Ultrafast control of nuclear spins using only microwave pulses: towards switchable solid-state quantum gates

We demonstrate the control of the alpha-proton nuclear spin, I=1/2, coupled to the stable radical CH(COOH)2, S=1/2, in a gamma-irradiated malonic acid single crystal using only microwave pulses. We show that, depending on the state of the electron spin mS=+/-1/2, the nuclear spin can be locked in a desired state or oscillate between mI=+1/2 and mI=-1/2 on the nanosecond time scale. This approach provides a fast and efficient way of controlling nuclear spin qubits and also enables the design of switchable spin-based quantum gates by addressing only the electron spin.Comment: 5 pages, 4 figure

PRELIMINARY SPECTROSCOPIC STUDY OF FE-BEARING CLAY MINERALS IN ALTERED PILLOW LAVAS FROM LAMIA AREA, GREECE1

Γεωλογικό υλικό, πρασινωπού χρώματος, το οποίο απαντά σε εξαλλοιωμένες μαξιλαροειδείς λάβες του Τριασικού στην περιοχή της Λαμίας, μελετάται για πρώτη φορά στη βιβλιογραφία. Σύμφωνα με τα δεδομένα XRD και SEM-EDS αποτελείται κυρίως από ασβεστίτη, ζεόλιθους και ορυκτά της αργίλου. Από την ομάδα των ζεολίθων, απαντούν τομσονίτης και ανάλκιμο. Τα ορυκτά της αργίλου, σύμφωνα με XRD και φασματοσκοπικές μετρήσεις FTIR και Mössbauer, συνιστούν Fe-ούχα φάση της ομάδας ιλλίτη-γλαυκονίτη-σελαδονίτη (πιθανότατα Fe-ιλλίτη)Geological material, of greenish color, filling interspaces in altered Triassic pillow lavas of Lamia area (central Greece) was studied, for the first time in the literature. According to XRD and SEM-EDS data it predominantly consists of calcite, zeolites and clay minerals. The zeolites concern thomsonite and analcime. The clay minerals, on the basis of XRD, FTIR and Mössbauer spectroscopic measurements, constitute a Fe-bearing phase of the illlite-glauconite-celadonite group (most likely Fe-illite)

PRELIMINARY SPECTROSCOPIC STUDY OF FE-BEARING CLAY MINERALS IN ALTERED PILLOW LAVAS FROM LAMIA AREA, GREECE1

Γεωλογικό υλικό, πρασινωπού χρώματος, το οποίο απαντά σε εξαλλοιωμένες μαξιλαροειδείς λάβες του Τριασικού στην περιοχή της Λαμίας, μελετάται για πρώτη φορά στη βιβλιογραφία. Σύμφωνα με τα δεδομένα XRD και SEM-EDS αποτελείται κυρίως από ασβεστίτη, ζεόλιθους και ορυκτά της αργίλου. Από την ομάδα των ζεολίθων, απαντούν τομσονίτης και ανάλκιμο. Τα ορυκτά της αργίλου, σύμφωνα με XRD και φασματοσκοπικές μετρήσεις FTIR και Mössbauer, συνιστούν Fe-ούχα φάση της ομάδας ιλλίτη-γλαυκονίτη-σελαδονίτη (πιθανότατα Fe-ιλλίτη)Geological material, of greenish color, filling interspaces in altered Triassic pillow lavas of Lamia area (central Greece) was studied, for the first time in the literature. According to XRD and SEM-EDS data it predominantly consists of calcite, zeolites and clay minerals. The zeolites concern thomsonite and analcime. The clay minerals, on the basis of XRD, FTIR and Mössbauer spectroscopic measurements, constitute a Fe-bearing phase of the illlite-glauconite-celadonite group (most likely Fe-illite)

Sensing iron availability via the fragile [4Fe-4S] cluster of the bacterial transcriptional repressor RirA

Rhizobial iron regulator A (RirA) is a global regulator of iron homeostasis in many nitrogen-fixing Rhizobia and related species of α-proteobacteria. It belongs to the widespread Rrf2 super-family of transcriptional regulators and features three conserved Cys residues that characterise the binding of an iron–sulfur cluster in other Rrf2 family regulators. Here we report biophysical studies demonstrating that RirA contains a [4Fe–4S] cluster, and that this form of the protein binds RirA-regulated DNA, consistent with its function as a repressor of expression of many genes involved in iron uptake. Under low iron conditions, [4Fe–4S] RirA undergoes a cluster conversion reaction resulting in a [2Fe–2S] form, which exhibits much lower affinity for DNA. Under prolonged low iron conditions, the [2Fe–2S] cluster degrades to apo-RirA, which does not bind DNA and can no longer function as a repressor of the cell's iron-uptake machinery. [4Fe–4S] RirA was also found to be sensitive to O2, suggesting that both iron and O2 are important signals for iron metabolism. Consistent with this, in vivo data showed that expression of RirA-regulated genes is also affected by O2. These data lead us to propose a novel regulatory model for iron homeostasis, in which RirA senses iron via the incorporation of a fragile iron–sulfur cluster that is sensitive to iron and O2 concentrations

A redox-induced spin-state cascade in a mixed-valent Fe3 (μ3 -O) triangle.

One-electron reduction of a pyrazolate-bridged triangular Fe3 (μ3 -O) core induces a cascade wherein all three metal centers switch from high-spin Fe(3+) to low-spin Fe(2.66+) . This hypothesis is supported by spectroscopic data ((1) H-NMR, UV-vis-NIR, infra-red, (57) Fe-Mössbauer, EPR), X-ray crystallographic characterization of the cluster in both oxidation states and also density functional theory. The reduction induces substantial contraction in all bond lengths around the metal centers, along with diagnostic shifts in the spectroscopic parameters. This is, to the best of our knowledge, the first example of a one-electron redox event causing concerted change in multiple iron centers

Spectroscopic and nanoscale characterization of blue-coloured smithsonite (ZnCO3) from Lavrion historical mines (Greece)

Spectroscopic and microscopic (particularly HRTEM) techniques were used to investigate the origin of the colour of natural blue Zn-carbonate (smithsonite). Blue smithsonite is rich in copper, but substitution of zinc cations by copper cations, as proposed in the past for the origin of the colour, is questionable considering the absence of anhydrous divalent copper carbonates in nature. In this work, optical microscopy, SEM-EDS, XRD and laser micro-Raman could not resolve distinct phases either than Zn-carbonate, while NIR spectra excluded known chromophore Cu-hydroxycarbonate minerals. HRTEM studies however could clearly resolve nano-sized (3-7 nm) Cu-rich inclusions (specifically Si/Ca/Cu/As-rich inclusions of at least one phase), which are organised in bands with no topotaxial relation to bulk smithsonite. Electron-beam sensitivity of the samples, even at low electron current densities, did not allow the exact identification of the inclusions. However, it can be safely suggested, for the first time in the literature, that they are the cause of the blue colour in smithsonite

In-depth synthetic, physicochemical and in vitro biological investigation of a new ternary V(IV) antioxidant material based on curcumin.

Curcumin is a natural product with a broad spectrum of beneficial properties relating to pharmaceutical applications, extending from traditional remedies to modern cosmetics. The biological activity of such pigments, however, is limited by their solubility and bioavailability, thereby necessitating new ways of achieving optimal tissue cellular response and efficacy as drugs. Metal ion complexation provides a significant route toward improvement of curcumin stability and biological activity, with vanadium being a representative such metal ion, amply encountered in biological systems and exhibiting exogenous bioactivity through potential pharmaceuticals. Driven by the need to optimally increase curcumin bioavailability and bioactivity through complexation, synthetic efforts were launched to seek out stable species, ultimately leading to the synthesis and isolation of a new ternary V(IV)-curcumin-(2,2’-bipyridine) complex. Physicochemical characterization (elemental analysis, FT-IR, Thermogravimetry (TGA), UV-Visible, NMR, ESI-MS, Fluorescence, X-rays) portrayed the solid-state and solution properties of the ternary complex. Pulsed-EPR spectroscopy, in frozen solutions, suggested the presence of two species, cis- and trans-conformers. Density Functional Theory (DFT) calculations revealed the salient features and energetics of the two conformers, thereby complementing EPR spectroscopy. The well-described profile of the vanadium species led to its in vitro biological investigation involving toxicity, cell metabolism inhibition in S. cerevisiae cultures, Reactive Oxygen Species (ROS)-suppressing capacity, lipid peroxidation, and plasmid DNA degradation. A multitude of bio-assays and methodologies, in comparison to free curcumin, showed that it exhibits its antioxidant potential in a concentration-dependent fashion, thereby formulating a bioreactivity profile supporting development of new efficient vanado-pharmaceuticals, targeting (extra)intra-cellular processes under (patho)physiological conditions

A general synthetic route for the preparation of high-spin molecules: Replacement of bridging hydroxo ligands in molecular clusters by end-on azido ligands

Abstract A general method of increasing the ground-state total spin value of a polynuclear 3d-metal complex is illustrated through selected examples from cobalt(II) and nickel(II) cluster chemistry that involves the dianion of the gem-diol form of di-2-pyridyl ketone and carboxylate ions as organic ligands. The approach is based on the replacement of hydroxo bridges, that most often propagate antiferromagnetic exchange interactions, by the end-on azido ligand, which is a ferromagnetic coupler