Midcourse maneuver operations program

Midcourse Maneuver Operations Program /MMOP/ computes the required velocity change to correct a spacecraft trajectory. The program establishes the existence of maneuvers which satisfy spacecraft constraints, explores alternate trajectories in the event that some out-of-tolerance condition forces a change in plans, and codes the maneuvers into commands

Recovery from disturbance requires resynchronization of ecosystem nutrient cycles

Nitrogen (N) and phosphorus (P) are tightly cycled in most terrestrial ecosystems, with plant uptake more than 10 times higher than the rate of supply from deposition and weathering. This near-total dependence on recycled nutrients and the stoichiometric constraints on resource use by plants and microbes mean that the two cycles have to be synchronized such that the ratio of N:P in plant uptake, litterfall, and net mineralization are nearly the same. Disturbance can disrupt this synchronization if there is a disproportionate loss of one nutrient relative to the other. We model the resynchronization of N and P cycles following harvest of a northern hardwood forest. In our simulations, nutrient loss in the harvest is small relative to postharvest losses. The low N:P ratio of harvest residue results in a preferential release of P and retention of N. The P release is in excess of plant requirements and P is lost from the active ecosystem cycle through secondary mineral formation and leaching early in succession. Because external P inputs are small, the resynchronization of the N and P cycles later in succession is achieved by a commensurate loss of N. Through succession, the ecosystem undergoes alternating periods of N limitation, then P limitation, and eventually co-limitation as the two cycles resynchronize. However, our simulations indicate that the overall rate and extent of recovery is limited by P unless a mechanism exists either to prevent the P loss early in succession (e.g., P sequestration not stoichiometrically constrained by N) or to increase the P supply to the ecosystem later in succession (e.g., biologically enhanced weathering). Our model provides a heuristic perspective from which to assess the resynchronization among tightly cycled nutrients and the effect of that resynchronization on recovery of ecosystems from disturbance

Finding Untriggered Gamma-Ray Transients in the Fermi GBM Data

No abstract availabl

Evaluation of an alternative ruxolitinib dosing regimen in patients with myelofibrosis: an open-label phase 2 study

Abstract Background Ruxolitinib improves splenomegaly and symptoms in patients with intermediate-2 or high-risk myelofibrosis; however, nearly half develop grade 3/4 anemia and/or thrombocytopenia, necessitating dose reductions and/or transfusions. We report findings from an open-label phase 2 study exploring a dose-escalation strategy aimed at preserving clinical benefit while reducing hematological adverse events early in ruxolitinib treatment. Methods Patients with myelofibrosis received ruxolitinib 10 mg twice daily (BID), with incremental increases of 5 mg BID at weeks 12 and 18 for lack of efficacy (maximum, 20 mg BID). Symptom severity was measured using the Myelofibrosis Symptom Assessment Form Total Symptom Score (MFSAF TSS). Results Forty-five patients were enrolled, 68.9% of whom had a Dynamic International Prognostic Scoring System score of 1 to 2 (i.e., intermediate-1 disease risk). Median percentage change in spleen volume from baseline to week 24 was − 17.3% (≥ 10% reduction achieved by 26 patients [57.8%]), with a clear dose response. Median percentage change in MFSAF TSS from baseline at week 24 was − 45.6%, also with a dose response. The most frequent treatment-emergent adverse events were anemia (26.7%), fatigue (22.2%), and arthralgias (20.0%). Grade 3/4 anemia (20.0%) and dose decreases due to anemia (11.1%) or thrombocytopenia (6.7%) were infrequent. Conclusions A dose-escalation approach may mitigate worsening anemia during early ruxolitinib therapy in some patients with myelofibrosis. Trial registration ClinicalTrials.gov identifier, NCT01445769 . Registered September 23, 2011.https://deepblue.lib.umich.edu/bitstream/2027.42/145195/1/13045_2018_Article_642.pd

CacheZoom: How SGX Amplifies The Power of Cache Attacks

In modern computing environments, hardware resources are commonly shared, and parallel computation is widely used. Parallel tasks can cause privacy and security problems if proper isolation is not enforced. Intel proposed SGX to create a trusted execution environment within the processor. SGX relies on the hardware, and claims runtime protection even if the OS and other software components are malicious. However, SGX disregards side-channel attacks. We introduce a powerful cache side-channel attack that provides system adversaries a high resolution channel. Our attack tool named CacheZoom is able to virtually track all memory accesses of SGX enclaves with high spatial and temporal precision. As proof of concept, we demonstrate AES key recovery attacks on commonly used implementations including those that were believed to be resistant in previous scenarios. Our results show that SGX cannot protect critical data sensitive computations, and efficient AES key recovery is possible in a practical environment. In contrast to previous works which require hundreds of measurements, this is the first cache side-channel attack on a real system that can recover AES keys with a minimal number of measurements. We can successfully recover AES keys from T-Table based implementations with as few as ten measurements.Comment: Accepted at Conference on Cryptographic Hardware and Embedded Systems (CHES '17

Analysis of Sub-threshold Short Gamma-ray Bursts in Fermi GBM Data

The Fermi Gamma-ray Burst Monitor (GBM) is currently the most prolific detector of Gamma-Ray Bursts (GRBs). Recently the detection rate of short GRBs (SGRBs) has been dramatically increased through the use of ground-based searches that analyze GBM continuous time tagged event (CTTE) data. Here we examine the efficiency of a method developed to search CTTE data for sub-threshold transient events in temporal coincidence with LIGO/Virgo compact binary coalescence triggers. This targeted search operates by coherently combining data from all 14 GBM detectors by taking into account the complex spatial and energy dependent response of each detector. We use the method to examine a sample of SGRBs that were independently detected by the Burst Alert Telescope on board the Neil Gehrels Swift Observatory, but which were too intrinsically weak or viewed with unfavorable instrument geometry to initiate an on-board trigger of GBM. We find that the search can successfully recover a majority of the BAT detected sample in the CTTE data. We show that the targeted search of CTTE data will be crucial in increasing the GBM sensitivity, and hence the gamma-ray horizon, to weak events such as GRB 170817A. We also examine the properties of the GBM signal possibly associated with the LIGO detection of GW150914 and show that it is consistent with the observed properties of other sub-threshold SGRBs in our sample. We find that the targeted search is capable of recovering true astrophysical signals as weak as the signal associated with GW150914 in the untriggered data.Comment: 10 pages, 9 figures, 1 table, submitted to Ap