Kinetic resolution of alkyne-substituted quaternary oxindoles via copper catalysed azide-alkyne cycloadditions

Kinetic resolution of alkyne-substituted quaternary oxindoles via copper catalysed azide-alkyne cycloaddition

Asymmetric copper catalyzed azide-alkyne cycloadditions

Since its discovery independently by Sharpless and Meldal in 2002, the copper-catalyzed azide–alkyne cycloaddition (CuAAC) has become a ubiquitous molecular linking platform. Easy access to substituted 1,4-triazoles can be exploited to engender asymmetry to a myriad of potentially useful targets in high yields. Utilizing the CuAAC to form chiral triazolic products in a single step is an attractive and powerful approach for the synthetic chemist. The area of asymmetric CuAAC is still in its infancy compared to more established asymmetric metal-mediated transformations; however, this leads to exciting challenges that need to be overcome to usher in the next era in the story of the triazole and click chemistry in general. This review details the steps taken into asymmetric CuAAC and the exciting results achieved thus far. [Note that diagrams accompany this abstract in the published version and can be found at http://dx.doi.org/10.1021/acscatal.6b00996.

On the power counting of loop diagrams in general relativity

A class of loop diagrams in general relativity appears to have a behavior which would upset the utility of the energy expansion for quantum effects. We show through the study of specific diagrams that cancellations occur which restore the expected behaviour of the energy expansion. By considering the power counting in a physical gauge we show that the apparent bad behavior is a gauge artifact, and that the quantum loops enter with a well behaved energy expansion.Comment: 29 pages, uses axodraw and epsfig.tex, one small .eps file is included. The full PostScript version is also available as http://het.phast.umass.edu/students/kakukk/powercount_hepth.p

An NMR-based nanostructure switch for quantum logic

We propose a nanostructure switch based on nuclear magnetic resonance (NMR) which offers reliable quantum gate operation, an essential ingredient for building a quantum computer. The nuclear resonance is controlled by the magic number transitions of a few-electron quantum dot in an external magnetic field.Comment: 4 pages, 2 separate PostScript figures. Minor changes included. One reference adde

On B_s -> mu+ mu- and Cold Dark Matter Scattering in the MSSM with Non-Universal Higgs Masses

We show that present experimental constraints on B_s -> mu+ mu- decay and the CDMS upper limit on the cold dark matter elastic scattering cross section already have significant impact on the parameter space of the minimal supersymmetric extension of the Standard Model (MSSM) with non-universal supersymmetry-breaking scalar masses for the Higgs multiplets (NUHM). The relaxation of scalar universality in the MSSM allows the possibility of a relatively light mass M_A for the pseudoscalar Higgs boson. The present upper limit on B_s -> mu+ mu- already excludes much of the scope for this possibility in the NUHM, in contrast to the constrained MSSM with universal scalar masses (CMSSM), where B_s -> mu+ mu- decay does not exclude any ranges of parameters not already excluded by b -> s \gamma decay. Cold dark matter scattering is also enhanced for small M_A, but the impact of present upper limit on B_s -> mu+ mu- on the NUHM parameter space is in many cases greater than that of the CDMS scattering limit, particularly at large tanb.Comment: 17 pages, 14 eps figure

Ulcerative Colitis Physician Team-Work in the Treatment

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68011/2/10.1177_000992286400300203.pd

Physical Optimization of Quantum Error Correction Circuits

Quantum error correcting codes have been developed to protect a quantum computer from decoherence due to a noisy environment. In this paper, we present two methods for optimizing the physical implementation of such error correction schemes. First, we discuss an optimal quantum circuit implementation of the smallest error-correcting code (the three bit code). Quantum circuits are physically implemented by serial pulses, i.e. by switching on and off external parameters in the Hamiltonian one after another. In contrast to this, we introduce a new parallel switching method that allows faster gate operation by switching all external parameters simultaneously. These two methods are applied to electron spins in coupled quantum dots subject to a Heisenberg coupling H=J(t) S_1*S_2 which can generate the universal quantum gate `square-root-of-swap'. Using parallel pulses, the encoding for three-bit quantum error correction in a Heisenberg system can be accelerated by a factor of about two. We point out that parallel switching has potential applications for arbitrary quantum computer architectures.Comment: 13 pages, 6 figure

Quantum-Hall Quantum-Bits

Bilayer quantum Hall systems can form collective states in which electrons exhibit spontaneous interlayer phase coherence. We discuss the possibility of using bilayer quantum dot many-electron states with this property to create two-level systems that have potential advantages as quantum bits.Comment: 4 pages, 4 figures included, version to appear in Phys. Rev. B (Rapid Communications