Microscopic theory of indistinguishable single-photon emission from a quantum dot coupled to a cavity: The role of non-Markovian phonon-induced decoherence

We study the fundamental limit on single-photon indistinguishability imposed by decoherence due to phonon interactions in semiconductor quantum dot-cavity QED systems. Employing an exact diagonalization approach we find large differences compared to standard methods. An important finding is that short-time non-Markovian effects limit the maximal attainable indistinguishability. The results are explained using a polariton picture that yields valuable insight into the phonon-induced dephasing dynamics.Comment: published version, comments are very welcom

PQL: A Declarative Query Language over Dynamic Biological Schemata

We introduce the PQL query language (PQL) used in the GeneSeek genetic data integration project. PQL incorporates many features of query languages for semi-structured data. To this we add the ability to express metadata constraints like intended semantics and database curation approach. These constraints guide the dynamic generation of potential query plans. This allows a single query to remain relevant even in the presence of source and mediated schemas that are continually evolving, as is often the case in data integration

Electricity demand in primary aluminum smelting

The demand for electricity by primary aluminum smelters is estimated econometrically. Cross section data is used, including plant data for the U.S. and Norway and a national average for Japan. The data are sampled for two periods, one before and one after the 1973-74 energy price increase. The paper estimates the elasticity of substitution between electricity and an aggregate of all other inputs, assumed to exist. The estimated value of 0.1 is low, but significantly different from zero. Large price in- creases, such as the equalization of hydro and other power prices are found to result in substantial energy savings

Hva kan være aktuell sykepleie til eldre brukere av hjemmesykepleie som opplever ensomhet?

Oppgavens tittel er ”Ensomhet hos eldre hjemmeboende”. Med denne oppgaven ønsket jeg å belyse hva som kan være aktuell sykepleie til eldre brukere av hjemmesykepleie som opplever ensomhet. Og jeg håpet at bacheloroppgaven kunne være med på å øke innsikt og forståelse for ensomhet hos bruker i hjemmesykepleien. Ut i fra dette kom jeg frem til problemstillingen: ”Hva kan være aktuell sykepleie til eldre brukere av hjemmesykepleie som opplever ensomhet?”. I oppgaven har jeg brukt kvalitativ litteraturstudie som metode. Etter endt oppgave har jeg konkludert med at ensomhet hos eldre hjemmeboende er et stort problem, som det er viktig at sykepleier griper fatt i. Aktuell sykepleie til disse brukerne vil være å skape en relasjon til brukeren, kartlegge nettverket, nettverkintervensjon, være sosialt tilstede når en er hjemme hos brukeren, samt informere, motivere og oppmuntre bruken til å delta i ulike aktiviteter for eldre og skaffe seg et telefonnettverk

The energy price shock and the 1974-75 recession

Research supported by MIT's Center for Energy Policy Research

An analysis of oil supply disruption scenarios

This report brings the results of simulations of some oil supply disruptions on the M.I.T. Energy Laboratory Energy Macro Model. This model has previously been used to study the macroeconomic effects of the 1973-74 and 1979 oil price shocks, as well as for policy simula- -tions related to these historical events (Mork and Hall, 1980a, 1980b, 1981). Recent extensions of the model allow it to be used for simulation of possible future oil supply disruptions, such as the loss of oil deliveries from Saudi Arabia or the entire Persian Gulf region.The extensions go mainly in the direction of more explicit modeling of thedomestic energy sector and of the world oil market. Although very important, these extensions are still in an experimental stage. Richard Gilbert of the University of California at Berkeley provided invaluable help in modeling the domestic energy sector. The short-run functioning of the world oil market was modeled along the lines suggested by Chao and Manne (1980). Sanjay Srivastava provided useful research assistance in preparing and programming the solution algorithm for the model. None of these persons are, however, in any way responsible for the contents of this report.Three basic disruption scenarios are analyzed, of 3, 10, and 18 million barrels per day (mmbd) on the world level, respectively. Disruptions are modeled as leftward shifts in the world supply curve for oil (OPEC's 'price reaction' curve). All disruptions are assumed to last for one year, but another three years are assumed to be needed to restore the lost capacity. Each disruption scenario is simulated under three different policy assumptions. The first case assumes no new policy. The second case assumes a specific tariff on oil imports, rising from $2.50 in 1981 to a long-run value of$10.00 in 1984. In the third case, an ad valorem tariff is introduced gradually in the same way, from 7.5 percent of the world price in 1981 to 30 percent in 1984. As a last exercise, a 10 mmbd disruption is simulated under the assumption that all relative prices adjust perfectly to clear all markets.Oil supply disruptions are found to add substantially to inflation during the disruption year and to cause substantial real losses. For a 10 mmbd disruption (the possible loss of Saudi Arabia), 6.4 percentage points are expected to be added to the inflation rate in the disruption year, and the net social cost in real terms is projected as $489 billion in 1980 dollars. An 18 mmbd disruption (the possible loss of the Persian Gulf) is expected to lead to an 8 percent drop in real GNP in the year of the disruption, to add 14 percent to the inflation rate and 6.5 percent to the unemployment rate in the same year, and to incur a net loss of$1,010 billion in 1980 dollars.The two tariffs are found to lead to very similar results. The ad valorem tariff may hold a slight edge over the specific tariff by reducing transfer the real income to oil exporters during a disruption by slightly more than it increases the loss due to unemployment. Both tariffs are, however, clearly inferior to the alternative of no new policy because of the added losses and inefficiencies in normal periods.If all prices and wages were free to adjust instantaneously, so that full employment were maintained everywhere during a disruption, then the world oil market would be.much higher and the price increase more than three times as high. This effect of unemployment on oil prices provides an automatic stabilizer in the world market and is an important part of the explanation of the apparent resilience of the U.S. economy to large disturbances in the world oil market

Energy Prices, Inflation, and Recession, 1974-1975

The energy price shock depressed real output by two percent in 1974 and by five percent in 1975, according to our results. Prices rose by four percent in 1974 and by another two percent in 1975. These conclusions are derived from an aggregate model of the U.S. economy with an explicit role of energy in production. The distinction between expected and unexpected shocks is an important part of the model. We also examine monetary and fiscal policies that might have offset the energy shock.

Knowledge Transformations between Frame Systems and RDB Systems

For decades, researchers in knowledge representation (KR) have argued for and against various choices in KR formalisms, such as Rules, Frames, Semantic nets, and Formal logic. In this paper, we present a set of transformations that can be used to move knowledge across two fundamentally different KR formalisms: Frame-based systems and Relational database systems (RDBs). We also describe partial implementations of these transformations for a specific pair of such systems: Protégé and the Postgres RDB system

Carbon export by small particles in the Norwegian Sea

Despite its fundamental role in controlling the Earth's climate, present estimates of global organic carbon export to the deep sea are affected by relatively large uncertainties. These uncertainties are due to lack of observations as well as disagreement among methods and assumptions used to estimate carbon export. Complementary observations are thus needed to reduce these uncertainties. Here we show that optical backscattering measured by Bio-Argo floats can detect a seasonal carbon export flux in the Norwegian Sea. This export was most likely due to small particles (i.e., 0.2–20 μm), was comparable to published export values, and contributed to long-term carbon sequestration. Our findings highlight the importance of small particles and of physical mixing in the biological carbon pump and support the use of autonomous platforms as tools to improve our mechanistic understanding of the ocean carbon cycle