The transport properties of disordered solids have been the subject of much work since at least the 1950% but with a new burst of activity during the 1980s which has survived up to the present day. There have been numerous reviews of a more or less specialized nature. The present review aims to fill the niche for a non-specialized review of this very active area of research.The basic concepts behind the theory are introduced with more detailed sections covering experimental results, one-dimensional localization, scaling theory, weak localization, magnetic field effects and fluctuations. This review was received in its present form in June 1993. 0034-4885/93/121469+96559.S0 @ 1993 1OP Publishing Ltd 1469 p c( exp(-cuR -B A ) .(4)

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We have developed, confirmed, and now validated a pragmatic molecular classification tool (ProMisE) that provides consistent categorization of tumors and identifies four distinct prognostic molecular subtypes. ProMisE can be applied to diagnostic samples and thus could be used to inform surgical procedure(s) and/or need for adjuvant therapy. Based on the IOM guidelines this classifier is now ready for clinical evaluation through prospective clinical trials.

We find an interference effect for electron-phonon interactions in coupled semiconductor quantum dots that can dominate the nonlinear transport properties even for temperatures close to zero. The intradot electron tunneling process leads to a "shake up" of the phonon system and is dominated by a double-slit-like interference effect of spontaneously emitted phonons. The effect is closely related to subradiance of photons (Dicke effect) in a laser-trapped two-ion system and explains the oscillations in the nonlinear current-voltage characteristics of coupled dots observed recently. PACS numbers: 73.23.Hk, 42.50.Fx, 71.38. + i Spontaneous emission is one of the fundamental concepts of quantum mechanics that can be traced back to such early works as those of Albert Einstein [1]. An excited state of a single atom decays exponentially due to the coupling to photons. In a system of two atoms interacting via the common photon field, the decay splits into a subradiant and a superradiant channel. This effect is a precursor of the famous Dicke superradiance phenomenon [2] and was verified experimentally in the spontaneous emission of photons from two trapped ions only three years ago [3].Recently, in a completely different physical system, the emission of phonons from two artificial atoms has been observed [4]. Here, the coupling to the phonon degrees of freedom turned out to dominate the nonlinear electron transport through semiconductor double quantum dots even at mK temperatures.Double quantum dots are well-defined artificial systems for the study of interaction [5] and coherent timedependent [6] effects. Here, we propose a theory for a new nonlinear transport effect in double quantum dots which corresponds to the Dicke effect, i.e., the collective decay of real atoms. In our theory, the tunneling of single electrons through coupled artificial atoms is renormalized by the interaction with piezoelectric acoustic phonons and leads to an orthogonality catastrophe of the phonon bath if an electron tunnels between the dots. This "boson shake up" effect [7,8] is determined by an effective density of states r͑v͒ of the phonon modes Q that couple to the tunneling process. These interfere as in a double slit experiment when interacting with the electron densities in the two dots. As a result, r͑v͒ shows oscillations on a scale v d : c s ͞d, where c s is the speed of sound and d the distance between the centers of the two dots. It turns out that the nonlinear current peak as a function of the difference´between the two relevant many-particle energies is determined by the shape of r͑v ´͞h͒. Furthermore, this quantity is analogous to the rate for emission of subradiant photons from two laser-trapped ions [3], when c s is replaced by the speed of light and d by the distance of the ions. Thus, both phenomena are physically closely related. This provides the microscopic mechanism for the oscillations observed recently in a double dot current spectrum [4]. We predict that future experiments with artificial atoms can exploit this anal...