Mode Size Research Articles

Acoustoelectric conversion and deep-subwavelength acoustic focusing based on Fresnel zone plates

Fresnel zone plates (FZP) with quasi-planar structure and ultrathin thickness are capable of focusing light or acoustic waves efficiently. In this paper, we employ the FZP to manipulate the wave fields and suggest two acoustic functionalities. On one hand, by placing the moving coil-type microphone near the focal point of the FZP, enhanced acoustoelectric conversion is realized. The measured output voltage and power attained are 18.5 mV and 130 nW, respectively, which are 5.1 and 27.3 times that obtained without the FZP. On the other hand, by setting a tapered tube near the focal point of the FZP, deep-subwavelength and efficient localization of acoustic waves at the tube end (the mode size is around λ/20) are suggested theoretically. The cascaded focusing scheme leads to an enhancement of the acoustic intensity of the hotspot by more than 8700 times. The results are useful for realizing acoustic energy harvesting, strong mode localization, and acoustic-field enhancement.

Impacts of artificial reef on community structure and functional traits of macrobenthos near Furong Island, Shandong, China.

To evaluate the ecological restoration effect of artificial reefs and explore the impacts of artificial reefs age on the structure and functional traits of the macrobenthos community, two artificial reef areas with different reef ages in the coastal waters of Furong Island, Laizhou Bay were investigated in May, August, and October 2019. A total of 120 macrobenthos species were identified in the three seasons, including 72 species in the control area, 74 species in the artificial reef with short age (1 year), and 80 species in the artificial reef with greater age (4-5 years). Nihonotrypaea harmandi was the dominant species in all areas. The biomass, abundance, Shannon diversity index, Margalef species richness index of macrobenthos communities were all in order of reef area with greater age > reef area with lower age > control area, and the biomass and abundance in the reef area with greater age were significantly higher than those in the other two areas. The composition and relative abundance of functional traits of macrobenthos communities in the reef area and the control area were different. However, the dominant categories of traits in different areas were consistent, including deposit-feeder, burrower, medium body size, medium life span, high body flexibility and infauna. The composition and relative abundance of functional traits of macrobenthos communities in the reef area and the control area were different mainly in feeding mode, habitat, and body size. The relative abundance of smaller individuals (1-3 cm) and suspension feeders in the reef area was higher than those in the control area, while predator abundance was lower, and such effect became more pronounced with increasing reef age. The reef area was significantly higher than the control area in functional diversity, but without significant difference in functional redundancy. The results of abundance/biomass comparison curve and marine biotic index showed that the benthic ecological quality in the study area was good. The macrobenthos community was slightly disturbed after 1 year of reef construction, while the conservation effect of macrobenthic resources and the benthic ecological quality were significantly improved after 4-5 years of reef placement.

Power-scaled CW Alexandrite lasers

We present several strategies for increasing the output laser power of near-diffraction limited continuous-wave Alexandrite lasers pumped by fibre-coupled red laser diodes. Laser mode size control using a convex mirror with the varying thermal lens is shown to be an efficient method for generating record levels of output power from a diode-pumped Alexandrite laser. 8.6 W is obtained with M^{2}<1.1 and an optical efficiency of 27%. 735–790 nm wavelength tuning is demonstrated with > {2.5},hbox {W} and a record dual-wavelength output power of 4.2 W. In a ring-cavity geometry, 5.1 W is obtained with M^{2}<1.1 showing promising potential for multi-watt single-longitudinal-mode operation. Detailed laser cavity modelling including thermal lens analysis is also provided.

Understanding and probing of sub-femtometer resolutions utilizing acoustic plasmon resonances in graphene-dielectric-metal hybrid-structures

It has been demonstrated that acoustic plasmon resonances (APRs) with mode sizes of a few nanometers and large momentums can be excited at nanogaps between graphene and metal surfaces by the far-field coupling. Here, we consider a graphene-dielectric-metal hybrid-structure (GDMHS) for excited APRs by the far-field, analyze the physical process of the formation of the APRs, and analytically present a simplified model to predict APR wavelengths for greatly improving the efficiency of experiments using spectrometers. Furthermore, we show that the GDMHS can function as a plasmon ruler to resolve ultrasmall changes of dimensions or materials in the nanogaps by tracing spectral shifts with extremely high sensitivities. Both analytical and numerical investigations prove that a sub-femometer (sub-fm) resolution for probing changes in the thickness of the dielectric spacer is reached by monitoring spectral shifts of the lowest-order APR mode, which is tens to hundreds of times higher than the previously reported results at the same structural scale. Moreover, the smallest detectable change in the refractive index (RI) of the dielectric spacer is on the order of 10−6 RI unit (RIU) when APRs are used to sense material changes of the spacer. Impressively, such APR sensors can be actively tuned over a broad frequency band of interest by adjusting the chemical potential of graphene. Besides sensing applications with ultra-high sensitivity, the APR modes also demonstrate the tremendous potential in enhanced infrared molecule spectroscopy and exploring strong light−matter interactions at the deep sub-wavelength nanoscale.

High-performance thin-film lithium niobate electro-optic modulator based on etching slot andultrathin silicon film.

An electro-optic modulator (EOM) is an indispensable component to connect the electric and optical fields. Here, we propose a high-performance, thin-film lithium niobate-based EOM, where the modulation waveguide is formed by an etching slot on the lithium niobate film and the deposit of an ultrathin silicon film in the slot region. Therefore, a small mode size and high mode energy can be simultaneously achieved in the LN region with a high EO coefficient, which will be beneficial to increase the EO overlap and gradually decrease in the mode size. Further, we employed a waveguide structure to construct a typical Mach-Zehnder interference-type EOM. According to the requirements of high-speed traveling wave modulation, we conduct the index matching, impedance matching, and low-loss operation. From the results, the key half-wave voltage length product and 3dB modulation bandwidth are, respectively, 1.45Vcm and 119GHz in a modulation length of 4mm. Moreover, a larger 3dB bandwidth also can be achieved by shortening the modulation length. Therefore, we believe the proposed waveguide structure and EOM will provide new ways to enhance the performance of LNOI-based EOMs.

Size-Resolved Field Performance of Low-Cost Sensors for Particulate Matter Air Pollution.

Particulate matter (PM) air pollution is a major health hazard. The health effects of PM are closely linked to particle size, which governs its deposition in (and penetration through) the respiratory tract. In recent years, low-cost sensors that report particle concentrations for multiple-sized fractions (PM1.0, PM2.5, PM10) have proliferated in everyday use and scientific research. However, knowledge of how well these sensors perform across the full range of reported particle size fractions is limited. Unfortunately, erroneous particle size data can lead to spurious conclusions about exposure, misguided interventions, and ineffectual policy decisions. We assessed the linearity, bias, and precision of three low-cost sensor models, as a function of PM size fraction, in an urban setting. Contrary to manufacturers' claims, sensors are only accurate for the smallest size fraction (PM1). The PM1.0-2.5 and PM2.5-10 size fractions had large bias, noise, and uncertainty. These results demonstrate that low-cost aerosol sensors (1) cannot discriminate particle size accurately and (2) only report linear and precise measures of aerosol concentration in the accumulation mode size range (i.e., between 0.1 and 1 μm). We recommend that crowdsourced air quality monitoring networks stop reporting coarse (PM2.5-10) mode and PM10 mass concentrations from these sensors.

Biogenic Synthesis of Fluorescent Carbon Dots (CDs) and Their Application in Bioimaging of Agricultural Crops.

Fluorescent nanoparticles have a transformative potential for advanced sensors and devices for point-of-need diagnostics and bioimaging, bypassing the technical burden of meeting the assay performance requirements. Carbon dots (CDs) are rapidly emerging carbon-based nanomaterials. Regardless of their fate, they will find increasing applications. In this study, a simple approach for synthesizing CDs from fruit peels was developed. The CDs were fabricated from Annona squamosa (L.) peels using a carbonization technique through microwave-assisted hydrothermal digestion at temperatures around 200 °C. Synthesized CDs were detected using a UV transilluminator for the preliminary confirmation of the presence of fluorescence. UV-Vis spectrophotometry (absorbance at 505 nm) analysis, zeta potential measurement (-20.8 mV), nanoparticles tracking analysis (NTA) (average size: 15.4 nm and mode size: 9.26 nm), photoluminescence, and Fourier transform infrared (FT-IR) analysis were used to identify the capping functional groups on the CDs. The total quantum yield exhibited was 8.93%, and the field emission scanning electron microscopy (FESEM) showed the size range up to 40 nm. The germinating mung bean (Vigna radiata (L.)) seeds were incubated with biogenically synthesized CDs to check the absorption of CDs by them. The fluorescence was observed under a UV-transilluminator in the growing parts of seeds, indicating the absorption of CDs during the germination, development, and growth. These fluorescent CDs could be used as a bioimaging agent. This novel method of synthesizing CDs was found to be eco-friendly, rapid, and cost-effective.

Compact integrated mode-size converter using a broadband ultralow-loss parabolic-mirror collimator.

In this Letter, we propose and demonstrate an integrated mode-size converter (MSC) with a compact footprint, low losses, and a broad bandwidth. By exploiting a parabolic mirror, the divergent light from a narrow waveguide (450 nm) is collimated to match the mode size of a wide waveguide (10 µm). The measured insertion loss (IL) is ≈ 0.15 dB over a 100-nm bandwidth. The mode-size conversion is achieved with a footprint as small as ≈ 20 × 32 µm2, which is much shorter than the linear taper length required to attain the same level of losses.

Structural and dynamic heterogeneity in associative networks formed by artificially engineered protein polymers.

This work investigates static gel structure and cooperative multi-chain motion in associative networks using a well-defined model system composed of artificial coiled-coil proteins. The combination of small-angle and ultra-small-angle neutron scattering provides evidence for three static length scales irrespective of protein gel design which are attributed to correlations arising from the blob length, inter-junction spacing, and multi-chain density fluctuations. Self-diffusion measurements using forced Rayleigh scattering demonstrate an apparent superdiffusive regime in all gels studied, reflecting a transition between distinct "slow" and "fast" diffusive species. The interconversion between the two diffusive modes occurs on a length scale on the order of the largest correlation length observed by neutron scattering, suggesting a possible caging effect. Comparison of the self-diffusive behavior with characteristic molecular length scales and the single-sticker dissociation time inferred from tracer diffusion measurements supports the primarily single-chain mechanisms of self-diffusion as previously conceptualized. The step size of the slow mode is comparable to the root-mean-square length of the midblock strands, consistent with a single-chain walking mode rather than collective motion of multi-chain aggregates. The transition to the fast mode occurs on a timescale 10-1000 times the single-sticker dissociation time, which is consistent with the onset of single-molecule hopping. Finally, the terminal diffusivity depends exponentially on the number of stickers per chain, further suggesting that long-range diffusion occurs by molecular hopping rather than sticky Rouse motion of larger assemblies. Collectively, the results suggest that diffusion of multi-chain clusters is dominated by the single-chain pictures proposed in previous coarse-grained modeling.

Parameter selection and experimental study of the rock particle crushing effect using an image-based method

When maging is used to detect the crushing effect of rock particles, the selected characterization parameters are important factors affecting the results. The image-based detection system is composed of three parts: an image acquisition system, a storage platform, and a digital image processing system.The influence of loading mode and feeding particle size on rock crushing degree and rock morphology characteristics after crushing are analyzed respectively; The crushing ratio and sand-forming ratio of limestone, limestone and granite under shear and extrusion loads are analyzed. The experimental results show that the crushing ratio and sand formation rate play a key role in the crushing of rocks composed of different materials under shear compression loading. The effect analysis of crushing under the feed particle size of 9.5 mm to 16mm shows that there is a great correlation between edges and corners, roundness and overall contour. It provides a basis for the follow-up research on intelligent mine construction and equipment optimization, and is worthy of further popularization and application.

First evidence of multiple paternity and hybridisation in Australian sawsharks

Context Knowledge of sawshark reproductive biology is limited to general parameters such as reproductive mode and litter size. The mating system is currently unknown. Aim To test for multiple paternity in the common (Pristiophorus cirratus) and southern (Pristiophorus nudipinnis) sawshark and investigate the occurrence of hybridisation between these two species. Methods Pups from a single litter of each species and an adult P. nudipinnis displaying mismatches in its morphology and mitochondrial DNA were genotyped with nuclear single-nucleotide polymorphisms (SNPs). Multiple paternity was assessed using pairwise relatedness and sibship analysis, and hybridisation was examined using three approaches (principal-component analysis, admixture analysis and clustering with NewHybrids). Key results Multiple paternity was detected in both species, with two males siring the seven-pup litter in P. cirratus and two males siring the two-pup litter in P. nudipinnis. Hybridisation between the two species was also confirmed, with the mismatched adult identified as a first-generation hybrid. Conclusions The mating system of sawsharks involves polyandry, and hybridisation between the two co-occurring Australian species is possible. Implications These results provide new information on sawshark reproductive biology and highlight the need for combined use of mitochondrial and nuclear markers in future genetic studies involving these species.

Photocatalytic degradation of azo dyes by ultra-small green synthesized silver nanoparticles

BackgroundThe presence of toxic dyes in wastewater is a serious problem for human health. In this work, the degradation of commercial azo dyes sold over-the counter in Mexico was studied, using as a photocatalyst ultra-small silver nanoparticles (AgNPs) green synthesized. MethodsFor the first time, the successful green synthesis of ultra-small AgNPs using, as both reducing-stabilizing agents (RSa), the aqueous extract of Pelargonium hortorum (Phf) flower or Allium fistulosum (Afs) stem, is reported. AgNPs were characterized by ultraviolet-visible (UV–Vis) and attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopies, field emission scanning electron microscopy-energy dispersive spectroscopy (FE-SEM-EDS), and field emission transmission electron microscopy (FE-TEM). Significant findingsThe morphology of the AgNPs, in both cases, are spherical. AgNPs synthesized with Phf (AgNPs/Phf), which have a mode size of 2 nm (41.9%) and a bandgap of 2.38 eV, resulted in a photocatalytic degradation efficiency of 95%. On the other hand, AgNPs synthesized with Afs (AgNPs/Afs), which have a mode size of 0.6 nm (37.8%) and a bandgap of 2.43 eV, presented a photocatalytic efficiency of 100%. The photocatalytic efficiency and bandgap of the synthesized AgNPs were found to be inversely proportional to the AgNPs size; i.e. the smaller the AgNPs, the higher photocatalytic degradation, and bandgap exhibited.

The Role of Elastography in Predicting the Grade of Mammary Ductal Carcinoma

Background: Elastography is an imaging technique which has been used in the last decades and its role in breast masses characterization is well established. However, its value for predicting breast cancer grading is yet to be studied. Objective: To determine the role of strain elastography in the prediction of the grade of mammary ductal carcinoma. Methods: A cross sectional study enrolled 44 female patients with Breast Imaging Reporting and Data System (BI-RADS) Category 5 breast mass. Complete B-mode and elastographic ultrasound examination of the breast was performed with evaluation of the elastoscore and strain ratio. Correlation with the detailed histopathological report was done for cases that were proved to be ductal type breast carcinoma. Results: Significant correlation was found between the speculated outline of the tumor and grade III tumor (p=0.03). Breast tumors with higher Elastography/B mode size ratio (&gt;1) and with high elasticity score (score 5) were significantly associated with grade III (p=0.02). The mean strain ratio of masses was significantly higher among grade III breast tumors (p&lt;0.001). Conclusion: Elastography is a helpful non-invasive tool that has the potential for predicting breast ductal carcinoma grade and by such predicting the prognosis. Keywords: Breast ductal carcinoma, strain elastography, ductal carcinoma grades Citation: Said TTM, Sheet AT, Nuaman BN. The role of elastography in predicting the grade of mammary ductal carcinoma. Iraqi JMS. 2022; 20(2): 233-238. doi: 10.22578/IJMS.20.2.10

ICDP Oman Drilling Project: varitextured gabbros from the dike–gabbro transition within drill core GT3A

Abstract. The Oman ophiolite (Samail massif, Sultanate of Oman) is the largest sub-aerial exposure of oceanic lithosphere on Earth and provides the opportunity to study the accretion and alteration of oceanic lithosphere formed under fast-spreading conditions. Drill hole GT3A (23∘06′50.7′′ N, 58∘12′42.2′′ E) of the ICDP (International Continental Scientific Drilling Program) Oman Drilling Project with a length of 400 m aimed at penetrating the dike–gabbro transition of the Samail ophiolite paleocrust in order to shed light on the role of the axial melt lens (AML) during accretion of the lower plutonic crust. AMLs beneath fast-spreading mid-ocean ridges are sandwiched between the sheeted dike complex and the uppermost gabbros and are believed to feed the upper crust and, at least partially, the underlying crystal mush. Typical gabbroic rocks from dike–gabbro transitions of fast-spreading systems are the so-called “varitextured gabbros”, often showing considerable variations in mineral mode, texture and grain size, which are regarded as the frozen fillings of axial melt lenses. Here, we present a detailed petrographic, microanalytical and bulk-chemical investigation of 36 mafic rocks from the drill hole GT3A, which represent mostly varitextured gabbros, revealing a complex formation with several evolution stages. Poikilitic domains formed first, corresponding to an early crystallization stage, where only plagioclase and clinopyroxene of more primitive composition crystallized. Later, domains of granular textures containing also interstitial amphibole and Fe–Ti oxide were formed. This stage is characterized by a magma evolution that underwent crystal fractionation established by lower temperatures due to more efficient hydrothermal cooling at the margin of the AML. A last stage is characterized by pervasive hydrothermal alteration, where all primary minerals have been altered under temperature conditions, varying from the magmatic regime down to greenschist facies. A highlight of this stage is amphiboles showing noticeable compositional zoning. The observation of peculiar microgranular domains, representing relics of stoped exogenic material from the sheeted dike complex, documents the upward migration of an AML in a replenishment event, forcing the AML to burn through previously altered sheeted dikes. This process is responsible for significant assimilation of hydrothermally altered components, indicated by a marked Cl enrichment in the outer zones of magmatic amphiboles. Petrological modeling involving gabbros and basalts revealed that the GT3A rock suite followed a fractional crystallization evolution trend, with a primitive MORB as parental melt with an estimated water content of 0.2 wt % to 0.8 wt %. The modeled liquid lines of descent suggest a magmatic evolution via fractional crystallization, where the basalts correspond to frozen liquids, while the gabbros, especially the more primitive ones, show a significant cumulate component.

Surface water and aerosol spatiotemporal dynamics and influence mechanisms over drylands

Under the background of global warming and excessive human activities, much surface water in drylands is experiencing rapid degradation or shrinkage in recent years. The shrinkage of surface water, especially the degradation of lakes and their adjacent wetlands in drylands, may lead to the emergence of new salt dust storm hotspots, which causes greater danger. In this paper, based on high spatial resolution global surface water (GSW) and multiangle implementation of atmospheric correction (MAIAC) AOD data, we systematically analyze the dynamic characteristics of surface water and aerosols in typical drylands (Central Asia, CA) between 2000 and 2018. Simultaneously, combined with auxiliary environment variables, we explore the driving mechanisms of surface water on the regional salt/sand aerosols on different spatial scales. The results show that the seasonal surface water features an increasing trend, especially a more dramatic increase after 2015, and the permanent surface water indicates an overall decrease, with nearly 54.367 % at risk of receding and drying up. In typical lakes (Aral Sea and Ebinur Lake), the interannual change feature of the surface water area (WA) is that a continuous decrease during the study period occurs in Aral Sea area, yet a significant improvement has occurred in Ebinur Lake after 2015, and the degradation of Ebinur Lake takes place later and its recovery earlier than Aral Sea. The aerosol optical depth (AOD) in CA shows obvious seasonal variation, with the largest in spring (0.192 ± 0173), next in summer (0.169 ± 0.106), and the smallest in autumn (0.123 ± 0.065). The interannual variation of AOD exhibits an increase from 2000 to 2018 in CA, with high AOD areas mainly concentrated in the Taklamakan Desert and some lake beds resulting from lake degradation, including Aral Sea and Ebinur Lake. The AOD holds a similar trend between Aral Sea and Ebinur Lake on an interannual scale. And the AOD over Ebinur Lake is lower than that over Aral Sea in magnitude and lags behind in reaching the peak compared with Aral Sea. The WA change can significantly affect aerosol variation directly or indirectly on the aerosol load or mode size, but there are obvious differences in the driving mechanisms, acting paths, and influence magnitude of WA on aerosols on different spatial scales. In addition, the increase of WA can significantly directly suppress the increase of Ångström exponent (AE), and the effects of WA on AOD are realized majorly by an indirect approach. From the typical lake perspective, the effects of WA on aerosol in Aral Sea are achieved via an indirect path; and the decrease of WA can indirectly promote the AOD rise, and directly stimulate the AE growth in Ebinur Lake.

Hybrid Image Graphene Polaritons with Extremely Confined Mode and Field Enhancement in the Terahertz Regime

AbstractGuiding terahertz waves below the diffraction limit of light typically excite graphene plasmons (GPs). However, the mode confinements of conventional GPs using graphene–dielectric interfaces are limited. To further squeeze the optical mode sizes, a graphene–dielectric–metal (GDM) configuration supporting an image graphene plasmon (IGP) has been reported recently through the plasmon interactions in a graphene sheet and its mirror image inside a metal with out‐of‐phase charge oscillations. This study proposes a waveguide structure consisting of a cylindrical dielectric wire over a GDM to achieve an ultraconfined mode area by coupling a dielectric waveguide and an IGP mode. Furthermore, this work examines the dependence of waveguide dimensions and material properties on the mode characteristics of the proposed hybrid IGP (HIGP). This HIGP achieves plasmon wavelengths 20 times shorter and normalized propagation lengths twice longer than GPs, accompanying a mode size of 3 × 10−8A0, where A0 is the diffraction‐limited mode area. Moreover, the simple structure makes the HIGP easy to be verified experimentally. This work demonstrates that the HIGP delivering strong light–matter interactions at extremely compact dimensions can be exploited for building highly integrated, enhanced nonlinear, high‐resolution sensing and imaging THz devices.

The occurrence of lower-than-expected bulk NCCN values over the marginal seas of China - Implications for competitive activation of marine aerosols

In this study, we combined the measured bulk particle number concentration (NCN), particle number size distribution (PNSD) and bulk cloud condensation nuclei concentration (NCCN) at various supersaturation (SS) levels to investigate competitive activation of aerosols in the marine atmospheres over the marginal seas of China during two winter campaigns Campaign A (December 9-19, 2019) and Campaign B (December 28, 2019-January 16, 2020). During the two campaigns, we observed various categories of aerosols, i.e., long-range transport continental aerosols, clean marine aerosols, grown new particles ranging from nucleation mode to larger sizes, and grown pre-existing particles ranging from Aitken mode to accumulation mode size, etc. We found that the measured NCCN increased by only approximately 30 % with increases in SS levels from 0.2 % to 1.0 %, e.g., (1.8 ± 1.4) × 103 cm−3 at SS = 0.2 % and (2.4 ± 1.4) × 103 cm−3 at SS = 1.0 % during Campaign A. We further calculated the hygroscopicity parameter kappa (κ) by combining simultaneously measured PNSD and bulk NCCN to explore the causes. The calculated κ values were below 0.1 at SS = 0.4 % during the 72 % (or 88 %) period of Campaign A (or Campaign B). When κ values below 0.1 (or 0.2) were excluded, the remaining κ values were apparently reasonable, with an average of 0.22 (or 0.36) and a standard deviation of 0.10 (or 0.21) at SS = 0.4 % during Campaign A (or Campaign B). The unexpectedly lower κ values were discussed in terms of competitive activation of aerosols in marine atmospheres together with its net contribution to lowering the measured bulk NCCN below the expected value.

Exploratory study to assess feasibility of intracerebral hemorrhage detection by point of care cranial ultrasound

BackgroundLimited studies have evaluated the use of ultrasound for detection of intracerebral hemorrhage (ICH) using diagnostic ultrasound Transcranial Doppler machines in adults. The feasibility of ICH detection using Point of care Ultrasound (POCUS) machines has not been explored. We evaluated the feasibility of using cranial POCUS B mode imaging performed using intensive care unit (ICU) POCUS device for ICH detection with a secondary goal of mapping optimal imaging technique and brain topography likely to affect sensitivity and specificity of ICH detection with POCUS.Materials and methodsAfter obtaining IRB approval, a blinded investigator performed cranial ultrasound (Fujifilm, Sonosite® Xporte, transcranial and abdominal presets) through temporal windows on 11 patients with intracerebral pathology within 72 h of last CT/MRI (computed tomography scan/magnetic resonance imaging) brain after being admitted to a neurocritical care unit in Aug 2020 and Nov 2020–Mar 2021. Images were then compared to patient’s CT/MRI to inform topography. Inferential statistics were reported.ResultsMean age was 57 (28–77 years) and 6/11 were female. Six patients were diagnosed with ICH, 3 with ischemic stroke, 1 subarachnoid hemorrhage, and 1 brain tumor. The sensitivity and specificity of point of care diagnosis of ICH compared to CT/MRI brain was 100% and 50%, respectively. Mean time between ultrasound scan and CT/MRI was 13.3 h (21 min–39 h). Falx cerebri, choroid calcification and midbrain-related artifacts were the most reproducible hyperechoic signals. Abdominal preset on high gain yielded less artifact than Transcranial Doppler preset for cranial B mode imaging. False positive ICH diagnosis was attributed to intracerebral tumor and midbrain-related artifact.ConclusionsOur exploratory analysis yielded preliminary data on use of point of care cranial ultrasound for ICH diagnosis to inform imaging techniques, cranial topography on B mode and sample size estimation for future studies to evaluate sensitivity and specificity of cranial POCUS in adult patients. This pilot study is limited by small sample size and over representation of ICH in the study. Cranial POCUS is feasible using POCUS machines and may have potential as a screening tool if validated in adequately powered studies.

Plasmon emission by interlayer excitons in twisted bilayers: Effect of large plasmonic wavevector components

While the emission of localized plasmons is often treated in the real-space picture, working in wavevector space makes it possible to resolve the contributions of various plasmonic Fourier components. By calculating the rate of plasmon emission by interlayer excitons in twisted ${\mathrm{MoSe}}_{2}/{\mathrm{WSe}}_{2}$ van der Waals heterostructures as a function of plasmon localization, twist angle, and temperature, we show that a much wider range of exciton states can radiate into subwavelength plasmon modes than into free space. Most of the emission in this case takes place via plasmonic Fourier components that exceed the maximum photon wavevector in free space. We demonstrate that this provides an avenue for continued Purcell scaling of the emission rate with mode size. Furthermore, the scaling is well in excess of the Purcell trend for sufficiently large twist angles and strong plasmonic localization.

Effects of emission sources on the particle number size distribution of ambient air in the residential area

Particle size distribution is a major factor in the health and climate effects of ambient aerosols, and it shows a large variation depending on the prevailing atmospheric emission sources. In this work, the particle number size distributions of ambient air were investigated at a suburban detached housing area in northern Helsinki, Finland, during a half-year period from winter to summer of 2020. The measurements were conducted with a scanning mobility particle sizer (SMPS) with a particle size range of 16–698 nm (mobility diameter), and the events with a dominant particle source were identified systematically from the data based on the time of the day and different particle physical and chemical properties. During the measurement period, four different types of events with a dominant contribution from either wood-burning (WB), traffic (TRA), secondary biogenic (BIO), or long-range transported (LRT) aerosol were observed. The particle size was the largest for the LRT events followed by BIO, WB, and TRA events with the geometric mean diameters of 72, 62, 57, and 41 nm, respectively. BIO and LRT produced the largest particle mode sizes followed by WB, and TRA with the modes of 69, 69, 46, and 25 nm, respectively. Each event type had also a noticeably different shape of the average number size distribution (NSD). In addition to the evaluation of NSDs representing different particle sources, also the effects of COVID-19 lockdown on specific aerosol properties were studied as during the measurement period the COVID-19 restrictions took place greatly reducing the traffic volumes in the Helsinki area in the spring of 2020. These restrictions had a significant contribution to reducing the concentrations of NOx and black carbon originating from fossil fuel combustion concentration, but insignificant effects on other studied variables such as number concentration and size distribution or particle mass concentrations (PM1, PM2.5, or PM10).