This article describes some key fundamentals that are common to all JavaScript engines — and not just V8, the engine the authors work on. As a JavaScript developer, having a deeper understanding of how JavaScript engines work helps you reason about the performance characteristics of your code.

This article explains JavaScript engine optimization pipeline trade-offs, and describes how engines such as V8 speed up accesses to prototype properties. As a JavaScript developer, having a deeper understanding of how JavaScript engines work helps you reason about the performance characteristics of your code.

Working on my mental fitness, says Dominic Thiem

The European X-ray Free-Electron Laser (EuXFEL) delivers extremely intense (>1012 photons pulse−1 and up to 27000 pulses s−1), ultrashort (<100 fs) and transversely coherent X-ray radiation, at a repetition rate of up to 4.5 MHz. Its unique X-ray beam parameters enable novel and groundbreaking experiments in ultrafast photochemistry and material sciences at the Femtosecond X-ray Experiments (FXE) scientific instrument. This paper provides an overview of the currently implemented experimental baseline instrumentation and its performance during the commissioning phase, and a preview of planned improvements. FXE's versatile instrumentation combines the simultaneous application of forward X-ray scattering and X-ray spectroscopy techniques with femtosecond time resolution. These methods will eventually permit exploitation of wide-angle X-ray scattering studies and X-ray emission spectroscopy, along with X-ray absorption spectroscopy, including resonant inelastic X-ray scattering and X-ray Raman scattering. A suite of ultrafast optical lasers throughout the UV–visible and near-IR ranges (extending up to mid-IR in the near future) with pulse length down to 15 fs, synchronized to the X-ray source, serve to initiate dynamic changes in the sample. Time-delayed hard X-ray pulses in the 5–20 keV range are used to probe the ensuing dynamic processes using the suite of X-ray probe tools. FXE is equipped with a primary monochromator, a primary and secondary single-shot spectrometer, and a timing tool to correct the residual timing jitter between laser and X-ray pulses.

Total scattering measurements enable understanding of the structural disorder in crystalline materials by Fourier transformation of the total structure factor, S(Q), where Q is the magnitude of the scattering vector. In this work, the direct calculation of total scattering from a crystalline structural model is proposed. To calculate the total scattering intensity, a suitable Q-broadening function for the diffraction profile is needed because the intensity and the width depend on the optical parameters of the diffraction apparatus, such as the X-ray energy resolution and divergence, and the intrinsic parameters. X-ray total scattering measurements for CeO2 powder were performed at beamline BL04B2 of the SPring-8 synchrotron radiation facility in Japan for comparison with the calculated S(Q) under various optical conditions. The evaluated Q-broadening function was comparable to the full width at half-maximum of the Bragg peaks in the experimental total scattering pattern. The proposed calculation method correctly accounts for parameters with Q dependence such as the atomic form factor and resolution function, enables estimation of the total scattering factor, and facilitates determination of the reduced pair distribution function for both crystalline and amorphous materials.

Model building into experimental maps is a key element of structural biology, but can be both time consuming and error prone for low-resolution maps. Here we present Namdinator, an easy-to-use tool that enables the user to run a molecular dynamics flexible fitting simulation followed by real-space refinement in an automated manner through a pipeline system. Namdinator will modify an atomic model to fit within cryo-EM or crystallography density maps, and can be used advantageously for both the initial fitting of models, and for a geometrical optimization step to correct outliers, clashes and other model problems. We have benchmarked Namdinator against 39 deposited cryo-EM models and maps, and observe model improvements in 34 of these cases (87%). Clashes between atoms were reduced, and the model-to-map fit and overall model geometry were improved, in several cases substantially. We show that Namdinator is able to model large-scale conformational changes compared to the starting model. Namdinator is a fast and easy tool for structural model builders at all skill levels. Namdinator is available as a web service (https://namdinator.au.dk), or it can be run locally as a command-line tool.

X-ray diffraction studies of crystals under pressure and quantitative experimental charge density analysis are among the most demanding types of crystallographic research. A successful feasibility study of the electron density in the mineral grossular under 1 GPa pressure conducted at the CRISTAL beamline at the SOLEIL synchrotron is presented in this work. A single crystal was placed in a diamond anvil cell, but owing to its special design (wide opening angle), short synchrotron wavelength and the high symmetry of the crystal, data with high completeness and high resolution were collected. This allowed refinement of a full multipole model of experimental electron distribution. Results are consistent with the benchmark measurement conducted without a diamond-anvil cell and also with the literature describing investigations of similar structures. Results of theoretical calculations of electron density distribution on the basis of dynamic structure factors mimic experimental findings very well. Such studies allow for laboratory simulations of processes which take place in the Earth's mantle.

A calculation procedure for X-ray total scattering and the pair distribution function from a crystalline structural model is presented. It allows one to easily and precisely deal with diffraction-angle-dependent parameters such as the atomic form factor and the resolution of the optics.

A portable small-angle X-ray scattering instrument with geometrical dimensions suitable for installation at the D22 instrument was designed and constructed for simultaneous small-angle X-ray and neutron scattering experiments at ILL.

Based on decades of cutting-edge research, the 15,000-square-foot Hall of Human Origins offers visitors an immersive, interactive journey through 6 million years of human evolution spelling out how defining characteristics of the human species have evolved during millions of years in response to a changing world.

The post New Hall of Human Origins points to environmental change as major force in evolution of hominins appeared first on Smithsonian Insider.

A research team from The Smithsonian Environmental Research Center and Virginia's Old Dominion University will be awarded $110,999 to develop a tool to help seagrass restorers predict which places will be the best for planting seagrasses, the Virginia Sea Grant has announced.

The post Environmental Research Center to help with Chesapeake Bay seagrass restoration appeared first on Smithsonian Insider.

The expanded and remodeled Mathias Laboratory, named in honor of U.S. Senator Charles "Mac" Mathias Jr. (1922-2010) (R-Md.) will have a low environmental impact on all fronts, from where it gets its power to where it gets its materials.

The post New Mathias Lab at Environmental Research Center will have low environmental impact appeared first on Smithsonian Insider.

The new research reveals that from the period between 1100-1600 small agricultural settlements up and down the Delaware River Valley caused a 50-percent increase in sediment runoff into the Delaware River.

The post Study reveals environmental impact of American Indian farms centuries before Europeans arrived in North America appeared first on Smithsonian Insider.

Marmosets on track for obesity appeared to be more efficient in their feeding behavior. “Although all animals consumed the same amount of liquid, the ones […]

The post Obese marmosets are more developmentally advanced as infants, study shows appeared first on Smithsonian Insider.

The world’s coasts are home to more than 70 percent of the human population and experience intense development as a result. The rate of environmental […]

The post Smithsonian Environmental Research Center Marks 50 Years of Making a Difference appeared first on Smithsonian Insider.

Karolina Losenkova, Mariachiara Zuccarini, Marika Karikoski, Juha Laurila, Detlev Boison, Sirpa Jalkanen, and Gennady G. Yegutkin

Extracellular adenosine mediates diverse anti-inflammatory, angiogenic and vasoactive effects and becomes an important therapeutic target for cancer, which has been translated into clinical trials. This study was designed to comprehensively assess adenosine metabolism in prostate and breast cancer cells. We identified cellular adenosine turnover as a complex cascade, comprised of (a) the ectoenzymatic breakdown of ATP via sequential nucleotide pyrophosphatase/phosphodiesterase-1, ecto-5’-nucleotidase/CD73 and adenosine deaminase reactions, and ATP re-synthesis through counteracting adenylate kinase and nucleoside diphosphokinase; (b) the uptake of nucleotide-derived adenosine via equilibrative nucleoside transporters; and (c) the intracellular adenosine phosphorylation into ATP by adenosine kinase and other nucleotide kinases. The exposure of cancer cells to 1% O₂ for 24 hours triggered ~2-fold up-regulation of CD73, without affecting nucleoside transporters, adenosine kinase activity and cellular ATP content. The ability of adenosine to inhibit the tumor-initiating potential of breast cancer cells via receptor-independent mechanism was confirmed in vivo using a xenograft mouse model. The existence of redundant pathways controlling extracellular and intracellular adenosine provides a sufficient justification for reexamination of the current concepts of cellular purine homeostasis and signaling in cancer.

The post Device at the Smithsonian Environmental Research Center examines how phytoplankton would react if the ozone layer vanished appeared first on Smithsonian Insider.

Follow botanist Candy Feller of the Smithsonian Environmental Research Center as she conducts field work on mangrove ecosystems at Carrie Bow Cay, a Smithsonian field research station in the Caribbean.

The post Mangroves research by Candy Feller, Smithsonian Environmental Research Center botanist appeared first on Smithsonian Insider.

On crime scene investigation shows, forensic scientists use remnants of genetic material to solve mysteries in a matter of hours. Researchers at the Smithsonian Environmental […]

The post Environmental “Forensics” Pieces Together Mysterious Plant Invasion appeared first on Smithsonian Insider.

Is it foolish to be optimistic about our environment and its future prospects? Every day, we hear dire warnings about the health of the planet […]

The post The Argument for Environmental Optimism: Opinion by Smithsonian Secretary David J. Skorton appeared first on Smithsonian Insider.

A tiny invasive insect from Asia might have an effect on Chesapeake Bay waters. The emerald ash borer is killing millions of ash trees in […]

The post Invasive ash borer found in Smithsonian Environmental Research Center forest; ash deaths may impact Chesapeake waters appeared first on Smithsonian Insider.

Experimental electron-density studies based on high-resolution diffraction experiments allow halogen bonds between heavy halogens to be classified. The topological properties of the electron density in Cl⋯Cl contacts vary smoothly as a function of the inter­action distance. The situation is less straightforward for halogen bonds between iodine and small electronegative nucleophiles, such as nitro­gen or oxygen, where the electron density in the bond critical point does not simply increase for shorter distances. The number of successful charge–density studies involving iodine is small, but at least individual examples for three cases have been observed. (a) Very short halogen bonds between electron-rich nucleophiles and heavy halogen atoms resemble three-centre–four-electron bonds, with a rather symmetric heavy halogen and without an appreciable σ hole. (b) For a narrow inter­mediate range of halogen bonds, the asymmetric electronic situation for the heavy halogen with a pronounced σ hole leads to rather low electron density in the (3,−1) critical point of the halogen bond; the properties of this bond critical point cannot fully describe the nature of the associated inter­action. (c) For longer and presumably weaker contacts, the electron density in the halogen bond critical point is only to a minor extent reduced by the presence of the σ hole and hence may be higher than in the aforementioned case. In addition to the electron density and its derived properties, the halogen–carbon bond distance opposite to the σ hole and the Raman frequency for the associated vibration emerge as alternative criteria to gauge the halogen-bond strength. We find exceptionally long C—I distances for tetra­fluoro­diiodo­benzene molecules in cocrystals with short halogen bonds and a significant red shift for their Raman vibrations.

A new type of X-ray LLL interferometer, a `hard' interferometer, which has both a base and a `ceiling', is tested for experimental investigations. The tested interferometer has no preliminary uncontrollable moiré and can be used for object and deformation investigations.

Weather and environmental forecasts made several weeks to months in advance can someday be as widely used and essential as current predictions of tomorrow’s weather are, but first more research and sustained investment are needed, says a new report from the National Academies of Sciences, Engineering, and Medicine.

The U.S. Department of Health and Human Services (HHS) should lead efforts among federal partners and stakeholders to design, implement, and evaluate a multipronged, evidence-based national strategy to reduce stigma toward people with mental and substance use disorders, says a new report from the National Academies of Sciences, Engineering, and Medicine.

The Gulf Research Program (GRP) of the National Academies of Sciences, Engineering, and Medicine today announced grant awards for seven new projects totaling $5.3 million.

While the U.S. Department of Veterans Affairs (VA) provides mental health care of comparable or superior quality to care provided in private and non-VA public sectors, accessibility and quality of services vary across the VA health system, leaving a substantial unmet need for mental health services among veterans of the recent wars in Afghanistan and Iraq, says a new congressionally mandated report from the National Academies of Sciences, Engineering, and Medicine.

The National Academies of Sciences, Engineering, and Medicine are launching an Academies-wide initiative to transform how the nation addresses the complex issues associated with environmental health—a field that examines how the environment affects human health.

The National Academy of Medicine today announced Kenneth Wells is the recipient of the 2018 Rhoda and Bernard Sarnat International Prize in Mental Health, for his work developing quality and outcomes approaches to psychiatry and mental health, fostering a generation of clinical investigators and mental health system leaders, and championing partnered, participatory research to advance equity for under-resourced populations.

The Gulf Research Program (GRP) of the National Academies of Sciences, Engineering, and Medicine today announced awards for nine new grant projects totaling $3.2 million.

If the dilute and dispose approach for disposing of the surplus plutonium in the Waste Isolation Pilot Plant (WIPP) is fully implemented, the U.S. Department of Energy (DOE) should use two independent review teams to develop public trust in and improve its decisions, says a new interim report by the National Academies of Sciences, Engineering, and Medicine.

Over the next several decades as the global population grows, society will be faced with pressing challenges such as providing reliable supplies of food and water, diminishing climate change and adapting to its impacts, and building healthy, resilient cities.

A new report from the National Academies of Sciences, Engineering, and Medicine – which reviews a separate report by a federally funded laboratory that examines options for treating low-activity radioactive waste at the Hanford Nuclear Reservation -- is available for public comment until Oct. 31.

A new report from the National Academies of Sciences, Engineering, and Medicine calls for a comprehensive national agenda to improve mental, emotional, and behavioral (MEB) health in children and youth. Despite advances in research, rates of depression, suicide and self-harm among young people have been increasing.

The National Academy of Medicine today announced Daniel Weinberger is the recipient of the 2019 Rhoda and Bernard Sarnat International Prize in Mental Health, for his fundamental role in elucidating the biological origins and genetic expressions of schizophrenia, and for transforming how clinicians, researchers, and the public understand mental illness.

The U.S. is a clear leader in the global bioeconomy landscape, but faces challenges from decentralized leadership, inadequate talent development, cybersecurity vulnerabilities, stagnant investment in fundamental research, and international competition, according to Safeguarding the Bioeconomy, a new report from the National Academies of Sciences, Engineering, and Medicine.

Today the National Academies of Sciences, Engineering, and Medicine released its review of the National Toxicology Program’s (NTP) draft monograph Systematic Review of Fluoride Exposure and Neurodevelopmental and Cognitive Health Effects.

Scientists involved in a pan-European project to develop better methods of risk assessment say maps that show such cumulative risks geographically are easy to interpret and should be considered as practical tools for conveying risk information to decision makers and the general public.

A recent study has assessed the lifecycle environmental impact during the production and use phase of three battery types for plug-in hybrid (PHEV) and full performance battery electric vehicles (BEV). The study indicates that newer lithium-ion (Li-ion) technologies outperform current nickel-metal hydride (NiMH) batteries and identifies processes contributing to 13 environmental impacts

A new analysis of how to encourage pro-environmental behaviour highlights four effective techniques: goal-setting, prompts or reminders, witnessing the behaviour of others and introducing new behaviours that correspond with existing beliefs.

A new German study suggests that residents??? level of satisfaction with their urban neighbourhood can be predicted from their perceptions of multiple and co-occurring burdens, such as poor air quality, lack of green space, noise and low cleanliness.

Citizen science is not only a tool for collecting valuable scientific data, it can also enable participants to reconnect with nature and encourage pro-conservation behaviour, new research has shown. Participants in a French butterfly monitoring programme reported making wildlife-friendly changes to their gardens as a result of taking part in the initiative.

A recent study has investigated how waste disposal sites in southern Italy have affected residents living nearby. Villagers reported being annoyed by odours, but the perceptions of residents living in the village closest to the facilities were possibly influenced by receiving financial compensation for the presence of the facilities.

The global production, trade and use of goods and services has a significant impact on the environment — and rates of consumption are rising. A new study combines two assessment methods to quantify the impact of European trade on the environment. It finds that, overall, the EU was a net importer of environmental impact from 2000 to 2010, that machinery, equipment and vehicles contributed most to the EU’s export impacts and that the EU’s trade balance (import impact minus export impact) is increasing over time. The two assessment methods complement one another well and could form the basis for future country or region-wide studies, suggest the researchers, by enabling a detailed analysis of individual steps within a product’s trade flow, while also providing a larger picture of the overall process.

As 3D printing, also known as additive manufacturing (AM), begins to replace conventional manufacturing, the environmental impacts of its implementation must be assessed. This study conducted a life cycle assessment (LCA) to investigate the environmental and resource implications of using AM to manufacture the metal parts of an engine in a light distribution truck. In the LCA, the impacts of both present and possible future states of AM technology were compared with current conventional manufacturing. The results suggest that there are potential environmental and resource benefits1 to AM technologies, but that these benefits rely on the achievement of a clean energy source and further technological development.