Measurements Of Optical Properties Research Articles

Optical Property Measurement and Temperature Monitoring in High-Intensity Focused Ultrasound Therapy by Diffuse Optical Tomography: A Correlation Study

In this article, we propose a new approach utilizing diffuse optical tomography (DOT) to monitoring the changes in tissues’ optical properties and temperature in high-intensity focused ultrasound (HIFU) therapy. By correlating the tissue reduced scattering coefficient (μs’) reconstructed by DOT and the temperature measured by a thermocouple, the quantitative relationship between μs’ and temperature in HIFU treatment was explored. The experiments were conducted using porcine and chicken breast muscle tissues during HIFU; the temperature of each tissue sample was recorded using a thermocouple. To incorporate the temperature dependency of tissue optical properties, both polynomial and exponential models were utilized to fit the experimental data. The results show that the change of μs’ during HIFU treatment could be detected in real-time using DOT and that this change of μs’ is quantitatively correlated with tissue temperature. Furthermore, while the tissue-type-dependent relationship between μs’ and temperature is non-linear in nature, it is stable and repeatable. Therefore, our approach has the potential to be used to predict temperature of tissue during HIFU treatment.

Shortwave infrared spatial frequency domain imaging for non-invasive measurement of tissue and blood optical properties.

.SignificanceThe shortwave infrared (SWIR) optical window (∼900 to 2000 nm) has attracted interest for deep tissue imaging due to the lower scattering of light. SWIR spatial frequency domain imaging (SWIR SFDI) provides wide-field tissue optical property measurements in this wavelength band. Key design and performance characteristics, such as portability, wavelength selection, measurement resolution, and the effect of skin have not yet been addressed for SWIR SFDI.AimTo fabricate and characterize a SWIR SFDI system for clinical use.ApproachThe optimal choice of wavelengths was identified based on optical property uncertainty estimates and imaging depth. A compact light-emitting diode-based dual wavelength SWIR SFDI system was fabricated. A two-layer inverse model was developed to account for the layered structure of skin. Performance was validated using tissue-simulating phantoms and in-vivo measurements from three healthy subjects.ResultsThe SWIR SFDI system had a resolution of at least at 880 nm and at 1100 nm. The two-layer inverse model reduced the error in deeper layer extractions by at least 24% in the phantom study. The two-layer model also increased the contrast between superficial vessels and the surrounding tissue for in-vivo measurements.ConclusionThe clinic-ready SWIR SFDI device is sensitive to small optical property alterations in diffuse media, provides enhanced accuracy in quantifying optical properties in the deeper layers in phantoms, and provided enhanced contrast of subcutaneous blood vessels.

Vertically Resolved Aerosol Chemistry in the Low Boundary Layer of Beijing in Summer.

Air quality in Beijing has been improved significantly in recent years; however, our knowledge of the vertically resolved aerosol chemistry in summer remains poor. Here, we carried out comprehensive measurements of aerosol composition, gaseous species, and aerosol optical properties on a meteorological tower in Beijing in summer and compared with those measured in winter. Our results showed that aerosol liquid water (ALW) contributing approximately 50% of the total mass with higher values aloft played a crucial role in aerosol formation. Particularly, the higher nitrate concentration in city aloft than at the ground level during daytime was mainly due to the enhanced gas-particle partitioning driven by ALW and particle acidity. The vertical profiles of organic aerosol (OA) factors varied more differently in the urban boundary layer. Although the ubiquitous decreases in primary OA with the increase in height were mainly due to the influences of local emissions and vertical convection, the vertical differences in oxygenated OA between summer and winter may be related to the photochemical processing of different biogenic and anthropogenic volatile organic compounds. The single-scattering albedo, brown carbon, and absorption Ångstrom exponent of aerosol particles also presented different vertical profiles between day and night due to the vertical changes in aerosol chemistry.

Investigating the effects of intermolecular interactions on nonlinear optical properties of binary mixtures with high repetition rate femtosecond laser pulses

Measurements of nonlinear optical (NLO) properties of different binary mixtures having carbon disulfide (CS2) as the common component, namely CS2-acetone, CS2-cyclopentanone, CS2-toluene, and CS2-carbon tetrachloride (CCl4), are carried out by using the z-scan technique. Open-aperture z-scan (OAZS) and close-aperture z-scan (CAZS) experiments are performed to determine the nonlinear absorption coefficient (β) and nonlinear refractive index (n2) of all binary liquid mixtures at various compositions of the components by employing a pulsed, high repetition rate (HRR) femtosecond laser. Also, we were able to use the flowing liquid to measure NLO properties in the CS2-acetone binary mixture to remove the cumulative thermal effects produced due to the pulsed HRR laser light. Nonlinear refractive index (n2) values are found to be influenced by the weak dipole-induced dipole intermolecular interactions between the nonpolar CS2 and polar acetone as well as cyclopentanone of the respective binary mixtures. On the contrary n2 values are not found to be affected by the intermolecular interactions in CS2-toluene and CS2-CCl4 binary mixtures. In comparison, the nonlinear absorption coefficient (β) values are not found to be affected by the same in all different sets of binary mixtures.

Structural and optical properties of Ba0.5Sr0.5TiO3 thin films on single crystalline substrates

The present investigation reports on structural and microstructural information of the Ba0.5Sr0.5TiO3 (BST-0.5) film deposited over single crystalline Si (100), MgO (100), and LaAlO3 (100) substrate using pulsed laser deposition (PLD) method. In this study, initial experiments were carried out by depositing BST-0.5 films at 1023 K and with oxygen partial pressures of 0.13 Pa and 13.33 Pa on Si (100) substrates. X-ray diffraction (XRD) analysis indicated the formation of a highly crystalline perovskite cubic phase for film deposited at substrate temperature 1023 K. Another set of depositions were carried out at the substrate temperature of 873 K and 1023 K and with oxygen partial pressure of 13.33 Pa. The XRD analysis indicated that deposition at 13.33 Pa has produced BST-0.5 films of increased crystallinity at the substrate temperature of 1023 K. Raman spectra obtained for BST thin film deposited on these three substrates confirmed the formation of the cubic phase. BST thin films were also prepared on LaAlO3 (100) and MgO (100) to investigate the optical properties of film prepared under the best deposition conditions such as 1023 K and 13.33 Pa. The bandgap energies were found to be in the range of 3.93–3.97 eV for these substrates. The measurements of optical properties of the BST-0.5 film coated on LaAlO3 substrate showed about ∼75% transmittance compared to MgO substrate. Higher extinction coefficient for the BST-0.5 thin film was observed for the film coated on MgO substrate in the UV and visible region compared to that of the film coated on LaAlO3 substrate. The refractive index as a function of wavelength was found to be 1.945 and 2.023 for BST-0.5 thin film coated on MgO and LaAlO3, respectively. The enhanced optical properties of the BST film coated on LaAlO3 substrate are discussed in relation to higher crystallinity and epitaxial growth of thin films obtained because of lower lattice mismatch.

Experience in the Application of Hydrocarbon Optical Studies in Oil Field Development

This article reviews the results of measurement of optical properties of oil, such as polarimetry, refractometric, luminescent-bituminological research, IR-spectrometry and UV-visible-NIR spectrometry used to solve geo-bituminology development of hydrocarbon deposits. The authors pay special attention to optical research in the field of UV-visible-NIR electromagnetic radiation, the results of which allow us to estimate the residual oil reserves, separate production for each formation during the operation of multi-layer objects, determine the producing gas-oil ratio, density and content of hydrocarbons, efficiency of hydraulic fracturing, flow-reducing technologies, and injection of solvents of heavy oil sediments, etc. The published approaches to methods of optical research, which are carried out by laboratories or in-well devices, have been analyzed. This article analyzes the main advantages and disadvantages of current technologies for determining the optical properties of oil. The authors propose wellhead devices for determining the optical properties of oil in UV-visible-NIR radiation (190–1100 nm) and their functional schemes, with a description of the operating principle.

Sustainable removal of 17α-ethynylestradiol from aqueous environment using rare earth doped lanthanum manganite nanomaterials

The pure water scarcity is a serious, emerging issue and this affects roughly the 40% of the world’s population thus new efficient wastewater treatment techniques are required. Lanthanum manganite (LaMnO3), is one of the most promising and efficient photocatalysts for the degradation of organic pollutants. In this work, undoped and Eu, Ho, Tb doped LaMnO3materials were successfully synthesized via sol–gel process using citric acid as chelating agent. The as-obtained samples are well crystallized within the perovskite structure and from the optical properties measurements it is determined that the value for the band gap energy is not influenced by the doping, i.e.Eg ~ 3.4 eV for all samples. In the photocatalytic studies,the potential water purification possibility is proved for the newly synthesized perovskite nanomaterials, and the best removal efficiency was reached in the presence of LMO:Ho, when 77% of endocrine disruptors EE2 (e.g. 17α-ethynilestradiol) was degraded after 30 min of UV irradiation. In addition, there usability of the LMO:Ho nanomaterials was also investigated. Based on the reutilization findings, it can be concluded that the mentioned photocatalyst has not lost its efficiency after three successive runs for photodegradation. Furthermore, the possible mechanism of the photocatalytic degradation of EE2, using different scavengers was also determined, and among the applied scavengers, the most important role had EDTA × 2Na, NaF and p-benzoquinone. According to our findings, the EE2 degradation mechanism mostly took place via positively charged holes,●OHadsradicals, as well as throughO2•−radicals, however they had a weaker effect on the degradation efficiency.

Preferential Location of Dopants in the Amorphous Phase of Oriented Regioregular Poly(3‐hexylthiophene‐2,5‐diyl) Films Helps Reach Charge Conductivities of 3000 S cm−1

AbstractDoping polymer semiconductors is a central topic in plastic electronics and especially in the design of novel thermoelectric (TE) materials. In this contribution, it has been demonstrated that doping of oriented semicrystalline P3HT thin films with the dopant tris(4‐bromophenyl)ammoniumyl hexachloroantimonate), known as magic blue (MB), helps reach charge conductivities of 3000 S cm−1 and TE power factors of 170 ± 30 μW mK−2 along the polymer chain direction. A combination of transmission electron microscopy, polarized optical absorption spectroscopy, Rutherford backscattering, and TE property measurements helps clarify the conditions necessary to achieve such high charge conductivities. A comparative study with different dopants demonstrates that the doping mechanism is intimately related to the semicrystalline structure of the polymer and whether crystalline, amorphous or both phases are doped. The highest charge mobilities are observed when the dopant MB is preferentially located in the amorphous phase of P3HT, leaving the structure of P3HT nanocrystals almost unaltered. In this case, the P3HT nanocrystals are doped from their interface with the surrounding amorphous phase. These results indicate that doping preferentially the amorphous phase of semicrystalline polymer semiconductors is an effective strategy to reduce polaron localization, enhance charge mobilities, and improve TE power factors.

RbLiZn5(PO4)4 and BaLiZn3(PO4)3: two new zinc orthophosphates with all tetrahedra-based anion frameworks

Inorganic functional materials based on phosphates have attracted heavy attention due to diverse structures and ravishing properties. Two new zinc orthophosphates, RbLiZn5(PO4)4 and BaLiZn3(PO4)3, have been obtained through hydrothermal and high temperature solid reaction respectively. RbLiZn5(PO4)4, which is the first rubidium lithium zinc phosphate, crystallizes in a monoclinic space group of C2/c featuring a three-dimensional (3D) [LiZn5(PO4)4]– anion framework composed of parallel 2D [(Zn2(PO4)2]∞ slab and [ZnLi(PO4)4]∞ chains, which are formed by the ZnO4 and LiO4 groups connected with isolated PO4 groups. BaLiZn3(PO4)3, which is the first barium lithium zinc phosphate, crystallizes in an orthorhombic space group of Pccn with the 3D [(LiZn)Zn2PO7]4– anion skeleton created by two mirror-symmetric zigzag [Zn(ZnLi)O7]∞ chains connected with isolated PO4 groups through corner-sharing. The Rb+ and Ba2+ are located in the empty space of the structure as the counter cations. Besides crystal structures analysis, thermal stability and optical properties measurements as well as theoretical studies of the title phosphates were conducted.

Comments on “Experimental Measurement of Physical, Transport, and Optical Properties of Binary Mixtures of n‑Hexyl Pyridinium Nitrate [HPy][NO3] Ionic Liquid with Water, Ethanol, and Acetonitrile at 298.15 K and 101 kPa”

Comments on “Experimental Measurement of Physical, Transport, and Optical Properties of Binary Mixtures of n‑Hexyl Pyridinium Nitrate [HPy][NO3] Ionic Liquid with Water, Ethanol, and Acetonitrile at 298.15 K and 101 kPa”

Small Organic Molecular-Based Hybrid Halides with High Photoluminescence Quenching Temperature.

Organic-inorganic metal halides (OIMHs) exhibit excellent photoelectric properties; however, their high-temperature light-emission stability requires further improvement. Here, we report three isostructural OIMHs (C2H8N)4InCl7, (C2H8N)4SbCl7, and (C2H8N)4SbBr7 (C2H8N+ = dimethylammonium). They are all crystallized in the P21212 space group with a zero-dimensional (0D) structure, with orange-red photoluminescence (PL) under 365 nm UV excitation. Among them, (C2H8N)4InCl7 exhibits the strongest PL with a photoluminescence quantum yield (PLQY) of 13.9% at room temperature. Optical property measurements and density functional theory unveil that the luminescence of (C2H8N)4InCl7 at 405 and 620 nm is due to free exciton and self-trapped exciton emission, respectively. It is worth noting that (C2H8N)4InCl7 shows a high PL quenching temperature, maintaining 50% of its room-temperature PL intensity at 425 K, which is rare in OIHMs. This is much higher than the application temperature of phosphors in practical solid-state lighting applications (363-383 K). In this temperature range, the luminous intensity of (C2H8N)4InCl7 exceeds 60% of that at room temperature. The high PL quenching temperature observed in (C2H8N)4InCl7 indicates the potential of OIMHs for applications in phosphor-converted light-emitting diodes.

Direct measurement of optical properties of glacier ice using a photon-counting diffuse LiDAR

AbstractThe production of meltwater from glacier ice, which is exposed at the margins of land ice during the summer, is responsible for a large proportion of glacier mass loss. The rate of meltwater production from glacier ice is especially sensitive to its physical structure and chemical composition which combine to determine the albedo of glacier ice. However, the optical properties of near-surface glacier ice are not well known since most prior work has focused on laboratory-grown ice or deep cores. Here, we demonstrate a measurement technique based on diffuse propagation of nanosecond-duration laser pulses in near-surface glacier ice that enables the independent measurement of the scattering and absorption coefficients, allowing for a complete description of the processes governing radiative transfer. We employ a photon-counting detector to overcome the high losses associated with diffuse optics. The instrument is highly portable and rugged, making it optimally suited for deployment in remote regions. A set of measurements taken on Crook and Collier Glaciers, Oregon, serves as a demonstration of the technique. These measurements provide insight into both physical structure and composition of near-surface glacier ice and open new avenues for the analysis of light-absorbing impurities and remote sensing of the cryosphere.

Spatial modulation spectroscopy of semiconductors using dynamic gratings

Subject of study. Several characterization methods that utilize recording and reading out of dynamic gratings to analyze functional materials are proposed. Method. The methods are based on pulsed recording of thin and volume dynamic gratings followed by reconstruction using continuous laser emission to facilitate the detection of the formation and relaxation dynamics of the recorded diffraction grating. Nonlinear optical, thermo-optic, and kinetic properties of condensed media were obtained based on the measured kinetics of the diffracted signals. Main results. The performance characteristics of a dynamic grating method were analyzed for characterization and parameter measurements of functional materials. In particular, the efficacy of the measurement of the kinetic properties for pulsed recordings of thin and volume holographic gratings was demonstrated. The lifetimes of the short- and long-lived trap levels involved in recording of the dynamic grating were determined in a photorefractive bismuth silicate crystal and the dependence of the diffraction efficiency of the gratings on the intensity of the recording radiation was determined. The advantages of using an additional grating (homodyne) to enable the separation of the contributions of different simultaneously manifesting nonlinearity mechanisms were demonstrated. This method was applied to monocrystalline germanium. A method for assessing the thickness of a film on the surface of a sample based on the amplitude of an oscillating component related to a sound wave propagating in air in the vicinity of the film’s surface was also proposed. A silicon dioxide film was considered as an example. The application of the diffraction to different orders on volume dynamic gratings was proposed for the measurement of the nonlinear optical susceptibility of the fifth and higher orders. The proposed approach was evaluated on photorefractive crystals and semiconductor media. The kinetic and thermo-optic properties, including the time of the population of trap levels, thermo-optic coefficient, and thermal diffusivity, of the media were determined. Practical significance. The proposed characterization methods facilitate the isolation of different nonlinearity mechanisms involved in the formation of dynamic gratings and the measurement of nonlinear optical, thermo-optic, and kinetic properties (optical susceptibilities of different orders, thermo-optic coefficient, thermal diffusivity, and lifetimes of free-charge carriers and trap levels).

Correlative imaging of the spatio-angular dynamics of biological systems with multimodal instant polarization microscope.

The spatial and angular organization of biological macromolecules is a key determinant, as well as informative readout, of their function. Correlative imaging of the dynamic spatio-angular architecture of cells and organelles is valuable, but remains challenging with current methods. Correlative imaging of spatio-angular dynamics requires fast polarization-, depth-, and wavelength-diverse measurement of intrinsic optical properties and fluorescent labels. We report a multimodal instant polarization microscope (miPolScope) that combines a broadband polarization-resolved detector, automation, and reconstruction algorithms to enable label-free imaging of phase, retardance, and orientation, multiplexed with fluorescence imaging of concentration, anisotropy, and orientation of molecules at diffraction-limited resolution and high speed. miPolScope enabled multimodal imaging of myofibril architecture and contractile activity of beating cardiomyocytes, cell and organelle architecture of live HEK293T and U2OS cells, and density and anisotropy of white and grey matter of mouse brain tissue across the visible spectrum. We anticipate these developments in joint quantitative imaging of density and anisotropy to enable new studies in tissue pathology, mechanobiology, and imaging-based screens.

Insights into the honeycomb ordered Li3(MnM)SbO6 (M(II) = Co, Ni, Zn, Mg) and Li3(CoMʹ)SbO6 (Mʹ(II) = Ni, Zn, Mg) oxides

The present study deals with the designing of new honeycomb layered oxides, Li3(MnM)SbO6 (M(II) = Co, Ni, Zn, Mg) and Li3(CoMʹ)SbO6 (Mʹ(II) = Ni, Zn, Mg) belonging to the monoclinic (S. G. C2/m) layered structural family. A cationic mixing of Li+ and Mn2+ is expected for the solid solution members, Li3(MnM)SbO6 (M(II) = Co, Ni, Zn, Mg) similar to Li3Mn2SbO6. Li3(CoMʹ)SbO6 (Mʹ(II) = Ni, Zn, Mg) oxides also synthesized through high temperature solid state methods, adopt monoclinic (S. G. C2/m) structures as confirmed by the profile fitting of the PXRD measurements. Notably, the formation of Li3(MnMg)SbO6 and Li3(CoMg)SbO6 is worth highlighting since Li3Mg2SbO6 and Li3Co2SbO6 are known in thermodynamically stable orthorhombic (S. G. Fddd) rock salt superstructures. Variable temperature magnetic susceptibility measurements of the Mn2+ based oxides register an antiferromagnetic (AFM) ordering at low temperatures (<20 K) except Li3(MnZn)SbO6 and Li3(MnMg)SbO6. In addition, the divergence (∼40–60 K) between ZFC (Zero Field Cooled) and FC (Field Cooled) data appearing in Li3(MnCo)SbO6, Li3(MnNi)SbO6, and Li3(MnMg)SbO6 indicate the possible impurity of Mn3O4. Isothermal magnetization measurements at 300 K confirm typical paramagnetic behavior and a non-linear behavior at 2 K, suggesting the presence of competing ferromagnetic interactions. All the members of the series, Li3(CoMʹ)SbO6 (Mʹ(II) = Ni, Zn, Mg), exhibit clear AFM transition below 15 K. Isothermal magnetization measurements for Li3(CoNi)SbO6 shows sign of spin-flop transition at magnetic field 2.1 T similar to Li3Co2SbO6. In comparison, Li3(CoZn)SbO6 and Li3(CoMg)SbO6 only show a sigmoidal curve at 2 K. Optical property measurements revealed the transitions arising from the presence of the (MnM)2+ and (CoMʹ)2+ cations.

High-Performance Mid-IR to Deep-UV van der Waals Photodetectors Capable of Local Spectroscopy at Room Temperature.

The ability to perform broadband optical spectroscopy with subdiffraction-limit resolution is highly sought-after for a wide range of critical applications. However, sophisticated near-field techniques are currently required to achieve this goal. We bypass this challenge by demonstrating an extremely broadband photodetector based on a two-dimensional (2D) van der Waals heterostructure that is sensitive to light across over a decade in energy from the mid-infrared (MIR) to deep-ultraviolet (DUV) at room temperature. The devices feature high detectivity (>109 cm Hz1/2 W-1) together with high bandwidth (2.1 MHz). The active area can be further miniaturized to submicron dimensions, far below the diffraction limit for the longest detectable wavelength of 4.1 μm, enabling such devices for facile measurements of local optical properties on atomic-layer-thickness samples placed in close proximity. This work can lead to the development of low-cost and high-throughput photosensors for hyperspectral imaging at the nanoscale.

Optical properties and spectral dependence of aerosol light absorption over the Brazilian Pantanal

Characterizing optical properties of aerosols, particularly the absorption processes, is fundamental for understanding the role of these particles in ecosystems as well as the climate, in general. Currently, changes in precipitation regimes in the southern Amazon basin have resulted in a considerable increase in biomass burning, whereby large amounts of aerosols and gases are emitted into the atmosphere. These increased emissions can impact the ecosystem, modifying mass and energy flows at the surface. This study, motivated by the need for more aerosol observations was the result of a long-term campaign carried out in the Brazilian Pantanal, which provided continuous in-situ measurements of aerosol optical properties between January 2017 and December 2019. From these data, optical properties of aerosols were quantified and analyzed seasonally. Corrected estimates for absorption coefficient (σabs) and Angstrom absorption exponent (αabs) were utilized to characterize the spectral dependence of absorption by aerosols. With additional measurements of the scattering coefficient (σscat), it was possible to evaluate the single scattering albedo (ω0). The mean values for σabs, σscat, ω0 at 525 nm and αabs 370–880 nm during the wet season were 0.66 ± 0.58 Mm−1, 6.16 ± 5.75 Mm−1, 0.90 ± 0.06 and 1.43 ± 0.49, respectively. These values, within measurement uncertainties, were similar to results found in the central Amazon. During the dry season, absorption and scattering increased approximately 88% and 86%, respectively, providing strong evidence for the contribution of local and regional emissions from biomass burning. The values of ω0 did not reveal significant seasonal differences, however, a sharp reduction was observed, medians below 0.8, at the beginning of the burning period, which was associated with more recent local burnings and, therefore, greater absorption. The mean values evaluated for different spectral intervals reveal a strong contribution of brown carbon (BrC) during the dry season, with medians of 1.78 and 0.87 for the intervals of 370–590 nm and 590–880 nm, respectively. This work also quantified BC concentrations for the dry and wet seasons, obtaining mean values of 0.75 ± 0.83 and 0.12 ± 0.09 μgm−3, respectively. In general, a striking similarity was encountered for aerosol optical properties between the Pantanal and the Central Amazon during the wet season. The results presented here characterize the background values for aerosol optical properties in the Pantanal, and the additional effects resulting from biomass burning emissions, therefore providing essential information to assess the effects these particles have on the ecosystem.

Band gap, complex dielectric function, and optical properties of Sb-doped lead-free KNN piezo-ceramics analyzed by VEELS-TEM

Sb-doped KNN (Na0.9K0.1Nb0.97Sb0.03O3, KNNS) is an environment-friendly lead-free ferroelectric and it has high piezoelectric response. A band gap energy Eg = 3.58 eV for KNNS was evaluated by valence electron energy loss spectroscopy (VEELS), which has not been reported in the literature. The zero loss peak (ZLP) was extracted by the reflected tail model, results were gotten by the Fourier-log method. Single scattering dispersion (SSD) was used to execute the Kramers-Krӧnig analysis, thence: complex dielectric function (ε1 and ε2) based on KNNS, and optical properties were obtained; The static refractive index n(0)(nKNNS) resulted to be 2.21, which mathematically is about a square root of dielectric constant, coinciding with that obtained experimentally. Also, a peak at n1=4.1 eV and n2=9.42 eV located in the near ultraviolet was observed. Understanding the different applications of KNNS in optoelectronic devices is vital, also it is worth mentioning that many articles overlook the relativistic effects in the band gap, dielectric function, and the optical properties measurements.

Aerosol particle properties at a remote tropical rainforest in Borneo

This paper aims to investigate aerosol particle properties and their seasonal variabilities at a remote tropical forest site. It also attempts to study the relationship between aerosol particles and dynamic atmospheric processes that modulate aerosol variability. Mass concentrations for particles smaller than 10 μm aerodynamic diameter (PM10) and optical aerosol particle properties were measured at Danum Valley tropical rainforest in Borneo Island. The particle mass concentrations were measured using a Tapered Element Oscillating Microbalance (TEOM). Measurements of aerosol particle optical properties, i.e., the particle light absorption and scattering coefficients, were conducted using a Multi-Angle Absorption Photometer (MAAP) and nephelometer, respectively. The single scattering albedo (SSA) and scattering Angstrom exponent (SAE) were calculated from the aerosol scattering and absorption coefficients. The results showed that the daily average of PM10 mass concentrations was 12.3 μgm−3, while the particle light absorption coefficients at wavelength 637 nm and scattering coefficients at wavelength 525 nm were reported as 2.7 Mm−1 and 21.7 Mm−1, respectively. The daily average SSA and SAE recorded were 0.89 and 1.44, respectively. The SSA showed no seasonal variations while higher SAE was observed during the dry season due to the influence of biomass burning originating from the southern region of Borneo. The wavelet analysis showed strong intra-seasonal cycles (12–20 and 32–64 days) which suggest the influence of Quasi-BiWeekly (QBW) oscillation and Madden-Julian Oscillation (MJO) on the aerosol variability over the tropics. The analysis also showed seasonal and annual variability bands, generally associated with the dry and wet seasons over the region.

Brown carbon from biomass burning imposes strong circum-Arctic warming

Brown carbon from biomass burning imposes strong circum-Arctic warming