Prediction and measurement of radiation damage to CMOS devices on board spacecraft

The CMOS Radiation Effects Measurement (CREM) experiment is presently being flown on the Explorer-55. The purpose of the experiment is to evaluate device performance in the actual space radiation environment and to correlate the respective measurements to on-the-ground laboratory irradiation results. The experiment contains an assembly of C-MOS and P-MOS devices shielded in front by flat slabs of aluminum and by a practically infinite shield in the back. Predictions of radiation damage to C-MOS devices are based on standard environment models and computational techniques. A comparison of the shifts in CMOS threshold potentials, that is, those measured in space to those obtained from the on-the-ground simulation experiment with Co-60, indicates that the measured space damage is smaller than predicted by about a factor of 2-3 for thin shields, but agrees well with predictions for thicker shields

Emerging Topics in Textual Modelling

This is the final version. Available on open access via the link in this recordOCL 2019: Object Constraint Language and Textual Modeling 2019. 19th International Workshop in OCL and Textual Modeling (OCL 2019) co-located with IEEE/ACM 22nd International Conference on Model Driven Engineering Languages and Systems (MODELS 2019), 16 September 2019, Munich, GermanyThe 19th edition of the OCL workshop featured a lightning talk session where authors were invited to present their recent work and open questions related to textual modeling in general and OCL in particular. These 5 minute presentations triggered fruitful discussions within the OCL community on the usage of textual modeling, model validation, and specific technical points of the OCL specification. This community paper provides an overview of the presented contributions (one per section), as well as a summary of the questions and discussions they have triggered during the session

Crystal Structure of a Nonsymbiotic Plant Hemoglobin

Background: Nonsymbiotic hemoglobins (nsHbs) form a new class of plant proteins that is distinct genetically and structurally from leghemoglobins. They are found ubiquitously in plants and are expressed in low concentrations in a variety of tissues including roots and leaves. Their function involves a biochemical response to growth under limited O2 conditions. Results: The first X-ray crystal structure of a member of this class of proteins, riceHb1, has been determined to 2.4 Å resolution using a combination of phasing techniques. The active site of ferric riceHb1 differs significantly from those of traditional hemoglobins and myoglobins. The proximal and distal histidine sidechains coordinate directly to the heme iron, forming a hemichrome with spectral properties similar to those of cytochrome b5. The crystal structure also shows that riceHb1 is a dimer with a novel interface formed by close contacts between the G helix and the region between the B and C helices of the partner subunit. Conclusions: The bis-histidyl heme coordination found in riceHb1 is unusual for a protein that binds O2 reversibly. However, the distal His73 is rapidly displaced by ferrous ligands, and the overall O2 affinity is ultra-high (KD ≈ 1 nM). Our crystallographic model suggests that ligand binding occurs by an upward and outward movement of the E helix, concomitant dissociation of the distal histidine, possible repacking of the CD corner and folding of the D helix. Although the functional relevance of quaternary structure in nsHbs is unclear, the role of two conserved residues in stabilizing the dimer interface has been identified

Necessary and sufficient optimality conditions for scheduling unit time jobs on identical parallel machines

In this paper we characterize optimal schedules for scheduling problems with parallel machines and unit processing times by providing necessary and sufficient conditions of optimality. We show that the optimality conditions for parallel machine scheduling are equivalent to detecting negative cycles in a specially defined graph. For a range of the objective functions, we give an insight into the underlying structure of the graph and specify the simplest types of cycles involved in the optimality conditions. Using our results we demonstrate that the optimality check can be performed by faster algorithms in comparison with existing approaches based on sufficient conditions

Proposed astrophysical test of Lorentz invariance

Working in the context of a Lorentz-violating extension of the standard model we show that estimates of Lorentz symmetry violation extracted from ultra-high energy cosmic rays beyond the Greisen-Kuzmin-Zatsepin (GZK) cutoff allow for setting bounds on parameters of that extension. Furthermore, we argue that a correlated measurement of the difference in the arrival time of gamma-ray photons and neutrinos emitted from active galactic nuclei or gamma-ray bursts may provide a signature of possible violation of Lorentz symmetry. We have found that this time delay is energy independent, however it has a dependence on the chirality of the particles involved. We also briefly discuss the known settings where the mechanism for spontaneous violation of Lorentz symmetry in the context of string/M-theory may take place.Comment: Typos corrected. Version to appear in Phys. Rev.

High-Energy Tests of Lorentz Invariance

We develop a perturbative framework with which to discuss departures from exact Lorentz invariance and explore their potentially observable ramifications. Tiny non-invariant terms introduced into the standard model Lagrangian are assumed to be renormalizable (dimension $\le 4$), invariant under $SU(3)\otimes SU(2)\otimes U(1)$ gauge transformations, and rotationally and translationally invariant in a preferred frame. There are a total of 46 independent TCP-even perturbations of this kind, all of which preserve anomaly cancellation. They define the energy-momentum eigenstates and their maximal attainable velocities in the high-energy limit. The effects of these perturbations increase rapidly with energy in the preferred frame, more rapidly than those of TCP-odd perturbations. Our analysis of Lorentz-violating kinematics reveals several striking new phenomena that are relevant both to cosmic-ray physics ({\it e.g.,} by undoing the GZK cutoff) and neutrino physics ({\it e.g.,} by generating novel types of neutrino oscillations). These may lead to new and sensitive high-energy tests of special relativity.Comment: 33 pages, uses harvmac. This 2nd revision corrects two typos, an error in the Appendix, and includes further acknowledgement

Ownership and control in a competitive industry

We study a differentiated product market in which an investor initially owns a controlling stake in one of two competing firms and may acquire a non-controlling or a controlling stake in a competitor, either directly using her own assets, or indirectly via the controlled firm. While industry profits are maximized within a symmetric two product monopoly, the investor attains this only in exceptional cases. Instead, she sometimes acquires a noncontrolling stake. Or she invests asymmetrically rather than pursuing a full takeover if she acquires a controlling one. Generally, she invests indirectly if she only wants to affect the product market outcome, and directly if acquiring shares is profitable per se. --differentiated products,separation of ownership and control,private benefits of control

The Edgeworth-Kuiper debris disk

(Abridged) The Edgeworth-Kuiper belt with its presumed dusty debris is a natural reference for extrsolar debris disks. We employ a new algorithm to eliminate the inclination and the distance selection effects in the known TNO populations to derive expected parameters of the "true" EKB. Its estimated mass is M_EKB=0.12 M_earth, which is by a factor of \sim 15 larger than the mass of the EKB objects detected so far. About a half of the total EKB mass is in classical and resonant objects and another half is in scattered ones. Treating the debiased populations of EKB objects as dust parent bodies, we then "generate" their dust disk with our collisional code. Apart from accurate handling of collisions and direct radiation pressure, we include the Poynting-Robertson (P-R) drag, which cannot be ignored for the EKB dust disk. Outside the classical EKB, the radial profile of the optical depth approximately follows tau \sim r^-2 which is roughly intermediate between the slope predicted analytically for collision-dominated (r^-1.5) and transport-dominated (r^-2.5) disks. The cross section-dominating grain size still lies just above the blowout size (\sim 1...2 \microm), as it would without the P-R transport. However, if the EKB were by one order of magnitude less massive, the optical depth profile would fall off as tau \sim r^-3, and the cross section-dominating grain size would shift from \sim 1...2\microm to ~100 \microm. These properties are seen if dust is assumed to be generated only by known TNOs. If the solar system were observed from outside, the thermal emission flux from the EKB dust would be about two orders of magnitude lower than for solar-type stars with the brightest known infrared excesses observed from the same distance. Herschel and other new-generation facilities should reveal extrasolar debris disks nearly as tenuous as the EKB disk. The Herschel/PACS instrument should be able to detect disks at a \sim 1...2M_EKB level.Comment: 18 pages, 14 figures, accepted for publication in A&