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The rates of reaction of hydroxyl radicals with a large number of aliphatic compounds have been determined. These include carboxylate ions, alcohols, glycols, and ethers, as well as two series of substituted methanes and acetate ions. The reactivities of aliphatic compounds towards OH radicals are dependent on both the inductive and the resonance effects, as expressed by Hamrnett's a-function. The reactivities of long-chain compounds are the sum of the partial reactivities of C-H bonds a t different positions in the molecule. This corroborates the assumption that the general pattern of reactions of OH radicals with aliphatic compounds involves the abstraction of H atoms in the rate-determining step. Only in specific cases w a s a charge-transfer mechanism indicated. A general parallelism is observed between the reactions of OH radicals and those of H atoms.RATE constants for reactions of hydroxyl radicals with some aliphatic compounds, determined by competition kinetics, were recently reported-l-' It has been suggested that the RH + OH reaction involves hydrogen-abstraction in the rate-determining step,6,8-12 resulting in the formation of a R* free radical and a water molecule.

In light of the COVID-19 outbreak caused by the novel coronavirus, companies and institutions have instructed their employees to work from home as a precautionary measure to reduce the risk of contagion. Employees, however, have been exposed to different security risks because of working from home. Moreover, the rapid global spread of COVID-19 has increased the volume of data generated from various sources. Working from home depends mainly on cloud computing (CC) applications that help employees to efficiently accomplish their tasks. The cloud computing environment (CCE) is an unsung hero in the COVID-19 pandemic crisis. It consists of the fast-paced practices for services that reflect the trend of rapidly deployable applications for maintaining data. Despite the increase in the use of CC applications, there is an ongoing research challenge in the domains of CCE concerning data, guaranteeing security, and the availability of CC applications. This paper, to the best of our knowledge, is the first paper that thoroughly explains the impact of the COVID-19 pandemic on CCE. Additionally, this paper also highlights the security risks of working from home during the COVID-19 pandemic.

Over the past years, vehicular ad hoc networks (VANETs) have been commonly used in intelligent traffic systems. VANET's design encompasses critical features that include autonomy, distributed networking, and rapidly changing topology. The characteristics of VANET and its implementations for road safety have attracted considerable industry and academia interest, particularly in research involving transport systems enhancement that could potentially save lives. Message broadcasting in an open access system, such as VANET, is the main and utmost challenging problem with regard to security and privacy in VANETs. Various studies on VANET security and privacy have been proposed. Nevertheless, none has considered overall privacy requirements such as unobservability. In order to address these shortcomings, we propose a VANET based privacy-preserving communication scheme (VPPCS), which meets the requirements for content and contextual privacy. It leverages elliptic curve cryptography (ECC) and an identity-based encryption scheme. We have carried out a detailed security analysis (burrows-abadi-needham (BAN) logic, random oracle model, security of proof, and security attributes) to validate and verify the proposed scheme. The analysis has shown that our scheme is secure and also shown to be effective in a performance evaluation. The proposed scheme does not only meet the previously mentioned security and privacy requirements, but also impervious to various types of attacks such as replay, impersonation, modification, and man-in-themiddle attacks.INDEX TERMS BAN logic, privacy-preserving, elliptic curve, random oracle model, identity-based cryptography.

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Purpose. To evaluate the corneal endothelial cell density and morphology in normal Egyptian eyes. Methods. In total, 568 healthy eyes of 568 Egyptian volunteers aged 20 to 85 years were examined using noncontact specular microscopy for the central corneal thickness (CCT), mean endothelial cell density (MCD), coefficient of variation (CV) in cell area, mean cell area (MCA), and hexagonal cell (Hex) percentage. Variables were compared between sexes and between different age groups. Results. The mean CCT, MCD, and MCA were 514.45 ± 43.04 μm, 2647.50 ± 382.62 cells/mm2, and 390.59 ± 149.94 μm2, respectively. MCD and MCA showed no significant differences between men and women (P=0.171 and 0.099, respectively), whereas CV (%) and Hex (%) showed significant differences (P=0.024 and 0.015, respectively). CCT (P=0.007, r = −0.113) and MCD (P<0.001, r = −0.357) exhibited a significant negative correlation with age, whereas CV (%) (P<0.001, r = 0.341) and MCA (P=0.008, r = 0.111) exhibited a significant positive correlation. The mean rate of endothelial cell loss from 20 to 85 years of age was 0.3% per year. Conclusions. Our results provide normative data for the corneal endothelium in healthy Egyptian eyes, thus increasing the knowledge base for corneal endothelial cell parameters in healthy Egyptian eyes. Furthermore, our findings can be used as baseline values for comparisons between Egyptian and other populations and for studies of the endothelial cell reserve and capacity for intraocular surgery and corneal transplantation.

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Aim. To investigate corneal endothelial cell morphological in children with type 1 diabetes and to determine the systemic and local factors that contribute to these changes. Methods. One hundred sixty eyes of 80 children with type 1 diabetes and 80 eyes of 40 normal children as a control during the period from July 2015 to February 2016 underwent full clinical and ophthalmologic examination. We measured the central corneal thickness (CCT), endothelial cell density (ECD), ploymegathism, and pleomorphism using a noncontact specular microscope. Results. The mean age of the diabetic children was 8.22 ± 3.11 years. The mean duration of type 1 diabetes was 3.51 ± 2.23 years. The mean CCT was significantly higher: 537 ± 33.41 microns (right eye), in the diabetic group compared to the control group. The mean ECD in patients with type 1 diabetes was 3149.84 ± 343.75 cells/mm2 (right eye), and it was significantly lower than in the control group. Furthermore, pleomorphism was significantly lower 48.73 ± 5.43% (right eye), in the diabetic group compared to the control group. The mean polymegathism was significantly higher 37.96 ± 5.61% (right eye), in the diabetic group compared to the control group. All of these changes are significantly correlated only with the duration of diabetes. Conclusions. Diabetic children have thicker corneas, lower ECD, an increased polymegathism, and a decreased pleomorphism. The duration of diabetes is the factor that affects all of these changes. To what extent these changes affect visional function on long term needs to be investigated in further studies.