Estimation of the interior density of a small body given its gravity field

2021 ◽  
Author(s):  
Alfonso Caldiero ◽  
Sébastien Le Maistre ◽  
Véronique Dehant
Keyword(s):  
Gravity Field ◽  
Small Body

scholarly journals Heterogeneous mass distribution of the rubble-pile asteroid (101955) Bennu

2020 ◽  
Vol 6 (41) ◽  
pp. eabc3350 ◽  
Author(s):  
D. J. Scheeres ◽  
A. S. French ◽  
P. Tricarico ◽  
S. R. Chesley ◽  
Y. Takahashi ◽  
...  
Keyword(s):  
Gravity Field ◽  
Mass Distribution ◽  
Small Body ◽  
Parent Body ◽  
Constant Density ◽  
Internal Mass ◽  
Shape Model ◽  
Rapid Rotation ◽  
Insight Into ◽  
Rubble Pile

The gravity field of a small body provides insight into its internal mass distribution. We used two approaches to measure the gravity field of the rubble-pile asteroid (101955) Bennu: (i) tracking and modeling the spacecraft in orbit about the asteroid and (ii) tracking and modeling pebble-sized particles naturally ejected from Bennu’s surface into sustained orbits. These approaches yield statistically consistent results up to degree and order 3, with the particle-based field being statistically significant up to degree and order 9. Comparisons with a constant-density shape model show that Bennu has a heterogeneous mass distribution. These deviations can be modeled with lower densities at Bennu’s equatorial bulge and center. The lower-density equator is consistent with recent migration and redistribution of material. The lower-density center is consistent with a past period of rapid rotation, either from a previous Yarkovsky-O’Keefe-Radzievskii-Paddack cycle or arising during Bennu’s accretion following the disruption of its parent body.

scholarly journals Brief Introduction of Promoting the Chinese Program For Exploring the Martian System

2012 ◽  
Vol 10 (H16) ◽  
pp. 165-165
Author(s):  
Jinsong Ping ◽  
Xian Shi ◽  
Nianchuan Jian ◽  
Sujun Zhang ◽  
Mingyuan Wang ◽  
...  
Keyword(s):  
Gravity Field ◽  
Tracking System ◽  
Small Body ◽  
Open Loop ◽  
Deep Space Exploration ◽  
Global Gravity ◽  
Rosetta Mission ◽  
Phobos Grunt ◽  
Loop Technique ◽  
Mission Teams

AbstractFollowing the progress of Chinese deep space exploration step, since 2006 we started a Mars mission, Yinghuo-1, by join in the Phobos-Grunt mission of Russia. A satellite bus platform and onboard payloads as well as an innovative open-loop radio tracking system have been developed by mission team. Also, together with Russian and German colleagues, we developed a kind of in-beam tracking method for measuring the rotation and nutation of Phobos, and developed the 1st Phobos global gravity field for the mission. We are promoting the Chinese new mission for Mars exploration. Although the joint YH-1 & Phobos-Grunt mission failed, the new techniques and knowledge developed by mission teams may benifit the future missions. In fact, the open-loop technique have been applied into lunar and other planetary missions, and the method in developing Phobos global gravity field will be used in the study of Rosetta mission and future Chinese mission for small body.

Estimating Small-Body Gravity Field from Shape Model and Navigation Data

2010 ◽  
Vol 33 (1) ◽  
pp. 212-221 ◽  
Author(s):  
Ryan S. Park ◽  
Robert A. Werner ◽  
Shyam Bhaskaran
Keyword(s):  
Gravity Field ◽  
Small Body ◽  
Shape Model ◽  
Navigation Data

The Impact of Missing and Error-Prone Auxiliary Information on Sparse-Matrix Sub-Population Parameter Estimates

Methodology ◽  
2015 ◽  
Vol 11 (3) ◽  
pp. 89-99 ◽  
Author(s):  
Leslie Rutkowski ◽  
Yan Zhou
Keyword(s):  
Sparse Matrix ◽  
Small Body ◽  
Auxiliary Information ◽  
Poor Quality ◽  
Quality Data ◽  
Estimation Methods ◽  
Parameter Estimates ◽  
Population Parameter ◽  
Conditioning Model ◽  
The Impact

Abstract. Given a consistent interest in comparing achievement across sub-populations in international assessments such as TIMSS, PIRLS, and PISA, it is critical that sub-population achievement is estimated reliably and with sufficient precision. As such, we systematically examine the limitations to current estimation methods used by these programs. Using a simulation study along with empirical results from the 2007 cycle of TIMSS, we show that a combination of missing and misclassified data in the conditioning model induces biases in sub-population achievement estimates, the magnitude and degree to which can be readily explained by data quality. Importantly, estimated biases in sub-population achievement are limited to the conditioning variable with poor-quality data while other sub-population achievement estimates are unaffected. Findings are generally in line with theory on missing and error-prone covariates. The current research adds to a small body of literature that has noted some of the limitations to sub-population estimation.

Risk Factors for Bleeding during Treatment of Acute Venous Thromboembolism

1996 ◽  
Vol 76 (05) ◽  
pp. 682-688 ◽  
Author(s):  
Jos P J Wester ◽  
Harold W de Valk ◽  
Karel H Nieuwenhuis ◽  
Catherine B Brouwer ◽  
Yolanda van der Graaf ◽  
...  
Keyword(s):  
Risk Factors ◽  
Venous Thromboembolism ◽  
Surface Area ◽  
Body Surface Area ◽  
Body Surface ◽  
Small Body ◽  
Bleeding Risk ◽  
Risk Scores ◽  
Risk Of Bleeding ◽  
Acute Venous Thromboembolism

Summary Objective: Identification of risk factors for bleeding and prospective evaluation of two bleeding risk scores in the treatment of acute venous thromboembolism. Design: Secondary analysis of a prospective, randomized, assessor-blind, multicenter clinical trial. Setting: One university and 2 regional teaching hospitals. Patients: 188 patients treated with heparin or danaparoid for acute venous thromboembolism. Measurements: The presenting clinical features, the doses of the drugs, and the anticoagulant responses were analyzed using univariate and multivariate logistic regression analysis in order to evaluate prognostic factors for bleeding. In addition, the recently developed Utrecht bleeding risk score and Landefeld bleeding risk index were evaluated prospectively. Results: Major bleeding occurred in 4 patients (2.1%) and minor bleeding in 101 patients (53.7%). For all (major and minor combined) bleeding, body surface area ≤2 m2 (odds ratio 2.3, 95% Cl 1.2-4.4; p = 0.01), and malignancy (odds ratio 2.4, 95% Cl 1.1-4.9; p = 0.02) were confirmed to be independent risk factors. An increased treatment-related risk of bleeding was observed in patients treated with high doses of heparin, independent of the concomitant activated partial thromboplastin time ratios. Both bleeding risk scores had low diagnostic value for bleeding in this sample of mainly minor bleeders. Conclusions: A small body surface area and malignancy were associated with a higher frequency of bleeding. The bleeding risk scores merely offer the clinician a general estimation of the risk of bleeding. In patients with a small body surface area or in patients with malignancy, it may be of interest to study whether limited dose reduction of the anticoagulant drug may cause less bleeding without affecting efficacy.

Creating a ‘Masala’ Self: Bicultural Identity in Desi Young Adult Novels

2010 ◽  
Vol 3 (2) ◽  
pp. 119-133 ◽  
Author(s):  
Michelle Superle
Keyword(s):  
Young Adult ◽  
Young People ◽  
Identity Development ◽  
Small Body ◽  
The United States ◽  
Young Adult Fiction ◽  
Bicultural Identity ◽  
The United Kingdom ◽  
Institutional Forces ◽  
Cultural Identity Development

In the past two decades, the previously silent voices of diasporic Indian writers for young people have emerged, and a small body of texts has begun to develop in the United States and the United Kingdom. One of the major preoccupations of these texts is cultural identity development, especially in the novels published for a young adult audience, which often feature protagonists in the throes of an identity crisis. For example, the novels The Roller Birds of Rampur (1991) by Indi Rana, Born Confused (2002) by Tanuja Desai Hidier, and The Not-So-Star-Spangled Life of Sunita Sen (2005) by Mitali Perkins all focus on an adolescent girl coping with her bicultural identity with angst and confusion, and delineate the ways her self-concept and relationships are affected. The texts are empowering in their suggestion that young people have the agency to explore and create their own balanced bicultural identities, but like other young adult fiction, they ultimately situate adolescents within insurmountable institutional forces that are much more powerful than any individual.

The Transnational Women's Rights Movement and the World Economy

2020 ◽  
Vol 6 (2) ◽  
pp. 145-173 ◽  
Author(s):  
Heidi E. Rademacher
Keyword(s):  
Women's Rights ◽  
Small Body ◽  
World System ◽  
World Society ◽  
Women’S Rights ◽  
Social Movement Organizations ◽  
Global Movement ◽  
Negative Effect ◽  
Society Perspective ◽  
The Impact

Promoting the ratification of the Convention on the Elimination of All Forms of Discrimination against Women (CEDAW) was a key objective of the transnational women's movement of the 1980s and 1990s. Yet, few studies examine what factors contribute to ratification. The small body of literature on this topic comes from a world-society perspective, which suggests that CEDAW represented a global shift toward women's rights and that ratification increased as international NGOs proliferated. However, this framing fails to consider whether diffusion varies in a stratified world-system. I combine world-society and world-systems approaches, adding to the literature by examining the impact of women's and human rights transnational social movement organizations on CEDAW ratification at varied world-system positions. The findings illustrate the complex strengths and limitations of a global movement, with such organizations having a negative effect on ratification among core nations, a positive effect in the semiperiphery, and no effect among periphery nations. This suggests that the impact of mobilization was neither a universal application of global scripts nor simply representative of the broad domination of core nations, but a complex and diverse result of civil society actors embedded in a politically stratified world.

Management of Intraoperative Fluid Balance and Blood Conservation Techniques in Adult Cardiac Surgery

2011 ◽  
Vol 14 (1) ◽  
pp. 28 ◽  
Author(s):  
George Vretzakis ◽  
Athina Kleitsaki ◽  
Diamanto Aretha ◽  
Menelaos Karanikolas
Keyword(s):  
Cardiac Surgery ◽  
Blood Cell ◽  
Fluid Balance ◽  
Blood Product ◽  
Blood Donation ◽  
Autologous Blood ◽  
Small Body ◽  
Risk Indicators ◽  
Blood Transfusions ◽  
Blood Conservation

Blood transfusions are associated with adverse physiologic effects and increased cost, and therefore reduction of blood product use during surgery is a desirable goal for all patients. Cardiac surgery is a major consumer of donor blood products, especially when cardiopulmonary bypass (CPB) is used, because hematocrit drops precipitously during CPB due to blood loss and blood cell dilution. Advanced age, low preoperative red blood cell volume (preoperative anemia or small body size), preoperative antiplatelet or antithrombotic drugs, complex or re-operative procedures or emergency operations, and patient comorbidities were identified as important transfusion risk indicators in a report recently published by the Society of Cardiovascular Anesthesiologists. This report also identified several pre- and intraoperative interventions that may help reduce blood transfusions, including off-pump procedures, preoperative autologous blood donation, normovolemic hemodilution, and routine cell saver use.A multimodal approach to blood conservation, with highrisk patients receiving all available interventions, may help preserve vital organ perfusion and reduce blood product utilization. In addition, because positive intravenous fluid balance is a significant factor affecting hemodilution during cardiac surgery, especially when CPB is used, strategies aimed at limiting intraoperative fluid balance positiveness may also lead to reduced blood product utilization.This review discusses currently available techniques that can be used intraoperatively in an attempt to avoid or minimize fluid balance positiveness, to preserve the patient's own red blood cells, and to decrease blood product utilization during cardiac surgery.

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