Coded beam searching for bi-directional optical wireless communication system

In a communication system with steerable laser beams, the transmitter must find the direction towards the receiver. This requires a feedback loop such that the receiver can signal that the correct direction has been found. However, the receiver may not be able to instantly give high-resolution feedback if the beam hits its detector. At least during the acquisition phase, thus before transmitter and receiver are aligned in both directions, this feedback channel typically has a wider beam and a much lower bandwidth, thus a (possibly random) latency and a lower time resolution. It is often not practical to adaptively widen the optical beam during acquisition, but even if one designs for an adaptive beam width, it is not evident that this accelerates the search as we argue in this paper. The paper also describes a suitable address coding scheme based on maximum-length Linear Feedback Shift Register sequences, that accelerates the search significantly

Gd(III)-Gd(III) Relaxation-Induced Dipolar Modulation Enhancement for In-Cell Electron Paramagnetic Resonance Distance Determination

In-cell distance determination by electron paramagnetic resonance (EPR) spectroscopy reveals essential structural information about biomacromolecules under native conditions. We demonstrate that the pulsed EPR technique RIDME (relaxation induced dipolar modulation enhancement) can be utilized for such distance determination. The performance of in-cell RIDME has been assessed at Q-band using stiff molecular rulers labeled with Gd(III)-PyMTA and microinjected into Xenopus laevis oocytes. The overtone coefficients are determined to be the same for protonated aqueous solutions and inside cells. As compared to in-cell DEER (double electron-electron resonance, also abbreviated as PELDOR), in-cell RIDME features approximately 5 times larger modulation depth and does not show artificial broadening in the distance distributions due to the effect of pseudosecular terms

catena-Poly[[[trans-diaqua­bis(pyridine-κN)cobalt(II)]-μ-(4-{N′-[1-(3-acetyl-4-methyl-1H-pyrazol-5-yl)ethyl­idene]hydrazino}benzoato-κ3 O:N,N′)-[bis­(pyridine-κN)cobalt(III)]-μ-(4-{N′-[1-(3-acetyl-4-methyl-1H-pyrazol-5-yl)ethyl­idene]hydrazino}benzoato-κ3 N,N′:O)]perchlorate 3.66-hydrate]

The title compound, {[Co2(C15H14N4O3)2(C5H5N)4(H2O)2]ClO4·3.66H2O}n, is a one-dimensional coordination polymer, with both CoII and CoIII centres in its structure. The ligand environment surrounding CoIII is formed by two N,N-chelating pyrazole-containing ligands and two pyridine mol­ecules in axial positions. The high-spin CoII ions, situated at crystallographic centres of inversion, exhibit a distorted octa­hedral coordination mode. The ClO4 − anion is linked to the polymer chain via hydrogen bonds. The chains are connected by hydrogen bonds to produce a three-dimensional structure

Molecular quantum spin network controlled by a single qubit

Scalable quantum technologies will require an unprecedented combination of precision and complexity for designing stable structures of well-controllable quantum systems. It is a challenging task to find a suitable elementary building block, of which a quantum network can be comprised in a scalable way. Here we present the working principle of such a basic unit, engineered using molecular chemistry, whose control and readout are executed using a nitrogen vacancy (NV) center in diamond. The basic unit we investigate is a synthetic polyproline with electron spins localized on attached molecular sidegroups separated by a few nanometers. We demonstrate the readout and coherent manipulation of very few ($\leq 6$) of these $S=1/2$ electronic spin systems and access their direct dipolar coupling tensor. Our results show, that it is feasible to use spin-labeled peptides as a resource for a molecular-qubit based network, while at the same time providing simple optical readout of single quantum states through NV-magnetometry. This work lays the foundation for building arbitrary quantum networks using well-established chemistry methods, which has many applications ranging from mapping distances in single molecules to quantum information processing.Comment: Author name typ

Investigating the dynamic nature of the ABC transporters: ABCB1 and MsbA as examples for the potential synergies of MD theory and EPR applications

ABC transporters are primary active transporters found in all kingdoms of life. Human multidrug resistance transporter ABCB1, or P-glycoprotein, has an extremely broad substrate spectrum and confers resistance against chemotherapy drug treatment in cancer cells. The bacterial ABC transporter MsbA is a lipid A flippase and a homolog to the human ABCB1 transporter, with which it partially shares its substrate spectrum. Crystal structures of MsbA and ABCB1 have been solved in multiple conformations, providing a glimpse into the possible conformational changes the transporter could be going through during the transport cycle. Crystal structures are inherently static, while a dynamic picture of the transporter in motion is needed for a complete understanding of transporter function. Molecular dynamics (MD) simulations and electron paramagnetic resonance (EPR) spectroscopy can provide structural information on ABC transporters, but the strength of these two methods lies in the potential to characterise the dynamic regime of these transporters. Information from the two methods is quite complementary. MD simulations provide an all atom dynamic picture of the time evolution of the molecular system, though with a narrow time window. EPR spectroscopy can probe structural, environmental and dynamic properties of the transporter in several time regimes, but only through the attachment sites of an exogenous spin label. In this review the synergistic effects that can be achieved by combining the two methods are highlighted, and a brief methodological background is also presented