Tunneling induced quantum interference experienced by an incident probe in asymmetric double quantum wells can easily be modulated by means of an external control light beam. This phenomenon, which is here examined within the dressed-state picture, can be exploited to devise a novel all-optical ultrafast switch. For a suitably designed semiconductor heterostructure, the switch is found to exhibit frequency bandwidths of the order of 0.1 THz and response and recovery times of about 1 ps. DOI: 10.1103/PhysRevLett.95.057401 PACS numbers: 78.67.De, 42.50.Gy, 42.50.Hz, 78.66.Fd Transmission and switching of data using all-optical devices is currently the ultimate goal of most telecommunication research. To build all-optical networking systems, optical analogues of existing microelectronics devices must clearly be found. Interesting proposals toward the realization of fast switches, for instance, have already been brought forward whereas important steps toward their actual implementation are now being made. Schemes based on dipole-dipole interactions [1], nonlinear Bragg diffraction [2], photonic band-gap materials [3], as well as those most recent ones based on quantum interference in atomic media [4 -7] all seem to be quite promising.This Letter describes a proof-of-principle study demonstrating that tunable tunneling induced quantum interference in asymmetric quantum wells can be exploited to devise an efficient new mechanism for ultrafast and broadband all-optical switching working at low temperatures (T 10 K). Unlike most familiar switching schemes based on photo-induced changes of the medium macroscopic refractive index [3] or other less usual ones based instead on virtual excitation of spin-polarized excitons [8] or on switchable mirrors made of thin polycrystalline films [9], this mechanism relies on quantum interference and hence it is quite sensitive. Quantum interference based phenomena such as, e.g., coherent population trapping [10], electromagnetically induced transparency [11], lasing without inversion [12], and light speed reduction [13] have recently attracted considerable attention. For many potential applications, solid-state solutions to implement these effects, first predicted and observed in dilute atomic media, are preferred and are now being sought after. In solid media [14] only few proposals followed the original idea of making use of quantum interference to devise an optical switch, first suggested [4] to work and recently observed [6] on a four-level atomic system.We investigate the steady-state and transient behavior of a weak probe light signal incident upon an asymmetric quantum well. The probe can be stopped in the presence of an external control switch beam but made instead to propagate with little absorption when the switch beam is off. The different response depends, respectively, on whether tunneling induced quantum interference is quenched or well developed. Such a control of quantum interference hinges on the creation of a new dipole allowed intersubband transition. Large pro...

BackgroundSPARC (secreted protein, acidic and rich in cysteine) is closely related with the progress, invasion and metastasis of malignant tumor and angiogenesis.MethodsUsing human colon adenocarcinoma tissues (hereinafter referred to as colon cancer) and their corresponding non-diseased colon from 114 patients' biopsies, the expression of SPARC and vascular endothelial growth factor (VEGF) were investigated by immunohistochemistry staining to assessment the relationship between SPARC and VEGF, as well as their prognostic significance in patients. Evaluation of VEGF expression level with the same tissues was used to establish the antigenic profiles, and the marker of CD34 staining was used as an indicator of microvessel density (MVD).ResultsSPARC expression was mainly in the stromal cells surrounding the colon cancer, and was significant difference in those tissues with the lymph node metastasis and differentiation degree of tumor. Expression of SPARC was significantly correlated with the expression of VEGF and MVD in colon cancer tissues. Patients with low or absence expressing SPARC had significantly worse overall survival and disease-free survival in a Single Factor Analysis; Cox Regression Analysis, SPARC emerged as an overall survival and disease-free survival independent prognostic factor for colon cancer.ConclusionThe low expression or absence of stromal SPARC was an independent prognostic factor for poor prognosis of colon cancer. SPARC maybe involved in the regulation of anti-angiogenesis by which it may serve as a novel target for colon cancer treatment as well as a novel distinctive marker.

Genomic amplification of the distal portion of chromosome 3q, which encodes a number of oncogenic proteins, is one of the most frequent chromosomal abnormalities in malignancy. Here we functionally characterise a non-protein product of the 3q region, the long noncoding RNA (lncRNA) PLANE, which is upregulated in diverse cancer types through copy number gain as well as E2F1-mediated transcriptional activation. PLANE forms an RNA-RNA duplex with the nuclear receptor co-repressor 2 (NCOR2) pre-mRNA at intron 45, binds to heterogeneous ribonucleoprotein M (hnRNPM) and facilitates the association of hnRNPM with the intron, thus leading to repression of the alternative splicing (AS) event generating NCOR2-202, a major protein-coding NCOR2 AS variant. This is, at least in part, responsible for PLANE-mediated promotion of cancer cell proliferation and tumorigenicity. These results uncover the function and regulation of PLANE and suggest that PLANE may constitute a therapeutic target in the pan-cancer context.

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