33,818 research outputs found
Dynamic crystallization of silicate melts
Two types of furnaces with differing temperature range capabilities were used to provide variations in melt temperatures and cooling rates in a study of the effects of heterogeneous nucleation on crystallization. Materials of chondrule composition were used to further understanding of how the disequilibrium features displayed by minerals in rocks are formed. Results show that the textures of natural chondrules were duplicated. It is concluded that the melt history is dominant over cooling rate and composition in controlling texture. The importance of nuclei, which are most readily derived from preexisting crystalline material, support an origin for natural chondrules based on remelting of crystalline material. This would be compatible with a simple, uniform chondrule forming process having only slight variations in thermal histories resulting in the wide range of textures
Comparison of data on Mutation Frequencies of Mice Caused by Radiation - Low Dose Model -
We propose LD(Low Dose) model, the extension of LDM model which was proposed
in the previous paper [Y. Manabe et al.: J. Phys. Soc. Jpn. 81 (2012) 104004]
to estimate biological damage caused by irradiation. LD model takes account of
all the considerable effects including cell death effect as well as
proliferation, apoptosis, repair. As a typical example of estimation, we apply
LD model to the experiment of mutation frequency on the responses induced by
the exposure to low levels of ionizing radiation. The most famous and extensive
experiments are those summarized by Russell and Kelly [Russell, W. L. & Kelly,
E. M: Proc. Natl Acad. Sci. USA 79 (1982) 539-541], which are known as
'Mega-mouse project'. This provides us with important information of the
frequencies of transmitted specific-locus mutations induced in mouse
spermatogonia stem-cells. It is found that the numerical results of the
mutation frequency of mice are in reasonable agreement with the experimental
data: the LD model reproduces the total dose and dose rate dependence of data
reasonably. In order to see such dose-rate dependence more explicitly, we
introduce the dose-rate effectiveness factor (DREF). This represents a sort of
preventable effects such as repair, apoptosis and death of broken cells, which
are to be competitive with proliferation effect of broken cells induced by
irradiation.Comment: subimitting to J. Phys. Soc. Jpn, 32 pages, 8 figure
Assessment of Variable-cycle Engines for Mach 2.7 Supersonic Transports
Three proposed SCAR propulsion systems in terms of aircraft range for a fixed payload and take-off gross weight with a design cruise Mach number 2.7 are evaluated. The effects of various noise and operational restraints are determined and sensitivities to some of the more important performance variables are presented for the most probable design noise and operational restraint case. Critical areas requiring new or improved technology for each cycle are delineated
VOCALIZATION OF THE CROCODILE SKINK, TRIBOLONOTUS GRACILIS (DE ROOY, 1909), AND EVIDENCE OF PARENTAL CARE.
The crocodile or spiny skinks, Tribolonotus, comprise eight secretive semi-fossorial lizards, which are generally found under vegetation in the immediate vicinity of water (Greer and Parker, 1968; O'Shea, 1991, 1994; Rogner, 1997). Tribolonotus gracilis (Figure 1) and Tribolonotus novaeguineae are restricted to New Guinea, while the remaining six species range throughout Indonesia, Manus, New Britain, Bougainville, and the Solomon Islands (McCoy, 1980; O'Shea, 1991, 1994). Because scant life history information is available for the genus Tribolonotus, the purpose of the present contribution is to document the vocalization and parental care of T. gracilis
Multivariable control theory applied to hierarchial attitude control for planetary spacecraft
Multivariable control theory is applied to the design of a hierarchial attitude control system for the CARD space vehicle. The system selected uses reaction control jets (RCJ) and control moment gyros (CMG). The RCJ system uses linear signal mixing and a no-fire region similar to that used on the Skylab program; the y-axis and z-axis systems which are coupled use a sum and difference feedback scheme. The CMG system uses the optimum steering law and the same feedback signals as the RCJ system. When both systems are active the design is such that the torques from each system are never in opposition. A state-space analysis was made of the CMG system to determine the general structure of the input matrices (steering law) and feedback matrices that will decouple the axes. It is shown that the optimum steering law and proportional-plus-rate feedback are special cases. A derivation of the disturbing torques on the space vehicle due to the motion of the on-board television camera is presented. A procedure for computing an upper bound on these torques (given the system parameters) is included
A Mathematical Model for Estimating Biological Damage Caused by Radiation
We propose a mathematical model for estimating biological damage caused by
low-dose irradiation. We understand that the Linear Non Threshold (LNT)
hypothesis is realized only in the case of no recovery effects. In order to
treat the realistic living objects, our model takes into account various types
of recovery as well as proliferation mechanism, which may change the resultant
damage, especially for the case of lower dose rate irradiation. It turns out
that the lower the radiation dose rate, the safer the irradiated system of
living object (which is called symbolically "tissue" hereafter) can have
chances to survive, which can reproduce the so-called dose and dose-rate
effectiveness factor (DDREF).Comment: 22 pages, 6 Figs, accepted in Journal of the Physical Society of
Japa
The Kauffman Index: Startup Activity National Trends - 2016
This report provides a broad index measure of business startup activity in the United States. It is an equally weighted index of three normalized measures of startup activity:The Rate of New Entrepreneurs in the economy, calculated as the percentage of adults becoming entrepreneurs in a given month.The Opportunity Share of New Entrepreneurs, calculated as the percentage of new entrepreneurs driven primarily by "opportunity" vs. "necessity."The Startup Density of a region, measured as the number of new employer businesses normalized by total business population
The Kauffman Index: Startup Activity - Metropolitan Area and City Trends 2015
How can I actually measure the entrepreneurial activity in my region? This is a question we at the Kauffman Foundation often hear from economic and policy leaders. As cities around the globe rally to foster entrepreneurship, the challenge of how to consistently measure and benchmark progress remains largely unanswered. While anecdotal evidence abounds, most ecosystems struggle to answer straightforward, yet often elusive, questions: How many new startups does our city or state have? How much are our ventures growing? How many of our businesses are surviving? To begin to answer these questions and address this challenge, we introduce the new Kauffman Index of Entrepreneurship, the first and largest index tracking entrepreneurship across city, state, and national levels for the United States. In this release, we introduce the Kauffman Index: Startup Activity—the first of various research installments under the umbrella of the new Kauffman Index of Entrepreneurship.For the past ten years, the original Kauffman Index— authored by Robert W. Fairlie—has been an early indicator for entrepreneurship in the United States, used by entrepreneurs and policymakers, from the federal to state and local levels. The Kauffman Index also has been one of the most requested and far-reaching entrepreneurship indicators in the United States and, arguably, the world. In the policy world, the Index has been referenced in multiple testimonies to the U.S. Senate and House of Representatives, by U.S. Embassies and Consulates across various countries—including nations like Spain, Ukraine, and United Kingdom—by multiple federal agencies, by state governments and governors from fifteen states— from Arizona to New York—and by the White House's office of the President of the United States. On the academic side, more than 200 research papers quote the Kauffman Index. In media circles, the Kauffman Index has been highlighted in more than 100 media channels, including most major publications like The New York Times, The Wall Street Journal, TIME, CNN, the Financial Times, and Harvard Business Review. Originally, the Kauffman Index tracked one of the earliest measures of business creation: When and how many people first start working for themselves, becoming entrepreneurs. Now, we are expanding it to include other dimensions of entrepreneurship. The new and expanded Kauffman Index of Entrepreneurship 2015 remains focused primarily on entrepreneurial outcomes, as opposed to inputs. That means we are more concerned with actual results of entrepreneurial activity—things like new companies and growth rates.The Kauffman Index: Startup Activity algorithm presented in this report takes into account three variables:* Rate of New Entrepreneurs* Opportunity Share of New Entrepreneurs* Startup Densit
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