Presence Of Th Research Articles

Effect of nano-hydroxyapatite and phosphate on thorium toxicity – Arabidopsis transcriptomic study

Thorium (Th) is a ubiquitous element but elevated concentrations caused by anthropogenic or natural activities pose health and environmental risks. Plants may be exposed accidentally or during the remediation of contaminated sites. Therefore, in this study, we analyzed the effect of thorium on Arabidopsis plants by RNA-seq profiling. Since Th and phosphorus form insoluble phosphates, we focused on the effect of Th in the presence/absence of phosphate in wild-type and mutants with altered phosphate management. Furthermore, we investigated the effect of hydroxyapatite nanoparticles, which are considered as material for in situ remediation, on Th toxicity. The highest number of DEGs was recorded in the combination of P absence and Th presence while the lowest in the presence of Th together with hydroxyapatite. Besides a high number of genes involved in stress response, Th also induced the transcription of genes involved in response to P starvation, indicating that Th decreased the availability of P. P deficiency caused by Th contributed to the phytotoxic effect of Th. We observed that nano-hydroxyapatite significantly reduced Th toxicity. Nano-hydroxyapatite also served as a source of inorganic P for the plants, but caused deficiency of essential metals indicated by up-regulation of genes involved in their acquisition.

Separation of Thorium from Light Rare Earth Elements from Monazite Chloride Leach Liquor

Monazite is one of the main light rare earth element (REE) minerals and is associated with the presence of Th. This poses challenges in processing due to the strong radiation present in this mineral. However, the use of Th as a nuclear fuel, after the transformation of 232Th into 233U, has been considered a better option than the currently more widespread use of 235U. Therefore, the separation of Th from the REE after leaching is an essential step that requires optimization. In this study, the treatment of a leach solution in a hydrochloric medium from dephosphorized monazite is addressed. The separation of Th from light REEs was performed by solvent extraction with Cyanex 572 or 272. The tests considered included (1) the ratio of the monazite leaching liquor and organic solution, (2) the initial pH values, and (3) the concentration of the extractants. The aqueous-phase samples were analyzed by Inductively Coupled Plasma Optical Emission spectroscopy (ICP-OES). It was observed that at low pH, 60% of the Th was extracted by Cyanex 272 and 90% by Cyanex 572 in one single step. Acidity had little effect on Th extraction. The extractions of light REEs by Cyanex 272 and 572 were negligible in most cases, but for pH values greater than 2, Cyanex 272 extracted a considerable fraction of these elements, which did not occur with Cyanex 572. The results show that Th can be easily separated from light REEs in an acidic and hydrochloric medium by both Cyanex 272 and Cyanex 572.

Exploring the role of redox mediator within mesoporous carbon using Thionine and LiTFSIwater-in-salt electrolytes

Despite the dramatically increasing research effort dedicated to redox-active electrolytes towards improved supercapacitor capacitance, the research concerning charging mechanisms remains sparse. This is particularly true for porous materials such as porous carbon. Whereas some charging mechanisms have been discussed for microporous materials, the mechanisms occurring within mesoporous materials are mostly unexplored. Herein, a new redox mediator - Thionine (Th) - in highly-concentrated LiTFSI, was used as a supercapacitor electrolyte to explore these mechanisms. The addition of Th modifies the viscosity and thermal properties of the electrolyte without affecting the ionic conductivity. Electrochemical measurements confirmed that the presence of Th endows an additional pseudocapacitance in mesoporous carbon but not in microporous carbon. Based on these contrasting phenomena, the charging mechanism and solvated structure were studied by Molecular Dynamics (MD) and Density Functional Theory (DFT) simulation. DFT simulation disclosed that it has an ion association effect between TFSI and Th due to their opposite charge. Two MD models were built with different porosities: 0.9 nm (micropores) and 3 nm (mesopores). It was found that Th molecules cannot enter micropores whereas their insertion into the mesopores was possible. Once inside the mesopores, Th can interact with the inner carbon wall via hydrogen bonding thus stabilizing the redox molecule within the mesopore which can then provide a redox contribution to the charging process. The present work helps to build a deeper understanding of the activity of redox-active molecules in mesoporous materials by elucidating the exact adsorption and charging mechanisms within a microporous system. This paves the way for the design of advanced redox-active electrolytes for supercapacitors.

A potential sensor for assessing thorium (IV) based on Albuterol sulfate fluorescence enhancement: A density functional theory (DFT) study

• Introducing a new fluorescent sensor for assessing Th(IV) in environmental samples. • Fluorescence mechanism was discussed. • HOMO and LUMO energy levels has been calculated by DFT. This study introduces a potential fluorescence sensor for assessing thorium (Th(IV)) in aquatic environments. In the presence of Th(IV), Albuterol Sulfate ( ABS ) 4-[2-( tert -butylamino)-1-hydroxyethyl]-2-(hydroxymethyl)phenol; sulfuric acid exhibits significant fluorescence enhancement at 600 nm. The current ABS ligand sensor shows wide linear range from 6.0 × 10 −8 – 2.5 × 10 −7 mol/L and pH range of 4–6. Interestingly, when all evaluated interference ions coexisted, the change in fluorescence emission intensity of ABS -Th complex was roughly 2.3 %. The binding mode is studied and indicating a 2:1 complex formation between ABS ligand and Th (IV). Density functional theory (DFT) has been utilized to examine the interaction characteristics between the present ABS ligand sensor and Th(IV) and to compute the geometric configuration of the ABS and ABS -Th through the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels. The interaction properties exhibit considerable effect on the HOMO and LUMO properties of the complexes, as well as a fluorescence enhancement that could be attributable to the heavy atom effect of Th (IV). The ABS sensor shows remarkable features and provides good performance compared to some of the optical sensors, making it a potential new fluorescence sensor for Th(IV) assessment.

Relating Metopic Severity to Mid-term Aesthetic Outcomes: A Machine Learning Approach

PURPOSE: Aesthetic deterioration after surgical treatment of metopic craniosynostosis may manifest as bitemporal hollowing (TH), lateral orbital retrusion (LOR), or frontal bone irregularities (FBI). Patients with these complications have reoperation rates of 18-46%. To date, there have been few longitudinal studies assessing the effect of pre-operative dysmorphology on aesthetic outcomes in this cohort. This study evaluates the relationship between metopic severity, including the use of CranioRateTM, a novel metopic synostosis severity measure, and mid-term aesthetic outcomes. MATERIALS AND METHODS: Patients with non-syndromic metopic craniosynostosis who underwent bi-frontal orbital advancement and remodeling (BFOAR) between 2012 and 2017 were reviewed. Metopic synostosis severity was determined based on pre-operative CT assessment of IFA and CranioRateTM. CranioRateTM is a machine learning algorithm trained to recognize morphologic features of metopic synostosis and generate quantitative severity ratings including metopic severity score (MSS) and cranial morphology deviation (CMD). Frontal and lateral photographs of patients with at least four years post-operative follow-up were assessed by attending craniofacial surgeons using masked three-rater aesthetic grading of clinical photos (n=39). Graders assessed Whitaker score as well as the presence of TH, LOR, FBI, or a ‘catch-all’ category of visible irregularities. Binary logistic regression was used to assess predictors of TH, LOR, FBI, and VI. Multinomial logistic regression was used to assess predictors of Whitaker classification. RESULTS: The average age at preoperative CT scan was 7.7 ± 3.4 months and the average age at BFOAR was 9.9 ± 3.1 months. The average MSS was 6.3 ± 2.7 out of 10 and average CMD was 200.4 ± 44.7 out of 300. Average IFA for the cohort was 116.8° ± 13.8° (range 93° - 138°). The average time from operation to aesthetic assessment was 5.4 ± 1.0 years (range 4.1 – 7.8 years). ‘Any visible irregularity’ was present in 87.2% (n = 34) of patients, temporal hollowing in 76.9% (n = 30), frontal bone irregularities in 61.5% (n = 24), and lateral orbital retrusion in 20.5% (n = 8). Most patients received a median Whitaker classification of II (61.5%, n =24), followed by class III (23.1%, n = 9). There was a significant association between MSS and age at CT scan, with younger patients having more severe metopic severity scores (r = -.451, p = .004). Similarly, MSS and IFA were negatively associated, with a higher MSS correlating to a lower IFA (r = -.371, p = .034). MSS was found to be the only independent predictor of visible irregularities (OR 2.18, B = .780, p = .024). Decreased age at surgery (OR, 1.08; 95% CI, 1.05 to 2.6, p = .002) and increased length of follow up (OR, 1.59; 95% CI, 1.59 to 3.54, p <.001) were significantly associated with a worse median Whitaker score. No impact of surgical technique, including parietal bone graft use or interpositional bone graft size, was demonstrated (p > .05 for both). CONCLUSION: More severe cases of metopic craniosynostosis show increased rates of cumulative aesthetic dysmorphologies. Measures of pre-operative metopic severity are predictive of mid-term aesthetic outcomes.

Geochemical and Isotope Anomalies in Sioma River Gorge, Western Tajikistan

For a better understanding of the previously observed increased natural radioactivity at the confluence of the Varzob and Sioma rivers, Central Tajikistan, the activity concentration of natural radioactive 40K, Th and U daughters as well as of the anthropogenic 137Cs were determined in nine locations covering the entire Sioma River. The radiometric determinations evidenced, in addition to increased activity concentrations of Th and U daughter radionuclides, an anomalous accumulation of anthropic 137Cs and natural 210Pb in the middle of the Sioma gorge. Complementarily, the mass fractions of natural Th and U determined by instrumental neutron activation analysis evidenced an increased presence of Th and U, which, in some places, overpasses six-times the average mass fraction found in the upper continental crust. The possible influence of active air transport from the southern Tadjik plane during the Afghani storms, as well as the presence of actinide-rich minerals, were analyzed and discussed.

Effects of thorium on bacterial, microalgal and micromeiofaunal community structures in a periphytic biofilm

Few ecotoxicity studies are available on thorium (Th) which hinders the ability to evaluate its ecotoxicological risk. Its release in the environment is often associated with the extraction of rare earth elements and uranium, as well as the field applications of phosphate fertilizers. This study investigates the effects of Th on microbial communities of periphytic biofilms. Ceramic plates were left to colonize for one month in the laboratory with a biofilm sampled from Cap Rouge river (QC, Canada). Plates were randomly placed in channels containing culture media representing three different conditions: a control condition (C0; background Th concentrations of 0.004 ± 0.002 nM), a low Th concentration condition (C1; 0.18 ± 0.09 nM Th) and a moderately high Th condition (C10; 8.7 ± 3.4 nM) for up to 4 weeks. The presence of Th modified the diatom community by changing its taxonomic structure, reducing diversity and increasing cell density. The taxonomic structure of the bacterial community, followed by 16S metabarcoding analysis, was affected with a significant decrease in Pseudanabaena and Shingopyxis genera in the two Th exposed conditions. No direct toxic effect of Th was observed on counted micromeiofauna but the changes in diatom and bacterial communities could explain the higher number of individual diatoms and micromeiofauna observed in Th-exposed conditions. This work shows that low concentrations of Th can modify biofilm structure, which, in turn, could disturb its ecologically key functions.

Utilizing neutronics modelling to predict changing Pu ratios in UO2 in the presence of Th

The isotopic fractions of plutonium produced in a reactor are of significant value as nuclear forensic signatures, and the mechanisms of their production and alteration should be investigated thoroughly. A series of neutronics calculations were made on a typical UO2 PWR setup, introducing (Th, U)O2 MOX rods gradually, to investigate how the presence of Th affects the 240Pu/239Pu and 242Pu/239Pu ratios in the remaining UO2 fuel rods. A relationship is found that links the percentage change in these ratios, with the burnup and Th content in the configuration. In an extreme case, it was found that the presence of Th may increase the ratio of 242Pu/239Pu by as much as 3.5% at low burnup.

Characterization of novel thorium tolerant Ochrobactrum intermedium AM7 in consort with assessing its EPS-Thorium binding

Currently, radioactive waste is disposed primarily by burial in a deep geological repository. Microorganisms thriving in such contaminated environment show tolerance to radionuclides. In the present study the bacterial flora, from soil sample collected from an area around atomic power station exposed to radionuclides and heavy metals, was cultivated and assessed for thorium (Th) tolerance. Of all the isolates, strain AM7 identified as O. intermedium was selected since it could thrive at high levels of Th (1000 mg L−1). AM7 was characterized physico-chemically and its culture medium was optimized using central composite design of response surface methodology for assessing its growth properties in presence of Th. The strain also showed exceptional exopolysaccharide (EPS) production and its yield was further analyzed using one factor study to investigate the influence of each medium component. On supplementing the EPS medium with Th, no significant decrease in yield was observed. FTIR spectroscopy revealed the functional groups of EPS involved in EPS-Th binding. To the best of our knowledge, this is the first report showing exceptional Th-tolerance by any bacteria. Such study will help other researchers to strategize an environment-friendly way of radwaste disposal.

MicroPIXE analysis of removal of aqueous U(VI) by S. intermedia and P. stratiotes in the presence of Th(IV)

In this work, Spirodela intermedia and Pistia stratiotes, autochthonous floating macrophytes, were used to remove aqueous UO22+ (1 and 10 mg.L−1) under laboratory conditions. The influence of Th4+(1 mg.L−1) was studied for the highest concentration of U(VI).All the parameters of the bioremediation process, bioconcentration factors (BCFs) in roots and leaves and translocation factors (TFs), were achieved by microPIXE quantification. This analysis was carried out using a 50-MeV 16O5+ beam with the aid of the heavy-ion microprobe at the TANDAR Laboratory in Buenos Aires. High resolution 2D maps of the in vivo elemental distribution in macrophytes for different conditions were obtained. Both plants have the ability to accumulate a large amount of U(VI) yielding BCFs > 500. Only S. intermedia can additionally uptake Th(IV) reaching a high BCF (>300 at 96 h) but the plant does not survive; Th was detected within the chlorenchyma ([Th] ≅ 30 µg.g−1).

Determination of the REE content, geological age, and absorbed alpha dose of allanite mineral from Palawan, Philippines

Allanite is a common accessory mineral in igneous rocks that contains significant amounts of rare‐earth elements (REEs), thorium (Th), and uranium (U). The presence of Th and U in the allanite exposes it to radiation resulting in radiation damage in its crystal structure and further leads to metamictization. Hence, allanite can be used as a natural analogue to assess the long‐term radiation effects in materials for high‐level nuclear waste disposal. It provides information on the effect of α‐decay on the crystal structure including the stability and integrity of the material. In this study, the absorbed α‐dose of allanite from Ombo, Palawan, Philippines, was estimated from the Th and U content and geological age of the mineral using X‐ray fluorescence and gamma‐ray spectrometry. The amount of Th and REE was measured to be around 1.37 and ~30.4 wt.%, respectively. Radiometric dating using gamma‐ray spectrometry estimated the age of the allanite mineral to be around 24–35 million years. Having obtained the amount of radioactivity and the time of exposure, the corresponding absorbed α‐dose was estimated to be at 2.84 × 1014 α‐decays/mg. Results suggest that the allanite mineral studied has not accumulated significant radiation damage to cause amorphization and still exhibit a crystalline structure. This study may provide data on the properties of allanite or silicate matrices as part of the ongoing studies on silicate minerals as natural analogues.

Conditions affecting the release of thorium and uranium from the tailings of a niobium mine

Determinations of the mobility of metals from tailings is a critical part of any assessment of the environmental impacts of mining activities. The leaching of thorium and uranium from the tailings of different processing stages of a niobium mine was investigated for several pH, ionic strengths and concentrations of natural organic matter (NOM). The pH of the leaching solution did not have a noticeable impact on the extraction of Th, however, for pH values below 4, increased U mobilization was observed. Similarly, only a small fraction of Th (0.05%, ≤15 μg kg−1) and U (1.22%, ≤6 μg kg−1) were mobilized from the tailings in the presence of environmentally relevant concentrations of Ca, Mg or Na. However, in the presence of 10 mg L−1 of fulvic acid, much higher concentrations of ca. 700 μg kg−1 of Th and 35 μg kg−1 of U could be extracted from the tailings. Generally, colloidal forms of Th and dissolved forms of U were mobilized from the tailings, however, in the presence of the fulvic acid, both dissolved and colloidal forms of the two actinides were observed. Single Particle ICP-MS was used to confirm the presence of Th (and U) containing colloids where significant numbers (up to 107 mL−1) of Th and U containing colloids were found, even in 0.2 μm filtered extracts. Although mass equivalent diameters in the range of 6–13 nm Th and 6–9 nm for U could be estimated (based upon the presence of an oxyhydroxide), most of the colloidal mass was attributed to larger (>200 nm) heterocomposite particles.

La(III) and Ce(III) biosorption on sulfur functionalized marine brown algae Cystoseira indica by xanthation method: Response surface methodology, isotherm and kinetic study

In this study, chemically modified Cystoseira indica brown algae by xanthation method was utilized to study the biosorption of La(III) and Ce(III) ions from the aqueous solutions under batch mode. The effects of four variables including pH (2–6), temperature (25–55 °C), biosorbent dosage (0.5–2.5 g L–1) and initial metal concentration (50–250 mg L–1) were evaluated and optimized using Response Surface Methodology (RSM) based on the Central Composite Design (CCD). A low P–value and high coefficient of determination (R2) implied the accuracy and validity of the proposed quadratic models. The results showed that the xanthation improved the performance of C. indica than the intact and Ca–pretreated ones. Performing experiments under optimal condition sets produced maximum biosorption capacities of 185.44 and 172.33 mg g–1 for La(III) and Ce(III), respectively. In order to characterize the provided biosorbents, FTIR analyses were carried out. Results revealed that the dominant functional groups in the binding process were hydroxyl, carboxyl and amide in the intact algae while xanthation caused addition of sulfur groups that participated in binding process and increased the sorption capacities of both metal ions. The equilibrium and kinetic studies revealed that the Freundlich isotherm model and the double–exponential kinetic model were in the better fitness with the La(III) and Ce(III) experimental data. Moreover, the results showed that the presence of Th(IV) ions decreased the biosorption capacities of both metal ions. In conclusion, the present work showed that the xanthated C. indica could be a proper biosorbent for La(III) and Ce(III) biosorption from aqueous solutions.

Characterization of Malaysian Monazite Concentrate for The Recovery of Thorium Dioxide

Malaysia has many potential mineral resources including some heavy and light rare earth element (HREE and LREE’s) minerals, such as Monazite and Xenotime. Their occurrence is in association with ores containing phosphates and oxides of Cerium (Ce), Lanthanum (La), Neodymium (Nd) and Thorium (Th). Mineralogical characterization of Malaysian Monazite concentrate for the recovery of Thorium dioxide (ThO2) has been carried out in this study. Scanning Electron Microscope (SEM) equipped with an Energy Dispersive X-ray Analyser (EDX) was used to assess the morphology and elemental composition of the mineral. The latter analysis showed that EDX surface analysis detected P-Kα Th-Mα, La-Lα, Ce-Lα and Nd-Lα as the major elements. The SEM micrographs with the EDX analysis revealed the morphological characteristics of Monazite which showed angled and irregular structures with dark coloured patches of Al, Si and Mn based inclusions. XRF analysis confirmed the presence of Th (8.52 wt.%) and U (0.25 wt.%). XRF also showed that the major rare earth elements (REE) of interest (> 5 wt.%) such as Ce, Nd and La were abundant in the mineral. XRD analysis identified LaPO4, CePO4 and NdPO4 as the major phases. Thorium phosphate (Th4(PO4)4) phase was not detected via XRD due to stronger X-ray reflection from the rare earth phosphates. The information collected from this study will help in developing a suitable process of treatment for the local Monazite, thereby facilitating the mineral to be used a domestic source of Th and other associated REE’s.

Thyroid hormone regulates protease expression and activation of Notch signaling in implantation and embryo development.

A clinical association between thyroid dysfunction and pregnancy complications has been extensively reported; however, the molecular mechanisms through which TH might regulate key events of pregnancy have not been elucidated yet. In this respect, we performed in vivo studies in MMI-induced hypothyroid pregnant mice, evaluating the effect of hypothyroidism on the number of implantation sites, developing embryos/resorptions and pups per litter, at 4.5, 10.5, 18.5 days post-coitum (dpc) and at birth. We also studied the expression of major molecules involved in implantation and placentation, such as the proteases ISPs, MMPs, TIMPs and Notch pathway-related genes. Our results demonstrate that hypothyroidism may have a dual effect on pregnancy, by initially influencing implantation and by regulating placental development at later stages of gestation. To further elucidate the role of TH in implantation, we performed in vitro studies by culturing 3.5 dpc blastocysts in the presence of TH, with or without endometrial cells used as the feeder layer, and studied their ability to undergo hatching and outgrowth. We observed that, in the presence of endometrial feeder cells, TH is able to anticipate blastocyst hatching by upregulating the expression of blastocyst-produced ISPs, and to enhance blastocyst outgrowth by upregulating endometrial ISPs and MMPs. These results clearly indicate that TH is involved in the bidirectional crosstalk between the competent blastocyst and the receptive endometrium at the time of implantation.

Simultaneous photometric microplate assay for free and total thiamine using gold nanoparticles and alkaline phosphatase

A photometric method is described for the determination of free and total thiamine (TH; vitamin B1) in food samples. It is based on the use of gold nanoparticles (AuNPs) which aggregate in the presence of TH owing to the interaction of its sulfur atom with the AuNPs. This is accompanied by a color change from wine red to purple-blue and an increase in absorbance at 590 nm. The effect is not observed for TH phosphates which, however, can be determined, as demonstrated for the example of TH pyrophosphate as a model ester, by treating them with alkaline phosphatase (ALP) which hydrolyses such esters. The use of two sample aliquots, one with and one without ALP, allows the determination of free and total TH, respectively. The dynamic range extends from 0.15 to 3.5 μM, and the detection limit is 54 nM of TH. The method has been applied to the analysis of spiked food samples and gave recoveries that ranged between 88.8 and 100.7 %.

Decreased Salinity and Actinide Mobility: Colloid-Facilitated Transport or pH Change?

Colloids have been implicated in influencing the transport of actinides and other adsorbed contaminants in the subsurface, significantly increasing their mobility. Such colloid-facilitated transport can be induced by changes in groundwater chemistry that occur, for example, when high ionic strength contaminant plumes are displaced by infiltrating rainwater. We studied the transport and mobility of Th(IV), as an analogue for Pu(IV) and other tetravalent actinides [An(IV)], in saturated columns packed with a natural heterogeneous subsurface sandy sediment. As expected, decreases in ionic strength both promoted the mobilization of natural colloids and enhanced the transport of previously adsorbed Th(IV). However, colloid-facilitated transport played only a minor role in enhancing the transport of Th(IV). Instead, the enhanced transport of Th(IV) was primarily due to the pH-dependent desorption of Th(IV) caused by the change in ionic strength. In contrast, the adsorption of Th(IV) had a marked impact on the surface charge of the sandy sediment, significantly affecting the mobility of the colloids. In the absence of Th(IV), changes in ionic strength were ineffective at releasing colloids while in the presence of Th(IV), decreases in ionic strength liberated significant concentrations of colloids. Therefore, under the conditions of our experiments which mimicked acidic, high ionic strength groundwater contaminant plumes, Th(IV) had a much greater effect on colloid transport than colloids had on Th(IV) transport.

Th(IV) ion-imprinted polymer for selective solid-phase extraction of Th(IV) and its analytical applications

A new Th(IV) ion-imprinted polymer (IIP) was synthesized for the separation and recovery of trace Th(IV) ion from river water sample. Th(IV) IIP was prepared by copolymerization of methyl methacrylate (monomer) and ethylene glycol dimethacrylate (cross-linker) in the presence of Th(IV)-thiosemicarbazide-4-vinyl pyridine ternary complex wherein Th(IV) ion is the imprint ion and is used to form the imprinted polymer. Thorium(IV) ion was eluted with 10 mL of 1 M HCl. The polymers have been characterized by surface area measurements, fourier transform infrared spectroscopy, microanalysis and scanning electron microscopy analysis. The adsorption capacity of the imprinted polymer was found to be 0.290 mmol g−1, which is much higher than most of the reported IIPs. The optimum pH for quantitative enrichment is 4.0. The relative selectivity coefficient values of the imprinted polymer for Th(IV)/Pb(II), Th(IV)/Zn(II), Th(IV)/Cu(II), Th(IV)/Ni(II), Th(IV)/Cd(II) and Th(IV)/Co(II) are 37.13, 37.40, 30.34, 35.69, 37.63 and 36.28, respectively. The lowest concentration that could be determined by Arsenazo III spectrophotometric method below which the recovery becomes non-quantitative is 5 μg L−1.

Radiological and Toxic Risk Assessment of Nigerian Kohl as Cosmetic Compared with Imported Kohl Cosmetics

A total of 38 different samples of Kohl comprising of 23 indigenous mined products and 15 imported products as control and were analyzed for general elemental composition but with particular interest in those reported to be of relevance (As, Cd, Hg, Ni, Co and Sb) in cosmetics. Energy dispersive X-ray Fluorescence Analysis EDXRA was used for the assay. Only Pb, As, Ni and Cr were detected among the elements of interest. Mean Pb concentrations of 277300 ppm; Ni at 2256 ppm concentration; and As at 810 ppm which are considerably higher than their safety limits (20 ppm p<0.01) were obtained in both the indigenous and imported products. The same risk was statistically observed to be involved following the use of both local and imported kohl products. Again Pb concentrations in excess of what was claimed on the labels of the imported kohl products were observed (p<0.01), hence the need for scrutiny of imported products by the relevant agency. The high concentration of Cr (7460 ppm, p<0.05) in the imported samples signifies its presence as colorant and the need for chromium control for the brands concerned. Also the observed presence of Th in the indigenous (local) samples suggests that Nigerian products may be of radiological effect to health. Measurements were made of gross alpha and beta count of indigenous mined and imported kohl samples The results reveals that all the forms of kohl products assayed, emit both particles but with β’s count substantially higher than the α’s (p<0.5) at a mean β count 4695×10-3 cpm and α count as 283×10-3 cpm. One of the samples from Zamfara State of Nigeria (known for Pb poisoning due to mining activities) shows an exceptionally high count in both α = 8998100 cpm and β = 9315700 cpm which reveals that products from Zamfara State, need a special attention. Application of this product is therefore very much likely to produce radiation damage to the cornea due to low penetration of α and to the internal tissue of the eye due to the relatively high penetration of β s. However, the non-existence of defined safety limits for these particles in Kohl as cosmetic, suggests the need for further research.

Synthesis of poly(N-isopropylacrylamide) with a low molecular weight and a low polydispersity index by single-electron transfer living radical polymerization

The single-electron transfer living radical polymerization (SET-LRP) method in the presence of chain transfer agent was used to synthesize poly(N-isopropylacrylamide) [poly(NIPAM)] with a low molecular weight and a low polydispersity index. This was achieved using Cu(I)/2,2′-bipyridine as the catalyst, 2-bromopropionyl bromide as the initiator, 2-mercaptoethanol as the chain transfer agent (TH), and N,N-dimethylformamide (DMF) as the solvent at 90 °C. The copper nanoparticles with diameters of 16 ± 3 nm were obtained in situ by the disproportionation of Cu(I) to Cu(0) and Cu(II) species in DMF at 22 °C for 24 h. The molecular weights of poly(NIPAM) produced were significantly higher than the theoretical values, and the polydispersities were less than 1.18. The chain transfer constant (Ctr) was found to be 0.051. Although the kinetic analysis of SET-LRP in the presence of TH corroborated the characteristics of controlled/living polymerization with pseudo-first-order kinetic behavior, the polymerization also exhibited a retardation period (k > ktr). The influence of molecular weight on lower critical solution temperature (LCST) was investigated by refractometry. Our experimental results explicitly elucidate that the LCST values increase slightly with decreasing molecular weight. Reversibility of solubility and collapse in response to temperature well correlated with increased molecular weight of poly(NIPAM). © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011