in coastal tidal wetland habitats through the inversion of physical models has vital practical significance for monitoring ecosystem function, environmental restoration, the global carbon, and nitrogen cycles. The objectives of this research were to map leaf area index (LAI), chlorophyll content, as well as the sensible heat flux, latent heat flux, and productivity in Chongming Dongtan coastal tidal wetland habitats of China and to provide a mapping protocol of biophysical and biochemical properties in Chongming Dongtan wetland for environmental protection and restoration as well as assessment and monitoring. In order to obtain significant information for biodiversity protection and management, a method based on the Soil Canopy Observation of Photosynthesis and Energy fluxes model and lookup table approach has been developed. The results derived from our study contain the reflectance values of Scirpus mariqueter and Phragmites australis spectra are lower than those commonly found for vegetated areas. This may be caused by the dark soil background and low LAI. Moreover, as for the values of latent heat flux (between 120 and 190 W m − 2) and productivity (between 3 and 14 μmol m − 2 s − 1), mudflats are lower than vegetation. However, the values of sensible heat flux (between 140 and 170 W m − 2) of mudflats are higher than that of vegetation.

Dark-habituation increases the dark-background-contingent upshift of gaze in macaque monkeys

What is the effect of prior experience on sensorimotor behavior? We studied the following intriguing behavior: monkeys fixating a small target direct their gaze above the target if the background is dark. Fixating a target once on a bright background, then on a dark background, yields 2 gaze directions, typically one above the other; hence the name, ‘dark-background-contingent upshift of gaze', which is abbreviated as ‘upshift’. Is the upshift only an attempt to avoid using the fovea in the dark? If it is, we might expect to also observe a downshift and a sideshift. We studied gaze direction in a large group of 10 rhesus monkeys from Tübingen, to which we added published data from 4 cynomolgus monkeys from Rehovot. The upshift was ubiquitous, and there was no systematic sideshift. What is the function of the upshift? Is it related to vision in the dark? Here, we concentrate on the effect of the monkeys’ previous training. Seven of the 14 monkeys were accustomed to working in the dark (‘dark-habituated’), while the other 7 had worked in bright ambient light (‘bright-habituated’). The main result of this study is that the dark-habituated monkeys had a much larger upshift: the mean upshift was 2.2° in the dark-habituated monkeys, versus 0.5° in the bright-habituated. Thus, the upshift depends on habituation; the size of the upshift reflects months-long cumulative experience. These findings suggest that the function of the upshift is indeed related to seeing in the dark.

Azobenzene with sulfonamide group deprotonated by green developer for moisture detection and water jet rewritable paper

Recently, based on the principle of proton transfer, the binary system composed of dye with a ionizable hydrogen atom and deprotonic reagent has become as an important type of water-jet rewritable paper (WJRP) for saving papers. In this paper, azo dye with sulfonamide group (2,2′-bis 4-methylbenzenesulfonamido azobenzene, SA) has been designed to detect moisture in organic solvents and prepare WJRP with yellow texts on a dark red background based on the water-inducing protonation between N–H of azo dye deprotonated by anions (e.g., H2PO4− and OAc−). The color and absorption spectra of the deprotonated species were restored to their original state after the reaction of the anionic dye with water. The interaction mode of azo dye and anion was verified by the titration of UV–Vis and 1H NMR spectroscopy. These findings show opportunities for the development of colorful and environmental friendly WJRP.

Perspectives.

![Figure][1]</img> Title: Brain Star (2017), Oil on Acrylic, 36 × 48 inches. In this painting, I drew a visual parallel between the undulating structures of the limbic system and the spirals of the Milky Way. The bright forms on a dark background represent a play on the appearance of immunostained

CAM18sl brightness prediction for unrelated saturated stimuli including age effects.

Modelling the influence of age on the perception of brightness of visual stimuli is an important topic for indoor and outdoor lighting. As people get older, the transmittance of the ocular media becomes lower, especially in the blue wavelength region. This paper reports on an experimental study aiming to evaluate how the brightness perception of red and blue stimuli is affected by the age of the observer. A matching experiment has been set up in which both young (25 years old on average) and older (70 years old on average) adult observers had to match the brightness of a blue stimulus with the brightness of a red stimulus, both surrounded by a dark background (unrelated stimuli). A significant difference in brightness perception between the two groups of observers was found. In particular, older people report a decrease in brightness perception for the blue stimuli compared to younger people. The results show that the brightness correlate of the colour appearance model CAM18sl (applied with zero luminance background) adequately predicts the matching results of young observers, but failed to predict the results obtained by the older observers. As CAM18sl is built on cone fundamentals which include the transmittance of the ocular media and consider the age of the observer as an input parameter, the authors developed the idea to substitute the cone fundamentals for a young observer by the cone fundamentals for a 70 years old observer. This updated CAM18sl performed very well for the older observer as well, on condition that the transmittance of the ocular media is isolated and kept out of the normalization of the cone fundamentals.

A new species of nurse-frog (Aromobatidae, Allobates) from the Amazonian forest of Loreto, Peru.

We describe a new species of nurse-frog (Aromobatidae, Allobates) from the Amazonian forest of Loreto, Peru using morphological, acoustic and genetic data. Our phylogenetic analysis placed Allobates sieggreenae sp. nov. as the sister species of A. trilineatus, the most similar-looking species and with which it was previously confused. However, the new species has a brown dorsum, solid dark brown lateral dark stripe not fading towards groin, adult males with few and sparse melanophores over a cream background on chin, chest, and belly, dark transverse bars absent on thighs, and an advertisement call formed by a trill of single notes (in A. trilineatus dorsum dark brown, blackish brown lateral dark stripe, paler from mid-body to groin, adult males with a dark background color on chin, chest, and belly due to a dense layer of melanophores, dark transverse bar present on dorsal surface of thighs, and trills of paired notes). Allobates sieggreenae is known from two localities of Amazonian white-sand forest ecosystems east of the Ucayali River.

Optimization of Local Contrast Factor with Adaptive Brightness Improvement: Impact on Mammogram Image Analysis

Mammography has been known worldwide as the most common imaging modalities utilized for early detection of breast cancer. The mammographic images produced are in greyscale, however they often produced low contrast images, contain artefacts and noise, as well as non-uniform illumination. These limitations can be overcame in the pre-processing stage with the image enhancement process. Therefore, in this research we developed an optimized enhancement framework where the local contrast factor is manipulated to preserve details of the image. This method aims to improve the overall image visibility without altering histogram of the original image, which will affect the segmentation and classification processes. We performed dark background removal in the image histogram at early stage to increase the efficiency of new mean histogram calculation. Then, the histogram is separated into two partitions to allow histogram clipping process to be conducted individually for underexposed and overexposed areas. Consequently, the local contrast factor optimization is conducted to preserve the image details. The results from our proposed method are compared with other methods by the measurement of peak signal-to-noise ratio, structural similarity index, average contrast, and average entropy difference. The results portrayed that our proposed method yield better quality over the others with highest peak signal-to-noise ratio of 32.676. In addition, in terms of qualitative analysis, our proposed method depicted betterlesion segmentation with smoother shape of the lesion.

Colour agreement between try-in paste and resin cement: effect of background on zirconia-reinforced lithium silicate.

To investigate colour agreement between different shades of Panavia V5 resin cement and their try-in pastes under zirconia-reinforced lithium silicate ceramics. Forty-four zirconia-reinforced lithium silicate ceramic specimens were prepared at 0.8 ± 0.01 mm thickness. Composite resin tooth-shaded background specimens were obtained in two shades. Resin cement specimens were fabricated at 0.1-mm thickness. Colour difference values (ΔE) between Aquagel and both the try-in paste and resin cement were calculated using the CIE-Lab system. The CIEDE2000 (ΔE00) colour formula was used to determine colour differences. The three-way ANOVA test and a multiple comparisons test were used for statistical analysis (α = 0.05). A statistically significant difference was found between the ΔE00 values obtained from the cement shade colour measurements for all specimens (P < 0.05). According to the three-way ANOVA test, lower ΔE00 values were observed in the try-in paste group compared to the resin cement group. The ΔE00 values were significantly affected by the cement shade and tooth-shaded background (P < 0.05). The colour agreement between the try-in pastes and the corresponding resin cement differed, and the try-in pastes could not mask the dark dental background as much as the corresponding resin cement.

Evaluation of enhanced darkfield microscopy and hyperspectral imaging for rapid screening of TiO2 and SiO2 nanoscale particles captured on filter media.

Here we report on initial efforts to evaluate enhanced darkfield microscopy (EDFM) and light scattering Vis-NIR hyperspectral imaging (HSI) as a rapid screening tool for the offline analysis of mixed cellulose ester (MCE) filter media used to collect airborne nanoparticulate from work environments. For this study, the materials of interest were nanoscale titanium dioxide (TiO2 ) and silicon dioxide (SiO2 ; silica), chosen for their frequent use in consumer products. TiO2 and SiO2 nanoscale particles (NPs) were collected on MCE filter media and were imaged and analyzed via EDFM-HSI. When visualized by EDFM, TiO2 and SiO2 NPs were readily apparent as bright spherical structures against a dark background. Moreover, TiO2 and SiO2 NPs were identified in hyperspectral images. EDFM-HSI images and data were compared to scanning transmission electron microscopy (STEM), a NIST-traceable technique for particle size analysis, and the current gold standard for offline analysis of filter media. As expected, STEM provided more accurate sizing and morphology data when compared to EDFM-HSI, but is not ideal for rapid screening of the presence of NPs of interest since it is a costly, low-throughput technique. In this study, we demonstrate the utility of EDFM-HSI in rapidly visualizing and identifying TiO2 and SiO2 NPs on MCE filters. This screening method may prove useful in expediting time-to-knowledge compared to electron microscopy. Future work will expand this evaluation to other industrially relevant NPs, other filter media types, and real-world filter samples from occupational exposure assessments.

Imaging the dipole scattering of an optically levitated dielectric nanoparticle

We experimentally observe the dipole scattering of a nanoparticle using a high numerical aperture (NA) imaging system. The optically levitated nanoparticle provides an environment free of a particle–substrate interaction. We illuminate the silica nanoparticle in vacuum with a 532 nm laser beam orthogonally to the propagation direction of the 1064 nm trapping laser beam strongly focused by the same high NA objective used to collect the scattering, which results in a dark background and high signal-noise ratio. The dipole orientations of the nanoparticle induced by the linear polarization of the incident laser are studied by measuring the scattering light distribution in the image and the Fourier space (k-space) as we rotate the illuminating light polarization. The polarization vortex (vector beam) is observed for the special case, when the dipole orientation of the nanoparticle is aligned along the optical axis of the microscope objective. Our work offers an important platform for studying the scattering anisotropy with Kerker conditions.