Foraging Leaf-Cutting Ants Learn to Reject Vitis vinifera ssp. vinifera Plants that Emit Herbivore-Induced Volatiles

Leaf-cutting ants (LCAs) are dominant herbivores of the Neotropics, as well as economically important pests. Their foraging ecology and patterns/mechanisms of food selection have received considerable attention. Recently, it has been documented that LCAs exhibit a delayed rejection of previously accepted food plants following treatment with a fungicide that makes the plants unsuitable as substrate for their symbiotic fungus. Here, we investigated whether LCAs similarly reject plants with induced chemical defenses, by combining analysis of volatile emissions with dual-choice bioassays that used LCA subcolonies (Atta sexdens L.). On seven consecutive days, foraging ants were given the choice between leaf disks from untreated control plants and test plants of Vitis vinifera ssp. vinifera L. treated with the phytohormone jasmonic acid (JA) to mimic herbivore attack. Chemical analysis revealed the emission of a characteristic set of herbivore-induced volatile organic compounds (VOC) from JA-induced plants. Dual-choice experiments indicated that workers did not show any preference initially, but that they avoided JA-treated plants from day five onwards. Our finding that A. sexdens foragers learn to avoid VOC-emitting plants, which are likely detrimental to their symbiotic fungus, represents the first evidence for avoidance learning in attine ants toward plants with induced defenses.     

Analysis of pressureless sintering of titanium diboride ceramics with nickel,cobalt, and tungsten carbide additives

The mechanisms during pressureless sintering of TiB₂ with 0–50 wt.% Ni were analysed by differential dilatometry after mechanical alloying with hard metal beads. Three main stages of sintering could be identified by means of the changing dilatation rate. The first interval (200–600 °C) comprises reactions with oxygen and moisture (H₃BO₃, B₂O₃ formation, melting, evaporation). The second stage (600–700 °C) is governed by solid state sintering and reactions of Ni and/or Co with TiB₂ yielding Ni₃B, Ni₂B, the corresponding Co-compounds and the ternary ω-phase of W₂NiB₂-type. The third main shrinkage interval is due to liquid phase sintering (987–1640 °C) and is accompanied by a significant weight-loss. Both precipitation of ω-phase as well as a (Ti,W)B₂ solid solution in form of a core-shell structure are responsible for a grain growth retardation and the homogeneous microstructure. The results explain well all features reported in the corresponding literature while encountering the role of WC, too.     

Time-domain optical mammography: initial clinical results on detection and characterization of breast tumors

Mammograms of 35 patients suspected of breast cancer were taken along craniocaudal and mediolateral projections with a dual-wavelength scanning laser pulse mammograph measuring time-resolved transmittance. Among 26 tumors known from routine clinical diagnostics, 17 tumors were detected retrospectively in optical mammograms. Effective tumor optical properties derived from a homogeneous model were used to deduce physiological information. All tumors exhibited increased total hemoglobin concentration and decreased or unchanged blood oxygen saturation compared with surrounding healthy tissue. Scatter plots based on a pixelwise analysis of individual mammograms were introduced and applied to represent corelations between characteristic quantities derived from measured distributions of times of flight of photons.     

Poly(2‐(dimethylamino)ethyl methacrylate) Brushes with Incorporated Nanoparticles as a SERS Active Sensing Layer

A simple, fast, and versatile approach to the fabrication of outstanding surface enhanced Raman spectroscopy (SERS) substrates by exploiting the optical properties of the Ag nanoparticles and functional as well as organizational characteristics of the polymer brushes is reported. First, poly(2‐(dimethylamino)ethyl methacrylate) brushes are synthesized directly on glassy carbon by self‐initiated photografting and photopolymerization and thoroughly characterized in terms of their thickness, wettability, morphology, and chemical structure by means of ellipsometry, contact angle, AFM, and XPS, respectively. Second, Ag nanoparticles are homogeneously immobilized into the brush layer, resulting in a sensor platform for the detection of organic molecules by SERS. The surface enhancement factor (SEF) as determined by the detection of Rhodamine 6G is calculated as 6 × 10⁶.     

HiL simulation for testing joint stability after total knee arthroplasty

Instability of total knee replacements (TKRs) remains one of the most prevalent complications after total knee arthroplasty. Especially the actual event of instability involving complex interactions between implant components and soft tissue structures is not well understood. Therefore, the purpose of this work is to introduce a novel approach for testing TKRs with respect to stability of the artificial knee joint based on a mechatronic hardware-in-the-loop (HiL) test system. The mechanical test setup is composed of an industrial robot with a compliant support for the endoprosthesis to be tested. It interacts with a biomechanical multibody model consisting of all relevant body parts of the lower extremity incorporating ligament structures of the knee joint. According to the movement angles and reaction forces/torque provided by the multibody model, the robot rotates and loads the femoral component with respect to the tibial component. The resulting position and loading of the femoral component are measured and fed back into the model, thus closing the control loop for HiL simulations. The functional principle of the HiL simulation is proven by simulating a passive flexion movement of a bicondylar, posterior cruciate ligament retaining TKR using the described biomechanical multibody model.