Creating the Future of Microspace Technology

The Advanced Space Technology Program (ASTP) at the Defense Advanced Research Projects Agency (DARPA) has recently initiated a series of technology development efforts as part of its drive to enhance the cost effectiveness and responsiveness of defense space systems. These efforts focus on reducing spacecraft size, cost, weight, and power consumption, while simultaneously improving performance. The technology initiatives which are underway span a broad spectrum of efforts at the satellite system and subsystem levels, as well as some which focus on individual components and materials. The technology initiatives which DARPA is pursuing will enhance large, major satellites via technology insertions of cost effective, leading edge technologies in a timely fashion, and will facilitate a new class of small highly capable satellites. This paper will highlight some of the new efforts which have been initiated by ASTP in the past year

Applications of Small Satellites for Defense Space Communication Systems and Technology Development: Pegasus Flight-2 and the Launch of Microsat

DARPA\u27s seven Microsats were placed into orbit on the second flight of the Pegasus. The Microsat program objective is to assess the tactical utility of small, low-cost communications satellites. This paper describes the changes made to the Pegasus since its first flight, provides an overview of the Microsat demonstration program, and outlines the preliminary results of the Pegasus launch. Finally, the near-term Army and Navy demonstration plans for Microsat are discussed

Utilization of Small Commercial Grade Nickel Cadmium (NiCd) Cells in Low Earth Orbit (LEO) Applications

The Defense Advanced Research Projects Agency (DARPA) has sponsored the Advanced Space Technology Program (ASTP) to enhance the cost-effectiveness and responsiveness of military space systems. One of the major themes of this program is the development of highly capable small satellites, generally referred to as \u27\u27LightSats, which can perform selected defense missions at relatively low cost. A key element of the programmatic approach is the utilization of commercial grade parts and practices where practical, as opposed to the much more conservative aerospace grade parts. ASTP has incorporated commercial grade batteries into its first generation LightSats; however, an attempt has been made to study the trade-offs and design considerations to optimally employ these batteries on small satellites. For certain applications, particularly for small relatively inexpensive satellites, commercial grade cells may be a viable alternative to aerospace cells. Differences between aerospace and commercial grade cells range from physical construction and technology incorporated, to the level of quality control in manufacturing. These differences are reflected in both greater cost and increased lead time for the aerospace cells. Our research and experience suggest that certain manufacturing technologies are preferable when considering commercial cells for space applications. Once the cell type is chosen, candidate cells must be thoroughly screened to insure survival and acceptable performance in the space environment. To insure optimal performance, cells should be rigorously matched in electrical characteristics when forming batteries. Test procedures should be tailored to fit the application in order to yield the best performance in a specific physical, electrical, and operational environment. An acceptance test plan for screening and matching cells is discussed. The present paper is the first in a series of reports which will document the approach, results, and lessons learned from ASTP\u27s commercial battery studies

Utilization of the Multiple Access Communications Satellite (MACSAT) in Support of Tactical Communications

Two MACSATs were launched on May 9, 1990 on a Scout launch vehicle from Vandenberg Air Force Base, California. After a short on-orbit check-out, these research and development satellites were placed into service providing operational communications support to 2d Marine Aircraft Wing units deployed to the Persian Gulf in support of Operations Desert Shield and Desert Storm. This support was provided from August 1990 until Operation Desert Storm was completed in April 1991. During this time, many lessons were learned that are directly applicable to the design and fielding of future small tactical communications satellites. This paper will highlight some of the lessons learned from supporting Operation Desert Shield, as well as other communications support missions

Columnar Cell Lesion and Apocrine Hyperplasia of the Breast: Is There a Common Origin? The Role of Prolactin-induced Protein

Noninvasive breast lesions encompass a heterogeneous group of risk indicators and nonobligate precursors of breast cancer, such as apocrine hyperplasia (AH) and columnar cell lesions (CCLs). Given the different expression of ER and ER-regulated genes in AH and CCL, these two alterations are currently considered discrete conditions. However, whether they share early biologic changes is not clear to date. Here, we sought to define the clinicopathologic and immunohistochemical features of a prospective series of combined lesions made up by CCLs and AH forming a continuum within single terminal duct-lobular units. The study group included 19 cases, whereas 25 cases of synchronous contiguous CCLs and AH served as control group. The different components of each case were subjected to immunohistochemical analysis for ER, PR, AR, HER2, BCL2, CCND1, MUC1, and PIP. Although CCLs and AHs arising in continuity showed opposite patterns of ER expression, the PIP-positive apocrine signature was consistently present in both components. In conclusion, apocrine changes are highly recurrent in CCLs growing within foci of AH, regardless of the ER activation. Our results suggest that PIP-positive and PIP-negative CCLs are likely to represent biologically distinct conditions and that apocrine changes might occur earlier than ER activation in the natural history of breast precursor lesions

Association between red cell distribution width and response to methotrexate in rheumatoid arthritis

Red cell distribution width (RDW) is an unconventional biomarker of inflammation. We aimed to explore its role as a predictor of treatment response in rheumatoid arthritis (RA). Eighty-two RA patients (55 females), median age [interquartile range] 63 years [52-69], were selected by scanning the medical records of a rheumatology clinic, to analyze the associations between baseline RDW, disease activity scores and inflammatory markers, as well as the relationship between RDW changes following methotrexate (MTX) and treatment response. The lower the median baseline RDW, the greater were the chances of a positive EULAR response at three months, 13.5% [13.0-14.4] being among those with good response, vs 14.0% [13.2-14.7] and 14.2% [13.5- 16.0] (p=0.009) among those with moderate and poor response, respectively. MTX treatment was followed by a significant RDW increase (p<0.0001). The increase of RDW was greater among patients with good EULAR response, becoming progressively smaller in cases with moderate and poor response (1.0% [0.4-1.4] vs. 0.7 [0.1-2.0] vs. 0.3 [-0.1-0.8]; p=0.03). RDW is a strong predictor of early response to MTX in RA. RDW significantly increases after MTX initiation in parallel to treatment response, suggesting a role as a marker of MTX effectiveness

On the dispersion of solid particles in a liquid agitated by a bubble swarm

This article deals with the dispersion of solid particles in a liquid agitated by a homogeneous swarm of bubbles. The scale of interest lies between the plant scale (of the order of the tank) and the microscale (less than the bubble diameter). The strategy consists in simulating both the twophase flow of deforming bubbles and the motion of solid particles. The evolution of the spatial distribution of particles together with the encounter and entrainment phenomena is studied as a function of the void fraction and the relative size and mass of particles. The influence of the shape of the bubble and of the model of forces that govern the motion of particles is also considered

Inflammatory markers predict insulin sensitivity in active rheumatoid arthritis but not in psoriatic arthritis

Whether the insulin resistance commonly observed in patients with inflammatory arthritis is a disease-specific feature and/or is limited to a disease phase (i.e., it occurs only during phases of high disease activity) is unknown. Fifty-three rheumatoid arthritis (RA) and 44 psoriatic arthritis (PsA) patients were recruited consecutively along with 194 controls matched for age, sex and body mass index for a case-control study. All underwent an oral glucose tolerance test, the results of which were analysed to derive the following indexes: homeostatic model of insulin resistance (HOMA-IR), insulin sensitivity index (ISI) and early insulin sensitivity index (EISI). These data were related to anthropometric, clinical and laboratory findings. Metabolic parameters of patients and controls were similar. Neither inflammatory markers nor disease activity scores were related to glucose metabolism for the generality of RA and PsA patients; however, by restricting the analysis to the subset of RA patients with residual disease activity, an association emerged between erythrocyte sedimentation rate, on the one hand, and fasting insulin (β=0.46, p=0.047) and HOMA-IR (β=0.44, p=0.02), on the other. Moreover, C-reactive protein (CRP) levels were associated with plasma glucose and insulin levels measured 120 min after the glucose load (β=0.91, p=0.0003 and β=0.77, p=0.0006, respectively); ISI and EISI were predicted by CRP (β=-0.79, p=0.0006; β=-0.80, p=0.0001, respectively). The same did not hold true for PsA patients. The association between systemic inflammation and insulin resistance indexes is a feature of RA with residual disease activity, not a universal feature of inflammatory arthritides

Kelvin-Helmholtz instability in the presence of variable viscosity for mudflow resuspension in estuaries

The temporal stability of a parallel shear flow of miscible fluid layers of dif- ferent density and viscosity is investigated through a linear stability analysis and direct numerical simulations. The geometry and rheology of this Newto- nian fluid mixing can be viewed as a simplified model of the behavior of mud- flow at the bottom of estuaries for suspension studies. In this study, focus is on the stability and transition to turbulence of an initially laminar configuration. A parametric analysis is performed by varying the values of three control pa- rameters, namely the viscosity ratio, the Richardson and Reynolds numbers, in the case of initially identical thickness of the velocity, density and viscosity profiles. The range of parameters has been chosen so as to mimic a wide variety of real configurations. This study shows that the Kelvin-Helmholtz instability is controlled by the local Reynolds and Richardson numbers of the inflection point. In addition, at moderate Reynolds number, viscosity strat- ification has a strong influence on the onset of instability, the latter being enhanced at high viscosity ratio, while at high Reynolds number, the influ- ence is less pronounced. In all cases, we show that the thickness of the mixing layer (and thus resuspension) is increased by high viscosity stratification, in particular during the non-linear development of the instability and especially pairing processes. This study suggests that mud viscosity has to be taken into account for resuspension parameterizations because of its impact on the inflec- tion point Reynolds number and the viscosity ratio, which are key parameters for shear instabilities