Machine learning (ML) methods offer a promising route to the construction of universal molecular potentials with high accuracy and low computational cost. It is becoming evident that integrating physical principles into these models, or utilizing them in a Δ-ML scheme, significantly enhances their robustness and transferability. This paper introduces PM6-ML, a Δ-ML method that synergizes the semiempirical quantum-mechanical (SQM) method PM6 with a state-of-the-art ML potential applied as a universal correction.
View Article and Find Full Text PDFThe development and benchmarking of computational chemistry methods rely on comparison with benchmark data. More and larger benchmark datasets are becoming available, and working efficiently with them is a necessity. The Cuby framework provides rich functionality for working with datasets, comes with many ready-to-use predefined benchmark sets, and interfaces with a wide range of computational chemistry software packages.
View Article and Find Full Text PDFNeuro Endocrinol Lett
December 2023
Loss of consciousness ranks among very common causes for emergency medical service actions and is common occurrence in the emergency department. Its differential diagnosis is very broad and includes many possible causes, not in the least an intoxication. The same applies to convulsive states.
View Article and Find Full Text PDFThe Cretaceous-Paleogene (KPg) boundary, one of Earth's five major extinction events, occurred just before the appearance of Placentalia in the fossil record. The Gobi Desert, Mongolia and the Western Interior of North America have important fossil mammals occurring just before and after the KPg boundary (e.g.
View Article and Find Full Text PDFObjectives: In the ASPECT-NP trial, ceftolozane/tazobactam was non-inferior to meropenem for treating nosocomial pneumonia; efficacy outcomes by causative pathogen were to be evaluated.
Methods: Mechanically ventilated participants with hospital-acquired/ventilator-associated bacterial pneumonia were randomized to 3 g ceftolozane/tazobactam (2 g ceftolozane/1 g tazobactam) q8h or 1 g meropenem q8h. Lower respiratory tract (LRT) cultures were obtained ≤36 h before first dose; pathogen identification and susceptibility were confirmed at a central laboratory.
J Chem Theory Comput
March 2021
The new R739×5 data set from the Non-Covalent Interactions Atlas series (www.nciatlas.org) focuses on repulsive contacts in molecular complexes, covering organic molecules, sulfur, phosphorus, halogens, and noble gases.
View Article and Find Full Text PDFBackground: Nosocomial pneumonia due to antimicrobial-resistant pathogens is associated with high mortality. We assessed the efficacy and safety of the combination antibacterial drug ceftolozane-tazobactam versus meropenem for treatment of Gram-negative nosocomial pneumonia.
Methods: We conducted a randomised, controlled, double-blind, non-inferiority trial at 263 hospitals in 34 countries.
Graphite oxide is the most widely used precursor for the synthesis of graphene through top-down methods. We demonstrate a significant influence of nitric acid concentration on the structure and composition of the graphite oxide prepared by graphite oxidation. In general, two main chlorate-based oxidation methods are currently used for graphite oxide synthesis: the Staudenmaier method using 98 wt % nitric acid, and the Hofmann method with 68 wt % nitric acid.
View Article and Find Full Text PDFA new member of the family of graphene derivatives, namely, graphene acid with a composition close to C (COOH) , was prepared by oxidation of graphene oxide. The synthetic procedure is based on repeated oxidation of graphite with potassium permanganate in an acidic environment. The oxidation process was studied in detail after each step.
View Article and Find Full Text PDFGraphene sheets exhibit fast heterogeneous electron transfer at the edges while at the basal plane the electron transfer is much slower. Carbon nanotubes (CNTs) represent fascinating quasi-1-dimensional materials due to their electronic and mechanical properties which enable the formation of (unlike graphene) robust, flexible and well defined three dimensional structures. Because CNTs are created from "rolled up" graphene sheets, exposing mostly inactive walls, they generally exhibit poor electrochemical properties.
View Article and Find Full Text PDFGraphane is one of the most intensively studied derivatives of graphene. Here we demonstrate the evaluation of exact degree of graphene hydrogenation using the Clemmensen reduction reaction and deuterium labeling. The Clemmensen reduction reaction is based on application of zinc in an acid environment.
View Article and Find Full Text PDFDoped graphene materials are of huge importance because doping with electron-donating or electron-withdrawing groups can significantly change the electronic structure and impact the electronic and electrochemical properties of these materials. It is highly important to be able to produce these materials in large quantities for practical applications. The only method capable of large-scale production is the oxidative treatment of graphite to graphene oxide, followed by its consequent reduction.
View Article and Find Full Text PDFTree-building with diverse data maximizes explanatory power. Application of molecular clock models to ancient speciation events risks a bias against detection of fast radiations subsequent to the Cretaceous-Paleogene (K-Pg) event. Contrary to Springer et al.
View Article and Find Full Text PDFTo discover interordinal relationships of living and fossil placental mammals and the time of origin of placentals relative to the Cretaceous-Paleogene (K-Pg) boundary, we scored 4541 phenomic characters de novo for 86 fossil and living species. Combining these data with molecular sequences, we obtained a phylogenetic tree that, when calibrated with fossils, shows that crown clade Placentalia and placental orders originated after the K-Pg boundary. Many nodes discovered using molecular data are upheld, but phenomic signals overturn molecular signals to show Sundatheria (Dermoptera + Scandentia) as the sister taxon of Primates, a close link between Proboscidea (elephants) and Sirenia (sea cows), and the monophyly of echolocating Chiroptera (bats).
View Article and Find Full Text PDFTo engage people in biodiversity and other environmental issues, one must provide the opportunity for enhanced understanding that empowers individuals to make choices and take action based on sound science and reliable recommendations. To this end, we must acknowledge some real challenges. Recent surveys show that, despite growing public concern, environmental issues still rank below many other problems, such as terrorism, health care, the economy, and (in the U.
View Article and Find Full Text PDFEstimates of the time of origin for placental mammals from DNA studies span nearly the duration of the Cretaceous period (145 to 65 million years ago), with a maximum of 129 million years ago and a minimum of 78 million years ago. Palaeontologists too are divided on the timing. Some support a deep Cretaceous origin by allying certain middle Cretaceous fossils (97-90 million years old) from Uzbekistan with modern placental lineages, whereas others support the origin of crown group Placentalia near the close of the Cretaceous.
View Article and Find Full Text PDFOn the basis of a carbon isotopic record of both marine carbonates and organic matter from the Triassic-Jurassic boundary to the present, we modeled oxygen concentrations over the past 205 million years. Our analysis indicates that atmospheric oxygen approximately doubled over this period, with relatively rapid increases in the early Jurassic and the Eocene. We suggest that the overall increase in oxygen, mediated by the formation of passive continental margins along the Atlantic Ocean during the opening phase of the current Wilson cycle, was a critical factor in the evolution, radiation, and subsequent increase in average size of placental mammals.
View Article and Find Full Text PDFWe describe several fossils referable to Gomphos elkema from deposits close to the Paleocene-Eocene boundary at Tsagan Khushu, Mongolia. Gomphos shares a suite of cranioskeletal characters with extant rabbits, hares, and pikas but retains a primitive dentition and jaw compared to its modern relatives. Phylogenetic analysis supports the position of Gomphos as a stem lagomorph and excludes Cretaceous taxa from the crown radiation of placental mammals.
View Article and Find Full Text PDFA massive effort to sample mammals for genes has yielded new proposals for the branching architecture of the great radiation of placental mammals. Some of these are notably discrepant with morphologically based analyses, but they suggest new research that should address several major outstanding issues.
View Article and Find Full Text PDFProc Natl Acad Sci U S A
May 2001
The current massive degradation of habitat and extinction of species is taking place on a catastrophically short timescale, and their effects will fundamentally reset the future evolution of the planet's biota. The fossil record suggests that recovery of global ecosystems has required millions or even tens of millions of years. Thus, intervention by humans, the very agents of the current environmental crisis, is required for any possibility of short-term recovery or maintenance of the biota.
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