Analysis of a Near Real-Time Optimal Attitude Control for Satellite Simulators

Dynamic optimization of spacecraft attitude reorientation maneuvers can result in significant savings in attitude determination and control system size, mass, and power. Optimal control theory is generally applied using an open loop trajectory which is vulnerable to disturbances. A closed loop implementation of optimal control has been difficult to achieve due to the computational requirements needed to quickly compute solutions to the optimal control problem. This research focuses on evaluating a near real-time optimal control (RTOC) system for large angle slew maneuvers on the Air Force Institute of Technology\u27s spacecraft simulator called SimSat. A near RTOC algorithm computes optimal control solutions at a rate of 0.4 Hz using a pseudospectral-based solver. The solutions or trajectories are then resampled at a fixed time step of 100 Hz and fed forward to a closed loop on SimSat. This algorithm is developed and tested on the hardware and compared to simulated and hardware results of a proportional-integral-derivative (PID) controller and an open loop optimal control controller for 90 degree and 180 degree Z-axis rotations. The benefits of decreased time to complete the maneuver and increased accuracy at the end of the optimal maneuver are shown to be improvements over traditional over PID control and open loop optimal control

The eIF4F and eIFiso4F Complexes of Plants: An Evolutionary Perspective

Translation initiation in eukaryotes requires a number of initiation factors to recruit the assembled ribosome to mRNA. The eIF4F complex plays a key role in initiation and is a common target point for regulation of protein synthesis. Most work on the translation machinery of plants to date has focused on flowering plants, which have both the eIF4F complex (eIF4E and eIF4G) as well as the plant-specific eIFiso4F complex (eIFiso4E and eIFiso4G). The increasing availability of plant genome sequence data has made it possible to trace the evolutionary history of these two complexes in plants, leading to several interesting discoveries. eIFiso4G is conserved throughout plants, while eIFiso4E only appears with the evolution of flowering plants. The eIF4G N-terminus, which has been difficult to annotate, appears to be well conserved throughout the plant lineage and contains two motifs of unknown function. Comparison of eIFiso4G and eIF4G sequence data suggests conserved features unique to eIFiso4G and eIF4G proteins. These findings have answered some questions about the evolutionary history of the two eIF4F complexes of plants, while raising new ones

Multi-Shooting Differential Dynamic Programming for Hybrid Systems using Analytical Derivatives

Differential Dynamic Programming (DDP) is a popular technique used to generate motion for dynamic-legged robots in the recent past. However, in most cases, only the first-order partial derivatives of the underlying dynamics are used, resulting in the iLQR approach. Neglecting the second-order terms often slows down the convergence rate compared to full DDP. Multi-Shooting is another popular technique to improve robustness, especially if the dynamics are highly non-linear. In this work, we consider Multi-Shooting DDP for trajectory optimization of a bounding gait for a simplified quadruped model. As the main contribution, we develop Second-Order analytical partial derivatives of the rigid-body contact dynamics, extending our previous results for fixed/floating base models with multi-DoF joints. Finally, we show the benefits of a novel Quasi-Newton method for approximating second-order derivatives of the dynamics, leading to order-of-magnitude speedups in the convergence compared to the full DDP method.Comment: https://www.youtube.com/watch?v=C0h6mEpcnA

Self-referenced continuous-variable quantum key distribution protocol

We introduce a new continuous-variable quantum key distribution (CV-QKD) protocol, self-referenced CV-QKD, that eliminates the need for transmission of a high-power local oscillator between the communicating parties. In this protocol, each signal pulse is accompanied by a reference pulse (or a pair of twin reference pulses), used to align Alice's and Bob's measurement bases. The method of phase estimation and compensation based on the reference pulse measurement can be viewed as a quantum analog of intradyne detection used in classical coherent communication, which extracts the phase information from the modulated signal. We present a proof-of-principle, fiber-based experimental demonstration of the protocol and quantify the expected secret key rates by expressing them in terms of experimental parameters. Our analysis of the secret key rate fully takes into account the inherent uncertainty associated with the quantum nature of the reference pulse(s) and quantifies the limit at which the theoretical key rate approaches that of the respective conventional protocol that requires local oscillator transmission. The self-referenced protocol greatly simplifies the hardware required for CV-QKD, especially for potential integrated photonics implementations of transmitters and receivers, with minimum sacrifice of performance. As such, it provides a pathway towards scalable integrated CV-QKD transceivers, a vital step towards large-scale QKD networks.Comment: 14 pages, 10 figures. Published versio

Combined systemic and hepatic artery infusion pump chemo-therapy as a liver-directed therapy for colorectal liver metastasis-review of literature and case discussion

Colorectal cancer (CRC) is the third most prevalent malignancy and the second most common cause of death in the US. Liver is the most common site of colorectal metastases. About 13% of patients with colorectal cancer have liver metastasis on initial presentation and 50% develop them during the disease course. Although systemic chemotherapy and immunotherapy are the mainstay treatment for patients with metastatic disease, for selected patients with predominant liver metastasis, liver-directed approaches may provide prolonged disease control when combined with systemic treatments. Hepatic artery infusion pump (HAIP) chemotherapy is an approach which allows direct infusion of chemotherapeutic into the liver and is especially useful in the setting of multifocal liver metastases. When combined with systemic chemotherapy, HAIP improves the response rate, provides more durable disease control, and in some patients leads to successful resection. To ensure safety, use of HAIP requires multidisciplinary collaboration between interventional radiologists, medical oncologists, hepatobiliary surgeons and treatment nurses. Here, we review the benefits and potential risks with this approach and provide our single institution experience on two CRC patients successfully treated with HAIP in combination with systemic chemotherapy. We provide our recommendations in adopting this technique in the current era for patient with colorectal liver metastases

Decreased apoptosome activity with neuronal differentiation sets the threshold for strict IAP regulation of apoptosis

Despite the potential of the inhibitor of apoptosis proteins (IAPs) to block cytochrome c–dependent caspase activation, the critical function of IAPs in regulating mammalian apoptosis remains unclear. We report that the ability of endogenous IAPs to effectively regulate caspase activation depends on the differentiation state of the cell. Despite being expressed at equivalent levels, endogenous IAPs afforded no protection against cytochrome c–induced apoptosis in naïve pheochromocytoma (PC12) cells, but were remarkably effective in doing so in neuronally differentiated cells. Neuronal differentiation was also accompanied with a marked reduction in Apaf-1, resulting in a significant decrease in apoptosome activity. Importantly, this decrease in Apaf-1 protein was directly linked to the increased ability of IAPs to stringently regulate apoptosis in neuronally differentiated PC12 and primary cells. These data illustrate specifically how the apoptotic pathway acquires increased regulation with cellular differentiation, and are the first to show that IAP function and apoptosome activity are coupled in cells

Rapid Targeted Gene Disruption in Bacillus Anthracis

Anthrax is a zoonotic disease recognized to affect herbivores since Biblical times and has the widest range of susceptible host species of any known pathogen. The ease with which the bacterium can be weaponized and its recent deliberate use as an agent of terror, have highlighted the importance of gaining a deeper understanding and effective countermeasures for this important pathogen. High quality sequence data has opened the possibility of systematic dissection of how genes distributed on both the bacterial chromosome and associated plasmids have made it such a successful pathogen. However, low transformation efficiency and relatively few genetic tools for chromosomal manipulation have hampered full interrogation of its genome. Results: Group II introns have been developed into an efficient tool for site-specific gene inactivation in several organisms. We have adapted group II intron targeting technology for application in Bacillus anthracis and generated vectors that permit gene inactivation through group II intron insertion. The vectors developed permit screening for the desired insertion through PCR or direct selection of intron insertions using a selection scheme that activates a kanamycin resistance marker upon successful intron insertion. Conclusions: The design and vector construction described here provides a useful tool for high throughput experimental interrogation of the Bacillus anthracis genome and will benefit efforts to develop improved vaccines and therapeutics.Chem-Bio Diagnostics program from the Department of Defense Chemical and Biological Defense program through the Defense Threat Reduction Agency (DTRA) B102387MNIH GM037949Welch Foundation F-1607Cellular and Molecular Biolog