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1.
Accid Anal Prev ; 200: 107534, 2024 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-38552346

RESUMEN

Mobility and environmental benefits of Green Light Optimal Speed Advisory (GLOSA) systems have been reported by many previous research studies, however, there is insufficient knowledge on the safety implications of such an application. For safe deployment of GLOSA system, it is most critical to identify and address potential safety issues in the design process. It can be argued that implementation of GLOSA system can improve safety by reducing traffic conflicts associated with the interrupted traffic flow at signalised intersections. However, more research findings are needed from field and simulation based studies to evaluate the impacts on safety under a variety of real-world scenarios. As part of the LEVITATE (Societal Level Impacts of Connected and Automated Vehicles) project under European Union's Horizon 2020 Programme, the main objective of this study is to examine the safety impacts of GLOSA under mixed traffic compositions with varying market penetration rates (MPR) of connected and automated vehicles (CAVs). A calibrated and validated microsimulation model (developed in Aimsun) of the greater Manchester area was used for this study where three signalised intersections in a corridor were identified for implementing GLOSA system. An improved algorithm was developed by identifying the potential issues/limitations in some of the GLOSA algorithms found in literature. Behaviours of CAVs were modelled based on the findings of a comprehensive literature review. Safety analysis was performed through processing the simulated vehicular trajectories in the surrogate safety assessment model (SSAM) by the Federal Highway Administration (FHWA). The surrogate safety assessment results showed small improvement in safety with the GLOSA implementation at multiple intersections in the test network only at low MPR (20%) scenarios of CAVs, as compared to the respective without GLOSA scenarios. No or rather slightly lower improvement in safety was observed with GLOSA implementation under mixed fleet scenarios with 40 % or higher 1st Generation or 2nd Generation CAVs, as compared to the respective scenarios without GLOSA. The implementation of GLOSA system was also found to have some impact on the traffic conflict types (although not consistent across all MPR scenarios), where rear-end conflicts were found to decrease while a slight increase was observed in lane-change conflicts.


Asunto(s)
Accidentes de Tránsito , Conducción de Automóvil , Humanos , Accidentes de Tránsito/prevención & control , Seguridad , Luz Verde , Simulación por Computador
2.
Accid Anal Prev ; 195: 107424, 2024 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-38091887

RESUMEN

Cooperative, Connected and Automated Mobility (CCAM) enabled by Connected and Autonomous Vehicles (CAVs) has potential to change future transport systems. The findings from previous studies suggest that these technologies will improve traffic flow, reduce travel time and delays. Furthermore, these CAVs will be safer compared to existing vehicles. As these vehicles may have the ability to travel at a higher speed and with shorter headways, it has been argued that infrastructure-based measures are required to optimise traffic flow and road user comfort. One of these measures is the use of a dedicated lane for CAVs on urban highways and arterials and constitutes the focus of this research. As the potential impact on safety is unclear, the present study aims to evaluate the safety impacts of dedicated lanes for CAVs. A calibrated and validated microsimulation model developed in AIMSUN was used to simulate and produce safety results. These results were analysed with the help of the Surrogate Safety Assessment Model (SSAM). The model includes human-driven vehicles (HDVs), 1st generation and 2nd generation autonomous vehicles (AVs) with different sets of parameters leading to different movement behaviour. The model uses a variety of cases in which a dedicated lane is provided at different type of lanes (inner and outer) of highways to understand the safety effects. The model also tries to understand the minimum required market penetration rate (MPR) of CAVs for a better movement of traffic on dedicated lanes. It was observed in the models that although at low penetration rates of CAVs (around 20%) dedicated lanes might not be advantageous, a reduction of 53% to 58% in traffic conflicts is achieved with the introduction of dedicated lanes in high CAV MPRs. In addition, traffic crashes estimated from traffic conflicts are reduced up to 48% with the CAVs. The simulation results revealed that with dedicated lane, the combination of 40-40-20 (i.e., 40% human-driven - 40% 1st generation AVs- 20% 2nd generation AVs) could be the optimum MPR for CAVs to achieve the best safety benefits. The findings in this study provide useful insight into the safety impacts of dedicated lanes for CAVs and could be used to develop a policy support tool for local authorities and practitioners.


Asunto(s)
Accidentes de Tránsito , Conducción de Automóvil , Humanos , Accidentes de Tránsito/prevención & control , Vehículos Autónomos , Seguridad , Simulación por Computador
3.
Org Lett ; 25(34): 6429-6433, 2023 Sep 01.
Artículo en Inglés | MEDLINE | ID: mdl-37589335

RESUMEN

A collective synthesis of 3,6-dideoxysugars, including seven naturally known congeners, has been reported using commercially available methyl lactates in five steps. The essential tandem process involving the olefin cross-metathesis and isomerization steps was enabled by the dual function of Grubbs-II catalyst, affording the products in good yields and providing concise and practical access to a class of biologically important deoxysugars.

4.
Org Lett ; 25(19): 3497-3501, 2023 05 19.
Artículo en Inglés | MEDLINE | ID: mdl-37154579

RESUMEN

This report describes a streamlined synthesis of immunosuppressive mycestericin E and G through a highly stereoselective nitroso-ene cyclization in 11-12 steps using readily available materials. The stereochemical outcome in the formation of a Nα-quaternary stereogenic center is rationalized by a trajectory based on the polar diradical intermediate and subsequent hydrogen transfer. Julia olefination offers a facile chain elongation method that presents a viable strategy for structural derivatization in future medicinal applications.


Asunto(s)
Inmunosupresores , Ciclización , Estereoisomerismo
5.
Org Lett ; 25(11): 1929-1934, 2023 Mar 24.
Artículo en Inglés | MEDLINE | ID: mdl-36913431

RESUMEN

Amino deoxysugars are abundant in nature and play an important role in various biological functions, promoting numerous efforts to synthesize their structurally unique motifs. In this report, a de novo approach from a readily available lactic acid derivative is devised to construct several amino deoxysugars embedded in natural products, featuring a novel nitroso-ene-type cyclization to introduce a nitrogen atom into the carbon framework. This efficient synthesis provides an unprecedented synthetic route to explore the nitroso-ene cyclization to accumulate intriguing amino deoxysugars.

6.
Molecules ; 27(13)2022 Jul 05.
Artículo en Inglés | MEDLINE | ID: mdl-35807568

RESUMEN

Lemonomycin (1) was first isolated from the fermentation broth of Streptomyces candidus in 1964. The complete chemical structure was not elucidated until 2000 with extensive spectroscopic analysis. Lemonomycin is currently known as the only glycosylated tetrahydroisoquinoline antibiotic. Its potent antibacterial activity against Staphylococcus aureus and Bacillus subtilis and complex architecture make it an ideal target for total synthesis. In this short review, we summarize the research status of lemonomycin for biological activity, biosynthesis, and chemical synthesis. The unique deoxy aminosugar-lemonose was proposed to play a crucial role in biological activity, as shown in other antibiotics, such as arimetamycin A, nocathiacin I, glycothiohexide α, and thiazamycins. Given the self-resistance of the original bacterial host, the integration of biosynthesis and chemical synthesis to pursue efficient synthesis and further derivatization is in high demand for the development of novel antibiotics to combat antibiotic-resistant infections.


Asunto(s)
Infecciones Estafilocócicas , Tetrahidroisoquinolinas , Antibacterianos/química , Humanos , Pruebas de Sensibilidad Microbiana , Staphylococcus aureus
7.
Chem Rec ; 22(1): e202100197, 2022 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-34473401

RESUMEN

The construction of a structurally rigid architecture with chiral complexity, necessary to enhance the interaction with binding sites of drug targets, has been adapted as an intriguing approach in drug development. In the past few years, we have been interested in the synthesis of biologically significant and bridged alkaloids via novel synthetic methods and strategies based on recognition of the privileged pattern. Therefore, nitroso-ene and aza-Wacker cyclizations were elevated for the first time to construct bridged alkaloids, such as hosieine A, kopsone, melinonine-E and strychnoxanthine. Mechanistic investigations, including computational calculations for nitroso-ene reaction and deuterated experiments for aza-Wacker reaction, enable us to gain more insights into the chemical reactivity and selectivity of specific functional groups in developing viable synthetic methods.


Asunto(s)
Alcaloides , Ciclización , Estereoisomerismo
8.
Org Lett ; 20(8): 2386-2390, 2018 04 20.
Artículo en Inglés | MEDLINE | ID: mdl-29595983

RESUMEN

An unprecedented N-substituent of the amide was found to be crucial for the successful annulation to establish 2-azabicyclo[3.3.1]nonane and other ring skeletons in good yield. The novel catalytic aza-Wacker annulation methodology was further illustrated in the concise syntheses and the absolute configuration determinations of melinonine-E and strychnoxanthine.

9.
Angew Chem Int Ed Engl ; 56(38): 11599-11603, 2017 09 11.
Artículo en Inglés | MEDLINE | ID: mdl-28703404

RESUMEN

A type II nitroso-ene cyclization was developed for the construction of morphan derivatives with good functional-group tolerance. DFT calculations revealed that the nitroso-ene reaction proceeds in a stepwise manner involving diradical or zwitterionic intermediates. The rate-determining step is C-N bond formation, followed by a rapid hydrogen-transfer step with a chair-conformation transition state. The current approach was also successfully applied in the first total synthesis of (±)-kopsone, a highly strained yet simple morphan-type alkaloid isolated from Kopsia macrophylla.

10.
Angew Chem Int Ed Engl ; 55(21): 6280-4, 2016 05 17.
Artículo en Inglés | MEDLINE | ID: mdl-27072483

RESUMEN

A stereodivergent strategy enabled by bioinspired oxa-Michael cyclization was developed for the synthesis of functionalized tetrahydropyrans on the basis of the inherent symmetry in 1,3-diols, the symmetries of which were tunable by stereoselective hydroboration of an allene with a variety of alkylborane reagents and subsequent allylation of an aldehyde. The mechanism-based utilization of monoalkyl borane in the hydroboration and allylation cascade is unprecedented.

11.
Guang Pu Xue Yu Guang Pu Fen Xi ; 35(9): 2420-3, 2015 Sep.
Artículo en Chino | MEDLINE | ID: mdl-26669141

RESUMEN

The content of copper in natural water is very low, and direct determination is difficult. Therefore, it is very meaningful for the combination of efficient separation-enrichment technology and highly sensitive detection. Based on the high adsorption capacity of Cu(II) onto nano-sized ZnO, a novel method by using nano-sized ZnO as adsorbent and graphite furnace atomic absorption spectrometry as determination means was in this work. The adsorption behaviors of Cu(II) on nano-sized ZnO was studied. Effects of acidity, adsorption equilibrium time, adsorbent dosage and coexisting ions on adsorption rates were investigated. The results showed that the adsorption efficiency was above 95% in a pH range from 3.0 to 7.0. Compared with other adsorbents for trace element enrichment such as activated carbon, nano-sized TiO2 powder, the most prominent advantage is nano-sized ZnO precipitate with the concentrated element can directly dissolved in HCl solution without any filtration and desorption process can directly analyzed by graphite furnace atomic absorption spectrometry or inductively coupled plasma atomic emission spectrometry. Compared with colloid nano materials, nano-sized ZnO is the true solution after dissolving have small matrix effect and viscosity more suitable for graphite furnace atomic absorption spectrometry or inductively coupled plasma atomic emission spectrometry detection. The proposed method possesses low detection limit (0.13 µg · L(-1)) and good precision (RSD=2.2%). The recoveries for the analysis of environmental samples were in a rang of 91.6%~92.6% and the analysis results of certified materials were compellent by using the proposed method.

12.
Guang Pu Xue Yu Guang Pu Fen Xi ; 32(5): 1397-400, 2012 May.
Artículo en Chino | MEDLINE | ID: mdl-22827099

RESUMEN

A novel method for preconcentration of ultra-trace germanium and determination by hydride generation atomic fluorescence spectrometry (HGAFS) was presented in this work. When the pH values of solution were 6.0-8.0, the adsorption efficiency of nano-sized TiO2 colloid for germanium was 97.0%-99.0% in a short time. Nano-sized TiO2 colloid was used to concentrate the ultra-trace germanium in water sample due to its high absorption capacity. After centrifugation, the supernatant fluid was removed. The sediment which contained the concentrated Ge(IV) was inverted to colloid by adding HCl of certain concentration. Ge(IV) in colloid was directly determined by HGAFS. The proposed method possesses low detection limit (3sigma) (0.060 microg x L(-1)) and good precision (the relative standard deviation (RSD) is 2.0%, n=6). The method is was also quite simple and time saving (without any filtration and desorption process). Satisfactory results were obtained when applying this method to the determination of ultra-trace germanium in water samples.

13.
Guang Pu Xue Yu Guang Pu Fen Xi ; 27(3): 592-4, 2007 Mar.
Artículo en Chino | MEDLINE | ID: mdl-17554930

RESUMEN

A novel crosslinked chitosan(CCTS) not dissolved in acidic or alkaline solutions was synthesized by the crosslinking reaction of chitosan (CTS) with crosslinking agent (3-chloro-1,2-epoxypropane). The adsorption capability of Pd(II ) by CCTS was studied at different pH value. The results showed that the adsorption efficiency was above 98% after preconcentration for 20 minutes when pH values were 1-4. The effects of preconcentration time, dosage of CCTS, adsorption capacity of CCTS, sample volume, coexistent elements, and elution of Pd(II) were investigated. The mechanism of adsorption of CCTS for Pd(II) was discussed. A novel method for the preconcentration and separation of trace Pd(II) with crosslinked chitosan (CCTS) and its determination in water by graphite furnace atomic absorption spectrometry has been developed. The detection limit (3sigma, n=8) was 0.143 microg x L(-1), the relative standard deviation(RSD) was less than 5.47%, and this preconcentration method was used to detect Pd(II) in lake water and sea water with recoveries of 92%-96%. It also can be used to recycle Pd(II).


Asunto(s)
Quitosano/química , Reactivos de Enlaces Cruzados/química , Grafito/química , Plomo/aislamiento & purificación , Espectrofotometría Atómica/métodos , Concentración de Iones de Hidrógeno , Plomo/química , Espectroscopía Infrarroja por Transformada de Fourier , Temperatura
14.
Anal Sci ; 22(10): 1319-22, 2006 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-17038769

RESUMEN

A novel method for prevention of the oxidation of Sb(III) during sample pretreatment, preconcentration of Sb(III) and Sb(V) with nanometer size titanium dioxide (rutile) and speciation analysis of antimony, has been developed. Antimony(III) could be selectively determined by flow injection-hydride generation-atomic absorption spectrometry, coexisting with Sb(V). Trace Sb(III) and Sb(V) were all adsorbed onto 50 m g TiO2 from 500 ml solution at pH 3.0 within 15 min, then eluted by 10 ml of 5 mol/l HCl solution. One eluent was directly used for the analysis of Sb(III); to the other eluent was added 0.5 g KI and 0.2 g thiourea to reduce Sb(V) to Sb(III), then the mixture was used for the determination of total antimony. The antimony(V) content is the mathematical difference of the two concentrations. Detection limits (based on 3sigma of the blank determinations, n=11) of 0.05 ng/ml for Sb(III) and 0.06 ng/ml for Sb(V), were obtained.

15.
Huan Jing Ke Xue ; 27(6): 1140-3, 2006 Jun.
Artículo en Chino | MEDLINE | ID: mdl-16921950

RESUMEN

Nanometer size titanium dioxide modified with 3,5-dinitrosalicylic acid (3,5-DA) was prepared using chemical adsorption method. The influences of surface modification on the adsorption of p-nitrophenol (PNP) and the dispersion in solvent such as water, benzene and ethanol were studied. The 3,5-dinitrosalicylic acid is bonded to the surface hydroxyl from TiO2 nanoparticles, results in the formation of a stable, six-ring complex which color is buff. The 3, 5-DA-modified TiO2 nanoparticles have good dispersive capacity in water, benzene and ethanol. Under the optimum conditions such as pH value 3, adsorption time 10 min, the adsorption ratio of PNP by TiO2 is improved from 43% to 99.9% through surface modification. A new method could be used to remove directly 3 approximately 10mg/L PNP, and the residual concentrations is below the integrated wastewater discharge standard (GB 8978-1996).


Asunto(s)
Nanopartículas del Metal/química , Nitrofenoles/química , Salicilatos/química , Titanio/química , Adsorción , Nitrofenoles/aislamiento & purificación , Eliminación de Residuos Líquidos/métodos
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