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Graphene sheets were functionalized covalently with an appropriate linker as a novel vector for p-DNA delivery into mammalian cells. The transfected cancer cells produced green fluorescence as an indicator of successful gene delivery.

Increased global energy consumption has resulted in more waste and greenhouse gas emissions.

Applying the isoconversional method to data obtained from thermogravimetric analysis (TGA) can provide vital kinetic information. In this work, the thermal decomposition and oxidation of the antidiabetic drug glimepiride is analyzed in the presence of N2 and O2. The study was done with and without metal oxide catalysts to explore their potential application in solid wastewater upgrading. The analysis was conducted using thermogravimetric analysis. The isoconversional methods of Kissinger–Akahira–Sunose and Friedman were used to estimate the effective activation energies as a function of the extent of conversion (α). Density functional calculations were used to estimate the bond dissociation energies in glimepiride. The Ea values obtained from the Friedman method and the DFT calculations indicate an initial S–N bond breaking in glimepiride. The pre-exponential factor (A) and the kinetic triplet (ΔH‡, ΔS‡, and ΔG‡) are also discussed. When glimepiride oxidation was studied in the presence of the metal oxides, the catalyst activity was found to follow the order $${\text{VO}}_{{2}} > {\text{ CuO }} > {\text{ MnO}}_{{2}} > {\text{ Al}}_{{2}} {\text{O}}_{{3}} > {\text{ TiO}}_{{2}}$$ VO 2 > CuO > MnO 2 > Al 2 O 3 > TiO 2 .

In this study, the thermal decomposition of glimepiride, a common antidiabetic drug, was analyzed in the presence of N2 and O2 and various metal oxide catalysts. The analysis was conducted using TGA. The results showed that there were two significant mass losses in the presence of N2, that correspond to thermal decomposition of the drug. When N2 was replaced by O2, an additional mass loss was observed that corresponds to the oxidation of the drug at higher temperature. Density functional theory was implemented to explain the thermo-oxidative decomposition of the drug. The isoconversional method was also used to deduce the activation energies of the process. Upon all catalysts used, vanadium oxide was the most efficient in lowering the temperature required for thermal decomposition. The results of this study pave way for future work into purifying wastewater from pharmaceuticals via adsorption using metal oxides catalysts.

This work is a first attempt to understand the mechanism of metformin thermal decomposition under inert conditions. Thermal gravimetric analysis coupled with mass spectrometry was used to probe the thermal degradation reactions. Density functional theory and second-order perturbation (MP2) theoretical calculations were used to construct a reaction mechanism for metformin decomposition. It was evident that the reactions are initiated via formation of methyl radicals, and ammonia via 1.3-H shift, followed by a series of different secondary reaction pathways. The formation of cyanamide, dimethylamine and HCN were among the main secondary products. The proposed mechanism is important for future treatment of wastewater containing metformin and similar drugs formulations, and their possible conversion to useful commodities.

Oil sands exploitation in Alberta relies on water-intensive processes that result in large amounts of oil sand process-affected water (OSPW). Tailings ponds are used to store OSPW in accordance with government regulations. One of the main challenges of these tailings ponds is the settling of fine particles which, without treatment, would remain suspended for decades. This study introduces a novel application for the oxy-cracking technique to enhance fine particle settling through simultaneous oxidation and cracking reactions: residual bitumen and hydrocarbons are cracked and solubilized in the liquid phase, freeing the fine particles to agglomerate and settle faster. The pathway for this process is determined by the kinetics parameters, and it releases minimal CO2. A full lumped kinetics model study is presented to describe the oxy-cracking reaction. Settling enhancement and dewaterability were studied using the initial settling rate (ISR) and capillary suction time (CST) methods. After oxy-cracking, the ...

The [2+2] cycloreversion of silacyclobutane (SCB) and its two methyl-substituted derivatives, 1-methyl-1-silacyclobutane (MSCB) and 1,1-dimethyl-1-silacyclobutane (DMSCB), were studied using ab initio quantum chemistry calculations. The second-order Moller-Plesset (MP2) perturbation theory, complete active space self-consistent field (CASSCF), and coupled clusters methods were used to explore both the concerted and the stepwise cycloreversions of the three molecules. In addition to the orbital symmetry-forbidden supra-supra [2s+2s] transition state, a new orbital symmetry-allowed supra-antara [2s+2a] transition state was discovered for the concerted route for all three molecules. Both methyl substitution and temperature play a role in the kinetic competition between the [2s+2s] and [2s+2a] routes. At 0 and 298 K, the concerted [2s+2a] cycloreversion is kinetically more favorable than the [2s+2s] cycloreversion for SCB, but the opposite is true for MSCB and DMSCB. With increasing temperatures to above 600 and 1800 K, the [2s+2a] cycloreversion becomes more favorable for MSCB and DMSCB, respectively. The methyl substitutions on Si atoms also affect the stability of the diradical intermediate formed by Si-C bond rupture, leading to a less stable diradical with increasing methyl groups.

Water pollution by emerging pollutants such as pharmaceutical and personal care products is one of today's biggest challenges. The presence of these emerging contaminants in water has raised increasing concern due to their frequent appearance and persistence in the aquatic ecosystem and threat to health and safety. The antidiabetic drug glimepiride, GPD, is among these compounds, and it possesses adverse effects on human health if not carefully administered. Several conventional processes were proposed for the elimination of these persistent contaminants, and adsorption is among them. Therefore, in this study, the adsorptive removal of GPD from water using multi-walled carbon nanotubes (MWCNT) supported on silica was explored on a fixed-bed column. The effects of bed-height, solution pH, and flow rate on the adsorptive removal of GPD were investigated. The obtained adsorption parameters using Sips, Langmuir, and Freundlich models were used to investigate the continuous adsorption. The results showed that the drug removal is improved with the increasing bed height; however, it decreased with the flow rate. The effect of pH indicated that the adsorption is significantly affected and increased in acidic medium. The convection-dispersion model coupled with Freundlich isotherm was developed and used to describe the adsorption breakthrough curves. The maximum adsorption capacity (qm) was 275.3 mg/g, and the axial dispersion coefficients were ranged between 3.5 and 9.0 × 105 m2/s. The spent adsorbent was successfully regenerated at high pH by flushing with NaOH.

Pharmaceutical compounds are emerging contaminants that have been detected in surface water across the world. Because conventional wastewater treatment plants are not designed to treat such pollutants, new technologies are needed to degrade and oxidize such contaminants. The newly developed oxy-cracking process was utilized to treat the antidiabetic drug, metformin. The process, which involved partial oxidation of metformin in alkaline aqueous medium, proved to decompose the drug into small organic molecules, with minimum emission of CO2, therefore, increasing its biodegradability and removal from industrial treatment plants. The reaction gaseous products were probed by online gas chromatography. The liquid phase before and after oxy-cracking was analyzed for total carbon content by TOC and gas chromatography mass spectrometry. The products formed from the nitrogen-rich drug included ammonia, amines, amidines, and urea derivatives. A reaction mechanism for the oxy-cracking process is proposed. Because the hydroxyl radical (˙OH) is believed to play a central role in the oxy-cracking process, the mechanism is initiated by ˙OH attacks on metformin, followed by single decomposition or isomerization steps into stable products. The reactions were investigated using density functional theory calculations and validated using high quality 2nd order Moller–Plesset perturbation theory energy calculations.

An efficient method for the preparation of crystalline tantalum carbide (TaC) was reported using a new methyl-substituted precursor, 1-methylsilacyclobutane (MSCB), in the hot-wire chemical vapor deposition process with a tantalum filament. The ability of MSCB to produce methyl radicals on heated Ta filament allows for the formation of crystalline TaC (cubic Fm -3 m ) in a wide temperature range of 1600–2200 °C. This corroborates the key role of the radical species formed via the precursor's decomposition on the hot metal wire in the type of metal alloys formed on the wire surface. The growth rate of TaC achieved at 0.12 μm/min and 0.35 μm/min, respectively, for 1600 °C and 2200 °C is much higher than the value obtained from using CH 4 /H 2 mixtures as the C-containing precursor. Crystalline ditungsten carbide (W 2 C) was formed by treating the tungsten filament with MSCB at the relatively high temperatures of 2200–2400 °C, with a deposition rate of 2.1 μm/min at 2400 °C. The method reported in this work is a useful method to produce crystalline TaC or W 2 C without the use of the corrosive metal halide precursors.

Oxy-cracking is a combination of oxidation and cracking reactions for converting heavy hydrocarbons into commodity products with minimal emission of CO2. This reaction takes place in basic aqueous media, at mild operation temperatures (200–230 °C) and pressures (500–750 psi). In this study, the main goal is to understand the oxy-cracking mechanism, involving oxidation and cracking reactions, of solid hydrocarbons represented by the model molecule Quinolin-65 (Q-65). In the experimental part, the oxy-cracking reaction was performed in a Parr batch reactor operated at an optimized oxygen partial pressure of 750 psi and temperatures between 200 °C and 230 °C. The reaction products were characterized by FTIR spectroscopy, TOC analysis, GC, NMR spectroscopy, and XPS. We found that the main products are composed of organic carboxylic, phenolic, and carbonyl-containing compounds, with small amounts of inorganic carbon (IC). In the theoretical part of the study, a comprehensive computational modeling of Q-65 reactivity was performed using high-level quantum theoretical calculations. The reaction studies indicated the attack of the hydroxyl radical (OH˙) and hydroxide anion (OH−) on the Q-65 molecule. The theoretical study employed the density functional theory (DFT) and the second-order Moller–Plesset perturbation theory (MP2) to study the reaction mechanisms under the same experimental conditions. Both the theoretical and the experimental studies confirmed the complexity of the reaction kinetics. The reaction kinetic results suggested that the Q-65 oxy-cracking reaction went through a parallel-consecutive reaction in which oxidative decomposition took place in the first step producing different aromatic intermediates. These intermediates were oxy-cracked consecutively into different organic acids and a small amount of CO2 gas.

The drug metformin is the most prescribed drug to treat type II diabetes and has been recently reported to have anticancer activities. Because of its wide use, its potential risk on the environment is extremely concerning. In this study, the mechanism and the thermodynamics of the thermo-oxidative decomposition of the metformin were investigated as part of a new solution for the pharmaceutical contamination of water bodies. Thermogravimetry and mass spectrometry were used to demonstrate the metformin thermo-oxidative decomposition under air in the temperature range 25–800 °C. The isoconversional methods of Kissinger-Akahira Sunose (KAS) and Friedman (FR) were implemented to deduce the trends of effective activation energies. As expected, the effective activation energy (Eα) of the reaction was dependent on the reaction temperature, suggesting multi-step reactions. The Eα ranged from 100 to 145 kJ/mol and 200–300 kJ/mol for the KAS and FR methods, respectively. The kinetic triplet, Aα, ΔS‡, and ΔG‡ were also determined by finding the appropriate reaction model. Theoretical calculations were implemented to propose a full reaction mechanism. The oxidation of metformin was investigated with both molecular O2(t) and atomic O(t) oxygen. The experimental results were then explained under the light of the computational data to explain the variation of Eα with temperature, and the competition between the O2(t)/O(t) species.

This is an investigation of the adsorptive removal of anthraquinone dyes, resembled by Alizarin, by utilizing maghemite iron oxide (γ-Fe2O3) nanoparticles in aqueous media. The adsorption process was affected by several parameters such as solution pH, adsorbent amount, contact time, and temperature. After optimizing the parameters affecting the adsorption, the process was successful in removing Alizarin dye with an efficiency exceeding 95%. Best adsorption results were achieved at a pH of 11 and contact time of 60 min. The adsorption was shown to follow the Langmuir model suggesting a monolayer and homogeneous coverage. The maximum adsorption capacity (qm) was found to be 23.2 mg/g at pH = 11. A thermodynamic study showed that the adsorption process is exothermic and spontaneous at room temperature. The Gibbs free energy of adsorption (-6.79 kJ/mol) obtained in this study suggests a physisorption process. This finding has facilitated the regeneration of the Fe2O3 nanocatalyst. Both NaOH and HNO3 at dilute levels were tested for the regeneration of the nanocatalyst. Regeneration with HNO3 was successful up to four successive removal cycles with an efficiency >80%. Photodegradation experiments utilizing a UV light were also successful in maximizing the adsorption removal efficiency. A sorption mechanism based on the results obtained in this work is also proposed.

Healthcare spending in most of the Organisation for Economic Co-operation and Development countries is expected to reach up to 14% of GDP by 2060. Physicians as the primary point of contact across the healthcare continuum and being largely in control of the clinical process are well-positioned to influence the cost and quality of healthcare, as well as to lead and shape healthcare improvements. Thus, it is essential to design the most appropriate reimbursement model that can support and drive the desired physician behaviours. In this article, a hybrid compensation model is proposed which comprises of a base salary and individual bonus – where base salary is pegged at the average market rate according to the physician’s qualifications, skills and experience, and the individual bonus is adjusted according to both the ‘group-level’ and ‘individual-level’ performance. The proposed reimbursement model has the flexibility to be applied in different care settings after tailoring the performance metrics to suit the organisation’s desired goals, e.g. using indicators from the NHS’s Quality and Outcomes Framework for a primary care setting. However, administering the physician’s incentive component in our proposed model would likely be relatively complex, given the need to account for the physician’s ‘group-level’ affiliations, which could range from the physician’s role in a specific clinical program to his/her association with the parent clinical department. Thus, it would be crucial to ensure that the necessary supporting resources and infrastructure are in place, e.g. robust information systems that can measure, collect, analyse and report data in an accurate and timely manner, which would coincide with health organisations’ increasing focus on the use of information systems in delivering effective value-based healthcare.

In this study, the thermal oxidation of an asphaltene model molecule, Quinolin-65, was investigated using the density functional theory (DFT) and the second-order Moller–Plesset (MP2) perturbation theory. The reactions studied involved thermal decompositions as well as the interactions between the model molecule and singlet atomic (O1D) and molecular (O21Δ) oxygen. The theoretical study was performed under conditions similar to those of the uncatalyzed thermal oxidation of asphaltenes. A new reaction pathway for the loss of the olefin chain in Quinolin-65 via a 1,3-hydrogen shift mechanism was revealed. Thermogravimetric analysis of Quinolin-65 was also performed and the reaction products were probed by a mass spectrometer. Both the theoretical study and the thermogravimetric analysis concluded that the thermo-oxidative decomposition of Quinolin-65 is a complex multi-step reaction process, which involves different reaction pathways. The thermodynamic parameters obtained in this study showed that the reaction process should start with the loss of the olefin chain in the Quinolin-65 molecule, followed by the oxidation of the aromatic chain, to produce mainly, H2O, CO2, and SO2.

The reaction kinetics of the decomposition of 1,3-disilacyclobutane (DSCB) was investigated using a hot-wire chemical vapor deposition reactor. The reaction products were monitored using a vacuum ultraviolet laser single-photon ionization source coupled with a time-of-flight mass spectrometer. Steady-state approximation was used to determine the rate constants for three main decomposition pathways of DSCB: the exocyclic H 2 elimination ( k 1 ), the cycloreversion ( k 2 ), and the ring-opening via 1,2-H shift ( k 3 ). Separate k 2 and k 3 were not obtained, but 2 k 2 + k 3 and k 1 were determined. The activation energy (E a ) for the exocyclic H 2 elimination reaction was determined to be 63.5 kJ·mol − 1 . Compared to the E a value of 43.6 kJ·mol − 1 previously obtained under collision-free conditions at much lower pressures, the value from this work is higher. This is attributed to the filament aging caused by the formation of silicon carbide (SiC) and tungsten sub-carbide (W 2 C) on the wire surface. The heterogeneous reactions on the metal surface also led to a much faster decay constant, k overall , for DSCB than those for each individual decomposition pathway, k 1 and 2 k 2 + k 3 .

Metal wires (typically made of W or Ta) serve as catalysts to decompose the precursor gases to form reactive species in the technique of catalytic chemical vapor deposition. The reactions of these reactive species with the heated wire cause structural changes in the wire, which affect its catalytic properties and lifetime. Here, we report a systematic study on characterizing the structural changes in W and Ta wires when they are exposed to 1,3-disilacylobutane, a useful single-source precursor for SiC film deposition. We have shown that filament temperature, reaction time, and filament material are among the important factors in determining the nature of metal alloys formed. Formation of crystalline W2C, SiC, and W5Si3 (weak) was observed on W, whereas crystalline TaC, SiC, and Ta5Si3 (weak) were formed on Ta. While both filaments proved to form cubic crystalline 3C-SiC at low temperatures, alloying has taken different paths at higher temperatures. Between 1400 and 2400 °C, alloying in W was dominated by ...

The reaction kinetics of the decomposition of 1-methylsilacyclobutane (MSCB) in a hot wire chemical vapor deposition (HWCVD) reactor was investigated. The stable reaction products were monitored using vacuum ultraviolet laser single photon ionization in tandem with time-of-flight mass spectrometry. Steady-state approximation was used to determine the rate constants of three individual decomposition pathways of MSCB, i.e., cycloreversion to form ethene and methylsilene (R1), ring opening to form propene and methylsilylene (R2), and exocyclic Si-CH3 bond cleavage to form ˙CH3 radicals (R3). The activation energies (Ea) for R2 and R3 in a HWCVD reactor were determined to be 86.6 kJ mol-1 and 106 kJ mol-1, respectively. The fact that these Ea values are close to those obtained for the MSCB decomposition on metal surfaces under collision-free conditions indicates that the heterogeneous reactions on the hot wire surface govern the gas-phase reaction kinetics in the HWCVD reactor. In addition, the Ea values obtained from a theoretical study of the decomposition kinetics using ab initio calculations at the CCSD(T)/6-311++G(3d,2p)//MP2/6-311++G(d,p) level were 62.9 kcal mol-1 (i.e., 263 kJ mol-1), 62.0 kcal mol-1 (i.e., 259 kJ mol-1), and 86.2 kcal mol-1 (i.e., 361 kJ mol-1) for R1, R2, and R3, respectively. The much lower experimental Ea values compared with those from the theoretical calculations clearly suggest that the tungsten filament in the HWCVD reactor catalyzed the decomposition.

In this study, two dicationic asymmetrical diamine/copper(II) nitrate salt complexes of the general formula trans-[CuII(NN')(2)center dot H2O](NO3)(2) were successfully synthesized using N,N-dimethylethylenediamine and N,N-diethylethylenediamine as asymmetrical diamine ligands. The structure of complex 2 was identified by X-ray single crystal diffraction analysis confirming that the bidentate ligand N,N-dimethylethylenediamine forms a penta-coordinated complex with an H2O molecule located around the copper(II) ion in a trans configuration. It was found that the metal centre is coordinated in a distorted square pyramidal fashion with a tau value of 0.274. The desired complexes were fully characterized using, MS, UV-Vis, CV, FTIR, TG/DTA, and Hirshfeld surface computational analysis. High level theoretical calculations were also performed in order to investigate the complexes structure, conformers, vibrational frequencies, and their excited states., The authors would like to extend their sincere appreciation to the Deanship of Scientific Research at King Saud University for funding this Research group NO (RG -257-1436-1437). The authors are also grateful to the Western Canada Research Grid., info:eu-repo/semantics/publishedVersion

Despite increasing data regarding clinical outcomes following transvaginal hybrid NOTES cholecystectomy (TVC), a consensus regarding safety based on comparative studies has yet to be reached. The aim of this systematic review and meta-analysis was to compare safety and clinical outcomes of TVC with conventional laparoscopic cholecystectomy (CLC) for the treatment of benign gallstone disease. A comprehensive search for published studies comparing TVC and CLC was performed. Review of each study was conducted and data were extracted. All pooled outcome measures were determined using random-effects models. Data were retrieved from 14 studies describing 1,145 patients. There was no difference in total complications (POR = 0.68; 95 % CI 0.40–1.14; P = 0.14), incidence of bile duct injury (POR = 1.33; 95 % CI 0.31–5.66; P = 0.70), Clavien–Dindo Grade II (POR = 0.48; 95 % CI 0.14–1.60; P = 0.23) or Grade III (POR = 0.63; 95 % CI 0.24–1.65; P = 0.34) complications between TCV and CLC. Time of return to normal activities was significantly reduced in the TVC group (WMD = −4.86 days; 95 % CI −9.33 to −0.39; P = 0.03), and there was a non-significant reduction in postoperative pain on days 1 (WMD = −0.80; 95 % CI −1.60 to 0.01; P = 0.05) and 3 (WMD = −0.89; 95 % CI −1.77 to −0.01; P = 0.05). TVC is safe when performed by appropriately trained surgeons and may be associated with a faster return to normal activities and decreased postoperative pain.

The kinetics and thermochemistry of the decomposition pathways for 1,3-disilacyclobutane (1,3-DSCB) in the gas phase were studied using the second-order Møller-Plesset (MP2) perturbation theory and coupled cluster methods with single, double, and perturbative triple excitations (CCSD(T)). The reactions examined include 2 + 2 cycloreversion to form two silenes by either a concerted or a stepwise mechanism, 1,1-, 1,2-, and 1,3-H(2) elimination, and the ring-opening initiated by 1,2-H shift to form an open-chain 1,3-disilabut-1-ylidene, which undergoes further decomposition to produce two pairs of silene/silylene species. The structures of the transition states for the concerted and the stepwise 2 + 2 cycloreversion pathways are found to resemble closely those reported for the head-to-tail and head-to-head dimerization, respectively. Comparison of the activation barriers demonstrates unambiguously that the stepwise cycloreversion (ΔH(0)(‡) = 66.1 kcal/mol) is favored over the concerted one (ΔH(0)(‡) = 77.3 kcal/mol). A new pathway was established from the 1,4-diradical intermediate in the stepwise cycloreversion to form 1-silylmethylsilene via 1,3-H shift. The concerted 1,1-H(2) elimination is shown to have the lowest activation barrier of all H2 elimination reactions. Overall, the 1,2-H shift in 1,3-DSCB with concerted ring-opening to form 1,3-disilabut-1-ylidene is the most kinetically and thermodynamically favorable decomposition pathway, both at 0 and 298 K.

The gas-phase reaction chemistry of using 1-methylsilacyclobutane (MSCB) in the hot-wire chemical vapor deposition (CVD) process has been investigated by studying the decomposition of MSCB on a heated tungsten filament and subsequent gas-phase reactions in a reactor. Three pathways exist to decompose MSCB on the filament to form ethene/methylsilene, propene/methylsilylene, and methyl radicals. The activation energies for forming propene and methyl radical, respectively, are determined to be 68.7 ± 1.3 and 46.7 ± 2.5 kJ·mol(-1), which demonstrates the catalytic nature of the decomposition. The secondary gas-phase reactions in the hot-wire CVD reactor are characterized by the competition between a free radical chain reaction and the cycloaddition of silene reactive species produced either from the primary decomposition of MSCB on the filament or the isomerization of silylene species. At lower filament temperatures of 1000-1100 °C and short reaction time (t ≤ 15 min), the free radical chain reaction is equally important as the silene chemistry. With increasing filament temperature and reaction time, silene chemistry predominates.

The primary decomposition of 1,3-disilacyclobutane (DSCB) on a tungsten filament and its secondary gas-phase reactions in a hot-wire chemical vapor deposition (CVD) reactor have been studied using laser ionization mass spectrometry. Under the collision-free conditions, DSCB decomposes on the W filament to produce H2 molecules with an activation energy of 43.6 ± 4.1 kJ·mol(-1). With the help of the isotope labeling and chemical trapping methods, the mechanistic details in the secondary gas-phase reactions important in the hot-wire CVD reactor setup have been examined. The dominant pathway has been demonstrated to be the insertion of the cyclic 1,3-disilacyclobut-1-ylidene, generated by exocyclic Si-H bond rupture, into the Si-H bond in DSCB to form 1,1'-bis(1,3-disilacyclobutane) (174 amu). The successful trapping of 1,3-disilacyclobut-1-ylidene by both 1,3-butadiene and trimethylsilane provides compelling evidence for the existence of this cyclic silylene species in the hot-wire CVD reactor with DSCB. Other reactions operating in the reactor include the DSCB cycloreversion to form silene and the ring opening of DSCB via 1,2-H shift to produce silene/methylsilylene and 1-methylsilene/silylene. The introduction of an additional Si atom in the four-membered ring monosilacyclobutane molecule has caused two major changes in the reaction chemistry assumed by DSCB: (1) The endocyclic cycloreversion reactions that dominate in the decomposition of monosilacyclobutane molecules only play a much less important role in the dissociation of DSCB; and (2) the exocyclic bond cleavages are promoted in DSCB due to the ring stabilization caused by the introduction of one additional Si atom.