Looking Inside Micro- and Nano-Mechanical Pillar Resonators: A Picosecond Ultrasonics Approach

Pillar-shaped Gallium arsenide (GaAs) micromechanical resonators are fabricated, and the feasibility to measure the inside of the pillars in the axial direction with laser-induced GHz ultrasound based on picosecond ultrasonics is tested. Measurements on the pillars with head sizes in the µm range show excellent agreement with theoretical predictions.publishe

Determining Young's modulus via the eigenmode spectrum of a nanomechanical string resonator

We present a method for the in situ determination of Young's modulus of a nanomechanical string resonator subjected to tensile stress. It relies on measuring a large number of harmonic eigenmodes and allows us to access Young's modulus even for the case of a stress-dominated frequency response. We use the proposed framework to obtain Young's modulus of four different wafer materials, comprising three different material platforms amorphous silicon nitride, crystalline silicon carbide, and crystalline indium gallium phosphide. The resulting values are compared with theoretical and literature values where available, revealing the need to measure Young's modulus on the sample material under investigation for precise device characterization.publishe

Observing polarization patterns in the collective motion of nanomechanical arrays

In recent years, nanomechanics has evolved into a mature field, and it has now reached a stage which enables the fabrication and study of ever more elaborate devices. This has led to the emergence of arrays of coupled nanomechanical resonators as a promising field of research serving as model systems to study collective dynamical phenomena such as synchronization or topological transport. From a general point of view, the arrays investigated so far can be effectively treated as scalar fields on a lattice. Moving to a scenario where the vector character of the fields becomes important would unlock a whole host of conceptually interesting additional phenomena, including the physics of polarization patterns in wave fields and their associated topology. Here we introduce a new platform, a two-dimensional array of coupled nanomechanical pillar resonators, whose orthogonal vibration directions encode a mechanical polarization degree of freedom. We demonstrate direct optical imaging of the collective dynamics, enabling us to analyze the emerging polarization patterns, follow their evolution with drive frequency, and identify topological polarization singularities.publishe

Cutting Edge: Novel Vaccination Modality Provides Significant Protection against Mucosal Infection by Highly Pathogenic Simian Immunodeficiency Virus

Vaccine induced protection against infection by HIV or highly pathogenic and virulent SIV-strains has been limited. Here, in a proof of concept study, we show that a novel vaccine approach significantly protects Rhesus macaques from mucosal infection by the highly pathogenic strain SIV(mac251). We vaccinated 3 cohorts of 12 macaques each with live, irradiated vaccine cells secreting the modified ER chaperone gp96(−)Ig. Cohort 1 was vaccinated with cells secreting gp96(SIV)Ig carrying SIV peptides. Cohort 2 in addition received recombinant envelope protein SIV-gp120. Cohort 3 was injected with cells secreting gp96-Ig (no SIV antigens) vaccines. Cohort 2 was protected from infection. After seven rectal challenges with highly pathogenic SIV(mac251) the hazard ratio was 0.27 corresponding to a highly significant, 73% reduced risk of viral acquisition. The apparent success of the novel vaccine modality recommends further study

Gp96SIVIg immunization induces potent polyepitope specific, multifunctional memory responses in rectal and vaginal mucosa

The ER-resident chaperone gp96, when released by cell lysis, induces an immunogenic chemokine signature and causes innate immune activation of DC and NK cells. Here we show that intraperitoneal immunization with a genetically engineered, secreted form of gp96, gp96-Ig chaperoning SIV antigens, induces high levels of antigen specific CD8 CTL in the rectal and vaginal mucosa of Rhesus macaques. The frequency of SIV Gag- and SIV Tat-tetramer positive CD8 CTL in the intestinal mucosa reached 30-50% after the third immunization. Tetramer positive CD8 CTL expressed appropriate functional (granzyme B) and migration markers (CD103). The polyepitope specificity of the mucosal CD8 and CD4 response is evident from a strong, multifunctional cytokine response upon stimulation with peptides covering the gag, tat and env proteins. Induction of powerful mucosal effector CD8 CTL responses by cell-based gp96(SIV)-Ig immunization may provide a pathway to the development of safe and effective SIV/HIV vaccines

Overall survival in the OlympiA phase III trial of adjuvant olaparib in patients with germline pathogenic variants in BRCA1/2 and high-risk, early breast cancer

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