16,365 research outputs found
The One Dimensional Damped Forced Harmonic Oscillator Revisited
In this paper we give a general solution to the problem of the damped
harmonic oscillator under the influence of an arbitrary time-dependent external
force. We employ simple methods accessible for beginners and useful for
undergraduate students and professors in an introductory course of mechanics.Comment: 4 Latex page
On the completeness of impulsive gravitational wave space-times
We consider a class of impulsive gravitational wave space-times, which
generalize impulsive pp-waves. They are of the form ,
where is a Riemannian manifold of arbitrary dimension and carries
the line element with the line
element of and the Dirac measure. We prove a completeness result
for such space-times with complete Riemannian part .Comment: 13 pages, minor changes suggested by the referee
Keys to Understanding and Addressing Consumer Perceptions and Concerns about Processed Foods
Some processed food products have been targeted lately as “evils” that are preventing us from maintaining healthy lives. From the perspective of the food industry community, it seems as if this is one of those issues that should fade away with time, since the benefits of food processing are very obvious to us. We have never been so wrong! The challenges in front of us are big, and we need to do a better job of communicating with consumers about the benefits food processing offers, including increasing the availability of high-quality foods year round. We also need to promote the work being done by food scientists to continually and efficiently respond to human food requirements globally. At the same time, we must recognize those elements in the food processing culture that need attention and that can be misinterpreted by consumers. As food scientists we need to learn about consumer perceptions of food technology and devise strategies that can be implemented to affect consumer perceptions positively
Keys to Understanding and Addressing Consumer Perceptions and Concerns about Processed Foods
Some processed food products have been targeted lately as “evils” that are preventing us from maintaining healthy lives. From the perspective of the food industry community, it seems as if this is one of those issues that should fade away with time, since the benefits of food processing are very obvious to us. We have never been so wrong! The challenges in front of us are big, and we need to do a better job of communicating with consumers about the benefits food processing offers, including increasing the availability of high-quality foods year round. We also need to promote the work being done by food scientists to continually and efficiently respond to human food requirements globally. At the same time, we must recognize those elements in the food processing culture that need attention and that can be misinterpreted by consumers. As food scientists we need to learn about consumer perceptions of food technology and devise strategies that can be implemented to affect consumer perceptions positively
Wannier-Stark ladders in one-dimensional elastic systems
The optical analogues of Bloch oscillations and their associated
Wannier-Stark ladders have been recently analyzed. In this paper we propose an
elastic realization of these ladders, employing for this purpose the torsional
vibrations of specially designed one-dimensional elastic systems. We have
measured, for the first time, the ladder wave amplitudes, which are not
directly accessible either in the quantum mechanical or optical cases. The wave
amplitudes are spatially localized and coincide rather well with theoretically
predicted amplitudes. The rods we analyze can be used to localize different
frequencies in different parts of the elastic systems and viceversa.Comment: 10 pages, 6 figures, accepted in Phys. Rev. Let
Dopamine D 4 Receptor-Deficient Mice Display Cortical Hyperexcitability
The dopamine D(4) receptor (D(4)R) is predominantly expressed in the frontal cortex (FC), a brain region that receives dense input from midbrain dopamine (DA) neurons and is associated with cognitive and emotional processes. However, the physiological significance of this dopamine receptor subtype has been difficult to explore because of the slow development of D(4)R agonists and antagonists the selectivity and efficacy of which have been rigorously demonstrated in vivo. We have attempted to overcome this limitation by taking a multidimensional approach to the characterization of mice completely deficient in this receptor subtype. Electrophysiological current and voltage-clamp recordings were performed in cortical pyramidal neurons from wild-type and D(4)R-deficient mice. The frequency of spontaneous synaptic activity and the frequency and duration of paroxysmal discharges induced by epileptogenic agents were increased in mutant mice. Enhanced synaptic activity was also observed in brain slices of wild-type mice incubated in the presence of the selective D(4)R antagonist PNU-101387G. Consistent with greater electrophysiological activity, nerve terminal glutamate density associated with asymmetrical synaptic contacts within layer VI of the motor cortex was reduced in mutant neurons. Taken together, these results suggest that the D(4)R can function as an inhibitory modulator of glutamate activity in the FC.Fil: Rubinstein, Marcelo. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Instituto de Investigaciones en IngenierĂa GenĂ©tica y BiologĂa Molecular "Dr. HĂ©ctor N. Torres"; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Cepeda, Carlos. University of California at Los Angeles; Estados UnidosFil: Hurst, Raymond S.. University of California at Los Angeles; Estados UnidosFil: Flores Hernandez, Jorge. University of California at Los Angeles; Estados UnidosFil: Ariano, Marjorie A.. The Chicago Medical School; Estados UnidosFil: Falzone, Tomas Luis. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Instituto de Investigaciones en IngenierĂa GenĂ©tica y BiologĂa Molecular "Dr. HĂ©ctor N. Torres"; ArgentinaFil: Kozell, Laura B.. Oregon Health Sciences University; Estados UnidosFil: Meshul, Charles K.. Oregon Health Sciences University; Estados UnidosFil: Bunzow, James R.. Oregon Health Sciences University; Estados UnidosFil: Low, Malcolm J.. Oregon Health Sciences University; Estados UnidosFil: Levine, Michael S.. University of California at Los Angeles; Estados UnidosFil: Grandy, David K.. Oregon Health Sciences University; Estados Unido
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