UV Absorption Measurements Research Articles

Routine online assessment of dialysis dose: Ionic dialysance or UV‐absorbance monitoring?

For three-weekly hemodialysis, a single-pool Kt/V target of at least 1.4 together with a minimal dialysis dose Kt at 45 L for men and 40 L for women per each session is currently recommended. Fully automatic online calculation of Kt and Kt/V from conductivity or UV-absorbance measurements in the dialysate is standardly implemented on some hemodialysis monitors and makes it possible to estimate the dialysis dose without the need for blood or dialysate samples. Monitoring the UV-absorbance of the spent dialysate is the most direct method for estimating Kt/V as it does not require an estimate of V. Calculation of ionic dialysance from conductivity measurements is the most direct method for estimating Kt and BSA-scaled dialysis dose. Both ionic dialysance monitoring and UV-absorbance monitoring may help detect a change in urea clearance occurring during the session, but this change must be interpreted differently depending on the monitoring being considered. An abrupt decrease in urea clearance results in a decrease in ionic dialysance but, paradoxically, a sudden increase in estimated urea clearance provided by dialysate UV-absorbance monitoring. Healthcare teams who monitor both ionic dialysance and UV-absorbance in their hemodialysis units must be clearly informed of this difficulty.

Biodegradation and metabolic pathway of anthraquinone dyes by Trametes hirsuta D7 immobilized in light expanded clay aggregate and cytotoxicity assessment

Biodegradation and metabolic pathways of three anthraquinone dyes, Reactive Blue 4 (RB4), Remazol Brilliant Blue − R (RBBR), and Acid Blue 129 (AB129) by Trametes hirsuta D7 fungus immobilized in light expanded clay aggregate (LECA) were investigated. Morphological characteristics observed with scanning electron microscope (SEM) showed successful immobilization of the fungus in LECA. Based on UV absorbance measurement, immobilized T. hirsuta D7 effectively degraded 90%, 95%, and 96% of RB4, RBBR and AB129, respectively. Metabolites were identified with high-resolution mass spectrometry (HRMS) and degradation pathway of the dyes by T. hirsuta D7 was proposed. Toxicity assay on human dermal fibroblast (HDF) showed that anthraquinone dyes exhibits significant toxicity of 35%, 40%, and 34% reduction of cell viability by RB4, RBBR, and AB129, respectively. Fungal treatment resulted in an abatement of the toxicity and cell viability was increased up to 94%. The data clearly showed the effectiveness of immobilized T. hirsuta D7 in LECA on detoxification of anthraquinone dyes. This study provides potential and fundamental understanding of wastewater treatment using the newly isolated fungus T. hirsuta D7.

Photography-based photometry: High throughput UV photometric analysis without scientific equipment based on contact printing photography and common imaging devices

This work introduces photography-based photometry, as complementary to digital image colorimetry, by demonstrating that historical photography can be repurposed to enable UV photometric analysis, using inexpensive and ubiquitous materials. Analysis is performed by illuminating the samples with UV radiation and then capturing the transmitted irradiation on the surface of a photographic paper through photochemical reduction of its photosensitive coating. A visible image is then formed on the paper surface and is recorded as a digital photograph. The color intensity of the image is directly proportional to the concentration of the analytes in the sample and is quantified in the RGB color system. By selecting the appropriate light source and photosensitive paper, sensitivity to light can be selected to approximate the absorbance spectra of the target analyte thus accomplishing good selectivity and high sensitivity. On the basis of this principle, a variety of assays were used to demonstrate that photography-based photometry, can be used to perform accurate UV absorbance measurements over a wide spectral range, in a high throughput format (i.e. microtiter plates) and at low cost as compared to expensive microplate spectrophotometers. Depending on the photosensitivity of the photographic paper, linear ranges and detection limits that are similar or lower up to an order of magnitude to those obtained with standard spectrophotometry were achieved. Importantly, a single device configuration can be used for all assays, irrespectively of the maximum absorbance wavelength, which significantly simplifies its operation thus holding great promise for routine applications in resource-limited settings even by non-experts.

Removal of pharmaceuticals from nitrified urine by adsorption on granular activated carbon

Nitrification and distillation of urine allow for the recovery of all nutrients in a highly concentrated fertilizer solution. However, pharmaceuticals excreted with urine are only partially removed during these two process steps. For a sustainable and safe application, more extensive removal of pharmaceuticals is necessary. To enhance the pharmaceutical removal, which is already occurring during urine storage, nitrification and distillation, an adsorption column with granular activated carbon (GAC) can be included in the treatment train. We executed a pilot-scale study to investigate the adsorption of eleven indicator pharmaceuticals on GAC. During 74 days, we treated roughly 1000 L of pre-filtered and nitrified urine spiked with pharmaceuticals in two flow-through GAC columns filled with different grain sizes. We compared the performance of these columns by calculating the number of treated bed volumes until breakthrough and carbon usage rates. The eleven spiked pharmaceuticals were candesartan, carbamazepine, clarithromycin, diclofenac, emtricitabine, hydrochlorothiazide, irbesartan, metoprolol, N4-acetylsulfamethoxazole, sulfamethoxazole and trimethoprim. At the shortest empty bed contact time (EBCT) of 25 min, immediate breakthrough was observed in both columns shortly after the start of the experiments. Strong competition by natural organic material (NOM) could have caused the low pharmaceutical removal at the EBCT of 25 min. At EBCTs of 70, 92 and 115 min, more than 660 bed volumes could be treated until breakthrough in the column with fine GAC. The earliest breakthrough was observed for candesartan and clarithromycin. On coarse GAC, only half the number of bed volumes could be treated until breakthrough compared to fine GAC. The probable reason for the later breakthrough with fine GAC is the smaller intraparticle diffusive path length. DOC and UV absorbance measurements at 265 nm indicated that both parameters can be used as indicators for the breakthrough of pharmaceuticals. In contrast to pharmaceuticals and DOC, the nutrient compounds ammonium, nitrate, phosphate, potassium and sulfate were not removed significantly. A comparison with literature values suggests that the amount of GAC needed to remove pharmaceuticals from human excreta could be reduced by nearly two orders of magnitude, if urine were treated on site instead of being discharged and treated in a centralized wastewater treatment plant.

Viral hepatitis in the Peruvian Amazon: Ethnomedical context and phytomedical resource

Ethnopharmacological relevanceAn extensive ethnopharmacological survey was carried out in the Peruvian Amazonian district of Loreto with informants of various cultural origins from the surroundings of Iquitos (capital city of Loreto) and from 15 isolated riverine Quechua communities of the Pastaza River.A close attention was paid to the medical context and plant therapy, leading to the selection of 35 plant species (45 extracts). The extracts were tested for antiviral activity against HCV with counting of Huh-7 cellular death in case of toxicity, and cytotoxicity was evaluated in HepG2 cells.Aim of the study: The aim of the study was to inventory the plants used against hepatitis in Loreto, then to evaluate their antiviral activity and to suggest a way to improve local therapeutic strategy against viral hepatitis, which is a fatal disease that is still increasing in this area. Materials and methodsAn ethnographic survey was carried out using “participant-observation” methodology and focusing on plant therapy against hepatitis including associated remedies. 45 parts of plant were extracted with methanol and tested in vitro for anti-HCV activity in 96-well plate, using HCV cell culture system with immunofluorescent detection assisted by automated confocal microscopy. Toxicity of plant extracts was also evaluated in microplates on hepatic cells by immunofluorescent detection, for the Huh-7 nuclei viability, and by UV-absorbance measurement of MTT formazan for cytotoxicity in HepG2 cells. ResultsIn vitro assay revealed interesting activity of 18 extracts (50% infection inhibition at 25 μg/mL) with low cytotoxicity for 15 of them. Result analysis showed that at least 30% of HCV virus were inhibited at 25 μg/mL for 60% of the plant extracts. Moreover, the ethnomedical survey showed that remedies used with low and accurate dosing as targeted therapy against hepatitis are usually more active than species indicated with more flexible dosing to alleviate symptoms of hepatic diseases. ConclusionTogether with bibliographic data analysis, this study supported the traditional medicinal uses of many plants and contributed to a better understanding of the local medical system. It also permitted to refine the therapeutic plant indications regarding patients’ liver injuries and vulnerability.Only 2 of the 15 most active plant species have already been studied for antiviral activity against hepatitis suggesting new avenues to be followed for the 13 other species.

Experimental and theoretical investigations on optical properties of multiferroic PrCrO3 ortho-chromite compound

The PrCrO3 ceramic compound was prepared by the sol-gel route. The optical properties of this ceramic were characterized by UV–Vis absorption spectroscopy. By direct investigation of the UV absorption measurements and using the Tauc model, we have determined the direct optical band gap estimated between 3.26 and 3.20 eV. Furthermore, the Urbach energy, the optical extinction coefficient and the refractive index were calculated on the basis of absorbance measurements. The skin depth, the optical conductivity as well as the dispersion energy parameters as a function of the wavelength of the incident photon were determined and discussed. The emissions are attributed to the d-d transitions of Cr3+ ion in PrCrO3. A theoretical crystal-field analysis of the visible lines associated to the Cr3+(3d3) ion transition occupying an Oh site symmetry in PrCrO3 is realized which leads to a satisfactory correlation between experimental and calculated energy levels. The electronic structure was compared with the reported for Cr3+ ion in RECrO3 (RE = Er, Tm, Yb, Lu, Y) ceramics. The obtained results show that our compound may be proposed as a good candidate for opto-electronic devices.

Development of UV Spectrophotometric Procedures for Determination of Amlodipine and Celecoxib in Formulation: Use of Scaling Factor to Improve the Sensitivity

FDA has recently approved a new fixed-dose combination of amlodipine besylate (AMD) and celecoxib (COX) for the treatment of hypertension and osteoarthritis. No analytical method has been reported for analysis of these two analytes so far. Hence, to monitor the quality and quantity in the formulation of AMD and COX a simple, accurate, precise, economical, and eco-friendly spectroscopic analytical method has been established. The first method involves the determination of AMD and COX by the first derivative UV spectroscopic method with scaling factor 10. However, the second method was based on the direct measurement of UV absorbance of AMD at 364.3 nm and ratio first derivative UV spectroscopic method for COX. Both methods showed good linearity in the range of 5 to 40 μg/ml for COX, whereas AMD showed linearity in the range of 0.5 to 10 μg/ml in first derivative method with scaling factor 10 and 1 to 10 μg/ml in the second method with good correlation coefficient (R2 > 0.998). Both the methods were validated for LOD, LOQ, accuracy, precision, recovery studies, and stability as per the ICH guidelines, and the validated results were well within the acceptable range. Both the methods were successfully utilized for the determination of AMD and COX in the presence of each other in the formulation, and statistically compared between the proposed methods. Therefore, the proposed procedures can be utilized for regular quality control studies.

Small-scale approach for precrystallization screening in GPCR X-ray crystallography.

G protein-coupled receptors (GPCRs) are important pharmaceutical targets. Knowledge of their 3D structures is critical to understanding mechanisms of drug action. Low cellular expression, purification yield, and in vitro instability are substantial hurdles to the successful determination of GPCR structure. Intense effort is required to optimize a receptor's protein sequence and purification procedure, increasing the complexity of the precrystallization process. Here, we present a procedure for a small-scale precrystallization screen that involves detecting GPCR expression levels in Spodoptera frugiperda (Sf9) culture by flow cytometry and evaluating GPCR stability by size-exclusion chromatography and UV absorbance measurements. The example procedure uses the smallest volumes of Sf9 cell culture that will yield sufficient quantities of purified protein for intrinsic UV absorbance analysis and is amenable to medium throughput with the same constructs and conditions that would be scaled up for crystallization trials. The protocol takes 8 d to complete and requires expertise in cell culture, protein purification, and chromatography.

Inner filter effect, suspended solids and nitrite/nitrate interferences in fluorescence measurements of wastewater organic matter

In this study, it was assessed the effectiveness to correct for inner filter effect (IFE) the fluorescence spectra of several wastewaters (i.e., primary, secondary and tertiary wastewater effluents) and wastewater-impacted surface waters using a common method based on UV absorbance measurements. In samples of secondary/tertiary wastewater effluents and surface waters, IFE was severe at excitation wavelengths <240 nm, and it was low (4–11%) at excitation wavelengths >340 nm. On the contrary, IFE has always been significant in primary wastewater effluents. After IFE correction, linear relationship was observed between fluorescence and absorbance in dilution series across the full excitation-emission matrix (EEM), although some distortions were still present. Particularly, experimental data showed the presence of static/dynamic quenching of fluorescence due to nitrite/nitrate, which cannot be corrected by IFE correction methods. Indeed, after addition of different nitrate/nitrite concentrations in wastewater (3–40 mg/L as N), the estimated static/dynamic quenching error (QE) after IFE correction was often >20% for tyrosine and tryptophan-like fluorescence measured at excitation <240 nm. However, the QE was low (<5–10%) for fluorescence measured at excitation >240 nm. Overall, the QE increased with the increase of nitrite/nitrate concentration in wastewater. Total suspended solids (TSS) (i.e., particulate organic matter) in water produced intense fluorescence peaks in the tyrosine-like and tryptophan-like region of EEM, and TSS increased the absorbance values at all the excitation wavelengths of the UV–visible absorption spectra in unfiltered samples compared to 0.7 μm filtered samples. On the contrary, tertiary effluents employing full scale sand filtration (TSS < 2–4 mg/l) had similar UV absorbance and fluorescence spectra to 0.7 μm filtered samples. Finally, it was observed that uncorrected fluorescence intensities in the humic-like region of EEM were similar in both filtered and unfiltered samples, and it was independent of TSS concentration, dilution factor and water quality.

Absorbance and EEM fluorescence of wastewater: Effects of filters, storage conditions, and chlorination.

Aim of this study was to delineate sample handling procedures for accurate fluorescence and UV absorbance measurements of wastewater organic matter. Investigations were performed using different wastewater qualities, including primary, secondary and tertiary wastewater effluents, and a wastewater-impacted surface water. Filtration by 0.7 μm glass microfiber filter, 0.45 μm polyvinylidene fluoride (PVDF) membrane, 0.45 μm cellulose nitrate membrane, and 0.45 μm polyethersulfone (PES) syringe filter released manufacture impurities in water that affected fluorescence measurements. However, pre-washing of filter by Milli-Q water was able to eliminate these interferences. Different storage conditions were tested, including storage of filtered and unfiltered samples under different temperatures (25 °C, 4 °C,-20 °C). According to the obtained results, the best practice of wastewater samples preservation was sample filtration at 0.7/0.45 μm immediately after collection followed by storage at 4 °C. However, the time of storage that assured changes of these spectroscopic measurements that do not exceed the 10% of the original value was dependent on water quality and selected wavelengths (i.e., selected fluorescing organic matter component). As a general rule, it is advisable to perform fluorescence and UV absorbance measurements as soon as possible after collection avoiding storage times of filtered water longer than 2 days. Finally, addition of chlorine doses typical for wastewater disinfection mainly affected tryptophan-like components, where changes that exceed the 10% of the fluorescence intensity measured in the unchlorinated sample were observed even at very low doses (≥1 mg/L). On the contrary, tyrosine-like and humic-like components showed changes <10% at chlorine doses of 0.5-5 mg/L.

Chemical composition, antibacterial properties, and mechanism of Smilax china L. polyphenols.

This work aimed at investigating the chemical composition, antibacterial properties, and effect mechanism of Smilax china L. polyphenols (SCLP). SCLP was extracted and purified, and then, its eighteen polyphenolic compounds were identified by LC-MS/MS analysis. SCLP exhibited antibacterial activity against five bacteria (Salmonella typhimurium, Listeria monocytogenes, Staphylococcus aureus, Bacillus subtilis, and Escherichia coli) with minimum inhibitory concentration in a range of 195.31 to 781.25 μg/mL. Escherichia coli and Staphylococcus aureus showed a higher sensitivity to SCLP. Notably, when combined with antibiotics, the SCLP-thiamphenicol and SCLP-gatifloxacin combinations showed additional properties against Escherichia coli and Staphylococcus aureus, while SCLP-streptomycin and SCLP-penicillin combinations exhibited dramatically synergistic effects. In addition, the changes in permeability and integrity of the cell membrane and cell wall were observed by measuring UV absorption, extracellular AKP concentration, FTIR spectroscopy, and scanning electron microscopy. It is speculated that the mechanism of action of SCLP on bacteria may be described as destruction of bacterial cell wall and cell membrane. In conclusion, SCLP was a potential natural antimicrobial substance with strong antimicrobial activity, which may reduce the use of antibiotics or combat drug-resistant bacteria through synergistic combination with antibiotics.

Greywater treatment by ornamental plants and media for an integrated green wall system

Greywater recycling through natural vegetated systems provides a low cost and sustainable approach to manage urban water scarcity but is space intensive. This study aims to treat greywater naturally using ornamental plant species that can be integrated vertically into green building structures and elucidate the main removal mechanisms occurring therein. To this end, various regional ornamental plants and growing media were tested in column experiments, with a bi-daily application-rest cycle of 500 mL. d−1 per plant. Removal percentages greater than 90% were achieved for all contaminants monitored (organics, solids, nitrogen and phosphorus) when using high surface area, small-diameter media such as coco coir, spent coffee grounds and sand. Media selection was found to be a much more dominant factor than plant selection for treatment performance. Using media replacement and plant removal studies, it was found that nitrification was linked with the presence of plant roots in the media. The removal rates of hydrophilic and hydrophobic organics were also analyzed and effluent specific UV absorbance measurements demonstrated hydrophobic compounds, which are typically more toxic in nature, were successfully removed from the system. This study demonstrates the complex interactions between the media, microbes, plant roots and greywater in natural treatment systems and their potential as an innovative approach for greywater treatment in the urban built environment.

Design, synthesis and DNA interaction studies of new fluorescent platinum complex containing anti-HIV drug didanosine

Forming coordination complexes with nucleoside analogues may be helpful in studying anti-tumour activity of them. Therefore, to improve the clinical efficacy of nucleoside analogue and design new ones, a new fluorescent platinum (Pt) complex with anti-human immunodeficiency virus drug didanosine (ddI); K[PtCl(OCH3)2(ddI)]; was synthesized and characterized. The ultraviolet–visible (UV-vis) spectroscopy, infrared, thermogravimetric analysis, mass assignments and elemental analysis confirmed the preparation of the complex. The molecular ion peaks seen at the positive mass spectrum of Pt complex confirm coordination of the drug to metal centre. The interaction of this complex with calf thymus DNA (ct-DNA) was studied using several spectroscopic techniques such as UV absorption, fluorescence spectroscopy and dynamic viscosity measurements. Hyperchromism of the band in the UV-vis spectra and the intrinsic binding constant (0.56 ± 0.25) × 104 M−1, decreasing in Hoechst-DNA fluorescence by adding Pt complex concentration and also relatively small changes in DNA viscosity indicated that this complex could interact as a groove-binder. According to the UV spectra and the fluorescence quenching of the complex in our case seems to be primarily caused by complex formation between the Pt complex and DNA. The thermodynamic parameters showed that hydrogen bond and van der Waals interactions play main roles in the binding of Pt complex to ct-DNA. The free energy values are negative, showing the spontaneity of the Pt complex–DNA binding. The docking simulation was performed and the results confirm a preference of groove site of synthesized complex on DNA helix. The knowledge gained from this study will be helpful to further understand the DNA binding mechanism and can also provide much fruitful information for designing a new type of anti-cancer drugs.Communicated by Ramaswamy H. Sarma

Application of preheating treatment in up- and down-regulating the glycation process of dietary proteins

Heating is the most commonly used treatment in food industry. This work reported the influence of preheating treatment (PT, 98 °C) on the following glycation behavior of bovine serum albumin (BSA), β-lactoglobulin (β-Lg) and β-casein (β-CN) at 90 °C. The PT was shown to induce both the unfolding and aggregation of proteins, which changed their subsequent glycation kinetics based on measurements of free amino group content and UV absorbance at 294 and 420 nm. Ten minutes of PT unfolded the globular structures of BSA and β-Lg and exposed more glycation sites, which largely up-regulated their glycation degrees. By contrast, 40 min of PT induced more severe aggregation in BSA and β-Lg during PT and the subsequent glycation process, which hid a portion of glycation sites and down-regulated their glycation degree. The glycation behavior of β-CN was almost not affected by PT, possibly due to its intrinsic disordered structure and high thermal stability. Proteomics analysis showed that PT resulted in changes in the number of glycated structures and preference of lysine residues to be glycated. These results suggested PT as an effective way in regulating the glycation behavior of dietary proteins, depending on PT duration and structure of treated protein.

Quantification of nitric acid using photolysis induced fluorescence for use in chemical kinetic studies

Previous laboratory investigations have predominantly relied on UV absorption measurement of [HNO3]. Whilst direct, this measurement is difficult at temperatures <298 K, where heterogeneous loss to cold surfaces is significant. Single and two photon photodissociation of HNO3 was studied in N2 and He at 193 and 248 nm, and a unique HNO3 detection method was established using two photons at 248 nm, with good reproducibility and limit of detection (∼1.25 × 1014 cm−3). Emissions from excited products have been identified spectroscopically, over a range of pressures and laser energies to support the HNO3 quantification method.

Tropospheric Ozone Assessment Report: Tropospheric ozone from 1877 to 2016, observed levels, trends and uncertainties

From the earliest observations of ozone in the lower atmosphere in the 19th century, both measurement methods and the portion of the globe observed have evolved and changed. These methods have different uncertainties and biases, and the data records differ with respect to coverage (space and time), information content, and representativeness. In this study, various ozone measurement methods and ozone datasets are reviewed and selected for inclusion in the historical record of background ozone levels, based on relationship of the measurement technique to the modern UV absorption standard, absence of interfering pollutants, representativeness of the well-mixed boundary layer and expert judgement of their credibility. There are significant uncertainties with the 19th and early 20th-century measurements related to interference of other gases. Spectroscopic methods applied before 1960 have likely underestimated ozone by as much as 11% at the surface and by about 24% in the free troposphere, due to the use of differing ozone absorption coefficients.There is no unambiguous evidence in the measurement record back to 1896 that typical mid-latitude background surface ozone values were below about 20 nmol mol–1, but there is robust evidence for increases in the temperate and polar regions of the northern hemisphere of 30–70%, with large uncertainty, between the period of historic observations, 1896–1975, and the modern period (1990–2014). Independent historical observations from balloons and aircraft indicate similar changes in the free troposphere. Changes in the southern hemisphere are much less. Regional representativeness of the available observations remains a potential source of large errors, which are difficult to quantify.The great majority of validation and intercomparison studies of free tropospheric ozone measurement methods use ECC ozonesondes as reference. Compared to UV-absorption measurements they show a modest (~1–5% ±5%) high bias in the troposphere, but no evidence of a change with time. Umkehr, lidar, and FTIR methods all show modest low biases relative to ECCs, and so, using ECC sondes as a transfer standard, all appear to agree to within one standard deviation with the modern UV-absorption standard. Other sonde types show an increase of 5–20% in sensitivity to tropospheric ozone from 1970–1995.Biases and standard deviations of satellite retrieval comparisons are often 2–3 times larger than those of other free tropospheric measurements. The lack of information on temporal changes of bias for satellite measurements of tropospheric ozone is an area of concern for long-term trend studies.

High molecular weight humic-like substances in carboneous aerosol of Ulaanbaatar city

Total carbon content of the atmospheric suspended particulate matters consisted of as high as 89-93% organic carbon (OC) in Ulaanbaatar aerosol without showing seasonal variation. However, limited aerosol measurements have been conducted on these OC rich aerosols particularly for high molecular weight constituents. In order to address the gap above, abundance of high molecular weight humic-like substances (HULIS) in total suspended particulates (TSP) from Ulaanbaatar atmospheric aerosol were determined for the first time. HULIS molecular structure was characterised for different seasons using carbon content and UV absorbance measurements coupled with solid phase extraction methods. Although, HULIS contributions to water soluble organic fraction of the winter and summer aerosols were similar HULIS carbon concentration was higher in winter samples (9-37 mg·L-1) than in summer (2-6 mg·L-1). Consequently quantity of aromatic moieties and degree of aromaticity varied between seasons.

On the discrepancy between the X-ray and UV absorption measurements of O vi in the local ISM

ABSTRACT The total amount of O vi present in the interstellar medium (ISM) obtained via absorption measurements in UV and X-ray spectra is currently in disagreement, with the latter being significantly larger (by a factor of 10 or more) than the former. Previous works have proposed that the blend of the O vi Kα line (22.032 Å) with the O ii Kβ-L12 line (22.04 Å) could account for the stronger absorption observed in the X-ray spectra. Here, we present a detailed study of the oxygen absorption in the local ISM, implementing our new model IGMabs which includes photoabsorption cross-sections of highly ionized species of abundant elements as well as turbulence broadening. By analysing high-resolution Chandra spectra of 13 low-mass X-ray binaries (LMXBs) and 29 extragalactic sources, we have estimated the column densities of O i – O iii and from O vi – O viii along multiple line-of-sights. We find that in most cases the O ii Kβ-L12 line accounts for &amp;lt;30${{\ \rm per\ cent}}$ of the total O vi K α + O ii K β. We conclude that the amount of O ii predicted by our model is still insufficient to explain the discrepancy between X-ray and UV measurements of O vi column densities.

Synthesis, antibacterial activity and DNA interactions of lanthanide(III) complexes of N(4)-substituted thiosemicarbazones

This paper reports the synthesis and detailed characterization of six novel lanthanide complexes of La(III), Eu(III) and Nd(III) with N(4)-substituted thiosemicarbazones derived from the 2-carboxybenzaldehyde. The IR, 1H-NMR and 13C-NMR spectroscopic studies confirmed the coordination of the thiocarbonyl (C=S), azomethine (C=N) and carboxylate (COO-) groups to the metal centers, and the carboxylate was coordinated in a bidentate manner. The elemental and thermal analyses suggest that lanthanide complexes were formed in 1:2 molar ratios (metal:ligand). The molar conductivity values confirmed the non-electrolytic nature of the complexes. The interaction of these complexes with calf thymus DNA (CT-DNA) was investigated by UV absorption and viscosity measurements. It was found that the Eu(III) and Nd(III) complexes could roll along the DNA strands through groove interactions. Furthermore, lanthanide complexes could promote the oxidative cleavage of plasmid pBR322 in a high-oxidative stress environment. Finally, the Schiff base ligands (L) and their complexes were evaluated for their antibacterial activities against gram-positive and gram-negative bacteria using a microdilution procedure. The results indicate that the lanthanide complexes exhibit more potent antibacterial activity than the free ligands.

Techno-economic assessment of surrogate-based real-time control and monitoring of secondary effluent ozonation at pilot scale

During secondary effluent ozonation, real-time control of the ozone dose based on the water quality is essential to minimize operational costs and by-product formation (i.e. two of the main hurdles hindering a fast implementation of the technology). In this pilot-scale study, the ozone dose was controlled via online UV absorbance (UVA254) measurements. Only one sensor was used although a ΔUVA254-based control strategy was applied. The practical implications of online spectral sensors and the effect of effluent dynamics in terms of load (i.e. Dissolved Organic Carbon or DOC concentration) and composition (i.e. reactivity) was studied in relation to the applied control strategies. The one sensor approach – presented for the first time to the best of the authors’ knowledge – reduced the negative impact of sensor fouling. The use of manual and ultrasonic cleaning is recommended as it results in significantly less fouling (i.e. a factor of 6 difference). Additionally, the variable effluent reactivity showed to be more influential than the effluent load in determining the ozone dose. The use of ΔUVA254 ensured the supply of the required ozone doses during varying water quality and weather conditions, and at lower operational costs than more common control strategies (up to 22% of savings). Flow or load proportional strategies were not able to cope with the dynamic ozone demand of the effluent. However, the required additional response time of the ΔUVA254-strategy might be a disadvantage and could be tackled using hybrid control approaches including load-based dosing (i.e. O3:DOC ratio based) and the use of a combined feedback-feedforward system.