Purdue University

About: Purdue University is a education organization based out in West Lafayette, Indiana, United States. It is known for research contribution in the topics: Population & Heat transfer. The organization has 73219 authors who have published 163563 publications receiving 5775236 citations. The organization is also known as: Purdue & Purdue-West Lafayette.

Open-Field Behavior in the Rat: what does it Mean?

Abstract: The rationale underlying the use of the open-field test is roughly as follows. Many mammals, when exposed to strange or noxious stimuli, will typically “freeze.” Freezing appears to have adaptative significance in that it is more difficult for a predator to observe a nonmoving animal. A second consequence of exposure to such stimuli is that this will often trigger off activity in the autonomic nervous system. One of the results of such activity is that the animal will defecate. Thus, an emotional animal may be defined as one which, when exposed to noxious or novel stimuli, does not move about and will defecate. To construct such a set of stimuli for the laboratory rat, which is our most common experimental subject, is relatively easy. All we have to do is place the rat into an environment that is distinctly different from any environment he has previously encountered. The open field meets these requirements since it is an apparatus in which the rat has not previously been placed and since its dimensions are vastly greater than the boundaries of his usual living quarters. These conditions should ensure that the open field is both strange and at least mildly noxious to the rat. By drawing appropriately sized squares on the floor of the open field, it is possible to quantify activity by recording the number of squares the animal enters during a given unit of time. One easily quantifies defecation by counting the number of boluses dropped during the testing interval. Given these data the operational definition of an emotional animal is one that has a low activity score and a high defecation score. I believe that the above statements fairly represent the rationale for the use of the open-field test. My statements are reasonable, they have ethological validity and they are, of course, completely circular. We can state, if we wish, that emotionality is that which the open-field test measures and feel safe, secure, and smug behind such a statement. If we do this, however, we are avoiding one quite unpleasant aspect of reality: How do we demonstrate the validity of the statement that the open-field test measures the construct of emotionality? What I should like to do today is describe two experiments that give general validity to the use of the open-field test as a measure of the construct of emotional reactivity. However, these data also indicate that the test measures a second behavioral dimension, so that there are certain difficulties in the interpretation of the open-field activity score.

On the performance of random vector quantization limited feedback beamforming in a MISO system

Abstract: In multiple antenna wireless systems, beamforming is a simple technique for guarding against the negative effects of fading. Unfortunately, beamforming requires the transmitter to have knowledge of the forward-link channel which is often not available a priori. One way of overcoming this problem is to design the beamforming vector using a limited number of feedback bits sent from the receiver to the transmitter. In limited feedback beamforming, the beamforming vector is restricted to lie in a codebook that is known to both the transmitter and receiver. Random vector quantization (RVQ) is a simple approach to codebook design that generates the vectors independently from a uniform distribution on the complex unit sphere. This correspondence presents performance analysis results for RVQ limited feedback beamforming

Gold Nanorods as Contrast Agents for Biological Imaging: Optical Properties, Surface Conjugation and Photothermal Effects

Abstract: Gold nanorods (NRs) have plasmon-resonant absorption and scattering in the near-infrared (NIR) region, making them attractive probes for in vitro and in vivo imaging. In the cellular environment, NRs can provide scattering contrast for darkfield microscopy, or emit a strong two-photon luminescence due to plasmon-enhanced two-photon absorption. NRs have also been employed in biomedical imaging modalities such as optical coherence tomography or photoacoustic tomography. Careful control over surface chemistry enhances the capacity of NRs as biological imaging agents by enabling cell-specific targeting, and by increasing their dispersion stability and circulation lifetimes. NRs can also efficiently convert optical energy into heat, and inflict localized damage to tumor cells. Laser-induced heating of NRs can disrupt cell membrane integrity and homeostasis, resulting in Ca(2+) influx and the depolymerization of the intracellular actin network. The combination of plasmon-resonant optical properties, intense local photothermal effects and robust surface chemistry render gold NRs as promising theragnostic agents.