Thermal stress cycling of GaAs solar cells

A thermal cycling experiment was performed on GaAs solar cells to establish the electrical and structural integrity of these cells under the temperature conditions of a simulated low-Earth orbit of 3-year duration. Thirty single junction GaAs cells were obtained and tests were performed to establish the beginning-of-life characteristics of these cells. The tests consisted of cell I-V power output curves, from which were obtained short-circuit current, open circuit voltage, fill factor, and cell efficiency, and optical micrographs, spectral response, and ion microprobe mass analysis (IMMA) depth profiles on both the front surfaces and the front metallic contacts of the cells. Following 5,000 thermal cycles, the performance of the cells was reexamined in addition to any factors which might contribute to performance degradation. It is established that, after 5,000 thermal cycles, the cells retain their power output with no loss of structural integrity or change in physical appearance

Coherent Destruction of Coulomb Blockade Peaks in Molecular Junctions

Coherent electronic transport in single-molecule junctions is investigated in the Coulomb blockade regime. Both the transmission phase and probability are calculated for junctions with various contact symmetries. A dramatic suppression of the Coulomb blockade peaks is predicted for junctions where multiple atomic orbitals of the molecule couple to a single electrode although the charging steps are unaffected.Comment: 6 pages, 4 figure

Optomechanical magnetometry with a macroscopic resonator

We demonstrate a centimeter-scale optomechanical magnetometer based on a crystalline whispering gallery mode resonator. The large size of the resonator allows high magnetic field sensitivity to be achieved in the hertz to kilohertz frequency range. A peak sensitivity of 131 pT per root Hz is reported, in a magnetically unshielded non-cryogenic environment and using optical power levels beneath 100 microWatt. Femtotesla range sensitivity may be possible in future devices with further optimization of laser noise and the physical structure of the resonator, allowing applications in high-performance magnetometry

Система обнаружения с беспроводной зарядкой на основе катушки с крестовидной перемычкой и активной системой управления аккумулятором

The article presents a detection system with spider web coil-based wireless charging. Commonly available metal detectors are sold as handheld systems, which enable only progressive, lengthy, time-consuming search. Importantly, a part of the investigated area can thus be easily missed, and the probability that a metal object will not be found increases substantially. This problem, however, is eliminable via the automatic position tracking mode embedded in the solution obtained through our research. The proposed system facilitates using the spider web coil simultaneously for wireless charging and metal detection by pulse induction. The topology of the detector can emit variable pulse lengths, thus allowing the device to detect more types of metal and to adapt itself to the permeability of the soil. The coil has a branch in a relevant part of the winding to reduce undesirable electromagnetic interference during the charging. On the transmitting side of the topology, impedance matching is included to maintain the maximum spatial gap variability. By changing the position of the receiving side, the output voltage changes; therefore, a high efficiency DC/DC converter is employed. The individual battery cells demonstrate different internal resistances, requiring us to apply a new method to balance the cells voltage. The system can be utilized on self-guided vehicles or drones; advantageously, a GPS resending the coordinates to a mesh radio allows for accurate positioning. With the mesh topology, potential cooperation between the multiple systems is possible. The setup utilizes the same coil for wireless power transfer and detection.В статье представлена система обнаружения с беспроводной зарядкой на основе катушки с крестообразной перемычкой. Обычно доступные металлоискатели продаются в виде переносных систем, которые позволяют осуществлять только постепенный, длительный и трудоемкий поиск. Важно отметить, что часть исследуемой зоны, таким образом, может быть легко пропущена, и вероятность того, что металлический объект не будет найден, существенно возрастает. Эта проблема устраняется с помощью автоматического режима отслеживания местоположения, встроенного в решение, полученное в результате наших исследований. Предлагаемая система облегчает одновременное использование катушки с крестообразной перемычкой для беспроводной зарядки и обнаружения металла с помощью импульсной индукции. Топология детектора может излучать переменную длину импульсов, что позволяет устройству обнаруживать больше типов металлов и адаптироваться к проницаемости почвы. Катушка имеет ответвление в соответствующей части обмотки, чтобы уменьшить нежелательные электромагнитные помехи во время зарядки. На передающей стороне топологии включено согласование импеданса для поддержания максимальной изменчивости пространственного зазора. При изменении положения приемной стороны изменяется выходное напряжение, поэтому используется высокоэффективный преобразователь постоянного тока в постоянный. Отдельные элементы батареи демонстрируют различные внутренние сопротивления, что требует применения нового метода для балансировки напряжения элементов. Система может быть использована на самонаводящихся транспортных средствах или беспилотных летательных аппаратах; GPS, успешно отправляющие координаты на многоканальное радио, обеспечивают точное позиционирование. При наличии многоканальной топологии возможно потенциальное сотрудничество между разнообразными системами. В установке используется одна и та же катушка для беспроводной передачи и обнаружения энергии

Subdiffraction-Limited Quantum Imaging within a Living Cell

We report both subdiffraction-limited quantum metrology and quantum-enhanced spatial resolution for the first time in a biological context. Nanoparticles are tracked with quantum-correlated light as they diffuse through an extended region of a living cell in a quantum-enhanced photonic-force microscope. This allows spatial structure within the cell to be mapped at length scales down to 10 nm. Control experiments in water show a 14% resolution enhancement compared to experiments with coherent light. Our results confirm the long-standing prediction that quantum-correlated light can enhance spatial resolution at the nanoscale and in biology. Combined with state-of-the-art quantum light sources, this technique provides a path towards an order of magnitude improvement in resolution over similar classical imaging techniques

The number of transmission channels through a single-molecule junction

We calculate transmission eigenvalue distributions for Pt-benzene-Pt and Pt-butadiene-Pt junctions using realistic state-of-the-art many-body techniques. An effective field theory of interacting $\pi$-electrons is used to include screening and van der Waals interactions with the metal electrodes. We find that the number of dominant transmission channels in a molecular junction is equal to the degeneracy of the molecular orbital closest to the metal Fermi level.Comment: 9 pages, 8 figure

Biological measurement beyond the quantum limit

Quantum noise places a fundamental limit on the per photon sensitivity attainable in optical measurements. This limit is of particular importance in biological measurements, where the optical power must be constrained to avoid damage to the specimen. By using non-classically correlated light, we demonstrated that the quantum limit can be surpassed in biological measurements. Quantum enhanced microrheology was performed within yeast cells by tracking naturally occurring lipid granules with sensitivity 2.4 dB beyond the quantum noise limit. The viscoelastic properties of the cytoplasm could thereby be determined with a 64% improved measurement rate. This demonstration paves the way to apply quantum resources broadly in a biological context