Characterization of Shewanella oneidensis MtrC: a cell-surface decaheme cytochrome involved in respiratory electron transport to extracellular electron acceptors

MtrC is a decaheme c-type cytochrome associated with the outer cell membrane of Fe(III)-respiring species of the Shewanella genus. It is proposed to play a role in anaerobic respiration by mediating electron transfer to extracellular mineral oxides that can serve as terminal electron acceptors. The present work presents the first spectropotentiometric and voltammetric characterization of MtrC, using protein purified from Shewanella oneidensis MR-1. Potentiometric titrations, monitored by UV–vis absorption and electron paramagnetic resonance (EPR) spectroscopy, reveal that the hemes within MtrC titrate over a broad potential range spanning between approximately +100 and approximately -500 mV (vs. the standard hydrogen electrode). Across this potential window the UV–vis absorption spectra are characteristic of low-spin c-type hemes and the EPR spectra reveal broad, complex features that suggest the presence of magnetically spin-coupled low-spin c-hemes. Non-catalytic protein film voltammetry of MtrC demonstrates reversible electrochemistry over a potential window similar to that disclosed spectroscopically. The voltammetry also allows definition of kinetic properties of MtrC in direct electron exchange with a solid electrode surface and during reduction of a model Fe(III) substrate. Taken together, the data provide quantitative information on the potential domain in which MtrC can operate

Checks, Not Balances

Critics of the administrative state who would revive the nondelegation doctrine and embrace the unitary theory of executive power often assume that each branch’s powers are capable of precise definition, functionally distinct from the others, and that the formal boundaries between each branch are sacrosanct. This Article situates these critiques in Founding Era and nineteenth century debates about the structure of the Constitution. In the 1780s, the AntiFederalists objected to the Constitution for failing to enumerate a precise taxonomy of each branch’s powers, for failing to specify that each branch’s powers were exclusive, and for failing to make government officials sufficiently accountable to the voting public. The drafters responded that the Anti-Federalist approach would neither support effective government nor prevent the branches from acting tyrannically. Rather than develop a scheme of discrete and precisely divided powers, as the Anti-Federalists proposed, the drafters preferred precise rules of inter-branch coordination to ensure that no one branch dominates the others. This debate continued throughout the nineteenth and early twentieth centuries, with influential legal minds such as Daniel Webster and Joseph Story rejecting the Anti-Federalist theory of separation of powers. We call this a theory of separation of powers based on a principle of anti-domination. On this view, the separation of powers is breached only if one branch deprives another of its procedural capacity to check the others. We further argue that this theory (a) provides a plausible account of the Framers’ understanding; (b) has had significant purchase in the development of interbranch relations since the Founding and thus can serve as a kind of rational reconstruction of historical practice; and (c) is consistent with the relevant constitutional text and the overall constitutional structure

Accretion of Planetary Material onto Host Stars

Accretion of planetary material onto host stars may occur throughout a star's life. Especially prone to accretion, extrasolar planets in short-period orbits, while relatively rare, constitute a significant fraction of the known population, and these planets are subject to dynamical and atmospheric influences that can drive significant mass loss. Theoretical models frame expectations regarding the rates and extent of this planetary accretion. For instance, tidal interactions between planets and stars may drive complete orbital decay during the main sequence. Many planets that survive their stars' main sequence lifetime will still be engulfed when the host stars become red giant stars. There is some observational evidence supporting these predictions, such as a dearth of close-in planets around fast stellar rotators, which is consistent with tidal spin-up and planet accretion. There remains no clear chemical evidence for pollution of the atmospheres of main sequence or red giant stars by planetary materials, but a wealth of evidence points to active accretion by white dwarfs. In this article, we review the current understanding of accretion of planetary material, from the pre- to the post-main sequence and beyond. The review begins with the astrophysical framework for that process and then considers accretion during various phases of a host star's life, during which the details of accretion vary, and the observational evidence for accretion during these phases.Comment: 18 pages, 5 figures (with some redacted), invited revie

Against Political Theory in Constitutional Interpretation

Judges and academics have long relied on the work of a small number of Enlightenment political theorists-—particularly Locke, Montesquieu, and Blackstone—-to discern meaning from vague and ambiguous constitutional provisions. This Essay cautions that Enlightenment political theory should rarely, if ever, be cited as an authoritative source of constitutional meaning. There are three principal problems with constitutional interpretation based on eighteenth-century political theory. First, Enlightenment thinkers developed distinct and incompatible theories about how to structure a republican form of government. That makes it difficult to decide which among the conflicting theories should possess constitutional significance. Second, the Framers did not write the Constitution in the image of the philosophy of Montesquieu, Locke, or Blackstone. Instead, they developed a new form of government to meet what they perceived to be the needs of a nascent republic. And third, the Constitution itself departs from the dominant strands of Enlightenment political theory in crucial respects. For example, while some Enlightenment theorists advocated for precisely divided federal powers, the Framers favored a system of procedural checks, not formal separation. Thus, while Enlightenment works can be normatively persuasive or act as a guide to historical meaning, they should be treated as presumptively irrelevant in constitutional interpretation. Unless the party who would invoke an Enlightenment political theorist can produce evidence of consensus or common ground about that theory from an episode of American constitutional debate, the theorist’s prescriptions are no more probative than any other work of normative political theory

Against Political Theory in Constitutional Interpretation

Judges and academics have long relied on the work of a small number of Enlightenment political theorists—particularly Locke, Montesquieu, and Blackstone—to discern meaning from vague and ambiguous constitutional provisions. This Essay cautions that Enlightenment political theory should rarely, if ever, be cited as an authoritative source of constitutional meaning. There are three principal problems with constitutional interpretation based on eighteenth-century political theory. First, Enlightenment thinkers developed distinct and incompatible theories about how to structure a republican form of government. That makes it difficult to decide which among the conflicting theories should possess constitutional significance. Second, the Framers did not write the Constitution in the image of the philosophy of Montesquieu, Locke, or Blackstone. Instead, they developed a new form of government to meet what they perceived to be the needs of a nascent republic. And third, the Constitution itself departs from the dominant strands of Enlightenment political theory in crucial respects. For example, while some Enlightenment theorists advocated for precisely divided federal powers, the Framers favored a system of procedural checks, not formal separation. Thus, while Enlightenment works can be normatively persuasive or act as a guide to historical meaning, they should be treated as presumptively irrelevant in constitutional interpretation. Unless the party who would invoke an Enlightenment political theorist can produce evidence of consensus or common ground about that theory from an episode of American constitutional debate, the theorist’s prescriptions are no more probative than any other work of normative political theory

Interpretation of inverted photocurrent transients in organic lead halide perovskite solar cells: proof of the field screening by mobile ions and determination of the space charge layer widths

In Methyl Ammonium Lead Iodide (MAPI) perovskite solar cells, screening of the built-in field by mobile ions has been proposed as part of the cause of the large hysteresis observed in the current/voltage scans in many cells. We show that photocurrent transients measured immediately (e.g. 100 μs) after a voltage step can provide direct evidence that this field screening exists. Just after a step to forward bias, the photocurrent transients are reversed in sign (i.e. inverted), and the magnitude of the inverted transients can be used to find an upper bound on the width of the space charge layers adjacent to the electrodes. This in turn provides a lower bound on the mobile charge concentration, which we find to be ≳1 × 1017 cm−3. Using a new photocurrent transient experiment, we show that the space charge layer thickness remains approximately constant as a function of bias, as expected for mobile ions in a solid electrolyte. We also discuss additional characteristics of the inverted photocurrent transients that imply either an unusually stable deep trapping, or a photo effect on the mobile ion conductivity

Consistent phenological shifts in the making of a biodiversity hotspot: the Cape flora

Background The best documented survival responses of organisms to past climate change on short (glacial-interglacial) timescales are distributional shifts. Despite ample evidence on such timescales for local adaptations of populations at specific sites, the long-term impacts of such changes on evolutionary significant units in response to past climatic change have been little documented. Here we use phylogenies to reconstruct changes in distribution and flowering ecology of the Cape flora - South Africa's biodiversity hotspot - through a period of past (Neogene and Quaternary) changes in the seasonality of rainfall over a timescale of several million years. Results Forty-three distributional and phenological shifts consistent with past climatic change occur across the flora, and a comparable number of clades underwent adaptive changes in their flowering phenology (9 clades; half of the clades investigated) as underwent distributional shifts (12 clades; two thirds of the clades investigated). Of extant Cape angiosperm species, 14-41% have been contributed by lineages that show distributional shifts consistent with past climate change, yet a similar proportion (14-55%) arose from lineages that shifted flowering phenology. Conclusions Adaptive changes in ecology at the scale we uncover in the Cape and consistent with past climatic change have not been documented for other floras. Shifts in climate tolerance appear to have been more important in this flora than is currently appreciated, and lineages that underwent such shifts went on to contribute a high proportion of the flora's extant species diversity. That shifts in phenology, on an evolutionary timescale and on such a scale, have not yet been detected for other floras is likely a result of the method used; shifts in flowering phenology cannot be detected in the fossil record

The Long-Baseline Neutrino Experiment: Exploring Fundamental Symmetries of the Universe

The preponderance of matter over antimatter in the early Universe, the dynamics of the supernova bursts that produced the heavy elements necessary for life and whether protons eventually decay --- these mysteries at the forefront of particle physics and astrophysics are key to understanding the early evolution of our Universe, its current state and its eventual fate. The Long-Baseline Neutrino Experiment (LBNE) represents an extensively developed plan for a world-class experiment dedicated to addressing these questions. LBNE is conceived around three central components: (1) a new, high-intensity neutrino source generated from a megawatt-class proton accelerator at Fermi National Accelerator Laboratory, (2) a near neutrino detector just downstream of the source, and (3) a massive liquid argon time-projection chamber deployed as a far detector deep underground at the Sanford Underground Research Facility. This facility, located at the site of the former Homestake Mine in Lead, South Dakota, is approximately 1,300 km from the neutrino source at Fermilab -- a distance (baseline) that delivers optimal sensitivity to neutrino charge-parity symmetry violation and mass ordering effects. This ambitious yet cost-effective design incorporates scalability and flexibility and can accommodate a variety of upgrades and contributions. With its exceptional combination of experimental configuration, technical capabilities, and potential for transformative discoveries, LBNE promises to be a vital facility for the field of particle physics worldwide, providing physicists from around the globe with opportunities to collaborate in a twenty to thirty year program of exciting science. In this document we provide a comprehensive overview of LBNE's scientific objectives, its place in the landscape of neutrino physics worldwide, the technologies it will incorporate and the capabilities it will possess.Comment: Major update of previous version. This is the reference document for LBNE science program and current status. Chapters 1, 3, and 9 provide a comprehensive overview of LBNE's scientific objectives, its place in the landscape of neutrino physics worldwide, the technologies it will incorporate and the capabilities it will possess. 288 pages, 116 figure

Pan-cancer Alterations of the MYC Oncogene and Its Proximal Network across the Cancer Genome Atlas

Although theMYConcogene has been implicated incancer, a systematic assessment of alterations ofMYC, related transcription factors, and co-regulatoryproteins, forming the proximal MYC network (PMN),across human cancers is lacking. Using computa-tional approaches, we define genomic and proteo-mic features associated with MYC and the PMNacross the 33 cancers of The Cancer Genome Atlas.Pan-cancer, 28% of all samples had at least one ofthe MYC paralogs amplified. In contrast, the MYCantagonists MGA and MNT were the most frequentlymutated or deleted members, proposing a roleas tumor suppressors.MYCalterations were mutu-ally exclusive withPIK3CA,PTEN,APC,orBRAFalterations, suggesting that MYC is a distinct onco-genic driver. Expression analysis revealed MYC-associated pathways in tumor subtypes, such asimmune response and growth factor signaling; chro-matin, translation, and DNA replication/repair wereconserved pan-cancer. This analysis reveals insightsinto MYC biology and is a reference for biomarkersand therapeutics for cancers with alterations ofMYC or the PMN