Calculations of Particle Bombardment due to Dust and Charged Particles in the ISM on the Project Starshot Gram-Scale Interstellar Probe

The Breakthrough Initiatives Project Starshot proposes to send a gram-scale laser driven spacecraft to the Alpha Centauri system in a 20 year mission travelling at v=0.2c. One of the challenges of this mission as the spacecraft moves through the interstellar medium is the presence of dust and gas (mostly hydrogen). The dust has a typical matter-density of 2.57*10^-27 g/cm3 with typical particle mass being 3*10^-13 g although some of the largest particles may be 5*10^-9 g in mass. These dust particle will deposit 10^12-10^16 MeV onto the spacecraft with an energy flux of order 0.3 J/sm2. We consider the erosion of the spacecraft frontal area due to dust and also heating effects. We attempt to characterise the likely environment for the starshot mission and estimate the particle bombardment shielding requirements in terms of mass and thickness of material. Current analysis estimates that the likely erosion rates are of order 10^-11-10^-8 g/s and that the frontal area temperature for the models examined in this paper will be 135.2 K depending on the ratio of frontal area to radiating area. For an assumed shielding material with atomic number range 3-13 (Lithium to Aluminium), and for spacecraft geometries with radii ~1 mm and cylindrical length 5 mm, over a 21.5 year mission duration, this would suggest a shielding thickness of 1.4 - 3 mm. This would also suggest a shielding mass in the range 0.01 - 0.05 g; depending on the material choice, spacecraft size and chosen geometry. This would represent between 1 - 5% of the total mass, assuming a spacecraft mass of 1g (driven by a 100 GW laser power). We also examine the additional effects of charged particles and estimate the stopping power and penetration range for different materials.Comment: 14 pages, 3 figures, presented FISW, New York, June 2017, presented 60th Cospar, Pasadena, July 2018, presented NASA JSC, Houston, February 201

Preserving the Ocean Circulation: Implications for Climate Policy

Climate modelers have recognized the possibility of abrupt climate changes caused by a reorganization of the North Atlantic's current pattern (technically known as a thermohaline circulation collapse). This circulation system now warms north-western Europe and transports carbon dioxide to the deep oceans. The posited collapse of this system could produce severe cooling in north-western Europe, even when general global warming is in progress. In this paper we use a simple integrated assessment model to investigate the optimal policy response to this risk. Adding the constraint of avoiding a thermohaline circulation collapse would significantly reduce the allowable greenhouse gas emissions in the long run along an optimal path. Our analysis implies that relatively small damages associated with a collapse (less than 1 % of gross world product) would justify a considerable reduction of future carbon dioxide emissions.

Process for forming layers on substrates

The present invention is generally directed to various processes and systems for forming layers and coatings on substrates, such as semiconductor wafers and solar cells. In one embodiment, the process of the present invention is directed to forming a layer on a substrate from a liquid precursor. The liquid precursor is atomized and exposed to light energy. Besides light energy, the parent material may also be exposed to an electric field and/or to sonic energy. In an alternative embodiment of the present invention a stress measurement device monitors stress in the substrate as a layer is deposited on the substrate. This stress measurement information is then sent to a controller for automatically controlling the amount of energy, such as light energy being emitted onto the substrate

Density functional theory study of the nematic-isotropic transition in an hybrid cell

We have employed the Density Functional Theory formalism to investigate the nematic-isotropic capillary transitions of a nematogen confined by walls that favor antagonist orientations to the liquid crystal molecules (hybrid cell). We analyse the behavior of the capillary transition as a function of the fluid-substrate interactions and the pore width. In addition to the usual capillary transition between isotropic-like to nematic-like states, we find that this transition can be suppressed when one substrate is wet by the isotropic phase and the other by the nematic phase. Under this condition the system presents interface-like states which allow to continuously transform the nematic-like phase to the isotropic-like phase without undergoing a phase transition. Two different mechanisms for the disappearance of the capillary transition are identified. When the director of the nematic-like state is homogeneously planar-anchored with respect to the substrates, the capillary transition ends up in a critical point. This scenario is analogous to the observed in Ising models when confined in slit pores with opposing surface fields which have critical wetting transitions. When the nematic-like state has a linearly distorted director field, the capillary transition continuously transforms in a transition between two nematic-like states.Comment: 31 pages, 10 figures, submitted to J. Chem. Phy

Mean field approaches to the totally asymmetric exclusion process with quenched disorder and large particles

The process of protein synthesis in biological systems resembles a one dimensional driven lattice gas in which the particles (ribosomes) have spatial extent, covering more than one lattice site. Realistic, nonuniform gene sequences lead to quenched disorder in the particle hopping rates. We study the totally asymmetric exclusion process with large particles and quenched disorder via several mean field approaches and compare the mean field results with Monte Carlo simulations. Mean field equations obtained from the literature are found to be reasonably effective in describing this system. A numerical technique is developed for computing the particle current rapidly. The mean field approach is extended to include two-point correlations between adjacent sites. The two-point results are found to match Monte Carlo simulations more closely

Systems, methods and computer program products for prediction of defect-related failures in integrated circuits

Systems, methods and computer program products for predicting defect-related failures in integrated circuits produced by an integrated circuit fabrication process identify objects in a circuit layout for the integrated circuit design, each object having a location in the circuit layout and a reliability connectivity in the integrated circuit design. Sample object defects are generated for the identified objects, each sample object defect representing a defect produced in an object by the integrated circuit fabrication process and having a defect magnitude associated therewith. An accelerated life defect influence model is identified for each sample object defect, relating the lifetime of an object to the defect magnitude of a defect in the object. Sample object lifetimes are generated from the defect magnitudes associated with the sample object defects according to the corresponding identified accelerated life defect influence models. A prediction of the reliability of integrated circuits is generated from the sample object lifetimes according to the reliability connectivity of the associated objects in the integrated circuit design. Preferably, the accelerated life defect influence models include log-linear regression models, which may include deterministic object lifetime functions, each relating the defect magnitude of the at least one sample object defect to one object lifetime value, and log-linear object lifetime distributions, each relating the defect magnitude of a sample object defect to a plurality of object lifetime values