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Collaborative adaptive governance has become a prominent, if not dominant, framework for thinking about multi-scalar and cross-jurisdictional environmental management. The literature broadly and consistently suggests that learning and collaboration are two key dimensions for adaptive governance and that inter-organizational networks provide the institutional framework for addressing social-ecological system challenges. Surprisingly little scholarship addresses the influence of network structure on an organization’s capacity to engage in adaptive governance. In the following, we establish a quantifiable, statistical relationship between network structure (i.e., organizations and their arrangement among a network) and organizational capacity for collaborative adaptive governance. We use a linear network autocorrelation model (lnam) to test the relationship between organizational capacity for adaptive governance (operationalized as capacity for learning and collaboration) and how that relates to network structure across the three hypothesis: (1) that social position – operationalized as network centrality – is related to organizational capacity, (2) that subgroup or community structure – operationalized as modularity – is related to organizational capacity, and (3) that there is a social contagion effect of organizational capacity for adaptive governance. Our results identify an empirical relationship between organizational-level collaborative and learning capacity and those organizations in positions of brokerage. This work contributes to our understanding of the role of bridging organizations and networks for large-scale environmental management.

Weddell seals (Leptonychotes weddellii) are a well-studied species of phocid with an apparent sensitivity to immobilising agents. Mortality as high as 31% has been reported during field immobilisation. This study investigated the use of a benzodiazepine in combination with an opioid agonist/antagonist for sedation in Weddell seal pups as part of a physiological study.During the 2017 and 2019 Antarctic pupping seasons, 18 Weddell seal pups were sedated by intramuscular administration of a combination of midazolam and butorphanol or intravenous midazolam alone. Individuals were sedated at 1, 3, 5 and 7 weeks of age. Naltrexone and flumazenil were used to reverse sedation. The combination was 100% effective in providing appropriate sedation for the intended procedures.Analyses were performed to investigate relationships between dose administered, age, individual reactions, adverse effects and changes in dive physiology. Transient apnoea (10-60 seconds) was the most frequently observed adverse effect. No sedation-associated morbidity or mortality occurred.The sample size is small and there is no pharmacokinetic information for either sedative or reversal in phocid species.The combination of midazolam (0.2-0.3 mg/kg) and butorphanol (0.1-0.2 mg/kg) provided safe and effective sedation, with reversible effects, in Weddell seal pups.

Successful buried unexploded ordnance (UXO) detection in shallow water (

ImportanceThe lack of racial and ethnic diversity in the US medical profession is a well-recognized problem, and racial and ethnic representation is highly variable across the medical specialties. Residency selection is a crucial juncture at which diversity and representation in specialties can be increased.ObjectiveTo identify factors associated with residency application rates for medical specialties by race and ethnicity.Design, Setting, and ParticipantsThis national cross-sectional study of medical student residency applications used American Association of Medical Colleges data on 2019-2020 applicants and information about the racial and ethnic characteristics of practicing physicians (including medical school faculty) and department chairs. A total of 26 320 applicants to medical residency programs, 592 296 practicing physicians, and 2121 department chairs across the US were included. Residency application rates for 18 medical specialties were evaluated.Main Outcomes and MeasuresThe main outcome was the specialty representation quotient (SRQ), which estimated the extent to which students from a racial or ethnic group were overrepresented (an SRQ >1) or underrepresented (an SRQ ResultsAmong 26 320 specialty-specific applications to medical residency programs in 18 specialties, 90 (0.3%) were from American Indian or Alaska Native students, 6718 (25.5%) were from Asian students, 2575 (9.8%) were from Black students, 1896 (7.2%) were from Hispanic students, and 15 041 (57.1%) were from White students. Among 592 296 practicing physicians, 2777 (0.5%) were American Indian or Alaska Native, 117 358 (19.8%) were Asian, 36 639 (6.2%) were Black, 41 071 (6.9%) were Hispanic, and 394 451 (66.6%) were White. Among 2121 department chairs, 5 (0.2%) were American Indian or Alaska Native, 212 (10.0%) were Asian, 86 (4.1%) were Black, 88 (4.1%) were Hispanic, and 1730 (81.6%) were White. The specialties with the greatest representation among applicants from racial and ethnic groups underrepresented in medicine (URM) were family medicine (SRQ, 1.70), physical medicine and rehabilitation (SRQ, 1.60), and obstetrics and gynecology (SRQ, 1.47). The specialties with the lowest URM representation among applicants were plastic surgery (SRQ, 0.47), otolaryngology (SRQ, 0.53), and orthopedic surgery (SRQ, 0.86). Membership in AΩA was negatively associated with SRQ among American Indian or Alaska Native students only (β = –0.11; 95% CI, –0.17 to –0.05; P = .002). Racial and ethnic representation among practicing physicians was positively associated with SRQ for American Indian or Alaska Native students (β = 6.05; 95% CI, 4.26-7.85; P P P P = .02).Conclusions and RelevanceThis study’s findings suggest that the propensity of medical students, particularly those from racial and ethnic minority groups, to apply to a given specialty for residency was associated with the representation of their racial or ethnic group among the specialty’s practicing physicians. Future work to characterize the mechanisms of occupational sorting may guide interventions to improve equity within the physician workforce.

Pathology in the dentate gyrus, including sclerosis, is a hallmark of temporal lobe epilepsy, and reduced inhibition to dentate granule cells may contribute to epileptogenesis. The perisomatic-targeting axonal boutons of parvalbumin-expressing interneurons decrease in proportion with granule cells in temporal lobe epilepsy. In contrast, dendrite-targeting axonal boutons of somatostatin-expressing interneurons sprout exuberantly in temporal lobe epilepsy. A third major class of GABAergic interneurons expresses cannabinoid receptor type 1 (CB1) on their terminal boutons, but there is conflicting evidence as to whether these boutons are increased or decreased in temporal lobe epilepsy. Naturally occurring temporal lobe epilepsy in California sea lions, with unilateral or bilateral sclerosis, offers the benefit of neuroanatomy and neuropathology akin to humans, but with the advantage that the entirety of both hippocampi from control and epileptic brains can be studied. Stereological quantification in the dentate gyrus revealed that sclerotic hippocampi from epileptic sea lions had fewer CB1-labeled boutons than controls. However, the reduction in the number of granule cells was greater, resulting in increased CB1-labeled boutons per granule cell in sclerotic hippocampi at temporal levels. This suggests that although CB1-expressing boutons are decreased in sclerotic dentate gyri, surviving cells have enhanced innervation from these boutons in epileptic sea lions.

Author(s): Johnson, Shawn; Brush, Lisa; Farrell, Sharon; Landry, Devin | Abstract: Tending to long-term landscape health and resilience is a highly complex enterprise. To address this complexity, we must imagine and facilitate a community-based response that is just as complex, inclusive, interdependent, informed, deliberative, and adaptive as the challenges we face. Conservation and stewardship partnerships are a now-familiar way to try to tackle this monumental task. However, successful conservation partnerships are not possible without leadership that can explore shared values amidst dissenting views, navigate complex and technical information to bring all parties to a shared understanding of the issues, manage conflict and facilitate difficult conversations, and approach these multi-faceted challenges with humility and empathy. This is both the challenge and the opportunity of collaborative leadership. The series of papers in this issue of Parks Stewardship Forum on “Collaborating Well” explores what makes collaborative leadership work. This introductory piece illustrates why collaborative leadership is so critical to meet our landscape stewardship needs. The article on the Partnership Impact Model goes beyond describing this work and delves into how to measure its impact. Moreover, the article on peer learning provides examples of how to advance collaborative leadership successes by sharing critical knowledge, experience, and skills with others. Within all of these facets of collaborative leadership are social and cross-cultural competencies that further enable this work.

Author(s): Navalkha, Chandni; Levitt, James N.; Johnson, Shawn; Farrell, Sharon | Abstract: Learning and exchange among peers (“peer learning”) is an important process shaping and enabling landscape conservation and stewardship. As a practice that connects practitioners working at the landscape scale within and across regions—and that dedicates time and resources to supporting meaningful exchange—peer learning builds and strengthens the relationships at the core of the collaboration and partnership that are central to meeting shared goals and needs. This article explores peer learning and its role in learning, demonstrating, and building collaborative leadership. It also offers two examples of peer learning initiatives and their on-the-ground outcomes: the Large Landscape Peer Learning Initiative, a program coordinated by the Lincoln Institute of Land Policy to bring together an international group of landscape conservation practitioners for shared problem-solving; and the Landscape Conservation Catalyst Fund Program, an initiative of the Network for Landscape Conservation to create a learning-exchange community among grantees to support the development of place-based partnerships.

e18555 Background: Disparities in cancer screening have been well documented during the Covid-19 pandemic. However, there are limited patient-reported data describing the prevalence and drivers of patient hesitancy towards cancer screening and willingness to resume screening. As health systems continue to experience pandemic-related capacity strain, there is an urgent need for innovative models of re-engaging patients in preventive screening. To address this issue, we developed a medical student-led, high-touch outreach model to re-engage primary care patients at Brookside Community Health Center in cancer screening. Methods: We iteratively optimized semi-structured call scripts and surveys in English and Spanish to contact patients overdue for mammography screening. Student callers included medical and pre-medical students with native Spanish fluency. Using the call script, students identified patient-reported barriers and facilitated mammogram scheduling for consenting patients. For consenting patients, student callers placed a telephone encounter with a pended screening mammogram order in the electronic medical record. PCP confirmation of the order triggered outreach by the radiology department for mammogram scheduling. Patients also received reminder calls from students the week of their appointment. Primary outcomes include screening consent rates, mammogram scheduling and completion rates, and screening results. Patient survey responses were securely recorded using the REDCap survey platform. Results: 198 patients were eligible for the intervention. 60% are primarily Spanish-speaking and 81% are insured by Medicaid. 145 patients (73%) have successfully been contacted, of which 129 (89%) consented for mammogram screening. 74 (57%) of the consenting patients have scheduled their mammogram and 38 (29%) have completed their mammogram. 36% of consenting Spanish-speaking patients with active mammogram orders did not have a mammogram scheduled, compared to 9% of consenting English-speaking. To date, 6 patients had abnormal mammograms requiring subsequent diagnostic imaging, and 1 patient was diagnosed with ductal carcinoma in situ requiring oncologic care. Qualitative analysis of patient surveys found that primary barriers to screening included factors associated with the Covid-19 pandemic (32.9% of contacted patients), lack of awareness of overdue status (25.9%) and patient unavailability (e.g. outside of country) (20%). Conclusions: In this single-center quality improvement study, we found that patients had a high willingness to engage in cancer screening during the pandemic and that trainees can play a vital role in re-engaging patients in preventative care. The disparity between Spanish and English-speaking patients’ ability to schedule a mammogram after the consent process suggests that patients with limited English proficiency face additional challenges in accessing screenings.

Recent modeling and field experimentation has shown very-shallow-water acoustic imaging of buried unexploded ordnance (UXO) can place stringent requirements on the sonar transmit system. Achieving high-resolution imagery requires large transmit bandwidth. Imaging deeply buried UXO requires low operating frequencies and high source levels to overcome sediment attenuation. Imaging UXO near the sediment–water interface requires short transmit waveforms that require projectors with a low mechanical quality factor for accurate reproduction. This work presents the results of a recent design study, device fabrication, and acoustic testing of a new projector intended for operation as part of a buried UXO imaging system. The analysis will focus on the design and material selection of the head mass and the ring stack used in the tonpilz device. The head mass design trade considered construction from aluminum or an aluminum beryllium metal matrix composite (AlBeMet). The ring stack design trade considered traditional polycrystalline lead zirconate titanate (PZT), ternary single crystal lead indium niobium–lead indium manganese niobium titanate (PIN-PMN-PT), and textured manganese doped lead magnesium niobate–lead zirconate titanate (Mn-PMN-PZT). Finite element simulations and measured results will be presented.

Current methods of tagging events in a particular context, when deciding which ones pose a security risk on an enterprise network are inadequate. For example, changes in an environment, such as a larger number of HIPAA violations by certain user roles, can pose a risk to specific organizational functions or cyber infrastructure. To compound the problem, different information owners typically specify different user contexts based on differing organizational or individual needs. To address this problem, we developed an approach that utilizes semantic annotations, a technique that can aid in the understanding of how an event may affect knowledge of information in a domain. In this approach, semantic annotations are used to enable the tagging of events in accordance with differing organizational goals and user preferences. This work can be used to flag possible security violations and assist in their prevention.

Extensive scar tissue formation often occurs after severe burn injury, trauma, or as one of complications after surgical intervention. Despite significant therapeutic advances, it is still a significant challenge to manage massive scar tissue formation while also promoting normal wound healing. The goal of this study was to investigate the therapeutic effect of bone mesenchymal stem cells (BMSCs) that were genetically modified to overexpress transforming growth factor-beta 3 (TGF-β3), an inhibitor of myofibroblast proliferation and collagen type I deposition, on full-thickness cutaneous wound healing in a rabbit model. Twenty-four rabbits with surgically-induced full-thickness cutaneous wounds created on the external ear (1.5 × 1.5 cm, two wounds/ear) were randomized into four groups: (G1), wounds with no special treatment but common serum-free culture medium as negative controls; (G2), topically-applied recombinant adenovirus, expressing TGF-β3/GFP; (G3), topically-applied BMSCs alone; (G4), topically-applied BMSCs transfected with Ad-TGF-β3/GFP (BMSCsTGF-β3); and (G5), an additional normal control (n = 2) with neither wound nor treatment on the external ear skin. The sizes of wounds on the ear tissues were grossly examined, and the scar depth and density of wounds were histologically evaluated 21, 45, and 90 days after surgical wound creation. Our results demonstrated that G4 significantly reduced the wound scar depth and density, compared to G1~3. Numbers of cells expressing GFP significantly increased in G4, compared to G2. The protein expression of TGF-β3 and type III collagen in G4 significantly increased, while the ratio of type I to type III collagen was also significantly reduced, which is similar to the tissue architecture found in G5, as compared the other treatment groups. In conclusion, transplantation of BMSCsTGF-β3 remarkably improves wound healing and reduces skin scar tissue formation in an animal model, which may potentially provide an alternative in the treatment of extensive scar tissue formation after soft tissue injury.

The July 2027 impact date for the hypothetical asteroid 2017 PDC, that is the subject of an emergency response exercise, leaves just over ten years to implement a deflection approach. The analyses herein allocate four years to the design, fabrication, assembly, test and launch of a notional high-power Ion Beam Deflection (IBD) vehicle to meet a launch readiness date no later than May 2021. Using this launch date along with estimates for the vehicle mass and performance characteristics of the electric propulsion system, low-thrust trajectory analyses indicate a 2.56-year flight time to rendezvous with 2017 PDC. This would leave 3.6 years to execute the actual deflection phase. A 160-kW IBD vehicle could deflect 2017 PDC by at least one Earth radius within this time provided the asteroid's actual diameter was less than about 140 m and its density was 2 g/cm 3 or less. Larger diameters and/or higher densities would require a higher power IBD vehicle, multiple IBD vehicles, or a longer deflection phase. Ion beam deflection is largely independent of the characteristics of the threat object, but its effectiveness, like all deflection approaches, is sensitive to both the asteroid mass and the time available for deflection. The characteristics of IBD, i.e., large standoff distance between the spacecraft and the asteroid surface, as well as ion beam divergence angles of a few degrees, facilitate the possible simultaneous use of multiple IBD vehicles to improve the performance and robustness of the asteroid deflection. The 65-cm diameter, 20-kW NEXIS ion thruster developed in support of the Jupiter Icy Moons Orbiter mission concept is particularly well suited for application to a high-power IBD system. It has demonstrated a small ion beam divergence angle and operation at 20 kW for over 2000 h. Completion of the development and flight qualification of this technology would significantly reduce the risk and time necessary to respond to the discovery of potentially hazardous asteroid in the size range of 50- to 140-m diameter.

As small satellites and CubeSats demonstrate their value as science-capable platforms, the community is pushing to improve reliability while expanding performance capabilities. The attitude control...

A series of new polycyclic aromatic hydrocarbon compounds based on (4,10-disubstituted-dibenzo[def,mno]chrysene-6,12-dione) and 4,10 di-substituted 6,12-bis(triisopropylsilylethynyl)dibenzo[def,mno]chrysene are reported with tunable electronic properties through varied molecular architecture. Starting with an inexpensive commercially available textile dye known as Vat Orange #3, (4,10-dibromo-dibenzo[def,mno] chrysene-6,12-dione) we extended the conjugation at the 4- and 10-positions by the attachment of both electron rich and deficient hexylvinylphthalimide, thiophene, hexylthiophene, triphenylamine, and hexylbithiophene aromatic groups, and studied the resultant optoelectronic properties. By applying various synthetic metal-catalyzed reactions, soluble dibenzo[def,mno]chrysene and dibenzo[def,mno]chrysene-6,12-dione derivatives were achieved with optical edge band gaps between 2.30 eV and 1.65 eV.

The objective of large landscape conser vation is to mitigate complex ecological problems through interventions at multiple and overlapping scales. Implementation requires coordination among a diverse network of individuals and organizations to integrate local-scale conservation activities with broad-scale goals. This requires an understanding of the governance options and how governance regimes achieve objectives or provide performance evaluation across both space and time. However, empirical assessments measuring network-governance performance in large landscape conservation are limited. We describe a well-established large landscape conser vation network in North America, the Roundtable on the Crown of the Continent, to explore the application of a social-ecological performance evaluation framework. Systematic approaches to setting goals, tracking progress, and collecting data for feedback can help guide adaptation. Applying the established framework to our case study provides a means of evaluating the effectiveness of network governance in large landscape conservation.

Conservation of large landscapes requires three interconnected types of leadership: collaborative leadership, in which network members share leadership functions at different points in time; distributive leadership, in which network processes provide local opportunities for members to act proactively for the benefit of the network; and architectural leadership, in which the structure of the network is intentionally designed to allow network processes to occur. In network governance, each leadership approach is necessary to achieve sustained, successful outcomes. We discuss each of these approaches to leadership and offer specific practices for leaders of networks, including: shaping the network's identity and vision, attracting members, instilling leadership skills in members, and advancing common interests. These practices are then illustrated in case studies.

Recent technology advancements in microelectric propulsion will enable the next generation of small spacecraft to perform trajectory and attitude maneuvers with significant ΔV requirements, provide thrust over long mission durations, and replace reaction wheels for attitude control. These advancements will open up the class of mission architectures achievable by small spacecraft to include formation flying, proximity operations, and precision pointing missions in both low Earth orbit and interplanetary destinations. The goal of this study is to establish the optimal performance parameters for future microelectric propulsion technology that are applicable to a broad range of flight demonstration platforms (for example, dedicated 3- to 12-unit CubeSats to evolved expendable launch vehicle secondary payload adaptor-class spacecraft) for a variety of applications, including low Earth orbit and Earth escape orbit transfers, travel to interplanetary destinations, hover and drag makeup missions, and performing r...

Patients with BRCA-associated triple-negative breast cancer (TNBC) have few effective treatment options. PARP inhibitors are promising, and we recently showed they induce an influx of white blood cells, including CD8+ T cells and macrophages into the tumor. The influx of CD8+ cells, mediated by activation of the STING pathway in tumor cells, contributes substantially to efficacy of PARP inhibition in mice. Strikingly, in these studies the greatest infiltration of immune cells into the tumor was macrophages. Given that objective responses to PARP inhibition have been observed in clinical trials but the benefits are transitory, we hypothesized that this was due to a suppressive tumor microenvironment, driven by tumor macrophages. To better understand the molecular basis of resistance to PARP inhibitors, we used high-dimensional single-cell immune profiling on human TNBC. We observed a ≥10-fold increase in TAMs in BRCA-associated TNBC compared to BRCA-wild-type TNBC. Using a preclinical model of BRCA1-deficient triple-negative breast cancer, we found that PARP inhibitors not only further increased TAM abundance but also induced functional and phenotypic changes associated with STING pathway activation, antigen presentation, and chemokine and cytokine signaling. PARP inhibitors increased the frequency of TAMs expressing costimulatory molecules CD80 and CD86 as well as the activation and maturation marker CD40, which are indicative of an antitumor phenotype. We also identified a novel negative feedback mechanism that limits the functionality of the anti-tumor TAMs and is consistent with induction of an immune-suppressive macrophage population. Utilizing transcriptomic, proteomic, and metabolic profiling of ex vivo cultured human myeloid cells, we identified multiple biologic processes associated with PARP inhibition, showing that these drugs directly affect macrophage states and phenotypes. Remarkably, in the preclinical BRCA1-deficient TNBC model, the novel combination of PARP inhibition with macrophage modulation significantly extended remissions obtained with PARP inhibitor therapy only, and this advantage persisted when treatment was discontinued, suggestive of a durable reprogramming of the tumor microenvironment. Moreover, CD8+ cells were required for the extension of PARP inhibitor-induced remissions, suggesting that targeting macrophages lifted the constraints imposed by protumor macrophages on CD8+ T cell-mediated tumor cell killing. We identify mechanisms related to macrophage and T-cell activation that increase PFS and provide evidence that TAMs may serve as targets for new therapeutic interventions designed to overcome PARP inhibitor resistance in BRCA-associated TNBC. Citation Format: Anita K. Mehta, Emily M. Cheney, Jessica A. Castrillon, Jia-Ren Lin, Mateus de Oliveira Taveira, Christina A. Hartl, Nathan T. Johnson, William M. Oldham, Marian Kalocsay, Sarah A. Boswell, Olmo Sonzogni, Constantia Pantelidou, Brett P. Gross, Shawn Johnson, Deborah A. Dillon, Sandro Santagata, Judy E. Garber, Nadine Tung, Elizabeth A. Mittendorf, Gerburg M. Wulf, Geoffrey I. Shapiro, Peter K. Sorger, Jennifer L. Guerriero. PARP inhibition modulates the infiltration, phenotype, and function of tumor-associated macrophages (TAMs) in BRCA-associated breast cancer and can be augmented by harnessing the antitumor potential of TAMs [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2019 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(3 Suppl):Abstract nr A105.

Cyber analysts tend to respond to anomalous events manually, often using subjective judgment that can lead to responses that are less than optimal. Additionally, analysts tend to report on events and share cyber knowledge in unstructured, textual formats, which not only require more time to parse – thus taking more time to respond – but also lead to multiple conclusions from the same input. To remedy this, we have proposed a framework designed to provide an analyst with a set of timely and accurate courses of action in response to events, in some cases automating those responses. As part of this framework, we have created a playbook specification format that allows analysts to specify the right course of action to take in response to events, given certain risk conditions and mission context. In addition to providing the specification format, we have also created an initial ontology to help analysts build their playbook contents and have laid out a notional architecture that can operationalize these playbooks. Our playbook format can help standardize how analysts should respond to events, thus decreasing the time to response and enabling analysts to share key knowledge in a common format. Ultimately, this should increase the efficacy of security operations center personnel.

Extensive scar tissue formation often occurs after severe burn injury, trauma, or as one of complications after surgical intervention. Despite significant therapeutic advances, it is still a significant challenge to manage massive scar tissue formation while also promoting normal wound healing. The goal of this study was to investigate the therapeutic effect of bone mesenchymal stem cells (BMSCs) that were genetically modified to overexpress transforming growth factor-beta 3 (TGF-β

Electric propulsion may play a crucial role in the implementation of the gravity tractor planetary defense technique. Gravity tractors were devised to take advantage of the mutual gravitational force between a spacecraft flying in formation with the target celestial body to slowly alter the celestial body's trajectory. No physical contact is necessary, which bypasses issues associated with surface contact such as landing, anchoring, or spin compensation. The gravity tractor maneuver can take several forms, from the originally proposed constant thrust in-line hover to the offset halo orbit. Both can be enhanced with the collection of mass at the asteroid. The form of the gravity tractor ultimately impacts the required thrust magnitude to maintain the formation, as well as constraints on the vectoring of the thrust direction. Solar electric propulsion systems provide an efficient mechanism for tugging the spacecraft-asteroid system due to their high specific impulse. Electric propulsion systems can generate thrust continuously at high efficiency, which is an ideal property for gravity tractors that may require years of operation to achieve the desired deflection because of the very low coupling force provided by the gravitational attraction. The performance and feasibility of the deflection are predicated on having the propulsion capability to maintain the gravity tractor. This paper describes the impacts of constraining the solar electric propulsion thrust magnitude and thrust vectoring capability. It is shown that uncertainty in asteroid density and size, when combined with the enforcement of the electric propulsion constraints, can preclude the feasibility of certain gravity tractor configurations. Additionally, odd thruster configurations are shown to drive the gimbal performance and to have major impacts on eroding incident spacecraft surfaces due to plume interaction. Center of gravity movement further exacerbates issues with gimbaling and plume interaction. A tighter plume divergence angle is therefore always desired, but this paper shows that there is an optimal momentum balance between plume interaction and asteroid-plume avoidance. Several gravity tractor techniques are compared based on metrics of time efficacy, as measured by the induced asteroid delta-V per unit time, and mass efficiency, as measured by the induced asteroid delta-V per unit mass of fuel. Given the propulsion constraints, halo orbits can be infeasible for smaller asteroids unless the mass of the spacecraft is augmented with collected material through a technique called the Enhanced Gravity Tractor. Another proposed method is to alter the halo period by canting the thrusters. In-line hover gravity tractors can always be moved along the net thrust direction to conform to the given propulsion system at the expense of performance, except in the case of smaller asteroids with propulsion systems that are limited in lower throttle range or maximum gimbal angle. Alternative strategies, such as on-off pulsing the thrusters to lower the effective thrust are considered. An example is described for deflecting asteroid 2008 EV 5 (341843), which currently serves as the reference asteroid for the proposed Asteroid Redirect Robotic Mission.

Current design practices use a strength-based design approach to design gusset plate connections in special concentrically braced frames (SCBFs), in which the expected tensile and compressive capacities of the brace are used to design the gusset plate and the weld used to connect the brace to the frame. To achieve brace end rotation, the gusset plate is sized using a linear offset rule, and large, uneconomical gusset plate connections may result. A research program was undertaken to improve the economy and performance of gusset plate connections. A new approach is proposed in which the gusset plate design is based on a balanced design approach in which the yield mechanisms of the brace are balanced with the yield mechanisms of the connection and the failure modes of the system to achieve a target yielding hierarchy and suppress unwanted failure modes. Full-scale one-story, one-bay frames were designed and tested to investigate the seismic performance of current and proposed design methods. In the test program, variations in balance factors between the brace, gusset plate, and weld were considered to study the proposed method, to evaluate possible yield mechanisms and failure modes, and to obtain the desired yielding hierarchy. Comparison of the observed and measured performance of each specimen is made and specific design expressions to improve the seismic engineering of SCBF systems are proposed.

The transportation sector is changing, influenced by concurrent, ongoing, dynamic trends that could dramatically affect the future energy landscape, including effects on the potential for greenhouse gas emissions reductions. Battery cost reductions and improved performance coupled with a growing number of electric vehicle model offerings are enabling greater battery electric vehicle market penetration, and advances in fuel cell technology and decreases in hydrogen production costs are leading to initial fuel cell vehicle offerings. Radically more efficient vehicles based on both conventional and new drivetrain technologies reduce greenhouse gas emissions per vehicle-mile. Net impacts also depend on the energy sources used for propulsion, and these are changing with increased use of renewable energy and unconventional fossil fuel resources. Connected and automated vehicles are emerging for personal and freight transportation systems and could increase use of low- or non-emitting technologies and systems; however, the net effects of automation on greenhouse gas emissions are uncertain. The longstanding trend of an annual increase in transportation demand has reversed for personal vehicle miles traveled in recent years, demonstrating the possibility of lower-travel future scenarios. Finally, advanced biofuel pathways have continued to develop, highlighting low-carbon and in some cases carbon-negative fuel pathways. We discuss the potentialmore » for transformative reductions in petroleum use and greenhouse gas emissions through these emerging transportation-sector technologies and trends and present a Clean Transportation Sector Initiative scenario for such reductions, which are summarized in Table ES-1.« less

Recent technology advancements in Micro Electric Propulsion (MEP) will enable the next generation of small spacecraft to perform trajectory and attitude maneuvers with significant ΔV requirements, provide thrust over long mission durations, and replace reaction wheels for attitude control. These advancements will open up the class of mission architectures achievable by small spacecraft to include formation flying, proximity operations, and precision pointing missions in both LEO and interplanetary destinations. The goal of this study is to establish the optimal performance parameters for future MEP technology that are applicable to a broad range of flight demonstration platforms (e.g. dedicated 3–12U CubeSats to ESPA-class spacecraft ), for a variety of applications, including LEO and Earth escape orbit transfers, travel to interplanetary destinations, hover and drag make-up missions, and performing reaction wheel-free attitude control. An integrated systems-level model for propulsion, spacecraft (power, data, telecommunication, thermal management), and orbit and attitude maneuvers is developed to support solution space exploration. MEP system performance parameters are derived that maximize the performance capability subject to realistic system-level constraints in the context of upcoming mission opportunities where MEP is enabling or advantageous relative to other technologies.

The physical and electrical properties of non-crystalline Ta- and Hf-alumiunates, (Ta 2 O 5 ) x (Al 2 O 3 ) 1− x and (HfO 2 ) x (Al 2 O 3 ) 1− x , respectively, were studied. As-deposited films were homogeneous and pseudo-binary in character with increased thermal stability with respect to the respective end-member oxides. Capacitance–voltage and current density–voltage data as a function of temperature demonstrate that the Ta and Hf d-states of the alloys act as localized electron traps, and are at an energy approximately equal to the conduction band offset of Ta 2 O 5 and HfO 2 with respect to Si. This work correlates the studies of Ta- and Hf-aluminates to develop a qualitative conduction band energy level scheme for the two alloys where the interfacial electrical properties are dominated by electron traps of the respective transition metal atoms, and/or or network defects associated with the alloy.

Deep-Space Optical Communications is a key emerging technology that is being pursued for high data-rate communications, which may enable rates up to ten times more than current Ka-band technology. Increasing the frequency of communication, from Ka-band to optical, allows for a higher data rate transfers. However, as the frequency of communication increases, the beam divergence decreases. Less beam divergence requires more accurate and precise pointing to make contact with the receiver. This would require a three-order-of-magnitude improvement from Ka-Band (~ 1 mrad) to optical (~ 1 urad) in the required pointing. Finding an architecture that can provide the necessary pointing capability is driven by many factors, such as allocated signal loss due to pointing, range to Earth, spacecraft disturbance profile, spacecraft base pointing capability, isolation scheme, and detector characteristics. We have developed a suite of tools to 1) flow down a set of pointing requirements (Error Budget Tool), 2) determine a set of architectures capable of meeting the requirements (Pointing Architecture Tool), and 3) assess the performance of possible architecture over the mission trajectory (Systems Engineering Tool). This paper describes the three tools and details their use through the case study of the Asteroid Retrieval Mission. Finally, this paper details which aspects of the pointing, acquisition, and tracking subsystem still require technology infusion, and the future steps needed to implement these pointing architectures.

Presents experimental results on single-event-induced breakdown in sub-5-nm plasma-enhanced SiO/sub 2/, nitrided SiO/sub 2/, Al/sub 2/O/sub 3/, HfO/sub 2/, and Zr/sub 0.4/Si/sub 1.6/O/sub 4/ dielectrics typical of current and future-generation commercial gate oxides. These advanced oxides are found to be quite resistant to ion-induced breakdown. Radiation-induced soft breakdown was observed in some films with 342 MeV Au (LET=80 MeV/mg/cm/sup 2/) but not 340 MeV I (LET=60 MeV/mg/cm/sup 2/). The critical voltage to hard breakdown was found to scale with the square root of the physical oxide thickness, not with the energy stored on the gate capacitance. Alternative dielectrics with equivalent oxide thickness substantially below their physical thickness were found to exhibit significantly higher voltage to hard breakdown than SiO/sub 2/ counterparts. All of the samples reached ion-induced hard breakdown at applied voltages well above typical operating power-supply voltages; these findings bode well for the use of advanced commercial integrated circuits in space systems.

Characterization by Auger electron spectroscopy (AES) and Fourier transformation infrared spectroscopy (FTIR) confirms (Ta2O5)x(Al2O3)1−x alloys are homogeneous pseudo-binary alloys with increased thermal stability with respect to end member oxides, Ta2O5 and Al2O3. Capacitance–voltage (C–V) and current density–voltage (J–V) data as a function of temperate show that the Ta d-states of the alloys act as localized electron traps, and are at an energy approximately equal to the conduction band offset of Ta2O5 with respect to Si.

Noncrystalline Al2O3 dielectric films have been synthesized by remote plasma enhanced chemical vapor deposition (RPECVD) and deposited on (i) H-terminated Si(100) and (ii) on SiO2 prepared by remote plasma assisted oxidation and RPECVD on Si(100) substrates using organometallic source gases injected downstream from a He/O2 plasma. Chemical composition and morphology of the Al2O3 films and their interfaces have been studied by Auger electron spectroscopy (AES), Fourier transform infrared spectroscopy, nuclear resonance profiling (NRP), and x-ray diffraction (XRD). Previous studies in which Al2O3 was deposited by thermal CVD, rapid thermal CVD, (RTCVD), direct PECVD, and physical vapor deposition generally resulted in relatively thick SiO2 or Al-silicate interfacial layers which impact adversely on the highest attainable capacitance. In line AES and NRP indicate the as-deposited RPECVD films are fully oxidized on deposition, and their interfaces can be chemically abrupt with Si oxide or Al silicate interfac...

This research identifies four significant limitations on the performance of high- k alternative gate dielectrics that derive from inherent relationships between (i) chemical bonding and physical properties, and (ii) device operation. These include interfacial band offset energies, thermal stability against chemical phase separation, coordination dependent dielectric constants, and interfacial fixed charge. Then these are applied to transition metal silicate alloys, e.g., (ZrO 2 ) x (SiO 2 ) 1− x . The paper also includes results for other high- k oxides, Al 2 O 3 and Ta 2 O 5 , and their alloys that relate to the issues addressed in this paper, and in particular help to put the results on the silicate alloys into a better perspective. This portion of the paper provides additional perspective with regard to the differences in the chemical and physical limitations of elemental oxides and binary oxide alloys.