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[Display omitted] • N/C replacement changes the electronic configuration and considerably decrease the electronic energies. • Nitrogen positions effect leads to different destabilization energies. • Lp-Lp repulsion effect slightly destabilizes the benchmark systems. • The N/C replacement increase the IMHB strength. • N/C substitution decrease the π-ED, which contradicts the predictions of the RAHB theory. This study systematically investigates the impact of N/C substitution in β-aminoacrolein/β-thioaminoacrolein derivatives at various theoretical levels. Key electronic energy components, including electron configuration, nitrogen atom positioning, lone pair-lone pair (Lp-Lp) repulsion, and resonance-assisted hydrogen bonding (RAHB), are evaluated. Results reveal that electron configuration contributes the most stabilizing energy (∼-16 Hartree), while nitrogen positioning and Lp-Lp repulsions destabilizes structures, following the trend: N2 < N1 < N3. RAHB energies are strongly influenced by nitrogen count, with stability improving in the order: N1 (−0.0145) < N2 (−0.0273) < N3 (−0.0370) < N1N2 (−0.0418) < N1N3 (−0.0515) < N2N3 (−0.0643) < N1N2N3 (-0.0788H). Furthermore, energetic, structural, spectral, and topological descriptors support these findings. Interestingly, the aromaticity index indicates a slight reduction in π-electron delocalization (π-ED) with N/C substitution, challenging conventional RAHB theory. [ABSTRACT FROM AUTHOR]

A denial‐of‐service (DoS) attack is a serious attack that targets web applications. According to Imperva, DoS attacks in the application layer comprise 60% of all the DoS attacks. Nowadays, attacks have grown into application‐ and business‐layer attacks, and vulnerability‐analysis tools are unable to detect business‐layer vulnerabilities (logic‐related vulnerabilities). This paper presents the business‐layer dynamic application security tester (BLDAST) as a dynamic, black‐box vulnerability‐analysis approach to identify the business‐logic vulnerabilities of a web application against DoS attacks. BLDAST evaluates the resiliency of web applications by detecting vulnerable business processes. The evaluation of six widely used web applications shows that BLDAST can detect the vulnerabilities with 100% accuracy. BLDAST detected 30 vulnerabilities in the selected web applications; more than half of the detected vulnerabilities were new and unknown. Furthermore, the precision of BLDAST for detecting the business processes is shown to be 94%, while the generated user navigation graph is improved by 62.8% because of the detection of similar web pages. [ABSTRACT FROM AUTHOR]

The trapping of methylglyoxal (MGO) by flavonoid aglycones has been studied using the quantum mechanical calculations at the M06-2X/6-31g (d,p) level of theory. The process can be initiated by MGO transfer on the top of flavonoid aglycone and is sequentially continued by proton transfer from hydronium ion to flavonoid aglycone, MGO and finally a H 2 O molecule. With respect to the proposed mechanism, the selected flavonoid aglycones allow us to investigate the effects of some structural properties, especially the effects of hydroxyl substituents, on the MGO trapping efficacy using the energetics and results of population analysis. The nearest carbon atoms to the hydroxyl carrier carbon of ring A (C6 and C8) are suitable positions for MGO trapping; the results show that the C8 position is more active than C6 in this process. The MGO trapping efficacy strongly depends on the number of hydroxyl groups of the ring A. The energy barrier decreases with the increase in the number of intermolecular hydrogen bonds and proton transfer between the rings A and C. Although the substituents located on various rings have role on the MGO scavenging activity of flavonoid aglycones, the effects of substituents located at the rings A and C are higher than those located at B. [ABSTRACT FROM AUTHOR]

According to the resonance assisted hydrogen bond (RAHB) theory, the π-electron delocalization (π-ED) promotes the intramolecular hydrogen bond (IMHB). Since the relation between the IMHB and π-ED are not well known, in the present work, the linear correlations between the descriptors of π-ED and estimated IMHB energies were systematically investigated. In this regard, the significance of π-ED in chelated forms of the benchmark systems by various descriptors, such as λ, λ′, HOMA, NICS, PDI, ATI, FLU and FLUπ were evaluated. On the other hand, the IMHB energy of RAHB units by some adopted models, such as RRM, RBM, GCM, IRM and OCM are estimated. Furthermore, we explored all of the possible linear correlations between the π-ED indices and various IMHB energies to judge about the performance of RAHB theory. According to our results, it was found that there are great liner correlations between the RRM, RBM and GCM than IRM and OCM methods with some of the π-electron delocalization indices; RRM: λ′ > FLU > λ > HOMA > FLUπ ≈ ATI > PDI > NICS(1) > NICS(0) RBM: λ′ > λ > HOMA > FLU > FLUπ > ATI > PDI > NICS(1) > NICS(0) GCM: λ′ ≈ HOMA > λ > PDI > FLU > FLUπ > NICS(1) > ATI > NICS(0). Surprisingly, the bond order factor of Gilli (λ′), which introduced similar to λ, has the best linear relationship with the IMHB energies. Consequently, the linear coefficients between the RRM, RBM and GCM energies with HOMA, λ and λ′ descriptors are in agreement with the RAHB theory. [ABSTRACT FROM AUTHOR]

[Display omitted] • The energetic, geometrical, topological and molecular orbital descriptors indicate that the chalcogen bond is stronger than the pnicogen bond. • The presence of multiple interactions in a complex reduces the strength of individual interactions, which represents a negative shared presence in the system. • The cooperativity effects for chalcogen bond are stronger than those of pnicogen bond. • Cooperativity energy indicates that the ternary and quaternary complexes is less stable than in binary complexes. • Evaluation of the aromaticity the triazine ring show that with an incerement in the numbers of non-covalent interactions, the aromaticity character of TA ring decreased. In the present study, the strength, nature and cooperativity effects of chalcogen and pnicogen bonds in a set of complexes between the triazine (TA) with SHF and PH 2 F are investigated at M06-2X/6–311++G (d, p) and CCSD/6–311++G (d, p) levels of theory. According to the results, the absolute values of complexation energies of chalcogen bonded systems are greater than the corresponding pnicogen bonded complexes. The simultaneous presence of two or three non-covalent interactions leads to negative cooperativity effects. Furthermore, the electron density values of chalcogen bonded complexes are more than their pnicogen ones, which emphasizes the stronger interactions in the former systems. Also, the Lp N → σ* X-F interaction has been attenuated in the presence of two or three interactions, which is attributed to the presence of negative cooperativity effects. Finally, the aromaticity indices values show with an increase in the number of non-covalent interactions, the TA ring aromaticity character is decreased. [ABSTRACT FROM AUTHOR]