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Parameterization of the size-resolved particle activation ratio (AR) is useful for the prediction and analysis of the cloud condensation nuclei (CCN) number concentration ( N CCN ). Critical issues for the application of AR parameterizations in models are (1) the consistency of the different parameterization schemes in terms of fitting AR curves and (2) the applicability of the estimate of N CCN under different aerosol conditions. These issues are discussed in this study based on summertime measurements of the size-resolved AR in the North China Plain. By comparing parameterized AR curves, variations in the fitting parameters and application to N CCN calculations, the consistency of the three existing parameterization schemes is confirmed. Based on an analysis using representative AR fitting parameters, the method commonly used to calculate N CCN with a fixed AR was found to be accurate, except during periods affected by strong black carbon (BC) emissions or new particle formation (NPF) events. The N CCN value was overestimated by approximately 10% when BC aerosol emissions were abundant and deviated from the 1:1 line by 15% during NPF events. The bias of the calculated N CCN due to these significant emission or aerosol production events cannot be eliminated by using the appropriate representative fitting parameters. Under these circumstances, accurate prediction of N CCN requires real-time aerosol hygroscopicity data based on CCN measurements. This research furthers our understanding of the relationship between aerosol cloud activation and aerosol spectra. [ABSTRACT FROM AUTHOR]

Optimal nano-sized drug carrier requires long blood circulation, selective extravasation, and efficient cell uptake. Here we develop a charge-convertible nanoplatform based on Pt(IV) prodrug loaded NaYF 4 :Yb,Tm upconversion nanoparticles (UCNs), followed by coating a layer of PEG-PAH-DMMA polymer (UCNs-Pt(IV)@PEG-PAH-DMMA). The polymer endows the platform with high biocompatibility, initial nano-size for prolonged blood circulation and selective extravasation. Especially, the anionic polymer can response to the mild acidic stimulus (pH ∼6.5) of tumor extracellular microenvironment and experience charge-shifting to a cationic polymer, resulting in electrostatic repulsion and releases of positive UCNs-Pt(IV). The positive UCNs-Pt(IV) nanoparticles have high affinity to negative cell membrane, leading to efficacious cell internalization. Simultaneously, the ultraviolet (UV) light emitted from UCNs upon near-infrared (NIR) light irradiation, together with the reductive glutathione (GSH) in cancer cells efficiently activate the Pt(IV) prodrug to highly cytotoxic Pt(II), realizing NIR photon improved chemotherapy. The experimental results reveal the charge convertibility, low adverse effect and markedly enhanced tumor ablation efficacy upon NIR laser irradiation of this smart nanoplatform. Moreover, combining the inherent upconversion luminescence (UCL) and computed tomography (CT) imaging capabilities, an alliance of cancer diagnosis and therapy has been achieved. [ABSTRACT FROM AUTHOR]

Abstract: Manual visual inspection is currently used in the modern Hard Disk assembly process. This research shows a feasible design to automate the visual inspection process based on wavelength dependant detection. Two defect detection algorithms, one - computationally simple and another - complex, are explored in this paper. The developed system meets the performance of the current manual inspection method while providing high accuracy in targeted defects. [Copyright &y& Elsevier]

Size-resolved Particle Activation Ratio (SPAR), defined as the size-dependence of CCN activity of aerosol particles, is generally parameterized by a scheme that neglects the contribution of nearly-hydrophobic particles. In this paper, it was found that nearly-hydrophobic particles can contribute up to 20% to the CCN activity for large particles and the estimation of particle hygroscopicity would be significantly biased using the original parameterization scheme. An improved parameterization scheme considering the contribution of nearly-hydrophobic particles was proposed and applied on measurements conducted at a rural site in the North China Plain during summer 2013. For hygroscopic particles in range of 50–70 nm diameter, which might be dominated by organic compounds, their number fraction (f n) and midpoint activation diameter (D a) fitted with the improved scheme were up to 20% lower than the parameters fitted with the original scheme. Both parameterization schemes of SPAR were further applied in a comparison study of aerosol hygroscopicity measurements between Cloud Condensation Nuclei (CCN) Counter coupled with Differential Mobility Analyzer (DMA-CCNC) and Hygroscopicity Tandem Differential Mobility Analyzer (HTDMA) during the Xianghe Campaign. Applying the improved scheme, the correlations of derived f n for hygroscopic particles between measurements of DMA-CCNC and HTDMA were improved (R increased by up to 0.2 with the uncertainty of the regression to be about 10%). In addition, for particles smaller than 100 nm, the size-dependence of hygroscopicity parameter and the diurnal cycle of f n derived using the improved scheme, based on the DMA-CCNC measurements were more consistent with those derived with the HTDMA measurements. These results highlight the importance of considering nearly-hydrophobic particles in SPAR curves fitting and in the calculation of aerosol hygroscopicity based on DMA-CCNC measurements. • A new parameterization scheme for SPAR considering the contribution of the nearly-hydrophobic particles is proposed. • The fitting parameters using the improved scheme were up to 20% lowered for hygroscopic particles. • The derived aerosol hygroscopicity using the improved scheme agrees better with aerosol hygroscopicity derived from HTDMA. [ABSTRACT FROM AUTHOR]

Atmospheric ammonia (NH 3) as the most important alkaline gas in the atmosphere has attracted much attention in recent years due to its critical role in haze formation, especially on the North China Plain (NCP). Comprehensive studies are needed for investigating diurnal variations of NH 3 and underlying mechanisms in different seasons and their potential impacts on atmospheric chemistry. In this study, continuous long-term observation (Mar. 2016 to May 2017) of NH 3 at a rural site in the NCP was used to characterize the diurnal variation of NH 3 in different seasons and to unveil its causes and potential impacts on atmospheric chemistry. NH 3 concentrations displayed rapid increases during the morning, reaching very prominent peaks mostly between 8:00 to 11:00 LT. Such frequent (55%) morning peaks were mainly caused by the evaporation of dew and guttation water droplets. Average dew and guttation water volume concentrations of 750 mL m−2 was estimated for spring, which resulted in approximate NH 3 emissions of 800 ng m−2 s− 1. Such high emission fluxes from dew and guttation water evaporation have never been reported before, suggesting dew and guttation droplets to be significant night-time reservoirs and strong morning sources for NH 3. In light of recent studies putting forward that NH 3 can promote the heterogeneous formation of HONO and nitrate under high humidity conditions, we investigated the differences in HONO and aerosol chemical composition diurnal variations between days with and without NH 3 morning spikes during November. HONO, nitrate and sulfate concentrations were significantly higher for days with NH 3 morning spikes, with HONO displaying a morning peak near that of NH 3. These results demonstrate that the prevailing NH 3 morning spikes on the NCP have significant influences on aerosol formation and atmospheric chemistry. NH 3 emission mitigation strategies and regulations are urgently needed. • Highly frequent morning peaks of NH 3 caused by dew and guttation water. • Dew and guttation water exhibit very high NH 3 storage and emission capacity. • NH 3 diurnal variation has potential impact on rapid haze formation. Dew and guttation water exhibit very high NH 3 storage and emission capacity, causing highly frequent NH 3 morning peaks, inducing rapid haze formation in the North China Plain. [ABSTRACT FROM AUTHOR]

Aerosol surface area concentration ( S A ) is crucial for studying atmospheric chemical reactions happened in aerosol water or on aerosol surface. However, there is no commercial instrument that can provide direct measurements of ambient S A . In this paper, we propose a method to calculate ambient S A based only on measurements of a three-wavelength humidified nephelometer system, which measures aerosol optical properties at three wavelengths under dry state and different relative humidity (RH) conditions. Two critical steps are required in this method: (1) Calculating surface area concentration of ambient aerosols in dry state, S A (dry) , using a trained random forest machine learning model based only on optical properties measured by the "dry" nephelometer. The proposed machine learning method is evaluated with particle number size distributions (PNSD) datasets from eight field campaigns conducted on the North China Plain during different seasons. The square of correlation coefficients between predicted and calculated S A (dry) for PNSD is about 0.99, the average ratio between predicted and calculated S A (dry) is 1.01 and 70% of data points has a relative difference less than 10%. (2) Calculating the surface area growth factor f S (RH) of ambient aerosol particles due to water uptake using the proposed f S (RH) parameterization scheme f S (RH) = (1 + κ S R H 100 − R H) 2 3 , and the hygroscopicity parameter κ S can be calculated using measured aerosol light scattering enhancement factor and Å ngstr o ¨ m exponent. The ambient S A values during two field campaigns which are conducted on the North China Plain (Wangdu campaign and Gucheng campaign, in summer and winter respectively) are calculated using the proposed method. The ambient S A ranges from 42 to 1871 μ m 2 / c m 3 with an average of 319 μ m 2 / c m 3 during Wangdu campaign, and ranges from 19 to 4156 μ m 2 / c m 3 with an average of 788 μ m 2 / c m 3 during Gucheng campaign. Drastic daily variations of ambient S A are observed during these two campaigns. The results demonstrate that aerosol hygroscopic growth impacts significantly on variations in ambient S A especially under high RH conditions. The f S (RH) ranges from near 1 to 4 with an average of 1.4 during Wangdu campaign, and ranges from near 1 to 2.7 with an average of 1.3 during Gucheng campaign. The results indicate that the larger RH, the more sensitive f S (RH) becomes to variations in κ S which highlights that real-time measurements of aerosol hygroscopicity are required for accurate calculations of ambient S A . The advantage of the proposed method is that the ambient S A can be obtained solely based on measurements of a three-wavelength humidified nephelometer system, facilitating real-time measurements of ambient S A and promoting studies in aerosol heterogeneous reactions. • Humidified nephelometer system performs great in predicting aerosol surface area. • Proposed method can be used in different regions. • Aerosol hygroscopic growth impacts significantly on aerosol surface area. [ABSTRACT FROM AUTHOR]

Upconversion nanoparticles (UCNPs), particularly those that are highly doped, possess outstanding properties and have demonstrated tremendous application potential. However, novel fine-tuning strategies are urgently required to enhance the upconversion luminescence (UCL) performance of UCNPs. In this study, a series of core–multishell UCNPs highly doped with Ho3+ and Yb3+ ions were synthesized via the oleate route. The X-ray diffraction (XRD), transmission electron microscopy (TEM), and UCL spectra and decay times, and pump power dependency of the synthesized UCNPs were used to examine their morphology, size, and the UCL properties. Ce3+ ions were introduced to enhance Ho3+-based red UCL, and their doping strategy was also optimized based on summarized UCL trends and detailed UCL mechanism analysis. NaHoF 4 :Gd3+@NaGdF 4 :Yb3+,Ce3+@NaGdF 4 :Yb3+ UCNPs that had 10 mol% Ce3+ dopants in their middle shells exhibited better UCL properties than the larger traditional NaGdF 4 :Yb3+,Ce3+,Ho3+ UCNPs, probably because of the combined influence of the energy interactions between the Ce3+ ions and surface groups, sensitizing energy enhancement by active shells, and the positive cooperation between the Ce3+ ions and highly-doped core–shell structures. In this study, the phenomenon of UCL decrease resulting from Ce3+ ion doping was explored. Using unique core–multishell structures with highly-doped activators and sensitizers placed within and outside the structures, respectively, the UCL decrease due to Ce3+ ion doping was attributed to a competition for photons. Doping the UCNPs with Ce3+ ions near the UCNP surfaces favors Ho3+-based red UCL. Our study findings can deepen the understanding of the Ho3+-based UCL mechanisms and increase the potential uses of NaHoF 4 materials in photo-induced therapy. When Ce3+ ions are doped near the nanoparticle surface, they might have energy interactions with surface groups to relieve phonon energy shortage and thus enhance the efficiency of cross-relaxation between Ho3+ and Ce3+ ions. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract The light scattering enhancement factor f (RH), defined as the ratio of the light scattering coefficient (σ S P ) observed under an elevated relative humidity (RH) conditions to that under dry conditions, is a crucial parameter for estimating aerosol direct radiative effects and atmospheric visibility. In this paper, a new f (RH) parameterization scheme considering both the influence of aerosol chemical compositions and that of particle number size distribution (PNSD) is proposed based on in situ measurements in the North China Plain. The development of this parameterization scheme includes three steps. First, aerosol hygroscopicity parameter κ is parameterized with aerosol chemical compositions. Then, the ratio between f (RH) fitted parameter κ s c a (f (R H) = 1 + κ s c a R H 100 − R H ) and κ is introduced to correlate f (RH) with κ. The ratio, influenced mostly by PNSD, is described as a function of scattering Ångström exponent (SAE) because the SAE can represent the predominant size of aerosol particles to some extent. Finally, f (RH) cycle is parameterized with κ s c a . Validation results show that a good consistency between the parameterized and measured f (RH = 80%) is achieved and the correlation coefficient is 0.80. This parameterization scheme between aerosol chemistry and f (RH) can be used in chemical transport models for reducing uncertainties in estimations of direct aerosol radiative forcing and air quality assessments. Highlights • A relationship between the f (RH) fitted parameter (κ sca) and the aerosol hygroscopicity parameter (κ f(RH)) is found. • The ratio of κ sca and κ f(RH) increases linearly with the increase of the scattering Ångström exponent. • A new parameterization of f (RH) considering the aerosol chemical compositions is developed. [ABSTRACT FROM AUTHOR]

The remediation of toxic persistent organic contaminants in the environment has raised a need for effective cleanup methods. In this study, an integrated remediation technique based on biodegradation of naphthalene using Bacillus fusiformis and Fenton oxidation of their degraded metabolites using nanoscale zero-valent iron (nZVI). A 99.0% naphthalene was biodegraded by B . fusiformis in 96 h, while only 59.4% chemical oxygen demand (COD) was removed, indicating that the degraded metabolites existed in solution. To further degrade the metabolites, nanoscale zero-valent iron (nZVI) was used as heterogeneous catalyst for Fenton-like oxidation of the metabolites after biodegradation lasting 40 h. Results showed that the total the removal COD increased from 36.4% to 91.6% at pH 3.0, 1.0 g L −1 nZVI, 10.0 mM L −1 H 2 O 2 and temperature of 35 °C. Scanning electron microscopy (SEM) showed the aggregation and corrosion of nZVI. X-ray diffraction (XRD) confirmed the existence of Fe 0 and the presence of iron oxide (Fe(II)) and iron oxohydroxide (Fe(III)). A possible degradation pathway was proposed since two naphthalene metabolites (1-Naphthalenol and 1,4-Naphthalenedione) were detected by GC–MS. [ABSTRACT FROM AUTHOR]

Abstract: The International Technology Roadmap for Semiconductors (ITRS) identifies production test data as an essential element in improving design and technology in the manufacturing process feedback loop. One of the observations made from the high-volume production test data is that dies that fail due to a systematic failure have a tendency to form certain unique patterns that manifest as defect clusters at the wafer level. Identifying and categorising such clusters is a crucial step towards manufacturing yield improvement and implementation of real-time statistical process control. Addressing the semiconductor industry’s needs, this research proposes an automatic defect cluster recognition system for semiconductor wafers that achieves up to 95% accuracy (depending on the product type). [Copyright &y& Elsevier]

Size-resolved particle activation ratio (SPAR), the size-dependent ability of aerosol particles to form cloud condensation nuclei (CCN), is generally parameterized by a formula with sigmoidal shape with three key parameters. However, our understanding about the intrinsic relationship between the sigmoidal shape function and aerosol hygroscopicity distribution remains incomplete. In this study, the relationship between SPAR and particle hygroscopicity distribution is mathematically derived and relationships between key parameters for SPAR and particle hygroscopicity distribution are manifested, making it clear for the physical understanding of key CCN spectral characteristics. On the basis of the mathematically derived SPAR parameterization, a simplified method to calculate SPAR parameters (including maximum activation fraction (MAF), critical diameter and its heterogeneity of CCN-active particles) based on hygroscopicity distribution data is proposed. This simplified method is applied to Hygroscopicity Tandem Differential Mobility Analyzer (HTDMA) field measurement datasets around the world for the meta-analysis of regional and seasonal characteristics of CCN activity. It was found that, for CCN-active particles in polluted regions, the MAF can reach lower values, and the variations of both hygroscopicity and its heterogeneity can be larger, compared with those in clean regions. In summer, the MAF and the hygroscopicity of CCN can reach higher values than those in winter. In addition, the variations of SPAR parameters among different campaigns are large and thus measurements of CCN Counter or HTDMA are needed to specify the SPAR parameters at a specific site during a specific period. The bulk CCN activity at different SSs are also calculated based on the calculated SPAR by considering the measured particle number size distribution. The mathematical derivation and physical interpretation of SPAR parameterization in this study can further the understanding of CCN activity based on particle hygroscopicity distribution. The proposed simplified method to calculate SPAR parameters based on HTDMA measurements allows meta-analysis of SPAR parameters and helps expand the CCN activity datasets around the world. • Relationship between Size-resolved particle activation ratio and hygroscopicity distribution is mathematically derived. • A simplified method to calculate SPAR parameters based on hygroscopicity distribution data is proposed. • Meta-analysis of CCN activity is conducted based on HTDMA field measurement datasets in references. [ABSTRACT FROM AUTHOR]

Cloud condensation nuclei (CCN) spectra, that indicate the dependence of CCN number concentrations (N CCN) on supersaturation, are important factors in aerosol–cloud interactions. Owing to the lack of direct measurements of N CCN , calculating the CCN spectra based on conventional observational data of aerosols is important to obtain N CCN ; however, this is challenging owing to the complex relationship between aerosol properties and CCN activity. Machine learning techniques have recently been applied to estimate N CCN and found to be a promising method for CCN prediction. In this study, the random forest (RF) model was applied to predict CCN spectral parameters using the observation data measured in four campaigns in the North China Plain, and the effects of chemical and optical properties of aerosol on the estimation of CCN spectra were investigated. The results show that the RF model trained with the data of one campaign can be used to estimate CCN spectral parameters in another campaign, with the coefficient of determination between the estimated and measured CCN spectral parameters being approximately 0.5. The deviations of the estimation by the RF model may result from the difference in both the aerosol properties and measurement uncertainties among different campaigns, whose influence on the deviations can be further magnified by overfitting the RF model. Further analysis revealed that the major aerosol properties among the input variables of the RF model were the mass concentration of black carbon and aerosol hemispheric backscattering fraction at a wavelength of 450 nm. In addition, the roles of chemical compositions of aerosol in estimating CCN spectra parameters are different among different campaigns because the poor correlation between aerosol chemical compositions and CCN spectra parameter can affect the performance of the RF model. For estimating CCN spectra, using aerosol optical properties, including the hemispheric backscattering fraction and absorption coefficient, as model inputs is more recommended than using aerosol chemical properties. • Random forest model is used to estimate CCN spectra based on observation data in the North China Plain. • Mass concentration of black carbon and hemispheric backscattering fraction are the most important input variables. • Aerosol optical properties data are recommended in estimation of CCN spectra parameters. [ABSTRACT FROM AUTHOR]

Particle microphysical and chemical properties, including particle number size distribution (PNSD) and chemical composition of both ambient PM 1 and PM 10 particles were measured in the North China Plain (NCP) during the Multiphase chemistry experiment in Fogs and Aerosols in the North China Plain (McFAN) campaign in November 2018. Focused on the differences of measured PNSD between PM 1 and PM 10 , the variations of aerosol microphysical and chemical properties in fog were analyzed and their corresponding influence on fog droplets evolution was evaluated. Two nighttime fog events were observed on the 12th and 13th November, respectively. During fog events, PNSDs of particles with diameter larger than ∼200 nm sampled from the PM 10 inlet were similar to those after fogs. But in particle size range larger than 200 nm, particles number concentration sampled from the PM 1 inlet were very few and much lower than those after fogs, indicating that some particles larger than 200 nm have grown into droplets with diameter larger than 1 μm and thus were not detected under the PM 1 inlet. No significant decrease in particle number concentration larger than ∼200 nm was detected under the PM 10 inlet after the dissipation of these fog events, suggesting that fog droplets were generally smaller than 10 μm and could be sampled by the PM 10 inlet. The additional particles sampled in PM 10 in fogs demonstrated a normal distribution, which indicates that they belonged to an individual particle group externally mixed with those sampled under the PM 1 impactor and could outgrow 1 μm either through hygroscopic growth or through activation. This can lead to uncertainties in droplet number concentration estimations within fog from microphysical and chemical properties measurements of the aerosol with assumption of fully internal mixture. We find that PM 1 hygroscopicity derived from particle chemical composition measurements was overestimated, which may result in significant bias in the estimated droplets number concentration in the North China Plain. These results and approaches in this study can improve the understanding of aerosol microphysical properties in fogs and the corresponding influence of aerosol particles on fog microphysics. [Display omitted] • Simultaneous measurements of PM1 and PM10 during fog events in the North China Plain. • Differences between PNSDs of PM1 and PM10 suggest additional particles in PM10 different from PM1. • Ignoring external mixing state of PM10 leads to an overestimated droplet number concentration. [ABSTRACT FROM AUTHOR]

Abstract: CoFeIIFeIII-layered double hydroxide (LDH) hollow spheres with two distinctly different hierarchical morphologies—flower-like and raspberry-like, involving edge-on and face-on oriented LDH platelets as building blocks, respectively—can be fabricated by tuning the rate of addition of NaOH solution in a coprecipitation process with sulfonated polystyrene spheres as a template. Ex situ pH-dependent microscopic observations of the formation of the flower-like LDH shells shows the details of non-classic nucleation and growth underlying the edge-on orientation. After calcination, the resulting CoFe2O4 materials retain the hierarchical morphology of the corresponding LDH precursor. The hollow CoFe2O4 spheres with raspberry-like morphology exhibit magnetic properties comparable to a reference material obtained by calcination of a conventional LDH powder precursor. Similar materials with tunable magnetic properties can be prepared by virtue of the flexibility in LDH layer composition. The CoFeIIFeIII-LDH spheres with a raspberry-like morphology may be also be prepared by using a scalable procedure involving separate ultra-rapid nucleation and aging steps in a modified colloid mill reactor. The results reported here may open up the possibility of producing shell structures with controllable morphologies and properties on a large scale. [Copyright &y& Elsevier]

The current conventional photo-therapeutic agents often show low therapy efficacy because of their single treatment model, the limited penetration depth of excitation light and hypoxia in the tumor microenvironment (TME). Herein, a new type of phthalocyanine manganese (MnPcE 4) photosensitizer with strong NIR absorption was designed and fabricated for the first time, and was used to modify pure Bi nanomaterials to obtain an intelligent multifunctional Bi/MnPcE 4 nanocomposites. The Mn2+ in the Bi/MnPcE 4 nanocomposite could catalyze H 2 O 2 to generate O 2 , thus helping to overcome TME hypoxia and enhancing the photodynamic therapy (PDT) efficacy. Further, the nanocomposites showed excellent T 1 -weighted MRI performance. Our novel use of a pure metal Bi core, offers lower toxicity, higher CT imaging performance, and a photothermal therapy (PTT) effect triggered by 808 nm near infrared (NIR) laser. Moreover, in vivo fluorescence imaging (in vivo FL) vividly showed that the nanocomposite rapidly accumulates in tumor sites due to the enhanced permeability and retention (EPR) effect and metabolized in the organs. The presence of Bi enables the use of these nanocomposites as a CT contrast agent, and the Mn content enables them to be used in MRI. This triple imaging ability implies that our nanocomposites have a high potential for use in imaging directed tumor therapy. Image 1 [ABSTRACT FROM AUTHOR]