1,201 research outputs found
Attributes of GRB Pulses: Bayesian Blocks Analysis of TTE Data; a Microburst in GRB 920229
Bayesian Blocks is a new time series algorithm for detecting localized
structures (spikes or shots), revealing pulse shapes, and generally
characterizing intensity variations. It maps raw counting data into a maximum
likelihood piecewise constant representation of the underlying signal. This
bin-free method imposes no lower limit on measurable time scales. Applied to
BATSE TTE data, it reveals the shortest know burst structure -- a spike
superimposed on the main burst in GRB 920229 = Trigger 1453, with rise and
decay timescales ~ few 100 microseconds.Comment: 5 pages, 2 figures; presented at the 4th Huntsville Gamma-ray Burst
Symposiu
The Chasm Between the Human and Chimpanzee Genomes: A Review of the Evolutionary Literature
Data has been extracted from secular literature that is contrary to the common claim that very few genetic differences exist between chimpanzees and humans. We found that significant reported differences exist in genomic similarity and gene regulation between chimpanzees and humans. The DNA sequence differences and genetic mechanisms reported in the literature support the conclusion that significant and unbridgeable genetic differences exist between humans and chimpanzees that defy evolutionary claims of a common ancestor
Upgrade of the Minos+ Experiment Data Acquisition for the High Energy NuMI Beam Run
The Minos+ experiment is an extension of the Minos experiment at a higher
energy and more intense neutrino beam, with the data collection having begun in
the fall of 2013. The neutrino beam is provided by the Neutrinos from the Main
Injector (NuMI) beam-line at Fermi National Accelerator Laboratory (Fermilab).
The detector apparatus consists of two main detectors, one underground at
Fermilab and the other in Soudan, Minnesota with the purpose of studying
neutrino oscillations at a base line of 735 km. The original data acquisition
system has been running for several years collecting data from NuMI, but with
the extended run from 2013, parts of the system needed to be replaced due to
obsolescence, reliability problems, and data throughput limitations.
Specifically, we have replaced the front-end readout controllers, event
builder, and data acquisition computing and trigger processing farms with
modern, modular and reliable devices with few single points of failure. The new
system is based on gigabit Ethernet TCP/IP communication to implement the event
building and concatenation of data from many front-end VME readout crates. The
simplicity and partitionability of the new system greatly eases the debugging
and diagnosing process. The new system improves throughput by about a factor of
three compared to the old system, up to 800 megabits per second, and has proven
robust and reliable in the current run.Comment: 3 page
Price discrimination and patent policy
Patent and antitrust policy are often presumed to be in conflict. As an
important example, there is ongoing controversy about whether price discrimination by a
patent holder is an illegal or socially undesirable exploitation of monopoly power. In this
article. we show that no conflict exists in many price discrimination cases. Even ignoring
the (dynamic) effects on incentives for innovation, third-degree price discrimination by
patent holders can raise (static) social welfare. In fact, Pareto improvements may well
occur. Welfare gains occur because price discrimination allows patent holders: (a) to open
new markets and (b) to achieve economies of scale or learning. Further, even in cases where
discrimination incurs static welfare losses, it may be efficient relative to other mechanisms,
such as length of patent life, for rewarding innovators with profits.Center for Energy Policy Research of the MIT Energy Laborator
The Control System for the X-33 Linear Aerospike Engine
The linear aerospike engine is being developed for single-stage -to-orbit (SSTO) applications. The primary advantages of a linear aerospike engine over a conventional bell nozzle engine include altitude compensation, which provides enhanced performance, and lower vehicle weight resulting from the integration of the engine into the vehicle structure. A feature of this integration is the ability to provide thrust vector control (TVC) by differential throttling of the engine combustion elements, rather than the more conventional approach of gimballing the entire engine. An analysis of the X-33 flight trajectories has shown that it is necessary to provide +/- 15% roll, pitch and yaw TVC authority with an optional capability of +/- 30% pitch at select times during the mission. The TVC performance requirements for X-33 engine became a major driver in the design of the engine control system. The thrust level of the X-33 engine as well as the amount of TVC are managed by a control system which consists of electronic, instrumentation, propellant valves, electro-mechanical actuators, spark igniters, and harnesses. The engine control system is responsible for the thrust control, mixture ratio control, thrust vector control, engine health monitoring, and communication to the vehicle during all operational modes of the engine (checkout, pre-start, start, main-stage, shutdown and post shutdown). The methodology for thrust vector control, the health monitoring approach which includes failure detection, isolation, and response, and the basic control system design are the topic of this paper. As an additional point of interest a brief description of the X-33 engine system will be included in this paper
Oscillatory Flows Induced by Microoganisms Swimming in Two Dimensions
We present the first time-resolved measurements of the oscillatory velocity field induced by swimming unicellular microorganisms. Confinement of the green alga C. reinhardtii in stabilized thin liquid films allows simultaneous tracking of cells and tracer particles. The measured velocity field reveals complex time-dependent flow structures, and scales inversely with distance. The instantaneous mechanical power generated by the cells is measured from the velocity fields and peaks at 15 fW. The dissipation per cycle is more than 4 times what steady swimming would require
Measuring Oscillatory Velocity Fields Due to Swimming Algae
Single cells exhibit a diverse array of swimming strategies at low Reynolds number to search for nutrients, light, and other organisms. The fluid flows generated by their locomotion are important to understanding biomixing and interactions between cells in suspension..
Topical Tritiated Thymidine for Epidermal Growth Fraction Determination
Direct autoradiographic identification of the epidermal growth fraction (GF) requires the delivery of tritiated thymidine ([3H]dThd) to the skin during the time interval of an entire cell cycle. The GF in normal human epidermis has not been directly measured using this technique because the systemic infusion of radioactive [3H]dThd in benign skin conditions is precluded by ethical considerations. Studies were undertaken to assess the feasibility of measuring the epidermal GF in vivo by the topical delivery of [3H]dThd. The percutaneous penetration of [3dThd in various vehicles was evaluated to select an effective topical delivery system. A vehicle consisting of Azone, isopropanol, and water (2:49:49) was the best of 4 different vehicles tested. The optimal penetration of [3H]dThd, with respect to the concentration of Azone over a range of 0–4%, was achieved at 2%. During the initial 24h following a single topical application of [3H]dThd to hairless mice the labeling increased linearly with time. In vivo studies in hairless mice produced a GF of 95% by both continuous systemic [3H]dThd infusion, and by twice daily topical [3H]dThd. Azone vehicles induced epidermal hyperplasia which was minimized by lowering the Azone concentration and by decreasing the frequency of applications from 24 to 48h. These studies establish the rationale for using topical delivery of [3H]dThd for the in vivo measurement of epidermal GF
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