Decrease In Light Absorption Research Articles

Two different approaches for source apportionment of ambient black carbon in highly polluted environments

The aethalometer model (AM) is widely used for source apportionment (SA) of black carbon (BC) in regions with mixed BC sources despite being initially developed for a relatively simplistic and low-pollution environments. The present study interrogates the applicability of AM in highly polluted metropolitan environments by comparing its results with the more nuanced Positive Matrix Factorization (PMF) model. The measurements were conducted in Delhi during the winter and summer season. PMF apportions the BC into diverse sources by taking help from complementary trace elemental measurements, thereby acknowledging the complex pollution landscape of the Delhi region. The AM estimates BCbb (BC from biomass burning) and BCff (BC from fossil fuel combustion) contributions as 48.3% and 51.7% during the winter and 16.6% and 83.4% during the summer, respectively.In contrast, the PMF model-derived biomass burning factor is the dominant source of BC during both winter and summer seasons, contributing 53.9% and 44% of the total BC, respectively. The decrease in light absorption at UV wavelengths of biomass-burning aerosols owing to escalated ambient aging is posited to be the reason for BCbb underprediction by the AM model during summers. Furthermore, while the AM model identifies fossil fuel combustion as the only other BC source apart from biomass burning, the PMF model apportions BC to five additional sources during winter, including vehicle emissions (22.9%), Pb-rich factor (10%), power plant (5.7%), waste incineration (4%) and industrial emission (3.6%). The contribution of these BC sources during summer is vehicular emission (16.5%), power plant (14.5%), waste incineration (11.5%), Pb-rich factor (9.5%), and industrial emission (4%). Additionally, the spectral variation of the light absorption properties of black carbon (bBCabs) and brown carbon (bBrCabs), delta-C effect, and sensitivity of the AM are reported for the study period. The present study cautions that BC source apportionment can be complex in highly polluted metropolitan environments, and complementary tracer measurements are recommended for reliable results.

8226 A Diagnostic Challenge: Factitious Hypobicarbonatemia in Severe Hypertriglyceridemia

Abstract Disclosure: U. Rafat: None. S. Azmat: None. M. Siddiqui: None. R. Alshantti: None. D. Kircheva: None. V. Trendafilova: None. Background: Serum CO2 levels measured by a chemistry analyzer usually correlate with calculated bicarbonate levels on an ABG. There are some instances however, when this is not the case. Severe hypertriglyceridemia can cause serum bicarbonate levels to appear falsely low on metabolic panel. Clinical Case: A 48-year-old man was referred to Endocrinology Clinic for evaluation of hypogonadism and severe hypertriglyceridemia. Routine labs revealed a plasma CO2 of 11 mmol/L (20-31). Na was 133 mmol/L (136-145), K was 4.4 mmol/L (3.5-4.7), Chloride was 101 mmol/L (98-109) and anion gap was 25 (8-20) measured using a Siemens Vista enzymatic chemistry analyzer. His triglycerides were > 1100 mg/dL (0-150), above upper detection limits of the analyzer. The patient reported fatigue and mild abdominal pain. He was admitted to the hospital for further evaluation. His lipase was 41 U/L (12-73), lactic acid 1.2 mmol/L (0.50-2.20). ABG showed pH of 7.41, HCO3 of 26.6 mmol/L (22-29), and anion gap of 7 (10-20). The patient was well-appearing with normal vital signs and normal physical exam. He was made NPO and started on pravastatin, fenofibrate and fish oil. Once his triglycerides were < 1000 mg/dL, he was started on a very low-fat, low-carbohydrate diet. The CO2 level on BMP normalized on day 3 of hospitalization, when triglycerides measured 1010 mg/dL. No other treatment was given for the low CO2 levels. It does not appear that other lab indices were significantly affected by the hypertriglyceridemia. Review of Literature: A BMP measures serum total carbon dioxide using a chemistry analyzer using either an enzymatic/spectro-photometric method, or an electrode-based method; an ABG sample calculates plasma bicarbonate with the Henderson-Hasselbach equation, using the pH and partial pressure of pCO2 in the sample. Enzymatic analyzers measure CO2 using spectrophotometry and decrease in light absorbance is proportional to the sample’s CO2 levels. It is postulated that severely high triglycerides can interfere with this reaction and cause spuriously low CO2 levels, a phenomenon called pseudohypobicarbonatemia. One proposed mechanism for interference with the enzymatic assay method is turbidity causing a falsely low measured CO2 level. Verghese et al found that the severity of the CO2 measurement error positively correlates with the severity of triglyceride elevation. Conclusion: Awareness of the phenomenon of hypertriglyceridemia-induced pseudohypobicarbonatemia can prevent misdiagnosis or delays in diagnosis, as well as unwarranted testing and treatment. Presentation: 6/3/2024

Assessing and predicting the influence of chromophoric dissolved organic matter on light absorption by phytoplankton in boreal lakes

AbstractMany boreal lakes are colored brown due to strong light absorption by chromophoric dissolved organic matter (CDOM), which reduces light penetration into the water column. However, the influence of CDOM on the fraction of photosynthetically utilizable radiation (PUR) absorbed by phytoplankton from the photosynthetically active radiation (PAR) entering the lake (i.e., PUR/PAR) remains largely unknown. Here, we (1) quantified PUR/PAR values and examined the major water quality parameters determining PUR/PAR from 128 sampled boreal lakes, (2) predicted PUR/PAR values for 2250 reference boreal lakes, and (3) estimated the response of PUR/PAR to typical browning trends reported in earlier studies. The PUR/PAR values ranged from 0.4% to 17% in the sampled lakes, and a logarithmic model including CDOM and chlorophyll a (Chl a) concentration was the most parsimonious for predicting PUR/PAR values. Applying the model to the reference lakes, PUR/PAR values ranged from 0.5% to 20% (median 3%). In the model, an increase in CDOM content decreases the PUR/PAR value, but a concurrent increase in Chl a concentration with the CDOM partly compensates the negative effect of CDOM on the PUR/PAR values. Assuming that browning increases both CDOM and Chl a contents, as found for our reference lakes, our model suggests that the decrease in light absorption by phytoplankton in response to a typical degree of browning is only moderate. The moderate response of the PUR/PAR to browning may be explained by photoacclimation of phytoplankton to lowered light availability, and/or an increased loading of nutrients to lakes both leading to higher Chl a concentration.

Time‐Resolved Measurements of PM2.5 Chemical Composition and Brown Carbon Absorption in Nanjing, East China: Diurnal Variations and Organic Tracer‐Based PMF Analysis

AbstractTo understand diurnal variations in PM2.5 composition and aerosol extract absorption, PM2.5 samples were collected at intervals of 2 hr from 8:00 to 20:00 and 6 hr from 20:00 to 8:00 (the next day) in northern Nanjing, China, during the winter and summer of 2019–2020 and analyzed for bulk components, organic tracers, and light absorption of water and methanol extracts—a proxy measure of brown carbon (BrC). Diurnal patterns of measured species reflected the influences of primary emissions and atmospheric processes. Light absorption coefficients of water (Abs365,w) and methanol extracts (Abs365,m) at 365 nm shared a similar diurnal profile peaking at 18:00–20:00, generally following changes in biomass burning tracers. However, Abs365,w, Abs365,m, and their normalizations to organic aerosols increased at 14:00–16:00, earlier than that of levoglucosan in the late afternoon, which was attributed to secondarily formed BrC. The methanol extracts showed a less drastic decrease in light absorption at night than the water extracts and elevated absorption efficiency during 2:00–8:00. This is due to the fact that the water‐insoluble OC has a longer lifetime and stronger light absorption than the water‐soluble OC. According to the source apportionment results solved by positive matrix factorization (PMF), biomass burning and secondary formation were the major BrC sources in northern Nanjing, with an average total relative contribution of about 90%. Compared to previous studies, diurnal source cycles were added to the PMF simulations in this work by using time‐resolved speciation data, which avoided misclassification of BrC sources.

Crystalline Phase Segregation of Quantum-Dots-Passivated CH3NH3PbI3 Film via Argon Plasma Treatment

In this study, a composite perovskite film composed of lead cesium triiodide (CsPbI3) quantum dots (QDs) and methylammonium lead iodide (CH3NH3PbI3; MAPbI3) was proposed. The CsPbI3 QDs prepared by hot-injecting were used as an anti-solvent in precursors to passivate the surface of this composite perovskite film. The further argon (Ar) plasma treatment improves the surface of the film. The effects of the powers from 100 to 200 W on the composite perovskite film structure, chemical element composition, and optical properties were studied. The experimental results demonstrate that the CsPbI3 QDs passivation boosts the ultraviolet light absorption (350–450 nm) and inhibits the formation of the PbI2 phase. Furthermore, Ar plasma treatment effectively improved CsPbI3 QDs passivation on MAPbI3 film. The powers lower than 140 W cause C=O bonds to dissolve and coordination bonds to form between OA carboxyl moieties and undercoordinated Pb2+ ions. At 160 and 140 W, the obvious crystal phase segregation and a decrease in light absorption are observed, respectively. Meanwhile, the strong bombardment of Ar ions at higher than 160 W causes the severe degradation of MAPbI3 film.

Effect of photooxidation on size distribution, light absorption, and molecular compositions of smoke particles from rice straw combustion

Organic aerosol (OA) emitted from biomass burning (BB) impacts air quality and global radiation balance. However, the comprehensive characterization of OA remains poorly understood because of the complex evolutionary behavior of OA in atmospheric processes. In this work, smoke particles were generated from rice straw combustion. The effect of OH radicals photooxidation on size distribution, light absorption, and molecular compositions of smoke particles was systematically investigated. The results showed that the median diameters of smoke particles increased by a factor of approximately 1.2 after photooxidation. In the particle compositions, although both non-polar fractions (n-hexane-soluble organic carbon, HSOC) and polar fractions (water-soluble organic carbon, WSOC) underwent photobleaching after aging, the photobleaching properties of HSOC (1.87–2.19) was always higher than that of WSOC (1.52–1.33). Besides, the light-absorbing properties of HSOC were higher than that of WSOC, showing a factor of approximately 1.75 times for mass absorption efficiency at 365 nm (MAE365). Consequently, the simple forcing efficiency (SFE) caused by absorption showed that HSOC has higher radiation effects than WSOC. After photooxidation, the concentration of 16 PAHs in HSOC fractions significantly decreased by 15.3%–72.5%. In WSOC fractions, the content of CHO, CHONS, and CHOS compounds decreased slightly, while the content of CHON compounds increased. Meantime, the variations in molecular properties supported the decrease in light absorption of WSOC fractions. These results reveal the aging behavior of smoke particles, then stress the importance of non-polar organic fractions in particles, providing new insights into understanding the atmospheric pollution caused by BB smoke particles.

Absorption Analysis of Photosystem I in Different Plants for Biohybrid Solar Cell Applications

Biohybrid solar cells, which are inspired by photosynthesis process in plants, are new low‐cost and environmentally friendly solar cells. In this kind of solar cells, photosystem I (PSI), which is the main part of photosynthesis process, is used as light absorber layer. Herein, PSI is extracted from some easily accessible plants, including spinach, Tung‐Oh, chye sim, local endive, beet greens, leek, Swiss chard, and romaine lettuce, and their light absorbance properties are studied. It is shown that the optical bandgap of PSI extracted from all of these plants is about 1.8 eV which indicates the potential of these plants for use in biohybrid solar cells. It is shown that, due to the higher light absorbance, spinach is the best plant for this kind of solar cells. Also, the effect of temperature on light absorbance of PSI extracted from spinach is investigated and shows that the light absorbance of PSI considerably decreases at high‐temperature values. Furthermore, alkaline and acidic environments on PSI light absorbance are studied and shows that the alkaline pH stress has no destructive effect on light absorbance, while the acidic pH stress causes a considerable decrease in light absorbance which is important in biohybrid solar cell fabrication.

Fe-MOF by ligand selective pyrolysis for Fenton-like process and photocatalysis: Accelerating effect of oxygen vacancy

BackgroundThe combination of Fenton catalyst and photocatalyst will lead to the decrease in light absorption on the photocatalyst, and it is difficult for Fe3+ to be converted into Fe2+on the Fenton catalyst, resulting in poor Fenton-like process and photocatalysis effect. Preparing catalysts containing oxygen vacancies (OVs) can simultaneously increase the light absorption and the cycle of Fe(Ⅲ) to Fe(Ⅱ) to improve the catalytic efficiency of Fenton-like process and photocatalysis. MethodsA mesoporous H-MIL53 with OV was constructed by ligand selective pyrolysis. The formation mechanism of H-MIL-53 vacancy was analyzed by XPS, EPR, FTIR and TG. Significant findingsXPS, EPR, FTIR and TG showed that calcination caused the fracture of Fe-O bond resulted in OV and coordinative unsaturated Fe site. H-MIL-53 showed higher degradation efficiency of tetracycline hydrochloride (93%) and high recycling performance. The electron-rich OV could activate the dissolved oxygen to produce •O2− through phot-introduced electrons, while the electron-poor iron site can activate H2O2 to produce •OH. These results provide a new direction for the construction of metal-organic framework (MOF) containing OV for application in Fenton-like process and photocatalysis.

Fe/SiO2 Composite Coated Optical Fiber for Corrosion Monitoring

It is important to monitor and locate internal corrosion over the long-distance natural gas pipelines in real time before catastrophic failures to ensure safe, secure, and reliable transportation of natural gas and reduce the environmental impact from methane emission. Optical fiber based sensors provide many advantageous features, especially the distributed sensing over a long distance and the inertness in the presence of flammable gas, among others. To take advantage of these features, corrosion proxy sensing materials are a key enabling component for an optical fiber corrosion sensor. We have previously demonstrated a distributed optical fiber corrosion sensor, and reported early results on Fe/SiO2 composite coating. To further improve the sensing performance, detailed studies were performed to investigate the Fe/SiO2 composite coating. The Fe/SiO2 composite layers are coated onto the optical fiber using sol-gel and electroless plating methods, respectively, with controlled morphologies. The coating is characterized with SEM and XPS. Tested in corrosive solutions at room temperature, optical responses are measured for corrosion monitoring. The light transmission increases as Fe dissolves away due to the decrease in light absorption of the metallic layer. Different morphologies are compared to optimize sensing performance of the Fe/SiO2 composite coated optical fiber corrosion sensor.

Formation and evolution of brown carbon during aqueous-phase nitrate-mediated photooxidation of guaiacol and 5-nitroguaiacol

Light absorbing organic aerosols, which are commonly referred to as brown carbon (BrC), have important climate impacts. Phenolic compounds are a class of aromatic compounds that are known BrC precursors. Inorganic nitrate is a ubiquitous component of atmospheric aerosols, clouds, and fog. The photolysis of inorganic nitrate in atmospheric aqueous phases generates a variety of reactive oxygen species and reactive nitrogen species that can facilitate the photooxidation of organic compounds to form BrC. In this study, we investigated the formation and evolution of BrC from the aqueous-phase photooxidation of guaiacol and 5-nitroguaiacol initiated by inorganic nitrate photolysis. Guaiacol and 5-nitroguaiacol are two water-soluble phenolic compounds that are commonly found in fossil fuel and biomass burning emissions. Upon illumination in the presence of sodium nitrate, guaiacol and 5-nitroguaiacol reacted rapidly to form BrC. The reaction rates and quantities of BrC formed depended on the initial sodium nitrate concentration. The reaction rates of guaiacol were substantially faster than those of 5-nitroguaiacol. The electron-withdrawing nitro functional group on 5-nitroguaiacol's aromatic ring likely had a deactivating effect on the ring's reactivity, which contributed to 5-nitroguaiacol's lower reactivity compared to guaiacol. The major products produced during the initial stages of photooxidation were formed by the addition of nitro and/or nitroso groups to guaiacol and 5-nitroguaiacol. These products likely strongly absorbed near-UV and/or visible light, which led to an observed increase in light absorption (i.e., photo-enhancement) in the near-UV and visible range. Greater photo-enhancement was observed during the nitrate-mediated photooxidation of guaiacol. This indicated that the presence of nitro functional group(s) on the aromatic ring of phenolic compounds will impact the extent of photo-enhancement during BrC formation. Further photooxidation caused the initial products to fragment into smaller molecules that do not absorb near-UV and visible light. This resulted in an observed decrease in light absorption (i.e., photo-bleaching). These results highlight how aqueous-phase inorganic nitrate photolysis can drive the formation of BrC by facilitating the photooxidation of organic compounds.

Effect of ozone aging on light absorption and fluorescence of brown carbon in soot particles: The important role of polycyclic aromatic hydrocarbons

The evolution of brown carbon (BrC) during atmospheric aging, including the changes in optical properties and chemical compositions, is still unclear. Light absorption and fluorescence of BrC fraction extracted from fresh and ozonized propane soot particles by methanol were systematically measured, which showed that (1) the mass absorption efficiencies (MAE) sharply decreased by ozone (O3) aging (e.g., 1.2 ± 0.3–0.8 ± 0.1 m2 g−1 for MAE365), but changed slowly with increased O3 concentration (e.g., from 0.7 ± 0.2–0.8 ± 0.1 m2 g−1 for MAE365); (2) the fluorescence emission peaks were blue shifted, implying a loss of conjugated structures; (3) excitation–emission matrix analysis suggested that humic-like substances, charge transfer complexes, and polycyclic aromatic hydrocarbon (PAH)-like substances were the main chromophores. The PAH loss, accompanied by the decline of surface C˭C content, contributed more to the change of optical properties than the oxygenated PAH formation, thereby leading to the decrease in light absorption and fluorescence with O3 aging. This research reveals the importance of identifying the components responsible for optical properties in investigating the evolution of BrC during atmospheric aging, and is benefit for improving the evaluation of BrC’s radiative forcing.

In vitro evaluation of physical and chemical parameters involved in aPDT of Aggregatibacter actinomycetemcomitans.

Periodontitis is an infectious disease characterized by the destruction of supporting tissues. Antimicrobial photodynamic therapy (aPDT) has been proposed as an improved method for eliminating microorganisms. Its efficiency depends on the correct use of physical and chemical parameters. Thus, these parameters and their relations were evaluated in this study with the purpose of establishing lethal conditions for combating bacterial agents. Diode lasers and light-emitting diodes (LEDs) were characterized to evaluate the absorption profile and resonance of methylene blue (MB) and toluidine blue O (TBO). The relations between light energy density and photosensitizer absorption were determined. Two methodologies were used to evaluate the effects of aPDT against Aggregatibacter actinomycetemcomitans. LED light exhibited a broad emission spectrum with a peak light wavelength of 637 nm and 99% purity. The resonance intensity of MB was higher with diode laser irradiation, and TBO showed higher resonance intensity with LED irradiation. There was no difference in the absorption profile of photosensitizers using diode lasers or LEDs, and variations in power density did not result in an increasing or decrease in light absorption. A. actinomycetemcomitans was susceptible to photodynamic processes. Emission spectra and peak light wavelengths of light sources combined with the absorption profiles of photosensitizers were the main parameters involved in determining the efficiency of photodynamic effects. Power density did not alter the light absorption of photosensitizers. The association between adequate irradiation characteristics and photosensitizer absorption results in complete inactivation of A. actinomycetemcomitans. In addition, the bactericidal effect was not altered by an increase in energy densities.

Effect of source variation on the size and mixing state of black carbon aerosol in urban Beijing from 2013 to 2019: Implication on light absorption.

Black carbon (BC) is the most important aerosol light-absorbing component, and its effect on radiation forcing is determined by its microphysical properties. In this study, two microphysical parameters of refractory BC (rBC), namely, size distribution and mixing state, in urban Beijing from 2013 to 2019 were investigated to understand the effects of source changes over the past years. The mass equivalent diameter of rBC (Dc) exhibited bimodal lognormal distributions in all seasons, with the major modes accounting for most (>85%) of the rBC masses. The mass median diameter (MMD) was obviously larger in winter (209nm) than in summer (167nm) likely due to the contribution of more rBC with larger Dc from solid fuel combustion and enhanced coagulation of rBC in polluted winter. More rBC particles were thickly coated in winter, with the number fraction of thickly coated rBC (fcoatBC) ranging within 29%-48% compared with that of 12%-14% in summer. However, no evidential increase in BC light-absorption capability was observed in winter. This finding was likely related to the lower absorption efficiency of larger rBC in winter, which partly offset the coating-induced light enhancement. Two stage of decreases in MMD and fcoatBC were observed, accompanied with a persistent decrease in rBC loading, thereby reflecting the discrepant effects of source control measures on rBC loading and physical properties. The control measures in the earlier stage before 2016 was more efficient to reduce the rBC loading but slightly influenced the microphysical properties of rBC. As of 2016, the reduction in rBC concentration slowed down because of its low atmospheric loading. However, rBC showed a more obvious decrease in its core size and became less coated. The decrease in fcoatBC may have weakened the BC absorption and accelerated the decrease in light absorption resulting from the reduction in rBC loading.

Light-controllable Fano resonance in azo-dye-doped all-dielectric multilayer structure

Active modulation of Fano resonance by light is demonstrated for an all-dielectric multilayer system containing an azo-dye-doped layer. The sample studied consists of a polystyrene layer doped with disperse red 1 (azo dye) molecules, a polyvinyl alcohol layer, and a pure polystyrene layer. In a Kretschmann attenuated-total-reflection configuration, angle-scan reflection spectra of the sample were measured with blue probe light under blue light pumping. The Fano line shape was found to change systematically depending on the intensity of the pump light. Analyses based on electromagnetic calculations of the spectra and field distributions in the layers indicate that the Fano resonance observed is generated by coupling between a broad half-leaky guided mode supported by the azo-dye-doped layer and a sharp planar waveguide mode supported by the pure polystyrene layer. The systematic changes in the Fano line shape under pump light irradiation can be well understood by a systematic decrease in light absorption in the azo-dye-doped polystyrene layer; the decrease in light absorption is due to a decrease in the extinction coefficient of the layer arising from the photoisomerization of azo dye molecules.

Optical Fiber-Based Corrosion Sensor with Fe/SiO2 Coating

Nondestructive online corrosion sensors serve as a powerful tool for structural health monitoring in oil and natural gas industry, energy infrastructure, buildings, and geotechnical structures to improve security, reliability, and sustainability. The ability to monitor corrosion online before the structural integrity is compromised can have a significant impact on preventing catastrophic events resulting from corrosion. Based on a concept of using corrosion proxy materials to probe corrosivity, we have demonstrated a distributed corrosion sensor using the Fe thin film coated optical fiber in previous studies. To improve the sensing capability, a Fe/SiO2 composite coating is integrated onto the optical fiber in the present work. The Fe/SiO2 layer is coated onto the optical fiber using sol-gel and electroless plating methods, and then the coating is characterized with SEM and XPS. The Fe/SiO2 coated optical fiber is tested in corrosive solutions at room temperature to measure the optical response as an indicator for corrosion. The light transmission increases as Fe dissolves away due to the decrease in light absorption. The Fe/SiO2 composite coating and the optical fiber configuration are optimized to improve the sensor quality.

Effect of concentration and temperature on the formation of wheat hydrogel and xerogel pattern

The colloidal nature of wheat flour could be utilized in engineering the physical structure of food systems. Gelatinization behavior of starch in wheat flour was studied to develop a wheat hydrogel and the impact of hydrogel characteristics in drying was observed in xerogel surface structure. Effect of variation in wheat flour concentration was analyzed by least gelation concentration and pasting parameters. It showed 10% (w/v) of gelatinized wheat flour suspension can be able to form a three-dimensional polymer network during retrogradation. Influence of hydrogel formation temperature was studied by solubility, swelling power, transmittance, contact angle and surface tension at different temperatures. Increase in solubility and swelling power indicates, leaching of more starch components and binding of more water molecules. The decrease in light absorbance indicates loss of crystallinity and birefringence due to disruption of granular structure. Contact angle and surface tension showed its impact on the increase in spreading coefficient at higher temperatures. Different concentration (5–15% (w/v)) of wheat flour suspension were subjected to heat from 30 to 100 °C; at each 5% (w/v) rise in concentration and 10 °C rise in temperature, a xerogel was developed and observed. It was found that 10% (w/v) of wheat flour suspension gelatinized at 90 °C showed better integrity and surface structure without cracks and deformations. The developed xerogel could serve as a snack food and also a carrier material for bioactive components in functional foods and nutraceuticals.

INVESTIGATION OF INTERACTION OF BROMPHENOL SYNTHES WITH CATIONIC POLYACRYLAMIDES AND APPLICATION OF IT IN THE ANALYSIS

The aim of this work was to study the interaction of bromophenol blue with cationic polyacrylamides and the development on this basis of a simple, rapid and highly sensitive technique for determining the content of copolymers of acrylamide and the chloromethylated polymer in waters containing moderate amounts of strong electrolytes. The changes in the spectra are similar to those observed for the same dyes in the presence of cationic surfactant micelles. It is shown that two types of effects appear in the presence of polymers: the shift of the acid-base equilibrium caused by the formation of the ionic associate polymer-dye and the aggregation of the dye. Optimal conditions for the formation of the ion associate are established. The presence of salts in concentrations above the critical leads to a decrease in light absorption, the appearance of a negative systematic error. The application of the photometric titration method makes it possible to compensate to a certain extent the interfering effect of inorganic ions. In the presence of inorganic salts, the shape of the photometric titration curve near the end point of the titration is washed out, but its position remains practically unchanged, which makes it possible to determine the polymer flocculant in the presence of not very large concentrations of inorganic salts. Spectrophotometric methods for determining the content of CPAA FO in production solutions or natural waters with a low level of mineralization by methods of a calibration curve and photometric titration have been developed. Method of a calibration curve allow allows to determine polymer in the range of concentrations 0,12 –1,8 μg/L. The limit of determination of CPAA FO is 0.088 μg/L. The methods are tested on artificial mixtures and artesian water.

The Effect of Curcumin on Growth and Adherence of Major Microorganisms Causing Tooth Decay

Background and objective: Streptococcus mutans and Lactobacillus acidophilus are bacteria producing tooth decay which by adhering to tooth surfaces contribute to its pathogenesis. By increasing bacterial resistance to antibiotics, along with other high-cost of treatment, the use of natural antibacterial agents is essential. In this regard, the role of curcumin on the adhesion process of cariogenic pathogens has been studied.& para;& para;Materials and Methods: The bacterial strains of Streptococcus mutans (PTCC1683) and Lactobacillus acidophilus (PTCC1643) were obtained from the Iranian Research Organization for Science and Technology). The early growth of the bacteria was carried out in BHI medium, and then the concentration of microorganisms reached the half-MacFar-land standard, and using different concentrations of curcumin (1, 2, 4, 8, 16, 31, 25, 52, 62, 125, 250, 500 mu g/mI) obtained by serial dilution method the substances were mixed. BHI medium without bacteria was considered as negative control. Then samples were incubated for 24 hours at 37 degrees C in anaerobic conditions for determining the minimum inhibitory concentration. Inhibitory concentrations determined in the previous step were used to determine adhesion using the amount of light absorbance determination method.& para;& para;Results: The minimum inhibitory concentration of growth was determined in both bacterial strains of 250 mu g/ml. The results showed a decrease in light absorption with increasing curcumin concentration (P<0.001), which indicates a high correlation (correlation coefficient of -0.93) of curcumin concentrations with reverse adhesion.& para;& para;Conclusion: Adhesion is the most important factor in tooth decay and its reduction is an effective solution in preventing the disease. Considering the inhibitory role of curcumin on growth and binding of bacterial strains, this curcuminoid agent is considered as a potent anti-decay agent.

Neosartorya glabra polygalacturonase produced from fruit peels as inducers has the potential for application in passion fruit and apple juices

Summary Polygalacturonases are enzymes with the biotechnological potential for use in fruit juice clarification and for the enhancement of filtration efficiency. The aim of this work was to assess the production of polygalacturonase by the fungus Neosartorya glabra by means of solid-state and submerged fermentation using fruit peel residues as the carbon source, and also apply the enzyme in the clarification and decrease in viscosity of passion fruit and apple juices. The highest polygalacturonase (4.52 U/g/h) production was obtained by means of submerged fermentation in Vogel´s medium (1964) containing orange peel – Bahia variety (Citrus sinensis), at a concentration of 1.5% (w/v, dried mass) at 30-35°C for 72 h. The polygalacturonase of the crude extract presented optimal activity at 60°C and pH 5.5. The enzyme retained around 90% of the initial activity after 180 minutes at 40°C, and 50% of the initial activity after 150 minutes at 50°C. The enzyme was shown to be stable at acid pH values (3.0-6.5) after 120 minutes at 25oC. All these favourable enzymatic properties make the polygalacturonase attractive for potential uses in the industry of pectin-rich fruit juices, since the application of the crude extract to passion fruit (Passiflora edulis) juice caused an 80% reduction in viscosity and 75% decrease in light absorbance. In the processing of apple pulp juice (Malus domestica), there was a 50% reduction in viscosity and 78% decrease in light absorbance.

Photo-induced orientation behaviors of azobenzene liquid crystal copolymers for photonic crystals

Light response inside is improved by decrease of light absorption near surface based on LC cooperative orientation.