1,415 research outputs found
Laser angle sensor
A laser angle measurement system was designed and fabricated for NASA Langley Research Center. The instrument is a fringe counting interferometer that monitors the pitch attitude of a model in a wind tunnel. A laser source and detector are mounted above the model. Interference fringes are generated by a small passive element on the model. The fringe count is accumulated and displayed by a processor in the wind tunnel control room. This report includes optical and electrical schematics, system maintenance and operation procedures
Metal-insulator transition and electroresistance in lanthanum/calcium manganites La_<1-x>Ca_<x>MnO_<3> (x = 0-0.5) from voltage-current-temperature surfaces
Of the perovskites, ABX_, a subset of special interest is the family in
which the A site is occupied by a lanthanide ion, the B site by a rare earth
and X is oxygen, as such materials often exhibit a large change in electrical
resistance in a magnetic field, a phenomenon known as "colossal"
magnetoresistance (MR). Two additional phenomena in this family have also drawn
attention: the metal-insulator transition (MIT) and electroresistance (ER). The
MIT is revealed by measuring resistance as a function of temperature, and
observing a change in the sign of the gradient. ER - the dependence of the
resistance on applied current - is revealed by measuring resistance as a
function of applied current. Up until now, the phenomena of MIT and ER have
been treated separately. Here we report simultaneous observation of the MIT and
ER in the lanthanum/calcium manganites. We accomplish this by measuring
voltage-current curves over a wide temperature range (10-300 K) allowing us to
build up an experimental voltage surface over current-temperature axes. These
data directly lead to resistance surfaces. This approach provides additional
insight into the phenomena of electrical transport in the lanthanum/calcium
manganites, in particular the close connection of the maximum ER to the
occurrence of the MIT in those cases of a paramagnetic insulator (PMI) to
ferromagnetic metal (FMM) transition.Comment: 15 pages, 12 figure
Grain Boundary Structures in f.c.c, and b.c.c. Metals and Sites for Segregated Impurities
The key features leading to low-energy grain boundaries in metals are discussed by reference to computer-simulated structures and geometrical analysis in terms of atom packing. Low energy is found to be associated with boundary structures consisting of relatively dense packing, and this can in turn be expressed in terms of the space-filling packing of coordination polyhedra. The geometrical method of analysis is shown to be well suited to the identification of interfacial sites for segregated impurities
Coriolis force in Geophysics: an elementary introduction and examples
We show how Geophysics may illustrate and thus improve classical Mechanics
lectures concerning the study of Coriolis force effects. We are then interested
in atmospheric as well as oceanic phenomena we are familiar with, and are for
that reason of pedagogical and practical interest. Our aim is to model them in
a very simple way to bring out the physical phenomena that are involved.Comment: Accepted for publication in European Journal of Physic
Both Trait and State Mindfulness Predict Lower Aggressiveness via Anger Rumination: a Multilevel Mediation Analysis
Trait mindfulness, or the capacity for nonjudgmental, present-centered attention, predicts lower aggression in cross-sectional samples, an effect mediated by reduced anger rumination. Experimental work also implicates state mindfulness (i.e., fluctuations around one's typical mindfulness) in aggression. Despite evidence that both trait and state mindfulness predict lower aggression, their relative impact and their mechanisms remain unclear. Higher trait mindfulness and state increases in mindfulness facets may reduce aggression-related outcomes by (1) limiting the intensity of anger, or (2) limiting rumination on anger experiences. The present study tests two hypotheses: First, that both trait and state mindfulness contribute unique variance to lower aggressiveness, and second, that the impact of both trait and state mindfulness on aggressiveness will be uniquely partially mediated by both anger intensity and anger rumination. 86 participants completed trait measures of mindfulness, anger intensity, and anger rumination, then completed diaries for 35 days assessing mindfulness, anger intensity, anger rumination, anger expression, and self-reported and behavioral aggressiveness. Using multilevel zero-inflated regression, we examined unique contributions of trait and state mindfulness facets to daily anger expression and aggressiveness. We also examined the mediating roles of anger intensity and anger rumination at both trait and state levels. Mindfulness facets predicted anger expression and aggressiveness indirectly through anger rumination after controlling for indirect pathways through anger intensity. Individuals with high or fluctuating aggression may benefit from mindfulness training to reduce both intensity of and rumination on anger
Generalized Rosenfeld scalings for tracer diffusivities in not-so-simple fluids: Mixtures and soft particles
Rosenfeld [Phys. Rev. A 15, 2545 (1977)] noticed that casting transport
coefficients of simple monatomic, equilibrium fluids in specific dimensionless
forms makes them approximately single-valued functions of excess entropy. This
has predictive value because, while the transport coefficients of dense fluids
are difficult to estimate from first principles, excess entropy can often be
accurately predicted from liquid-state theory. Here, we use molecular
simulations to investigate whether Rosenfeld's observation is a special case of
a more general scaling law relating mobility of particles in mixtures to excess
entropy. Specifically, we study tracer diffusivities, static structure, and
thermodynamic properties of a variety of one- and two-component model fluid
systems with either additive or non-additive interactions of the hard-sphere or
Gaussian-core form. The results of the simulations demonstrate that the effects
of mixture concentration and composition, particle-size asymmetry and
additivity, and strength of the interparticle interactions in these fluids are
consistent with an empirical scaling law relating the excess entropy to a new
dimensionless (generalized Rosenfeld) form of tracer diffusivity, which we
introduce here. The dimensionless form of the tracer diffusivity follows from
knowledge of the intermolecular potential and the transport / thermodynamic
behavior of fluids in the dilute limit. The generalized Rosenfeld scaling
requires less information, and provides more accurate predictions, than either
Enskog theory or scalings based on the pair-correlation contribution to the
excess entropy. As we show, however, it also suffers from some limitations,
especially for systems that exhibit significant decoupling of individual
component tracer diffusivities.Comment: 15 pages, 10 figure
Representation of agency workers: the representation of agency workers in Europe at national and local level in France, Netherlands, Sweden, Poland and the UK: final report 2009
Nipple Sparing Mastectomy Techniques: A Literature Review and an Inframammary Technique
Nipple sparing mastectomy (NSM) has quickly become an accepted technique for patients with selected cancers and for risk reducing surgery. Much of its surgical acceptance over the last decade has been based on the low risk of nipple areolar complex (NAC) occurrence in breast cancer patients. Improved patient satisfaction due to improved cosmetic outcomes with reconstruction have also driven its popularity. We reviewed current English journals to determine the NSM techniques which achieve the lowest complications, best outcomes, and best patient satisfaction. We researched studies showing reductions in complications with improved surgical techniques and patient selection which have been implicated in improved results. In the studies reviewed, incision placement, away from the nipple, resulted in the lowest rates of ischemic nipple complications and the best cosmetic outcomes. The effect of other factors such as surgeon experience and thickness of skin flap development were more difficult to prove. Leaving a 2-3 mm rim of tissue around the nipple bundle was shown to help preserve the nipple vascularity. Lower complication rates with improved outcomes and patient satisfaction were reported in the literature in patients with B or smaller cup sizes, non-smokers, and patients with lower body mass index (BMI). Incision placement, away from the nipple, with preservation of a 2-3 mm rim of tissue around the nipple bundle along with careful patient selection were the most significant variables reviewed which helped to lower complications rates of NSM. Coordinated surgical planning with the breast and plastic surgeons to determine the best surgical approach for each individual patient is necessary to obtain the best results. Although short-term oncologic follow-up seems to be acceptable, longer follow-up will still be needed to define the best breast cancer surgical candidates for the nipple sparing approach
Landlord Tenant Relations: A Report of the Landlord Tenant Relations Subcommittee of the North-Central Regional Land Tenure Committee
- …