University of California, Santa Barbara

About: University of California, Santa Barbara is a education organization based out in Santa Barbara, California, United States. It is known for research contribution in the topics: Population & Laser. The organization has 30281 authors who have published 80852 publications receiving 4626827 citations. The organization is also known as: UC Santa Barbara & UCSB.

The Holographic principle

Abstract: There is strong evidence that the area of any surface limits the information content of adjacent spacetime regions, at $1.4\ifmmode\times\else\texttimes\fi{}{10}^{69}$ bits per square meter. This article reviews the developments that have led to the recognition of this entropy bound, placing special emphasis on the quantum properties of black holes. The construction of light sheets, which associate relevant spacetime regions to any given surface, is discussed in detail. This article explains how the bound is tested, and its validity is demonstrated in a wide range of examples. A universal relation between geometry and information is thus uncovered. It has yet to be explained. The holographic principle asserts that its origin must lie in the number of fundamental degrees of freedom involved in a unified description of spacetime and matter. It must be manifest in an underlying quantum theory of gravity. This article surveys some successes and challenges in implementing the holographic principle.

Cognitive Theory of Multimedia Learning

Abstract: Abstract A fundamental hypothesis underlying research on multimedia learning is that multimedia instructional messages that are designed in light of how the human mind works are more likely to lead to meaningful learning than those that are not. The cognitive theory of multimedia learning (CTML) is based on three cognitive science principles of learning: the human information processing system includes dual channels for visual/pictorial and auditory/verbal processing (i.e., dual-channels assumption); each channel has limited capacity for processing (i.e., limited capacity assumption); and active learning entails carrying out a coordinated set of cognitive processes during learning (i.e., active processing assumption). The cognitive theory of multimedia learning specifies five cognitive processes in multimedia learning: selecting relevant words from the presented text or narration, selecting relevant images from the presented illustrations, organizing the selected words into a coherent verbal representation, organizing selected images into a coherent pictorial representation, and integrating the pictorial and verbal representations and prior knowledge. Multimedia instructional messages should be designed to prime these processes. The Case for Multimedia Learning What is the rationale for a theory of multimedia learning? People learn more deeply from words and pictures than from words alone. This assertion – which can be called the multimedia principle – underlies much of the interest in multimedia learning. For thousands of years, words have been the major format for instruction – including spoken words, and within the last few hundred years, printed words.

Quantum information processing using quantum dot spins and cavity QED

Abstract: The electronic spin degrees of freedom in semiconductors typically have decoherence times that are several orders of magnitude longer than other relevant time scales. A solid-state quantum computer based on localized electron spins as qubits is therefore of potential interest. Here, a scheme that realizes controlled interactions between two distant quantum dot spins is proposed. The effective long-range interaction is mediated by the vacuum field of a high finesse microcavity. By using conduction-band-hole Raman transitions induced by classical laser fields and the cavity-mode, parallel controlled-not operations, and arbitrary single qubit rotations can be realized.

Effects of biodiversity on the functioning of trophic groups and ecosystems

Abstract: Over the past decade, accelerating rates of species extinction have prompted an increasing number of studies to reduce species diversityexperimentallyandexaminehowthisalterstheefficiency by which communities capture resources and convert those into biomass 1,2 . So far, the generality of patterns and processes observed in individual studies have been the subjects of considerable debate 3–7 .Here wepresent aformal meta-analysis of studies thathaveexperimentallymanipulatedspeciesdiversitytoexamine how it affects the functioning of numerous trophic groups in multiple types of ecosystem. We show that the average effect of decreasing species richness is to decrease the abundance or biomass of the focal trophic group, leading to less complete depletion of resources used by that group. At the same time, analyses reveal that the standing stock of, and resource depletion by, the most species-rich polyculture tends to be no different from that of the single most productive species used in an experiment. Of the known mechanisms that might explain these trends, results are most consistent with what is called the ‘sampling effect’, which occurs when diverse communities are more likely to contain and become dominated by the most productive species. Whether this mechanism is widespread in natural communities is currently controversial. Patterns we report are remarkably consistent for four different trophic groups (producers, herbivores, detritivores and predators) and two major ecosystem types (aquatic and terrestrial). Collectively, ouranalysessuggestthat theaverage species loss does indeed affect the functioning of a wide variety of organisms and ecosystems, but the magnitude of these effects is ultimatelydeterminedbytheidentityofspeciesthataregoingextinct.

Chronology, causes and progression of the Messinian salinity crisis

Abstract: The Messinian salinity crisis is widely regarded as one of the most dramatic episodes of oceanic change of the past 20 or so million years (1–3). Earliest explanations were that extremely thick evaporites were deposited in a deep and desiccated Mediterranean basin that had been repeatedly isolated from the Atlantic Ocean1,2, but elucidation of the causes of the isolation — whether driven largely by glacio-eustatic or tectonic processes — have been hampered by the absence of an accurate time frame. Here we present an astronomically calibrated chronology for the Mediterranean Messinian age based on an integrated high-resolution stratigraphy and ‘tuning’ of sedimentary cycle patterns to variations in the Earth's orbital parameters. We show that the onset of the Messinian salinity crisis is synchronous over the entire Mediterranean basin, dated at 5.96 ± 0.02 million years ago. Isolation from the Atlantic Ocean was established between 5.59 and 5.33 million years ago, causing a large fall in Mediterranean water level followed by erosion (5.59–5.50 million years ago) and deposition (5.50–5.33 million years ago) of non-marine sediments in a large ‘Lago Mare’ (Lake Sea) basin. Cyclic evaporite deposition is almost entirely related to circum-Mediterranean climate changes driven by changes in the Earth's precession, and not to obliquity-induced glacio-eustatic sea-level changes. We argue in favour of a dominantly tectonic origin for the Messinian salinity crisis, although its exact timing may well have been controlled by the ∼400-kyr component of the Earth's eccentricity cycle.