Nitrogen substituted cyclic enediynes: synthesis, thermal reactivity and complexation with metal ions

A number of N-substituted cyclic enediynes (azaenediynes) have been synthesized via Pd(0)-catalysed ene-yne coupling followed by N-alkylation. The simplest of them, a 10-membered monocyclic enediyne 1, underwent Bergman cyclization (BC) at 23°C with a half-life of 72 h. The kinetics of BC slowed down considerably by fusing a benzene ring onto the enediyne. Several novel bis(azaenediyne)s and bis(diazaenediyne)s 3-6 have been synthesized. Their onset temperatures for BC were lowered under metal ion complexation conditions

Modeling reaction time within a traffic simulation model

Human reaction time has a substantial effect on modeling of human behavior at a microscopic level. Drivers and pedestrian do not react to an event instantaneously; rather, they take time to perceive the event, process the information, decide on a response and finally enact their decision. All these processes introduce delay. As human movement is simulated at increasingly fine-grained resolutions, it becomes critical to consider the delay due to reaction time if one is to achieve accurate results. Most existing simulators over-simplify the reaction time implementation to reduce computational overhead and memory requirements. In this paper, we detail the framework which we are developing within the SimMobility Short Term Simulator (a microscopic traffic simulator), which is capable of explicitly modeling reaction time for each person in a detailed, flexible manner. This framework will enable modelers to set realistic reaction time values, relying on the simulator to handle implementation and optimization considerations. Following this, we report our findings demonstrating the impact of reaction time on traffic dynamics within several simulation scenarios. The findings indicate that in the incorporation of reaction time within microscopic simulations improves the traffic dynamics that produces more realistic traffic condition.Singapore-MIT Alliance for Research and Technolog

SimMobility Short-Term: An Integrated Microscopic Mobility Simulator

This paper presents the development of an integrated microscopic mobility simulator, SimMobility Short-Term (ST). The simulator is integrated because its models, inputs and outputs, simulated components, and code base are integrated within a multiscale agent- and activity-based simu- lation platform capable of simulating different spatiotemporal resolutions and accounting for different levels of travelers’ decision making. The simulator is microscopic because both the demand (agents and its trips) and the supply (trip realization and movements on the network) are microscopic (i.e., modeled individually). Finally, the simulator has mobility because it copes with the multimodal nature of urban networks and the need for the flexible simulation of innovative transportation ser - vices, such as on-demand and smart mobility solutions. This paper follows previous publications that describe SimMobility’s overall framework and models. SimMobility is an open-source, multiscale platform that considers land use, transportation, and mobility-sensitive behavioral models. SimMobility ST aims at simulating the high-resolution movement of agents (traffic, transit, pedestrians, and goods) and the operation of different mobility services and control and information systems. This paper presents the SimMobility ST modeling framework and system architecture and reports on its successful calibration for Singapore and its use in several scenarios of innovative mobility applications. The paper also shows how detailed performance measures from SimMobility ST can be integrated with a daily activity and mobility patterns simulator. Such integration is crucial to model accurately the effect of different technologies and service operations at the urban level, as the identity and preferences of simulated agents are maintained across temporal decision scales, ensuring the consistency and accuracy of simulated accessibility and performance measures of each scenario.Singapore. National Research Foundation (CREATE program)Singapore-MIT Alliance. Center. Future Urban Mobility Interdisciplinary Research Grou

Synthesis, reactivity and conformational preferences of novel enediynyl peptides: a possible scaffold for β-sheet capping turns

Novel enediynyl tripeptides 2(a-c) in fully protected forms have been prepared via a sequence of palladium(o)-based Sonogashira coupling. The thermal reactivity of these peptides was shown to be dependent upon the nature of the side chain in the amino acids. Analysis of the CD-spectra of these peptides as well as the variation of chemical shifts with temperature revealed the presence of a β-sheet nucleating conformation in equilibrium with a conformation induced by H-bond formation between the CO and NH belonging to the enediynyl amino acid

Use of nitrones in the synthesis of potential antihypercholesterolemic and antibacterial mono and tricyclic β-lactams

1508-1513The hydroxyethyl group at C-3 of a number of monocyclic β-lactams 2a-d is elaborated by a series of reactions to the appropriate side chain meant for acting as cholesterol absorption inhibitor without perturbing the sensitive β-lactam moiety. In addition, a novel tricyclic β-lactam 2e has also been synthesized using the nitrone cycloaddition approach

Use of nitrones in the synthesis of potential antihypercholesterolemic and antibacterial mono and tricyclic β-lactams

Synthesis of β-lactams 2a-e and the various functionalized ones 8a, 10a and 8b, 10b starting from the nitrones 4a-e have been described

Active site mapping of porcine liver esterase (PLE) and porcine pancreatic lipase (PPL): Stereo and regiochemical outcome of hydrolysis of conformationally constrained esters†

974-980The regio and stereoselectivity of PLE and PPL-catalyzed hydrolysis of a number of conformationally constrained substrates have been studied. The results are discussed based on the existing active site models for the two enzymes

Active site geometry of porcine pancreatic lipase: an interesting switchover from Jones' to Seebach's model

Porcine pancreatic lipase (PPL)-catalyzed hydrolysis of cis 3-acetoxyethyl-1,4-diphenyl and cis 3-acetoxyethyl-1-phenyl-4-(2-furyl) β-lactams 1a and 1b proceeded with opposite stereoselectivity while the corresponding thienyl β-lactam 1c showed no selectivity at all. An explanation based upon the dominance of hydrophobic and polar pockets in governing the stereoselectivity has been proposed

Examining impacts of time-based pricing strategies in public transportation: A study of Singapore

Peak and off-peak pricing strategies are an important policy tool used to spread peak demand in public transportation systems. This study uses an agent-based simulator (SimMobility Mid-term) to examine the impact of pricing (off-peak fare discounts) strategies used in Singapore. The aim of the paper is to demonstrate the capabilities of the simulator, and types of detailed performance indicators it can provide, in order to examine the effects of complex public transport pricing policies. Behavioral models within the simulator are calibrated with relevant datasets such as household travel survey, smart card, GPS probe data from taxis and traffic counts for the Singapore network. Nine (09) time-based pricing strategies are examined that consist of a combination of free pre-peak travel on Mass Rapid Transit (MRT) and an off-peak discount for integrated transit (public buses, MRT and Light Rail Transit (LRT)). Changes in public transport ridership, mode shares, operator\u27s revenue and denied boarding are used as indicators to examine the impacts of pricing strategies. The effects of these policies are also examined on segments of the population in terms of income level, person type and gender. Results indicate that off-peak discounts spread PM peak demand and attract individuals to public transportation. However, the availability of fare discounts in all off-peak periods results in adverse impacts during the AM peak because many commuters shift the return leg rather than the initial leg of their journey. The study concludes with suggestions on how to explore more effective pricing strategies, i.e. providing fare discounts only during off-peak periods that surround AM peak

Factors Affecting Pulmonary Artery Catheterisation in Patients Undergoing Coronary Artery Bypass Grafting: A Cross-sectional Study

Introduction: The Pulmonary Artery (PA) catheter continues to be used for monitoring haemodynamic parameters in the majority of patients undergoing Coronary Artery Bypass Grafting (CABG) surgeries, despite concerns raised regarding costeffectiveness and safety issues. Sometimes, placement takes longer or is difficult just by looking at the pressure waves. There are several factors that may influence the duration of Pulmonary Artery Catheter (PAC) insertion. Aim: To determine the factors affecting PAC in anaesthetised patients undergoing elective CABG. Materials and Methods: A single-centred, cross-sectional study was conducted in the Cardiothoracic and Vascular Surgery operation theartre at IPGME&R and SSKM Hospital, Kolkata, India including 138 patients aged 35-65 years of either sex undergoing elective CABG surgery in a tertiary care hospital in Eastern India. The attempt to perform successful first-time catheterisation or failure of the PAC done by a resident cardioanaesthesiologist was noted, as well as whether catheterisation was successfully done within a specified time or not. This time was obtained as the 75th percentile of the time taken for catheter placement for the first 30 cases catheterised in the first attempt. For ease of analysis, all first attempt successful cases were considered as Group A (n=125), and all first attempt failure cases as Group B (n=13). The study data on various parameters were recorded on a proforma and summarised as the mean and standard deviation for normally distributed numerical variables, median and interquartile range for skewed numerical variables, and counts and percentages for categorical variables. A p-value <0.05 was considered statistically significant. Results: A total of 138 patients were analysed during the entire study. There was a predominance of male patients (82.6%) with a male-to-female ratio of 114:24. The first attempt failure rate of successful PAC was 13 out of 138, i.e., 9.42% (95% confidence interval 4.55% to 14.29%). The cut-off time for the procedure as the 75th percentile of the first 30 successful cases is 269 seconds. The number of cases in which it was done within this time was 109 cases, i.e., 78.99%. There was a significant difference (p<0.05) in terms of body weight, body surface area, and neck length between the two groups. Conclusion: Increased body weight and increased body surface area are significant factors associated with difficult PAC placement. On the other hand, short neck length is a significant factor for taking more time in the placement of the catheter