A new device analysis technique is discussed which may prove useful in characterizing critical timing paths and analyzing timing related failure modes in high clock rate VLSI circuits. A focussed ...laser is used to inject localized photocurrent at the drain of a single transistor as the device is tested. The resulting effects on circuit performance have been studied and it is shown that individual circuit path propagation delays can be increased in this manner. To assign a relative value to a measurement, the operating frequency, power supply voltage or injected photocurrent level can be varied with the others fixed until the device just fails. Models, circuit simulations and experimental results obtained using this technique on a simple gate and results measured on CMOS microprocessors are given in this paper. Possible applications of the technique beyond the analysis of frequency sensitive failures include experimentally locating performance limiting timing paths in a circuit and assessing a circuit's sensitivity to process or failure mechanism induced drifts in device parameters which affect timing.
Psi4 is an ab initio electronic structure program providing methods such as Hartree–Fock, density functional theory, configuration interaction, and coupled-cluster theory. The 1.1 release represents ...a major update meant to automate complex tasks, such as geometry optimization using complete-basis-set extrapolation or focal-point methods. Conversion of the top-level code to a Python module means that Psi4 can now be used in complex workflows alongside other Python tools. Several new features have been added with the aid of libraries providing easy access to techniques such as density fitting, Cholesky decomposition, and Laplace denominators. The build system has been completely rewritten to simplify interoperability with independent, reusable software components for quantum chemistry. Finally, a wide range of new theoretical methods and analyses have been added to the code base, including functional-group and open-shell symmetry adapted perturbation theory, density-fitted coupled cluster with frozen natural orbitals, orbital-optimized perturbation and coupled-cluster methods (e.g., OO-MP2 and OO-LCCD), density-fitted multiconfigurational self-consistent field, density cumulant functional theory, algebraic-diagrammatic construction excited states, improvements to the geometry optimizer, and the “X2C” approach to relativistic corrections, among many other improvements.
The aim of this work was 2-fold: (1) to evaluate current knowledge and identify key directions in the study of sluggish cognitive tempo (SCT); and (2) to arrive at a consensus change in terminology ...for the construct that reflects the current science and may be more acceptable to researchers, clinicians, caregivers, and patients.
An international Work Group was convened that, in early 2021, compiled an online archive of all research studies on SCT and summarized the current state of knowledge, noted methodological issues, and highlighted future directions, and met virtually on 10 occasions in 2021 to discuss these topics and terminology.
Major progress has been made over the last decade in advancing our understanding of SCT across the following domains of inquiry: construct measurement and stability; genetic, environmental, pathophysiologic, and neuropsychological correlates; comorbid conditions; functional impairments; and psychosocial and medication interventions. Findings across these domains are summarized, and potential avenues to pursue in the next generation of SCT-related research are proposed. Following repeated discussions on terminology, the Work Group selected “cognitive disengagement syndrome” (CDS) to replace “SCT” as the name for this construct. This term was deemed to best satisfy considerations that should apply when selecting terms for a condition or syndrome, as it does not overlap with established terms for other constructs, is not offensive, and reflects the current state of the science.
It is evident that CDS (SCT) has reached the threshold of recognition as a distinct syndrome. Much work remains to further clarify its nature (eg, transdiagnostic factor, separate disorder, diagnostic specifier), etiologies, demographic factors, relations to other psychopathologies, and linkages to specific domains of functional impairment. Investigators are needed with interests and expertise spanning basic, clinical, and translational research to advance our understanding and to improve the lives of individuals with this unique syndrome.
Bismuth ferrite (BiFeO3) is one of the most widely studied multiferroics. The coexistence of ferroelectricity and antiferromagnetism in this compound has driven an intense search for electric‐field ...control of the magnetic order. Such efforts require a complete understanding of the various exchange interactions that underpin the magnetic behavior. An important characteristic of BiFeO3 is its noncollinear magnetic order; namely, a long‐period incommensurate spin cycloid. Here, the progress in understanding this fascinating aspect of BiFeO3 is reviewed, with a focus on epitaxial films. The advances made in developing the theory used to capture the complexities of the cycloid are first chronicled, followed by a description of the various experimental techniques employed to probe the magnetic order. To help the reader fully grasp the nuances associated with thin films, a detailed description of the spin cycloid in the bulk is provided. The effects of various perturbations on the cycloid are then described: magnetic and electric fields, doping, epitaxial strain, finite size effects, and temperature. To conclude, an outlook on possible device applications exploiting noncollinear magnetism in BiFeO3 films is presented. It is hoped that this work will act as a comprehensive experimentalist's guide to the spin cycloid in BiFeO3 thin films.
A thorough, critical review of the literature concerning the room‐temperature multiferroic BiFeO3 is presented. Specifically, research exploring the structure and behavior of the incommensurate spin cycloid is addressed. After elucidating the importance of this magnetic oxide for functional devices and nanotechnologies, possible techniques for probing the spin cycloid, alongside perturbations and behavior under various external stimuli, are discussed.
Although central to much biological research, the identification of species is often difficult. The use of DNA barcodes, short DNA sequences from a standardized region of the genome, has recently ...been proposed as a tool to facilitate species identification and discovery. However, the effectiveness of DNA barcoding for identifying specimens in species-rich tropical biotas is unknown. Here we show that cytochrome c oxidase I DNA barcodes effectively discriminate among species in three Lepidoptera families from Area de Conservacion Guanacaste in northwestern Costa Rica. We found that 97.9% of the 521 species recognized by prior taxonomic work possess distinctive cytochrome c oxidase I barcodes and that the few instances of interspecific sequence overlap involve very similar species. We also found two or more barcode clusters within each of 13 supposedly single species. Covariation between these clusters and morphological and/or ecological traits indicates overlooked species complexes. If these results are general, DNA barcoding will significantly aid species identification and discovery in tropical settings.
Mr Lugovoi has admitted meeting Mr Litvinenko in London but has denied any involvement in his murder and said the culprits might be trying to frame him. He could not be reached for comment yesterday, ...but Reuters reported that when told of UK plans to extradite him, he gave "full-hearted healthy laughter". He told Russia's Itar-Tass news agency he had received no official information on possible extradition. "However, if this happens, I am pre-pared to defend my good name and reputation in any court." Mr Lugovoi and Mr Dimitri Kovtun both came from military families and graduated from an elite military institute closely tied to the Soviet defence ministry and the KGB. Mr Lugovoi worked in the Kremlin guard and then the KGB's Ninth Department, responsible for protecting top Communist Party - and later Russian government - officials. He left in 1996 for the security service of Mr Boris Berezovsky, then one of Russia's most powerful oligarchs, where he got to know Mr Litvinenko. After Mr Berezovsky fell out with Mr Putin and fled Russia, Mr Lugovoi served a brief prison term, accused of helping a jailed former Berezovsky associate in an escape attempt. On his release, he went into business, which now includes a private security company and a share in a drinksfactory.
Psi4NumPy demonstrates the use of efficient computational kernels from the open-source Psi4 program through the popular NumPy library for linear algebra in Python to facilitate the rapid development ...of clear, understandable Python computer code for new quantum chemical methods, while maintaining a relatively low execution time. Using these tools, reference implementations have been created for a number of methods, including self-consistent field (SCF), SCF response, many-body perturbation theory, coupled-cluster theory, configuration interaction, and symmetry-adapted perturbation theory. Furthermore, several reference codes have been integrated into Jupyter notebooks, allowing background, underlying theory, and formula information to be associated with the implementation. Psi4NumPy tools and associated reference implementations can lower the barrier for future development of quantum chemistry methods. These implementations also demonstrate the power of the hybrid C++/Python programming approach employed by the Psi4 program.
We describe automated technologies to probe the structure of neural tissue at nanometer resolution and use them to generate a saturated reconstruction of a sub-volume of mouse neocortex in which all ...cellular objects (axons, dendrites, and glia) and many sub-cellular components (synapses, synaptic vesicles, spines, spine apparati, postsynaptic densities, and mitochondria) are rendered and itemized in a database. We explore these data to study physical properties of brain tissue. For example, by tracing the trajectories of all excitatory axons and noting their juxtapositions, both synaptic and non-synaptic, with every dendritic spine we refute the idea that physical proximity is sufficient to predict synaptic connectivity (the so-called Peters’ rule). This online minable database provides general access to the intrinsic complexity of the neocortex and enables further data-driven inquiries.
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•Tape-based pipeline for electron microscopic reconstruction of brain tissue•Annotated database of 1,700 synapses from a saturated reconstruction of cortex•Excitatory axon proximity to dendritic spines not sufficient to predict synapses
Automated technologies probing the structure of neural tissue at nanometer resolution generate a saturated reconstruction of a sub-volume of mouse neocortex, refuting the idea that physical proximity is sufficient to predict excitatory synaptic connectivity.
A major resistance mechanism in Gram-negative bacteria is the production of β-lactamase enzymes. Originally recognized for their ability to hydrolyze penicillins, emergent β-lactamases can now confer ...resistance to other β-lactam drugs, including both cephalosporins and carbapenems. The emergence and global spread of β-lactamase-producing multi-drug-resistant “superbugs” has caused increased alarm within the medical community due to the high mortality rate associated with these difficult-to-treat bacterial infections. To address this unmet medical need, we initiated an iterative program combining medicinal chemistry, structural biology, biochemical testing, and microbiological profiling to identify broad-spectrum inhibitors of both serine- and metallo-β-lactamase enzymes. Lead optimization, beginning with narrower-spectrum, weakly active compounds, provided 20 (VNRX-5133, taniborbactam), a boronic-acid-containing pan-spectrum β-lactamase inhibitor. In vitro and in vivo studies demonstrated that 20 restored the activity of β-lactam antibiotics against carbapenem-resistant Pseudomonas aeruginosa and carbapenem-resistant Enterobacteriaceae. Taniborbactam is the first pan-spectrum β-lactamase inhibitor to enter clinical development.
Astraptes fulgerator, first described in 1775, is a common and widely distributed neotropical skipper butterfly (Lepidoptera: Hesperiidae). We combine 25 years of natural history observations in ...northwestern Costa Rica with morphological study and DNA barcoding of museum specimens to show that A. fulgerator is a complex of at least 10 species in this region. Largely sympatric, these taxa have mostly different caterpillar food plants, mostly distinctive caterpillars, and somewhat different ecosystem preferences but only subtly differing adults with no genitalic divergence. Our results add to the evidence that cryptic species are prevalent in tropical regions, a critical issue in efforts to document global species richness. They also illustrate the value of DNA barcoding, especially when coupled with traditional taxonomic tools, in disclosing hidden diversity.
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