Exchange Coupling in a Linear Chain of Three Quantum-Dot Spin Qubits in Silicon.

Quantum gates between spin qubits can be implemented leveraging the natural Heisenberg exchange interaction between two electrons in contact with each other. This interaction is controllable by electrically tailoring the overlap between electronic wave functions in quantum dot systems, as long as they occupy neighboring dots. An alternative route is the exploration of superexchange-the coupling between remote spins mediated by a third idle electron that bridges the distance between quantum dots.

Three-waveform bidirectional pumping of single electrons with a silicon quantum dot.

Semiconductor-based quantum dot single-electron pumps are currently the most promising candidates for the direct realization of the emerging quantum standard of the ampere in the International System of Units. Here, we discuss a silicon quantum dot single-electron pump with radio frequency control over the transparencies of entrance and exit barriers as well as the dot potential. We show that our driving protocol leads to robust bidirectional pumping: one can conveniently reverse the direction of the quantized current by changing only the phase shift of one driving waveform with respect to the others.

An accurate single-electron pump based on a highly tunable silicon quantum dot.

Nanoscale single-electron pumps can be used to generate accurate currents, and can potentially serve to realize a new standard of electrical current based on elementary charge. Here, we use a silicon-based quantum dot with tunable tunnel barriers as an accurate source of quantized current. The charge transfer accuracy of our pump can be dramatically enhanced by controlling the electrostatic confinement of the dot using purposely engineered gate electrodes.

Single-shot readout of an electron spin in silicon.

The size of silicon transistors used in microelectronic devices is shrinking to the level at which quantum effects become important. Although this presents a significant challenge for the further scaling of microprocessors, it provides the potential for radical innovations in the form of spin-based quantum computers and spintronic devices. An electron spin in silicon can represent a well-isolated quantum bit with long coherence times because of the weak spin-orbit coupling and the possibility of eliminating nuclear spins from the bulk crystal.

Transport spectroscopy of single phosphorus donors in a silicon nanoscale transistor.

We have developed nanoscale double-gated field-effect-transistors for the study of electron states and transport properties of single deliberately implanted phosphorus donors. The devices provide a high-level of control of key parameters required for potential applications in nanoelectronics. For the donors, we resolve transitions corresponding to two charge states successively occupied by spin down and spin up electrons.

Post-translational modifications of the four conserved lysine residues within the collagenous domain of adiponectin are required for the formation of its high molecular weight oligomeric complex.

Adiponectin is a multifunctional adipokine that circulates as several oligomeric complexes in the blood stream. However, the molecular basis that regulates the production of the adiponectin oligomers remains largely elusive. We have shown previously that several conserved lysine residues (positions 68, 71, 80, and 104) within the collagenous domain of adiponectin are modified by hydroxylation and glycosylation (Wang, Y.

Angiopoietin-like protein 4 decreases blood glucose and improves glucose tolerance but induces hyperlipidemia and hepatic steatosis in mice.

Angiopoietin-like protein 4 (ANGPTL4) is a circulating protein predominantly expressed in adipose tissue and liver. Several recent studies demonstrated that ANGPTL4 is the target gene of peroxisome proliferation activators, the agonists of which are widely used as the antidiabetic and lipid-lowering drugs. Here we provide evidence that ANGPTL4 is a blood-borne hormone directly involved in regulating glucose homeostasis, lipid metabolism, and insulin sensitivity.

Testosterone selectively reduces the high molecular weight form of adiponectin by inhibiting its secretion from adipocytes.

The antidiabetic hormone adiponectin circulates in blood as several oligomeric complexes, and the ratios between them are critical in determining insulin sensitivity. In this study we investigated the role of testosterone in regulating the oligomeric complex distribution of adiponectin. Gel filtration analysis revealed that circulating adiponectin existed as the forms of high molecular weight (HMW), middle molecular weight, and low molecular weight complexes in both human and mice.

Adiponectin ameliorates dyslipidemia induced by the human immunodeficiency virus protease inhibitor ritonavir in mice.

Although the clinical application of HIV protease inhibitors (PIs) has markedly reduced HIV-related morbidity and mortality, it is now recognized that PI-based therapy often causes serious metabolic disorders, including hyperlipidemia and premature atherosclerosis. The etiology of these adverse effects remains obscure. Here, we demonstrate that deficiency of the fat-derived hormone adiponectin might play a role.