Using 3D NAND Flash Memory in SSDs to Improve Storage and Performance

[excerpt] In the rapid development process of data storage, 3D NAND is the next generation of this technology in which the semiconductor flash cells of the solid-state drive (SSD) are stacked vertically to increase storage density and read / write efficiency. Originally announced by Toshiba in 2007, but with Samsung creating the first commercially available 3D NAND SSD in 2013, the technology is still extremely new to the market. Despite this, it has already proven to be far more effective and reliable than its 2D NAND counterpart. However, the question remains is it worth the upgrade

Scaling Up Automated Verification: A Case Study and a Formalization IDE for Building High Integrity Software

Component-based software verification is a difficult challenge because developers must specify components formally and annotate implementations with suitable assertions that are amenable to automation. This research investigates the intrinsic complexity in this challenge using a component-based case study. Simultaneously, this work also seeks to minimize the extrinsic complexities of this challenge through the development and usage of a formalization integrated development environment (F-IDE) built for specifying, developing, and using verified reusable software components. The first contribution is an F-IDE built to support formal specification and automated verification of object-based software for the integrated specification and programming language RESOLVE. The F-IDE is novel, as it integrates a verifying compiler with a user-friendly interface that provides a number of amenities including responsive editing for model-based mathematical contracts and code, assistance for design by contract, verification, responsive error handling, and generation of property-preserving Java code that can be run within the F-IDE. The second contribution is a case study built using the F-IDE that involves an interplay of multiple artifacts encompassing mathematical units, component interfaces, and realizations. The object-based interfaces involved are specified in terms of new mathematical models and non-trivial theories designed to encapsulate data structures and algorithms. The components are designed to be amenable to modular verification and analysis

Port Flow Test System

Solar Turbines Gas Compressor Engineering Division of San Diego, California called upon the Mechanical Engineering students of California Polytechnic University, San Luis Obispo to provide recommendations for optimization of compressor end cap port design. Various sizes of compressors have end caps with numerous ports that exchange fluids between the inside and outside of the working fluid pressure vessel. Because so many ports must exist on the end caps, unusual flow paths are created to supply the appropriate location within the compressor. These flow paths commonly consist of a drilled inlet hole which intersects with a sudden expansion. The sudden expansion is deemed the “fly cut” because of its semicircular shape. Sudden expansions in general cause very high energy losses in fluid flow. This is one of the primary concerns when designing the compressor end cap port layout. Due to the unusual nature of the fly cuts found in Solar Turbines’ end caps, published information on the pressure losses for this particular flow path do not exist. For this reason, Solar Turbines were required to base their port design on the best information available, including: historical compressor design methods, conservative design analysis estimates, and computational fluid mechanics software. Of these options, the computational method could provide the best estimate but only if validated experimentally. In response to this problem, PreFlow Systems was formed and investigated the solution of designing, building, and testing a scaled experimental test apparatus. This report outlines the details involved in every aspect of the project, including: technical specifications and objectives, design conceptualization, engineering analysis, manufacturing, testing, and results. Each of these phases was crucial in creating the final flow test apparatus which simulated the gas port flow of Solar Turbines’ compressor end caps. This apparatus ultimately provided an experimental basis for concluding that computation fluid mechanics software is a reasonable aide in end cap port design

A Metabolic Dependency for Host Isoprenoids in the Obligate Intracellular Pathogen Rickettsia parkeri Underlies a Sensitivity to the Statin Class of Host-Targeted Therapeutics.

Gram-negative bacteria in the order Rickettsiales have an obligate intracellular growth requirement, and some species cause human diseases such as typhus and spotted fever. The bacteria have evolved a dependence on essential nutrients and metabolites from the host cell as a consequence of extensive genome reduction. However, it remains largely unknown which nutrients they acquire and whether their metabolic dependency can be exploited therapeutically. Here, we describe a genetic rewiring of bacterial isoprenoid biosynthetic pathways in the Rickettsiales that has resulted from reductive genome evolution. Furthermore, we investigated whether the spotted fever group Rickettsia species Rickettsia parkeri scavenges isoprenoid precursors directly from the host. Using targeted mass spectrometry, we found that infection caused decreases in host isoprenoid products and concomitant increases in bacterial isoprenoid metabolites. Additionally, we report that treatment of infected cells with statins, which inhibit host isoprenoid synthesis, prohibited bacterial growth. We show that growth inhibition correlates with changes in bacterial size and shape that mimic those caused by antibiotics that inhibit peptidoglycan biosynthesis, suggesting that statins lead to an inhibition of cell wall synthesis. Altogether, our results describe a potential Achilles' heel of obligate intracellular pathogens that can potentially be exploited with host-targeted therapeutics that interfere with metabolic pathways required for bacterial growth.IMPORTANCE Obligate intracellular pathogens, which include viruses as well as certain bacteria and eukaryotes, are a subset of infectious microbes that are metabolically dependent on and unable to grow outside an infected host cell because they have lost or lack essential biosynthetic pathways. In this study, we describe a metabolic dependency of the bacterial pathogen Rickettsia parkeri on host isoprenoid molecules that are used in the biosynthesis of downstream products, including cholesterol, steroid hormones, and heme. Bacteria make products from isoprenoids, such as an essential lipid carrier for making the bacterial cell wall. We show that bacterial metabolic dependency can represent a potential Achilles' heel and that inhibiting host isoprenoid biosynthesis with the FDA-approved statin class of drugs inhibits bacterial growth by interfering with the integrity of the cell wall. This work supports the potential to treat infections by obligate intracellular pathogens through inhibition of host biosynthetic pathways that are susceptible to parasitism

Bayesian total evidence dating reveals the recent crown radiation of penguins

The total-evidence approach to divergence-time dating uses molecular and morphological data from extant and fossil species to infer phylogenetic relationships, species divergence times, and macroevolutionary parameters in a single coherent framework. Current model-based implementations of this approach lack an appropriate model for the tree describing the diversification and fossilization process and can produce estimates that lead to erroneous conclusions. We address this shortcoming by providing a total-evidence method implemented in a Bayesian framework. This approach uses a mechanistic tree prior to describe the underlying diversification process that generated the tree of extant and fossil taxa. Previous attempts to apply the total-evidence approach have used tree priors that do not account for the possibility that fossil samples may be direct ancestors of other samples. The fossilized birth-death (FBD) process explicitly models the diversification, fossilization, and sampling processes and naturally allows for sampled ancestors. This model was recently applied to estimate divergence times based on molecular data and fossil occurrence dates. We incorporate the FBD model and a model of morphological trait evolution into a Bayesian total-evidence approach to dating species phylogenies. We apply this method to extant and fossil penguins and show that the modern penguins radiated much more recently than has been previously estimated, with the basal divergence in the crown clade occurring at ~12.7 Ma and most splits leading to extant species occurring in the last 2 million years. Our results demonstrate that including stem-fossil diversity can greatly improve the estimates of the divergence times of crown taxa. The method is available in BEAST2 (v. 2.4) www.beast2.org with packages SA (v. at least 1.1.4) and morph-models (v. at least 1.0.4).Comment: 50 pages, 6 figure

Improving the Viability of New Farmers\u27 Operations Through the Use of Profit Teams

Profit teams comprise multiple consultants engaged to support farmer decision making by holistically analyzing farm challenges. We tested the idea of using profit teams to help advanced beginning farmers, those who are beyond start-up but have been in business less than 10 years, address constraints to growing their businesses. These new entrepreneurs often have entered agriculture without a family farming history or a connection to Extension. We describe the processes of selecting farmers and administering teams, and we highlight significant improvements in quality of life, production, and profitability reported by 35 farmers. Our lessons learned may guide other educators and funders in developing profit teams for their beginning farmer clients

Formal Reasoning Using an Iterative Approach with an Integrated Web IDE

This paper summarizes our experience in communicating the elements of reasoning about correctness, and the central role of formal specifications in reasoning about modular, component-based software using a language and an integrated Web IDE designed for the purpose. Our experience in using such an IDE, supported by a 'push-button' verifying compiler in a classroom setting, reveals the highly iterative process learners use to arrive at suitably specified, automatically provable code. We explain how the IDE facilitates reasoning at each step of this process by providing human readable verification conditions (VCs) and feedback from an integrated prover that clearly indicates unprovable VCs to help identify obstacles to completing proofs. The paper discusses the IDE's usage in verified software development using several examples drawn from actual classroom lectures and student assignments to illustrate principles of design-by-contract and the iterative process of creating and subsequently refining assertions, such as loop invariants in object-based code.Comment: In Proceedings F-IDE 2015, arXiv:1508.0338