Spectra of sub-Dirac operators on certain nilmanifolds

We study sub-Dirac operators that are associated with left-invariant bracket-generating sub-Riemannian structures on compact quotients of nilpotent semi-direct products $G=\mathbb{R}^n\rtimes_A\mathbb{R}$. We will prove that these operators admit an $L^2$-basis of eigenfunctions. Explicit examples show that the spectrum of these operators can be non-discrete and that eigenvalues may have infinite multiplicity

Investigations on the shear capacity of stainless steel for its use in steel and composite bridge construction

The paper deals with the shear capacity and the shear buckling behaviour of plates made of (lean) duplex stainless steel. For this purpose, twelve experimental tests on torsionally loaded square box girders were carried out to investigate the shear capacity. Two different materials and three different buckling slendernesses were investigated. An FE model was created and calibrated using the experimental results. Subsequently, a parameter study was carried out in order to be able to cover a larger buckling slenderness range. The experimental and numerical results were then compared with the specifications of EN 1993-1-4 and an assessment of the specifications is provided

Structural Behaviour of Hybrid Steel-Glass Beams

Steel-glass beams consisting of steel flanges and a glass web connected by bondingrepresent a new kind of transparent structural members. This paper deals with theparticular structural behaviour of flexible composed hybrid beams regardingspecific material characteristics of steel, glass and particularly adhesive, which isdecisive for structural behaviour

A Dimer to Bridge Early Autophagosomal Membranes

The Atg1/ULK complex plays a key role in the early stages of autophagosome assembly. In this issue, Ragusa et al. reveal the molecular basis for some interactions within this complex, finding that the crescent-shaped Atg17 dimer is critical for autophagy, whereas Atg1 may have the ability to cluster membranes

A new Eurocode-compliant design approach for cold-formed steel sections

A new, Eurocode-compliant design approach based on the Direct Strength Method (DSM) combined with EN 1993-1-3 was developed for the design of thin-walled cold-formed steel sections. The new design approach transfers cross-sectional resistance according to DSM, based on numerical elastic buckling analyses on the gross cross-section, into the global stability check according to EN 1993-1-3. Experimental investigations on various perforated and unperforated cold-formed sections in compression and bending serve to verify the new design approach. In addition, a numerical model was developed, it was calibrated on the test results and used for further parametric analyses on the load-carrying capacity of cold-formed sections

Proteins Needed for Vesicle Budding from the Golgi Complex Are Also Required for the Docking Step of Homotypic Vacuole Fusion

Vam2p/Vps41p is known to be required for transport vesicles with vacuolar cargo to bud from the Golgi. Like other VAM-encoded proteins, which are needed for homotypic vacuole fusion, we now report that Vam2p and its associated protein Vam6p/Vps39p are needed on each vacuole partner for homotypic fusion. In vitro vacuole fusion occurs in successive steps of priming, docking, and membrane fusion. While priming does not require Vam2p or Vam6p, the functions of these two proteins cannot be fulfilled until priming has occurred, and each is required for the docking reaction which culminates in trans-SNARE pairing. Consistent with their dual function in Golgi vesicle budding and homotypic fusion of vacuoles, approximately half of the Vam2p and Vam6p of the cell are recovered from cell lysates with purified vacuoles

A novel in vitro assay reveals SNARE topology and the role of Ykt6 in autophagosome fusion with vacuoles

Autophagy is a catabolic pathway that delivers intracellular material to the mammalian lysosomes or the yeast and plant vacuoles. The final step in this process is the fusion of autophagosomes with vacuoles, which requires SNARE proteins, the homotypic vacuole fusion and protein sorting tethering complex, the RAB7-like Ypt7 GTPase, and its guanine nucleotide exchange factor, Mon1-Ccz1. Where these different components are located and function during fusion, however, remains to be fully understood. Here, we present a novel in vitro assay to monitor fusion of intact and functional autophagosomes with vacuoles. This process requires ATP, physiological temperature, and the entire fusion machinery to tether and fuse autophagosomes with vacuoles. Importantly, we uncover Ykt6 as the autophagosomal SNARE. Our assay and findings thus provide the tools to dissect autophagosome completion and fusion in a test tube