Heat-Cleaned Nextel in MMOD Shielding

Meteoroid and orbital debris (MMOD) shielding can include NextelTM ceramic cloth in the outer layers of the shielding to enhance MMOD breakup. The Nextel fabric can contain size (or sizing) which aids in manufacture of the fabric. Sizing is a starch, oil or waxy material that is added to the rovings and yarns to protect the fibers from being cut or broken during the fabric manufacturing process and by later handling. For spacecraft applications, sizing is removed by heat-cleaning to reduce/eliminate off-gassing during vacuum operations. After the sizing is removed, the fibers in the woven fabric are prone to breakage during handling which reduces fabric strength. Because heat-cleaned Nextel tends to shed fibers that can be irritating to workers, the usual practice for hypervelocity impact tests is to use Nextel with sizing. The reduced strength of heat-cleaned Nextel does not typically effect the performance of MMOD shields with Nextel used in outer layers of the shield, because the density and areal density of the ceramic fibers in the fabric control MMOD breakup (not fabric strength). This paper provides data demonstrating that hypervelocity impact protection performance is not adversely altered for shields containing heat-cleaned Nextel compared to Nextel with sizing

Data driven nets: a maximally concurrent, procedural, parallel process representation for distributed control systems

technical reportA procedural parallel process representation, known as data-driven nets is described. The sequencing mechanism of the data-driven representation is based on the principle of data dependency. Operations are driven into action by the arrival of the required working set of input operands. Execution of DDN processes is side-effect free, and influence in the net representation is transparaent. Data-driven nets have several advantages over many of the existing parallel process representations. These nets are capable of representing parallelism below the statement level, and in addition may be arbitrarily pipelined. Data-driven nets are simpler than other data-flow schema in that no distinction need be made between control and data. A process model for data-driven nets is given and a number of properties of the model are discussed. The operating rules for data-driven nets are completely asynchronous and the nets therefore serve as an excellent low-level process notation for distributed systems

Mathematical representation for VLSI arrays

Journal ArticleThis paper introduces a methodology for mapping algorithmic description into a concurrent implementation on silicon. This methodology can help in the solution of important problems using a new technique for the representation of highly parallel networks. This new approach for the representation of computational networks was inspired by the systolic array approach [H. T. Kung & Leiserson 78], and by the linear approach to computational networks [Cohen 78]. It creates tools which will enable the creation of new high performance implementations as well as verification tools. This approach is more complex than the linear approach [Gill 66, Cohen 78]. but can also be used to verify computation networks

A characterization of parallel systems

technical reporta taxonomy for parallel processing systems is presented which has some advantages over previous taxonomies. The taxonomy characterizes parallel processing systems using four parameters: topology, communication, granularity, and operation. These parameters and used repetitively in a hierarchical fashion to produce a taxonomic structure which is extensible to the level of detail desired. Topology describes the structure of the priniciple interconnections. Communication describes the flow of data and programs through the system. Granularity describes the size of the largest repeated element, or grain. Operation describes the important functional properties of each grain, especially the ratio of storage to logic circuitry. Granularity and topology are structural parameters, while operation and communication are functional parameters which describe the behavior of the system components. A final section of this paper includes examples of the application of the taxonomy to several parallel processing systems

Data Flow Program Graphs

Data flow languages form a subclass of the languages which are based primarily upon function application (i.e., applicative languages). By data flow language we mean any applicative language based entirely upon the notion of data flowing from one function entity to another or any language that directly supports such flowing. This flow concept gives data flow languages the advantage of allowing program definitions to be represented exclusively by graphs. Graphical representations and their applications are the subject of this article

Aortic Aneurysms in Loeys-Dietz Syndrome - A Tale of Two Pathways?

Loeys-Dietz syndrome (LDS) is a connective tissue disorder that is characterized by skeletal abnormalities, craniofacial malformations, and a high predisposition for aortic aneurysm. In this issue of the JCI, Gallo et al. developed transgenic mouse strains harboring missense mutations in the genes encoding type I or II TGF-β receptors. These mice exhibited several LDS-associated phenotypes. Despite being functionally defective, the mutated receptors enhanced TGF-β signaling in vivo, inferred by detection of increased levels of phosphorylated Smad2. Aortic aneurysms in these LDS mice were ablated by treatment with the Ang II type 1 (AT1) receptor antagonist losartan. The results from this study will foster further interest into the potential therapeutic implications of AT1 receptor antagonists

Projectile Density Effects on Shield Performance

In the past, the orbital debris environment was modeled as consisting entirely of aluminum particles. As a consequence, most of the impact test database on spacecraft micro-meteoroid and orbital debris (MMOD) shields, and the resulting ballistic limit equations used to predict shielding performance, has been based on using aluminum projectiles. Recently, data has been collected from returned spacecraft materials and other sources that indicate higher and lower density components of orbital debris also exist. New orbital debris environment models such as ORDEM2008 provide predictions of the fraction of orbital debris in various density bins (high = 7.9 g/cu cm, medium = 2.8 g/cu cm, and low = 0.9-1.1 g/cu cm). This paper describes impact tests to assess the effects of projectile density on the performance capabilities of typical MMOD shields. Updates to shield ballistic limit equations are provided based on results of tests and analysis

Vascular co-option in lung cancer metastatic to the eye after treatment with bevacizumab

Abstract Background Chemotherapy with bevacizumab alters the angiogenic environment, and therefore, the growth and spread of metastases. We present a patient with metastatic lung adenocarcinoma to the eye with findings suggestive of retinal vascular co-option. Methods Case report. Results A 57-year-old male, receiving systemic bevacizumab for metastatic lung adenocarcinoma, presented with vitreous opacities and clumped deposits adherent to the retinal vessels. No choroidal metastases were present. Diagnostic vitrectomy yielded cellular evidence of adenocarcinoma, with thyroid transcription factor-1 staining confirming a lung primary. Conclusion The perivascular growth of small foci of metastatic vitreous cells suggests vascular co-option from the native retinal circulation. Similar modification of metastatic disease by bevacizumab has been observed in animal models and selected human cases

Mycobiome of the Bat White Nose Syndrome (WNS) Affected Caves and Mines reveals High Diversity of Fungi and Local Adaptation by the Fungal Pathogen Pseudogymnoascus (Geomyces) destructans

The investigations of the bat White Nose Syndrome (WNS) have yet to provide answers as to how the causative fungus Pseudogymnoascus (Geomyces) destructans (Pd) first appeared in the Northeast and how a single clone has spread rapidly in the US and Canada. We aimed to catalogue Pd and all other fungi (mycobiome) by the culture-dependent (CD) and culture-independent (CI) methods in four Mines and two Caves from the epicenter of WNS zoonotic. Six hundred sixty-five fungal isolates were obtained by CD method including the live recovery of Pd. Seven hundred three nucleotide sequences that met the definition of operational taxonomic units (OTUs) were recovered by CI methods. Most OTUs belonged to unidentified clones deposited in the databases as environmental nucleic acid sequences (ENAS). The core mycobiome of WNS affected sites comprised of 46 species of fungi from 31 genera recovered in culture, and 17 fungal genera and 31 ENAS identified from clone libraries. Fungi such as Arthroderma spp., Geomyces spp., Kernia spp., Mortierella spp., Penicillium spp., and Verticillium spp. were predominant in culture while Ganoderma spp., Geomyces spp., Mortierella spp., Penicillium spp. and Trichosporon spp. were abundant is clone libraries. Alpha diversity analyses from CI data revealed that fungal community structure was highly diverse. However, the true species diversity remains undetermined due to under sampling. The frequent recovery of Pd indicated that the pathogen has adapted to WNS-afflicted habitats. Further, this study supports the hypothesis that Pd is an introduced species. These findings underscore the need for integrated WNS control measures that target both bats and the fungal pathogen.Comment: 59 pages, 7figure