Stark effect on the exciton spectra of vertically coupled quantum dots: horizontal field orientation and non-aligned dots

We study the effect of an electric-field on an electron-hole pair in an asymmetric system of vertically coupled self-assembled quantum dots taking into account their non-perfect alignment. We show that the non-perfect alignment does not qualitatively influence the exciton Stark effect for the electric field applied in the growth direction, but can be detected by application of a perpendicular electric field. We demonstrate that the direction of the shift between the axes of non-aligned dots can be detected by rotation of a weak electric field within the plane of confinement. Already for a nearly perfect alignment the two-lowest energy bright exciton states possess antilocked extrema as function of the orientation angle of the horizontal field which appear when the field is parallel to the direction of the shift between the dot centers

Attenuation of hedgehog/GLI signaling by NT1721 extends survival in pancreatic cancer.

BackgroundPancreatic cancer is one of the most lethal malignancies due to frequent late diagnosis, aggressive tumor growth and metastasis formation. Continuously raising incidence rates of pancreatic cancer and a lack of significant improvement in survival rates over the past 30 years highlight the need for new therapeutic agents. Thus, new therapeutic agents and strategies are urgently needed to improve the outcome for patients with pancreatic cancer. Here, we evaluated the anti-tumor activity of a new natural product-based epidithiodiketopiperazine, NT1721, against pancreatic cancer.MethodsWe characterized the anticancer efficacy of NT1721 in multiple pancreatic cancer cell lines in vitro and in two orthotopic models. We also compared the effects of NT1721 to clinically used hedgehog inhibitors and the standard-of-care drug, gemcitabine. The effect of NT1721 on hedgehog/GLI signaling was assessed by determining the expression of GLI and GLI target genes both in vitro and in vivo.ResultsNT1721 displayed IC50 values in the submicromolar range in multiple pancreatic cancer cell lines, while largely sparing normal pancreatic epithelial cells. NT1721 attenuated hedgehog/GLI signaling through downregulation of GLI1/2 transcription factors and their downstream target genes, which reduced cell proliferation and invasion in vitro and significantly decreased tumor growth and liver metastasis in two preclinical orthotopic mouse models of pancreatic cancer. Importantly, treatment with NT1721 significantly improved survival times of mice with pancreatic cancer compared to the standard-of-care drug, gemcitabine.ConclusionsFavorable therapeutics properties, i.e. 10-fold lower IC50 values than clinically used hedgehog inhibitors (vismodegib, erismodegib), a 90% reduction in liver metastasis and significantly better survival times compared to the standard-of-care drug, gemcitabine, provide a rational for testing NT1721 in the clinic either as a single agent or possibly in combination with gemcitabine or other therapeutic agents in PDAC patients overexpressing GLI1/2. This could potentially result in promising new treatment options for patients suffering from this devastating disease

Production and mixing of scalar mesons in ηc\eta_c and χc1\chi_{c1} decays

We briefly discuss how the chiral unitary approach in coupled channels and $SU(3)$ symmetry can be used to describe the production of $f_0(500)$, $f_0(980)$ and $a_0(980)$ in the $\chi_{c1} \to \eta \pi^+ \pi^-$ reaction, recently measured by the BESIII collaboration. In this reaction a very strong peak for the $a_0(980)$ can be seen in the $\eta\pi$ invariant mass, while clear signals for the $f_0(500)$ and $f_0(980)$ appear in the one of $\pi^+\pi^-$. Next, we show the predictions made with the same model for the analogous decay $\eta_c \to \eta \pi^+ \pi^-$, which could also be measured experimentally. We discuss the differences of these two reactions which are interesting to test the picture where these scalar mesons are dynamically generated from the interaction of pairs of pseudoscalars. Furthermore, we comment on a new recent work where the same model was used to study the $a_0(980) - f_0(980)$ mixing in the $\chi_{c1} \to \pi^0 \pi^0 \eta$ and $\chi_{c1} \to \pi^0 \pi^+ \pi^-$ reactions, showing that quantitative agreement with the experimental measurement of this mixing, also performed by BESIII, can be obtained, revealing interesting aspects of the dynamics of this process and the importance of coupled channels.Comment: Talk presented at the XVII International Conference on Hadron Spectroscopy and Structure - Hadron2017, 25-29 September, 2017, University of Salamanca, Salamanca, Spain. arXiv admin note: substantial text overlap with arXiv:1707.0722

Direct evidence for a piezoelectriclike effect in coherently strained SiGe/Si heterostructures

A hybrid acoustic spectroscopy technique has been used to demonstrate the (reversible) conversion of high frequency electric fields into longitudinal acoustic waves within a modulation-doped pseudomorphic Si/Si0.88Ge0.12/Si heterostructure. This provides compelling evidence for the existence of a piezoelectriclike coupling within such structures

Historic Light Curve and Long-term Optical Variation of BL Lacertae 2200+420

In this paper, historical optical(UBVRI) data and newly observed data from the Yunnan Observatory of China(about100 years) are presented for BL Lacertae. Maximum variations in UBVRI: 5.12, 5.31, 4.73, 2.59, and 2.54 and color indices of U-B = -0.11 +/- 0.20, B-V= 1.0 +/- 0.11, V-R= 0.73 +/- 0.19, V-I= 1.42 +/- 0.25, R-I= 0.82 +/- 0.11, and B-I= 2.44 +/- 0.29 have been obtained from the literature; The Jurkevich method is used to investigate the existence of periods in the B band light curve, and a long-term period of 14 years is found. The 0.6 and 0.88 year periods reported by Webb et al.(1988) are confirmed. In addition, a close relation between B-I and B is found, suggesting that the spectra flattens when the source brightens.Comment: 21 pages, 6 figures, 2 table, aasms4.sty, to be published in ApJ, Vol. 507, 199

Interface relaxation in electrophoretic deposition of polymer chains: Effects of segmental dynamics, molecular weight, and field

Using different segmental dynamics and relaxation, characteristics of the interface growth is examined in an electrophoretic deposition of polymer chains on a three (2+1) dimensional discrete lattice with a Monte Carlo simulation. Incorporation of faster modes such as crankshaft and reptation movements along with the relatively slow kink-jump dynamics seems crucial in relaxing the interface width. As the continuously released polymer chains are driven (via segmental movements) and deposited, the interface width $W$ grows with the number of time steps $t$, $W \propto t^{\beta},$ ($\beta \sim 0.4$--$0.8)$, which is followed by its saturation to a steady-state value $W_s$. Stopping the release of additional chains after saturation while continuing the segmental movements relaxes the saturated width to an equilibrium value ($W_s \to W_r$). Scaling of the relaxed interface width $W_r$ with the driving field $E$, $W_r \propto E^{-1/2}$ remains similar to that of the steady-state $W_s$ width. In contrast to monotonic increase of the steady-state width $W_s$, the relaxed interface width $W_r$ is found to decay (possibly as a stretched exponential) with the molecular weight.Comment: 5 pages, 7 figure