Maximum TL Research Articles

Biochar derived from watermelon rinds as regenerable adsorbent for efficient removal of thallium(I) from wastewater

Discarded watermelon rinds were used to prepare porous biochars, which act as regenerable adsorbents for treating both synthetic and real Tl-containing wastewater. The primary biochar prepared under pyrolysis temperature of 500 °C was found to be the most effective for Tl(I) removal. The primary biochar had the best Tl(I) removal efficacy over a wide pH range (4–12), followed by the KOH-modified and HCl-modified biochar. Maximum Tl(I) adsorption capacity reached 178.4 mg/g, which is superior to that of other biochar. Strong resistance to the interference from co-existing cations and organics on Tl(I) removal was also observed during treatment of complex synthetic and real industrial wastewater. Characterization techniques such as X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectra, high resolution transmission electron microscope (HRTEM), and X-ray photoelectron spectroscopy (XPS) reveal that the K- and Cl-rich primary biochar acts as regenerable amphibious ion exchange resins to perform reversible adsorption and desorption of Tl(I). The biochar derived from watermelon rinds exhibits effective Tl(I) removal performance and strong regenerability, and is a promising adsorbent for Tl(I) removal with excellent application prospects.

Efficient removal of thallium(I) from wastewater using flower-like manganese dioxide coated magnetic pyrite cinder

The development of highly selective, effective, and regenerable adsorbents with good separability for thallium (Tl) removal remains a challenge. In this study, a hierarchical composite containing MnO2 and magnetic pyrite cinder was fabricated to remove Tl(I) from wastewater. SEM, TEM, XRD, BET, and VSM analyses indicate that the hierarchical composite was composed of amorphous, flower-like MnO2 as outer coating and magnetite-dominated pyrite cinder as inner core, with a specific surface area of 29.1 m2/g and saturation magnetization of 15.4 emu/g. Good Tl(I) adsorption was achieved over a wide pH range from 2 to 12. A maximum Tl(I) adsorption capacity of 320 mg/g was attained at pH 12. The presence of Na+, Mg2+, and humic acid had little effect on Tl(I) removal, indicating the high selectivity of this adsorbent. The adsorption isotherm data were better fitted by the Langmuir model, while the pseudo-second order model was more suitable for describing the kinetic data. The composite was effectively regenerated using 1 mol/L HCl solution in only 5 min, and the Tl(I) adsorption capacity of the composite did not change significantly even after the fifth regeneration. Tl(I) removal was mainly achieved via surface complexation, followed by oxidation and electrostatic attraction. This flower-shaped MnO2 coated pyrite cinder composite shows promise for Tl(I) removal due to its excellent efficiency, selectivity, separability, and reusability.

Effect of rare earth doping on optical and spectroscopic characteristics of BaZrO3:Eu3+,Tb3+ perovskites

This paper reports structural investigations of rare earth doped BaZrO3 phosphors synthesized by Solid state reaction technique with varying concentrations of Eu3+ and Tb3+ from 0 mol% to 2 mol%. The synthesized phosphors show enhanced variable emissions in the visible region corresponding to different hypersensitive electronic transitions of Eu3+ and Tb3+ ions. With cubic structure confirmed in XRD analysis, the FESEM images show uniform grain connectivity and homogeneity of prepared samples. The TEM micrographs of the synthesized phosphors show agglomerated irregular structures. The synthesized phosphors were also subjected to FTIR, Raman, EDXS analysis along with studies of thermoluminescent and photoluminescent characteristics. On subjecting to 229 nm (UV) excitation, the phosphors show enhanced PL emissions corresponding to 571 nm (5D0-7F0), 591 nm (5D0-7F1), 615 nm (5D0-7F2) and 678 nm (5D0-7F4) hypersensitive transitions of Eu3+ ions and emission peaks at 489 nm (5D4-7F6), 539 nm (5D4-7F5), 589 nm (5D4-7F4) and 632 nm (5D4-7F3) accounting for electronic transitions of Tb3+ ions respectively. The computed average PL lifetime is 14.014 s. In the TL analysis, the second order of kinetics with the activation energy varying from 5.0 × 10−1 eV to 6.6 × 10−1 eV is reported. The maximum TL lifetime is estimated as 19.4985 min in the TL lifetime analysis.

Effect of dopants on the TL response of the new LiF:Mg,Cu,Ag material

The new TL LiF:Mg,Cu,Ag material was prepared and investigated in this study. The TL intensity of LiF:Mg,Cu,Ag is strongly dependent on the concentration of dopants and the preparation procedure. Any small change in these factors can cause alterations in TL response. In this study, the influence of Cu and Ag concentrations on the response of the LiF:Mg,Cu,Ag sample was investigated and showed that the height of the low, main and high temperature peaks changes with Ag concentration. Their intensities increased with increasing Ag concentration to a maximum value and decreased with higher Ag concentration. It was also found that Cu concentration less than 0.05 mol% influences the maximum peak height and TL intensity. The optimum Cu and Ag concentrations were found to be 0.05 and 0.1 mol% at 1005 °C QT, respectively. The role of dopants in LiF:Mg,Cu,Ag material was also investigated. The results showed that presence of three dopants is important for having material with sensitivity higher than LiF:Mg,Ti. The Mg dopant plays a crucial role in the formation of the trapping center and the position of the main dosimetric peak.

Dependence of the peak shift, peak height and FWHM of thermoluminescence peaks on the heating rate and trap parameters

The temperature shift of the maximum TL intensity towards higher temperatures with increasing heating rate is a well known phenomenon. The explanation of such phenomenon is qualitatively understandable. In the present work we predict the temperature shift of the peak intensity quantitatively by analyzing synthetic general-order glow peaks. The obtained expression correlates the temperature shift with the heating rate and the trap parameters. Similar expressions to predict the peak height and the full width at half maximum (FWHM) at higher heating rates are also given. The errors involved in applying these expressions are within the expected experimental errors. The obtained expressions resulted in two new versions of the existing various heating rates methods to evaluate the activation energy which can be used irrespective of the order of kinetics. One of these methods was applied to the TL data of LiF:Mg,Ti and Al2O3:C and shows excellent agreement with the published values for the activation energy. In addition, a new expression to correct for the temperature lag was given which shows little improvement in predicting the correct peak temperature when compared with the existing one.

Thermoluminescence and Photoluminescence Study of Erbium Doped CaY2O4 Phosphor

Phosphor doped with erbium ion with variable concentration (0.5–2 mol%) was synthesized by solid state reaction method. CaY2O4:Er3+ phosphor is characterized by X-ray diffraction technique for structural analysis and crystallite size calculation. Average crystallite size was found to be nearly 58 nm. Two prominent TL glow peaks found at 163°C associated with higher temperature peak 340°C. The peak intensity of higher temperature (340°C) peak was less as compared to lower temperature peak (163°C) because the deep trapping formation is less in case of UV irradiation. Sample shows good TL glow curve and for variable UV exposure time maximum TL intensity was found at 20 min UV exposure which is optimized UV exposure time. Sample was studied by photoluminescence emission spectra excited by xenon flash lamp with nearly 360 nm and four prominent peaks found at wavelengths 445, 525, 553, and 565 nm; here the 445 and 565 nm peak were intense as compared to others. From the PL emission spectra, it is concluded that the color tenability of prepared CaY2O4:Er3+ was blue-green and it is verified by CIE coordinate. Kinetic parameters of prepared phosphor were calculated by computerized glow curve deconvolution (CGCD) technique.

Food web of the intertidal rocky shore of the west Portuguese coast – Determined by stable isotope analysis

The characterization of food web structure, energy pathways and trophic linkages is essential for the understanding of ecosystem functioning. Isotopic analysis was performed on food web components of the rocky intertidal ecosystem in four sites along the Portuguese west coast. The aim was to 1) determine the general food web structure, 2) estimate the trophic level of the dominant organisms and 3) track the incorporation of organic carbon of different origins in the diet of the top consumers. In this food web, fish are top consumers, followed by shrimp. Anemones and gastropods are intermediate consumers, while bivalves and zooplankton are primary consumers. Macroalgae Bifurcaria bifurcata, Ulva lactuca, Fucus vesiculosus, Codium sp. and phytoplankton are the dominant producers. Two energy pathways were identified, pelagic and benthic. Reliance on the benthic energy pathway was high for many of the consumers but not as high as previously observed in subtidal coastal food webs. The maximum TL was 3.3, which is indicative of a relatively short food web. It is argued that the diet of top consumers relies directly on low levels of the food web to a considerable extent, instead of on intermediate levels, which shortens the trophic length of the food web.

Species richness and abundance of non-cryptic fish species in the Philippines: a global center of reef fish diversity

The Philippines is dubbed the ‘global center of marine biodiversity’ for having the greatest number of reef fish species per unit area in the world, mainly based on analysis of museum collections. However, to date, there is no national assessment of the status of Philippine reef fish species based on species abundance and distribution. We conducted underwater visual census belt transect surveys of all non-cryptic reef fish, to explore spatial trends in fish biodiversity and to assess the national status of Philippine reef fish species. We found that most places in the Philippines still hold high numbers of non-cryptic reef fish species, with 54 % of the surveyed transects having ≥22 reef fish species per 100 m2. However, only 13 % of all recorded species had high abundances (≥0.81 individuals per 100 m2) and wide distributions (≥291,964 km2) (category A species), while 33 % had either low abundances or restricted distributions (category B species), and 54 % exhibited both low abundances and restricted distributions (category C species). In addition, 97 % of the large-bodied species (maximum TL > 30.1 cm) were assigned to category B or C—a matter of concern, since 47 % of the recorded large-bodied species in our study are food-fish. The findings of our study present the most recent (2012–2013) national assessment for all non-cryptic reef fish species using standardized methods, and highlight the need for conservation action for many Philippine reef fish species, upon which many Filipinos derive benefits such as food, income, livelihood, and recreation.

Spawning, maturity, growth and movement of Platycephalus fuscus (Cuvier, 1829) (Platycephalidae): fishery management considerations

The dusky flathead (Platycephalus fuscus) is an important teleost harvested by recreational and commercial fishers throughout its endemic distribution along eastern Australia. This study indicates that the species has an extended spawning period throughout the austral summer, with females in spawning condition occurring in lower estuarine and coastal waters. Total length (L50) and age (A50) at which 50% (±1 SE) of the population was mature was 31.72 (±1.08) cm TL and 1.22 (±0.44) years for males and 56.75 (±0.60) cm TL and 4.55 (±0.13) years for females. The von Bertalanffy growth parameters differed significantly between sexes; females grew faster and attained a greater maximum TL and age than males. The largest female was 98.5 cm TL (7.5 kg), and the oldest 16 years, whereas the largest male was 61.5 cm TL (1.58 kg) and 11 years of age. A tag-and-release study identified the exchange of sub-adult and mature-sized individuals among estuaries. Determinations of length-based management regulations for the species are compounded by the large gender-based differences in growth and length-at-maturity. Current minimum legal lengths of 30–40 cm TL protect approximately 3–9% of the female spawning population. Alternative management options, including harvest slot sizes, need to be investigated and tested.

Thallium contamination of soils/vegetation as affected by sphalerite weathering: A model rhizospheric experiment

The environmental stability of Tl-rich sphalerite in two contrasting soils was studied. Rhizospheric conditions were simulated to assess the risk associated with sulfide microparticles entering agricultural (top)soils. The data presented here clearly demonstrate a significant effect of 500μM citric acid, a model rhizospheric solution, on ZnS alteration followed by enhanced Tl and Zn release. The relative ZnS mass loss after 28 days of citrate incubation reached 0.05 and 0.03wt.% in Cambisol and Leptosol samples respectively, and was up to 4 times higher, compared to H2O treatments. Incongruent (i.e., substantially increased) mobilization of Tl from ZnS was observed during the incubation time. Generally higher (long-term) stability of ZnS with lower Tl release is predicted for soils enriched in carbonates. Furthermore, the important role of silicates (mainly illite) in the stabilization of mobilized Tl, linked with structural (inter)layer Tl–K exchange, is suggested. Thallium was highly bioavailable, as indicated by its uptake by white mustard; maximum Tl amounts were detected in biomass grown on the acidic Cambisol. Despite the fact that sulfides are thought as relatively stable phases in soil environments, enhanced sulfide dissolution and Tl/trace element release (and bioaccumulation) can be assumed in rhizosphere systems.

Design and test research on semi-active muffler system based on the H-Q tube

In this paper, one type of semi-active muffler system is designed to reduce diesel engine exhaust noise, especially the low frequency noise. The muffler is based on the principle of Herschel-Quincke tube. Different from other mufflers, this one can change the control fundamental frequency with valves. In the certain control frequency interval between two adjacent fundamental frequencies, it can meet the resonance condition by the stepper motor automatically. Both the valves and the stepper motor are under command of the designed controller. Transmission loss and insertion loss experiments of the muffler have been conducted. Experimental results show that the semi-active muffler has a substantial noise reduction: from 35 to 100 Hz. The maximum TL of the muffler is approaching 35 dB. The IL has an average of 11 dB attenuation in the entire range of 35 to 100 Hz.

The real world transmission loss chamber: A work in progress

A “real world” transmission loss (RWTL) chamber was recently added to the undergraduate acoustics program at Columbia College Chicago. It aims to demonstrate concepts of transmission loss to students and to provide a “less-than-ideal” environment for construction evaluation prior to certified tests with full-size samples. Each side of the chamber can be used as either “send” or “receive,” and both speaker and microphone placements are infinitely variable. The noise floor can also be adjusted to illustrate potential issues in field tests. Measurements are taken simultaneously from multiple positions, then averaged to yield TL values and an overall isolation rating. Given its construction, the chamber is not expected to produce results as per existing standards as its small size results in modal effects and non-diffuse conditions on both sides of the tested partition. This study’s first goal was to better understand the performance limitations of the RWTL chamber by conducting a thorough evaluation of its maximum TL and modal properties. The second goal was to optimize the chamber’s testing methodology in order to more closely reflect certified laboratory results; this was done by utilizing recently obtained certified data from a door manufacturer who tested reduced-sized samples in the RWTL chamber.

Synthesis and dosimetry characteristics of a new high sensitivity TLD phosphor NaLi2PO4:Eu3+

A new highly sensitive, low-Z (Zeff ≈ 10.8) TLD phosphor, Eu3+ doped NaLi2PO4, was successfully synthesized via solid state diffusion method. The formation of the single phase compound was confirmed by Powder X-Ray diffraction (PXRD) analysis. Variation of the doping level has shown that the impurity (Eu3+) concentration for maximum TL sensitivity is 0.5 mol%. Heat treatments given to achieve the high TL sensitivity of this phosphor also showed that it needs to be annealed at 973 K for 1 h. Incorporation of the impurity in the Eu+3 states was confirmed by the PL emission peaks. The TL glow curve consists of a prominent dosimetry peak at around 458 K besides small shoulders on both sides at around 400 and 500 K. The dose response of the phosphor was found to be sub-linear up to 10 Gy of the dose and later it becomes linear till it start saturating beyond 1 kGy. The TL sensitivity of the newly developed NaLi2PO4:Eu3+ phosphor to γ radiation from 137Cs (in the linear dose range) was compared to some standard commercially available phosphors, such as, TLD-100, TLD-400, TLD-700H and TLD-900. It was found to be much more sensitive than these phosphors except TLD-700H, which is ∼2 times more sensitive. Easy method of synthesis, simple glow curve structure, high sensitivity, low fading, wide range of doses and very good reusability make the phosphor a suitable candidate for the TL dosimetry.

Synthesis, characteristics and thermoluminescent dosimetry features of γ-irradiated Ce doped CaF2 nanophosphor

Nanoparticles of cerium doped calcium fluoride (CaF2:Ce) were synthesized for the first time using the hydrothermal method. The formation of nanostructures was confirmed by X-ray diffraction (XRD) patterns, indicating cubic lattice structure for the particles produced. Their shape and size were observed by scanning electron microscopy (SEM). Thermoluminescence characteristics were studied by having the samples irradiated by gamma rays of 60Co source. The optimum thermal treatment of 400°C for 30min was found for the produced nanoparticles. The Tm−Tstop and computerized glow curve deconvolution (CGCD) methods, used to determine the number of component glow peaks and kinetic parameters, indicated seven overlapping glow peaks on the TL glow curve at approximately 394, 411, 425, 445, 556, 594 and 632K. A linear dose response of up to 2000Gy, was observed for the prepared nanoparticles. Maximum TL sensitivity was found at 0.4mol% of Ce impurity. Other TL dosimetry features, including reusability and fading, were also presented and discussed.

The effect of pre-irradiation annealing on the thermoluminescence of LiF:Mg, Cu, P phosphor grown by EFG technique

LiF crystal doped with magnesium (Mg), copper (Cu) and phosphorous (P) was grown in the form of multicrystalline sheet using Edge-defined film-fed growth (EFG) technique for dosimetry application. These crystals were grown in argon gas atmosphere using graphite crucible and stainless steel die. Dosimetry peak was observed at 210 °C for as-grown crystal. As reported earlier LiF:Mg, Cu, P is a highly sensitive material but losses its sensitivity if annealed at temperature above 240 °C. In this paper, the effect of annealing temperature on thermoluminescence glow-curve structure, maximum peak temperature, peak height and integrated area of the glow peak of EFG grown samples was investigated in detail. Annealing temperature range from 220 °C to 500 °C was considered for the study. Experimental results of the obtained glow curve show that with increase in annealing temperature, glow peak shift towards higher temperature region with substantial increase in TL intensity. Annealing at 500 °C for 10 min gave maximum TL intensity with main dosimetry peak positioned at 233 °C. Change in the defect structure with different pre-annealing temperature was analysed using trapping parameters. ► LiF:Mg, Cu, P phosphor in crystal form has been prepared using EFG technique. ► TL intensity increases with increasing annealing temperature from 220 °C to 500 °C ► Highest TL intensity is observed at annealing temperature of 500 °C ► Advantage of EFG technique for developing TL phosphor is discussed.

Abstract 19728: Translesional Time to Determine Complete Bidirectional Block Across the Cavotricuspid Isthmus

Introduction: The goal of ablation of typical atrial flutter is to create complete bidirectional block across the cavotricuspid isthmus (CTI). The purpose of this study was to document whether there was a transisthmus time that is associated with complete bidirectional isthmus block (CBIB). Methods: Thirty consecutive patients who had CTI ablation procedures were assessed. A circular right atrial mapping catheter, coronary sinus catheter, and electroanatomical mapping were used in all patients. Before ablation, points were marked medial and lateral to the planned line and bidirectional conduction times were assessed. Post ablation bidirectional conduction times were assessed again at the points medial and lateral to the line. The translesional time (TL) was defined as the difference in bidirectional conduction time recorded lateral to the line from medial to the line. CBIB was verified by reversal of activation of the right atrium on the circular mapping catheter and/or documentation of widely spaced double potentials. Results: CBIB was achieved in 29/30 patients. The average baseline counterclockwise (CCW) conduction time across the CTI was 43 +/- 22 msec The average baseline clockwise (CW) conduction time was 42 +/- 16 msec. The average baseline TL was 10 msec CCW, and 9 msec CW. The longest baseline TL was 52 msec CCW and 28 msec CW . Post ablation, the average CCW conduction time was 149 msec, and CW was 150 msec in patients with CBIB. The average TL in patients with CBIB was 116 msec CCW and 111 msec CW. The shortest TL associated with CBIB was 90 msec CCW and 91 msec CW. The maximum TL associated with incomplete block was 68 msec. Conclusions: A bidirectional TL of greater 90 msec was predictive of CBIB after typical atrial flutter ablation, and could be used simplify assessment of CBIB during CTI ablation.

Electron-Trap model: TL mechanism in BaSO4 nanophosphor—A new approach

Barium sulphate nanophosphor was synthesized through the water–ethanol (70vol%) mixed solvent system by varying the concentration ratios of the basic reagents. The optimum concentration of the basic reagents was fixed on the basis of minimum crystalline size through X-ray diffraction (XRD) analysis. The Field Emission Scanning Electron Microscopy (FESEM) analysis shows that the particles are in spherical shape without agglomeration and the size is around 30nm. The TL glow curve measurements were carried out for as synthesized sample (different doses) and different annealing temperatures (100–1000°C). From annealing process, 800°C is the optimum temperature for getting maximum TL intensity. The possible mechanism for getting the TL glow curve is explained briefly through the Electron-Trap model. Further, the structural and morphological characterizations of 800°C annealed sample were carried out through XRD and FESEM analyses. The results show no structural changes. However, increase in crystalline size is noticed for annealed sample (around 50nm) compared to the unannealed (around 30nm) one.

Enhancement of lipid accumulation in Scenedesmus obliquus by Optimizing CO2 and Fe3+ levels for biodiesel production

The effects of cultivation of Scenedesmus obliquus in nutrient medium supplemented with 0.03%, 3, 9% and 12% CO2 or 2.5–20mgL−1 of Fe3+ on dry weight of biomass (DW), total lipid accumulation (TL contents) and total lipid productivity (TLP) were evaluated under indoor conditions. The accumulation of TL and TLP showed an increasing trend with increasing of CO2 or Fe3+ levels. In cultures with 12% CO2 or 20mg/L Fe3+, maximum TL contents of 33.14% and 28.12%, respectively were obtained. These lipids displayed a fatty acid profile which is suitable for biodiesel production as the most abundant compounds were oleic (32.19–34.44%), palmitic (29.54–25.12%) and stearic (12.26–16.58% of total FAMEs) acids. The properties of biodiesel obtained from S. obliquus, were the same with those specification for biodiesel standards including ASTM D 6751 (American Society for Testing Material) and the European Standard En 14214. Thus, S. obliquus biomass could be used as suitable feedstock for biodiesel production.

Luminescence characteristics of Ca1−xSrxS:Ce nanophosphors

Luminescence characteristics of Ca1−xSrxS:Ce (x=0, 0.25, 0.50, 1) nanophosphors have been investigated. XRD of all the samples show a single cubic phase of Ca1−xSrxS:Ce. TEM micrographs exhibit the rod like structure of the samples with a decrease in diameter with decreasing amount of Ca. The results of TEM were found to be in good agreement with the XRD results. The photoluminescence spectrum comprises of a main peak in the range 480–510nm with a shoulder in the range 530–565nm, which may be ascribed to transitions from 5d–4f levels of cerium in the mixed host lattice. The red shift in the emission wavelength with increasing Ca content may be correlated with the change in crystal field of mixed host lattice for different Ca and Sr concentrations. We have also investigated TL response of Ca1−xSrx:Ce to 60Co-γ rays. All the samples with different Sr and Ca contents show different TL response. TL response for the sample with x=0.75 shows the simplest TL glow curve with the maximum TL intensity, for which we have calculated the activation energy using glow curve deconvolution functions.

Nonlinear dose dependence of TL and LM-OSL within the one trap-one center model

In a recent paper, it has been shown that strong sub-linearity of the occupancy n0 of trapping states far from saturation can be explained by the simplest model of one trap-one recombination center (OTOR). In the present work we report on results of numerical simulation of dose dependence of the TL maximum under similar conditions. In some cases, the TL maximum is found to be strictly proportional to the filling of the traps, but this is not always the case. Different sublinear dose-dependence functions of the trap occupancy and the maximum TL are demonstrated. With the same sets of parameters, curves of LM-OSL have also been simulated; superlinear as well as sublinear dependencies on the excitation dose have been found.