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SYNTHESIS AND APPLICATION OF PHOTOLUMINESCENT DOPED LANTHANIDE OXIDE MICROSPHERES USING THE REACTION-DIFFUSION FRAMEWORK (RDF)
Get PDFSelf-organization is the spontaneous process whereby some form of overall spatiotem poral order arises from synergies between parts of an initially disordered system. It occurs in open systems driven away from thermal equilibrium. Liesegang banding is a type of far-from-equilibrium self-organizing phenomenon that emerges due to the coupling of diffusion to precipitation chemical reactions[1]. We can exploit Liesegang banding to make crystalline material via the so-called reaction-diffusion framework (RDF); a method which allows control over the size, morphology, and composition of crystalline solids[2]. In this work, we are particularly interested in studying the optical properties of lanthanide-doped lanthanum oxide mono-dispersed spheres synthesized in an agar hydrogel matrix via the reaction-diffusion framework (RDF). Having long excited state lifetimes in the millisecond range, resistance to photobleaching, and low toxicity, Lanthanide-doped luminescent inorganic nanoparticles give rise to promising possibilities for light-emitting applications, bioassays, and bioimaging[3], [4].
First, the lanthanum hydroxide crystals (pure and doped) are precipitated by pouring an outer electrolyte of concentrated ammonia onto agar gel containing the lanthanide salts in given initial proportions. Macroscopically, the resulting lanthanum hydroxide material forms a set of Liesegang bands. SEM images of individual bands reveal a microscopic hierarchical structure of nano-platelets selfassembling into exquisitely shaped nano- and micro- spheres[2].The average size of the spheres depends on the selection of a specific Liesegang band and the resulting set. As expected, RDF provides a green, fast and easy synthetic route to obtain lanthanide-doped nanoparticles. The dopants used include erbium, samarium, europium and terbium ions. The lanthanide doped La2O3 :Ln3+ (Ln = Eu, Sm, Eu, Tb) phosphors[5] are obtained from the corresponding hydroxide by calcination. The emission spectra of the lanthanide-doped La2O3 phosphors are found to exhibit 2 classic sharp easily recognizable inner-shell 4f-4f transitions which span both the visible and near-infrared (NIR) ranges[4].
[1] A. Lewis, M. Seckler, H. Kramer, and G. Van Rosmalen, Industrial crystallization: fundamentals and applications. Cambridge University Press, 2015.
[2] G. A. Al Akhrass, M. Ammar, H. El-Rassy, and M. Al-Ghoul, “Self-assembled lanthanum hydroxide microspheres within a reaction–diffusion framework: Synthesis,
characterization, control and application,” RSC advances, vol. 6, no. 5, pp. 3433–3439, 2016.
[3] X. Chen, Y. Liu, and D. Tu, Lanthanide-doped luminescent nanomaterials. Springer, 2016.
[4] J.-C. G. B¨unzli, “Lanthanide luminescence for biomedical analyses and imaging,” Chemical reviews, vol. 110, no. 5, pp. 2729–2755, 2010.
[5] R. Yadav, S. Dhoble, and S. Rai, “Improved photon upconversion photo luminescence and intrinsic optical bistability from a rare earth co-doped lanthanum oxide phosphor via bi 3+ doping,” New Journal of Chemistry, vol. 42, no. 9, pp. 7272–7282, 2018
Attack on Titan and The Hunger Games: Dystopias with an Orwellian Foundation
Get PDFDystopia as a genre has gained the attention of literary scholars as many dystopian works have been analyzed for the elements, reflections, and sociopolitical critiques they carry. 1984 is a popular dystopia, written by George Orwell, which became the stepping stone for other dystopian works. Among these works are The Hunger Games trilogy, by Suzanne Collins, and Attack on Titan, by Hajime Isayama. In this thesis, I explored both texts in the light of 1984, and it became evident that they follow the patterns and integrate elements from the Orwellian dystopia. Then, I explored the character development in all three works, and it showed how the literary medium, the style of the author, and the purpose of the character affect the method and depth of development
STANDARDS AND PITFALLS IN ADMINISTRATING PERFORMANCE GUARANTEES IN CONSTRUCTION CONTRACTS
No full textPerformance guarantees are used to protect project owners against the contractor’s weak performance. Various international forms of general conditions, such as FIDIC and others, necessitate the use of this financial instrument in every construction contract. However, when circumstances lead employers to call on the performance guarantee, ambiguity prevails around the legal principles, as well as the contractual procedures to be followed when using this form of security.
Furthermore, employers’ entitlement to receive money under the guarantee is not well defined, and the limitations of contractors’ non-performance are not clearly specified especially in the case of first demand performance guarantee.
In addition to this, different interpretations may rise between parties due to a possible lack in drafting the performance guarantee itself, or due to a contradiction in the terms and conditions of guarantee.
This thesis sets out a reference containing a comprehensive overview and recommendations to be considered by contracts’ practitioners while dealing with performance guarantees, assisting them in avoiding potential pitfalls.
This is achieved first by understanding the available information provided in literature review, standard forms of conditions, and laws concerning the performance guarantee. We also address the language and different wording used in drafting the letter of guarantees. Finally, we investigate real-life situations where the performance guarantee is called by the beneficiary.
Major findings show that agreement between parties on the terms of use of guarantee is of significant importance in the early stages of contract negotiation. Moreover, attention to country laws, and consistent guarantee terms, are critical while drafting a new performance guarantee
Wide Tangent Photon Field Versus Electron Field in the Treatment of Internal Mammary Lymph Nodes in Patients With Left Breast Cancer: A Decision-Making Flowchart
Get PDFPurpose: This study of internal mammary lymph node chain (IMC) irradiation in patients with left breast cancer aimed at comparing the merits of using, on one hand, a dedicated direct IMC electron field versus a wide tangent photon field covering both breast and IMC on the other. The objective was to produce guidelines allowing clinicians to readily determine the preferred method for each patient. Methods and Materials: For 19 patients with cancer of the left breast/chest wall, we produced 2 treatment plans each using a different technique: the electron technique using 2 standard opposed photon tangents covering only the breast or chest wall along with a matching adjacent electron field targeting the IMC only or the wide tangent technique using 2 opposed wide tangents covering simultaneously IMC and breast or chest wall. All plans were then optimized for acceptable target coverage. Results: For patients where the left anterior descending coronary artery (LAD) was located outside of the wide tangent fields (13 patients), the wide tangent technique resulted in lower dose to the LAD, left lung, and heart. When the LAD was inside the wide tangents (6 patients), dose was lower with the electron technique for LAD and heart. In all cases, regardless of LAD location, the wide tangent technique returned strictly superior dose homogeneity but much higher right (contralateral) breast dose. Conclusions: A flowchart was produced based on LAD location that allows the clinician to readily determine the preferred technique for each patient without having to perform and compare 2 treatment plans, thus saving valuable planning time. © 2023 The Author
Formative interventions for science teachers’ expansive learning and practices with multilingual learners: A case study from Lebanon
No full textThis paper illustrates utilising cultural historical activity theory (CHAT) and the methodology of formative intervention as a responsive capacity-building framework for enhancing science teachers’ professional development and system-level capacity in multilingual settings. We report findings from the initial Change Laboratory (CL) meetings of an ongoing formative intervention project with two schools. CL meetings are explored as ‘dialogic’ spaces for teachers, teacher-leaders and researchers to explore research-based notions alongside practical knowledge for transformative professional development that upholds teacher agency and leverages multilingual students’ diverse resources. Data included meeting transcripts, classroom observations, researcher notes and classroom artefacts. Results showed that higher levels of dialogic struggle around the role of language in teaching and learning science allowed one school’s participants to challenge deficit orientations that allot the home language a lower status and to begin adopting more linguistically responsive practices to enhance their diverse students’ science learning. We discuss the differences between the two schools through the notion of ‘boundary-crossing.’. © 2023 International Professional Development Association (IPDA)
Microbial inactivation kinetics of UV LEDs and effect of operating conditions: A methodological critical analysis
No full textTiny ultraviolet (UV) light-emitting diodes (LED)s that are replacing the conventional energy-intensive mercury UV lamps have gained interest since the early 2000's because of their promising advantages. In the context of microbial inactivation (MI) of waterborne microbes, disinfection kinetics of those LEDs exhibited variations among studies, in terms of varying the UV wavelength, the exposure time, power, and dose (UV fluence) as well as other operational conditions. While reported results may appear contradictory when examined separately, they probably are not when analyzed collectively. As such, in this study, we carry out a quantitative collective regression analysis of the reported data to shed light on the kinetics of MI by the emerging UV LEDs technology alongside the effects of varying operational conditions. The main goal is to identify dose response requirements for UV LEDs and to compare them to traditional UV lamps in addition to ascertaining optimal settings that could help in achieving the optimal inactivation outcome for comparable UV doses. The analysis showed that kinetically, UV LEDs are as effective as conventional mercury lamps for water disinfection, and at times more effective, especially for UV resistant microbes. We defined the maximal efficiency at two wavelengths, 260–265 nm and 280 nm, among a wide range of available LED wavelengths. We also defined the UV fluence per log inactivation of tested microbes. At the operational level, we identified existing gaps and developed a framework for a comprehensive analysis program for future needs. © 2023 Elsevier B.V
Ketogenic Diet and the Skin
No full textIn dermatology, the role of dietary modifications as a means to manage or prevent skin disorders has recently gained special attention among patients and physicians. This is especially true for the currently popular ketogenic diet (KD), which comprises low carbohydrate, high fat, and adequate amount of protein. Recent evidence from basic science research, small clinical trials, population studies, and reports has presented promising potential role of KD as a supplementary or adjuvant treatment in different cutaneous disorders mainly due to its anti-inflammatory properties. This review is directed at raising awareness among dermatologists on the potential uses of KD in managing skin disorders, such as acne, psoriasis, and hidradenitis suppurativa, among others. In addition, cutaneous adverse reactions, such as prurigo pigmentosa and nutritional deficiencies, which have been associated with KD, are also discussed in this review
THE IMPACT OF A SEVERE ECONOMIC AND FINANCIAL CRISIS ON CONSTRUCTION THE CASE OF LEBANON
Get PDFThe Lebanese crises, including economic and political instability, have had a significant impact on construction projects and contracting companies in the country. The purpose of this thesis study is to document and evaluate this impact, by examining the challenges faced by both construction projects and contracting companies in the current climate. The study adopts both qualitative and quantitative research methods, including interviews with industry professionals and surveys of construction companies. Through this research, the study aims to identify the key factors that have disrupted the conventional way of administering construction projects, to assess the impact of the financial and economic crises on both construction projects and contracting firms, and to propose potential mitigation measures sorted according to Porter‘s strategies (1980) to address these challenges. In addition to the above, the study focuses on calculating the Relative Importance Index (RII) of factors causing delays for Lebanese construction crises and the effectiveness of mitigation measures adopted by practitioners amid the crises. The results of the RII analysis indicate that the most important factor causing delay during the financial and economic crises is the necessity for currency conversion for procurement purposes and the continuous fluctuation of construction materials. The study also finds that the most effective mitigation measure adopted by practitioners is to secure projects funded by foreign currency, decrease profit margins to secure more projects and others. This study provides valuable insights for policymakers, industry professionals, and other stakeholders in the construction industry to address the challenges faced by construction projects and contracting companies in Lebanon
Predicting water quality variability in a Mediterranean hypereutrophic monomictic reservoir using Sentinel 2 MSI: the importance of considering model functional form
Get PDFAnthropogenic eutrophication is a global environmental problem threatening the ecological functions of many inland freshwaters and diminishing their abilities to meet their designated uses. Water authorities worldwide are being pressed to improve their abilities to monitor, predict, and manage the incidence of harmful algal blooms (HABs). While most water quality management decisions are still based on conventional monitoring programs that lack the needed spatio-temporal resolution for effective lake/reservoir management, recent advances in remote sensing are providing new opportunities towards better understanding water quality variability in these important freshwater systems. This study assessed the potential of using the Sentinel 2 Multispectral Instrument to predict and assess the spatio-temporal variability in the water quality of the Qaraoun Reservoir, a poorly monitored Mediterranean hypereutrophic monomictic reservoir that is subject to extensive periods of HABs. The work first evaluated the ability to transfer and recalibrate previously developed reservoir-specific Landsat 7 and 8 water quality models when used with Sentinel 2 data. The results showed poor transferability between Landsat and Sentinel 2, with most models experiencing a significant drop in their predictive skill even after recalibration. Sentinel 2 models were then developed for the reservoir based on 153 water quality samples collected over 2 years. The models explored different functional forms, including multiple linear regressions (MLR), multivariate adaptive regression splines (MARS), random forests (RF), and support vector regressions (SVR). The results showed that the RF models outperformed their MLR, MARS, and SVR counterparts with regard to predicting chlorophyll-a, total suspended solids, Secchi disk depth, and phycocyanin. The coefficient of determination (R 2) for the RF models varied between 85% for TSS up to 95% for SDD. Moreover, the study explored the potential of quantifying cyanotoxin concentrations indirectly from the Sentinel 2 MSI imagery by benefiting from the strong relationship between cyanotoxin levels and chlorophyll-a concentrations. © 2023, The Author(s), under exclusive licence to Springer Nature Switzerland AG
A Nonlinear Recession Model for Horizontal Aquifers
Get PDFRecession analysis is a powerful tool for determining the hydraulic characteristics of a riparian aquifer. The basis of the method relies on two analytical solutions of the nonlinear Boussinesq equation: one applies to a uniform water table profile in a semi-infinite aquifer while the other pertains to a hypothetical initial profile in a finite aquifer. Both solutions assume that the water depth in the adjoining stream is negligible. In the present work, a nonlinear solution of the one-dimensional Boussinesq equation is derived using the traveling wave approximation. The solution better represents the field conditions as it pertains to a uniform water table profile in a finite aquifer that is adjoining a stream with a non-zero water level. It allows the derivation of simple algebraic expressions for the recession of the water table, the flow rate, and the associated drainage volume. Approximations relating the discharge rate to the outflow volume were also obtained for practical implementation in the estimation of the hydraulic parameters of the aquifer. A comparison of the proposed methodology of parameter estimation with the standard method of recession analysis showed that the present approach is superior as it avoids the pitfalls associated with the classical method, especially when daily discharge values with inherent observational errors are used. Application of the recession model to real-world cases demonstrates its effectiveness in the estimation of the catchment-scale hydraulic conductivity and drainable porosity. © 2023. American Geophysical Union. All Rights Reserved