Coherent magnetization precession in ferromagnetic (Ga,Mn)As induced by picosecond acoustic pulses.

We show that the magnetization of a thin ferromagnetic (Ga,Mn)As layer can be modulated by picosecond acoustic pulses. In this approach a picosecond strain pulse injected into the structure induces a tilt of the magnetization vector M, followed by the precession of M around its equilibrium orientation. This effect can be understood in terms of changes in magnetocrystalline anisotropy induced by the pulse. A model where only one anisotropy constant is affected by the strain pulse provides a good description of the observed time-dependent response.

Predictive value of PD-L1 based on mRNA level in the treatment of stage IV melanoma with ipilimumab.

INTRODUCTION: PD-L1 is established as a predictive marker for therapy of non-small cell lung cancer with pembrolizumab. Furthermore, PD-L1 positive melanoma has shown more favorable outcomes when treated with anti-PD1 antibodies and dacarbazine compared to PD-L1 negative melanoma. However, the role of PD-L1 expression with regard to response to checkpoint inhibition with anti-CTLA-4 is not clear, yet. In addition, the lack of standardization in the immunohistochemical assessment of PD-L1 makes the comparison of results difficult. In this study, we investigated the PD-L1 gene expression with a new fully automated technique via RT-PCR and correlated the findings with the response to the anti-CTLA-4 antibody ipilimumab. MATERIALS AND METHODS: Within a retrospective multi-center trial, PD-L1 gene expression was evaluated in 78 melanoma patients in a total of 111 pre-treatment tumor samples from 6 skin cancer centers and analyzed with regard to response to ipilimumab. For meaningful statistical analysis, the cohort was enriched for responders with 30 responders and 48 non-responders. Gene expression was assessed by quantitative RT-PCR after extracting mRNA from formalin-fixed paraffin embedded tumor tissue and correlated with results from immunohistochemical (IHC) stainings. RESULTS AND DISCUSSION: The evaluation of PD-L1 expression based on mRNA level is feasible. Correlation between PD-L1 expression as assessed by IHC and RT-PCR showed varying levels of concordance depending on the antibody employed. RT-PCR should be further investigated to measure PD-L1 expression, since it is a semi-quantitative method with observer-independent evaluation. With this approach, there was no statistical significant difference in the PD-L1 expression between responders and non-responders to the therapy with ipilimumab. The evaluation of PD-L1 expression based on mRNA level is feasible. Correlation between PD-L1 expression as assessed by IHC and RT-PCR showed varying levels of concordance depending on the antibody employed. RT-PCR should be further investigated to measure PD-L1 expression, since it is a semi-quantitative method with observer-independent evaluation. With this approach, there was no statistical significant difference in the PD-L1 expression between responders and non-responders to the therapy with ipilimumab.

Analysis of leukocyte activation during acute rejection of pulmonary allografts in noninfected and cytomegalovirus-infected rats.

After human lung transplantation acute rejection and cytomegalovirus (CMV) infections may occur, probably contributing to the development of chronic rejection. We established a model of subacute allograft rejection in rats to analyze leukocyte activation and effects of a CMV infection. Histoincompatible lung transplants (BN/LEW) without immunosuppression (group A) and lungs of initially immunosuppressed animals (group B) were analyzed. The production of inflammatory mediators (interleukin-6, tumor necrosis factor alpha, nitric oxides) and the expression of MHC class II antigens by alveolar and lung tissue macrophages were significantly enhanced during the alloresponse. In recipients without immunosuppression (group A) allograft necrosis was detected by day 6, whereas group B allografts were fully rejected by day 25. In allografts of immunosuppressed, CMV-infected animals (group C) the CMV infection was clearly aggravated and the number of activated lung tissue macrophages was increased when compared with noninfected allografts or isografts. The subacute model provides the advantage of allowing us to study mechanisms of acute rejection without the effects of reperfusion injury. Furthermore these findings underline the role of inflammatory mediators produced by macrophages during rejection.

Lasing from active optomechanical resonators.

Planar microcavities with distributed Bragg reflectors (DBRs) host, besides confined optical modes, also mechanical resonances due to stop bands in the phonon dispersion relation of the DBRs. These resonances have frequencies in the 10- to 100-GHz range, depending on the resonator's optical wavelength, with quality factors exceeding 1,000. The interaction of photons and phonons in such optomechanical systems can be drastically enhanced, opening a new route towards the manipulation of light. Here we implemented active semiconducting layers into the microcavity to obtain a vertical-cavity surface-emitting laser (VCSEL). Thereby, three resonant excitations--photons, phonons and electrons--can interact strongly with each other providing modulation of the VCSEL laser emission: a picosecond strain pulse injected into the VCSEL excites long-living mechanical resonances therein. As a result, modulation of the lasing intensity at frequencies up to 40 GHz is observed. From these findings, prospective applications of active optomechanical resonators integrated into nanophotonic circuits may emerge.