Amines and boranes are the archetypical Lewis bases and acids, respectively. The former can readily undergo one-electron oxidation to give radical cations, whereas the latter are easily reduced to ...afford radical anions. Here, we report the synthesis of a neutral tricoordinate boron derivative, which acts as a Lewis base and undergoes one-electron oxidation into the corresponding radical cation. These compounds can be regarded as the parent borylene (H-B:) and borinylium (H-B +. ), respectively, stabilized by two cyclic (alkyl)(amino)carbenes. Ab initio calculations show that the highest occupied molecular orbital of the borane as well as the singly occupied molecular orbital of the radical cation are essentially a pair and a single electron, respectively, in the p(π) orbital of boron.
Hydrogen storage holds a crucial place for the future of the world in terms of green energy. Two-dimensional materials, in particular, are important in this regard. The aim of this study is to ...evaluate the performance of MoS2 which is one of the most popular member of two-dimensional materials family. To do this, bulk and exfoliated MoS2 were used. Firstly, the liquid phase exfoliation method was employed to obtain exfoliated MoS2 layers. Then, the hydrogen storage potential of the bulk and exfoliated MoS2 was addressed under 1, 3, 5, 7, and 9 bar hydrogen pressure. After the absorption process, all the samples were characterized using XRD, Raman Spectrometer, and BET ahead of evaluating their hydrogen storage potential. The XRD pattern showed that the peak positions of bulk and exfoliated MoS2 were not affected critically by hydrogen storage. In the Raman spectra, the A1g and E2g1 peaks of all hydrogenated materials shifted to low wavelengths. Moreover, the BET measurements revealed that the specific surface area and the pore size of the bulk MoS2 were 12.31 m2/g and ≤67.46 nm respectively. Additionally, the specific surface area and the pore size of the exfoliated MoS2 were 23.16 m2/g and ≤69.28 nm, respectively. The hydrogen storage potential of the bulk and the exfoliated MoS2 was evaluated through an MFC in sccm unit. The bulk and exfoliated MoS2 stored 220 and 450 sccm hydrogen, respectively. Besides, the weight percent hydrogen storage for H–MoS2 and H-exfoliated MoS2 was determined to be 1.2 and 2.4 wt%, respectively. In summary, this study has shown that exfoliated MoS2, one of the two-dimensional materials, can play a critical role for hydrogen storage due to their high specific surface area.
•Exploring MoS2 for hydrogen storage, both in bulk and exfoliated forms, reveals promising 2D material capabilities.•Exfoliated MoS2 layers were successfully produced by liquid phase exfoliation method.•AFM confirms formation of few-layer nanosheets with thicknesses ranging from 2 to 6 nm (2–5 layers).•Exfoliated MoS2, stores up to 450 sccm and 2.4 % wt of hydrogen, surpassing the hydrogen capacity of MoS2 at 7 bar.
•HCWs face a high risk of SARS-CoV-2 transmission during serving health care.•Transmission may also occur in nonmedical areas while speaking or eating.•Proper use of PPE and basic infection control ...precautions are essential.
To investigate the specific risk factors for novel coronavirus (SARS-CoV-2) transmission among health care workers (HCWs) in a tertiary care university hospital.
Upper respiratory samples of HCWs were tested for SARS-CoV-2 by reverse transcriptase polymerase chain reaction. A case-control study was conducted to explore the possible risk factors that lead to SARS-CoV-2 transmission to HCWs.
Of 703 HCWs screened between March 20 and May 20, 2020, 50 (7.1%) were found to be positive for SARS-CoV-2. The positivity rates for SARS-CoV-2 among physicians, nurses, cleaning personnel, and the other occupations were 6.3%, 8.0%, 9.1%, and 2.6%, respectively. The infection rate was 8.3% among HCWs who worked in COVID-19 units and 3.4% among those who did not work in coronavirus disease 2019 (COVID-19) units (RR = 2.449, confidence interval = 1.062-5.649, P= .027). The presence of a SARS-CoV-2 positive person in the household (P = .016), inappropriate use of personnel protective equipment while caring for patients with COVID-19 infection (P = .003), staying in the same personnel break room as an HCW without a medical mask for more than 15 minutes (P = .000), consuming food within 1 m of an HCW (P = .003), and failure to keep a safe social distance from an HCW (P = .003) were statistically significant risk factors for infection.
HCWs have a high risk for SARS-CoV-2 transmission while providing care to COVID-19 patients. Transmission may also occur in nonmedical areas of the hospital while speaking or eating. Periodic screening of HCWs for SARS-CoV-2 may enable early detection and isolation of infected HCWs.
Room temperature hydrogenation of an SIDep‐stabilized diboryne (SIDep=1,3‐bis(diethylphenyl)‐4,5‐dihydroimidazol‐2‐ylidene) and a cAAC‐supported diboracumulene ...(cAAC=1‐(2,6‐diisopropylphenyl)‐3,3,5,5‐tetramethylpyrrolidin‐2‐ylidene) provided the first selective route to the corresponding 1,2‐dihydrodiborenes. DFT calculations showed an overall exothermic (ΔG=19.4 kcal mol−1) two‐step asynchronous H2 addition mechanism proceeding via a bridging hydride.
No catalyst needed: Two new carbene‐stabilized 1,2‐dihydrodiborenes have been synthesized by the direct and selective monohydrogenation of boron–boron multiple bonds under mild conditions. Theoretical calculations show a two‐step asynchronous H2 addition mechanism proceeding via a bridging hydride.
Abstract
The recent growth in digital marketing investments and revenues has attracted the attention of both marketing practitioners and scholars. However, this growth has dramatically increased ...users' exposure to ad messages, encouraging consumers to avoid them. Therefore, ad avoidance has become a major problem for marketing practitioners. Although researchers have become much more interested in this subject over the past two decades, the body of knowledge on ad avoidance in the digital environment remains fragmented due to the lack of a comprehensive review. Therefore, a holistic overview study is needed that focuses on the big picture and can help researchers to understand the literature comprehensively. This study aims to provide a comprehensive understanding of the topic using a systematic literature review approach on digital ad avoidance. To this end, we provide an in‐depth content analysis of 56 relevant articles published in 31 peer‐reviewed scientific journals up to December 31, 2021. Based on a theories, contexts, characteristics, and methods (TCCM) framework, the study results shed light on ‘what do we know, how do we know, and where should research about digital ad avoidance research be heading?’ Additionally, drawing on the content analysis, we have presented an integrative framework that considers antecedents, outcomes, mediators, and moderators, which can help develop the field systematically and guide future research. By doing so, we think this review meets the need to give an overview of the state‐of‐the‐art scientific body of knowledge on digital ad avoidance and makes important and solid contributions to the literature, practical implications, and future research directions based on the findings.
Quantum chemical calculations using DFT (BP86, M05‐2X) and ab initio methods (CCSD(T), SCS‐MP2) have been carried out on the borylene complexes (BH)L2 and nitrogen cation complexes (N+)L2 with the ...ligands L=CO, N2, PPh3, NHCMe, CAAC, and CAACmodel. The results are compared with those obtained for the isoelectronic carbones CL2. The geometries and bond dissociation energies of the ligands, the proton affinities, and adducts with the Lewis acids BH3 and AuCl were calculated. The nature of the bonding has been analyzed with charge and energy partitioning methods. The calculated borylene complexes (BH)L2 have trigonal planar coordinated boron atoms which possess rather short BL bonds. The calculated bond dissociation energies (BDEs) of the ligands for complexes where L is a carbene (NHC or CAAC) are very large (De=141.6–177.3 kcal mol−1) which suggest that such species might become isolated in a condensed phase. The borylene complexes (BH)(PPh3)2 and (BH)(CO)2 have intermediate bond strengths (De=90.1 and 92.6 kcal mol−1). Substituted homologues with bulky groups at boron which protect the boron atom from electrophilic attack might also be stable enough to become isolated. The BDE of (BH)(N2)2 is much smaller (De=31.9 kcal mol−1), but could become observable in a low‐temperature matrix. The proton affinities of the borylene complexes are very large, particularly for the bulky adducts with L=PPh3, NHCMe, CAACmodel and CAAC and thus, they are superbases. All (BH)L2 molecules bind strongly AuCl either η1 (L=N2, PPh3, NHCMe, CAAC) or η2 (L=CO, CAACmodel). The BDEs of H3B(BH)L2 adducts which possess a hitherto unknown boron→boron donor–acceptor bond are smaller than for the AuCl complexes. The strongest bonded BH3 adduct that might be isolable is (BH)(PPh3)2BH3 (De=36.2 kcal mol−1). The analysis of the bonding situation reveals that (BH)L2 bonding comes mainly from the orbital interactions which has three major contributions, that is, the donation from the symmetric (σ) and antisymmetric (π||) combination of the ligand lone‐pair orbitals into the vacant MOs of BH L→(BH)←L and the L←(BH)→L π backdonation from the boron lone‐pair orbital. The nitrogen cation complexes (N+)L2 have strongly bent LNL geometries, in which the calculated bending angle varies between 113.9° (L=N2) and 146.9° (L=CAAC). The BDEs for (N+)L2 are much larger than those of the borylene complexes. The carbene ligands NHC and CAAC but also the phosphane ligands PPh3 bind very strongly between De=358.4 kcal mol−1 (L=PPh3) and De=412.5 kcal mol−1 (L=CAACmodel). The proton affinities (PA) of (N+)L2 are much smaller and they bind AuCl and BH3 less strongly compared with (BH)L2. However, the PAs (N+)L2 for complexes with bulky ligands L are still between 139.9 kcal mol−1 (L=CAACmodel) and 168.5 kcal mol−1 (L=CAAC). The analysis of the (N+)L2 bonding situation reveals that the binding interactions come mainly from the L→(N+)←L donation while L←(N+)→L π backdonation is rather weak.
Quantum chemical calculations suggest that the bonding model for carbones CL2 in terms of donor–acceptor interactions L→C←L is also valid for the isoelectronic systems (BH)L2 and (N+)L2. The nature of the donor–acceptor bonds and the theoretically predicted equilibrium geometries and bond dissociation energies of (BH)L2, (N+)L2 and CL2 with L=CO, N2, PPh3 and the carbene ligands NHCMe, CAACmodel, and CAAC are discussed (see figure). NHC=N‐heterocyclic carbene; CAAC=cyclic alkyl amino carbene.
Knowledge of the normal pattern and variations of the blood supply of the right colon is crucial for better outcomes after colon surgery.
The purpose of this study was to describe the precise ...vascular anatomy of the right colon according to surgical perspective.
Adult fresh cadavers were dissected between January 2013 and October 2015, focusing on the venous and arterial anatomy of the right side of the colon.
Macroscopic anatomical dissections were performed on 111 adult fresh cadavers with emphasis on the vascular anatomy of the right colon. The colic tributaries of the superior mesenteric artery and vein were documented in writing. Furthermore, the dissections were recorded with a video camera.
The incidence of colic arteries arising from the superior mesenteric artery included ileocolic artery, 100%; right colic artery, 33.3%; middle colic artery, 100%; and accessory middle colic artery, 11,7%. All 111 cadavers had a single ileocolic vein, which drained into the superior mesenteric vein in 103 cases (92.8%), into the gastro-pancreatico-colic trunk in 7 cases (6.3%), and into the jejunal trunk in 1 case (0.9%). The drainage site of the ileocolic vein to the superior mesenteric vein varied, and in 9% of cases the ileocolic vein did not accompany the ileocolic artery. The gastro-pancreatico-colic trunk was detected in 87 cases (78.4%); with several forms of the origin of the respective branches, the gastropancreatic trunk was detected in 24 cases (21.6), and the classic gastrocolic trunk of Henle was not detected. Variations were found in the formation and drainage routes of other venous colic tributaries of the superior mesenteric vein.
This study is limited by its use of cadavers in that it is impossible to trace each vessel to its origin in live surgery.
Surgeons must watch, observe, and bear in mind that vascular variations can occur. Awareness of these complex variations may improve the quality of surgery and may prevent devastating complications during right-sided colon resections.
Fear of missing out (FoMO) is a psychological construct that recently emerged in the age of social media. This study aims to provide an overview of the progress on FoMO research and offer a future ...research agenda based on FoMO-related scientific articles published. We carried out this aim using a two-stage methodological approach, based on an initial pool of 314 peer-reviewed articles in the Scopus database: (1) co-citation analysis, a bibliometric analysis technique, with a subset of 103 articles to show how FoMO research develops intellectually; and (2) a systematic review to discuss clusters that emerged after co-citation analysis. Results of the co-citation analysis uncovered four clusters: (1) social media, (2) negative affectivity, (3) problematic social media use, and (4) problematic smartphone use. We discuss the content of each cluster in the context of central themes, key theoretical influences, and characteristic methodological approaches. We also present a future research agenda based on this discussion. In conclusion, this study provides an up-to-date overview that can assist researchers in understanding and designing future FoMO research and for practitioners to improve the well-being of society or users.
We review user-generated video (UGV)-research in hospitality and tourism (H&T), provide an overview of its current-state, and suggest ways forward. We adopted a systematic literature review ...methodology and reviewed 66 articles with TCM (theory/context/methodology) framework. UGV-research focuses on (i) destination image perception, (ii) short-form videos and travel live-streaming, (iii) behavioral intentions, and (iv) crisis management. Theoretical development is diverse, given the descriptive nature of research questions, but it is still in its infancy. The context varies by H&T setting, type of social media platform, population, and country. Research methods and techniques range from traditional analysis to advanced machine learning or artificial intelligence-based quantitative approaches, predominantly qualitative methods.
Deprotonation of (cAAC)BH2(CN) provided clean access to the stable boryl anion, (cAAC)BH(CN)−. Whereas the addition of soft electrophiles occurred at the nucleophilic boron center, harder silyl ...electrophiles added to the harder terminal cyano nitrogen. The resulting (cAAC)BH(CNSiPh3) species behaved like a silylium boryl nucleophile as well as a neutral silylisonitrile borylene.
Whereas the salt metathesis of soft electrophiles with the (cyano)hydroboryl anion (cAAC)B(CN)H− occurs at the nucleophilic boron center, comparatively harder silyl electrophiles add to the harder terminal cyano nitrogen. The resulting (cAAC)BH(CNSiR3) species behave as both zwitterionic silylium boryl and neutral silylisonitrile borylene, a BI compound accessed through simple deprotonation and salt metathesis. cAAC=cyclic (alkyl)(amino)carbene.
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