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1.
J Lipid Atheroscler ; 13(2): 194-211, 2024 May.
Artigo em Inglês | MEDLINE | ID: mdl-38826181

RESUMO

Objective: This study investigated the relationship of fetuin-A with coronary calcification, carotid atherosclerosis, and mortality risk in non-dialysis chronic kidney disease (CKD). Methods: The study included 135 adult patients with CKD at stages 3-5, who were divided into coronary artery calcification (CAC) and non-CAC groups. We excluded current smokers and individuals with diabetes mellitus, inflammatory conditions, liver diseases, acute kidney failure, chronic hemodialysis, and cancer. We conducted kidney function tests, complete blood counts, and measured serum levels of fetuin-A, tumor necrosis factor-alpha (TNF-α), high-sensitivity C-reactive protein (hs-CRP), interleukin-6 (IL-6), total cholesterol (TC), total triglycerides (TG), high-density lipoprotein cholesterol, and low-density lipoprotein cholesterol. Cardiac spiral computed tomography was used to calculate the CAC score, employing the Agatston method. Carotid ultrasonography was performed to assess carotid intima-media thickness (CIMT) and to detect the presence of plaques. Results: CAC patients had considerably higher levels of TNF-α (p<0.001), IL-6 (p<0.001), hs-CRP (p=0.006), TC, TG, parathyroid hormone (PTH) (p<0.001) and phosphorus (p<0.001) than non-CAC patients. They also had significantly lower levels of fetuin-A (p<0.001). Fetuin-A was considerably lower in CKD subgroups as CKD progressed. Fetuin-A (p=0.046), age (p=0.009), TNF-α (p=0.027), IL-6 (p=0.005), TG (p=0.002), PTH (p=0.002), and phosphorus (p=0.004) were significant predictors of CAC. CAC and fetuin-A were strong predictors of all-cause mortality and cardiovascular (CV) mortality. Fetuin-A was a significant predictor of CIMT (p=0.045). Conclusion: Fetuin-A reliably predicted CAC and CIMT. Fetuin-A and CAC emerged as significant risk factors for all-cause and CV mortality in non-dialysis CKD.

2.
BMC Nephrol ; 25(1): 103, 2024 Mar 18.
Artigo em Inglês | MEDLINE | ID: mdl-38500101

RESUMO

BACKGROUND: Globally, there are regional and time-based variations in the prevalence, etiology, and prognosis of rapidly progressive glomerulonephritis (RPGN). Prognosis of RPGN is poor, with a higher risk of death and end stage renal disease (ESRD) even with immunosuppressive medications. In the Middle East and North Africa, the studies on this disease are very limited. Therefore, we determined the predictors of outcome of RPGN. METHODS: We retrospectively assessed 101 adult patients over age of 18, diagnosed with RPGN based on renal biopsy illustrating crescents in ≥ 50% of the glomeruli. Patients who had crescents in their renal biopsies that were < 50% and those who refused to consent to a renal biopsy were excluded. We categorized the patients into 3 groups based on immunohistochemistry; type I, type II and type III. Then, depending on renal loss, we divided them into ESRD and non-ESRD groups. The clinical history and physical examination were retrieved. Additionally, 24-hour urine protein, urine analysis, renal function tests, serum albumin, complete blood count, antinuclear antibodies, anti-double stranded DNA antibodies, ANCA antibodies and serum complement levels were checked. Each patient underwent a kidney biopsy for immunohistochemistry and light microscopy. The percentage of crescentic glomeruli, number of sclerosed glomeruli, tertiary lymphoid organ (TLO), neutrophil infiltration, endocapillary or mesangial hypercellularity, interstitial fibrosis with tubular atrophy (IFTA) were analyzed. Primary outcomes (remission, ESRD and mortality) and secondary outcomes were assessed. RESULTS: Type II was the most frequent cause of RPGN (47.5%), followed by type III (32.7%) and type I (19.8%). 32 patients (31.7%) died during follow up, whereas 60 patients (59.4%) developed ESRD. In 41 patients (40.6%), remission occurred. Oliguria, serum creatinine, and need for HD at presentation were significantly increased in ESRD group compared to non-ESRD group (P < 0.001 for each). Mesangial proliferation, IFTA, TLO formation, sclerotic glomeruli and fibrous crescents were also significantly increased in ESRD group in comparison to non-ESRD group (P < 0.001 for each). Glomerulosclerosis (P = 0.036), and IFTA (P = 0.008) were predictors of ESRD. Infections (P = 0.02), respiratory failure (P < 0.001), and heart failure (P = 0.004) were mortality risk factors. CONCLUSION: Type II RPGN was the most common. Infection was the most frequent secondary outcome. Oliguria, glomerulosclerosis, the requirement for hemodialysis at presentation, IFTA and TLO formation were predictors of ESRD. Respiratory failure, heart failure and infections were significant predictors of mortality.


Assuntos
Glomerulonefrite , Insuficiência Cardíaca , Falência Renal Crônica , Nefrite , Insuficiência Respiratória , Adulto , Humanos , Estudos Retrospectivos , Glomerulonefrite/diagnóstico , Oligúria , Progressão da Doença , Rim/patologia , Nefrite/complicações , Falência Renal Crônica/diagnóstico , Insuficiência Cardíaca/complicações , Insuficiência Respiratória/complicações
3.
Ann Saudi Med ; 43(5): 298-308, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37805814

RESUMO

BACKGROUND: The most common and lethal consequence of chronic kidney disease (CKD) is atherosclerotic cardiovascular disease. The persistent inflammation present in CKD increases hepcidin levels. Iron accumulates in the arterial wall in atherosclerosis. Hepcidin-25 was thought to accelerate the development of atherosclerotic plaques by blocking iron release from macrophages. Therefore, we sought to determine the relationship between hepcidin-25 and asymptomatic atherosclerosis in non-dialysis CKD patients. OBJECTIVES: Investigate the relationship between hepcidin-25 and subclinical atherosclerosis in non-dialysis CKD patients. DESIGN: Cross-sectional SETTINGS: Outpatient clinic for urology and nephrology at a university hospital SUBJECTS AND METHODS: Participants above the age of 18 years included a group of healthy controls and a group of CKD patients who were not routinely maintained on hemodialysis. The latter group was further divided according to eGFR into CKD-3, CKD-4 and CKD-5 subgroups. We excluded patients with comorbidities, patients with chronic liver disease, and other conditions or habits. CBC, kidney function tests, and serum levels of hepcidin-25 (SH-25), TNF-α, IL-6, high-sensitivity C-reactive protein (hs-CRP), TC, TG, LDL-C and HDL-C were assessed. To measure carotid intima media thickness (CIMT) and determine presence of plaques, carotid ultrasonography was performed. The near or far walls of common carotid artery, bulb, and internal carotid artery were used to measure CIMT. MAIN OUTCOME MEASURES: SH-25 association and indicators of subclinical atherosclerosis. SAMPLE SIZE: 128 participants, the control group (n=25) and the non-hemodialysis CKD patients (n=103) RESULTS: The CKD patients had significantly higher serum levels of markers of inflammation including IL-6, TNF-α, and hs-CRP (P<.001 for each) compared to the controls. There was a significantly higher level of TC, TG and LDL-C (P<.001 for each) and a lower level of HDL-C (P<.001) in the CDK patients compared to controls. SH-25 was considerably higher in all CKD subgroups, especially with progression of CKD. CIMT was increased in CKD patients especially CKD-4 and CKD-5 subgroups when compared to healthy participants (P<.001 for each). In the patient group, CIMT showed a positive correlation with SH-25, (r=.65 and P<.001), IL-6 (r=.65, P<.001), TNF-α (r=.71, P<.001), and hs-CRP (r=.52, P<.001). The ROC curve study showed that SH-25 (AUC=.86, P<.001), IL-6 (AUC=.83, P<.001), hs-CRP (AUC=.72, P<.001), TNF-α (AUC=.82, P<.001) were strong predictors of subclinical atherosclerosis in the CKD patients. CONCLUSIONS: SH-25 and CIMT had a positive relationship in CKD patients. The ROC curve showed that SH-25 is a reliable predictor of carotid atherosclerosis. Therefore, we suggest that SH-25 is a vital biomarker of asymptomatic atherosclerosis. LIMITATIONS: Single-center.


Assuntos
Aterosclerose , Insuficiência Renal Crônica , Humanos , Adolescente , Espessura Intima-Media Carotídea , Proteína C-Reativa/metabolismo , Hepcidinas , Interleucina-6 , Fator de Necrose Tumoral alfa , Estudos Transversais , LDL-Colesterol , Aterosclerose/etiologia , Insuficiência Renal Crônica/complicações , Inflamação , Ferro , Fatores de Risco
4.
Trauma Case Rep ; 47: 100883, 2023 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-37587919

RESUMO

Tendon injuries in weightlifters is known to be associated with steroid use. Bilateral simultaneous quadriceps tendon rupture (BSQTR) is extremely rare with few cases reported in literature in young athletes. Unlike patellar tendon ruptures, they are more common in older age individuals. These injuries can jeopardize an athlete's career. In this paper, we report a very rare case of BSQTR in an elite bodybuilder who sustained a high mechanism trauma while squatting heavyweights. He sustained bilateral anterior cruciate ligament (ACL) injury and a left ankle fracture. All injuries were treated surgically except for the left ACL as it was asymptomatic on follow-up. The challenge in this case was to treat his injuries and to regain his baseline functional status in the shortest period of time. Following treatment, the patient had a satisfactory clinical outcome with focused rehabilitation. Despite the devastating trauma, the patient was able to progress throughout the treatment plan and has regained his baseline functional status in less than 18 months and has resumed his competitive bodybuilding career. From the available literature, this is the first case to be reported with such combined injuries that was treated and showed a satisfactory outcome in a short period of time.

5.
J Chromatogr Sci ; 61(7): 644-655, 2023 Aug 19.
Artigo em Inglês | MEDLINE | ID: mdl-35523719

RESUMO

Determination of penicillin residues in different industrial effluents including wastewater and air samples is important to prevent exposure to residual amounts of penicillin and the development of antibiotic resistance. A green high performance liquid chromatography (HPLC) method coupled with diode array detection has been developed and validated for multiplex determination of nine penicillin antibiotics in the industrial air dust and wastewater environmental samples of penicillin facility in addition to the monitoring of facility surface cleaning. Separation was performed on C18 column with gradient elution of methanol and phosphate buffer (pH 4) at a flow rate of 1.5 mL min-1 and ultra violet (UV) detection at 220 nm. Low limits of detection were achieved (0.1-0.3 µg mL-1) indicating good sensitivity of the proposed. The method was applied for ensuring the efficiency of cleaning validation after worst-case selection. Recovery studies of the studied penicillins from fortified stainless steel and polycarbonate surfaces and swabs were between 91.91 and 100.22% with relative standard deviation 0.11-1.79%. The presence of any of the studied penicillins in wastewater samples from penicillin plant drainage was checked. Also, total air dust concentration (mg m-3) and % of penicillin active material residues in air dust were calculated from the area of the exposed group in suspension, tablet and vial production lines. The proposed method can be recommended for routine analysis of air and wastewater environmental samples for the detection of penicillin antibiotics at low levels as well as monitoring of facility surface cleaning with high accuracy and precision.


Assuntos
Penicilinas , Águas Residuárias , Penicilinas/análise , Penicilinas/química , Cromatografia Líquida de Alta Pressão/métodos
6.
J Orthop Case Rep ; 13(12): 80-85, 2023 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-38162369

RESUMO

Introduction: Alkaptonuria (AKU) is a rare autosomal-recessive multisystemic disease. It is caused by a mutant homogentisate dioxygenase coding gene, leading to the accumulation of homogentisic acid (HGA), hence systemic manifestations. Renal manifestations and tendon rupture are rarely reported. Case Report: We report a 60-year-old male with chronic kidney disease for over a decade who was initially misdiagnosed with ankylosing spondylitis and rheumatoid arthritis. Later on, the patient presented to our institute with a non-synchronized (8 years) acute quadriceps tendon rupture. Conclusion: Physicians should be aware of the importance of prophylactic measures in the management of AKU, which is mainly medical management, to reduce the accumulation of HGA in the body. We further emphasize this point to reduce the incidence of subsequent tendon ruptures, as it significantly affects the quality of life.

7.
World J Clin Cases ; 10(32): 11702-11711, 2022 Nov 16.
Artigo em Inglês | MEDLINE | ID: mdl-36405291

RESUMO

Diabetic ketoacidosis (DKA) and hyperosmolar hyperglycemia state (HHS) are two life-threatening metabolic complications of diabetes that significantly increase mortality and morbidity. Despite major advances, reaching a uniform consensus regarding the diagnostic criteria and treatment of both conditions has been challenging. A significant overlap between these two extremes of the hyperglycemic crisis spectrum poses an additional hurdle. It has well been noted that a complete biochemical and clinical patient evaluation with timely diagnosis and treatment is vital for symptom resolution. Worldwide, there is a lack of large-scale studies that help define how hyperglycemic crises should be managed. This article will provide a comprehensive review of the pathophysiology, diagnosis, and management of DKA-HHS overlap.

10.
Biology (Basel) ; 11(2)2022 Feb 04.
Artigo em Inglês | MEDLINE | ID: mdl-35205108

RESUMO

Preserving the flower shelf life of damask rose is a crucial matter in promoting its economic viability. Chitosan nanoparticles (CSNPs) and 1-methylcyclopropene (1-MCP) may potentially decrease the postharvest loss of several horticultural commodities, but no findings on damask rose have been published. Therefore, the aim of this research was to study the effect of 1-MCP (400 mg m-3) and either the pre- or postharvest application of CSNPs (1%) on maintaining the quality of damask rose flowers during storage at 4 or 20 °C. The shelf life of damask rose has been significantly extended, along with a reduction in weight loss due to 1-MCP, CSNPs and pre-CSNP treatments. 1-MCP or CSNP applications have resulted in a higher relative water content, volatile oil, total anthocyanins, total carotenoids, total phenolics and antioxidant activity. Ethylene evolution, H2O2 generation and malondialdehyde content were significantly decreased due to 1-MCP or CSNPs treatment, and hence, the cell membrane functions have been maintained. The 1-MCP or CSNP-treated flowers have shown higher activities of catalase and ascorbate peroxidase and lower activities of polyphenol oxidase and lipoxygenase in comparison to untreated flowers. Our results showed that the postharvest application of 1-MCP or CSNPs is a very promising method to maintain the postharvest quality of damask rose during storage.

11.
Plants (Basel) ; 11(3)2022 Feb 02.
Artigo em Inglês | MEDLINE | ID: mdl-35161393

RESUMO

Plant biostimulants (BIOs) have been identified as among the best agricultural practices over the past few decades. Ginger extract (GE) and fulvic acid (FA) are a new family of multifunctional BIOs that positively affect development processes in plants. However, the underlying mechanisms that influence these development processes are still unknown. The objective of this study was to determine how GE and FA affect the plant growth and productivity in damask rose. Furthermore, the mechanisms of these BIOs that regulate the performance of this plant were investigated. Damask rose plants were foliar-sprayed with GE (5, 10 and 15 mg L-1) or FA (1, 3 and 5 g L-1), while control plants were sprayed with tap water. The results showed that GE or FA foliar applications enhanced plant height and branch number much more than the control; however, FA treatment was more effective than GE. Intriguingly, flower number, flower yield, relative water content, and total chlorophyll content were all improved by either GE or FA, paying attention to reducing the blind shoot number per plant. Relative to the control, foliar application with 15 mg L-1 GE or 3 mg L-1FA increased the flower number by 16.11% and 19.83% and the flower yield per hectare by 40.53% and 52.75%, respectively. Substantial enhancements in volatile oil content and oil yield were observed due to GE and FA treatments, especially with the highest concentrations of both BIOs. The treatments of GE and FA considerably improved the total soluble sugars, total phenolic content, total anthocyanin content, and total carotenoid content, more so with FA. Additionally, the contents of N, P, K, Mg, Fe, and Zn elements were also enhanced by applying either GE or FA, especially at higher levels of both BIOs. In sum, our findings illuminate the potential functions of exogenous application of GE and FA in improving the growth, flower yield, and volatile oil yield in damask rose through enhancing the phytochemical and nutrient profiles. Applications of GE and FA can, thus, be a promising approach for enhancing the productivity of damask rose.

12.
Molecules ; 25(22)2020 Nov 19.
Artigo em Inglês | MEDLINE | ID: mdl-33228258

RESUMO

In the current study, eco-structured and efficient removal of the veterinary fluoroquinolone antibiotic sarafloxacin (SARA) from wastewater has been explored. The adsorptive power of four agro-wastes (AWs) derived from pistachio nutshells (PNS) and Aloe vera leaves (AV) as well as the multi-walled carbon nanotubes (MWCNTs) has been assessed. Adsorbent derived from raw pistachio nutshells (RPNS) was the most efficient among the four tested AWs (%removal '%R' = 82.39%), while MWCNTs showed the best adsorptive power amongst the five adsorbents (%R = 96.20%). Plackett-Burman design (PBD) was used to optimize the adsorption process. Two responses ('%R' and adsorption capacity 'qe') were optimized as a function of four variables (pH, adsorbent dose 'AD' (dose of RPNS and MWCNTs), adsorbate concentration [SARA] and contact time 'CT'). The effect of pH was similar for both RPNS and MWCNTs. Morphological and textural characterization of the tested adsorbents was carried out using FT-IR spectroscopy, SEM and BET analyses. Conversion of waste-derived materials into carbonaceous material was investigated by Raman spectroscopy. Equilibrium studies showed that Freundlich isotherm is the most suitable isotherm to describe the adsorption of SARA onto RPNS. Kinetics' investigation shows that the adsorption of SARA onto RPNS follows a pseudo-second order (PSO) model.


Assuntos
Agricultura , Ciprofloxacina/análogos & derivados , Nanotubos de Carbono/química , Águas Residuárias/química , Poluentes Químicos da Água/isolamento & purificação , Adsorção , Análise de Variância , Ciprofloxacina/química , Ciprofloxacina/isolamento & purificação , Concentração de Íons de Hidrogênio , Cinética , Nanotubos de Carbono/ultraestrutura , Pistacia/química , Espectroscopia de Infravermelho com Transformada de Fourier , Análise Espectral Raman , Termogravimetria
13.
Molecules ; 25(20)2020 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-33092200

RESUMO

In the current study, a smart approach for synthesizing trimethyl ethoxysilane-decorated magnetic-core silica-nanoparticles (TMS-mcSNPs) and its effectiveness as nanosorbents have been exploited. While the magnetite core was synthesized using the modified Mössbauer method, Stöber method was employed to coat the magnetic particles. The objective of this work is to maximize the magnetic properties and to minimize both particle size (PS) and particle size distribution (PSD). Using a full factorial design (2k-FFD), the influences of four factors on the coating process was assessed by optimizing the three responses (magnetic properties, PS, and PSD). These four factors were: (1) concentration of tetraethyl-orthosilicate (TEOS); (2) concentration of ammonia; (3) dose of magnetite (Fe3O4); and (4) addition mode. Magnetic properties were calculated as the attraction weight. Scanning electron microscopy (SEM) was used to determine PS, and standard deviation (±SD) was calculated to determine the PSD. Composite desirability function (D) was used to consolidate the multiple responses into a single performance characteristic. Pareto chart of standardized effects together with analysis of variance (ANOVA) at 95.0 confidence interval (CI) were used to determine statistically significant variable(s). Trimethyl ethoxysilane-functionalized mcSNPs were further applied as nanosorbents for magnetic solid phase extraction (TMS-MSPE) of organophosphorus and carbamate pesticides.


Assuntos
Nanopartículas Magnéticas de Óxido de Ferro/química , Praguicidas/síntese química , Silanos/síntese química , Compostos de Trimetilsilil/síntese química , Magnetismo , Nanopartículas de Magnetita/química , Nanocompostos/química , Tamanho da Partícula , Praguicidas/química , Silanos/química , Dióxido de Silício/química , Extração em Fase Sólida , Compostos de Trimetilsilil/química
14.
Cureus ; 12(7): e9046, 2020 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-32782865

RESUMO

Epidermodysplasia verruciformis (EV) is an uncommon disorder that is transmitted in an autosomal recessive manner. It is characterized by increased susceptibility to human papillomavirus (HPV) infection, which presents with hypo- or hyperpigmented macular lesions, pityriasis versicolor-like lesions, and an early tendency to transform into skin cancer. We present a case of a 36-year-old female with complaints of asymptomatic, multiform lesions over the face, neck, chest, and upper arms. Histopathology was suggestive of EV, and our patient was given oral isotretinoin 20 mg/day and advised strict photoprotection.

15.
Cureus ; 12(2): e6909, 2020 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-32190464

RESUMO

Prurigo pigmentosa (PP) is a rare, inflammatory, idiopathic skin disorder, which typically presents as symmetrically scattered pruritic erythematous reticulated papules with occasional vesicles. PP has been primarily a disease of the trunk and the neck, and, to the authors' knowledge, there has been only two reported cases of PP where the forehead/facial areas were involved worldwide. Interestingly, there have not been any reported cases of after bariatric surgery PP with facial involvement. Herein, we present a case of PP after laparoscopic sleeve gastrectomy with involvement of the face, chest, and back.

16.
Pak J Biol Sci ; 23(1): 55-62, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31930883

RESUMO

BACKGROUND AND OBJECTIVE: Cyanobacteria grown under abiotic stress affect on some metabolites that used as promising for foods and feeds biotechnology. Thus, the objective of the study was to evaluate the 3 local cyanobacteria isolates for production of foods and feeds under various concentration of phosphorus. MATERIAL AND METHODS: Cyanobacteria namely; Anabaena sp., Merismopedia tenuissima and Spirulina platensis were grown photoautotrophically in modified medium. The growth pattern in the medium containing various phosphorus concentrations were followed and harvested around 14 days. RESULTS: A decrease in phosphorus concentrations by 50% led to an increase in chlorophyll-a of M. tenuissima and S. platensis. The application of high concentration of phosphorus (+100%) to the culture of Anabaena sp. led to an increase in dry weight and growth rate by 0.382 mg mL-1 and 0.013 h-1, respectively. The deficiency of phosphorus concentrations led to a decrease in carbohydrate contents of Anabaena, Merismopedia and Spirulina with compared to the control culture. In general, the total lipid contents of Anabaena sp. and M. tenuissima were stimulated by phosphorus deficiency. The phosphorus-free media and increase in phosphorus concentration by 100% resulted in an increase in protein fractions such as soluble, insoluble, globulins, prolamines, glutelins and total protein content of Anabaena sp. The application of high concentration of phosphorus (+100%) to the culture of S. platensis led to an increase in total lipid contents in comparison to control. The highest phycobiliprotein contents of S. platensis were recorded at 50% phosphorus deficiency. CONCLUSION: Cyanobacteria has a soft cell wall that makes it especially easy to digest and is additionally full of live active enzymes which further enhances metabolism and the efficient intake of nutrients.


Assuntos
Biotecnologia , Cianobactérias , Microbiologia de Alimentos , Fósforo/metabolismo
18.
Sci Rep ; 9(1): 17624, 2019 11 26.
Artigo em Inglês | MEDLINE | ID: mdl-31772267

RESUMO

Alkoxysilanes and organoalkoxysilanes are primary materials in several industries, e.g. coating, anti-corrosion treatment, fabrication of stationary phase for chromatography, and coupling agents. The hydrolytic polycondensation reactions and final product can be controlled by adjusting the hydrolysis reaction, which was investigated under a variety of conditions, such as different alkoxysilanes, solvents, and catalysts by using gas chromatography. The hydrolysis rate of alkoxysilanes shows a dependence on the alkoxysilane structure (especially the organic attachments), solvent properties, and the catalyst dissociation constant and solubility. Some of the alkoxysilanes exhibit intramolecular catalysis. Hydrogen bonding plays an important role in the enhancement of the hydrolysis reaction, as well as the dipole moment of the alkoxysilanes, especially in acetonitrile. There is a relationship between the experimentally calculated polarity by the Taft equation and the reactivity, but it shows different responses depending on the solvent. It was found that negative and positive charges are respectively accumulated in the transition state in alkaline and acidic media. The reaction mechanisms are somewhat different from those previously suggested. Finally, it was found that enthalpy-entropy compensation (EEC) effect and isokinetic relationships (IKR) are exhibited during the hydrolysis of CTES in different solvents and catalysts; therefore, the reaction has a linear free energy relationship (LFER).

19.
Front Chem ; 7: 552, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31457003

RESUMO

Date pits (DPs) have been recycled into a low-cost adsorbent for removing of selected heavy metals (HMs) from artificially contaminated aqueous solutions. Adsorption of targeted HMs, both by raw date pits (RDP) and burnt date pits (BDP) was tested. Results showed that BDP is more efficient as an adsorbent and mostly adsorbing Cu(II). A novel approach; fractional factorial design (2 k-p - FrFD) was used to build the experimental pattern of this study. The effects of four factors on the maximum percentage (%) of removal (Y) were considered; pH, adsorbent dose (AD), heavy metal concentration (HMC), and contact time (CT). Statistically significant variables were detected using Pareto chart of standardized effects, normal and half-normal plots together with analysis of variance (ANOVA) at 95.0 confidence intervals (CI). Optimizing (maximizing) the percentage (%) removal of Cu(II) by BDP, was performed using optimization plots. Results showed that the factors: pH and adsorbent dose (AD) affect the response positively. Scanning electron microscopy (SEM) was used to study the surface morphology of both adsorbents while fourier-transform infrared spectroscopy (FTIR) was employed to get an idea on the functional groups on the surface and hence the adsorption mechanism. Raman spectroscopy was used to characterize the prepared adsorbents before and after adsorption of Cu(II). Equilibrium studies show that the adsorption behavior differs according to the equilibrium concentration. In general, it follows Langmuir isotherm up to 155 ppm, then Freundlich isotherm. Free energy of adsorption (ΔG ad) is -28.07 kJ/mole, when equilibrium concentration is below 155 ppm, so the adsorption process is spontaneous, while (ΔG ad) equals +17.89 kJ/mole above 155 ppm, implying that the process is non-spontaneous. Furthermore, the adsorption process is a mixture of physisorption and chemisorption processes, which could be endothermic or exothermic reactions. The adsorption kinetics were described using a second order model.

20.
Polymers (Basel) ; 11(3)2019 Mar 21.
Artigo em Inglês | MEDLINE | ID: mdl-30960521

RESUMO

Scientists from various different fields use organo-trialkoxysilanes and tetraalkoxysilanes in a number of applications. The silica-based materials are sometimes synthesized without a good understanding of the underlying reaction kinetics. This literature review attempts to be a comprehensive and more technical article in which the kinetics of alkoxysilanes polymerization are discussed. The kinetics of polymerization are controlled by primary factors, such as catalysts, water/silane ratio, pH, and organo-functional groups, while secondary factors, such as temperature, solvent, ionic strength, leaving group, and silane concentration, also have an influence on the reaction rates. Experiments to find correlations between these factors and reaction rates are restricted to certain conditions and most of them disregard the properties of the solvent. In this review, polymerization kinetics are discussed in the first two sections, with the first section covering early stage reactions when the reaction medium is homogenous, and the second section covering when phase separation occurs and the reaction medium becomes heterogeneous. Nuclear magnetic resonance (NMR) spectroscopy and other techniques are discussed in the third section. The last section summarizes the study of reaction mechanisms by using ab initio and Density Functional Theory (DFT) methods alone, and in combination with molecular dynamics (MD) or Monte Carlo (MC) methods.

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