43,786 research outputs found
Finding the Origin of the Pioneer Anomaly
Analysis of radio-metric tracking data from the Pioneer 10/11 spacecraft at
distances between 20 - 70 astronomical units (AU) from the Sun has consistently
indicated the presence of an anomalous, small, constant Doppler frequency
drift. The drift can be interpreted as being due to a constant acceleration of
a_P= (8.74 \pm 1.33) x 10^{-8} cm/s^2 directed towards the Sun. Although it is
suspected that there is a systematic origin to the effect, none has been found.
As a result, the nature of this anomaly has become of growing interest. Here we
present a concept for a deep-space experiment that will reveal the origin of
the discovered anomaly and also will characterize its properties to an accuracy
of at least two orders of magnitude below the anomaly's size. The proposed
mission will not only provide a significant accuracy improvement in the search
for small anomalous accelerations, it will also determine if the anomaly is due
to some internal systematic or has an external origin. A number of critical
requirements and design considerations for the mission are outlined and
addressed. If only already existing technologies were used, the mission could
be flown as early as 2010.Comment: 21 SS pages, 4+1 figures. final changes for publicatio
Entanglement of separate nitrogen-vacancy centers coupled to a whispering-gallery mode cavity
We present a quantum electrodynamical model involving nitrogen-vacancy
centers coupled to a whispering-gallery mode cavity. Two schemes are considered
to create W state and Bell state, respectively. One of the schemes makes use of
the Raman transition with the cavity field virtually excited; The other enables
the Bell state preparation and quantum information transfer by virtue of dark
state evolution and adiabatic passage, which is tolerant to ambient noise and
experimental parameter fluctuations. We justify our schemes by considering the
experimental feasibility and challenge using currently available technology.Comment: 8 pages and 5 figure
Ontwikkelingsvooruitsigte in die Oos-Transvaalse Laeveld
Hierdie landstreek is ongetwyfeld die deel van ons land waar in die naaste toekoms die grootste ontwikkeling gaan plaasvind, nie alleen op landbougebied nie, maar ook op minerale-en nywerheidsgebied
Agtergrond, persoonlikheid en ekonomiese denke
Dit is die bedoeling om hier, in ’n baie kort bestek en slegs in hooftrekke, aan te toon dat die ekonomiese denke onafskeidbaar verbonde is aan die persoonlikheid en agtergrond van die ekonoom
Los gedagtes oor die plek van landbou in ons volkshuishouding.
Die bepaling van die plek van landbou in enige volkshuishouding kan van meer as een aspek benader word
„In die jaar 2000.”
Die mens is gewoonlik bevrees vir wat die more te voorskyn mag bring.Die geskiedenis laat hom nie toe om van sy erfenis weg te vlug nie. Terselfdertyd is dit die geskiedenis wat die mens in staat stel om met ’n enigsinsvoorbedagte beplanning op te tree. Alle lewe is ’n proses en alle prosesseis van nature iets dinamies. Dit is tevergeefs om daarna te strewe, metenige hoop van sukses, om ’n oomblik van die verlede te herwin. Suksesis nooit finaal nie. As die mens ’n beter muisval bou, sal die natuur mettertyd’n skelmer muis baar
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