Invited review. Bond dissociation enthalpies in benzene derivatives and effect of substituents: an overview of density functional theory (B3LYP) based computational approach

In this review, we have mainly focused on the recent computational studies on the bond dissociation enthalpies (BDE) of the X‒H bonds of the para and meta substituted benzene derivatives (3Y-C6H4X‒H and 4Y-C6H4X‒H with X = O, S, Se, NH, PH, CH2, SiH2 and Y = H, F, Cl, CH3, OCH3, NH2, CF3, CN, NO2). In addition, the remote substituent effects on the BDE(X‒H), the radical stability and parent one have also been discussed in terms of the calculated ground state effect, radical effect and total effect. Model chemistry of ROB3LYP/6-311++G(d,p)//B3LYP/6-311G(d,p) can reproduce the BDE values with the accuracy of 1.0‒2.0 kcal/mol. The good linear correlations between Hammett constants and BDE values were discovered for both para and meta substitutions in phenols, thiophenols, benzeneselenols, anilines and phenylposphines with the R-squared lager than 0.94. In contrast, it does not occur in case of toluenes and phenylsilanes.Keywords. Benzene derivatives, density functional theory, bond dissociation enthalpies, substituent effects, radical effect, ground state effect, total effect, Hammett constants

Primary pulmonary T-cell lymphoma mimicking asthma and community-acquired pneumonia: a rare case report

Primary pulmonary T-cell lymphoma (PPTL) is a rare disease. Diagnosing PPTL is challenging due to non-specific clinical symptoms and imaging. A 32-year-old female presented with persistent fever, cough, and dyspnoea. The symptoms were initially treated as asthma and community-acquired pneumonia without improvement. Chest computed tomography (CT) revealed bilateral consolidations with a CT angiogram sign, and flexible bronchoscopy showed infiltrative lesions causing bronchial stenosis. Histopathological examination of the tissue biopsy identified T-cell lymphoma through immunohistochemical staining positive for CD3. This case highlights the importance of considering differential diagnoses such as PPTL in patients with atypical presentations of asthma or non-resolving pneumonia. This case also demonstrates the diagnostic utility of flexible bronchoscopy in identifying airway obstruction due to malignant cells, which can mimic asthma

Confinement mechanism of FRP-confined concrete columns

Strengthening concrete columns by externally wrapping fibre reinforced polymer (FRP) around the perimeter of column sections is rapidly growing. This strengthening technique confines the column cores thus increases their carrying loads and ductility. This thesis is concerned with the confinement mechanism of FRPconfined concrete. Particular attention is given to a new technique for strengthening existing concrete columns. The confinement mechanism of FRP-confined concrete is comprehensively investigated and analysed, which resulted in confinement models for FRP-confined concrete columns. The confinement model for FRP-confined circular concrete columns covers a wide range of unconfined concrete strengths with higher accuracy than other existing models. The confinement model for FRP-confined rectangular concrete columns takes the stress concentration at the corners of sections into account, which has not been done by previous studies. In addition, this study introduces the use of artificial neural network (ANN) to generate analytical equations for calculating the compressive strength and strain of FRP-confined rectangular concrete columns. These equations significantly increase the accuracy compared to existing models. Additionally, the progressive failure mechanism of FRP-confined concrete that has not been previously investigated is experimentally studied. Experimental results show that the maximum usable strain of 1% recommended by ACI 440.2R (2008) and Concrete Society (2012) is un-conservative for FRP-confined concrete. A new model is then proposed to calculate the residual strength of a concrete core at a given axial strain. Finally, a new practical method called circularisation technique is proposed to strengthen existing square reinforced concrete columns. The new technique significantly increases the axial capacity of the existing square columns. Through experimental studies, the proposed technique was verified for not only normal strength concrete but also high strength concrete. Two sets of experimental testing proved the viability of the proposed circularization technique

The Role of Apparent Diffusion Coefficient in the Differentiation between Cerebellar Medulloblastoma and Brainstem Glioma

For certain clinical circumstances, the differentiation between cerebellar medulloblastoma and brainstem glioma is essential. We aimed to evaluate the role played by the apparent diffusion coefficient (ADC) values in the differentiation between cerebellar medulloblastomas and brainstem gliomas in children. The institutional review board approved this prospective study. Brain magnetic resonance imaging (MRI), including diffusion-weighted imaging (DWI) and ADC, was assessed in 32 patients (median age: 7.0 years), divided into two groups, a medulloblastoma group (group 1, n = 22) and a brainstem glioma group (group 2, n = 10). The Mann–Whitney U test was utilized to compare tumor ADCmax, ADCmin, ADCmean, and ADCsd values, and their ratios with the parenchyma values between the two groups. Receiver operating characteristic (ROC) curve analysis and the Youden index were used to calculate the cut-off value, along with the area under the curve (AUC), sensitivity, and specificity. The median ADCmax, ADCmin, and ADCmean values were significantly higher in group 2 than in group 1 (p < 0.05). The median ratios of ADCmin and ADCmean to the parenchyma were significantly higher in group 2 than in group 1 (p < 0.05). The ROC analysis showed that the AUC for the ADCmean ratio was the highest among these parameters, at 98.2%. The ADCmean tumor to parenchyma ratio was a significant and effective parameter for the differentiation between pediatric medulloblastomas and brainstem gliomas

Strengthening square reinforced concrete columns by circularisation and FRP confinement

A technique called circularisation where segmental circular concrete covers made of different concrete strengths (40 MPa, 80 MPa and 100 MPa) was used to change a square column to a circular column. The applicability of the circularisation method was experimentally studied for a wide range of concrete strengths (from 40 MPa to 100 MPa). The behaviour of the strengthened specimens under different loading conditions including concentric loading, eccentric loading (25 mm and 50 mm) and flexural bending is investigated. The experimental results demonstrate that using high strength concrete (HSC) for the additional covers to strengthen existing square reinforced concrete (RC) columns provides higher load-carrying capacity than covers made of normal strength concrete. The HSC covers and the concrete cores worked as a composite material to failure. The FRP strain at peak load was observed for the purpose of estimating the specimens’ capacity. The distribution of FRP strain around the circumference of the column section is also reported

Permanence and positive bounded solutions of Kolmogorov predator-prey system

Our main purpose is to present some criteria for the permanence and existence of a positive bounded solution of Kolmogorov predator-prey system. Under certain conditions, it is shown that the system is permanent and there exists a solution which is defined on the whole \bbb{R} and whose components are bounded from above and from below by positive constants