Optical control of coherent interactions between quantum dot electron spins

Coherent interactions between spins in quantum dots are a key requirement for quantum gates. We have performed pump-probe experiments in which pulsed lasers emitting at different photon energies manipulate two distinct subsets of electron spins within an inhomogeneous InGaAs quantum dot ensemble. The spin dynamics are monitored through their precession about an external magnetic field. These measurements demonstrate spin precession phase shifts and modulations of the magnitude of one subset of oriented spins after optical orientation of the second subset. The observations are consistent with results from a model using a Heisenberg-like interaction with microeV-strength.Comment: 5 pages, 4 figure

Complex phenotype in an Italian family with a novel mutation in SPG3A.

Mutations in the SPG3A gene represent a significant cause of autosomal dominant hereditary spastic paraplegia with early onset and pure phenotype. We describe an Italian family manifesting a complex phenotype, characterized by cerebellar involvement in the proband and amyotrophic lateral sclerosis-like syndrome in her father, in association with a new mutation in SPG3A. Our findings further widen the notion of clinical heterogeneity in SPG3A mutations

Room-Temperature Alternative to the Arbuzov Reaction: The Reductive Deoxygenation of Acyl Phosphonates

The reductive deoxygenation of acyl phosphonates using a Wolff−Kishner-like sequence is described. This transformation allows direct access to alkyl phosphonates from acyl phosphonates at room temperature. The method can be combined with acyl phosphonate synthesis into a one pot, four-step procedure for the conversion of carboxylic acids into alkyl phosphonates. The methodology works well for a variety of aliphatic acids and shows a functional group tolerance similar to that of other hydrazone-forming reactions

Evolution of magnetic fields in stars across the upper main sequence

To properly understand the physics of upper main sequence stars it is particularly important to identify the origin of their magnetic fields. Recently, we confirmed that magnetic fields appear in Ap stars of mass below 3 M_sun only if they have already completed at least approximately 30% of their main-sequence lifetime. The absence of stars with strong magnetic fields close to the ZAMS might be seen as an argument against the fossil field theories. Here we present the results of our recent magnetic survey with FORS1 at the VLT in polarimetric mode of a sample of A, B and Herbig Ae stars with previously undetected magnetic fields and briefly discuss their significance for our understanding of the origin of the magnetic fields in intermediate mass stars.Comment: 6 pages, 3 figures, to appear in "Magnetic Fields in the Universe: From Laboratory and Stars to Primordial Structures", AIP Conference Proceedings 78

Hetero-Diels–Alder reactions of hetaryl and aryl thioketones with acetylenic dienophiles

Selected hetaryl and aryl thioketones react with acetylenecarboxylates under thermal conditions in the presence of LiClO4 or, alternatively, under high-pressure conditions (5 kbar) at room temperature yielding thiopyran derivatives. The hetero-Diels–Alder reaction occurs in a chemo- and regioselective manner. The initially formed [4 + 2] cycloadducts rearrange via a 1,3-hydrogen shift sequence to give the final products. The latter were smoothly oxidized by treatment with mCPBA to the corresponding sulfones.The authors thank the National Science Center (Cracow, Poland) for generous financial support (Grant Maestro-3 (Dec- 2012/06/A/ST5/00219). Skilful performance of microanalyses by Ms Hanna Jatczak and Ms Agnieszka Cieślińska (University of Łódź) is gratefully acknowledge

Experimental Evaluation of SDN-Controlled, Joint Consolidation of Policies and Virtual Machines

Middleboxes (MBs) are ubiquitous in modern data centre (DC) due to their crucial role in implementing network security, management and optimisation. In order to meet network policy's requirement on correct traversal of an ordered sequence of MBs, network administrators rely on static policy based routing or VLAN stitching to steer traffic flows. However, dynamic virtual server migration in virtual environment has greatly challenged such static traffic steering. In this paper, we design and implement Sync, an efficient and synergistic scheme to jointly consolidate network policies and virtual machines (VMs), in a readily deployable Mininet environment. We present the architecture of Sync framework and open source its code. We also extensively evaluate Sync over diverse workload and policies. Our results show that in an emulated DC of 686 servers, 10k VMs, 8k policies, and 100k flows, Sync processes a group of 900 VMs and 10 VMs in 634 seconds and 4 seconds respectively

Sulfenate Anion Catalysis: Reactions And Precatalysts Development

Organocatalysts have been a hot area of exploration, due to both concept novelty and significant reactivity. Multiple mechanisms have been proved and used to design new organocatalysts. Examples include thioureas, which have been designed to accelerate chemical transformation through hydrogen bonds. Initially found by Schering and Hoffman-La, prolines have been widely used in asymmetric aldol reactions. This dissertation investigated an unprecedented organocatalyst: sulfenate anions. In Chapter 1, sulfenate anions are introduced as a new type of organocatalyst. It has been well established that the sulfenate anions act both as nucleophiles and leaving groups. For prove-of-concept, a variety of benzyl halides were successfully coupled to form stilbenes. More challenging sulfenate anions precatalysts, including DMSO performed well in these catalytic reactions. Preliminary mechanistic studies were conducted, identifying α-deprotenated sulfoxide as the resting state. In Chapter 2, we further investigated the sulfenate anions capability as organocatalysts. Due to the instability of sulfenate anions in air, sulfoxides precursors are usually used and generate sulfenate anions in situ through base induced beta-hydrogen elimination or thermolysis. tert-Butyl sulfoxides were examined as a new type of organocatalysts precursor with iso-butylene as a byproduct. It is noteworthy that sulfenate anions generated from tert-butyl sulfoxides remain stable in high temperature under inert atmosphere and retain similar reactivity compared with sulfenate anions formed using general conditions in the model reaction of benzyl halides coupling. In Chapter 3, further research was performed in exploring the reaction possibility of sulfenate anions. A cross-coupling reaction of benzyl halides and benzaldehydes derivatives was achieved to form alkyne compounds. A broad scope of alkyne products, including multiple functional groups and heterocycles, demonstrated the value of sulfenate anion catalysts in synthetic chemistry. The reactivity of different functionalized sulfenate anions and sulfoxide precatalysts were examined. Further optimization was conducted to overcome multiple side reactions. Moreover, preliminary mechanism study revealed the role of sulfenate anions in the reaction. In Chapter 4, convenient scalable sulfenate anions precatalysts were developed and their utility demonstrated in a scalable alkyne synthesis