19,219 research outputs found
Dangling-bond spin relaxation and magnetic 1/f noise from the amorphous-semiconductor/oxide interface: Theory
We propose a model for magnetic noise based on spin-flips (not
electron-trapping) of paramagnetic dangling-bonds at the
amorphous-semiconductor/oxide interface. A wide distribution of spin-flip times
is derived from the single-phonon cross-relaxation mechanism for a
dangling-bond interacting with the tunneling two-level systems of the amorphous
interface. The temperature and frequency dependence is sensitive to three
energy scales: The dangling-bond spin Zeeman energy delta, as well as the
minimum (E_min) and maximum (E_max) values for the energy splittings of the
tunneling two-level systems. We compare and fit our model parameters to a
recent experiment probing spin coherence of antimony donors implanted in
nuclear-spin-free silicon [T. Schenkel {\it et al.}, Appl. Phys. Lett. 88,
112101 (2006)], and conclude that a dangling-bond area density of the order of
10^{14}cm^{-2} is consistent with the data. This enables the prediction of
single spin qubit coherence times as a function of the distance from the
interface and the dangling-bond area density in a real device structure. We
apply our theory to calculations of magnetic flux noise affecting SQUID devices
due to their Si/SiO_2 substrate. Our explicit estimates of flux noise in SQUIDs
lead to a noise spectral density of the order of 10^{-12}Phi_{0}^{2} {Hz}^{-1}
at f=1Hz. This value might explain the origin of flux noise in some SQUID
devices. Finally, we consider the suppression of these effects using surface
passivation with hydrogen, and the residual nuclear-spin noise resulting from a
perfect silicon-hydride surface.Comment: Final published versio
A Growth model for DNA evolution
A simple growth model for DNA evolution is introduced which is analytically
solvable and reproduces the observed statistical behavior of real sequences.Comment: To be published in Europhysics Letter
Of the significance of business relationships
The Industrial Network Theory aims to describe and explain the business relationships and networks in which the focal firm is deeply embedded. One of its major propositions is that business relationships somehow influence, to different extents and over time, the focal firmâs survival. This pertains to the diverse and time-varying significance of business relationships for the focal firm. It has often been implicitly sustained that such significance is strongly related to the role played by business relationships and consequently the relationship outcomes accruing to the focal firm. The logic underlying the relationship significance proposition is outwardly oriented, somewhat overlooking the focal firmâs inside and in particular the conspicuous influence of business relationships on what the focal firm does competently both within and across its vertical boundaries. Arguably, the (predominantly âfunctionalâ) network-based arguments currently advanced represent a necessary but not sufficient condition for relationship significance. This conceptual paper tentatively suggests that there may be missing a supplementary (essentially internal) explanation supported by Competence-based Theories of the Firm.Industrial Network Theory; relationship significance proposition
The strategic relevance of business relationships: a preliminary assessment
The ubiquitous contention within the Industrial Networks literature - that business relationships are one of the firmÂŽs most important resources - has not been, in our viewpoint, thoroughly explored. Hence we argue that the âResource-based View of the Firmâ (âRBVâ) may complement the network-based reasoning on the strategic relevance of business relationships. A theoretical framework is proposed â a competence-based view of the firm â which solves RBVÂŽs terminological and inconsistency problems and, more importantly, assures compatibility with the network perspectiveÂŽs assumptions. The possibility of cross-fertilizing the Industrial Networks and RBV theories seems not only real, but also conceptually profitable for both theoretical fields.Business Relationships, Industrial Networks, Resource-Based View of the Firm, Competence-Based View of the Firm
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