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Remote Steric and Electronic Effects of N-Heterocyclic Carbene Ligands on Alkene Reactivity and Regioselectivity toward Hydrocupration Reactions: The Role of Expanded-Ring N-Heterocyclic Carbenes

Hussein AA, Ariffin A

J Org Chem, 2023 Sep 15;88(18):13009-13021.
PMID: 37649423 DOI: 10.1021/acs.joc.3c01121

The remote groups in N-heterocyclic carbene (NHC) ligands have a significant influence on metal-catalyzed reactions. We examine how remote bulkiness, electronic groups, and expanded-ring NHCs (ER-NHCs) influence alkene reactivity and regioselectivity toward hydrocupration using density functional theory calculations. The impact of remote steric bulkiness on the Cu-H insertion rate is analyzed, revealing a strong correlation between the steric substituent constant and rate ratio, where a bulky group increases the rate due to reduced steric effects in the transition state (TS). The steric properties of the examined catalysts (with a remote group R2 = CPh3, CHPh2, CH2Ph, CH3, and H) and their corresponding TSs are found to be modulated greatly by the remote steric substitution group and the ring size of the NHC ligand. Enhanced bulkiness enhances the nucleophilic Cu-H moiety. The remote electronic groups have a smaller impact on insertion barrier compared to that of steric hindrance. Furthermore, ER-NHC exploration indicates that NHCs with over five-membered rings have a significantly negative influence on the reaction rate. Finally, with a highly bulky group (R2 = CPh3), anti-Markovnikov insertion preference is attributed to high interaction energy and improved steric properties. Overall, our findings here provide valuable insights for the development of a more effective catalyst in metal-catalyzed reactions.
Fulltext Performance Evaluation of Localization Accuracy for a Log-Normal Shadow Fading Wireless Sensor Network under Physical Barrier Attacks

Hussein AA, Rahman TA, Leow CY

Sensors (Basel), 2015;15(12):30545-70.
PMID: 26690159 DOI: 10.3390/s151229817

Localization is an apparent aspect of a wireless sensor network, which is the focus of much interesting research. One of the severe conditions that needs to be taken into consideration is localizing a mobile target through a dispersed sensor network in the presence of physical barrier attacks. These attacks confuse the localization process and cause location estimation errors. Range-based methods, like the received signal strength indication (RSSI), face the major influence of this kind of attack. This paper proposes a solution based on a combination of multi-frequency multi-power localization (C-MFMPL) and step function multi-frequency multi-power localization (SF-MFMPL), including the fingerprint matching technique and lateration, to provide a robust and accurate localization technique. In addition, this paper proposes a grid coloring algorithm to detect the signal hole map in the network, which refers to the attack-prone regions, in order to carry out corrective actions. The simulation results show the enhancement and robustness of RSS localization performance in the face of log normal shadow fading effects, besides the presence of physical barrier attacks, through detecting, filtering and eliminating the effect of these attacks.
Fulltext Robust multiple frequency multiple power localization schemes in the presence of multiple jamming attacks

Hussein AA, Leow CY, Rahman TA

PLoS One, 2017;12(5):e0177326.
PMID: 28493977 DOI: 10.1371/journal.pone.0177326

Localization of the wireless sensor network is a vital area acquiring an impressive research concern and called upon to expand more with the rising of its applications. As localization is gaining prominence in wireless sensor network, it is vulnerable to jamming attacks. Jamming attacks disrupt communication opportunity among the sender and receiver and deeply impact the localization process, leading to a huge error of the estimated sensor node position. Therefore, detection and elimination of jamming influence are absolutely indispensable. Range-based techniques especially Received Signal Strength (RSS) is facing severe impact of these attacks. This paper proposes algorithms based on Combination Multiple Frequency Multiple Power Localization (C-MFMPL) and Step Function Multiple Frequency Multiple Power Localization (SF-MFMPL). The algorithms have been tested in the presence of multiple types of jamming attacks including capture and replay, random and constant jammers over a log normal shadow fading propagation model. In order to overcome the impact of random and constant jammers, the proposed method uses two sets of frequencies shared by the implemented anchor nodes to obtain the averaged RSS readings all over the transmitted frequencies successfully. In addition, three stages of filters have been used to cope with the replayed beacons caused by the capture and replay jammers. In this paper the localization performance of the proposed algorithms for the ideal case which is defined by without the existence of the jamming attack are compared with the case of jamming attacks. The main contribution of this paper is to achieve robust localization performance in the presence of multiple jamming attacks under log normal shadow fading environment with a different simulation conditions and scenarios.
Association of azoospermia factor region deletions in infertile male subjects among Malaysians

Hussein AA, Vasudevan R, Patimah I, Prashant N, Nora FA

Andrologia, 2015 Mar;47(2):168-77.
PMID: 24528375 DOI: 10.1111/and.12240

Azoospermia factor region (AZF) deletions (AZFa, AZFb, AZFc and AZFd) in the Y chromosome were analysed in male infertility subjects in various populations with conflicting results. This study comprised of 54 infertile males and 63 fertile controls, and the frequency of AZFa, AZFb, AZFc and AZFd deletions were determined using conventional polymerase chain reaction (PCR) as well as real-time PCR-high resolution melting analysis-based methods. The results of this study showed that, three of 54 cases (5.55%) had AZF (a, b and c) deletions (two had AZFc and one had AZFa deletions). Four cases were found to have AZFd deletions (7.4%) with two of them being associated with AZFc deletions (P = 0.028). The frequency of AZF (a, b and c) deletions in Malaysian infertile male subjects was found to be comparable with other populations. AZFd deletions were found to be significant (P < 0.05) in male infertility and it may be associated with other types of AZF deletions.
Fulltext The ability of digital breast tomosynthesis to reduce additional examinations in older women

Gharaibeh M, Alfwares AA, Elobeid E, Khasawneh R, Rousan L, El-Heis M, et al.

Front Med (Lausanne), 2023;10:1276434.
PMID: 38076239 DOI: 10.3389/fmed.2023.1276434

AIMS: To assess the diagnostic performance of digital breast tomosynthesis (DBT) in older women across varying breast densities and to compare its effectiveness for cancer detection with 2D mammography and ultrasound (U/S) for different breast density categories. Furthermore, our study aimed to predict the potential reduction in unnecessary additional examinations among older women due to DBT.
METHODS: This study encompassed a cohort of 224 older women. Each participant underwent both 2D mammography and digital breast tomosynthesis examinations. Supplementary views were conducted when necessary, including spot compression and magnification, ultrasound, and recommended biopsies. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and area under the curve (AUC) were calculated for 2D mammography, DBT, and ultrasound. The impact of DBT on diminishing the need for supplementary imaging procedures was predicted through binary logistic regression.
RESULTS: In dense breast tissue, DBT exhibited notably heightened sensitivity and NPV for lesion detection compared to non-dense breasts (61.9% vs. 49.3%, p 0.05) between DBT and the four dependent variables.
CONCLUSION: Our findings indicate that among older women, DBT does not significantly decrease the requirement for further medical examinations.
Cross-Country Discrepancies in Monkeypox Vaccine Hesitancy Among Postgraduate and Undergraduate Medical Students

Hussein M, Siddiq A, Ismail HM, Mansy N, Ellakwa DE, Nassif M, et al.

Disaster Med Public Health Prep, 2024 May 02;18:e82.
PMID: 38695200 DOI: 10.1017/dmp.2024.50

BACKGROUND: Medical students hold significant importance, as they represent the future of healthcare provision. This study aimed to explore psychological antecedents towards the monkeypox (mpox) vaccines among postgraduate and undergraduate medical students across countries.
METHODS: A cross-sectional survey was conducted among medical students aged 18 years old and above in 7 countries; Egypt, Romania, Malaysia, and Yemen, Iraq, India, and Nigeria. We used social media platforms between September 27 and November 4, 2022. An anonymous online survey using the 5C scale was conducted using snowball and convenience Sampling methods to assess the 5 psychological antecedents of vaccination (i.e., confidence, constraints, complacency, and calculation, as well as collective responsibility).
RESULTS: A total of 2780 participants were recruited. Participants' median age was 22 years and 52.1% of them were males. The 5C psychological antecedents of vaccination were as follows: 55% were confident about vaccination, 10% were complacent, 12% experienced constraints, and 41% calculated the risk and benefit. Lastly, 32% were willing to be vaccinated for the prevention of infection transmission to others. The Country was a significant predictor of confidence, complacency, having constraints, and calculation domains (P < 0.001). Having any idea about the mpox vaccine was linked to 1.6 times higher odds of being more confident [OR = 1.58 (95% CI, 1.26-1.98), P < 0.001] Additionally, living in a rural area significantly increased complacency [OR = 1.42 (95% CI, 1.05-1.95), P = 0.024] as well as having anyone die from mpox [OR = 3.3 (95% CI, 1.64-6.68), P < 0.001]. Education level was associated with increased calculation [OR = 2.74 (95% CI, 1.62-4.64), P < 0.001]. Moreover, being single and having no chronic diseases significantly increased the calculation domain [OR = 1.40 (95% CI, 1.06-1.98), P = 0.02] and [OR = 1.54 (95% CI, 1.10-2.16), P = 0.012] respectively. Predictors of collective responsibility were age 31-45 years [OR = 2.89 (95% CI, 1.29-6.48), P = 0.01], being single [OR = 2.76 (95% CI, 1.94 -3.92), P < 0.001], being a graduate [OR = 1.59 (95% CI (1.32-1.92), P < 0.001], having no chronic disease [OR = 2.14 (95% CI, 1.56-2.93), P < 0.001], and not knowing anyone who died from mpox [OR = 2.54 (95% CI, 1.39-4.64), P < 0.001), as well as living in a middle-income country [OR = 0.623, (95% CI, 0.51-0.73), P < 0.001].
CONCLUSIONS: This study underscores the multifaceted nature of psychological antecedents of vaccination, emphasizing the impact of socio-demographic factors, geographic location, and awareness, as well as previous experiences on individual attitudes and collective responsibility towards vaccination.