Characterization Of Superparamagnetic Iron Oxide Nanoparticles With Different Surfactants - In Search Of Optimum Synthesis Parameters For Mri Application

Superparamagnetic iron oxide nanoparticles (SPIONs) have been extensively studied for various biomedical applications, such as magnetic resonance imaging (MRI) contrast agents, and hyperthermia. The most common approach used to produce SPIONs is co-precipitation method. However, problem due to agglomeration and the broad size distribution of nanoparticles prepared by co-precipitation method hinder their application progress in MRI. Therefore, this study aims to produce a highly stabilized and monodispersed SPIONs for MRI contrast agents. In this thesis, SPIONs were synthesized with different surfactants (tri-sodium citrate, polyvinylpyrrolidone (PVP), chitosan, cetyl trimethylammonium bromide (CTAB) and citric acid) using the one pot co-precipitation method for surface modification and to ensure excellent colloidal stability in water. In addition, the synthesis parameters such as surfactant concentration, pH, and temperature of reaction were optimized to obtain stabilized SPIONs. The SPIONs prepared in the presence of tri-sodium citrate formed the most stable SPIONs due to improved physiological condition, dispersion and stabilization in aqueous solution. In addition, citrate-SPIONs displayed the highest zeta potential (ζ= -44.0 mV) and saturation magnetization (Ms=53.9 emu g-1) compared with other samples, due to the ability of three carboxylate groups dissociated from the citrate to strongly bind to the surface of SPIONs. The TEM measurements of the different SPIONs indicated that the type of surfactant affects their average particle sizes and size distribution. In addition, the presence of defects within the spinel structure, i.e., oxidation of the SPIONs, seems to be also influenced by the choice of surfactant

The Impact of Intellectual Capital on Operational Performance in Jordanian Service Companies: Evidence from the Amman Stock Exchange

Purpose: This study seeks to determine how intellectual capital (IC) affects the operational effectiveness of service companies listed on the Jordanian Amman Stock Exchange (ASE).   Theoretical framework: The study is based on the concept of intellectual capital, which encompasses human capital, structural capital, and relational capital. These dimensions are examined to understand their influence on operational performance.   Design/Methodology/Approach: The study population consists of 40 service companies listed on the ASE, with a sample of 22 companies selected for analysis. Data collection relied on secondary sources, including reports and bulletins issued by the ASE between 2017 and 2021. Regression analysis is used in the study to look at the connections between several operational performance metrics and intellectual capital.   Findings: The findings reveal that human capital and structural capital have a significant positive impact on operational flexibility. Human capital and relational capital significantly influence cost efficiency. Structural capital, company size, and company age show significant effects on the inventory turnover rate. Human capital positively affects the asset turnover rate, while structural and relational capital do not exhibit significant effects.   Research, Practical & Social implications:  This study offers insightful information about the connection between intellectual property and operational effectiveness in service businesses listed on the ASE. The findings have practical implications for enhancing operational capabilities and efficiency within these organizations. Additionally, the study contributes to the existing knowledge on intellectual capital's impact on operational performance and fills a gap in the understanding of this relationship in the Jordanian context.   Originality/Value:  This study is one of the first to investigate how intellectual capital affects the performance of operational aspects in service businesses listed on the ASE in Jordan. By focusing on the unique characteristics of the Jordanian market, the study adds to the body of knowledge and advances knowledge of the function that intellectual capital plays in influencing operational success

Direct recruitment of CRK and GRB2 to VEGFR-3 induces proliferation, migration, and survival of endothelial cells through the activation of ERK, AKT, and JNK pathways

AbstractVascular endothelial growth factor receptor-3 (VEGFR-3) plays a key role for the remodeling of the primary capillary plexus in the embryo and contributes to angiogenesis and lymphangiogenesis in the adult. However, VEGFR-3 signal transduction pathways remain to be elucidated. Here we investigated VEGFR-3 signaling in primary human umbilical vein endothelial cells (HUVECs) by the systematic mutation of the tyrosine residues potentially involved in VEGFR-3 signaling and identified the tyrosines critical for its function. Y1068 was shown to be essential for the kinase activity of the receptor. Y1063 signals the receptor-mediated survival by recruiting CRKI/II to the activated receptor, inducing a signaling cascade that, via mitogen-activated protein kinase kinase-4 (MKK4), activates c-Jun N-terminal kinase-1/2 (JNK1/2). Inhibition of JNK1/2 function either by specific peptide inhibitor JNKI1 or by RNA interference (RNAi) demonstrated that activation of JNK1/2 is required for a VEGFR-3–dependent prosurvival signaling. Y1230/Y1231 contributes, together with Y1337, to proliferation, migration, and survival of endothelial cells. Phospho-Y1230/Y1231 directly recruits growth factor receptor–bonus protein (GRB2) to the receptor, inducing the activation of both AKT and extracellular signal–related kinase 1/2 (ERK1/2) signaling. Finally, we observed that Y1063 and Y1230/Y1231 signaling converge to induce c-JUN expression, and RNAi experiments demonstrated that c-JUN is required for growth factor–induced prosurvival signaling in primary endothelial cells

Precipitation Variability and Probabilities of Extreme Events in the Eastern Mediterranean Region (Latakia Governorate-Syria as a Case Study)

This study aimed at analysis of the general-index change for the mean annual and seasonal precipitation in six stations in Latakia Governorate (Syria). The data of precipitation were collected for 40 consecutive years (1970–2010) in order to figure out the extent of the changes and variability in precipitation rates and the impact of this change on changes in the potential density that might cause extremely high or low precipitation rates according to Gumbel distribution of the extreme precipitation rates. Results revealed a decrease of the annual precipitation rates in all stations, the reduction in precipitation ranged from 46 to 210 mm during the whole period of the study. Spring, however, recorded the highest and statistically significant reduction, which reached 46–210 mm, while winter precipitation increased by 21–82 mm. Spring also has witnessed a decrease of about 3–9% of the total annual precipitation as compared to winter precipitation which increased by 5–8% of the total. The potential density of extremely high winter precipitation rates increased in all stations as indicated from Gumbel distribution in winter, and a greater increase took place in the probabilities of occurrence of the extremely low spring precipitation rates. This shows significant probability of occurrence of drought during spring season. By contrast, probabilities of winter precipitation rates increased more, thus winter is relatively more humid than before and spring is relatively drier than before

E/Z reversible photoisomerization of methyl orange doped polyacrylic acid-based polyelectrolyte brush films

The photoswitching behavior of the polyacrylic acid (PAA) doped by methyl orange (MO) brush film was investigated using spectral analysis of UV-Vis absorbance, Fourier Transformation Infrared spectroscopy, 2D electrical conductivity mapping and Atomic Force Microscopy. The kinetics and time evolution of the photoisomerization of the PAA-MO PEBs film from E-state to Z-state by UV-light irradiation, and reverse thermal relaxation to E-state was explored. The results confirm that the photoisomerization kinetics of the overall peak is the superposition of the photoisomerization kinetics of (Formula presented.) transition, low- and high-frequency of the (Formula presented.) transition bands. The E–Z transformation led to transforming the azobenzene from flat with no dipole moment to 3.0 D dipole moment. Hence, the electrical conductivity escalated accordingly. The transformation of E-state to Z-state led to the collapse of the formed brushes because of the angular rotational momentum consequent to E–Z isomerization

تحسين الخواص الحرارية والبنيوية لمطاط النتريل بوتاديين من خلال الفلكنة الإشعاعية

أجريت الفلكنة الإشعاعية لمتراكبات من مطاط النتريل بوتاديين (Nitrile Butadiene Rubber) الذي يحتوي نسب مختلفة من الكربون الأسود (Carbon Black) باستخدام أشعة غاما بجرعات تصل إلى (300 KGy). بينت نتائج الدراسة انخفاض نسبة انتباج المتراكبات المطاطية في زيتي الهيدروليك والمحرك مع زيادة الجرعة الإشعاعية وكذلك مع زيادة نسبة التحميل بالكربون الأسود، غير أن هذه النسبة تزداد بشكل بسيط بزيادة درجة حرارة الزيت المدروس. كما بينت نتائج التحليل الحراري للمتراكبات زيادة درجة حرارة التزجج مع زيادة الجرعة الإشعاعية نتيجة للتشابك المستحث إشعاعياً الذي يعمل على تقييد حرية حركة سلاسل المطاط النتريلي. دُرس أيضاً تأثير الجرعة الإشعاعية في مقدار تآكل المتراكبات من خلال قياس حجم الجزء المتآكل من المادة، وتبين أن مقاومة التآكل تزداد بزيادة الجرعة الإشعاعية حتى (150 KGy) ومن ثم تأخذ بالتناقص

Ab initio studies of electronic structure of defects in PbTe

Understanding the detailed electronic structure of deep defect states in narrow band-gap semiconductors has been a challenging problem. Recently, self-consistent ab initio calculations within density functional theory (DFT) using supercell models have been successful in tackling this problem. In this paper, we carry out such calculations in PbTe, a well-known narrow band-gap semiconductor, for a large class of defects: cationic and anionic substitutional impurities of different valence, and cationic and anionic vacancies. For the cationic defects, we study a series of compounds RPb2n-1Te2n, where R is vacancy or monovalent, divalent, or trivalent atom; for the anionic defects, we study compounds MPb2nTe2n-1, where M is vacancy, S, Se or I. We find that the density of states (DOS) near the top of the valence band and the bottom of the conduction band get significantly modified for most of these defects. This suggests that the transport properties of PbTe in the presence of impurities can not be interpreted by simple carrier doping concepts, confirming such ideas developed from qualitative and semi-quantitative arguments

Knowledge and Attitude towards Monkeypox among the Lebanese Population and their Attitude towards Vaccination

Monkeypox is a currently re-emerging disease in the world and several cases have been detected in Lebanon. For this reason, an assessment of the knowledge and attitude of the Lebanese population towards monkeypox and smallpox or monkeypox vaccines had to be done. A cross-sectional study was conducted using a questionnaire developed from previous literature among a sample of Lebanese residents. It recorded the sociodemographic characteristics and comorbidities of the participants and analyzed the patterns of knowledge and attitudes in Lebanon. Among 493 participants, it was found that there is a generally low knowledge of and an average attitude toward monkeypox. However, knowledge is better with higher educational levels, COVID-19 vaccination, and residency in the south of Lebanon and poorer with marriage and residency in Beirut. Attitude is better in females but poorer with higher educational levels. Several other effectors have been devised too. As for vaccination, taking the smallpox vaccine as a proactive measure is predicted with previous COVID-19 vaccination and better attitude but not in the residents of the north of Lebanon and married Lebanese residents. Higher educational levels and a better attitude were positive predictions of taking the monkeypox vaccine whenever it is developed. This study provided insights into the level of knowledge and attitude towards monkeypox and its vaccines, which can be a rich resource when proactive measures are developed

Spatio-temporal analysis for extreme temperature indices over the Levant region

The temporal and spatial trends of 16 climate extreme indices based on daily maximum and minimum temperatures during the period 1987-2016 at 28 stations distributed across Israel and Palestine in the Levant region were annually and seasonally analysed. The Man-Kendall test and the Sen's slope estimator were employed for the trend analysis. Results showed that the region has significantly experienced a dominant warming trend for the last three decades, with more intense changes for minimum temperatures than for maximum. At annual scale, maximum values of minimum temperatures exhibited significant increasing trends up to 0.68{\deg}C/decade. Changes detected were more pronounced than those for the absolute extreme temperature indices, with 93 and 89% of stations significantly showed increasing trends in TX90p and TN90p, respectively. The duration and fixed threshold extreme indices confirmed the trend toward a warming, with the 86% of the stations exhibited significant increasing trends in the annual SU25 and TR20. Moreover, 57% of stations showed significant increasing trends in their SU30 index. At seasonal scale, the analysis of trends for extreme temperature indices showed intense and broad significant increasing trends in all absolute extreme temperature indices. In summer, more than 75% of total stations exhibited significant increasing trends for warm days and warm nights. In winter and spring, 71% of the total stations also showed significant increasing trends in SU25 index, whereas the percentage of stations reached 82% in summer and 64% in autumn for significant increasing trends in TR20 index. Finally, the influence of large-scale circulation patterns on temperature extremes was examined. The results highlighted the presence of significant correlations between most of the selected extreme temperature indices and the North Sea-Caspian pattern at annual and seasonal scales